Advancements in the production of meltblown fibres

Henry

Pourdeyhimi

et al. 2020

Self Cite

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 cuttingedge meltblowing technologies, meltblown PVDF could become the separator in next-generation Li-ion batteries.

Section: ■ Introductionmentioning

confidence: 99%

Fabrication and Characterization of Meltblown Poly(vinylidene difluoride) Membranes

Henry

Pourdeyhimi

et al. 2020

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“…We used an experimental-grade PVDF Kynar resin RC 10,287 (Arkema, Inc). The resin has low molecular weight (MW) (15–100 kDa), a melt viscosity of 0.2 kP at 230 °C at a shear rate of 100 s –1 , and a 2.0 poly-dispersity index (PDI). ,, After drying the resin overnight at 70 °C, we prepared meltblown mats using a 1.2 m Reifenhauser-Reicofil Meltblown pilot line at the Nonwovens Institute at NC State University . Based on our previous work, , the temperatures of both the die and the impinging air jets were held at 240 °C and fibrous mats were fabricated at a basis weight (BW) of 40 g/m 2 with the following process variables (the designation M1, M2, and M3 are abbreviations for these conditions and referenced in the Results and Discussion section): M1.…”

Section: Methodsmentioning

confidence: 99%

Structure–Performance Relationships of Li-Ion Battery Fiber-Based Separators

Petrecca

Williams

et al. 2022

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.

“…The resin has a low molecular weight (15–100 kDa), melt viscosity at 230 °C of 20 Pa·s at a shear rate of 100 s –1 , and a 2.0 polydispersity index. Chain-transfer agents in a high level during polymerization were used to create a polymer with high melt strength and extensional viscosity, ideal for meltblowing. − …”

Section: Methodsmentioning

confidence: 99%

“…Among other polymers, polyvinylidene difluoride (PVDF) is a suitable candidate for battery separators due to the presence of C–F groups, which contribute to good chemical stability, low degree of crystallinity, and high polarity for an enhanced electrolyte wettability. − An advantageous manner to produce nonwoven PVDF separators is meltblowing, which is an established nonwoven process with high-volume manufacturing capability. To be melt-blowable, one desirable characteristic is that the polymer resin has a high melt-flow rate, but commercial PVDF resins did not possess this property until recently. − On the other hand, nonwoven PVDF from electrospinning has been widely studied as a battery separator . Electrospun PVDF has attracted the attention of the scientific community as a separator in Li-ion batteries − and filtration media. − Table summarizes reports on the use of PVDF in battery separators, and these studies are expanded upon below.…”

Section: Introductionmentioning

confidence: 99%

Meltblown Polyvinylidene Difluoride as a Li-Ion Battery Separator

Henry

Pourdeyhimi

et al. 2021

Self Cite

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.