Bioinspired quasi-solid-state electrolyte enabling thermal safety and high-performance sodium metal batteries

Sodium metal batteries hold great promise for next-generation high-energy-density storage. However, their practical implementation is constrained by electrolyte flammability and unstable electrolyte-electrode interfaces. Herein, the quasi-solid-state composite electrolyte is developed by constructing a biomimetic hierarchical ion-transport architecture inspired by plant root system. Long-range ion-percolation pathways are established by KH560-functionalized halloysite nanotubes (KHNTs) serving as "primary roots," while in situ polymerized poly(1,3-dioxolane) (PDOL) "lateral roots" bridge inorganic-organic interfaces to form a seamless ion-relay network. Furthermore, the internal Al-OH groups of KHNT promote anion dissociation and capture. Whereas, the external O-Si-O linkages compete with PDOL for coordination sites, effectively accelerating Na⁺ hopping kinetics and ion conduction. Consequently, the ionic conductivity of 5.62 ms cm^-1, the Na⁺ transference number of 0.766 are achieved, alongside a electrochemical window up to 5.1 V. Symmetric Na||Na cells with stable cycling exceeding 3600 h, and Na||Na₃V₂(PO₄)₃ cells maintain 92.8% capacity after 1600 cycles at 2C. Additionally, pouch cells test further confirm excellent thermal and mechanical robustness with ultralow heat release.