Negative electrode material, method for producing the same, and lithium ion battery

Abstract

The present application relates to a negative electrode material and a method for producing the same, and to a lithium ion battery. [Solution] The negative electrode material includes a core and a coating layer provided on at least a portion of the surface of the core, the core includes porous carbon and an active material filled into the porous carbon pore structure, the porous carbon has a first pore structure having a pore diameter of 2 nm or less and a second pore structure having a pore diameter of more than 2 nm, the ratio of the pore volume of the first pore structure to the total pore volume of the porous carbon is 40% or more, and the second pore structure has a filling rate of 95% or more, and the negative electrode material of the present application has the advantages of being able to effectively suppress volume expansion, high rate performance, high capacity, and good cycle performance.

Description

Technical Field

[0001] This application claims priority based on a Chinese patent application filed with the China National Intellectual Property Administration on June 29, 2022, with an application number of 2022107575432 and an application title of "Negative Electrode Material and Its Manufacturing Method, and Lithium-Ion Battery", and incorporates all of its content herein by reference.

[0002] This application relates to the technical field of negative electrode materials, and specifically, particularly relates to negative electrode materials and their manufacturing methods, and lithium-ion batteries.

Background Art

[0003] Silicon is the second most abundant element in the earth's crust, is a common semiconductor material, and has already become an important technical foundation indispensable to modern high-tech society. Monolithic silicon is widely used in aspects such as energy, semiconductors, silicone, and metallurgical industries, and plays an important role. Currently, the negative electrode materials of mature commercial lithium-ion batteries are mainly graphite-based carbon materials, but the theoretical lithium storage capacity of carbon materials is only 372 mAh / g, which cannot meet the demand for high-energy density materials. Silicon, as a negative electrode material for lithium-ion batteries, has a high theoretical capacity (about 4200 mAh / g), has a capacity 10 times that of commercial graphite, and has great potential in terms of energy storage.

[0004] Currently, due to the rapid volume expansion effect existing in the silicon negative electrode material during the cycling process, it ultimately causes pulverization and fragmentation of the material and serious attenuation of the battery's cycle performance. Therefore, how to manufacture a negative electrode material with high capacity and excellent cycle performance is a difficult problem in the field of lithium-ion batteries.

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of the above, the present application provides a negative electrode material with high conductivity, which can effectively suppress volume expansion, improve the capacity performance and cycle performance of the negative electrode material, and a method for manufacturing the same, as well as a lithium-ion battery.

[0006] In a first aspect, the present application provides a negative electrode material, comprising a core and a coating layer provided on at least a part of the surface of the core, wherein the core comprises porous carbon and an active material filled in the pore structure of the porous carbon, the porous carbon has a first pore structure with a pore diameter of 2 nm or less and a second pore structure with a pore diameter greater than 2 nm, the ratio of the pore volume of the first pore structure to the total pore volume of the porous carbon is 40% or more, and the second pore structure provides a negative electrode material with a filling rate of 95% or more.

[0007] In some alternative embodiments, the negative electrode material further comprises an active material distributed between the porous carbons.

[0008] In some alternative embodiments, the median diameter D1 of the porous carbon and the median diameter D2 of the active material satisfy the condition of 0.4 ≦ D1 / D2 ≦ 6.

[0009] In some alternative embodiments, the median diameter D1 of the porous carbon and the median diameter D2 of the active material satisfy the condition of 0.5 ≦ D1 / D2 ≦ 4.5.

[0010] In some alternative embodiments, the active material has a median diameter of 1 nm to 300 nm.

[0011] In some alternative embodiments, the active material has a morphology including at least one of rod-like, spherical, ellipsoidal, and sheet-like.

[0012] In some alternative embodiments, the active material comprises at least one of Li, Na, K, Sn, Ge, Si, SiOx (0 < x < 2), Fe, Mg, Ti, Zn, Al, Ni, P, and Cu.

[0013] In some alternative embodiments, the porous carbon includes at least one of carbon black, a regular mesoporous carbon material, and a nanoporous carbon material.

[0014] In some alternative embodiments, the porous carbon has a median diameter of 1 nm to 500 nm.

[0015] In some alternative embodiments, the core has a median diameter of 0.8 μm to 10 μm.

[0016] In some alternative embodiments, the coating layer includes at least one of a carbon layer, a metal oxide layer, a polymer layer, and a nitride layer.

[0017] In some alternative embodiments, the carbon layer includes at least one of soft carbon, crystalline carbon, amorphous carbon, and hard carbon.

[0018] In some alternative embodiments, the metal oxide layer includes at least one of oxides of Sn, Ge, Fe, Si, Cu, Ti, Na, Mg, Al, Ca, and Zn.

[0019] In some alternative embodiments, the nitride layer includes at least one of silicon nitride, aluminum nitride, titanium nitride, and tantalum nitride.

[0020] In some alternative embodiments, the coating layer has a thickness of 10 nm to 500 nm.

[0021] In some alternative embodiments, the polymer layer includes at least one of polyaniline, polyacrylic acid, polyurethane, polydopamine, polyacrylamide, sodium carboxymethyl cellulose, polyimide, and polyvinyl alcohol.

[0022] In some alternative embodiments, the negative electrode material has a specific surface area of 10 m 2 / g or less.

[0023] In some alternative embodiments, the negative electrode material has a median diameter of 0.5 μm to 20 μm.

[0024] In some alternative embodiments, the negative electrode material has a porosity of 10% or less.

[0025] In a second aspect, an embodiment of the present application provides a method for manufacturing a negative electrode material,

[0026] mixing a raw material containing porous carbon and an active material in a vacuum to obtain a precursor, wherein the porous carbon has a first pore structure with a pore diameter of 2 nm or less and a second pore structure with a pore diameter greater than 2 nm, and the ratio of the pore volume of the first pore structure to the total pore volume of the porous carbon is 40% or more, the filling rate of the second pore structure is 95% or more, and the vacuum mixing includes a step with a vacuum degree of 10 Pa or less,

[0027] and a step of coating the precursor to obtain a negative electrode material.

[0028] In some alternative embodiments, the median diameter D1 of the porous carbon and the median diameter D2 of the active material satisfy the condition of 0.4 ≦ D1 / D2 ≦ 6.

[0029] In some alternative embodiments, the median diameter D1 of the porous carbon and the median diameter D2 of the active material satisfy the condition of 0.5 ≦ D1 / D2 ≦ 4.5.

[0030] In some alternative embodiments, the active material has a median diameter of 1 nm to 300 nm.

[0031] In some alternative embodiments, the active material contains at least one of Li, Na, K, Sn, Ge, Si, SiOx (0 < x < 2), Fe, Mg, Ti, Zn, Al, Ni, P, and Cu.

[0032] In some alternative embodiments, the porous carbon includes at least one of carbon black, regular mesoporous carbon material, and nanoporous carbon.

[0033] In some alternative embodiments, the porous carbon has a median diameter of 1 nm to 500 nm.

[0034] In some alternative embodiments, the mass ratio of the porous carbon to the active material is 40:(10 - 80).

[0035] In some alternative embodiments, before vacuum mixing the raw materials including the porous carbon and the active material, it further includes the step of adding an auxiliary agent and a solvent.

[0036] In some alternative embodiments, the auxiliary agent includes at least one of polyvinyl alcohol, n-octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecylbenzenesulfonate, n-eicosanoic acid, palmitic acid, myristic acid, undecylic acid, fatty acid, cetyltrimethylammonium bromide, and polyvinylpyrrolidone.

[0037] In some alternative embodiments, the solvent includes at least one of phenol, methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, n-hexane, cyclohexane, ethyl acetate, chloroform, carbon tetrachloride, methyl acetate, acetone, and pentanol.

[0038] In some alternative embodiments, the mass ratio of the auxiliary agent to the porous carbon is (0.05 - 3):100.

[0039] In some alternative embodiments, the mass ratio of the solvent to the porous carbon is 100:(15 - 55).

[0040] In some alternative embodiments, the vacuum mixing includes at least one of a twin-screw planetary vacuum mixer, a planetary vacuum mixer, a planetary vacuum disperser, a ribbon vacuum mixer, a multi-functional vacuum mixer, a vacuum disperser, and a vacuum emulsifier.

[0041] In some alternative embodiments, after the vacuum mixing, a drying treatment is further performed, and the vacuum mixing is carried out for a time of 0.5 hour to 15 hours.

[0042] In some alternative embodiments, after the vacuum mixing, a drying treatment is further performed, and the drying treatment is carried out at a temperature of -50°C to 500°C.

[0043] In some alternative embodiments, after the vacuum mixing, a drying treatment is further performed, and the drying treatment is carried out for a time of 0.5 hour to 15 hours.

[0044] In some alternative embodiments, after the vacuum mixing, a drying treatment is further performed, and the drying treatment includes at least one of a rotary evaporator, a vacuum oven, a spray dryer, a heat treatment furnace, and a freeze dryer.

[0045] In some alternative embodiments, the step of coating the precursor to obtain the negative electrode material specifically includes mixing the precursor and the coating material and performing heat treatment.

[0046] In some alternative embodiments, the coating material includes at least one of a carbon material, a metal oxide material, a polymer material, and a nitride material.

[0047] In some alternative embodiments, the carbon material includes at least one of soft carbon, hard carbon, crystalline carbon, and amorphous carbon.

[0048] In some alternative embodiments, the metal oxide material includes at least one of oxides of Sn, Ge, Fe, Si, Cu, Ti, Na, Mg, Al, Ca, and Zn.

[0049] In some alternative embodiments, the nitride material includes at least one of silicon nitride, aluminum nitride, titanium nitride, and tantalum nitride.

[0050] In some alternative embodiments, the coating material includes at least one of a carbon material, a metal oxide material, a polymer material, and a nitride material, and the polymer material includes at least one of polyaniline, polyacrylic acid, polyurethane, polydopamine, polyacrylamide, sodium carboxymethyl cellulose, polyimide, and polyvinyl alcohol.

[0051] In some alternative embodiments, the Precursor mass ratio of... to the coating material is 100:(5 - 100).

[0052] In some alternative embodiments, the heat treatment is at a temperature of 400°C to 900°C.

[0053] In some alternative embodiments, the heat treatment has a heat preservation time of 1 hour to 12 hours.

[0054] In some alternative embodiments, the heat treatment has a heating rate of 1°C / min to 15°C / min.

[0055] In some alternative embodiments, the heat treatment is carried out in a protective atmosphere, and the protective atmosphere includes at least one of nitrogen gas, helium gas, neon gas, argon gas, and krypton gas.

[0056] In some alternative embodiments, the Precursor further includes a step of pulverizing and sieving the obtained material after mixing... and the coating material and performing heat treatment.

[0057] In some alternative embodiments, the pulverizing device includes at least one of a mechanical pulverizer, a pneumatic pulverizer, and a crusher.

[0058] In some alternative embodiments, the sieving has a screen mesh size of 10 mesh to 800 mesh.

[0059] In a third aspect, an embodiment of the present application provides a lithium-ion battery, including the negative electrode material described in the first aspect or the negative electrode material manufactured by the manufacturing method described in the second aspect.

[0060] The technical means of the present application has at least the following beneficial effects.

[0061] The core of the negative electrode material of the present application includes porous carbon and an active material. The first pore structure of the porous carbon is micropores (average pore diameter is 2 nm or less), and the micropores with a volume occupancy rate of 40% or more provide a separate space for the expansion of the active material, effectively alleviating the volume expansion, and avoiding or reducing the pulverization of the negative electrode material due to huge volume changes and stress during the process of lithium insertion and extraction. The second pore structure of the porous carbon is pores with a pore diameter larger than 2 nm. By filling the active material into the second pore structure of the porous carbon, the filling rate of the second pore structure is made 95% or more, improving the material capacity. At the same time, it avoids stress concentration caused by the material and the problem of electrolyte penetration, retains an appropriate number of small pores in the negative electrode material, avoids pores with too large a pore diameter, and due to the synergistic effect of the two types of pore structures, the negative electrode material of the present application has the advantages of effectively suppressing volume expansion, high rate performance, high capacity, and good cycle performance. In the negative electrode material of the present application, the coating layer provided on at least a part of the surface of the core reduces the direct contact between the active material and the electrolyte in the core, reduces the occurrence of side reactions between the negative electrode material and the electrolyte, thereby improving the specific capacity of the negative electrode material, further suppressing the volume expansion of the negative electrode material, improving the conductivity of the negative electrode material, simultaneously improving the transmission efficiency of lithium ions, and being advantageous for improving the rate performance and cycle performance of the negative electrode material.

[0062] The manufacturing method of the negative electrode material of this application obtains a precursor by vacuum mixing a raw material containing porous carbon and an active material. Among them, the porous carbon raw material contains a pore structure with two types of pore diameters. Here, the first pore structure of the porous carbon is micropores (pore diameter is 2 nm or less), and the second pore structure of the porous carbon is pores with a pore diameter larger than 2 nm. This application fills the active material into the larger second pore structure of the porous carbon by means of vacuum mixing, and under a vacuum pressure of 10 Pa or less, the filling rate of the second pore structure reaches 95% or more. The existence of the second pore structure avoids stress concentration and electrolyte penetration problems in the material. Finally, coating the precursor can, on the one hand, avoid the decrease in the initial Coulomb efficiency and specific capacity caused by the electrolyte entering the negative electrode material and causing side reactions, and on the other hand, relieve the volume expansion of the active material, Negative electrode material reduce the overall volume expansion, and reduce the swelling of the electrode sheet. The manufacturing method of this application is simple. By selecting porous carbon with a specific pore structure and a specific size, the active material is filled into the second pore structure inside the porous carbon, effectively suppressing volume expansion, and further improving the rate performance, specific capacity, and cycle performance of the negative electrode material.

Brief Description of the Drawings

[0063] Hereinafter, this application will be further described with reference to the drawings and examples.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0064] To better understand the technical solution of this application, the following will describe the embodiments of this application in detail with reference to the accompanying drawings.

[0065] It should be clear that the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative work are included in the protection scope of this application.

[0066] The terms used in the embodiments of this application are only for the purpose of explaining specific embodiments and are not intended to limit this application. The singular forms "one", "the foregoing" and "said" used in the embodiments and claims of this application are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0067] It should be understood that the term "and / or" used in this specification only explains the relationship of the related objects and indicates that three types of relationships are possible. For example, A and / or B can indicate three situations: A exists alone, A and B exist simultaneously, and B exists alone. Also, the character " / " in this specification generally indicates that the related objects before and after are in an "or" relationship.

[0068] Embodiments of the present application provide a negative electrode material. As shown in FIG. 1, the negative electrode material includes a core 1 and a coating layer 2 provided on at least a part of the surface of the core 1. As shown in FIG. 2, the core 1 includes porous carbon 11 and an active material 12 filled in the pore structure of the porous carbon 11. Here, the porous carbon 11 has a first pore structure 111 with a pore diameter of 2 nm or less and a second pore structure 112 with a pore diameter greater than 2 nm. The ratio of the pore volume of the first pore structure 111 to the total pore volume of the porous carbon 11 is 40% or more, and the filling rate of the second pore structure 112 is 95% or more.

[0069] In the above solution, the core 1 of the negative electrode material of the present application includes porous carbon 11 and an active material 12. The porous carbon 11 includes two types of pore structures with different pore diameters. Among them, the first pore structure 111 of the porous carbon 11 is micropores (pore diameter of 2 nm or less), and the micropores with a volume occupancy rate of 40% or more provide a separate space for the expansion of the active material 12, effectively relieve the volume expansion, and avoid or reduce the pulverization of the negative electrode material due to huge volume changes and stresses during the process of lithium insertion and extraction. The second pore structure 112 of the porous carbon 11 is pores with a pore diameter greater than 2 nm. Since the second pore structure is likely to cause stress concentration and electrolyte penetration, it is necessary to fill the second pore structure as much as possible. The active material 12 is filled in the second pore structure 112 of the porous carbon 11, and the filling rate of the active material in the second pore structure 112 is 95% or more, which can improve the material capacity, and at the same time reduce the problems of stress concentration and electrolyte penetration caused by the second pore structure, retain an appropriate number of small pores in the negative electrode material, reduce pores with too large pore diameters, and the synergistic effect of the two types of pore structures enables the negative electrode material of the present application to effectively suppress volume expansion, and has the advantages of high rate performance, high capacity, and good cycle performance. In the negative electrode material of the present application, the coating layer provided on at least a part of the surface of the core reduces the direct contact between the active material in the core and the electrolyte, reduces the occurrence of side reactions between the negative electrode material and the electrolyte, thereby improving the specific capacity of the negative electrode material, further suppressing the volume expansion of the negative electrode material, improving the conductivity of the negative electrode material, and at the same time improving the transmission efficiency of lithium ions, which is advantageous for improving the rate performance and cycle performance of the negative electrode material.

[0070] In some embodiments, the porous carbon 11 has a first pore structure 111 with a pore diameter of 2 nm or less and a second pore structure 112 with a pore diameter greater than 2 nm. Specifically, the pore diameter of the first pore structure 111 may specifically be, for example, 0.05 nm, 0.07 nm, 0.1 nm, 0.3 nm, 0.5 nm, 0.8 nm, 1 nm, 1.5 nm, and 2 nm. Of course, other values within the above range may also be used and are not limited here. The pore diameter of the second pore structure 112 may specifically be, for example, 2.5 nm, 5 nm, 10 nm, 20 nm, 100 nm, 150 nm, 200 nm, 250 nm, and 300 nm. Of course, other values within the above range may also be used and are not limited here.

[0071] In the porous carbon of the present application, the first pore structure 111 is a pore with a pore diameter of 2 nm or less, and the second pore structure 112 is a pore with a pore diameter greater than 2 nm. The first pore structure 111 with a small pore diameter can effectively relieve the volume expansion of the active material 12, reduce the expansion of the electrode film, and improve the safety of the battery. The second pore structure 112 has a larger pore size than the first pore structure 111. The active material is filled in the second pore structure 112 with a large pore diameter, which can reduce stress concentration due to the second pore structure and the penetration of the electrolyte, and at the same time improve the capacity of the negative electrode material.

[0072] The ratio of the pore volume of the first pore structure 111 to the total pore volume of the porous carbon 11 may specifically be, for example, 40%, 45%, 50%, 55%, 60%, 65%, and 70%. Of course, other values within the above range may also be used and are not limited here. If the ratio of the pore volume of the first pore structure 111 is less than 40%, the volume expansion of silicon cannot be effectively relieved. The ratio of the pore volume of the first pore structure 111 to the total pore volume of the porous carbon 11 is preferably 45% or more.

[0073] The filling rate of the second pore structure 112 may specifically be, for example, 95%, 96%, 97%, 98%, 99%, etc. Of course, it may also be other values within the above range and is not limited here. If the filling rate of the second pore structure 112 is less than 95%, problems such as stress concentration in the material and penetration of the electrolyte are likely to occur. Note that the filling rate of the second pore structure 112 may be the filling rate of the active material 12 in the pores, may be the filling rate of the coating layer material and the active material in the pores, and preferably is the filling rate of the active material in the pores, which is advantageous for improving the capacity of the negative electrode material.

[0074] In some embodiments, as shown in FIG. 3, the negative electrode material further includes an active material 12 distributed among the porous carbon 11, that is, the active material 12 is filled in the pore structure of the porous carbon 11 and at the same time the active material 12 is also distributed among the porous carbon 11 particles.

[0075] In some embodiments, the median diameter D1 of the porous carbon 11 and the median diameter D2 of the active material 12 satisfy the condition of 0.4 ≤ D1 / D2 ≤ 6. For example, D1 / D2 may be 0.4, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 6, etc. Of course, it may also be other values within the above range, and is not limited here. By satisfying the condition of 0.4 ≤ D1 / D2 ≤ 6 for the median diameter D1 of the porous carbon 11 and the median diameter D2 of the active material 12, a core structure with good bonding between the active material 12 and the porous carbon 11 can be obtained. When the condition of 0.4 ≤ D1 / D2 ≤ 1 is satisfied, most of the active material 12 is uniformly distributed between the porous carbons 11 and indirectly contacts through the porous carbon 11 as a buffer layer. When the condition of 1 ≤ D1 / D2 ≤ 6 is satisfied, most of the active material 12 is filled in the pore structure of the porous carbon 11, and a small part of the active material 12 is uniformly distributed between the porous carbons 11. The active material distributed in this way can significantly reduce the direct contact between the active materials 12. Therefore, by controlling the ratio of D1 / D2, the volume expansion of the active material 12 can be buffered by the porous carbon with a high porosity, the direct contact between the active materials 12 can be avoided, and at the same time, the pulverization of the negative electrode material can be reduced. When the ratio of D1 / D2 is greater than 6, that is, the particle size of the porous carbon 11 is much larger than the particle size of the active material 12. On the one hand, the bonding property between the porous carbon 11 and the active material 12 distributed between the porous carbons 11 deteriorates. On the other hand, the volume of the porous carbon 11 in the core 1 exceeds the volume of the active material 12, the porosity inside the material increases, and the capacity of the material does not improve. When the ratio of D1 / D2 is less than 0.4, that is, the particle size of the active material 12 is much larger than the particle size of the porous carbon 11, it is easy to have direct contact between the active materials 12, and "collision contact" between the active materials is easily formed. In the process of lithium release and absorption, the large deformation generated is likely to cause pulverization and deformation of the active material 12, and the structural stability of the negative electrode material decreases. It is preferable that the median diameter D1 of the porous carbon and the median diameter D2 of the active material satisfy the condition of 0.5 ≤ D1 / D2 ≤ 4.5.

[0076] In the elemental distribution spectrum obtained by scanning the SEM cross-section of the core of the negative electrode material using X-ray diffraction, the distribution surfaces of C and the active material elements are in a uniform diffusion state.

[0077] In some embodiments, the active material includes at least one of dot-shaped, spherical, ellipsoidal, and sheet-shaped forms.

[0078] In some embodiments, the active material has a median diameter of 1 nm to 300 nm, specifically, it may be 1 nm, 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, etc. Of course, other values within the above range may also be used and are not limited here. The average particle size of the active material 12 is preferably 5 nm to 200 nm, and more preferably 5 nm to 80 nm.

[0079] In some embodiments, the active material includes at least one of Li, Na, K, Sn, Ge, Si, SiOx (0 < x < 2), Fe, Mg, Ti, Zn, Al, Ni, P, and Cu. As understood, the active material located between the porous carbons 11 and the active material located in the second pore structure of the porous carbon 11 may be the same, different, partially the same, or partially different.

[0080] In some embodiments, when both the active material located between the porous carbons 11 and the active material located in the second pore structure of the porous carbon 11 are silicon particles, the core 1 includes the porous carbon 11 and silicon particles. The silicon particles together with the porous carbon constitute the core, and the silicon particles are uniformly distributed with the porous carbon. The silicon particles provide a lithium storage capacity, and the porous carbon 11 is in the charge and discharge process Silicon particlesBy buffering the volume change and improving the conductivity of the silicon particles, the rate performance of the battery can be improved. The porous carbon 11 has a first pore structure 111 and a second pore structure 112. Among them, the pore diameter of the first pore structure 111 is smaller than that of the second pore structure 112, and the silicon particles are filled in the second pore structure 112. Since the silicon particles are wrapped by the porous carbon, Negative electrode material while improving the conductivity of, it is possible to avoid the aggregation of silicon particles. In the negative electrode material of this embodiment, the silicon particles are located between and inside the porous carbon 11, improving the conductivity of the negative electrode material, further improving the rate performance of the negative electrode material, and at the same time relaxing the volume expansion of the silicon nanoparticles.

[0081] In some embodiments, the porous carbon 11 includes at least one of carbon black, a regular mesoporous carbon material (CMK), and a nanoporous carbon material (NCP).

[0082] In some embodiments, the median diameter of the porous carbon 11 is 1 nm to 500 nm. Specifically, it may be 1 nm, 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, etc. Of course, other values within the above range may also be used, and are not limited here. The median diameter of the porous carbon 11 is preferably 5 nm to 200 nm, and more preferably 5 nm to 150 nm.

[0083] In some embodiments, the median diameter of the core 1 is 0.8 μm to 10 μm. Specifically, it may be 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc. Of course, other values within the above range may also be used, and are not limited here.

[0084] In some embodiments, the coating layer 2 includes at least one of a carbon layer, a metal oxide layer, a polymer layer, and a nitride layer. The installation of the coating layer 2 can, on the one hand, reduce the initial Coulombic efficiency and specific capacity by allowing the electrolyte to enter the negative electrode material and cause side reactions, and on the other hand, alleviate the volume expansion of silicon, reduce the volume expansion of the entire composite material, and reduce the swelling of the electrode sheet.

[0085] In some embodiments, the carbon layer includes at least one of soft carbon, hard carbon, crystalline carbon, and amorphous carbon in terms of material.

[0086] In some embodiments, the metal oxide layer includes at least one of oxides of Sn, Ge, Fe, Si, Cu, Ti, Na, Mg, Al, Ca, and Zn in terms of material.

[0087] In some embodiments, the nitride layer includes at least one of silicon nitride, aluminum nitride (AlN), titanium nitride (TiN), and tantalum nitride (TaN) in terms of material.

[0088] In some embodiments, the polymer layer includes at least one of polyaniline, polyacrylic acid, polyurethane, polydopamine, polyacrylamide, sodium carboxymethyl cellulose, polyimide, and polyvinyl alcohol in terms of material.

[0089] In some embodiments, the coating layer 2 has a thickness of 10 nm to 500 nm. Specifically, it may be 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, etc. Of course, other values within the above range may also be used and are not limited here. As can be understood, the coating layer 2 can reduce the contact between silicon and the electrolyte, reduce the formation of the passivation film, and improve the reversible capacity of the battery. By controlling the thickness of the coating layer 2 within the above range, the conductivity of the negative electrode material can be increased, the volume expansion of the negative electrode material can be suppressed, and at the same time, the transmission efficiency of lithium ions can be improved, which is beneficial to improving the high-rate charge and discharge performance, cycle performance, and overall performance of the negative electrode material.

[0090] In some embodiments, the negative electrode material has a specific surface area of 10 m 2 / g or less. Specifically, it may be 1 m 2 / g, 2 m 2 / g, 3 m 2 / g, 4 m 2 / g, 5 m 2 / g, 6 m 2 / g, 7 m 2 / g, 8 m 2 / g, 9 m 2 / g, and 10 m 2 / g, etc. Of course, other values within the above range may also be used and are not limited here. As can be understood, by controlling the specific surface area of the negative electrode material within the above range, it is beneficial to suppress the volume expansion of the negative electrode material and improve the cycle performance of the negative electrode material.

[0091] In some embodiments, the negative electrode material has a median diameter of 0.5 μm to 20 μm. Specifically, it may be 0.5 μm, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 15 μm, 18 μm, 20 μm, etc. Of course, it may also be other values within the above range, and is not limited here. The negative electrode material preferably has a median diameter of 0.8 μm to 12 μm, and more preferably 1 μm to 8 μm. As can be understood, by controlling the median diameter of the negative electrode material within the above range, it is advantageous for improving the cycle performance of the negative electrode material.

[0092] In some embodiments, the negative electrode material has a porosity of 10% or less. Specifically, it may be 1%, 2%, 2.5%, 5%, 7%, 8.5%, 10%, etc. Of course, it may also be other values within the above range, and is not limited here. The negative electrode material preferably has a porosity of 5% or less, and more preferably 2.5% or less. If the porosity of the negative electrode material is too large, the tap density of the material will decrease, and furthermore, the energy density of the material will decrease.

[0093] In a second aspect, the present application provides a method for manufacturing the negative electrode material. As shown in FIG. 4,

[0094] In step S100, a raw material containing porous carbon and an active material is vacuum mixed to obtain a precursor. Among them, the porous carbon has a first pore structure with a pore diameter of 2 nm or less and a second pore structure with a pore diameter larger than 2 nm. The ratio of the pore volume of the first pore structure to the total pore volume of the porous carbon is 40% or more. The second pore structure has a filling rate of 95% or more, and the vacuum mixing has a vacuum degree of 10 Pa or less.

[0095] Step S200 includes subjecting the precursor to a coating treatment to obtain a negative electrode material.

[0096] In the above solution, the method for manufacturing the negative electrode material of the present application is a method of obtaining a precursor by vacuum mixing a raw material containing porous carbon and an active material. Among them, the porous carbon raw material includes a pore structure with two types of pore diameters. Here, the first pore structure 111 of the porous carbon 11 is a micropore (pore diameter of 2 nm or less), and the second pore structure 112 of the porous carbon 11 is a pore with a pore diameter larger than 2 nm. The present application fills the active material into the larger second pore structure 112 of the porous carbon by means of vacuum mixing, and under a vacuum pressure of 10 Pa or less, the filling rate of the second pore structure 112 reaches 95% or more, and the presence of the second pore structure 112 avoids stress concentration and electrolyte penetration problems in the material. Finally, coating the precursor can, on the one hand, avoid the first Coulombic efficiency and specific capacity from decreasing due to the electrolyte entering the negative electrode material and causing side reactions Of the negative electrode material and on the other hand, relieve the volume expansion of the active material, Negative electrode material reduce the overall volume expansion, and reduce the swelling of the electrode sheet. The manufacturing method of the present application is simple. By selecting porous carbon with a specific pore structure and a specific size, the active material is filled into the second pore structure 112 inside the porous carbon 11, effectively suppressing the volume expansion, and further improving the rate performance, specific capacity and cycle performance of the negative electrode material.

[0097] Hereinafter, the manufacturing method of the present application will be specifically described in combination with examples,

[0098] In step S100, a precursor is obtained by vacuum mixing a raw material containing porous carbon and an active material. Among them, the porous carbon has a first pore structure and a second pore structure. The average pore diameter of the first pore structure is 2 nm or less, the average pore diameter of the second pore structure is larger than 2 nm, the ratio of the pore volume of the first pore structure to the total pore volume of the porous carbon is 40% or more, the filling rate of the second pore structure is 95% or more, and the degree of vacuum for vacuum mixing is 10 Pa or less.

[0099] In some embodiments, the average pore diameter of the first pore structure 111 may be, specifically, 0.05 nm, 0.07 nm, 0.1 nm, 0.3 nm, 0.5 nm, 0.8 nm, 1 nm, 1.5 nm, 2 nm, etc. Of course, it may also be other values within the above range and is not limited here.

[0100] In some embodiments, the porous carbon 11 has a first pore structure 111 with a pore diameter of 2 nm or less and a second pore structure 112 with a pore diameter greater than 2 nm. The average pore diameter of the second pore structure 112 may be, specifically, 2.5 nm, 5 nm, 10 nm, 20 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, etc. Of course, it may also be other values within the above range and is not limited here.

[0101] In the porous carbon of the present application, the first pore structure 111 is a pore with a pore diameter of 2 nm or less, and the second pore structure 112 is a pore with a pore diameter greater than 2 nm. The first pore structure 111 with a small pore diameter can effectively relieve the volume expansion of the active material 12, reduce the expansion of the electrode film, and improve the safety of the battery. The second pore structure 112 has a larger pore size than the first pore structure 111, and the active material is filled in the second pore structure 112 with a large pore diameter, and the stress concentration and electrolyte penetration caused by the second pore structure 112 can be reduced.

[0102] In some embodiments, the ratio of the pore volume of the first pore structure 111 to the total pore volume of the porous carbon 11 may be, specifically, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc. Of course, it may also be other values within the above range and is not limited here. When the ratio of the pore volume of the first pore structure 111 is less than 40%, the volume expansion of silicon cannot be effectively relieved. The ratio of the pore volume of the first pore structure 111 to the total pore volume of the porous carbon 11 is preferably 45% or more.

[0103] In some embodiments, this application controls the degree of vacuum in the vacuum mixing to 10 Pa or less, so that the filling rate of the second pore structure 112 is 95% or more. In this application, the vacuum mixing means that the degree of vacuum is specifically 10 -7 Pa, 10 -6 Pa, 10 -5 Pa, 10 -4 Pa, 10 -3 Pa, 10 -2 Pa, and may be 10 Pa or the like. Of course, other values within the above range may also be used, and are not limited here. This application controls the filling rate of the active material in the porous carbon by vacuum mixing treatment, so that the active material is filled as much as possible in the second pore structure in the porous carbon. When the degree of vacuum is greater than 10 Pa, the degree of vacuum is too low, and the generated acting force is difficult to fill the active material into the corresponding pores, resulting in a decrease in the filling rate of the second pore structure. When the degree of vacuum is less than 10 -7 Pa, it is necessary to arrange a separate molecular pump, which increases the additional cost. Also, if the degree of vacuum is too high, the introduced silicon source gas will be rapidly sucked out, the reaction will not be in time, and the filling rate of the active material will decrease.

[0104] In some embodiments, the active material contains at least one of Li, Na, K, Sn, Ge, Si, SiOx (0 < x < 2), Fe, Mg, Ti, Zn, Al, Ni, P, and Cu.

[0105] In some embodiments, the median diameter D1 of the porous carbon and the median diameter D2 of the active material satisfy the condition of 0.4 ≦ D1 / D2 ≦ 6. For example, they may be 0.4, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, and 6, etc. Of course, other values within the above range may also be used, and are not limited here. As can be understood, by limiting the ratio of the median diameter D1 of the porous carbon to the median diameter D2 of the active material within the above range, the obtained precursor structure includes porous carbon 11, active material 12 filled in the pore structure of porous carbon 11, and active material 12 distributed between porous carbon 11. Porous carbon 11 and active material 12 WellA structure that can be uniformly dispersed and well-dispersed can be formed, and there is no direct contact between the active materials or only a small amount of direct contact exists. Most of them indirectly contact through porous carbon as a buffer layer. The volume expansion of the active materials can be buffered by the particle layer of porous carbon with a high porosity, and at the same time, the pulverization of the material can be reduced. When the ratio of D1 / D2 is greater than 6, that is, the particle size of the porous carbon 11 is much larger than the particle size of the active material 12. On the one hand, the binding property between the porous carbon 11 and the active material 12 distributed between the porous carbon 11 becomes poor. On the other hand, the volume of the porous carbon 11 in the core 1 exceeds the volume of the active material 12, the porosity inside the material increases, and the capacity of the material does not improve. When the ratio of D1 / D2 is less than 0.4, that is, the particle size of the active material 12 is much larger than the particle size of the porous carbon 11, it is easy to have direct contact between the active materials, and "collision contact" between the active materials is easily formed. In the process of lithium release and absorption, the huge deformation generated is likely to cause pulverization and deformation of the active material 12, and the structural stability of the negative electrode material decreases. It is preferable that the median diameter D1 of the porous carbon and the median diameter D2 of the active material satisfy the condition of 0.5 ≤ D1 / D2 ≤ 4.5.

[0106] In some embodiments, the active material has a median diameter of 1 nm to 300 nm, specifically, it may be 1 nm, 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, etc. Of course, other values within the above range may also be used and are not limited here. The active material preferably has a median diameter of 5 nm to 200 nm, and more preferably 5 nm to 80 nm.

[0107] In some embodiments, the porous carbon includes at least one of carbon black, regular mesoporous carbon material, and nanoporous carbon material.

[0108] In some embodiments, the median diameter of the porous carbon is from 1 nm to 500 nm, specifically, it may be 1 nm, 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, etc. Of course, it may also be other values within the above range and is not limited here.

[0109] In some embodiments, the mass ratio of the porous carbon to the active material is 40:(10 - 80). Specifically, the mass ratio of the porous carbon, the active material, and the silicon material may be 40:10, 40:20, 40:30, 40:40, 40:50, 40:60, 40:70, and 40:80, etc. Of course, it may also be other values within the above range and is not limited here. By controlling the mass ratio of the porous carbon to the active material within the above range, it is advantageous to obtain a uniformly dispersed core material, which is advantageous for improving the cycle performance and structural stability of the material.

[0110] In some embodiments, the vacuum mixing includes at least one of a biaxial planetary vacuum mixer, a planetary vacuum mixer, a planetary vacuum disperser, a ribbon vacuum mixer, a multifunctional vacuum mixer, a vacuum disperser, and a vacuum emulsifier.

[0111] In some embodiments, the time of the vacuum mixing is from 0.5 h to 15 h. Specifically, it may be 0.5 h, 1 h, 3 h, 5 h, 7 h, 9 h, 10 h, 12 h, 14 h, 15 h, etc. Of course, it may also be other values within the above range and is not limited here.

[0112] In some embodiments, before vacuum mixing the raw materials containing the porous carbon and the active material, a step of adding an auxiliary agent and a solvent is included. That is, step S100 includes a step of putting the porous carbon, the active material, and the auxiliary agent into a solvent for vacuum mixing and drying treatment to obtain a precursor.

[0113] In some embodiments, the auxiliary agent includes at least one of polyvinyl alcohol, n-octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecylbenzenesulfonate, n-eicosanoic acid, palmitic acid, myristic acid, undecylic acid, fatty acid, cetyltrimethylammonium bromide, and polyvinylpyrrolidone. By modifying the surfaces of the active material and the pore structure of the porous carbon, the auxiliary agent can facilitate the easier penetration of the active material particles into the pores of the porous carbon.

[0114] In some embodiments, the solvent includes at least one of an organic solvent and a non-organic solvent. The organic solvent includes at least one of phenol, methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, n-hexane, cyclohexane, ethyl acetate, chloroform, carbon tetrachloride, methyl acetate, acetone, and pentanol. The non-organic solvent includes at least one of water, liquid ammonia, liquid carbon dioxide, and a superacid of liquid sulfur dioxide.

[0115] In some embodiments, the mass ratio of the auxiliary agent to the porous carbon is (0.05 - 3):100. Specifically, it may be 0.05:100, 0.1:100, 1:100, 2:100, 3:100, etc. Of course, other values within the above range are also possible and are not limited here.

[0116] In some embodiments, the mass ratio of the solvent to the porous carbon is 100:(15 - 55). Specifically, it may be 100:15, 100:20, 100:25, 100:30, 100:35, 100:40, 100:50, 100:55, etc. Of course, other values within the above range are also possible and are not limited here.

[0117] In some embodiments, after vacuum mixing the raw material containing the porous carbon and the active material, a drying treatment is performed.

[0118] In some embodiments, the drying treatment is carried out at a temperature of -50°C to 500°C. Specifically, it may be -50°C, -40°C, -30°C, -20°C, 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, etc. Of course, it may also be other values within the above range, and it is not limited here. As understood, the drying treatment may be a low-temperature freeze-drying treatment or a high-temperature drying treatment.

[0119] In some embodiments, the drying treatment is carried out for a time of 0.5 h to 15 h. Specifically, it may be 0.5 h, 1 h, 3 h, 5 h, 7 h, 9 h, 10 h, 12 h, 14 h, 15 h, etc. Of course, it may also be other values within the above range, and it is not limited here.

[0120] In some embodiments, the drying treatment apparatus includes at least one of a rotary evaporator, a vacuum oven, a spray dryer, a heat treatment furnace, and a freeze dryer.

[0121] In some embodiments, coating the precursor specifically includes the step of mixing the precursor and the coating material and performing heat treatment to obtain the negative electrode material. By coating with the coating material, on the one hand, it is possible to avoid the decrease in the initial Coulomb efficiency and specific capacity caused by the electrolyte entering the negative electrode material and causing side reactions. On the other hand, it can alleviate the volume expansion of silicon, reduce the overall volume expansion of the composite material, and reduce the swelling of the electrode sheet.

[0122] In some embodiments, the coating material includes at least one of a carbon material, a metal oxide material, a polymer material, and a nitride material.

[0123] In some embodiments, the carbon material includes at least one of soft carbon, hard carbon, crystalline carbon, and amorphous carbon.

[0124] In some embodiments, the metal oxide material includes at least one of oxides of Sn, Ge, Fe, Si, Cu, Ti, Na, Mg, Al, Ca, and Zn.

[0125] In some embodiments, the nitride material includes at least one of silicon nitride, aluminum nitride, titanium nitride, and tantalum nitride.

[0126] In some embodiments, the polymer material includes at least one of polyaniline, polyacrylic acid, polyurethane, polydopamine, polyacrylamide, sodium carboxymethyl cellulose, polyimide, and polyvinyl alcohol.

[0127] In some embodiments, the mass ratio of the precursor to the coating material is 100:(5 - 100), specifically, it may be 100:5, 100:10, 100:20, 100:30, 100:40, 100:50, 100:60, 100:70, 100:80, 100:90, and 100:100, etc. Of course, other values within the above range may also be used and are not limited here. When the mass ratio of the precursor to the coating material is less than 100:100, the thickness of the coating layer is too thin, which is disadvantageous for increasing the conductivity of the negative electrode material, and due to the weak volume expansion suppression performance of the negative electrode material, the cycle performance deteriorates. When the mass ratio of the precursor to the coating material is greater than 100:5, the thickness of the coating layer is too thick, resulting in a decrease in the lithium ion transmission efficiency and a reduction in the overall performance of the negative electrode material.

[0128] In some embodiments, the heat treatment is at a temperature of 400°C - 900°C, specifically, it may be 400°C, 500°C, 600°C, 700°C, 800°C, and 900, etc. Of course, other values within the above range may also be used and are not limited here.

[0129] In some embodiments, the heat treatment has a holding time of 1 h to 12 h. Specifically, it may be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, etc. Of course, other values within the above range may also be used and are not limited here.

[0130] In some embodiments, the heat treatment has a heating rate of 1 °C / min to 15 °C / min. Specifically, it may be 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, 10 °C / min, 11 °C / min, 12 °C / min, 13 °C / min, 14 °C / min, 15 °C / min, etc. Of course, other values within the above range may also be used and are not limited here.

[0131] In some embodiments, the heat treatment is carried out in a protective atmosphere, and the protective atmosphere contains at least one of nitrogen gas, helium gas, neon gas, argon gas, and krypton gas.

[0132] In some embodiments, after the heat treatment, the process further includes crushing and sieving the obtained material.

[0133] In some embodiments, the crushing device includes at least one of a mechanical crusher, a pneumatic crusher, and a breaker.

[0134] In some embodiments, for sieving, the size of the screen mesh is 10 mesh to 800 mesh. Specifically, it may be 10 mesh, 50 mesh, 100 mesh, 200 mesh, 300 mesh, 400 mesh, 500 mesh, 600 mesh, 700 mesh, 800 mesh, etc. Of course, other values within the above range may also be used and are not limited here.

[0135] In a third aspect, the present application provides a lithium-ion battery, and the lithium-ion battery includes the above negative electrode material or a negative electrode material manufactured by the above manufacturing method.

[0136] As is apparent to those skilled in the art, the method for manufacturing the lithium-ion battery described above is merely an example. Other methods commonly used in the art can be adopted without departing from the scope of the present application.

[0137] Hereinafter, the examples of the present application will be further described separately with multiple examples. However, the present application is not limited to the following specific examples. It may be appropriately modified and implemented without changing the scope of the main claim.

[0138] Example 1 (1) Silicon nanoparticles and porous carbon particles were measured by a BET tester and screened by a Malvern particle size measuring device to obtain silicon nanoparticles with a median diameter of 17 nm and porous carbon particles with a median diameter of 20 nm. Among them, the porous carbon particles are specifically carbon black, and the volume occupancy rate of pores with a pore diameter of 2 nm or less (micropores) in the porous carbon particles is 60%. (2) The screened silicon nanoparticles, porous carbon particles, and polyvinyl alcohol were placed in phenol at a mass ratio of 50:25:25. Then, the vacuum degree was controlled to 0.1 Pa in a planetary vacuum ball mill, and ball milling was performed for 2 hours, followed by rotary evaporation drying at 120 °C to obtain a precursor. (3) The precursor and phenol resin were mixed at a mass ratio of 50:45, and the mixed material was placed in a high-temperature box furnace. Nitrogen gas was introduced, and heat treatment was performed at 820 °C for 4 hours of heat preservation. (4) The obtained sample was pulverized, screened, and classified to obtain a negative electrode material.

[0139] The negative electrode material manufactured in this example has a core-shell structure. The core includes porous carbon and silicon nanoparticles distributed in the porous carbon pore structure, and the shell is a carbon coating layer. Among them, the porous carbon has a first pore structure and a second pore structure. The numerical values of the volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0140] As shown in Fig. 6, it is the XRD diagram of the negative electrode material manufactured in Example 1. As can be seen from Fig. 6, there are peak-to-peak of silicon in the product.

[0141] As shown in Fig. 7, it is the first charge-discharge curve of the negative electrode material manufactured in Example 1. As can be seen from Fig. 7, the first charge-discharge capacity of the material is high, and the first Coulomb efficiency is also high.

[0142] As shown in Fig. 8, it is the cycle characteristic curve diagram of the negative electrode material manufactured in Example 1. As can be seen from Fig. 8, the negative electrode material manufactured in this example has excellent cycle performance, and the capacity retention rate after 100 cycles is 92.1%.

[0143] Example 2 (1) Silicon nanoparticles and porous carbon particles were measured by a BET tester and sieved by a Malvern particle size measuring device to obtain silicon nanoparticles with a median diameter of 50 nm and porous carbon particles with a median diameter of 40 nm. Among them, the porous carbon particles are specifically carbon black, and the volume occupancy rate of the pores with a pore diameter of 2 nm or less (micropores) in the porous carbon particles is 45%. (2) The sieved silicon nanoparticles, porous carbon particles, and polyvinyl alcohol were placed in phenol according to a mass ratio of 50:25:25. Then, the vacuum degree was controlled to 0.1 Pa in a planetary vacuum ball mill, and ball milling was carried out for 2 hours, followed by rotary evaporation drying at 120 °C to obtain a precursor. (3) The precursor and phenol resin were mixed according to a mass ratio of 50:45, and the mixed material was put into a high-temperature box furnace, nitrogen gas was introduced, and heat treatment was carried out at 820 °C for 4 hours of heat preservation. (4) The obtained sample was pulverized, sieved, and classified to obtain a negative electrode material.

[0144] As shown in Fig. 5, it is an SEM chart of the negative electrode material manufactured in Example 1. The negative electrode material manufactured in this example has a core-shell structure. The core includes porous carbon, silicon nanoparticles distributed in the porous carbon pore structure, and silicon nanoparticles distributed between the porous carbons. The shell is a carbon coating layer. Among them, the porous carbon has a first pore structure and a second pore structure. The second pore structure is filled with silicon nanoparticles. The numerical values of the volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0145] Example 3 (1) Measure silicon nanoparticles and porous carbon particles with a BET tester, and screen them with a Malvern particle size measuring device to obtain silicon nanoparticles with a median diameter of 30 nm and porous carbon particles with a median diameter of 50 nm. The porous carbon particles are specifically Ketjen black. The volume occupancy rate of pores with a pore diameter of 2 nm or less (micropores) in the porous carbon particles is 49%. (2) Place the sieved silicon nanoparticles, porous carbon particles, and polyvinyl alcohol in isopropyl alcohol according to a mass ratio of 50:35:22. Then, control the vacuum degree to 0.01 Pa with a biaxial planetary vacuum mixer and mix for 4 hours. Rotate and evaporate to dryness at 150 °C to obtain a precursor. (3) Mix the precursor and sucrose according to a mass ratio of 50:55, put the mixed material into a high-temperature box furnace, introduce nitrogen gas, heat-treat it under the condition of 920 °C, and keep it warm for 3 hours. (4) Crush, screen, and classify the obtained sample to obtain a negative electrode material.

[0146] The negative electrode material manufactured in this example has a core-shell structure. The core includes porous carbon, silicon nanoparticles distributed in the porous carbon pore structure, and silicon nanoparticles distributed between the porous carbons. The shell is a carbon coating layer. Among them, the porous carbon has a first pore structure and a second pore structure. The second pore structure is filled with silicon nanoparticles. The numerical values of the volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0147] Example 4 (1) Measure silicon nanoparticles and porous carbon particles with a BET tester, and screen them with a Malvern particle size measuring device to obtain silicon nanoparticles with a median diameter of 20 nm and porous carbon particles with a median diameter of 30 nm. The porous carbon particles are specifically MCM-41, and the volume occupancy rate of pores with a pore diameter of 2 nm or less (micropores) in the porous carbon particles is 55%. (2) Place the sieved silicon nanoparticles, porous carbon particles, and polyvinyl alcohol in butanol at a mass ratio of 50:31:18, and then control the vacuum degree to 10 -5 Pa in a vacuum disperser, mix for 5 hours, and rotary evaporate to dryness at 220 °C to obtain a precursor. (3) Mix the precursor and glucose at a mass ratio of 50:45, put the mixed material into a high-temperature box furnace, introduce nitrogen gas, heat-treat it under the condition of 780 °C, and keep it warm for 5 hours. (4) Grind, screen, and classify the obtained sample to obtain the negative electrode material.

[0148] The negative electrode material manufactured in this example has a core-shell structure. The core includes porous carbon, silicon nanoparticles distributed in the porous carbon pore structure, and silicon nanoparticles distributed between the porous carbon. The shell is a carbon coating layer. Among them, the porous carbon has a first pore structure and a second pore structure. The volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0149] Example 5 (1) Measure silicon nanoparticles and porous carbon particles with a BET tester, and screen them with a Malvern particle size measuring device to obtain silicon nanoparticles with a median diameter of 60 nm and porous carbon particles with a median diameter of 80 nm. The porous carbon particles are specifically ordered mesoporous carbon (CMK-3), and the volume occupancy rate of pores with a pore diameter of 2 nm or less (micropores) in the porous carbon particles is 62%. (2) The sieved silicon nanoparticles, porous carbon particles, and polyvinyl alcohol are placed in phenol at a mass ratio of 40:25:25, and then, in a ribbon vacuum mixer, the vacuum degree is controlled to 1.5 Pa and mixed for 2 hours, followed by rotary evaporation drying at 120 °C to obtain a precursor. (3) The precursor and polyvinylamine are mixed and heat-treated at 350 °C. (4) The obtained sample is pulverized, sieved, and classified to obtain the negative electrode material.

[0150] The negative electrode material produced in this example has a core-shell structure. The core contains porous carbon, silicon nanoparticles distributed in the porous carbon pore structure, and silicon nanoparticles distributed between the porous carbon. The shell is a polymer coating layer. Among them, the porous carbon has a first pore structure and a second pore structure, and the numerical values of the volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0151] Example 6 (1) SiO particles and porous carbon particles are measured by a BET tester and sieved by a Malvern particle size measuring device to obtain SiO particles with a median diameter of 25 nm and porous carbon particles with a median diameter of 20 nm. The porous carbon particles are specifically NCP. The volume occupancy rate of the micropores of the porous carbon particles is 70%. (2) The sieved SiO particles, porous carbon particles, and polyvinyl alcohol are placed in phenol at a mass ratio of 30:25:15, and then, in a vacuum mixer, the vacuum degree is controlled to 3 Pa and mixed for 8 hours, followed by rotary evaporation drying at 150 °C to obtain a precursor. (3) The precursor and asphalt are mixed at a mass ratio of 30:25, the mixed material is placed in a high-temperature box furnace, nitrogen gas is introduced, heat-treated under the condition of 980 °C, and kept warm for 3 hours. (4) The obtained sample is pulverized, sieved, and classified to obtain the negative electrode material.

[0152] The negative electrode material produced in this example has a core-shell structure. The core includes porous carbon, SiO particles distributed in the porous carbon pore structure, and SiO particles distributed between the porous carbon. The shell is a carbon coating layer. Among them, the porous carbon has a first pore structure and a second pore structure, and the numerical values of the volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the SiO particles are shown in Table 1.

[0153] Example 7 (1) Silicon nanoparticles and porous carbon particles were measured by a BET tester and screened by a Malvern particle size measuring device to obtain nano-silicon with a median diameter of 50 nm and porous carbon particles with a median diameter of 40 nm. Among them, the porous carbon particles are specifically carbon black, and the volume occupancy rate of the pore diameter of the porous carbon particles of 2 nm or less (micropores) is 45%. (2) The screened silicon nanoparticles, porous carbon particles, and polyvinyl alcohol were placed in phenol according to a mass ratio of 30:25:15. Then, the vacuum degree was controlled to 5 Pa in a vacuum mixer and mixed for 8 hours, and then rotary evaporation drying was carried out at 150 °C to obtain a precursor. (3) The precursor and asphalt were mixed according to a mass ratio of 30:25, and the mixed material was put into a high-temperature box furnace, nitrogen gas was introduced, heat treatment was carried out under the condition of 980 °C, and heat preservation was carried out for 3 hours. (4) The obtained sample was pulverized, screened, and classified to obtain the above-mentioned negative electrode material.

[0154] The negative electrode material produced in this example has a core-shell structure. The core includes porous carbon, nanoparticles distributed in the porous carbon pore structure, and silicon nanoparticles distributed between the porous carbon. The shell is a carbon coating layer. Among them, the porous carbon has a first pore structure and a second pore structure, and the numerical values of the volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0155] Example 8 Different from Example 2, the vacuum degree in step (2) is replaced with 10 -7 Pa.

[0156] The negative electrode material manufactured in this example has a core-shell structure. The core includes porous carbon and silicon nanoparticles distributed between the silicon nanoparticles and the porous carbon in the porous carbon pore structure. The shell is a carbon coating layer. Among them, the porous carbon has a first pore structure and a second pore structure, and the numerical values of the volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0157] Example 9 Different from Example 2, the vacuum degree in step (2) is replaced with 10 Pa.

[0158] The negative electrode material manufactured in this example has a core-shell structure. The core includes porous carbon and silicon nanoparticles distributed between the silicon nanoparticles and the porous carbon in the porous carbon pore structure. The shell is a carbon coating layer. Among them, the porous carbon has a first pore structure and a second pore structure, and the numerical values of the volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0159] Example 10 Different from Example 2, the precursor and titanium oxide are mixed at a mass ratio of 50:35.

[0160] The negative electrode material manufactured in this example has a core-shell structure. The core includes porous carbon and silicon nanoparticles distributed between the silicon nanoparticles and the porous carbon in the porous carbon pore structure. The shell is a titanium oxide coating layer. The first pore structure and the second pore structure are formed in the porous carbon, and the numerical values of the volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0161] Example 11 Different from Example 2, the precursor and silicon nitride are mixed at a mass ratio of 50:35.

[0162] The negative electrode material manufactured in this example has a core-shell structure. The core includes porous carbon, silicon nanoparticles distributed in the porous carbon pore structure, and silicon nanoparticles distributed in the porous carbon voids. The shell is a silicon nitride coating layer. In the porous carbon, a first pore structure and a second pore structure are formed. The numerical values of the volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0163] Example 12 Different from Example 2, the median diameter of the silicon nanoparticles is 50 nm, and the size of the median diameter of the porous carbon particles is 250 nm.

[0164] The negative electrode material manufactured in this example has a core-shell structure. The core includes porous carbon, silicon nanoparticles distributed in the porous carbon pore structure, and silicon nanoparticles distributed between the porous carbon. The shell is a carbon coating layer. Among them, the porous carbon has a first pore structure and a second pore structure, and the second pore structure is filled with silicon nanoparticles. The numerical values of the volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0165] Example 13 Different from Example 2, the median diameter of the silicon nanoparticles is 50 nm, and the size of the median diameter of the porous carbon particles is 20 nm.

[0166] The negative electrode material manufactured in this example has a core-shell structure. The core includes porous carbon, silicon nanoparticles distributed in the porous carbon pore structure, and silicon nanoparticles distributed between the porous carbon. The shell is a carbon coating layer. Among them, the porous carbon has a first pore structure and a second pore structure, and the second pore structure is filled with silicon nanoparticles. The numerical values of the volume occupancy rate of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0167] Example 14 Unlike Example 2, the porous carbon particles are specifically carbon black, and the volume occupancy of pores with a pore diameter of 2 nm or less (micropores) in the porous carbon particles is 40.1%.

[0168] The negative electrode material produced in this example has a core-shell structure. The core includes porous carbon, silicon nanoparticles distributed in the porous carbon pore structure, and silicon nanoparticles distributed between the porous carbon. The shell is a carbon coating layer. Among them, the porous carbon has a first pore structure and a second pore structure. The second pore structure is filled with silicon nanoparticles. The numerical values of the volume occupancy of the first pore structure, the filling rate of the second pore structure, the median diameter of the porous carbon, and the median diameter of the silicon nanoparticles are shown in Table 1.

[0169] Example 15 Unlike Example 1, the degree of vacuum in step (2) is replaced with 10 -8 Pa.

[0170] Comparative Example 1 Unlike Example 1, the volume occupancy of pores with a pore diameter of 2 nm or less (micropores) in the porous carbon particles is 30%.

[0171] Comparative Example 2 Unlike Example 1, the degree of vacuum in step (2) is replaced with 15 Pa.

[0172] Comparative Example 3 Unlike Example 1, in step (2), the silicon nanoparticles, the porous carbon particles, and polyvinyl alcohol are mixed and treated with a planetary mixer.

[0173] <Performance Measurement> 1. Etch the silicon in the core of the negative electrode material using a hydrofluoric acid solution, measure the size of the pore volume of the pore structure by the BET pore distribution analysis method, and calculate the pore volume ratio of the first pore structure and the second pore structure of the porous carbon in the pore volume occupied by the porous carbon.

[0174] 2. Measure the volume V1 of the second pore structure of the material before etching the active material in the negative electrode material. After etching silicon, measure the volume of the second pore structure as V2. (V2 - V1) / V2 is the filling rate of the active material in the second pore structure.

[0175] 3. Measure the median diameter of the material using a Malvern particle size distribution analyzer.

[0176] 4. Observe 200 carbon materials and active material particles under a scanning electron microscope, and use Nano measure to statistically analyze the median diameters of the two types of substances.

[0177] 5. Measure the specific surface area of the negative electrode material using a Micromeritics TriStar3020 specific surface area and pore size analyzer. Weigh a certain mass of powder, completely degas it under vacuum heating to remove surface adsorbed substances, and then use the nitrogen gas adsorption method to calculate the specific surface area of the particles based on the amount of nitrogen gas adsorbed.

[0178] 6. Adopt the micropore distribution analysis method to measure the pore volume of the negative electrode material. The pore volume is ΔV, measure the true density P of the negative electrode material, and calculate to obtain the porosity of the negative electrode material = ΔV / (ΔV + 1 / P).

[0179] 7. Measure the electrochemical performance by the following method.

[0180] The negative electrode material, conductive agent, and binder are dissolved in water and mixed at a mass ratio of 94:1:5, with the solid content controlled to 50%. It is then applied to a copper foil current collector and vacuum dried to produce a negative electrode sheet. Subsequently, a ternary positive electrode sheet (lithium nickel manganese cobalt oxide NCM523) manufactured by a conventional mature process, an electrolyte of 1 mol / L lithium hexafluorophosphate LiPF6 / (ethylene carbonate EC + dimethyl carbonate DMC + ethyl methyl carbonate EMC) (v / v = 1:1:1), a Celgard 2400 separator, and a shell are assembled into a 18650 cylindrical battery cell using a normal production process. The charge and discharge test of the cylindrical battery is carried out using LAND battery test equipment manufactured by Wuhan LAND electronics Co., Ltd. Under normal temperature conditions, constant current charge and discharge are performed at 0.2C, and the charge and discharge voltage is set to 2.75 - 4.2V. The initial reversible capacity, initial charge capacity, and initial discharge capacity are obtained. Initial Coulomb efficiency = initial discharge capacity / initial charge capacity.

[0181] Repeat 100 cycles, record the discharge capacity as the remaining capacity of the lithium-ion battery, and the capacity retention rate = (remaining capacity / initial capacity) × 100%.

[0182] Measurement of the pole piece expansion rate (%) after 30 cycles: The negative electrode material is mixed with graphite, prepared to a fixed capacity (450 mAh / g), applied to form a pole piece, the thickness D1 of the pole piece is measured, then it is assembled into a button-type battery for testing. After 30 cycles, the battery is removed and the thickness D2 of the pole piece is tested again. The pole piece expansion rate = (D2 - D1) / D1 * 100%.

[0183] The measurement results are shown in Table 1.

[0184]

Table 1

[0185] From the data in Table 1, in the negative electrode materials manufactured in Examples 1 to 13 of the present application, the active material is uniformly dispersed in the pores of the porous carbon, forming a structure in which it is well dispersed. There is no direct contact between the active materials, or only a small amount exists, and most of them are in indirect contact through the porous carbon as a buffer layer. By the first pore structure with a high volume occupancy rate of the porous carbon, the volume expansion of the active material can be buffered, improving the rate performance of the negative electrode material and at the same time being advantageous for alleviating the volume expansion of the silicon nanoparticles. Also, when the active material is filled in the porous carbon, the filling rate of the second pore structure of the porous carbon is 95% or more, improving the material capacity and at the same time being able to avoid stress concentration and electrolyte penetration by the material. It can be seen that the negative electrode material of the present application has the advantages of effectively suppressing volume expansion, having good structural stability, high rate performance, high capacity, and good cycle performance.

[0186] In Example 15, during the manufacturing process, the degree of vacuum in the vacuum treatment is less than 10 -7 Pa, If the degree of vacuum is too high, the introduced silicon source gas will be rapidly sucked out, the reaction will not be in time, the filling rate of the second pore structure decreases, and the structural stability and capacity retention rate of the negative electrode material are lower than those in Example 1.

[0187] From Comparative Example 1, it can be seen that if the volume occupancy rate of the first pore structure in the porous carbon is too small, the negative electrode material cannot completely alleviate the volume expansion.

[0188] From Comparative Example 2, it can be seen that when the degree of vacuum in the vacuum treatment is greater than 10 Pa, the filling rate of the second pore structure decreases, and the structural stability and capacity retention rate of the negative electrode material decrease.

[0189] From Comparative Example 3, when the negative electrode material is prepared by the conventional mixing method, the filling rate of the second pore structure is 45%, much lower than 99.4% of Example 1. Stress concentration is likely to occur in the negative electrode material, the cycle performance of the material decreases, and the expansion rate is large.

[0190] Although the above embodiments have described the detailed process apparatus and process flow of the present application, the present application is not limited to the above detailed process apparatus and process flow. That is, the applicant has stated that the present application can be implemented even without the above detailed process apparatus and process flow. As will be apparent to those skilled in the art, any improvements to the present application, the equivalent substitution of each raw material of the products of the present application, the addition of auxiliary components, and the selection options of specific methods are all within the scope of the claims and the disclosure scope of the present application.

Claims

1. A negative electrode material, comprising a core and a coating layer provided on at least a part of the surface of the core, wherein the core comprises porous carbon and an active material filled in the pore structure of the porous carbon, the porous carbon has a first pore structure with a pore diameter of 2 nm or less and a second pore structure with a pore diameter greater than 2 nm, the ratio of the pore volume of the first pore structure to the total pore volume of the porous carbon is 40% or more, the filling rate of the second pore structure is 95% or more, and the coating layer has a thickness of 10 nm to 500 nm.

2. The negative electrode material according to Claim 1, characterized by satisfying at least one of the following (1) to (9). (1) The negative electrode material further comprises an active material distributed between the porous carbons. (2) The median diameter D1 of the porous carbon and the median diameter D2 of the active material satisfy the condition of 0.4 ≦ D1 / D2 ≦ 6. (3) The median diameter D1 of the porous carbon and the median diameter D2 of the active material satisfy the condition of 0.5 ≦ D1 / D2 ≦ 4.

5. (4) The active material has a median diameter of 1 nm to 300 nm. (5) The active material has a morphology including at least one of dot-like, spherical, ellipsoidal, and sheet-like. (6) The active material contains at least one of Li, Na, K, Sn, Ge, Si, SiO x (0 < x < 2), Fe, Mg, Ti, Zn, Al, Ni, P, and Cu. (7) The porous carbon contains at least one of carbon black, regular mesoporous carbon material, and nanoporous carbon material. (8) The porous carbon has a median diameter of 1 nm to 500 nm. (9) The core has a median diameter of 0.8 μm to 10 μm.

3. The negative electrode material according to Claim 1, wherein the coating layer comprises at least one of a carbon layer, a metal oxide layer, a polymer layer, and a nitride layer, and the coating layer satisfies at least one of the following (1) to (5). (1) The carbon layer contains at least one of soft carbon, crystalline carbon, amorphous carbon, and hard carbon. (2) The metal oxide layer contains at least one of oxides of Sn, Ge, Fe, Si, Cu, Ti, Na, Mg, Al, Ca, and Zn. (3) The nitride layer contains at least one of silicon nitride, aluminum nitride, titanium nitride, and tantalum nitride in terms of material. (4) The polymer layer contains at least one of polyaniline, polyacrylic acid, polyurethane, polydopamine, polyacrylamide, sodium carboxymethyl cellulose, polyimide, and polyvinyl alcohol in terms of material.

4. The negative electrode material according to claim 1, characterized by satisfying at least one of the following (1) to (3). (1) The negative electrode material has a specific surface area of 10 m ２ / g or less, (2) The negative electrode material has a median diameter of 0.5 μm to 20 μm. (3) The negative electrode material has a porosity of 10% or less.

5. A method for manufacturing the negative electrode material according to any one of claims 1 to 4, comprising a step of vacuum-mixing a raw material containing porous carbon and an active material to obtain a precursor, wherein the porous carbon has a first pore structure with a pore diameter of 2 nm or less and a second pore structure with a pore diameter greater than 2 nm, the ratio of the pore volume of the first pore structure to the total pore volume of the porous carbon is 40% or more, the filling rate of the second pore structure is 95% or more, and the vacuum mixing is a step with a degree of vacuum of 10 Pa or less, and a step of coating the precursor to obtain a negative electrode material.

6. The manufacturing method according to claim 5, characterized by satisfying at least one of the following (1) to (7). (1) The median diameter D1 of the porous carbon and the median diameter D2 of the active material satisfy the condition of 0.4 ≤ D1 / D2 ≤ 6. (2) The median diameter D1 of the porous carbon and the median diameter D2 of the active material satisfy the condition of 0.5 ≤ D1 / D2 ≤ 4.

5. (3) The median diameter of the active material is 1 nm to 300 nm. (4) The active material contains at least one of Li, Na, K, Sn, Ge, Si, SiO x (0 < x < 2), Fe, Mg, Ti, Zn, Al, Ni, P, and Cu. (5) The porous carbon contains at least one of carbon black, a regular mesoporous carbon material, and a nanoporous carbon material. (6) The porous carbon has a median diameter of 1 nm to 500 nm. (7) The mass ratio of the porous carbon to the active material is 40:(10 - 80).

7. The manufacturing method according to claim 5, further comprising a co - agent and a solvent in a raw material containing a porous carbon and an active material, and satisfying at least one of the following (1) to (4). (1) The co - agent contains at least one of polyvinyl alcohol, n - octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecylbenzenesulfonate, n - eicosanoic acid, palmitic acid, myristic acid, undecylic acid, fatty acid, cetyltrimethylammonium bromide, and polyvinylpyrrolidone; (2) The solvent contains at least one of phenol, methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n - butanol, isobutanol, n - hexane, cyclohexane, ethyl acetate, chloroform, carbon tetrachloride, methyl acetate, acetone, and pentanol; (3) The mass ratio of the co - agent to the porous carbon is (0.05 - 3):100; (4) The mass ratio of the solvent to the porous carbon is 100:(15 - 55).

8. The manufacturing method according to claim 7, characterized by satisfying at least one of the following (1) to (5). (1) In the vacuum mixing, the apparatus includes at least one of a twin - shaft planetary vacuum mixer, a planetary vacuum mixer, a planetary vacuum disperser, a ribbon vacuum mixer, a multifunctional vacuum mixer, a vacuum disperser, and a vacuum emulsifier; (2) The vacuum mixing time is 0.5 hour to 15 hours; (3) After the vacuum mixing, a drying treatment is further performed, and the drying treatment temperature is - 50°C to 500°C; (4) After the vacuum mixing, a drying treatment is further performed, and the drying treatment time is 0.5 hour to 15 hours; (5) After the vacuum mixing, a drying treatment is further performed, and the drying treatment apparatus includes at least one of a rotary evaporator, a vacuum oven, a spray dryer, a heat treatment furnace, and a freeze dryer.

9. The step of obtaining a negative electrode material by coating the precursor is specifically a step of mixing and heat - treating the precursor and a coating material, and the manufacturing method according to claim 5, characterized by satisfying at least one of the following (1) to (13). (1) The coating material contains at least one of a carbon material, a metal oxide, a polymer material, and a nitride; (2) The coating material includes at least one of a carbon material, a metal oxide material, a polymer material, and a nitride material, and the carbon material includes at least one of soft carbon, hard carbon, crystalline carbon, and amorphous carbon. (3) The coating material includes at least one of a carbon material, a metal oxide material, a polymer material, and a nitride material, and the metal oxide material includes at least one of oxides of Sn, Ge, Fe, Si, Cu, Ti, Na, Mg, Al, Ca, and Zn. (4) The coating material includes at least one of a carbon material, a metal oxide material, a polymer material, and a nitride material, and the polymer material includes at least one of polyaniline, polyacrylic acid, polyurethane, polydopamine, polyacrylamide, sodium carboxymethyl cellulose, polyimide, and polyvinyl alcohol. (5) The coating material includes at least one of a carbon material, a metal oxide material, and a nitride material, and the nitride material includes at least one of silicon nitride, aluminum nitride, titanium nitride, and tantalum nitride. (6) The mass ratio of the precursor to the coating material is 100:(5 - 100). (7) The heat treatment is at a temperature of 400°C to 900°C. (8) The heat treatment has a heat preservation time of 1 hour to 12 hours. (9) The heat treatment has a heating rate of 1°C / min to 15°C / min. (10) The heat treatment is performed in a protective atmosphere, and the protective atmosphere includes at least one of nitrogen gas, helium gas, neon gas, argon gas, and krypton gas. (11) After mixing the precursor and the coating material and performing the heat treatment, the obtained material is further subjected to a step of pulverizing and sieving. (12) After mixing the precursor and the coating material and performing the heat treatment, the obtained material is further subjected to a step of pulverizing and sieving, and the pulverizing device includes at least one of a mechanical pulverizer, a pneumatic pulverizer, and a crusher. (13) After mixing the precursor and the coating material and performing the heat treatment, the obtained material is further subjected to a step of pulverizing and sieving, and the sieving is such that the screen mesh size is 10 mesh to 800 mesh.

10. A lithium ion battery, comprising the negative electrode material according to any one of Claims 1 to 4.

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