Recent advances on battery separators based on poly(vinylidene fluoride) and its copolymers for lithium-ion battery applications

Lithium-ion batteries represent one of the most suitable systems for effective energy storage for a wide range of applications, such as smartphones, laptops, electric vehicles, or even home storage systems. Among the different battery components, the separator plays an essential role in the performance of the batteries; its most relevant characteristics are (micro)structure, wettability, thermal and mechanical properties, and ionic conductivity value. This work provides a comprehensive review of the current state of the art in lithium-ion battery separator membranes based on poly(vinylidene fluoride) (PVDF) and its copolymers. The most recent developments in the last two years are presented, focusing on the different separator types that have been developed with the aim of improving wettability, thermal characteristics, and cycling behavior. The most used types of PVDF separators are composites, polymer blends, and the combination of both. Among the most common fillers, metal–organic frameworks, ionic liquids, and ceramic particles have been used for the development of PVDF-based composites and polymers such as poly(m-phenylene isophthalamide), poly(acrylonitrile), poly(tetrafluoroethylene), or poly(methyl methacrylate), for the development of polymer blends. Electrospinning is one of the most used processing techniques to improve wettability, thermal stability, and mechanical properties. The wettability of separators has been also improved by using PVDF as a coating on commercial separators. It is shown that PVDF-based battery separators can play an important role in the next generation of high-performance batteries.Portuguese Foundation for Science and Technology (FCT): projects UID/FIS/04650/2020, PTDC/FIS-MAC/28157/2017, grant SFRH/BPD/112547/2015, and investigator FCT contract 2020.04028.CEECIND (C.M.C.) as well as by the POCH and European Union. Financial support from the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK, and PIBA (PIBA-2018-06) programs is also acknowledge