Symmetric effect on electrical double-layer characteristics and molecular assembly interplay in imidazolium-based Ionic liquid electrolytes in supercapacitor models

M Armstrong and N Chiangraeng and M Jitvisate and S Rimjaem and K Tashiro and P Nimmanpipug, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 26, 25808-25818 (2024).

DOI: 10.1039/d4cp03017f

Studies on the ion-layer formation of imidazolium-based ionic liquids have extensively explored how to improve in-depth knowledge of electrical double-layer (EDL) properties. In this computational study, 1-alkyl-methylimidazolium bis(trifluoromethylsulfonyl)imide (CnmimNTf2), namely, C1mimNTf2 and C2mimNTf2, inside a simulated supercapacitor were investigated to expose an symmetric alkyl chain effect. Molecular dynamic simulations of a supercapacitor model with graphite electrodes were conducted. Changes in charging dynamics and EDL structures at different voltages were studied. Although C1mimNTf2 equilibrated much quicker than C2mimNTf2, surface charge development on the symmetrical imidazolium ionic liquid was slower than that on the asymmetrical counterpart. Physical EDL structural analysis showed that C1mimNTf2 could not rearrange in a rigid co-ion layer, whereby the C1mim+ cation stayed adsorbed on the positive electrode throughout all the tested voltages. The strongly attached C1mim+ on the electrode surface contributed to low responsiveness in symmetrical C1mimNTf2, which was supported by lower overall differential capacitance (CD) magnitude and less sharp CD wings at high voltage when compared to C2mimNTf2. Studies on the ion-layer formation of imidazolium-based ionic liquids have extensively explored how to improve in-depth knowledge of electrical double-layer (EDL) properties.

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