δ-MnO2纳米线的制备与电化学性能
The Preparation and Electrochemical Performance of δ-MnO2 Nanowire

以MnSO4、(NH4)2S2O8为反应物,(NH4)2SO4为模板试剂,利用水热法制备了δ-MnO2纳米线.分别采用XRD、SEM、N2吸附/脱附等方法对试样的晶体结构、形貌、比表面积进行了表征.用循环伏安、恒流充放电、交流阻抗和循环稳定性测试等方法测试其电化学性能.结果表明:δ-MnO2具有纳米线状结构和较大的比表面积(82.43 m2？g-1),在6 mol？L-1 KOH电解液中,当扫描速率为2 mV？s-1时,δ-MnO2纳米线的比电容为127.60 F？g-1,高于β-MnO2的比电容(60.89 F？g-1),充放电循环2 500次后其容量和库仑效率保持稳定.在电流密度为0.4 A？g-1时,组装的AC/6 mol？L-1 KOH/δ-MnO2装置的功率密度为36.45 W？kg-1,能量密度为10.33 Wh？kg-1.
The δ-MnO2 nanowires are prepared by hydrothermal synthesis method using MnSO4,(NH4)2S2O8 as reactants and(NH4)2SO4 as templates.Their crystal structure,morphology,specific surface area are characterized by scanning electron microscopy,X-ray diffraction,nitrogen adsorption-desorption at 77 K,respectively.Their electrochemical performances in 6 mol？L-1 KOH solution are evaluated by cyclic voltammetry,galvanostatic charge-discharge and electrochemical impedance spectroscopy.The specific capacitance of δ-MnO2 nanowires(127.60 F？g-1)is much higher than that of β-MnO2(60.89 F？g-1)at the scan rate of 2 mV？s-1.The δ-MnO2 nanowires remain excellent cycling stability and the capacitance is no evident fading after a 2 500-cycle charge-discharge.The asymmetric supercapacitors of AC/6 mol？L-1 KOH/δ-MnO2 present the energy density of 10.33 Wh？kg-1 at the power density of 36.45 W？kg-1 at the 0.4 A？g-1 current density