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

Abstract

The present disclosure relates to the field of negative electrode materials, and provides a negative electrode material and a manufacturing method thereof, and a lithium ion battery, wherein the negative electrode material comprises an aggregate containing an active material and a carbon material, wherein the aggregate has a porosity of ≦10% and an indentation hardness of ≧100 MPa. The negative electrode material provided in the present disclosure can effectively suppress the volume expansion of the negative electrode material and improve the battery cycle performance.

Description

Technical Field

[0001] (Cross - reference to related applications) This application claims the priority of the Chinese patent application with the application number “202110727563.0” and the title “Negative electrode material, its manufacturing method, and lithium - ion battery” filed with the China National Intellectual Property Administration on June 29, 2021, and all of its content is incorporated herein by reference in its entirety.

[0002] This disclosure belongs to the field of lithium - ion battery negative electrode materials, and this disclosure relates to a negative electrode material, its manufacturing method, and a lithium - ion battery.

Background Art

[0003] Conventional lithium - ion batteries have advantages such as high energy density, high output power, long cycle life, and low environmental pollution, so they are widely applied in electric vehicles and consumer electronics products. In order to improve the energy density of the battery, the research and development of silicon - based negative electrode materials are becoming increasingly mature. However, during the process of lithium release and intercalation of the negative electrode material, the volume expansion is large. In particular, the silicon - based negative electrode material can reach more than 300% volume expansion during the process of lithium release and intercalation. By pulverizing and falling off from the current collector during the charge - discharge process, the electrical contact between the negative electrode active material and the current collector is lost, resulting in poor electrochemical performance, capacity attenuation, reduced cycle stability, and difficulty in commercial application.

[0004] Therefore, how to suppress the volume expansion of the negative electrode material and improve the cycle stability of the material has become an urgent problem to be solved currently.

Summary of the Invention

[0005] This disclosure provides a negative electrode material, where the negative electrode material includes an aggregate containing an active material and a carbon material. Here, the porosity of the aggregate ≤10%, and the indentation hardness of the aggregate ≥100 MPa.

[0006] In some embodiments, the active material includes at least one of silicon oxide, elemental non-metal, elemental metal, and an alloy of the elemental metal and silicon.

[0007] In some embodiments, the elemental metal includes at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al, and Cu.

[0008] In some embodiments, the elemental non-metal includes at least one of Si and P.

[0009] In some embodiments, the silicon oxide is SiO x (where 0 < x ≦ 2).

[0010] In some embodiments, the alloy of the elemental metal and silicon includes at least one of silicon-lithium alloy, silicon-sodium alloy, silicon-potassium alloy, silicon-tin alloy, silicon-germanium alloy, silicon-iron alloy, silicon-magnesium alloy, silicon-titanium alloy, silicon-zinc alloy, silicon-aluminum alloy, and silicon-copper alloy.

[0011] In some embodiments, the median diameter of the active material is 1 nm to 500 nm.

[0012] In some embodiments, the carbon material includes at least one of amorphous carbon, crystalline carbon, and mesocarbon microbeads.

[0013] In some embodiments, the amorphous carbon includes at least one of hard carbon and soft carbon.

[0014] In some embodiments, the mass ratio of the active material to the carbon material is (30 to 70):(10 to 70).

[0015] In some embodiments, the density of the aggregate is (ρ 2 -ρ1 ) / ρ2 ≤ 5%, where ρ1 is the measured density of the aggregate and ρ2 is the Theory density of the aggregate, that is, the sum of the values obtained by multiplying the mass percentage of each component in the aggregate by the theoretical density of each component.

[0016] In some embodiments, the aggregate further contains a metal oxide.

[0017] In some embodiments, the metal oxide is distributed in the active material, and the carbon material is filled between the active material and the metal oxide.

[0018] In some embodiments, there are pores between the active material and the metal oxide, and the carbon material is filled in the pores.

[0019] In some embodiments, the general formula of the metal oxide is M x O y where 0.2 ≤ y / x ≤ 3, and M contains at least one of Sn, Ge, Fe, Cu, Ti, Na, Mg, Al, Ca, and Zn.

[0020] In some embodiments, the metal oxide exhibits a flake shape and / or a strip shape.

[0021] In some embodiments, the aspect ratio of the metal oxide is greater than 2.

[0022] In some embodiments, the mass ratio of the active material to the metal oxide is (30 - 70):(1 - 20).

[0023] In some embodiments, the aggregate further contains a conductivity improver.

[0024] In some embodiments, the conductivity improver contains at least one of an alloy material and conductive carbon.

[0025] In some embodiments, the alloy material includes at least one of a zinc alloy, an aluminum alloy, a copper alloy, a silicon alloy, a nickel alloy, and a titanium alloy.

[0026] In some embodiments, the conductive carbon includes one of graphite fibers, carbon nanotubes, graphite sheets, conductive carbon fibers, and graphene.

[0027] In some embodiments, the conductivity of the conductivity improver is 10 0 S / m to 10 8 S / m.

[0028] In some embodiments, the conductivity improver exhibits a flake shape and / or a strip shape.

[0029] In some embodiments, the aspect ratio of the conductivity improver is 2 to 5000.

[0030] In some embodiments, the mass ratio of the conductivity improver to the active material is (0.1 to 10):100.

[0031] In some embodiments, the negative electrode material further includes a carbon layer covering at least a part of the surface of the aggregate.

[0032] In some embodiments, the coverage rate of the carbon layer on the surface of the aggregate is 1% to 100%.

[0033] In some embodiments, the material of the carbon layer includes amorphous carbon.

[0034] In some embodiments, the thickness of the carbon layer is 10 nm to 1500 nm.

[0035] In some embodiments, the median diameter of the negative electrode material is 0.5 μm to 30 μm.

[0036] In some embodiments, the negative electrode material has a specific surface area ≤ 10 m2 It is / g.

[0037] The present disclosure provides a method for manufacturing a negative electrode material, comprising: manufacturing a precursor using a mixture containing an active material, a first carbon source, and a solvent; performing a densification treatment on the precursor to obtain an aggregate having a porosity of 10% or less and an indentation hardness of 100 MPa or more.

[0038] In some embodiments, the first carbon source includes at least one of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt.

[0039] In some embodiments, the active material includes at least one of silicon oxide, a non-metal simple substance, a metal simple substance, and an alloy of the metal simple substance and silicon.

[0040] In some embodiments, the metal simple substance includes at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al, and Cu.

[0041] In some embodiments, the non-metal simple substance includes at least one of Si and P.

[0042] In some embodiments, the silicon oxide includes SiO x (where 0 < x ≤ 2).

[0043] In some embodiments, the alloy of the simple metal and silicon includes at least one of a silicon-lithium alloy, a silicon-sodium alloy, a silicon-potassium alloy, a silicon-tin alloy, a silicon-germanium alloy, a silicon-iron alloy, a silicon-magnesium alloy, a silicon-titanium alloy, a silicon-zinc alloy, a silicon-aluminum alloy, and a silicon-copper alloy.

[0044] In some embodiments, the mass ratio of the active material to the first carbon source is (15 to 120):(10 to 50).

[0045] In some embodiments, the solvent is an organic solvent.

[0046] In some embodiments, the organic solvent includes an alcohol-based solvent.

[0047] In some embodiments, the alcohol-based solvent includes at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerin, n-butanol, isobutanol, and pentanol.

[0048] In some embodiments, the mixture is subjected to a drying treatment to obtain the precursor.

[0049] In some embodiments, the temperature of the drying treatment is 40°C to 300°C, and the time of the drying treatment is 1 h to 15 h.

[0050] In some embodiments, the method for manufacturing the mixture specifically includes sequentially performing ultrasonic treatment and polishing treatment on the active material, the first carbon source, and the solvent.

[0051] In some embodiments, the time of the ultrasonic treatment is 15 to 45 min.

[0052] In some embodiments, the time of the polishing treatment is 3 to 8 h.

[0053] In some embodiments, the mixture also contains a metal oxide.

[0054] In some embodiments, the general formula of the metal oxide is M x O y where 0.2 ≦ y / x ≦ 3, and where M includes at least one of Sn, Ge, Fe, Cu, Ti, Na, Mg, Al, Ca, and Zn.

[0055] In some embodiments, the metal oxide exhibits a flake shape and / or a strip shape.

[0056] In some embodiments, the aspect ratio of the metal oxide is greater than 2.

[0057] In some embodiments, the mass ratio of the active material, the metal oxide, and the first carbon source is (15 - 120):(1 - 20):(10 - 50).

[0058] In some embodiments, the mixture also contains a conductivity improver.

[0059] In some embodiments, the conductivity improver includes at least one of an alloy material and conductive carbon.

[0060] In some embodiments, the alloy material includes at least one of a zinc alloy, an aluminum alloy, a copper alloy, a silicon alloy, a nickel alloy, and a titanium alloy.

[0061] In some embodiments, the conductive carbon includes one of graphite fiber, carbon nanotube, graphite sheet, conductive carbon fiber, and graphene.

[0062] In some embodiments, the conductivity of the conductivity improver is 10 0 S / m to 10 8 S / m.

[0063] In some embodiments, the conductivity improver exhibits a flaky and / or strip shape.

[0064] In some embodiments, the aspect ratio of the conductivity improver is from 2 to 5000.

[0065] In some embodiments, the mass ratio of the conductivity improver to the active material is (0.1 to 10):100.

[0066] In some embodiments, the mixture also contains an additive.

[0067] In some embodiments, the additive includes at least one of a surfactant and a coupling agent.

[0068] In some embodiments, the surfactant includes at least one of n-octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecylbenzenesulfonate, n-eicosanoic acid, palmitic acid, myristic acid, undecanoic acid, hexadecyltrimethylammonium bromide, and polyvinylpyrrolidone.

[0069] In some embodiments, the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane.

[0070] In some embodiments, the mass ratio of the active material, the metal oxide, the additive, and the first carbon source is (15 to 120):(1 to 20):(1 to 10):(10 to 50).

[0071] In some embodiments, the densification treatment includes performing a fusion treatment and a primary heat treatment on the precursor in sequence.

[0072] In some embodiments, the fusion treatment includes mechanofusion.

[0073] In some embodiments, the rotational speed of the fusion machine used for the mechanofusion is 500 r / min to 3000 r / min.

[0074] In some embodiments, the blade gap width of the fusion machine used for the mechanofusion is 0.01 cm to 0.5 cm.

[0075] In some embodiments, the time of the mechanofusion is at least 0.5 h.

[0076] In some embodiments, the primary heat treatment includes a primary carbonization treatment.

[0077] In some embodiments, the temperature of the primary carbonization treatment is 500 °C to 1200 °C, and the time of the primary carbonization treatment is 1 h to 10 h.

[0078] In some embodiments, the primary carbonization treatment is performed in an atmosphere of a protective gas, and the protective gas includes at least one of nitrogen gas, helium gas, neon gas, argon gas, and krypton gas.

[0079] In some embodiments, the primary heat treatment further includes a secondary carbonization treatment, and the secondary carbonization treatment is performed after the fusion treatment.

[0080] In some embodiments, the secondary carbonization treatment includes at least one of vapor phase coating, solid phase coating, and liquid phase coating.

[0081] In some embodiments, a carbon coating treatment is performed on the aggregate.

[0082] In some embodiments, the carbon coating treatment includes performing a secondary heat treatment after mixing the aggregate and a second carbon source.

[0083] 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 asphalt.

[0084] In some embodiments, the mass ratio of the aggregate to the second carbon source is (10 to 100):(10 to 70).

[0085] In some embodiments, the temperature of the secondary heat treatment is 600°C to 1200°C, and the time of the secondary heat treatment is 1 h to 10 h.

[0086] In some embodiments, the secondary heat treatment is performed in an atmosphere of a protective gas, and the protective gas includes at least one of nitrogen gas, helium gas, neon gas, argon gas, and krypton gas.

[0087] A lithium ion battery, wherein the lithium ion battery includes the negative electrode material as described above, or a negative electrode material manufactured by the method for manufacturing a negative electrode material as described above.

Brief Description of the Drawings

[0088] To more clearly explain the technical means of the embodiments of the present disclosure, the drawings necessary for use in the embodiments are briefly introduced below. The following drawings exemplarily represent the embodiments of the present disclosure. The dimensional ratios in the drawings cannot directly correspond to the actual ratios of the embodiments. At the same time, it should be understood that the following drawings only show some embodiments of the present disclosure and should not be regarded as limiting the scope.

Figure 1

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Mode for Carrying Out the Invention

[0089] The advantages of the embodiments in the content of the invention are described in the embodiments part of the following specification, some are obvious based on the specification, or can be obtained by some of the embodiments of the examples of the present disclosure.

[0090] Hereinafter, with reference to the drawings, the technical means of the present disclosure will be further described by means of several embodiments.

[0091] To make the objectives, technical means and advantages of the present disclosure clearer, the present disclosure will be described in more detail below with reference to the drawings and examples. It should be understood that the examples described here are only for explaining the present disclosure and do not limit the present disclosure. Also, the technical features according to each embodiment of the present disclosure described below can be combined with each other as long as they do not conflict with each other. On the premise of not departing from the principle of the embodiments of the present disclosure, several further improvements and modifications can be made, and these improvements and modifications are also regarded as within the protection scope of the embodiments of the present disclosure.

[0092] In one embodiment, a negative electrode material is provided, which has excellent structural stability, effectively suppresses the volume expansion of the negative electrode material, and improves the battery cycle performance. In another embodiment, a manufacturing method of the above negative electrode material is provided, and the manufacturing method can reduce the manufacturing cost. In still another embodiment, a lithium-ion battery is provided.

[0093] The negative electrode material of one embodiment includes an aggregate containing an active material and a carbon material, where the porosity of the aggregate ≤ 10%, and the indentation hardness of the aggregate ≥ 100 MPa.

[0094] The negative electrode material of this embodiment includes aggregates, and the porosity of the aggregates is low, that is, its density is high. On the one hand, it is advantageous for improving the energy density of the composite material. On the other hand, for a material with a high density, even if the carbon layer on the surface of the surface aggregates is damaged, it is difficult for the electrolyte to penetrate into the aggregates, which is advantageous for protecting the internal active material particles, reducing the contact probability between the electrolyte and the active material, and thereby forming a stable solid electrolyte film. Moreover, the highly densified aggregates have a high indentation hardness, 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.

[0095] The porosity of the aggregates in this embodiment is 10% or less. Specifically, the porosity of the aggregates may be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9% or 9.5%, etc. Of course, other values within the above range may also be used, and it is not limited here. As can be understood, a low porosity of the aggregates, that is, a high density, is advantageous for forming a stable solid electrolyte film and reducing the contact between the electrolyte and the active material. In one embodiment, the porosity of the aggregates is 5% or less. In one embodiment, the porosity of the aggregates is 3% or less.

[0096] The indentation hardness of the aggregate is 100 MPa or more. Specifically, the indentation hardness of the aggregate may be, for example, 100 MPa, 200 MPa, 250 MPa, 300 MPa, 400 MPa, 450 MPa, 500 MPa, 600 MPa, 750 MPa, 800 MPa, 900 MPa, 1000 MPa, 1150 MPa, 1200 MPa, or 1250 MPa. Of course, it may be other values within the above range and is not limited here. Since it has strong rigidity, the stability of the particle structure is high, and it can resist a certain volume expansion stress, thereby reducing expansion and improving the stability of the battery cycle. In one embodiment, the indentation hardness of the aggregate is 200 MPa or more. In one embodiment, the indentation hardness of the aggregate is 400 MPa or more.

[0097] In some embodiments, the active material refers to a substance that can react with lithium to release and store lithium. The active material includes at least one of silicon oxides, non-metal simple substances, metal simple substances, and alloys of metal simple substances and silicon.

[0098] In some embodiments, the metal simple substance includes at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al, and Cu.

[0099] In some embodiments, the non-metal simple substance includes at least one of Si and P.

[0100] In some embodiments, the silicon oxide includes SiO x (where 0 < x ≤ 2).

[0101] In some embodiments, the alloy of metal simple substance and silicon includes at least one of silicon-lithium alloy, silicon-sodium alloy, silicon-potassium alloy, silicon-tin alloy, silicon-germanium alloy, silicon-iron alloy, silicon-magnesium alloy, silicon-titanium alloy, silicon-zinc alloy, silicon-aluminum alloy, and silicon-copper alloy.

[0102] In some embodiments, the median diameter of the active material is from 1 nm to 500 nm. Specifically, it may be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, or 500 nm, etc., or other values within the above range, and is not limited herein. Through multiple tests, it has been confirmed that the nanostructured active material particles have high structural properties and can suppress the volume expansion of silicon. However, since the nano-scale active particles have a large surface energy, aggregation is likely to occur during the charge and discharge process, and the particle size of the active material is too small, resulting in a high manufacturing process cost. In one embodiment, the median diameter of the active material is from 1 nm to 200 nm. In one embodiment, the median diameter of the active material is from 1 nm to 100 nm.

[0103] In some embodiments, the carbon material includes at least one of amorphous carbon, crystalline carbon, and mesocarbon microbeads. In some embodiments, the amorphous carbon includes at least one of hard carbon and soft carbon. As can be understood, the carbon material can improve the conductivity of the aggregate and reduce the porosity of the aggregate to make the aggregate denser.

[0104] In some embodiments, the mass ratio of the active material to the carbon material is (30 - 70):(10 - 70). Specifically, the mass ratio of the active material to the carbon material may be 30:10, 30:40, 30:50, 30:70, 40:10, 40:50, 40:70, 50:30, 50:60, 60:10, 60:50, 70:10, 70:40, or 70:70, etc. Of course, it may also be other values within the above range and is not limited herein.

[0105] In some embodiments, the density of the aggregate satisfies the relationship that the difference value between the measured density of the aggregate and the density of the aggregate is ≤ 5%. The measured density of the aggregate and Theory the density satisfies the relationship that the difference value ≤ 5%. The measured density of the aggregate and TheoryThe closer the density, the smaller the difference, indicating fewer pores inside the particles and being dense, which is beneficial for forming a stable solid electrolyte membrane and reducing the contact between the electrolyte and the active material. Specifically, the aggregate density satisfies the relational expression of (ρ 2 -ρ 1 ) / ρ2≦5%, where ρ1 is the measured density of the aggregate and ρ2 is the Theory density, that is, the sum of the values obtained by multiplying the mass percentage of each component in the aggregate by the theoretical density of each component. In a specific example, when the aggregate contains an active material and a carbon material, ρ2 = the mass percentage of the active material in the aggregate × the theoretical density of the active material + the mass percentage of the carbon material in the aggregate × the theoretical density of the carbon material.

[0106] In some embodiments, the aggregate further contains a metal oxide. By compounding the metal oxide with the active material, the expansion of the active material can be reduced, the long-term cycle performance can be improved, and the aggregate has a higher indentation hardness. In one embodiment, when the aggregate further contains a metal oxide, the indentation hardness of the aggregate ≧ 150 MPa, further, the indentation hardness of the aggregate ≧ 200 MPa, and furthermore, the indentation hardness of the aggregate ≧ 400 MPa. At this time, the Theory density ρ2 of the aggregate = the mass percentage of the active material in the aggregate × the theoretical density of the active material + the mass percentage of the metal oxide in the aggregate × the theoretical density of the metal oxide + the mass percentage of the carbon material in the aggregate × the theoretical density of the carbon material.

[0107] In some embodiments, in the aggregate, the metal oxide is distributed in the active material, and the carbon material is filled between the active material and the metal oxide. Specifically, there are pores between the active material and the metal oxide, and the pores are filled with the carbon material. As can be understood, due to the pore structure formed by the active material and the metal oxide, the carbon material is filled in the pores, the structural stability of the aggregate can be improved, it can resist a certain volume expansion stress, and the expansion can be reduced.

[0108] In some embodiments, the general formula of the metal oxide is M x O ywhere 0.2 ≦ y / x ≦ 3, and where M contains at least one of Sn, Ge, Fe, Cu, Ti, Na, Mg, Al, Ca, and Zn. Specifically, the metal oxide is GeO 2 , SnO 2 , ZnO, TiO 2 , Fe 3 O 4 , MgO, SiO 2 , CuO, etc. may be used. In this technical means, the selected metal oxide has a low volume expansion change rate in the lithium intercalation process compared to the active material. Therefore, by combining the metal oxide and the active material, the expansion of the active material can be reduced, and the long-term cycle performance can be improved.

[0109] In some embodiments, the metal oxide exhibits a flake shape and / or a strip shape.

[0110] In some embodiments, the aspect ratio of the metal oxide is greater than 2. When the metal oxide is in strip shape, the aspect ratio specifically refers to the ratio of the length of the metal oxide to the particle diameter, where the particle diameter here refers to the maximum straight-line distance between two points on the peripheral edge of the cross-section perpendicular to the length direction of the strip-shaped metal oxide. When the metal oxide is in flake shape, the aspect ratio specifically refers to the ratio of the length to the width of the flake-shaped metal oxide. Specifically, the aspect ratio of the metal oxide may be 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, etc. Of course, other values within the above range may also be used, and it is not limited here. Through multiple tests, when the aspect ratio of the metal oxide is greater than 2, the physical bonding force between the metal oxide and the active material can be improved, and the network structure formed by both can be improved, thereby buffering the volume expansion change of the active material and improving the cycle performance.

[0111] In some embodiments, the mass ratio of the active material to the metal oxide is (30 - 70):(1 - 20). Specifically, the mass ratio of the active material to the metal oxide is, for example, 30:5, 30:15, 30:20, 40:5, 40:15, 40:20, 50:10, 50:20, 60:10, 60:25, or 70:20. Naturally, other values within the above range may also be used and are not limited herein. If the content of the metal oxide is too high, the initial efficiency of the material will decrease. If the content of the metal oxide is too low, the rigidity of the aggregate structure will decrease, and the particle circulation stability will decrease.

[0112] In some embodiments, the aggregate further includes a conductivity improver. On the one hand, the conductivity improver can provide more carrier transmission channels, thereby promoting the transmission of carriers inside the material. On the other hand, it has better mechanical properties and can improve the stability of the material as a structural support.

[0113] In one embodiment, the indentation hardness of the aggregate is ≥ 150 Mpa. In one embodiment, the indentation hardness of the aggregate is ≥ 200 Mpa. In one embodiment, the indentation hardness of the aggregate is ≥ 400 Mpa. At this time, the... Theory The density ρ2 = the mass percentage of the active material in the aggregate of the active material × the theoretical density of the active material + the mass percentage of the metal oxide in the aggregate of the metal oxide × the theoretical density of the metal oxide + the mass percentage of the carbon material in the aggregate of the carbon material × the theoretical density of the carbon material + the mass percentage of the conductivity improver in the aggregate of the conductivity improver × the theoretical density of the conductivity improver.

[0114] In some embodiments, the conductivity improver includes at least one of an alloy material and conductive carbon.

[0115] In some embodiments, the alloy material includes at least one of a zinc alloy, an aluminum alloy, a copper alloy, a silicon alloy, a nickel alloy, and a titanium alloy.

[0116] In some embodiments, the conductive carbon includes one of graphite fibers, carbon nanotubes, graphite sheets, conductive carbon fibers, and graphene.

[0117] In some embodiments, the conductivity of the conductivity improver is 10 0 S / m to 10 8 S / m. Specifically, the conductivity of the conductivity improver is 10 S / m, 100 S / m, 1000 S / m, 10 4 S / m, 10 5 S / m, 10 6 S / m or 10 7 S / m, and naturally, other values within the above range may also be possible and are not limited here.

[0118] In some embodiments, the conductivity improver exhibits a flake shape and / or a strip shape.

[0119] In some embodiments, the aspect ratio of the conductivity improver is 2 to 5000. When the conductivity improver is in the shape of a strip, the aspect ratio specifically refers to the ratio of the length of the conductivity improver particles to the particle diameter of the particles. Here, the particle diameter refers to the maximum linear distance between two points on the cross-sectional periphery perpendicular to the length direction of the strip-shaped conductivity improver. When the metal oxide is in the shape of a flake, the aspect ratio specifically refers to the ratio of the length to the width of the flake-shaped conductivity improver. Specifically, the aspect ratio of the conductivity improver may be 2, 5, 10, 15, 20, 33, 50, 60, 70, 80, 90, 100, 150, 600, 780, 890, 1300, 1500, 2000, 3000, 4000, 5000, etc., and naturally, other values within the above range may also be possible and are not limited here. Through multiple tests, it has been confirmed that the conductivity improver with an aspect ratio within this range has excellent mechanical properties, can improve the stability of the material as a structural support, thereby buffering the volume expansion change of the active material and improving the cycle performance.

[0120] In some embodiments, the mass ratio of the conductivity improver to the active material is (0.1 to 10):100. Specifically, the mass ratio of the conductivity improver to the active material is, for example, 0.1:100, 0.5:100, 1:100, 2:100, 2.6:100, 3:100, 3.5:100, 4:100, 4.8:100, 6:100, 7:100, 8.5:100, or 10:100. Of course, other values within the above range may be used and are not limited herein.

[0121] In some embodiments, the negative electrode material further includes a carbon layer covering at least a part of the surface of the aggregate. Note that part or all of the surface of the aggregate may be covered with the carbon layer. In some embodiments, the coverage rate of the carbon layer on the surface of the aggregate is 1% to 100%. Note that the coverage rate in the present disclosure refers to the degree to which the surface of the aggregate is covered with the carbon layer. Specifically, the coverage rate is 1%, 5%, 10%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%. Of course, other values within the above range may be used and are not limited herein.

[0122] In some embodiments, the material of the carbon layer includes amorphous carbon.

[0123] In some embodiments, the thickness of the carbon layer is 10 nm to 1500 nm. As can be understood, the carbon layer covering the surface of the aggregate can reduce the contact between the active material and the electrolyte, reduce the formation of the passive film, and improve the reversible capacity of the battery. Specifically, the thickness of the carbon layer is, for example, 10 nm, 50 nm, 180 nm, 200 nm, 350 nm, 400 nm, 550 nm, 700 nm, 850 nm, 900 nm, 1050 nm, 1200 nm or 1500 nm. Of course, other values within the above range may be used and are not limited herein. If the carbon layer is too thick and the carbon occupancy is too high, it is disadvantageous to obtain a composite material with a high specific capacity. If the carbon layer is too thin, it is disadvantageous to increase the conductivity of the anode material, and the suppression performance against the volume expansion of the material is weak, resulting in poor long-term cycle performance. In one embodiment, the thickness of the carbon layer is 50 nm to 800 nm. In one embodiment, the thickness of the carbon layer is 100 nm to 500 nm.

[0124] In some embodiments, the median diameter of the anode material is 0.5 μm to 30 μm. Specifically, the median diameter of the anode material is, for example, 0.5 μm, 1 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 25 μm or 30 μm. Of course, other values within the above range may be used and are not limited herein. As can be understood, controlling the median diameter of the anode material within the above range is advantageous for improving the cycle performance of the anode material.

[0125] In some embodiments, the specific surface area of the anode material is 10 m 2 / g or less. Specifically, the specific surface area of the anode material is, for example, 0.5 m 2 / g, 1 m 2 / g, 2 m 2 / g, 3 m 2 / g, 5 m 2 / g, 7 m 2 / g, 8 m 2 / g or 10 m 2 / g or the like, and of course, other values within the above range may be used and are not limited here. As understood, controlling the specific surface area of the negative electrode material within the above range is advantageous for suppressing volume expansion and improving the cycle performance of the negative electrode material.

[0126] In the present disclosure, the median diameter refers to the average particle diameter and is measured by a Malvern particle size analyzer. The Malvern particle size analyzer utilizes the scattering phenomenon of particles with respect to light and comprehensively converts the particle size distribution of the measured particles based on the distribution of scattered light energy.

[0127] Note that the negative electrode materials of the above embodiments can be arbitrarily combined as long as they do not conflict with each other. For example, they can be limited by combining the indentation hardness of the aggregate, the porosity, and the density.

[0128] A method for manufacturing a negative electrode material according to an embodiment includes Step S10 of manufacturing a precursor with a mixture of an active material, a first carbon source, and a solvent; Step S20 of performing a densification treatment on the precursor to obtain an aggregate with a porosity ≤ 10% and an indentation hardness ≥ 100 MPa; Step S30 of performing a carbon coating treatment on the aggregate to obtain a negative electrode material.

[0129] In the method for manufacturing a negative electrode material according to the present disclosure, by performing a densification treatment on the precursor, the indentation hardness of the negative electrode material can be improved, the stability of the particle structure can be improved, and at the same time, the connection stability between the active material and the first carbon source can be improved, and the porosity can be reduced, thereby reducing the expansion rate of the negative electrode material and improving the cycle stability.

[0130] Hereinafter, the manufacturing method of the present disclosure will be specifically described with reference to examples. In step S10, a precursor is manufactured with a mixture of an active material, a first carbon source, and a solvent. In some embodiments, the first carbon source includes at least one of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt.

[0131] In some embodiments, the active material refers to a substance that can react with lithium to release and store lithium. The active material includes at least one of an alloy of a simple metal and silicon, an oxide of silicon, a simple metal, and a simple non-metal. In some embodiments, the simple metal includes at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al, and Cu. In some embodiments, the simple non-metal includes at least one of Si and P. In some embodiments, the oxide of silicon includes SiO x (where 0 < x ≤ 2). In some embodiments, the alloy of a simple metal and silicon includes at least one of a lithium-silicon alloy, a sodium-silicon alloy, a potassium-silicon alloy, a tin-silicon alloy, a germanium-silicon alloy, an iron-silicon alloy, a magnesium-silicon alloy, a titanium-silicon alloy, a zinc-silicon alloy, an aluminum-silicon alloy, and a copper-silicon alloy.

[0132] In some embodiments, the mass ratio of the active material to the first carbon source is (15 - 120):(10 - 50). Specifically, the mass ratio of the active material to the first carbon source is, for example, 100:15.9, 100:21.9, 100:24.5, 100:9.5, 100:9.5, 100:9.5, 100:9.5, or 100:9.5. Naturally, other values within the above range are also possible and are not limited here.

[0133] In some embodiments, the mixing method of the mixture includes magnetic stirring, mechanical stirring, ultrasonic dispersion, grinding dispersion, and the like. By adopting grinding dispersion, the active material can be dispersed, avoiding the aggregation of the active material and dispersing the active material into small nanoparticles.

[0134] In some embodiments, the method for manufacturing the mixture specifically includes sequentially performing ultrasonic treatment and grinding treatment on the active material, the first carbon source, and the solvent. In some embodiments, the time of the ultrasonic treatment is 15 to 45 minutes. Specifically, the time of the ultrasonic treatment is, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes. Naturally, other values within the above range may also be used and are not limited here. In some embodiments, the time of the grinding treatment is 3 to 8 hours. Specifically, the time of the grinding treatment is, for example, 4 hours, 5 hours, 6 hours, or 7 hours. Naturally, other values within the above range may also be used and are not limited here. By sufficiently grinding, the mixing of the components can be made more uniform.

[0135] Specifically, the active material, the first carbon source, and the solvent are mixed to obtain a precursor solution, and by wet ball milling the precursor solution, the particle size of the particles in the precursor solution reaches 1 nm to 500 nm. Specifically, the particle size of the particles in the precursor solution may be, for example, 1 nm, 5 nm, 10 nm, 15 nm, 50 nm, 100 nm, 150 nm, 200 nm, 300 nm, 400 nm, or 500 nm, and is not limited here.

[0136] In some embodiments, the solvent includes an organic solvent. In some embodiments, the organic solvent includes an alcohol-based solvent. Specifically, the alcohol-based solvent includes at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerin, n-butanol, isobutanol, and pentanol. By adding each component to the organic solvent and performing wet ball milling, the mixing uniformity of the components can be improved and it is beneficial for rapid drying.

[0137] In some embodiments, the mixture is dried to obtain a precursor. In some embodiments, the temperature of the drying process is 40°C to 300°C, and the time of the drying process is 1 h to 15 h. Specifically, the temperature of the drying process is, for example, 50°C, 70°C, 100°C, 120°C, 150°C, 200°C, 220°C, 250°C, etc. Of course, other values within the above range may also be used and are not limited herein. Specifically, the time of the drying process is, for example, 1.5 h, 2 h, 2.5 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h or 14 h, etc. Of course, other values within the above range may also be used and are not limited herein. The drying process method may be, for example, in-furnace drying, freeze drying, stirring evaporation drying, spray drying, etc. The drying process in this example can remove the solvent in the precursor solution as much as possible.

[0138] In some embodiments, the mixture also contains a metal oxide. In some embodiments, the general formula of the metal oxide is M x O y where 0.2 ≤ y / x ≤ 3, and where M contains at least one of Sn, Ge, Fe, Cu, Ti, Na, Mg, Al, Ca, and Zn. Specifically, the metal oxide may be, for example, GeO 2 、SnO 2 、ZnO、TiO 2 、Fe 3 O 4 、MgO、SiO 2 、CuO, etc.

[0139] In some embodiments, the metal oxide exhibits a flake shape and / or a strip shape.

[0140] In some embodiments, the aspect ratio of the metal oxide is greater than 2. When the metal oxide is strip-shaped, the aspect ratio specifically refers to the ratio of the length of the particle to the particle diameter of the particle. When the metal oxide is flake-shaped, the aspect ratio specifically refers to the ratio of the length to the width of the flake-shaped metal oxide. Specifically, the aspect ratio of the metal oxide may be 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 12, 15, 17, 18, or 22, etc., or other values within the above range, and is not limited herein. Through multiple tests, when the aspect ratio of the metal oxide is 2 or less, by controlling the aspect ratio of the metal oxide, the physical bonding force between the metal oxide and the active material can be improved, and the network structure formed by both can be improved, thereby better buffering the volume expansion change of the active material and improving the cycle performance.

[0141] In some embodiments, the mass ratio of the active material, the metal oxide, and the first carbon source is (15 - 120):(1 - 20):(10 - 50). Specifically, the mass ratio of the active material, the metal oxide, and the first carbon source may be 15:1:10, 20:3:25, 50:8:35, 60:9:38, 70:11:45, 90:15:40, 100:9:15.9, 100:5:21.9, 100:2:24.5, 100:9:19.5, 100:9:19.5, 100:9:19.5, 100:11:19.5, 100:9.5:19.5, etc. Of course, other values within the above range are also possible and are not limited herein.

[0142] In some embodiments, the mixture further contains a conductivity improver.

[0143] In one embodiment, a conductivity improver is added in the step of mixing the active material, the first carbon source, and the solvent. In some embodiments, the conductivity improver includes at least one of an alloy material and conductive carbon.

[0144] In some embodiments, the alloy material includes at least one of a zinc alloy, an aluminum alloy, a copper alloy, a silicon alloy, a nickel alloy, and a titanium alloy.

[0145] In some embodiments, the conductive carbon includes one of graphite fibers, carbon nanotubes, graphite sheets, conductive carbon fibers, and graphene.

[0146] In some embodiments, the conductivity of the conductivity improver is 10 0 S / m to 10 8 S / m. The conductivity of the conductivity improver may 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., and of course, other values within the above range may also be possible and are not limited here. In some embodiments, the conductivity improver exhibits a flake shape and / or a strip shape. In some embodiments, the aspect ratio of the conductivity improver is 2 to 5000. Specifically, the aspect ratio of the conductivity improver may be 2, 5, 10, 15, 20, 33, 50, 60, 70, 80, 90, 100, 150, 600, 780, 890, 1300, 1500, 2000, 3000, 4000, 5000, etc., and of course, other values within the above range may also be possible and are not limited here.

[0147] In some embodiments, the mass ratio of the conductivity improver to the active material is (0.1 to 10):100. Specifically, the mass ratio of the conductivity improver to the active material is 0.1:100, 0.5:100, 1:100, 2:100, 2.6:100, 3:100, 3.5:100, 4:100, 4.8:100, 6:100, 7:100, 8.5:100, or 10:100, etc. Of course, other values within the above range may also be possible and are not limited here.

[0148] In some embodiments, the mixture also includes an additive. The additive in such embodiments can effectively improve the connection stability between the active material and the carbon material and form a strong system. In some embodiments, the additive includes at least one of a surfactant and a coupling agent. Tests have confirmed that adopting the above types of additives can effectively improve the connection stability between the active material and the carbon material, form a strong system, reduce the porosity, thereby reducing the expansion rate of the anode material and improving the cycle stability.

[0149] In some embodiments, the surfactant includes, but is not limited to, at least one of n-octadecanoic acid, lauric acid, polyacrylic acid (PAA), sodium dodecylbenzenesulfonate (SDBS), n-eicosanoic acid, palmitic acid, myristic acid, undecanoic acid, hexadecyltrimethylammonium bromide, and polyvinylpyrrolidone (PVP).

[0150] In some embodiments, silane coupling agents include, but are not limited to, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane.

[0151] In some embodiments, the mass ratio of the active material, metal oxide, additive, and first carbon source is (15 - 120):(1 - 20):(1 - 10):(10 - 50). Specifically, the mass ratio of the active material, metal oxide, additive, and first carbon source can be 100:9:5.9:15.9, 100:5:8:21.9, 100:2:5:24.5, 100:9:5:19.5, 100:9:11:19.5, 100:9:10.5:19.5, 100:11:5.5:19.5, 100:9.5:6.9:19.5, etc. Naturally, other values within the above range are also possible and are not limited here.

[0152] In step S20, the precursor is subjected to a densification treatment to obtain an aggregate with a porosity of ≤ 10% and an indentation hardness of ≥ 100 MPa.

[0153] In some embodiments, the densification treatment includes sequentially performing a fusion treatment and a primary heat treatment on the precursor. By performing the fusion treatment on the precursor, the indentation hardness of the anode material can be improved, and by further performing the primary heat treatment, the stability of the particle structure can be improved, and at the same time, the connection stability between the active material and the first carbon source can be improved, and the porosity can be reduced. Of course, in other embodiments, for example, other methods such as processes like press molding, isostatic pressing, dipping, etc. can be used to perform the densification treatment, as long as the porosity of the aggregate is ≤ 10% and the indentation hardness is ≥ 100 MPa.

[0154] In some embodiments, the fusion treatment is mechanofusion. By the fusion treatment, the connection between the active material and the carbon material can be effectively strengthened, the pores between them can be reduced, and the densification can be improved. In some embodiments, the rotational speed of the fusion machine used for mechanofusion is 500 r / min to 3000 r / min. Specifically, it may be 500 r / min, 1000 r / min, 1500 r / min, 2000 r / min, 2500 r / min, or 3000 r / min, etc. Of course, other values within the above range may also be used and are not limited here. The blade gap width of the fusion machine is 0.01 cm to 0.5 cm. Specifically, it may be 0.01 cm, 0.05 cm, 0.1 cm, 0.15 cm, 0.2 cm, 0.25 cm, 0.3 cm, or 0.5 cm, etc. Of course, other values within the above range may also be used and are not limited here. The time of mechanofusion is at least 0.5 h. Specifically, it may be 0.5 h, 0.8 h, 0.9 h, 1.0 h, 1.5 h, or 2 h, etc. Of course, other values within the above range may also be used and are not limited here.

[0155] In some embodiments, the primary heat treatment includes a primary carbonization treatment.

[0156] In some embodiments, the mixture after the fusion treatment is fed into a high-temperature box furnace for primary carbonization treatment to carbonize the first carbon source and tightly connect the active material and the carbon material. The mode of the primary carbonization treatment may be, for example, atmospheric pressure firing, vacuum firing, or hot press firing.

[0157] In some embodiments, the temperature of the primary carbonization treatment is 500°C to 1200°C, and the time of the primary carbonization treatment is 1 h to 10 h. Specifically, the temperature of the primary carbonization treatment is, for example, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, etc. Of course, other values within the above range may also be used and are not limited herein. Specifically, the time of the primary carbonization treatment is, for example, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, or 15 h, etc. Of course, other values within the above range may also be used and are not limited herein.

[0158] The heating rate of the primary carbonization treatment is 1°C / min to 30°C / min. Specifically, it may be 1°C / min, 5°C / min, 10°C / min, 15°C / min, 20°C / min, 25°C / min, or 30°C / min, etc. Of course, other values within the above range may also be used and are not limited herein.

[0159] In one embodiment, the heating rate of the primary heat treatment is 1°C / min to 15°C / min.

[0160] In some embodiments, the primary carbonization treatment is carried out in an atmosphere of a protective gas, and the protective gas contains at least one of nitrogen gas, helium gas, neon gas, argon gas, and krypton gas.

[0161] In some embodiments, the primary heat treatment further includes a secondary carbonization treatment, and the secondary carbonization treatment is carried out after the fusion treatment. The secondary carbonization treatment is carried out after the fusion treatment and before the primary carbonization treatment, or after the primary carbonization treatment. By the secondary carbonization treatment, the porosity of the material can be further reduced.

[0162] In some embodiments, the secondary carbonization treatment includes at least one of gas-phase coating, solid-phase coating, and liquid-phase coating. In some embodiments, the reaction temperature of the solid-phase coating is 500°C to 1200°C, specifically, it may be 600°C, 700°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, etc., but is not limited thereto. The reaction time is 1 h to 12 h, specifically, it may be 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, etc., but is not limited thereto. In some embodiments, the reaction temperature of the liquid-phase coating is 500°C to 1200°C, specifically, it may be 600°C, 700°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, etc., but is not limited thereto. The reaction time is 1 h to 12 h, specifically, it may be 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, etc., but is not limited thereto.

[0163] In some embodiments, the gas-phase coating includes chemical vapor deposition. The reaction temperature of the chemical vapor deposition is 600°C to 1050°C, specifically, it may be 600°C, 700°C, 800°C, 850°C, 900°C, 950°C, 1000°C, or 1050°C, etc., and of course, other values within the above range may also be possible and are not limited herein. The chemical vapor deposition time is 0.5 h to 2 h, specifically, it may be 0.5 h, 0.8 h, 1.0 h, 1.5 h, 1.8 h, or 2 h, etc., and of course, other values within the above range may also be possible and are not limited herein.

[0164] As can be understood, when decomposing the carbon source gas by chemical vapor deposition, it is decomposed into zero-dimensional single carbon atom radicals or one-dimensional short carbon chains, and when stacked on each other, they become more compact, which is advantageous for forming an aggregate with a dense structure, advantageous for the integrity of the material conductive network and the stability of the structure, and advantageous for improving the cycle stability of the negative electrode material.

[0165] In one embodiment, the reaction temperature of the chemical vapor deposition is 800°C to 1000°C.

[0166] In some embodiments, the carbon source gas in the chemical vapor deposition process includes at least one of methane, ethylene, acetylene, benzene, toluene, xylene, styrene, and phenol.

[0167] In step S30, the aggregate is carbon-coated to obtain the negative electrode material.

[0168] Note that the negative electrode material of this embodiment may not be carbon-coated. In this case, step S30 can be omitted.

[0169] In some embodiments, the carbon coating process includes mixing the aggregate and a second carbon source and then performing a secondary heat treatment.

[0170] 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 asphalt.

[0171] In some embodiments, the particle size of the aggregate is 0.5 μm to 15 μm. Specifically, it may be 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 10 μm, 12 μm, 15 μm, etc. Of course, other values within the above range may also be used, and it is not limited here. By controlling the particle size within the above range, it is advantageous to obtain a product with high pressing hardness. Tests have confirmed that if the particles of the aggregate are too large, the densification degree is low, the connection is not tight, and the pressing hardness is small.

[0172] In some embodiments, the mass ratio of the aggregate to the second carbon source is (10 to 100):(10 to 70). Specifically, the mass ratio of the aggregate to the second carbon source is, for example, 10:20, 20:10, 100:25, 100:35, 100:45, 100:55, 100:65, etc. Of course, other values within the above range are also possible and are not limited here.

[0173] In some embodiments, the mixing method of the aggregate and the second carbon source includes magnetic stirring, mechanical stirring, ultrasonic dispersion, abrasive dispersion, etc.

[0174] In some embodiments, the secondary heat treatment method may be, for example, atmospheric pressure firing, vacuum firing, or hot press firing.

[0175] In some embodiments, the temperature of the secondary heat treatment is 600°C to 1200°C, and the time of the secondary heat treatment is 1 h to 10 h. Specifically, the temperature of the secondary heat treatment is, for example, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1200°C, 1200°C, etc. Of course, other values within the above range are also possible and are not limited here. The time of the secondary heat treatment is, for example, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, or 15 h, etc. Of course, other values within the above range are also possible and are not limited here.

[0176] In some embodiments, the heating rate during the secondary heat treatment is 1 to 30°C / min. For example, preferably, the heating rate during the secondary heat treatment may be 1 to 15°C / min. The heating rate during the secondary heat treatment is 1°C / min to 30°C / min, and specifically may be 1°C / min, 5°C / min, 10°C / min, 15°C / min, 20°C / min, 25°C / min, or 30°C / min, etc. Of course, other values within the above range are also possible and are not limited here.

[0177] In one embodiment, the heating rate during the primary heat treatment is 1°C / min to 15°C / min.

[0178] In some embodiments, the secondary heat treatment is performed in an atmosphere of a protective gas, and the protective gas contains at least one of nitrogen gas, helium gas, neon gas, argon gas, and krypton gas.

[0179] In this technical means, since the negative electrode material manufactured by the above manufacturing method coats a carbon layer on the surface of the aggregate formed by the active material and the carbon material, it is possible to suppress the expansion during the cycling process of the material. The aggregate, which is its core structure, has a high indentation hardness and strong rigidity, so it can effectively resist the stress of a certain volume expansion, which is advantageous for maintaining the structural stability of the negative electrode material, thereby reducing the expansion rate and improving the battery cycling performance. The aggregate has a low porosity and high density, which is advantageous for forming a stable solid electrolyte film, reducing the contact between the electrolyte and the active material, reducing the volume expansion of the material, and improving the cycling performance.

[0180] The present disclosure further provides a lithium-ion battery including the above negative electrode material.

Examples

[0181] The following are typical and non-limiting examples of the present disclosure.

[0182] Example 1 The manufacturing method of the negative electrode material of this example includes the following steps.

[0183] (1) Si powder with a median diameter of 100 nm, SiO particles with an aspect ratio of 22, lauric acid, and phenol resin are added to a 40% ethylene glycol solution at a mass ratio of 60:4.5:3.9:22.9, ultrasonically dispersed for more than 10 min to obtain a dispersion solution, and then the dispersion solution is placed in a ball mill and polished and dispersed for 4 hours to obtain a precursor solution. Next, a drying treatment is performed, the drying temperature is 190 °C, and the time is 3 h to obtain a precursor.

[0184] (2) Place the precursor in a fusion machine. The rotation speed of the fusion machine is 500 r / min, the blade gap width of the fusion machine used for mechanofusion is 0.05 cm, and the mechanofusion time is 0.5 h. Place the material after fusion in a heat treatment furnace, then pass nitrogen gas through it and perform primary heat treatment at 600 °C for 3 h of heat preservation to obtain an aggregate.

[0185] (3) Mix the aggregate and glucose at a mass ratio of 30:45. Then place the mixed material in a high-temperature box furnace, pass nitrogen gas through it, perform secondary heat treatment at 1000 °C, keep it warm for 6 h, then pulverize it and sieve it through a 500-mesh sieve to obtain a negative electrode material.

[0186] The negative electrode material manufactured in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes Si powder, SiO particles, and a carbon material. The mass ratio of silicon powder, SiO particles, and carbon material is 55.9:4.3:39.8. The median diameter of the negative electrode material is 16 μm, the specific surface area is 5.2 m 2 / g, and the average thickness of the carbon layer is 166 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 5.5%. As a result of measuring the aggregate particles using a nanoindenter, the indentation hardness of the aggregate is 330 MPa on average. The difference between the measured density of the aggregate and the Theory densities of silicon powder, SiO particles, and carbon material is 0.9%.

[0187] Figure 2 is a scanning electron microscope image of the negative electrode material manufactured in Example 1, and the peak position of the silicon peak exists in the X-ray diffraction pattern of Figure 3.

[0188] Example 2 The manufacturing method of the negative electrode material of this example includes the following steps.

[0189] (1) Si powder with a median diameter of 80 nm, GeO with an aspect ratio of 12 2Particles, palmitic acid, and polyvinylpyrrolidone were added to a propanol solution at a mass ratio of 40:1.8:8:21.9, ultrasonically dispersed for more than 15 min to obtain a dispersion solution, and then the dispersion solution was put into a ball mill and ground and dispersed for 3 hours to obtain a precursor solution. Then, it was dried at 190 °C for 3 h to obtain a precursor.

[0190] (2) The precursor was placed in a fusion machine with a rotation speed of 800 r / min, a blade gap width of 0.15 cm, and a fusion time of 1.5 h. The fused material was put into a heat treatment furnace, then nitrogen gas was passed through, heated to 900 °C for the first heat treatment, and kept warm for 3 h to obtain an aggregate.

[0191] (3) The aggregate and sucrose were mixed at a mass ratio of 20:45. Then, the mixed material was placed in a high-temperature box furnace, nitrogen gas was passed through, secondary heat treatment was carried out at 900 °C, kept warm for 5 h, then pulverized, and sieved through a 500-mesh sieve to obtain a negative electrode material.

[0192] The negative electrode material manufactured in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes Si powder, GeO 2 particles, and a carbon material. The mass ratio of Si powder, GeO 2 particles to the carbon material is 63.3:2.9:33.8. The median diameter of the negative electrode material is 12 μm, the specific surface area is 3.2 m 2 / g, and the average thickness of the carbon layer is 154 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 4.9%. As a result of measuring the aggregate particles using a nanoindenter, the indentation hardness of the aggregate is 540 MPa on average. The difference between the measured density of the aggregate and the Theory densities of silicon powder, SiO particles, and carbon material in the aggregate is 2.09%.

[0193] Example 3 The manufacturing method of the negative electrode material of this example includes the following steps.

[0194] (1) Si powder with a median diameter of 50 nm and SnO with an aspect ratio of 62 Particles, linoleic acid, and polyethylene were added to a 40% ethanol solution at a mass ratio of 20:1:5:24.5, ultrasonically dispersed for more than 25 min to obtain a dispersion solution, then the dispersion solution was placed in a ball mill and ground and dispersed for 8 h to obtain a precursor solution, and then a drying treatment was performed. The drying temperature was 200 °C and the time was 3 h to obtain a precursor.

[0195] (2) The precursor was placed in a fusion machine. The rotation speed of the fusion machine was 600 r / min, the blade gap width of the fusion machine was 0.3 cm, and the fusion time was 3 h. The fused material was put into a heat treatment furnace, and then nitrogen gas was introduced for primary heat treatment at 900 °C for 5 h of heat preservation to obtain an aggregate.

[0196] (3) The aggregate and asphalt were mixed at a mass ratio of 30:55. Then the mixed material was placed in a high-temperature box furnace, nitrogen gas was introduced, secondary heat treatment was performed at 950 °C for 2 h of heat preservation, and then it was pulverized and sieved through a 500-mesh sieve to obtain a negative electrode material.

[0197] The negative electrode material produced in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes Si powder, SnO 2 particles, and a carbon material. The mass ratio of the Si powder, SnO 2 particles to the carbon material is 48.1:2.3:49.6. The median diameter of the negative electrode material is 8.4 μm, the specific surface area is 4.2 m 2 / g, and the average thickness of the carbon layer is 79 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 6.5%. As a result of measuring the aggregate particles using a nanoindenter, the indentation hardness of the aggregate is on average 116 MPa. The difference between the measured density of the aggregate and the 2 densities of the Si powder, SnO Theory particles and the carbon material in the aggregate is 2.78%.

[0198] Example 4 The manufacturing method of the negative electrode material of this example includes the following steps.

[0199] (1) Si powder with a median diameter of 20 nm, ZnO particles with an aspect ratio of 18, oleic acid, and polyethylene glycol were added to an n-butanol solution at a mass ratio of 40:10.5:9:29.5, ultrasonically dispersed for more than 45 min to obtain a dispersion solution, and then the dispersion solution was placed in a ball mill and ground and dispersed for 6 h to obtain a precursor solution. Next, a drying treatment was performed, the drying temperature was 250 °C, and the time was 2.5 h to obtain a precursor.

[0200] (2) The precursor was placed in a fusion machine, the rotation speed of the fusion machine was 900 r / min, the blade gap width of the fusion machine was 0.4 cm, and the mechanofusion time was 3 h. The fused material was placed in a heat treatment furnace, and then nitrogen gas was passed through for a primary heat treatment at 780 °C for 8 h of heat preservation to obtain an aggregate.

[0201] (3) The aggregate and asphalt were mixed at a mass ratio of 40:45, and then the mixed material was placed in a high-temperature box furnace, nitrogen gas was passed through, a secondary heat treatment was performed at 950 °C for 6 h of heat preservation, and then it was pulverized and sieved through a 500-mesh sieve to obtain a negative electrode material.

[0202] The negative electrode material produced in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes Si powder, ZnO particles, and a carbon material. The mass ratio of the Si powder, ZnO particles, and carbon material is 51.3:13.5:35.2. The median diameter of the negative electrode material is 6.4 μm, the specific surface area is 3.2 m 2 / g, and the average thickness of the carbon layer is 155 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 8.5%. As a result of measuring the aggregate particles using a nanoindenter, the indentation hardness of the aggregate is on average 556 MPa. The difference between the measured density of the aggregate and the Theory densities of the Si powder, ZnO particles, and carbon material in the aggregate was 3.98%.

[0203] Example 5 The manufacturing method of the negative electrode material of this example includes the following steps.

[0204] (1) Si powder with a median diameter of 50 nm, TiO particles with an aspect ratio of 18, capric acid, and asphalt are added to an ethylene glycol solution at a mass ratio of 80:9:10:9.5, ultrasonically dispersed for more than 45 min to obtain a dispersion solution, and the dispersion solution is further placed in a ball mill and ground and dispersed for 6 h to obtain a precursor solution. Next, a drying treatment is performed, the drying temperature is 150 °C, and the time is 5 h to obtain a precursor. 2 Particles, capric acid, and asphalt are added to an ethylene glycol solution at a mass ratio of 80:9:10:9.5, ultrasonically dispersed for more than 45 min to obtain a dispersion solution, and the dispersion solution is further placed in a ball mill and ground and dispersed for 6 h to obtain a precursor solution. Next, a drying treatment is performed, the drying temperature is 150 °C, and the time is 5 h to obtain a precursor.

[0205] (2) The precursor is placed in a fusion machine, the rotation speed of the fusion machine is 650 r / min, the blade gap width of the fusion machine is 0.35 cm, and the fusion time is 2 h. The fused material is placed in a heat treatment furnace, and then helium gas is passed through for a primary heat treatment at 600 °C for 6 h of heat preservation. After that, the heat-treated material is pulverized and placed in a vapor deposition furnace. The temperature in the vapor deposition furnace is 1000 °C, and methane is passed through for 1.5 h of deposition to form a carbon material and obtain an aggregate.

[0206] (3) The aggregate and asphalt are mixed at a mass ratio of 50:35, and then the mixed material is placed in a high-temperature box furnace, nitrogen gas is passed through, and a secondary heat treatment is performed at 920 °C for 5 h of heat preservation. After that, it is pulverized and sieved through a 500-mesh sieve to obtain a negative electrode material.

[0207] The negative electrode material manufactured in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes Si powder, TiO 2 Particles, and a carbon material. The mass ratio of the Si powder, TiO 2 Particles to the carbon material is 65.2:7.3:27.5. The median diameter of the negative electrode material is 6 μm, the specific surface area is 2.3 m 2 / g, and the average thickness of the carbon layer is 418 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 3.5%. As a result of measuring the aggregate particles using a nanoindenter, the average indentation hardness of the aggregate is 756 MPa. The difference between the measured density of the aggregate and the densities of the Si powder, TiO 2 Particles, and carbon material in the aggregate is 4.38%. Theory Density and the difference between the measured density of the aggregate and the densities of the Si powder, TiO

[0208] Example 6 The manufacturing method of the negative electrode material of this example includes the following steps.

[0209] (1) Si powder with a median diameter of 50 nm, TiO particles with an aspect ratio of 17, capric acid, and asphalt are added to an ethylene glycol solution at a mass ratio of 22:8:10:16.5, ultrasonically dispersed for more than 45 min to obtain a dispersion solution, and then the dispersion solution is placed in a ball mill and ground and dispersed for 4 hours to obtain a precursor solution. Next, a drying treatment is performed to obtain a precursor. 2

[0210] (2) The precursor is placed in a fusion machine. The rotation speed of the fusion machine is 800 r / min, the blade gap width of the fusion machine is 0.2 cm, and the fusion time is 3 h. The material after fusion is placed in a heat treatment furnace, and then helium gas is passed through for a primary heat treatment at 770 °C for 5 h of heat preservation. Then, the material after heat treatment is pulverized and placed in a vapor deposition furnace. The temperature in the vapor deposition furnace is 900 °C, acetylene gas is passed through, and deposition is carried out for 0.5 h to form a carbon material and obtain an aggregate.

[0211] (3) The aggregate and asphalt are mixed at a mass ratio of 35:50. Then, the mixed material is placed in a high-temperature box furnace, nitrogen gas is passed through, and a secondary heat treatment is performed at 920 °C for 4 h of heat preservation. After that, it is pulverized and sieved through a 500-mesh sieve to obtain a negative electrode material.

[0212] The negative electrode material manufactured in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes Si powder, TiO particles, and a carbon material. The mass ratio of Si powder, TiO particles, and carbon material is 39.1:14.5:46.4. The median diameter of the negative electrode material is 5.2 μm, the specific surface area is 1.3 m 2 / g, and the average thickness of the carbon layer is 511 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 1.5%. As a result of measuring the aggregate particles using a nanoindenter, the indentation hardness of the aggregate is on average 356 MPa. The measured density of the aggregate and Si powder, TiO 2 2 2 ​​​The difference between the density of the particles and the carbon material Theory was 1.58%.

[0213] Example 7 The method for manufacturing the negative electrode material of this example includes the following steps.

[0214] (1) Ge powder with a median diameter of 100 nm, ZnO particles with an aspect ratio of 8, oleic acid, and fructose were added to an ethylene glycol solution at a mass ratio of 90:11:5.5:18.9, ultrasonically dispersed for more than 45 min to obtain a dispersion solution, and then the dispersion solution was put into a ball mill and ground and dispersed for 8 h to obtain a precursor solution. Next, a drying treatment was performed, the drying temperature was 190 °C, and the time was 3 h to obtain a precursor.

[0215] (2) The precursor was placed in a fusion machine, the rotation speed of the fusion machine was 900 r / min, the blade gap width of the fusion machine was 0.3 cm, and the fusion time was 3 h. Next, it was placed in a vapor deposition furnace, the temperature in the vapor deposition furnace was 1050 °C, acetylene gas was passed through, and deposition was performed for 1 h to form a carbon material and obtain an aggregate.

[0216] (3) The aggregate and asphalt were mixed at a mass ratio of 45:40, and then the mixed material was placed in a high-temperature box furnace, nitrogen gas was passed through, secondary heat treatment was performed under the condition of 1020 °C, after heat preservation for 2 h, it was pulverized, and passed through a 500-mesh sieve to obtain a negative electrode material.

[0217] The negative electrode material manufactured in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes Ge powder, ZnO particles, and a carbon material. The mass ratio of Ge powder, ZnO particles, and carbon material contained in the aggregate is 65.3:8:26.7. The median diameter of the negative electrode material is 11.2 μm, the specific surface area is 3.3 m 2 / g, and the average thickness of the carbon layer is 310 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 3.2%. As a result of measuring the aggregate particles using a nanoindenter, the indentation hardness of the aggregate is on average 446 MPa. The measured density of the aggregate and the Ge powder, ZnO particles, and carbon material in the aggregateTheory The difference in density was 5.11%.

[0218] Example 8 The method for manufacturing the negative electrode material of this example includes the following steps.

[0219] (1) Al powder with a median diameter of 120 nm, Fe particles with an aspect ratio of 18 3 O 4 particles, lauric acid, and asphalt were added to a 40% ethanol solution at a mass ratio of 20:2:6.9:10, ultrasonically dispersed for more than 45 min to obtain a dispersion solution, and then the dispersion solution was placed in a ball mill and ground and dispersed for 4 hours to obtain a precursor solution. Next, a drying treatment was performed, the drying temperature was 200 °C, and the time was 3 h to obtain a precursor.

[0220] (2) The precursor was placed in a fusion machine, the rotation speed of the fusion machine was 650 r / min, the blade gap width of the fusion machine was 0.5 cm, and the fusion time was 3 h. The material after fusion was placed in a heat treatment furnace, and then primary heat treatment was performed at 790 °C for 4 h of heat preservation to obtain an aggregate.

[0221] (3) The aggregate and asphalt were mixed at a mass ratio of 100:45, and then the mixed material was placed in a high-temperature box furnace, nitrogen gas was passed through, secondary heat treatment was performed at 820 °C, after 4 h of heat preservation, it was pulverized and sieved through a 500-mesh sieve to obtain a negative electrode material.

[0222] The negative electrode material manufactured in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes Al powder, Fe 3 O 4 particles, and a carbon material. The mass ratio of Al powder, Fe 3 O 4 particles to the carbon material is 59.6:5.96:34.44. The median diameter of the negative electrode material is 16.2 μm, and the specific surface area is 4.3 m 2 / g, and the average thickness of the carbon layer is 351 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 4.0%. As a result of measuring the aggregate particles using a nanoindenter, the average indentation hardness of the aggregate is 292 MPa. The difference between the measured density of the aggregate and the 3 O 4 densities of the Al powder, Fe Theory particles and the carbon material in the aggregate was 4.78%.

[0223] Example 9 The difference between this example and Example 1 is that the mass ratio of Si powder with a median diameter of 100 nm, SiO particles with an aspect ratio of 22, lauric acid, and phenolic resin in step 1) is 15:2:1.5:12.5, and the primary heat treatment temperature in step 2) is 1200 °C.

[0224] The negative electrode material produced in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes silicon powder, SiO particles, and a carbon material. The mass ratio of the Si powder, SiO particles, and carbon material is 51.3:6.8:41.9. The median diameter of the negative electrode material is 14.7 μm, and the specific surface area is 3.2 m 2 / g, and the average thickness of the carbon layer is 378 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 3.5%. As a result of measuring the aggregate particles using a nanoindenter, the average indentation hardness of the aggregate is 380 MPa. The difference between the measured density of the aggregate and the Theory densities of the Si powder, SiO particles, and carbon material in the aggregate was 0.99%.

[0225] Example 10 The difference between this example and Example 1 is that the mass ratio of Si powder with a median diameter of 100 nm, SiO particles with an aspect ratio of 22, lauric acid, and phenolic resin in step 1) is 120:15.5:5.9:45.9, and the secondary heat treatment temperature in step 3) is 600 °C.

[0226] The negative electrode material manufactured in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes Si powder, SiO particles, and a carbon material. The mass ratio of the Si powder, SiO particles, and carbon material is 60.7:7.8:31.5. The median diameter of the negative electrode material is 17.7 μm, the specific surface area is 6.1 m 2 / g, and the average thickness of the carbon layer is 240 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 4.8%. As a result of measuring the aggregate particles using a nanoindenter, the average indentation hardness of the aggregate is 160 MPa. The difference between the measured density of the aggregate and the Theory densities of the Si powder, SiO particles, and carbon material in the aggregate was 8.18%.

[0227] Example 11 The difference between this example and Example 1 is that the mass ratio of the Si powder with a median diameter of 100 nm, SiO particles with an aspect ratio of 22, CNTs with a diameter of 20 nm, lauric acid, and phenol resin in step 1) is 60:4.5:0.9:3.9:22.9, and other parameters remain unchanged.

[0228] The negative electrode material manufactured in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes silicon powder, SiO particles, CNTs, and a carbon material. The mass ratio of the Si powder, SiO particles, CNTs, and carbon material is 60.7:5.8:1.9:31.6. The median diameter of the negative electrode material is 13.7 μm, the specific surface area is 5.1 m 2 / g, and the average thickness of the carbon layer is 221 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 7.8%. As a result of measuring the aggregate particles using a nanoindenter, the average indentation hardness of the aggregate is 375 MPa. The difference between the measured density of the aggregate and the Theory densities of the Si powder, SiO particles, and carbon material in the aggregate is 9.4%.

[0229] Example 12 The difference between this example and Example 1 is that the carbon coating treatment step in step 3) is not performed.

[0230] The negative electrode material manufactured in this example contains aggregates, and the aggregates contain silicon powder, SiO particles, and a carbon material. The mass ratio of the silicon powder, SiO particles, and carbon material is 55.9:4.3:39.8. The median diameter of the negative electrode material is 14.9 μm, and the specific surface area is 3.8 m 2 / g. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregates is 6.7%. As a result of measuring the aggregate particles using a nanoindenter, the indentation hardness of the aggregates is on average 240 MPa. The difference between the measured density of the aggregates and the Theory densities of the Si powder, SiO particles, and carbon material in the aggregates was 0.9%.

[0231] Example 13 The method for manufacturing the negative electrode material of this example includes the following steps.

[0232] (1) Si powder with a median diameter of 100 nm, lauric acid, and phenolic resin are added to a 40% ethylene glycol solution in a mass ratio of 60:3.9:22.9, ultrasonically dispersed for more than 10 min to obtain a dispersion solution, and then the dispersion solution is put into a ball mill and ground and dispersed for 4 h to obtain a precursor solution. Next, a drying treatment is performed, the drying temperature is 190 °C, and the time is 3 h to obtain a precursor.

[0233] (2) The precursor is placed in a fusion machine. The rotation speed of the fusion machine is 500 r / min, the blade gap width of the fusion machine used for the mechanofusion is 0.05 cm, and the mechanofusion time is 0.5 h. The material after fusion is placed in a heat treatment furnace, and then nitrogen gas is passed through to perform a primary heat treatment at 600 °C for 3 h of heat preservation to obtain a negative electrode material.

[0234] The negative electrode material manufactured in this example contains aggregates, and the aggregates contain Si powder and a carbon material. The mass ratio of silicon powder to carbon material is 55.1:44.9. The median diameter of the negative electrode material is 14.6 μm, and the specific surface area is 4.7 m 2 / g. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregates is 5.8%. As a result of measuring the aggregate particles using a nanoindenter, the average indentation hardness of the aggregates is 195 MPa. The difference between the measured density of the aggregates and the Theory densities of silicon powder and carbon material is 1.1%.

[0235] Example 14 The difference between this example and Example 1 lies in the difference in step 1). In step 1), Si powder with a median diameter of 100 nm, lauric acid, and phenolic resin were added to a 40% ethylene glycol solution in a mass ratio of 60:5.9:45, ultrasonically dispersed for more than 10 min to obtain a dispersion solution, and then the dispersion solution was placed in a ball mill and ground and dispersed for 4 h to obtain a precursor solution. Next, a drying treatment was performed, the drying temperature was 190 °C, and the time was 3 h to obtain a precursor.

[0236] The negative electrode material manufactured in this example contains aggregates and a carbon layer coated on the surface of the aggregates. The aggregates contain Si powder and a carbon material. The mass ratio of silicon powder to carbon material is 45.9:54.1. The median diameter of the negative electrode material is 12.5 μm, and the specific surface area is 3.1 m 2 / g, and the average thickness of the carbon layer is 425 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregates is 4.9%. As a result of measuring the aggregate particles using a nanoindenter, the average indentation hardness of the aggregates is 208 MPa. The difference between the measured density of the aggregates and the Theory densities of silicon powder and carbon material is 0.6%.

[0237] Example 15 The difference between this example and Example 1 lies in the difference in step 1). In step 1), Si powder with a median diameter of 100 nm, FeSi 2, lauric acid, and phenolic resin were added to a 40% ethylene glycol solution at a mass ratio of 60:4.5:3.9:22.9, and ultrasonic dispersion was carried out for more than 10 min to obtain a dispersion solution. Further, the dispersion solution was placed in a ball mill and ground and dispersed for 4 h to obtain a precursor solution. Next, a drying treatment was performed, the drying temperature was 190 °C, and the time was 3 h to obtain a precursor.

[0238] The negative electrode material produced in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes Si powder and a carbon material. The silicon powder and FeSi 2 The mass ratio of the carbon material is 55.3:4.2:40.5. The median diameter of the negative electrode material is 14.9 μm, and the specific surface area is 4.9 m 2 / g. The average thickness of the carbon layer is 176 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 5.3%. As a result of measuring the aggregate particles using a nanoindenter, the average indentation hardness of the aggregate is 319 MPa. The difference between the measured density of the aggregate and the Theory densities of the silicon powder and the carbon material is 0.8%.

[0239] Example 16 The negative electrode material was produced in basically the same manner as in Example 1, except that lauric acid was not added.

[0240] The negative electrode material produced in this example includes an aggregate and a carbon layer coated on the surface of the aggregate. The aggregate includes Si powder, SiO particles, and a carbon material. The mass ratio of the Si powder, the SiO particles, and the carbon material is 55.9:4.2:39.4. The median diameter of the negative electrode material is 15.8 μm, and the specific surface area is 5.0 m 2 / g. The average thickness of the carbon layer is 159 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregate is 6.2%. As a result of measuring the aggregate particles using a nanoindenter, the average indentation hardness of the aggregate is 278 MPa. The difference between the measured density of the aggregate and the Theory densities of the silicon powder, the SiO particles, and the carbon material in the aggregate is 4.8%.

[0241] Example 17 The negative electrode material was produced in basically the same manner as in Example 1, except that the aspect ratio of SiO was 2.1.

[0242] The negative electrode material produced in this example includes aggregates and a carbon layer coated on the surface of the aggregates. The aggregates include silicon powder, SiO particles, and a carbon material. The mass ratio of the silicon powder, SiO particles, and carbon material is 55.4:4.3:39.9. The median diameter of the negative electrode material is 17.8 μm, and the specific surface area is 5.4 m 2 / g. The average thickness of the carbon layer is 169 nm. As a result of measuring the aggregate particles using the mercury intrusion method, the porosity of the aggregates is 6.0%. As a result of measuring the aggregate particles using a nanoindenter, the average indentation hardness of the aggregates is 244 MPa. The difference between the measured density of the aggregates and the Theory densities of the silicon powder, SiO particles, and carbon material in the aggregates was 8.9%.

[0243] Comparative Example 1 The negative electrode material was produced in basically the same manner as in Example 1, except that the melting treatment was not performed.

[0244] In this comparative example, the porosity of the aggregates is 22.4%, the average indentation hardness of the aggregates is 50.3 MPa, and the difference between the measured density of the aggregates and the Theory densities of the silicon powder, SiO particles, and carbon material in the aggregates is 10.1%.

[0245] Test Method (1) Coin-type battery test The electrochemical cycle performance was tested by the following method. That is, the produced silicon-carbon composite negative electrode material, conductive agent, and adhesive were dissolved and mixed in a solvent at a mass percentage of 94:1:5, and the solid content was controlled to 50%. It was applied to a copper foil current collector and vacuum dried to produce a negative electrode sheet. Next, a ternary positive electrode sheet produced by a conventional mature process, 1 mol / L LiPF 6 / An ethylene carbonate + dimethyl carbonate + methyl ethyl carbonate (v / v = 1:1:1) electrolyte solution, a Celgard 2400 separator, and a housing are assembled by a conventional manufacturing process to obtain a lithium-ion coin-type battery. Using a micrometer, the initial thickness of the electrode sheet of the lithium-ion battery is measured as H0. The charge-discharge test of the lithium-ion battery is carried out on a LAND battery test system of Wuhan Jin Nuo Electronics Co., Ltd. at room temperature conditions with a constant current charge-discharge at 0.2C, and the charge-discharge voltage is limited to 2.75 - 4.2V to obtain the initial reversible capacity, the initial cycle charge capacity, and the initial cycle discharge capacity. The initial Coulomb efficiency = initial cycle discharge capacity / initial cycle charge capacity.

[0246] The cycle is repeated 50 times, and using a micrometer, the thickness of the electrode sheet of the lithium-ion battery at this time is measured as H1. After 50 cycles, the expansion rate = (H1 - H0) / H0 × 100%.

[0247] The cycle is repeated 100 times, the discharge capacity is recorded as the remaining capacity of the lithium-ion battery, and the capacity retention rate = remaining capacity / initial capacity × 100%.

[0248] (2) Porosity test of the aggregate The porosity was measured by the mercury intrusion method using a mercury porosimeter. The porosity was measured at least 3 times, and the arithmetic mean of at least 3 times was used as the measurement result.

[0249] (3) Indentation hardness test of the aggregate The indentation hardness was measured by a nanoindenter, and an indentation hardness test was carried out by applying a load of 0.6N and an indentation depth of 0.5μm.

[0250] (4) Test method for specific surface area The specific surface area of the negative electrode material is tested using a micrometer specific surface area measuring instrument.

[0251] (5) Test method for conductivity The conductivity of the negative electrode material is tested using a powder resistivity tester.

[0252] The results of the above performance tests are as follows.

[0253]

Table 1

[0254] As shown in Table 1, the negative electrode materials produced in Examples 1-17 had a porosity of the aggregates ≦ 10% and an indentation hardness ≧ 100 MPa. The negative electrode sheets produced from the negative electrode materials had improved expansion rate, cycle life, and initial efficiency. This is because the aggregates with high indentation hardness in the negative electrode material improve the structural stability, maintain the structural stability in the expansion-shrinkage process as much as possible, and can reduce the probability of the carbon layer being destroyed. Moreover, since the aggregates have the characteristic of low porosity, even if the surface carbon layer is destroyed, due to factors such as the surface tension of the aggregates, it is difficult for the electrolyte to penetrate inside, and the electrochemical performance can be improved.

[0255] In the production process of the negative electrode material of Example 16, compared with Example 1, no additive was added, and the connection between the active particles, the carbon matrix, and the metal oxide was not as tight. Therefore, the obtained aggregates had a lower indentation hardness and a weaker buffering and suppressing effect on expansion.

[0256] In the production process of the negative electrode material of Comparative Example 1, since the fusion treatment was not performed, the precursor was difficult to form aggregates with high indentation hardness, and the porosity was too high. During the long-term cycle process, the surface carbon layer structure was easily destroyed by volume expansion, and further the core structure was destroyed. The electrolyte was easily penetrated into the particles, a thick SEI film was formed, consuming a large amount of active lithium ions. Its cycle capacity retention rate was only 80.1%. Compared with the cycle capacity retention rate of 94.1% in Example 1, it was significantly decreased. And the expansion rate of the electrode sheet was 49.2%, which was significantly improved compared with the expansion rate of the electrode sheet of 35.3% in the example. As can be seen from this, the fusion treatment can improve the indentation hardness of the aggregates, effectively improve the battery cycle performance, and suppress the expansion.

Industrial Applicability

[0257] As described above, the present disclosure provides a negative electrode material, a method for manufacturing the same, and a lithium ion battery. Since the negative electrode material has excellent structural stability, it can effectively suppress the volume expansion of the negative electrode material and improve the battery cycle performance, and the manufacturing method can reduce the manufacturing cost.

Claims

1. comprising an aggregate containing an active material, a metal oxide, and a carbon material, the porosity of the aggregate is 10% or less, and the indentation hardness of the aggregate is 100 MPa or more, the active material is at least one of silicon oxide, Si, P, a metal element, and an alloy of the metal element and silicon, the carbon material is at least one of amorphous carbon and mesocarbon microbeads, The metal oxide is GeO 2 , ZnO, and TiO 2 The negative electrode material is characterized by being at least one selected from the group consisting of

2. The negative electrode material according to claim 1, wherein the metal element contains at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al, and Cu.

3. The oxide of silicon is SiO x (where 0 < x ≤ 2), the negative electrode material according to claim 1.

4. The negative electrode material according to claim 1, wherein the alloy of the metal element and silicon contains at least one of a lithium-silicon alloy, a sodium-silicon alloy, a potassium-silicon alloy, a tin-silicon alloy, a germanium-silicon alloy, an iron-silicon alloy, a magnesium-silicon alloy, a titanium-silicon alloy, a zinc-silicon alloy, an aluminum-silicon alloy, and a copper-silicon alloy.

5. The negative electrode material according to claim 1, wherein the median diameter of the active material is 1 nm to 500 nm.

6. The negative electrode material according to claim 1, wherein the mass ratio of the active material to the carbon material is (30 to 70):(10 to 70).

7. When the measured density of the aggregate is ρ1 and the theoretical density of the aggregate (that is, the sum of the values obtained by multiplying the mass percentage of each component in the aggregate by the theoretical density of each component) is ρ2, the negative electrode material according to claim 1 satisfies the relationship (ρ2 - ρ1) / ρ2 ≤ 5%.

8. The negative electrode material according to claim 1, wherein the mass ratio of the active material to the metal oxide is (30 to 70):(1 to 20), and satisfies at least one of the following characteristics (1) and (2). (1) The metal oxide is distributed in the active material, and the carbon material is filled between the active material and the metal oxide; (2) There are pores between the active material and the metal oxide, and the carbon material is filled in the pores.

9. The aggregate further contains a conductivity improver, the conductivity improver contains at least one of an alloy material and conductive carbon, and the alloy material is at least one of a zinc alloy, an aluminum alloy, a copper alloy, a silicon alloy, a nickel alloy, and a titanium alloy. The conductive carbon is one of graphite fibers, carbon nanotubes, graphite sheets, conductive carbon fibers, and graphene, The conductivity of the conductivity improver is 10 0 S / m to 10 8 S / m, and the negative electrode material according to claim 1.

10. The negative electrode material further includes a carbon layer covering at least a part of the surface of the aggregate, and the coverage rate of the carbon layer on the surface of the aggregate is 1% to 100%, The material of the carbon layer includes amorphous carbon, The thickness of the carbon layer is 10 nm to 1500 nm. The negative electrode material according to claim 1.

11. The median diameter of the negative electrode material is 0.5 μm to 30 μm, The specific surface area of the negative electrode material is 10 m 2 / g or less. The negative electrode material according to claim 1.

12. A lithium-ion battery comprising the negative electrode material according to any one of claims 1 to 11.

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