POSITIVE ELECTRODE ACTIVE MATERIAL WHOSE CONCENTRATION PROFILE OF LITHIUM IS DIFFERENT AT SURFACE PART AND INSIDE OF PRIMARY PARTICLE, PREPARATION METHOD THEREOF, LITHIUM ION SECONDARY BATTERY USING THE ACTIVE MATERIAL, AND LITHIUM-CONTAINING COMPOSITION SUITABLE FOR THE ACTIVE MATERIAL

摘要

PURPOSE: Provided are a positive electrode active material, its preparation method, a lithium ion secondary battery using the positive electrode active material whose internal resistance is hardly increased, and a lithium-containing composition suitable for a positive electrode active material of a lithium ion secondary battery. CONSTITUTION: The positive electrode active material comprises a lithium metal oxide as a main component, wherein the concentration of lithium at the surface part of a primary particle is lower than that at the inside of the primary particle. Preferably the primary particle has an average particle size of about 0.2-3 micrometers, and the inside comprises a lithium metal oxide having a composition represented by Li_x Ni_(1-y) M_y O2, wherein M is at least one element selected from the group consisting of cobalt, aluminum, manganese, chromium, iron, boron, titanium, magnesium and vanadium; 0.6=x=1.2; and 0=y=0.5.