Methods for Determination of the Degree of Iron Oxidation in LiFePO4

Abstract

Abstract:The disposal of LiFePO 4 (LFP) cathode material through oxidation in an air atmosphere is explained by its high chemical activity and high surface area (especially for nanoparticles). In this article, new methods for the determination of the degree of iron oxidation in LFP (oxidation degree) are taken into consideration, specifically those which do not require complicated hardware support. The proposed methods are based on electrochemical oxidation (coulometric method) and chemical oxidation (chemical oxidation in alkaline and acidic solutions). As an arbitration method for analyzing the iron state, the method of Mössbauer spectroscopy (being the most proven and reliable method) was chosen. With respect to the proposed methods for determination of the oxidation degree, the most reliable and quick approach is the titrimetric method (oxidation in an acidic medium), which is in good correlation with Mossbauer spectroscopy. The coulometric method is also able to determine the material oxidation degree (with some approximation), but it requires a number of conditions in order to eliminate errors.

Study of Delithiation Process Features in LixFe0.8M0.2PO4 (M = Mg, Mn, Co, Ni) by Mössbauer Spectroscopy

“…Mossbauer spectroscopy is often used to study ironcontaining materials including cathodes of lithium-ion batteries. It is used to carry out phase analysis 26−28 for determination of charge degree 29 and investigation of exchange interactions. 30 Also, dependences of hyperfine spectral parameters on the charge degree can be used to study the mechanism of the delithiation process.…”

“…Mössbauer spectroscopy is often used to study iron-containing materials including cathodes of lithium-ion batteries. It is used to carry out phase analysis − for determination of charge degree and investigation of exchange interactions . Also, dependences of hyperfine spectral parameters on the charge degree can be used to study the mechanism of the delithiation process. , Previously, we carried out Mössbauer studies of doped lithium iron phosphates ,− in order to detect local states of iron cations with different nearest-cation environments and determine the dopant distribution.…”