In situ interface engineering of highly nitrogen-rich triazine-based covalent organic frameworks for an ultra-stable, dendrite-free lithium-metal anode

Uncontrollable dendrite growth and a lack of safety and reliability in lithium-metal batteries (LMBs) severely restrict their commercial progress; therefore, designing highly safe and stable LMBs still face huge challenges. Herein, we in situ constructed highly nitrogen-rich triazine-based covalent organic frameworks (COFs) (N content: 47.04 at%) with a high Young's modulus (3.51 GPa) on a Li-metal surface with multiple lithiophilic sites and artificial SEI layers to reduce side reactions, induce uniform Li+ flux and Li plating/stripping, and suppress dendrite growth. Theoretical and experimental analysis confirmed that the strongly lithiophilic and highly nitrogen-rich structure of COFs has multiple adsorption sites and high Li adsorption energy, which spontaneously forms a rigid organic/inorganic hybrid protection layer with rich Li-N and highly ordered pore structures, thereby inducing uniform Li+ flux and Li plating/stripping, decreasing Li+ migration energy barrier, enhancing Li+ mobility, and suppressing Li-dendrite growth. As expected, COF@Li symmetric cells achieved an ultra-long cycling stability of over 8000 h at 5 mA cm(-2) (5 mA h cm(-2)) and 1600 h at 20 mA cm(-2) (20 mA h cm(-2)). Importantly, the LiFePO4||COF@Li full cell exhibited an excellent cycling stability of over 1000 cycles at 5 C. This work provides an effective in situ interface engineering strategy to fabricate highly nitrogen-rich COFs as rigid, multiple-site lithiophilic protection layers on the Li metal surface for ultra-stable, dendrite-free LMBs.