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

Lithium (Li)-metal batteries (LMBs) have the highest theoretical energy density of current battery designs and thus have enormous potential for use in energy storage. However, the safety problems caused by dendrite growth and unstable interphases on the Li anode severely impede their development. Covalent organic frameworks (COFs) containing 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 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 a Li⁺ conductivity of 9.8 mS cm^{− 1} at room temperature and a single-ion-conducting 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 achieved 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% over 100 cycles. These findings demonstrate the effectiveness of our redox-active and anionic COFs and that they should have practical utility in LMB-based energy-storage devices.