Resistor-Network Modeling of Ionic Conduction in Polymer Electrolytes

Gostick, Jeff T.; Weber, Adam Z.

doi:10.1016/j.electacta.2015.03.126

Cited by 49 publications

(43 citation statements)

References 81 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The results presented here help improve the current state of understanding of the structure‐swelling correlation in PFSA ionomers, which has been a subject of a number of recent papers discussing the critical role of the change in ionomer morphology during hydration. [37,46,51,57a,59]…”

Section: Resultsmentioning

confidence: 99%

Nanostructure/Swelling Relationships of Bulk and Thin‐Film PFSA Ionomers

Kusoglu

Dursch

Weber

2016

Adv Funct Materials

168

282

View full text Add to dashboard Cite

Perfluorinated sulfonic acid (PFSA) ionomers are the most widely used solid electrolyte in electrochemical technologies due to their remarkable ionic conductivity with simultanous mechanical stability, imparted by their phase‐separated morphology. In this work, the morphology and swelling of PFSA ionomers (Nafion and 3M) as bulk membranes (>10 μm) and dispersion‐cast thin films (<100 nm) are investigated to identify the roles of equivalent weight (EW) and side‐chain length across lengthscales. Humidity‐dependent structural changes as well as different PFSA chemistries are explored in the thin‐film regime, allowing for the development of thickness‐EW phase diagrams. The ratio of macroscopic (thickness) to nanoscopic (domain spacing) swelling during hydration is found to be affine (1:1) in thin films, but increases as the thickness approaches bulk values, revealing the existence of a mesoscale organization governing the multiscale swelling in PFSAs. Ionomer chemistry, in particular EW, is found to play a key role in altering the confinement‐driven structural changes, including thin‐film anisotropy, with phase separation becoming weaker as the film thickness is reduced below 25 nm or as EW is increased. For the lower‐EW 3M PFSA ionomers, confinement appears to induce even stronger phase separation accompanied by domain alignment parallel to the substrate.

show abstract

Section: Resultsmentioning

confidence: 99%

Nanostructure/Swelling Relationships of Bulk and Thin‐Film PFSA Ionomers

Kusoglu

Dursch

Weber

2016

Adv Funct Materials

168

282

View full text Add to dashboard Cite

show abstract

“…[39,54,55] (a) (b) Figure 6 (a) Conductivity of AsR and PT Nafion XL membranes measured at 30°C as a function of relative humidity and in liquid water, which was measured separately. [39,54,55] (a) (b) Figure 6 (a) Conductivity of AsR and PT Nafion XL membranes measured at 30°C as a function of relative humidity and in liquid water, which was measured separately.…”

Section: Conductivitymentioning

confidence: 99%

Structure/property relationship of Nafion XL composite membranes

Shi

Weber

Kusoglu

2016

Journal of Membrane Science

136

138

View full text Add to dashboard Cite

Perfluorosulfonic-acid (PFSA) ionomer membranes (most commonly Nafion ® ) are currently the prototypical proton-exchange-membrane in polymer-electrolyte fuel cells (PEFCs), for which durability still represents a technical barrier to their commercialization. In an effort to address the durability demands, PFSA membranes with reinforcement and/or stabilizers have become of great interest as they have demonstrated superior durability in PEFCs compared to their unreinforced analogues. One such particular membrane that is tailored for enhanced durability and commonly employed in PEFCs is Nafion XL, a Nafion-based ionomer membrane with mechanical reinforcement and chemical stabilizers. Despite an increasing number of recent studies demonstrating its improved lifetime in accelerated stress testing (AST), its structure and transport properties have not been investigated in a systematic fashion. In this paper, we report water uptake, dimensional change, conductivity, and mechanical properties of Nafion XL membrane, as well as its strong anisotropy, in comparison to (unreinforced) Nafion 212 membrane.Moreover, water-domain spacing and crystallinity of Nafion XL membrane, determined from small-and wide-angle X-ray scattering (SAXS/WAXS) experiments, are correlated with the measured properties to establish a structure/property relationship, and discussed within the context of composite materials. It is also found that (pre)conditioning of the membrane by heating in water at different temperatures could have significant impacts on its structure/property relationship, in particular, the mechanical stability and conductivity, which were related to morphological changes observed from microscopy 2 studies. The findings reported here not only provide a new dataset that can be used for PEFC performance and durability modeling but also benefit the efforts on developing composite ionconductive membranes. 1.Highlights  The composite Nafion XL membrane's structure/property relationship is investigated  Impact of pretreatment on membrane's transport and mechanical properties are shown  Membrane's composite morphology are revealed through TEM, SEM and SAXS/WAXS

show abstract

“…50 Further analyses of crossover based on the dilute solution approximation have been recently performed. 51,52 Models based on the resistor-and pore-network methodology 53 and concentrated solution theory [54][55][56][57] have also been developed to simulate the transport of species through the ion-exchange membranes.…”

Section: Mathematical Modelmentioning

confidence: 99%

In Situ Potential Distribution Measurement and Validated Model for All-Vanadium Redox Flow Battery

Gandomi

Aaron

Zawodzinski

et al. 2015

J. Electrochem. Soc.

100

View full text Add to dashboard Cite

An in situ, local potential measurement technique was further developed and applied to all-vanadium redox flow batteries to determine the potential distribution within multilayer electrodes of the battery. Micro-scale potential probes enabled in situ measurement of local potential in electrode layers between the cell flow field and membrane. The local redox potentials were recorded for different operating conditions and states of charges. To further analyze the behavior of potential distribution in the through-plane direction, a mathematical model was developed and the species distribution as well as the flux density of any individual component was modeled in terms of contributions from convective, diffusive and electrophoretic fluxes at each operating condition. Good agreement was achieved between the mathematical model prediction and experimental data with maximum error of 8%. Both mathematical simulation and experimental data confirmed the distribution of potential in the through plane direction as a function of discharge current density, predicting the lowest potential in a region close to the flow plate. Redox flow batteries have many benefits including energy efficiency, capital cost, and life cycle costs compared with other gridscale energy storage technologies.1 Multiple chemistries have been developed for redox flow batteries such as iron-chromium, 2 allvanadium, 3 bromine-polysulfide 4 and zinc-bromine. 5 Among these many chemistries, the all-vanadium redox flow battery (VRFB) has been studied in great detail and is relatively mature with several fullsize systems in operation around the world. The VRFB employs the V (I I )/V (I I I ) redox couple at the negative side and the V (I V )/V (V ) redox couple at the positive side, in the form of V O 2+ and V O + 2 . The kinetics associated with reduction and oxidation of vanadium species are known to be very complex 6,7 In this paper, the following simplified set of global half-reactions are adopted for the negative and positive electrodes.One advantage of VRFBs is that in utilizing the same element, vanadium, as active species in both negative and positive electrolytes, crossover of active species does not foul the electrolyte, and results only in decreased coulombic efficiency. Storage capacity can be regained through electrolyte rebalancing. The VRFB also has a wide operating temperature range from −5 • C to 50• C 8 and fast response (around 350 μs) for start-up and switching between charging and discharging processes, using a sulfuric and hydrochloric acid mixture. 9Cost is still the major barrier to VRFB commercialization. Zhang et al.10 estimated that the cell stack is one of the highest cost components with 31% of capital cost from a base case VRFB. One way to decrease the stack cost is to increase the power density of the VRFB during charge-discharge cycles, allowing for smaller stacks for the same power.11 In order to achieve high power density, the cells should operate at high current density with decreased polarization losses (activation, ohmic an...

show abstract

Resistor-Network Modeling of Ionic Conduction in Polymer Electrolytes

Cited by 49 publications

References 81 publications

Nanostructure/Swelling Relationships of Bulk and Thin‐Film PFSA Ionomers

Nanostructure/Swelling Relationships of Bulk and Thin‐Film PFSA Ionomers

Structure/property relationship of Nafion XL composite membranes

In Situ Potential Distribution Measurement and Validated Model for All-Vanadium Redox Flow Battery

Contact Info

Product

Resources

About