We fabricated lithium cobalt oxide (LiCoO 2 , LCO) electrodes in the absence and presence of TiO 2 layers as cathodes for lithium-ion batteries (LIBs) using a sputtering deposition method under an Ar atmosphere. In particular, TiO 2 coating layers on sputtered LCO electrodes were directly deposited in a layer-by-layer form with varying TiO 2 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 TiO 2 layers in TiO 2 -coated LCO electrodes were controlled from $2 to $10 nm. These TiO 2 -coated LCO electrodes exhibited superior electrochemical performance, i.e. high capacities (93-107 mA h g À1 @0.5C), improved retention of >60% after 100 cycles, and high-rate cycling properties (64 mA h g À1 @1C after 100 cycles). Such an improved performance of TiO 2 -coated LCO electrodes was found to be attributed to relieved volumetric expansion of LCO and protection of LCO electrodes against HF generated during cycling.
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