A rechargeable aqueous electrolytic MnO2/Zn battery (EMZB) based on a reversible Mn2+/MnO2 two-electron redox reaction in an acidic electrolyte is very attractive for large-scale energy storage due to its high output voltage, large gravimetric capacity, and low cost. However, severe hydrogen evolution corrosion (HEC) of the Zn anode in an acidic electrolyte limits its application. Here, a proton-trapping agent (PTA) is introduced in the electrolyte to improve the electrochemical performance of the EMZB. Experimental results and theoretical calculations demonstrate that HEC of the Zn electrode can be effectively mitigated through high binding energy between the protons and PTA. The optimized EMZB regulated by a PTA of acetate (EMZB-20% Ac) delivers a high discharge voltage of 1.91 V and over 400 stable cycles at 1 C, which is more than 5 times the cycle life of the battery without PTA. EMZB-20% Ac also shows a Coulombic efficiency of 90.7% at a high areal capacity of 8 mAh cm-2 and an energy retention of 83.6% after 1000 cycles at 5 C with an areal capacity of 1 mAh cm-2. This work provides a promising electrolyte regulation strategy for the design and application of a high-performance EMZB and other energy storage systems.
Keywords: acidic electrolyte; electrolytic MnO2/Zn battery; hydrogen evolution corrosion; large-scale energy storage; proton-trapping agent.