PEO-based organic-inorganic composite solid electrolyte membrane and preparation method thereof

Abstract

The invention relates to a PEO-based organic-inorganic composite solid electrolyte membrane and a preparation method thereof. The electrolyte membrane is prepared by heating and curing a blend solution of a PLA organic solution and a PEO / LITFSI / LATP mixed solution. The PEO-based organic-inorganic composite solid electrolyte membrane and the preparation method thereof provided by the invention have the effects that due to the existence of the PLA / PEO blending system, the degradability of the solid electrolyte can be realized, and the mechanical property of the solid electrolyte can be enhanced. In addition, the inorganic lithium salt and the organic lithium salt are mixed, so that the solid electrolyte is endowed with excellent ionic conductivity, and the mechanical property of the solid electrolyte is further improved. Therefore, the PEO-based organic-inorganic solid electrolyte and the preparation method thereof provided by the invention can bring important contributions to high energy density, long cycle life and excellent safety performance of an all-solid-state battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-solid-state battery material preparation, and specifically relates to a PEO-based organic-inorganic composite solid electrolyte membrane and a preparation method thereof. Background Art

[0002] With the growing global demand for renewable energy and efficient energy storage devices, the development of battery technology has become a critical research area. Lithium-ion batteries, due to their high energy density, high reversibility, and safety, have become a research hotspot in the battery field. However, current commercial lithium-ion batteries suffer from issues such as flammable organic electrolytes and the formation of lithium dendrites. Once a battery short circuit occurs, a large amount of heat is released internally, causing the organic electrolyte to combust and posing a serious safety hazard. Even some of the current "star" electric vehicles have experienced more than a dozen fire and explosion accidents in recent years. Furthermore, organic electrolytes present several other challenges: a narrow electrochemical window makes them difficult to pair with the latest high-voltage cathode materials and high-capacity lithium metal anodes; lithium ions are not the sole charge carrier, and when operating at high currents, the ion concentration gradient creates an increase in battery internal resistance and a decrease in performance; operating temperatures are limited (safe operating temperature 0-40°C); and organic electrolytes are prone to react with electrode materials to form a solid-electrolyte interface, which continuously consumes the electrolyte and anode, resulting in a continuous decrease in battery capacity.

[0003] In this context, solid electrolytes, as a new type of electrolyte material, have gradually attracted widespread attention from researchers due to their excellent energy density, wide operating temperature, extended service life and other great advantages, and they do not have problems such as leakage, corrosion, flammability and volatility. The application of solid electrolytes provides new possibilities for the development of lithium-ion batteries and is an effective way to solve the poor safety of batteries and improve energy density and power density.

[0004] At present, solid electrolytes are divided into polymer electrolytes and inorganic solid electrolytes according to their composition. Polymer electrolytes are flexible and easy to process, and have good contact with the electrode interface, but they have the disadvantage of low ionic conductivity; inorganic solid electrolytes have excellent ionic conductivity and lithium ion transference number, strong mechanical properties, but have poor wettability with the electrode interface and high interface contact impedance. Therefore, the significant disadvantages of single-component solid electrolytes hinder their application in all-solid-state batteries. Organic / inorganic composite solid electrolytes combine the advantages of inorganic and polymer electrolytes and can overcome the shortcomings of each other, and are considered to be one of the options with the most promising commercial applications.

[0005] Therefore, the development of an organic-inorganic composite solid electrolyte membrane and its preparation method can not only overcome the drawback of low conductivity of traditional polymer electrolytes at room temperature, but also fully utilize the superior mechanical properties of inorganic electrolytes to meet the modern society's demand for high-performance, low-cost, and safe batteries. This technological innovation will provide important support for the development of all-solid-state batteries and has broad application potential in the field of new energy storage. Summary of the Invention

[0006] In order to solve the above problems, the present invention aims to provide a PEO-based organic-inorganic composite solid electrolyte membrane and a preparation method thereof.

[0007] In order to achieve the above-mentioned purpose, the PEO-based organic-inorganic composite solid electrolyte membrane provided by the present invention is made by heating and curing a blend of a PLA (polylactic acid) organic solution and a PEO / LITFSI / LATP (polyethylene oxide / lithium bis(trifluoromethylsulfonyl)imide / lithium titanium aluminum phosphate) mixed solution.

[0008] The PLA organic solution consists of PLA powder and DCM (dichloromethane) solution, wherein the molar mass of the PLA powder is 150,000-200,000 g / mol, the DCM solution is analytically pure, and the solid content of the PLA organic solution is 30-40%.

[0009] The PEO / LITFSI / LATP mixed solution consists of PEO powder, LITFSI powder, LATP powder and an anhydrous acetonitrile solution, wherein the mass ratio of PEO powder to the above-mentioned PLA powder is 1-1.5:1; the molar ratio of PEO powder to LITFSI powder is EO:LI=16-18:1; the LATP powder accounts for 5-30% of the total mass of the PLA powder, PEO powder, LITFSI powder and LATP powder; and the solid content of the PEO / LITFSI / LATP mixed solution is 30-40%.

[0010] The method for preparing a PEO-based organic-inorganic composite solid electrolyte membrane provided by the present invention comprises the following steps performed in sequence:

[0011] 1) Drying PLA powder, PEO powder, LITFSI powder, and LATP powder in a desiccator for 12-24 hours to remove moisture before use; first weighing PEO powder and PLA powder separately at a mass ratio of PEO:PLA = 1-1.5:1, then weighing LITFSI powder at a molar ratio of EO:Li = 16-18:1, and finally weighing LATP powder at a mass ratio of 5-30% of the total mass of the PLA powder, PEO powder, LITFSI powder, and LATP powder;

[0012] 2) slowly adding the PLA powder obtained in step 1) to the DCM solution, sealing the mixture in an iodine volumetric flask, and magnetically stirring for 2-4 hours until the mixture is completely dissolved to prepare a PLA organic solution, which is then stored away from light and heat until further use;

[0013] 3) The LATP powder obtained in step 1) was slowly added to the anhydrous acetonitrile solution and stirred at room temperature for 4-5 hours until uniformly dispersed. LITFSI powder was then added and stirred until the LATP powder and LITFSI powder were uniformly dispersed and no obvious particulate matter was present. PEO powder was then slowly added to the above solution in two portions while vigorously stirring. The solution was then poured into an iodine volumetric flask, sealed, and magnetically stirred for 6-12 hours until uniformly mixed to prepare a PEO / LITFSI / LATP mixed solution. The solution was then stored away from light and heat until further use.

[0014] 4) transferring the PLA organic solution prepared in step 2) to the PEO / LITFSI / LATP mixed solution prepared in step 3), magnetically stirring the solution at 50-60° C. for 6-12 hours until the mixture is uniformly mixed, then defoaming the mixture in a defoamer, and then pouring the mixture into a polytetrafluoroethylene mold using a solution casting method. The mixture is placed in a glove box and dried at room temperature for 12-24 hours to evaporate part of the solvent, and then placed in a vacuum oven and dried at 50-60° C. for 12-16 hours to evaporate all of the solution, thereby preparing a PEO-based organic-inorganic composite solid electrolyte membrane;

[0015] 5) The polytetrafluoroethylene mold is removed from the vacuum oven, and the prepared PEO-based organic-inorganic composite solid electrolyte membrane is taken out with tweezers and cut into different sizes using a punch to fit lithium-ion batteries of different sizes.

[0016] Compared with the prior art, the PEO-based organic-inorganic composite solid electrolyte membrane and its preparation method provided by the present invention have the following beneficial effects:

[0017] First, by blending the two high molecular polymers PLA and PEO, not only the mechanical properties of the composite electrolyte membrane are improved, but also the electrochemical properties of the electrolyte membrane are improved. However, due to the presence of PLA crystals, salts tend to dissolve in PEO. Therefore, LATP inorganic lithium salt is added to reduce the order of the polymer chain segments, improve the mobility of the polymer chain segments, thereby inhibiting polymer crystallization, increasing the proportion of amorphous regions, improving ionic conductivity, and further improving mechanical properties. The use of organic-inorganic solid electrolytes improves battery safety, reduces the risk of leakage, and achieves better thermal management. Not only can it achieve a flexible and lightweight design for all-solid-state batteries for use in emerging markets such as wearable devices, it can also achieve all-solid-state batteries with higher energy density, significantly improve the cruising range of electric vehicles and meet the needs of aerospace equipment. These advantages make the present invention have broad application potential and market value in the field of new energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 (a) and (b) are the AC impedance diagram and ionic conductivity diagram of the PEO-based organic-inorganic composite solid electrolyte membrane provided by the present invention at room temperature (25°C):

[0019] Figure 2 (a) and (b) are the AC impedance diagram and ionic conductivity diagram of the PEO-based organic-inorganic composite solid electrolyte membrane provided by the present invention at 60°C, respectively:

[0020] Figure 3 This is the electrochemical window test diagram of the PEO-based organic-inorganic composite solid electrolyte membrane provided by the present invention at 60°C:

[0021] Figure 4 (a)-(f) are scanning electron microscope (SEM) characterization images of the organic-inorganic composite solid electrolyte membrane provided in the comparative example of the present invention and the PEO-based organic-inorganic composite solid electrolyte membrane provided in Examples 1-5 at 100 microns, respectively. DETAILED DESCRIPTION

[0022] Example 1:

[0023] The method for preparing a PEO-based organic-inorganic composite solid electrolyte membrane provided in this embodiment 1 includes the following steps performed in sequence:

[0024] 1) PLA powder, PEO powder, LITFSI powder, and LATP powder were dried in a desiccator for 24 hours to remove moisture before use; PEO powder and PLA powder were weighed at a mass ratio of PEO:PLA = 1:1, LITFSI powder was weighed at a molar ratio of EO:Li = 16:1, and LATP powder was weighed at a mass ratio of 5% of the total mass of the PLA powder, PEO powder, LITFSI powder, and LATP powder;

[0025] 2) The PLA powder obtained in step 1) was slowly added to the DCM solution, and the mixture was sealed in an iodine volumetric flask. The mixture was magnetically stirred for 4 hours until completely dissolved to prepare a PLA organic solution, and the solution was stored away from light and heat until further use;

[0026] 3) The LATP powder obtained in step 1) was slowly added to the anhydrous acetonitrile solution and stirred at room temperature for 4 hours until uniformly dispersed. LITFSI powder was then added and stirred until the LATP powder and LITFSI powder were uniformly dispersed and no obvious particulate matter was present. PEO powder was then slowly added to the above solution in two portions while vigorously stirring. The solution was then poured into an iodine volumetric flask, sealed, and magnetically stirred for 12 hours until uniformly mixed to prepare a PEO / LITFSI / LATP mixed solution. The solution was then stored away from light and heat until further use.

[0027] 4) transferring the PLA organic solution prepared in step 2) to the PEO / LITFSI / LATP mixed solution prepared in step 3), magnetically stirring the mixture at 60° C. for 12 hours until uniformly mixed, defoaming the mixture in a defoamer, and then pouring the mixture into a polytetrafluoroethylene mold using a solution casting method. The mixture was placed in a glove box and dried at room temperature for 24 hours to evaporate part of the solvent, and then placed in a vacuum oven and dried at 60° C. for 12 hours to evaporate all of the solution, thereby preparing a PEO-based organic-inorganic composite solid electrolyte membrane;

[0028] 5) The polytetrafluoroethylene mold is removed from the vacuum oven, and the prepared PEO-based organic-inorganic composite solid electrolyte membrane is taken out with tweezers and cut into different sizes using a punch to fit lithium-ion batteries of different sizes.

[0029] Performance: Compared with the organic-inorganic composite solid electrolyte membrane provided in the following comparative example 1, the ionic conductivity of the PEO-based organic-inorganic composite solid electrolyte membrane provided in this example 1 can reach 3.5×10 -5 S / cm, and the ionic conductivity at 60°C can reach 7.4×10 -2S / cm, and the electrochemical window can reach 4.8V, indicating that the addition of 5% organic lithium salt (LATP) can improve the conductivity and electrochemical stability of the electrolyte, and compared with the SEM image of Comparative Example 1, the flatness of the PEO-based organic-inorganic composite solid electrolyte membrane provided in Example 1 is improved, and the wrinkle distribution is more uniform and dense.

[0030] Example 2:

[0031] The method for preparing the organic-inorganic composite solid electrolyte membrane provided in this embodiment 2 includes the following steps performed in sequence:

[0032] 1) PLA powder, PEO powder, LITFSI powder, and LATP powder were dried in a desiccator for 24 hours to remove moisture before use; PEO powder and PLA powder were weighed at a mass ratio of PEO:PLA = 1:1, LITFSI powder was weighed at a molar ratio of EO:Li = 16:1, and LATP powder was weighed at a mass ratio of 10% of the total mass of the PLA powder, PEO powder, LITFSI powder, and LATP powder;

[0033] 2) The PLA powder obtained in step 1) was slowly added to the DCM solution, and the mixture was sealed in an iodine volumetric flask. The mixture was magnetically stirred for 4 hours until completely dissolved to prepare a PLA organic solution, and the solution was stored away from light and heat until further use;

[0034] 3) The LATP powder obtained in step 1) was slowly added to the anhydrous acetonitrile solution and stirred at room temperature for 4 hours until uniformly dispersed. LITFSI powder was then added and stirred until the LATP powder and LITFSI powder were uniformly dispersed and no obvious particulate matter was present. PEO powder was then slowly added to the above solution in two portions while vigorously stirring. The solution was then poured into an iodine volumetric flask, sealed, and magnetically stirred for 12 hours until uniformly mixed to prepare a PEO / LITFSI / LATP mixed solution. The solution was then stored away from light and heat until further use.

[0035] 4) transferring the PLA organic solution prepared in step 2) to the PEO / LITFSI / LATP mixed solution prepared in step 3), magnetically stirring the mixture at 60° C. for 12 hours until uniformly mixed, defoaming the mixture in a defoamer, and then pouring the mixture into a polytetrafluoroethylene mold using a solution casting method. The mixture was placed in a glove box and dried at room temperature for 24 hours to evaporate part of the solvent, and then placed in a vacuum oven and dried at 60° C. for 12 hours to evaporate all of the solution, thereby preparing a PEO-based organic-inorganic composite solid electrolyte membrane;

[0036] 5) The polytetrafluoroethylene mold is removed from the vacuum oven, and the prepared PEO-based organic-inorganic composite solid electrolyte membrane is taken out with tweezers and cut into different sizes using a punch to fit lithium-ion batteries of different sizes.

[0037] Performance: Compared with the organic-inorganic composite solid electrolyte membrane provided in Comparative Example 1, the ionic conductivity of the PEO-based organic-inorganic composite solid electrolyte membrane provided in Example 2 can reach 7.2×10 -5 S / cm, and the ionic conductivity at 60°C can reach 8.5×10 -2 S / cm, and the electrochemical window can reach 4.8V, indicating that the addition of 10% organic lithium salt (LATP) can improve the conductivity and electrochemical stability of the electrolyte, and compared with the SEM image of Comparative Example 1, the flatness of the PEO-based organic-inorganic composite solid electrolyte membrane provided in Example 2 is improved, and the wrinkle distribution is more uniform and dense.

[0038] Example 3:

[0039] The method for preparing the organic-inorganic composite solid electrolyte membrane provided in this embodiment 3 includes the following steps performed in sequence:

[0040] 1) PLA powder, PEO powder, LITFSI powder, and LATP powder were dried in a desiccator for 24 hours to remove moisture before use; PEO powder and PLA powder were weighed at a mass ratio of PEO:PLA = 1:1, LITFSI powder was weighed at a molar ratio of EO:Li = 16:1, and LATP powder was weighed at a mass ratio of 15% of the total mass of the PLA powder, PEO powder, LITFSI powder, and LATP powder;

[0041] 2) The PLA powder obtained in step 1) was slowly added to the DCM solution, and the mixture was sealed in an iodine volumetric flask. The mixture was magnetically stirred for 4 hours until completely dissolved to prepare a PLA organic solution, and the solution was stored away from light and heat until further use;

[0042] 3) The LATP powder obtained in step 1) was slowly added to the anhydrous acetonitrile solution and stirred at room temperature for 4 hours until uniformly dispersed. LITFSI powder was then added and stirred until the LATP powder and LITFSI powder were uniformly dispersed and no obvious particulate matter was present. PEO powder was then slowly added to the above solution in two portions while vigorously stirring. The solution was then poured into an iodine volumetric flask, sealed, and magnetically stirred for 12 hours until uniformly mixed to prepare a PEO / LITFSI / LATP mixed solution. The solution was then stored away from light and heat until further use.

[0043] 4) transferring the PLA organic solution prepared in step 2) to the PEO / LITFSI / LATP mixed solution prepared in step 3), magnetically stirring the mixture at 60° C. for 12 hours until uniformly mixed, defoaming the mixture in a defoamer, and then pouring the mixture into a polytetrafluoroethylene mold using a solution casting method. The mixture was placed in a glove box and dried at room temperature for 24 hours to evaporate part of the solvent, and then placed in a vacuum oven and dried at 60° C. for 12 hours to evaporate all of the solution, thereby preparing a PEO-based organic-inorganic composite solid electrolyte membrane;

[0044] 5) The polytetrafluoroethylene mold is removed from the vacuum oven, and the prepared PEO-based organic-inorganic composite solid electrolyte membrane is taken out with tweezers and cut into different sizes using a punch to fit lithium-ion batteries of different sizes.

[0045] Performance: Compared with the organic-inorganic composite solid electrolyte membrane provided in Comparative Example 1, the ionic conductivity of the PEO-based organic-inorganic composite solid electrolyte membrane provided in Example 3 can reach 1.6×10 -4 S / cm, and the ionic conductivity at 60°C can reach 9.6×10 -2 S / cm, and the electrochemical window can reach 4.8V, indicating that the addition of 15% organic lithium salt (LATP) can improve the conductivity and electrochemical stability of the electrolyte, and compared with the SEM image of Comparative Example 1, the flatness of the PEO-based organic-inorganic composite solid electrolyte membrane provided in Example 3 is improved, and the wrinkle distribution is more uniform and dense.

[0046] Example 4:

[0047] The method for preparing the organic-inorganic composite solid electrolyte membrane provided in this embodiment 4 includes the following steps performed in sequence:

[0048] 1) PLA powder, PEO powder, LITFSI powder, and LATP powder were dried in a desiccator for 24 hours to remove moisture before use; PEO powder and PLA powder were weighed at a mass ratio of PEO:PLA = 1:1, LITFSI powder was weighed at a molar ratio of EO:Li = 16:1, and LATP powder was weighed at a mass ratio of 20% of the total mass of the PLA powder, PEO powder, LITFSI powder, and LATP powder;

[0049] 2) The PLA powder obtained in step 1) was slowly added to the DCM solution, and the mixture was sealed in an iodine volumetric flask. The mixture was magnetically stirred for 4 hours until completely dissolved to prepare a PLA organic solution, and the solution was stored away from light and heat until further use;

[0050] 3) The LATP powder obtained in step 1) was slowly added to the anhydrous acetonitrile solution and stirred at room temperature for 4 hours until uniformly dispersed. LITFSI powder was then added and stirred until the LATP powder and LITFSI powder were uniformly dispersed and no obvious particulate matter was present. PEO powder was then slowly added to the above solution in two portions while vigorously stirring. The solution was then poured into an iodine volumetric flask, sealed, and magnetically stirred for 12 hours until uniformly mixed to prepare a PEO / LITFSI / LATP mixed solution. The solution was then stored away from light and heat until further use.

[0051] 4) transferring the PLA organic solution prepared in step 2) to the PEO / LITFSI / LATP mixed solution prepared in step 3), magnetically stirring the solution at 60° C. for 10 hours until the mixture is uniformly mixed, then defoaming the mixture in a defoamer, and then pouring the mixture into a polytetrafluoroethylene mold by a solution casting method. The mixture is dried at room temperature for 12 hours to evaporate part of the solvent, and then placed in a vacuum oven and dried at 60° C. for 12 hours to evaporate all of the solution, thereby preparing a PEO-based organic-inorganic composite solid electrolyte membrane;

[0052] 5) The polytetrafluoroethylene mold is removed from the vacuum oven, and the prepared PEO-based organic-inorganic composite solid electrolyte membrane is taken out with tweezers and cut into different sizes using a punch to fit lithium-ion batteries of different sizes.

[0053] Performance: Compared with the organic-inorganic composite solid electrolyte membrane provided in Comparative Example 1, the ionic conductivity of the PEO-based organic-inorganic composite solid electrolyte membrane provided in Example 4 can reach 4.2×10 -5 S / cm, and the ionic conductivity at 60°C can reach 6.8×10 -2 S / cm, and the electrochemical window can reach 4.8V, indicating that the addition of 20% organic lithium salt (LATP) can improve the conductivity and electrochemical stability of the electrolyte. Figure 4 Small-scale agglomeration can be clearly seen on the surface of the sample of Example 4.

[0054] Example 5:

[0055] The method for preparing the organic-inorganic composite solid electrolyte membrane provided in this embodiment 5 includes the following steps performed in sequence:

[0056] 1) PLA powder, PEO powder, LITFSI powder, and LATP powder were dried in a desiccator for 24 hours to remove moisture before use; PEO powder and PLA powder were weighed at a mass ratio of PEO:PLA = 1:1, LITFSI powder was weighed at a molar ratio of EO:Li = 16:1, and LATP powder was weighed at a mass ratio of 30% of the total mass of the PLA powder, PEO powder, LITFSI powder, and LATP powder;

[0057] 2) The PLA powder obtained in step 1) was slowly added to the DCM solution, and the mixture was sealed in an iodine volumetric flask. The mixture was magnetically stirred for 4 hours until completely dissolved to prepare a PLA organic solution, and the solution was stored away from light and heat until further use;

[0058] 3) The LATP powder obtained in step 1) was slowly added to the anhydrous acetonitrile solution and stirred at room temperature for 4 hours until uniformly dispersed. LITFSI powder was then added and stirred until the LATP powder and LITFSI powder were uniformly dispersed and no obvious particulate matter was present. PEO powder was then slowly added to the above solution in two portions while vigorously stirring. The solution was then poured into an iodine volumetric flask, sealed, and magnetically stirred for 12 hours until uniformly mixed to prepare a PEO / LITFSI / LATP mixed solution. The solution was then stored away from light and heat until further use.

[0059] 4) transferring the PLA organic solution prepared in step 2) to the PEO / LITFSI / LATP mixed solution prepared in step 3), magnetically stirring the mixture at 60° C. for 12 hours until uniformly mixed, defoaming the mixture in a defoamer, and then pouring the mixture into a polytetrafluoroethylene mold using a solution casting method. The mixture was placed in a glove box and dried at room temperature for 24 hours to evaporate part of the solvent, and then placed in a vacuum oven and dried at 60° C. for 12 hours to evaporate all of the solution, thereby preparing a PEO-based organic-inorganic composite solid electrolyte membrane;

[0060] 5) The polytetrafluoroethylene mold is removed from the vacuum oven, and the prepared PEO-based organic-inorganic composite solid electrolyte membrane is taken out with tweezers and cut into different sizes using a punch to fit lithium-ion batteries of different sizes.

[0061] Performance: Compared with the organic-inorganic composite solid electrolyte membrane provided in Comparative Example 1, the ionic conductivity of the PEO-based organic-inorganic composite solid electrolyte membrane provided in Example 5 can reach 2.4×10 -5 S / cm, and the ionic conductivity at 60°C can reach 1.38×10 -2 S / cm, and the electrochemical window can reach 4.8V, indicating that the excessive addition of 30% organic lithium salt (LATP) will lead to a decrease in the conductivity of the electrolyte, but the electrochemical stability is still improved, and Figure 4It can be clearly seen that there is obvious agglomeration on the surface of the sample in Example 5.

[0062] Comparative Example 1:

[0063] The preparation method of the organic-inorganic composite solid electrolyte provided in this comparative example comprises the following steps performed in sequence:

[0064] 1) PLA powder, PEO powder, and LITFSI powder were dried in a desiccator for 24 hours to remove moisture before use; PEO powder and PLA powder were weighed at a mass ratio of PEO:PLA = 1:1, and LITFSI powder was weighed at a molar ratio of EO:Li = 16:1 without adding LATP powder;

[0065] 2) The PLA powder prepared in step 1) was slowly added to the DCM solution, and the mixture was sealed in an iodine volumetric flask. The mixture was magnetically stirred for 4 hours until completely dissolved, and then stored away from light and heat for later use;

[0066] 3) Slowly add the LITFSI powder prepared in step 1) to the anhydrous acetonitrile solution and stir at room temperature for 4 hours until uniformly dispersed. Then, slowly add the PEO powder to the above solution in two portions while vigorously stirring until uniformly dispersed. Then, pour into an iodine volumetric flask, seal it, and magnetically stir it for 12 hours until uniformly mixed to prepare a PEO / LITFSI / LATP mixed solution. Protect from light and heat until further use.

[0067] 4) transferring the mixed solution from step 2) to step 3) to obtain a mixed solution, and magnetically stirring the mixed solution at 60° C. for 12 hours until the mixture is uniformly mixed, then transferring the mixed solution to a defoamer for defoaming, and then pouring the mixed solution into a polytetrafluoroethylene mold by a solution casting method, placing the mixed solution in a glove box and drying it at room temperature for 24 hours to evaporate part of the solvent, and then placing the mixed solution in a vacuum oven and drying it at 60° C. for 12 hours to evaporate all the solution, thereby preparing an organic-inorganic composite solid electrolyte membrane;

[0068] 5) The polytetrafluoroethylene mold is taken out of the vacuum oven, and the prepared organic-inorganic composite solid electrolyte membrane is taken out with tweezers and cut into different sizes with a punch to fit lithium-ion batteries of different sizes.

[0069] Performance: The ionic conductivity of the organic-inorganic composite solid electrolyte membrane provided in this comparative example 1 can reach 3.0×10 -5 S / cm, and the ionic conductivity at 60°C can reach 4.3×10 -2S / cm, it can be seen that there is a significant gap in ionic conductivity between the comparative example 1 without adding inorganic lithium salt (LATP) and the examples 1-4 with adding 5-20% inorganic lithium salt (LATP), and its electrochemical stability is lower than that of the PEO-based organic-inorganic composite solid electrolyte membrane with added LATP. In addition, it can be seen from the SEM image of the comparative example 1 that there is obvious wrinkling. With the increase of the amount of LATP powder added, the flatness is improved and the wrinkle distribution is more uniform and dense.

[0070] Therefore, by comparing the test results of Comparative Example 1 with those of Examples 1-5, it can be seen that the PEO-based organic-inorganic composite solid electrolyte membrane provided by the present invention achieves the highest ionic conductivity at room temperature and 60°C when 15% LATP is added, and also exhibits good electrochemical stability and surface micromorphology. Taking all these advantages into account, this PEO-based organic-inorganic composite solid electrolyte membrane is conducive to achieving high energy density in all-solid-state batteries.

Claims

1. A PEO-based organic-inorganic composite solid electrolyte membrane, characterized in that: The PEO-based organic-inorganic composite solid electrolyte membrane is prepared by heating and solidifying a mixed solution of a PLA organic solution and a PEO / LITFSI / LATP mixed solution.

2. The PEO-based organic-inorganic composite solid electrolyte membrane according to claim 1, characterized in that: The PLA organic solution consists of PLA powder and DCM solution, wherein the molar mass of the PLA powder is 150,000-200,000 g / mol, the DCM solution is analytically pure, and the solid content of the PLA organic solution is 30-40%.

3. The PEO-based organic-inorganic composite solid electrolyte membrane according to claim 1, characterized in that: The PEO / LITFSI / LATP mixed solution consists of PEO powder, LITFSI powder, LATP powder and an anhydrous acetonitrile solution, wherein the mass ratio of PEO powder to the above-mentioned PLA powder is 1-1.5:1; the molar ratio of PEO powder to LITFSI powder is EO:LI=16-18:1; the LATP powder accounts for 5-30% of the total mass of the PLA powder, PEO powder, LITFSI powder and LATP powder; and the solid content of the PEO / LITFSI / LATP mixed solution is 30-40%.

4. A method for preparing a PEO-based organic-inorganic composite solid electrolyte membrane according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps performed in sequence: 1) Drying PLA powder, PEO powder, LITFSI powder, and LATP powder in a desiccator for 12-24 hours to remove moisture before use; first weighing PEO powder and PLA powder separately at a mass ratio of PEO:PLA = 1-1.5:1, then weighing LITFSI powder at a molar ratio of EO:Li = 16-18:1, and finally weighing LATP powder at a mass ratio of 5-30% of the total mass of the PLA powder, PEO powder, LITFSI powder, and LATP powder; 2) Slowly adding the PLA powder obtained in step 1) to the DCM solution, sealing the mixture in an iodine volumetric flask, and magnetically stirring for 2-4 hours until the mixture is completely dissolved to prepare a PLA organic solution, which is then stored away from light and heat for later use; 3) The LATP powder obtained in step 1) was slowly added to the anhydrous acetonitrile solution and stirred at room temperature for 4-5 hours until uniformly dispersed. LITFSI powder was then added and stirred until the LATP powder and LITFSI powder were uniformly dispersed and no obvious particulate matter was present. PEO powder was then slowly added to the above solution in two portions while vigorously stirring. The solution was then poured into an iodine volumetric flask, sealed, and magnetically stirred for 6-12 hours until uniformly mixed to prepare a PEO / LITFSI / LATP mixed solution. The solution was then stored away from light and heat until further use. 4) transferring the PLA organic solution prepared in step 2) to the PEO / LITFSI / LATP mixed solution prepared in step 3), magnetically stirring the solution at 50-60° C. for 6-12 hours until the mixture is uniformly mixed, then defoaming the mixture in a defoamer, and then pouring the mixture into a polytetrafluoroethylene mold using a solution casting method. The mixture is placed in a glove box and dried at room temperature for 12-24 hours to evaporate part of the solvent, and then placed in a vacuum oven and dried at 50-60° C. for 12-16 hours to evaporate all of the solution, thereby preparing a PEO-based organic-inorganic composite solid electrolyte membrane; 5) The polytetrafluoroethylene mold is removed from the vacuum oven, and the prepared PEO-based organic-inorganic composite solid electrolyte membrane is taken out with tweezers and cut into different sizes using a punch to fit lithium-ion batteries of different sizes.

Images