Synthesis and charge/discharge properties of cellulose derivatives carrying free radicals

Ethyl cellulose derivatives [EC-T and EC-P] and cellulose acetate derivatives [CA-T and CA-P] carrying TEMPO or PROXY radicals (TEMPO = 2,2,6,6-tetramethyl-1-piperidinyloxy, PROXY = 2,2,5,5-tetramethyl-1-pyrrolidinyloxy) were synthesized with moderate number-average molecular weights of 62 400-126 000 in 84-88% yield by the reaction of 4-carboxy-TEMPO or 3-carboxy-PROXY with residual hydroxyl group of ethyl cellulose or cellulose acetate. All the free radical-containing cellulose derivatives demonstrated reversible charge/discharge processes, whose discharge capacities were 42.8-61.1 A h/kg. In particular, the CA-T-based cell displayed two-stage discharge process, and the first-stage discharge capacity reached 29.5 A h/kg which corresponds to 74% of its theoretical value, and that of the total capacity was 61.1 A h/kg which approaches up to 153% of the theoretical value for one-electron redox reaction.