SnP₃/Carbon Nanocomposite as an Anode Material for Potassium-Ion Batteries

New anode materials with large capacity and long cyclability for next-generation potassium-ion batteries (PIBs) are required. PIBs are in the initial stage of investigation and only a few anode materials have been explored. In this study, for the first time, an SnP₃/C nanocomposite with superior cyclability and rate performance was evaluated as an anode for PIBs. The SnP₃/C nanocomposite was synthesized by a facile and cost-effective high-energy ball-milling technique. The SnP₃/C electrode delivered a first reversible capacity of 410 mAh g^-1 and maintained 408 mAh g^-1 after 50 cycles at a specific current of 50 mA g^-1. After 80 cycles at a high specific current of 500 mA g^-1, a high capacity of 225 mAh g^-1 remained. From a crystallographic analysis, it was suggested that the SnP₃/C nanocomposite underwent a sequential and reversible conversion and alloying reactions. The excellent cycling stability and rate capability of the SnP₃/C electrode were attributed to the nanosized SnP₃ particles and carbon buffer layer, which supplied channels for the migration of K-ions and mitigated the stress induced by a large volume change during potassiation/depotassiation. In addition, a full cell composed of the SnP₃/C nanocomposite anode and potassium Prussian blue cathode exhibited a reversible capacity of 305 mAh g^-1 at a specific current of 30 mA g^-1 and retained 71.7% of the original capacity after 30 cycles. These results are important for understanding the electrochemical process of the SnP₃/C nanocomposite and using the SnP₃/C as an anode for PIBs.