A composite electrolyte film for improving ion conductivity of a solid-state battery and a method of manufacturing the same

Abstract

This application discloses a composite electrolyte membrane for improving the ionic conductivity of solid-state batteries and its preparation method, relating to the field of lithium-ion battery technology. The preparation method of the composite electrolyte membrane includes the following steps: LATP coated with graphite-like carbon nitride and polydopamine-modified 2-methylimidazolium zinc salt are added to tetraethylene glycol dimethyl ether and dispersed evenly; then lithium bis(trifluoromethanesulfonyl)imide and benzoyl peroxide are added and stirred evenly at room temperature; subsequently, polyethylene oxide is added and stirred evenly at room temperature; the mixture is coated onto a polytetrafluoroethylene plate, transferred to a vacuum oven for heating, and hot-pressed to obtain the composite electrolyte membrane. The electrolyte membrane provided by this application has excellent ionic conductivity and mechanical strength.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a composite electrolyte membrane for improving the ionic conductivity of solid-state batteries and its preparation method. Background Technology

[0002] Lithium-ion batteries are widely used in portable devices such as mobile phones and watches, as well as in automotive power, special equipment, and energy storage power stations. Currently, liquid lithium-ion batteries use organic electrolytes, which pose safety hazards such as leakage, combustion, and corrosion, affecting battery safety performance. To address this issue, solid-state electrolytes have become a research hotspot. As a key technology for optimizing liquid batteries, they can effectively improve battery safety, avoid the risks associated with organic electrolytes, and are an important way to promote the application of lithium-ion batteries in high-safety-demand fields such as automobiles.

[0003] Solid electrolytes are generally classified into three categories: inorganic ceramic electrolytes, polymer solid electrolytes, and organic-inorganic composite solid electrolytes. Inorganic ceramic electrolytes possess high ionic conductivity and a wide electrochemical stability window, but their high hardness makes it difficult to form good contact with electrodes, resulting in high interfacial impedance and affecting practical applications. Conversely, polymer solid electrolytes are flexible electrolytes with good contact with both electrodes, but their ion transport mechanism through chain segment movement leads to low ionic conductivity, poor high-voltage resistance, and a typically narrow electrochemical stability window. Organic-inorganic composite solid electrolytes are materials that combine a polymer matrix with inorganic fillers to improve electrolyte performance. These composite electrolytes combine the advantages of both ceramic and polymer electrolytes, exhibiting excellent electrochemical performance and good interfacial compatibility, making them a current research hotspot.

[0004] Organic-inorganic composite solid electrolytes consist of a polymer matrix, inorganic fillers, lithium salts, and other components. Polyethylene oxide (PEO) is one of the commonly used polymer matrices. However, the high crystallinity of PEO at room temperature hinders polymer segment movement and lithium-ion movement, resulting in relatively low conductivity. Furthermore, the mechanical weaknesses of polymer solid electrolytes in the solid state are insufficient to physically prevent the dangerous penetration of lithium dendrites at high temperatures or high current densities. Summary of the Invention

[0005] In order to provide a solid battery composite electrolyte membrane with high ionic conductivity and mechanical strength, this application provides a composite electrolyte membrane for improving the ionic conductivity of solid batteries and a method for preparing the same.

[0006] This application provides a composite electrolyte membrane for improving the ionic conductivity of solid-state batteries, employing the following technical solution: A composite electrolyte membrane for improving the ionic conductivity of solid-state batteries comprises, by mass percentage, 35-45% polyethylene oxide, 12-15% lithium bis(trifluoromethanesulfonyl)imide, 10-19.5% LATP coated with graphite-like carbon nitride, 3-6% polydopamine-modified 2-methylimidazolium zinc salt, 22-30% tetraethylene glycol dimethyl ether, and 0.5-2% benzoyl peroxide.

[0007] Preferably, the raw materials comprise, by mass percentage, 40% polyethylene oxide, 13.5% lithium bis(trifluoromethanesulfonyl)imide, 15% graphite-like carbon nitride-coated LATP, 5.5% polydopamine-modified 2-methylimidazolium zinc salt, 25% tetraethylene glycol dimethyl ether, and 1% benzoyl peroxide.

[0008] Preferably, the graphite-like carbon nitride-coated LATP is prepared from the following raw materials in parts by weight: 10-15 parts LATP powder, 3.5-5.25 parts dicyandiamide, and 40-60 parts anhydrous ethanol.

[0009] Preferably, the method for preparing the LATP powder includes the following steps: Lithium hydroxide, aluminum oxide, titanium dioxide, and diammonium hydrogen phosphate are mixed and placed in a ball mill jar. Anhydrous ethanol is added, and the mixture is ball-milled at 200-300 rpm for 12-15 hours to obtain a uniformly dispersed mixed solution. The mixed solution is dried in an oven at 80-90℃ for 10-12 hours, then removed and ground for 30-40 minutes. The resulting powder is heated in a muffle furnace to 400-500℃ and held for 6-8 hours. Subsequently, the temperature is raised to 800-900℃ and held for 8-10 hours. After cooling, LATP blocks are obtained. The LATP blocks are ball-milled for 12-15 hours, dried, ground, and sieved to obtain LATP powder.

[0010] Preferably, the molar ratio of lithium hydroxide, aluminum oxide, titanium dioxide, and diammonium hydrogen phosphate is 1.3:0.15:1.7:3.

[0011] Preferably, the method for preparing the graphite-like carbon nitride-coated LATP includes the following steps: The prepared LATP powder was mixed with dicyandiamide and placed in a ball mill jar. Anhydrous ethanol was added, and the mixture was ball milled at 200-300 rpm for 12-14 h to obtain a uniformly dispersed mixed solution. The mixed solution was dried in an oven at 80-90℃ for 10-12 h, then removed and ground for 30-40 min. The obtained powder was heated to 500-600℃ in a muffle furnace and held for 1-1.5 h. After cooling, it was ground to obtain LATP coated with graphite-like carbon nitride.

[0012] Preferably, the polydopamine-modified 2-methylimidazolium zinc salt is prepared from the following raw materials in parts by weight: 0.2-0.4 parts dopamine hydrochloride, 100-200 parts Tris buffer solution, and 0.4-0.8 parts 2-methylimidazolium zinc salt nanoparticles.

[0013] Preferably, the preparation method of the polydopamine-modified 2-methylimidazolium zinc salt includes the following steps: Dopamine hydrochloride was added to Tris buffer solution and stirred until homogeneous; then 2-methylimidazolium zinc salt nanoparticles were added and contacted at 25-35℃ and 150-300rpm for 2-3 hours. The mixture was then dialyzed for 2-3 days, and the resulting suspension was dried at 60-80℃ to obtain polydopamine-modified 2-methylimidazolium zinc salt.

[0014] This application provides a method for preparing a composite electrolyte membrane to improve the ionic conductivity of solid-state batteries, which adopts the following technical solution: A method for preparing a composite electrolyte membrane to improve the ionic conductivity of a solid-state battery includes the following steps: LATP coated with graphite-like carbon nitride and polydopamine-modified 2-methylimidazolium zinc salt were dispersed evenly in tetraethylene glycol dimethyl ether, followed by the addition of lithium bis(trifluoromethanesulfonyl)imide and benzoyl peroxide. The mixture was stirred evenly at room temperature, and then polyethylene oxide was added. The mixture was stirred at room temperature for 14-18 hours and coated onto a polytetrafluoroethylene plate. The plate was then transferred to a vacuum oven and heated at 70-80°C for 12-16 hours. Finally, it was hot-pressed at 1-2 MPa for 2-3 minutes to obtain the composite electrolyte membrane.

[0015] Preferably, the thickness of the composite electrolyte membrane is 90-120 μm.

[0016] In summary, this application includes at least one of the following beneficial technical effects: 1. This application crosslinks PEO and TEGDME and introduces components containing double bonds to form a three-dimensional network structure, which inhibits polymer crystallization and improves ionic conductivity. At the same time, the hot pressing process promotes close contact between the filler and the polymer interface, reducing interfacial impedance. The modification of polydopamine promotes the uniform dispersion of ZIF-8 in PEO. ZIF-8 can effectively reduce the crystallinity of the polymer electrolyte, effectively improve the tensile strength of the composite electrolyte membrane, and effectively inhibit lithium dendrite puncture. Meanwhile, the large pore structure of ZIF-8 allows anions in the lithium salt to be adsorbed in the pores, which is conducive to ion transport.

[0017] 2. This application fundamentally solves the problem of side reactions caused by direct contact between LATP and lithium, which can lead to battery failure, by coating the surface of LATP with g-C3N4. The prepared LATP@CN is combined with PEO to prepare a composite solid electrolyte membrane, which improves the interface problem between the solid electrolyte and the lithium anode and enhances the stability of the solid battery. Detailed Implementation

[0018] The present application will be further described in detail below with reference to the embodiments.

[0019] The chemical reagents used in the preparation examples, embodiments, and comparative examples provided in this invention are all commercially available products, and their brands and manufacturers are as follows: Dopamine hydrochloride, Shanghai Maclean Biochemical Technology Co., Ltd., Product No.: D806618; 2-Methylimidazolium zinc salt nanoparticles, Hubei Nuona Technology Co., Ltd.; Tetraethylene glycol dimethyl ether, Shanghai Maclean Biochemical Technology Co., Ltd., Product No.: T819541; Lithium bis(trifluoromethanesulfonyl)imide, Shanghai Jiahe Herong Biotechnology Co., Ltd.; Benzoyl peroxide, Shanghai Aladdin Biochemical Technology Co., Ltd., Product No.: B104630; Polyethylene oxide, Shanghai Maclean Biochemical Technology Co., Ltd., Product No.: P823142, Purity: average Mv~600,000, powder.

[0020] Preparation Example 1: Preparation of LATP coated with graphite-like carbon nitride Preparation Example 1.1 S1. Mix 10g lithium hydroxide, 6.39g alumina, 56.69g titanium dioxide, and 165.42g diammonium hydrogen phosphate in a ball mill jar, add 550mL anhydrous ethanol, and ball mill at 200rpm for 15h with a ball-to-material ratio of 5:1 to obtain a uniformly dispersed mixed solution. Dry the mixed solution in an oven at 80℃ for 12h, then remove it and grind it for 30min. Heat the obtained powder in a muffle furnace to 400℃ and hold for 8h, then raise the temperature to 800℃ and hold for 10h. After cooling, LATP blocks are obtained. Ball mill the LATP blocks for 12h and dry them with a ball-to-material ratio of 5:1 and anhydrous ethanol as the dispersant. Grind and pass through a 100-mesh sieve to obtain LATP powder. S2. Mix 10g of the prepared LATP powder with 3.5g of dicyandiamide in a ball mill jar, add 40g of anhydrous ethanol, and ball mill at 200rpm for 14h with a ball-to-powder ratio of 5:1 to obtain a uniformly dispersed mixed solution. Dry the mixed solution in an oven at 80℃ for 12h, then take it out and grind it for 30min. Heat the obtained powder to 500℃ in a muffle furnace, keep it at that temperature for 1.5h, cool it, and then grind it to obtain LATP coated with graphite-like carbon nitride.

[0021] Preparation Example 1.2 S1. Mix 10g lithium hydroxide, 6.39g alumina, 56.69g titanium dioxide, and 165.42g diammonium hydrogen phosphate in a ball mill jar, add 550mL anhydrous ethanol, and ball mill at 250rpm for 13.5h with a ball-to-material ratio of 5:1 to obtain a uniformly dispersed mixed solution. Dry the mixed solution in an oven at 85℃ for 11h, then remove it and grind it for 35min. Heat the obtained powder in a muffle furnace to 450℃ and hold for 7h, then raise the temperature to 850℃ and hold for 9h. After cooling, LATP blocks are obtained. Ball mill the LATP blocks for 13.5h and dry them with a ball-to-material ratio of 5:1 and anhydrous ethanol as the dispersant. Grind and pass through a 100-mesh sieve to obtain LATP powder. S2. Mix 12.5g of the prepared LATP powder with 4.38g of dicyandiamide in a ball mill jar, add 50g of anhydrous ethanol, and ball mill at 250rpm for 13h with a ball-to-powder ratio of 5:1 to obtain a uniformly dispersed mixed solution. Dry the mixed solution in an oven at 85℃ for 11h, then take it out and grind it for 35min. Heat the obtained powder to 550℃ in a muffle furnace, keep it at that temperature for 1.25h, cool it, and then grind it to obtain LATP coated with graphite-like carbon nitride.

[0022] Preparation Example 1.3 S1. Mix 10g lithium hydroxide, 6.39g alumina, 56.69g titanium dioxide, and 165.42g diammonium hydrogen phosphate in a ball mill jar, add 550mL anhydrous ethanol, and ball mill at 300rpm for 12h with a ball-to-material ratio of 5:1 to obtain a uniformly dispersed mixed solution. Dry the mixed solution in an oven at 90℃ for 10h, then grind it for 40min. Heat the obtained powder in a muffle furnace to 500℃ and hold for 6h, then raise the temperature to 900℃ and hold for 8h. After cooling, LATP blocks are obtained. Ball mill the LATP blocks for 15h and then dry them with a ball-to-material ratio of 5:1 and anhydrous ethanol as the dispersant. Grind and pass through a 100-mesh sieve to obtain LATP powder. S2. Mix 15g of the prepared LATP powder with 5.25g of dicyandiamide in a ball mill jar, add 60g of anhydrous ethanol, and ball mill at 300rpm for 12h with a ball-to-powder ratio of 5:1 to obtain a uniformly dispersed mixed solution. Dry the mixed solution in an oven at 90℃ for 10h, then take it out and grind it for 40min. Heat the obtained powder to 600℃ in a muffle furnace, keep it at that temperature for 1h, cool it, and then grind it to obtain LATP coated with graphite-like carbon nitride.

[0023] Preparation Example 2: Preparation of Polydopamine-Modified 2-Methylimidazolium Zinc Salt Preparation Example 2.1 0.2 g of dopamine hydrochloride was added to 100 g of Tris buffer solution (pH 9) and stirred until homogeneous; then 0.4 g of 2-methylimidazolium zinc salt nanoparticles were added and contacted at 25 °C and 150 rpm for 2 h. The mixture was then dialyzed for 2 days, and the resulting suspension was dried at 60 °C to obtain polydopamine-modified 2-methylimidazolium zinc salt.

[0024] Preparation Example 2.2 0.3 g of dopamine hydrochloride was added to 150 g of Tris buffer solution (pH 9) and stirred until homogeneous; then 0.6 g of 2-methylimidazolium zinc salt nanoparticles were added, and the mixture was contacted at 30 °C and 225 rpm for 2.5 h. The mixture was then dialyzed for 2.5 days, and the resulting suspension was dried at 70 °C to obtain polydopamine-modified 2-methylimidazolium zinc salt.

[0025] Preparation Example 2.3 0.4 g of dopamine hydrochloride was added to 200 g of Tris buffer solution (pH 9) and stirred until homogeneous; then 0.8 g of 2-methylimidazolium zinc salt nanoparticles were added and contacted at 35 °C and 300 rpm for 3 h. The mixture was then dialyzed for 3 days, and the resulting suspension was dried at 80 °C to obtain polydopamine-modified 2-methylimidazolium zinc salt.

[0026] Example 1

[0027] 19.5g of LATP coated with graphite-like carbon nitride prepared in Preparation Example 1.1 and 3g of polydopamine-modified 2-methylimidazolium zinc salt prepared in Preparation Example 2.1 were added to 30g of tetraethylene glycol dimethyl ether and magnetically stirred until uniformly dispersed. Then, 12g of lithium bis(trifluoromethanesulfonyl)imide and 0.5g of benzoyl peroxide were added and magnetically stirred until uniformly dispersed at room temperature. Subsequently, 35g of polyethylene oxide was added and magnetically stirred at room temperature for 14h. The mixture was then coated onto a polytetrafluoroethylene plate and transferred to a vacuum oven and heated at 70°C for 12h. Finally, it was hot-pressed at 1MPa for 2min to obtain a composite electrolyte membrane with a thickness of 120μm.

[0028] Example 2

[0029] 15g of graphite-phase carbon nitride-coated LATP prepared in Preparation Example 1.1 and 5.5g of polydopamine-modified 2-methylimidazolium zinc salt prepared in Preparation Example 2.1 were added to 25g of tetraethylene glycol dimethyl ether and magnetically stirred until uniformly dispersed. Then, 13.5g of lithium bis(trifluoromethanesulfonyl)imide and 1g of benzoyl peroxide were added and magnetically stirred until uniformly dispersed at room temperature. Subsequently, 40g of polyethylene oxide was added and magnetically stirred at room temperature for 14h. The mixture was then coated onto a polytetrafluoroethylene plate and transferred to a vacuum oven for heating at 70°C for 12h. Finally, it was hot-pressed at 1MPa for 2min to obtain a composite electrolyte membrane with a thickness of 120μm.

[0030] Example 3

[0031] 10g of LATP coated with graphite-like carbon nitride prepared in Preparation Example 1.1 and 6g of polydopamine-modified 2-methylimidazolium zinc salt prepared in Preparation Example 2.1 were added to 22g of tetraethylene glycol dimethyl ether and magnetically stirred until uniformly dispersed. Then, 15g of lithium bis(trifluoromethanesulfonyl)imide and 2g of benzoyl peroxide were added and magnetically stirred until uniformly dispersed at room temperature. Subsequently, 45g of polyethylene oxide was added and magnetically stirred at room temperature for 14h. The mixture was then coated onto a polytetrafluoroethylene plate and transferred to a vacuum oven for heating at 70°C for 12h. Finally, it was hot-pressed at 1MPa for 2min to obtain a composite electrolyte membrane with a thickness of 120μm.

[0032] Example 4

[0033] 19.5g of graphite-phase carbon nitride-coated LATP prepared in Preparation Example 1.2 and 3g of polydopamine-modified 2-methylimidazolium zinc salt prepared in Preparation Example 2.2 were added to 30g of tetraethylene glycol dimethyl ether and magnetically stirred until uniformly dispersed. Then, 12g of lithium bis(trifluoromethanesulfonyl)imide and 0.5g of benzoyl peroxide were added and magnetically stirred until uniformly dispersed at room temperature. Subsequently, 35g of polyethylene oxide was added and magnetically stirred at room temperature for 16h. The mixture was then coated onto a polytetrafluoroethylene plate and transferred to a vacuum oven for heating at 75°C for 14h. Finally, it was hot-pressed at 1.5MPa for 2.5min to obtain a composite electrolyte membrane with a thickness of 110μm.

[0034] Example 5

[0035] 19.5g of graphite-phase carbon nitride-coated LATP prepared in Preparation Example 1.3 and 3g of polydopamine-modified 2-methylimidazolium zinc salt prepared in Preparation Example 2.3 were added to 30g of tetraethylene glycol dimethyl ether and magnetically stirred until uniformly dispersed. Then, 12g of lithium bis(trifluoromethanesulfonyl)imide and 0.5g of benzoyl peroxide were added and magnetically stirred until uniformly dispersed at room temperature. Subsequently, 35g of polyethylene oxide was added and magnetically stirred at room temperature for 18h. The mixture was then coated onto a polytetrafluoroethylene plate and transferred to a vacuum oven for heating at 70°C for 16h. Finally, it was hot-pressed at 2MPa for 3min to obtain a composite electrolyte membrane with a thickness of 90μm.

[0036] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that an equal amount of unmodified 2-methylimidazolium zinc salt was used in Comparative Example 1 instead of the polydopamine-modified 2-methylimidazolium zinc salt prepared in Preparation Example 2.1.

[0037] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 does not contain the polydopamine-modified 2-methylimidazolium salt prepared in Preparation Example 2.1.

[0038] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that an equal amount of unmodified LATP powder was used in Comparative Example 3 instead of the graphite-like carbon nitride coated LATP prepared in Preparation Example 1.1.

[0039] Performance testing I. Ionic Conductivity Test: The composite electrolyte membranes obtained in Examples 1-5 and Comparative Examples 1-3 were cut into circular pieces with a diameter of 15 mm. A 15 mm diameter stainless steel sheet was used as the blocking electrode, and the electrolyte was placed between the two stainless steel sheets to obtain a symmetrical cell with a stainless steel sheet|electrolyte|stainless steel sheet structure. The ionic conductivity (δ) was then measured using an AC impedance spectroscopy device (VMP3) and a 4294 sensor in the 100 MHz to 0.1 Hz frequency band. The results are shown in Table 1. δ=L / (R×S), δ is the ionic conductivity (mS / cm), L is the thickness of the electrolyte membrane (cm), R is the measured resistance (mS), and S is the area of ​​the electrolyte (cm²). 2 ).

[0040] II. Tensile Strength Test: The tensile properties of the composite solid electrolyte membranes for lithium batteries prepared in Examples 1-5 and Comparative Examples 1-3 were determined according to GB / T 1040.2-2006 "Determination of Tensile Properties of Plastics - Part 2: Test Conditions for Molded and Extruded Plastics". The test instrument was a universal tensile testing machine. The test conditions were 25°C and a tensile rate of 15 mm / min. Each sample was tested more than 5 times. Before the test, the prepared samples were allowed to stand at room temperature (25°C) for more than 48 hours. The results are shown in Table 1.

[0041] The specific test results are as follows:

[0042] As can be seen from the test results in Table 1, the composite electrolyte membrane for improving the ionic conductivity of solid-state batteries provided in this application embodiment has significantly higher ionic conductivity and tensile strength compared to the comparative example.

[0043] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A composite electrolyte membrane for improving the ionic conductivity of solid-state batteries, characterized in that: The raw materials, by mass percentage, include 35-45% polyethylene oxide, 12-15% lithium bis(trifluoromethanesulfonyl)imide, 10-19.5% LATP coated with graphite-like carbon nitride, 3-6% polydopamine-modified 2-methylimidazolium zinc salt, 22-30% tetraethylene glycol dimethyl ether, and 0.5-2% benzoyl peroxide.

2. The composite electrolyte membrane for improving the ionic conductivity of solid-state batteries according to claim 1, characterized in that: The raw materials, by mass percentage, include 40% polyethylene oxide, 13.5% lithium bis(trifluoromethanesulfonyl)imide, 15% graphite-like carbon nitride-coated LATP, 5.5% polydopamine-modified 2-methylimidazolium zinc salt, 25% tetraethylene glycol dimethyl ether, and 1% benzoyl peroxide.

3. The composite electrolyte membrane for improving the ionic conductivity of solid-state batteries according to claim 1, characterized in that: The graphite-like carbon nitride-coated LATP is prepared from the following raw materials in parts by weight: 10-15 parts LATP powder, 3.5-5.25 parts dicyandiamide, and 40-60 parts anhydrous ethanol.

4. The composite electrolyte membrane for improving the ionic conductivity of solid-state batteries according to claim 3, characterized in that: The preparation method of the LATP powder includes the following steps: lithium hydroxide, aluminum oxide, titanium dioxide, and diammonium hydrogen phosphate are mixed and placed in a ball mill jar, anhydrous ethanol is added, and the mixture is ball-milled at 200-300 rpm for 12-15 h to obtain a uniformly dispersed mixed solution. The mixed solution is dried in an oven at 80-90℃ for 10-12 h, then removed and ground for 30-40 min. The obtained powder is heated in a muffle furnace to 400-500℃ and held for 6-8 h, then heated to 800-900℃ and held for 8-10 h. After cooling, LATP blocks are obtained. The LATP blocks are ball-milled for 12-15 h, dried, ground, and sieved to obtain LATP powder.

5. The composite electrolyte membrane for improving the ionic conductivity of solid-state batteries according to claim 4, characterized in that: The molar ratio of lithium hydroxide, aluminum oxide, titanium dioxide, and diammonium hydrogen phosphate is 1.3:0.15:1.7:

3.

6. The composite electrolyte membrane for improving the ionic conductivity of solid-state batteries according to claim 3, characterized in that: The method for preparing the graphite-like carbon nitride-coated LATP includes the following steps: The prepared LATP powder was mixed with dicyandiamide and placed in a ball mill jar. Anhydrous ethanol was added, and the mixture was ball milled at 200-300 rpm for 12-14 h to obtain a uniformly dispersed mixed solution. The mixed solution was dried in an oven at 80-90℃ for 10-12 h, then removed and ground for 30-40 min. The obtained powder was heated to 500-600℃ in a muffle furnace and held for 1-1.5 h. After cooling, it was ground to obtain LATP coated with graphite-like carbon nitride.

7. The composite electrolyte membrane for improving the ionic conductivity of solid-state batteries according to claim 1, characterized in that: The polydopamine-modified 2-methylimidazolium zinc salt is prepared from the following raw materials in parts by weight: 0.2-0.4 parts dopamine hydrochloride, 100-200 parts Tris buffer solution, and 0.4-0.8 parts 2-methylimidazolium zinc salt nanoparticles.

8. A composite electrolyte membrane for improving the ionic conductivity of solid-state batteries according to claim 7, characterized in that: The preparation method of the polydopamine-modified 2-methylimidazolium zinc salt includes the following steps: Dopamine hydrochloride was added to Tris buffer solution and stirred until homogeneous; then 2-methylimidazolium zinc salt nanoparticles were added and contacted at 25-35℃ and 150-300rpm for 2-3 hours. The mixture was then dialyzed for 2-3 days, and the resulting suspension was dried at 60-80℃ to obtain polydopamine-modified 2-methylimidazolium zinc salt.

9. A method for preparing a composite electrolyte membrane for improving the ionic conductivity of a solid-state battery according to any one of claims 1-8, characterized in that: Includes the following steps: LATP coated with graphite-like carbon nitride and polydopamine-modified 2-methylimidazolium zinc salt were dispersed evenly in tetraethylene glycol dimethyl ether, followed by the addition of lithium bis(trifluoromethanesulfonyl)imide and benzoyl peroxide. The mixture was stirred evenly at room temperature, and then polyethylene oxide was added. The mixture was stirred at room temperature for 14-18 hours and coated onto a polytetrafluoroethylene plate. The plate was then transferred to a vacuum oven and heated at 70-80°C for 12-16 hours. Finally, it was hot-pressed at 1-2 MPa for 2-3 minutes to obtain the composite electrolyte membrane.

10. The method for preparing a composite electrolyte membrane for improving the ionic conductivity of a solid-state battery according to claim 9, characterized in that: The thickness of the composite electrolyte membrane is 90-120 μm.

Images