Lithium-ion Battery Separator Microstructural and Mechanical Properties Degradation Induced by Fast Charging Conditions

Lithium-ion batteries are key technology for electrified vehicles to reduce carbon emissions. To optimize charging and prevent short-circuits, the mechanical and physico-chemical properties of battery separators were analyzed under fast charging conditions. After 400, 800 and 1600 cycles of fast charging and discharge, six battery pouch cells were fully discharged and disassembled. The pristine and cycled separators were examined using various analytical techniques (scanning electron microscope, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy) and mechanical testing (uniaxial tensile and biaxial punch tests). Results showed a decline in mechanical toughness and ductility with increased cycles, but no noticeable chemical degradation. The study will present the mechanisms behind separator damage under fast charging conditions.