In a bid to develop a separator with improved thermal shrinkage that critically affects internal short-circuit failures of lithium-ion batteries, we demonstrate a new approach, which is based on introducing microporous composite coating layers onto both sides of a polyethylene (PE) separator. The composite coating layers consist of alumina (Al2O3) nanoparticles and polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) gel polymer electrolytes. The microporous structure of the composite coating layers is considered a crucial factor governing the thermal shrinkage and electrochemical performance of the separators. The microporous structure is determined by controlling the phase inversion, specifically the solvent-nonsolvent miscibility, in the coating solutions. To quantitatively identify the effect of the solvent-nonsolvent miscibility, three different nonsolvents are chosen in the decreasing order of solubility parameter (δ) difference against the solvent (acetone, δ=20MPa1/2), which are respectively water (δ=48MPa1/2), butyl alcohol (δ=29MPa1/2), and isopropyl alcohol (δ=24MPa1/2). The microporous structure of the composite coating layers becomes more developed with the increase of not only the nonsolvent content but also the solubility parameter difference between acetone and nonsolvent. Based on this observation, we investigate the influence of the morphological variations on the thermal shrinkage and electrochemical performance of the composite separators.
Bibliographical noteFunding Information:
This work was supported by National Research Foundation of Korea Grant funded by the Korean Government ( 2009-0070967 ). We are grateful to Dr. E.K. Shim and Mr. J.S. Kim at Technosemi Chem, Mr. S.H. Kim at Arkema Korea, and Mr. B.J. Choi at ExxonMobil Korea for their supply of samples. We also express deep appreciation to Dr. K.J. Kim and Mr. Y.N. Cho at KETI for their kind assistance in the characterization of electrochemical performance.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Physical and Theoretical Chemistry
- Filtration and Separation