Boosting the Coulombic Efficiency of a Graphite Cathode
Graphite is a popular anode material in electric vehicle batteries, as it is both conductive and readily available. It is also a very tough and durable material, which is important for EV battery manufacturing and operation.
Despite its ubiquity as an anode, the performance of graphite is still in need of improvement. There are several approaches that could be used to boost the coulombic efficiency of graphite cathodes. Some of these approaches involve ex-situ modification of the graphite surface or tailoring the electrolyte composition.
One of the most effective approaches is to introduce film forming additives into the electrolyte, since it has been demonstrated that these additives can enhance coulombic efficiency for pre-lithiated lithium ion cell cathodes and even for standard graphite electrodes (as well as for lithium carbonate cells). For example, Placke and co-workers showed that introduction of small PF6-, TFSI-, and AlCl4- anions into an ionic liquid system increased the anion intercalation voltage by up to 1 mV.
Another approach to improve the coulombic efficiency of graphite electrodes is to use a water-soluble binder. This is a very recent development in the field of electrode preparation and is accompanied by many advantages regarding both cost and sustainability.
Nevertheless, the application of such a binder for the preparation of graphite electrodes requires careful and thorough considerations to ensure that the binder does not interfere with the ionic intercalation mechanism and, in particular, to avoid the formation of dissolved anions or cations that would lead to lowered ICE. A further step in this regard is to optimize the pH of the ionic liquid.
