Fabrication of co‐PVDF/modacrylic/SiO₂ nanofibrous membrane: Composite separator for safe and high performance lithium‐ion batteries

Abstract

Highly porous free‐standing co‐poly(vinylidene fluoride)/modacrylic/SiO2 nanofibrous membrane was developed using electrically‐assisted solution blow spinning method. The performance and the potential of the membrane as a lithium‐ion battery separator were investigated. The addition of modacrylic enhanced the solution spinnability that resulted in defect‐free membranes. Moreover, the presence of modacrylic enhanced the dimensional and thermal stabilities, while the addition of hydrophilic SiO2 nanoparticle enhanced both mechanical property and ionic conductivity. Combustion test results illustrated that the presence of modacrylic provide flame retarding property over a set of different polymeric‐based membranes. Electrochemical performance results showed that the developed membrane can increase the battery capacity compared with the commercial separator.

Solution Blow Spinning of the Benzimidazole-Containing Aramid Nanofibers for Separators of Lithium-Ion Batteries

“…The above demerits were diminished when PEO was introduced in the 2.0 wt % solution of HA. With a mass ratio of HA/PEO = 10/1, the zero-shear-rate viscosity of the solution sample of HA/PEO-10:1 was 5.38 × 10 3 mPa·s as shown in Figure S2a, just within the appropriate viscosity zone for SBS . The slope of the viscosity dropping with the increased shear rate also declined.…”

“…With a mass ratio of HA/PEO = 10/1, the zero-shear-rate viscosity of the solution sample of HA/PEO-10:1 was 5.38 × 10 3 mPa•s as shown in Figure S2a, just within the appropriate viscosity zone for SBS. 47 The slope of the viscosity dropping with the increased shear rate also declined. At a shear rate of 10 2 s −1 , the apparent viscosity of HA/PEO-10:1 was 1.22 × 10 3 mPa•s, locating just between that of HA-2.0 wt % dilute (3.67 × 10 2 mPa•s) and HA-4.2 wt % solution (4.72 × 10 3 mPa•s) without PEO incorporation as shown in Figure S2a.…”

“…With respect to spinning methods, the new emerging solution blow spinning (SBS) opens up the possibility for industrial scale production of nanofibers. , In SBS, a high velocity of airflow is used to shear the spinning solution, promote the solvent volatilization, and generate the fibers from ultrafine to nanosizes. − Compared with electrospinning, the advantage of SBS is its high yield, short preparation time, and high usage value. The high-voltage electrostatic field support is not required in the SBS process, which makes the method safer, and the complexity of the device is also reduced.…”

Recent Advances on Materials for Lithium-Ion Batteries

“…The ionic conduction of the separators is a direct consequence of their wettability and uptake, as the electrolyte plays a key role on the electrochemical properties of the system. In this regard, composite separators are intensively used, and different combinations of polymer matrix and specific fillers are being developed, such as, boehmite/polyacrylonitrile (BM/PAN) [219], 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) into polyacrylonitrile (PAN) [220], PVDF containing titanium dioxide (TiO 2 ) and graphene oxide (GO) [189], PVDF with 13X zeolite [195] and PVDF with modacrylic and SiO 2 [221], polyacrylonitrile (PAN)/helical carbon nanofibers(HCNFs)@PVDF/UiO-66 composite [222], cellulose/Poly (vinylidene fluoride-hexafluoropropylene) membrane with titania nanoparticles [202], polyimide (PI) with ZSM-5 zeolite as filler [190] and PVDF with titanium hydroxide (Ti(OH) x ) [223], polyethylene terephthalate (PET) combined with inorganic zirconia (ZrO 2 ) [224], silica-coated expanded polytetrafluoroethylene separator [225], poly(vinyl alcohol) (PVA) with ZrO 2 nanoparticles [226], poly(vinyl alcohol) (PVA) with submicron spindle-shaped CaCO 3 [227], poly(vinyl alcohol)/melamine composite nanofiber membrane containing LATP nanocrystals [228], and poly(m-phenylene isophthalamide) (PMIA) with SiO 2 nanoparticles [229], among others, mainly with the main focus on improving the electrochemical properties. In particular, separators based on PVDF coated with ZnO have been developed with higher ionic conductivity (2.261 mS•cm −1 ), high porosity (85.1%), favorable electrolyte wettability (352%), and lower interfacial impedance (220 Ω) [198].…”

The Role of Separator Thermal Stability in Safety Characteristics of Lithium-ion Batteries

“…Frontier organic separators made of polyimide, 10,20,21 polyphenylene sulfide, 22 polybenzimidazole, 23,24 polyester, 25 polydopamine, 26 poly(ether ether ketone), 27 and aramid 28 present high tortuosity and porosity that satisfy interfacial compatibilities and improved thermal stabilities by showing strong flame-retardant and anti-shrinkage properties. Moreover, separators with diverse doped nanoparticles and coating layers, such as ceramics of SiO 2 , [29][30][31][32][33] Al 2 O 3 , [34][35][36] Sb 2 O 3 , 37 AlOOH, 38 biomass of ethylcellulose, 39 zeolitic imidazolate framework 40,41 and vermiculite 42 are also practical strategies to reform their safety characteristics. These modifications can optimize contact angles of non-aqueous electrolyte droplets for better wettability with non-aqueous electrolytes, while suppressing the thermal shrinkage and deformation of the woven skeleton at high temperatures above 200 °C.…”