Electrochemical studies on surface coated LiCoVO 4 with Al 2O 3 derived from carboxylate-alumoxane for lithium-ion cells

Abstract

Various wt.% of Al 2O 3 derived from methoxyethoxy-alumoxane (MEA-alumoxane) were coated by a simple mechano-thermal method on the LiCoVO 4 particles, which were synthesized by a citric acid–urea polymeric method. Powder XRD patterns confirmed that the prepared LiCoVO 4 crystalline sample had an inverse spinel structure when heated at 773 K for 5 h in air and the LiCoVO 4 materials coated with Al 2O 3 showed no evidence of secondary phase peaks. TEM images of LiCoVO 4 identified that the nanosized particles ranged ∼100–120 nm and Al 2O 3 coating had an average thickness of ∼20 nm over the fine particle of LiCoVO 4. XPS binding energy data indicated that the presence of two different types O 1s ions corresponds to alumina and core LiCoVO 4 material. The charge and discharge study indicated that the 0.5 wt.% Al 2O 3 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 d Q/d V versus voltage plots revealed that the slower impedance growth for the Al 2O 3 surface coated LiCoVO 4 cathode material.