Carboxyl-CNTs Act as “Defensive Shield” to Boost Proton Insertion for Stable and Fast-Charging Aqueous Zn-Mn Batteries

Proton insertion mechanism with fast reaction kinetics is attracting more and more attention for high-rate and durable aqueous Zn─MnO₂ batteries. However, hydrated Zn²⁺ insertion reaction accompanied with Jahn–Teller effect and Mn³⁺ disproportionation generally leads to sluggish rate capability and irreversible structure transformation. Here, carboxyl-carbon nanotubes supported α-MnO₂ nanoarrays (C─MnO₂) cathode is successfully fabricated by a convent grinding process for high-performance Zn batteries. Specifically, the carboxyl-carbon nanotubes (CNTs) skeleton endows α-MnO₂ with a shorter ion diffusion route and more active sites for proton adsorption, benefiting to the fast electron transport and reversible structure evolution of MnO₂. More importantly, electronegative carboxyl groups and Mn─O─C interfacial bonds can effectively restrain Mn²⁺ dissolution and shuttle for improved structural integrity and redox reactivity. Consequently, the C─MnO₂ cathode exhibits high capacity, superior rate capability, and outstanding cycling stability over 10 000 cycles. Even at ultra-high mass loading (20 mg cm⁻²), the Zn//C─MnO₂ punch cell displays excellent capacity (202 mAh) and 94.5% capacity retention after 114 cycles, providing new insights for the practical application of advanced Zn-Mn batteries.