Ni–Mn hydroxides as new high power electrode materials for supercapacitor applications

The coprecipitation of Ni and Mn hydroxides followed by freeze drying results in the formation of agglomerated 20–30 nm particles of complex hydroxide with spinel-like structure. The thermal decomposition of this hydroxide causes the formation of ilmenite-type complex oxide at T > 300 °C without considerable changes in the Ni and Mn valence states according to X-ray photoelectron spectroscopy data. Further processing at T ≤ 400 °C is accompanied by significant particle intergrowth though their internal structure remains nanostructured. Ni–Mn oxide- and hydroxide-based electrodes revealed a significant reversible electrochemical activity in the alkaline electrolytes and an extended operating voltage window (~ 1.8 V). Ni–Mn ilmenite-based electrode materials demonstrated a low fade rate and high specific electrochemical capacity values at high discharge rates (up to 70 mAh g− 1 at I = 70 mA cm− 2) that makes feasible their application in high rate batteries and electrochemical supercapacitors.