Proton-Trapping Agent for Mitigating Hydrogen Evolution Corrosion of Zn for an Electrolytic MnO₂/Zn Battery

Abstract

A rechargeable aqueous electrolytic MnO 2 /Zn battery (EMZB) based on a reversible Mn 2+ /MnO 2 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.

Aqueous MnO2/Mn2+ electrochemistry in batteries: progress, challenges, and perspectives

“…In addition, pH buffer additives, such as HAc and Al 3+ , significantly improve the cyclic stability of the Zn anode while ensuring reversible cathode chemistry. 113,124,125 Furthermore, the structural design of the battery system can provide suitable operational environments for both the cathode and anode. [126][127][128] First, novel decoupling electrolytes with different pH values have been proven to be one of the practical methods.…”

“…In addition, pH buffer additives, such as HAc and Al 3+ , significantly improve the cyclic stability of the Zn anode while ensuring reversible cathode chemistry. 113,124,125…”

Mn deposition/dissolution chemistry and its contemporary application in R&D of aqueous batteries

“…One strategy to suppress the impact of H + migration to the anolyte is to employ a proton trapping agent (PTA), as demonstrated by Sun. et al (Sun et al, 2022). PTAs are a category of salts containing weak acidic ions, such as H 2 PO 4 − , C 6 H 5 O 7 3-, and Ac − , that are capable of trapping H + , as shown in Figure 3.…”

“…Sun. et al (Sun et al, 2022) suggested that CH 3 OO − has the best ability to suppress HER, enabling the reversible plating and stripping of the Zn anode. They increased the lifetime of their Zn/MnO 2 cell 5-fold to 400 cycles by using 1 M MnSO 4 + 0.15 M H 2 SO 4 + 0.1 M NaCl as the catholyte and Schematic illustration of the working mechanism of the proton trapping agent.…”

“…They increased the lifetime of their Zn/MnO 2 cell 5-fold to 400 cycles by using 1 M MnSO 4 + 0.15 M H 2 SO 4 + 0.1 M NaCl as the catholyte and Schematic illustration of the working mechanism of the proton trapping agent. Reproduced with copyright from ACS (Sun et al, 2022).…”