Li—Ni-based composite oxide particles for non-aqueous electrolyte secondary battery, process for producing the same, and non-aqueous electrolyte secondary battery
The present invention relates to Li—Ni-based composite oxide particles comprising Mn, and Co and/or Al, wherein Co and Al are uniformly dispersed within the particles, and Mn is present with a gradient of its concentration in a radial direction of the respective particles such that a concentration of Mn on a surface of the respective particles is higher than that at a central portion thereof. The Li—Ni-based composite oxide particles can be produced by allowing an oxide and a hydroxide comprising Mn to mechanically adhere to Li—Ni-based oxide comprising Co and/or Al; and then heat-treating the obtained material at a temperature of not lower than 400° C. and not higher than 1,000° C. The Li—Ni-based composite oxide particles of the present invention are improved in thermal stability and alkalinity.
1. Li—Ni-based composite oxide particles comprising secondary particles of Li—Ni-based oxide particles having a Li—Mn-based composite oxide being present on a surface of the respective secondary particle with a composition represented by the formula:
Li x2 (Mn 1-z2 M2 z2 ) y2 O 2
where M2 is at least one metal selected from the group consisting of Co, Ni, Al, Fe, Mg, Zr, Ti and B; and x2, y2 and z2 satisfy 1/2<x2≦4/3, 2/3≦y2≦1 and 0≦z2<4/5, respectively,
Co and/or Al being present therewithin, and
a concentration of Mn being increased from a center toward a surface of the respective particles.
2. Li—Ni-based composite oxide particles according to claim 1 , wherein the secondary particles of the Li—Ni-based oxide particles as core particles have a composition represented by the formula:
Li x1 (Ni 1-y1-z1-w1 Co y1 Mn z1 M1 w1 )O 2
(where x1, y1, z1 and w1 satisfy 0.9≦x1≦1.3, 0.1≦y1≦0.3, 0.0≦z1≦0.3 and 0≦w1≦0.1, respectively; and M1 is at least one metal selected from the group consisting of Al, Fe, Mg, Zr, Ti and B).
3. The Li—Ni-based composite oxide particles of claim 1 , wherein x2=4/3 and y2=2/3.
4. The Li—Ni-based composite oxide particles of claim 1 , wherein when using a negative electrode comprising a material capable of absorbing and desorbing a metallic lithium or a lithium ion, an exothermic peak temperature as measured by differential thermal analysis at a positive electrode under the condition that the cell is charged to 4.5 V is not lower than 240° C.
5. The Li—Ni-based composite oxide particles of claim 1 , wherein the average primary particle diameter of the Li—Mn composite oxide which is coated or allowed to be present on the core particles is 0.1 to 3.0 μm.
6. The Li—Ni-based composite oxide particles of claim 1 , wherein the content of the Li—Mn composite oxide which is coated on the secondary particles of the Li—Ni-based oxide forming the core particles is not less than 0.3% by weight and not more than 20% by weight based on the weight of the Li—Ni oxide.
7. The Li—Ni-based composite oxide particles of claim 1 , wherein the average secondary particle diameter of the secondary particles forming the core particles is 5 to 20 μm.