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In this study, we experimentally measure the viscosity, η, and ionic conductivity, σ, of 1 mol kg−1 LiPF6 dissolved in a binary solvent of ethylene carbonate (EC) and propylene carbonate (PC) by varying the EC content from 0 to 60 vol%. Replacing EC with PC does not significantly influence on the mechanism of flow and ionic conduction. The state of solvent solvating to Li+ is analyzed using Raman spectra and 13C-NMR; the quantitative analysis suggests that the preference of EC in the Li+ solvation shell is almost similar to that of PC. The diffusion coefficient, D, of each species, Li+, PF6−, EC, and PC, is determined by pulse-gradient spin-echo NMR. In the electrolyte system dealt in this study, the molar conductivity is dominated by only the D of the charge carriers. The hydrodynamic Stokes radius of all constituent species is expressed in terms of D and η using the Stokes–Einstein relation. As for coordinated-Li+, a comparison between the Stokes radius and the van der Waals radius or the radius considering the free volume suggests that Li+ diffuses while dragging not only a coordination shell that can be spectroscopically detected but also an outer shell that binds loosely to Li+.

Some of the Benzimidazole-linked polymers (BILPs) are a class of porous organic polymers that have high porosities, large specific surface areas, and high thermal and chemical stability. Owing to these properties, BILPs can be used in various applications including solid electrolytes for renewable energy utilization. In this study, we carried out the boran-modification of a kind of BILPs, in order to increase the Li ion conductivity by decreases the interaction between lithium ions and the anion backbone. The resulting B-TFB-HAB-BILP materials have an ionic conductivity of 2.9 × 10−6 S cm−1 at 30 °C, which increases to 1.4 × 10−4 S cm−1 at room temperature with the addition of the ionic liquid, PP13[TFSA]. This can be attributed to the suppression of resistance at the grain boundary. A coin cell with an organic cathode active material, B-TFB-HAB-BILP/PP13[TFSA] as the quasi-solid electrolyte, and Li foil as the anode exhibited an initial discharge capacity of 223 mAh g−1 (76 % of theoretical capacity). Our study can aid in the realization of organic rechargeable batteries with high gravimetric energy density.