Influence of Graphite Choice on Lithium Plating in Li-Ion Cells at -30°C

摘要

The most surprising finding from this work was that the impedance rise at low temperature was not significantly impacted by the choice of graphite or even the choice in active material. The main rise in impedance occurs in the mid-frequency range. Processes that occur in this frequency range are generally interfacial in nature. This means that the responsible phenomenon is independent of the active material and is most likely an electrolyte-interface effect. It should be noted that materials with high surface areas do appear to help the power performance at low temperature, but this is only part of the solution. Cells based on hard carbon and Li_4Ti_5O_(12) as the negative electrode were much less likely to deposit lithium because they operate at potentials well above lithium potential. Efforts are underway to investigate the influence of electrolyte properties such as composition, viscosity, density, and wettability at low temperature.