Preferential solid electrolyte interphase formation on graphite and post-oxidative cathode-electrolyte interphase...

Area of Science:

• Electrochemistry
• Materials Science
• Battery Technology

Background:

• Interfacial instability at graphite anodes and high-voltage degradation of LiCoO2 cathodes limit lithium-ion battery performance.
• Developing effective electrolyte additives is crucial for enhancing battery stability and longevity.

Purpose of the Study:

• To investigate 2,2,2-trifluoroethyl methanesulfonate (TM) as a bifunctional film-forming electrolyte additive.
• To address interfacial issues at both graphite anodes and LiCoO2 cathodes in lithium-ion batteries.

Main Methods:

• Density functional theory (DFT) calculations to understand TM's electrochemical behavior.
• Electrochemical analyses including cycling performance and impedance measurements.
• Fabrication and testing of Li||graphite half-cells and graphite||LiCoO2 pouch cells.

Main Results:

• TM preferentially decomposes on the graphite anode, forming a stable solid electrolyte interphase (SEI) that suppresses electrolyte reduction.
• TM aids in forming a protective cathode-electrolyte interphase (CEI) on LiCoO2, mitigating oxidation and cobalt dissolution.
• TM-containing cells show significantly improved capacity retention (323.7 mAh·g-1 vs. 104.4 mAh·g-1 in half-cells) and better low-temperature performance.

Conclusions:

• TM acts as an effective dual-interface modifier for both anode and cathode.
• TM represents a practical strategy for interphase engineering in high-voltage and low-temperature lithium-ion batteries.