A high voltage redox shuttle additive, tetraethyl-2,5-di-tert-butyl-1,4-phenylene diphosphate (TEDBPDP), has been synthesized and explored as an overcharge protection additive for lithium-ion cells. Cyclic voltammetry results indicate that the new shuttle molecule exhibits an oxidation potential at 4.8 V vs.Li/Li+, the highest one of any redox shuttles ever synthesized and reported in the literature. The charge–discharge tests for lithium ion cells with LiMn2O4 and Li1.2Ni0.15Co0.1Mn0.55O2 as cathode materials indicated that the TEDBPDP additive can provide successful overcharge protection at 4.75 V vs.Li/Li+, which is a suitable redox shuttle additive for high voltage cathode materials. In addition, the incorporated organophosphate groups in the molecule structure can provide an additional safety feature as a flame retardant additive, making this high-voltage redox shuttle even more attractive.
