Helical Covalent Polymers with Unidirectional Ion Channels as Single Lithium-Ion Conducting Electrolytes

Single-ion conducting polymer electrolytes have attracted great attention as safe alternatives to liquid electrolytes in high energy density lithium-ion batteries. Herein, we report the first example of a crystalline anionic helical polymer as a single lithium-ion conducting solid polymer electrolyte (SPE). Single-crystal X-ray analysis shows that the polymer folds into densely packed double helices, with bundles of unidirectional negatively charged channels formed that can facilitate lithium-ion transportation. Such a helical covalent polymer (HCP) exhibits excellent room temperature lithium-ion conductivity (1.2 x 10(-3 )S.cm(-1)) in the absence of external lithium salts, a high transference number (0.84), low activation energy (0.14 eV), and a wide electrochemical stability window (0.2-5 V). We found that nonflammable, nonvolatile ionic liquid can serve as a solvating medium and excellent conductivity enhancer (>1000 times increase). These ion-conducting properties are comparable to the best polyethylene oxide-based polymer electrolytes mixed with lithium salts. Finally, we show that the solvated HCP SPE enables the reversible cycling of an all-solid-state cell prepared with a high-voltage NMC 811 cathode. Our study opens up new possibilities for developing next-generation high-performance solid-state electrolytes. [GRAPHICS] .

Automated summary

This study presents a crystalline anionic helical polymer as a single lithium-ion conducting solid polymer electrolyte, demonstrating excellent ion-conducting properties suitable for high-energy density lithium-ion batteries. By using a nonvolatile ionic liquid as a solvating medium and conductivity enhancer, conductivity can be greatly increased. The findings open up new possibilities for the development of next-generation high-performance solid-state electrolytes.