Thermal conversion performance, kinetic mechanism, and products of electric vehicle lithium battery diaphragms

The proliferation of waste lithium batteries is on the rise; however, the thermal treatment attributes of these batteries are largely overlooked, and the conversion mechanism of lithium battery separators remains unclear. This study marks the first comprehensive to compare the thermal degradation characteristics, kinetic parameters and mechanisms, thermal degradation products, and degradation pathways of polypropylene (PP) and polyethylene (PE) lithium battery diaphragms. The pyrolysis temperatures for the PP and PE were 340–500 and 440–530 °C, respectively. PP and PE exhibited average activation energies of 65.19–73.04 and 207.62–209.40 kJ/mol, respectively. At 600–800 °C, the yields of PP and PE pyrolysis gases and gasoline products increased with increasing temperature, while the yields of diesel and paraffin products decreased. The most dominant products generated from the pyrolysis of PP and PE were olefins, and the amount of olefin products from PE increased with increasing pyrolysis temperature. CH3 fracture was the first reaction step that occurred during PP pyrolysis. Our study provides useful information for industrial recycling, disposal, and utilization of electric vehicle lithium battery separators as well as data on the pyrolysis behaviours and transformation mechanisms of polyolefin wastes.