Solid-state electrolyte based on sodium thioantimonate and preparation method and application thereof

Abstract

The application relates to a sodium thioantimonate-based solid-state electrolyte and a preparation method and application thereof, which comprises sodium thioantimonate and a polyvinylidene fluoride-hexafluoropropylene copolymer, wherein the sodium thioantimonate is dispersed in the polyvinylidene fluoride-hexafluoropropylene copolymer. The sodium thioantimonate-based solid-state electrolyte provided by the application has good ion conductivity, and can effectively improve the cycle stability, sodium ion migration selectivity and overall electrochemical performance of a sodium ion battery.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and in particular to a solid electrolyte based on sodium antimonythioate, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries, due to their abundant resources, low cost, and relatively high safety, are gradually becoming a strong alternative to lithium-ion batteries. The electrolyte, as a crucial medium for the migration of sodium ions between the positive and negative electrodes, directly affects the battery's safety, cycle life, and electrochemical performance. Traditional liquid electrolytes suffer from problems such as flammability, leakage, and insufficient interfacial stability, easily triggering side reactions and sodium dendrite growth during charge and discharge, thus increasing the risk of short circuits. Therefore, developing solid-state electrolytes to replace liquid electrolytes is of great significance for improving the safety and cycle stability of sodium-ion batteries.

[0003] In sodium-ion solid electrolytes, solid polymer electrolytes have attracted attention due to their advantages such as light weight, good flexibility, excellent processability, and low cost. Among them, polyvinylidene fluoride (PVDF)-hexafluoropropylene (HCF) copolymers have good film-forming properties and chemical stability, making them a commonly used polymer electrolyte matrix. However, single PVDF-HCF copolymer electrolytes still suffer from limited ion transport capacity, low sodium ion transference number, and insufficient interfacial stability, which limits battery cycle performance and rate capability. Although existing inorganic filler modification methods can improve polymer electrolyte performance to some extent, ordinary inorganic fillers have limited ability to control sodium ion selective migration and interfacial stability. Therefore, there is an urgent need to develop a PVDF-HCF copolymer-based composite solid electrolyte membrane with good ion transport capacity, interfacial stability, and film-forming properties. Summary of the Invention

[0004] In view of this, the present invention aims to provide a solid electrolyte based on sodium thioantimonate, its preparation method and application.

[0005] A first aspect of the present invention relates to a solid electrolyte based on sodium thioantimonate, comprising sodium thioantimonate and polyvinylidene fluoride-hexafluoropropylene copolymer, wherein the sodium thioantimonate is dispersed in the polyvinylidene fluoride-hexafluoropropylene copolymer.

[0006] The second invention relates to a method for preparing the sodium thioantimonate-based solid electrolyte of the present invention, comprising the following steps:

[0007] i) Add polyvinylidene fluoride-hexafluoropropylene copolymer to an organic solvent and mix thoroughly to obtain a polyvinylidene fluoride-hexafluoropropylene copolymer solution;

[0008] ii) Add sodium thioantimonate to the polyvinylidene fluoride-hexafluoropropylene copolymer solution obtained in step i), mix well, and obtain a sodium thioantimonate / polyvinylidene fluoride-hexafluoropropylene copolymer mixed suspension;

[0009] iii) Cast and dry the mixed suspension obtained in step ii) to obtain a solid electrolyte based on sodium thioantimonate.

[0010] A third aspect of the invention relates to the sodium thioantimonate-based solid electrolyte of the present invention and the application of the sodium thioantimonate-based solid electrolyte obtained by the preparation method according to the present invention in a secondary battery.

[0011] This invention involves a composite reaction of a polymer and sodium antimonothioate at room temperature, resulting in a uniform three-dimensional composite network structure formed between a polyvinylidene fluoride-hexafluoropropylene copolymer polymer matrix and inorganic sodium antimonothioate. In this structure, the inorganic sodium antimonothioate provides stable sodium ion channels while enhancing the mechanical strength and thermal stability of the polymer membrane. This composite network effectively inhibits the growth of sodium dendrites at the electrode / electrolyte interface, improves interfacial stability, and promotes sodium salt dissociation through interfacial interactions, thereby increasing the sodium ion transference number and overall ionic conductivity. The prepared composite membrane exhibits excellent membrane continuity, mechanical strength, and ion conductivity, providing a safe, stable, and long-cycle-life solid-state electrolyte solution for sodium-ion batteries. Attached Figure Description

[0012] Figure 1 This is a graph showing the constant current charge-discharge test data for Example 1.

[0013] Figure 2 This is a graph showing the constant current charge-discharge test data for Example 2.

[0014] Figure 3 This is a graph showing the constant current charge-discharge test data for Example 3.

[0015] Figure 4 This is a graph showing the constant current charge-discharge test data for Example 4.

[0016] Figure 5 The graph shows the ionic conductivity test data for Examples 1-4.

[0017] Figure 6 This is a graph showing the ion mobility number test data for Example 1.

[0018] Figure 7 This is a graph showing the ion mobility number test data for Example 2.

[0019] Figure 8 This is a graph showing the ion mobility number test data for Example 3.

[0020] Figure 9This is a graph showing the ion mobility number test data for Example 4. Detailed Implementation

[0021] The invention will be described in more detail below.

[0022] As used herein, the term “comprising” and its synonyms “including” and “containing” mean “including but not limited to”, and are not intended to exclude, for example, other additives, components, integers or steps.

[0023] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that the ranges 60-110 and 80-120 will also be understood.

[0024] Unless otherwise specified, all steps in this application may be performed sequentially, randomly, or simultaneously. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially, or steps (a) and (b) performed simultaneously. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0025] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0026] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0027] Unless otherwise specified, the operations mentioned in this application are performed at room temperature and normal pressure.

[0028] Unless otherwise specified, all concentrations and proportions mentioned in this application are based on weight.

[0029] Unless otherwise specified, the operations mentioned in this application can be performed in a manner known to those skilled in the art.

[0030] Unless otherwise specified, the equipment, apparatus, instruments, parts, materials, reagents, etc. mentioned in this application can be obtained by means known to those skilled in the art.

[0031] Unless otherwise specified, the parameters mentioned in this application, such as pore size, specific surface area, capacity retention, coulombic efficiency, and interfacial charge resistance, can be measured by means known to those skilled in the art.

[0032] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention.

[0033] product

[0034] According to one aspect of the present invention, a solid electrolyte based on sodium thioantimonate is provided, comprising sodium thioantimonate and polyvinylidene fluoride-hexafluoropropylene copolymer, wherein the sodium thioantimonate is dispersed in the polyvinylidene fluoride-hexafluoropropylene copolymer.

[0035] Unbound by any particular theory, the inventors unexpectedly discovered that in the sodium thioantimonate-based solid electrolyte of this invention, the polyvinylidene fluoride-hexafluoropropylene copolymer polymer matrix and sodium thioantimonate uniformly form a three-dimensional composite network structure. In this structure, sodium thioantimonate provides stable sodium ion channels. The formed three-dimensional composite network effectively inhibits the growth of sodium dendrites at the electrode / electrolyte interface, improves interface stability, and promotes sodium salt dissociation through interfacial interactions, thereby increasing the sodium ion transport number and overall ionic conductivity.

[0036] In particular, the inventors unexpectedly discovered that as the sodium thioantimonate content increases, the number of interfaces between the polyvinylidene fluoride-hexafluoropropylene copolymer and sodium thioantimonate increases. This is beneficial for improving the local coordination environment of sodium ions and forming a more continuous ion transport path, thereby improving the ionic conductivity and sodium ion transference number of the solid electrolyte. However, the sodium thioantimonate content is not always better the higher it is. When the sodium thioantimonate content is too high, the distance between inorganic particles decreases, making them prone to local enrichment or agglomeration. This leads to a reduction in the proportion of usable polymer / inorganic interfaces and may also disrupt the continuity of the polymer matrix, increasing the tortuosity of the ion transport path, thus decreasing the ion transport performance and interfacial stability of the solid electrolyte. Therefore, the inventors found that when the ratio of sodium thioantimonate to polyvinylidene fluoride-hexafluoropropylene copolymer is within a suitable range, it can form a sufficient number of interconnected polymer / inorganic interfaces while maintaining the continuity of the polymer matrix, thereby giving the solid electrolyte higher ionic conductivity, sodium ion transference number, and better battery cycle performance.

[0037] The polyvinylidene fluoride-hexafluoropropylene copolymer mentioned in this invention has a hexafluoropropylene unit content of 10-15% by mass, preferably about 12%, and a weight-average molecular weight of 300,000-500,000, preferably about 400,000. In one embodiment of this invention, the polyvinylidene fluoride-hexafluoropropylene copolymer can be a commercially available product, such as P875306 from Shanghai Maclean Biochemical Technology Co., Ltd.

[0038] In one embodiment, in the solid electrolyte of the present invention, the weight ratio of sodium thioantimonate to polyvinylidene fluoride-hexafluoropropylene copolymer is 1:(1~10), preferably 1:(2~10), more preferably 1:(2~6), and even more preferably 1:(3~5). This allows the sodium thioantimonate-based solid electrolyte of the present invention to provide good electrochemical performance, such as good ionic conductivity, sodium ion transference number, and good rate and cycle performance for the battery.

[0039] In one embodiment, in the solid electrolyte of the present invention, sodium thioantimonate comprises 5-45% by weight, preferably 5-35% by weight, more preferably 15-35% by weight, and even more preferably 15-25% by weight; and polyvinylidene fluoride-hexafluoropropylene copolymer comprises 55-95% by weight, preferably 65-95% by weight, more preferably 65-85% by weight, and even more preferably 75-85% by weight, based on the total weight of the solid electrolyte. Therefore, the sodium thioantimonate-based solid electrolyte of the present invention can benefit from providing good electrochemical performance, such as good ionic conductivity, sodium ion transport number, and good rate and cycle performance for the battery.

[0040] In one embodiment, the sodium thioantimonate-based solid electrolyte of the present invention is composed of sodium thioantimonate and polyvinylidene fluoride-hexafluoropropylene copolymer, wherein the sodium thioantimonate is dispersed in the polyvinylidene fluoride-hexafluoropropylene copolymer. Preferably, the weight ratio of sodium thioantimonate to polyvinylidene fluoride-hexafluoropropylene copolymer is 1:(1~10), more preferably 1:(2~10), more preferably 1:(2~6), and even more preferably 1:(3~5). Alternatively, the sodium thioantimonate is 5~45% by weight, preferably 5~35% by weight, more preferably 15~35% by weight, and even more preferably 15~25% by weight; the polyvinylidene fluoride-hexafluoropropylene copolymer is 55~95% by weight, preferably 65~95% by weight, more preferably 65~85% by weight, and even more preferably 75~85% by weight, based on the total weight of the solid electrolyte. Therefore, the sodium thioantimonate-based solid electrolyte of the present invention can provide good electrochemical performance, such as good ionic conductivity, sodium ion transference number, and good rate and cycle performance for the battery.

[0041] In one embodiment, the thickness of the solid electrolyte of the present invention is 0.05~0.35 mm, more preferably 0.15~0.25 mm. This allows the sodium thioantimonate-based solid electrolyte of the present invention to provide good electrochemical performance, such as good ionic conductivity, sodium ion transference number, and good rate and cycle performance for the battery.

[0042] Preparation method

[0043] According to another aspect of the present invention, the present invention provides a method for preparing the sodium thioantimonate-based solid electrolyte of the present invention, comprising the following steps: i) adding polyvinylidene fluoride-hexafluoropropylene copolymer to an organic solvent and mixing evenly to obtain a polyvinylidene fluoride-hexafluoropropylene copolymer solution; ii) adding sodium thioantimonate to the polyvinylidene fluoride-hexafluoropropylene copolymer solution obtained in step i) and mixing evenly to obtain a sodium thioantimonate / polyvinylidene fluoride-hexafluoropropylene copolymer mixed suspension; iii) casting and drying the mixed suspension obtained in step ii) to obtain a sodium thioantimonate-based solid electrolyte.

[0044] The polyvinylidene fluoride-hexafluoropropylene copolymer mentioned in the preparation method of this invention is as described above.

[0045] In one embodiment, in the preparation method of the present invention, the weight ratio of sodium thioantimonate to polyvinylidene fluoride-hexafluoropropylene copolymer is 1:(1~10), preferably 1:(2~10), more preferably 1:(2~6), and even more preferably 1:(3~5). This allows the sodium thioantimonate-based solid electrolyte of the present invention to provide good electrochemical performance, such as good ionic conductivity, sodium ion transference number, and good rate and cycle performance for the battery.

[0046] In the preparation method of the present invention, considering that the organic solvent is completely evaporated after drying after casting, leaving only sodium thioantimonate and polyvinylidene fluoride-hexafluoropropylene copolymer, it can be considered that the weight ratio of sodium thioantimonate to polyvinylidene fluoride-hexafluoropropylene copolymer used in the preparation process is the same as the weight ratio of sodium thioantimonate to polyvinylidene fluoride-hexafluoropropylene copolymer in the finished product.

[0047] The term "casting" in the preparation method of this invention refers to pouring the sodium thioantimonate / polyvinylidene fluoride-hexafluoropropylene copolymer mixed suspension obtained in step ii) into a mold or container (e.g., a polytetrafluoroethylene mold or a polytetrafluoroethylene dish), so that the mixed suspension is evenly spread at the bottom of the mold or container. In the preparation method of this invention, the thickness of the obtained solid electrolyte is adjusted by controlling the amount of mixed suspension added and the casting area, followed by drying to form a film. In one embodiment, in the preparation method of this invention, a sodium thioantimonate-based solid electrolyte with a thickness of 0.05~0.35 mm, more preferably 0.15~0.25 mm, is obtained in step iii). This allows the sodium thioantimonate-based solid electrolyte of this invention to provide good electrochemical performance, such as good ionic conductivity, sodium ion transport number, and good rate and cycle performance for the battery.

[0048] In the preparation method of the present invention, the organic solvent can be any solvent known to those skilled in the art for providing a liquid matrix for film formation. In one embodiment, the organic solvent in the preparation method of the present invention can be selected from N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), acetone, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), and combinations thereof. In a preferred embodiment, the organic solvent is selected from N-methylpyrrolidone, tetrahydrofuran, and combinations thereof, preferably a combination of N-methylpyrrolidone and tetrahydrofuran, and the volume ratio of N-methylpyrrolidone to tetrahydrofuran is 1:1. Therefore, the sodium thioantimonate-based solid electrolyte of the present invention can provide good electrochemical performance, such as good ionic conductivity, sodium ion transport number, and good rate and cycle performance for the battery.

[0049] In the preparation method of the present invention, the drying in step iii) can be a drying method known to those skilled in the art, particularly a drying method that facilitates the evaporation of organic solvents. In one embodiment, in the preparation method of the present invention, the drying in step iii) is vacuum drying at 40~70°C, preferably 40~60°C, and at -0.04 to -0.12 MPa for 48~72 hours, preferably 55~65 hours. This allows the sodium thioantimonate-based solid electrolyte of the present invention to provide good electrochemical performance, such as good ionic conductivity, sodium ion transference number, and good rate and cycle performance for the battery.

[0050] application

[0051] In another aspect, the present invention also provides the application of the sodium thioantimonate-based solid electrolyte of the present invention and the sodium thioantimonate-based solid electrolyte obtained by the preparation method according to the present invention in secondary batteries, especially in sodium battery secondary batteries.

[0052] The term "secondary battery" used in this invention refers to a chemical power source that achieves the interconversion of electrical energy and chemical energy through a reversible electrochemical reaction, capable of repeated charge-discharge cycles; it is also known as a storage battery. Its essential difference from a primary battery is that after discharge, the active materials at the positive and negative electrodes can be regenerated by applying an external reverse current, restoring its power supply capability.

[0053] Example

[0054] Preparation of solid electrolytes based on sodium thioantimonate

[0055] Example 1

[0056] Step 1: Add 0.60g of polyvinylidene fluoride-hexafluoropropylene copolymer (P875306 from Shanghai Maclean Biochemical Technology Co., Ltd., with a hexafluoropropylene unit mass ratio of 12% and a weight average molecular weight of 400,000) to a mixed solvent of 10ml of tetrahydrofuran and N-methylpyrrolidone, wherein the volume ratio of tetrahydrofuran to N-methylpyrrolidone is 1:1. Stir at 70℃ to obtain a homogeneous polyvinylidene fluoride-hexafluoropropylene copolymer solution.

[0057] Step 2: Add 0.067g of sodium thioantimonate powder (wherein, the weight fraction of sodium thioantimonate powder in the obtained solid product, i.e., the solid electrolyte based on sodium thioantimonate, is 10wt%, based on the total weight of the solid electrolyte based on sodium thioantimonate) to the polyvinylidene fluoride-hexafluoropropylene copolymer solution obtained in Step 1, and stir thoroughly at room temperature to obtain a homogeneous sodium thioantimonate / polyvinylidene fluoride-hexafluoropropylene copolymer mixed suspension.

[0058] Step 3: Cast the mixed suspension obtained in Step 2 into a polytetrafluoroethylene mold (the mold casting area is approximately 30 cm²). 2 The solution was then placed in a vacuum oven and dried at 50°C and -0.08 MPa for 60 hours to allow the organic solvent to evaporate completely, resulting in a solid electrolyte that is a self-supporting composite membrane with a thickness of approximately 0.20 mm.

[0059] Example 2

[0060] Step 1: Add 0.60g of polyvinylidene fluoride-hexafluoropropylene copolymer (P875306 from Shanghai Maclean Biochemical Technology Co., Ltd., with a hexafluoropropylene unit mass ratio of 12% and a weight average molecular weight of 400,000) to a mixed solvent of 10ml of tetrahydrofuran and N-methylpyrrolidone, wherein the volume ratio of tetrahydrofuran to N-methylpyrrolidone is 1:1. Stir at 70℃ to obtain a homogeneous polyvinylidene fluoride-hexafluoropropylene copolymer solution.

[0061] Step 2: Add 0.15g of sodium thioantimonate powder (wherein, the weight fraction of sodium thioantimonate powder in the obtained solid product, i.e., the solid electrolyte based on sodium thioantimonate, is 20wt%, based on the total weight of the solid electrolyte based on sodium thioantimonate) to the polyvinylidene fluoride-hexafluoropropylene copolymer solution obtained in Step 1, and stir thoroughly at room temperature to obtain a homogeneous sodium thioantimonate / polyvinylidene fluoride-hexafluoropropylene copolymer mixed suspension.

[0062] Step 3: Cast the mixed suspension obtained in Step 2 into a polytetrafluoroethylene mold (the mold casting area is approximately 30 cm²). 2 The organic solvent was then placed in a vacuum oven and dried at 50°C and -0.08 MPa for 60 hours to completely evaporate, resulting in a solid electrolyte that is a self-supporting composite membrane with a thickness of approximately 0.20 mm.

[0063] Example 3

[0064] Step 1: Add 0.60g of polyvinylidene fluoride-hexafluoropropylene copolymer (P875306 from Shanghai Maclean Biochemical Technology Co., Ltd., with a hexafluoropropylene unit mass ratio of 12% and a weight average molecular weight of 400,000) to a mixed solvent of 10ml of tetrahydrofuran and N-methylpyrrolidone, wherein the volume ratio of tetrahydrofuran to N-methylpyrrolidone is 1:1. Stir at 70℃ to obtain a homogeneous polyvinylidene fluoride-hexafluoropropylene copolymer solution.

[0065] Step 2: Add 0.258g of sodium thioantimonate powder (wherein, the weight fraction of sodium thioantimonate powder in the obtained solid product, i.e., the solid electrolyte based on sodium thioantimonate, is 30wt%, based on the total weight of the solid electrolyte based on sodium thioantimonate) to the polyvinylidene fluoride-hexafluoropropylene copolymer solution obtained in Step 1, and stir thoroughly at room temperature to obtain a homogeneous sodium thioantimonate / polyvinylidene fluoride-hexafluoropropylene copolymer mixed suspension.

[0066] Step 3: Cast the mixed suspension obtained in Step 2 into a polytetrafluoroethylene mold (the mold casting area is approximately 30 cm²). 2The organic solvent was then placed in a vacuum oven and dried at 50°C and -0.08 MPa for 60 hours to completely evaporate, resulting in a solid electrolyte that is a self-supporting composite membrane with a thickness of approximately 0.23 mm.

[0067] Example 4

[0068] Step 1: Add 0.60g of polyvinylidene fluoride-hexafluoropropylene copolymer (P875306 from Shanghai Maclean Biochemical Technology Co., Ltd., with a hexafluoropropylene unit mass ratio of 12% and a weight average molecular weight of 400,000) to a mixed solvent of 10ml of tetrahydrofuran and N-methylpyrrolidone, wherein the volume ratio of tetrahydrofuran to N-methylpyrrolidone is 1:1. Stir at 70℃ to obtain a homogeneous polyvinylidene fluoride-hexafluoropropylene copolymer solution.

[0069] Step 2: Add 0.40 g of sodium thioantimonate powder (wherein, the weight fraction of sodium thioantimonate powder in the obtained solid product, i.e., the solid electrolyte based on sodium thioantimonate, is 40 wt%, based on the total weight of the solid electrolyte based on sodium thioantimonate) to the polyvinylidene fluoride-hexafluoropropylene copolymer solution obtained in Step 1, and stir thoroughly at room temperature to obtain a homogeneous sodium thioantimonate / polyvinylidene fluoride-hexafluoropropylene copolymer mixed suspension.

[0070] Step 3: Cast the mixed suspension obtained in Step 2 into a polytetrafluoroethylene mold (the mold casting area is approximately 30 cm²). 2 The mixture was then placed in a vacuum oven and dried at 50°C and -0.08 MPa for 60 hours to completely evaporate the organic solvent, resulting in a solid electrolyte that is a self-supporting composite membrane with a thickness of approximately 0.26 mm.

[0071] test

[0072] Test 1: Constant Current Charge and Discharge Test

[0073] Testing equipment: LAND battery testing system

[0074] Test batteries: The sodium thioantimonate-based solid electrolytes prepared in Examples 1-4 were assembled with sodium metal anodes and commercial sodium vanadium phosphate cathodes to form the test batteries of Examples 1-4 (CR2032 type batteries). The structure was sodium anode / solid electrolyte membrane based on sodium thioantimonate / sodium vanadium phosphate cathode, for subsequent testing.

[0075] Test conditions: At room temperature, charge / discharge voltage range of 2~3.8V. Initial charge / discharge at 59mA g. -1 Activation was performed at a current density of 118 mA g, and cycle performance was tested at 118 mA g. -1The experiment was conducted at current density.

[0076] Test in Example 1

[0077] The test battery of Example 1 was tested. The test results are shown below. Figure 1 .

[0078] Depend on Figure 1 It can be seen that the sodium-ion secondary battery assembled based on the sodium thioantimonate solid electrolyte prepared in Example 1 has a capacity retention of 84.8% and a coulombic efficiency of 99.59% after 100 cycles.

[0079] Test in Example 2

[0080] The test battery of Example 2 was tested. The test results are shown below. Figure 2 .

[0081] Depend on Figure 2 It can be seen that the sodium-ion secondary battery assembled based on the sodium thioantimonate solid electrolyte prepared in Example 2 has a capacity retention of 90.5% and a coulombic efficiency of 99.82% after 100 cycles.

[0082] Test in Example 3

[0083] The test battery of Example 3 was tested. The test results are shown below. Figure 3 .

[0084] Depend on Figure 3 It can be seen that the sodium-ion secondary battery assembled based on the sodium antimony thioate solid electrolyte prepared in Example 3 has a capacity retention of 85.6% and a coulombic efficiency of 99.77% after 100 cycles.

[0085] Test in Example 4

[0086] The test battery of Example 4 was tested. The test results are shown below. Figure 4 .

[0087] Depend on Figure 4 It can be seen that the sodium-ion secondary battery assembled based on the sodium antimony thioate solid electrolyte prepared in Example 4 has a capacity retention of 73.1% and a coulombic efficiency of 99.21% after 100 cycles.

[0088] Test 2: Ionic Conductivity Test

[0089] Testing apparatus: Electrochemical workstation

[0090] Test cells: The sodium thioantimonate-based solid electrolytes prepared in Examples 1-4 were placed between two stainless steel barrier electrodes to assemble the test cells of Examples 1-4 (CR2032 type cells), with the structure of stainless steel / solid electrolyte membrane based on sodium thioantimonate / stainless steel.

[0091] Test conditions: AC impedance test was conducted at room temperature, with a test frequency range of 0.01Hz to 1MHz and an AC disturbance voltage of 10mV.

[0092] The ionic conductivity of a solid electrolyte membrane is calculated using the following formula:

[0093]

[0094] Where σ is the ionic conductivity, L is the thickness of the solid electrolyte film, and R... b The bulk resistance is obtained from the AC impedance spectrum, and A is the effective contact area between the solid electrolyte membrane and the stainless steel electrode.

[0095] Test in Example 1

[0096] The test battery of Example 1 was tested. The test results are shown below. Figure 5 (The results are presented as data from Experiment Example 1).

[0097] The bulk resistance of the solid electrolyte membrane was obtained based on AC impedance spectroscopy. Combined with the membrane thickness and effective contact area, calculations were performed to determine that the ionic conductivity of the sodium antimony thioate composite solid electrolyte membrane prepared in Example 1 was 1.306 mS / cm at room temperature. -1 .

[0098] Test in Example 2

[0099] The test battery of Example 2 was tested. The test results are shown below. Figure 5 (The results are presented as data from Experiment Example 2).

[0100] The bulk resistance of the solid electrolyte membrane was obtained based on AC impedance spectroscopy. Combined with the membrane thickness and effective contact area, calculations were performed to determine that the ionic conductivity of the sodium antimony thioate composite solid electrolyte membrane prepared in Example 1 was 1.357 mS / cm at room temperature. -1 .

[0101] Test in Example 3

[0102] The test battery of Example 3 was tested. The test results are shown below. Figure 5 (The results are presented as data from Experiment Example 3).

[0103] The bulk resistance of the solid electrolyte membrane was obtained from the AC impedance spectroscopy, and calculated based on the thickness and effective contact area of ​​the solid electrolyte membrane. The ionic conductivity of the sodium antimony thioate composite solid electrolyte membrane prepared in Example 1 was found to be 1.330 mS / cm at room temperature. -1 .

[0104] Test in Example 4

[0105] The test battery of Example 4 was tested. The test results are shown below. Figure 5 (The results are presented as data from Experiment Example 4).

[0106] The bulk resistance of the solid electrolyte membrane was obtained based on AC impedance spectroscopy. Combined with the membrane thickness and effective contact area, calculations were performed to determine that the ionic conductivity of the sodium antimony thioate composite solid electrolyte membrane prepared in Example 1 was 1.287 mS / cm at room temperature. -1 .

[0107] Test 3: Sodium ion transport number test

[0108] Testing apparatus: Electrochemical workstation

[0109] Test cells: The solid electrolytes based on sodium thioantimonate prepared in Examples 1-4 were placed between two sodium metal electrodes to assemble the test cells of Examples 1-4 (CR2032 type cells), with the structure of sodium metal / solid electrolyte membrane based on sodium thioantimonate / sodium metal.

[0110] Test conditions: The sodium ion transport number of the composite solid electrolyte membrane was determined using DC polarization combined with AC impedance spectroscopy. First, the test cell was subjected to AC impedance spectroscopy at a frequency range of 0.01 Hz to 1 MHz, with an AC disturbance voltage of 10 mV. The interfacial resistance R0 before polarization was obtained from the AC impedance spectrum. Subsequently, a constant DC bias of 10 mV was applied to the test cell at room temperature, and the change in current over time was recorded to obtain the time-current polarization curve. The initial current I0 and steady-state current I0 were then obtained from the time-current polarization curve. s After the polarization current reaches a stable state, the AC impedance of the test cell is tested again, and the interface resistance R after polarization is obtained from the AC impedance spectrum after polarization. s .

[0111] The sodium ion transport number is calculated using the following formula:

[0112]

[0113] Among them, t Na⁺ The sodium ion transport number is given, ΔV is the DC polarization voltage, and I0 and I... sThese are the initial current and steady-state current, respectively, R0 and R... s These are the interface resistances before and after polarization, respectively.

[0114] Test in Example 1

[0115] Sodium ion transport number tests were performed on the test battery of Example 1. The AC impedance spectra and time-current polarization curves before and after polarization are shown in the figure. Figure 6 .

[0116] The initial current I0 was obtained from the time-current polarization curve as 4.43 μA, and the steady-state current I... s The value is 3.76 μA; the interface resistance R0 before polarization is 2101 Ω, obtained from the AC impedance spectra before and after polarization, and the interface resistance R after polarization is 3.76 μA. s It is 2394Ω.

[0117] According to the formula above, the sodium ion transference number of the composite solid electrolyte membrane prepared in Example 1 is 0.5887.

[0118] Test in Example 2

[0119] Sodium ion transference number tests were performed on the test battery of Example 2. The AC impedance spectra and time-current polarization curves before and after polarization are shown in the figure. Figure 7 .

[0120] The initial current I0 was obtained from the time-current polarization curve as 8.17 μA, and the steady-state current I... s The value is 5.96 μA; the interface resistance R0 before polarization is 221 Ω, obtained from the AC impedance spectra before and after polarization, and the interface resistance R after polarization is 5.96 μA. s It is 295Ω.

[0121] According to the formula above, the sodium ion transference number of the composite solid electrolyte membrane prepared in Example 2 is 0.7249.

[0122] Test in Example 3

[0123] Sodium ion transference number tests were performed on the test battery of Example 3. The AC impedance spectra and time-current polarization curves before and after polarization are shown in the figure. Figure 8 .

[0124] The initial current I0 was obtained from the time-current polarization curve as 21.14 μA, and the steady-state current I... s The value is 11.70 μA; the interface resistance R0 before polarization is 267 Ω, obtained from the AC impedance spectra before and after polarization, and the interface resistance R after polarization is 11.70 μA. s It is 511Ω.

[0125] According to the formula above, the sodium ion transference number of the composite solid electrolyte membrane prepared in Example 3 is 0.5995.

[0126] Test in Example 4

[0127] Sodium ion transport number tests were performed on the test battery of Example 4. The AC impedance spectra and time-current polarization curves before and after polarization are shown in the figure. Figure 9 .

[0128] The initial current I0 was obtained from the time-current polarization curve as 29.25 μA, and the steady-state current I... s The value is 15.90 μA; the interface resistance R0 before polarization is 49 Ω, obtained from the AC impedance spectra before and after polarization, and the interface resistance R after polarization is 15.90 μA. s It is 91Ω.

[0129] According to the formula above, the sodium ion transference number of the composite solid electrolyte membrane prepared in Example 4 is 0.5426.

[0130] The parameters and performance data of Examples 1-4 are summarized in Table 1 below.

[0131] Table 1: Parameters and performance data of Examples 1-4

[0132] Parameters and performance Example 1 Example 2 Example 3 Example 4 Sodium thioantimonate content (by weight %) 10 20 30 40 Polyvinylidene fluoride-hexafluoropropylene copolymer content (wt%) 90 80 70 60 Sodium antimonate thioate: polyvinylidene fluoride-hexafluoropropylene copolymer (by weight) 1:9 1:4 1:2.33 1:1.5 Corresponding battery capacity retention rate (%) 84.8 90.5 85.6 73.1 Corresponding battery coulombic efficiency (%) 99.59 99.82 99.77 99.21 <![CDATA[Ionic conductivity (mS / cm -1) > 1.306 1.357 1.330 1.287 Sodium ion transport number 0.5887 0.7249 0.5995 0.5426

[0133] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A solid electrolyte based on sodium antimonothioate, comprising sodium antimonothioate and polyvinylidene fluoride-hexafluoropropylene copolymer, wherein, Sodium thioantimonate is dispersed in polyvinylidene fluoride-hexafluoropropylene copolymer.

2. The solid electrolyte according to claim 1, wherein, The weight ratio of sodium thioantimonate to polyvinylidene fluoride-hexafluoropropylene copolymer is 1:(1~10), preferably 1:(2~10), more preferably 1:(2~6), and even more preferably 1:(3~5).

3. The solid electrolyte according to claim 1, wherein, Sodium thioantimonate is 5-45% by weight, preferably 5-35% by weight, more preferably 15-35% by weight, and even more preferably 15-25% by weight; polyvinylidene fluoride-hexafluoropropylene copolymer is 55-95% by weight, preferably 65-95% by weight, more preferably 65-85% by weight, and even more preferably 75-85% by weight, based on the total weight of the solid electrolyte.

4. The solid electrolyte according to any one of claims 1 to 3, wherein the thickness is 0.05 to 0.35 mm, more preferably 0.15 to 0.25 mm.

5. A method for preparing the sodium thioantimonate-based solid electrolyte according to claims 1 to 4, comprising the following steps: i) Add polyvinylidene fluoride-hexafluoropropylene copolymer to an organic solvent and mix thoroughly to obtain a polyvinylidene fluoride-hexafluoropropylene copolymer solution; ii) Add sodium thioantimonate to the polyvinylidene fluoride-hexafluoropropylene copolymer solution obtained in step i), mix well, and obtain a sodium thioantimonate / polyvinylidene fluoride-hexafluoropropylene copolymer mixed suspension; iii) Cast and dry the mixed suspension obtained in step ii) to obtain a solid electrolyte based on sodium thioantimonate.

6. The method according to claim 5, wherein the weight ratio of sodium thioantimonate to polyvinylidene fluoride-hexafluoropropylene copolymer is 1:(1~10), preferably 1:(2~10), more preferably 1:(2~6), and even more preferably 1:(3~5).

7. The method according to claim 5 or 6, wherein, In step iii), a solid electrolyte based on sodium thioantimonate with a thickness of 0.05 to 0.35 mm, more preferably 0.15 to 0.25 mm, is obtained.

8. The method according to claim 5 or 6, wherein, The organic solvent is selected from N-methylpyrrolidone, tetrahydrofuran, and combinations thereof; preferably, the organic solvent is a combination of N-methylpyrrolidone and tetrahydrofuran, and the volume ratio of N-methylpyrrolidone to tetrahydrofuran is 1:

1.

9. The method according to claim 5 or 6, wherein, The drying process is performed at 40~70℃, preferably 40~60℃, and under vacuum at -0.04 to -0.12MPa for 48~72 hours, preferably 55~65 hours.

10. The application of the sodium thioantimonate-based solid electrolyte according to any one of claims 1-4 and the sodium thioantimonate-based solid electrolyte obtained by the method according to any one of claims 5-9 in a secondary battery.

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