A solid electrolyte membrane and a preparation method thereof

Abstract

A solid electrolyte membrane and a preparation method thereof belong to the technical field of secondary batteries. The solid electrolyte membrane includes: a skeleton and a solid electrolyte. The material of the skeleton is a natural material. The skeleton is provided with through holes, and the average diameter of the through holes is 30 nm to 50 nm. The solid electrolyte is filled in the through holes of the skeleton. By using a natural material as the skeleton material, the solid electrolyte membrane has good environmental friendliness. And filling the solid electrolyte in the skeleton material enables it to be used as the solid electrolyte membrane of a solid-state battery, effectively improving the energy density of the battery. At the same time, the skeleton material can effectively resist the puncture of lithium dendrites, reducing the possibility of generating short-circuit points and effectively improving the safety performance of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and more particularly, to a solid electrolyte membrane and a preparation method thereof. Background Art

[0002] As one of the key components of a lithium-ion battery, the electrolyte is closely related to the electrochemical performance of the battery, such as cycle life, safety, and capacity. Currently, the most widely used electrolyte in the market is mainly an organic liquid electrolyte, but it is prone to problems such as leakage, combustion, and explosion of organic solvents, posing a great safety hazard. Using a non-flammable solid electrolyte to replace the organic liquid electrolyte is one of the main ways to solve the safety performance of lithium-ion batteries. However, the current solid electrolyte membranes are usually obtained by chemical engineering preparation methods, and their environmental friendliness is poor. Summary of the Invention

[0003] The present application provides a solid electrolyte membrane and a preparation method thereof, which use natural materials as the constituent materials of the solid electrolyte membrane, having good environmental friendliness.

[0004] In a first aspect, an embodiment of the present application provides a solid electrolyte membrane, which includes:

[0005] A skeleton, the material of the skeleton being a natural material, the skeleton being provided with through holes, and the average diameter of the through holes being 30 nm to 50 nm;

[0006] A solid electrolyte, the solid electrolyte being filled in the through holes of the skeleton.

[0007] In the above implementation process, by using natural materials as the skeleton material, the solid electrolyte membrane has good environmental friendliness. And filling the solid electrolyte in the skeleton material can be applied as the solid electrolyte membrane of a solid-state battery, effectively improving the energy density of the battery. At the same time, the skeleton material can effectively resist the puncture of lithium dendrites, reducing the possibility of generating short-circuit points and effectively improving the safety performance of the battery.

[0008] As an optional implementation manner, the natural material is a natural fiber material;

[0009] Preferably, the natural fiber material is lignocellulose.

[0010] In the above implementation process, when the natural fiber material is used as the skeleton, it can relatively easily form relatively suitable through holes to fill the solid electrolyte. And lignocellulose can be obtained relatively easily, which is beneficial to the large-scale preparation of the solid electrolyte membrane.

[0011] As an optional implementation manner, the fiber length of the natural fiber material is 3 mm to 5 mm; and / or

[0012] The average diameter of the through holes is 35 nm to 45 nm; and / or

[0013] The thickness of the framework is 20 μm to 1 mm.

[0014] In the above implementation process, by controlling the fiber length, through hole diameter and thickness of the framework material, etc., it is beneficial to the safety and energy density of the battery, and also beneficial to the battery to pursue thinness and lightness.

[0015] As an alternative implementation manner, the mass ratio of the framework to the solid electrolyte is 1:(1.1 - 1.2); and / or

[0016] The electrolyte residue amount on the surface of the solid electrolyte membrane ≤ 0.7 g / m 2 .

[0017] In the above implementation process, by controlling the mass ratio of the framework to the solid electrolyte within a certain range, it is beneficial for the solid electrolyte to completely fill the through holes of the entire framework, and thus beneficial to the energy density and ion conduction. By controlling the electrolyte residue amount on the surface of the solid electrolyte membrane, it is beneficial to the apparent quality of the product, and also beneficial to its cooperation with other components during battery assembly.

[0018] As an alternative implementation manner, the solid electrolyte includes a lithium salt, a dispersant and a binder; and / or

[0019] The mass ratio of the lithium salt, the dispersant and the binder is (2 - 3):1:(0.5 - 1); and / or

[0020] The lithium salt includes at least one of lithium chloride, lithium carbonate, lithium sulfate and lithium hexafluorophosphate; and / or

[0021] The dispersant includes PVA; and / or

[0022] The binder includes at least one of methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate and octyl acrylate.

[0023] In the above implementation process, by controlling the mass ratio of the salt, the dispersant and the binder, it is beneficial for the solid electrolyte slurry to have a better viscosity during the preparation process, beneficial for the retention effect of the solid electrolyte slurry in the framework, and also beneficial for maintaining a more appropriate lithium ion concentration in the solid electrolyte, and beneficial for the ion conduction ability of the solid electrolyte membrane.

[0024] Second, the embodiments of the present application also provide a method for preparing a solid electrolyte membrane, and the method includes:

[0025] A skeleton is obtained. The material of the skeleton is a natural material, and the skeleton is provided with through holes;

[0026] The skeleton is immersed in an electrolyte paste so that the electrolyte paste fills the through holes of the skeleton, and a semi-finished product is obtained;

[0027] The semi-finished product is dried so that the electrolyte paste is transformed into a solid electrolyte, and a solid electrolyte membrane is obtained.

[0028] In the above implementation process, by using a natural material as the skeleton material, the solid electrolyte membrane has good environmental friendliness. And filling the solid electrolyte in the skeleton material enables it to be used as the solid electrolyte membrane of a solid-state battery, effectively improving the energy density of the battery. At the same time, the skeleton material can effectively resist the puncture of lithium dendrites, reducing the possibility of generating short-circuit points and effectively improving the safety performance of the battery.

[0029] As an alternative implementation, the obtaining of the skeleton includes:

[0030] Lignin is removed from natural wood chips, and then freeze-drying is carried out to obtain a skeleton.

[0031] In the above implementation process, by using the method of freeze-drying for drying, it is beneficial to the structural integrity of the skeleton material and also beneficial to reducing the possibility of the skeleton deforming.

[0032] As an alternative implementation, the temperature of the freeze-drying is -60°C to -40°C; and / or

[0033] The pressure of the freeze-drying is -50 Pa to -100 Pa.

[0034] In the above implementation process, by controlling the process parameters of the freeze-drying, it is more beneficial to the structural integrity of the skeleton material.

[0035] As an alternative implementation, the method of removing lignin is soaking with a removing solution; and / or

[0036] The molar concentration of the removing solution is 0.1 mol / L to 1.7 mol / L; and / or

[0037] The removing solution includes at least one of hypochlorite and chlorite.

[0038] In the above implementation process, by controlling the concentration of the removing solution, it is beneficial to the removal effect of other substances in the wood, and at the same time, it is beneficial to maintaining the lignocellulose structure in the wood.

[0039] As an alternative implementation, the natural wood chips are pine wood, birch wood or balsa wood; and / or

[0040] The thickness of the natural wood chips is 25 μm to 2 mm.

[0041] As an alternative embodiment, before the drying, the method further includes:

[0042] scraping the surface of the semi-finished product; and / or

[0043] The end timing of the scraping treatment is that the residual amount of the electrolyte paste on the skeleton surface of the semi-finished product ≤ 1.5 g / m 2 .

[0044] As an alternative embodiment, the drying temperature is 60°C to 90°C; and / or

[0045] The drying time is 1 h to 3 h. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0047] Figure 1 Scanning electron microscope image of the solid electrolyte membrane provided by the embodiment of the present application;

[0048] Figure 2 Flow schematic diagram of the method provided by the embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] The following will describe the implementation schemes of the present application in detail in combination with the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0050] Current solid electrolyte membranes are usually obtained by chemical engineering methods, and their environmental friendliness is poor. Some people have proposed to jointly prepare a separator from lignocellulose, binder, stabilizer, etc. and apply it to a battery with a liquid electrolyte, which can improve the wetting effect of the separator on the electrolyte, but the energy density of this battery still needs to be improved. Some people have also proposed to use lignocellulose as a slurry to coat at least one side of a polymer-based membrane to form a composite membrane, which can be applied to solid-state batteries and improve the energy density of the batteries. However, during the charge and discharge process of the battery, due to the insufficient or unsmooth transfer of ions, lithium dendrites will form on the polymer-based membrane in the coating composed of lignocellulose, and the lithium dendrites will pierce through the composite membrane to form short-circuit points, thus triggering battery safety problems.

[0051] Therefore, the present application intends to provide a solid electrolyte membrane with environmental friendliness, while also taking into account energy density and safety. It uses the environmentally friendly natural material lignocellulose as the framework material and fills the through-holes in it with a solid electrolyte.

[0052] Figure 1 It is the cross-sectional scanning electron microscope image of the solid electrolyte membrane provided by the embodiment of the present application, as Figure 1 shown, the embodiment of the present application provides a solid electrolyte membrane, the solid electrolyte membrane includes: a framework and a solid electrolyte. The material of the framework is a natural material, the framework is provided with through-holes, and the average diameter of the through-holes is 30 nm to 50 nm. The solid electrolyte is filled in the through-holes of the framework.

[0053] In some embodiments, the natural material is a natural fiber material. Preferably, the natural fiber material is lignocellulose. When the natural fiber material is used as the framework, it can relatively easily form more suitable through-holes to fill the solid electrolyte. And lignocellulose can be obtained relatively easily, which is beneficial to the large-scale preparation of the solid electrolyte membrane.

[0054] In some embodiments, the fiber length of the natural fiber material is 3 mm to 5 mm; the average diameter of the through-holes is 35 nm to 45 nm; the thickness of the framework is 20 μm to 1 mm. By controlling the fiber length, through-hole diameter and thickness of the framework material, etc., it is beneficial to the safety and energy density of the battery, and it is also beneficial for the battery to pursue thinness and lightness.

[0055] Exemplarily, the fiber length of the natural fiber material can be 3 mm, 3.2 mm, 3.4 mm, 3.6 mm, 3.8 mm, 4 mm, 4.2 mm, 4.4 mm, 4.6 mm, 4.8 mm, 5 mm, etc., and it can also be any value within the range of 3 mm to 5 mm. The average diameter of the through holes can be 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 47 nm, 48 nm, 49 nm, 50 nm, etc., and it can be any value within the range of 30 nm to 50 nm. The thickness of the skeleton can be 0.02 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, etc., and it can also be any value within the range of 20 μm to 1 mm.

[0056] In some embodiments, the mass ratio of the skeleton to the solid electrolyte is 1:(1.1 - 1.2). By controlling the mass ratio of the skeleton to the solid electrolyte within a certain range, it is beneficial for the solid electrolyte to completely fill the through holes of the entire skeleton, and thus beneficial for the energy density and ion conduction.

[0057] Exemplarily, the mass ratio of the skeleton to the solid electrolyte can be 1:1.1, 1:1.11, 1:1.12, 1:1.13, 1:1.14, 1:1.15, 1:1.16, 1:1.17, 1:1.18, 1:1.19, 1:1.2, etc., and it can also be any value within the range of 1:(1.1 - 1.2).

[0058] In some embodiments, the electrolyte residue amount on the surface of the solid electrolyte membrane ≤ 0.7 g / m 2 . By controlling the electrolyte residue amount on the surface of the solid electrolyte membrane, it is beneficial for the apparent quality of the product, and at the same time, it is also beneficial for its cooperation with other components during battery assembly, thereby achieving better battery cycle performance.

[0059] In some embodiments, the solid electrolyte includes a lithium salt, a dispersant, and a binder. Further, the mass ratio of the lithium salt, the dispersant, and the binder is (2-3):1:(0.5-1). By controlling the mass ratio of the salt, the dispersant, and the binder, it is beneficial for the solid electrolyte slurry to have a good viscosity during the preparation process, which is conducive to the retention effect of the solid electrolyte slurry in the skeleton. At the same time, it is also beneficial to maintain a suitable lithium ion concentration in the solid electrolyte, which is conducive to the ion conduction ability of the solid electrolyte membrane. Among them, the lithium salt can be selected from at least one of lithium chloride, lithium carbonate, lithium sulfate, and lithium hexafluorophosphate. The dispersant can be selected from PVA, for example, it can be a mixture of PVA and a lithium salt (the mass content of PVA is 1%-5%). The binder can be selected from at least one of methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, and octyl acrylate.

[0060] Exemplarily, the mass ratio of the lithium salt, the dispersant, and the binder can be 2:1:0.5, 2.5:1:0.5, 3:1:0.5, 2:1:0.7, 2.5:1:0.7, 3:1:0.7, 2:1:1, 2.5:1:1, or 3:1:1, etc. It can also be any value within the range of (2-3):1:(0.5-1).

[0061] By using natural materials as the skeleton material for the battery, the solid electrolyte membrane has good environmental friendliness. And by filling the solid electrolyte in the skeleton material, it can be used as the solid electrolyte membrane of a solid-state battery, effectively improving the energy density of the battery. At the same time, the skeleton material can effectively resist the puncture of lithium dendrites, reducing the possibility of generating short-circuit points and effectively improving the safety performance of the battery.

[0062] Figure 2 Schematic flow diagram of the method provided by the embodiments of the present application, as Figure 2 shown, the embodiments of the present application provide a method for preparing a solid electrolyte membrane, the method includes:

[0063] S1. Obtain a skeleton, the material of the skeleton is a natural material, and the skeleton is provided with through holes;

[0064] In some embodiments, obtaining the skeleton includes: removing lignin from natural wood chips and then performing freeze-drying to obtain the skeleton. By using the freeze-drying method for drying, it is beneficial to the structural integrity of the skeleton material and also beneficial to reducing the possibility of the skeleton deforming.

[0065] Specifically, in this embodiment, the preparation process of the framework can be as follows: slice natural wood into pieces with a certain thickness (it can be sliced longitudinally or transversely), immerse the sliced wood with a certain thickness into the lignin removal solution, and then wash the sliced wood after removing cellulose; freeze-dry the washed sliced wood to obtain the framework. The washing process can be as follows: under the condition of ultrasonic assistance at 30 - 50 kHz, wash with a hydrochloric acid solution with a concentration of 0.0016 mol / L - 0.0032 mol / L for 30 - 60 min, monitor the pH value of the cleaning solution during the process, and the pH range is 6 - 8; then wash with deionized water 3 - 5 times until the color of the cleaning solution becomes transparent.

[0066] In some embodiments, the natural wood slices are pine wood, birch wood or balsa wood. The thickness of the natural wood slices is 25 μm - 2 mm.

[0067] In some embodiments, the lignin removal method is to soak with the removal solution; further, the molar concentration of the removal solution is 0.1 mol / L - 1.7 mol / L. By controlling the concentration of the removal solution, it is beneficial to the removal effect of other substances in the wood, and at the same time, it is beneficial to maintaining the lignocellulose structure in the wood. Among them, the removal solution includes at least one of hypochlorite and chlorite.

[0068] In some embodiments, the temperature of the freeze-drying is -60°C - -40°C; the pressure of the freeze-drying is -50 Pa - -100 Pa. By controlling the process parameters of the freeze-drying, it is more beneficial to the structural integrity of the framework material.

[0069] S2. Immerse the framework in the electrolyte paste so that the electrolyte paste fills the through holes of the framework to obtain a semi-finished product;

[0070] Specifically, in this embodiment, the preparation process of the semi-finished product can be as follows: under negative pressure, immerse the framework in the electrolyte paste (lithium ion concentration 1.5 - 2 mol / L. Evacuate under -0.6 - -0.4 MPa for 1 hour) until the electrolyte paste completely infiltrates into the spatial structure of the framework to form a semi-finished product (observe the filling degree through slicing under a magnifying glass. After filling, the obtained product has a weight increase of 150% - 250% compared to the original substrate). It can be understood that the filling degree of the electrolyte paste in the semi-finished product is positively correlated with the filling effect of the electrolyte in the final solid electrolyte membrane product.

[0071] In some embodiments, before the drying, the method further includes: scraping the surface of the semi-finished product. Further, the end time of the scraping process is that the residual amount of the electrolyte paste on the surface of the framework of the semi-finished product ≤ 1.5 g / m 2It can be understood that the residual amount of the electrolyte paste on the surface of the semi-finished product skeleton is positively correlated with the electrolyte residue on the surface of the solid electrolyte membrane. Controlling the residual amount of the electrolyte paste is beneficial to controlling the appearance and performance of the final product.

[0072] S3. Dry the semi-finished product to convert the electrolyte paste into a solid electrolyte, obtaining a solid electrolyte membrane.

[0073] In some embodiments, the drying temperature is 60°C to 90°C; the drying time is 1h to 3h.

[0074] The method includes steps of slicing wood, removing lignin, purifying, and freeze-drying. By using natural materials as the skeleton material, the solid electrolyte membrane has good environmental friendliness. And filling the solid electrolyte in the skeleton material enables its application as the solid electrolyte membrane of a solid-state battery, effectively improving the energy density of the battery. At the same time, the skeleton material can effectively resist the puncture of lithium dendrites, reducing the possibility of generating short-circuit points and effectively improving the safety performance of the battery. Also, the decomposition temperature of the skeleton material is between 215°C and 410°C, which is beneficial to increasing the safe operating temperature of the battery.

[0075] The following further describes the solid electrolyte membrane of the present application in detail with reference to embodiments.

[0076] Examples and Comparative Examples

[0077] A solid electrolyte membrane is prepared as follows:

[0078] Step 1: Slice natural wood to a certain thickness;

[0079] Step 2: Immerse the sliced wood into the lignin removal solution, where the removal solution is selected from hypochlorite with a molar concentration of 0.9 mol / L.

[0080] Step 3: Wash the cellulose-removed sliced wood. Specifically, the washing process is as follows: Under the condition of 40 kHz ultrasonic assistance, wash with a 0.0024 mol / L hydrochloric acid solution for 45 min, monitor the pH value of the washing solution during the process, with the pH range being 6 - 8; then wash multiple times with deionized water until the color of the washing solution becomes transparent;

[0081] Step 4: Freeze-dry the washed sliced wood to obtain a skeleton, where the freeze-drying temperature is -50°C and the freeze-drying pressure is -75 Pa;

[0082] Step 5: Under negative pressure conditions, the skeleton is immersed in the electrolyte paste (vacuumed at -0.5 MPa for 1 hour) until the electrolyte paste completely infiltrates into the spatial structure of the skeleton, forming a semi-finished product, and the surface of the semi-finished product is scraped.

[0083] Step 6: Finally, the semi-finished product is heated and dried to obtain a solid electrolyte membrane. Among them, the heating temperature is 75 °C and the heating time is 2 h.

[0084] The key parameters of each example and comparative example are controlled as shown in the following table.

[0085]

[0086]

[0087] In the above table, the test process for the electrolyte residue amount on the surface of the solid electrolyte membrane is as follows: Take a solid electrolyte membrane with an area of 50 mm * 50 mm, scrape the electrolyte on the surface, and the scraping operation is repeated 5 times. Test the weight of the scraped material until the measured weight data does not exceed 1% for 3 consecutive times, which is recorded as the electrolyte residue amount on the surface.

[0088] Perform performance tests on the lithium-ion batteries assembled from the solid electrolyte membranes obtained in each example and comparative example. The specific test process is as follows:

[0089] Energy density test: At 65 ± 1 °C, under the condition of constant current / constant voltage of 1 A, charge the lithium-ion battery to 4.5 V, let it stand for 10 min, and discharge it at a constant current of 0.5 A to the cut-off voltage of 3.1 V (5 batteries in each group). Detect the energy of each battery, and then calculate the energy density of the lithium-ion battery according to the following formula: Energy density (Wh / L) = Energy / Mass (where W represents watt, h represents hour, and mass represents the mass of the battery cell).

[0090] Ion diffusion coefficient test: Measured by cyclic voltammetry, the scanning rate is 0.2 mV / s. During the test, the temperature is controlled at 23 ± 1 °C and the humidity is controlled at 35% - 40%.

[0091] Safety test: Adopt the normal temperature external short-circuit rate test. Test 100 lithium-ion batteries with the electrolyte membrane of the present invention to judge the safety performance. During the test, the external resistance is controlled at 90 ± 10 mΩ and the temperature is controlled at 20 ± 1 °C. When the battery temperature drops to 20% lower than the peak temperature and the short-circuit time is greater than 24 h, the test is terminated. The condition for passing the judgment is that the battery does not catch fire or explode.

[0092] The results are shown in the following table.

[0093]

[0094] As can be seen from the above table, compared with traditional electrolytes, the solid electrolyte membrane prepared by the embodiments of the present application has higher energy density and better safety.

[0095] From the data comparison of Examples 1 to 3 and Comparative Examples 1 to 2, it can be obtained that as the average diameter of the through-holes in the skeleton increases, the ion diffusion coefficient shows a trend of first increasing and then decreasing. When the average diameter of the through-holes is controlled within 30 - 50 nm, the ion diffusion coefficient can be controlled above 1.727×10 -10 cm 2 / s.

[0096] From the data comparison of Example 2 and Examples 4 to 7, it can be obtained that as the thickness of the skeleton increases, the safety shows a gradually improving trend. At the same time, in order to pursue thinness and lightness, controlling the thickness of the skeleton within 0.02 - 1 mm is a better range.

[0097] From the data comparison of Example 2 and Examples 8 to 11, it can be obtained that as the proportion of lithium salt in the solid electrolyte increases, both the energy density and the ion diffusion coefficient show a trend of first improving and then deteriorating. When the proportion of lithium salt to dispersant in the solid electrolyte is controlled at (2 - 3):1, the energy density can be controlled above 257 Wh / kg, and the ion diffusion coefficient can be controlled above 1.623×10 -10 cm 2 / s.

[0098] From the data comparison of Example 2 and Examples 12 to 13, it can be obtained that as the proportion of binder in the solid electrolyte increases, the energy density shows a gradually deteriorating trend, and the ion diffusion coefficient shows a trend of first improving and then deteriorating. When the proportion of dispersant to binder in the solid electrolyte is controlled at 1:(0.5 - 1), the energy density can be controlled above 236 Wh / kg, and the ion diffusion coefficient can be controlled above 1.710×10 -10 cm 2 / s.

[0099] From the data comparison of Example 2 and Examples 14 to 16, it can be obtained that as the mass ratio of the solid electrolyte to the skeleton gradually decreases, both the energy density and the ion diffusion coefficient show a trend of first improving and then deteriorating. When the mass ratio of the solid electrolyte to the skeleton is controlled at 1:(1.1 - 1.2), the energy density can be controlled above 241 Wh / kg, and the ion diffusion coefficient can be controlled above 1.738×10 -10 cm 2 / s.

[0100] From the data comparison between Example 2 and Examples 17 to 18, it can be obtained that with the gradual increase in the electrolyte residue amount on the surface of the solid electrolyte membrane, both the energy density and the ion diffusion coefficient show a gradually deteriorating trend. By controlling the electrolyte residue amount on the surface of the solid electrolyte membrane at 0.7 g / m 2 hereinafter, the energy density can be controlled above 242 Wh / kg, and the ion diffusion coefficient can be controlled above 1.837×10 -10 cm 2 / s.

[0101] The above are only specific embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A solid electrolyte membrane, characterized in that: The solid electrolyte membrane comprises: A skeleton, wherein the preparation method of the skeleton comprises: removing lignin from natural wood chips, followed by freeze-drying to obtain the skeleton, wherein the skeleton is provided with through holes, and the average diameter of the through holes is 30 nm to 50 nm; A solid electrolyte is filled in the through holes of the skeleton; the residual amount of electrolyte on the surface of the solid electrolyte membrane is 0.5-0.7 g / m 2 The test process of the residual electrolyte on the surface of the solid electrolyte membrane is as follows: take a solid electrolyte membrane with an area of ​​50mm*50mm, scrape the electrolyte on the surface, repeat the scraping operation 5 times, and test the weight of the scraped material until the difference in the measured weight data for 3 consecutive times does not exceed 1%, which is counted as the residual electrolyte on the surface.

2. The solid electrolyte membrane according to claim 1, characterized in that The fiber length in the skeleton is 3 mm to 5 mm; and / or The average diameter of the through holes is 35 nm to 45 nm; and / or The thickness of the skeleton is 20 μm to 1 mm.

3. The solid electrolyte membrane according to claim 1, characterized in that The mass ratio of the skeleton to the solid electrolyte is 1:(1.1-1.2).

4. The solid electrolyte membrane according to claim 1, characterized in that The solid electrolyte comprises a lithium salt, a dispersant and a binder; and / or The mass ratio of the lithium salt, the dispersant and the binder is (2-3):1:(0.5-1); and / or The lithium salt comprises at least one of lithium chloride, lithium carbonate, lithium sulfate and lithium hexafluorophosphate; and / or The dispersant comprises PVA; and / or The binder includes at least one of methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate and octyl acrylate.

5. A method for preparing a solid electrolyte membrane, characterized in that: The method comprises: The natural wood chips are subjected to lignin removal and then freeze-dried to obtain a skeleton, wherein the skeleton is provided with through holes, and the average diameter of the through holes is 30 nm to 50 nm; Immersing the skeleton in electrolyte paste so that the electrolyte paste fills the through holes of the skeleton to obtain a semi-finished product; Scraping the surface of the semi-finished product; The scraped semi-finished product is dried to convert the electrolyte paste into a solid electrolyte to obtain a solid electrolyte membrane, wherein the electrolyte residue on the surface of the solid electrolyte membrane is 0.5-0.7 g / m 2 The test process of the residual electrolyte on the surface of the solid electrolyte membrane is as follows: take a solid electrolyte membrane with an area of ​​50mm*50mm, scrape the electrolyte on the surface, repeat the scraping operation 5 times, and test the weight of the scraped material until the difference in the measured weight data for 3 consecutive times does not exceed 1%, which is counted as the residual electrolyte on the surface.

6. The method for preparing a solid electrolyte membrane according to claim 5, characterized in that: The lignin removal method is to soak in a removal liquid; and / or The molar concentration of the removal solution is 0.1 mol / L to 1.7 mol / L; and / or The removal solution includes at least one of hypochlorite and chlorite.

7. The method for preparing a solid electrolyte membrane according to claim 5, characterized in that: The natural wood pieces are pine, birch or balsa wood; and / or The thickness of the natural wood sheet is 25 μm to 2 mm.

8. The method for preparing a solid electrolyte membrane according to claim 5, characterized in that: The scraping treatment is terminated when the residual amount of electrolyte paste on the surface of the skeleton of the semi-finished product is ≤1.5g / m 2 .

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