Enhancement of Li Ion Conductivity by Electrospun Polymer Fibers and Direct Fabrication of Solvent-Free Separator Membranes for Li Ion Batteries

Abstract

Poly(ethylene oxide) (PEO)-based polymer fibers, containing different amounts of the conductive salt LiBF and the plasticizer succinonitrile, were prepared by an electrospinning process. This process resulted in fiber membranes of several square centimeters area and an overall thickness of ∼100 μm. All membranes are characterized by scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, impedance spectroscopy, cyclic voltammetry (CV), and solid-state NMR spectroscopy, to evaluate the influence of the preparation process and the composition on the conductivity of the materials. Impedance spectroscopy was used to measure the conductivities and activation barriers for the different membranes. The highest conductivity of 2 × 10 S/cm at room temperature and 9 × 10 S/cm at 328 K is reached for a PEO/SN/LiBF (36:8:1) membrane, featuring an activation energy of 31 kJ/mol. Li mobilities, as deduced from the evaluation of the temperature dependence of the Li NMR line width and the overall electrochemical performance, are found to be distinctively superior to nonspun samples, synthesized via conventional solution casting. The same trend was found for the conductivities. NMR spectroscopy clearly substantiated that the mobility of the PEO segments drastically increases with the addition of succinonitrile pushing the conductivity to reasonable high values. In CV experiments the reversible Li transport through the dry membrane was evaluated and proved. This study shows that electrospinning provides a direct synthesis of solvent-free solid-state electrolyte membranes, ready to use in electrochemical applications.

Composite polymer electrolytes based on electrospun thermoplastic polyurethane membrane and polyethylene oxide for all‐solid‐state lithium batteries

“…Lithium ion batteries have been widely used in electric vehicles, portable devices, drones and other energy storage fields recently due to their higher energy density and the environmental issues . However, commercial lithium ion batteries which use organic solvents as electrolytes suffer from potential safety risks such as combustion, leakage and explosion .…”

Morphology and electrochemical and mechanical properties of polyethylene‐oxide‐based nanofibrous electrolytes applicable in lithium ion batteries

“…A linear trend of ionic conduction with temperature (regression line approximately 1) confirmed the Arrhenius relationship for the electrospun electrolyte. In SPEs with Arrhenius behavior, ions migrate from one site to another neighboring site in the polymer matrix . Considering the effect of polymer concentration on ionic conduction and the mechanism of ion transport in electrospun electrolytes, it seems that ion migration happens mostly along nanofiber walls.…”

“…So far, there has been little discussion regarding the electrospinning technique for the fabrication of SPEs. According to an investigation carried out by Freitag et al ., electrospinning is an easy and quick route toward electrospun SPE fabrication. Compared with SPEs, nanofibrous electrolytes have shown greater ion conductivity due to their highly porous structures .…”

“…According to an investigation carried out by Freitag et al ., electrospinning is an easy and quick route toward electrospun SPE fabrication. Compared with SPEs, nanofibrous electrolytes have shown greater ion conductivity due to their highly porous structures . Despite interesting results indicating the potential of the electrospinning technique in the fabrication of all‐solid‐state electrolytes, the effects of structural parameters such as polymer, salt and plasticizer concentrations have not yet been examined.…”

Evaluating the electrochemical properties of PEO‐based nanofibrous electrolytes incorporated with TiO2 nanofiller applicable in lithium‐ion batteries

“…Most previous studies have applied film casting method for the fabrication of the SPEs. However, as highlighted by Freitag et al, electrospinning is an easy and highly efficient technique for the fabrication of the polymeric electrolytes. Compared with the solution casting method, electrospinning provides electrospun polymeric mats with higher ion conductivity and superior electrochemical behavior …”