Facile manufacture technique for lithium-ion batteries composite separator via online construction of fumed SiO2 coating

Booming aspiration of advanced energy storage equipment elevates lithium-ion batteries vastly. Whereas separator with inferior porous structure and compatibility mismatches battery internal medium and raises ion transference rampart. Herein, fumed SiO2 compound separator is designed via ingenious bidirectional drawing technique to optimize the porous structure and realize fumed SiO2 coating online construction during the pore formation process of β-crystal polypropylene (β-iPP) synchronously. Crystal structure measurement, pore construction diagnosis, and physical properties tests disclose that the fumed SiO2 thins coarse fibril structure and homogenizes porous construction of separator. The de-bonding of fumed SiO2/β-iPP interfaces also remains SiO2 on the top-surface and pore internal wall of separator and thus realizes the SiO2 coating online construction, which eliminate the steps required by coating after fabrication of the separator and greatly reduce the production difficulty and cost. Also, the prepared composite separators present reinforced thermal dimensional stability and electrolyte wettability benefited by the SiO2 coating. Electrochemical impedance spectroscopy and cycle tests further uncover that hydrophilic SiO2 nanoparticles lower lithium-ion migration rampart within separator and enhance compatibility with electrodes, which stifles cell resistances and gives LIBs superior high ratio discharge property and cycling durability.