Recent advances in functionalized separator for dendrites-free and stable lithium metal batteries

Abstract

Lithium (Li) metal anode is considered the “Holy grail” for the most promising next-generation rechargeable lithium metal batteries (LMBs) because of ultra-high theoretical specific capacity, ultra-low reduction potential and small density. However, uncontrolled lithium dendrite growth and inevitable side reaction seriously hindered the application of practical LMBs because of the deteriorating electrochemical performances and exacerbating the safety issues of LMBs. Thus, improving the electrochemical performances of LMBs by constructed of functionalized separator is promising for overcoming the above-mentioned challenges due to its' significantly advantages, such as enhancing mechanical and thermal stability, regulating the diffusion and migration of Li ions, homogenizing Li ion flux, forming protective layer on Li anode surfaces, etc. The relational investigations have significantly increased since 2020, while the comprehensive reviews on this research direction are relatively rare, especially in the detailed mechanism aspects. In this review, an overview in functionalized separator for stable LMBs is discussed in detail. Firstly, the current issues of LMBs are in-depth discussion and the general strategies are summarized. Subsequently, the requirements and limitations of separator, as well as the advantages of functionalized separator are summarized and reviewed. Most importantly, the protection mechanisms and research advances of advanced functionalized separator are comprehensively discussed and summarized. Furthermore, the applications of functionalized separator in rechargeable lithium metal-based full cells are reviewed. Finally, the challenges and potential opportunities for the future development and rational design of functionalized separator are highlighted in rechargeable LMBs to obtain future research directions related to the significant strategy of constructing dendrite-free and stable LMBs.