Advanced separators based on aramid nanofiber (ANF) membranes for lithium-ion batteries: a review of recent progress

Abstract

Lithium-ion batteries (LIBs) have brought great significance and convenience not only in our daily lives, but also in the fields of industrial manufacturing and energy storage. Although the separator is an inactive component in a cell that does not engage in reactions, it has a significant impact on the battery's capacity, cycle performance, and most significantly, its safety and reliability. However, as the need for better safety and reliability, greater energy capacity, faster charge rate, and longer service life grows, conventional commercial polyolefin-based membrane separators often struggle to satisfy the LIB growth requirements and balance the properties of advanced electrode materials. Although great efforts have been made to improve the comprehensive properties of the existing and forthcoming separators, there is not a single separator that can meet all requirements for different battery applications. Considering that aramid nanofiber (ANF)-based membranes have been developed in recent years with superior strength and modulus, excellent thermal stability and unique structure, they have been considered among the most promising candidates for next-generation separators. This review firstly summarizes the requirements and development of high-performance separators, then the characteristics and advantageous properties of ANFs and ANF films are discussed, indicating that the ANF separator will be a promising building block for the next-generation of high-performance LIB separators. Furthermore, the recent application progress and challenges of the ANF-based membrane separators in the classifications of ANF coated separators, pure ANF separators, composite ANF separators, and ANF solid-state electrolytes are summarized and critically discussed, along with a particular focus on the possible strategies to control and regulate the porous structure of the pure ANF separator. The possible challenges and perspectives for the future development of the emerging ANF-based separators are also highlighted.