Solid-state electrolyte, composite electrolyte thin film and preparation method and application thereof

Abstract

This application discloses a solid electrolyte, a composite electrolyte thin film, its preparation method, and its application. This invention belongs to the field of all-solid-state batteries. The main invention involves incorporating a sulfide electrolyte with high ionic conductivity, Li, into a PEO-LiTFSI system. 5.4+x PS 4.4+ x Cl 1.6‑x This process improves the lithium-ion transference number and electrochemical performance, resulting in a composite solid-state electrolyte film with high lithium-ion transference number and excellent electrochemical performance. The assembled all-solid-state battery exhibits high capacity and excellent long-cycle performance.

Description

Technical Field

[0001] This application relates to a solid electrolyte, a composite electrolyte film, its preparation method and application, and belongs to the field of solid-state batteries. Background Technology

[0002] Among various solid-state electrolytes, poly(ethylene oxide) (PEO)-based composite polymer electrolytes (CPEs) are promising due to their high flexibility, excellent solvation ability for lithium salts, and good mechanical / chemical stability against lithium metal. However, PEO-based CPEs typically exhibit high crystallinity and show a 10-1 crystal volume at room temperature. -6 The low Li+ conductivity (S / cm) and dendrite penetration through the polymer at low critical current densities also plague these systems. Each of these problems hinders their feasibility in commercially viable all-solid-state lithium-ion batteries (ASSLB).

[0003] Dispersing ceramic particles in a polymer matrix is ​​an effective way to improve the ionic conductivity of SPE (Solid Polymer Expansion Molding), while also enhancing its electrochemical stability and mechanical strength. The addition of these ceramic particle fillers is believed to either hinder polymer crystallization or contribute to a highly conductive interface layer between the polymer and ceramic. Ceramic fillers are generally classified into two categories: inactive fillers that do not participate in lithium-ion conduction (e.g., Al₂O₃ and SiO₂) and active materials that participate in lithium-ion transport (e.g., Li₃N). However, high ionic conductivity (>10⁻⁶) is a significant factor. -4 Scm1) When they have very high filler content (e.g., >30 wt%), these composites can be obtained, leading to unsatisfactory processability, mechanical properties, and poor battery performance. The high reactivity of lithium leads to severe parasitic reactions with PEO-based CPEs, forming a solid electrolyte interphase (SEI) at the Li / electrolyte interface. This SEI continues to grow during battery operation, causing uneven lithium plating, resulting in rapid Li dendrite growth and eventual short circuits in the battery. Summary of the Invention

[0004] To address the aforementioned problems with existing preparation techniques, the present invention aims to propose a customized additive for PEO-based CPE, which has recently been proven to improve its Li- content. + Effective strategies for improving conductivity and optimizing its interfacial chemistry with lithium metal. Ideal electrolyte additive: Li 5.4+x PS 4.4+x Cl 1.6-x It should react synergistically with lithium metal to form a mechanically and chemically stable SEI layer. The additive is soluble in PEO and has the ability to diffuse to the lithium metal / electrolyte interface to react.

[0005] According to one aspect of this application, a solid electrolyte with the chemical formula Li is provided.5.4+x PS 4.4+x Cl 1.6-x , where 0≤x≤1.

[0006] According to another aspect of this application, a method for preparing the above-mentioned solid electrolyte is provided, comprising the following steps:

[0007] Under an inactive gas atmosphere, Li2S, P2S5, and LiCl are mixed, ball-milled at high energy, pressed into tablets, heat-treated, and pulverized to obtain the solid electrolyte.

[0008] The inert gas atmosphere includes a nitrogen atmosphere and an inert gas atmosphere;

[0009] The high-energy ball mill rotates at a speed of 400–600 r / min;

[0010] The high-energy ball milling time is 600–2400 min;

[0011] The high-energy ball milling ball-to-material ratio is 20:1;

[0012] The pressure of the tablet compression is 5-15 MPa;

[0013] The heat treatment temperature is 400–600°C;

[0014] The heating rate of the heat treatment is 1–10 °C / min;

[0015] The heat treatment time is 600-1000 min.

[0016] According to another aspect of this application, a composite electrolyte film is provided, the composite electrolyte film being composed of polyethylene oxide, LiTFSI and the above-mentioned solid electrolyte;

[0017] The mass ratio of polyethylene oxide, LiTFSI, and the aforementioned solid electrolyte is 70:20:1 to 40:10:1.

[0018] According to another aspect of this application, a method for preparing the above-mentioned composite electrolyte thin film is provided, comprising the following steps:

[0019] Under an inactive gas atmosphere, polyethylene oxide, LiTFSI and the solid electrolyte of claim 1 are mixed, dissolved in acetonitrile, stirred until uniform and transparent, coated on a polytetrafluoroethylene plate, and vacuum dried to obtain the composite electrolyte film.

[0020] The stirring speed is 300-400 rpm;

[0021] The stirring time is 5 to 10 hours.

[0022] The vacuum drying temperature is 50–60°C;

[0023] The vacuum drying time is 20-30 hours.

[0024] According to another aspect of this application, an all-solid-state lithium-ion battery is provided, employing the aforementioned composite electrolyte film.

[0025] This invention discloses a method for designing, preparing, and applying a composite solid-state electrolyte thin film. This invention belongs to the field of sulfide solid-state batteries. The main method involves adding a sulfide solid-state electrolyte with high ionic conductivity to PEO-LiTFSI, which provides a channel for lithium-ion transport, resulting in the synergistic migration of lithium ions and high ionic conductivity. The assembled all-solid-state battery exhibits extremely high capacity and excellent long-cycle performance.

[0026] The beneficial effects that this application can produce include:

[0027] (1) By adding effective additives, the lithium-ion transference number, ionic conductivity, etc. of its PEO-based thin film are enhanced.

[0028] (2) Add Li 5.4+x PS 4.4+x Cl 1.6-x Adding additives can effectively reduce the crystallinity of PEO and improve its various properties.

[0029] (3) Provides a channel for lithium-ion transport and improves its electrochemical performance. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is the XRD pattern of Embodiment 1 of the present invention;

[0032] Figure 2 The lithium-ion transference number was determined by the polarization DC method in Example 1 of this invention.

[0033] Figure 3 This is a graph showing the long-cycle performance of the all-solid-state battery at 60°C in Embodiment 1 of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0035] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0036] Example 1

[0037] Weigh out 0.5g PEO, 0.181g LiTFSI, and 0.00681g ball-milled Li₂ with high ionic conductivity. 5.4 PS 4.4 C 1.6 The mixture was dissolved in acetonitrile solution and magnetically stirred at 300–400 rpm for 5 hours until it became homogeneous and transparent. The solution was evenly spread onto a polytetrafluoroethylene (PTFE) plate using a spatula to allow most of the acetonitrile to evaporate. The plate was then transferred to a vacuum drying oven at 60°C for 12 hours to remove any remaining acetonitrile. After drying, it was cut into 19 mm diameter separators and stored in a glove box for later use. A mixture of LFP, PVDF, and Ketjen Black (8:1:1 mass ratio) was ground, dissolved in NMP, and dried in an oven for 12 hours for use as the positive electrode. An all-solid-state battery was assembled using a composite solid-state electrolyte membrane as the separator and lithium foil as the negative electrode. Long-cycle testing was conducted at a 1C current density, and the battery maintained a capacity of 143 mAh g⁻¹ after 500 cycles. -1 .

[0038] Figure 1 The XRD pattern of Embodiment 1 of the present invention, with Li added. 5.4+x PS 4.4+x Cl 1.6-x The crystallinity of PEO was greatly reduced after the addition of additives;

[0039] Figure 2 The lithium-ion transference number measured by the polarized DC method in Example 1 of this invention is significantly improved;

[0040] Figure 3 This is a graph showing the long-cycle performance of the all-solid-state battery at 60°C in Embodiment 1 of the present invention.

[0041] Example 2

[0042] Weigh out 0.5g PEO, 0.181g LiTFSI, and 0.01362g ball-milled Li₂ with high ionic conductivity. 5.4 PS 4.4 C 1.6The mixture was dissolved in acetonitrile solution and magnetically stirred at 300–400 rpm for 5 hours until it became homogeneous and transparent. The solution was evenly spread onto a polytetrafluoroethylene (PTFE) plate using a spatula to allow most of the acetonitrile to evaporate. The plate was then transferred to a vacuum drying oven at 60°C for 12 hours to remove any remaining acetonitrile. After drying, it was cut into 19 mm diameter separators and stored in a glove box for later use. A mixture of LFP, PVDF, and Ketjen Black (mass ratio 8:1:1) was ground, dissolved in NMP, and dried in an oven for 12 hours for use as the positive electrode. An all-solid-state battery was assembled using a composite solid-state electrolyte membrane as the separator and a lithium-ion negative electrode, and long-cycle experiments were conducted at a 1C current density.

[0043] Example 3

[0044] Weigh 0.5g PEO and 0.181g LiTFSI. Dissolve the mixture in acetonitrile solution and stir magnetically at 300-400 rpm for 5 hours until it becomes homogeneous and transparent. Spread the solution evenly on a polytetrafluoroethylene plate with a spatula to allow most of the acetonitrile to evaporate. Then, transfer the plate to a vacuum drying oven at 60°C for 12 hours to remove the remaining acetonitrile. After drying, cut it into 19mm diameter separators and store them in a glove box for later use. Mix and grind LFP, PVDF, and Ketjen Black in a mass ratio of 8:1:1, dissolve in NMP, and dry in an oven for 12 hours before using it as the positive electrode. Assemble an all-solid-state battery using a composite solid electrolyte membrane as the separator and a lithium foil negative electrode. Conduct a long-cycle test at a 1C current density. The battery cycled 500 times and maintained a capacity of 103 mAh g⁻¹. -1 .

[0045] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A solid electrolyte, characterized in that, The chemical formula is Li 5.4+x PS 4.4+x Cl 1.6-x , where 0≤x≤1.

2. A method for preparing the solid electrolyte according to claim 1, characterized in that, Includes the following steps: Under an inactive gas atmosphere, Li2S, P2S5, and LiCl are mixed, ball-milled at high energy, pressed into tablets, heat-treated, and pulverized to obtain the solid electrolyte.

3. The preparation method according to claim 2, characterized in that, The inert gas atmosphere includes a nitrogen atmosphere and an inert gas atmosphere; The high-energy ball mill rotates at a speed of 400–600 r / min; The high-energy ball milling time is 600–2400 min; The pressure of the tablet compression is 5-15 MPa; The heat treatment temperature is 400–600°C; The heating rate of the heat treatment is 1–10 °C / min; The heat treatment time is 600-1000 min.

4. A composite electrolyte film, characterized in that, The composite electrolyte film is composed of polyethylene oxide, LiTFSI and the solid electrolyte of claim 1; The mass ratio of polyethylene oxide, LiTFSI, and the solid electrolyte according to claim 1 is 70:20:1 to 40:10:

1.

5. A method for preparing the composite electrolyte thin film according to claim 4, characterized in that, Includes the following steps: Under an inactive gas atmosphere, polyethylene oxide, LiTFSI and the solid electrolyte of claim 1 are mixed, dissolved in acetonitrile, stirred, coated on a polytetrafluoroethylene plate, and vacuum dried to obtain the composite electrolyte film.

6. The preparation method according to claim 5, characterized in that, The stirring speed is 300-400 rpm; The stirring time is 5 to 10 hours.

7. The preparation method according to claim 5, characterized in that, The vacuum drying temperature is 50–60°C; The vacuum drying time is 20-30 hours.

8. A fully solid-state lithium-ion battery, characterized in that, The composite electrolyte film according to claim 4 is used.

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