阅读说明：本技术 固体电解质、其制备方法、包括其的经保护的正极、电化学电池和电化学设备 (Solid electrolyte, method for preparing same, protected positive electrode comprising same, electrochemical cell and electrochemical device ) 是由 郑成均 权赫祚 尹钾仁 金柱植 于 2021-06-02 设计创作，主要内容包括：本发明涉及固体电解质、其制备方法、包括其的经保护的正极、电化学电池和电化学设备。固体电解质,其包括由式1或3表示的化合物,所述化合物具有-30℃或更低的玻璃化转变温度、和玻璃或玻璃-陶瓷结构,其中,在式1中,Q为Li、或者Li与如下的组合：Na、K或其组合,M为三价阳离子、或其组合,X为不同于F的卤素、拟卤素、OH、或其组合,Z为单价阴离子、或其组合,1<A<5,0≤z<1,0≤z1≤1,和0≤k<1,在式3中,Q为Li、或者Li与如下的组合：Na、K或其组合,M为三价阳离子、或其组合,X为不同于F的卤素、拟卤素、OH、或其组合,Z为单价阴离子、或其组合,0<a≤1,0<b≤1,0<a+b,a+b＝4-A,1<A<5,0≤z<1,0≤z1≤1,和0≤k<1。式1AQX-Ga-(1-z)M-(z1)(F-(1-k)Cl-(k))-(3-3z)Z-(3z1)式3AQX-aM-(z1)Z-(3z1)-bGa-(1-z)(F-(1-k)Cl-(k))-(3-3z)。(The present invention relates to a solid electrolyte, a method for preparing the same, a protected positive electrode including the same, an electrochemical cell, and an electrochemical device. A solid electrolyte comprising a compound represented by formula 1 or 3, the compound having a glass transition temperature of-30 ℃ or less, and a glass or glass-ceramic structure,wherein, in formula 1, Q is Li, or a combination of Li and: na, K, or a combination thereof, M is a trivalent cation, or a combination thereof, X is a halogen other than F, a pseudohalogen, OH, or a combination thereof, Z is a monovalent anion, or a combination thereof, 1<A<5，0≤z<1, 0. ltoreq. z 1. ltoreq.1, and 0. ltoreq. k<In formula 3, Q is Li, or a combination of Li and: na, K, or a combination thereof, M is a trivalent cation, or a combination thereof, X is a halogen other than F, a pseudohalogen, OH, or a combination thereof, Z is a monovalent anion, or a combination thereof, 0<a≤1，0<b≤1，0<a+b，a+b＝4‑A，1<A<5，0≤z<1, 0. ltoreq. z 1. ltoreq.1, and 0. ltoreq. k<1. Formula 1AQX-Ga 1‑z M z1 (F 1‑k Cl k ) 3‑3z Z 3z1 Formula 3AQX-aM z1 Z 3z1 ‑bGa 1‑z (F 1‑k Cl k ) 3‑3z 。)

1. A solid electrolyte comprising:

a compound represented by formula 1 or formula 3,

wherein the compound represented by formula 1 or formula 3 has a glass transition temperature of-30 ℃ or less, and a glass or glass-ceramic structure:

formula 1

AQX-Ga_1-zM_z1(F_1-kCl_k)_3-3zZ_3z1

Wherein, in the formula 1,

q is Li, or a combination of Li and: na, K or a combination thereof,

m is a trivalent cation, or combination thereof,

x is a halogen other than F, a pseudohalogen, OH, or a combination thereof,

z is a monovalent anion, or a combination thereof,

1< A <5, 0< z <1, 0< z 1< 1, and 0< k <1,

formula 3

AQX-aM_z1Z_3z1-bGa_1-z(F_1-kCl_k)_3-3z

Wherein, in formula 3, Q is Li, or a combination of Li and: na, K or a combination thereof,

m is a trivalent cation, or combination thereof,

x is a halogen other than F, a pseudohalogen, OH, or a combination thereof,

z is a monovalent anion, or a combination thereof,

0< a <1, 0< b <1, 0< a + b, a + b-4-a, 1< a <5, 0< z <1, 0< z 1< 1, and 0< k < 1.

2. The solid electrolyte of claim 1, wherein the solid electrolyte has a loss modulus of 100 pascals or greater.

3. The solid electrolyte according to claim 1, wherein the solid electrolyte has a water content of 5 wt% or less with respect to the total weight of the solid electrolyte.

4. The solid electrolyte of claim 3, wherein the solid electrolyte has a water content of 0.1 wt% to 5 wt% relative to the total weight of the solid electrolyte.

5. The solid electrolyte of claim 1, wherein the compound represented by formula 1 or 3 includes a compound represented by formula 2:

formula 2

ALiX-Ga_1-zM_z1(F_1-kCl_k)_3-3zZ_3z1

Wherein, in formula 1, M is a trivalent cation, or a combination thereof,

x is a halogen other than F, a pseudohalogen, OH, or a combination thereof,

z is a monovalent anion, or a combination thereof,

1< A <5, 0< z <1, 0< z 1< 1, and 0< k < 1.

6. The solid electrolyte of claim 1, wherein a and b are not both simultaneously 1, and 2< a < 4.

7. The solid electrolyte of claim 1, wherein the compound represented by formula 1 or 3 includes a compound represented by formula 4:

formula 4

ALiX-aM_z1Z_3z1-bGa_1-z(F_1-kCl_k)_3-3z

Wherein, in formula 4, M is a trivalent cation, or a combination thereof,

x is a halogen other than F, a pseudohalogen, OH, or a combination thereof,

z is a monovalent anion, or a combination thereof,

0< a <1, 0< b <1, 0< a + b, a + b ═ 4-a, 1< a <4, 0< z <1, 0< z 1< 1, and 0< k < 1.

8. The solid electrolyte of claim 1, wherein the solid electrolyte has a lithium ion conductivity of 0.1mS/cm or greater at 25 ℃.

9. The solid electrolyte according to claim 1, wherein, In formula 1 or 3, M is In, Sc, Al, Tl, Y, B, La, or a combination thereof.

10. The solid electrolyte according to claim 1, wherein, in formula 1 or 3, Z is halogen, pseudohalogen, or a combination thereof.

11. The solid electrolyte according to claim 1, wherein, in formula 1 or 3, X is Cl, Br, I, or a combination thereof, and

z is Cl, Br, I, SCN, OCN, CN, OH, N₃Or a combination thereof.

12. The solid electrolyte according to claim 1, wherein the compound of formula 1 or 3 is one selected from compounds represented by formulae 5 to 7:

formula 5

ALiCl-GaF₃

Wherein, in formula 5, A is 2, 3, or 4,

formula 6

ALiBr-GaF₃

Wherein, in formula 6, A is 2, 3, or 4,

formula 7

ALiCl-aM_z1Z_3z1-bGaF₃

Wherein, in formula 7, A is 2 or 3,

z is Cl or OH, and Z is Cl or OH,

m is La, In, Sc, Al, Tl, Y, B, La, or a combination thereof,

0< a <1, 0< b <1, 0< a + b, a + b-4-a, and 0 ≦ z1 ≦ 1.

13. The solid electrolyte according to claim 1, wherein the compound represented by formula 1 or 3 is 2LiCl-GaF₃、3LiCl-GaF₃、4LiCl-GaF₃、3LiBr-GaF₃、2LiCl-LiOH-GaF₃、3LiCl-0.1LaCl₃-0.9GaF₃、3LiCl-0.1InCl₃-0.9GaF₃、3LiCl-0.1ScCl₃-0.9GaF₃、3LiCl-0.1AlCl₃-0.9GaF₃、3LiCl-0.1TlCl₃-0.9GaF₃、3LiCl-0.1YCl₃-0.9GaF₃、3LiCl-0.1BCl₃-0.9GaF₃、2LiBr-GaF₃、4LiBr-GaF₃、2LiClO₄-GaF₃、2LiClO₄-LiOH-GaF₃、3LiCl-NaCl-GaF₃、3LiCl-0.2LaCl₃-0.8GaF₃、3LiCl-0.2InCl₃-0.8GaF₃、3LiCl-0.3LaCl₃-0.7GaF₃、3LiCl-0.3InCl₃-0.7GaF₃、3LiCl-0.5LaCl₃-0.5GaF₃、3LiCl-0.5InCl₃-0.5GaF₃、3LiCl-0.2ScCl₃-0.8GaF₃、3LiCl-0.3ScCl₃-0.7GaF₃、3LiCl-0.5ScCl₃-0.5GaF₃、3LiCl-0.2AlCl₃-0.8GaF₃、3LiCl-0.3AlCl₃-0.7GaF₃、3LiCl-0.5AlCl₃-0.5GaF₃、3LiCl-0.2BCl₃-0.8GaF₃、3LiCl-0.3BCl₃-0.7GaF₃、3LiCl-0.5BCl₃-0.5GaF₃、3LiCl-0.2TlCl₃-0.8GaF₃、3LiCl-0.3TlCl₃-0.7GaF₃、3LiCl-0.5TlCl₃-0.5GaF₃、3LiCl-0.2YCl₃-0.8GaF₃、3LiCl-0.3YCl₃-0.7GaF₃、3LiCl-0.5YCl₃-0.5GaF₃、2LiCl-GaF₂Cl、4LiCl-GaF₂Cl、3LiBr-GaF₂Cl、2LiCl-LiOH-GaF₂Cl、2LiCl-1NaCl-GaF₃、2LiCl-1KCl-GaF₃、3LiCl-GaF₂Cl、2LiCl-0.1AlCl₃-0.9GaF₃、2LiCl-0.1ScCl₃-0.9GaF₃、2LiCl-0.1BCl₃-0.9GaF₃、2LiCl-0.1YCl₃-0.9GaF₃、4LiCl-0.1AlCl₃-0.9GaF₃、4LiCl-0.1ScCl₃-0.9GaF₃、4LiCl-0.1BCl₃-0.9GaF₃、4LiCl-0.1YCl₃-0.9GaF₃Or a combination thereof.

14. The solid electrolyte according to claim 1, wherein the Cl2p peak of the compound represented by formula 1 or 3 has a binding energy of 199 electron volts to 203 electron volts when measured by X-ray photoelectron spectroscopy.

15. The solid electrolyte as claimed in claim 1, wherein the compound represented by formula 1 or 3 exhibits a main peak at a diffraction angle of 25 ° 2 θ -35 ° 2 θ and a sub-peak at a diffraction angle of 48 ° 2 θ -65 ° 2 θ, when determined by X-ray diffraction analysis using Cu K α radiation.

16. The solid electrolyte as claimed in claim 1, wherein the compound represented by formula 1 or 3 has peaks at diffraction angles of 29 ° 2 θ -31 ° 2 θ, 33 ° 2 θ -35 ° 2 θ, and 49 ° 2 θ -51 ° 2 θ, when measured by X-ray diffraction analysis using Cu ka radiation, or

Has peaks at diffraction angles of 29 DEG 2 theta-31 DEG 2 theta, at 33 DEG 2 theta-35 DEG 2 theta, at 59 DEG 2 theta-61 DEG 2 theta, and at 62 DEG 2 theta-64 DEG 2 theta when measured by X-ray diffraction analysis using Cu Ka radiation.

17. The solid electrolyte of claim 1, wherein the solid electrolyte has a storage modulus of 100 megapascals or less.

18. The solid electrolyte of claim 1, wherein the solid electrolyte has a thickness of 100 microns or less.

19. The solid electrolyte of claim 1, wherein the solid electrolyte has an activation energy of 200 milli-electron volts to 500 milli-electron volts at 25 ℃.

20. The solid electrolyte of claim 1, wherein the ionic conductivity of the solid electrolyte is 10mS/cm or more at 25 ℃ when the solid electrolyte has a water content of 10 to 30 wt%.

21. The solid electrolyte as claimed in claim 1, wherein the compound represented by formula 1 has a clay property at-60 ℃ to 160 ℃.

22. The solid electrolyte as claimed in claim 1, wherein, when the compound represented by formula 1 has a glass-ceramic structure, the ceramic content of the compound is 0.1 wt% to 30 wt% based on the total weight of the solid electrolyte.

23. A protected positive electrode comprising:

a positive electrode; and

a layer comprising the solid electrolyte of any one of claims 1-22 on the positive electrode.

24. An electrochemical device comprising a solid electrolyte as claimed in any one of claims 1 to 22.

25. The electrochemical device of claim 24, wherein the electrochemical device is an electrochemical cell, a battery, a supercapacitor, a fuel cell, a sensor, or an electrochromic device.

26. An electrochemical cell, comprising:

a positive electrode;

a negative electrode, and

a solid electrolyte as claimed in any one of claims 1 to 22 disposed between the positive electrode and the negative electrode.

27. The electrochemical cell as recited in claim 26, wherein the positive electrode includes a compound represented by formula 1.

28. The electrochemical cell of claim 26, wherein the negative electrode comprises lithium metal or a lithium alloy.

29. The electrochemical cell of claim 26, wherein the solid electrolyte is of the form: an electrolyte protective film, a positive electrode protective film, a negative electrode protective film, a positive electrode electrolyte, or a combination thereof.

30. The electrochemical cell of claim 26, wherein the electrochemical cell is a solid secondary battery,

the solid secondary battery further includes an oxide solid electrolyte, and has a positive electrode/solid electrolyte/oxide solid electrolyte/lithium negative electrode structure; or

The solid secondary battery further includes an electrolyte containing an ionic liquid and an oxide solid electrolyte, and has a positive electrode/electrolyte containing an ionic liquid/oxide solid electrolyte/oxide solid electrolyte/lithium negative electrode structure.

31. The electrochemical cell of claim 30, wherein the oxide solid electrolyte is: formula Li_3+xLa₃M₂O₁₂The garnet ceramic of (1), wherein M is Te, Nb, or Zr, and x is an integer of 1 to 10; formula Li_xPO_yN_zOf lithium phosphorus oxynitride of (1), wherein 0<x<1，0<y<1, and 0<z<1；Li_xP_yO_zN_kWherein x is more than or equal to 2.7 and less than or equal to 3.3, y is more than or equal to 0.8 and less than or equal to 1.2, z is more than or equal to 3.5 and less than or equal to 3.9, and k is more than or equal to 0.1 and less than or equal to 0.5; li_wPO_xN_yS_zWherein 0 is<w<1，0<x<1，0<y<1, and 0<z<1；Li_1+x+yAl_xTi_2-xSi_yP_3-yO₁₂Wherein 0 is<x<2 and 0. ltoreq. y<3；BaTiO₃；Pb(Zr_xTi_1-x)O₃Wherein x is more than or equal to 0 and less than or equal to 1; pb_1-xLa_xZr_1-yTi_yO₃Wherein 0 is less than or equal to x<1 and 0. ltoreq. y<1；Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃；HfO₂；SrTiO₃；SnO₂；CeO₂；Na₂O；MgO；NiO；CaO；BaO；ZnO；ZrO₂；Y₂O₃；Al₂O₃；TiO₂；SiO₂；SiC；Li₃PO₄；Li_xTi_y(PO₄)₃Wherein 0 is<x<2 and 0<y<3；Li_xAl_yTi_z(PO₄)₃Wherein 0 is<x<2，0<y<1, and 0<z<3；Li_1+x+y(Al_aGa_1-a)_x(Ti_bGe_1-b)_2-xSi_yP_3-yO₁₂Wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, a is more than or equal to 0 and less than or equal to 1, and b is more than or equal to 0 and less than or equal to 1; li_xLa_yTiO₃Wherein 0 is<x<2 and 0<y<3；Li_xGe_yP_zS_wWherein 0 is<x<4，0<y<1，0<z<1, and 0<w<5；Li_xN_yWherein 0 is<x<4 and 0<y<2；Li_xSi_yS_zWherein 0 is<x<3，0<y<2, and 0<z<4；Li_xP_yS_zWherein 0 is<x<3，0<y<3, and 0<z<7；Li₂O；LiF；LiOH；Li₂CO₃；LiAlO₂；Li₂O-Al₂O₃-SiO₂-P₂O₅-TiO₂-GeO₂A ceramic; or a combination thereof.

32. A method of preparing the solid electrolyte of any one of claims 1-22, the method comprising:

provide for

QX and Ga_1-z(F_1-kCl_k)_3-3zThe mixture of (a) and (b),

QX、M_z1Z_3z1and Ga_1-z(F_1-kCl_k)_3-3zA mixture of (A) or (B)

QX and Ga_1-zM_z1(F_1-kCl_k)_3-3zZ_3z1A mixture of (a); and

mechanically grinding the mixture to prepare a compound represented by formula 1 or 3.

33. The method of claim 32, further comprising, after the mechanically milling, resting the mechanically milled mixture.

34. The method of claim 33, wherein the temperature of the mixture subjected to the mechanical milling is controlled to 80 ℃ or less by allowing the mixture to stand.

35. The method of claim 32, wherein the mechanical milling is ball milling, air jet milling, bead milling, roller milling, hand milling, planetary ball milling, agitator ball milling, vibratory milling, mechanical fusion milling, table milling, planetary milling, attritor milling, disc milling, form milling, NAUTA milling, nobila milling, high speed mixing, or a combination thereof.

36. The method of claim 32, wherein the mechanical milling is at 400rpm to 900 rpm.

37. The method of claim 32, wherein

QX is LiX or a mixture of LiX with: NaX, KX, or a combination thereof;

LiX is LiCl, LiBr, LiOH or LiClO₄Or a combination thereof;

NaX is NaCl, NaBr, or a combination thereof;

KX is KCl, KBr, or a combination thereof;

M_z1Z_3z1is LaCl₃、InCl₃、AlCl₃、YCl₃、TlCl₃、ScCl₃、BCl₃Or a combination thereof;

Ga_1-z(F_1-kCl_k)_3-3zis GaF₃(ii) a And

Ga_1-zM_z1(F_1-kCl_k)_3-3zZ_3z1is LaCl₃GaF₃、InCl₃GaF₃、AlCl₃GaF₃、YCl₃GaF₃、TlCl₃GaF₃、ScCl₃GaF₃、BCl₃GaF₃Or a combination thereof.

Technical Field

The present disclosure relates to a solid electrolyte, a method of preparing the same, and an electrochemical device including the same.

Background

The solid secondary battery includes a positive electrode, a solid electrolyte, and a negative electrode. For solid electrolytes among these components, high ionic conductivity is desired.

The solid electrolyte includes a sulfide-based solid electrolyte and an oxide-based solid electrolyte. In order to use these solid electrolytes in solid secondary batteries, it is desirable to reduce grain boundaries between crystal particles of the solid electrolyte.

In the case where a solid secondary battery is manufactured using a sulfide-based solid electrolyte as a solid electrolyte, the solid secondary battery may be manufactured by pressing the sulfide-based solid electrolyte. Also, a solid secondary battery using a sulfide-based solid electrolyte may generate toxic sulfide gas when exposed to air. Therefore, a sulfide solid electrolyte for a solid secondary battery desirably provides improved manufacturability and has improved good stability in air.

In the case of manufacturing a solid secondary battery using an oxide-based solid electrolyte as a solid electrolyte, improvement in uniformity of interfacial adhesion between the solid electrolyte and a positive electrode is desired due to physical properties of the oxide-based solid electrolyte.

Disclosure of Invention

Provided are a novel solid electrolyte and a method for preparing the same.

An electrochemical device including the solid electrolyte is provided.

An electrochemical cell comprising the solid electrolyte is provided.

Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments of the disclosure.

According to an aspect of one embodiment, there is provided a solid electrolyte including a compound represented by formula 1 or formula 3,

wherein the compound represented by formula 1 or formula 3 has a glass transition temperature of-30 ℃ or less, and a glass or glass-ceramic structure:

formula 1

AQX-Ga_1-zM_z1(F_1-kCl_k)_3-3zZ_3z1

Wherein, in the formula 1,

q is Li, or a combination of Li and: na, K or a combination thereof,

m is a trivalent cation, or combination thereof,

x is a halogen other than F, a pseudohalogen, OH, or a combination thereof,

z is a monovalent anion, or a combination thereof,

1< A <5, 0< z <1, 0< z 1< 1, and 0< k <1,

formula 3

AQX-aM_z1Z_3z1-bGa_1-z(F_1-kCl_k)_3-3z

Wherein, in formula 3, Q is Li, or a combination of Li and: na, K or a combination thereof,

m is a trivalent cation, or combination thereof,

x is a halogen other than F, a pseudohalogen, OH, or a combination thereof,

z is a monovalent anion, or a combination thereof,

0< a <1, 0< b <1, 0< a + b, a + b-4-a, 1< a <5, 0< z <1, 0< z 1< 1, and 0< k < 1.

According to an aspect of another embodiment, there is provided a battery comprising a protected positive electrode comprising: a positive electrode; and a layer including the solid electrolyte on the positive electrode.

According to an aspect of another embodiment, there is provided an electrochemical device including the solid electrolyte.

In accordance with an aspect of another embodiment, there is provided an electrochemical cell comprising: a positive electrode, a negative electrode, and the solid electrolyte disposed between the positive electrode and the negative electrode.

According to an aspect of another embodiment, there is provided a method of preparing the solid electrolyte, the method including: providing QX and Ga_1-z(F_1-kCl_k)_3-3zMixture of (1), QX, M_z1Z_3z1And Ga_1-z(F_1-kCl_k)_3-3zOr QX and Ga_1-zM_z1(F_1-kCl_k)_3-3zZ_3z1A mixture of (a); and mechanically milling the mixture to prepare a compound represented by formula 1 or formula 3.

Drawings

The above and other aspects, features, and advantages of some embodiments of the present disclosure will become more apparent from the following description considered in conjunction with the accompanying drawings, in which:

fig. 1 is a graph of intensity (in arbitrary units (a.u.)) versus diffraction angle (°, 2 θ) and illustrates X-ray diffraction (XRD) spectra of the compounds obtained according to examples 1 to 3;

FIG. 2 illustrates the results of a scanning electron microscopy analysis of the compound of example 1;

FIGS. 3A-3D are each a plot of intensity (in arbitrary units) versus binding energy (in electron volts (eV)) and illustrate the results of X-ray photoelectron spectroscopy (XPS) analysis of the compound of example 1;

FIG. 4A is a plot of conductivity (Siemens per centimeter (S/cm)) versus temperature (1000/T (1/K)) and shows the results of an Arrhenius (Arrhenius) analysis of the compounds of examples 1-4;

FIG. 4B is the current (microamperes per square centimeter (. mu.A/cm)²) Vs. voltage (V) vs. Li/Li⁺) And illustrates the results of cyclic voltammetry analysis of the compound of example 1;

FIG. 5 is a plot of specific heat (Watts per gram (W/g)) versus temperature (deg.C) and illustrates the results of Differential Scanning Calorimetry (DSC) analysis of the compounds of examples 1-3 and comparative example 9;

FIG. 6 is a plot of modulus (pascal (Pa)) versus angular frequency (radians per second (rad/s)) illustrating the storage and loss moduli of the compounds of examples 1-3;

fig. 7 is a graph of ionic conductivity (siemens per centimeter (S/cm)) versus water content (percent by weight (%)) and illustrates the change in ionic conductivity as a function of water content for a solid electrolyte comprising the compound of example 1;

fig. 8A and 8B are images illustrating formability of a solid electrolyte including the compound of example 1;

FIGS. 9A and 9B are diagrams showing the state of the interface of the positive electrode and the Solid Electrolyte (SE), respectively, and the Solid Electrolyte (SE) and the oxide-based solid electrolyte Li_6.5La₃Zr_1.5Ta_0.5O₁₂(LLZTO) Scanning Electron Microscope (SEM) images of interface states;

FIGS. 10A-10F are the results of energy dispersive X-ray spectroscopy (EDS) analysis of a solid electrolyte including the compound of example 1;

fig. 11A is a schematic cross-sectional view illustrating an embodiment of the structure of a solid secondary battery;

fig. 11B is a schematic cross-sectional view illustrating an embodiment of the structure of a solid secondary battery;

FIG. 12 is a plot of voltage (volts (V) versus Li/Li⁺) For capacity (mAh/cm) in milliampere-hour/square centimeter²) And illustrating the manufacture of the solid secondary battery of example 1Voltage curve (profile);

FIG. 13 is the imaginary impedance (Z ", ohm. cm)²) To real part impedance (Z', ohm. cm)²) And illustrates the impedance characteristics at 60 c of the solid secondary battery of manufacturing example 1;

FIG. 14 is a plot of voltage (volts (V) versus Li/Li⁺) For capacity (mAh/cm)²) And illustrates a voltage curve of the solid secondary battery of manufacturing example 2;

FIG. 15 is the derivative of capacity with respect to voltage (dQ/dV, mAh/cm)²V) versus voltage (V, vs. Li/Li)⁺) A graph showing the cycle characteristics of the solid secondary battery of manufacturing example 2;

FIG. 16 is a graph showing capacity (mAh/cm)²) A graph of the number of cycles and illustrating a change in capacity with respect to the number of cycles of manufacturing the solid secondary battery of example 2;

fig. 17 to 19 are each a schematic cross-sectional view illustrating an embodiment of the structure of a solid secondary battery;

FIG. 20 is a plot of weight (%)% versus temperature (. degree. C.) showing the results of thermogravimetric analysis of LiCl used as the starting material in example 2;

FIG. 21 shows imaginary impedance (-Z)_imOmega) versus real part impedance (Z)_reΩ) and illustrates the impedance characteristics of the compound prepared according to example 8.

Detailed Description

Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as limited to the descriptions set forth herein. Accordingly, the embodiments are described below to illustrate aspects only by referring to the drawings. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. The expression "at least one of" when preceding or following a list of elements modifies the entire list of elements and does not modify individual elements of the list.

It will be understood that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present.

It will be understood that, although the terms "first," "second," "third," etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a "first element," "component," "region," "layer" or "portion" discussed below could be termed a second element, component, region, layer or portion without departing from the teachings herein.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the terms "a", "an", "the" and "at least one" do not denote a limitation of quantity, and are intended to include both the singular and the plural, unless the context clearly dictates otherwise. For example, "an element(s)" has the same meaning as "at least one element" unless the context clearly dictates otherwise. "at least one" should not be construed as limiting "a (a, an)". "or" means "and/or". It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

Spatially relative terms such as "below," "lower," "above," "upper," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the term "below" may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

As used herein, "about" or "approximately" includes the stated value and is meant to be within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art in view of the measurement in question and the error associated with measurement of the particular quantity (i.e., limitations of the measurement system). For example, "about" may mean within one or more standard deviations, or within ± 30%, 20%, 10%, or 5%, of the stated value.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the present disclosure and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Embodiments are described herein with reference to cross-sectional views that are schematic illustrations of idealized embodiments. As such, deviations from the shapes of the figures as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, regions illustrated or described as flat may typically have rough and/or non-linear features. Also, corners illustrated as sharp may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims.

Hereinafter, embodiments of the solid electrolyte, the method of preparing the same, and the electrochemical device and the electrochemical cell each including the solid electrolyte will be described in more detail.

According to one aspect, there is provided a solid electrolyte including a compound represented by formula 1 or 3, wherein the compound represented by formula 1 or 3 has a glass transition temperature of-30 ℃ or less and a glass or glass-ceramic structure.

Formula 1

AQX-Ga_1-zM_z1(F_1-kCl_k)_3-3zZ_3z1

Wherein, in the formula 1,

q is Li, or a combination of Li and: na, K or a combination thereof,

m is a trivalent cation, or combination thereof,

x is a halogen other than F, a pseudohalogen, OH, or a combination thereof,

z is a monovalent anion, or a combination thereof,

1< A <5, 0< z <1, 0< z 1< 1, and 0< k <1,

formula 3

AQX-aM_z1Z_3z1-bGa_1-z(F_1-kCl_k)_3-3z

Wherein, in formula 3, Q is Li, or a combination of Li and: na, K or a combination thereof,

m is a trivalent cation, or combination thereof,

x is a halogen other than F, a pseudohalogen, OH, or a combination thereof,

z is a monovalent anion, or a combination thereof,

0< a <1, 0< b <1, 0< a + b, a + b-4-a, 1< a <5, 0< z <1, 0< z 1< 1, and 0< k < 1.

The term "glass" as used herein refers to an amorphous material that exhibits a glass transition phenomenon. The term "glass-ceramic" refers to a mixture of an amorphous material and at least one crystalline material. In glass-ceramics, two components are observed, a glass phase (i.e., amorphous phase) and a ceramic phase (i.e., crystalline phase).

The compound of formula 1 and a solid electrolyte including the same may exhibit a glass transition phenomenon, and the solid electrolyte may have a glass transition temperature lower than an operating temperature of a battery. Thus, it may be easy to form a desired solid electrolyte.

The above glass transition phenomenon can be confirmed by Differential Scanning Calorimetry (DSC) analysis. The compound of formula 1 may have a glass transition temperature of about-40 ℃ or less, -50 ℃ or less, -60 ℃ or less, or, for example, about-60 ℃ to about-70 ℃, or about-40 ℃ to about-70 ℃, about-45 ℃ to about-65 ℃, or about-50 ℃ to about-60 ℃.

In order to manufacture a solid secondary battery having improved safety, it is desired to develop a solid secondary battery employing an oxide-based solid electrolyte that is stable in air. However, and without wishing to be bound by theory, it is understood that the contact between the solid electrolyte and the positive electrode is not uniform at its interface due to the hard physical properties of the oxide-based solid electrolyte. In order to provide a more uniform contact between the positive electrode and the oxide-based solid electrolyte, a high-temperature sintering process of the positive electrode and the oxide-based solid electrolyte has been proposed.

However, when a high-temperature sintering process is used, it is difficult to provide a battery structure through full consolidation (total consolidation) of the solid secondary battery while also satisfying the overall characteristics of the battery. In order to solve these problems, it has been proposed to introduce an ionic liquid electrolyte between an oxide-based solid electrolyte and a positive electrode to allow the oxide-based solid electrolyte and the positive electrode to be in more uniform contact with each other. However, the introduction of the ionic liquid electrolyte according to this method may cause the current collector to be corroded by the ionic liquid electrolyte and complicate the process in designing the stack structure of the battery.

Accordingly, in order to solve the above-mentioned problems, the present inventors have disclosed a solid electrolyte comprising a compound represented by formula 1 and having a glass or glass-ceramic structure.

The solid electrolyte according to the embodiment is a halogen compound-based solid electrolyte having good formability, and can be provided without using high voltage (high voltage is used for manufacturing a solid secondary battery using a sulfide-based solid electrolyte). When a battery is manufactured using the disclosed solid electrolyte, interface characteristics having improved uniformity between the solid electrolyte and a positive electrode are provided.

The compound of formula 1 includes gallium (Ga), fluorine (F), and a halogen other than F, and thus includes different halogens.

In formula 1, M is an element having an oxidation number of +3, and may be, for example, In, Sc, Al, Tl, Y, B, La, or a combination thereof, and Z may be halogen, pseudohalogen, or a combination thereof.

The term "oxidation number" as used herein refers to the average oxidation number.

As used herein, a "pseudohalogen" is a molecule that includes two or more electronegative atoms and, like a halogen, produces a monovalent anion similar to a halide ion. Examples of pseudohalogens are Cyanide (CN), cyanate (OCN), thiocyanate (SCN), azide (N)₃) Or OH.

In one or more embodiments, the solid electrolyte may have a water content of about 5 weight percent (wt%) or less, 0 wt%, or greater than 0 wt% and 5 wt% or less, based on the total weight of the solid electrolyte.

The solid electrolyte may have a water content of, for example, 0 wt%.

The term "water content" as used herein refers to the water present in and/or on the surface of the solid electrolyte.

In a solid electrolyte sensitive to moisture, the absorbed moisture may decompose to generate a large amount of gas, and thus deteriorate the battery. Therefore, the content of moisture in the solid electrolyte is generally reduced.

However, in the solid electrolyte according to the embodiment, even when the water content is more than 0% by weight and about 5% by weight or less, both the viscosity characteristics and the conductivity may be improved, which is different from other solid electrolytes.

The solid electrolyte may have a water content of about 0.1 wt% to about 5 wt%, about 0.5 wt% to about 5 wt%, about 1 wt% to about 2 wt%, for example about 1.5 wt% to about 1.8 wt%, based on the total weight of the solid electrolyte.

The water content of the solid electrolyte may be determined using, for example, thermogravimetric analysis methods. In thermogravimetric analysis, the water content of the solid electrolyte can be measured using a thermogravimetric analyzer such as TA Instruments SDT-Q600 in air at a heating/cooling rate of 2 ℃/min in the temperature range from 100 ℃ to 900 ℃ and determined from the weight loss before and after 100 ℃, e.g., at 100 ℃.

In one or more embodiments, the water content of the solid electrolyte may vary depending on the water content of QX in the starting materials used to form the solid electrolyte comprising the compound of formula 1 or formula 3, e.g., i) QX and Ga_1-z(F_1-kCl_k)_3-3zIi) QX, M_z1Z_3z1And Ga_1-z(F_1-kCl_k)_3-3zOr iii) QX and Ga_{1- z}M_z1(F_1-kCl_k)_3-3zZ_3z1A mixture of (a). Here, 0. ltoreq. z<1。

Formula 1

AQX-Ga_1-zM_z1(F_1-kCl_k)_3-3zZ_3z1

Wherein, in the formula 1,

q is Li, or a combination of Li and: na, K or a combination thereof,

m is a trivalent cation, or combination thereof,

x is a halogen other than F, a pseudohalogen, OH, or a combination thereof,

z is a monovalent anion, or a combination thereof,

1< A <5, 0< z <1, 0< z 1< 1, and 0< k <1,

formula 3

AQX-aM_z1Z_3z1-bGa_1-z(F_1-kCl_k)_3-3z

Wherein, in formula 3, Q is Li, or a combination of Li and: na, K or a combination thereof,

m is a trivalent cation, or combination thereof,

x is a halogen other than F, a pseudohalogen, OH, or a combination thereof,

z is a monovalent anion, or a combination thereof,

0< a <1, 0< b <1, 0< a + b, a + b-4-a, 1< a <5, 0< z <1, 0< z 1< 1, and 0< k < 1. In formula 1 or formula 3, a and b are not both 1 at the same time, and 2< a < 4.

For example, QX can be LiCl.

The water content of QX can be about 5 wt% or less, about 0 wt%, about 0.5 wt% to about 5 wt%, about 1 wt% to about 4 wt%, for example about 2 to about 3.5 wt%.

To obtain QX having a water content of about 5 wt.% or less, the heat treatment may be further conducted at about 100 ℃ to about 190 ℃, about 130 ℃ to about 185 ℃, e.g., about 140 ℃ to about 180 ℃. By this heat treatment process, the water content in QX can be further reduced. The heat treatment time may vary depending on the heat treatment temperature, and may range, for example, from about 1 to about 20 hours, from about 2 to about 15 hours, or from about 5 to about 13 hours.

In the solid electrolyte according to one or more embodiments, moisture may form a complex (complex) with the compound of formula 1 constituting the solid electrolyte and thus have a hydrate form.

In the solid electrolyte according to one or more embodiments, moisture may exist in a form of being adsorbed on a surface of the solid electrolyte. In the solid electrolyte according to one or more embodiments, moisture may be adsorbed on a surface of the solid electrolyte and contained inside the solid electrolyte. In the solid electrolyte according to one or more embodiments, the water content may be highest on the surface of the solid electrolyte and may gradually decrease toward the inside thereof.

In formula 1 or 3, X may be Cl, Br, I, or a combination thereof, and Z may be Cl, Br, I, SCN, OCN, CN, OH, N₃Or isCombinations thereof.

In formula 1 or 3, when Q is a combination of Li and Na, K, or a combination thereof, the mole fraction of Na and K can be from about 0.1 to about 0.9, from about 0.1 to about 0.6, for example, or from about 0.1 to about 0.5. The total mole fraction of Li to Na and K may be 1.

In formula 1, Q may be Li or a combination of Li and Na.

In formula 1, z is more than or equal to 0 and less than 0.5, z is more than or equal to 0 and less than or equal to 0.4, z is more than or equal to 0 and less than or equal to 0.3, z is more than or equal to 0 and less than or equal to 0.2, or z is more than or equal to 0 and less than or equal to 0.1.

The compound of formula 1 or 3 may be a compound represented by formula 2.

Formula 2

ALiX-Ga_1-zM_z(F_1-kCl_k)_3-3zZ_3z

In formula 2, M may be a trivalent cation, or a combination thereof,

x can be a halogen other than F, a pseudohalogen, OH, or a combination thereof,

z may be a monovalent anion, or a combination thereof,

1< A <5, 0< z <1, 0< z 1< 1, and 0< k < 1. In formula 3, a and b are not both 1. In formulas 1 and 3, 1< A <4, 2< A <4, or 2< A < 4.

In the formulas 1 and 3, z is more than or equal to 0 and less than or equal to 0.5, z is more than or equal to 0 and less than or equal to 0.4, z is more than or equal to 0 and less than or equal to 0.3, z is more than or equal to 0 and less than or equal to 0.2, or z is more than or equal to 0 and less than or equal to 0.1.

In one or more embodiments, the compound of formula 1 or 3 may be a compound represented by formula 4.

Formula 4

ALiX-aM_z1Z_3z1-bGa_1-z(F_1-kCl_k)_3-3z

Wherein, in formula 4, M may be a trivalent cation or a combination thereof,

x can be a halogen other than F, a pseudohalogen, OH, or a combination thereof,

z may be a monovalent anion, or a combination thereof,

0< a <1, 0< b <1, 0< a + b, a + b ═ 4-a, 1< a <4, 0< z <1, 0< z 1< 1, and 0< k < 1. In formula 4, a and b are not both 1 at the same time.

In one or more embodiments, the solid electrolyte may have an ionic conductivity at room temperature (25 ℃) of about 0.1mS/cm or greater, about 0.3mS/cm or greater, about 1mS/cm or greater, about 2mS/cm or greater, or about 3mS/cm or greater.

In one or more embodiments, the solid electrolyte may have an ionic conductivity at room temperature (25 ℃) of from about 0.2mS/cm to about 4mS/cm, such as from about 3.2mS/cm to about 3.4 mS/cm. Since the solid electrolyte has high ionic conductivity, an electrochemical cell including the solid electrolyte may have further reduced internal resistance.

The solid electrolyte may have an activation energy at 25 ℃ of about 200meV to about 500 meV.

For example, the compound of formula 1 or 3 can be a compound of formulae 5-7, or a combination thereof.

Formula 5

ALiCl-GaF₃

In formula 5, a may be 2, 3, or 4.

Formula 6

ALiBr-GaF₃

In formula 6, a may be 2, 3, or 4.

Formula 7

ALiCl-aM_z1Z_3z1-bGaF₃

In formula 7, A may be 2 or 3,

z can be Cl or OH,

m can be La, In, Sc, Al, Tl, Y, B, La, or combinations thereof,

0< a <1, 0< b <1, 0< a + b, a + b-4-a, and 0 ≦ z1 ≦ 1.

In formula 7, a is 0.1. ltoreq. a.ltoreq.0.5, and b is 0.1. ltoreq. b.ltoreq.1.

For example, the compound of formula 1 or 3 can be 2LiCl-GaF₃、3LiCl-GaF₃、4LiCl-GaF₃、3LiBr-GaF₃、2LiCl-LiOH-GaF₃、3LiCl-0.1LaCl₃-0.9GaF₃、3LiCl-0.1InCl₃-0.9GaF₃、3LiCl-0.1ScCl₃-0.9GaF₃、3LiCl-0.1AlCl₃-0.9GaF₃、3LiCl-0.1TlCl₃-0.9GaF₃、3LiCl-0.1YCl₃-0.9GaF₃、3LiCl-0.1BCl₃-0.9GaF₃、2LiBr-GaF₃、4LiBr-GaF₃、2LiClO₄-GaF₃、2LiClO₄-LiOH-GaF₃、3LiCl-NaCl-GaF₃、3LiCl-0.2LaCl₃-0.8GaF₃、3LiCl-0.2InCl₃-0.8GaF₃、3LiCl-0.3LaCl₃-0.7GaF₃、3LiCl-0.3InCl₃-0.7GaF₃、3LiCl-0.5LaCl₃-0.5GaF₃、3LiCl-0.5InCl₃-0.5GaF₃、3LiCl-0.2ScCl₃-0.8GaF₃、3LiCl-0.3ScCl₃-0.7GaF₃、3LiCl-0.5ScCl₃-0.5GaF₃、3LiCl-0.2AlCl₃-0.8GaF₃、3LiCl-0.3AlCl₃-0.7GaF₃、3LiCl-0.5AlCl₃-0.5GaF₃、3LiCl-0.2BCl₃-0.8GaF₃、3LiCl-0.3BCl₃-0.7GaF₃、3LiCl-0.5BCl₃-0.5GaF₃、3LiCl-0.2TlCl₃-0.8GaF₃、3LiCl-0.3TlCl₃-0.7GaF₃、3LiCl-0.5TlCl₃-0.5GaF₃、3LiCl-0.2YCl₃-0.8GaF₃、3LiCl-0.3YCl₃-0.7GaF₃、3LiCl-0.5YCl₃-0.5GaF₃、2LiCl-GaF₂Cl、4LiCl-GaF₂Cl、3LiBr-GaF₂Cl、2LiCl-LiOH-GaF₂Cl、2LiCl-1NaCl-GaF₃、2LiCl-1KCl-GaF₃、3LiCl-GaF₂Cl、2LiCl-0.1AlCl₃-0.9GaF₃、2LiCl-0.1ScCl₃-0.9GaF₃、2LiCl-0.1BCl₃-0.9GaF₃、2LiCl-0.1YCl₃-0.9GaF₃、4LiCl-0.1AlCl₃-0.9GaF₃、4LiCl-0.1ScCl₃-0.9GaF₃、4LiCl-0.1BCl₃-0.9GaF₃、4LiCl-0.1YCl₃-0.9GaF₃Or a combination thereof.

The Cl2p peak obtained by X-ray photoelectron spectroscopy (XPS) analysis of the compound of formula 1 or 3 may occur at a binding energy of about 199eV to about 203 eV. The above-mentionedCl2p peaks (peaks associated with Ga-X, e.g. Ga-Cl bonds) with LiX and GaF₃May be shifted towards higher binding energies than the Cl2p peak of the simple blend.

In one or more embodiments, the compound of formula 1 or 3 may exhibit a main peak at a diffraction angle (2 θ) of 25 ° to 35 ° and a sub-peak at a diffraction angle (2 θ) of 48 ° to 65 ° when analyzed by XRD using Cu K α radiation. The term "main peak" as used herein refers to a peak having the maximum intensity, and the main peak as well as the secondary peak are related to the crystallization characteristics like LiCl, and the secondary peak has a smaller intensity than the main peak.

In one or more embodiments, the compound of formula 1 may exhibit peaks at diffraction angles (2 θ) of 29 ° to 31 °, 33 ° to 35 °, and 49 ° to 51 °, as obtained by XRD using Cu ka radiation.

In one or more embodiments, the compound of formula 1 may exhibit peaks in a diffraction angle (2 θ) region of 29 ° to 31 °, a diffraction angle (2 θ) region of 33 ° to 35 °, a diffraction angle (2 θ) region of 59 ° to 61 °, and a diffraction angle (2 θ) region of 62 ° to 64 °, as obtained by XRD using Cu K α radiation.

The rheological properties of the solid electrolyte according to one or more embodiments will now be described.

The solid electrolyte may have a loss modulus of about 100Pa or more, about 1,000Pa or more, about 10,000Pa or more, about 100,000Pa or more, for example, about 100,000Pa to about 1,000,000Pa, and the solid electrolyte may have a loss modulus of about 100MPa or less, about 50MPa or less, or about 30MPa or less, wherein the upper and lower limits are independently combinable. In one or more embodiments, the solid electrolyte may have a loss modulus of from about 1MPa to about 50MPa, or from about 1MPa to about 30 MPa.

The loss modulus (G ") and the storage modulus (G') may be measured according to ASTM D4065, D4440, or D5279, and may be evaluated by measuring the viscosity of the solid electrolyte while changing the shear rate using a rheometer. In more detail, the viscosity of the solid electrolyte may be measured using a cone-plate rheometer, such as a TA Instruments AR 2000 analyzer.

After a solid electrolyte (sample) having a thickness of about 1 millimeter (mm) was disposed between a cone having a cone angle of 2 ° and a plate having a diameter of 40mm, the interval between the cone and the plate was adjusted, and then stress was applied to the sample while changing the shear rate to perform rheological evaluation.

The solid electrolyte may have flexible properties and may be manufactured into a thin film having a thickness of 100 micrometers (μm) or less. The solid electrolyte may have a thickness of, for example, from about 1 μm to about 100 μm, such as from about 1 μm to about 50 μm. Since the solid electrolyte has flexible properties, it is possible to make it easy to manufacture a flexible solid secondary battery using the solid electrolyte.

The composition of the solid electrolyte can be measured by Inductively Coupled Plasma (ICP) spectroscopy.

In one or more embodiments, the solid electrolyte may have an ionic conductivity of 10mS/cm or more when the solid electrolyte has a water content of about 10 wt% to about 30 wt% based on the total weight of the solid electrolyte. The solid electrolyte may exhibit a characteristic in which ion conductivity rapidly increases when absorbing moisture. Thus, the solid electrolyte can be used as an electrochemical-based sensor such as a moisture sensor due to excellent sensitivity to moisture.

The temperature at which the viscosity characteristics of the solid electrolyte are maintained may be about-60 ℃ to about 160 ℃.

When the compound of formula 1 or 3 has a glass-ceramic structure, the amount of the ceramic may be about 0.1 wt% to 30 wt%, based on the total weight of the solid electrolyte. The amount of the ceramic may vary depending on the amount of QX, e.g., LiCl, among the starting materials for forming the solid electrolyte including the compound of formula 1 or 3.

The compound of formula 1 or 3 can be electrochemically stable at a voltage of about 2.0V to about 4.6V, e.g., about 2.4V to about 4.1V, relative to lithium metal. The compound of formula 1 or 3 may be present in the form of particles. The particles may have an average particle diameter of about 5nm to about 500 μm, such as about 100nm to about 100 μm, such as about 1 μm to about 50 μm, and have a mean particle diameter of about 0.01m²A/g of about 1000m²In g, e.g. about 0.5m²A/g of about 100m²Specific surface area in g.

A method of preparing a solid electrolyte according to one or more embodiments will be described.

First, i) QX and Ga may be provided_1-z(F_1-kCl_k)_3-3zIi) QX, M_z1Z_3z1And Ga_1-z(F_1-kCl_k)_3-3zOr iii) QX and Ga_1-zM_z1(F_1-kCl_k)_3-3zZ_3z1A mixture of (a). By mechanically milling the mixture, a solid electrolyte can be obtained.

The amounts of the components in the composition may be stoichiometrically controlled to obtain the compound represented by formula 1. In said mixture, i.e. i) QX and Ga_1-z(F_1-kCl_k)_3-3zIi) QX, M_z1Z_3z1And Ga_1-z(F_1-kCl_k)_3-3zOr iii) QX and Ga_1-zM_z1(F_1-kCl_k)_3-3zZ_3z1Q, X, M, Z, and z are as defined for Q, X, M, Z, and z in formula 1 or 3.

Mechanical grinding applies the following principle: the surface energy is generated by mechanical energy to cover the interface with high surface energy by adhesion and/or fusion.

Mechanical milling can be performed via mechanical friction of the components in the mixture, and for example, compressive stress can be mechanically applied via rotation at a rotational speed of about 100rpm to about 3,000rpm, about 300rpm to about 1,000rpm, or about 500rpm to about 800 rpm.

The mechanical milling may be performed, for example, using a method of ball milling, air jet milling, bead milling, roll milling, planetary milling, hand milling, high energy ball milling, stirred ball milling, vibratory milling, mechanical fusion milling, table milling, attritor milling, disc milling, shaped (shape) milling, NAUTA milling, nobila milling, high speed mixing, or a combination thereof, but is not limited thereto. Mechanical milling can be carried out using, for example, ball milling, air jet milling, bead milling, roll milling, planetary milling, hand milling, and the like.

The mechanical milling can be carried out, for example, under an inert atmosphere. The inert atmosphere may be created using an inert gas such as nitrogen, argon, helium, and the like.

The solid electrolyte preparation method may further include, after the mechanical milling, a step of standing. By this step of standing, the temperature of the product from the mechanical milling can be cooled down. By this step of standing, for example, the temperature of the product from the mechanical milling can be controlled to 80 ℃ or less, e.g., about 20 ℃ to 80 ℃.

For the solid electrolyte according to one or more embodiments, a separate heat treatment process may be omitted, unlike other methods of preparing the solid electrolyte. After the mechanical milling of the mixture for forming a solid electrolyte according to one or more embodiments, no separate heat treatment is performed. If the heat treatment process is further performed, it may be difficult to obtain the solid electrolyte according to one or more embodiments.

By mechanical milling of the mixture as described above, it may be possible to control the particle size of the product obtained by the mechanical milling. The particle size of the product obtained by said mechanical milling may be controlled to be about 1 μm or less, about 0.01 μm to about 0.9 μm, about 0.01 μm to about 0.7 μm, for example about 0.01 to about 0.5 μm. When the particle size is controlled as described above, the final solid electrolyte may have an improved density. The term "particle size" as used herein may refer to the diameter of a particle when the particle is spherical or the length of the long axis when the particle is non-spherical.

The mechanical milling may be, for example, high energy milling. The high energy milling may be performed, for example, with a Pulverisette 7Premium line apparatus at about 300rpm to about 1000rpm, or about 400rpm to about 900 rpm. By such high-energy milling, the sizes of the components of the mixture may become fine and the reaction therebetween occurs more easily, and thus the solid electrolyte may be prepared in a shorter time.

After this step of standing is performed once, the mechanical grinding step and the standing step may be repeatedly performed. One cycle of the mechanical grinding and resting steps may be performed repeatedly, for example for a total of 50-100 cycles.

Although the mechanical milling time and the standing time may be variable, for example, the standing time may be controlled to be shorter than the mechanical milling time. The mechanical milling time can be, for example, from about 5 minutes to about 20 hours, such as from about 5 hours to about 15 hours, and the resting time can be, for example, from about 1 minute to about 15 minutes, from about 2 minutes to about 10 minutes, or about 5 minutes.

In a method according to one or more embodiments, QX may be LiX, or a mixture of LiX with: NaX, KX, or a combination thereof. LiX can be LiCl, LiBr, LiOH, LiClO₄Or a combination thereof.

The NaX, KX, or combination thereof may be NaCl, NaBr, KCl, KBr, or combination thereof.

In a method according to one or more embodiments, M_z1Z_3z1Can be LaCl₃、InCl₃、AlCl₃、YCl₃、TlCl₃、ScCl₃、BCl₃Or a combination thereof; ga_1-z(F_1-kCl_k)_3-3zMay be GaF₃(ii) a And Ga_1-zM_z1(F_1-kCl_k)_3-3zZ_3zCan be LaCl₃GaF₃、InCl₃GaF₃、AlCl₃GaF₃、YCl₃GaF₃、TlCl₃GaF₃、ScCl₃GaF₃、BCl₃GaF₃Or a combination thereof.

According to another aspect, an electrochemical device is provided, comprising a solid electrolyte according to one or more embodiments.

The electrochemical device may be, for example, an electrochemical cell, a battery, a supercapacitor, a fuel cell, a sensor, or an electrochromic device. The sensor may be, for example, a moisture sensor.

According to another aspect, an electrochemical cell is provided comprising a solid electrolyte according to one or more embodiments.

The electrochemical device may be a secondary battery including: a positive electrode, a negative electrode, and a solid electrolyte according to one or more embodiments interposed between the positive electrode and the negative electrode.

The secondary battery may be a secondary battery including a solid electrolyte, including: a positive electrode; a negative electrode including lithium; and a solid electrolyte according to one or more embodiments interposed between the positive electrode and the negative electrode. The secondary battery may be, for example, a lithium secondary battery, a lithium air battery, or a solid secondary battery. For example, the secondary battery may be a solid secondary battery.

The electrochemical cell may be used to provide a primary or secondary battery. The shape of the electrochemical cell is not particularly limited, and may be, for example, a coin, a button, a sheet, a stack, a cylinder, a plane, or a corner. The electrochemical cell according to one or more embodiments may be used in a middle-or large-sized battery for electric vehicles.

The electrochemical cell may be, for example, a solid secondary battery using a precipitation-type negative electrode. The precipitation-type anode denotes an anode having a coating layer not including an anode active material at the time of assembly of an electrochemical cell, and the anode active material is formed by precipitation of the anode active material such as lithium metal after charging of the electrochemical cell.

The solid electrolyte according to one or more embodiments may be a positive electrode electrolyte (catholyte), an electrolyte protective film, a positive electrode protective film, a negative electrode protective film, or a combination thereof. The protected positive electrode includes a positive electrode and a layer including the solid electrolyte, i.e., a positive electrode protective film, thereon. The protected anode includes an anode and a layer including the solid electrolyte, i.e., an anode protective film, thereon.

The solid electrolyte according to one or more embodiments may have a high oxidation stability potential of about 3.5V or more with respect to Li/Li +, for example, 4.6 to 5.0V or more with respect to Li/Li +, and thus may be applicable as a positive electrode electrolyte, for example, a positive electrode electrolyte for an all-solid secondary lithium battery.

The solid electrolyte according to one or more embodiments may replace an electrolyte including an ionic liquid of a solid secondary battery using an existing oxide-based solid electrolyte.

The solid electrolyte according to one or more embodiments may be prepared using the compound of formula 1 or 3, and a sintering process may be avoided. The solid electrolyte according to one or more embodiments is flexible and has good formability, and thus may have a free form. For example, the solid electrolyte according to one or more embodiments may be formed by a roll-to-roll process as an electrolyte having a thickness of about 100 μm or less.

The electrochemical cell may be a solid secondary battery. The solid secondary battery according to one or more embodiments may further include an oxide-based solid electrolyte that is stable in air.

The solid secondary battery may have a cathode/solid electrolyte/oxide-based solid electrolyte/lithium anode structure, wherein the solid secondary battery has layers as shown and in the order stated.

The solid secondary battery may further include an ionic liquid-containing electrolyte and an oxide-based solid electrolyte to provide a positive electrode/ionic liquid-containing electrolyte/oxide-based solid electrolyte/oxide-based solid electrolyte/lithium negative electrode structure, wherein the solid secondary battery has the layers as shown and in the order stated.

The lithium negative electrode may be a lithium metal electrode or a lithium alloy electrode. When such a lithium anode is employed, the solid secondary battery can have a high energy density per volume.

The oxide-based solid electrolyte may include garnet-based ceramics (Li)_3+xLa₃M₂O₁₂) (wherein M may be Te, Nb, or Zr, and x may be an integer of 1 to 10); lithium phosphorus oxynitride (Li)_xPO_yN_zWherein 0 is<x<1，0<y<1, and 0<z<1)(LiPON)；Li_xP_yO_zN_k(wherein 2.7)X is not less than 3.3, y is not less than 0.8 and not more than 1.2, z is not less than 3.5 and not more than 3.9, and k is not less than 0.1 and not more than 0.5); li_wPO_xN_yS_z(wherein 0)<w<1，0<x<1，0<y<1, and 0<z<1)；Li_1+x+yAl_xTi_2-xSi_yP_3-yO₁₂(wherein 0)<x<2 and 0. ltoreq. y<3)；BaTiO₃；Pb(Zr_xTi_1-x)O₃Wherein x is more than or equal to 0 and less than or equal to 1; pb_1-xLa_xZr_1-yTi_yO₃(PLZT) (wherein 0. ltoreq. x<1 and 0. ltoreq. y<1)；Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃(PMN-PT)；HfO₂；SrTiO₃；SnO₂；CeO₂；Na₂O；MgO；NiO；CaO；BaO；ZnO；ZrO₂；Y₂O₃；Al₂O₃；TiO₂；SiO₂(ii) a SiC; lithium phosphate (Li)₃PO₄) (ii) a Lithium titanium phosphate (Li)_xTi_y(PO₄)₃) (wherein 0)<x<2 and 0<y<3) (ii) a Lithium aluminum titanium phosphate (Li)_xAl_yTi_z(PO₄)₃) (wherein 0)<x<2，0<y<1, and 0<z<3)；Li_1+x+y(Al_aGa_1-a)_x(Ti_bGe_1-b)_2-xSi_yP_3-yO₁₂(wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, a is more than or equal to 0 and less than or equal to 1, and b is more than or equal to 0 and less than or equal to 1); lithium lanthanum titanate (Li)_xLa_yTiO₃Wherein 0 is<x<2 and 0<y<3) (ii) a Lithium germanium thiophosphate (Li)_xGe_yP_zS_w) (wherein 0)<x<4，0<y<1，0<z<1, and 0<w<5) (ii) a Lithium nitride based glasses (Li)_xN_yWherein 0 is<x<4 and 0<y<2) (ii) a Based on SiS₂Glass (Li)_xSi_yS_zWherein 0 is<x<3，0<y<2, and 0<z<4) (ii) a Based on P₂S₅Glass (Li)_xP_yS_zWherein 0 is<x<3，0<y<3, and 0<z<7)；Li₂O；LiF；LiOH；Li₂CO₃；LiAlO₂(ii) a Based on Li₂O-Al₂O₃-SiO₂-P₂O₅-TiO₂-GeO₂The ceramic of (4); or a combination thereof.

As the oxide-based solid electrolyte, for example, a garnet-based oxide-based solid electrolyte having good reduction stability when in contact with a lithium negative electrode may be used. For example, as the oxide-based solid electrolyte, garnet-based ceramics (e.g., Li) may be used_3+xLa₃M₂O₁₂) (where M can be Te, Nb, or Zr, and x can be an integer from 1 to 10), such as LLZO (e.g., Li)_6.5La₃Zr_1.5Ta_0.5O₁₂)。

The solid electrolyte according to one or more embodiments may be used as a cathode protective film in a solid secondary battery using an oxide-based solid electrolyte stable in air to effectively reduce a reaction between the oxide-based solid electrolyte and a cathode. The solid electrolyte according to one or more embodiments may be used as a positive electrode coating material to form a positive electrode protective film.

Fig. 11A is a schematic cross-sectional view illustrating the structure of a solid secondary battery according to an embodiment.

Referring to fig. 11A, the oxide-based first solid electrolyte 93 and the solid electrolyte 92 according to the embodiment may be sequentially disposed on the anode 91, and the cathode 90 is disposed adjacent to the solid electrolyte 92. Therefore, the solid electrolyte 92 is disposed between the oxide-based first solid electrolyte 93 and the positive electrode 90, and the solid electrolyte 92 and the positive electrode 90 can be uniformly in contact with each other without an electrolyte containing an ionic liquid. The solid electrolyte 92 may have good compatibility with the oxide-based first solid electrolyte 93, and thus is used as a positive electrode electrolyte instead of an electrolyte containing an ionic liquid. The ionic liquid-containing electrolyte may be, for example, a liquid electrolyte containing an ionic liquid.

The ionic liquid can include, for example, bis (trifluoromethanesulfonyl) imide N-methyl-N-propylpyrrolidinium, bis (trifluoromethanesulfonyl) imide N-butyl-N-methylpyrrolidinium, bis (trifluoromethanesulfonyl) imide 1-butyl-3-methylimidazolium, bis (trifluoromethanesulfonyl) imide 1-ethyl-3-methylimidazolium, or a combination thereof.

Fig. 11B illustrates the structure of the solid secondary battery according to the embodiment.

Referring to fig. 11B, an electrolyte 94 containing an ionic liquid may be disposed on the positive electrode 90, and an oxide-based second solid electrolyte 93', a solid electrolyte 92 according to an embodiment, and an oxide-based first solid electrolyte 93 may be sequentially disposed on the electrolyte 94 containing an ionic liquid. The anode 91 may be disposed adjacent to the oxide-based first solid electrolyte 93. The anode 91 may be a lithium anode.

Due to the presence of the solid electrolyte 92 according to the embodiment, a high voltage for complete consolidation may be avoided and the positive electrode and the solid electrolyte may have improved uniformity at the contact interface therebetween.

The structure of a solid secondary battery 1 according to another embodiment will be described with reference to fig. 17.

As shown in fig. 17, a solid secondary battery 1 according to an embodiment may include a cathode 10, an anode 20, and a solid electrolyte 30 according to an embodiment.

The positive electrode 10 may include a positive electrode collector 11 and a positive electrode active material layer 12.

For use as the positive electrode current collector 11, for example, plate structures or foil structures each made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof may be used. The positive electrode collector 11 may be omitted.

The positive electrode active material layer 12 may include a positive electrode active material and a solid electrolyte. The solid electrolyte included in the positive electrode 10 may be the same as (similar to) or different from the solid electrolyte 30.

The positive active material may be any positive active material capable of reversibly intercalating and deintercalating lithium ions. For example, the positive active material may be prepared using Lithium Cobalt Oxide (LCO), lithium nickel oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide. These positive electrode active materials may be used alone or in a combination of two or more.

The positive active material may be, for example, a lithium transition metal oxide such as LiNi_xCo_yAl_zO₂(NCA) or LiNi_xCo_yMn_zO₂(NCM) (wherein 0<x<1，0<y<1，0<z<1, and x + y + z ═ 1).

The positive electrode active material may be covered with a coating layer. In one or more embodiments, the coating layer may be any suitable coating layer for a positive electrode active material of a solid secondary battery. Examples of the coating layer may include, for example, Li₂O-ZrO₂。

When the cathode active material is formed of a lithium transition metal oxide such as NCA or NCM and includes nickel (Ni), the capacity density of the solid secondary battery 1 may be increased, and elution of lithium from the cathode active material in a charged state may be reduced. Therefore, the long-term reliability and the cycle characteristics of the solid secondary battery 1 according to the embodiment can be improved.

The positive electrode active material may be in the form of particles, such as elliptical or spherical particles. The positive electrode active material may have a particle diameter within a range of the positive electrode active material applied to the solid secondary battery, without particular limitation. In addition, the amount of the cathode active material of the cathode 10 is not particularly limited, and may be in the range of being applied to a cathode of a solid secondary battery. The particle size, shape, and amount of the positive electrode active material can be determined without undue experimentation.

In addition, the positive electrode 10 may include the positive electrode active material and the solid electrolyte as described above, and other additives such as a conductive agent, a binder, a filler, a dispersant, or an ion-conducting aid, which may be appropriately mixed.

Examples of the conductive agent that can be mixed into the positive electrode 10 include graphite, carbon black, acetylene black, ketjen black, carbon fiber, and metal powder. Examples of the binder that can be mixed into the positive electrode 10 include Styrene Butadiene Rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. The filler, the dispersant, and the ion-conducting auxiliary that may be mixed into the positive electrode 10 may be any suitable materials for an electrode of a solid secondary battery.

The anode 20 may include an anode current collector 21 and a first anode active material layer 22.

The anode active material included in the first anode active material layer 22 may be in the form of particles, for example. The negative active material in the form of particles may have an average particle diameter of, for example, about 4 μm or less, 3 μm or less, about 2 μm or less, about 1 μm or less, or about 900nm or less. The negative active material in the form of particles may have an average particle diameter of, for example, about 10nm to about 4 μm or less, about 10nm to about 3 μm or less, about 10nm to about 2 μm or less, about 10nm to about 1 μm or less, or about 10nm to about 900nm or less. When the anode active material has an average particle diameter within these ranges, this may further facilitate reversible absorption and/or desorption of lithium during charge and discharge. The average particle diameter of the negative electrode active material is, for example, a median diameter (D50) measured using a laser particle size distribution analyzer.

The anode active material included in the first anode active material layer 22 may include, for example, a carbonaceous anode active material, a metal or metalloid anode active material, or a combination thereof.

In particular, the carbonaceous anode active material may be amorphous carbon. The amorphous carbon may be, for example, Carbon Black (CB), Acetylene Black (AB), Furnace Black (FB), Ketjen Black (KB), graphene, etc., but is not limited thereto. The amorphous carbon can be any suitable amorphous carbon material. The amorphous carbon may be carbon having no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphitic carbon.

The metal or metalloid negative active material includes gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof, but is not limited thereto. The metal or metalloid anode active material may be any suitable material used in the art as a metal anode active material or a metalloid anode active material that forms an alloy or compound with lithium. For example, nickel (Ni) is not a metal negative active material because it does not form an alloy with lithium.

The first anode active material layer 22 includes a single kind of anode active material selected from these anode active materials or a mixture of a plurality of different anode active materials. For example, the first anode active material layer 22 includes amorphous carbon alone, or gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof. In another example, the first anode active material layer 22 includes a mixture of amorphous carbon and: gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or combinations thereof. The mixing ratio in the mixture of amorphous carbon and, for example, gold may be, for example, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1 by weight, but is not limited thereto. The mixing ratio may be any suitable ratio selected according to the desired characteristics of the solid secondary battery 1. When the anode active material has such a composition, the solid secondary battery 1 has further improved cycle characteristics.

The anode active material included in the first anode active material layer 22 includes, for example, a mixture of amorphous carbon first particles and metal or metalloid second particles. The metal or metalloid includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), and the like. In other embodiments, the metalloid is a semiconductor. The amount of the second particles is about 8 wt% to about 60 wt%, about 10 wt% to about 50 wt%, about 15 wt% to about 40 wt%, or about 20 wt% to 30 wt% relative to the total weight of the mixture. When the amount of the second particles is within these ranges, for example, the solid secondary battery 1 has further improved cycle characteristics.

The first anode active material layer 22 includes, for example, a binder. The binder may be, for example, Styrene Butadiene Rubber (SBR), Polytetrafluoroethylene (PTEE), polyvinylidene fluoride (PVDF), polyethylene, vinylidene fluoride/hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto. The adhesive may be any suitable material used in the art as an adhesive. The adhesive may be composed of a single adhesive or a plurality of different adhesives.

By including a binder in the first anode active material layer 22, the first anode active material layer 22 is stabilized on the anode current collector 21. In addition, despite changes in the volume and/or relative position of the first anode active material layer 22 during charge and discharge, cracking of the first anode active material layer 22 is suppressed. For example, in the case where the first anode active material layer 22 does not include a binder, the first anode active material layer 22 may be easily detached from the anode current collector 21. The portion of the anode current collector 21 from which the first anode active material layer 22 is detached is exposed and contacts the solid electrolyte 30, and therefore, there is a high possibility that a short circuit occurs. The first anode active material layer 22 is formed by, for example: the slurry in which the material constituting the first anode active material layer 22 is dispersed is coated on the anode current collector 21, and the slurry is dried. By including a binder in the first anode active material layer 22, the anode active material may be stably dispersed in the slurry. For example, when the slurry is coated on the negative electrode current collector 21 using a screen printing method, clogging of a screen (for example, clogging due to aggregation of the negative electrode active material) may be suppressed.

The thickness of the first anode active material layer 22 may be, for example, about 50% or less, about 40% or less, about 30% or less, about 20% or less, about 10% or less, or about 5% or less of the thickness of the cathode active material layer. The thickness of the first negative electrode active material layer may be, for example, about 1 μm to about 20 μm, about 2 μm to about 10 μm, or about 3 μm to about 7 μm. When the thickness of the first anode active material layer (d22) is too small, lithium dendrites formed between the first anode active material layer 22 and the anode current collector 21 collapse the first anode active material layer 22, and therefore, it is difficult to improve the cycle characteristics of the solid secondary battery 1. When the thickness of the first anode active material layer 22 is excessively increased, the energy density of the solid secondary battery 1 is decreased, and the internal resistance of the solid secondary battery 1 caused by the first anode active material layer 22 is increased, and therefore, it is difficult to improve the cycle characteristics of the solid secondary battery 1.

For example, the negative electrode collector 21 may include a material that does not react with lithium, i.e., a material that forms neither an alloy nor a compound with lithium. The material constituting the negative electrode current collector 21 is, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or the like, but is not limited thereto. Any suitable material known in the art for use in negative electrode current collectors may be used. The negative electrode collector 21 may be composed of one of the metals listed above, or may be composed of an alloy or a coating material of two or more metals thereof. The negative electrode collector 21 may be in the form of a plate or a foil, for example.

The first anode active material layer 22 may further include additives used in existing solid secondary batteries, such as a filler, a dispersant, an ion conductor, and the like.

Referring to fig. 18, for example, the solid secondary battery 1 further includes a thin film 24 including an element capable of forming an alloy with lithium on the negative electrode current collector 21. The thin film 24 may be disposed between the anode current collector 21 and the first anode active material layer 22. The thin film 24 includes, for example, an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium is, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., but is not limited thereto, and may be any suitable element known in the art capable of forming an alloy with lithium. The thin film 24 is made of one of these metals, or an alloy of these different metals. When the thin film 24 is disposed on the anode current collector 21, for example, the second anode active material layer (not shown) deposited between the thin film 24 and the first anode active material layer 22 may have a more planarized form, and the solid secondary battery 1 may have further improved cycle characteristics.

The thin film 24 may have a thickness of, for example, from about 1nm to about 800nm, from about 10nm to about 700nm, from about 50nm to about 600nm, or from about 100nm to about 500 nm. When the thickness of the thin film 24 is less than 1nm, it may be difficult to exert the function of the thin film 24. When the thickness of the film 24 is too large, the film 24 itself absorbs lithium, so that the deposition amount of lithium on the negative electrode is reduced, thereby lowering the energy density and cycle characteristics of the solid secondary battery 1. The thin film 24 may be provided on the negative electrode collector 21, for example, by a vacuum deposition method, a sputtering method, a plating method, or the like. However, the embodiments are not necessarily limited to these methods, and any method capable of forming the thin film 24 in the art may be used.

Referring to fig. 19, the solid secondary battery 1a further includes a second anode active material layer 23 formed by charging, for example, between the anode current collector 21 and the solid electrolyte 30. For example, the solid secondary battery 1a further includes a second anode active material layer 23 formed between the anode current collector 21 and the first anode active material layer 22, for example, by charging. Although not shown, the solid secondary battery 1 further includes a second anode active material layer 23 formed between the solid electrolyte 30 and the first anode active material layer 22, for example, by charging. Although not shown, the solid secondary battery 1 further includes a second anode active material layer 23 formed in the first anode active material layer 22 by, for example, charging.

The second anode active material layer 23 is a metal layer containing lithium or a lithium alloy. The metal layer includes lithium or a lithium alloy. Therefore, since the second anode active material layer 23 is a metal layer containing lithium, the second anode active material layer 23 may function as, for example, a lithium reservoir. The lithium alloy is, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., but is not limited thereto, and may be any suitable lithium alloy used In the art. The second anode active material layer 23 may be composed of one of these alloys or lithium, or may be composed of a different alloy.

The second anode active material layer 23 has, for example, but is not particularly limited to, the following thickness: about 1 μm to about 1,000 μm, about 1 μm to about 500 μm, about 1 μm to about 200 μm, about 1 μm to about 150 μm, about 1 μm to about 100 μm, or about 1 μm to about 50 μm. When the thickness of the second anode active material layer 23 is too small, the second anode active material layer 23 may hardly function as a lithium reservoir. When the thickness of the second anode active material layer 23 is too large, the mass and volume of the solid secondary battery 1 increase, and conversely, the cycle characteristics thereof may be deteriorated. The second anode active material layer 23 may be, for example, a metal foil having a thickness within these ranges.

In the solid secondary battery 1, for example, the second anode active material layer 23 is provided between the anode current collector 21 and the first anode active material layer 22 before the assembly of the solid secondary battery, or the second anode active material layer 23 is deposited between the anode current collector 21 and the first anode active material layer 22 by charging after the assembly of the solid secondary battery 1.

In the case where the second anode active material layer 23 is provided between the anode electrode current collector 21 and the first anode active material layer 22 before the assembly of the solid secondary battery 1, the second anode active material layer 23 is a metal layer including lithium and serves as a lithium reservoir. The solid secondary battery 1 including the second anode active material layer 23 has further improved cycle characteristics. For example, before the assembly of the solid secondary battery 1, a lithium foil may be disposed between the anode current collector 21 and the first anode active material layer 22.

In the case where the second anode active material layer 23 is deposited by charging after the assembly of the solid secondary battery 1, the energy density of the solid secondary battery 1 is increased because the second anode active material 23 is not present when the solid secondary battery 1 is assembled. For example, when the solid secondary battery 1 is charged, the solid secondary battery 1 is charged to exceed the charge capacity of the first anode active material layer 22. That is, the first anode active material layer 22 is overcharged. At the initial stage of charging, lithium is absorbed in the first anode active material layer 22. That is, the anode active material included in the first anode active material layer 22 forms an alloy or a compound with lithium ions transferred from the cathode 10. When charging proceeds to exceed the capacity of the first anode active material layer 22, for example, lithium is precipitated on the rear surface of the first anode active material layer 22, that is, between the anode current collector 21 and the first anode active material layer 22, and a metal layer corresponding to the second anode active material layer 23 is formed from the precipitated lithium. The second anode active material layer 23 is a metal layer mainly composed of lithium (i.e., lithium metal). This result is obtained, for example, because: the anode active material included in the first anode active material layer 22 is composed of a material that forms an alloy or a compound with lithium. During discharge, lithium in the first anode active material layer 22 and the metal layer as the second anode active material layer 23 is ionized and migrates toward the cathode 10. Therefore, in the solid secondary battery 1, lithium may be used as the anode active material. Further, since the first anode active material layer 22 covers the second anode active material layer 23, the first anode active material layer 22 functions as a protective layer for the second anode active material layer 23 (i.e., a metal layer) and, at the same time, suppresses precipitation growth of lithium dendrites. Therefore, short circuits and capacity reduction in the solid secondary battery 1 are suppressed, and as a result, the solid secondary battery 1 has improved cycle characteristics. Further, in the case where the second anode active material layer 23 is deposited by charging after the assembly of the solid secondary battery 1, the anode current collector 21, the first anode active material layer 22, and the region therebetween are, for example, a Li-free region that does not contain lithium (Li) metal or a Li alloy in an initial state of the solid secondary battery or after discharge.

Referring to fig. 19, the solid secondary battery 1a according to the embodiment has a structure in which the second anode active material layer 23 is disposed on the anode current collector 21 and the solid electrolyte 30 is directly disposed on the first anode active material layer 22. The second anode active material layer 23 is, for example, a lithium metal layer or a lithium alloy layer. The solid electrolyte may be the solid electrolyte according to any embodiment, or may further include a second solid electrolyte in addition to the solid electrolyte according to the embodiment.

The second solid electrolyte may include, for example, an oxide-based solid electrolyte, a sulfide-based electrolyte, or a combination thereof.

The sulfide-based solid electrolyte may include, for example, Li₂S-P₂S₅、Li₂S-P₂S₅LiX (where X may be a halogen such as I or Cl), Li₂S-P₂S₅-Li₂O、Li₂S-P₂S₅-Li₂O-LiI、Li₂S-SiS₂、Li₂S-SiS₂-LiI、Li₂S-SiS₂-LiBr、Li₂S-SiS₂-LiCl、Li₂S-SiS₂-B₂S₃-LiI、Li₂S-SiS₂-P₂S₅-LiI、Li₂S-B₂S₃、Li₂S-P₂S₅-Z_mS_n(wherein m and n may each be a positive number, and Z may be one of Ge, Zn and Ga), Li₂S-GeS₂、Li₂S-SiS₂-Li₃PO₄、Li₂S-SiS₂-Li_pMO_q(wherein P and q may each be a positive number, and M may be one of P, Si, Ge, B, Al, Ga, and In). The sulfide-based solid electrolyte material can be obtained by mixing a starting material (e.g., Li)₂S or P₂S₅) Processed using a melt quenching process or a mechanical milling process. Further, after the treatment, a heat treatment may be performed. The sulfide-based solid electrolyte may be amorphous, crystalline, or a mixture thereof.

The second solid electrolyte may use the sulfide-based solid electrolyte material as described above including at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements, for example, including Li₂S-P₂S₅The material of (1). When the second solid electrolyte is used comprising Li₂S-P₂S₅In the case of a sulfide-based solid electrolyte material, Li₂S to P₂S₅Mixed molar ratio of (Li)₂S:P₂S₅) May be selected to be in the range of, for example, about 50:50 to about 90: 10.

The solid electrolyte 30 may further include a binder.

The binder included in the solid electrolyte 30 may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene. The binder of the solid electrolyte 30 may be the same as or different from the binders of the cathode active material layer 12 and the first anode active material layer 22.

One or more embodiments of the present disclosure will now be described in detail with reference to the following examples. However, these examples are for illustrative purposes only and are not intended to limit the scope of one or more embodiments of the present disclosure.

Examples

Example 1

LiCl (water content: 3.43% by weight) and GaF₃Mixed at a 2:1 molar ratio to obtain a mixture, and the mixture was subjected to high energy milling for 10 minutes by ball milling at 700rpm using a pulveresette 7Premium line apparatus. After the high-energy milling, the resulting product was cooled down by standing for 5 minutes (one cycle). This cycle of high energy milling and resting steps was repeated for a total of 72 cycles, thereby obtaining the compound in the form of clay having the composition as in table 1.

Examples 2 and 3

Compounds in the form of clay having the compositions as in table 1 were obtained according to the same method as in example 1, except that: LiCl is added to GaF₃The mixing molar ratio of (a) was changed to 3:1 and 4:1, respectively.

Example 4

Compounds in the form of clay having the composition as in table 1 were obtained according to the same method as in example 2, except that: LiBr was used instead of LiCl.

Example 5

Compounds in the form of clay having the compositions as in table 1 were obtained according to the same method as in example 1, except that: using LiCl, LiOH, and GaF₃Instead of LiCl and GaF₃And LiCl, LiOH, and GaF₃The mixing molar ratio of (1) to (2).

Example 6

Compounds in the form of clay having the compositions as in table 1 were obtained according to the same method as in example 1, except that: using LiCl, LaCl₃And GaF₃Instead of LiCl and GaF₃And LiCl, LaCl₃And GaF₃The mixing molar ratio of (1) to (2) is 3:0.1: 0.9.

Example 7

Compounds in the form of clay having the compositions as in table 1 were obtained according to the same method as in example 1, except that: using LiCl, InCl₃And GaF₃Instead of LiCl and GaF₃And is combined withAnd LiCl, InCl₃And GaF₃The mixing molar ratio of (1) to (2) is 3:0.1: 0.9.

Example 8

LiCl (water content: 3.43% by weight) was dried in a vacuum oven at 180 ℃ for 12 hours to obtain anhydrous LiCl.

A compound in the form of clay was obtained according to the same method as in example 1, except that: the anhydrous LiCl was used in place of LiCl (water content: 3.43 wt%), and LiCl and GaF₃The mixing molar ratio of (a) was changed to 3: 1.

Examples 1-1 to 1-3

Compounds in the form of clay having the compositions as in table 1 were obtained according to the same method as in example 1, except that: the composition of the starting materials was varied to obtain compounds having the compositions as in table 1.

Examples 1-4 to 1-7

Compounds in the form of clay having the compositions as in table 1 were obtained according to the same method as in example 1, except that: the composition of the starting materials was varied to obtain compounds having the compositions as in table 1.

Comparative example 1

Compounds in powder form having compositions as in table 1 were obtained according to the same method as in example 1, except that: LiOH was used instead of LiCl, and LiOH and GaF₃The mixing molar ratio of (a) to (b) is 3: 1.

Comparative example 2

Compounds in powder form having compositions as in table 1 were obtained according to the same method as in example 1, except that: using Li₂O replaces LiCl, and Li₂O and GaF₃The mixing molar ratio of (1: 1).

Comparative example 3

Compounds in powder form having compositions as in table 1 were obtained according to the same method as in example 1, except that: using LiCl and LaF₃Instead of LiCl and GaF₃And LiCl and LaF₃The mixing molar ratio of (a) to (b) is 3: 1.

Comparative example 4

Compounds in powder form having compositions as in table 1 were obtained according to the same method as in example 1, except that: using LiCl and InF₃Instead of LiCl and GaF₃And LiCl and InF₃The mixing molar ratio of (a) to (b) is 3: 1.

Comparative example 5

Compounds in powder form having compositions as in table 1 were obtained according to the same method as in example 1, except that: using LiCl and Ga₂O₃Instead of LiCl and GaF₃And LiCl and Ga₂O₃The mixing molar ratio of (a) to (b) is 6: 1.

Comparative example 6

Mixing LiCl and GaF₃Mixed at a 2:1 molar ratio to obtain a mixture, and the mixture was subjected to high energy milling for 10 minutes by ball milling at 700rpm using a pulveresette 7Premium line apparatus.

After the high-energy milling, the resulting product was cooled down by standing for 5 minutes (one cycle). After the cooling step, heat treatment was performed at 200 ℃ for 720 minutes.

In comparative example 6, a compound exhibiting a glass transition phenomenon could not be obtained by the above process.

Comparative example 7

Compounds in powder form having compositions as in table 1 were obtained according to the same method as in example 1, except that: using LiCl and GaCl₃Instead of LiCl and GaF₃And LiCl and GaCl₃The mixing molar ratio of (a) to (b) is 3: 1.

Comparative example 8

Compounds in powder form having compositions as in table 1 were obtained according to the same method as in example 1, except that: using LiCl and GaCl₃Instead of LiCl and GaF₃And LiCl and GaCl₃The mixing molar ratio of (1: 1).

Comparative example 9

Compounds in powder form having compositions as in table 1 were obtained according to the same method as in example 1, except that: using LiCl and ScCl₃In place of LiCl and GaF₃And LiCl and ScCl₃The mixing molar ratio of (a) to (b) is 3: 1.

TABLE 1

Comparative example 10

Mixing LiCl and GaF₃Mixed at a 1:1 molar ratio to obtain a mixture, and the mixture was subjected to high energy milling for 10 minutes by ball milling at 700rpm using a pulveresette 7Premium line apparatus. After the high-energy milling, the resulting product was cooled down by standing for 5 minutes (one cycle). This cycle of high energy milling and resting steps was repeated for a total of 72 cycles.

The resulting product was heat-treated at about 300 ℃ to obtain LiCl-GaF in the form of powder₃。

Comparative example 11

LiGaCl was obtained in the form of powder according to the same method as in comparative example 10₄Except as follows: using LiCl and GaCl₃Instead of LiCl and GaF₃。

Comparative example 12

Mixing LiCl and GaF₃Mixing at a 1:1 molar ratio to prepare LiCl and GaF in powder form₃The blend of (1).

Comparative example 13

Mixing NaCl and GaF₃Mixed at a 1:1 molar ratio to obtain a mixture, and the mixture was subjected to high energy milling for 10 minutes by ball milling at 700rpm using a pulveresette 7Premium line apparatus. After the high-energy milling, the resulting product was cooled down by standing for 5 minutes (one cycle). This cycle of high-energy milling and resting steps was repeated for a total of 72 cycles, thereby obtaining NaCl-GaF in powder form₃。

As obtained in comparative example 13The obtained NaCl-GaF₃As a result of Differential Scanning Calorimetry (DSC), NaCl-GaF was found₃Exhibits no glass transition phenomenon and has a low ionic conductivity of 0.005 mS/cm.

Production example 1: manufacture of solid secondary battery

First, a positive electrode was manufactured according to the following process.

Reacting LiNi_0.8Co_0.15Mn_0.05O₂(NCM), a conductive agent (Super-P; Timcal Ltd.), polyvinylidene fluoride (PVdF), and N-methylpyrrolidone were mixed to obtain a positive electrode active material layer forming composition. In the positive electrode active material layer-forming composition, the mixing weight ratio of NCM, conductive agent, and PVDF was 97:1.5:1.5, wherein the amount of N-methylpyrrolidone was about 137g when the amount of NCM was 97 g.

After the positive electrode active material layer forming composition was coated on an aluminum foil (having a thickness of about 15 μm) and dried at 25 ℃, the dried product was dried at about 110 ℃ in vacuum, thereby manufacturing a positive electrode.

Impregnating the positive electrode with an electrolyte comprising an ionic liquid. The ionic liquid-containing electrolyte is obtained by: bis (trifluoromethanesulfonyl) imide N-methyl-N-propylpyrrolidinium (PYR13TFSI) as an ionic liquid and lithium bistrifluoromethanesulfonimide (LiTFSI) as a lithium salt were mixed, and the mixture was stirred at room temperature (25 ℃). The mixing weight ratio of the ionic liquid to the lithium salt is 10: 100.

A lithium metal negative electrode (having a thickness of about 20 μm) was disposed on a current collector (copper foil), and an oxide-based first solid electrolyte, a solid electrolyte containing the compound of example 1, and an oxide-based second solid electrolyte were stacked on the lithium metal negative electrode and then bonded together by applying about 250MPa according to a Cold Isostatic Pressing (CIP) method, thereby manufacturing a structure of the lithium negative electrode/the oxide-based first solid electrolyte/the oxide-based second solid electrolyte.

LLZO (Li) was used separately_6.5La₃Zr_1.5Ta_0.5O₁₂) Membrane and LLZO(Li_6.5La₃Zr_1.5Ta_0.5O₁₂) A membrane as the first oxide-based solid electrolyte and the second oxide-based solid electrolyte. The solid electrolyte comprising the compound of example 1 was formed in a thickness of 100 μm by uniaxial pressing under a pressure of 200 MPa.

Attaching a positive electrode impregnated with the electrolyte containing an ionic liquid to an upper surface of a structure of a lithium negative electrode/a first oxide-based solid electrolyte/a second oxide-based solid electrolyte, and heat-treating at about 60 ℃, thereby manufacturing a sandwich-type secondary battery including the lithium negative electrode/the first oxide-based solid electrolyte/the second oxide-based solid electrolyte/the liquid electrolyte containing an ionic liquid/the positive electrode.

Production example 2: manufacture of solid secondary battery

First, a positive electrode was manufactured according to the following process.

Reacting LiNi_0.8Co_0.15Mn_0.05O₂(NCM), a conductive agent (Super-P; Timcal Ltd.), polyvinylidene fluoride (PVdF), and N-methylpyrrolidone were mixed to obtain a positive electrode active material layer forming composition. In the positive electrode active material layer-forming composition, the mixing weight ratio of NCM, conductive agent, and PVDF was 97:1.5:1.5, and the amount of N-methylpyrrolidone was about 137g when the amount of NCM was 97 g.

After the positive electrode active material layer forming composition was coated on an aluminum foil (having a thickness of about 15 μm) and dried at 25 ℃, the dried product was dried at about 110 ℃ in vacuum, thereby manufacturing a positive electrode.

A lithium metal negative electrode (having a thickness of about 20 μm) was disposed on a current collector (copper foil), and an oxide-based solid electrolyte (LLZTO: Li)_6.5La₃Zr_1.5Ta_0.5O₁₂) Is disposed on the lithium metal cathode, and a solid electrolyte comprising the compound of example 1 is disposed on the oxide-based solid electrolyte. Subsequently, the positive electrode is disposed on the solid electrolyte and then subjected to cold isostatic pressing(CIP) method was pressed together by applying about 250MPa for 3 minutes, thereby manufacturing a solid secondary battery including a lithium negative electrode/LLZO film/solid electrolyte/positive electrode comprising the compound of example 1.

The solid electrolyte comprising the compound of example 1 was formed in a thickness of 100 μm by uniaxial pressing under a pressure of 200 MPa.

Evaluation example 1: x-ray diffraction (XRD) analysis

XRD spectra of the compounds obtained according to examples 1 to 3 were measured, and the results are shown in fig. 1. For XRD spectroscopic measurements, Cu ka radiation was used and the X-ray diffraction analysis was performed using Bruker's D8 Advance.

Referring to FIG. 1, it is observed that the compound of example 1 (2 LiCl-GaF)₃) Exhibits a main peak at a diffraction angle (2 theta) of 29 DEG to 31 DEG and a sub-peak in the vicinity of a diffraction angle (2 theta) of 50 deg. It was observed that the compound of example 2 (3 LiCl-GaF)₃) And the compound of example 3 (4 LiCl-GaF)₃) Exhibits main peaks at diffraction angles (2 theta) of 29 to 31 DEG and sub-peaks at diffraction angles (2 theta) of 50 DEG, 59 DEG and 63 deg.

Evaluation example 2: scanning electron microscopy

Scanning Electron Microscopy (SEM) was performed on the compound of example 1. SEM analysis was performed using a Hitachi SU 8030 FE-SEM. The SEM analysis results are shown in fig. 2.

Referring to fig. 2, it was found that the compound of example 1 had an amorphous phase because no grain boundary was formed. Evaluation example 3: x-ray photoelectron spectroscopy (XPS)

The binding energy of the compound of example 1 was measured using an X-ray photoelectron spectrometer (Thermo Fisher Scientific, Multilab-2000), and the analysis results are shown in FIGS. 3A-3D.

The upper panels in FIGS. 3A to 3D respectively show the results of XPS analysis of Li1s, Ga 2p3/2, F1s, and Cl2p for the compound of example 1, and the lower panels in FIGS. 3A to 3D respectively show LiCl, GaF, and the like for comparison with the upper panels₃、GaF₃And LiCl.

Referring to fig. 3A, the Li1s peak of the compound of example 1 appears to be different from the LiCl peak.

Referring to FIGS. 3B and 3C, the Ga 2p3/2 and F1s peaks of the compound of example 1 appear to be similar to those of GaF₃Peak to peak results are identical. Furthermore, as is clear from FIG. 3D, the Cl2p peak attributed to Ga-Cl bond of the compound of example 1 was observed in the binding energy region of 200-203 eV.

From the results of FIG. 3D, it was found that LiX and GaF were combined₃Compared to the Cl2p peak of the simple blend of example 1, the Cl2p peak of the compound of example 1 is shifted toward the high binding energy direction. From the results, it was found that LiCl and GaF were different from those obtained according to comparative example 12₃The compound of example 1 is a complex with Ga-Cl bonds.

Evaluation example 4: measurement of ion conductivity and activation energy

(1) Examples 1 to 7, examples 1-1 to 1-7, and comparative examples 1 to 8, 12, and 13

The compounds in the form of clay (also referred to as clay compounds) of examples 1 to 7 and examples 1-1 to 1-7 and the compounds in the form of powder (also referred to as powder compounds) of comparative examples 1 to 8, 12 and 13 were analyzed in terms of ion conductivity and activation energy as follows. About 0.2g of each of the clay compounds of examples 1 to 7 and 1-1 to 1-7 was placed in the form of SUS/compound/SUS between SUS plates each having a diameter of 16mm and a thickness of 500 μm, and a uniaxial pressure of 100-200kg was applied thereto for 10 seconds, thereby forming a circular SUS/compound/SUS structure. About 1g of each of the powder compounds of comparative examples 1 to 8, 12 and 13 was placed in a tablet press having a diameter of 13mm, and 5 tons of uniaxial pressure was applied for 2 minutes, thereby forming a disk-shaped wafer. SUS electrodes were placed on the opposite sides of the respective wafers and pressure was applied at a torque of 4Nm, thereby forming a SUS/wafer/SUS structure.

The resistance of each SUS/wafer/SUS structure was measured at an open circuit voltage in a range of-20 ℃ to 80 ℃ while changing 10mV of alternating current from 1MHz to 0.01Hz using a potentiostatic impedance measurement method to perform impedance evaluation, and the result is shown in fig. 4A.

Obtaining the total resistance (R) from the impedance result_{General assembly}) And from this value via the electrode surfaceThe product and the correction for the wafer thickness were used to calculate the conductivity values. From the results of Electrochemical Impedance Spectroscopy (EIS) measured while changing the temperature of the chamber into which each sample was loaded, the value of activation energy (Ea) for lithium (Li) ion conduction was calculated. The value of the conductivity measured with respect to the temperature in the range of 298K-378K is converted into Arrhenius diagram of equation 1 (Ln (σ T) vs. 1/T), and the value of the activation energy (Ea) is calculated from the slope of the Arrhenius diagram.

Equation 1

σT＝A exp(Ea/RT)

In equation 1, Ea is activation energy, T represents absolute temperature, a represents a pre-exponential factor, R is a gas constant, and σ represents conductivity.

The values of activation energy obtained according to the above procedures are shown in table 2, and the ion conductivity of each compound is shown in fig. 4A.

TABLE 2

As shown in fig. 4A, the compounds of examples 1 to 4 were found to have excellent ionic conductivities in various temperature ranges. In particular, as shown in FIG. 4A, the compound of example 1 exhibited an ionic conductivity of 3.4mS/cm at room temperature (25 ℃). Referring to table 2, it was also found that the compounds of examples 1 to 7 have greatly improved conductivity compared to the compounds of comparative examples 1 to 4, 6 to 8, 12 and 13. The ionic conductivity of the compound of comparative example 5 was not measured because it was outside the measurable range.

The compounds of examples 1, 1-5, 2, 3, 5 to 9 exhibited lower activation energies of less than 0.37 eV/atom than the activation energies of the compounds of comparative examples 1 to 3. Thus, when the activation energy of the compound is decreased, the compound exhibits improved ion conductivity at low temperature.

Further, the compounds of examples 1-1 to 1-3 exhibited ion conductivities at levels comparable to those of the compound of example 1. The compounds of examples 1-4 and 1-5 also exhibited excellent conductivity, and the compounds of examples 1-6 and examples 1-7 exhibited conductivity similar to that of the compound of example 6.

(2) Example 8

The ion conductivity of the compound in the clay form obtained according to example 8 was evaluated in the same manner as the compound in the clay form applied to example 1, and the evaluation results are shown in fig. 21 and table 3.

Fig. 21 illustrates the impedance characteristics of the compound in the form of clay obtained according to example 8.

TABLE 3

Examples	Composition of	Ionic conductivity (at room temperature, mS/cm)
			Example 8	3LiCl-GaF3	1.4

Referring to fig. 21 and table 3, it was found that the compound of example 8 has excellent ionic conductivity.

Evaluation example 5: cyclic voltammetry

Adhering Li to Li by Cold Isostatic Pressing (CIP) at 250MPa for 3 minutes_6.5La₃Zr_1.5Ta_0.5O₁₂(LLZTO, Toshima Manufacturing Co.) after one surface of the wafer, a compound in the form of clay of example 1 as an electrolyte was disposed on the other surface of the LLZTO wafer by uniaxial pressing at 500kg, thereby forming a Li/LLZTO/electrolyte structure.

The Li/LLZTO/electrolyte structure was analyzed by cyclic voltammetry (scan rate of 0.2mV/s and voltage of 0.01V-5.0V). The results of the cyclic voltammetry analysis are shown in fig. 4B.

Referring to FIG. 4B, the compound of example 1 was found to be at up to 4.1V_Li/Li+The following is stable. Evaluation example 6: differential scanning calorimetry

Differential Scanning Calorimetry (DSC) was performed on the compounds of examples 1 to 3 and the compound of comparative example 9. DSC was performed using a TA Instruments Discovery DSC under a nitrogen atmosphere at a start temperature of-80 ℃, an end temperature of 160 ℃, and a ramp rate of 10 ℃/minute.

The results of the DSC analysis are shown in fig. 5. In FIG. 5, 2LiCl-GaF₃、3LiCl-GaF₃And 4LiCl-GaF₃Respectively represent the compounds of examples 1 to 3, and 3LiCl-ScCl₃The compound of comparative example 9 is shown.

The compounds of examples 1 to 3 exhibited a glass transition phenomenon, as shown in fig. 5. The glass transition phenomenon at 60 ℃ or higher refers to a phenomenon in which viscosity and rubber-like properties are exhibited at a certain temperature or higher, and a characteristic in which the slope of heat flow with respect to temperature changes at a certain temperature in a DSC chart and the same above and below the certain temperature is exhibited.

The compound of example 1 has a glass transition temperature of-62.2 ℃, which indicates that the compound of example 1 has glass characteristics in the range of the battery operating temperature of-20 ℃ to 60 ℃.

The compound of example 2 has a glass transition temperature of-64.0 ℃ and the compound of example 3 has a glass transition temperature of-61.9 ℃.

DSC analysis was performed on the compounds of comparative examples 9 to 13 under the same conditions as those for the DSC analysis of the compound of example 1.

As a result of DSC analysis, the compounds of comparative examples 9 to 13 did not exhibit a glass transition phenomenon in the temperature range of-60 ℃ to-30 ℃, unlike the compounds of examples 1 to 3.

Evaluation example 7: analysis of rheological Properties

The viscosity was measured using a rheometric measuring device, i.e. a cone-plate rheometer (TA Instruments AR 2000). Electrolyte samples using the compounds of examples 1 to 3, respectively, were each placed between a cone having a cone angle of 2 ° and a plate having a diameter of 40mm, and then the interval between the cone and the plate was adjusted. Here, each electrolyte sample was prepared at a thickness of about 1mm by applying a pressure of 5MPa to the compound in the form of clay with a uniaxial press.

After obtaining the cone/electrolyte/plate structure by the above process, the cone was repeatedly rotated, and rheological evaluation was performed at room temperature (25 ℃) at 1% strain while changing the shear rate. The shear rate is in the range of 1.0rad/s to 62.08 rad/s.

The storage modulus and loss modulus of each sample were measured simultaneously while changing the angular frequency values.

The measurement results are shown in fig. 6. The storage modulus and loss modulus for each sample at an angular frequency of 10rad/s are shown in Table 4.

TABLE 4

Examples	Composition of	Storage modulus (Pa)	Loss modulus (Pa)
				Example 1	2LiCl-GaF3	1,805,000(1.805MPa)	592,200
Example 2	3LiCl-GaF3	1,895,000(1.895MPa)	852,600
				Example 3	4LiCl-GaF3	495,600(0.496MPa)	481,900

The compounds of examples 1 to 3 exhibited loss modulus and storage modulus characteristics as shown in table 4.

The rheological properties of the compounds of comparative examples 1 to 8 were evaluated using the same rheological property evaluation method as applied to the compounds of examples 1 to 3.

As a result of the evaluation, the compounds of examples 1 to 3 exhibited rheological characteristics. Unlike the compounds of examples 1 to 3, no rheological behaviour was observed which was exhibited in the compounds of comparative examples 1 to 8.

Evaluation example 8: scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) analysis

SEM-EDS analysis was performed on the solid secondary battery of manufacturing example 2 to investigate the interface state of the positive electrode, the Solid Electrolyte (SE), and the LLZTO solid electrolyte and the distribution state of the solid electrolyte in the positive electrode. SEM-EDS analysis was performed using a Hitachi SU 8030 FE-SEM.

Fig. 9A and 9B are SEM images showing the interface state of the cathode and the Solid Electrolyte (SE) and the interface state of the Solid Electrolyte (SE) and the LLZTO solid electrolyte, respectively. FIGS. 10A-10F are images showing the results of an EDS analysis, where FIGS. 10A-10C are compared to FIG. 9A, and FIGS. 10D-10F are compared to FIG. 9B.

It was found that the bonding of the positive electrode and the Solid Electrolyte (SE) was well achieved, and the interface state and the bonding state of the Solid Electrolyte (SE) and the LLZTO solid electrolyte were good, as shown in fig. 9A. Referring to fig. 10A to 10F, it was found that Ga, F, and Cl, which are components of the compound of example 1, were uniformly distributed, and were particularly found to permeate into the porous positive electrode.

Evaluation example 9: charging and discharging curves

The solid secondary battery of manufacturing example 1 was charged at 60 ℃ at a voltage of 0.2mA/cm in the range of 2.85-4.2V²Charge and discharge at a current rate. The solid secondary battery was charged with a constant current of 0.067C for 15 hours until the battery voltage reached 4.2V, and then discharged with a constant current of 0.067C for 15 hours until the battery voltage reached 2.85V. C-rate is a measure of the rate at which a battery is charged or discharged relative to its maximum capacity. The 1C rate means the current that will be discharged within 1 hour of the total capacity.

The voltage curves after charging and discharging are shown in fig. 12. Fig. 13 illustrates impedance characteristics of the solid secondary battery at 60 ℃.

Referring to fig. 12 and 13, it was found that the solid electrolyte including the compound of example 1 has excellent compatibility with the garnet-based solid electrolyte. It was also found that the solid secondary battery of production example 1 reversibly exhibited about 3mAh/cm²A capacity of approximately 3.2mAh/cm²The design capacity of (2).

The charge and discharge curves of the batteries of comparative examples 1 to 3 were evaluated in the same manner as the method of evaluating the charge and discharge curves of the solid secondary battery of production example 1.

As a result of the evaluation, it was found that the batteries of manufacturing comparative examples 1 to 3 had inferior characteristics compared to the secondary solid-state battery of manufacturing example 1.

Evaluation example 10: charge-discharge curve and cycle characteristics

The solid secondary battery of production example 2 and the solid secondary batteries of production comparative examples 1 to 3 were charged under the same conditions as those in evaluation example 9 at 60 ℃, a voltage range of 2.85 to 4.2V, and 0.3mA/cm²And the cycle characteristics of the solid secondary battery were evaluated in a 60 ℃ thermostat.

After charging with a constant current of 0.1C for 10 hours until the cell voltage reached 4.2V, discharging was performed with a constant current of 0.1C for 20 hours until the cell voltage reached 2.85V (1 st cycle).

The voltage curves and cycle characteristics after the 1 st charge and discharge cycles are shown in fig. 14-16, respectively.

Referring to fig. 14, it was found that the solid secondary battery of manufacturing example 2 has excellent compatibility with LLZO garnet, and the solid electrolyte of manufacturing example 1 can be used as the solid electrolyte in the secondary battery.

Referring to fig. 15, it was found that the solid secondary battery of production example 2 was operable when the solid electrolyte was used as a solid electrolyte for a positive electrode.

Referring to fig. 16, it was found that the solid secondary battery of manufacturing example 2 exhibited good cycle characteristics.

Evaluation example 11: water sensitivity

A change in ion conductivity according to the introduction of moisture in the compound of example 1 was observed. The change in ionic conductivity when the compound was mixed with water in an amount of 10 wt%, 20 wt%, or 30 wt% was investigated. The results are shown in FIG. 7.

Referring to fig. 7, gelation by moisture absorption was observed when exposed to air. It was observed that the ionic conductivity of the solid electrolyte was increased when the water content was 10 wt%, 20 wt%, or 30 wt%.

Evaluation example 12: formability

The compound of example 1 in the form of clay was evaluated for moldability.

As shown in fig. 8A and 8B, the compound of example 1 can be freely shaped as desired, like rubber or clay.

The compounds of comparative examples 9 to 13 in powder form were evaluated for moldability.

As a result of the formability evaluation, the compounds of comparative examples 9 to 13 did not exhibit flexible properties, and it was difficult to shape the compounds as desired.

Evaluation example 13: thermogravimetric analysis

The clay-form compound (3 LiCl-GaF) prepared in example 2 was measured by thermogravimetric analysis₃) And the water content of LiCl used as starting material. Thermogravimetric analysis was performed using a TA instruments SDT-Q600 thermogravimetric analyzer (u.s.a) in air at a heating/cooling rate of 2 ℃/min over a temperature range of 100 ℃ to 900 ℃.

The results of thermogravimetric analysis of the starting material LiCl are shown in fig. 20.

As a result of thermogravimetric analysis, the starting material LiCl had a water content of about 3.43 wt%, as shown in FIG. 20, and the compound of example 2 (3 LiCl-GaF)₃) Having a water content of about 1.7% by weight.

As described above, according to one or more embodiments, the solid electrolyte may exhibit improved ionic conductivity at room temperature. The solid electrolyte may also have flexibility and clay characteristics, and thus have excellent formability, and thus may be useful in manufacturing a flexible solid secondary battery. The solid electrolyte can be used as a lithium ion conductor and as a positive electrode electrolyte due to improved lithium stability and high oxidation potential.

It is to be understood that the embodiments described herein are to be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within various embodiments should typically be considered as available for other similar features or aspects in other embodiments. Although one or more embodiments have been described with reference to the accompanying drawings, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope defined by the following claims.