Chao Huikuan, Wang Zhen-Gang
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
J Phys Chem Lett. 2020 Mar 5;11(5):1767-1772. doi: 10.1021/acs.jpclett.0c00023. Epub 2020 Feb 19.
Room-temperature ionic liquids (RTILs) are synthetic electrolytes with electrochemical stability superior to that of conventional aqueous-based electrolytes, allowing a significantly enlarged electrochemical window for application as capacitors. In this study, we propose a variant of an existing RTIL model for solvent-free RTILs, accounting for both ion-ion correlations and nonelectrostatic interactions. Using this model, we explore the phenomenon of spontaneous surface charge separation in RTIL capacitors and find that this transition is a common feature for realistic choices of the model parameters in most RTILs. In addition, we investigate the effects of asymmetric preferential ion adsorption on this charge separation transition and find that proximity of the transition in this case can result in greatly enhanced energy storage. Our work suggests that differential chemical treatment of electrodes can be a simple and useful means for optimizing energy storage in RTIL capacitors.
室温离子液体（RTILs）是一种合成电解质，其电化学稳定性优于传统的水基电解质，从而为用作电容器提供了显著扩大的电化学窗口。在本研究中，我们针对无溶剂RTILs提出了一种现有RTIL模型的变体，该模型同时考虑了离子-离子相关性和非静电相互作用。使用该模型，我们探究了RTIL电容器中自发表面电荷分离现象，并发现这种转变是大多数RTILs中模型参数实际选择的一个共同特征。此外，我们研究了不对称优先离子吸附对这种电荷分离转变的影响，发现在这种情况下接近转变可导致储能大大增强。我们的工作表明，电极的差异化学处理可能是优化RTIL电容器储能的一种简单而有用的方法。
