| As equal important to batteries for the future, supercapacitors have been intensely investigated because of their environmental friendliness, high power density and cycling stability. On the basis of charge storage mechanism, supercapacitor can be classified into pseudocapacitors and electric double layer capacitors (EDLCs). Transition-metal oxides are always widely investigated as pseudocapacitive materials with quite high theoretical specific faradic capacitance. Because of the high specific surface area, active carbon materials are typical electrode materials for EDLCs. In this thesis we will design the nano-arrayed anode and fabricate the matched cathode. Then we use the prepared anode and cathode to assemble neutral aqueous supercapacitors and all-solid-state supercapacitors. The anode and cathode electrodes will be tested in the neutral aqueous supercapacitors and all-solid-state supercapacitors respectively. We expect to provide scientific reference to improve the performance of supercapacitors. The main research content of this thesis is as follows:(1)We propose and realize a high potential Ni0.25 Mn0.75O@C solid-solution nano-array which growing directly on Ti substrate with in-situ carbon modification by facile hydro-thermal method. First of all we adopt control variable method to obtain the ideal experimental preparation and test conditions of active material:Ti substrate treated by HCl, tht mole ratio of Ni and Mn with 1:3 in the precursor solution, the hydro-thermal condition of 120℃,450℃ in Ar to anneal, the voltage window of 0-1.4V, the 1 mol/L LiCl electrolyte, in-situ modification with 0.25g/50ml activated carbon in the precursor solution. The results show that pure MnO has ultra wide charge/discharge window of 0-1.4 V in neutral aqueous LiCl electrolyte. The equivalent series resistance (ESR) and unstable structure of electrodes was overcome by the Ni-Mn-O@C solid-solution nano-array. In-sute carbonization results in three important changes for Ni-Mn-O solid solution:firstly, the homogeneous carbon in the surface of electrode ameliorate the electrode/electrolyte interface; then, the in-sute carbonization further improve the uniform of NW array; more importantly, the microstructure of Ni0.25Mn0.75O@C becomes porous. The solid-solution and in-situ carbon modification greatly improve the electrochemical properties of manganese oxides. The areal capacitance was improved by 6 fold from 39.43 mF cm-2 (MnO) to 242.86 mF cm-2 (Ni0.25Mn0.75O@C). While, Nio.25Mno.750@C, with higher initial capacitance than MnO and Ni0.25Mn0.75O, still has 89% capacitance remain after 500 cycles, and even 73% retention after 5000 cycles.(2) To assemble a full cell, we use the clean nickel as current collector to preparate AC anode with tunable capacity. After a series of experiments, we choose the mixed solution with 1.46g/20mL activated carbon concentration to make the AC anode. By using 1.4 V Nio.25Mno.750@C as cathode and AC as anode, we assemble high voltage aqueous asymmetric supercapacitor and all-solid-state asymmetric supercapacitor device, which both have high working voltage window (0-2.4 V), good rate capability, high cycling stability and ideal capacitive behavior. Furthermore, with a wide voltage window of 0-2.4 V and ultra-thin characteristic (170.75 μm), the all-solid-state device exhibits excellent volumetric capacitance (6.88 F cm-3), high volumetric energy (4.72 mWh cm-3) and power densities (776 mW cm-3) as well as impressive cycling life of over 5000 cycles. |
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