Phosphorus/Carbon Composite Anode for Potassium-Ion Batteries: Insights into High Initial Coulombic Efficiency and Superior Cyclic Performance

Potassium-ion batteries recently start to attract attention because potassium is abundant in the Earth’s crust and the commercial graphite anode works well in potassium-ion batteries. However, the relatively low theoretical capacity of the graphite (279 mAh g–1) may limit the future application of potassium-ion batteries. Here we report a phosphorus (P)/activated carbon (AC) composite prepared by a vaporization–condensation–conversion approach. While the higher P loadings result in greater capacities of the P/AC composites, the relatively lower P loadings lead to superior cyclic performance; for example, the P/AC composite with 45 wt % of P (named PAC-50) delivered a maximum capacity of 430 mAh g–1 while the one with 32 wt % of P (named PAC-35) exhibited 70% capacity retention after 500 cycles. More importantly, by controlling the P content the initial Coulombic efficiency (ICE) can be optimized, reaching the highest value of 84% when the P content is 45 wt % (named PAC-50). The decreased surface area and the reduced oxygen-containing groups account for the high ICEs.