Preparation Of Nickel-based Composites And Their Application In Supercapacitors

With the increasing demand for clean,sustainable and reliable energy storage equipment,the design and assembly of supercapacitors with superior power density,fast charge/discharge rate and long cycling lifespan are attracting increasing interests,but also facing great challenges.Nevertheless,their further commercialization is still suffered from the relatively low energy density and poor rate performance which are determined by the structure and electrochemical properties of electroactive materials.Therefore,exploring and preparing electrode materials possessing optimal structures and considerable efforts play a key role in improving the electrochemical performance of SCs.In this paper,we designed and prepared nickel metal-organic framework microspheres anchored directly on reduced graphene oxide(Ni-MOF/rGO)by a facile hydrothermal and successive calcining process.In addition,Co-CH@NiCoMn-CH core/shell structures on the surface of Ni foam were successfully synthesized by the two-step hydrothermal method.These composites were applied to supercapacitors,and their electrochemical properties were studied.Details are as follows:1.Ni-based MOF nanospheres on reduced graphene oxide(Ni-MOF/rGO)composite as electrode material for high performance supercapacitor was prepared by simple hydrothermal and calcination method.After annealing treatment at an optimized temperature of 300?,the obtained Ni-MOF/rGO-300 composite shows the best electrochemical performance.Specifically,the Ni-MOF/rGO-300 composite shows an excellent specific capacitance of 954 F g-1.Meanwhile,an ASC device is assembled by using Ni-MOF/rGO-300 and activated carbon(AC)as positive and negative electrodes separately and exhibits a good energy density of 17.13 Wh kg-1.The excellent electrochemical properties can be credited to the synergistic effects between the unique structures of Ni-MOF and rGO,which makes the Ni-MOF/rGO composite a potential electrode material for high performance supercapacitors.2.The core-shell structure of Co-CH nanowire arrays(NWAs)and nickel-cobalt-manganese ternary hydroxides(NiCoMn-CH)ultrathin nanosheets were successfully synthesized on the surface of foam Ni by two-step hydrothermal method.Since the combination of Co-CH and NiCoMn-CH nanostructures has a significant synergistic effect,the obtained electrodes exhibit excellent conductivity and high specific surface area,an unprecedented high specific capacitance(up to 3224 F g-1)and an ultralong cycling stability(92.4%retention after 6000 successive charge-discharge cycles).Meanwhile,an asymmetric supercapacitor device assembled of the Co-CH@NiCoMn-CH hierarchical nanostructures as positive electrode and activated carbon(AC)as negative electrode delivers good energy density of 20.31 W h kg-1.This methodology could be generalized to the design of other novel structured nanomaterials for energy storage devices and other applications.