Integrated Covalent Organic Framework/Carbon Nanotube Composite as Li-Ion Positive Electrode with Ultra-High Rate Performance

Covalent organic frameworks (COFs) are promising electrode materials for Li-ion batteries. However, the utilization of redox-active sites embedded within COFs is often limited by the low intrinsic conductivities of bulk-grown material, resulting in poor electrochemical performance. Here, a general strategy is developed to improve the energy storage capability of COF-based electrodes by integrating COFs with carbon nanotubes (CNT). These COF composites feature an abundance of redox-active 2,7-diamino-9,10-phenanthrenequinone (DAPQ) based motifs, robust beta-ketoenamine linkages, and well-defined mesopores. The composite materials (DAPQ-COFX-where X = wt% of CNT) are prepared by in situ polycondensation and have tube-type core-shell structures with intimately grown COF layers on the CNT surface. This synergistic structural design enables superior electrochemical performance: DAPQ-COF50 shows 95% utilization of redox-active sites, long cycling stability (76% retention after 3000 cycles at 2000 mA g(-1)), and ultra-high rate capability, with 58% capacity retention at 50 A g(-1). This rate translates to charging times of approximate to 11 s (320 C), implying that DAPQ-COF50 holds excellent promise for high-power cells. Furthermore, the rate capability outperformed all previous reports for carbonyl-containing organic electrodes by an order of magnitude; indeed, this power density and the rapid (dis)charge time are competitive with electrochemical capacitors.

Automated summary

A general strategy was developed to improve the energy storage capability of COF-based electrodes by integrating COFs with carbon nanotubes (CNT). This synergistic structural design enabled superior electrochemical performance, with high utilization of redox-active sites, long cycling stability, and ultra-high rate capability. The rate capability of these composite materials outperformed previous reports for carbonyl-containing organic electrodes, making them competitive with electrochemical capacitors in terms of power density and rapid charge-discharge time.