Surface modified lithium-containing composite oxide particles, positive electrode using the particles, and non-aqueous electrolyte secondary battery
Surface modified lithium-containing composite oxide particles include base material particles of lithium-containing composite oxide, zirconium hydroxide or zirconium oxide, and at least one lithium salt selected from the group consisting of Li 2 ZrF 6 , Li 2 TiF 6 , Li 3 PO 4 , Li 2 SO 4 and Li 2 SO 4 .H 2 O. The zirconium hydroxide or zirconium oxide, and the at least one lithium salt are attached to a surface of the base material particle. The lithium-containing composite oxide is represented by the formula: Li p N x M y O z F a . N is at least one element selected from the group consisting of Co, Mn and Ni; M is at least one element selected from the group consisting of Al, elements of group 2, and transition metal elements other than N; 0.9<p<1.1; 0.85<x<1.0; 0<y<0.15; 1.9<z<2.1; x+y=1; and 0<a<0.05.
1. Surface modified lithium-containing composite oxide particles comprising:
base material particles of lithium-containing composite oxide which is represented by the formula: Li p N x M y O z F a , wherein N is at least one element selected from the group consisting of Co, Mn and Ni, M is at least one element selected from the group consisting of Al, elements of group 2, and transition metal elements other than N, 0.9≤p<1.1, 0.85≤x≤1.0, 0≤y≤0.15, 1.9≤z≤2.1, x+y=1, and 0≤a≤0.05;
zirconium hydroxide or zirconium oxide; and
at least one lithium salt selected from the group consisting of Li 2 ZrF 6 , Li 2 TiF 6 , Li 3 PO 4 , Li 2 SO 4 and Li 2 SO 4 .H 2 O, the zirconium hydroxide or zirconium oxide and the at least one lithium salt being attached to a surface of the base material particle,
wherein the value calculated by dividing the number of moles N Zr of the zirconium hydroxide and zirconium oxide attached to the surface of the base material particle by the total number of moles N m+n of M and N contained in the lithium-containing composite oxide (N Zr /N m+n ) is 0.0004<N Zr /N m+n <0.003, and
wherein the value calculated by dividing the number of moles N a of the at least one lithium salt attached to the surface of the base material particle by the total number of moles N m+n of M and N contained in the lithium-containing composite oxide (N a /N m+n ) is 0.001<N a /N m+n <0.01.
2. The surface modified lithium-containing composite oxide particles according to claim 1 , wherein the value calculated by dividing N Zr by N a (N Zr /N a ) is 0.05≤N Zr /N a ≤2.0.
3. The surface modified lithium-containing composite oxide particles according to claim 1 , wherein the lithium salt is Li 2 ZrF 6 or Li 3 PO 4 .
4. The surface modified lithium-containing composite oxide particles according to claim 1 , wherein zirconium oxide is attached to the surface of the base material particle.
5. The surface modified lithium-containing composite oxide particles according to claim 1 , wherein N is Co.
6. The surface modified lithium-containing composite oxide particles according to claim 1 , wherein M is at least one element selected from the group consisting of Al, Zr and Mg.
7. The surface modified lithium-containing composite oxide particles according to claim 1 , wherein in a powder X-ray diffraction spectrum using CuKα radiation, the integral width of a diffraction peak of (110) plane at 2θ=66.5±1° of the surface modified lithium-containing composite oxide particles is from 0.08 to 0.20°.
8. The surface modified lithium-containing composite oxide particles according to claim 1 , wherein the mode diameter of the particle size distribution of the surface modified lithium-containing composite oxide particles is from 15 to 25 μm, and the shoulder peak of the surface modified lithium-containing composite oxide particles is from 4 to 10 μm.
9. A positive electrode for a non-aqueous electrolyte secondary battery, comprising:
a cathode active material comprising the surface modified lithium-containing composite oxide particles as defined in claim 1 ;
a conductive materials; and
a binder.
10. A non-aqueous electrolyte secondary battery, comprising:
a positive electrode as defined in claim 9 ;
a negative electrode;
a non-aqueous electrolyte; and
an electrolytic solution.
11. The surface modified lithium-containing composite oxide particles according to claim 3 , wherein zirconium oxide is attached to the surface of the base material particle.
12. The surface modified lithium-containing composite oxide particles according to claim 11 , wherein N is Co.
13. The surface modified lithium-containing composite oxide particles according to claim 12 , wherein M is at least one element selected from the group consisting of Al, Zr and Mg.
14. The surface modified lithium-containing composite oxide particles according to claim 13 , wherein the value calculated by dividing the number of moles N Zr of the zirconium oxide attached to the surface of the base material particle by the total number of moles N m+n of M and N contained in the lithium-containing composite oxide (N Zr /N m+n ) is 0.0005<N Zr /N m+n <0.002.
15. The surface modified lithium-containing composite oxide particles according to claim 14 , wherein the value calculated by dividing the number of moles N a of the at least one lithium salt attached to the surface of the base material particle by the total number of moles N m+n of M and N contained in the lithium-containing composite oxide (N a /N m+n ) is 0.001<N a /N m+n <0.005.