Endowing rapid Na + conduction by architecture design of Na 3 Zr 2 Si 2 PO 12 in composite electrolytes for ultralong lifespan quasi‐solid‐state sodium metal batteries

Abstract Solid‐state sodium batteries offer new opportunities for emerging applications with sensitivity to safety and cost. However, the prevailing composite electrolyte structure, as a core component, is still poorly conductive to Na ions. Herein, a 3D architecture design of Na + conductive Na 3 Zr 2 Si 2 PO 12 framework is introduced to in situ compound with polymer electrolyte, subtly inducing an anion‐enriched interface that acts as rapid ion immigration channel. Multiple continuous and fast Na + transport pathways are built via the amorphization of polymer matrix, the consecutive skeleton, and the induced anion‐adsorbed interface, resulting in a high ionic conductivity of 4.43 × 10 −4 S·cm −1 . Notably, the design of 3D skeleton not only enables the content of inorganic part exceeds 60 wt% without any sign of agglomeration, but also endows the composite electrolyte reach a high transference number of 0.61 by immobilizing the anions. The assembled quasi‐solid‐state cells exhibit high practical safety and can stably work for over 1500 cycles with 83.1% capacity retention. This tactic affords new insights in designing Na + conductive composite electrolytes suffering from slow ion immigration for quasi‐solid‐state sodium batteries.