Effect of Interfaces on the Segmental Dynamics of Polymer Electrolyte in Lithium Ion Batteries*

A polymer electrolyte consisting of a polymer host such as poly(ethylene oxide) (PEO) and a lithium salt may be used in solid-state lithium ion batteries as the electrolyte layer between the battery electrodes or as the catholyte in the battery cathode. In a solid-state battery, the polymer electrolyte may face many interfaces, as ceramic fillers being added to the electrolyte layer and as a catholyte being blended with the active cathode material. The segmental mobility of the polymer electrolyte determines its ion transport rate. In this work we use quasi-elastic neutron scattering (QENS) to examine the presence of interfaces on the segmental mobility of polymer electrolytes. Two examples are investigated. In the first example the segmental dynamics of a composite electrolyte consisting of a polymer electrolyte and ceramic fillers is discussed. In the second example the effect of the cathode active material on the segmental dynamics of the polymer electrolyte in a composite cathode is investigated. These results shed light on strategies to synthesize interfaces for optimized polymer electrolyte performance in a lithium ion battery.