Scalable and Ultrathin Dual Entangled Network Polymer Electrolytes for Safe Solid‐State Sodium Batteries

Abstract Identifying ultrathin and flexible solid‐state electrolytes with high ionic conductivity and low interfacial resistance is crucial for scale‐up production of solid‐state sodium (Na) metal batteries (SSMBs). However, the challenges of poor processing scalability, insufficient intrinsic mechanical strength, and limited ionic transport capacity remain unaddressed. Herein, an ultrathin 9.7 µm solid‐state electrolyte membrane featuring a dual‐polymer entangled network is meticulously engineered through an arrayed multi‐nozzle electrospinning technique with a swelling and hot pressing process using polyacrylonitrile and poly(ether‐block‐amide), which exhibits an exceptional voltage tolerance, enhanced tensile strength, and superior thermal stability. The soft ether oxygens segments in multiblock copolymers complex with Na + to promote the rapid hopping transport of Na + . Meanwhile, interconnected electronegative channels based on carbonyl and cyanogen groups serve as Na + conduits to smooth ion fluctuations and accelerate Na + selective conduction simultaneously. The obtained inorganic‐organic composite solid electrolyte interface with the improved mechanical strength of ultrathin solid‐state electrolytes effectively suppresses Na dendrites with low overpotential over 500 h. The solid‐state cells paired with layered oxides deliver a capacity retention of over 91.1% between 25 °C and 65 °C, and assembled pouch cells exhibit impressive energy density over 100 cycles, showing great potential for large‐scale application of ultrathin structure in the SSMBs.