兰州大学机构库 >物理科学与技术学院
氮掺杂石墨烯/棉纤维复合柔性电极的电容性能研究
Alternative TitleCapacitive Performance of Flexible N-doped Graphene /Cotton Fiber Composite Electrode
赵媛媛
Thesis Advisor潘孝军
2018-04-16
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword棉纤维 柔性超级电容器 石墨烯 氮掺杂
Abstract

随着可穿戴式和便携式电子产品的不断兴起和发展,如可弯曲显示器,电子纸、可弯曲智能手机等。为了适应这类柔性电子产品的开发和设计要求,柔性超级电容器(Flexible Supercapacitors, FSC)已经受到越来越多研究者的关注而成为一个重要的储能器件研究领域。因此,设计和制备具有良好机械弹性、高能量密度、高功率密度以及良好的循环稳定性的电极材料是影响柔性电容器性能关键因素。本论文选择廉价、可再生棉纤维作为电容器电极研究的基础材料,通过与氧化石墨烯复合以及氮掺杂等方法设计构造了不同结构的复合电极材料。

主要研究内容和结果如下:(1)采用直接碳化的方法制备碳化棉纤维电极材料。研究碳化条件参数对于棉纤维作为电容的电极材料的形貌、机械性能和电化学性能的影响。研究结果表明:碳化温度的上升会导致材料拉伸极限强度减小,即机械性能下降。而氨气处理过程有利于提高纤维的可拉伸性。从电化学性能角度来看,氨气处理后的纤维的比电容量较氩气处理的纤维更高。同样在氨气气氛中,在900℃温度下碳化后的纤维的导电性800℃碳化后的纤维导电性较差,倍率性能更低(低于10%)。(2)采用抽滤法制备氮掺杂棉纤维/石墨烯层状复合材料。研究石墨烯与棉纤维的混合质量比对复合材料的形貌及电化学性能的影响。通过抽滤法将棉纤维与氮掺杂石墨烯进行复合。对比棉纤维/石墨烯复合比例为6:4、7:3、8:2和9:1的样品的各项表征结果显示,混合比例为8:2的复合材料兼具有较高的比电容量(在1 A/g的电流密度下达到138 F/g),较好的倍率性能(当电流密度为20 F/g时,样品的电容保持率为32%),以及较优的阻抗特性。对于混合比例为8:2棉纤维/石墨烯复合材料,改变氨化时间分别为2 h、3 h和4 h,研究结果表明,氨化时间为3h时,复合材料的电容性能表现最佳。(3)采用冷冻干燥法制备氮掺杂棉纤维/石墨烯三维复合材料。研究复合氧化石墨烯浓度和氨化时间对于复合材料电容性能的影响,并对对称型电容器件进行柔韧性及电容性能的表征。对于不同浓度氧化石墨烯复合的棉纤维/石墨烯复合柔性材料的研究,根据一系列的电化学测试结果分析表明:复合氧化石墨烯浓度为的 5 mg/mL纤维材料(GO-5)在各电流密度下呈现最高值,在1 A/g的电流密度时的比电容量达到291 F/g,并且在20 F/g的电流密度下依然能够保持41%的电容量。对于不同氨化时间的棉纤维/石墨烯复合柔性材料的研究,NGC-3具有最高比例的吡啶型氮和吡咯型氮,以及最低比例的季型氮和氮氧基团。并且NGC-3具有最高的比孔容量,对应BET比表面积达到631 m2/g。在对样品NGC-3进行了10000次变电流密度的循环充放电测试后,由第10000次充放电循环计算得到的比电容值相比循环初始时比电容值升高了11%。当组装的对称型器件NGC-3//NGC-3从初始状态被弯折到90°或者180°,最后在恢复到初始状态过程中,CV曲线的形状均为准矩形形状且并未发生显著的变化。此外,柔性器件的器件NGC-3//NGC-3的能量密度在0.2 A/g的电流密度下达5 Wh/kg。

Other Abstract

Energy storage devices has arisen due to their potential applications in wearable and portable electronic products, typically roll-up displays, electronic paper, and wearable systems for personal multimedia. Despite these advances, the real bottleneck hindering flexible electronics from becoming ubiquitous in practical products is in constructing flexible and deformable energy storage devices. Current electronic devices are still too heavy, thick and bulky to match flexibility requirements. In order to realize the needed mechanical properties, energy storage devices that are light, thin and flexible must be developed.

In this work, cotton fiber, which is low cost and renewable, was chosen as the precursor of electrode material for flexible supercapacitor. And single cotton or composite flexible electrodes by combining with graphene oxide and nitrogen doping were designed and constructed. The main contents and results are as follows:(1) The synthesis of cotton fiber carbide via direct carbonization method. The effects of carbonation parameters on the morphology, mechanical properties and electrochemical properties of cotton fiber as capacitor electrode materials were investigated. The results show that the increase of carbonization temperature will lead to the decrease of tensile ultimate strength, that is, mechanical properties decrease. The process of ammonia treatment can improve the extensibility of the fiber. Moreover, the specific capacitance of the fibers treated by ammonia is higher than that of the argon treated ones. In addition, the conductivity and rate performance of the fibers carbonized at 900℃ is worse than that of 800℃ carbonized ones.(2) The synthesis of nitrogen doped fiber/graphene layered composite material via vacuum filtration method. The influence of the mixed mass ratio of graphene and cotton fiber on the morphology and electrochemical properties of the composites was investigated. The results showed that the mixing ratio of 8:2 (fiber/graphene) composite with high specific capacitance (up to 138 F/g at the current density of 1 A/g), better rate performance (when the current density is 20 F/g. The capacitance retention rate is 32%), and the optimal impedance characteristics. The results also showed that the capacitance performance of the cotton fiber/graphene composites with a mixture ratio of 8:2 is the best as the ammoniation time is 3 h.(3) The synthesis of 3D nitrogen doped cotton fiber/graphene composite of was prepared by freeze-drying method. The effects of graphene oxide concentration and ammoniation time on the capacitance properties of composite materials were studied, and the flexibility and capacitance properties of symmetrical capacitance devices were characterized. The results of a series of electrochemical analysis showed that the composite of graphene oxide (GO-5) concentration presented the highest specific capacitance value in different density current (the specific capacitance reached 291 F/g, and still able to maintain 41% of the capacity at the current density of 20 F/g). Moreover, the cotton fiber/graphene composite, which processed in ammoniation with 3 h (NGC-3) has the highest proportion of pyridine nitrogen and pyrrole nitrogen, as well as the lowest proportion of quaternary nitrogen and nitrogen oxygen groups. In addition, NGC-3 has the highest specific pore volume and the specific surface area of 631 m2/g. After 10000 cycles of charge and discharge test with variable current density, the specific capacitance calculated by 10000th cycles increased by 11% compared with the initial value of NGC-3. More importantly, the shape of the CV curve is all quasi rectangular and there is no significant change as the symmetrical device NGC-3//NGC-3 is bent from the initial state to 90 degree or 180 degree, and finally, recovering to the initial state. The energy density of the device NGC-3//NGC-3 of the flexible device reaches 5 Wh/kg under the current density of 0.2 A/g.

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/230206
Collection物理科学与技术学院
Recommended Citation
GB/T 7714
赵媛媛. 氮掺杂石墨烯/棉纤维复合柔性电极的电容性能研究[D]. 兰州. 兰州大学,2018.
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