Probing the Fast Lithium-Ion Transport in Small-Molecule Solid Polymer Electrolytes by Solid-State NMR

Low-molecular-weight poly(ethylene oxides) (PEOs) were used in the synthesis of cyclodextrin (CD)-based solid polymer electrolytes to reduce the coordination strength between the Li + ions and the ligands and facilitate lithium-ion transport. The produced samples demonstrated fast dynamics of the Li + species dissociated from the polymer chains, which is considered to play a key role in fast lithium-ion transport. As revealed from 1 H and 7 Li high-resolution NMR, choosing a low-molecular-weight PEO chain improved the mobility and, by increasing the temperature, the amount of mobile Li + species was significantly increased in the samples. Enhancement (3 orders of magnitude) in the ionic conductivity of the samples was achieved. This study provides insight into fast Li + ion transport in CD PEO/Li + crystals and significantly facilitates the ionic conduction enhancement of tunnel-like CD-based polymer electrolytes.