Synthesis and electrochemical characteristics of Li[Ni1/3Mn1/3Co1/3]O2 using co-precipitation

Abstract

Recently, the layered lithium transition metal oxides LiMO2 (M = Co, Ni, Mn, etc.) have been extensively studied as cathode materials for lithium ion secondary batteries. The LiCoO2 has been commercialized but has still some problems, such as its high cost, moderate, and toxicity. LiNiO2 and LiMnO2 have been extensively studied as possible alternatives to LiCoO2. However, LiNiO2 known to difficult to be synthesized in the stoichiometrical form and delithiated LixNiO2 has thermally instability due to decompose exothermally at around 200 oC and LiMnO2 was observed to undergo a detrimental phase transformation to a spinel phase during cycling. Recently, a concept of a one-to-one solid solution with atomic scale of LiNiO2, LiMnO2 and LiCoO2 i.e., Li[Ni1/3Mn1/3Co1/3]O2, was adopted by Ohzuku et al. However any other reporters did not referred the improvement of electrochemical properties in view of morphology and commercial possibility. In this work, we have try for certification of spherical particles in many times, actually it is hard to synthesize high density multi component hydroxides with Ni, Mn, Co because of its various oxidation numbers. In spite of these disadvantages, we successfully obtained spherical multi component hydroxides(c.a. 10 ㎛) such as (Ni1/3Mn1/3Co1/3)(OH)x with 1.8 g/cm3 high tap-density, also prepared spherical Li[Ni1/3Mn1/3Co1/3]O2 with 2.2 g/cm3 high tap-density from (Ni1/3Mn1/3Co1/3)(OH)x. The spherical high density Li[Ni1/3Mn1/3Co1/3]O2 cathode materials were greatly improved reversible capacity of about 160, 170 and 180 mAh/g at 4.3 V, 4.4 V and 4.5 V with good cyclability.