Reducing impedance to ionic flux in capacitive deionization with Bi-tortuous activated carbon electrodes coated with asymmetrically charged polyelectrolytes

Abstract

Capacitive deionization (CDI) with electric double layers is an electrochemical desalination technology in which porous carbon electrodes are polarized to reversibly store ions. Planar composite CDI electrodes exhibit poor energetic performance due the resistance associated with salt depletion and tortuous diffusion in the macroporous structure. In this work, we investigate the impact of bi-tortuosity on desalination performance by etching macroporous patterns along the length of activated carbon porous electrodes in a flow-by CDI architecture. Capacitive electrodes were also coated with thin asymmetrically charged polyelectrolytes to improve ion-selectivity while maintaining the bitortuous macroporous channels. Under constant current operation, the equivalent circuit resistance in CDI cells operating with bi-tortuous electrodes was approximately 2.2 times less than a control cell with unpatterned electrodes, leading to significant increases in working capacitance (20–22 to 26.7–27.8 F g −1 ), round-trip efficiency (52–71 to 71–80%), and charge efficiency (33–59 to 35–67%). Improvements in these key performance indicators also translated to enhanced salt adsorption capacity, rate, and most importantly, the thermodynamic efficiency of salt separation (1.0–2.0 to 2.2–4.1%). These findings demonstrate that the use of bi-tortuous electrodes is a novel approach of reducing impedance to ionic flux in CDI.

Asymmetric Membrane Capacitive Deionization Using Anion-Exchange Membranes Based on Quaternized Polymer Blends

“…The highest ENAS value (Q20 membrane) was comparable to some literature values obtained for a symmetric cell employing both a commercial AEM and CEM; 49 however, it was slightly lower than those for polyelectrolyte-coated activated carbon electrodes. 55 …”

Enabling fast charging of lithium-ion batteries through secondary- /dual- pore network: Part I - Analytical diffusion model

“…Several authors [7][8][9][10][11][12][13][14][15][16][17][18][19][20][22][23][24][25] have proposed different electrode architectures to reduce the tortuosity factor and improve electrochemical cell performance through experiments and modeling. These methods are listed in Table 1 and are detailed below.…”

“…Cast electrodes are structured with linear macropore cut using flat micro-mill. This technique has been employed for water desalination through capacitive deionization [19,20]. In capacitive deionization, anions and cations are removed from feedwater solution by way of capacitive adsorption into electric double-layers [19].…”

“…Here, the channel walls' function is to guide the lithium stripping and plating process and to confine the volume change, while channels are filled with lithium metal. The SPN architectures are not limited to the battery field as they have also been investigated for solid oxide fuel cells [16,32,33,34,35] and other applications [19,20,36,37].…”

“…‫ܦ‬ = ‫ܦ‬ ‫ܦ‬ = ߝ ߬ [1] ߬ = ߛߝ ଵିఈ [2] Advances in LIB electrode manufacturing have, to a certain extent, enabled control of the electrode microstructure architecture. For example, several groups [7][8][9][10][11][12][13][14][15][16][17][18][19][20] have experimentally tested architectures tailored specifically to increase the through-plane ionic diffusion for fast charge application by adding channels or groove-like large pores oriented along the electrode thickness (cf. Fig.…”