Xiong Ting, Yu Zhi Gen, Lee Wee Siang Vincent, Xue Junmin
National University of Singapore, Department of Materials Science and Engineering, Singapore, 117573, Singapore.
Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, 117546, Singapore.
ChemSusChem. 2018 Sep 21;11(18):3307-3314. doi: 10.1002/cssc.201801076. Epub 2018 Aug 10.
Widening the voltage window is often proposed as a way to increase the energy density of aqueous supercapacitors. However, attempting to operate beyond the aqueous supercapacitor stability region can undermine the supercapacitor reliability due to pronounced electrolyte decomposition, which can lead to a significant self-discharge process. To minimize this challenge, charge injection by grafting o-benzenediol onto the carbon electrode is proposed through a simple electrochemical cycling technique. Due to charge injection from o-benzenediol into the carbon electrode, the equilibrium potential of the individual electrode can be reduced. In addition, due to its small molecular size, charge distribution, which is commonly faced by bulk pseudocapacitive materials, is also avoided. The assembled supercapacitor based on the o-benzenediol-grafted carbon demonstrated a maximum energy density of 24 Wh kg and a maximum power density of 69 kW kg , with a retention of 89 % after 10 000 cycles at 10 A g . A low self-discharge of about 4 h was recorded; this could be attributed to the low driving force arising from the lower equilibrium potential. Thus, the proposed technique may provide insight towards the tuning of the equilibrium potential to attain reliable, high-performing supercapacitors with a low self-discharge process.
扩大电压窗口通常被认为是提高水系超级电容器能量密度的一种方法。然而，试图在水系超级电容器稳定区域之外运行可能会因明显的电解质分解而损害超级电容器的可靠性，这可能导致显著的自放电过程。为了尽量减少这一挑战，通过一种简单的电化学循环技术，提出了将邻苯二酚接枝到碳电极上进行电荷注入的方法。由于邻苯二酚向碳电极的电荷注入，可以降低单个电极的平衡电位。此外，由于其分子尺寸小，还避免了块状赝电容材料常见的电荷分布问题。基于邻苯二酚接枝碳组装的超级电容器表现出最大能量密度为24 Wh kg和最大功率密度为69 kW kg，在10 A g下循环10000次后保留率为89%。记录到约4小时的低自放电；这可能归因于较低平衡电位产生的低驱动力。因此，所提出的技术可能为调节平衡电位以获得具有低自放电过程的可靠、高性能超级电容器提供思路。
