Superionic Li-ion Transport in a Single-Ion Conducting Polymer Blend Electrolyte

Single-ion conducting polymers (SICs) are promising candidates for the next generation of safer polymer electrolytes, due to their stability and high transference number. However, the conductivity in SICs is often limited by the mobility of the polymer backbone due to the ionic coupling. We present polymer blend electrolytes, consisting of a new single Li-ion conducting polymer blended with poly(ethylene oxide) (PEO). Dielectric relaxation spectroscopy is used to probe the ion transport properties and segmental dynamics of these systems and X-ray scattering is used to evaluate the morphology. The PEO associates with the ionic aggregates of the SIC, forming a miscible blend with pathways that promote ion transport. At high PEO content, ionic conductivity greater than 10^-5 S/cm and 10^-4 S/cm is achieved at 90°C and 130°C, respectively. A comparison of conductivity and polymer relaxation times shows that the high PEO content blends exhibit superionic transport, in which there is some decoupling of the Li-ion from the backbone. This superionic transport is not commonly found in single Li-ion conductors at temperatures with a mobile polymer, and thus this work presents a critical step for establishing design rules of superionic transport in SICs.