A novel Mn²⁺-additive free Zn/MnO₂ battery with 2.4 V voltage window and enhanced stability

Recently, aqueous Zn/MnO₂ batteries have attracted considerable attention due to their safety, low cost, and environmental friendliness. However, capacity decay caused by Mn dissolution greatly limits their further development. Herein, the synergistic effect of cathode passivation and electrolyte engineering was employed to widen the voltage window and improve the cycling stability of Zn/ε-MnO₂ batteries. The cathode passivation process not only inhibits water decomposition at high voltage but also suppresses the Mn dissolution during discharge process. Meanwhile, the addition of LiTFSI in electrolyte can also effectively suppress the hydrogen evolution, significantly improving the Coulombic efficiency (CE) and stability of Zn stripping/plating processes. As a result, voltage window of 0.8–2.4 V is achieved and the dissolved Mn²⁺ ions are redeposited on the cathode at ≈ 2.2 V. The Mn²⁺-additive free Zn/ε-MnO₂ battery maintains 80% capacity even after 300 cycles at 0.5 A g⁻¹ and exhibits long term stability of more than 2000 cycles at 5.0 A g⁻¹ with a specific capacity of 113 mAh g⁻¹.