Electrochemically stable tunnel-type α-MnO2-based cathode materials for rechargeable aqueous zinc-ion batteries
Yannis De Luna, Asma Al-Sulaiti, Mohammad I. Ahmad, Hassan Nimir, Nasr Bensalah
Abstract
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.