Reversible Electrodeposition and Dissolution of Manganese Dioxide Cathodes in Aqueous Manganese Batteries.

Sammanfattning

Aqueous zinc-manganese batteries have regained attention as potential candidates for next-generation electrochemical energy storage technologies due to their inherent safety, environmental friendliness, considerable voltage and specific capacity. In weakly acidic or near-neutral electrolytes, manganese dioxide (MnO2) undergoes a reversible MnO2/Mn2+ redox process via electrodeposition-dissolution mechanisms in the reactive aqueous environment rather than solid-state ion diffusion. However, poor cycle stability and irreversible capacity loss of the in-situ generated MnO2 cathode still limit its practical application. This thesis investigates the reversible electrodeposition and dissolution mechanisms of the MnO2 cathode. Electrochemical methods, such as galvanostatic charge-discharge measurements, operando pH monitoring, and online electrochemical mass spectrometry were combined to study the redox kinetics of Mn2+ under different electrolyte compositions and pH conditions. The study reveals that the electrochemical behavior of MnO2 in aqueous systems (such as voltage-capacity profiles and reaction mechanisms) is directly related to the interfacial pH and anion species. This work contributes to advancing the development of durable, high-performance, and environmentally friendly aqueous manganese batteries for possible large-scale electrochemical energy storage applications.