Thermal and Ion Transport Properties in Salt-Containing POEM/PEO Polymer Electrolyte Blends

The pursuit of new electrolytes for lithium batteries to create the safer and more dense forms of energy storage that are necessary for the implementation and increasing demand for electric vehicles, renewable energy systems, and personal electronics. One solution to this is the development of solid polymer electrolytes, which would allow for the creation of safe and energy dense lithium batteries. Poly(ethylene oxide), PEO, has been studied extensively as a solid polymer electrolyte for rechargeable lithium batteries, but performs poorly at low temperatures due to its semicrystalline nature. To remedy this, we blend PEO with an amorphous, conductive, polymer, poly(oligo ethylene oxide methacrylate) (POEM). We have created a matrix of data that allows for exploration of the relationship between polymer structure, salt concentrations, and the physical, thermal, and electrochemical properties of these blends in order to understand how the presence of EO-containing side chains impact system dynamics and increase conductivity. Using differential scanning calorimetry (DSC) and electrical impedance spectroscopy (EIS), we have observed deviations in glass transition temperatures from predicted values as well as increased conductivity as compared to PEO electrolytes in several of the polymer blend electrolytes. We further investigate and explain the mechanisms behind unexpected glass transition temperatures and conductivity behavior and their relationships with POEM size and side chain length.