Electron‐Switching Astaxanthin Enables Programmable Triple‐Phase Interface Chemistry for High‐Loading All‐Solid‐State Lithium–Sulfur Batteries

ABSTRACT

All‐solid‐state lithium–sulfur batteries (ASSLSBs) promise high energy density and intrinsic safety, yet their performance is fundamentally constrained by unstable triple‐phase interfaces among sulfur, conductive carbon, and solid electrolytes. Such instability leads to sluggish solid–solid sulfur redox kinetics, hindered charge transport, and severe chemo‐mechanical degradation. Herein, we demonstrate a biomolecular strategy using astaxanthin (AXT) as an electron‐switching interfacial regulator to simultaneously address these coupled challenges. Combined experimental and theoretical analysis reveal that AXT modulates electrolyte decomposition pathways in a coverage‐dependent manner via a localized “electron pocket” effect, favoring the formation of electrochemically active Li ₂ S over insulating LiCl. Meanwhile, polar oxygen functional groups in AXT establish low‐potential corridors that facilitate Li ⁺ transport and stabilize key intermediates, thereby accelerating sulfur redox kinetics. In addition, the chain‐like molecular architecture of AXT acts as a flexible scaffold to buffer volume fluctuations and preserve interfacial contact integrity during cycling. Consequently, AXT‐modified ASSLSBs achieve exceptional electrochemical performance under high sulfur loading conditions, delivering an areal capacity of 16.56 mAh cm ⁻² at 9.49 mg cm ⁻² sulfur loading. This work establishes a biomolecule‐driven electronic engineering paradigm for programmable interface chemistry, offering a general strategy toward high‐energy‐density and durable solid‐state batteries.