Synthesis and Characterization of Network Type Single Ion Conductors

New single ion conductors were synthesized by grafting the allyl group-containing lithium salt, lithium bis(allylmalonato)borate (LiBAMB), onto allyl group-containing comb-branch polyacrylate or polymethacrylate ethers by means of hydrosilylation. The highest ambient temperature conductivity of 3.5 × 10-7 S cm-1 was obtained for a polyacrylate ether-based single ion conductor containing eight EO units in the side chain and five EO units in the cross-linking side chain, to which the anion was fixed with a salt concentration of EO/Li = 20. For polyacrylate ether-based single ion conductors, an increase of chain length in both side chains and cross-linking anion chains favors an increase of ionic conductivity. The addition of 50 wt % EC/DMC (1/1, wt/wt) increased the ionic conductivity by more than 2 orders of magnitude due to both the increase in ionic mobility from the liquid phase and the increase in the concentration of free ions from the high dielectric constant of the solvent. The preliminary Li/Li cycling profiles of dry polyacrylate- and polymethacrylate ether-based single ion conductors are encouraging as almost no concentration polarization or relaxation was observed. The observed increase in cell potential with cycling is apparently due to an increase in the interfacial impedance associated with the SEI layer, and the cell failure is accompanied by the decomposition of the ester bond of the polyacrylate backbone.