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.