Poly(5-vinylbenzothiadiazole) for High-Performance Lithium-Ion Batteries

Redox-active polymers have recently become promising candidates for next-generation electrode materials in lithium-ion batteries. Materials made from small molecules with one or multiple reversible redox states are required to develop high energy density organic electrodes. Here, we focus our attention on 2,1,3-benzothiadiazole (BTZ), a widely employed organic electron acceptor with a suitable redox potential (−1.48 V vs Ag/Ag+ in acetonitrile) and a large theoretical charge-storage capacity (164.5 mAh/g). In this study, we synthesized gram quantities of poly(5-vinylbenzothiadiazole) from BTZ in three synthetic steps and employed a versatile and scalable radical polymerization protocol to make the final polymer. Lithium–organic hybrid batteries using this polymer as a cathode displayed a high specific capacity of 140 mAh/g at a charge/discharge potential of 1.70 V vs Li/Li+. This polymer showed promising performance and high stability, reaching up to 85% of the theoretical capacity and maintaining 99% coulombic efficiency after 500 cycles at 1C.