Design of Mn‐Rich Trimetallic Mn 1‐x Cu x Co 2 O 4 Nanorods and 2 D Quasi‐Nanosheets for Enhanced Li‐Ion Storage and High‐Energy‐Density Supercapacitor Applications

Abstract In this study, Mn 1‐x Cu x Co 2 O 4 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 0.75 Cu 0.25 Co 2 O 4 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 0.75 Cu 0.25 Co 2 O 4 exhibits excellent cycling stability, with a capacity retention of 114% after 600 cycles. In supercapacitor studies, the Mn 0.75 Cu 0.25 Co 2 O 4 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 0.75 Cu 0.25 Co 2 O 4 //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 0.75 Cu 0.25 Co 2 O 4 compound as a highly promising electrode material for practical energy storage applications.