Magnetic properties of mixed sodium-lithium iron fluorophosphate NaLiFePO4F cathode material

Jae Yeon Seo,Chul Sung Kim,Hyunkyung Choi

doi:10.1063/1.5043038

Abstract

Mixed sodium-lithium iron fluorophosphates NaLiFePO4F was synthesized by solid-state route. The crystal and magnetic properties were investigated by X-ray diffraction (XRD) measurement, vibrating sample magnetometer (VSM), and Mössbauer spectroscopy. The crystal structure of NaLiFePO4F was determined to be orthorhombic with space group of Pnma. The cell parameters of NaLiFePO4F are as follows: a0 = 10.9661 Å, b0 = 6.3693 Å, c0 = 11.4342 Å, and V = 798.6377 Å3. The temperature-dependence of the zero-field-cooled (ZFC) and field-cooled (FC) curves was examined by VSM at 100 Oe from 4.2 to 295 K. We determined the Néel temperature (TN = 22 K) and spin reorientation temperature (TS = 13 K). The Mössbauer spectra of NaLiFePO4F were taken at various temperatures ranging from 4.2 to 295 K. At below TS, the electric quadrupole splitting (ΔEQ) decreased and magnetic hyperfine field (Hhf) increased with decrease temperature due to spin-orbit coupling.

Highlights

Olivine-type LiFePO4 has attracted attention owing to its desirable characteristics, including low cost, environmental friendliness of large-scale applications, and safety
Many research efforts to date have focused only on the electrochemical performance of these fluorophosphates.[8,9,10]. Understanding their magnetic properties is very important because their magnetic structure and properties are strongly related to their electrochemical performance, which would facilitate the design of new materials for Na-ion or Li-ion batteries.[10,11,12]
From the refined X-ray diffraction (XRD) pattern, the structure of NaLiFePO4F was determined to be orthorhombic with the space group Pnma and was confirmed the crystal structure of single phase

Summary

Introduction

Olivine-type LiFePO4 has attracted attention owing to its desirable characteristics, including low cost, environmental friendliness of large-scale applications, and safety. Pure olivine materials exhibit poor performance because LiFePO4 has lower electronic conductivity than other materials. To overcome this limitation, various preparation methods have been used.[1,2,3,4,5] Recently, sodiumlithium fluorophosphates has been reported for use as a cathode in cells. Fluorophosphate materials exhibit structural, thermal, and a high energy storage capacity combined with electrochemical stability.[6,7,8,9]. Many research efforts to date have focused only on the electrochemical performance of these fluorophosphates.[8,9,10] Understanding their magnetic properties is very important because their magnetic structure and properties are strongly related to their electrochemical performance, which would facilitate the design of new materials for Na-ion or Li-ion batteries.[10,11,12]

Methods

Results

Conclusion