Negative electrode material, negative electrode sheet, and battery

Abstract

A negative electrode material, a negative electrode sheet, and a battery, which relate to the field of negative electrode materials. The negative electrode material comprises a silicon-based material, graphite, and a carbon material located on at least part of the surface of the silicon-based material and / or graphite. Raman mapping is used to test the negative electrode material, and a Raman mapping spectrogram thereof contains a first type of spectral lines having a characteristic peak within the range of 500 cm-1 to 520 cm-1 and a second type of spectral lines having no characteristic peak within the range of 500 cm-1 to 520 cm-1. By controlling the intensity relationship of the characteristic peaks in the two types of spectral lines, the negative electrode material has a relatively high specific capacity and a good electrolyte wettability, and a prepared negative electrode sheet has a low resistivity.

Description

Anode material, anode plate, battery

[0001] This application claims priority to Chinese patent application No. 202311804698.8, filed on December 25, 2023. This application incorporates the entire text of the aforementioned Chinese patent application. Technical Field

[0002] The present application relates to the technical field of negative electrode materials, and in particular to negative electrode materials, negative electrode sheets, and batteries. Background Art

[0003] Lithium-ion batteries are widely used in electric vehicles and consumer electronics due to their high energy density, long cycle life, low environmental pollution, and lack of memory effect. Anode materials are a crucial component of lithium-ion batteries, directly impacting key battery performance indicators such as energy density, cycle life, and safety. Currently, commercial lithium-ion batteries primarily utilize graphite-based anode materials, but their theoretical specific capacity is only 372 mAh / g, making them difficult to meet the demands of high-energy-density lithium-ion batteries. Silicon-based anode materials, as lithium-ion battery anode materials, possess high specific capacity and are a candidate for the next generation of high-energy-density lithium-ion batteries. However, due to variations in silicon morphology, composition, and particle size, the fabrication of these materials into anodes presents a series of challenges, the most notable of which are the wettability of the electrode in the electrolyte and a decrease in electrical conductivity.

[0004] Therefore, how to improve the wettability and conductivity of silicon-based negative electrode materials while increasing the specific capacity of the negative electrode materials is a technical problem that still needs to be solved.

[0005] Summary of the Invention

[0006] The purpose of the present application is to provide a negative electrode material, a negative electrode plate, and a battery. The negative electrode material of the present application has a high specific capacity, and can also improve the wettability of the negative electrode material and reduce the resistivity of the negative electrode plate.

[0007] In a first aspect, the present application provides a negative electrode material, comprising a silicon-based material and graphite, and a carbon material located on at least a portion of the surface of the silicon-based material and / or graphite;

[0008] The negative electrode material was tested by Raman scanning. In the Raman scanning spectrum of the negative electrode material, the peaks at 500 cm -1 ~520cm -1 There are characteristic peaks of the first type of spectral lines and 500cm -1 ~520cm -1 The second type of spectral lines does not have characteristic peaks within the range;

[0009] In the first type of spectral lines, at 500cm -1~520cm -1 There is a characteristic peak with intensity I1 at 1345cm -1 ~1355cm -1 There is a characteristic peak with an intensity of I2 at 1570cm -1 ~1610cm -1 There is a characteristic peak in the range with an intensity of I3;

[0010] In the second type of spectral lines, at 1345cm -1 ~1355cm -1 There is a characteristic peak in the range with an intensity of I2 ’ , at 1570cm -1 ~1610cm -1 There is a characteristic peak in the range with an intensity of I3 ’ ;

[0011] in: 0.01≤K≤10.

[0012] In a second aspect, the present application provides a negative electrode plate, which includes the negative electrode material described in the first aspect; the resistivity of the negative electrode plate is ≤5Ω·cm.

[0013] In a third aspect, the present application provides a battery, comprising the negative electrode material described in the first aspect.

[0014] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:

[0015] The negative electrode material provided by the present application comprises a silicon-based material and graphite, and a carbon material located on at least a portion of the surface of the silicon-based material and / or graphite. The negative electrode material is tested by Raman surface scanning. In the Raman surface scanning spectrum of the negative electrode material, the carbon material containing 500cm -1 ~520cm -1 There are characteristic peaks of the first type of spectral lines and 500cm -1 ~520cm -1 There is no second type of spectral line with characteristic peaks within the range. The first type of spectral line can represent the Raman spectrum of particles mainly containing silicon-based materials. -1 ~520cm -1 The characteristic peak intensity in the range is I1, at 1345 cm -1 ~1355cm -1 The characteristic peak intensity in the range is I2, at 1570 cm -1 ~1610cm -1 The characteristic peak intensity in the range is I3. Due to the presence of carbon material on the surface of silicon-based materials, it can be detected at 1345 cm -1~1355cm -1 Range and 1570cm -1 ~1610cm -1 The second type of spectral line can represent the Raman spectrum of particles containing graphite, at 1345cm -1 ~1355cm -1 The characteristic peak intensity in the range is I2 ’ , at 1570cm -1 ~1610cm -1 The characteristic peak intensity in the range is I3 ’ I1 / (I2+I3) can represent the exposure degree of silicon-based materials in negative electrode materials, I2 ’ / (I2 ’ +I3 ’ ) can represent the degree of defects on the graphite surface in the negative electrode material, I2 / (I2+I3)+I2 ’ / (I2 ’ +I3 ’ ) can represent the total defect level of the carbon material on the surface of the negative electrode material. When too much silicon is exposed on the surface of the negative electrode material or the defect level of the surface carbon material is high, during the charge and discharge cycle of the battery prepared from the negative electrode material, the side reaction between the negative electrode material and the electrolyte in the battery is intensified, and the thickness of the solid electrolyte film on the surface of the negative electrode material also increases. At this time, although the electrolyte wetting ability is relatively increased, the resistivity of the negative electrode sheet will also increase; in addition, the content of active lithium ions consumed during the charge and discharge cycle of the battery increases, and the first coulomb efficiency of the negative electrode material decreases. When too little silicon-based material is exposed on the surface of the negative electrode material or the defect level of the surface carbon material is very low, the electrolyte wetting ability of the negative electrode material decreases, and some silicon-based materials and graphite are difficult to be activated, which is not conducive to the electrochemical performance. This application achieves this by controlling I1 / (I2+I3) and I2 / (I2+I3)+I2 ’ / (I2 ’ +I3 ’ ) ratio is in the range of 0.01 to 10, which can find a balance between the degree of silicon exposure and the degree of defects in the surface carbon material. On the one hand, it ensures that the silicon-based material in the negative electrode material is less exposed. On the other hand, the degree of defects in the surface carbon material is used to improve the wettability of the negative electrode material to the electrolyte, and comprehensively control the thickness of the solid electrolyte film layer formed on the surface of the negative electrode material during the charge and discharge process. The prepared negative electrode sheet has a lower resistivity, which further increases the stability and durability of the negative electrode sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present application is further described below with reference to the accompanying drawings and examples.

[0017] FIG1 is a schematic flow chart of a method for preparing a negative electrode material provided in an embodiment of the present application.

[0018] FIG2 is a diagram showing the distribution of silicon-based materials and graphite within the scanning range of the negative electrode material prepared in Example 1.

[0019] FIG3 is a Raman surface scanning spectrum of the negative electrode material prepared in Example 1.

[0020] FIG4 is a volume-based cumulative particle size distribution width diagram of the negative electrode material prepared in Example 1. DETAILED DESCRIPTION

[0021] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0022] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0023] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0024] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0025] In a first aspect, the present application provides a negative electrode material, the negative electrode material comprising a silicon-based material and graphite, and a carbon material located on at least a portion of the surface of the silicon-based material and / or graphite;

[0026] Raman surface scanning was used to test the negative electrode material. In the Raman surface scanning spectrum of the negative electrode material, there is a 500cm -1 ~520cm -1 There are characteristic peaks of the first type of spectral lines and 500cm -1 ~520cm -1 The second type of spectral lines does not have characteristic peaks within the range;

[0027] In the first type of spectral line, at 500cm -1 ~520cm -1 There is a characteristic peak with intensity I1 at 1345cm -1 ~1355cm -1There is a characteristic peak with an intensity of I2 at 1570cm -1 ~1610cm -1 There is a characteristic peak in the range with an intensity of I3;

[0028] In the second type of spectral line, at 1345cm -1 ~1355cm -1 There is a characteristic peak in the range with an intensity of I2 ’ , at 1570cm -1 ~1610cm -1 There is a characteristic peak in the range with an intensity of I3 ’ ;

[0029] in: 0.01≤K≤10.

[0030] The negative electrode material provided by the present application includes an active material and a carbon material located on at least a portion of the surface of the active material, wherein the active material includes a silicon-based material and graphite. The negative electrode material is tested by Raman surface scanning. In the Raman surface scanning spectrum of the negative electrode material, the 500cm -1 ~520cm -1 There are characteristic peaks of the first type of spectral lines and 500cm -1 ~520cm -1 There is no second type of spectral line with characteristic peaks within the range. The first type of spectral line can represent the Raman spectrum of particles mainly containing silicon-based materials. -1 ~520cm -1 The characteristic peak intensity in the range is I1, at 1345 cm -1 ~1355cm -1 The characteristic peak intensity in the range is I2, at 1570 cm -1 ~1610cm -1 The characteristic peak intensity in the range is I3. Due to the presence of carbon material on the surface of silicon-based materials, it can be detected at 1345 cm -1 ~1355cm -1 Range and 1570cm -1 ~1610cm -1 The second type of spectral line can represent the Raman spectrum of particles containing graphite, at 1345cm -1 ~1355cm -1 The characteristic peak intensity in the range is I2 ’ , at 1570cm -1 ~1610cm -1 The characteristic peak intensity in the range is I3 ’ I1 / (I2+I3) can represent the exposure degree of silicon-based materials in negative electrode materials, I2 ’ / (I2’ +I3 ’ ) can represent the degree of defects on the graphite surface in the negative electrode material, I2 / (I2+I3)+I2 ’ / (I2 ’ +I3 ’ ) can represent the total defect level of the carbon material on the surface of the negative electrode material. When too much silicon is exposed on the surface of the negative electrode material or the defect level of the surface carbon material is high, the side reaction between the negative electrode material and the electrolyte in the battery is intensified. During the charge and discharge cycle of the battery prepared from the negative electrode material, the thickness of the solid electrolyte film on the surface of the negative electrode material also increases. At this time, although the electrolyte wetting ability is relatively increased, the resistivity of the negative electrode sheet will also increase. In addition, the content of active lithium ions consumed increases, and the first coulomb efficiency of the negative electrode material decreases. When too little silicon-based material is exposed on the surface of the negative electrode material or the defect level of the surface carbon material is very low, the electrolyte wetting ability of the negative electrode material decreases, and some electrochemically active components in the negative electrode material are difficult to be activated, which is not conducive to the performance of the electrochemically active components in the negative electrode material. This application achieves this by controlling I1 / (I2+I3) and I2 / (I2+I3)+I2 ’ / (I2 ’ +I3 ’ ) is in the range of 0.01 to 10, which can find a balance between the degree of silicon exposure and the degree of defects in the surface carbon material. On the one hand, it ensures that fewer silicon particles in the negative electrode material are exposed. On the other hand, the degree of defects in the surface carbon material is used to improve the wetting ability of the negative electrode material to the electrolyte, and comprehensively control the thickness of the solid electrolyte film layer formed on the surface of the negative electrode material during the charge and discharge process. The prepared negative electrode sheet has a lower resistivity, which further increases the stability and durability of the negative electrode sheet.

[0031] In some embodiments, I1 / (I2+I3) and I2 / (I2+I3)+I2 ’ / (I2 ’ +I3 ’ ) can be specifically 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.8, 1.0, 1.5, 2.0, 2.5, 3, 4, 5, 6, 7, 8, 9 or 10, etc., and of course it can also be other values ​​within the above range, which is not limited here. When the ratio is controlled within the above range, an appropriate amount of silicon-based material is exposed on the surface of the negative electrode material, the side reaction between the negative electrode material and the electrolyte can be effectively controlled, and the thickness of the solid electrolyte film on the surface of the negative electrode material can also be effectively controlled. At this time, the electrolyte infiltration ability is relatively increased, and the negative electrode material can have good electrolyte infiltration ability, thereby reducing the resistivity of the negative electrode sheet. Preferably, I1 / (I2+I3) and I2 / (I2+I3)+I2 ’ / (I2 ’ +I3’ ) is in the range of 0.4 to 10.

[0032] In some embodiments, the range of I1 / (I2+I3) is 0.1 to 2.3, specifically 0.1, 0.5, 1, 1.8, 2.0, 2.1, 2.2 or 2.3, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0033] In some embodiments, the range of I2 / (I2+I3) is 0.1 to 0.8, specifically 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or 0.8, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0034] In some embodiments, I2 ’ / (I2 ’ +I3 ’ ) is in the range of 0.1 to 0.61, and can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 or 0.61, etc., and can be other values ​​within the above range, which is not limited here. It can be understood that I1 / (I2+I3) and I2 / (I2+I3)+I2 ’ / (I2 ’ +I3 ’ ) is controlled within the above range, the electrolyte wetting ability of the negative electrode material can be further improved, thereby reducing the resistivity of the negative electrode sheet.

[0035] In some embodiments, the silicon-based material includes at least one of amorphous silicon, crystalline silicon, silicon oxide, and silicate.

[0036] In some embodiments, the silicon-based material includes silicon oxide, and the silicon oxide includes silicon and oxygen, and the atomic ratio of the silicon to the oxygen is 0 to 2, excluding 0.

[0037] In some embodiments, the silicon-based material comprises silicon oxide, the chemical formula of which is SiO x , where 0<x≤2. Specifically, SiO x Specifically, it can be SiO 0.5 、SiO 0.7 、SiO 0.9 、SiO、SiO 1.2 、SiO 1.5 、SiO 1.8 、SiO 1.9 etc., not limited here.

[0038] Silicon oxide can be represented by the general formula SiO x(0<x≤2). It can be a material formed by dispersing silicon in SiO2; or it can be a material having a tetrahedral structural unit, with the silicon atom located at the center of the tetrahedral structural unit and oxygen atoms and / or silicon atoms located at the four vertices of the tetrahedral structural unit.

[0039] In some embodiments, the average particle size of the silicon-based material is 1 nm to 10 μm, and can specifically be 1 nm, 10 nm, 50 nm, 100 nm, 1 μm, 1.8 μm, 2 μm, 2.5 μm, 3 μm, 3.6 μm, 5 μm, 6 μm, 6.5 μm, 7 μm, 7.8 μm, 8.5 μm, 9 μm, 9.8 μm or 10 μm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0040] In some embodiments, the silicon-based material further comprises a metal element M, where M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu, and Mn. It is understood that a small amount of the metal element M can be doped into either the carbon material or the silicon-based material. The metal element M can improve the conductivity of the negative electrode material and enhance the structural strength of the negative electrode material. Preferably, M is Mg and / or Li.

[0041] In some embodiments, in the negative electrode material, the silicon-based material and the graphite are dispersed with each other in the form of particles.

[0042] In some embodiments, the graphite includes at least one of natural graphite, artificial graphite, expanded graphite, and graphite oxide. Graphite is a material with high conductivity, low volume expansion, high initial efficiency, and stable cycling performance. By combining graphite with silicon-based materials, the conductivity of the negative electrode material can be comprehensively improved and its expansion can be reduced.

[0043] In some embodiments, the carbon material includes at least one of amorphous carbon and graphitized carbon. The carbon material can be located on the surface of the silicon-based material particles, or on the surface of the graphite particles, or the graphite particles and the silicon-based material particles can be secondary granulated and then carbon-coated to form secondary particles, which is not limited here. In some embodiments, the thickness of the carbon layer is 1nm to 1000nm, and can specifically be 1nm, 5nm, 10nm, 15nm, 20nm, 50nm, 80nm, 100nm, 150nm, 200nm, 400nm, 500nm, 700nm, 800nm, 900nm, 1000nm, etc., which is not limited here. Controlling the thickness of the carbon layer within the above range can increase the conductivity of the negative electrode material, which is conducive to obtaining a negative electrode material with a high specific capacity; and the carbon layer can effectively alleviate the volume expansion of the active material and improve the long cycle performance of the negative electrode material. Preferably, the thickness of the carbon layer is 50nm to 800nm; more preferably, the thickness of the carbon layer is 100nm to 500nm.

[0044] In some embodiments, the particle size distribution width of the negative electrode material is P, 1.0≤P≤2.2, P=(D 05 +D 99 ) / (2*D 50 ). The specific value of the ratio of P can be 1.0, 1.1, 1.3, 1.5, 1.6, 1.8, 2.0, 2.1 or 2.2, etc., which are not limited here. When the particle size distribution of the negative electrode material is controlled within the above range, it means that the negative electrode material has a wider particle size distribution, which helps to improve the uniform distribution of silicon-based materials and graphite, is beneficial to increase the gram capacity of the negative electrode material, and helps to improve the electrical conductivity of the negative electrode material. It should be noted that the particle size distribution width of the negative electrode material is measured based on all particles.

[0045] It should be noted that the volume-based cumulative particle size distribution of the particle size distribution is measured by laser diffraction method. D05 represents the particle size corresponding to the cumulative particle size distribution percentage of the powder reaching 5%, D50 represents the particle size corresponding to the cumulative particle size distribution percentage reaching 50%, and D99 represents the particle size corresponding to the cumulative particle size distribution percentage reaching 99%. 05 +D 99 ) / (2*D 50 ) is used to define the particle size distribution of the negative electrode material. The nano-scale silicon-based material formed by vapor deposition can be included in the particle size planning, which can cover the size of most negative electrode material particles.

[0046] When the negative electrode material satisfies 1.0≤P≤2.2, the size and number of large and small particles in the negative electrode material are well matched, which is conducive to the full dispersion of the particles and tends to form a densely packed structure with small particles embedded in the contact gaps between large particles, thereby helping to improve the tap density of the negative electrode material. When the ratio is too small, the particle sizes of large and small particles in the negative electrode material are very close, and there are large pores in the contact between the particles, which is not conducive to the formation of a densely packed structure. When the ratio is too large, the particle size and number of large and small particles in the negative electrode material are greatly different. Among them, a large number of small particles tend to agglomerate themselves and it is difficult to form a densely packed structure matching the large particles, and the distribution uniformity is reduced.

[0047] In some embodiments, the powder conductivity of the negative electrode material under a pressure of 20 kN is greater than 30 S / cm, and may specifically be 30 S / cm, 31 S / cm, 32 S / cm, 33 S / cm, 35 S / cm, 36 S / cm, 37 S / cm, 38 S / cm, or 40 S / cm, etc., without limitation herein. Controlling the powder conductivity of the negative electrode material within the above range is beneficial for improving the conductivity of the negative electrode material and reducing the resistivity of the negative electrode sheet.

[0048] In some embodiments, the contact angle of the negative electrode material is greater than 110°. In the present application, controlling the contact angle of the negative electrode material within the above range is beneficial to improving the electrolyte wetting ability of the negative electrode material.

[0049] In some embodiments, the median particle size D of the negative electrode material is 50 It is 2μm to 12μm, and specifically can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 5μm, 6μm, 8μm, 9μm, 10μm or 12μm, etc., which is not limited here.

[0050] In some embodiments, the tap density of the negative electrode material is ≥ 0.7 g / cm 3 The tap density of the negative electrode material can be specifically 0.7 g / cm 3 , 0.75g / cm 3 、0.81g / cm 3 , 0.85g / cm 3 , 0.89g / cm 3 , 0.91g / cm 3 , 0.95g / cm 3 , 0.99g / cm 3 , 1.0g / cm 3 , 1.05g / cm 3 , 1.1g / cm 3 , 1.13g / cm 3 , 1.18g / cm 3 , 1.2g / cm 3 , 1.25g / cm 3 , 1.3g / cm 3 , 1.38g / cm 3 or 1.4 g / cm 3 etc., not limited here.

[0051] In some embodiments, the mass content of silicon in the negative electrode material is 1% to 80%, and the mass content of carbon is 20% to 99%. The mass content of silicon can be 1%, 2%, 8%, 10%, 12%, 15%, 30%, 50%, 55%, 58%, 60%, 65%, 69%, 70%, or 80%, and the mass content of carbon can be 20%, 30%, 40%, 50%, 55%, 58%, 60%, 65%, 69%, 70%, 80%, or 90%, etc. Of course, other values ​​within the above ranges are also possible and are not limited here. Preferably, the mass content of silicon in the negative electrode material is 3.5% to 31.5%, specifically 3.5%, 10%, 10.1%, 10.2%, 10.3%, 10.5%, 11%, 31.5%, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0052] In a second aspect, an embodiment of the present application provides a method for preparing a negative electrode material, comprising the following steps:

[0053] The graphite is placed in a modification solution containing an acid solution or an alkaline solution for modification treatment, wherein the concentration of the acid solution or the alkaline solution is less than 2 mol / L, the modification treatment temperature is 20° C. to 30° C., the modification treatment time is 10 h to 48 h, and then dried to obtain modified graphite;

[0054] The modified graphite is vapor-deposited using a reaction gas containing a silicon source gas to obtain a mixture of a silicon-based material and the modified graphite, wherein the vapor deposition process is carried out in a fluidized bed reactor and an auxiliary carrier gas is added during the vapor deposition process;

[0055] The mixture is placed at 550° C. to 1000° C. using a gaseous carbon source to perform a gaseous carbon coating treatment to obtain a negative electrode material.

[0056] The preparation method of the negative electrode material provided by the present application comprises the following steps: firstly modifying the graphite to improve the defectivity of the graphite; then compounding the modified graphite with a silicon-based material by vapor deposition to achieve uniform mixing of the silicon-based material and the modified graphite, thereby reducing the segregation of the silicon-based material; finally, subjecting the mixture of the two to vapor-phase carbon coating at 550°C to 1000°C, thereby effectively reducing the defectivity of the graphite surface and adjusting the defectivity of the carbon material on the surface of the silicon-based material and the surface of the graphite, thereby making I1 / (I2+I3) and I2 / (I2+I3)+I2 ’ / (I2 ’ +I3 ’) ratio is in the range of 0.01 to 10, which can find a balance between the degree of silicon exposure and the degree of defects in the surface carbon material. Under the premise of ensuring that the first coulombic efficiency of the negative electrode material is at a high level, the degree of defects in the carbon materials on the silicon-based material and the graphite surface is used to improve the electrolyte wetting ability of the negative electrode material. The small amount of silicon-based material exposed on the surface of the negative electrode material can also be used to generate a solid electrolyte membrane layer of appropriate thickness during the charge and discharge cycle, thereby improving the electrical conductivity of the electrode.

[0057] The following is a detailed introduction to this solution, as shown in Figure 1, which includes the following steps:

[0058] Step S100: placing graphite in a modification solution for modification, and drying to obtain modified graphite.

[0059] In some embodiments, the median particle size of graphite is 6 μm to 20 μm, preferably 6 μm to 12 μm, specifically 6 μm, 8 μm, 10 μm, 12 μm, etc., which are not limited here. Controlling the particle size of graphite is beneficial to controlling the particle size of the final negative electrode material and improving the particle structure stability of the negative electrode material. In some embodiments, graphite includes at least one of natural graphite, artificial graphite, expanded graphite and graphite oxide. Graphite is a material with high conductivity, small volume expansion, high first efficiency and stable cycle performance. By compounding graphite and silicon-based materials, the conductivity of the negative electrode material can be comprehensively improved and the expansion can be reduced.

[0060] In some embodiments, the modification step includes placing the graphite in an acid solution or an alkaline solution for modification.

[0061] In some embodiments, the acid solution includes at least one of a hydrochloric acid solution, a sulfuric acid solution, and a nitric acid solution.

[0062] In some embodiments, the alkaline solution includes at least one of a sodium hydroxide solution, a potassium hydroxide solution, and a lithium hydroxide solution.

[0063] In some embodiments, the concentration of the acid solution or the alkaline solution is less than 2 mol / L, specifically 1.9 mol / L, 1.85 mol / L, 1.8 mol / L, 1.6 mol / L, 1.5 mol / L, 1.2 mol / L or 1.0 mol / L, etc., which is not limited here.

[0064] In some embodiments, the temperature of the modification treatment is 20° C. to 30° C. The temperature of the modification treatment can be 20° C., 21° C., 22° C., 23° C., 25° C., 28° C., 29° C., or 30° C., etc. Of course, other values ​​within the above range can also be used, which is not limited here.

[0065] In some embodiments, the modification treatment time is 10h to 48h. Specifically, the modification treatment time can be 10h, 13h, 15h, 18h, 20h, 24h, 25h, 28h, 36h, 42h or 48h, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0066] In the present application, by controlling the temperature, time and concentration of the modification solution of the modification treatment, the degree of surface defects of the graphite can be adjusted, which is beneficial to improving the degree of cracking of the gaseous carbon source and silicon source gas during the subsequent gas phase deposition and gas phase carbon coating process, making the composite of graphite particles with silicon-based materials and carbon materials more uniform and sufficient, and thus the degree of defects of the carbon material on the surface of the graphite particles can be adjusted.

[0067] In some embodiments, the modification step further comprises washing the modified product until the product is washed to neutrality.

[0068] In some embodiments, the drying temperature is 45° C. to 80° C. The drying temperature can be 45° C., 48° C., 50° C., 54° C., 58° C., 60° C., 65° C., 68° C., 75° C., or 80° C., and other values ​​within the above range are also possible, and are not limited thereto.

[0069] In some embodiments, the drying time is 3 hours to 48 hours. The drying time can be 3 hours, 6 hours, 8 hours, 12 hours, 15 hours, 18 hours, 20 hours, 24 hours, 25 hours, 28 hours, 36 hours, 42 hours, or 48 hours, etc. Of course, other values ​​within the above range can also be used, which is not limited here.

[0070] In step S200 , modified graphite is subjected to vapor deposition using a reaction gas containing a silicon source gas to obtain a mixture of a silicon-based material and modified graphite.

[0071] In some embodiments, the deposition temperature of vapor deposition is 300° C. to 700° C., specifically 300° C., 350° C., 400° C., 450° C., 500° C., 520° C., 550° C., 600° C., 650° C., or 700° C. It is understood that the above temperature range is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0072] In some embodiments, the deposition time of vapor deposition is 2 hours to 8 hours; specifically, it can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0073] In some embodiments, the flow rate of the silicon source gas is 0.1 L / min to 15 L / min, specifically 0.1 L / min, 0.5 L / min, 1.0 L / min, 2.0 L / min, 3 L / min, 5 L / min, 6 L / min, 8 L / min, 10 L / min, 12 L / min or 15 L / min, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0074] In some embodiments, an auxiliary carrier gas is also added during the vapor deposition process, and the flow rate of the auxiliary carrier gas is 0.5L / min to 25L / min, specifically 0.5L / min, 1.0L / min, 2.0L / min, 3L / min, 5L / min, 6L / min, 8L / min, 10L / min, 12L / min, 15L / min, 18L / min, 20L / min or 25L / min, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0075] In some embodiments, the auxiliary carrier gas includes at least one of nitrogen, argon, helium, neon, carbon dioxide, hydrogen, and carbon monoxide. Under the disturbance of the auxiliary carrier gas, the graphite is in dynamic motion, and silicon particles formed after the decomposition of the silicon source gas come into contact with the dynamic graphite, thereby achieving uniform mixing of the graphite and the silicon-based material. This can reduce the self-agglomeration of nanoparticles, thereby reducing localized excessive stress in the negative electrode material during the charge and discharge process, reducing particle breakage, and improving the cycle performance of the negative electrode material.

[0076] In some embodiments, the raw material of the silicon source gas includes at least one of monosilane, disilane, monochlorosilane, dichlorosilane, trichlorosilane, tetrachlorosilane, and methylsiloxane.

[0077] In some embodiments, the median particle size of the silicon-based material is 1 nm to 10 μm, specifically 1 nm, 10 nm, 50 nm, 100 nm, 1 μm, 1.8 μm, 2 μm, 2.5 μm, 3 μm, 3.6 μm, 5 μm, 6 μm, 6.5 μm, 7 μm, 7.8 μm, 8.5 μm, 9 μm, 9.8 μm or 10 μm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0078] In some embodiments, step S200 includes mixing modified graphite with a raw material containing metal M to obtain a composite; and vapor-depositing the composite using a reaction gas containing a silicon source gas to obtain a mixture of silicon-based material, modified graphite, and doped metal M.

[0079] In some embodiments, the silicon-based material further comprises a metal element M, where M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu, and Mn. It is understood that a small amount of the metal element M can be doped into the carbon material or the silicon-based active material. The metal element M can improve the conductivity of the negative electrode material and enhance the structural strength of the negative electrode material. Preferably, M is Mg and / or Li.

[0080] In some embodiments, the silicon-based material includes silicon oxide, and the silicon oxide includes silicon and oxygen. The atomic ratio of the silicon to oxygen is 0 to 2, and 0 is not included.

[0081] In some embodiments, the silicon-based material includes silicon oxide, the chemical formula of which is SiO x , where 0<x≤2. Specifically, SiO x Specifically, it can be SiO 0.5 、SiO 0.7 、SiO 0.9 、SiO、SiO 1.2 、SiO 1.5 、SiO 1.8 、SiO 1.9 etc., not limited here.

[0082] Silicon oxide can be represented by the general formula SiO x (0<x≤2). It can be a material formed by dispersing silicon particles in SiO2; or it can be a material having a tetrahedral structural unit, with the silicon atom located at the center of the tetrahedral structural unit and oxygen atoms and / or silicon atoms located at the four vertices of the tetrahedral structural unit.

[0083] In some embodiments, based on 100 wt % of the mass of the modified graphite, the amount of the metal M added to the modified graphite is less than 20 wt %.

[0084] In some embodiments, the silicon-based material and the graphite in the mixture are dispersed with each other in the form of particles.

[0085] Step S300 , performing a gas-phase carbon coating treatment on the mixture using a gas-phase carbon source to obtain a negative electrode material.

[0086] In some embodiments, the raw material of the gaseous carbon source includes at least one of methane, ethane, ethylene, acetylene, propyne, propylene, propane, formaldehyde, acetaldehyde, methanol, toluene, benzene, styrene and phenol;

[0087] In some embodiments, the flow rate of the gaseous carbon source is 0.2 L / min to 18 L / min; specifically, it can be 0.2 L / min, 0.5 L / min, 1.0 L / min, 2.0 L / min, 3 L / min, 5 L / min, 6 L / min, 8 L / min, 10 L / min, 15 L / min or 18 L / min, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0088] In some embodiments, the temperature of the vapor phase carbon coating treatment is 550° C. to 1000° C., specifically 550° C., 600° C., 650° C., 700° C., 820° C., 850° C., 900° C., 950° C., or 1000° C. It is understood that the above temperature is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0089] In some embodiments, the time of the gas-phase carbon coating treatment is 1 hour to 6 hours, specifically 1 hour, 2 hours, 3 hours, 4 hours, 5 hours or 6 hours, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0090] In some embodiments, the vapor phase carbon coating process is performed under a protective atmosphere.

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

[0092] In some embodiments, the carbon material is located on the surface of the active material to form a carbon layer. The carbon material can be located on the surface of silicon-based material particles, or on the surface of graphite particles, or the graphite particles and silicon-based material particles can be granulated and coated to form secondary particles, without limitation.

[0093] In some embodiments, the thickness of the carbon layer is 1 nm to 1000 nm, and specifically can be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 400 nm, 500 nm, 700 nm, 800 nm, 900 nm, 1000 nm, etc., without limitation herein. Controlling the carbon layer thickness within the above range can increase the conductivity of the negative electrode material, which is conducive to obtaining a negative electrode material with a high specific capacity; the carbon layer can also effectively alleviate the volume expansion of the active material, improving the long-cycle performance of the negative electrode material. Preferably, the carbon layer has a thickness of 50 nm to 800 nm; more preferably, the carbon layer has a thickness of 100 nm to 500 nm.

[0094] On the third aspect, the present application provides a negative electrode plate, which includes the above-mentioned negative electrode material, and the resistivity of the negative electrode plate is ≤5Ω·cm. The resistivity can specifically be 5Ω·cm, 4.5Ω·cm, 4Ω·cm, 3Ω·cm, 2.8Ω·cm, 2.5Ω·cm, 2.2Ω·cm, 2.0Ω·cm, 1.9Ω·cm, 1.6Ω·cm, 1.2Ω·cm or 1.0Ω·cm, etc., which are not limited here. It can be understood that the resistivity of the negative electrode plate is within the above range. This is because the electrolyte wetting ability of the negative electrode material is improved, resulting in the electrolyte being able to fully infiltrate the negative electrode material on the negative electrode plate, thereby improving the electron transmission efficiency, and the contact between the silicon-based material, graphite and carbon material is good. The resistivity of the plate is reduced, so that the plate has excellent rate performance.

[0095] In a fourth aspect, the present application provides a battery comprising the above-mentioned negative electrode material. The electrochemical device may specifically be a lithium-ion battery, a sodium-ion battery, etc., which is not limited here.

[0096] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

[0097] Example

[0098] Example 1

[0099] (1) Graphite with D50 = 8 μm was placed in a 1 mol / L HCl solution and stirred for 4 h, then allowed to stand at 30 °C for 24 h. After removing the solution, it was rinsed with clean water until neutral, and finally baked in an oven at 80 °C for 12 h to obtain modified graphite.

[0100] (2) The modified graphite was placed in a fluidized bed reactor, monosilane gas was introduced, the monosilane gas flow rate was 5 L / min, the carrier gas (argon) rate was set to 7.5 L / min, and the reaction was carried out at 400°C for 6 hours to obtain a mixture of silicon particles and graphite particles.

[0101] (3) Adjust the temperature of the fluidized bed reactor to 800°C, switch the inlet gas to methane, the gas flow rate is 8 L / min, and perform gas phase carbon coating treatment for 4 hours. Cool to room temperature and discharge to obtain the negative electrode material.

[0102] The negative electrode material prepared in the present application includes a silicon-based material and graphite, and a carbon material located on at least a portion of the surface of the silicon-based material and / or graphite. The active substance includes silicon element and graphite, and the carbon material includes amorphous carbon.

[0103] FIG2 is a diagram showing the distribution of silicon-based materials and graphite within the scanning range of the negative electrode material prepared in Example 1. FIG3 is a Raman surface scanning spectrum of the negative electrode material prepared in Example 1, 500-520 cm -1 The spectrum with peaks at the displacement corresponds to the spectrum of particles mainly composed of silicon-based materials, 500-520cm -1 The spectrum without a peak at φ corresponds to the spectrum of particles mainly composed of graphite. Figure 4 is a volume-based cumulative particle size distribution width diagram of the negative electrode material prepared in Example 1. Other parameters of the negative electrode material are detailed in Table 1-2.

[0104] Example 2

[0105] (1) Graphite with D50 = 6 μm was placed in a 1 mol / L HCl solution and stirred for 4 h, then allowed to stand at 30 °C for 24 h. After removing the solution, the graphite was rinsed with clean water until neutral, and finally baked in an oven at 80 °C for 12 h to obtain modified graphite.

[0106] (2) The modified graphite was placed in a fluidized bed reactor, monosilane gas was introduced, the monosilane gas flow rate was 5 L / min, the carrier gas (argon) rate was set to 7.5 L / min, and the reaction was carried out at 500°C for 6 hours to obtain a mixed powder of silicon particles and graphite particles.

[0107] (3) Adjust the temperature of the fluidized bed reactor to 600°C, switch the inlet gas to methane, and use a gas flow rate of 8 L / min. Perform gas-phase carbon coating for 2 hours, cool to room temperature, and discharge to obtain the negative electrode material.

[0108] The negative electrode material prepared in the present application includes an active substance and a carbon material located on at least a portion of the surface of the active substance, the active substance includes silicon and graphite, and the carbon material includes amorphous carbon.

[0109] For other parameters of the negative electrode material, please see Table 1-2.

[0110] Example 3

[0111] (1) Artificial graphite with a D50 of 12 μm was placed in a 1 mol / L HCl solution and stirred for 4 h. The solution was then allowed to stand at 30°C for 24 h. The solution was removed and the surface was rinsed with clean water until neutral. Finally, the surface was baked in an oven at 80°C for 12 h to obtain modified graphite.

[0112] (2) The modified graphite was placed in a fluidized bed reactor, monosilane gas was introduced, the monosilane gas flow rate was 5 L / min, the carrier gas (argon) rate was set to 7.5 L / min, and the reaction was carried out at 400°C for 6 hours to obtain a mixed powder of silicon particles and graphite particles.

[0113] (3) Adjust the temperature of the fluidized bed reactor to 800°C, switch the inlet gas to methane, the gas flow rate is 8 L / min, and perform gas phase carbon coating treatment for 4 hours. Cool to room temperature and discharge to obtain the negative electrode material.

[0114] The negative electrode material prepared in this embodiment includes an active material and a carbon material located on at least a portion of the surface of the active material. The active material includes a silicon-based material and graphite. The silicon-based material contains silicon.

[0115] For other parameters of the negative electrode material, please see Table 1-2.

[0116] Example 4

[0117] (1) Natural flake graphite with a D50 of 10 μm was placed in a 1 mol / L HCl solution and stirred for 4 h. The solution was then allowed to stand at 30°C for 24 h. The solution was removed and the mixture was rinsed with clean water until neutral. Finally, the modified graphite was baked in an oven at 80°C for 12 h.

[0118] (2) The modified graphite was placed in a fluidized bed reactor, monosilane gas was introduced, the monosilane gas flow rate was 6 L / min, the carrier gas (argon) rate was set to 7.5 L / min, and the reaction was carried out at 400°C for 8 hours to obtain a mixed powder of silicon particles and graphite particles.

[0119] (3) Adjust the temperature of the fluidized bed reactor to 700°C, switch the inlet gas to methane, the gas flow rate is 8 L / min, and perform gas phase carbon coating treatment for 6 hours. Cool to room temperature and discharge to obtain the negative electrode material.

[0120] The negative electrode material prepared in this embodiment includes an active material and a carbon material located on at least a portion of the surface of the active material. The active material includes a silicon-based material and graphite. The silicon-based material contains silicon.

[0121] For other parameters of the negative electrode material, please see Table 1-2.

[0122] Example 5

[0123] The difference from Example 1 is that:

[0124] (1) Graphite with D50 = 8 μm was placed in a 1.8 mol / L NaOH solution and stirred for 4 h, then allowed to stand at 30 °C for 24 h. After removing the solution, the graphite was rinsed with clean water until neutral, and finally baked in an oven at 70 °C for 12 h to obtain modified graphite.

[0125] Example 6

[0126] The difference from Example 1 is that:

[0127] (1) Graphite with D50 = 8 μm was placed in a 1 mol / L HCl solution and stirred for 4 h, then allowed to stand at 25 °C for 10 h. After removing the solution, it was rinsed with clean water until neutral, and finally baked in an oven at 80 °C for 12 h to obtain modified graphite.

[0128] Example 7

[0129] The difference from Example 1 is that:

[0130] (2) The modified graphite was placed in a fluidized bed reactor, monochlorosilane gas was introduced, the monochlorosilane gas flow rate was 15 L / min, the carrier gas (argon) rate was set to 25 L / min, and the reaction was carried out at 300°C for 8 hours to obtain a mixture of silicon-based material and graphite particles.

[0131] Example 8

[0132] The difference from Example 1 is that:

[0133] (2) The modified graphite is placed in a fluidized bed reactor, dimethylsiloxane gas is introduced, the methylsiloxane gas flow rate is 5 L / min, the carrier gas (argon) rate is set to 7.5 L / min, and the reaction is carried out at 400°C for 6 hours to obtain a mixture of silicon-based material and graphite particles, wherein the silicon-based material includes at least one of silicon element and silicon oxide.

[0134] Example 9

[0135] The difference from Example 1 is that:

[0136] (3) Adjust the temperature of the fluidized bed reactor to 800°C, switch the inlet gas to acetylene, the gas flow rate is 18 L / min, and perform gas phase carbon coating treatment for 2 hours. Cool to room temperature and discharge to obtain the negative electrode material.

[0137] Example 10

[0138] The difference from Example 1 is that:

[0139] (3) Adjust the temperature of the fluidized bed reactor to 1000°C, switch the gas introduced to methane, with a gas flow rate of 0.2 L / min, perform gas-phase carbon coating treatment for 6 hours, cool to room temperature and discharge to obtain the negative electrode material.

[0140] Example 11

[0141] The difference from Example 1 is that:

[0142] (1) Graphite with D50 = 8 μm was placed in a 1 mol / L HCl solution and stirred for 4 h, then allowed to stand at 30°C for 24 h. After removing the solution, it was rinsed with clean water until neutral, and finally baked in an oven at 80°C for 12 h to obtain modified graphite, and lithium metal powder (D50 = 1 μm) with a mass percentage of 5 wt% was added to obtain a mixture of silicon-based material and graphite particles, wherein the silicon-based material includes lithium silicate.

[0143] Example 12

[0144] The difference from Example 1 is that:

[0145] (1) Graphite with D50 = 8 μm was placed in a 1.5 mol / L HCl solution and stirred for 8 h, then allowed to stand at 30 °C for 24 h. After removing the solution, it was rinsed with clean water until neutral, and finally baked in an oven at 80 °C for 12 h to obtain modified graphite.

[0146] Comparative Example 1

[0147] The difference from Example 1 is that:

[0148] (1) Graphite with a D50 of 10 μm was placed in a 1 mol / L HCl solution and stirred for 4 h. The solution was then allowed to stand at 30°C for 24 h. The solution was removed and the graphite was rinsed with clean water until neutral. Finally, the modified graphite was baked in an oven at 80°C for 12 h.

[0149] (2) The modified graphite was placed in a fluidized bed reactor, monosilane gas was introduced at a gas flow rate of 5 L / min, the carrier gas rate was set to 7.5 L / min, and the reaction was carried out at 300°C for 6 hours to obtain a mixed powder of silicon particles and graphite particles.

[0150] (3) Adjust the temperature of the fluidized bed reactor to 500°C, switch the gas introduced to methane, with a gas flow rate of 8 L / min, perform gas-phase carbon coating treatment for 2 h, cool to room temperature and discharge to obtain the negative electrode material.

[0151] Comparative Example 2

[0152] The difference from Example 1 is that:

[0153] Skip step (1) and go directly to step (2).

[0154] The parameters of the negative electrode materials are detailed in Table 1-2.

[0155] Comparative Example 3

[0156] The difference from Example 12 is that:

[0157] (3) Adjust the temperature of the fluidized bed reactor to 300°C, switch the inlet gas to methane, the gas flow rate is 8 L / min, and perform gas phase carbon coating treatment for 4 hours. Cool to room temperature and discharge to obtain the negative electrode material.

[0158] Test Method

[0159] (1) Particle size of negative electrode materials and silicon-based materials:

[0160] The particle size test method for negative electrode material particles refers to GB / T 19077-2016. It can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd. in the UK. The particle size distribution range of the negative electrode material is tested using the Malvern laser particle size analyzer (Mastersizer 3000). The volume-based cumulative particle size distribution for particle size distribution is measured using laser diffraction. D05 represents the particle size corresponding to the 5% cumulative particle size distribution percentage of the powder, D50 represents the particle size corresponding to the 50% cumulative particle size distribution percentage (i.e., median particle size), and D80 represents the particle size corresponding to the 80% cumulative particle size distribution percentage.

[0161] Average particle size of silicon-based materials: Observe silicon-based material particles through field emission scanning electron microscopy or transmission electron microscopy, directly measure the particle sizes of 5-10 silicon-based material particles using a scale, and take the average value of the particle sizes as the average particle size of the silicon-based material.

[0162] (2) Test method for the tap density of negative electrode materials:

[0163] Reference is made to GB / T 5162-2006 / ISO 3953:1993 "Metal powders - Determination of tap density." Tests were performed using a Quantachrome tap density analyzer (Quantachrome DAT-4-220) from Anton Paar (Shanghai) Trading Co., Ltd. The tap density, T, is the value after 1000 vibrations, with a charge of 60 g, and is expressed in g / cm². 3 .

[0164] (3) Powder conductivity test of negative electrode materials

[0165] The powder conductivity of the material was tested using the equipment and methods specified in BTRTC / ZY / 02-093, "Powder Conductivity Test Operation Instructions," from BTR Corporation. The testing equipment was sourced from Mitsubishi Chemical Corporation of Japan. Test parameters included an initial resistance magnitude of -3 and a voltage limit of 10V. Ensure that the sample thickness was 3-5mm at a pressure of 20kN. Pressure settings included 4kN, 8kN, 12kN, 16kN, and 20kN. The electrode radius was 0.7mm, and the sample radius was 10mm.

[0166] (4) Raman test of negative electrode materials:

[0167] The Raman spectrum of the powder was measured using a Renishaw In Via confocal Raman microscope from Japan, with 200 Raman spectra collected. The test parameters were: laser wavelength 532nm, test range 120μm×120μm, step size 4μm. The test results were processed using the instrument's own software. When processing the data, the baseline of all Raman spectra at each point was first removed, and the peak search parameters were adjusted to obtain the peak intensity of each peak. 500cm -1 ~520cm -1 The characteristic peaks within the range are the first type of spectral lines, 500cm -1 ~520cm -1 The spectrum without characteristic peaks within the range is the second type of spectrum. In particular, the baseline after processing is around 0 as the standard, and the other processing steps are based on the initial parameters of the software. -1 ~520cm -1 When the peak intensity of the highest peak in the range is less than or equal to 100, it is considered that there is no target characteristic peak.

[0168] (5) Liquid absorption capacity test of negative electrode materials

[0169] A negative electrode sheet was prepared using a ratio of 95.3:1.3:1.5:1.9 for negative electrode material: sodium carboxymethyl cellulose (MAC350HC): conductive carbon black: styrene-butadiene rubber (451B). The negative electrode sheet was placed in a glove box, and 5 mL of electrolyte was dripped onto a 5 cm x 5 cm negative electrode sheet using a pipette. The time it took for the electrolyte to be completely absorbed was recorded.

[0170] (6) Contact angle test method of negative electrode material:

[0171] The contact angle of the negative electrode material to water was measured using the sessile drop method. The sample powder was placed in a powder groove and pressed tightly. The test was then performed using a contact angle meter (Shanghai Xuanyi Chuangxi Industrial Equipment Co., Ltd., model XG-CAMB3).

[0172] (7) Resistivity test of negative electrode:

[0173] A negative electrode sheet was fabricated using a ratio of 95.3:1.3:1.5:1.9 for negative electrode material: sodium carboxymethyl cellulose (MAC350HC): conductive carbon black: styrene-butadiene rubber (451B). Nine random points on a 50 cm x 50 cm square block were tested using a sheet resistance meter, and the average value was taken as the resistivity of the material.

[0174] (8) Withholding capacity and initial effectiveness test

[0175] The negative electrode materials prepared in Examples 1 to 12 and Comparative Examples 1 to 3 were assembled into button batteries: negative electrode plates were made according to the ratio of negative electrode material: sodium carboxymethyl cellulose (MAC350HC): conductive carbon black: styrene-butadiene rubber (451B) = 95.3:1.3:1.5:1.9.

[0176] The battery assembly was carried out in an argon glove box, with a metal lithium sheet as the negative electrode, the electrolyte being 1 mol / L lithium hexafluorophosphate LiPF6 + ethylene carbonate (EC) + methyl ethyl carbonate (EMC), and the separator being a polyethylene / propylene composite microporous membrane. The electrochemical performance was tested on a battery testing instrument with a charge and discharge voltage of 0.01 to 1.5 V.

[0177] The battery cycle life is the number of charge and discharge cycles when the capacity retention rate decays to 80%.

[0178] First coulombic efficiency = first cycle discharge capacity / first cycle charge capacity.

[0179] Table 1 is the Raman data test results of the negative electrode material, and Table 2 is the test results of the negative electrode material and battery performance.

[0180] Table 1 Raman data test results of negative electrode materials

[0181] Table 2 Negative electrode materials and battery performance test results

[0182] According to the data in Table 1, the negative electrode materials prepared in Examples 1 to 12 of the present application control the K value within the range of 0.01 to 10, and can find a balance between the degree of silicon exposure and the degree of defects in the surface carbon material. On the one hand, it ensures that fewer silicon particles in the negative electrode material are exposed, and on the other hand, the degree of defects in the surface carbon material is utilized to improve the wettability of the negative electrode material to the electrolyte. The prepared negative electrode plate has a lower resistivity, further increasing the stability of the plate.

[0183] For the negative electrode material of Comparative Example 1, the gas phase carbon coating temperature is too low during the preparation process, resulting in the K value of the negative electrode material being out of the range of 0.01 to 10, and the electrolyte infiltration ability of the negative electrode material is reduced. Compared with Example 1, the resistivity of the electrode sheet prepared from the negative electrode material is also greatly increased.

[0184] In the negative electrode material of Comparative Example 2, the graphite was not modified during the preparation process, which may lead to poor subsequent coating and modification effects. The surface morphology of the silicon particles and the graphite particles is too different, which greatly increases the resistivity of the electrode.

[0185] For the negative electrode material of Comparative Example 3, the temperature of the gas-phase carbon coating treatment during the preparation process is too low, the degree of defects of the carbon material on the surface of the negative electrode material is high, the K value of the negative electrode material is significantly lower than the K value of the embodiment, its electrolyte wettability is good, and the thickness of the electrolyte membrane is too large, resulting in a significant increase in the resistivity of the electrode.

[0186] In addition, by comparing the test results of Example 1 and Example 11, it can be found that doping metal into the silicon-based material can improve the conductivity and tap density of the negative electrode material.

[0187] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A negative electrode material, characterized in that: The negative electrode material includes a silicon-based material and graphite, and a carbon material located on at least a portion of the surface of the silicon-based material and / or graphite; The negative electrode material was tested by Raman scanning. In the Raman scanning spectrum of the negative electrode material, the -1 ~520cm -1 There are characteristic peaks of the first type of spectral lines and 500cm -1 ~520cm -1 The second type of spectral lines does not have characteristic peaks within the range; In the first type of spectral lines, at 500cm -1 ~520cm -1 There is a characteristic peak in the range with intensity I1 at 1345cm -1 ~1355cm -1 There is a characteristic peak in the range with an intensity of I2 at 1570cm -1 ~1610cm -1 There is a characteristic peak in the range with an intensity of I3; In the second type of spectral lines, at 1345cm -1 ~1355cm -1 There is a characteristic peak in the range with intensity I2' at 1570cm -1 ~1610cm -1 There is a characteristic peak in the range with intensity I3'; in, 0.01≤K≤10。 2. The negative electrode material according to claim 1, characterized in that The particle size distribution width of the negative electrode material is P, and P=(D 05 +D 99 ) / (2*D 50 ), and 1.0≤P≤2.

2.

3. The negative electrode material according to claim 1, characterized in that The powder conductivity of the negative electrode material under a pressure of 20 kN is greater than 30 S / cm.

4. The negative electrode material according to claim 1, characterized in that The silicon-based material includes at least one of amorphous silicon, crystalline silicon, silicon oxide and silicate.

5. The negative electrode material according to claim 1, characterized in that The graphite includes at least one of natural graphite, artificial graphite, expanded graphite and oxidized graphite.

6. The negative electrode material according to claim 1, characterized in that In the negative electrode material, I1 / (I2+I3) is in the range of 0.1 to 2.3, and / or I2 / (I2+I3) is in the range of 0.1 to 0.8, and / or I2' / (I2'+I3') is in the range of 0.1 to 0.

61.

7. The negative electrode material according to claim 1, characterized in that The mass content of silicon in the negative electrode material is 1% to 80%, and / or the mass content of carbon is 20% to 99%.

8. The negative electrode material according to claim 1, characterized in that The tap density of the negative electrode material is ≥0.7 g / cm 3 .

9. The negative electrode material according to claim 1, characterized in that The carbon material includes at least one of amorphous carbon and graphitized carbon.

10. The negative electrode material according to claim 1, characterized in that The 0.4≤K≤10.

11. The negative electrode material according to claim 4, characterized in that The silicon-based material includes silicon oxide, and the silicon oxide includes silicon element and oxygen element. The atomic ratio of the silicon element to the oxygen element is 0 to 2, and 0 is not included.

12. The negative electrode material according to claim 4, characterized in that The silicon-based material includes silicon oxide, and the chemical formula of the silicon oxide is SiO x , where 0<x≤2.

13. The negative electrode material according to claim 1, characterized in that The silicon-based material also includes a metal M element, and the M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu, and Mn.

14. A negative electrode plate, characterized in that: The negative electrode plate comprises the negative electrode material according to any one of claims 1 to 13, and the resistivity of the negative electrode plate is ≤5Ω·cm.

15. A lithium ion battery, characterized in that: The lithium-ion battery comprises the negative electrode material according to any one of claims 1 to 13.

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