Dynamic pH‐Regulation Promoting Mn 2+ ‐Dominated Dissolution/Deposition for Ultra‐Stable Zinc Ion Batteries

Abstract The pH value has great significance on the electrochemical performance of Mn‐based cathodes for zinc ion batteries with near‐neutral electrolytes. In this work, CuO/MnO 2 compound featuring hybrid nanophases is proposed as the cathode material. During electrochemical redox reactions, local pH‐regulation is caused by the proton‐consumption reaction of reversible Cu‐based conversion. The dynamic pH regulation would facilitate the generation of Zn 4 SO 4 (OH) 6 ·4H 2 O and the dissolution of MnO 2 , thereby promoting Zn 4 SO 4 (OH) 6 ·4H 2 O‐assisted redox reactions. Additionally, the MnO 2 nanophase would supplement extra Mn 2+ into the electrolyte, benefiting the Mn 2+ involved redox reaction. The hybrid nanophase system can promote Mn 2+ ‐dominated dissolution/deposition reaction, and render the CuO/MnO 2 cathode with high rate capacity and durable cycling life. The experiments show that the resulting full battery with CuO/MnO 2 hybrid cathode performs a rate capacity of 486.5 mAh g −1 at 0.5 A g −1 , and even 94.4 mAh g −1 at 20 A g −1 . 85.3% capacity retention after 30 000 charging/discharging cycles indicates the ultra‐long lifespan. Furthermore, we believe the strategy of dynamic pH‐regulation during electrochemical reactions would be an effective measure to maximize the admirable performance of zinc ion batteries.