Physical and electrochemical chattels of phosphonium ionic liquid-based solid and gel-polymer electrolyte for lithium secondary batteries

摘要

In this work, a methodical study on the influence of ionic conductivity on polymer electrolyte with different weight percentages of ionic liquid and plas-ticizers had been investigated in detail. Solution casting method has been employed for preparing polymer electrolyte (PE) blend having poly(vinyli-denefluoride-co-hexafluoropropylene) P(VdF-co-HFP) as polymer, trihexylte-tradecylphosphonium bis(trifluoromethylsulfonyl) amide [P_(14,6,6,6)][Tf_2N] as ionic liquid and ethylene carbonate (EC) as well as propylene carbonate (PC) in 1: 1 ratio as plasticizers. The polymer electrolyte has been found out stable up to 450 °C, as measured from Thermal gravimetric analysis (TGA). Impedance spectral analysis reveals that the ionic conductivity of SPEs is 3.209 × 10~(-6) S/cm at 303 K with 25 wt% of ionic liquid. The addition of plasticizers (EC + PC (60 wt%)) results in two orders of magnitude of higher ionic conductivity (3.40 × 10~(-4) S/cm at 303 K), than that of SPEs. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) are performed to study the physico-chemical characteristics of polymer electrolytes. Electrochemical stability, potential window and discharge characteristics of the coin cell containing the electrolytes and LiFePO_4 electrode were investigated using linear and cyclic voltammetry.