Preparation And The Study Of Supercapacitive Properties Of Nickel Cobalt Based Sulfide/hollow Carbon Microsphere Composite Materials

With the rapid development of modern society,the problems of the energy depletion and environmental degradation have become increasingly solemn.Therefore,it is particularly important to explore clean and recyclable new energy sources to address these problems.As one of the most potential energy storage devices,supercapacitors have some specifict advantages,such as outstanding power property,fast charge-discharge ability and ranking cycling stability.However,the low energy density limits its further applications.In this paper,hollow carbon microspheres were prepared by the St(?)ber method with Si O₂as the hard template,which is doped with B and N.Then,Co S₂/DHCM and Ni Co₂S₄/DHCM composite material were obtained by hydrothermal methods,and its structure characterization,electrochemical performance test and the performance test of hybrid supercapacitors were carried out.Key research findings of this paper are as follows:(1)hollow carbon microspheres(DHCM)was synthysized by a St(?)ber method with Si O₂hard template,and further utilized as carbon sources to prepare the boron and nitrogen co-doped hollow carbon microspheres(B,N-DHCM)by hydrothermal approach utilizing ammonium tetraborate tetrahydrate(NH₄B₅O₈·4H₂O)as boron and nitrogen sources.Compared with the undoped DHCM,the as-obtained B,N-DHCM displays improved capacitive properties,its specific capacitance is 221.5 F g^-1at 1 A g^-1,the specific capacitance remains104.1 F g^-1at 20 A g^-1,and the capacitance retention is 91%after 10,000cycles at 3 A g^-1.The enhanced capacitive performances result from the synergistic effect of the unique double-layered mesopore-rich hollow structure with a large specific surface area and the modification of B and N co-doping.(2)Co S₂/DHCM composites were prepared by two steps of oil bath reflux and hydrothermal method.The results show that the specific capacity of the composite electrode material is 608.7 F g^-1at 1 A g^-1,which is higher than the prepared Co S₂electrode(418.9 F g^-1).Compared with the Co S₂electrode,the capacity retention rate of Co S₂/DHCM electrode is 77.6%after 2000 cycles at 3 A g^-1,which shows its excellent cycle performance.The enhanced electrochemical performance of the Co S₂/DHCM electrode is attributed to the synergistic effect between the two components.The Co S₂/DHCM and the B,N-DHCM was used as the positive and negative electrode to construct hybrid supercapacitor,respectively.The energy density of the device is 28.4 Wh kg^-1at the power density of 313.9 W kg^-1,and the capacity retention rate is 82.3%at3 A g^-1after 5000 cycles.(3)Ni Co₂S₄/DHCM composites were prepared by oil bath reflux and hydrothermal methods,which were used as supercapacitor materials.Electrochemical tests show that the Ni Co₂S₄/DHCM electrode exhibits excellent electrochemical performance with a specific capacity of 938.4 F g^-1at 1 A g^-1,capacity retention of 69.1%at 50 A g^-1,and capacity retention of 77.1%after 2000 cycles at 3 A g^-1.Its excellent electrochemical performance is attributed to its unique composite structure,which contributes to shortening the ion and electron transport channels and inhibiting structural changes during the charging and discharging process.By utilizing Ni Co₂S₄/DHCM electrode and B,N-DHCM electrode as the positive and negative electrodes respectively,the hybrid supercapacitor was assembled,which shows the energy density of 35.8 Wh kg^-1at a power density of 240.2 W kg^-1,and the capacity retention of 85.2%at 3 A g^-1after 5000 cycles.