Sub-Nanometer Confined Ions and Solvent Molecules Intercalation Capacitance in Microslits of 2D Materials

Yaqing Guo; Xufeng Hong; Yaqiong Su; Wen Luo; Ruohan Yu; Jinsong Wu; Emiel J M Hensen; Liqiang Mai; Yuancheng Cao

doi:10.1002/smll.202104649

Sub-Nanometer Confined Ions and Solvent Molecules Intercalation Capacitance in Microslits of 2D Materials

Small. 2021 Dec;17(49):e2104649. doi: 10.1002/smll.202104649. Epub 2021 Oct 22.

Authors

Yaqing Guo¹, Xufeng Hong², Yaqiong Su^{3

4}, Wen Luo², Ruohan Yu², Jinsong Wu², Emiel J M Hensen³, Liqiang Mai², Yuancheng Cao⁵

Affiliations

¹ Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China.
² State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, 430070, P. R. China.
³ Laboratory of Inorganic Materials and Catalysis, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P. O. Box 513, Eindhoven, MB, 5600, The Netherlands.
⁴ Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), State Key Laboratory of Physical Chemistry of Solid Surfaces, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
⁵ State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China.

PMID: 34677910
DOI: 10.1002/smll.202104649

Abstract

The ion intercalation behavior in 2D materials is widely applied in energy storage, electrocatalysis, and desalination. However, the detailed effect of ions on the performance, combining the influence of interlayer force and the change of solvent shell, is far less well understood. Here the solvated alkali metal ions with different sizes are intercalated into the lattice of 2D materials with different spacings (Ti₃ C₂ T_x , δ-MnO₂ , and reduced graphene oxide) to construct the intercalation model related with sub-nanometer confined ions and solvent molecules to further understand the intercalation capacitance. Based on electrochemical methods and density functional theory calculation, the ions lose the electrostatic shielding solvent shell or shorten the distance between the layers, resulting in a significant increase in capacitance. It is found that the intercalation capacitance arises from the diffusion of solvated ions and is controlled by quantum and electrochemical capacitance for desolvated ions. This effect of solvation structure on performance can be applied in a variety of electrochemical interface studies and provides a new research view for energy storage mechanisms.

Keywords: intercalation capacitance; quantum capacitance; solvent shell; sub-nanometer confined ions.

Abstract

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