Synergistic engineering of electronic structure and particle size in SnSe@CNF anode toward high performance potassium ion batteries

Abstract

SnSe is a promising anode candidate for rechargeable potassium-ion batteries due to its high theoretical capacity and natural abundance. However, it suffers from poor rate capability and cyclic stability originating from intrinsically low electronic conductivity, sluggish electrochemical reaction kinetics and accompanied colossal volume change. Herein, Cu-doped SnSe nanoparticles encapsulated in carbon nanofibers (i.e. Sn1-xCuxSe@CNF) are prepared by electrospinning method. Such composite anode achieves modulated electronic structure and high-rate performance for efficient K ion storage. Theoretical calculations indicate that Cu-doping alters the local charge distribution and interlayer binding energy of SnSe, enabling enhanced electronic conductivity and refined SnSe nanoparticles. Furthermore, Cu nanoclusters formed in-situ in the discharging process facilitate the decomposition of K2Se and improves the reversibility of the relevant conversion reaction. Benefiting from the multiple effects of Cu-doping, it delivers a high specific capacity of 292 mAh/g at 0.1 A/g and 143 mAh/g at 5 A/g. This work provides a fundamental understanding of the doping engineering and would help to guide the rational design of conversion/alloying-type anodes.