Charge/Discharge Interface of LFP Cathode Material Revealed by Atomic-Resolution Electron Microscopy

What is it about?

Phase boundary structure of lithium iron phosphate (LixFePO4, LFP) cathode material subjected to chemical delithiation was investigated by atomic resolution HAADF-STEM and EELS analysis. While the Li-rich/Li-poor phase interface plane was found to be parallel to the orthorhombic {100} plane, a complex relationship between lattice variations and Li composition deviated from a simple Vegard’s law was observed.

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Photo by Kumpan Electric on Unsplash

Photo by Kumpan Electric on Unsplash

Why is it important?

LiFePO4 (LFP) is an important cathode material for lithium ion batteries (LIBs) exhibiting high thermal stability and good cycle performance. Its electrochemical properties are characterized by two kinetic and thermodynamic features; the one-dimensional (1D) Li diffusion along the b-axis (<010> direction in the orthorhombic lattice) and the strong phase separation with large lattice mismatches, the latter makes charge/discharge properties more complicated. Technically, carbon coating onto the specimen surface prior to TEM and STEM analysis greatly reduced the irradiation damage. Knowledge about the electro-chemical responses and Li diffusion kinetics of cathode materials will contribute to the development of improved lithium battery systems.