Design and synthesis of dendritic Co₃O₄@Co₂(CO₃)(OH)₂ nanoarrays on carbon cloth for high-performance supercapacitors

Cobalt carbonate hydroxide possesses interesting capacitive properties due to the unique crystal structure. Herein, the hierarchical Co₃O₄@Co₂(CO₃)(OH)₂ dendritic structure was fabricated on carbon cloth with Co₃O₄ nanoneedles as the inner core to enhance the conductivity. The loading efficiency of Co₂(CO₃)(OH)₂ nanowhiskers had improved obviously, and the nanowires provided more electrochemical sites to facilitate the superior electrochemical energy storage capacity of supercapacitor. The dendritic electrode with the core–shell structure had a high area-specific capacitance (1541 mF cm⁻² at 1 mA cm⁻²), good rate capacitance (only 18.1% specific capacitance lost when the current density increased to 5 mA cm⁻²), as well as better electrochemical cycle stability (a capacitance retention of 72.1% after 5000 cycles at a high current density of 5 mA cm⁻²). The dendritic Co₃O₄@Co₂(CO₃)(OH)₂ and activated carbon as cathode and anode, respectively, were used to assemble an asymmetric supercapacitor, possessing the better area-specific capacitance of 87 mF cm⁻² as well as well-deserved longevity retaining approximately 97.3% of initial capacitance even after 10,000 cycles at 1 mA cm⁻². The excellent properties stemmed from electro-active sites galore, strong adhesion between the core and shell, superior conductivity, as well as excellent ion transfer. The novel materials and feasible strategy are promising for next-generation hybrid supercapacitor with high performance.