Effect of Binders in Composite Solid Electrolytes on Electrode‐Electrolyte Contact for Low‐Operating‐Pressure All‐Solid‐State Batteries

ABSTRACT Sulfide‐based all‐solid‐state batteries (ASSBs) are promising next‐generation energy storage devices, yet their practical application is hindered by pressure dependence—arising from electrolyte brittleness and interfacial contact loss under dynamic volume changes during cycling, which demands high stacking/operating pressures. Herein, we design sulfide‐based composite solid electrolytes (CSEs) with organic components and systematically investigate their functional mechanisms. Mechanical‐physical tests reveal that the organic components enhance initial solid‐solid contact via adhesive effects and forming transitional interface, while buffering volume‐pressure variations via elastic strain accommodation. Electrochemical characterizations further verify these stabilizing effects. Using lithium–sulfur batteries as a model system, the CSE‐based ASSBs achieved stable long‐term cycling (over 1000 cycles without capacity decay) under low pressure (12.5 MPa), and retained 78% capacity after 300 cycles at 5 MPa (compatible with practical manufacturing conditions). The CSE's effectiveness was also validated for other cathode systems.‌ This work not only decouples the mechanical‐electrochemical roles of organic components in CSEs but also provides mechanistic insights for electrolyte layer design, guiding the development of pressure‐independent ASSBs toward scalable production.