Rational Design of ZnMn₂ O₄ Quantum Dots in a Carbon Framework for Durable Aqueous Zinc-Ion Batteries

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 Mn³⁺ disproportionation often lead to irreversible structural transformation and Mn²⁺ dissolution, deteriorating the cycling stability of ZIBs. Herein, ZnMn₂ O₄ quantum dots (ZMO QDs) were introduced into a porous carbon framework by in-situ electrochemically inducing Mn-MIL-100-derived Mn₃ O₄ quantum dots and the carbon composite. In such ZMO QDs and carbon composite, the quantum dot structure endows ZnMn₂ O₄ with a shorter ion diffusion route and more active sites for Zn²⁺ . 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.