Interface modification layer and preparation method and application thereof

Abstract

The invention discloses an interface modification layer as well as a preparation method and application thereof. The interface modification layer comprises an electron barrier layer and a lithium-philic interlayer which are sequentially arranged on the surface of a solid electrolyte, the material of the electron blocking layer is selected from at least one of lithium oxyphosphorus nitride, lithium fluoride, lithium nitride, lithium chloride, lithium bromide, lithium iodide and lithium oxynitride, and the material of the lithium-loving interlayer is selected from at least one of germanium, silver, gallium, sodium, potassium, magnesium, aluminum, calcium, strontium, barium and titanium. The interface modification layer can prevent lithium nucleation induced by electron leakage in the solid electrolyte, reduce the risk of short circuit, reduce the interface impedance, improve the lithium ion flux uniformity and interface wettability, and improve the overall performance and cycle stability of the battery.

Description

Technical Field

[0001] The invention relates to the field of batteries, and in particular to an interface modification layer of a solid electrolyte, a preparation method and applications thereof. Background Art

[0002] Solid-state lithium metal batteries have attracted much attention in the field of electric vehicles and energy storage systems due to their excellent safety and the potential to break through the energy density limitations of lithium-ion batteries. However, the construction of commercial high-performance solid-state batteries faces many challenges at the lithium metal / solid electrolyte interface. On the one hand, chemical impurities and physical defects on the surface of the solid electrolyte make it difficult for it to come into close contact with lithium metal. On the other hand, under high current density, lithium dendrites are prone to appear in the solid electrolyte, causing short circuits and resulting in battery failure.

[0003] Past improvement strategies include constructing three-dimensional porous nano-scaffolds, introducing polymer buffer layers, and using wetting agents, but the lithium dendrite problem still exists. The first reason is the uneven interface, which originates from the microstructural defects of the physical boundary between lithium metal and solid electrolyte, resulting in excessive local current density, causing lithium metal to grow preferentially; the second reason is the difference in atomic structure and density of the solid electrolyte grain boundary, whose elastic modulus is about 50% lower, making it easy for cracks and lithium dendrites to grow along it.

[0004] In addition, the lithium metal / solid electrolyte interface characteristics seriously affect battery dynamics and short circuit formation. Although the lithium-philic interlayer can reduce the interface resistance, lithium dendrite short circuits will still occur under long-term cycling or medium-to-high current density. Moreover, ordinary solid electrolytes have non-negligible electronic conductivity, which is higher at grain boundaries or defects, and will become electron conduction paths, prompting lithium metal to preferentially nucleate and grow, increasing the risk of short circuits. Summary of the invention

[0005] In order to overcome the defects in the prior art, the first purpose of the present invention is to provide an interface modification layer of a solid electrolyte, the second purpose of the present invention is to provide a method for preparing the interface modification layer of a solid electrolyte, the third purpose of the present invention is to provide a solid electrolyte, and the fourth purpose of the present invention is to provide a solid-state lithium metal battery.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, an interface modification layer is provided, the interface modification layer comprising an electron blocking layer and a lithium-philic interlayer sequentially arranged on the surface of a solid electrolyte; the material of the electron blocking layer is selected from at least one of lithium oxyphosphorus nitride, lithium fluoride, lithium nitride, lithium chloride, lithium bromide, lithium iodide, and lithium oxynitride, and the material of the lithium-philic interlayer is selected from at least one of germanium, silver, gallium, sodium, potassium, magnesium, aluminum, calcium, strontium, barium, and titanium.

[0008] Preferably, the material of the electron blocking layer is selected from lithium phosphorus oxynitride.

[0009] Preferably, the material of the lithium-philic interlayer is selected from germanium.

[0010] The present invention sequentially arranges an electron blocking layer and a lithium-philic interlayer on the surface of the solid electrolyte. The electron blocking layer can effectively passivate the interface electron transmission pathway, prevent lithium nucleation induced by electron leakage inside the solid electrolyte, and reduce the risk of short circuit; the lithium-philic interlayer has good interface contact with the lithium metal negative electrode, which can reduce the interface impedance, improve the uniformity of lithium ion flux and interface wettability, and enhance the overall performance and cycle stability of the battery. The electron blocking layer and the lithium-philic interlayer work synergistically to solve the key problems of poor interface contact and lithium dendrite short circuit.

[0011] In a solid-state lithium metal battery, the movement paths of lithium ions during charging and discharging are as follows:

[0012] Charging process: Lithium ions are stripped from the positive electrode material because the external voltage applied during charging causes the lithium ions in the positive electrode material to overcome the inter-ionic forces and chemical barriers, leave the original lattice position, and enter the solid electrolyte. Lithium ions migrate through the solid electrolyte, which has ionic conductivity and allows lithium ions to move inside it. At this time, the lithium ions will move toward the negative electrode, and their movement speed and difficulty are affected by the properties of the solid electrolyte such as the ionic conductivity. When the lithium ions reach the electron blocking layer, the electron blocking layer mainly allows lithium ions to pass through, while inhibiting the passage of electrons, ensuring that the electron transmission during the lithium ion transmission process will not cause adverse effects, such as the formation of lithium dendrites. Then the lithium ions will pass through the lithium-philic interlayer, which can improve the interface contact and reduce the interface impedance between the solid electrolyte and the electrode. Finally, the lithium ions reach the negative electrode and are deposited in the lithium metal negative electrode to form lithium metal, completing the charging process.

[0013] Discharge process: Lithium ions are stripped from the lithium metal negative electrode. Due to the chemical potential difference between the negative electrode and the positive electrode, lithium ions are stripped from the lithium metal of the negative electrode and begin to move toward the positive electrode. Lithium ions pass through the lithium-philic interlayer, which can improve the interface contact and reduce the interface impedance between the solid electrolyte and the electrode. After passing through the electron blocking layer, the electron blocking layer continues to ensure ion transmission while blocking the transmission of electrons. Lithium ions enter the solid electrolyte and move in the solid electrolyte. Finally, lithium ions are deposited in the positive electrode material to complete the discharge process.

[0014] Preferably, the thickness of the electron blocking layer is 10 nm to 300 nm. Further preferably, the thickness of the electron blocking layer is 150 nm. This thickness can ensure the electron blocking effect and inhibit electron leakage, while taking into account the ion conductivity, avoiding the reduction of ion transmission efficiency due to excessive thickness, and ensuring efficient and stable operation of the battery.

[0015] Preferably, the thickness of the lithium-philic interlayer is 50 nm to 200 nm. Further preferably, the thickness of the lithium-philic interlayer is 100 nm. This thickness range can ensure full contact with the lithium metal negative electrode, improve interfacial wettability and reduce interfacial impedance, and will not increase the cost and battery volume due to excessive thickness, which helps to improve the battery kinetic performance and cycle life.

[0016] In a second aspect, a method for preparing an interface modification layer of a solid electrolyte comprises the following steps:

[0017] An electron blocking layer is formed on the surface of the solid electrolyte, and the material of the electron blocking layer is selected from lithium phosphorus oxynitride (LiPON), lithium fluoride (LiF), lithium nitride (Li 3 The electron blocking layer may be made of at least one of lithium chloride (LiN), lithium bromide (LiBr), lithium iodide (LiI), and lithium oxynitride (LiNxOy, where x and y are positive integers). Further preferably, the material of the electron blocking layer is selected from LiPON.

[0018] A lithium-philic interlayer is formed on the surface of the electron blocking layer, and the material of the lithium-philic interlayer is selected from at least one of germanium (Ge), silver (Ag), gallium (Ga), sodium (Na), potassium (K), magnesium (Mg), aluminum (Al), calcium (Ca), strontium (Sr), barium (Ba), and titanium (Ti). More preferably, the material of the lithium-philic interlayer is selected from Ge.

[0019] The electron blocking layer formed first can completely cover the surface defects of the solid electrolyte to prevent lithium nucleation and growth, and then form a lithium-philic interlayer on its surface to optimize the negative electrode wettability and lithium ion transport performance. The distributed layer-by-layer preparation is simple to operate and easy to control, and can effectively realize the function of the interface modification layer and improve the performance of the solid electrolyte.

[0020] Preferably, the electron blocking layer and the lithium-philic interlayer are formed on the surface of the solid electrolyte by at least one method of physical vapor deposition, chemical vapor deposition, electroplating, solution deposition or spraying. The interface modification layer can be prepared by different methods to provide flexibility for actual production. Manufacturers can choose a suitable method according to their own conditions, which is conducive to promoting the industrial application of technology, reducing costs and improving production efficiency. Further preferably, the electron blocking layer and the lithium-philic interlayer are formed on the surface of the solid electrolyte by a physical vapor deposition method, which is simple to operate and easy to control. Among them, physical vapor deposition (PVD) evaporates metals, alloys or compounds at high temperature and then deposits them on the surface of solid electrolytes by physical means; chemical vapor deposition (CVD) uses gaseous precursor reactants to form solid deposits on the surface of solid electrolytes through chemical reactions; electroplating is a method of depositing metals or alloys on the surface of solid electrolytes using the principle of electrolysis; solution deposition uses the chemical reaction or physical process of solutes in the solution to precipitate related substances on the surface of solid electrolytes and form a coating; spraying is to spray a coating or material containing specific ingredients in a mist form onto the surface of the solid electrolyte to form the desired covering layer.

[0021] Preferably, the preparation method further comprises the following steps: pre-treating the surface of the solid electrolyte. Further preferably, the pre-treating step comprises grinding and chemically cleaning the surface of the solid electrolyte. Grinding and chemically cleaning the surface can remove pollutants and defects, enhance the interface bonding force, improve the stability and effectiveness of the interface modification layer, and enhance the battery performance.

[0022] In a third aspect, a composite solid electrolyte including the above-mentioned interface modification layer comprises a solid electrolyte matrix and an interface modification layer arranged on the solid electrolyte matrix, wherein the solid electrolyte matrix is ​​a garnet-type solid electrolyte, a perovskite-type solid electrolyte or a sodium superion conductor (NASICON) solid electrolyte.

[0023] Further preferably, the solid electrolyte matrix is ​​a tantalum-doped garnet-type solid electrolyte (Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO)). It uses a tantalum-doped garnet-type solid electrolyte, which has a very high ionic conductivity (about 1 mS cm -1 ) and excellent mechanical properties, and good electrochemical and chemical compatibility with lithium metal anode.

[0024] In a fourth aspect, a solid-state lithium metal battery including the above-mentioned interface modification layer includes a positive electrode, a negative electrode, and a composite solid electrolyte arranged between the positive electrode and the negative electrode. The composite solid electrolyte includes a solid electrolyte matrix and an interface modification layer arranged on the solid electrolyte matrix, and the interface modification layer is in contact with the negative electrode.

[0025] Preferably, the positive electrode material is selected from one or more of lithium cobalt oxide, lithium manganese oxide, ternary nickel cobalt manganese lithium, lithium nickel manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate;

[0026] The negative electrode material is metallic lithium or a lithium alloy.

[0027] Preferably, the interface between the composite solid electrolyte and the positive electrode is treated with ionic liquid wetting.

[0028] Further preferably, the anions in the ionic liquid include one or more of tetrafluoroborate, hexafluorophosphate, bis(fluorosulfonyl)imide and bis(trifluoromethanesulfonyl)imide, and the cations include one or more of quaternary ammonium, imidazole, pyridine, thiazole, piperidine and morpholine. Through the wetting treatment with ionic liquid, the interface impedance can be significantly reduced, and the charge and discharge efficiency and power performance can be improved.

[0029] Further preferably, the amount of the ionic liquid is 5 to 20 μL, which can ensure the wetting effect and avoid side reactions or performance degradation, thereby ensuring the optimization and stability of battery performance.

[0030] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0031] 1. The present invention sets an interface modification layer of a multilayer structure including an electron blocking layer and a lithium-philic interlayer on the surface of the solid electrolyte. The electron blocking layer can passivate the electron transmission pathway, fundamentally suppress the lithium nucleation problem caused by electron leakage, ensure the electrochemical stability inside the battery, and extend the service life of the battery. The lithium-philic interlayer has good lithium-philic properties, greatly improves the contact condition with the lithium metal negative electrode, reduces the interface impedance, promotes the uniform transmission of lithium ions, improves the reaction kinetics of the battery, and lays the foundation for the efficient operation of the battery at the microscopic level.

[0032] 2. Tantalum-doped garnet solid electrolyte itself has high ionic conductivity, excellent mechanical properties, and good electrochemical and chemical compatibility, providing an excellent channel for the rapid migration of lithium ions and ensuring the basic performance of the battery.

[0033] 3. The use of ionic liquid wetting treatment at the interface between the solid electrolyte and the positive electrode effectively reduces the interface impedance, enhances the ion transmission efficiency between the positive and negative electrodes, further improves the charge and discharge performance of the battery, and optimizes the working effect of the battery at the local interface.

[0034] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are described in detail below. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Embodiment 1:

[0037] An interface modification layer is provided between a solid electrolyte and a negative electrode of a solid-state lithium metal battery. The interface modification layer comprises an electron blocking layer and a lithium-philic interlayer sequentially provided on the surface of the solid electrolyte. The material of the electron blocking layer is selected from lithium oxyphosphorus nitride (LiPON), lithium fluoride (LiF), lithium nitride (Li 3 The lithium-philic interlayer material is selected from at least one of germanium (Ge), silver (Ag), gallium (Ga), sodium (Na), potassium (K), magnesium (Mg), aluminum (Al), calcium (Ca), strontium (Sr), barium (Ba), and titanium (Ti).

[0038] In a possible implementation, the electron blocking layer is formed by mixing at least two materials selected from lithium phosphorus oxynitride, lithium fluoride, lithium nitride, lithium chloride, lithium bromide, lithium iodide, and lithium oxynitride to form a thin film on the surface of the solid electrolyte.

[0039] In one possible embodiment, the lithium-philic interlayer is formed by mixing at least two materials selected from the group consisting of germanium, silver, gallium, sodium, potassium, magnesium, aluminum, calcium, strontium, barium, and titanium to form a thin film on the surface of the solid electrolyte.

[0040] In a possible implementation, the electron blocking layer is formed of a thin film of at least two materials selected from lithium phosphorus oxynitride, lithium fluoride, lithium nitride, lithium chloride, lithium bromide, lithium iodide, and lithium oxynitride, which are stacked on the surface of the solid electrolyte.

[0041] In a possible embodiment, the lithium-philic interlayer is formed of a thin film of at least two materials selected from germanium, silver, gallium, sodium, potassium, magnesium, aluminum, calcium, strontium, barium, and titanium, respectively, and the layers are stacked on the surface of the electron blocking layer.

[0042] In an optional embodiment, the material of the electron blocking layer is selected from lithium oxyphosphorus nitride, that is, a thin film formed by lithium oxyphosphorus nitride covers the surface of the solid electrolyte as an electron blocking layer. The material of the lithium-philic interlayer is selected from germanium, that is, a thin film formed by germanium covers the surface of the electron blocking layer as a lithium-philic interlayer.

[0043] The thickness of the electron blocking layer is 10 nm to 300 nm. In a possible implementation manner, the thickness of the electron blocking layer is 150 nm.

[0044] The thickness of the lithium-philic interlayer is 50 nm to 200 nm. In a possible implementation, the thickness of the lithium-philic interlayer is 100 nm.

[0045] Embodiment 2:

[0046] A method for preparing an interface modification layer based on Example 1 comprises the following steps:

[0047] Step 1: Solid electrolyte surface pretreatment step

[0048] The prepared tantalum-doped garnet solid electrolyte sheet was polished in turn using 600, 1500, and 2000 sandpaper. The purpose of polishing is to remove impurities that may be attached to the surface of the solid electrolyte sheet during the preparation process and the uneven parts of the surface, so as to obtain a clean, smooth and well-consistent surface, providing a good substrate for the subsequent multi-layer deposition process. After polishing, the thickness of the solid electrolyte sheet is about 700μm and the relative density is about 93%.

[0049] Step 2: Setting up the electron blocking layer (LiPON thin film deposition)

[0050] The pretreated solid electrolyte sheet was placed in a vacuum thermal evaporator integrated in the glove box to ensure that the basic pressure in the glove box was maintained at less than 1×10 -6 The above environment can avoid the interference of impurity gases during the deposition process and ensure the purity and quality of the film.

[0051] Set the parameters of the thermal evaporator to control the deposition rate At this deposition rate, the LiPON material in the evaporation source is evaporated and deposited on the surface of the solid electrolyte sheet to form a LiPON film (electron blocking layer) with a thickness of 150nm. This thickness is selected after multiple experimental optimizations. A LiPON film that is too thin may not be able to effectively achieve the electron blocking function, while a film that is too thick may excessively reduce the ionic conductivity of the solid electrolyte and affect the overall performance of the battery.

[0052] After the deposition is completed, the solid electrolyte sheet with LiPON film is transferred to an annealing furnace in an argon atmosphere and annealed at 600°C for 2 hours. The annealing process can promote atomic diffusion and interface fusion between the particles of LiPON film and solid electrolyte, improve the contact between the two, enhance the stability and bonding force of the interface, and thus improve the performance of the entire solid electrolyte system.

[0053] Step 3: Setting up the Lithium-philic Interlayer (Ge Thin Film Deposition)

[0054] After the annealing of the LiPON film is completed, the position of the solid electrolyte sheet in the vacuum thermal evaporator remains unchanged. The Ge material in the evaporation source is evaporated and deposited on the surface of the LiPON film at a deposition rate of 100 nm to form a Ge film (lithium-philic interlayer) with a thickness of 100 nm. As a lithium-philic interlayer, the thickness of the Ge film must be selected to ensure that it can form a good interface contact with the lithium metal negative electrode and reduce the interface impedance, while also avoiding the increase in cost and battery volume due to excessive thickness. Since Ge is in direct contact with the lithium metal negative electrode, it is arranged after the LiPON film in the deposition order to better play its role in lithium-philicity and improving the wettability of the negative electrode.

[0055] Embodiment 3:

[0056] A composite solid electrolyte comprising the above-mentioned interface modification layer, the composite solid electrolyte comprising a solid electrolyte matrix and an interface modification layer arranged on the solid electrolyte matrix, the interface modification layer being the interface modification layer in Example 1 and Example 2. The solid electrolyte matrix is ​​a garnet-type solid electrolyte, a perovskite-type solid electrolyte or a sodium superion conductor-type solid electrolyte. In one possible embodiment, the solid electrolyte matrix is ​​a tantalum-doped garnet-type solid electrolyte.

[0057] Embodiment 4:

[0058] A method for preparing a composite solid electrolyte based on Example 3, the composite solid electrolyte comprising a solid electrolyte matrix and an interface modification layer disposed on the solid electrolyte matrix, the solid electrolyte matrix being a tantalum-doped garnet-type solid electrolyte, comprising the following steps:

[0059] Step 1: Preparation of solid electrolyte matrix

[0060] Weigh 268.8 g of LiOH·H 2 O, 489g of La 2 O 3 , 132.6g of Ta 2 O 5 and 100.8 g of ZrO 2As a raw material for synthesizing tantalum-doped garnet-type solid electrolyte powder, 20 wt% excess LiOH·H 2 O, the purpose of which is to compensate for the Li component that may be volatilized and lost during the subsequent sintering process to ensure that the chemical composition of the final product meets expectations.

[0061] The above raw materials are fully mixed to ensure that the raw materials are evenly distributed, providing a good foundation for the subsequent solid phase reaction.

[0062] The mixed raw materials are transferred to an alumina crucible, and the alumina crucible is placed in a high-temperature furnace, the temperature is set to 900°C, and the calcination time is maintained for 12 hours. In this process, the raw materials undergo a solid-phase reaction at high temperature and gradually form a cubic tantalum-doped garnet-type solid electrolyte Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 In this process, too high a temperature or too long a time may lead to crystal structure defects or impurity formation, while too low a temperature or insufficient time may result in incomplete reaction and failure to obtain the ideal LLZTO phase.

[0063] After the calcined product is cooled to room temperature, it is taken out and placed in a ball mill. The speed of the ball mill is set to 200 rpm, and the ball milling operation is performed for up to 10 hours. Through the ball milling process, the blocky LLZTO product is gradually broken and refined, and finally a fine powder with a particle size in the range of 5 to 10 μm is obtained. Appropriate ball milling time and speed are crucial to obtain fine powder with uniform particle size, which not only affects the subsequent molding process, but also affects the performance of the final product.

[0064] The LLZTO fine powder obtained by ball milling was placed in a mold and pressed into particles with a diameter of 10 mm under a pressure of 0.5 MPa to 2.5 MPa. Subsequently, the pressed particles were placed in a high-temperature sintering furnace and sintered at 1100°C for 10 hours in air. At the same time, 0.2 wt% of γ-Al was added. 2 O 3 As a sintering agent, tantalum-doped garnet-type solid electrolyte sheets were prepared. The sintering process helps to improve the density and mechanical strength of the particles and make the structure of LLZTO particles more stable.

[0065] Step 2: Solid electrolyte surface pretreatment step

[0066] The prepared tantalum-doped garnet solid electrolyte sheet was polished in turn using 600, 1500, and 2000 sandpaper. The purpose of polishing is to remove impurities that may be attached to the surface of the solid electrolyte sheet during the preparation process and the uneven parts of the surface, so as to obtain a clean, smooth and well-consistent surface, providing a good substrate for the subsequent multi-layer deposition process. After polishing, the thickness of the solid electrolyte sheet is about 700μm and the relative density is about 93%.

[0067] Step 3: Setting up the electron blocking layer (LiPON film deposition)

[0068] The pretreated tantalum-doped garnet solid electrolyte sheet was placed in a vacuum thermal evaporator integrated in the glove box to ensure that the basic pressure in the glove box was maintained at less than 1×10 -6 The above environment can avoid the interference of impurity gases during the deposition process and ensure the purity and quality of the film.

[0069] Set the parameters of the thermal evaporator to control the deposition rate At this deposition rate, the LiPON material in the evaporation source is evaporated and deposited on the surface of the tantalum-doped garnet-type solid electrolyte sheet to form a LiPON film (electron blocking layer) with a thickness of 150nm. This thickness is selected after multiple experimental optimizations. A LiPON film that is too thin may not be able to effectively achieve the electron blocking function, while a film that is too thick may excessively reduce the ionic conductivity of the solid electrolyte and affect the overall performance of the battery.

[0070] After the deposition is completed, the tantalum-doped garnet-type solid electrolyte sheet with LiPON film is transferred to an annealing furnace in an argon atmosphere and annealed for 2 hours at a temperature of 600°C. The annealing process can promote atomic diffusion and interface fusion between the particles of the LiPON film and the tantalum-doped garnet-type solid electrolyte sheet, improve the contact between the two, enhance the stability and bonding strength of the interface, and thus improve the performance of the entire solid electrolyte system.

[0071] Step 4: Setting up the Lithium-philic Interlayer (Ge Thin Film Deposition)

[0072] After the annealing treatment of the LiPON film is completed, the position of the tantalum-doped garnet-type solid electrolyte sheet in the vacuum thermal evaporator remains unchanged. The Ge material in the evaporation source is evaporated and deposited on the surface of the LiPON film at a deposition rate of 100 nm to form a Ge film (lithium-philic interlayer) with a thickness of 100 nm, thereby preparing a composite solid electrolyte. As a lithium-philic interlayer, the thickness of the Ge film must be selected to ensure that it can form a good interface contact with the lithium metal negative electrode and reduce the interface impedance, while also avoiding the increase in cost and battery volume due to excessive thickness. Since Ge is in direct contact with the lithium metal negative electrode, it is arranged after the LiPON film in the deposition order to better play its role in lithium-philicity and improving the wettability of the negative electrode.

[0073] Embodiment 5:

[0074] A solid-state lithium metal battery including the composite solid electrolyte of Example 4, comprising a positive electrode, a negative electrode, and a composite solid electrolyte disposed between the positive electrode and the negative electrode, wherein the composite solid electrolyte comprises a solid electrolyte matrix and an interface modification layer disposed on the solid electrolyte matrix, wherein the interface modification layer is in contact with the negative electrode.

[0075] In a possible embodiment, the positive electrode material is selected from one or more of lithium cobalt oxide, lithium manganese oxide, ternary nickel cobalt manganese lithium, lithium nickel manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate. The negative electrode material is metallic lithium or a lithium alloy.

[0076] In one possible embodiment, the interface between the composite solid electrolyte and the positive electrode is treated with an ionic liquid. The anions in the ionic liquid include one or more of tetrafluoroborate, hexafluorophosphate, bis(fluorosulfonyl)imide and bis(trifluoromethanesulfonyl)imide, and the cations include one or more of quaternary ammonium, imidazole, pyridine, thiazole, piperidine and morpholine. The amount of the ionic liquid used is 5 to 20 μL.

[0077] Embodiment 6:

[0078] A method for preparing a button battery having the composite solid electrolyte of Example 4 comprises the following steps:

[0079] A 300 μm thick lithium foil was cut into a diameter of 5 or 9 mm and used as an electrode material.

[0080] The cut lithium foil is pasted on both sides of the composite solid electrolyte. When pasting, it is necessary to ensure that the lithium foil is in close contact with the solid electrolyte so that lithium ions can be smoothly transferred between the solid electrolyte and the lithium foil.

[0081] The composite solid electrolyte and related components with lithium foil attached are assembled according to the assembly specifications of 2032 button batteries. During the assembly process, it is necessary to ensure that the positions of various components are accurate, and the connection between the electrode and the composite solid electrolyte is tight and stable to avoid problems such as short circuit or poor contact.

[0082] After assembly, the button cell was placed in an oven at 120°C overnight. This process can enhance the good contact between lithium metal and the composite solid electrolyte. Through proper heating treatment, it can promote the diffusion of atoms and the fusion of the interface, improve the stability of the interface and the efficiency of lithium ion transmission.

[0083] Embodiment 7:

[0084] A method for preparing a solid-state lithium metal battery based on Example 5 comprises the following steps:

[0085] Weigh the active material LFP powder, conductive agent Super P and binder PVDF in a weight ratio of 8:1:1. Mix the weighed materials with the solvent NMP and use a stirring device to fully stir until a uniform slurry is formed. During the stirring process, the stirring speed and time must be controlled to ensure that the components are fully mixed and no agglomeration occurs. Apply the resulting slurry on aluminum foil, and the coating process must ensure the uniformity of the coating thickness and surface smoothness. In one possible embodiment, the area loading mass of the active material is 3 to 3.5 mg / cm 2 After coating, the aluminum foil is placed in a vacuum furnace and dried at 70°C to prepare the positive electrode. The solvent NMP must be completely removed during the drying process to prevent the residual solvent from having an adverse effect on the battery performance. At the same time, the drying temperature and time must be controlled to avoid changes in the structure and performance of the positive electrode material due to excessively high temperature or excessively long time.

[0086] The prepared positive electrode, the composite solid electrolyte (including a tantalum-doped garnet-type solid electrolyte and the interface modification layer in Example 2 disposed on the tantalum-doped garnet-type solid electrolyte) and a lithium foil negative electrode are assembled.

[0087] Finally, a small amount of ionic liquid (2M LiFSI in Pyr13FSI) is used to improve the interface contact between the positive electrode particles and the composite solid electrolyte. An appropriate amount of ionic liquid is added dropwise to the contact area between the positive electrode and the composite solid electrolyte. The anions and cations in the ionic liquid can interact with the surface of the positive electrode material and the solid electrolyte, reduce the interfacial impedance, and improve the charge and discharge efficiency and power performance of the battery. In one possible embodiment, the amount of ionic liquid used is 5 to 20 μL, which can not only ensure the wetting effect, but also avoid problems such as side reactions or performance degradation caused by excessive use.

[0088] Comparative Example 1:

[0089] A solid-state lithium metal battery, the preparation method of the solid-state lithium metal battery is the same as that in Example 7, except that: no interface modification layer is provided on the surface of the tantalum-doped garnet-type solid electrolyte, that is, no electron blocking layer and lithium-philic interlayer are provided.

[0090] Comparative Example 2:

[0091] A solid-state lithium metal battery, the preparation method of the solid-state lithium metal battery is the same as that in Example 7, except that: only a Ge film is provided on the surface of the tantalum-doped garnet solid electrolyte.

[0092] Comparative Example 3:

[0093] A solid-state lithium metal battery, the preparation method of the solid-state lithium metal battery is the same as that in Example 7, except that: only a LiPON film is provided on the surface of the tantalum-doped garnet solid electrolyte.

[0094] The solid-state lithium metal batteries obtained in Example 7 and Comparative Examples 1, 2, and 3 were heated at 60°C at 1.0 mA cm -2 The cycle performance test was carried out at a higher current density of . The test results are shown in Table 1.

[0095] Group Cycle times Capacity retention rate (%) Coulomb efficiency (%) Example 7 3000 93 99.96 Comparative Example 1 800 72 94.12 Comparative Example 2 1200 81 98.74 Comparative Example 3 900 87 98.63

[0096] Table 1

[0097] As shown in Table 1, the interface modification layer of the present invention has the best improvement effect on the performance of lithium metal batteries.

[0098] In Comparative Example 1, significant interface degradation was observed in the lithium metal battery without an interface modification layer, pores and voids were found at the interface and within the solid electrolyte, and the corresponding lithium metal battery had the worst performance. In contrast, in the present invention, the Ge / LiPON-coated LLZTO maintained the initial interface structure, showing good wettability with lithium and a stable LiPON interlayer without delamination or obvious defect formation.

[0099] Comparative Example 2 proves that the lithium-philic interlayer Ge film provides a very low interface resistance by enhancing the wettability of lithium metal on the LLZTO solid electrolyte, thereby improving the battery performance. Although it exhibits low interface resistance, short circuit is inevitable at the subsequent high current density. This is because non-negligible electron conduction occurs in the solid electrolyte covered by the Ge film, resulting in lithium nucleation and the growth of lithium dendrites. In the present invention, an electron blocking layer (such as a LiPON film) is provided before the lithium-philic interlayer (such as a Ge film), which effectively solves this problem, suppresses the lithium nucleation and lithium dendrite growth caused by electron conduction from the root, greatly improves the cycle stability of the battery at high current density, and fully reflects the advantages of the multi-layer interface modification layer structure design of the present invention.

[0100] Comparative Example 3 demonstrates that the electron-blocking LiPON film can reduce the electron conduction through the solid electrolyte even at high temperature / high voltage while maintaining sufficiently high lithium ion conductivity. When a higher DC voltage is applied to the solid electrolyte without an interface modification layer, the electronic conductivity increases rapidly. This further highlights the importance of the synergistic effect of the lithium-philic interlayer (such as Ge film) and the electron-blocking layer (such as LiPON film) in the present invention. Both are indispensable and jointly ensure the stability of the battery interface during the charge and discharge process and improve the overall performance of the battery.

[0101] The above results indicate that the interface modification layer formed by the stacking of Ge thin film and LiPON thin film contributes to the stability of the interface during repeated stripping and plating of lithium.

[0102] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. An interface modification layer, characterized in that: The interface modification layer includes an electron blocking layer and a lithium-philic interlayer sequentially arranged on the surface of the solid electrolyte; the material of the electron blocking layer is selected from at least one of lithium oxyphosphorus nitride, lithium fluoride, lithium nitride, lithium chloride, lithium bromide, lithium iodide, and lithium oxynitride, and the material of the lithium-philic interlayer is selected from at least one of germanium, silver, gallium, sodium, potassium, magnesium, aluminum, calcium, strontium, barium, and titanium.

2. The interface modification layer according to claim 1, characterized in that: The thickness of the electron blocking layer is 10nm to 300nm; Preferably, the thickness of the electron blocking layer is 150 nm.

3. The interface modification layer according to claim 1, characterized in that The thickness of the lithium-philic interlayer is 50nm to 200nm; Preferably, the thickness of the lithium-philic interlayer is 100 nm.

4. A method for preparing an interface modification layer of a solid electrolyte, characterized in that: The following steps are involved: forming an electron blocking layer on the surface of the solid electrolyte, wherein the material of the electron blocking layer is selected from at least one of lithium phosphorus oxynitride, lithium fluoride, lithium nitride, lithium chloride, lithium bromide, lithium iodide, and lithium oxynitride; A lithium-philic interlayer is formed on the surface of the electron blocking layer, and a material of the lithium-philic interlayer is selected from at least one of germanium, silver, gallium, sodium, potassium, magnesium, aluminum, calcium, strontium, barium, and titanium.

5. The method for preparing an interface modification layer of a solid electrolyte according to claim 4, characterized in that: The electron blocking layer and the lithium-philic interlayer are formed on the surface of the solid electrolyte by at least one method selected from the group consisting of physical vapor deposition, chemical vapor deposition, electroplating, solution deposition, and spraying.

6. The method for preparing an interface modification layer of a solid electrolyte according to claim 4, characterized in that: The preparation method further comprises the following steps: pre-treating the surface of the solid electrolyte; Preferably, the pretreatment step comprises polishing the surface of the solid electrolyte.

7. A composite solid electrolyte comprising the interface modification layer according to any one of claims 1 to 3, characterized in that: The invention comprises a solid electrolyte matrix and an interface modification layer arranged on the solid electrolyte matrix. The solid electrolyte matrix is ​​a garnet-type solid electrolyte, a perovskite-type solid electrolyte or a sodium superion conductor-type solid electrolyte.

8. A solid-state lithium metal battery comprising the interface modification layer according to any one of claims 1 to 3, characterized in that: The invention comprises a positive electrode, a negative electrode, and a composite solid electrolyte arranged between the positive electrode and the negative electrode. The composite solid electrolyte comprises a solid electrolyte matrix and an interface modification layer arranged on the solid electrolyte matrix, and the interface modification layer is in contact with the negative electrode.

9. The solid-state lithium metal battery according to claim 8, characterized in that: The positive electrode material is selected from one or more of lithium cobalt oxide, lithium manganese oxide, ternary nickel cobalt manganese lithium, lithium nickel manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate; The negative electrode material is metallic lithium or a lithium alloy.

10. The solid-state lithium metal battery according to claim 8, characterized in that: The interface between the solid electrolyte and the positive electrode is treated with ionic liquid wetting; Preferably, the anions in the ionic liquid include one or more of tetrafluoroborate, hexafluorophosphate, bis(fluorosulfonyl)imide and bis(trifluoromethanesulfonyl)imide, and the cations include one or more of quaternary ammonium, imidazole, pyridine, thiazole, piperidine and morpholine; Preferably, the amount of the ionic liquid used is 5 to 20 μL.