Interface modification method of solid-state electrolyte, solid-state electrolyte and application

Abstract

This invention relates to a method for interface modification of a solid electrolyte, the solid electrolyte itself, and its applications. The interface modification method includes: pretreating an oxide solid electrolyte, then immersing it in an anhydrous composite acid working solution composed of an inorganic acid and an organic macromolecular acid for ultrasonic treatment; utilizing the inorganic acid to decompose residual alkali on the surface, while simultaneously utilizing the steric hindrance effect of the organic macromolecular acid to restrict H... + The etching process involves penetration into the bulk phase, achieving self-limiting etching where the reaction automatically stops after the residual alkali is exhausted; after the residual alkali is removed, phosphate ions react with surface Li... + The reaction generates Li3PO4 nanocrystals in situ. Organic macromolecular acids chelate and coordinate with surface metal ions to form a metal-organic complex network. These networks cross-link and interpenetrate, forming a hybrid protective layer with a gradually changing compositional transition region in situ. Finally, after washing and drying, the modified solid electrolyte is obtained. This invention completes alkali removal and film formation in a single step at room temperature. The process is simple and applicable to various crystalline oxide solid electrolytes.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery materials technology, and in particular to an interface modification method for a solid electrolyte, a solid electrolyte, and its applications. Background Technology

[0002] Oxide solid electrolytes, such as garnet-type lithium lanthanum zirconium oxide (Li7La3Zr2O) 12 (LLZO for short), perovskite-type lithium lanthanum titanium oxide (Li 0.33 La 0.56 TiO3 (LLTO) and NASICON-type lithium titanium aluminum phosphate (Li 1.3 Al 0.3 Ti 1.7 (PO4)3 (LATP) and similar electrolytes are considered highly promising inorganic solid-state electrolyte systems due to their high room-temperature ionic conductivity and good chemical stability to metallic lithium. However, these oxide electrolytes readily undergo side reactions with moisture and carbon dioxide in the air, forming an insulating "residual alkali" layer on their surface, mainly composed of LiOH and Li2CO3. This layer not only severely hinders lithium-ion transport (leading to extremely high interfacial impedance) but also causes interfacial deterioration and lithium dendrite growth during cycling in all-solid-state batteries.

[0003] Currently, the main technical solutions for removing residual alkali include: high-temperature calcination, water washing / acid washing, surface coating, anhydrous organic acid treatment, and physical polishing. Existing literature reports methods such as chemical etching by immersing LLZO in solutions of dilute hydrochloric acid (HCl), dilute nitric acid (HNO3), or dilute phosphoric acid (H3PO4) to rapidly decompose surface carbonates using strong acids; or gently removing residual alkali by immersing LLZO in solutions of weak organic acids such as acetic acid and citric acid; and mechanically removing the residual alkali layer by physically grinding the surface of LLZO ceramic sheets with sandpaper or a polishing machine. However, the above technical solutions have the following drawbacks.

[0004] (1) Mechanical grinding cannot be applied to thin film or irregularly shaped LLZO electrolytes, resulting in extremely poor processing adaptability. Furthermore, the mechanical stress during grinding can easily introduce microcracks on the ceramic surface and subsurface. These cracks will become the preferred path for lithium dendrites to penetrate during battery cycling, accelerating battery short-circuit failure.

[0005] (2) The reaction of inorganic strong acids is too violent and non-selective. While rapidly dissolving Li2CO3, a large amount of free H+ is released. + It will uncontrollably interact with Li in the LLZO lattice + Deep H occurs + / Li +The exchange process disrupts the crystal structure of the garnet phase, leading to an irreversible decrease in the bulk ionic conductivity. Simultaneously, excessive etching with strong acid causes grain boundary corrosion and surface porosity, increasing surface roughness and hindering uniform contact with metallic lithium.

[0006] (3) Although the reaction of organic weak acid is mild and protects the bulk structure of LLZO, its alkali removal efficiency is low and it is difficult to completely remove the thick Li2CO3 passivation layer. The treated surface often has insoluble organic lithium salt by-products, resulting in a limited decrease in interfacial impedance.

[0007] As can be seen from the above, the existing technology has a problem that it is impossible to achieve both "efficient alkali removal" and "low damage to maintain structure". Moreover, the existing methods only stay at the "cleaning" level and fail to actively build a protective layer with high ionic conductivity and lithium affinity on the exposed LLZO surface while removing alkali.

[0008] Therefore, there is a need for an interface modification method that can achieve residual alkali removal and in-situ reconstruction of the interface layer in a single step under mild conditions, as well as an oxide solid electrolyte with a well-preserved bulk lattice, a gradient structure with extremely low interface impedance, and an ultrathin lithium-loving hybrid layer with "self-limiting reaction in-situ generation". Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for interface modification of solid electrolytes, a solid electrolyte itself, and its applications. This addresses the problem that in existing methods for removing residual alkali from the surface of oxide solid electrolytes, a single inorganic acid can easily lead to bulk H₂. + / Li + The technical problems caused by deep exchange and grain boundary over-corrosion, low efficiency of single organic acid alkali removal and limited reduction in interfacial impedance, and the fact that existing methods only stay at the "cleaning" level and cannot actively build a high ionic conductivity and lithium-loving protective layer while removing alkali, are that it is difficult to achieve both "efficient alkali removal" and "low damage to maintain structure" and that the improvement of interfacial performance is insufficient.

[0010] To achieve the above objectives, in a first aspect, the present invention provides an interface modification method for a solid electrolyte, the modification method comprising:

[0011] Step S1: The surface of the solid electrolyte to be treated is cleaned with anhydrous organic solvent and then dried under an inert atmosphere to obtain a pretreated solid electrolyte; wherein the solid electrolyte to be treated is an oxide inorganic solid electrolyte.

[0012] Step S2: Under an inert atmosphere, an inorganic acid, an organic macromolecular acid, and an anhydrous organic solvent are mixed to obtain an anhydrous composite acid working solution; wherein, at least one of the inorganic acid and the organic macromolecular acid contains phosphate.

[0013] Step S3: Immerse the pretreated solid electrolyte in the composite acid working solution and perform ultrasonic treatment to allow the inorganic acid to react with the residual alkali on the surface of the pretreated solid electrolyte to remove the residual alkali. Simultaneously, the organic macromolecular acid is adsorbed on the surface of the pretreated solid electrolyte, and the steric hindrance effect restricts the inorganic acid from penetrating into the bulk phase. After the residual alkali is removed, the phosphate ions in the anhydrous composite acid working solution react with the lithium ions on the surface of the pretreated solid electrolyte to generate Li3PO4 nanocrystals in situ. At the same time, the organic macromolecular acid chelates and coordinates with the metal ions M on the surface of the pretreated solid electrolyte to form a metal-organic complex network. The two are cross-linked and interpenetrating through POM bridge bonds to form a hybrid protective layer in situ, resulting in a solid electrolyte with a hybrid protective layer on the surface.

[0014] Step S4: The solid electrolyte with the hybrid protective layer is sequentially washed with anhydrous organic solvent and vacuum dried to obtain an interface-modified solid electrolyte.

[0015] Preferably, the oxide inorganic solid electrolyte includes one or more of the following: garnet-type lithium lanthanum zirconium oxide solid electrolyte (LLZO), garnet-type tantalum-doped lithium lanthanum zirconium oxide solid electrolyte (LLZTO), perovskite-type lithium lanthanum titanium oxide solid electrolyte (LLTO), perovskite-type fluorine-doped lithium lanthanum titanium oxide solid electrolyte (LLTOF), or NASICON-type lithium titanium aluminum phosphate solid electrolyte (LATP).

[0016] Preferably, the inorganic acid includes phosphoric acid and / or hydrochloric acid; the inorganic acid accounts for 0.05% to 2.0% of the total mass of the anhydrous composite acid working solution.

[0017] The organic macromolecular acid includes phytic acid and / or citric acid; the mass of the organic macromolecular acid accounts for 0.1% to 5.0% of the total mass of the anhydrous composite acid working solution.

[0018] The molar ratio of the inorganic acid to the organic macromolecular acid is 1:5 to 3:1.

[0019] The pH of the anhydrous composite acid working solution is 2.5 to 4.0.

[0020] Preferably, the molar ratio of the inorganic acid to the organic macromolecular acid is 3:1.

[0021] The inorganic acid is phosphoric acid; the mass of the phosphoric acid accounts for 0.2% of the total mass of the anhydrous composite acid working solution.

[0022] The organic macromolecular acid is phytic acid; the mass of the phytic acid accounts for 0.5% of the total mass of the anhydrous composite acid working solution.

[0023] Preferably, the anhydrous organic solvent includes anhydrous ethanol; the water content of the anhydrous organic solvent is <50ppm.

[0024] The inert atmosphere includes one or more of nitrogen, argon, or helium.

[0025] The vacuum drying temperature is 80℃~150℃, and the time is 20 minutes~3 hours.

[0026] Preferably, the ultrasonic treatment is performed at a temperature of 20°C to 40°C for 1 minute to 10 minutes, and at an ultrasonic frequency of 40 kHz.

[0027] In a second aspect, the present invention provides a solid electrolyte modified by the interface modification method described in the first aspect, wherein the interface-modified solid electrolyte comprises: a solid electrolyte and a hybrid protective layer attached to the surface of the solid electrolyte.

[0028] Preferably, the hybrid protective layer is an organic-inorganic hybrid layer formed by the interpenetration of Li3PO4 nanocrystals and organic macromolecular acid-metal chelates.

[0029] The thickness of the hybrid protective layer is 5 nm to 8 nm.

[0030] Preferably, a transition region with a compositional gradient of 2 nm to 5 nm is provided between the surface layer of the solid electrolyte and the hybrid protective layer; the content of Li3PO4 nanocrystals in the transition region increases gradient from the inside to the outside surface.

[0031] Thirdly, the present invention provides an all-solid-state lithium battery, the all-solid-state lithium battery comprising the interface-modified solid electrolyte described in the first aspect.

[0032] The present invention provides an interface modification method for a solid electrolyte, a solid electrolyte, and its application, which has the following technical effects.

[0033] (1) The present invention provides a method for modifying the interface of a solid electrolyte, which modifies the interface of the solid electrolyte through a one-step wet chemical method with the synergistic effect of inorganic-organic composite acids. Specifically, the oxide solid electrolyte to be treated is first cleaned and dried with anhydrous ethanol. Then, an anhydrous ethanol composite acid working solution containing inorganic acid and organic macromolecular acid is prepared under an inert atmosphere. Next, the pretreated solid electrolyte is completely immersed in the composite acid working solution and ultrasonically treated at a certain temperature. During this process, the H2O provided by the inorganic acid... + Rapidly decomposes residual alkali on the surface of solid electrolytes, while organic macromolecular acids are adsorbed onto the surface through steric hindrance, limiting H+. + It penetrates deep into the bulk phase, achieving self-limiting etching where the reaction automatically stops after the residual alkali is exhausted, and after the residual alkali is removed, the phosphate ions and surface Li +In situ, Li3PO4 nanocrystals are generated. Organic macromolecular acids chelate and coordinate with surface metal ions to form a metal-organic complex network. The two are cross-linked and interpenetrating through POM bridges, forming a hybrid protective layer and a compositional gradient transition region below it in situ. Finally, after ultrasonic cleaning with anhydrous ethanol and vacuum drying, a modified solid electrolyte with a Li3PO4 nanocrystal / organometallic chelate interpenetrating hybrid layer on the surface is obtained.

[0034] The interface modification method provided by this invention has a simple and easy-to-operate process for alkali removal and film formation, and is suitable for large-scale production.

[0035] (2) After the solid electrolyte is modified by the interface modification method provided by the present invention, an ultrathin hybrid protective layer with a compositional gradient transition region is formed in situ on the surface under the premise that the bulk structure is intact. This layer has multiple functions such as high ion conduction, electronic insulation, flexible lithium affinity and thermal stability. It completely removes the high-resistance residual alkali layer and eliminates the interface lattice mismatch, greatly reduces the lithium ion interface transport resistance, enables the ultra-wetting uniform deposition of lithium metal and effectively suppresses lithium dendrites, thereby significantly improving the interface stability, cycle reliability and safety of the solid electrolyte.

[0036] (3) When the interface-modified solid electrolyte provided by the present invention is applied to an all-solid-state battery, the interface-modified solid electrolyte has a gradient hybrid layer, which forms a low-impedance chemical bonding interface with the electrode, which can improve lithium-ion conduction and improve the rate performance of the battery. The surface of the interface-modified solid electrolyte guides the uniform deposition of lithium metal through its lithiophilic and uniform ion distribution characteristics, effectively suppressing lithium dendrite growth, so that the cycle life and coulombic efficiency of the battery at higher current densities can be improved by orders of magnitude. The dense interface layer of the interface-modified solid electrolyte blocks side reactions, enhances the chemical stability against high-voltage cathodes and humid environments, and improves the capacity retention and energy density of the battery. Finally, under the premise of ensuring that the bulk ion conduction is not affected, the cycle stability, rate performance, environmental adaptability and safety of the all-solid-state battery are comprehensively improved. Attached Figure Description

[0037] Figure 1 A flowchart of an interface modification method for a solid electrolyte provided in an embodiment of the present invention.

[0038] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the interface-modified solid electrolyte provided in Embodiment 1 of the present invention.

[0039] Figure 3 The image shows the XRD pattern of the interface-modified solid electrolyte provided in Embodiment 2 of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0042] This invention provides an interface modification method for solid electrolytes, such as... Figure 1 As shown, it includes the following steps.

[0043] Step S1: The surface of the solid electrolyte to be treated is cleaned with anhydrous organic solvent and then dried under an inert atmosphere to obtain the pretreated solid electrolyte.

[0044] The solid electrolyte to be processed is an oxide inorganic solid electrolyte.

[0045] Oxide inorganic solid electrolytes include one or more of the following: garnet-type lithium lanthanum zirconium oxide solid electrolyte (LLZO), garnet-type tantalum-doped lithium lanthanum zirconium oxide solid electrolyte (LLZTO), perovskite-type lithium lanthanum titanium oxide solid electrolyte (LLTO), perovskite-type fluorine-doped lithium lanthanum titanium oxide solid electrolyte (LLTOF), or NASICON-type lithium titanium aluminum phosphate solid electrolyte (LATP).

[0046] Preferably, the chemical formula of LLZO is Li7La3Zr2O. 12 The chemical formula of LLZTO is Li. 6.4 La3Zr 1.4 Ta 0.6 O 12 The chemical formula of LLTO is Li. 0.33 La 0.56 TiO3; LATP has the chemical formula Li 1.3 Al 0.3 Ti 1.7 (PO4)3; the chemical formula of LLTOF is Li 0.33 La 0.56 TiO 3-x F x , 0≤x≤0.2.

[0047] Anhydrous organic solvents include: anhydrous ethanol; the water content of anhydrous organic solvents is <50ppm.

[0048] Inert atmospheres include one or more of nitrogen, argon, or helium atmospheres.

[0049] Step S1 must be performed under an inert atmosphere because the residual alkali on the surface of the oxide solid electrolyte originates from its side reactions with moisture and carbon dioxide in the air. The purpose of step S1 is to remove contaminants from the surface of the oxide solid electrolyte and dry it, providing a clean surface for subsequent treatment. If cleaning and drying are performed in a normal air environment, the exposed fresh surface will react again with moisture and carbon dioxide in the air, regenerating residual alkali, rendering the pretreatment meaningless. Therefore, cleaning and drying must be carried out in an inert atmosphere, such as an Ar or N2 glove box, to ensure that the surface remains fresh and clean without residual alkali regeneration before treatment.

[0050] Step S2: Under an inert atmosphere, an inorganic acid, an organic macromolecular acid, and an anhydrous organic solvent are mixed to obtain an anhydrous composite acid working solution.

[0051] Among them, at least one of the inorganic acid and the organic macromolecular acid contains phosphate.

[0052] The inorganic acid includes phosphoric acid and / or hydrochloric acid; the inorganic acid accounts for 0.05% to 2.0% of the total mass of the anhydrous composite acid working solution, and can be any value within this range, such as 0.05%, 0.10%, 0.50%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Preferably, the inorganic acid is phosphoric acid; the mass of phosphoric acid accounts for 0.2% of the total mass of the anhydrous composite acid working solution.

[0053] The organic macromolecular acid includes phytic acid and / or citric acid; the mass of the organic macromolecular acid accounts for 0.1% to 5.0% of the total mass of the anhydrous composite acid working solution, and can be any value within this range, such as: 0.1%, 0.5%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, 3.0%, 3.2%, 3.4%, 3.6%, 3.8%, 4.0%, 4.2%, 4.4%, 4.6%, 4.8%, 5.0%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Preferably, the organic macromolecular acid is phytic acid; the mass of phytic acid accounts for 0.5% of the total mass of the anhydrous composite acid working solution.

[0054] When the inorganic acid is phosphoric acid, phosphoric acid directly releases PO4 after the base removal reaction. 3+ With surface Li +The reaction produces Li3PO4 nanocrystals. When the inorganic acid is hydrochloric acid and the organic macromolecular acid is phytic acid, the phosphate groups in the phytic acid molecule can also provide a phosphorus source to participate in the formation of Li3PO4 during the chelation coordination process. Both pathways can achieve in-situ formation of Li3PO4 nanocrystals, but the PO4 directly provided by phosphoric acid is more efficient. 3+ The reaction efficiency is higher, making it the preferred option.

[0055] The molar ratio of inorganic acid to organic macromolecular acid is 1:5 to 3:1, and can be any molar ratio within this range, such as 1:5, 1:4, 1:3, 1:2, 1:1, 3:1, etc., but is not limited to the listed molar ratios; other unlisted values ​​within this range are also applicable. The preferred molar ratio of inorganic acid to organic macromolecular acid is 3:1.

[0056] This invention controls the molar ratio of inorganic acid to organic macromolecular acid within the range of 1:5 to 3:1, aiming to ensure sufficient H+ in the anhydrous composite acid working solution. + While thoroughly removing alkali, sufficient macromolecules can control the steric hindrance self-limitation of the solid electrolyte surface and fully cross-link to form a film, achieving an optimal dynamic balance between alkali removal and film formation. Exceeding the upper limit of the above range will lead to excessive corrosion of the bulk phase due to insufficient steric hindrance, damaging the surface structure of the solid electrolyte; falling below the lower limit of the above range will result in incomplete alkali removal and film formation failure due to insufficient acidity, leading to deterioration of interfacial impedance.

[0057] The pH of the anhydrous composite acid working solution is 2.5–4.0.

[0058] The inorganic acid used in this invention can rapidly neutralize and decompose the dense and insulating residual alkali layer of Li₂CO₃ and / or LiOH on the surface of solid electrolytes, generating soluble lithium salts (such as lithium phosphate or lithium chloride) and gas (CO₂). This achieves the purpose of removing the high-resistivity residual alkali layer at the interface and enabling smooth lithium-ion transport. When phosphoric acid is selected as the inorganic acid, after the alkali removal reaction is completed, the residual phosphate ions (PO₄²⁻)... 3- Lithium ions (Li) that can be extracted from the surface of a solid electrolyte + The reaction occurs, generating in situ Li3PO4 nanocrystals with high ionic conductivity and electronic insulation. These form the inorganic framework in the hybrid protective layer, providing a fast channel for lithium ions to cross the interface while blocking electrons to avoid internal short circuits.

[0059] Inorganic acids react first with organic macromolecular acids, rapidly decomposing residual alkali and exposing the exposed surface of the solid electrolyte, providing reaction sites for the adsorption and chelation of organic macromolecular acids. Simultaneously, the concentration of the inorganic acid determines the driving force of the reaction; a suitable concentration ensures thorough alkali removal, but excessively high concentrations without the restraint of organic acids can lead to over-corrosion. In other words, inorganic acids preferentially react with residual alkali on the surface, completing interface purification; organic macromolecular acids then adsorb onto the freshly exposed surface, forming a steric hindrance protective layer that inhibits H+. + Infiltration into the bulk phase. Inorganic and organic acids work in succession over time and complement each other functionally, thereby simultaneously achieving thorough de-alkali removal and bulk phase structure protection.

[0060] Inert atmospheres include one or more of nitrogen, argon, or helium atmospheres.

[0061] Step S2 must be carried out under an inert atmosphere because if prepared in ordinary air, moisture in the environment will quickly dissolve in the anhydrous organic solvent, making the system hydrated. This moisture, once in subsequent processing steps, will react with the oxide solid electrolyte, interfering with the subsequent interface modification process. Furthermore, the composite acid working solution contains basic functional groups (such as the phosphate groups of phytic acid), which may absorb carbon dioxide from the air, altering the pH value and affecting the controllability and reproducibility of the reaction.

[0062] Step S3: Immerse the pretreated solid electrolyte in the composite acid working solution and perform ultrasonic treatment to obtain a solid electrolyte with a hybrid protective layer on the surface.

[0063] Specifically, the pretreated solid electrolyte is immersed in a composite acid working solution and subjected to ultrasonic treatment, which causes the inorganic acid to react with the residual alkali on the surface of the pretreated solid electrolyte to remove the residual alkali. At the same time, the organic macromolecular acid is adsorbed on the surface of the pretreated solid electrolyte, and the steric hindrance effect restricts the inorganic acid from penetrating into the bulk phase. After the residual alkali is removed, the phosphate ions in the anhydrous composite acid working solution react with the lithium ions on the surface of the pretreated solid electrolyte to generate Li3PO4 nanocrystals in situ. At the same time, the organic macromolecular acid chelates and coordinates with the metal ions M on the surface of the pretreated solid electrolyte to form a metal-organic complex network. The two are cross-linked and interpenetrating through POM bridge bonds to form a hybrid protective layer in situ, thus obtaining a solid electrolyte with a hybrid protective layer on the surface.

[0064] The ultrasonic treatment temperature is 20℃~40℃, the time is 1 minute~10 minutes, and the ultrasonic frequency is 40kHz.

[0065] Step S4: The solid electrolyte with the hybrid protective layer is sequentially washed with anhydrous organic solvent and vacuum dried to obtain the interface-modified solid electrolyte.

[0066] Among them, anhydrous organic solvents include: anhydrous ethanol; the water content of anhydrous organic solvents is <50ppm.

[0067] The vacuum drying temperature is 80℃~150℃, and the time is 20 minutes~3 hours.

[0068] This invention provides an interface-modified solid electrolyte, comprising: a solid electrolyte and a hybrid protective layer attached to the surface of the solid electrolyte.

[0069] The hybrid protective layer is an organic-inorganic hybrid layer formed by the interpenetration of Li3PO4 nanocrystals and organic macromolecular acid-metal chelates.

[0070] The thickness of the hybrid protective layer is 5 nm to 8 nm.

[0071] A 2nm to 5nm thick transition region with gradually changing composition is provided between the surface layer of the solid electrolyte and the hybrid protective layer; the content of Li3PO4 nanocrystals in the transition region increases from the inside to the outside surface.

[0072] The interface-modified solid electrolyte described above in this embodiment of the invention can be assembled with the positive and negative electrodes to form an all-solid-state battery. Because the interface-modified solid electrolyte has a gradient hybrid layer, which forms a low-impedance chemical bonding interface with the electrode, it can improve lithium-ion conduction and enhance the battery's rate performance. The surface of the interface-modified solid electrolyte, through its lithiophilic and uniform ion distribution characteristics, guides the uniform deposition of lithium metal, effectively suppressing lithium dendrite growth, resulting in an order-of-magnitude improvement in cycle life and coulombic efficiency at higher current densities. The dense interface layer of the interface-modified solid electrolyte blocks side reactions, enhancing chemical stability against high-voltage positive electrodes and humid environments, thus improving the battery's capacity retention and energy density. Ultimately, while ensuring that bulk ion conduction remains unaffected, the cycle stability, rate performance, environmental adaptability, and safety of the all-solid-state battery are comprehensively improved.

[0073] To better understand the technical solution provided by the present invention, the following uses several specific examples to illustrate the interface modification method of the solid electrolyte provided by the present invention, and the characteristics of the interface-modified solid electrolyte.

[0074] The testing methods and calculation methods for the various indicators involved in the embodiments and comparative examples of this invention are as follows.

[0075] 1. Determination of residual alkali content: An acid-base titration method (using Li₂CO₃ as an example) is employed. Specifically, 1g of solid electrolyte sample powder (hereinafter referred to as the sample) is dispersed in 20mL of deionized water, sonicated for 10min at 200W power and 40kHz frequency. After sonication, the suspension is centrifuged at 4000 r / min for 5min. 10mL of the supernatant is placed in a titration vessel, and then titrated with 0.01mol / L HCl standard solution to pH=8.3 using an automatic potentiometric titrator. The volume of HCl consumed is recorded, and the residual alkali content is calculated according to the following formula (using Li₂CO₃ as an example): The residual alkali Li₂CO₃ content = (concentration of hydrochloric acid standard solution × volume of HCl consumed × molar mass of Li₂CO₃) / (2 × sample mass × 1000) × 100%; where the unit of hydrochloric acid standard solution concentration is mol / L, the unit of HCl consumed is ml, the molar mass of Li₂CO₃ is 73.89 g / mol, and the unit of sample mass is g. If the solid electrolyte is a ceramic sheet, it needs to be pre-ground into powder before testing; the solid electrolyte ceramic sheet prepared in this embodiment of the invention has a dense hybrid protective layer on its surface. This layer has a certain chemical stability and also has an insulating effect. During short-term grinding, it can effectively prevent contact with water and CO₂ in the air, and will not regenerate a large amount of residual alkali. The ground powder can be directly used for testing.

[0076] 2. Crystal structure: Characterized by X-ray diffraction, with CuKα as the target material, 2θ = 10°~80°, scanning speed 2° / min, and step size 0.02°.

[0077] 3. Ionic conductivity test: Sample powder was placed in a stainless steel mold and pressed into a φ10mm disc at 200MPa. It was then placed in a muffle furnace under air conditions and sintered at 1050℃ for 4 hours. Gold electrodes were sputtered on both sides at a sputtering current of 20mA for 60s, resulting in a thickness of approximately 100nm. EIS testing (1Hz–1MHz) was performed at room temperature using an electrochemical workstation, and the bulk resistivity R was read from the EIS spectrum. b The ionic conductivity σ1 is calculated using the following formula: σ1 = L / (R b ×A), where L is the thickness of the ceramic disc (in cm, measured by a micrometer); R b A is the bulk resistance (Ω); A is the area of ​​the electrode (cm²). 2 Based on the diameter of the disc, A = π × (d / 2) 2 =0.785cm 2 ).

[0078] 4. Interfacial Impedance (ASR): The sample powder was mixed with PEO and LiTFSI at a mass ratio of 50:50, hot-pressed into a film (100 μm thick), and a Li|solid electrolyte membrane|Li symmetric cell was assembled. EIS testing was performed at 60℃. The total resistance was divided by the electrode area (0.785 cm²). 2 ).

[0079] The assembly process of Li|solid electrolyte membrane|Li symmetric battery is as follows: In a glove box filled with argon gas, lithium sheets are cut into 14mm diameter discs and assembled in the following order: negative electrode shell, stainless steel gasket, lithium metal sheet, solid electrolyte membrane, lithium metal sheet, stainless steel gasket, stainless steel spring sheet, and positive electrode shell. The battery is then sealed using a button cell sealing machine. After assembly, the battery is transferred to a 60℃ oven and left to stand for 12 hours.

[0080] 5. Interfacial ionic conductivity σ²: Interfacial ionic conductivity represents the conductivity of Li. + The ease with which the electrolyte crosses the interface layer between the solid electrolyte and metallic lithium. This is calculated by converting the ASR (Aspect Ratio) and the interface layer thickness (measured by TEM), using the formula σ² = d / ASR, where d represents the interface layer thickness (nm).

[0081] 6. Critical current density (CCD): Tested using an electrochemical workstation. The current density was measured at the voltage drop point of the symmetric cell at room temperature with increments of 0.1 mA / cm² for 30 minutes each.

[0082] 7. Cycle stability: Used to evaluate the interface stability and cycle life of all-solid-state lithium batteries during long-term constant current charge-discharge processes, specifically at 0.2 mA / cm². 2 0.2mAh / cm 2 Constant current charging and discharging at current density.

[0083] 8. Thermal stability: TGA-DTA, air atmosphere, heating to 600℃ at 10℃ / min.

[0084] 9. Interface bonding strength: The scratch method is used, with a loading rate of 10 N / min and a scratch length of 5 mm.

[0085] Example 1 This embodiment provides a method for modifying the interface of a solid electrolyte, and a solid electrolyte modified by the interface, specifically including the following steps.

[0086] (1) In an argon-filled glove box, the surface of the solid electrolyte to be treated was cleaned with anhydrous ethanol, and then dried at 70°C under an argon atmosphere to remove the anhydrous ethanol, thus obtaining the pretreated solid electrolyte. The solid electrolyte to be treated was an LLZO ceramic sheet with a diameter of 12 mm and a thickness of 1 mm.

[0087] (2) Under an argon atmosphere, 0.2g of anhydrous phosphoric acid and 0.5g of dehydrated phytic acid were dissolved in 100g of anhydrous ethanol and stirred for 30 minutes to mix evenly, so as to obtain an anhydrous composite acid working solution with a pH value of 3.0.

[0088] (3) Immerse the pretreated solid electrolyte in the composite acid working solution and sonicate it at 25°C for 5 minutes to obtain a solid electrolyte with a hybrid protective layer on the surface.

[0089] (4) The solid electrolyte with the hybrid protective layer was ultrasonically cleaned three times with anhydrous ethanol for 2 minutes each time, and then vacuum dried at 120°C for 8 hours to obtain the interface-modified solid electrolyte LLZO, which is a ceramic sheet with the chemical formula Li7La3Zr2O. 12 .

[0090] The XRD pattern of the interface-modified solid electrolyte surface provided in this embodiment is as follows: Figure 2 As shown in the XRD pattern, the characteristic peaks of Li₂CO₃ on the LLZO surface completely disappeared after treatment with a phosphoric acid-phytic acid composite acid, and the grain boundaries remained intact and uncorroded. Furthermore, Figure 2 The paper also provides the XRD pattern of the cubic phase of LLZO (standard PDF card No. 45-0109) and the XRD pattern of Li2CO3 (standard PDF card No. 22-1141, with characteristic peaks at 2θ≈21.3°, 30.6°, and 37.5°).

[0091] The interface-modified solid electrolyte provided in this embodiment, as observed by scanning electron microscopy, shows that a uniform and dense hybrid protective layer is formed on the surface of the interface-modified solid electrolyte. There is a compositional gradient transition layer between this protective layer and the substrate, and no clear phase interface exists.

[0092] The interfacial ionic conductivity of the solid electrolyte decreased from approximately 4.3 × 10⁻⁶ before treatment. -9 S / cm increased to approximately 6.3 × 10 -8 S / cm; Symmetrical cells at 0.5 mA / cm 2 After more than 1200 hours of stable cycling, the overpotential was only about 25 mV, and there was no short circuit throughout the entire process.

[0093] Example 2 This embodiment provides a method for modifying the interface of a solid electrolyte, and a solid electrolyte modified by the interface, specifically including the following steps.

[0094] (1) In an argon-filled glove box, the surface of the solid electrolyte to be treated was cleaned with anhydrous ethanol, and then dried at 70°C under an argon atmosphere to remove the anhydrous ethanol, thus obtaining the pretreated solid electrolyte. The solid electrolyte to be treated was an LLZTO ceramic sheet with a diameter of 12 mm and a thickness of 1 mm.

[0095] (2) Under an argon atmosphere, 0.15 g of anhydrous phosphoric acid and 0.6 g of anhydrous citric acid were dissolved in 100 g of anhydrous ethanol and stirred for 30 minutes to obtain an anhydrous composite acid working solution with a pH of 3.0. The molar ratio of anhydrous phosphoric acid to anhydrous citric acid was 1:3.

[0096] (3) The pretreated solid electrolyte is immersed in the composite acid working solution and subjected to ultrasonic treatment at 30°C for 8 minutes at 40 kHz to obtain a solid electrolyte with a hybrid protective layer on the surface.

[0097] (4) The solid electrolyte with the hybrid protective layer was ultrasonically cleaned three times with anhydrous ethanol for 2 minutes each time, and then vacuum dried at 120°C for 8 hours to obtain the interface-modified solid electrolyte LLZTO, with the chemical formula Li. 6.4 La3Zr 1.4 Ta 0.6 O 12 .

[0098] The XRD results of the interface-modified solid electrolyte prepared in this embodiment are as follows: Figure 3 As shown, the results indicate that the polycarboxylic acid structure can effectively chelate La on the LLZTO surface. 3+ / Zr 4+ It works synergistically with phosphoric acid to achieve self-limiting etching and in-situ film formation. After treatment, residual alkali is completely removed, and XRD shows an intact bulk structure.

[0099] The interfacial impedance of the symmetrical cell was measured to be 22 Ω·cm. 2 At 0.3 mA / cm 2 It can maintain a stable cycle time of over 800 hours.

[0100] Example 3 This embodiment provides a method for modifying the interface of a solid electrolyte, and a solid electrolyte modified by the interface, specifically including the following steps.

[0101] (1) In an argon-filled glove box, the surface of the solid electrolyte to be treated was cleaned with anhydrous ethanol, and then dried at 70°C under an argon atmosphere to remove the anhydrous ethanol, thus obtaining the pretreated solid electrolyte. The solid electrolyte to be treated was a Ta-doped LLZTO ceramic sheet with a diameter of 12 mm and a thickness of 1 mm.

[0102] (2) Under an argon atmosphere, 0.05 g of anhydrous hydrogen chloride and 0.8 g of dehydrated phytic acid were dissolved in 100 g of anhydrous ethanol and stirred for 30 minutes to obtain an anhydrous composite acid working solution with a pH of 3.2. The molar ratio of anhydrous hydrogen chloride to dehydrated phytic acid was 1:1.

[0103] (3) The pretreated solid electrolyte is immersed in the composite acid working solution and subjected to ultrasonic treatment at 20°C for 5 minutes at 40 kHz to obtain a solid electrolyte with a hybrid protective layer on the surface.

[0104] (4) The solid electrolyte with the hybrid protective layer was ultrasonically cleaned three times with anhydrous ethanol for 2 minutes each time, and then vacuum dried at 100°C for 10 hours to obtain the interface-modified solid electrolyte LLZTO, with the chemical formula Li. 6.4 La3Zr 1.4 Ta 0.6 O 12 .

[0105] Test results: Inorganic HCl provides highly efficient alkali removal, while phytic acid macromolecules provide self-limiting corrosion inhibition and chelation film formation functions. Residual alkali on the surface of the treated solid electrolyte was completely removed, and XRD testing showed no damage to the bulk structure of the solid electrolyte.

[0106] The interfacial impedance of the symmetrical cell was measured to be 18 Ω·cm. 2 At 0.5 mA / cm 2 It can withstand stable cycles for more than 1000 hours.

[0107] Example 4 This embodiment provides a method for modifying the interface of a solid electrolyte, and a solid electrolyte modified by the interface, specifically including the following steps.

[0108] (1) In an argon-filled glove box, the surface of the solid electrolyte to be treated was cleaned with anhydrous ethanol, and then dried at 70°C under an argon atmosphere to remove the anhydrous ethanol, thus obtaining the pretreated solid electrolyte. The solid electrolyte to be treated was an LLZO ceramic sheet with a diameter of 12 mm and a thickness of 1 mm.

[0109] (2) Under an argon atmosphere, 0.05 g of anhydrous phosphoric acid and 0.1 g of dehydrated phytic acid were dissolved in 100 g of anhydrous ethanol and stirred for 30 minutes to obtain an anhydrous composite acid working solution with a pH of 4.0. The molar ratio of anhydrous phosphoric acid to dehydrated phytic acid was 1:1.2.

[0110] (3) The pretreated solid electrolyte is immersed in the composite acid working solution and subjected to ultrasonic treatment at 10°C for 40 kHz for 15 minutes to obtain a solid electrolyte with a hybrid protective layer on the surface.

[0111] (4) The solid electrolyte with the hybrid protective layer was ultrasonically cleaned three times with anhydrous ethanol for 2 minutes each time, and then vacuum dried at 80°C for 12 hours to obtain the interface-modified solid electrolyte LLZO with the chemical formula Li7La3Zr2O. 12 .

[0112] Test results: The residual alkali on the surface of the treated solid electrolyte was completely removed, and XRD test showed that the structure of the bulk solid electrolyte was intact; The interfacial impedance of the symmetrical cell was measured to be 35 Ω·cm. 2 At 0.2 mA / cm 2 The stable cycle time exceeded 600 hours, proving that the method of the present invention can still work effectively under extremely mild conditions, with a wide process window and great operational flexibility.

[0113] Example 5 This embodiment provides a method for modifying the interface of a solid electrolyte, and a solid electrolyte modified by the interface, specifically including the following steps.

[0114] (1) In an argon-filled glove box, the surface of the solid electrolyte to be treated was cleaned with anhydrous ethanol, and then dried at 70°C under an argon atmosphere to remove the anhydrous ethanol, thus obtaining the pretreated solid electrolyte. The solid electrolyte to be treated was an LLTOF ceramic sheet with a diameter of 12 mm and a thickness of 1 mm.

[0115] (2) Under an argon atmosphere, 0.1 g of anhydrous phosphoric acid and 0.6 g of dehydrated phytic acid were dissolved in 100 g of anhydrous ethanol and stirred for 30 minutes to mix evenly, resulting in an anhydrous composite acid working solution with a pH of 3.5. The molar ratio of anhydrous phosphoric acid to dehydrated phytic acid was 1:3.5.

[0116] (3) The pretreated solid electrolyte is immersed in the composite acid working solution and subjected to ultrasonic treatment at 20°C for 6 minutes at 40 kHz to obtain a solid electrolyte with a hybrid protective layer on the surface.

[0117] (4) The solid electrolyte with the hybrid protective layer was ultrasonically cleaned three times with anhydrous ethanol for 2 minutes each time, and then vacuum dried at 100°C for 10 hours to obtain the interface-modified solid electrolyte LLTOF with the chemical formula Li. 0.33 La 0.56 TiO 2.9 F0 .1 .

[0118] Scanning electron microscopy revealed that the interface-modified solid electrolyte prepared in this embodiment has a dense amorphous hybrid layer with a thickness of about 7 nm, which is uniformly coated on the LLTOF matrix.

[0119] The interfacial impedance of the symmetrical cell was tested at 1850 Ω·cm without treatment. 2 Reduced to 38Ω·cm 2 At 0.2 mA / cm 2 The system can maintain stable operation for more than 700 hours.

[0120] Example 6 This embodiment provides a method for modifying the interface of a solid electrolyte, and a solid electrolyte modified by the interface, specifically including the following steps.

[0121] (1) In an argon-filled glove box, the surface of the solid electrolyte to be treated was cleaned with anhydrous ethanol, and then dried at 70°C under an argon atmosphere to remove the anhydrous ethanol, thus obtaining the pretreated solid electrolyte. The solid electrolyte to be treated was an LATP ceramic sheet with a diameter of 12 mm and a thickness of 1 mm.

[0122] (2) Under an argon atmosphere, 0.15 g of anhydrous phosphoric acid and 0.5 g of dehydrated phytic acid were dissolved in 100 g of anhydrous ethanol and stirred for 30 minutes to obtain an anhydrous composite acid working solution with a pH of 3.2. The molar ratio of anhydrous phosphoric acid to dehydrated phytic acid was 1:2.

[0123] (3) The pretreated solid electrolyte is immersed in the composite acid working solution and subjected to ultrasonic treatment at 25°C for 5 minutes at 40 kHz to obtain a solid electrolyte with a hybrid protective layer on the surface.

[0124] (4) The solid electrolyte with the hybrid protective layer was ultrasonically cleaned three times with anhydrous ethanol for 2 minutes each time, and then vacuum dried at 100°C for 10 hours to obtain the interface-modified solid electrolyte LATP, with the chemical formula Li. 1.3 Al 0.3 Ti 1.7 (PO4)3;

[0125] The XRD test results show that the interface-modified solid electrolyte LATP prepared in this embodiment has a complete structure and no impurity phase is generated.

[0126] The interfacial impedance of the symmetrical cell was tested from 1250 Ω·cm. 2 Reduced to 55Ω·cm 2 At 0.2 mA / cm 2 After more than 600 hours of stable cycling, the overpotential is approximately 30mV.

[0127] To better illustrate the effects of the embodiments of the present invention, a comparative example is provided to be made with the embodiments described above.

[0128] Comparative Example 1 This comparative example uses the same batch of LLZO ceramic sheets (chemical formula Li7La3Zr2O) as in Example 1. 12 It was then ultrasonically dispersed in a 0.2wt% phosphate ethanol solution at 25°C for 5 min.

[0129] Test results: Although the residual alkali on the surface of the LLZO ceramic sheet was removed, the interfacial resistance (ASR) was as high as 480 Ω·cm. 2 This is 60 times that of Example 1; the interfacial ionic conductivity (converted from ASR) is only about 6.3 × 10⁻⁶. -9 S / cm, an order of magnitude lower than in Example 1; symmetric cells at 0.5 mA / cm 2 A short circuit occurred after only 150 hours of the next cycle, with a critical current density (CCD) below 0.5 mA / cm². 2 Cause of failure: No phytic acid limiting corrosion, H + Deep exchange leads to damage to the bulk structure of LLZO and severe deterioration of interfacial properties. Although the bulk ionic conductivity of Comparative Example 1 decreased slightly, it was not the main cause of interfacial failure. The main reason was the surge in ASR caused by grain boundary corrosion.

[0130] Comparative Example 2 This comparative example uses the same batch of LLZO ceramic sheets (chemical formula Li7La3Zr2O) as in Example 1. 12 It was ultrasonically dispersed in 0.2wt% anhydrous phytic acid ethanol solution at 25℃ for 5 min.

[0131] Test results showed that the treated LLZO contained a large amount of residual alkali; the ASR was as high as 920 Ω·cm. 2 The cleaning effect is weak. This is because phytic acid is a weak acid and cannot effectively decompose thick layers of lithium carbonate.

[0132] Table 1 summarizes the test data for Examples 1-6 and Comparative Examples 1-2.

[0133] Table 1 The comparative analysis of the test data in Table 1 shows that: Compared to Comparative Example 1 (single phosphoric acid treatment, without phytic acid protection), the ASR of each embodiment of the present invention increased from 480 Ω·cm. 2 Significantly reduced to 8Ω·cm 2 ~55Ω·cm 2 This reduces the conductivity by approximately 9 to 60 times, with the interfacial ionic conductivity decreasing from 6.3 × 10⁻⁶. -9 S / cm increased to 1.1×10 -8 ~6.3×10 -8 S / cm, critical current density from below 0.5 mA / cm 2Increased to 0.5–1.5 mA / cm 2 The cycle life was extended from less than 150 hours to over 600-1200 hours. Although both Comparative Example 1 and Example 1 could completely remove residual alkali from the surface of the solid electrolyte, Comparative Example 1 lacked the steric hindrance self-limitation protection of phytic acid, resulting in a large amount of H₂. + Penetration into the bulk phase triggers grain boundary corrosion, leading to a sharp increase in interfacial impedance. Lithium dendrites preferentially penetrate at corrosion microcracks, ultimately resulting in early short-circuit failure even at low current densities. The comparison between Example 1 and Comparative Example 1 clearly demonstrates that single inorganic acid treatment can remove residual alkali but damages the structure; single phosphoric acid, while effective at removing alkali, severely corrodes grain boundaries, resulting in excessively high impedance; and single phytic acid is ineffective at removing alkali. This invention, however, through the synergistic effect of phosphoric acid and phytic acid, simultaneously completes alkali removal, self-limiting protection of the bulk phase, and in-situ reconstruction of the hybrid interfacial layer in the same composite treatment solution, achieving a comprehensive improvement in interfacial performance, including low interfacial impedance, high critical current density, and ultra-long cycle life.

[0134] Compared to Comparative Example 2 (treated with phytic acid alone, without the use of inorganic acid), the residual alkali in each embodiment of the present invention was completely removed (Comparative Example 2 had a large amount of residual alkali remaining). The ASR decreased from 920 Ω·cm² to 8-55 Ω·cm² (a reduction of approximately 17-115 times), and the cycle life was extended from less than 50 hours to over 600-1200 hours. Furthermore, each embodiment could perform normal charge-discharge tests and accurately measure CCD and interface ionic conductivity. In contrast, Comparative Example 2, due to its excessively high interface impedance and the double-layer impedance barrier formed by residual alkali and organic byproducts, could not complete the CCD and interface ionic conductivity tests normally. Comparative Example 2 relied solely on the weak acidity of phytic acid, which could not completely decompose the Li₂CO₃ passivation layer. Moreover, a large amount of insoluble organic lithium salt byproducts remained on the surface after the reaction. The combined effect of these two factors resulted in extremely high interface impedance and a sharp increase in polarization, causing the battery to fail in a very short time. This demonstrates that while single organic acid treatment can protect the surface structure of the solid dielectric, it cannot completely purify the interface. The present invention, by introducing inorganic acid into the composite acid system, provides sufficient H₂ for the alkali removal reaction. + The driving force ensures that residual alkali is efficiently and completely removed, thus providing a clean reaction substrate for subsequent in-situ film formation, enabling the hybrid protective layer to grow in situ on the freshly exposed solid electrolyte surface, achieving a comprehensive improvement in interface performance.

[0135] In summary, the interface modification method for solid electrolytes provided by this invention is applicable to different acid combinations (phosphoric acid-phytic acid, phosphoric acid-citric acid, hydrochloric acid-phytic acid) and a wide range of process conditions (10-40°C, low to conventional concentrations). It is also applicable to various crystal systems of oxide solid electrolytes, such as garnet type (LLZO, LLZTO), perovskite type (LLTO, LLTOF), and NASICON type (LATP), providing a simple, universal, and easily scalable solution for interface engineering of all-solid-state lithium batteries.

[0136] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for modifying the interface of a solid electrolyte, characterized in that, The modification method includes: Step S1: The surface of the solid electrolyte to be treated is cleaned with anhydrous organic solvent and then dried under an inert atmosphere to obtain a pretreated solid electrolyte; wherein the solid electrolyte to be treated is an oxide inorganic solid electrolyte. Step S2: Under an inert atmosphere, an inorganic acid, an organic macromolecular acid, and an anhydrous organic solvent are mixed to obtain an anhydrous composite acid working solution; wherein, at least one of the inorganic acid and the organic macromolecular acid contains phosphate. Step S3: Immerse the pretreated solid electrolyte in the composite acid working solution and perform ultrasonic treatment to allow the inorganic acid to react with the residual alkali on the surface of the pretreated solid electrolyte to remove the residual alkali. Simultaneously, the organic macromolecular acid is adsorbed on the surface of the pretreated solid electrolyte, and the steric hindrance effect restricts the inorganic acid from penetrating into the bulk phase. After the residual alkali is removed, the phosphate ions in the anhydrous composite acid working solution react with the lithium ions on the surface of the pretreated solid electrolyte to generate Li3PO4 nanocrystals in situ. At the same time, the organic macromolecular acid chelates and coordinates with the metal ions M on the surface of the pretreated solid electrolyte to form a metal-organic complex network. The two are cross-linked and interpenetrated through POM bridge bonds to form a hybrid protective layer in situ, resulting in a solid electrolyte with a hybrid protective layer on the surface. Step S4: The solid electrolyte with the hybrid protective layer is sequentially washed with anhydrous organic solvent and vacuum dried to obtain an interface-modified solid electrolyte.

2. The interface modification method according to claim 1, characterized in that, The oxide inorganic solid electrolyte includes one or more of the following: garnet-type lithium lanthanum zirconium oxide solid electrolyte (LLZO), garnet-type tantalum-doped lithium lanthanum zirconium oxide solid electrolyte (LLZTO), perovskite-type lithium lanthanum titanium oxide solid electrolyte (LLTO), perovskite-type fluorine-doped lithium lanthanum titanium oxide solid electrolyte (LLTOF), or NASICON-type lithium titanium aluminum phosphate solid electrolyte (LATP).

3. The interface modification method according to claim 1, characterized in that, The inorganic acid includes phosphoric acid and / or hydrochloric acid; the inorganic acid accounts for 0.05% to 2.0% of the total mass of the anhydrous composite acid working solution. The organic macromolecular acid includes phytic acid and / or citric acid; the mass of the organic macromolecular acid accounts for 0.1% to 5.0% of the total mass of the anhydrous composite acid working solution; The molar ratio of the inorganic acid to the organic macromolecular acid is 1:5 to 3:1; The pH of the anhydrous composite acid working solution is 2.5 to 4.

0.

4. The interface modification method according to claim 3, characterized in that, The molar ratio of the inorganic acid to the organic macromolecular acid is 3:1; The inorganic acid is phosphoric acid; the mass of the phosphoric acid accounts for 0.2% of the total mass of the anhydrous composite acid working solution; The organic macromolecular acid is phytic acid; the mass of the phytic acid accounts for 0.5% of the total mass of the anhydrous composite acid working solution.

5. The interface modification method according to claim 1, characterized in that, The anhydrous organic solvent includes: anhydrous ethanol; the water content of the anhydrous organic solvent is <50ppm; The inert atmosphere includes one or more of nitrogen, argon, or helium. The vacuum drying temperature is 80℃~150℃, and the time is 20 minutes~3 hours.

6. The interface modification method according to claim 1, characterized in that, The ultrasonic treatment is performed at a temperature of 20℃ to 40℃ for 1 minute to 10 minutes, and at an ultrasonic frequency of 40kHz.

7. A solid electrolyte modified by the interface modification method according to any one of claims 1-6, characterized in that, The interface-modified solid electrolyte includes: a solid electrolyte and a hybrid protective layer attached to the surface of the solid electrolyte.

8. The interface-modified solid electrolyte according to claim 7, characterized in that, The hybrid protective layer is an organic-inorganic hybrid layer formed by the interpenetration of Li3PO4 nanocrystals and organic macromolecular acid-metal chelates. The thickness of the hybrid protective layer is 5 nm to 8 nm.

9. The interface-modified solid electrolyte according to claim 7, characterized in that, The solid electrolyte has a 2nm to 5nm thick transition region with gradually changing composition between its surface layer and the hybrid protective layer; the content of Li3PO4 nanocrystals in the transition region increases gradually from the inside to the outside surface.

10. An all-solid-state lithium battery, characterized in that, The all-solid-state lithium battery includes the interface-modified solid electrolyte as described in any one of claims 7-9.

Images