Zn²⁺-blocking effects of a proton-rich polyaniline layer enable Ah-level Zn-MnO₂ batteries

Low-cost and high-theoretical capacity manganese dioxide (MnO₂) has garnered great attention in developing aqueous Zn-MnO₂ batteries (AZMBs). However, achieving high-capacity and long-cycle-life AZMBs remains challenging owing to “dead” MnO₂ formation and irreversible Zn²⁺ insertion. Herein, we introduced polyaniline (PANI) to provide a proton-rich micro-environment for organic modified MnO₂ (denoted as P-MnO₂) as an effective cathode with carbon nanotubes as conductive networks. The P-MnO₂ cathode exhibits a remarkable capacity of 510 mAh g⁻¹ at 0.2 A g⁻¹ and a capacity retention of 87% over 14 000 cycles at 5 A g⁻¹. Even under a high loading of 23.5 mg cm⁻², the as-constructed Zn//P-MnO₂ pouch cell demonstrates a capacity of 275 mAh after 110 cycles at 0.73 mA cm⁻². Its maximum capacity could even reach up to 1.5 Ah at 0.15 mA cm⁻², with a coulombic efficiency of 99.1%. Elemental mapping reveals that proton conductive PANI acts as a “Zn²⁺ filter”, selectively blocking Zn²⁺ insertion while facilitating proton transport, thereby preventing irreversible ZnMn₂O₄ generation and stimulating deposited MnO₂ reuse. Combined in/ex situ characterizations and theoretical calculations confirm the formation of interfacial Mn-N bonds and their functions to improve the structural robustness of the P-MnO₂ cathode, demonstrating the great potential of organic-inorganic interface engineering for advanced AZMBs.