Design of Mn‐Rich Trimetallic Mn_1‐xCu_xCo₂O₄ Nanorods and 2 D Quasi‐Nanosheets for Enhanced Li‐Ion Storage and High‐Energy‐Density Supercapacitor Applications

Abstract In this study, Mn_1‐xCu_xCo₂O₄ compounds with varying Mn and Cu concentrations are synthesized and evaluated their Li‐ion storage and supercapacitor performances. Leveraging nanorods and 2D quasi‐nanosheet structures, the Mn‐rich Mn_0.75Cu_0.25Co₂O₄ material demonstrates an initial discharge/charge capacity of 1010.30/720.49 mAh g⁻¹ at 0.1 A g⁻¹. Even at 2 A g⁻¹, it retains a discharge capacity of 494.10 mAh g⁻¹, showcasing superior rate capability. The Mn‐rich Mn_0.75Cu_0.25Co₂O₄ exhibits excellent cycling stability, with a capacity retention of 114% after 600 cycles. In supercapacitor studies, the Mn_0.75Cu_0.25Co₂O₄ achieved a remarkable specific capacitance of 1626 F g⁻¹ (271 mA h g⁻¹) at 1 A g⁻¹, and a rate capability of 64.5% at 30 A g⁻¹, and 94% cyclic stability after 5000 charge/discharge cycles at 20 A g⁻¹.A Mn_0.75Cu_0.25Co₂O₄//activated carbon hybrid device delivers a specific capacitance of 327 F g⁻¹ (145.5 mA h g⁻¹) at 1 A g⁻¹ and exhibits 83% cyclic stability with 98% coulombic efficiency after 10 000 cycles at 20 A g⁻¹. Furthermore, the device achieves high energy and power densities of 116 Wh kg⁻¹ and 24 kW kg⁻¹, respectively. These findings underscore the potential of the Mn‐rich Mn_0.75Cu_0.25Co₂O₄ compound as a highly promising electrode material for practical energy storage applications.