基于对苯二酚/碳纳米管阵列氧化还原增强固态超级电容器的研究

Redox-enhanced solid-state supercapacitor based on hydroquinone-containing gel electrolyte/carbon nanotube arrays

通过在电解液中引入氧化还原活性物质可以有效提高能量密度且不降低功率密度.考虑到离子电导率以及环境安全等因素,本文在传统酸性凝胶电解质PVA/H3PO4中引入了氧化还原特性的有机小分子物质—对苯二酚(HQ),然后与具有高比表面积及垂直取向结构的碳纳米管阵列(ACNT)进行复合,设计制备了对称"三明治"结构的氧化还原增强型固态超级电容器ACNT@PVA@HQ,并系统研究了碳管取向结构以及孔隙间隙对ACNT@PVA@HQ器件电化学性能以及电荷储存机理的影响.实验表明,极少量对苯二酚活性物质(0.1%,摩尔分数)的加入,可以使ACNT@PVA@HQ器件的体积比容量相比纯ACNT@PVA器件提升6.4倍,同时保持了极高的倍率性能和循环稳定性.进一步利用溶剂蒸发的方法制备了高密度取向的碳管阵列(DACNT),组装的DACNT@PVA@HQ器件在电流密度11.1 mA·cm^–2下,其比电容量高达385 mF·cm^–2(1674 mF·cm–3),在平均功率密度大小为0.96 mW·cm^–2(4.17 mW·cm–3)的条件下,其最大能量密度可以达到0.06 mW·h·cm^–2(0.26 mW·h·cm–3),优于众多文献报道的结果.实验证明取向结构的阵列可以有效缩短离子迁移路径,提高电荷的转移效率,使得器件具有良好的倍率性能和更低的内阻.这种新型的氧化还原增强型超级电容器不但具有优秀的电化学储能性质,还满足环保、安全的理念,为未来新能源装置的开发提供了新思路,具有良好的应用前景.

By introducing redox active substances into electrolyte,the energy density can be effectively increased without reducing the power density.Considering the influence of ionic conductivity and environmental safety,we introduce the redox small molecule hydroquinone(HQ)into the PVA/H3PO4 gel electrolyte,which then will recombine with the carbon nanotube arrays(ACNT)possessing high specific surface area and vertical orientation structure.The symmetrical"sandwich"type redox-enhanced solid-state super capacitor is then designed and prepared.We systematically study the effects of oriented structure and pore space on the electrochemical properties of the ACNT@PVA@HQ device and charge storage mechanism.With the addition of hydroquinone(0.1%,mol%),the specific capacitance of ACNT@PVA@HQ composite device increases 6.4 times compared with that of the ACNT@PVA,and maintains the extremely high rate performance and cyclic stability.When the current density increases 10 times,the specific capacitance of the device still possesses 85%of the original value.The energy storage mechanism is mainly ascribed to a diffusion-control behavior at a low scan rate while it will change into a capacitive behavior at a high scan speed.Furthermore,we prepare highly densified oriented carbon nanotube arrays(DACNT)by solvent evaporation,enhancing the mechanical stability of carbon nanotube arrays and improving the specific capacitance and energy density of the devices.Compared with the specific capacitance of ACNT and random carbon nanotube(CCNT),that of DACNT@PVA@HQ device under the current density of 11.1 mA·cm^–2 increases up to 385 mF·cm^–2(1674 mF·cm–3),which is 6.6 times higher than that of the CCNT@PVA@HQ device and 18 times higher than that of the ACNT@PVA device.The maximum energy density can finally reach as high as 0.06 mW·h·cm^–2(0.26 mW·h·cm–3),which is much better than those of many other reported CNTs-based devices.The oriented structure of the arrays effectively shortens the ion migration path of the device,achieving a good rate performance and lower internal resistance.This new type of redox-enhanced solid-state supercapacitor not only has excellent electrochemical energy storage properties,but also meets the requirements for environmental protection and safety.This design provides a new idea for developing the new energy devices in the future,which has a good prospect in practical applications.