Enhanced overcharge performance of nano-LiCoO2 by novel Li3VO4 surface coatings

Abstract

LiCoO₂ nanoparticles were coated with 3.4 and 5.5 wt% of lithium vanadate (Li₃VO₄) by a wet-chemical and sintering method. When the electrode containing 5.5-wt% Li₃VO₄-coated LiCoO₂ was overcharged to 4.5 V at a current of 30 mA g⁻¹ (∼0.2 C), ∼85% of the initial discharge capacity after 100 charge–discharge cycles was maintained, compared to only ∼67% for the electrode with bare LiCoO₂ nanoparticles. The electrode with 5.5 wt% coating can also deliver 115 mA h g⁻¹ discharge capacity at a current of 1200 mA g⁻¹ (∼8 C) and a discharge–charge voltage of 4.5 V, which is twice the capacity of the bare LiCoO₂ sample. The improvement of overcharge cyclability and high-rate capability was believed to be due to the structurally protective Li₃VO₄ surface coating with good Li-ion conductivity.