Effect of Li⁺ Affinity on Ionic Conductivities in Melt-Blended Nitrile Rubber/Polyether

Substituting flammable liquid electrolytes with solid polymer electrolytes (SPEs) presents a serious challenge in improving the safety of lithium-ion batteries. Even though SPEs are a safer choice, their ionic transport properties are still lower than those of their liquid counterparts (<10–4 S·cm–1 at room temperature). Here, we report the preparation of a blend of polymers used as SPEs in lithium-ion batteries. Composed of an elastomer, hydrogenated nitrile butadiene rubber (HNBR), and poly(ethylene oxide) (PEO), this blend combines the high conductivity of PEO and the stable properties of HNBR and shows better flexibility than a pristine PEO SPE. It is worth noting that the addition of HNBR, coupled with the intrinsic LiTFSI salt concentration, also reduces the crystallinity and melting temperature of typical PEO-LiTFSI SPEs; this also explains the higher ionic conductivity at low temperature (1.18 × 10–4 S·cm–1 at 40 °C). Given these initial results, we may conclude that this polymer blend is a promising candidate as an SPE for all solid-state lithium-ion batteries.