Alumina nanocoating of polymer separators for enhanced thermal and electrochemical performance of Li-ion batteries

A chemical-wet impregnation method was adopted in this study to synthesize alumina-coated separators using commercially available alumina nanoparticles and poly (vinylidene fluoride-hexafluoro-propylene) binder to further improve the safety and performance of lithium-ion batteries (LIBs). Three trilayered polymer separators were uniformly coated with alumina nanoparticles with different densities. It was shown that the alumina-coated nanolayers significantly improved electrolyte affinity, mass uptake of electrolyte, thermal resistance, and dimensional stability of the separators. The discharge capacity of Li4Ti5O12 anode with alumina-coated separators was evaluated to be 166 mAh g(-1) at 0.1C and 160 mAh g(-1) at 1C. The alumina-coated layers boasted ionic conductivity within the LIB's architecture and reduced internal resistance. The thermal shrinkage of alumina-coated separators was greatly decreased, compared with the bare (as-received) membranes because the nanocoating layer served as a robust and protective layer providing a superior thermal insulation without adversely affecting mass transport characteristics within the LIBs' internal architecture.