Sol–gel deposition of silica nanospheres onto polymeric separators for improved performance of Li-ion batteries

• Published in: Journal of the Taiwan Institute of Chemical Engineers 2017-12, Vol.81, p.199-205
• Main Authors: Xie, Jian-De, Fu, Chun-Chieh, Liao, Chun-Chieh, Juang, Ruey-Shin
• Format: Article
• Language: English
• Subjects: Electrochemical performance; Lithium-ion batteries; Polymeric separator; Silica coating; Sol–gel method
• ISSN: 1876-1070; 1876-1089
• DOI: 10.1016/j.jtice.2017.10.031

•This work adopts a sol–gel method to coat SiO2 spheres onto polymeric separators.•The loading of silica serves as a factor in affecting thermal stability of battery.•The presence of silica improves rate capability and dimensional/thermal stability.•An appropriate amount of SiO2 features wettability and mass uptake of electrolyte.•This deposition method is attractive for Li-ion batteries due to its simplicity. This work presents an efficient sol–gel method to coat SiO2 nanopheres onto tri-layered polymeric separators for Li-ion batteries, consisting of Li4Ti5O12 (LTO) anode/Li cathode. The surface density of silica nanospheres with diameter of 300–500 nm is chosen as controlling factor in affecting the electrochemical performance and thermal stability of Li-ion batteries. The SiO2 deposition on the polymeric separators exhibits not only an enhanced thermal and dimensional stability but also an improved rate capability and inner resistance. The excellent performance originates from the formation of robust skeleton to stabilize the separators, allowing a superior insulation and mass transport barrier against volatile compounds generated during thermal decomposition process. An appropriate amount of SiO2 nanospheres still features a highly porous structure, imparting favorable liquid wettability, high mass uptake of electrolyte, and superior ionic conductivity. Accordingly, the sol–gel deposition method is believed to attract interests for applications in Li-ion batteries due to its simplicity, effectiveness, and multi-functionality. The left figures show the top-view FE-SEM images of different polymeric separators: (a) U, (b) S1, (c) S2, and (d) S3, which represent the amount of tetraethoxysilane of 0, 1.5, 3.0, and 6.0 ml in the colloidal suspension, respectively. The right figures illustrate thermal shrinkage of bare and silica-coated separators, where the separators are subjected to heat treatment at 60–180 °C for 10 min. It is seen that the silica-coated separators exhibit a reduced thermal shrinkage as compared to bare separator within the entire temperature range. This reveals that the sol–gel deposition of SiO2 nanospheres offers an efficient thermal insulation technique in enhancing thermal resistance of separators. [Display omitted]