Nafion/Aquivion-Based Composite Lithium Ion Exchange Membranes for High Capacity Li-S Batteries

摘要

Lithiated Nafion (Li-Naf) and lithiated Aquivion (Li-Aqu) ion exchange membranes are applied as electrolyte and separator to prevent the polysulfide shuttle effect in LiS batteries. The production and characterization of Li-Naf, Li-Aqu, and their composites (2:1, 1:1, and 1:2; w/w) are carried out. The ion exchange capacity and polysulfide transition of the produced membranes are examined and structural characterizationes are conducted via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and field emission scanning electron microscopy (FESEM). CR~2032 half cells are assembled in order to perform electrochemical analysis. The electrochemical performances of the membranes are investigated by cyclic voltammetry, electrochemical impe- dance spectroscopy and galvanostatic charge-discharge tests. Due to the low equivalent weight of Aquivion, the ion exchange capacity and ionic conductivity of the membrane enhance with the increasing amount of Li-Aqu in the composite membrane. Because of the synergistic effect of Nafion and Aquivion, Li-Naf: Li-Aqu/1:2 composite offers 61.2% capacity retention and the best electrochemical discharge capacity of 826 mAhg~(-1) after 100 charge-discharge cycles. As a result, Nafion and Aquivion composite membranes can successfully inhibit the shuttle movement of negatively charged polysulfide species while allowing the transition of positively charged lithium ions for high performed LiS batteries.