Enhanced K0.5Mn2O4 hollow nano-spheres cathode for aqueous zinc ion battery

Abstract

Aqueous zinc ion batteries (AZIBs) have been looked upon as the most prospective energy storage systems, primarily because of their notable advantages of enhanced safety and cost-effectiveness. Manganese based materials are among the best choices for AZIBs by the reason of the considerable theoretical capacity and the appropriate operating voltage. Unfortunately, the intrinsic unsatisfactory electrical conductivity and collapse of crystal structure in electrochemical reaction process hamper the development of the materials. Here, we prepared layered K_0.5Mn₂O₄•1.84H₂O hollow nano-spheres (MCHS@K_0.5Mn₂O₄) with abundant oxygen defects through hydrothermal process and evaluated their electrochemical properties in AZIBs. Using various characterization and analysis techniques, we found that mesoporous carbon hollow spheres (MCHS) provide a stable electronic conducting framework for K_0.5Mn₂O₄. The oxygen defects generated during the synthesis process can be filled by O²⁻ from irreversibly intercalated H₂O, weakening the interaction between guest ion and host material. This leads to an increase in ionic diffusion coefficients by 2–3 orders of magnitude, thereby enhancing ion migration ability. Under the synergistic effect of the enhanced electronic and ionic transport properties, MCHS@K_0.5Mn₂O₄ delivers a high specific capacity of 251 mAh g⁻¹ and excellent cycling stability with a low capacity fading rate of 0.47 ‰ per cycle.