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

Redox-active TNCOF provides ordered nanochannels and regulates Li + deposition. • TNCOF suppresses the decomposition of PEO and guides the formation of a Li 2 O-rich. • Li S battery with TNCOF retains 86.26% capacity after 100 cycles at 0.2C. • LFP battery maintains 93.46% after 400 cycles at 0.5C and 80.95% after 900 cycles at 1C. 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 ( t Li + ) of 0.45. Moreover, the TNCOF promotes homogeneous Li nucleation and induces the formation of Li 2 O-rich solid electrolyte interphase (SEI). Impressively, the assembled all-solid-state Li S battery delivers a retention of 86.26% over 100 cycles at 0.2C. More notably, the LiFePO 4 |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. Download: Download high-res image (102KB) Download: Download full-size image