Lithium-nickel-cobalt-manganese containing composite oxide
Coagulated particles of nickel-cobalt-manganese hydroxide wherein primary particles are coagulated to form secondary particles are synthesized by allowing an aqueous solution of a nickel-cobalt-manganese salt, an aqueous solution of an alkali-metal hydroxide, and an ammonium-ion donor to react under specific conditions; and a lithium-nickel-cobalt-manganese-containing composite oxide represented by a general formula, Li p Ni x Mn 1-x-y Co y O 2-q F q (where 0.98≦p≦1.07, 0.3≦x≦0.5, 0.1≦y≦0.38, and 0≦q≦0.05), which is a positive electrode active material for a lithium secondary cell having a wide usable voltage range, a charge-discharge cycle durability, a high capacity and high safety, is obtained by dry-blending coagulated particles of nickel-cobalt-manganese composite oxyhydroxide formed by making an oxidant to act on the coagulated particles with a lithium salt, and firing the mixture in an oxygen-containing atmosphere.
1. A lithium-nickel-cobalt-manganese-containing composite oxide represented by a general formula, Li p Ni x Mn 1-x-y Co y O 2-q F q (where 0.98≦p≦1.07, 0.3≦x≦0.5, ⅓≦y≦0.38,and 0≦q≦0.05), formed by synthesizing coagulated particles of a nickel-cobalt-manganese composite hydroxide wherein primary particles obtained by precipitating the nickel-cobalt-manganese composite hydroxide are coagulated to form secondary particles, by supplying an aqueous solution of a nickel-cobalt-manganese salt, an aqueous solution of an alkali-metal hydroxide and an ammonium-ion donor continuously or intermittently to a reaction system, and making the reaction proceed in the state wherein the temperature of said reaction system is substantially constant within a range between 30 and 70° C., and pH is maintained at a substantially constant value within a range between 10 and 13; synthesizing coagulated particles of a nickel-cobalt-manganese composite oxyhydroxide by making an oxidant act on said coagulated composite hydroxide particles; and dry-blending at least said composite oxyhydroxide and a lithium salt, and firing the mixture in an oxygen-containing atmosphere,
wherein an atomic ratio of Ni and Mn is 1±0.05.
2. The lithium-nickel-cobalt-manganese-containing composite oxide according to claim 1 , wherein the compressed powder has a density of 2.6 g/cm 2 or more.
3. The lithium-nickel-cobalt-manganese-containing composite oxide according to claim 1 , wherein the composite oxide has an R-3m rhombohedral structure.
4. The lithium-nickel-cobalt-manganese-containing composite oxide according to claim 1 , wherein x has a range of 0.32≦x≦0.42.