STRUCTURAL PHASE TRANSITION AND ELECTRODE CHARACTERISTICS OF LiMn_(2-x)Mg_xO_4 POSITIVE ELECTRODE MATERIAL FOR THE LITHIUM SECONDARY BATTERY

摘要

With in mind improving the cycle performance of 4V class lithium manganese oxide positive electrode material for the lithium secondary battery, we have been investigated the effects of partial substitution of Mn by another metal. The crystal phase transition in the quaternary spinel LiMn_(2-x)Mg_xO_4 was studied by neutron powder diffraction at 200K and DSC measurements at low temperatures. We find that substituting Mn by Mg resulted in a more stable crystal structure with the Jahn-Teller transition suppressed down to low temperature. The charge-discharge characteristics of these positive electrode active materials were investigated at 4V range. Although the discharge capacity decreased with increasing Mg content, the cycle performance was improved with increasing Mg content.