Evaluation of Commercial Lithium-Ion Cells Based on Composite Positive Electrode for Plug-In Hybrid Electric Vehicle (PHEV) Applications

Abstract

Lithium-ion cells with composite positive electrodes are attractive and promising for EV and PHEV applications. For powertrain applications, the battery packs are required to have multiple-cell configurations, where some battery management is needed to protect cells from experiencing overcharging and overdischarging. Here, we show how to analyze the effect of slight overdischarge in a graphite || {LixMn1/3Ni1/3Co1/3O2 + LixMn2O4} cell, when it was overdischarged to 2.0 V. We found a peculiar behavior at low voltages that is imputable to the composite nature of the positive electrode. Under certain circumstances, due to differences in kinetic limitations in each of the constituents in the composite electrode, although LixMn1/3Ni1/3Co1/3O2 were discharged normally, LixMn2O4 could be overdischarged to Li2Mn2O4 and cause capacity fade.