An Artificial Interface for High Cell Voltage Aqueous-Based Electrochemical Capacitors

Marco Olarte,Pierre-Louis Taberna,Marie-Joelle Menu,Patrice Simon,Marie Gressier

doi:10.1149/1945-7111/ac10f5

Abstract

Aqueous electrolytes are very effective for supercapacitor applications but their narrow electrochemical potential window (∼1 V) and associated limited energy currently limits their use. Here, we demonstrate a new strategy to enlarge the potential window by designing an artificial interface (ai). An effective ai was achieved via a mixture of siloxanes doped with an ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI TFSI). Indeed, the as-deposited ai on the carbon-based electrode hinders the electron charge transfer but not the ionic charge transfer, making the ai ionic conductive. As a result, a cell voltage of about 1.8 V was obtained in aqueous electrolyte-EMI HSO4 1 mol l−1 in water. Used as a membrane, the ai was found to be ionically specific to EMI+; the proton transference number being close to zero. These results show the strategy of developing an ai at the electrode/electrolyte interface could represent a new path for aqueous-based carbon-carbon supercapacitors to reach higher cell voltages, providing both higher specific energy and power.

Highlights

To cite this version: Marco Olarte, Marie-Joëlle Menu, Patrice Simon, Marie Gressier, Pierre-Louis Taberna
We succeeded in preparing a high voltage supercapacitor operating in aqueous electrolyte by tailoring the carbon electrode/electrolyte interface
We developed a passive layer, termed as artificial interface, which avoids electronic transfer but allows for ionic conduction; as a result, the ion absorption/desorption process needed to form the electrochemical double layer can be achieved

Summary

RT zi F ln

Charged membranes being far from ideal behaviour,[44,45] the model used to characterize the diffusivity of ions through the artificial interface as a supported membrane is derived from the Nernst-Plank equations via the theory TeorellMeyer-Sievers (TMS), proposed by Teorell, Meyer and Sievers,[46,47] which describes the equilibrium potentials across a membrane splitting two reservoirs at different electrolyte concentrations, depending on different anion and cation diffusivities. We used a modified model derived from Lefebvre et al.,[48] as shown in Eq 1 the dimensionless membrane potential, in which the equilibrium potential is made up of two main contributions: the Donnan potential (ΔEDonnan), accounting for the inter-diffusion region between the membrane and the electrolyte; the diffusion potential due to the concentration gradient (ΔEDiff ). As reported by Ghosh et al, we added the α parameter before the Donnan contribution from non-idealities.[49]

FΔEm RT

Results and Discussion

Conclusions