Thermal structure modification of birnessite-type manganese oxide doped with cob

2019-09-12 10:36:31

The phase oxide deg birnessite

责任者: Sasaki, Teruhito;Komaba, Shinichi;Kumagai, Naoaki;Ogata, Atsushi;Fujiwara, Makiko;Yashiro, Hitoshi 单位: Department of Frontier Materials and Functional Engineering, Graduate School of Engineering, Iwate University, Morioka, Iwate 020-8851, Japan 来源出处: Electrochemistry,2005,73(4):290-297 摘要: The thermal property of the K-birnessite-type MnO2 doped with cobalt was examined in the temperature range up to 600°C by means of TG-DTA, XRD and TEM measurements. The Co doped birnessite phase, KxMn 1-yCoyO2·zH2O (x = 0-0.37, y = 0-0.22, z = 0.19-0.28), was gradually transformed to the hollandite MnO 2 phase having a (2 × 2) tunnel structure on heat treating in the temperature range between 350 and 450°C, though undoped birnessite was transformed at 300°C. A single phase of high crystalline hollandite was formed at 550°C. The XRD measurement showed that the nano-composite manganese oxide consisting of the birnessite phase and the hollandite phase was formed at 350 - 450°C in the course of annealing the birnessite oxide. The electrochemical properties of the birnessite and its calcined products were examined as cathodes for rechargeable lithium batteries. The birnessite / hollandite composite formed at around 350°C exhibited a S-shaped smooth discharge curve with an average potential of 2.8 V vs. Li/Li+ and better performances with the initial discharge capacity of 238 mAh/g and the cycling capacity of about 170 - 205 mAh/g during 10 cyclings. 关键词: Secondary batteries;Manganese compounds;Doping (additives);Cobalt;Thermodynamic properties;Nanostructured materials;Electrochemistry;Annealing;Calcination;Lithium secondary battery;Birnessite;Hollandite;Mn(1-x)CoxO2;Manganese oxide