Temperature-Driven Anisotropic Mg²⁺ Doping for a Pillared LiCoO₂ Interlayer Surface in High-Voltage Applications

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• High-voltage lithium cobalt oxide (LiCoO2) offers high volumetric energy density for lithium-ion batteries.
• Capacity fading in LiCoO2 at high voltages (4.6 V) is caused by parasitic reactions and oxygen loss.
• Developing stable high-voltage cathode materials is crucial for next-generation batteries.

Purpose of the Study:

• To investigate the effect of anisotropic magnesium (Mg2+) doping on the surface of LiCoO2.
• To understand the mechanism by which Mg2+ doping enhances electrochemical performance.
• To improve the cycling stability and energy density of LiCoO2 at high operating voltages.

Main Methods:

• Temperature-driven anisotropic doping of Mg2+ into LiCoO2.
• Surface analysis to observe Mg2+ distribution and its effect on the (003) plane.
• Electrochemical testing to evaluate cycling performance and capacity retention at 4.6 V.

Main Results:

• Mg2+ dopants preferentially segregate to the surface, specifically the (003) plane.
• Doping lowers cobalt valence, reduces O 2p-Co 3d orbital hybridization, and forms surface Li+/Co2+ anti-sites.
• Surface Mg2+ doping effectively suppresses lattice oxygen loss.
• Modified LiCoO2 exhibits excellent cycling stability at 4.6 V, retaining 92.7% capacity after 100 cycles at 1C.

Conclusions:

• Anisotropic surface doping with Mg2+ is a viable strategy to enhance the high-voltage performance of LiCoO2.
• This method significantly improves cycling stability and energy density by mitigating parasitic reactions and oxygen loss.
• The findings offer a promising pathway for developing advanced cathode materials for high-energy lithium-ion batteries.