Addition of Zwitterions to Single-ion Conducting Ionomers*

Applications of polymeric materials in energy-related areas are severely hampered by their limited conductivity at room temperature. The continuing pursuit of maximizing their room-temperature conductivity has driven novel design of polymeric systems. Ion aggregates are believed to be one of the major causes that stymies the ion conduction, due to the decreased mobile ion density and slowed segmental motion. Recently, much attention was drawn on additives that increase the dielectric constant due to its significant role in promoting conduction of small mobile ions such as lithium. Zwitterions are promising candidates for this purpose, owning to a large molecular dipole from covalently bonded cation and anion. Here, we studied a series of imidazolium-sulfonate zwitterions that are used as additives in single-ion conducting ionomers. Significant increases in both dielectric constant and ionic conductivity are reported. This work highlights the significance of zwitterion for promoting the conductivity, which benefits their further applications in a wide range of polymers.