A composite material current collector, its preparation method, and a lithium metal battery

Abstract

This invention relates to a composite material current collector, its preparation method, and a lithium metal battery. The composite material current collector comprises a current collector material and an optional solid electrolyte material. The current collector has a bilayer structure: one layer is a three-dimensional electrode structure containing finger-like pores, and the other layer is a dense electrode structure. Batteries assembled using the composite material current collector provided by this invention exhibit superior electrochemical performance, demonstrating higher discharge capacity, greater discharge power, and longer cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of lithium metal battery technology, and relates to a composite material current collector, its preparation method, and a lithium metal battery. Background Technology

[0002] Lithium-ion batteries, currently the most widely used chemical energy source, are limited by their theoretical energy density and can no longer meet the demands of societal development. Lithium metal batteries, with their theoretical energy density more than ten times that of lithium-ion batteries, have the potential to replace lithium-ion batteries as the next generation of primary chemical energy sources, and therefore have received widespread attention and research worldwide.

[0003] A lithium metal battery consists of a positive electrode, a negative electrode, and an electrolyte. Its main difference from a lithium-ion battery is that the active material in the negative electrode is lithium metal. Lithium metal batteries can be classified into aqueous electrolyte lithium metal batteries, organic electrolyte lithium metal batteries, and solid electrolyte lithium metal batteries based on their electrolytes.

[0004] Although organic electrolyte lithium metal batteries have achieved some application results, the instability of organic electrolytes with lithium metal greatly limits the development of this electrolyte system, especially when the specific surface area of ​​the lithium metal used is larger, the more severe the side reactions between the organic electrolyte and lithium metal become. At the same time, electrolyte evaporation and leakage also negatively impact battery safety. However, batteries using solid-state electrolyte systems can effectively solve these problems.

[0005] The performance indicators of solid electrolytes in lithium metal batteries include lithium-ion conductivity, physical stability in contact with lithium metal, and chemical and electrochemical stability. Solid electrolytes already used in lithium metal batteries include polymer electrolytes and inorganic solid electrolytes. Among them, LLZTO, an inorganic solid electrolyte, exhibits high lithium-ion conductivity at room temperature and very high stability in contact with lithium metal. However, poor solid-solid contact between LLZTO and the current collector leads to increased interfacial impedance. Furthermore, because the electrochemical reaction occurs at the three-phase interface of electrolyte-current collector-active material, the insufficient contact sites between the solid electrolyte LLZTO and the current collector limit the battery's discharge capacity and rate performance.

[0006] CN117747928A discloses a solid electrolyte slurry, a composite current collector, and a secondary battery. The solid electrolyte slurry simultaneously contains a conductive agent, a lithium supplement agent, a solid electrolyte, and an aqueous binder, and uses p-hydroxyphenylacetamide as a dispersant, which exhibits excellent dispersion of all components. By coating the aforementioned solid electrolyte slurry and water onto the surface of the current collector, a composite current collector is obtained. The current collector exhibits relatively small fluctuations in internal resistance; however, the contact points between the current collector and the solid electrolyte remain limited, restricting the electrochemical performance of the battery.

[0007] Therefore, designing a better electrode for lithium metal batteries, solving the interface problem between the electrolyte and the current collector, increasing the number of reactive sites, and improving the electrochemical performance of lithium metal batteries have become one of the key research focuses in this field. Summary of the Invention

[0008] The problem the invention aims to solve

[0009] This invention aims to provide a composite material current collector, its preparation method, and a lithium metal battery, particularly a composite material current collector capable of reducing the interfacial impedance between the electrolyte and the current collector. The preparation method of this invention can obtain a three-dimensional structure of the current collector (especially a three-dimensional structure integrating the solid electrolyte and the current collector), which increases the electrochemical reaction sites of the electrode, thereby improving the discharge rate and cycle stability of the electrode, and effectively reducing the interfacial contact impedance between the solid electrolyte and the current collector.

[0010] Solution for solving the problem

[0011] [1] A composite material current collector, comprising a current collector material and an optional solid electrolyte material, wherein the composite material current collector has a double-layer structure, one layer being a three-dimensional electrode structure and the other layer being a dense electrode structure, wherein the three-dimensional electrode structure contains finger-like pores.

[0012] [2] According to the composite material current collector described in [1], wherein,

[0013] The current collector material is a negative electrode current collector material, preferably Cu, Ag or Ni;

[0014] The solid electrolyte material is an inorganic solid electrolyte or a polymer electrolyte, preferably a garnet-type solid electrolyte, and more preferably LLZTO, LLZO or a mixture thereof.

[0015] [3] The composite material current collector according to [1] or [2], wherein the average pore diameter of the finger-shaped pores is 5 to 80 μm, preferably 30 to 70 μm, and more preferably 40 to 50 μm.

[0016] [4] The composite material current collector according to any one of [1] to [3], wherein the overall thickness of the composite material current collector is 10 to 600 μm, preferably 100 to 500 μm, and more preferably 400 to 500 μm.

[0017] [5] The composite material current collector according to any one of [1] to [4], wherein the thickness of the dense electrode structure is 2 to 400 μm, preferably 30 to 200 μm, and more preferably 40 to 60 μm.

[0018] [6] The method for preparing the composite material current collector according to any one of [1] to [5] includes the following steps:

[0019] (1) Using the oxide of the current collector material as the current collector precursor material, the current collector precursor material and the optional solid electrolyte material are mixed and ball-milled to obtain functional powder;

[0020] (2) Mix the solvent, dispersant and binder and ball mill them to obtain a mixed solution;

[0021] (3) The functional powder obtained in step (1) and the mixed solution obtained in step (2) are mixed and ball-milled to obtain slurry X;

[0022] (4) Mix the toner, solvent, dispersant and binder and ball mill them to obtain slurry Y;

[0023] (5) Using a double-layer coating method, slurry X is applied to the upper layer and slurry Y to the lower layer, and then coated onto the surface of a thermoplastic polyester film tape to obtain a preform.

[0024] (6) Place the embryo obtained in step (5) into the flocculant to complete the exchange of solvent and flocculant in the embryo and the solidification of the embryo, and then dry it;

[0025] (7) Soak the product obtained in step (6) in an alcoholic solution of lithium chloride. After soaking, rinse off the excess lithium chloride and then dry it.

[0026] (8) The product obtained in step (7) is sintered in an air atmosphere to remove carbon powder, solvent, dispersant, binder and thermoplastic polyester film tape.

[0027] (9) The product obtained in step (8) is placed in a sealed crucible under a lithium carbonate atmosphere and sintered.

[0028] (10) The product obtained in step (9) is reduced and sintered with hydrogen to obtain a composite material current collector.

[0029] [7] According to the preparation method described in [6], the mass ratio of the solid electrolyte material to the current collector precursor material is 0 to (3:1), preferably 0 to (2:1), and more preferably 1:9 to 1:1.

[0030] [8] According to the preparation method described in [6] or [7], wherein the current collector precursor material comprises at least two kinds of particles with different particle sizes;

[0031] Preferably, among the two types of particles with different sizes, the average particle size of the larger particle is 1 to 20 μm, the particle size ratio of the larger particle to the smaller particle is 5:1 to 40:1, and the mass ratio is 0.1:1 to 3:1.

[0032] More preferably, among the two types of particles with different diameters, the average particle size of the larger particle is 5 to 15 μm, the particle size ratio of the larger particle to the smaller particle is 10:1 to 30:1, and the mass ratio is 0.3:1 to 2:1.

[0033] [9] The preparation method according to any one of [6] to [8], wherein, if a solid electrolyte material is present, the solid electrolyte material comprises at least two kinds of particles with different particle sizes;

[0034] Preferably, among the two types of particles with different sizes, the average particle size of the larger particle is 1 to 20 μm, the particle size ratio of the larger particle to the smaller particle is 5:1 to 40:1, and the mass ratio is 0.1:1 to 3:1.

[0035] More preferably, among the two types of particles with different diameters, the average particle size of the larger particle is 5 to 15 μm, the particle size ratio of the larger particle to the smaller particle is 10:1 to 30:1, and the mass ratio is 0.3:1 to 2:1.

[0036]

[10] According to the preparation method described in [6] or [7], wherein, if a solid electrolyte material is present, the current collector precursor material and the solid electrolyte material are two particles with different particle sizes;

[0037] Preferably, among the two types of particles with different sizes, the average particle size of the larger particle is 1 to 20 μm, the particle size ratio of the larger particle to the smaller particle is 5:1 to 40:1, and the mass ratio is 0.1:1 to 3:1.

[0038] More preferably, among the two types of particles with different diameters, the average particle size of the larger particle is 5 to 15 μm, the particle size ratio of the larger particle to the smaller particle is 10:1 to 30:1, and the mass ratio is 0.3:1 to 2:1.

[0039]

[11] According to the preparation method described in [9], in step (1), the functional powder includes functional powder A and functional powder B; the preparation method of functional powder A is: mixing and ball milling a large-particle-size solid electrolyte material with a small-particle-size current collector precursor material; the preparation method of functional powder B is: mixing and ball milling a large-particle-size current collector precursor material with a small-particle-size solid electrolyte material.

[0040]

[12] The preparation method according to any one of [6] to

[11] , wherein,

[0041] The carbon powder is graphite or carbon black;

[0042] The solvent is NMP or MBA;

[0043] The dispersant is PVP, PVA, or CS;

[0044] The adhesive is PESf, PVDF, or PAN;

[0045] The flocculant is water, ethanol, or acetone.

[0046]

[13] The preparation method according to any one of [6] to

[12] , wherein,

[0047] The drying temperature in step (6) is 60–80°C;

[0048] The drying temperature in step (7) is 60–80°C;

[0049] The sintering temperature in step (8) is 700–900℃;

[0050] The sintering temperature in step (9) is 800–1000℃;

[0051] The sintering temperature in step (10) is 500-800℃.

[0052]

[14] A lithium metal battery comprising a composite material current collector as described in any one of [1] to [5] or a composite material current collector obtained by any one of the preparation methods described in [6] to

[13] .

[0053] The effects of the invention

[0054] This invention provides a composite material current collector (such as a negative electrode current collector) with a specific structure and composition, comprising a current collector material and further comprising a solid electrolyte. This composite material current collector has a three-dimensional structure with uniformly sized finger-like pores, possessing the conductivity of a current collector and the ion-conducting function of a solid electrolyte. Furthermore, it has more electrochemically active sites between itself and metallic lithium, effectively improving the contact efficiency between the current collector and the solid electrolyte and enhancing the discharge performance of the electrode.

[0055] The three-dimensional composite electrode structure with finger-shaped pores provided by this invention allows for adjustment of the size and density of the finger-shaped pores. The axial direction of the finger-shaped pores is perpendicular to the surface of the composite electrode, which facilitates the delivery of the active material, metallic lithium, into the interior of the composite electrode. Furthermore, the close contact between the solid electrolyte and the current collector (such as the negative electrode current collector) forms continuous ion transport channels and electron transport channels, creating a large number of three-phase interfaces and active sites, which can improve the discharge capacity and discharge power of the lithium metal battery.

[0056] Experimental results show that the battery assembled using the composite material current collector provided by this invention has superior electrochemical performance, exhibiting higher discharge capacity, greater discharge power, and longer cycle stability. Attached Figure Description

[0057] Figure 1 This is a flowchart of the preparation process of the composite electrode (composite material current collector) in Example 1.

[0058] Figure 2 This is a schematic diagram of the mechanical ball milling coating process.

[0059] Figure 3 This is a schematic diagram of the double-layer coating method.

[0060] Figure 4 The results of scanning electron microscopy (SEM) observation of the cross-sectional finger-shaped hole structure of the composite electrode prepared in Example 1 are shown.

[0061] Figure 5 The image shows the SEM observation results of the interface between the dense skin layer and the finger-like pore layer of the composite electrode prepared in Example 1.

[0062] Figure 6 The image shows the XRD pattern of the composite electrode prepared in Example 1; the upper image is the XRD pattern of the composite electrode, and * represents the three crystal planes of Cu; the lower image is the standard card of LLZTO. Detailed Implementation

[0063] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0064] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0065] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0066] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0067] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "implementation," etc., refer to specific elements (e.g., features, structures, properties, and / or characteristics) related to that embodiment, which are included in at least one of the embodiments described herein and may or may not be present in other embodiments. Furthermore, it should be understood that these elements may be combined in any suitable manner in various embodiments.

[0068] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0069] In this instruction manual, when "room temperature" or "room temperature" is used, the temperature can be 15-30°C, or more specifically 15-25°C, such as 20°C.

[0070] In this invention, "composite material current collector" is the same as "composite electrode".

[0071] In this invention, "particle size" refers to the average particle size, and "particles with larger particle size" refers to particles with a larger average particle size.

[0072] [Composite material current collector]

[0073] The composite material current collector provided by this invention includes a current collector material and an optional solid electrolyte material. The composite material current collector has a bilayer structure: one layer is a three-dimensional electrode structure, and the other layer is a dense electrode structure. The three-dimensional electrode structure contains finger-like pores. The bilayer structure of the composite material current collector of this invention can be clearly seen using SEM, as shown in the SEM image of the composite material current collector obtained in Example 1. Figure 4 As shown, the upper layer is a three-dimensional electrode structure (containing finger-like pore structures), and the lower layer is a dense electrode structure (also known as a dense skin layer or dense layer).

[0074] In this invention, the three-dimensional electrode structure and the dense electrode structure have the same composition, both consisting of a current collector material and an optional solid electrolyte material. In some embodiments, the three-dimensional electrode structure and the dense electrode structure have the same composition, both consisting of a current collector material and a solid electrolyte material.

[0075] In some embodiments, the composite material current collector provided by the present invention includes a current collector material and a solid electrolyte material.

[0076] In other embodiments, the composite current collector provided by the present invention includes a current collector material (i.e., excluding a solid electrolyte material). Experiments have shown that composite current collectors including a current collector material but excluding a solid electrolyte material can also achieve good results, such as higher discharge power and longer cycle stability.

[0077] In some embodiments, the current collector material is a negative electrode current collector material, such as Cu, Ag, or Ni.

[0078] In some embodiments, the current collector material is a positive electrode current collector material, such as Al, Ag, or Ni.

[0079] In some embodiments, the solid electrolyte material is an inorganic solid electrolyte or a polymer electrolyte, preferably a garnet-type solid electrolyte, such as LLZTO, LLZO, or a mixture thereof.

[0080] In some specific embodiments, the average pore size of the finger-shaped pores in the composite material current collector of the present invention is 5 to 80 μm, preferably 30 to 70 μm, more preferably 40 to 50 μm, such as 10 μm, 20 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 60 μm, 75 μm, etc.

[0081] In some specific embodiments, the overall thickness of the composite material current collector of the present invention is 10–600 μm, preferably 100–500 μm, more preferably 400–500 μm, such as 50 μm, 100 μm, 200 μm, 250 μm, 300 μm, 350 μm, 450 μm, 550 μm, etc. In the present invention, "overall thickness" refers to the thickness of the overall structure of the composite material current collector, that is, the thickness of the overall structure including the three-dimensional electrode structure and the dense electrode structure. In the present invention, the overall thickness of the composite material current collector cannot be too thin; if it is too thin, the three-dimensional structure in the composite material cannot form a sufficient number of reaction sites. At the same time, it cannot be too thick either; if it is too thick, it is not conducive to lithium-ion transport away from the positive electrode.

[0082] In some specific embodiments, the thickness of the dense electrode structure in the composite material current collector of the present invention is 2 to 400 μm, preferably 30 to 200 μm, more preferably 40 to 60 μm, such as 10 μm, 20 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 65 μm, 70 μm, 80 μm, 100 μm, 150 μm, 250 μm, etc.

[0083] [Preparation method of composite material current collector]

[0084] This invention provides a method for preparing the above-mentioned composite material current collector, which includes the following steps:

[0085] (1) Using the oxide of the current collector material as the current collector precursor material, the current collector precursor material and the optional solid electrolyte material are mixed and ball-milled to obtain functional powder;

[0086] (2) Mix the solvent, dispersant and binder and ball mill them to obtain a mixed solution;

[0087] (3) The functional powder obtained in step (1) and the mixed solution obtained in step (2) are mixed and ball-milled to obtain slurry X;

[0088] (4) Mix the toner, solvent, dispersant and binder and ball mill them to obtain slurry Y;

[0089] (5) Using a double-layer coating method, slurry X is applied to the upper layer and slurry Y to the lower layer, and then coated onto the surface of a thermoplastic polyester film tape to obtain a preform.

[0090] (6) Place the embryo obtained in step (5) into the flocculant to complete the exchange of solvent and flocculant in the embryo and the solidification of the embryo, and then dry it;

[0091] (7) Soak the product obtained in step (6) in an alcoholic solution of lithium chloride. After soaking, rinse off the excess lithium chloride and then dry it.

[0092] (8) The product obtained in step (7) is sintered in an air atmosphere to remove carbon powder, solvent, dispersant, binder and thermoplastic polyester film tape.

[0093] (9) The product obtained in step (8) is placed in a sealed crucible under a lithium carbonate atmosphere and sintered.

[0094] (10) The product obtained in step (9) is reduced and sintered with hydrogen to obtain a composite material current collector.

[0095] In some embodiments, when preparing the composite material current collector of the present invention, an oxide of the current collector material is used as the current collector precursor material. In some embodiments, the current collector precursor material is a negative electrode current collector precursor material, such as CuO, Ag2O, or NiO. Correspondingly, the composite material current collector of the present invention can be used as a negative electrode current collector. However, the preparation method of the composite material current collector of the present invention is also applicable to the preparation of positive electrode current collectors; simply replace the current collector precursor material with a positive electrode current collector precursor material. In other embodiments, the current collector precursor material is a positive electrode current collector precursor material, such as Al2O3, NiO, Ag2O, or Ag.

[0096] In some embodiments, the mass ratio of the solid electrolyte material to the current collector precursor material is 0 to (3:1), preferably 0 to (2:1), and more preferably 1:9 to 1:1. For example, this mass ratio can be 1:20, 1:10, 1:5, 1:2, 1.2:1, 1.5:1, etc.

[0097] In some embodiments, the current collector precursor material comprises particles of at least two sizes, for example, particles of a larger size and particles of a smaller size. In some preferred embodiments, among the two particle sizes, the average particle size of the larger particle is 1-20 μm (preferably 5-15 μm, such as 8 μm, 10 μm, 12 μm, etc.), the particle size ratio of the larger particle to the smaller particle is 5:1-40:1 (preferably 10:1-30:1, such as 15:1, 20:1, 25:1, etc., specifically values ​​can be: the average particle size of the larger particle is 10 μm and the average particle size of the smaller particle is 500 nm, the average particle size of the larger particle is 5 μm and the average particle size of the smaller particle is 500 nm, etc.), and the mass ratio is 0.1:1-3:1 (preferably 0.3:1-2:1, such as 0.4:1, 0.5:1, 0.8:1, 1:1, 1.5:1, etc.).

[0098] In some embodiments, the composite current collector contains a solid electrolyte material, which includes at least two different particle sizes, for example, particles of two sizes, namely, larger particles and smaller particles. In some preferred embodiments, among the two particle sizes, the average particle size of the larger particle is 1-20 μm (preferably 5-15 μm, such as 8 μm, 10 μm, 12 μm, etc.), the particle size ratio of the larger particle to the smaller particle is 5:1-40:1 (preferably 10:1-30:1, such as 15:1, 20:1, 25:1, etc., specifically values ​​can be: the average particle size of the larger particle is 10 μm and the average particle size of the smaller particle is 500 nm, the average particle size of the larger particle is 5 μm and the average particle size of the smaller particle is 500 nm, etc.), and the mass ratio is 0.1:1-3:1 (preferably 0.3:1-2:1, such as 0.4:1, 0.5:1, 0.8:1, 1:1, 1.5:1, etc.).

[0099] In some embodiments, the composite material current collector contains a solid electrolyte material. That is, the composite material current collector provided by this invention includes a current collector material and a solid electrolyte material. The current collector precursor material and the solid electrolyte material are particles of two different sizes: larger-diameter particles and smaller-diameter particles. In this embodiment, the larger-diameter particles can be either the current collector precursor material or the solid electrolyte material; the smaller-diameter particles can also be either the solid electrolyte material or the current collector precursor material. In some preferred embodiments, among the two particle sizes, the average particle size of the larger particle is 1-20 μm (preferably 5-15 μm, such as 8 μm, 10 μm, 12 μm, etc.), the particle size ratio of the larger particle to the smaller particle is 5:1-40:1 (preferably 10:1-30:1, such as 15:1, 20:1, 25:1, etc., specifically values ​​can be: the average particle size of the larger particle is 10 μm and the average particle size of the smaller particle is 500 nm, the average particle size of the larger particle is 5 μm and the average particle size of the smaller particle is 500 nm, etc.), and the mass ratio is 0.1:1-3:1 (preferably 0.3:1-2:1, such as 0.4:1, 0.5:1, 0.8:1, 1:1, 1.5:1, etc.).

[0100] In some implementations, in step (1), the solid electrolyte material includes at least two types of particles with different particle sizes, namely, a large-particle-size solid electrolyte material and a small-particle-size solid electrolyte material, and the current collector precursor material includes at least two types of particles with different particle sizes, namely, a large-particle-size current collector precursor material and a small-particle-size current collector precursor material.

[0101] In some preferred embodiments, in step (1), the functional powder comprises functional powder A and functional powder B; the preparation method of functional powder A is: mixing and ball milling a large-particle-size solid electrolyte material with a small-particle-size current collector precursor material; the preparation method of functional powder B is: mixing and ball milling a large-particle-size current collector precursor material with a small-particle-size solid electrolyte material.

[0102] In the preparation method of this invention, all materials are mixed by ball milling (mechanical ball milling). Ultrasonic or stirring methods are not suitable for this invention. First, the materials in this invention have varying densities; mixing them by ultrasound or stirring will result in sedimentation, leading to uneven mixing. Second, the preparation method of this invention involves a large amount of solid material. After mixing solid and liquid materials, the resulting slurry is quite viscous, and ultrasonic or stirring methods will also result in uneven mixing. Furthermore, ball milling can coat the two types of particles. In this invention, the mechanical ball milling coating process is described below. Figure 2Mechanical ball milling can ball-mill and coat particles of two different sizes to obtain mechanically coated particles in which the coated particles (smaller size) coat the main particles (larger size). In some embodiments of the present invention, the functional powder contains particles of two different sizes, which can play a supporting role in the composite material current collector structure.

[0103] In this invention, the rotation speed of the ball mill is not particularly limited, as long as it can make the material mix evenly and fully coat it. The rotation speed of the ball mill can be 100 to 500 RPM, such as 200 RPM, 300 RPM, 400 RPM, etc.

[0104] In this invention, the ball milling time is not particularly limited, as long as the material is mixed evenly and fully coated. The ball milling time can be 30 min to 48 h, for example, 30 min, 40 min, 1 h, 4 h, 8 h, 10 h, 20 h, 24 h, 30 h, 40 h, etc.

[0105] In some embodiments, the solvent used in this invention may be NMP (N-methylpyrrolidone), MBA (N,N'-methylenebisacrylamide), etc.

[0106] In some embodiments, the dispersant used in this invention may be PVP (polyvinylpyrrolidone), PVA (polyvinyl alcohol), CS (chitosan), etc.

[0107] In some embodiments, the adhesive used in this invention can be PESf (polyphenylene ether sulfone), PVDF (polyvinylidene fluoride), PAN (polyacrylonitrile), etc.

[0108] In some implementations, in step (2), the mass of the solvent is 0.5 to 2 times that of the functional powder in step (1), for example, 0.6 times, 0.7 times, 0.75 times, 0.8 times, 0.9 times, 1 time, 1.5 times, etc.

[0109] In some implementations, in step (2), the mass of the dispersant is 0.01 to 0.2 times that of the functional powder in step (1), for example, 0.02 times, 0.03 times, 0.05 times, 0.08 times, 0.1 times, 0.12 times, 0.15 times, etc.

[0110] In some implementations, in step (2), the mass of the adhesive is 0.01 to 0.5 times that of the functional powder in step (1), for example, 0.03 times, 0.05 times, 0.07 times, 0.09 times, 0.1 times, 0.15 times, 0.2 times, etc.

[0111] In this invention, the type of toner is not particularly limited; any type of toner is applicable. In some embodiments, the toner of this invention can be graphite, carbon black, etc. In some embodiments, in step (4), the mass of the toner is 0.1 to 2 times that of the functional powder in step (1), for example, 0.2 times, 0.3 times, 0.4 times, 0.6 times, 0.8 times, 1 time, 1.5 times, etc.

[0112] In some implementations, in step (4), the mass of the solvent is 0.5 to 2 times that of the functional powder in step (1), for example, 0.6 times, 0.7 times, 0.75 times, 0.8 times, 0.9 times, 1 time, 1.5 times, etc.

[0113] In some implementations, in step (4), the mass of the dispersant is 0.01 to 0.2 times that of the functional powder in step (1), for example, 0.02 times, 0.03 times, 0.05 times, 0.08 times, 0.1 times, 0.12 times, 0.15 times, etc.

[0114] In some implementations, in step (4), the mass of the adhesive is 0.01 to 0.5 times that of the functional powder in step (1), for example, 0.03 times, 0.04 times, 0.05 times, 0.07 times, 0.09 times, 0.1 times, 0.15 times, 0.2 times, etc.

[0115] In this invention, the size and density of the finger pores can be controlled by adjusting the ratio of solvent, dispersant, and binder, thus controlling the phase transformation process. For example, compared to Example 1, increasing the ratio of solvent, dispersant, and binder in Example 4 (compared to functional powder) can significantly increase the pore size of the finger pores.

[0116] In some implementations, steps (3) and (4) require degassing of slurry X and slurry Y. In some specific implementations, vacuum degassing can be used to degas slurry X and slurry Y, for example, in a vacuum oven; the degassing temperature can be 60–100°C, for example 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, etc.; the degassing time can be 40–70 min, for example 40 min, 50 min, 60 min, etc.

[0117] In this invention, a double-layer coating method is used to uniformly coat slurry X and slurry Y onto the surface of a thermoplastic polyester film strip. In some embodiments, in step (5), the thermoplastic polyester can be PET (polyethylene terephthalate), PBT (polybutylene terephthalate), etc. Figure 3 As shown, a film scraper (film scraper) is used in conjunction with a double-layer doctor blade and a double-head casting mold to apply an electrolyte-current collector precursor composite slurry (slurry X) onto the upper layer and slurry Y (as shown in the image). Figure 3The graphite slurry in the middle is in the lower layer, and the two layers are evenly coated on the surface of the PET film.

[0118] In some implementations, in step (5), the heights of the double-layer scrapers are 50–300 μm for the upper layer (e.g., 100 μm, 150 μm, 200 μm, 250 μm, 280 μm, etc.) and 360–600 μm for the lower layer (e.g., 400 μm, 450 μm, 500 μm, 550 μm, 580 μm, etc.).

[0119] In step (6) of this invention, the embryo is placed in a flocculant, allowing the solvent in the embryo to undergo a phase transition with the flocculant. In some embodiments, the flocculant can be water, ethanol, acetone, etc. In some embodiments, the embryo is placed in the flocculant for 8 to 12 hours, for example, 9 hours, 10 hours, 11 hours, etc.

[0120] In some implementations, in step (6), the drying temperature is 60-80°C, such as 70°C, 75°C, 80°C, etc.; the drying time is 24-36h, such as 24h, 30h, etc.

[0121] In some embodiments, the soaking time of lithium chloride in the alcohol solution in step (7) is 0.5 to 1.5 hours, for example, 1 hour. In some specific embodiments, the mass concentration of the lithium chloride alcohol solution can be 5% to 40%, for example, 8%, 10%, 15%, 20%, 30%, etc. In some specific embodiments, the alcohol in the lithium chloride alcohol solution can be ethanol, methanol, n-propanol, or isopropanol, etc.

[0122] In this invention, the role of lithium chloride in step (7) is to provide a lithium environment for the product obtained in step (6), which can replenish lithium and prevent lithium loss.

[0123] In some implementations, after soaking in step (7), excess lithium chloride can be rinsed off with ammonia. In step (7), lithium chloride is chosen because, in addition to the above-mentioned effects, it is also easy to remove. For example, ammonia and excess lithium chloride can form ammonium chloride, which is then decomposed at high temperature in subsequent steps to remove chloride ions without affecting the purity of the product.

[0124] In some implementations, in step (7), the drying temperature is 60-80°C, such as 70°C, 75°C, 80°C, etc.; the drying time is 10-16h, such as 12h, 14h, etc.

[0125] In some implementations, the sintering temperature in step (8) is 700–900°C, such as 750°C, 800°C, 850°C, 880°C, etc. The sintering time is 4–8 hours, such as 5 hours, 6 hours, 7 hours, etc.

[0126] In some implementations, the sintering temperature in step (9) is 800–1000°C, such as 850°C, 900°C, 950°C, 990°C, etc. The sintering time is 2–4 hours, such as 2 hours, 3 hours, 4 hours, etc.

[0127] In this invention, the role of lithium carbonate in step (9) is to provide a lithium environment for the product obtained in step (8), which can replenish lithium and prevent lithium loss. In addition to the above-mentioned functions, the carbonate ions in lithium carbonate are also easily decomposed under high temperature conditions, thus not affecting the purity of the product.

[0128] In some implementations, the sintering temperature in step (10) is 500–800°C, such as 600°C, 700°C, 750°C, 780°C, etc. The sintering time is 2–4 hours, such as 2 hours, 3 hours, 4 hours, etc.

[0129] In some implementations, the temperature is lowered to room temperature after sintering in steps (8) to (10).

[0130] In some implementations, the heating rate can be 2-3°C / min, and the cooling rate can be 2-3°C / min.

[0131] In some implementations, the sintering in steps (8) through (10) can be carried out in a muffle furnace.

[0132] In this invention, the sintering in step (8) oxidizes and decomposes carbon powder, solvent, binder, dispersant, thermoplastic polyester film tape, etc., thereby removing the Y layer and film tape. The remaining X layer is then sintered in step (9) to obtain a double-layer structure containing a dense skin layer and a three-dimensional structure layer with finger pores. The sintering in step (10) is carried out in a hydrogen atmosphere to reduce the current collector precursor material (i.e., the oxide of the current collector material, such as CuO) to the current collector material (i.e., a metallic element, such as Cu). In some embodiments, the hydrogen atmosphere can be a pure hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas. In some embodiments, the inert gas can be argon, helium, nitrogen, etc. In some embodiments, the volume fraction of hydrogen in the mixed gas of hydrogen and inert gas can be 2%-50%, for example 5%, 10%, 15%, 20%, 30%, 40%, etc.

[0133] In this invention, the composite layer structure of layer X and layer Y prevents the current collector from breaking during drying and sintering. Layer Y provides support for layer X and has a certain degree of viscosity, allowing layer X to adhere well to its surface and ensuring that layer X can be smoothly coated onto the surface of layer Y. Furthermore, layer Y controls the depth of phase transformation in layer X, preventing finger-like pores from penetrating layer X and allowing a dense skin layer to form at the bottom of layer X. Without layer Y, the finger-like pores would penetrate layer X, preventing the formation of a dense skin layer.

[0134] [Lithium metal battery]

[0135] Furthermore, the present invention also provides a lithium metal battery comprising the aforementioned composite material current collector or a composite material current collector obtained by the aforementioned preparation method. In some specific embodiments, the lithium metal battery is assembled from the aforementioned composite material current collector or a composite material current collector obtained by the aforementioned preparation method.

[0136] The above-mentioned lithium metal battery can be prepared by assembling the above-mentioned composite material current collector, insulating membrane and lithium sheet, and depositing metallic lithium on the above-mentioned composite material current collector.

[0137] In some specific implementations, an electrolyte is added dropwise to the insulating diaphragm. The electrolyte can be a LiTFSI DME (ethylene glycol dimethyl ether) solution with a concentration of 0.5–2 mol / L, for example, 1 mol / L.

[0138] In some specific implementations, metallic lithium can be deposited on the aforementioned composite material current collector by electrochemical deposition.

[0139] Example

[0140] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0141] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention and not for limiting the claims of the present invention.

[0142] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0143] There are no particular restrictions on the purity of any of the raw materials used in this invention. It is preferred to use analytical grade or conventional purity in the field of lithium metal batteries.

[0144] To further illustrate this, the following detailed description of a composite material current collector and its preparation method, as well as a lithium metal battery, provided by the present invention, is provided in conjunction with embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are given only to further illustrate the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0145] Example 1

[0146] This embodiment provides a three-dimensional composite material current collector (composite electrode) and its preparation method, as well as a lithium metal battery, including the following steps:

[0147] S1. Fabrication process of composite electrodes (e.g.) Figure 1 As shown):

[0148] S1-1. Preparation of mixed powders for composite electrodes: 1.5g of LLZTO powder with an average particle size of 10μm (i.e., large-particle-size electrolyte powder) and 13.5g of CuO powder with an average particle size of 500nm (i.e., small-particle-size current collector powder) were mixed and ball-milled for mechanical coating (300RPM) for 40min to obtain powder A; 13.5g of CuO powder with an average particle size of 10μm (i.e., large-particle-size current collector powder) and 1.5g of LLZTO powder with an average particle size of 500nm (i.e., small-particle-size electrolyte powder) were mixed and ball-milled for mechanical coating (300RPM) for 40min to obtain powder B;

[0149] S1-2. Mix 22.75g of solvent NMP, 2.73g of binder PESf and 1.1g of dispersant PVP and ball mill (300RPM) for 4h to obtain a homogeneous solution;

[0150] S1-3. Take 15g of powder A and 15g of powder B, add them to the above mixed solution, and continue ball milling (300RPM) for 30h to obtain a uniform slurry X (i.e., composite powder slurry);

[0151] S1-4. Mix 9.87g graphite powder, 23.03g solvent NMP, 1.3g binder PESf and 0.8g dispersant PVP and ball mill (300RPM) for 24h to obtain a uniform slurry Y (i.e., toner slurry);

[0152] S1-5. Place slurry X and slurry Y into a vacuum oven and degas at 80°C for 40 minutes; use a film scraper and a double-headed scraper to cast slurry X and slurry Y in double layers onto a PET film strip, with film thicknesses of 300μm and 600μm respectively.

[0153] S1-6. The product after film scraping (i.e., composite powder / carbon powder double-layer green body) is quickly immersed in water as a flocculant for phase transformation and soaked for 10 hours; the product is taken out, air-dried at room temperature, and placed in a vacuum oven to dry at 80°C for 24 hours.

[0154] S1-7. Soak the dried product in 40 mL of 10% by mass lithium chloride ethanol solution for 1.5 h, then rinse off the excess lithium chloride with 25% ammonia water, and put it in an oven to dry at 80 °C for 12 h.

[0155] S1-8. The dried product is placed in a muffle furnace and kept at 850℃ for 6 hours in an air atmosphere to remove carbon (oxidative decomposition of carbon powder, solvent, binder and dispersant), and then cooled to room temperature at a rate of 3℃ / min.

[0156] S1-9. Place the decarbonized product in a sealed crucible in a lithium carbonate atmosphere, place the sealed crucible in a muffle furnace, and use an air atmosphere to heat and sinter at 975°C for 3 hours to obtain a dense skin layer / finger pore double-layer structure of the composite powder. Then cool to room temperature at a heating and cooling rate of 3°C / min.

[0157] S1-10. Place the product in an atmosphere furnace and reduce it at 750°C for 3 hours using a 5 vol% hydrogen-95 vol% argon atmosphere to reduce the current collector powder to elemental metal. Then cool it to room temperature at a heating / cooling rate of 3°C / min. Clean and dry the product to obtain the electrolyte-current collector composite electrode.

[0158] The composite electrode with the obtained three-dimensional structure was removed, and SEM testing was performed on the resulting composite electrode. The observation results are shown in [Figure number missing]. Figure 4 and Figure 5 This indicates that the composite electrode has a two-layer structure, namely a three-dimensional electrode structure containing finger-like pores and a dense electrode structure (dense layer), with uniform pore size. The overall thickness of the composite electrode is 433 μm, the thickness of the dense layer is 58.8 μm, and the average pore size of the finger-like pores is 44.1 μm.

[0159] The composite electrode was subjected to XRD analysis, and the results are shown below. Figure 6 The results showed that the composite electrode was composed of LLZTO and Cu with high purity.

[0160] S2. Preparation of lithium metal batteries:

[0161] S2-1. Assemble a battery by sequentially adding a composite electrode, an insulating membrane with 60 μL of electrolyte (1 mol / L LiTFSI dissolved in DME), and a lithium sheet. Deposit metallic lithium onto the composite electrode using an electrochemical deposition method to obtain a lithium metal battery.

[0162] Example 2

[0163] The difference between this embodiment and Embodiment 1 is that in step S1-1, the mixed powder for preparing the composite electrode is prepared by mixing and ball milling 7.5g of LLZTO powder with an average particle size of 10μm and 7.5g of CuO powder with an average particle size of 500nm for 40min to obtain powder A; and mixing and ball milling 7.5g of CuO powder with an average particle size of 10μm and 7.5g of LLZTO powder with an average particle size of 500nm for 40min to obtain powder B.

[0164] The overall thickness of the resulting composite electrode is 429 μm, the thickness of the dense layer is 58.3 μm, and the average pore size of the finger pores is 47.5 μm.

[0165] Example 3

[0166] The difference between this embodiment and Embodiment 1 is that in step S1-1, the mixed powder for preparing the composite electrode is prepared by mixing 4.5g of LLZTO powder with an average particle size of 10μm and 10.5g of CuO powder with an average particle size of 500nm and ball milling for 40min to obtain powder A; and mixing 4.5g of CuO powder with an average particle size of 10μm and 10.5g of LLZTO powder with an average particle size of 500nm and ball milling for 40min to obtain powder B.

[0167] The overall thickness of the resulting composite electrode is 435 μm, the thickness of the dense layer is 57.2 μm, and the average pore size of the finger pores is 45.6 μm.

[0168] Example 4

[0169] The difference between this embodiment and Embodiment 1 is that in step S1-1, the mixed powder for preparing the composite electrode is prepared by mixing 4.5g of LLZTO powder with an average particle size of 10μm and 10.5g of CuO powder with an average particle size of 500nm and ball milling for 40min to obtain powder A, without using powder B.

[0170] The overall thickness of the resulting composite electrode is 430 μm, the thickness of the dense layer is 49.2 μm, and the average pore size of the finger pores is 60.8 μm.

[0171] Example 5

[0172] The difference between this embodiment and Embodiment 1 is that the powder used to prepare the electrode in step S1-1 does not contain solid electrolyte components, but only current collector precursor components.

[0173] The overall thickness of the obtained electrode is 440 μm, the thickness of the dense layer is 47.8 μm, and the average pore size of the finger pores is 62.2 μm.

[0174] Example 6

[0175] The difference between this embodiment and Embodiment 1 is that in step S1-1, the mixed powder for preparing the composite electrode is prepared by: mixing and ball milling 13.5g of CuO powder with an average particle size of 500nm (300RPM) for 40min to obtain powder A; and mixing and ball milling 13.5g of LLZTO powder with an average particle size of 500nm (300RPM) for 40min to obtain powder B.

[0176] The overall thickness of the resulting composite electrode is 432 μm, the thickness of the dense layer is 48.8 μm, and the average pore size of the finger pores is 40.6 μm.

[0177] Comparative Example 1

[0178] The difference between this comparative example and Example 1 is that step S1 is omitted, and copper foil is used instead of composite electrodes in step S2-1 to assemble the battery.

[0179] Performance testing

[0180] The lithium metal batteries prepared in Examples 1-5 and Comparative Example 1 were subjected to rate charge / discharge tests, long-cycle stability tests, and coulombic efficiency tests using a blue electric field tester. The test rates of the batteries ranged from 0.5C to 8C (1C = 1 mA / cm²). 2 The test voltage range was -1 to 1V, and the cycle length was 10 to 400 times. The test results are shown in Table 1. The cycle stability in Table 1 refers to the stability of the battery's charge and discharge voltage within the specified cycle. Beyond this cycle, the voltage difference between the charge and discharge voltages continuously increases, eventually leading to battery failure.

[0181] Table 1 Performance test results of lithium metal batteries

[0182] Examples / Comparative Examples Rate performance (5 cycles) Coulomb efficiency maintained (≥97%) Cyclic stability Example 1 8C 88 cycles 289 cycles Example 2 4C 66 cycles 342 cycles Example 3 4C 63 cycles 134 cycles Example 4 4C 57 cycles 146 cycles Example 5 4C 46 cycles 225 cycles Example 6 4C 48 cycles 137 cycles Comparative Example 1 4C 10 cycles 134 cycles

[0183] Experimental results show that the battery assembled using the composite material current collector provided by this invention (e.g., Example 1) can increase the discharge capacity by 2 times or more compared to the conventional current collector; the long-term cycle stability is significantly improved, even by more than 2 times; the battery assembled using the composite material current collector provided by this invention can maintain a coulombic efficiency of over 97% after more than 40 cycles (even more than 80 cycles). Therefore, the battery assembled using the composite material current collector provided by this invention exhibits significantly improved electrochemical performance compared to the battery assembled using the conventional current collector.

[0184] It should be noted that although the technical solution of the present invention has been described with specific examples, those skilled in the art will understand that the present invention should not be limited thereto.

[0185] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A composite material current collector, comprising a current collector material and a solid electrolyte material, wherein the composite material current collector has a double-layer structure, one layer being a three-dimensional electrode structure and the other layer being a dense electrode structure, the three-dimensional electrode structure containing finger-like pores, the current collector material being Cu, Ag, or Ni, and the solid electrolyte material being a garnet-type solid electrolyte; the preparation method of the composite material current collector includes the following steps: (1) Using the oxide of the current collector material as the current collector precursor material, the current collector precursor material and the solid electrolyte material are mixed and ball-milled to obtain functional powder; (2) The solvent, dispersant and binder are mixed and ball-milled to obtain a mixed solution; (3) The functional powder obtained in step (1) and the mixed solution obtained in step (2) are mixed and ball-milled to obtain slurry X; (4) Mix the toner, solvent, dispersant and binder and ball mill to obtain slurry Y; (5) Using a double-layer coating method, slurry X is applied to the upper layer and slurry Y to the lower layer, and then coated onto the surface of a thermoplastic polyester film tape to obtain a preform; (6) Place the embryo obtained in step (5) into the flocculant to complete the exchange of solvent and flocculant in the embryo and the solidification of the embryo, and then dry it; (7) Soak the product obtained in step (6) in an alcoholic solution of lithium chloride. After soaking, rinse off the excess lithium chloride and then dry it. (8) The product obtained in step (7) is sintered in an air atmosphere to remove carbon powder, solvent, dispersant, binder and thermoplastic polyester film tape; (9) The product obtained in step (8) is placed in a sealed crucible under a lithium carbonate atmosphere and sintered. (10) The product obtained in step (9) is reduced and sintered with hydrogen to obtain a composite material current collector.

2. The composite material current collector according to claim 1, characterized in that, The solid electrolyte material is LLZTO, LLZO, or a mixture of the two.

3. The composite material current collector according to claim 1, characterized in that, The average diameter of the finger-shaped pores is 5~80μm.

4. The composite material current collector according to claim 3, characterized in that, The average diameter of the finger-shaped pores is 30~70 μm.

5. The composite material current collector according to claim 4, characterized in that, The average diameter of the finger-shaped pores is 40~50 μm.

6. The composite material current collector according to any one of claims 1 to 5, characterized in that, The overall thickness of the composite material current collector is 10~600 μm.

7. The composite material current collector according to claim 6, characterized in that, The overall thickness of the composite material current collector is 100~500 μm.

8. The composite material current collector according to claim 7, characterized in that, The overall thickness of the composite material current collector is 400~500 μm.

9. The composite material current collector according to any one of claims 1 to 5, characterized in that, The thickness of the dense electrode structure is 2~400 μm.

10. The composite material current collector according to claim 9, characterized in that, The thickness of the dense electrode structure is 30~200 μm.

11. The composite material current collector according to claim 10, characterized in that, The thickness of the dense electrode structure is 40~60 μm.

12. A method for preparing a composite material current collector according to any one of claims 1 to 11, comprising the following steps: (1) Using the oxide of the current collector material as the current collector precursor material, the current collector precursor material and the solid electrolyte material are mixed and ball-milled to obtain functional powder; (2) The solvent, dispersant and binder are mixed and ball-milled to obtain a mixed solution; (3) The functional powder obtained in step (1) and the mixed solution obtained in step (2) are mixed and ball-milled to obtain slurry X; (4) Mix the toner, solvent, dispersant and binder and ball mill to obtain slurry Y; (5) Using a double-layer coating method, slurry X is applied to the upper layer and slurry Y to the lower layer, and then coated onto the surface of a thermoplastic polyester film tape to obtain a preform; (6) Place the embryo obtained in step (5) into the flocculant to complete the exchange of solvent and flocculant in the embryo and the solidification of the embryo, and then dry it; (7) Soak the product obtained in step (6) in an alcoholic solution of lithium chloride. After soaking, rinse off the excess lithium chloride and then dry it. (8) The product obtained in step (7) is sintered in an air atmosphere to remove carbon powder, solvent, dispersant, binder and thermoplastic polyester film tape; (9) The product obtained in step (8) is placed in a sealed crucible under a lithium carbonate atmosphere and sintered. (10) The product obtained in step (9) is reduced and sintered with hydrogen to obtain a composite material current collector.

13. The preparation method according to claim 12, characterized in that, The mass ratio of the solid electrolyte material to the current collector precursor material is 1:20 to 3:

1.

14. The preparation method according to claim 13, characterized in that, The mass ratio of the solid electrolyte material to the current collector precursor material is 1:20 to 2:

1.

15. The preparation method according to claim 14, characterized in that, The mass ratio of the solid electrolyte material to the current collector precursor material is 1:9 to 1:

1.

16. The preparation method according to any one of claims 12 to 15, characterized in that, The current collector precursor material comprises particles of at least two different sizes.

17. The preparation method according to claim 16, characterized in that, Among the two types of particles with different diameters, the average diameter of the larger particle is 1~20 μm, the diameter ratio of the larger particle to the smaller particle is 5:1~40:1, and the mass ratio is 0.1:1~3:

1.

18. The preparation method according to claim 17, characterized in that, Among the two types of particles with different diameters, the average diameter of the larger particle is 5-15 μm, the diameter ratio of the larger particle to the smaller particle is 10:1-30:1, and the mass ratio is 0.3:1-2:

1.

19. The preparation method according to any one of claims 12 to 15, characterized in that, The solid electrolyte material comprises particles of at least two different sizes.

20. The preparation method according to claim 19, characterized in that, Among the two types of particles with different diameters, the average diameter of the larger particle is 1~20 μm, the diameter ratio of the larger particle to the smaller particle is 5:1~40:1, and the mass ratio is 0.1:1~3:

1.

21. The preparation method according to claim 20, characterized in that, Among the two types of particles with different diameters, the average diameter of the larger particle is 5-15 μm, the diameter ratio of the larger particle to the smaller particle is 10:1-30:1, and the mass ratio is 0.3:1-2:

1.

22. The preparation method according to claim 16, characterized in that, The solid electrolyte material comprises particles of at least two different sizes.

23. The preparation method according to claim 22, characterized in that, Among the two types of particles with different diameters, the average diameter of the larger particle is 1~20 μm, the diameter ratio of the larger particle to the smaller particle is 5:1~40:1, and the mass ratio is 0.1:1~3:

1.

24. The preparation method according to claim 23, characterized in that, Among the two types of particles with different diameters, the average diameter of the larger particle is 5-15 μm, the diameter ratio of the larger particle to the smaller particle is 10:1-30:1, and the mass ratio is 0.3:1-2:

1.

25. The preparation method according to any one of claims 12 to 15, characterized in that, The current collector precursor material and the solid electrolyte material are two different particle sizes.

26. The preparation method according to claim 25, characterized in that, Among the two types of particles with different diameters, the average diameter of the larger particle is 1~20 μm, the diameter ratio of the larger particle to the smaller particle is 5:1~40:1, and the mass ratio is 0.1:1~3:

1.

27. The preparation method according to claim 26, characterized in that, Among the two types of particles with different diameters, the average diameter of the larger particle is 5-15 μm, the diameter ratio of the larger particle to the smaller particle is 10:1-30:1, and the mass ratio is 0.3:1-2:

1.

28. The preparation method according to any one of claims 22 to 24, characterized in that, In step (1), the functional powder includes functional powder A and functional powder B; the preparation method of functional powder A is: mixing and ball milling a large-particle-size solid electrolyte material with a small-particle-size current collector precursor material; the preparation method of functional powder B is: mixing and ball milling a large-particle-size current collector precursor material with a small-particle-size solid electrolyte material.

29. The preparation method according to any one of claims 12 to 15, characterized in that, The carbon powder is graphite or carbon black; The solvent is N-methylpyrrolidone; The dispersant is polyvinylpyrrolidone, polyvinyl alcohol, or chitosan; The adhesive is polyphenylene ether sulfone, polyvinylidene fluoride, or polyacrylonitrile; The flocculant is water, ethanol, or acetone.

30. The preparation method according to any one of claims 12 to 15, characterized in that, The drying temperature in step (6) is 60~80℃; The drying temperature in step (7) is 60~80℃; The sintering temperature in step (8) is 700~900℃; The sintering temperature in step (9) is 800~1000℃; The sintering temperature in step (10) is 500~800℃.

31. A lithium metal battery comprising a composite material current collector as described in any one of claims 1 to 11 or a composite material current collector obtained by the preparation method described in any one of claims 12 to 30.

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