Enhancement of Meltdown Temperature of the Polyethylene Lithium-Ion Battery Separator via Surface Coating with Polymers Having High Thermal Resistance

Abstract

When a lithium-ion battery is overcharged, it starts to self-heat because of exothermic reactions occurring within the components of the cell. Separator shutdown is a useful safety feature for preventing thermal runaway reactions in lithium-ion batteries. The polyethylene (PE) separators used here had shutdown temperatures of around 135°C. Because the cell temperature continues to increase before actually beginning to cool even after shutdown, the separator should have a higher meltdown temperature than the shutdown temperature to work as an insulator even above the shutdown temperature. To enhance the meltdown temperature of the separator, in this study, a PE separator was coated with polymers synthesized from various ethylene glycol dimethacrylate monomers. When the separator was coated with polymer synthesized from diethylene glycol dimethacrylate (DEGDMA), its shutdown temperature and meltdown temperature were increased to 142 and 155°C, respectively. Furthermore, a slight increase in the air permeability of the separator was observed when the separator was coated with polymer synthesized from an ethanol solution containing the proper amount of DEGDMA.

Novel poly(vinylidene fluoride-trifluoroethylene)/poly(ethylene oxide) blends for battery separators in lithium-ion applications

“…Different host polymers have been used for SPE, among which stand out poly(ethylene) (PE) [5], poly(propylene) (PP) [6], poly(ethylene oxide (PEO) [7], poly(acrylonitrile) (PAN) [8], poly(vinylidene fluoride) and its copolymers [9]. One of the most used host polymer in SPE is PEO [10].…”

Reality and Future of Rechargeable Lithium Batteries

“…The PE layer offers a lower shutdown temperature; whereas the PP provides mechanical stability above the shutdown temperature (such as Celgard® [143]). The shutdown temperature and meltdown temperature were increased to 142 °C and 155 °C respectively, when the separator was coated with diethylene glycol dimethacrylate [144]. When silica nanoparticles were added to the separator, the meltdown temperature increased to 170 °C [145].…”

Nano SiO2 particle formation and deposition on polypropylene separators for lithium-ion batteries

“…Another recent approach was the coating of polyolefin based separators using inorganic particles due to the excellent thermal stability and wettability of inorganic particles with organic electrolytes. This approach significantly improves the thermal shrinkage and electrochemical performance of the separators [19][20][21][22][23][24][25][26]. However, in these studies, commercially available inorganic powders (such as clay, SiO 2 , Al 2 O 3 , etc.)…”