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One of the anode materials for lithium batteries-introduction of carbon anode materials

wallpapers Tech 2020-08-04
Graphite is soft and has a greasy feel. It is a non-metallic mineral with high-temperature resistance, oxidation resistance, corrosion resistance, thermal shock resistance, high strength, good toughness, high self-lubricating strength, thermal conductivity, and electrical conductivity—unique physical and chemical properties such as reliable performance.

Graphite has many excellent properties, so it is widely used in metallurgy, machinery, electrical, chemical, textile, national defense, and other industrial sectors, such as graphite molds, graphite electrodes, graphite refractories, graphite lubricating materials, graphite sealing materials, etc.

The ideal graphite has a layered structure. The layer is composed of SP2 carbon atoms to form a vast plane similar to a benzene ring. The carbon atoms between the layer planes are connected by δ bonds, with a bond length of 0.142nm and a bond angle of 120°. There is also a large π bond connecting all carbon atoms between the layers. The interlayer is 0.3354nm. Two crystal types: hexagonal crystal system-2H type (a) and rhombohedral crystal system-3R(b)Ø The two crystal types can be converted to each other: grinding and heating.

Lithium insertion mechanism of graphite

The theoretical capacity of graphite is 372mAh/g. Of course, only materials with a very high degree of graphitization can reach this value. However, all carbon materials have an irreversible capacity loss due to side reactions during the first charge and discharge. As the negative electrode potential decreases, it stops until the electrolyte components form a stable passivation film (SEI) on the negative electrode surface. Most of the capacity of graphite is in the range of 0.3~0.005V. Different voltage platforms correspond to different lithium insertion states, which are called fourth-order and third-order compounds, respectively... Finally, LiC6 is formed, reaching a theoretical capacity of 372mAh/g, and the interplanar spacing becomes 0.37.

Graphite is mainly divided into natural graphite and artificial graphite. Natural graphite needs to go through some treatment methods before it can be used as the negative electrode of the lithium-ion battery, such as our standard oxidation treatment and mechanical grinding.

As a harmful electrode material, graphite also has many shortcomings, such as the low potential of graphite, which forms an interface film with the electrolyte, and is easy to cause lithium evolution; the ion migration speed is slow, so the charge and discharge rate is low; the layered structure of graphite is inserted in lithium ions. Approximately 10% of deformation will occur during the process of unplugging, which will affect the cycle life of the battery.

Trunnano is one of the world's largest manufacturers of lithium battery anode materials. If you are interested, please contact Dr. Leo at brad@ihpa.net.

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