Mg-Pillared LiCoO₂ : Towards Stable Cycling at 4.6 V

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium cobalt oxide (LiCoO2) is a key cathode material for lithium-ion batteries.
• High-voltage charging (>4.35 V) of LiCoO2 leads to phase transitions, oxygen release, and electrolyte reactions, causing capacity fade.
• Existing cathode materials struggle with stability and performance degradation under demanding operating conditions.

Purpose of the Study:

• To develop a stabilized LiCoO2 cathode material for high-voltage lithium-ion batteries.
• To investigate the effect of magnesium (Mg) doping on the structural and electrochemical properties of LiCoO2.
• To enhance the cycling stability and capacity retention of LiCoO2 at elevated voltages.

Main Methods:

• Synthesis of Mg-pillared LiCoO2 via doping.
• Electrochemical characterization, including cycling tests and capacity retention measurements.
• Analysis of structural changes and surface chemistry using advanced techniques (implied).

Main Results:

• Mg ions act as pillars within the Li-slab of LiCoO2, preventing slab sliding during delithiation.
• A Li-Mg mixed structure at the surface suppresses interphase overgrowth and surface phase transformation.
• Mg-pillared LiCoO2 achieved 204 mAh g⁻¹ at 0.2 C and 84% capacity retention over 100 cycles at 1.0 C (3.0-4.6 V), outperforming pristine LiCoO2 (14% retention).

Conclusions:

• Mg-pillaring effectively suppresses detrimental phase transitions and surface reactions in LiCoO2 at high voltages.
• The enhanced structural integrity and surface stability lead to significantly improved electrochemical performance.
• Mg-pillared LiCoO2 presents a promising strategy for developing next-generation high-energy and long-life lithium-ion batteries.