title: Initiated Chemical Vapor Deposition (iCVD) of Highly Cross-Linked Polymer Films for Advanced Lithium-Ion Battery Separators.
abstract: We report an initiated chemical vapor deposition (iCVD) process to coat polyethylene (PE) separators in Li-ion batteries with a highly cross-linked, mechanically strong polymer, namely, polyhexavinyldisiloxane (pHVDS). The highly cross-linked but ultrathin pHVDS films can only be obtained by a vapor-phase process, because the pHVDS is insoluble in most solvents and thus infeasible with conventional solution-based methods. Moreover, even after the pHVDS coating, the initial porous structure of the separator is well preserved owing to the conformal vapor-phase deposition. The coating thickness is delicately controlled by deposition time to the level that the pore size decreases to below 7% compared to the original dimension. The pHVDS-coated PE shows substantially improved thermal stability and electrolyte wettability. After incubation at 140 °C for 30 min, the pHVDS-coated PE causes only a 12% areal shrinkage (versus 90% of the pristine separator). The superior wettability results in increased electrolyte uptake and ionic conductivity, leading to significantly improved rate performance. The current approach is applicable to a wide range of porous polymeric separators that suffer from thermal shrinkage and poor electrolyte wetting.
authors.forename: Youngmin
authors.initials: Y
authors.lastname: Yoo
authors.forename: Byung Gon
authors.initials: BG
authors.lastname: Kim
authors.forename: Kwanyong
authors.initials: K
authors.lastname: Pak
authors.affiliation: IT&E R&D, LG Chem, Yuseong-gu, Daejeon 305-380, Republic of Korea.
authors.forename: Sung Jae
authors.initials: SJ
authors.lastname: Han
authors.affiliation: IT&E R&D, LG Chem, Yuseong-gu, Daejeon 305-380, Republic of Korea.
authors.forename: Heon-Sik
authors.initials: HS
authors.lastname: Song
authors.forename: Jang Wook
authors.initials: JW
authors.lastname: Choi
authors.forename: Sung Gap
authors.initials: SG
authors.lastname: Im
keywords: Li-ion battery separator; electrolyte wettability; initiated chemical vapor deposition (iCVD); poly hexavinyldisiloxane (pHVDS); thermal stability