Deciphering the electrochemical behavior of Mn-based electrode-electrolyte coupling system toward advanced electrochemical energy storage devices

Mn-based aqueous electrochemical energy storage devices (AEESDs) are promising candidates for sus-tainable and flexible energy applications due to their environmental benignity, high theoretical capacity and versatile architecture. One of the effective strategies to boost their electrochemical performance is to in-troduce Mn2+ ions into the electrolyte, which can trigger a reversible solid/liquid reaction process of Mn2+/ MnO2 deposition/dissolution with a high capacity and an ideal electrochemical kinetics. However, the complex energy storage mechanism that involves the Mn2+/MnO2 deposition/dissolution and the intrinsic insertion/extraction of proton and metal ions remains elusive and poses a great challenge for the rational design of Mn-based AEESDs. Moreover, the insufficient dissolution of MnO2 can lead to the deterioration of performance, which hinders their practical applications. To address these issues, we systematically in-vestigate the Mn2+ ions added Mn-based AEESDs by employing a novel quasi-steady electrochemical measurement technique, and establish a kinetic evolution model to elucidate the solid/liquid reaction at different interface conditions. Furthermore, a full cell is assembled and measured to explore the real electrochemical process of Mn-based electrode with additive Mn2+ ions, which is influenced by the po-tential windows and charge-discharge rate. This study may provide new insights for the development of advanced AEESDs.(c) 2023 Elsevier B.V. All rights reserved.