阅读说明：本技术 用于锂离子电化学电池的电解质组合物 (Electrolyte composition for lithium-ion electrochemical cells ) 是由 朱利安·德莫 马莱内·奥斯瓦尔德 于 2018-12-21 设计创作，主要内容包括：一种用于锂离子电化学元件的电解质组合物,其包含：-至少一种锂四氟化物或六氟化物盐,-双(氟磺酰基)酰亚胺锂LiFSI盐,-碳酸亚乙烯酯,-硫酸亚乙酯,-选自环状或线性碳酸酯、环状或线性酯、环状或线性醚及其混合物中的至少一种有机溶剂。在锂离子电化学元件中使用该组合物增加了元件的使用寿命,特别是在低温和高温循环条件下。(An electrolyte composition for a lithium-ion electrochemical element, comprising: -at least one lithium tetrafluoride or hexafluoroide salt, -lithium bis (fluorosulfonyl) imide LiFSI salt, -vinylene carbonate, -ethylene sulfate, -at least one organic solvent selected from cyclic or linear carbonates, cyclic or linear esters, cyclic or linear ethers and mixtures thereof. The use of the composition in lithium-ion electrochemical components increases the useful life of the components, particularly under low and high temperature cycling conditions.)

1. An electrolyte composition comprising:

-at least one lithium tetrafluoride or hexafluoro salt,

-lithium bis (fluorosulfonyl) imide (LiFSI) salt,

-a vinylene carbonate (C-CO),

-an ethylene sulphate,

-at least one organic solvent selected from the group consisting of cyclic or linear carbonates, cyclic or linear esters, cyclic or linear ethers and mixtures thereof.

2. The electrolyte composition of claim 1, wherein the lithium tetrafluoride or hexafluoro salt is selected from lithium hexafluorophosphate, LiPF₆Lithium hexafluoroarsenate LiAsF₆Lithium hexafluoroantimonate LiSbF₆And lithium tetrafluoroborate LiBF₄。

3. The electrolyte composition of claim 1 or 2, wherein lithium ions from the lithium bis (fluorosulfonyl) imide salt comprise at least 30% of the total amount of lithium ions present in the electrolyte composition.

4. The electrolyte composition of one of claims 1 to 3, wherein lithium ions from the lithium tetrafluoride or hexafluoroide salt constitute up to 70% of the total amount of lithium ions present in the electrolyte composition.

5. The electrolyte composition according to one of the preceding claims, wherein the mass percentage of vinylene carbonate represents between 0.1 and 5 mass% of the mass of the group consisting of the at least one lithium tetrafluoride or hexafluoride salt, the lithium bis (fluorosulfonyl) imide salt and the at least one organic solvent.

6. The electrolyte composition according to one of the preceding claims, wherein the mass percentage of ethylene sulfate is between 0.1 and 5 mass% of the mass of the group consisting of the at least one lithium tetrafluoride or hexafluoroide salt, the lithium bis (fluorosulfonyl) imide (LiFSI) salt and the at least one organic solvent.

7. The electrolyte composition according to one of the preceding claims, wherein:

-the ethylene sulfate accounts for 20 to 80 mass% of the mass of the group consisting of ethylene sulfate and vinylene carbonate, and

-vinylene carbonate accounts for 80 to 20 mass% of the mass of the group consisting of ethylene sulfate and vinylene carbonate.

8. The composition according to one of the preceding claims, wherein the at least one organic solvent is selected from cyclic carbonates, linear carbonates and mixtures thereof.

9. The composition according to claim 8, wherein the cyclic carbonate constitutes from 10 to 40 mass% of the mass of the at least one organic solvent, and the linear carbonate constitutes from 90 to 60 mass% of the mass of the at least one organic solvent.

10. The composition of claim 8 or 9, wherein the cyclic carbonate is selected from Ethylene Carbonate (EC) and Propylene Carbonate (PC).

11. The composition according to one of claims 8 to 10, wherein the linear carbonate is selected from dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC).

12. A lithium-ion electrochemical cell comprising:

-at least one negative electrode;

-at least one positive electrode;

-an electrolyte composition according to one of the preceding claims.

13. The electrochemical cell according to claim 12, wherein the negative electrode comprises a carbon-based active material, preferably graphite.

14. The electrochemical cell of claim 12 or 13, wherein the positive electrode active material comprises one or more of compounds i) through v):

-formula Li_xMn_1-y-zM'_yM”_zPO₄The compound i) of (a), wherein M 'and M' are different from each other and are selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo, wherein 0.8. ltoreq. x.ltoreq.1.2; y is more than or equal to 0 and less than or equal to 0.6; z is more than or equal to 0 and less than or equal to 0.2;

-formula Li_xM_2-x-y-z-wM'_yM”_zM”'_wO₂Compound ii) of (a), wherein M, M ', M "and M'" are selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo, with the proviso that M or M 'or M "or M'" are selected from Mn, Co, Ni or Fe;

m, M ', M ", and M'" are different from each other; wherein x is more than or equal to 0.8 and less than or equal to 1.4; y 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 0.5; w is more than or equal to 0 and less than or equal to 0.2, and x + y + z + w is less than 2.2;

-formula Li_xMn_2-y-zM'_yM”_zO₄The compound of (iii), wherein M 'and M' are selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, B,Y, Zr, Nb and Mo;

m 'and M' are different from each other, and 1. ltoreq. x.ltoreq.1.4; y is more than or equal to 0 and less than or equal to 0.6; z is more than or equal to 0 and less than or equal to 0.2;

-formula Li_xFe_1-yM_yPO₄Compound iv) of (a), wherein M is selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; and x is more than or equal to 0.8 and less than or equal to 1.2; y is more than or equal to 0 and less than or equal to 0.6;

-formula xLi₂MnO₃；(1-x)LiMO₂The compound of (v) wherein M is selected from the group consisting of Ni, Co and Mn and x.ltoreq.1.

15. The electrochemical cell of claim 14, wherein the positive electrode active material comprises compound i), wherein x ═ 1; m' represents at least one element selected from the group consisting of Fe, Ni, Co, Mg and Zn; 0< y <0.5 and z ═ 0.

16. The electrochemical cell of claim 14, wherein the positive electrode active material comprises compound ii), and

m is Ni;

m' is Mn;

m' is Co and

m' "is selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb and Mo;

wherein x is more than or equal to 0.8 and less than or equal to 1.4; y is more than 0 and less than or equal to 0.5; z is more than 0 and less than or equal to 0.5; w is more than or equal to 0 and less than or equal to 0.2, and x + y + z + w is less than 2.2.

17. The electrochemical cell of claim 14, wherein the positive electrode active material comprises compound ii) and M is Ni; m' is Co; m' is Al; x is more than or equal to 1 and less than or equal to 1.15; y > 0; z > 0; w is 0.

18. Use of an electrochemical cell according to one of claims 12 to 17 for storage, charging or discharging at a temperature of at least 80 ℃.

19. Use of an electrochemical cell according to one of claims 12 to 17 for storage, charging or discharging at a temperature of-20 ℃ or less.

Technical Field

The technical field of the invention is the field of electrolyte compositions for lithium ion rechargeable electrochemical cells.

Background

Lithium ion rechargeable electrochemical cells are known in the art. They are promising sources of electrical energy due to their high mass and volumetric energy density. They have at least one positive electrode (which may be a lithiated transition metal oxide) and at least one negative electrode (which may be graphite-based). However, such batteries have a limited service life when used at temperatures of at least 80 ℃. Their components degrade rapidly, resulting in short-circuiting of the battery or an increase in internal resistance. For example, the capacity loss of such a battery may reach 20% of its initial capacity after about 100 charge/discharge cycles at 85 ℃. In addition, it has been found that these batteries have a limited useful life when used at temperatures below-10 ℃.

The object was therefore to make available new lithium-ion electrochemical cells having an improved service life when used cyclically at temperatures of at least 80 ℃ or at temperatures below-10 ℃. This object is considered to be achieved when these cells are capable of operating under cycling conditions by performing at least 200 cycles, wherein the depth of discharge is 100% and the capacity loss is no more than 20% of their observed initial capacity.

Preferably, these new electrochemical cells are capable of cycling at very low temperatures, i.e., temperatures as low as about-20 ℃.

Disclosure of Invention

Accordingly, the present invention relates to an electrolyte composition comprising:

-at least one lithium tetrafluoride or hexafluoro salt,

-lithium bis (fluorosulfonyl) imide (LiFSI) salt,

-a vinylene carbonate (C-CO),

-an ethylene sulphate,

-at least one organic solvent selected from the group consisting of cyclic or linear carbonates, cyclic or linear esters, cyclic or linear ethers and mixtures thereof.

The electrolyte may be used in a lithium-ion electrochemical cell. Which enables the latter to operate at high temperatures (e.g. at least 80 c). It also enables the cell to operate at low temperatures (e.g., about-20 ℃).

According to one embodiment, the lithium tetrafluoride or hexafluoro salt is selected from lithium hexafluorophosphate LiPF₆Lithium hexafluoroarsenate LiAsF₆Lithium hexafluoroantimonate LiSbF₆And lithium tetrafluoroborate LiBF₄。

According to one embodiment, the lithium ions from the lithium bis (fluorosulfonyl) imide salt constitute at least 30 mol% of the total amount of lithium ions present in the electrolyte composition.

According to one embodiment, lithium ions from a lithium tetrafluoride or hexafluoro salt constitute up to 70 mol% of the total amount of lithium ions present in the electrolyte composition.

According to one embodiment, the mass percentage of vinylene carbonate is 0.1 to 5 mass% of the mass of the group consisting of the at least one lithium tetrafluoride or hexafluoride salt, lithium bis (fluorosulfonyl) imide salt, and the at least one organic solvent.

According to one embodiment, the mass percentage of ethylene sulfate is 0.1 to 5 mass% of the mass of the group consisting of the at least one lithium tetrafluoride or hexafluoride salt, the lithium bis (fluorosulfonyl) imide (LiFSI) salt, and the at least one organic solvent.

According to one embodiment, ethylene sulfate accounts for 20 to 80 mass% of the mass of the group consisting of ethylene sulfate and vinylene carbonate, and vinylene carbonate accounts for 80 to 20 mass% of the mass of the group consisting of ethylene sulfate and vinylene carbonate.

According to one embodiment, the at least one organic solvent is selected from the group consisting of cyclic carbonates, linear carbonates and mixtures thereof.

According to one embodiment, the cyclic carbonate accounts for 10 to 40 mass% of the mass of the at least one organic solvent, and the linear carbonate accounts for 90 to 60 mass% of the mass of the at least one organic solvent.

According to one embodiment, the cyclic carbonate is selected from Ethylene Carbonate (EC) and Propylene Carbonate (PC).

The linear carbonate is selected from dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC).

The invention also relates to a lithium-ion electrochemical cell comprising:

-at least one negative electrode;

-at least one positive electrode;

-an electrolyte composition as defined above.

According to one embodiment, the negative electrode comprises a carbon-based active material, preferably graphite.

According to one embodiment, the positive electrode active material comprises one or more of compounds i) to v):

-formula Li_xMn_1-y-zM'_yM”_zPO₄The compound i) of (a), wherein M 'and M' are different from each other and are selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo, wherein 0.8. ltoreq. x.ltoreq.1.2; y is more than or equal to 0 and less than or equal to 0.6; z is more than or equal to 0 and less than or equal to 0.2;

-formula Li_xM_2-x-y-z-wM'_yM”_zM”'_wO₂Compound ii) of (a), wherein M, M ', M "and M'" are selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo, with the proviso that M or M 'or M "or M'" are selected from Mn, Co, Ni or Fe; m, M ', M ", and M'" are different from each other; wherein x is more than or equal to 0.8 and less than or equal to 1.4; 0Y is not less than 0.5; z is more than or equal to 0 and less than or equal to 0.5; w is 0-0.2 and x + y + z + w<2.2；

-formula Li_xMn_2-y-zM'_yM”_zO₄Compound iii) of (a), wherein M 'and M' are selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; m 'and M' are different from each other, and 1. ltoreq. x.ltoreq.1.4; y is more than or equal to 0 and less than or equal to 0.6; z is more than or equal to 0 and less than or equal to 0.2;

-formula Li_xFe_1-yM_yPO₄Compound iv) of (a), wherein M is selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; and x is more than or equal to 0.8 and less than or equal to 1.2; y is more than or equal to 0 and less than or equal to 0.6;

-formula xLi₂MnO₃；(1-x)LiMO₂The compound of (v) wherein M is selected from the group consisting of Ni, Co and Mn, and x.ltoreq.1.

According to one embodiment, the positive electrode active material comprises a compound i), wherein x ═ 1; m' represents at least one element selected from the group consisting of Fe, Ni, Co, Mg and Zn; 0< y <0.5 and z ═ 0.

According to one embodiment, the positive electrode active material comprises compound ii), and

m is Ni;

m' is Mn;

m' is Co, and

m' "is selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb and Mo;

wherein x is more than or equal to 0.8 and less than or equal to 1.4; y is more than 0 and less than or equal to 0.5; z is more than 0 and less than or equal to 0.5; w is more than or equal to 0 and less than or equal to 0.2, and x + y + z + w is less than 2.2.

According to one embodiment, the positive electrode active material comprises compound ii) and M is Ni; m' is Co; m' is Al; x is more than or equal to 1 and less than or equal to 1.15; y > 0; z > 0; w is 0.

The invention also relates to the use of an electrochemical cell as described above for storage, charging or discharging at a temperature of at least 80 ℃.

The invention also relates to the use of an electrochemical cell as described above for storage, charging or discharging at a temperature lower than or equal to-20 ℃.

Drawings

Fig. 1 shows a diagram of the impedance at-40 ℃ for a reference cell a and a cell B according to the invention.

Fig. 2 shows the change in viscosity of the reference electrolyte composition a and the electrolyte composition B according to the invention as a function of temperature in the range of-20 ℃ to 60 ℃.

Fig. 3 shows at the top the gas chromatography spectrum of reference electrolyte composition a after 15 days of storage at 85 ℃. The spectrum at the bottom is the spectrum of electrolyte composition B according to the invention after storage under the same conditions.

Fig. 4 shows the change in capacity of battery a and battery B during cycling at 85 ℃.

Fig. 5 shows the capacity change of battery a and battery B during cycling at temperatures of 20 ℃, 0 ℃, -20 ℃, 25 ℃ and 85 ℃.

Fig. 6 shows the capacity change of cells C, D and E during cycling at 25 ℃ and 60 ℃.

Fig. 7 shows the capacity change of the batteries C, F and G during cycling at 25 ℃ and 60 ℃.

Fig. 8 shows at the top the gas chromatogram spectrum of electrolyte composition D at the end of the 60 ℃ cycle of a battery comprising electrolyte composition D. The bottom spectrum is the gas chromatography spectrum of electrolyte composition E at the end of the 60 ℃ cycle of the cell containing electrolyte composition E.

Fig. 9 shows at the top the gas chromatogram spectrum of electrolyte composition F at the end of the 60 ℃ cycle of a battery comprising electrolyte composition F. The bottom spectrum is the gas chromatography spectrum of electrolyte composition G at the end of the 60 ℃ cycle of the cell containing electrolyte composition G.

Fig. 10 shows the change in capacity of battery H, I, J, K and L during cycling at 85 ℃.

Fig. 11 shows the change in capacity of batteries M, N, O, P and Q during cycling at 85 ℃.

Fig. 12 shows the capacity change during cycling of the battery H, I, J, K and L at temperatures of 20 ℃, 0 ℃, -20 ℃, 25 ℃ and 85 ℃.

Fig. 13 shows the capacity change of the batteries M, N, O, P and Q during cycling at temperatures of 20 ℃, 0 ℃, -20 ℃, 25 ℃ and 85 ℃.

Detailed Description

Various components of the electrolyte composition according to the present invention and of the electrochemical cell comprising said electrolyte composition according to the present invention will be described below.

Electrolyte composition:

the electrolyte composition comprises at least one organic solvent in which the following compounds are dissolved:

-at least one lithium tetrafluoride or hexafluoro salt,

-lithium bis (fluorosulfonyl) imide (LiFSI) salt of formula:

-vinylene carbonates of formula:

-ethylene sulfate of the formula:

the at least one organic solvent is selected from cyclic or linear carbonates, cyclic or linear esters, cyclic or linear ethers or mixtures thereof.

Examples of cyclic carbonates are Ethylene Carbonate (EC), Propylene Carbonate (PC) and Butylene Carbonate (BC). Ethylene Carbonate (EC) and Propylene Carbonate (PC) are particularly preferred. The electrolyte composition may be free of cyclic carbonates other than EC and PC.

Examples of linear carbonates are dimethyl carbonate (DMC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC) and methyl propyl carbonate (PMC). Dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC) are particularly preferred. The electrolyte composition may be free of linear carbonates other than DMC and EMC.

The cyclic or linear carbonates and cyclic or linear esters may be substituted with one or more halogen atoms, such as fluorine.

Examples of linear esters are ethyl acetate, methyl acetate, propyl acetate, ethyl butyrate, methyl butyrate, propyl butyrate, ethyl propionate, methyl propionate and propyl propionate.

Examples of cyclic esters are gamma-butyrolactone and gamma-valerolactone.

Examples of linear ethers are dimethoxyethane and propylethyl ether.

An example of a cyclic ether is tetrahydrofuran.

According to one embodiment, the electrolyte composition comprises one or more cyclic carbonates, one or more cyclic ethers and one or more linear ethers.

According to one embodiment, the electrolyte composition comprises one or more cyclic carbonates, one or more linear carbonates and at least one linear ester.

According to one embodiment, the electrolyte composition comprises one or more cyclic carbonates, one or more linear carbonates and no linear esters. Preferably, the electrolyte composition does not comprise any solvent compounds other than cyclic or linear carbonates. In the case where the solvent compound is a mixture of a cyclic carbonate and a linear carbonate, the cyclic carbonate may account for up to 50 mass% of the sum of the masses of the carbonates, and the linear carbonate may account for at least 50 mass% of the sum of the masses of the carbonates. Preferably, the cyclic carbonate accounts for 10 to 40 mass% of the mass of the carbonate, and the linear carbonate accounts for 90 to 60 mass% of the carbonate. Preferred organic solvent mixtures are mixtures of EC, PC, EMC and DMC. The EC may be 5 to 15 mass% of the mass of the organic solvent mixture. The PC may be 15 to 25 mass% of the mass of the organic solvent mixture. EMC may occupy 20 to 30 mass% of the mass of the organic solvent mixture. The DMC may be present in an amount of 40 to 50 mass% based on the mass of the organic solvent mixture.

To prepare the electrolyte composition, first at least one lithium tetrafluoride or hexafluoro salt and lithium bis (fluorosulfonyl) imide (LiFSI) salt are dissolved in the at least one organic solvent. The nature of the lithium tetrafluoride or hexafluoro salt is not particularly limited. Examples include lithium hexafluorophosphate LiPF₆Lithium hexafluoroarsenate LiAsF₆Lithium hexafluoroantimonate LiSbF₆And lithium tetrafluoroborate LiBF₄. Lithium hexafluorophosphate LiPF is preferably chosen₆. It is also possible to dissolve lithium salts other than lithium tetrafluoride or hexafluoro salt and lithium bis (fluorosulfonyl) imide (LiFSI) salt in the at least one organic solvent. Preferably, the electrolyte composition does not comprise any lithium salt other than a lithium tetrafluoride or hexafluoro salt and a lithium bis (fluorosulfonyl) imide (LiFSI) salt. In particular, the electrolyte composition does not comprise lithium difluorophosphate LiPO₂F₂Nor lithium difluoro (oxalato) borate LiBF₂(C₂O₄)(LiDFOB)。LiPO₂F₂Are weakly dissociated. Li⁺PO₂F₂ ^-The form is almost non-existent. The electrolyte produced from the salt and the electrolyte using the salt have too low a conductivity to be used in a lithium ion battery. Due to its low ionic properties, LiPO₂F₂Solubility in the electrolyte is very poor. Therefore, the concentration thereof may not exceed 0.1 mol/L. On the other hand, the presence of LiDFOB may result in the generation of excess gas during its decomposition by reduction and oxidation. In addition, electrolytes incorporating the salts have low ionic conductivity.

Still preferably, the only lithium salt in the electrolyte composition is LiPF₆And LiFSI.

The total lithium ion concentration in the electrolyte composition is typically 0.1 to 3mol/L, preferably 0.5 to 1.5mol/L, more preferably about 1 mol/L.

Lithium ions from lithium tetrafluoride or hexafluoroide salts typically account for up to 70% of the total amount of lithium ions present in the electrolyte composition. They may also represent 1% to 70% of the total amount of lithium ions in the electrolyte composition. They may also represent 10% to 70% of the total amount of lithium ions in the electrolyte composition.

The lithium ions from the lithium bis (fluorosulfonyl) imide salt typically constitute at least 30% of the total amount of lithium ions present in the electrolyte composition. They may also represent 30% to 99% of the total amount of lithium ions present in the electrolyte composition. They may also represent 30% to 90% of the total amount of lithium ions in the electrolyte composition.

In a second step, vinylene carbonate and ethylene sulfate are added to a mixture comprising the at least one organic solvent and the lithium salt. These compounds act as additives that help stabilize the passivation layer that is formed on the surface of the negative electrode of the electrochemical cell during the first charge/discharge cycle of the cell. Additives other than vinylene carbonate and ethylene sulfate may also be added to the mixture.

In a preferred embodiment, the electrolyte composition does not comprise additives other than vinylene carbonate and ethylene sulfate. In particular, the electrolyte composition does not comprise sultones. The presence of sultones has the following disadvantages compared to ethylene sulfate: the passivation layer (SEI) on the surface of the negative electrode has lower conductivity in cold applications than when ethylene sulfate is present. Furthermore, for thermal applications, the passivation layer on the surface of the negative electrode is stronger and more difficult to dissolve in the electrolyte when ethylene sulfate is present than when sultone is present.

The amount of additive introduced into the mixture is measured by mass relative to the mass of the group consisting of lithium tetrafluoride or hexafluoroide salt, lithium bis (fluorosulfonyl) imide (LiFSI) salt, and the at least one organic solvent.

According to one embodiment, the mass percentage of vinylene carbonate is 0.1 to 5 mass%, preferably 0.5 to 3 mass%, more preferably 1 to 2 mass% of the mass of the group consisting of lithium tetrafluoride or hexafluoride salt, lithium bis (fluorosulfonyl) imide salt, and the at least one organic solvent.

According to one embodiment, the mass percentage of ethylene sulfate is 0.1 to 5 mass%, preferably 0.5 to 2 mass%, more preferably 1 to 2 mass% of the mass of the group consisting of the lithium tetrafluoride or hexafluoride salt, the lithium bis (fluorosulfonyl) imide salt, and the at least one organic solvent.

The ethylene sulfate may account for 20 to 80 mass% or 30 to 50 mass% of the total mass of the ethylene sulfate and vinylene carbonate. The vinylene carbonate may account for 80 to 20 mass% or 50 to 30 mass% of the combined mass of the ethylene sulfate and the vinylene carbonate.

Preferred electrolyte compositions comprise:

-0.1 to 0.7mol/L of at least one lithium tetrafluoride or hexafluoro salt, preferably LiPF₆；

-from 0.3 to 0.9mol/L of a lithium bis (fluorosulfonyl) imide (LiFSI) salt;

-vinylene carbonate in an amount of 1 to 3% by mass, preferably 2% by mass, of the mass of the group consisting of lithium tetrafluoride or hexafluoroide salt, lithium bis (fluorosulfonyl) imide salt and said at least one organic solvent;

0.5 to 2 mass% of ethylene sulfate, preferably 1 mass%, of the mass of the group consisting of lithium tetrafluoride or hexafluoro-chloride salt, lithium bis (fluorosulfonyl) imide salt and said at least one organic solvent.

Another preferred electrolyte composition comprises:

-0.6 to 0.8mol/L of at least one lithium tetrafluoride or hexafluoro salt, preferably LiPF₆；

-from 0.2 to 0.4mol/L of a lithium bis (fluorosulfonyl) imide (LiFSI) salt;

-vinylene carbonate in an amount of 1 to 3% by mass, preferably 2% by mass, of the mass of the group consisting of lithium tetrafluoride or hexafluoroide salt, lithium bis (fluorosulfonyl) imide salt and said at least one organic solvent;

0.5 to 2 mass% of ethylene sulfate, preferably 1 mass%, of the mass of the group consisting of lithium tetrafluoride or hexafluoro-chloride salt, lithium bis (fluorosulfonyl) imide salt and said at least one organic solvent.

Another preferred electrolyte composition comprises:

-0.05 to 0.2mol/L of at least one lithium tetrafluoride or hexafluoro salt, preferably LiPF₆；

-from 0.8 to 0.95mol/L of a lithium bis (fluorosulfonyl) imide (LiFSI) salt;

-vinylene carbonate in an amount of 1 to 3% by mass, preferably 2% by mass, of the mass of the group consisting of lithium tetrafluoride or hexafluoroide salt, lithium bis (fluorosulfonyl) imide salt and said at least one organic solvent;

0.5 to 2 mass% of ethylene sulfate, preferably 1 mass%, of the mass of the group consisting of lithium tetrafluoride or hexafluoro-chloride salt, lithium bis (fluorosulfonyl) imide salt and said at least one organic solvent.

Another preferred electrolyte composition comprises:

0.7mol/L LiPF₆；

-0.3mol/L of lithium bis (fluorosulfonyl) imide (LiFSI) salt;

-vinylene carbonate in an amount of 2 mass% with respect to the mass of the group consisting of lithium tetrafluoride or hexafluoroide salt, lithium bis (fluorosulfonyl) imide salt and said at least one organic solvent;

-1 mass% of ethylene sulfate with respect to the mass of the group consisting of lithium tetrafluoride or hexafluoro salt, lithium bis (fluorosulfonyl) imide salt and said at least one organic solvent.

Another preferred electrolyte composition comprises:

0.1mol/L LiPF₆；

-0.9mol/L of lithium bis (fluorosulfonyl) imide (LiFSI) salt;

-vinylene carbonate in an amount of 2 mass% with respect to the mass of the group consisting of lithium tetrafluoride or hexafluoroide salt, lithium bis (fluorosulfonyl) imide salt and said at least one organic solvent;

-1 mass% of ethylene sulfate with respect to the mass of the group consisting of lithium tetrafluoride or hexafluoro salt, lithium bis (fluorosulfonyl) imide salt and said at least one organic solvent.

Negative electrode active material:

the active material of the negative electrode (anode) of the electrochemical cell is preferably a carbonaceous material which may be selected from the group consisting of graphite, coke, carbon black and vitreous carbon.

In another preferred embodiment, the active material of the negative electrode comprises a silicon-based compound.

Positive electrode active material:

the positive electrode active material of the positive electrode (cathode) of the electrochemical cell is not particularly limited. It may be selected from:

-formula Li_xMn_1-y-zM'_yM”_zPO₄(LMP) wherein M 'and M' are different from each other and are selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo, wherein 0.8. ltoreq. x.ltoreq.1.2; y is more than or equal to 0 and less than or equal to 0.6; z is more than or equal to 0 and less than or equal to 0.2;

-formula Li_xM_2-x-y-z-wM'_yM”_zM”'_wO₂(LMO2) compound ii) wherein M, M ', M "and M'" are selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, W and Mo, with the proviso that M or M 'or M "or M'" are selected from Mn, Co, Ni or Fe; m, M ', M ", and M'" are different from each other; wherein x is more than or equal to 0.8 and less than or equal to 1.4; y 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 0.5; w is 0-0.2 and x + y + z + w<2.2；

-formula Li_xMn_2-y-zM'_yM”_zO₄(LMO) compound iii) wherein M 'and M' are selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo;

m 'and M' are different from each other, and 1. ltoreq. x.ltoreq.1.4; y is more than or equal to 0 and less than or equal to 0.6; z is more than or equal to 0 and less than or equal to 0.2;

-formula Li_xFe_1-yM_yPO₄Compound iv) of (a), wherein M is selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; and x is more than or equal to 0.8 and less than or equal to 1.2; y is more than or equal to 0 and less than or equal to 0.6;

-formula xLi₂MnO₃；(1-x)LiMO₂Compound v) of (1), wherein M is selected from Ni, Co and Mn,

and x is less than or equal to 1,

or mixtures of compounds i) to v).

An example of a compound i) is LiMn_1-yFe_yPO₄. A preferred example is LiMnPO₄。

The compound ii) may have the formula Li_xM_2-x-y-z-wM'_yM”_zM”'_wO₂Wherein x is more than or equal to 1 and less than or equal to 1.15; m represents Ni; m' represents Mn; m 'represents Co and M' is selected from B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, Mo or a mixture thereof; 2-x-y-z-w>0；y>0；z>0；w≥0。

The compound ii) may have the formula LiNi_1/3Mn_1/3Co_1/3O₂。

The compounds ii) may also have the formula Li_xM_2-x-y-z-wM'_yM”_zM”'_wO₂Wherein x is more than or equal to 1 and less than or equal to 1.15; m represents Ni; m' represents Co; m 'represents Al and M' is selected from B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, Mo or a mixture thereof; 2-x-y-z-w>0；y>0；z>0; w is more than or equal to 0. Preferably, x ═ 1; 2-x-y-z is more than or equal to 0.6 and less than or equal to 0.85; y is more than or equal to 0.10 and less than or equal to 0.25; z is 0.05-0.15 and w is 0.

The compound ii) may also be selected from LiNiO₂、LiCoO₂、LiMnO₂Ni, Co and Mn, which may be selected from Mg, Mn (except LiMnO)₂Outer), one or more elements of Al, B, Ti, V, Si, Cr, Fe, Cu, Zn and Zr.

An example of compound iii) is LiMn₂O₄。

An example of compound iv) is LiFePO₄。

An example of compound v) is Li₂MnO₃。

The positive electrode active material may be at least partially covered with a carbon layer.

Binders for positive and negative electrodes:

the positive and negative active materials of a lithium-ion electrochemical cell are typically mixed with one or more binders, the function of which is to bind the active material particles together and to bind them to the current collector on which they are deposited.

The binder may be selected from the group consisting of carboxymethylcellulose (CMC), styrene-butadiene copolymer (SBR), Polytetrafluoroethylene (PTFE), Polyamideimide (PAI), Polyimide (PI), styrene-butadiene rubber (SBR), polyvinyl alcohol, polyvinylidene fluoride (PVDF), and mixtures thereof. These binders may be used in the positive electrode and/or the negative electrode in general.

Current collector for positive and/or negative electrode:

the current collectors for the positive and negative electrodes are in the form of solid or perforated metal foils. The foil may be made of different materials. Examples include copper or copper alloys, aluminum or aluminum alloys, nickel or nickel alloys, steel, and stainless steel.

The current collector of the positive electrode is typically a foil made of aluminum or an alloy mainly containing aluminum. The current collector of the negative electrode is typically a foil made of copper or an alloy mainly containing copper. The thickness of the positive electrode foil may be different from the thickness of the negative electrode foil. The foil of the positive or negative electrode is typically 6 μm to 30 μm thick.

According to a preferred embodiment, the aluminum current collector of the positive electrode is covered by a conductive coating, such as carbon black, graphite.

Manufacturing of negative electrode:

the negative active material is mixed with one or more of the above binders and optionally a good conductive compound (e.g., carbon black). The result is an ink deposited on one or both sides of the current collector. The ink-coated current collector was laminated to adjust the thickness thereof. Thereby obtaining a negative electrode.

The composition of the ink deposited on the negative electrode may be as follows:

-75% to 96% of a negative active material, preferably 80% to 85%;

-2% to 15% of binder, preferably 5%;

-2% to 10% of a conductive compound, preferably 7.5%.

Fabrication of positive electrode:

the same procedure was used as for the negative electrode, but starting with the positive active material.

The composition of the ink deposited on the positive electrode may be as follows:

-75% to 96% of a negative active material, preferably 80% to 90%;

-2% to 15% binder, preferably 10%;

2% to 10% carbon, preferably 10%.

A spacer:

the material of the spacer may be selected from the following materials: polyolefins (e.g., polypropylene, polyethylene), polyesters, polymer-bonded fiberglass, polyimides, polyamides, polyaramides, polyamideimides, and cellulose. The polyester may be selected from the group consisting of polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Advantageously, the polyester or polypropylene or polyethylene comprises or is coated with a material selected from the group consisting of metal oxides, carbides, nitrides, borides, silicides and sulfides. The material may be SiO₂Or Al₂O₃。

Preparation of electrochemical assemblies:

an electrochemical assembly is formed by interposing a separator between at least one negative electrode and at least one positive electrode. The electrochemical assembly is inserted into the cell container. The battery container may be in the form of a parallelepiped or a cylinder. In the latter case, the electrochemical assembly is coiled to form a cylindrical electrode assembly.

Filling of the container:

the container provided with the electrochemical assembly is filled with the electrolyte composition as described above.

The battery according to the invention generally comprises a combination of the following elements:

a) at least one positive electrode whose active material is a lithium oxide of a transition metal comprising nickel, manganese and cobalt;

b) at least one negative electrode whose active material is graphite;

c) the electrolyte composition as described above;

d) a polypropylene spacer.

Applicants have found that the combination of two lithium salts (i.e., a lithium tetrafluoride or hexafluoroide salt and a lithium bis (fluorosulfonyl) imide (LiFSI) salt) with two additives (i.e., vinylene carbonate and ethylene sulfate) provides the following advantages:

reducing the impedance of the electrochemical cell.

Electrochemical cells can operate over a wide temperature range (i.e. -temperatures of-10 ℃ or even-20 ℃ up to as high as 80 ℃ or even 100 ℃).

Electrochemical cells have good cold power down to-40 ℃.

Electrochemical cells can be cycled with significant changes in ambient temperature.

The electrochemical cell capacity is lost more slowly when used under cycling conditions. The invention thus makes it possible to extend the service life of a battery operating under cycling conditions (whether it is used at low or high temperatures).

Gas formation in the case of cells with graphite-based anodes is reduced.

Reducing the self-discharge rate of the battery.

-the viscosity of the electrolyte composition is reduced.

Therefore, it is preferable that the electrolyte does not contain any lithium salt other than lithium tetrafluoride or hexafluoride salt and lithium bis (fluorosulfonyl) imide (LiFSI) salt, and does not contain any additive other than vinylene carbonate and ethylene sulfate.