Surface modification of Li[Ni0.35Co0.3Mn0.35]O-2 as a cathode material of lithium-ion batteries was carried out by hydrothermal treatment using lithium lanthanum titanate ([Li,La]TiO3). The modified surfaces were analyzed by morphology observation using transmission electron microscopy and by element investigation using X-ray photoelectron spectroscopy. It was thereupon found that the [Li,La]TiO3-coated layer formed by the surface modification played a definitive role in suppressing the solid electrolyte interface during repeated charge and discharge cycles. In addition, the thermal stability was enhanced by coated layer, resulting in an increase of the onset temperature to occur an exothermic reaction during thermal runaway.