Core-shell structure solid electrolyte and in-situ interface modification method thereof

Abstract

The invention discloses a solid electrolyte with a core-shell structure. The solid electrolyte comprises a core layer and a shell layer, wherein the core layer is prepared from an argyrodite type sulfide material; and the shell layer is made of a functional moisture-proof material rich in halogen and oxygen elements. The invention also discloses an in-situ interface modification method which comprises the following steps: S1, mixing the positive electrode material with the interface modifier; s2, performing heat treatment in an inert atmosphere; and S3, in the first charging and discharging process of the battery, generating a cathode electrolyte interfacial film rich in LiF through an in-situ electrochemical reaction. Through the core-shell structure design, the electrolyte material has good ionic conductivity in a low-humidity environment, and the requirement for the production environment is reduced. And the safety performance of the battery is greatly improved by the core-shell structure. The CEI layer rich in LiF, which is formed by an in-situ interface modification technology, has high ionic conductivity and excellent stability, so that the interface impedance of the whole battery is reduced, and the rate capability and the cycling stability of the battery are improved.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, specifically to a core-shell structured solid electrolyte and its in-situ interface modification method. Background Technology

[0002] Sulfide solid electrolytes are characterized by their high ionic conductivity (up to 10). -2 With its excellent ductility (on the order of S / cm), low grain boundary impedance, and good ductility, sulfide electrolytes are considered ideal materials for all-solid-state batteries. However, their practical application faces two major technical bottlenecks: First, poor humidity stability. Sulfide materials are extremely sensitive to moisture; when exposed to air, they react with water to generate toxic H2S gas, leading to electrolyte structure degradation and a decrease in ionic conductivity. Studies have shown that even in a dry environment with a dew point of -40°C, the conductivity of a typical Li6PS5Cl electrolyte decreases by more than 50% within 30 minutes. Second, solid-solid interface compatibility issues. When sulfide electrolytes come into contact with high-voltage cathode materials (such as lithium cobalt oxide and high-nickel ternary materials), they are prone to oxidative decomposition, generating ionicly conductive inert products, increasing interfacial impedance and the risk of capacity decay. Simultaneously, poor contact with the lithium metal anode can trigger dendrite growth and short circuits. While existing technologies have attempted to improve humidity stability through coating or additives, these often sacrifice ionic conductivity or process complexity. Summary of the Invention

[0003] The purpose of this invention is to provide a core-shell structured solid electrolyte and its in-situ interface modification method to solve the problems existing in the prior art.

[0004] To achieve the above objectives, the present invention provides a core-shell structured solid electrolyte comprising a core layer and a shell layer, wherein the core layer is composed of a sulfide material of the sulfide type with the chemical formula Li6PS5X, where X is a halogen element; the shell layer, covering the outside of the core layer, is composed of a functional moisture-resistant material rich in halogen and oxygen elements, and the shell layer thickness is 5-50 nm.

[0005] Furthermore, the core layer material includes Li6PS5I. 0.5 Cl 0.5 At least one of Li6PS5Cl or Li6PS5I.

[0006] Furthermore, the shell material is formed by reacting Li2O and perfluorohexyl iodide with the surface of the core layer.

[0007] The present invention also discloses an in-situ interface modification method for the above-mentioned solid electrolyte, characterized by comprising the following steps: S1, mixing the positive electrode material with an interface modifier to form a uniform coating; S2, performing heat treatment under an inert atmosphere to allow the modifier to react with the positive electrode surface to form a pre-modified layer; S3, generating a LiF-rich cathode electrolyte interface film through an in-situ electrochemical reaction during the first charge and discharge process of the battery.

[0008] Furthermore, the interface modifier in step S1 includes perfluorohexyl iodide, which has a mass ratio of 1:3 with the cathode material.

[0009] Furthermore, in step S2, the heat treatment conditions are 150-200℃ and 1-2 hours under an inert atmosphere.

[0010] This invention also discloses a method for preparing a core-shell structured solid electrolyte, used for the preparation of the aforementioned solid electrolyte, characterized by comprising the following steps: Z1, synthesizing core materials: ball milling Li2S, P2S5 and halides in stoichiometric ratio to obtain precursor powder; Z2, heat treatment crystallization: heat treating at 500-600℃ under vacuum conditions to form a sulfosilver germanite structured electrolyte; Z3, constructing the shell: mixing the core material with Li2O and perfluorohexyl iodoalkane, and heat treating at 300-400℃ under an inert atmosphere to form a core-shell structure.

[0011] Furthermore, the ball milling process was carried out at 500 rpm for 20 hours under argon protection, using n-heptane as a process control agent.

[0012] This invention, through a core-shell structure design, particularly the synergistic effect of iodine and oxygen elements in the shell, enables the electrolyte material to exhibit good ionic conductivity in low-humidity environments, reducing the requirements for the production environment and facilitating large-scale industrial manufacturing. The core-shell structure effectively suppresses the generation of hydrogen sulfide gas, while the stable interface layer inhibits the growth of lithium dendrites, significantly improving the battery's safety performance.

[0013] The LiF-rich CEI layer formed through in-situ interface modification technology exhibits high ionic conductivity and excellent stability, reducing the interfacial impedance of the full cell and improving its rate performance and cycle stability. The preparation method provided by this invention is highly compatible with existing battery manufacturing processes, does not require expensive specialized equipment, and facilitates technology transfer and large-scale application. Detailed Implementation

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] The core-shell structured solid electrolyte of the present invention includes a core layer and a shell layer. The core layer is composed of a sulfide material of silver-germanium sulfide type with the general chemical formula Li6PS5X, where X is a halogen element. The shell layer covers the outside of the core layer and is composed of a functional moisture-resistant material rich in halogen and oxygen elements. The shell layer has a thickness of 5-50 nm.

[0016] Furthermore, the core layer material includes Li6PS5I. 0.5 Cl 0.5 At least one of Li6PS5Cl or Li6PS5I.

[0017] Furthermore, the shell material is formed by reacting Li2O and perfluorohexyl iodide with the surface of the core layer.

[0018] Example 1: Preparation of core-shell structured solid electrolyte For the synthesis of the core materials, Li₂S (99.9% purity), P₂S₅ (99.9% purity), and LiI (99.9% purity) were weighed according to stoichiometry, with a molar ratio of Li₂S:P₂S₅:LiI = 70:25:5. The raw material mixture, along with n-heptane (as a process control agent), was placed in a planetary ball mill jar and ball-milled at 500 rpm for 20 hours under argon protection. After ball milling, the resulting slurry was vacuum-dried at 60°C for 12 hours to obtain the precursor powder.

[0019] Heat treatment crystallization: The precursor powder is placed in a quartz tube and evacuated to 10°C. -3 After Pa, the mixture was melt-sealed. It was then heat-treated at 550℃ for 5 hours and cooled to room temperature in the furnace to obtain the basic electrolyte material Li6PS5I with a sulforaphite-germanium oxide structure. 0.5 Cl 0.5 .

[0020] For shell construction, the aforementioned basic electrolyte material was mixed with an appropriate amount of Li₂O (99.5% purity) and perfluorohexyl iodide (as oxygen and fluorine sources), and an appropriate amount of anhydrous acetonitrile was added as a dispersant. The mixture was then stirred at 2000 rpm for 5 hours in a three-dimensional mixing apparatus. Subsequently, under argon protection, it was heat-treated at 300°C for 2 hours to allow the shell precursor to react with the surface of the core material, forming a dense core-shell structured electrolyte.

[0021] Example 2: In-situ Interface Modification Method For cathode material pretreatment, commercial high-voltage cathode material LiCoO2 (average particle size 5μm) was vacuum dried at 120℃ for 24 hours to completely remove moisture.

[0022] For interface modifier loading, dried LiCoO2 and perfluorohexyl iodide were mixed at a mass ratio of 3:1, and an appropriate amount of anhydrous ethanol was added as a dispersion medium. The mixture was then mixed at 1000 rpm for 3 hours in a three-dimensional mixing device to ensure uniform coating.

[0023] Heat treatment activation involves heat-treating the mixture at 150°C under argon protection for 1 hour to allow the interface modifier to undergo a preliminary reaction with the surface of the cathode material, forming a pre-modified layer.

[0024] Battery assembly and testing involved assembling the interface-modified cathode material with the core-shell solid electrolyte and lithium metal anode prepared in Example 1 into a solid-state battery. During the first charge and discharge of the battery, a LiF-rich cathode electrolyte interphase (CEI) film was generated at the cathode-electrolyte interface through an in-situ electrochemical reaction.

[0025] Test results: The interface impedance of the battery is 85 Ω·cm², and the capacity retention rate is 82% after 1000 cycles at 1C rate.

[0026] It should be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "joining," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

Claims

1. A core-shell structured solid-state electrolyte, characterized by, The core layer is composed of a argyrodite sulfide material with a chemical formula of Li6PS5X, wherein X is a halogen element; and the shell layer is coated on the outside of the core layer and is composed of a functional moisture-resistant material rich in halogen and oxygen elements, and has a thickness of 5-50 nm.

2. The solid-state electrolyte of claim 1, wherein, The core layer material is Li6PS5I 0.5 Cl 0.5 at least one of Li6PS5Cl or Li6PS5I.

3. The solid state electrolyte of claim 1, wherein, The shell layer material is formed by reacting Li2O and perfluorohexyl iodocane with the surface of the core layer.

4. An in situ interface modification method for the solid-state electrolyte of any one of claims 1-3, characterized by, The method comprises the following steps: S1, mixing the positive electrode material with an interface modifier to form a uniform coating; S2, performing heat treatment under an inert atmosphere to cause the modifier to react with the surface of the positive electrode to form a pre-modification layer; and S3, generating a cathode electrolyte interface film rich in LiF through in-situ electrochemical reaction during the first charge-discharge process of the battery.

5. The in situ interface modification method of claim 4, wherein, The interface modifier in the step S1 comprises perfluorohexyl iodocane, and the mass ratio of the perfluorohexyl iodocane to the positive electrode material is 1:

3.

6. The in situ interface modification method of claim 4, wherein, The heat treatment condition in the step S2 is 150-200°C, and the heat treatment is performed under inert atmosphere protection for 1-2 hours.

7. A method for the preparation of a core-shell structured solid-state electrolyte for the preparation of the solid-state electrolyte according to any one of claims 1 to 3, characterized in that The method comprises the following steps: Z1, synthesizing a core material: ball-milling Li2S, P2S5 and a halide according to stoichiometric ratios to obtain a precursor powder; Z2, heat treatment and crystallization: performing heat treatment at 500-600°C under vacuum to form an argyrodite structure electrolyte; and Z3, constructing a shell layer: mixing the core material with Li2O and perfluorohexyl iodocane, and performing heat treatment at 300-400°C under inert atmosphere to form a core-shell structure.

8. The preparation method according to claim 7, characterized in that, The ball-milling process is performed under argon protection at a rotation speed of 500 rpm for 20 hours, and n-heptane is used as a process control agent.