Investigation of mechanical properties of polyvinyl chloride–polyethylene oxide (PVC–PEO) based polymer electrolytes for lithium polymer cells

Abstract

Polymer electrolytes composed of a blend of polyvinyl chloride–polyethylene oxide (PVC–PEO) as a host polymer, lithium triflate (LiCF 3SO 3) as a salt, mixture of ethylene carbonate (EC) and dibuthyl phthalate (DBP) as plasticizers and silica (SiO 2) as the nanocomposite filler were studied. Results suggest that PVC–PEO blending exhibits improved mechanical strength compared to that of pure PEO. The introduction of LiCF 3SO 3 changes the mechanical properties of PVC–PEO blends from hard and brittle to soft and tough. In PVC–PEO:LiCF 3SO 3 (70:30) system, the Young’s modulus value decreases from 5.30 × 10 −1 MPa to 4.78 × 10 −4 MPa and the elongation at peak value increases from 3.71 mm to 32.09 mm with the incorporation of DBP and EC. The deteriorated mechanical properties with the addition of plasticizers are overcome with the addition of SiO 2 as nanocomposite filler. In PVC–PEO–LiCF 3SO 3–DBP–EC system, the addition of 5% SiO 2 increases the Young’s modulus value from 4.78 × 10 −4 MPa to 1.51 × 10 −3 MPa. The improvement of the mechanical properties reveals greater dispersion of SiO 2 particles in PVC–PEO blend based polymer electrolytes. In practical lithium polymer cells, inorganic fillers are frequently added to improve the mechanical strength of the electrolyte films.