Molten salt synthesis of α-MnO2/Mn2O3 nanocomposite as a high-performance cathode material for aqueous zinc-ion batteries

Thanks to low cost, high safety, and large energy density, aqueous zinc-ion batteries have attracted tremendous interest worldwide. However, it remains a challenge to develop high-performance cathode materials with an appropriate method that is easy to realize massive production. Herein, we use a molten salt method to synthesize nanostructured manganese oxides. The crystalline phases of the manganese oxides can be tuned by changing the amount of reduced graphene oxide added to the reactant mixture. It is found that the α-MnO2/Mn2O3 nanocomposite with the largest mass ratio of Mn2O3 delivers the best electrochemical performances among all the products. And its rate capability and cyclability can be significantly improved by modifying the Zn anode with carbon black coating and nanocellulose binder. In this situation, the nanocomposite can deliver high discharging capacities of 322.1 and 213.6 mAh g−1 at 0.2 and 3 A g−1, respectively. After 1000 cycles, it can retain 86.2% of the capacity at the 2nd cycle. Thus, this nanocomposite holds great promise for practical applications.