Hierarchical mesoporous CuMn2O4/ZnMn2O4 hollow microspheres as a cathode for aqueous zinc ion batteries

Abstract

Spinel-structured ZnMn₂O₄ has been studied as a promising cathode material for aqueous zinc-ion batteries (AZIBs) due to its high theoretical capacity and elevated operating voltage. However, extensive application remains hindered due to inherent limitations including low electrical conductivity and insufficient cycling stability. To address these challenges, we developed mesoporous CuMn₂O₄/ZnMn₂O₄ (CZMO) hollow microspheres composed of nanoparticles through a hydrothermal synthesis followed by calcination. Systematic electrochemical characterization reveals that the 2CZMO cathode (0.002 mol Cu-added CuMn₂O₄/ZnMn₂O₄ microspheres) exhibits best capacitance, delivering a specific capacity of 242 mAh g⁻¹ at 0.2 A g⁻¹ and demonstrating an exceptional capacity retention of 97.3% after 1000 cycles at 1 A g⁻¹. Ex situ XRD analysis demonstrated reversible lattice expansion during Zn²⁺ (de)intercalation processes, confirming the exceptional structural reversibility of the CuMn₂O₄/ZnMn₂O₄ cathode. This performance enhancement is attributed to the synergistic effects of CuMn₂O₄ and ZnMn₂O₄ phases, which improve charge transfer kinetics while maintaining structural integrity during repeated zinc ion insertion/extraction processes.