Cellulose‐Based Solid‐State Electrolytes for Solid‐State Lithium Metal Batteries: Advances in Functionalization Strategies and Interfacial Engineering

ABSTRACT Cellulose‐based solid‐state electrolytes (CBSEs) exhibit unique potential in addressing the interfacial stability and safety challenges of high‐energy‐density solid‐state lithium metal batteries (SSLMBs) due to their renewable properties, tunable hierarchical structures, and eco‐friendly advantages. This review focuses on the preparation strategies, functional design, and battery performance optimization mechanisms of CBSEs, systematically reviewing their research progress and challenges. First, we elucidate the structure–performance relationship based on six typical preparation methods, detailing the construction of microstructures and their electrochemical performance. Second, the multi‐scale interfacial stabilization mechanisms are revealed through the design of cellulose dimensions and structural regulation. Furthermore, we explore performance optimization strategies for CBSEs in the context of SSLMBs, proposing solutions to electrolyte material and structural design as well as interfacial issues. Finally, we point out future research directions that should focus on the analysis of multi‐scale mass transmission mechanisms, the design of wide temperature adaptability, and the development of scalable manufacturing processes. We emphasize the potential of CBSEs in compatibility with high‐voltage cathodes and closed‐loop recycling systems. This review provides a theoretical framework and technical pathway for constructing safe and sustainable next‐generation SSLMBs.