A review on nanofibrous separators towards enhanced mechanical properties for lithium-ion batteries

As one of the indispensable components in lithium-ion batteries (LIBs), separators play an important role in battery performance and safety issues. Nanofibrous separators have attracted a great number of attentions in recent years, not only due to the outstanding features like wide material applicability and versatile preparation process, but also because of the advantages including high porosity and high ionic conductivity that can endow the LIBs with excellent electrochemical performance. However, the relatively poor mechanical strength of nanofibrous separators cannot satisfy the need of battery assembly and also is liable to cause safety accidents, which has become the stumbling block to the development of nanofibrous separators. Actually, considerable works have been successful in improving the mechanical properties, although most of them are not intended. Therefore, in this review, we concentrate on the strategies employed to enhance the mechanical properties of nanofibrous separators, such as taking advantages of multicomponent or high-performance polymers, nanoparticles, additives, and post-treatment, by highlighting the recent achievements in robust separators fabricated by different methods. Future investigation directions, challenges and perspectives in improving the mechanical performance of LIB separators are also provided. We hope such a review could shed lights for the separator researches dedicated on the industrialized production, high safety and high performance for future battery developments.