Electron-Switching Astaxanthin Enables Programmable Triple-Phase Interface Chemistry for High-Loading All-Solid-State...

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 Li₂S 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.