Understanding high-energy-density Sn₄P₃ anodes for potassium-ion batteries

Abstract

Phosphorus-based anodes for alkali metal-ion batteries are attractive due to their high theoretical-specific capacity. However, their poor electrochemical performance caused by relatively large volume variations during cycling, low electrical conductivity, and severe electrolyte decomposition due to highly reactive phosphide surface hinder their potential applications. Herein, we confine Sn₄P₃ in N-doped carbon fibers as anode for potassium-ion batteries with enhanced cycling stability and high rate capability (160.7 mA hr g⁻¹ after 1,000 cycles at 500 mA g⁻¹). The Sn₄P₃ anodes undergo a sequential conversion (P to K₃P₁₁, K₃P) and alloying (Sn to KSn) reactions with synergistic K-storage mechanisms. Also, the electrolyte with potassium bis(fluorosulfonyl)imide salt can effectively suppress the dendrite growth in K stripping/plating, stabilize the solid-electrolyte interphase (SEI) layer, and avoid excessive side reactions, thus enhancing the electrode stability. This work provides a feasible approach to overcome the durability bottlenecks of K-ion batteries through regulating dendrite growth and SEI formation.