(625e) Modeling of High Transference Number Electrolytes for Fast Charging Lithium Ion Batteries

Fast charging remains a critical challenge inhibiting the rapid proliferation of lithium ion battery technology. In the most recent Technology Gap Assessment, the DOE emphasized the need for extreme fast charging (XFC) batteries which can be charged in 10 minutes or less while providing 200 miles of electric vehicle range.¹ We argue that engineering electrolytes with high Li⁺ transference number will be a crucial step towards achieving this goal. To demonstrate this, we turn to Newman’s original lithium ion battery model, and we show that electrolytes with modestly higher Li⁺ transference numbers (t₊) compared to traditional carbonate-based liquid electrolytes would enable faster charging, even if their conductivity was substantially lower than that of conventional electrolytes. We additionally note that high transference number electrolytes (HTNEs) prevent lithium plating at the graphite-electrolyte interface due to the dramatically reduced concentration polarization compared to standard liquid electrolytes (SLEs). Finally, we offer useful targets for the conductivity and t₊ required to meet and exceed the charge performance offered by SLEs.²

References

1. United States Department of Energy. Enabling Fast Charging: A Technology Gap Assessment. 2017.
2. Diederichsen, K. M.; McShane, E. J.; McCloskey, B. D., Promising Routes to a High Li+ Transference Number Electrolyte for Lithium Ion Batteries. ACS Energy Letters 2017.