Sol–gel processing and electrochemical characterization of monoclinic Li3FeF6

• Published in: Journal of sol-gel science and technology Vol. 71; no. 1; pp. 50 - 59
• Main Authors: Lieser, Georg, Schroeder, Melanie, Geßwein, Holger, Winkler, Volker, Glatthaar, Sven, Yavuz, Murat, Binder, Joachim R.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.07.2014; Springer; Springer Nature B.V
• Subjects: Acicular powders; Acicular structure; Ball milling; Cathodes; Ceramics; Chemistry; Chemistry and Materials Science; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Composites; Electrochemical analysis; Electrochemistry; Electrode materials; Electronegativity; Exact sciences and technology; Fluorides; Fluorine; General and physical chemistry; Glass; Inorganic Chemistry; Lithium; Lithium-ion batteries; Materials Science; Metal fluorides; Nanotechnology; Natural Materials; Optical and Electronic Materials; Organic chemistry; Original Paper; Performance tests; Rechargeable batteries; Sol-gel processes; Transition metals; X-ray diffraction; Lithium-ion batteries; Electrochemical performance; Lithium transition metal fluoride; Trifluoroacetic acid; Sol–gel processing; FeF; Cathode material; Li; Iron Fluorides; Transition metal; Sol―gel processing; Characterization; Acids; Sol gel process; Electrochemistry; Lithium ion; Lithium Fluorides
• ISSN: 0928-0707; 1573-4846
• DOI: 10.1007/s10971-014-3329-1

To find new cathode materials for future applications in lithium-ion batteries, lithium transition metal fluorides represent an interesting class of materials. In principle the Li intercalation voltage can be increased by replacing oxygen in the cathode host structure with the more electronegative fluorine. A facile pyrolytic sol–gel process with trifluoroacetic acid as fluorine source was established to synthesize monoclinic Li 3 FeF 6 using nontoxic chemicals. The acicular Li 3 FeF 6 powder was characterized with X-ray diffraction and a detailed structure model was calculated by Rietveld analysis. For the preparation of cathode films to cycle versus lithium monoclinic Li 3 FeF 6 was ball milled with carbon and binder down to nanoscale. After 100 cycles galvanostatic cycling (C/20) 47 % fully reversible capacity of the initial capacity (129 mAh/g) could be retained. To the best of our knowledge the results presented in this work include the first rate performance test for monoclinic Li 3 FeF 6 up to 1 C maintaining a capacity of 71 mAh/g. The redox reaction involving Fe 3+ /Fe 2+ during Li insertion/extraction was confirmed by post-mortem XPS and cyclic voltammetry.