Abstract
Copper selenide (Cu2Se) features high theoretical capacity and quasi-2D characteristics built by repeating sextuple layers of Se-Cu-Cu-Cu-Cu-Se, making it a fascinating anode for sodium-ion batteries (SIBs). However, it experiences huge volume variation during repeated discharge-charge processes. Here, a productive approach to preserve the structure of Cu2Se anode via in-situ coating conductive polymer carbon is proposed. As a demonstration, Cu2Se nanosheets encapsulated by polypyrrole (PPy) were anchored on Cu mesh (Cu2Se@PPy) and regarded as an electrode material for SIBs. The PPy shell enjoys double functions that improves the electronic conductivity as well as alleviates the significant volume swelling of Cu2Se. As a result, Cu2Se@PPy gives a satisfactory electrochemical performance, including high specific capacity of 293.0 mAh g(-1) at 1.0 A g(-1), impressive rate capacity (263.5 mAh g(-1) under 10.0 A g(-1) over 2000 cycles). This work describes the uncomplicated approaches available for designing high stability metal selenides anodes for sodium storage.