Red phosphorus filled biomass carbon as high-capacity and long-life anode for sodium-ion batteries

Red phosphorus is a promising anode material for sodium-ion batteries due to its low cost and superior theoretical capacity of 2596 mAh g(-1). However, intrinsically inferior conductivity and huge volume changes during sodiation/desodiation processes hinder its practical application. Herein, we report an integrated red phosphorus/N-doped biomass carbon composite via filling red phosphorus nano-particles into the nano-pores of N-doped carbon derived from a renewable coconut shell biomass. In the rational structural design, N-doped biomass carbon serves as hard template for embedding red phosphorus nano-particles, buffers the volume expansion of red phosphorus during sodiation processes, and enhances the conductivity of composite. The composite delivers a high reversible capacity of 2481 mAh g(-1) at 50 mA g(-1) with a higher 89% initial coulombic efficiency. When the current density increases by 100 times to 5000 mA g(-1), the capacity can remain 855 mAh g(-1). Moreover, the composite maintains a reversible capacity of 1857 mAh g(-1) at 500 mA g(-1) after 100 cycles, and 845 mAh g(-1) at 2000 mA g(-1) after 500 cycles. This work introduces abundant biomass into application of high performance electrode materials for sodium-ion batteries.