TY - JOUR
T1 - Highly Concentrated Asymmetric KTFSI for Aqueous Potassium Ion Batteries
AU - Kumaresan, Thileep Kumar
AU - Ikhe, Amol Bhairuba
AU - Park, Woon Bae
AU - Prabakar, S. J.Richard
AU - Noh, Hyeon Su
AU - Seo, Jung Yong
AU - Lee, Young Kook
AU - Sohn, Kee Sun
AU - Kwak, Joon Seop
AU - Pyo, Myoungho
N1 - Publisher Copyright:
© 2024 Wiley-VCH GmbH.
PY - 2024/10/11
Y1 - 2024/10/11
N2 - 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.
AB - 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.
KW - aqueous batteries
KW - asymmetric imide salts
KW - coordination
KW - potassium ion batteries
KW - water-in-salt-electrolyte
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U2 - 10.1002/aenm.202402011
DO - 10.1002/aenm.202402011
M3 - Article
AN - SCOPUS:85200037308
SN - 1614-6832
VL - 14
JO - Advanced Energy Materials
JF - Advanced Energy Materials
IS - 38
M1 - 2402011
ER -
