Silicon-carbon composite material as well as appearance evaluation standard and application thereof

Abstract

The invention provides a silicon-carbon composite material as well as an appearance evaluation standard and application thereof, and relates to the technical field of battery negative electrode materials. The silicon-carbon composite material comprises sphere-like silicon-carbon particles, and each sphere-like silicon-carbon particle comprises a silicon-carbon plane and a silicon-carbon transition cambered surface adjacent to the silicon-carbon plane; and the minimum value of the curvature of the cambered surface infinitesimal element of the silicon-carbon transition cambered surface at the joint of the silicon-carbon transition cambered surface and the silicon-carbon plane is 0. The material is of a sphere-like structure containing a plane and an adjacent transition cambered surface, the structure and a base body can form three-dimensional interlocking, mechanical binding force is enhanced, interface crack propagation is restrained, particles can be promoted to be directionally arranged to form regular and uniform slit-shaped channels / pores, the compression resistance and abrasion resistance of the material are improved, the stacking density is increased, and the contact area is increased. And the silicon-carbon composite material has excellent electrochemical performance. The shape evaluation standard represented by the polyhedron degree Q (0-1, the closer to 1, the closer to an ideal polyhedron) is provided, the problem that the shape of an existing polyhedral material lacks a unified evaluation standard is solved, a scheme is provided for similar polyhedral material evaluation, and material design, screening and application are promoted.

Description

A silicon-carbon composite material and its shape evaluation criteria and applications Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a silicon-carbon composite material and its shape evaluation standards and applications. Background Technology

[0002] Silicon-carbon composite materials are among the most promising anode materials for lithium-ion rechargeable batteries in recent years. Vapor-phase silicon-carbon anodes, which use porous carbon materials as a framework and are obtained through vapor-phase deposition of silanes and other gases, effectively improve the conductivity and ion conductivity of the composite material and reduce the volume effect during silicon delithiation / intercalation, making it one of the best structures for silicon-based anodes. The morphology of silicon-carbon composite materials also significantly affects their filling performance, packing morphology, flow morphology, surface and interface properties, and mechanical properties, thus influencing their application performance. Specifically, in lithium-ion battery applications, this may manifest as an impact on compaction density, interparticle adhesion, and electrode bonding strength, ultimately affecting the battery's energy density, rate capability, and cycle stability.

[0003] Due to their isotropic nature, spherical materials have very high structural strength and high material stability. Therefore, spherical silicon-carbon currently exhibits relatively good cycle stability in lithium battery anode applications; while ordinary bulk silicon-carbon exhibits poor cycle stability under the same silicon content conditions.

[0004] On the other hand, silicon-based materials exhibit lithium insertion expansion during cycling, while during delithiation contraction, due to the isotropic contraction of the spherical material's structure and the point contact between the spherical material, binder, conductive agent, and current collector, interface slippage and delamination are prone to occur, resulting in poor dynamics; while bulk materials perform slightly better in this regard.

[0005] Finding a material that combines the advantages of both morphologies has become crucial for improving material performance. Currently, no spherical material has been publicly reported that possesses the advantages of both spherical and bulk resins, and there is a lack of specific standards for qualitative and quantitative descriptions of such a material.

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

[0007] One of the objectives of this invention is to provide a silicon-carbon composite material comprising a plane and its adjacent transition arc surfaces, which can significantly improve the volumetric energy density of the silicon-carbon composite material, greatly alleviate cycle stress, and endow the battery with excellent cycle stability.

[0008] The second objective of this invention is to provide a standard for evaluating the shape of spherical materials.

[0009] The third objective of this invention is to provide a negative electrode.

[0010] The fourth objective of this invention is to provide a battery.

[0011] To achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a silicon-carbon composite material, the silicon-carbon composite material comprising quasi-spherical silicon-carbon particles, the quasi-spherical silicon-carbon particles comprising a silicon-carbon plane and an adjacent silicon-carbon transition arc surface; the minimum curvature of the arc surface micro-element at the junction of the silicon-carbon transition arc surface and the silicon-carbon plane is 0.

[0012] Furthermore, the silicon-carbon particles satisfy at least one of A1 to A4: A1, in the quasi-spherical silicon-carbon particles, the silicon-carbon plane and its adjacent silicon-carbon transition arc surface form a silicon-carbon flat arc surface combination; the total area of ​​the silicon-carbon flat arc surface combination on a single quasi-spherical silicon-carbon particle accounts for 0.2 to 1% of the surface area of ​​the quasi-spherical silicon-carbon particle; A2, the silicon-carbon plane is tangent to the silicon-carbon transition arc surface; A3, the curvature change of the silicon-carbon transition arc surface is continuous; A4, the quasi-spherical silicon-carbon particles also have silicon-carbon spherical surfaces.

[0013] Furthermore, the silicon-carbon particles satisfy at least one of B1 to B5: B1, the ratio k of the total area of ​​the silicon-carbon planes of a single spherical silicon-carbon particle to the outer surface area of ​​the particle. 1i The value is 0.2~0.99; B2, the number N of silicon-carbon planes in a single silicon-carbon particle. 1i The value is 1~20; B3, the relative standard deviation S of the total planar area of ​​all silicon-carbon particles of a single silicon-carbon particle. 1i The value is 0~0.2; B4, the polyhedrality Q of a single silicon-carbon particle. 1i The polyhedral degree Q is 0.5~1. 1i k is the ratio of the total area of ​​the silicon-carbon planes of a single silicon-carbon particle to the outer surface area of ​​that particle. 1i The number of silicon-carbon planes N 1i The relative standard deviation S of the area of ​​all silicon-carbon planes 1i The function whose expression is: B5. The ratio of the total area of ​​the silicon-carbon transition arc surface of a single silicon-carbon particle to the outer surface area of ​​the particle is 0.01 to 0.8.

[0014] Furthermore, the silicon-carbon composite material has at least one characteristic selected from C1 to C6: C1, the specific surface area of ​​the silicon-carbon composite material is 0.1 to 50 m². 2 / g, preferably 0.1~10 m 2 / g, further preferably 0.1~3 m 2 / g; C2, the true density of the silicon-carbon composite material measured by He is 1.8~2.3 g / cm³. 3 C3. The true density of the silicon-carbon composite material measured by N2 is 1.3~2.0 g / cm³. 3 C4. The silicon content of the silicon-carbon composite material is 10-90 wt%; preferably 30-70 wt%; C5. The median particle size d of the silicon-carbon composite material V50 The particle size is 1~100 μm, preferably 2~30 μm; C6, the particle size distribution of the silicon-carbon composite material is 0.5~1.8, preferably 0.5~1.2.

[0015] Furthermore, the silicon-carbon composite material is obtained by vapor deposition of silicon on a carbon material using a silicon-containing precursor; preferably, the vapor deposition temperature is 150~1000 ℃; preferably, the silicon-carbon composite material includes a coating layer.

[0016] Furthermore, the silicon-carbon composite material is obtained by vapor deposition of silicon on a carbon material using a silicon-containing precursor; the carbon material comprises quasi-spherical carbon particles, each quasi-spherical carbon particle comprising a carbon plane and an adjacent carbon transition arc surface; the minimum curvature of the arc surface micro-element at the junction of the carbon transition arc surface and the carbon plane is 0.

[0017] Furthermore, the carbon material in the silicon-carbon composite material is obtained by carbonizing and / or activating a carbon precursor; the carbon precursor comprises spherical resin particles, each spherical resin particle comprising a resin plane and an adjacent resin transition arc surface; the minimum curvature of the arc surface micro-element at the junction of the resin transition arc surface and the resin plane is 0.

[0018] Secondly, the present invention provides an evaluation standard for the polyhedral degree of a spherical material, characterized in that the spherical material comprises spherical particles, and the spherical material includes a plane and an adjacent transition arc surface; the evaluation standard is represented by the polyhedral degree Q of the spherical material, and the polyhedral degree Q of the spherical material is the same as the polyhedral degree Q of the spherical particles. i The average value, n is the number of spherical particles in the spherical material; for statistical convenience, n≥100.

[0019] The degree of polyhedron Q i k is the ratio of the total area of ​​the i-th spherical silicon-carbon particle's planar surface to the particle's outer surface area. j The number of silicon-carbon planes N j The relative standard deviation S of the area of ​​all silicon-carbon planes i The function whose expression is: .

[0020] Thirdly, the present invention provides a negative electrode, characterized in that the negative electrode comprises a negative electrode active material, the negative electrode active material comprising the silicon-carbon composite material described in the first aspect of the present invention.

[0021] Fourthly, the present invention provides a battery, characterized in that the battery includes a negative electrode, the negative electrode comprising the silicon-carbon composite material described in the first aspect of the present invention; preferably, the battery further includes at least one of a positive electrode, a separator, or an electrolyte.

[0022] Compared with existing technologies, the present invention has at least the following beneficial effects: The silicon-carbon composite material provided by the present invention comprises spherical silicon-carbon composite particles, the surface of which includes a plane and an adjacent transition arc surface, thus possessing the advantages of both spherical and bulk particles. Unlike the complete point contact of a sphere, each "face" of the spherical particle, although with rounded edges, still maintains a large area of ​​planar surface. During stacking, these "faces" form large-area, stable surface-to-surface or surface-to-line contact, rather than point contact. This significantly increases the effective contact area between particles, providing stronger mechanical interlocking and friction, thereby greatly improving the material's electrical conductivity, thermal conductivity, and overall stability. Compared to bulk particles, the presence of transitional arc surfaces allows particles to roll and fine-tune their positions during stacking, similar to spheres. This reduces the large number of irregular and unusable bridging gaps caused by interference from sharp edges and corners, making it easier to reach or approach the densest packing state, thus achieving a high overall packing density. The combination of planar surfaces and adjacent transitional arc surfaces acts as a bridge between planes and between planes and spheres, smoothly dispersing concentrated stress and avoiding stress concentration, thereby significantly improving the mechanical strength and wear resistance of the particles. Furthermore, the combination of planar and arc surfaces can create a three-dimensional interlock with the matrix, resulting in strong mechanical bonding and preventing crack propagation along the interface. The presence of the planar and arc surface combination also allows for the directional alignment of particles, making it easier to form more regular and uniformly sized slit-like channels or pores.

[0023] When applied to lithium-ion battery anodes, firstly, the spherical silicon-carbon composite material provided by this invention, with its transition arc surface acting like an arch bridge, disperses and buffers the volume expansion stress caused by silicon during charging and discharging, greatly alleviating capacity decay caused by particle breakage and continuous SEI film rupture; secondly, its planar surface increases the surface contact between silicon-carbon and silicon-carbon and between silicon-carbon and additives in the anode, which is more effective than the point contact of a sphere in suppressing relative particle displacement, thereby protecting the stability of the particle structure and SEI film; finally, the combination of the planar surface and the adjacent arc surface not only endows the material with high packing density and large surface contact area, but also directly improves the volumetric energy density of the battery, promotes the formation of more conductive pathways with lower resistance between particles, reduces the tortuosity of the packing gaps, improves the mass transfer kinetics of the electrolyte, enhances the electronic and ionic conductivity of the entire electrode, and significantly improves the rate performance of the anode.

[0024] Furthermore, since the silicon-carbon composite material of this invention inherently possesses polyhedral characteristics, a shape evaluation standard—polyhedrality Q—is proposed for the aforementioned silicon-carbon composite material. The Q value is used to assess how closely the shape of different silicon-carbon composite materials approximates a regular polyhedron, solving the problem of cross-shape comparison (cube, octahedron, dodecahedron, etc.). Regardless of the underlying polyhedron, its potential performance in specific applications can be evaluated and predicted using its Q value, achieving "different morphologies, same benchmark," greatly facilitating material design, selection, and application. Attached Figure Description

[0025] 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.

[0026] Figure 1 is a schematic diagram of the structure of a single particle of the silicon-carbon composite material provided by the present invention; Figure 2 is a flowchart of the calculation of the shape evaluation criteria provided by the present invention; Figure 3 is a SEM image of the silicon-carbon composite material provided in Example 1 of the present invention. Detailed Implementation

[0027] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In a first typical embodiment of the present invention, a silicon-carbon composite material is provided, the silicon-carbon composite material comprising near-spherical silicon-carbon particles, the near-spherical silicon-carbon particles comprising a silicon-carbon plane and an adjacent silicon-carbon transition arc surface; the minimum curvature of the arc surface micro-element at the junction of the silicon-carbon transition arc surface and the silicon-carbon plane is 0.

[0030] When the transition arc surface is tangent to the plane, the curvature of the arc surface at the connection point with the plane is equal to the curvature of the plane, which is 0; when the transition arc surface forms a certain angle with the plane, the curvature of the arc surface at the connection point with the plane is greater than 0.

[0031] Spherical particles can achieve the densest packing (such as face-centered cubic and hexagonal dense packing), with uniform and predictable pores. However, their main drawback is the small contact area, which is only point contact. When strong interparticle interactions are required, point contact limits mass transfer efficiency. When bulk materials are randomly packed, their sharp edges and corners interfere with each other, forming a large number of irregular and difficult-to-use bridging voids. This results in a non-uniform pore structure, even if the packing density is not low, making it easy for short circuits or dead zones to form when fluid passes through. The silicon-carbon composite material provided by this application includes quasi-spherical silicon-carbon particles. These spherical silicon-carbon particles include silicon-carbon planes and their adjacent silicon-carbon transition arc surfaces or silicon-carbon spheres. The silicon-carbon planes and their adjacent silicon-carbon transition arc surfaces form a silicon-carbon flat-arc surface combination, which is different from ordinary spherical silicon-carbon spheres and bulk silicon-carbon. Its arc surface structure combines with the adjacent planes, which can form a three-dimensional interlock with the matrix, resulting in strong mechanical bonding and preventing crack propagation along the interface. At the same time, the combination of flat and curved surfaces allows the particles to be oriented, making it easier to form more regular and uniformly sized slit-like channels or pores.

[0032] Spherical silicon-carbon particles possess advantages such as high packing density, large contact area, and high structural strength. In the battery field, this translates to significantly increased electrode density in the negative electrode, resulting in a substantial improvement in the volumetric energy density of silicon-carbon composite materials; a more uniform and dense conductive network within the electrode, providing an efficient pathway for electron transport; and an ideal geometric framework for effectively buffering the massive volume expansion of silicon, greatly alleviating cyclic stress and significantly improving the mechanical stability of the material, ultimately translating into superior cycle stability of the battery.

[0033] Figure 1 shows a schematic diagram of a single particle structure of the silicon-carbon composite material provided by this invention, where the shaded area represents the silicon-carbon plane and the blank area represents the silicon-carbon transition arc surface. Its unique shape design is characterized by the synergistic coexistence of the plane and the adjacent transition arc surface. This composite morphology cleverly integrates the core advantages of spherical particles and irregular block particles, achieving a revolutionary performance improvement. The presence of the plane constitutes the structural skeleton of the particle, which is key to achieving extremely high packing density. It allows multiple particles to achieve a highly regular and compact arrangement similar to "crystals" during filling, thereby filling more active material within a unit volume and significantly improving the processing capacity and efficiency of the device. The presence of the transition arc surface is the core of achieving excellent comprehensive performance. By eliminating sharp edges, it firstly fundamentally avoids stress concentration, significantly enhancing the mechanical strength and wear resistance of the particles; secondly, it guides the fluid to flow smoothly, significantly reducing system pressure drop and improving mass transfer efficiency; and thirdly, it makes the accessibility of the entire surface (including the planar area) more uniform, ensuring full utilization of active sites, thereby obtaining a high and efficient reaction / contact area.

[0034] In some specific embodiments, the silicon-carbon particles satisfy at least one of A1 to A4: A1, in the quasi-spherical silicon-carbon particles, the silicon-carbon plane and the adjacent silicon-carbon transition arc surface form a silicon-carbon flat arc surface combination; the total area of ​​the silicon-carbon flat arc surface combination on a single quasi-spherical silicon-carbon particle accounts for 0.2 to 1% of the surface area of ​​the quasi-spherical silicon-carbon particle; A2, the silicon-carbon plane is tangent to the silicon-carbon transition arc surface; A3, the curvature change of the silicon-carbon transition arc surface is continuous; A4, the quasi-spherical silicon-carbon particles also have silicon-carbon spherical surfaces.

[0035] In some embodiments, in the quasi-spherical carbon particles, the carbon plane and the adjacent carbon transition arc surface form a carbon plane-arc surface combination; the total area of ​​the carbon plane-arc surface combination on a single quasi-spherical carbon particle accounts for 0.2 to 1% of the surface area of ​​the quasi-spherical carbon particle, and may be, but is not limited to, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0.

[0036] In some embodiments, the silicon-carbon plane is tangent to the silicon-carbon transition arc surface.

[0037] In some embodiments, the curvature of the silicon-carbon transition arc surface changes continuously, and the curvature of the silicon-carbon transition arc surface can be 0~1 / R. max ~0(1 / R) max (This represents the maximum curvature of the silicon-carbon transition arc surface), indicating that both ends of the silicon-carbon transition arc surface are planar; in some embodiments, the curvature of the silicon-carbon transition arc surface can be 0~1 / R. max~1 / R1 (R1 is the radius of the sphere adjacent to the transition arc surface) represents that the two ends of the silicon-carbon transition arc surface are a plane and a sphere, respectively.

[0038] In some embodiments, the silicon-carbon particles satisfy at least one of B1 to B5: B1, the ratio k of the total area of ​​the silicon-carbon planes of a single spherical silicon-carbon particle to the outer surface area of ​​the particle. 1i The value is 0.2~0.99; B2, the number N of silicon-carbon planes in a single silicon-carbon particle. 1i The value is 1~20; B3, the relative standard deviation S of the total planar area of ​​all silicon-carbon particles of a single silicon-carbon particle. 1i The value is 0~0.2; B4, the polyhedrality Q of a single silicon-carbon particle. 1i The polyhedral degree Q is 0.5~1. 1i k is the ratio of the total area of ​​the silicon-carbon planes of a single silicon-carbon particle to the outer surface area of ​​that particle. 1i The number of silicon-carbon planes N 1i The relative standard deviation S of the area of ​​all silicon-carbon planes 1i The function whose expression is: B5. The ratio of the total area of ​​the silicon-carbon transition arc surface of a single silicon-carbon particle to the outer surface area of ​​the particle is 0.01 to 0.8.

[0039] In some embodiments, the ratio k of the sum of the planar areas of a single silicon-carbon particle to the outer surface area of ​​the particle is... 1i The value is 0.2~0.99, and can be, but is not limited to, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9; preferably, the k of a single silicon-carbon particle is... 1i The value is 0.5~0.9; more preferably, the k of a single silicon-carbon particle is... 1i The value is 0.7~0.9. k 1i Too high or too low a height is detrimental to its application in various practical scenarios. The synergistic coexistence of the planar surface and the adjacent transitional arc surface cleverly integrates the core advantages of spherical particles and irregular block particles. The presence of the planar surface is key to obtaining strong inter-particle interactions; the presence of the transitional arc surface is the core of achieving excellent overall performance.

[0040] In some embodiments, the number N of the planes of a single silicon-carbon particle 1i The value can be any integer from 1 to 20, and can be, but is not limited to, 1, 3, 5, 7, 9, 11, 13, 15, 17, or 20; preferably, the N of a single silicon-carbon particle is... 1i The value is any integer between 8 and 16; more preferably, the N of a single silicon-carbon particle is... 1iIt can be any integer between 10 and 14. In three-dimensional space, the coordination number of an ideal spherical dense packing is 12, so the optimal number of planes for silicon-carbon particles is 12. When the number of planes is too high, the silicon-carbon particles are closer to spherical; when the number of planes is too low, the silicon-carbon particles may have poor symmetry or face angles <90°, which can easily cause packing jamming and stress concentration.

[0041] In some embodiments, the relative standard deviation S of all planar areas of a single silicon-carbon particle 1i The S-value is 0~0.2, and can be, but is not limited to, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, or 0.20; preferably, the S-value of a single silicon-carbon particle is... 1i The relative standard deviation of the surface area of ​​a particle is 0 to 0.1. S represents the uniformity of the surface area. 1i The smaller the particle size, the better its consistency and the easier it is to reach or approach the densest packing state, thus achieving a high overall packing density.

[0042] In some embodiments, the polyhedral degree Q of a single silicon-carbon particle 1i The value is 0.5~1, and can be, but is not limited to, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95 or 1; preferably, the value of a single silicon-carbon particle Q is... 1i It ranges from 0.7 to 1. Q 1i For k 1i N 1i and S 1i The function, defined by its expression It can be known that k 1i N 1i and S 1i The closer Q is to the optimal value, 1i The closer the value is to 1.

[0043] In some embodiments, the ratio of the total area of ​​the silicon-carbon transition arc surface of a single silicon-carbon particle to the outer surface area of ​​the particle is 0.01 to 0.8, and may be, but is not limited to, 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or 0.8.

[0044] Furthermore, the silicon-carbon composite material has at least one characteristic selected from C1 to C6: C1, the specific surface area of ​​the silicon-carbon composite material is 0.1 to 50 m². 2 / g, preferably 0.1~10 m 2 / g, further preferably 0.1~3 m 2 / g; C2, the true density of the silicon-carbon composite material measured by He is 1.8~2.3 g / cm³. 3C3. The true density of the silicon-carbon composite material measured by N2 is 1.3~2.0 g / cm³. 3 C4. The silicon content of the silicon-carbon composite material is 10-90 wt%; preferably 30-70 wt%; C5. The median particle size d of the silicon-carbon composite material V50 The particle size is 1~100 μm, preferably 2~30 μm; C6, the particle size distribution of the silicon-carbon composite material is 0.5~1.8, preferably 0.5~1.2.

[0045] In some embodiments, the specific surface area of ​​the silicon-carbon composite material is 0.1~50 m². 2 / g; preferably 0.1~10m 2 / g; more preferably 0.1~3 m 2 / g. In some embodiments, the specific surface area of ​​the silicon-carbon composite material is 0.1~20m². 2 / g; In some embodiments, the specific surface area of ​​the silicon-carbon composite material is 0.1~15 m². 2 / g; In some embodiments, the specific surface area of ​​the silicon-carbon composite material is 0.1~12 m². 2 / g; In some embodiments, the specific surface area of ​​the silicon-carbon composite material is 0.1~10 m² / g. 2 / g; In some embodiments, the specific surface area of ​​the silicon-carbon composite material is 0.1~8 m². 2 / g; In some embodiments, the specific surface area of ​​the silicon-carbon composite material is 0.1~5 m². 2 / g; In some embodiments, the specific surface area of ​​the silicon-carbon composite material is 0.1~3 m². 2 / g; In some embodiments, the specific surface area of ​​the silicon-carbon composite material is 0.1~1 m². 2 / g; In some embodiments, the specific surface area of ​​the silicon-carbon composite material is 0.01~0.1 m². 2 / g. Generally, the lower the specific surface area of ​​silicon-carbon composite materials, the lower the processing gas production and the higher the initial efficiency; however, if the reduction in specific surface area comes from a large amount of coating, it may lead to a deterioration in kinetic performance.

[0046] In some embodiments, the true density of the silicon-carbon composite material measured by He is 1.8~2.3 g / cm³. 3 In some specific embodiments, the silicon-carbon composite material is obtained by vapor deposition of silicon on a carbon material using a silicon-containing precursor.

[0047] In some specific embodiments, the vapor deposition temperature is 150~1000 °C. In some specific embodiments, the vapor deposition temperature is 350~1000 °C; in some specific embodiments, the vapor deposition temperature is 350~900 °C; in some specific embodiments, the vapor deposition temperature is 350~800 °C; in some specific embodiments, the vapor deposition temperature is 350~700 °C.

[0048] In some specific embodiments, the silicon-carbon composite material includes a coating layer; in some specific embodiments, the coating layer is one or more of the following: an amorphous carbon layer, carbon nanotubes, graphene, a conductive polymer, an ion-conducting polymer, a solid electrolyte, or an artificial SEI.

[0049] In some embodiments, the silicon-carbon composite material is obtained by vapor deposition of silicon onto a carbon material using a silicon-containing precursor; the carbon material comprises near-spherical carbon particles, each near-spherical carbon particle comprising a carbon plane and an adjacent carbon transition arc surface; the minimum curvature of the arc surface micro-element at the junction of the carbon transition arc surface and the carbon plane is 0.

[0050] The structure of near-spherical carbon particles can be referenced in Figure 1, which shows the structure of near-spherical silicon-carbon particles. Similar to near-spherical silicon-carbon particles, near-spherical carbon particles can achieve highly ordered and compact packing, forming a uniform pore network and flow channels, significantly increasing the amount of active material per unit volume. Furthermore, the planar surface provides a large contact area for the carbon material, thereby improving its thermal and electrical conductivity. Compared to completely amorphous blocks, its planar framework provides better internal support, making it less prone to overall plastic deformation under pressure and enhancing overall rigidity. The transitional curved surface effectively disperses internal stress in the carbon material, reducing crack initiation and significantly improving crush resistance and wear resistance. Moreover, compared to the commonly angular carbon particles on the market, the absence of sharp edges reduces wear between particles and with equipment. The powder has good flowability, facilitating automated and uniform filling, and is beneficial for industrial applications.

[0051] In some specific embodiments, the carbon particles satisfy at least one of D1 to D4: D1, in the quasi-spherical carbon particles, the carbon plane and the adjacent carbon transition arc surface form a carbon plane-arc surface combination; the total area of ​​the carbon plane-arc surface combination on a single quasi-spherical carbon particle accounts for 0.2 to 1% of the surface area of ​​the quasi-spherical carbon particle; D2, the carbon plane is tangent to the carbon transition arc surface; D3, the curvature change of the carbon transition arc surface is continuous; D4, the quasi-spherical carbon particles also have carbon spherical surfaces.

[0052] In some embodiments, in the quasi-spherical carbon particles, the carbon plane and the adjacent carbon transition arc surface form a carbon plane-arc surface combination; the total area of ​​the carbon plane-arc surface combination on a single quasi-spherical carbon particle accounts for 0.2 to 1% of the surface area of ​​the quasi-spherical carbon particle, and may be, but is not limited to, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0.

[0053] In some embodiments, the carbon plane is tangent to the carbon transition arc surface.

[0054] In some embodiments, the curvature of the carbon transition arc surface changes continuously, and the curvature of the carbon transition arc surface can be 0~1 / R. max ~0(1 / R) max (This represents the maximum curvature of the carbon transition arc surface), indicating that both ends of the carbon transition arc surface are planes; in some embodiments, the curvature of the carbon transition arc surface can be 0~1 / R. max ~1 / R1 (R1 is the radius of the sphere adjacent to the transition arc surface) represents that the two ends of the carbon transition arc surface are a plane and a sphere, respectively.

[0055] In some embodiments, the carbon particles satisfy at least one of E1 to E5: E1, the ratio k of the total area of ​​the carbon planes of a single spherical carbon particle to the outer surface area of ​​the particle. 2i The value is 0.2~0.99; E2, the number N of carbon planes in a single carbon particle. 2i E3, the relative standard deviation S of the total carbon planar area of ​​a single carbon particle, is 1~20; 2i E4, the polyhedrality Q of a single carbon particle is 0~0.2. 2i The polyhedral degree Q is 0.5~1. 2i k is the ratio of the total area of ​​the carbon planes of a single carbon particle to the outer surface area of ​​that particle. 2i The number of carbon planes N 2i The relative standard deviation S of the area of ​​all carbon planes 2i The function whose expression is: E5. The ratio of the total area of ​​the carbon transition arc surface of a single carbon particle to the outer surface area of ​​the particle is 0.01 to 0.8.

[0056] In some embodiments, the ratio k of the sum of the planar areas of a single carbon particle to the outer surface area of ​​the particle is... 2i The value is 0.2~0.99, and can be, but is not limited to, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9; preferably, the k of a single carbon particle is... 2i The value is 0.5 to 0.9; more preferably, the k of a single carbon particle is... 2i It ranges from 0.7 to 0.9.

[0057] In some embodiments, the number N of the planes of a single carbon particle 2i The value is any integer from 1 to 20, and can be, but is not limited to, 1, 3, 5, 7, 9, 11, 13, 15, 17, or 20; preferably, the N of a single carbon particle is... 2i The N value is any integer between 8 and 16; more preferably, the N value of a single carbon particle is... 2i It can be any integer between 10 and 14.

[0058] In some embodiments, the relative standard deviation S of all planar areas of a single carbon particle 2i The S value is 0~0.2, and can be, but is not limited to, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, or 0.20; preferably, the S value of a single carbon particle is... 2i The range is 0 to 0.1.

[0059] In some embodiments, the polyhedral degree Q of a single carbon particle 2i The value is 0.5~1, and can be, but is not limited to, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95 or 1; preferably, the value of a single carbon particle Q is... 2i It ranges from 0.7 to 1. Q 2i For k 2i N 2i and S 2i The function, defined by its expression It can be known that k 2i N 2i and S 2i The closer Q is to the optimal value, 2i The closer the value is to 1.

[0060] In some embodiments, the ratio of the total area of ​​the carbon transition arc surface of a single carbon particle to the outer surface area of ​​the particle is 0.01 to 0.8, and may be, but is not limited to, 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or 0.8.

[0061] In some specific embodiments, the carbon material in the silicon-carbon composite material is obtained by carbonizing and / or activating a carbon precursor; the carbon precursor comprises spherical resin particles, each spherical resin particle comprising a resin plane and an adjacent resin transition arc surface; the minimum curvature of the arc surface micro-element at the junction of the resin transition arc surface and the resin plane is 0.

[0062] These spherical resin particles comprise resin planes and adjacent resin transition arc surfaces or resin spheres. The resin planes, arising from the mutual compression of the resin particles, differ from other planes (such as cutting planes, cross-sectional planes, wear planes, etc.), allowing for a high degree of tight fit between surfaces, significantly reducing gaps and defects at the interface. Simultaneously, the smooth contact surfaces enable uniform and direct transmission of pressure or shear force between particles, reducing stress concentration points and thus improving the overall load-bearing capacity and dimensional stability of the material. The resin transition arc surfaces, arising from the extrusion deformation of the spheres, differ from the spheres themselves. Acting as bridges between planes and between planes and spheres, they smoothly disperse concentrated stress, avoiding stress singularities and providing superior elastic buffering during deformation.

[0063] In some embodiments, the resin material may comprise natural or synthetic resins, specifically including, but not limited to, phenolic resins, furfural resins, polystyrene resins, polycarbonate, polyurethane, polyamide resins, etc.

[0064] In some specific embodiments, the resin particles satisfy at least one of F1 to F4: F1, in the quasi-spherical resin particles, the resin plane and the adjacent resin transition arc surface form a resin flat arc surface combination; on the single quasi-spherical resin particle, the total area of ​​the resin flat arc surface combination accounts for 0.2 to 1 of the surface area of ​​the quasi-spherical resin particle; F2, the resin plane is tangent to the resin transition arc surface; F3, the curvature change of the resin transition arc surface is continuous; F4, the quasi-spherical resin particles also have resin spherical surfaces.

[0065] In some embodiments, in the spherical resin particles, the resin plane and the adjacent resin transition arc surface form a resin flat arc surface combination; the total area of ​​the resin flat arc surface combination on a single spherical resin particle accounts for 0.2 to 1% of the surface area of ​​the spherical resin particle, and may be, but is not limited to, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0.

[0066] In some embodiments, the resin plane is tangent to the resin transition arc surface.

[0067] In some embodiments, the curvature of the resin transition arc surface changes continuously, and the curvature of the resin transition arc surface can be 0~1 / R. max ~0(1 / R) max (This represents the maximum curvature of the resin transition arc surface), indicating that both ends of the resin transition arc surface are planes; in some embodiments, the curvature of the resin transition arc surface can be 0~1 / R. max ~1 / R1 (R1 is the radius of the sphere adjacent to the transition arc surface) represents that the two ends of the resin transition arc surface are a plane and a sphere, respectively.

[0068] In some embodiments, the resin particles satisfy at least one of G1 to G5: G1, the ratio k of the total area of ​​the resin planes of a single spherical resin particle to the outer surface area of ​​the particle. 3i The value is 0.2~0.99; G2, the number N of resin planes in a single resin particle. 3i The value is 1~20; G3, the relative standard deviation S of the total resin planar area of ​​a single resin particle. 3i The value is 0~0.2; G4, the polyhedrality Q of a single resin particle. 3i The polyhedral degree Q is 0.5~1. 3i k is the ratio of the total area of ​​the resin planes of a single resin particle to the outer surface area of ​​that particle. 3i The number of resin planes N 3i The relative standard deviation S of all resin planar areas 3i The function whose expression is: G5. The ratio of the total area of ​​the resin transition arc surface of a single resin particle to the outer surface area of ​​the particle is 0.01 to 0.8.

[0069] In some embodiments, the ratio k of the sum of the planar areas of a single resin particle to the outer surface area of ​​the particle is... 3i The value is 0.2~0.99, and can be, but is not limited to, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9; preferably, the k of a single resin particle is... 3i The value is 0.5~0.9; more preferably, the k of a single resin particle is... 3i It ranges from 0.7 to 0.9.

[0070] In some embodiments, the number N of the planes of a single resin particle 3i N is any integer from 1 to 20, and can be, but is not limited to, 1, 3, 5, 7, 9, 11, 13, 15, 17, or 20; preferably, N of a single resin particle 3i It is any integer between 8 and 16; more preferably, N of a single resin particle 3i It can be any integer between 10 and 14.

[0071] In some embodiments, the relative standard deviation S of all planar areas of a single resin particle 3i The value is 0~0.2, and can be, but is not limited to, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, or 0.20; preferably, the S of a single resin particle is... 3i The range is 0 to 0.1.

[0072] In some embodiments, the polyhedral degree Q of a single resin particle 3i The value is 0.5~1, and can be, but is not limited to, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, or 1; preferably, the value of a single resin particle Q 3i It ranges from 0.7 to 1. Q 3i For k 3i N 3i and S 3i The function, defined by its expression It can be known that k 3i N 3i and S 3i The closer Q is to the optimal value, 3i The closer the value is to 1.

[0073] In some embodiments, the ratio of the total area of ​​the resin transition arc surface of a single resin particle to the outer surface area of ​​the particle is 0.01 to 0.8, and may be, but is not limited to, 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or 0.8.

[0074] In some specific embodiments, the median particle size d of the resin material V50 The median particle size is 1~100 μm; preferably, in some embodiments, the median particle size d of the resin particles is... V50 The median particle size is 2~50 μm; in some embodiments, the median particle size d of the resin particles is... V50 The median particle size is 3~30 μm; in some embodiments, the median particle size d of the resin particles is... V50 The median particle size is 3~20 μm; in some embodiments, the median particle size d of the resin particles is... V50 The particle size is 3~15 μm. The particle size of the resin material depends on the particle size requirements of the target material.

[0075] In some specific embodiments, the particle size distribution of the resin material is 0.5~1.8; preferably, in some embodiments, the particle size distribution of the resin material is 0.5~1.2; more preferably, in some embodiments, the particle size distribution of the resin material is 0.5~0.8. The particle size distribution reflects the concentration of the resin material; a smaller distribution means a higher concentration. High-concentration resin materials have a lower bulk density than low-concentration resin materials, but significantly increase the uniformity of the material, leading to a wider range of applications. The lower limit of the particle size distribution described in this invention is the limit that the inventors can currently achieve; it does not mean that resin materials with a smaller value have poor performance, and its theoretical minimum value is 0.

[0076] In the technical solution provided in this application, the spherical resin material can be obtained by extruding monodisperse ethyl resin microspheres. The specific steps are: ① Providing the median particle size d V50 The process involves: ① assembling monodisperse grade B resin microspheres with a particle size of 1-100 μm, a particle size distribution of 0.5-1.8 μm, and a degree of curing of 20-90%; ② preparing the resin microspheres described in ① into a stacked aggregate of resin microspheres; ③ applying pressure and heat to the stacked aggregate of resin microspheres described in ② to obtain an aggregate of quasi-spherical resin particles; ④ depolymerizing the aggregate of quasi-spherical resin particles described in ③ to obtain a quasi-spherical resin material, which contains quasi-polyhedral resin particles.

[0077] In a second typical embodiment of the present invention, an evaluation criterion for the polyhedral degree of a spherical material is provided, characterized in that the spherical material comprises spherical particles, and the spherical material includes a plane and an adjacent transition arc surface; the evaluation criterion is represented by the polyhedral degree Q of the spherical material, and the polyhedral degree Q of the spherical material is the same as the polyhedral degree Q of the spherical particles. i The average value, n is the number of spherical particles in the spherical material; for statistical convenience, n ≥ 100; the degree of polyhedron Q i k is the ratio of the total area of ​​the i-th spherical silicon-carbon particle's planar surface to the particle's outer surface area. j The number of silicon-carbon planes N j The relative standard deviation S of the area of ​​all silicon-carbon planes i The function whose expression is: .

[0078] Furthermore, when the morphology value Q of the polyhedral-like material is between 0.6 and 1, the polyhedral-like material is considered qualified. The above formula can also be simplified to: Wherein, ω1, ω2, and ω3 are the weights of indices f(k), f(N), and f(S), respectively, which are 0.35, 0.35, and 0.3 in this invention, but can be adjusted according to actual application needs. When the Q value is not within the preferred range, specific optimization can be performed based on the values ​​of indices f(k), f(N), and f(S). The value range of each index is 0~1, and a value less than 0.6 indicates that the index is unqualified.

[0079] In some embodiments, when k ranges from 0.5 to 0.7, the value of f(k) is 0.53 to 0.85; in some embodiments, when k ranges from 0.7 to 0.9, the value of f(k) is 0.85 to 1.00; in some embodiments, when k ranges from 0.9 to 1, the value of f(k) is 1.00 to 0.96. In some embodiments, when N ranges from 1 to 9, the value of f(N) is 0.15 to 0.87; in some embodiments, when N ranges from 10 to 14, the value of f(N) is 0.94 to 1.00; in some embodiments, when N ranges from 15 to 20, the value of f(N) is 0.87 to 0.37. In some embodiments, when S takes a value of 0 to 0.1, the value of f(S) is 1 to 0.82; in some embodiments, when S takes a value of 0.1 to 0.2, the value of f(S) is 0.82 to 0.67.

[0080] In a third typical embodiment of the present invention, a negative electrode is also provided, the negative electrode comprising a negative electrode active material, the negative electrode active material comprising the aforementioned silicon-carbon composite material.

[0081] In a fourth typical embodiment of the present invention, a battery is also provided, the battery comprising a negative electrode comprising the aforementioned silicon-carbon composite material; preferably, the battery further comprises at least one of a positive electrode, a separator, or an electrolyte.

[0082] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0083] Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0084] Example 1 (1) Preparation of spherical resin materials: ① Preparation of monodisperse stage B resin microspheres: d was prepared by suspension polymerization. V50 ① A slurry of ethyl phenolic resin microspheres with a diameter of 11 μm and a spacing of 0.5 mm was prepared; ② The obtained ethyl phenolic resin microsphere slurry was centrifuged to form a stacked aggregate of resin microspheres; ③ The stacked aggregate of resin microspheres was hot-pressed at a temperature of 200℃ and a pressure of 20 MPa to obtain an aggregate of near-spherical resin particles; ④ The aggregate of near-spherical resin particles was depolymerized to obtain a near-spherical resin material, which contains near-polyhedral resin particles.

[0085] (2) Preparation of spherical carbon materials ① Using the spherical resin obtained in this example as a carbon precursor, the carbon material was obtained by holding it at 900°C for 2 hours under a nitrogen atmosphere and then cooling it. ② The carbon material was activated with water at 800°C for 2 hours to obtain porous carbon material.

[0086] (3) Preparation of quasi-spherical silicon-carbon composite material: ① The quasi-spherical carbon material obtained in this embodiment is placed in a tube furnace and heated from room temperature to 500 ℃ at 2 ℃ / min in N2 atmosphere; ② Then the gas is changed to 20.0% SiH4-N2 mixed gas and kept at 500 ℃ for 4 h in 20.0% SiH4-N2 mixed atmosphere; ③ The gas is changed to 10.0% C2H2-N2 mixed gas and kept at 600 ℃ for 1 h; and then cooled naturally in N2 atmosphere to obtain silicon-carbon composite material.

[0087] The obtained near-spherical silicon-carbon composite material was observed using a scanning electron microscope. The images were analyzed using software, and the k-value of a particular near-spherical silicon-carbon particle was determined. 1i =0.91, N 1i =10、S 1i =0.02, therefore the morphology value Q of this silicon-carbon particle is... 1i The value is 0.97. Statistical calculations show that the morphology value Q of this silicon-carbon composite material is 0.97.

[0088] Example 2 (1) Preparation of spherical resin material: The preparation method is the same as that of spherical resin material in Example 1.

[0089] (2) The preparation of the spherical carbon material differs from that of the preparation of the spherical carbon material in Example 1 in that the activation time is 4 h.

[0090] (3) Preparation of quasi-spherical silicon-carbon composite material: The difference from the preparation of quasi-spherical silicon-carbon composite material in Example 1 is that the porous carbon material is the carbon material obtained in this example, and it is kept at 500 °C for 8 h in a 20% SiH4-N2 mixed atmosphere.

[0091] The obtained near-spherical silicon-carbon composite material was observed using a scanning electron microscope. The images were analyzed using software, and the k-value of a particular near-spherical silicon-carbon particle was determined. 1i =0.87, N 1i =8、S 1i =0.06, therefore the morphology value Q of this silicon-carbon particle is... 1i The value is 0.89. Statistical calculations show that the morphology value Q of this silicon-carbon composite material is 0.97.

[0092] Example 3 (1) Preparation of spherical resin material: The preparation method is the same as that of spherical resin material in Example 1.

[0093] (2) The preparation of the spherical carbon material differs from that of the preparation of the spherical carbon material in Example 1 in that the activation time is 6 h.

[0094] (3) Preparation of quasi-spherical silicon-carbon composite material: The difference from the preparation of quasi-spherical silicon-carbon composite material in Example 1 is that the porous carbon material is the carbon material obtained in this example, and it is kept at 500 °C for 10 h in a 20% SiH4-N2 mixed atmosphere.

[0095] The obtained near-spherical silicon-carbon composite material was observed using a scanning electron microscope. The images were analyzed using software, and the k-value of a particular near-spherical silicon-carbon particle was determined. 1i =0.93, N 1i =8、S 1i =0.04, therefore the morphology value Q of this silicon-carbon particle is... 1i The value is 0.90. Statistical calculations show that the morphology value Q of this silicon-carbon composite material is 0.97.

[0096] Example 4 (1) Preparation of spherical resin materials: ① Preparation of monodisperse stage B resin microspheres: d was prepared by suspension polymerization. V50 ① A slurry of ethyl phenolic resin microspheres with a diameter of 11 μm and a spacing of 0.5 mm was prepared; ② The obtained ethyl phenolic resin microsphere slurry was centrifuged to form a stacked aggregate of resin microspheres; ③ The stacked aggregate of resin microspheres was hot-pressed at a temperature of 150℃ and a pressure of 20 MPa to obtain an aggregate of quasi-spherical resin particles; ④ The aggregate of quasi-spherical resin particles was depolymerized to obtain a quasi-spherical resin material, which contains quasi-polyhedral resin particles.

[0097] (2) The preparation of the spherical carbon material differs from that of the preparation of the spherical carbon material in Example 2 in that the carbon precursor is the spherical resin material prepared in this example.

[0098] (3) Preparation of quasi-spherical silicon-carbon composite material: The difference between this and the preparation of the quasi-spherical silicon-carbon composite material in Example 2 is that the porous carbon material is the quasi-spherical carbon material obtained in this example.

[0099] The obtained near-spherical silicon-carbon composite material was observed using a scanning electron microscope. The images were analyzed using software, and the k-value of a particular near-spherical silicon-carbon particle was determined. 1i =0.50, N 1i =12、S 1i =0.02, therefore the morphology value Q of this silicon-carbon particle is... 1i The value is 0.82. Statistical calculations show that the morphology value Q of this silicon-carbon composite material is 0.80.

[0100] Example 5 (1) Preparation of spherical resin materials: ① Preparation of monodisperse stage B resin microspheres: d was prepared by suspension polymerization. V50 ① A slurry of ethyl phenolic resin microspheres with a diameter of 11 μm and a spacing of 0.9 mm was prepared; ② The obtained ethyl phenolic resin microsphere slurry was centrifuged to form a stacked aggregate of resin microspheres; ③ The stacked aggregate of resin microspheres was hot-pressed at a temperature of 200℃ and a pressure of 20 MPa to obtain an aggregate of quasi-spherical resin particles; ④ The aggregate of quasi-spherical resin particles was depolymerized to obtain a quasi-spherical resin material, which contains quasi-polyhedral resin particles.

[0101] (2) The preparation of the spherical carbon material differs from that of the preparation of the spherical carbon material in Example 2 in that the carbon precursor is the spherical resin material prepared in this example.

[0102] (3) Preparation of quasi-spherical silicon-carbon composite material: The difference between this and the preparation of the quasi-spherical silicon-carbon composite material in Example 2 is that the porous carbon material is the quasi-spherical carbon material obtained in this example.

[0103] The obtained near-spherical silicon-carbon composite material was observed using a scanning electron microscope. The images were analyzed using software, and the k-value of a particular near-spherical silicon-carbon particle was determined. 1i =0.88, N 1i =6、S 1i =0.07, therefore the morphology value Q of this silicon-carbon particle is... 1i The value is 0.81. Statistical calculations show that the morphology value Q of this silicon-carbon composite material is 0.83.

[0104] Example 6 (1) Preparation of spherical resin materials: ① Preparation of monodisperse stage B resin microspheres: d was prepared by suspension polymerization. V50 The process involves: ① preparing a slurry of ethyl phenolic resin microspheres with a diameter of 11 μm and a spacing of 1.5 mm; ② centrifuging the obtained ethyl phenolic resin microsphere slurry to form a stacked aggregate of resin microspheres; ③ hot-pressing the obtained stacked aggregate of resin microspheres at a temperature of 200℃ and a pressure of 20 MPa to obtain an aggregate of near-spherical resin particles; ④ depolymerizing the aggregate of near-spherical resin particles to obtain a near-spherical resin material, which contains near-polyhedral resin particles.

[0105] (2) The preparation of the spherical carbon material differs from that of the preparation of the spherical carbon material in Example 2 in that the carbon precursor is the spherical resin material prepared in this example.

[0106] (3) Preparation of quasi-spherical silicon-carbon composite material: The difference between this and the preparation of the quasi-spherical silicon-carbon composite material in Example 2 is that the porous carbon material is the quasi-spherical carbon material obtained in this example.

[0107] The obtained near-spherical silicon-carbon composite material was observed using a scanning electron microscope. The images were analyzed using software, and the k-value of a particular near-spherical silicon-carbon particle was determined. 1i =0.45, N 1i =5、S 1i =0.15, therefore the morphology value Q of this silicon-carbon particle is... 1i The value is 0.54. Statistical calculations show that the morphology value Q of this silicon-carbon composite material is 0.50.

[0108] Comparative Example 1 (1) Spherical Resin Material: A commercially available spherical resin material with a median particle size d V50 The particle size is 11.3 μm, the particle size distribution is 1.5, and the degree of curing is 100%.

[0109] (2) The preparation of the spherical carbon material differs from that of the preparation of the spherical carbon material in Example 2 in that the carbon precursor is the spherical resin material prepared in this comparative example.

[0110] (3) Preparation of quasi-spherical silicon-carbon composite material: The difference between this and the preparation of the quasi-spherical silicon-carbon composite material in Example 2 is that the porous carbon material is the spherical carbon material obtained in this comparative example.

[0111] The obtained spherical silicon-carbon composite material was observed using a scanning electron microscope. The images were analyzed using software scanning, and the k-value of a specific near-spherical silicon-carbon particle was determined. 1i =0、N 1i =0、S 1i =0, therefore the morphology value Q of the silicon-carbon particle is 0. 1i The value is 0.35. Statistical calculations show that the morphology value Q of this silicon-carbon composite material is 0.35.

[0112] Comparative Example 2 (1) Preparation of spherical resin materials: ① Preparation of monodisperse stage B resin microspheres: d was prepared by suspension polymerization. V50 ① A slurry of ethyl phenolic resin microspheres with a diameter of 11 μm and a spacing of 0.5 mm was prepared; ② The obtained ethyl phenolic resin microsphere slurry was centrifuged to form a stacked aggregate of resin microspheres; ③ The stacked aggregate of resin microspheres was hot-pressed at a temperature of 200℃ and a pressure of 200MPa to obtain an aggregate of quasi-spherical resin particles; ④ The aggregate of quasi-spherical resin particles was depolymerized to obtain a quasi-spherical resin material, which contains quasi-polyhedral resin particles.

[0113] (2) The preparation of the spherical carbon material differs from that of the preparation of the spherical carbon material in Example 2 in that the carbon precursor is the spherical resin material prepared in this comparative example.

[0114] (3) Preparation of quasi-spherical silicon-carbon composite material: The difference between this and the preparation of the quasi-spherical silicon-carbon composite material in Example 2 is that the porous carbon material is the quasi-spherical carbon material obtained in this example.

[0115] Because the hot-pressing conditions in this comparative example were quite stringent, the polyhedral particles in the resulting spherical resin material lacked resin transition arc surfaces and consisted only of resin planes, containing numerous angular structures. Correspondingly, the resulting spherical carbon material and spherical silicon-carbon material also lacked transition arc surfaces and contained numerous angular structures.

[0116] The obtained spherical silicon-carbon composite material was observed using a scanning electron microscope. The images were analyzed using software scanning, and the k-value of a specific near-spherical silicon-carbon particle was determined. 1i =1、N 1i =9、S 1i =0.02, therefore the morphology value Q of this silicon-carbon particle is... 1i The value is 0.93. Statistical calculations show that the morphology value Q of this silicon-carbon composite material is 0.94.

[0117] Test Method (I) Polyhedral Degree Test For spherical particles, taking the silicon-carbon composite material of Example 1 as an example, the surface information is obtained as follows: Two-dimensional images of spherical silicon-carbon particles are obtained by scanning electron microscopy (SEM) or electron microscopy. To ensure statistical representativeness, at least 100 independent and complete particles are selected and measured in at least three non-adjacent fields of view with typical characteristics for each sample using a systematic random sampling method. For each particle being tested, the two-dimensional image is analyzed using software or code to accurately delineate the contours of its planes and arcs, construct a three-dimensional model, and count the pixel area Ai (i=1,2,3,....n, n≥100) of the outer surface of a particle to represent the outer surface area of ​​the particle. The number N1i of all planes on the particle is counted, and the pixel area aij (j=1,2,3,....n) of each plane represents the area of ​​each plane of the particle being tested. Then the particle's , The silicon-carbon particles The silicon-carbon composite material The above methods are also applicable to the morphology characterization of near-spherical carbon materials and near-spherical resin materials.

[0118] (II) Silicon-carbon battery test Using the silicon-based composite material provided in the above examples and comparative examples as the negative electrode active material, negative electrode sheets were prepared respectively. The negative electrode sheets were prepared into CR2032 coin cells using conventional methods, and the electrical performance of the cells was tested. The specific test methods are as follows: 1. Half cell preparation and electrochemical performance test: (1) Half cell assembly: CR2032 coin cells were assembled in a glove box, with lithium metal sheet as the counter electrode, polypropylene microporous membrane as the separator, and LiPF6 dissolved in a mixture of ethyl carbonate (EC) and diethyl carbonate (DEC) (volume ratio EC:DEC=1:1), wherein the concentration of LiPF6 was 1 mol / L.

[0119] The battery was tested for charge and discharge using the LAND battery testing system.

[0120] (2) Cyclic specific capacity and initial efficiency test: After the CR2032 button cell was left to stand for 6 h, it was discharged to 0.005 V at 0.05 C, and then discharged to 0.005 V at 0.01 C; after standing for 5 min, it was charged to 1.5 V at a constant current of 0.05 C; the initial delithiation specific capacity of 0.8 V is the specific capacity (or mass specific capacity) of the electrode material, and the ratio of the initial delithiation capacity of 0.8 V to the initial lithium insertion capacity is the initial coulombic efficiency of the battery at 0.8 V.

[0121] (3) Rate testing method: After the coin cell battery completes the cycle capacity and initial efficiency test, the following rate charge-discharge cycles are performed: (1) Discharge to 0.005 V at 0.1 C and then charge to 1.5 V at 0.1 C, repeat 3 times, and record the discharge capacity and charge capacity each time; (2) Discharge to 0.005 V at 0.5 C and then charge to 1.5 V at 0.5 C, repeat 3 times, and record the discharge capacity and charge capacity each time; (3) Discharge to 0.005 V at 1 C and then charge to 1.5 V at 1 C, repeat 3 times, and record the discharge capacity and charge capacity each time. The 1C / 0.1C rate is obtained by dividing the 1C and 1.5V charge capacity of the 3rd cycle by the 0.1C and 1.5V charge capacity of the 3rd cycle.

[0122] 2. Full cell preparation and electrochemical performance testing: Using the silicon-based composite material provided in the above examples and comparative examples as the negative electrode active material, the electrode containing the negative electrode active material was used to prepare a soft-pack battery using conventional methods and the electrical performance was tested. The soft-pack battery was prepared in a dehumidified room with a dew point of -45 ℃. The battery was tested for charge and discharge cycles using the LANBTS battery testing system. The specific testing method was as follows: (1) Preparation of positive electrode: The positive electrode active material LiCoO2, conductive agent SuperP, binder PVDF and solvent NMP were mixed evenly in a mass ratio of 92:3:5:150 and then evenly coated on the positive electrode current collector. Then it was dried at 80℃ to obtain the positive electrode.

[0123] (2) Preparation of negative electrode sheet: The negative electrode active material, conductive agent SuperP, binder polyacrylic acid and solvent deionized water are mixed evenly in a mass ratio of 95:1:4:120 and then evenly coated on the negative electrode current collector. Then, it is dried at 100 °C to obtain the negative electrode sheet.

[0124] (3) The positive and negative electrode sheets are stacked in a square and separated by a polypropylene separator to form a battery cell, which is then packaged into an aluminum-plastic bag. An electrolyte of the appropriate capacity is injected into the aluminum-plastic bag, and the bag is vacuum sealed to obtain a soft-pack battery. The electrolyte is a mixture of LiPF6 EC and DEC, wherein the concentration of LiPF6 is 1 mol / L and the volume ratio of EC to DEC is 1:1.

[0125] (4) Formation and Capacity Testing: After liquid injection and sealing, the battery begins formation. It is placed in a constant temperature chamber at 25 ℃ for 12 h, then charged at a constant current of 0.02C to 3.3 V, placed for 30 min, charged at a constant current of 0.025C to 3.8 V, placed for 10 min, and charged at a constant current of 0.33C to 4.2 V. After formation, the battery is vacuum-sealed and then subjected to capacity testing. It is charged at a constant current of 0.33C to 4.45 V, placed for 10 min, discharged at a constant current of 1C to 3 V, placed for 10 min, and discharged at a constant current of 0.33C to 3 V. The capacity testing is then completed. The ratio of the discharge capacity to the charge capacity during the formation and capacity testing of the pouch battery is the initial efficiency of the battery.

[0126] (5) 25 ℃ cycle test: Place the battery in a 25 ℃ constant temperature chamber, charge it with a constant current of 1 C to 4.45 V, and then charge it with a constant voltage of 4.45 V to a current of 0.1 C; after standing for 10 min, discharge it with a constant current of 1 C to 3.0 V, and stand for 10 min. Repeat the above charging and discharging steps until the discharge capacity is lower than 80% of the discharge capacity of the first cycle. The number of cycles obtained at this time is the cycle life of the soft pack battery; record the capacity retention rate after 100 cycles.

[0127] Table 1. Polyhedrality of silicon-carbon composite materials in Examples 1-6 and Comparative Examples 1 and 2, numbered K. 1i N 1i S 1i Q 1i Example 1: 0.87~0.948~130.01~0.060.89-0.99 Example 2: 0.87~0.948~130.01~0.060.89-0.99 Example 3: 0.87~0.948~130.01~0.060.89-0.99 Example 4: 0.41~0.528~130.01~0.030.69-0.84 Example 5: 0.78~0.926~150.02~0.090.78-0.89 Example 6: 0.21~0.524~200.04~0.180.39-0.63 Comparative Example 1: 0.000.000.000.35 Comparative Example 2: 1.008~130~0.030.89-0.97 Table 2. Morphology values ​​Q and battery data analysis of silicon-carbon composite materials in Examples 1-6 and Comparative Examples 1 and 2. (Table 2 shows the specific surface area (m²) of the silicon-carbon composite materials.) 2 / g) Silicon content (%) 0.8 V Specific capacity (mAh / g) 0.8 V First-time efficiency (%) Capacity retention at 25℃ and 100 cycles (%) 1C / 0.1C rate of return (%) Example 1 0.97 1.14 0.71 494.57 7.60 98.78 6.1 Example 2 0.97 1.55 2.31 804.38 4.70 998 5.8 Example 3 0.97 1.26 0.12 006.98 6.10 99.18 5.9 Example 4 0.80 1.65 2.71 786.4 84.70 98.97 1.8 Example 5 0.83 1.25 2.21 814.38 4.00 98.67 6.4 Example 6 0.5 1.35 1.81 776.4 84.50 98.25 2.9 Comparative Example 1 0.35 1.55 2.91 786.78 4.90 98.33 4.2 Comparative Example 2 0.94 1.75 3.51 822.18 3.10 94.56 5.6 As shown in the table, this evaluation standard formula can convert the morphological comparison of spherical silicon-carbon composite materials into a numerical comparison of the polyhedrality Q. Data from Tables 1 and 2 show that the silicon-carbon composite materials described in Examples 1-3 are derived from the same spherical resin, and their polyhedrality Q is 0.97, the highest among all samples, and closest to an ideal regular polyhedron. In terms of electrochemical performance, they exhibit excellent overall performance: not only do they possess high cycling stability (capacity retention >98.7% after 100 cycles), but their rate performance (1C / 0.1C rate retention >85.8%) is also the best.

[0128] Carbon materials provided in Examples 1 to 6, as well as Comparative Examples 1 and 2, were deposited to obtain silicon-carbon composite materials. The silicon content of the silicon-carbon composite materials was controlled by adjusting the silicon deposition time according to the pore volume of the porous carbon, thereby controlling the specific capacity of the anode material. As shown in Table 2, the specific capacities (1776.4-1822.1 mAh / g) of Examples 2, 4, 5, and 6, and Comparative Example 1, are very close to their first-cycle efficiency (84.0%-84.9%). However, silicon undergoes significant volume expansion and contraction during charge and discharge. The transition arc surface in the spherical structure acts like an "arch bridge," smoothly dispersing concentrated stress throughout the particle, preventing stress concentration at sharp corners that could lead to particle breakage. Simultaneously, the large-area surface-to-surface contact between particles forms a strong mechanical interlock, suppressing relative particle displacement and jointly protecting the stability of the particle structure and the SEI film, thus delaying capacity decay. Therefore, the spherical silicon-carbon anode materials in Examples 1 to 6 exhibit good cycle performance, with a capacity retention rate exceeding 98.2% after 100 cycles.

[0129] Compared to Comparative Example 1 (Q=0.35), Examples 2 (Q=0.94) and Examples 4-6 (Q=0.50-0.83) had similar specific capacity and first-efficiency, but their rate performance (85.8% for Example 2 and 52.9%-76.4% for Examples 4-6) was significantly better than that of Comparative Example 1 (34.2%). This is because the combination of planar and curved surfaces of the near-spherical particles can form more regular and less tortuous slit-like pores when stacked. This is like building a straighter and wider "highway," which reduces the resistance to lithium ion penetration and transport in the electrolyte, thereby significantly improving the fast charge and discharge capability (i.e., rate performance). The data also revealed that the rate performance improved significantly with the increase of the morphology value Q (e.g., from 52.9% in Example 6 to 85.8% in Example 2), showing a positive correlation trend. Although Comparative Example 2 has a high Q value of 0.94, its k value is 1, lacking the combination of a transition arc surface and a flat arc surface. Therefore, it exhibits poor cycling performance (capacity retention rate of 92.5% after 100 cycles) and rate performance (rate retention rate of 65.6% at 1C / 0.1C). Furthermore, it can be noted that the morphology parameters Q (0.50-0.97) of Examples 2 and 4-6 are significantly better than the 0.35 of Comparative Example 1. This indicates that the morphology value Q can, to a certain extent, analyze and evaluate the electrochemical performance of silicon-carbon composite materials, transforming the originally qualitative "quasi-spherical" description into a quantitative indicator. This means that in the early stages of material preparation, the electrochemical performance of the final product can be predicted and optimized by controlling and measuring the Q value. For example, setting the Q value target above 0.8 can simultaneously achieve high specific capacity, high first-efficiency, excellent cycling stability, and rate performance, providing a clear direction and standard for the research and development of new materials.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A silicon-carbon composite material, the silicon-carbon composite material comprising near-spherical silicon-carbon particles, the near-spherical silicon-carbon particles comprising a silicon-carbon plane and an adjacent silicon-carbon transition arc surface; the minimum curvature of the arc surface micro-element at the junction of the silicon-carbon transition arc surface and the silicon-carbon plane is 0.

2. The silicon-carbon composite material according to claim 1, characterized in that, The silicon-carbon particles satisfy at least one of A1 to A4: A1, in the quasi-spherical silicon-carbon particles, the silicon-carbon plane and the adjacent silicon-carbon transition arc surface form a silicon-carbon flat arc surface combination; the total area of ​​the silicon-carbon flat arc surface combination on a single quasi-spherical silicon-carbon particle accounts for 0.2 to 1% of the surface area of ​​the quasi-spherical silicon-carbon particle; A2, the silicon-carbon plane is tangent to the silicon-carbon transition arc surface; A3, the curvature change of the silicon-carbon transition arc surface is continuous; A4, the quasi-spherical silicon-carbon particles also have silicon-carbon spherical surfaces.

3. The silicon-carbon composite material according to claim 1, characterized in that, The silicon-carbon particles satisfy at least one of B1 to B5: B1, the ratio k of the total area of ​​the silicon-carbon planes of a single spherical silicon-carbon particle to the outer surface area of ​​the particle. 1i The value is 0.2~0.99; B2, the number N of silicon-carbon planes in a single silicon-carbon particle. 1i The value is 1~20; B3, the relative standard deviation S of the total planar area of ​​all silicon-carbon particles of a single silicon-carbon particle. 1i The value is 0~0.2; B4, the polyhedrality Q of a single silicon-carbon particle. 1i The polyhedral degree Q is 0.5~1. 1i k is the ratio of the total area of ​​the silicon-carbon planes of a single silicon-carbon particle to the outer surface area of ​​that particle. 1i The number of silicon-carbon planes N 1i The relative standard deviation S of the area of ​​all silicon-carbon planes 1i The function whose expression is: B5. The ratio of the total area of ​​the silicon-carbon transition arc surface of a single silicon-carbon particle to the outer surface area of ​​the particle is 0.01 to 0.

8.

4. The silicon-carbon composite material according to claim 1, characterized in that, The silicon-carbon composite material has at least one characteristic selected from C1 to C6: C1, the specific surface area of ​​the silicon-carbon composite material is 0.1 to 50 m². 2 / g, preferably 0.1~10 m 2 / g, more preferably 0.1~3 m 2 / g; C2, the true density of the silicon-carbon composite material measured by He is 1.8~2.3 g / cm³. 3 C3. The true density of the silicon-carbon composite material measured by N2 is 1.3~2.0 g / cm³. 3 C4. The silicon content of the silicon-carbon composite material is 10-90 wt%; preferably 30-70 wt%; C5. The median particle size d of the silicon-carbon composite material V50 The particle size is 1~100 μm, preferably 2~30 μm; C6, the particle size distribution of the silicon-carbon composite material is 0.5~1.8, preferably 0.5~1.

2.

5. The silicon-carbon composite material according to claim 1, characterized in that, The silicon-carbon composite material is obtained by vapor deposition of silicon on a carbon material using a silicon-containing precursor; preferably, the vapor deposition temperature is 150~1000 ℃; preferably, the silicon-carbon composite material includes a coating layer.

6. The silicon-carbon composite material according to claim 1, characterized in that, The silicon-carbon composite material is obtained by vapor deposition of silicon on a carbon material using a silicon-containing precursor; the carbon material comprises quasi-spherical carbon particles, each quasi-spherical carbon particle comprising a carbon plane and an adjacent carbon transition arc surface; the minimum curvature of the arc surface micro-element at the junction of the carbon transition arc surface and the carbon plane is 0.

7. The silicon-carbon composite material according to claim 6, characterized in that, The carbon material in the silicon-carbon composite material is obtained by carbonizing and / or activating a carbon precursor; the carbon precursor comprises spherical resin particles, each spherical resin particle comprising a resin plane and an adjacent resin transition arc surface; the minimum curvature of the arc surface micro-element at the junction of the resin transition arc surface and the resin plane is 0.

8. A criterion for evaluating the polyhedrality of a spherical material, characterized in that, The quasi-spherical material comprises quasi-spherical particles, and the quasi-spherical material includes a plane and an adjacent transition arc surface; the evaluation criterion is represented by the polyhedrality Q of the quasi-spherical material, and the polyhedrality Q of the quasi-spherical material is the same as the polyhedrality Q of the quasi-spherical particles. i The average value, n is the number of spherical particles in the spherical material; For statistical convenience, n≥100; the polyhedral degree Q i k is the ratio of the total area of ​​the i-th spherical particle's plane to the particle's outer surface area. j The number of planes N j The relative standard deviation S of all planar areas i The function whose expression is: 。 9. Negative electrode, characterized in that, The negative electrode contains a negative electrode active material, which contains the silicon-carbon composite material according to any one of claims 1 to 7.

10. A battery, characterized in that, The battery includes a negative electrode, which comprises a silicon-carbon composite material as described in any one of claims 1 to 7; preferably, the battery further includes at least one of a positive electrode, a separator, or an electrolyte.

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