Construction of Polyionic Liquid Coating Layer Enables High Cyclic Stability of 4.5 V LiCoO₂ Cathode by In Situ...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• High-voltage LiCoO₂ (LCO) cathodes are crucial for high-energy-density portable electronics.
• LCO cathodes suffer from electrolyte side reactions and structural degradation at high voltages, limiting performance and safety.

Purpose of the Study:

• To develop a stable cathode/electrolyte interface for high-voltage LCO cathodes.
• To improve the cycle life and thermal stability of LCO batteries through interface modification.

Main Methods:

• In situ bulk polymerization of diallyldimethylammonium bis(trifluoromethanesulfonyl)imide (DMDA) monomer on the LCO cathode surface.
• Formation of a cross-linked polyionic liquid (PIL) layer, creating a polymerized DMDA (PDMDA) coating.
• Characterization of the PDMDA coating as an artificial solid electrolyte interphase (SEI).

Main Results:

• The PDMDA coating formed a thin, dense cathode-electrolyte interphase (CEI), effectively suppressing side reactions.
• The modified LCO cathode retained 80% of its initial capacity after 500 cycles at 1C (3-4.5 V), outperforming bare LCO.
• Enhanced thermal stability of the PDMDA-modified LCO cathode was observed.

Conclusions:

• The PDMDA coating acts as an effective artificial SEI, significantly improving the electrochemical performance and stability of high-voltage LCO cathodes.
• This interface modification strategy offers a promising route for the practical application of high-voltage LCO cathodes in safe lithium batteries.