Study On Flexible Solid-state Supercapacitor With Aligned Carbon Nanotube Arrays/redox Gel Electrolyte

The research and development of high performance flexible solid-state energy storage devices with portability,high stability and good biological security becomes the focus of contemporary energy industry development.Aligned carbon nanotube arrays(ACNT)has been confirmed as an ideal electrode material for supercapacitors and battery devices,which is due to regular pore structures,fast electron and ion transport channels.However,its super-hydrophobic characteristics and nano-meter gaps are not conducive to the penetration of aqueous gel electrolyte.It is also difficult to carry out conventional chemical modification and manipulation on ACNTs due to the poor mechanical strength.And it easily leads to the increase of internal resistance,the destruction of the array structure and the decrease of the rate performance.In this paper,we successfully infilled hydrogel electrolytes containing small redox active molecules into ACNT arrays assisted by the vacuum filtration.It solved the problem of the permeation of active gel electrolyte and increased the mechanical strength of the pristine ACNT.A high performance flexible solid-state super capacitor with symmetrical "sandwich" structure was then designed and made of polyaniline/carbon nanotube arrays(E-PANI@PVA@ACNT)by in-situ electrochemical polymerization.Compared with commercial entangled carbon nanotube powders,aligned carbon nanotube arrays ensures the composite devices to have high power density and excellent rate performance.Meanwhile the nano-meter sized gaps can greatly improve the cyclic stability and coulombic efficiency.In addition,the superior capacitor device with higher specific capacitance and higher energy density was fabricated by using the highly densified carbon nanotube arrays(DACNT),obtained by capillary force-induced shrinkage method.The specific capacitance reaches as high as 2.8 F·cm-3(0.65 F·cm-2)with the maximum energy density up to 0.39 mW·h·cm-3(0.09 mW·h·cm-2).In addition,we prepared another two kinds of devices from hydroquinone/carbon nanotube arrays(HQ@PVA@ACNT)and p-phenylenediamine/carbon nanotube arrays(PPD@PVA@ACNT)by using the redox-enhanced interfacial pseudocapacitive behavior.Except the excellent electrochemical energy storage performance,it shows that the nano-confinement effects of ACNT and the strong interaction between the active material and ACNT can effectively suppress self-discharge behavior.This new type of flexible solid-state supercapacitor not only has excellent electrochemical energy storage properties,but also meets the concept of environmental protection and safety,thus has a good application prospect.