Mixed Conducting Oxide Coating for Lithium Batteries

Thin,
uniform, and conformal coatings on the active electrode materials
are gaining more importance to mitigate degradation mechanisms in
lithium-ion batteries. To avoid polarization of the electrode, mixed
conductors are of crucial importance. Atomic layer deposition (ALD)
is employed in this work to provide superior uniformity, conformality,
and the ability to precisely control the stoichiometry and thickness
of the desired coating materials. We provide experimental and computational
guidelines for the need of mixed electronic and ionic conducting coating
materials, especially in the case where highly uniform and conformal
coatings are achieved. We report promising results for ALD-deposited
protective films achieved by doping fluorine (F) into a lithium vanadate
coating. The F-doped lithium vanadate coating at the optimal doping
level exhibits an electrical conductivity of 1.2 × 10–5 S·cm–1. Density functional theory calculations
corroborate enhanced mixed electronic and ionic conduction in F-doped
lithium vanadate through band structure analysis and climbing-image
nudge elastic band (CI-NEB) calculations. It has been demonstrated
that the experimentally determined optimal doping concentration aligns
well with that predicted by density functional theory calculations.
CI-NEB calculations have shown that the activation energy for lithium-ion
transport was the lowest for optimally doped lithium vanadate.