Ultralong‐Cycling Lithium Storage of SrGe ₂ O ₄ S Anode Enabled by In Situ Formed Oxysulfide Matrix

Abstract High‐energy lithium‐ion batteries (LIBs) demand next‐generation alloying‐type anodes with high capacity and low voltage. While silicon‐based anodes are in industrial use, commercial alloying‐type anodes still suffer from excessive volume expansion and inadequate cycle life. Even incorporating silicon‐carbon composites within graphite (typically <20% in commercial products) fails to resolve these limitations. Herein, we report a novel SrGe 2 O 4 S anode for ultralong‐cycling lithium storage. An oxysulfide matrix (Li₂O/SrS) was in situ formed around Ge nanodomains. Enabled by the strong covalency of soft S 2 ⁻ anions and the pinning effect of large Sr 2 ⁺ ions, this synergistic matrix has demonstrated capabilities to enhance interfacial compatibility with Ge, facilitate efficient Li⁺ transport, suppress agglomeration of Ge nanoparticles and buffer volume expansion, as evidenced by in/ex situ characterizations, density functional theory calculations, and finite element analysis simulations. The anode harvests a low charging medium voltage of 0.42 V and reversible capacity of 587 mA h g −1 at 0.1 A g −1 after 800 cycles (8300 h) with 93.2% capacity retention. The LiCoO 2 ||SrGe 2 O 4 S full cell delivers a high capacity of 142 mA h g −1 and energy density of 482 Wh kg −1 . This work sheds light on constructing functional matrix to relieve volume expansion and particle agglomeration of high‐capacity ultralong‐cycling alloying‐type anodes.