• A semisolid MnO2 slurry electrode enables reversible MnO2 deposition/dissolution within a CNT-percolated conductive network, achieving a high areal capacity of 60 mAh cm−2.
• The slurry system promotes the formation of highly conductive γ-MnO2 and achieves uniform MnO2 dissolution through enhanced charge transfer.
• The MnO2 slurry electrode offers strong scalability and regenerability, retaining 100% capacity after 180 cycles and reactivating inactive MnO2 via percolation.
• 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.