@article{luiso_petrecca_williams_christopher_velev_pourdeyhimi_fedkiw_2022, title={Structure-Performance Relationships of Li-Ion Battery Fiber-Based Separators}, volume={4}, ISSN={["2637-6105"]}, url={https://doi.org/10.1021/acsapm.2c00216}, DOI={10.1021/acsapm.2c00216}, abstractNote={Lithium-ion battery separators are receiving increased consideration from the scientific community. Many research efforts trend toward creating high-performance fiber-based battery separators with a small and uniform pore size to maximize ionic conductivity and cell discharge capacity. Here, we show that not only the pore size but also the pore size distribution has an important effect on these electrochemical properties. In this work, we studied nonwoven membranes fabricated from a single polymer, poly(vinylidene fluoride) (PVDF), with different pore sizes and pore size distributions using three different techniques (meltblowing, electrospinning, and shear spinning). We evaluate their performance as separators in Li-ion cells. Although meltblowing is commonly employed to produce commercial microfibers/nanofibers, electrospinning has been studied mostly in the academic literature. Shear spinning is an emerging method to fabricate nanofibrous material where, for this study, the morphology of the resulting PVDF membranes may be controlled from fibrous-like to nano-sheet-like with subsequent effects on the electrochemical properties. We show that the smaller the pore size and the wider the pore size distribution, the higher are the electrolyte uptake and ionic conductivity of the mats, resulting in improved in-use discharge capacity and rate capability of Li/LiCoO2 cells.}, number={5}, journal={ACS APPLIED POLYMER MATERIALS}, publisher={American Chemical Society (ACS)}, author={Luiso, Salvatore and Petrecca, Michael J. and Williams, Austin H. and Christopher, Jerush and Velev, Orlin D. and Pourdeyhimi, Behnam and Fedkiw, Peter S.}, year={2022}, month={May}, pages={3676–3686} }
 @article{luiso_henry_pourdeyhimi_fedkiw_2021, title={Meltblown Polyvinylidene Difluoride as a Li-Ion Battery Separator}, volume={3}, ISSN={["2637-6105"]}, url={https://doi.org/10.1021/acsapm.1c00221}, DOI={10.1021/acsapm.1c00221}, abstractNote={Among the types of Li-ion battery separators, the benefits of nonwoven mats are high porosity with low mass and low average production cost. Nonwoven polyvinylidene difluoride (PVDF) shows promise as a separator because of its chemical and mechanical stability and good absorption of organic electrolytes used in Li-ion cells. We investigated the use of a melt-blowable PVDF (Kynar resin RC 10,287, Arkema, Inc.) to produce meltblown PVDF mats, with the objective of elucidating its properties as a separator in Li-ion batteries. Meltblown PVDF mats were fabricated with high quality on a 1.2 m wide Reicofil R4 meltblown pilot line and subsequently consolidated through thermal compaction in a hydraulic press. The resulting mats showed high homogeneity (low roping and fiber entanglements), an average pore size as small as 0.9 μm, and average fiber diameter as small as 1.4 μm, yielding a high surface area and electrolyte uptake. After thermally compacting the nonwoven mat, the thickness and pore size decrease along with electrolyte absorbance and ionic conductivity. The highest conductivity of the electrolyte-infused mat was ∼9.6 mS/cm (room temperature with 1 M LiPF6 in ethylene carbonate/dimethyl carbonate 1:1 w/w), and the first-cycle capacity of a Li/LiCoO2 cell containing the meltblown PVDF separators was 140 mA h/g. Here, we assessed meltblown PVDF as a Li-ion battery separator by studying its physical, chemical, and electrochemical properties.}, number={6}, journal={ACS APPLIED POLYMER MATERIALS}, publisher={American Chemical Society (ACS)}, author={Luiso, Salvatore and Henry, James J. and Pourdeyhimi, Behnam and Fedkiw, Peter S.}, year={2021}, month={Jun}, pages={3038–3048} }
 @article{luiso_williams_petrecca_roh_velev_fedkiw_2021, title={Poly(Vinylidene Difluoride) Soft Dendritic Colloids as Li-Ion Battery Separators}, volume={168}, ISSN={["1945-7111"]}, url={https://doi.org/10.1149/1945-7111/abdfa7}, DOI={10.1149/1945-7111/abdfa7}, abstractNote={As an alternative to Li-ion battery (LIB) microporous membrane separators that are typically comprised of polyolefins, other materials and separator morphologies may yield increased cell performance. Here, we present a new class of LIB separators comprising poly(vinylidene difluoride) (PVDF)-based and highly branched, colloidal polymer particulates, called soft dendritic colloids, that are produced by shear-driven polymer precipitation within a turbulent nonsolvent flow followed by filtration. We show the morphology of the resulting PVDF particulates may be varied from fibrous dendritic colloids to thin and highly porous sheet-like particles. The use of PVDF leads to low thermal shrinkage (5% at 90 °C) and high tensile strength (<0.7% offset at 1000 psi), while the high porosity (up to 80%) and high particle surface area are responsible for high conductivity (1.2 mS cm −1 ) and electrolyte uptake (325%), and good cell capacity (112 mAh g −1 in Li/LiCoO 2 cell) with <10% loss after 50 cycles. Because shear-driven precipitation with filtration is a facile and versatile process to make a new class of polymeric LIB separators, soft dendritic colloids are promising candidates as separators for next-generation batteries.}, number={2}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, publisher={The Electrochemical Society}, author={Luiso, Salvatore and Williams, Austin H. and Petrecca, Michael J. and Roh, Sangchul and Velev, Orlin D. and Fedkiw, Peter S.}, year={2021}, month={Feb} }
 @article{luiso_williams_velev_pourdeyhimi_fedkiw_2020, title={An Ideal Structure for Li-Ion Battery Separators}, volume={MA2020-02}, url={https://doi.org/10.1149/MA2020-02453792mtgabs}, DOI={10.1149/MA2020-02453792mtgabs}, abstractNote={Among all types of Li-ion battery (LIB) separators, fibrous mats have the advantage of low cost, low mass, and high porosity. Fibrous Poly(Vinylidene difluoride) (PVDF) shows promising results because of its stability and affinity for electrolytes commonly employed in Li-ion cells. Despite numerous studies published on LIB separators, none reports structure-property relationships for the identification of an ideal structure. We investigated the properties of a melt-blowable PVDF and produced meltblown PVDF mats in scale-up equipment with the objective of elucidating its performance as a LIB separator. We also present a new class of LIB separators, PVDF-based highly-branched, colloidal polymer particulates called soft dendritic colloids that are produced by shear-driven polymer precipitation within a highly turbulent nonsolvent flow, followed by filtration. We show that the morphology of the resulting PVDF particulates can be modulated from fibrous soft dendritic colloids (SDC) to thin and highly porous sheet-like particles. Through a scale-up system, we obtained high-quality meltblown PVDF with high homogeneity, low number of defects, an average fiber diameter of 1.4 μm, and pore size as low as 0.9 μm. Small fiber diameter provides high-surface area and high-electrolyte uptake. We show interactions of the meltblown PVDF with the electrolyte lead to a morphology change in the fibers. The highest ionic conductivity was ~ 9.6 mS/cm, and the first-cycle capacity was 140 mAh/g (Li/LiCoO 2 ). After melt-pressing, the thickness and pore size decrease, but the mats electrolyte absorbency and conductivity decrease commensurately. PVDF SDC separators show high porosity (up to 80%) and high particle surface area, which results in high conductivity (1.2 mS/cm), high-electrolyte uptake (325%), and high-cell capacity (112 mAh/g in Li/LiCoO 2 cell) with <10% loss after 50 cycles. Both processes yield separators with low thermal shrinkage (<5% at 90 ºC) and high tensile strength (<0.5% offset at 1000 psi), with the highest-performing separator possessing low average fiber diameter with a wide diameter distribution. Both meltblowing and shear-driven precipitation are facile and versatile processes for high-volume fabrication of LIB separators with one single polymer without necessarily requiring post-processing and with characteristics similar to commercially available battery separators. Our findings show that battery separators should be fabricated with a low pore size (<2 µm) but also with a wide pore distribution. When the strength and openness of the micropores are coupled with a dense net of nanopores, an ideal Li-ion battery separator is obtained. References: Luiso, S., Henry, J. J., Pourdeyhimi, B. & Fedkiw, P. S. (2020). Fabrication and Characterization of Meltblown Poly(vinylidene difluoride) Membranes. ACS Appl. Polym. Mater. , 2, 2849–2857. S. Roh, A. H. Williams, R. S. Bang, S. D. Stoyanov, and O. D. Velev (2019). Soft dendritic microparticles with unusual adhesion and structuring properties. Nature Materials , vol. 18, no. 12. pp. 1315–1320.}, number={45}, journal={ECS Meeting Abstracts}, publisher={The Electrochemical Society}, author={Luiso, Salvatore and Williams, Austin H and Velev, Orlin D. and Pourdeyhimi, Behnam and Fedkiw, Peter S.}, year={2020}, month={Nov}, pages={3792–3792} }
 @article{luiso_henry_pourdeyhimi_fedkiw_2020, title={Fabrication and Characterization of Meltblown Poly(vinylidene difluoride) Membranes}, volume={2}, ISSN={2637-6105 2637-6105}, url={http://dx.doi.org/10.1021/acsapm.0c00395}, DOI={10.1021/acsapm.0c00395}, abstractNote={The
meltblowing process may be employed to produce high volume
of nonwoven poly­(vinylidene difluoride) (PVDF) mats with fine fibers
that lead to small pores. Although significant research has been reported
on electrospinning of PVDF, there are no studies reported on the formation
and characterization of PVDF meltblown mats because of the technological
barriers associated with meltblowing the polymer. We investigated
the fundamental properties and characteristics of experimental-grade
melt-blowable PVDF (Kynar resin RC 10,287, Arkema, Inc.) with the
objective of elucidating the structure–property process relationships
of the meltblown mats. We have produced high-quality meltblown PVDF
mats with a low solid-volume fraction (as low as 22%) and an average
fiber diameter varying from 2 to 6 μm. The electrochemical resistance
and absorbance capacity (electrolyte uptake up to 200%) of meltblown
PVDF make it suitable for battery separator applications. We show
that interactions of the meltblown PVDF with the electrolyte lead
to a morphology change in the fibers and a 3% decrease in crystallinity.
Using cutting-edge meltblowing technologies, meltblown PVDF could
become the separator in next-generation Li-ion batteries.}, number={7}, journal={ACS Applied Polymer Materials}, publisher={American Chemical Society (ACS)}, author={Luiso, Salvatore and Henry, James J. and Pourdeyhimi, Behnam and Fedkiw, Peter S.}, year={2020}, month={Jun}, pages={2849–2857} }
 @article{luiso_fedkiw_2020, title={Lithium-ion battery separators: Recent developments and state of art}, volume={20}, ISSN={2451-9103}, url={http://dx.doi.org/10.1016/j.coelec.2020.05.011}, DOI={10.1016/j.coelec.2020.05.011}, abstractNote={Lithium-ion battery separators are receiving increased consideration from the scientific community. Single-layer and multilayer separators are well-established technologies, and the materials used span from polyolefins to blends and composites of fluorinated polymers. The addition of ceramic nanoparticles and separator coatings improves thermal and mechanical properties, as well as electrolyte uptake and ionic conductivity. The state-of-art separators are actively involved in the cell chemistry through specific functional groups on their surface. Among the numerous properties, safety features and long cycle life are high-priority requirements for next-generation lithium-ion batteries.}, journal={Current Opinion in Electrochemistry}, publisher={Elsevier BV}, author={Luiso, Salvatore and Fedkiw, Peter}, year={2020}, month={Apr}, pages={99–107} }
 @article{huang_sodano_leonard_luiso_fedkiw_2017, title={Cobalt-Doped Iron Sulfide as an Electrocatalyst for Hydrogen Evolution}, volume={164}, ISSN={["1945-7111"]}, DOI={10.1149/2.0761704jes}, abstractNote={Iron disulfide (FeS2) promises an earth-abundant, low-cost alternative to platinum group metals for the hydrogen evolution reaction (HER), but its performance is currently limited by reactivity of active sites and poor electrical conductivity. Here we employ Ketjenblack (KB) as a support to create an Fe-based electrocatalyst with high-electrical conductivity and maximal active sites. Moreover, a systematic study on the role of cobalt (Co) dopant was carried out. Electrochemical results show enhancements in HER activity of Co-doped FeS2 [FexCo1−xS2, atomic content of Fe (x) = 0.98 – 0.32] in comparison to un-doped FeS2 in acidic electrolyte (pH = 0). The overpotential necessary to drive a current density of 10 mA/cm2 is −0.150 V and only decreases by 1 mV after 500 cycles of a durability test (cycling the potential between 0.0 and −0.15 V), indicating a long-term durability in acidic environment. This work suggests that FexCo1−xS2 offers a viable approach to improve the activity and durability of transition metal-sulfide electrocatalysts. © The Author(s) 2017. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0761704jes] All rights reserved.}, number={4}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Huang, Sheng-Yang and Sodano, Daniel and Leonard, Thomas and Luiso, Salvatore and Fedkiw, Peter S.}, year={2017}, pages={F276–F282} }