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 degrees C without considerable changes in the Ni and Mn valence states according to X-ray photoelectron spectroscopy data. Further processing at T <= 400 degrees 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 (similar to 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. (C) 2008 Elsevier B.V. All rights reserved.