Negative electrode material and battery

Abstract

The invention provides a negative electrode material and a battery. The negative electrode material comprises a silicon-based material and a carbon material located on at least part of the surface of the silicon-based material, the negative electrode material is provided with pores, the nitrogen adsorption specific surface area of all the pores in the negative electrode material is A1 m < 2 > / g, the nitrogen adsorption specific surface area of the pores with the pore diameter of more than 2nm is A2 m < 2 > / g, and the negative electrode material meets the following conditions: 1.5 < = A1 < = 5.5, 1 < = A2 < = 5, and 0.08 < = (A1-A2) / A1 < = 0.6. The negative electrode material has high specific capacity, high initial coulombic efficiency and excellent cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of negative electrode materials, in particular to a negative electrode material and a battery. BACKGROUND

[0002] New energy vehicles are the future development direction of the automobile market, and the core component is a lithium ion battery. With the development of the market, the demand for high capacity density batteries is increasing, and the use of new high specific capacity positive and negative electrode materials is one of the important methods to improve the energy density of the battery.

[0003] More and more new materials such as metals, oxides, and metal alloys are being applied as active materials in negative electrode materials to explore various ways to improve the energy density of the battery. Taking silicon-based negative electrode materials as an example, silicon-based negative electrode materials, as one of the above-mentioned active materials, are generally considered to be the next generation of negative electrode materials. They have ultra-high theoretical specific capacity (4200 mAh / g) and low delithiation potential (<0.5 V). The use of silicon-based negative electrode materials to replace pure graphite negative electrodes has become one of the effective ways to improve the specific capacity of the negative electrode. However, the poor electronic conductivity of silicon and the huge volume expansion during charging and discharging have hindered its commercial application, resulting in poor battery capacity and energy density and low cycle life.

[0004] Compared with silicon, silicon monoxide material has greatly reduced volume expansion during lithium intercalation and also has high theoretical specific capacity (>2000 mAh / g), and the preparation cost is low, so it has become a highly potential negative electrode material. However, silicon monoxide material generates Li2O and Li4SiO4 and other inactive products during lithium intercalation, which leads to the loss of part of Li activity, resulting in low first charge and discharge efficiency (<70%), which seriously affects its practical application.

[0005] Therefore, it is of great significance to develop a negative electrode material with high battery capacity and energy density, high first charge and discharge efficiency, and high cycle life. SUMMARY

[0006] The present application provides a negative electrode material and a battery. The negative electrode material can have high specific capacity, high first coulombic efficiency, and excellent cycle performance.

[0007] In a first aspect, the present application provides a negative electrode material, which comprises a silicon-based material and a carbon material located on at least part of the surface of the silicon-based material; the negative electrode material has pores, and the nitrogen adsorption specific surface area of all pores in the negative electrode material is A1 m 2 / g, the nitrogen adsorption specific surface area of pores with a pore size of 2 nm or more is A2 m 2 / g, and the negative electrode material satisfies 1.5≤A1≤5.5, 1≤A2≤5, and 0.08≤(A1-A2) / A1≤0.6.

[0008] In some embodiments, the total pore volume of the negative electrode material is 0.006 cm 3 / g~0.01 cm 3 / g.

[0009] In some embodiments, the contact angle of the negative electrode material with electrolyte having a lithium ion concentration of 1 mol / L is B1, the contact angle of the negative electrode material with water is B2, and the negative electrode material satisfies: 1

[0010] In some embodiments, 145≤B1≤155; 150≤B2≤160.

[0011] In some embodiments, 0.08

[0012] In some embodiments, the silicon-based material includes at least one of amorphous silicon, crystalline silicon, and silicon oxide;

[0013] In some embodiments, the carbon material includes at least one of amorphous carbon, carbon nanoparticles, carbon nanotubes, and graphene;

[0014] In some embodiments, the silicon-based material includes silicon oxide, the silicon oxide includes silicon elements and oxygen elements, and the atomic ratio of the silicon elements to the oxygen elements is 0~2, and does not include 0.

[0015] In some embodiments, the silicon-based material includes silicon oxide, and the chemical general formula of the silicon oxide is SiO x , wherein 0

[0016] In some embodiments, in the negative electrode material, the volume ratio of micropores in the total pore volume of all pores is 6%~9%, and the volume ratio of mesopores in the total pore volume of all pores is 80%~90%.

[0017] In some embodiments, the mass content of silicon elements in the negative electrode material is m Si %, and 53%≤m Si ≤64%.

[0018] In some embodiments, the mass content of oxygen elements in the negative electrode material is m O %, and 35%≤m O ≤37%.

[0019] In some embodiments, the mass content of carbon element in the negative electrode material is m C %, 1%≤m C ≤6%.

[0020] In some embodiments, the median particle size D 50 of the negative electrode material is 1 μm-10 μm;

[0021] In some embodiments, the specific surface area of the negative electrode material is ≤20 m 2 / g;

[0022] In some embodiments, the compaction density of the negative electrode material is 1.28 g / cm 3 -1.40 g / cm 3 ;

[0023] In some embodiments, the true density of the negative electrode material is 2.20 g / cm 3 -2.30 g / cm 3 ;

[0024] In some embodiments, the powder conductivity of the negative electrode material is 1 S / cm-3 S / cm.

[0025] In a third aspect, the present application provides a battery comprising the negative electrode material according to the first aspect or prepared by the method according to the second aspect.

[0026] The technical solution of the present application has at least the following beneficial effects:

[0027] The negative electrode material provided in the application is beneficial to improving the fine and close degree of the negative electrode material by controlling the specific surface area of all pores of the negative electrode material and the specific surface area of mesopores. A1-A2 can represent the specific surface area of pores with a pore size of 2 nm or less in all pores of the negative electrode material. When (A1-A2) / A1>0.6, the specific surface area of the pores with a pore size of 2 nm or less in the negative electrode material is too large, the side reaction between the negative electrode material and the electrolyte is intensified during the charge and discharge cycle process after the battery is prepared, and the initial coulomb efficiency of the negative electrode material decreases. When (A1-A2) / A1<0.08, the specific surface area of the pores with a pore size of 2 nm or less in the negative electrode material is too small, which makes it difficult for the electrolyte to quickly enter the negative electrode material, reduces the transmission efficiency of lithium ions, reduces the specific capacity and the initial coulomb efficiency of the negative electrode material, and further affects the energy density and the charging rate of the battery. The application controls 1.5≤A1≤5.5, 1≤A2≤5, and (A1-A2) / A1 is in the range of 0.08-0.6, so that the specific surface area of the pores in the negative electrode material is in a suitable range, which can not only ensure that the negative electrode material can be effectively infiltrated with the electrolyte and improve the transmission efficiency of lithium ions, but also reduce the side reaction between the negative electrode material and the electrolyte, improve the specific capacity and the initial coulomb efficiency of the negative electrode material, and improve the cycle stability of the negative electrode material. The battery prepared from the negative electrode material can also have a faster charge and discharge rate. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The discharge state schematic diagram of the battery provided in the application is shown. DETAILED DESCRIPTION

[0029] The following is a preferred embodiment of the application, and it should be pointed out that those skilled in the art can make several improvements and refinements without departing from the principles of the application, and these improvements and refinements are also considered within the protection scope of the application.

[0030] In a first aspect, the application provides a negative electrode material, which comprises a silicon-based material and a carbon material located on at least part of the surface of the silicon-based material; the negative electrode material has pores, and the pores include micropores and mesopores, wherein the nitrogen adsorption specific surface area of all pores in the negative electrode material is A1 m 2 / g, the nitrogen adsorption specific surface area of pores with a pore size of 2 nm or more is A2 m 2 / g, and the negative electrode material satisfies 1.5≤A1≤5.5, 1≤A2≤5, and 0.08≤(A1-A2) / A1≤0.6.

[0031] The negative electrode material provided in the application controls the specific surface area of all pores and the specific surface area of mesopores of the negative electrode material, wherein A1-A2 can represent the specific surface area of pores with a pore diameter of 2 nm or less in all pores of the negative electrode material. When (A1-A2) / A1>0.6, the specific surface area of pores with a pore diameter of 2 nm or less in the negative electrode material is too large, and the side reaction between the negative electrode material and the electrolyte is intensified during the charge-discharge cycle process after the battery is prepared, and the initial coulomb efficiency of the negative electrode material decreases. When (A1-A2) / A1<0.08, the specific surface area of pores with a pore diameter of 2 nm or less in the negative electrode material is too small, which makes it difficult for the electrolyte to quickly enter the negative electrode material, reduces the transmission efficiency of lithium ions, reduces the specific capacity and the initial coulomb efficiency of the negative electrode material, and further affects the energy density and the charging rate of the battery. The application controls 1.5≤A1≤5.5, 1≤A2≤5, and (A1-A2) / A1 is in the range of 0.08-0.6, and it can be understood that A1>A2, so that the specific surface area of the pores in the negative electrode material is in a suitable range, which can not only ensure that the negative electrode material can be effectively infiltrated with the electrolyte and improve the transmission efficiency of lithium ions, but also reduce the side reaction between the negative electrode material and the electrolyte, improve the specific capacity and the initial coulomb efficiency of the negative electrode material, and improve the cycle stability of the negative electrode material. The battery prepared from the negative electrode material can also have a faster charge-discharge rate.

[0032] In some embodiments, (A1-A2) / A1 can be specifically 0.08, 0.081, 0.085, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.59 or 0.6, and of course can also be other values in the above range.

[0033] In some embodiments, the specific surface area of all pores in the negative electrode material is A1 m 2 / g, 1.5≤A1≤5.5, and specifically A1 can be 1.5 m 2 / g, 1.8 m 2 / g, 2.0 m 2 / g, 2.5 m 2 / g, 2.8 m 2 / g, 3.0 m 2 / g, 3.5 m 2 / g, 4.0 m 2 / g, 4.5 m 2 / g, 4.8 m 2 / g, or 5.5 m 2 / g, and of course can also be other values in the above range, which are not limited herein.

[0034] In some embodiments, the specific surface area of pores with a pore diameter of 2 nm or more in the negative electrode material is A2 m 2 / g, 1≤A2≤5, and specifically A1 can be 1 m2 / g, 1.1 m 2 / g, 1.2 m 2 / g, 1.5 m 2 / g, 2.0 m 2 / g, 2.8 m 2 / g, 3.0 m 2 / g, 3.5 m 2 / g, 4.0 m 2 / g, 4.5 m 2 / g, 4.8 m 2 / g or 5.0 m 2 / g, etc., and of course other values within the above ranges are also possible and are not limited herein.

[0035] In some embodiments, the total pore volume of the negative electrode material is 0.006 cm 3 / g to 0.01 cm 3 / g, and specifically can be 0.006 cm 3 / g, 0.0065 cm 3 / g, 0.007 cm 3 / g, 0.0075 cm 3 / g, 0.008 cm 3 / g, 0.0085 cm 3 / g, 0.009 cm 3 / g, 0.0095 cm 3 / g or 0.01 cm 3 / g, etc., and of course other values within the above ranges are also possible and are not limited herein. The presence of an appropriate amount of pores in the negative electrode material can alleviate the volume expansion of the silicon-based material, and is conducive to the effective infiltration of the negative electrode material with the electrolyte and the improvement of the transmission efficiency of lithium ions.

[0036] In some embodiments, the contact angle of the negative electrode material with the electrolyte having a lithium ion concentration of 1 mol / L is B1, the contact angle of the negative electrode material with water is B2, and the negative electrode material satisfies: 1 < B2 / B1 < 1.1, and specifically B2 / B1 can be 1.01, 1.05, 1.06, 1.07, 1.08, 1.09 or 1.095, etc., and of course other values within the above ranges are also possible and are not limited herein. The electrolyte is formed by dissolving lithium hexafluorophosphate in an organic solvent, and the organic solvent is a mixture of methyl ethyl carbonate, vinyl carbonate and dimethyl carbonate in a volume ratio of 1:1:1.

[0037] The application controls the specific surface area of the pores of the negative electrode material, controls the ratio of the contact angle of the negative electrode material and electrolyte to the contact angle of the negative electrode material and water, when the ratio of B2 / B1 is within the above range, the electrolyte can quickly infiltrate the negative electrode material without affecting the coating dispersion state of the negative electrode material, the electrolyte quickly penetrates into the negative electrode material, which can improve the specific capacity, the first coulombic efficiency and the charging rate of the negative electrode material, and can also reduce the interface impedance of the electrolyte and the negative electrode material, and improve the cycle stability of the negative electrode material.

[0038] In some embodiments, the contact angle of the negative electrode material and the electrolyte with a lithium ion concentration of 1 mol / L is B1°, 145°≤B1≤155°, and specifically can be 145°, 147°, 148°, 150°, 152°, 153° or 155°, and of course can also be other values within the above range, which are not limited herein. When B1 is too small, the electrolyte can easily penetrate into the interior of the negative electrode material, the side reaction of the negative electrode material and the electrolyte is intensified, the irreversible consumption of active lithium ions increases, the specific capacity of the negative electrode material decreases, and the cycle retention rate decreases. When B1 is too large, the electrolyte is difficult to penetrate into the interior of the negative electrode material, although the side reaction is reduced, the impedance of the interface of the negative electrode material and the electrolyte increases, the specific capacity of the negative electrode material is difficult to effectively play, and the battery energy density decreases.

[0039] In some embodiments, the contact angle of the negative electrode material and water is B2°, 150°≤B2≤160°, and specifically can be 150°, 152°, 155°, 156°, 158°, 159° or 160°, and of course can also be other values within the above range, which are not limited herein.

[0040] In some embodiments, 0.08 < [(A1-A2) / A1] / (B2 / B1) < 0.7, and the ratio can be specifically 0.082, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, or 0.65, and the like, and of course can be other values within the above range, which are not limited herein. When the ratio of [(A1-A2) / A1] / (B2 / B1) is too small, it can be due to that (A1-A2) / A1 is too small, the specific surface area of the pores of the negative electrode material is small, the number of pores is small, the expansion effect of the negative electrode material is intensified, and the cycle performance of the negative electrode material is reduced; or it can be due to that B2 / B1 is too large, the contact angle between the negative electrode material and water is too large, which affects the dispersion state of the negative electrode material in the coating process, and causes the local expansion of the negative electrode sheet to be intensified in the charging and discharging process, thereby affecting the cycle performance of the battery. When the ratio of [(A1-A2) / A1] / (B2 / B1) is too large, it can be due to that (A1-A2) / A1 is too large, the electrolyte is easy to enter the pores of the negative electrode material, thereby causing the side reaction of the negative electrode material to be intensified, and the initial coulomb efficiency of the negative electrode material to be reduced; or it can be due to that B2 / B1 is too small, thereby causing the contact angle between the negative electrode material and the electrolyte to be too large, the electrolyte is difficult to penetrate into the interior of the negative electrode material particles, the impedance of the interface between the negative electrode material and the electrolyte is increased, and the specific capacity of the negative electrode material is difficult to be effectively exerted. The present application controls [(A1-A2) / A1] / (B2 / B1) within the above range, which is synergistically controlled from the two aspects of the contact angle of the electrolyte and the specific surface area of the pores of the negative electrode material, can reduce the side reaction between the electrolyte and the negative electrode material, improve the expansion effect of the negative electrode material, and is beneficial to obtaining a negative electrode material with high specific capacity, good cycle performance, and high initial coulomb efficiency. Preferably, 0.08 < [(A1-A2) / A1] / (B2 / B1) < 0.365.

[0041] In some embodiments, the silicon-based material includes at least one of amorphous silicon, crystalline silicon, and silicon oxide.

[0042] In some embodiments, the silicon oxide includes silicon elements and oxygen elements, and the atomic ratio of the silicon elements to the oxygen elements is 0-2, and 0 is excluded. The atomic ratio of the silicon elements to the oxygen elements can be specifically 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, and the like, which are not limited herein. Preferably, the atomic ratio of the silicon elements to the oxygen elements is 0-1, and 0 is excluded.

[0043] In some embodiments, the chemical formula of the silicon oxide is SiO xwherein 0 < x ≤ 2, x can be specifically 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., which are not limited herein. Preferably, 0 < x < 1. The silicon-oxygen material can be a material formed by dispersing silicon particles in SiO2, or a material having tetrahedral structural units, with silicon atoms at the center of the tetrahedral structural units and oxygen atoms and / or silicon atoms at the four vertices of the tetrahedral structural units.

[0044] In some embodiments, the carbon material comprises at least one of amorphous carbon, carbon nanoparticles, carbon nanotubes and graphene. Preferably, the carbon material comprises amorphous carbon, and the amorphous carbon and the silicon-based material are compounded, which can comprehensively improve the conductivity of the negative electrode material and reduce the expansion.

[0045] In some embodiments, the silicon-based material is dispersed in the carbon material, and the carbon material forms a conductive network for the silicon-based material, overcoming the poor conductivity of the silicon-based material (e.g. the silicon-oxygen material SiO x ) and facilitating the capacity development and cycle stability of the silicon-based material.

[0046] In some embodiments, in the negative electrode material, the volume ratio of the micropores in the total pore volume of all pores is 6% to 9%, and the volume ratio of the mesopores in the total pore volume of all pores is 80% to 90%. According to the definition of the International Union of Pure and Applied Chemistry (IUPAC), pores with a pore size less than 2 nm are called micropores; pores with a pore size greater than 50 nm are called macropores; and pores with a pore size between 2 nm and 50 nm are called mesopores (or called mesopores).

[0047] Specifically, the volume ratio of the micropores can be specifically 6%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 8%, 8.5%, 8.8% or 9%, etc., which are not limited herein. The volume ratio of the mesopores can be specifically 80%, 85%, 88%, 89% or 90%, etc., which are not limited herein.

[0048] In some embodiments, the negative electrode material has a median particle size D 50 of 1 μm to 10 μm; specifically, 1 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 5 μm, 6 μm, 8 μm, 9 μm or 10 μm, etc., which are not limited herein.

[0049] In some embodiments, the negative electrode material has a specific surface area ≤ 20 m 2 / g; specifically, 1.0 m 2 / g, 1.5 m / g, 2.0 m / g, 2.5 m / g, 3.0 m / g, 3.5 m / g, 4.0 m / g, 4.5 m / g, 5.0 m / g, 5.5 m / g, 6.0 m / g, 6.5 m / g, 7.0 m / g, 7.5 m / g, 8.0 m / g, 8.5 m / g, 9.0 m / g, 9.5 m / g, 10.0 m / g, 10.5 m / g, 11.0 m / g, 11.5 m / g, 12.0 m / g, 12.5 m / g, 13.0 m / g, 13.5 m / g, 14.0 m / g, 14.5 m / g, 15.0 m / g, 15.5 m / g, 16.0 m / g, 16.5 m / g, 17.0 m / g, 17.5 m / g, 18.0 m / g, 18.5 m / g, 19.0 m / g, 19.5 m / g, 20.0 m / g, etc., which are not limited herein.2 / g, 1.8m 2 / g, 2.0m 2 / g, 2.5m 2 / g, 3.0m 2 / g, 3.6m 2 / g, 4.0m 2 / g、5m 2 / g, 5.5m 2 / g, 6.0m 2 / g, 7.0m 2 / g, 8.0m 2 / g, 8.5m 2 / g, 10.0m 2 / g, 12.0m 2 / g, 15.0m 2 / g, 18.0m 2 / g or 20.0m 2 / g, but not limited to the listed values; other unlisted values ​​within this range also apply. Controlling the specific surface area of ​​the anode material within the above range is beneficial for improving its initial coulombic efficiency. When the specific surface area of ​​the anode material is too large, side reactions between the anode material and the electrolyte increase, consuming more active lithium ions and reducing the initial coulombic efficiency of the anode material. Preferably, the specific surface area of ​​the anode material is ≤10m². 2 / g.

[0050] In some embodiments, the compaction density of the negative electrode material is 1.28 g / cm³. 3 ~1.40g / cm 3 Specifically, it could be 1.28 g / cm³. 3 1.30g / cm 3 1.31 g / cm 3 1.32g / cm 3 1.33g / cm 3 1.35g / cm 3 1.38g / cm 3 1.39 g / cm 3 Or 1.40g / cm 3 etc. are not specified here.

[0051] In some embodiments, the true density of the negative electrode material is 2.20 g / cm³. 3 ~2.30g / cm 3 Specifically, it could be 2.20 g / cm³. 3 2.22 g / cm 3 2.23 g / cm 3 2.24 g / cm 3 2.25g / cm3 2.26 g / cm3 3 2.28 g / cm3 3 2.30 g / cm3 3 etc., without limitation.

[0052] In some embodiments, the powder conductivity of the negative electrode material is 1 S / cm to 3 S / cm at a pressure of 20 kN, specifically 1.0 S / cm, 1.1 S / cm, 1.3 S / cm, 1.5 S / cm, 1.8 S / cm, 2.0 S / cm, 2.5 S / cm, or 3 S / cm, etc., and of course, other values within the above range are also possible, without limitation. The powder conductivity of the negative electrode material is preferably beneficial to improve the cycle performance of the negative electrode material. When the powder conductivity of the negative electrode material is too small, the structure of the negative electrode material is looser or the conductive network is poorer, and the cycle stability is reduced.

[0053] In some embodiments, the mass content of silicon in the negative electrode material is m Si % and 53%≤m Si ≤64%; specifically 53%, 56%, 58%, 60%, 62%, 63%, or 64%, etc., and of course, other values within the above range are also possible, without limitation.

[0054] In some embodiments, the mass content of oxygen in the negative electrode material is m O % and 35%≤m O ≤37%; specifically 35%, 35.5%, 35.8%, 36%, 36.2%, 36.4%, 36.5%, 36.8%, or 37%, etc., and of course, other values within the above range are also possible, without limitation.

[0055] In some embodiments, the mass content of carbon in the negative electrode material is m C % and 1%≤m C ≤6%; specifically 1%, 2%, 3%, 4%, 4.5%, 5%, 5.5%, or 6%, etc., and of course, other values within the above range are also possible, without limitation.

[0056] In some embodiments, the non-graphitic carbon material is located on the surface of the silicon-based material to form a carbon layer. The non-graphitic carbon material can be located on the surface of the silicon-based material particles, or on the surface of the carbon material particles, or the silicon-based material particles and the carbon material particles can be secondarily granulated and coated to form secondary particles, without limitation.

[0057] In some embodiments, the thickness of the carbon layer is 1 nm to 1000 nm, and 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. If the carbon layer is too thick, the proportion of carbon is too high, which is not conducive to obtaining a high specific capacity negative electrode material. If the carbon layer is too thin, it is not conducive to increasing the conductivity of the negative electrode material and the volume expansion inhibition performance of the material is weak, resulting in poor long cycle performance. Controlling the thickness of the carbon layer in the above range is conducive to improving the conductivity and cycle stability of the negative electrode material. Preferably, the thickness of the carbon layer is 50 nm to 800 nm; more preferably, the thickness of the carbon layer is 100 nm to 500 nm.

[0058] In a second aspect, the application provides a preparation method of a negative electrode material, comprising the following steps:

[0059] In step S10, the silicon powder is placed in a mixed acid solution containing hydrofluoric acid and copper nitrate for primary acid washing, and then placed in a nitric acid solution for secondary acid washing, and the silicon powder after secondary acid washing is obtained through solid-liquid separation.

[0060] In step S20, the silicon powder after secondary acid washing without drying is subjected to surface plasma treatment to obtain a precursor, and the precursor comprises silicon monoxide.

[0061] In step S30, the precursor is subjected to carbon coating treatment to obtain a negative electrode material.

[0062] In the above scheme, the silicon powder is placed in a mixed acid solution for primary acid washing, and the hydrofluoric acid can etch the surface of the silicon powder. In the secondary acid washing process, the etching extends from the surface of the particles to the inside, so that the silicon powder forms fine and dense etching holes. Then the silicon powder is subjected to surface plasma treatment, and the plasma bombards the inside of the silicon particles along the etching holes on the surface of the silicon powder, and the etching holes continue to extend to the inside of the particles, increasing the total pore volume of the negative electrode material. At the same time, the plasma oxidizes the silicon particles, so that at least part of the silicon is oxidized to silicon monoxide. Finally, carbon coating treatment is used to form a carbon layer on the surface of the precursor. The existence of the carbon layer can reduce the side reaction between the active material and the electrolyte, improve the specific capacity and the first coulombic efficiency of the negative electrode material, and improve the cycle stability of the negative electrode material.

[0063] In step S10, the silicon powder is placed in a mixed acid solution containing hydrofluoric acid and copper nitrate for primary acid washing, and then placed in a nitric acid solution for secondary acid washing, and the silicon powder after secondary acid washing is obtained through solid-liquid separation.

[0064] In some embodiments, the concentration of the hydrofluoric acid is 4 mol / L to 10 mol / L, and can be 4 mol / L, 4 mol / L, 4 mol / L, 4 mol / L, 4 mol / L, 4 mol / L, or 4 mol / L, etc., without limitation.

[0065] In some embodiments, the amount of copper nitrate added to the mixed acid solution is 30 mmol to 40 mmol, and can be 30 mmol, 32 mmol, 34 mmol, 35 mmol, 36 mmol, 38 mmol, or 40 mmol, etc., without limitation.

[0066] In some embodiments, the silicon powder is added to the mixed acid solution in multiple times, and the stirring is performed for 2 h to 4 h for each acid washing.

[0067] In some embodiments, the stirring time for each acid washing can be 2 h, 2.5 h, 3 h, 3.5 h, or 4 h, etc., without limitation.

[0068] In some embodiments, the median particle size of the silicon powder is 1 μm to 5 μm, and can be 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm, etc., without limitation.

[0069] In some embodiments, the product after the acid washing is placed in a plastic centrifuge tube, the centrifugal speed is adjusted to 1000 r / min to 4000 r / min, and the solid-liquid separation is performed to obtain the silicon powder.

[0070] It can be understood that, after the silicon powder is added to the mixed acid solution, the hydrofluoric acid can etch the surface of the silicon powder, and in the state of centrifugal stirring, the etching extends from the surface to the inside of the particles, so that the silicon powder forms fine etching holes.

[0071] In some embodiments, a solution of H3NO3 with a concentration of 15 mol / L to 30 mol / L is prepared, then 15% ethanol by volume is added and stirred for 2 h to 4 h to obtain a secondary acid washing solution.

[0072] In some embodiments, the silicon powder after the first acid washing is placed in the secondary acid washing solution and continuously stirred for 2 h to 6 h, and then the solution is filtered by using a filter press to obtain the silicon powder.

[0073] In step S20, the silicon powder after the secondary acid washing without drying is subjected to surface plasma treatment to obtain a precursor, and the precursor includes silicon monoxide.

[0074] In some embodiments, the output current in the plasma furnace is 130 A to 160 A, and the output voltage is 5 V. Specifically, the output current can be 130 A, 135 A, 140 A, 145 A, 150 A, 155 A, or 160 A, etc., without limitation.

[0075] In some embodiments, the heating temperature during the plasma treatment is 400-600°C, and can be 400°C, 450°C, 500°C, 550°C, 580°C, or 600°C, etc.

[0076] In some embodiments, the plasma treatment time is 3-6h, and can be 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, or 6h, etc.

[0077] In some embodiments, the cooling water temperature of the plasma furnace is 30-60°C, and the cooling water mother pipe pressure is 0.3-0.6MPa. The cooling water temperature can be 30°C, 35°C, 40°C, 450°C, 50°C, 55°C, or 60°C, etc., and the cooling water mother pipe pressure can be 0.3MPa, 0.35MPa, 0.4MPa, 0.45MPa, 0.5MPa, 0.6MPa, etc.

[0078] In some embodiments, oxygen is introduced during the plasma treatment, and the oxygen concentration is >99%.

[0079] In step S30, the precursor is subjected to carbon coating treatment to obtain the negative electrode material.

[0080] In some embodiments, the carbon coating treatment includes one or more combinations of liquid phase coating, solid phase coating, and gas phase coating.

[0081] In some embodiments, the carbon coating treatment specifically includes uniformly mixing a liquid phase carbon source and the precursor to obtain a mixture.

[0082] In some embodiments, the mixing method includes at least one of VC mixing, fusion, three-eccentricity, hand mixing, kneading, spiral mixing, and ball milling.

[0083] In some embodiments, the liquid phase carbon source includes at least one of pitch, coal-based carbon, petroleum-based carbon, biomass, alkane, alkene, and alkyne. Specifically, the pitch includes at least one of coal tar pitch, petroleum pitch, and natural pitch.

[0084] In some embodiments, the carbon coating treatment further includes: after heating the mixture, introducing a protective gas and a carbon source gas, and subjecting the carbon source gas to thermal cracking to obtain a carbon coating product.

[0085] In some embodiments, the carbon source gas used in the gas phase carbon coating includes a hydrocarbon.

[0086] In some embodiments, the carbon source gas includes at least one of methane, acetylene, ethylene, ethane, propane, propylene, propyne, acetone, and benzene.

[0087] In some embodiments, the chemical vapor deposition device comprises at least one of a rotating chemical vapor deposition reaction furnace, a plasma enhanced chemical vapor deposition reaction furnace, a chemical vapor deposition tube furnace, and a fluidized bed. Specifically, the chemical vapor deposition device is at least one of a rotating furnace and a box furnace.

[0088] In some embodiments, the temperature of the thermal cracking is 300-1000℃, and specifically can be 300℃, 500℃, 600℃, 700℃, 800℃, 900℃, 950℃, or 1000℃, and of course can also be other values within the above range, which are not limited herein.

[0089] In some embodiments, the time of the thermal cracking is 2-10h, and specifically can be 2h, 4h, 5h, 6h, 8h, 9h, or 10h, and of course can also be other values within the above range, which are not limited herein.

[0090] In some embodiments, the carbon source gas is introduced under a protective gas.

[0091] In some embodiments, the protective gas comprises at least one of nitrogen, helium, neon, argon, krypton, and xenon.

[0092] In some embodiments, the thickness of the carbon layer is 1-1000nm, and specifically can be 1nm, 5nm, 10nm, 15nm, 20nm, 50nm, 80nm, 100nm, 150nm, 200nm, 400nm, 500nm, 700nm, 800nm, 900nm, 1000nm, and the like, which are not limited herein. 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 high specific capacity; and the carbon layer can effectively alleviate the volume expansion of the silicon-based material, and improve the long cycle performance of the negative electrode material. Preferably, the thickness of the carbon layer is 50-800nm; more preferably, the thickness of the carbon layer is 100-500nm.

[0093] Further, the method further comprises: screening and demagnetizing the material after the carbon coating treatment to obtain the negative electrode material.

[0094] In some embodiments, the screening method is any one of a fixed screen, a drum screen, a resonance screen, a roller screen, a vibrating screen, and a chain screen, and the mesh number of the screening is 100-500 meshes, and specifically can be 100 meshes, 200 meshes, 250 meshes, 325 meshes, 400 meshes, 500 meshes, and the like, and preferably, the mesh number of the screening is 250 meshes, and the particle size of the negative electrode material is controlled within the above range, which is conducive to improving the processing performance of the negative electrode material.

[0095] In some embodiments, the magnetic removal device is any one of a permanent drum magnetic separator, an electromagnetic iron remover, and a pulsating high gradient magnetic separator, and the magnetic removal is for finally controlling the content of magnetic substances in the negative electrode material, avoiding the influence of the magnetic substances on the discharge effect of the lithium ion battery and the safety of the battery during use.

[0096] The embodiment of the present application also provides a battery, Figure 1 The discharge state diagram of the battery provided by the embodiment of the present application is shown in Figure 1 As shown in the figure, the battery comprises a shell and an electrode assembly, and the electrode assembly comprises a positive electrode sheet 1, a negative electrode sheet 2 and a separator 3, and the separator 3 is arranged between the positive electrode sheet 1 and the negative electrode sheet 2. The electrode assembly can be a laminated structure, which is formed by alternately stacking the positive electrode sheet 1, the separator 3 and the negative electrode sheet 2 in sequence. In other embodiments, the electrode assembly can also be a wound structure, which is formed by winding the positive electrode sheet, the separator and the negative electrode sheet in sequence.

[0097] In some embodiments, the positive electrode sheet 1 comprises a positive electrode current collector 101 and a positive electrode active layer 102 arranged on at least one surface of the positive electrode current collector 101.

[0098] In some embodiments, the positive electrode current collector 101 can use an aluminum foil or a nickel foil, etc., and can also be any composite current collector disclosed in the prior art, such as but not limited to the aforementioned conductive foil (aluminum foil or nickel foil, etc.) and the current collector combined with a polymer substrate. The positive electrode active layer 102 comprises a positive electrode active material, and the positive electrode active material comprises a compound that reversibly intercalates and deintercalates metal ions.

[0099] In some embodiments, the positive electrode active material can include a lithium transition metal composite oxide, a sodium transition metal composite oxide, etc. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese and nickel.

[0100] In some embodiments, the positive electrode active material can include at least one of lithium cobaltate (LiCoO2), lithium nickel manganese cobalt ternary material (NCM), lithium manganate (LiMn2O4), lithium nickel manganate (LiNiMnO4) or lithium iron phosphate (LiFePO4), but is not limited thereto. 4) 0.5 Mn 1.5 O4) or lithium iron phosphate (LiFePO4).

[0101] In some embodiments, the negative electrode sheet 2 comprises a negative electrode current collector 201 and a negative electrode active material layer 202 arranged on at least one surface of the negative electrode current collector.

[0102] ​In some embodiments, the negative current collector 201 can use at least one of a copper foil, a nickel foil, a stainless steel foil, a titanium foil, or a carbon-based current collector, etc., and can also be any composite current collector disclosed in the prior art, such as but not limited to a current collector formed by combining the aforementioned conductive foils and polymer substrates. The negative active material layer 202 includes a negative electrode material, which is the negative electrode material of the first aspect described above or the negative electrode material obtained by the preparation method described above.

[0103] The battery provided by the embodiments of the present application has the advantages of high capacity, high initial efficiency, long cycle life, excellent rate performance, and low swelling. The battery can be a lithium ion battery, a sodium ion battery, a solid electrolyte battery, etc., without limitation.

[0104] The embodiments of the present application are further described below in multiple embodiments. The following embodiments are exemplary and are used to explain the present application, and cannot be understood as limiting the present application; it should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as understood by those skilled in the art in the technical field of the present application; the embodiments of the present application and the features in the embodiments can be combined with each other without conflict; many specific details are described in the following description in order to fully understand the present application, and the described embodiments are only part of the embodiments of the present application, not all the embodiments.

[0105] The embodiments of the present application are further described below in multiple embodiments.

[0106] Embodiment 1

[0107] A preparation method of a negative electrode material, comprising the following steps:

[0108] (1) 3 g of silicon powder with D50 = 3 μm is added into a 40 mmol Cu(NO3)2 and 4.6 mol / L HF mixed acid solution for one acid treatment in three times (1 g each time), and after stirring for 3 h, it is placed in a plastic centrifuge tube, the centrifugal speed is adjusted to 4000 r / min, after removing the solution in the centrifuge, the silicon powder is obtained. 15 mol / L H3NO3 and 15% ethanol are added again and stirred for 2 h, and then the silicon powder after centrifugation is added and stirred for 2 h for secondary acid treatment, and then the solution is filtered by a filter machine, and the acid-treated silicon powder is obtained.

[0109] (2) Put the silicon powder after acid treatment and without drying into a plasma furnace, control the output current of the plasma furnace to be 150 A, the output voltage to be 5 V, oxygen with a concentration > 99% is introduced into the plasma furnace, heat the silicon powder to 400 ℃ for 3 h, control the cooling water temperature in the plasma furnace to be 40 ℃, the mother tube pressure of the cooling water to be 0.6 MPa during the plasma process, turn off the current and voltage after the heat preservation is completed, and cool to obtain a precursor, wherein the precursor comprises silicon monoxide.

[0110] (3) Put the precursor into liquid pitch according to a mass ratio of 100:5, mix for 2 h, introduce acetylene under nitrogen protection, heat to 300 ℃, and take out after heat preservation for 4 h to obtain the negative electrode material.

[0111] According to the preparation steps of Example 1, Examples 2-10 are prepared, and the process parameters of each example are shown in Table 1.

[0112] Table 1. Process parameter summary table of negative electrode material

[0113]

[0114] Comparative Example 1

[0115] A preparation method of a negative electrode material, comprising the following steps:

[0116] (1) Put 1.5 kg of silicon and 1.5 kg of silicon dioxide into a vacuum furnace, heat to 1600 ℃ for 6 h after the vacuum degree is 100 Pa, and obtain silicon monoxide.

[0117] (2) After cooling to 1100 ℃, introduce acetylene to perform carbon coating treatment on the surface of the silicon monoxide, wherein the carbon content of the carbon-containing gas is about 30%, and the carbon coating amount is less than 3%, to obtain the negative electrode material.

[0118] Comparative Example 2

[0119] Different from Example 1 is that step (2) is not performed.

[0120] The performance of the negative electrode material prepared in the examples and comparative examples is tested, and the results of the above performance tests are shown in Tables 2-3:

[0121] Test method:

[0122] 1) Particle size of the negative electrode material:

[0123] The particle size test method refers to GB / T 19077-2016. The volume-based cumulative particle size distribution of the particles is measured by laser diffraction method, D10 represents the particle size corresponding to the volume cumulative particle size distribution percentage of 10%, D50 represents the particle size corresponding to the volume cumulative particle size distribution percentage of 50%, and D90 represents the particle size corresponding to the volume cumulative particle size distribution percentage of 90%.

[0124] 2) Test method of specific surface area and pore of negative electrode material:

[0125] Under constant low temperature, the adsorption amount of gas on the surface of solid at different relative pressures is measured, and then the monolayer adsorption amount of the sample is obtained based on the Brunauer-Emmett-Teller adsorption theory and its formula (BET formula), so as to calculate the specific surface area and total pore volume of the material.

[0126] Nitrogen adsorption specific surface area of mesopore (pore size greater than 2 nm): test relative pressure range: 0.05-0.30 Pa, pretreatment condition: 300℃, 1h, nitrogen purge, sample weight: 1 / 2-2 / 3 of the volume of the bubble tube.

[0127] Nitrogen adsorption specific surface area of all pores: test relative pressure range: 0-1 Pa, pretreatment condition: 300℃, 2h, vacuum. Sample weight: 0.15±0.3g.

[0128] 3) Proportion of pore volume of various types of pores in negative electrode material

[0129] Nitrogen adsorption technology is used to test the porosity and pore size distribution of the negative electrode material. As the pressure rises, nitrogen is first condensed in the pores with the smallest diameter, and the pressure rises until it reaches the saturation point, at which point all the pores are filled with liquid. Then the nitrogen pressure is gradually reduced to evaporate the liquid from the system. Analysis of the adsorption and desorption isotherms makes it possible to determine the pore volume and pore size distribution, as well as the respective pore volume of micropores, mesopores and macropores in the total pore volume.

[0130] 4) Test method of mass content of carbon element in negative electrode material:

[0131] The carbon content of the material is tested using an infrared carbon and sulfur analyzer (Germany Eltra, CSI).

[0132] 5) Test method of mass content of oxygen element in negative electrode material:

[0133] The mass content of oxygen in the negative electrode material is tested using an oxygen, nitrogen and hydrogen analyzer (Eltra, ONH-2000).

[0134] 6) Test method of mass content of silicon element in negative electrode material:

[0135] According to the measured mass content m of carbon element in the negative electrode material C , the mass content m of oxygen element O , the mass content of silicon element m is calculated Si = 1-m C -m O .

[0136] 7) Negative electrode material compaction density test method:

[0137] According to GB / T 24533-2019, the compaction density of the material is tested, and the test equipment adopts compaction density instrument (McNairn, CARVER 4350).

[0138] 8) Negative electrode material true density test method:

[0139] True density test: According to GB / T 24533-2019, the true density of the material is tested, and the test equipment adopts true density tester (Belsize, 3H-2000TD).

[0140] 9) Contact angle test of negative electrode material and electrolyte or water:

[0141] Contact angle: in-situ video contact angle measuring instrument is adopted.

[0142] Process: compress and smooth the surface of the sample powder, drop a certain volume of liquid at a certain height above it, record the process of liquid drop on the sample plane, and measure the contact angle of the liquid drop when the liquid drop and the plane are in contact (circular method).

[0143] 10) Powder conductivity test of negative electrode material

[0144] According to the equipment and method of BTRTC / ZY / 02-093 "Powder Conductivity Test Operation Instruction", the powder conductivity of the negative electrode material is tested. The test equipment is from Mitsubishi Chemical, Japan, and the test parameters are: the initial resistance order can be selected-3, the voltage limit can be selected 10V, and the sample mass is ensured to be 3-5mm thick under the pressure of 20KN. The pressure is set to 4, 8, 12, 16, 20KN. Electrode radius is 0.7mm, Sample radius is 10mm.

[0145] 11) Button cell test

[0146] The prepared negative electrode material, conductive carbon black and polyacrylic acid binder are mixed in a mass percentage of 75:15:10, dissolved in a solvent, coated on a copper foil current collector, vacuum dried, and a negative electrode sheet is prepared; a lithium metal sheet is used as a counter electrode, and a button cell is assembled in an argon-filled glove box. The charge-discharge test is carried out at a current density of 0.1C and in a charge-discharge interval of 0.01-1.5V.

[0147] 12) Electrochemical performance test

[0148] The prepared negative electrode material is mixed with graphite at a ratio of 10:90, and then mixed with sodium carboxymethyl cellulose CMC, binder styrene-butadiene rubber SBR, conductive agent Super-P and conductive agent KS-6 at a mass ratio of 92:2:2:2 to form a slurry, which is coated on a copper foil and vacuum dried and rolled to prepare a negative electrode sheet; then a ternary positive electrode sheet prepared by a conventional mature process, 1 mol / L LiPF6 / ethylene carbonate + dimethyl carbonate + methyl ethyl carbonate (v / v = 1:1:1) electrolyte, Celgard2400 separator and shell are assembled into a CR2016 simulation battery using a conventional production process. The cycle performance test uses a constant current charge-discharge experiment at a current of 30mA, and the charge-discharge voltage is limited to 0-1.5V. The LAND battery test system of Wuhan Jinuo Electronics Co., Ltd. is used for testing. The charge-discharge test is carried out at a current density of 0.1C and in a charge-discharge interval of 0.005V-1.5V.

[0149] The first coulombic efficiency = the first discharge capacity / the first charge capacity.

[0150] After 50 cycles, the thickness of the lithium ion battery electrode sheet at this time is measured by a micrometer, and the expansion rate after 50 cycles = (H1-H0) / H0*100%, H0 is the initial thickness of the electrode sheet.

[0151] After 100 cycles, the discharge capacity is recorded as the remaining capacity of the lithium ion battery; the capacity retention rate = remaining capacity / initial capacity*100%.

[0152] Table 2. Summary of performance test results of negative electrode material

[0153]

[0154] Table 3. Performance test results of negative electrode material

[0155]

[0156]

[0157] Table 4. Summary of electrochemical performance results of the battery

[0158]

[0159] According to the data in Tables 1 to 4, the control (A1-A2) / A1 is within the above range, so that the micropore specific surface area of the negative electrode material is within a suitable range, which can not only ensure that the negative electrode material can be effectively infiltrated with the electrolyte, improve the transmission efficiency of lithium ions, but also reduce the side reaction between the negative electrode material and the electrolyte, improve the specific capacity and the first coulombic efficiency of the negative electrode material, and improve the cycle stability of the negative electrode material. The battery prepared from the negative electrode material can also have a faster charge and discharge rate.

[0160] According to the data in Examples 1 to 3, as the concentration of HF or HNO3 increases, the etching holes of the silicon-based material increase, A1 of the negative electrode material increases, and A2 also increases, the total pore volume of the negative electrode material increases, and the tap density slightly decreases.

[0161] According to the test data of Example 1 and Examples 4 and 5, as the heating temperature in the plasma treatment process increases, the oxidation reaction rate of the silicon powder surface increases, and under the surface coating of silicon oxide, the bombardment of the plasma on the inside of the silicon particles decreases, A1 and A2 of the negative electrode material decrease, the total pore volume of the negative electrode material decreases, and the tap density slightly increases.

[0162] According to the test data of Example 1 and Examples 6 to 7, as the cooling water temperature in the plasma furnace increases, the bombardment of the plasma on the surface and inside of the silicon powder increases, A1 and A2 of the negative electrode material increase, the total pore volume of the negative electrode material increases, and the tap density slightly decreases.

[0163] According to the test data of Example 1 and Examples 8 to 9, the cooling water mother pipe pressure in the plasma furnace has little effect on the plasma treatment, and the related performance of the negative electrode material is close to that of Example 1.

[0164] According to the test data of Example 1 and Comparative Example 1, in Comparative Example 1, silicon and silicon dioxide are directly placed in a vacuum furnace to synthesize silicon monoxide at high temperature. During the high-temperature synthesis process, the negative electrode material forms many pores, A1 and A2 of the negative electrode material are too large, which leads to an increase in the side reaction between the negative electrode material and the electrolyte, a decrease in the specific capacity of the negative electrode material, a significant decrease in the first efficiency, and an increase in the swelling.

[0165] According to the test data of Example 1 and Comparative Example 2, in Comparative Example 2, no plasma treatment is performed, the bombardment of the plasma on the inside of the silicon particles decreases, A1 and A2 of the negative electrode material decrease significantly, the total pore volume of the negative electrode material decreases, the electrolyte is difficult to penetrate into the inside of the negative electrode material particles, the impedance of the interface between the negative electrode material and the electrolyte increases, the specific capacity of the negative electrode material is difficult to effectively exert, and the swelling increases after charge and discharge cycles.

[0166] Although the present application is disclosed with reference to the preferred embodiments, it is to be understood that the application is intended to cover all possible modifications and alterations in light of the above teachings. Therefore, the intended scope of the application is to be defined by the following claims.

Claims

1. A negative electrode material, characterized in that, The negative electrode material comprises a silicon-based material and a carbon material located on at least a portion of the surface of the silicon-based material; the negative electrode material has pores, wherein the nitrogen adsorption specific surface area of ​​all pores in the negative electrode material is Al m. 2 / g, the nitrogen adsorption specific surface area of ​​pores with a pore size of 2nm or larger is A2 m 2 / g, wherein the negative electrode material satisfies: 1.5≤A1≤5.5, 1≤A2≤5, and 0.08≤(A1-A2) / A1≤0.

6.

2. The negative electrode material according to claim 1, characterized in that, The total pore volume of the negative electrode material is 0.006 cm³. 3 / g~0.01cm 3 / g.

3. The negative electrode material according to claim 1, characterized in that, The contact angle between the negative electrode material and the electrolyte with a lithium ion concentration of 1 mol / L is B1, and the contact angle between the negative electrode material and water is B2. The negative electrode material satisfies the following condition: 1 < B2 / B1 < 1.

1. The electrolyte is formed by dissolving lithium hexafluorophosphate in an organic solvent, wherein the organic solvent is ethyl methyl carbonate, ethylene carbonate, and dimethyl carbonate in a volume ratio of 1:1:

1.

4. The negative electrode material according to claim 3, characterized in that, 145°≤B1≤155°; 150°≤B2≤160°.

5. The negative electrode material according to claim 3, characterized in that, 0.08<[(A1-A2) / A1] / (B2 / B1)<0.

7.

6. The negative electrode material according to any one of claims 1 to 5, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) The silicon-based material includes at least one of amorphous silicon, crystalline silicon and silicon oxide; (2) The carbon material includes at least one of amorphous carbon, carbon nanoparticles, carbon nanotubes and graphene; (3) The silicon-based material includes silicon oxide, which includes silicon and oxygen elements, and the atomic ratio of silicon to oxygen is 0 to 2, excluding 0; (4) The silicon-based material includes silicon oxide, and the general chemical formula of the silicon oxide is SiO. x , where 0 < x ≤ 2.

7. The negative electrode material according to any one of claims 1 to 5, characterized in that, In negative electrode materials, micropores account for 6% to 9% of the total pore volume, while mesopores account for 80% to 90% of the total pore volume.

8. The negative electrode material according to any one of claims 1 to 5, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) The mass content of silicon in the negative electrode material is m Si %, 53% ≤ m Si ≤64%; (2) The mass content of oxygen in the negative electrode material is m O %, 35% ≤ m O ≤37%; (3) The mass content of carbon in the negative electrode material is m C %, 1% ≤ m C ≤6%.

9. The negative electrode material according to any one of claims 1 to 5, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) The median particle size D of the negative electrode material 50 The size ranges from 1 μm to 10 μm. (2) The specific surface area of ​​the negative electrode material is ≤20m². 2 / g; (3) The compaction density of the negative electrode material is 1.28 g / cm³. 3 ~1.40g / cm 3 ; (4) The true density of the negative electrode material is 2.20 g / cm³. 3 ~2.30g / cm 3 ; (5) The powder conductivity of the negative electrode material is 1S / cm to 3S / cm.

10. A battery, characterized in that, Includes the negative electrode material as described in any one of claims 1 to 9.

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