Preparation Of Materials Based On The NiMn And Study Of Properties In Quasi-Solid State Supercapacitors

The syntheses of oxides,hydroxides and sulfides based on NiMn and their electrochemical properties in quasi-solid state supercapacitors were investigated.The contents of the exploration include the following aspects:The novel three-dimensional porous sponge-like nanostructure of Mn₂O₃ tiny nanosheets directly grown on Ni?OH?₂/Mn₂O₃ nanosheet skeleton was successfully prepared in situ on conductive Ni foam substrate by low-budget and facile two-step hydrothermal method.This method includeds two steps:first step is that synthesizing Ni?OH?₂/Mn₂O₃ on Ni foam substrate and second step is that regrowing Mn₂O₃nanosheets on Ni?OH?₂/Mn₂O₃ nanosheet arrays at higher temperature.The synergy function of Ni?OH?₂-Mn₂O₃ and its three-dimensional porous sponge-like structure morphologies that are composed of tiny interconnected radial nanosheets have vastly enhanced conduction property of electron in electrode materials and the contact range between the active materials and electrolyte.At the same time,the structure possessing open channel towards electrolyte also could provide convenient access to interior structure for electrolyte,which promotes release of the intercalation/deintercalation pressure of electrolyte ions.Therefore,the perfect sponge-like structure takes on an outstanding specific capacitance(2274.4 F g^-1 at 1 A g^-1).And a great cycling stability of 87%at 5 A g^-1 after 10000 cycles is also shown,mainly benefiting from the protection function of external Mn₂O₃ tiny nanosheets.Further more,the assembled quasi-solid-state asymmetric supercapacitor?ASC?,Ni?OH?₂/Mn₂O₃@Mn₂O₃ as positive materials and active carbon?AC?as negative materials,also displays a great specific capacitance with 117.1 F g^-1 at current density of 1 A g^-1,an excellent cycling property?remained 83%after 10000 cycles?and a high energy density of 41.6 Wh kg^-1.Therefore,Ni?OH?₂/Mn₂O₃@Mn₂O₃ could be one of the potential materials for application of energy storage-conversion devices.Ni-Mn hydroxides/Ni₃S₂ nanohybrid with nanosheet structure was successfully fabricated via tuning the Mn content and reaction conditions.The orderly open structure,heterogeneous Mn atoms and even-distributed Ni₃S₂ phase not only generate more electrochemical active sites,but also significantly promote electronic conductivity,thus enhancing electrochemical performance of hybrid structure.Servered as supercapacitive electrode,the Ni-Mn hydroxides/Ni₃S₂ presents high capacitance(1386.8 C g^-1 at 1 A g^-1),excellent rate performance(71%retention at 30 A g^-1)and suitable cycling stability?79%ratention after 5000 cycles?.After the coating of RGO nanosheet,the FeOOH@RGO electrode achives high capacity performance(180 C g^-1 at 1 A g^-1)and rate performance(66%retention even at 10 A g^-1).Furthermore,Ni-Mn hydroxides/Ni₃S₂//FeOOH@RGO quasi-solid-state asymmetric supercapacitor was developed,utilizing a positive Ni-Mn hydroxides/Ni₃S₂ electrode and a negative FeOOH@RGO electrode.The hybrid device could achieve high energy densities(53.8 Wh kg^-1 at 820 W kg^-1 and 26.2 Wh kg^-1 at 8200 W kg^-1)and still maintain 75%capacitance after enduring 5000 cycles,which attributes to fast diffusion dynamics of Ni-Mn hydroxides/Ni₃S₂ and FeOOH@RGO electrodes.The preparations of these electrode materials are very simple and the material resources are abundant and environmental.The electrode materials obtained show excellent specific capacitance,good rate performance,high energy density and appropriate stability in quasi-solid state supercapacitors.Therefore,they have broad application prospects in the energy storage equipments.