18650 1800mah battery.Lithium intercalation mechanism of graphite in lithium batteries

　　The theoretical capacity of graphite is 372mAh/g, and of course, only materials with a very high degree of graphitization can achieve this value. However, all carbon materials will experience irreversible capacity loss due to side reactions during the first charge and discharge. As the negative electrode potential decreases, it stops until the components in the electrolyte form a stable passivation film (SEI) on the negative electrode surface. There are four voltage platforms during the first discharge (as shown in the figure below), where A is the formation of SEI, and most of the graphite has a capacity in the range of 0.3-0.005V. In addition to A, different voltage platforms correspond to different lithium intercalation states, known as fourth and third order compounds... Finally, LiC6 is formed, reaching a theoretical capacity of 372mAh/g, and the crystal plane spacing becomes 0.37.

　　The arrangement of graphite LiC6 ink sheets in the fully lithium intercalated state undergoes a transformation (as shown in the following figure): from ABABAB... to AAAA... arrangement. Some artificial graphite is difficult to convert into an arrangement and has a lower capacity.

　　Graphite is mainly divided into natural graphite and artificial graphite. Natural graphite requires some treatment methods to be used as the negative electrode of lithium-ion batteries, such as common oxidation treatment and mechanical grinding. Artificial graphite, on the other hand, transforms from organic matter (gaseous, liquid, solid) to graphite, and the specific operation method can be determined by oneself.

　　Having said so much, of course, it's because he's the most widely used. Of course, as the anode material, graphite also has many shortcomings, such as the low potential of graphite, which forms an interface facial mask with the electrolyte, and is easy to cause lithium precipitation; The ion migration speed is slow, therefore the charge discharge rate is low; The layered structure of graphite undergoes about 10% deformation during the insertion and removal of lithium ions, which affects the cycling life of the battery.

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