Charging/Discharging Dynamics in Two-Dimensional Titanium Carbide (MXene) Slit Nanopore: Insights from molecular dynamic study. (1st April 2016)

• Record Type: Journal Article
• Authors: Xu, Kui; Ji, Xiao; Zhang, Bao; Chen, Chi; Ruan, Yunjun; Miao, Ling; Jiang, Jianjun
• Is Part Of: Electrochimica acta. Volume 196(2016)
• Page Start: 75
• Page End: 83
• Publication Date: 2016-04-01
• Subjects: Supercapacitor -- MXene -- Slit Nanopore -- Molecular dynamics; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2016.02.165
• Languages: English
• ISSNs: 0013-4686

Abstract

Graphical abstract: Highlights: Ionic insertion and exchange and ionic diffusion inside the MXene (Ti3 C2 (OH)2 ) slit nanopore during galvanostatic cycling process is simulated. Charge storage takes place by a fast counter-ion insertion and counter-ion/co-ion exchange during charge/discharge process. Spatial distribution of ions and orientation of cation dipoles vary cyclically to screen the external electric potential. A complement to the restriction of the in situ measurements in understanding the underlying charge storage mechanism. Abstract: While most theoretical studies on slit nanopore electrodes are limited in their static properties, understanding the dynamic charge storage is crucial for promoting their electrochemical performance in the field of energy storage systems. In this article, the charging/discharging dynamics in MXene (Ti3 C2 (OH)2 ) electrode featuring intrinsic slit nanopore with room temperature ionic liquid are investigated by molecular dynamic simulation. The galvanostatic cycling is modeled to help to understand the dynamic charge storage mechanism. The simulation results show that the electrolyte ions spontaneously wet the Ti3 C2 (OH)2 slit nanopore in the absence of external potential, even at 0.7 nm layer distance pore case. An intriguing electroneutrality breakdown and faster diffusion property is observed inside the nanopore. During charge/discharge process, the charge storage takes place by a fast counter-ion insertion and counter-ion/co-ion exchange. Besides, the spatial distribution of ions and the orientation of the cation dipoles inside the pore vary cyclically alone with the charge/discharge process, which helps to screen the external electric potential. Having elucidated the charge mechanism, we investigate the layer distance factor and show that the ions exhibit more significantly acceleration and more ordered dipole orientation inside the narrower pore. This will help Ti3 C2 (OH)2 electrode with narrower pore exhibit better power performance.