Conjugated two-dimensional covalent organic frameworks as the high-performance anode for lithium-ion batteries: Mechanism and prediction

It is significant in developing high-performance carbonaceous materials (CMs) for lithium-ion batteries (LIBs). The conjugated covalent organic frameworks (CCOFs), one subset of CMs, have spurred great research interest and possess great potential in the realm of negative electrode applications for LIBs. Many CMs and CCOFs are reported with highly anodic capacities outstripping that of graphite, and the underlying mechanism warrants further investigation. Herein, the mechanism of such high capacities is studied on an experimentally synthesized conjugated covalent organic framework (CCOF) by combing the first-principles calculation and electrochemical analysis. By probing the spatial and electronic interactions in the model CCOF during the lithiation process, the mechanism for the dense lithium arraying and concurrent lithiation behavior in CCOFs is revealed. And the microscopic origin of some electrochemical phenomena of CCOFs, such as the high capacity, lacking charging/ discharging plateaus, etc., are vividly comprehended. In addition, four analogous CCOFs are designed, and their electrochemical performances are briefly studied to verify the universality of the summarized mechanism. The critical factors of developing high-performance anodic CCOFs are predicted.