Binder-Free Ceramic Coated Separators Prepared By Polydopamine Treatment and RF-Sputtering

Most commercially available polyolefin separators are made of polyethylene (PE) and polypropylene (PP). Such separators have excellent mechanical strength, electrochemical stability and thermal shutdown properties, but their thermal properties are not sufficient to secure safety of large-format LIBs. As a result, most of separator manufacturers prefer to coat ceramic layer on at least one-side of the conventional polyolefin separators. However, this comes at an additional cost with the battery. Radio frequency (RF)-sputter process has been considered as an economically viable process to prepare ceramic separator coatings [1]. The major disadvantage associated with it is high operating temperature, which can give some thermal damage on polyolefin separator.

In this study, polydopamine is coated on a polyethylene separator which can improve the heat resistance of the polyethylene separators. Then using RF sputtering and Al₂O₃ targets, ceramic coatings are made on this separator. With a submicron polydopamine and ceramic coating layer, the coated polydopamine and Al₂O₃ (PDA) separator has sufficient thermal properties comparable to conventional ceramic coated separators. In addition, PDA separator is electrochemically evaluated by ion conductivity and uptake amount for wettability, impedance analysis, rate capability, and cycle life.

Acknowledgements

This research was financially supported by the Ministry of Education, Science and Technology (MEST) and National Research foundation (NRF) of Korea through the Human Resource Training Project for Regional Innovation (2014066977) and IT R&D program of MOTIE/KEIT (10046314).

References

[1] T. Lee, W. Kim, Y. Lee, M. Ryou, Y. Lee, Macromolecular Research, 22 (2014) 1190-1195