Differences in Interfacial Reactivity of Graphite and Lithium Metal Battery Electrodes Investigated Via Operando Gas...

Area of Science:

• Electrochemistry
• Materials Science
• Battery Technology

Background:

• Gaseous byproducts from lithium batteries significantly impact performance and safety.
• Cell swelling, a critical safety concern, is often linked to gas evolution within batteries.
• Understanding gas formation is crucial for developing safer and more efficient lithium batteries.

Purpose of the Study:

• To identify the types and amounts of gases produced in lithium batteries with graphite and lithium metal electrodes.
• To investigate the fate of ethylene gas, a primary byproduct of solid electrolyte interphase (SEI) formation.
• To elucidate previously overlooked SEI formation pathways.

Main Methods:

• Operando pressure measurements were employed to monitor gas buildup in real-time.
• Online electrochemical mass spectrometry (OEMS) was used to identify the chemical composition of evolved gases.
• Comparative analysis of gas evolution in batteries with graphite versus lithium metal electrodes was performed.

Main Results:

• Ethylene gas is a significant byproduct of SEI formation reactions in lithium batteries.
• Lithium metal electrodes rapidly consume ethylene gas, unlike graphite electrodes, unless pretreated.
• Polyolefins, such as polyethylene, are identified as potential products of ethylene consumption, indicating a gasless SEI formation pathway.

Conclusions:

• The consumption of ethylene by lithium metal electrodes represents a novel, gasless pathway for SEI formation.
• This finding challenges previous assumptions about SEI formation mechanisms and their associated gas products.
• Understanding these gas consumption and formation pathways is essential for mitigating lithium battery swelling and improving safety.