Calculation of the Limiting Rate of the Electrode Reaction on a Graphite Cathode of an Aluminum-Ion Current Source with 1-Ethyl-3-methylimidazolium Chloride

Abstract—A method for determining the sorption rate of chloroaluminate complexes on the graphite material as the main cathode reaction in aluminum-ion current sources with an ionic liquid as the electrolyte is proposed in terms of the approach of the standard chemical kinetics. The method is applied to the description of the rate of a one-electron cathode reaction presented as the sorption/desorption of the complexes on the electrode surface ignoring migration in the interlayer space of graphite. The experimental part is based on the selection of the measurement conditions and the ratio of components of the measuring cell in such a way that the rate of the cathode process would be specified by the rate of current generation in the whole cell. The rate of supply/removal of electrons as participants of the reaction can directly be related to the reaction rate on graphite. In this case, the point of reaching the limiting current on the polarization curve corresponds to the limiting chemisorption rate. The approach takes into account the influence of other limiting processes: the rate of electron removal/supply, the rate of ion removal/supply to and from the electrolyte volume, and the rate of anodic dissolution/deposition of aluminum. The calculated reaction rate for the EC-02 graphite material and low-temperature ionic liquid 1-ethyl-3-methylimidazolium chloride in a mixture with aluminum chloride (1 : 1.3) is calculated to be 46 μmol cm^–2 s^–1.