Anode and secondary battery

• US 9,634,330 B2
• Filed: 04/23/2009
• Issued: 04/25/2017
• Est. Priority Date: 04/23/2008
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Hirose, Takakazu, Kawase, Kenichi, Takada, Tomoo, Noguchi, Kazunori, Fujii, Takayuki
• Primary Examiner(s): Lee, James
• Application Number:
  US12/428,518
• Publication Number:
  US 20090269677A1
• Time in Patent Office: 2,924 Days
• Field of Search: 429121-347
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/0569 characterised by the solvents
• CPC Class Codes: H01M 10/0587 of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
• CPC Class Codes: H01M 2300/0037 Mixture of solvents
• CPC Class Codes: H01M 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/621 Binders
• CPC Class Codes: H01M 4/624 Electric conductive fillers
• CPC Class Codes: H01M 4/626 Metals
• 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

Abstract

A secondary battery capable of improving the cycle characteristics is provided. The secondary battery includes a cathode, an anode, and an electrolytic solution. The electrolytic solution is impregnated in a separator provided between the cathode and the anode. The anode has an anode structure on an anode current collector. The anode structure has a structure in which a plurality of anode active material particles having silicon are held by a plurality of metal fibers forming a three-dimensional network structure. Due to the plurality of metal fibers, sufficient conductive paths are obtained among the plurality of anode active material particles. Thus, compared to a general anode in which an active material layer is provided on a current collector made of a metal foil or the like, the current collectivity is improved.

Claims

1. A secondary battery comprising:

a cathode;

an anode comprising (i) a plurality of metal fibers forming a conductive three-dimensional network structure, (ii) a resin binder securing the metal fibers in a sheet structure, and (iii) a plurality of anode active material particles having silicon (Si) at least a portion of which are contained within the three-dimensional network structure and which contact the metal fibers, and

an electrolytic solution,

wherein,

the sheet structure is uncompressed,

at least part of the resin binder is carbonized,

the metal fibers function as a current collector,

the anode, cathode and electrolytic solution are wound together and form a wound structure, each of the cathode and anode are elongated structures that extend along an anode-extending direction, where the anode-extending direction of the anode is defined by a length of the anode that is longer than a width of the anode,

the plurality of metal fibers (i) do not form an intermetallic compound with an electrode reactant, (ii) have a diameter D from 1 μ

m to 15 μ

m, both inclusive, and (iii) have a ratio B/A between average cross sectional diameter A and average length B of the metal fibers is 2 or more, at least some of the metal fibers extend more along the anode-extending direction than orthogonal to the anode-extending direction to form a conductive path along the anode-extending direction, these metal fibers being such that when each is divided into a component in the extending direction and a component in a direction orthogonal to the extending direction in a cross section along the extending direction of the anode, ratio Y/X between dimension X of the component in the extending direction and dimension Y of the component in the direction orthogonal to the extending direction is less than 1,

an amount of the anode active material particles contained within the three-dimensional network structure is greater than an amount of the anode active material particles located on a surface of the three-dimensional network structure or in a vicinity of the surface of the three-dimensional network structure,

the anode active material particles have a median diameter of 0.1 μ

m to 30 μ

m, both inclusive, and

the sheet structure has (i) a thickness from 10 μ

m to 200 μ

m, both inclusive, (ii) a porosity from 20% to 95% both inclusive, and (iii) a tensile strength of 0.1 N/mm or more.

2. The secondary battery according to claim 1, wherein the plurality of metal fibers are connected to each other at least partially and thereby forming the three-dimensional network structure.

3. The secondary battery according to claim 1, wherein the metal fibers are at least one selected from the group consisting of titanium (Ti), iron (Fe), stainless, copper (Cu), aluminum (Al), zinc (Zn), silver (Ag), cobalt (Co), nickel (Ni), and chromium (Cr).

4. The secondary battery according to claim 1, wherein diameter D of the metal fibers is from 2 μ

m to 10 μ

m.

5. The secondary battery according to claim 1, wherein the plurality of metal fibers form a sheet.

6. The secondary battery according to claim 1, wherein the anode active material particles are a simple substance of silicon, a compound of silicon, an alloy of silicon, or any combination of them.

7. The secondary battery according to claim 1, wherein a median size of the anode active material particles is from 1 μ

m to 20 μ

m both inclusive.

8. The secondary battery according to claim 1, wherein the binder contains at least one resin selected from the group consisting of polyimide, polyamide, and polyamideimide.

9. The secondary battery according to claim 1, wherein the anode contains an anode electrical conductor containing a carbon material.

10. The secondary battery according to claim 1, wherein the anode includes an anode current collector and an arithmetic average roughness Ra of a surface of the anode current collector is 0.2 μ

m or more.

11. The secondary battery according to claim 1, wherein the electrolytic solution contains a solvent containing at least one of a chain ester carbonate having halogen represented by Chemical formula 1, a cyclic ester carbonate having halogen represented by Chemical formula 2, a cyclic ester carbonate having an unsaturated bond represented by Chemical formula 3 to Chemical formula 5, sultone, and an acid anhydride:

Chemical formula 1

12. The secondary battery according to claim 11, wherein the chain ester carbonate having halogen represented by the Chemical formula 1 is fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, or bis(fluoromethyl) carbonate, the cyclic ester carbonate having halogen represented by the Chemical formula 2 is 4-fluoro-1,3-dioxolane-2-one or 4,5-difluoro-1,3-dioxolane-2-one, the cyclic ester carbonate having an unsaturated bond represented by the Chemical formula 3 is vinylene carbonate, the cyclic ester carbonate having an unsaturated bond represented by the Chemical formula 4 is vinylethylene carbonate, and the cyclic ester carbonate having an unsaturated bond represented by the Chemical formula 5 is methylene ethylene carbonate.

13. The secondary battery according to claim 1, wherein the electrolytic solution contains an electrolyte salt containing at least one selected from the group consisting of lithium hexafluorophosphate (LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium perchlorate (LiClO₄), lithium hexafluoroarsenate (LiAsF₆), compounds represented by Chemical formula 6 to Chemical formula 8, and compounds represented by Chemical formula 9 to Chemical formula 11:

14. The secondary battery according to claim 13, wherein the compound represented by the Chemical formula 6 is a compound represented by Chemical formulas 12(1) to 12(6), the compound represented by the Chemical formula 7 is a compound represented by Chemical formulas 13(1) to 13(8), and the compound represented by the Chemical formula 8 is a compound represented by Chemical formula 14

15. The secondary battery according to claim 1, wherein where anode utilization C(=(V1/V2)×

100;

%) is from 20% to 80% both inclusive where an insertion amount of an electrode reactant per unit area in the full charge state of the anode is V1 and an insertion amount of the electrode reactant capable of being electrochemically inserted into the anode per unit area is V2.

16. The secondary battery of claim 1, wherein the metal fibers forming a three-dimensional network structure serve as the anode current collector and there is no separate structure serving as the anode current collector.

17. The secondary battery of claim 1, wherein the anode active material particles include compounds of Si and one or more of Fe, Co, Ni, Ti, or Cu.

18. An anode comprising a plurality of metal fibers forming a conductive three-dimensional network structure, a carbonized resin binder securing the metal fibers in a sheet structure, and a plurality of anode active material particles having silicon (Si), at least some of which are contained within the three dimensional network structure and which contact the metal fibers, wherein:

(a) the metal fibers function as a current collector,

(b) the anode is an elongated structure that extends along an anode-extending direction, where the anode-extending direction of the anode is defined by a length of the anode that is longer than a width of the anode, and is capable of being wound,

(c) the metal fibers (i) do not form an intermetallic compound with an electrode reactant, (ii) have a diameter D from 1 μ

m to 15 μ

m, both inclusive, and (iii) have a ratio B/A between average cross sectional diameter A and average length B of the metal fibers is 2 or more,

(d) an amount of anode active material particles contained within the three-dimensional network structure is greater than an amount of anode active material particles located on a surface of the three-dimensional network structure or in a vicinity of the surface of the three-dimensional network structure,

(e) at least some of the plurality of metal fibers extend in a length direction more along an the anode-extending direction than orthogonal to the anode-extending direction to form a conductive path along the anode-extending direction, these metal fibers being such that when each is divided into a component in the extending direction and a component in a direction orthogonal to the extending direction in a cross section along the extending direction of the anode, ratio Y/X between dimension X of the component in the extending direction and dimension Y of the component in the direction orthogonal to the extending direction is less than 1,

(f) the particles have a median diameter of 0.1 μ

m to 30 μ

m, both inclusive,

(g) the sheet structure has (i) a thickness from 10 μ

m to 200 μ

m, both inclusive, (ii) a porosity from 20% to 95% both inclusive, and (iii) a tensile strength of the sheet is 0.1 N/mm or morel(h) the sheet structure is uncompressed.

19. The anode of claim 18, wherein the metal fibers forming a three-dimensional network structure serve as the anode current collector and there is no separate structure serving as the anode current collector.