In Situ Construction of (Ni,Mn)O/MnO2 Heterostructures with Suppressed Jahn-Teller Distortion for Ultralong-Life Aqueous Zinc-Ion Batteries.

Manganese dioxide (MnO2) is a promising cathode material for aqueous zinc-ion batteries due to its high theoretical capacity and low cost. However, its practical application is severely hindered by structural degradation caused by the Jahn-Teller distortion of Mn3+ ions and subsequent manganese dissolution. Herein, we propose an in situ constructed (Ni,Mn)O/MnO2 heterostructure to address these challenges. Experimental characterizations and density functional theory calculations reveal that the heterostructure can induce simultaneous upward shift of the Mn d-band center (εd) and O p-band center (εp), thereby optimizing Zn2+ adsorption kinetics and suppressing the detrimental Jahn-Teller distortion by restoring eg orbital degeneracy. Structurally, the larger ionic radius of Ni2+ introduces beneficial lattice strain, physically constraining the distortion of adjacent [MnO6] units. As a result, the NMO/MnO2-0.15 cathode delivers a high specific capacity of 606.2 mA h g-1 at 0.5 A g-1, good rate capability, and stable cycling stability with 79.2% capacity retention after 2000 cycles at 5 A g-1. This work demonstrates the effectiveness of in situ heterostructure engineering for stabilizing Mn-based cathodes.