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38. Highly Concentrated Asymmetric KTFSI for Aqueous Potassium Ion Batteries.

Author

Kumaresan, Thileep Kumar, Ikhe, Amol Bhairuba, Park, Woon‐Bae, Prabakar, S. J. Richard, Noh, Hyeon Su, Seo, Jung Yong, Lee, Young‐Kook, Sohn, Kee‐Sun, Kwak, Joon Seop, and Pyo, Myoungho

Subjects
POTASSIUM ions, AQUEOUS electrolytes, POTASSIUM salts, LOW temperatures, SUPERCOOLING
Abstract

Potassium imide salt (KCTFSI), featuring cyano (C≡N) and trifluoromethanesulfonyl (TFSI) branches, is reported for the first time as a promising electrolyte for aqueous potassium‐ion batteries (KIBs). In contrast to the limited solubility of symmetric KTFSI (1.5m), asymmetric KCTFSI achieves a high saturation concentration of 32.2m within a "water‐in‐salt" region. Experimental and theoretical studies reveal that the remarkable enhancement of solubility is associated with the asymmetry of CTFSI anions and likely the preferential formation of contact‐ion pairs through C≡N coordination. The 32.2m KCTFSI solution not only extends the electrochemical stability window (3.80 V on Al) but also maintains a liquid state at low temperatures (−15 °C) for an extended period, in sharp contrast to the immediate solidification of potassium bis(fluorosulfonyl)imide (KFSI, 30m) and potassium trifluoromethanesulfonate (KOTF, 22m) solutions. Thanks to its wide voltage window and supercooling behavior, KCTFSI demonstrates excellent compatibility with perylene‐3,4,9,10‐tetracarboxylic diimide (PTCDI) anode and KVPO4F (or K2Fe[Fe(CN)6]·2H2O) cathode over a wide temperature range. For instance, full cells of PTCDI/KCTFSI/KVPO4F exhibit reasonable cyclability with an average discharge voltage of 1.7 V over 300 charge/discharge cycles at −15 °C. it is anticipated that this work will inspire new designs of hybrid electrolytes based on CTFSI to advance the realization of viable aqueous KIBs. [ABSTRACT FROM AUTHOR]

Published
2024
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39. Influence of the Acetylene Flow Rate and Process Pressure on the Carbon Deposition Behavior by Thermal Chemical Vapor Deposition Process.

Author

Kwon, Gi-Hoon, Choi, Byoungho, Lee, Young-Kook, and Moon, Kyoungil

Subjects
CARBON films, CHEMICAL vapor deposition, TRANSMISSION electron microscopy, SCANNING electron microscopy, RAMAN spectroscopy
Abstract

We used the chemical vapor deposition process to deposit carbon film at a high temperature (900 °C). The carbon films were deposited on AISI 1006 foils using an acetylene gas. We analyzed the carbon film deposited on the surface using Raman spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy to define changes in the bonding structure of the carbon film. The results of Raman spectroscopy and high-resolution transmission electron microscopy revealed that as the acetylene flow rate increased, the shape of the deposited carbon film changed from graphene to graphite. In addition, in order to compare the quality of the carbon film in terms of mechanical and electrical properties, carbon films treated under various conditions were closely analyzed using nano-indenter and a sheet resistance meter. Therefore, the optimal condition (1 Torr-50 sccm) was selected in which graphene was uniformly deposited and had the lowest electrical resistance (500 Ω/sq) and highest hardness (12 GPa). [ABSTRACT FROM AUTHOR]

Published
2024
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