A negative electrode composite material for a battery

Abstract

This invention provides a negative electrode composite material for batteries, specifically relating to the field of lithium-ion battery technology. The negative electrode composite material comprises composite material particles; the composite material particles include secondary graphite clusters and nano-active particles; the secondary graphite clusters include primary graphite clusters and an adjacent transition region two; the primary graphite clusters include nano-graphite crystals and an adjacent transition region one; the nano-graphite crystals are composed of multiple layers of graphene sheets with consistent orientation; the nano-active particles are distributed in the nano-graphite crystals and / or the transition region one and / or the transition region two. This simultaneously achieves high specific capacity, high initial coulombic efficiency, excellent cycle retention, and high rate performance, fundamentally breaking through the performance bottleneck of traditional silicon-carbon composite materials in balancing conductivity, ion dynamics, and mechanical stability.

Description

Technical Field

[0001] This invention relates to the technical field of lithium-ion batteries, and in particular to a negative electrode composite material for batteries. Background Technology

[0002] With the rapid development of electric vehicles, large-scale energy storage, and portable electronic devices, the market has placed unprecedented demands on the energy density, power density, and cycle life of lithium-ion batteries. As a core component of lithium-ion batteries, the performance of the anode material directly determines the overall battery performance. Currently, commercially available lithium-ion battery anodes primarily use graphite-based materials, which offer advantages such as low cost, stable operating potential, and good cycle performance. However, graphite's theoretical specific capacity is relatively low (approximately 372 mAh / g), approaching its theoretical limit and making it difficult to meet the needs of next-generation high-energy-density batteries. Therefore, the development of high-capacity anode materials has become a research hotspot.

[0003] Among numerous candidate materials, silicon (Si) is considered the most promising next-generation anode material due to its extremely high theoretical specific capacity (approximately 3579 mAh / g), suitable delithiation potential, and abundant reserves. However, silicon-based anodes face severe volume expansion (>300%) during charge and discharge, leading to the pulverization and shedding of the active material, as well as loss of electrical contact with the current collector, resulting in a sharp capacity decay. Furthermore, the continuous volume change causes the SEI film on the silicon surface to repeatedly rupture and regenerate, constantly consuming electrolyte and active lithium, resulting in low coulombic efficiency and shortened cycle life.

[0004] To overcome the above problems, researchers generally adopt "nano-sizing" and "composite" strategies. Among them, combining nano-silicon with porous carbon is the most important technical route at present. However, existing silicon-carbon composite anode technology still has significant shortcomings: 1) Prominent interfacial side reactions: Traditional porous carbon usually contains a lot of amorphous carbon or disordered structures. These regions have high reactivity with electrolyte and nano-silicon particles, which can easily trigger continuous side reactions, which not only accelerate capacity decay and reduce cycle life, but also may bring safety hazards such as thermal runaway; 2) Imperfect conductive network: The disordered structure in the carbon skeleton reduces the overall electronic conductivity of the material, restricts the rapid charge transport, and results in limited rate performance improvement of composite materials, making it difficult to meet the requirements of high-power applications; 3) Insufficient structural stability: The mechanical strength of amorphous carbon regions is relatively weak, and it is difficult to continuously and effectively constrain the volume expansion of silicon during long-term cycling, eventually leading to the gradual failure of the electrode structure.

[0005] Therefore, there is an urgent need in this field for a novel anode composite material that not only contains high-capacity active material and conductive carbon, but more importantly, can solve the aforementioned interface and space problems from the perspective of microstructure design, achieve synergistic stability between active particles and carbon skeleton, and thus obtain an anode material with high capacity, long cycle life and excellent rate performance.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a negative electrode composite material for batteries to solve at least one of the above-mentioned technical problems.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A first aspect of the present invention provides a negative electrode composite material for batteries, the negative electrode composite material comprising composite material particles; the composite material particles comprising secondary graphite crystal clusters and nano-active particles; the secondary graphite crystal clusters comprising primary graphite crystal clusters and adjacent transition regions II; the primary graphite crystal clusters comprising nano-graphite crystals and adjacent transition regions I; the nano-graphite crystals being composed of multiple layers of graphene sheets with consistent orientation; the nano-active particles being distributed in the nano-graphite crystals, and / or the transition regions I, and / or the transition regions II.

[0009] Furthermore, the composite material particles satisfy at least one of the following characteristics: (1) The size of the nano-graphite crystals is 2~10 nm; (2) The number of layers of the nano-graphite crystals is 3 to 20; (3) The size of the first transition region is 1~3 nm; (4) The size of the primary graphite cluster is 10~500 nm; (5) The number of layers in the primary graphite cluster is 10 to 40; (65) The size of the second transition region is 5~30 nm; (76) The composite material particles I D / I G The ratio is 0.1 to 1.

[0010] Furthermore, in the aforementioned negative electrode composite material for batteries, at least a portion of the nano-active particles form chemical bonds or intermolecular forces with at least one in-plane carbon atom of the carbon plane in the nano-graphite crystal and / or carbon atoms at the edge of the carbon plane.

[0011] Furthermore, the composite material particles contain at least one of the following chemical bonds: (1) At least a portion of the contact interface between the nano-active particles and the nano-graphite crystals forms a chemical bond containing a carbon-Y (CY) bond, wherein Y is the elemental composition of the nano-active particles; (2) At least some of the nano-active particles and nano-graphite crystals form chemical bonds containing carbon-XY (CXY) bonds at the contact interface, where X is an element other than Y; (3) Chemical bonds are formed between at least partially interconnected nanographite crystals through carbon atoms on their edges or surfaces, the chemical bonds including π-π stacking, carbon-carbon single bond (CC) bond or carbon-carbon double bond (C=C) bond.

[0012] Furthermore, the nano-active particles are selected from elemental, alloy, or compound nanoparticles of at least one element selected from silicon, germanium, tin, phosphorus, antimony, and bismuth.

[0013] Furthermore, in the negative electrode composite material for batteries, at least two nano-graphite crystals exist in the region surrounding at least one of the nano-active particles, and the angle between the extension directions of the (002) lattice stripes of two adjacent nano-graphite crystals is 0°~150°, preferably 0°~100°.

[0014] Furthermore, in the aforementioned negative electrode composite material for batteries, at least 30% or more of the volume of the nano-active particles are embedded within the closed or semi-closed space formed by the stacking or enclosure of the nano-graphite crystals.

[0015] Furthermore, in the aforementioned negative electrode composite material for batteries, at least 30% or more of the volume of the nano-active particles are embedded between and / or at the edges of the carbon planes of the nano-graphite crystals.

[0016] Furthermore, the sheet size of the nano-graphite crystals is 5-200 nm; The number of graphene sheets in the nano-graphite crystals is greater than 5, preferably 5 to 20.

[0017] Furthermore, the outermost layer of the negative electrode composite material for the battery is also covered with a continuous carbon layer.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: The battery anode composite material of the present invention forms a multi-level ordered carbon framework by constructing nano-graphite crystals, primary graphite crystal clusters, and secondary graphite crystal clusters with a well-defined hierarchical structure. Nanoactive particles are distributed within the nano-graphite crystal body, transition region one as an intra-crystal / grain boundary buffer zone, and transition region two as an inter-crystal cluster connectivity network, achieving multiple synergistic effects: First, the uniformly oriented nano-graphite crystals provide high electronic conductivity and low-barrier lithium-ion transport channels along the (002) plane, significantly improving rate performance; Second, the multi-level transition regions serve as flexible interfaces and pores. The gap carrier not only accommodates and confines the volume expansion of active particles, but also forms a hierarchical interconnected ion transport pathway, alleviating stress concentration and enhancing cycle stability; thirdly, the embedded distribution of nano-active particles in multi-scale space strengthens the interfacial contact area and chemical coupling strength between the active material and the conductive framework, inhibiting pulverization and repeated SEI rupture, thereby simultaneously achieving high specific capacity, high initial coulombic efficiency, excellent cycle retention rate and high rate performance, fundamentally breaking through the performance bottleneck of traditional silicon-carbon composite materials in terms of conductivity, ion dynamics and mechanical stability. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 A schematic diagram of a negative electrode composite material for batteries; Figure 2 This is a schematic diagram showing that the crystal plane of the nano-graphite crystal is completely perpendicular to the cross-section of the contact point of the active particles. Figure 3 This is a schematic diagram showing that the crystal planes of the nano-graphite crystals are completely parallel to the cross-sections at the contact points of the active particles. Figure 4 This is a schematic diagram showing that the cross-sections of the crystal planes of nano-graphite crystals and the contact points of active particles are both parallel and perpendicular. Figure 5 This is a schematic diagram of the planar contact between active particles and nano-graphite crystals. Figure 6 A schematic diagram showing the active particles partially embedded in the plane of the nano-graphite crystals; Figure 7 A schematic diagram showing the complete embedding of active particles into the plane of nano-graphite crystals; Figure 8 This is a schematic diagram showing the contact between active particles and the edge of nano-graphite crystals. Figure 9A schematic diagram showing the active particles partially embedded in the edge of the nano-graphite crystals; Figure 10 A schematic diagram showing the active particles completely embedded in the edge of the nano-graphite crystals; Figure 11 A schematic diagram showing active particles embedded in the edge of nano-graphite crystals; Figure 12 TEM images of the graphite clusters obtained in Example 1; Figure 13 HRTEM image of the graphite cluster obtained in Example 1; Figure 14 For comparison, TEM images of the porous carbon prepared in Example 1 were obtained; Figure 15 For comparison, HRTEM images of the porous carbon prepared in Example 1 were obtained; Figure 16 Raman spectra of the nano-graphite crystals obtained in Example 1; Figure 17 Raman spectra of the nano-graphite crystals obtained in Example 2; Figure 18 Raman spectra of the nano-graphite crystals obtained in Example 3; Figure 19 Nanographite clusters / silicon prepared in Example 1 CVD HRTEM image of the composite material.

[0021] Icons: 001 - Nano-graphite crystals; 002 - Nano-active particles; 003 - Primary graphite crystal clusters; 004 - Secondary graphite crystal clusters; 005 - Transition region one; 006 - Transition region two. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0023] In the following, the terms “comprising,” “having,” and their cognates, which may be used in various embodiments of the invention, are intended only to indicate a particular feature, number, step, operation, element, component, or combination thereof, and should not be construed as excluding, firstly, the presence of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, or adding the possibility of one or more features, numbers, steps, operations, elements, components, or combinations thereof.

[0024] A first aspect of the present invention provides a negative electrode composite material for batteries, the negative electrode composite material comprising composite material particles; the composite material particles comprising secondary graphite crystal clusters and nano-active particles; the secondary graphite crystal clusters comprising primary graphite crystal clusters and adjacent transition regions II; the primary graphite crystal clusters comprising nano-graphite crystals and adjacent transition regions I; the nano-graphite crystals being composed of multiple layers of graphene sheets with consistent orientation; the nano-active particles being distributed in the nano-graphite crystals, and / or the transition regions I, and / or the transition regions II.

[0025] In some embodiments of the present invention Figure 1 A schematic diagram of the negative electrode composite material for batteries provided by the present invention is shown. Figure 1 As shown, nano-graphite crystals 001 are connected through transition region 1 (005) to form primary graphite crystal clusters 003. These primary clusters 003 then connect through transition region 2 (006) to form secondary graphite crystal clusters 004, with active nanoparticles 002 dispersed within them. The nano-graphite crystals 001 exhibit parallel lattice fringes. Notably, the nano-graphite crystals 001 in different regions of the figure show significant differences in lattice orientation; this multi-orientation distribution is a microscopic manifestation of the material's hierarchical structure. The nano-graphite crystals 001 are stacked and connected in a specific manner in three-dimensional space, forming not only a continuous and efficient electron conduction network but also naturally creating a rich hierarchical porosity system in the stacking gaps. This unique structural design allows the material to accommodate high-capacity active nanoparticles (such as silicon and tin) while maintaining overall structural stability. Particularly important is the decisive influence of the relative spatial orientation between the nano-graphite crystals and the loaded active nanoparticles on the battery performance. When the lattice fringes of nanographite crystals are perpendicular to the tangents on the surface of the active nanoparticles (i.e., the normal direction of the graphite layers points towards the particle surface), its layered structure provides a direct channel for lithium-ion transport. In this configuration, lithium ions can diffuse rapidly along the graphite interlayers and transfer to the interior of adjacent active nanoparticles with near-zero resistance. This orientation-optimized interface structure microscopically solves the problem of tortuous ion transport paths in traditional composite materials. It directly shortens the migration distance of lithium ions at the heterojunction and reduces charge transfer impedance, thereby significantly improving the rate performance and fast-charging capability of the battery at the material level. This discovery provides an important theoretical basis for designing high-performance composite electrode materials through crystallographic orientation modulation.

[0026] In some embodiments of the present invention, the contact points between the crystal planes of the nanographite crystals and the active sample are as follows: Figure 2 This is a schematic diagram showing that the crystal plane of the nano-graphite crystal is completely perpendicular to the cross-section of the contact point with the active particles. Figure 3 This is a schematic diagram showing that the crystal planes of the nano-graphite crystals are completely parallel to the cross-sections at the contact points with the active particles. Figure 4This is a schematic diagram showing that the cross-sections of the crystal planes of nano-graphite crystals and the contact points of active particles can be both parallel and perpendicular. Figure 5 This is a schematic diagram of the planar contact between active particles and nano-graphite crystals. Figure 6 This is a schematic diagram showing the active particles partially embedded in the plane of the nano-graphite crystals. Figure 7 This is a schematic diagram showing the complete embedding of active particles into the plane of nano-graphite crystals. Figure 8 This is a schematic diagram showing the contact between active particles and the edge of nano-graphite crystals. Figure 9 This is a schematic diagram showing the active particles partially embedded in the edge of the nano-graphite crystals. Figure 10 This is a schematic diagram showing the active particles completely embedded in the edge of the nano-graphite crystals. Figure 11 This is a schematic diagram of active particles embedded in the edge of nano-graphite crystals.

[0027] In some embodiments, nano-graphite cluster structures can be constructed through a variety of synthetic strategies. The core idea is to use carbon-rich precursors (such as specific bitumen or natural graphite) as a base, and achieve controllable graphitization and pore formation through hydrothermal reaction with structure-directing agents such as polymers and subsequent heat treatment.

[0028] Specifically, a typical method involves mixing asphalt (such as mesophase asphalt) with polyacrylonitrile (PAN), polyvinyl alcohol (PVA), or block copolymers, and then subjecting the mixture to high-temperature and high-pressure treatment in a hydrothermal reactor. In this process, the polymer acts not only as a carbon source but also as a soft template and steric barrier. The hydrothermal reaction promotes cross-linking and initial carbonization of the precursor, forming a composite with an initial topological structure. During subsequent high-temperature carbonization and graphitization, the polymer decomposes and releases gases (such as H2O, CO2, and NH3), leaving abundant mesopores and macropores in the material. Meanwhile, the asphalt-based carbon undergoes oriented growth and orderly stacking of graphite microcrystals under catalysis or high temperature, ultimately forming a porous cluster structure composed of nano-graphite crystals.

[0029] To introduce defect sites in the graphite lattice that are conducive to ion intercalation and capacitance storage, post-treatment methods such as pre-oxidation or strong acid oxidation can be used. The experimental procedure for the pre-oxidation method is typically as follows: the carbon material is heat-treated in air or an oxygen-containing atmosphere at a temperature range of 200–400°C for 1–4 hours. This process partially oxidizes the edges and basal surfaces of the carbon layer, forming oxygen-containing functional groups (such as carboxyl and hydroxyl groups) and causing structural distortions, thereby controllably introducing topological defects while preventing the collapse of the overall structure of the material.

[0030] The strong acid oxidation method is more radical: a typical step involves dispersing carbon materials in concentrated nitric acid, concentrated sulfuric acid, or a mixture thereof (such as H₂SO₄ / HNO₃ at a volume ratio of 1:1), and refluxing and stirring at 60–120 °C for 2–12 hours. After the reaction, the material is centrifuged, washed with water until neutral, and dried to obtain the oxidized modified material. This method, in addition to introducing a large number of oxygen-containing functional groups, also etches nanoscale pores into the carbon layer, significantly increasing the specific surface area and enhancing the material's hydrophilicity. However, it may partially disrupt the long-range graphite order, requiring subsequent mild heat treatment to restore conductivity. The above methods can be combined and optimized according to target properties (such as pore distribution, defect concentration, and conductivity) to achieve precise control over the structure of nano-graphite clusters.

[0031] The nano-graphite cluster structure is a multi-level structure composed of graphite clusters and channels. The graphite cluster is the smallest unit of the multi-level structure, which itself is composed of nano-graphite crystals and channels.

[0032] (1) The transition region includes a grain boundary and / or a channel; (2) The second transition region includes a second grain boundary and / or a second channel; (3) The transition region II forms a vein network surrounding the primary graphite crystal cluster.

[0033] Multiple nano-graphite crystals are interconnected by chemical bonds at their edges or surfaces (such as π-π stacking, CC bonds, and C=C bonds) to form graphite crystal clusters with internal channels (channel one). Multiple graphite crystal clusters then aggregate through larger channels (inter-cluster channels) to form multi-level graphite crystal clusters containing at least two levels of channels.

[0034] Furthermore, the composite material particles satisfy at least one of the following characteristics: (1) The size of the nano-graphite crystals is 2~10 nm; (2) The number of layers of the nano-graphite crystals is 3 to 20; (3) The size of the first transition region is 1~3 nm; (4) The size of the primary graphite cluster is 10~500 nm; (5) The number of layers in the primary graphite cluster is 10 to 40; (65) The size of the second transition region is 5~30 nm; (76) The composite material particles I D / I G The ratio is 0.1 to 1.

[0035] Furthermore, in the aforementioned negative electrode composite material for batteries, at least a portion of the nano-active particles form chemical bonds or intermolecular forces with at least one in-plane carbon atom of the carbon plane in the nano-graphite crystal and / or carbon atoms at the edge of the carbon plane.

[0036] Furthermore, the composite material particles contain at least one of the following chemical bonds: (1) At least a portion of the contact interface between the nano-active particles and the nano-graphite crystals forms a chemical bond containing a carbon-Y (CY) bond, wherein Y is the elemental composition of the nano-active particles; (2) At least some of the nano-active particles and nano-graphite crystals form chemical bonds containing carbon-XY (CXY) bonds at the contact interface, where X is an element other than Y, which can greatly enhance interface stability and charge transport.

[0037] (3) Chemical bonds are formed between at least partially interconnected nanographite crystals through carbon atoms on their edges or surfaces, the chemical bonds including π-π stacking, carbon-carbon single bond (CC) bond or carbon-carbon double bond (C=C) bond.

[0038] Furthermore, the nano-active particles are selected from elemental, alloy, or compound nanoparticles of at least one element selected from silicon, germanium, tin, phosphorus, antimony, and bismuth. The chemical composition of the nano-active particles can be independently selected within different levels of pores to achieve performance optimization.

[0039] Furthermore, at least a portion of the nano-active particles are in direct contact with the nano-graphite crystals. More preferably, the projected profile length of this contact accounts for more than 30% of the total projected profile length of the nano-active particles, in order to provide a sufficient electronic conduction interface.

[0040] Furthermore, in the aforementioned negative electrode composite material for batteries, at least two nano-graphite crystals exist in the region surrounding at least one of the nano-active particles, with the angle between the extension directions of the (002) lattice fringes of two adjacent nano-graphite crystals being 0°~150°, preferably 0°~100°. This spatial arrangement effectively enhances the constraint strength on the expansion of the active particles. The spatial arrangement of the nano-graphite crystals around the active particles has a significant impact on their structural strength. When the angle between the lattice fringes of two nano-graphite crystals is 180°, the nano-graphite crystals are in the same plane, resulting in the lowest structural strength; when the angle between the lattice fringes of two nano-graphite crystals is 0°, the nano-graphite crystals are in a parallel state, resulting in the highest structural strength.

[0041] Furthermore, the angle between the tangent at the contact point between the nano-active particle and the nano-graphite crystal and the extension direction of the (002) lattice fringes of the nano-graphite crystal is 0°~90°. This angle is preferably 30°~90°, and more preferably 60°~90°. Ions are transported between the layers of the nano-graphite crystal, resulting in the highest ion transport performance along the orientation direction of the lattice fringes. Therefore, the ion transport efficiency is highest when the edge of the nano-graphite crystal faces the active particle.

[0042] Furthermore, in the aforementioned negative electrode composite material for batteries, at least 30% or more of the volume of the nano-active particles are embedded within the closed or semi-closed space formed by the stacking or enclosure of the nano-graphite crystals.

[0043] Furthermore, in the aforementioned negative electrode composite material for batteries, at least 30% or more of the volume of the nano-active particles are embedded between and / or at the edges of the carbon planes of the nano-graphite crystals, thereby achieving better spatial confinement and interface coupling. In addition, compared to embedding into the edges of graphite crystal clusters, embedding the active particles within the closed or semi-closed spaces of the nano-graphite crystals can maximally limit the volume effect caused by the expansion of the active particles.

[0044] Furthermore, the sheet size of the nanographite crystals is 5-200 nm.

[0045] The size of the nanographite crystal layers affects the size of the channels between the nanographite crystals. Larger nanographite crystals (greater than 200 nm) create large channels, reducing the structural strength of the graphite clusters and composite materials. Conversely, smaller nanographite crystals (less than 5 nm) create small, ineffective channels, reducing the energy density of the composite materials. The thickness of the graphene layer within the nanographite crystals affects the structural strength of the graphite clusters or composite materials. When the nanographite crystals are few-layer or single-layer graphene, they may fracture during the volume expansion of the active particles, thus affecting the battery's lifespan.

[0046] Since ions are transported between the layers of graphite nanocrystals, the ion transport efficiency is reduced for active particles that are in simple direct contact with the surface of the graphite nanocrystals. However, when active particles are embedded into the graphite nanocrystals, conductivity and ion transport efficiency can be increased.

[0047] The outermost layer of the negative electrode composite material can also be coated with a continuous carbon layer to further buffer volume expansion, stabilize the SEI film, and improve the first coulombic efficiency.

[0048] The number of graphene sheets in the nano-graphite crystals is greater than 5, preferably 5 to 20.

[0049] Furthermore, the outermost layer of the negative electrode composite material for the battery is also covered with a continuous carbon layer.

[0050] This invention presents a multi-level nano-graphite crystal cluster-pore composite structure, providing a flexible and optimizable platform solution for high-performance anode materials. Existing technologies, whether traditional micron-sized graphite, silicon-carbon composites, or disordered hard carbon, often employ a single or simple "core-shell" structure, making it difficult to simultaneously meet multiple requirements such as ion transport, electronic conductivity, mechanical stability, and active material support. This invention, however, constructs nano-graphite crystals as the basic conductive units. These crystals self-assemble into a multi-level cluster structure, naturally forming a rich and interconnected pore network in the process. This design achieves precise functional division: the nano-graphite crystals ensure excellent intrinsic electronic conductivity; the multi-level cluster structure maintains the overall stability of the material macroscopically, preventing nanoparticle aggregation; and the controllable pores play a crucial role, serving as a three-dimensional highway for electrolyte storage and rapid ion transport, significantly improving rate performance, while also reserving space for subsequent functional modifications. Therefore, this structure itself is a powerful matrix, and its performance is no longer limited to a single material system. Instead, by filling the pores with high-capacity active particles such as silicon, tin, and metallic lithium, it is possible to customize the key indicators such as energy density and power density of the final product as needed, fundamentally overcoming the limitations of existing material structures being relatively fixed and performance improvement encountering bottlenecks.

[0051] First, this invention addresses the contradiction between high-rate fast charging and long cycle life from both kinetic and mechanical perspectives. For traditional graphite anodes, lithium ions must embed from the edges of the sheets, resulting in long diffusion paths within micron-sized particles. This leads to ion accumulation and lithium plating on the electrode surface during fast charging, severely compromising safety and accelerating degradation. For high-capacity silicon anodes, the dramatic volume expansion (>300%) is the root cause of structural breakage and cycle failure. The nano-graphite cluster-pore structure of this invention provides an integrated solution to these two classic problems. In terms of rate performance, the nanoscale graphite crystals shorten the solid-state diffusion distance of ions to its limit. More importantly, the well-developed mesopores and macropores between the clusters form continuous ion channels throughout the electrode, allowing for thorough electrolyte wetting and enabling ions to migrate rapidly as if in an open tunnel, thus supporting extremely high charge and discharge currents. Regarding cycle stability, this multi-level structure exhibits excellent mechanical robustness. On the one hand, the nanocrystals themselves can better adapt to lithiation stress; on the other hand, the pores and interfaces between the crystal clusters act as elastic buffers, effectively absorbing and dispersing the volume change stress of the active material (whether it is the graphite crystals themselves or the filler) during cycling, preventing the overall structure from collapsing due to stress concentration. Therefore, this material system can support fast charging and discharging similar to capacitors while maintaining excellent cycle life similar to graphite, achieving the best of both worlds.

[0052] Secondly, the porous structure provides a near-ideal nanoreactor or host framework for solving the inherent problems of next-generation high-capacity anode materials such as silicon and phosphorus. Currently, the commercialization of silicon-based anodes mainly adopts a composite route of nano-silicon and carbon coating, but it still faces problems such as easy agglomeration of silicon particles during cycling, expansion accumulation leading to coating layer rupture, and unstable solid-liquid interfaces. The pore-filling strategy proposed in this invention is a confinement concept. Its porous graphite crystal cluster framework is first and foremost a rigid-flexible conductive framework. The continuous graphite phase provides much higher electronic conductivity than amorphous carbon coatings, ensuring efficient electrochemical reactions. Secondly, the size-controllable pores constitute physical confinement units, which can isolate and confine active nanoparticles such as silicon in independent spaces, preventing them from migrating and agglomerating during cycling, and strictly limiting their volume expansion within local pore spaces, avoiding lateral propagation of expansion. In addition, the solid electrolyte interface film formed on the graphite framework surface is usually thinner and more stable than that formed on the silicon surface, which can reduce side reactions and electrolyte consumption. This silicon-locking structure within a graphite cage allows high-capacity active materials to fully realize their capacity potential while being effectively tamed, solving the fundamental problem of poor cycle stability and paving a practical technical path for achieving next-generation lithium-ion batteries with energy densities exceeding 400 Wh / kg.

[0053] Finally, this invention significantly optimizes the interfacial chemistry of the electrode through its structural design, thereby establishing an advantage in key practical indicators such as initial coulombic efficiency, voltage plateau, and energy efficiency. For any battery material, the properties of the solid electrolyte interphase (SEI) film formed in contact with the electrolyte are crucial. The large specific surface area of ​​silicon materials leads to the growth of excessive, unstable SEI films, continuously consuming active lithium and electrolyte, resulting in low initial efficiency and rapid capacity decay. In this invention, even when filled with high-capacity active particles, these particles are primarily encapsulated within the pores formed by graphite crystal clusters, thus significantly reducing the direct, large-area contact between the highly active material and the electrolyte. The primary SEI film will tend to form on the exposed, electrochemically stable graphite crystal surface, resulting in a denser and more stable SEI film. This not only helps improve initial coulombic efficiency and conserve valuable lithium resources but also maintains interfacial stability during long cycles, reducing persistent side reactions. Furthermore, the graphite crystal cluster framework provides a flat and near-0.1V (vs. Li) interface similar to that of a graphite anode. + The discharge voltage plateau of Li. Compared to the ramp voltage of hard carbon and the rapid drop in voltage at the end of discharge of silicon-based materials, the flat voltage plateau means that the battery can maintain a more stable operating voltage during discharge, output more stable power, and enable the battery management system to estimate the amount of charge more accurately, thereby improving the actual usable energy density and energy efficiency of the entire battery pack.

[0054] In summary, the negative electrode composite material provided by this invention is a material system with strong application adaptability and technological scalability, demonstrating enormous potential for meeting diverse future energy storage needs. From an application perspective, its superior rate performance and cycle life perfectly match the urgent needs of electric vehicles for ultra-fast charging and ultra-long battery life; its high energy density achieved through pore filling also meets the demands of consumer electronics and long-range electric vehicles for volumetric and gravimetric energy efficiency. From a technological evolution perspective, this platform has extremely strong compatibility and scalability: in addition to lithium-ion batteries, its open pore structure and excellent ion transport capabilities are also suitable for novel energy storage systems such as sodium-ion and potassium-ion batteries; the active materials used for filling can be expanded from silicon to tin, antimony, phosphorus, and even sulfur, adapting to different reaction mechanisms. Although the material currently faces engineering challenges such as complex preparation processes, cost control, and pore filling uniformity, its clear structural design corresponds to a performance regulation logic, providing materials scientists with a clear direction for optimization. Therefore, this invention represents a paradigm shift from passive improvement to active design. Through an ingenious biomimetic multi-level structure, it integrates properties such as conductivity, ion transport, mechanical stability, and active load, and is expected to become one of the key platform technologies to break through the current bottlenecks in energy storage technology, driving battery technology towards higher performance and more intelligent design.

[0055] The present invention also discloses a negative electrode, which comprises the above-mentioned negative electrode composite material for batteries as the negative electrode active material.

[0056] In addition, the present invention also provides a battery comprising a negative electrode made of the aforementioned negative electrode composite material for batteries.

[0057] In some embodiments, the battery may further include a positive electrode, a separator, and an electrolyte.

[0058] The present invention is further illustrated below with specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for illustrative purposes and should not be construed as limiting the invention in any way. Unless otherwise specified, the raw materials used in the embodiments and comparative examples of the present invention were carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0059] Preparation Example 1 (Changing the carbon source: preparing graphite clusters using commercially available oxidized pitch and polypyrrolidone) Step S1, mix commercially available oxidized asphalt (softening point 120 °C) and polypyrrolidone ( M n =30 kDa) were uniformly mixed at a mass ratio of 3:1 at high temperature to obtain a mixed dispersion sample.

[0060] Step S2: After prestabilizing the mixture obtained in S1 at 200 °C for 2 h, crush it and carbonize it at 850 °C for 2 h in an inert atmosphere.

[0061] In step S3, the carbonized material obtained in S2 is activated by steam in a tube furnace at 870 °C for 4 h, and then crushed and graded to obtain graphite crystal clusters.

[0062] High-resolution transmission electron microscopy (HRTEM) is used to characterize the microstructure of nanocrystalline materials. HRTEM can visually demonstrate the orientation of lattice fringes and other features within nanocrystals. To ensure the representativeness and reliability of the observation results, sufficient images must be acquired from multiple different regions of the sample to eliminate random biases caused by localized observations. Subsequently, specialized image processing software is used to systematically observe and measure the clear nanocrystals with typical structures within the images.

[0063] Figure 12 , Figure 13 The images show TEM and HRTEM images of the graphite clusters obtained in Example 1, respectively. The TEM image shows that the graphite clusters are composed of multiple nano-graphite crystals, with clear transition regions and porous structures between them. The HRTEM image shows the lattice orientation of the nano-graphite crystals, and that the lattice orientation of the graphite crystals in different regions varies to some extent. Figure 16 To obtain the Raman spectrum of the graphite cluster obtained in Example 1, the spectrum of the graphite cluster in Example 1 was calculated by integrating the peak areas of the D and G bands. I D / I G It is 0.92.

[0064] Preparation Example 2 (Changing the carbon source: Preparing graphite clusters using commercially available sulfonated pitch and polyvinyl alcohol) Step S1, mix commercially available sulfonated bitumen and polyvinyl alcohol (PVA) M n =25 kDa) was stirred in water at a mass ratio of 3:1 at 80 °C for 3 h to obtain a mixture, which was then reacted in a hydrothermal reactor at 200 °C for 4 h.

[0065] Step S2: After prestabilizing the mixture obtained in S1 at 200 °C for 2 h, crush it and carbonize it at 850 °C for 2 h in an inert atmosphere.

[0066] In step S3, the carbonized material obtained in S2 is activated by steam in a tube furnace at 870 °C for 4 h, and then crushed and graded to obtain nano-graphite crystals.

[0067] Figure 17 To obtain the Raman spectrum of the graphite cluster obtained in Example 2, the spectrum of the graphite cluster from Example 1 was calculated by integrating the peak areas of the D and G bands. ID / I G It is 0.38.

[0068] Preparation Example 3 (Changing the carbon source: preparing graphite clusters using commercially available graphite oxide and carboxymethyl cellulose) Step S1, mix commercially available graphite oxide and carboxymethyl cellulose ( M n =31 kDa) at a mass ratio of 3:1 N , N The mixture was stirred in dimethylacetamide at 80 °C, and oxaloyl chloride was added dropwise. The reaction was continued for 3 h to obtain a mixture.

[0069] Step S2: After prestabilizing the mixture obtained in S1 at 200 °C for 2 h, crush it and carbonize it at 850 °C for 2 h in an inert atmosphere.

[0070] In step S3, the carbonized material obtained in S2 is activated by steam in a tube furnace at 870 °C for 4 h, and then crushed and graded to obtain nano-graphite crystals.

[0071] Figure 18 To obtain the Raman spectrum of the graphite cluster obtained in Example 3, the spectrum of the graphite cluster from Example 1 was calculated by integrating the peak areas of the D and G bands. I D / I G It is 0.68.

[0072] Comparative Preparation Example 1 (Preparation of porous carbon using phenolic resin) In step S1, 2.0 g of resorcinol, 2.5 mL of formaldehyde, 4.0 mL of ammonia, and 100.0 mL of deionized water were added to a beaker. After sonication for 30 min, the mixture was stirred at 45 °C for 12 h, and the pH was adjusted to neutral with phosphoric acid. The mixture was then heated to 80 °C and stirred continuously for 1.5 h. When the reaction system cooled to 25 °C, the mixture was collected and freeze-dried for 24 h to obtain the precursor.

[0073] Step S2: The precursor obtained in S1 is placed in a tube furnace and carbonized under argon atmosphere (720 °C, 1.3 h, 10 °C min). –1 Carbonized material is obtained.

[0074] Step S3: Place 1.0 g of the carbonized material obtained in S2 into a tube furnace, introduce steam at 2.5 mL / min, and heat at 740°C for 2 h (heating rate: 10 °C / min). –1 After cooling to room temperature, porous carbon is obtained by washing and drying.

[0075] Figure 14 To compare with the TEM image of the porous carbon prepared in Example 1, it can be seen that the porous carbon is a single block and does not have a multi-level structure; Figure 15 For comparison, the HRTEM image of the porous carbon prepared in Example 1 showed no obvious graphite lattice striations.

[0076] Comparative Preparation Example 2 (Preparation of carbon materials using polyethylene and polyvinyl alcohol polymers) Step S1, mix commercially available polyethylene ( M n =150kg / mol) and polyvinyl alcohol ( M n =25 kDa) were uniformly mixed at a mass ratio of 3:1 at high temperature to obtain a mixed dispersion sample.

[0077] Step S2: After prestabilizing the mixture obtained in S1 at 200 °C for 2 h, crush it and carbonize it at 850 °C for 2 h in an inert atmosphere.

[0078] In step S3, the carbonized material obtained in S2 is activated by steam in a tube furnace at 870 °C for 4 h, and then crushed and graded to obtain carbon material.

[0079] The TEM results above show that highly graphitized nano-graphite crystals can be obtained by hydrothermal synthesis using asphalt compounded with different polymers. In contrast, no obvious graphite lattice striations can be observed in TEM when using traditional phenolic resins or when only polymers are added.

[0080] The physical parameters of the prepared examples and the comparative prepared examples were tested and statistically recorded in Table 1.

[0081] Table 1. Structural and property parameters of nano-graphite clusters

[0082] Example 1 Nanographite clusters / silicon were prepared by CVD deposition using the nanographite clusters prepared in Example 1. CVD Composite materials. The specific procedures are as follows: In step S1, the prepared nano-graphite crystal clusters are uniformly spread in a quartz boat within a horizontal tube furnace. The reaction chamber is sealed, and high-purity argon gas (purity >99.999%) is introduced, followed by three repeated purging cycles using a vacuum-refill method. Under the protection of an argon gas flow (flow rate 100 mL / min), the reaction chamber is heated to 600 °C at a heating rate of 5 °C / min and held at that temperature for 0.5 hours.

[0083] In step S2, after the heat preservation is completed, and the temperature is kept stable, high-purity silane gas (SiH4, diluted with high-purity argon to a volume concentration of 10%) is introduced into the reaction system together with the carrier gas (high-purity argon, flow rate 200 mL / min) at a total flow rate of 50 mL / min. The silicon infiltration reaction continues for 3 hours.

[0084] Step S3: After the reaction is complete, first stop the flow of the silane mixture, and then maintain the sample at 600°C for 0.5 hours under purging with pure argon (flow rate 300 mL / min). Subsequently, cool down to room temperature and remove the nano-graphite clusters / silicon under argon protection. CVD Composite materials.

[0085] Figure 19 Nanographite clusters / silicon prepared in Example 1 CVD HRTEM images of the composite material. Clear lattice fringes of silicon nanocrystals are visible, and the fringes of the graphite nanocrystals surrounding the different silicon nanocrystals exhibit orientational differences.

[0086] Example 2 Using the nano-graphite clusters prepared in Example 2, CVD deposition of nano-silicon was performed to prepare nano-graphite clusters / silicon. CVD Composite material. The specific operation is the same as in Example 1.

[0087] Example 3 Using the nano-graphite clusters prepared in Example 3, CVD deposition of nano-silicon was performed to prepare nano-graphite clusters / silicon. CVD Composite material. The specific operation is the same as in Example 1.

[0088] Example 4 This embodiment is basically the same as Embodiment 1, except that a mixed reaction gas is introduced in step S2. High-purity silane gas (SiH4, diluted to a volume concentration of 10% with high-purity argon) and high-purity germanane gas (GeH4, diluted to a volume concentration of 5% with high-purity argon) are introduced into the reaction system together with a carrier gas (high-purity argon, flow rate 200 mL / min) at a total flow rate of 50 mL / min (of which the flow rate of the SiH4 mixed gas is 40 mL / min and the flow rate of the GeH4 mixed gas is 10 mL / min). By adjusting the ratio of silane and germanane, silicon-germanium alloy nanoparticles are deposited on the surface of the nano-graphite clusters, thereby obtaining the nano-graphite cluster / silicon-germanium alloy CVD composite material. The remaining operating parameters, such as the heating program, reaction temperature, holding time, and post-processing, are consistent with those in Embodiment 1.

[0089] Example 5 In this embodiment, silicon and tin are first co-deposited on nano-graphite clusters using CVD, followed by the introduction of phosphorus through subsequent heat treatment to prepare a multi-element composite material. The specific operations are as follows: Step S1 is the same as step S1 in Example 1.

[0090] In step S2, after the heat preservation is completed, the temperature is maintained at a stable 550 °C. High-purity silane gas (SiH4, 10% by volume), tin tetrachloride vapor (SnCl4, carried by high-purity argon gas bubbling at a controlled temperature of 35 °C), and carrier gas (high-purity argon gas) are introduced into the reaction system together. The flow rate of the SiH4 mixture is controlled at 30 mL / min, the flow rate of the argon gas carrying SnCl4 is 20 mL / min, and the replenishing argon gas flow rate is 200 mL / min using a mass flow meter. The deposition reaction continues for 2 hours, forming silicon-tin composite nanoparticles on the surface and in the pores of the nano-graphite crystal clusters.

[0091] Step S3: The intermediate product obtained in step S2 is uniformly mixed with red phosphorus powder at a mass ratio of 100:5 and placed in a vacuum-sealed quartz tube. The quartz tube is placed in a muffle furnace and heated to 400°C at a rate of 2°C / min, and held at that temperature for 3 hours to allow phosphorus to sublimate and diffuse into or coat the surface of the silicon-tin composite particles. The mixture is then allowed to cool naturally to room temperature, and the product is removed. Under an inert atmosphere, it is treated at 300°C for 1 hour to remove unreacted red phosphorus from the surface, ultimately yielding a nano-graphite cluster / silicon-tin-phosphorus multi-component composite material.

[0092] Example 6 Step S1: The nano-graphite clusters obtained in Preparation Example 1 and bismuth nitrate (Bi(NO3)3·5H2O) were added to anhydrous ethanol at a mass ratio of 20:1, ultrasonically dispersed for 2 hours, and then stirred and evaporated at 60°C to obtain a solid mixture.

[0093] Step S2: The solid mixture from step S1 is placed in a tube furnace and heated to 500°C at 5°C / min under an argon atmosphere. The temperature is maintained for 2 hours to decompose the bismuth salt and recombine it with the graphite crystal cluster, thus obtaining bismuth-doped nano-graphite crystal clusters.

[0094] Step S3 is the same as in Example 1, using the bismuth-doped nano-graphite clusters obtained in step S2 as a substrate for CVD deposition of nano-silicon. The final result is a bismuth-doped nano-graphite cluster / silicon composite material.

[0095] Example 7 Step S1: Weigh 1.0 g of the nano-graphite crystal clusters obtained in Preparation Example 1, disperse them in 150 mL of ethylene glycol, and sonicate for 1.5 hours to form a uniform and stable suspension.

[0096] Step S2: Weigh 0.8 g of stannous chloride dihydrate (SnCl2·2H2O) and dissolve it in 50 mL of ethylene glycol. Stir until completely dissolved to obtain a tin salt precursor solution. To inhibit tin ion hydrolysis, a small amount of concentrated hydrochloric acid (about 0.5 mL) can be added to adjust the acidity of the solution.

[0097] In step S3, under a nitrogen atmosphere and with vigorous stirring, the tin salt precursor solution from step S2 is slowly added dropwise to the suspension from step S1. After the addition is complete, stirring continues for 30 minutes to allow tin ions to be fully adsorbed onto the surface of the nano-graphite crystal clusters. Subsequently, the mixture is heated to 160°C, and 50 mL of a freshly prepared ethylene glycol solution containing 1.5 g of sodium borohydride (NaBH4) is added dropwise to initiate the reduction reaction. The dropwise addition is controlled and completed in approximately 30 minutes. After the addition is complete, the reaction continues at 160°C for 2 hours to ensure that the tin ions are completely reduced to metallic tin nanoparticles and firmly loaded onto the graphite crystal clusters.

[0098] In step S4, after the reaction is complete, allow it to cool naturally to room temperature. Collect the black precipitate by centrifugation and wash it repeatedly with deionized water and anhydrous ethanol 3–5 times to remove residual solvent and reaction byproducts. Finally, place the washed product in a vacuum drying oven and dry it at 60°C for 12 hours to obtain the nano-graphite cluster / tin composite material.

[0099] Step S5 is the same as in Example 1, using the tin-doped nano-graphite clusters obtained in step S4 as a substrate for CVD deposition of nano-silicon. The final result is a tin-doped nano-graphite cluster / silicon composite material.

[0100] Comparative Example 1 By using the nano-graphite clusters prepared in Comparative Preparation Example 1, CVD deposition of nano-silicon was performed to prepare nano-graphite clusters / silicon. CVD Composite material. The specific operation is the same as in Example 1.

[0101] Comparative Example 2 By using the nano-graphite clusters prepared in Comparative Preparation Example 2, CVD deposition of nano-silicon was performed to prepare nano-graphite clusters / silicon. CVD Composite material. The specific operation is the same as in Example 1.

[0102] Test Example: Battery Testing Based on the silicon-based composite materials synthesized in the aforementioned examples and comparative examples, negative electrode sheets were prepared using them as negative electrode active materials. CR2032 coin cell half-cells were assembled using conventional processes, and their electrochemical performance was systematically evaluated. Specific test contents and methods are as follows: 1. Half-cell preparation and electrochemical performance testing: (1) Half-cell assembly: The CR2032 coin cell structure was assembled in an inert atmosphere glove box. A lithium metal sheet was used as the counter electrode, a polypropylene microporous membrane as the separator, and the electrolyte was 1 mol / L LiPF6 dissolved in an equal volume ratio of ethyl carbonate (EC) and diethyl carbonate (DEC). Subsequent charge-discharge performance tests were conducted using a LAND battery testing system.

[0103] (2) Measurement of specific capacity and initial coulombic efficiency: After the assembled coin cells were left to stand for 6 hours, they were first discharged to 0.005 V at a current density of 0.05 C, and then further discharged to the same cutoff voltage at 0.01 C. After standing for 5 minutes, they were charged to 1.5 V at a constant current of 0.05 C. The delithiation capacity corresponding to the 0.8 V plateau during the first charge cycle is the specific capacity of the electrode material (also known as the 0.8 V specific capacity). The ratio of this delithiation capacity to the initial lithium insertion capacity is defined as the initial coulombic efficiency of the battery (0.8 V initial efficiency).

[0104] 2. Full cell preparation and electrochemical testing: Using the aforementioned silicon-based composite material as the negative electrode active material, a pouch cell was fabricated according to conventional processes and assembled in a dry environment with a dew point of -45°C. Charge-discharge cycle evaluation was performed using the LANBTS testing system, with the specific steps as follows: (1) Preparation of positive electrode: The active material LiCoO2, conductive carbon black SuperP, binder PVDF and solvent NMP are mixed evenly in a mass ratio of 92:3:5:150, coated on the positive electrode current collector, and dried at 80°C to obtain the positive electrode sheet.

[0105] (2) Negative electrode preparation: The negative electrode active material, SuperP, binder polyacrylic acid and deionized water are mixed into a slurry in a mass ratio of 95:1:4:120, uniformly coated on the surface of the negative electrode current collector, and dried at 100°C to obtain the negative electrode sheet.

[0106] (3) Battery assembly: The positive and negative electrode sheets are stacked with a polypropylene separator to form a battery cell, which is then packaged in an aluminum-plastic film bag. An appropriate amount of electrolyte (1 mol / L LiPF6 in EC / DEC, volume ratio 1:1) is injected, and the battery is vacuum sealed to obtain a soft-pack battery.

[0107] (4) Formation and Capacity Testing: After encapsulation, the battery was left to stand at a constant temperature of 25°C for 12 hours, followed by the following sequential processes: constant current charging at 0.02C to 3.3V, followed by a 30-minute rest; charging at 0.025C to 3.8V, followed by a 10-minute rest; and charging at 0.33C to 4.2V. After formation, vacuuming was performed and the gas bag was cut. The battery was then charged at 0.33C to 4.45V, left to stand for 10 minutes, and then discharged at constant currents of 1C and 0.33C to 3.0V to complete the capacity testing. The ratio of the initial discharge capacity to the initial charge capacity is the initial coulombic efficiency of the entire battery.

[0108] (5) Room temperature cycle life test: Place the battery in a 25℃ constant temperature chamber, charge it with 1C constant current to 4.45V, switch to constant voltage charging until the current drops to 0.1C; after standing for 10 minutes, discharge it with 1C constant current to 3.0V, stand for 10 minutes, repeat the charge and discharge process until the capacity decays to less than 80% of the first discharge capacity, record the total number of cycles as the cycle life, and calculate the capacity retention rate of the 100th cycle.

[0109] (6) High-rate discharge performance test: Under the same temperature conditions, the charging steps are the same as (5), and the discharge stage is carried out using 3C constant current, while other conditions remain the same. The cycle life and capacity retention rate at the 100th cycle are recorded, and the ratio of 3C to 1C discharge capacity is calculated to evaluate the rate characteristics of the material.

[0110] 3. Data and its analysis Table 2 Electrochemical Information of Composite Materials

[0111] As shown in Table 2, Examples 1-3 demonstrate that increasing the size of the nano-graphite crystals can improve the first-efficiency and rate performance of the silicon-carbon anode material. Examples 4-7, based on the examples, increase the doping of different elements, which can improve the cycle performance of the silicon-carbon anode material.

[0112] Compared with Comparative Examples 1 and 2, both silicon-carbon composite materials with nano-graphite crystal hierarchical structures and silicon-carbon composite materials with nano-graphite crystal hierarchical structures doped with heterogeneous elements exhibit better cycling and rate performance.

[0113] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, 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 the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A negative electrode composite material for batteries, characterized in that, The negative electrode composite material for the battery comprises composite material particles; The composite material particles include secondary graphite clusters and nano-active particles; The secondary graphite cluster includes a primary graphite cluster and an adjacent transition region II. The primary graphite crystal cluster comprises nano-graphite crystals and an adjacent transition region. The nano-graphite crystals are composed of multiple layers of graphene sheets with consistent orientation. The nano-active particles are distributed in the nano-graphite crystals, and / or in transition region one, and / or transition region two.

2. The negative electrode composite material for batteries according to claim 1, characterized in that, The composite material particles satisfy at least one of the following characteristics: (1) The size of the nano-graphite crystals is 2~10 nm; (2) The number of layers of the nano-graphite crystals is 3 to 20; (3) The size of the first transition region is 1~3 nm; (4) The size of the primary graphite cluster is 10~500 nm; (65) The size of the second transition region is 5~30 nm; (76) The composite material particles I D / I G The ratio is 0.1 to 1.

3. The negative electrode composite material for batteries according to claim 1, characterized in that, At least a portion of the nano-active particles form chemical bonds or intermolecular forces with at least one in-plane carbon atom of a carbon plane in the nano-graphite crystal and / or carbon atoms at the edge of the carbon plane.

4. The negative electrode composite material for batteries according to claim 3, characterized in that, The composite material particles contain at least one of the following chemical bonds: (1) At least a portion of the contact interface between the nano-active particles and the nano-graphite crystals forms a chemical bond containing a carbon-Y (CY) bond, wherein Y is the elemental composition of the nano-active particles; (2) At least some of the nano-active particles and nano-graphite crystals form chemical bonds containing carbon-XY (CXY) bonds at the contact interface, where X is an element other than Y; (3) Chemical bonds are formed between at least partially interconnected nanographite crystals through carbon atoms on their edges or surfaces, the chemical bonds including π-π stacking, carbon-carbon single bond (CC) bond or carbon-carbon double bond (C=C) bond.

5. The negative electrode composite material for batteries according to any one of claims 1 to 4, characterized in that, The nano-active particles are selected from at least one elemental, alloy, or compound nanoparticles of silicon, germanium, tin, phosphorus, antimony, and bismuth.

6. The negative electrode composite material for batteries according to any one of claims 1 to 4, characterized in that, In the region surrounding at least one of the nano-active particles, there are at least two nano-graphite crystals, wherein the angle between the extension directions of the (002) lattice stripes of two adjacent nano-graphite crystals is 0° to 150°, preferably 0° to 100°.

7. The negative electrode composite material for batteries according to any one of claims 1 to 4, characterized in that, At least 30% or more of the volume of the nano-active particles are embedded in the closed or semi-closed space formed by the stacking or enclosure of the nano-graphite crystals.

8. The negative electrode composite material for batteries according to any one of claims 1 to 4, characterized in that, At least 30% or more of the volume of the nano-active particles are embedded between and / or at the edges of the carbon planes of the nano-graphite crystals.

9. The negative electrode composite material for batteries according to any one of claims 1 to 4, characterized in that, The sheet size of the nano-graphite crystals is 5-200 nm; The number of graphene sheets in the nano-graphite crystals is ≥5, preferably 5~20.

10. The negative electrode composite material for batteries according to any one of claims 1 to 4, characterized in that, The outermost layer of the negative electrode composite material for the battery is also covered with a continuous carbon layer.

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