Multiscale phase mapping of LiFePO4-based electrodes by transmission electron microscopy and electron forward...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Understanding lithium iron phosphate (LiFePO4) electrode behavior is crucial for advanced battery development.
• Phase distribution heterogeneity impacts electrochemical performance and cycle life.

Purpose of the Study:

• To investigate LiFePO4 and FePO4 phase distributions across various lithium contents in electrode cross-sections.
• To analyze these distributions from nanoscale to mesoscale using advanced microscopy techniques.

Main Methods:

• Transmission electron microscopy (TEM) for nanoscale imaging.
• Electron forward scattering diffraction (EFSD) for mesoscale phase mapping.
• Analysis of over 64,000 individual particles.

Main Results:

• Small LiFePO4 particles delithiate first at the nanoscale.
• A core-shell delithiation mechanism is observed in agglomerates at the mesoscale, favoring electrode porosities.
• Thick electrodes exhibit stratum-by-stratum lithiation from the electrolyte interface towards the current collector.

Conclusions:

• Electrode architecture and particle size significantly influence lithium-ion transport and phase transformation.
• Preferential pathways along porosities and nanoscale particle size effects dictate electrochemical response.
• The findings provide insights for designing more efficient LiFePO4 battery electrodes.