Novel synthesis of highly phosphorus-doped carbon as an ultrahigh-rate anode for sodium ion batteries

Carbonaceous materials are the most promising anode materials in electrochemical energy storage systems. However, poor electrochemical performance is a major obstacle to their practical use. Here, P-doped carbon balls (PCBs) are synthesized through a simple novel method, the solution plasma process (SPP), which is different from the conventional synthesis method, and used as an anode material in sodium ion batteries (SIBs). The PCBs synthesized by this approach show a high P content of about 4 at%. Meanwhile, P doping and disordered amorphous structures of PCBs provide abundant active sites and capacitive-dominant Na+ adsorption behavior, while large amounts of meso- and macropores shorten the Na+ diffusion distance, accelerating ion transport. The PCB anode material provides a high initial coulombic efficiency of about 75% and a high reversible capacity of 340 mAh g−1 at a current density of 1 A g−1. Even at an ultrahigh current density of 100 A g−1, an outstanding rate performance of 130 mA g−1 and reversible capacity of 83 mAh g−1 after 40,000 cycles provide excellent cycling stability. This synthesis strategy not only provides a very efficient approach to heteroatom doping but will also be a great impetus for the practical use of SIBs.