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 (CuFe₂O₄–NR@NiFe₂O₄–NS) via a two-step wet chemical technique. The unique core-shell (nanorods@nanosheets) nanostructures offer multiple redox couples (Cu²⁺, Fe³⁺, and Ni²⁺), smaller ion diffusion path, and faster electron movement. When evaluated as an individual electrode in aqueous potassium hydroxide solution, the as-synthesized CuFe₂O₄–NR@NiFe₂O₄–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 CuFe₂O₄–NR@NiFe₂O₄–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.