Non-aqueous secondary battery and method for producing the same

Abstract

A non-aqueous secondary battery of the present invention includes a positive electrode, a negative electrode and a non-aqueous electrolyte. The positive electrode includes a positive electrode material mixture layer containing a lithium-containing transition metal oxide. The negative electrode includes a negative electrode material mixture layer and a porous layer containing an insulating material unreactive with lithium formed thereon. The negative electrode material mixture layer includes a negative electrode material including a core and a carbon covering layer covering a surface of the core. The core includes a material containing silicon and oxygen at an atomic ratio x of the oxygen to the silicon of 0.5≦×≦1.5. The material containing silicon and oxygen has a peak at least in a range of 1850 to 1860 eV in an X-ray absorption near edge structure spectrum at the K absorption edge of Si in a state in which discharge of the battery is finished.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an example of a negative electrode precursor used to produce a negative electrode for a non-aqueous secondary battery of the present invention.

FIG. 2 is a schematic cross-sectional view of an example of a negative electrode for a non-aqueous secondary battery of the present invention.

FIG. 3 is a graph showing an X-ray absorption near edge structure spectrum at the K absorption edge of Si obtained before the first charge/discharge cycle (indicated by A) and that after the same (indicated by B) for the negative electrode material of Example 1.

Claims

1. A non-aqueous secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte, the positive electrode comprising a positive electrode material mixture layer containing a lithium-containing transition metal oxide,the negative electrode comprising a negative electrode material mixture layer and a porous layer formed on the negative electrode material mixture layer,the negative electrode material mixture layer including a negative electrode material comprising a core and a carbon covering layer covering a surface of the core, the core including a material comprising silicon and oxygen at an atomic ratio x of the oxygen to the silicon of 0.5≦x≦1.5,the porous layer containing an insulating material unreactive with lithium,wherein the material comprising silicon and oxygen has a peak at least in a range of 1850 to 1860 eV in an X-ray absorption near edge structure spectrum at the K absorption edge of Si in a state in which discharge of the battery is finished.

2. The non-aqueous secondary battery according to claim 1, wherein the material comprising silicon and oxygen includes a microcrystalline phase or amorphous phase of silicon.

3. The non-aqueous secondary battery according to claim 1, wherein the core comprises a composite including the material comprising silicon and oxygen and a conductive material having a lower specific resistance value than the material comprising silicon and oxygen.

4. The non-aqueous secondary battery according to claim 1, wherein the carbon covering layer is formed of a carbon produced by thermal decomposition of a hydrocarbon gas.

5. The non-aqueous secondary battery according to claim 1, wherein the porous layer contains the insulating material and an electron conductive material.

6. The non-aqueous secondary battery according to claim 5, wherein the insulating material is aluminum oxide or boehmite, and the electron conductive material is a carbon material.

7. The non-aqueous secondary battery according to claim 1, wherein the porous layer has a thickness of 2 to 10 μm.

8. A non-aqueous secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte, the positive electrode comprising a positive electrode material mixture layer containing a lithium-containing transition metal oxide,the negative electrode comprising a negative electrode material mixture layer and a porous layer formed on the negative electrode material mixture layer,the negative electrode material mixture layer including a negative electrode material comprising a core and a carbon covering layer covering a surface of the core, the core including a material comprising silicon and oxygen at an atomic ratio x of the oxygen to the silicon of 0.5≦x≦1.5,the porous layer containing an insulating material unreactive with lithium,wherein the material comprising silicon and oxygen contains lithium at an atomic ratio y of the lithium to the silicon of 0.8≦y≦2.4 in a state in which discharge of the battery is finished.

9. The non-aqueous secondary battery according to claim 8, wherein the material comprising silicon and oxygen comprises a microcrystalline phase or amorphous phase of silicon.

10. The non-aqueous secondary battery according to claim 8, wherein the core comprises a composite including the material comprising silicon and oxygen and a conductive material having a lower specific resistance value than the material comprising silicon and oxygen.

11. The non-aqueous secondary battery according to claim 8, wherein the carbon covering layer is formed of a carbon produced by thermal decomposition of a hydrocarbon gas.

12. The non-aqueous secondary battery according to claim 8, wherein the porous layer contains the insulating material and an electron conductive material.

13. The non-aqueous secondary battery according to claim 12, wherein the insulating material is aluminum oxide or boehmite, and the electron conductive material is a carbon material.

14. The non-aqueous secondary battery according to claim 8, wherein the porous layer has a thickness of 2 to 10 μm.

15. A method for producing a non-aqueous secondary battery comprising a positive electrode including a positive electrode material mixture layer containing a lithium-containing transition metal oxide, a negative electrode and a non-aqueous electrolyte, the method comprising the steps of: forming a negative electrode material mixture layer including a negative electrode material comprising a core and a carbon covering layer covering a surface of the core, the core including a material comprising silicon and oxygen at an atomic ratio x of the oxygen to the silicon of 0.5≦x≦1.5,forming, on the negative electrode material mixture layer, a buffer layer for suppressing a reaction between lithium and the negative electrode material,forming a lithium-containing layer on the buffer layer by a vapor deposition method, andallowing the lithium contained in the lithium-containing layer to be absorbed into the negative electrode material by an electrochemical reaction.

16. The method for producing a non-aqueous secondary battery according to claim 15, wherein the negative electrode material mixture layer is formed on a current collector.

17. The method for producing a non-aqueous secondary battery according to claim 15, wherein the buffer layer comprises a porous layer containing an insulating material unreactive with lithium.

18. The method for producing a non-aqueous secondary battery according to claim 15, wherein the lithium contained in the lithium-containing layer is introduced into the negative electrode material by bringing the negative electrode material mixture layer, the buffer layer and the lithium-containing layer into contact with the non-aqueous electrolyte.

19. The method for producing a non-aqueous secondary battery according to claim 15, wherein the lithium-containing layer is formed to have a thickness of 2 to 10 μm.

20. The method for producing a non-aqueous secondary battery according to claim 15, wherein the material comprising silicon and oxygen contains lithium at an atomic ratio y of the lithium to the silicon of 0.8≦y≦2.4 in a state in which discharge of the battery is finished.