Electrode structure for lithium secondary battery and secondary battery having such electrode structure

• US 20060127773A1
• Filed: 12/08/2005
• Published: 06/15/2006
• Est. Priority Date: 12/10/2004
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kawakami, Soichiro, Morita, Akira, Ogura, Takao
• Granted Patent: US 7,615,314 B2
• Time in Patent Office: Days
• US Class Current: 429/245
• CPC Class Codes: H01M 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/1395 of electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/366 as layered products
• CPC Class Codes: H01M 4/485 of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy H01M4/505, H01M4/525 take precedence
• CPC Class Codes: H01M 4/587 for inserting or intercalating light metals
• CPC Class Codes: H01M 4/621 Binders
• CPC Class Codes: H01M 4/622 being polymers
• CPC Class Codes: H01M 4/661 Metal or alloys, e.g. alloy coatings H01M4/669 take precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 29/10 Battery-grid making
• CPC Class Codes: Y10T 29/49115 including coating or impregnating

Abstract

In an electrode structure for a lithium secondary battery including: a main active material layer formed from a metal powder selected from silicon, tin and an alloy thereof that can store and discharge and capable of lithium by electrochemical reaction, and a binder of an organic polymer; and a current collector, wherein the main active material layer is formed at least by a powder of a support material for supporting the electron conduction of the main active material layer in addition to the metal powder and the powder of the support material are particles having a spherical, pseudo-spherical or pillar shape with an average particle size of 0.3 to 1.35 times the thickness of the main active material layer. The support material is one or more materials selected from a group consisting of graphite, oxides of transition metals and metals that do not electrochemically form alloy with lithium. Organic polymer compounded with a conductive polymer is used for the binder. There are provided an electrode structure for a lithium secondary battery having a high capacity and a long lifetime, and a lithium secondary battery using the electrode structure and having a high capacity, a high energy density and a long lifetime.

Claims

1. An electrode structure for a lithium secondary battery, comprising:

a main active material layer comprising a metal powder of a material selected from the group consisting of silicon, tin and an alloy thereof that can store and discharge lithium by electrochemical reaction, and a binder of an organic polymer; and

a current collector;

wherein (a) the main active material layer further comprises a powder of a support material for supporting electron conduction of the main active material layer in addition to the metal powder;

the powder of the support material are particles having a spherical, pseudo-spherical or pillar shape with an average particle size of 0.3 to 1.35 times an average thickness of the main active material layer; and

the support material comprises one or more materials selected from the group consisting of graphite, an oxide of a transitional metal selected from TiO₂, MoO₃ and WO₃, and a metal electrochemically not forming an alloy with Li which is selected from Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt and Au and an alloy thereof.

2. The electrode structure according to claim 1, wherein (b) an electron-conductive buffer layer is arranged between the current collector and the main active material layer of the electrode structure;

the buffer layer comprises a binder of an organic polymer, and particles of one or more materials selected from the group consisting of a conductive polymer, graphite, a metal electrochemically not forming an alloy with Li which is selected from Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt and Au and an alloy thereof, and an oxide of a transitional metal selected from TiO₂, MoO₃ and WO₃; and

an average particle size of the particles is 0.5 μ

m to 10 μ

m.

3. The electrode structure according to claim 1, wherein (c) a surface coat layer is arranged on the surface of the main active material layer of the electrode structure;

the surface coat layer has electron conductivity and ion transmissibility or ionic conductivity;

the surface coat layer comprises a binder of an organic polymer and particles of one or more materials selected from the group consisting of a conductive polymer, amorphous graphite, graphite, a metal electrochemically not forming an alloy with Li which is selected from Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt and Au and an alloy thereof, and an oxide of a transitional metal selected from TiO₂, MoO₃ and WO₃; and

an average secondary particle size of the particles is 0.5 μ

m to 10 μ

m.

4. The electrode structure according to claim 1, wherein (b) an electron-conductive buffer layer is arranged between the current collector and the main active material layer of the electrode structure;

the buffer layer comprises a binder of an organic polymer and particles of one or more materials selected from the group consisting of a conductive polymer, graphite, a metal electrochemically not forming an alloy with Li which is selected from Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt and Au and an alloy thereof, and an oxide of a transitional metal selected from TiO₂, MoO₃ and WO₃;

an average particle size of the particles is 0.5 μ

m to 10 μ

m; and

wherein (c) a surface coat layer is arranged on the surface of the main active material layer;

the surface coat layer has electron conductivity and ion transmissibility or ionic conductivity;

the surface coat layer comprises a binder of an organic polymer and particles of one or more materials selected from the group consisting of a conductive polymer, amorphous graphite, graphite, a metal electrochemically not forming an alloy with Li which is selected from Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt and Au and an alloy thereof and an oxide of a transitional metal selected from TiO₂, MoO₃ and WO₃;

an average secondary particle size of the particles is 0.5 μ

m to 10 μ

m.

5. The electrode structure according to claim 1, wherein the support material is graphite.

6. The electrode structure according to claim 3, wherein the surface coat layer comprises the binder of the organic polymer and the particles of graphite.

7. The electrode structure according to claim 2, wherein the binder of the main active material layer and the binder of the buffer layer are composed of the same material.

8. The electrode structure according to claim 3, wherein the binder of the main active material layer and the binder of the surface coat layer are composed of the same material.

9. The electrode structure according to claim 4, wherein the binder agent of the main active material layer, the binder agent of the buffer layer and the binder of the surface coat layer are composed of the same material.

10. The electrode structure according to claim 1, wherein a conductive organic polymer is dispersed in the binder.

11. The electrode structure according to claim 1, wherein an average particle size of primary particles for forming metal particles of the main active material layer is 0.05 μ

m to 5 μ

m.

12. The electrode structure according to claim 1, wherein a surface of metal particles of the main active material layer are coated with carbonaceous material of coal tar pitch.

13. The electrode structure according to claim 1, wherein a ten point average height Rz representing a surface roughness of the current collector is 0.7 μ

m to 3 μ

m.

14. The electrode structure according to claim 1, wherein the metal powder and the powder of the support material are compounded by a link material having a function of carrying out chemical bond or electron conduction between the metal powder and the powder of the support material.

15. A secondary battery comprising:

a negative electrode formed by using an electrode structure according to claim 1, a lithium ion conductor, and a positive electrode, wherein an oxidation reaction of lithium and a reduction reaction of lithium ions are utilized.

16. The secondary battery according to claim 15, wherein an expansion coefficient of the powder of the support material in the main active material layer of the negative electrode after charging is 1.5 times or less the powder before charging in a direction toward an oppositely disposed positive electrode.

17. The secondary battery according to claim 15, wherein a positive electrode material of the positive electrode comprises an oxide of lithium and a transition metal, and the oxide of lithium and the transition metal is coated with carbonaceous material of coal tar pitch.

18. The secondary battery according to claim 15, wherein the lithium ion conductor comprises an electrolyte solution prepared by dissolving lithium salt in a solvent, and a monomer of a vinyl compound is contained in the electrolyte solution at the time of assembling the secondary battery.

19. An electrode structure for a lithium secondary battery, comprising:

a main active material layer comprising;

a metal powder of a material selected from the group consisting of silicon, tin and an alloy thereof that can store and discharge lithium by electrochemical reaction;

hard carbon powder or carbon powder of graphite; and

a binder of an organic polymer, and

a current collector;

wherein the metal powder and the carbon powder are compounded by a link material having a function of carrying out chemical bond or electron conduction between the metal powder and the carbon powder.

20. The electrode structure according to claim 19, wherein the link material is coal tar pitch.

21. The electrode structure according to claim 20, wherein the coal tar pitch is contained at an amount of 0.1 to 3 wt % in the main active material layer.

22. The electrode structure according to claim 19, wherein the link material is amorphous carbon.

23. The electrode structure according to claim 22, wherein the amorphous carbon is carbonaceous material of coal tar pitch.

24. The electrode structure according to claim 23, wherein the amorphous carbon is contained at an amount of 1 to 10 wt % in the main active material layer.

25. The electrode structure according to claim 19, wherein the link material is a nonionic fluorine type surfactant having an ether bond or an ester bond.

26. The electrode structure according to claim 24, wherein the fluorine type surfactant is contained at an amount of 0.01 to 0.5 wt % in the main active material layer.

27. A lithium secondary battery comprising a negative electrode formed by using an electrode structure according to claim 19, a lithium ion conductor, and a positive electrode, wherein an oxidation reaction of lithium and a reduction reaction of lithium ions are utilized.

28. A method of producing the electrode structure according to claim 20, comprising:

a step of mixing the metal powder and the carbon powder with coal tar pitch at an amount of 0.1 to 3 wt %, and

a step of adding the binder to a mixture obtained in the above step, mixing them, and applying obtained mixture onto a plate-shaped metal current collector.

29. The method according to claim 28, wherein in the step of adding the binder to the mixture, mixing them and applying the obtained mixture onto the plate-shaped metal current collector, an solvent for the binder is added to and mixed with the mixture at the time of mixing the binder with the mixture.

30. A method of producing a lithium secondary battery, comprising a step of interposing a lithium ion conductor is between a negative electrode formed by using an electrode structure produced by a method according to claim 28 and a positive electrode.

31. A method of producing the electrode structure according to claim 23, comprising:

a step of mixing the metal powder and the carbon powder with coal tar pitch at an amount of 0.1 to 10 wt %, heat-treating mixture at 400 to 700°

C. under an inert gas to obtain compounded particles of the metal powder and the carbon powder; and

a step of mixing the particles and the binder, applying obtained mixture onto a plate-shaped metal current collector.

32. The method according to claim 31, wherein in the step of adding the binder to the mixture, mixing them and applying the obtained mixture onto the plate-shaped metal current collector, an solvent for the binder is added to and mixed with the mixture at the time of mixing the binder with the mixture.

33. A method of producing a lithium secondary battery, comprising a step of interposing a lithium ion conductor is between a negative electrode formed by using an electrode structure produced by the method according to claim 31 and a positive electrode.

34. A method of producing the electrode structure according to claim 25, comprising:

a step of mixing the metal powder and the carbon powder with a fluorine type surfactant at an amount of 0.1 to 0.5 wt %; and

a step of adding the binder to a mixture obtained in the above mixing step, mixing them, and applying obtained mixture onto a plate-shaped metal current collector.

35. The method according to claim 34, wherein in the step of adding the binder to the mixture, mixing them and applying the obtained mixture onto the plate-shaped metal current collector, an solvent for the binder is added to and mixed with the mixture at the time of mixing the binder with the mixture.

36. A method of producing a lithium secondary battery, comprising a step of interposing a lithium ion conductor is between a negative electrode formed by using an electrode structure produced by the method according to claim 34 and a positive electrode.