Electrochemical studies on LiCoO2 surface coated with Y3Al5O12 for lithium-ion cells

Synthesized yttrium aluminum garnet (YAG) sol was coated on the surface of the LiCoO2 cathode particles by an in situ sol–gel process, followed by calcination at 923 K for 10 h in air. Based on XRD, TEM, and ESCA data, a compact YAG kernel with an average thickness of ∼20 nm was formed on the surface of the core LiCoO2 particles, which ranged from ∼90 to 120 nm in size. The charge–discharge cycling studies for the coated materials suggest that 0.3 wt.% YAG-coated LiCoO2 heated at 923 K for 10 h in air, delivered a discharge capacity of 167 mAh g−1 and a cycle stability of about 164 cycles with a fading rate of 0.2 mAh cycle−1 at a 0.2C-rate between 2.75 and 4.40 V vs. Li/Li+. The differential capacity plots revealed that impedance growth was slower for YAG surface treated LiCoO2, when cells were charged at 4.40 V. DSC results exemplified that the exothermic peak at ∼468 K corresponded to the release of much less oxygen and greater thermal-stability.