Preparation method of solid electrolyte membrane

Abstract

The invention relates to a preparation method of a solid electrolyte membrane, and belongs to the field of solid electrolyte. The preparation method comprises the following steps: uniformly mixing active salt, a polymer, ceramic powder and an organic solvent to obtain a solid electrolyte solution; wherein the concentration of the active salt in the solid electrolyte solution is 0.5-1.5 mol / L, the mass ratio of the polymer to the ceramic powder is 1: (0.5-2), and the total mass of the active salt, the polymer and the ceramic powder accounts for 30-70 wt% of the solid electrolyte solution; placing a non-woven fabric in the solid electrolyte solution, dipping, taking out, and drying to obtain a solid electrolyte membrane blank; and performing compression molding on the solid-state electrolyte membrane blank, and performing annealing treatment under a vacuum condition to obtain the solid-state electrolyte membrane. The preparation method disclosed by the invention is simple and compact in process, can simply realize uniform distribution of the active substances in the non-woven fabric, is beneficial to reducing the preparation cost, and improves the performance of the solid electrolyte membrane.

Description

Technical Field

[0001] The invention relates to a method for preparing a solid electrolyte membrane, and belongs to the field of solid electrolytes. Background Art

[0002] In recent years, with the continuous development of energy technology, the application of solid-state batteries in energy storage systems, electric vehicles, power tools, aerospace and other fields has attracted widespread attention. Solid-state battery technology replaces electrolytes with solid electrolytes, which can greatly improve the energy density and safety of batteries.

[0003] At present, solid electrolytes can be divided into several categories, such as inorganic ceramic solid electrolytes and polymer solid electrolytes. There are some problems with the traditional preparation methods of solid electrolytes, such as high raw material costs, complex preparation processes, and low ionic conductivity of electrolytes. At the same time, how to make solid electrolytes into thin films with good mechanical properties has become the core bottleneck of solid-state battery applications. Non-woven fabrics are a low-cost, porous, and easy-to-process material with application prospects in the preparation of solid electrolyte membranes. However, there is currently no effective method to fully utilize non-woven fabrics in the preparation of solid electrolytes.

[0004] Chinese invention patent application specification CN109935893A discloses a solid electrolyte membrane, which is composed of a strip of non-woven fabric and a polymer solid electrolyte; the surface of the non-woven fabric is coated with a polymer solid electrolyte. The patent uses a coating method to composite the non-woven fabric with the electrolyte active material, which has high requirements for the coating operation, resulting in high preparation costs and is not conducive to popularization and application. Summary of the invention

[0005] In view of the shortcomings of the prior art, the object of the present invention is to provide a simpler method for preparing a solid electrolyte membrane.

[0006] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0007] A method for preparing a solid electrolyte membrane comprises the following steps:

[0008] S1. Evenly mix active salt, polymer, ceramic powder and organic solvent to obtain a solid electrolyte solution; wherein the concentration of active salt in the solid electrolyte solution is 0.5-1.5 mol / L, the mass ratio of polymer to ceramic powder is 1:0.5-2, and the total mass of active salt, polymer and ceramic powder in the solid electrolyte solution accounts for 30-70 wt%;

[0009] S2, placing the nonwoven fabric in a solid electrolyte solution, immersing it, taking it out, and drying it to obtain a solid electrolyte membrane blank;

[0010] S3, after the solid electrolyte membrane blank is pressed and formed, annealing is performed under vacuum conditions to obtain a solid electrolyte membrane.

[0011] Therefore, the present invention first mixes the active salt, polymer, ceramic powder and organic solvent evenly to form a solid electrolyte solution with a certain viscosity, so that the active salt, polymer, ceramic powder, etc. can be dispersed in the liquid phase; then, the non-woven fabric is immersed in the solid electrolyte solution, so that the non-woven fabric can fully absorb the solid electrolyte solution, and the active salt, polymer, ceramic powder and other electrolyte active substances are uniformly attached or embedded in the non-woven fabric. After drying, a loose solid electrolyte membrane blank containing active salt, polymer and ceramic powder can be obtained; by further pressing and molding, the loose solid electrolyte membrane blank is transformed into a relatively compact film-like blank, and then further annealing treatment is performed to improve the binding between the active substances inside the blank, so that a solid electrolyte membrane with excellent quality can be obtained.

[0012] Furthermore, before S2, the non-woven fabric is pretreated, specifically, the non-woven fabric is soaked in an organic solvent (optionally ethanol) for 1-2 hours, and then vacuum dried at 50-60° C. for 2-3 hours. In this way, impurities on the non-woven fabric can be effectively removed.

[0013] Furthermore, in S1, the active salt includes one or more of lithium salt and sodium salt.

[0014] Furthermore, in S1, the lithium salt includes LiPF6; and the sodium salt includes NaPF6.

[0015] Furthermore, in S1, the polymer includes one or more of polyethylene oxide (PEO) and PVDF; the ceramic powder includes Li7La3Zr2O 12 (LLZO), Al2O3 or more; the organic solvent is N-methylpyrrolidone (NMP).

[0016] Furthermore, in S2, the immersion time is 0.5-5 h, preferably 1.5-4.5 h, and further 3-4 h.

[0017] Further, in S2, the thickness of the non-woven fabric is 5-100 μm, preferably 10-90 μm, and more preferably 20-80 μm. Optionally, the non-woven fabric is one of polypropylene non-woven fabric, polyester non-woven fabric, and PVDF non-woven fabric.

[0018] Further, in S2, drying is performed at 60-120°C for 0.5-8h.

[0019] Furthermore, in S3, the molding is performed by pressing at a pressure of 5-20 MPa, preferably at a pressure of 10-15 MPa.

[0020] Further, in S3, the annealing treatment is performed at 100-150° C. for 0.5-3 h, preferably, the annealing treatment is performed at 110-140° C. for 1-2.5 h.

[0021] Furthermore, the thickness of the solid electrolyte membrane is 10-100 μm, preferably 15-85 μm, and more preferably 30-70 μm.

[0022] The preparation method of the present invention can solve the problems of poor mechanical properties, high preparation cost, complex process and low ion conductivity of solid electrolytes in the prior art.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The preparation method of the present invention is simple and compact, and can easily achieve uniform distribution of active substances in the non-woven fabric, which helps to reduce the preparation cost and improve the performance of the solid electrolyte membrane.

[0025] (2) The solid electrolyte membrane prepared by the preparation method of the present invention has good ionic conductivity, reaching more than 1 mS / cm, and also has excellent mechanical properties, with a tensile strength of up to 20 MPa.

[0026] (3) The present invention uses non-woven fabric as raw material. Non-woven fabric is inexpensive and widely available, which greatly reduces the preparation cost of the solid electrolyte.

[0027] (4) The entire preparation process of the present invention has relatively few steps, does not require complicated equipment and process conditions, and is easy to mass produce.

[0028] (5) In the present invention, the ionic conductivity of the solid electrolyte membrane is effectively improved by filling the pores of the non-woven fabric with active substances and performing post-treatment. At the same time, the mechanical strength of the solid electrolyte membrane is close to that of ordinary PE diaphragms, which can meet the requirements of application scenarios such as lithium batteries and sodium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a cross-sectional view of the solid electrolyte membrane of Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below in conjunction with the embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0031] Example 1

[0032] The method for preparing the solid electrolyte membrane of this embodiment comprises the following steps:

[0033] S1. Select a polypropylene nonwoven fabric (thickness of 20 μm), cut it into a size of 10 cm×10 cm, soak it in ethanol for 1 hour, and then dry it in a vacuum drying oven at 50° C. for 3 hours for use.

[0034] S2. Prepare a solid electrolyte solution for immersion, which consists of LiPF6, PEO, LLZO and NMP; wherein the concentration of LiPF6 is 0.8 mol / L, the mass ratio of PEO to LLZO is 1:0.5, and the amount of NMP added is controlled so that the total mass of LiPF6, PEO and LLZO in the solid electrolyte solution accounts for 60wt%.

[0035] S3. After the non-woven fabric pretreated in S1 is immersed in the solid electrolyte solution described in S2 for 1 hour, the non-woven fabric is taken out, dried at 80°C for 2 hours, and then pressed into a 50μ thick film-like solid electrolyte blank at a pressure of 10MPa.

[0036] S4. The membrane-like solid electrolyte body is placed in a vacuum environment and annealed at 100° C. for 3 hours to obtain a solid electrolyte membrane.

[0037] According to the test, the room temperature ionic conductivity of the solid electrolyte membrane reaches 1.2mS / cm, and the tensile strength of the solid electrolyte membrane is 20Mpa.

[0038] Example 2

[0039] The method for preparing the solid electrolyte membrane of this embodiment comprises the following steps:

[0040] S1. Use polyPVDF non-woven fabric (thickness of 11 μm), cut into 15 cm × 15 cm, soak in ethanol for 1 hour, dry at 60°C for 2 hours, and set aside.

[0041] S2. Prepare a solid electrolyte solution for immersion, which is composed of NaPF6, PVDF, inorganic ceramic powder (Al2O3), and NMP; wherein the concentration of NaPF6 is 1.5 mol / L, the mass ratio of polymer (PVDF) to inorganic ceramic powder (Al2O3) is 1:2, and the amount of NMP added is controlled so that the total mass of NaPF6, PVDF, inorganic ceramic powder (Al2O3), and NMP in the solid electrolyte solution accounts for 40wt%.

[0042] S3. After the non-woven fabric treated with S1 is immersed in the solid electrolyte solution of S2 for 2 hours, the non-woven fabric is taken out, dried at 120°C for 5 hours, and then pressed into a thin film solid electrolyte blank with a thickness of 25μ at a pressure of 20MPa.

[0043] S4. The thin film solid electrolyte body is vacuum annealed at 120° C. for 2 hours to obtain a solid electrolyte membrane.

[0044] The test showed that the room temperature ionic conductivity of the solid electrolyte membrane was 1.6 mS / cm and the tensile strength of the solid electrolyte membrane was 18 Mpa.

[0045] The contents explained in the above embodiments should be understood as these embodiments are only used to more clearly illustrate the present invention, and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

Claims

1. A method for preparing a solid electrolyte membrane, characterized in that: The steps include: S1. Evenly mix active salt, polymer, ceramic powder and organic solvent to obtain a solid electrolyte solution; wherein the concentration of active salt in the solid electrolyte solution is 0.5-1.5 mol / L, the mass ratio of polymer to ceramic powder is 1:0.5-2, and the total mass of active salt, polymer and ceramic powder in the solid electrolyte solution accounts for 30-70 wt%; S2, placing the nonwoven fabric in a solid electrolyte solution, immersing it, taking it out, and drying it to obtain a solid electrolyte membrane blank; S3, after the solid electrolyte membrane blank is pressed and formed, annealing is performed under vacuum conditions to obtain a solid electrolyte membrane.

2. The preparation method according to claim 1, characterized in that: In S1, the active salt includes one or more of lithium salt and sodium salt.

3. The preparation method according to claim 2, characterized in that: In S1, the lithium salt includes LiPF6; the sodium salt includes NaPF6.

4. The preparation method according to any one of claims 1 to 3, characterized in that In S1, the polymer includes one or more of polyethylene oxide and PVDF; the ceramic powder includes Li7La3Zr2O 12 (LLZO), Al2O3 or more; the organic solvent is N-methylpyrrolidone.

5. The preparation method according to any one of claims 1 to 3, characterized in that: S2, soak for 0.5-5h.

6. The preparation method according to any one of claims 1 to 3, characterized in that: In S2, the non-woven fabric is one of polypropylene non-woven fabric, polyester non-woven fabric and PVDF non-woven fabric; preferably, the thickness of the non-woven fabric is 5-100 μm.

7. The preparation method according to any one of claims 1 to 3, characterized in that: In S2, dry at 60-120°C for 0.5-8h.

8. The preparation method according to any one of claims 1 to 3, characterized in that: In S3, the molding is performed by compression molding at a pressure of 5-20 MPa.

9. The preparation method according to any one of claims 1 to 3, characterized in that: In S3, annealing is performed at 100-150° C. for 0.5-3 h.

10. The preparation method according to any one of claims 1 to 3, characterized in that: The thickness of the solid electrolyte membrane is 10-100 μm.

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