2,5-Di-tert-butyl-1,4-dimethoxybenzene (DDB, CAS number 7323-63-9), an aromatic compound with two methoxy groups at 2,5-positions and two tert-butyl groups at 1,4-positions of the benzene ring, is a very successful benchmark redox shuttle molecule developed for the lithium ion battery (LIB) systems. With two tert-butyl groups, DDB has rigid molecular structure with an outstanding electrochemical reversibility and stability.
DDB provides high-rate overcharge protection of lithium iron phosphate (LiFePO4) based Li-ion cells by a reversible and stable redox reaction at 3.9 V vs. Li/Liand more than 200 cycles of 100% overcharge per cycle at C/2 and 1C rate for LiFePO+ 4 cathode in LIBs.
Despite being a benchmark shuttle, DDB has relatively low solubility in the carbonate electrolyte and the redox potential that is insufficient for 4 V operation of LIBs, due to its low polarity induced from symmetric structure.