Advanced Ti₃C₂@ε-MnO₂ cathode as rechargeable aqueous zinc-ion batteries

Due to the low cost, high safety and easy assembly, rechargeable aqueous zinc-manganese oxide (Zn-MnO_x) batteries are the best devices for energy storage. However, poor conductivity of MnO_x results in the bad cycle performance. Herein, highly conductive and layered Ti₃C₂T_x MXene with rich terminations (T_x, for example, =O, —F, —OH) were used as carriers for MnO_x particles. Due to the electronegativity of the terminations, Mn²⁺ was intercalated into the layers and adsorbed on the surface of Ti₃C₂T_x MXene, making the generated Mn₃O₄ particles can firmly anchored, forming the Ti₃C₂@Mn₃O₄ composites. As for the cathode of zinc-ion batteries, Ti₃C₂@Mn₃O₄ was fully converted to Ti₃C₂@ε-MnO₂ during the 1st charge process. Thanks to the excellent conductivity and layered structure of Ti₃C₂T_x MXene, Ti₃C₂@ε-MnO₂ cathode presents excellent kinetic properties and electrochemical performance with a high specific capacity of 440 mA·h·g⁻¹ and high energy density (607 W·h·kg⁻¹) at 0.2 C (1 C=308 mA·h·g⁻¹), and the capacities increase from 270 mA·h·g⁻¹ to 480 mA·h·g⁻¹ after 150 cycles at 1 C. Excellent electrochemical performance, simple material preparation methods, combined with the low cost, high safety and easy assembly characteristics, enable the possible application of rechargeable aqueous Zn-MnO_x batteries in large-scale energy storage.