Unique CoWO4@WO3 heterostructured nanosheets with superior electrochemical performances for all-solid-state supercapacitors

Abstract

Transition metal oxide-based battery-type electrode materials with well-defined nanostructure have shown great potential in supercapacitors, due to their high electrical conductivity and superior redox activity. Herein, promising CoWO₄@WO₃-1 heterostructured nanosheets with rich oxygen vacancies are designed via a two-step in situ construction process and following thermal treatment. The CoWO₄@WO₃-1 heterostructured nanosheet arrays grown on a flexible carbon cloth substrate can provide an effective nanoporous framework, facilitate electrons/ions transport, and generate effective synergistic effect of high conductivity from WO₃ and superior redox activity from CoWO₄. As a result, the as-prepared CoWO₄@WO₃-1 electrodes exhibit a high area specific capacity of 578.6 mF cm⁻² at a current density of 0.5 mA cm⁻² and keep 98.38% capacity retention at 20 mA cm⁻² over 30 000 cycles. Additionally, all-solid-state supercapacitors assembled with CoWO₄@WO₃-1 as cathodes and O_v-NiMoO₄ as anodes show a maximum area energy density of 13.93 mW h cm⁻² and power density of 6502.11 mW cm⁻², keeping outstanding cycling stability of 98.1% capacity retention over 20 000 cycles.