Recent advances in performance-enhancement strategies for bimetallic spinel cobaltite battery-type electrodes in hybrid supercapacitors

Abstract The need for efficient and sustainable energy storage has driven the development of hybrid supercapacitors (HSCs). These devices combine capacitive and battery-type electrodes to deliver high energy and power densities. Designing advanced battery-type electrode materials is crucial for meeting industrial requirements for next-generation devices. Bimetallic spinel cobaltites (MCo 2 O 4 ; M = Mn, Fe, Ni, Cu, Zn, and Mg) are promising options. They provide high theoretical capacity, multiple redox-active sites, and robust structural stability. Recent studies have focused on various strategies to enhance performance. These include elemental doping, controlling morphology, direct growth on conductive substrates, and forming binary or ternary composites with carbon materials, metal oxides or sulfides, layered double hydroxides, conducting polymers, and emerging two-dimensional (2D) or framework materials. Understanding how structure influences performance is key to optimizing charge storage and electron transport. This review highlights progress in designing spinel cobaltite-based battery-type materials for HSCs, with an emphasis on strategies that boost electrochemical performance. It specifically highlights studies reporting on the specific capacity (C g⁻ 1 or mAh g⁻ 1 ), as this metric directly reflects the practical application of these materials in energy storage devices. The review also discusses the main challenges and future research directions for industrial translation and scalable development of advanced battery-type electrodes for high-performance HSCs. Graphical abstract Advances in performance-enhancement strategies for bimetallic spinel cobaltites (MCo 2 O 4 , M = Mn, Fe, Ni, Cu, Zn, Mg) as battery-type electrodes in hybrid supercapacitors. The diagram highlights key approaches, including morphology engineering, elemental doping, conductive substrate integration, carbon-based composites, metal oxide/sulfide and ternary composites, conducting polymer composites, and advanced 2D/framework materials, emphasizing the structure–property–performance relationship for optimized electrochemical behavior.