The challenge of electrolyte impregnation in the fabrication and operation of Li-ion and Li-S batteries

Modeling and simulations, coupled with selected experimental studies for validation, are employed to analyze electrolyte impregnation in battery fabrication, elucidate and assess its effects on battery operation. Digital twins of the electrolyte filling process or the cell cycling are based on continuum-level physicochemical models taking into account the pore size distribution of the porous cathode and separator, dissolution and precipitation of any solutes such as sulfur or sulfides; additionally, ion transport and redox reactions in the liquid electrolyte for simulations of battery cycling. Electrolyte impregnation highly depends on cell format, with a cylindrical Li-ion cell predicted to take up to 7 days under rest for homogeneous electrolyte distribution. Simulations of the electrolyte infiltration in Li-S coin cells revealed sulfur dissolution and reprecipitation, which was verified by experiments using in operando microscopy. Simulations of the first discharge of electrolyte-lean Li-S cells demonstrated the effects of poor micropore wetting by the electrolyte. A model for electrolyte infiltration for Li-ion and Li-S batteries, followed by model of cycling a Li-S cell unsaturated or saturated with electrolyte. Simulations follow, coupled with selected experimental studies, of electrolyte infiltration in a Li-ion cylindrical cell and Li-S coin cells with different amounts of electrolyte, and the first discharge of these Li-S cells saturated or unsaturated with electrolyte.image