Negative-electrode-free lithium metal battery monomer and preparation method of battery monomer

Abstract

The invention discloses a negative-electrode-free lithium metal battery monomer and a preparation method of the battery monomer. The battery monomer comprises a positive pole piece, a negative pole piece and a solid electrolyte membrane, wherein the solid electrolyte membrane is positioned between the positive pole piece and the negative pole piece; the negative-electrode-free lithium metal battery monomer comprises a first state and a second state; in the first state, the negative pole piece comprises a negative current collector and a metal halide modification layer positioned on at least one side of the negative current collector; in the second state, the negative pole piece comprises a negative current collector and an interface layer located on at least one side of the negative current collector, the interface layer comprises lithium halide and metal material particles, the lithium halide is a continuous phase, and the metal material particles are dispersed in the lithium halide in a dispersed phase mode. The negative-electrode-free lithium metal battery monomer can inhibit lithium dendrite growth and interface side reaction and reduce interface impedance, and has good cycle performance and safety performance.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and in particular relates to a negative electrode-free lithium metal battery cell and a method for preparing the battery cell. Background Technology

[0002] Lithium metal possesses an extremely low electrode potential (-3.04 V vs. standard hydrogen electrode) and an extremely high theoretical specific capacity (3860 mAh g⁻¹). -1 It is an ideal anode material for next-generation high-energy-density lithium metal batteries.

[0003] Solid-state lithium metal batteries have become the core development direction of next-generation power batteries due to their high energy density and intrinsic safety. Among them, anode-free solid-state lithium batteries do not require the pre-storage of metallic lithium during the manufacturing process. They achieve the anode function through a "current collector + in-situ lithium deposition" method. Compared with traditional batteries containing excess lithium, the energy density can be increased by more than 30%, while reducing costs and safety risks, showing significant industrialization potential.

[0004] However, during the operation of a cathodeless solid-state lithium battery, the in-situ deposited metallic lithium, due to its high reactivity, is prone to irreversible side reactions with the electrolyte, generating products with low ionic conductivity, which leads to an increase in interfacial impedance. In addition, due to its lack of a "host", metallic lithium is prone to uneven deposition of lithium metal during charging and discharging, which can easily form lithium dendrites that pierce the electrolyte layer, causing short circuits or even thermal runaway in the battery cell. On this basis, lithium loss caused by lithium dendrite growth and interfacial side reactions can also rapidly lead to battery capacity decay, thereby reducing the cycle performance of the battery cell. Summary of the Invention

[0005] This application provides a negative electrode-free lithium metal battery cell and a method for preparing the battery cell. The negative electrode-free lithium metal battery cell can suppress lithium dendrite growth and interfacial side reactions and reduce interfacial impedance, and has good cycle performance and safety performance.

[0006] The first aspect of this application provides a negative electrode-free lithium metal battery cell, including a positive electrode, a negative electrode and a solid electrolyte membrane, wherein the solid electrolyte membrane is located between the positive electrode and the negative electrode. A single negative electrode-free lithium metal battery cell includes a first state and a second state; In the first state, the negative electrode includes a negative current collector and a metal halide modification layer located on at least one side of the negative current collector; In the second state, the negative electrode includes a negative current collector and an interface layer located on at least one side of the negative current collector. The interface layer includes lithium halide and metal material particles, wherein the lithium halide is a continuous phase and the metal material particles are dispersed in the lithium halide as a dispersed phase.

[0007] During the first charge and discharge process of a negative electrode-free lithium metal battery, lithium ions will deposit on the negative electrode side to form lithium metal, which can then undergo an in-situ reduction reaction with the metal halide modification layer in the negative electrode-free lithium metal battery cell in the first state, generating an interface layer including lithium halide and metal material particles, thus transforming the negative electrode-free lithium metal battery cell from the first state to the second state.

[0008] Based on this, since lithium halides have high lithium-ion conductivity and almost no electronic conductivity, lithium halides, as a continuous phase in the interface layer, can provide continuous lithium-ion migration channels, thereby forming a stable lithium-ion transport network. This effectively reduces the ion transport impedance at the interface, and thus effectively avoids the current density concentration phenomenon caused by ion transport obstruction during lithium metal deposition. This helps to reduce lithium dendrite formation and battery cell capacity decay, and improves the cycle performance and safety performance of battery cells.

[0009] Furthermore, the metal material particles dispersed in lithium halide as a dispersed phase do not form a through-conductive framework in the interface layer, but rather form localized electron conduction points within the interface. This provides an electron channel for lithium nucleation without allowing a significant leakage of electrons to the solid electrolyte side. This controls lithium deposition to occur on the side of the interface layer closer to the negative electrode current collector, effectively preventing direct contact between metallic lithium and the electrolyte. This avoids the occurrence of side reactions, thereby preventing the increase in interface impedance and capacity decay caused by side reactions, and improving the cycle performance of the battery cell.

[0010] In addition, the metal material particles have good ductility, which helps to improve the mechanical properties and structural stability of the interface layer, and helps to improve the resistance of the interface layer to volume fluctuations caused by repeated lithium deposition / stripping, reduce the risk of lithium dendrites piercing the solid electrolyte layer, and further improve the safety performance and interface stability of the battery cell.

[0011] In some implementations, the negative current collector includes one or more metallic materials selected from copper, nickel, and stainless steel.

[0012] The negative electrode current collector is made of metal, which enables the metal halide modification layer to adhere to the surface of the negative electrode current collector through chemical bonding based on the in-situ redox reaction between the negative electrode current collector and halogen. This improves the adhesion of the metal halide modification layer, helps to prevent peeling during battery assembly and battery cycling, and improves the cycle stability of the battery cell.

[0013] In some embodiments, the thickness of the metal halide modification layer is 2 μm to 4 μm.

[0014] The thickness of the metal halide modification layer is 2μm to 4μm, which helps to control the thickness of the interface layer and avoid the adverse effects of an excessively thin or thick interface layer on the cycle performance of the battery cell.

[0015] In some embodiments, the metal halide modification layer includes one or more of cuprous iodide, cuprous bromide, cuprous chloride, ferrous iodide, ferrous bromide, ferrous chloride, nickel iodide, nickel bromide, and nickel chloride.

[0016] In some implementations, the thickness of the interface layer is 1 μm to 5 μm.

[0017] The thickness of the interface layer is 1μm to 5μm, which helps the interface layer to have sufficient mechanical properties while having good interfacial transport dynamics. This can avoid lithium dendrite penetration caused by an excessively thin interface layer, and also avoid the interface impedance being increased by an excessively thick interface layer, thus affecting the cycle performance of the battery.

[0018] In some implementations, the Young's modulus of the interface layer is 30 GPa to 50 GPa.

[0019] The Young's modulus of the interface layer is 30 GPa to 50 GPa, which enables the interface layer to have good mechanical properties and structural stability. It can effectively resist the volume fluctuations caused by repeated lithium deposition / stripping, reduce the risk of lithium dendrites piercing the solid electrolyte layer, and further improve the safety performance and interface stability of the battery cell.

[0020] In some embodiments, the activation energy for lithium ion migration in the interface layer is 3 kJ mol. -1 -5kJ mol -1 .

[0021] Generally, the lower the activation energy for lithium ion migration in the interface layer, the higher the lithium ion migration rate. The activation energy for lithium ion migration in the interface layer is controlled at 3 kJ / mol. -1 ~5kJ mol -1 This helps maintain high lithium-ion transport performance at the interface layer, thereby avoiding current density concentration caused by ion transport obstruction during lithium metal deposition. It also helps reduce lithium dendrite formation and capacity decay of individual cells, improving the cycle performance and safety of individual cells.

[0022] In some implementations, the mass fraction of lithium halide in the interface layer is 57% to 83%.

[0023] The mass fraction of lithium halide in the interface layer is 57% to 83%, which helps to form a stable lithium-ion transport network and effectively reduces the ion transport impedance at the interface.

[0024] In some implementations, the mass fraction of the metal material particles in the interface layer is 17% to 43%.

[0025] The mass fraction of metal material particles in the interface layer is 17% to 43%, which helps to prevent the dispersed phase metal material particles from forming a through conductive framework in the interface layer, but rather to form local electronic conduction points within the interface. This provides an electronic channel for lithium nucleation without allowing electrons to leak significantly to the solid electrolyte side.

[0026] In some embodiments, the particle size of the metal material is 5 nm to 200 nm.

[0027] Controlling the particle size of the metal material particles to 5nm to 200nm helps to give the metal material particles a high specific surface area, thereby providing abundant lithium nucleation sites and promoting uniform lithium deposition.

[0028] In some embodiments, the metallic material particles include one or more elemental and / or alloy particles selected from copper, nickel, and stainless steel.

[0029] In some embodiments, the solid electrolyte includes one or more of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes; preferably, the solid electrolyte membrane is a sulfide solid electrolyte.

[0030] Sulfide solid electrolytes have high ionic conductivity, which can ensure efficient ion migration at room temperature; and sulfide solid electrolytes have good chemical interface compatibility with lithium halides and low interface impedance, which can improve the cycle performance of battery cells while avoiding side reactions between lithium metal and sulfide solid electrolytes.

[0031] In some embodiments, the sulfide solid electrolyte includes Li 10 GeP2S 12 The electrolyte is one or more of the following: a solid electrolyte and a sulfide argyrodite electrolyte Li6PS5X, wherein X is any one of Cl, Br and I, and preferably, the sulfide solid electrolyte is Li6PS5Cl.

[0032] In some embodiments, the halide solid electrolyte includes one or more of ternary halide Li-MX type electrolyte and halide lithium ore type electrolyte Li3MX6, wherein M is any one of Y, Sc, In, Er, Zr, and X is any one of Cl, Br, and I.

[0033] In some embodiments, the oxide solid electrolyte includes a NASICON-type electrolyte Li. 1+x A x Ge 2-x (PO4)3 and Garnet-type electrolyte Li7La3Zr2O 12One or more of the following, where 0≤x≤0.8, and A is any one of Al and Ga.

[0034] In some embodiments, the polymer solid electrolyte includes one or more of polyoxyethylene polymer electrolyte, polyvinylidene fluoride polymer electrolyte, and polyacrylonitrile-based polymer electrolyte.

[0035] The second aspect of this application provides a method for preparing a negative electrode-free lithium metal battery cell, comprising: A negative electrode current collector is provided, wherein the material of the negative electrode current collector is a metallic material; The negative electrode current collector is contacted with a reaction medium containing halogen elements and / or metal halides to allow the negative electrode current collector to undergo an in-situ redox reaction with the halogen elements and / or metal halides, thereby obtaining a negative electrode sheet containing a metal halide modification layer, wherein the metal halide modification layer is located on at least one side of the negative electrode current collector. The first negative electrode-free lithium metal battery cell was obtained by assembling a positive electrode, a solid electrolyte membrane, and a negative electrode containing a metal halide modification layer. The reaction medium can be in the form of a gas phase, liquid phase, or solid phase. When the reaction medium is in the liquid phase, the halogen element and / or metal halide are dissolved or dispersed in the solvent to form a solution, emulsion, or slurry. When the reaction medium is in the solid phase, the halogen element and / or metal halide are in the form of powder.

[0036] By subjecting the negative electrode current collector to a gas-solid phase in-situ redox reaction with halogen elements and / or metal halide vapors, a negative electrode sheet containing a metal halide modification layer is obtained. This allows the metal halide modification layer to adhere to the surface of the negative electrode current collector through chemical bonding based on the in-situ redox reaction, thereby improving the adhesion of the metal halide modification layer. This helps to prevent the interface layer from peeling off during battery assembly and battery cycling, and improves the cycle stability of the battery cell.

[0037] In some embodiments, the method for preparing a single battery cell further includes: The first electrodeless lithium metal battery cell is subjected to a formation treatment so that the metal halide modification layer and the electrochemically deposited lithium metal undergo an in-situ reduction reaction to obtain the second electrodeless lithium metal battery cell. In the second negative electrode-free lithium metal battery cell, the negative electrode sheet includes a negative electrode current collector and an interface layer located on at least one side of the negative electrode current collector. The interface layer includes lithium halide and metal material particles, wherein the lithium halide is a continuous phase and the metal material particles are dispersed in the lithium halide as a dispersed phase.

[0038] An interface layer is obtained by in-situ reduction reaction of metal halide modified layer with electrochemically deposited lithium metal. This helps to improve the dispersion uniformity of metal particles in the interface layer, thereby forming uniform local electron conduction points in the interface layer, improving the deposition uniformity of lithium metal, and effectively reducing the risk of lithium dendrite formation.

[0039] In some embodiments, when the reaction medium is gaseous, the in-situ redox reaction is carried out in a closed or semi-closed container, the temperature inside the closed or semi-closed container is 15°C to 30°C, the exposure time of the negative electrode current collector inside the closed or semi-closed container is 0.5h to 2h, the total amount of halogen element and / or metal halide is 1g to 5g, and the effective volume of the closed or semi-closed container is 80mL to 200mL.

[0040] In some embodiments, when the reaction medium is a liquid phase, the solvent includes an organic solvent, such as one or more of ethanol, acetone, tetrahydrofuran, N-methylpyrrolidone, and xylene, and the concentration of the halogen element and / or metal halide in the solvent is 0.1 mol / L. -1 ~5mol L -1 The contact method is coating, spraying or dipping, and the coating thickness is 1μm to 10μm.

[0041] In some embodiments, when the reaction medium is a solid phase, halogen elements and / or metal halides in powder form are contacted with the negative electrode current collector under preset reaction temperature or preset reaction pressure conditions, wherein the preset reaction temperature is 20°C to 100°C and the preset reaction pressure is 0.1 MPa to 10 MPa.

[0042] A third aspect of this application provides a battery device comprising a negative electrode-free lithium metal battery cell of the first aspect, or a negative electrode-free lithium metal battery cell prepared by the method of the second aspect.

[0043] The fourth aspect of this application provides an electrical device comprising a negative electrode-free lithium metal battery cell of the first aspect, or a negative electrode-free lithium metal battery cell prepared by the method of the second aspect, or a battery device of the third aspect. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1This is a schematic diagram of the process for generating a copper iodide modified layer using iodine vapor in an in-situ gas-solid reaction in Example 1 of this application; Figure 2 These are SEM images and elemental distribution diagrams of the cross-section of the negative electrode sheet obtained in Embodiment 1 of this application; Figure 3 In the embodiments of this application, the Li|CuI@Cu and Li|Cu half-cells are deposited at 2mAh cm⁻¹. -2 Then, a current density of 0.3 mA / cm² was applied. -2 The single deposition / stripping capacity is 0.3 mAh cm⁻¹. -2 Electrochemical curves of constant current charge and discharge; Figure 4 This is a constant current charge-discharge curve of the NCM622|LPSCl|CuI@Cu electrodeless solid-state battery in the embodiments of this application; Figure 5(a) is a schematic diagram of the Young's modulus test results of the interface layer provided in Embodiment 2 of this application; Figure 5(b) is a schematic diagram of the Young's modulus test results of the CuI modified layer provided in Example 2 of this application; Figure 5(c) is a schematic diagram of the Young's modulus test results of pure LiI provided in Example 2 of this application; Figure 6 This is a constant current charge-discharge curve of the NCM622|LPSCl|Cu electrodeless solid-state battery in the embodiments of this application. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0048] As used in this application, the terms “comprising,” “containing,” and “including” are used in their open, non-restrictive sense.

[0049] Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0050] In the detailed description and claims, a list of items connected by the terms "one or more of," "one or more of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A or B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, or C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0051] A negative electrode-free battery cell typically refers to a battery cell in which no negative electrode active material layer is actively formed on the negative electrode side during the battery cell manufacturing process. For example, the negative electrode active material layer is not formed at the negative electrode through coating or deposition processes, or it is formed from a carbonaceous active material layer. During the first charge, ions gain electrons on the negative electrode side and deposit metal on the surface of the negative electrode current collector. During discharge, the metal can be converted back into ions and return to the positive electrode, achieving cyclic charging and discharging. Compared to other battery cells, a negative electrode-free battery cell can achieve a higher energy density due to the absence of a negative electrode active material layer. In some embodiments, to improve battery cell performance, some conventional materials that can be used as negative electrode active materials, such as carbon materials, can also be placed on the negative electrode side of the negative electrode-free battery cell. Although these materials have a certain capacity, because their content is small and they are not used as the main negative electrode active material in the battery cell, the battery cell constructed in this way can still be considered a negative electrode-free battery cell.

[0052] Lithium metal possesses an extremely low electrode potential (-3.04 V vs. standard hydrogen electrode) and an extremely high theoretical specific capacity (3860 mAh g⁻¹). -1 Solid-state lithium metal (SLM) is an ideal anode material for next-generation high-energy-density lithium metal batteries. Due to its high energy density and inherent safety, SLM batteries have become a core development direction for next-generation power batteries. Among them, anode-free SLM batteries do not require pre-storing lithium metal during the manufacturing process. They can achieve the anode function through a "current collector + in-situ lithium deposition" method. Compared to traditional batteries containing excess lithium, their energy density can be increased by more than 30%, while simultaneously reducing costs and safety risks, demonstrating significant industrialization potential.

[0053] However, the commercialization of electrodeless solid-state lithium batteries faces three core challenges: 1) Interface contact and uneven current problem: Copper current collector is the core conductive substrate on the negative electrode side, but the interface contact between copper and solid electrolyte (such as LPSCl, LLZO, etc.) is poor, resulting in uneven current distribution, which can easily cause local lithium metal deposition, leading to high polarization or even lithium dendrite problems. 2) Severe interfacial side reactions: Sulfide electrolytes typically have an electrochemical window <4.0 V, which is narrow. In-situ deposited lithium metal readily reacts with the electrolyte to generate low-ionic-conductivity products such as Li₂S and Li₃P, leading to increased interfacial impedance. Halide electrolytes (such as Li₃YCl₆) also face the risk of being reduced by lithium metal, resulting in deterioration of interfacial composition and structure. Some oxide electrolytes (such as LLZO) may also be reduced under localized high overpotentials, forming unstable interfacial phases. Some polymer electrolytes may undergo chemical decomposition on the lithium metal surface. These irreversible side reactions continuously consume active lithium and electrolyte, leading to a continuous increase in interfacial impedance and rapid capacity decay. 3) Lithium loss and lifespan limitations: Without a negative electrode system, there is no surplus lithium reserve. Lithium loss caused by lithium dendrite growth and interfacial side reactions will quickly lead to battery capacity decay. Batteries assembled with traditional copper current collectors often experience short circuits in the first cycle or failure within 5 cycles.

[0054] Currently, although some studies have attempted to address the aforementioned issues by introducing artificial interface layers, most methods have significant limitations. For example, the fabrication process is complex and difficult to scale up, and the introduced interface layer cannot simultaneously achieve key properties such as ionic conductivity, electronic conductivity, and mechanical strength, making it difficult to simultaneously achieve the multiple objectives of promoting uniform lithium deposition, suppressing dendrites, and blocking side reactions. Specifically, related technical solutions often only solve a single problem. For instance, improving interfacial contact by optimizing the electrolyte's mechanical properties or adjusting the surface roughness of the current collector cannot simultaneously meet the three core requirements of "high lithium-ion transport efficiency," "strong lithium dendrite suppression," and "effective isolation of interfacial side reactions." Furthermore, while simply thickening the sulfide electrolyte can improve the battery's resistance to lithium dendrites, it significantly increases the battery's internal resistance. While coating the electrolyte surface with inert layers such as Al2O3 or ZnO can isolate side reactions, it severely sacrifices the advantages of lithium-ion transport kinetics, affecting the battery's cycle performance.

[0055] To address the aforementioned technical problems, this application provides a cathode-free lithium metal battery cell and a method for preparing the battery cell. The cathode-free lithium metal battery cell can suppress lithium dendrite growth and interfacial side reactions and reduce interfacial impedance, exhibiting good cycle performance and safety performance.

[0056] The embodiments of this application will be described in detail below.

[0057] The first aspect of this application provides a negative electrode-free lithium metal battery cell, including a positive electrode, a negative electrode, and a solid electrolyte membrane, wherein the solid electrolyte membrane is located between the positive electrode and the negative electrode. A single negative electrode-free lithium metal battery cell includes a first state and a second state; In the first state, the negative electrode includes a negative current collector and a metal halide modification layer located on at least one side of the negative current collector; In the second state, the negative electrode includes a negative current collector and an interface layer located on at least one side of the negative current collector. The interface layer includes lithium halide and metal material particles, wherein the lithium halide is a continuous phase and the metal material particles are dispersed in the lithium halide as a dispersed phase.

[0058] In the first state of the electrodeless lithium metal battery cell, the metal halide modification layer can act as a chemical barrier layer to block the contact between the negative electrode current collector and the electrolyte, reducing possible side reactions during storage, transportation, and assembly. During the first charge and discharge process of the electrodeless lithium metal battery, lithium ions will deposit on the negative electrode side to form lithium metal, which can then undergo an in-situ reduction reaction with the metal halide modification layer in the electrodeless lithium metal battery cell in the first state, generating an interface layer including lithium halide and metal material particles, thus transforming the electrodeless lithium metal battery cell from the first state to the second state.

[0059] Based on this, since lithium halides have high lithium-ion conductivity and almost no electronic conductivity, lithium halides, as a continuous phase in the interface layer, can provide continuous lithium-ion migration channels, thereby forming a stable lithium-ion transport network. This effectively reduces the ion transport impedance at the interface, and thus effectively avoids the current density concentration phenomenon caused by ion transport obstruction during lithium metal deposition. This helps to reduce lithium dendrite formation and battery cell capacity decay, and improves the cycle performance and safety performance of battery cells.

[0060] Furthermore, the metal material particles dispersed in lithium halide as a dispersed phase do not form a through-conductive framework in the interface layer, but rather form localized electron conduction points within the interface. This provides an electron channel for lithium nucleation without allowing a significant leakage of electrons to the solid electrolyte side. This controls lithium deposition to occur on the side of the interface layer closer to the negative electrode current collector, effectively preventing direct contact between metallic lithium and the electrolyte. This avoids the occurrence of side reactions, thereby preventing the increase in interface impedance and capacity decay caused by side reactions, and improving the cycle performance of the battery cell.

[0061] In addition, the metal material particles have good ductility, which helps to improve the mechanical properties and structural stability of the interface layer, and helps to improve the resistance of the interface layer to volume fluctuations caused by repeated lithium deposition / stripping, reduce the risk of lithium dendrites piercing the solid electrolyte layer, and further improve the safety performance and interface stability of the battery cell.

[0062] In some embodiments, the negative current collector includes one or more metallic materials selected from copper, nickel, and stainless steel.

[0063] The negative electrode current collector is made of a metallic material, which enables the metal halide modification layer to adhere to the surface of the negative electrode current collector through chemical bonding based on the in-situ redox reaction between the negative electrode current collector and the halogen. For example, the in-situ redox reaction between the negative electrode current collector and the halogen can be carried out on the surface of the negative electrode current collector, thereby generating a metal halide modification layer in situ on the surface of the negative electrode current collector. This improves the adhesion of the metal halide modification layer, helps to avoid peeling during battery assembly and battery cycling, and improves the cycle stability of the battery cell.

[0064] In some embodiments, the thickness of the metal halide modified layer is 2 μm to 4 μm, for example, it can be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or any combination of the above values, preferably, the thickness of the metal halide modified layer is 3 μm.

[0065] The thickness of the metal halide modification layer is 2μm to 4μm, which helps to control the thickness of the interface layer and avoid the adverse effects of an excessively thin or thick interface layer on the cycle performance of the battery cell.

[0066] In some embodiments, the metal halide modification layer includes one or more of cuprous iodide, cuprous bromide, cuprous chloride, ferrous iodide, ferrous bromide, ferrous chloride, nickel iodide, nickel bromide, and nickel chloride, preferably, the metal halide is cuprous iodide.

[0067] The aforementioned metal halides can be directly generated at room temperature through a gas-solid reaction, with uniform reaction and stable film. They can be reduced to lithium halide and metal material particles during electrochemical processes, which helps to stabilize the formation of the interface layer.

[0068] In some embodiments, the thickness of the interface layer is 1 μm to 5 μm, for example, it can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or any combination of the above values.

[0069] The thickness of the interface layer is 1μm to 5μm, which helps the interface layer to have sufficient mechanical properties while having good interfacial transport dynamics. This can avoid lithium dendrite penetration caused by an excessively thin interface layer, and also avoid the interface impedance being increased by an excessively thick interface layer, thus affecting the cycle performance of the battery.

[0070] In some embodiments, the Young's modulus of the interface layer is 30 GPa to 50 GPa, for example, it can be 30 GPa, 35 GPa, 40 GPa, 45 GPa, 50 GPa or any of the above values.

[0071] The Young's modulus of the interface layer is 30 GPa to 50 GPa, which enables the interface layer to have good mechanical properties and structural stability. It can effectively resist the volume fluctuations caused by repeated lithium deposition / stripping, reduce the risk of lithium dendrites piercing the solid electrolyte layer, and further improve the safety performance and interface stability of the battery cell.

[0072] The Young's modulus of the interface layer can be determined by separating the negative electrode from the battery body, separating the interface layer in the negative electrode, and then testing it using a nanoindenter and atomic force microscope (AFM). The test temperature is 25℃.

[0073] In some embodiments, the activation energy for lithium ion migration in the interface layer is 3 kJ mol. -1 ~5 kJ mol -1 .

[0074] Generally, the lower the activation energy for lithium ion migration in the interface layer, the higher the lithium ion migration rate. The activation energy for lithium ion migration in the interface layer is controlled at 3 kJ / mol. -1 ~5 kJ mol -1 This helps maintain high lithium-ion transport performance at the interface layer, thereby avoiding current density concentration caused by ion transport obstruction during lithium metal deposition. It also helps reduce lithium dendrite formation and capacity decay of individual cells, improving the cycle performance and safety of individual cells.

[0075] The activation energy for lithium-ion migration in the interface layer can be determined by electrochemical impedance spectroscopy combined with Arrhenius equation fitting. Specifically: First, a symmetrical cell with an interface layer can be prepared, and then the symmetrical cell is placed in a series of isothermal environments at different temperatures (e.g., 25°C to 80°C) for electrochemical impedance spectroscopy testing, with a test frequency range of 1 MHz to 0.1 Hz. By fitting the obtained impedance spectrum using an equivalent circuit containing interface resistance units, the interface resistance value at each temperature can be accurately extracted. Subsequently, according to the Arrhenius relation, the activation energy for lithium-ion migration in the interface layer can be obtained by fitting the Arrhenius equation.

[0076] In some embodiments, the mass fraction of lithium halide in the interface layer is 57% to 83%.

[0077] The mass fraction of lithium halide in the interface layer is 57% to 83%, which helps to form a stable lithium-ion transport network and effectively reduces the ion transport impedance at the interface.

[0078] In some embodiments, the mass fraction of the metal material particles in the interface layer is 17% to 43%.

[0079] The mass fraction of metal material particles in the interface layer is 17% to 43%, which helps to prevent the dispersed phase metal material particles from forming a through conductive framework in the interface layer, but rather to form local electronic conduction points within the interface. This provides an electronic channel for lithium nucleation without allowing electrons to leak significantly to the solid electrolyte side.

[0080] In some embodiments, the particle size of the metal material is 5 nm to 200 nm. For example, it can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 130 nm, 135 nm, 140 nm, 145 nm, 150 nm, 155 nm, 160 nm, 165 nm, 170 nm, 175 nm, 180 nm, 185 nm, 190 nm, 195 nm, 200 nm, or any combination of the above values. Preferably, the particle size of the metal material is 10 nm to 80 nm.

[0081] Controlling the particle size of the metal material particles to 5nm to 200nm helps to give the metal material particles a high specific surface area, thereby providing abundant lithium nucleation sites and promoting uniform lithium deposition.

[0082] The particle size of metallic materials can be tested as follows: Using a JSM-7401F field emission electron scanning microscope (SEM) from Japan, acquire a SEM image of the negative electrode sheet. Randomly select a test sample with dimensions of 50mm x 100mm on the negative electrode sheet. Randomly select multiple test areas (e.g., 5 areas) within the test sample, and read the particle size of each metallic material particle in each test area at a certain magnification (e.g., 500x or higher). Count the number and particle size of metallic materials in each test area, and take the arithmetic mean of the particle sizes in all test areas as the particle size. To ensure the accuracy of the test results, multiple test samples (e.g., 10 samples) can be used, and the average value of each sample can be taken as the final test result. The testing instrument can be a ZEISS Sigma300. It should be noted that when the particles are irregularly shaped, the distance between the two farthest points on the particle should be taken as the particle size.

[0083] In some embodiments, the metallic material particles include one or more elemental particles selected from copper, nickel, and iron.

[0084] In some embodiments, the solid electrolyte includes one or more of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes, preferably, the solid electrolyte is a sulfide solid electrolyte.

[0085] Sulfide solid electrolytes have high ionic conductivity, which can ensure efficient ion migration at room temperature; and sulfide solid electrolytes have good chemical interface compatibility with lithium halides and low interfacial impedance, which can improve the cycle performance of battery cells while avoiding side reactions between lithium metal and electrolyte.

[0086] In some embodiments, the sulfide solid electrolyte includes Li 10 GeP2S 12 The electrolyte is one or more of the following: a solid electrolyte and a sulfide argyrodite electrolyte Li6PS5X, wherein X is any one of Cl, Br and I, and preferably, the sulfide solid electrolyte is Li6PS5Cl.

[0087] The interface layer construction method of this application does not depend on the specific chemical composition of the sulfide solid electrolyte, and is applicable to Li6PS5Cl, Li6PS5Br, and Li 10 GeP2S 12 Typical high-conductivity sulfides are all compatible, making them easy to promote in different systems of electrodeless solid-state lithium batteries.

[0088] In some embodiments, the halide solid electrolyte includes one or more of ternary halide Li-MX type electrolyte and halide lithium ore type electrolyte Li3MX6, wherein M is any one of Y, Sc, In, Er, Zr, and X is any one of Cl, Br, and I.

[0089] In some embodiments, the oxide solid electrolyte includes a NASICON-type electrolyte Li 1+x A x Ge 2-x (PO4)3 and Garnet-type electrolyte Li7La3Zr2O 12 One or more of the following, where 0≤x≤0.8, and A is any one of Al and Ga.

[0090] In some embodiments, the polymer solid electrolyte includes one or more of polyethylene oxide (PEO)-based polymer electrolytes, polyvinylidene fluoride (PVDF)-based polymer electrolytes, and polyacrylonitrile (PAN)-based polymer electrolytes. This type of electrolyte exhibits good flexibility and interfacial contact with lithium metal, enabling it to synergize with the interfacial layer provided by this invention, further optimizing the battery's interfacial stability and cycle performance.

[0091] Secondly, embodiments of this application provide a method for preparing a negative electrode-free lithium metal battery cell, comprising: S101: Provides a negative electrode current collector, wherein the material of the negative electrode current collector is a metallic material; S102: The negative electrode current collector is contacted with a reaction medium containing halogen elements and / or metal halides to allow the negative electrode current collector to undergo an in-situ redox reaction with the halogen elements and / or metal halides, thereby obtaining a negative electrode sheet containing a metal halide modification layer, wherein the metal halide modification layer is located on at least one side of the negative electrode current collector. S103: The first negative electrode-free lithium metal battery cell is obtained by assembling a positive electrode sheet, a solid electrolyte membrane and a negative electrode sheet containing a metal halide modification layer. The reaction medium can be in the form of a gas phase, liquid phase, or solid phase. When the reaction medium is in the liquid phase, the halogen element and / or metal halide are dissolved or dispersed in the solvent to form a solution, emulsion, or slurry. When the reaction medium is in the solid phase, the halogen element and / or metal halide are in the form of powder.

[0092] In some examples, a metal foil can be placed in a closed or semi-closed container containing a built-in halogen or metal halide. The metal foil can be copper foil, the halogen can be iodine, and the metal halide can be CuI. The halogen or metal halide can be placed at the bottom of the container, and the metal foil can be suspended above it by a support or grid, so that the metal foil does not come into direct contact with the halogen or metal halide. It can be left to stand at room temperature (15℃~30℃) for 0.5h~2h, allowing the vapor formed by the sublimation of the halogen or metal halide to undergo a gas-solid phase redox reaction with the surface of the metal foil. Taking the reaction of copper foil with iodine as an example, the reaction formula is: 2Cu + I2 → 2CuI After the reaction, a uniformly colored, dense metal halide modification layer with strong adhesion to the metal foil is obtained on the metal foil surface, resulting in a modified negative electrode current collector, i.e., a negative electrode sheet MX@M containing the metal halide modification layer, where M is the metal material corresponding to the metal foil, and X is the halogen element, which can be named CuI@Cu in this example. The thickness of the metal halide modification layer can be controlled by adjusting the exposure time, the effective volume of the container, and the amount of reactants. For example, the thickness of the metal halide modification layer can be controlled within the range of 2μm to 4μm.

[0093] This step can be completed at room temperature and does not rely on traditional PVD, CVD or plasma enhancement equipment, enabling large-area, low-cost modification of flexible metal foils.

[0094] By subjecting the negative electrode current collector to a gas-solid phase in-situ redox reaction with halogen elements and / or metal halide vapors, a negative electrode sheet containing a metal halide modification layer is obtained. This allows the metal halide modification layer to adhere to the surface of the negative electrode current collector through chemical bonding based on the in-situ redox reaction, thereby improving the adhesion of the metal halide modification layer. This helps to prevent the interface layer from peeling off during battery assembly and battery cycling, and improves the cycle stability of the battery cell.

[0095] In some embodiments, before contacting the negative electrode current collector with a reaction medium containing halogen elements and / or metal halides to allow the negative electrode current collector to undergo an in-situ redox reaction with the halogen elements and / or metal halides to obtain a negative electrode sheet containing a metal halide modified layer, the method for preparing the battery cell further includes: The negative electrode current collector is pretreated.

[0096] In practical applications, pretreatment may include cutting the commercial metal current collector to the required size. The commercial metal current collector can be a 9 μm thick copper foil. Subsequently, the metal current collector can be ultrasonically cleaned sequentially with anhydrous ethanol, acetone, or other organic solvents to remove oil, adsorbed water, and surface oxides. The cleaning time is preferably 10 to 20 minutes. After cleaning, it can be placed in an inert atmosphere or vacuum to dry for later use.

[0097] The above pretreatment process helps to improve the film uniformity of the metal halide modified layer and the bonding strength with the metal current collector.

[0098] In some embodiments, before assembling the positive electrode, the solid electrolyte membrane, and the negative electrode containing the metal halide modification layer to obtain the first negative electrode-free lithium metal battery cell, the preparation method of the battery cell further includes: Post-processing is performed on the negative electrode sheet containing a metal halide modification layer.

[0099] In practical applications, negative electrode sheets containing metal halide modified layers can be gently rinsed with anhydrous ethanol or other inert solvents to dissolve unreacted and physically adsorbed free reactants, avoiding the impact of residues on subsequent battery assembly and electrochemical testing; then dried under an inert atmosphere or vacuum conditions to ensure surface cleanliness and prevent the introduction of moisture and active impurities.

[0100] In some embodiments, the method for preparing a single battery cell further includes: The first electrodeless lithium metal battery cell is subjected to a formation treatment so that the metal halide modification layer and the electrochemically deposited lithium metal undergo an in-situ reduction reaction to obtain the second electrodeless lithium metal battery cell. In the second negative electrode-free lithium metal battery cell, the negative electrode sheet includes a negative electrode current collector and an interface layer located on at least one side of the negative electrode current collector. The interface layer includes lithium halide and metal material particles, wherein the lithium halide is a continuous phase and the metal material particles are dispersed in the lithium halide as a dispersed phase.

[0101] During the initial charge / discharge formation stage of a lithium metal battery cell in its first state without a negative electrode, the following irreversible electrochemical conversion process occurs: When lithium metal migrates from the positive electrode to the negative electrode side and arrives at the metal halide surface with electrons, the metal halide undergoes a reduction reaction. Taking CuI as an example, the metal halide modification layer is modified as follows: CuI + L + → LiI + Cu The reaction product is generated in situ in the region where the original metal halide modification layer was located, with lithium halide as the continuous matrix phase. The generated metal is uniformly dispersed in the form of nanoparticles or fine grains. Since lithium halide has high lithium-ion conductivity but almost no electron conductivity, while the generated metal has excellent electronic conductivity but is only discretely distributed in lithium halide, the two together constitute an interface layer with high ion transport performance, limited electron transport performance, and strong mechanical properties. Specifically: Because lithium halides have high lithium-ion conductivity and almost no electronic conductivity, they can provide continuous lithium-ion migration channels as a continuous phase in the interface layer, thus forming a stable lithium-ion transport network. This effectively reduces the ion transport impedance at the interface, thereby effectively avoiding the current density concentration caused by ion transport obstruction during lithium metal deposition. This helps reduce lithium dendrite formation and battery cell capacity decay, and improves the cycle performance and safety performance of battery cells.

[0102] Furthermore, the metal material particles dispersed in lithium halide as a dispersed phase do not form a through-conductive framework in the interface layer, but rather form localized electron conduction points within the interface. This provides an electron channel for lithium nucleation without allowing a significant leakage of electrons to the solid electrolyte side. This controls lithium deposition to occur on the side of the interface layer closer to the negative electrode current collector, effectively preventing direct contact between metallic lithium and the electrolyte. This avoids the occurrence of side reactions, thereby preventing the increase in interface impedance and capacity decay caused by side reactions, and improving the cycle performance of the battery cell.

[0103] Moreover, the metal material particles have good ductility, which helps to improve the mechanical properties and structural stability of the interface layer, and helps to improve the resistance of the interface layer to volume fluctuations caused by repeated lithium deposition / stripping, reduce the risk of lithium dendrites piercing the solid electrolyte layer, and further improve the safety performance and interface stability of the battery cell.

[0104] Furthermore, by performing an in-situ reduction reaction between the metal halide modification layer and the electrochemically deposited lithium metal to obtain an interface layer, it is helpful to improve the dispersion uniformity of metal particles in the interface layer, thereby forming uniform local electron conduction points in the interface layer, improving the deposition uniformity of lithium metal, and effectively reducing the risk of lithium dendrite formation.

[0105] It should be noted that, in the embodiments of this application, the first negative electrode-free lithium metal battery cell is the negative electrode-free lithium metal battery cell in the first state, and the second negative electrode-free lithium metal battery cell is the negative electrode-free lithium metal battery cell in the second state.

[0106] In some embodiments, when the reaction medium is gaseous, the in-situ redox reaction is carried out in a closed or semi-closed container, the temperature inside the closed or semi-closed container is 15°C to 30°C, the exposure time of the negative electrode current collector inside the closed or semi-closed container is 0.5h to 2h, the total amount of halogen elements and / or metal halides is 1g to 5g, and the effective volume of the closed or semi-closed container is 80mL to 200mL.

[0107] Using a closed or semi-closed container helps improve the concentration stability of halogen or halide vapors in the reaction environment, while preventing the escape of halogen reactants, thereby improving operational safety. The exposure time of the negative electrode current collector in the container is 0.5h to 2h, which can be adjusted according to actual needs, thereby adjusting the thickness of the metal halide modification layer.

[0108] In some embodiments, when the reaction medium is a liquid phase, the solvent includes an organic solvent, which includes one or more of ethanol, acetone, tetrahydrofuran, N-methylpyrrolidone, and xylene, and the concentration of the halogen element and / or metal halide in the solvent is 0.1 mol / L. -1 ~5mol L -1 The contact method is coating, spraying or dipping, and the coating thickness is 1μm to 10μm.

[0109] The selected solvents, such as ethanol, acetone, tetrahydrofuran, N-methylpyrrolidone, and xylene, facilitate the complete dissolution of halogens and / or metal halides, thereby improving the uniformity of contact between the reactants and the negative electrode current collector surface. The concentration of halogens and / or metal halides in the solvent is 0.1 mol / L.-1 ~5mol L -1 The thickness of the metal halide modification layer can be controlled by adjusting the concentration. The appropriate contact method can be flexibly selected according to actual needs, using coating, spraying, or immersion, to ensure sufficient contact between the reactants and the current collector surface. Furthermore, the coating thickness ranges from 1 μm to 10 μm, and the thickness of the metal halide modification layer can be further effectively controlled by adjusting the coating thickness.

[0110] In some embodiments, when the reaction medium is a solid phase, halogen elements and / or metal halides in powder form are contacted with the negative electrode current collector under preset reaction temperature or preset reaction pressure conditions, wherein the preset reaction temperature is 20°C to 100°C and the preset reaction pressure is 0.1 MPa to 10 MPa.

[0111] Halogen elements and / or metal halides are brought into contact with the negative electrode current collector in powder form. Controlling the reaction temperature within the preset range of 20℃ to 100℃ helps to improve the reaction rate and completeness while preventing thermal damage to the negative electrode current collector. Controlling the reaction pressure within the preset range of 0.1MPa to 10MPa further enhances the contact between the powder and the surface of the negative electrode current collector, thereby promoting the in-situ redox reaction between the powder and the negative electrode current collector, resulting in a denser metal halide-modified layer with improved adhesion.

[0112] The method for preparing negative electrode-free lithium metal battery cells provided in this application has mild reaction conditions, low requirements for equipment and environment, and is suitable for continuous processing of roll materials and industrial-scale production, and has good engineering application prospects.

[0113] In embodiments of this application, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material.

[0114] It is understood that the positive electrode active material layer can be disposed on one surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. This application does not impose any particular limitation on this.

[0115] The positive current collector can be a metal foil or a porous metal plate, such as foil or porous plate of metals or alloys thereof, such as aluminum, copper, nickel, titanium, iron, etc. In some embodiments of this application, the positive current collector is aluminum foil.

[0116] In some embodiments of this application, the positive electrode active material may be selected from at least one of the following: lithium manganese iron phosphate, lithium iron phosphate, lithium manganese phosphate, etc., olivine structure materials, NCM811, NCM622, NCM523, NCM333, etc., lithium cobalt oxide materials, lithium manganese oxide materials, and other metal oxides capable of lithium intercalation / deintercalation.

[0117] In some embodiments of this application, the positive electrode active material layer further includes a conductive agent selected from at least one of carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. Exemplarily, the carbon-based material is selected from carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, or any combination thereof. The metal-based material is selected from metal powder, metal fibers, copper, nickel, aluminum, or silver. The conductive polymer is a polyphenylene derivative.

[0118] In some embodiments of this application, the positive electrode sheet can be prepared by conventional dry processes suitable for solid-state batteries. For example, the positive electrode active material, solid electrolyte and conductive agent are dry-mixed to form a uniform composite positive electrode material; then the material is placed in a mold and pressed under a certain pressure to form a dense positive electrode sheet with good solid-solid contact.

[0119] Thirdly, embodiments of this application provide a battery device comprising a negative electrode-free lithium metal battery cell as described in the first aspect, or a negative electrode-free lithium metal battery cell prepared by the method described in the second aspect.

[0120] Fourthly, embodiments of this application provide an electrical device comprising a negative electrode-free lithium metal battery cell of the first aspect, or a negative electrode-free lithium metal battery cell prepared by the method of the second aspect, or a battery device of the third aspect.

[0121] In some embodiments, the electrical devices provided in this application are applicable to various electrical devices that use solid-state battery cells and battery devices, such as including but not limited to mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. Solid-state battery cells and battery devices are used to store or provide electrical energy.

[0122] Example The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0123] In the various embodiments and comparative examples of this application, battery cells are prepared using the following methods, and the performance of the battery cells is tested.

[0124] Example 1 Preparation method of battery cell Preparation of negative electrode sheets containing metal halide modified layers 1. Materials and Environment Metal current collector: Commercial high-purity rolled copper foil, 9μm thick; Reactant: Analytical grade elemental iodine particles, purity ≥ 99.5 wt%; Cleaning solvent: analytical grade anhydrous ethanol; Environmental protection: Argon glove box with water and oxygen content <0.1ppm, used for drying and storage; Reaction vessel: a glass petri dish with a diameter of about 10cm, which can be used in a semi-sealed manner.

[0125] 2. Preprocessing A 9μm thick copper foil substrate was cut into 3cm × 6cm rectangular pieces and placed in anhydrous ethanol. The pieces were then ultrasonically cleaned for 15 minutes at room temperature to remove surface oil, adsorbed water, and easily detachable oxides. After cleaning, the copper foil was removed and dried with nitrogen or argon gas, or dried in a vacuum oven at room temperature for 30 minutes, and then stored for later use.

[0126] 3. Iodine vapor undergoes an in-situ gas-solid reaction to generate a copper iodide-modified layer. like Figure 1 The diagram shows a flow chart of Example 1 of this application, illustrating the generation of a copper iodide modified layer using an in-situ gas-solid reaction with iodine vapor. 2.5 g of elemental iodine particles are weighed and evenly spread at the bottom of a glass petri dish inside a fume hood. Pretreated copper foil is placed on the upper support, ensuring no direct contact between the copper foil and the iodine particles. The petri dish is then covered to form a semi-closed space, and the reaction is allowed to proceed at room temperature (approximately 25 °C) for 1 hour.

[0127] During the reaction, elemental iodine sublimates into iodine vapor, which reacts with the copper foil surface in a gas-solid phase redox reaction. 2Cu + I2 → 2CuI Remove the copper foil after 1 hour, as follows: Figure 1 As shown, a uniformly colored CuI modification layer is formed on its surface.

[0128] 4. Post-processing After the gas-solid phase redox reaction was completed, the sample was rinsed with anhydrous ethanol to dissolve and remove the free iodine physically adsorbed on the surface until the rinsing solution was colorless. The sample was then transferred to an argon glove box for natural drying or dried by circulating gas. Afterward, the sample was cut into 10 mm diameter blanks to obtain negative electrode sheets with an in-situ CuI modified layer on the surface, denoted as CuI@Cu.

[0129] 5. Morphology and thickness confirmation Figure 2 This shows an SEM image and elemental distribution diagram of the cross-section of the negative electrode sheet prepared in Example 1. Figure 2 As can be seen from the content, the obtained CuI modified layer is continuous and dense, and has good bonding with the copper substrate, with a layer thickness of about 3 μm.

[0130] Preparation of electrolytes 1. In an argon-filled glove box, weigh 100.0 mg of Li6PS5Cl (LPSCI) sulfide solid electrolyte powder and place it in a solid battery mold with an inner diameter of 10 mm for assembly.

[0131] 2. Transfer the mold to the tablet press, apply a pressure of 3 tons (about 300 MPa), hold the pressure for 3 minutes to form a dense LPSCI electrolyte tablet.

[0132] Assembly of battery cells 1. Place a lithium metal sheet with a diameter of 8 mm and a thickness of 200 μm on one side of the LPSCI electrolyte sheet as the counter electrode / reference electrode.

[0133] 2. On the other side of the electrolyte sheet, place a CuI@Cu negative electrode sheet prepared in the previous step as the working electrode.

[0134] 3. Place the assembled battery mold containing the lithium-electrolyte-current collector sandwich structure on the battery support, tighten the screws to apply appropriate stacking pressure, and you will get the Li|CuI@Cu half cell.

[0135] Performance testing Cyclic performance testing: The Li|CuI@Cu half-cell was subjected to cycle performance testing under the following electrochemical test conditions: Test temperature: room temperature (approximately 25 °C); Initial cycle: current density 0.1 mA cm⁻¹ -2 Single deposition / stripping capacity: 0.1 mAh cm⁻¹ -2Subsequently, the parallel sample current density was increased to 0.3 mA cm⁻¹. -2 Single deposition / stripping capacity: 0.3 mAh cm⁻¹ -2 Voltage range: 0V~1V (with reference to the working electrode).

[0136] Test Results At 0.1mA cm -2 Under these conditions, the Li|CuI@Cu half-cell can cycle stably for approximately 200 hours (about 111 cycles), with minimal voltage polarization and no abrupt changes; when the current density is increased to 0.3 mA cm⁻¹... -2 At that time, the Li|CuI@Cu half-cell could still cycle stably for more than 55 hours; Pre-deposited 2mAh cm -2 After lithium, then at 0.3 mA cm -2 0.3mAh cm -2 After repeated cycles, the battery can operate stably for more than 1600 hours without short-circuit failure.

[0137] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the CuI@Cu negative electrode sheet in Example 1 was replaced with a commercially available high-purity rolled copper foil with a thickness of 9 μm, thereby preparing a Li|Cu half-cell.

[0138] Test Results like Figure 3 The image shows Li|CuI@Cu and Li|Cu half-cells deposited at 2 mAh cm⁻¹. -2 Then, a current density of 0.3 mA / cm² was applied. -2 The single deposition / stripping capacity is 0.3 mAh cm⁻¹. -2 The electrochemical curves of constant current charge-discharge at a current density of 0.1 mA cm⁻¹ -2 In the tests, the Li|Cu half-cell exhibited significant voltage fluctuations starting around the 21st cycle, followed by intensified polarization; when the current density increased to 0.3 mA cm⁻¹... -2 At that time, instability occurred and eventually short-circuited during the 6th cycle (approximately 13 hours). If a 2mAh cm⁻¹ deposit is pre-deposited... -2 After lithium-ion batteries undergo long-term cycling, the Li|Cu half-cell only lasts for about 465 hours before short-circuit failure.

[0139] Example 2 Preparation method of battery cell Preparation of positive electrode sheet In an argon-filled glove box, NCM622:acetylene black:LPSCl were weighed and mixed at a mass ratio of 7:2:1, and then thoroughly ground in an agate mortar for about 15 minutes to obtain a uniformly dispersed solvent-free composite cathode powder. 10 mg of the composite cathode powder was weighed and spread into a mold, then pressed under a pressure of 4.5t for 3 minutes to ensure good solid-solid contact with the electrolyte, thus obtaining the cathode sheet.

[0140] Assembly of battery cells The electrolyte sheet used is the LPSCI electrolyte sheet prepared in Example 1, and the negative electrode sheet used is the CuI@Cu negative electrode sheet prepared in Example 1. The positive electrode sheet, LPSCI electrolyte sheet and CuI@Cu negative electrode sheet prepared above are stacked in sequence to form an “NCM622 composite positive electrode|LPSCI electrolyte|CuI@Cu” structure. Then the above stacked structure is put into a solid-state battery mold and appropriate pressure is applied to make it form a tight contact, thus obtaining an NCM622|LPSCI|CuI@Cu negative electrode-free solid-state battery.

[0141] Performance testing Cyclic performance testing: The NCM622|LPSCl|CuI@Cu electrodeless solid-state battery was subjected to cycle performance testing under the following electrochemical test conditions: The first charge-discharge test was conducted at a charge-discharge rate of 0.05 C to evaluate the first-cycle capacity and coulombic efficiency; approximately 2.55 mAh cm⁻¹ was pre-deposited on the CuI@Cu side after the first charge. -2 The lithium, then at 30% of that capacity, or approximately 0.76 mAh cm⁻¹ -2 Multiple charge-discharge cycle tests were conducted to determine the working capacity.

[0142] Young's modulus test: After the first charge-discharge cycle of the NCM622|LPSCl|CuI@Cu electrodeless solid-state battery, the negative electrode was disassembled from the battery body, and the interface layer within the negative electrode was then separated. The separated interface layer sample was fixed on the sample stage of a nanoindenter and tested using a Berkovich diamond indenter. The test was conducted at a constant temperature of 25℃, with a maximum indentation load of 5 mN and a loading-holding-unloading cycle of 20 s. By analyzing the force-displacement curve during the unloading phase, the Young's modulus of the interface layer was calculated using the Oliver-Pharr method.

[0143] Simultaneously, mechanical property mapping of the same interface layer region was performed using atomic force microscopy (Bruker Dimension Icon). A RTESA-150 probe (elastic constant ~6 N / m) was used for scanning in PeakForce QNM mode, with a scanning frequency of 1 kHz and a scanning range of 5 μm × 5 μm. Through force curve analysis, Young's modulus values ​​at each point were calculated based on the Derjaguin-Muller-Toporov (DMT) model, ultimately obtaining the spatial distribution characteristics of the Young's modulus of the interface layer.

[0144] For the CuI@Cu negative electrode prepared in Example 1, the CuI modification layer was isolated, and the intrinsic Young's modulus of the CuI modification layer was characterized by nanoindentation and atomic force microscopy under the same test conditions. At least 5 different regions of each sample were tested, and the average value was taken as the final Young's modulus value to ensure the statistical reliability of the data.

[0145] The Young's modulus of pure LiI bulk material was tested. LiI powder was pressed into dense discs with a diameter of 8 mm under a pressure of 4 tons. The resulting LiI discs were placed on a nanoindenter stage and nanoindentation tests were performed under the same conditions as the previous test (maximum indentation load 5 mN, 25℃). The Young's modulus was calculated using the Oliver-Pharr method. Simultaneously, the mechanical properties of the LiI disc surface were mapped using atomic force microscopy in PeakForce QNM mode, and the spatial distribution of the Young's modulus of the LiI discs was obtained based on the DMT model. At least five different regions were tested for each sample, and the average value was taken as the final Young's modulus value to ensure the statistical reliability of the data.

[0146] Test Results like Figure 4 The image shows the constant current charge-discharge curve of the NCM622|LPSCl|CuI@Cu electrodeless solid-state battery. At a rate of 0.05C, the first discharge capacity of the battery is approximately 129.6 mAh g. -1 The initial coulombic efficiency is above 92%, and it can cycle stably for more than 10 cycles at a 0.05 C rate without significant voltage polarization increase. Approximately 2.55 mAh / cm² is pre-deposited on the CuI@Cu side after the first charge. -2 The lithium, then at 30% of that capacity, or approximately 0.76 mAh cm⁻¹ -2 In the multi-cycle charge-discharge test of the working capacity, it can be seen that the voltage curves of the first 10 cycles are basically the same, indicating that the interface layer formed by CuI conversion can support the uniform deposition / stripping of lithium for a long time without a negative electrode.

[0147] Figure 5(a) shows a schematic diagram of the Young's modulus test results of the interface layer provided in Example 2, Figure 5(b) shows a schematic diagram of the Young's modulus test results of the CuI modified layer provided in Example 2, and Figure 5(c) shows a schematic diagram of the Young's modulus test results of the pure LiI provided in Example 2. As can be seen from the figures, the interface layer obtained by the CuI modified layer has a higher Young's modulus, which can make the interface layer have good mechanical properties and structural stability, effectively resist the volume fluctuations caused by repeated lithium deposition / stripping, reduce the risk of lithium dendrites piercing the solid electrolyte layer, and further improve the safety performance and interface stability of the battery cell.

[0148] Comparative Example 2 The only difference between Comparative Example 2 and Example 2 is that the CuI@Cu negative electrode sheet in Example 2 was replaced with a commercially available high-purity rolled copper foil with a thickness of 9 μm, thereby preparing an NCM622|LPSCl|Cu negative electrode-free solid-state battery.

[0149] Test Results like Figure 6 The constant current charge-discharge curve of the NCM622|LPSCl|Cu electrodeless solid-state battery is shown. It can be seen that the electrolyte of the NCM622|LPSCl|Cu electrodeless solid-state battery short-circuits when the first charging voltage is about 4.00 V, and it cannot complete a complete cycle.

[0150] As can be seen from the above embodiments and comparative examples, if the interface layer provided in this application is not constructed on the surface of the negative electrode current collector, the deposited lithium will tend to grow disorderly on the electrolyte side and penetrate the electrolyte, resulting in premature failure of the negative electrode-free lithium metal battery. The interface layer provided in this application can significantly extend the cycle life of the negative electrode-free lithium metal battery and improve the first-cycle capacity and cycle stability of the negative electrode-free lithium metal battery.

[0151] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A negative electrode-free lithium metal battery cell, characterized in that, It includes a positive electrode, a negative electrode, and a solid electrolyte membrane, wherein the solid electrolyte membrane is located between the positive electrode and the negative electrode; The negative electrode-free lithium metal battery cell includes a first state and a second state; In the first state, the negative electrode sheet includes a negative current collector and a metal halide modification layer located on at least one side of the negative current collector; In the second state, the negative electrode sheet includes the negative current collector and an interface layer located on at least one side of the negative current collector. The interface layer includes lithium halide and metal material particles, wherein the lithium halide is a continuous phase and the metal material particles are dispersed in the lithium halide as a dispersed phase.

2. The negative electrode-free lithium metal battery cell according to claim 1, characterized in that, The negative electrode current collector includes one or more metallic materials selected from copper, nickel, and stainless steel.

3. The negative electrode-free lithium metal battery cell according to claim 1, characterized in that, The metal halide modified layer satisfies one or more of the following conditions: (1) The thickness of the metal halide modification layer is 2 μm to 4 μm; (2) The metal halide modification layer includes one or more of cuprous iodide, cuprous bromide, cuprous chloride, ferrous iodide, ferrous bromide, ferrous chloride, nickel iodide, nickel bromide, and nickel chloride.

4. The negative electrode-free lithium metal battery cell according to claim 1, characterized in that, The interface layer satisfies one or more of the following conditions: (1) The thickness of the interface layer is 1 μm to 5 μm; (2) The Young's modulus of the interface layer is 30 GPa to 50 GPa; (3) The activation energy for lithium ion migration in the interface layer is 3 kJ mol. -1 ~5 kJ mol -1 ; (4) The mass fraction of lithium halide in the interface layer is 57% to 83%; (5) The mass fraction of the metal material particles in the interface layer is 17% to 43%.

5. The negative electrode-free lithium metal battery cell according to claim 1, characterized in that, The metallic material particles satisfy one or more of the following conditions: (1) The particle size of the metal material particles is 5 nm to 200 nm; (2) The metal material particles include one or more elemental particles of copper, nickel, and iron.

6. The negative electrode-free lithium metal battery cell according to claim 1, characterized in that, The solid electrolyte includes one or more of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes and polymer solid electrolytes, preferably, the solid electrolyte is a sulfide solid electrolyte.

7. The negative electrode-free lithium metal battery cell according to claim 6, characterized in that, The solid electrolyte satisfies one or more of the following conditions: (1) The sulfide solid electrolyte includes Li 10 GeP2S 12 The electrolyte is one or more of the following: a solid electrolyte and a sulfide argyrodite electrolyte Li6PS5X, wherein X is any one of Cl, Br and I, and preferably, the sulfide solid electrolyte is Li6PS5Cl. (2) The halide solid electrolyte includes one or more of ternary halide Li-MX type electrolyte and halide lithium ore type electrolyte Li3MX6, wherein M is any one of Y, Sc, In, Er, Zr, and X is any one of Cl, Br, and I; (3) The oxide solid electrolyte includes NASICON-type electrolyte Li 1+x A x Ge 2-x (PO4)3 and Garnet-type electrolyte Li7La3Zr2O 12 One or more of the following, where 0 ≤ x ≤ 0.8, and A is any one of Al and Ga; (4) The polymer solid electrolyte includes one or more of polyoxyethylene polymer electrolyte, polyvinylidene fluoride polymer electrolyte, and polyacrylonitrile polymer electrolyte.

8. A method for preparing a negative electrode-free lithium metal battery cell, characterized in that, include: A negative electrode current collector is provided, wherein the material of the negative electrode current collector is a metallic material; The negative electrode current collector is contacted with a reaction medium containing halogen elements and / or metal halides to allow the negative electrode current collector to undergo an in-situ redox reaction with the halogen elements and / or metal halides, thereby obtaining a negative electrode sheet containing a metal halide modification layer, wherein the metal halide modification layer is located on at least one side of the negative electrode current collector. The positive electrode, the solid electrolyte membrane, and the negative electrode containing the metal halide modification layer are assembled to obtain the first negative electrode-free lithium metal battery cell. The reaction medium is in the form of a gas phase, liquid phase, or solid phase; when the reaction medium is in the liquid phase, the halogen element and / or metal halide are dissolved or dispersed in the solvent to form a solution, emulsion, or slurry; when the reaction medium is in the solid phase, the halogen element and / or metal halide are in the form of powder.

9. The preparation method according to claim 8, characterized in that, Also includes: The first electrodeless lithium metal battery cell is subjected to a formation process to allow the metal halide modification layer to undergo an in-situ reduction reaction with the electrochemically deposited lithium metal to obtain the second electrodeless lithium metal battery cell. In the second negative electrode-free lithium metal battery cell, the negative electrode sheet includes the negative electrode current collector and an interface layer located on at least one side of the negative electrode current collector. The interface layer includes lithium halide and metal material particles, wherein the lithium halide is a continuous phase and the metal material particles are dispersed in the lithium halide as a dispersed phase.

10. The method according to claim 8 or 9, characterized in that, The method satisfies one or more of the following conditions: (1) When the reaction medium is gas phase, the in-situ redox reaction is carried out in a closed container or a semi-closed container, the temperature inside the closed container or semi-closed container is 15℃~30℃, the exposure time of the negative electrode current collector inside the closed container or semi-closed container is 0.5h~2h, the total amount of the halogen element and / or metal halide is 1g~5g, and the effective volume of the closed container or semi-closed container is 80mL~200mL. (2) When the reaction medium is a liquid phase, the solvent includes an organic solvent, which includes one or more of ethanol, acetone, tetrahydrofuran, N-methylpyrrolidone, and xylene, and the concentration of the halogen element and / or metal halide in the solvent is 0.1 mol / L. -1 ~5mol L -1 The contact method is coating, spraying, or dipping, and the coating thickness is 1μm to 10μm; (3) When the reaction medium is a solid phase, the halogen element and / or metal halide in powder form are in contact with the negative electrode current collector under a preset reaction temperature or preset reaction pressure, wherein the preset reaction temperature is 20℃~100℃ and the preset reaction pressure is 0.1MPa~10MPa.

11. A battery device, characterized in that, The battery device comprises a negative electrode-free lithium metal battery cell as described in any one of claims 1-7, or a negative electrode-free lithium metal battery cell prepared by the method described in any one of claims 8-10.

12. An electrical appliance, characterized in that, The electrical device includes a negative electrode-free lithium metal battery cell as described in any one of claims 1-7, or a negative electrode-free lithium metal battery cell prepared by the method described in any one of claims 8-10, or the battery device as described in claim 11.

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