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

Abstract

The present application provides a negative electrode material and a preparation method thereof, and a lithium ion battery. The negative electrode material includes an active substance, and the active substance includes an aggregate and a micron SiO2 mixed with the aggregate. x Material, wherein the aggregates include nano-SiO x Material, wherein 0<x<2; the micron SiO x The mass proportion of the material in the active material is A, 10%≤A≤90%. The negative electrode material provided in this application can improve the capacity retention rate of the material during the cycle, reduce the expansion rate of the material, and improve the cycle stability of the material.

Description

Technical Field

[0001] The present application relates to the technical field of negative electrode materials, and in particular to negative electrode materials and preparation methods thereof, and lithium-ion batteries. Background Art

[0002] Existing lithium-ion batteries are widely used in electric vehicles and consumer electronics due to their high energy density, high output power, long cycle life, and low environmental pollution. To improve battery energy density, research and development of silicon anode materials is becoming increasingly mature. However, silicon anode materials experience significant volume expansion during lithium intercalation and deintercalation, particularly by over 300%. During charge and discharge, they pulverize and fall from the current collector, causing loss of electrical contact between the anode active material and the current collector. This leads to poor electrochemical performance, capacity fading, and decreased cycle stability, hindering their commercial application.

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

[0004] In view of this, the present application provides a negative electrode material and a preparation method thereof, and a lithium-ion battery, which can improve the capacity retention rate of the material during the cycle, reduce the expansion rate of the material, and improve the cycle stability of the material.

[0005] In a first aspect, the present application provides a negative electrode material, comprising an active substance, wherein the active substance comprises a first active substance and a second active substance mixed with each other, the first active substance comprises an aggregate formed by a nano-active substance, the porosity of the first active substance is M1, 10%<M1≤90%, the porosity of the second active substance is M2, M2≤10%, and the mass proportion of the second active substance in the active substance is Y, 10%≤Y≤90%.

[0006] In the above scheme, the negative electrode material includes active materials, including a first active material and a second active material. The first active material has a high porosity. Although the diffusion path of Li ions and electrons is short and it can have good electronic and ionic conductivity, the high specific surface area brought by the high porosity will lead to more side reactions, resulting in low initial efficiency. The second active material with low porosity can reduce the specific surface area on the one hand, thereby reducing side reactions. On the other hand, the second active material has good isotropy and structural stability, which can improve the material's first efficiency and initial discharge specific capacity without excessive loss (or even no loss) of cycle performance, and the overall electrochemical performance is better.

[0007] In some embodiments, the first active material and the second active material are each independently selected from at least one of natural graphite, artificial graphite, and silicon-based materials.

[0008] In some embodiments, the silicon-based material comprises SiO x 、SiO x / C and SiO x / M, wherein 0<x<2, M comprises at least one of alkali metal, alkaline earth metal, alkali metal oxide and alkaline earth metal oxide.

[0009] In some embodiments, the specific surface area of the first active material is N1,20m 2 / g≤N1≤100m 2 / g.

[0010] In some embodiments, the specific surface area of the second active material is N2,0.1m 2 / g≤N2<20m 2 / g.

[0011] In some embodiments, the specific surface area of the negative electrode material is 0.1 m 2 / g~100m 2 / g. In the second aspect, the present application provides a negative electrode material, including an active material, wherein the active material includes an aggregate and micron SiO mixed with the aggregate. x Material, wherein the aggregates include nano-SiO x Material, wherein 0<x<2; the micron SiO x The mass proportion of the material in the active substance is A, 10%≤A≤90%.

[0012] In some embodiments, the nano-SiO x The material includes at least one of nanotubes, nanowires, and nanospheres;

[0013] In some embodiments, the aggregate comprises SiO x Nanowires and / or SiO x Nanotubes are wound into a ball of particles.

[0014] In some embodiments, the mass proportion of the coil particles in the aggregate is ≥60%.

[0015] In some embodiments, the aggregate further comprises a x Nanowires and / or SiO x SiO on nanotubes x Nanospheres.

[0016] In some embodiments, the aggregate comprises SiO x Agglomerated particles formed by the aggregation of nanospheres.

[0017] In some embodiments, the SiO x The aspect ratio of the nanowire is (10-5000):1.

[0018] In some embodiments, the SiO x The average particle size of the nanosphere particles is 5nm to 200nm.

[0019] In some embodiments, the average particle size of the aggregates is 1 μm to 20 μm.

[0020] In some embodiments, the SiO x The mass percentage of the nanosphere particles in the active material is 5% to 20%.

[0021] In some embodiments, the micron SiO x The material particles are spherical or quasi-spherical.

[0022] In some embodiments, the micron SiO x The sphericity coefficient of the material particles is >0.95.

[0023] In some embodiments, the micron SiO x The diameter variance of the material particles is less than 0.2.

[0024] In some embodiments, the aggregates include Si crystalline particles with a particle size ranging from 10 nm to 200 nm.

[0025] In some embodiments, the micron SiO x The material includes Si crystal particles with a particle size ranging from 30 nm to 60 nm.

[0026] In some embodiments, the specific surface area of the aggregate is N1,20m 2 / g≤N1≤100m 2 / g.

[0027] In some embodiments, the micron SiO x The specific surface area of the material is N2, 0.1m 2 / g≤N2<20m 2 / g.

[0028] In some embodiments, the porosity of the aggregate is M1, 10%<M1≤90%.

[0029] In some embodiments, the micron SiO x The porosity of the material is M2, M2≤10%.

[0030] In some embodiments, the average particle size of the negative electrode material is 1 μm to 20 μm.

[0031] In some embodiments, the specific surface area of the negative electrode material is 0.1 m 2 / g~100m 2 / g.

[0032] In some embodiments, the negative electrode material further includes a carbon layer coated on at least a portion of the surface of the active material.

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

[0034] In some embodiments, carbon material is further distributed within the pores of the aggregate.

[0035] In some embodiments, the carbon layer has a thickness of 10 nm to 1500 nm.

[0036] In some embodiments, the porosity of the negative electrode material is 10% to 90%.

[0037] In some embodiments, the tap density of the negative electrode material is 0.2 g / cm 3 ~0.7g / cm 3 .

[0038] In some embodiments, the elastic modulus of the negative electrode material is 100 GPa to 190 GPa.

[0039] In some embodiments, the hardness of the negative electrode material is 1000 kg / mm 2 ~1100kg / mm 2 .

[0040] In a third aspect, the present application provides a method for preparing a negative electrode material, comprising the following steps:

[0041] In a protective atmosphere, a high-temperature beam is used to heat the raw materials for preparing SiO to melt to obtain an intermediate product, wherein the intermediate product contains SiO melt and SiO vapor, wherein the raw materials for preparing SiO include SiO y A mixture of SiO2 and Si element, containing SiO y and Si elemental substance, or a mixture containing SiO2 and Si elemental substance, wherein 0<y<2, and the mass proportion of Si elemental substance in the raw materials for preparing SiO is 0% to 20%; and

[0042] The intermediate product is subjected to a cooling treatment to obtain a negative electrode material containing an active substance.

[0043] Within the above range, by adding Si elemental particles to the SiO raw material, since the melting point of the Si elemental particles is lower than that of the SiO material, and the boiling point of the Si elemental particles is higher than that of the SiO material, the temperature difference between the melting point and boiling point of the eutectic of the Si elemental particles and the SiO material is widened, the efficiency of melting the raw materials for preparing SiO is increased, and the probability of generating a large number of nano-SiO particles caused by SiO sublimation is reduced; and through the cooling treatment, the formed nanowires, nanospheres and other particles are agglomerated to form aggregates, which reduces the specific surface area of the material, improves the stability of the material, reduces the probability of particle breakage during the cycle, avoids the repeated generation and destruction of the solid electrolyte membrane caused by the continuous penetration of the electrolyte, and is conducive to reducing the cycle expansion rate, thereby obtaining a higher cycle capacity retention rate.

[0044] In some embodiments, the average particle size of the raw materials for preparing SiO is 1 μm to 20 μm.

[0045] In some embodiments, the high temperature beam includes at least one of a plasma beam, an electron beam, or a laser beam.

[0046] In some embodiments, the heating temperature is 2000°C to 50000°C.

[0047] In some embodiments, the protective atmosphere includes at least one of argon, krypton, nitrogen, neon, and helium.

[0048] In some embodiments, the cooling rate of the cooling treatment is 200° C. / min to 400° C. / min.

[0049] In some embodiments, the high temperature beam is a plasma beam.

[0050] In some embodiments, the reactive gas for generating the plasma beam is a protective atmosphere, and the protective atmosphere includes at least one of argon, krypton, nitrogen, neon, and helium.

[0051] In some embodiments, the tangential gas velocity of the protective atmosphere is 0.5 m 3 / h~2.0m 3 / h.

[0052] In some embodiments, the radial gas velocity of the protective atmosphere is 0.5 m 3 / h~10m 3 / h.

[0053] In some embodiments, the axial gas velocity of the protective atmosphere is 0.1 m 3 / h~1m 3 / h.

[0054] In some embodiments, the feed rate of the raw materials for preparing SiO is 2 g / min to 20 g / min.

[0055] In some embodiments, the radio frequency power of the plasma generating device used for the plasma beam is 10 kW to 100 kW.

[0056] In some embodiments, the pressure of the plasma generating equipment used for the plasma beam is 100 torr to 1000 torr.

[0057] In some embodiments, a cooling protective atmosphere is used for cooling, and the cooling protective atmosphere is introduced at a rate of 1 m 3 / h~5m 3 / h.

[0058] In some embodiments, the method further includes introducing oxygen into the high-temperature beam, wherein the volume proportion of the oxygen introduced in the protective atmosphere is 0% to 20%.

[0059] In some embodiments, the oxygen introduction rate is 0.1m 3 / h~1m 3 / h.

[0060] In some embodiments, the method further comprises the step of subjecting the active material to a carbon coating treatment.

[0061] In some embodiments, the carbon coating step includes: mixing the active material with a carbon source and heat treating the mixture.

[0062] In some embodiments, the mass ratio of the active substance to the carbon source is 100:(2-20).

[0063] In some embodiments, the carbon source comprises a solid carbon source or a liquid carbon source.

[0064] In some embodiments, the solid carbon source comprises at least one of citric acid, glucose, asphalt, phenolic resin, and furfural resin.

[0065] In some embodiments, the liquid carbon source includes at least one of low-temperature liquid asphalt, furfuryl alcohol, glycidyl methacrylate, and triethylene glycol dimethacrylate.

[0066] In some embodiments, the mixing time is more than 5 minutes.

[0067] In some embodiments, the mixing method includes at least one of dry mixing, fusion processing, ball milling, three-dimensional mixing and fluidized bed mixing.

[0068] In some embodiments, the heat treatment temperature is 600°C to 1000°C.

[0069] In some embodiments, the heat treatment time is 1 hour to 72 hours.

[0070] In some embodiments, a protective gas is introduced during the heat treatment process.

[0071] In some embodiments, the protective gas includes at least one of nitrogen, helium, neon, argon, xenon, and krypton.

[0072] In some embodiments, the method further comprises the step of subjecting the active material to a carbon coating treatment.

[0073] In some embodiments, the carbon coating step includes: introducing a gaseous carbon source into the active material, and thermally cracking the gaseous carbon source to form a carbon layer on the surface of the active material.

[0074] In some embodiments, the gaseous carbon source comprises hydrocarbons.

[0075] In some embodiments, the gaseous carbon source includes at least one of methane, acetylene, ethylene, ethane, propane, propylene, propyne, acetone, and benzene.

[0076] In some embodiments, the thermal cracking temperature is 600°C-1000°C.

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

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

[0079] The negative electrode material provided in this application includes an active material, including a first active material and a second active material. The first active material has a high porosity. Although the diffusion path of Li ions and electrons is short and it can have good electronic and ionic conductivity, the high specific surface area brought by the high porosity will lead to more side reactions, thereby making the first efficiency low; the second active material with low porosity can reduce the specific surface area on the one hand, thereby reducing side reactions. On the other hand, the second active material has good isotropy and structural stability, which can improve the first efficiency and initial discharge specific capacity of the material without excessive loss of cycle performance, and the comprehensive electrochemical performance is better.

[0080] The negative electrode material provided by the present application includes an active material, wherein the aggregate has certain pores inside, which can provide a buffer space for the volume expansion of the silicon-based material, and the micron SiO xThe material can greatly reduce the specific surface area of the material, inhibit the occurrence of side reactions, improve the cycle capacity retention rate of the negative electrode material, and the spherical structure is more stable, reducing the probability of particle breakage during the cycle, thereby avoiding the repeated generation and destruction of the SEI film on the surface of the negative electrode material particles caused by the continuous penetration of the electrolyte; and the aggregates and micron SiO x The two materials work together to inhibit side reactions and help reduce the cycle expansion rate.

[0081] The method for preparing the negative electrode material provided in the present application increases the temperature difference between the melting point and boiling point of the eutectic of the Si elemental particles and the SiO material by adding Si elemental particles to the SiO raw material. Since the melting point of the Si elemental particles is lower than that of the SiO material, and the boiling point of the Si elemental particles is higher than that of the SiO material, the melting efficiency of the raw material for preparing SiO is increased, and the probability of generating a large number of nano-SiO particles due to SiO sublimation is reduced. Furthermore, through rapid cooling treatment, the formed nanowires, nanospheres, and other particles agglomerate to form aggregates, reducing the specific surface area of the material, improving the stability of the material, reducing the probability of particle breakage during the cycle, avoiding the repeated generation and destruction of the solid electrolyte membrane caused by continuous electrolyte penetration, and facilitating the reduction of the cycle expansion rate, thereby achieving a higher cycle capacity retention rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 A schematic diagram of a process for preparing a negative electrode material according to an embodiment of the present application;

[0083] Figures 2a to 2d This is an EDS image of the negative electrode material provided in Example 1;

[0084] Figures 3a to 3e This is a SEM image of the active material prepared in Example 2;

[0085] Figures 4a to 4b This is a SEM image of the active material prepared in Example 3;

[0086] Figure 5a to Figure 5b This is a SEM image of the active material prepared in Example 4;

[0087] Figure 5c This is the XRD pattern of the active material prepared in Example 4;

[0088] Figure 6 These are the first charge and discharge curves of the negative electrode materials prepared in Example 4 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0089] The following are preferred implementations of the embodiments of the present invention. It should be noted that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the embodiments of the present invention. These improvements and modifications are also considered to be within the scope of protection of the embodiments of the present invention.

[0090] The negative electrode material of one embodiment includes an active substance, the active substance includes a first active substance and a second active substance mixed together, the first active substance includes an aggregate formed by nano-active substances, the porosity of the first active substance is M1, 10%<M1≤90%, the porosity of the second active substance is M2, M2≤10%, and the mass proportion of the second active substance in the active substance is Y, 10%≤Y≤90%.

[0091] The negative electrode material provided in this application includes an active material, including a first active material and a second active material. The first active material has a high porosity. Although the diffusion path of Li ions and electrons is short and it can have good electronic and ionic conductivity, the high specific surface area brought by the high porosity will lead to more side reactions, thereby making the first efficiency low; the second active material with low porosity can reduce the specific surface area on the one hand, thereby reducing side reactions. On the other hand, the second active material has good isotropy and structural stability, which can improve the first efficiency and initial discharge specific capacity of the material without excessive loss (or even no loss) of cycle performance, and the comprehensive electrochemical performance is better.

[0092] In some embodiments, the first active material and the second active material are each independently selected from at least one of natural graphite, artificial graphite, and silicon-based materials.

[0093] Among them, silicon-based materials include SiO x 、SiO x / C and SiO x / M, wherein 0<x<2, M comprises at least one of alkali metal, alkaline earth metal, alkali metal oxide and alkaline earth metal oxide.

[0094] In some embodiments, the mass proportion of the second active substance in the active substance is Y, 10%≤Y≤90%, specifically 10%, 20%, 30%, 40%, 50%, 60%, 70% or 90%, etc., which is not limited here.

[0095] In some embodiments, the porosity of the first active substance can be specifically 11%, 20%, 30%, 40%, 50%, 60% or 90%, etc., which is not limited here. The porosity of the second active substance can be specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., which is not limited here.

[0096] In some embodiments, the specific surface area of the first active material is N1,20m 2 / g≤N1≤100m 2 / g; specifically it can be 20m 2 / g, 25m 2 / g、30m 2 / g, 40m 2 / g、45m 2 / g, 50m 2 / g, 60m 2 / g、70m 2 / g、80m 2 / g、90m 2 / g or 100m 2 / g, etc., and of course, it can also be other values within the above range, which is not limited here.

[0097] In some embodiments, the specific surface area of the second active material is N2,0.1m 2 / g≤N2<20m 2 / g; specifically 0.1m 2 / g, 0.25m 2 / g, 0.5m 2 / g、1m 2 / g, 2m 2 / g、5m 2 / g、6m 2 / g、9m 2 / g、10m 2 / g、15m 2 / g or 20m 2 / g, etc., and of course, it can also be other values within the above range, which is not limited here.

[0098] The negative electrode material of one embodiment includes an active material, and the active material includes an aggregate and micron SiO mixed with the aggregate. x Material, wherein the aggregates include nano-SiO x Materials, where 0 < x < 2; micrometer SiO x The mass proportion of the material in the active substance is A, 10%≤A≤90%.

[0099] The negative electrode material of this embodiment includes an active material, wherein the aggregate has certain pores inside, which can provide a buffer space for the volume expansion of the silicon-based material, and the micron SiO xThe material can greatly reduce the specific surface area of the material, inhibit the occurrence of side reactions, improve the cycle capacity retention rate of the negative electrode material, and the spherical structure is more stable, reducing the probability of particle breakage during the cycle, thereby avoiding the repeated generation and destruction of the SEI film on the surface of the negative electrode material particles caused by the continuous penetration of the electrolyte; and the aggregates and micron SiO x The two materials work together to inhibit side reactions and help reduce the cycle expansion rate.

[0100] In some embodiments, micron SiO x The mass proportion of the material in the active substance is A, 10%≤A≤90%, and can be 10%, 20%, 30%, 40%, 50%, 60%, 70% or 90%, etc., which is not limited here.

[0101] In some embodiments, the average particle size of the aggregates is 1 μm to 20 μm; the aggregates can effectively reduce the specific surface area of the material, thereby reducing the contact between the material and the electrolyte and inhibiting the occurrence of side reactions.

[0102] In some embodiments, micron SiO x The material particles are spherical or quasi-spherical, micron SiO x The sphericity coefficient of the material particles is >0.95, and can be specifically 0.96, 0.97, 0.98, 0.99, etc., without limitation here. The higher the sphericity of the particles, the more they can maintain structural stability during the cycle, prevent the SEI film from being repeatedly generated and broken, and help improve the cycle performance of the material.

[0103] In this embodiment, the sphericity of a particle is defined as the ratio of the particle's area-equivalent diameter to the particle's perimeter-equivalent diameter. When the sphericity is 1, the particle is strictly spherical. The sphericity is calculated as Q = ds / dc, where ds is the particle's area-equivalent diameter and dc is the particle's perimeter-equivalent diameter.

[0104] In the actual measurement process, a scanning electron microscope can be used to capture the two-dimensional morphology of the active material, and the captured SEM image can be imported into Image-Pro Plus image analysis software to calculate the sphericity of the particles.

[0105] In some embodiments, micron SiO x The diameter variance of the material particles is less than 0.2.

[0106] Specifically, obtain micron SiO xThe SEM image of the material particles uses image analysis software to automatically identify the particles and then manually separate them to improve the accuracy of the results. For the spherical particles in the surface morphology of the sample obtained by SEM, randomly select a point on the sphere and another point at the farthest end corresponding to it, and randomly select twenty points to obtain the length of these twenty lines, and thus calculate the micron SiO x The average diameter of the material particles and the micron SiO x The diameter variance of the material particles. x The diameter variance of the material particles is less than 0.2, indicating that the diameter lengths of the twenty particles are distributed within a narrow length range, reflecting their high sphericity.

[0107] In some embodiments, micron SiO x The material includes Si crystal particles with a particle size ranging from 30 nm to 60 nm.

[0108] In some embodiments, the mass proportion of aggregates in the active substance is 60% to 90%, specifically 60%, 70%, 80%, 85%, 90%, etc.

[0109] In some embodiments, nano-SiO x The material includes at least one of nanotubes, nanowires, and nanospheres.

[0110] In some embodiments, the aggregates include nanowires and / or SiO x The nanotubes are wound into coil particles, and the mass proportion of the coil particles in the aggregate is ≥60%.

[0111] In some embodiments, the mass proportion of the yarn ball particles in the aggregate is ≥60%, which can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, 95% or 99%, etc., which is not limited here.

[0112] In some embodiments, the aggregate comprises x Nanowires and / or SiO x SiO on nanotubes x Nanospheres.

[0113] In some embodiments, the aggregate comprises SiO x Agglomerated particles of nanospheres, SiO x The mass proportion of the agglomerated particles formed by the aggregation of nanospheres in the aggregate is 0% to 10%.

[0114] It can be understood that the aggregates have pores both on the surface and inside, which can effectively inhibit the volume expansion of the active material.

[0115] In some embodiments, SiOx The aspect ratio of the nanowires is (10-5000):1; specifically, it can be 10:1, 50:1, 150:1, 500:1, 800:1, 1000:1, 1200:1, 1500:1, 1800:1, 2000:1, 3000:1, 4000:1 or 5000:1, etc. Of course, it can also be other values within the above range, which is not limited here.

[0116] In some embodiments, SiO x The length of the nanowire is 10 nm to 200 nm, and can be specifically 10 nm, 20 nm, 30 nm, 50 nm, 60 nm, 80 nm, 100 nm, 120 nm, 150 nm or 200 nm, etc., which is not limited here.

[0117] In some embodiments, SiO x The average particle size of the nanosphere particles is 5 nm to 200 nm; specifically, it can be 5 nm, 10 nm, 20 nm, 50 nm, 60 nm, 70 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 190 nm or 200 nm, etc., which is not limited here.

[0118] In some embodiments, the average particle size of the aggregates is 1 μm to 20 μm; specifically, it can be 1 μm, 2 μm, 3 μm, 4 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm or 20 μm, etc., which is not limited here.

[0119] In some embodiments, the aggregates include Si crystalline particles having a particle size ranging from 10 nm to 200 nm.

[0120] In some embodiments, the active material further comprises SiO x Nanosphere particles, SiO x The mass proportion of the nanosphere particles in the active substance is 5% to 20%, specifically 5%, 8%, 10%, 12%, 15%, 16%, 17%, 18% or 20%, etc., which is not limited here.

[0121] In some embodiments, the porosity of the aggregate can be 11%, 20%, 30%, 40%, 50%, 60% or 90%, etc., which is not limited here. x The porosity of the material may be specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., which is not limited here.

[0122] In some embodiments, the specific surface area of the aggregate is N1,20m 2 / g≤N1≤100m 2 / g; specifically it can be 20m 2 / g, 25m 2 / g、30m 2 / g, 40m 2 / g、45m 2 / g, 50m 2 / g, 60m 2 / g、70m 2 / g、80m 2 / g、90m 2 / g or 100m 2 / g, etc., and of course, it can also be other values within the above range, which is not limited here.

[0123] In some embodiments, micron SiO x The specific surface area of the material is N2, 0.1m 2 / g≤N2<20m 2 / g; specifically 0.1m 2 / g, 0.25m 2 / g, 0.5m 2 / g、1m 2 / g, 2m 2 / g、5m 2 / g、6m 2 / g、9m 2 / g、10m 2 / g、15m 2 / g or 20m 2 / g, etc., and of course, it can also be other values within the above range, which is not limited here.

[0124] In some embodiments, the average particle size of the negative electrode material is 1 μm to 20 μm; specifically, it can be 1 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm or 20 μm, etc., and of course it can also be other values within the above range, which are not limited here. It can be understood that the particle size distribution of the negative electrode material will directly affect the pulping process and volume energy density of the battery. Under the same volume filling ratio, the larger the particle size of the material, the wider the particle size distribution, and the lower the viscosity of the slurry, which is conducive to increasing the solid content and reducing the difficulty of coating. In addition, the particle size distribution is also related to the specific surface area. The larger the particle size, the smaller the specific surface area.

[0125] In some embodiments, the specific surface area of the negative electrode material is 0.1 m 2 / g~100m 2 / g; specifically 0.1m 2 / g, 0.5m 2 / g, 2m 2 / g、5m 2 / g、10m2 / g、15m 2 / g, 20m 2 / g, 25m 2 / g、30m 2 / g、38m 2 / g, 40m 2 / g, 50m 2 / g、80m 2 / g or 100m 2 / g, etc., of course, it can also be other values within the above range, which is not limited here. It can be understood that the specific surface area of the negative electrode material has a great influence on the kinetic performance of the battery and the formation of the solid electrolyte membrane (SEI). For example, nanomaterials generally have a higher specific surface area, which can shorten the transmission path of lithium ions, reduce the surface current density, and improve the kinetic performance of the battery, and have therefore been widely studied. However, such materials are often unable to be put into practical use, mainly because the large specific surface area will aggravate the decomposition of the electrolyte during the first cycle of the battery, resulting in a lower first coulombic efficiency. Therefore, the specific surface area is controlled within the above range to improve the first coulombic efficiency of the battery. Preferably, the specific surface area of the negative electrode material is 5m 2 / g to 40m 2 / g.

[0126] In some embodiments, the negative electrode material further includes a carbon layer covering at least a portion of the surface of the active material.

[0127] By carbon coating the active material, the specific surface area can be reduced, thus avoiding the decrease in discharge capacity and ICE caused by the increase in side reactions with the electrolyte; at the same time, micron SiO x The material can effectively shorten the Li+ diffusion path, thereby improving ionic conductivity; and the pores inside the aggregate provide a buffer space for the volume expansion of the active material, which is beneficial to improving the capacity retention and expansion performance during the material cycle.

[0128] In some embodiments, carbon materials are also distributed in the pores of the aggregate. That is, the carbon materials in the carbon layer can also be filled inside the aggregate or between the aggregates to enhance the binding effect on the aggregate structure, which is also conducive to reducing the cyclic expansion rate of the material. Compared with SiO x The nanosphere particles are dispersed in the carbon material skeleton, which can make the expansion inhibition effect of the negative electrode material more obvious.

[0129] In some embodiments, the material of the carbon layer includes amorphous carbon;

[0130] In some embodiments, the carbon layer has a thickness of 10 nm to 1500 nm;

[0131] In some embodiments, the porosity of the negative electrode material is 10% to 90%. The porosity of the negative electrode material can specifically be 10%, 20%, 35%, 48%, 50%, 65%, 70%, 85%, or 90%, etc., and of course other values within the above range are also possible, and are not limited here. It can be understood that an appropriate porosity helps to alleviate the volume expansion of the negative electrode material. Excessive porosity will significantly reduce the volumetric energy density of the material. Preferably, the porosity of the negative electrode material is 10% to 30%.

[0132] In some embodiments, the tap density of the negative electrode material is 0.2 g / cm 3 ~0.7g / cm 3 Specific examples include 0.2g / cm 3 , 0.3g / cm 3 , 0.4g / cm 3 , 0.5g / cm 3 , 0.6g / cm 3 or 0.7g / cm 3 Of course, it can also be other values within the above range, which is not limited here. It can be understood that controlling the tap density of the negative electrode material within the above range is beneficial to improving the energy density of the material.

[0133] In some embodiments, the elastic modulus of the negative electrode material is 100 GPa to 190 GPa; specifically, it can be 100 GPa, 120 GPa, 140 GPa, 150 GPa, 170 GPa or 190 GPa, etc. Of course, it can also be other values within the above range, which is not limited here.

[0134] In some embodiments, the hardness of the negative electrode material is 1000 kg / mm 2 ~1100kg / mm 2 , specifically 1000kg / mm 2 、1030kg / mm 2 、1050kg / mm 2 、1070kg / mm 2 、1080kg / mm 2 or 1100kg / mm 2 Of course, it can also be other values within the above range, which is not limited here.

[0135] It should be noted that the negative electrode materials of the above embodiments can be combined arbitrarily as long as they are not contradictory to each other.

[0136] On the other hand, the present application also provides a method for preparing a negative electrode material, such as Figure 1 As shown, the following steps are included:

[0137] Step S10, in a protective atmosphere, using a high temperature beam to heat the raw materials for preparing SiO to melt to obtain an intermediate product, the intermediate product containing SiO melt and SiO vapor, wherein the raw materials for preparing SiO include SiO y A mixture of SiO2 and Si element, containing SiO y At least one of a mixture of Si and a simple substance, and a mixture containing SiO2 and a simple substance, wherein 0<y<2, and the mass proportion of Si in the raw material for preparing SiO is 0% to 20%;

[0138] Step S20: Cooling the intermediate product to obtain a negative electrode material containing an active substance.

[0139] The method for preparing the negative electrode material provided in the present application increases the temperature difference between the melting point and boiling point of the eutectic of the Si elemental particles and the SiO material by adding Si elemental particles to the SiO raw material. Since the melting point of the Si elemental particles is lower than that of the SiO material, and the boiling point of the Si elemental particles is higher than that of the SiO material, the melting efficiency of the raw material for preparing SiO is increased, and the probability of generating a large number of nano-SiO particles due to SiO sublimation is reduced. Furthermore, through rapid cooling treatment, the formed nanowires, nanospheres, and other particles agglomerate to form aggregates, reducing the specific surface area of the material, improving the stability of the material, reducing the probability of particle breakage during the cycle, avoiding the repeated generation and destruction of the solid electrolyte membrane caused by continuous electrolyte penetration, and facilitating the reduction of the cycle expansion rate, thereby achieving a higher cycle capacity retention rate.

[0140] The preparation method of the present application is described in detail below with reference to the examples:

[0141] Step S10: In a protective atmosphere, a high-temperature beam is used to heat the raw materials for preparing SiO until they are melted to obtain an intermediate product.

[0142] The average particle size of the raw materials for preparing SiO2 is 1 μm to 20 μm, and can be 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc., which is not limited here. As long as the active material SiO2 is finally obtained, x , 0<x<2.

[0143] In some embodiments, the raw materials for preparing SiO include SiO y A mixture of SiO2 and Si element, containing SiO y At least one of a mixture of SiO2 and Si elemental substance, and a mixture containing SiO2 and Si elemental substance, wherein 0<y<2.

[0144] In some embodiments, the high temperature beam includes at least one of a plasma beam, an electron beam, or a laser beam.

[0145] In some embodiments, the heating temperature is 2000-50000°C.

[0146] In some embodiments, the protective atmosphere includes at least one of argon, krypton, nitrogen, neon, and helium.

[0147] Before the raw materials for preparing SiO are transported into the high-temperature beam, the raw materials for preparing SiO may be mixed to ensure uniform mixing.

[0148] In some embodiments, the mixing method includes at least one of mechanical stirring, ultrasonic dispersion, and grinding dispersion. Of course, it is understood that the mixing method is not limited to the above methods, and any method that can fully disperse the raw materials for preparing SiO2 can be used.

[0149] In some embodiments, the high temperature beam is a plasma beam. It is understandable that the plasma method is used to prepare micron SiO x Material, micron SiO x The sphericity of the material particles can be greatly improved, which can further maintain structural stability during the cycle, prevent the SEI film from being repeatedly generated and broken, and help improve the recycling performance of the material.

[0150] Step S10 is performed in a plasma generating device and specifically includes:

[0151] Protective atmosphere was used as the reaction gas, and the tangential gas velocity of the protective atmosphere was controlled to be 0.5 m 3 / h~2.0m 3 / h, the radial gas velocity of the protective atmosphere is 0.5m 3 / h~10m 3 / h, the axial gas velocity of the protective atmosphere is 0.1m 3 / h~1m 3 / h; the radio frequency power of the plasma generating equipment is 10 kW to 100 kW; the pressure of the plasma generating equipment is 100 torr to 1000 torr;

[0152] The raw materials for preparing SiO2 are transported through a protective atmosphere, and the feeding rate of the raw materials for preparing SiO2 is controlled to be 2 g / min to 20 g / min.

[0153] It can be understood that the plasma method can be used to prepare micron SiO by precisely controlling various factors that affect the plasma spheroidization process, including the atmosphere used (atmosphere type, radial, tangential and axial speeds of the atmosphere), the radio frequency frequency of the plasma equipment, the pressure in the cavity, the feed rate, the cooling rate of the atmosphere, etc. xThe control of material parameters directly affects the proportion of different morphologies in the material, thereby affecting the specific surface area and porosity of the negative electrode material, affecting the capacity and first coulombic efficiency (ICE) and cycle performance of the negative electrode material.

[0154] In some embodiments, the tangential gas velocity of the protective atmosphere may be 0.5 m 3 / h、0.6m 3 / h、0.8m 3 / h、1.0m 3 / h、1.2m 3 / h、1.5m 3 / h、1.8m 3 / h or 2.0m 3 / h, etc.

[0155] In some embodiments, the radial gas velocity of the protective atmosphere may be specifically 0.5 m 3 / h、1m 3 / h、1.5m 3 / h、2m 3 / h、3m 3 / h、4m 3 / h、5m 3 / h、8m 3 / h、9m 3 / h or 10m 3 / h, etc.

[0156] In some embodiments, the axial gas velocity of the protective atmosphere may be 0.1 m 3 / h、0.2m 3 / h、0.3m 3 / h、0.5m 3 / h、0.8m 3 / h、0.9m 3 / h or 1.0m 3 In some embodiments, the radio frequency power of the plasma generating device can be 10kw, 20kw, 30kw, 40kw, 50kw, 60kw, 70kw, 80kw, 90kw or 100kw, etc., which is not limited here.

[0157] In some embodiments, the pressure of the plasma generating device can be 100 torr, 200 torr, 300 torr, 400 torr, 500 torr, 600 torr, 700 torr, 800 torr, 900 torr or 1000 torr, etc., which is not limited here.

[0158] In some embodiments, the mass proportion of Si elemental element in the raw materials for preparing SiO2 is 0% to 20%, and specifically can be 1%, 2%, 5%, 8%, 10%, 15%, 18%, 20%, etc., without limitation herein. For example, if the total mass of Si element in the raw materials for preparing SiO2 is 100g, the mass of the added Si powder can be 5g, 10g, 15g, or 18g, which are only examples here.

[0159] By adding a certain proportion of Si powder, micron SiO x Material particles, compared to SiO x Nanowires or nanospheres can greatly reduce the specific surface area of the material and inhibit the occurrence of side reactions, thereby ensuring that the negative electrode material has a high cycle capacity retention rate. The spherical structure is more stable, reducing the probability of particle and solid electrolyte membrane breakage during the cycle, thereby avoiding the repeated generation and destruction of the solid electrolyte membrane caused by continuous penetration of the electrolyte, which is conducive to obtaining a lower cycle expansion rate.

[0160] It can be understood that when a certain proportion of Si powder is added to SiO powder, its melting point is <1410℃, boiling point is >2355℃, and the melting and boiling point range increases to >945℃, while the melting and boiling point range of single SiO is only <180℃. It can be seen that adding Si powder can greatly increase the melting and boiling point range of raw materials. In turn, it can greatly reduce the possibility of SiO particles sublimation and improve the micron SiO x The sphericity of the material.

[0161] In some embodiments, the method further includes introducing oxygen into the high-temperature beam, wherein the volume fraction of oxygen in the protective atmosphere is 0% to 20%. A greater volume fraction of oxygen in the protective atmosphere results in a greater amount of inactive substances produced during the reaction, and the cyclic performance of the reaction product decreases. A smaller volume fraction of oxygen in the protective atmosphere results in a greater volume expansion rate of the reaction product, and the cyclic performance decreases.

[0162] In some embodiments, the oxygen feed rate is 0.1 m 3 / h~1m 3 / h, specifically 0.1m 3 / h、0.2m 3 / h、0.4m 3 / h、0.5m 3 / h、0.7m 3 / h、0.9m 3 / h or 1.0m 3 / h, etc., are not limited here.

[0163] Specifically, the addition of oxygen is conducive to the generation of more SiO x Nanosphere particles, reducing SiO xNanowire formation, SiO x Nanosphere particles can be grown on SiO x The ends of the nanowires are either attached to SiO x Nanowire; SiO x Nanosphere particles can also agglomerate to form aggregates. Specifically, the aggregates include SiO x Nanowires and / or SiO x Nanotubes are wound into coil particles; aggregates also include particles attached to SiO x Nanowires and / or SiO x SiO on nanotubes x Nanospheres; aggregates also include SiO x Agglomerated particles formed by the aggregation of nanospheres.

[0164] That is, the addition of oxygen can increase the proportion of nanosphere particles in the active material. Compared with nanowires, under the same volume conditions, nanosphere particles have the smallest specific surface area and can better suppress the occurrence of side reactions. Moreover, the expansion of nanosphere particles is isotropic, while nanowires have a higher aspect ratio, resulting in significant differences in the expansion along the axial and radial directions of the nanowires. When the active material is prepared into an electrode, the arrangement of the nanosphere particles in space will not have a significant effect on the expansion of the material. However, the rolling direction of the nanowires radially parallel or perpendicular to the electrode will have a significant effect on its expansion, that is, the orientation of the nanowires will affect the expansion of the electrode, while the spheres eliminate the influence of their orientation during the electrode preparation process. Therefore, the addition of oxygen can promote the formation of nanosphere particles, which is beneficial to reducing the expansion rate and cycle stability of the material.

[0165] Moreover, by adjusting the addition ratio of Si elemental particles or oxygen, the SiO prepared by plasma method can be precisely controlled. x The value of x in the figure can be used to select silicon oxide negative electrode materials for different application scenarios, and more detailed control of capacity, first efficiency, cycle and rate performance can be achieved. At the same time, by adjusting the addition ratio of Si elemental particles or oxygen, the addition of micronized SiO x The mass proportion of the material in the active material and the mass proportion of particles with different structures in all aggregates are conducive to adjusting the negative electrode material in the desired direction.

[0166] In some embodiments, SiO x The aspect ratio of the nanowires is (500-5000):1; specifically, it can be 500:1, 800:1, 1000:1, 1200:1, 1500:1, 1800:1, 2000:1, 3000:1, 4000:1, or 5000:1, etc., and other values within the above range are also possible and are not limited here. It should be noted that the aspect ratio specifically refers to the ratio of the particle length to the particle diameter.

[0167] Step S20: Cooling the intermediate product to obtain a negative electrode material containing an active substance.

[0168] In some embodiments, the cooling rate of the cooling treatment is 120°C / h to 600°C / h. Specifically, the cooling protective atmosphere introduction rate is 120°C / h, 150°C / h, 180°C / h, 200°C / h, 250°C / h, 300°C / h, 350°C / h, 400°C / h, 450°C / h, 550°C / h or 600°C / h. It can be understood that rapid cooling is conducive to the rapid condensation of SiO vapor and SiO melt to form micron SiO x Preferably, the cooling rate of the cooling treatment is 200°C / h to 400°C / h.

[0169] In some embodiments, a cooling protective atmosphere is used for cooling, and the cooling protective atmosphere is introduced at a rate of 1 to 5 m / s. 3 / h. Specifically, the cooling protective atmosphere is introduced at a rate of 1m 3 / h、1.5m 3 / h、2m 3 / h、2.5m 3 / h、3m 3 / h、4m 3 / h or 5m 3 / h, etc.

[0170] In some embodiments, the temperature of the cooled protective atmosphere is between 10°C and 40°C.

[0171] Step S30: Carbon-coating the active material to obtain a negative electrode material.

[0172] It can be understood that carbon coating treatment can increase the conductivity of the active material and buffer the huge volume change of the active material during the lithium insertion and extraction process. In addition, the carbon layer can optimize the conductive network of the negative electrode material and minimize the direct contact between the surface of the negative electrode material particles and the electrolyte, thereby alleviating the decomposition of the negative electrode material by the electrolyte and improving the cycle performance of the battery.

[0173] It should be noted that the negative electrode material of this embodiment may not be carbon coated, in which case step S30 may be omitted. In some embodiments, the carbon coating step includes: mixing the active material with a carbon source and heat treating the mixture to form a carbon layer on the surface of the active material.

[0174] In some embodiments, the carbon source includes a solid carbon source or a liquid carbon source, and the carbon source may be an organic carbon source.

[0175] Specifically, the solid carbon source includes at least one of citric acid, glucose, asphalt, phenolic resin and furfural resin. The liquid carbon source includes at least one of low-temperature liquid asphalt, furfuryl alcohol, glycidyl methacrylate and triethylene glycol dimethacrylate.

[0176] In some embodiments, the mass ratio of the active substance to the carbon source is 100:(2-20); specifically, the mass ratio of the active substance to the carbon source is 100:2, 100:10, 100:15, 100:18, etc., and of course it can also be other values within the above range, which is not limited here.

[0177] The temperature of the heat treatment is 600°C to 1000°C, and specifically can be 600°C, 700°C, 800°C, 850°C, 900°C, 950°C, 1000°C, etc.

[0178] In some embodiments, the heat treatment time is 1 h to 72 h, specifically 1 h, 6 h, 10 h, 12 h, 15 h, 24 h, 36 h, 48 h, 60 h or 72 h, etc.

[0179] In some embodiments, a protective gas is passed during the heat treatment process, and the protective gas includes at least one of nitrogen, helium, neon, argon, and krypton.

[0180] In some embodiments, the mixing method may include dry mixing, fusion processing, ball milling processing, suction filtration processing, heating reflux, three-dimensional mixing, fluidized bed mixing, etc.

[0181] The equipment used for carbon coating can be selected from at least one of a rotary kiln, a box kiln, a roller kiln, a tunnel kiln, and a push plate kiln.

[0182] In other embodiments, the aggregates may be carbon-coated in other ways, such as gas-phase carbon coating, and the equipment used for gas-phase coating may be a rotary kiln and a box furnace.

[0183] Specifically, the carbon coating treatment step includes: introducing a gaseous carbon source into the active material, thermally cracking the gaseous carbon source, and forming a carbon layer on the surface of the active material.

[0184] In some embodiments, the mass ratio of the active material to the second carbon source is 100:(2-20). The mass ratio of the active material to the second carbon source is 100:2, 100:10, 100:15, 100:18, etc., and of course other values within the above range are also possible and are not limited here.

[0185] In some embodiments, the gaseous carbon source includes hydrocarbons. Specifically, the gaseous carbon source includes at least one of methane, acetylene, ethylene, ethane, propane, propylene, propyne, acetone, and benzene.

[0186] The temperature of thermal cracking is 600°C to 1000°C, specifically 600°C, 700°C, 800°C, 850°C, 900°C, 950°C, 1000°C, etc.

[0187] In some embodiments, the heat treatment time is 1 h to 72 h, specifically 1 h, 6 h, 10 h, 12 h, 15 h, 24 h, 36 h, 48 h, 60 h or 72 h, etc.

[0188] It can be understood that carbon coating treatment can increase the tap density of the material and improve the energy density of the material.

[0189] It should be noted that the negative electrode material of this embodiment may not be carbon-coated and is not limited to the two carbon-coating methods mentioned above.

[0190] In some embodiments, after the heat treatment, at least one of crushing, screening and demagnetization is further performed; preferably, after the heat treatment, crushing, screening and demagnetization are further performed in sequence.

[0191] In some embodiments, the pulverization method is any one of a mechanical pulverizer, a jet pulverizer, and a low-temperature pulverizer.

[0192] In some embodiments, the screening method is any one of a fixed screen, a drum screen, a resonance screen, a roller screen, a vibrating screen, and a chain screen, and the screening mesh number is ≥500 mesh. Specifically, the screening mesh number can be 500 mesh, 600 mesh, 700 mesh, 800 mesh, etc. The particle size of the negative electrode material is controlled within the above range, which is beneficial to improving the cycle performance of the negative electrode material.

[0193] The present application also provides a lithium-ion battery comprising the above-mentioned negative electrode material.

[0194] The following further describes the embodiments of the present invention in multiple embodiments. The embodiments of the present invention are not limited to the following specific embodiments. Within the scope of the unchanged main rights, appropriate changes can be made to the implementation.

[0195] Example 1

[0196] Prepare the negative electrode material as follows:

[0197] (1) SiO powder (d 50 =5μm) and silicon (d 50 =5μm) as a raw material, added to the plasma jet filled with Ar gas, the RF power of the plasma jet process was controlled to be 20kW, the pressure generated by the plasma was 450torr, and the radial air flow rate was 2m 3 / h, tangential airflow rate is 1.6m3 / h and the axial air flow rate is 0.7m 3 / h, the feed rate of raw materials for preparing SiO is 8g / min; during the injection process, the high-temperature gas flow is limited to the axial range;

[0198] (2) After the reaction is completed, the SiO droplets and SiO vapor are quickly cooled in a water cooling device at the tail of the plasma flame. The micron particles adhere to the wall of the water cooling device after solidification. The cooling protective atmosphere (argon) is introduced at a rate of 1m 3 / h, and SiO powder was obtained.

[0199] (3) Using glucose as a carbon source, glucose and the obtained SiO powder were heated, dried and mixed in a roller kiln, and carbonized at 600°C using argon as a protective atmosphere to obtain a SiO / C composite negative electrode material.

[0200] The negative electrode material prepared in this embodiment includes an active material and a carbon layer coated on the surface of the active material. The average particle size of the negative electrode material is 5 μm and the specific surface area is 10 m 2 / g, tap density is 0.5g / cm 3 The carbon layer has an average thickness of 200 nm. The active material includes aggregates and micron-SiO materials, wherein the aggregates account for 80% of the active material by mass, the porosity of the aggregates is 33%, and the porosity of the micron-SiO materials is 5%. The aggregates include coil particles formed by winding SiO nanowires and / or SiO nanotubes, with the coil particles accounting for 70% of the aggregate by mass. The aggregates also include SiO nanospheres attached to the SiO nanowires and / or SiO nanotubes. The aggregates include agglomerated particles formed by agglomerating SiO nanospheres. The SiO nanowires have an aspect ratio of 500:1, the aggregates include Si crystalline particles with a particle size range of 50 nm to 100 nm, and the micron-SiO materials include Si crystalline particles with a particle size range of 40 nm to 50 nm. The sphericity coefficient of the micron-SiO material particles is 0.98, and the diameter variance of the micron-SiO material particles is 0.16. Figures 2a to 2d This is the EDS image of the negative electrode material provided in Example 1. The Si and O elements on the surface of the aggregate are distributed relatively evenly.

[0201] Example 2:

[0202] (1) Using SiO powder (d 50 =3μm) and silicon (d 50 =3μm) as a raw material, added to the plasma jet filled with Ar gas, the RF power of the plasma jet process was controlled to be 100kW, the pressure generated by the plasma was 200torr, and the radial airflow rate was 8m 3 / h, tangential airflow rate is 0.8m 3 / h and the axial air flow rate is 0.3m 3 / h, the feed rate of raw materials for preparing SiO is 4g / min; during the injection process, the high-temperature gas flow is limited to the axial range;

[0203] (2) After the reaction is completed, the SiO droplets are quickly cooled in a water cooling device at the tail of the plasma flame. The micron particles adhere to the wall of the water cooling device after solidification. The cooling protective atmosphere (argon) is introduced at a rate of 4m 3 / h, and SiO powder was obtained.

[0204] (3) Using low-temperature liquid asphalt as a carbon source, the asphalt and the obtained SiO powder were fused in a rotary kiln and carbonized at 800°C using nitrogen as a protective atmosphere to obtain a SiO / C composite negative electrode material.

[0205] The negative electrode material prepared in this embodiment includes an active material and a carbon layer coated on the surface of the active material. The average particle size of the negative electrode material is 3 μm and the specific surface area is 15 m 2 / g, tap density is 0.4g / cm 3 The carbon layer has an average thickness of 500 nm. The active material includes aggregates and micronized SiO materials, wherein the aggregates account for 85% of the active material by mass; the porosity of the aggregates is 30%, and the porosity of the micronized SiO materials is 6%; the aggregates include coiled particles formed by winding SiO nanowires and / or SiO nanotubes, with the coiled particles accounting for 66% of the aggregates by mass; the aggregates also include SiO nanospheres attached to SiO nanowires and / or SiO nanotubes; and the aggregates include agglomerated particles formed by agglomerating SiO nanospheres. The SiO nanowires have an aspect ratio of 300:1, the aggregates include Si crystalline particles with a particle size range of 150 nm to 180 nm, and the micronized SiO material particles include Si crystalline particles with a particle size range of 30 nm to 50 nm. The sphericity coefficient of the micronized SiO material particles is 0.97, and the diameter variance of the micronized SiO material particles is 0.15.

[0206] Figure 3a to Figure 3b This is the SEM image of the active material prepared in Example 2. Figures 3c to 3d This is the SEM image of the negative electrode material prepared in Example 2. After carbon coating, the morphology of the active material is well maintained, and the aggregate structure is maintained. It can be seen that carbon coating does not affect the morphology and structure of the active material, and can also achieve large-scale particle aggregation between nanoparticles through carbon materials, and the material has stronger conductive properties.

[0207] Example 3:

[0208] (1) The SiO powder (d 50 =9μm) and silicon (d 50 =9μm) as a raw material and simultaneously introduce a protective atmosphere (argon) and 10% by volume of O2, which are added to the plasma jet filled with Ar gas. The RF power of the plasma jet process is controlled to be 30kW, the pressure generated by the plasma is 600torr, and the radial airflow rate is 6m 3 / h, tangential airflow rate is 1.2m 3 / h and the axial air flow rate is 0.6m 3 / h, the feed rate of raw materials for preparing SiO is 4g / min; during the injection process, the high-temperature gas flow is limited to the axial range;

[0209] (2) After the reaction is completed, the SiO droplets and SiO vapor are quickly cooled in a water cooling device at the tail of the plasma flame. The micron particles adhere to the wall of the water cooling device after solidification. The cooling protective atmosphere (argon) is introduced at a rate of 2m 3 / h, and SiO powder was obtained.

[0210] (3) Using methane as a carbon source, methane and the obtained SiO powder were mixed in a rotary kiln, and nitrogen was used as a protective atmosphere to carbonize at 900 °C to obtain a SiO / C composite negative electrode material.

[0211] The negative electrode material prepared in this embodiment includes an active material and a carbon layer coated on the surface of the active material. The average particle size of the negative electrode material is 10 μm and the specific surface area is 9 m 2 / g, and the tap density is 0.6g / cm 3 , the average thickness of the carbon layer is 800nm.

[0212] The active material includes aggregates and micron SiO materials, wherein the mass proportion of the aggregates in the active material is 88%, the porosity of the aggregates is 26%, and the porosity of the micron SiO materials is 3%; the aggregates include coil particles formed by winding SiO nanowires and / or SiO nanotubes, and the coil particles account for 61% of the mass of the aggregates; the aggregates also include SiO nanospheres attached to the SiO nanowires and / or SiO nanotubes; the aggregates include agglomerated particles formed by agglomeration of SiO nanospheres; the aspect ratio of the SiO nanowires is 100:1, the aggregates include Si crystalline particles with a particle size range of 50nm to 200nm, and the micron SiO materials include Si crystalline particles with a particle size range of 30nm to 50nm; the sphericity coefficient of the micron SiO material particles is 0.99, and the diameter variance of the micron SiO material particles is 0.18.

[0213] Figures 4a to 4bThis is the SEM image of the active material prepared in Example 3. Figure 4a It can be seen that the aggregates include agglomerated particles formed by the aggregation of SiO nanospheres; Figure 4b It can be seen that the aggregates also include SiO nanospheres attached to SiO nanowires and / or SiO nanotubes. The nanowires in this example are significantly thicker and bamboo-like compared to Examples 1 and 2, because the addition of O2 increases the diameter of the nanowires.

[0214] Example 4:

[0215] (1) The SiO powder (d 50 =5μm) as raw materials and irregular shaped Si powder (d 50 =20μm), added to the plasma jet filled with Ar gas, the RF power of the plasma jet process was controlled to be 30kW, the pressure generated by the plasma was 500torr, and the radial air flow rate was 5m 3 / h, tangential airflow rate is 1.5m 3 / h and the axial air flow rate is 0.5m 3 / h, the feed rate of the raw materials for preparing SiO is 4g / min; during the injection process, the high-temperature gas flow is limited to the axial range, and oxygen is introduced, and the volume proportion of the oxygen introduced is 10% of the protective atmosphere (Ar gas);

[0216] (2) After the reaction is completed, the SiO droplets and SiO vapor are quickly cooled in a water cooling device at the tail of the plasma flame. The micron particles adhere to the wall of the water cooling device after solidification. The cooling protective atmosphere (argon) is introduced at a rate of 2m 3 / h, and SiO powder was obtained.

[0217] (3) Using acetylene as a carbon source, acetylene and the obtained SiO powder were mixed in a rotary kiln, and nitrogen was used as a protective atmosphere, and carbonized at 850 ° C to obtain a SiO / C composite negative electrode material.

[0218] The negative electrode material prepared in this embodiment includes an active material and a carbon layer coated on the surface of the active material. The average particle size of the negative electrode material is 12 μm and the specific surface area is 8 m 2 / g, and the tap density is 0.65g / cm 3 , the average thickness of the carbon layer is 10000nm.

[0219] The active material includes aggregates and micron SiO materials, wherein the mass proportion of the aggregates in the active material is 62%, the porosity of the aggregates is 28%, and the porosity of the micron SiO materials is 4%; the aggregates include coil particles formed by winding SiO nanowires and / or SiO nanotubes, and the coil particles account for 72% of the mass of the aggregates; the aggregates also include SiO nanospheres attached to the SiO nanowires and / or SiO nanotubes; the aggregates include agglomerated particles formed by agglomerating SiO nanospheres; the aspect ratio of the SiO nanowires is 180:1, the aggregates include Si crystalline particles with a particle size range of 50nm to 140nm, and the micron SiO materials include Si crystalline particles with a particle size range of 20nm to 40nm; the sphericity coefficient of the micron SiO material particles is 0.96, and the diameter variance of the micron SiO material particles is 0.14.

[0220] Figure 5a to Figure 5b This is the SEM image of the active material prepared in Example 4. Figure 5a and Figure 5b It can be seen that the aggregates also include SiO nanospheres attached to SiO nanowires and / or SiO nanotubes.

[0221] Figure 5c This is the EDS image of the active material prepared in Example 4, as shown in Figure 5c It can be seen that the surface of the micron SiO material particles is smooth. This is because the addition of Si material increases the melting and boiling point range of the eutectic, ensuring partial melting of the material, thereby obtaining an active material formed by the combination of aggregates and micron SiO material particles.

[0222] Example 5:

[0223] (1) Using SiO obtained by air flow classification after crushing 1.8 Powder (d 50 =5μm) as raw materials and irregular shaped Si powder (d 50 =15μm), added to the plasma jet filled with Ar gas, the RF power of the plasma jet process was controlled to be 30kW, the pressure generated by the plasma was 500torr, and the radial air flow rate was 8m 3 / h, tangential airflow rate is 2.0m 3 / h and the axial air flow rate is 1m 3 / h, the feed rate of the raw materials for preparing SiO is 10g / min; during the injection process, the high-temperature gas flow is limited to the axial range, and oxygen is introduced, and the volume proportion of the protective atmosphere (Ar gas) is 5%;

[0224] (2) After the reaction is completed, the SiO droplets and SiO vapor are quickly cooled in a water cooling device at the tail of the plasma flame. The micron particles adhere to the wall of the water cooling device after solidification. The cooling protective atmosphere (argon) is introduced at a rate of 2m 3 / h, and SiO powder was obtained.

[0225] (3) Using acetylene as a carbon source, acetylene and the obtained SiO powder were mixed in a rotary kiln, and nitrogen was used as a protective atmosphere, and carbonized at 850 ° C to obtain a SiO / C composite negative electrode material.

[0226] The negative electrode material prepared in this embodiment includes an active material and a carbon layer coated on the surface of the active material. The average particle size of the negative electrode material is 10 μm and the specific surface area is 7.5 m 2 / g, and the tap density is 0.68g / cm 3 , the average thickness of the carbon layer is 1000nm.

[0227] The active material includes aggregates and micron SiO materials, wherein the mass proportion of the aggregates in the active material is 65%, the porosity of the aggregates is 32%, and the porosity of the micron SiO materials is 5%; the aggregates include coil particles formed by winding SiO nanowires and / or SiO nanotubes, and the coil particles account for 80% of the mass of the aggregates; the aggregates also include SiO nanospheres attached to the SiO nanowires and / or SiO nanotubes; the aggregates include agglomerated particles formed by agglomerating SiO nanospheres; the aspect ratio of the SiO nanowires is 50:1, the aggregates include Si crystalline particles with a particle size range of 50nm to 150nm, and the micron SiO materials include Si crystalline particles with a particle size range of 30nm to 60nm; the sphericity coefficient of the micron SiO material particles is 0.97, and the diameter variance of the micron SiO material particles is 0.13.

[0228] Example 6:

[0229] The difference from Example 4 is that (1) the SiO powder (d 50 =5μm) as raw materials and irregular shaped Si powder (d 50 =15μm), added to the plasma jet filled with Ar gas, the RF power of the plasma jet process was controlled to be 30kW, the pressure generated by the plasma was 500torr, and the radial air flow rate was 5m 3 / h, tangential airflow rate is 1.5m 3 / h and the axial air flow rate is 0.5m 3 / h, the feed rate of the raw materials for preparing SiO is 4 g / min; during the injection process, the high-temperature gas flow is limited to the axial range, and oxygen is introduced, and the volume proportion of the protective atmosphere (Ar gas) is 10%.

[0230] The negative electrode material prepared in this embodiment includes an active material and a carbon layer coated on the surface of the active material. The average particle size of the negative electrode material is 13 μm and the specific surface area is 6.8 m 2 / g, and the tap density is 0.6g / cm 3 , the average thickness of the carbon layer is 1000nm.

[0231] The active material includes aggregates and micron SiO materials, wherein the mass proportion of the aggregates in the active material is 68%, the porosity of the aggregates is 23%, and the porosity of the micron SiO materials is 3%; the aggregates include coil particles formed by winding SiO nanowires and / or SiO nanotubes, and the coil particles account for 78% of the mass of the aggregates; the aggregates also include SiO nanospheres attached to the SiO nanowires and / or SiO nanotubes; the aggregates include agglomerated particles formed by agglomeration of SiO nanospheres; the aspect ratio of the SiO nanowires is 80:1, the aggregates include Si crystalline particles with a particle size range of 10nm to 100nm, and the micron SiO materials include Si crystalline particles with a particle size range of 30nm to 50nm; the sphericity coefficient of the micron SiO material particles is 0.98, and the diameter variance of the micron SiO material particles is 0.17.

[0232] Example 7:

[0233] (1) Using SiO obtained by air flow classification after crushing 1.2 Powder (d 50 =5μm) as raw materials and irregular shaped Si powder (d 50 =20μm), added to the plasma jet filled with Ar gas, the RF power of the plasma jet process was controlled to be 30kW, the pressure generated by the plasma was 500torr, and the radial airflow rate was 8m 3 / h, tangential airflow rate is 2.0m 3 / h and the axial air flow rate is 1m 3 / h, the feed rate of raw materials for preparing SiO is 10g / min; during the injection process, the high-temperature gas flow is limited to the axial range;

[0234] (2) After the reaction is completed, the SiO droplets and SiO vapor are quickly cooled in a water cooling device at the tail of the plasma flame. The micron particles adhere to the wall of the water cooling device after solidification. The cooling protective atmosphere (argon) is introduced at a rate of 5m 3 / h, and SiO powder was obtained.

[0235] (3) Using acetylene as a carbon source, acetylene and the obtained SiO powder were mixed in a rotary kiln, and nitrogen was used as a protective atmosphere, and carbonized at 850 ° C to obtain a SiO / C composite negative electrode material.

[0236] The negative electrode material prepared in this embodiment includes an active material and a carbon layer coated on the surface of the active material. The average particle size of the negative electrode material is 12 μm and the specific surface area is 8 m 2 / g, and the tap density is 0.62g / cm 3 , the average thickness of the carbon layer is 1200nm.

[0237] The active material includes aggregates and micron SiO materials, wherein the mass proportion of the aggregates in the active material is 63%, the porosity of the aggregates is 27%, and the porosity of the micron SiO materials is 5%; the aggregates include coil particles formed by winding SiO nanowires and / or SiO nanotubes, and the coil particles account for 73% of the mass of the aggregates; the aggregates also include SiO nanospheres attached to the SiO nanowires and / or SiO nanotubes; the aggregates include agglomerated particles formed by agglomerating SiO nanospheres; the aspect ratio of the SiO nanowires is 140:1, the aggregates include Si crystalline particles with a particle size range of 60nm to 140nm, and the micron SiO materials include Si crystalline particles with a particle size range of 30nm to 55nm; the sphericity coefficient of the micron SiO material particles is 0.98, and the diameter variance of the micron SiO material particles is 0.12.

[0238] Example 8:

[0239] The difference from Example 4 is that the cooling protective atmosphere (argon) in step (2) is introduced at a rate of 0.5 m 3 / h.

[0240] The negative electrode material prepared in this embodiment includes an active material and a carbon layer coated on the surface of the active material. The average particle size of the negative electrode material is 11 μm and the specific surface area is 7 m 2 / g, and the tap density is 0.55g / cm 3 , the average thickness of the carbon layer is 1000nm.

[0241] The active material includes aggregates and micron SiO materials, wherein the mass proportion of the aggregates in the active material is 70%, the porosity of the aggregates is 25%, and the porosity of the micron SiO materials is 4%; the aggregates include coil particles formed by winding SiO nanowires and / or SiO nanotubes, and the coil particles account for 72% of the mass of the aggregates; the aggregates also include SiO nanospheres attached to the SiO nanowires and / or SiO nanotubes; the aggregates include agglomerated particles formed by agglomerating SiO nanospheres; the aspect ratio of the SiO nanowires is 10:1, the aggregates include Si crystalline particles with a particle size range of 100nm to 200nm, and the micron SiO materials include Si crystalline particles with a particle size range of 50nm to 60nm; the sphericity coefficient of the micron SiO material particles is 0.91, and the diameter variance of the micron SiO material particles is 0.19.

[0242] Example 9:

[0243] The difference from Example 4 is that the amount of Si powder added in step (1) accounts for 30% by mass of Si in the raw materials for preparing SiO.

[0244] The negative electrode material prepared in this embodiment includes an active material and a carbon layer coated on the surface of the active material. The average particle size of the negative electrode material is 13 μm and the specific surface area is 6 m 2 / g, and the tap density is 0.68g / cm 3 , the average thickness of the carbon layer is 1000nm.

[0245] Active materials include aggregates and micronized SiO 0.7 The mass ratio of the aggregate in the active material is 58%, the porosity of the aggregate is 34%, and the porosity of the micron SiO material is 3%; the aggregate includes SiO 0.7 Nanowires and / or SiO 0.7 The nanotubes are wound into coil particles, which account for 72% of the mass of the aggregate. The aggregate also includes particles attached to SiO 0.7 Nanowires and / or SiO 0.7 SiO on nanotubes 0.7 Nanospheres; aggregates including SiO 0.7 Agglomerated particles formed by nanospheres; SiO 0.7 The aspect ratio of the nanowires is 50:1, the aggregates include Si crystalline particles with a particle size range of 50nm to 180nm, and the micron SiO material includes Si crystalline particles with a particle size range of 40nm to 60nm; the micron SiO 0.7 The sphericity coefficient of the material particles is 0.97, and the diameter variance of the micron SiO material particles is 0.11.

[0246] Example 10:

[0247] The difference from Example 4 is that (1) the SiO powder (d 50 =5μm) as raw materials and irregular shaped Si powder (d 50 =5μm), added to the plasma jet filled with Ar gas, the RF power of the plasma jet process was controlled to be 30kW, the pressure generated by the plasma was 500torr, and the radial airflow rate was 5m 3 / h, tangential airflow rate is 1.5m 3 / h and the axial air flow rate is 0.5m 3 / h, the feed rate of the raw materials for preparing SiO is 4 g / min; during the injection process, the high-temperature gas flow is limited to the axial range, and oxygen is introduced, and the volume proportion of the oxygen introduced is 20% of the protective atmosphere (argon).

[0248] The negative electrode material prepared in this embodiment includes an active material and a carbon layer coated on the surface of the active material. The average particle size of the negative electrode material is 13 μm and the specific surface area is 6.8 m 2 / g, and the tap density is 0.6g / cm 3 , the average thickness of the carbon layer is 1000nm.

[0249] The active material includes aggregates and micron SiO materials, wherein the mass proportion of the aggregates in the active material is 68%, the porosity of the aggregates is 32%, and the porosity of the micron SiO materials is 4%; the aggregates include coil particles formed by winding SiO nanowires and / or SiO nanotubes, and the coil particles account for 70% of the mass of the aggregates; the aggregates also include SiO nanospheres attached to the SiO nanowires and / or SiO nanotubes; the aggregates include agglomerated particles formed by agglomeration of SiO nanospheres; the aspect ratio of the SiO nanowires is 150:1, the aggregates include Si crystalline particles with a particle size range of 100nm to 160nm, the micron SiO materials include Si crystalline particles with a particle size range of 30nm to 45nm; the micron SiO 0.7 The sphericity coefficient of the material particles is 0.96, and the diameter variance of the micron SiO material particles is 0.14.

[0250] Example 11:

[0251] The difference from Example 4 is that no carbon coating treatment is performed.

[0252] The negative electrode material prepared in this embodiment includes an active material, and the average particle size of the negative electrode material is 12 μm and the specific surface area is 8.5 m 2 / g, and the tap density is 0.65g / cm 3 .

[0253] The active material includes aggregates and micron SiO materials, wherein the mass proportion of the aggregates in the active material is 62%, the porosity of the aggregates is 31%, and the porosity of the micron SiO materials is 5%; the aggregates include coil particles formed by winding SiO nanowires and / or SiO nanotubes, and the coil particles account for 72% of the mass of the aggregates; the aggregates also include SiO nanospheres attached to the SiO nanowires and / or SiO nanotubes; the aggregates include agglomerated particles formed by agglomeration of SiO nanospheres; the aspect ratio of the SiO nanowires is 50:1, the aggregates include Si crystalline particles with a particle size range of 80nm to 200nm, and the micron SiO materials include Si crystalline particles with a particle size range of 30nm to 55nm; the sphericity coefficient of the micron SiO material particles is 0.96, and the diameter variance of the micron SiO material particles is 0.14.

[0254] Comparative Example 1:

[0255] (1) Using the SiO2 (d 50 =5μm) as raw material;

[0256] (2) Using acetylene as a carbon source, acetylene and the obtained SiO powder were mixed in a rotary kiln, and nitrogen was used as a protective atmosphere to carbonize at 900°C to obtain a SiO / C composite negative electrode material.

[0257] The negative electrode material prepared in this comparative example includes an active material and a carbon layer coated on the surface of the active material. The average particle size of the negative electrode material is 5.5 μm and the specific surface area is 2.2 m 2 / g, and the tap density is 0.85g / cm 3 The average thickness of the carbon layer is 1000nm. The active material includes micron-sized irregular SiO powder.

[0258] Comparative Example 2:

[0259] (1) The SiO powder (d 50 =5μm) as a raw material, added to the plasma jet filled with Ar gas, the RF power of the plasma jet process was controlled to be 30kW, the pressure generated by the plasma was 500torr, and the radial airflow rate was 5m 3 / h, tangential airflow rate is 1.5m 3 / h and the protective atmosphere (argon) Ar rate is 0.5m 3 / h, the feed rate of raw materials for preparing SiO is 4g / min; during the injection process, the high-temperature gas flow is limited to the axial range;

[0260] (2) The SiO2 melt is completely volatilized to form SiO2 vapor, which is rapidly cooled in the water cooling device at the tail of the plasma flame. The micron particles adhere to the wall of the water cooling device after solidification. The cooling protective atmosphere (argon) is introduced at a rate of 5 m / s. 3 / h, and SiO powder was obtained.

[0261] (3) Using acetylene as a carbon source, acetylene and the obtained SiO powder were mixed in a rotary kiln, and nitrogen was used as a protective atmosphere, and carbonized at 850 ° C to obtain a SiO / C composite negative electrode material.

[0262] The negative electrode material prepared in this comparative example includes an active material and a carbon layer coated on the surface of the active material. The average particle size of the negative electrode material is 0.2 μm and the specific surface area is 70 m 2 / g, tap density is 0.1g / cm 3 The average thickness of the carbon layer is 1000 nm. The active material includes SiO nanowires with an aspect ratio of 200:1.

[0263] Test Method

[0264] (1) Test method for the sphericity of micron SiO material particles:

[0265] Apply the conductive adhesive used for SEM testing to the sample stage. Use a toothpick to pick up sample powder. Gently shake your arm to allow the powder to gently fall onto the adhesive. Use an ear bulb to blow away loose powder. Repeat this step until a layer of powder is evenly distributed across the adhesive surface. To ensure randomness and statistical accuracy, move the sample stage randomly during capture, taking 3-5 consecutive SEM images of the material.

[0266] The captured SEM images were imported into Image-Pro Plus image analysis software to identify and divide the powder particles in the images. The area and perimeter of the effective particles in the images were then obtained in the software. The results were exported to an Excel table. Multiple sphericities were calculated according to the sphericity calculation formula, and the average sphericity was calculated based on the calculated sphericities.

[0267] In order to intuitively characterize the sphericity of the particles in each field of view, the data results are plotted as a scatter plot, that is, the horizontal axis is the particle number and the vertical axis is the sphericity. The vertical range corresponding to the scatter plot is required to be <0.1 (that is, the sphericity is between 0.9 and 1.0).

[0268] (2) Test method for the mass ratio of aggregates in active substances:

[0269] Since the aggregates and micron SiO xThe tap density and specific surface area of the material particles are different. When NaOH is used to etch the above two particles, the aggregate is etched much faster than the micron SiO x That is, during the reaction process, the etching of aggregates occurs first and is accompanied by the etching of some micron SiO x The surface of the material particles is corroded.

[0270] During the actual test, 20 g of active material was placed in 4 L of 0.4 mol / L NaOH solution, and the etching reaction was fully carried out in a 30°C water bath. During the process, the rate at which the active material dissolved in the NaOH solution was observed. When the reaction rate decreased significantly, the reaction was stopped and the reaction time t1 was recorded. Finally, the remaining sample was filtered, washed, and dried to obtain a mass of m1.

[0271] At the same time, weigh 20g of micron SiO x The material particles were placed in 4L of 0.4mol / L NaOH solution and fully etched in a 30°C water bath. The reaction was stopped when the reaction time reached t1. After filtration, washing and drying, the mass of the remaining sample was m2.

[0272] Among them, (20-m1) is the aggregates consumed by the reaction and some micron SiO x Material particles, and (20-m2) is only the micron SiO that participates in the reaction within t1 time x The mass of the material particles dissolved on the surface, from which it can be obtained that the mass of the aggregate particles in 20g of sample is (20-m1)-(20-m2)=m2-m1, so the mass proportion of the aggregate in the active substance is (m2-m1) / 20.

[0273] (3) Test method for the mass ratio of yarn balls in aggregates:

[0274] The first method is to randomly select three areas with an area of 100mm*75mm for SEM photography, then use ProSEM software to open the pre-saved SEM image, and then select a typical feature (aggregate) in this 2D image for measurement. Click the "Find Similar" button to find similar features. ProSEM automatically finds similar features in the image and measures each one, so that all SiO x Nanowires and / or SiO x The volume percentage of the coiled particles formed by entangled nanotubes.

[0275] (4) Test method for average particle size of negative electrode material:

[0276] The particle size distribution range of the negative electrode material is tested by Malvern laser particle size analyzer.

[0277] (5) Test method for the porosity of negative electrode materials:

[0278] The porosity was measured by mercury intrusion porosimetry. The porosity was measured at least three times, and the arithmetic average of the three measurements was used as the measurement result.

[0279] (6) Test method for specific surface area of negative electrode material:

[0280] The specific surface area of powder samples was measured using the gas adsorption method at low temperatures controlled by liquid nitrogen cooling. At liquid nitrogen temperature, the equilibrium amount of nitrogen adsorbed on a surface is related to its specific surface area and other properties. By combining the relationship between the adsorption amount and relative pressure during the adsorption process, various models can be fitted to calculate the specific surface area. Micropore Specific Surface Area and Pore Size Analyzer, Manufacturer: Micromeritics, USA, Model: ASAP2460.

[0281] (7) Test method for tap density of negative electrode material:

[0282] The test is performed using a GeoPyc 1365 Micrometer tap density meter. Specifically, a certain mass of powder sample is placed in a sample tube. The instrument applies a certain pressure in the horizontal direction through the piston. The instrument rotates and vibrates the sample tube at a certain frequency for a period of time. The ratio of the sample mass to the volume after tapping is calculated in g / cm. 3 .

[0283] (8) Button battery test

[0284] The following method was used to test the electrochemical cycling performance: the prepared negative electrode material, conductive carbon black, and binder (acrylic resin) were dissolved in a solvent at a mass ratio of 75:15:10, mixed with a solid content of 50%, coated on a copper foil current collector, and vacuum-dried to produce a negative electrode plate. A metal lithium plate was used as the counter electrode, and button cells were assembled in an argon-filled glove box. Charge and discharge tests were performed at a current density of 0.1C with a charge and discharge range of 0.01-1.5V. The initial thickness of the lithium-ion battery plate was measured as H0 using a micrometer. The first reversible specific capacity, first cycle charge capacity, and first cycle discharge capacity were obtained by cyclic charge and discharge. First coulombic efficiency = first cycle discharge capacity / first cycle charge capacity.

[0285] Repeat the cycle for 50 times, and use a micrometer to measure the thickness of the lithium-ion battery electrode, which is H1. The expansion rate after 50 cycles = (H1-H0) / H0×100%.

[0286] Repeat 100 cycles and record the discharge capacity as the remaining capacity of the lithium-ion battery; capacity retention rate = remaining capacity / initial capacity*100%.

[0287] The results of the above performance tests are as follows:

[0288] Table 1. Performance comparison results

[0289]

[0290] Figure 6 The first charge and discharge curves of the negative electrode materials prepared in Example 4 and Comparative Example 1 of the present invention are as follows: Figure 6 As shown, the negative electrode material prepared in Comparative Example 1 includes micron-sized active material particles, which do not have an aggregate structure and cannot provide a buffer space for the volume expansion of the silicon-based material. As a result, during the cycle, the particles are easily broken, the capacity retention rate decreases, and the cycle expansion rate increases.

[0291] The active material of the negative electrode material prepared in Example 4 includes aggregates and micron SiO materials. From the test results, it can be seen that Example 4 has better capacity retention and lower cycle expansion rate than Comparative Example 1.

[0292] As shown in Table 1, the negative electrode materials prepared in Examples 1 to 9, including an active material and a carbon layer coated on the surface of the active material, wherein the active material includes aggregates and micronized SiO materials, have significantly improved cycle expansion rate and capacity retention rate. The capacity retention rate of the materials in Examples 1-4 can stably reach above 90%, and their expansion rate is at least 3% lower than that of Comparative Example 1. Among them, the capacity retention rate of Example 4, which has the best performance, reached 92.6% (nearly 12% higher than Comparative Example 1), and the cycle expansion rate was reduced by nearly 5% compared to Comparative Example 1.

[0293] Among them, during the preparation process of the negative electrode material of Example 8, the introduction rate of the cooling protective atmosphere (argon) is too low, the SiO vapor / droplets cannot be cooled in time, and the particles are prone to adhesion, or the shape of the spherical particles cannot be maintained, and the particles are easily broken during the cycle, which reduces the capacity retention rate of the battery and increases the cycle expansion rate.

[0294] In the preparation process of the negative electrode material of Example 9, the amount of Si powder added to the raw material for preparing SiO is too large, which is conducive to the production of more micronized SiO materials, reducing the specific surface area of the material and increasing the tap density. However, too many Si single particles will result in the final formation of SiO x The small x value and low O content lead to the degradation of the intrinsic expansion effect caused by the presence of crystalline Si, which leads to a significant decrease in the capacity retention rate of the battery and a significant increase in the cycle expansion rate.

[0295] During the preparation of the negative electrode material of Example 10, excessive oxygen addition increased the mass proportion of the nano-spherical particles in the material, that is, the mass proportion of the coiled particles in the aggregate decreased. At the same time, the addition of O increased the amount of inactive buffer substances such as Li2O and Li4SiO4 generated during the lithium insertion and extraction process of the material, which is beneficial to its cycle performance. However, excessive O2 introduction may cause excessive oxidation of the generated SiOx surface, and the dense oxide layer will severely limit its specific capacity.

[0296] During the preparation of the negative electrode material of Example 11, the active material was not carbon-coated, and there was no carbon material to alleviate the huge volume expansion during charging and discharging; and the electrical conductivity of the material deteriorated. Due to the dangling bonds on the surface of the silicon-oxygen material, the electrolyte decomposed, the cycle stability of the battery deteriorated, and the expansion rate increased.

[0297] During the preparation of the negative electrode material in Comparative Example 1, the active material was directly carbon-coated. Although the material's specific surface area decreased and its tap density increased, resulting in fewer side reactions, it did not undergo the plasma shaping process. However, because it lacked the smaller specific surface area of the spheres and the internal pore structure created by the intertwined nanowires and nano-spherical particles, it could not utilize the buffer space provided by the spherical structure and internal pores. This resulted in a decrease in the material's cycling performance and an increase in its expansion rate.

[0298] During the preparation of the negative electrode material of Comparative Example 2, the SiO melt in step (2) is completely vaporized to form SiO vapor, which is then rapidly cooled to form nanowires. Due to the low tap density and increased specific surface area of the material, the side reactions between the material and the electrolyte increase. At the same time, the high specific surface area and high reactivity of the material reduce the coulombic efficiency of the battery, the large amount of liquid electrolyte absorbed leads to a decrease in energy density, an increase in battery cost, and the accelerated growth of the solid electrolyte interface affects the cycle stability of the battery. That is, too many nanowire particles will deteriorate the cycle performance of the material due to the excessive thickness of the solid electrolyte interface (SEI) film generated.

[0299] Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the claims. Any person skilled in the art may make several possible changes and modifications without departing from the concept of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

Claims

1. A negative electrode material, characterized in that The active material comprises an active substance and a carbon layer coated on at least a portion of the surface of the active substance, wherein the active substance comprises an aggregate and micron SiO2 mixed with the aggregate. x material, wherein the aggregate comprises SiO x Nanowires and / or SiO x Nanotubes are wound into coil particles, the mass proportion of the coil particles in the aggregate is ≥60%, wherein 0<x<2; the porosity of the aggregate is M1, 10%<M1≤90%; the micron SiO x The porosity of the material is M2, M2≤10%; the micron SiO x The mass proportion of the material in the active substance is A, 10%≤A≤90%.

2. The negative electrode material according to claim 1, characterized in that Contains at least one of the following features (1) to (2): (1) The aggregate also includes a body attached to the SiO x Nanowires and / or SiO x SiO on nanotubes x Nanospheres; (2) the SiO x The aspect ratio of the nanowire is (10-5000):

1.

3. The negative electrode material according to claim 1, characterized in that The aggregates include SiO x Agglomerated particles formed by the aggregation of nanospheres.

4. The negative electrode material according to claim 3, characterized in that Contains at least one of the following features (1) to (2): (1) the SiO x The average particle size of the nanospheres is 5nm to 200nm; (2) the SiO x The mass proportion of the nanospheres in the active material is 5% to 20%.

5. The negative electrode material according to claim 1, characterized in that Contains at least one of the following features (1) to (8): (1) The average particle size of the aggregates is 1 μm to 20 μm; (2) The micron SiO x The material is spherical or quasi-spherical; (3) The micron SiO x The sphericity coefficient of the material is >0.95; (4) The micron SiO x The diameter variance of the material is less than 0.2; (5) The aggregates include Si crystalline particles with a particle size ranging from 10 nm to 200 nm; (6) The micron SiO x The material includes Si crystalline particles with a particle size ranging from 30 nm to 60 nm; (7) The specific surface area of the aggregate is N1,20m 2 / g≤N1≤100m 2 / g; (8) The micron SiO x The specific surface area of the material is N2, 0.1m 2 / g≤N2<20m 2 / g.

6. The negative electrode material according to claim 1, characterized in that Contains at least one of the following features (1) to (9): (1) The average particle size of the negative electrode material is 1 μm to 20 μm; (2) The specific surface area of the negative electrode material is 0.1m 2 / g~100m 2 / g; (3) The material of the carbon layer includes amorphous carbon; (4) Carbon material is also distributed in the pores of the aggregate; (5) The thickness of the carbon layer is 10 nm to 1500 nm; (6) The porosity of the negative electrode material is 10% to 90%; (7) The tap density of the negative electrode material is 0.2 g / cm 3 ~0.7g / cm 3 ; (8) The elastic modulus of the negative electrode material is 100 GPa to 190 GPa; (9) The hardness of the negative electrode material is 1000 kg / mm 2 ~1100kg / mm 2 .

7. A method for preparing the negative electrode material according to any one of claims 1 to 6, characterized in that: The following steps are involved: In a protective atmosphere, a high-temperature beam is used to heat a raw material for preparing SiO to melt to obtain an intermediate product, wherein the intermediate product contains SiO melt and SiO vapor, wherein the high-temperature beam includes at least one of a plasma beam, an electron beam and a laser beam; the raw material for preparing SiO includes SiO y A mixture of SiO2 and Si element, containing SiO y and Si elemental substance, or a mixture containing SiO2 and Si elemental substance, wherein 0<y<2, and the mass proportion of Si elemental substance in the raw materials for preparing SiO is greater than 0% and less than or equal to 20%; and The intermediate product is subjected to a cooling treatment to obtain an active substance, wherein the cooling rate of the cooling treatment is 200°C / min to 400°C / min, and the active substance is subjected to a carbon coating treatment to obtain a negative electrode material containing the active substance.

8. The preparation method according to claim 7, characterized in that At least one of the following features (1) to (3): (1) The average particle size of the raw materials for preparing SiO is 1 μm to 20 μm; (2) The heating temperature is 2000° C. to 50000° C.; (3) The protective atmosphere includes at least one of argon, krypton, nitrogen, neon and helium.

9. The preparation method according to claim 7, characterized in that The invention comprises at least one of the following features (1) to (9): (1) The high-temperature beam is a plasma beam; (2) The reaction gas for generating the plasma beam includes a protective atmosphere, and the protective atmosphere includes at least one of argon, krypton, nitrogen, neon, and helium; (3) The tangential gas velocity of the protective atmosphere is 0.5 m 3 / h~2.0m 3 / h; (4) The radial gas velocity of the protective atmosphere is 0.5 m 3 / h~10m 3 / h; (5) The axial gas velocity of the protective atmosphere is 0.1m 3 / h~1m 3 / h; (6) The feed rate of the raw materials for preparing SiO is 2 g / min to 20 g / min; (7) The radio frequency power of the plasma generating equipment used for the plasma beam is 10 kW to 100 kW; (8) The pressure of the plasma generating equipment used for the plasma beam is 100 torr to 1000 torr; (9) Use cooling protective atmosphere for cooling treatment, and the cooling protective atmosphere is introduced at a rate of 1m 3 / h~5m 3 / h.

10. The preparation method according to claim 7, characterized in that Includes at least one of the following features (1) to (2): (1) The method further includes introducing oxygen into the high-temperature beam, wherein the volume ratio of the oxygen introduced in the protective atmosphere is 0% to 20%; (2) The oxygen introduction rate is 0.1m 3 / h~1m 3 / h.

11. The preparation method according to any one of claims 7 to 10, characterized in that: The carbon coating step includes: mixing the active material with a carbon source, heat treating, and including at least one of the following features (1) to (9): (1) The mass ratio of the active substance to the carbon source is 100:(2-20); (2) The carbon source includes a solid carbon source or a liquid carbon source; (3) The solid carbon source includes at least one of citric acid, glucose, asphalt, phenolic resin and furfural resin; (4) The liquid carbon source comprises at least one of low-temperature liquid asphalt, furfuryl alcohol, glycidyl methacrylate, and triethylene glycol dimethacrylate; (5) The mixing time is more than 5 minutes; (6) The mixing method includes at least one of dry mixing, fusion treatment, ball milling, three-dimensional mixing and fluidized bed mixing; (7) The temperature of the heat treatment is 600°C to 1000°C; (8) The heat treatment time is 1 hour to 72 hours; (9) A protective gas is introduced into the heat treatment process, and the protective gas includes at least one of nitrogen, helium, neon, argon, xenon and krypton.

12. The preparation method according to any one of claims 7 to 10, characterized in that: The carbon coating treatment step includes: introducing a gaseous carbon source into the active material, thermally cracking the gaseous carbon source, so that a carbon layer is formed on the surface of the active material; and includes at least one of the following features (1) to (3): (1) The gaseous carbon source includes hydrocarbons; (2) The gaseous carbon source includes at least one of methane, acetylene, ethylene, ethane, propane, propylene, propyne, acetone and benzene; (3) The temperature of the thermal cracking is 600°C-1000°C.

13. A lithium-ion battery, comprising the negative electrode material according to any one of claims 1 to 6 or the negative electrode material prepared by the preparation method according to any one of claims 7 to 12.

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