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

Abstract

The application relates to a negative electrode material and a preparation method thereof and a lithium ion battery, and comprises an aggregate, the aggregate comprises an active substance, a carbon material and a doped element, the carbon material shows, in a Raman diagram obtained by using a measuring light source with a wavelength of 532 nm through a Raman spectrum method, a G band at 1530 cm ‑1 to 1630 cm ‑1 A D band is observed at 1280 cm ‑1 to 1380 cm ‑1 , and a ratio I D / I G between the peak intensity I D of the D band and the peak intensity I G of the G band is 1-2.5. The disclosed negative electrode material can significantly improve the first efficiency of the composite material and greatly improve the cycle performance stability.

Description

Technical Field

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

[0002] In recent years, lithium-ion batteries have been 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. For example, silicon-carbon anode materials have been partially applied in power batteries and other fields. However, due to their significant volume expansion, silicon anode materials tend to pulverize during cycling, detaching from the current collector and losing electrical contact, resulting in rapid degradation of cycle performance. Furthermore, high initial efficiency is required for anodes in full-cell applications. Currently, graphite anodes generally have initial efficiencies above 93%, while silicon anode materials typically have initial efficiencies of around 80-85%, leading to poor specific capacity utilization in finished battery designs. Methods to improve initial efficiency are needed, such as anode pre-lithiation, but existing lithium replenishment methods are complex, dangerous, and require sophisticated equipment. Therefore, other methods are needed to improve the initial efficiency of silicon-based materials, thus limiting the further application of silicon anodes.

[0003] Therefore, how to improve initial efficiency while simplifying the process and reducing costs is an urgent problem to be solved. Summary of the Invention

[0004] In order to overcome the above-mentioned defects, this application provides a negative electrode material and its preparation method, as well as a lithium-ion battery, which is beneficial to improving the initial efficiency of the negative electrode material. The preparation method can simplify the process and reduce the manufacturing cost.

[0005] In a first aspect, an anode material includes an aggregate comprising an active material, a carbon material, and a dopant element; the carbon material is shown in a Raman spectrum obtained by Raman spectroscopy using a measuring light source with a wavelength of 532 nm, exhibiting a Raman spectrum at 1530 cm⁻¹. -1 Up to 1630cm -1 G-band was observed at 1280 cm. -1 Up to 1380cm -1 The D band was observed, and the peak intensity I of the D band was... D Peak intensity I of G band G The ratio between I D / I G It ranges from 1 to 2.5.

[0006] The addition of doping elements can promote the bonding of carbon materials with active substances and increase the graphitization degree of carbon materials, thereby improving conductivity. Doping elements induce highly active and selective active sites in carbon materials. These active sites are more likely to bind to the surface of active substances, forming more stable connections. On the other hand, due to the increased activity and lower energy barrier, the rearrangement resistance of carbon atoms is reduced, making it easier to form an ordered arrangement during high-temperature heat treatment. This is manifested as an increase in local short-range order and a partial improvement in graphitization degree.

[0007] In a second aspect, an anode material includes an aggregate comprising an active substance, a carbon material, and a dopant element, wherein the dopant element is capable of inducing the carbon material to generate Lewis acid active sites, and at least a portion of the active substance binds to the carbon material through the Lewis acid active sites.

[0008] The electronegativity of the doped atom and the carbon atom differs greatly. The introduction of the doped atom causes the charge distribution of the carbon atom to be uneven, generating Lewis acid sites. This induces highly active and selective active sites in the carbon material. These active sites are more likely to bind to the surface of the active material, forming a more stable connection.

[0009] In one embodiment, the doping element includes at least one of fluorine, nitrogen, and phosphorus.

[0010] In one embodiment, at least one of the active material and the carbon material contains the dopant element.

[0011] In one embodiment, the dopant element is distributed on the surface and / or inside the active material.

[0012] In one embodiment, the dopant element is distributed on the surface and / or inside the carbon material.

[0013] In one embodiment, the dopant element in the aggregate is present in an amount of 50 ppm to 20,000 ppm.

[0014] In one embodiment, the carbon material is porous, and at least a portion of the active material fills the pores.

[0015] In one embodiment, the pore volume of the carbon material is ≥0.35 cm³. 3 / g.

[0016] In one embodiment, the active substance includes active particles.

[0017] In one embodiment, the active substance includes Li, Na, K, Sn, Ge, Si, Fe, Mg, Ti, Zn, Al, P, Cu, and SiO. x At least one of them, where 0 < x ≤ 2.

[0018] In one embodiment, the median particle size of the active material is 1 nm to 300 nm.

[0019] In one embodiment, the carbon material includes at least one of crystalline carbon, amorphous carbon, artificial graphite, natural graphite, soft carbon, hard carbon, amorphous carbon, carbon nanotubes, carbon fibers, and graphene.

[0020] In one embodiment, the mass ratio of the active substance to the carbon material is (90-10):(10-90).

[0021] In one embodiment, the aggregate further includes a metal oxide.

[0022] In one embodiment, at least a portion of the metal oxide fills the pores between the carbon materials.

[0023] 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.

[0024] In one embodiment, the mass ratio of the active substance to the metal oxide is (30-100):(0.5-10).

[0025] In one embodiment, the metal oxide is in the form of sheets and / or strips.

[0026] In one embodiment, the aspect ratio of the metal oxide is greater than 2.

[0027] In one embodiment, the shortest distance between the metal oxides is ≥100nm.

[0028] In one embodiment, the aggregate further includes a conductivity enhancer.

[0029] In one embodiment, at least a portion of the conductive enhancer fills the pores between the carbon materials.

[0030] In one embodiment, the conductivity enhancer includes at least one of an alloy material and conductive carbon.

[0031] In one embodiment, the conductivity of the conductive enhancer is 100 S / m to 10 S / m. 8 S / m.

[0032] In one embodiment, the conductive enhancer is in the form of sheets and / or strips.

[0033] In one embodiment, the mass ratio of the conductivity enhancer to the active substance is (0.01-15):(50-100).

[0034] In one embodiment, the aspect ratio of the conductive reinforcing agent is 2 to 5000.

[0035] In one embodiment, the negative electrode material further includes a carbon layer covering at least a portion of the surface of the aggregate.

[0036] In one embodiment, the material of the carbon layer includes amorphous carbon.

[0037] In one embodiment, the thickness of the carbon layer is 10 nm to 5000 nm.

[0038] In one embodiment, the negative electrode material further includes an oxide layer formed on at least a portion of the surface of the active material.

[0039] In one embodiment, the thickness of the oxide layer is 1 nm to 100 nm.

[0040] In one embodiment, the oxide layer has pores.

[0041] In one embodiment, the median particle size of the negative electrode material is 0.5 μm to 30 μm.

[0042] In one embodiment, the specific surface area of ​​the negative electrode material is ≤10m². 2 / g.

[0043] In one embodiment, the mass ratio of the aggregate to the carbon layer is (90-10):(10-90).

[0044] In one embodiment, the porosity of the aggregate is ≤10%, and the compressive strength of the aggregate is ≥100 MPa.

[0045] In one embodiment, the aggregate density satisfies the following relationship: (p1-p2) / p2≤5%, where p1 is the test density of the aggregate, p2 is the average density of the aggregate, and p2 is the sum of the mass percentage of each component in the aggregate multiplied by the theoretical density of each component.

[0046] Secondly, a method for preparing a negative electrode material, the method comprising the following steps:

[0047] A precursor is prepared by mixing an active material, a dopant, a first carbon source, and a solvent.

[0048] The precursor is subjected to a heat treatment at 800℃ to 980℃ to obtain an aggregate.

[0049] In one embodiment, the active substance includes Li, Na, K, Sn, Ge, Si, Fe, Mg, Ti, Zn, Al, P, Cu, and SiO. x At least one of them, where 0 < x ≤ 2;

[0050] In one embodiment, the dopant includes at least one of a fluorine source, a phosphorus source, and a nitrogen source.

[0051] In one embodiment, the fluorine source includes fluorides, and the fluorides include at least one of hydrogen fluoride, lithium fluoride, ammonium fluoride, potassium fluoride, aluminum fluoride, magnesium fluoride, sodium fluoride, calcium fluoride, tetrabutylammonium fluoride, triethylmethoxymethylammonium fluoride, ammonium fluoroborate, and tetrabutylammonium fluoroborate.

[0052] In one embodiment, the phosphorus source includes at least one of triphenylphosphine, tetraphenylphosphine bromide, sodium 1-butyl-3-methylimidazolium hexafluorophosphate, phosphine, sodium phosphate, sodium phosphite, elemental phosphorus, sodium hydrogen phosphate, sodium dihydrogen phosphate, sodium hydrogen phosphite, and phosphoric acid.

[0053] In one embodiment, the nitrogen source includes at least one of ammonia, ammonium chloride, ammonium carbonate, ammonium bicarbonate, urea, thiourea, lithium nitride, melamine, and hydrazine hydrate.

[0054] 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.

[0055] In one embodiment, the mass ratio of the active material, dopant, and first carbon source is (30-120):(0.9-20):(10-50);

[0056] In one embodiment, the solvent includes an organic solvent.

[0057] In one embodiment, the organic solvent includes at least one selected from ethanol, ethylene glycol, propanol, butanol, and n-pentanol.

[0058] In one embodiment, the step of mixing the active material, dopant, first carbon source, and solvent specifically involves dispersing the active material in an organic solvent and then adding the dopant and first carbon source.

[0059] In one embodiment, the step of preparing the precursor further includes at least one of mixing the active substance, dopant, first carbon source, and solvent and then dispersing and drying the mixture.

[0060] In one embodiment, the dispersion treatment includes at least one of mechanical stirring, ultrasonic dispersion, and grinding dispersion.

[0061] In one embodiment, the drying temperature is 30°C to 400°C, and the drying time is 1 hour to 15 hours.

[0062] In one embodiment, at least one of an additive, a metal oxide, and a conductivity enhancer is added during the step of mixing the active material, the dopant, the first carbon source, and the solvent.

[0063] In one embodiment, the additive includes at least one of surfactants and coupling agents.

[0064] In one embodiment, the additive includes a surfactant, which 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.

[0065] In one embodiment, the additive includes a coupling agent, which includes a silane coupling agent, specifically γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, or γ-methacryloyloxypropyltrimethoxysilane.

[0066] In one embodiment, the mass ratio of the additive to the active substance is (0.01-5):(50-100).

[0067] 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.

[0068] In one embodiment, the metal oxide is in the form of sheets and / or strips.

[0069] In one embodiment, the aspect ratio of the metal oxide is greater than 2.

[0070] In one embodiment, the mass ratio of the metal oxide to the active substance is (0.5-10):(30-100).

[0071] In one embodiment, the mass ratio of the conductivity enhancer to the active material is (0.01-15):(50-100).

[0072] In one embodiment, the conductivity of the conductivity enhancer is 10. 0 S / m~10 8 S / m.

[0073] In one embodiment, the conductive enhancer is in the form of sheets and / or strips.

[0074] In one embodiment, the aspect ratio of the conductive reinforcing agent is 2 to 5000.

[0075] In one embodiment, the conductivity enhancer includes at least one of an alloy material and conductive carbon.

[0076] In one embodiment, before the precursor undergoes a heat treatment, the precursor is further subjected to a densification treatment, such that the porosity of the aggregate is ≤10% and the compressive hardness is ≥100 MPa.

[0077] 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.

[0078] In one embodiment, the fusion process is mechanical fusion.

[0079] In one embodiment, the rotational speed of the fusion machine used for mechanical fusion is 500 r / min to 3000 r / min.

[0080] In one embodiment, the gap width between the fusion machine cutters used in the mechanical fusion is 0.01cm to 0.5cm.

[0081] In one embodiment, the mechanical fusion time is at least 0.5 hours.

[0082] In one embodiment, the duration of the heat treatment is 1 to 5 hours.

[0083] In one embodiment, the primary heat treatment is performed in a protective atmosphere.

[0084] In one embodiment, the protective atmosphere includes at least one of nitrogen, helium, neon, argon, and krypton.

[0085] In one embodiment, the method further includes carbon coating the aggregate.

[0086] In one embodiment, the carbon coating process includes: mixing the aggregate with a second carbon source and performing a secondary heat treatment.

[0087] 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.

[0088] In one embodiment, the mass ratio of the aggregate to the second carbon source is (20-100):(10-80).

[0089] In one embodiment, the temperature of the secondary heat treatment is 800℃~900℃, and the time of the secondary heat treatment is 1h~5h;

[0090] In one embodiment, the secondary heat treatment is performed in a protective atmosphere.

[0091] In one embodiment, the protective atmosphere includes at least one of nitrogen, helium, neon, argon, and krypton.

[0092] In one embodiment, after the secondary heat treatment, at least one of crushing, sieving, and demagnetizing is performed.

[0093] In one embodiment, the sieve mesh size is ≥500 mesh.

[0094] Thirdly, a lithium-ion battery comprising the aforementioned negative electrode material or a negative electrode material prepared according to the aforementioned preparation method.

[0095] The technical solution of this application has at least the following beneficial effects: the addition of dopant elements can promote the bonding between carbon materials and active substances, and further enhance the graphitization degree of carbon materials, thereby improving conductivity. Dopant elements induce highly active and selective active sites in carbon materials. These active sites, on the one hand, more easily bond with the surface of active substances, forming more stable connections; on the other hand, due to increased activity and lower energy barriers, the rearrangement resistance of carbon atoms is reduced, making it easier to form ordered arrangements during high-temperature heat treatment, manifested as an increase in local short-range order and a partial improvement in graphitization degree.

[0096] The preparation method provided in this application is simple to operate and can be applied to large-scale production. 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

[0097] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0098] Figure 1 This is a flowchart illustrating a method for preparing a negative electrode material according to one embodiment. Detailed Implementation

[0099] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0100] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0101] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0102] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0103] One embodiment of the negative electrode material includes an aggregate comprising an active material, a carbon material, and a dopant element. The carbon material is shown in a Raman spectroscopy image obtained using a measurement light source with a wavelength of 532 nm, at 1530 cm⁻¹. -1 Up to 1630cm -1 G-band was observed at 1280 cm. -1 Up to 1380cm -1 The D band was observed, and the peak intensity I of the D band was... D Peak intensity I of G band G The ratio between I D / I G It ranges from 1 to 2.5.

[0104] The doping elements in this embodiment induce highly active and selective active sites in carbon materials. These active sites are more likely to bind to the surface of active materials and form more stable connections. On the other hand, due to the increased activity, the energy barrier is lowered, the rearrangement resistance of carbon atoms is reduced, and they are more likely to form ordered arrangements during high-temperature heat treatment. This is manifested as an increase in local short-range order and a partial increase in graphitization, thereby improving the conductivity of carbon materials.

[0105] Specifically, I D / I G It can be 1, 1.2, 1.5, 1.7, 1.8, 2, 2.1, 2.2, or 2.5, or other values ​​within the above range, which are not limited here. Preferably, I D / I G The graphitization degree of carbon materials is between 1.7 and 2.3, within which the graphitization degree can achieve favorable electronic conductivity.

[0106] One embodiment of the negative electrode material includes an aggregate comprising an active material, a carbon material, and a dopant element. The dopant element can induce the carbon material to generate Lewis acid active sites, and at least a portion of the active material binds to the carbon material through the Lewis acid active sites.

[0107] The addition of doping elements can promote the bonding of carbon materials with active substances and increase the graphitization degree of carbon materials, thereby improving conductivity. The dopant atom and carbon atom have vastly different electronegativity; the introduction of the dopant atom results in an uneven charge distribution of carbon atoms, creating Lewis acid sites. This induces highly active and selective active sites in the carbon material, which more easily bind to the surface of the active substance, forming a more stable bond.

[0108] It should be noted that dopants exist in aggregates in atomic form.

[0109] In some embodiments, the doping element includes at least one of fluorine, nitrogen, and phosphorus; it is understood that the doping element can be fluorine, nitrogen, or phosphorus; it can also be a combination of fluorine and nitrogen, or a combination of fluorine and phosphorus, or a combination of nitrogen and phosphorus; it can also contain fluorine, nitrogen, and phosphorus simultaneously.

[0110] In some embodiments, the dopant element content in the aggregate is 50 ppm to 20,000 ppm. Specific dopant element contents can be 50 ppm, 100 ppm, 500 ppm, 1000 ppm, 2000 ppm, 4000 ppm, 5000 ppm, 10000 ppm, 20000 ppm, etc.; other values ​​within the above range are also possible and are not limited here. Within this range, the graphitization degree of the carbon material can be effectively improved, which is beneficial to improving the interfacial stability of the active material, thereby improving the cycle stability of the material; the initial efficiency, expansion rate, and cycle life of the anode material are all improved. The dopant element content can be obtained by testing methods such as ion chromatography, component analysis, or energy dispersive X-ray spectroscopy (EDX analysis).

[0111] In some embodiments, at least one of the active material and the carbon material contains a dopant element.

[0112] In some embodiments, the dopant element is distributed on the surface and / or inside the active material. When the dopant element is located inside the active material, some of the dopant element replaces atoms in the crystal structure of the material and forms valence bonds with neighboring atoms, while some of the dopant element is distributed in lattice defects in the crystal structure. For example, in Si material, fluorine replaces silicon atoms in the silicon crystal structure and forms fluorine-silicon bonds with neighboring silicon atoms, or it can be distributed in lattice defects in the silicon-based material crystal structure.

[0113] In other embodiments, the dopant element is distributed on the surface and / or inside the carbon material. When the dopant element is located inside the distributed carbon material, some of the dopant element replaces atoms in the carbon material's crystal structure and forms valence bonds with neighboring carbon atoms, while some of the dopant element is distributed in lattice defects in the carbon crystal structure.

[0114] Of course, in some embodiments, the dopant element is distributed both on the surface and / or inside the active material and on the surface and / or inside the carbon material.

[0115] It should be noted that, since the doping content of the doping elements is extremely low, it is insufficient to form a long-range ordered structure, and will not cause significant changes to the crystal structure of the material itself, thus better maintaining the structural stability of the material.

[0116] In some embodiments, the active material is distributed between or on the surface of the carbon material in the aggregate; preferably, the active material is uniformly dispersed in the carbon material.

[0117] In some embodiments, the carbon material is porous, and the pores are filled with at least some active material. This filling method can effectively utilize the pores formed between the carbon materials, so that the active material dispersed in the pores has a certain deformation space when the volume changes during charging and discharging, thereby reducing the stress and strain damage caused by the volume change.

[0118] In some embodiments, the pore volume of the carbon material is ≥0.35 cm³. 3 / g. The pore volume of the carbon material includes the pore volume of the pore structure formed between carbon materials and the pore volume of porous carbon materials (the porous structure of the carbon material itself). It possesses a pore volume of not less than 0.35 cm⁻¹. 3 The pore size ( / g) has two main advantages: firstly, the internal pores can effectively accommodate active materials, providing space for their expansion; secondly, an appropriate pore size can provide more channels for carbon penetration during the subsequent carbon coating process, which is beneficial for carbon coating.

[0119] In some embodiments, the active substance includes active particles.

[0120] In some embodiments, the active material refers to a substance that can react with lithium to perform lithium intercalation / deintercalation. Specifically, active materials include Li, Na, K, Sn, Ge, Si, Fe, and SiO. x (0<x≤2), at least one of Mg, Ti, Zn, Al, P and Cu; the active material can be a metallic element. In some embodiments, the active material can specifically be Si particles, Sn particles, Ge particles, or Al particles. In other embodiments, the active material can also be a silicon-lithium alloy, a silicon-magnesium alloy, etc. Of course, it should be noted that in some cases, the active material includes elemental particles and alloys.

[0121] In some embodiments, the median particle size of the active material is 1 nm to 300 nm. Specifically, it can be 1 nm, 5 nm, 10 nm, 50 nm, 75 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, etc., and there is no specific limitation. It can be understood that controlling the median particle size of the active material within the above range is beneficial to improving the cycle performance of the negative electrode material.

[0122] In some embodiments, the carbon material includes at least one of crystalline carbon, amorphous carbon, artificial graphite, natural graphite, soft carbon, hard carbon, amorphous carbon, carbon nanotubes, carbon fibers, and graphene.

[0123] In some embodiments, the mass ratio of the active material to the carbon material is (90-10):(10-90). Specifically, it can be 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, etc., and there is no specific limitation.

[0124] In some embodiments, the porosity of the aggregate is ≤10%, and the compressive strength of the aggregate is ≥100 MPa.

[0125] At this point, the aggregate has low porosity, meaning it is very dense. This helps to improve the energy density of the composite material. Furthermore, even if the surface layer of the high-density material is damaged, the electrolyte is less likely to penetrate into the interior of the aggregate, which helps protect the internal active material particles and reduces the chance of contact between the electrolyte and the active material, thus facilitating the formation of a stable solid electrolyte membrane. In addition, the highly dense 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.

[0126] In some embodiments, the porosity of the aggregates is ≤10%. Specifically, the porosity of the aggregates can be 10%, 9%, 9.5%, 8%, 8.5%, 7.5%, 7%, 6.5%, 6%, or 5%, etc., and of course, other values ​​within the above range are also possible and are not limited here. Understandably, a lower porosity in the aggregates, i.e., a 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 aggregates is ≤5%, and more preferably, the porosity of the aggregates is ≤3%.

[0127] The aggregate has a pressure resistance ≥100 MPa; specifically, the pressure resistance of the aggregate can be 100 MPa, 150 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 amount of volume expansion stress, thereby reducing expansion and improving battery cycle stability. Preferably, the pressure resistance of the aggregate is ≥200 MPa, more preferably, the pressure resistance of the aggregate is ≥400 MPa.

[0128] 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.

[0129] 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;

[0130] Where p2 is the sum of the mass percentage of each component in the aggregate multiplied by the theoretical density of each component.

[0131] In a specific example, when the aggregate includes active material and carbon material, p2 = mass percentage of active material in the aggregate * theoretical density of active material + mass percentage of carbon material in the aggregate * theoretical density of carbon material.

[0132] In some embodiments, the aggregates also include metal oxides. Combining metal oxides with the active material can reduce the expansion of the active material, improve long-cycle performance, and give the aggregates higher pressure resistance. It should be noted that, in this case, the average density p2 of the aggregates = (mass percentage of active material in the aggregates * theoretical density of the active material) + (mass percentage of metal oxide in the aggregates * theoretical density of the metal oxide) + (mass percentage of lithium-containing carbon material in the aggregates * theoretical density of the carbon material).

[0133] At this point, when the aggregate also includes metal oxides, fluorine is distributed within or on the surface of the metal oxides. When fluorine is located within the distributed metal oxides, some fluorine replaces atoms in the metal oxide crystal structure and forms valence bonds with neighboring atoms; some dopant elements are distributed in lattice defects within the metal oxide crystal structure. Specifically, if the metal oxide is SnO2, it replaces Sn atoms in the SnO2 crystal structure and forms valence bonds with neighboring atoms, or it can be distributed in lattice defects within the crystal structure.

[0134] In some embodiments, at least a portion of the metal oxide fills the pores between the carbon materials.

[0135] 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; specifically, the metal oxide can be any one of GeO2, SnO2, ZnO, TiO2, Fe3O4, MgO, SiO2 and CuO.

[0136] In some embodiments, the mass ratio of the active material to the metal oxide is (30-100):(0.5-10). Specifically, it can be 30:0.5, 40:1, 50:2, 60:2, 70:3, 80:6, 90:7.5, 100:10, or 100:2, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0137] In some embodiments, the metal oxide is in the form of sheets and / or strips.

[0138] 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 buffering the volume expansion changes of the active material and improving cycle performance.

[0139] In some embodiments, the shortest distance between metal oxides is ≥100 nm. Controlling the shortest distance allows for the filling of active materials between metal oxides, enabling the metal oxides to act as structural supports and enhance material stability, thereby buffering volume expansion changes of the active materials and improving cycle performance. Specifically, the distance can be 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, or 400 nm, etc. In this embodiment, the shortest distance between metal oxides refers to the shortest straight-line distance between any two metal oxide particles. Preferably, the spacing between metal oxides is ≥200 nm. The distance testing method is as follows: Prepare samples by cross-sectioning any metal oxide, select any particles, and test the shortest distance between any two metal oxides within the particles. Measure at least 50 times and take the average value.

[0140] In some embodiments, the aggregate also includes a conductivity enhancer, which on the one hand can provide more channels for charge carrier transport, thereby enhancing the transport of charge carriers within the material; on the other hand, it also has excellent mechanical properties and can serve as a structural support to enhance the stability of the material.

[0141] At this time, when the aggregate also includes a conductive reinforcing agent, fluorine is also distributed inside or on the surface of the conductive reinforcing agent material; when fluorine is located inside the conductive reinforcing agent material, some fluorine replaces atoms in the crystal structure of the conductive reinforcing agent material and forms valence bonds with neighboring atoms, and some dopant elements are distributed in the lattice defects in the crystal structure of the conductive reinforcing agent material.

[0142] When the aggregate includes an active material, a conductivity enhancer, and a carbon material, p2 = (mass percentage of active material in the aggregate) * theoretical density of active material + (mass percentage of conductivity enhancer in the aggregate) * theoretical density of conductivity enhancer + (mass percentage of carbon material in the aggregate) * theoretical density of carbon material.

[0143] When the aggregate includes active material, metal oxide, conductive enhancer and carbon material, p2 = mass percentage of active material in the aggregate * theoretical density of active material + mass percentage of metal oxide in the aggregate * theoretical density of metal oxide + mass percentage of conductive enhancer in the aggregate * theoretical density of conductive enhancer + mass percentage of carbon material in the aggregate * theoretical density of carbon material.

[0144] In some embodiments, at least a portion of the conductive enhancer fills the pores between the carbon materials.

[0145] In some embodiments, the conductive reinforcing agent includes at least one of an alloy material and conductive carbon; wherein the conductive carbon may include at least one of carbon nanotubes, carbon fibers, and graphite fibers.

[0146] In some embodiments, the conductivity of the conductivity enhancer is 100 S / m to 10 S / m. 8 S / m. Specifically, the conductivity of the conductive enhancer can be 1 S / m, 10 S / m, 100 S / m, 10 3 S / m, 10 4 S / m, 10 5 S / m, 10 8 S / m, etc.

[0147] In some embodiments, the conductivity enhancer is in the form of sheets and / or strips.

[0148] In some embodiments, the mass ratio of the conductive enhancer to the active material is (0.01–15):(50–100). Specifically, it can be 0.01:50, 15:50, 0.05:55, 0.1:60, 1:50, 5:60, 7.5:75, 10:80, or 15:100, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0149] In some embodiments, the aspect ratio of the conductive reinforcing agent is 2 to 5000. 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, 3000, 4000, 5000, 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.

[0150] In some embodiments, the negative electrode material further 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. The carbon layer 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.

[0151] In some implementations, the carbon layer is made of amorphous carbon.

[0152] In some embodiments, the thickness of the carbon layer is 10 nm to 5000 nm. Specifically, the thickness of the carbon layer can be 10 nm, 50 nm, 100 nm, 400 nm, 500 nm, 750 nm, 1000 nm, 1500 nm, 2000 nm, 2500 nm, 3000 nm, 4000 nm, 5000 nm, etc., or other values ​​within the above range, which are not limited here. If the carbon layer is too thick, it is not conducive to high-rate charge and discharge of the material, reducing the overall performance of the negative electrode material; if the carbon layer is too thin, it is not conducive to increasing the conductivity of the negative electrode material and has weak performance in suppressing the volume expansion of the material, resulting in a long-cycle performance-price difference.

[0153] In some embodiments, the median particle size of the negative electrode material is 0.5 μm to 30 μm, specifically 0.5 μm, 1.5 μm, 3 μm, 10 μm, 16 μm, 26 μm, etc., or other values ​​within the above range, which 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. Preferably, the median particle size of the negative electrode material is 1.5 μm to 15 μm.

[0154] In some embodiments, the specific surface area of ​​the negative electrode material is ≤10m². 2 / g, specifically 10m 2 / g、7m 2 / g、6m 2 / g、4m 2 / g、2m 2 / g, 1m 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. Preferably, the specific surface area of ​​the negative electrode material is ≤5m². 2 / g.

[0155] In some embodiments, the mass ratio of the aggregate to the carbon layer is (90-10):(10-90), specifically 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, etc., and there is no specific limitation.

[0156] In some embodiments, the negative electrode material further includes an oxide layer formed on at least a portion of the surface of the active material; when the active material is silicon particles, the oxide layer is silicon oxide.

[0157] In some embodiments, the thickness of the oxide layer is 1 nm to 100 nm. The thickness of the oxide layer can be 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc., or other values ​​within the above range, which are not limited here.

[0158] In some embodiments, the oxide layer has pores, thereby providing space for the expansion of the active material and reducing the volume expansion effect of the active material.

[0159] 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.

[0160] like Figure 1 As shown, another embodiment of the method for preparing the negative electrode material includes the following steps:

[0161] Step S100: The precursor is prepared by mixing the active material, dopant, first carbon source and solvent.

[0162] Step S200: The precursor is subjected to a heat treatment at 800℃~980℃ to obtain aggregates;

[0163] Step S300: The aggregate is carbon coated to obtain the negative electrode material.

[0164] The negative electrode material prepared by the method of this embodiment includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes an active material, a carbon material, and a dopant element. The carbon material is shown in the Raman spectrum obtained by Raman spectroscopy using a measurement light source with a wavelength of 532 nm. The image shows the carbon material at 1530 cm⁻¹. -1 Up to 1630cm -1 G-band was observed at 1280 cm. -1 Up to 1380cm -1 The D band was observed, and the peak intensity I of the D band was... D Peak intensity I of G band G The ratio between I D / I G It ranges from 1 to 2.5.

[0165] By adding dopants to the active material and carbon source, the addition of dopants can promote the bonding between the carbon material and the active material, and also increase the graphitization degree of the carbon material, thereby improving conductivity. Dopants induce highly active and selective active sites in the carbon material. These active sites are more likely to bind to the surface of the active material, forming more stable connections. Furthermore, due to increased activity and lower energy barriers, the resistance to carbon atom rearrangement is reduced, making it easier to form an ordered arrangement during high-temperature heat treatment, manifested as an increase in local short-range order and a partial improvement in graphitization degree. Moreover, the addition of dopants helps improve the stability of the active material interface, thereby improving the cycle stability of the material; the initial efficiency, expansion rate, and cycle life of the anode material are all improved.

[0166] The preparation method of this application is described in detail below with reference to the embodiments:

[0167] Step S100: The precursor is prepared by mixing the active material, dopant, first carbon source and solvent.

[0168] In some embodiments, the median particle size of the active material is 1–300 nm. Specifically, it can be 1 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 200 nm, 250 nm, 300 nm, etc., or other values ​​within the above range, which are not limited here. Controlling the median particle size of the active material within the above range is beneficial to improving the cycle performance of the negative electrode material.

[0169] In some embodiments, the active material includes Li, Na, K, Sn, Ge, Si, and SiO. x (0 < x ≤ 2), at least one of Fe, Mg, Ti, Zn, Al, P, or Cu; the active material can be a metallic element. In some embodiments, the active material can specifically be Si particles, Sn particles, Ge particles, or Al particles. In other embodiments, the active material can also be a silicon-lithium alloy, a silicon-magnesium alloy, etc. Of course, it should be noted that in some cases, the active material includes elemental particles and alloys.

[0170] In some embodiments, the active material is SiO2. x When (0 < x ≤ 2), the addition of fluoride as the dopant can effectively promote the SiO2 production process. x The disproportionation transformation forms Si and SiO2, resulting in a more uniform SiO2 coating layer, which is beneficial to the stability and improvement of the silicon interface and improves the cycling stability of the material. Moreover, the fluoride will etch the oxide layer on the silicon surface to obtain pores, thereby providing space for silicon expansion and reducing the volume expansion effect of silicon.

[0171] In some embodiments, the dopant includes at least one of a fluorine source, a phosphorus source, and a nitrogen source. Using this type of dopant, the electronegativity difference between the doped atoms and carbon atoms is significant. The introduction of the dopant atoms results in an uneven charge distribution of carbon atoms, creating Lewis acid sites. These active sites are more likely to bind to the surface of the active material, forming a more stable connection. Furthermore, due to increased activity and a lower energy barrier, the rearrangement resistance of carbon atoms is reduced, making it easier to form an ordered arrangement during high-temperature heat treatment, manifested as an increase in local short-range order and a partial improvement in graphitization. Moreover, the addition of dopant elements helps improve the stability of the active material interface, thereby improving the cycle stability of the material; the initial efficiency, expansion rate, and cycle life of the anode material are all improved.

[0172] In some embodiments, the fluorine source includes fluorides, said fluorides including at least one of hydrogen fluoride, lithium fluoride, ammonium fluoride, potassium fluoride, aluminum fluoride, magnesium fluoride, sodium fluoride, calcium fluoride, tetrabutylammonium fluoride, triethylmethoxymethylammonium fluoride, ammonium fluoroborate, and tetrabutylammonium fluoroborate.

[0173] In some embodiments, the phosphorus source includes at least one selected from triphenylphosphine, tetraphenylphosphine bromide, sodium 1-butyl-3-methylimidazolium hexafluorophosphate, phosphine, sodium phosphate, sodium phosphite, elemental phosphorus, sodium hydrogen phosphate, sodium dihydrogen phosphate, sodium hydrogen phosphite, and phosphoric acid.

[0174] In some embodiments, the nitrogen source includes at least one of ammonia, ammonium chloride, ammonium carbonate, ammonium bicarbonate, urea, thiourea, lithium nitride, melamine, and hydrazine hydrate.

[0175] In some embodiments, the first carbon source includes at least one selected from 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.

[0176] In some embodiments, the mass ratio of the active material, dopant, and first carbon source is (30-120):(0.9-20):(10-50). Specifically, the mass ratio of the active material, dopant, and first carbon source can be 30:0.9:10, 40:5:15, 70:10:20, 60:12:30, 80:20:50, 100:10:10, 110:5:20, 120:3:15, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0177] In some embodiments, the solvent includes an organic solvent. Specifically, the organic solvent includes at least one selected from methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, and pentanol. Adding the components to an organic solvent for wet ball milling can improve the homogeneity of component mixing and facilitate rapid drying.

[0178] In some embodiments, the step of mixing the active material, dopant, first carbon source, and solvent specifically involves dispersing the active material in an organic solvent and then adding the dopant and first carbon source.

[0179] In some embodiments, the step of preparing the precursor further includes at least one of mixing the active substance, dopant, first carbon source, and solvent and then dispersing or drying the mixture.

[0180] Preferably, the active material, dopant, first carbon source, and solvent are mixed and then dispersed and dried sequentially.

[0181] In some embodiments, the dispersion process includes at least one of mechanical stirring, ultrasonic dispersion, and grinding dispersion; it avoids particle agglomeration and can disperse the active material into smaller nanoparticles.

[0182] In some embodiments, the drying temperature is 30℃ to 400℃, and the drying time is 1h to 15h; specifically, it can be 30℃, 40℃, 50℃, 80℃, 100℃, 120℃, 150℃, 180℃, 200℃, 250℃, 280℃, 300℃, or 400℃, etc., and the drying time is 1h to 15h, specifically 1h, 3h, 5h, 7h, 9h, 10h, 12h, or 15h, etc. The drying method can be, for example, oven drying, freeze drying, stirring evaporation, spray drying, etc. The drying process in this embodiment can remove the solvent in the precursor solution as much as possible.

[0183] In some embodiments, an additive is added during the mixing step of the active material, dopant, first carbon source, and solvent. This additive effectively enhances the bonding stability between the active material and the carbon material, thereby forming a robust system.

[0184] In some embodiments, the additives include at least one of surfactants and coupling agents. Experiments have shown that using this type of additive can effectively enhance the bonding stability between the active material and the carbon material, forming a robust system and reducing porosity; thereby reducing the expansion rate of the negative electrode material and increasing cycle stability.

[0185] Specifically, the surfactants include, but are not limited to, at least one of octadecanoic acid, lauric acid, polyacrylic acid (PAA), sodium dodecylbenzenesulfonate (SDBS), icosanoic acid, palmitic acid, tetradecanoic acid, undecanoic acid, hexadecyltrimethylammonium bromide, and polyvinylpyrrolidone (PVP).

[0186] The coupling agent includes silane coupling agents, specifically including but not limited to at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane and γ-methacryloyloxypropyltrimethoxysilane.

[0187] In some embodiments, the mass ratio of the active substance to the additive is 50–100:0.01–5.

[0188] In some embodiments, at least one of a metal oxide and a conductivity enhancer is added during the step of mixing the active material, dopant, first carbon source and solvent.

[0189] 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.

[0190] In some embodiments, the metal oxide is in the form of sheets and / or strips.

[0191] In some implementations, the aspect ratio of the metal oxide is greater than 2.

[0192] In some embodiments, the mass ratio of the conductivity enhancer to the active material is (0.01-15):(50-100).

[0193] In some embodiments, the conductivity of the conductivity enhancer is 10. 0 S / m~10 8 S / m.

[0194] In some embodiments, the conductivity enhancer is in the form of sheets and / or strips.

[0195] In some embodiments, the aspect ratio of the conductive reinforcing agent is 2 to 5000.

[0196] In some embodiments, the conductivity enhancer includes at least one of an alloy material and conductive carbon.

[0197] In some embodiments, prior to a heat treatment of the precursor, a densification treatment is also performed on the precursor so that the porosity of the aggregate is ≤10% and the compressive hardness is ≥100 MPa.

[0198] 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.

[0199] 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 aggregate is ≤10% and the pressure resistance is ≥100MPa.

[0200] In some embodiments, the rotational speed of the fusion machine used for mechanical fusion is 500 r / min to 3000 r / min;

[0201] In some embodiments, the tool gap width of the fusion machine used for mechanical fusion is 0.01cm to 0.5cm;

[0202] In some implementations, the mechanical fusion time is at least 0.5 hours.

[0203] Step S200: The precursor is subjected to a heat treatment at 800℃~980℃ to obtain the aggregate.

[0204] In some embodiments, the primary heat treatment method may be, for example, vacuum sintering, hot pressing sintering, or atmospheric pressure sintering. The temperature of the primary heat treatment is 800℃ to 980℃, specifically 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, etc., or other values ​​within the above range, which are not limited here.

[0205] In some implementations, the processing time is 1 hour to 5 hours, specifically 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, etc., or other values ​​within the above range, which are not limited here.

[0206] In some embodiments, the heat treatment is carried out in a protective atmosphere; specifically, the protective atmosphere includes at least one of nitrogen, helium, neon, argon, and krypton.

[0207] In some embodiments, after a heat treatment, a pulverization operation is performed, and the pulverization method is any one of a mechanical pulverizer, an air jet mill, or a cryogenic pulverizer.

[0208] Step S300: The aggregate is carbon coated to obtain the negative electrode material.

[0209] It should be noted that the negative electrode material in this embodiment may not be carbon coated, in which case step S30 may be omitted.

[0210] In some embodiments, the specific steps of the carbon coating process may include: mixing the aggregate with a second carbon source and performing a secondary heat treatment.

[0211] 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.

[0212] In some embodiments, the mass ratio of the aggregate to the second carbon source is (20-100):(10-80). The mass ratio of the aggregate to the second carbon source can be 20:10, 30:15, 50:60, 80:30, 90:20, 100:10, etc., or other values ​​within the above range, which are not limited here.

[0213] In some embodiments, the secondary heat treatment can be performed by, for example, vacuum sintering, hot pressing sintering, or atmospheric pressure sintering. The temperature of the secondary heat treatment is 800℃ to 900℃. Specifically, it can be 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, etc., or other values ​​within the above range, which are not limited here.

[0214] In some implementations, the secondary heat treatment time is 1h to 5h; specifically, it can be 1h, 2h, 3h, 4h, 5h, etc., or other values ​​within the above range, which are not limited here.

[0215] In some embodiments, the secondary heat treatment is carried out in a protective atmosphere; the protective atmosphere includes at least one of nitrogen, helium, neon, argon, and krypton.

[0216] 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.

[0217] In some implementations, the pulverization method is any one of a mechanical pulverizer, an air jet mill, or a cryogenic pulverizer.

[0218] 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.

[0219] 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.

[0220] Thirdly, this application provides a lithium-ion battery, which comprises the negative electrode material described in the first aspect or the negative electrode material prepared by the preparation method described in the second aspect.

[0221] 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.

[0222] Example 1

[0223] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0224] 1) Silicon particles with a median particle size of 50 nm were dispersed in an ethanol solution (volume percentage concentration of 40%), and then triethylmethoxymethylammonium fluoride and phenolic resin were added and mixed evenly. The mass ratio of silicon particles, triethylmethoxymethylammonium fluoride and phenolic resin was 50:4.3:24.5. Then, the mixture was dried at 150°C for 5 hours to obtain the precursor.

[0225] 2) The precursor is placed in a heat treatment furnace, argon gas is introduced, the temperature is raised to 900℃, and the reaction is carried out for 3 hours to obtain aggregates;

[0226] 3) Mix the aggregate and asphalt at a mass ratio of 40:30, stir and disperse evenly, and then dry them at 150℃ for 5 hours. Add the dried material to a high-temperature box furnace, introduce nitrogen, and heat treat it at 890℃ for 3 hours. Then crush it and sieve it through a 500-mesh sieve to obtain the negative electrode material.

[0227] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, and fluorine doped into the carbon material and silicon powder. The median particle size of the negative electrode material is 13 μm, and the specific surface area is 6.2 m². 2 / g, the average thickness of the carbon layer is 559nm; the fluorine content of the aggregate is 600ppm; the Raman spectrum of the carbon material obtained by Raman spectroscopy using a measuring light source with a wavelength of 532nm is shown at 1530cm. -1 Up to 1630cm -1 The observed G-band and at 1280 cm -1 Up to 1380cm -1 The observed D band, and the peak intensity I of the D band. D Peak intensity I of G band G The ratio between I D / I G It is 2.01.

[0228] The aggregate particles were tested using mercury porosimetry, revealing a porosity of 10.6%. Nanoindentation was used to test the aggregate particles, yielding an average compressive hardness of 45 MPa. The tested density of the aggregate differed from the average density of silicon powder and carbon materials by 2.1%.

[0229] Example 2

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

[0231] 1) Silica particles with a median particle size of 70 nm were dispersed in an ethanol solution (volume percentage concentration of 40%), and then triethylmethoxymethylammonium fluoride and sucrose were added and mixed evenly. The mass ratio of silica particles, tetrabutyl fluoroborate and glucose was 39:1.3:38.4. The mixture was then dried at 200 °C for 3.5 h to obtain the precursor.

[0232] 2) Place the precursor in a heat treatment furnace, introduce argon gas, raise the temperature to 920℃, and react for 4 hours to obtain aggregates;

[0233] 3) After the aggregate is crushed, the aggregate and phenolic resin are mixed at a mass ratio of 30:40, stirred and dispersed evenly, and then dried. The dried material is then added to a high-temperature box furnace, nitrogen is introduced, and it is heat-treated at 890℃ for 3 hours. After that, it is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0234] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, and fluorine doped into the carbon material and silicon powder. The median particle size of the negative electrode material is 12.1 μm, and the specific surface area is 3.2 m². 2 / g, the average thickness of the carbon layer is 739nm, and the fluorine content of the aggregate is 920ppm; the Raman spectrum of the carbon material obtained by Raman spectroscopy using a measuring light source with a wavelength of 532nm is shown at 1530cm.-1 Up to 1630cm -1 The observed G-band and at 1280 cm -1 Up to 1380cm -1 The observed D band, and the peak intensity I of the D band. D Peak intensity I of G band G The ratio between I D / I G It is 1.99.

[0235] Example 3

[0236] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0237] 1) Disperse silicon particles with a median particle size of 30 nm in ethylene glycol, then sonicate for 10 min, add 1.5 wt% H2O2 additive, sonicate for 20 min, dry, and mix with LiF and fructose to obtain a precursor; wherein the mass ratio of silicon particles, LiF and fructose is 30:3:35.

[0238] 2) Place the precursor in a heat treatment furnace, introduce argon gas, raise the temperature to 800℃, and react for 5 hours to obtain aggregates;

[0239] 3) Then, the aggregate and asphalt are mixed at a mass ratio of 40:35, stirred and dispersed evenly, and then dried at 100°C for 5 hours. After that, the dried material is added to a high-temperature box furnace, nitrogen is introduced, and it is heat-treated at 900°C for 2 hours. Then, it is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0240] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, and fluorine doped into the carbon material and silicon powder. The median particle size of the negative electrode material is 12.1 μm, and the specific surface area is 5.2 m². 2 / g, with an average carbon layer thickness of 5.7nm, and a fluorine content of 1030ppm in the aggregates, the carbon material is shown in the Raman spectrum obtained by Raman spectroscopy using a measuring light source with a wavelength of 532nm at 1530cm. -1 Up to 1630cm -1 The observed G-band and at 1280 cm -1 Up to 1380cm -1 The observed D band, and the peak intensity I of the D band. D Peak intensity I of G band G The ratio between I D / I G It is 1.94.

[0241] Example 4

[0242] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0243] 1) Disperse silicon particles with a median particle size of 80 nm in propanol, then sonicate for 10 min, then add MgF2 and glucose and mix evenly. The mass ratio of silicon particles, MgF2 and pitch is 45:1.3:33.5. After drying at 250℃ for 2 h, the precursor is obtained.

[0244] 2) Place the precursor in a heat treatment furnace, introduce argon gas, heat to 900℃, and react for 3 hours to obtain aggregates.

[0245] 3) Then, the aggregate and asphalt are mixed at a mass ratio of 40:37, stirred and dispersed evenly, and then dried at 250°C for 2 hours. Subsequently, the dried material is added to a high-temperature box furnace, nitrogen is introduced, and it is heat-treated at 800°C for 3 hours. After that, it is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0246] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, and fluorine doped into the carbon material and silicon powder. The median particle size of the negative electrode material is 9.1 μm, and the specific surface area is 4.2 m². 2 / g, with an average carbon layer thickness of 5.7nm, and a fluorine content of 590ppm in the aggregates, the carbon material is shown in the Raman spectrum obtained by Raman spectroscopy using a measuring light source with a wavelength of 532nm at 1530cm. -1 Up to 1630cm -1 The observed G-band and at 1280 cm -1 Up to 1380cm -1 The observed D band, and the peak intensity I of the D band. D Peak intensity I of G band G The ratio between I D / I G It is 2.05.

[0247] Example 5

[0248] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0249] 1) Disperse silicon particles with a median particle size of 20 nm in butanol, then add tetrabutylammonium fluoride and polyvinyl chloride and mix evenly. The mass ratio of silicon particles, tetrabutylammonium fluoride and polyvinyl chloride is 30:0.9:33.5. After drying at 300℃ for 1 h, the precursor is obtained.

[0250] 2) Place the precursor in a heat treatment furnace, introduce argon gas, raise the temperature to 880℃, and react for 3 hours to obtain aggregates;

[0251] 3) Then, the aggregate and phenolic resin are mixed in a mass ratio of 55:65, stirred and dispersed evenly, and then dried. The dried material is then added to a high-temperature box furnace, nitrogen is introduced, and the material is heat-treated at 800°C for 3 hours. After that, it is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0252] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, and fluorine doped into the carbon material and silicon powder. The median particle size of the negative electrode material is 15.1 μm, and the specific surface area is 2.2 m². 2 / g, the average thickness of the carbon layer is 667nm; the fluorine content of the aggregate is 15060ppm. The Raman spectrum of the carbon material obtained by Raman spectroscopy using a measuring light source with a wavelength of 532nm is shown at 1530cm⁻¹. -1 Up to 1630cm -1 The observed G-band and at 1280 cm -1 Up to 1380cm -1 The observed D band, and the peak intensity I of the D band. G Peak intensity I of G band D The ratio between I D / I G It is 1.85.

[0253] Example 6

[0254] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0255] 1) Disperse silicon particles with a median particle size of 120 nm in n-pentanol, then add ammonium fluoroborate and glucose and mix evenly. The mass ratio of silicon particles, ammonium fluoroborate and glucose is 30:2.0:48.5. After drying at 300℃ for 1 h, the precursor is obtained.

[0256] 2) Place the precursor in a heat treatment furnace, introduce argon gas, heat to 980℃, and react for 3 hours to obtain aggregates.

[0257] 3) Then, the aggregate and phenolic resin are mixed in a mass ratio of 44:50, stirred and dispersed evenly, and then dried. The dried material is then added to a high-temperature box furnace, nitrogen is introduced, and it is heat-treated at 900℃ for 3 hours. After that, it is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0258] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, and fluorine doped into the carbon material and silicon powder. The median particle size of the negative electrode material is 10.1 μm, and the specific surface area is 2.0 m². 2 / g, with an average carbon layer thickness of 967nm; the fluorine content of the aggregates is 9620ppm. The Raman spectrum of the carbon material obtained by Raman spectroscopy using a measuring light source with a wavelength of 532nm is shown at 1530cm⁻¹. -1 Up to 1630cm -1 The observed G-band and at 1280 cm -1 Up to 1380cm -1 The observed D band, and the peak intensity I of the D band. D Peak intensity I of G band G The ratio between I D / I G It is 1.9.

[0259] Example 7

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

[0261] 1) Silicon particles with a median particle size of 50 nm were dispersed in an ethanol solution (volume percentage concentration of 40%), and then triethylmethoxymethylammonium fluoride and phenolic resin were added and mixed evenly. The mass ratio of silicon particles, triethylmethoxymethylammonium fluoride and phenolic resin was 50:4.3:24.5. Then, the mixture was dried at 150°C for 5 hours to obtain the precursor.

[0262] 2) Place the precursor in a fusion machine at a speed of 500 r / min. The blade gap width of the fusion machine used for mechanical fusion is 0.05 cm, and the mechanical fusion time is 0.5 h. Place the fused material in a heat treatment furnace and then introduce argon gas at 900℃ for a heat treatment, hold for 3 h, and obtain aggregates.

[0263] 3) Mix the aggregate and asphalt at a mass ratio of 40:30, stir and disperse evenly, and then dry them at 150℃ for 5 hours. Add the dried material to a high-temperature box furnace, introduce nitrogen, and heat treat it at 890℃ for 3 hours. Then crush it and sieve it through a 500-mesh sieve to obtain the negative electrode material.

[0264] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, and fluorine doped into the carbon material and silicon powder. The median particle size of the negative electrode material is 13 μm, and the specific surface area is 6.2 m². 2The aggregate has a density of / g, an average carbon layer thickness of 559nm, and a fluorine content of 600ppm. The porosity of the aggregate particles was 4.4% when tested using mercury porosimetry. The average compressive hardness of the aggregate was 223MPa when tested using a nanoindenter. The density difference between the aggregate and the average density of the silicon powder and carbon materials was 2.1%.

[0265] Example 8

[0266] The method for preparing the negative electrode material in this embodiment includes the following steps:

[0267] 1) Disperse Ge particles with a median particle size of 20 nm in butanol, then add tetrabutylammonium fluoride and polyvinyl chloride and mix evenly. The mass ratio of Ge particles, tetrabutylammonium fluoride and polyvinyl chloride is 100:20:50. After drying at 300℃ for 1 h, the precursor is obtained.

[0268] 2) Place the precursor in a fusion machine with a rotation speed of 1500 r / min, a blade gap width of 0.3 cm, and a fusion time of 1 h; place the fused material in a heat treatment furnace, then introduce nitrogen gas and perform a heat treatment at 900℃ for 3 h to obtain aggregates;

[0269] 3) Mix the aggregate and asphalt at a mass ratio of 50:10, stir and disperse evenly, and then dry them at 150℃ for 5 hours. Add the dried material to a high-temperature box furnace, introduce nitrogen, and heat treat it at 890℃ for 3 hours. Then crush it and sieve it through a 500-mesh sieve to obtain the negative electrode material.

[0270] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, and fluorine doped into the carbon material and silicon powder. The median particle size of the negative electrode material is 12 μm, and the specific surface area is 5.9 m². 2 The aggregate has a density of / g and an average carbon layer thickness of 102nm; the fluorine content is 8040ppm; the porosity of the aggregate particles was tested using mercury porosimetry, and the average compressive hardness was 4.3%; the average compressive hardness of the aggregate particles was tested using a nanoindenter, and the average compressive hardness was 198MPa. The density of the aggregate differs from the average density of the silicon powder and carbon materials by 1.8%.

[0271] Example 9

[0272] The difference between this embodiment and Embodiment 1 is that step 1) is different, and an additive is added in step 1).

[0273] The specific step 1) involves dispersing silicon particles with a median particle size of 50 nm in an ethanol solution (volume percentage concentration of 40%), then adding triethylmethoxymethylammonium fluoride, phenolic resin, and lauric acid and mixing them evenly. The mass ratio of silicon particles, triethylmethoxymethylammonium fluoride, phenolic resin, and lauric acid is 50:4.3:24.5:3.3. The mixture is then dried at 150°C for 5 hours to obtain the precursor.

[0274] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, and fluorine doped into the carbon material and silicon powder. The median particle size of the negative electrode material is 13 μm, and the specific surface area is 6.2 m². 2 The aggregate has a density of / g, an average carbon layer thickness of 559nm, and a fluorine content of 602ppm. The porosity of the aggregate particles was 11.5% when tested using mercury porosimetry. The average compressive hardness of the aggregate was 69MPa when tested using a nanoindenter. The density difference between the aggregate and the average density of the silicon powder and carbon materials was 2.6%.

[0275] Example 10

[0276] The difference between this embodiment and embodiment 7 is that step 1) is different, and an additive is added in step 1).

[0277] The specific step 1) involves dispersing silicon particles with a median particle size of 50 nm in an ethanol solution (volume percentage concentration of 40%), then adding triethylmethoxymethylammonium fluoride, phenolic resin, and γ-aminopropyltriethoxysilane and mixing them evenly. The mass ratio of silicon particles, triethylmethoxymethylammonium fluoride, phenolic resin, and γ-aminopropyltriethoxysilane is 50:4.3:24.5:3.3. Then, the mixture is dried at 150°C for 5 hours to obtain the precursor.

[0278] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, and fluorine doped into the carbon material and silicon powder. The median particle size of the negative electrode material is 13 μm, and the specific surface area is 6.2 m². 2 The aggregate has a density of / g and an average carbon layer thickness of 559nm; the fluorine content is 605ppm; the porosity of the aggregate particles is 3.6% as determined by mercury porosimetry; and the average compressive hardness of the aggregate is 365MPa as determined by nanoindentation. The density of the aggregate differs from the average density of the silicon powder and carbon materials by 2.2%.

[0279] Example 11

[0280] The difference between this embodiment and Embodiment 1 is that step 1) is different, in which a metal oxide is added.

[0281] The specific step 1) involves dispersing silicon particles with a median particle size of 50 nm in an ethanol solution (volume percentage concentration of 40%), then adding triethylmethoxymethylammonium fluoride, phenolic resin, and GeO2 particles with an aspect ratio of 12 and mixing them evenly. The mass ratio of silicon particles, triethylmethoxymethylammonium fluoride, phenolic resin, and GeO2 particles is 50:4.3:24.5:1.9. Then, the mixture is dried at 150°C for 5 hours to obtain the precursor.

[0282] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, GeO2 particles, carbon material, and fluorine doped into the carbon material, GeO2 particles, and silicon powder. The median particle size of the negative electrode material is 13 μm, and the specific surface area is 6.2 m². 2 The aggregate has a density of / g, an average carbon layer thickness of 559nm, and a fluorine content of 601ppm. The aggregate porosity was 10.2% when tested using mercury porosimetry. The average compressive hardness of the aggregate was 78MPa when tested using a nanoindenter. The density difference between the aggregate and the average density of silicon powder and carbon materials was 2.3%, and the minimum spacing between metal oxides was 26nm.

[0283] Example 12

[0284] The difference between this embodiment and embodiment 7 is that step 1) is different, in which a metal oxide is added.

[0285] Step 1) Specifically, 1) Silicon particles with a median particle size of 50 nm are dispersed in an ethanol solution (volume percentage concentration of 40%), and then triethylmethoxymethylammonium fluoride, phenolic resin, and ZnO particles with an aspect ratio of 8 are added and mixed evenly. The mass ratio of silicon particles, triethylmethoxymethylammonium fluoride, phenolic resin, and ZnO particles is 50:4.3:24.5:3.6. Then, the product is dried at 150°C for 5 hours to obtain the precursor.

[0286] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, ZnO particles, and fluorine doped into the carbon material, silicon powder, and ZnO particles. The median particle size of the negative electrode material is 13 μm, and the specific surface area is 6.2 m². 2The aggregate has a density of / g, an average carbon layer thickness of 559nm, and a fluorine content of 608ppm. The aggregate porosity was 5.0% when tested using mercury porosimetry. The average compressive hardness of the aggregate was 284MPa when tested using a nanoindenter. The density difference between the aggregate and the average density of silicon powder and carbon materials was 1.9%. The minimum spacing between the metal oxide particles was 106nm.

[0287] Example 13

[0288] The difference between this embodiment and Embodiment 1 is that step 1) is different, in which a conductivity enhancer is added.

[0289] The specific step 1) involves dispersing silicon particles with a median particle size of 50 nm in an ethanol solution (volume percentage concentration of 40%), then adding triethylmethoxymethylammonium fluoride, phenolic resin, and carbon nanotubes (CNTs) with a diameter of 20 nm and mixing them evenly. The mass ratio of silicon particles, triethylmethoxymethylammonium fluoride, phenolic resin, and CNTs is 50:4.3:24.5:0.5. Then, the mixture is dried at 150°C for 5 hours to obtain the precursor.

[0290] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, CNTs, carbon material, and fluorine doped into the carbon material, CNTs, and silicon powder. The median particle size of the negative electrode material is 13 μm, and the specific surface area is 6.2 m². 2 The aggregate has a density of / g, an average carbon layer thickness of 559nm, and a fluorine content of 600ppm. The aggregate porosity was 10.7% when tested using mercury porosimetry. The average compressive hardness of the aggregate was 62MPa when tested using a nanoindenter. The density difference between the aggregate and the average density of the silicon powder and carbon material was 3.6%.

[0291] Example 14

[0292] The difference between this embodiment and embodiment 7 is that step 1) is different, in which a conductivity enhancer is added.

[0293] Step 1) Specifically, 1) Silicon particles with a median particle size of 50 nm are dispersed in an ethanol solution (volume percentage concentration of 40%), and then triethylmethoxymethylammonium fluoride, phenolic resin, and FeSi2 with an aspect ratio of 18 are added and mixed evenly. The mass ratio of silicon particles, triethylmethoxymethylammonium fluoride, phenolic resin, and FeSi2 is 50:4.3:24.5:2.1. Then, the product is dried at 150°C for 5 hours to obtain the precursor.

[0294] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, FeSi2, carbon material, and fluorine doped into the carbon material, FeSi2, and silicon powder. The median particle size of the negative electrode material is 13 μm, and the specific surface area is 6.2 m². 2 The aggregate has a density of / g and an average carbon layer thickness of 559nm; the fluorine content is 610ppm; the porosity of the aggregate particles was tested using mercury porosimetry, and the average compressive hardness was 4.5%; the average compressive hardness of the aggregate was tested using a nanoindenter, and the average compressive hardness was 205MPa. The density of the aggregate differs from the average density of the silicon powder and carbon materials by 1.2%.

[0295] Example 15

[0296] The difference between this embodiment and Embodiment 1 is that step 1) is different, in which a conductivity enhancer and a metal oxide are added.

[0297] The specific step 1) involves dispersing silicon particles with a median particle size of 50 nm in an ethanol solution (volume percentage concentration of 40%), then adding triethylmethoxymethylammonium fluoride, phenolic resin, SiO particles with an aspect ratio of 22, and CNTs with a diameter of 20 nm and mixing them evenly. The mass ratio of silicon particles, triethylmethoxymethylammonium fluoride, phenolic resin, SiO particles, and CNTs is 50:4.3:24.5:2.9:0.3. Then, the mixture is dried at 150°C for 5 hours to obtain the precursor.

[0298] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, SiO particles, CNTs, carbon materials, and fluorine elements doped into the carbon materials, SiO particles, CNTs, and silicon powder. The median particle size of the negative electrode material is 13 μm, and the specific surface area is 6.2 m². 2 The aggregate has a density of / g, an average carbon layer thickness of 559nm, and a fluorine content of 590ppm. The porosity of the aggregate particles was 12.9% when tested using mercury porosimetry. The average compressive hardness of the aggregate was 99MPa when tested using a nanoindenter. The density of the aggregate differs from the average density of the silicon powder and carbon materials by 2.1%.

[0299] Example 16

[0300] The difference between this embodiment and embodiment 7 is that step 1) is different, in which metal oxide and conductivity enhancer are added.

[0301] Step 1) Specifically, 1) Silicon particles with a median particle size of 50 nm are dispersed in an ethanol solution (volume percentage concentration 40%), and then triethylmethoxymethylammonium fluoride, phenolic resin, TiO2 particles with an aspect ratio of 17 and nickel-silicon alloy with an aspect ratio of 50 are added and mixed evenly. The mass ratio of silicon particles, triethylmethoxymethylammonium fluoride, phenolic resin, TiO2 particles and nickel-silicon alloy is 50:4.3:24.5:3.9:1.1. Then, drying is performed at a temperature of 150℃ for 5 hours to obtain the precursor.

[0302] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, TiO2 particles, nickel-silicon alloy, carbon material, and fluorine doped into the carbon material, TiO2 particles, nickel-silicon alloy, and silicon powder. The median particle size of the negative electrode material is 13 μm, and the specific surface area is 6.2 m². 2 The aggregate has a density of / g, an average carbon layer thickness of 559nm, and a fluorine content of 598ppm. The porosity of the aggregate particles was 10.9% when tested using mercury porosimetry. The average compressive hardness of the aggregate particles was 229MPa when tested using a nanoindenter. The density difference between the aggregate and the average density of the silicon powder and carbon material was 1.9%.

[0303] Example 17

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

[0305] 1) Al particles with a median particle size of 50 nm were dispersed in ethylene glycol and then sonicated for 10 min. After that, 1.5 wt% H2O2 additive was added and mixed evenly, and sonicated for 20 min. After drying, it was mixed with aluminum fluoride and fructose to obtain the precursor. The mass ratio of Al particles, LiF and fructose was 120:10:50.

[0306] 2) Place the precursor in a heat treatment furnace, introduce argon gas, heat to 950℃, and react for 1.5 hours to obtain aggregates;

[0307] 3) Then, the aggregate and asphalt are mixed at a mass ratio of 100:15, stirred and dispersed evenly, and then dried at 100°C for 5 hours. After that, the dried material is added to a high-temperature box furnace, nitrogen is introduced, and it is heat-treated at 900°C for 2 hours. Then, it is crushed and sieved through a 500-mesh sieve to obtain the negative electrode material.

[0308] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes Al powder, carbon material, and fluorine doped into the carbon material, Al powder, and silicon powder. The median particle size of the negative electrode material is 11 μm, and the specific surface area is 3.9 m². 2 / g, with an average carbon layer thickness of 98nm; the fluorine content of the aggregate is 2190ppm.

[0309] Example 18

[0310] The difference between this embodiment and Embodiment 1 is that carbon coating is not performed, i.e., step 3 is not included.

[0311] The negative electrode material prepared in this embodiment comprises an aggregate, which includes silicon powder, carbon material, and fluorine doped into the carbon material and silicon powder. The median particle size of the negative electrode material is 13 μm, and the specific surface area is 26.2 m². 2 / g; the fluorine content of the aggregates is 890ppm.

[0312] Example 19

[0313] The nano-silicon-based composite anode material was prepared using essentially the same method as in Example 5, except that the fluorine content in the aggregates was 20,000 ppm and the heat treatment temperature in step 2) was 980°C. Example I D / I G It is 1.5.

[0314] Example 20

[0315] The nano-silicon-based composite anode material was prepared using essentially the same method as in Example 5, except that the fluorine content in the aggregate was 21890 ppm, followed by heat treatment.

[0316] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, and fluorine. The mass ratio of silicon powder to carbon material is 63.0:37.0. The median particle size of the negative electrode material is 13.8 μm, and the specific surface area is 6.6 m². 2 / g, the average thickness of the carbon layer is 565nm; the fluorine content of the aggregate is 21890ppm. Example I D / I G It is 1.8.

[0317] Example 21

[0318] The nano-silicon-based composite anode material was prepared using essentially the same method as in Example 5, except that the fluorine content in the aggregates was 50 ppm and the heat treatment temperature in step 2) was 980°C. Example I D / I G It is 2.1.

[0319] Example 22

[0320] The nano-silicon-based composite anode material was prepared using essentially the same method as in Example 5, except that the fluorine content in the aggregate was 39 ppm, followed by heat treatment.

[0321] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder, carbon material, and fluorine. The mass ratio of silicon powder to carbon material is 62.5:37.5. The median particle size of the negative electrode material is 12.8 μm, and the specific surface area is 5.9 m². 2 / g, the average thickness of the carbon layer is 549nm; the fluorine content of the aggregate is 39ppm. Example I D / I G It is 2.31.

[0322] Example 23

[0323] Nano-silicon-based composite anode materials were prepared using essentially the same method as in Example 1, except that triphenylphosphine was used as the dopant, and the dopant content was the same as in Example 1. Example I D / I G It is 2.1.

[0324] Example 24

[0325] Nano-silicon-based composite anode materials were prepared using essentially the same method as in Example 1, except that tetraphenylphosphine bromide was used as the dopant, and the dopant content was the same as in Example 1. Example I D / I G It is 2.05.

[0326] Example 25

[0327] Nano-silicon-based composite anode materials were prepared using essentially the same method as in Example 1, except that lithium nitride was used as the dopant, and the doping element content was the same as in Example 1. Example I D / I G It is 1.9.

[0328] Example 26

[0329] Nano-silicon-based composite anode materials were prepared using essentially the same method as in Example 1, except that the dopant used was thiourea, and the dopant content was the same as in Example 1. Example I D / I G It is 1.85.

[0330] Comparative Example 1

[0331] The nano-silicon-based composite anode material was prepared using a method essentially the same as that in Example 1, except that no fluoride was added before direct mixing and subsequent heat treatment.

[0332] The negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coating the surface of the aggregate. The aggregate includes silicon powder and carbon material, with a mass ratio of silicon powder to carbon material of 63.3:36.7. The median particle size of the negative electrode material is 13.5 μm, and the specific surface area is 6.3 m². 2 / g, with an average carbon layer thickness of 561nm; the fluorine content of the aggregates was 0ppm. This comparative example's I... D / I G It is 2.5.

[0333] Performance testing

[0334] The electrochemical cycle performance was tested using the following method: The negative electrode materials, conductive agent, and binder prepared in Examples 1-26 and Comparative Example 1 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 a negative electrode sheet was obtained. Then, a ternary positive electrode sheet prepared using conventional mature processes, a 1 mol / L LiPF6 / ethyl cellulose + dimethyl carbonate + methyl ethyl carbonate (v / v = 1:1:1) electrolyte, a Celgard 2400 separator, and a casing were assembled into an 18650 cylindrical cell using conventional manufacturing processes. The charge-discharge tests of the cylindrical cells were conducted on the LAND battery testing system of Wuhan Jinno Electronics Co., Ltd., under room temperature conditions, with a constant current charge-discharge of 0.2C and a charge-discharge voltage limited to 2.75–4.2V, obtaining the initial reversible capacity, the first charge capacity, and the first discharge capacity. The initial coulombic efficiency was calculated as: first discharge capacity / first charge capacity.

[0335] 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%.

[0336] Repeat the cycle 100 times and record the discharge capacity as the remaining capacity of the lithium-ion battery; capacity retention rate = remaining capacity / initial capacity * 100%.

[0337] The results of the above performance tests are as follows:

[0338] Table 1. Performance Comparison Results

[0339]

[0340]

[0341] As shown in Table 1, the negative electrode materials prepared in Examples 1 to 26 can obtain carbon materials with a higher degree of graphitization by adding doping elements to the aggregates, thereby improving the conductivity of the negative electrode materials, providing space for silicon expansion and reducing the volume expansion effect of silicon.

[0342] Example 19, with the addition of fluorine-containing components exceeding 20,000 ppm, showed inferior initial efficiency, expansion rate, and cycle life compared to the embodiments of the present invention, indicating performance degradation.

[0343] In Example 22, the addition of fluorine-containing components was less than 50 ppm, resulting in poor graphitization of the carbon material. Consequently, the electrode plate made from the prepared negative electrode active material had lower initial efficiency, expansion rate, and cycle life than the embodiment of the present invention, leading to performance degradation.

[0344] In Comparative Example 1, the anode material prepared without fluoride showed a decrease in both initial coulombic efficiency and cycle capacity retention.

[0345] The applicant declares that the detailed process equipment and process flow of this invention are illustrated through the above embodiments, but this invention is not limited to the above detailed process equipment and process flow, that is, it does not mean that this invention must rely on the above detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the products of this invention, additions of auxiliary components, and selection of specific methods, all fall within the protection scope and disclosure scope of this invention.

Claims

1. A negative electrode material, characterized in that, The invention comprises an aggregate and a carbon layer covering at least a portion of the surface of the aggregate. The aggregate includes an active material, a carbon material, and a dopant element, wherein at least one of the active material and the carbon material contains the dopant element. The carbon material has pores, and at least a portion of the active material fills the pores. The median particle size of the active material is 1 nm to 300 nm. The dopant element can induce the carbon material to generate Lewis acid active sites, and at least a portion of the active material binds to the carbon material through the Lewis acid active sites. The doping element is one of fluorine, nitrogen, and phosphorus, and the content of the doping element in the aggregate is 50 ppm to 20000 ppm; the Raman spectrum of the carbon material obtained by Raman spectroscopy using a measuring light source with a wavelength of 532 nm is shown at 1530 cm⁻¹. -1 Up to 1630cm -1 G-band was observed at 1280 cm. -1 Up to 1380cm -1 The D band was observed, and the peak intensity I of the D band was... D Peak intensity I of G band G The ratio between I D / I G It ranges from 1 to 2.

5.

2. The negative electrode material according to claim 1, characterized in that, Includes at least one of the following features (1) to (3): (1) The doping element is distributed on the surface and / or inside the active material; (2) The doping element is distributed on the surface and / or inside the carbon material; (3) The pore volume of the carbon material is ≥0.35 cm³. 3 / g.

3. The negative electrode material according to claim 1 or 2, characterized in that, It includes at least one of the following features (1) to (4): (1) The active substance includes active particles; (2) The active substances include Li, Na, K, Sn, Ge, Si, Fe, Mg, Ti, Zn, Al, P, Cu and SiO. x At least one of them, where 0 < x ≤ 2; (3) The carbon material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, carbon nanotubes, carbon fibers and graphene; (4) The mass ratio of the active substance to the carbon material is (90~10):(10~90).

4. The negative electrode material according to claim 1 or 2, characterized in that, The aggregate further includes a metal oxide, which contains at least one of the following characteristics (1) to (6): (1) At least a portion of the metal oxide fills the pores between the carbon materials; (2) 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; (3) The mass ratio of the active substance to the metal oxide is (30~100):(0.5~10); (4) The metal oxide is in the form of flakes and / or strips; (5) The aspect ratio of the metal oxide is greater than 2; (6) The shortest distance between the metal oxides is ≥100nm.

5. The negative electrode material according to claim 1 or 2, characterized in that, The aggregate further includes a conductivity enhancer, the conductivity enhancer comprising at least one of the following features (1) to (6): (1) At least a portion of the conductive reinforcing agent fills the pores between the carbon materials; (2) The conductive reinforcing agent includes at least one of alloy materials and conductive carbon; (3) The conductivity of the conductive enhancer is 10. 0 S / m ~10 8 S / m; (4) The conductive enhancer is in the form of sheets and / or strips; (5) The mass ratio of the conductive enhancer to the active substance is (0.01~15):(50~100); (6) The aspect ratio of the conductive reinforcing agent is 2 to 5000.

6. The negative electrode material according to claim 1 or 2, characterized in that, Includes at least one of the following features (1) to (10): (1) The material of the carbon layer includes amorphous carbon; (2) The thickness of the carbon layer is 10 nm to 5000 nm; (3) The negative electrode material further includes an oxide layer formed on at least a portion of the surface of the active material; (4) The negative electrode material further includes an oxide layer formed on at least a portion of the surface of the active material, the thickness of the oxide layer being 1 nm to 100 nm; (5) The negative electrode material further includes an oxide layer formed on at least a portion of the surface of the active material, the oxide layer having pores; (6) The median particle size of the negative electrode material is 0.5µm~30µm; (7) The specific surface area of ​​the negative electrode material is ≤10m². 2 / g; (8) The mass ratio of the aggregate to the carbon layer is (90-10):(10-90); (9) The porosity of the aggregate is ≤10%, and the compressive strength of the aggregate is ≥100MPa; (10) The aggregate density satisfies the following relationship: (p1-p2) / p2≤5%, where p1 is the test density of the aggregate, p2 is the average density of the aggregate, and p2 is the mass percentage of each component in the aggregate. The sum of the theoretical densities of all components.

7. A lithium-ion battery, characterized in that, The lithium-ion battery comprises the negative electrode material as described in any one of claims 1 to 6.

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