Analysis of Charge Storage Behavior in Redox-electrolyte Based Battery-like-systems: A Case Study on Zr-doped Ceria

Redox-additives are used as a cost-effective means to improve low-temperature charge-storage capacity for aqueous-supercapacitors. From a technology-development standpoint, there are challenges associated with a lack of standard techniques to measure the redox-additive based device-parameters. This, in turn, yields a relatively poor understanding of the charge-storage processes, especially in battery-like supercapacitors. With this as a backdrop, this work undertakes an analysis of Ce0.9Zr0.1O2@Ni-foam/KOH-K3Fe(CN)(6) electrode/electrolyte system. Here, a method is presented that enables the delineation of the contribution of the effective-mass of the redox-additive on the electrode-surface. This method demonstrates that the effective electrolyte-mass has a similar to 38.5 to similar to 15% contribution toward charge-storage with increasing scan rates (1 to 80 mVs(-1)). The diffusion-controlled trends are duly analyzed using the well-established Trasatti analysis; these also serve as a reasonable benchmark for the method reported here. Hence the method is expected to be of use for other hybrid-supercapacitor systems as well.