Engineering of protective surfaces for retarding selenium leaching by self-growth of rGO@Ni Se on carbon nanofibers for potassium ion batteries

Abstract

K-ion batteries (PIBs) are promising alternatives to Li-ion and Na-ion batteries (LIBs/SIBs). However, the ionic radius of K+ (1.38 Å) is larger than that of Li+ (0.76 Å), consequently leading to sluggish diffusion, low capacity, and poor cycling performance in intercalation- and conversion-type K-storage technologies. To address these issues, rGO-coated nickel selenide on carbon nanofiber (rGO@NixSey-CNF) and nickel selenide on carbon nanofiber (NixSey-CNF) were developed as anode electrodes for PIBs. To improve the electrochemical properties and prevent Se leaching during the charging/discharging of nickel selenide, the surface of the NixSey particles was coated with rGO. The rGO coating not only protected Se but also improved the conductivity and cycling performance. rGO@NixSey-CNF delivered an excellent charge-specific capacity of ∼ 126 mAh g−1 at 100 mA g−1 over 200 cycles, with an initial coulombic efficiency of approximately 50 %, as well as 50 % capacity retention, attributed to the retarded leaching of Se through the rGO coating. These findings provide new insights for developing highly reversible Ni-based anode materials for advanced PIBs.