A H${}^{+}$/Li${}^{+}$ ion exchange induced spinel ion-conductive interphase stabilizes 4.5 V LiCoO${}_2$ in sulfide-based all-solid-state lithium battery

All-solid-state lithium batteries (ASSLIBs) show significant promise as the next-generation energy technology due to their high energy density and inherent safety. However, the severe interface reactions between solid electrolyte and the high-voltage cathodes pose a major challenge, particularly at higher charge voltages. Herein, a H${}_3$PO${}_4$-triggered H${}^{+}$/Li${}^{+}$ exchange strategy is proposed to covert LiCoO${}_2$ (LCO) surface to spinel Co${}_3$O${}_4$/Li${}_3$PO${}_4$ ionic-conductive interphase. This spinel interphase presents a thickness of 15 nm and good affinity with LCO, which provides long-lasting protection to suppress interfacial parasitic reactions. Besides, both spinel Co${}_3$O${}_4$ and amorphous Li${}_3$PO${}_4$ feature high ionic conductivity compared to bulk LCO, thereby facilitating the interfacial ionic transportation. With such modification, ASSLIBs delivers high specific capacity (146.2 mAh g${}^{-1}$ at 0.1 C), outstanding rate performance (116.4 mAh g${}^{-1}$ at 2 C), and long-term cyclability (350 cycles at 0.5 C) under a cut-off voltage of 4.3 V versus Li/Li${}^{+}$. Moreover, this robust spinel interphase further improves the stable cycling (168.9 mAh g${}^{-1}$ at 0.1 C for 100 cycles) under elevated cut-off voltage (4.5 V vs Li/Li${}^{+}$). This finding highlights the H${}^{+}$/Li${}^{+}$ exchange to convert LCO surface to a spinel ionic-conductive interphase, which poses new insights for interface design in ASSLIBs. (© 2024 Wiley‐VCH GmbH)