A Red Phosphorus-Graphite Anode for K-ion Batteries

Red phosphorus (RP) is a promising anode material for potassium-ion batteries because of its theoretical capacity of 865mAhg–1 delivered at an average potential of 0.5V vs K+/K. However, its alloy reaction to form KP entails a volume expansion of 162% resulting in severe stresses that lead to SEI and electrode fracture, loss of electric contact, and ultimately reduced cycle life. Moreover, its low electronic conductivity (10 -14 Scm–1) limits rate capability. Here, we report a RP-graphite composite prepared by a two step ball milling procedure to control particle size and optimize carbon coating. Electrodes prepared with the composites achieve high capacity (723mAhg–1) at C/20 and retaining 75% at 5C. It also shows very good cycling stability, retaining more than 96% of the capacity after 100 cycles at 1C.