Sustainable Li-salt loading of cellulose nanocrystal enables robust ion transport channels in solid-state electrolytes

The high energy density and inherent safety feature of solid-state lithium metal batteries (SSLMBs) have drawn considerable interest. Nevertheless, the widespread deployment of SSLMBs remains constrained by insufficient ionic conductivity. Herein, we report a high-performance Li-salt-loaded cellulose nanocrystal-reinforced PVDF-HFP solid-state electrolyte (Li-CPSE) through a sustainable freeze-casting, salt-loading, and in situ photopolymerization strategy. This design enables vertically aligned ion-transport pathways, integrates internal Li + reservoirs with stabilized interfacial chemistry, and constructs a mechanically robust rigid-flexible 3D framework. Owing to these synergistic advantages, Li-CPSE exhibits fast Li + transport (1.06 mS cm −1 at 30 °C), a reduced activation barrier (0.18 e V ), and a broad electrochemical window reaching 5.0 V. Meanwhile, SSLMBs based on Li-CPSE exhibit long-term cycling durability, retaining 98.2% of the original capacity over 500 cycles in Li/LiFePO 4 cells. Flexible pouch cell further demonstrated excellent mechanical resilience and cycling stability, retaining 92.2% capacity over 70 cycles with an average coulombic efficiency of 99.9%, while continuously powering LEDs under bending and cutting. Additionally, bipolar stacking of two pouch cells delivers 6.78  V , sufficient to power commercial 5.3 V devices. The work highlights a scalable and sustainable strategy for advancing high-performance polymer electrolytes toward practical SSLMB applications.