Electrochemical aspects of the deintercalation of layered AMO2 compounds

✍ Scribed by S. Kikkawa; S. Miyazaki; M. Koizumi

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 213 KB
• Volume: 14
• Category: Article
• ISSN: 0378-7753
• DOI: 10.1016/0378-7753(85)88035-6

✦ Synopsis

The electrochemical deintercalation of AMOz compounds, where A = Li or Na, and M = Cr, Co or Fe, was investigated. The open circuit voltage of A/lM AClO%-propylene carbonate/A,MOz cells and the chemical diffusion constant, D, of alkali in AXM02 were measured using a currentpulse relaxation technique. The cells made from lithium compounds showed an OCV of about 4 V. The voltage increased continuously with charging. The cell OCV of sodium compounds increased discontinuously in the range 2.4 -3.2 V. The discontinuity was related to the change of MO2 layer stacking in the deintercalation process. The highest diffusivity of D(Na) = 5 X 10e8 cm2 s-' was observed in Na,CoO, (0.5 < x < 0.6). Diffusion constants were larger for trigonal prismatically surrounded sodium than for that octahedrally coordinated. Lithium diffused faster than sodium in the compounds having the same kind of transition metal in an octahedral environment.