Electrolyte filling and formation of lithium-ion cells

It is common practice that the liquid electrolyte is injected into the cell once other components are packed together and have formed a cell of the desired geometry. This injection marks the beginning of the electrolyte filling process, during which the electrolyte is allowed to infiltrate the porous electrodes and the separator layers and wet the originally dry components of the cell. The formation step follows the filling step as the fully wetted cell undergoes a few initial cycles to form an electronically passive layer on the electrode.The electrolyte filling/wetting and formation of lithium-ion battery cells are two very time-consuming steps, which have direct influences on the product's final cost, performance, and safety. An improvement in this step will reduce the processing time of the cells, helping unleash their full functionality and alleviate their safety concerns. In this chapter, the importance of complete electrolyte wetting, the trade-off between cost and performance, and the latest technologies used to predict and assess the extent of electrolyte filling are discussed.