New fluorophosphate Li2−xNaxFe[PO4]F as cathode material for lithium ion battery

• Published in: Journal of power sources Vol. 244; pp. 87 - 93
• Main Authors: Ben Yahia, Hamdi, Shikano, Masahiro, Koike, Shinji, Sakaebe, Hikari, Tabuchi, Mitsuharu, Kobayashi, Hironori
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15-12-2013; Elsevier
• Subjects: Applied sciences; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Fluorophosphate; Ion Exchange; Lithium ion battery; Materials; Mӧssbauer spectroscopy; Positive electrode; Positive electrode; Lithium ion battery; Ion Exchange; Mӧssbauer spectroscopy; Fluorophosphate; Phosphates; Lithium ion batteries; Cathode; Lithium Sulfides; Secondary cell; Moessbauer spectrometry; NMR spectrometry; Electrode material; Phosphorus Compounds; Inorganic anion; Mössbauer spectroscopy; Ion exchange; Fluophosphates
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2013.03.128

The new compound Li1.65Na0.35Fe[PO4]F with the Li2Ni[PO4]F structure has been prepared from the analogous LiNaFe[PO4]F phase by ion exchange using LiBr in ethanol at 90 °C. The sample was characterized by powder X-ray diffraction, 57Fe Mӧssbauer spectroscopy, and electrochemical measurements. Li1.65Na0.35Fe[PO4]F crystallizes with orthorhombic symmetry, space group Pnma, with a = 10.5093(5) Å, b = 6.4999(2) Å, c = 11.0483(5) Å, V = 754.70(7) Å3, and Z = 8. The 57Fe Mӧssbauer data collected at different stages of galvanometric cycling confirmed that only 1 mol of alkali metal is extractable between 1.0 V and 5.1 V vs. Li+/Li with a discharge capacity between 135 and 145 mA h g−1. Li/Na electrochemical ion exchange occurs during cycling and leads to a lithium rich phase.
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•Li2Fe[PO4]F was prepared from LiNaFe[PO4]F by ion exchange using LiBr in ethanol.•Li2Fe[PO4]F and LiNaFe[PO4]F crystallize with the Li2Ni[PO4]F-type structure.•It is different from the Tavorite Li1+xFe[PO4]F- and the layered Na2Fe[PO4]F-type.•57Fe Mӧssbauer were collected at different stages of the galvanometric cycling.•Up to 1 mol of alkali metal is extractable between 1.0 V and 5.1 V vs. Li+/Li.