Unlocking Reversible Mn<sup>2+</sup>/MnO<sub>2</sub> Chemistry in Semisolid Slurry Electrodes for High-Performance Aqueous Zn-Mn Batteries.

Abstract

Electrolytic Zn-MnO₂ batteries are promising candidates for safe and sustainable energy storage owing to their high voltage, environmental benignity, and cost-effectiveness. However, practical applications are hindered by the poor conductivity and the irreversible dissolution of conventional ε-MnO₂ deposits. Herein, we report a scalable semisolid slurry electrode architecture that enables stable MnO₂ deposition/dissolution using a three-dimensional percolating network of carbon nanotubes (CNTs) as both conductive matrix and deposition host. The slurry system promotes the formation of highly conductive γ-MnO₂ owing to enhanced charge transfer kinetics, enabling overall dissolution rather than the localized separation typically seen in traditional electrodes. The Zn-MnO₂ slurry cell exhibits a reversible areal capacity approaching 60 mAh cm^-2. Moreover, the flowable nature of the slurry allows electrochemically inactive MnO₂ formed during dissolution to be reconnected and reactivated by CNTs in the rheological network, ensuring deep utilization and cycling stability. This work establishes a slurry electrode strategy to improve electrolytic MnO₂ reactions and offers a viable pathway toward renewable aqueous batteries for grid-scale applications.