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

Polymer electrolytes composed of a blend of polyvinyl chloride-polyethylene oxide (PVC-PEO) as a host polymer, lithium triflate (LiCF₃SO₃) as a salt, mixture of ethylene carbonate (EC) and dibuthyl phthalate (DBP) as plasticizers and silica (SiO₂) 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 LiCF₃SO₃ changes the mechanical properties of PVC-PEO blends from hard and brittle to soft and tough. In PVC-PEO:LiCF₃SO₃ (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 SiO₂ as nanocomposite filler. In PVC-PEO-LiCF₃SO₃-DBP-EC system, the addition of 5% SiO₂ 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 SiO₂ 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.