Additive-Regulated Interface Chemistry Enables Depolarization for Ultra-High Capacity LiCoO₂

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• High-energy-density lithium-ion batteries require stable cycling of LiCoO2 (LCO) cathodes at high voltages.
• Interfacial degradation and polarization limit LCO performance at elevated cut-off voltages.

Purpose of the Study:

• To investigate the depolarization effects of cyclic organosiloxane additive V4D4 on LCO cathode performance.
• To enhance the interfacial charge transfer and stability of LCO||Li cells at high operating voltages.

Main Methods:

• Addition of V4D4 to the electrolyte of LCO||Li cells.
• Electrochemical cycling at a high upper cut-off voltage of 4.55 V.
• Analysis of the cathode-electrolyte interphase (CEI) formation and composition.

Main Results:

• V4D4 addition enhanced LCO capacity to 220 mA h g-1 at 4.55 V.
• V4D4 stabilized the LCO surface by preventing HF/H2O formation and stabilizing lattice oxygen.
• A stable, ultrathin CEI composed of silicon compounds and LiF was formed, reducing interfacial resistance.
• Capacity retention of ~97% after 200 cycles was achieved with V4D4 and FEC.

Conclusions:

• V4D4 effectively mitigates polarization and enhances the electrochemical performance of LCO cathodes at high voltages.
• The formation of a robust CEI by V4D4 is crucial for long-term cycling stability and high energy density.
• V4D4 represents a promising strategy for developing advanced high-voltage lithium-ion batteries.