Prediction of Charge-Discharge and Impedance Characteristics of Electric Double-Layer Capacitors Using Porous Electrode Theory

Abstract

Two first-principles modeling methods were used to analyze and quantitatively predict performance characteristics of Electric DoubleLayer Capacitors (EDLCs), namely Time-Domain Current Method (TDCM) and Frequency-Domain Admittance Method (FDAM). TDCM was used to model galvanostatic discharge characteristics of capacitor while FDAM was used to model the impedance spectra. Both the methods showed excellent agreement with experimental impedance and galvanostatic discharge performance of various electrochemical capacitors made using two different commercial carbons. Details at the macroscopic (porous electrode theory) and microscopic (double layer theory) level were incorporated into the models. The methods were also able to follow changes in capacitance and resistance of the capacitor during cycling. Furthermore, FDAM was used to validate the performance of a large-scale commercial EDLC capacitor. Electrochemical capacitors are receiving considerable attention as energy storage devices that can meet the energy and power demands for electric vehicles, renewable energy storage, smart grid, and energy harvesting technologies. [1][2][3][4] Energy in these capacitors is stored either in the form of electrostatic ionic charge at electrode/electrolyte interface or through fast faradaic interactions that contribute to pseudocapacitance at the interface. [5][6][7][8][9] Transient electroanalytical techniques such as galvanostatic charge/discharge and impedance spectroscopy are the key tools that are used to assess both the EDLC's materials characteristics and device performance. Development of mathematical models that accurately describe the interfacial phenomenon and validation through experimental observation is critical to further our understanding of the complexity of electrostatic/electrochemical interaction that occurs at the electrode/electrolyte interface.The development of models for EDLCs ties very deeply with the mathematical modeling of non-faradaic phenomena at the microscopic level. In these length scales, the double layer structure is described in terms of a diffuse/Gouy-Chapman layer and compact/Helmholtz layer. The compact layer will then be further divided into inner Helmholtz plane (IHP), that contain specifically adsorbed ions, and outer Helmholtz plane, which contains solvated ions that are attracted to the electrode due to charge interactions. To apply this conceptual picture to transient electroanalytical techniques, many different variations exist based upon the mathematical details and the choice of non-faradaic effects to be included/excluded in the models, e.g. specific adsorption, diffuse layer, and compact layer.Among all non-faradaic phenomena related to the double layer structure, the diffuse layer is one of the most intensively studied. The earliest treatment came by direct incorporation of the Gouy-ChapmanStern theory for different electroanalytical techniques, with some analytical solutions in the form of hypergeometric functions given in cases where they are possible. [10][11][12][13][14][...

In Situ Growth of Novel Graphene Nanostructures in Reduced Graphene Oxide Microspherical Assembly with Restacking‐Resistance and Inter‐Particle Contacts for Energy Storage Devices

“…Additionally, EIS measurements were performed on the coin cells at frequencies between 200 kHz and 10 mHz with an amplitude of 10 mV using a Bio‐Logic instrument. Furthermore, to calculate the reciprocal which represents the time constant of GT/GnS@rGB and c‐rGB, a Bode plot was provided for frequency and real and imaginary capacitance, which is determined as follows: [ 63,65 ] where the complex form of capacitance C(w) was introduced by a real capacitance part C ′( w ) and an imaginary capacitance C ″( w ). Z ′( w ) and Z ″( w ) are the real and imaginary terms of the complex impedance Z ( w ), respectively; and w = 2πf represents the angular frequency.…”

Biomass-Based Carbon Electrodes in the Design of Supercapacitors: An Electrochemical Point of View

“…A detailed analysis of the electrochemical behavior by electrochemical impedance spectroscopy (EIS) experiments and non-linear complex fitting (NLCF) of their equivalent circuits has been conducted. Nyquist diagrams show an electrolyte resistance (R S )of2Ω approximately, as well as, non-ideal impedance loop for both N 2 -made and Ar-made electrodes suggesting a non-ideal charge storage process at the electrochemical interface [44,45].…”

Acacia auriculiformis–Derived Bimodal Porous Nanocarbons via Self-Activation for High-Performance Supercapacitors

“…The pore clogging results in the increase of resistance, which can be accurately identified from impedance spectra. Fading in capacitance, increased impedance, and a distinct change in Bode plot with cycling could be attributed to increased resistance and electrolyte loss (Hasyim et al, 2017)The self-discharge curves of OSSc were plotted after charging to 2.3 V at 1.0 A/g. The OCP was recorded at regular intervals for 100 min with the cell showing 43% retention after charging up to 2.3 V. Two self-discharge models were employed to identify the major mechanism responsible for the selfdischarge (Barzegar et al, 2017).…”