Construction of dual metal ferrite-based core-shell nanostructures as low-cost multimetal electrode for boosting energy density of flexible asymmetric supercapattery

We report the synthesis and fabrication of economically cheaper and binder-free hierarchical core-shell nanostructures of copper ferrite nanorods and nickel ferrite nanosheets (CuFe 2 O 4 –NR@NiFe 2 O 4 –NS) via a two-step wet chemical technique. The unique core-shell (nanorods@nanosheets) nanostructures offer multiple redox couples (Cu 2+, Fe 3+, and Ni 2+ ), smaller ion diffusion path, and faster electron movement. When evaluated as an individual electrode in aqueous potassium hydroxide solution, the as-synthesized CuFe 2 O 4 –NR@NiFe 2 O 4 –NS electrode demonstrate superior electrochemical behaviour with concurrent specific capacity of 1366 C g −1 at current rate 1 A g −1, and 94% capacity retention over 10,000 cycles. A flexible asymmetric supercapattery device is assembled comprising positive electrode of CuFe 2 O 4 –NR@NiFe 2 O 4 –NS and negative electrode of reduced graphene oxide (rGO) with PVA-KOH semisolid electrolyte. The ASC cell manifest enhanced specific energy of 72 Wh kg −1, specific power of 0.287 kW kg −1 and outstanding cycle life (~97% of retention over 10,000 cycles at 10 A g −1 ). The superior specific capacity, capacity retention, and excellent cyclic life endow such multimetal ferrite-based core-shell architecture with tremendous potential for use as electrode materials for fabricating next generation energy storage devices.