Interlayer Hydrogen-Bonded Covalent Organic Framework with High Rate and Ultra-Long Stability as Positive Electrode...

Covalent organic frameworks (COFs) have become promising organic electrode materials for lithium-ion batteries (LIBs) due to their diverse structures and properties. However, relatively little researches are done on the effect of noncovalent hydrogen bonds on COFs structure and their electrochemical performance. Here, an interlayer hydrogen-bonded is designed with N─H···O═C interactions in the main chain of polyimide BTH-NT COF with ultrahigh wettability and stability for the first time as a positive electrode material of LIBs. The existence of a hydrogen bond is directly confirmed by variable temperature infrared spectroscopy (VT-IR) and density functional theory (DFT) calculations. By incorporating single-walled carbon nanotubes (CNT) through an in situ controlled strategy, the conductivity and carbonyl active site utilization of BTH-NT COF are greatly enhanced. As a cathode material for LIBs, BTH-NT COF@CNT50 delivers extremely excellent rate performance and cycle stability with a discharge capacity of 94.6 mAh g^-1 and retention of 95.6% at 10 A g^-1 after 27 000 cycles, which is one of the COF cathode materials with the longest cycle life so far. Moreover, BTH-NT COF@CNT50 can also be processed into a binder-free self-supporting electrode without a current collector and dry-process electrode, which delivers a stable discharge capacity serving as the cathode of LIBs.