Red Phosphorus Potassium-Ion Battery Anodes.

Phosphorus (P) possesses the highest theoretical specific capacity (865 mA h g-1) among all the elements for potassium-ion battery (PIB) anodes. Although Red P (RP) has intrinsic advantages over its allotropes, including low cost and nontoxicity, and simpler preparation, it is yet unknown to effectively activate it into a high-performance PIB anode. Here, high-performance RP PIB anodes are reported. Two important factors are found to facilitate RP react with K-ions reversibly: i) nanoscale RP particles are dispersed evenly in a conductive carbon matrix composed of multiwall carbon nanotubes and Ketjen black that provide an efficient electrical pathway and a tough scaffold. ii) The results of X-ray photoelectron spectroscopy spectrum and the electrochemical performance perhaps show that no P-C bond formation is beneficial to allow K-ions to react with RP effectively. As a result, the RP/C electrodes deliver a reversible specific capacity of ≈750 mA h g-1 and exhibit a high-rate capability (≈300 mA h g-1 at 1000 mA g-1). RP/C full cells using potassium manganese hexacyanoferrate as cathode show a long cycling life (680 cycles) at a current density of 1000 mA g-1, in addition, a pouch-type battery is built to demonstrate practical applications.