Metal lithium / mixed conductive interlayer / inorganic solid electrolyte integrated electrode and preparation method thereof, battery

Abstract

The application provides a metal lithium / mixed conductive intermediate layer / inorganic solid electrolyte integrated electrode and a preparation method and application thereof. The integrated electrode comprises an inorganic solid electrolyte sheet, a mixed conductive intermediate layer and a metal lithium layer. The mixed conductive intermediate layer is located on one surface of the inorganic solid electrolyte sheet, and the metal lithium layer is located on the surface of the mixed conductive intermediate layer. The mixed conductive intermediate layer is a heteroatom-doped hard carbon skeleton lithiation product. The hard carbon skeleton lithiation product comprises hard carbon and LiC x , and one or more of LiF, Li2S, Li3N and LiCl. The integrated electrode can effectively improve the wettability of the interface between the metal lithium and the inorganic solid electrolyte, significantly reduce the interface impedance, adapt to the volume change in the cycle process through the mixed conductive intermediate layer, reduce the interface stress, uniform the interface electric field, induce the uniform nucleation and deposition of the metal lithium, and inhibit the growth of lithium dendrites. The integrated electrode can be widely applied to solid-state batteries, quasi-solid-state batteries and semi-solid-state batteries.

Description

Technical Field

[0001] This invention belongs to the field of solid-state lithium metal battery technology, specifically relating to an integrated electrode of lithium metal / hybrid conductive intermediate layer / inorganic solid electrolyte, its preparation method and application. Background Technology

[0002] Solid-state lithium metal batteries (SLMs) boast advantages such as high safety, high energy density, high power density, and long cycle life, making them a strong contender for next-generation energy storage technology. The key component of SLMs is the solid electrolyte. Compared to traditional liquid batteries, the solid electrolyte, which is less prone to leakage and explosion, completely replaces the liquid electrolyte and separator, significantly reducing the risk of thermal runaway. Secondly, due to the high mechanical strength of the solid electrolyte, it effectively suppresses the formation and growth of lithium dendrites. Simultaneously, the integration of the solid electrolyte and separator reduces the weight and volume of the battery pack, making the battery lighter and more efficient.

[0003] However, solid-state lithium metal batteries still face several challenges on the road to commercialization, one of the most pressing issues being the lithium metal / solid electrolyte interface. Due to its extremely high reducing properties, lithium metal readily reacts with high-valence metal cations (such as Ti) in the solid electrolyte when in contact with it. 4+ 、Ge 4+ The reaction between lithium metal and solid electrolytes (SEE) leads to high impedance at the interface. Simultaneously, due to the rigidity of the solid electrolyte and residual alkali on its surface, the contact between lithium metal and the solid electrolyte at the interface is limited to point-to-point contact. This not only hinders lithium-ion transport and increases the battery's internal resistance, leading to decreased battery performance, but in some extreme cases, it can even cause lithium dendrites to penetrate the solid electrolyte, resulting in safety issues. The unstable lithium metal / solid electrolyte interface and severe lithium dendrite growth significantly limit the commercial application of lithium metal anodes. Developing an interface modification strategy to address the incompatibility of the lithium metal / solid electrolyte interface and effectively suppress lithium dendrite formation is key to solving these problems.

[0004] In recent years, many researchers have introduced metal interlayers into the lithium metal / solid electrolyte interface using methods such as magnetron sputtering and atomic layer deposition to improve interfacial performance. However, these interlayers exert their modification effect through limited chemical reactions or alloying with lithium metal. The interfacial reaction products, due to their poor ductility and compressibility, cannot withstand large volume changes and can cause cracks at the lithium metal / solid electrolyte interface. Therefore, researchers have sought to reduce interfacial stress during volume expansion by introducing soft interfaces. CN110444731A uses a composite method of ionic liquid and polymer to promote the formation of ionic liquid films at the lithium metal / solid electrolyte interface, thereby introducing a flexible modification layer to reduce stress changes in solid-state batteries during cycling. CN117638074A uses a protective layer formed by the curing of polymer hydrogel and lithium salt to prevent side reactions between lithium metal and the inorganic solid electrolyte, resulting in better battery cycle performance. However, these soft interfaces lack sufficient mechanical strength and cannot effectively suppress the growth of lithium dendrites under high current density, thus leading to battery short circuits. Furthermore, the introduced polymers often reduce the ionic conductivity at the interface. CN118472253A utilizes a graphene-boron compound to form a self-supporting artificial intermediate layer with good ductility and not too soft to regulate the lithium metal / sulfide solid electrolyte interface. Although this improves the ionic / electron conductivity at the interface, related studies have shown that the long-range ordered layered structure inside graphene is not conducive to the vertical transport of lithium ions at the interface. Summary of the Invention

[0005] To address the aforementioned technical issues, this application provides an integrated electrode of lithium metal / hybrid conductive intermediate layer / inorganic solid electrolyte, its preparation method, and its application.

[0006] To achieve the above objectives, this application proposes the following technical solution:

[0007] In a first aspect, an integrated electrode of lithium metal / mixed conductive interlayer / inorganic solid electrolyte is provided, comprising an inorganic solid electrolyte sheet, a mixed conductive interlayer, and a lithium metal layer. The mixed conductive interlayer is located on one surface of the inorganic solid electrolyte sheet, and the lithium metal layer is located on the surface of the mixed conductive interlayer away from the inorganic solid electrolyte sheet. The mixed conductive interlayer is a lithiation product of a heteroatom-doped hard carbon framework. The heteroatoms doped in the hard carbon framework are one or more of N, F, S, Cl, Na, and K. The lithiation product of the heteroatom-doped hard carbon framework includes hard carbon and LiC. x And one or more of LiF, Li2S, Li3N, and LiCl.

[0008] Furthermore, the inorganic solid electrolyte sheet is one or more of oxide solid electrolytes, halide solid electrolytes, and sulfide solid electrolytes.

[0009] Furthermore, the inorganic solid electrolyte sheet is selected from one or more of the following: garnet-type oxide solid electrolyte, sodium superionic conductor solid electrolyte, lithium superionic conductor solid electrolyte, and perovskite solid electrolyte.

[0010] Furthermore, the garnet-type oxide solid electrolyte is one or more of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), lithium lanthanum zirconium niobium oxide (LLZNO), and lithium gallium lanthanum zirconium oxide (LGLZO).

[0011] Furthermore, the sodium superionic conductor solid electrolyte is one or more of lithium aluminum titanium phosphate (LATP) and lithium aluminum germanium phosphate (LAGP).

[0012] Furthermore, the lithium superionic conductor solid electrolyte is one or more of lithium germanium vanadium oxide (LGVO) and lithium germanium phosphorus sulfide (LGPS).

[0013] Furthermore, the perovskite-type solid electrolyte is ABO3, wherein A is one or more of Ca, Sr, and La; and B is one or more of Al and Ti.

[0014] Furthermore, the thickness of the doped hard carbon layer is 2~3 μm.

[0015] Secondly, a method for preparing an integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte is provided, including:

[0016] An inorganic solid electrolyte sheet is formed on one surface by forming a doped hard carbon layer, thereby obtaining an inorganic solid electrolyte sheet with a doped hard carbon layer on its surface; the doping atoms of the doped hard carbon layer are one or more of N, F, S, K, Na, and Cl;

[0017] Under vacuum conditions with a water content of <0.01ppm or in an inert gas atmosphere, the lithium metal sheet is first heated to a molten state, and then the side of the inorganic solid electrolyte sheet with the doped hard carbon layer is placed on the molten lithium metal. The lithiation reaction is carried out at a certain temperature to obtain an integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte.

[0018] Furthermore, the thickness of the hybrid conductive intermediate layer is 2~3 μm.

[0019] Furthermore, the process of forming a doped hard carbon layer on the surface of the inorganic solid electrolyte sheet includes: coating a carbon source precursor onto the surface of the inorganic solid electrolyte sheet, and then pyrolyzing it in an argon atmosphere or a nitrogen atmosphere.

[0020] Furthermore, the carbon source precursor includes biomass, and optionally sugars and synthetic resins.

[0021] Furthermore, the sugar is selected from at least one of starch, glucose, and sucrose;

[0022] Furthermore, the synthetic resin is selected from at least one of phenolic resin, epoxy resin, and urea-formaldehyde resin;

[0023] Furthermore, the biomass is selected from at least one of egg white, honey, coconut shell, walnut shell, straw, wood, camellia shell, and bamboo powder;

[0024] Furthermore, the pyrolysis includes: first performing low-temperature heat treatment at 400~500℃, and then performing high-temperature heat treatment at 600~1000℃;

[0025] Furthermore, the low-temperature heat treatment lasts for 2-4 hours; the high-temperature heat treatment lasts for 2-4 hours.

[0026] Furthermore, the temperature of the heated lithium metal sheet is 200~350℃.

[0027] Furthermore, the insulation temperature is 300~400℃.

[0028] Furthermore, the inorganic solid electrolyte sheet is one or more of oxide solid electrolytes, halide solid electrolytes, and sulfide solid electrolytes.

[0029] Furthermore, the inorganic solid electrolyte sheet is selected from one or more of the following: garnet-type oxide solid electrolyte, sodium superionic conductor solid electrolyte, lithium superionic conductor solid electrolyte, and perovskite solid electrolyte.

[0030] Furthermore, the garnet-type oxide solid electrolyte is one or more of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), lithium lanthanum zirconium niobium oxide (LLZNO), and lithium gallium lanthanum zirconium oxide (LGLZO).

[0031] Furthermore, the sodium superionic conductor solid electrolyte is one or more of lithium aluminum titanium phosphate (LATP) and lithium aluminum germanium phosphate (LAGP).

[0032] Furthermore, the lithium superionic conductor solid electrolyte is one or more of lithium germanium vanadium oxide (LGVO) and lithium germanium phosphorus sulfide (LGPS).

[0033] Furthermore, the perovskite-type solid electrolyte is ABO3, wherein A is one or more of Ca, Sr, and La; and B is one or more of Al and Ti.

[0034] Furthermore, the hybrid conductive intermediate layer is a lithiation product of a heteroatom-doped hard carbon framework; the lithiation product of the heteroatom-doped hard carbon framework includes LiC.x One or more of the following substances: LiF, Li2S, Li3N, LiCl, and hard carbon.

[0035] Thirdly, a battery is provided, including the aforementioned integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte or the integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte prepared by the aforementioned preparation method, wherein the battery is a semi-solid-state battery, a quasi-solid-state battery or an all-solid-state battery.

[0036] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects:

[0037] To address the issue of interfacial wettability of lithium metal / inorganic solid electrolytes, a hybrid conductive intermediate layer generated by lithiation of a heteroatom-doped hard carbon framework is proposed to improve the wettability of solid electrolytes to lithium metal. The lithilated hard carbon exhibits excellent lithium affinity, significantly reducing interfacial impedance.

[0038] To address the stress problem at the lithium metal / inorganic solid electrolyte interface caused by volume expansion, a hybrid conductive interlayer generated after lithiation of a heteroatom-doped hard carbon framework is proposed to reduce interfacial stress. The lithilated hard carbon framework possesses the excellent ductility and compressibility of carbon itself, allowing it to adapt to the volume changes that occur during solid-state lithium metal battery cycling, thus reducing interfacial stress.

[0039] To address the problem of lithium dendrite growth at the lithium metal / inorganic solid electrolyte interface, a hybrid conductive interlayer generated by lithiation of a heteroatom-doped hard carbon framework is proposed to achieve a dendrite-free interface. This hybrid conductive interlayer can homogenize the interfacial electric field and provide a fast and smooth transport path for ions, thereby inducing uniform nucleation and deposition of lithium metal at the interface and suppressing lithium dendrite growth.

[0040] The integrated electrode provided can be widely used in solid-state batteries, quasi-solid-state batteries, and semi-solid-state batteries.

[0041] The provided method for preparing the integrated electrode of lithium metal / hybrid conductive intermediate layer / inorganic solid electrolyte is simple and easy to implement, which is conducive to industrial application. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1The XRD patterns are of the heteroatom-doped hard carbon frameworks provided in Examples 1 and 3.

[0044] Figure 2 The image shown is a cross-sectional image of the modified oxide solid electrolyte ceramic sheet provided in Example 1 using a scanning electron microscope.

[0045] Figure 3 This is a deposition morphology diagram of the modified lithium metal in Example 1 on a heteroatom-doped hard carbon framework.

[0046] Figure 4 The AC impedance diagram of the symmetrical battery after the modification method provided in Example 1.

[0047] Figure 5 The symmetric cell modified according to the method provided in Example 1 operates at 1.0 mA / cm². 2 Long-term cycling performance at current density.

[0048] Figure 6 The critical current density diagrams are for the modified symmetrical batteries of Example 1 and Comparative Example 1.

[0049] Figure 7 The image shows a cross-sectional image of the interface of a symmetrical battery modified by the method provided in Example 1 after long-term cycling using a scanning electron microscope.

[0050] Figure 8 This is an XPS image of the hybrid conductive intermediate layer in Example 1.

[0051] Figure 9 The graph shows the charge-discharge curves of the semi-solid-state lithium metal battery constructed in Example 1 at 0.1C.

[0052] Figure 10 The graph shows the charge-discharge curves of the quasi-solid-state lithium metal battery constructed in Example 2 at 0.1C.

[0053] Figure 11 The symmetric cell after the modification method provided for Comparative Example 1 operates at 0.1 mA / cm². 2 Long-term cycling performance at current density.

[0054] Figure 12 This is a schematic diagram of the modification methods for Example 1 and Comparative Example 1.

[0055] Figure 13 The symmetric cell after the modification method provided for Comparative Example 2 operates at 0.1 mA / cm². 2 Long-term cycling performance at current density. Detailed Implementation

[0056] Some embodiments of the present invention provide an integrated lithium metal / mixed conductive interlayer / inorganic solid electrolyte electrode, comprising an inorganic solid electrolyte sheet, a mixed conductive interlayer, and a lithium metal layer. The mixed conductive interlayer is located on one surface of the inorganic solid electrolyte sheet (i.e., the mixed conductive interlayer covers or coats one surface of the inorganic solid electrolyte sheet), and the lithium metal layer is located on the surface of the mixed conductive interlayer away from the inorganic solid electrolyte sheet (i.e., the lithium metal layer covers or coats the surface of the mixed conductive interlayer away from the inorganic solid electrolyte sheet). The mixed conductive interlayer is a lithiation product of a heteroatom-doped hard carbon framework; the heteroatoms doped in the hard carbon framework are one or more of N, F, S, Cl, Na, and K; the lithiation product of the heteroatom-doped hard carbon framework includes hard carbon and LiC. x And one or more of LiF, Li2S, Li3N, and LiCl.

[0057] In some preferred embodiments, the inorganic solid electrolyte sheet is one or more of oxide solid electrolyte, halide solid electrolyte, and sulfide solid electrolyte; more preferably, the inorganic solid electrolyte sheet is selected from one or more of garnet-type oxide solid electrolyte, sodium superion conductor solid electrolyte, lithium superion conductor solid electrolyte, and perovskite solid electrolyte; and even more preferably, it is a garnet-type oxide solid electrolyte.

[0058] The garnet-type oxide solid electrolyte is one or more of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), lithium lanthanum zirconium niobium oxide (LLZNO), and lithium gallium lanthanum zirconium oxide (LGLZO).

[0059] The sodium superionic conductor solid electrolyte is one or more of lithium aluminum titanium phosphate (LATP) and lithium aluminum germanium phosphate (LAGP).

[0060] The lithium superionic conductor solid electrolyte is one or more of LGVO and LGPCO.

[0061] The perovskite-type solid electrolyte is ABO3, wherein A is one or more of Ca, Sr, and La; and B is one or more of Al and Ti.

[0062] In some preferred embodiments, the thickness of the hybrid conductive intermediate layer is 2~3μm, such as 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3μm, etc.

[0063] Based on an ion / electron hybrid conductive interlayer, an interface modification method was designed that can reduce interfacial stress, improve the wettability of the lithium metal / inorganic solid electrolyte interface, and effectively suppress lithium dendrite growth.

[0064] Specifically, some embodiments of the present invention provide a method for preparing an integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte, including:

[0065] An inorganic solid electrolyte sheet is formed on one surface by forming a doped hard carbon layer, thereby obtaining an inorganic solid electrolyte sheet with a doped hard carbon layer on its surface; the doping atoms of the doped hard carbon layer are one or more of N, F, S, K, Na, and Cl;

[0066] Under vacuum conditions with a water content of <0.01ppm or in an inert gas atmosphere, the lithium metal sheet is first heated to a molten state. Then, the side of the inorganic solid electrolyte sheet with the doped hard carbon layer is placed into the molten lithium metal and kept at a certain temperature to carry out a lithiation reaction. This causes the hard carbon skeleton on its surface to undergo a lithiation reaction with the lithium metal, resulting in an intermediate layer with mixed conductive properties. Subsequently, a mixed conductive intermediate layer containing the hard carbon skeleton lithiation product with heteroatom doping is formed at the interface between the negative electrode and the solid electrolyte to modify the interface between the negative electrode and the solid electrolyte, resulting in an integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte.

[0067] A heteroatom-doped hard carbon framework is introduced by high-temperature pyrolysis of a carbon source precursor on the surface of an inorganic solid electrolyte. Compared to graphite and soft carbon, the lithiated hard carbon framework possesses the good ductility and flexibility of carbon itself, while also exhibiting a certain mechanical strength. This significantly improves interfacial wettability, reduces interfacial stress, and effectively inhibits lithium dendrite growth. A high-temperature molten lithium metal anode is placed on this hard carbon framework and undergoes a lithiation reaction, forming an intermediate layer with mixed ionic / electronic conductivity at the interface between the anode and the inorganic solid electrolyte. Molten lithium metal adheres to this intermediate layer, thus fabricating an integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte. This method significantly improves the interfacial wettability and stability between the inorganic solid electrolyte and the lithium metal anode. The introduced mixed conductive intermediate layer homogenizes the interfacial electric field, providing a fast and smooth ion transport path, thereby promoting uniform nucleation and deposition of lithium metal at the interface. This achieves a dendrite-free interface and improves the cycle stability and safety of solid-state batteries at high current densities in a simple and low-cost manner.

[0068] In some preferred embodiments, the thickness of the doped hard carbon layer is 2~3μm, such as 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3μm, etc.

[0069] In some preferred embodiments, forming a doped hard carbon layer on the surface of the inorganic solid electrolyte sheet includes: coating a carbon source precursor onto the surface of the inorganic solid electrolyte sheet, and then pyrolyzing it in an argon atmosphere or a nitrogen atmosphere.

[0070] One or more carbon source precursors are uniformly mixed and dispersed by one or more methods such as stirring, grinding, and ball milling, and then coated onto the surface of an inorganic solid electrolyte sheet.

[0071] The coating is selected from one or more methods such as spin coating, coagulation, and spraying.

[0072] The inert gas can be a conventional inert gas in the art, such as argon, helium, neon, etc.

[0073] In some preferred embodiments, the heating and melting of the lithium metal sheet and the heat preservation lithiation reaction are both carried out inside a glove box.

[0074] In some preferred embodiments, the carbon source precursor includes biomass, and optionally sugars and synthetic resins. That is, the carbon source precursor can be biomass, or it can be a mixture of at least one of sugars and synthetic resins with biomass.

[0075] In some preferred embodiments, the sugar is selected from at least one of starch, glucose, and sucrose.

[0076] In some preferred embodiments, the synthetic resin is selected from at least one of phenolic resin, epoxy resin, and urea-formaldehyde resin.

[0077] In some preferred embodiments, the biomass is selected from at least one of egg white, honey, coconut shell, walnut shell, straw, wood, camellia shell, and bamboo powder.

[0078] In some preferred embodiments, the pyrolysis includes: first performing low-temperature heat treatment at 400~500℃ (e.g., 400℃, 420℃, 450℃, 480℃, 500℃, etc.), and then performing high-temperature heat treatment at 600~1000℃ (e.g., 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, etc.).

[0079] In some preferred embodiments, the temperature of the heated lithium metal sheet is 200~350℃, such as 200℃, 220℃, 250℃, 280℃, 300℃, 320℃, 350℃, etc.

[0080] In some preferred embodiments, the insulation temperature is 300~400℃, such as 300℃, 320℃, 350℃, 380℃, 400℃, etc.

[0081] In some preferred embodiments, the inorganic solid electrolyte sheet is one or more of oxide solid electrolyte, halide solid electrolyte, and sulfide solid electrolyte; preferably, the inorganic solid electrolyte sheet is selected from one or more of garnet-type oxide solid electrolyte, sodium superion conductor solid electrolyte, lithium superion conductor solid electrolyte, and perovskite solid electrolyte; more preferably, it is a garnet-type oxide solid electrolyte.

[0082] The garnet-type oxide solid electrolyte is one or more of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), lithium lanthanum zirconium niobium oxide (LLZNO), and lithium gallium lanthanum zirconium oxide (LGLZO).

[0083] The sodium superionic conductor solid electrolyte is one or more of lithium aluminum titanium phosphate (LATP) and lithium aluminum germanium phosphate (LAGP).

[0084] The lithium superionic conductor type solid electrolyte is one or more of lithium germanium vanadium oxide (LGVO) and lithium germanium phosphorus sulfur (LGPS).

[0085] The perovskite-type solid electrolyte is ABO3, wherein A is one or more of Ca, Sr, and La; and B is one or more of Al and Ti.

[0086] In some preferred embodiments, the mixed conductive intermediate layer is a lithiation product of a heteroatom-doped hard carbon framework; the heteroatom-doped hard carbon framework lithiation product includes LiC. x One or more of the following substances: LiF, Li2S, Li3N, LiCl, and hard carbon.

[0087] The present invention also provides a battery comprising the aforementioned integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte or the integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte prepared by the aforementioned preparation method, wherein the battery is a semi-solid-state battery, a quasi-solid-state battery or an all-solid-state battery.

[0088] In some embodiments, the positive electrode active material in the positive electrode of the solid-state battery is selected from one or more of the following: layered positive electrode materials [lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium-rich manganese-based positive electrode materials], spinel-type positive electrode materials [lithium manganese oxide (LiMn2O4)], and olivine-type positive electrode materials [lithium iron phosphate (LiFePO4)].

[0089] In some embodiments, the solid-state battery further includes a positive electrode-side electrolyte; the positive electrode-side electrolyte is one or both of a liquid electrolyte and a polymer solid electrolyte.

[0090] Some embodiments also provide a method for preparing the above-described battery, comprising the following steps:

[0091] The aforementioned integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte, optional electrolyte or polymer electrolyte, and positive electrode are assembled into a battery. It is worth noting that when the assembled battery is a semi-solid-state battery, an electrolyte can be added; when the assembled battery is a quasi-solid-state battery, a polymer electrolyte can be added.

[0092] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0093] Example 1

[0094] A method for optimizing the negative electrode interface of a solid metal lithium battery based on a hybrid conductive intermediate layer, wherein the solid electrolyte is a garnet-type oxide solid electrolyte LLZTO (lithium lanthanum zirconium tantalum oxide) ceramic sheet, the carbon source precursor is the biomass precursor egg white and the sugar precursor sucrose; the positive electrode electrolyte is a liquid electrolyte; and the positive electrode material is NCM811.

[0095] (1) Preparation of precursor: First, mix egg white and sucrose thoroughly in a beaker and beat with a stirrer to form a meringue with cross-linked protein and sucrose molecules.

[0096] (2) Interface modification: The oxide solid electrolyte LLZTO ceramic sheet was placed on a heating table for low-temperature preheating. Then, protein paste was coated onto the surface of the preheated ceramic sheet. The ceramic sheet coated with protein paste was sent into a tube furnace and pretreated by heating to 400℃ at 5℃ / min and holding for 2 hours. Then, it was pyrolyzed at 800℃ at 5℃ / min and held for 2 hours. This introduced a hard carbon framework (doped with N, F, S, K, Na, Cl) with a thickness of 2~3μm on the surface of the ceramic sheet, resulting in an oxide solid electrolyte ceramic sheet LLZTO@C with a hard carbon framework introduced on the surface. The XRD pattern is shown in the figure. Figure 1 As shown, the SEM image is as follows: Figure 2 As shown, from Figure 2 It can be seen that the thickness of the hard carbon layer is relatively uniform and it is in very close contact with LLZTO, which is beneficial to reducing the interfacial impedance.

[0097] (3) Assembling the negative electrode lithium metal: The lithium metal sheet was placed on a heating stage and heated to a molten state at 300°C. The modified oxide solid electrolyte ceramic sheet LLZTO@C was then placed into the molten lithium metal and kept at 350°C for a period of time to initiate the lithiation reaction. This resulted in the formation of a mixed conductive intermediate layer containing heteroatom-doped hard carbon framework lithiation products at the interface between the negative electrode and LLZTO. After the molten lithium metal completely wetted the ceramic sheet, it was cooled to obtain the Li|LLZTO@C integrated electrode. All the above operations were carried out in a glove box with a water content of <0.01ppm.

[0098] To investigate the ability of heteroatom-doped hard carbon to suppress lithium dendrite formation, a battery with the structure "Li / mixed conductive interlayer / LLZTO / heteroatom-doped hard carbon" was assembled. Lithium was deposited on the heteroatom-doped hard carbon side, and the capacity increased from 0.1 mAh / cm². -2 Increased to 0.6 mAh cm -2 SEM image as follows Figure 3 As shown, from Figure 3 It can be seen that metallic lithium is deposited in a large spherical morphology on a heteroatom-doped hard carbon framework, with a diameter of approximately 5 μm. The grown lithium cores are uniform and smooth, avoiding whisker-like or dendritic growth; at a capacity of 0.1 mAh cm⁻¹ -2 and 0.3mAh cm -2 At that time, the morphology of the entire substrate consisted of a single layer of large spherical lithium. The nucleated lithium was coated with hard carbon to form a Li@C structure. This carbon-coated structure made the electric field around the lithium nucleus more uniform and promoted the isotropic growth of lithium. This shows that the introduction of heteroatom-doped hard carbon framework can effectively suppress the growth of lithium dendrites. These improvements are mainly due to the effective control of lithium nucleation and subsequent growth processes.

[0099] Assembly of all-solid-state metal-symmetric batteries:

[0100] Similarly, the other side of the LLZTO is processed in the same way as steps (1), (2), and (3) above to obtain a Li / LLZTO@C / Li symmetrical cell, and finally the cell is packaged for testing.

[0101] The current impedance diagram of the assembled symmetrical battery is shown below. Figure 4 As shown, the EIS results indicate that the modified all-solid-state lithium metal symmetric battery has a low interfacial impedance.

[0102] The assembled all-solid-state lithium metal symmetric battery achieves 1.0 mA / cm². 2 The long-term cycling performance at current density is shown in the figure. Figure 5 As shown, the modified all-solid-state lithium metal symmetric battery can achieve a current of 1.0 mA cm⁻¹. -2The modified interface exhibits excellent stability after 2000 hours of stable cycling at high current density, effectively suppressing lithium dendrite growth. The voltage curve remains flat and smooth during cycling, indicating that lithium ions have a rapid kinetic transport channel at the interface.

[0103] The critical current density diagram of the assembled symmetrical cell is shown below. Figure 6 As shown, from Figure 6 It can be seen that the modified all-solid-state lithium metal symmetric battery has an ultra-high critical current density, which is 4.0 mA cm⁻¹. -2 No short circuit occurred even at the current density.

[0104] Cross-sectional images of the interface of the assembled symmetrical cell after long-term cycling, as shown in the scanning electron microscope image. Figure 7 As shown, from Figure 7 It can be seen that the Li / LLZTO solid electrolyte interface still maintains excellent close contact, indicating that it has quite good stability.

[0105] After disassembling the all-solid-state symmetric battery following long-cycle operation and removing metallic lithium, XPS analysis was performed on the hybrid conductive intermediate layer on the surface of the LLZTO ceramic sheet. The results are as follows: Figure 8 As shown, the full spectrum exhibits strong C, O, and F signals and relatively weak Cl, N, and S signals, indicating that the interface of the hybrid conductive interlayer after cycling contains substances such as LiF, Li2CO3, Li3N, and LiCl. This further demonstrates that the doping elements in the hybrid conductive interlayer of the Li|LLZTO@C integrated electrode have achieved lithiation.

[0106] Assembly of semi-solid-state lithium metal batteries:

[0107] Preparation of NCM811 cathode sheet: NCM811 (lithium nickel cobalt manganese oxide) ternary cathode material, conductive carbon, and binder were weighed in a mass ratio of 8:1:1. The above materials were first dry-milled for a period of time to uniformly mix them, and then an appropriate amount of organic solvent NMP was added for wet milling to obtain a uniform slurry. This slurry was coated onto an aluminum foil current collector, baked for a period of time, and then cut into sheets to obtain NCM811 cathode sheets.

[0108] The prepared NCM811 positive electrode, Li|LLZTO@C integrated electrode, and liquid electrolyte (1MLiPF6inDMC:EC:EMC=1:1:1 Vol% with 1%VC) were assembled to obtain a semi-solid-state lithium metal battery.

[0109] The charge-discharge curves of the obtained semi-solid-state lithium metal battery at 0.1C are shown in the figure below. Figure 9 As shown, from Figure 9It can be seen that solid-state lithium metal batteries exhibit excellent charge and discharge performance, further demonstrating their potential for commercial application.

[0110] Example 2

[0111] Assembly of quasi-solid-state lithium metal batteries:

[0112] Preparation of LiFePO4 cathode: LiFePO4, conductive carbon, and binder were weighed in a mass ratio of 8:1:1. The above materials were first dry-milled for a period of time to uniformly mix them, and then an appropriate amount of organic solvent NMP was added for wet milling to obtain a uniform slurry. This slurry was coated onto an aluminum foil current collector, baked for a period of time, and then cut into sheets to obtain the LiFePO4 cathode.

[0113] The prepared LiFePO4 cathode, the Li|LLZTO@C integrated electrode prepared in Example 1, and the polymer solid electrolyte PDOL (poly-1,3-dioxane) were assembled to obtain a quasi-solid-state lithium metal battery.

[0114] The charge-discharge curves of the assembled quasi-solid-state lithium metal battery at 0.1C are shown in the figure below. Figure 10 As shown, from Figure 10 It can be seen that solid-state lithium metal batteries exhibit excellent charge and discharge performance.

[0115] Example 3

[0116] The difference between this embodiment and embodiment 1 is only in step (2), which is as follows: Interface modification: The oxide solid electrolyte LLZTO ceramic sheet is placed on a heating platform for low-temperature preheating. Then, protein cream is coated onto the surface of the preheated ceramic sheet. The ceramic sheet coated with protein cream is sent into a tube furnace and heated directly to 600~1000℃ at 5℃ / min for high-temperature pyrolysis and held for two hours. This introduces a hard carbon framework (doped with N, F, S, K, Na, Cl) with a thickness of 2~3μm on the surface of the ceramic sheet, resulting in an oxide solid electrolyte ceramic sheet LLZTO@C with a hard carbon framework introduced on the surface. Its XRD pattern is shown in the figure. Figure 1 As shown. The remaining steps are the same to obtain an all-solid-state lithium metal symmetric battery.

[0117] Comparing the XRD patterns of the hard carbon frameworks obtained in Examples 1 and 3, it was found that the peak intensity of the (002) peak of the pretreated hard carbon in Example 1 decreased and the position shifted to a lower diffraction angle, indicating that the pretreated hard carbon in Example 1 has a more disordered structure, which greatly improves the ion storage capacity and provides more lithium ion binding sites.

[0118] Comparative Example 1

[0119] The only difference between this comparative example and Example 1 is that the carbon source precursor is phenolic resin and sucrose; phenolic resin and sucrose are mixed in anhydrous ethanol in a certain proportion to form a precursor solution in which phenolic resin and sucrose molecules cross-link.

[0120] The symmetric battery and the all-solid-state lithium metal symmetric battery were assembled using the same method as in Example 1.

[0121] The assembled symmetrical cell operates at 0.1 mA / cm². 2 The long-term cycling performance at current density is shown in the figure. Figure 11 As shown, from Figure 11 It can be seen that the hard carbon framework without heteroatom doping has poor stability, which leads to significant polarization in the all-solid-state lithium metal symmetric battery after 100 hours.

[0122] The critical current density diagram of the assembled symmetrical battery is shown below. Figure 6 As shown, from Figure 6 It can be seen that, compared with the symmetrical battery assembled in Example 1, the symmetrical battery assembled in this comparative example has a lower critical current density, further indicating that the hard carbon framework without heteroatom doping has poor stability. Analysis shows that this is because the doping elements in the mixed conductive layer formed in Example 1 achieved lithiation. The lithilated LiF, Li3N, etc., can reduce the Li-... + The energy barrier for diffusion at the interface, uniform Li + Flux, promoting Li + Uniform deposition at the interface.

[0123] Schematic diagrams of the modification methods in Example 1 and Comparative Example 1 are shown below. Figure 12 As shown in Example 1, as e, f, g, and h, the prepared protein cream was applied to an LLZTO ceramic sheet using a cotton swab. The protein cream solidified on the ceramic sheet, and then the sheet was carbonized in a tube furnace to obtain a ceramic sheet with a hard carbon layer on the surface. Finally, the molten lithium was bonded to the hard carbon layer and lithiation was achieved. As shown in Comparative Example 2, as a, b, c, and d, the prepared mixture was applied to an LLZTO ceramic sheet using a dropper. After carbonization in a tube furnace, a hard carbon layer was obtained on the surface. Finally, the molten lithium was bonded to the hard carbon layer and lithiation was achieved.

[0124] Comparative Example 2

[0125] The material preparation method of this comparative example is basically the same as that of Example 1, except that the thickness of the heteroatom-doped hard carbon framework introduced on the surface of the LLZTO ceramic sheet is about 10 μm.

[0126] Assemble the all-solid-state lithium metal symmetric battery using the same method as in Example 1.

[0127] The assembled symmetrical cell operates at 0.1 mA / cm². 2The long-term cycling performance at current density is shown in the figure. Figure 13 As shown, from Figure 13 It can be seen that the all-solid-state lithium metal symmetric battery exhibits obvious polarization after 580 hours, and the voltage curve shows an "arc shape" in the early stage of cycling. This is because the transport of lithium ions at the interface is blocked, resulting in an ion diffusion concentration gradient. This indicates that the thicker hard carbon framework becomes a blocking layer for lithium ion migration.

[0128] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte, characterized in that, include: An inorganic solid electrolyte sheet is formed on one surface by forming a doped hard carbon layer, thereby obtaining an inorganic solid electrolyte sheet with a doped hard carbon layer on its surface; the doping atoms of the doped hard carbon layer are one or more of N, F, S, and Cl; The process of forming a doped hard carbon layer on the surface of an inorganic solid electrolyte sheet includes: coating a carbon source precursor onto the surface of the inorganic solid electrolyte sheet, and then pyrolyzing it in an argon atmosphere or a nitrogen atmosphere. The carbon source precursor is biomass, or a combination of biomass and at least one selected from sugars and synthetic resins; the biomass is selected from at least one selected from egg white, honey, coconut shell, walnut shell, straw, wood, camellia shell, and bamboo powder. Under vacuum conditions with a water content of <0.01ppm or in an inert gas atmosphere with a water content of <0.01ppm, the lithium metal sheet is first heated to a molten state, and then the side of the inorganic solid electrolyte sheet with the doped hard carbon layer is placed on the molten lithium metal. The lithiation reaction is carried out at a certain temperature to obtain an integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte.

2. The method for preparing the integrated lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte electrode as described in claim 1, characterized in that, The thickness of the doped hard carbon layer is 2~3 μm.

3. The method for preparing the integrated lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte electrode as described in claim 1, characterized in that, The sugars are selected from at least one of starch, glucose, and sucrose; The synthetic resin is selected from at least one of phenolic resin, epoxy resin, and urea-formaldehyde resin.

4. The method for preparing the integrated lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte electrode as described in claim 1, characterized in that, The pyrolysis includes: first performing low-temperature heat treatment at 400~500℃, and then performing high-temperature heat treatment at 600~1000℃.

5. The method for preparing the integrated lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte electrode as described in claim 4, characterized in that, The low-temperature heat treatment lasts for 2-4 hours; the high-temperature heat treatment lasts for 2-4 hours.

6. The method for preparing the integrated lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte electrode as described in claim 1, characterized in that, The temperature of the heated lithium metal sheet is 200~350℃.

7. The method for preparing the integrated lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte electrode as described in claim 1, characterized in that, The insulation temperature is 300~400℃.

8. The method for preparing the integrated lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte electrode as described in claim 1, characterized in that, The inorganic solid electrolyte sheet is one or more of oxide solid electrolytes, halide solid electrolytes, and sulfide solid electrolytes.

9. The method for preparing the integrated lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte electrode as described in claim 1, characterized in that, The inorganic solid electrolyte sheet is selected from one or more of the following: garnet-type oxide solid electrolyte, sodium superion conductor solid electrolyte, lithium superion conductor solid electrolyte, and perovskite solid electrolyte. The garnet-type oxide solid electrolyte is one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium niobium oxide, and lithium gallium lanthanum zirconium oxide. The sodium superionic conductor type solid electrolyte is one or more of lithium titanium aluminum phosphate and lithium germanium aluminum phosphate; The lithium superion conductor type solid electrolyte is one or more of lithium germanium vanadium oxide and lithium germanium phosphorus sulfur. The perovskite-type solid electrolyte is ABO3, wherein A is one or more of Ca, Sr, and La; and B is one or more of Al and Ti.

10. An integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 9.

11. The integrated electrode of lithium metal / mixed conductive intermediate layer / inorganic solid electrolyte as described in claim 10, characterized in that, The device comprises an inorganic solid electrolyte sheet, a mixed conductive intermediate layer, and a lithium metal layer. The mixed conductive intermediate layer is located on one surface of the inorganic solid electrolyte sheet, and the lithium metal layer is located on the surface of the mixed conductive intermediate layer away from the inorganic solid electrolyte sheet. The mixed conductive intermediate layer is a lithiation product of a heteroatom-doped hard carbon framework. The lithiation product of the heteroatom-doped hard carbon framework includes hard carbon and LiC. x And one or more of LiF, Li2S, Li3N, and LiCl.

12. A battery, characterized in that, The battery includes the integrated electrode of lithium metal / hybrid conductive intermediate layer / inorganic solid electrolyte as described in claim 10 or 11, wherein the battery is a semi-solid-state battery, a quasi-solid-state battery, or an all-solid-state battery.

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