Influence of electrolyte and redox active electrode materials properties on working mechanism and performance of manganese oxide-based supercapacitors. (1st June 2022)

• Record Type: Journal Article
• Authors: Popardowski, A.; Pasierb, P.
• Is Part Of: Electrochimica acta. Volume 416(2022)
• Publication Date: 2022-06-01
• Subjects: Charge storage mechanism -- MnO2 -- Water-based electrolyte -- Diffusion coefficient -- Electrolyte selection; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2022.140257
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: Prototype supercapacitors were constructed using MnO2 powders with different crystal structure and morphology. Capacitances of supercapacitors were compared for water-based electrolytes with different cations. Determined capacitances were correlated with parameters describing the used cations properties for different MnO2 -derived electrode materials. Diffusion coefficient of cations was found to be the controlling parameter of observed capacitance. Abstract: In this work the pseudocapacitors based on graphite foil/manganese oxide powder electrodes, Celgard TM separator foil, and different water-based electrolytes were manufactured. Commercially available MnO2 (Sigma-Aldrich) with average grain size of 10 µm, milled – 0.1 µm, milled and reduced in 5vol.% of H2 in Ar atmosphere (10 h at 600 °C) were used for electrode formation. The influence of electrolytes on the performance of pseudocapacitors was tested using cyclic voltamperometry. The electrolytes were based on cations with different: valence (Na +, K +, Ca 2+ and Al 3+ ), activity (a), hydrated ion size (rh ), specific ionic conductivity of electrolyte (λ), diffusion coefficient (D) and these parameters were correlated with determined capacitances. The highest capacitances were observed for K + -based electrolytes, which can be explained by the smallest rh and the highest D for this cation. Such direct explanation was not possible for other cations as the parameters describing the electrolyte properties are depends on each other and should be analyzed in conjunction. The observed correlations shows that the diffusion coefficient is the most valuable parameter for selection of the electrolyte for pseudocapacitor applications. The influence of electrode materials properties must be also taken into account, as the crystal structure, grain size, morphology or electrical properties influence the mechanism of charge accumulation of different ions, as it was simultaneously observed in this work. Graphical abstract: Image, graphical abstract