CuMn2O4 as a Dual Redox-Active Cathode Material for Aqueous Mg-Ion Batteries

Abstract Manganese-based oxides are attractive cathode materials for aqueous magnesium-ion batteries (AMIBs) due to their high theoretical capacity, abundant resources, and environmental friendliness but suffer from poor conductivity, manganese dissolution, and structural degradation during cycling. In this work, CuMn2O4 is proposed as a dual redox-active cathode material for AMIBs. During discharge, lattice copper ions are extracted and in-situ reduced to metallic copper, which contributes to capacity and enhances electronic conductivity. Consequently, CuMn2O4 delivers highly enhanced capacity (211 mAh g−1 at 100 mA g−1) and cycling stability compared to monometallic Mn3O4. Moreover, the aqueous Mg∥CuMn2O4 full cell achieves an average discharge voltage of 1.80 V and stable cycling for over 50 cycles. This study confirms the feasibility of CuMn2O4 as a high-performance cathode material for AMIBs and provides insights for developing low-cost, high-performance multivalent-ion battery cathode materials.