Crystalline MnCO₃@Amorphous MnO Composite as Cathode Material for High-Performance Aqueous Zinc-Ion Batteries

Rechargeable aqueous zinc-ion batteries (RAZIBs) have received extensive attention because of their advantages of low cost, high safety, and nontoxicity. However, problems such as dissolution of the active cathode material, dendrites/passivation of the zinc anode, and slow reaction kinetics hindered their further applications. In this work, a crystalline/amorphous composite-type material composed of crystalline MnCO₃ and amorphous MnO was prepared and used as the cathode material for RAZIBs. The MnCO₃@amorphous MnO (MnCO₃@A-MnO) composite possesses the merits of both the pure crystalline phase of MnCO₃ and the amorphous phase of MnO, which can deliver better electrochemical performance than the corresponding single component in repeated cycles. In addition, crystalline MnCO₃ undergoes a complex phase transition to the active MnO₂ during the first charge process, providing the composite with a stable structure and additional electrochemical capacity. The electrochemical measurement results indicate that the MnCO₃@A-MnO electrode can display high reversible discharge capacity at 0.1 A g^-1, excellent rate performance at 5.0 A g^-1, and long cycling stability over 2000 cycles, showing great potential as a cathode material for high-performance RAZIBs.