Ion transport properties in salt-doped polymer electrolytes*

Polymer electrolytes with high lithium-ion conductivity provide a route toward improved safety and performance of lithium-ion batteries. For instance, conventional Li salt-doped poly(ethylene oxide) (PEO) shows high conductivity while it suffers from a lower lithium-ion contribution to the conductivity (the lithium transport number, t+). Single-ion conductors (SICs) in which the anions are immobilized by tethering to the polymer backbone have a high lithium transport number while the conductivity is relatively low since lithium is the only mobile ion and strongly interacts with tethered anion. Here, we report polymer electrolytes by mixing bis(trifluoromethane sulfonyl)imides tethered polyacrylate(PA) with a high content of Li bis(trifluoromethane sulfonyl)imide (LiTFSI) salt. As a SIC, PA itself shows low conductivity but is capable of solubilizing very high quantities of salt (LiTFSI). As a result, LiTFSI-doped PA shows comparable or higher ionic conductivity than the industry benchmark PEO. In addition, the LiTFSI-doped PA shows a high transport number ( t+ > 0.5), indicating that the system is promising as a polymer electrolyte.