Electrochemical performance of LiCoO 2 cathodes by surface modification using lanthanum aluminum garnet

LiCoO ₂ particles were coated with various wt.% of lanthanum aluminum garnets (3LaAlO ₃:Al ₂O ₃) by an in situ sol-gel process, followed by calcination at 1123 K for 12 h in air. X-ray diffraction (XRD) patterns confirmed the formation of a 3LaAlO ₃:Al ₂O ₃ compound and the in situ sol-gel process synthesized 3LaAlO ₃:Al ₂O ₃-coated LiCoO ₂ was a single-phase hexagonal α-NaFeO ₂-type structure of the core material without any modification. Scanning electron microscope (SEM) images revealed a modification of the surface of the cathode particles. Transmission electron microscope (TEM) images exposed that the surface of the core material was coated with a uniform compact layer of 3LaAlO ₃:Al ₂O ₃, which had an average thickness of 40 nm. Galvanostatic cycling studies demonstrated that the 1.0 wt.% 3LaAlO ₃:Al ₂O ₃-coated LiCoO ₂ cathode showed excellent cycle stability of 182 cycles, which was much higher than the 38 cycles sustained by the pristine LiCoO ₂ cathode material when it was charged at 4.4 V.