Negative electrode material and manufacturing method thereof, battery

Abstract

The present disclosure provides a negative electrode material, a manufacturing method thereof, and a battery. The negative electrode material includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the coating layer containing a carbonaceous material, and the graphite surface and / or the coating layer containing nitrogen atoms, with the uniformity of the doping concentration of the nitrogen atoms represented by A, where A≦0.5. In the negative electrode material provided by the present disclosure, the uniform doping of nitrogen atoms can adjust the energy band structure of the graphite negative electrode material, promote kinetic transfer, and improve the first coulomb efficiency; in addition, the incorporation of nitrogen atoms can generate pseudocapacitive properties in the material, thereby improving the lithium storage capacity of the negative electrode material.

Description

[Technical Field]

[0001] The present disclosure relates to the technical field of negative electrode materials, and more particularly to negative electrode materials and methods for producing the same, and batteries. [Background technology]

[0002] Lithium-ion battery energy storage systems are widely used in fields such as portable electronics, electric vehicles, and drones due to their advantages such as high energy density, no memory effect, and long cycle life. Current lithium-ion batteries still have considerable room for performance optimization. The electrochemical performance of lithium-ion batteries is closely related to the cathode and anode materials. Specifically, anode materials must possess properties such as a low lithium storage potential, high lithium storage capacity, and fast electron conduction. Graphite anode materials have become the mainstream choice for lithium-ion battery anode materials due to their excellent overall electrochemical performance and affordable price. However, further improvements in terms of lithium storage capacity and initial coulombic efficiency are still needed.

[0003] At present, the industry mainly employs a method of modifying spherical natural graphite by coating at least a portion of its surface to create a core-shell structure with a graphite core and a soft carbon shell, thereby reducing direct contact between the electrolyte and the natural graphite and reducing side reactions between the graphite and the electrolyte, thereby improving the initial efficiency and expansion performance of the graphite anode. However, these existing methods do not solve the problem of the non-uniformity of the introduced shell and the occurrence of side reactions between the non-uniform shell or the uncoated graphite surface and the electrolyte, which causes the initial efficiency and lithium storage capacity of the entire material to remain somewhat low.

[0004] Therefore, how to improve the initial coulombic efficiency of the negative electrode material while also improving the lithium storage capacity remains a technical challenge in the field. Summary of the Invention

[0005] The present disclosure provides an anode material, a manufacturing method thereof, and a battery that can not only promote kinetic transfer and improve first coulombic efficiency, but also further improve lithium storage capacity by introducing nitrogen atoms to generate pseudocapacitive properties in the material.

[0006] According to a first aspect, the present disclosure provides an anode material, comprising: a core; and a coating layer located on at least a portion of the core; wherein the anode material is doped with nitrogen atoms; The uniformity of the doping concentration of the nitrogen atoms is A, and the uniformity A is obtained by the following measurement method: Randomly obtain five negative electrode material particles, and randomly select n regions from each negative electrode material particle. Detect the energy spectrum signal of nitrogen element using a scanning electron microscope-energy dispersive spectrometer (SEM-EDS) to measure the number occupancy of nitrogen atoms in each region. Calculate the average number occupancy of nitrogen atoms as R. The uniformity is

number

[0007] In some embodiments, the core contains graphite and the coating layer contains a carbonaceous material; the surface of the graphite and / or the coating layer contains the nitrogen atoms. In some embodiments, the powder conductivity of the core is ρ1, the powder conductivity of the negative electrode material is ρ2, and 1.01≦ρ2 / ρ1≦10. In some embodiments, the R n is not zero. In some embodiments, the core comprises at least one of synthetic graphite and natural graphite.

[0008] In some embodiments, the coating layer has a thickness of 1 nm to 100 nm. In some embodiments, the mass content of nitrogen atoms in the negative electrode material is 0.01% to 3%. In some embodiments, the specific surface area of ​​the negative electrode material is 0.1 m 2 / g~5m 2 / g. In some embodiments, the median particle size of the negative electrode material is 1 μm to 30 μm. In some embodiments, the tap density of the negative electrode material is 0.75 g / cm 3 ~1.1g / cm 3 is. In some embodiments, the coating layer contains at least one of hard carbon, soft carbon, and graphitized carbon. In some embodiments, the mass content of the coating layer in the negative electrode material is 0.1% to 10%.

[0009] According to a second aspect, the present disclosure provides a method for manufacturing a semiconductor device comprising: obtaining a precursor by polymerizing a mixed solution containing graphite, a nitrogen-containing organic monomer, and an oxidizing agent; and carbonizing the precursor to obtain a negative electrode material.

[0010] In some embodiments, the graphite comprises at least one of synthetic graphite and natural graphite. In some embodiments, the graphite has a median particle size of 1 μm to 30 μm. In some embodiments, the nitrogen-containing organic monomer comprises at least one of methylaniline, sulfamic acid, aminosalicylic acid, aminoterephthalic acid, aniline, diphenylamine, phenylenediamine, trianiline, ethylaniline, and nitroaniline.

[0011] In some embodiments, the oxidizing agent comprises at least one of ammonium persulfate, hydrogen peroxide, iron chloride, and aluminum chloride. In some embodiments, the molar concentration of the oxidizing agent in the mixed solution is 0.1 mol / L to 2 mol / L. In some embodiments, the mass ratio of the graphite to the nitrogen-containing organic monomer is 100:(0.1 to 45). In some embodiments, the polymerization reaction time is 1 hour to 30 hours. In some embodiments, the temperature of the polymerization reaction is from 1°C to 95°C. In some embodiments, the polymerization reaction is carried out under agitation.

[0012] In some embodiments, a nitrogen-containing polymer formed by polymerizing the nitrogen-containing organic monomer is wrapped around the surface of the graphite. In some embodiments, the step of polymerizing a mixed solution containing graphite, a nitrogen-containing organic monomer, and an oxidizing agent includes preparing a mixed solution containing graphite, a pH adjuster, and a nitrogen-containing organic monomer, and then adding an oxidizing agent to the mixed solution to obtain a mixed solution. In some embodiments, the mixture has a pH of 1-10. In some embodiments, the pH adjuster comprises at least one of an acidic pH reagent and an alkaline pH reagent. In some embodiments, the pH adjuster comprises at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid. In some embodiments, the pH adjuster comprises at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate. In some embodiments, the carbonization process is carried out under a protective atmosphere. In some embodiments, the protective atmosphere comprises at least one of nitrogen gas, helium gas, neon gas, argon gas, krypton gas, and xenon gas. In some embodiments, the carbonization temperature is 500°C to 2500°C. In some embodiments, the temperature rise rate in the carbonization treatment is 0.5° C. / min to 5.0° C. / min. In some embodiments, the heat retention time for the carbonization treatment is 1 hour to 20 hours.

[0013] According to a third aspect, the present disclosure provides a battery including the above-described negative electrode material or a negative electrode material produced by the above-described production method.

[0014] The technical means according to the present disclosure have at least the following beneficial effects. The anode material provided herein includes a core and a coating layer located on at least a portion of the core, the anode material being doped with nitrogen atoms. The uniformity of the nitrogen doping concentration is A, and when A≦0.5, the coating layer is continuously and uniformly distributed on the graphite surface, effectively and uniformly adjusting the energy band structure of the graphite material, promoting dynamics transfer, and improving the initial Coulombic efficiency. The highly uniform introduction of nitrogen atoms also generates pseudocapacitive properties in the anode material, further improving the lithium storage capacity. The uniform doping of nitrogen atoms reduces side reactions between the coating layer and the electrolyte, reducing the penetration of anions and solvent molecules in the electrolyte into the particles, thereby increasing the reversible capacity of the anode material and improving the initial Coulombic efficiency.

[0015] The method for manufacturing anode materials disclosed herein involves polymerizing a mixed solution containing graphite, a nitrogen-containing organic monomer, and an oxidant. The resulting nitrogen-containing polymer is then wrapped around the graphite surface. The nitrogen-containing polymer then undergoes a carbonization process to obtain a uniformly nitrogen-doped anode material. The in-situ polymerization allows the nitrogen-containing organic monomer molecules to be uniformly introduced onto the graphite particle surface, enhancing the uniformity of nitrogen doping on the graphite particle surface. This simplifies the manufacturing process and facilitates industrial production. The resulting anode material has a uniform surface coverage, uniform nitrogen doping, and a controlled specific surface area, reducing irreversible reactions between the anode material and the electrolyte during the first cycle. The uniform nitrogen doping adjusts the energy band structure of the graphite material, promoting dynamics transfer and improving the initial Coulombic efficiency. The introduction of nitrogen atoms also creates pseudocapacitive properties in the material, further enhancing its lithium storage capacity. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a process flow chart of the method for manufacturing the negative electrode material provided in this disclosure. [Figure 2a] FIG. 2a shows scanning electron micrographs of the negative electrode material provided in Example 1 of the present disclosure at different magnifications. [Figure 2b] FIG. 2b shows scanning electron micrographs of the negative electrode material provided in Example 1 of the present disclosure at different magnifications. [Figure 3] FIG. 3 is a schematic diagram of the measurement of nitrogen element doping concentration in different regions of the scanning electron microscope image of the negative electrode material provided in Example 2 of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0017] In order to better explain the present disclosure and facilitate understanding of the technical solutions of the present disclosure, the present disclosure will be described in more detail below. However, the following examples are merely simple illustrations of the present disclosure and do not represent or limit the scope of protection of the present disclosure, which is governed by the claims.

[0018] At present, the industry mainly uses surface coating to modify graphite, creating a core-shell structure with a graphite core and a soft carbon shell, reducing direct contact between the electrolyte and graphite and reducing side reactions between the graphite and the electrolyte. At present, further improvements are still expected in graphite anode materials in terms of lithium storage capacity and first coulomb efficiency. Heterogeneous nitrogen doping is one effective method for improving the lithium storage performance of graphite anode materials.

[0019] The current mainstream technology involves doping graphite with nitrogen. For example, graphite can be oxidized to obtain expanded graphite, followed by a high-temperature solid-state reaction with nitrogen-containing compound molecules and water vapor to achieve nitrogen doping. The nitrogen doping in such graphite materials is not uniform, and in some cases exhibits a doping concentration gradient decrease, such as a high surface doping concentration but a low internal doping concentration. The non-uniform nitrogen doping in these graphite materials results in some graphite surfaces not being coated with nitrogen, making side reactions between the graphite and the electrolyte more likely to occur. Even after graphite coating, it is still difficult to improve the problem of non-uniform nitrogen doping, resulting in the overall initial effect and lithium storage capacity of the anode material still being somewhat low.

[0020] Based on the above, according to a first aspect, the present disclosure provides an anode material, the anode material including a core and a coating layer located on at least a portion of the surface of the core, the anode material being doped with nitrogen atoms, and the doping concentration of the nitrogen atoms having a uniformity A, where A≦0.5.

[0021] The anode material provided herein includes a core and a coating layer located on at least a portion of the core. The anode material is doped with nitrogen atoms. The uniformity of the nitrogen doping concentration is A, and when A≦0.5, the coating layer is more uniformly and continuously coated on the graphite surface, effectively and uniformly adjusting the energy band structure of the graphite material, promoting dynamics transfer, and improving the initial Coulombic efficiency. The highly uniform introduction of nitrogen atoms also generates pseudocapacitive properties in the anode material, further improving its lithium storage capacity. The uniform doping of nitrogen atoms reduces side reactions between the coating layer and the electrolyte, reducing the penetration of anions and solvent molecules in the electrolyte into the particles, thereby increasing the reversible capacity of the anode material and improving the initial Coulombic efficiency. Here, the uniformity A can be measured using the following method:

[0022] Five negative electrode material particles are randomly obtained, and n regions are randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element is detected by a scanning electron microscope-energy dispersive spectrometer, and the number occupancy of nitrogen atoms in each region is measured. The average number occupancy of nitrogen atoms is calculated as R; The uniformity is

number

[0023] The energy dispersive spectrometer analyzes the type and content of constituent elements in a microscopic region of the anode material, and in combination with a scanning electron microscope, quantifies the nitrogen atoms in each region and measures R at multiple positions. n The variance of -R indirectly reflects the doping uniformity of nitrogen atoms in the anode material. Therefore, the energy spectrum signal of nitrogen element is detected by energy spectrum measurement, and the uniformity A is defined to represent the uniformity of nitrogen atoms in the anode material.

[0024] In some embodiments, R n represents the nitrogen atom occupancy measured in the nth region, and R n It can be seen that the number occupancy of nitrogen atoms in each unit area of ​​n randomly selected unit areas is not zero, which not only improves the uniformity of nitrogen doping but also makes the coating layer more uniform, which is more beneficial to comprehensively improving the capacity and initial effect of the negative electrode material.

[0025] Specifically, the uniformity A of the doping concentration of nitrogen atoms may be, but is not limited to, 0.01, 0.05, 0.1, 0.12, 0.15, 0.16, 0.18, 0.2, 0.4, 0.5, etc. In some embodiments, the graphite includes at least one of artificial graphite and natural graphite.

[0026] In some embodiments, the core contains graphite and the coating layer contains a carbonaceous material; the graphite surface and / or the coating layer contain the nitrogen atoms.

[0027] Natural graphite is flake graphite, a natural crystalline graphite, which is shaped like fish scale and belongs to the hexagonal crystal system, exhibiting a layered structure, and has good properties such as high temperature resistance, electrical conductivity, heat conduction, lubrication, plasticity, and acid and alkali resistance. Artificial graphite is a graphite material obtained by carbonizing organic matter and then subjecting it to high-temperature graphitization treatment. In some embodiments, the graphite comprises spherical graphite, which is natural graphite.

[0028] In some embodiments, the median particle size of the graphite is 1 μm to 30 μm, and more specifically, may be 1 μm, 5 μm, 8 μm, 10 μm, 11 μm, 13 μm, 16 μm, 18 μm, 20 μm, 23 μm, 26 μm, or 30 μm, but is not limited to the above-mentioned numerical values, and other unrecited numerical values ​​within the numerical range are also applicable. As a result of multiple tests, it was found that controlling the median particle size of the graphite within the above range reduces the specific surface area of ​​the graphite, reduces contact between the graphite and the electrolyte, and is advantageous in suppressing the occurrence of side reactions. Preferably, the median particle size of the graphite is 5 μm to 20 μm.

[0029] In some embodiments, the mass content of carbon in the graphite is ≧95%, and may be, for example, 95%, 96%, 97%, 97.5%, 98.3%, 98.8%, or 99%, but is not limited to the above-listed values, and other unlisted values ​​within the range are also applicable. Preferably, the mass content of carbon in the graphite is ≧99%.

[0030] In some embodiments, the thickness of the coating layer is 1 nm to 100 nm, and specifically may be 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, or 100 nm, but is not limited to the above-mentioned numerical values, and other unspecified numerical values ​​within the numerical range are also applicable.

[0031] In some embodiments, the coating layer includes a carbonaceous material, and the carbonaceous material includes at least one of hard carbon, soft carbon, and graphitized carbon. The coating layer has good compatibility with the electrolyte, ensuring the stability of the electrical performance of the negative electrode material during charging and discharging. Illustratively, the carbonaceous material in the coating layer is derived from at least one of polymers, such as petroleum asphalt, coal asphalt, modified asphalt, mesophase asphalt, resin, and cross-linked polymer, and is formed by carbonization.

[0032] In some embodiments, the mass content of nitrogen atoms in the negative electrode material is 0.01% to 3%, and specifically may be 0.01%, 0.05%, 0.1%, 0.5%, 0.7%, 0.8%, 1%, 2%, 3%, etc., but is not limited to the above-mentioned numerical values, and other numerical values ​​not listed within the numerical range are also applicable.

[0033] In some embodiments, the powder conductivity of graphite is ρ1, and the powder conductivity of the negative electrode material is ρ2, where 1.01≦ρ2 / ρ1≦10. It is particularly noted that the powder conductivity of graphite refers to the powder conductivity of uncoated and undoped graphite raw material, and the powder conductivity of the negative electrode material refers to the conductivity of graphite after it is coated with a coating layer and doped with nitrogen.

[0034] In some embodiments, the specific surface area of ​​the negative electrode material is 0.1 m 2 / g~5m 2 / g, specifically, 0.1m 2 / g, 0.3m 2 / g, 0.5m 2 / g, 1.0m 2 / g, 1.8m 2 / g, 2.6m 2 / g, 3.5m 2 / g, 5.0m 2 / g, but of course other values ​​within the above range are also acceptable and are not limited thereto. As a result of multiple tests, the applicant has found that controlling the specific surface area of ​​the negative electrode material within the above range is advantageous in improving the cycle performance of a lithium-ion battery manufactured from the negative electrode material.

[0035] In some embodiments, the median particle size of the negative electrode material is 1 μm to 30 μm, and more specifically, may be 1 μm, 3 μm, 6 μm, 8 μm, 9 μm, 10 μm, 12 μm, 14 μm, 15 μm, 17 μm, 20 μm, 22 μm, 25 μm, or 30 μm, but is not limited to the above-mentioned numerical values, and other unrecited numerical values ​​within the numerical range are also applicable.

[0036] In some embodiments, the tap density of the negative electrode material is 0.75 g / cm 3 ~1.1g / cm 3 Specifically, 0.75 g / cm 3 , 0.8g / cm 3 , 0.85g / cm 3 , 0.9g / cm 3 , 0.92g / cm 3 , 1.0g / cm 3 , 1.02g / cm 3 , 1.05g / cm 3 or 1.1 g / cm 3 However, it is to be understood that other values ​​within the above range may also be used, and the present disclosure does not limit the scope of the present disclosure. As a result of multiple tests, the applicant has found that controlling the tap density of the negative electrode material within the above range is advantageous for improving the energy density of a lithium-ion battery manufactured from the negative electrode material.

[0037] In some embodiments, the negative electrode material contains amorphous carbon, and the mass content of the amorphous carbon is 0.1% to 10%, specifically, 0.1%, 0.5%, 1%, 1.5%, 3%, 3.5%, 4%, 6%, 8%, 10%, etc., but is not limited thereto.

[0038] According to a second aspect, the present disclosure provides a method for producing a negative electrode material, the method including the following steps, as shown in FIG. S10: A mixed solution containing graphite, a nitrogen-containing organic monomer, and an oxidizing agent is polymerized to obtain a precursor; S20: The precursor is carbonized to obtain the negative electrode material.

[0039] The composite anode material fabrication method disclosed herein involves polymerizing a mixed solution containing graphite, a nitrogen-containing organic monomer, and an oxidizing agent. The resulting nitrogen-containing polymer is then wrapped around the graphite surface. The nitrogen-containing polymer then undergoes a carbonization process to obtain a uniformly nitrogen-doped anode material. The nitrogen-containing organic monomer molecules are uniformly introduced onto the graphite particle surface through an in situ liquid-phase oxidation-reduction reaction, enhancing the uniformity of nitrogen doping on the graphite particle surface. This simplifies the fabrication process and facilitates industrial production. The resulting anode material has a uniform surface coverage and nitrogen doping, and the specific surface area of ​​the anode material is controlled within an appropriate range, thereby reducing irreversible reactions between the anode material and the electrolyte during the first cycle. The uniform doping of nitrogen atoms adjusts the energy band structure of the graphite material, promoting kinetic transfer and improving the initial Coulombic efficiency. The introduction of nitrogen atoms also creates pseudocapacitive properties in the anode material, further enhancing its lithium storage capacity.

[0040] The manufacturing method provided in this disclosure will now be described in detail. S10: A mixed solution containing graphite, a nitrogen-containing organic monomer, and an oxidizing agent is polymerized to obtain a precursor. In some embodiments, step S10 includes preparing a mixed solution containing graphite, a pH adjuster, and a nitrogen-containing organic monomer, and then adding an oxidizing agent to the mixed solution to obtain a mixed solution. In some embodiments, the graphite comprises at least one of synthetic graphite and natural graphite. Natural graphite is flake graphite, a natural crystalline graphite, which is shaped like fish scale and belongs to the hexagonal crystal system, exhibiting a layered structure, and has good properties such as high temperature resistance, electrical conductivity, heat conduction, lubrication, plasticity, and acid and alkali resistance. Artificial graphite is a graphite material obtained by carbonizing organic matter and then subjecting it to high-temperature graphitization treatment. In some embodiments, the graphite comprises spherical graphite, which is natural graphite.

[0041] In some embodiments, the median particle size of the graphite is 1 μm to 30 μm, and more specifically, may be 1 μm, 5 μm, 8 μm, 10 μm, 11 μm, 13 μm, 16 μm, 18 μm, 20 μm, 23 μm, 26 μm, or 30 μm, but is not limited to the above-mentioned numerical values, and other unrecited numerical values ​​within the numerical range are also applicable. As a result of multiple tests, it was found that controlling the median particle size of the graphite within the above range reduces the specific surface area of ​​the graphite, reduces contact between the graphite and the electrolyte, and is advantageous in suppressing the occurrence of side reactions. Preferably, the median particle size of the graphite is 5 μm to 20 μm.

[0042] In some embodiments, the mass content of carbon in the graphite is ≧95%, and may be, for example, 95%, 96%, 97%, 97.5%, 98.3%, 98.8%, or 99%, but is not limited to the above-listed values, and other unlisted values ​​within the range are also applicable. Preferably, the mass content of carbon in the graphite is ≧99%.

[0043] In some embodiments, the pH of the mixture is 1 to 10, and specifically may be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, but may also be other values ​​within the above range and is not limited thereto.

[0044] In some embodiments, the pH adjuster includes at least one of an acidic chemical reagent and an alkaline chemical reagent. Specifically, the acidic pH adjuster may be at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid, and the alkaline pH adjuster may be at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate. It should be noted that the pH value of the mixture may be adjusted according to the polymerization reaction environment required for different nitrogen-containing organic monomers.

[0045] The mixed solution further contains a solvent, which may be water, an alcohol-based organic solvent, or the like, specifically water, methanol, ethanol, n-propanol, isopropanol, tert-butanol, or the like, and is not limited thereto as long as it is a solvent that can dissolve the nitrogen-containing organic monomer and the oxidizing agent.

[0046] In some embodiments, the nitrogen-containing organic monomer includes at least one of methylaniline, sulfamic acid, aminosalicylic acid, aminoterephthalic acid, aniline, diphenylamine, phenylenediamine, trianiline, ethylaniline, and nitroaniline, but is not limited thereto, and other nitrogen-containing organic monomers are also applicable to the present disclosure. As can be understood, the nitrogen-containing organic monomer can undergo in situ polymerization under appropriate conditions to form a nitrogen-containing polymer, which is three-dimensionally crosslinked and coated on the surface of the graphite particles.

[0047] In some embodiments, the mass ratio of graphite to nitrogen-containing organic monomer is 100:(0.1 to 45), specifically, 100:0.1, 100:1, 100:5, 100:8, 100:10, 100:15, 100:25, 100:35, 100:45, etc., but is not limited to these numerical values, and other unrecited numerical values ​​within the numerical range are also applicable. Controlling the mass ratio of graphite raw material to nitrogen-containing organic monomer can avoid a polymer coating layer that is too thick, which would affect capacity; and can also avoid a polymer coating that is too thin, which would result in an incomplete polymer coating layer and further affect the doping uniformity of nitrogen atoms. In the present disclosure, controlling the mass ratio of graphite to nitrogen-containing organic monomer ensures the formation of a uniform polymer coating layer on the surface of the graphite particles, thereby enhancing the doping uniformity of nitrogen atoms in the graphite particles.

[0048] In some embodiments, the oxidizing agent comprises at least one of ammonium persulfate, hydrogen peroxide, iron chloride, and aluminum chloride. As can be appreciated, the addition of an oxidizing agent can facilitate the polymerization reaction of the nitrogen-containing organic monomer.

[0049] In some embodiments, the molar concentration of the oxidizing agent in the mixed solution is 0.1 mol / L to 2 mol / L, and specifically may be 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L, 1.1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.7 mol / L, or 2 mol / L, but is not limited to the above-mentioned values, and other values ​​not listed within the range are also applicable.

[0050] In some embodiments, the duration of the polymerization reaction is 1 hour to 30 hours, and specifically may be 1 hour, 5 hours, 8 hours, 10 hours, 15 hours, 18 hours, 20 hours, 23 hours, 26 hours, 30 hours, and the like.

[0051] In some embodiments, the temperature of the polymerization reaction is 1°C to 95°C, and specifically may be 1°C, 6°C, 10°C, 14°C, 20°C, 26°C, 32°C, 40°C, 46°C, 50°C, 75°C, 80°C, 95°C, etc., but is not limited thereto.

[0052] In some embodiments, the polymerization reaction is carried out under stirring conditions, and the nitrogen-containing polymer formed by polymerizing the nitrogen-containing organic monomer wraps around the surface of the graphite.

[0053] In the present disclosure, by controlling the temperature, time, and amount of oxidizing agent added during the polymerization reaction, it is possible to promote a sufficient polymerization reaction of the nitrogen-containing organic monomer, and the nitrogen-containing polymer formed by polymerizing the monomer under stirring can be more uniformly wrapped around the surface of the graphite. In some embodiments, the stirring speed is 50 r / min to 800 r / min, and specifically may be 50 r / min, 100 r / min, 150 r / min, 200 r / min, 250 r / min, 300 r / min, 400 r / min, 500 r / min, 700 r / min, or 800 r / min, but is not limited to the above-mentioned numerical values, and other unrecited numerical values ​​within the numerical range are also applicable. Controlling the stirring speed within the above range is advantageous for the polymer produced by the polymerization reaction to wrap more uniformly around the surface of the graphite.

[0054] S20: The precursor is carbonized under a protective atmosphere to obtain a negative electrode material. In some embodiments, the carbonization temperature is 500°C to 2500°C, and may be, for example, 500°C, 600°C, 650°C, 800°C, 1000°C, 1300°C, 1500°C, 2000°C, 2200°C, or 2500°C. However, the present invention is not limited to these values, and other values ​​within the range are equally applicable. As can be seen, controlling the carbonization temperature within an appropriate range can reduce thermal decomposition of the polymer due to excessively high temperatures and insufficient carbonization of the polymer due to excessively low temperatures. By adequately carbonizing the polymer coating layer, the impedance of the product can be reduced, and nitrogen atoms can be doped inward from the surface of the negative electrode material particles, thereby improving the uniformity of nitrogen doping in the surface layer of the negative electrode material particles. Preferably, the carbonization reaction temperature is 800°C to 2200°C.

[0055] In some embodiments, the heat retention time for the carbonization treatment is 1 hour to 20 hours, and specifically may be 1 hour, 3 hours, 7 hours, 10 hours, 11 hours, 13 hours, 16 hours, 17 hours, 18 hours, 20 hours, etc., but is not limited to the above-mentioned numerical values, and other numerical values ​​not specified within the numerical range are also applicable.

[0056] In some embodiments, the carbonization process is carried out under a protective atmosphere, the protective atmosphere comprising at least one of nitrogen gas, helium gas, neon gas, argon gas, krypton gas, and xenon gas.

[0057] In some embodiments, the temperature rise rate in the carbonization treatment is 0.5°C / min to 5.0°C / min, and specifically may be 0.5°C / min, 1°C / min, 1.7°C / min, 2.5°C / min, 3.0°C / min, 4°C / min, 5°C / min, etc., but is not limited to the above-mentioned numerical values, and other unmentioned numerical values ​​within the numerical range are also applicable.

[0058] According to a third aspect, the present disclosure provides a battery, the battery comprising an anode material according to the first aspect described above or an anode material produced by the method according to the second aspect described above.

[0059] In other embodiments, the negative electrode material may be utilized in lithium ion batteries or other electrochemical devices such as sodium ion batteries. It should be understood by those skilled in the art that the above-described method for manufacturing a lithium ion battery is merely an example, and other methods commonly used in the art may be employed without departing from the scope of the present disclosure.

[0060] The following describes the embodiments of the present disclosure in more detail, with reference to several examples. The embodiments of the present disclosure are not limited to the following specific examples, and may be modified as appropriate within the scope of protection.

[0061] Example 1 The method for producing the negative electrode material according to this embodiment includes the following steps. (1) 500 g of graphite and 1000 ml of deionized water were mixed uniformly, and a phosphoric acid solution was added to adjust the pH value to 5. 25 g of aniline monomer was added, and the mixture was thoroughly stirred to form a mixed solution. (2) The above mixed solution was placed in a water bath at 4°C and stirred. While controlling the stirring speed at 300 r / min, 60 ml of an aqueous solution of ammonium persulfate (concentration = 2 mol / L) was added. After completion, the mixture was stirred continuously for 10 hours to allow the polymerization reaction to proceed, and the precursor was obtained by solid-liquid separation. (3) In a nitrogen gas atmosphere, the precursor was heated to 1150°C and then carbonized for 4 hours to obtain the negative electrode material. The negative electrode material prepared in this example includes a core and a coating layer located on at least a portion of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Figure 2a is a scanning electron microscope image of the negative electrode material prepared in Example 1, and Figure 2b is a scanning electron microscope image of the negative electrode material prepared in Example 1 at a different magnification. As shown in Figures 2a and 2b, the surfaces of the negative electrode material particles prepared in Example 1 were generally smooth. Five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected using a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, none of R1 to R6 is 0.

[0062] Example 2 The method for producing the negative electrode material according to this embodiment includes the following steps. (1) 500 g of graphite and 1,000 ml of deionized water were mixed uniformly, and a phosphoric acid solution was added to adjust the pH value to 5. 40 g of phenylenediamine monomer was added, and the mixture was thoroughly stirred to form a mixed solution. (2) The above mixed solution was placed in a water bath at 4°C and stirred. While controlling the stirring speed at 500 r / min, 150 ml of an aqueous solution of ammonium persulfate (concentration = 2 mol / L) was added. After completion of the stirring, the mixture was stirred continuously for 10 hours to allow the polymerization reaction to proceed, and the precursor was obtained by solid-liquid separation. (3) The precursor was heated to 1250°C under a nitrogen gas atmosphere and then carbonized for 4 hours to obtain the negative electrode material. The negative electrode material prepared in this example includes a core and a coating layer located on at least a portion of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Figure 3 is a schematic diagram of the measurement of the nitrogen doping concentration in different regions of the scanning electron microscope image of the negative electrode material provided in Example 2 of the present disclosure. As shown in Figure 3, five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected by a scanning electron microscope-energy dispersive spectrometer, and the nitrogen atom number occupancy rate R of each region was calculated. n As a result of measuring, it was found that none of R1 to R6 was 0. Furthermore, the average value of the nitrogen atom number occupancy rate was calculated to be R=0.07, which indicates that uniform doping of nitrogen elements is achieved in the negative electrode material.

[0063] Example 3 (1) 500 g of graphite and 1000 ml of deionized water were mixed uniformly, and a phosphoric acid solution was added to adjust the pH value to 5. 50 g of diphenylamine monomer was added, and the mixture was thoroughly stirred to form a mixed solution. (2) The above mixed solution was placed in a water bath at 4°C and stirred. While controlling the stirring speed at 400 r / min, 120 ml of an aqueous solution of ammonium persulfate (concentration = 2 mol / L) was added. After completion of the stirring, the mixture was stirred continuously for 15 hours to allow the polymerization reaction to proceed, and the precursor was obtained by solid-liquid separation. (3) In a nitrogen gas atmosphere, the precursor was heated to 1150°C and then carbonized for 4 hours to obtain the negative electrode material. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Five negative electrode material particles were randomly obtained, and 10 regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected by a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. nAs a result of measuring, none of R1 to R6 is 0.

[0064] Example 4 It differs from Example 1 in the following respects. (1) 500 g of artificial graphite and 1000 ml of deionized water were mixed uniformly, and a hydrochloric acid solution was added to adjust the pH value to 5. 15 g of aniline monomer was added, and the mixture was thoroughly stirred to form a mixed solution. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Five negative electrode material particles were randomly obtained, and 10 regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected by a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, none of R1 to R6 is 0.

[0065] Example 5 (1) 500 g of natural graphite and 1,000 ml of deionized water were mixed uniformly, and sodium hydroxide solution was added to adjust the pH value to 8. 20 g of sulfamic acid monomer was added, and the mixture was thoroughly stirred to form a mixed solution. (2) The above mixed solution was placed in a water bath at 4°C and stirred. While controlling the stirring speed at 300 r / min, 50 ml of an aqueous solution of ammonium persulfate (concentration = 2 mol / L) was added. After completion of the stirring, the mixture was stirred continuously for 10 hours to allow the polymerization reaction to proceed, and the precursor was obtained by solid-liquid separation. (3) In a nitrogen gas atmosphere, the precursor was heated to 1150°C and then carbonized for 4 hours to obtain the negative electrode material. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing soft carbon. Five negative electrode material particles were randomly obtained, and 10 regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected by a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, none of R1 to R6 is 0.

[0066] Example 6 (1) 500 g of artificial graphite (D50 = 2 μm) and 1000 ml of deionized water were mixed uniformly, and sodium hydroxide solution was added to adjust the pH value to 4. 25 g of aniline monomer was added, and the mixture was thoroughly stirred to form a mixed solution. (2) The above mixed solution was placed in a water bath at 4°C and stirred. While controlling the stirring speed at 300 r / min, 50 ml of an aqueous solution of ammonium persulfate (concentration = 2 mol / L) was added. After completion of the stirring, the mixture was stirred continuously for 10 hours to allow the polymerization reaction to proceed, and the precursor was obtained by solid-liquid separation. (3) The precursor was heated to 1250°C under an argon gas atmosphere and then carbonized for 4 hours to obtain the negative electrode material. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Five negative electrode material particles were randomly obtained, and 10 regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected by a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, none of R1 to R6 is 0.

[0067] Example 7 (1) 500 g of artificial graphite (D50 = 25 μm) and 1000 ml of deionized water were mixed uniformly, and sodium hydroxide solution was added to adjust the pH value to 4. 25 g of aniline monomer was added, and the mixture was stirred thoroughly to form a mixed solution. (2) The above mixed solution was placed in a water bath at 4°C and stirred. While controlling the stirring speed at 300 r / min, 50 ml of an aqueous solution of ammonium persulfate (concentration = 2 mol / L) was added. After completion of the stirring, the mixture was stirred continuously for 10 hours to allow the polymerization reaction to proceed, and the precursor was obtained by solid-liquid separation. (3) The precursor was heated to 1250°C under an argon gas atmosphere and then carbonized for 4 hours to obtain the negative electrode material. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Five negative electrode material particles were randomly obtained, and 10 regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected by a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, none of R1 to R6 is 0.

[0068] Example 8 Example 8 differs from Example 1 in the following respects. (1) 500 g of graphite and 1000 ml of deionized water were mixed uniformly, and a phosphoric acid solution was added to adjust the pH value to 5. 0.5 g of aniline monomer was added, and the mixture was thoroughly stirred to form a mixed solution. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected using a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, none of R1 to R6 is 0.

[0069] Example 9 Example 9 differs from Example 1 in the following respects. (1) 500 g of graphite and 1000 ml of deionized water were mixed uniformly, and a phosphoric acid solution was added to adjust the pH value to 5. 225 g of aniline monomer was added, and the mixture was thoroughly stirred to form a mixed solution. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected using a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, none of R1 to R6 is 0.

[0070] Example 10 Example 10 differs from Example 1 in that the water bath temperature is 25°C, but the other ingredients, amounts used and production method are the same as those in Example 1. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected using a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, none of R1 to R6 is 0.

[0071] Example 11 Example 11 differs from Example 1 in that 20 ml of 3% hydrogen peroxide solution is used as the oxidizing agent, but the other ingredients, amounts used, and manufacturing method are the same as Example 1. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected using a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, none of R1 to R6 is 0.

[0072] Example 12 Example 12 is different from Example 1 in that the nitrogen-containing organic monomer is nitroaniline, but the other components, amounts used, and production method are the same as those of Example 1. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected using a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, none of R1 to R6 is 0.

[0073] Example 13 Example 13 is different from Example 1 in that the maximum heat treatment temperature is 1250°C, but the other components, amounts used and production method are the same as those of Example 1. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected using a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, none of R1 to R6 is 0.

[0074] Example 14 Example 14 differs from Example 1 in that the nitrogen-containing organic monomer is nitroaniline and the pH value is adjusted to 9 by adding sodium hydroxide solution, but the other components, amounts used, and manufacturing method are the same as Example 1. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected using a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, R1, R3, R4, R5, and R6 are all non-zero, but R2 is zero.

[0075] Example 15 Example 15 differs from Example 1 in that the amount of sulfamic acid monomer added is 225 g and the maximum heat treatment temperature is 2200°C, but the other components, amounts used, and production method are the same as Example 1. The negative electrode material produced in this example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite, the graphite surface and the coating layer containing nitrogen atoms, and the coating layer containing hard carbon. Five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected using a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, none of R1 to R6 is 0.

[0076] Comparative Example 1 (1) 500 g of graphite and 1000 ml of deionized water were mixed uniformly, and the pH value was adjusted to 5 by adding hydrochloric acid solution. The mixture was placed in a water bath at 4°C and vigorously stirred, and the solid-liquid separation was carried out to obtain the intermediate product. (2) The intermediate product was heated to 1150°C under a nitrogen gas atmosphere and then carbonized for 4 hours to obtain a negative electrode material. The negative electrode material produced in this comparative example contains graphite. Five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected using a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, R1 to R6 are all 0.

[0077] Comparative Example 2 Comparative Example 2 differs from Example 1 in that no ammonium persulfate solution was added when carrying out step (2), but the other components, amounts used, and production method were the same as those of Example 1. The negative electrode material produced in this comparative example includes a core and a coating layer located on at least a portion of the surface of the core, the core containing graphite and the coating layer containing a polymer. Five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected using a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, R1, R4, R5, and R6 are not zero, but R2 and R3 are zero.

[0078] Comparative Example 3 (1) Similar to Example 7, 500 g of artificial graphite (D50=25 μm) and 1000 ml of deionized water were mixed uniformly, and the pH value was adjusted to 5 by adding hydrochloric acid solution. The mixture was placed in a water bath at 4°C and vigorously stirred. After solid-liquid separation, an intermediate product was obtained. (2) The intermediate product was heated to 1150°C under a nitrogen gas atmosphere and then carbonized for 4 hours to obtain a negative electrode material. The negative electrode material produced in this comparative example contains graphite. Five negative electrode material particles were randomly obtained, and six regions were randomly selected from each negative electrode material particle. The energy spectrum signal of nitrogen element was detected using a scanning electron microscope-energy dispersive spectrometer, and the number occupancy rate R of nitrogen atoms in each region was calculated. n As a result of measuring, R1 to R6 are all 0.

[0079] Measurement method (1) Measurement method for average particle size of negative electrode material The particle size distribution range of the negative electrode material is measured by a Malvern laser granulometer. (2) Method for measuring tap density of negative electrode material The negative electrode material is placed in the sample chamber of the tap density meter, and the sample volume is recorded after 1000 vibrations. The tap density can then be calculated from the mass-to-volume ratio. (3) Measurement method for the specific surface area of ​​negative electrode materials The amount of gas adsorbed onto a solid surface at constant and low temperatures and under different relative pressures is measured, and then the monolayer adsorption amount of the sample is calculated based on the Brunauer-Emmett-Teller adsorption theory and its equation (BET equation), and the specific surface area of ​​the material is calculated based on this. (4) Observation of the microscopic shape of the surface of negative electrode material particles The microscopic shape of the surface of the negative electrode material is observed using an S-4800 scanning electron microscope. (5) Method for measuring nitrogen element content in negative electrode material particles The nitrogen element content in a single particle of graphite is measured using a scanning electron microscope with an attached component called an energy dispersive spectrometer.

[0080] (6) Measurement method for nitrogen doping uniformity A in negative electrode material Randomly obtain five negative electrode material particles, and randomly select n regions of 1 μm × 1 μm from each negative electrode material particle. Detect the energy spectrum signal of nitrogen element using a scanning electron microscope-energy dispersive spectrometer (SEM-EDS) to measure the number occupancy of nitrogen atoms in each region, and calculate the average number occupancy of nitrogen atoms as R. The uniformity is

number

[0081] (7) Measurement of powder conductivity Using a resistivity meter (ST-2255A manufactured by Suzhou Jeong Electronics Co., Ltd.), 5 g of powder sample was taken and subjected to a constant pressure of 8000 kg ± 2 kg in an electronic press, maintained for 15 to 25 seconds. The sample was placed between the electrodes of the meter, and the sample height was set to h (cm), the voltage across both ends to U, the current to I, and the resistance to R (KΩ). The area of ​​the powder after sheeting was S = 3.14 cm. 2 and obtain the powder conductivity by the formula δ=h / (S×R) / 1000, whose unit is S / m.

[0082] (8) Measurement of electrochemical performance Each negative electrode material prepared in the Examples and Comparative Examples was dissolved in deionized water in a mass ratio of 96.5:1.5:1 (negative electrode material, carboxymethyl cellulose, styrene-butadiene rubber) to adjust the solid content to 50%. This solution was applied to a copper foil current collector and vacuum-dried to obtain a negative electrode sheet. A lithium metal sheet was used as the counter electrode, and the battery was assembled into a button cell in an argon-filled glove box. Charge-discharge measurements were performed at a current density of 0.1 C over a charge-discharge range of 0.01 to 1.5 V. The initial reversible specific capacity, first-cycle charge capacity, and first-cycle discharge capacity were obtained by cyclic charge-discharge. The initial coulombic efficiency = first-cycle discharge capacity / first-cycle charge capacity. The results of the above performance measurements are as follows:

[0083] Table 1: Negative electrode materials and battery performance parameters produced in each example and comparative example [Table 1]

[0084] As can be seen from Table 1, the measurement data for Examples 1 to 12 indicate that a mixed solution containing graphite, a nitrogen-containing organic monomer, and an oxidant is polymerized to form a nitrogen-containing polymer that wraps around the graphite surface. The nitrogen-containing polymer then undergoes a carbonization process to obtain a uniformly nitrogen-doped anode material. The in situ polymerization under mild conditions allows the nitrogen-containing organic monomer molecules to be uniformly introduced onto the graphite particle surface, enhancing the uniformity of nitrogen doping on the graphite particle surface. By controlling the specific surface area of ​​the anode material within an appropriate range, the irreversible reaction between the anode material and the electrolyte during the first cycle can be reduced, thereby increasing the reversible capacity of the battery. Furthermore, the uniform nitrogen doping also adjusts the energy band structure of the graphite material, improving the initial Coulombic efficiency.

[0085] Comparing Example 14 with Example 1, it was found that in the prepared negative electrode material, the number occupancy of nitrogen atoms in one unit area out of n randomly selected unit areas was zero, which resulted in a relatively poor uniformity of nitrogen doping on the graphite surface, and the capacity and initial effect of the negative electrode material were also reduced compared to Example 1.

[0086] Comparing Comparative Example 1 with Example 1, it was found that the capacity of the graphite anode material produced was only 361.1 mAh / g (Comparative Example 1) because no nitrogen-containing organic monomer was added to the mixed solution during the production process of the anode material. This made it difficult to improve the product performance, and this resulted in a decrease in the reversible capacity and initial coulombic efficiency of the battery compared to Example 1. As can be seen from this, adding an appropriate amount of nitrogen-containing organic monomer allows the polymer formed by polymerization to wrap around the surface of the graphite particles, resulting in a high capacity and high initial coulombic efficiency of the resulting graphite anode material.

[0087] Comparing Comparative Example 2 with Example 2, it was found that the absence of oxidation treatment during the manufacturing process of the graphite negative electrode material resulted in a lower nitrogen content in the manufactured negative electrode material and poor uniformity. However, the presence of the polymer coating layer reduced the conductivity of the negative electrode material, resulting in a slight decrease in the battery specific capacity to 361.3 mAh / g and a slight decrease in the initial coulombic efficiency to 92.6%.

[0088] Comparing Comparative Example 3 with Example 7, it was found that in the manufacturing process of the graphite negative electrode material, artificial graphite was used as the raw material and no nitrogen-containing organic monomer was added to the mixed solution. Therefore, compared to Example 1, the capacity of the manufactured graphite negative electrode material was reduced to 349.7 mAh / g (Comparative Example 3), and both the capacity and initial coulombic efficiency of the negative electrode material were somewhat reduced.

[0089] As described above, the present disclosure has been disclosed by the preferred embodiments, but is not intended to limit the scope of the claims. Anyone skilled in the art can make some possible changes and modifications without departing from the concept of the present disclosure. Therefore, the protection scope of the present disclosure shall be governed by the scope defined by the claims of the present disclosure.

[0090] This disclosure claims priority to a Chinese patent application filed with the State Intellectual Property Office on August 24, 2023, bearing application number 202311076468.4 and entitled "Negative electrode material and manufacturing method thereof, for lithium ion batteries," the entire contents of which are incorporated herein by reference.

Claims

1. A negative electrode material, a core and a coating layer located on at least a portion of the surface of the core, wherein the negative electrode material is doped with nitrogen atoms; The uniformity of the doping concentration of the nitrogen atoms is represented by A, and the uniformity A is obtained by the following measurement method: Randomly obtain five negative electrode material particles, and randomly select n regions of 1 μm × 1 μm from each negative electrode material particle. Detect the energy spectrum signal of nitrogen element using a scanning electron microscope-energy dispersive spectrometer, measure the number occupancy of nitrogen atoms in each region, and calculate the average number occupancy of nitrogen atoms as R; The uniformity is [Equation 1] and A≦0.5, where R ｎ represents the number occupancy of nitrogen atoms measured in the nth region, and n is a natural number ≧5.

2. the core contains graphite, and the coating layer contains a carbonaceous material; 2. The negative electrode material according to claim 1, wherein the nitrogen atoms are contained in the surface of the graphite and / or the coating layer.

3. 2. The negative electrode material according to claim 1, wherein the powder conductivity of the core is ρ1, the powder conductivity of the negative electrode material is ρ2, and 1.01≦ρ2 / ρ1≦10.

4. The negative electrode material satisfies at least one of the following characteristics: (1) The R ｎ is not zero, (2) the core contains at least one of artificial graphite and natural graphite; (3) the thickness of the coating layer is 1 nm to 100 nm; (4) The negative electrode material according to claim 1, wherein the mass content of nitrogen atoms in the negative electrode material is 0.01% to 3%.

5. The negative electrode material satisfies at least one of the following characteristics: (1) The specific surface area of ​​the negative electrode material is 0.1 m ２ / g to 5m ２ / g, (2) the median particle size of the negative electrode material is 1 μm to 30 μm; (3) The tap density of the negative electrode material is 0.75 g / cm ３ ~1.1 g / cm ３ and (4) The coating layer contains at least one of hard carbon, soft carbon, and graphitized carbon, (5) The negative electrode material according to any one of claims 1 to 4, characterized in that the mass content of the coating layer in the negative electrode material is 0.1% to 10%.

6. A method for producing a negative electrode material, comprising: obtaining a precursor by polymerizing a mixed solution containing graphite, a nitrogen-containing organic monomer, and an oxidizing agent; and a step of carbonizing the precursor to obtain a negative electrode material.

7. The method has at least one of the following characteristics: (1) The graphite includes at least one of artificial graphite and natural graphite; (2) The median particle size of the graphite is 1 μm to 30 μm, (3) The nitrogen-containing organic monomer includes at least one of methylaniline, sulfamic acid, aminosalicylic acid, aminoterephthalic acid, aniline, diphenylamine, phenylenediamine, trianiline, ethylaniline, and nitroaniline; (4) The oxidizing agent includes at least one of ammonium persulfate, hydrogen peroxide, iron chloride, and aluminum chloride; (5) The molar concentration of the oxidizing agent in the mixed solution is 0.1 mol / L to 2 mol / L; (6) The mass ratio of the graphite to the nitrogen-containing organic monomer is 100:(0.1 to 45), (7) The polymerization reaction time is 1 hour to 30 hours, (8) The temperature of the polymerization reaction is 1°C to 95°C; (9) The polymerization reaction is carried out under stirring, (10) The polymerization reaction is carried out under stirring, and the stirring speed is 50 r / min to 800 r / min; (11) The manufacturing method according to claim 6, characterized in that a nitrogen-containing polymer formed by polymerizing the nitrogen-containing organic monomer is wound around the surface of the graphite.

8. 7. The manufacturing method according to claim 6, wherein the step of polymerizing a mixed solution containing graphite, a nitrogen-containing organic monomer, and an oxidizing agent comprises preparing a mixed solution containing graphite, a pH adjuster, and a nitrogen-containing organic monomer, and then adding an oxidizing agent to the mixed solution to obtain a mixed solution.

9. The method has at least one of the following characteristics: (1) the pH of the mixture is 1 to 10; (2) The pH adjuster includes at least one of an acidic pH reagent and an alkaline pH reagent; (3) The pH adjuster includes at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid, (4) The manufacturing method according to claim 8, wherein the pH adjuster includes at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate.

10. The method has at least one of the following characteristics: (1) the carbonization treatment is carried out under a protective atmosphere; (2) The protective atmosphere includes at least one of nitrogen gas, helium gas, neon gas, argon gas, krypton gas, and xenon gas; (3) The temperature of the carbonization treatment is 500°C to 2500°C, (4) The temperature rise rate of the carbonization treatment is 0.5°C / min to 5.0°C / min, (5) The manufacturing method according to any one of claims 6 to 8, characterized in that the heat retention time for the carbonization treatment is 1 hour to 20 hours.

11. A battery comprising the anode material according to any one of claims 1 to 5 or the anode material produced by the method for producing the anode material according to any one of claims 6 to 10.

Images