阅读说明：本技术 一种阴阳离子共掺杂的富钠相反钙钛矿型固态电解质材料及其制备方法和全固态钠电池 (Negative and positive ion co-doped sodium-rich opposite perovskite type solid electrolyte material, preparation method thereof and all-solid-state sodium battery ) 是由 李驰麟 樊胜胜 雷萌 胡九林 于 2020-05-28 设计创作，主要内容包括：本发明公开一种阴阳离子共掺杂的富钠相反钙钛矿型固态电解质材料及其制备方法和全固态钠电池。所述固态电解质材料的化学组成为：Na-(3-x)A-(x/2)SO-(4)F-(1-y)B-(y),其中0<x≤0.5,0<y≤0.5,A为Mg、Ca、Sr或Ba中至少一种；B为Cl、Br或I中至少一种。(The invention discloses a negative and positive ion co-doped sodium-rich opposite perovskite type solid electrolyte material, a preparation method thereof and an all-solid-state sodium battery. The chemical composition of the solid electrolyte material is as follows: na (Na) 3‑x A x/2 SO 4 F 1‑y B y Wherein 0 is<x≤0.5，0<y is less than or equal to 0.5, A is at least one of Mg, Ca, Sr or Ba; b is at least one of Cl, Br or I.)

1. An anion-cation co-doped sodium-rich opposite perovskite type solid electrolyte material is characterized by comprising the following chemical components: na (Na)_3-xA_x/2SO₄F_1-yB_yWherein 0 is<x≤0.5，0<y is less than or equal to 0.5, A is the middle to the middle of Mg, Ca, Sr or BaOne kind of the compound is used; b is at least one of Cl, Br or I.

2. The solid state electrolyte material of claim 1, wherein 0< x ≦ 0.2, 0< y ≦ 0.3.

3. The solid electrolyte material according to claim 1 or 2, characterized in that a is Mg or Ca and B is Cl.

4. The solid state electrolyte material according to any one of claims 1 to 3, characterized in that the solid state electrolyte material is Na_2.98Mg_0.01SO₄F_0.95Cl_0.05、Na_2.9Mg_0.05SO₄F_0.95Cl_0.05Or Na_2.9Ca_0.05SO₄F_0.95Cl_0.05。

5. The method for producing the anion-cation co-doped sodium-rich opposite perovskite type solid electrolyte material according to any one of claims 1 to 4, wherein the method for producing comprises: mixing the raw materials of the solid electrolyte material according to a stoichiometric ratio to obtain a mixture; and forming the mixture, and sintering at 450-750 ℃ for 4-40 hours in a heat preservation manner to obtain the negative and positive ion co-doped sodium-rich opposite perovskite type solid electrolyte material.

6. The method according to claim 5, wherein the temperature is raised to 450 to 750 ℃ at a temperature raising rate of 2 to 6 ℃/min.

7. A production method according to claim 5 or 6, characterized in that the raw material of the solid electrolyte material includes a compound formed by A and F and/or a compound formed by B and Na.

8. The method according to any one of claims 5 to 7, wherein before the mixture is molded, a process of adding a solvent and a ball milling medium to the mixture to perform ball milling is further included; preferably, the ratio of mixture, solvent, ball milling medium is 1 g: 30mL of the following: (1.5-30) g; more preferably, the solvent is one of absolute ethyl alcohol, absolute methyl alcohol and absolute n-butyl alcohol.

9. An all-solid-state sodium battery comprising the anion-cation co-doped sodium-rich opposite perovskite type solid electrolyte material according to any one of claims 1 to 4.

10. The all-solid-state sodium battery of claim 9, further comprising a positive electrode and a negative electrode; preferably, the positive electrode is at least one of prussian blue or a derivative thereof, potassium rose bengal, a polyanion framework compound and a layered transition metal oxide, and the negative electrode is a metal sodium sheet or a Na — Sn alloy.

Technical Field

The invention belongs to the technical field of new energy, and particularly relates to a negative and positive ion co-doped sodium-rich opposite perovskite type solid electrolyte material, a preparation method thereof and an all-solid-state sodium battery.

Background

In recent years, with the increasingly prominent energy crisis and environmental problems, the demand for clean energy is particularly strong, and particularly in the fields of new energy electric vehicles and energy storage systems based on green power grids, the use and popularization of secondary batteries have prompted the industry and academia to put more attention on the research of novel frameworks and key materials thereof. At present, two major problems of the lithium ion battery based on an organic electrolyte system are difficult to overcome, one is that the flammability, toxicity and corrosivity of the electrolyte easily cause danger and pollution to the environment, and the other is that the separation of lithium metal dendrite on an electrode-electrolyte interface easily pierces a diaphragm to cause short circuit of the battery. The use of solid electrolyte is expected to solve the two problems, however, the lithium resource required by the lithium ion solid electrolyte is limited, and the long-term demand of the solid lithium battery is difficult to meet. Therefore, there is a need to develop a sodium ion solid electrolyte material with abundant resources and low price, and develop a solid sodium battery architecture based on the material to solve the above problems.

The design and preparation of solid electrolyte materials have been the key and difficult points of solid-state battery research. In recent years, some sodium solid state electrolyte structural prototypes have been developed. Early beta '' -Al₂O₃(Na₂O·(5-7)Al₂O₃) Excellent ion conductivity at high temperatures has been widely studied; however, the synthesis temperature thereof needs to exceed 1600 ℃, and NaAlO is easily formed at the grain boundary thereof₂Impurity phases, the moisture sensitivity of which leads to a decrease in ionic conductivity. Subsequently, NASICON type (e.g., Na)_1+3xZr₂(P_1-xSiO₄)₃) The ionic conductivity of the electrolyte may exceed 10 at room temperature^-4Scm^-1And therefore are of great interest; however, their practical application is hampered by large interfacial resistance and rapid penetration of dendrites at grain boundaries. More recently, sulfide-based sodium ion conductors, such as cubic Na₃PS₄Due to its high ionic conductivity (2X 10 at room temperature)^-4S cm^-1) Thereby attracting people's attention; however, the capacity of the sulfide-based solid-state battery rapidly decreases due to passivation of the electrode-electrolyte interface caused by the presence of interfacial side reactions. In the last decade, hydride-based NaIon conductors are also widely studied because of their rich structural symmetry and phase change modulation capabilities. The sodium-rich opposite perovskite type solid electrolyte has rich sodium migration sites, so that the electrolyte has potential sodium ion rapid conductivity, the synthesis temperature is low, the interface stability is high in a wide temperature range, and the attention of a plurality of researchers is attracted; however, except for Na₃OX, other structural prototypes of this type of solid-state electrolyte and their doping strategies are very lacking.

In summary, there is a need in the art to develop a sodium solid electrolyte material system for all-solid-state sodium batteries with high ionic conductivity, low electronic conductivity and wide electrochemical window, and the material needs simple preparation process and low cost, and is suitable for large-scale application.

Disclosure of Invention

The invention aims to provide a novel sodium-rich opposite perovskite type solid electrolyte material for a solid sodium battery, a preparation method thereof and the solid sodium battery based on the solid electrolyte system, and sodium ion conductivity of a sodium-rich opposite perovskite structure prototype is upgraded by regulating and controlling a cation and anion co-doping formula.

In a first aspect, the invention provides an anion-cation co-doped sodium-rich opposite perovskite type solid electrolyte material, which comprises the following chemical compositions: na (Na)_3-xA_x/2SO₄F_1-yB_yWherein 0 is<x≤0.5，0<y is less than or equal to 0.5. The values of x and y cannot be too large, which causes the content of the impurity phase in the synthesized solid electrolyte to be high, and is not favorable for ion conduction.

Preferably, a is at least one of Mg, Ca, Sr, or Ba; b is at least one of Cl, Br or I. A is higher than the ionic valence of Na and the radius difference cannot be too large; b is larger than F in ionic radius and is located in the same main group. For example, a is not Al, which has an ionic radius much smaller than that of Na, and the unit cell shrinks sharply after substitution, resulting in structural instability.

In the invention, the sodium-rich opposite perovskite type solid electrolyte material Na obtained by co-doping anions and cations_3-xA_{x/ 2}SO₄F_1-yB_yHas abundant sodium migration sites. The invention firstly proposes to use the sodium-doped lithium ion battery as a sodium solid electrolyte, and manufactures more sodium vacancy defects and enlarges the unit cell volume and the migration channel size of the sodium-doped lithium ion battery by co-doping anions and cations. Wherein, the process of forming Na vacancy defects by substituting divalent cations for monovalent Na ions is as follows: MgF₂→Mg^· _Na+V′_Na+2F_F. The ionic conductivity can be improved by three orders of magnitude. The electrolyte does not need to use expensive rare earth metal elements and redox active transition metal elements, and the used raw materials have low price and are suitable for large-scale industrial production.

Preferably, 0< x < 0.2, 0< y < 0.3. The values of x and y are in the range, the doped electrolyte has low impurity phase content and a large number of Na vacancy defects, and the performance of the ionic conductivity is greatly improved.

Preferably, A is Mg or Ca and B is Cl. The beneficial effects of selecting the elements A and B are as follows: the raw materials are cheap; the structural stability of the doped electrolyte is not greatly influenced; the generated Na vacancy defects are stable and are beneficial to ion conduction.

Preferably, the solid electrolyte material is Na_2.98Mg_0.01SO₄F_0.95Cl_0.05、Na_2.9Mg_0.05SO₄F_0.95Cl_0.05Or Na_2.9Ca_0.05SO₄F_0.95Cl_0.05。

In a second aspect, the invention further provides a preparation method of the anion-cation co-doped sodium-rich opposite perovskite type solid electrolyte material, wherein the preparation method comprises the following steps: mixing the raw materials of the solid electrolyte material according to a stoichiometric ratio to obtain a mixture; and forming the mixture, and sintering at 450-750 ℃ for 4-40 hours in a heat preservation manner to obtain the negative and positive ion co-doped sodium-rich opposite perovskite type solid electrolyte material.

Preferably, the temperature is raised to 450-750 ℃ at a rate of 2-6 ℃/min.

Preferably, the raw material of the solid electrolyte material includes a compound formed by a and F and/or a compound formed by B and Na. When a compound composed of elements other than a and F is selected as a raw material, or a compound composed of elements other than B and Na is selected as a raw material, it is difficult to remove excessive elements during synthesis to generate a hetero phase, which is disadvantageous to rapid ion conduction, difficult to increase ion conductivity, and may cause an increase in synthesis cost due to an excessively high sintering temperature.

Preferably, before the mixture is formed, a process of adding a solvent and a ball milling medium into the mixture for ball milling is also included; preferably, the ratio of mixture, solvent, ball milling medium is 1 g: 30mL of the following: (1.5-30) g; more preferably, the solvent is one of absolute ethyl alcohol, absolute methyl alcohol and absolute n-butyl alcohol.

Preferably, the ball milling rotation speed is 200 to 400r/min, and the ball milling time is 6 to 20 hours.

The preparation method of the negative and positive ion co-doped sodium-rich opposite perovskite type solid electrolyte material does not generate any toxic and harmful substance, is green and environment-friendly, is easy to operate, has simple process flow and low synthesis temperature, and is easy to realize large-scale mass production. The preparation method expands the improvement potential of the solid-state battery in the aspects of doping, surface modification and the like so as to hopefully overcome the technical problems existing in the current solid-state battery framework and the key electrolyte material thereof.

In a third aspect, the invention also provides an all-solid-state sodium battery. The all-solid-state sodium battery comprises the anion-cation co-doped sodium-rich opposite perovskite type solid electrolyte material.

The all-solid-state sodium battery further comprises a positive electrode and a negative electrode. Preferably, Na or Na-Sn is used as the negative electrode, Prussian blue derivative or its derivative (Na)₄Fe(CN)₆、Fe₄[Fe(CN)₆]₃) Potassium rose bengal (K)₂C₆O₆) Polyanionic framework compound (Na)₃V₂(PO₄)₃) Layered transition metal oxide (Na [ Fe ]_1/2Mn_1/2]O₂) As the positive electrode.

The invention has the beneficial effects that:

(1) the invention firstly provides an anti-perovskite compound Na_3-xA_x/2SO₄F_1-yB_yEspecially Na_3-xA_x/2SO₄F_1-yCl_yUse in solid state sodium batteries;

(2) the invention firstly provides that the anion and cation are codoped with the anti-perovskite compound to obtain Na_3-xA_x/2SO₄F_1-yB_yEspecially Na_3-xA_x/2SO₄F_1-yCl_yThe doping strategy can be used for manufacturing sodium vacancy defects, enlarging a sodium ion migration channel and effectively improving the ionic conductivity of the electrolyte material; in addition, the composition of the present invention does not contain a large amount of redox active ingredient, anion SO₄ ^2-And F^-Is stable per se, so that the interface side reaction can be avoided, and the formation of an impurity phase at the interface can be avoided.

(3) The material disclosed by the invention is cheap and easily available in raw materials in the production and preparation process, simple in synthesis process flow, low in synthesis temperature, free of toxic and harmful substances, green and environment-friendly, and easy to realize large-scale mass production.

Drawings

FIG. 1 shows Na synthesized by the solid phase sintering method obtained in example 1_2.98Mg_0.01SO₄F_0.95Cl_0.05XRD pattern of (a);

FIG. 2 shows Na synthesized by the solid phase sintering method in example 1_2.98Mg_0.01SO₄F_0.95Cl_0.05SEM picture of (1);

FIG. 3 shows Na synthesized by the solid phase sintering method in example 2_2.98Mg_0.01SO₄F_0.95Cl_0.05An ac impedance plot during the cool down phase;

FIG. 4 shows Na synthesized by the solid phase sintering method in example 2_2.98Mg_0.01SO₄F_0.95Cl_0.05Arrhenius plots at the cooling stage;

FIG. 5 shows Na synthesized by the solid phase sintering method in example 3_2.98Mg_0.01SO₄F_0.95Cl_0.05Prussian blue (Fe) as a solid electrolyte₄[Fe(CN)₆]₃) An electrochemical curve chart of the solid-state sodium battery is obtained by taking the Na-Sn alloy as a cathode and taking the Na-Sn alloy as an anode;

FIG. 6 shows Na synthesized by the solid phase sintering method in comparative example 3₃SO₄F, alternating-current impedance diagram in the cooling stage.

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative of, and not restrictive on, the present invention.

The chemical formula of the sodium-rich opposite perovskite type solid electrolyte material is Na_3-xA_x/2SO₄F_1-yB_yWherein, 0<x≤0.5，0<y is less than or equal to 0.5, A is at least one of Mg, Ca, Sr or Ba; b is at least one of Cl, Br or I. The invention designs and synthesizes the anti-perovskite sodium solid electrolyte for the first time by an anion and cation co-doping method, and manufactures a sodium vacancy defect by anion and cation co-doping, thereby enlarging a sodium ion migration channel and obviously improving the sodium ion conductivity. While Na vacancies are obtained by pure cation doping, ion channels in the solid electrolyte are still small, resulting in a still slow ion conduction rate; although the crystal lattice can be enlarged and the ion channel can be enlarged by simply using anion doping, Na vacancies in the solid electrolyte are still less, and the ion conduction capability is still insufficient; and the co-doping of the anions and the cations can simultaneously increase Na vacancy structure and enlarge ion channels, thereby obviously enhancing the ion transmission capability and upgrading the ion conductivity performance of the solid electrolyte.

In addition, the material structure of the present invention is of an anti-perovskite type, and other types of fluorine-based solid electrolyte materials such as A_xM_yF_x+3yIn contrast, there are essential differences in crystal structure, chemical composition, doping species, synthesis method, defect type, transport mechanism. The material of the invention has rich Na sites and is based on Na₃SO₄The co-doping of the anions and cations of the F compound is realized in order to manufacture a large amount of Na vacancy defectsAnd the migratable sites of Na ions are increased, and the ion conduction channel is enlarged, so that the spatial conduction of the Na ions is accelerated, and the ion conductivity of the Na ions is improved.

The sodium-rich opposite perovskite type solid electrolyte material can be prepared by a solid-phase sintering method. The method for synthesizing the sodium-rich opposite perovskite type electrolyte material through solid-phase reaction is beneficial to improving the density of the solid electrolyte, so that the solid electrolyte has the potential of subsequent doping regulation. The high-temperature solid-phase sintering synthesis method can comprise the following steps: mixing various raw materials required by the sodium solid electrolyte to be synthesized according to the stoichiometric ratio and then carrying out planetary ball milling; and tabletting the mixture obtained by ball milling, and preserving the heat for 4-40 hours at the temperature of 450-750 ℃ to obtain the sodium-rich phase-enriched anti-perovskite solid electrolyte material. In the ball milling process, the ratio of the total weight of raw materials, the solvent and the ball milling beads (also called as 'ball milling medium') is 1 g: (0-30) mL: (1.5-30) g, preferably 1 g: (0.1-3) mL: (1.5-6) g. As an example, the raw material is Na in a stoichiometric ratio₂SO₄，NaCl，NaBr，NaI，MgF₂，CaF₂，SrF₂，BaF₂Several of NaF. The solvent is at least one of absolute ethyl alcohol, absolute methyl alcohol and absolute n-butyl alcohol.

In the preparation method, the raw material selection principle is as follows: elements contained in the raw materials are necessary to be composition elements of the product, otherwise, redundant elements are difficult to remove in the synthesis process, and impurity phases are generated, so that the rapid conduction of ions is not facilitated; in order to remove certain excess elements, it may result in excessive sintering temperatures, resulting in additional synthesis costs.

As an example, the preparation method comprises the steps of:

adding a certain amount of MgF₂Or CaF₂、NaF、Na₂SO₄And NaCl as Na_3-xA_x/2SO₄F_1-yB_yBall milling uniformly according to the stoichiometric ratio to obtain a mixture; wherein A is Mg or Ca, and B is Cl. The rotation speed of the ball mill can be 200-400 r/min, and the ball milling time can be 6-20 h. In some embodiments, the slurry resulting from the ball milling is dried to obtain a mixture.

Then, the mixture was dried, ground and tabletted. For example, the diameter of the electrolyte disk obtained by tabletting is 10mm, the thickness of the disk is 1-3mm, and the pressure required for tabletting is 7-16 MPa.

And (3) placing the pressed sheet in a muffle furnace for high-temperature solid-phase reaction, and reacting for 4-40 hours at 450-750 ℃ to obtain the required product. For example, the temperature can be raised to 450-750 ℃ at a temperature raising rate of 2-6 ℃/min to perform a high temperature solid phase reaction.

And (3) carrying out high-temperature solid-phase reaction to obtain a wafer for testing a solid-state battery, or plating gold layers on the two sides of the wafer for testing the conductivity.

In addition, the invention also provides the construction of a solid sodium battery comprising the sodium-rich opposite perovskite type solid electrolyte.

As an example, in a solid-state sodium battery based on a sodium-rich reverse perovskite-type solid electrolyte, the solid-state electrolyte is Na as described above_3-xA_x/2SO₄F_1-yB_yThe positive electrode material is Prussian blue or its derivative (Na)₄Fe(CN)₆、Fe₄[Fe(CN)₆]₃) Polyanionic framework compound (Na)₃V₂(PO₄)₃) Potassium rose bengal (K)₂C₆O₆) Layered transition metal oxide (Na [ Fe ]_{1/ 2}Mn_1/2]O₂) The negative electrode is a metal sodium sheet or Na-Sn alloy.

The invention firstly converts Na into Na_2.98Mg_0.01SO₄F_0.95Cl_0.05As a sodium solid electrolyte material, Na or Na-Sn as a negative electrode, Prussian blue derivative (Na)₄Fe(CN)₆、Fe₄[Fe(CN)₆]₃) Potassium rose bengal (K)₂C₆O₆) Polyanionic framework compound (Na)₃V₂(PO₄)₃) Layered transition metal oxide (Na [ Fe ]_1/2Mn_1/2]O₂) As the positive electrode, to assemble a solid sodium battery for electrochemical cycling.

In order to further illustrate the present invention, the invention is described below in conjunction with specific examples, which are intended to be illustrative only and not limiting. The invention is not limited to the embodiments described above, but rather, many modifications and variations may be made by one skilled in the art without departing from the scope of the invention. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Example 1

Na_2.98Mg_0.01SO₄F_0.95Cl_0.05Solid-phase sintering preparation of sodium solid electrolyte:

MgF₂、NaF、Na₂SO₄And NaCl are weighed according to the stoichiometric ratio, mixed and ball-milled, and the mass of the mixed powder, the ball-milled beads and the absolute ethyl alcohol are 12g, 36g and 18g respectively. The ball milling time is 12h, and the rotating speed is 300 r/min. Transferring the ball-milled slurry to an oven at 60 ℃ for drying for 24h, and fully grinding by using an agate mortar. 220mg of the ground powder was pressed under a pressure of 8MPa to form a wafer having a diameter of 10mm and a thickness of 1.1 mm. And (3) keeping the wafer at 500 ℃ in a muffle furnace for 36h, wherein the heating rate is 4 ℃/min. Na (Na)_2.98Mg_0.01SO₄F_0.95Cl_0.05XRD of the solid electrolyte is shown in fig. 1, indicating that the prepared material is substantially phase pure. The SEM is shown in figure 2, which shows that micron-scale solid electrolyte materials with the size of 2-8 microns can be successfully prepared.

Example 2

Conductivity testing of solid electrolyte sheets:

na prepared in example 1_2.98Mg_0.01SO₄F_0.95Cl_0.05Gold layers were plated on both sides of the solid electrolyte wafer, and an ac impedance test was performed using a double electrode structure of a shimuralok battery case. As shown in the ac impedance spectrum of fig. 3, the test temperature was decreased from 60 ℃ to 40 ℃, and the test was performed after 1 hour of each temperature. The ionic conductivity is stabilized at 0.7-1 × 10 at 60 deg.C^-4Scm^-1In the meantime. Arrhenius point is shown in FIG. 4, 60 deg.CThe activation energy to 40 ℃ is around 0.275 eV.

Example 3

Based on Na_2.98Mg_0.01SO₄F_0.95Cl_0.05Construction and testing of solid state sodium cells with solid electrolyte:

fe to be synthesized₄[Fe(CN)₆]₃Powder, conductive carbon Super P and a binder PVDF are mixed according to the weight ratio of 7: 2: 1, adding a proper amount of NMP dropwise to prepare uniform slurry, coating the uniform slurry on an aluminum foil current collector, and then placing the aluminum foil current collector in a vacuum oven for more than 6 hours at 80 ℃. Mixing Na_2.98Mg_0.01SO₄F_0.95Cl_0.05Fe is respectively stuck on two surfaces of the solid electrolyte sheet₄[Fe(CN)₆]₃And assembling the positive electrode and the Na-Sn alloy negative electrode into a button cell in a glove box filled with argon. As shown in FIG. 5, the solid sodium cell was operated at 60 ℃ and 0.05mA cm^-2Can be successfully charged and discharged under the current density condition, and the first-circle discharge capacity is 91.0mAhg^-1And after the battery is cycled for 20 circles, the discharge capacity is still 77.0mAhg^-1。

Industrial applicability: the raw materials used in the production and preparation process are cheap and easily available, the synthesis process flow is simple, the synthesis temperature is low, toxic and harmful substances are not generated, the method is green and environment-friendly, and large-scale mass production is easy to realize.

Comparative example 1

Na₃SO₄F_0.95Cl_0.05Solid-phase sintering preparation and conductivity test of sodium solid electrolyte: NaF and Na₂SO₄And NaCl are weighed according to the stoichiometric ratio, mixed and ball-milled, and the mass of the mixed powder, the ball-milled beads and the absolute ethyl alcohol are 12g, 36g and 18g respectively. The ball milling time is 12h, and the rotating speed is 300 r/min. Transferring the ball-milled slurry to an oven at 60 ℃ for drying for 24h, and fully grinding by using an agate mortar. 220mg of the ground powder was pressed under a pressure of 8MPa to form a wafer having a diameter of 10mm and a thickness of 1.1 mm. And (3) keeping the wafer at 500 ℃ in a muffle furnace for 36h, wherein the heating rate is 4 ℃/min. The impedance test shows that the ionic conductivity of the material is not obviously improved. The main reason is that no Na vacancy defect exists in the structure of the compound, and the ion conduction is difficult.

Comparative example 2

Na_2.98Mg_0.01SO₄Solid-phase sintering preparation and conductivity test of sodium solid electrolyte: NaF and Na₂SO₄And MgF₂And weighing and mixing according to the stoichiometric ratio, and performing ball milling, wherein the mass of the mixed powder, the mass of the ball milling beads and the mass of the absolute ethyl alcohol are 12g, 36g and 18g respectively. The ball milling time is 12h, and the rotating speed is 300 r/min. Transferring the ball-milled slurry to an oven at 60 ℃ for drying for 24h, and fully grinding by using an agate mortar. 220mg of the ground powder was pressed under a pressure of 8MPa to form a wafer having a diameter of 10mm and a thickness of 1.1 mm. And (3) keeping the wafer at 500 ℃ in a muffle furnace for 36h, wherein the heating rate is 4 ℃/min. The ionic conductivity of the material is not obviously improved by impedance tests. The main reason is that the ion conduction channel is narrow and the ion conduction speed is slow by adopting the cation doping only although Na vacancy defects are generated.

Comparative example 3

Na₃SO₄Solid-phase sintering preparation and conductivity test of sodium solid electrolyte: mixing NaF and Na₂SO₄And weighing and mixing according to the stoichiometric ratio, and performing ball milling, wherein the mass of the mixed powder, the mass of the ball milling beads and the mass of the absolute ethyl alcohol are 12g, 36g and 18g respectively. The ball milling time is 12h, and the rotating speed is 300 r/min. Transferring the ball-milled slurry to an oven at 60 ℃ for drying for 24h, and fully grinding by using an agate mortar. 220mg of the ground powder was pressed under a pressure of 8MPa to form a wafer having a diameter of 10mm and a thickness of 1.1 mm. And (3) keeping the wafer at 500 ℃ in a muffle furnace for 36h, wherein the heating rate is 4 ℃/min. Synthesized undoped compound Na₃SO₄F, the electrochemical impedance was measured under the test conditions of example 2, and as shown in FIG. 6, the ionic conductivity was 4.54X 10 at 60 ℃^-8S cm^-1。