Sudden Capacity Loss in Lithium Metal Cells

Rechargeable Li-metal batteries have higher energy density relative to batteries based upon intercalation electrodes. They are therefore attractive energy storage candidates for electric vehicles. However, a main barrier to their commercial deployment is a relatively short cycle life. Re-engineering the electrolyte offers advantages towards acceptable cycle life; however, the cells exhibit a sudden capacity loss. In this presentation, we detail a new method for analyzing voltage profiles during cycling to differentiate between the capacity loss originating from loss of cathode capacity loss versus growth in cell resistance. We show that sudden capacity loss is preceded by acceleration of the rate of growth of cell resistance. Cycling of multiple cells suggested that this behavior is sensitive to the initial quantity of electrolyte. Alternatively, the cathode capacity degraded at a constant rate independent of the electrolyte quantity. Loss of active lithium and/or the loss of active cathode material were not the primary causes of sudden capacity loss. Rather, consumption and decomposition of electrolyte led to the drastic capacity loss at end of life.