NiS2@CoS2 nanocrystals encapsulated in N-doped carbon nanocubes for high performance lithium/sodium ion batteries

A novel and bottom-up approach has been applied to synthesize bi-metal Ni-Co coordination polymer@polydopamine (NiCoCP@PDA) core-shell nanocubes by polymerization of PDA layer on the surface of NiCoCP nanocubes. After thermally induced sulfurization processes, biactive NiS2@CoS2 hetero-nanocrystals encapsulated into N-doped carbon core-shell nanocubes has been successfully prepared. When used as anodes materials for lithium ion batteries (LIBs) and sodium ion batteries (SIBs), the novel bicontinuous carbon wrapped NiS2@CoS2 nanocrystals hierarchical structures show excellent lithium/sodium ion storage capacities with high specific capacities, good rate capabilities and stable cycling stability. The enhanced electrochemical performance is attributed to the interconnected porous structures and large amount of mesoporous structures, which effectively reduce the diffusion length for lithium ions and electrons, buffer volume expansion during the lithium/sodium ion insertion/extraction processes and retained structural integrity due to double carbon frameworks.