| In the past few decades,with the ever-increasing depletion of fossil energy,it is in urgent need to solve the problems caused by the severe harsh environment and energy shortages.Therefore,the development of new environmentally friendly energy storage devices has become a hot research direction today.Supercapacitors have received extensive attention from researchers because of their good cycle life,ultra-high power density and other advantages.However,its lower energy density limits its further development and application.Cobalt-nickel sulfide(NCS)has a high specific capacity and excellent electrochemical performance activity,but because it is subjected to mechanical stress during long-term charging and discharging,the structure collapses,and finally the cycle life is greatly reduced.Therefore,this paper proposes a phosphorus-doped hollow carbon sphere as the base material of cobalt and nickel sulfide.The hollow structure effectively alleviates the structural collapse of cobalt and nickel sulfide,and obtains cobalt sulfide with ultra-high cycle life and high electrochemical performance.Cobalt-nickel sulfide nanocone array/phosphorus-doped porous hollow carbon sphere(NCS NCAs/PHCS)composite material.In this paper,tetraphenylphosphonium bromide was used as the phosphorus source,sodium lauryl sulfate and polyether F127 were used as template directing agents,and glucose was used as the carbon source.The soft template method and chemical activation method were used to prepare phosphorus-doped hollow carbon spheres(PHCS).Then,using PHCS as the base material,a cobalt-nickel sulfide nanocone arrays was grown on the PHCS by a two-step hydrothermal method to obtain the NCS NCAs/PHCS composite material.In addition,this paper also prepared different morphologies of cobalt-nickel sulfide/phosphorus-doped hollow carbon spheres(NCS/PHCS)composites by changing the first hydrothermal time and urea content,and further explored the morphological changes.Influence on the properties of NCS/PHCS composites.The research results show that it is an effective method to improve their capacitive behavior as well as enhance their cycling performance by using phosphorus-doped hollow carbon spheres.In particular,the nanocone array grown on the PHCS can not only further provide an electron transmission path but also increases their electrical conductivity.Under the condition that the hydrothermal time in the first step is 8 h and the urea content is 0.18 g,the prepared NCS NCAs/PHCS composite material has the best electrochemical performance.Under the three-electrode system,the maximum specific capacity can reach up to 1760 F·g-1at 2 A·g-1,NCS NCAs/PHCS can also have a capacitance retention rate of 88.6%at 20 A·g-1after 10,000 cycles,which far exceeds the 69.8%capacitance retention rate of pure cobalt-nickel sulfide materials.In order to further improve the commercial value of NCS NCAs/PHCS composite materials,this paper also uses NCS NCAs/PHCS as the positive electrode and PHCS as the negative electrode to assemble the NCS NCAs/PHCS//PHCS asymmetric supercapacitor.Through the electrochemical performance test,it can be seen that the asymmetric supercapacitor has a specific capacity of 128 F·g-1 at a current density of1 A·g-1.Under the high current density of 20 A·g-1,the asymmetric capacitor has been charged and discharged for ten thousand times,and it can still have an ultra-high capacitance retention rate of 89.6%.After calculation,the NCS NCAs/PHCS//PHCS asymmetric supercapacitor reaches a maximum energy density of 46.5 Wh·kg-1 at 777W·kg-1. |
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