Ultrathin elastic solid electrolyte membrane and preparation method thereof

Abstract

The present invention discloses an ultrathin elastic solid electrolyte membrane and a preparation method thereof. The solid electrolyte membrane comprises an inorganic solid electrolyte coated with a polyionic liquid, a polymer matrix and a lithium salt; the inorganic solid electrolyte coated with the polyionic liquid accounts for 10 to 80% of the mass of the solid electrolyte membrane; the mass ratio of the polymer matrix to the lithium salt is 5:1 to 1:1; in the inorganic solid electrolyte coated with the polyionic liquid, the polyionic liquid accounts for 0.5-1% of the mass of the inorganic solid electrolyte; in the polyionic liquid monomer, the cation is 4-butylvinylimidazole, and the anion is any one of bistrifluoromethanesulfonic acid imide ion, bromide ion and hexafluorophosphate ion; the inorganic solid electrolyte is Li3Zr2Si2PO4 12 The polymer matrix comprises either PVDF or PVDF-HFP; the anion of the lithium salt is consistent with the anion of the polyionic liquid monomer. The ultrathin solid electrolyte membrane prepared by the present invention has a thickness of approximately 7 to 15 μm, is lightweight and uniform, has excellent elastic strength and stability, and can be produced on a large scale.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid electrolyte preparation, and in particular relates to an ultra-thin elastic solid electrolyte membrane and a preparation method thereof. Background Art

[0002] For decades, the rapid development of lithium-ion batteries has enabled them to dominate the energy storage field. However, the market has raised more challenges and requirements for high energy density and safety and reliability. The unstable solid electrolyte interface in liquid organic electrolytes and the growth of lithium dendrites lead to low Coulombic efficiency and safety issues.

[0003] Solid-state batteries are considered one of the ultimate solutions. High-performance solid-state electrolytes can match high-voltage cathodes and lithium metal anodes, which is of great significance for the development of high-energy-density and safe solid-state lithium metal batteries (LMBs).

[0004] The solid polymer electrolytes reported so far include polyethylene (PEO) based, polyacrylonitrile (PAN) based, polypropylene carbonate (PPC) based and polyvinylidene fluoride (PVDF) based. Compared with other polymers, PVDF based electrolytes have advantages such as high mechanical strength and good thermal stability. However, since the solvent DMF is generally used in the preparation process, it is difficult to completely dry it and there are residual solvents, which faces many problems. For example, there is a strong interaction between DMF and Li salts to form [Li(DMF) x ] + Solvated molecules, which are transported through PVDF chains, can achieve high ionic conductivity of solid electrolyte membranes. However, the presence of DMF causes the electrochemical window of the electrolyte to narrow and continues to decompose at high potentials. At the same time, DMF also undergoes serious side reactions with metallic lithium. On the other hand, in order to resist lithium dendrites and improve the stability of the PVDF-based electrolyte / lithium metal interface, some active fillers including LATP are usually added to the electrolyte membrane to improve the mechanical properties and lithium stability of the PVDF electrolyte. However, these inorganic solid electrolyte fillers are prone to continuous defluorination of PVDF polymers, which reduces the ionic conductivity of the composite electrolyte and increases the interface resistance between the active filler and PVDF. In particular, when the inorganic electrolyte content is high, such as more than 50wt%, the solid electrolyte slurry is difficult to disperse, resulting in problems such as uneven film thickness. Summary of the Invention

[0005] The purpose of the present invention is to provide a new type of ultra-thin elastic solid electrolyte membrane to overcome the problems of uneven thickness, inability to resist lithium dendrites, unstable electrochemical performance, etc. of traditional PVDF-based solid electrolyte membranes.

[0006] In order to achieve the above-mentioned object, the present invention provides an ultrathin elastic solid electrolyte membrane, comprising: an inorganic solid electrolyte coated with a polyionic liquid, a polymer matrix and a lithium salt; wherein the inorganic solid electrolyte coated with the polyionic liquid accounts for 10 to 80% of the mass of the solid electrolyte membrane; the mass ratio of the polymer matrix to the lithium salt is 5:1 to 1:1; in the inorganic solid electrolyte coated with the polyionic liquid, the polyionic liquid accounts for 0.5 to 1% of the mass of the inorganic solid electrolyte; in the monomer of the polyionic liquid, the cation is 4-butylvinylimidazole, and the anion is any one of bistrifluoromethanesulfonic acid imide, bromide, and hexafluorophosphate; the inorganic solid electrolyte is Li3Zr2Si2PO4 12 ; The polymer matrix includes any one of PVDF and PVDF-HFP; the anion of the lithium salt is consistent with the anion of the polyionic liquid monomer.

[0007] Optionally, the inorganic solid electrolyte coated with polyionic liquid accounts for 60-80% of the mass of the solid electrolyte membrane.

[0008] Optionally, the solid electrolyte membrane has a thickness of 7 to 15 μm.

[0009] Optionally, the elastic elongation of the solid electrolyte membrane is ≥300%.

[0010] Optionally, the inorganic solid electrolyte Li3Zr2Si2PO 12 It is composed of sodium ion conductor Na3Zr2Si2PO 12 Obtained after ion exchange.

[0011] The present invention also provides a method for preparing the above-mentioned ultra-thin elastic solid electrolyte membrane, comprising:

[0012] Step 1: Sodium superion conductor Na3Zr2Si2PO 12 The lithium salt and the ionic liquid are placed in a reaction container and mixed evenly, wherein the concentration of the lithium salt in the ionic liquid is 0.1 mol / L-0.5 mol / L, and the lithium salt and Na3Zr2Si2PO 12 The molar ratio is 3:1;

[0013] Step 2: Place the reaction vessel in a homogeneous reactor, rotate and stir at a speed of 40-60 rpm / min for 72-144 hours at a temperature of 100-200°C to make the sodium superion conductor Na3Zr2Si2PO 12 The sodium ions in the lithium salt exchange with the lithium ions in the lithium salt;

[0014] Step 3: Take out the reaction solution in the reaction container, centrifuge and dry to obtain ionic liquid-coated Li3Zr2Si2PO12 ;

[0015] Step 4: Li3Zr2Si2PO coated with the ionic liquid 12 Polymerization to obtain polyionic liquid-coated Li3Zr2Si2PO 12 ;

[0016] Step 5: In an argon atmosphere, the polymer matrix is ​​dissolved in N,N-dimethylformamide to obtain a mixed solution A, the mixed solution A is stirred at room temperature until the solution is clear, and then a lithium salt is added to obtain a mixed solution B, and the polyionic liquid-coated Li3Zr2Si2PO4 is added to the stirred mixed solution B. 12 The mixed solution C was obtained and stirred at room temperature for 12-24 hours;

[0017] Step 6: pour the mixed solution C onto a glass vessel, place it in a protective atmosphere at 50-70° C. for 16-24 hours, and evaporate the solvent to obtain the solid electrolyte membrane.

[0018] Optionally, in step 4, the ionic liquid-coated Li3Zr2Si2PO 12 The photopolymerization was initiated by a photoinitiator to generate polyionic liquid-coated Li3Zr2Si2PO 12 .

[0019] Optionally, the photoinitiator is acrylic acid / N-isopropylacrylamide monomer.

[0020] Optionally, in step 4, the polyionic liquid coated Li3Zr2Si2PO 12 The absolute value of the zeta potential is ≥61 mV.

[0021] The beneficial effects of the present invention are:

[0022] 1) Polyionic liquid-coated Li3Zr2Si2PO 12 The material has a very high absolute value of zeta potential, is extremely stable, and is easily dispersed in solid electrolyte membrane slurries without agglomeration. This has a positive effect on the preparation of electrolyte membrane slurries, such as reducing the difficulty of film formation and obtaining a thin and uniform solid electrolyte membrane. Furthermore, even with the addition of a large amount of inorganic particles, it can still be well dispersed, and inorganic particles can improve the mechanical strength of the solid electrolyte membrane. Therefore, the present invention can simultaneously take into account the mechanical properties and thickness of the solid electrolyte membrane, resulting in a thin, uniform, and mechanically strong solid electrolyte membrane.

[0023] 2) When the inorganic solid electrolyte content is high, the existing solid electrolyte film is brittle and has a large interface impedance. 12The surface of the polymer itself has excellent elasticity, and the solid electrolyte membrane prepared from it has excellent elastic strength. This can reduce the contact impedance of the solid electrolyte / electrode interface in solid-state batteries on the one hand, and resist the penetration of lithium dendrites on the other hand, achieving long-term and uniform lithium deposition on the lithium metal negative electrode.

[0024] 3) The presence of polyionic liquids creates a strong interaction between the inorganic particles and the DMF molecules, tightly securing the remaining DMF solvent. On the one hand, DMF significantly improves ionic conductivity. Because the remaining DMF is liquid, ionic conductivity is improved, and the ionic liquid's restraint on DMF simultaneously controls its dissociation, retaining its advantages while minimizing its disadvantages. On the other hand, the DMF solvent is immobilized in the solid electrolyte membrane, preventing it from dissociating into the solid electrolyte / electrode interface and causing decomposition reactions, thereby improving the electrochemical window of the solid electrolyte membrane.

[0025] 4) Li3Zr2Si2PO obtained by ion exchange method 12 It has high ionic conductivity and excellent air stability and electrochemical stability, which not only has a positive effect on improving the comprehensive performance of the solid electrolyte membrane, but also Li3Zr2Si2PO 12 The air stability will also reduce the difficulty of the film making process and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a SEM image of the cross section of the ultrathin elastic solid electrolyte membrane prepared in Example 1 of the present invention.

[0027] Figure 2a The polyionic liquid coated Li3Zr2Si2PO prepared in Example 2 of the present invention 12 Zeta potential test value; Figure 2b Li3Zr2Si2PO4 prepared in Comparative Example 1 of the present invention without ionic liquid coating 12 Zeta potential test value.

[0028] Figure 3 This is a SEM image of the surface of the ultrathin elastic solid electrolyte membrane prepared in Example 2 of the present invention.

[0029] Figure 4a This is a mechanical property curve of the ultrathin elastic solid electrolyte membrane prepared in Example 3 of the present invention; Figure 4b This is a photo of the ultrathin elastic solid electrolyte membrane prepared in Example 3; Figure 4c This is a mechanical property curve of the solid electrolyte membrane prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0030] Existing solid polymer electrolytes (PVDF)-based electrolytes typically use the solvent DMF during their preparation, which is difficult to completely dry and leaves residual solvent. For example, if DMF migrates to the solid electrolyte / electrode interface, it can cause instability. Since DMF is not resistant to high voltages, the interface can be easily damaged during charging.

[0031] To this end, the present invention develops an innovative strategy to firmly fix the residual DMF in the solid electrolyte membrane and build a stable interface between the high-voltage positive electrode and the lithium metal negative electrode.

[0032] The present invention utilizes ionic liquid to coat inorganic solid electrolyte to form a polyionic liquid-coated inorganic solid electrolyte. Since the adsorption energy between DMF and PVDF is -0.22eV, and the adsorption energy between DMF and ionic liquid is -0.37eV, the ionic liquid is more likely to catch free DMF. The presence of polyionic liquid causes strong interactions between inorganic particles and DMF molecules, which can tightly fix residual DMF solvent, making it difficult to dissociate to the interface, making the interface more stable. Since the DMF solvent is fixed in the solid electrolyte membrane, it will not dissociate to the solid electrolyte / electrode interface, causing the generation of decomposition reaction, thereby improving the electrochemical window of the solid electrolyte membrane. On the other hand, the presence of DMF can improve ionic conductivity.

[0033] Specifically, the present invention provides an ultrathin elastic solid electrolyte membrane comprising: an inorganic solid electrolyte coated with a polyionic liquid, a polymer matrix, and a lithium salt. In the inorganic solid electrolyte coated with the polyionic liquid, the polyionic liquid accounts for 0.5-1% of the mass of the inorganic solid electrolyte; in the monomer of the polyionic liquid, the cation is 4-butylvinylimidazole, and the anion is any one of a bistrifluoromethanesulfonic acid imide ion, a bromide ion, and a hexafluorophosphate ion; the inorganic solid electrolyte is Li3Zr2Si2PO4 12 . The polymer matrix includes any one of PVDF and PVDF-HFP. The anion of the lithium salt is consistent with the anion of the polyionic liquid monomer, that is, when the anion of the ionic liquid is bistrifluoromethanesulfonamide ion, the lithium salt is lithium bistrifluoromethanesulfonamide (LiTFSI); when the anion of the ionic liquid is bromide ion, the lithium salt is lithium bromide (LiBr); when the anion of the ionic liquid is hexafluorophosphate ion, the lithium salt is lithium hexafluorophosphate (LiPF6).

[0034] The inorganic solid electrolyte coated with the polyionic liquid accounts for 10-80% of the mass of the solid electrolyte membrane. 12It has a very high absolute value of zeta potential, is extremely stable, and is easily dispersed in the solid electrolyte membrane slurry without agglomeration. The content of the inorganic solid electrolyte coated with the polyionic liquid can be very high, such as 60-80% of the mass of the solid electrolyte membrane, to improve the mechanical strength of the solid electrolyte membrane.

[0035] The mass ratio of the polymer matrix to the lithium salt is 5:1 to 1:1.

[0036] Due to good dispersibility and strong film-forming ability, the film thickness can be made very thin and uniform. The thickness of the solid electrolyte membrane of the present invention can be 7 to 15 μm, and the film thickness is uniform and has excellent elasticity.

[0037] The method for preparing the ultrathin elastic solid electrolyte membrane of the present invention comprises:

[0038] Step 1: Sodium superion conductor Na3Zr2Si2PO 12 The lithium salt and the ionic liquid are placed in a reaction container and mixed evenly, wherein the concentration of the lithium salt in the ionic liquid is 0.1 mol / L-0.5 mol / L, and the lithium salt and Na3Zr2Si2PO 12 The molar ratio is 3:1.

[0039] Step 2: Place the reaction vessel in a homogeneous reactor, rotate and stir at a speed of 40-60 rpm / min for 72-144 hours at a temperature of 100-200°C to make the sodium superion conductor Na3Zr2Si2PO 12 The sodium ions in the electrolyte exchange with the lithium ions in the lithium salt.

[0040] Step 3: Take out the reaction solution in the reaction container, centrifuge and dry to obtain ionic liquid-coated Li3Zr2Si2PO 12 .

[0041] Step 4: Li3Zr2Si2PO coated with the ionic liquid 12 Polymerization to obtain polyionic liquid-coated Li3Zr2Si2PO 12 In some embodiments, the ionic liquid-coated Li3Zr2Si2PO 12 The photopolymerization was initiated by a photoinitiator to generate polyionic liquid-coated Li3Zr2Si2PO 12 Wherein, the photoinitiator can be selected from acrylic acid / N-isopropylacrylamide monomer, and the equation for initiating photopolymerization is as follows:

[0042]

[0043] Step 5: In an argon atmosphere, the polymer matrix is ​​dissolved in N,N-dimethylformamide to obtain a mixed solution A, the mixed solution A is stirred at room temperature until the solution is clear, and then a lithium salt is added to obtain a mixed solution B, and the polyionic liquid-coated Li3Zr2Si2PO4 is added to the stirred mixed solution B. 12 , to obtain a mixed solution C, which was stirred at room temperature for 12-24h.

[0044] Step 6: pour the mixed solution C onto a glass vessel, place it in a protective atmosphere at 50-70°C for 16-24 hours, evaporate the solvent to obtain the solid electrolyte membrane. 12 The polyionic liquid on the surface can absorb the residual solvent DMF that has not been dried in the solid electrolyte membrane and fix DMF on the Li3Zr2Si2PO 12 The surface of inorganic particles is not easy to be freed to the solid electrolyte / electrode interface.

[0045] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0046] Example 1

[0047] A method for preparing a solid electrolyte membrane comprises the following steps:

[0048] Step 1: 0.03532g of sodium superion conductor Na3Zr2Si2PO 12 Mix evenly with 0.574 g LiTFSI and 10 mL ionic liquid (4-butylvinyl imidazole bis(trifluoromethanesulfonyl)imide salt) and place in a reactor;

[0049] Step 2: Place the reaction kettle into a homogeneous reactor and stir at a speed of 50 rpm / min for 144 h at a temperature of 100°C;

[0050] Step 3: Take out the product from the reactor, centrifuge and dry it to obtain Li3Zr2Si2PO4 coated with ionic liquid. 12 ;

[0051] Step 4: dissolve the product obtained in step 3 in ethanol and use 1 molar equivalent of acrylic acid / N-isopropylacrylamide (molar ratio of 1:1) as an initiator to prepare polyionic liquid-coated Li3Zr2Si2PO4 by solution polymerization at 70°C. 12 ;

[0052] Step 5: 0.48 g of PVDF was dissolved in 12 g of DMF in an argon atmosphere to obtain a mixed solution A. The mixed solution A was stirred at room temperature until the solution was clear, and then 0.16 g of LiTFSI was added to obtain a mixed solution B. 0.13 g of the prepared polyionic liquid-coated Li3Zr2Si2PO 12 The mixed solution C was obtained and stirred at room temperature for 24 h;

[0053] Step 6: pour the mixed solution C onto a glass vessel, place it in a protective atmosphere at 60° C. for 24 hours, and evaporate the solvent to obtain the solid electrolyte membrane.

[0054] like Figure 1 , which is a SEM image of a cross section of the ultra-thin elastic solid electrolyte membrane prepared in Example 1. It can be seen from the figure that the solid electrolyte membrane is very dense and uniform, with a thickness of about 10 μm.

[0055] Example 2

[0056] A method for preparing a solid electrolyte membrane comprises the following steps:

[0057] Step 1: 0.03532g of sodium superion conductor Na3Zr2Si2PO 12 Mix evenly with 0.574 g LiTFSI and 10 mL ionic liquid (4-butylvinyl imidazole bis(trifluoromethanesulfonyl)imide salt) and place in a reactor;

[0058] Step 2: Place the reaction kettle into a homogeneous reactor and stir at a speed of 50 rpm / min for 72 h at a temperature of 180°C;

[0059] Step 3: Take out the product from the reactor, centrifuge and dry it to obtain Li3Zr2Si2PO4 coated with ionic liquid. 12 ;

[0060] Step 4: dissolve the product obtained in step 3 in ethanol and use 1 molar equivalent of acrylic acid / N-isopropylacrylamide (molar ratio of 1:1) as an initiator to prepare polyionic liquid-coated Li3Zr2Si2PO4 by solution polymerization at 70°C. 12 ;

[0061] Step 5: 0.48 g of PVDF was dissolved in 12 g of DMF in an argon atmosphere to obtain a mixed solution A. The mixed solution A was stirred at room temperature until the solution was clear, and then 0.16 g of LiTFSI was added to obtain a mixed solution B. 1.55 g of the prepared polyionic liquid-coated Li3Zr2Si2PO 12 The mixed solution C was obtained and stirred at room temperature for 24 h;

[0062] Step 6: pour the stirred mixed solution C onto a glass vessel, place it in a protective atmosphere at 60° C. for 24 hours, and evaporate the solvent to obtain the solid electrolyte membrane with a thickness of about 15 μm.

[0063] Comparative Example 1

[0064] A method for preparing a solid electrolyte membrane comprises the following steps:

[0065] Step 1: 0.03532g of sodium superion conductor Na3Zr2Si2PO 12 Mix evenly with 0.574 g LiTFSI and 10 mL ionic liquid (4-butylvinyl imidazole bis(trifluoromethanesulfonyl)imide salt) and place in a reactor;

[0066] Step 2: Place the reaction kettle into a homogeneous reactor and stir at a speed of 50 rpm / min for 72 h at a temperature of 180°C;

[0067] Step 3: Take out the product from the reactor and wash it with ethanol, centrifuge it, and dry it to obtain Li3Zr2Si2PO 12 ;

[0068] Step 5: 0.48 g of PVDF was dissolved in 12 g of DMF in an argon atmosphere to obtain a mixed solution A. The mixed solution A was stirred at room temperature until the solution was clear, and then 0.16 g of LiTFSI was added to obtain a mixed solution B. 1.55 g of Li3Zr2Si2PO4 was added to the mixed solution B. 12 The mixed solution C was obtained and stirred at room temperature for 24 h;

[0069] Step 6: pour the stirred mixed solution C onto a glass vessel, place it in a protective atmosphere at 60° C. for 24 hours, and evaporate the solvent to obtain the solid electrolyte membrane with a thickness of about 15 μm.

[0070] Figure 2a The polyionic liquid coated Li3Zr2Si2PO prepared in Example 2 12 The Zeta potential test value is -65.5mV. Zeta potential is a measure of the strength of mutual repulsion or attraction between particles. The smaller the molecules or dispersed particles, the higher the absolute value of the Zeta potential (positive or negative), and the more stable the system, meaning that the solution or dispersion resists aggregation. It is generally believed that when the absolute value of the particle Zeta potential is greater than 61mV, the system has excellent stability. Figure 2b Solid electrolyte Li3Zr2Si2PO prepared as a comparative example 12The Zeta potential measured without polyionic liquid coating is -8.41 mV. This indicates that polyionic liquid coating significantly increases the absolute value of the Zeta potential, demonstrating that polyionic liquid coating effectively improves system stability, allowing the inorganic solid electrolyte to be easily dispersed in the solid electrolyte membrane slurry, resulting in easy film formation with uniform and controllable thickness.

[0071] Figure 3 This is a SEM image of the surface of the ultrathin elastic solid electrolyte membrane prepared in Example 2. It can be seen from the figure that even in the presence of the added polyionic liquid-coated Li3Zr2Si2PO 12 In the case of very high content (70%, by formula: mass Li3Zr2Si2PO12 / (quality Li3Zr2Si2PO12 +Quality PVDF +Quality LiTFSI ) calculation), the nano-sized inorganic particles can still be evenly distributed in the solid electrolyte membrane, proving that the polyionic liquid-coated Li3Zr2Si2PO 12 It is very stable and not easy to agglomerate.

[0072] Example 3

[0073] A method for preparing a solid electrolyte membrane comprises the following steps:

[0074] Step 1: 0.03532g of sodium superion conductor Na3Zr2Si2PO 12 Mix evenly with 0.574 g LiTFSI and 10 mL ionic liquid and place in a reactor;

[0075] Step 2: Place the reaction kettle into a homogeneous reactor and stir at a speed of 50 rpm / min for 72 h at a temperature of 180°C;

[0076] Step 3: Take out the product from the reactor, centrifuge and dry it to obtain Li3Zr2Si2PO4 coated with ionic liquid. 12 ;

[0077] Step 4: dissolve the product obtained in step 3 in ethanol, and use 1 molar equivalent of acrylic acid / N-isopropylacrylamide (molar ratio of 1:1) as an initiator to prepare polyionic liquid-coated Li3Zr2Si2PO4 by solution polymerization at 70°C. 12 ;

[0078] Step 5: 0.48 g of PVDF was dissolved in 12 g of DMF in an argon atmosphere to obtain a mixed solution A. The mixed solution A was stirred at room temperature until the solution was clear, and then 0.16 g of LiTFSI was added to obtain a mixed solution B. 0.48 g of the prepared polyionic liquid-coated Li3Zr2Si2PO 12 The mixed solution C was obtained and stirred at room temperature for 24 h;

[0079] Step 6: pour the stirred mixed solution C onto a glass vessel, place it in a protective atmosphere at 60° C. for 24 hours, and evaporate the solvent to obtain the solid electrolyte membrane with a thickness of about 7 μm.

[0080] Comparative Example 2

[0081] In an argon atmosphere, 0.48 g of PVDF was dissolved in 12 g of DMF to obtain a mixed solution A. The mixed solution A was stirred at room temperature until the solution was clear, and then 0.16 g of LiTFSI was added to obtain a mixed solution B. The prepared 0.48 g of Li3Zr2Si2PO4 was added to the mixed solution B. 12 The mixed solution C was obtained and stirred at room temperature for 24 h;

[0082] The stirred mixed solution C was poured onto a glass vessel, placed in a protective atmosphere at 60° C. for 24 hours, and the solvent was evaporated to obtain the solid electrolyte membrane with a thickness of about 7 μm.

[0083] Figure 4a The mechanical properties curve of the ultra-thin elastic solid electrolyte membrane prepared in Example 3 shows that the elongation at break of the membrane is over 300% even when the membrane is very thin, showing excellent elastic strength. The solid electrolyte membrane prepared in Example 3 is divided into two sections of identical shape and size. One section is not treated and the other section is subjected to ultimate stretching. Figure 4b As shown in the figure, 1 represents the untreated solid electrolyte membrane and 2 represents the stretched solid electrolyte membrane. It can be seen that the length of 2 is significantly greater than three times the length of 1, demonstrating that the solid electrolyte membrane prepared by the present invention is highly elastic. This has a positive effect on reducing the contact impedance of the solid electrolyte / electrode interface in solid-state batteries, while also resisting the penetration of lithium dendrites and achieving long-term uniform lithium deposition on the lithium metal negative electrode.

[0084] Figure 4c This is the mechanical property curve of the solid electrolyte membrane prepared in Comparative Example 2. It can be seen that if the inorganic solid electrolyte material coated with polyionic liquid is not used, the elongation at break of the membrane is only 78%.

[0085] In summary, the solid electrolyte membrane provided by the present invention uses a lithium superion conductor in situ coated with a polyionic liquid as an inorganic solid electrolyte component, has the advantages of high conductivity, high elastic strength, and air stability and lithium stability, and is easy to achieve large-scale production.

[0086] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. An ultrathin elastic solid electrolyte membrane, characterized in that: include: An inorganic solid electrolyte coated with a polyionic liquid, a polymer matrix, and a lithium salt; wherein the inorganic solid electrolyte coated with the polyionic liquid accounts for 10-80% of the mass of the solid electrolyte membrane; the mass ratio of the polymer matrix to the lithium salt is 5:1-1:1; in the inorganic solid electrolyte coated with the polyionic liquid, the polyionic liquid accounts for 0.5-1% of the mass of the inorganic solid electrolyte; in the polyionic liquid monomer, the cation is 4-butylvinylimidazole, and the anion is any one of bistrifluoromethanesulfonic acid imide ion, bromide ion, and hexafluorophosphate ion; the inorganic solid electrolyte is Li3Zr2Si2PO 12 ; The polymer matrix includes any one of PVDF and PVDF-HFP; the anion of the lithium salt is consistent with the anion of the polyionic liquid monomer, and the thickness of the solid electrolyte membrane is 7µm ~15 µm.

2. The ultra-thin elastic solid electrolyte membrane according to claim 1, wherein The inorganic solid electrolyte coated with the polyionic liquid accounts for 60-80% of the mass of the solid electrolyte membrane.

3. The ultra-thin elastic solid electrolyte membrane according to claim 1, wherein The elastic elongation of the solid electrolyte membrane is ≥300%.

4. The ultra-thin elastic solid electrolyte membrane according to claim 1, wherein The inorganic solid electrolyte Li3Zr2Si2PO 12 It is composed of sodium ion conductor Na3Zr2Si2PO 12 Obtained after ion exchange.

5. A method for preparing an ultrathin elastic solid electrolyte membrane according to any one of claims 1 to 4, characterized in that: include: Step 1: Sodium superion conductor Na3Zr2Si2PO 12 The lithium salt and ionic liquid are placed in a reaction container and mixed evenly, wherein the concentration of the lithium salt in the ionic liquid is 0.1 mol / L-0.5 mol / L, the lithium salt and Na3Zr2Si2PO 12 The molar ratio is 3:1; Step 2: Place the reaction vessel in a homogeneous reactor, rotate and stir at a speed of 40-60 rpm / min for 72-144 hours at a temperature of 100-200°C to make the sodium superion conductor Na3Zr2Si2PO 12 The sodium ions in the lithium salt exchange with the lithium ions in the lithium salt; Step 3: Take out the reaction solution in the reaction container, centrifuge and dry to obtain ionic liquid-coated Li3Zr2Si2PO 12 ; Step 4: Li3Zr2Si2PO coated with the ionic liquid 12 Polymerization to obtain polyionic liquid-coated Li3Zr2Si2PO 12 ; Step 5: In an argon atmosphere, the polymer matrix is ​​dissolved in N,N-dimethylformamide to obtain a mixed solution A, the mixed solution A is stirred at room temperature until the solution is clear, and then a lithium salt is added to obtain a mixed solution B, and the polyionic liquid-coated Li3Zr2Si2PO4 is added to the stirred mixed solution B. 12 The mixed solution C was obtained and stirred at room temperature for 12-24 hours; Step 6: pour the mixed solution C onto a glass vessel, place it in a protective atmosphere at 50-70° C. for 16-24 hours, and evaporate the solvent to obtain the solid electrolyte membrane.

6. The method for preparing an ultrathin elastic solid electrolyte membrane according to claim 5, wherein: In step 4, the ionic liquid-coated Li3Zr2Si2PO 12 The photopolymerization was initiated by a photoinitiator to generate polyionic liquid-coated Li3Zr2Si2PO 12 .

7. The method for preparing an ultrathin elastic solid electrolyte membrane according to claim 6, wherein: The photoinitiator is acrylic acid / N-isopropylacrylamide monomer.

8. The method for preparing an ultrathin elastic solid electrolyte membrane according to claim 5, wherein: In step 4, the polyionic liquid coated Li3Zr2Si2PO 12 The absolute value of the zeta potential is ≥61 mV.

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