线团形貌层状二氧化锰的制备及其在不对称电化学电容器中的应用

将无定型MnO2在1 mol/L NaOH水溶液中150℃水热处理12 h后,得到了具有线团形貌的层状二氧化锰。利用XRD、SEM和低温N2吸-脱附等手段对样品的形貌和结构进行了表征。采用循环伏安、恒流充放电以及交流阻抗技术对样品的电化学性质进行了研究。研究结果表明,在三电极体系中,线团状MnO2在0~1.0 V(vs.SCE)的电压范围内具有较好的电容性质,其质量比电容为154 F/g。利用线团状MnO2为正极,石墨烯为负极以及1 mol/L Na2SO4水溶液为电解液组装了不对称型的电化学电容器。电化学测试表明,该电容器可在0~1.8 V的电压范围内可逆循环,其能量密度为21.6 W·h/kg,远远高于基于线团状MnO2(4.86 W·h/kg)和石墨烯(4.3 W·h/kg)的对称型电容器。

Preparation of Clew-like MnO2 with Layered Structure as High-performance Asymmetric Electrochemical Capacitor Electrodes

Clew-like MnO2(CMnO2) with a specific capacitance of 154 F/g within a potential window of 0~1.0 V vs saturated calomel electrode has been synthesized by hydrothermally treating the precursor of as synthesized MnO2 in a solution of 1 mol/L NaOH at 150 ℃ for 12 h. The morphology and structure of the obtained material were examined by XRD, SEM and N2 adsorption-desorption. The capacitive properties were characterized by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopies. The results indicate that the CMnO2 exhibits good capacitive performance in a three-electrode cell with a mass specific capacitance of 154 F/g. An asymmetrical electrochemical capacitor(EC) was assembled using CMnO2 as the positive electrode and graphene(GR) as the negative electrode, respectively. The asymmetrical EC can cycle reversibly in a cell potential of 0~1.8 V and gives a high energy density of 21.6 W·h/kg, which is much higher than those of symmetrical ECs based on CMnO2(4.86 W·h/kg) and GR(4.3 W·h/kg). Moreover, the asymmetrical EC presents a high power density(9 kW/kg at 8.1 W·h/kg) and excellent cycling performance of 83% retention after 1000 cycles.