Negative electrode material and preparation method thereof, and lithium ion battery

Abstract

This application relates to the field of anode materials, providing anode materials, their preparation methods, and lithium-ion batteries. The anode material comprises aggregates, which include active materials and carbon materials. The porosity of the anode material is ≤10%, and the target region ratio D in the anode material is ≥15%. The target region ratio D is obtained through the following testing method: The SEM cross-section of the anode material particle is divided into regions of area A×B, where A and B are both ≤1 micrometer. The distribution of active materials in all regions of a single anode material particle is statistically analyzed. The number of regions with a spacing of 10nm~300nm between active materials is counted as N1, and the total number of regions with a spacing less than 10nm and greater than 300nm between active materials is counted as N2. The target region ratio X of a single anode material particle is defined as X=N1 / N2. 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] Lithium-ion batteries are widely used in electric vehicles and consumer electronics due to their advantages such as high energy density, high output power, long cycle life, and low environmental pollution. To improve battery energy density, the research and development of silicon anode materials has become increasingly mature. However, the volume expansion of anode materials during lithium insertion / extraction is significant, especially for silicon anode materials, where the volume expansion can exceed 300%. During charge and discharge, these materials can pulverize and fall off the current collector, causing a loss of electrical contact between the active material and the current collector. This results in deteriorated electrochemical performance, capacity decay, and decreased cycle stability, hindering commercial applications.

[0003] Therefore, how to suppress the volume expansion of the negative electrode material and improve the cycle stability of the material is an urgent problem to be solved. Summary of the Invention

[0004] In view of this, this application provides a negative electrode material and its preparation method, and a lithium-ion battery, which can effectively suppress the volume expansion of the negative electrode material and improve the cycle performance of the battery. The preparation method can reduce the preparation cost.

[0005] In a first aspect, there is a negative electrode material comprising an aggregate, the aggregate comprising an active material and a carbon material, wherein the porosity of the negative electrode material is ≤10%, and the proportion D of the target region in the negative electrode material is ≥15%.

[0006] The target area ratio D is obtained through the following testing method:

[0007] 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 the active material in all regions of a single negative electrode material particle is statistically analyzed. The number of regions with a spacing of 10nm~300nm between the active materials is counted as N1, and the total number of regions with a spacing of less than 10nm and greater than 300nm between the active materials is counted as N2. The target region ratio X of a single negative electrode material particle is defined as X = N1 / N2, and D is the arithmetic mean of the X values ​​of any 5 negative electrode material particles.

[0008] The negative electrode material in this embodiment includes an aggregate, which comprises an active material, a carbon material, and a conductivity enhancer. The target region ratio D of the negative electrode material is ≥15%. By controlling the target region ratio D within this range, the active material maintains an appropriate spacing, effectively preventing self-agglomeration and loss of electrical contact during lithium insertion / extraction. This also facilitates the subsequent penetration of carbon material, enhancing the bonding between the active material and the carbon material, thereby improving the electrochemical performance of the material. The aggregate has a low porosity, preventing electrolyte from easily penetrating into the aggregate. This aggregate structure helps protect the internal active material particles, effectively suppressing the volume expansion of the negative electrode material, reducing the expansion rate, and improving battery cycle performance.

[0009] 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.

[0010] In one embodiment, the median particle size of the active material is 1 nm to 500 nm.

[0011] In one embodiment, the carbon material includes at least one of amorphous carbon, crystalline carbon, hard carbon, soft carbon, and mesophase carbon microspheres.

[0012] In one embodiment, the mass ratio of the active substance to the carbon material is (20~70):(10~80).

[0013] In one embodiment, the aggregate further includes a metal oxide.

[0014] In one embodiment, the metal oxide is distributed in the active material, and the carbon material is filled between the active material and the metal oxide.

[0015] In one embodiment, there are pores between the active material and the metal oxide, and the pores are filled with the carbon material.

[0016] 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.

[0017] In one embodiment, the metal oxide is in the form of sheets and / or strips.

[0018] In one embodiment, the aspect ratio of the metal oxide is greater than 2.

[0019] In one embodiment, the mass ratio of the metal oxide to the active substance is (1~20):100.

[0020] In one embodiment, the aggregate further includes a conductivity enhancer.

[0021] In one embodiment, the conductivity enhancer includes at least one of an alloy material and conductive carbon.

[0022] In one embodiment, the conductive carbon includes at least one of carbon nanotubes, carbon fibers, and graphite fibers.

[0023] In one embodiment, the conductivity of the conductivity enhancer is >10. 2 S / m.

[0024] 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.

[0025] In one embodiment, the mass ratio of the conductive enhancer to the active substance is (0.1~10):100.

[0026] In one embodiment, the tensile strength of the conductive reinforcing agent is ≥500MPa.

[0027] In one embodiment, the negative electrode material further includes a carbon layer covering at least a portion of the surface of the aggregate.

[0028] In one embodiment, the material of the carbon layer includes amorphous carbon.

[0029] In one embodiment, the thickness of the carbon layer is from 10 nm to 1500 nm.

[0030] In one embodiment, the median particle size of the negative electrode material is 0.5µm to 30µm.

[0031] In one embodiment, the specific surface area of ​​the negative electrode material is ≤10m². 2 / g.

[0032] In one embodiment, the pressure resistance of the negative electrode material is ≥50MPa.

[0033] In one embodiment, the porosity of the negative electrode material is ≤10%.

[0034] Secondly, this application provides a method for preparing a negative electrode material, comprising the following steps:

[0035] The active substance, the first carbon source and the solvent are mixed and fully dispersed, and then the solvent is removed to obtain the first precursor.

[0036] The first precursor is subjected to a heat treatment to obtain the second precursor; and

[0037] The second precursor is densified to obtain aggregates.

[0038] In the above scheme, the active material, the first carbon source and the solvent are mixed in stages to improve the dispersion of the active material in the first precursor. The first precursor obtained by the staged mixing is then subjected to a heat treatment to obtain the second precursor. The second precursor is then subjected to a densification treatment. During the densification treatment, the above materials agglomerate to form aggregates, which can improve the dispersion of the active material in the aggregates and reduce the porosity of the aggregates. The whole preparation process is simple, and the prepared negative electrode material can effectively suppress volume expansion, reduce the expansion rate and improve the battery cycle performance.

[0039] 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.

[0040] 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.

[0041] In one embodiment, the mass ratio of the first carbon source to the active substance is (5~40): 100;

[0042] In one embodiment, the solvent includes an organic solvent.

[0043] In one embodiment, the organic solvent includes at least one selected from methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, and pentanol.

[0044] In one embodiment, an additive is also added during the step of fractionally mixing the active substance, the first carbon source, and the solvent.

[0045] In one embodiment, the additive includes at least one of surfactants and coupling agents.

[0046] In one embodiment, the surfactant includes at least one selected from octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecylbenzenesulfonate, icosanoic acid, palmitic acid, tetradecanoic acid, undecanoic acid, hexadecyltrimethylammonium bromide, and polyvinylpyrrolidone.

[0047] In one embodiment, the coupling agent includes a silane coupling agent, which includes γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0048] In one embodiment, the mass ratio of the active substance to the additive is (15~120):(1~10).

[0049] In one embodiment, a metal oxide is also added during the step of fractionally mixing the active substance, the first carbon source, and the solvent.

[0050] 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.

[0051] In one embodiment, the metal oxide is in the form of sheets and / or strips.

[0052] In one embodiment, the aspect ratio of the metal oxide is greater than 2.

[0053] In one embodiment, the mass ratio of the metal oxide to the active substance is (1~20):100.

[0054] In one embodiment, a conductivity enhancer is also added during the step of graded mixing of the active material, the first carbon source, and the solvent.

[0055] In one embodiment, the mass ratio of the conductive enhancer to the active substance is (0.1~10):100.

[0056] In one embodiment, the conductivity enhancer includes at least one of an alloy material and conductive carbon.

[0057] In one embodiment, the conductive carbon includes at least one of carbon nanotubes, carbon fibers, and graphite fibers.

[0058] In one embodiment, the conductivity of the conductivity enhancer is >10. 2 S / m.

[0059] In one embodiment, the conductive enhancer is in the form of sheets and / or strips.

[0060] In one embodiment, the aspect ratio of the conductive reinforcing agent is 2 to 3000.

[0061] In one embodiment, the fully dispersed treatment method includes at least one of mechanical stirring, ultrasonic dispersion, and grinding dispersion.

[0062] In one embodiment, the mixing of the active substance, the first carbon source, and the solvent is carried out in a stepwise mixing manner.

[0063] In one embodiment, the mixing of the active substance, the first carbon source, and the solvent specifically involves: mixing the active substance with the solvent to form a first premix, mixing the first carbon source with the solvent to form a second premix, and then mixing the first premix with the second premix.

[0064] In one embodiment, the step of preparing the first precursor includes mixing the active substance, the first carbon source and the solvent in a graded manner, and then drying the mixture to obtain the first precursor.

[0065] In one embodiment, the drying process is carried out at a temperature of 40°C to 600°C for a duration of 1 hour to 15 hours.

[0066] 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.

[0067] In one embodiment, the fusion process is mechanical fusion.

[0068] In one embodiment, the rotational speed of the fusion machine used for mechanical fusion is 300 r / min to 3000 r / min.

[0069] In one embodiment, the gap width between the fusion machine cutters used in the mechanical fusion is 0.01cm to 0.9cm.

[0070] In one embodiment, the mechanical fusion time is at least 0.5 hours.

[0071] In one embodiment, the temperature of the first heat treatment is 600℃~1200℃, and the time of the first heat treatment is 1h~10h.

[0072] In one embodiment, the primary heat treatment process is conducted with a protective gas.

[0073] In one embodiment, the protective gas includes at least one of nitrogen, helium, neon, argon, and krypton.

[0074] In one embodiment, the method further includes carbon coating the aggregate.

[0075] In one embodiment, the carbon coating process includes: mixing the second precursor with the second carbon source and performing a secondary heat treatment.

[0076] In one embodiment, the mass ratio of the second precursor to the second carbon source is (30~100):(10~70).

[0077] In one embodiment, the carbon coating process includes: mixing the aggregate with a second carbon source and performing a secondary heat treatment.

[0078] 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.

[0079] In one embodiment, the mass ratio of the aggregate to the second carbon source is (15~100):(10~70).

[0080] In one embodiment, the temperature of the secondary heat treatment is 600℃~1200℃, and the time of the secondary heat treatment is 1h~10h.

[0081] In one embodiment, the secondary heat treatment process is conducted with a protective gas.

[0082] In one embodiment, the protective gas includes at least one of nitrogen, helium, neon, argon, and krypton.

[0083] 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.

[0084] The technical solution of this application has at least the following beneficial effects:

[0085] The negative electrode material of this embodiment includes an aggregate, which comprises an active material, a carbon material, and a conductivity enhancer. The target region ratio D of the negative electrode material is ≥15%. Within this range, the active material maintains an appropriate spacing, effectively preventing self-agglomeration and loss of electrical contact during lithium insertion / extraction. It also facilitates the subsequent penetration of carbon material, enhancing the bonding between the active material and the carbon material, thereby improving the electrochemical performance of the material. The aggregate has a small porosity, preventing electrolyte from easily penetrating into the aggregate. This aggregate structure helps protect the internal active material particles, effectively suppressing the volume expansion of the negative electrode material, reducing the expansion rate, and improving battery cycle performance.

[0086] Secondly, the method for preparing the negative electrode material provided in this application involves graded mixing of the active material, the first carbon source, and the solvent, which can improve the dispersion of the active material in the first precursor. The first precursor obtained by graded mixing is then subjected to a heat treatment to obtain a second precursor. The second precursor is then subjected to a densification treatment. During the densification treatment, the above-mentioned materials agglomerate to form aggregates, which can improve the dispersion of the active material in the aggregates and reduce the porosity of the aggregates. The entire preparation process is simple, and the prepared negative electrode material can effectively suppress volume expansion, reduce the expansion rate, and improve the battery cycle performance.

[0087] The preparation method provided in this application is applicable to large-scale production, and the prepared negative electrode material can effectively improve the stability of lithium battery charge-discharge cycle and effectively reduce the expansion rate of the negative electrode material. Attached Figure Description

[0088] Figure 1 A schematic flowchart illustrating the preparation method of the negative electrode material provided in the embodiments of this application;

[0089] Figure 2 A scanning electron microscope (SEM) image of the negative electrode material prepared in Example 1 of this invention;

[0090] Figure 3 The image shows the XRD pattern of the negative electrode material prepared in Example 1 of this invention.

[0091] Figure 4 The first charge-discharge curve of the negative electrode material prepared in Example 1 of this invention;

[0092] Figure 5 The cycling performance curve of the negative electrode material prepared in Example 1 of this invention is shown. Detailed Implementation

[0093] 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.

[0094] One embodiment of the negative electrode material includes an aggregate comprising an active material and a carbon material, wherein the porosity of the negative electrode material is ≤10%, and the proportion D of the target region in the negative electrode material is ≥15%.

[0095] The target area ratio D is obtained through the following testing method:

[0096] 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 the active material in all regions of a single negative electrode material particle is statistically analyzed. The number of regions with a spacing of 10nm~300nm between the active materials is counted as N1, and the total number of regions with a spacing of less than 10nm and greater than 300nm between the active materials is counted as N2. The target region ratio X of a single negative electrode material particle is defined as X = N1 / N2, and D is the arithmetic mean of the X values ​​of any 5 negative electrode material particles.

[0097] The negative electrode material in this embodiment includes an aggregate, which comprises active material and carbon material. The target region ratio D of the negative electrode material is ≥15%. Within this range, the active material maintains an appropriate spacing, effectively preventing self-agglomeration and loss of electrical contact during lithium insertion / extraction. It also facilitates the subsequent penetration of carbon material, enhancing the bonding between the active material and carbon material, thereby improving the electrochemical performance of the material. The aggregate has a small porosity, preventing electrolyte from easily penetrating into the aggregate. This aggregate structure helps protect the internal active material particles, effectively suppressing the volume expansion of the negative electrode material, reducing the expansion rate, and improving battery cycle performance.

[0098] The porosity of the negative electrode material is ≤10%. At this level, the porosity of the negative electrode material is low, meaning its density is very high. On the one hand, this helps to improve the energy density of the composite material. On the other hand, even if the surface of the high-density material is damaged, the electrolyte is not easy to penetrate into the interior of the aggregate, which helps to protect the internal active material particles and reduce the probability of contact between the electrolyte and the active material, thus facilitating the formation of a stable solid electrolyte membrane. Furthermore, the high-density aggregate has high pressure resistance and hardness, which can offset the stress effect caused by expansion, improve the structural stability of the negative electrode material, effectively suppress the volume expansion of the negative electrode material, reduce the expansion rate, and improve the battery cycle performance.

[0099] In some embodiments, 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, without limitation. 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 ≤3%.

[0100] In some embodiments, the pressure resistance of the negative electrode material is ≥50 MPa. Specifically, the pressure resistance of the negative electrode material can be 50 MPa, 250 MPa, 300 MPa, 450 MPa, 500 MPa, 750 MPa, 900 MPa, 1150 MPa, 1200 MPa, or 1250 MPa, 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 volume expansion stress, thereby reducing expansion and improving the cycle stability of the battery. Preferably, the pressure resistance of the negative electrode material is ≥100 MPa, and more preferably, the pressure resistance of the negative electrode material is ≥200 MPa.

[0101] In some implementations, 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.

[0102] 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.

[0103] Where p2 is the mass percentage of each component in the aggregate. The sum of the theoretical densities of all components.

[0104] 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. Theoretical density of active material + mass percentage of conductivity enhancer in aggregate Theoretical density of conductive enhancer + mass percentage of carbon material in aggregate Theoretical density of carbon materials.

[0105] When the aggregate includes active material, metal oxide, conductivity enhancer, and carbon material, p2 = mass percentage of active material in the aggregate. Theoretical density of active material + mass percentage of metal oxide in aggregate Theoretical density of metal oxide + mass percentage of conductivity enhancer in aggregate Theoretical density of conductive enhancer + mass percentage of carbon material in aggregate Theoretical density of carbon materials.

[0106] In some implementations, the active material refers to a substance that can react with lithium to perform lithium intercalation / deintercalation.

[0107] 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. Elemental metals refer to the aforementioned elemental metals, metal oxides refer to oxides of the aforementioned metals, and metal alloys refer to alloys containing at least one of the aforementioned metals.

[0108] 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.

[0109] 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.

[0110] 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 particles have strong structural integrity, which can suppress silicon volume expansion. However, due to the large surface energy of nanoscale silicon-based active particles, aggregation is easily formed 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.

[0111] In some embodiments, the carbon material includes at least one of amorphous carbon, crystalline carbon, hard carbon, soft carbon, and mesophase carbon microspheres.

[0112] In some embodiments, the mass ratio of the active material to the carbon material is (20~70):(10~80). Specifically, it can be 20:10, 20:20, 20:30, 20:50, 20:60, 20:80, 40:10, 40:50, 40:80, 50:70, 50:80, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0113] 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.

[0114] In some embodiments, metal oxides are distributed within the active material in the aggregate, and carbon material is filled between the active material and the metal oxides.

[0115] Specifically, there are pores between the active material and the metal oxide, 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 stresses, and reduce expansion.

[0116] 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.

[0117] In some embodiments, the metal oxide is in the form of flakes and / or strips.

[0118] 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.

[0119] 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.

[0120] In some embodiments, the aggregate also includes a conductivity enhancer.

[0121] In some embodiments, 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 dispersion N is obtained by the following test method: the SEM cross-section of the negative electrode material particle is divided into a region with an area of ​​A×B, where A and B are both ≤1 micrometer. The distribution of the conductive reinforcing agent in all regions of a single negative electrode material particle is counted. The number of regions with a spacing of <10nm between conductive reinforcing agents is counted as Na, and the number of regions with a spacing of ≥10nm between conductive reinforcing agents is counted as Nb. The dispersion C of the 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.

[0122] 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.

[0123] 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.

[0124] The conductive enhancer is distributed inside and / or on the surface of the aggregate.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] In some embodiments, the conductive carbon includes at least one of carbon nanotubes, carbon fibers, and graphite fibers.

[0129] In some embodiments, the alloy material has an electrical conductivity >10. 2 Alloys with S / m and tensile strength ≥ 500 MPa.

[0130] 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.

[0131] 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.

[0132] In some embodiments, the conductivity enhancer is in the form of sheets and / or strips.

[0133] 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 length to the particle diameter; when the metal oxide 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.

[0134] In some embodiments, the tensile strength of the conductive reinforcing agent is ≥500 MPa. It should be noted that when the tensile strength of the conductive reinforcing agent is too low, it is difficult for the agent to resist 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, 520 MPa, 550 MPa, 580 MPa, 600 MPa, 650 MPa, 700 MPa, 750 MPa, or 800 MPa, 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, allowing it to act 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.

[0135] In some application methods, the mass ratio of the conductive enhancer to the active material is (0.1~10):100. Specifically, it can be 0.1:100, 0.5:100, 0.8:100, 1:100, 2:100, 3:100, 5:100, 6:100, 7:100, 8:100, 10:100, etc. Of course, other values ​​within the above range are also possible, and are not limited here.

[0136] 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.

[0137] In some implementations, the carbon layer comprises amorphous carbon.

[0138] 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.

[0139] 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 the volume expansion suppression performance of the material is weak, resulting in a poor long-cycle performance. Preferably, the thickness of the carbon layer is 50nm~800nm; more preferably, the thickness of the carbon layer is 100nm~500nm.

[0140] 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.

[0141] In some embodiments, the median particle size of the negative electrode material is 0.5µm to 30µm. Specifically, it can be 0.5µm, 1µm, 5µm, 8µm, 10µm, 13µm, 15µm, 18µm, 20µm, 25µm, or 30µm, 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.

[0142] 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.

[0143] 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.

[0144] On the other hand, this application provides a method for preparing a negative electrode material, such as... Figure 1 As shown, the method includes the following steps:

[0145] Step S10: Mix and fully disperse the active substance, the first carbon source and the solvent, then remove the solvent to obtain the first precursor;

[0146] Step S20: Perform a heat treatment on the first precursor to obtain the second precursor; and

[0147] Step S30: The second precursor is densified to obtain aggregates.

[0148] The preparation method of this embodiment involves mixing and fully dispersing the active material, the first carbon source, and the solvent to improve the dispersion of the active material in the first precursor. The first precursor obtained by graded mixing is then subjected to a heat treatment to obtain a second precursor. The second precursor is then subjected to a densification treatment. During the densification treatment, the above-mentioned materials agglomerate to form aggregates, which can improve the dispersion of the active material in the aggregates and reduce the porosity of the aggregates. The entire preparation process is simple, and the prepared negative electrode material can effectively suppress volume expansion, reduce the expansion rate, and improve the battery cycle performance.

[0149] The preparation method of this application is described in detail below with reference to the embodiments:

[0150] Step S10: Mix the active substance, the first carbon source and the solvent and disperse them thoroughly, then remove the solvent to obtain the first precursor.

[0151] In some embodiments, the active material, the first carbon source, and the solvent are mixed using a staged mixing method. Specifically, the active material and the solvent can be mixed to form a first premix, or the first carbon source and the solvent can be mixed to form a second premix, and then the first premix and the second premix are mixed to achieve staged mixing. It is understood that those skilled in the art can select appropriate staged mixing operations according to the specific components of the active material, the first carbon source, and the solvent, based on the staged mixing principle, to ensure sufficient dispersion of the active material, so as to achieve a target region ratio D ≥ 15% in the final negative electrode material.

[0152] In some embodiments, the method of achieving sufficient dispersion includes at least one of mechanical stirring, ultrasonic dispersion, and grinding dispersion. Of course, it is understood that sufficient dispersion is not limited to the above methods; any method that can sufficiently disperse the active material to achieve a target region ratio D ≥ 15% in the final negative electrode material is acceptable.

[0153] In some implementations, the active material refers to a substance that can react with lithium to perform lithium intercalation / deintercalation.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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, aggregation is easily formed 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.

[0158] 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.

[0159] In some embodiments, the 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.

[0160] In some embodiments, an additive is added to the step of fractionally mixing the active material, the first carbon source, and the solvent. This 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.

[0161] In some embodiments, the mass ratio of the first carbon source to the active substance is (5~40):100; specifically, it can be 5:100, 10:100, 15:100, 20:100, 25:100, 30:100, 35:100, 38:100, or 40:100, etc. The mass ratio of the first carbon source to the active substance should not be too high, that is, the content of the first carbon source should not be too high, as this is not conducive to the formation of a high-porosity precursor and affects subsequent processing.

[0162] In some embodiments, the additive includes at least one of surfactants and coupling agents.

[0163] 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.

[0164] Coupling agents include silane coupling agents, including γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0165] In some embodiments, a conductivity enhancer is also added during the step of graded mixing of the active material, additives, first carbon source and solvent.

[0166] In some embodiments, the conductivity enhancer includes at least one of an alloy material and conductive carbon.

[0167] In some embodiments, the conductive carbon includes at least one of carbon nanotubes, carbon fibers, and graphite fibers.

[0168] 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.

[0169] In some embodiments, the conductivity enhancer is in the form of sheets and / or strips.

[0170] 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.

[0171] In some embodiments, the mass ratio of the conductive enhancer to the active material is (0.1~10):100. Specifically, the mass ratio of the conductive enhancer to the active material is 0.1:100, 0.5:100, 1:100, 2:100, 2.6:100, 3:100, 3.5:100, 4:100, 4.8:100, 6:100, 7:100, 8.5:100, or 10:100, etc. Of course, other values ​​within the above range are also possible, and are not limited here.

[0172] In some embodiments, a metal oxide is also added during the step of fractionally mixing the active substance, additive, first carbon source and solvent.

[0173] 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.

[0174] In some embodiments, the metal oxide is in the form of flakes and / or strips.

[0175] In some implementations, the aspect ratio of the metal oxide is greater than 2.

[0176] 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, 10:100, 15:100, 20:100, 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.

[0177] In some embodiments, preparing the first precursor further includes dispersing the mixed mixture.

[0178] In some embodiments, the dispersion treatment includes at least one of mechanical stirring, ultrasonic dispersion, and grinding dispersion. Preferably, grinding dispersion is used to disperse the active material, preventing it from agglomerating and dispersing it into smaller nanoparticles. Preferably, wet ball milling is used, with the dispersion time controlled between 0.5 h and 10 h. Thorough grinding ensures more uniform mixing of the components, resulting in active material particles with a diameter of 1 nm to 500 nm.

[0179] In some embodiments, the active substance, the first carbon source and the solvent are mixed and dispersed in stages, and then the solvent is removed to obtain the first precursor. The solvent removal method includes drying.

[0180] In some embodiments, the drying temperature is 40℃~600℃, specifically 40℃, 50℃, 80℃, 100℃, 120℃, 250℃, 380℃, 400℃, 500℃, 580℃ or 600℃, etc., and the drying time is 1h~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.

[0181] The dried first precursor can also be dispersed, which can be grinding dispersion, with a dispersion time of 0.5h-9h, specifically 0.5h, 1.5h, 2.5h, 3.5h, 4.5h, 5.5h, 7.5h or 9h, etc. In this embodiment, grinding dispersion controls the particle size after dispersion.

[0182] In some embodiments, a second carbon source may be added during the dispersion of the dried first precursor, with the mass ratio of the first precursor to the second carbon source being (10~80):10. After dispersion, a second drying is performed to obtain a carbon-coated first precursor.

[0183] Step S20: Perform a heat treatment on the first precursor to obtain the second precursor.

[0184] In some implementations, the heat treatment process may be, for example, vacuum sintering, hot pressing sintering, or atmospheric pressure sintering.

[0185] In some embodiments, the temperature of the primary heat treatment is 600℃ to 1200℃, for example, 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, 1200℃, etc. Preferably, the temperature of the primary heat treatment is 600℃ to 1000℃.

[0186] 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.

[0187] 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.

[0188] The heat treatment process is carried out with a protective gas, which includes at least one of nitrogen, helium, neon, argon and krypton.

[0189] Step S30: The second precursor is densified to obtain an aggregate. The densification process ensures that the porosity of the obtained aggregate is ≤10% and the compressive hardness of the aggregate is ≥50MPa.

[0190] 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.

[0191] 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.

[0192] In some implementations, the porosity of the final negative electrode material is ≤10%, and the compressive strength of the negative electrode material is ≥50MPa. In this case, the porosity and compressive strength of the aggregate can be controlled according to the condition of the final carbon coating layer, so that the porosity and compressive strength of the negative electrode material can reach the target values.

[0193] In some implementations, during fusion, the rotational 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.

[0194] Step S40: The aggregate is carbon coated to obtain the negative electrode material.

[0195] It should be noted that the negative electrode material in this embodiment may not be carbon coated, in which case step S40 can be omitted. In some embodiments, the carbon coating process includes: mixing the aggregate with a second carbon source and performing a secondary heat treatment to form a carbon layer on the surface of the aggregate.

[0196] 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.

[0197] In some embodiments, the mass ratio of the aggregate to the second carbon source is (20~100):(10~120); specifically, the mass ratio of the aggregate 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.

[0198] In other embodiments, the aggregates may be carbon-coated in other ways. Specifically, the carbon coating process includes mixing the second precursor with the second carbon source and performing a secondary heat treatment to form a carbon layer on the surface of the second precursor.

[0199] In some embodiments, the mass ratio of the second precursor to the second carbon source is (30~100):(10~70). The mass ratio of the second precursor to the second carbon source is 50:25, 100:20, 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.

[0200] In some embodiments, the temperature of the secondary heat treatment is 600℃~1200℃, for example, it can be 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, 1200℃, etc. Preferably, the temperature of the secondary heat treatment is 600℃~1000℃.

[0201] 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.

[0202] In some embodiments, the heating rate during the secondary 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 the secondary heat treatment is 1℃ / min to 15℃ / min.

[0203] In some embodiments, the secondary processing is carried out with a protective gas, including at least one of nitrogen, helium, neon, argon, and krypton.

[0204] In some implementations, the mixing method may include magnetic stirring, mechanical stirring, ultrasonic dispersion, grinding dispersion, etc.

[0205] It should be noted that the negative electrode material in this embodiment may not be carbon coated, and is not limited to the two carbon coating methods mentioned above.

[0206] 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.

[0207] In some implementations, the pulverization method is any one of a mechanical pulverizer, an air jet mill, or a cryogenic pulverizer.

[0208] 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.

[0209] 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.

[0210] This application also provides a lithium-ion battery, including the aforementioned negative electrode material.

[0211] 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.

[0212] The target area ratio D was obtained through the following testing method:

[0213] 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 active material in all regions of a single negative electrode material particle is statistically analyzed. The number of regions with a spacing of 10nm to 300nm between active materials is counted as N1, and the total number of regions with a spacing of less than 10nm and greater than 300nm between active materials is counted as N2. The target region ratio X of a single negative electrode material particle is defined as X = N1 / N2, and A is the arithmetic mean of the X values ​​of any 5 negative electrode material particles.

[0214] Example 1

[0215] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0216] (1) Silicon powder with a median particle size of 100 nm, alkylphenol polyoxyethylene ether and phenolic resin were added to ethylene glycol solution in a mass ratio of 50:3.6:16.4. The solution was ultrasonically dispersed for 160 min to obtain a dispersion solution. The dispersion solution was then placed in a ball mill for 6 hours to obtain a first precursor solution. The solution was then freeze-dried to obtain the first precursor.

[0217] (2) The first precursor is placed in a heat treatment furnace, nitrogen is introduced and the temperature is raised to 890°C for a heat treatment, and the temperature is held for 4 hours to obtain the second precursor.

[0218] (3) The second precursor was placed in the fusion machine, the rotation speed of the fusion machine was 400 r / min; the gap width of the fusion machine tool used for mechanical fusion was 0.8 cm; the mechanical fusion time was 2h, and aggregates were obtained.

[0219] (4) The aggregate and sucrose are mixed in a mass ratio of 80:89. The mixed material is then placed in a high-temperature box furnace, nitrogen is introduced, and a second heat treatment is performed at 850°C. After holding at the temperature for 4 hours, the material is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0220] 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 and carbon material, and the mass ratio of silicon powder to carbon material is 64.6:35.4.

[0221] The median particle size of the anode material is 13.2 µm, and the specific surface area is 3.5 m². 2 / g, with an average carbon layer thickness of 350nm.

[0222] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 15%.

[0223] 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 2.0%.

[0224] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 155 MPa.

[0225] 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.

[0226] Example 2

[0227] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0228] (1) Silicon powder with a median particle size of 40 nm, γ-aminopropyltriethoxysilane and phenolic resin were added to ethylene glycol solution in a mass ratio of 60:2.6:17.4 and ultrasonically dispersed for 60 min to obtain a dispersion solution. The dispersion solution was then placed in a ball mill for grinding and dispersion for 6 hours to obtain the first precursor solution. Then, the solution was freeze-dried to obtain the first precursor.

[0229] (2) The first precursor is placed in a heat treatment furnace, nitrogen is introduced and the temperature is raised to 850°C for a heat treatment, and the temperature is held for 4 hours to obtain the second precursor.

[0230] (3) The second precursor is placed in the fusion machine with a rotation speed of 600 r / min, a blade gap width of 0.7 cm, and a fusion time of 1.5 h to obtain aggregates.

[0231] (4) The aggregate and asphalt are mixed in a mass ratio of 70:64. The mixed material is then placed in a high-temperature box furnace, nitrogen is introduced, and a second heat treatment is performed at 850°C. After holding at the temperature for 4 hours, the material is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0232] 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 and carbon material, and the mass ratio of silicon powder to carbon material is 61.6:38.4.

[0233] The median particle size of the negative electrode material is 12.2 µm, and the specific surface area is 3.1 m². 2 / g, with an average carbon layer thickness of 380nm.

[0234] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 35%.

[0235] 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 1.6%.

[0236] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 231 MPa.

[0237] Example 3

[0238] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0239] (1) Add silicon powder with a median particle size of 30 nm, sodium dodecylbenzenesulfonate and citric acid to ethylene glycol solution in a mass ratio of 45:4.6:14.4, and ultrasonically disperse for 40 min to obtain a dispersion solution. Then place the dispersion solution in a ball mill and grind and disperse for 6 hours to obtain a precursor solution. Then freeze-dry the solution to obtain the precursor.

[0240] (2) The first precursor is placed in a heat treatment furnace, nitrogen is introduced and the temperature is raised to 800°C for a heat treatment, and the temperature is held for 4 hours to obtain the second precursor.

[0241] (3) Place the second precursor in the fusion machine. The rotation speed of the fusion machine is 400 r / min; the blade gap width of the fusion machine is 0.6 cm; the fusion time is 2.5 h, and aggregates are obtained.

[0242] (4) The aggregate and asphalt are mixed in a mass ratio of 40:54. The mixed material is then placed in a high-temperature box furnace, nitrogen is introduced, and a second heat treatment is performed at 850°C. After holding at the temperature for 2 hours, the material is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0243] 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 and carbon material, and the mass ratio of silicon powder to carbon material is 57.1:42.9.

[0244] The median particle size of the anode material is 10.2 µm, and the specific surface area is 2.1 m². 2 / g, with an average carbon layer thickness of 580nm.

[0245] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 45%.

[0246] 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 2.3%.

[0247] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 123 MPa.

[0248] Example 4

[0249] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0250] (1) Add silicon powder with a median particle size of 80 nm, undecanoic acid and fructose to butanol solution in a mass ratio of 40:2.6:7.4, and ultrasonically disperse for 60 min to obtain a dispersion solution. Then place the dispersion solution in a ball mill and grind and disperse for 8 hours to obtain the first precursor solution. Then spray dry to obtain the first precursor.

[0251] (2) The first precursor is placed in a heat treatment furnace, nitrogen is introduced and the temperature is raised to 820°C for a heat treatment, and the temperature is held for 4 hours to obtain the second precursor.

[0252] (3) Place the second precursor in the fusion machine. The rotation speed of the fusion machine is 480 r / min; the blade gap width of the fusion machine is 0.6 cm; the fusion time is 3 h to obtain aggregates.

[0253] (4) The aggregate and phenolic resin are mixed in a mass ratio of 38:63. The mixed material is then placed in a high-temperature box furnace, nitrogen is introduced, and a second heat treatment is performed at 880°C. After holding at the temperature for 2 hours, the material is 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 coated on the surface of the aggregate. The aggregate includes nano-silicon powder and carbon material, and the mass ratio of silicon powder to carbon material is 49.4:50.6.

[0255] The median particle size of the anode material is 10.5 µm, and the specific surface area is 2.0 m². 2 / g, with an average carbon layer thickness of 680nm.

[0256] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 52%.

[0257] 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 3.1%.

[0258] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 301 MPa.

[0259] Example 5

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

[0261] (1) Add silicon powder with a median particle size of 40 nm, γ-methacryloxypropyltrimethoxysilane and pitch to butanol solution in a mass ratio of 46:4.5:13.5, and ultrasonically disperse for 60 min to obtain a dispersion solution. Then place the dispersion solution in a ball mill and grind and disperse for 4 hours to obtain the first precursor solution. Then spray dry to obtain the first precursor.

[0262] (2) The first precursor is placed in a heat treatment furnace, nitrogen is introduced and the temperature is raised to 720°C for heat treatment. The temperature is held for 3 hours to obtain the second precursor.

[0263] (3) Place the second precursor in the fusion machine. The rotation speed of the fusion machine is 580 r / min; the blade gap width of the fusion machine is 0.5 cm; the fusion time is 2 h to obtain aggregates.

[0264] (4) The aggregate and phenolic resin are mixed in a mass ratio of 58:63. The mixed material is then placed in a high-temperature box furnace, nitrogen is introduced, and a second heat treatment is performed at 880°C. After holding at the temperature for 2 hours, the material is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0265] 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 and carbon material, and the mass ratio of silicon powder to carbon material is 47.2:52.8.

[0266] The median particle size of the anode material is 13.5 µm, and the specific surface area is 1.9 m². 2 / g, with an average carbon layer thickness of 850nm.

[0267] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 38%.

[0268] 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 2.4%.

[0269] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 266 MPa.

[0270] Example 6

[0271] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0272] (1) Ge powder with a median particle size of 40 nm, octadecanoic acid and glucose were added to a propanol solution in a mass ratio of 46:4.5:9.5 and ultrasonically dispersed for 80 min to obtain a dispersion solution. The dispersion solution was then placed in a ball mill and ground for 4 hours to obtain a first precursor solution. Then, spray drying was performed to obtain the first precursor.

[0273] (2) The first precursor is placed in a heat treatment furnace, nitrogen is introduced and the temperature is raised to 790°C for a heat treatment, and the temperature is held for 3 hours to obtain the second precursor.

[0274] (3) The second precursor is placed in the fusion machine with a rotation speed of 540 r / min, a blade gap width of 0.8 cm, and a fusion time of 2 h to obtain aggregates.

[0275] (4) The aggregate and phenolic resin are mixed in a mass ratio of 88:70. Then the mixed material is placed in a high-temperature box furnace, nitrogen is introduced, and a second heat treatment is carried out at 980°C. After holding at the temperature for 2 hours, the material is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0276] 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-Ge powder and carbon material, and the mass ratio of Ge powder to carbon material is 70.8:29.2.

[0277] The median particle size of the anode material is 14.5 µm, and the specific surface area is 4.9 m². 2 / g, with an average carbon layer thickness of 310nm.

[0278] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 65%.

[0279] 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 2.8%.

[0280] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 89 MPa.

[0281] Example 7

[0282] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0283] (1) Sn powder with a median particle size of 80 nm, hexadecyltrimethylammonium bromide and phenolic resin were added to an ethanol solution in a mass ratio of 66:4.5:15.5 and ultrasonically dispersed for 90 min to obtain a dispersion solution. The dispersion solution was then placed in a ball mill and ground for 5 hours to obtain a first precursor solution. Then, spray drying was performed to obtain the first precursor.

[0284] (2) The first precursor is placed in a heat treatment furnace, nitrogen is introduced and the temperature is raised to 890°C for a heat treatment, and the temperature is held for 2 hours to obtain the second precursor.

[0285] (3) The second precursor was placed in the fusion machine with a rotation speed of 640 r / min, a blade gap width of 0.8 cm, and a fusion time of 4 h to obtain aggregates.

[0286] (4) The aggregate and asphalt are mixed in a mass ratio of 100:75. The mixed material is then placed in a high-temperature box furnace, nitrogen is introduced, and a second heat treatment is performed at 920°C. After holding at the temperature for 2 hours, the material is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0287] 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 and carbon material, and the mass ratio of Sn powder to carbon material is 63.5:36.5.

[0288] The median particle size of the negative electrode material is 11.5 µm, and the specific surface area is 3.1 m². 2 / g, with an average carbon layer thickness of 350nm.

[0289] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 75%.

[0290] The porosity of the negative electrode material particles was tested using the mercury porosimetry method, and the porosity of the negative electrode material was 1.4%.

[0291] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 117 MPa.

[0292] Example 8

[0293] Example 8 is largely the same as Example 1, except that:

[0294] (1) Silicon powder with a median particle size of 100 nm was dispersed in an ethylene glycol solution, and alkylphenol polyoxyethylene ether and phenolic resin were dispersed in the ethylene glycol solution. The above liquids were mixed under stirring and ultrasonically dispersed for 10 min to obtain a dispersion solution. The dispersion solution was then placed in a ball mill for grinding and dispersion for 6 hours to obtain a first precursor solution. Then, the solution was freeze-dried to obtain the first precursor.

[0295] The heat treatment temperature in step (2) is 1200℃.

[0296] 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 and carbon material, and the mass ratio of silicon powder to carbon material is 64.6:35.4.

[0297] The median particle size of the anode material is 14.8 µm, and the specific surface area is 3.7 m². 2 / g, with an average carbon layer thickness of 400nm.

[0298] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 78%.

[0299] 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 2.6%.

[0300] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 167 MPa.

[0301] Example 9

[0302] Example 9 is largely the same as Example 1, except that the secondary heat treatment temperature in step (4) is 600°C.

[0303] 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 silicon powder and carbon material, and the mass ratio of silicon powder to carbon material is 64.6:35.8.

[0304] The median particle size of the anode material is 13.8 µm, and the specific surface area is 3.1 m². 2 / g, with an average carbon layer thickness of 420nm.

[0305] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 40%.

[0306] 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 3.5%.

[0307] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 133 MPa.

[0308] Example 10

[0309] Example 10 is largely the same as Example 1, except that the secondary heat treatment step in step (4) is not performed.

[0310] The negative electrode material prepared in this embodiment includes an aggregate, which includes silicon powder and carbon material, with a mass ratio of silicon powder to carbon material of 64.1:32.8.

[0311] The median particle size of the anode material is 14.5 µm, and the specific surface area is 3.8 m². 2 / g, with an average carbon layer thickness of 380nm.

[0312] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 26%.

[0313] 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 6.7%.

[0314] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 59 MPa.

[0315] Example 11

[0316] The negative electrode material was prepared in basically the same way as in Example 1, except that no additive (alkylphenol polyoxyethylene ether) was added in step (1).

[0317] 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 and carbon material, and the mass ratio of silicon powder to carbon material is 64.8:35.2.

[0318] The median particle size of the anode material is 13.8 µm, and the specific surface area is 3.9 m². 2 / g, with an average carbon layer thickness of 360nm.

[0319] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 16%.

[0320] 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 9.6%.

[0321] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 95 MPa.

[0322] Example 12

[0323] The negative electrode material was prepared in a manner that was basically the same as in Example 1, except that: in step (1), metal oxide (SiO) was added, and the mass ratio of SiO to silicon powder was 5:100.

[0324] 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 and carbon material, and the mass ratio of silicon powder, SiO and carbon material is 63.8:4.5:31.7.

[0325] The median particle size of the anode material is 11.8 µm, and the specific surface area is 3.5 m². 2 / g, with an average carbon layer thickness of 320nm.

[0326] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 18%.

[0327] 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 2.5%.

[0328] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 195 MPa.

[0329] Example 13

[0330] The negative electrode material was prepared in a manner that was basically the same as in Example 1, except that: in step (1), a conductive enhancer (single-walled carbon nanotubes) with a tensile strength of 59 GPa was added, and the mass ratio of single-walled carbon nanotubes to silicon powder was 1.5:100.

[0331] 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 and carbon material, and the mass ratio of silicon powder, CNT and carbon material is 64.8:1.1:34.1.

[0332] The median particle size of the anode material is 10.4 µm, and the specific surface area is 2.1 m². 2 / g, with an average carbon layer thickness of 360nm.

[0333] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 18.8%.

[0334] 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 2.9%.

[0335] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 175 MPa.

[0336] Comparative Example 1

[0337] The negative electrode material was prepared in a manner that was basically the same as in Example 1, except that: step (1) was not subjected to grinding and dispersion treatment.

[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-silicon powder and carbon material, and the mass ratio of silicon powder to carbon material is 60.8:38.2.

[0339] The median particle size of the anode material is 10.4 µm, and the specific surface area is 4.6 m². 2 / g, with an average carbon layer thickness of 320nm.

[0340] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 2%.

[0341] 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 6.8%.

[0342] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 48 MPa.

[0343] Comparative Example 2

[0344] The negative electrode material was prepared in basically the same way as in Example 1, except that: step (3) was not fused.

[0345] 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 and carbon material, and the mass ratio of silicon powder to carbon material is 76.2:35.2.

[0346] The median particle size of the anode material is 21.6 µm, and the specific surface area is 6.9 m². 2 / g, with an average carbon layer thickness of 680nm.

[0347] Using the above-mentioned test method for the target region ratio D, the target region ratio D in the negative electrode material is 6%.

[0348] 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%.

[0349] The negative electrode material particles were tested using a nanoindenter, and the average compressive hardness of the negative electrode material was 44 MPa.

[0350] Test methods

[0351] (1) Button cell battery test

[0352] The electrochemical cycle performance was tested using the following method: The prepared silicon-carbon composite negative electrode material, conductive agent, and binder were dissolved and mixed 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 assembled using conventional production processes to obtain a lithium-ion coin cell battery. The initial electrode thickness of the lithium-ion battery was measured as H0 using a micrometer. The charge-discharge test of the lithium-ion battery was 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, obtaining the initial reversible capacity, first charge capacity, and first discharge capacity. The initial coulombic efficiency = first discharge capacity / first charge capacity.

[0353] 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%.

[0354] Repeat the cycle 100 times, recording the discharge capacity as the remaining capacity of the lithium-ion battery; Capacity retention rate = Remaining capacity / Initial capacity 100%.

[0355] (2) Porosity test of aggregates:

[0356] Porosity was determined by mercury porosimetry. Porosity was measured at least three times, and the arithmetic mean of the three measurements was used as the result.

[0357] The results of the above performance tests are as follows:

[0358] Table 1. Performance Comparison Results

[0359]

[0360] 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 active materials in the negative electrode material maintain an appropriate spacing, which effectively avoids the self-aggregation of the active materials, prevents the loss of electrical contact during the lithium insertion / extraction process, enhances the bonding between the active materials and the carbon materials, and thus improves the electrochemical performance of the negative electrode material.

[0361] 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 anode material exhibits excellent cycle performance, with a capacity retention rate of 93.1% after 100 cycles. This is because the aggregate has a small porosity, and the electrolyte does not easily penetrate into the interior of the aggregate. The aggregate structure is beneficial for protecting the internal active material particles, effectively suppressing the volume expansion of the anode material, reducing the expansion rate, and improving the battery cycle performance.

[0362] As shown in Table 1, the negative electrode materials prepared in Examples 1 to 10 include aggregates, wherein the aggregates comprise active materials and carbon materials. By controlling the spacing of the active materials within the aggregates, the dispersion of the active materials is ensured, preventing the active materials from tending to agglomerate and ensuring smooth carrier transport channels within the aggregates. This avoids soft agglomeration of particles, and maintaining appropriate spacing between the active materials also facilitates the subsequent penetration of carbon materials, enhancing the bonding force between the active materials and carbon materials, thereby improving the electrochemical performance of the material. The aggregates have a small porosity, making it difficult for the electrolyte to penetrate into the interior of the aggregates. This aggregate structure helps protect the internal active material particles, effectively suppressing the volume expansion of the negative electrode material, reducing the expansion rate, and improving battery cycle performance.

[0363] In Example 8, the anode material was prepared at an excessively high temperature during the first heat treatment, which resulted in the formation of a small amount of inactive SiC material, causing a decrease in the reversible capacity and initial coulombic efficiency of the anode material.

[0364] In the preparation process of the negative electrode material in Example 9, the secondary heat treatment temperature was too low, resulting in incomplete carbonization of the carbon source coated on the surface of the aggregate, which reduced the conductivity of the negative electrode material and decreased the initial coulombic efficiency of the negative electrode material.

[0365] In the preparation process of the negative electrode material in Example 10, the surface of the aggregate was not coated with carbon, and no carbon layer was formed. As a result, the conductivity of the negative electrode material decreased, and the initial coulombic efficiency decreased.

[0366] In the preparation of the negative electrode material in Example 11, no additives were added, and the connection between the active particles and the carbon material was not tight. Therefore, the stability of the aggregate structure decreased, and the effect of expansion buffering and suppression was weakened.

[0367] In the preparation process of the negative electrode material of Example 12, a metal oxide was added during the step of graded mixing of the active material, additives, first carbon source, and solvent. This improved the rigidity of the aggregate structure, increased the cycling stability of the particles, and reduced the electrode expansion rate after cycling. In the preparation process of the negative electrode material of Example 13, a conductivity enhancer was added during the step of graded mixing of the active material, additives, first carbon source, and solvent. This effectively improved carrier transport within the aggregate, enhanced the conductivity of the aggregate, and increased the initial coulombic efficiency of the negative electrode material. Furthermore, the conductivity enhancer effectively improved the structural stability of the aggregate, increased the cycling stability of the particles, and reduced the electrode expansion rate after cycling.

[0368] In the preparation process of the negative electrode material of Comparative Example 1, the raw materials were not ground and dispersed in step (1), the uniformity of the mixture of active material and carbon material decreased, the active material was not sufficiently dispersed in the raw materials, resulting in a significant decrease in the spacing between active materials in the aggregates of the negative electrode material, a decrease in the dispersion of active materials, a tendency of active materials to agglomerate, easy blockage of charge carrier transport channels inside the aggregates, and a decrease in the electrochemical performance of the material.

[0369] In the preparation process of the negative electrode material of Comparative Example 2, the precursor in step (2) was not fused, the overall structure tended to be loose, the connection stability between the active material and the carbon material was poor, the pores between the active material and the carbon material increased, which led to a decrease in the structural strength of the aggregate, a significant decrease in the compressive strength, and difficulty in resisting the stress changes brought about by the expansion effect of the active material, resulting in an increase in the expansion rate.

[0370] 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 anode material comprises an aggregate, which includes an active material, a conductive reinforcing agent, and a carbon material. The conductive reinforcing agent includes at least one of an alloy material and conductive carbon. The conductive carbon includes at least one of carbon nanotubes, carbon fibers, and graphite fibers. The carbon material includes amorphous carbon, which includes at least one of hard carbon and soft carbon. The porosity of the anode material is ≤10%, and the compressive strength of the anode material is ≥100 MPa. Furthermore, the proportion D of the target region in the anode material is ≥15%. The target area ratio D is obtained through the following testing 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 the active material in all regions of a single negative electrode material particle is statistically analyzed. The number of regions with a spacing of 10nm~300nm between the active materials is counted as N1, and the total number of regions with a spacing of less than 10nm and greater than 300nm between the active materials is counted as N2. The target region ratio X of a single negative electrode material particle is defined as X=N1 / N2, and D is the arithmetic mean of the X values ​​of any 5 negative electrode material particles.

2. The negative electrode material according to claim 1, characterized in that, It includes at least one of the following features (1) to (3): (1) The active substance includes at least one of Li, Na, K, Sn, Ge, Si, 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 mass ratio of the active substance to the carbon material is (20~70):(10~80).

3. The negative electrode material according to any one of claims 1 to 2, characterized in that, It includes at least one of the following features (1) to (7): (1) The aggregate further includes metal oxides; (2) The metal oxide is distributed in the active material, and the carbon material is filled between the active material and the metal oxide; (3) There are pores between the active material and the metal oxide, and the pores are filled with the carbon material; (4) the metal oxide has a general chemical formula of 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. (5) The metal oxide is in the form of flakes and / or strips; (6) The aspect ratio of the metal oxide is greater than 2; (7) The mass ratio of the metal oxide to the active substance is (1~20):

100.

4. The negative electrode material according to any one of claims 1 to 2, characterized in that, It includes at least one of the following features (1) to (10): (1) The conductivity of the conductive enhancer is >10. 2 S / m; (2) 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; (3) The mass ratio of the conductive enhancer to the active substance is (0.1~10):100; (4) The tensile strength of the conductive reinforcing agent is ≥500MPa; (5) The negative electrode material further includes a carbon layer covering at least a portion of the surface of the aggregate; (6) The material of the carbon layer includes amorphous carbon; (7) The thickness of the carbon layer is 10 nm to 1500 nm; (8) The median particle size of the negative electrode material is 0.5µm~30µm; (9) The specific surface area of ​​the negative electrode material is ≤10m². 2 / g; (10) The porosity of the negative electrode material is ≤10%.

5. A method for preparing a negative electrode material as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The active substance, conductive enhancer, additive, first carbon source and solvent are mixed and fully dispersed, and then the solvent is removed to obtain the first precursor; The first precursor is subjected to a heat treatment to obtain the second precursor; and The second precursor is densified to obtain aggregates.

6. The preparation method according to claim 5, characterized in that, Includes at least one of the following features (1) to (20): (1) The active substance includes at least one of Li, Na, K, Sn, Ge, Si, 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 mass ratio of the first carbon source to the active substance is (5~40): 100; (4) The solvent includes organic solvents; (5) The organic solvent includes at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol and pentanol; (6) The additives include at least one of surfactants and coupling agents; (7) 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; (8) The coupling agent includes a silane coupling agent, which includes γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane; (9) The mass ratio of the active substance to the additive is (15~120):(1~10); (10) The step of mixing the active material, the first carbon source and the solvent in a graded manner also includes the addition of metal oxides; (11) 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; (12) The metal oxide is in the form of flakes and / or strips; (13) The aspect ratio of the metal oxide is greater than 2; (14) The mass ratio of the metal oxide to the active substance is (1~20):100; (15) The mass ratio of the conductive enhancer to the active substance is (0.1~10):100; (16) The conductive reinforcing agent includes at least one of alloy materials and conductive carbon; (17) The conductive carbon includes at least one of carbon nanotubes, carbon fibers, and graphite fibers; (18) The conductivity of the conductive enhancer is >10. 2 S / m; (19) The conductive enhancer is in the form of sheets and / or strips; (20) The aspect ratio of the conductive reinforcing agent is 2 to 3000.

7. The preparation method according to claim 6, characterized in that, Includes at least one of the following features (1) to (5): (1) The fully dispersed treatment method includes at least one of mechanical stirring, ultrasonic dispersion, and grinding dispersion; (2) The active substance, the first carbon source and the solvent are mixed in a stepwise mixing manner; (3) The mixing of the active substance, the first carbon source and the solvent specifically involves: mixing the active substance with the solvent to form a first premix, mixing the first carbon source with the solvent to form a second premix, and then mixing the first premix with the second premix. (4) The step of preparing the first precursor includes mixing and dispersing the active substance, the first carbon source and the solvent in stages, and then drying the mixture to obtain the first precursor; (5) The drying process is performed at a temperature of 40℃ to 600℃ for 1h to 15h.

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

9. The preparation method according to claim 5, 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 second precursor with the second carbon source and performing a secondary heat treatment; (3) The mass ratio of the second precursor to the second carbon source is (30~100):(10~70); (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 (20~100):(10~120); (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 4 or the negative electrode material prepared by the preparation method according to any one of claims 5 to 9.

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