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In this work, the physical, transport and electrochemical properties of various electrolytic solutions containing the 1-propyl-1-methylpyrrolidinium bis[fluorosulfonyl]imide ([C3C1pyr][FSI]) mixed with the lithium bis[(trifluoromethyl)sulfonyl]imide (Li[TFSI]) over a wide range of compositions are reported as a function of temperature at atmospheric pressure. First, the ionicity, lithium transference number, and transport properties (viscosity and conductivity) as well as the volumetric properties (density and molar volume) were determined as a function of lithium salt concentration from 293 to 343 K. Second, the self-diffusion coefficient of each ion in solution was measured by nuclear magnetic resonance (NMR) spectroscopy with pulsed field gradients (PFG). Moreover, an analysis of the collected nuclear Overhauser effect (NOE) data along with ab initio and COSMO-RS calculations was conducted to depict intra and intermolecular neighbouring within the electrolytic mixtures. Based on this analysis, and as expected, all activation energies increase with the Li[TFSI] concentration in solution, and all activation energies were determined from the self-diffusion data for all ions. Interestingly, regardless of the composition in solution, these activation energies were similar, except for those determined for the [FSI]− anion. The activation energy of [FSI]− self-diffusion relatively decreases compared to the other ions as the lithium salt concentration increases. Furthermore, the lithium transference was strongly affected by the lithium salt concentration, reaching an optimal value and an ionicity of approximately 50 % at a molality close to 0.75 mol · kg−1. Finally, these electrolytes were used in lithium-ion batteries (i.e. Li/NMC and LTO/NMC), demonstrating a clear relationship between the electrolyte formulation, its transport parameters and battery performance.

We report the preparation of solvent-free polymer electrolytes via a free radical copolymerization of methacrylate-based oligomers in the presence of LiTFSI. Properties of the electrolytes were then studied as a function of their compositions. Furthermore, the incorporation of a room temperature ionic liquid (RTIL) into the copolymer electrolyte to form a gel polymer electrolyte (GPE) is also reported. The high miscibility of the oligomers in the RTIL enables the preparation of the GPEs by a one-step method using the in situ free radical copolymerization. The GPEs have a dry aspect and are free-standing; they also exhibit an ionic conductivity close to 4 × 10–4 S cm–1 at 25 °C and to 1.45 × 10–3 S cm–1 at 65 °C. Furthermore, the GPEs have been used as electrolytes in a Li/Electrolyte/LiNi1/3Mn1/3Co1/3O2 battery. Specific capacities of 79 mAh g–1 and 118 mAh g–1 were reached at the C/5 and C/10 rate, respectively.

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