Highly safe aqueous rechargeable batteries via electrolyte regeneration using Pd-MnO2 catalytic cycle

Abstract

Long-term operation of aqueous Zn-ion batteries causes Zn metal corrosion at the anode due to the thermodynamic instability of Zn in aqueous electrolytes, leading to significant hydrogen (H2) accumulation, which seriously endangers battery safety. Herein, we propose a self-regulating battery based on internal electrolyteregeneration mechanisms that control H2 production/annihilation reactions automatically and effectively suppress the pressure increase and electrolyte depletion within the cell. This is accomplished by activating a waterregenerating chemical reaction between MnO2 on the cathode and H2 via a Pd catalyst, which significantly relieves the reaction's endothermicity. By electrochemically charging the cell, the resultant Mn2+ and Zn2+ ions in the electrolyte can be easily reversed to their original chemical states, i.e., MnO2 and Zn metal on the cathode and anode, respectively. This new strategy overcomes the safety challenge posed by H2 accumulation, which is one of the key hurdles to the commercialization of aqueous rechargeable batteries.