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Prospects of anode materials for power batteries natural graphite VS artificial graphite
The energy density of lithium-ion batteries largely depends on the negative electrode material. From commercialization to the present, the most mature negative electrode material used in lithium-ion batteries is graphite.
Compared with other carbon materials, graphite materials have the advantages of high electronic conductivity, large lithium ion diffusion coefficient, high lithium insertion capacity and low lithium insertion potential. In addition, graphite materials have a wide range of sources and low prices. They are the anode materials used earlier and are currently the mainstream anode materials for lithium-ion batteries.
Graphite materials are mainly divided into artificial graphite and natural graphite.
In 2018, the total permeability of natural graphite and artificial graphite was approximately 93%, of which artificial graphite accounted for 69%, natural graphite accounted for 24%, and other graphite accounted for 7%.
Natural graphite is mainly divided into amorphous graphite and flake graphite.
Amorphous graphite has low purity, and the graphite crystal plane spacing is 0.336 nm. It is mainly a hexahedral graphite crystal plane order structure, that is, the graphite layers are arranged in the order of ABAB..., and the orientation between individual crystallites shows anisotropy. However, after processing, the microcrystalline particles have a certain interaction with each other, and the formation of massive or granular particles has isotropic properties.
The crystallinity of flake graphite is high, the lamella structure is unitized, and it has obvious anisotropy. This structure determines that the volume of graphite changes greatly during the process of lithium insertion and extraction, which leads to the destruction of the graphite layer structure, which in turn causes a large irreversible capacity loss and a drastic deterioration of cycle performance.
As the negative electrode graphite of lithium-ion batteries, flake graphite has the disadvantage of large irreversible capacity for the first time, and the flake graphite has poor cycle performance and high current charge and discharge performance. Therefore, in use, it is often focused on the modification of natural graphite to improve its own structural shortcomings and improve battery performance.
Artificial graphite is mainly divided into MCMB, soft carbon and hard carbon according to different processing technology.
The artificial graphite anode material is made by calcining needle coke, petroleum coke, pitch coke and other raw materials at a certain temperature, then pulverizing, grading, and high-temperature graphitization. Its high crystallinity is formed by high-temperature graphitization.
With the outbreak of the global power battery market, the comprehensive requirements for material cost, processing performance, energy density, cycle life, fast charge rate and other factors have increased, and artificial graphite has gradually become the first choice for lithium battery anode materials.
With the continuous expansion of the power battery market, artificial graphite has become the most important material in my country's anode materials. It is estimated that China's artificial graphite demand will reach 265,000 tons in 2025.
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