Graphite materials prospects: natural graphite VS artificial graphite
The lithium-ion battery is popular for its high capacity, high voltage, high cycle stability, high energy density, no environmental pollution, and other excellent performance, known as green energy and leading power in the 21st century, has a wide range of civil and national defense application prospects.
At present, lithium-ion batteries and their key materials have become the focus of attention of various countries and also the high-tech industry supported by China's energy field.
The 2019 Nobel Prize in Chemistry has been awarded to Professors John Bannister Goodenough, Stanley Whittingham, and Akira Yoshino for their contributions to the development of lithium batteries.
The energy density of lithium-ion batteries depends largely on the anode material. From the commercialization of lithium-ion batteries to now, the most mature anode material used is mainly graphite.
Compared with other carbon materials, graphite materials have the advantages of high electronic conductivity, large lithium-ion diffusion coefficient, high lithium embedding capacity, and low lithium embedding potential. In addition, graphite materials are widely used and cheap, so they are the early cathode materials and the mainstream anode materials of lithium-ion batteries.
With the embedding of lithium ions in the graphite anode more and more deeply, the surface color of the anode also gradually changes, from black to black to dark yellow and finally to gold, the graphite anode has also completed the transformation from C to LiC12 to LiC6, thus completing the charging process.
Graphite materials are mainly divided into artificial graphite and natural graphite.
In 2018, the combined permeability of natural and artificial graphite was about 93%, with artificial graphite accounting for 69%, natural graphite for 24%, and other graphite for 7%.
Natural graphite size particles are different, particle size distribution is wide, untreated natural graphite can not be used as an anode material directly, need to be used after a series of processing, and artificial graphite in the morphology and particle size distribution is more consistent.
The capacity of natural graphite is high, the compaction density is high, the price is cheaper, but because the particle size is different, the surface defects are more, the compatibility with the electrolyte is poor, and the side reaction is more; The performance of artificial graphite is more balanced, good circulation performance, and the compatibility of electrolyte is better, so the price will be more expensive.
Natural graphite has advantages of cost and specific capacity, but its cycle life is low and consistency is lower than artificial graphite. Compared with natural modified graphite, artificial graphite technology is more mature, and its electrolyte compatibility is better.
In addition, natural graphite is mainly used in small lithium batteries and lithium batteries for general use electronic products, artificial graphite is widely used in automotive power batteries and high-end electronic products with excellent cycling performance, large charging and discharging efficiency, and electrolyte compatibility, and other significant advantages.
Natural graphite is mainly divided into amorphous graphite and flake graphite.
The purity of amorphous graphite is low, the spacing of graphite crystal planes is 0.336 nm, and it is mainly hexahedral graphite crystal plane ordering structure, that is, the graphite layer according to ABAB...In order, the orientation of individual microcrystals presents anisotropy, but after processing, the microcrystalline particles interact with each other to a certain extent and form massive or granular particles with isotropy properties.
The crystallinity of flake graphite is high, the lamellar structure is unitary and has obvious anisotropy. This structure determines that the volume of graphite changes greatly in the process of lithium intercalation and deintercalation, resulting in the destruction of the structure of the graphite layer, resulting in a largely irreversible capacity loss and severe deterioration of cyclic performance.
When used as anode graphite of lithium-ion battery, flake graphite has the disadvantage of large irreversible capacity for the first time, and the cycle performance and high current charge-discharge performance of flake graphite are poor. Therefore, modification research on natural graphite is often focused on when used to improve its structure shortcomings and improve battery performance.
Artificial graphite according to the different processing technology, is mainly divided into MCMB, soft carbon, and hard carbon.
The artificial graphite anode material is the needle coke, petroleum coke, asphalt coke, and other raw materials calcined at a certain temperature, and then after crushing, grading, high-temperature graphitization made, its high crystallinity is formed by high-temperature graphitization.
With the explosion of the global power battery market, the comprehensive requirements of material cost, processing performance, energy density, cycle life, fast charging rate, and other factors are improving, and artificial graphite has gradually become the preferred anode material for a lithium battery.
In recent years, benefiting from the growth of power battery production brought by the demand for new energy vehicles, the global artificial graphite market demand has increased year by year. In 2018, the global artificial graphite demand reached 127,000 tons, up 39.6% year on year, and the market demand is expected to reach 425,000 tons in 2025.
In 2018, China's artificial graphite demand reached 86,000 tons, up 32.3% year on year, and shipments reached 133,000 tons, up 33% year on year.
With the continuous expansion of the power battery market, artificial graphite has become the most important material in China's anode materials, and it is expected that the demand for artificial graphite in China will reach 265,000 tons in 2025.
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