Journal
ADVANCED ENERGY MATERIALS
Volume 11, Issue 39, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/aenm.202101880
Keywords
covalent organic frameworks; Li-ion cells; positive electrode; ultra-high rate performance
Categories
Funding
- Engineering and Physical Sciences Research Council (EPSRC) [EP/N004884/1]
- Leverhulme Trust via the Leverhulme Research Centre for Functional Materials Design
- EPSRC [EP/R020744/1]
- China Scholarship Council (CSC)
- University of Strathclyde
- EPSRC [EP/R020744/1, EP/N004884/1] Funding Source: UKRI
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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.
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.
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