Dynamic Redox Control through Charge Compensation Enables a Structurally Adaptive Interphase for Stable Li Metal Anodes.

Abstract

Lithium metal anodes are pivotal for next-generation all-solid-state batteries due to their ultrahigh energy density and intrinsic safety. Nonetheless, practical deployment is impeded by cycling-induced solid electrolyte interphase reconstruction, which leads to lithium dendrite proliferation and interfacial failure. Here, the redox-mediated interphase is constructed to stabilize the lithium interface in sulfide-based all-solid-state batteries. Synchrotron X-ray absorption spectroscopy reveals that the interfacial redox reorientation is governed by a charge-compensated mechanism involving correlated electronic and coordination evolution of Bi- and S-related interfacial species. The interplay of Li3Bi and Li3PS4 species triggers the spontaneous assembly of a dual-layer interphase: an inner lithophilic Li3Bi layer and an outer electron-blocking Li3ClO/LiCl layer. The configuration evolves through a kinetically favored Bi3+ → Bi0 reduction alongside Li3Bi alloying, promoting uniform Li deposition and stripping. The resulting Li-symmetric cell delivers a critical current density of 3 mA cm-2 and exhibits stable cycling at 1 mA cm-2. The results demonstrate that redox reorientation can not only drive structural adaptation of the interphase but also modulate its composition to stabilize the Li metal interface.