How much Li is needed for anode in Li metal battery?

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Battery life in Li metal batteries is often linked to Li quantity, with lower N/P ratios indicating shorter lifespans due to Li consumption.
• This Li consumption is complicated by factors like solid electrolyte interphase (SEI) growth and electrolyte depletion, making optimal Li anode quantity guidelines difficult to establish.

Purpose of the Study:

• To investigate the relationship between Li anode thickness, SEI evolution, and electrochemical performance in Li metal batteries.
• To determine the critical factors that limit Li consumption and trigger capacity fade.

Main Methods:

• Studied Li||NCM811 cells with varying Li anode thicknesses in an ester-based electrolyte.
• Tracked the evolution of the Li anode and SEI during cycling.
• Monitored electrochemical performance throughout the battery's life.

Main Results:

• Fresh Li consumption is finite and ceases when Li is depleted or electrolyte wetting of the Li/SEI interface fails.
• This cessation point marks a critical turning point, leading to rapid capacity decline.
• A direct correlation was found between fresh Li consumption and SEI growth.

Conclusions:

• The study clarifies that Li consumption in Li metal batteries is not continuous and has defined limits.
• Understanding these limits and their correlation with SEI growth is crucial for improving long-term cycling stability.
• Findings provide insights into failure mechanisms and strategies for enhancing Li metal battery longevity.