Synthesis and electrochemical properties of nanosized LiFeO2 particles with a layered rocksalt structure for lithium batteries

Abstract Layered rocksalt-type LiFeO 2 particles ( O 3-LiFeO 2 ) with average particle sizes of ca. 40 and 400 nm were synthesized by an ion exchange reaction from α -NaFeO 2 precursors. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images confirmed the formation of nanosized O 3-LiFeO 2 . 40-nm LiFeO 2 exhibited a higher discharge capacity (115 mAh g −1 ) than 400-nm LiFeO 2 (80 mAh g −1 ), and also had better rate characteristics. The downsizing effect and cation disorder between the lithium and iron layers may have improved the electrochemical activity of the LiFeO 2 particles. Transmission electron microscopy (TEM) observation indicated a phase transition from O 3-LiFeO 2 to a cubic lattice system during the electrochemical process. The cubic lithium iron oxide exhibited stable electrochemical reactions based on the Fe 2+ /Fe 3+ and Fe 2+ /Fe 0 redox couples at voltages between 4.5 and 1.0 V. The discharge capacities of 40-nm LiFeO 2 were ca. 115, 210, and 390 mAh g −1 under cutoff voltages of 4.5–2.0 V, 4.5–1.5 V, and 4.5–1.0 V, respectively.