Optimization of Design Parameters and Operating Conditions of Electrochemical Capacitors for High Energy and Power Performances

Abstract

Theoretical expressions for performance parameters of different electrochemical capacitors (ECs) were optimized by writing MATLAB scripts to solve them and also via MATLAB R2014a optimization tool box. Performance of different kind of ECs at given circumstances were compared through theoretical equations and simulation of various models subject to conditions of device components, using optimal coefficient associated to battery-kind material and constant associated to electrolyte material KBMopt and KEopt , as well as our symmetric electric double layer capacitor (EDLC) experimental data. Estimations of performance parameters were feasible and achievable once details of electrodes mass ratio, operating potential range ratio and specific capacitance of electrolyte are known. Performances of asymmetric EC with suitable electrode mass and operating potential range ratios using aqueous electrolytes, and that with suitable electrode mass and operating potential range ratios using organic electrolyte with appropriate operating potential range and specific capacitance were factors of 2.2 and 5.56, respectively, greater than those of symmetric EDLC and asymmetric EC using the same aqueous electrolyte, respectively. This enhancement came along with reduction in cell mass and volume. Also, storable and deliverable energies of asymmetric EC with suitable electrode mass and operating potential range ratios using proper organic electrolyte were factor of 12.9 greater than those of symmetric EDLC using aqueous electrolyte, with reduction in cell mass and volume. Storable energy, energy density and power density of asymmetric EDLC with suitable electrode mass and operating potential range ratios using proper organic electrolyte were factor of 5.56 higher than those of similar symmetric EDLC using aqueous electrolyte with reduction in cell mass and volume by a factor 1.77. Also, introduction of asymmetric EDLC with the same type of electrode, and suitable electrodes mass ratio, working potential range ratios and proper organic electrolyte enhanced performance of conventional symmetric EDLC using aqueous electrolyte with reduction in cell mass and volume. These results can obviously reduce number of experiments to determine optimum manufacturing state of EC, and also demonstrated that institution of asymmetric electrode and organic electrolyte was very successful in improving performance of EC with reduction in cell mass and volume. These results can as well be a guideline for design, fabrication and operation of electrochemical capacitor with outstanding storable energy, energy and power densities. Key words: Electrodes symmetry; Modelling and simulation; Performance parameters; Electrolytes type; Working potential range; Asymmetric capacitors.