Reversible anion intercalation into graphite from aluminum perchlorate "water‐in‐salt" electrolyte. (1st February 2022)

• Record Type: Journal Article
• Authors: Zafar, Zahid Ali; Abbas, Ghulam; Silhavik, Martin; Knizek, Karel; Kaman, Ondrej; Sonia, Farjana J.; Kumar, Prabhat; Jiricek, Petr; Houdková, Jana; Frank, Otakar; Cervenka, Jiri
• Is Part Of: Electrochimica acta. Volume 404(2022)
• Publication Date: 2022-02-01
• Subjects: Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2021.139754
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: Aluminum perchlorate-based "Water-in-Salt" electrolyte with a wide electrochemical stability window of 4 V. Reversible ClO4 − anion (de)intercalation into HOPG cathode with a capacity of ∼35 mAh.g −1 and Coulombic efficiency over 95% for 2000 cycles. Investigation of ClO4 − anion (de)intercalation into HOPG cathode using in-situ Raman spectroscopy, in-situ XRD, and ex-situ XPS. Abstract: Anion intercalated graphite has achieved tremendous attention for the application as cathode materials in dual-ion batteries due to their high working potentials, reversibility, and low cost. However, the process of anion intercalation into graphite requires high oxidative stability of the electrolytes and high reaction potentials above 1.4 V vs. Ag/AgCl (4.5 V vs. Li + ). Reaching such high potentials is difficult with conventional aqueous electrolytes due to their limited electrochemical window. Here, we demonstrate a highly concentrated "water-in-salt" electrolyte of aluminum perchlorate that demonstrates a wide electrochemical stability window of 4.0 V. The "water-in-salt" electrolyte suppresses the dissociation of water at high potentials, facilitating a stable and reversible perchlorate (ClO4 − ) anion intercalation into the graphite with a Coulombic efficiency of over 95% for more than 2000 cycles. The structural and chemical changes of the anion-intercalated graphite are studied by Operando Raman, Operando X-ray diffraction, and X-ray photoelectron spectroscopy. Our study provides an insight into ClO4 − anion intercalation into graphite in the supersaturated aluminum perchlorate "water-in-salt" electrolyte, demonstrating a suitable platform for future high-voltage aqueous energy storage systems. Graphical Abstract: A "water-in-salt" electrolyte of aluminum perchlorate with a wide electrochemical stability window of 4.0 V is prepared. The electrolyte facilitates a stable and reversible anion (ClO4 − ) intercalation into the graphite, reaching more than 98% Coulombic efficiency over 2000 cycles. Image, graphical abstract .