Flexible　lithium-ion　batteries　(FLIBs)　have　garnered　significant　research　interest　as　critical　energy　storage　components,　driven　by　rapid　advancements　in　deformable　electronic　systems.　However,　it　is　a　challenge　to　simultaneously　realize　adequate　flexibility,　stability,　and　energy　density　for　FLIBs.　Cellulose-based　materials　demonstrate　inherent　flexibility,　lightweight　characteristics,　high　surface　area,　and　cost-effectiveness,　enabling　their　promising　utilization　in　electrode　architectures　for　high-energy-density　flexible　battery　systems.　In　this　review,　we　summarize　the　recent　research　progress　of　the　application　of　cellulose-based　materials　in　FLIBs,　with　special　emphasis　on　roles　of　cellulose-based　materials　in　electrodes　of　FLIBs.　Firstly,　the　roles　of　cellulose-based　materials　in　FLIBs＇　anodes　are　categorized　into　four　distinct　types:　precursor,　binder,　skeleton,　and　modification　layer,　accompanied　by　an　overall　review　of　recent　advances.　Similarly,　their　multifunctional　contributions　in　FLIBs　cathodes　are　also　systematically　classified　into　three　categories:　binder,　skeleton,　and　modification　layers,　with　corresponding　progress　in　each　domain　comprehensively　summarized.　Finally,　the　challenges　and　possible　future　directions　of　cellulose-based　materials　in　FLIBs　are　proposed,　aiming　to　accelerate　the　rapid　research　and　development　for　practical　applications　and　commercialization　of　this　advanced　technology.