Impact of size on energy storage performance of graphene based supercapacitor electrode
Impact of size on energy storage performance of graphene based supercapacitor electrode
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DOI：
10.1016/j.electacta.2016.10.020
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发表时间：
2016-11
影响因子：
6.6
通讯作者：
Luhua Lu;Wanfei Li;Lisha Zhou;Yijie Zhang;Zhao Zhang;Ying Chen;Jinghai Liu;Liwei Liu;Wei C
中科院分区：
文献类型：
--
作者：
Luhua Lu;Wanfei Li;Lisha Zhou;Yijie Zhang;Zhao Zhang;Ying Chen;Jinghai Liu;Liwei Liu;Wei C
石墨烯及其聚集体的结构调控对于提高石墨烯超级电容器的性能具有重要意义。然而，很少有人研究石墨烯尺寸对其储能性能的影响。在这项工作中，我们通过声化学方法定制了尺寸从微米到几十纳米的氧化石墨烯。将不同尺寸的石墨烯氧化物经热处理后转化为石墨烯，作为电极材料，以离子液体为电解液构建超级电容器。电化学分析表明，石墨烯的储能性能与其结构特征(比表面积和电化学活性边位置)之间没有明显的正相关关系，这与我们的常识相反。基于对石墨烯电极的结构和电化学分析，我们认为减小石墨烯的尺寸会导致其边缘活性降低，这是因为富含SP3-碳缺陷的边缘的芳香结构被破坏，电荷难以传递和穿透。如果石墨烯的尺寸非常小，则用于双层电容设置的实际可用区域不包括这些电荷不可触及的边缘区域。因此，增加小尺寸石墨烯的边缘对其电容的提高没有积极的影响。此外，石墨烯的结构对体电极的等效串联电阻有重要影响。尺寸减小的石墨烯的层间电荷转移频率增加，缺陷边增加的石墨烯层间的电荷转移电阻增大，归因于尺寸减小的石墨烯电极的功率密度降低。
Manipulating structure of graphene and its aggregates has been found to be important for graphene based supercapacitor performance enhancement. However, seldom work has investigated impact of graphene size on its energy storage performance. In this work we have tailored size of graphene oxide from micrometers to tens of nanometers via sonochemical approach. The converted graphene by thermal annealing graphene oxides of different size have been used as electrode materials for constructing supercapacitor with electrolyte of ionic liquid. Electrochemical analysis indicates that there is no obviously positively correlation between energy storage performance and structure characters (specific surface area and electrochemical active edge sites) of graphene, which is contrary to our common knowledge. Based on structure and electrochemical analysis of graphene electrodes, we proposed that reducing the size of graphene results in low edge activity of it for the disrupted aromatic structure on the edges with enriched sp3-carbon defects, where electrical charge is hard to transfer to and through. The practical available area for double layer capacitance setup does not include these electrical charge inaccessible edge regions if the size of graphene is very small. And thus increasing edges of small size graphene has no positive impact on its capacitance enhancement. Furthermore, structure of graphene has shown key influence on equivalent series resistance of bulk electrode. Increased charge transfer frequency between graphene layers of size reduced graphene and higher charge transfer resistance between layers of graphene with increased defective edge were attributed to reduced power density of electrode of graphene with reduced size.