Synthesis and electrochemical performance of core-shell NiCo2S4@nitrogen, sulfur dual-doped carbon composites via confined sulfidation strategy in a polydopamine nanoreactor

Abstract Nickel cobalt binary sulfides (NiCo 2 S 4 ) have attracted huge attention as a promising anode material for lithium-ion batteries (LIBs). Herein, a polydopamine (PDA) shell with a controlled thickness was in-situ polymerized on a nanohorn-shaped Ni-Co precursor (Ni-Co-Pre), thus obtaining a core-shell Ni-Co-Pre@PDA, and then a high-temperature sulfidation was utilized to convert the Ni-Co-Pre@PDA into the NiCo 2 S 4 confined in nitrogen, sulfur co-doped hollow carbon nanohorns (NiCo 2 S 4 @NS-HCN) using cheap and environmental-friendly sulfur powder as sulfur sources. During the sulfidation, the Ni-Co-Pre core was converted into the NiCo 2 S 4 , while the PDA shell as a nanoreactor was carbonized into the NS-HCN with simultaneous co-doping of nitrogen and sulfur. Benefitting from high-efficiency redox reactions of NiCo 2 S 4 and efficient structural protections of conductive carbon shells, the NiCo 2 S 4 @NS-HCN electrodes showed significantly enhanced electrochemical properties including high reversible specific capacity of 1235 mA h g -1 at 0.1 A g -1 and excellent rate/cycling capability (69% capacity retention after 100 cycles). This study thus provides a simple and efficient confined sulfidation strategy for construction of binary transition-metal sulfides for LIB anode materials.