Preparation And Electrochemical Storage Properties Of Metallic Compounds Coated By Polypyrrole

Electrode material was the key factor of the new energy storage device performance,such as supercapacitor and lithium-ion battery.That was a hot spot in recent research of energy storage materials.In the number of electrode materials,transition metal compound CoMoO₄ and NiCo₂S₄ material has advantages of high theoretical specific capacity,simple preparation technology and environmental friendly,etc.Unfortunately,CoMoO₄ and NiCo₂S₄ has low electrical conductivity and bad rate performance,what is more serious is that CoMoO₄ and NiCo₂S₄ will cause large stress in the electrochemical reaction,it would be generated pulverization and inactivation of electrode materials in long cycle.In order to achieved electrode materials of both high capacity,high conductivity and high cycle life,this article will prepared polypyrrole?PPy?layer coated on the surface of CoMoO₄ pillar array and NiCo₂S₄ nanotube array,using the high conductivity and excellent stability of the polypyrrole to improve rate performance and cycle life of CoMoO₄ and NiCo₂S₄ material,the main research contents and results are as follow:?1?Hydrothermal method and high temperature calcination technology was used to prepare CoMoO₄ nanoflake-assembling porous pillar array on the nickel foam substrate,and then the electrochemical polymerization technology was used to prepare polypyrrole coated on CoMoO₄ nanoflake-assembling porous pillar array.The phase of CoMoO₄ nanoflake-assembling porous pillar array coated by PPy?CoMoO₄@PPy?were characterized by XRD and FTIR,SEM test found that nanoscale thickness of polypyrrole composites present a complete integrated coating on CoMoO₄ pillar array.Composite material was assembled into three electrode system for test its pseudocapacitance performance.The results showed that specific capacitance of CoMoO₄@PPy was 1195 F g-1 in the current density of 200 mA g-1,that was higher than 1173 F g-1 of CoMoO₄,the specific capacitance of CoMoO₄@PPy remain as the initial value 85.7% after 3000 cycles at a current density of 100 mA·g-1,but the uncoated CoMoO₄ remains 52%.Electrochemical tests shows that CoMoO₄@PPy have high specific capacity,structure is more stable in the process of charging and discharging.?2?The two steps hydrothermal method was adopted to prepare NiCo₂S₄ nanotube arrays directly in the nickel foam substrate,and then it was coating polypyrrole layer in NiCo₂S₄ nanotube array use the electrochemical polymerization technology.The phase of NiCo₂S₄ nanotube array coated by PPy?NiCo₂S₄@PPy?were characterized by XRD and FTIR,SEM and TEM test reveals the composites presented 8 nm polypyrrole fully coated layer on the NiCo₂S₄ nanotube array.Composite material was assembled into three electrode system for test its pseudocapacitance performance.The results presented that discharge specific capacitance of NiCo₂S₄@PPy compared with uncoated NiCo₂S₄ growth from 1242 to 1493 F g-1 increased by 20%.In rate performance test,the specific capacitance of NiCo₂S₄@PPy achieved 2 times than uncoated NiCo₂S₄ at the current density is 24 mA cm-2.When current density from large current return to 1 mA cm-2,the specific capacitance of NiCo₂S₄@PPy specific reached 98% of the initial specific capacitance,which is 1605 F g-1,but the uncoated NiCo₂S₄ retention rate was only 82%.The NiCo₂S₄@PPy as supercapacitor electrode materials have high specific capacity,good rate performance and excellent electrochemical stability.?3?Forthermore,this paper studied the electrochemical energy storage performance of CoMoO₄@PPy and NiCo₂S₄@PPy as lithium ion battery anode material.The study found that the specific capacity of CoMoO₄@PPy composite material reached 1084 mAh g-1,22% higher specific capacity than those uncoated CoMoO₄ materials under current density of 0.2 C.Under the current density of 0.2 C,NiCo₂S₄@PPy nanotube arrays composite materials given to keep at a rate of 85%,uncoated NiCo₂S₄ material at a rate of 65% after 100 cycles.Coated of Polypyrrole can improve energy storage performance and cycle stability of the electrode material of CoMoO₄ and NiCo₂S₄ array,that was mainly because of high conductivity of polypyrrole coated was improved the electronic conductivity of composite material as a whole,and weakened the structure destruction and pulverization of CoMoO₄ and NiCo₂S₄ material in the process of take off the embedded of Li⁺,which shows the coating effect and synergistic effect of two materials after compound.