Effects of carbon on electrochemical performance of red phosphorus (P) and carbon composite as anode for sodium ion batteries

Red phosphorus/graphite (P/G) and red phosphorus/carbon nanotube (P/CNT) composites were prepared by ball milling red phosphorus with CNTs and graphite, respectively. The electrochemical results show superior electrochemical performances of the P/G and P/CNT composites compared with that of the reference sample milled with Super-P carbon. After 70 cycles, the P/G and P/CNT composites remained 771.6 and 431.7 mA h g−1, with 68 % and 50 % capacity retention, respectively. With increasing the milling time (20 h), CNTs were cut into short pieces and then broken into carbon rings and sheets which were well mixed with red phosphorus. The morphology of the P/CNT composite can buffer the large volume changes from alloying and de-alloying during cycling, resulting in the enhanced cycling stability.