Hierarchical hollow nanospheres of imine-based covalent organic frameworks with built-in Ag sites for fast-charging lithium metal batteries.

Lithium metal is deemed to be the ultimate anode material for high-energy-density and fast-charging lithium batteries. However, issues of dendritic deposition and frangible solid electrolyte interphases must be resolved for lithium metal anodes. Herein, a hybrid interfacial layer, hierarchical hollow nanospheres assembled from lithiophilic imine-based covalent organic frameworks and built-in Ag sites (Ag@ICOFs), has been applied to regulate the interfacial lithium ion flux and enhance the anode stability for effectively inhibiting dendrite formation. The hollow ICOFs play important roles in enhancing electrolyte infiltration caused by ordered porous channels and promoting uniform lithium distribution due to the superior lithiophilic ability of binding sites (C[double bond, length as m-dash]N groups and benzene rings). Moreover, the filling of Ag can induce internal deposition in hollow Ag@ICOFs nanospheres when lithium metal tends to grow vertically. The dendrite-free lithium development is further verified by electrochemical electrode measurements and theoretical calculation. As a result, a synergistic enhancement in electrochemical performance is realized through stable long-term 1000 cycles and excellent capacity retention (87.3%) at a quick charge/discharge of 5C in a full cell paired with a LiFePO cathode. This work provides a fresh exploration of constructing functional nanomaterials with hierarchical structures for energy storage.