| As new type of energy storge devices,supercapacitors have tremendous application prospects because of the advantages of high power density,excellent stability,low cost and environmental friendiness.However,compared with lithium batteries,supercapacitors have low energy density,which limits their practical applications.Electrode materials play an important role in electrochemical perfomance of supercapacitors,which have become one of research hotpot in the field of energy storge.Recently,due to the high theorectical specific capacity,excellent electrical conductivity,and abundant raw materials,transition metal compounds have been considered to be ideal electrode materials,which have been arosen wide research attentions.In order to obtain electrode materials with higher energy density and excellent stability,in this paper,sulfur/cobalt/nickel/oxygen composites are synthesized by hydrothermal electrochemical deposition method with carbon fiber paper as the positive electrode and nickel foam as the negative electrode.The effects of deposition temerature,deposition current densities and deposition time on the composition,morphology,structure and electrochemical performance were studied.Finally,the optimal composite electrode materials was served as the positive electrode and an asymmetric supercapacitor?AS?were assembled with activated carbon as the negative electrode.The supercapacitive performance of the AS was evaluated.The main research contents are as follows:?1?Under the condition of the constant deposition current density of 8mA·cm-2,when the deposition temperature were 90? and 100?,the as-achieved phases were hexagonal Ni5O?OH?9 and cubic Co9S8.At the deposition temperature of 110?,the products were composed of Ni5O?OH?9,Co9S8 and monoclinic Ni5?CO3?4?OH?2·4.5H2O.At the deposition temperatures of 120? and 130?,the products were composed of Ni5?CO3?4?OH?2·4.5H2O,Co9S8 and hexagonal Ni3S2.Themicromorphology of as-synthesized samples prepared by hydrothermal electrochemical deposition method exhibited nanoflakes morphology.The electrode material prepared at a deposition temperature of 120? has the best cycling stablity and its capacitance retention could rentain up to 80% of the initial specific capacitance after 2800 cycles at 2 A·g-1.?2?Under the condition of the fixed deposition temperature of 120?.When the deposition current density was 6mA·cm-2,the products were composed of Ni5O?OH?9 and Co9S8.At the deposition current density of 8mA·cm-2,the as-achieved phases are Co9S8,Ni5?CO3?4?OH?2·4.5H2O and Ni3S2.At the deposition current density of 10mA·cm-2,the products were composed of Ni5O?OH?9 and Co9S8.As the deposition current density increases,the nanosheets were interlaced one another to form a three-dimensional porous structure,which become denser,and tend to agglomerate to form spherical particles.The electrode material at a deposition current density of 8mA·cm-2 showed high specific capacitances of 127.8 mAh·g-1 at the current density of 1 A·g-1 and its stability was the most excellent among the three electrode materials.?3?The deposition temperature and deposition current density was fixed at 120? and 8mA·cm-2 respectively.At the deposition time of 5min,the products were composed of Ni5O?OH?9 and Co9S8.When the deposition time was 15min,the products were composed of Co9S8 and Ni5?CO3?4?OH?2·4.5H2O.At the deposition time of 30min,45min,60min,the as-achieved phases were all Co9S8,Ni5?CO3?4?OH?2·4.5H2O and Ni3S2.Among the electrode materials of these five deposition time,the electrode material at the deposition time of 15min shows the best stability,with 80%retention after 8000 continuous charege-discharge cycles at a current density of 2 A·g-1.?4?The optimal preparation parameters were 120?,8mA·cm-2,15min.As-achieved Co9S8/Ni5?CO3?4?OH?2·4.5H2O composite and activated carbon were used as the positive electrode and negative electrode respectively,which were assemble an asymmetric supercapacitor.The supercapacitor achieved an energy density of 48.62 Wh·kg-1 at a power density of 216.9W·kg-1,and 28.68 Wh·kg-1at 4338.2W·kg-1.In addition,the asymmetric capacitor has excellent cycling stability and its capacitance retention could be retained up to 188.5% of the initial value after 10800 cycles. |
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