Redox-active covalent organic framework electrolyte modulates interfacial Li⁺ deposition for stable solid-state...

Solid polymer electrolytes (SPEs) have been widely recognized as promising candidates for safe and high-energy-density solid-state lithium metal batteries. Nevertheless, their practical application is hampered by critical challenges in mechanical properties, ionic transport and interfacial stability. In this work, a redox-active covalent organic framework (denoted as TNCOF) is proposed to modulate interfacial Li⁺ deposition behavior. The TNCOF featuring abundant carbonyls and triazine rings, not only facilitates Li salt dissociation and provides ordered ion conduction pathways but also regulates the local Li⁺ environment through its redox-active units. Consequently, the optimized composite polymer electrolyte (CPE-8%TNCOF) exhibits an excellent performance with an ionic conductivity of 8.35 × 10^-4 S cm^-1, a lithium-ion transfer number ( [Formula: see text] ) of 0.45. Moreover, the TNCOF promotes homogeneous Li nucleation and induces the formation of Li₂O-rich solid electrolyte interphase (SEI). Impressively, the assembled all-solid-state LiS battery delivers a retention of 86.26% over 100 cycles at 0.2C. More notably, the LiFePO₄|CPE-8%TNCOF|Li battery delivers a discharge capacity of 143 mA h g^-1 after 400 cycles at 0.5C, corresponding to capacity retention of 93.46%, and maintains stable operation for 1000 cycles at 1C. This study provids new design ideas and reliable experimental basis for redox-mediated interfacial engineering in solid-state lithium metal batteries.