Investigation of the Kinetics of rechargeable aqueous zinc ion batteries

Rechargeable aqueous zinc ion batteries are currently receiving much attention as large-scale energy storage systems due to their inherent safety, fast ion kinetics, low cost materials and environmental friendliness. Considering the recent literature, the state-of-the-art zinc ion battery combines a manganese oxide cathode, a planar zinc foil anode and an aqueous, mildly acidic electrolyte [1]. Even though the corresponding electrochemical models are subject to recent discussions [2] it is possible to derive basic kinetic parameters allowing a further development of the cell design and electrode composition. For this purpose in this study, zinc foil is used as the anode, a slightly acidic zinc sulphate solution as electrolyte and a stainless steel foil coated with manganese dioxide as the cathode. The coating process of the cathode may greatly influence the kinetics of the battery due to the fact that the cathode thickness, the porosity and the particle size are decisive for the overall performance of the battery. The cathode slurry is a mixture of manganese dioxide, carbon black, binder and distilled water. Previous studies showed that particularly the particle size of the manganese oxide in the cathode has great influence on the capacity of the battery [3]. In order to understand the kinetics of the coated cathode it was investigated if the electrochemical process is mass or charge transfer controlled and corresponding parameters of the Butler-Volmer equation are determined by electrochemical characterization of the samples. These kinetic parameters are identified in order to implement a simulation model allowing a further optimization of the battery cell architecture and the required electrode properties.