Electrochemically Active Mn²⁺ Enabling High-Performance Aqueous Zinc Ion Batteries

Aqueous zinc ion batteries (AZIBs) are limited by low energy density and poor cycle life. Electrolyte engineering is one of the most effective approaches to address the challenges. In this study, MnSO4 was selectively incorporated into the cost-effective hybrid electrolyte (ZnSO4+K2SO4, Zn0.5K0.25) to improve the energy density and lifespan. Ex situ techniques of XRD and SEM confirmed the electrodeposition of Mn2+ into porous MnO2 nanosheets and uniformly covered the Prussian blue cathode surface, forming the nanoporous//3D open framework interface with improved kinetics. Furthermore, the porous MnO2 nanosheets also contributed to the improved capacity, rate performance and cycling stability. The performance was noteworthy with a discharge capacity of 365.4 mAh g–1 (0.5 A g–1) and 156.7 mAh g–1 (3.0 A g–1). The capacity retention reached a remarkable 120% after 1200 cycles. Additionally, the full cell exhibited a high energy density of 299.3 Wh kg–1. These findings provide valuable insights for improving the energy density and cycle stability of AZIBs.