Nickel-cobalt-maganese-based compound particles and process for producing the nickel-cobalt-manganese-based compound particles, lithium composite oxide particles and process for producing the lithium composite oxide particles, and non-aqueous electrolyte secondary battery
The present invention relates to nickel-cobalt-manganese-based compound particles which have a volume-based average secondary particle diameter (D50) of 3.0 to 25.0 μm, wherein the volume-based average secondary particle diameter (D50) and a half value width (W) of the peak in volume-based particle size distribution of secondary particles thereof satisfy the relational formula: W≦0.4×D50, and can be produced by dropping a metal salt-containing solution and an alkali solution to an alkali solution at the same time, followed by subjecting the obtained reaction solution to neutralization and precipitation reaction. The nickel-cobalt-manganese-based compound particles according to the present invention have a uniform particle size, a less content of very fine particles, a high crystallinity and a large primary particle diameter, and therefore are useful as a precursor of a positive electrode active substance used in a non-aqueous electrolyte secondary battery.
1. Nickel-cobalt-manganese-based compound particles having a volume-based average secondary particle diameter (D50) of 3.0 to 25.0 μm, in which the volume-based average secondary particle diameter (D50) and a half value width (W) of a peak in volume-based particle size distribution of secondary particles thereof satisfy the following relational formula 1:
W≦ 0.4× D 50. (Relational Formula 1)
2. Nickel-cobalt-manganese-based compound particles according to claim 1 , wherein when a molar ratio (mol %) of Ni:Co:Mn in the particles is expressed by x:y:z, x is 5 to 65 mol %, y is 5 to 65 mol %, and z is 5 to 55 mol % with the proviso that a sum of x, y and z is 100 mol % (x+y+z=100 mol %).
3. A process for producing the nickel-cobalt-manganese-based compound particles as defined in claim 1 , comprising the steps of:
preparing a reaction apparatus comprising a reactor equipped with a stirrer and a draft tube and connected with a concentrator;
previously introducing an alkali solution into the reactor; and continuously dropping a solution comprising metal salts comprising nickel, cobalt and manganese, and an alkali solution into the alkali solution previously introduced into the reactor from above a surface of the reaction solution to subject the resulting mixed solution to neutralization and precipitation reaction to thereby produce the nickel-cobalt-manganese-based compound particles,
in which a part of a reaction slurry produced during the above reaction is withdrawn from a mid portion of the reactor and introduced into the concentrator, and the slurry concentrated in the concentrator is introduced again into the reactor such that a direction of the concentrated slurry introduced into the reactor is the same as a direction of a turning flow of the reaction slurry in the reactor to produce the nickel-cobalt-manganese-based compound particles, followed by subjecting the reaction slurry comprising the thus produced nickel-cobalt-manganese-based compound particles to filtration, washing with water and drying at a temperature of 150 to 250° C.
4. A process for producing the nickel-cobalt-manganese-based compound particles according to claim 3 , wherein sodium hydroxide and ammonia are used as the alkali solution.
5. Lithium composite oxide particles comprising at least nickel, cobalt and manganese, and having a volume-based average secondary particle diameter (D50) of 3.0 to 25.0 μm, in which the volume-based average secondary particle diameter (D50) and a half value width (W) of a peak in volume-based particle size distribution of secondary particles thereof satisfy the following relational formula 2:
W≦ 0.4× D 50. (Relational Formula 2)
6. Lithium composite oxide particles according to claim 5 , wherein when a molar ratio (mol %) of Ni:Co:Mn in the particles is expressed by x:y:z, x is 5 to 65 mol %, y is 5 to 65 mol %, and z is 5 to 55 mol % with the proviso that a sum of x, y and z is 100 mol % (x+y+z=100 mol %), and a molar ratio of Li to a total amount of nickel, cobalt and manganese [lithium/(nickel+cobalt+manganese)] is 0.90 to 1.20.
7. A process for producing lithium composite oxide particles, comprising the steps of:
mixing the nickel-cobalt-manganese-based compound particles as defined in claim 1 with a lithium compound; and subjecting the resulting mixture to heat treatment at a temperature of 800 to 1100° C.
8. A non-aqueous electrolyte secondary battery using the lithium composite oxide particles as defined in claim 5 as a positive electrode active substance.