Anthraquinone-Based Silicate Covalent Organic Frameworks as Solid Electrolyte Interphase for High-Performance Lithium-Metal Batteries

Lithium (Li)-metal batteries (LMBs) possess the highest theoretical energy density among current battery designs and thus have enormous potential for use in energy storage. However, the development of LMBs is severely hindered by safety concerns arising from dendrite growth and unstable interphases on the Li anode. Covalent organic frameworks (COFs) incorporating either redox-active or anionic moieties on their backbones have high Li-ion (Li⁺) conductivities and mechanical/chemical stabilities, so are promising for solid-electrolyte interphases (SEI) in LMBs. Here, we synthesized anthraquinone-based silicate COFs (AQ-Si-COFs) that contained both redox-active and anionic sites via condensation of tetrahydroxy-anthraquinone with silicon dioxide. The nine Li⁺ mediated charge/discharge processes enabled the AQ-Si-COF to demonstrate an ionic conductivity of 9.8 mS cm⁻¹ at room temperature and a single-ion-conductive transference number of 0.92. Computational studies also supported the nine Li⁺ mechanism. We used AQ-Si-COF as the solid electrolyte interphase on the Li anode. The LMB cells with LiCoO₂ cathode attained a maximum reversible capacity of 188 mAh g⁻¹ at 0.25 C during high-voltage operation. Moreover, this LMB cell demonstrated suppressed dendrite growth and stable cyclability, with its capacity decreasing by less than 3% up to 100 cycles. These findings demonstrate the effectiveness of our redox-active and anionic COFs and their practical utility as SEI in LMB.