Selenium-doped carbon nanotubes/nickel selenide coaxial nanocables for energy storage

Coaxial nanocable heterostructures consisting of highly conductive carbon nanomaterial core and active transition-metal compound sheath are promising potential candidates for advanced energy storage materials. Herein, the multi-functional selenium‐doped carbon nanotubes/nickel selenide coaxial nanocables with chemical bonding interface are prepared by using an electroless deposition combined with the following chemical vapor reaction process, in which the nickel layer is first deposited onto the carbon nanotube core and subsequently transformed in-situ into the nickel selenide sheath by the controlled selenization reaction at elevated temperature. Such coaxial structure provides the large active material/electrolyte contact area, and the fast diffusion and transfer of mass and charge in the electrochemical process, thus which endows superior supercapacitive and good lithium storage performances. The coaxial nanocables exhibit a high specific capacity of 340.0 mAh g−1 at 1 A g−1 as an electrode for supercapacitor, and a lithium storage capacity of 600.0 mAh g−1 at 0.1 A g−1 as an anode for lithium-ion batteries. A supercapacitor based on the nanocables delivers a high energy density of 70.0 Wh kg−1 at 803.0 W kg−1 and long cycling stability with 65.0% capacitance retention after 8000 cycles at 10 A g−1.