Abstract: The present invention relates to a positive electrode active material having improved capacity characteristic and life cycle characteristic, and a method of preparing the same, and specifically, to a positive electrode active material for a lithium secondary battery, wherein the positive electrode active material comprises a compound represented by Formula 1 above and allowing reversible intercalation/deintercalation of lithium, and from a crystal structure analysis of the positive electrode active material by a Rietveld method in which space group R-3m is used in a crystal structure model on the basis of an X-ray diffraction analysis, the thickness of MO slab is 2.1275 ? or less, the thickness of inter slab is 2.59 ? or greater, and the cation mixing ratio between Li and Ni is 0.5% or less, and a method of preparing the same.

Abstract: Disclosed is a method for preparing sustained release microparticles which release a physiologically active substance for long periods of time. The sustained release microparticles are prepared through a multi-emulsion process. A drug of interest is dissolved or dispersed in each of at least two oils to give at least two primary oil phases or emulsions. Each oil phase or emulsion contains a biodegradable polymer. The least two primary oil phases or emulsions are dispersed in one aqueous phase, synchronously or in succession. From the drug-dispersed solution, the organic solvents are removed to produce microparticles. Therefore, the drugs such as leutenizing hormone releasing hormones can be continuously released in vivo for prolonged periods of time, bringing about an improvement in the therapeutic effect.