TiO₂-coated LiCoO₂ electrodes fabricated by a sputtering deposition method for lithium-ion batteries with enhanced...

We fabricated lithium cobalt oxide (LiCoO₂, LCO) electrodes in the absence and presence of TiO₂ layers as cathodes for lithium-ion batteries (LIBs) using a sputtering deposition method under an Ar atmosphere. In particular, TiO₂ coating layers on sputtered LCO electrodes were directly deposited in a layer-by-layer form with varying TiO₂ sputtering times from 60 to 120 s. These sputtered electrodes were heated at 600 °C in an air atmosphere for 3 h. The thicknesses of TiO₂ layers in TiO₂-coated LCO electrodes were controlled from ∼2 to ∼10 nm. These TiO₂-coated LCO electrodes exhibited superior electrochemical performance, i.e. high capacities (93-107 mA h g^-1@0.5C), improved retention of >60% after 100 cycles, and high-rate cycling properties (64 mA h g^-1@1C after 100 cycles). Such an improved performance of TiO₂-coated LCO electrodes was found to be attributed to relieved volumetric expansion of LCO and protection of LCO electrodes against HF generated during cycling.