Department of Chemical and Biomolecular Engineering, School of Energy Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Rayong 21210, Thailand.
Nanoscale. 2017 Sep 21;9(36):13630-13639. doi: 10.1039/c7nr02554h.
Manganese dioxide (MnO) has been widely used as an active material for high-performance supercapacitors due to its high theoretical capacitance, high cycling stability, low cost, and environmental friendliness. However, the effect of its crystallographic phase on charge storage performances and mechanisms is not yet clear. Herein, MnO-based supercapacitors with different structures including nanospheres, nanorods, nanotubes, and nanosheets have been fabricated and investigated. Among such structures, δ-MnO nanosheets exhibit the highest specific capacitance of 194.3 F g at 1 A g when compared with other phases and shapes. The maximum specific energy of the δ-MnO nanosheet supercapacitor is 23.4 W h kg at 971.6 W kg and the maximum specific power is 4009.2 W kg at 15.9 W h kg with a capacity retention of 97% over 15 000 cycles. The δ-MnO nanosheet mainly stores charges via a diffusion-controlled mechanism at the scan rates of 10-100 mV s, whilst the α-MnO with different morphologies including nanospheres, nanorods, and nanotubes store charges via a non-faradaic or non-diffusion controlled process especially at fast scan rates (50-100 mV s). Understanding the charge storage performance and mechanism of the MnO nanostructures with different crystallographic phases and morphologies may lead to the further development of supercapacitors.
二氧化锰（MnO）由于其高理论电容、高循环稳定性、低成本和环境友好性，已被广泛用作高性能超级电容器的活性材料。然而，其晶相对电荷存储性能和机制的影响尚不清楚。在此，制备并研究了具有不同结构的基于 MnO 的超级电容器，包括纳米球、纳米棒、纳米管和纳米片。在这些结构中，δ-MnO 纳米片在 1 A g 时具有最高的比电容 194.3 F g，与其他相和形状相比。δ-MnO 纳米片超级电容器的最大比能量为 23.4 W h kg，在 971.6 W kg 时最大比功率为 4009.2 W kg，在 15.9 W h kg 时容量保持率为 97%，经过 15000 次循环后仍保持 97%。δ-MnO 纳米片主要通过扩散控制机制在 10-100 mV s 的扫描速率下存储电荷，而具有不同形态（包括纳米球、纳米棒和纳米管）的α-MnO 通过非法拉第或非扩散控制过程存储电荷，特别是在快速扫描速率（50-100 mV s）下。了解具有不同晶相和形态的 MnO 纳米结构的电荷存储性能和机制可能会促进超级电容器的进一步发展。
