Single-step flash-heat synthesis of red phosphorus/graphene flame-retardant composite as flexible anodes for sodium-ion batteries

Red phosphorus (RP) has attracted considerable attention as the anode for high-performance Na-ion batteries, owing to its low cost and high theoretical specific capacity of ∼ 2,600 mAh/g. In this study, a facile single-step flash-heat treatment was developed to achieve the reduction of graphene oxide (GO) and the simultaneous deposition of RP onto the reduced graphene oxide (rGO) sheets. The resulting RP/rGO composite was shown to be a promising candidate for overcoming the issues associated with the poor electronic conductivity and large volume variation of RP during cycling. The RP/rGO flexible film anode delivered an average capacity of 1,625 mAh/g during 200 cycles at a charge/discharge current density of 1 A/g. Average charge capacities of 1,786, 1,597, 1,324, and 679 mAh/g at 1, 2, 4, and 6 A/g current densities were obtained in the rate capability tests. Moreover, owing to the RP component, the RP/rGO film presented superior flame retardancy compared to an rGO film. This work thus introduces a highly accessible synthesis method to prepare flexible and safe RP anodes with superior electrochemical performance toward Na-ion storage.