Low‐Pressure All‐Solid‐State Lithium–Sulfur Batteries: Challenges and Design Principles

ABSTRACT All‐solid‐state lithium–sulfur batteries (ASSLSBs) are promising for high‐energy and safe energy storage, yet their practical operation remains constrained by the reliance on external stack pressure (usually > 80 MPa, even exceeding 120 MPa). While pressure can improve solid–solid contact, it primarily acts as a compensatory component rather than a fundamental solution, and introduces substantial penalties in cell‐level energy density and engineering complexity. Here, we present a pressure‐centered perspective and show that the degradation of ASSLSBs under low‐pressure (< 0.1 MPa) conditions originates from a chemo‐mechanical mismatch among reaction‐induced volume change, interfacial chemistry, charge transport, and mechanical response. This mismatch is commonly reflected as cathode contact loss, interphase growth, and lithium anode instability. On this basis, we outline key challenges and design principles for low‐pressure ASSLSBs, focusing on maintaining reaction accessibility, constructing adaptive ion‐conducting phases, and stabilizing solid–solid interfaces. Eliminating pressure dependence, rather than accommodating it, is essential for translating ASSLSBs into practical energy storage systems.