ISSRNS 2008 − abstracts IN-SITU HIGH-PRESSURE OBSERVATION OF JAHN-TELLER EFFECT IN LITHIUM-MANGANESE OXIDES

A secondary battery is a crucial part of portable and high-performance electrical devices such as personal computers, mobile phones, digital cameras, and video movies. The high cost and high toxicity of cobalt has created enormous interest in development of less expensive, environmentally benign manganese-based cathodes as an alternative to cobalt-based cathodes for rechargeable lithium batteries. The spinel oxides, LixMn3-xO4 are being intensively pursued in this regard. LiMn2O4 shows two plateaus in voltage versus capa-city plots. For one of them, around 3 V, one can observe drastic capacity fading upon cycling due to the macrosco-pic volume change associated with a cooperative Jahn-Teller distortion. The cyclability can be improved by increasing the average oxidation state of manganese through a substitution of lithium for manganese in Li1+xMn2-xO4. Such substitutions suppress Jahn-Teller distortions. Li4Mn5O12 is known to show better cyclability in the 3 V region than LiMn2O4. Likewise, a cubic symmetry can be preserved at low temperature due to lithium insertion into the manganese lattice sites