Chloride‐Regulated Depolymerization of Aluminosilicate Networks for Fast Ion Transport Compliant Interfaces in Sustainable All‐Solid‐State Sodium Batteries

ABSTRACT All‐solid‐state sodium‐ion batteries (ASSSIBs) provide a sustainable and cost‐effective solution for large‐scale energy storage. Sodium aluminosilicate (NASO) represents a resource‐sustainable electrolyte option owing to their low cost, natural abundance, and electrochemical stability. However, their strong covalent network leads to intrinsic low ionic conductivity, and poor interfacial compatibility. This work employs Cl incorporation to depolymerize the hyperconnected covalent network of NASO, forming a modified NaAlSiOCl (NASOC) structure with discrete short‐chain segments, which turns stress‐induced large‐scale cooperative rearrangement into localized deformation. Replacing a strong O─bridge with a weaker Cl─bridge further reduces the Young's modulus. Additionally, chloride doping effectively reduces the Na + migration barrier by decreasing both the elastic deformation energy and the chemical binding energy. Consequently, this Cl‐mediated depolymerization approach simultaneously reduces stiffness and improves ionic conductivity. The optimized NASOC electrolyte exhibits a low Young's modulus of ∼5 GPa and a high Na + conductivity of 0.45 mS cm −1 , which together facilitate superior ion transport and intimate electrode contact. The ASSSIBs employing NASOC retain 80.9% of their capacity after 500 cycles at 0.1 C. This work demonstrates a Cl‐mediated depolymerization strategy that concurrently enhances ionic conductivity and mechanical compliance in solid electrolytes, providing key insights for designing high‐performance and sustainable energy storage materials.