Negative electrode material and battery

Abstract

The application relates to a negative electrode material and a battery, the negative electrode material comprising a carbon matrix and silicon particles, wherein the silicon particles are dispersed in the carbon matrix; the negative electrode material is tested by using a Raman spectrum, the negative electrode material has a first characteristic peak at 520+ / -10 cm ‑1 , the peak intensity of the first characteristic peak is I A , has a second characteristic peak at 960+ / -10 cm ‑1 , the peak intensity of the second characteristic peak is I B , has a third characteristic peak at 480+ / -10 cm ‑1 , and the peak intensity of the third characteristic peak is I C ; the following relationship exists among I A , I B and I C : 0.3<=I A / (I B +I C ) <=0.6; and the negative electrode material satisfies: alpha<=10%. The negative electrode material and the battery provided by the application can improve the capacity, expansion performance and cycle performance of the negative electrode material.

Description

[0001] This application claims priority to the patent application with the application number 202410020730.1, the application name "Negative electrode material and its preparation method, negative electrode sheet and lithium ion battery", which was filed on January 8, 2024 with the State Intellectual Property Office. TECHNICAL FIELD

[0002] The present application belongs to the technical field of negative electrode materials, and in particular, it is especially related to a negative electrode material and a battery. BACKGROUND

[0003] In recent years, with the development of the market, the integration of power devices, and the increasing functionality, the demand for energy supply is increasing. Lithium ion batteries are not only widely used in mobile devices such as smartphones and portable computers, but also applied in electric vehicles, power tools and other fields. Developing lithium ion batteries with higher energy density is the current trend. The positive and negative electrode materials are the core of the battery, which determines the working efficiency of the battery. Currently, the commercial negative electrode material is graphite, and its capacity has approached the theoretical limit, with limited room for further improvement. Therefore, there is an urgent need to develop a new generation of high-energy-density negative electrode materials.

[0004] Silicon negative electrodes are generally considered to be the next generation of battery negative electrode materials, with advantages such as high capacity, abundant source, and relative safety. However, silicon negative electrodes have a severe volume expansion effect during the cycling process, which leads to material pulverization and fragmentation, and the cycling decay of the material is very fast. To address this issue, there are multiple solutions, including structural design of silicon, nanocrystallization, and porosity technology; composite coating and other methods to improve; new electrolyte, binder modification to improve silicon electrode, etc.

[0005] However, the existing solutions still have many deficiencies in solving the performance of silicon, and there is still a lot of room for improvement in the long cycle performance of silicon negative electrode materials. SUMMARY

[0006] The present application provides a negative electrode material and a battery, which can improve the capacity, expansion performance and cycle performance of the negative electrode material.

[0007] In a first aspect, the present application provides a negative electrode material, comprising a carbon matrix and silicon particles, wherein the silicon particles are dispersed in the carbon matrix.

[0008] The negative electrode material is tested by Raman spectroscopy, and the negative electrode material has a first characteristic peak at 520±10cm -1 -1, and the peak intensity of the first characteristic peak is I A ; a second characteristic peak at 960±10cm -1 -1, and the peak intensity of the second characteristic peak is I B ; a third characteristic peak at 480±10cm -1has a third characteristic peak, the peak intensity of the third characteristic peak being I C , I A , I B , I C , and I A there is the following relationship: 0.3≤I B / (I C +I 3 )≤0.6; and the negative electrode material satisfies: α≤10%;

[0009] wherein, α is obtained by the following test method:

[0010] In the electron microscope image shown by the SEM section treatment of a single negative electrode material particle, a square region of 10 μm×10 μm is selected, the cross-sectional area of the negative electrode material particle in the square region is S, the sum of the cross-sectional areas of all the pores with a pore diameter greater than 50 nm in the cross-section of the negative electrode material particle in the square region is S1, α' = S1 / S, and α is the arithmetic average of the α' values of at least 10 negative electrode material particles.

[0011] In some embodiments, the negative electrode material has pores, wherein the volume ratio of mesopores in the total pore volume of all pores is 25% to 95%; and / or the total pore volume of the negative electrode material is 0.001 cm 3 / g to 0.1 cm 3 / g.

[0012] In some embodiments, the negative electrode material after removal of silicon particles has pores, and the total pore volume of the negative electrode material after removal of silicon particles is 0.4 cm 3 / g to 1.5 cm 3 / g; and / or the average pore diameter of the pores of the negative electrode material after removal of silicon particles is 1.0 nm to 5.2 nm.

[0013] In some embodiments, at least part of the surface of the negative electrode material has a carbon layer, the surface of the negative electrode material is tested by Raman spectroscopy, the negative electrode material has a characteristic peak D at 1350±10 cm -1 , the peak intensity of the characteristic peak D being I D , and a characteristic peak G at 1580±10 cm -1 , the peak intensity of the characteristic peak G being I G , and I A , I D , and I G there is the following relationship: (I D +I G ) / I A ≥10.

[0014] In some embodiments, at least part of the silicon particles are inside the particles of the carbon matrix.

[0015] In some embodiments, the carbon matrix comprises at least one of hard carbon and soft carbon.

[0016] In some embodiments, the carbon matrix comprises porous carbon, which comprises at least one of activated carbon, activated carbon fiber, carbon black, capacitive carbon, mesoporous carbon, carbon nanotube and carbon molecular sieve.

[0017] In some embodiments, the mass percentage of oxygen element in the negative electrode material is ≤5wt%.

[0018] In some embodiments, the mass percentage of carbon element in the negative electrode material is 30wt%-60wt%.

[0019] In some embodiments, the mass percentage of silicon element in the negative electrode material is 30wt%-65wt%.

[0020] In some embodiments, at least part of the surface of the negative electrode material has a carbon layer, and the thickness of the carbon layer is 0.1nm-3000nm.

[0021] In some embodiments, the negative electrode material further comprises other active particles, and the other active particles comprise at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al, P and Cu.

[0022] In some embodiments, the silicon particles comprise at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, composite of crystalline silicon and amorphous silicon.

[0023] In some embodiments, the silicon particles comprise amorphous silicon.

[0024] In some embodiments, the average particle size of the silicon particles is 1nm-100nm.

[0025] In some embodiments, the specific surface area of the negative electrode material is 1m 2 / g-500m 2 / g, and the specific surface area of the negative electrode material after removing the silicon particles is 800m 2 / g-2500m 2 / g.

[0026] In some embodiments, the compaction density of the negative electrode sheet prepared from the negative electrode material is 1.3g / cm 3 -1.9g / cm 3 ; and / or the critical pressure P of the negative electrode sheet prepared from the negative electrode material is greater than or equal to 100MPa.

[0027] In a second aspect, the application provides a battery comprising the negative electrode material of the first aspect.

[0028] The technical solution of the application has at least the following beneficial effects:

[0029] The negative electrode material provided by the application is a composite of silicon particles and a carbon matrix. The volume expansion of the silicon particles can be alleviated by the carbon matrix, and the local overexpansion stress of the negative electrode material can be reduced. The first characteristic peak of the negative electrode material can be used to represent the resonance vibration peak between Si-Si atoms (i.e., unoxidized Si). The peak intensity and shape can reflect the crystal structure and impurity content of the silicon particles. When the first characteristic peak deviates, it can reflect the stress distribution on the surface of the Si single crystal. The second characteristic peak is used to represent the Si-O-Si vibration peak, which represents the structure and mass of the silicon oxide. The third characteristic peak is used to represent the Si-O vibration peak, which represents the thickness and mass of the surface oxide layer of the silicon particles. Controlling 0.3≤I A / (I B +I C )≤0.6 can control the oxidation degree of the silicon particles in the negative electrode material within a reasonable range. The appropriate amount of oxide on the surface of the silicon particles can reduce the side reactions caused by the contact between the silicon particles and the electrolyte, and can also reduce the existence of excessive oxide to reduce the specific capacity and the first coulombic efficiency of the negative electrode material. In addition, the appropriate amount of oxide on the surface of the silicon particles can also play a passivation role, reducing the side reactions between the exposed Si in the negative electrode material and the aqueous solution during the subsequent electrode tab pulping process, and reducing the gas production problem during the electrode tab pulping process. In the present application, the area ratio α value of the macropores in the cross section of the negative electrode material particles, i.e., the negative electrode material particles have few macropores, can reduce the cracks generated in the negative electrode material during the cycle process, reduce the risk of direct contact between the silicon particles and the electrolyte, and reduce the side reactions. In the present application, I A / (I B +I C ) of the negative electrode material is controlled, reducing the contact between the silicon particles and the electrolyte in the negative electrode material. The two work together to further reduce the direct contact between the silicon particles and the electrolyte in the negative electrode material. The negative electrode material has a stable solid-state electrolyte film on the surface, which improves the specific capacity of the negative electrode material while improving the cycle stability of the negative electrode material. BRIEF DESCRIPTION OF DRAWINGS

[0030] The application will be further described below in conjunction with the drawings and examples.

[0031] Figure 1 The flow chart of the preparation of the negative electrode material of the present application is shown in Figure 1.

[0032] Figure 2a The SEM image of the negative electrode material prepared in Example 1 of the present application is shown in Figure 2.

[0033] Figure 2b SEM image of a section of the negative electrode material prepared in Example 1 of the present application;

[0034] Figure 3 XRD pattern of the negative electrode material prepared in Example 1 of the present application;

[0035] Figure 4 First charge-discharge curve of the negative electrode material prepared in Example 1 of the present application;

[0036] Figure 5 Cycle performance curve of the negative electrode material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0037] In order to better understand the technical solutions of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0038] It should be clear that the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0039] The terms used in the embodiments of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0040] It should be understood that the term "and / or" used herein is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0041] Terms:

[0042] "Micro-pore" is used herein to refer to a pore with a diameter less than 2 nm.

[0043] "Mesopore" is used herein to refer to a pore with a diameter of 2-50 nm.

[0044] "Macropore" is used to refer to a pore with a diameter greater than 50 nm.

[0045] The negative electrode material provided by the embodiments of the present application comprises a carbon matrix and silicon particles, and the silicon particles are dispersed in the carbon matrix.

[0046] The negative electrode material is tested by Raman spectroscopy, and the negative electrode material has a Raman spectrum at 520±10 cm-1 has a first characteristic peak with a peak intensity of I A ; has a second characteristic peak at 960±10 cm -1 , the peak intensity of the second characteristic peak being I B ; has a third characteristic peak at 480±10 cm -1 , the peak intensity of the third characteristic peak being I C , I A , I B and I C satisfy the following relationship: 0.3≤I A / (I B +I C )≤0.6; and the negative electrode material satisfies: α≤10%;

[0047] wherein, α is obtained by the following test method:

[0048] In the image shown by the SEM section treatment of a single negative electrode material particle, any 10 μm×10 μm square region is selected, the cross-sectional area of the negative electrode material particle in the square region is S, the sum of the cross-sectional areas of all the pores with a pore size greater than 50 nm in the cross-section of the negative electrode material particle in the square region is S1, α' = S1 / S, and α is the arithmetic average of the α' values of at least 10 negative electrode material particles.

[0049] The negative electrode material provided in the present application is a composite of silicon particles and a carbon matrix. The volume expansion of the silicon particles can be alleviated by the carbon matrix, and the local overexpansion stress of the negative electrode material can be reduced. The first characteristic peak of the negative electrode material can be used to characterize the resonance vibration peak between Si-Si atoms (i.e. unoxidized Si), and the peak intensity and shape thereof can reflect the crystal structure and impurity content of the silicon particles. When the first characteristic peak deviates, it can reflect the stress distribution on the surface of the Si single crystal. The second characteristic peak is used to characterize the Si-O-Si vibration peak, which represents the silicon oxide structure and quality. The third characteristic peak is used to characterize the Si-O vibration peak, which represents the thickness and quality of the surface oxide layer of the silicon particles. Controlling 0.3≤I A / (I B +I C)≤0.6, the oxidation degree of the silicon particles in the negative electrode material can be controlled within a reasonable range, and the appropriate amount of oxide on the surface of the silicon particles can reduce the side reaction caused by the contact between the silicon particles and the electrolyte, and can also reduce the existence of excessive oxide to reduce the specific capacity and the first coulomb efficiency of the negative electrode material; and the appropriate amount of oxide on the surface of the silicon particles can also play a passivation role, reducing the side reaction between the exposed Si in the negative electrode material and the aqueous solution in the subsequent electrode tab pulping process, and reducing the gas production problem in the electrode tab pulping process. In the present application, the area ratio α value of the macropores in the cross section of the negative electrode material particles, i.e., the negative electrode material particles have few macropores, can reduce the cracks generated in the negative electrode material during the cycle process, reduce the risk of direct contact between the silicon particles and the electrolyte, and reduce the side reaction. In the present application, the I A / (I B +I C ) reduces the contact between the silicon particles and the electrolyte in the negative electrode material, and the two work together to further reduce the direct contact between the silicon particles and the electrolyte in the negative electrode material. The negative electrode material has a stable solid-state electrolyte film on the surface, which improves the specific capacity of the negative electrode material while improving the cycle stability of the negative electrode material.

[0050] It can be understood that there are usually some macropores (>50nm) with relatively large diameters in the negative electrode material. On the one hand, the macropores are the preferential expansion points of cracks in the cycle process of the battery prepared by the negative electrode material; on the other hand, the silicon particles deposited in the macropores will produce a large expansion stress during the lithium extraction process, and the accumulated stress is easy to grow cracks near the macropores, and the electrolyte is easy to enter the inside of the negative electrode material along the cracks extending along the macropores, causing the performance of the negative electrode material to deteriorate; on the other hand, the macropores also affect the compaction performance of the negative electrode material, causing the compaction performance of the negative electrode material to decrease.

[0051] In the present application, the area ratio of the macropores in the cross section of the negative electrode material particles is controlled to be a≤10%, which can be 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, and of course can also be other values within the above range, which is not limited in the present application. Within the above limited range, it indicates that the number of macropores in the cross section of the negative electrode material is small or the pore size of the macropores is small, which is beneficial to improve the compaction density of the negative electrode material, reduce the specific surface area, improve the structural stability of the negative electrode material, so that the negative electrode material is not easy to break in the processing process, thereby improving the processing performance and cycle performance of the negative electrode material. If a is greater than 10%, the pore size of the macropores in the cross section of the negative electrode material is too large or the number of macropores is too large, and in the charging and discharging process of the battery prepared by the negative electrode material, the electrolyte is easy to be immersed into the inside of the negative electrode material particles, which increases the side reaction between the negative electrode material and the electrolyte. Moreover, as the position of stress concentration in the negative electrode material, the pore size of the macropores is too large or the number of macropores is too large, which makes the negative electrode material particles prone to breakage, pulverization and other problems in the process of deintercalation / lithiation, resulting in rapid decay of the cycle performance of the battery prepared by the negative electrode material. In the present application, by controlling the area ratio of the macropores in the cross section of the negative electrode material particles, the negative electrode material particles have very few macropores, which can reduce the cracks of the negative electrode material in the cycle process, reduce the risk of direct contact between the silicon particles in the negative electrode material and the electrolyte, and reduce the side reaction between the negative electrode material and the electrolyte. More preferably, the area ratio of the macropores in the cross section of the negative electrode material particles is controlled to be a≤4%.

[0052] In some embodiments, the pores in the negative electrode material include micropores and mesopores.

[0053] In some embodiments, in the negative electrode material, the volume ratio of the mesopores in the total pore volume of the negative electrode material is 25%-95%. Specifically, it can be 25%, 30%, 35%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 92% or 95%, and the like, which is not limited herein. Preferably, the volume ratio of the mesopores in the total pore volume of the negative electrode material is 80%-95%.

[0054] It should be noted that the pores in the negative electrode material are mainly mesopores, and when the battery prepared by the negative electrode material is charged and discharged, the mesopores in the negative electrode material can provide a buffer space for the expansion of the silicon particles, on the other hand, ensure the dispersion distribution of the stress in the negative electrode material; when the negative electrode material is applied in a lithium ion battery, it can improve the specific capacity of the negative electrode material, and also can alleviate the volume expansion of the silicon particles, improve the particle strength of the negative electrode material, reduce the material structure collapse and breakage in the process of electrode rolling or cycling, thereby improving the cycle performance and electrochemical performance of the negative electrode material under the synergistic effect of the above overall structure.

[0055] In some embodiments, the total pore volume of the negative electrode material is 0.001 cm3 / g~0.1cm 3 / g, the total pore volume of the negative electrode material can be specifically 0.001cm 3 / g, 0.002cm 3 / g, 0.005cm 3 / g, 0.008cm 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, 0.07cm 3 / g, 0.08cm 3 / g, 0.09cm 3 / g or 0.1cm 3 / g, etc., and of course other values ​​within the above range are also possible and are not limited here. The total pore volume of the negative electrode material within the above range can not only increase the specific capacity of the negative electrode material, but also ensure that the negative electrode material can retain an appropriate amount of pores to alleviate the volume expansion caused by the silicon particles during the lithium insertion and extraction process, which is beneficial to improving the cycle performance of the battery prepared with the negative electrode material.

[0056] In some embodiments, at least a portion of the surface of the negative electrode material has a carbon layer, and the surface of the negative electrode material is tested using Raman spectroscopy. The negative electrode material has a carbon layer at 1350±10 cm -1 There is a characteristic peak D at the position, and the peak intensity of the characteristic peak D is I D , at 1580±10cm -1 There is a characteristic peak G at the position, and the peak intensity of the characteristic peak G is I G ,(I D +I G ) / I A ≥10. (I D +I G ) / I A The specific value can be 10, 12, 14, 15, 16, 17, 18, 19, 20, 22, 24, 25, 30 or 35, etc., and of course it can also be other values ​​within the above range, which is not limited here. It can be understood that the provision of the carbon layer can reduce the side reactions caused by the electrolyte entering the negative electrode material, thereby improving the initial coulombic efficiency and capacity of the negative electrode material. On the other hand, the carbon layer can cooperate with the carbon matrix to alleviate the volume expansion of the silicon particles, reduce the volume expansion of the entire negative electrode material, and reduce the swelling of the electrode sheet prepared from the negative electrode material. AThe characteristic peak of Si is represented, and the characteristic peak of C is much stronger than that of Si, that is, there is almost no exposed Si particle on the surface of the particle, indicating that the carbon layer on the surface of the negative electrode material is relatively dense and complete, which helps to reduce the direct contact between the electrolyte and the silicon particles and reduce the occurrence of side reactions.

[0057] In the present application, the negative electrode material is soaked in a 1M nitric acid solution for 4h, then a 20% mass fraction of HF acid solution is added dropwise into the negative electrode material, yellow smoke is generated, and the solution is repeatedly added dropwise until no yellow smoke is generated; finally, the residue is digested with a 1M nitric acid solution, then washed and dried to obtain the negative electrode material after removing the silicon particles.

[0058] In some embodiments, the carbon matrix comprises at least one of hard carbon, soft carbon. It can be understood that the carbon matrix selected from the above materials can all play the role of supporting framework, and also has good electrical conductivity, which ensures the electrical conductivity of the negative electrode material.

[0059] In some embodiments, the carbon matrix comprises porous carbon.

[0060] In some embodiments, the porous carbon comprises at least one of activated carbon, activated carbon fiber, carbon black, capacitive carbon, mesoporous carbon, carbon nanotube and carbon molecular sieve.

[0061] In some embodiments, the negative electrode material after removing the silicon particles has pores.

[0062] In some embodiments, the average pore size of the pores of the negative electrode material after removing the silicon particles is 1.0nm-5.2nm. Specifically, it can be 1.0nm, 1.5nm, 1.8nm, 2.0nm, 2.1nm, 2.2nm, 2.5nm, 2.8nm, 3.0nm, 3.2nm, 3.5nm, 4.0nm, 4.5nm or 5.2nm, etc., which is not limited here. The negative electrode material after removing the silicon particles is the carbon matrix, and the pore size of the pores of the carbon matrix is too small, the gaseous precursor of the silicon particles is difficult to penetrate into the pores, and the shell structure is easily formed on the surface of the carbon matrix, which leads to the decrease of the content of the silicon particles in the negative electrode material and the decrease of the specific capacity of the negative electrode material; when the pore size of the pores of the carbon matrix is too large, although it is beneficial to the filling of the silicon particles, it may cause the uneven distribution of the silicon particles, silicon segregation and other problems, thereby leading to the uneven expansion of the negative electrode material, the excessive local expansion stress, the particle breakage and other problems, and further leading to the decrease of the electrochemical performance of the negative electrode material. Therefore, controlling the average pore size of the pores of the carbon matrix within the above range is beneficial to the compounding of the carbon matrix and the silicon particles, which improves the rate performance of the negative electrode material, and is also beneficial to buffering the volume expansion of the silicon particles and improving the structural stability of the negative electrode material.

[0063] In some embodiments, the specific surface area of the negative electrode material after removing the silicon particles is 800m2 / g~2500m 2 / g. Specifically, it can be 800m 2 / g, 1000m 2 / g, 1200m 2 / g, 1500m 2 / g, 1800m 2 / g, 2000m 2 / g, 2200m 2 / g, 2400m 2 / g or 2500m 2 / g, etc., and of course, it can also be other values within the above range, which are not limited herein.

[0064] In some embodiments, the total pore volume of the negative electrode material after removing the silicon particles is 0.4cm 3 / g~1.5cm 3 / g. Specifically, it can be 0.4cm 3 / g, 0.5cm 3 / g, 0.6cm 3 / g, 0.9cm 3 / g, 1.0cm 3 / g, 1.2cm 3 / g, 1.3cm 3 / g, 1.4cm 3 / g or 1.5cm 3 / g, etc., and of course, it can also be other values within the above range, which are not limited herein. The total pore volume of the negative electrode material (i.e., the carbon matrix) after removing the silicon particles in the present application is within the above range, which can provide sufficient space for accommodating the silicon particles, thereby improving the specific capacity of the negative electrode material and ensuring that the negative electrode material can reserve an appropriate amount of pores for relieving the volume expansion caused by the deintercalation of lithium during the intercalation of lithium, which is beneficial to improving the cycle performance of the negative electrode material.

[0065] In some embodiments, the silicon particles include at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, a composite of crystalline silicon and amorphous silicon; specifically, the silicon alloy can be a silicon-lithium alloy, a silicon-magnesium alloy, etc., and of course, it should be noted that in some cases, the silicon alloy includes elemental silicon particles and an alloy.

[0066] In some embodiments, the silicon particles include amorphous silicon and / or crystalline silicon; preferably, the silicon particles include amorphous silicon, which expands isotropically during the intercalation of lithium, which can reduce the collapse of the pore structure, inhibit the rapid decay of the specific capacity, and improve the intercalation cycle performance of the negative electrode material.

[0067] In some embodiments, the negative electrode material further comprises other active particles, which comprise at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al, P and Cu. The other active particles can be metal elements.

[0068] In some embodiments, the other active particles can be Sn particles, Ge particles, Al particles, and in some other embodiments, the other active particles can also be silicon-lithium alloy, silicon-magnesium alloy, etc. It should be noted that in some cases, the other active particles comprise both elemental particles and alloys.

[0069] In some embodiments, at least part of the silicon particles are located inside the carbon matrix particles. The silicon particles located in the carbon matrix can improve the conductivity of the negative electrode material through the carbon matrix, and at the same time reduce the direct contact of the silicon particles with the electrolyte and reduce the occurrence of side reactions.

[0070] In some embodiments, the silicon oxide comprises silicon elements and oxygen elements, and the atomic ratio of the silicon elements and the oxygen elements is 0-2, and 0 is not included. The atomic ratio of the silicon elements and the oxygen elements 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., which are not limited herein. Preferably, the atomic ratio of the silicon elements and the oxygen elements is 0-1, and 0 is not included.

[0071] In some embodiments, the chemical formula of the silicon oxide is SiO x wherein 0

[0072] In some embodiments, the average particle size of the silicon particles is 0.1 nm to 100 nm, and can be 0.1 nm, 0.5 nm, 1 nm, 10 nm, 30 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm, or other values within the above range, which are not limited in the present application. Within the above range, the mechanical stress of the silicon particles during expansion decreases with the decrease of the particle size, and the size reduction can shorten the electron and ion transport path, and the size reduction of the silicon particles increases the gap between adjacent silicon particles, which can reserve space for expansion. It can be understood that the average particle size of the silicon particles within the above range can ensure the battery capacity of the lithium ion battery and reduce the irreversible capacity loss. Preferably, the average particle size of the silicon particles is 1 nm to 50 nm, and more preferably, the average particle size of the silicon particles is 0.1 nm to 5 nm.

[0073] In some embodiments, the morphology of the silicon particles includes at least one of a point, a sphere, an ellipsoid and a sheet, and the morphology of the silicon particles can be selected according to actual needs, which are not limited herein.

[0074] In some embodiments, the purity of the silicon particles is greater than 99%, and it can be understood that high-purity silicon particles are beneficial to Li-Si alloying with lithium and improve the cycle performance of the lithium ion battery.

[0075] In some embodiments, the mass content of carbon in the negative electrode material is 30 wt% to 60 wt%, and can be 30 wt%, 40 wt%, 50 wt%, 55 wt% or 60 wt%, or other values within the above range, which are not limited herein.

[0076] In some embodiments, the mass content of silicon in the negative electrode material is 30 wt% to 65 wt%, and can be 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt% or 65 wt%, or other values within the above range, which are not limited herein. Preferably, the mass content of silicon in the negative electrode material is 35 wt% to 55 wt%.

[0077] In some embodiments, the mass ratio of silicon element to carbon element in the negative electrode material is 0.8-2.0, and can be 0.8, 0.9, 0.92, 0.95, 0.98, 1.0, 1.01, 1.02, 1.05, 1.1, 1.2, 1.5, 1.6, 1.8, 1.9 or 2.0, etc., which is not limited herein. When the mass ratio of silicon element to carbon element in the negative electrode material is <0.8, the specific capacity of the negative electrode material decreases, but the overall cycle performance improves. When the mass ratio of silicon element to carbon element in the negative electrode material is ≥2.0, the specific capacity of the negative electrode material increases with the increase of silicon content, but the volume expansion effect of silicon is obvious, the cycle performance of the negative electrode material is affected, and the capacity ratio also decreases. Controlling within the above range is beneficial to improving the overall specific capacity and cycle stability of the negative electrode material.

[0078] In some embodiments, the median particle size of the negative electrode material is ≤25 μm, for example, it can be 1 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm or 25 μm, etc., and of course it can also be other values within the above range, which is not limited herein. Controlling the median particle size of the negative electrode material within the above range is beneficial to improving the cycle performance of the negative electrode material.

[0079] In some embodiments, the negative electrode material further comprises a coating layer distributed on at least part of the surface of the carbon matrix. The coating layer is arranged on one hand to reduce the side reaction of electrolyte entering the interior of the negative electrode material, thereby improving the initial efficiency and capacity of the negative electrode material, and on the other hand, the coating layer can cooperate with the carbon matrix to relieve the volume expansion of the active material, reduce the volume expansion of the entire negative electrode material, and reduce the swelling of the negative electrode material prepared into a pole piece.

[0080] In some embodiments, the coating layer comprises a carbon layer, and the material of the carbon layer comprises at least one of graphene, soft carbon, hard carbon and conductive polymer. Specifically, the conductive polymer comprises at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, poly-3-hexylthiophene, poly-p-phenylenevinylene, polypyridine and polyphenylvinyl.

[0081] In some embodiments, the thickness of the carbon layer is 0.1 nm-3000 nm, and can be 0.1 nm, 1 nm, 50 nm, 100 nm, 500 nm, 1000 nm, 2000 nm or 3000 nm, etc., and of course it can also be other values within the above range, which is not limited herein. Preferably, the thickness of the coating layer is 0.5 nm-1000 nm, and more preferably, the thickness of the carbon layer is 5 nm-500 nm.

[0082] In some embodiments, the mass percentage of oxygen element in the negative electrode material is ≤5wt%. Specifically, the mass percentage of oxygen element in the negative electrode material can be 0wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, without being limited herein. It can be understood that if the mass content of oxygen element is too high, the silicon-based material in the negative electrode material will be partially oxidized. Controlling the mass content of oxygen element in the negative electrode material within the above range is beneficial to improve the specific capacity of the negative electrode material and reduce the formation of low-activity silicon dioxide.

[0083] In some embodiments, the specific surface area of the negative electrode material is 1m 2 / g~500m 2 / g. Specifically, the specific surface area of the negative electrode material can be 1m 2 / g, 2m 2 / g, 4m 2 / g, 5m 2 / g, 10m 2 / g, 50m 2 / g, 100m 2 / g, 150m 2 / g, 200m 2 / g, 250m 2 / g, 300m 2 / g, 350m 2 / g, 400m 2 / g, 450m 2 / g or 500m 2 / g, and of course can also be other values within the above range, without being limited herein. Controlling the specific surface area of the negative electrode material within the above range can inhibit the volume expansion of the negative electrode material, which is beneficial to improve the cycle performance of the negative electrode material.

[0084] In some embodiments, the compaction density of the negative electrode material is 0.8g / cm 3 ~1.3g / cm 3 , specifically can be 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.1g / cm 3 , 1.2g / cm 3 or 1.3g / cm 3 , and of course can also be other values within the above range, without being limited herein.

[0085] The present application provides a preparation method of a negative electrode material, as shown in the following scheme: Figure 1 The preparation process of the negative electrode material of the present application includes the following steps:

[0086] Step S100, pre-treating the porous carbonaceous raw material to obtain a carbon matrix, the pre-treating the porous carbonaceous raw material comprises the following steps:

[0087] The porous carbonaceous raw material is subjected to a pressurized treatment, and the pressure of the pressurized treatment is greater than or equal to 100 MPa.

[0088] Or under the condition that the vacuum pressure is 0.1 Pa to 500 Pa, the porous carbonaceous raw material is immersed in a treatment solution, and the treatment solution comprises an organic compound.

[0089] Step S200, performing gas phase deposition on the carbon matrix by using a gas phase active substance precursor to obtain a composite.

[0090] Step S300, pre-oxidizing the composite, and then performing carbon coating treatment by using a carbon source to obtain the negative electrode material.

[0091] In the above scheme, the carbon matrix is obtained by pretreating the porous carbonaceous raw material. The pretreatment can be pressurization treatment or impregnation treatment of the porous carbonaceous raw material with a treatment solution. The pressurization treatment causes cracks to occur preferentially in the pores with a large pore size or the pores with a large pore size are directly crushed, and the micropores and mesopores with a small pore size are retained during the pressurization treatment, so that the number of macropores in the carbon matrix is reduced. The treatment solution is impregnated into the porous carbonaceous raw material, and the treatment solution includes an organic compound. During the impregnation process, due to the capillary effect, the molecules of the treatment solution are difficult to enter the micropores and are mainly filled into the mesopores and macropores of the porous carbonaceous raw material. The organic compound can be preferentially filled into the macropores of the porous carbonaceous raw material, so that the macropores are converted into macropores, mesopores or micropores with a small pore size, thereby facilitating an increase in the number of micropores and mesopores in the carbon matrix, a reduction in the number and volume ratio of macropores in the carbon material, and a reduction in the porosity of the carbon matrix. Then, the carbon matrix is subjected to gas-phase deposition of a gas-phase active substance precursor. On the one hand, the number and volume ratio of macropores are small, so that the deposition of the gas-phase active substance precursor in the porous carbon matrix is uniform, the active substance generated from the gas-phase active substance precursor is less likely to agglomerate in the porous carbon matrix, and the volume expansion of the negative electrode material is reduced. On the other hand, the active substance generated from the gas-phase active substance precursor is filled in the carbon matrix, further reducing the number and volume ratio of macropores in the negative electrode material, so that the area ratio of the pores with a pore size greater than 50 nm in the cross section of the negative electrode material is less than or equal to 10%, thereby facilitating an increase in the tap density of the negative electrode material, an improvement in the compaction performance of the negative electrode material, and a reduction in the problems such as cracking and breaking of the negative electrode material during the pressing process. Finally, the composite is subjected to pre-oxidation treatment, so that a proper amount of silicon oxide is formed on the surface of the silicon particles in the composite. The proper amount of oxide on the surface of the silicon particles can reduce the side reactions caused by the contact between the silicon particles and the electrolyte, and can also reduce the existence of excessive oxide to reduce the specific capacity and the first coulombic efficiency of the negative electrode material. In addition, the proper amount of oxide on the surface of the silicon particles can also play a passivation role, reducing the side reactions between the exposed Si in the negative electrode material and the aqueous solution during the subsequent slurry preparation process of the electrode sheet, and reducing the gas production problem during the slurry preparation process of the electrode sheet. After carbon coating treatment, the direct contact between the silicon particles and the electrolyte in the negative electrode material is further reduced, and the prepared negative electrode material can have high capacity, high first efficiency, high cycle performance and excellent processing performance.

[0092] The preparation method of the application will be specifically described below in combination with the following embodiments.

[0093] In step S100, the porous carbonaceous raw material is pretreated to obtain a carbon matrix.

[0094] In some embodiments, step S100 includes pressurization treatment of the porous carbonaceous raw material to obtain the carbon matrix, and the pressure of the pressurization treatment is greater than or equal to 100 MPa.

[0095] In some embodiments, the pressure of the pressurized treatment is greater than or equal to 100 MPa, and can be 100 MPa, 150 MPa, 200 MPa, 250 MPa, 300 MPa, 350 MPa, 400 MPa, 500 MPa, or 650 MPa, or other values within the above range, without limitation. The pressure of the pressurized treatment is relatively high, and the pressurized treatment of the porous carbonaceous raw material causes cracks to occur at the large pores of the porous carbonaceous raw material, and then the porous carbonaceous raw material breaks, thereby reducing the number of large pores in the porous carbonaceous raw material. Preferably, the pressure of the pressurized treatment is greater than or equal to 150 MPa. If the pressure of the pressurized treatment is less than 100 MPa, cracks cannot be guaranteed to occur at the large pores of the porous carbonaceous raw material, and the number of large pores in the porous carbonaceous raw material is relatively high, which is not conducive to improving the tap density of the negative electrode material.

[0096] In some embodiments, the pressurized treatment is performed for 0.5 h to 10 h, and can be 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, or 10 h, or other values within the above range, without limitation.

[0097] In some embodiments, the pressurized treatment device includes at least one of a cold rolling mill and a molding press.

[0098] In some embodiments, the pressurized treatment is followed by a step of crushing and sieving the pressurized treatment product. In the crushing process, part of the porous carbonaceous raw material is easily broken from the large pores where cracks have occurred, further reducing the number of large pores in the carbon matrix.

[0099] In some embodiments, the mesh size of the sieving is 10 mesh to 500 mesh, and can be 10 mesh, 50 mesh, 100 mesh, 200 mesh, 300 mesh, 400 mesh, or 500 mesh, or other values within the above range, without limitation.

[0100] In some embodiments, the step S100 includes immersing the porous carbonaceous raw material in a treatment solution under a vacuum pressure of 0.1 Pa to 500 Pa to obtain a carbon matrix, and the treatment solution includes an organic compound with a molecular weight greater than 10,000.

[0101] In some embodiments, the vacuum pressure is 0.1 Pa to 500 Pa, and can be specifically 0.1 Pa, 1 Pa, 10 Pa, 50 Pa, 100 Pa, 200 Pa, 300 Pa, 400 Pa or 500 Pa, and can also be other values within the above range, which are not limited in the present application. Within the above range, the pressure on the surface of the porous carbonaceous raw material is less than the pressure of the treatment solution, which can enable the treatment solution to penetrate into the porous carbonaceous raw material, so that the treatment solution enters the interior of the porous carbonaceous raw material through the pores or defects of the porous carbonaceous raw material, thereby achieving the purpose of filling the macropores in the porous carbonaceous raw material and reducing the number or pore size of the macropores. If the vacuum pressure is greater than 500 Pa, it is easy to cause cracks in part of the mesopores and micropores, so that the porosity of the porous carbon is too low, which is not conducive to the deposition of silicon particles. If the vacuum pressure is less than 0.1 Pa, it cannot be ensured that the treatment solution penetrates into the porous carbonaceous raw material, resulting in a large number of macropores in the porous carbonaceous raw material.

[0102] In some embodiments, the treatment solution comprises a solute and a solvent, and the solute comprises at least one of polysaccharides, proteins, nucleic acids, citric acid, cyclohexane, isopropyl alcohol, chloroethylene, a vinyl polymer and a monomer cross-linked polymer. The monomer cross-linked polymer can be, for example, polyurethane, polyimide, polyacrylic acid, poly-N-methyl pyrrolidone, polyamine and polyvinyl alcohol, etc. The protein is a macromolecular protein, which can be, for example, soybean protein and collagen, etc. The main components of soybean protein include 11S globulin and 7S globulin, and the molecular weight of 11S globulin is 340 kDa and the molecular weight of 7S globulin is 440 kDa. The polysaccharides can be, for example, starch and cellulose, etc. The particle size of the solute molecules in the above treatment solution is large, which is conducive to preferentially filling the macropores during the impregnation treatment, so that the pore size of the macropores is reduced, while the pore size of the micropores is too small, so that the treatment solution is difficult to enter the micropores due to capillary action, so that the number of macropores in the porous carbonaceous raw material is greatly reduced, and the number of mesopores and micropores is increased.

[0103] In some embodiments, the solvent comprises water and an organic solvent, and the organic solvent comprises at least one of an alcohol solvent, an ether solvent, an aliphatic hydrocarbon solvent, a ketone solvent and dimethyl sulfoxide, and can also be other types of solvents, which are not limited in the present application.

[0104] In some embodiments, the treatment solution comprises a vinyl polymer grafted polyether polyol, and the vinyl polymer can be, for example, polyethylene and polyvinyl chloride, etc.

[0105] In some embodiments, the particle size of the solute is greater than or equal to 0.5 nm, specifically can be 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 8 nm, 10 nm or 15 nm, etc., of course, it can also be other values within the above range, which is not limited herein. It can be understood that the particle size of the solute particle in the treatment solution refers to the equivalent volume diameter, that is, the diameter of the ball with the same volume as the solute particle in the treatment solution, for example, the particle size of the solute can be measured by BI-90Plus laser particle size analyzer / Zeta potential instrument using DLS (dynamic light scattering) principle.

[0106] In some embodiments, the concentration of the treatment solution is 1 mol / L to 15 mol / L, specifically can be 1 mol / L, 3 mol / L, 5 mol / L, 7 mol / L, 10 mol / L, 12 mol / L or 15 mol / L, etc., of course, it can also be other values within the above range, which is not limited herein. Within the above range, it is beneficial for the solute in the treatment solution to enter the pores of the porous carbonaceous raw material, thereby improving the utilization efficiency of the solute.

[0107] In some embodiments, the impregnation time is 1 h to 15 h, specifically can be 1 h, 3 h, 5 h, 7 h, 10 h, 12 h or 15 h, etc., of course, it can also be other values within the above range, which is not limited herein.

[0108] In some embodiments, the impregnation equipment includes a vacuum impregnation machine.

[0109] In some embodiments, after the porous carbonaceous raw material is impregnated in the treatment solution, it further includes the step of drying the impregnated material.

[0110] In some embodiments, the drying temperature is -40°C to 600°C, specifically can be -40°C, -20°C, -10°C, 0°C, 30°C, 50°C, 100°C, 200°C, 300°C, 400°C, 500°C or 600°C, etc., of course, it can also be other values within the above range, which is not limited herein.

[0111] In some embodiments, the drying time is 0.5 h to 24 h, specifically can be 0.5 h, 1 h, 3 h, 5 h, 8 h, 12 h, 16 h, 20 h or 24 h, etc., of course, it can also be other values within the above range, which is not limited herein.

[0112] In some embodiments, the porous carbonaceous raw material is prepared by the following method: carbonizing a carbon source, and mixing the carbonized material and an activating agent to perform an activation treatment.

[0113] In some embodiments, the carbon source includes at least one of lignin, coconut shell, fruit shell, peanut shell, rice husk, coal-based biomass, and resin. The coal-based biomass is also known as biomass briquette, such as sawdust, agricultural waste, and paper, etc. The resin can be polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polystyrene (PS), etc.

[0114] In some embodiments, the carbonization temperature is 600-900℃, and can be 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, or 900℃, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0115] In some embodiments, the carbonization time is 1-20h, and can be 1h, 3h, 5h, 10h, 12h, 15h, 18h, and 20h, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0116] In some embodiments, the carbonization is carried out under a protective gas atmosphere, and the protective gas includes at least one of nitrogen, helium, neon, argon, krypton, and xenon.

[0117] In some embodiments, after obtaining the carbonization treatment material, the method further includes: performing acid pickling on the carbonization treatment material, and the acid for the acid pickling is at least one of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, phosphoric acid, perchloric acid, acetic acid, and benzoic acid.

[0118] In some embodiments, the concentration of the acid pickling solution is 1-10mol / L, and can be 1mol / L, 3mol / L, 5mol / L, 8mol / L, or 10mol / L, etc. Of course, it can also be other values within the above range, which is not limited herein. It can be understood that the purpose of the acid pickling is to remove impurities in the material. After the carbonization treatment material is pickled with acid, it is washed with deionized water, and the product is washed to be close to neutral.

[0119] In some embodiments, the acid pickling time is 3-8h, and can be 3h, 4h, 5h, 6h, 7h, or 8h, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0120] In some embodiments, the activation agent used in the activation treatment can be a gaseous activation agent or a solid activation agent. Exemplarily, the gaseous activation agent includes at least one of water vapor, oxygen, and air, and the solid activation agent includes an alkaline substance, and the alkaline substance includes at least one of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and rubidium hydroxide.

[0121] In some embodiments, when the activating agent is a gaseous activating agent, it reacts with carbon at high temperature through gaseous water vapor, oxygen and air to generate hydrogen and carbon monoxide, and the carbonization treatment obtained material is etched by the reaction to obtain a carbon matrix with activated pores.

[0122] In some embodiments, the concentration of the gaseous activating agent is 3% to 20%, specifically, it can be 3%, 5%, 7%, 9%, 10%, 12%, 15%, 18% and 20%, and of course it can also be other values within the above range, which is not limited herein. Within the above limited range, the activating agent has a larger amount and stronger activation ability, which can form more and uniformly distributed activated pores in the carbonization treatment obtained material, which is beneficial for the subsequent active material such as silicon particles to be filled in the activated pores.

[0123] It can be understood that when the activating agent is water vapor, the concentration of water vapor can be considered as the humidity of water vapor.

[0124] In some embodiments, when the activating agent is a solid activating agent, the mass ratio of the carbonization treatment obtained material to the activating agent is 1:(0.5-30), specifically, it can be 1:0.5, 1:1, 1:5, 1:10, 1:20 and 1:30, and of course it can also be other values within the above range, which is not limited herein. Within the above limited range, the activating agent has a larger amount and stronger activation ability, which can form more and uniformly distributed activated pores in the carbonization treatment obtained material, which is beneficial for the subsequent active material such as silicon particles to be filled in the activated pores.

[0125] In some embodiments, the activation treatment time is 1h to 20h, for example, it can be 1h, 5h, 8h, 10h, 12h, 15h, 18h or 20h, and of course it can also be other values within the above range, which is not limited herein.

[0126] In some embodiments, the activation treatment temperature is 500℃ to 1200℃, specifically, it can be 500℃, 600℃, 700℃, 800℃, 900℃, 950℃, 1000℃, 1100℃ and 1200℃, and of course it can also be other values within the above range, which is not limited herein.

[0127] It can be understood that the porous carbon raw material can also be directly purchased from commercial channels.

[0128] Step S200, using a gaseous active material precursor to perform vapor deposition on the carbon matrix to obtain a negative electrode material.

[0129] The application adopts a gas-phase active substance precursor to perform gas-phase deposition on a carbon matrix. The gas-phase active substance precursor generates an active substance capable of filling micropores in the carbon matrix, further reducing the volume ratio of micropores in the negative electrode material, improving the compaction density of the negative electrode material, reducing the specific surface area, reducing the problems of crushing and cracking of the negative electrode material in the process of a compression roller, improving the processing performance and cycle performance of the negative electrode material. Moreover, the active substance is deposited in the micropores of the carbon matrix and is not prone to silicon segregation, which is conducive to improving the tap density of the negative electrode material and further improving the capacity, initial efficiency and cycle performance of the negative electrode material.

[0130] In some embodiments, the gas-phase active substance precursor comprises a gaseous silicon source.

[0131] In some embodiments, the gaseous silicon source comprises at least one of silane, disilane and trisilane.

[0132] In some embodiments, the gas-phase active substance precursor has a flow concentration of 5% to 30%, specifically 5%, 8%, 10%, 12%, 15%, 18%, 20%, 23%, 26%, 28% or 30%, or other values within the above range, which are not limited herein.

[0133] In some embodiments, the temperature of the gas-phase deposition is 300°C to 800°C, specifically 300°C, 400°C, 500°C, 600°C, 700°C and 800°C, or other values within the above range, which are not limited herein.

[0134] In some embodiments, the holding time of the gas-phase deposition is 2h to 25h, specifically 2h, 5h, 10h, 15h, 20h and 25h, or other values within the above range, which are not limited herein.

[0135] The application controls the temperature, time and flow concentration of the gas-phase active substance precursor of the gas-phase deposition, controls the mass ratio of silicon to carbon in the composite, and enables the negative electrode material prepared from the composite to have high capacity and initial efficiency.

[0136] In step S300, the composite is subjected to a pre-oxidation treatment, and then subjected to a carbon coating treatment using a carbon source to obtain a negative electrode material.

[0137] In some embodiments, a mixed gas containing an oxidizing gas and a protective gas is introduced into the composite, and the temperature is raised to 100-500°C, and the holding time is 0.1-300min to obtain a pre-oxidized precursor.

[0138] In some embodiments, the oxidizing gas comprises oxygen, O3, NO xat least one of hydrogen, hydrogen peroxide, water vapor, bromine, and the like.

[0139] In some embodiments, the protective gas comprises at least one of nitrogen, argon, helium, hydrogen, and the like.

[0140] In some embodiments, the volume ratio of the oxidizing gas is 0.01% to 10%, specifically, 0.01%, 0.1%, 0.2%, 0.5%, 0.8%, 1.0%, 1.5%, 2%, 3%, 5%, 6%, 8%, or 10%, or the like, and of course, other values within the above range are also possible, which are not limited herein, based on 100% of the volume of the mixed gas.

[0141] In some embodiments, the carbon source comprises at least one of a gaseous carbon source and a solid carbon source.

[0142] In some embodiments, the gaseous carbon source comprises at least one of acetylene, methane, propylene, benzene, ethanol, methanol, ethylene, propane, and butane.

[0143] In some embodiments, the flow rate of the gaseous carbon source is 0.1 L / min to 100 L / min, specifically, 0.1 L / min, 1 L / min, 10 L / min, 30 L / min, 60 L / min, 100 L / min, or the like, and of course, other values within the above range are also possible, which are not limited herein.

[0144] In some embodiments, the solid carbon source comprises at least one of sucrose, fructose, glucose, asphalt, phenolic resin, polyimide, citric acid, epoxy resin, amino resin, polystyrene, polyacrylic acid, carboxymethyl cellulose, and cellulose acetate butyrate.

[0145] In some embodiments, the mass ratio of the solid carbon source to the precursor is (1 to 100): 100, specifically, 1:100, 10:100, 30:100, 50:100, 80:100, and 100:100, or the like, and of course, other values within the above range are also possible, which are not limited herein.

[0146] In some embodiments, the temperature of the carbon coating treatment is 600°C to 1100°C, specifically, 600°C, 650°C, 700°C, 800°C, 900°C, 1000°C, and 1000°C, or the like, and of course, other values within the above range are also possible, which are not limited herein. If the temperature of the carbon coating treatment is lower than 600°C, the carbon source is not fully carbonized, and a relatively dense carbon layer cannot be obtained. If the temperature of the carbon coating treatment is higher than 1100°C, the grain size of the silicon particles rapidly increases, and the cycle performance and expansion performance of the negative electrode material deteriorate.

[0147] In some embodiments, the heat preservation time of the carbon coating treatment is 2h-10h, and can be specifically 2h, 5h, 7h, 8h, 10h, or other values within the above range, which are not limited in the present application.

[0148] In some embodiments, the method further comprises the step of screening or grading the carbon-coated product.

[0149] The present application also provides a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode active material distributed on one side of the negative electrode current collector, and the negative electrode active material comprises the negative electrode material or the negative electrode material prepared by the above preparation method.

[0150] In some embodiments, the critical pressure resistance P of the negative electrode sheet is greater than or equal to 100MPa, and can be specifically 100MPa, 120MPa, 150MPa, 200MPa, 250MPa, 300MPa, 350MPa, 400MPa, 500MPa, 600MPa, or other values within the above range, which are not limited in the present application. Within the above range, the critical pressure resistance P of the negative electrode material of the present application is relatively large, indicating that the negative electrode sheet has excellent pressure resistance, which is beneficial to improve the processing performance of the negative electrode sheet. It can be understood that the critical pressure resistance refers to the pressure when the negative electrode sheet is in a critical state, that is, the maximum pressure at which the negative electrode material particles do not break in the negative electrode sheet. The critical pressure resistance of the negative electrode sheet is obtained by the following test method: the thickness of the negative electrode sheet is 60μm, and the cross section of a single negative electrode sheet is observed under pressure by using an electron scanning microscope SEM. The minimum pressure corresponding to the breakage of the negative electrode material particles is P.

[0151] In some embodiments, the compaction density of the negative electrode sheet is 1.3g / cm 3 -1.9g / cm 3 , and can be specifically 1.3g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 , or other values within the above range, which are not limited in the present application. Within the above range, the compaction density of the negative electrode sheet of the present application is relatively large, and the internal pore size of the negative electrode sheet is relatively small, which is beneficial to improve the capacity, the first efficiency and the cycle performance of the negative electrode sheet.

[0152] The present application also provides a battery comprising the negative electrode material or the negative electrode material prepared by the above preparation method.

[0153] In some embodiments, the battery of the present application comprises a lithium ion battery or a sodium ion battery, which can be any one of a cylindrical battery and a square battery.

[0154] Those skilled in the art will understand that the above-described method for preparing a lithium ion battery is only an example. Other methods commonly used in the art can be employed without departing from the content disclosed in the present application.

[0155] The embodiments of the present application are further described in the following examples. The embodiments of the present application are not limited to the following specific examples. Within the scope of the rights, appropriate changes can be made.

[0156] Example 1

[0157] (1) Coconut shells were subjected to carbonization treatment at a carbonization temperature of 850°C, and then were subjected to acid washing with 8 mol / L hydrochloric acid for 3 h. The obtained material was dried and then was subjected to activation treatment with a mixed gas of water vapor and nitrogen gas, wherein the water vapor concentration was 8%, the activation time was 7 h, and the activation temperature was 750°C, to obtain a carbonized material.

[0158] (2) The carbonized material was placed in a molding machine, and was subjected to pressing at a pressure of 250 MPa for 50 min. Then, the pressed material was crushed, pulverized, and sieved to obtain a carbon matrix.

[0159] (3) The carbon matrix was placed in a CVD device, and then silane was introduced into the CVD device. The silane concentration was controlled to be 5%, and the temperature was raised to 480°C. The reaction was performed for 9 h to obtain a composite.

[0160] (4) A mixed gas of 0.03% oxygen and nitrogen was introduced into the composite, and the temperature was raised to 230°C. The holding time was 100 min to obtain a precursor.

[0161] (5) The precursor was placed in a reaction furnace, and methane gas was introduced at a concentration of 12%. The temperature was raised to 720°C, and the heat treatment was performed for 2 h. The obtained material was sieved and classified to obtain a negative electrode material.

[0162] In the present example, the negative electrode material comprises a carbon matrix and silicon particles, and the silicon particles are dispersed in the carbon matrix.

[0163] Figure 2a SEM image of the negative electrode material prepared in Example 1, Figure 2b SEM image of the particle cross-section of the negative electrode material prepared in Example 1, obtained by Figure 2a and Figure 2b It can be seen that the negative electrode material contains a small amount of macropores.

[0164] Figure 3: This is the XRD pattern of the negative electrode material prepared in Example 1. The silicon particles in the negative electrode material prepared in Example 1 are amorphous silicon.

[0165] Figure 4 The first charge-discharge curve of the negative electrode material prepared in Example 1 is Figure 3 It can be seen that the negative electrode material has a high first charge and discharge capacity of 1933 mAh / g and a first efficiency of 92.5%.

[0166] Figure 5 The cycle performance curve of the negative electrode material prepared in Example 1 is shown in FIG. Figure 4 It can be seen that the negative electrode material has excellent cycle performance, and the capacity retention rate after 500 cycles is 90.8%.

[0167] Example 2

[0168] The difference from Example 1 is that:

[0169] (1) Commercial resin-based porous carbon was used as raw material. The porous carbon material was placed in a vacuum impregnation machine, benzyl alcohol was added, the vacuum pressure was set to 100 Pa, vacuum impregnation was performed for 50 min, and then heat treated at 600 °C for 4 h to obtain a carbon matrix.

[0170] (2) The carbon substrate was placed in a CVD device, and then silane was introduced into the CVD device, with the silane concentration controlled at 9%. The temperature was raised to 480° C. and the reaction was carried out for 9 hours to obtain a composite.

[0171] The subsequent steps are the same as those in Example 1.

[0172] In this embodiment, the negative electrode material includes a carbon matrix and silicon particles, wherein the silicon particles are dispersed in the carbon matrix. Other parameters of the negative electrode material are shown in Tables 1 and 2.

[0173] Example 3

[0174] (1) Phenolic resin was used as raw material and carbonized at 900 °C. The carbonized material was then mixed with KOH at a mixing ratio of 100:5. The mixture was then activated at 880 °C for 9 h to obtain a carbon matrix.

[0175] (2) The carbon substrate was placed in a CVD device, and then silane was introduced into the CVD device, with the silane concentration controlled at 14%. The temperature was raised to 480° C. and the reaction was carried out for 9 hours to obtain a composite.

[0176] The subsequent steps are the same as those in Example 1.

[0177] In this embodiment, the negative electrode material includes a carbon matrix and silicon particles, wherein the silicon particles are dispersed in the carbon matrix. Other parameters of the negative electrode material are shown in Tables 1 and 2.

[0178] Example 4

[0179] (1) The fruit shell is carbonized at a temperature of 950°C, and then is acid washed with 4 mol / L hydrochloric acid for 5 h. The obtained material is dried and then activated by passing a mixed gas of water vapor and nitrogen, wherein the concentration of water vapor is 7%, the activation time is 9 h, and the activation temperature is 920°C, to obtain a carbonized material.

[0180] (2) The carbonized material is placed in a vacuum impregnator, 20% starch solution is added, the vacuum pressure is set to 70 pa, vacuum impregnation is performed for 150 min, and then heat treatment is performed at 580°C for 4 h to obtain a carbon matrix.

[0181] (3) The carbon matrix is placed in a CVD device, silane is introduced into the CVD device, the concentration of silane is controlled to be 10%, the temperature is raised to 480°C, and reaction is performed for 9 h to obtain a composite.

[0182] The subsequent steps are the same as those in Example 1.

[0183] In this example, the negative electrode material comprises a carbon matrix and silicon particles, and the silicon particles are dispersed in the carbon matrix. The other parameters of the negative electrode material are shown in Tables 1 and 2.

[0184] Example 5

[0185] (1) The fruit shell is carbonized at a temperature of 950°C, and then is acid washed with 4.5 mol / L hydrochloric acid for 5 h. The obtained material is dried and then activated by passing a mixed gas of water vapor and nitrogen, wherein the concentration of water vapor is 6.9%, the activation time is 8 h, and the activation temperature is 690°C, to obtain a carbonized material.

[0186] (2) The carbonized material is placed in a vacuum impregnator, dodecane is added, the vacuum pressure is set to 15 pa, vacuum impregnation is performed for 150 min, and then heat treatment is performed at 600°C for 4 h to obtain a carbon matrix.

[0187] (3) The carbon matrix is placed in a CVD device, silane is introduced into the CVD device, the concentration of silane is controlled to be 5%, the temperature is raised to 540°C, and reaction is performed for 5 h to obtain a composite.

[0188] The subsequent steps are the same as those in Example 1.

[0189] In this example, the negative electrode material comprises a carbon matrix and silicon particles, and the silicon particles are dispersed in the carbon matrix. The other parameters of the negative electrode material are shown in Tables 1 and 2.

[0190] Example 6

[0191] (1) Bitumen is used as a raw material, NaOH is added for activation, the mass ratio is 100:2.3, the activation time is 8 h, and the activation temperature is 760°C to obtain a carbonized material.

[0192] (2) Put the carbonized material into a vacuum impregnator, add 10% starch solution, set the vacuum pressure to 15 Pa, vacuum impregnate for 150 min, and then heat treat at 600°C for 4 h to obtain a carbon matrix.

[0193] (3) Put the carbon matrix into a CVD device, then introduce silane into the CVD device, control the silane concentration to be 5%, heat to 540°C, and react for 4 h to obtain a composite.

[0194] The subsequent steps are the same as in Example 1. In this example, the negative electrode material comprises a carbon matrix and silicon particles, and the silicon particles are dispersed in the carbon matrix. The other parameters of the negative electrode material are shown in Tables 1 and 2.

[0195] Example 7

[0196] The difference from Example 1 is only that the pressure in step (2) is 250 MPa, and the pressing is performed for 30 min.

[0197] Example 8

[0198] The difference from Example 1 is only that the pressure in step (2) is 240 MPa, and the pressing is performed for 50 min.

[0199] Example 9

[0200] The difference from Example 1 is only that the pressure in step (2) is 230 MPa, and the pressing is performed for 50 min.

[0201] Example 10

[0202] The difference from Example 1 is only that in step (4), a mixed gas of 0.05% water vapor and nitrogen is introduced into the composite, heated to 230°C, and held for 100 min to obtain a precursor.

[0203] Example 11

[0204] The difference from Example 1 is only that in step (4), a mixed gas of 0.05% H2O2 and nitrogen is introduced into the composite, heated to 230°C, and held for 100 min to obtain a precursor.

[0205] Example 12

[0206] The difference from Example 1 is only that in step (4), a mixed gas of 0.03% oxygen and nitrogen is introduced into the composite, heated to 630°C, and held for 100 min to obtain a precursor.

[0207] Example 13

[0208] The difference from Example 1 is only that: (4) a mixture gas of 5% oxygen and nitrogen is passed into the compound, the temperature is raised to 230°C, and the holding time is 100 min to obtain the precursor.

[0209] Example 14

[0210] The difference from Example 1 is only that: (4) a mixture gas of 0.03% oxygen and nitrogen is passed into the compound, the temperature is raised to 230°C, and the holding time is 360 min to obtain the precursor.

[0211] Comparative Example 1

[0212] The difference from Example 1 is only that: the pressure is 90 MPa

[0213] In this comparative example, the negative electrode material comprises a carbon matrix and silicon particles, and the silicon particles are dispersed in the carbon matrix. Other parameters of the negative electrode material are shown in Tables 1 and 2.

[0214] Comparative Example 2

[0215] The difference from Example 2 is only that: the setting pressure in step (2) is normal pressure.

[0216] In this comparative example, the negative electrode material comprises a carbon matrix and silicon particles, and the silicon particles are dispersed in the carbon matrix. Other parameters of the negative electrode material are shown in Tables 1 and 2.

[0217] Comparative Example 3

[0218] The difference from Example 1 is only that: the carbonized material is not put into the molding machine for molding treatment.

[0219] Comparative Example 4

[0220] The difference from Example 1 is only that:

[0221] (4) a mixture gas of 15% oxygen and nitrogen is passed into the compound, the temperature is raised to 230°C, and the holding time is 100 min to obtain the precursor.

[0222] Performance test

[0223] 1. Test method for pore size and pore volume ratio of negative electrode material:

[0224] The carbon material is tested by using the iPore620 pore size tester of Link Physical and Chemical Co., Ltd. and the BET pore size distribution test method. The pore size distribution data of the carbon material are obtained by DFT simulation analysis using the isothermal adsorption characteristic curve of nitrogen, and then the total pore volume, the pore volume ratio of micropores, mesopores and macropores in the total pore volume of the carbon material are obtained.

[0225] 2. SEM section processing is performed on the negative electrode material particles, and the area of a single negative electrode material particle and the area of all pores are counted and calculated using the Aztec Feature software of the SEM electron microscope OXFORD Instruments, specifically:

[0226] (1) Electron microscope and energy spectrum conditions

[0227] Electron microscope: select a region of the target particle as monodisperse as possible, and adjust appropriate parameters (accelerating voltage 20 kV or 15 kV, electron beam rotation 0 degrees) to obtain a clear backscattered field of view.

[0228] Energy spectrum: turn on the AZtec Feature software during testing, and perform probe cooling; when the energy spectrum probe constant blue indicator light is on, start testing.

[0229] (2) Test process

[0230] Provide a reference sample substrate of the negative electrode material of the present application, first move the field of view to the reference sample substrate, adjust the brightness and contrast, obtain the image gray scale of the reference sample substrate, and ensure that the gray scale of the negative electrode material particles and the reference sample substrate is pulled apart. Note: after the reference image gray scale is adjusted, the brightness and contrast of the electron microscope cannot be adjusted again.

[0231] Move the field of view to the monodisperse negative electrode material particles, collect the BSE electron image, adjust and set the appropriate threshold range, so that the field of view has typical characteristic particles, moderate size and gray scale, and the particle marking in the field of view is optimized. (The particles can be selected at that time by threshold filtering, multiple-image resolution filtering, pixel filtering and secondary image filtering)

[0232] Set the negative electrode material particle detection mode, filtering conditions and collection time, etc., and the filtering condition selects a pore with a pore size greater than 50 nm, after setting is completed, click to detect the negative electrode material particles, and obtain the list information of the negative electrode material particles that meet the conditions (for example: pore number, element list and content, etc.) on the right side of the software.

[0233] When the AZtec Feature is run, the user can check all detected features in this interface, and can reposition and reacquire images and spectra for specified features. After highlighting the feature of interest (i.e., the pore with a pore size greater than 50 nm in the present application), a 10 μm x 10 μm square region is selected, the cross-sectional area of the negative electrode material particle in the square region is S, the sum of the cross-sectional areas of all pores with a pore size greater than 50 nm in the cross-section of the negative electrode material particle in the square region is S1, and a' = S1 / S, and then the arithmetic mean of the a' values of at least 10 negative electrode material particles is calculated, that is, a.

[0234] 3. The median particle size of the negative electrode material is tested by a laser particle size analyzer.

[0235] 4. After etching silicon particles in the negative electrode material using HF, the average pore size of the pores is tested using a Micromeritics ASAP 2460 full-automatic specific surface and porosity analyzer. The gas used in the test is CO2 or N2.

[0236] 5. Method for testing the average particle size of silicon particles and carbon matrix: the maximum cross-sectional length of 20 silicon particles is tested using a high-power microscope, and then the average value of the cross-sectional lengths of multiple silicon particles is calculated, which is the average particle size of the silicon particles. Similarly, the maximum cross-sectional length of 20 carbon matrices is tested using a high-power microscope, and then the average value of the cross-sectional lengths of multiple carbon matrices is calculated, which is the average particle size of the silicon particles.

[0237] 6. The electrochemical performance of the negative electrode material is tested by the following method:

[0238] The negative electrode material, the conductive agent and the binder with a mass ratio of 94:1:5 are dissolved in a solvent, the solid content is controlled at 50%, the above mixture is coated on a copper foil current collector, vacuum dried, and then the compaction density is controlled at 1.7-1.8 g / cm 3 , the thickness of the electrode sheet is 60-70 microns, the rolling is performed, and the negative electrode sheet is prepared; then the ternary positive electrode sheet prepared by the traditional mature process, the 1 mol / L LiPF6 / EC+DMC+EMC (v / v / v=1:1:1) electrolyte, the Celgard2400 separator, and the shell are assembled into a 18650 cylindrical single battery by using the conventional production process. The charge-discharge test of the cylindrical battery is performed on a LAND battery test system of Wuhan Jinuo Electronics Co., Ltd. under normal temperature conditions, 0.2C constant current charge-discharge, and the charge-discharge voltage is limited to 2.75-4.2V. The test results are shown in Tables 1-2, wherein Examples 1-11 are denoted as S1-S11, and Comparative Examples 1-4 are denoted as D1-D4.

[0239] 7. The negative electrode sheet is tested for pressure resistance by the following method:

[0240] The negative electrode material, the conductive agent and the binder with a mass ratio of 94:2:4 are dissolved in a solvent, the solid content is controlled at 30%, the above mixture is coated on a copper foil current collector, vacuum dried to obtain a negative electrode sheet, and then the negative electrode sheet is rolled by a roll mill according to the set pressure, the thickness of the negative electrode sheet is controlled at 60-70 microns, and then the cross-section of the negative electrode sheet is tested to observe whether there is particle crushing in the negative electrode sheet. When particle crushing occurs, the minimum pressure value corresponding to the particle crushing is the critical pressure P of the negative electrode sheet.

[0241] 8. The compaction density of the negative electrode sheet is tested according to Appendix L of GBT 24533-2019.

[0242] Table 1. Performance parameters of negative electrode materials of various embodiments and comparative examples

[0243]

[0244]

[0245] Table 2. Alpha test of negative electrode materials of various embodiments and comparative examples

[0246]

[0247] According to Tables 1 and 2, the number of macropores and the macropore volume in the negative electrode material prepared in the present application are small, satisfying a≤10%, which can effectively reduce the specific surface area of the negative electrode material, reduce the occurrence of side reactions between the negative electrode material and the electrolyte during the first charge-discharge process, and reduce gas production; at the same time, I A / (I B +I C ), reduces the contact between the silicon particles in the negative electrode material and the electrolyte, and the synergistic effect of the two further reduces the direct contact between the silicon particles and the electrolyte. The negative electrode material has a stable solid-state electrolyte film on the surface, which improves the specific capacity of the negative electrode material and the cycle stability of the negative electrode material.

[0248] According to the test data of Example 1 and Examples 7-9, the decrease of the impregnation pressure of the carbonized material or the shortening of the impregnation time will affect the total pore volume and the average pore size of the carbon matrix. Generally, as the impregnation pressure decreases, the amount of treatment solution penetrating into the porous carbonaceous raw material decreases, the total pore volume of the carbon matrix increases, and the average pore size also increases. This will result in a decrease in the volume ratio of mesopores in the negative electrode material after the deposition of silicon particles, an increase in the number and volume ratio of macropores in the negative electrode material, an increase in the value of a, and a slight decrease in the cycle performance of the negative electrode material.

[0249] According to the test data of Example 1 and Examples 10-14, the capacity of the negative electrode material changes with the degree of oxidation of the precursor. The higher the degree of oxidation, the lower the capacity, but the better the cycle performance.

[0250] In Comparative Examples 1 and 2, the pressure applied to the porous carbonaceous raw material in Comparative Example 1 is too small, resulting in a large number of macropores in the negative electrode material and a large pore size, which leads to problems such as low capacity, low first efficiency, and poor cycle performance of the negative electrode material. Moreover, when the negative electrode material is prepared into a negative electrode sheet, the critical pressure P and the compaction density of the negative electrode sheet are small, which leads to the deterioration of the processing performance of the negative electrode sheet.

[0251] In Comparative Example 3, the carbonized material is not subjected to the molding treatment in the molding machine, so that the number of macropores in the negative electrode material is significantly increased, the silicon particles are not effectively filled into the micropores of the carbon matrix, and part of the silicon particles are located on the surface of the carbon matrix, resulting in the problems of low capacity, low first efficiency and poor cycle performance of the negative electrode material. Moreover, the negative electrode material is prepared into a negative electrode sheet, and the critical pressure P and the compacted density of the negative electrode sheet are small, resulting in the deterioration of the processing performance of the negative electrode sheet.

[0252] In Comparative Example 4, the amount of oxygen introduced is too large, resulting in the problem of too high oxidation degree of the silicon particles in the negative electrode material, and the capacity and the first coulombic efficiency of the negative electrode material are significantly reduced.

[0253] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art based on the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A negative electrode material, characterized in that comprising a carbon matrix and silicon particles, wherein the silicon particles are dispersed in the carbon matrix; The negative electrode material was tested by Raman spectroscopy. The negative electrode material -1 There is a first characteristic peak at the position, and the peak intensity of the first characteristic peak is I A ; at 960±10 cm -1 There is a second characteristic peak at the position, and the peak intensity of the second characteristic peak is I B ; at 480±10 cm -1 There is a third characteristic peak at the position, and the peak intensity of the third characteristic peak is 1 C , then I A , I B with I C The following relationship exists: 0.3≤I A / (I B +I C )≤0.6; and the negative electrode material satisfies: α≤10%; Among them, α is obtained by the following test method: In the electron microscope image shown by SEM cross-section processing of a single negative electrode material particle, a square area of ​​10μm×10μm is selected, the cross-sectional area of ​​the negative electrode material particle in the square area is S, and the sum of the cross-sectional areas of all pores with a pore diameter greater than 50nm in the cross section of the negative electrode material particle in the square area is S1, α'=S1 / S, α is the arithmetic mean of the α' values ​​of at least 10 negative electrode material particles.

2. The negative electrode material according to claim 1, characterized in that The negative electrode material has pores, wherein the volume proportion of mesopores in the total pore volume of the negative electrode material is 25% to 95%; and / or the total pore volume of the negative electrode material is 0.001cm 3 / g~0.1 cm 3 / g.

3. The negative electrode material according to claim 1, characterized in that The negative electrode material after the silicon particles are removed has pores, and the total pore volume of the negative electrode material after the silicon particles are removed is 0.4 cm 3 / g~1.5cm 3 / g; and / or, the average pore size of the pores of the negative electrode material after removing the silicon particles is 1.0nm~5.2nm.

4. The negative electrode material according to claim 1, characterized in that At least part of the surface of the negative electrode material has a carbon layer, and the surface of the negative electrode material is tested by Raman spectroscopy. -1 There is a characteristic peak D at the position, and the peak intensity of the characteristic peak D is I D , at 1580±10cm -1 There is a characteristic peak G at the position, and the peak intensity of the characteristic peak G is I G , then I A , I D , I G There is the following relationship: (I D +I G ) / I A ≥10.

5. The negative electrode material according to any one of claims 1 to 4, characterized in that At least a portion of the silicon particles are located inside the carbon matrix particles.

6. The negative electrode material according to any one of claims 1 to 4, characterized in that The negative electrode material has at least one of the following characteristics: (1) The carbon matrix includes at least one of hard carbon and soft carbon; (2) The carbon matrix includes porous carbon, and the porous carbon includes at least one of activated carbon, carbon black, capacitive carbon, mesoporous carbon, carbon nanotubes and carbon molecular sieves; (3) The mass proportion of oxygen in the negative electrode material is ≤5wt%; (4) The mass percentage of carbon element in the negative electrode material is 30wt% to 60wt%; (5) The mass percentage of silicon in the negative electrode material is 30 wt% to 65 wt%; (6) At least part of the surface of the negative electrode material has a carbon layer, and the thickness of the carbon layer is 0.1 nm to 3000 nm.

7. The negative electrode material according to any one of claims 1 to 4, characterized in that The negative electrode material has at least one of the following characteristics: (1) The negative electrode material further includes other active particles, and the other active particles include at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al, P and Cu; (2) The silicon particles include at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, and a composite of crystalline silicon and amorphous silicon; (3) The silicon particles include amorphous silicon; (4) The average particle size of the silicon particles is 1 nm to 100 nm.

8. The negative electrode material according to any one of claims 1 to 4, characterized in that The specific surface area of ​​the negative electrode material is 1m 2 / g~500m 2 / g, and the specific surface area of ​​the negative electrode material after removing silicon particles is 800 m 2 / g~2500m 2 / g.

9. The negative electrode material according to any one of claims 1 to 4, characterized in that The compacted density of the negative electrode sheet made from the negative electrode material is 1.3 g / cm 3 ~1.9g / cm 3 , and / or, the critical pressure P of the negative electrode sheet made of the negative electrode material is greater than or equal to 100 MPa.

10. A battery, characterized in that: The battery comprises the negative electrode material according to any one of claims 1 to 9.

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