CN-121470485-B - Battery-grade graphite, preparation method, application and lithium ion battery

Abstract

The invention belongs to the technical field of battery materials, and particularly relates to battery-grade graphite, a preparation method, application and a lithium ion battery. The preparation method of the battery grade graphite comprises the steps of mixing biomass, boron additives and water, drying to obtain boron doped biomass powder, carrying out pyrolysis carbonization on the boron doped biomass powder to obtain boron doped pyrolytic carbon, carrying out flash joule thermal pyrolysis on the boron doped pyrolytic carbon to obtain graphitized carbon, and carrying out acid washing, drying, ball milling and sieving on the graphitized carbon in sequence to obtain the battery grade graphite. The invention successfully converts low-value biomass wastes such as lignin into high-performance battery-grade graphite anode materials through a simple and efficient process route of boron-doped carbonization-flash joule thermal pyrolysis-acid washing-ball milling. The method not only realizes the efficient recovery and value-added utilization of the waste carbon source, but also has low cost of raw materials and simple integral process, and has remarkable industrial application potential and economic benefit.

Inventors

• DONG ZHIGUO
• LI YAN
• JIN FUQIANG
• XIE XINPING
• LIU WENHAO
• Anqing Nenhua
• Emil Babaev
• GUAN WEI
• CHEN LEI
• YANG HAIPING
• ZHAO YUYING
• LI TIANJIN
• HUA DONGLIANG
• YANG SHUANGXIA
• ZHAO YUXIAO

Assignees

• 山东省科学院能源研究所
• 华中科技大学

Dates

Publication Date

20260508

Application Date

20260106

Claims (9)

1. 1. The preparation method of the battery grade graphite is characterized by comprising the following steps of: mixing biomass, boron additives and water, and drying to obtain boron doped biomass powder; pyrolyzing and carbonizing the boron doped biomass powder to obtain boron doped pyrolytic carbon; carrying out flash joule thermal pyrolysis on boron-doped pyrolytic carbon to prepare graphitized carbon; Sequentially carrying out acid washing, drying, ball milling and sieving treatment on graphitized carbon to obtain battery grade graphite; The voltage range of the flash joule thermal pyrolysis is 150-170V, the peak temperature is 3400-4000 ℃, the electrifying time is 0.5-3 s, and the vacuum degree is 1-5 Pa; The mixing mass ratio of the biomass to the boron additive is 20 (2-5); The flash joule thermal pyrolysis is non-indirect heating; the biomass is one or more of lignin, cellulose, starch, glucose or straw; the boron-based additive is one or more of boric acid, elemental boron, boron carbide and borate.
2. 2. The method of claim 1, wherein the drying temperature is 40-100 ℃ and the drying time is 12-48 h.
3. 3. The method for preparing battery grade graphite according to claim 1, wherein the pyrolysis atmosphere for pyrolysis and carbonization is one or more of nitrogen, argon, helium and carbon dioxide; The pyrolysis carbonization temperature is 700-1000 ℃, the heating rate is 5-20 ℃ per minute, the heat preservation time is 0.5-3 h, and the gas flow is 50-200 mL per minute.
4. 4. The preparation method of the battery grade graphite according to claim 1, wherein the acid solution adopted in the acid washing is one of hydrochloric acid, sulfuric acid and nitric acid, the concentration range of the acid solution is 1-3 mol/L, the solid-liquid ratio in the acid washing process is 1 (5-10), and the acid washing time is 2-8 h; the drying temperature is 80-100 ℃ and the drying time is 12-24 h; the ball milling speed is 400-600 rpm, and the ball milling time is 1-6 h; the screening particle size range of the screening treatment is 400-600 meshes.
5. 5. A battery grade graphite produced by the method of producing a battery grade graphite of any one of claims 1-4.
6. 6. The battery grade graphite of claim 5, wherein the battery grade graphite has a specific surface area of 5.80-8.30 m 2 /g, a graphitization degree of 88.70-92.08%, a coefficient of variation of 0.015-0.05%, an electrical conductivity of 146.43-206.22S/cm, and a powder compaction density of 1.17-2.37g/cm 3 .
7. 7. The battery grade graphite of claim 5 wherein the battery grade graphite is boron doped graphite having a boron doping level of 0.41% to 0.83%.
8. 8. Use of the battery grade graphite of any one of claims 5-7 in a negative electrode of a lithium ion battery.
9. 9. A lithium ion battery characterized in that the battery grade graphite of any one of claims 6-7 is used as a negative electrode.

Description

Battery-grade graphite, preparation method, application and lithium ion battery Technical Field The invention belongs to the technical field of battery materials, and particularly relates to battery-grade graphite, a preparation method, application and a lithium ion battery. Background Lithium ion batteries are widely used as efficient energy storage and conversion devices in the fields of consumer electronics, electric automobiles, large-scale energy storage power stations and the like. The performance of the negative electrode material in a lithium ion battery directly determines the overall energy density, power density and service life of the battery. At present, a commercial lithium ion battery generally adopts a graphite material as a negative electrode, which is mainly beneficial to rich sources, higher theoretical specific capacity (about 372 mAh/g), stable charge and discharge platform, excellent cycle performance and mature preparation process. The existing preparation method of the graphite anode material mainly comprises a high-temperature carbonization method, a chemical vapor deposition method, a sol-gel method, a hydrothermal method and the like. However, the existing preparation process generally has the problems of high energy consumption, complex process, high cost, insufficient performance of the obtained material and the like. Lignin is the second most abundant natural high molecular polymer in natural reserves, mainly derived from a large number of byproducts of paper industry and biomass refining processes. At present, most lignin is directly burnt or utilized with low value, so that not only is the resource wasted, but also the environmental pressure is brought. From the chemical structure, lignin molecules contain a large number of aromatic ring structures formed by phenylpropane units, and the lignin molecules are ideal precursors for preparing graphite carbon materials in theory. At present, the mainstream method for synthesizing graphite materials by taking biomass (such as lignin) as a precursor relies on traditional high-temperature heat treatment, but the problems of high energy consumption, long period and the like generally exist. Meanwhile, the carbon material prepared by directly using lignin as a precursor through high-temperature pyrolysis generally presents a highly disordered amorphous structure, and has low graphitization degree and poor crystallinity. The electron conductivity of the lithium ion battery is obviously lower than that of ideal graphite, and the lithium ion battery anode material has the problems of poor rate performance, low reversible capacity, insufficient cycle stability and the like when being used as a lithium ion battery anode material, so that the application of the lithium ion battery anode material in an actual battery is severely limited. Disclosure of Invention The invention aims to provide battery grade graphite, a preparation method, application and a lithium ion battery, so that the defects of the prior art are overcome, and the carbon source in the lignin is recovered and converted into battery grade graphite through a series of operations such as carbonization, flash joule thermal pyrolysis, acid washing, ball milling and the like on the boron-doped lignin, so that the high-value utilization of the low-value lignin is realized, the whole process is simple, the raw material cost is low, and the application prospect is good. In order to achieve the above purpose, the technical scheme of the invention is as follows: In a first aspect, the invention provides a method for preparing battery grade graphite, comprising the following steps: mixing biomass, boron additives and water, and drying to obtain boron doped biomass powder; pyrolyzing and carbonizing the boron doped biomass powder to obtain boron doped pyrolytic carbon; carrying out flash joule thermal pyrolysis on boron-doped pyrolytic carbon to prepare graphitized carbon; Sequentially carrying out acid washing, drying, ball milling and sieving treatment on graphitized carbon to obtain battery grade graphite; the voltage range of flash joule thermal pyrolysis is 150-170V, the peak temperature is 3000-4000 ℃, the electrifying time is 0.5-3 s, and the vacuum degree is 1-5 Pa. The biomass such as lignin adopted in the invention contains a large amount of oxygen-containing functional groups such as phenolic hydroxyl groups, ether bonds and the like in the molecular structure. These functional groups can undergo strong intermolecular interactions with boron-based additives such as boric acid in an aqueous solution through hydrogen bonds or coordination bonds. This effect allows a highly uniform dispersion of boron element between lignin molecular chains to be achieved during the solution mixing stage. The introduction of boron in the boron-doped pyrolytic carbon can catalyze the graphitization process of the carbon, and the graphitization energy barrier is reduced. At the same time, the pyrolyt