Reliably and accurately estimate energy in super-capacitor via a model of cyclic voltammetry

Abstract

As effective energy storage device super-capacitors have been widely applied in energy storage field. Cyclic voltammetry (CV) test is utilized to characterize the electrochemical performance of super-capacitors. Even if there are basic formulas to estimate specific capacitance by integral of CV, the integrable model of CV was not given in these literatures. Meanwhile, storage energy during one CV has not been known up to now. Researchers are keen to be able to calculate energy from CV. However, most current studies have not already provided integrable model of CV which is in any shape. The establishment of the accurate CV model is an important basis to realize the reliable estimation of energy density in super-capacitors via CV measurement, and also a necessary work to develop the super-capacitors management system. To fill this gap of knowledge, correct basic formula for calculation energy (density) is provided in this work for the first time in this work. To reliably and accurately calculate energy (density), a novel equivalent circuit model as dynamic model in explicit functional form of quasi ellipse shape of CV is established in this work. This quasi ellipse shape model of CV was validated on a set of thirty-five experimental CV curves, the results calculated from quasi ellipse model agree well with the experimental data because the essential novelty of the proposed model is that it is from Kirchhoff's current law and this law tells us how to calculate the total current density of a parallel circuit. Because this quasi ellipse shape model of CV is confirmed through experimental results and the integral of the model is also in explicit functional form, reliable and accurate energy (density) of each CV curve was also obtained. As another essential innovation of the proposed methodology is that quantitative relationship between the scan rate, potential window, intrinsic performance parameters of super-capacitor, measurement temperature, bending angle and energy (density) is quantitatively searched, this work makes a significant practical contribution and it makes impact on the research work on the research community. Hence, more scientific and practical significance of CV can be gained from the passage of this article.