Abstract MgCo2O4 microflowers (MFs) assembled with porous nanosheets were prepared through a facile hydrothermal method with a post calcination treatment of the precursors at 400 °C for 3 h in air. No surfactant or template was used during the synthetic process. These MgCo2O4 MFs possessed a BET specific surface area of 39.1 m2 g−1 with an average pore size of 37 nm. The electrochemical performance was evaluated in a typical three-electrode system using 2 M of KOH aqueous solution as electrolyte, and the results indicated that such MgCo2O4 MFs exhibited a high specific capacitance of 749.2 F g−1 at 1 A g−1 as well as a high rate capability of approximate 73.3% with the current density increasing from 1 to 15 A g−1. After 5000 charge-discharge cycles at 5 A g−1, a specific capacitance of 435.3 F g−1 with 67.8% capacitance retention of its initial value and Coulombic efficiency of about 100% could be reached. In addition, an asymmetric supercapacitor (ASC) was fabricated with MgCo2O4 MFs as the positive electrode and activated carbon (AC) as the negative electrode. The ASC delivered a high energy density of 35.2 Wh kg−1 at a power density of 859.2 W kg−1. At a higher power density of 7415.3 W kg−1, the energy density still reached 29.3 Wh kg−1. The ASC also showed a good cycling stability with 100.9% specific capacitance retention after 5000 cycles at 5 A g−1. The unique MgCo2O4 MFs with mesoporous structures are beneficial for the rapid Faradic reactions because sufficient contact between electrolyte/electrode material and short diffusion path for ions/electrons can be ensured. The current synthesis is involved in simple operation and low cost, and can be extended to the preparation of other binary transitional metal oxides as electrode materials for the next-generation advanced supercapacitors.

中文翻译：

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水热合成花状MgCo2O4多孔微结构作为非对称超级电容器的高性能电极材料

摘要 MgCo2O4 微花 (MFs) 与多孔纳米片组装在一起，通过简单的水热法制备，前体在 400°C 下在空气中煅烧 3 小时。在合成过程中没有使用表面活性剂或模板。这些 MgCo2O4 MF 的 BET 比表面积为 39.1 m2 g-1，平均孔径为 37 nm。在使用 2 M KOH 水溶液作为电解质的典型三电极系统中评估电化学性能，结果表明这种 MgCo2O4 MFs 在 1 A g-1 下表现出 749.2 F g-1 的高比电容以及随着电流密度从 1 增加到 15 A g-1，具有大约 73.3% 的高倍率能力。在 5 A g-1 下进行 5000 次充放电循环后，比电容为 435.3 F g-1，67。可以达到其初始值的 8% 电容保持率和约 100% 的库仑效率。此外，以MgCo2O4 MFs为正极，活性炭（AC）为负极，制备了不对称超级电容器（ASC）。ASC 在 859.2 W kg-1 的功率密度下提供了 35.2 Wh kg-1 的高能量密度。在 7415.3 W kg-1 的更高功率密度下，能量密度仍达到 29.3 Wh kg-1。ASC 还显示出良好的循环稳定性，在 5 A g-1 下循环 5000 次后比电容保持率为 100.9%。具有介孔结构的独特 MgCo2O4 MFs 有利于快速法拉第反应，因为可以确保电解质/电极材料之间的充分接触和离子/电子的短扩散路径。目前的合成涉及操作简单，成本低，