The Effect of Fibrous Tows and Weave Pattern on Carbon Cloths as Electrodes in Redox Flow Batteries

Abstract

The electrochemical and fluid dynamic performance of redox flow batteries is strongly influenced by the microstructure of the porous electrodes. Carbon cloths are a potential candidate whose hierarchical structure affects length scales associated with electrolyte flow; however, few studies have investigated the electrochemical behavior spanning from the fibrous tow to the bulk weave pattern. Here, we explore commercially activated weave patterns (plain, 8-harness satin, 2×2 basket) in an aqueous environment while quantifying reactive transport for individual tows and simulating fiber bundle electrochemical activity through multiphysics modeling. We then evaluate each woven electrode in a redox flow cell, measuring the pressure loss, polarization, and galvanostatic cycling behavior before comparing the mass-transfer relationships. We find the weave pattern strongly correlates with flow cell pressure drop, while the carbon fibers per tow influence electrochemistry and mass-transport scaling. Collectively, these results offer new insights into how advanced carbon cloths structures impact flow cell performance.

Electrochemical Residence Time Distribution as a Diagnostic Tool for Redox Flow Batteries

“…26 The electrolytes consisted of a 50% state-of charge (SOC) mixture of 50 mM iron (II) chloride tetrahydrate (98%, Sigma Aldrich, FeCl 2 ) and 50 mM iron (III) chloride hexahydrate (97%, Sigma Aldrich, FeCl 3 ) with 1 M hydrochloric acid (37% Sigma Aldrich, HCl) to act Electrode surface area characterization.-The measured surface area was estimated using Brunauer-Emmett-Teller (BET) analysis with Kr as the operating gas. The Kr BET values for the FH23 and 1071 HCB electrodes are reported in Greco et al 28 and Tenny et al, 27 respectively, with the experimental set-up described in detail in Greco et al 28 To summarize, the Kr BET measurements used a Micromeritics 3Flex surface characterization analyzer (Micromeritics), metering Kr isotherms at ca. 77 K to extract multipoint BET values across a relative pressure range of 0.06-0.20.…”

“…28 For comparative purposes in this work N 2 BET was performed by AvCarb Material Solutions (Lowell, MA) with an ASAP 2020 Plus Physisorption (Micromeritics) as detailed in previous work. 29 Fluid dynamic measurements.-The pressure drop across each electrode was measured with the FTFF and IDFF 14 in an approach similar to our prior work 26,27 and represented in Fig. 1a.…”

“…Further details can be found in prior work. 27 Graphs of the polarization results can be found in section 1 of the Supporting Information for each cell configuration.…”

“…One-dimensional (1D) porous electrode model.-The iR-corrected single-electrolyte cell polarization data was subsequently fit to a 1D porous electrode model 14,31 as described in our previous work. 26,27 For brevity, the second-order ordinary differential equation is shown in Eq. 3…”

“…The measured electrolyte properties and their standard error with the denotations of # for n = 2 and ## for n = 3, all taken from Ref. 27, where n represents an independent measurement.…”