Design of multiple electrode structures based on nano Ni3S2 and carbon nanotubes for high performance supercapacitors

3D-networked CNT–Ni3S2–CNT-A supported by Ni foam was rationally designed and synthesized via a multistep transformation approach. The intriguing and individual nanostructures endow the hybrid composites with outstanding electrochemical performance with an areal specific capacitance of 13 400 mF cm−2 at the current density of 10 mA cm−2 and an excellent rate capacity of 96.04% at 50 mA cm−2. The corresponding asymmetric supercapacitor assembled with CNT–Ni3S2–CNT-A (positive electrode) and active carbon (negative electrode) delivered a high energy density of 75.2 W h kg−1 at the power density of 2416 W kg−1, an excellent areal capacitance (425 mF cm−2 at 3 mA cm−2) and electrochemical cycling stability (90.6% retention after 10 000 cycles). The dual function of CNTs is responsible for the impressive electrochemical performance; the inner CNT provides more electrodeposition sites for higher capacitance while the outer high electrical conductivity CNT acts as highways for faster electron transportation. The rational design concept of this work is versatile and scalable for combining transition-metal sulfides with carbon materials for high performance supercapacitors.