Characterization of SEO/LiTFSI Electrolytes by Electrochemistry and X-ray Scattering at High Salt Concentrations

Polymer electrolytes have been studied extensively as a non-flammable alternative to commonly used liquid electrolyte in rechargeable lithium metal anode batteries. Polystyrene-block-poly(ethylene oxide) (SEO)/Lithinum bis(trifluoromethanesulfonyl)imide (LiTFSI) is a well studied and ideal choice making use of the polystyrene block to provide structural rigidity while the poly(ethylene oxide) block functions well as a charge carrier. Presented is a full electrochemical characterization of this system in the concentration range of r = 0.01 to r = 0.50. Notably, the system experiences a steep drop in the maximum applicable current before potential diverges, or limiting current, between the concentrations of r = 0.20 and r = 0.25. The limiting current then plateaus between concentrations of r = 0.25 and r = 0.50. Here we aim to explain this behavior using small angle x-ray scattering (SAXS) to probe morphology changes and wide angle x-ray scattering (WAXS) to study crystallization behavior surrounding this drop in limiting current.