Prepation Of Nickel-based Electrode Materials For Supercapacitor Application And Its Electrochemial Performance

Supercapacitors, with high power density, ultrafast charging-discharging time, and long lifecycle performance, have become the most promising energy-storage devices. Nickel-based materials have attracted great interest due to its high theoretical specific capacitance.Firstly, a novel three-demensional hierarchical porous nickel oxide(Ni O) was fabricated by a sol-gel method, of which the biomaterial artemia cyst shells and polyvinylpyrrolidone were used as hard template and chemistry template, separately. It can be found that, nikel oxide maintain a perfect three-demensional hierarchical porous structure assembled by multiple-layered porous nanosheets in the calcination temparatrue of 500℃. The hierarchical porous Ni O shows a BET surface of 70.02 m2 g-1. The electrochemical performance of Ni O-500 was carried out in 6 M KOH, exhibits relatively high specific capacitance value of 482.86 F g-1 at a current density of 1 A g-1, good rate performance(95.8 % capacity retention from 1 to 10 A g-1) as well as good cycling performance(~96 % retention upon 2000 charge/discharge cycles at 10 A g-1).Then, ultrathin layered structure of nickel-cobalt hydroxide/reduced graphene oxide composites was synthesized by one step hydrothermal method. L-ascorbic acid(LAA), the reductant of graphene oxide, can control the morphology the nickel-cobalt hydroxide nanoplates. It can be found that, small and thin Ni-Co hydroxide nanoplates are fully and uniformly tiled on the surfaces of reduced graphene oxide sheets at the LAA content of 60 mg, forming Ni Co/r GO-LAA60 with a unique thin layer structure with 2 nm. The layers stack loosely. The electrochemical performance of Ni Co/r GO-LAA60 was carried out in 6M KOH, which displays high specific capacitance of 1691 F g-1 at at a current density of 0.5 A g-1, good rate performance(81.8 % of capacitance retention from 0.5 to 10 A g-1, 78.5% of capacitance retention from 0.5 to 40 A g-1), as well as good cycling stability(97.3% within 1000 cycles, 68.3 % within 10000 cycles).Besides, an assymmetic supercapacitor has been fabricated using Ni Co/r GO-LAA60 as positive electrode and 3D hierarchical porous carbon(HPC) as negative electrode in chapter 4. Ni Co/r GO-LAA60//HPC presents good electrochemical performance in the potential window of 1.6 V. This asymmetric supercapacitor exhibits maximum specific capacitance value of 167.4 F g-1 in 0.1 A g-1, good rate performance(67 % of capacitance retention from 0.5 to 10 A g-1) and excellent cycling stability(76 % retention within 17000 cycles). Ni Co/r GO-LAA60//HPC also shows the highest density of 56.1 W h kg-1 at power density of 76 W kg-1.