Reconciling mechanical robustness and ion transport via in-situ rigid-flexible networks for fast-charging and wide-temperature sodium batteries.

Gel polymer electrolytes for next-generation sodium-metal batteries (SMBs) are limited by a trade-off between mechanical robustness and ionic conductivity, which hampers fast-charging and wide-temperature applications. Herein, we address this challenge via an innovative rigid-flexible coupled polymer network, specifically synthesized by copolymerizing flexible butyl acrylate (BA) monomers with rigid triallyl isocyanurate (TAIC) crosslinkers. The rigid TAIC framework imparts exceptional mechanical integrity and electrochemical stability, while the polymerized BA matrix effectively confines solvents, enabling efficient ion-transport pathways. Moreover, the polymer network regulates the Na+ solvation environment, thereby inducing a stable, inorganic-rich solid electrolyte interphase. The rationally designed electrolyte (pBAT-1/8) achieves an ultrahigh Young's modulus of 40 MPa (125 MPa of the pBAT-1/8 skeleton) to effectively suppress dendrites, while maintaining high ionic conductivities (0.33, 1.58, and 2.11 mS cm-1 at -10, 30, and 70 °C, respectively) and a high Na+ transference number (0.51). Consequently, Na|pBAT-1/8|Na demonstrates stable cycling over 1500 h at 0.1 mA cm-2. Remarkably, Na|pBAT-1/8|Na3V2(PO4)3 cells deliver exceptional capacity of 92.7 mAh g-1 at 5C after 2600 cycles and operate reliably under harsh conditions, including high cathode mass loading (10.3 mg cm-2), high cut-off voltage (4.5 V), and broad operating temperature range (-10 to 70 °C). This work offers a transformative strategy to decouple mechanical and transport properties for practical high-energy-density SMBs.