Abstract:Amorphous carbon monoliths with tunable microstructures
are candidate
anodes for future lithium-based energy storage. Enhancing lithium
storage capability and solid-state diffusion kinetics are the precondition
for practical applications. Transforming intrinsic oxygen-rich defects
into active sites and engineering enlarged interlayer spacing are
of great importance. Herein, a novel explosion strategy is designed
based on oxalate pyrolysis producing CO and CO2 to successfully
prepare lignin-derived carbon monol… Show more
Amorphous carbons are promising candidates as the anode materials for potassium-ion hybrid capacitors (PIHCs). The insufficient storage sites and inferior diffusion kinetics limit their potassium-ion storage capability. Edge nitrogen and morphology engineering are effective pathways to construct accessible active sites and enhanced diffusion kinetics. However, the organic integration of both pathways in amorphous carbon is still challenging. Herein, a “twice-cooking” strategy, including two-step carbonization processes at 700 °C, is designed to synthesize edge-nitrogen-rich lignin-derived carbon nanosheet framework (EN-LCNF). In the first-step carbonization process, the staged gas releases of CO and CO2 from CaC2O4 decomposition exfoliate the carbon matrix into a carbon nanosheet framework. In the second-step carbonization process, the generated CaO reacts with the cyanamide units of graphitic carbon nitride (g-C3N4) to form an edge-nitrogen-rich framework, which is then integrated into the meso-/macropores of carbon nanosheet framework through sp3-hybridized C–N bonds. EN-LCNF with a high edge-nitrogen level of 7.0 at.% delivers an excellent capacity of 310.3 mAh g−1 at 50 mA g−1, a robust rate capability of 126.4 mAh g−1 at 5000 mA g−1, and long cycle life. The as-assembled PIHCs based on EN-LCNF anode and commercial activated carbon cathode show a high energy density of 110.8 Wh kg−1 at a power density of 100 W kg−1 and excellent capacitance retention of 98.7% after 6000 cycles. This work provides a general strategy for the synthesis of edge-nitrogen-rich lignin-derived carbon materials for advanced potassium-ion storage.
Graphical Abstract
Amorphous carbons are promising candidates as the anode materials for potassium-ion hybrid capacitors (PIHCs). The insufficient storage sites and inferior diffusion kinetics limit their potassium-ion storage capability. Edge nitrogen and morphology engineering are effective pathways to construct accessible active sites and enhanced diffusion kinetics. However, the organic integration of both pathways in amorphous carbon is still challenging. Herein, a “twice-cooking” strategy, including two-step carbonization processes at 700 °C, is designed to synthesize edge-nitrogen-rich lignin-derived carbon nanosheet framework (EN-LCNF). In the first-step carbonization process, the staged gas releases of CO and CO2 from CaC2O4 decomposition exfoliate the carbon matrix into a carbon nanosheet framework. In the second-step carbonization process, the generated CaO reacts with the cyanamide units of graphitic carbon nitride (g-C3N4) to form an edge-nitrogen-rich framework, which is then integrated into the meso-/macropores of carbon nanosheet framework through sp3-hybridized C–N bonds. EN-LCNF with a high edge-nitrogen level of 7.0 at.% delivers an excellent capacity of 310.3 mAh g−1 at 50 mA g−1, a robust rate capability of 126.4 mAh g−1 at 5000 mA g−1, and long cycle life. The as-assembled PIHCs based on EN-LCNF anode and commercial activated carbon cathode show a high energy density of 110.8 Wh kg−1 at a power density of 100 W kg−1 and excellent capacitance retention of 98.7% after 6000 cycles. This work provides a general strategy for the synthesis of edge-nitrogen-rich lignin-derived carbon materials for advanced potassium-ion storage.
Graphical Abstract
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