Atomic Layer Deposited MgO: A Lower Overpotential Coating for Li[Ni_0.5Mn_0.3Co_0.2]O₂ Cathode

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Lithium nickel manganese cobalt oxide (Li[Ni_0.5Mn_0.3Co_0.2]O₂ or NMC) is a key cathode material for high-energy lithium-ion batteries.
• Surface degradation and limited ion transport can hinder NMC cathode performance, especially at high charge/discharge rates.
• Atomic layer deposition (ALD) offers precise control for applying ultrathin coatings to modify material surfaces.

Purpose of the Study:

• To synthesize an ultrathin magnesium oxide (MgO) coating on NMC cathode material using ALD.
• To investigate the impact of MgO coating on the electrochemical performance of NMC cathodes.
• To compare the efficacy of MgO coating against other ALD coatings like Al₂O₃ and ZrO₂.

Main Methods:

• Ultrathin MgO coating was synthesized on NMC using atomic layer deposition (ALD).
• An in-situ quartz crystal microbalance sensor monitored ALD growth and film density.
• Electrochemical performance was evaluated using half-cell assemblies, including cyclic voltammetry and long-range cycling tests.

Main Results:

• ALD-deposited MgO coating improved the Li-diffusion coefficient on the NMC cathode surface.
• MgO-coated NMC exhibited lower overpotential and enhanced rate performance compared to uncoated NMC.
• The MgO coating demonstrated superior capacity retention over uncoated NMC during extended cycling.

Conclusions:

• Ultrathin MgO coatings applied via ALD effectively improve the surface properties of NMC cathodes.
• The enhanced Li-ion diffusion and reduced overpotential contribute to superior rate capability.
• MgO-coated NMC cathodes show significant potential for advanced lithium-ion battery applications due to improved cycling stability.