During the first charge and discharge of the liquid lithium ion battery, the electrode material reacts with the electrolyte at the solid-liquid phase interface to form a passivation layer covering the surface of the electrode material. This passivation layer is an interfacial layer characterized by a solid electrolyte, which is referred to as a solid electrolyte interface film referred to as an SEI film.
The formation process of the SEI film, that is, the electrochemical reaction process. When the voltage reaches a certain value, a series of physicochemical changes occur on the surface of the negative electrode. In actual production, it is mainly the formation of a film by the formation of a battery.