DOUBLE-LAYER CATHODE ACTIVE MATERIALS FOR HIGH CAPACITY & HIGH RATE CAPABILITY, METHOD OF PREPARING THEREOF AND LITHIUM SECONDARY BATTERY USING THEREBY

摘要

Provided are a positive electrode active material for a lithium secondary battery which is high in capacity and charge density, is improved in lifetime characteristics and is excellent in thermal stability, and its preparation method. The positive electrode active material has a dual layer structure which comprises an inner part represented by Li_delta [Ni_x Co_(1-2x) Mn_x]O2 (wherein 1.0<=delta<=1.2 and 0.01<=x<=0.5), and an outer part represented by Li_delta [Ni_x Co_y Mn_(1-(x+y))]O2 (wherein 1.0<=delta<=1.2, 0.5<=x<=1.0 and 0.01<=y<=0.2) or Li_delta CoO2 (wherein 1.0<=delta<=1.2). Preferably the thickness of the outer part is 5-50 % of the total thickness of the positive electrode active material; the inner part has an average diameter of 1-8 micrometers; and the entire particle of positive electrode active material has an average diameter of 9-20 micrometers.