In this work, we report an alternative approach to self-assemble low crystalline ultra-thin MnO₂ nano-sheets into MnO₂ nano-spheres by a cost-effective, one-pot and instant ultrasonic synthesis without the assistance of acid or template within an hour for high performance and high rate supercapacitors. The MnO₂ nano-spheres are demonstrated to be excellent working electrodes in a three-electrode cell revealing remarkable specific capacitance of 309 F g⁻¹ at the current density of 1.0 A g⁻¹ and good cyclic stability with capacitance retention of 90% after 5000 cycles in 1 M Na₂SO₄ electrolyte aqueous solution. Further, an aqueous asymmetrical supercapacitor (MnO₂//AC) device was constructed whose maximum workable potential window for the MnO₂//AC device reached 0–2.0 V. MnO₂//AC illustrated an energy density of 40 Wh kg⁻¹ with a maximum power density of 19000 W kg⁻¹. Besides, this device sustained a long cycle life with 85% capacitance retention after 5000 cycles.

在这项工作中，我们报告了一种可替代的方法，该方法可 通过经济高效的一锅法和即时超声合成方法将低结晶超薄MnO ₂ 纳米片自组装成MnO ₂纳米球，而无需借助酸或模板一个小时的高性能和高速率超级电容器。MnO ₂ 纳米球被证明是三电极电池中的优良工作电极，在 1.0 A g ^-1的电流密度下显示出明显的309 F g ^-1的比电容， 良好的循环稳定性，经过90％的电容保持率在1 M Na ₂ SO _4中进行5000次循环 电解质水溶液。此外，水性不对称超级电容器（MNO ₂ // AC）设备构造，其最大可操作的电位窗的的MnO ₂ // AC装置达到0-2.0 V.的MnO ₂ // AC 40所示瓦千克的能量密度^-1 最大功率密度为19000 W kg ^-1。此外，该器件在5000次循环后仍保持了85％的电容保持率，从而延长了循环寿命。