Se‐dopant Modulated Selective Co‐Insertion of H⁺ and Zn²⁺ in MnO₂ for High‐Capacity and Durable Aqueous Zn‐Ion Batteries

Abstract

Abstract MnO 2 is commonly used as the cathode material for aqueous zinc‐ion batteries (AZIBs). The strong Coulombic interaction between Zn ions and the MnO 2 lattice causes significant lattice distortion and, combined with the Jahn–Teller effect, results in Mn 2+ dissolution and structural collapse. While proton intercalation can reduce lattice distortion, it changes the electrolyte pH, producing chemically inert byproducts. These issues greatly affect the reversibility of Zn 2+ intercalation/extraction, leading to significant capacity degradation of MnO 2 . Herein, we propose a novel method to enhance the cycling stability of δ‐MnO 2 through selenium doping (Se−MnO 2 ). Our work indicates that varying the selenium doping content can regulate the intercalation ratio of H + in MnO 2 , thereby suppressing the formation of ZnMn 2 O 4 by‐products. Se doping mitigates the lattice strain of MnO 2 during Zn 2+ intercalation/deintercalation by reducing Mn−O octahedral distortion, modifying Mn−O bond length upon Zn 2+ insertion, and alleviating Mn dissolution caused by the Jahn–Teller effect. The optimized Se−MnO 2 (Se concentration of 0.8 at.%) deposited on carbon nanotube demonstrates a notable capacity of 386 mAh g −1 at 0.1 A g −1 , with exceptional long‐term cycle stability, retaining 102 mAh g −1 capacity after 5000 cycles at 3.0 A g −1 .