Radical polymer grafted graphene for high-performance Li+/Na+ organic cathodes

Covalently grafting redox-active polymer to graphene sheets is a practical approach for developing high-performance organic cathode materials. Here, we report a facile preparation of radical polymer poly(2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl methacrylate) (PTMA) grafted graphene sheets (rGO) composites (rGO-g-PTMA) with various PTMA contents via one-step radical polymerization, and their applications as cathodes for Li-ion/Na-ion batteries. The energy storage capacity of rGO-g-PTMA is determined by the relative contribution from the battery-type redox reaction of PTMA and the pseudocapacitive behavior of rGO sheets. The optimized rGO-g-PTMA50 composite with 50 wt% of PTMA shows excellent energy storage performance, which is almost two times higher than that of the physically blended rGO/PTMA50 owing to reduced solubility of PTMA in electrolyte solution and improved electrical conductivity. As cathode materials for Li-ion/Na-ion batteries, rGO-g-PTMA50 shows superior performance including high capacity, good cycling and rate stability. Hence, this covalently bonded radical polymers on graphene provide new option for developing high-performance organic cathode materials for Li-ion/Na-ion batteries.