Lithium ion battery negative electrode material and preparation method thereof

Abstract

The application provides a lithium ion battery negative electrode material and a preparation method thereof, and relates to the technical field of lithium ion batteries. The lithium ion battery negative electrode material comprises a negative electrode material base body and a conductive agent-polymer composite powder coating layer coated on the surface of the negative electrode material base body; the conductive agent-polymer composite powder coating layer is composed of an amorphous carbon base body and a conductive agent uniformly dispersed and anchored in the amorphous carbon base body, forming a continuous conductive network structure. The coating layer is derived from the "conductive agent-polymer composite powder". The polymer is a solid hard particle before heat treatment. During heat treatment, the polymer does not melt and flow, but directly pyrolyzes and carbonizes, directly changing from a solid particle to a solid amorphous carbon base body. The uneven distribution and agglomeration caused by the liquid phase flow of the coating agent are avoided. The uniformity and structural stability are ensured, and the material makes the production process simple and has high universality.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a lithium-ion battery anode material and its preparation method. Background Technology

[0002] With the increasing demand for high-power charging and discharging in electric vehicles and portable electronic devices, the development of lithium-ion batteries with excellent fast-charging performance has become a research hotspot. As a core component of the battery, the performance of the anode material is crucial. Graphite anodes are widely used due to their high theoretical capacity and stable cycle performance, but their inherent layered structure limits the rapid insertion and extraction of lithium ions, making it difficult to meet fast-charging requirements. To overcome this limitation, surface modification of graphite anodes has become an effective strategy. By constructing a uniform and highly conductive coating layer on the surface of graphite particles, interfacial stability can be effectively improved, electrolyte decomposition can be suppressed, and ion and electron transport rates can be enhanced, thereby significantly improving the fast-charging performance and cycle life of the material.

[0003] Currently, various coating modification schemes for graphite anode materials have been proposed in existing technologies. However, while pursuing high performance, the complexity of the process, cost, and environmental issues are becoming increasingly prominent. For example, one existing technology employs a graphene doping and stepwise fusion coating scheme, the core of which lies in using graphene-modified asphalt to coat graphite aggregates in multiple rounds and heat-treat. However, this technology has significant shortcomings: First, the production process is lengthy, involving multiple independent mixing, fusion, and heat treatment steps, resulting in large equipment investment, high energy consumption, and numerous process control points, increasing production uncertainty and cost. Second, the solid-phase asphalt coating method used is difficult to achieve uniform dispersion during industrial mixing, easily causing problems such as uneven coating layer thickness and asphalt agglomeration and adhesion, ultimately affecting the consistency of product performance.

[0004] Existing technologies include schemes that attempt to improve the uniformity of coating. These schemes employ a liquid-phase coating method, where coating agents such as asphalt or resin are preheated and then blended with conductive agents and dispersants to form a modified liquid-phase system, which is then used to coat graphite aggregates. While this approach improves the uniformity of the coating layer to some extent, it also introduces new problems. The process requires additional solvents, dispersants, and preheating steps, making the process more complex. Furthermore, the use of solvents may lead to volatile organic compound emissions and subsequent recycling issues, posing environmental risks. In addition, the conductive agent still carries the risk of agglomeration during subsequent carbonization, potentially affecting the continuity and stability of the conductive network in the coating layer.

[0005] Therefore, there is an urgent need to provide a lithium-ion battery anode material and its preparation method, which can meet the requirements of simple and efficient process, green and environmentally friendly, while also making the anode material coating more uniform and improving the continuity and stability of the conductive network of the coating layer. Summary of the Invention

[0006] This application provides a lithium-ion battery anode material and its preparation method to solve the technical problems of cumbersome composite coating process, uneven coating layer, and difficulty in applying to new anode materials such as silicon-based materials.

[0007] In a first aspect, this application provides a lithium-ion battery anode material, including an anode material matrix and a conductive agent-polymer composite powder coating layer coated on the surface of the anode material matrix; the conductive agent-polymer composite powder coating layer is composed of an amorphous carbon matrix and a conductive agent uniformly dispersed and anchored therein, forming a continuous conductive network structure.

[0008] The coating layer, derived from the above scheme, originates from a "conductive agent-polymer composite powder." Before heat treatment, the polymer is a solid, hard particle. Through dry ball milling, it forms a microscopically uniform composite with the conductive agent. During heat treatment, the polymer does not melt or flow; instead, it undergoes direct pyrolysis and carbonization, transforming from solid particles into a solid amorphous carbon matrix. This direct transformation from solid particles to a solid amorphous carbon matrix fundamentally avoids uneven distribution and agglomeration caused by the liquid phase flow of the coating agent (such as asphalt). The resulting "amorphous carbon matrix + anchoring conductive agent" structure ensures uniformity and structural stability. Furthermore, this material allows for a simple production process and high versatility.

[0009] In one possible design, the conductive agent includes one or two of graphene and carbon nanotubes; the polymer is at least one of polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyimide (PI), phenolic resin, furan resin and epoxy resin.

[0010] Through the above methods, polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyimide (PI), phenolic resin, furan resin, and epoxy resin are all polymers with high carbonization rates, thermosetting properties, or the ability to maintain their shape during pyrolysis. During pyrolysis, they directly form solid carbon through chemical cross-linking and aromatization, without passing through a viscous flow state; this is the chemical basis for achieving uniform coating. Graphene and carbon nanotubes can be physically embedded, adhered to, or partially entangled on the surface and shallow layers of these polymers, forming a "core-shell" or "embedded" composite powder unit. The polymer particles act as a supporting framework, fixing and separating the nano-conductive agents, preventing their spontaneous aggregation.

[0011] In one possible design, the thickness of the conductive agent-polymer composite powder coating layer is 50nm-500nm.

[0012] Through the above scheme, the thickness of the conductive agent-polymer composite powder coating layer is controlled between 50nm and 500nm. When the coating layer thickness is less than 50nm, it is difficult to form a continuous and dense conductive network structure. Some surfaces of the negative electrode material substrate may not be completely covered, which may lead to discontinuities in the conductive network, obstructed electron transport paths, direct contact between the electrolyte and the active material, exacerbated side reactions, and insufficient volume expansion buffering capacity, especially for silicon-based materials. A thickness greater than 50nm is sufficient to ensure the formation of a complete amorphous carbon coating layer after polymer carbonization, effectively isolating the electrolyte while providing sufficient mechanical support. When the coating layer thickness exceeds 500nm, the diffusion path of lithium ions in the solid phase increases significantly, which may lead to a decrease in rate performance and a reduction in the overall specific capacity of the material due to the excessive proportion of inactive components. The 500nm thickness upper limit ensures that the coating layer will not become a bottleneck for lithium ion transport while maintaining a high energy density.

[0013] In one possible design, the anode material matrix includes a graphite substrate and / or a silicon-based material, with a particle size D50 of 7μm-30μm.

[0014] The above-described method results in a conductive agent-polymer composite powder coating layer with excellent toughness and conductivity. Furthermore, it is not limited by the material of the anode substrate, being suitable not only for graphite substrates but also for novel anode materials such as silicon-based substrates. The particle size D50 of the anode substrate is not less than 7μm, avoiding the surge in specific surface area caused by excessively fine particles, as well as the resulting excessively large specific surface area and processing difficulties. A particle size D50 of not more than 30μm prevents particles from easily settling during coating, resulting in a rough electrode surface and a lower upper limit for compaction density, thereby ensuring high manufacturing yield, consistency, and high volumetric energy density of the battery.

[0015] In one possible design, a vapor-deposited carbon layer is also provided on the surface of the conductive agent-polymer composite powder coating layer, with the vapor-deposited carbon layer coating the outer surface of the conductive agent-polymer composite powder coating layer.

[0016] By using the above method, a denser and more uniform ultrathin carbon film (vapor-deposited carbon layer) can be deposited on the already formed excellent conductive agent-polymer composite powder coating layer, which can further fill microscopic defects and optimize the electrode / electrolyte interface, thereby potentially improving the performance to the top level.

[0017] In a second aspect, this application provides a method for preparing a lithium-ion battery anode material as described in the first aspect, comprising the steps of: providing an anode material matrix; mixing conductive agent powder and solid polymer powder by dry ball milling at a first preset mass ratio to obtain a conductive agent-polymer composite powder coating agent; mixing the anode material matrix and the conductive agent-polymer composite powder coating agent by dry mixing at a second preset mass ratio to obtain a dry-coated mixture; and subjecting the dry-coated mixture to a heat treatment process to carbonize the polymer to form an amorphous carbon coating layer, thereby obtaining the anode material.

[0018] The above scheme combines solid polymer powder and conductive agent through mechanical force, pre-fixing the conductive agent onto the polymer particles to form a microscopically uniform composite unit. This eliminates the risk of free agglomeration of the conductive agent at the downstream stage. Using solid composite powder for dry coating eliminates the need for any solvents, avoiding the pollution, recovery, and drying problems associated with liquid-phase methods, greatly simplifying the process. The dry-coated mixture undergoes heat treatment, carbonizing the polymer to form an amorphous carbon coating layer, which is crucial for structural shaping. The polymer undergoes solid-solid pyrolysis, directly transforming into amorphous carbon while simultaneously anchoring the conductive agent in situ. This process generates no liquid phase, fundamentally avoiding inhomogeneities caused by the flow of the coating agent itself (such as asphalt). This results in a simple composite coating process for anode materials, producing a uniform coating layer, and this method is applicable to novel anode materials such as silicon-based materials, demonstrating high versatility.

[0019] In one possible design, the conductive agent is one or two of graphene and carbon nanotubes; the polymer is at least one of polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyimide (PI), phenolic resin, furan resin and epoxy resin.

[0020] The above scheme selects graphene / carbon nanotubes as the conductive agent because of their extremely high intrinsic conductivity and large specific surface area, which facilitates interaction (entanglement and embedding) with polymer particles through ball milling. The polymers selected are PAN, PI, phenolic resins, etc., because they are all high-carbonization precursors that directly form carbon through chemical cross-linking during pyrolysis, without going through a viscous flow state, thus maintaining their shape.

[0021] In one possible design, the first preset mass ratio is (1-3):100. With the above approach, too little conductive agent results in a discontinuous network, while too much leads to high costs and may hinder ion transport. Experiments determined that a ratio of (1-3):100 is sufficient; within this range, a small amount of highly efficient conductive agent is adequately dispersed and loaded by the polymer particles. After subsequent carbonization, these anchored, small but widely distributed conductive agents are sufficient to construct a continuous three-dimensional conductive network within the amorphous carbon matrix, achieving a significant improvement in conductivity at minimal cost.

[0022] In one possible design, the second preset mass ratio is 100:(5-10). The above scheme limits the amount of coating agent added to 5%-10%. At this ratio, the conductive agent-polymer composite powder content, after pyrolysis and carbonization (with weight loss), precisely forms a thin layer that completely covers the surface of the negative electrode material matrix. This thin layer is sufficient to achieve all functions of interface modification, conductive network construction, and mechanical buffering, while controlling the proportion of inactive substances within an optimal range, maximizing the material's volumetric energy density and specific capacity.

[0023] In one possible design, when the negative electrode material matrix is ​​a graphite substrate, the graphite substrate is: natural graphite and / or artificial graphite; when the negative electrode material matrix is ​​a silicon-based material, the silicon-based material is: elemental silicon, silicon suboxide (SiOx) or silicon-carbon composite material.

[0024] Using the above methods, anode material matrices such as natural graphite, artificial graphite, elemental silicon, silicon suboxide, and silicon-carbon composites can all be coated using the above methods.

[0025] In one possible design, the dry mixing process includes: placing the negative electrode material matrix and the conductive agent-polymer composite powder coating agent in a high-speed mixer at a second preset mass ratio, and mixing for at least 1 hour under an inert atmosphere; the heat treatment process includes: heating the dry coating mixture at a heating rate of 2℃ / min-10℃ / min, the heat treatment temperature being 800℃-1100℃, and the holding time being 1 hour-3 hours.

[0026] The above method involves dry mixing for at least 1 hour to ensure that the solid composite powder adheres fully and evenly to the surface of each matrix particle, thereby achieving uniform coating.

[0027] The heating rate is 2℃ / min - 10℃ / min, which allows for the gradual pyrolysis of the polymer and avoids the violent release of volatiles that could cause cracks or peeling of the coating layer.

[0028] Temperatures of 800℃-1100℃ are used to ensure that the polymer is fully carbonized to form amorphous carbon with good conductivity, while avoiding excessively high temperatures that could damage the matrix structure, especially for silicon-based materials.

[0029] Insulating for 1 to 3 hours ensures that the pyrolysis and carbonization reactions are complete and sufficient, guaranteeing the stability and performance consistency of the coating structure.

[0030] In one possible design, after the dry coating mixture is subjected to a heat treatment process to carbonize the polymer and form an amorphous carbon coating layer to obtain the negative electrode material, the process further includes the following steps: post-processing steps of sieving and demagnetizing the obtained negative electrode material; and / or, performing surface vapor deposition carbon treatment on the surface of the conductive agent-polymer composite powder coating layer to form a vapor-deposited carbon layer, such that the vapor-deposited carbon layer coats the outer surface of the conductive agent-polymer composite powder coating layer.

[0031] Through the above method, a denser and more uniform ultrathin carbon film (vapor-deposited carbon layer) is deposited on the already formed excellent conductive agent-polymer composite powder coating layer, which further fills the micro-defects and optimizes the electrode / electrolyte interface, thereby potentially improving the performance to the top level.

[0032] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of this application are described below. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of one of the coating steps for the negative electrode material of a lithium-ion battery provided in one embodiment of this application.

[0035] Figure 2 This is a schematic diagram of the second step in the coating process of the lithium-ion battery negative electrode material provided in one embodiment of this application.

[0036] Figure 3 This is a flowchart illustrating a method for preparing a lithium-ion battery anode material according to one embodiment of this application.

[0037] Figure 4 This is a flowchart of a method for preparing a lithium-ion battery anode material according to another embodiment of this application.

[0038] Explanation of reference numerals in the attached figures: 100, conductive agent; 200, polymer particles; 300, conductive agent-polymer composite powder coating layer; 400, negative electrode material matrix; 500, negative electrode material. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims and drawings of this application are intended to cover non-exclusive inclusion.

[0041] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0042] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists, A and B exist simultaneously, or B exists. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0043] Furthermore, the terms "first," "second," etc., in the specification and claims of this application or in the aforementioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.

[0044] In the description of this application, unless otherwise stated, "multiple" means two or more (including two), and similarly, "multiple groups" means two or more (including two groups).

[0045] Surface modification of graphite anodes is a key and effective technical means to improve the overall performance of lithium-ion batteries, especially those aiming for high energy density and fast charging. Externally, surface modification constructs an artificially designed and stable physical and chemical barrier between graphite and the electrolyte. Internally, it optimizes the electron conduction and ion transport environment on the graphite particle surface.

[0046] In related technologies, whether it is the scheme of graphene doping and stepwise fusion coating or the scheme of liquid phase coating, which involves preheating coating agents such as asphalt or resin, mixing them with conductive agents and dispersants to form a modified liquid phase system, and then coating the graphite aggregate, there are certain problems. They cannot achieve the effect of simple process and uniform coating.

[0047] In view of this, embodiments of this application provide a lithium-ion battery anode material and its preparation method. The preparation method includes the following steps: providing an anode material matrix; dry ball milling and mixing conductive agent powder and solid polymer powder at a first preset mass ratio to obtain a conductive agent-polymer composite powder coating agent; dry mixing the anode material matrix and the conductive agent-polymer composite powder coating agent at a second preset mass ratio to obtain a dry-coated mixture; and heat-treating the dry-coated mixture to carbonize the polymer and form an amorphous carbon coating layer, thereby obtaining the anode material. By mechanically combining the solid polymer powder and the conductive agent, the conductive agent is pre-fixed onto the polymer particles, forming a microscopically uniform composite unit. This eliminates the risk of free agglomeration of the conductive agent at the downstream end. Using solid composite powder for dry coating eliminates the need for any solvents, avoiding the pollution, recycling, and drying problems of liquid-phase methods, greatly simplifying the process. The heat treatment process of the dry-coated mixture to carbonize the polymer and form an amorphous carbon coating layer is the core of structural shaping. The polymer undergoes solid-solid pyrolysis, directly transforming into amorphous carbon while simultaneously anchoring the conductive agent in situ. This process generates no liquid phase, fundamentally avoiding inhomogeneities caused by the flow of the coating agent itself (such as asphalt). This results in a simple composite coating process for the anode material, producing a uniform coating layer. Furthermore, this method is applicable to novel anode materials such as silicon-based materials, demonstrating high versatility.

[0048] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0049] Figure 1 This is a schematic diagram of one of the coating steps for the lithium-ion battery negative electrode material provided in this embodiment. Figure 2 This is a schematic diagram of the second step in the coating process of the lithium-ion battery negative electrode material provided in this embodiment. Please refer to... Figure 1 and Figure 2 This application provides a lithium-ion battery negative electrode material 500, including: a negative electrode material substrate 400 and a conductive agent-polymer composite powder coating layer 300 coated on the surface of the negative electrode material substrate 400.

[0050] The negative electrode material matrix 400 can be natural graphite or artificial graphite, or it can be elemental silicon, silicon suboxide or silicon-carbon composite material.

[0051] In this embodiment, the negative electrode material matrix 400 is artificial graphite, which can be obtained by graphitizing petroleum coke, needle coke, etc.

[0052] The conductive agent-polymer composite powder coating layer 300 is composed of an amorphous carbon matrix and a conductive agent 100 uniformly dispersed and anchored therein, forming a continuous conductive network structure.

[0053] Understandably, the polymer is a solid, hard particle before heat treatment, and its microstructure is flocculent. During heat treatment, the polymer does not melt and flow, but directly undergoes pyrolysis and carbonization, transforming from solid particles into a solid amorphous carbon matrix. This process of transforming solid particles directly into a solid amorphous carbon matrix fundamentally avoids the uneven distribution and agglomeration caused by the liquid phase flow of the coating agent (such as asphalt). The final structure of "amorphous carbon matrix + anchoring conductive agent 100" ensures uniformity and structural stability.

[0054] In this embodiment, the thickness of the conductive agent-polymer composite powder coating layer is controlled between 50 nm and 500 nm. When the coating layer thickness is less than 50 nm, it is difficult to form a continuous and dense conductive network structure. Some surfaces of the negative electrode material substrate may not be completely covered, which may lead to discontinuities in the conductive network, obstructed electron transport paths, direct contact between the electrolyte and the active material, exacerbated side reactions, and insufficient volume expansion buffering capacity, especially for silicon-based materials. A thickness greater than 50 nm is sufficient to ensure that a complete amorphous carbon coating layer is formed after polymer carbonization, effectively isolating the electrolyte while providing sufficient mechanical support. When the coating layer thickness exceeds 500 nm, the diffusion path of lithium ions in the solid phase increases significantly, which may lead to a decrease in rate performance and a decrease in the overall specific capacity of the material due to the excessive proportion of inactive components. The upper limit of 500 nm ensures that the coating layer does not become a bottleneck for lithium ion transport while maintaining a high energy density.

[0055] In this embodiment, the conductive agent 100 is one or two of graphene and carbon nanotubes; the polymer is at least one of polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyimide (PI), phenolic resin, furan resin and epoxy resin.

[0056] Polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyimide (PI), phenolic resins, furan resins, and epoxy resins are all polymers with high carbonization rates, thermosetting properties, or the ability to maintain their shape during pyrolysis. During pyrolysis, they directly form solid carbon through chemical crosslinking and aromatization, without passing through a viscous flow state, thus enabling uniform coating.

[0057] Graphene and carbon nanotubes can be physically embedded, adhered to, or partially entangled on the surface and shallow layer of these polymers, forming a "core-shell" or "embedded" composite powder unit. The polymer particles act as a supporting framework, fixing and separating the nano-conductive agent 100, preventing its spontaneous aggregation.

[0058] In some embodiments, a denser and more uniform ultrathin carbon film (vapor-deposited carbon layer) can be deposited on the already formed excellent conductive agent-polymer composite powder coating layer to further fill microscopic defects and optimize the electrode / electrolyte interface, thereby potentially improving performance to the highest level.

[0059] Figure 3 This is a flowchart illustrating the preparation method of the lithium-ion battery anode material 500 provided in this embodiment. Please refer to the reference. Figure 1 , Figure 2 and Figure 3 Based on the above embodiments, this application provides a method for preparing a lithium-ion battery anode material 500, comprising: Step 1: Provide a negative electrode material substrate 400.

[0060] The particle size D50 of the negative electrode material matrix 400 is 7μm-30μm. A particle size D50 of not less than 7μm avoids a surge in specific surface area caused by excessively fine particles, as well as excessively large specific surface area and processing difficulties. A particle size D50 of not more than 30μm prevents particles from easily settling during coating, resulting in a rough electrode surface and a lower upper limit for compaction density, thereby ensuring high battery manufacturing yield, consistency, and high volumetric energy density.

[0061] In this embodiment, the particle size D50 of the negative electrode material matrix 400 is 15μm-20μm. The negative electrode material matrix 400 includes: a graphite substrate and / or a silicon-based material. When the negative electrode material matrix 400 is a graphite substrate, the graphite substrate can be natural graphite and / or artificial graphite.

[0062] In this embodiment, the graphite substrate is artificial graphite, and its preparation method may include: crushing, shaping and graphitizing coke raw materials to obtain artificial graphite as a subsequent matrix, wherein the artificial graphite matrix is ​​not pre-doped with any conductive agent 100.

[0063] It is understandable that the coke source can be coal-based or oil-based coke, and it can be granulated once or twice. The secondary granulation can be granulation before or after graphitization.

[0064] When the negative electrode material substrate 400 is a silicon-based material, the silicon-based material can be elemental silicon, silicon suboxide (SiOx), or silicon-carbon composite material.

[0065] Step 2: Dry ball milling is performed to mix conductive agent 100 powder and solid polymer powder at a first preset mass ratio to obtain conductive agent 100-polymer composite powder coating agent.

[0066] It is understandable that the conductive agent 100 powder can be a powder made from one or both of graphene and carbon nanotubes. Graphene or carbon nanotubes have extremely high intrinsic conductivity and large specific surface area, making them easy to interact with polymer particles through ball milling (entanglement, embedding).

[0067] Solid polymer powders can be powders made from at least one of polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyimide (PI), phenolic resin, furan resin, and epoxy resin. PAN, PVA, PI, phenolic resin, etc., are all precursors with high carbonization rates. During pyrolysis, they are chemically cross-linked directly into carbon without going through a viscous flow state and can maintain their shape.

[0068] The first preset mass ratio is (1-3):100. Too little conductive agent 100 results in a discontinuous network, while too much is costly and may hinder ion transport. In this embodiment, the (1-3):100 ratio was experimentally determined. Within this range, a small amount of highly efficient conductive agent 100 is sufficient to be fully dispersed and loaded by the polymer particles. After subsequent carbonization, these anchored, small but widely distributed conductive agents 100 are sufficient to construct a continuous three-dimensional conductive network in the amorphous carbon matrix, achieving a significant improvement in conductivity at the lowest cost.

[0069] In this embodiment, the dry ball milling mixing method is as follows: the conductive agent 100 powder and the solid polymer powder are added to the planetary ball mill at a first preset mass ratio, and ball milled at a speed of 300r / min-400r / min for 2-4 hours under nitrogen protection to obtain the conductive agent 100-polymer composite powder.

[0070] Step 3: The negative electrode material matrix 400 and the conductive agent 100-polymer composite powder coating agent are dry-mixed according to the second preset mass ratio to obtain a dry-coated mixture.

[0071] In this embodiment, the second preset mass ratio is 100:(5-10).

[0072] The coating agent addition is limited to 5%-10%. At this ratio, the conductive agent 100-polymer composite powder content, after pyrolysis and carbonization (with weight loss), precisely forms a thin layer that completely covers the surface of the negative electrode material matrix 400. This thin layer is sufficient to achieve all functions of interface modification, conductive network construction, and mechanical buffering, while controlling the proportion of inactive materials within an optimal range, maximizing the material's volumetric energy density and specific capacity.

[0073] In this embodiment, the dry mixing process includes: placing the negative electrode material matrix 400 and the conductive agent 100-polymer composite powder coating agent in a high-speed mixer at a second preset mass ratio, and mixing them under an inert atmosphere for at least 1 hour; the heat treatment process includes: heating the dry coating mixture at a heating rate of 2℃ / min-10℃ / min, the heat treatment temperature being 800℃-1100℃, and the holding time being 1 hour-3 hours.

[0074] Understandably, dry mixing should be carried out for at least 1 hour to ensure that the solid composite powder adheres fully and evenly to the surface of each matrix particle to achieve uniform coating.

[0075] The heating rate is 2℃ / min - 10℃ / min, which allows for the gradual pyrolysis of the polymer and avoids the violent release of volatiles that could cause cracks or peeling of the coating layer.

[0076] Temperatures of 800℃-1100℃ are used to ensure that the polymer is fully carbonized to form amorphous carbon with good conductivity, while avoiding excessively high temperatures that could damage the matrix structure, especially for silicon-based materials.

[0077] Insulating for 1 to 3 hours ensures that the pyrolysis and carbonization reactions are complete and sufficient, guaranteeing the stability and performance consistency of the coating structure.

[0078] Step 4: The dry-coated mixture is subjected to a heat treatment process to carbonize the polymer and form an amorphous carbon coating layer, thus obtaining the negative electrode material 500.

[0079] Solid polymer powder and conductive agent 100 are mechanically compounded, pre-fixing the conductive agent 100 onto the polymer particles to form a microscopically uniform composite unit. This eliminates the risk of free agglomeration of the conductive agent 100 at the later stage. Using solid composite powder for dry coating eliminates the need for any solvents, avoiding the pollution, recovery, and drying problems associated with liquid-phase methods, greatly simplifying the process. The dry-coated mixture undergoes a heat treatment process, carbonizing the polymer to form an amorphous carbon coating layer, which is crucial for structural shaping. The polymer undergoes solid-solid pyrolysis, directly converting into amorphous carbon, while simultaneously anchoring the conductive agent 100 in situ. This process generates no liquid phase, fundamentally avoiding inhomogeneity caused by the flow of the coating agent itself (such as asphalt).

[0080] Figure 4 This is a flowchart illustrating the preparation method of the lithium-ion battery anode material provided in this embodiment. Please refer to it. Figure 4 In this embodiment, after step 4, step 5 is also included, which is a post-processing step of sieving and demagnetizing the obtained negative electrode material; and / or, surface vapor deposition carbon treatment is performed on the surface of the conductive agent-polymer composite powder coating layer to form a vapor-deposited carbon layer, so that the vapor-deposited carbon layer coats the outer surface of the conductive agent-polymer composite powder coating layer.

[0081] The post-processing steps of sieving and demagnetizing the obtained negative electrode material may include: sieving the cooled material, for example, passing it through a 300-mesh (approximately 48 μm) or 400-mesh (approximately 38 μm) sieve, to remove any small amount of agglomerates that may be generated during the reaction and to obtain a product with a uniform particle size distribution; followed by demagnetization treatment, for example, using a permanent magnet separator or electromagnetic separator with an intensity of not less than 8000 Gauss, to thoroughly remove any magnetic metal impurities that may be mixed into the material, ensuring the consistency and safety of the final negative electrode material product.

[0082] Understandably, the role of surface vapor deposition carbon treatment is to deposit a denser and more uniform vapor-deposited carbon layer (ultra-thin carbon film) on the already formed excellent conductive agent-polymer composite powder coating layer. This further fills the microscopic defects of the conductive agent-polymer composite powder coating layer and optimizes the electrode / electrolyte interface, enabling the construction of an extremely dense, continuous, and conductive network to compensate for the potential deficiencies of the preceding processes and obtain top-level electrochemical performance.

[0083] Through the preparation method of the lithium-ion battery anode material in the above embodiments, the conductive agent is uniformly and firmly fixed on the polymer carrier. During the heat treatment process, the conductive agent is uniformly distributed on the surface of the graphite particles, constructing a continuous and stable conductive network, effectively reducing electron transport impedance, and enabling the prepared anode material to have excellent rate performance. In addition, the amorphous carbon coating layer formed after polymer carbonization is dense and uniform, which can effectively reduce side reactions between the graphite surface and the electrolyte, and reduce irreversible capacity loss. At the same time, this coating layer does not affect the insertion and extraction of lithium ions, thereby ensuring that the material has high capacity and first-time efficiency.

[0084] Example 1 This embodiment provides a lithium-ion battery anode material, which is prepared by the following method: (1) Preparation of artificial graphite matrix: After crushing, shaping and granulating petroleum coke, graphitization treatment is carried out at 3000℃, and after sieving, an artificial graphite matrix with a particle size D50 of 15μm is obtained.

[0085] (2) Preparation of CNT / polymer composite coating agent: 2 kg of multi-walled carbon nanotubes (CNT) and 100 kg of polyacrylonitrile (PAN) powder were added to a planetary ball mill and ball milled at 300 r / min for 2 hours under nitrogen protection to obtain CNT-PAN composite powder.

[0086] (3) Dry coating: Take 10 kg of the composite powder from step (2) and 100 kg of the artificial graphite matrix from step (1) and put them into a high-speed mixer. Mix at 500 rpm for 60 minutes under a nitrogen atmosphere.

[0087] (4) Heat treatment: Transfer the mixed materials into an atmosphere furnace, heat them to 900°C at 5°C / min under nitrogen protection, hold for 2 hours, and then cool naturally.

[0088] (5) Post-processing: The cooled material is screened and demagnetized to obtain the final negative electrode material product A1.

[0089] Example 2 This embodiment provides a lithium-ion battery anode material, which is prepared by the following method: The difference from Example 1 is that in step (2), the polymer used is polyvinyl alcohol (PVA), and the mass ratio of CNT to PVA is 1.5:100. In step (4), the heat treatment temperature is 1000℃. The resulting product is denoted as A2.

[0090] Comparative Example 1 The difference from Example 1 is that the ball milling preparation of the composite powder in step (2) is not performed. Instead, the artificial graphite matrix and graphene powder are first mixed, then wet-mixed and stepwise fused with asphalt powder (replacing the polymer), followed by high-temperature graphitization. The resulting product is denoted as D1.

[0091] Comparative Example 2 The difference from Example 1 is that the ball milling in step (2) is not performed. Instead, the liquid phase asphalt is pretreated by stirring at 400°C for 2 hours, then graphene and sodium lignosulfonate (dispersant) are added and mixed to form a modified liquid phase coating agent, which is then mixed with the artificial graphite matrix and carbonized. The resulting product is designated as D2.

[0092] Comparative Example 3 (without ball milling pretreatment) The difference from Example 1 is that the ball milling in step (2) is not performed. The three components, CNT, PAN powder, and artificial graphite matrix, are directly mixed by dry mixing in step (3), with the other conditions the same as in Example 1. The resulting product is designated as D3.

[0093] Test example: The following tests were performed on the products A1, A2, D1, D2, and D3 obtained above: First Charge / Discharge Test: Obtain the capacity for the first efficiency and the first cycle. Procedure: At standard temperature, charge the battery to the upper limit voltage at a specific current (e.g., 0.1C), then allow it to rest; finally, discharge it to the cutoff voltage. Output: First efficiency (%) = (first discharge capacity / first charge capacity) x 100%; Specific capacity (mAh / g) = discharge capacity / mass of active material.

[0094] DC Internal Resistance Test: Measure DCR. Procedure: At a specified SOC point (e.g., 50%), apply a short-duration (e.g., 10 seconds) high-current pulse (e.g., 1C) to the battery for charging and discharging, and record the voltage transient. Output: DCR (mΩ) = Voltage change / Current.

[0095] Fast charging performance test: Evaluates fast charging capability and capacity retention at different charging rates. Procedure: Fully charge the battery at different charging currents (e.g., 0.2C, 0.5C, 1C, 2C), then discharge it at the standard current. Output: Actual discharge capacity at each charging rate; calculate the capacity retention relative to the standard capacity; evaluate fast charging performance.

[0096] Cycle life test: Evaluate long-term capacity decay and determine cycle life. Procedure: Perform continuous charge-discharge cycles (e.g., 2C / 2C) on the battery at 25°C within a specified charge-discharge rate and voltage range. Output: Check the discharge capacity periodically (e.g., every 50 cycles). The number of cycles required for the discharge capacity to decay to 80% of the initial capacity is the battery's cycle life. The results of comparing products A1, A2, D1, D2, and D3 above are shown in Table 1. Table 1:

[0097] As can be seen from the results in Table 1 above, the overall performance of products A1 and A2 obtained in Examples 1 and 2 is better than that of Comparative Examples 1 to 3. The average first-time efficiency is 0.5% higher, the average capacity is increased by 1 mAh / g, the average DC internal resistance (DCR) is reduced by more than 0.5 mohm, the average fast charging capability is improved by more than 0.5C, and the average 2C / 2C cycle life at 25°C is improved by more than 500 cycles.

[0098] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A lithium-ion battery anode material, characterized in that, include: Negative electrode material matrix; And a conductive agent-polymer composite powder coating layer covering the surface of the negative electrode material matrix; the conductive agent-polymer composite powder coating layer is composed of an amorphous carbon matrix and a conductive agent uniformly dispersed and anchored therein.

2. The lithium-ion battery anode material according to claim 1, characterized in that, The conductive agent includes one or two of graphene and carbon nanotubes; the polymer is at least one of polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyimide (PI), phenolic resin, furan resin and epoxy resin.

3. The lithium-ion battery anode material according to claim 1, characterized in that, The thickness of the conductive agent-polymer composite powder coating layer is 50nm-500nm.

4. The lithium-ion battery anode material according to claim 1, characterized in that, The negative electrode material matrix includes a graphite substrate and / or a silicon-based material, and the particle size D50 of the negative electrode material matrix is ​​7μm-30μm.

5. The lithium-ion battery anode material according to claim 1, characterized in that, The conductive agent-polymer composite powder coating layer is further provided with a vapor-deposited carbon layer on its surface, which coats the outer surface of the conductive agent-polymer composite powder coating layer.

6. A method for preparing a lithium-ion battery anode material as described in any one of claims 1 to 5, characterized in that, Including the following steps: Provide the substrate for the negative electrode material; The conductive agent powder and the solid polymer powder are dry ball-milled and mixed at a first preset mass ratio to obtain a conductive agent-polymer composite powder coating agent. The negative electrode material matrix and the conductive agent-polymer composite powder coating agent are dry-mixed at a second preset mass ratio to obtain a dry-coated mixture. The dry-coated mixture is subjected to a heat treatment process to carbonize the polymer and form an amorphous carbon coating layer, thereby obtaining the negative electrode material.

7. The preparation method according to claim 6, characterized in that, The first preset mass ratio is (1-3):100; and / or, The second preset mass ratio is 100:(5-10).

8. The preparation method according to claim 6, characterized in that, When the negative electrode material matrix is ​​a graphite substrate, the graphite substrate is: natural graphite and / or artificial graphite; When the negative electrode material matrix is ​​a silicon-based material, the silicon-based material is: elemental silicon, silicon suboxide (SiOx), or silicon-carbon composite material.

9. The preparation method according to claim 6, characterized in that, The dry mixing process includes: placing the negative electrode material matrix and the conductive agent-polymer composite powder coating agent in a high-speed mixer at a second preset mass ratio, and mixing them under an inert atmosphere for at least 1 hour; The heat treatment process includes: heating the dry-coated mixture at a heating rate of 2℃ / min-10℃ / min, the heat treatment temperature being 800℃-1100℃, and the holding time being 1 hour-3 hours.

10. The preparation method according to claim 6, characterized in that, After subjecting the dry-coated mixture to a heat treatment process to carbonize the polymer and form an amorphous carbon coating layer to obtain the negative electrode material, the process further includes the following steps: The post-processing steps include sieving and demagnetizing the obtained negative electrode material; and / or performing surface vapor deposition carbon treatment on the surface of the conductive agent-polymer composite powder coating layer to form a vapor-deposited carbon layer, such that the vapor-deposited carbon layer coats the outer surface of the conductive agent-polymer composite powder coating layer.

Images