A nonaqueous potassium-ion hybrid capacitor enabled by two-dimensional diffusion pathways of dipotassium terephthalate. Issue 7 (17th December 2018)

• Record Type: Journal Article
• Authors: Luo, Yuwen; Liu, Luojia; Lei, Kaixiang; Shi, Jifu; Xu, Gang; Li, Fujun; Chen, Jun
• Is Part Of: Chemical science. Volume 10:Issue 7(2019)
• Page Start: 2048
• Page End: 2052
• Publication Date: 2018-12-17
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c8sc04489a
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Potassium-ion hybrid capacitor is enabled by fast diffusion, facile reaction kinetics and small volume change of dipotassium terephthalate and its comparability to the non-faradaic capacitive kinetics of activated carbon, and hence shows high power and energy density. Abstract : Nonaqueous potassium-ion hybrid capacitors (KIHCs) are faced with limited redox reaction kinetics of electrodes for accommodation of large-sized K + . Here, dipotassium terephthalate (K2 TP) is applied as an organic negative electrode to provide comparable reaction kinetics with a non-faradaic activated carbon (AC) positive electrode to boost the electrochemical performance of KIHCs. It is revealed that the large exchange current density and fast two-dimensional (2D) diffusion pathways of K + in K2 TP determined by density functional theory (DFT) calculations ensure its fast redox reaction and transport kinetics. The as-constructed KIHC presents both high energy and power densities of 101 W h kg −1 and 2160 W kg −1 based on the mass of the two electrodes (41.5 W h kg −1 and 885.2 W kg −1 based on the mass of the two electrodes and electrolyte), respectively, and a superior capacity retention of 97.7% after 500 cycles. The excellent electrochemical performance is attributed to the fast kinetics, good structural flexibility, and small volume change (9.4%) of K2 TP upon K + insertion/extraction, and its good compatibility with the AC positive electrode in 1, 2-dimethoxyethane (DME)-based electrolyte. This will promote application of organic materials in hybrid capacitors and the development of KIHCs.