Strain‐Based In Situ Study of Anion and Cation Insertion into Porous Carbon Electrodes with Different Pore Sizes

Abstract

The expansion of porous carbon electrodes in a room temperature ionic liquid (RTIL) is studied using in situ atomic force microscopy (AFM). The effect of carbon surface area and pore size/pore size distribution on the observed strain profile and ion kinetics is examined. Additionally, the influence of the potential scan rate on the strain response is investigated. By analyzing the strain data at various potential scan rates, information on ion kinetics in the different carbon materials is obtained. Molecular dynamics (MD) simulations are performed to compare with and provide molecular insights into the experimental results; this is the first MD work investigating the pressure exerted on porous electrodes under applied potential in a RTIL electrolyte. Using MD, the pressure exerted on the pore wall is calculated as a function of potential/charge for both a micropore (1.2 nm) and a mesopore (7.0 nm). The shape of the calculated pressure profile matches closely with the strain profiles observed experimentally.

The Effect of Water and Confinement on Self-Assembly of Imidazolium Based Ionic Liquids at Mica Interfaces

“…Recent diffraction studies at highly charged dielectric interfaces suggest, that a charge-stacking mechanism with stacked layers of oppositely charged ions controls charge compensation in the first layers of solid/IL interfaces 9 . Similarly, force probe experiments under potential control support the charge-stacking model at high surface charge and low water content in electrochemical systems 10 11 . On the other hand at low surface charging around the potential of zero charge no pronounced layering can be observed and bulk IL structure dominates the interface on mica 12 13 .…”

“…In particular, the data for [C 2 MIm][Tf 2 N] compares well with our previous measurements 12 and data by Sakai et al 27 indicating a final compression layer at D ~ 5 Å, and weak structuring at larger distances. Compared to Sakai et al 27 we rely on a statistical analysis of data measured multiple times and over different areas as suggested by Black et al 10 11 . In the statistical analysis we find that structured layering at the outer layers in dry IL is statistically not pronounced (see Figure S3 ), while it appears pronounced in individual force distance measurements.…”

Capillary evaporation of the ionic liquid [EMIM][BF4] in nanoscale solvophobic confinement

“…(2)]. 63,[80][81][82] We conclude by noting that small changes in the flexibility of confining plates, not included here, can significantly impact the thermodynamics and kinetics of capillary evaporation 60 and can be used to further tune solvophobic effects in IL-based systems.…”

Controlling the actuation properties of MXene paper electrodes upon cation intercalation

“…20 nm). This technique has been broadly used as an in situ probe to monitor the dimensional changes of battery [19][20][21][22][23], pseudocapacitor [24,25], and EDLC electrodes [26,27]. Another key advantage of these experiments is that they can be performed at various charging and discharging rates.…”