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

Abstract Proton insertion mechanism with fast reaction kinetics is attracting more and more attention for high‐rate and durable aqueous Zn─MnO 2 batteries. However, hydrated Zn 2+ insertion reaction accompanied with Jahn–Teller effect and Mn 3+ disproportionation generally leads to sluggish rate capability and irreversible structure transformation. Here, carboxyl‐carbon nanotubes supported α‐MnO 2 nanoarrays (C─MnO 2 ) cathode is successfully fabricated by a convent grinding process for high‐performance Zn batteries. Specifically, the carboxyl‐carbon nanotubes (CNTs) skeleton endows α‐MnO 2 with a shorter ion diffusion route and more active sites for proton adsorption, benefiting to the fast electron transport and reversible structure evolution of MnO 2 . More importantly, electronegative carboxyl groups and Mn─O─C interfacial bonds can effectively restrain Mn 2+ dissolution and shuttle for improved structural integrity and redox reactivity. Consequently, the C─MnO 2 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─MnO 2 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.