The Study Of Performance And Preparation Of PVDF As Separator For Lithium Ion Battery And Untifouling Membrane

The preparation of polymer electrolyte membrane and antifouling membrane with high quality is one of the most efficient methods to improvement electrochemical and antifouling characteristics of the membrane. In this paper, the Polyvinylidene Fluoride(PVDF) and Polyacrylonitrile(PAN) polymer electrolyte and antifouling membranes were prepared by L-S phase inversion and the effect of preparation methods and additives(GO, Si O2 and GO-Si O2)on membrane characteristics was investigated. The results show that:Firstly, PVDF/PAN/Si O2 polymer electrolyte membranes based on non-woven fabrics were prepared via introducing a chemical reaction into Loeb- Sourirajan(L-S) phase inversion process. It was found that physical properties(porosity, electrolyte uptake and ionic conductivity) and electrochemical properties were obviously improved. A favorable membrane structure with fully connective porous and uniform pore size distribution was obtained. The effects of PVDF/PAN weight ratio on the morphology, crystallinity, porosity and electrochemical performances of membranes were studied. The optimized PVDF/PAN(70/30 w/w)(designated as Mpc30) polymer electrolyte membrane delivered excellent electrolyte uptake of 246.8% and the highest ionic conductivity of 3.32 × 10-3 S /cm with electrochemical stability up to 5.0 V(vs. Li/Li+). In terms of cell performance, the Li/Mpc30 polymer electrolyte/Li Fe PO4 battery exhibited satisfactory electrochemical properties including high discharge capacity of 149 m Ah/g at 0.2 C-rate and good discharge performance at different current densities.Secondly, the synthesized Graphene Oxide–Silica(GO-Si O2) nanocomposite was prepared by the hydrolysis of Tetraethoxysilane(TEOS) in the mixture solution of ethanol and NH3·H2O with the presence of GO nanosheets suspension. Then the novel improved antifouling hybrid PVDF microfiltration membrane doping with GO-Si O2 nanocomposite was fabricated by the non-solvent induced phase separation(NIPS) method, the permeability and flux recovery ratio of membranes increases with increasing loading amounts of GO-Si O2 and PVP additive to maximum before falling back a low value. In addition, the morphology, hydrophilicity, permeation and antifouling performances of membranes were improved by doping with different nanoparticles(GO, Si O2 and GO-Si O2). Especially, incorporation of GO-Si O2 nanocomposite with membrane was shown to have more uniformly pores size distribution and asymmetric structure with improved porosity. The optimized PVDF/GO-Si O2 membrane achieved the highest pure water flux(850 L/(m2·h) and flux recovery ratio(62%) when the content of GO-Si O2 is 0.5 wt. %(based on the weight of PVDF) and PVP is 1 wt. %(in the casting solution). This membrane also exhibited the good hydrophilicity(contact angle of 68.3o), the lowest irreversible fouling ratio(37.4%) and best satisfactory antifouling stability in the long term operation.