Non-aqueous electrolyte secondary battery

1. A nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte,

wherein the positive electrode contains a lithium transition metal oxide, having a layered structure, containing at least Ni and also contains a tungsten compound and/or a molybdenum compound;

the percentage of Ni is greater than 90.00 mole percent with respect to the sum of the molar amounts of metal elements, excluding lithium, in the lithium transition metal oxide;

the amount of the tungsten compound and/or the molybdenum compound is 0.1 mole percent to 1.5 mole percent with respect to the sum of the molar amounts of the metal elements, excluding lithium, in the lithium transition metal oxide in terms of tungsten element and/or molybdenum element; and

wherein the lithium transition metal oxide is represented by the formula Li a Ni x M 1-x O 2 (where 0.95≤a≤1.20, 0.94≤x, and M is at least one element selected from Co, Mn, and Al),

wherein the nonaqueous electrolyte contains a lithium salt containing a P—O bond in its molecule and a nitrile compound.

2. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the lithium transition metal oxide is composed of secondary particles formed by the aggregation of primary particles and

the tungsten compound and/or the molybdenum compound is attached to the surfaces of at least either of the primary particles and secondary particles of the lithium transition metal oxide.

3. The nonaqueous electrolyte secondary battery according to claim 2 , wherein the tungsten compound and/or the molybdenum compound is attached to the surfaces of the primary particles and secondary particles of the lithium transition metal oxide.

4. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the tungsten compound and/or the molybdenum compound is at least one compound selected from oxides and lithium composite oxides.

5. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the phase transition of the lithium transition metal oxide occurs at a potential of 4.15 V (vs. Li/Li+) to 4.25 V (vs. Li/Li+).

6. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the lithium transition metal oxide is represented by the formula Li a Ni x Co y Al z O 2 (where 0.95≤a≤1.20, 0.90<x, 0<y<0.10, and 0<z<0.10).

7. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the lithium salt containing the P—O bond in its molecule is lithium difluorophosphate.

8. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the nitrile compound is adiponitrile.

9. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the positive electrode contains the tungsten compound.

10. The nonqueous electrolyte secondary battery according to claim 9 , wherein the lithium transition metal oxide is composed of secondary particles formed by aggregation of primary particles and the tungsten compound is attached to an outer surface of at least one of the primary particles or the secondary particles.

11. The nonqueous electrolyte secondary battery according to claim 10 , wherein the tungsten compound is attached to the outer surface of the primary particles and the secondary particles.

12. The nonqueous electrolyte secondary battery according to claim 9 , wherein the tungsten compound is at least one compound selected from oxides and lithium composite oxides.

13. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the lithium transition metal oxide is represented by the formula LiNi 0.94 Co 0.03 Al 0.03 O 2 .