Electrochemically stable tunnel-type α-MnO(2)-based cathode materials for rechargeable aqueous zinc-ion batteries

The purpose of this study is the synthesis of α-MnO(2)-based cathode materials for rechargeable aqueous zinc ion batteries by hydrothermal method using KMnO(4) and MnSO(4) as starting materials. The aim is to improve the understanding of Zn(2+) insertion/de-insertion mechanisms. The as-prepared solid compounds were characterized by spectroscopy and microscopy techniques. X-ray diffraction showed that the hydrothermal reaction forms α-MnO(2) and Ce(4+)-inserted MnO(2) structures. Raman spectroscopy confirmed the formation of α-MnO(2) with hexagonal MnO(2) and Ce-MnO(2) structures. Scanning electron microscopy (SEM) confirmed the formation of nanostructured MnO(2) (nanofibers) and Ce-MnO(2) (nanorods). The electrochemical performance of MnO(2) was evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) tests in half-cells. CV results showed the reversible insertion/de-insertion of Zn(2+) ions in MnO(2) and Ce-MnO(2). GCD cycling tests of MnO(2) and Ce-MnO(2) at 2500 mA/g demonstrated an impressive electrochemical performance, excellent cycling stability throughout 500 cycles, and high rate capability. The excellent electrochemical performance and the good cycling stability of MnO(2) and Ce-MnO(2) nanostructures by simple method makes them promising cathode materials for aqueous rechargeable zinc-ion batteries.