Dissociation of Lithium Salt in Block Copolymer

Transport properties of polymer electrolytes are the key information for battery design, especially with concentrated system, due to the complicated interactions between the components. Therefore, understanding the ion interaction between the elements would improve the comprehension of the complex transport behaviors of concentrated systems. In this study, the interaction between lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polystyrene (PS) - poly(ethylene oxide) (PEO) diblock copolymer was investigated using Fourier transform infrared (FTIR) spectroscopy and density functional theory (DFT) simulation. A systematic approach enabled the quantification of polymer swelling and validated the Beer-Lambert law by using the inert polymer block as a reference of the IR intensity. The spectral changes of the PEO and the anomeric effect identified via the simulation indicated PEO-Li⁺ coordination. This work showed how well-controlled spectroscopy experiments can be used for quantitative study of ion dissociation and interactions in concentrated and complicated electrolyte systems.