Electro-Spun Poly(vinylidene fluoride) Nanofiber Web as Separator for Lithium Ion Batteries: Effect of Pore Structure and Thickness

Abstract

Electro-spun nanofiber web is highly attractive as a separator for lithium ion batteries because of its high electrical properties. In moving toward wider battery applications of the nanofiber separators, a deeper understanding on the structure and property relationship is highly meaningful. In this regard, we prepared electro-spun poly(vinylidene fluoride) (PVdF) webs with various thicknesses (10.5~100 µm) and investigated their structures and electrochemical performances. As the thickness of the web is decreased, a decrease of porosity and an increase of pore size are resulted in. For the 10.5 µm-thick separator, a minor short-circuit was detected, stressing the importance of reducing pore-size on prevention of short-circuit. However, above the thickness of 21 µm, well-connected, submicron-sized pores are generated, and, with lowering the separator thickness, discharge capacity and rate capability are enhanced owing to the lowered area-specific resistance.

Towards separator safety of lithium-ion batteries: a review

“…A thinner separator is conducive to lower electrochemical impedance and high lithium ion migration number. 27,28 Therefore, a thinner separator is ideal on the premise of ensuring battery safety. The progress in mechanical strength of thick separators sacrifices space for active materials and reduces the energy density.…”

A Light-Thin Chitosan Nanofiber Separator for High-Performance Lithium-Ion Batteries

“…Due to the demand for high-energy-density LIBs, there is a trend to pursue thinner and lighter separators [18]. Reducing the separator thickness can increase the porosity of the separator and also shorten the migration path of ions, thus decreasing the internal resistance [19]. Horvath et al [20] reported a semiempirical equation which showed that energy density was lightly improved by adjusting the separator volume.…”

A high-strength PPESK/PVDF fibrous membrane prepared by coaxial electrospinning for lithium-ion battery separator

“…12,13 Furthermore, the fibrous membrane exhibits excellent wettability to liquid electrolyte because of the extensive choice of high polar polymers, which greatly improves the electrochemical property of lithium-ion battery. To date, a large number of polymers including polyvinyli-denefluoride (PVDF), 14,15 polyacrylonitrile (PAN), 16 poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), 17 –19 poly (methyl methacrylate) (PMMA), 20 polyvinyl acetate (PVA), 21 polyvinyl chloride (PVC), 22 polyethylene terephthalate (PET), 23 polyimide (PI), 24,25 nylon 6,6, 26 and cellulose 27,28 have been fabricated as lithium-ion battery separators using the electrospinning technique. Generally, the separator needs to be mechanically strong, so that it could withstand the tensile stress in the process of the winding operation during battery assembly.…”