title: Self-assembly of PEI/SiO2 on polyethylene separators for Li-ion batteries with enhanced rate capability.
abstract: A simple and environmentally friendly self-assembly process of oppositely charged polymer PEI and inorganic oxide SiO2 was demonstrated for the construction of an ultrathin layer on the surface of PE separator. The XPS, FT-IR, SEM, and EDS characterizations give clear evidence of the successful self-assembly of PEI and SiO2 without significantly increasing the thickness and sacrificing the pristine porous structure of PE separator. This process improves a variety of crucial properties of PE separator such as the electrolyte wetting, the electrolyte uptake, the thermal stability, the ionic conductivity, Li+ transference number, the electrochemical stability and the compatibility with lithium electrode, endowing lithium-ion battery (Li as anode and LiCoO2 as cathode) with excellent capacity retention at high C-rates and superior cycling performance. At the current density of 5 C, the cell with PE separator almost loses all the capacity. In contrast, the cell with (PEI/SiO2)-modified PE separator still holds 45.2% of the discharge capacity at 0.2 C. The stabilized SEI formation and high Li+ transference number of (PEI/SiO2)-modified PE separator were interpreted to be the substantial reasons leading to the remarkably enhanced battery performance, rendering some new insights into the role of the separator in lithium-ion batteries.
authors.affiliation: Research Centre of Nanoscience and Nanotechnology, Shanghai University , Shanghai 200444, China.
authors.forename: Zhuyi
authors.initials: Z
authors.lastname: Wang
authors.forename: Fangling
authors.initials: F
authors.lastname: Guo
authors.forename: Cheng
authors.initials: C
authors.lastname: Chen
authors.forename: Liyi
authors.initials: L
authors.lastname: Shi
authors.forename: Shuai
authors.initials: S
authors.lastname: Yuan
authors.forename: Lining
authors.initials: L
authors.lastname: Sun
authors.forename: Jiefang
authors.initials: J
authors.lastname: Zhu
keywords: Li-ion battery; rate capability; self-assembly; separator; surface modification