The Influence of Electrolyte Volume on Calendaric Aging of Lithium‐Ion Batteries

Abstract

Lithium‐ion cells with graphite anodes and nickel–manganese–cobalt oxide (NMC622) cathodes are filled with three different amounts of electrolyte. During formation, incremental capacity analysis indicates small differences in the formation processes between cells with insufficient electrolytes to fill all pores and those with an electrolyte volume above the total pore volume of the cell. Complimentary analysis of the gases developed during formation shows that the composition of these cells differs from the cells with a sufficient electrolyte. The aging of cells under high temperature (60 °C) and high constant voltage of 4.2 V is studied. During aging, cells with higher amounts of electrolyte degrade substantially slower. Based on data available from electrical tests, a theory explaining the volume‐dependent rise of resistance and capacity decay is proposed.