| With the rapidly growing demand for eco-friendly and sustainable energy storage/conversion device,supercapacitors have emerged as one of the most promising candidates,which possess fast charge/discharge capability,no memory effect,high current discharge capability as well as ultrahigh power density.Nevertheless,the scarcity of energy density seriously restricts their further application fields.In order to obtain high energy density,we can prepare new self-supporting electrode materials with high specific capacity and widen the voltage window.The main work in this thesis are as follows:(1)Co0.21Ni0.79MoO4 nanosheets are grown on conductive nickel meshes by simple hydrothermal reaction.And a series of P-Co0.21Ni0.79MoO4-n(n=1,2 and 3)products were prepared using different amounts of NaH2PO2·H2O,that is,n=0.2,0.4,and 0.8 g via a solid/gas-phase reaction involving Co0.21Ni0.79MoO4 and PH3 reactants.Element P incorporation into the P-Co0.21Ni0.79MoO4-n lattice can produce a large number of electrochemical active reaction sites and enhance efficiently surface reactivity,and thus leading to the enhanced electrochemical performance.When the dose of phosphorus source is 0.4 g,the obtained P-Co0.21Ni0.79MoO4-2 electrode has the best electrochemical performance.The optimized P-Co0.21Ni0.79MoO4-2 provides a large specific capacity of 547.1 F g-1 even at 20 A g-1,as well as excellent electrochemical stability.Furthermore,the assembled ACS(P-Co0.21Ni0.79MoO4-2//AC)exhibits ultrahigh energy density of 12.5 Wh kg-1 at power density of 7479.1 W kg-1,as well as good cycling stability with 91%capacity retention after 5000 cycles.(2)The 3D hierarchical core-shell structure N iCo2S4@NiMoO4·xH2O nano needle-like arrays anchored on Ni foam was manufactured by multi-step hydrothermal and sulfur anion exchange processes.The positive synergistic effect between NiCo2S4 nanoneedles inner core and NiMoO4·xH2O nanosheets outer shell will significantly optimize the overall electrochemical properties of the electrode and obtain the high performance supercapacitor.Therefore,the as-prepared NiCo2S4@NiMoO4·xH2O electrode acquires a high specific capacity of 830.2 F g-1 at 2 A g-1,which is much higher than that of single NiCo2S4 or NiMoO4-xH2O.Subsequently,the NiCo2S4@NiMoO4·xH2O electrode is assembled into an asymmetric supercapacitor,which shows a high energy density of 19.3 Wh kg-1 at 795.7 W kg-1.Besides,it also exhibits an outstanding cycling stability with 89.9%capacitance retention after continuous 5000 cycles at 1 A g-1,indicating its promising applications in high-performance supercapacitors.(3)The TMSs/Ni/C-NFs film was obtained through electrospinning and three-step heat treatment process.The nano fibers are tightly woven into interconnected networks,which not only have ultra-robust flexibility,but also effectively mitigate the volume changes of nanoparticles during long-term cycling,and thus leading to the improved structure stability.Benefiting from such unique structural features,the obtained TMSs/Ni/C-NFs anode exhibited a fairly high reversible capacity of 1246.9 mAh g-1 and outstanding rate performance as well as long-term cycle stability.The LIC assembled by using the TMSs/Ni/C-NFs film as anode and AC as cathode can deliver a good energy density of 182.0 Wh kg-1 at 121.1 W kg-1.In addition,the TMS s/Ni/C-NFs//AC LIC showed excellent cyclic stability with a capacity retention of 79%after 2000 cycles. |
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