Vertically oriented carbon nanotube as a stable frame to support the Co0.85Se nanoparticles for high performance supercapacitor electrode

Highlights: • We fabricate successfully VOCNT@Co_0.85Se/NF as an additive-free supercapacitor electrode. • The VOCNT@Co_0.85Se/NF electrode presents remarkable rate capability and cycling stability at higher specific capacitance. • The VOCNT with unique and stable structure is responsible for superior electrochemical properties. -- Abstract: With a facile spraying chemical vapor deposition technique and a subsequent hydrothermal method, well dispersed Co_0.85Se nanoparticles supported on a stable frame of vertically oriented carbon nanotube (VOCNT) were synthesized and pressed directly on nickel foam (NF) for additive-free supercapacitor electrode. The fabricated electrode (VOCNT@Co_0.85Se/NF) displayed a high specific capacity of 638 F g⁻¹ under 1 A g⁻¹, a good rate performance (87.8% capacity maintaining when the current density increased from 1 to 30 A g⁻¹), and a remarkable cyclic stability (about 97.3% of the capacity retention over 5000 charging-discharging cycles). The excellent properties of VOCNT@Co_0.85Se/NF electrode could be ascribed to the involvement of the VOCNT with uniquely aligned structure and proper intertube distance, which is helpful to the quick transport of electron/ions and reduces the volume deformation during various charging-discharging tests to effectively prevent the internal structure collapsing. Furthermore, the assembled asymmetric device based on the VOCNT@Co_0.85Se/NF electrode possesses a energy density of 21.47 Wh·kg⁻¹ at 325 W kg⁻¹. This research reveals that unique VOCNT@Co_0.85Se/NF could be regarded as potential candidate electrode with super cycle stability and rate performance for supercapacitors.