Electrochemical studies on surface coated LiCoVO4 with Al2O3 derived from carboxylate-alumoxane for lithium-ion cells

Various wt.% of Al2O3 derived from methoxyethoxy-alumoxane (MEA-alumoxane) were coated by a simple mechano-thermal method on the LiCoVO4 particles, which were synthesized by a citric acid–urea polymeric method. Powder XRD patterns confirmed that the prepared LiCoVO4 crystalline sample had an inverse spinel structure when heated at 773 K for 5 h in air and the LiCoVO4 materials coated with Al2O3 showed no evidence of secondary phase peaks. TEM images of LiCoVO4 identified that the nanosized particles ranged ~100–120 nm and Al2O3 coating had an average thickness of~ 20 nm over the fine particle of LiCoVO4. XPS binding energy data indicated that the presence of two different types O 1s ions corresponds to alumina and core LiCoVO4 material. The charge and discharge study indicated that the 0.5 wt.% Al2O3 derived from MEA-alumoxane coated material delivered an initial discharge capacity of 68 mAh g−1 at 3.0–4.5 V and the cycle stability after 20 cycles was stable without any drastic capacity fade normally exhibited by inverse spinel materials. The dQ/dV versus voltage plots revealed that the slower impedance growth for the Al2O3 surface coated LiCoVO4 cathode material.