Functionalized cellulose as quasi single-ion conductors in polymer electrolyte for all-solid–state Li/Na and Li S batteries

Solid polymer electrolytes (SPEs) with new functionalized ethyl cellulose bearing a lithium/sodium fluorosulfonylimide group (Ethyl cellulose-LiFSI/NaFSI) is proposed as quasi single ion (Li+/Na+) conducting polymer electrolyte for all-solid-state lithium and sodium batteries. The degree of ethyl cellulose functionalization by anion of lithium and sodium salt measured by elemental analysis was 48 and 53%, respectively. The complex of Li(FSI-ethyl cellulose)/PEO exhibits a Li-ion transference number of TLi+ = 0.9, and a Na ion transference number of TNa+ = 0.6 for Na(FSI-ethyl cellulose),which are much higher than those reported for ambipolar LiFSI or NaFSI/PEO SPEs under the same measurement conditions. The generated SPEs showed a high electrochemical and mechanical stability as well as a practical ionic conductivity value of ~10−4 S·cm−1 at 80 °C. All solid-state lithium, sodium and Li/Sulfur cells cycled with quasi single ion conducting hybrid SPE exhibit reversible cycling and good performance at 70 °C, making them promising, environmentally benign and cost-effective candidates for use in advanced energy storage systems.