Studies of Aromatic Redox Shuttle Additives for LiFePO[sub 4]-Based Li-Ion Cells

Fifty eight aromatic organic molecules were screened as chemical shuttles to provide overcharge protection for /graphite and Li-ion cells. The majority of the molecules were based on methoxybenzene and on dimethoxybenzene with a variety of ligands added to explore their effect. The added ligands affect the redox potential of the molecules through their electron-withdrawing effect and affect the stability of the radical cation. Of all the molecules tested, only 2,5-di-tert-butyl-1,4-dimethoxybenzene shows an appropriate redox potential of vs and long-term stability during extended abusive overcharge totaling over of 100% overcharge per cycle. The reasons for the success of this molecule are explored.