High Performance LiCoO[sub 2] Cathode Materials at 60°C for Lithium Secondary Batteries Prepared by the Facile Nanoscale Dry-Coating Method

Abstract

A mass scalable dry-coating method was used on a LiCoO2 cathode to improve cycling stability at 60 degrees C and, in contrast to the conventional wet-coating method, this one did not require a solvent. Electrochemical results of the MgF2, Al2O3, and TiO2 coatings on LiCoO2 cathodes showed a fast capacity fade, resulting in < 10% capacity retention at 60 degrees C under 1C rate cycling, whereas an uncoated cathode showed 64% retention. This difference was believed to be because the residual coating layers which did not react with the bulk layer accelerated the side reactions with the electrolytes at 60 degrees C, leading to increased formation of the surface films. However, when MgCO3 and AlPO4 were used for dry coating, the coating layers completely disappeared, but a higher concentration of coating elements was found near the surfaces. Overall, the cathodes coated with MgCO3 and AlPO4 exhibited 79 and 88% capacity retention, respectively, at 60 degrees C under 1C rate cycling.