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

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.