Synthesis of microcrystalline ZnO as an anodic material via a solvothermal method, and its electrochemical performance in Ni/Zn redox battery

[Display omitted] •A well-microcrystalline ZnO was prepared by a conventional solvothermal route.•A hexagonal rod shape was exhibited in the powdered ZnO particles.•CV redox curve exhibited a superior electrochemical activity in KOH electrolyte.•The ZnO in KOH electrolyte showed the improved cycle stabilities until 100th cycles.•The growth of zinc dendrites could be suppressed in KOH electrolyte. Highly crystalline ZnO microparticles were prepared by a conventional solvothermal route by adding ethylenediamine (EDA). The product was analyzed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) to investigate its crystallinity and morphology. The ZnO microparticles showed high purity and perfect crystallinity, and hexagonal rod shapes (width 5.0μm×length 15.0μm) were seen in the powdered particles. ZnO microparticles (0.5M) were dissolved in 4.0M LiOH, NaOH, and KOH alkaline electrolytes in order to evaluate their electrochemical properties. The cyclic voltammetry (CV) curves revealed that the micro-sized hexagonal ZnO rods dissolved in KOH electrolyte exhibited superior electrochemical activity to those dissolved in LiOH and NaOH electrolytes. The micro-sized hexagonal ZnO rods in KOH electrolyte showed a significantly improved cycle stability until the 100th cycle, and reached a discharge capacity of 143.6mAhg−1, an efficiency of 86%, and a discharge voltage of 1.72V at a current density of 30mAcm−2. Moreover, during repeated charging-discharging cycles, the growth of zinc dendrites was suppressed, resulting in improved cycle stability in Ni/Zn redox batteries.