Transferring lithium ions in nanochannels: A PEO/Li⁺ solid polymer electrolyte design

A new category of crystalline polymer electrolyte prepared by the supramolecular self-assembly of polyethylene oxide (PEO), α-cyclodextrin (α-CD), and LiAsF₆ is reported. The polymer electrolyte consists of the nanochannels formed by α-CDs in which the PEO/Li ⁺ complexes are confined. The nanochannels formed by α-CD provide the pathway for the directional motion of Li⁺ ions and at the same time prevent the access of the anions by size exclusion, resulting in good separation of the Li⁺ ions and the anions. The conductivity of the reported material is 30 times higher than that of the comparable PEO/Li ⁺ complex crystal at room temperature. By using state-of-art solid-state NMR spectroscopy, the structure and dynamics of the material were investigated in detail. The dynamics of the Li⁺ ions was studied and correlated to the ionic conductivity of the material. A new category of crystalline polymer electrolyte has been prepared by the supramolecular self-assembly of PEO (see picture, black), α-cyclodextrin (α-CD, blue), and LiAsF₆. In this polymer electrolyte, the nanochannels formed by α-CD provide the pathway for the directional motion of Li ⁺ ions (colored spheres, 5 different environments) and at the same time prevent access of the anions by size exclusion, thereby resulting in good separation of the Li⁺ ions and the anions.