Capacity failure on cycling or storage of lithium-ion batteries with Li-Mn-O ternary phases having spinel-framework structure and its possible solution

Instability of Li-Mn-O ternary phases having a spinel-framework structure e specially at temperatures above 50 degrees C is a problem in designing lith ium-ion batteries with these materials. This paper describes the solubility of manganese ions from these materials in 1 M LiPF6EC/DNIC (2/1 by volume) , X-ray diffraction (XRD) analysis of these materials after solubility test s, and cycle tests of lithium cells with these materials at room temperatur e or at temperature higher than 50 degrees C. Severe damage was observed in both solubility and cycle tests when Li-Mn-O ternary phases were operated or stored at temperatures higher than 50 degrees C. The XRD examinations in dicated that the spinel-framework structure changed in its line shape and l ocation. In order to cope with this problem, we intensively examined the ad dition of transition metal elements into Li-Mn-O phases and found possible solution on this problem. One of the possible materials is Li[Cr0.1Mn1.9]O- 4 (Fd3m) which shows excellent performance on cycling and storage at 50 deg rees C. (C) 1999 Elsevier Science S.A. All rights reserved.