Ionic-Liquid-Assisted Synthesis of Mixed-Phase Manganese Oxide Nanorods for a High-Performance Aqueous Zinc-Ion Battery.

Aqueous zinc-ion batteries (ZIBs) provide a safer and cost-effective energy storage solution by utilizing nonflammable water-based electrolytes. Although many research efforts are focused on optimizing zinc anode materials, developing suitable cathode materials is still challenging. In this study, one-dimensional, mixed-phase MnO nanorods are synthesized using ionic liquid (IL). Here, the IL acts as a structure-directing agent that modifies MnO morphology and introduces mixed phases, as confirmed by morphological, structural, and X-ray photoelectron spectroscopy (XPS) studies. The MnO nanorods developed by this method are utilized as a cathode material for ZIB application in the coin-cell configuration. As expected, Zn//MnO nanorods show a significant increase in their capacity to 347 Wh kg at 100 mA g, which is better than bare MnO nanowires (207.1 Wh kg) synthesized by the chemical precipitation method. The battery is highly rechargeable and maintains good retention of 86% of the initial capacity and 99% Coulombic efficiency after 800 cycles at 1000 mA g. The XPS, X-ray diffraction, and in-depth electrochemical analysis confirm that MnO octahedra experience insertion/extraction of Zn with high reversibility. This study suggests the potential use of MnO nanorods to develop high-performance and durable battery electrode materials suitable for large-scale applications.