Gas generation mechanism due to electrolyte decomposition in commercial lithium-ion cell

To elucidate the gas generation mechanism due to electrolyte decomposition in commercial lithium-ion cells after long cycling, we developed a device w hich can accurately determine the volume of generated gas in the cell. Expe riments on LixC6/Li1-xCoO2 cells using electrolytes such as 1 M LiPF6 in pr opylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (E MC), and diethyl carbonate (DEC) are presented and discussed. In the nomina l voltage range (4.2-2.5 V), compositional change due mainly to ester excha nge reaction occurs, and gaseous products in the cell are little. Generated gas volume and compositional change in the electrolyte are detected largel y in overcharged cells, and we discussed that gas generation due to electro lyte decomposition involves different decomposition reactions in overcharge d and overdischarged cells. (C) 1999 Elsevier Science S.A. All rights reser ved.