Ion dynamics, rheology and electrochemical performance of UV cross-linked gel polymer electrolyte for Li-ion battery

The structural, vibrational, thermal, rheological, electrical, and dielectric properties of a series of UV cross-linked gel polymer electrolyte membranes, comprising ionic liquid, carbonate plasticizers, and lithium tetrafluoroborate salt, are investigated using x-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, rheology, and broadband dielectric spectroscopy. Rheological studies suggest that the synthesized gel polymer electrolyte membranes exhibit stable elastic behavior. The ionic transport mechanism and relaxation dynamics are systematically studied using broadband dielectric spectroscopy. The conductivity of these semi-interpenetrating polymer network based gel polymer electrolytes is found to be similar to 10-3 S cm-1. The composition, which shows the highest conductivity value of 6.69x10-3 S cm-1 at ambient temperature, is also mechanically very much stable at a yield stress of 872 Pa. Hence, this gel polymer electrolyte is worthy of the device fabrication. Finally, coin cell batteries are fabricated using these gel polymer electrolyte membranes and their electrochemical performance is analyzed using electrochemical impedance spectroscopy. The optimized gel polymer electrolyte membrane shows long-term oxidative stability against lithium. The batteries also exhibit excellent cyclability.