Synthesis of Polymer Electrolytes Based on Poly(ethylene oxide) and an Anion-Stabilizing Hard Polymer for Enhancing Conductivity and Cation Transport

We have investigated a new methodology for improving the ionic conductivity and cation transport of polymer electrolytes by incorporating an anion-stabilizing hard polymer. A lamellar-forming poly(ethylene oxide-b-dithiooxamide) (PEO-b-PDTOA) block copolymer having enhanced ion conduction and mechanical strength, arising from PEO and PDTOA, respectively, was synthesized. Compared to a simple PEO/PDTOA blend, lithium salt-doped PEO-b-PDTOA exhibited significantly enhanced ionic conductivity, which is ascribed to efficient ion transport along the nanoscale PEO domains. Strikingly, by applying a dc polarization voltage, the inclusion of PDTOA afforded a high ratio of the steady state to the initial current flow of 0.67 for the PEO-b-PDTOA electrolytes, surpassing the value of 0.31 observed for conventional PEO-salt electrolytes. A key reason for achieving enhanced cation transport was the hydrogen bonding interactions between the thioamide moieties of PDTOA and the anions of lithium salts. This work provides fascinating experimental insights into the enhancement of cation transport of polymer electrolytes without chemically bonded negative charges and has implications for fast charging energy storage systems.