Optimizing Carbon Coating Process for Lithium-Rich LiFePO₄ Cathode Materials.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• Stoichiometric LiFePO4 (LFP) suffers from poor ionic and electronic conductivity, limiting its application in lithium-ion batteries.
• Li-rich LiFePO4 (Li-rich LFP) offers improved conductivity but requires optimized synthesis for enhanced performance.
• The influence of carbon coating strategies on Li-rich LFP's structural and electrochemical characteristics remains incompletely understood.

Purpose of the Study:

• To investigate the impact of carbon precursor addition timing on the crystal structure and electrochemical performance of Li-rich LFP.
• To compare two distinct synthesis routes: carbon precursor addition before Li-rich LFP crystal formation (C/BLF) and after (C/ALF).
• To elucidate how carbon coating process sequence affects the material's properties.

Main Methods:

• Synthesis of Li-rich LFP via two methods: C/BLF and C/ALF.
• Characterization of crystal structure, unit cell volume, and carbon coating density.
• Electrochemical performance evaluation, including discharge capacity and overpotential measurements.

Main Results:

• The C/ALF synthesis process resulted in a larger unit cell volume and a denser carbon coating layer compared to C/BLF.
• The C/ALF sample demonstrated a lower overpotential (0.54 V).
• The C/ALF sample exhibited a higher discharge capacity (~134.13 mAhg⁻¹).

Conclusions:

• The sequence of carbon coating significantly influences the crystal structure and electrochemical performance of Li-rich LFP.
• The C/ALF method, where carbon is added after crystal formation, is superior for achieving enhanced electrochemical properties.
• Optimizing carbon coating strategies is crucial for advancing Li-rich LFP materials for battery applications.