Design And Fabrication Of Carbon Cloth Based Anode Materials For Flexible Supercapacitors

Supercapacitors is an energy storage device between traditional capacitors and batteries,combining the benefits of high energy density,high safety and long life.At the same time,with the development of new materials and flexible electronic devices,a large number of flexible,portable and foldable electronic devices are entering our lives.Besides,the flexible energy storage devices have attracted great focus by matching to the new electronic devices.In addition,the flexible supercapacitors possess the property of supercapacitor properties,excellent mechanical flexibility and research on flexible supercapacitors is getting hotter.Among them,the design of the electrode material plays a key role to affecting the performance of flexible supercapacitors.In this paper,electrode materials of flexible supercapacitors were studied.Carbon cloth excellent in conductivity,lightness and flexibility was used as a flexible substrate to fabricate two kinds of electrode materials,which was used for flexible supercapacitors.At last,we study the power density and energy density of asymmetric flexible supercapacitors that fabricated by the two electrode materials as negative electrode and suitable positive electrode.The main contents of this paper are as follows:?1?The commercial carbon cloth is oxidized by a wet chemical treatment method and then activated in molten NaNH₂ to obtain an activated carbon cloth?MACC?.The obtained MACC possess many advantages,including moderate oxygen functional groups and nitrogen heteroatoms,excellent wettability,large surface area,high conductivity and excellent mechanical strength and flexibility.As electrode,the MACC demonstrates a high areal capacitance of 744.5 mF cm^-2 at a current density of 1 mA cm^-2,and 692.0 mF cm^-2 at a high current density of 50 mA cm^-2 with the capacitance retention as high as 92.93%in 6 M KOH.Furthermore,the MACC//Co?OH?₂ flexible asymmetrical supercapacitors are fabricated based on the MACC electrode and Co?OH?₂ electrode using aqueous electrolytes.The assembled aqueous supercapacitors can release an areal capacitance of 373.9 mF cm^-2 under the current density of 2 mA cm^-2,and the corresponding energy density is up to 1.49 mWh cm^-3 at the power density of 19.45 mW cm^-3.The results show that the prepared MACC has the value of being applied to flexible supercapacitors.?2?The?-Fe₂O₃/C nanoarrays on carbon cloth with tetsubo-like structure was synthesized as a negative electrode for flexible supercapacitor by a template replacement method.The characterizations indicated that these?-Fe₂O₃/C nanoarrays are hollow structure and composed of?-Fe₂O₃ nanocrystals and carbon nanoparticles.In addition,there are plenty of mesopores existed between these?-Fe₂O₃ nanocrystals and carbon nanoparticles.Due to the hollow porous structure of?-Fe₂O₃/C nanoarrays and the presence of carbon nanoparticles not only in favor of accelerating the transport of electron and ion in?-Fe₂O₃/C electrode,but also increasing the active sites for energy storage,the as-synthesized?-Fe₂O₃/C electrode delivered much enhanced electrochemical performance including a high specific capacitance up to 430.8 mF cm^-2 and 391.8 F g^-1 at a current density of 1 mA cm^-2,good rate capability with a capacitance retention of 73.2%of capacitance retention at 10 mA cm^-2 and great cycling stability with only 8.2%capacitance loss after 4000 cycles at a scan rate of 200mV s^-1.By using?-Fe₂O₃/C as negative electrode and MnO₂ as positive electrode,an asymmetric supercapacitor was assembled to examine the electrochemical performance of?-Fe₂O₃/C in-depth.Benefit from the unique design of the?-Fe₂O₃/C electrode,the asymmetric supercapacitor exhibited a high energy density of 0.64 mW h cm^-3 at the power density of 14.8 mW cm^-3 in 1M Na₂SO₄ electrolyte and 0.56 mWh cm^-3 at the power density of 16.8 mW cm^-3 in Na₂SO₄/CMC gel electrolyte.The above results show that the"tetsubo-like"?-Fe₂O₃/C nano-array electrode material loaded on carbon cloth can be well applied to flexible supercapacitors.