Rational Design of ZnMn2O4 Quantum Dots in a Carbon Framework for Durable Aqueous Zinc‐Ion Batteries

Abstract Manganese oxides are promising cathode materials for aqueous zinc‐ion batteries (ZIBs) due to their high energy density and low cost. However, in their discharging processes, the Jahn–Teller effect and Mn 3+ disproportionation often lead to irreversible structural transformation and Mn 2+ dissolution, deteriorating the cycling stability of ZIBs. Herein, ZnMn 2 O 4 quantum dots (ZMO QDs) were introduced into a porous carbon framework by in‐situ electrochemically inducing Mn‐MIL‐100‐derived Mn 3 O 4 quantum dots and the carbon composite. In such ZMO QDs and carbon composite, the quantum dot structure endows ZnMn 2 O 4 with a shorter ion diffusion route and more active sites for Zn 2+ . The conductive carbon framework is beneficial to the fast transport of electrons. Furthermore, at the interface between the ZMO QDs and the carbon matrix, the Mn−O−C bonds are formed. They can effectively suppress the Jahn–Teller effect and manganese dissolution of discharge products. Therefore, Zn/ZMO QD@C batteries display remarkably enhanced electrochemical performance.