title: Electrode Mass Balancing as an Inexpensive and Simple Method to Increase the Capacitance of Electric Double-Layer Capacitors.
abstract: Symmetric electric double-layer capacitors (EDLCs) have equal masses of the same active material in both electrodes. However, having equal electrode masses may prevent the EDLC to have the largest possible specific capacitance if the sizes of the hydrated anions and cations in the electrolyte differ because the electrodes and the electrolyte may not be completely utilized. Here we demonstrate how this issue can be resolved by mass balancing. If the electrode masses are adjusted according to the size of the ions, one can easily increase an EDLC's specific capacitance. To that end, we performed galvanostatic cycling to measure the capacitances of symmetric EDLCs with different electrode mass ratios using four aqueous electrolytes- Na2SO4, H2SO4, NaOH, and KOH (all with a concentration of 1 M)-and compared these to the theoretical optimal electrode mass ratio that we calculated using the sizes of the hydrated ions. Both the theoretical and experimental values revealed lower-than-1 optimal electrode ratios for all electrolytes except KOH. The largest increase in capacitance was obtained for EDLCs with NaOH as electrolyte. Specifically, we demonstrate an increase of the specific capacitance by 8.6% by adjusting the electrode mass ratio from 1 to 0.86. Our findings demonstrate that electrode mass balancing is a simple and inexpensive method to increase the capacitance of EDLCs. Furthermore, our results imply that one can reduce the amount of unused material in EDLCs and thus decrease their weight, volume and cost.
authors.affiliation: Department of Natural Sciences, Mid Sweden University, Sundsvall, Sweden.
authors.forename: Britta
authors.initials: B
authors.lastname: Andres
authors.affiliation: Department of Natural Sciences, Mid Sweden University, Sundsvall, Sweden.
authors.forename: Ann-Christine
authors.initials: AC
authors.lastname: Engström
authors.affiliation: Department of Natural Sciences, Mid Sweden University, Sundsvall, Sweden.|STT Emtec AB, Sundsvall, Sweden.
authors.forename: Nicklas
authors.initials: N
authors.lastname: Blomquist
authors.affiliation: Department of Natural Sciences, Mid Sweden University, Sundsvall, Sweden.
authors.forename: Sven
authors.initials: S
authors.lastname: Forsberg
authors.affiliation: Department of Chemical Engineering, Mid Sweden University, Sundsvall, Sweden.
authors.forename: Christina
authors.initials: C
authors.lastname: Dahlström
authors.affiliation: Department of Natural Sciences, Mid Sweden University, Sundsvall, Sweden.
authors.forename: Håkan
authors.initials: H
authors.lastname: Olin