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

• Published in: Solid state ionics 2018-12, Vol.327, p.83-92
• Main Authors: Yunis, Ruhamah, Girard, Gaetan M.A., Wang, Xiaoen, Zhu, Haijin, Bhattacharyya, Aninda J., Howlett, Patrick, MacFarlane, Douglas R., Forsyth, Maria
• Format: Article
• Language: English
• Subjects: Batteries; Bis(fluorosulfonyl)imide; Chemical synthesis; Differential scanning calorimetry; Dynamic mechanical analysis; Electrochemical impedance spectroscopy; Electrolytes; Fourier transforms; Free-standing membrane; Gravimetric analysis; Ionic liquids; Lithium; Lithium batteries; Lithium-ion battery; NMR; Nuclear magnetic resonance; Poly(diallyldimethylammonium); Polymer; Polymers; Reflectance; Solid state; Ternary systems; Trimethylisobutylphosphonium
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2018.10.018

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. [Display omitted] •With the increasing electrolyte content from 40 to 70 wt%, the ternary FSI system changed from relatively robust membranes to a soft gel appearance.•A free standing transparent membrane with 60:40 wt% (FSI system) Electrolyte (3.8 m LiFSI in trimethylisobutylphosphonium bis(fluorosulfonyl)imide (P111i4FSI):Poly(diallyldimethylammonium) bis(fluorosulfonyl)imide (PDADMA FSI) has been prepared.•This 60:40 wt% (FSI system) ternary system has superior transport and electrochemical performance than mixed anion system.•With the increasing amount of electrolyte, a lower glass transition (Tg), high conductivity and high diffusivity of 1H, 19F and 7Li is observed, which also leads to a high transport of lithium.