Cathode coatings are being developed to improve lithium-ion batteries. In this effort, LiCoO2 particles were coated with NH4AlF4 by a simple dry-coating process to enhance capacity retention on a 4.5 V cutoff cycling. Compared with pristine LiCoO2, this coating greatly improved the electrode cyclability and rate capability. Electrochemical impedance spectroscopy and a cobalt dissolution test showed that the NH4AlF4 coating protected the LiCoO2 particle surface from HF and, thus, suppressed the increase in interfacial impedance between the cathode and electrolyte that occurred with an uncoated cathode material. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3430642] All rights reserved.