Atomic Layer Deposition of Al–W–Fluoride on LiCoO(2) Cathodes: Comparison of Particle- and Electrode-Level Coatings

[Image: see text] Atomic layer deposition (ALD) of the well-known Al(2)O(3) on a LiCoO(2) system is compared with that of a newly developed AlW(x)F(y) material. ALD coatings (∼1 nm thick) of both materials are shown to be effective in improving cycle life through mitigation of surface-induced capacity losses. However, the behaviors of Al(2)O(3) and AlW(x)F(y) are shown to be significantly different when coated directly on cathode particles versus deposition on a composite electrode composed of active materials, carbons, and binders. Electrochemical impedance spectroscopy, galvanostatic intermittent titration techniques, and four-point measurements suggest that electron transport is more limited in LiCoO(2) particles coated with Al(2)O(3) compared with that in particles coated with AlW(x)F(y). The results show that proper design/choice of coating materials (e.g., AlW(x)F(y)) can improve capacity retention without sacrificing electron transport and suggest new avenues for engineering electrode–electrolyte interfaces to enable high-voltage operation of lithium-ion batteries.