Morphology And Performance Of NiCo₂O₄ As Supercapacitor Electrode Regulated By Soft Template Method

Nickel Cobaltite(Ni Co2O4)has attracted tremendous attention because of its low cost,environmental friendly and high electrochemical activity.However,there still exist some disadvantages when acted as the supercapacitor electrode,such as low specific capacitance and poor cycle life.In order to improve capacitive performance,Ni Co2O4 materials with novel morphologies are prepared through hydrothermal reaction by soft template method in this paper.We not only compare their electrochemical properties,but discuss the regulatory mechanism of polyvinyl pyrrolidone(PVP)and hexadecyltrimethylammonium bromide(CTAB)as soft template agents during the synthesis process of Ni Co2O4.The details are summarized as follows:1、The NCO/PVP-x(x=0,0.125,0.25,0.5)samples are synthesized with different PVP contents by hydrothermal method.The results demonstrate that the content of PVP has a significant effect on the morphology of samples.NCO/PVP-0.125 is apparent as the fine grainy structure and NCO/PVP-0.5 is irregular,while NCO/PVP-0.25 displays a unique elliptical morphology with flower-like surface.Its large specific surface area and pore volume are 108.90 m2/g and 0.37 cm3/g,which helps to increase the contact area between electrode material and electrolyte,also improve the electrode performance.When used as the supercapacitor electrode,NCO/PVP-0.25 achieves high specific capacitance of1272 F/g and retention rate of 83.4 % after 1000 cycles at 2 A/g.Furthermore,it still remains 875.2 F/g when current density increased to 10 A/g.2、 The NCO/CTAB-x(x=0.05,0.15,0.25,0.35)samples are prepared with various CTAB dosages through hydrothermal process.When CTAB is insufficient or excessive,the products become scattered arrangement.When CTAB amount is 0.15 g,Ni Co2O4 particles with uniform porous and regular morphology are formed,whose specific surface area and pore volume are 99.01 m2/g and 0.25 cm3/g,respectively.The porous structure is in favor of reducing the transfer distances of electrons and ions,also promoting the rapid electrochemical reaction.When acted as the supercapacitor electrode,NCO/CTAB-0.15 shows a capacitance of 1361.2 F/g at 2 A/g with cycling stability of 78.6 % after 1000 cycles.Besides,when the current density increases to 10 A/g,it still exhibits specificcapacitance of 830.0 F/g.3、The novel rambutan-like NCO/PVP-CTAB sample is successfully synthesized in a facile hydrothermal route using PVP and CTAB as co-templates,whose specific surface area and pore volume are 109.62 m2/g and 0.30 cm3/g,respectively,which helps to provide much more electrochemical active site.When used as the supercapacitor electrode,NCO/PVP-CTAB delivers a specific capacitance as high as 2201.7 and 1296.8 F/g at current densities of 2 and 20 A/g.Additionally,it exhibits excellent capacitance retention of 80.6 % after 1000 continuous cycles at 10 A/g.