PEO-based solid electrolyte diaphragm and preparation method thereof

Abstract

The invention discloses a PEO-based solid electrolyte diaphragm and a preparation method thereof.The preparation method comprises the steps that a polypropylene diaphragm is subjected to oxidation treatment and cleaning and impurity removal treatment, and an oxidized polypropylene diaphragm is obtained; and soaking the oxidized polypropylene diaphragm in an electrolyte solution formed by PEO and lithium salt, and carrying out vacuum drying after a certain time to obtain the PEO-based solid electrolyte diaphragm. According to the invention, the oxidized polypropylene diaphragm is used as a support and is compounded with the PEO electrolyte to prepare the PEO-based solid electrolyte diaphragm with relatively high mechanical strength, so that the problem of poor mechanical property of the PEO-based solid electrolyte can be solved, and the PEO-based solid electrolyte diaphragm can be used for large-scale winding or lamination structure battery production.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy batteries, and in particular relates to a PEO-based solid electrolyte diaphragm and a preparation method thereof. Background Art

[0002] According to the different components of solid electrolytes, solid-state batteries are mainly divided into oxide solid-state batteries, sulfide solid-state batteries and polymer solid-state batteries. Among them, the polymer solid electrolyte used in polymer solid-state batteries has the advantages of good flexibility and good interface compatibility, making it the most promising solid-state battery for industrialization. The polymer matrix includes: polyethylene oxide (PEO), (polyvinylidene fluoride) PVDF, (polymethyl methacrylate) PMMA and (polyacrylonitrile) PAN. PEO is a commonly used polymer matrix with a wide voltage window and good film-forming properties, and is often used to form polymer solid electrolytes. However, there are also some problems with the PEO polymer matrix, such as poor mechanical properties, easy to be punctured by dendrites, resulting in battery short circuits; slow migration speed at room temperature, low ionic conductivity, and difficulty working at room temperature. These problems limit the practical application range of PEO-type polymer electrolytes.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] In view of the above problems, the main purpose of the present invention is to provide a PEO-based solid electrolyte membrane and a preparation method thereof. By using an oxidized polypropylene membrane as a support and compounding it with a PEO electrolyte to prepare a PEO-based solid electrolyte membrane with high mechanical strength, the problem of poor mechanical properties of PEO-based solid electrolytes can be solved, and the membrane can be used for large-scale winding or laminated structure battery production.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a PEO-based solid electrolyte membrane, the preparation method comprising the following steps:

[0007] S1, oxidizing and cleaning the polypropylene diaphragm to obtain an oxidized polypropylene diaphragm;

[0008] S2, dissolving PEO and lithium salt in a solvent to obtain an electrolyte solution;

[0009] S3, soaking the oxidized polypropylene membrane in the electrolyte solution for a certain period of time and then vacuum drying it to obtain a PEO-based solid electrolyte membrane.

[0010] Further, in step S1, the oxidation treatment includes: immersing the polypropylene diaphragm in a KMnO4 solution to perform an oxidation reaction;

[0011] And / or, the polypropylene separator has a thickness of 5 to 11 μm.

[0012] Furthermore, the temperature of the oxidation reaction is 60 to 80°C;

[0013] And / or, the oxidation reaction time is 12 to 24 hours;

[0014] And / or, the concentration of the KMnO4 solution is 0.1-0.8 mol / L.

[0015] Furthermore, in step S1, the cleaning and impurity removal treatment includes: soaking the oxidized polypropylene diaphragm in deionized water to remove the KMnO4 solution remaining on the surface; then soaking it in dilute hydrochloric acid to remove the MnO2 remaining on the surface, and finally washing it with distilled water and ethanol respectively, and drying it to obtain an oxidized polypropylene diaphragm.

[0016] Furthermore, the concentration of the dilute hydrochloric acid is 0.01-0.1 mol / L.

[0017] Further, in step S2, the mass ratio of PEO to lithium salt is 5:0.5-1;

[0018] And / or, the average molecular weight of the PEO is 100,000 to 500,000;

[0019] And / or, the lithium salt includes one or a mixture of at least two of LiPF6, LiFSI, LiTFSI and LiClO4;

[0020] And / or, in the electrolyte solution, the mass concentration of PEO is 0.05 g / ml;

[0021] And / or, in the electrolyte solution, the mass concentration of lithium salt is 0.005-0.01 g / ml.

[0022] Further, in step S3, the oxidized polypropylene membrane is immersed for 0.5 to 2 hours;

[0023] And / or, the vacuum drying time is 8 to 36 hours;

[0024] And / or, the vacuum drying temperature is 35-55°C.

[0025] Furthermore, the thickness of the PEO-based solid electrolyte membrane is 60 to 140 μm.

[0026] In a second aspect, the present invention provides a PEO-based solid electrolyte membrane prepared by the preparation method described in the first aspect.

[0027] Furthermore, the PEO-based solid electrolyte membrane has a 180° peel strength of 2.0 to 5.5 N / m and a tensile strength of 800 to 1500 Kgf / cm 2 .

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] 1. The preparation method of the present invention improves the bonding force between PEO and the polypropylene membrane by compounding the PEO and the oxidized polypropylene membrane to prepare a PEO-based solid electrolyte membrane. Compared with the PEO solid electrolyte membrane, it has stronger peeling strength and good industrial production and processing stability.

[0030] 2. The PEO-based solid electrolyte diaphragm prepared by the present invention has strong mechanical strength, small internal resistance and stable cycle performance; it can simultaneously realize the functions of diaphragm and electrolyte, simplify the solid-state battery manufacturing process, and can be used for large-scale winding or stacked structure battery production. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described below in conjunction with examples. The embodiments of the present invention are implemented on the premise of the technical scheme of the present invention, and detailed implementation methods and processes are given. It should be clear to those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention, and the protection scope of the present invention is not limited to the following embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present invention.

[0032] The process parameters in the embodiments of the present invention that do not specify specific conditions are generally carried out under conventional conditions. Unless otherwise specified and / or specified, all numerical values ​​involving the amount of components are "weight or mass values ​​or ratios" from beginning to end. Unless otherwise specified, the raw materials used in the present invention can be obtained from commercially available products.

[0033] In the present invention, the endpoints and any values ​​of the disclosed ranges are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in the present invention.

[0034] According to a first aspect of the present invention, a method for preparing a PEO-based solid electrolyte membrane is provided, the preparation method comprising the following steps:

[0035] S1, oxidizing and cleaning the polypropylene diaphragm to obtain an oxidized polypropylene diaphragm;

[0036] S2, dissolving PEO and lithium salt in a solvent to obtain an electrolyte solution;

[0037] S3, soaking the oxidized polypropylene membrane in the electrolyte solution for a certain period of time and then vacuum drying it to obtain a PEO-based solid electrolyte membrane.

[0038] The present invention prepares a PEO-based solid electrolyte membrane by directly compounding PEO with an oxidized polypropylene membrane, thereby improving the bonding force between PEO and the polypropylene membrane. Compared with a PEO solid electrolyte membrane, the PEO-based solid electrolyte membrane has stronger peeling strength and good industrial production and processing stability.

[0039] The PEO-based solid electrolyte diaphragm prepared by the present invention has strong mechanical strength, small internal resistance and stable cycle performance; it can simultaneously realize the functions of diaphragm and electrolyte, simplify the solid-state battery manufacturing process, and can be used for large-scale winding or laminated structure battery production.

[0040] As an optional embodiment of the preparation method of the present invention, in step S1, the oxidation treatment includes: immersing the polypropylene diaphragm in a KMnO4 solution for oxidation reaction; further, the temperature of the oxidation reaction is 60-80°C (such as 61°C, 63°C, 65°C, 67°C, 69°C, 71°C, 73°C, 75°C, 77°C, 79°C, etc.), and / or, the oxidation reaction time is 12-24h (such as 13h, 15h, 17h, 19h, 21h, 23h, etc.), at the same temperature, the longer the reaction time, the better the oxidation effect of the diaphragm, the rougher the surface, the stronger the subsequent bonding with PEO, and the lower the tensile strength of the composite finished product;

[0041] And / or, the thickness of the polypropylene diaphragm is 5 to 11 μm (such as 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.), within this range, the thicker the polypropylene diaphragm, the greater the tensile strength of the composite finished product;

[0042] And / or, the concentration of the KMnO4 solution is 0.1-0.8 mol / L (such as 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, etc.).

[0043] As an optional embodiment of the preparation method of the present invention, in step S1, the cleaning and impurity removal treatment includes: soaking the oxidized polypropylene diaphragm in deionized water to remove the KMnO4 solution remaining on the surface; then soaking it in dilute hydrochloric acid to remove the MnO2 remaining on the surface, and finally washing it with distilled water and ethanol respectively, and obtaining the oxidized polypropylene diaphragm after drying.

[0044] As an optional embodiment of the preparation method of the present invention, the concentration of the dilute hydrochloric acid is 0.01-0.1 mol / L (such as 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, etc.).

[0045] As an optional embodiment of the preparation method of the present invention, in step S2, the mass ratio of PEO to lithium salt is 5:0.5-1 (such as 5:0.5, 5:0.6, 5:0.7, 5:0.8, 5:0.9, etc.);

[0046] And / or, the average molecular weight of the PEO is 100,000 to 500,000 (e.g., 110,000, 150,000, 200,000, 250,000, 300,000, 350,000, 400,000, 450,000, etc.);

[0047] And / or, the lithium salt comprises one or a mixture of at least two of LiPF6, LiFSI, LiTFSI and LiClO4;

[0048] And / or, in the electrolyte solution, the mass concentration of PEO is 0.05 g / ml;

[0049] And / or, in the electrolyte solution, the mass concentration of the lithium salt is 0.005-0.01 g / ml (such as 0.006 g / ml, 0.007 g / ml, 0.008 g / ml, 0.009 g / ml, etc.).

[0050] As an optional embodiment of the preparation method of the present invention, in step S3, the immersion time of the oxidized polypropylene diaphragm is 0.5 to 2 hours (such as 0.6 hours, 0.8 hours, 1 hour, 1.2 hours, 1.5 hours, 1.7 hours, etc.). Within this range, the longer the immersion time, the more PEO is adsorbed and the thicker the finished product.

[0051] And / or, the vacuum drying time is 8 to 36 hours (such as 9 hours, 12 hours, 16 hours, 19 hours, 24 hours, 28 hours, 32 hours, etc.);

[0052] And / or, the vacuum drying temperature is 35-55°C (such as 36°C, 38°C, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, etc.), and the drying temperature affects the flatness of the finished product. The higher the temperature, the lower the flatness.

[0053] As an optional embodiment of the preparation method of the present invention, the preparation method comprises the following steps:

[0054] S1. Soak a polypropylene membrane of a certain thickness in a KMnO4 solution, react at a certain temperature for a certain time, and then take it out; then soak it in deionized water to remove the KMnO4 solution remaining on the surface; then soak it in a dilute hydrochloric acid solution to remove the MnO2 remaining on the surface, and finally wash it with distilled water and ethanol respectively, and dry it at 60°C for 12 hours to obtain an oxidized polypropylene membrane;

[0055] S2, adding PEO and lithium salt into acetonitrile solvent, and quickly mixing by heating and magnetic stirring to obtain an electrolyte solution;

[0056] S3. The oxidized polypropylene membrane is immersed in the electrolyte solution, taken out after a certain period of time, and vacuum dried at a certain temperature for 24 hours to obtain a PEO-based solid electrolyte membrane.

[0057] In the present invention, the solvent used in step S2 is a nitrile solvent, which can be acetonitrile or other existing nitrile solvents.

[0058] According to a second aspect of the present invention, there is provided a PEO-based solid electrolyte membrane prepared by the preparation method described in the first aspect.

[0059] The PEO-based solid electrolyte membrane of the present invention has a 180° peel strength of 2.0 to 5.5 N / m and a tensile strength of 800 to 1500 Kgf / cm 2 .

[0060] The present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0061] Example 1

[0062] A method for preparing a PEO-based solid electrolyte membrane comprises the following steps:

[0063] S1. Soak a polypropylene membrane (thickness 9 μm, length 15 cm, width 2 cm) in a 0.1 mol / L KMnO4 solution, react at 80°C for 12 h for oxidation treatment, and then take it out;

[0064] S2, soaking the oxidized polypropylene diaphragm obtained in step S1 in deionized water to remove the KMnO4 solution remaining on the surface of the diaphragm, then soaking the diaphragm in 0.02 mol / L dilute hydrochloric acid solution to remove the MnO2 remaining on the surface, and finally washing the diaphragm with distilled water and ethanol respectively, and drying at 60° C. for 12 h to obtain an oxidized polypropylene diaphragm;

[0065] S3, adding 5 g PEO (molecular weight 400,000) and 0.6 g LiClO4 into 100 ml acetonitrile solvent, heating and magnetically stirring to obtain an electrolyte solution;

[0066] S4. Soak the oxidized polypropylene membrane in the electrolyte solution, take it out after 0.5 h, and vacuum dry it at 40° C. for 24 h to obtain a PEO-based solid electrolyte membrane.

[0067] Example 2

[0068] A method for preparing a PEO-based solid electrolyte membrane comprises the following steps:

[0069] S1. Soak a polypropylene membrane (thickness 9 μm, length 15 cm, width 2 cm) in a 0.1 mol / L KMnO4 solution, react at 80°C for 24 h for oxidation treatment, and then take it out;

[0070] S2, soaking the oxidized polypropylene diaphragm obtained in step S1 in deionized water to remove the KMnO4 solution remaining on the surface of the diaphragm, then soaking the diaphragm in 0.02 mol / L dilute hydrochloric acid solution to remove the MnO2 remaining on the surface, and finally washing the diaphragm with distilled water and ethanol respectively, and drying at 60° C. for 12 h to obtain an oxidized polypropylene diaphragm;

[0071] S3, adding 5 g PEO (molecular weight 400,000) and 0.6 g LiClO4 into 100 ml acetonitrile solvent, heating and magnetically stirring to obtain an electrolyte solution;

[0072] S4. Soak the oxidized polypropylene membrane in the electrolyte solution, take it out after 0.5 h, and vacuum dry it at 40° C. for 24 h to obtain a PEO-based solid electrolyte membrane.

[0073] Example 3

[0074] A method for preparing a PEO-based solid electrolyte membrane comprises the following steps:

[0075] S1. Soak a polypropylene membrane (thickness 9 μm, length 15 cm, width 2 cm) in a 0.1 mol / L KMnO4 solution, react at 80°C for 12 h for oxidation treatment, and then take it out;

[0076] S2, soaking the oxidized polypropylene diaphragm obtained in step S1 in deionized water to remove the KMnO4 solution remaining on the surface of the diaphragm, then soaking the diaphragm in 0.02 mol / L dilute hydrochloric acid solution to remove the MnO2 remaining on the surface, and finally washing the diaphragm with distilled water and ethanol respectively, and drying at 60° C. for 12 h to obtain an oxidized polypropylene diaphragm;

[0077] S3, adding 5 g PEO (molecular weight 400,000) and 0.6 g LiClO4 into 100 ml acetonitrile solvent, heating and magnetically stirring to obtain an electrolyte solution;

[0078] S4. Soak the oxidized polypropylene membrane in the electrolyte solution, take it out after 1 hour, and vacuum dry it at 40° C. for 24 hours to obtain a PEO-based solid electrolyte membrane.

[0079] Example 4

[0080] A method for preparing a PEO-based solid electrolyte membrane comprises the following steps:

[0081] S1. Soak a polypropylene membrane (thickness 9 μm, length 15 cm, width 2 cm) in a 0.1 mol / L KMnO4 solution, react at 80°C for 12 h for oxidation treatment, and then take it out;

[0082] S2, soaking the oxidized polypropylene diaphragm obtained in step S1 in deionized water to remove the KMnO4 solution remaining on the surface of the diaphragm, then soaking the diaphragm in 0.02 mol / L dilute hydrochloric acid solution to remove the MnO2 remaining on the surface, and finally washing the diaphragm with distilled water and ethanol respectively, and drying at 60° C. for 12 h to obtain an oxidized polypropylene diaphragm;

[0083] S3, adding 5 g PEO (molecular weight 400,000) and 0.6 g LiClO4 into 100 ml acetonitrile solvent, heating and magnetically stirring to obtain an electrolyte solution;

[0084] S4. Soak the oxidized polypropylene membrane in the electrolyte solution, take it out after 2 hours, and vacuum dry it at 40° C. for 24 hours to obtain a PEO-based solid electrolyte membrane.

[0085] Comparative Example 1

[0086] A method for preparing a PEO-based solid electrolyte membrane comprises the following steps:

[0087] S1, add 5g PEO (molecular weight 400,000) and 0.6g LiClO4 into 100ml acetonitrile solvent, heat and magnetically stir to obtain an electrolyte solution;

[0088] S4. Soak a polypropylene membrane (thickness 9 μm, length 15 cm, width 2 cm) in the electrolyte solution, take it out after 0.5 h, and vacuum dry it at 40° C. for 24 h to obtain a PEO-based solid electrolyte membrane.

[0089] Comparative Example 2

[0090] A method for preparing a PEO solid electrolyte film comprises the following steps:

[0091] S1, add 5g PEO (molecular weight 400,000) and 0.6g LiClO4 into 100ml acetonitrile solvent, heat and magnetically stir to obtain an electrolyte solution;

[0092] S2, pouring the electrolyte solution onto a glass plate (with a hard plastic film attached to the glass plate), and applying the solution to form a film by a scraper to obtain a wet film;

[0093] S3, place the glass plate covered with the wet film at room temperature for 1 hour;

[0094] S4. After standing still, the glass plate covered with the wet film is placed in an oven and vacuum dried at 40° C. for 24 hours to obtain a PEO solid electrolyte film.

[0095] test

[0096] (1) The thickness, 180° peel strength and tensile strength of the PEO-based solid electrolyte membrane obtained in Examples 1-4 and Comparative Examples 1-2 were tested respectively. The tensile strength test method was: a universal testing machine was used to test at a speed of 5 cm / min; the 180° peel strength test method was: 3M tape was attached to the surface of the sample, and the roller was rolled 3 times in the same direction by natural gravity. One end of the treated sample was vertically fixed on the upper clamp of the universal testing machine, and the lower clamp clamped the 3M tape, and the test was performed at a speed of 5 cm / min. The test data are shown in the following table:

[0097]

[0098]

[0099] From the above test results, it can be seen that the thickness of the PEO-based solid electrolyte membrane obtained in Examples 1 to 4 is 62 to 136 μm, the 180° peel strength is 2.3 to 5.2 N / m, and the tensile strength is 812 to 1490 Kgf / cm 2. Among them, in Examples 1 and 2, as the oxidation time of the polypropylene membrane changes, the thickness and 180° peel strength of the PEO-based solid electrolyte membrane obtained in Example 1 after oxidation for 12 hours are smaller than those of the PEO-based solid electrolyte membrane obtained in Example 2 after oxidation for 24 hours, but the tensile strength is higher. This is because at the same oxidation reaction temperature, the longer the reaction time, the better the oxidation effect of the polypropylene membrane, the rougher the surface, and the stronger the bonding with PEO.

[0100] In Examples 1, 3, and 4, as the immersion time of the oxidized polypropylene membrane in the electrolyte solution increases, the obtained PEO-based solid electrolyte membrane adsorbs more PEO, the thickness of the finished product increases, the 180° peel strength decreases, and the tensile strength decreases first and then increases.

[0101] By comparing Example 1 with Comparative Example 1, it can be seen that the polypropylene diaphragm in Comparative Example 1 is not oxidized and the surface is not damaged. The obtained diaphragm has high tensile strength, but low peel strength, PEO is easy to fall off, and is not conducive to large-scale production; while in Example 1, the polypropylene diaphragm is oxidized and then compounded with PEO, which improves the bonding force between PEO and the polypropylene diaphragm, so that the PEO-based solid electrolyte diaphragm has good tensile strength and peel strength, has strong mechanical strength, can simultaneously realize the functions of diaphragm and electrolyte, and is convenient for large-scale production.

[0102] By comparing Example 1 with Comparative Example 2, it can be seen that the supported PEO-based solid electrolyte membrane (Example 1) is thinner and has significantly improved mechanical tensile strength than the unsupported PEO solid electrolyte film (Comparative Example 2).

[0103] (2) The polarization voltage and cycle stability of the PEO-based solid electrolyte membranes obtained in Example 1 and Comparative Example 1 at 60° C. were tested respectively, wherein the battery assembly and testing process are as follows:

[0104] The active material (LiFePO4), conductive agent (SuperP) and binder (PVDF) are uniformly dispersed in 1-methyl-2-pyrrolidone (NMP) in a mass ratio of 8:1:1 and coated on aluminum foil. Dry at 60°C for 24 hours, then use a punch to cut the aluminum foil into discs with a diameter of 13 mm, with a loading of 1.1-1.3 mg / cm. The PEO-based solid electrolyte membranes prepared in Example 1 and Comparative Example 1 are respectively placed in a glove box with an argon atmosphere, and the batteries are assembled using a CR2025 button battery shell. Assemble the LiFePO4 / SPE / Li solid-state battery without dripping liquid electrolyte. After assembly, use a grinder to press the battery. After standing at 60°C for 6 hours, a 0.2C (1C=170mAh / g) charge and discharge cycle test is performed at 60°C using a blue electric charge and discharge instrument, with a voltage range of 2.5-3.65V. The test data is as follows:

[0105] sample Polarization voltage(V) Cycle stability number of turns Example 1 0.04 224 Comparative Example 1 0.28 65

[0106] The PEO-based solid electrolyte membrane obtained in Example 1 uses a polypropylene membrane that has been oxidized. Compared with the PEO-based solid electrolyte membrane obtained in Comparative Example 1 without using an oxidized membrane, the membrane has a smaller polarization voltage and better cycle stability, indicating that using an oxidized polypropylene membrane as a support can reduce the internal resistance of the PEO-based solid electrolyte membrane and give it good interface stability.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A method for preparing a PEO-based solid electrolyte membrane, characterized in that: The preparation method comprises the following steps: S1, oxidizing and cleaning the polypropylene diaphragm to obtain an oxidized polypropylene diaphragm; S2, dissolving PEO and lithium salt in a solvent to obtain an electrolyte solution; S3, soaking the oxidized polypropylene membrane in the electrolyte solution for a certain period of time and then vacuum drying it to obtain a PEO-based solid electrolyte membrane.

2. The preparation method according to claim 1, characterized in that: In step S1, the oxidation treatment includes: immersing the polypropylene diaphragm in a KMnO4 solution to perform an oxidation reaction; And / or, the polypropylene separator has a thickness of 5 to 11 μm.

3. The preparation method according to claim 2, characterized in that: The temperature of the oxidation reaction is 60-80°C; And / or, the oxidation reaction time is 12 to 24 hours; And / or, the concentration of the KMnO4 solution is 0.1-0.8 mol / L.

4. The preparation method according to claim 2, characterized in that: In step S1, the cleaning and impurity removal treatment includes: soaking the oxidized polypropylene diaphragm in deionized water to remove the KMnO4 solution remaining on the surface; then soaking it in dilute hydrochloric acid to remove the MnO2 remaining on the surface, and finally washing it with distilled water and ethanol respectively, and drying it to obtain an oxidized polypropylene diaphragm.

5. The preparation method according to claim 4, characterized in that: The concentration of the dilute hydrochloric acid is 0.01-0.1 mol / L.

6. The preparation method according to claim 1, characterized in that: In step S2, the mass ratio of PEO to lithium salt is 5:0.5-1; And / or, the average molecular weight of the PEO is 100,000 to 500,000; And / or, the lithium salt includes one or a mixture of at least two of LiPF6, LiFSI, LiTFSI and LiClO4; And / or, in the electrolyte solution, the mass concentration of PEO is 0.05 g / ml; And / or, in the electrolyte solution, the mass concentration of lithium salt is 0.005-0.01 g / ml.

7. The preparation method according to claim 1, characterized in that: In step S3, the oxidized polypropylene membrane is immersed for 0.5 to 2 hours; And / or, the vacuum drying time is 8 to 36 hours; And / or, the vacuum drying temperature is 35-55°C.

8. The preparation method according to claim 1, characterized in that: The thickness of the PEO-based solid electrolyte membrane is 60 to 140 μm.

9. A PEO-based solid electrolyte membrane, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

10. The PEO-based solid electrolyte membrane according to claim 9, characterized in that: 180° peel strength 2.0~5.5N / m, tensile strength 800~1500Kgf / cm 2 .

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