Atomic Layer Deposition of Al–W–Fluoride on LiCoO₂ Cathodes: Comparison of Particle- and Electrode-Level Coatings

摘要

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.