Guo Yaqi, Liu Wei, Wu Ruitao, Sun Lanju, Zhang Yuan, Cui Yongpeng, Liu Shuang, Wang Huanlei, Shan Baohong
School of Materials Science and Engineering , Ocean University of China , Qingdao 266100 , China.
ACS Appl Mater Interfaces. 2018 Nov 7;10(44):38376-38386. doi: 10.1021/acsami.8b14304. Epub 2018 Oct 25.
Synthesis of the electrode materials of sodium-ion storage devices from sustainable precursors via green methods is highly desirable. In this work, we fabricated a unique N, O dual-doped biocarbon nanosheet with hierarchical porosity by direct pyrolysis of low-cost cuttlebones and simple air oxidation activation (AOA) technique. With prolonging AOA time, thickness of the carbon sheets could be reduced controllably (from 35 to 5 nm), which may lead to tunable preparation of carbon nanosheets with a certain thickness. Besides, an unexpected increase in N-doping amount from 7.5 to 13.9 atom % was observed after AOA, demonstrating the unique role of AOA in tuning the doped heteroatoms of carbon matrix. This was also the first example of increasing N-doping content in carbons by treatment in air. More importantly, by optimizing the thickness of carbon sheets and heteroatom doping via AOA, superior sodium capacity-cycling retention-rate capability combinations were achieved. Specifically, a current state-of-the-art Na storage capacity of 640 mAh g was obtained, which was comparable with the lithium-ion storage in carbon materials. Even after charging/discharging at large current densities (2 and 10 A g) for 10 000 cycles, the as-obtained samples still retained the capacities of 270 and 138 mAh g, respectively, with more than 90% retention. The assembled sodium-ion capacitors also delivered a high integrated energy-power density (36 kW h kg at an ultrahigh power density of 53 000 W kg) and good cycling stability (90.5% of capacitance retention after 8000 cycles at 5 A g).
通过绿色方法从可持续前驱体制备钠离子存储器件的电极材料是非常可取的。在这项工作中，我们通过低成本乌贼骨的直接热解和简单的空气氧化活化（AOA）技术制备了一种具有分级孔隙率的独特的N、O双掺杂生物碳纳米片。随着AOA时间的延长，碳片的厚度可以可控地减小（从35纳米减小到5纳米），这可能导致可调节制备具有一定厚度的碳纳米片。此外，在AOA之后观察到N掺杂量意外地从7.5原子%增加到13.9原子%，这证明了AOA在调节碳基体掺杂杂原子方面的独特作用。这也是通过空气处理增加碳中N掺杂含量的首个实例。更重要的是，通过AOA优化碳片厚度和杂原子掺杂，实现了优异的钠容量-循环保持率能力组合。具体而言，获得了目前最先进的640 mAh g的钠存储容量，这与碳材料中的锂离子存储相当。即使在大电流密度（2和10 A g）下充放电10000次循环后，所得样品仍分别保留了270和138 mAh g的容量，保持率超过90%。组装的钠离子电容器还具有高的综合能量-功率密度（在53000 W kg的超高功率密度下为36 kW h kg）和良好的循环稳定性（在5 A g下8000次循环后电容保持率为90.5%）。
