The anion effect in ternary electrolyte systems using poly(diallyldimethylammonium) and phosphonium-based ionic liquid with high lithium salt concentration

© 2018 Poly(dialyldimethylammonium) (PDADMA) is a popular host for ion gel or composite polymer electrolytes for lithium batteries. Novel ternary systems are synthesised in this work by mixing high concentrations of lithium salt (lithium bis(fluorosulfonyl)imide (LiFSI)) with trimethylisobutylphosphonium bis(fluorosulfonyl)imide ([P111i4FSI) and PDADMA FSI. The aim of this work is to provide a comparison of the FSI-system with NTf2-system. Phase behaviour, structure and transport properties of these ternary systems were investigated using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), electrochemical impedance spectroscopy (EIS), attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) and solid state nuclear magnetic resonance (solid-state NMR). A free standing flexible and transparent membrane is obtained with 60:40 wt% (Electrolyte (3.8 m LiFSI in P111i4FSI (LiFSI/IL)): PDADMA FSI), attaining a conductivity of 0.49 mS/cm at 40 °C with a Li+ transference number of 0.21 at 50 °C.