TFSI-Based Single-Ion Conducting Polymer Electrolytes for Solid State Batteries

The development of high performance ion conducting materials that are lightweight and flexible with improved safety are imperative for next generation energy storage technologies, including lithium (Li)-ion batteries, sodium (Na)-ion batteries, supercapacitors, fuel cells, flow batteries, and many others. High-performance solid-state polymer electrolytes have the potential to address various challenges in electrical energy storage devices if they can meet the requirements of (i) high ionic conductivity; (ii) sufficient mechanical strength; (iii) high transport number; and (iv) wide electrochemical stability window. However, dry polymer electrolytes lack sufficient ionic conductivity to meet cell power requirements. While improving ion conductivity of polymer electrolytes is generally a challenge due to a trade-off between ion conductivity and polymer segmental dynamics, mechanically robust single-ion conducting solid polymer electrolytes provide promise due to maintaining high transport number and enabling high conductance. This presentation will discuss our progress on the design of trifluoromethanesulfonimide (TFSI)-based single-ion conducting polymer electrolytes for Li- and Na- ion batteries, as well as other energy storage applications. Specifically, we have successfully synthesized TFSI-functionalized polynorbornene (PNB) derivatives. Due to the polyolefinic structure of PNB backbone, TFSI-PNBs form a new family of single-ion conducting polymers with particularly high mechanical and electrochemical stability. In addition, the ionic conductivity of TFSI-PNB is significantly higher (8 orders of magnitude) compared to other TFSI-based polymer electrolytes such as TFSI-polystyrene or TFSI-polymethacrylate. The structure-property relationships of ion conductivity, plasticization, mechanical and electrochemical properties as well as their cell performance will be discussed.