Investigation of the Effect of Depth of Discharge/State of Charge Limitations, C-Rate, and Temperature on the Lifetime of Nmc/Silicon-Graphite Pouch Cells

Electric vehicles are consistently being adopted by the consumer market. The associated range anxiety of purchasing an electric vehicle can be partially put at ease by looking at real driving data that shows the average driving distance in a day is under 75 km. These limited driving days represent days with a partial battery cycle. Partial cycling ranges are an interesting area of research particularly for silicon-graphite composite electrodes, where different cycling ranges can have large impacts on the lifetime of the cell. In this study, we investigate the two active anode materials of metallurgical silicon and a silicon-carbon composite at five cycling ranges: 60%–0%, 80%–0%, 100%–0%, 100%–40%, and 100%–60%. The cells used in this study contribute ∼70% of their capacity from silicon or Si-C representing an interesting difference from silicon/graphite composite anodes featuring minimal silicon capacity. The cycling ranges that focus on cycling the graphite portions of the electrode and only occasionally use the silicon capacity show great capacity retention over their lifetime. Whereas the cells using predominantly using silicon capacity experience rapid capacity fading. This choice becomes an important distinction when trying to extend the lifetime of a vehicle’s battery pack.