Positive electrode active material for nonaqueous electrolyte secondary batteries, method for producing the same, positive electrode for nonaqueous electrolyte secondary batteries incorporating the positive electrode active material, and nonaqueous electrolyte secondary battery incorporating the positive electrode
A positive electrode active material according to an aspect of the present invention for nonaqueous electrolyte secondary batteries contains a lithium transition metal composite oxide that has a compound in contact with its surface, the compound containing a rare earth metal and silicic acid and/or boric acid. A positive electrode according to an aspect of the present invention has a positive electrode collector and a positive electrode mixture layer formed on at least one surface of the positive electrode collector. The positive electrode mixture layer contains a positive electrode active material, a binder, and a conductive agent. The positive electrode active material contains a lithium transition metal composite oxide that has a compound in contact with its surface, the compound containing a rare earth metal and silicic acid and/or boric acid.
1. A positive electrode active material for nonaqueous electrolyte secondary batteries, the positive electrode active material comprising a lithium transition metal composite oxide having a compound in contact with a surface thereof, the compound containing a rare earth metal and silicic acid and/or boric acid.
2. The positive electrode active material according to claim 1 for nonaqueous electrolyte secondary batteries, wherein the compound contains a rare earth metal and silicic acid.
3. The positive electrode active material according to claim 1 for nonaqueous electrolyte secondary batteries, wherein the compound contains a rare earth metal and boric acid.
4. The positive electrode active material according to claim 2 for nonaqueous electrolyte secondary batteries, wherein the compound consists of a rare earth metal and silicic acid.
5. The positive electrode active material according to claim 3 for nonaqueous electrolyte secondary batteries, wherein the compound consists of a rare earth metal and boric acid.
6. The positive electrode active material according to claim 1 for nonaqueous electrolyte secondary batteries, wherein the rare earth metal is at least one metal selected from lanthanum, neodymium, samarium, erbium, and ytterbium.
7. A positive electrode for nonaqueous electrolyte secondary batteries, the positive electrode active material comprising a positive electrode collector and a positive electrode mixture layer formed on at least one surface of the positive electrode collector, the positive electrode mixture layer containing a positive electrode active material according to claim 1 , a binder, and a conductive agent.
8. A nonaqueous electrolyte secondary battery comprising the positive electrode according to claim 7 , a negative electrode, and a nonaqueous electrolyte.
9. The positive electrode active material according to claim 2 ,
wherein the compound comprises Ln 2 Si 2 O 5 and Ln is a rare earth metal.
10. The positive electrode active material according to claim 2 ,
wherein the compound comprises Ln 2 SiO 7 and Ln is a rare earth metal.
11. The positive electrode active material according to claim 2 ,
wherein the compound comprises A x Ln y SiO z and A is an alkali metal, Ln is a rare earth metal, 0≤x<4, 0<y≤2, and z is a value that makes a charge of the compound 0.
12. The positive electrode active material according to claim 3 ,
wherein the compound comprises LnBO 3 and Ln is a rare earth metal.
13. The positive electrode active material according to claim 3 ,
wherein the compound comprises A a Ln b (BO 3 ) 3 and A is an alkali metal, Ln is a rare earth metal, 0≤a<3, and 0<b≤2.
14. The positive electrode active material according to claim 3 ,
wherein the compound comprises B c Ln d (BO 3 ) 4 and B is an alkaline earth metal, Ln is a rare earth metal, 0≤c<3, and 0<d≤2.
15. A positive electrode active material for nonaqueous electrolyte secondary batteries, the positive electrode active material comprising,
a lithium transition metal composite oxide with a surface layer,
wherein the surface layer consists of a rare earth metal, silicic acid and/or boric acid, and optionally an alkali metal.