Coupling particle ordering and spherulite growth in mixed molecular weight poly(ethylene oxide) solid state electrolytes

The transition to a carbon neutral society is dependent on the growing use of renewable electrical energy, made possible by electrochemical energy storage devices, such as batteries. Currently most of these needs are met by Lithium-ion batteries (LIBs), however, decades of optimization have resulted in plateauing LIB performances with restrictions on charge rate, energy density and power. Solid state electrolytes (SSE) with high ion conductivity solve the issue of flammability and can mitigate dendrite growth, permitting greater energy density devices with less restricted operating conditions. Organic solid electrolytes based on polymers such as poly(ethylene oxide) (PEO) have a high donor number for Li ions and are spaced at a favourable distance to promote ion hopping, achieve suitable electrode contact and benefit from simple processability. We have recently revealed significant conductivity optimisation of PEO based SSE by mixing select molecular weight (MW) PEO with desired ratio, evidenced by spherulite morphology. Investigation of these structures across the nano- to macro- scale is required to inform preparation parameters for PEO based SSE.