Nanofiller-based novel hybrid composite membranes for high-capacity lithium-sulfur batteries

Herein, Al2O3 nanofiller-reinforced lithiated Nafion:Aquivion hybrid composite ion-exchange membranes have been produced by mixing lithiated Nafion and Aquivion ionomers. After the electrochemical tests, the Li-Naf : Li-Aqu/1 : 2 compound, which offers the best electrochemical performance, was selected. Lithiated hybrid composite membranes were obtained by reinforcing Al2O3 nanofillers at different rates to this composition. The ion exchange capacity, polysulfide transition and solvent uptake of the obtained membranes were investigated and the structural characterizations were applied by tensile test, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and membrane morphology was examined with Field Emission Scanning Electron Microscopy (FESEM). For performing the electrochemical tests, CR2032 half cells were designed. Electrochemical characterizations of the produced membranes were carried out by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), and galvanostatic charge-discharge tests. The best electrochemical performance was achieved with 868 mAhg−1 discharge capacity and 63.8 % capacity retention when Li-Naf : Li-Aqu/1 : 2 composition was reinforced with 1 % Al2O3 nanofiller. As a result, lithiated hybrid composite ion exchange membranes could prevent the shuttle effect of polysulfides while enabling the passing of Li ions for high-performance Li−S batteries

Nafion/aquivion-based composite lithium ion exchange membranes for high capacity Li-S batteries

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 Li−S 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 characterizations are conducted via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and field emission scanning electron microscopy (FESEM). CR2032 half cells are assembled in order to perform electrochemical analysis. The electrochemical performances of the membranes are investigated by cyclic voltammetry, electrochemical impedance 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 Li−S batteries