Anode materials and their preparation methods, lithium-ion batteries

Abstract

This application relates to the field of anode materials, providing anode materials and their preparation methods, and lithium-ion batteries. The anode material includes an aggregate comprising an active material, a carbon material, and a conductive reinforcing agent. The conductive reinforcing agent has a tensile strength ≥ 500 MPa, and the dispersion N of the conductive reinforcing agent in the anode material is ≥ 1. The SEM cross-section of the anode material particles is divided into regions of area A × B, where A and B are both ≤ 1 micrometer. The distribution of the conductive reinforcing agent in all regions of a single anode material particle is statistically analyzed. The number of regions with a spacing < 10 nm between conductive reinforcing agents is denoted as Na, and the number of regions with a spacing ≥ 10 nm between conductive reinforcing agents is denoted as Nb. The dispersion C of the conductive reinforcing agent in a single anode material particle is defined as C = Nb / Na, where N is the arithmetic mean of the C values ​​of any five anode material particles. The anode material provided by this application can effectively suppress the volume expansion of the anode material and improve the battery cycle performance.

Description

Technical Field

[0001] This application relates to the field of negative electrode material technology, specifically to negative electrode materials and their preparation methods, and lithium-ion batteries. Background Technology

[0002] Electrified new energy vehicles represent the future direction of the automotive market, and their core component is the lithium-ion battery. As the market develops, the demand for high-capacity batteries is increasing, and adopting novel high-specific-capacity positive and negative electrode materials is one of the important methods to improve battery energy density.

[0003] More and more new materials such as metals, oxides, and metal alloys are being used as active materials in anode materials to continuously explore various ways to improve battery energy density. Taking silicon-based anode materials as an example, silicon-based anode materials, as one of the aforementioned active materials, are widely considered the next generation of anode materials. Their ultra-high theoretical specific capacity (4200 mAh / g) and low delithiation potential (<0.5V), coupled with silicon's slightly higher voltage plateau than graphite, make it less prone to surface lithium plating during charging, resulting in better safety performance and making them highly regarded. However, silicon-based anode materials experience repeated expansion and contraction during charge and discharge, resulting in a high volume change rate. The SEI film formed on the surface also ruptures during expansion and contraction, exposing new interfaces. These new interfaces continuously form new SEI films, causing the outer SEI layer to thicken, leading to poor battery cycle performance. The volume expansion problem prevalent in anode materials limits their further application.

[0004] Therefore, how to suppress the volume expansion of the negative electrode material and improve its cycle stability is an urgent problem to be solved. Summary of the Invention

[0005] Therefore, it is necessary to provide anode materials and their preparation methods, as well as lithium-ion batteries, which can effectively suppress the volume expansion of anode materials and improve battery cycle performance.

[0006] In a first aspect, there is a negative electrode material, characterized in that the negative electrode material comprises aggregates.

[0007] The aggregate comprises an active substance, a carbon material, and a conductive reinforcing agent; the tensile strength of the conductive reinforcing agent is ≥500MPa, and the dispersion N of the conductive reinforcing agent in the negative electrode material is ≥1.

[0008] The dispersion N is obtained through the following test method:

[0009] The SEM cross-section of the negative electrode material particle is divided into regions with an area of ​​A×B, where A and B are both ≤1 micrometer. The distribution of conductive reinforcing agent in all regions of a single negative electrode material particle is statistically analyzed. The number of regions with a spacing of <10nm between conductive reinforcing agents is denoted as Na, and the number of regions with a spacing of ≥10nm between conductive reinforcing agents is denoted as Nb. The dispersion C of conductive reinforcing agent in a single negative electrode material particle is defined as C=Nb / Na, where N is the arithmetic mean of the C values ​​of any 5 negative electrode material particles.

[0010] In the above scheme, the negative electrode material includes an aggregate, which comprises an active material, a carbon material, and a conductive reinforcing agent. The tensile strength of the conductive reinforcing agent is ≥500MPa, and the dispersion N of the conductive reinforcing agent in the negative electrode material is ≥1. The uniform dispersion of the conductive reinforcing agent effectively improves the transport of charge carriers within the aggregate and enhances the conductivity of the aggregate. A conductive material with a tensile strength ≥500MPa is selected as the conductive reinforcing agent, which has excellent mechanical properties. At the same time, controlling the dispersion N of the conductive reinforcing agent to be ≥1 ensures that the conductive reinforcing agent is uniformly distributed in the negative electrode material. The conductive reinforcing agent can act as a structural support to enhance the stability of the negative electrode material. The spaces between the conductive reinforcing agents can fill the active material, reducing the stress changes caused by the expansion of the active material and strengthening the structural strength of the aggregate. It has been verified that the above negative electrode material has a low expansion rate and good cycle stability.

[0011] In one embodiment, the conductive enhancer is distributed in the active material, and the carbon material is filled between the active material and the conductive enhancer.

[0012] In one embodiment, the carbon material and the conductive enhancer have pores, and the pores are filled with the active substance.

[0013] In one embodiment, the conductivity enhancer includes at least one of an alloy material and conductive carbon.

[0014] In one embodiment, the conductive carbon includes at least one of carbon nanotubes, carbon fibers, and graphite fibers.

[0015] In one embodiment, the mass ratio of the active substance, the carbon material, and the conductive enhancer is (20-70):(10-70):(3-20).

[0016] In one embodiment, the conductive reinforcing agent is in the form of sheets and / or strips, and the aspect ratio of the conductive reinforcing agent is 2 to 3000.

[0017] In one embodiment, the conductivity of the conductivity enhancer is >10. 2 S / m.

[0018] In one embodiment, the aspect ratio of the conductive reinforcing agent is 2 to 3000.

[0019] In one embodiment, the aggregate further includes a metal oxide.

[0020] In one embodiment, the general chemical formula of the metal oxide is M. x O y , 0.2≤y / x≤3, wherein M includes at least one of Sn, Ge, Si, Fe, Cu, Ti, Na, Mg, Al, Ca and Zn.

[0021] In one embodiment, the metal oxide is in the form of a sheet and / or a strip, and the aspect ratio of the metal oxide is greater than 2.

[0022] In one embodiment, the mass ratio of the metal oxide to the active substance is (1-20):100.

[0023] In one embodiment, the active substance includes at least one selected from Li, Na, K, Sn, Ge, Si, SiO, Fe, Mg, Ti, Zn, Al, P, and Cu.

[0024] In one embodiment, the median particle size of the active material is 1 nm to 500 nm.

[0025] In one embodiment, the carbon material includes at least one of amorphous carbon, crystalline carbon, hard carbon, soft carbon, and mesophase carbon microspheres.

[0026] In one embodiment, the negative electrode material further includes a carbon layer covering at least a portion of the surface of the aggregate.

[0027] In one embodiment, the material of the carbon layer includes amorphous carbon.

[0028] In one embodiment, the thickness of the carbon layer is from 10 nm to 1500 nm.

[0029] In one embodiment, the median particle size of the negative electrode material is 0.5 μm to 30 μm.

[0030] In one embodiment, the specific surface area of ​​the negative electrode material is ≤10m². 2 / g.

[0031] In one embodiment, the porosity of the negative electrode material is ≤10%, and the pressure resistance of the negative electrode material is ≥50MPa.

[0032] In one embodiment, the aggregate density satisfies the following relationship: (p1-p2) / p2≤5%, where p1 is the test density of the aggregate, p2 is the average density of the aggregate, and p2 is the sum of the mass percentage of each component in the aggregate multiplied by the theoretical density of each component.

[0033] Secondly, this application provides a method for preparing a negative electrode material, comprising the following steps:

[0034] A conductive reinforcing agent with a tensile strength ≥500MPa is added to the first solvent and dispersed to obtain a dispersion.

[0035] The precursor is prepared by mixing the active substance, the dispersion, the first carbon source, and the second solvent; and

[0036] The precursor is subjected to a single heat treatment to obtain the aggregate.

[0037] The preparation method provided in this application involves first dispersing a conductive enhancer in a first solvent to obtain a dispersion solution, and then mixing the dispersion solution with an active material, a first carbon source, and a second solvent in different proportions to obtain a precursor. This ensures uniform dispersion of the conductive enhancer within the precursor, which effectively improves carrier transport within the aggregate and enhances the conductivity of the aggregate. The method utilizes a conductive material with a tensile strength ≥500 MPa as the conductive enhancer, which acts as a structural support to enhance the stability of the negative electrode material, strengthen the structural strength of the aggregate, avoid stress changes caused by the expansion effect of the active material, maintain the structural stability of the aggregate, and help suppress the expansion rate of the negative electrode material. Furthermore, the preparation process is simple and controllable.

[0038] In one embodiment, the active substance includes at least one selected from Li, Na, K, Sn, Ge, Si, SiO, Fe, Mg, Ti, Zn, Al, P, and Cu.

[0039] In one embodiment, the first carbon source includes at least one of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt.

[0040] In one embodiment, the conductive reinforcing agent includes at least one of alloy materials, carbon nanotubes, carbon fibers, and graphite fibers.

[0041] In one embodiment, the conductive reinforcing agent is in the form of sheets and / or strips, and the aspect ratio of the conductive reinforcing agent is 2 to 3000.

[0042] In one embodiment, the tensile strength of the conductive reinforcing agent is ≥500MPa.

[0043] In one embodiment, the conductivity of the conductivity enhancer is >10. 2 S / m.

[0044] In one embodiment, the mass ratio of the active substance, the conductive enhancer, and the first carbon source is (15-120):(1-20):(10-50).

[0045] In one embodiment, the first solvent includes at least one of an organic solvent, an inorganic solvent, and a mixed solvent formed by mixing an organic solvent and an inorganic solvent. In another embodiment, the second solvent includes an organic solvent.

[0046] In one embodiment, the organic solvent includes at least one selected from methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, and pentanol.

[0047] In one embodiment, the inorganic solvent includes at least one of water, liquid carbon dioxide, liquid ammonia, liquid sulfur dioxide, thionyl chloride, thioyl chloride, lead acetate, hydrogen cyanide, hydrazine hydrate, thioyl fluoride, copper ammonia solution, sulfuric acid, nitric acid, hydrogen fluoride, polyphosphoric acid, and superacid.

[0048] In one embodiment, an additive is also added in the step of preparing the precursor by mixing the active substance, the dispersion, the first carbon source, and the second solvent.

[0049] In one embodiment, the additive includes at least one of surfactants and coupling agents.

[0050] In one embodiment, the surfactant includes at least one of octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecylbenzenesulfonate, icosanoic acid, palmitic acid, tetradecanoic acid, undecanoic acid, hexadecyltrimethylammonium bromide, and polyvinylpyrrolidone.

[0051] In one embodiment, the coupling agent includes a silane coupling agent, which includes γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0052] In one embodiment, the mass ratio of the conductive enhancer to the additive is (1-20):(1-10).

[0053] In one embodiment, a metal oxide is also added during the step of mixing the active substance, the dispersion, the first carbon source, and the second solvent.

[0054] In one embodiment, the general chemical formula of the metal oxide is M. x O y, 0.2≤y / x≤3, wherein M includes at least one of Sn, Ge, Si, Fe, Cu, Ti, Na, Mg, Al, Ca and Zn.

[0055] In one embodiment, the metal oxide is in the form of a sheet and / or a strip, and the aspect ratio of the metal oxide is greater than 2.

[0056] In one embodiment, the mass ratio of the metal oxide to the active substance is (1-20):100.

[0057] In one embodiment, the preparation of the precursor further includes at least one of the following: mixing the active substance, the dispersion, the first carbon source, and the second solvent, followed by dispersion treatment and drying treatment.

[0058] In one embodiment, the dispersion treatment includes at least one of mechanical stirring, ultrasonic dispersion, and grinding dispersion.

[0059] In one embodiment, the drying temperature is 30°C to 400°C, and the drying time is 1 hour to 15 hours.

[0060] In one embodiment, before the precursor is heat-treated, the precursor is further subjected to a densification treatment, such that the porosity of the aggregate is ≤10% and the compressive hardness of the aggregate is ≥50MPa.

[0061] In one embodiment, the densification process includes at least one of the following: fusion process, kneading and extrusion process, molding process, isostatic pressing process, and impregnation process.

[0062] In one embodiment, the fusion process is mechanical fusion.

[0063] In one embodiment, the rotational speed of the fusion machine used for mechanical fusion is 300 r / min to 3000 r / min.

[0064] In one embodiment, the tool gap width of the fusion machine used for mechanical fusion is 0.01cm to 0.9cm.

[0065] In one embodiment, the mechanical fusion time is at least 0.5 hours.

[0066] In one embodiment, the temperature of the primary heat treatment is 600℃ to 1200℃, and the duration of the primary heat treatment is 1h to 10h.

[0067] In one embodiment, the primary heat treatment process is conducted with a protective gas, which includes at least one of nitrogen, helium, neon, argon, and krypton.

[0068] In one embodiment, the method further includes carbon coating the aggregate.

[0069] In one embodiment, the carbon coating process includes: mixing the precursor with a second carbon source and performing a secondary heat treatment.

[0070] In one embodiment, the mass ratio of the precursor to the second carbon source is (20-100):(10-80).

[0071] In one embodiment, the carbon coating process includes: mixing the aggregate with a second carbon source and performing a secondary heat treatment;

[0072] In one embodiment, the second carbon source includes at least one of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt.

[0073] In one embodiment, the mass ratio of the aggregate to the second carbon source is (15-100):(10-70);

[0074] In one embodiment, the temperature of the secondary heat treatment is 600℃~1200℃, and the time of the secondary heat treatment is 1h~10h;

[0075] In one embodiment, the secondary heat treatment process is carried out using a protective gas;

[0076] In one embodiment, the protective gas includes at least one of nitrogen, helium, neon, argon, and krypton.

[0077] Thirdly, this application provides a lithium-ion battery, the lithium-ion battery comprising the negative electrode material described in the first aspect or the negative electrode material prepared according to the preparation method described in the second aspect.

[0078] The technical solution of this application has at least the following beneficial effects:

[0079] The negative electrode material provided in this application includes an aggregate comprising an active material, a carbon material, and a conductive reinforcing agent. The conductive reinforcing agent has a tensile strength ≥ 500 MPa, and the dispersion N of the conductive reinforcing agent in the negative electrode material is ≥ 1. The uniform dispersion of the conductive reinforcing agent effectively improves the transport of charge carriers within the aggregate, thereby enhancing the conductivity of the aggregate. A conductive material with a tensile strength ≥ 500 MPa is selected as the conductive reinforcing agent, which possesses excellent mechanical properties. Simultaneously, controlling the dispersion N ≥ 1 ensures that the conductive reinforcing agent is uniformly distributed in the negative electrode material. The conductive reinforcing agent can act as a structural support, enhancing the stability of the negative electrode material. The spaces between the conductive reinforcing agents can fill the active material, reducing stress changes caused by the expansion of the active material and strengthening the structural strength of the aggregate. Verification has shown that the above-mentioned negative electrode material has a low expansion rate and good cycle stability.

[0080] The preparation method provided in this application involves first dispersing a conductive enhancer in a first solvent to obtain a dispersion solution, and then mixing the dispersion solution with an active material, a first carbon source, and a second solvent in different proportions to obtain a precursor. This ensures uniform dispersion of the conductive enhancer within the precursor, which effectively improves carrier transport within the aggregate and enhances the conductivity of the aggregate. The method utilizes a conductive material with a tensile strength ≥500 MPa as the conductive enhancer, which acts as a structural support to enhance the stability of the negative electrode material, strengthen the structural strength of the aggregate, avoid stress changes caused by the expansion effect of the active material, maintain the structural stability of the aggregate, and help suppress the expansion rate of the negative electrode material. Furthermore, the preparation process is simple and controllable. Attached Figure Description

[0081] Figure 1 A schematic flowchart illustrating the preparation method of the negative electrode material provided in the embodiments of this application;

[0082] Figure 2 The image shows a scanning electron microscope (SEM) image of the negative electrode material prepared in Example 1 of this invention.

[0083] Figure 3 The image shows the XRD pattern of the negative electrode material prepared in Example 1 of this invention.

[0084] Figure 4 The first charge-discharge curve of the negative electrode material prepared in Example 1 of this invention;

[0085] Figure 5 The cycling performance curve of the negative electrode material prepared in Example 1 of this invention is shown. Detailed Implementation

[0086] The following are preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the protection scope of the present invention.

[0087] One embodiment of the negative electrode material includes an aggregate, the aggregate comprising an active material, a carbon material, and a conductive reinforcing agent; the tensile strength of the conductive reinforcing agent is ≥500MPa, and the dispersion N of the conductive reinforcing agent in the negative electrode material is ≥1;

[0088] The dispersion N is obtained through the following test method:

[0089] The SEM cross-section of the negative electrode material particle is divided into regions with an area of ​​A×B, where A and B are both ≤1 micrometer. The distribution of conductive reinforcing agent in all regions of a single negative electrode material particle is statistically analyzed. The number of regions with a spacing of <10nm between conductive reinforcing agents is denoted as Na, and the number of regions with a spacing of ≥10nm between conductive reinforcing agents is denoted as Nb. The dispersion C of conductive reinforcing agent in a single negative electrode material particle is defined as C=Nb / Na, where N is the arithmetic mean of the C values ​​of any 5 negative electrode material particles.

[0090] Uniform dispersion of conductive reinforcing agents can effectively improve carrier transport within aggregates, enhancing their conductivity. Furthermore, conductive reinforcing agents can effectively improve the structural stability and strength of aggregates, preventing stress changes caused by the expansion effect of active materials and maintaining structural stability. This, in turn, improves the cycling stability of the material and reduces the expansion rate. By controlling the tensile strength of the conductive reinforcing agent to ≥500 MPa, it exhibits superior mechanical properties and can serve as a structural support to enhance material stability. By controlling the minimum spacing between conductive reinforcing agents, the spaces between them can be filled with active materials, allowing the conductive reinforcing agents to act as a structural support to enhance material stability, thereby buffering the volume expansion changes of the active materials and improving cycling performance.

[0091] The tensile strength of the conductive reinforcing agent can be 500MPa, 800MPa, 1GPa, 5GPa, 10GPa, 25GPa, 30GPa, 45GPa or 50GPa, etc., or other values ​​within the above range, which are not limited here.

[0092] The conductive enhancer is distributed inside and / or on the surface of the aggregate.

[0093] In some embodiments, a conductivity enhancer is distributed within the active material, with carbon material filling the space between the active material and the conductivity enhancer. Understandably, by distributing the conductivity enhancer within the active material, the conductivity of the active material can be improved, thereby enhancing the transport of charge carriers within the active material.

[0094] In some embodiments, there are pores between the carbon material and the conductive reinforcing agent, and these pores are filled with active material. Understandably, the carbon material and the conductive reinforcing agent form a porous structure, which enhances the structural strength of the aggregate within the pores of the active material. This porous structure can resist stress changes caused by the expansion of the active material, thus maintaining the structural stability of the aggregate.

[0095] In some embodiments, the active material refers to a substance that can react with lithium to perform lithium insertion / extraction. The active material includes at least one of elemental metals, metal oxides, and metal alloys. Further, the metal includes at least one of Li, Na, K, Sn, Ge, Si, Fe, Mg, Ti, Zn, Al, P, and Cu.

[0096] In some embodiments, the active substance includes at least one selected from Li, Na, K, Sn, Ge, Si, SiO, Fe, Mg, Ti, Zn, Al, P, and Cu.

[0097] In some embodiments, the active material can be the aforementioned elemental metal, and more specifically, it can be Si, Sn, Ge, or Al. In other embodiments, the active material can be an alloy formed from at least two of the aforementioned metals, such as a silicon-lithium alloy or a silicon-magnesium alloy. In still other embodiments, the active material can be an oxide of the aforementioned metals, such as silicon suboxide. It should be noted that in some cases, the active material includes at least two of the following: elemental metals, metal alloys, and metal oxides.

[0098] In some embodiments, the active material is in the form of particles, with a median particle size of 1 nm to 500 nm. Specifically, it can be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, or 500 nm, etc., or other values ​​within the above range, which are not limited here. Through numerous experiments, it has been found that nanoscale active materials have high surface energy and are prone to aggregation during charging and discharging. The strong structural integrity of the particles can suppress the volume expansion of the active particles. However, due to the large surface energy of nanoscale active particles, they are prone to aggregation during charging and discharging. If the particle size of the active material is too small, the production process cost is high. Preferably, the median particle size of the active material is 1 nm to 200 nm, more preferably 1 nm to 100 nm.

[0099] In some embodiments, the carbon material includes at least one of amorphous carbon, crystalline carbon, hard carbon, soft carbon, and mesophase carbon microspheres.

[0100] In some embodiments, the conductivity enhancer includes at least one of an alloy material and conductive carbon. Of course, it is understood that any other conductive material with a tensile strength ≥ 500 MPa can be used as a conductivity enhancer.

[0101] In some embodiments, the conductive carbon includes at least one of carbon nanotubes, carbon fibers, and graphite fibers.

[0102] In some embodiments, the alloy material has an electrical conductivity >10. 2 Alloys with S / m and tensile strength ≥ 500 MPa.

[0103] In some embodiments, the alloy material includes at least one selected from silicon alloys, aluminum alloys, copper alloys, and lithium alloys. Further, the silicon alloy includes at least one selected from nickel-silicon alloys, iron-silicon alloys, copper-silicon alloys, silicon-manganese alloys, and aluminum-silicon alloys.

[0104] In some embodiments, the conductivity of the conductivity enhancer is >10. 2 S / m. Specifically, the conductivity of the conductive enhancer can be 100 S / m, 10 3 S / m, 10 4 S / m, 10 5 S / m, 10 8 S / m, etc. Conductivity enhancers within this range can effectively improve carrier transport within the aggregate, thereby enhancing the conductivity of the aggregate.

[0105] In some embodiments, the conductivity enhancer is in the form of sheets and / or strips.

[0106] In some embodiments, the aspect ratio of the conductive reinforcing agent is 2 to 3000. It should be noted that when the conductive reinforcing agent is in the form of strips, the aspect ratio specifically refers to the ratio of the particle's length to its diameter; when the conductive reinforcing agent is in the form of sheets, the aspect ratio specifically refers to the ratio of the length to the width of the sheet-like conductive reinforcing agent. Specifically, the aspect ratio of the conductive reinforcing agent can be 2, 30, 46, 150, 360, 670, 800, 900, 1500, 2000, or 3000, etc., and of course, other values ​​within the above range are also possible, without limitation. Multiple experiments have shown that conductive reinforcing agents with aspect ratios within this range possess superior mechanical properties and can serve as structural supports to enhance the stability of the material, thereby buffering the volume expansion changes of the active material and improving cycle performance.

[0107] In some embodiments, the mass ratio of the active material, carbon material, and conductive reinforcing agent is (20–70):(10–70):(3–20). Specifically, it can be 20:10:3, 50:70:10, 30:70:15, 25:50:12, 20:60:10, 25:70:8, 70:10:10, 70:50:20, 70:25:15, 50:50:10, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0108] In some embodiments, the aggregates also include metal oxides. Combining metal oxides with active substances can reduce the expansion of active substances, improve long-cycle performance, and give the aggregates higher compressive strength.

[0109] In some embodiments, metal oxides and conductive enhancers are distributed in the active material within the aggregate, and carbon material is filled between the active material and the metal oxides, and between the active material and the conductive enhancer.

[0110] Specifically, there are pores between the active material and the metal oxide, and between the active material and the conductive enhancer, and these pores are filled with carbon material. Understandably, the porous structure formed by the active material and the metal oxide, allowing the carbon material to fill the pores, can improve the structural stability of the aggregate, resist certain volume expansion stress, and reduce expansion.

[0111] In some embodiments, the general chemical formula of the metal oxide is M. x O y 0.2≤y / x≤3, where M includes at least one of Sn, Ge, Si, Fe, Cu, Ti, Na, Mg, Al, Ca, or Zn; specifically, the metal oxide can be SiO, GeO2, SnO2, ZnO, TiO2, Fe3O4, MgO, SiO2, CuO, etc. The selected metal oxide exhibits a lower volume expansion rate during the lithium intercalation process than the active material. Therefore, combining the metal oxide with the active material can reduce the expansion of the active material and improve long-cycle performance.

[0112] In some embodiments, the metal oxide is in the form of flakes and / or strips.

[0113] In some embodiments, the aspect ratio of the metal oxide is greater than 2. It should be noted that when the metal oxide is elongated, the aspect ratio specifically refers to the ratio of the particle's length to its diameter; when the metal oxide is plate-shaped, the aspect ratio specifically refers to the ratio of the length to the width of the plate-shaped metal oxide. Specifically, the aspect ratio of the metal oxide can be 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 12, 15, 17, 18, 22, etc., or other values ​​within the above range, which are not limited here. Multiple experiments have shown that when the aspect ratio of the metal oxide is greater than 2, it can enhance the physical bonding force between the metal oxide and the active material, thereby better buffering the volume expansion changes of the active material and improving cycle performance.

[0114] In some embodiments, the mass ratio of metal oxide to active material is (1-20):100. Specifically, the mass ratio of metal oxide to active material can be 1:100, 1.5:100, 2:100, 3:100, 4.5:100, 5:100, 6:100, 7:100, 8:100, 9:100, etc. Other values ​​within the above range are also possible and are not limited here. Excessive metal oxide content leads to a decrease in the initial efficiency of the material, while insufficient metal oxide content results in a decrease in the rigidity of the aggregate structure and a decrease in particle cycling stability.

[0115] In some embodiments, the porosity of the negative electrode material is ≤10%, and the pressure resistance of the negative electrode material is ≥50MPa.

[0116] At this point, the anode material has low porosity, meaning it has high density. This helps to increase the energy density of the material. Furthermore, even if the surface layer of the high-density material is damaged, the electrolyte is less likely to penetrate into the aggregate, which helps protect the internal active material particles and reduces the chance of contact between the electrolyte and the active material, thus facilitating the formation of a stable solid electrolyte membrane. In addition, the high-density anode material has high pressure resistance and hardness, which can offset the stress effect caused by expansion, improve the structural stability of the anode material, effectively suppress the volume expansion of the anode material, reduce the expansion rate, and improve the battery cycle performance.

[0117] In some embodiments, the porosity of the negative electrode material is ≤10%. Specifically, the porosity of the negative electrode material can be 10%, 9%, 9.5%, 8%, 8.5%, 7.5%, 7%, 6.5%, 6%, or 5%, etc., and of course, other values ​​within the above range are also possible and are not limited here. Understandably, a lower porosity in the negative electrode material, i.e., higher density, is beneficial for forming a stable solid electrolyte membrane and reducing the contact between the electrolyte and the active material. Preferably, the porosity of the negative electrode material is ≤5%, and more preferably, the porosity of the negative electrode material is ≤3%.

[0118] The pressure resistance of the negative electrode material is ≥50MPa; specifically, the pressure resistance of the negative electrode material can be 50MPa, 250MPa, 300MPa, 450MPa, 500MPa, 750MPa, 900MPa, 1150MPa, 11200MPa, or 1250MPa, etc., or other values ​​within the above range, which are not limited here. Because it has strong rigidity and high particle structure stability, it can resist a certain amount of volume expansion stress, thereby reducing expansion and improving battery cycle stability. Preferably, the pressure resistance of the negative electrode material is ≥100MPa, more preferably, the pressure resistance of the negative electrode material is ≥200MPa.

[0119] In some embodiments, the aggregate density satisfies the following relationship: the difference between the tested density of the aggregate and the average density of the aggregate is ≤5%. The closer the density of the aggregate particles is to the average density, the smaller the difference, indicating fewer pores and a denser structure inside the particles. This is beneficial for forming a stable solid electrolyte membrane and reducing the contact between the electrolyte and the active material.

[0120] Specifically, the aggregate density is calculated as follows: (p1-p2) / p2≤5%, where p1 is the test density of the aggregate and p2 is the average density of the aggregate.

[0121] Where p2 is the sum of the mass percentage of each component in the aggregate multiplied by the theoretical density of each component.

[0122] In a specific example, when the aggregate includes an active material, a conductivity enhancer, and a carbon material, p2 = the mass percentage of the active material in the aggregate * the theoretical density of the active material + the mass percentage of the conductivity enhancer in the aggregate * the theoretical density of the conductivity enhancer + the mass percentage of the carbon material in the aggregate * the theoretical density of the carbon material.

[0123] When the aggregate includes active material, metal oxide, conductive enhancer and carbon material, p2 = mass percentage of active material in the aggregate * theoretical density of active material + mass percentage of metal oxide in the aggregate * theoretical density of metal oxide + mass percentage of conductive enhancer in the aggregate * theoretical density of conductive enhancer + mass percentage of carbon material in the aggregate * theoretical density of carbon material.

[0124] Furthermore, the negative electrode material also includes a carbon layer covering at least a portion of the surface of the aggregate. Preferably, the carbon layer is distributed on the surface of the aggregate.

[0125] In some implementations, the carbon layer is made of amorphous carbon.

[0126] In some embodiments, the thickness of the carbon layer is from 10 nm to 1500 nm. Understandably, the carbon layer coating the surface of the aggregate can reduce the contact between the active material and the electrolyte, reduce the formation of a passivation film, and improve the reversible capacity of the battery.

[0127] Specifically, the thickness of the carbon layer can be 10nm, 50nm, 180nm, 200nm, 350nm, 400nm, 550nm, 700nm, 850nm, 900nm, 1050nm, 1200nm, or 1500nm, etc., or other values ​​within the above range, which are not limited here. If the carbon layer is too thick, the carbon content is too high, which is not conducive to obtaining a composite material with high specific capacity; if the carbon layer is too thin, it is not conducive to increasing the conductivity of the negative electrode material and has weak performance in suppressing the volume expansion of the material, resulting in a poor long-cycle performance. Preferably, the thickness of the carbon layer is 50nm to 800nm; more preferably, the thickness of the carbon layer is 100nm to 500nm.

[0128] It should be noted that in some embodiments, the porosity of the anode material after the aggregate surface is coated with a carbon layer is ≤10%, and the pressure resistance is ≥50MPa. Maintaining the overall porosity and pressure resistance of the anode material within this range can further improve the performance of the anode material.

[0129] In some embodiments, the median particle size of the negative electrode material is 0.5 μm to 30 μm. Specifically, it can be 0.5 μm, 1 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 25 μm, or 30 μm, etc., and of course, other values ​​within the above range are also possible and are not limited here. Understandably, controlling the median particle size of the negative electrode material within the above range is beneficial to improving the cycle performance of the negative electrode material.

[0130] In some embodiments, the specific surface area of ​​the negative electrode material is ≤10m². 2 / g. Specifically, it can be 10m. 2 / g、8m 2 / g、7m 2 / g、5m 2 / g、3m 2 / g、2m 2 / g、1m 2 / g or 0.5m 2 / g, etc., can also be other values ​​within the above range, and are not limited here. Understandably, controlling the specific surface area of ​​the negative electrode material within the above range is beneficial for suppressing volume expansion and improving the cycle performance of the negative electrode material.

[0131] It should be noted that the negative electrode materials of the above embodiments can be combined arbitrarily without contradicting each other, such as combining and limiting the pressure resistance, porosity and density of the aggregates.

[0132] Another embodiment of the method for preparing the negative electrode material, such as Figure 1 As shown, it includes the following steps:

[0133] Step S10: Add a conductive reinforcing agent with a tensile strength ≥ 500 MPa to the first solvent and disperse it to obtain a dispersion.

[0134] Step S20: The precursor is prepared by mixing the active substance, the dispersion, the first carbon source, and the second solvent.

[0135] Step S30: The precursor is subjected to a single heat treatment to obtain aggregates;

[0136] Step S40: Carbon coating is applied to the aggregate to obtain the negative electrode material.

[0137] The negative electrode material prepared by the preparation method of this embodiment includes an aggregate and a carbon coating layer covering the surface of the aggregate. The aggregate includes an active substance, a carbon material, and a conductive reinforcing agent. The tensile strength of the conductive reinforcing agent is ≥500MPa, and the dispersion of the conductive reinforcing agent in the particles is ≥1.

[0138] The preparation method of this embodiment involves first dispersing the conductive enhancer in a first solvent to obtain a dispersion solution. Then, the dispersion solution is mixed with the active material, the first carbon source, and the second solvent in different ratios to obtain a precursor, which ensures uniform dispersion of the conductive enhancer within the precursor. Uniform dispersion of the conductive enhancer can effectively improve the transport of charge carriers within the aggregate and enhance the conductivity of the aggregate. A conductive material with a tensile strength ≥500MPa is selected as the conductive enhancer. The conductive enhancer can act as a structural support to enhance the stability of the negative electrode material, strengthen the structural strength of the aggregate, avoid stress changes caused by the expansion effect of the active material, maintain the structural stability of the aggregate, and help suppress the expansion rate of the negative electrode material. Furthermore, the preparation process is simple and controllable.

[0139] The preparation method of this application is described in detail below with reference to the embodiments:

[0140] Step S10: Add a conductive reinforcing agent with a tensile strength ≥ 500 MPa to the first solvent and disperse it to obtain a dispersion.

[0141] The tensile strength of the conductive reinforcing agent should be ≥500 MPa. It should be noted that if the tensile strength of the conductive reinforcing agent is too low, it will be difficult for the agent to withstand the stress changes caused by the expansion of the active material, making it difficult to maintain the stability of the aggregate structure and hindering the improvement of the material's cycle performance. Specifically, the tensile strength of the conductive reinforcing agent can be 500 MPa, 800 MPa, 1 GPa, 6 GPa, 10 GPa, 15 GPa, 30 GPa, 35 GPa, or 80 GPa, etc., or other values ​​within the above range, which are not limited here. Multiple experiments have shown that controlling the tensile strength of the conductive reinforcing agent within the above range results in superior mechanical properties. It can serve as a structural support to enhance the stability of the material, thereby buffering the volume expansion changes of the active material and improving cycle performance.

[0142] In some embodiments, the first solvent includes an inorganic solvent, an organic solvent, or a mixture of organic and inorganic solvents. The organic solvent includes at least one selected from methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, and pentanol; the inorganic solvent includes water, liquid carbon dioxide, liquid ammonia, liquid sulfur dioxide, thionyl(di)chloride, thioyl chloride, lead acetate, hydrogen cyanide, hydrazine hydrate, thioyl fluoride, copper ammonia solution, sulfuric acid, nitric acid, hydrogen fluoride, polyphosphoric acid, and superacids.

[0143] In some embodiments, the dispersion treatment includes at least one of mechanical stirring, ultrasonic dispersion, and grinding dispersion. Preferably, grinding dispersion is used, as thorough grinding allows for more uniform mixing of the components. The conductivity enhancer is first added to the first solvent for dispersion, ensuring that the conductivity enhancer is dispersed as uniformly as possible in the first solvent, thereby preventing agglomeration of the conductivity enhancer. In some embodiments, the dispersion time can be controlled between 0.5 h and 10 h.

[0144] Step S20: The precursor is prepared by mixing the active substance, dispersion, first carbon source and second solvent.

[0145] In some embodiments, the active material refers to a substance that can react with lithium to perform lithium insertion / extraction. The active material includes at least one of elemental metals, metal oxides, and metal alloys. Further, the metal includes at least one of Li, Na, K, Sn, Ge, Si, Fe, Mg, Ti, Zn, Al, P, and Cu.

[0146] In some embodiments, the active substance includes at least one selected from Li, Na, K, Sn, Ge, Si, SiO, Fe, Mg, Ti, Zn, Al, P, and Cu.

[0147] In some embodiments, the active material can be the aforementioned elemental metal, and more specifically, it can be Si, Sn, Ge, or Al. In other embodiments, the active material can be an alloy formed from at least two of the aforementioned metals, such as a silicon-lithium alloy or a silicon-magnesium alloy. In still other embodiments, the active material can be an oxide of the aforementioned metals, such as silicon suboxide. It should be noted that in some cases, the active material includes at least two of the following: elemental metals, metal alloys, and metal oxides.

[0148] In some embodiments, the active material is in the form of particles, with a median particle size of 1 nm to 500 nm. Specifically, it can be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, or 500 nm, etc., or other values ​​within the above range, which are not limited here. Through numerous experiments, it has been found that nanoscale active materials have high surface energy and are prone to aggregation during charging and discharging. The strong structural integrity of the particles can suppress the volume expansion of the active particles. However, due to the large surface energy of nanoscale active particles, they are prone to aggregation during charging and discharging. If the particle size of the active material is too small, the production process cost is high. Preferably, the median particle size of the active material is 1 nm to 200 nm, more preferably 1 nm to 100 nm.

[0149] In some embodiments, the first carbon source includes at least one of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt.

[0150] In some embodiments, the second solvent includes an organic solvent. The organic solvent includes at least one selected from methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, and pentanol.

[0151] In some embodiments, the conductivity enhancer includes at least one of an alloy material and conductive carbon.

[0152] In some embodiments, the conductive carbon includes at least one of carbon nanotubes, carbon fibers, and graphite fibers.

[0153] In some embodiments, the conductivity of the conductivity enhancer is >10. 2 S / m; specifically, the conductivity of the conductive enhancer can be 100 S / m, 10 3 S / m, 10 4 S / m, 10 5 S / m, 10 8 S / m, etc.

[0154] In some embodiments, the conductivity enhancer is in the form of sheets and / or strips.

[0155] In some embodiments, the aspect ratio of the conductive reinforcing agent is 2 to 3000. It should be noted that when the conductive reinforcing agent is in the form of strips, the aspect ratio specifically refers to the ratio of the particle's length to its diameter; when the conductive reinforcing agent is in the form of sheets, the aspect ratio specifically refers to the ratio of the length to the width of the sheet-like conductive reinforcing agent. Specifically, the aspect ratio of the conductive reinforcing agent can be 2, 30, 46, 150, 360, 670, 800, 900, 1500, 2000, or 3000, etc., and of course, other values ​​within the above range are also possible, without limitation. Multiple experiments have shown that conductive reinforcing agents with aspect ratios within this range possess superior mechanical properties and can serve as structural supports to enhance the stability of the material, thereby buffering the volume expansion changes of the active material and improving cycle performance.

[0156] In some embodiments, the mass ratio of the active material, the conductivity enhancer, and the first carbon source is (15–120):(1–20):(10–50). Specifically, it can be 20:10:20, 50:10:10, 100:20:15, 100:20:10, 80:10:10, 80:1:10, 80:5:50, 50:20:20, 120:20:50, 120:20:10, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0157] In some embodiments, an additive is also added in the step of preparing the precursor by mixing the active material, the dispersion, the first carbon source, and the second solvent. The additive can effectively enhance the bonding stability between the active material and the first carbon source, thereby forming a robust system and reducing the electrode expansion rate.

[0158] In some embodiments, the mass ratio of active substance to additive is (15-120):(1-10). Specifically, the mass ratio of active substance to additive can be 15:1, 15:5, 15:10, 50:1, 55:2, 65:10, 70:2, 80:5, 90:8, 100:1, 100:10, 120:5, etc., and is not limited here.

[0159] In some embodiments, the additive includes at least one of surfactants and coupling agents.

[0160] Surfactants include at least one of octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecylbenzenesulfonate, icosanoic acid, palmitic acid, tetradecanoic acid, undecanoic acid, hexadecyltrimethylammonium bromide, and polyvinylpyrrolidone.

[0161] Coupling agents include silane coupling agents. Silane coupling agents include γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0162] In some embodiments, a metal oxide is also added in the step of preparing the precursor by mixing the active substance, the dispersion, the first carbon source, and the second solvent.

[0163] In some embodiments, the general chemical formula of the metal oxide is M. x O y , 0.2≤y / x≤3, wherein M includes at least one of Sn, Ge, Si, Fe, Cu, Ti, Na, Mg, Al, Ca and Zn.

[0164] In some embodiments, the metal oxide is in the form of flakes and / or strips.

[0165] In some implementations, the aspect ratio of the metal oxide is greater than 2.

[0166] In some embodiments, the mass ratio of metal oxide to active material is (1-20):100. Specifically, the mass ratio of metal oxide to active material can be 1:100, 1.5:100, 2:100, 3:100, 4.5:100, 5:100, 6:100, 7:100, 8:100, 9:100, etc. Other values ​​within the above range are also possible and are not limited here. Excessive metal oxide content leads to a decrease in the initial efficiency of the material, while insufficient metal oxide content results in a decrease in the rigidity of the aggregate structure and a decrease in particle cycling stability.

[0167] In some embodiments, the step of preparing the precursor further includes dispersing the active substance, the conductivity enhancer, the first carbon source, and the solvent after mixing them.

[0168] In some embodiments, the dispersion treatment includes at least one of mechanical stirring, ultrasonic dispersion, and grinding dispersion; preferably, grinding dispersion is used, so that the active material can be dispersed, avoiding agglomeration, and can be dispersed into smaller nanoparticles. Preferably, wet ball milling is used, and the wet ball milling dispersion time can be controlled between 0.5 h and 10 h. Thorough grinding can make the components more uniformly mixed, so that the particle size of the active material reaches 1 nm to 500 nm.

[0169] In some embodiments, the precursor is dried prior to heat treatment.

[0170] In some embodiments, the drying temperature is 30℃ to 400℃, specifically 30℃, 40℃, 50℃, 80℃, 100℃, 120℃, 150℃, 180℃, 200℃, 250℃, 280℃, 300℃, or 400℃, etc., and the drying time is 1h to 15h, specifically 1h, 3h, 5h, 7h, 9h, 10h, 12h, or 15h, etc., and the drying method can be, for example, oven drying, freeze drying, stirring evaporation, spray drying, etc., and the drying process in this embodiment can remove the solvent in the precursor solution as much as possible.

[0171] In some embodiments, the precursor is further subjected to a densification treatment before heat treatment. The densification treatment is performed to achieve an aggregate porosity ≤10% and a compressive hardness ≥50 MPa.

[0172] In some embodiments, the densification process includes at least one of the following: fusion process, kneading and extrusion process, molding process, isostatic pressing process, and impregnation process.

[0173] In some embodiments, the fusion process is mechanical fusion. By fusing the precursor, the pressure resistance of the negative electrode material is improved, followed by a heat treatment to enhance the stability of the particle structure. This also strengthens the connection stability between the active material and the first carbon source, reducing porosity. Of course, in other embodiments, other methods can be used for densification, such as molding, isostatic pressing, or impregnation, as long as the porosity of the aggregates is ≤10% and the pressure resistance is ≥50MPa.

[0174] In some embodiments, during fusion, the rotation speed of the fusion machine is 300 r / min to 3000 r / min, specifically 300 r / min, 1000 r / min, 1500 r / min, 2000 r / min, 2500 r / min, or 3000 r / min, etc.; the blade gap width of the fusion machine is 0.01 cm to 0.9 cm, specifically 0.01 cm, 0.05 cm, 0.1 cm, 0.15 cm, 0.2 cm, 0.25 cm, 0.3 cm, 0.5 cm, 0.9 cm, etc.; the fusion time is at least 0.5 h, specifically 0.5 h, 0.8 h, 0.9 h, 1.0 h, 1.5 h, or 2 h, etc., and is not limited here.

[0175] Step S30: Perform a heat treatment on the precursor to obtain the aggregate.

[0176] In some implementations, the heat treatment process may be, for example, vacuum sintering, hot pressing sintering, or atmospheric pressure sintering.

[0177] In some embodiments, the temperature of the primary heat treatment is 600°C to 1200°C, for example, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, etc. Preferably, the temperature of the primary heat treatment is 600°C to 1000°C.

[0178] In some implementations, the heat treatment time is 1 hour to 10 hours, for example, it can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours.

[0179] The heating rate during heat treatment is 1℃ / min to 30℃ / min, specifically 1℃ / min, 5℃ / min, 10℃ / min, 15℃ / min, 20℃ / min, 25℃ / min, or 30℃ / min, etc. For example, preferably, the heating rate during heat treatment is 1℃ / min to 15℃ / min.

[0180] The heat treatment process is carried out with a protective gas, which includes at least one of nitrogen, helium, neon, argon and krypton.

[0181] Step S40: Carbon coating is applied to the aggregate to obtain the negative electrode material.

[0182] It should be noted that the negative electrode material in this embodiment may not be carbon coated, in which case step S30 can be omitted.

[0183] In some embodiments, the carbon coating process includes mixing the precursor with a second carbon source and performing a secondary heat treatment.

[0184] In some embodiments, the second carbon source includes at least one of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and bitumen.

[0185] In some embodiments, the precursor particle size is 0.5 μm to 20 μm, specifically 0.5 μm, 1 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, or 20 μm, etc., or other values ​​within the above range, which are not limited here. Understandably, controlling the average particle size of the anode material within the above range is beneficial to improving the cycle performance of the anode material.

[0186] In some embodiments, the mass ratio of the precursor to the second carbon source is (20-100):(10-80). Specifically, the mass ratio of the precursor to the second carbon source is 100:25, 100:35, 100:45, 100:55, 100:65, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0187] In some embodiments, the temperature of the secondary heat treatment is 600℃~1200℃.

[0188] In some implementations, the secondary heat treatment time is 1 hour to 10 hours.

[0189] In some embodiments, the heating rate during secondary heat treatment is 1°C / min to 30°C / min.

[0190] In some embodiments, the secondary heat treatment process is carried out with a protective gas, which includes at least one of nitrogen, helium, neon, argon and krypton.

[0191] In some implementations, the mixing method may include magnetic stirring, mechanical stirring, ultrasonic dispersion, grinding dispersion, etc.

[0192] In some embodiments, other methods can be used to carbon-coat the aggregates. Specifically, the carbon-coating process includes mixing the aggregates with a second carbon source and performing a secondary heat treatment to form a carbon layer on the surface of the aggregates.

[0193] In some embodiments, the mass ratio of the aggregate to the second carbon source is (15-100):(10-70); specifically, the mass ratio of the precursor to the second carbon source is 100:25, 100:35, 100:45, 100:55, 100:65, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0194] In some embodiments, the temperature of the secondary heat treatment is 600℃ to 1200℃, for example, 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, 1200℃, etc. Preferably, the temperature of the secondary heat treatment is 600℃ to 1000℃.

[0195] In some implementations, the secondary heat treatment time is 1 hour to 10 hours, for example, it can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours.

[0196] In some embodiments, the heating rate during the secondary heat treatment is 1°C / min to 30°C / min, specifically 1°C / min, 5°C / min, 10°C / min, 15°C / min, 20°C / min, 25°C / min, or 30°C / min, etc. For example, preferably, the heating rate during the heat treatment is 1°C / min to 15°C / min.

[0197] In some embodiments, the secondary heat treatment process is carried out with a protective gas, which includes at least one of nitrogen, helium, neon, argon and krypton.

[0198] It should be noted that the negative electrode material in this embodiment is not limited to the two carbon coating methods described above.

[0199] In some embodiments, after the secondary heat treatment, at least one of crushing, sieving, and demagnetizing is performed; preferably, after the secondary heat treatment, crushing, sieving, and demagnetizing are performed sequentially.

[0200] In some implementations, the pulverization method is any one of a mechanical pulverizer, an air jet mill, or a cryogenic pulverizer.

[0201] In some implementations, the screening method is any one of fixed screen, drum screen, resonant screen, roller screen, vibrating screen, and chain screen, and the screening mesh is ≥500 mesh. Specifically, the screening mesh can be 500 mesh, 600 mesh, 700 mesh, 800 mesh, etc. Controlling the particle size of the negative electrode material within the above range is beneficial to improving the cycle performance of the negative electrode material.

[0202] In some implementations, the demagnetizing equipment is any one of a permanent magnet drum magnetic separator, an electromagnetic iron remover, or a pulsed high-gradient magnetic separator. Demagnetization is to ultimately control the magnetic content of the negative electrode material, thereby avoiding the impact of magnetic materials on the discharge effect of the lithium-ion battery and the safety of the battery during use.

[0203] This application also provides a lithium-ion battery, which includes the above-mentioned negative electrode material.

[0204] Those skilled in the art will understand that the methods for preparing lithium-ion batteries described above are merely examples. Other methods commonly used in the art can be employed without departing from the disclosure of this application.

[0205] The embodiments of the present invention will be further described below with reference to several examples. However, the embodiments of the present invention are not limited to the specific embodiments described below. Appropriate modifications can be made within the scope of the original claims.

[0206] The dispersion N of the conductivity enhancer in the following examples and comparative examples was obtained through the following test methods:

[0207] The prepared negative electrode material was cross-sectioned using SEM. The SEM cross-section of a single negative electrode material particle was divided into regions with an area of ​​1 μm × 1 μm. The distribution of conductive reinforcing agents in all regions of a single negative electrode material particle was statistically analyzed. The number of regions with a spacing of <10 nm between conductive reinforcing agents was denoted as Na, and the number of regions with a spacing of ≥10 nm between conductive reinforcing agents was denoted as Nb. The dispersion C of conductive reinforcing agents in a single negative electrode material particle was defined as C = Nb / Na, where N is the arithmetic mean of the C values ​​of any 5 negative electrode material particles.

[0208] Example 1

[0209] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0210] (1) A material with an aspect ratio of 500, a tensile strength of 65 GPa, and an electrical conductivity of 1.5*10⁻⁶ is used. 6 Multi-walled carbon nanotubes with a median particle size of 100 nm were added to anhydrous ethanol at a mass ratio of 5% and dispersed by grinding for 5 hours to obtain a dispersion. Then, nano-silicon with a median particle size of 100 nm, the dispersion, polyacrylic acid and phenolic resin were added to an ethylene glycol solution at a mass ratio of 40:3.9:1.6:15.9. The mixture was sonicated for 60 minutes and then dispersed by grinding in a ball mill for 9 hours to obtain a precursor solution. Finally, the precursor was obtained by spray drying at 190℃ for 3 hours.

[0211] (2) Place the precursor in a fusion machine with a rotation speed of 450 r / min; the blade gap width of the fusion machine used for mechanical fusion is 0.8 cm; the mechanical fusion time is 1 h; place the fused material under nitrogen protection at 890 ℃ for heat treatment and keep it at that temperature for 4 h to obtain aggregates.

[0212] (3) The aggregate and asphalt were mixed at a mass ratio of 100:49. The mixed material was then placed in a high-temperature box furnace, nitrogen was introduced, and carbon coating was performed at 820°C. After heat preservation for 4 hours, the material was crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0213] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes nano-silicon powder, multi-walled carbon nanotubes and carbon materials. The mass ratio of nano-silicon powder, multi-walled carbon nanotubes and carbon materials is 49.6:2.6:47.8. The multi-walled carbon nanotubes are distributed in the aggregate.

[0214] The median particle size of the negative electrode material is 13.2 μm, and the specific surface area is 3.3 m². 2 / g, with a carbon layer thickness of 450nm.

[0215] Using the above-mentioned test method for the dispersion N of conductive reinforcing agent, the dispersion N of conductive reinforcing agent (multi-walled carbon nanotubes) is 9.5.

[0216] The porosity of the negative electrode material particles was tested using the mercury intrusion porosimetry method, and the porosity of the negative electrode material was 3.9%.

[0217] The negative electrode material particles were tested using a nanoindenter, and the average compressive strength of the negative electrode material was found to be 231 MPa. The tested density of the negative electrode material differed from the average density of silicon powder and carbon materials by 3.2%.

[0218] Figure 2 This is a scanning electron microscope (SEM) image of the negative electrode material prepared in Example 1 of this invention. Figure 3 The XRD pattern of the negative electrode material prepared in Example 1 of this invention is shown below. Figure 3 As shown, silicon peaks exist in the negative electrode material.

[0219] Example 2

[0220] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0221] (1) A material with an aspect ratio of 100, a tensile strength of 1.5 GPa, and an electrical conductivity of 1.2 × 10⁻⁶ is used. 5 Graphite fibers with a median particle size of 3 nm were added to anhydrous ethanol at a mass ratio of 3% and dispersed by grinding for 10 hours to obtain a dispersion. Then, nano-silicon with a median particle size of 30 nm, the dispersion, oleic acid, and sucrose were added to the ethanol solution at a mass ratio of 30:1.9:5.6:25.9. The mixture was sonicated for 50 minutes and then dispersed by grinding in a ball mill for 7 hours to obtain a precursor solution. The precursor solution was then spray-dried at 150°C for 3 hours to obtain the precursor.

[0222] (2) Place the precursor in a fusion machine with a rotation speed of 650 r / min; the blade gap width of the fusion machine used for mechanical fusion is 0.4 cm; the mechanical fusion time is 3 h; place the fused material under argon protection at 980 ℃ for heat treatment and keep it at that temperature for 2 h to obtain aggregates.

[0223] (3) The aggregate and phenolic resin are mixed in a mass ratio of 70:55. The mixed material is then placed in a high-temperature box furnace, nitrogen is introduced, and carbon coating is performed at 840°C. After heat preservation for 4 hours, the material is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0224] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes nano-silicon powder, graphite fiber and carbon material. The mass ratio of nano-silicon powder, graphite fiber and carbon material is 55.6:6.2:38.2. The graphite fiber is distributed in the aggregate.

[0225] The median particle size of the negative electrode material is 12.8 μm, and the specific surface area is 4.7 m². 2 / g, with a carbon layer thickness of 320nm.

[0226] The dispersion N of the conductive reinforcing agent was tested using the above-mentioned test method, and the dispersion N of the conductive reinforcing agent (graphite fiber) was 14.

[0227] The porosity of the anode material was 4.5% when the aggregate particles were tested using the mercury porosimetry method.

[0228] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 128 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 2.9%.

[0229] Example 3

[0230] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0231] (1) A material with an aspect ratio of 2000, a tensile strength of 129 GPa, and an electrical conductivity of 3*10 6 Single-walled carbon nanotubes with a median particle size of 60 nm were added at a mass ratio of 2% to a mixed solution of water and ethanol (water:ethanol mass ratio = 1:1) and dispersed by grinding for 10 h to obtain a dispersion. Then, nano-silicon with a median particle size of 60 nm, the dispersion, decanoic acid and fructose were added to an ethylene glycol solution at a mass ratio of 40:2.9:3.6:36.9 and sonicated for 70 min. After that, the mixture was dispersed by grinding in a ball mill for 5 h to obtain a precursor solution. Then, the precursor was obtained by spray drying at 200 °C for 1.5 h.

[0232] (2) Place the precursor in a fusion machine with a rotation speed of 300 r / min; the blade gap width of the fusion machine used for mechanical fusion is 0.5 cm; the mechanical fusion time is 1 h; place the fused material under argon protection at 700℃ for heat treatment and keep it at that temperature for 4 h to obtain aggregates.

[0233] (3) The aggregate and asphalt were mixed at a mass ratio of 100:47. The mixed material was then placed in a high-temperature box furnace, nitrogen was introduced, and carbon coating was performed at 920°C. After heat preservation for 3 hours, the material was crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0234] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes nano-silicon powder, single-walled carbon nanotubes and carbon materials. The mass ratio of nano-silicon powder, single-walled carbon nanotubes and carbon materials is 43.9:2.1:54.0. The single-walled carbon nanotubes are distributed in the aggregate.

[0235] The median particle size of the negative electrode material is 9.8 μm, and the specific surface area is 5.3 m². 2 / g, with a carbon layer thickness of 600nm.

[0236] Using the above-mentioned test method for the dispersion N of conductive reinforcing agent, the dispersion N of single-walled carbon nanotubes for conductive reinforcing agent is 20.

[0237] The porosity of the anode material was 3.8% when the aggregate particles were tested using mercury porosimetry.

[0238] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 201 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 1.9%.

[0239] Example 4

[0240] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0241] (1) A material with an aspect ratio of 55, a tensile strength of 502 MPa, and an electrical conductivity of 2.2*10⁻⁶ is used. 2 A nickel-silicon alloy with a median particle size of S / m was added to anhydrous ethanol at a mass ratio of 5% and dispersed by grinding for 6 hours to obtain a dispersion. Then, nano-silicon with a median particle size of 50 nm, the dispersion, sodium dodecylbenzenesulfonate, and glucose were added to an ethylene glycol solution at a mass ratio of 50:2.9:3.6:44.1. The mixture was ultrasonicated for 50 minutes and then dispersed by ball milling for 6 hours to obtain a precursor solution. Finally, the solution was spray-dried at 140℃ for 3 hours to obtain the precursor.

[0242] (2) Place the precursor in a fusion machine with a rotation speed of 600 r / min; the blade gap width of the fusion machine used for mechanical fusion is 0.45 cm; the mechanical fusion time is 2 h; place the fused material under argon protection at 790 ℃ for heat treatment and keep it at that temperature for 4 h to obtain aggregates.

[0243] (3) The aggregate and asphalt were mixed at a mass ratio of 100:37. The mixed material was then placed in a high-temperature box furnace, nitrogen was introduced, and carbon coating was performed at 960°C. After heat preservation for 3 hours, the material was crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0244] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes nano-silicon powder, nickel-silicon alloy, and carbon material, with a mass ratio of 46.9:2.8:50.3. The nickel-silicon alloy is distributed within the aggregate.

[0245] The median particle size of the negative electrode material is 12 μm, and the specific surface area is 4.3 m². 2 / g, with a carbon layer thickness of 580nm.

[0246] The dispersion N of the conductive reinforcing agent was tested using the above-mentioned test method, and the dispersion N of the conductive reinforcing agent (nickel-silicon alloy) was 11.

[0247] The porosity of the anode material was 5.2% when the aggregate particles were tested using the mercury porosimetry method.

[0248] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 109 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 3.2%.

[0249] Example 5

[0250] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0251] (1) A material with an aspect ratio of 35, a tensile strength of 560 MPa, and an electrical conductivity of 6.2 × 10⁻⁶... 2 A silicon-iron alloy with a median particle size of 50 nm was added to propanol at a mass ratio of 1.5% and dispersed by grinding for 8 hours to obtain a dispersion. Then, nano-silicon with a median particle size of 50 nm, the dispersion, polysorbate-80, and citric acid were added to an ethylene glycol solution at a mass ratio of 49:3.9:4.6:34.1. The mixture was ultrasonicated for 50 minutes and then dispersed by grinding in a ball mill for 6 hours to obtain a precursor solution. Finally, the precursor was obtained by spray drying at 120°C for 3 hours.

[0252] (2) Place the precursor in the fusion machine, the rotation speed of the fusion machine is 300 r / min; the blade gap width of the fusion machine used for mechanical fusion is 0.6 cm; the mechanical fusion time is 2 h; place the fused material under argon protection at 890℃ for heat treatment, keep it at the temperature for 4 h, and obtain aggregates.

[0253] (3) The aggregate and asphalt were mixed at a mass ratio of 100:44. The mixed material was then placed in a high-temperature box furnace, nitrogen was introduced, and carbon coating was performed at 920°C. After heat preservation for 3 hours, the material was crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0254] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes nano-silicon powder, iron-silicon alloy, and carbon material, with a mass ratio of 50.4:3.8:45.8. The iron-silicon alloy is distributed within the aggregate.

[0255] The median particle size of the negative electrode material is 15 μm, and the specific surface area is 3 m².2 / g, with a carbon layer thickness of 430nm.

[0256] The dispersion N of the conductive reinforcing agent was tested using the above-mentioned test method, and the dispersion N of the conductive reinforcing agent (iron-silicon alloy) was 33.

[0257] The porosity of the anode material was 2.6% when the aggregate particles were tested using mercury porosimetry.

[0258] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 188 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 2.1%.

[0259] Example 6

[0260] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0261] (1) A material with an aspect ratio of 45, a tensile strength of 679 MPa, and an electrical conductivity of 4.2 × 10⁻⁶ MPa is used. 3 A copper-silicon alloy with a mass ratio of S / m was added to propanol at a mass ratio of 2.5% and milled for 4 hours to obtain a dispersion. Then, Ge particles with a median particle size of 50 nm, the dispersion, polysorbate-20, and citric acid were added to an ethylene glycol solution at a mass ratio of 78:2.9:3.6:44.1. The mixture was ultrasonicated for 90 minutes and then milled and dispersed in a ball mill for 3 hours to obtain a precursor solution. Finally, the solution was spray-dried at 180°C for 3 hours to obtain the precursor.

[0262] (2) Place the precursor in a fusion machine with a rotation speed of 600 r / min; the blade gap width of the fusion machine used for mechanical fusion is 0.5 cm; the mechanical fusion time is 2 h; place the fused material under argon protection at 890℃ for heat treatment and keep it at that temperature for 4 h to obtain aggregates.

[0263] (3) The aggregate and asphalt were mixed at a mass ratio of 100:34. The mixed material was then placed in a high-temperature box furnace, nitrogen was introduced, and carbon coating was performed at 950°C. After heat preservation for 3 hours, the material was crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0264] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes nano-Ge powder, copper-silicon alloy, and carbon material, with a mass ratio of 67.4:4.8:26.8. The copper-silicon alloy is distributed within the aggregate.

[0265] The median particle size of the negative electrode material is 14.8 μm, and the specific surface area is 3.9 m². 2 / g, with a carbon layer thickness of 206nm.

[0266] The dispersion N of the conductive reinforcing agent was tested using the above-mentioned test method, and the dispersion N of the conductive reinforcing agent (copper-silicon alloy) was 13.

[0267] The porosity of the anode material was 5.6% when the aggregate particles were tested using mercury porosimetry.

[0268] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 345 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 3.8%.

[0269] Example 7

[0270] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0271] (1) Carbon fibers with an aspect ratio of 350, a tensile strength of 4.2 GPa, and an electrical conductivity of 5.6 S / m were added to butanol at a mass ratio of 3% and dispersed by grinding for 6 hours to obtain a dispersion. Then, Sn particles with a median particle size of 120 nm, the dispersion, coconut oil fatty acid diethanolamide, and sucrose were added to an ethylene glycol solution at a mass ratio of 90:6.9:2.6:26.1. The mixture was sonicated for 100 min and then dispersed by grinding in a ball mill for 4 hours to obtain a precursor solution. Then, the precursor was obtained by spray drying at a temperature of 150 °C for 3 hours.

[0272] (2) Place the precursor in a fusion machine with a rotation speed of 600 r / min; the blade gap width of the fusion machine used for mechanical fusion is 0.7 cm; the mechanical fusion time is 2 h; place the fused material under argon protection at 890 ℃ for heat treatment and keep it at that temperature for 2 h to obtain aggregates.

[0273] (3) The aggregate and phenolic resin are mixed at a mass ratio of 100:45. The mixed material is then placed in a high-temperature box furnace, nitrogen is introduced, and carbon coating is performed at 950°C. After heat preservation for 3 hours, the material is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0274] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes nano-Sn powder, carbon fibers, and carbon materials, with a mass ratio of nano-Sn powder, carbon fibers, and carbon materials of 69.5:4.5:26.0. The carbon fibers are distributed within the aggregate.

[0275] The median particle size of the negative electrode material is 12.8 μm, and the specific surface area is 5.9 m². 2 / g, with a carbon layer thickness of 160nm.

[0276] The dispersion N of the conductive reinforcing agent was tested using the above-mentioned test method, and the dispersion N of the conductive reinforcing agent (carbon fiber) was 24.

[0277] The porosity of the anode material was 3.1% when the aggregate particles were tested using mercury porosimetry.

[0278] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 289 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 1.5%.

[0279] Example 8

[0280] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0281] (1) A material with an aspect ratio of 900, a tensile strength of 55 GPa, and an electrical conductivity of 5.2 × 10⁻⁶ is used. 6 Carbon nanotubes with a median particle size of 80 nm were added to butanol at a mass ratio of 2.3% and dispersed by grinding for 12 h to obtain a dispersion. Then, Si particles with a median particle size of 80 nm, the dispersion, SiO with an aspect ratio of 18, γ-methacryloyloxypropyltrimethoxysilane, and sucrose were added to an ethylene glycol solution at a mass ratio of 50:3.9:3.0:6.6:33.1. The mixture was ultrasonicated for 120 min and then dispersed by ball milling for 8 h to obtain a precursor solution. Finally, the precursor was spray-dried at 140 °C for 3 h to obtain a precursor.

[0282] (2) Place the precursor in a fusion machine with a rotation speed of 1000 r / min; the blade gap width of the fusion machine used for mechanical fusion is 0.8 cm; the mechanical fusion time is 2 h; place the fused material under argon protection at 890 ℃ for heat treatment and keep it at that temperature for 2 h to obtain aggregates.

[0283] (3) The aggregate and phenolic resin are mixed at a mass ratio of 100:55. The mixed material is then placed in a high-temperature box furnace, nitrogen is introduced, and carbon coating is performed at 950°C. After heat preservation for 8 hours, the material is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0284] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes nano-Si powder, carbon nanotubes, SiO, and carbon materials, with a mass ratio of 46.2:2.5:6.5:44.8. The carbon nanotubes are distributed within the aggregate.

[0285] The median particle size of the negative electrode material is 9.8 μm, and the specific surface area is 4.3 m². 2 / g, with a carbon layer thickness of 460nm.

[0286] The dispersion N of the conductive reinforcing agent was tested using the above-mentioned test method, and the dispersion N of the conductive reinforcing agent (carbon nanotube) was 25.

[0287] The porosity of the anode material was 4.5% when the aggregate particles were tested using the mercury porosimetry method.

[0288] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 142 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 3.2%.

[0289] Example 9

[0290] The negative electrode material was prepared using a method essentially the same as in Example 1, except that no additive (polyacrylic acid) was added. Step (1) involved adding nano-silicon with a median particle size of 100 nm, multi-walled carbon nanotubes with an aspect ratio of 500 and a tensile strength of 65 GPa, and phenolic resin to an ethylene glycol solution at a mass ratio of 40:3.9:15.9, sonicating for 60 min, and then grinding and dispersing in a ball mill for 9 h to obtain a precursor solution; then spray drying was performed at a temperature of 190 °C for 3 h to obtain the precursor.

[0291] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes nano-silicon powder, multi-walled carbon nanotubes and carbon materials. The mass ratio of nano-silicon powder, multi-walled carbon nanotubes and carbon materials is 49.6:2.6:47.8. The multi-walled carbon nanotubes are distributed in the aggregate.

[0292] The median particle size of the anode material is 13.2 μm, the specific surface area is 3.3 m² / g, and the carbon layer thickness is 450 nm.

[0293] Using the above-mentioned test method for the dispersion N of conductive reinforcing agent, the dispersion N of conductive reinforcing agent (multi-walled carbon nanotubes) is 7.4.

[0294] The porosity of the anode material was 6.9% when the aggregate particles were tested using mercury porosimetry.

[0295] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 205 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 3.1%.

[0296] Example 10

[0297] The difference between this embodiment and embodiment 1 is that step (2) is different. Specifically, step (2) involves placing the precursor under nitrogen protection at 890°C for heat treatment and holding it at that temperature for 4 hours to obtain aggregates.

[0298] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes nano-silicon powder, multi-walled carbon nanotubes and carbon materials. The mass ratio of nano-silicon powder, multi-walled carbon nanotubes and carbon materials is 49.6:2.6:47.8. The multi-walled carbon nanotubes are distributed in the aggregate.

[0299] The median particle size of the negative electrode material is 13.2 μm, and the specific surface area is 3.3 m². 2 / g, with a carbon layer thickness of 450nm.

[0300] Using the above-mentioned test method for the dispersion N of conductive reinforcing agent, the dispersion N of conductive reinforcing agent (multi-walled carbon nanotubes) is 10.

[0301] The porosity of the anode material was 10.5% when the aggregate particles were tested using mercury porosimetry.

[0302] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 45 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 2.2%.

[0303] Example 11

[0304] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0305] (1) A material with an aspect ratio of 500, a tensile strength of 65 GPa, and an electrical conductivity of 1.5*10⁻⁶ is used. 6 Multi-walled carbon nanotubes with a median particle size of 100 nm were added to anhydrous ethanol at a mass ratio of 5% and dispersed by grinding for 5 hours. Nano-silicon, multi-walled carbon nanotubes, and phenolic resin with a median particle size of 100 nm were added to an ethylene glycol solution at a mass ratio of 40:3.9:15.9 and sonicated for 60 minutes. Then, the solution was dispersed by grinding in a ball mill for 9 hours to obtain a precursor solution. Finally, the solution was spray-dried at 190 °C for 3 hours to obtain the precursor.

[0306] (2) The precursor was heat-treated at 890°C for 4 hours under nitrogen protection to obtain aggregates.

[0307] (3) The aggregate and asphalt were mixed at a mass ratio of 100:49. The mixed material was then placed in a high-temperature box furnace, nitrogen was introduced, and carbon coating was performed at 820°C. After heat preservation for 4 hours, the material was crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0308] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes nano-silicon powder, multi-walled carbon nanotubes and carbon materials. The mass ratio of nano-silicon powder, multi-walled carbon nanotubes and carbon materials is 49.6:2.6:47.8. The multi-walled carbon nanotubes are distributed in the aggregate.

[0309] The median particle size of the negative electrode material is 13.2 μm, and the specific surface area is 3.3 m². 2 / g, with a carbon layer thickness of 450nm.

[0310] The dispersion N of the conductive reinforcing agent was tested using the above-mentioned test method, and the dispersion N of the conductive reinforcing agent (multi-walled carbon nanotubes) was 9.

[0311] The porosity of the anode material was 11.4% when the aggregate particles were tested using mercury porosimetry.

[0312] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 26 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 4.4%.

[0313] Example 12

[0314] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0315] (1) A material with an aspect ratio of 500, a tensile strength of 65 GPa, and an electrical conductivity of 1.5*10⁻⁶ is used. 6 Multi-walled carbon nanoparticles with a median particle size of 100 nm were added to anhydrous ethanol at a mass ratio of 5% and dispersed by grinding for 5 hours to obtain a dispersion. Nano-silicon with a median particle size of 100 nm, the dispersion, TiO2 particles with an aspect ratio of 17, and phenolic resin were added to an ethylene glycol solution at a mass ratio of 40:3.9:0.5:15.9. The mixture was ultrasonicated for 60 minutes and then dispersed by grinding in a ball mill for 9 hours to obtain a precursor solution. Then, it was spray-dried at 190℃ for 3 hours to obtain the precursor.

[0316] (2) The precursor was heat-treated at 890°C under nitrogen protection for 4 hours to obtain aggregates.

[0317] (3) The aggregate and asphalt were mixed at a mass ratio of 100:49. The mixed material was then placed in a high-temperature box furnace, nitrogen was introduced, and carbon coating was performed at 820°C. After heat preservation for 4 hours, the material was crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0318] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes nano-silicon powder, multi-walled carbon nanotubes, TiO2 particles and carbon materials. The mass ratio of nano-silicon powder, multi-walled carbon nanotubes, TiO2 particles and carbon materials is (47.6):(2.6):(2.0):(46.8). The multi-walled carbon nanotubes are distributed in the aggregate.

[0319] The median particle size of the negative electrode material is (12) μm, and the specific surface area is (6.8) m².2 / g, with a carbon layer thickness of 450nm.

[0320] Using the above-mentioned test method for the dispersion N of conductive reinforcing agent, the dispersion N of conductive reinforcing agent (multi-walled carbon nanotubes) is 8.8.

[0321] The porosity of the anode material was 9.8% when the aggregate particles were tested using mercury porosimetry.

[0322] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 55 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 3.9%.

[0323] Example 13

[0324] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0325] (1) A material with an aspect ratio of 500, a tensile strength of 65 GPa, and an electrical conductivity of 1.5*10⁻⁶ is used. 6 Multi-walled carbon nanotubes with a median particle size of 5 nm were added to anhydrous ethanol at a mass ratio of 5% and dispersed by grinding for 5 hours to obtain a dispersion. Nano-Si with a median particle size of 50 nm, the dispersion, and phenolic resin were added to an ethylene glycol solution at a mass ratio of 15:1:10. The solution was ultrasonicated for 60 minutes and then dispersed by grinding in a ball mill for 9 hours to obtain a precursor solution. Then, the solution was spray-dried at 190°C for 3 hours to obtain the precursor.

[0326] (2) Place the precursor in a fusion machine with a rotation speed of 800 r / min; the blade gap width of the fusion machine used for mechanical fusion is 0.8 cm; the mechanical fusion time is 1 h; place the fused material under nitrogen protection at 1000 ℃ for heat treatment and keep it at that temperature for 3 h to obtain aggregates.

[0327] (3) The aggregate and asphalt are mixed in a mass ratio of 15:10. The mixed material is then placed in a high-temperature box furnace, nitrogen is introduced, and carbon coating is performed at 1000℃. After heat preservation for 4 hours, the material is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0328] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes nano-silicon powder, multi-walled carbon nanotubes and carbon materials. The mass ratio of nano-silicon powder, multi-walled carbon nanotubes and carbon materials is (58.2):(2.1):(39.7). The multi-walled carbon nanotubes are distributed in the aggregate.

[0329] The median particle size of the anode material is (14.3) μm, the specific surface area is (2.8) m2 / g, and the carbon layer thickness is (380) nm.

[0330] The dispersion N of the conductive reinforcing agent was tested using the above-mentioned test method, and the dispersion N of the conductive reinforcing agent (multi-walled carbon nanotubes) was 1.4.

[0331] The porosity of the anode material was 2.7% when the aggregate particles were tested using the mercury porosimetry method.

[0332] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 164 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 2.0%.

[0333] Example 14

[0334] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0335] (1) A material with an aspect ratio of 1000, a tensile strength of 65 GPa, and an electrical conductivity of 1.5 × 10⁻⁶ is used. 6 Multi-walled carbon nanotubes with a median particle size of 50 nm were added to a mixture of liquid ammonia and water (volume ratio 1:1) at a mass ratio of 1.0% and dispersed by grinding for 8 hours to obtain a dispersion. Nano-Sn with a median particle size of 50 nm, the dispersion, and phenolic resin were added to an ethylene glycol solution at a mass ratio of 120:2:50 and sonicated for 60 minutes. Then, the mixture was dispersed by grinding in a ball mill for 9 hours to obtain a precursor solution. Finally, the precursor was obtained by spray drying at 190°C for 3 hours.

[0336] (2) Place the precursor in the fusion machine. The rotation speed of the fusion machine is 800 r / min. The blade gap width of the fusion machine used for mechanical fusion is 0.8 cm. The mechanical fusion time is 1 h. The fused material is placed under nitrogen protection at 890℃ for heat treatment and kept at the temperature for 3 h to obtain aggregates.

[0337] (3) The aggregate and asphalt are mixed in a mass ratio of 100:50. The mixed material is then placed in a high-temperature box furnace, nitrogen is introduced, and carbon coating is performed at 800°C. After heat preservation for 4 hours, the material is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0338] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes nano-Sn powder, multi-walled carbon nanotubes and carbon materials. The mass ratio of nano-Sn powder, multi-walled carbon nanotubes and carbon materials is (69.5):(1.1):(29.4). The multi-walled carbon nanotubes are distributed in the aggregate.

[0339] The median particle size of the negative electrode material is (16) μm, and the specific surface area is (3.7) m². 2 / g, with a carbon layer thickness of (144)nm.

[0340] The dispersion N of the conductive reinforcing agent was tested using the above-mentioned test method, and the dispersion N of the conductive reinforcing agent (multi-walled carbon nanotubes) was 45.

[0341] The porosity of the anode material was 3.7% when the aggregate particles were tested using mercury porosimetry.

[0342] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 199 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 1.5%.

[0343] Example 15

[0344] The difference from Example 1 is that no carbon coating was performed. Step (3) is not included.

[0345] The negative electrode material prepared in this embodiment includes an aggregate, which includes nano-silicon powder, multi-walled carbon nanotubes and carbon materials. The mass ratio of nano-silicon powder, multi-walled carbon nanotubes and carbon materials is 49.6:2.6:47.8, and the multi-walled carbon nanotubes are distributed in the aggregate.

[0346] The median particle size of the anode material is 13.2 μm, the specific surface area is 3.3 m² / g, and the carbon layer thickness is 450 nm.

[0347] Using the above-mentioned test method for the dispersion N of conductive reinforcing agent, the dispersion N of conductive reinforcing agent (multi-walled carbon nanotubes) is 9.8.

[0348] The porosity of the anode material was 9.8% when the aggregate particles were tested using mercury porosimetry.

[0349] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 67 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 3.7%.

[0350] Example 16

[0351] The negative electrode material was prepared using essentially the same method as in Example 1, except that the aspect ratio of the conductive enhancer was 1.9.

[0352] The difference from Example 1 is that no carbon coating was performed. Step (3) is not included.

[0353] The negative electrode material prepared in this embodiment includes an aggregate, which includes nano-silicon powder, multi-walled carbon nanotubes and carbon materials. The mass ratio of nano-silicon powder, multi-walled carbon nanotubes and carbon materials is 49.6:2.6:47.8, and the multi-walled carbon nanotubes are distributed in the aggregate.

[0354] The median particle size of the anode material is 13.2 μm, the specific surface area is 3.3 m² / g, and the carbon layer thickness is 450 nm.

[0355] The dispersion N of the conductive reinforcing agent was tested using the above-mentioned method, and the dispersion N of the conductive reinforcing agent (multi-walled carbon nanotubes) was 11.

[0356] The porosity of the anode material was 3.5% when the aggregate particles were tested using the mercury porosimetry method.

[0357] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 89 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 2.9%.

[0358] Comparative Example 1

[0359] The negative electrode material was prepared using essentially the same method as in Example 4, except that a nickel-silicon material with a tensile strength of 253 MPa was selected.

[0360] The negative electrode material prepared in this embodiment includes an aggregate, which includes nano-silicon powder, nickel-silicon material and carbon material. The mass ratio of nano-silicon powder, nickel-silicon material and carbon material is 49.6:2.6:47.8, and the nickel-silicon material is distributed in the aggregate.

[0361] The median particle size of the anode material is 13.2 μm, the specific surface area is 3.3 m² / g, and the carbon layer thickness is 450 nm.

[0362] Using the above-mentioned test method for the dispersion N of conductive reinforcing agent, the dispersion N of conductive reinforcing agent (nickel-silicon material) is 7.9.

[0363] The porosity of the anode material was 7.2% when the aggregate particles were tested using mercury porosimetry.

[0364] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 48 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 2.7%.

[0365] Comparative Example 2

[0366] The negative electrode material was prepared using essentially the same method as in Example 1, except that no conductivity enhancer was added.

[0367] The negative electrode material prepared in this embodiment includes an aggregate, which includes nano-silicon powder, multi-walled carbon nanotubes and carbon materials. The mass ratio of nano-silicon powder, multi-walled carbon nanotubes and carbon materials is 49.6:2.6:47.8, and the multi-walled carbon nanotubes are distributed in the aggregate.

[0368] The median particle size of the anode material is 13.2 μm, the specific surface area is 3.3 m² / g, and the carbon layer thickness is 450 nm.

[0369] The porosity of the anode material was 4.3% when the aggregate particles were tested using mercury porosimetry.

[0370] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 102 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 2.5%.

[0371] Comparative Example 3

[0372] The negative electrode material was prepared in basically the same way as in Example 1, except that the raw materials were not ground and dispersed in step (1).

[0373] The negative electrode material prepared in this embodiment includes an aggregate, which includes nano-silicon powder, multi-walled carbon nanotubes and carbon materials. The mass ratio of nano-silicon powder, multi-walled carbon nanotubes and carbon materials is 49.6:2.6:47.8, and the multi-walled carbon nanotubes are distributed in the aggregate.

[0374] The median particle size of the anode material is 13.2 μm, the specific surface area is 3.3 m² / g, and the carbon layer thickness is 450 nm.

[0375] The dispersion N of the conductive reinforcing agent was tested using the above-mentioned test method, and the dispersion N of the conductive reinforcing agent (multi-walled carbon nanotubes) was 0.2.

[0376] The porosity of the anode material was 6.9% when the aggregate particles were tested using mercury porosimetry.

[0377] The aggregate particles were tested using a nanoindenter, and the average compressive strength of the anode material was found to be 114 MPa. The tested density of the anode material differed from the average density of silicon powder and carbon materials by 3.3%.

[0378] Test methods

[0379] (1) Button cell test

[0380] The electrochemical cycle performance was tested using the following method: The prepared silicon-carbon composite negative electrode material, conductive agent, and binder were dissolved in a solvent at a mass ratio of 94:1:5, with the solid content controlled at 50%. This mixture was then coated onto a copper foil current collector, vacuum dried, and the negative electrode sheet was obtained. Then, a ternary positive electrode sheet prepared using conventional mature processes, a 1 mol / L LiPF6 / ethylene carbonate + dimethyl carbonate + methyl ethyl carbonate (v / v = 1:1:1) electrolyte, a Celgard 2400 separator, and a casing were manufactured using conventional processes to obtain a lithium-ion battery. The initial electrode thickness of the lithium-ion battery was measured as H0 using a micrometer. The charge-discharge tests of the lithium-ion battery were conducted on the LAND battery testing system of Wuhan Jinno Electronics Co., Ltd., under room temperature conditions, with a constant current charge-discharge of 0.2C and a charge-discharge voltage limited to 2.75–4.2V. The initial reversible capacity, first charge capacity, and first discharge capacity were obtained. The initial coulombic efficiency was calculated as: first discharge capacity / first charge capacity.

[0381] Repeat the cycle 50 times. Use a micrometer to measure the thickness of the electrode in the lithium-ion battery at this time, which is H1. After 50 cycles, the expansion rate is (H1-H0) / H0×100%.

[0382] Repeat the cycle 100 times and record the discharge capacity as the remaining capacity of the lithium-ion battery; capacity retention rate = remaining capacity / initial capacity * 100%.

[0383] (2) Aspect ratio of the conductive reinforcing agent:

[0384] The aspect ratio of the conductive reinforcing agent was tested using AFM. The conductive reinforcing agent was ultrasonically dispersed, then dropped onto a glass slide to prepare the sample. After drying, the sample was placed for AFM testing. The length (L) and width (W) of at least 100 conductive reinforcing agents were measured. The aspect ratio of a single agent was calculated as D = L / W. The average value of the 100 agents was then used as the aspect ratio of the sample.

[0385] The results of the above performance tests are shown in Table 1:

[0386] Table 1

[0387]

[0388]

[0389] Figure 4 The first charge-discharge curve of the negative electrode material prepared in Example 1 of this invention is shown below. Figure 4 As shown, the negative electrode material prepared in Example 1 has a high initial charge-discharge capacity and a high initial efficiency. This is because the conductivity enhancer in the negative electrode material improves the transport of charge carriers inside the aggregate and enhances the conductivity of the aggregate, resulting in excellent electrochemical performance of the negative electrode material.

[0390] Figure 5 The cycling performance curve of the negative electrode material prepared in Example 1 of this invention is shown below. Figure 5 As shown, the negative electrode material has excellent cycling performance, with a capacity retention rate of 93.1% after 100 cycles. This is because the conductive enhancer can effectively improve the structural stability of the aggregate, strengthen the structural strength of the aggregate, avoid stress changes caused by the expansion effect of the active material, maintain the structural stability of the aggregate, thereby improving the cycling stability of the material and reducing the expansion rate.

[0391] As shown in Table 1, the negative electrode materials prepared in Examples 1 to 8 include aggregates, wherein the aggregates include active materials, conductivity enhancers, and carbon materials. The conductivity enhancers are distributed within the aggregates, effectively improving the transport of charge carriers within the aggregates, enhancing the conductivity of the aggregates, and effectively improving the structural stability and strength of the aggregates. This avoids stress changes caused by the expansion effect of the active materials, maintains the structural stability of the aggregates, thereby improving the cycle stability of the material and reducing the expansion rate.

[0392] In Example 9, no additives were added during the preparation of the negative electrode material. The connection between the active particles and the carbon material and the conductive enhancer was not tight, resulting in a decrease in the stability of the aggregate structure and a weakening of the expansion buffering and suppression effect.

[0393] In the preparation process of the negative electrode material of Comparative Example 3, the conductive reinforcing agent was not ground and dispersed in step (1), the uniformity of mixing of active material, conductive reinforcing agent and carbon material decreased, and the conductive reinforcing agent was not sufficiently dispersed in the raw materials. As a result, the minimum spacing between conductive reinforcing agents in the aggregates of negative electrode material decreased significantly, which was not conducive to the formation of a network structure between conductive reinforcing agent and carbon material. The structural strength of the aggregates decreased, making it difficult to resist the stress changes brought about by the expansion effect of active material, and the expansion rate increased.

[0394] In the preparation process of the negative electrode material of Comparative Example 1, the tensile strength of the conductive reinforcing agent in step (1) is 48 MPa. The tensile strength of the conductive reinforcing agent is too low, and the conductive reinforcing agent is difficult to resist the stress changes caused by the expansion of the active material, making it difficult to maintain the stability of the aggregate structure, which is not conducive to improving the cycle performance of the material and the battery expansion rate increases.

[0395] In the preparation process of the negative electrode material of Comparative Example 2, no conductivity enhancer was added. The aggregate only consisted of active material and carbon material. The conductivity of the aggregate decreased, the transport efficiency of charge carriers inside the aggregate decreased, and the stress generated by the expansion of the active material made the aggregate structure easy to be destroyed. It was difficult to maintain the stability of the aggregate structure, which was not conducive to improving the cycle performance of the material and the battery expansion rate increased.

[0396] In the preparation process of the negative electrode material in Example 16, the aspect ratio of the conductive reinforcing agent was 1.9. The bonding between the conductive reinforcing agent and the active material was not strong, the overall structure tended to be loose, the structural strength of the aggregate decreased, and it was difficult to resist the stress changes brought about by the expansion effect of the active material, resulting in an increased expansion rate.

[0397] Although this application discloses preferred embodiments as described above, it is not intended to limit the claims. Any person skilled in the art can make several possible changes and modifications without departing from the concept of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims of this application.

Claims

1. A negative electrode material, characterized in that, The negative electrode material includes an aggregate, which includes an active material, a carbon material, and a conductive reinforcing agent; the conductive reinforcing agent has a tensile strength ≥500MPa, an aspect ratio of 35~2000, and a dispersion N ≥1 in the negative electrode material. The dispersion N is obtained through the following test method: The SEM cross-section of the negative electrode material particle is divided into regions with an area of ​​A×B, where A and B are both ≤1 micrometer. The distribution of conductive reinforcing agent in all regions of a single negative electrode material particle is statistically analyzed. The number of regions with a spacing of <10nm between conductive reinforcing agents is denoted as Na, and the number of regions with a spacing of ≥10nm between conductive reinforcing agents is denoted as Nb. The dispersion C of conductive reinforcing agent in a single negative electrode material particle is defined as C=Nb / Na, where N is the arithmetic mean of the C values ​​of any 5 negative electrode material particles.

2. The negative electrode material according to claim 1, characterized in that, It contains one of the following features (1) to (2): (1) The conductive enhancer is distributed in the active material, and the carbon material is filled between the active material and the conductive enhancer; (2) There are pores between the carbon material and the conductive enhancer, and the pores are filled with the active substance.

3. The negative electrode material according to claim 1 or 2, characterized in that, It includes at least one of the following features (1) to (5): (1) The conductive reinforcing agent includes at least one of alloy materials and conductive carbon; (2) The conductive carbon includes at least one of carbon nanotubes, carbon fibers and graphite fibers; (3) The mass ratio of the active substance, the carbon material and the conductive enhancer is (20~70):(10~70):(3~20); (4) The conductive enhancer is in the form of sheets and / or strips; (5) The conductivity of the conductive enhancer is >10. 2 S / m.

4. The negative electrode material according to any one of claims 1 to 3, characterized in that, It includes at least one of the following features (1) to (5): (1) The aggregate further includes metal oxides; (2) The aggregate further includes a metal oxide, the general chemical formula of which is M x O y , 0.2≤y / x≤3, wherein M includes at least one of Sn, Ge, Si, Fe, Cu, Ti, Na, Mg, Al, Ca and Zn; (3) The aggregate further includes a metal oxide, which is in the form of a sheet and / or a strip; (4) The aggregate further includes a metal oxide, wherein the aspect ratio of the metal oxide is greater than 2; (5) The aggregate further includes a metal oxide, wherein the mass ratio of the metal oxide to the active substance is (1~20):

100.

5. The negative electrode material according to any one of claims 1 to 4, characterized in that, It includes at least one of the following features (1) to (10): (1) The active substance includes at least one of Li, Na, K, Sn, Ge, Si, SiO, Fe, Mg, Ti, Zn, Al, P and Cu; (2) The median particle size of the active material is 1 nm to 500 nm; (3) The carbon material includes at least one of amorphous carbon, crystalline carbon, hard carbon, soft carbon and mesophase carbon microspheres; (4) The negative electrode material further includes a carbon layer covering at least a portion of the surface of the aggregate; (5) The negative electrode material further includes a carbon layer covering at least a portion of the surface of the aggregate, wherein the material of the carbon layer includes amorphous carbon; (6) The negative electrode material further includes a carbon layer covering at least a portion of the surface of the aggregate, the thickness of the carbon layer being 10 nm to 1500 nm; (7) The median particle size of the negative electrode material is 0.5µm~30µm; (8) The specific surface area of ​​the negative electrode material is ≤10m². 2 / g; (9) The porosity of the negative electrode material is ≤10%, and the pressure resistance of the negative electrode material is ≥50MPa; (10) The aggregate density satisfies the following relationship: (p1-p2) / p2≤5%, where p1 is the test density of the aggregate and p2 is the average density of the aggregate; p2 is the sum of the mass percentage of each component in the aggregate and the theoretical density of each component.

6. A method for preparing a negative electrode material, characterized in that, Includes the following steps: A conductive reinforcing agent with a tensile strength ≥500MPa and an aspect ratio of 35~2000 is added to the first solvent and dispersed to obtain a dispersion. A precursor is prepared by mixing the active substance, the dispersion, the additive, the first carbon source, and the second solvent, wherein the additive includes at least one of a surfactant and a coupling agent; and The precursor is subjected to a single heat treatment to obtain the aggregate.

7. The preparation method according to claim 6, characterized in that, Includes at least one of the following features (1) to (22): (1) The active substance includes at least one of Li, Na, K, Sn, Ge, Si, SiO, Fe, Mg, Ti, Zn, Al, P and Cu; (2) The first carbon source includes at least one of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt; (3) The conductive reinforcing agent includes at least one of alloy materials and conductive carbon; (4) The conductive carbon includes at least one of carbon nanotubes, carbon fibers, and graphite fibers; (5) The conductive enhancer is in the form of sheets and / or strips; (6) The conductivity of the conductive enhancer is >10. 2 S / m; (7) The mass ratio of the active material, the conductive enhancer and the first carbon source is (15~120):(1~20):(10~50); (8) The first solvent includes at least one of organic solvent, inorganic solvent, and mixed solvent formed by mixing organic solvent and inorganic solvent; (9) The second solvent includes an organic solvent; (10) The organic solvent includes at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol and pentanol; (11) The inorganic solvent includes at least one of water, liquid carbon dioxide, liquid ammonia, liquid sulfur dioxide, thionyl chloride, thioyl chloride, lead acetate, hydrogen cyanide, hydrazine hydrate, thioyl fluoride, copper ammonia solution, sulfuric acid, nitric acid, hydrogen fluoride, polyphosphoric acid, and superacid; (12) The surfactant includes at least one of octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecylbenzenesulfonate, icosanoic acid, palmitic acid, tetradecanoic acid, undecanoic acid, hexadecyltrimethylammonium bromide and polyvinylpyrrolidone; (13) The coupling agent includes a silane coupling agent, which includes γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane. (14) The mass ratio of the active substance to the additive is (15~120):(1~10); (15) A metal oxide is also added in the step of mixing the active substance, the dispersion, the first carbon source and the second solvent; (16) The general chemical formula of the metal oxide is M x O y , 0.2≤y / x≤3, wherein M includes at least one of Sn, Ge, Si, Fe, Cu, Ti, Na, Mg, Al, Ca and Zn; (17) The metal oxide is in the form of flakes and / or strips; (18) The aspect ratio of the metal oxide is greater than 2; (19) The mass ratio of the metal oxide to the active substance is (1~20):100; (20) The step of preparing the precursor further includes at least one of the following: mixing the active substance, the dispersion, the first carbon source and the second solvent and then dispersing or drying the mixture; (21) The dispersion treatment includes at least one of mechanical stirring, ultrasonic dispersion and grinding dispersion; (22) The drying temperature is 30℃~400℃ and the drying time is 1h~15h.

8. The preparation method according to claim 6 or 7, characterized in that, Includes at least one of the following features (1) to (9): (1) Before the precursor is heat-treated, the precursor is further densified so that the porosity of the aggregate is ≤10% and the compressive hardness of the aggregate is ≥50MPa. (2) The densification treatment includes at least one of the following: fusion treatment, kneading and extrusion treatment, molding treatment, isostatic pressing treatment, and impregnation treatment; (3) The fusion process described is mechanical fusion; (4) The rotational speed of the fusion machine used for the mechanical fusion is 300 r / min to 3000 r / min; (5) The tool gap width of the fusion machine used for mechanical fusion is 0.01cm~0.9cm; (6) The mechanical fusion time is at least 0.5 h; (7) The primary heat treatment temperature is 600℃~1200℃, and the primary heat treatment time is 1h~10h; (8) The primary heat treatment process is conducted with a protective gas. (9) The protective gas includes at least one of nitrogen, helium, neon, argon and krypton.

9. The preparation method according to any one of claims 6 to 8, characterized in that, Includes at least one of the following features (1) to (9): (1) The method further includes carbon coating the aggregate; (2) The carbon coating process includes: mixing the precursor with the second carbon source and performing a secondary heat treatment; (3) The mass ratio of the precursor to the second carbon source is (20~100):(10~80); (4) The carbon coating process includes: mixing the aggregate with a second carbon source and performing a secondary heat treatment; (5) The second carbon source includes at least one of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride and asphalt; (6) The mass ratio of the aggregate to the second carbon source is (15~100):(10~70); (7) The temperature of the secondary heat treatment is 600℃~1200℃, and the time of the secondary heat treatment is 1h~10h; (8) The secondary heat treatment process is conducted with a protective gas; (9) The protective gas includes at least one of nitrogen, helium, neon, argon and krypton.

10. A lithium-ion battery, the lithium-ion battery comprising the negative electrode material according to any one of claims 1 to 5 or the negative electrode material prepared by the preparation method according to any one of claims 6 to 9.

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