Non-aqueous electrolyte secondary battery and positive electrode active material therefor

1. A positive electrode active material for a non-aqueous electrolyte secondary battery comprising:

a manganese oxide having a spinel structure,

said manganese oxide being represented by the general formula: Li 1+a Mn 2−x−a M x O 4+y , where M is one or more transition metal elements having an oxidation number of 2 or greater, M≠Mn, 0.17≦x≦0.5, 0.2≦y≦0.5 and 0≦a≦0.2,

wherein said manganese oxide has a lattice constant of 8.16 angstroms to 8.2 angstroms.

2. The positive electrode active material for a non-aqueous electrolyte secondary battery in accordance with claim 1 ,

wherein said one or more transition metal elements comprises at least one element selected from the group consisting of Ni, Fe and Ti.

3. The positive electrode active material for a non-aqueous electrolyte secondary battery in accordance with claim 1 ,

wherein said manganese oxide has an average particle size of 1 μm to 30 μm.

4. The positive electrode active material for a non-aqueous electrolyte secondary battery in accordance with claim 1 ,

wherein, when said positive electrode active material is charged using a counter electrode comprising a metal lithium, a charge capacity of said positive electrode active material obtained until a potential thereof relative to said counter electrode reaches 2.5 V to 3.0 V is 110 mAh/g or more.

5. A positive electrode active material for a non-aqueous electrolyte secondary battery comprising:

a manganese oxide having a spinel structure,

said manganese oxide being represented by the general formula: Li 1+a Mn 2−α−β−a M 1 α M 2 β O 4+y , where M 1 is at least one element selected from the group consisting of Ni and Fe, M 2 is a transition metal element other than Ni and Fe having an oxidation number of two or greater, α+β=x, 0<α, 0≦β, 0.1≦x≦0.5, 0.2<y≦0.5 and 0≦a≦0.2,

wherein said manganese oxide has a lattice constant of 8.16 angstroms to 8.2 angstroms.

6. A non-aqueous electrolyte secondary battery comprising:

a positive electrode containing a positive electrode active material,

said positive electrode active material comprising:

a manganese oxide having a spinel structure,

said manganese oxide being represented by the general formula: Li 1+a Mn 2−x−a M x O 4+y , where M is one or more transition metal elements having an oxidation number of 2 or greater, M≠Mn, 0.17≦x≦0.5, 0.2<y≦0.5 and 0≦a≦0.2

a negative electrode containing a negative electrode active material, and

a lithium ion-conductive non-aqueous electrolyte,

wherein an end-of-charge voltage of said battery is set to 3.5 V or less, and an end-of-discharge voltage of said battery is set to 2.5 V or greater.

7. The non-aqueous electrolyte secondary battery in accordance with claim 6 ,

wherein said negative electrode active material comprises at least one selected from the group consisting of silicon simple substance, a silicon oxide, a silicon carbide, a silicon nitride and a silicon alloy.

8. The non-aqueous electrolyte secondary battery in accordance with claim 7 ,

wherein said silicon alloy comprises a phase A composed mainly of silicon and a phase B comprising an intermetallic compound comprising one or more transition metal elements and silicon element, and

said one or more transition metal elements comprises at least one element selected from the group consisting of Ti, Zr, Ni, Cu and Fe.

9. The non-aqueous electrolyte secondary battery in accordance with claim 8 , wherein said intermetallic compound comprises TiSi 2 .

10. A charge/discharge system comprising:

a non-aqueous electrolyte secondary battery,

a charger for charging said non-aqueous electrolyte secondary battery, and

a discharge controller for said non-aqueous electrolyte secondary battery,

said non-aqueous electrolyte secondary battery comprising a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material and a lithium ion-conductive non-aqueous electrolyte,

said positive electrode active material comprising a manganese oxide having a spinel structure, said manganese oxide being represented by the general formula: Li 1+a Mn 2−x−a M x O 4+y , where M is a transition metal element having an oxidation number of 2 or greater, M≠Mn, 0.17≦x≦0.5, 0.2<y≦0.5 and 0≦a≦0.2,

said charger being set to have an end-of-charge voltage of said battery of 3.5 V or less, and

said discharge controller being set to have an end-of-discharge voltage of said battery of 2.5 V or greater.

11. The non-aqueous electrolyte secondary battery in accordance with claim 6 , wherein 0.2≦y≦0.5.

12. The non-aqueous electrolyte secondary battery in according with claim 6 , wherein said negative electrode active material comprises silicon element.

13. The charge/discharge system in accordance with claim 10 , wherein 0.2≦y≦0.5.

14. The charge/discharge system in accordance with claim 10 , wherein said negative electrode active material comprises silicon element.