Abstract Defect engineering is one of the main ways to adjust the internal structure and electrochemical performance of materials. Therefore, we prepared MnO2 ultra-thin nanosheets loading on Ni foam as a supercapacitor electrode through hydrothermal process and vacuum annealing, which not only obtained oxygen defects on the surface, but also led to a shift in the valence of Mn4+ to Mn3+. The results indicate that the optimal electrode can achieve high specific capacitance of 522 F/g at a current density of 1 A/g and excellent cycling performance of 95.24 % at 5,000 cycles. Then, we assembled an asymmetric supercapacitor using the sample annealed for 45 min as the positive electrode and activated carbon as the negative electrode in the 1 M Na2SO4 electrolyte to investigate the practical application. The asymmetric supercapacitor with a large voltage window of 0-2 V and an energy density of 18.06 Wh/kg at a power density of 1 kW/kg with a promising electrochemical stability was assembled. This article provides a simple method to improve electrochemical performance of transition metal oxide electrodes in supercapacitors by introducing defects.

中文翻译：

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用于高性能超级电容器的具有氧缺陷的真空退火 MnO2 超薄纳米片

摘要 缺陷工程是调整材料内部结构和电化学性能的主要途径之一。因此，我们通过水热工艺和真空退火制备了负载在泡沫镍上的 MnO2 超薄纳米片作为超级电容器电极，不仅在表面获得了氧缺陷，而且还导致 Mn4+ 的价态向 Mn3+ 转变。结果表明，最佳电极在 1 A/g 的电流密度下可实现 522 F/g 的高比电容，并在 5,000 次循环时具有 95.24% 的优异循环性能。然后，我们在 1 M Na2SO4 电解液中使用退火 45 分钟的样品作为正极，活性炭作为负极组装了一个不对称超级电容器，以研究实际应用。组装了具有 0-2 V 大电压窗口和 18.06 Wh/kg 能量密度、1 kW/kg 功率密度、具有良好电化学稳定性的非对称超级电容器。本文提供了一种通过引入缺陷来提高超级电容器中过渡金属氧化物电极电化学性能的简单方法。