Thermal and electrochemical behavior of yttria-stabilized zirconia coated LiCoO2 during overcharge tests

Sol-gel synthesized yttria-stabilized zirconia (YSZ) ceramic powders were coated on LiCoO2 cathode particles by a simple mechano-thermal process, calcined at 923 K for 10 h. The XRD patterns of YSZ-coated LiCoO2 revealed a single-phase hexagonal alpha-NaFeO2-type structure with Rim symmetry of the core material without any modification. The surface of LiCoO2 particles was coated with a uniform layer of YSZ that had an average thickness of similar to 20 run, as observed from TEM images. The different binding energies of O 1 s XPS data exhibited the presence of oxygen ions corresponding to the surface coated YSZ and LiCoO2. The galvanostatic cycling studies for the coated materials suggest that 2.0 wt.% YSZ-coated LiCoO2 delivered a stable capacity of 160 mAh g(-1) between 2.75 V and 4.4 V vs. Li and a good cycle stability of about 142 cycles. The impedance growth was slower for LiCoO2 surface coated with YSZ, when cells were charged at 4.4 V and 4.5 V. DSC results illustrated that the oxygen evolution exothermic peak at about 458 K was significantly smaller for YSZ-coated cathode materials. (C) 2008 Elsevier B.V. All rights reserved