One-pot synthesis of heterogeneous Co₃O₄-nanocube/Co(OH)₂-nanosheet hybrids for high-performance flexible asymmetric all-solid-state supercapacitors

A novel heterogenous Co₃O₄-nanocube/Co(OH)₂-nanosheet hybrid is prepared by a controllable facile one-pot hydrothermal reaction. The resulting Co₃O₄ nanocubes are highly uniform in morphology, and are distributed uniformly on the individual Co(OH)₂ nanosheets. Such unique nanostructural features show significant advantages for applications as flexible supercapacitor electrodes in terms of enhanced durability and capacitance. The as-prepared electrode has offered a large capacitance of 1164 F g⁻¹ at 1.2 A g⁻¹. When being paired with activated carbon, the resulting flexible all-solid-state device exhibited a maximum energy density of 9.4 mWh cm⁻³. It is worthwhile noting that this as-assembled device showed little capacitance decay after over 5000 cycles with 97.4% retention of its original specific capacitance. Such a high performance outperforms most metal oxides-based electrodes and shows the advantages of the hybrid strategy, which shed light on exploring robust and cheap electrode materials for high-performance flexible supercapacitors.