Negative electrode material, manufacturing method thereof, and secondary battery

Abstract

The present application relates to a negative electrode material, a method for producing the same, and a secondary battery. The negative electrode material includes secondary particles, the secondary particles include aggregated primary particles, and the primary particles and the secondary particles have a density of 10≦D2 50 / D1 max ≦40(I)D2 min / D2 50 ≧0.08(II)D2 50 / D2 max ≧0.24(III), and in formulas (I), (II) and (III), D1 max is the maximum particle size of the primary particles, and D2 50 is the median diameter of the secondary particles, and D2 min is the minimum particle size of secondary particles, and D2 max is the maximum particle size of the secondary particles. In the present application, by limiting the size relationship between the primary particles and the secondary particles and the particle size distribution of the secondary particles, the primary particles and the secondary particles have good matching, improving the cycle stability of the negative electrode material and reducing the volume expansion effect of the negative electrode material.

Description

[Technical Field]

[0001] This application claims priority from a Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on September 29, 2022, bearing application number 202211199579X and entitled "Negative electrode material and manufacturing method thereof, and secondary battery," the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the technical field of negative electrode materials, and in particular to a negative electrode material and a method for producing the same, and a secondary battery. [Background technology]

[0003] In recent years, with the development of the market, there has been an increasing demand for high-energy density anode materials, especially in the field of electric vehicles. Currently, the only commercially available anode material is graphite, but its capacity is already close to its theoretical upper limit and there is limited room for further improvement, so the development of a new generation of high-energy density anode materials is urgently needed.

[0004] Silicon anodes are next-generation anode materials, boasting advantages such as high capacity, abundant sources, and relative safety. However, silicon anode materials experience rapid volume expansion during cycling, which can lead to material pulverization and shattering, resulting in rapid battery cycle decay. Currently, various solutions to this problem exist, including silicon structural design and the use of nano-sized, porous, and composite coating methods. However, the structures and processes used to suppress volume expansion are all complex, and their effectiveness in suppressing volume expansion as capacity increases is limited.

[0005] Therefore, it is necessary to further reduce the volume expansion effect of the negative electrode material. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present application is to provide a negative electrode material that can improve capacity and cycle stability while suppressing volume expansion, a method for producing the same, and a secondary battery. [Means for solving the problem]

[0007] To achieve the above object, in a first aspect, the present application provides a negative electrode material, the negative electrode material including secondary particles, the secondary particles including aggregated primary particles, and the primary particles and the secondary particles satisfy the following relationship: 10≦D2 50 / D1 max ≦40 (I) D2 min / D2 50 ≧0.08 (II) D2 50 / D2 max ≧0.24 (III) (In formulas (I), (II) and (III), D1 max is the maximum particle size of the primary particles, and D2 50 is the median diameter of the secondary particles, and D2 min is the minimum particle size of secondary particles, and D2 max is the maximum particle size of the secondary particles.)

[0008] In one possible embodiment, the primary particles comprise at least one of Li, SiOx, Na, K, Sn, Ge, Si, Fe, Mg, Ti, Zn, Al, P and Cu, of which 0 <x<2である。

[0009] In one possible embodiment, the bulk density of the primary particles is 0.7 g / cm 3 The following is the result.

[0010] In one possible embodiment, the median diameter D1 of the primary particles 50 is less than 0.2 μm.

[0011] In one possible embodiment, the median diameter D2 of the secondary particles 50 The range is 0.5 μm to 20 μm.

[0012] In one possible embodiment, the maximum particle size D1 of the primary particles max The range is 0.1 μm to 0.4 μm.

[0013] In one possible embodiment, the minimum particle size D2 of the secondary particles min The range is 0.5 μm to 4 μm.

[0014] In one possible embodiment, the maximum particle size D2 of the secondary particles max The range is 6 μm to 20 μm.

[0015] In one possible embodiment, the specific surface area of ​​the negative electrode material is 10 m 2 / g or less.

[0016] In one possible embodiment, the negative electrode material has a porosity of 10% or less.

[0017] In one possible embodiment, the negative electrode material has a sphericity of 0.7 or more.

[0018] In one possible embodiment, the negative electrode material further comprises a coating layer present on at least a portion of the surface of the primary particles and / or the secondary particles.

[0019] In one possible embodiment, the coating layer Ingredients The material includes at least one of a carbon material, graphene, silicon carbide, a metal oxide, and a nitride.

[0020] In one possible embodiment, the coating layer Ingredients The carbon material includes at least one of soft carbon, hard carbon, crystalline carbon, and amorphous carbon.

[0021] In one possible embodiment, the coating layer Ingredientscomprises a metal oxide, the metal oxide comprising at least one of titanium oxide, aluminum oxide, lithium oxide, cobalt oxide, and vanadium oxide.

[0022] In one possible embodiment, the coating layer Ingredients comprises a nitride, the nitride comprising at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride, and carbon nitride.

[0023] In one possible embodiment, the coating layer has a thickness of 1 nm to 500 nm.

[0024] In a second aspect, embodiments of the present application provide a method for producing a negative electrode material, granulating a mixed material containing primary particles and an adhesive to obtain a precursor; heat-treating the precursor to carbonize the adhesive to obtain a heat-treated product; The heat-treated product is pulverized and classified to obtain secondary particles that satisfy the following relationship with the primary particles, thereby obtaining a negative electrode material: 10≦D2 50 / D1 max ≦40 (I) D2 min / D2 50 ≧0.08 (II) D2 50 / D2 max ≧0.24 (III) (In formulas (I), (II) and (III), D1 max is the maximum particle size of the primary particles, and D2 50 is the median diameter of the secondary particles, and D2 min is the minimum particle size of secondary particles, and D2 max is the maximum particle size of the secondary particles.)

[0025] In one possible embodiment, the median diameter of the primary particles is less than or equal to 0.2 μm.

[0026] In one possible embodiment, the primary particles comprise at least one of Li, SiOx, Na, K, Sn, Ge, Si, Fe, Mg, Ti, Zn, Al, P and Cu, of which 0 <x<2である。

[0027] In one possible embodiment, the adhesive comprises at least one of starch, cellulose, tannin, gum arabic, sodium alginate, styrene butadiene rubber, butyl rubber, cellulose ester, ene-based polymer, polyamide, polyacrylic ester, epoxy resin, phenolic resin, furan resin, unsaturated polyester, acrylic resin, and polyimide.

[0028] In one possible embodiment, the mass ratio of the primary particles to the adhesive is 100:(5 to 55).

[0029] In one possible embodiment, the mixture of primary particles and adhesive further comprises a solvent.

[0030] In one possible embodiment, the solvent comprises at least one of phenol, an alcohol-based solvent, an ether-based solvent, and an alkane-based solvent.

[0031] In one possible embodiment, the mass ratio of the solvent to the primary particles is 100:(5-40).

[0032] In one possible embodiment, the method further comprises dispersing the mixed material containing the primary particles and the adhesive prior to the step of granulating the mixed material containing the primary particles and the adhesive.

[0033] In one possible embodiment, the dispersion treatment includes at least one selected from the group consisting of magnetic stirring, mechanical stirring, abrasive dispersion, and ultrasonic dispersion.

[0034] In one possible embodiment, the temperature of the heat treatment is 500°C to 1000°C.

[0035] In one possible embodiment, the incubation time for the heat treatment is 30 minutes to 900 minutes.

[0036] In one possible embodiment, the heat treatment is carried out in a protective atmosphere, the protective atmosphere comprising at least one of nitrogen gas, argon gas, and helium gas.

[0037] In one possible embodiment, the median diameter of the material obtained by pulverization is 0.5 μm to 15 μm.

[0038] In one possible embodiment, the maximum particle size of the material obtained by pulverization is 5 μm to 45 μm.

[0039] In one possible embodiment, after the classification treatment, the method further comprises removing particles having a particle size of 0.5 μm or less from the material obtained by the classification treatment.

[0040] In one possible embodiment, the method further comprises pre-pulverizing and pre-classifying the precursor before the step of heat-treating the precursor to carbonize the adhesive.

[0041] In one possible embodiment, the pre-grinding further comprises at least one of mechanical grinding, airflow grinding, ultrafine grinding, wet grinding, extrusion grinding and split grinding.

[0042] In one possible embodiment, the median diameter of the material obtained by the pre-pulverization is 0.5 μm to 20 μm.

[0043] In one possible embodiment, the maximum particle size of the material obtained by the pre-grinding is 5 μm to 45 μm.

[0044] In one possible embodiment, the particle size of the material obtained in said pre-classification is greater than 0.5 μm.

[0045] In one possible embodiment, the method further comprises subjecting the precursor and the coating material to a fusion treatment before the step of heat treating the precursor to carbonize the adhesive.

[0046] In one possible embodiment, the coating material comprises at least one of a carbon source, graphene, silicon carbide, a metal oxide, and a nitride.

[0047] In one possible embodiment, the coating material comprises a carbon source, the carbon source comprising at least one of soft carbon, hard carbon, crystalline carbon, and amorphous carbon.

[0048] In one possible embodiment, the coating material comprises a metal oxide, the metal oxide comprising at least one of titanium oxide, aluminum oxide, lithium oxide, cobalt oxide and vanadium oxide.

[0049] In one possible embodiment, the coating material comprises a nitride, the nitride comprising at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride and carbon nitride.

[0050] In one possible embodiment, the fusing process device includes at least one of a mechanical fusing machine, a fusing stirrer, and a convection fusing machine.

[0051] In one possible embodiment, the duration of the fusion treatment is 30 minutes to 150 minutes.

[0052] In a third aspect, the present application provides a secondary battery, the secondary battery comprising the anode material according to the first aspect or the anode material produced by the method according to the second aspect. [Effects of the Invention]

[0053] Compared with the prior art, the present application can achieve the following beneficial effects:

[0054] The negative electrode material provided in the present application limits the particle size relationship between the primary particles and the secondary particles, thereby making the primary particles stack relatively closely together in the secondary particles, reducing the adhesion between primary particles caused by primary particles being too large, and reducing the phenomenon of secondary particles formed by aggregation bursting into powder during charging and discharging. At the same time, it is possible to avoid primary particles being too small, which would otherwise cause excessive aggregation to form secondary particles with too large a size. By controlling the particle size relationship between the primary particles and the secondary particles, the structural stability of the negative electrode material is improved, and the presence of small and large secondary particles is effectively reduced, making the particle size distribution of the secondary particles relatively concentrated, thereby improving the cycle stability and capacity of the negative electrode material and reducing the volume expansion effect of the negative electrode material. [Brief explanation of the drawings]

[0055] In order to more clearly describe the technical solutions of the embodiments of the present application or the prior art, the following briefly introduces drawings necessary for describing the embodiments or the prior art. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without any creative efforts. [Figure 1] 1 is a flowchart showing the production of a negative electrode material according to the present application. [Figure 2] 1 is a scanning electron microscope (SEM) chart of the negative electrode material prepared in Example 1 of the present application. [Figure 3] 1 is an XRD chart of the negative electrode material produced in Example 1 of the present application. [Figure 4] FIG. 2 is a diagram showing the initial charge-discharge curve of the negative electrode material prepared in Example 1 of the present application. [Figure 5] FIG. 2 is a cycle characteristic curve diagram of the negative electrode material prepared in Example 1 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0056] In order to better understand the technical solution of the present application, the following describes in detail the embodiments of the present application with reference to the accompanying drawings.

[0057] It should be clear that the described embodiments are only some of the embodiments of the present application, but not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0058] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features, whereby a feature qualified by "first" or "second" may explicitly or implicitly include one or more of the said features.

[0059] To facilitate understanding of this application, certain terms are defined herein where appropriate. Unless otherwise defined herein, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art.

[0060] As used herein, the term "primary particle" refers to a particle unit that forms a single particle or secondary particle that is not aggregated.

[0061] The present application provides a negative electrode material, comprising secondary particles, the secondary particles comprising aggregated primary particles, wherein the primary particles and the secondary particles satisfy the following relationship: 10≦D2 50 / D1 max ≦40 (I) D2 min / D2 50 ≧0.08 (II) D2 50 / D2 max ≧0.24 (III) In formulas (I), (II) and (III), D1 max is the maximum particle size of the primary particles, and D2 50 is the median diameter of the secondary particles, and D2 min is the minimum particle size of secondary particles, and D2max is the maximum particle size of the secondary particles of the negative electrode material.

[0062] Generally, primary particles tend to spontaneously aggregate to form secondary particles, resulting in a wide particle size distribution range for the secondary particles and a loose structure. The anode material provided in the present application limits the particle size relationship between the primary particles and the secondary particles, thereby making the stacking pattern of the primary particles relatively tight, reducing the adhesion between the primary particles due to excessively large particle size, and reducing the bursting and pulverization phenomenon of the aggregated secondary particles during charging and discharging. At the same time, it is possible to avoid excessive aggregation of the primary particles due to excessively small particle size to form excessively large secondary particles. By controlling the particle size relationship between the primary particles and the secondary particles, the structural stability of the anode material is improved, and the existence of small and large secondary particles is effectively reduced, making the particle size distribution of the secondary particles relatively concentrated, thereby improving the cycle stability and capacity of the anode material and reducing the volume expansion effect of the anode material.

[0063] In this application, 10≦D2 50 / D1 max ≦40, specifically, D2 50 / D1 max may be 10, 15, 20, 25, 30, 35, 40, etc., and may of course be other values ​​within the above range, and are not limited thereto. Within the above range, the particle size of the primary particles and secondary particles is appropriate, the degree of matching between the primary particles and secondary particles is high, and the primary particles in the secondary particles are densely stacked, making the particles in the negative electrode material less likely to powder, and allowing for good release of stress caused by expansion during the charge and discharge process, improving the cycle performance of the material and suppressing expansion. The maximum value D1 of the primary particles max If the value is too large, the adhesion between particles will be small, powdering will occur easily, cycle performance will decrease, and the maximum value D1 of the primary particles will maxIf it is too small, the interaction force between particles becomes strong, the adhesion between particles becomes strong, and it is easy to form secondary particles with too large size. Secondary particles with too large size are difficult to release the stress caused by expansion during the charge-discharge process, resulting in the secondary particles falling off from the current collector or the current collector being damaged, and the performance of the material deteriorates.

[0064] D2 min / D2 50 ≧0.08, specifically, D2 min / D2 50 may be 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, etc., or other values within the above range, and are not limited here. Within the above limited range, the number of fine powders in the secondary particles is small, the distribution of the content of the active component in the material is relatively uniform, the particle size distribution of the secondary particles is concentrated, the expansion difference between the secondary particles can be reduced, and the structural stability of the material can be improved. [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​0.8 , SiO1, SiO 1.2 , SiO 1.5 , SiO 1.8 or SiO 1.9 Naturally, other particles within the above range may also be used, and the present invention is not limited thereto.

[0068] In some embodiments, the sphericity of the primary particles is >0.7, and preferably the sphericity of the primary particles is >0.9.

[0069] In some embodiments, the bulk density of the primary particles is 0.7 g / cm 3 The bulk density of the primary particles is specifically 0.7 g / cm or less. 3 , 0.6g / cm 3 , 0.5g / cm 3 , 0.4g / cm 3 , 0.3g / cm 3 , 0.2g / cm 3 , 0.1g / cm 3 The bulk density of the primary particles may be, but is not limited to, 0.4 g / cm or other values ​​within the above range. 3 It is preferable that the concentration is 0.2 g / cm or less. 3 It is even more preferable that:

[0070] In some embodiments, the median diameter of the primary particles is 0.2 μm or less, and specifically may be 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 60 nm, 80 nm, 100 nm, 130 nm, 150 nm, 200 nm, etc., or other values ​​within the above range, and is not limited thereto. The median diameter of the primary particles is preferably 5 nm to 200 nm, and more preferably 10 nm to 200 nm.

[0071] In some embodiments, the maximum particle size D1 of the primary particles max The range is 0.1 μm to 0.4 μm, and specifically, D1 maxSpecifically, the maximum particle diameter D1 of the primary particles may be 0.1 μm, 0.20 μm, 0.3 μm, 0.4 μm, etc., and may of course be other values ​​within the above range, and is not limited thereto. max Controlling the content of the primary particles within the above range means that the particle size of the primary particles of the present invention is small, the particles are less likely to powder, and the stability of the negative electrode material can be improved.

[0072] In some embodiments, the minimum particle size D2 of the secondary particles min The range is 0.5 μm to 4 μm, specifically, D2 min D2 may be 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, etc., and may of course be other values ​​within the above range, and is not limited here. min Controlling the content of SiO2 within the above range means that the number of fine particles in the negative electrode material is relatively small, which contributes to the negative electrode material having the advantage of long cycle life.

[0073] In some embodiments, the maximum particle size D2 of the secondary particles max The range is 6 μm to 20 μm, specifically, D2 max D2 may be 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc., and may of course be other values ​​within the above range, and is not limited here. max By controlling the temperature to fall within the above range, the expansion of the material can be suppressed relatively well, which contributes to improving the performance of the material.

[0074] In some embodiments, D2 50 The range is 0.5 μm to 20 μm, specifically, D2 50 D2 may be 0.5 μm, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 13 μm, 17 μm, 19 μm, 20 μm, etc., and may of course be other values ​​within the above range, and is not limited here. 50 By controlling D2 within the above range, the average particle size of the resulting negative electrode material as a whole becomes smaller, which contributes to reducing the volume expansion of the negative electrode material. 50The thickness is preferably 0.8 μm to 12 μm, and more preferably 1 μm to 8 μm.

[0075] In some embodiments, the specific surface area of ​​the negative electrode material is greater than 10 m 2 / g or less, and the specific surface area of ​​the negative electrode material is specifically 10 m 2 / g, 9m 2 / g, 8m 2 / g, 7m 2 / g, 6m 2 / g, 5m 2 / g, 3m 2 / g, etc., and of course other values ​​within the above range are also possible, and are not limited here.

[0076] In some embodiments, the porosity of the negative electrode material is 10% or less, specifically, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 2.5%, 2%, 1%, etc., and of course, other values ​​within the above range are also possible and are not limited thereto. Controlling the porosity of the negative electrode material within the above range indicates that the electrolyte is less likely to penetrate into the material, contributing to improved stability of the negative electrode material. The porosity of the negative electrode material is preferably 5% or less, and more preferably 2.5% or less.

[0077] In some embodiments, the sphericity of the negative electrode material is 0.7 or more, and specifically, the sphericity of the negative electrode material may be 0.7, 0.8, 0.9, etc., and a sphericity within the above range contributes to improving the processing performance of the material.

[0078] In some embodiments, the negative electrode material further comprises a coating layer on at least a portion of the surfaces of the primary particles and / or secondary particles. Preferably, a coating layer is present on the surfaces of the primary particles and a coating layer is also present on the surfaces of the secondary particles, and the materials of the two coating layers may be the same or different.

[0079] In some embodiments, the coating layer Ingredients The material includes at least one of a carbon material, graphene, silicon carbide, a metal oxide, and a nitride.

[0080] In some embodiments, when the coating layer is made of a carbon material, the secondary particles may be dispersed and embedded in the carbon material, i.e., the secondary particles are dispersed in the carbon material to form a silicon-carbon composite, and the carbon material forms a conductive network among the secondary particles, which is beneficial to the capacity of the negative electrode material, and the presence of the carbon material buffers the volume expansion of the particles, improving cycle stability.

[0081] In some embodiments, a carbon coating layer is formed on the surface of the primary particles, and the primary particles having the carbon coating layer aggregate to form secondary particles, which contributes to improving the cycle stability of the negative electrode material.

[0082] In some embodiments, the carbon material comprises at least one of soft carbon, hard carbon, crystalline carbon, and amorphous carbon.

[0083] In one possible embodiment, the metal oxide comprises at least one of titanium oxide, aluminum oxide, lithium oxide, cobalt oxide and vanadium oxide.

[0084] In one possible embodiment, the nitride comprises at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride and carbon nitride.

[0085] In some embodiments, the thickness of the coating layer is 1 nm to 500 nm. Specifically, the thickness of the coating layer may be 1 nm, 5 nm, 10 nm, 30 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, etc., and of course may be other values ​​within the above range and is not limited thereto.

[0086] The present application further provides a method for producing the above-mentioned negative electrode material, as shown in FIG. A mixed material containing primary particles and an adhesive Granulation obtaining a precursor; heat-treating the precursor to carbonize the adhesive to obtain a heat-treated product; The heat-treated product is pulverized and classified to obtain secondary particles that satisfy the following relationship with the primary particles, thereby obtaining a negative electrode material: 10≦D2 50 / D1 max ≦40 (I) D2 min / D2 50 ≧0.08 (II) D2 50 / D2 max ≧0.24 (III) In formulas (I), (II) and (III), D1 max is the maximum particle size of the primary particles, and D2 50 is the median diameter of the secondary particles, and D2 min is the minimum particle size of secondary particles, and D2 max is the maximum particle size of the secondary particles.

[0087] In the above technical solution, the present application uses a mixture of primary particles and adhesive as raw material to produce secondary particles, and through heat treatment, pulverization and classification processes, the particle size distribution of the secondary particles is relatively concentrated and the particle size is appropriate, so that the primary particles and secondary particles in the present application have good compatibility, reduce the volume expansion of the negative electrode material, and improve the structural stability and cycle performance of the negative electrode material.

[0088] The manufacturing method of the present invention will be specifically described below.

[0089] In step 100, a mixed material including primary particles and an adhesive is granulated to obtain a precursor.

[0090] In some embodiments, the median diameter of the primary particles is 0.2 μm or less, specifically, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 60 nm, 80 nm, 100 nm, 130 nm, 150 nm, and 200 nm, among others, although other values ​​within the above range are also possible and are not limited thereto. The median diameter of the primary particles is preferably 5 nm to 200 nm, more preferably 10 nm to 200 nm. Currently, most negative electrode materials for secondary batteries are constructed by assembling / constructing primary particles into secondary particles using specific means or methods. In this process, the morphological parameters and sizes of the primary and secondary particles are very important and determine the basic performance of the material. The present application selects primary particles of an appropriate size, specifically, by selecting raw materials with a median diameter of less than 0.2 μm, so that the particle sizes of the raw materials are similar in size. Furthermore, secondary particles are constructed using primary particles with similar particle sizes, thereby achieving good matching between the primary and secondary particles and improving the electrochemical performance of the negative electrode material. If the particle size of the secondary particles produced is too large, the material will be loose, the structure will be unstable, and it will be prone to collapse and expansion; if the particle size of the secondary particles produced is too small, the tap density of the material will decrease, which is disadvantageous for improving the energy density of the material; and if the particle size is too small, the specific surface area of ​​the material will increase, which will reduce the initial efficiency of the material.

[0091] In some embodiments, the mixed material of the primary particles and adhesive further comprises a solvent, and the solvent comprises at least one of phenol, an alcohol-based solvent, an ether-based solvent, and an alkane-based solvent, where the alcohol-based solvent may be, for example, ethanol, ethylene glycol, glycerin, etc., the ether-based solvent may be, for example, ethyl ether, and the alkane-based solvent may be, for example, n-hexane, toluene, xylene, etc.

[0092] In some embodiments, the mass ratio of the solvent to the primary particles is 100:(5 - 40). Specifically, the mass ratio of the solvent to the primary particles can be 100:0.5, 100:10, 100:20, 100:30, 100:40, etc. Of course, other values within the above range are also possible and are not limited here.

[0093] In some embodiments, the primary particles contain at least one of Li, SiOx (0 < x < 2), Na, K, Sn, Ge, Si, Fe, Mg, Ti, Zn, Al, P, and Cu.

[0094] In some embodiments, the primary particles contain SiO x (0 < x < 2), specifically, SiO 0.1 , SiO 0.3 , SiO 0.5 , SiO 0.7 , SiO 0.8 , SiO1, SiO 1.2 , SiO 1.5 , SiO 1.8 or SiO 1.9 etc., and of course, other particles within the above range are also possible and are not limited here.

[0095] In some embodiments, the sphericity of the primary particles > 0.7, preferably, the sphericity of the primary particles > 0.9. Since the sphericity of the primary particles is higher and the structure is more stable during the cycle process, the problem of crushing of the material particles caused by the repeated formation of the SEI film can be avoided.

[0096] In some embodiments, the adhesive contains at least one of starch, cellulose, tannin, gum arabic, sodium alginate, styrene - butadiene rubber, butyl rubber, cellulose ester, ene - based polymer, polyamide, polyacrylate, epoxy resin, phenolic resin, furan resin, unsaturated polyester, acrylic resin, and polyimide.

[0097] In some embodiments, the mass ratio of the primary particles to the adhesive is 100:(5 to 55), specifically, the mass ratio of the primary particles to the adhesive is 100:5, 100:10, 100:20, 100:30, 100:40, 100:55, etc., and of course, other values ​​within the above range may also be used and are not limited here.

[0098] In some embodiments, the method further includes a step of dispersing the mixed material including the primary particles and the adhesive prior to the step of granulating the mixed material including the primary particles and the adhesive, which disperses the active material in the material, prevents the active material from agglomerating, and disperses the active material into relatively small nanoparticles.

[0099] In some embodiments, the dispersion process comprises at least one of magnetic stirring, mechanical stirring, abrasive dispersion, and ultrasonic dispersion.

[0100] Step S200: The precursor is heat-treated to carbonize the adhesive, and a heat-treated product is obtained.

[0101] In some embodiments, the method further comprises pre-grinding and pre-classifying the precursor prior to heat treating the precursor to carbonize the adhesive.

[0102] In some embodiments, prior to pre-grinding, the mixed material containing the primary particles and adhesive needs to be dried to facilitate the subsequent grinding process.

[0103] In some embodiments, the pre-grinding comprises at least one of mechanical grinding, airflow grinding, ultrafine grinding, wet grinding, extrusion grinding, and cracking grinding.

[0104] In some embodiments, the median diameter of the material obtained after pre-pulverization is 0.5 μm to 20 μm, specifically 0.5 μm, 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 20 μm, etc., and of course other values ​​within the above range are also possible and not limited thereto. The median diameter of the material obtained after pre-pulverization is preferably 1 μm to 15 μm, and more preferably 2 μm to 8 μm.

[0105] In some embodiments, the maximum particle size of the material obtained after pre-pulverization is 5 μm to 45 μm, specifically 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, etc., and of course other values ​​within the above range are also possible and not limited thereto. The maximum particle size of the material obtained after pre-pulverization is preferably 5 μm to 35 μm, and more preferably 6 μm to 30 μm.

[0106] In the present application, the median size and maximum particle size of the particles after pre-milling are limited, thereby making the particle size of the particles after milling relatively uniform.

[0107] In some embodiments, the particle size of the material obtained by pre-classification is greater than 0.5 μm, i.e., the classification process removes particles with a particle size of 0.5 μm or less, improving the uniformity of the particle size distribution of the active material in the material.

[0108] In some embodiments, the method further includes a step of fusing the precursor and the coating material prior to the step of heat treating the precursor to carbonize the adhesive, which is understood to occur after the pre-crushing and pre-classification steps.

[0109] In some embodiments, the coating material comprises at least one of a carbon source, graphene, silicon carbide, a metal oxide, and a nitride.

[0110] In some embodiments, the carbon source comprises at least one of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt.

[0111] In one possible embodiment, the coating layer Ingredients comprises a metal oxide, the metal oxide comprising at least one of titanium oxide, aluminum oxide, lithium oxide, cobalt oxide, and vanadium oxide.

[0112] In one possible embodiment, the coating layer Ingredients comprises a nitride, the nitride comprising at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride, and carbon nitride.

[0113] In some embodiments, the equipment for the fusion process includes at least one of a mechanical fusion mixer, a fusion stirrer, and a convection fusion mixer.

[0114] In some embodiments, the fusion treatment time is 30 minutes to 150 minutes, and specifically, the fusion treatment time may be 30 minutes, 50 minutes, 70 minutes, 90 minutes, 100 minutes, 110 minutes, 130 minutes, 150 minutes, etc., but of course, other values ​​within the above range may also be used and are not limited here.

[0115] In some embodiments, the cutter gap of the fusion process is 0.1 cm to 0.5 cm. Specifically, the cutter gap of the fusion process may be 0.1 cm, 0.2 cm, 0.3 cm, 0.4 cm, 0.5 cm, etc., and of course may be other values ​​within the above range, and is not limited thereto.

[0116] In some embodiments, the heat treatment temperature is 500°C to 1000°C. Specifically, the heat treatment temperature may be 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, etc., and of course, may be other values ​​within the above range and is not limited thereto.

[0117] In some embodiments, the heat treatment is carried out for a period of 30 to 900 minutes. Specifically, the heat treatment may be carried out for a period of 30, 60, 120, 360, 480, 720, 800, or 900 minutes, but may be carried out for other periods within the above ranges and is not limited thereto.

[0118] In some embodiments, the heat treatment is performed in a protective atmosphere, and the protective atmosphere comprises any of nitrogen gas, argon gas, and helium gas.

[0119] Step S300: The heat-treated product is pulverized and classified to obtain secondary particles that satisfy the following relationship with the primary particles, thereby obtaining a negative electrode material: 10≦D2 50 / D1 max ≦40 (I) D2 min / D2 50 ≧0.08 (II) D2 50 / D2 max ≧0.24 (III)

[0120] In some embodiments, the milling comprises at least one of mechanical milling, air milling, ultrafine milling, wet milling, extrusion milling, and cracking milling.

[0121] In some embodiments, the median diameter of the material obtained by pulverization is 0.5 μm to 15 μm, and specifically may be 0.5 μm, 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, etc., and may of course be other values ​​within the above range, and is not limited thereto. The median diameter of the material obtained by pulverization is preferably 1 μm to 13 μm, and more preferably 2 μm to 10 μm.

[0122] In some embodiments, the maximum particle size of the material obtained by pulverization is 5 μm to 45 μm, specifically 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, etc., and of course other values ​​within the above range are also possible and not limited thereto. The maximum particle size of the material obtained by pulverization is preferably 5 μm to 40 μm, and more preferably 6 μm to 30 μm.

[0123] In some embodiments, the method further comprises removing particles having a particle size of 0.5 μm or less from the material obtained by the classification process after the classification process. The material having a particle size of 0.5 μm or less is fine particles. It is understood that removing the fine particles reduces the expansion difference between different particles in the material and improves the stability of the composite material for application in secondary batteries.

[0124] In some embodiments, 10≦D2 50 / D1 max ≦40, specifically, D2 50 / D1 max may be 10, 15, 20, 25, 30, 35, 40, etc., and may of course be other values ​​within the above range, and are not limited thereto. Within the above range, the particle size of the primary particles and secondary particles is appropriate, the degree of matching between the primary particles and secondary particles is high, and the primary particles in the secondary particles are densely stacked, making the particles in the negative electrode material less likely to powder, and allowing for good release of stress caused by expansion during the charge and discharge process, improving the cycle performance of the material and suppressing expansion. The maximum value D1 of the primary particles maxIf the value is too large, the adhesion between particles will be small, powdering will occur easily, cycle performance will decrease, and the maximum value D1 of the primary particles will max If the interparticle size is too small, the interparticle force becomes strong, the interparticle adhesion becomes strong, and secondary particles with excessively large sizes are easily formed. These excessively large secondary particles have difficulty releasing stress caused by expansion during charge and discharge, and the secondary particles may fall off the current collector or the current collector may be destroyed, resulting in a decrease in the performance of the negative electrode material.

[0125] In some embodiments, D2 min / D2 50 ≧0.08, specifically, D2 min / D2 50 may be 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, etc., and may of course be other values ​​within the above range, and is not limited thereto. Within the above limited range, the number of fine powders in the secondary particles is small, the distribution of the active ingredient content in the material is relatively uniform, the expansion difference between the secondary particles can be reduced, and the structural stability of the material can be improved.

[0126] In some embodiments, D2 50 / D2 max ≧0.24, specifically, D2 50 / D2 max may be 0.24, 0.28, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, etc., and may of course be other values ​​within the above range, and are not limited thereto. Within the above limited range, the particle size distribution of the secondary particles is concentrated and there are few large secondary particles, which effectively reduces the volume expansion of the material and improves the cycle performance of the material.

[0127] The examples of the present application further disclose secondary batteries comprising the negative electrode materials described herein or prepared by the methods described herein. [Example]

[0128] The present application will be further described below by dividing it into several examples. However, the present application is not limited to the following specific examples. They may be modified as appropriate without changing the scope of the main claims.

[0129] Example 1

[0130] (1) The nanosilicon particles were measured by a bulk density tester and sieved by a Malvern particle size analyzer to determine the median diameter D1 50 is 50nm, D1 max = 155 nm, volume density 0.29 g / cm 3 of nanosilicon is obtained.

[0131] (2) The nanosilicon obtained in step (1) and polyvinyl alcohol are added to phenol in a mass ratio of 100:28, then ball milled in a planetary ball mill for 2 hours, and dried by rotary evaporation at 120°C to obtain a first precursor.

[0132] (3) The second precursor is obtained by pre-pulverizing and pre-classifying the first precursor, and has a median diameter of 7.1 μm and a maximum particle size of 23.8 μm.

[0133] (4) The second precursor and phenolic resin were mixed in a mass ratio of 50:35, and then fusion was carried out. The fusion time was 40 minutes, and the cutter gap was 0.1 cm. The fused material was then placed in a high-temperature box furnace, nitrogen gas was introduced, and the material was heat-treated at 820°C and kept at that temperature for 4 hours.

[0134] (5) The material obtained in step (4) is crushed and classified to obtain the negative electrode material.

[0135] The negative electrode material manufactured in this example includes a carbon material and secondary particles dispersed in the carbon material, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer. The primary particles include nanosilicon particles, and the median diameter D2 of the negative electrode material is 50 is 3.6 μm, and the minimum particle size D2 min is 0.6 μm, and the maximum particle size D2max is 10.8 μm, and the sphericity of the negative electrode material is 0.89.

[0136] As shown in FIG. 2, which is an SEM chart of the negative electrode material prepared in Example 1 of the present application, it clearly shows that the size distribution of the secondary particles is relatively uniform.

[0137] As shown in FIG. 3, which is the XRD chart of the negative electrode material prepared in Example 1 of the present application, it clearly shows that the product contains a silicon peak position.

[0138] As shown in FIG. 4, which shows the initial charge-discharge curve of the negative electrode material prepared in Example 1 of the present application, it is clear that the initial charge-discharge capacity and initial efficiency of the negative electrode material are high.

[0139] As shown in FIG. 5, which is the cycle performance curve of the negative electrode material prepared in Example 1 of the present application, it is clear that the negative electrode material has excellent cycle performance, with a capacity retention rate of 93.1% after 100 cycles.

[0140] Example 2

[0141] (1) Nano silicon particles Bulk density The median diameter D1 was measured by a tester and sieved by a Malvern particle size analyzer. 50 is 20nm, D1 max = 103 nm, volume density 0.39 g / cm 3 Nanosilicon having a molecular weight of 10 ...

[0142] (2) The nanosilicon obtained in step (1) and fructose are added to ethylene glycol in a mass ratio of 100:48, then ball milled in a planetary ball mill for 62 hours, and then rotary evaporated and dried at 150°C to obtain a first precursor.

[0143] (3) The second precursor is obtained by pre-pulverizing and pre-classifying the first precursor, and has a median diameter of 3.5 μm and a maximum particle size of 10.8 μm.

[0144] (4) The second precursor and glucose were mixed in a mass ratio of 50:35, and then fused for 30 minutes with a cutter gap of 0.15 cm. The mixed material was then placed in a high-temperature box furnace, nitrogen gas was introduced, and the mixture was heat-treated at 820°C and kept at that temperature for 4 hours.

[0145] (4) The obtained sample is crushed and classified to obtain the negative electrode material.

[0146] The negative electrode material manufactured in this example includes a carbon material and secondary particles dispersed in the carbon material, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer. The primary particles include nanosilicon particles, and the median diameter D2 of the negative electrode material is 50 is 1.8 μm, and the minimum particle size D2 min is 0.32 μm, and the maximum particle size D2 max is 5.8 μm, and the sphericity of the negative electrode material is 0.83.

[0147] Example 3

[0148] (1) Nano silicon particles Bulk density The median diameter D1 was measured by a tester and sieved by a Malvern particle size analyzer. 50 is 20nm, D1 max = 111 nm, volume density 0.14 g / cm 3 Nanosilicon having a molecular weight of 10 ...

[0149] (2) The nanosilicon obtained in step (1) and fructose are added to ethylene glycol in a mass ratio of 100:58, then ball milled in a planetary ball mill for 9 hours, and the first precursor is rotary evaporated to dryness at 150°C.

[0150] (3) The second precursor is obtained by pre-pulverizing and pre-classifying the first precursor, and has a median diameter of 8.3 μm and a maximum particle size of 16.8 μm.

[0151] (4) The second precursor and asphalt were mixed in a mass ratio of 45:35, and then fused for 60 minutes with a cutter gap of 0.15 cm. The mixed material was then placed in a high-temperature box furnace, nitrogen gas was introduced, and the mixture was heated to 920°C and kept at that temperature for 4 hours.

[0152] (5) The material obtained in step (4) is crushed and classified to obtain the negative electrode material.

[0153] The negative electrode material manufactured in this example includes a carbon material and secondary particles dispersed in the carbon material, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer. The primary particles include nanosilicon particles, and the median diameter D2 of the negative electrode material is 50 is 4.3 μm, and the minimum particle size D2 min is 0.78 μm, and the maximum particle size D2 max is 14.5 μm, and the sphericity of the negative electrode material is 0.92.

[0154] Example 4

[0155] (1) Nano silicon particles Bulk density The median diameter D1 was measured by a tester and sieved by a Malvern particle size analyzer. 50 is 100nm, D1 max = 249 nm, volume density 0.59 g / cm 3 Nanosilicon having a molecular weight of 10 ...

[0156] (2) The nanosilicon obtained in step (1) and asphalt are added to butanol in a mass ratio of 90:48, then ball milled in a planetary ball mill for 4 hours, and rotary evaporated to dryness at 150°C to obtain a first precursor.

[0157] (3) The second precursor is obtained by pre-pulverizing and pre-classifying the first precursor, and has a median diameter of 11.3 μm and a maximum particle size of 20.7 μm.

[0158] (4) The second precursor and graphene were mixed in a mass ratio of 40:25, and then fused for 20 minutes with a cutter gap of 0.25 cm. The mixed material was then placed in a high-temperature box furnace, nitrogen gas was introduced, and the mixture was heat-treated at 950°C and kept at that temperature for 6 hours.

[0159] (5) The material obtained in step (4) is crushed and classified to obtain the negative electrode material.

[0160] The negative electrode material manufactured in this example includes secondary particles and graphene layers located on the surfaces of the secondary particles, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have carbon material coating layers. The primary particles include nanosilicon particles, and the median diameter D2 of the negative electrode material is 50 is 8.2 μm, and the minimum particle size D2 min is 1.08 μm, and the maximum particle size D2 max is 16.5 μm, and the sphericity of the negative electrode material is 0.95.

[0161] Example 5

[0162] (1) Nano silicon particles Bulk density The median diameter D1 was measured by a tester and sieved by a Malvern particle size analyzer. 50 is 30nm, D1 max = 115 nm, volume density 0.25 g / cm 3 Nanosilicon having a molecular weight of 10 ...

[0163] (2) The nanosilicon obtained in step (1) and asphalt are added to isopropanol in a mass ratio of 90:48, then ball milled in a planetary ball mill for 4 hours, and freeze-dried at -40°C to obtain the first precursor.

[0164] (3) The second precursor is obtained by pre-pulverizing and pre-classifying the first precursor, and has a median diameter of 5.9 μm and a maximum particle size of 15 μm.

[0165] (4) The second precursor and polyethylene glycol were mixed in a mass ratio of 40:25, and then fused for 50 minutes with a cutter gap of 0.15 cm. The mixed material was then placed in a high-temperature box furnace, nitrogen gas was introduced, and the mixture was heat-treated at 950°C and kept at that temperature for 4 hours.

[0166] (5) The material obtained in step (4) is crushed and classified to obtain the negative electrode material.

[0167] The negative electrode material manufactured in this example includes a carbon material and secondary particles dispersed in the carbon material, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer. The primary particles include nanosilicon particles, and the median diameter D2 of the negative electrode material is 50 is 4.2 μm, and the minimum particle size D2 min is 0.68 μm, and the maximum particle size D2 max is 10.5 μm, and the sphericity of the negative electrode material is 0.86.

[0168] Example 6

[0169] (1) Nano silicon particles Bulk density The median diameter D1 was measured by a tester and sieved by a Malvern particle size analyzer. 50 is 150nm, D1 max = 314 nm, volume density 0.68 g / cm 3 Nanosilicon having a molecular weight of 10 ...

[0170] (2) The nanosilicon obtained in step (1) and glucose are added to propanol in a mass ratio of 80:68, then ball milled in a planetary ball mill for 4 hours, and rotary evaporated to dryness at 150°C to obtain the first precursor.

[0171] (3) The second precursor is obtained by pre-pulverizing and pre-classifying the first precursor, and has a median diameter of 5.8 μm and a maximum particle size of 9.8 μm.

[0172] (4) The second precursor and titanium nitride were mixed in a mass ratio of 60:55, and then fused for 40 minutes with a cutter gap of 0.1 cm. The mixed material was then placed in a high-temperature box furnace, nitrogen gas was introduced, and the mixture was heat-treated at 750°C and kept at that temperature for 4 hours.

[0173] (5) The material obtained in step (4) is crushed and classified to obtain the negative electrode material.

[0174] The negative electrode material manufactured in this example includes secondary particles and a titanium nitride layer located on the surface of the secondary particles, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer, and the primary particles include nanosilicon particles, and the median diameter D2 of the negative electrode material is 50 is 3.2 μm, and the minimum particle size D2 min is 0.57 μm, and the maximum particle size D2 max is 8.9 μm, and the sphericity of the negative electrode material is 0.78.

[0175] Example 7

[0176] (1) Nano silicon particles Bulk density The median diameter D1 was measured by a tester and sieved by a Malvern particle size analyzer. 50 is 180nm, D1 max = 478 nm, volume density 0.70 g / cm 3 Nanosilicon having a molecular weight of 10 ...

[0177] (2) The nanosilicon obtained in step (1) and glucose are added to propanol in a mass ratio of 60:48, then ball milled in a planetary ball mill for 4 hours, and dried by rotary evaporation at 150°C to obtain a first precursor.

[0178] (3) The second precursor is obtained by pre-pulverizing and pre-classifying the first precursor, and has a median diameter of 12.1 μm and a maximum particle size of 20.8 μm.

[0179] (4) The second precursor and silicon carbide were mixed in a mass ratio of 65:35, and then fused for 80 minutes with a cutter gap of 0.15 cm. The mixed material was then placed in a high-temperature box furnace, nitrogen gas was introduced, and the mixture was heat-treated at 850°C and kept at that temperature for 4 hours.

[0180] (5) The material obtained in step (4) is crushed and classified to obtain the negative electrode material.

[0181] The negative electrode material manufactured in this example includes secondary particles and silicon carbide layers located on the surfaces of the secondary particles, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have carbon material coating layers, and the primary particles include nanosilicon particles, and the median diameter D2 of the negative electrode material is 50 is 9.0 μm, and the minimum particle size D2 min is 1.57 μm, and the maximum particle size D2 max is 17.8 μm, and the sphericity of the negative electrode material is 0.76.

[0182] Example 8

[0183] The difference from Example 1 is step (4): the second precursor and the phenolic resin are mixed in a mass ratio of 50:35, and then the resulting material is placed in a high-temperature box furnace, nitrogen gas is introduced, and the material is heat-treated at 820°C and kept at that temperature for 4 hours.

[0184] The negative electrode material manufactured in this example includes a carbon material and secondary particles dispersed in the carbon material, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer. The primary particles include nanosilicon particles, and the median diameter D2 of the negative electrode material is 50 is 4.9 μm, and the minimum particle size D2 min is 0.39 μm, and the maximum particle size D2 max is 18.4 μm, and the sphericity of the negative electrode material is 0.94.

[0185] Example 9

[0186] The difference from Example 1 is that the nano silicon particles are replaced with nano germanium particles, among which the D1 50 is 30nm, D1 max = 220 nm, bulk density 0.26 g / cm 3 is.

[0187] The negative electrode material manufactured in this example includes a carbon material and secondary particles dispersed in the carbon material, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer. The primary particles include nano-germanium particles, and the median diameter D2 of the negative electrode material is 50 is 3.5 μm, and the minimum particle size D2 min is 0.3 μm, and the maximum particle size D2 max is 12.5 μm, and the sphericity of the negative electrode material is 0.88.

[0188] Example 10

[0189] The difference from Example 1 is that the nanosilicon particles are replaced with nanotin particles, of which D1 50 is 28nm, D1 max = 185 nm, bulk density 0.25 g / cm 3 is.

[0190] The negative electrode material manufactured in this example includes a carbon material and secondary particles dispersed in the carbon material, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer. The primary particles include nano-tin particles, and the median diameter D2 of the negative electrode material is 50 is 3.6 μm, and the minimum particle size D2 min is 0.4 μm, and the maximum particle size D2 max is 10.9 μm, and the sphericity of the negative electrode material is 0.89.

[0191] Example 11

[0192] The difference from Example 1 is that the phenolic resin in step (4) is replaced with silicon nitride.

[0193] The negative electrode material produced in this example includes secondary particles, and the surfaces of the secondary particles include a silicon nitride coating layer. The secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer. The primary particles include nanosilicon particles, and the median diameter D2 of the negative electrode material is 50 is 3.4 μm, and the minimum particle size D2 min is 0.5 μm, and the maximum particle size D2 max is 11.7 μm, and the sphericity of the negative electrode material is 0.91.

[0194] Example 12

[0195] The difference from Example 1 is step (2), in which the nanosilicon and polyvinyl alcohol obtained in step (1) are added to phenol in a mass ratio of 100:28, and the mixture is rotary evaporated and dried at 120°C to obtain a first precursor.

[0196] The negative electrode material manufactured in this example includes a carbon material and secondary particles dispersed in the carbon material, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer. The primary particles include nanosilicon particles, and the median diameter D2 of the negative electrode material is 50 is 6.0 μm, and the minimum particle size D2 min is 0.82 μm, and the maximum particle size D2 max is 22.2 μm, and the sphericity of the negative electrode material is 0.52.

[0197] Example 13

[0198] The difference from Example 1 is that the nano silicon particles are replaced with nano SiO particles, among which the D1 of the nano SiO particles 50 is 80nm, D1 max = 320 nm, bulk density 0.36 g / cm 3 is.

[0199] The negative electrode material manufactured in this example includes a carbon material and secondary particles dispersed in the carbon material, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer. The primary particles include nano-SiO particles, and the median diameter D2 of the negative electrode material is 50 is 4.5 μm, and the minimum particle size D2 min is 0.4 μm, and the maximum particle size D2 max is 13.5 μm, and the sphericity of the negative electrode material is 0.93.

[0200] Comparative Example 1

[0201] (1) By sieving the nanosilicon particles, the median diameter D1 50 obtains 300nm nanosilicon.

[0202] (2) The nanosilicon obtained in step (1) and polyvinyl alcohol are added to phenol in a mass ratio of 100:28, then ball milled in a planetary ball mill for 2 hours, and dried by rotary evaporation at 120°C to obtain the first precursor.

[0203] (3) The second precursor is obtained by pre-pulverizing and pre-classifying the first precursor, and has a median diameter of 7.1 μm and a maximum particle size of 23.8 μm.

[0204] (4) The second precursor and phenolic resin were mixed in a mass ratio of 50:35, and then fused. The fusion time was 40 minutes, and the cutter gap was 0.1 cm. The fused material was then placed in a high-temperature box furnace, nitrogen gas was introduced, and the material was heat-treated at 820°C and kept at that temperature for 4 hours.

[0205] (5) The material obtained in step (4) is crushed and classified to obtain the negative electrode material.

[0206] The negative electrode material produced in this comparative example includes a carbon material and secondary particles dispersed in the carbon material, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer. The primary particles include nanosilicon particles, and the median diameter D2 of the negative electrode material is 50is 7.2 μm, and the minimum particle size D2 min is 0.42 μm, and the maximum particle size D2 max is 33.8 μm, and the sphericity of the negative electrode material is 0.89.

[0207] Comparative Example 2

[0208] The difference from Example 1 is that the crushing and classification treatments were not carried out.

[0209] The negative electrode material produced in this comparative example includes a carbon material and secondary particles dispersed in the carbon material, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer. The primary particles include nanosilicon particles, and the median diameter D2 of the negative electrode material is 50 is 5.2 μm, and the minimum particle size D2 min is 0.31 μm, and the maximum particle size D2 max is 33.8 μm, and the sphericity of the negative electrode material is 0.67.

[0210] Comparative Example 3

[0211] The difference from Example 1 is that the primary particles D1 used max is 0.3 μm.

[0212] The negative electrode material produced in this comparative example includes a carbon material and secondary particles dispersed in the carbon material, the secondary particles include aggregated primary particles, and the surfaces of the primary particles have a carbon material coating layer, and the primary particles include nanosilicon particles. 50 = 2 μm, D2 min =0.3μm, D2 max =15 μm, and the sphericity of the negative electrode material is 0.67.

[0213] Test Method: 1. The median diameter, minimum particle size and maximum particle size of the material are measured using a Malvern particle size analyzer, and the measurement standard is ISO13320:2009. 2. Bulk Density Tester Measure the bulk density of the material using vinegar do. 3. Use a specific surface area tester to measure the specific surface area of ​​the material. 4. Measure the porosity of the material using static volumetric method or mercury intrusion method. 5. Use a particle sphericity analyzer to measure the sphericity of the material. 6. Measure the electrochemical cycle performance using the following method:

[0214] The negative electrode material, conductive agent, and adhesive were dissolved and mixed in water in a mass ratio of 94:1:5 to control the solid content to 50%, and then coated on a copper foil current collector and vacuum dried to produce a negative electrode sheet. Subsequently, a ternary positive electrode sheet (lithium nickel manganese cobalt oxide NCM523) manufactured using a conventional mature process, 1 mol / L lithium hexafluorophosphate LiPF6 / (ethylene carbonate EC + dimethyl carbonate DMC + ethyl methyl carbonate EMC) (v / v = 1:1:1) electrolyte, Celgard 2400 separator, and shell were assembled into an 18650 cylindrical battery cell using the standard production process. The cylindrical battery was tested using LAND battery test equipment from Wuhan Jinnuo Electronics Co., Ltd., at room temperature, with a constant current of 0.2C charging and discharging, and the charge / discharge voltage was limited to 2.75 to 4.2V, to obtain the initial reversible specific capacity and initial coulombic efficiency (ICE). The battery was then subjected to 100 charge / discharge cycles at a current density of 1C, with a charge / discharge range of 0.01V to 5V, to obtain the capacity retention rate and thickness expansion rate of the electrode pieces after 50 cycles.

[0215] The test results are shown in Tables 1 and 2.

[0216] [Table 1]

[0217] [Table 2]

[0218] As shown in the data in Tables 1 and 2 above, the negative electrode materials, primary particles, and secondary particles produced in Examples 1 to 12 of the present application were 10≦D2 50 / D1 max ≦40, D2 min / D2 50 ≧0.08, and D2 50 / D2 max ≧0.24, the primary particles and secondary particles have good matching, which ultimately reduces the amount of fine powder in the negative electrode material, concentrates the particle size of the secondary particles, improves the cycle stability of the negative electrode material, and reduces the volume expansion effect of the negative electrode material.

[0219] The negative electrode material produced in Comparative Example 1 had nanosilicon particles that were too large, which reduced the adhesion between the primary particles, increased the volume expansion of the negative electrode material, increased the rate of secondary particle rupture during charging and discharging, and reduced the cycle capacity retention rate.

[0220] The negative electrode material produced in Comparative Example 2 was not subjected to pulverization or classification, and therefore the particle size distribution of the negative electrode material was wide, a certain amount of fine powder was present, and the volume expansion of the material was large.

[0221] The negative electrode material produced in Comparative Example 3 was D2 50 , D1 max , D2 max and D2 min Although all of the single parameters are within the preferred range, 10≦D2 50 / D1 max ≦40, D2 50 / D2 max ≧0.24 is not satisfied, and the volume expansion of the negative electrode material is large.

[0222] The above is only a preferred embodiment of the present application, and is not intended to limit the present application. Those skilled in the art may have various modifications and variations to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. An anode material, the anode material including secondary particles, the secondary particles including aggregated primary particles, the primary particles and the secondary particles satisfy the following relationship: The primary particles are SiO x (0<x<2), including at least one of Sn, Ge, and Si; Median diameter D1 of the primary particles 50 The range is 5 nm to 200 nm, The median diameter D2 of the secondary particles 50 The range is 1.8 μm to 12 μm, The maximum particle size D1 of the primary particles max The range is 0.1 μm to 0.4 μm, The minimum particle size D2 of the secondary particles min The range is 0.5 μm to 4 μm, The maximum particle size D2 of the secondary particles max The range of the negative electrode material is 6 μm to 20 μm. 10≦D2 50 / D1 max ≦40 (I) D22 min / D2 50 ≧008 (II) D2 50 / D2 max ≧0.24 (III) (In formulas (I), (II) and (III), D1 max is the maximum particle size of the primary particles, and D2 50 is the median diameter of the secondary particles, and D2 min is the minimum particle size of secondary particles, and D2 max is the maximum particle size of the secondary particles.)

2. The bulk density of the primary particles is 0.7 g / cm 3 2. The negative electrode material according to claim 1, wherein:

3. The negative electrode material according to claim 1, wherein the negative electrode material satisfies at least one of the following characteristics (1) to (3): (1) The specific surface area of ​​the negative electrode material is 10 m 2 / g or less, (2) the porosity of the negative electrode material is 10% or less; (3) The sphericity of the negative electrode material is 0.7 or more.

4. 2. The negative electrode material according to claim 1, further comprising a coating layer present on at least a portion of the surface of the primary particles and / or the secondary particles.

5. 5. The negative electrode material according to claim 4, wherein the coating layer satisfies at least one of the following (1) to (5): (1) The material of the coating layer includes at least one of a carbon material, graphene, silicon carbide, a metal oxide, and a nitride; (2) The material of the coating layer includes a carbon material, and the carbon material includes at least one of soft carbon, hard carbon, crystalline carbon, and amorphous carbon; (3) The material of the coating layer includes a metal oxide, and the metal oxide includes at least one of titanium oxide, aluminum oxide, lithium oxide, cobalt oxide, and vanadium oxide; (4) The material of the coating layer includes a nitride, and the nitride includes at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride, and carbon nitride; (5) The thickness of the coating layer is 1 nm to 500 nm.

6. granulating a mixed material containing primary particles and an adhesive to obtain a precursor; heat-treating the precursor to carbonize the adhesive to obtain a heat-treated product; A method for producing a negative electrode material, comprising: pulverizing and classifying the heat-treated product to obtain secondary particles that satisfy the following relationship with the primary particles, thereby obtaining a negative electrode material: The primary particles are SiO x (0<x<2), including at least one of Sn, Ge, and Si; Median diameter D1 of the primary particles 50 The range is 5 nm to 200 nm, The median diameter D2 of the secondary particles 50 The range is 1.8 μm to 12 μm, The maximum particle size D1 of the primary particles max The range is 0.1 μm to 0.4 μm, The minimum particle size D2 of the secondary particles min The range is 0.5 μm to 4 μm, The maximum particle size D2 of the secondary particles max The range of the thickness is 6 μm to 20 μm. 10≦D2 50 / D1 max ≦40 (I) D22 min / D2 50 ≧008 (II) D2 50 / D2 max ≧0.24 (III) (In formulas (I), (II) and (III), D1 max is the maximum particle size of the primary particles, and D2 50 is the median diameter of the secondary particles, and D2 min is the minimum particle size of secondary particles, and D2 max is the maximum particle size of the secondary particles.)

7. The manufacturing method according to claim 6, characterized in that it comprises at least one of the following features (1) to (13): (1) The adhesive contains at least one of starch, cellulose, tannin, gum arabic, sodium alginate, styrene-butadiene rubber, butyl rubber, cellulose ester, ene-based polymer, polyamide, polyacrylic acid ester, epoxy resin, phenolic resin, furan resin, unsaturated polyester, acrylic resin, and polyimide; (2) the mass ratio of the primary particles to the adhesive is 100:(5 to 55); (3) The mixed material of the primary particles and the adhesive further contains a solvent; (4) The mixed material of the primary particles and the adhesive further contains a solvent, and the solvent contains at least one of phenol, an alcohol-based solvent, an ether-based solvent, and an alkane-based solvent; (5) The mixed material of the primary particles and the adhesive further contains a solvent, and the mass ratio of the solvent to the primary particles is 100:(5 to 40); (6) The method further includes dispersing the mixed material containing the primary particles and the adhesive before the step of granulating the mixed material containing the primary particles and the adhesive; (7) The method further includes dispersing the mixed material including the primary particles and the adhesive before the step of granulating the mixed material including the primary particles and the adhesive, and the dispersion treatment includes at least one of magnetic stirring, mechanical stirring, abrasive dispersion, and ultrasonic dispersion; (8) The temperature of the heat treatment is 500°C to 1000°C; (9) The heat-retaining time of the heat treatment is 30 minutes to 900 minutes. (10) The heat treatment is performed in a protective atmosphere, and the protective atmosphere contains at least one of nitrogen gas, argon gas, and helium gas; (11) The median diameter of the material obtained by the pulverization is 0.5 μm to 15 μm; (12) The maximum particle size of the material obtained by pulverization is 5 μm to 45 μm; (13) After the classification treatment, the method further comprises removing particles having a particle size of 0.5 μm or less from the material obtained by the classification treatment.

8. 7. The method according to claim 6, wherein at least one of the following characteristics (1) to (5) is satisfied: (1) The method further includes pre-pulverizing and pre-classifying the precursor before the step of heat-treating the precursor to carbonize the adhesive; (2) The method further includes pre-pulverizing and pre-classifying the precursor before the step of heat-treating the precursor to carbonize the adhesive, and the pre-pulverizing includes at least one of mechanical pulverization, airflow pulverization, ultrafine powder pulverization, wet pulverization, extrusion pulverization, and split pulverization; (3) The method further includes pre-pulverizing and pre-classifying the precursor before the step of heat-treating the precursor to carbonize the adhesive, and the median diameter of the material obtained by the pre-pulverization is 0.5 μm to 20 μm; (4) The method further includes pre-pulverizing and pre-classifying the precursor before the step of heat-treating the precursor to carbonize the adhesive, and the maximum particle size of the material obtained by the pre-pulverization is 5 μm to 45 μm; (5) The method further includes pre-grinding and pre-classifying the precursor before the step of heat-treating the precursor to carbonize the adhesive, and the particle size of the material obtained by the pre-classification exceeds 0.5 μm.

9. 7. The method according to claim 6, wherein at least one of the following characteristics (1) to (7) is satisfied: (1) The method further includes fusing the precursor and the coating material before the step of heat-treating the precursor to carbonize the adhesive; (2) The method further includes, before the step of heat-treating the precursor to carbonize the adhesive, fusing the precursor with a coating material, wherein the coating material includes at least one of a carbon source, graphene, silicon carbide, a metal oxide, and a nitride; (3) The method further includes fusing the precursor and the coating material before the step of heat-treating the precursor to carbonize the adhesive, wherein the coating material includes a carbon source, and the carbon source includes at least one of sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt; (4) The method further includes fusing the precursor and a coating material before the step of heat-treating the precursor to carbonize the adhesive, wherein the coating material includes a metal oxide, and the metal oxide includes at least one of titanium oxide, aluminum oxide, lithium oxide, cobalt oxide, and vanadium oxide; (5) The method further includes fusing the precursor with a coating material before the step of heat-treating the precursor to carbonize the adhesive, wherein the coating material includes a nitride, and the nitride includes at least one of titanium nitride, vanadium nitride, cobalt nitride, nickel nitride, and carbon nitride; (6) The method further includes fusing the precursor and the coating material before the step of heat-treating the precursor to carbonize the adhesive, and the fusing device includes at least one of a mechanical fusing machine, a fusing stirrer, and a convection fusing machine; (7) The method further includes fusing the precursor and the coating material before the step of heat-treating the precursor to carbonize the adhesive, and the fusing time is 30 minutes to 150 minutes.

10. A secondary battery comprising the negative electrode material according to any one of claims 1 to 5.

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