Method for removing lithium carbonate on surface of garnet electrolyte in situ to form interface layer

Abstract

The invention belongs to the technical field of surface modification of solid electrolyte materials, and relates to a method for forming an interface layer on the surface of garnet electrolyte by removing lithium carbonate in situ, which comprises the following steps: 1, substrate pretreatment: selecting a garnet type solid electrolyte substrate with a Li2CO3 impurity layer on the surface, cleaning and drying; 2, a metal oxide film is deposited through magnetron sputtering, specifically, the pretreated base material is subjected to reactive deposition in oxygen or oxygen / argon mixed atmosphere through a metal target material to form an oxide film, the oxide film is a non-lithiated metal oxide, and the oxide film covers the surface of the base material; 3, heat treatment induced in-situ solid-solid reaction: carrying out heat treatment on the deposited matrix material to generate lithiated transition metal oxide; in the heat treatment process, the deposited oxide is promoted to react with Li2CO3 on the surface to generate a lithium compound interface layer with lithium affinity, the dual functions of impurity removal and conduction layer construction are achieved, and the interface functionalization level is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte material surface modification technology, specifically relating to a method for in-situ delithium carbonate removal to form an interface layer on the surface of a garnet electrolyte. Background Technology

[0002] With the increasing demand for high-energy-density, long-life, and high-safety energy storage systems, all-solid-state lithium metal batteries, as one of the core technologies for next-generation energy devices, are receiving widespread attention from academia and industry. Among various solid-state electrolyte materials, garnet-type oxide solid-state electrolytes, especially Li7La3Zr2O... 12 Lithium carbonate (LLZO) is widely regarded as an ideal choice for achieving high-performance solid-state batteries due to its excellent lithium-ion conductivity, good thermal stability, and high mechanical strength. However, during sintering, processing, or storage, the surface of LLZO readily reacts with carbon dioxide and moisture in the environment, forming a layer of lithium carbonate (Li2CO3) impurity film. This impurity layer is electrochemically unstable and has extremely low lithium-ion conductivity, severely hindering lithium-ion cross-interface transport and leading to increased interfacial impedance. Furthermore, due to its poor mechanical properties, it is prone to cracking and detachment during battery assembly and cycling, resulting in poor interfacial contact and even inducing lithium dendrite growth, posing safety hazards. These problems have become key obstacles restricting the widespread application of LLZO in solid-state batteries.

[0003] Although existing research has attempted to remove the Li₂CO₃ layer from the surface of LLZO through various methods, including high-temperature heat treatment, dilute acid cleaning, ion beam bombardment, plasma etching, atomic layer deposition, and sol-gel coating, these methods have the following shortcomings: Firstly, high-temperature treatment may cause changes in the bulk structure of LLZO or even secondary contamination, while liquid-phase etching methods have a narrow processing window, are cumbersome to operate, and may introduce new impurities or residual solvents. Secondly, even if the Li₂CO₃ layer is successfully removed, the LLZO surface lacks an effective lithium-affinity conductive layer after treatment, making it difficult to achieve stable contact with metallic lithium. This easily leads to the formation of new interfacial barriers, resulting in persistently high interfacial impedance and poor cycle stability. Therefore, most existing technologies only focus on impurity removal, neglecting the reconstruction of the overall interfacial conductivity and lithium affinity, and fundamentally failing to solve the mismatch and instability problem of the solid electrolyte / lithium metal interface.

[0004] Therefore, there is an urgent need for an interfacial conductive layer that can remove impurities while constructing a dense interfacial layer on the LLZO surface, which has good lithium wettability, electrochemical stability and structural compactness, so as to reduce interfacial impedance, suppress lithium dendrite growth and improve cycle life. Summary of the Invention

[0005] This invention employs magnetron sputtering technology to precisely deposit an ultrathin metal oxide film (such as TiO2, Nb2O5, etc.) on the surface of LLZO, and induces an in-situ solid-solid reaction between the film and surface Li2CO3 during subsequent heat treatment to form Li2MO. x The lithium-ionized conductive layer not only effectively eliminates the impurity layer and restores the interfacial activity, but also achieves good wetting of lithium metal and stable interfacial contact, providing a process-controllable, effective and industrially promising interface engineering method for the development of solid-state batteries.

[0006] This invention provides the following technical solution: a method for in-situ delithiation of lithium carbonate on the surface of garnet electrolyte to form an interface layer, comprising the following steps:

[0007] Step 1, Substrate Pretreatment: Select garnet-type solid electrolyte substrate ceramic sheets, sintered blocks or powders with a Li2CO3 impurity layer on the surface as substrate materials. Clean the substrate materials with anhydrous ethanol and acetone in sequence to remove surface dust and organic contaminants, and then dry to remove surface adsorbed moisture. Garnet-type solid electrolytes can be in sheet, block, film or powder form, and are suitable for solid battery components of different configurations, including but not limited to separators, interface layers or composite electrode frame materials.

[0008] Step 2: Magnetron sputtering deposition of metal oxide thin films: The pretreated substrate material is fixed on the sample stage of the magnetron sputtering equipment, and an oxide thin film is formed by reaction deposition of metal targets in an oxygen or oxygen / argon mixed atmosphere. The metal targets include: Ti, Nb, Si, Fe, Mn, Co, Ni, and Ta. The oxide thin film is a non-lithiated metal oxide, and the oxide thin film covers the surface of the substrate material. A garnet-type solid electrolyte substrate with a surface lithium carbonate (LiCO) impurity layer is placed in a vacuum chamber, and an ultra-thin and uniform metal oxide thin film is deposited on its surface using magnetron sputtering technology.

[0009] Step 3: Heat Treatment Induces In-Situ Solid-Solid Reaction: The deposited substrate material is heat-treated in an inert atmosphere or vacuum environment. An in-situ solid-solid reaction occurs between the oxide film and the Li₂CO₃ impurity layer, generating a lithiated transition metal oxide. Heat treatment of the sample after oxide deposition promotes an in-situ solid-solid reaction between the deposited metal oxide and the naturally formed Li₂CO₃ impurity layer on the solid electrolyte surface, generating a lithiophilic lithiated metal oxide interfacial conductive layer. This interfacial conductive layer is a dense, continuously distributed lithium compound layer with excellent lithium metal wettability, electrochemical stability, and interfacial conductivity. It effectively reduces the interfacial impedance between lithium metal and the garnet-type solid electrolyte, inhibits the formation and penetration of lithium dendrites, and improves the interfacial cycle stability and overall safety of the battery.

[0010] This invention has high versatility and scalability, can be adapted to garnet-type electrolyte matrices with different compositions and various metal oxide modification systems, and is compatible with existing solid-state battery manufacturing processes and heat treatment equipment, making it suitable for large-scale mass production and industrial applications.

[0011] Preferably, in step 2, the magnetron sputtering is radio frequency magnetron sputtering, and the magnetron sputtering parameters include: target power 50-150W, atmosphere composition volume ratio Ar:O2 = 9:1, total chamber pressure 0.5-1.0Pa, sputtering time 5-30 minutes; substrate material temperature is room temperature or heated to no more than 100℃, oxide film thickness is 5-20nm; the deposition thickness of the metal oxide film is controlled between 5-20nm to ensure sufficient reaction with surface Li2CO3 and not affect the diffusion ability of lithium ions.

[0012] Preferably, in step 3, the heat treatment conditions include: a heating rate of 2-10℃ / min, a holding temperature of 300℃-600℃, a holding time of 30 minutes to 2 hours, and an atmosphere of Ar or a vacuum degree better than 10. -3 Pa. The heat treatment step ensures the completeness of the in-situ reaction and avoids excessive diffusion of oxides or the occurrence of side reactions.

[0013] Preferably, in step 2, the metal oxide in the oxide film includes at least one of the following: Ta₂O₅, Nb₂O₅, SiO₂, Fe₂O₃, MnO₂, Co₃O₄, NiO, and TiO₂; and the transition metal oxide in step 2 is Li₂MO. x Type of compound, where M is a metal element in a metal oxide, O x This indicates the oxygen content in the formula.

[0014] Preferably, in step 1, the garnet-type solid electrolyte matrix is ​​composed of Li7La3Zr2O 12 The oxide system with a garnet-type solid electrolyte matrix includes: Li7La3Zr2O 12 、Li6La3ZrTaO 12 Li 6.5 La3Zr 1.5 Ta 0.5 O 12 Li6La3ZrNbO 12 Li 6.5 La3Zr 1.5 Nb 0.5 O 12 Garnet-type solid electrolytes and their doped or modified derivatives have a garnet-type crystal structure.

[0015] Preferably, in step 3, the lithiated transition metal oxides generated include: LiTaO3, LiNbO3, Li4SiO4, LiFeO2, LiMn2O4, LiCoO2, LiNiO2, and Li2TiO3. The lithiated interface conductive layer formed by the in-situ reaction is a lithium compound with good electrochemical stability and lithium-ion affinity; the lithiated interface conductive layer can effectively suppress unstable contact between metallic lithium and the original Li2CO3 layer, improve the deposition uniformity of metallic lithium, and suppress problems such as voids, lithium dendrites, and contact failure.

[0016] Preferably, in step 1, the garnet-type solid electrolyte matrix has a cubic phase crystal structure.

[0017] Preferably, in step 1, the lithium-ion conductivity of the garnet-type solid electrolyte matrix is ​​not less than 10. -4 S·cm -1 The garnet-type solid electrolyte matrix was not subjected to strong acid washing treatment.

[0018] Preferably, in step 1, the pretreated garnet-type solid electrolyte substrate is immediately subjected to magnetron sputtering deposition of a metal oxide thin film in step 2.

[0019] The beneficial effects of this invention are:

[0020] 1. This invention enables precise and controllable deposition of metal oxide thin films using magnetron sputtering technology, exhibiting good uniformity, repeatability, and large-area scalability, making it suitable for industrial-scale production.

[0021] 2. This invention introduces an in-situ solid-solid reaction mechanism, which promotes the reaction between the deposited oxide and the surface Li2CO3 during the heat treatment process to generate a lithium compound interface layer with lithium affinity, which has the dual functions of "impurity removal" and "conductivity layer construction", significantly improving the level of interface functionalization.

[0022] 3. The interface layer obtained by this invention is dense and crack-free, with excellent chemical and electrochemical stability. It can effectively control the lithium deposition morphology, reduce void formation and interface failure, and enhance the long-cycle stability and high-rate capability of the battery.

[0023] 4. The method of the present invention has strong adaptability and can be widely applied to various garnet-type solid electrolytes and different types of transition metal oxide systems, and has good versatility and scalability.

[0024] 5. This invention provides a simple, high-performance, and scalable method for modifying the interface of a solid electrolyte, providing an effective technical path for the large-scale application of high-energy-density and high-safety solid lithium metal batteries, and has important theoretical significance and broad application prospects. Attached Figure Description

[0025] Figure 1 Example 1 of the method for in-situ delithiation of lithium carbonate on the surface of a garnet electrolyte to form an interface layer according to the present invention uses an interface impedance diagram of an LLZO type solid electrolyte modified with Ta2O5.

[0026] Figure 2 In Example 1 of this invention, a symmetric cell using a Ta₂O₅-modified LLZO-type solid electrolyte was used at a current density of 0.1 mA / cm². -2 Cyclic stability plot at time;

[0027] Figure 3 This is a schematic diagram of the method steps of the present invention. Detailed Implementation

[0028] The related technologies of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] like Figures 1-3 As shown, this embodiment overcomes the problems in the prior art such as the difficulty in completely removing the lithium carbonate impurity film on the surface of LLZO solid electrolyte, poor interfacial lithiophilicity, high interfacial impedance, and easy induction of lithium dendrites. This embodiment not only effectively eliminates Li2CO3 on the LLZO surface, but also utilizes magnetron sputtering to deposit metal oxides and induce an in-situ solid-solid reaction with the surface lithium carbonate impurity film, thereby generating a lithium-based interface layer with good lithium wettability and interfacial conductivity. Furthermore, it can in-situ construct a lithium-based interface conductive layer with good electrochemical stability and lithium wettability, thus significantly improving interface stability, reducing interfacial impedance, and inhibiting lithium dendrite growth. The technical solution of this invention will be further described in detail below with reference to specific embodiments. The specific steps of this embodiment are as follows:

[0030] Step 1. Matrix pretreatment:

[0031] Commercially available or laboratory-synthesized LLZO ceramic sheets, sintered blocks, or powders are selected as the matrix material. The LLZO used should possess a cubic crystal structure and a lithium-ion conductivity of not less than 10. -4 S·cm -1 Furthermore, no strong acid washing treatment was performed on the surface to ensure that the original Li2CO3 impurity layer is still retained on the surface.

[0032] The LLZO sample was placed in an ultrasonic cleaner and cleaned sequentially with anhydrous ethanol and acetone for 5 minutes to remove surface dust and organic contaminants. It was then dried at 80°C for 1 hour, or in a vacuum drying oven to remove adsorbed moisture. To prevent further thickening of Li₂CO₃ due to air exposure, it is recommended to immediately transfer the sample to the magnetron sputtering chamber for subsequent processing after pretreatment.

[0033] Step 2. Magnetron sputtering deposition of metal oxide thin films:

[0034] The pretreated LLZO sample is fixed on the sample stage of a magnetron sputtering device. A metal oxide target, such as Ti, Nb, Si, Fe, Mn, Co, Ni, or Ta, is selected, and an oxide film is deposited by reaction of the metal target in an oxygen or oxygen / argon mixed atmosphere. The deposited sample surface appears pale gray or light yellow, varying slightly depending on the selected metal oxide. At this point, the film is a non-lithiated metal oxide, covering the LLZO surface containing Li₂CO₃ impurities.

[0035] Radio frequency magnetron sputtering is preferred, with the following typical parameters set: target power: 50-150W; atmosphere composition: Ar:O2 = 9:1 (volume ratio); total chamber pressure: 0.5-1.0Pa; sputtering time: 5-30 minutes, determined according to the required film thickness; substrate temperature: room temperature or heated to no more than 100℃; film thickness controlled within the range of 5-20nm to ensure continuous, uniform, and dense film layers, and to facilitate the full progress of subsequent in-situ reactions.

[0036] Step 3. Heat treatment to induce in-situ solid-solid reaction:

[0037] The deposited sample is placed in a tube furnace or vacuum furnace and heat-treated in an inert atmosphere (such as argon or nitrogen) or a vacuum environment. Typical heat treatment conditions are as follows: heating rate: 2-10℃ / min; holding temperature: 400-500℃ (preferably 450℃); holding time: 30 minutes to 2 hours; atmosphere: high-purity Ar or vacuum degree better than 10. -3 Pa. During this process, the metal oxide film undergoes an in-situ solid-solid reaction with the underlying Li2CO3 impurity layer to generate a lithium-modified transition metal oxide (Li2MO). x (where M is Ti, Nb, Si, etc.), specific reaction examples are as follows:

[0038] TiO2 + Li2CO3 → Li2TiO3 + CO2↑

[0039] Nb₂O + Li₂CO₃ → LiNbO₃ + CO₂↑

[0040] SiO2 + Li2CO3 → Li4SiO4 + CO2↑

[0041] The reaction takes place at the solid-state interface, and the reaction products are distributed between the original impurity layer and the metal oxide film, forming a continuous and dense lithium-ion conductive layer, thus avoiding secondary pollution or liquid-phase residue problems.

[0042] Step 4. Interface Evaluation and Performance Testing:

[0043] The treated LLZO samples can be used to assemble symmetrical lithium metal batteries or full cell structures, for interfacial impedance testing, cycle performance evaluation, and observation of lithium deposition morphology, typically exhibiting a significantly reduced interfacial impedance (<100 Ω·cm). 2 The excellent cycle stability (>500 hours without short circuit) verifies the effectiveness of the processing method of the present invention in improving the performance of solid-state batteries.

[0044] Example

[0045] Example 1: In-situ removal of Li2CO3 from the surface of LLZO solid electrolyte to form a LiTaO3 interface layer:

[0046] First, a commercially available sintered cubic LLZO ceramic sheet with dimensions of 10 mm × 10 mm × 1 mm was selected as the solid electrolyte. The sample was treated with air at 600℃ for 3 hours to induce the formation of a certain amount of Li2CO3 impurity layer on its surface.

[0047] Subsequently, a Ta target was introduced into a high-vacuum magnetron sputtering apparatus, with an applied radio frequency power of 150 W, the stage temperature maintained at room temperature, the argon / oxygen flow rate ratio set to 20 sccm / 5 sccm, and the total pressure maintained at 0.5 Pa. A Ta₂O₅ film with a thickness of approximately 10 nm was deposited on the LLZO surface over a time of approximately 15 min. The sample was continuously rotated during sputtering to ensure film uniformity.

[0048] After deposition, the sample was placed in air and heat-treated at 700℃ for 1 hour. This process promoted the reaction between Ta2O5 and surface Li2CO3, forming a LiTaO3 interface layer. This interface layer is a dense, continuous lithiated conductive layer that is tightly bonded to the LLZO substrate. Interface structure analysis showed that the surface Li2CO3 was largely eliminated, successfully transforming into Li2TaO3. Simultaneously, scanning electron microscopy indicated that the film was crack-free and had a smooth, continuous surface.

[0049] Subsequently, a Li / LLZO / Li symmetric cell was assembled, and electrochemical tests were performed at 60 °C. The AC impedance spectroscopy results showed that the interfacial impedance increased from the initial approximately 1200 Ωcm. 2 Reduced to approximately 180 Ωcm 2 ; at 0.1 mAcm -2After 1000 hours of cycling under constant current charge and discharge conditions, there was no significant voltage shift or increase in polarization, demonstrating excellent interface stability and dendrite suppression capability.

[0050] Example 2: In-situ removal of Li2CO3 from the surface of LLZTO solid electrolyte to form a LiNbO3 interface layer:

[0051] First, a commercially available sintered cubic LLZTO ceramic sheet with dimensions of 12mm × 12mm × 1mm was selected as the solid electrolyte. The sample was placed in air at 600℃ for 3 hours to enrich its surface with a Li2CO3 electrochemical inert layer.

[0052] Subsequently, an Nb metal target was used in a high-vacuum RF magnetron sputtering system. The RF power was set to 120 W, the stage temperature was maintained at room temperature, the argon / oxygen flow rates were 20 sccm / 4 sccm, and the total pressure was controlled at 0.4 Pa. An Nb₂O₅ film with a thickness of approximately 12 nm was deposited on the LLZTO surface over a time of 18 min. During sputtering, the sample was kept rotating at a constant speed to ensure uniform film coverage.

[0053] After deposition, the sample was placed in a muffle furnace and heat-treated at 680°C in air for 2 hours to induce an in-situ solid-solid reaction between Nb₂O₅ and surface Li₂CO₃, forming a LiNbO₃ lithiated conductive interface layer. This interface layer bonded well with the substrate, without obvious delamination or cracks, and exhibited excellent mechanical and chemical stability.

[0054] Interface structure analysis results showed that XRD detected characteristic peaks of the LiNbO3 phase, and XPS spectra showed a significant decrease in the intensity of the original Li2CO3 peak. Simultaneously, the valence state characteristics of Nb indicated the formation of LiNbO3, verifying the effectiveness of the interfacial reaction. Scanning electron microscopy images showed a continuous and dense film with a uniform surface morphology and no obvious defects.

[0055] The treated LLZTO was used as the electrolyte to assemble a Li / LLZTO / Li symmetric cell, and its electrochemical performance was tested at 60 °C. AC impedance spectroscopy showed that the interfacial impedance decreased from approximately 1500 Ωcm before treatment. 2 Decreased to approximately 210 Ωcm 2 At 0.1 mA cm -2 Under long-term charge-discharge cycle testing at current density, it operated stably for more than 1200 hours, with the polarization voltage always maintained below 50mV. No short circuits or abrupt changes occurred at the interface, demonstrating good interface wettability and the ability to suppress dendrite growth.

[0056] Example 3: In-situ removal of Li2CO3 from the surface of LLZTO solid electrolyte to form a Li4SiO4 interface layer:

[0057] First, a commercially available sintered cubic LLZTO ceramic sheet with dimensions of 12mm × 12mm × 1mm was selected as the solid electrolyte. The sample was placed in air at 600℃ for 3 hours to enrich its surface with a Li2CO3 electrochemical inert layer.

[0058] Subsequently, a Si target was used in a high-vacuum RF magnetron sputtering system. The RF power was set to 100W, the stage temperature was maintained at room temperature, the argon / oxygen flow rates were 20 sccm / 6 sccm, and the total pressure was controlled at 0.4 Pa. The deposition time was 10 min, and a SiO2 film with a thickness of approximately 10 nm was deposited on the LLZTO surface. During the sputtering process, the sample was kept rotating at a constant speed to ensure uniform film coverage.

[0059] After deposition, the sample was placed in a muffle furnace and heat-treated at 750°C in air for 2 hours to induce an in-situ solid-solid reaction between SiO2 and surface Li2CO3, forming a Li4SiO4 lithiated conductive interface layer. This interface layer bonded well with the substrate, without obvious delamination or cracks, and exhibited excellent mechanical and chemical stability.

[0060] Interface structure analysis results showed that XRD detected characteristic peaks of the Li4SiO4 phase, and XPS spectra showed a significant decrease in the intensity of the original Li2CO3 peak. Simultaneously, the valence state characteristics of Si indicated the formation of Li4SiO4, verifying the effectiveness of the interface reaction. Scanning electron microscopy images showed a continuous and dense film with a uniform surface morphology and no obvious defects.

[0061] The treated LLZTO was used as the electrolyte to assemble a Li / LLZTO / Li symmetric cell, and its electrochemical performance was tested at 60 °C. AC impedance spectroscopy showed that the interfacial impedance decreased from approximately 1400 Ωcm before treatment. 2 Decreased to approximately 205Ωcm 2 At 0.1 mA cm -2 Under long-term charge-discharge cycle testing at current density, it operated stably for more than 1000 hours, with the polarization voltage always maintained below 50mV. No short circuits or abrupt changes occurred at the interface, demonstrating good interface wettability and the ability to suppress dendrite growth.

[0062] Example 4: In-situ removal of Li2CO3 from the surface of LLZTO solid electrolyte to form a LiFeO2 interface layer:

[0063] First, a commercially available sintered cubic LLZTO ceramic sheet with dimensions of 12mm × 12mm × 1mm was selected as the solid electrolyte. The sample was placed in air at 600℃ for 3 hours to enrich its surface with a Li2CO3 electrochemical inert layer.

[0064] Subsequently, an Fe target was used in a high-vacuum RF magnetron sputtering system. The RF power was set to 100W, the stage temperature was maintained at room temperature, the argon / oxygen flow rates were 20 sccm / 6 sccm, and the total pressure was controlled at 0.4 Pa. The deposition time was 10 min, and a Fe2O3 film with a thickness of approximately 10 nm was deposited on the LLZTO surface. During the sputtering process, the sample was kept rotating at a constant speed to ensure uniform film coverage.

[0065] After deposition, the sample was placed in a muffle furnace and heat-treated at 750°C in air for 2 hours to induce an in-situ solid-solid reaction between SiO2 and surface Li2CO3, forming a LiFeO2 lithiated conductive interface layer. This interface layer bonded well with the substrate, without obvious delamination or cracks, and exhibited excellent mechanical and chemical stability.

[0066] Interface structure analysis results showed that XRD detected characteristic peaks of the LiFeO2 phase, while XPS spectra showed a significant decrease in the intensity of the original Li2CO3 peak. Simultaneously, the valence state characteristics of Fe indicated the formation of LiFeO2, verifying the effectiveness of the interfacial reaction. Scanning electron microscopy images revealed a continuous and dense film with a uniform surface morphology and no obvious defects.

[0067] The treated LLZTO was used as the electrolyte to assemble a Li / LLZTO / Li symmetric cell, and its electrochemical performance was tested at 60 °C. AC impedance spectroscopy showed that the interfacial impedance decreased from approximately 1400 Ωcm before treatment. 2 Decreased to approximately 230 Ωcm 2 At 0.1 mA cm -2 Under long-term charge-discharge cycle testing at current density, it operated stably for more than 1000 hours, with the polarization voltage always maintained below 60mV. No short circuits or abrupt changes occurred at the interface, demonstrating good interface wettability and the ability to suppress dendrite growth.

[0068] Example 5: In-situ removal of Li2CO3 from the surface of LLZTO solid electrolyte to form a LiMnO2 interface layer:

[0069] First, a commercially available sintered cubic LLZTO ceramic sheet with dimensions of 12mm × 12mm × 1mm was selected as the solid electrolyte. The sample was placed in air at 600℃ for 3 hours to enrich its surface with a Li2CO3 electrochemical inert layer.

[0070] Subsequently, a Mn target was used in a high-vacuum RF magnetron sputtering system. The RF power was set to 100W, the stage temperature was maintained at room temperature, the argon / oxygen flow rates were 20 sccm / 6 sccm, and the total pressure was controlled at 0.4 Pa. The deposition time was 10 min, and a MnO2 film with a thickness of approximately 10 nm was deposited on the LLZTO surface. During the sputtering process, the sample was kept rotating at a constant speed to ensure uniform film coverage.

[0071] After deposition, the sample was placed in a muffle furnace and heat-treated at 750°C in air for 2 hours to induce an in-situ solid-solid reaction between MnO2 and surface Li2CO3, forming a LiMnO2 lithiated conductive interface layer. This interface layer bonded well with the substrate, without obvious delamination or cracks, and exhibited excellent mechanical and chemical stability.

[0072] Interface structure analysis results showed that XRD detected characteristic peaks of the LiMnO2 phase, and XPS spectra showed a significant decrease in the intensity of the original Li2CO3 peak. Simultaneously, the valence state characteristics of Mn indicated the formation of LiMnO2, verifying the effectiveness of the interfacial reaction. Scanning electron microscopy images showed a continuous and dense film with a uniform surface morphology and no obvious defects.

[0073] The treated LLZTO was used as the electrolyte to assemble a Li / LLZTO / Li symmetric cell, and its electrochemical performance was tested at 60 °C. AC impedance spectroscopy showed that the interfacial impedance decreased from approximately 1500 Ωcm before treatment. 2 Decreased to approximately 190 Ωcm 2 At 0.1 mA cm -2 Under long-term charge-discharge cycle testing at current density, it operated stably for more than 1000 hours, with the polarization voltage always maintained below 45mV. No short circuits or abrupt changes occurred at the interface, demonstrating good interface wettability and the ability to suppress dendrite growth.

[0074] Example 6: In-situ removal of Li2CO3 from the surface of LLZTO solid electrolyte to form a LiCoO2 interface layer:

[0075] First, a commercially available sintered cubic LLZTO ceramic sheet with dimensions of 12mm × 12mm × 1mm was selected as the solid electrolyte. The sample was placed in air at 600℃ for 3 hours to enrich its surface with a Li2CO3 electrochemical inert layer.

[0076] Subsequently, a Co target was used in a high-vacuum RF magnetron sputtering system. The RF power was set to 140 W, the stage temperature was maintained at room temperature, the argon / oxygen flow rates were 20 sccm / 6 sccm, and the total pressure was controlled at 0.4 Pa. The deposition time was 10 min, and a CoO2 film with a thickness of approximately 10 nm was deposited on the LLZTO surface. During the sputtering process, the sample was kept rotating at a constant speed to ensure uniform film coverage.

[0077] After deposition, the sample was placed in a muffle furnace and heat-treated at 700°C in air for 2 hours to induce an in-situ solid-solid reaction between CoO2 and surface Li2CO3, forming a LiCoO2 lithiated conductive interface layer. This interface layer bonded well with the substrate, without obvious delamination or cracks, and exhibited excellent mechanical and chemical stability.

[0078] Interface structure analysis results showed that XRD detected characteristic peaks of the LiCoO2 phase, while XPS spectra showed a significant decrease in the intensity of the original Li2CO3 peak. Simultaneously, the valence state characteristics of Mn indicated the formation of LiCoO2, verifying the effectiveness of the interfacial reaction. Scanning electron microscopy images revealed a continuous and dense film with a uniform surface morphology and no obvious defects.

[0079] The treated LLZTO was used as the electrolyte to assemble a Li / LLZTO / Li symmetric cell, and its electrochemical performance was tested at 60 °C. AC impedance spectroscopy showed that the interfacial impedance decreased from approximately 1550 Ωcm before treatment. 2 Decreased to approximately 204 Ωcm 2 At 0.1 mA cm -2 Under long-term charge-discharge cycle testing at current density, it operated stably for more than 1000 hours, with the polarization voltage always maintained below 50mV. No short circuits or abrupt changes occurred at the interface, demonstrating good interface wettability and the ability to suppress dendrite growth.

[0080] In summary, this invention provides a simple, high-performance, and scalable method for modifying the interface of a solid electrolyte. A continuous, dense, structurally stable, and highly lithium-affinity lithiated interface conductive layer is formed in situ on the LLZO surface. This interface layer not only completely eliminates the interfacial impedance and electrochemical instability problems caused by the original Li₂CO₃ electrochemical inert layer, but also effectively improves the interfacial wettability and electron / ion conductivity between the solid electrolyte and metallic lithium, thereby significantly reducing interfacial impedance and improving the uniformity of interfacial reactions and cycle stability. This provides an effective technical path for the large-scale application of high-energy-density, high-safety solid-state lithium metal batteries, and has significant theoretical implications and broad application prospects.

[0081] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for in-situ delithium carbonate removal to form an interface layer on the surface of a garnet electrolyte, characterized in that, Includes the following steps: Step 1, Substrate Pretreatment: Select garnet-type solid electrolyte matrix ceramic sheets, sintered blocks or powders with a Li2CO3 impurity layer on the surface as matrix materials. Clean the matrix materials with anhydrous ethanol and acetone in sequence to remove surface dust and organic contaminants, and then dry to remove surface adsorbed moisture. Step 2: Magnetron sputtering deposition of metal oxide thin films: The pretreated substrate material is fixed on the sample stage of the magnetron sputtering equipment, and an oxide thin film is formed by reaction deposition of a metal target in an oxygen or oxygen / argon mixed atmosphere. The metal target includes: Ti, Nb, Si, Fe, Mn, Co, Ni, Ta. The oxide thin film is a non-lithiated metal oxide, and the oxide thin film covers the surface of the substrate material. Step 3, Heat treatment induces in-situ solid-solid reaction: The deposited substrate material is heat-treated in an inert atmosphere or vacuum environment, and the oxide film and the Li2CO3 impurity layer undergo an in-situ solid-solid reaction to generate lithiated transition metal oxide.

2. The method for in-situ delithiation of lithium carbonate to form an interface layer on the surface of a garnet electrolyte according to claim 1, characterized in that, In step 2, the magnetron sputtering is radio frequency magnetron sputtering. The magnetron sputtering parameters include: target power 50-150W, atmosphere composition volume ratio Ar:O2 = 9:1, total chamber pressure 0.5-1.0Pa, sputtering time 5-30 minutes; the substrate material temperature is room temperature or heated to no more than 100℃, and the oxide film thickness is 5-20nm.

3. The method for in-situ delithiation of lithium carbonate to form an interface layer on the surface of a garnet electrolyte according to claim 1, characterized in that, In step 3, the heat treatment conditions include: a heating rate of 2-10℃ / min, a holding temperature of 300℃-600℃, a holding time of 30 minutes to 2 hours, and an atmosphere of Ar or a vacuum degree better than 10. -3 Pa.

4. The method for in-situ delithiation of lithium carbonate to form an interface layer on the surface of a garnet electrolyte according to claim 1, characterized in that, In step 2, the metal oxide in the oxide film includes at least one of the following: Ta₂O₅, Nb₂O₅, SiO₂, Fe₂O₃, MnO₂, Co₃O₄, NiO, and TiO₂; the transition metal oxide in step 2 is Li₂MO. x Type of compound, where M is a metal element in a metal oxide, O x This indicates the oxygen content in the formula.

5. The method for in-situ delithiation of lithium carbonate to form an interface layer on the surface of a garnet electrolyte according to claim 1, characterized in that, In step 1, the garnet-type solid electrolyte matrix is ​​composed of Li7La3Zr2O 12 The oxide system of the structure, the garnet-type solid electrolyte matrix includes: Li7La3Zr2O 12 、Li6La3ZrTaO 12 Li 6.5 La3Zr 1.5 Ta 0.5 O 12 Li6La3ZrNbO 12 Li 6.5 La3Zr 1.5 Nb 0.5 O 12 The garnet-type solid electrolyte matrix and its doped or modified derivatives have a garnet-type crystal structure.

6. The method for in-situ delithiation of lithium carbonate to form an interface layer on the surface of a garnet electrolyte according to claim 1, characterized in that, In step 3, the lithium-ionized transition metal oxides include: LiTaO3, LiNbO3, Li4SiO4, LiFeO2, LiMn2O4, LiCoO2, LiNiO2, and Li2TiO3.

7. The method for in-situ delithiation of lithium carbonate to form an interface layer on the surface of a garnet electrolyte according to claim 1, characterized in that, In step 1, the garnet-type solid electrolyte matrix has a cubic phase crystal structure.

8. The method for in-situ delithiation of lithium carbonate to form an interface layer on the surface of a garnet electrolyte according to claim 1, characterized in that, In step 1, the lithium-ion conductivity of the garnet-type solid electrolyte matrix is ​​not less than 10. -4 S·cm -1 The garnet-type solid electrolyte matrix was not subjected to strong acid washing treatment.

9. The method for in-situ delithiation of lithium carbonate to form an interface layer on the surface of a garnet electrolyte according to claim 1, characterized in that, In step 1, the pretreated garnet-type solid electrolyte substrate is immediately subjected to magnetron sputtering deposition of metal oxide thin films in step 2.

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