Experimental Study of Electronic and Ionic Conductivity of a Carbon-Based Slurry Electrode Used in Advanced Electrochemical Energy Systems

Abstract

Focusing on the application of carbon slurry electrodes in advanced electrochemical power and energy storage systems, the electrical conductivity of such electrodes is thoroughly investigated experimentally. A slurry electrode made from steam-activated Norit is analyzed to estimate its electronic and ionic conductivities separately. A single-pass rectangular flow channel with three different widths of 4.1, 3.6, and 3.1 cm is used to investigate the effect of the flow channel geometry on slurry electrode conductivity. Three different slurry concentrations of 5, 10, and 15 wt % are investigated, while electronic and ionic conductivities are separately measured using distilled water and sulfuric acid as electrolytes. The charge conduction improvement due to the availability of more charge-carrying particles in the slurry is quantified, and it is shown that up to about 220 and 120% increase in electronic conductivities can be achieved by increasing carbon loading from 5 to 10 and 15 wt %, respectively. Analysis of slurry conductivity variations from a static condition to a flow rate of 280 mL min–1 with different channel widths and concentrations shows that the slurry conductivity reaches a maximum value at an intermediate flow rate and is then gradually decreased. The optimum working condition of a slurry electrode is finally discussed.

Electronical Conductivity Improvement of Carbon-Based Slurry Electrodes Using Carbon Foams for Enhanced Performance in Advanced Electrochemical Energy Storage Systems

“… 19 It is evident from Figures 4 a,c,e and 5 a,c,e that the ionic conductivity is almost 3 orders of magnitude higher than the electronic conductivity; thus, ionic conductivity has a controlling role in regulating the overall electrical conductivity of acid-based slurries used in these experiments. It must also be noted that the ions can be absorbed on carbon particles’ porous surfaces (in the present study, the ions are at least 4 orders of magnitude smaller than the carbon particles, 19 and the ion gradients are distorted); since the particles are behaving as charge sources, they interrupt normal ion gradients in a slurry. Therefore, any interruption in ion conduction throughout the slurries can be translated to a reduction in the overall electrical conductivity of the system.…”

“… 18 , 19 For the water-based slurry, electronic conductivity is enhanced due to the formation of this sedimented layer of carbon particles. 18 , 19 For the acid-based slurry, the supernatant consists mainly of acid, and ions freely move to CC; thus, the ionic conductivity is also increased as a result of particle sedimentation.…”

“…Before starting the experiments, the developed setup is calibrated using a known conductivity reference solution (KCL); the calibration results have been discussed in our previous work. 19 Cell constant ( k ) is defined after calibrating the developed slurry conductivity measurement test rig. Potassium chloride (∼conductivity 4.5 mS·cm –1 ) is used as the reference liquid to carry out the calibration process.…”

“…The interconnected porous structure could also increase active sites for charge transfer and maximize CC's surface area. 36 Many studies have theoretically and experimentally investigated slurry electrode systems' ionic and electronic conductivities, 1,3,[19][20][21][22][23]40,41,46 and some studies have been conducted to measure the electrical conductivity of CFs separately. 37−39,42−44 However, to the best of the authors' knowledge, no research or measured data have been reported in the literature on conductivity enhancement of slurry electrodes after adding CFs.…”

“… 1 , 11 , 14 Numerous efforts have been documented in the literature on enhancing charge transfer in slurry electrodes, most of which focus on increasing carbon particles in the electrolyte or adding conductive agents such as CB. 19 − 23 This charge conduction is mainly regulated by the interaction and collision frequency between current collectors (CCs) to particles and among charged–uncharged particles. By increasing the mass loading of the particles, more particles are available to form a conductive layer that promotes charge transfer.…”