Novel redox shuttle additive for high-voltage cathode materials

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.