Thermal characteristics of LixMn2O4 spinel

The heat generation characteristics of LixMn2O4 spinel as a positive electr ode material were measured in situ during cycling of Li/LixMn2O4 cell, usin g an isothermal microcalorimeter in combination with a battery tester. The total heat generation rate is dependent on the concentration of lithium in LixMn2O4. By separating irreversible heat from the total heat rate, using,d e interruption technique, the concentration dependence is shown to be mainl y due to the reversible heat of the cell, which shows a cooling-heating-coo ling-heating cycle, during charge/discharge. This thermal characteristic ma y be explained from the phase diagram of LixMn2O4, in agreement with recent reports on the phase-change behavior. The dependence of the thermal charac teristics on the current level is weak at a low C rate, but increases steep ly from C/3 to IC rate. Although voltage profiles of charge and discharge s howed similar behavior, the range of discontinuity (between 4.1 and 4.0 V) is not identical for charge and discharge. While the voltage profile is aff ected by irreversibility (charge vs. discharge), the thermal profile is bar ely affected by it. (C) 2001 The Electrochemical Society. [DOI: 10.1149/1.1 387224] All rights reserved.