Covalent organic framework-based solid-state electrolytes for lithium metal batteries: from materials to applications

Solid-state lithium metal batteries (SSLMBs) have attracted extensive attention due to their excellent safety and high energy density. In SSLMB systems, solid-state electrolytes (SSEs) are considered to be some of the most important components. However, SSEs still face challenges such as low room-temperature ionic conductivity and poor interfacial stability. In recent years, covalent organic frameworks (COFs), with their highly ordered pore structures, tunable functional groups, and excellent chemical stability, have been regarded as a rising star for employment in SSEs. This paper reviews recent research progress of COFs as single solid electrolytes and composite solid electrolytes, with a focus on their advantages in improving ionic conductivity and lithium-ion transference number, constructing single-ion conductors, and enhancing interfacial stability. On this basis, the article further summarizes the key strategies for improving the performance of COF-based SSEs, covering directions such as material design, structural regulation, and interface engineering. Finally, this paper proposes that future research should focus on improving ionic conductivity, developing green large-scale synthesis methods, deeply understanding the structure-performance coupling mechanism, and realizing multi-functional integrated design. It is our hope that this review will inspire future research on high-performance COF-based SSEs for SSLMBs.