We performed constant-potential molecular dynamics simulations to analyse the double-layer structure and capacitive performance of supercapacitors composed of conductive metal–organic framework (MOF) electrodes and ionic liquids. The molecular modelling clarifies how ions transport and reside inside polarized porous MOFs, and then predicts the corresponding potential-dependent capacitance in characteristic shapes. The transmission line model was adopted to characterize the charging dynamics, which further allowed evaluation of the capacitive performance of this class of supercapacitors at the macroscale from the simulation-obtained data at the nanoscale. These ‘computational microscopy’ results were supported by macroscopic electrochemical measurements. Such a combined nanoscale-to-macroscale investigation demonstrates the potential of MOF supercapacitors for achieving unprecedentedly high volumetric energy and power densities. It gives molecular insights into preferred structures of MOFs for accomplishing consistent performance with optimal energy–power balance, providing a blueprint for future characterization and design of these new supercapacitor systems.
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The theoretical and experimental data presented in this work are available from the corresponding authors on reasonable request.
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G.F., S.B., Ming Chen, L.N., Mingyu Chen, T.W., J.W., R.W. and J.F. acknowledge the funding support from the National Natural Science Foundation of China (51876072, 51836003) and Shenzhen Basic Research Project (JCYJ20170307171511292). S.B. and R.W. thank the China Scholarship Council for financial support. A.A.K. acknowledges the Leverhulme Trust for funding (RPG-2016-223), HUST for the support of this project through the HUST Honorary Professorship, and Imperial College for the support of this form of collaboration between the involved HUST and Imperial groups, and thanks the Imperial College–MIT seed fund for supporting the collaboration between the two universities. M.D., H.B. and T.C. thank the Army Research Office (W911NF-17-1-0174) for support. The computation was completed using the Tianhe II supercomputer in the National Supercomputing Center in Guangzhou. Part of the characterization was performed at the Analytical & Testing Center of HUST.
The authors declare no competing interests.
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Bi, S., Banda, H., Chen, M. et al. Molecular understanding of charge storage and charging dynamics in supercapacitors with MOF electrodes and ionic liquid electrolytes. Nat. Mater. (2020). https://doi.org/10.1038/s41563-019-0598-7