Working principle of polymer lithium-ion batteries

　　Lithium ion batteries generally use lithium cobalt oxide, nickel cobalt manganese lithium, and lithium iron phosphate as the positive electrode, graphite as the negative electrode, LiPF6+EC+DMC as the electrolyte, and aluminum plastic film packaging as the outer shell. During charging, lithium ions detach from the lattice of the positive electrode layered oxide, migrate to the surface of the layered negative electrode through organic electrolyte, and then embed into the lattice of graphite material. At the same time, the remaining electrons reach the negative electrode from the external circuit. On the contrary, during discharge, lithium ions detach from the graphite lattice and return to the positive oxide lattice. Under normal charging and discharging conditions, the insertion and detachment of lithium ions between layered graphite and oxides generally only cause changes in interlayer spacing, without causing damage to the crystal structure. With the charging and discharging process, the chemical structure of the positive and negative electrode materials remains basically unchanged. Therefore, in terms of the reversibility of charging and discharging reactions, lithium-ion batteries are an ideal reversible battery. The process of lithium ions entering the electrode is called embedding, and the process of coming out of the electrode is called detachment. During charging and discharging, lithium ions move back and forth between the positive and negative electrodes of the battery, rocking back and forth like a rocking chair. Therefore, some people vividly refer to lithium ion batteries as "rocking chair batteries".

　　Electrochemical reaction mechanism of polymer lithium-ion batteries

　　Electrode reaction equation:

　　Positive electrode reaction: LiCoO2=Li1-xCoO2+xLi++xe-

　　Negative reaction: C+xLi++xe -=CLix

　　Total battery reaction: LiCoO2+C=Li1-xCoO2+CLix

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