Long-Term Operando Quantification of Li Plating on Graphite Anodes

Area of Science:

• Materials Science
• Electrochemistry
• Spectroscopy

Background:

• Lithium plating on graphite anodes is a critical safety and degradation issue in lithium-ion batteries.
• Non-destructive quantification of lithium plating is essential for understanding battery aging mechanisms.

Purpose of the Study:

• To quantify lithium plating evolution (onset, amount, reversibility) in LiFePO4/graphite batteries using operando NMR.
• To investigate the impact of temperature and electrolyte additives on lithium plating and battery degradation.

Main Methods:

• Operando variable-temperature electrochemical solid-state 7Li nuclear magnetic resonance (NMR) spectroscopy.
• Cycling of LiFePO4/graphite batteries at 25 and 45 °C with different electrolytes (including VC and LiDFOB additives).
• Monitoring Coulombic efficiency (CE) and state of health (SoH) alongside NMR measurements.

Main Results:

• A three-stage lithium plating trend was observed across battery cycles.
• Coulombic efficiency drops strongly correlate with increased lithium plating and dead lithium formation.
• Vinylene carbonate (VC) suppressed plating and dead lithium, while LiDFOB initially delayed plating but led to abrupt degradation.
• Elevated temperatures improved plating reversibility but intensified SEI formation and reduced cycle life.

Conclusions:

• Lithium plating is a key driver of battery degradation, linked to electrolyte decomposition and SEI growth.
• Electrolyte additives and temperature management strategies can mitigate lithium plating, but require careful optimization.
• Understanding plating dynamics is crucial for developing safer and longer-lasting energy storage systems.