Ion transport in gel and gel–liquid systems for LiClO₄-doped PMMA at the meso- and nanoscales

Abstract

Solid and gel electrolytes offer significant advantages for cycle stability and longevity in energy storage technologies. These advantages come with trade-offs such as reduced conductivity and ion mobility, which can impact power density in storage devices even at the nanoscale. Here we propose experiments aimed at exploring the ion transport properties of a hybrid electrolyte system of liquid and gel electrolytes with meso and nanoscale components. We focus on single pore systems featuring LiClO-propylene carbonate and LiClO-PMMA gel, which are model electrolytes for energy storage devices. We identified conditions at which the systems considered featured rectifying current-voltage curves, indicating a preferential direction of ion transport. The presented ion current rectification suggests different mechanisms arising from the unique hybrid system: (i) PMMA structure imposing selectivity in fully immersed systems and (ii) ionic selectivity linked to ion sourcing from media of different ionic mobility. These mechanisms were observed to interplay with ion transport properties linked to nanopore structure i.e. cylindrical and conical.

Electrokinetic Phenomena in Organic Solvents

“…43 The switch of surface charge polarity from negative in water to positive in propylene carbonate was agnostic to the pore material and occurred in pores prepared in PET, polycarbonate, and even glass pipettes. 43,55 Previous experiments were performed with conically shaped nanopores, which in symmetric electrolyte conditions rectify ion current such that the I−V curve asymmetry informs on the polarity of surface charges. With the ground electrode placed at the narrow side of the cone-shaped pores, a negatively charged nanopore in aqueous solutions rectified the current such that negative currents were higher than positive currents.…”

Strong Electroosmotic Coupling Dominates Ion Conductance of 1.5 nm Diameter Carbon Nanotube Porins

“…I on transport and associated ionic equilibria feature prominently in a variety of condensed phase phenomena from energy storage in batteries 1 and colloidal stability 2 in materials science to plant growth 3 and nerve signal propagation in biology. 4 A large number of these phenomena involves ions traveling through and interacting in confined spaces that typically reach nanoscale dimensions.…”

Enhancing Ion Transport through Nanopores in Membranes for Salinity Gradient Power Generation

“…The literature also contains various gel-assisted techniques for enhancing the ion transport in conical- and cylindrical-shaped nanopores (see gel-assisted ion transport in Figure ). ,,, Lin et al used high-molecular-weight poly l -lysine to fill conical mesopores with a tip diameter of around 400 nm and found that the addition of the gel significantly improved the ion selectivity of the nanopores compared to that of bare nanopores as a result of an ICP effect near the tip of the nanopore. ,, Yeh et al showed that the maximum power generation of a nanopore filled with poly­(vinyl alcohol) (PVA) gel electrolyte was around 100% higher than that of an aqueous nanopore since the gel lowered the internal membrane resistance through a negative surface charge polyelectrolyte-like increase in the space-charge-governed phenomenon.…”

“…143,144,150,151 Lin et al 143 used high-molecular-weight poly L-lysine to fill conical mesopores with a tip diameter of around 400 nm and found that the addition of the gel significantly improved the ion selectivity of the nanopores compared to that of bare nanopores as a result of an ICP effect near the tip of the nanopore. 143,152,153 Yeh et al 150 showed that the maximum power generation of a nanopore filled with poly(vinyl alcohol) (PVA) gel electrolyte was around 100% higher than that of an aqueous nanopore since the gel lowered the internal membrane resistance through a negative surface charge polyelectrolyte-like increase in the space-charge-governed phenomenon. Various techniques have been employed for the fabrication of multipore membranes, including reactive ion etching, plasma etching, track etching, and so on.…”