| Based on the global consensus on "carbon neutrality",the demand for renewable and sustainable clean energy is increasing,and supercapacitors have become the strong candidate for energy storage equipment and can be widely used in high-power equipment because of the fast charge-discharge and good cycle stability.As one of the most critical components of supercapacitor,the design of electrode materials has been invested in a lot of research work.Among them,nickel-manganese based compounds can achieve high energy storage through fast Faraday oxidation-reduction reaction,which has attracted much attention in recent years because of their high oxidation-reduction activity and low cost.However,the low conductivity of metal oxides/hydroxides limits the actual specific capacity,and the agglomeration of electrode materials has become an urgent problem to be solved,which may also seriously affect ion/electron transport.In this paper,nickel-manganese compounds are taken as the basic research object.From the aspect of ion/electron transport,nickel-manganese compounds are combined with graphene,silver nanowires and other high conductivity materials to construct three-dimensional electrode materials by various methods such as morphology regulation and structure design,thereby effectively improving the electrochemical performance of nickel-manganese compounds.The main results are as follows:(1)Nickel-manganese oxide(NiMnO3)powder is successfully prepared by coprecipitation method and compounded with reduced graphene oxide(rGO)during the reduction process of rGO.And then the morphology,structure and electrochemical performance of NiMnO3/rGO composite at different mass ratios are investigated.Among them,graphene effectively improves the electronic transport of the composite because of its excellent electronic conductivity,and its unique two-dimensional structure also shows a positive impact on improving the morphology of the composite and providing more active sites.Thus,the specific capacitance is slightly improved compared with NiMnO3,that is,the specific capacitance can reach 344.78 F·g-1 at 2 A·g-1.(2)The micro-flower like NiMn layered double hydroxide/silver nanowires(NiMn LDH/Ag NWs)composites for high-performance supercapacitors are constructed by hydrothermal method.It is found that silver nanowires not only ensure excellent electronic conductivity,but also have a positive impact on the growth of LDH nanosheets.Compared with Ni(OH)2,NiMn LDH has significantly increased layer spacing,and its unique three-dimensional opening structure finally realizes fast ion transport.In particular,NiMn LDH/Ag NWs with 0.6 mmol Ag NWs exhibits the highest specific capacitance of 1436.30 F·g-1 at 2 A·g-1,and good cycle stability of 80.65%after 1000 charge/discharge cycles at 50 A·g-1.NiMn LDH/Ag NWs//AC obtains a maximum energy density of 71.95 Wh·kg-1 at the power density of 1548.55 W·kg-1.When the power density is 1548.55 W·kg-1,NiMn LDH/Ag NWs//AC reaches the maximum energy density,namely 71.95 Wh·kg-1.(3)NiMnO3/Ni(OH)2 is in-situ grown on nickel foam(NF)by hydrothermal method,which has both higher potential window of oxide and better specific capacitance of hydroxide.In addition,Ag NWs are introduced to synthesize NiMnO3/Ni(OH)2/Ag NWs to achieve higher energy density.Ag NWs can be used to control the structure and morphology of the composite electrode materials,and significantly improve the electrochemical performance.Moreover,conductive NF reduces the diffusion resistance between the electrode and electrolyte,and also promotes ion/electron transmission,making the specific capacitance of NiMnO3/Ni(OH)2/Ag NWs reach 2103.17 F·g-1 at 2 A·g-1,showing 94.43%good cycle stability after 1000 cycles.When the power density of NiMnO3/Ni(OH)2/Ag NWs//AC is 1699.87 W·kg-1,the maximum energy density of 81.11 Wh·kg-1 is obtained. |
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