NEGATIVE ELECTRODE MATERIAL AND ASSOCIATED PREPARATION METHOD, AND BATTERY

Abstract

A negative electrode material and a preparation method therefor, and a battery. The negative electrode material comprises an active material. The surface density of the negative electrode material is β, which is greater than or equal to 80%, wherein the β is measured by using the following measuring method: soaking the negative electrode material having a mass of m1 g in a hydrofluoric acid dissolving solution having a mass fraction of 20% for 1 hour, cleaning and drying same to obtain m2 g of a material, and calculating the surface density β of the negative electrode material according to the formula β=m2 / m1×100%. Since the surface of the negative electrode material has a high density, the dissolution amount of the negative electrode material during a cycling process can be reduced, and therefore a reaction of dissolved silicon particles with an electrolyte solution is reduced and the value of gas production by the negative electrode material is effectively reduced; and the negative electrode material has a small total pore volume and a more compact structure, thereby reducing the permeation amount of the electrolyte solution in the negative electrode material during the cycling process, and improving the cycling performance of the negative electrode material.

Description

Negative electrode material and preparation method thereof, and battery

[0001] This application claims the priority of three patent applications: Chinese patent application No. 202311289564.7, filed with the State Intellectual Property Office on September 28, 2023, with application number 202311289564.7 and application name “Negative electrode material and preparation method thereof, lithium-ion battery”; Chinese patent application No. 202311832248.X, filed with the State Intellectual Property Office on December 27, 2023, with application number 202311832248.X and application name “Negative electrode material and battery”; and Chinese patent application No. 202410205115.8, filed with the State Intellectual Property Office on February 23, 2024, with application number 202410205115.8 and application name “Negative electrode material and battery”. The entire contents of these three patent applications are incorporated by reference into this application. Technical Field

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

[0003] Lithium-ion batteries have the advantages of high energy density, long service life and no environmental pollution, and have been widely used in the 3C field. With the development of the market, lithium-ion batteries are not only widely used in mobile devices such as smartphones and laptops, but also in large equipment such as electric vehicles and power tools. In order to improve the energy density of batteries, the research and development of silicon-based negative electrode materials are becoming increasingly mature. Silicon-based negative electrode materials include silicon-based active substances and a coating layer on their surface. However, the coating effect of the coating layer of existing silicon-based negative electrode materials is poor. During the preparation of silicon-based negative electrode materials into lithium-ion batteries, the dissolved silicon particles will come into contact with the electrolyte, resulting in the problem of gas production.

[0004] Therefore, how to reduce the reaction between silicon particles and electrolyte and lower the gas production value is an urgent problem that needs to be solved.

[0005] Application Contents

[0006] The present application provides a negative electrode material, a preparation method thereof, and a battery. The surface of the negative electrode material has a high density, which can reduce the reaction between silicon particles and the electrolyte, reduce the gas production value, and improve the cycle performance of the material.

[0007] In a first aspect, the present application provides a negative electrode material, the negative electrode material comprising an active substance, the surface density of the negative electrode material being β, wherein β is ≥80%;

[0008] Wherein, the β is measured by the following test method:

[0009] The negative electrode material with a mass of m1 g was immersed in a hydrofluoric acid solution with a mass fraction of 20% for 1 hour, and then washed and dried to obtain m2 g of material. The surface density of the negative electrode material was calculated to be β = m2 / m1×100%.

[0010] In a second aspect, the present application provides a battery comprising the negative electrode material described above.

[0011] The technical solution of this application has at least the following beneficial effects:

[0012] The negative electrode material provided in the present application includes an active substance, and the surface density β of the negative electrode material is ≥80%. Within this range, the dissolution amount of the negative electrode material during the cycle can be reduced, thereby reducing the reaction between the dissolved active substance and the electrolyte, effectively reducing the gas production value of the negative electrode material; and it can also reduce the side reactions occurring when the electrolyte contacts the active substance, thereby improving the cycle performance of the lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG1 is a scanning electron microscope (SEM) image of the negative electrode material prepared in Example 1 of the present application.

[0014] FIG2 is an XRD diagram of the negative electrode material prepared in Example 1 of the present application.

[0015] FIG3 is the first charge and discharge curve of the negative electrode material prepared in Example 1 of the present application.

[0016] FIG4 is a cycle performance curve of the negative electrode material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0017] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limiting the present application.

[0018] Lithium-ion batteries have the advantages of high energy density, long service life and no environmental pollution, and have been widely used in the 3C field. With the development of the market, lithium-ion batteries are not only widely used in mobile devices such as smartphones and laptops, but also in large equipment such as electric vehicles and power tools. In order to improve the energy density of batteries, the research and development of silicon-based negative electrode materials are becoming increasingly mature. Silicon-based negative electrode materials include silicon-based active substances and a coating layer on their surface. However, the coating effect of the coating layer of existing silicon-based negative electrode materials is poor. During the preparation of silicon-based negative electrode materials into lithium-ion batteries, the dissolved silicon particles will come into contact with the electrolyte, resulting in the problem of gas production.

[0019] In a first aspect, the present application provides a negative electrode material, the negative electrode material comprising an active material, wherein the surface density of the negative electrode material is β, and the β is ≥80%;

[0020] Wherein, the β is measured by the following test method:

[0021] The negative electrode material with a mass of m1 g was immersed in a hydrofluoric acid solution with a mass fraction of 20% for 1 hour, and then washed and dried to obtain m2 g of material. The surface density of the negative electrode material was calculated to be β = m2 / m1×100%.

[0022] In the above scheme, the negative electrode material includes an active substance, and the surface density β of the negative electrode material is ≥80%. Within this range, the dissolution amount of the negative electrode material during the cycle can be reduced, thereby reducing the reaction between the active substance dissolved in the negative electrode material and the electrolyte, effectively reducing the gas production value of the negative electrode material; and it can also reduce the side reactions occurring when the electrolyte contacts the active substance in the negative electrode material, thereby improving the cycle performance of the ion battery prepared with the negative electrode material.

[0023] In some embodiments, the surface density of the negative electrode material is ≥80%, specifically 80%, 82%, 85%, 86%, 89%, 90%, 92%, 95% or 98%, etc., and of course other values ​​within the above range can also be used. It can be understood that, ideally, the surface density of the negative electrode material is 100%. At this time, the surface density of the negative electrode material is high. When the negative electrode material is placed in a dissolving solution, the active substance in the negative electrode material will not dissolve, and then no dissolved active substance will contact the dissolving solution and react. However, the surface density of the negative electrode material prepared by the conventional method is insufficient. The negative electrode material will have a certain amount of dissolution in the dissolving solution, and the dissolving solution contains dissolved active substances. At this time, the surface density of the negative electrode material can be defined by the amount of dissolved active substances, that is, the surface density β = m2 / m1×100%.

[0024] It should be noted that the dissolving solution used in this application is a hydrofluoric acid solution with a mass fraction of 20%, and the dissolving solution is in excess.

[0025] The above tests show that the surface density β of the negative electrode material of the present application is ≥80%. Within this range, the high surface density of the negative electrode material can effectively inhibit direct contact between the active material in the negative electrode material and the water in the slurry during the slurry preparation process, reducing the occurrence of side reactions and lowering the gas production value of the negative electrode material. In addition, the negative electrode material can also reduce the amount of active material dissolved during the charge and discharge cycle, thereby reducing the side reaction between the dissolved active material and the electrolyte, which can also effectively reduce the gas production value of the negative electrode material.

[0026] In some embodiments, the active material includes a carbon matrix and silicon particles, and at least a portion of the silicon particles are located inside the carbon matrix particles.

[0027] In some embodiments, the carbon matrix has pores, and the silicon particles are located within the pores of the carbon matrix. As will be appreciated, the carbon matrix can serve as a supporting framework and has good electrical conductivity, thereby improving the conductivity of the negative electrode material. Furthermore, the silicon particles can be located within the carbon matrix, reducing contact between the silicon particles and the electrolyte, ensuring the stability of the SEI film, and improving the initial coulombic efficiency. Furthermore, the porous carbon matrix can effectively mitigate the volume expansion of the silicon particles during cycling, thereby improving cycling performance.

[0028] In some embodiments, the carbon matrix includes at least one of artificial graphite, natural graphite, amorphous carbon, activated carbon, mesophase carbon microbeads, carbon nanotubes, carbon nanofibers, porous carbon, and graphene. It is understood that the carbon matrix selected from the above materials can all serve as a supporting skeleton and also have good electrical conductivity to ensure the electrical conductivity of the negative electrode material. Furthermore, the silicon particles deposited within the carbon matrix have excellent lithium storage properties.

[0029] In some embodiments, the silicon particles include at least one of crystalline silicon, silicon oxide, amorphous silicon, silicon alloy, and composite particles of crystalline silicon and amorphous silicon. The types of carbon matrix and silicon particles can be selected according to actual needs and are not limited here.

[0030] In some embodiments, the silicon oxide includes silicon and oxygen, and the atomic ratio of silicon to oxygen is 0 to 2, excluding 0. The atomic ratio of silicon to oxygen can be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2, etc., without limitation. Preferably, the atomic ratio of silicon to oxygen is 0 to 1, excluding 0.

[0031] In some embodiments, the chemical formula of silicon oxide is SiO x , wherein 0<x<2, x can be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 and 1.9, etc., which are not limited here. Preferably, 0 <x<1。

[0032] In some embodiments, the average particle size of the silicon particles is 0.1nm to 50nm. Optionally, the average particle size of the silicon particles can specifically be 0.1nm, 10nm, 20nm, 30nm, 40nm and 50nm, etc., or other values ​​within the range, which can be selected according to actual needs and are not limited here. The mechanical stress during silicon particle expansion decreases as the particle size decreases, and the electron and ion transmission paths can be shortened after the size is reduced. At the same time, the size of the silicon particles decreases, and the gaps between adjacent silicon particles increase, which can reserve space for expansion. It can be understood that the average particle size of the silicon particles is within the above range, which can ensure the battery capacity of the lithium-ion battery and reduce irreversible capacity loss. Preferably, the average particle size of the silicon particles is 0.1nm to 20nm, and more preferably, the average particle size of the silicon particles is 0.1nm to 5nm.

[0033] In some embodiments, the morphology of the silicon particles includes at least one of a dot-like shape, a spherical shape, an ellipsoidal shape, and a flake-like shape. The morphology of the silicon particles can be selected according to actual needs and is not limited here.

[0034] In some embodiments, the purity of the silicon particles is greater than 99%. It can be understood that high-purity silicon particles are beneficial for Li-Si alloying with lithium, thereby improving the cycle performance of lithium-ion batteries.

[0035] In some embodiments, the total pore volume of the negative electrode material is 0.001 cm 3 / g~0.1cm 3 / g, specifically 0.001cm 3 / g, 0.005cm 3 / g, 0.006cm 3 / g, 0.007cm 3 / g, 0.01cm 3 / g, 0.02cm 3 / g, 0.03cm 3 / g, 0.04cm 3 / g, 0.05cm 3 / g, 0.06cm 3 / g, 0.08cm 3 / g or 0.1cm 3 / g, etc., of course, it can also be other values ​​within the above range, which is not limited here. After filling with silicon particles, the remaining pores can reserve space for the volume expansion of silicon particles, alleviate the expansion effect of the negative electrode material, improve the cycle stability of the negative electrode material, and can also absorb or accommodate a small amount of gas produced by the side reaction of some silicon particles and electrolyte, thereby improving the gas production phenomenon of the negative electrode material. Preferably, the total pore volume of the negative electrode material is 0.001cm 3 / g~0.02cm 3 / g, the total pore volume of the negative electrode material is controlled within this range, which can effectively reduce the amount of electrolyte that directly penetrates into the particles of the negative electrode material through the pore structure.

[0036] In some embodiments, the volume proportion of pores with a pore diameter of less than 10 nm in the negative electrode material in the total pore volume is ≥80%; specifically, it can be 80%, 82%, 85%, 87%, 90%, 93%, 95% or 99%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0037] In the above scheme, while controlling the surface density of the negative electrode material to ≥80%, the total pore volume of the negative electrode material is controlled to be 0.001cm 3 / g~0.1cm 3 / g, the volume proportion of pores with a pore diameter of less than 10nm in the total pore volume is ≥80%. During the charge and discharge process, the pores can reserve space for the volume expansion generated by the lithium insertion and extraction process of silicon particles. The present application effectively alleviates the volume expansion of silicon particles during the cycle by controlling the synergistic effect of the surface density of the negative electrode material and the pores in the negative electrode material, reduces the particle breakage of the negative electrode material, and improves the cycle performance of the negative electrode material. At the same time, the volume proportion of pores with a pore diameter of less than 10nm in the total pore volume is ≥80%, that is, the proportion of pores with a pore diameter of more than 10nm is small, and there are very few large pores in the negative electrode material particles, which can reduce the generation of cracks in the negative electrode material during the cycle, reduce the risk of direct contact between silicon particles and the electrolyte, and reduce side reactions. In some embodiments, while the surface density β of the negative electrode material is ≥80%, the negative electrode material has pores, and the pores include micropores and mesopores, wherein the ratio of the pore volume of the micropores to the pore volume of the mesopores is (1 to 45): (55 to 99).

[0038] Specifically, the pore volume ratio of micropores to mesopores can be 1:99, 5:95, 10:90, 20:80, 30:65, 40:50 or 45:55, etc., which is not limited here. In the present application, the pore volume of mesopores accounts for a larger proportion, and the pore volume of micropores accounts for a smaller proportion. Since the size of molecules generated by the electrolyte is generally smaller than or equal to the pore size of the micropores, the micropores have a strong capillary adsorption capacity, and the adsorption capacity of the negative electrode material is largely proportional to the pore volume of the micropores, that is, as the volume of the micropores increases, the adsorption capacity of the negative electrode material increases, and then the side reaction of the negative electrode material and the electrolyte will increase.

[0039] In the present application, the ratio of the pore volume of micropores to the pore volume of mesopores is controlled to be (1-45): (55-99), which effectively reduces the pore volume ratio of micropores in the negative electrode material, that is, the active sites for side reactions between the negative electrode material and the electrolyte are reduced, thereby reducing the thickening of the solid electrolyte membrane on the surface of the negative electrode material caused by the continuous intrusion of the electrolyte, which is beneficial to improving the cycle performance of the negative electrode material; in addition, the increased volume ratio of mesopores can reserve sufficient buffer space for the volume expansion of silicon particles, which is beneficial to improving the particle structure stability of the negative electrode material. The present application controls the surface density of the negative electrode material and the volume ratio of micropores and mesopores in the negative electrode material, and the two work synergistically to reduce the dissolution of silicon particles, reduce the side reactions between the negative electrode material and the electrolyte, effectively alleviate the volume expansion of silicon particles during the cycle, reduce the particle breakage of the negative electrode material, and comprehensively improve the cycle performance of the negative electrode material.

[0040] In some embodiments, the pore volume of mesopores in the negative electrode material accounts for ≥80%; specifically, it can be 80%, 82%, 85%, 87%, 90%, 93%, 95% or 99%, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0041] In some embodiments, the pore volume of the micropores in the negative electrode material is ≤10%, and can be specifically 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1% or 0%, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0042] In some embodiments, the pore volume of macropores in the negative electrode material is ≤20%, and can be specifically 20%, 18%, 15%, 12%, 10%, 8%, 7%, 5%, 4%, 3% or 2%, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0043] It can be understood that controlling the volume ratio of micropores, mesopores and macropores in the negative electrode material within the above range can improve the uniformity of the distribution of silicon particles inside the negative electrode material. Since most of the pores are mesopores, the volume expansion of silicon particles can be effectively alleviated, and the local expansion stress caused by the uneven volume change of silicon particles during the cycle of the negative electrode material can be reduced, resulting in excessive breakage and pulverization of the negative electrode material, thereby improving the cycle stability of the negative electrode material.

[0044] In some embodiments, the average pore size of the negative electrode material is 0.4 nm to 50 nm; specifically, it can be 0.4 nm, 1 nm, 1.5 nm, 2 nm, 3 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm or 50 nm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0045] In some embodiments, the negative electrode material after the silicon particles are removed has pores, and the pores include micropores.

[0046] In some embodiments, in the negative electrode material after removing the silicon particles, the volume proportion of pores with a pore diameter of less than 2 nm in the total pore volume is ≥70%; specifically, it can be 70%, 75%, 80%, 85%, 90%, 95% or 99%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0047] In some embodiments, the negative electrode material after the silicon particles are removed has pores, including micropores and mesopores. In the negative electrode material after the silicon particles are removed, pores with a pore diameter of 5 nm or less account for ≥85% of the total pore volume; specifically, this percentage may be 85%, 87%, 89%, 90%, 92%, 95%, 97%, or 99%, etc., and other values ​​within the aforementioned range are also possible and are not limited herein.

[0048] In some embodiments, in the negative electrode material after removing the silicon particles, the volume proportion of pores with a pore diameter of less than 10 nm in the total pore volume is ≥95%; specifically, it can be 95%, 96%, 97%, 98% or 99%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0049] It can be understood that after removing the silicon particles, the volume ratio of the pores of the negative electrode material (i.e., the carbon matrix) is controlled within the above range. The pores can accommodate most of the silicon particles, reduce the silicon segregation formed by the deposition of silicon particles on the surface of the carbon matrix, increase the content of silicon particles in the carbon matrix and the uniformity of the distribution of silicon particles, thereby improving the specific capacity and mechanical properties of the negative electrode material.

[0050] In some embodiments, the negative electrode material after the silicon particles are removed further includes macropores.

[0051] In some embodiments, the total pore volume of all pores in the negative electrode material after removing the silicon particles is 0.5 cm 3 / g~1.5cm 3 / g; specifically 0.5cm 3 / g, 0.6cm 3 / g, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1.0cm 3 / g, 1.1cm 3 / g, 1.2cm 3 / g, 1.3cm 3 / g, 1.4cm 3 / g or 1.5cm 3 / g, etc., of course, it can also be other values ​​within the above range, which is not limited here. It can be understood that the negative electrode material after removing the silicon particles has abundant pores, which can accommodate the silicon particles and reserve space for the volume expansion of the silicon particles. Preferably, the total pore volume of all pores in the negative electrode material after removing the silicon particles is 1.0cm 3 / g~1.5cm 3 / g.

[0052] In the present application, the total pore volume of the negative electrode material containing silicon particles is greatly reduced compared to the negative electrode material without silicon particles. This is because the silicon particles are relatively uniformly filled, so that the pore volume of most pores is reduced after filling with silicon particles. This shows that the pores of the carbon matrix are effectively and relatively uniformly filled with silicon particles, thereby improving the specific capacity of the negative electrode material.

[0053] In some embodiments, the specific surface area of ​​the negative electrode material after removing the silicon particles is 500m 2 / g~2000m 2 / g; the specific surface area can be 500m 2 / g、800m 2 / g、1000m 2 / g、1200m 2 / g、1400m 2 / g、1600m 2 / g、1800m 2 / g, 1900m 2 / g or 2000m 2 / g, etc., of course, it can also be other values ​​within the above range, which is not limited here. Preferably, the specific surface area of ​​the negative electrode material after removing the silicon particles is 1200m 2 / g~2000m 2 / g.

[0054] In some embodiments, at least a portion of the surface of the negative electrode material has a coating layer, and the material of the coating layer includes a carbon material.

[0055] In some embodiments, the carbon material includes at least one of amorphous carbon and graphitized carbon.

[0056] It can be understood that the coating layer located at the outermost layer of the negative electrode material has good electrical conductivity on the one hand, which can improve the electrical conductivity of the negative electrode material. On the other hand, it can coat the silicon particles exposed on the surface of the carbon matrix, reducing the continuous oxidation of the exposed silicon particles during the placement process, reducing the specific capacity and the reduction of the first coulomb efficiency (ICE) of the negative electrode material; the coating layer can also reduce the direct contact between the active material and the electrolyte, ensuring the stability of the SEI film, thereby improving the first coulomb efficiency of the negative electrode material. In addition, during the coating process, the material of the coating layer will further fill the gaps inside the active material, reducing the total pore volume of the negative electrode material, which can effectively reduce the amount of electrolyte that directly penetrates into the particles of the negative electrode material through the pore structure, reducing the side reactions that occur when the electrolyte contacts the active material, and improving the cycle performance of the ion battery prepared with the negative electrode material.

[0057] In some embodiments, the thickness of the coating layer is 1 nm to 300 nm. Optionally, the thickness of the coating layer can be specifically 1 nm, 50 nm, 150 nm, 200 nm, 250 nm and 300 nm, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that the coating layer can reduce the solubility of the negative electrode material, thereby reducing the gas production of the dissolved silicon particles reacting with the electrolyte. Controlling the thickness of the coating layer within the above range is beneficial to maintaining the stability of the particle structure of the negative electrode material during the cycle, reducing the exposed Si on the surface of the negative electrode material, reducing the exposed silicon causing a large amount of SEI to be generated during the charge and discharge process, and improving the specific capacity and electrochemical performance of the negative electrode material. Preferably, the thickness of the coating layer is 1 nm to 50 nm, and more preferably, the thickness of the coating layer is 1 nm to 30 nm.

[0058] In some embodiments, the mass proportion of the coating layer in the negative electrode material is ≤10%, and specifically can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% or 1%, etc., and of course, it can also be other values ​​within the above range, which is not limited here. It is understandable that the coating layer can reduce the solubility of the negative electrode material, thereby reducing the amount of gas produced by the reaction of dissolved silicon particles with the electrolyte. The mass proportion of the coating layer in the negative electrode material is within the above range, which can ensure the amount of lithium that can be inserted into the negative electrode material, thereby ensuring the charge and discharge capacity of the lithium-ion battery prepared with the negative electrode material.

[0059] In some embodiments, the median particle size D of the negative electrode material is 50≤10μm, specifically 10μm, 9μm, 8μm, 7μm, 6μm, 5μm, 4μm, 3μm, 2μm or 1μm, etc., and of course other values ​​within the above range are also possible, which are not limited here. It can be understood that the median particle size refers to the particle size of the negative electrode material in the middle position after the particles of the negative electrode material are sorted by size. The median particle size of the negative electrode material is within the above range, which can ensure the time for lithium ion insertion and extraction, so that the negative electrode material can achieve a state of rapid and sufficient lithium insertion, thereby ensuring the charge and discharge performance of the lithium-ion battery.

[0060] In some embodiments, the particle size distribution of the negative electrode material satisfies: 0.9≤(D 90 -D 10 ) / D 50 ≤5; specifically, it can be 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4, 4.5, or 5, etc., and of course, it can also be other values ​​within the above range, which is not limited here. The particle size distribution of the negative electrode material is within the above range. Large particles with larger particle sizes and small particles with smaller particle sizes of the negative electrode material can cooperate with each other, and the small particles fill the pores between the large particles, which can increase the tap density of the negative electrode material.

[0061] In some embodiments, the specific surface area of ​​the negative electrode material is ≤10m 2 / g, specifically 10m 2 / g、8.9m 2 / g, 6.8m 2 / g, 5.5m 2 / g, 4.2m 2 / g、4m 2 / g、3m 2 / g, 2.5m 2 / g, 2m 2 / g or 1m 2 / g, etc., of course, it can also be other values ​​within the above range, which is not limited here. It is understandable that the specific surface area of ​​the negative electrode material will affect the contact area between the negative electrode material and the electrolyte. The specific surface area of ​​the negative electrode material within the above range can reduce the amount of lithium ions consumed by the SEI film formed during the initial charge and discharge process of the lithium-ion battery, and reduce the irreversible capacity loss of the lithium-ion battery. Preferably, the specific surface area of ​​the negative electrode material is ≤5m 2 / g.

[0062] In some embodiments, the compacted density of the negative electrode material is 0.8 g / cm 3 ~1.3g / cm 3 , specifically 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3, 1.1g / cm 3 , 1.2g / cm 3 or 1.3 g / cm 3 Of course, it can also be other values ​​within the above range, which is not limited here.

[0063] In some embodiments, the tap density of the negative electrode material is 0.5 g / cm 3 ~1.5g / cm 3 , specifically 0.5g / cm 3 , 0.6g / cm 3 , 0.7g / cm 3 , 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.1g / cm 3 , 1.2g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 or 1.5g / cm 3 Of course, it can also be other values ​​within the above range, which is not limited here.

[0064] In some embodiments, the powder conductivity of the negative electrode material under a pressure of 20 kN is 0.5 S / cm to 5 S / cm, specifically 0.5 S / cm, 0.8 S / cm, 1.0 S / cm, 1.2 S / cm, 1.5 S / cm, 2 S / cm, 3 S / cm, 4 S / cm, or 5.0 S / cm, etc., and of course other values ​​within the above range are also possible, and are not limited here. Controlling the powder conductivity of the negative electrode material within the above range can effectively improve the electrochemical performance of the negative electrode material. Preferably, the powder conductivity of the negative electrode material under a pressure of 20 kN is 0.5 S / cm to 2 S / cm.

[0065] In some embodiments, the mass content of carbon element in the negative electrode material is 20% to 80%, specifically 20%, 25%, 30%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0066] In some embodiments, the mass content of silicon in the negative electrode material is 20% to 60%, specifically 20%, 25%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 55% or 60%, etc., and of course other values ​​within the above range are also possible, and are not limited here. It can be understood that controlling the mass content of silicon within the above range can effectively control the volume expansion of the negative electrode material and the capacity of the negative electrode material at the same time. Preferably, the mass content of silicon in the negative electrode material is 45% to 55%.

[0067] In some embodiments, the negative electrode material further includes trace metal elements, and the trace metal elements include at least one of Fe, Co, Ni, Cr, Zn, Cu and Al.

[0068] In some embodiments, in the negative electrode material, the mass proportion of trace metal elements is ≤200ppm, specifically 200ppm, 180ppm, 160ppm, 150ppm, 140ppm, 130ppm, 120ppm, 100ppm or 50ppm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0069] In some embodiments, the average gas production of the negative electrode slurry prepared from the negative electrode material is ≤1 mL / kg / day when placed in a 25°C environment for 7 days, and can specifically be 1 mL / kg / day, 0.8 mL / kg / day, 0.6 mL / kg / day, 0.5 mL / kg / day, 0.4 mL / kg / day, 0.3 mL / kg / day, 0.2 mL / kg / day or 0.1 mL / kg / day, etc., and of course it can also be other values ​​within the above range, which is not limited here. The gas production value of the negative electrode material of the present application is controlled within the above range. It can be seen that most of the silicon particles can be relatively evenly distributed in the pores of the carbon matrix, and the direct contact between the silicon particles and the electrolyte is reduced, thereby reducing the side reaction of the dissolved silicon particles with the electrolyte (i.e., silicon is hydrolyzed into silicate and hydrogen), which can also effectively reduce the gas production value of the negative electrode material. When the surface density of the negative electrode material is insufficient, the gas production value of the negative electrode material will increase significantly.

[0070] In a second aspect, the present application provides a method for preparing a negative electrode material, comprising the following steps:

[0071] Step S10, preparing a composite, the composite including an active substance and a catalyst;

[0072] Step S20 , coating the composite to obtain a negative electrode material; wherein the surface density of the negative electrode material is β, and β is ≥ 80%.

[0073] In the above scheme, a catalyst is added during the preparation of the active material. During the coating process, the catalyst prompts the coating material to form a high-density coating layer on the surface of the active material, thereby solving the problem that when the coating layer is prepared by vapor deposition in the prior art, a high cracking temperature is used to ensure complete cracking of the gas source, resulting in the consumption of highly active silicon particles by the reaction with the carbon matrix, thereby ensuring the charge and discharge capacity of the lithium-ion battery.

[0074] In the prior art, the gas sources commonly used in gas phase coating, such as methane and acetylene, require relatively high temperatures (methane>1000°C, acetylene>800°C) to be completely cracked to form a relatively dense coating layer. However, at high temperatures, due to the high activity of the deposited silicon particles, SiC is usually generated. Therefore, gas phase coating is currently usually carried out at lower temperatures (500°C~800°C). However, at temperatures of 500°C~800°C, the gas source precursor is not fully cracked, the carbon coating layer formed on the particle surface is not dense, and there are a large number of incomplete cracking products, resulting in the gas production problem cannot be completely solved.

[0075] The preparation method of the present application is described in detail below with reference to the examples:

[0076] In step S10 , the specific steps of preparing the composite include: soaking the carbon substrate in a solution containing a catalyst, and depositing silicon particles on the product after solid-liquid separation to obtain the composite.

[0077] In some embodiments, the carbon matrix used in the above preparation method includes at least one of artificial graphite, natural graphite, amorphous carbon, activated carbon, mesophase carbon microbeads, carbon nanotubes, carbon nanofibers and graphene. It can be understood that the carbon matrix selected from the above materials can all play the role of supporting the skeleton and have good electrical conductivity to ensure the electrical conductivity of the negative electrode material.

[0078] In some embodiments, the prepared carbon matrix is ​​immersed in a catalyst solution so that the catalyst adheres to the surface or interior of the carbon matrix. The catalyst solution is a salt solution containing at least one of Cu, Ni, Co, Fe and B. It can be understood that the catalyst contains the above elements, which can reduce the temperature during the coating process and achieve a dense coating layer at a lower temperature.

[0079] In some embodiments, the carbon matrix has pores, including micropores, mesopores, and macropores.

[0080] In some embodiments, in the carbon matrix, the volume proportion of pores with a pore diameter of less than 2 nm in the total pore volume is ≥70%; specifically, it can be 70%, 75%, 80%, 85%, 90%, 95% or 99%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0081] In some embodiments, in the carbon matrix, the volume proportion of pores with a pore diameter of less than 5 nm in the total pore volume is ≥85%; specifically, it can be 85%, 87%, 89%, 90%, 92%, 95%, 97% or 99%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0082] In some embodiments, in the carbon matrix, the volume proportion of pores with a pore diameter of less than 10 nm in the total pore volume is ≥95%; specifically, it can be 95%, 96%, 97%, 98% or 99%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0083] It can be understood that when the pore volume ratio of the carbon matrix is ​​controlled within the above range, the pores can accommodate most of the silicon particles, reduce the silicon segregation formed by the deposition of silicon particles on the surface of the carbon matrix, increase the content of silicon particles in the carbon matrix and the uniformity of the distribution of silicon particles, thereby improving the specific capacity and mechanical properties of the negative electrode material.

[0084] In some embodiments, the carbon substrate has a specific surface area of ​​500 m 2 / g~2000m 2 / g; the specific surface area can be 500m 2 / g、800m 2 / g、1000m 2 / g、1200m 2 / g、1400m 2 / g、1600m 2 / g、1800m 2 / g、1900m 2 / g or 2000m 2 / g, etc., of course, it can also be other values ​​within the above range, which is not limited here. Preferably, the specific surface area of ​​the carbon matrix is ​​1200m 2 / g~2000m 2 / g.

[0085] In some embodiments, the total pore volume of all pores in the carbon matrix is ​​0.5 cm 3 / g~1.5cm 3 / g; specifically 0.5cm 3 / g, 0.6cm 3 / g, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1.0cm 3 / g, 1.1cm 3 / g, 1.2cm 3 / g, 1.3cm 3 / g, 1.4cm3 / g or 1.5cm 3 / g, etc., and of course, other values ​​within the above range can also be used, which are not limited here. It can be understood that the carbon matrix has abundant pores, which can accommodate silicon particles and reserve space for the volume expansion of silicon particles. Preferably, the total pore volume of all pores in the carbon matrix is ​​0.6cm 3 / g~1.0cm 3 / g.

[0086] In some embodiments, the concentration of the solution containing the catalyst is 0.1mol / L to 2.5mol / L. Optionally, the concentration can be specifically 0.1mol / L, 0.5mol / L, 1.2mol / L and 2.5mol / L, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that the concentration of the catalyst within the above range helps to improve the surface density of the negative electrode material. If the catalyst concentration is too high, the content of the catalyst attached to the carbon matrix will be too high, which will lead to an increase in the thickness of the surface coating layer of the negative electrode material. Excessive coating thickness will make it difficult for the electrolyte to effectively infiltrate the negative electrode material particles, hindering the transmission of lithium ions and reducing the rate performance of the negative electrode material.

[0087] In some embodiments, the soaking time is 10 to 60 minutes. Alternatively, the soaking time may be 10 minutes, 20 minutes, 30 minutes, 50 minutes, 60 minutes, or other values ​​within this range. This range can be selected based on actual needs and is not limited herein. It will be appreciated that a soaking time within this range can increase the amount of catalyst adhered, thereby helping to improve the surface density of the negative electrode material.

[0088] In some embodiments, the drying temperature is 80°C to 120°C, specifically 80°C, 90°C, 100°C, 110°C or 120°C, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0089] In some embodiments, the silicon particles include at least one of crystalline silicon, silicon oxide, amorphous silicon, a silicon alloy, or a composite of crystalline silicon and amorphous silicon. The type of silicon particles can be selected based on actual needs and is not limited herein. The silicon alloy can include a silicon-lithium alloy, a silicon-magnesium alloy, a silicon-nickel alloy, and the like.

[0090] In some embodiments, the silicon oxide includes silicon and oxygen, and the atomic ratio of silicon to oxygen is 0 to 2, excluding 0. The atomic ratio of silicon to oxygen can be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2, etc., without limitation. Preferably, the atomic ratio of silicon to oxygen is 0 to 1, excluding 0.

[0091] In some embodiments, the chemical formula of silicon oxide is SiO x , wherein 0<x<2, x can be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 and 1.9, etc., which are not limited here. Preferably, 0 <x<1。

[0092] In some embodiments, the average particle size of the silicon particles is 0.1nm to 50nm. Optionally, the average particle size of the silicon particles can specifically be 0.1nm, 10nm, 20nm, 30nm, 40nm and 50nm, etc., or other values ​​within the range, which can be selected according to actual needs and are not limited here. The mechanical stress during silicon particle expansion decreases as the particle size decreases, and the electron and ion transmission paths can be shortened after the size is reduced. At the same time, the size of the silicon particles decreases, and the gaps between adjacent silicon particles increase, which can reserve space for expansion. It can be understood that the average particle size of the silicon particles is within the above range, which can ensure the battery capacity of the lithium-ion battery and reduce irreversible capacity loss. Preferably, the average particle size of the silicon particles is 0.1nm to 20nm, and more preferably, the average particle size of the silicon particles is 0.1nm to 5nm.

[0093] In some embodiments, the morphology of the silicon particles includes at least one of a dot-like shape, a spherical shape, an ellipsoidal shape, and a flake-like shape. The morphology of the silicon particles can be selected according to actual needs and is not limited here.

[0094] In some embodiments, the purity of the silicon particles is greater than 99%. It can be understood that high-purity silicon particles are beneficial for Li-Si alloying with lithium, thereby improving the cycle performance of lithium-ion batteries.

[0095] In some embodiments, the silicon particles may be deposited by vapor deposition or liquid deposition. The deposition method of the silicon particles may be selected according to actual needs and is not limited here.

[0096] Preferably, the silicon particles are deposited by vapor phase chemical deposition, and the steps include: introducing a silicon-containing gas source and reacting the gas phase chemical deposition reaction with the carbon matrix.

[0097] In some embodiments, the silicon-containing gas source includes at least one of monosilane, disilane, trisilane, and tetrasilane, which can be selected according to actual needs and is not limited here.

[0098] In some embodiments, the concentration of the silicon-containing gas source is 1% to 80%. Optionally, the concentration of the silicon-containing gas source can be 1%, 13%, 26%, 43%, 55%, 68%, 80%, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0099] In one embodiment, the introduced gas includes a silicon-containing source gas and an auxiliary carrier gas, wherein the auxiliary carrier gas can dilute the silicon-containing source gas and help control the residence time of the silicon-containing source gas. The auxiliary carrier gas includes at least one of nitrogen, argon, and helium.

[0100] In some embodiments, the volume ratio of the silicon-containing gas source and the auxiliary carrier gas is 1:(1-10), specifically 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, etc., or other values ​​within the range, which can be selected within the above range according to actual needs.

[0101] In some embodiments, the introduced gas further includes a doping gas, specifically NH3 or PH3.

[0102] In some embodiments, the gas pressure of the vapor phase chemical deposition reaction is 10 kPa to normal pressure.

[0103] In some embodiments, the temperature of the vapor deposition reaction is 300°C to 800°C, and the holding time is 1 hour to 15 hours. Optionally, the temperature can be 300°C, 420°C, 500°C, 600°C, 700°C, 750°C, and 800°C, and the holding time can be 1 hour, 3 hours, 4 hours, 6 hours, 7 hours, 8 hours, 10 hours, 12 hours, and 15 hours, or other values ​​within the range. It can be selected according to actual needs and is not limited here. Preferably, the temperature of the vapor chemical deposition reaction is 400°C to 600°C, and the holding time of the vapor chemical deposition reaction is 2 hours to 6 hours.

[0104] By controlling the reaction parameters of vapor phase chemical deposition, the gas phase silicon source can penetrate into the carbon matrix, decompose in the pores of the carbon matrix, and deposit to form silicon particles with a suitable particle size.

[0105] In some embodiments, a liquid silicon source may be used for compounding with the carbon matrix. The liquid silicon source includes at least one of monochlorosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane. When a liquid silicon source is used, the compounding pressure may be 1 mTorr to 760 mTorr, and the compounding temperature may be 300°C to 450°C.

[0106] In some embodiments, the thickness of the coating layer prepared in step S20 is 1 nm to 300 nm. Optionally, the thickness of the coating layer can be specifically 1 nm, 50 nm, 150 nm, 200 nm, 250 nm and 300 nm, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that the coating layer can reduce the solubility of the negative electrode material, thereby reducing the gas production of the dissolved silicon particles reacting with the electrolyte. Controlling the thickness of the coating layer within the above range is beneficial to maintaining the stability of the particle structure of the negative electrode material during the cycle, reducing the dissolution of silicon particles, and is beneficial to improving the transmission efficiency of lithium ions and enhancing the charge and discharge performance of the negative electrode material. Preferably, the thickness of the coating layer is 1 nm to 50 nm, and more preferably, the thickness of the coating layer is 1 nm to 30 nm.

[0107] In some embodiments, the mass proportion of the coating layer in the negative electrode material is ≤10%. It can be understood that the coating layer can reduce the solubility of the negative electrode material, thereby reducing the gas production of the dissolved silicon particles reacting with the electrolyte. The mass proportion of the coating layer in the negative electrode material is within the above range, which can ensure the amount of lithium that can be inserted into the negative electrode material, thereby ensuring the charge and discharge capacity of the lithium-ion battery prepared from the negative electrode material.

[0108] In some embodiments, coating the composite comprises: mixing the composite with a coating material and performing a heat treatment, wherein the coating material comprises a carbon material.

[0109] In some embodiments, the carbon material includes at least one of amorphous carbon and graphitized carbon.

[0110] In some embodiments, the mass ratio of the active substance to the coating material is 100:(1-100). Optionally, the mass ratio can be 100:1, 100:10, 100:20, 100:40, 100:60, 100:70 and 100:100, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0111] In some embodiments, coating the composite comprises: mixing the composite with a coating material and performing heat treatment, wherein the heat treatment temperature is 400° C. to 800° C., and the heat treatment holding time is 1 hour to 15 hours.

[0112] In some embodiments, the heat treatment temperature is 400°C to 800°C, and the heat treatment holding time is 1h to 15h. Optionally, the temperature can be 400°C, 500°C, 600°C, and 800°C, etc., and the time can be 1h, 3h, 5h, 6h, 8h, 10h, 11h, 12h, and 15h, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0113] In some embodiments, the heat treatment is performed under a protective gas, and the protective gas includes at least one of nitrogen, helium, neon, argon and krypton, which can be selected according to actual needs and is not limited here.

[0114] In the above technical solution, the active material surface is coated to form a coating layer. This can reduce the electrolyte from entering the negative electrode material and causing side reactions that lead to a decrease in initial coulombic efficiency and specific capacity. It can also further address the large volume expansion of the negative electrode material, improve the conductivity of the negative electrode material, and thus reduce the volume expansion of the entire negative electrode material and reduce electrode sheet swelling. During the coating process, a small amount of coating material will enter the pores of the negative electrode material.

[0115] It should be noted that the coating process of the present application is carried out on the premise of reducing the crystal form changes of the silicon-carbon negative electrode material.

[0116] Preferably, in step S20 , the composite is subjected to a carbon coating treatment, and the carbon coating treatment includes at least one of solid-phase carbon coating, liquid-phase carbon coating, and gas-phase carbon coating.

[0117] In some embodiments, the carbon coating process is gas-phase carbon coating, and the steps include: heating the composite, introducing a protective gas and a carbon source gas, and thermally cracking the carbon source gas to obtain a negative electrode material.

[0118] In some embodiments, the carbon source gas is a hydrocarbon.

[0119] In some embodiments, the carbon source gas includes at least one of methane, ethane, propane, ethylene, acetylene, gaseous benzene, gaseous toluene, gaseous xylene, gaseous ethanol, and gaseous acetone.

[0120] In some embodiments, protective gas and carbon source gas are introduced and the gas pressure is maintained in the range of 1-10 kPa.

[0121] In some embodiments, the temperature of thermal cracking is 400°C to 800°C, and the holding time is 0.5h to 18h. Optionally, the temperature can be 400°C, 500°C, 600°C, 700°C and 800°C, etc., and the holding time can be 0.5h, 1.5h, 3h, 5h, 6h, 7h, 8h, 10h and 18h, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0122] In some embodiments, the volume ratio of the carbon source gas to the protective gas is 1:(0.1-20). Optionally, the volume ratio can be 1:0.1, 1:1, 1:2, 1:5, 1:10, 1:15 and 1:20, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0123] In some embodiments, the flow rate of the carbon source gas is 100 sccm to 500 sccm; specifically, it may be 100 sccm, 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm, 450 sccm, or 500 sccm, etc., and other values ​​within the above range are also possible and are not limited here. Preferably, the flow rate of the carbon source gas is 200 sccm to 300 sccm.

[0124] By controlling the volume ratio of the carbon source gas to the protective gas, the gas flow rate, the reaction pressure and other parameters, the carbon material obtained by the cracking of the carbon source gas can be deposited on the surface of the composite.

[0125] In some embodiments, the deposition and coating of the carbon source gas is performed under the condition that the reaction furnace is rotating, so as to achieve homogeneous in-situ carbon coating on the surface of the composite.

[0126] In some embodiments, the carbon coating process is solid-phase carbon coating, and the steps include: carbonizing a mixture obtained by mixing the composite with a solid-phase carbon source to obtain a negative electrode material.

[0127] In some embodiments, the carbonization temperature is 400° C. to 800° C., and the carbonization time is 1 hour to 15 hours. Optionally, the temperature may be 400° C., 500° C., 600° C., 700° C., and 800° C., and the time may be 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 9 hours, 11 hours, 12 hours, and 15 hours, or other values ​​within the range. These values ​​may be selected based on actual needs and are not limited herein.

[0128] In some embodiments, the solid carbon source includes at least one of sugars, esters, hydrocarbons, organic acids, and high molecular weight polymers.

[0129] In some embodiments, the solid carbon source includes at least one of polyvinyl chloride, polyvinyl butyral, polyacrylonitrile, polyacrylic acid, polyethylene glycol, polypyrrole, polyaniline, sucrose, glucose, maltose, citric acid, asphalt, furfural resin, epoxy resin and phenolic resin.

[0130] In some embodiments, the mass ratio of the solid carbon source to the active substance is 100:(10-200). Optionally, the mass ratio can be 100:10, 100:40, 100:60, 100:100, 100:130, 100:160 and 100:200, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0131] In some embodiments, the carbon coating process is liquid-phase carbon coating, and the steps include: carbonizing a mixture obtained by mixing the composite with a liquid-phase carbon source to obtain a negative electrode material.

[0132] In some embodiments, the mass ratio of the liquid carbon source to the active substance is 100:(5-300). Optionally, the mass ratio can be 100:5, 100:10, 100:60, 100:150, 100:200, 100:240 and 100:300, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0133] In some embodiments, the liquid carbon source includes at least one of n-hexane, toluene, benzene, xylene, methanol, ethanol, propanol, butanol, pentanol, acetone, butanone, 2-pentanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and pentyl acetate.

[0134] In some embodiments, the temperature of the carbonization treatment is 400°C to 800°C, and the time of the carbonization treatment is 1h to 15h. Optionally, the temperature can be 400°C, 500°C, 600°C, 700°C and 800°C, etc., and the time can be 1h, 3h, 5h, 7h, 9h, 10h, 12h, 13h and 15h, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0135] In a third aspect, the present application provides a battery comprising the aforementioned negative electrode material or the negative electrode material prepared by the aforementioned preparation method. The battery may be an electrochemical device such as a lithium-ion battery or a sodium-ion battery, without limitation herein.

[0136] Those skilled in the art will understand that the above-described method for preparing a lithium-ion battery is merely an example, and other methods commonly used in the art may be employed without departing from the disclosure of this application.

[0137] The following further illustrates the embodiments of the present application in multiple embodiments. The embodiments of the present application are not limited to the following specific embodiments. Within the scope of the unchanged main rights, appropriate changes can be made to the implementation.

[0138] Test method:

[0139] 1. Density β test: Soak m1 g of negative electrode material in a 20% hydrofluoric acid solution for 1 hour, then wash and dry to obtain m2 g of material. The surface density of the negative electrode material is calculated as β = m2 / m1×100%.

[0140] 2. Coating thickness: The material is sectioned using a FIB-SEM device, and the average coating thickness is measured using the SEM:

[0141] 3. Test method for pore volume and proportion of carbon matrix and negative electrode material after removing silicon particles:

[0142] The pore volume of a carbon matrix refers to the total pore volume per unit mass of the carbon matrix. It can be measured through gas adsorption. Nitrogen adsorption is a technique that characterizes the porosity and pore size distribution of a material by causing gas to condense within the pores of a solid. As pressure increases, the gas condenses first in the pores with the smallest diameters, and the pressure increases until saturation is reached, at which point all pores are filled with liquid. The nitrogen pressure is then gradually reduced to allow the liquid to evaporate from the system. Analysis of the adsorption and desorption isotherms allows the determination of the pore volume and pore size distribution, as well as the contribution of micropores, mesopores, and macropores to the total pore volume. Silicon particles are removed from the anode material by soaking it in a 1M nitric acid solution for 4 hours. A 20% by mass HF acid solution is then added dropwise to the anode material, producing yellow smoke. This addition is repeated until the solution ceases to produce yellow smoke. Finally, the residue is digested with a 1M nitric acid solution, then washed and dried to obtain the anode material after the active material has been removed.

[0143] 4. Gas production test:

[0144] Disperse carboxymethyl cellulose (CMC) in water at a mass ratio of 1.4% for gluing. After uniform dispersion, take 10g of the glue solution and mix it with 10g of the negative electrode material to obtain a slurry. Put the slurry into an aluminum-plastic film bag and record the slurry mass. Then seal it to form a sealed aluminum-plastic film bag.

[0145] Secure the sealed aluminum-plastic film bag to the bottom of the container and completely immerse it in water. Record the volume of the bag. After a fixed period (24 hours), record the volume of the bag again. Calculate the gas production of the silicon anode material based on the change in the volume of the aluminum-plastic film (unit: mL / g). 5. Silicon Particle Type: Use X-ray diffractometer (XRD) to measure diffraction peaks to confirm the type of silicon particles.

[0146] 6. Test of silicon mass content in negative electrode material:

[0147] Use a box-type atmosphere furnace (brand: Nanyang Xinyu, model: SA2-9-17TP) to burn in an oxygen atmosphere, so that the silicon and silicon oxide in the sample react to form silicon dioxide. After the carbon burns, it is converted into carbon dioxide and discharged. The mass content of silicon in the negative electrode material is weighed and calculated.

[0148] 8. Powder resistivity test:

[0149] The volume resistivity of the sample is measured using the four-probe method. The instrument tests the resistance of the powder at five pressure points: 4, 8, 12, 16, and 20 kN. The computer then automatically calculates the conductivity and resistivity of the powder.

[0150] 9. Test of mass content of trace metal elements in carbon matrix:

[0151] The mass content of each metal trace element (Fe, Co, Ni, Cr, Zn, Cu, Al, etc.) in the carbon matrix was tested by ICP emission spectrometry, and the testing equipment model was PEoptima 8000.

[0152] 10. Test of carbon content in negative electrode materials:

[0153] Using the German Bruker / German Airt infrared carbon and sulfur analyzer G4 ICARUS HF / CS-i, the sample is burned in a high-temperature, oxygen-rich state. The carbon element it contains is oxidized to carbon dioxide and enters the infrared detector with the carrier gas. The carbon content is calculated by quantitatively analyzing the changes in the infrared absorption wavelength intensity of the carbon dioxide signal.

[0154] 11. Electrical performance test:

[0155] Electrochemical cycling performance was tested using the following method: the negative electrode material, conductive agent, and binder were dissolved in a solvent at a ratio of 94:1:5 by mass, with a solids content controlled at 50%. The mixture was then coated onto a copper foil current collector and vacuum-dried to produce the negative electrode. 18650 cylindrical cells were then assembled using conventional production processes using a conventionally prepared ternary positive electrode, a 1 mol / L LiPF6 / EC+DMC+EMC (v / v = 1:1:1) electrolyte, a Celgard 2400 separator, and a casing. Cylindrical battery charge and discharge tests were conducted on a LAND battery test system from Wuhan Jinnuo Electronics Co., Ltd. at room temperature, with a constant current of 0.2C and a voltage limit of 2.75 to 4.2V.

[0156] It should be noted that in the following embodiments, the average particle size of the silicon particles deposited in the carbon matrix by the silicon source is 0.1nm~50nm, the purity of the silicon particles is greater than 99%, the thickness of the coating layer is 1nm~300nm, and the mass proportion of the coating layer in the negative electrode material is ≤10%.

[0157] Example 1:

[0158] (1) Using bamboo charcoal as raw material, carbonizing it and then acid washing it to obtain a porous carbon matrix;

[0159] (2) adding the porous carbon substrate into a 2 mol / L copper nitrate solution, soaking for 0.5 hours, and then vacuum drying at 80° C. to obtain a carbon substrate containing the catalyst;

[0160] (3) placing the carbon substrate containing the catalyst in a CVD reaction chamber, repeatedly purging the reaction chamber with nitrogen for 3 to 5 minutes, then turning off the nitrogen and introducing argon gas at a flow rate of 400 sccm, heating to 500°C at a heating rate of 8°C / min, and staying at this temperature for 1 hour, then turning on monosilane, and introducing a mixed gas of monosilane and argon into the CVD equipment, with a volume concentration ratio of monosilane to argon of 1:3 (silicon-containing gas concentration of 25%), a total gas concentration of 100 sccm, and keeping the temperature for 5 hours, then turning off the silane gas, and cooling to room temperature to obtain a composite;

[0161] (4) Phenolic resin and the composite were mixed in a mass ratio of 1:4, mixed with a VC mixing machine for 10 minutes, and then placed in a high-temperature box furnace, evacuated to 5 kPa, and introduced with nitrogen. Carbonization treatment was performed at 580 ° C and 5 kPa. After keeping the temperature for 2 hours, the product was cooled, crushed, sieved, and then graded to obtain the negative electrode material.

[0162] The negative electrode material prepared in this embodiment includes a carbon matrix, silicon particles, and a coating layer located on the surface of the silicon-based active material. Some silicon particles are located in the pores of the carbon matrix, and the coating layer includes a carbon layer.

[0163] Example 2:

[0164] The difference from Example 1 is that: (2) the carbon substrate with pores is added to a 2 mol / L ferric nitrate solution, soaked for 0.5 hours, and then vacuum-dried at 80° C. to obtain a carbon substrate containing the catalyst;

[0165] The negative electrode material prepared in this embodiment includes a carbon matrix, silicon particles, and a coating layer located on the surface of the silicon-based active material. Some silicon particles are located in the pores of the carbon matrix, and the coating layer includes a carbon layer.

[0166] Example 3:

[0167] The difference from Example 1 is that: (2) the carbon substrate having pores is added to a 0.7 mol / L boric acid solution, soaked for 0.5 hours, and then treated at 900° C. to obtain a carbon substrate containing a catalyst;

[0168] The negative electrode material prepared in this embodiment includes a carbon matrix, silicon particles, and a coating layer located on the surface of the silicon-based active material. Some silicon particles are located in the pores of the carbon matrix, and the coating layer includes a carbon layer.

[0169] Example 4:

[0170] The difference from Example 1 is that:

[0171] (2) mixing a porous carbon matrix and nickel carbonate in a mass ratio of 100:2, drying, and treating at 960° C. to obtain a carbon matrix containing a catalyst;

[0172] The negative electrode material prepared in this embodiment includes a carbon matrix, silicon particles, and a coating layer located on the surface of the silicon-based active material. Some silicon particles are located in the pores of the carbon matrix, and the coating layer includes a carbon layer.

[0173] Example 5:

[0174] The difference from Example 1 is that:

[0175] (4) The epoxy resin and the composite were mixed in a mass ratio of 1:3, mixed with a VC mixing machine for 10 minutes, and then placed in a high-temperature box furnace, evacuated to 5 kPa, and introduced with nitrogen. Carbonization treatment was performed at 580 ° C and 5 kPa. After keeping the temperature for 2 hours, the product was cooled and crushed, sieved, and then graded to obtain the negative electrode material.

[0176] The negative electrode material prepared in this embodiment includes a carbon matrix, silicon particles, and a coating layer located on the surface of the silicon-based active material. Some silicon particles are located in the pores of the carbon matrix, and the coating layer includes a carbon layer.

[0177] Example 6:

[0178] The difference from Example 1 is that:

[0179] (4) Phenolic resin and the composite were mixed in a mass ratio of 1:4, mixed with a VC mixing machine for 10 minutes, and then placed in a high-temperature box furnace, evacuated to 5 kPa, and introduced with nitrogen. Carbonization treatment was performed at 680 ° C and 5 kPa. After keeping the temperature for 2 hours, the product was cooled, crushed, sieved, and then graded to obtain the negative electrode material.

[0180] The negative electrode material prepared in this embodiment includes a carbon matrix, silicon particles, and a coating layer located on the surface of the silicon-based active material. Some silicon particles are located in the pores of the carbon matrix, and the coating layer includes a carbon layer.

[0181] Example 7:

[0182] The difference from Example 1 is that:

[0183] (4) Phenolic resin and the composite were mixed in a mass ratio of 1:4, mixed with a VC mixing machine for 10 minutes, and then placed in a high-temperature box furnace, evacuated to 5 kPa, and introduced with nitrogen. Carbonization treatment was performed at 720 ° C and 5 kPa. After keeping the temperature for 2 hours, the product was cooled, crushed, sieved, and then graded to obtain the negative electrode material.

[0184] Example 8:

[0185] The difference from Example 1 is that:

[0186] (4) Phenolic resin and the composite were mixed in a mass ratio of 1:4 and mixed with a VC mixing machine for 10 minutes. The mixed materials were then placed in a high-temperature box furnace, evacuated to 5 kPa, and nitrogen was introduced. Carbonization treatment was performed at 800°C and 5 kPa. After keeping the temperature for 2 hours, the product was cooled, crushed, sieved, and then graded to obtain the negative electrode material.

[0187] The negative electrode material prepared in this embodiment includes a carbon matrix, silicon particles, and a coating layer located on the surface of the silicon-based active material. Some silicon particles are located in the pores of the carbon matrix, and the coating layer includes a carbon layer.

[0188] Example 9:

[0189] The difference from Example 1 is that:

[0190] (3) placing the carbon substrate containing the catalyst in a CVD reaction chamber, repeatedly purging the reaction chamber with nitrogen for 3 to 5 minutes, then turning off the nitrogen and introducing argon gas at a flow rate of 400 sccm, heating to 500°C at a heating rate of 8°C / min, and staying at this temperature for 1 hour, then turning on monosilane, and introducing a mixed gas of monosilane and argon into the CVD equipment, with a volume concentration ratio of monosilane to argon of 1:8 (silicon-containing gas concentration of 11.1%), a total gas concentration of 100 sccm, and keeping the temperature for 5 hours, then turning off the monosilane gas, and cooling to room temperature to obtain a composite;

[0191] The negative electrode material prepared in this embodiment includes a carbon matrix, silicon particles, and a coating layer located on the surface of the silicon-based active material. Some silicon particles are located in the pores of the carbon matrix, and the coating layer includes a carbon layer.

[0192] Example 10:

[0193] The difference from Example 1 is that: (3) the carbon substrate containing the catalyst is placed in a CVD reaction chamber, and the reaction chamber is repeatedly purged with nitrogen for 3 to 5 minutes, then the nitrogen is turned off and argon gas is introduced at a flow rate of 400 sccm, the temperature is raised to 500°C, the heating rate is 8°C / min, and the mixture is kept at this temperature for 1 hour, and then silane is turned on, and a mixed gas of silane and argon is introduced into the CVD equipment, the volume concentration ratio of silane to argon is 1:5 (the silicon-containing gas concentration is 16.7%), and the total gas concentration is 100 sccm. The temperature is kept for 5 hours, and then the silane gas is turned off and the temperature is cooled to room temperature to obtain a composite;

[0194] The negative electrode material prepared in this embodiment includes a carbon matrix, silicon particles, and a coating layer located on the surface of the silicon-based active material. Some silicon particles are located in the pores of the carbon matrix, and the coating layer includes a carbon layer.

[0195] Example 11:

[0196] The difference from Example 1 is that: (3) the carbon substrate containing the catalyst is placed in a CVD reaction chamber, the reaction chamber is repeatedly purged with nitrogen for 3 to 5 minutes, then the nitrogen is turned off and argon gas is introduced at a flow rate of 400 sccm, the temperature is raised to 500°C, the heating rate is 8°C / min, and the mixture is kept at this temperature for 1 hour, then silane is turned on, and a mixed gas of silane and argon is introduced into the CVD equipment, the volume concentration ratio of silane to argon is 1:3 (the concentration of silicon-containing gas is 25%), the total gas concentration is 100 sccm, the temperature is kept for 5 hours, and then the silane gas is turned off and the temperature is cooled to room temperature to obtain a composite;

[0197] The negative electrode material prepared in this embodiment includes a carbon matrix, silicon particles, and a coating layer located on the surface of the silicon-based active material. Some silicon particles are located in the pores of the carbon matrix, and the coating layer includes a carbon layer.

[0198] Example 12:

[0199] The difference from Example 1 is that: (3) the carbon substrate containing the catalyst is placed in a CVD reaction chamber, the reaction chamber is repeatedly purged with nitrogen for 3 to 5 minutes, then the nitrogen is turned off and argon gas is introduced at a flow rate of 400 sccm, the temperature is raised to 500°C, the heating rate is 8°C / min, and the mixture is kept at this temperature for 1 hour, then silane is turned on, and a mixed gas of silane and argon is introduced into the CVD equipment, the volume concentration ratio of silane to argon is 1:4 (the concentration of silicon-containing gas is 20%), the total gas concentration is 100 sccm, the temperature is kept for 8 hours, and then the silane gas is turned off and the temperature is cooled to room temperature to obtain a composite;

[0200] The negative electrode material prepared in this embodiment includes a carbon matrix, silicon particles, and a coating layer located on the surface of the silicon-based active material. Some silicon particles are located in the pores of the carbon matrix, and the coating layer includes a carbon layer.

[0201] Comparative Example 1:

[0202] (1) Using bamboo charcoal as raw material, carbonizing it and then acid washing it to obtain a porous carbon matrix;

[0203] (2) adding the porous carbon substrate into a 2 mol / L copper nitrate solution, soaking for 0.5 hours, and then vacuum drying at 80° C. to obtain a carbon substrate containing the catalyst;

[0204] (3) placing the carbon substrate containing the catalyst in a CVD reaction chamber, repeatedly purging the reaction chamber with nitrogen for 3 to 5 minutes, then turning off the nitrogen and introducing argon gas at a flow rate of 400 sccm, heating to 500°C at a heating rate of 8°C / min, and staying at this temperature for 1 hour, then turning on monosilane, and introducing a mixed gas of silane and argon into the CVD equipment, with a volume concentration ratio of monosilane to argon of 1:3 (silicon-containing gas concentration of 25%), a total gas concentration of 100 sccm, and keeping the temperature for 5 hours, then turning off the silane gas, and cooling to room temperature to obtain a composite;

[0205] The negative electrode material prepared in this embodiment includes a carbon matrix and silicon particles.

[0206] Comparative Example 2:

[0207] (1) Using bamboo charcoal as raw material, carbonizing it and then acid washing it to obtain a porous carbon matrix;

[0208] (2) placing the carbon substrate in a CVD reaction chamber, repeatedly purging the reaction chamber with nitrogen for 3 to 5 minutes, then turning off the nitrogen and introducing argon gas at a flow rate of 400 sccm, heating to 500°C at a heating rate of 8°C / min, and staying at this temperature for 1 hour, then turning on silane, and introducing a mixed gas of silane and argon into the CVD equipment, with a volume concentration ratio of silane to argon of 1:3 (silicon-containing gas concentration of 25%), and a total gas concentration of 100 sccm, keeping the temperature for 5 hours, then turning off the silane gas, and cooling to room temperature to obtain a composite;

[0209] (4) Phenolic resin and the composite were mixed in a mass ratio of 1:4, mixed with a VC mixing machine for 10 minutes, and then placed in a high-temperature box furnace, evacuated to 5 kPa, and introduced with nitrogen. Carbonization treatment was performed at 580 ° C and 5 kPa. After keeping the temperature for 2 hours, the product was cooled, crushed, sieved, and then graded to obtain the negative electrode material.

[0210] The negative electrode material prepared in this embodiment includes a carbon matrix, silicon particles, and a coating layer located on the surface of the silicon-based active material. Some silicon particles are located in the pores of the carbon matrix, and the coating layer includes a carbon layer.

[0211] Table 1. Parameters of negative electrode materials after removing silicon particles

[0212] Table 2. Parameters of negative electrode materials

[0213] Table 3. Parameters of negative electrode materials

[0214] Table 4. Performance test results of examples and comparative examples

[0215] According to the data in Tables 1 to 4, Examples 1 to 4 mainly explore the correlation between the surface density of the negative electrode material and the catalyst in the carbon matrix when the silicon content is similar. According to the data, compared with Examples 1 to 2 or Example 4, the total pore volume of the negative electrode material after removing the silicon particles in Example 3 is larger, and more pores can accommodate the catalyst, so that the thickness of the coating layer is also affected in the subsequent carbon coating process. The surface density of the negative electrode material in Example 3 is relatively high, and different catalysts have little effect on the coating layer on the surface of the negative electrode material.

[0216] According to the data in Tables 1 to 4, Examples 5 to 8 mainly explore the correlation between the surface density of the negative electrode material and the thickness of the coating layer when the silicon content is similar. According to the data, in Example 1 and Examples 5 to 8, the amount of coating material added in Example 5 is increased compared to Example 1, and the surface density of the negative electrode material is increased; in Example 6, the carbonization treatment temperature is increased during the carbon coating process compared to Example 1, and the surface density of the negative electrode material is also increased; however, as the carbonization temperature continues to increase, the surface density of the negative electrode material decreases slightly with the increase in temperature, because excessively high temperatures will cause part of the carbon material to gasify. Preferably, during the carbon coating process, the carbonization temperature is preferably 580°C to 720°C. Due to the presence of an appropriate amount of catalyst in the carbon matrix, the carbonization temperature during the carbon coating process can be reduced, and a dense coating layer can be obtained at a lower temperature.

[0217] The data in Tables 1-4 show that Examples 9-12 primarily explore the effects of varying silicon content on negative electrode materials. Increasing silicon content increases the specific capacity and expansion effect of the negative electrode material. Because the negative electrode material has a coating, its surface density varies little, and the gas generation values ​​of the negative electrode material also fluctuate slightly.

[0218] Compared with Example 1, Comparative Example 1 does not undergo coating treatment. The surface density of the negative electrode material is greatly reduced, the solid electrolyte membrane formed by the side reaction between the negative electrode material and the electrolyte is thickened, and a large amount of active lithium ions are consumed. The initial coulombic efficiency of the battery is greatly reduced, the volume expansion rate of the battery after cycling is also greatly increased, and the gas production value increases.

[0219] The negative electrode material prepared in Comparative Example 2 did not contain a catalyst. Because the carbon matrix lacked a catalyst, the carbon material struggled to fill the pores within the carbon matrix. Instead, the carbon material primarily coated the surface of the negative electrode material, significantly increasing the total pore volume. Simultaneously, the surface density of the negative electrode material decreased, and the gas production value of the negative electrode material also significantly increased.

[0220] The above describes in detail the structure, features and effects of the present application based on the embodiments shown in the drawings. The above is only a preferred embodiment of the present application, but the present application does not limit the scope of implementation to what is shown in the drawings. Any changes made in accordance with the concept of the present application, or modifications to equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the description and drawings, should be within the scope of protection of the present application.

Claims

1. A negative electrode material, characterized in that: The negative electrode material comprises an active material, the surface density of the negative electrode material is β, and the β is ≥ 80%; Wherein, the β is measured by the following test method: The negative electrode material with a mass of m1g is immersed in a hydrofluoric acid solution with a mass fraction of 20% for 1 hour, and then washed and dried to obtain m2g of material. The surface density of the negative electrode material is calculated to be β=m2 / m1×100%.

2. The negative electrode material according to claim 1, characterized in that: The active material includes a carbon matrix and silicon particles, and at least a portion of the silicon particles are located inside particles of the carbon matrix.

3. The negative electrode material according to claim 1, characterized in that: The negative electrode material has pores, and the pores include micropores and mesopores, wherein the ratio of the pore volume of the micropores to the pore volume of the mesopores is (1-45):(55-99).

4. The negative electrode material according to claim 3, characterized in that: The negative electrode material has at least one of the following characteristics: (1) The pore volume of micropores is ≤10%; (2) The pore volume of mesopores accounts for ≥80%; (3) The pore volume proportion of macropores is ≤20%.

5. The negative electrode material according to claim 1, characterized in that: The negative electrode material has pores, and the negative electrode material has at least one of the following characteristics: (1) The total pore volume of the negative electrode material is 0.001 cm 3 / g~0.1cm 3 / g; (2) The average pore diameter of the pores of the negative electrode material is 0.4 nm to 50 nm; (3) In the negative electrode material, the volume proportion of pores with a pore diameter of less than 10 nm in the total pore volume is ≥ 80%.

6. The negative electrode material according to claim 5, characterized in that: The negative electrode material has at least one of the following characteristics: (1) In the negative electrode material after the silicon particles are removed, the volume proportion of pores with a pore diameter of less than 2 nm in the total pore volume is ≥ 70%; (2) In the negative electrode material after the silicon particles are removed, the volume proportion of pores with a pore diameter of less than 5 nm in the total pore volume is ≥ 85%; (3) In the negative electrode material after the silicon particles are removed, the volume proportion of pores with a pore diameter of less than 10 nm in the total pore volume is ≥ 95%; (4) The specific surface area of ​​the negative electrode material after removing the silicon particles is 500m 2 / g~2000m 2 / g; (5) The total pore volume of all pores in the negative electrode material after removing silicon particles is 0.5 cm 3 / g~1.5cm 3 / g.

7. The negative electrode material according to claim 2, characterized in that The negative electrode material has at least one of the following characteristics: (1) The silicon particles include at least one of crystalline silicon, silicon oxide, amorphous silicon, silicon alloy, and composite particles of crystalline silicon and amorphous silicon; (2) The average particle size of the silicon particles is 0.1 nm to 50 nm; (3) The carbon matrix includes at least one of artificial graphite, natural graphite, amorphous carbon, activated carbon, mesophase carbon microbeads, carbon nanotubes, carbon nanofibers, porous carbon and graphene.

8. The negative electrode material according to claim 2, characterized in that The negative electrode material has at least one of the following characteristics: (1) The mass content of silicon in the negative electrode material is 20% to 60%; (2) The mass content of carbon in the negative electrode material is 20% to 80%; (3) The negative electrode material includes trace metal elements, and the trace metal elements include at least one of Fe, Co, Ni, Cr, Zn, Cu and Al; (4) The negative electrode material includes trace metal elements with a mass percentage of ≤200 ppm.

9. The negative electrode material according to claim 1, characterized in that The average gas production of the negative electrode slurry prepared from the negative electrode material when placed in a 25° C. environment for 7 days is ≤1 mL / g / day.

10. The negative electrode material according to any one of claims 1 to 9, characterized in that: The surface of the negative electrode material has a coating layer, and the material of the coating layer includes a carbon material.

11. The negative electrode material according to claim 10, characterized in that The negative electrode material has at least one of the following characteristics: (1) The carbon material includes at least one of amorphous carbon and graphitized carbon; (2) The coating layer has a thickness of 1 nm to 300 nm; (3) The mass proportion of the coating layer in the negative electrode material is ≤10%.

12. The negative electrode material according to any one of claims 1 to 9, characterized in that: The negative electrode material has at least one of the following characteristics: (1) The median particle size of the negative electrode material is ≤10 μm; (2) The particle size distribution of the negative electrode material satisfies: 0.9≤(D 90 -D 10 ) / D 50 ≤5.

13. The negative electrode material according to any one of claims 1 to 9, characterized in that: The negative electrode material has at least one of the following characteristics: (1) The specific surface area of ​​the negative electrode material is ≤10m 2 / g; (2) The compaction density of the negative electrode material is 0.8 g / cm 3 ~1.3g / cm 3 ; (3) The tap density of the negative electrode material is 0.5 g / cm 3 ~1.5g / cm 3 .

14. 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 0.5 S / cm to 5 S / cm.

15. A battery, characterized in that: The battery comprises the negative electrode material according to any one of claims 1 to 14.