Polyrrole-encapsulated Cu2Se nanosheets in situ grown on Cu mesh for high stability sodium-ion battery anode

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 (Cu2[email protected]) 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, Cu2[email protected] 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.