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