A study of the overcharge reaction of lithium-ion batteries

The overcharge behavior of prismatic lithium ion batteries was studied unde r abusive conditions. Experimental cells were constructed with a systematic variation in cell balance and overcharge tested to the point of failure. T his test demonstrated that the point of cell rupture tracked the amount of cathode in the cell, independent of the amount of anode material. The rate of charge was found to be an important parameter, as cells overcharged at l ow charge rates remained hermetic while high charge rates (C/2 and above) r esulted in cell rupture. The internal temperature of the cells monitored du ring overcharge was found to be as high as 199 degreesC, which was 93 degre esC higher than the external skin temperature of the cell. Coin cell tests identified the cathode as the source of heat produced in the cell, and Rdc measurements identified a large increase in cell resistance past the full d elithiation point of LixCoO2. (C) 2001 Elsevier Science B.V. All rights res erved.