Negative electrode material, preparation method thereof and battery

Abstract

The invention provides a negative electrode material and a preparation method thereof, and a battery, the negative electrode material comprises an active substance, the active substance comprises a carbon matrix and silicon particles, the carbon matrix has holes, and at least part of the silicon particles are distributed in the holes of the carbon matrix; the negative electrode material contains an oxygen element and a nitrogen element, the mass content of the oxygen element is A%, and the mass content of the nitrogen element is B%; the powder conductivity of the negative electrode material is PS / m and meets the following relation: (A + B) / P is less than or equal to 3. According to the negative electrode material provided by the invention, the gas production phenomenon of the negative electrode material can be reduced on the premise of keeping relatively high electronic conductivity.

Description

Technical Field

[0001] The present application relates to the technical field of anode materials. Specifically, it relates to anode materials, their preparation methods, and batteries. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, long cycle life, low environmental pollution, and no memory effect, so they are widely used in electric vehicles and consumer electronic products. In recent years, with the rapid development of electric vehicles, the demand for higher energy density lithium-ion batteries has been increasing day by day, which has prompted researchers to search for battery materials with higher energy density and better cycle performance. The anode and cathode materials are the core of the battery and determine the working efficiency of the battery. At present, the commercial anode material is graphite, and its capacity has approached the theoretical upper limit, and the room for further improvement is limited. Therefore, there is an urgent need to develop a new generation of high energy density anode materials. Among them, silicon-based anode materials are generally considered to be the next generation of battery anode materials, with advantages such as high capacity, rich sources, and relative safety.

[0003] Silicon anodes are generally considered to be the next generation of battery anode materials, with advantages such as high capacity, rich sources, and relative safety. However, silicon anodes have a severe volume expansion effect during the cycling process, resulting in material pulverization and fragmentation, and the cycle attenuation of the material is very fast. Usually, the silicon-carbon composite method is used to suppress the volume expansion of silicon, but there is a gas generation problem in the process of manufacturing the electrode sheet of the silicon-carbon anode material, which brings potential safety hazards and limits its application. Summary of the Invention

[0004] The present application provides an anode material, its preparation method, and a battery, which are beneficial to reducing the gas generation phenomenon of the anode material while maintaining a relatively high electronic conductivity.

[0005] In a first aspect, the present application provides an anode material, including an active substance, the active substance includes a carbon matrix and silicon particles, the carbon matrix has pores, and at least part of the silicon particles are distributed in the pores of the carbon matrix;

[0006] The anode material contains oxygen element and nitrogen element, the mass content of the oxygen element is A%, and the mass content of the nitrogen element is B%; the powder conductivity of the anode material is P S / m, and the following relationship is satisfied: (A + B) / P ≤ 3.

[0007] In some embodiments, in the anode material, the mass content of the oxygen element is A%, 0 < A ≤ 3.

[0008] In some embodiments, in the anode material, the mass content of the nitrogen element is B%, 0 < B ≤ 3.

[0009] In some embodiments, the surface and / or pores of the carbon matrix have functional groups, and the functional groups include at least one of hydroxyl, carboxyl, carbonyl, lipid group, cyclic lipid group, and amino group.

[0010] In some embodiments, the carbon matrix includes at least one of hard carbon, soft carbon, graphite, mesocarbon microbeads, activated carbon, porous carbon, mesoporous carbon, and carbon gel.

[0011] In some embodiments, the total pore volume of the carbon matrix is ≥ 0.4 cm 3 / g.

[0012] In some embodiments, the pores in the carbon matrix include micropores, and the volume ratio of the micropores in the total pore volume is ≥ 80%.

[0013] In some embodiments, the average pore diameter of the pores in the carbon matrix is ≤ 5 nm.

[0014] In some embodiments, the porosity of the carbon matrix is 40% - 60%.

[0015] In some embodiments, the silicon particles include at least one of elemental silicon, silicon oxide, silicon alloy, and silicon-carbon composite.

[0016] In some embodiments, the average particle diameter of the silicon particles is 0.1 nm - 500 nm.

[0017] In some embodiments, the mass content of silicon element in the silicon particles is ≥ 99%.

[0018] In some embodiments, a carbon layer is further included on at least part of the surface of the active material.

[0019] In some embodiments, the carbon layer includes at least one of graphitic carbon and amorphous carbon.

[0020] In some embodiments, the median particle size D of the negative electrode material 50 ≤ 10 μm.

[0021] In some embodiments, the specific surface area of the negative electrode material is ≤ 5 m 2 / g.

[0022] In some embodiments, the gas production of the negative electrode material in 6 days is M mL / g, and M ≤ 0.2.

[0023] In some embodiments, the powder conductivity of the negative electrode material is P S / m, and P ≥ 0.01 S / m.

[0024] In a second aspect, the present application provides a method for preparing a negative electrode material, including the following steps:

[0025] Perform a primary carbonization treatment on a mixture including a carbon source and a modifying substance to obtain a precursor, wherein the modifying substance includes a nitrogen-containing compound and an oxygen-containing compound;

[0026] Perform a secondary carbonization treatment on the precursor to obtain a carbon matrix, wherein the temperature of the secondary carbonization treatment is higher than that of the primary carbonization treatment;

[0027] Compound the carbon matrix with pores and silicon particles to obtain a negative electrode material, wherein at least part of the silicon particles are distributed in the pores of the carbon matrix.

[0028] In some embodiments, the carbon source includes at least one of bamboo charcoal, coconut shell, resin, starch, and fruit shell.

[0029] In some embodiments, the temperature of the primary carbonization treatment is 600°C to 900°C.

[0030] In some embodiments, the time of the primary carbonization treatment is 2h to 10h.

[0031] In some embodiments, the nitrogen-containing compound includes at least one of urea, ammonium acetate, methanolamine, ammonium chloride, ammonium nitrate, and N,N-dimethylformamide.

[0032] In some embodiments, the mass ratio of the carbon source to the nitrogen-containing compound is 100:(0.5 to 100).

[0033] In some embodiments, the method further includes: subjecting the product of the primary carbonization treatment to an activation treatment in a mixed gas of nitrogen and water vapor.

[0034] In some embodiments, the method further includes: subjecting the product of the primary carbonization treatment to an activation treatment in a mixed gas of nitrogen and water vapor; wherein the concentration of the water vapor is 0.1% to 30%.

[0035] In some embodiments, the method further includes: subjecting the product of the primary carbonization treatment to an activation treatment in a mixed gas of nitrogen and water vapor; the temperature of the activation treatment is 380°C to 2000°C, and the time of the activation treatment is 0.5h to 30h.

[0036] In some embodiments, the method further includes: subjecting the product of the primary carbonization treatment to a primary activation treatment in a mixed gas of nitrogen and water vapor, and then subjecting the primary activation product to a secondary activation treatment, the temperature of the activation treatment is 380°C to 2000°C, and the time of the activation treatment is 0.5h to 30h.

[0037] In some embodiments, the temperature of the secondary carbonization treatment is 900°C to 2000°C.

[0038] In some embodiments, the time of the secondary carbonization treatment is 1 h to 30 h.

[0039] In some embodiments, the step of compounding the carbon matrix with pores and silicon particles includes: performing chemical vapor deposition on the carbon matrix with pores using a silicon source gas to obtain an active material.

[0040] In some embodiments, the silicon source gas includes at least one of silane, disilane, trichlorosilane, and dichlorosilane.

[0041] In some embodiments, the average particle size of the carbon matrix is 1 μm to 15 μm.

[0042] In some embodiments, the average pore size of the carbon matrix is 0.1 nm to 5 nm.

[0043] In some embodiments, the volume concentration ratio of the silicon source gas is 1% to 90%.

[0044] In some embodiments, the deposition time of the chemical vapor deposition is 0.1 h to 15 h.

[0045] In some embodiments, the deposition temperature of the chemical vapor deposition is 300 °C to 800 °C.

[0046] In some embodiments, the method further includes: performing carbon coating treatment on the active material to obtain a negative electrode material; the carbon coating treatment includes at least one of solid-phase carbon coating, liquid-phase carbon coating, and gas-phase carbon coating.

[0047] In a third aspect, the present application provides a battery, and the battery includes the above negative electrode material or the negative electrode material prepared according to the above preparation method.

[0048] The technical solution of the present application has at least the following beneficial effects:

[0049] The negative electrode material provided by the present application includes an active material, the active material includes a carbon matrix and silicon particles, the carbon matrix has pores, and at least part of the silicon particles are distributed in the pores of the carbon matrix, which can improve the capacity of the negative electrode material. Moreover, the negative electrode material contains a small amount of oxygen and nitrogen elements. The doping of a small amount of nitrogen and oxygen elements can provide lone pairs of electrons, and the lone pairs of electrons participate in the π-π conjugate system of the carbon matrix, thereby forming a larger p-π conjugate system and further increasing the electronic conductivity of the negative electrode material; however, the presence of oxygen and nitrogen elements is likely to react with solvent molecules or hydrogen radicals in the electrolyte to generate some gases (such as CO 2 、CO、NH 2etc.), the gas generation phenomenon will affect the safety performance of the battery. Therefore, in this application, it is controlled that (A + B) / P ≤ 3. Within this range, controlling the relationship between the mass contents of oxygen and nitrogen and the electronic conductivity of the anode material is beneficial to reducing the gas generation phenomenon of the anode material while maintaining a relatively high electronic conductivity. The pores existing in the carbon matrix are beneficial to alleviating the volume expansion of the anode material during the cycling process, maintaining structural stability, and reducing the collapse of the material structure caused by volume expansion during the lithium insertion and extraction process of the anode material. The pores in the carbon matrix can also adsorb a small amount of gas, which can further reduce the gas generation phenomenon of the anode material, thereby improving the cycling performance of the anode material.

[0050] The preparation method of the anode material provided by this application uses a mixture of a carbon source and a modifying substance for primary carbonization treatment, so that the modifying substance can be doped in the carbon matrix. Then, through secondary carbonization treatment, controlling the temperature of the secondary carbonization treatment to be higher than that of the primary carbonization treatment can increase the graphitization degree of the carbon matrix by means of high temperature and improve the electronic conductivity of the carbon matrix itself. In addition, during the secondary carbonization treatment process, more oxygen-containing or nitrogen-containing groups volatilize, and thus the mass contents of nitrogen and oxygen in the carbon matrix can be controlled. The doping of a small amount of nitrogen and oxygen elements can provide lone pairs of electrons, and the lone pairs of electrons participate in the π-π conjugate system of the carbon matrix, thereby forming a larger p-π conjugate system and further increasing the electronic conductivity of the anode material. Finally, the above carbon matrix is compounded with silicon particles, which can improve the capacity of the anode material; the pores existing in the carbon matrix are beneficial to alleviating the volume expansion of the silicon particles during the cycling process of the anode material, maintaining structural stability, and reducing the collapse of the material structure caused by volume expansion during the lithium insertion and extraction process of the anode material. The pores in the carbon matrix can also adsorb a small amount of gas, which can further reduce the gas generation phenomenon of the anode material, thereby improving the cycling performance of the anode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 is the process flow chart of the preparation method of the anode material provided by this application.

[0052] Figure 2 is the XRD pattern of the anode material prepared in Example 1 of the present invention.

[0053] Figure 3 is the schematic diagram of the first charge and discharge curve of the anode material prepared in Example 1 of the present invention.

[0054] Figure 4 is the schematic diagram of the cycling performance curve of the anode material prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] To better illustrate the present application and facilitate understanding of its technical solution, the present application will be further described in detail below. However, the following embodiments are merely simple examples of the present application and do not represent or limit the scope of the claimed protection of the present application. The scope of protection of the present application shall be subject to the claims.

[0056] In a first aspect, the present application provides a negative electrode material, which includes an active material. The active material includes a carbon matrix and silicon particles. The carbon matrix has pores, and at least part of the silicon particles are distributed in the pores of the carbon matrix.

[0057] The negative electrode material contains oxygen element and nitrogen element. The mass content of the oxygen element is A%, and the mass content of the nitrogen element is B%.

[0058] The powder conductivity of the negative electrode material is P S / m, and the following relationship is satisfied: (A + B) / P ≤ 3.

[0059] For the negative electrode material provided by the present application, the negative electrode material includes an active material. The active material includes a carbon matrix and silicon particles. The carbon matrix has pores, and at least part of the silicon particles are distributed in the pores of the carbon matrix, which can improve the capacity of the negative electrode material. Moreover, the negative electrode material contains a small amount of oxygen element and nitrogen element. The doping of a small amount of nitrogen element and oxygen element can provide lone pairs of electrons, and the lone pairs of electrons participate in the π-π conjugate system of the carbon matrix, thereby forming a larger p-π conjugate system and further increasing the electronic conductivity of the negative electrode material. However, the presence of oxygen element and nitrogen element is likely to react with solvent molecules or hydrogen radicals in the electrolyte to generate some gases (such as CO 2 、CO、NH 2 etc.). The gas generation phenomenon will affect the safety performance of the battery. Therefore, the present application controls (A + B) / P ≤ 3 within this range, controls the relationship between the mass content of oxygen and nitrogen and the electronic conductivity of the negative electrode material, which is beneficial to reducing the gas generation phenomenon of the negative electrode material while maintaining a high electronic conductivity. The pores existing in the carbon matrix are beneficial to alleviating volume expansion during the cycling process of the negative electrode material, maintaining structural stability, and reducing the collapse of the material structure caused by volume expansion during the lithium insertion and extraction process of the negative electrode material. The pores in the carbon matrix can also adsorb a small amount of gas, which can further reduce the gas generation phenomenon of the negative electrode material, thereby improving the cycling performance of the negative electrode material.

[0060] In some embodiments, in the negative electrode material, the mass content of the oxygen element is A%, 0 < A ≤ 3; the specific value of A can be 0.1, 0.2, 0.4, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8 or 3, etc., which is not limited herein. Preferably, the mass content of the oxygen element 0 < A% ≤ 1.5%.

[0061] In some embodiments, in the negative electrode material, the mass content of nitrogen element is B%, where 0 < B ≤ 3; specifically, the value of B can be 0.1, 0.2, 0.4, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8, or 3, etc., and there is no limitation here. Controlling the nitrogen element content in the negative electrode material within the above range can improve the specific capacity of the negative electrode material. Preferably, 0.1% ≤ B% ≤ 0.5%.

[0062] In some embodiments, the carbon matrix includes at least one of hard carbon, soft carbon, graphite, mesocarbon microbeads, activated carbon, porous carbon, mesoporous carbon, and carbon gel.

[0063] In some embodiments, the surface and / or pores of the carbon matrix have functional groups, and the functional groups include at least one of hydroxyl group, carboxyl group, carbonyl group, lipid group, cyclic lipid group, and amino group.

[0064] In some embodiments, the nitrogen element and oxygen element exist in the form of atomic doping on the surface and / or in the pores of the carbon matrix. Specifically, it can be in the pores of the carbon matrix and / or at the surface defects.

[0065] In some embodiments, the total pore volume of the carbon matrix ≥ 0.4 cm 3 / g, specifically, it can be 0.4 cm 3 / g, 0.5 cm 3 / g, 0.8 cm 3 / g, 1 cm 3 / g, 1.1 cm 3 / g, 1.3 cm 3 / g, 1.5 cm 3 / g, or 1.8 cm 3 / g, etc. Of course, it can also be other values within the above range, and there is no limitation here. Preferably, the total pore volume of the carbon matrix ≥ 0.5 cm 3 / g; further preferably, the total pore volume of the carbon matrix ≥ 0.7 cm 3 / g.

[0066] In some embodiments, the pores in the carbon matrix include micropores with a pore diameter less than 2 nm, and the proportion of micropores ≥ 80%. Specifically, the proportion of micropores can be 80%, 82%, 85%, 88%, 90%, 92%, 93%, 95%, 98%, or 99%, etc., and there is no limitation here. It can be understood that the size of the silicon particles deposited in the pores of the carbon matrix is determined by the size of the pores. The higher the proportion of micropores, the smaller the average pore diameter of the pores, and the smaller the silicon particles deposited in the pores. The small silicon particles deposited in the pores of the carbon matrix result in small volume expansion of the negative electrode material during the cycling process, which is beneficial to improving the cycling performance of the negative electrode material. Preferably, the proportion of micropores ≥ 90%; further preferably, the proportion of micropores ≥ 95%.

[0067] In some embodiments, the average pore diameter of the pores in the carbon matrix is ≤ 5 nm, specifically, it can be 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm or 5 nm, etc. Of course, it can also be other values within the above range, which are not limited herein. It can be understood that the average pore diameter of the pores in the carbon matrix will affect the size of the silicon particles located in the pores. Controlling the average pore diameter of the pores in the carbon matrix can adjust the size of the silicon particles and reduce the phenomenon of excessive expansion stress caused by the accumulation of local silicon particles. Preferably, the average pore diameter of the pores in the carbon matrix is ≤ 2 nm; more preferably, the average pore diameter of the pores in the carbon matrix is ≤ 1.8 nm.

[0068] In some embodiments, the porosity of the carbon matrix is 40% - 60%, specifically, it can be 40%, 41%, 43%, 45%, 48%, 50%, 52%, 54%, 56%, 58% or 60%, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0069] In some embodiments, the silicon particles include at least one of silicon, silicon oxide, silicon alloy and silicon-carbon composite. Specifically, the silicon can be amorphous silicon, crystalline silicon or a composite of crystalline silicon and amorphous silicon, etc., which are not limited herein. The silicon alloy can be a silicon-lithium alloy, a silicon-magnesium alloy, a silicon-nickel alloy, etc., which are not limited herein.

[0070] In some embodiments, the average particle size of the silicon particles is 0.1 nm - 500 nm, specifically, it can be 1 nm, 5 nm, 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 300 nm, 350 nm, 400 nm or 500 nm, etc. Of course, it can also be other values within the above range, which are not limited herein. Silicon particles with suitable sizes can improve the distribution uniformity of the silicon particles and the carbon matrix, reduce the segregation phenomenon of the silicon particles, and improve the cycling performance of the negative electrode material. Preferably, the average particle size of the silicon particles is 1 nm - 10 nm; further preferably, the average particle size of the silicon particles is 1 nm - 5 nm.

[0071] In some embodiments, the mass content of silicon in the silicon particles is ≥ 99%. When the mass content of silicon in the silicon particles is within the above range, it is beneficial to improve the purity of the silicon particles and reduce impurities.

[0072] In some embodiments, the negative electrode material further includes a carbon material located on at least a part of the surface of the active material. Understandably, the carbon material can, to a certain extent, reduce the volume expansion effect of the negative electrode material as a buffer layer while enhancing the conductivity of the negative electrode material; the carbon material can also reduce the direct contact between the active material and the electrolyte, inhibit the excessive growth of the SEI film on the surface of the negative electrode material, stabilize the interface of the negative electrode material, and improve the Coulomb efficiency of the negative electrode material.

[0073] In some embodiments, the carbon material includes at least one of graphitic carbon and amorphous carbon. The presence of the carbon material on the surface of the active material can increase the conductivity of the negative electrode material, stabilize the interface of the negative electrode material, reduce the direct contact between silicon particles and the electrolyte, reduce the occurrence of side reactions, and improve the rate performance and cycling performance of the negative electrode material.

[0074] In some embodiments, the median particle size D50 of the negative electrode material is ≤ 10 μm, specifically it can be 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, etc. Of course, it can also be other values within the above range, which are not limited herein. It can be understood that controlling the median particle size of the negative electrode material within the above range is beneficial to improving the cycling performance of the negative electrode material.

[0075] In some embodiments, the specific surface area of the negative electrode material is ≤ 5 m 2 / g, specifically it can be 0.1 m 2 / g, 0.5 m 2 / g, 1 m 2 / g, 1.5 m 2 / g, 2 m 2 / g, 2.5 m 2 / g, 3 m 2 / g, 3.5 m 2 / g, 4 m 2 / g, 4.5 m 2 / g or 5 m 2 / g, etc. Of course, it can also be other values within the above range, which are not limited herein. Controlling the specific surface area of the negative electrode material within the above range is beneficial to improving the initial efficiency and cycling performance of the lithium battery made of this negative electrode material.

[0076] In some embodiments, the gas production of the negative electrode material in 6 days is M mL / g, and M ≤ 0.2. The gas production of the negative electrode material can specifically be 0.2 mL / g, 0.18 mL / g, 0.15 mL / g, 0.12 mL / g, 0.10 mL / g, 0.08 mL / g, 0.05 mL / g or 0.01 mL / g, etc. Of course, it can also be other values within the above range, which are not limited herein. Controlling the gas production of the negative electrode material within the above range can improve the cycling stability and safety of the negative electrode material.

[0077] The test method for the gas generation amount of the negative electrode material is as follows: Add 20 g of the negative electrode material to 50 g of a styrene-butadiene rubber solution to obtain a mixture, encapsulate the mixture with an aluminum-plastic film, and place it in a 2000 mL sealed container, and store it at a temperature of 45 °C. The gas generation amount of the negative electrode material in 6 days is measured to be M mL / g.

[0078] In some embodiments, the powder conductivity of the negative electrode material is P S / m, P≥0.01 S / m. The powder conductivity can specifically be 0.01 S / m, 0.02 S / m, 0.03 S / m, 0.05 S / m, 0.08 S / m, 0.1 S / m, 0.2 S / m, or 1 S / m, etc. Of course, it can also be other values within the above range, which is not limited here.

[0079] In a second aspect, the present application provides a method for preparing a negative electrode material, as Figure 1 shown, including the following steps:

[0080] Step S10, perform a primary carbonization treatment on a mixture including a carbon source and a modifying substance to obtain a precursor;

[0081] Step S20, perform a secondary carbonization treatment on the precursor to obtain a carbon matrix, wherein the temperature of the secondary carbonization treatment is higher than that of the primary carbonization treatment;

[0082] Step S30, compound the carbon matrix with pores and silicon particles to obtain a negative electrode material, wherein at least part of the silicon particles are distributed in the pores of the carbon matrix.

[0083] The method for preparing the negative electrode material provided by the present application uses a mixture of a carbon source and a modifying substance for a primary carbonization treatment, so that the modifying substance can be doped in the carbon matrix. Then, through a secondary carbonization treatment, controlling the temperature of the secondary carbonization treatment to be higher than that of the primary carbonization treatment, the graphitization degree of the carbon matrix can be improved by means of high temperature, and the electronic conductivity of the carbon matrix itself can be increased; in addition, during the secondary carbonization treatment, more oxygen-containing or nitrogen-containing groups volatilize, and the mass content of nitrogen and oxygen in the carbon matrix can be controlled. The doping of a small amount of nitrogen and oxygen elements can provide lone pairs of electrons, and the lone pairs of electrons participate in the π-π conjugate system of the carbon matrix, thereby forming a larger p-π conjugate system and further increasing the electronic conductivity of the negative electrode material. Finally, the above carbon matrix is compounded with silicon particles, which can improve the capacity of the negative electrode material; the pores existing in the carbon matrix are beneficial to alleviating the volume expansion of silicon particles during the cycling process, maintaining structural stability, reducing the collapse of the material structure caused by volume expansion during the lithium insertion and extraction process of the negative electrode material, effectively reducing the occurrence of side reactions between the negative electrode material and the electrolyte, and further improving the cycling performance of the negative electrode material.

[0084] The following is a detailed description in combination with specific embodiments:

[0085] Step S10, subject a mixture including a carbon source and a modifying substance to a primary carbonization treatment to obtain a precursor, wherein the modifying substance includes a nitrogen-containing compound and an oxygen-containing compound.

[0086] In some embodiments, the carbon source includes at least one of fruit shell, starch, coconut shell, rice husk, peanut shell, coal, lignin, sugar, resin, etc.

[0087] In some embodiments, the temperature of the primary carbonization treatment is 600°C to 900°C, specifically, it can be 600°C, 650°C, 700°C, 750°C, 800°C, 850°C or 900°C, etc., which is not limited herein; the time of the carbonization treatment is 1h to 15h, specifically, it can be 1h, 3h, 5h, 8h, 10h, 12h, 13h, 14h or 15h, etc., which is not limited herein.

[0088] In some embodiments, the nitrogen-containing compound includes at least one of urea, ammonium acetate, methylamine, ammonium chloride, ammonium nitrate and N,N-dimethylformamide. It can be understood that nitrogen-containing compounds of the urea type itself contain oxygen and nitrogen elements, so as to achieve doping modification of the carbon source. Even if a compound such as ammonium chloride does not contain oxygen, during the primary carbonization treatment, oxygen in the environment can participate in the doping modification together with the nitrogen element in the modifying substance.

[0089] In some embodiments, the mass ratio of the carbon source to the nitrogen-containing compound is 100:(0.5 - 100), specifically, it can be 100:0.5, 100:1, 100:5, 100:10, 100:20, 100:30, 100:50, 100:60, 100:80, 100:90 or 100:100, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0090] In some embodiments, the method further includes: subjecting the product of the primary carbonization treatment to an activation treatment in a mixed gas of nitrogen and water vapor. It can be understood that through the activation treatment, it is beneficial for silicon particles to be directionally deposited into the pores of the carbon matrix during the subsequent silicon deposition process, reducing the deposition of silicon particles on the surface of the carbon matrix.

[0091] The activation treatment method includes at least one of physical activation treatment and chemical activation treatment. Specifically, chemical activation can be to use an alkali solution as an activator to treat the product of the primary carbonization treatment. Physical activation can be to use at least two of water vapor, oxygen and air for activation treatment.

[0092] In some embodiments, the volume concentration of water vapor is 0.1% to 30%, specifically it can be 0.1%, 1%, 2%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 25% or 30%, etc., which is not limited herein.

[0093] In some embodiments, the temperature of the activation treatment is 380°C to 2000°C, and the time of the activation treatment is 0.5 h to 30 h. Specifically, the temperature of the activation treatment can be 380°C, 400°C, 500°C, 800°C, 1000°C, 1200°C, 1500°C, 1800°C or 2000°C, etc., which is not limited herein. The time of the activation treatment can specifically be 0.5 h, 1 h, 3 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 24 h or 30 h, etc., which is not limited herein.

[0094] In the present application, by controlling the volume concentration of water vapor, the temperature and time of the activation treatment, the activation efficiency of the primary carbonization product can be improved, so that the carbon matrix can have a rich pore structure, and the surface and / or pores of the carbon matrix after the activation treatment contain oxygen-containing functional groups (such as carboxyl groups, carbonyl groups, etc.), or exist in the form of doped atoms at positions such as the carbon matrix skeleton, skeleton gaps, and defects. A small amount of oxygen-containing functional groups can provide lone pairs of electrons after subsequent carbonization treatment, and the lone pairs of electrons participate in the π-π conjugate system of the carbon matrix, thereby forming a larger p-π conjugate system and further increasing the electronic conductivity of the anode material.

[0095] In some embodiments, the carbon matrix includes at least one of hard carbon, soft carbon, graphite, mesophase carbon microspheres, activated carbon, porous carbon, mesoporous carbon, and carbon gel.

[0096] In some embodiments, the total pore volume of the carbon matrix ≥ 0.4 cm 3 / g, specifically it can be 0.4 cm 3 / g, 0.5 cm 3 / g, 0.8 cm 3 / g, 1 cm 3 / g, 1.1 cm 3 / g, 1.3 cm 3 / g, 1.5 cm 3 / g or 1.8 cm 3 / g, etc. Of course, it can also be other values within the above range, which is not limited herein. Preferably, the total pore volume of the carbon matrix ≥ 0.5 cm 3 / g; more preferably, the total pore volume of the carbon matrix ≥ 0.7 cm 3 / g.

[0097] In some embodiments, the pores include micropores with a pore diameter less than 2 nm, and the proportion of the micropores is ≥ 80%. Specifically, the proportion of the micropores can be 80%, 82%, 85%, 88%, 90%, 92%, 93%, 95%, 98% or 99%, etc., without limitation herein. Preferably, the proportion of the micropores is ≥ 90%; more preferably, the proportion of the micropores is ≥ 95%.

[0098] In some embodiments, the porosity of the carbon matrix is 40% - 60%, and specifically can be 40%, 41%, 43%, 45%, 48%, 50%, 52%, 54%, 56%, 58% or 60%, etc. Of course, it can also be other values within the above range, without limitation herein.

[0099] Step S20: Perform secondary carbonization treatment on the precursor to obtain a carbon matrix, wherein the temperature of the secondary carbonization treatment is higher than that of the primary carbonization treatment.

[0100] In some embodiments, the temperature of the secondary carbonization treatment is 900°C - 2000°C; the temperature of the secondary carbonization treatment can be 900°C, 1000°C, 1050°C, 1200°C, 1300°C, 1400°C, 1500°C, 1800°C or 2000°C, etc., without limitation herein. Preferably, the temperature of the secondary carbonization treatment is 900°C - 1800°C; more preferably, it is 900°C - 1300°C.

[0101] In some embodiments, the time of the secondary carbonization treatment is 1 h - 30 h, and specifically can be 1 h, 3 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 24 h or 30 h, etc., without limitation herein.

[0102] Step S30: Compound the carbon matrix with pores with silicon particles to obtain a negative electrode material, wherein at least part of the silicon particles are distributed in the pores of the carbon matrix.

[0103] In some embodiments, the step of compounding the carbon matrix with pores with silicon particles includes: performing chemical vapor deposition on the carbon matrix with pores using a silicon source gas to obtain an active material.

[0104] In some embodiments, the silicon source gas includes at least one of silane, disilane, trichlorosilane and dichlorosilane.

[0105] In some embodiments, the volume concentration ratio of the silicon source gas is 1% - 90%, and the volume concentration ratio of the silicon source gas can specifically be 1%, 5%, 10%, 15%, 20%, 30%, 50%, 60%, 70%, 80% or 90%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0106] In some embodiments, the deposition time of the vapor deposition is 0.1 h to 15 h. The deposition time can specifically be 0.1 h, 0.5 h, 1 h, 3 h, 5 h, 6 h, 8 h, 10 h, 12 h, 15 h, etc., which is not limited herein.

[0107] In some embodiments, the deposition temperature of the vapor deposition is 300 °C to 800 °C. The deposition temperature can specifically be 300 °C, 350 °C, 400 °C, 500 °C, 600 °C, 650 °C, 700 °C, 800 °C, etc. Of course, it can also be other values within the above range, which is not limited herein. It can be understood that controlling the temperature of the vapor deposition within the above range is beneficial to controlling the crystal form of the silicon particles, reducing the crystallinity of the silicon particles, reducing the conversion of amorphous silicon to crystalline silicon, thereby reducing the volume expansion of the negative electrode material and improving the cycling performance of the negative electrode material.

[0108] In some embodiments, the method further includes: performing carbon coating treatment on the active material to obtain the negative electrode material; the carbon coating treatment includes at least one of solid-phase carbon coating, liquid-phase carbon coating, and gas-phase carbon coating.

[0109] It can be understood that performing carbon coating treatment on the active material to form a carbon material on at least part of the surface of the active material can, on the one hand, reduce the direct contact between the negative electrode material and the electrolyte, reduce the occurrence of side reactions between the negative electrode material and the electrolyte, and thereby improve the electrochemical performance of the negative electrode material; on the other hand, it can also relieve the mechanical stress caused by the volume expansion of the negative electrode material, improve the structural stability of the negative electrode material, enhance the interfacial stability, and thereby improve the cycling performance of the negative electrode material.

[0110] In some embodiments, the steps of the carbon coating treatment specifically include: heating the active material and then introducing a protective gas and a carbon source gas, and the carbon source gas undergoes thermal cracking to obtain the negative electrode material with a carbon material on its surface.

[0111] In some embodiments, the steps of the carbon coating treatment specifically include: heating the active material and then introducing a protective gas and a carbon source gas, and the carbon source gas undergoes thermal cracking to obtain the negative electrode material, wherein the carbon source gas is a hydrocarbon.

[0112] In some embodiments, the carbon source gas includes at least one of methane, ethylene, acetylene, propyne, propylene, propane, toluene, benzene, styrene, and phenol.

[0113] In some embodiments, the temperature of the thermal cracking is 600 °C to 1000 °C, and the time of the thermal cracking is 30 min to 24 h.

[0114] Specifically, the temperature of thermal cracking can be 600°C, 620°C, 650°C, 680°C, 700°C, 760°C, 870°C, 900°C, 920°C, 950°C, 980°C, 1000°C, etc., which is not limited herein. The time of thermal cracking can be specifically 30 min, 1 h, 3 h, 5 h, 8 h, 12 h, 15 h, 18 h, 20 h, 22 h, 24 h, etc., which is not limited herein.

[0115] In some embodiments, the steps of carbon coating treatment specifically include: carbonizing a mixture obtained by mixing an active material and a solid-phase carbon source to obtain a negative electrode material.

[0116] In some embodiments, the temperature of carbonization treatment is 500°C to 1000°C, and the time of carbonization treatment is 30 min to 24 h.

[0117] Specifically, the temperature of carbonization treatment can be 500°C, 540°C, 580°C, 600°C, 620°C, 650°C, 680°C, 700°C, 760°C, 870°C, 900°C, 920°C, 950°C, 980°C, 1000°C, etc., which is not limited herein. The time of carbonization treatment can be specifically 30 min, 1 h, 3 h, 5 h, 8 h, 12 h, 15 h, 18 h, 20 h, 22 h, 24 h, etc., which is not limited herein.

[0118] In some embodiments, the solid-phase carbon source includes at least one of sugars, esters, hydrocarbons, organic acids, and high molecular polymers.

[0119] In some embodiments, the solid-phase carbon source includes at least one of polyvinyl chloride, polyvinyl butyral, polyacrylonitrile, polyacrylic acid, polyethylene glycol, polypyrrole, polyaniline, sucrose, glucose, maltose, citric acid, pitch, furfural resin, epoxy resin, and phenolic resin.

[0120] In some embodiments, the mass ratio of the solid-phase carbon source to the negative electrode material is (1 to 200):100, specifically it can be 1:100, 2:100, 5:100, 10:100, 50:100, 100:100, 150:100, 180:100, 200:100, etc., which is not limited herein.

[0121] In some embodiments, the steps of carbon coating treatment specifically include: carbonizing a mixture obtained by mixing an active material and a liquid-phase carbon source to obtain a negative electrode material.

[0122] In some embodiments, the mass ratio of the liquid-phase carbon source to the anode material is (1-200):100, specifically, it can be 1:100, 2:100, 5:100, 10:100, 50:100, 100:100, 150:100, 180:100, or 200:100, etc., which is not limited herein.

[0123] In some embodiments, the liquid-phase carbon source includes at least one of n-hexane, toluene, benzene, xylene, methanol, ethanol, propanol, butanol, pentanol, acetone, butanone, 2-pentanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and pentyl acetate.

[0124] In some embodiments, the temperature of the carbonization treatment is 600°C to 1200°C, and the time of the carbonization treatment is 2h to 20h.

[0125] Specifically, the temperature of the carbonization treatment can be 600°C, 620°C, 650°C, 680°C, 700°C, 760°C, 870°C, 900°C, 920°C, 950°C, 980°C, 1000°C, 1020°C, 1080°C, 1100°C, 1160°C, or 1200°C, etc., which is not limited herein. The time of the carbonization treatment can specifically be 2h, 3h, 5h, 8h, 12h, 15h, 18h, 20h, 22h, 24h, 25h, 26h, 28h, or 30h, etc., which is not limited herein.

[0126] In some embodiments, the carbon coating treatment is carried out under a protective atmosphere, and the protective atmosphere includes at least one of nitrogen, helium, neon, argon, and krypton.

[0127] In some embodiments, the method further includes: shaping, screening, and grading the carbon-coated treatment product to obtain an anode material with a carbon material on the surface, and the shaping treatment includes at least one of crushing, grinding, ball milling, and air crushing.

[0128] In a third aspect, the present application provides a battery, which includes the anode material as described in the first aspect or the anode material prepared by the anode material preparation method as described in the second aspect. The battery can be a lithium-ion battery or a sodium-ion battery, etc., which is not limited herein.

[0129] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0130] Example 1

[0131] The preparation method of the anode material in this example includes the following steps:

[0132] (1) Mix bamboo charcoal and urea in a mass ratio of 100:1. The mixture is subjected to a primary carbonization treatment at a temperature of 750 °C for 5 h. The primary carbonization product is placed under steam and nitrogen for a primary activation treatment, with steam:nitrogen = 0.1:90 (volume ratio), a primary activation temperature of 650 °C, and a primary activation time of 4 h to obtain a primary activation product. The primary activation product is placed in a heat treatment furnace for a secondary activation at a temperature of 950 °C for 3 h to obtain a precursor.

[0133] (2) Place the precursor in a heat treatment furnace for a secondary carbonization treatment at a temperature of 900 °C for 10 h to obtain a carbon matrix with an average pore size of 1.8 nm, and the carbon matrix has pores.

[0134] (3) Place the carbon matrix in a chemical vapor deposition equipment CVD, then introduce silane into the CVD equipment, control the volume concentration of silane to be 40%, heat up to 600 °C, and carry out a gas-phase deposition reaction for 4 h to obtain a composite.

[0135] (4) Mix the composite and asphalt in a mass ratio of 50:15, then place the mixed material in a high-temperature box furnace, introduce nitrogen, carry out a solid-phase carbon coating treatment at 520 °C for 2 h, crush and screen the carbon coating treatment product, and then classify it to obtain a negative electrode material.

[0136] The negative electrode material prepared in the embodiment of the present application includes an active substance and a carbon material on the surface of the active substance. The active substance includes a carbon matrix and silicon particles. The carbon matrix has pores, and at least part of the silicon particles are distributed in the pores of the carbon matrix.

[0137] Figure 2 XRD pattern of the negative electrode material prepared in Example 1 of the present invention, as Figure 2 shown, the active substance in the negative electrode material is amorphous. Figure 3 Schematic diagram of the first charge-discharge curve of the negative electrode material prepared in Example 1 of the present invention, as Figure 3 shown, the first charge-discharge capacity of the negative electrode material is 1938 mAh / g, and the first Coulomb efficiency is 93.1%. The negative electrode material has better electrochemical performance. Figure 4 Schematic diagram of the cycle performance curve of the negative electrode material prepared in Example 1 of the present invention, as Figure 4 shown, the capacity retention rate of the battery made of the negative electrode material after 50 cycles is 93.1%. It can be seen that the negative electrode material has excellent cycle performance.

[0138] Example 2

[0139] The preparation method of the negative electrode material in this embodiment includes the following steps:

[0140] (1) Commercial porous carbon and ethanolamine are mixed in a mass ratio of 100:1.5, and the mixture is subjected to a primary carbonization treatment at a primary carbonization temperature of 850 °C for 8 h to obtain a precursor.

[0141] (2) The precursor is placed in a heat treatment furnace for a secondary carbonization treatment at a temperature of 1900 °C for 12 h to obtain a carbon matrix with an average pore size of 3.9 nm, and the carbon matrix has pores.

[0142] (3) The carbon matrix is placed in a chemical vapor deposition equipment CVD, and then silane is introduced into the CVD equipment. The volume concentration of silane is controlled at 20%, and the temperature is raised to 550 °C for a gas phase deposition reaction for 4 h to obtain a composite.

[0143] (4) Methane is continuously introduced into the chemical vapor deposition equipment. The volume concentration of methane is controlled at 29%, and the temperature is raised to 650 °C for a gas phase carbon coating treatment for 4 h. The product of the carbon coating treatment is crushed, screened, and then classified to obtain a negative electrode material.

[0144] Example 3

[0145] (1) Coconut shell and ammonium chloride are mixed in a mass ratio of 100:0.5, and the mixture is subjected to a primary carbonization treatment at a primary carbonization temperature of 700 °C for 15 h; the primary carbonization product is placed under steam and nitrogen for a primary activation treatment, steam:nitrogen = 0.5:90 (volume ratio), the primary activation temperature is 750 °C, and the primary activation time is 4 h to obtain a primary activation product; the primary activation product is placed in a heat treatment furnace for a secondary activation at a secondary activation temperature of 850 °C for 5 h to obtain a precursor.

[0146] (2) The precursor is placed in a heat treatment furnace for a secondary carbonization treatment at a temperature of 1000 °C for 6 h to obtain a carbon matrix with an average pore size of 1.7 nm, and the carbon matrix has pores.

[0147] (3) The carbon matrix is placed in a chemical vapor deposition equipment CVD, and then silane is introduced into the CVD equipment. The volume concentration of silane is controlled at 31%, and the temperature is raised to 500 °C for a gas phase deposition reaction for 4 h to obtain a composite.

[0148] (4) Acetylene is continuously introduced into the chemical vapor deposition equipment. The volume concentration of acetylene is controlled at 45%, and the temperature is raised to 650 °C for a gas phase carbon coating treatment for 4 h. The product of the carbon coating treatment is crushed, screened, and then classified to obtain a negative electrode material.

[0149] The negative electrode material prepared in the embodiments of the present application includes an active substance, the active substance includes a carbon matrix and silicon particles, the carbon matrix has pores, and at least part of the silicon particles are distributed in the pores of the carbon matrix.

[0150] Example 4

[0151] (1) Mix the fruit shell and ammonium bicarbonate according to a mass ratio of 100:3.3, subject the mixture to a primary carbonization treatment, the primary carbonization temperature is 710 °C, and keep the temperature for 6 h; place the primary carbonization product under water vapor and nitrogen for a primary activation treatment, water vapor: nitrogen = 0.9:90 (volume ratio), the primary activation temperature is 550 °C, and the primary activation time is 5 h to obtain a primary activation product; place the primary activation product in a heat treatment furnace for a secondary activation, the secondary activation temperature is 880 °C, and the secondary activation time is 5 h to obtain a precursor.

[0152] (2) Place the precursor in a heat treatment furnace for a secondary carbonization treatment, the temperature of the secondary carbonization treatment is 1200 °C, and keep the temperature for 16 h to obtain a carbon matrix with an average pore size of 2.1 nm, and the carbon matrix has pores.

[0153] (3) Place the carbon matrix in a chemical vapor deposition device CVD, then introduce silane into the CVD device, control the volume concentration of silane to be 11%, heat up to 560 °C, and carry out a gas-phase deposition reaction for 4 h to obtain a composite.

[0154] (4) Continuously introduce propylene into the chemical vapor deposition device, control the volume concentration of propylene to be 45%, heat up to 690 °C for a gas-phase carbon coating treatment, keep the temperature for 4 h, crush, screen, and then classify the carbon coating treatment product to obtain the negative electrode material.

[0155] Example 5

[0156] (1) Mix bamboo charcoal and urea according to a mass ratio of 100:1, subject the mixture to a primary carbonization treatment, the primary carbonization temperature is 750 °C, and keep the temperature for 5 h; place the primary carbonization product under water vapor and nitrogen for an activation treatment, water vapor: nitrogen = 0.1:90 (volume ratio), the activation temperature is 550 °C, and the activation time is 24 h to obtain a precursor.

[0157] (2) Place the precursor in a heat treatment furnace for a secondary carbonization treatment, the temperature of the secondary carbonization treatment is 1500 °C, and keep the temperature for 10 h to obtain a carbon matrix with an average pore size of 2.1 nm, and the carbon matrix has pores.

[0158] (3) Place the carbon matrix in a chemical vapor deposition device CVD, then introduce silane into the CVD device, control the volume concentration of silane to be 40%, heat up to 600 °C, and carry out a gas-phase deposition reaction for 4 h to obtain a composite.

[0159] (4) Mix the composite with asphalt at a mass ratio of 50:15. Subsequently, place the mixed material into a high-temperature box furnace, introduce nitrogen, and conduct solid-phase carbon coating treatment at 520 °C for 2 h. Crush, screen, and then classify the carbon-coated treatment product to obtain the anode material.

[0160] Example 6

[0161] (1) Mix commercial porous carbon, ethanolamine, and urea at a mass ratio of 100:1.0:0.5. Perform a primary carbonization treatment on the mixture at a primary carbonization temperature of 600 °C for 8 h to obtain a precursor.

[0162] (2) Place the precursor in a heat treatment furnace for a secondary carbonization treatment at a temperature of 1300 °C for 12 h to obtain a carbon matrix with an average pore size of 2.2 nm. The carbon matrix has pores.

[0163] (3) Place the carbon matrix in a chemical vapor deposition equipment CVD, and then introduce silane into the CVD equipment. Control the volume concentration of silane to be 40%, heat up to 550 °C, and conduct a chemical vapor deposition reaction for 4 h to obtain a composite.

[0164] (4) Continue to introduce methane into the chemical vapor deposition equipment, control the volume concentration of methane to be 35%, heat up to 800 °C for chemical vapor carbon coating treatment, and keep it warm for 4 h. Crush, screen, and then classify the carbon-coated treatment product to obtain the anode material.

[0165] Example 7

[0166] The difference from Example 1 is:

[0167] (2) Place the precursor in a heat treatment furnace for a secondary carbonization treatment at a temperature of 2100 °C for 10 h to obtain a carbon matrix with an average pore size of 5.8 nm. The carbon matrix has pores.

[0168] Example 8

[0169] The difference from Example 1 is:

[0170] (1) Mix bamboo charcoal and urea at a mass ratio of 100:1. Perform a primary carbonization treatment on the mixture at a primary carbonization temperature of 750 °C for 5 h; place the primary carbonization product under steam and nitrogen for a primary activation treatment, steam:nitrogen = 2:90 (volume ratio), the primary activation temperature is 650 °C, and the primary activation time is 4 h to obtain a primary activation product; place the primary activation product in a heat treatment furnace for a secondary activation at a secondary activation temperature of 950 °C and a secondary activation time of 15 h to obtain a precursor.

[0171] Example 9

[0172] Different from Example 1:

[0173] (1) Bamboo charcoal and urea are mixed in a mass ratio of 100:2.3. The mixture is subjected to a primary carbonization treatment at a primary carbonization temperature of 750 °C for 5 h. The primary carbonization product is placed under steam and nitrogen for a primary activation treatment, with steam:nitrogen = 0.1:90 (volume ratio), a primary activation temperature of 650 °C, and a primary activation time of 4 h to obtain a primary activation product. The primary activation product is placed in a heat treatment furnace for a secondary activation at a secondary activation temperature of 950 °C for 30 h to obtain a precursor.

[0174] Comparative Example 1

[0175] Different from Example 1: Step (2) is not carried out.

[0176] Comparative Example 2

[0177] (1) Bamboo charcoal is subjected to a primary carbonization treatment at a primary carbonization temperature of 750 °C for 5 h. The primary carbonization product is placed under steam and nitrogen for a primary activation treatment, with steam:nitrogen = 0.1:90 (volume ratio), a primary activation temperature of 650 °C, and a primary activation time of 4 h to obtain a precursor.

[0178] (2) The precursor is placed in a heat treatment furnace for a secondary carbonization treatment at a temperature of 700 °C for 10 h to obtain a carbon matrix with an average pore size of 1.8 nm, and the carbon matrix has pores.

[0179] (3) The carbon matrix is placed in a chemical vapor deposition equipment CVD, and then silane is introduced into the CVD equipment. The volume concentration of silane is controlled at 40%, and the temperature is raised to 600 °C for a chemical vapor deposition reaction for 4 h to obtain a composite.

[0180] (4) The composite and asphalt are mixed in a mass ratio of 50:15. Subsequently, the mixed material is placed in a high-temperature box furnace, nitrogen is introduced, and solid-phase carbon coating treatment is carried out at 520 °C for 2 h. The carbon coating treatment product is crushed, screened, and then classified to obtain the negative electrode material.

[0181] Testing method:

[0182] (1) Testing method for the specific surface area of the negative electrode material:

[0183] The specific surface area is measured using a Micromeritics TriStar 3000 specific surface area and pore size analyzer equipment from the United States.

[0184] (2) Testing method for the total pore volume of the negative electrode material or the carbon matrix:

[0185] The test was carried out using the ASAP2460 equipment of Micromeritics Instrument Corporation in the United States. The pore volume V was calculated within the pore size range using the BJH Desorption cumulative volume of pores model in the pore size range.

[0186] Micropore and mesopore analysis was performed using Micromeretics ASAP 2460. At the liquid nitrogen temperature, the equilibrium adsorption amount of nitrogen on the object surface is related to its pore size and other characteristics. Combining the law of the change of the adsorption amount with the relative pressure during the adsorption process, various models can be fitted to calculate the pore size. The report generated by the software calculates the pore size distribution, total pore volume, and pore volume within a certain range using the density functional theory (abbreviated as DFT) method.

[0187] (3) Test method for the pore size of the negative electrode material or carbon matrix:

[0188] Take an appropriate amount of sample particles and measure the pore size and porosity of the pores under a transmission electron microscope (TEM).

[0189] (4) Test method for the particle size of silicon particles:

[0190] Observe the nano-silicon particles through a field emission scanning electron microscope or a transmission electron microscope, directly measure the particle sizes of 5-10 nano-silicon particles through the scale, and take the average value of the particle sizes as the final particle size of the nano-silicon particles.

[0191] (5) Test method for the particle size of the negative electrode material:

[0192] Use a Malvern laser particle size analyzer MS3000. According to the principle that the intensity distribution of the scattered light generated by particles in all directions depends on the particle size, large particles have a small scattering angle and small particles have a large scattering angle. Thus, the particle size distribution of the particles is obtained using the intensity distribution of the scattered light by laser diffraction.

[0193] (6) Test for the gas generation value of the negative electrode material:

[0194] Add the negative electrode material to 50 g of styrene-butadiene rubber solution to obtain a mixture, encapsulate the mixture using an aluminum-plastic film, and place it in a 2000 mL sealed container, and store it at a temperature of 45 °C. The gas generation amount of the negative electrode material after 6 days is measured to be M mL / g.

[0195] (7) Test for the mass content of oxygen atoms and nitrogen atoms in the negative electrode material:

[0196] Measure the N and O elements in the material using a hydrogen, oxygen, and nitrogen analyzer ELTRA ONH2000, and the test standard is ISO17053:2005.

[0197] (8) Powder conductivity test method for the negative electrode material:

[0198] According to the national standard GBT 30835-2014, using a resistivity tester (Suzhou Jingge Electronics ST-2255A), take 5 g of powder sample, press it with an electronic press at a constant pressure of 8000 kg ± 2 kg for 15 - 25 s, place the sample between the electrodes of the tester, with the sample height h (cm), the voltage U at both ends, the current I, and the resistance R (KΩ). The area S of the powder compacted tablet is 3.14 cm 2 , and the powder conductivity is calculated according to the formula δ = h / (S*R) / 1000, with the unit of S / m.

[0199] (9) Electrochemical performance test

[0200] Dissolve the negative electrode materials prepared in the examples and comparative examples, the negative electrode material, carboxymethyl cellulose, and styrene-butadiene rubber in N-methylpyrrolidone according to a mass ratio of 94:1:5, control the solid content to be 50%, coat it on the copper foil current collector, and vacuum dry it to obtain the negative electrode sheet; use a ternary positive electrode sheet (NCM523), 1 mol / L lithium hexafluorophosphate LiPF6 / (ethylene carbonate EC + dimethyl carbonate DMC + ethyl methyl carbonate EMC) (v / v = 1:1:1) electrolyte, Celgard 2400 separator, and assemble 18650 cylindrical single cells using a conventional production process for the shell. The charge and discharge tests of the cylindrical battery are carried out on the LAND battery test system of Wuhan Jinnuo Electronics Co., Ltd. Under normal temperature conditions, charge and discharge at a constant current of 0.2C, and limit the charge and discharge voltage to 2.75 - 4.2V. Obtain the first reversible capacity, the first charge capacity, and the first discharge capacity. The first Coulomb efficiency = the first discharge capacity / the first charge capacity.

[0201] Repeat 50 - week cycles, record the discharge capacity as the remaining capacity of the lithium-ion battery; the capacity retention rate = the remaining capacity / the initial capacity * 100%.

[0202] The results of the above performance tests are as follows:

[0203] Table 1. Performance parameters of the negative electrode materials and their batteries prepared in each example and comparative example.

[0204]

[0205] According to the data in Table 1, for the anode materials prepared in Examples 1 to 9, a primary carbonization treatment is carried out using a mixture of a carbon source and a modifying substance, enabling the modifying substance to be doped in the carbon matrix. Then, a secondary carbonization treatment is performed, with the temperature of the secondary carbonization treatment controlled to be higher than that of the primary carbonization treatment. The graphitization degree of the carbon matrix can be enhanced by means of high temperature, improving the electronic conductivity of the carbon matrix itself. Additionally, during the secondary carbonization treatment, more oxygen-containing or nitrogen-containing groups volatilize, enabling the control of the mass contents of nitrogen and oxygen in the carbon matrix. The doping of a small amount of nitrogen and oxygen elements can provide lone pairs of electrons, and the lone pairs of electrons participate in the π-π conjugate system of the carbon matrix, thereby forming a larger p-π conjugate system and further increasing the electronic conductivity of the anode material. Finally, the above carbon matrix is compounded with silicon particles, which can increase the capacity of the anode material; the pores present in the carbon matrix are beneficial for alleviating the volume expansion of silicon particles during the cycling process of the anode material, maintaining structural stability, and reducing the collapse of the material structure caused by volume expansion during the lithium insertion and extraction process of the anode material. The pores in the carbon matrix can also adsorb a small amount of gas, further reducing the gas generation phenomenon of the anode material, and thus improving the cycling performance of the anode material.

[0206] According to the test data of Examples 1 to 4, as the mass content of nitrogen element decreases, the initial reversible capacity of the anode material also shows a downward trend. Preferably, the mass content of the nitrogen element is 0.1% - 0.5%.

[0207] According to the test data of Example 1 and Example 7 in Table 1, the secondary carbonization temperature of Example 7 is too high. The excessive carbonization temperature will increase the graphitization degree of the carbon matrix. Although the powder conductivity of the anode material is improved, due to the collapse of some pores in the carbon matrix caused by the excessive carbonization temperature, more subsequent silicon is deposited on the surface of the carbon matrix rather than in the pores, and the silicon content in the anode material also decreases. Since part of the silicon is deposited on the surface of the carbon matrix, the volume expansion of the anode material is aggravated, and the initial Coulombic efficiency and cycling performance of the anode material decrease compared with Example 1.

[0208] According to the test data of Example 1 and Comparative Example 1 in Table 1, during the preparation of the anode material in Comparative Example 1, no secondary carbonization treatment is carried out, and more oxygen-containing or nitrogen-containing groups remain in the carbon matrix. The mass contents of nitrogen and oxygen in the anode material increase significantly. Without the secondary carbonization treatment, the graphitization degree of the carbon matrix decreases, and the conductivity of the carbon matrix itself drops significantly. Even though the doping of a small amount of nitrogen and oxygen elements in the oxygen-containing or nitrogen-containing groups can provide lone pairs of electrons, it is difficult to significantly improve the electronic conductivity of the anode material; as a result, the capacity attenuation, initial Coulombic efficiency, and cycling performance of the anode material decrease.

[0209] According to the test data of Example 1 and Comparative Example 2 in Table 1, it can be seen that during the preparation of the negative electrode material in Comparative Example 2, no modifying substances were added, and there were not enough nitrogen-containing groups and oxygen-containing groups to cooperate with the carbon matrix to form carbon-carbon conjugation. Moreover, the secondary carbonization temperature was lower than the primary carbonization temperature, resulting in a significant decrease in the conductivity of the carbon matrix and thus a significant decrease in the electronic conductivity of the negative electrode material, leading to capacity attenuation, a decrease in the first Coulombic efficiency, and a decline in the cycling performance of the negative electrode material.

[0210] The applicant declares that the present invention uses the above-mentioned examples to illustrate the detailed process equipment and process flow of the present invention. However, the present invention is not limited to the above-mentioned detailed process equipment and process flow, that is, it does not mean that the present invention must rely on the above-mentioned detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A negative electrode material, characterized in that, it includes an active material, the active material includes a carbon matrix and silicon particles, the carbon matrix has pores, and at least part of the silicon particles are distributed in the pores of the carbon matrix; the negative electrode material contains oxygen element and nitrogen element, the mass content of the oxygen element is A%, and the mass content of the nitrogen element is B%; the powder conductivity of the negative electrode material is P S / m, and the following relationship is satisfied: (A + B) / P ≤ 3.

2. The negative electrode material according to claim 1, characterized in that, it satisfies at least one of the following technical characteristics: (1) In the negative electrode material, the mass content of the oxygen element is A%, 0 < A ≤ 3; (2) In the negative electrode material, the mass content of the nitrogen element is B%, 0 < B ≤ 3; (3) The surface and / or pores of the carbon matrix have functional groups, and the functional groups include at least one of hydroxyl group, carboxyl group, carbonyl group, lipid group, cyclic lipid group and amino group.

3. The negative electrode material according to claim 1 or 2, characterized in that, it satisfies at least one of the following technical characteristics: (1) The carbon matrix includes at least one of hard carbon, soft carbon, graphite, mesophase carbon microspheres, activated carbon, porous carbon, mesoporous carbon and carbon gel; (2) The total pore volume of the carbon matrix ≥ 0.4 cm 3 / g; (3) The pores in the carbon matrix include micropores, and the volume ratio of the micropores in the total pore volume is ≥ 80%; (4) The average pore diameter of the pores in the carbon matrix is ≤ 5 nm; (5) The porosity of the carbon matrix is 40% - 60%; (6) The silicon particles include at least one of elemental silicon, silicon oxide, silicon alloy and silicon-carbon composite; (7) The average particle size of the silicon particles is 0.1 nm - 500 nm; (8) The mass content of silicon element in the silicon particles is ≥ 99%.

4. The negative electrode material according to claim 3, characterized in that, it further includes a carbon material located on at least part of the surface of the active material, and it satisfies at least one of the following technical characteristics: (1) The carbon material includes at least one of graphitic carbon and amorphous carbon; (2) The median particle size D of the negative electrode material 50 ≤ 10 μm; (3) The specific surface area of the negative electrode material ≤ 5m 2 / g; (4) The gas production amount of the negative electrode material in 6 days is M mL / g, M ≤ 0.2; (5) The powder conductivity of the negative electrode material is P S / m, P ≥ 0.01 S / m.

5. A preparation method of a negative electrode material, characterized in that, it includes the following steps: Performing a primary carbonization treatment on a mixture including a carbon source and a modifying substance to obtain a precursor, wherein the modifying substance includes a nitrogen-containing compound and an oxygen-containing compound; Performing a secondary carbonization treatment on the precursor to obtain a carbon matrix, wherein the temperature of the secondary carbonization treatment is higher than that of the primary carbonization treatment; Composite the carbon matrix with pores and silicon particles to obtain a negative electrode material, wherein at least part of the silicon particles are distributed in the pores of the carbon matrix.

6. The preparation method according to claim 5, characterized in that, it satisfies at least one of the following technical characteristics: (1) The carbon source includes at least one of bamboo charcoal, coconut shell, resin, starch and fruit shell; (2) The temperature of the primary carbonization treatment is 600°C - 900°C; (3) The time of the primary carbonization treatment is 2 h - 10 h; (4) The nitrogen-containing compound includes at least one of urea, ammonium acetate, methylamine, ammonium chloride, ammonium nitrate, and N,N-dimethylformamide; (5) The mass ratio of the carbon source to the nitrogen-containing compound is 100:(0.5 - 100); (6) The method further includes: subjecting the primary carbonization product to activation treatment in a mixed gas of nitrogen and water vapor; (7) The method further includes: subjecting the primary carbonization product to activation treatment in a mixed gas of nitrogen and water vapor; wherein the concentration of the water vapor is 0.1% - 30%; (8) The method further includes: subjecting the primary carbonization product to activation treatment in a mixed gas of nitrogen and water vapor; the temperature of the activation treatment is 380°C - 2000°C, and the time of the activation treatment is 0.5 h - 30 h; (9) The method further includes: subjecting the primary carbonization product to primary activation treatment in a mixed gas of nitrogen and water vapor, and then subjecting the primary activation product to secondary activation treatment, the temperature of the activation treatment is 380°C - 2000°C, and the time of the activation treatment is 0.5 h - 30 h.

7. The preparation method according to claim 5, characterized in that, it satisfies at least one of the following technical features: (1) The temperature of the secondary carbonization treatment is 900°C - 2000°C; (2) The time of the secondary carbonization treatment is 1 h - 30 h.

8. The preparation method according to claim 5, characterized in that, The step of compounding the porous carbon matrix with silicon particles includes: performing chemical vapor deposition on the porous carbon matrix using a silicon source gas to obtain an active substance; it satisfies at least one of the following technical features: (1) The silicon source gas includes at least one of silane, disilane, trichlorosilane, and dichlorosilane; (2) The average particle size of the carbon matrix is 1 μm - 15 μm; (3) The average pore diameter of the carbon matrix is 0.1 nm - 5 nm; (4) The volume concentration ratio of the silicon source gas is 1% - 90%; (5) The deposition time of the chemical vapor deposition is 0.1 h - 15 h; (6) The deposition temperature of the chemical vapor deposition is 300°C - 800°C.

9. The preparation method according to claim 8, characterized in that, further includes: performing carbon coating treatment on the active substance to obtain a negative electrode material; the carbon coating treatment includes at least one of solid-phase carbon coating, liquid-phase carbon coating, and gas-phase carbon coating.

10. A battery, characterized in that, the battery includes the negative electrode material described in any one of claims 1 - 4 or the negative electrode material prepared by the negative electrode material preparation method described in any one of claims 5 - 9.

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