Method Comparison for Deconvoluting Capacitive and Pseudo-Capacitive Contributions to Electrochemical Capacitor Electrode Behavior

Abstract

Several electrochemical methods have been developed to determine the contribution of different charge storage mechanisms, such as via the electrical double layer and diffusion-limited processes, to electrochemical capacitor behavior. This includes using cyclic voltammetry (CV) data at different sweep rates to obtain the relationship between voltammetric current and sweep rate, and also the relationship between voltammetric charge and sweep rate.Step potential electrochemical spectroscopy (SPECS) also has been used to effectively differentiate between different charge storage mechanisms. Herein we compare these three methods experimentally and also discuss their advantages and limitations toward differentiating between different charge storage mechanisms. These methods have been applied to electrolytic manganese dioxide (EMD) in 0.5 M K 2 SO 4 between 0.0-0.8 V (vs SCE). It was found that in all cases, the specific capacitance was decreased by increasing the sweep rate. The capacitance-sweep rate dependence was only found to be accurate in a short range of low sweep rates. Overall there was good agreement between the SPECS and current-sweep rate dependence models over the full range of sweep rates. However, the SPECS method provided more precise information about the kinetic behavior of the electrochemical cell through a full range of sweep rates.

Energy Storage Data Reporting in Perspective—Guidelines for Interpreting the Performance of Electrochemical Energy Storage Systems

“…[10] Recently, Donne et al, developed Step Potential Electrochemical Spectroscopy (SPECS) to separate the diffusion-limited process from the electrical double-layer contribution. [11] Simon et al proposed a general qualitative method called MUltiple Step ChronoAmperometry (MUSCA) to minimize ohmic drop contributions, thus allowing electrochemical kinetics studies of pseudocapacitive electrodes. [12] In all cases, truly pseudocapacitive materials will show the following: linear peak current responses versus scanning rate (i ∝ v), symmetric redox peaks with little to no separation (Figure 1b, 1e), highly reversible charge transfer, electrochemical impedance spectra, or Nyquist plots, typical of capacitive materials (see section 5, Fig.…”

Boosting the electrochemical properties of carbon materials as bipolar electrodes by introducing oxygen functional groups

“…To thoroughly understand the electrochemical processes of electrode capacitance, Bruce Dunn divided the capacitance into surface-controlled and diffusion-controlled contributions. [19][20][21][22] The magnitude of diffusion-controlled capacitance decreases with increasing scan rate, while surface-controlled capacitance remains constant with increasing scan rate. [23][24][25] As a potential energy storage material, it is necessary to understand the charge storage mechanism of carbon-based supercapacitors in order to guide the application of electrodes.…”

Nitrogen‐Doped Porous Graphene Coated with Fe3O4 Nanoparticles for Advanced Supercapacitor Electrode Material with Improved Electrochemical Performance

“…With the aim of better understanding the origin of the high C s of NPGF‐2 that shows obvious battery‐type characteristics, we tried to explore the composition of its C s . This is because, as reported elsewhere, [ 3,42–45 ] there are two processes that contribute to the total capacitance, namely, surface‐limiting (capacitive) process and diffusion‐controlled process. Therefore, it is extremely valuable to investigate the contribution of each process to its high C s .…”

“…By linearly fitting Equation () at a fixed potential, the values of k 1 and k 2 were obtained respectively from the slope of the fitted straight line and its intercept on the y ‐axis, and the current contributed by different processes could be further calculated. Although unavoidable errors exist in this method due to the lack of abundant data points, the severe polarization in the electrochemical process, and the intrinsic limitations of this formula, [ 44 ] we can still find some regular patterns in Figure a. At different scan rates, the contribution of the two processes to the total C s is different.…”