Silica Nanowires Reinforced with Poly(vinylidene fluoride‐co‐hexafluoropropylene): Separator for High‐Performance Lithium Batteries

Abstract

Separators are key components that physically separate and chemically connect the anode and cathode to guarantee the safety and cycle stability of batteries. Herein, based on the building concept of a bird's nest, we have developed separators comprising SiO 2 nanowires reinforced with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP). In particular, the hybrid separators with 39% of PVDF-HFP exhibit much enhanced tensile strength, Young's moduli, flexibility, and elongation as a result of a strong crosslink effect, compared to bare SiO 2 nanowire separator, while yet maintaining excellent electrolyte wettability, high ionic conductivity, and wide electrochemical window. Moreover, the hybrid separators also demonstrate excellent thermal stability and dendrite suppression capability. Lithium metal batteries assembled using the hybrid separators with LiFePO 4 as the cathode achieve excellent rate performance and cyclic stability. The discharge capacities attained at a current density equivalent to 0.2 C and 2 C rate are 157 and 126 mAh g À 1 , respectively. A capacity of 99 mAh g À 1 is still maintained at 2 C rate after 500 cycles. This study illuminates SiO 2 nanowires reinforced with PVDF-HFP as promising separators for high-energy, high-power and safe lithium batteries.

Mechanically Robust and Safe Separators Based on Inorganic Nanofibers for Lithium-Ion Batteries

“…When the additional amount of LP was 10 wt %, the maximum tensile strength of the composite separator reached 16.28 MPa, which is about 10 times higher than the original HAP NWs separator, and about 1.7 times higher than that of commercial PP separators (9.49 MPa, Figure S8). Compared with the reported separators (Figure c), ,,,,− the composite BHLP separator has the highest tensile strength, demonstrating novel mechanical strength. In addition, BHLP separators have a lower thickness than the most reported ceramic-based separators, indicating that such a unique composite separator is expected to meet the requirements of industrial production and safe operation.…”

“…Among the reported ceramic separators, the creation of elongated ceramic nanowires and simple composites with organic materials to boost the mechanical strength of ceramic separators has aroused much interest. Du et al , successfully prepared SiO 2 nanowires with diameters of 50 nm and lengths up to 40 μm by pickling and dispersing asbestos. The tensile strength of the composite separator with poly vinylidene fluoride-hexafluoropropylene (PVDF-HFP) binder reaches 6.3 MPa, which is approximately 3.5 times that of pure SiO 2 nanowire separators.…”

Advances in Nanofibrous Materials for Stable Lithium-Metal Anodes

“…Du and co-workers fabricated a composite separator cross-linked by silica nanowires and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), of which SiO 2 accounted for up to 61%, and the separator exhibited high thermal stability and dendrite inhibition. 138 In short, researchers have made significant progress for fabricating nanofiber separators, which have broad application prospects in LMBs. Compared with traditional polyolefin separators, nanofiber separators exhibit interconnected porous structures, which are beneficial to improve porosity, liquid retention, and ion transport rate.…”

“…The lithium-sulfur batteries with Z-PMIA separators exhibited stable cycling performance at 80 °C (Figure h). Du and co-workers fabricated a composite separator cross-linked by silica nanowires and poly­(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP), of which SiO 2 accounted for up to 61%, and the separator exhibited high thermal stability and dendrite inhibition …”

Clay‐Originated Two‐Dimensional Holey Silica Separator for Dendrite‐Free Lithium Metal Anode

“…[36][37][38] Benefiting from the excellent high-temperature resistance and high polarity, SiO 2 has been widely used as the coating materials. [39] Creatively, Goodenough et al [40] directly spray-coated SiO 2 nanoparticles on the surface of LiCoO 2 (LCO) cathode to serve as the separator. The Li//LCO battery showed comparable cycle performance to that using a commercial separator under small volume of liquid electrolyte.…”