Phosphorus-Amine-Based Synthesis of Nanoscale Red Phosphorus for Application to Sodium-Ion Batteries

Current methods for synthesizing nanoscale red phosphorus (NRP), including ball-milling and vaporization-condensation, have various limitations. More effective engineering of the properties of these materials would promote their application in sodium-ion batteries. Herein, we report a simple phosphorus-amine-based method for the scalable preparation of NRP with high yield. We confirm that red phosphorus is highly soluble in ethylenediamine and that addition of H⁺ precipitates a network of NRP, where the size distribution is controlled by the H⁺ concentration. Through the use of this method, uniform NRP with particle sizes of 5-10 nm was dispersed in situ on the surfaces of reduced graphene oxide (rGO) with a controllable loading ratio. We attribute the formation of this structure to strong adsorption between the red phosphorus-ethylenediamine complex and rGO. The binding between NRP/Na₃P and rGO effectively stabilized the NRP on rGO throughout charging/discharging processes, therefore enabling the NRP-rGO composite to deliver a high capacity of 2057 mA h g^-1 at a current density of 100 mA g^-1 and excellent long-cycling performance.