Flat non-aqueous electrolyte secondary cell

• US 6,521,373 B1
• Filed: 08/17/2000
• Issued: 02/18/2003
• Est. Priority Date: 08/27/1999
• Status: Expired due to Term

• Current Assignee: Hitachi Maxell Limited (Hitachi, Ltd.)
• Original Assignee: Toshiba Battery Co., Ltd. (Toshiba Corporation)
• Inventors: Sakai, Hirotaka, Suzuki, Masami, Shikota, Masataka, Udagawa, Kazuo, Hayami, Muneto, Yoda, Kiyoto, Hirahara, Satoshi, Iizuka, Kazuo, Ishihara, Naomi
• Primary Examiner(s): Chaney, Carol
• Assistant Examiner(s): Martin, Angela J
• Application Number:
  US09/641,267
• Time in Patent Office: 915 Days
• Field of Search: 429/162, 429/127, 429/124, 429/94
• US Class Current: 429/162
• CPC Class Codes: H01M 10/0427 Button cells
• CPC Class Codes: H01M 10/0431 Cells with wound or folded electrodes H01M10/045 takes precedence
• CPC Class Codes: H01M 10/052 Li-accumulators
• 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 10/0568 characterised by the solutes
• CPC Class Codes: H01M 10/0569 characterised by the solvents
• CPC Class Codes: H01M 10/0583 of accumulators with folded construction elements except wound ones, i.e. folded positive or negative electrodes or separators, e.g. with "Z"-shaped electrodes or separators
• CPC Class Codes: H01M 10/0585 of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
• 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 2004/021 Physical characteristics, e.g. porosity, surface area
• CPC Class Codes: H01M 2006/106 Elliptic wound cells
• CPC Class Codes: H01M 4/13 Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• CPC Class Codes: H01M 4/587 for inserting or intercalating light metals
• CPC Class Codes: H01M 4/669 Steels
• CPC Class Codes: H01M 50/109 of button or coin shape
• CPC Class Codes: H01M 50/119 Metals
• CPC Class Codes: H01M 50/133 Thickness
• CPC Class Codes: H01M 50/3425 in the form of rupturable membranes or weakened parts, e.g. pierced with the aid of a sharp member
• CPC Class Codes: H01M 50/545 formed by the casing of the cells cup shaped terminals adapted for cells having curved cross-section H01M50/56
• CPC Class Codes: H01M 6/10 with wound or folded electrodes
• CPC Class Codes: H01M 6/103 : Cells with electrode of only one polarity being folded or wound
• CPC Class Codes: H01M 6/164 : by the solvent
• 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

In a flat non-aqueous electrolyte secondary cell comprising an electricity-generating element including at least a cathode, a separator and an anode and a non-aqueous electrolyte in the inside of a cathode case, a plurality of electrode units each consisting of the cathode and the anode opposite to each another via the separator are laminated to form an electrode group, or an electrode unit in a sheet form consisting of the cathode and the anode opposite to each another via the separator is wound to form an electrode group, or a sheet-shape cathode is wrapped with the separator except for a part contacting at inner face of cathode case and a sheet-shaped anode is set on the sheet-shaped cathode in a right angled position each other and then these cathode and anode are bent alternately to form an electrode group, and the total sum of the areas of the opposing cathode and anode in this electrode group is larger than the area of the opening of an insulating gasket in a sealed portion in the cathode case or than the area of an opening in a sealed plate in a sealed portion in the cathode case, whereby the discharge capacity upon heavy-loading discharge is significantly increased as compared with the conventional cells. Accordingly, while the size of the cell is small, the discharge capacity is increased as described above, and thus it is possible to provide a highly utilizable flat non-aqueous electrolyte secondary cell. Further, in said flat non-aqueous electrolyte secondary cell, problems which may be caused by the increased discharge capacity in the cell can be solved by improving the solvent and supporting electrolyte for the electrolyte or by various improvements in the cathode and anode cases.

Claims

1. A flat non-aqueous electrolyte secondary cell comprising a metallic anode case also serving as an anode terminal and a metallic cathode case also serving as a cathode terminal fit to each other via an insulating gasket, the anode or cathode case having a caulked opening-sealed structure and having in the inside thereof an electricity-generating element including at least a cathode, a separator and an anode and a non-aqueous electrolyte, wherein an electrode unit in a sheet form consisting of the cathode and the anode opposite to each other via the separator is wound to form an electrode group, and the total sum of the areas of the opposing cathode and anode in this electrode group is larger than the area of the opening of said insulating gasket.

2. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein the electrode group comprising a sheet-shaped electrode unit wound therein has been pressurized such that the cathode- and anode-opposing face is in a parallel direction to the flat plane of the flat cell.

3. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein the cathode and the anode, both in a sheet form, are wound via a separator, and the cathode and anode are bent and wound such that the cathode- and anode-opposing face is in a parallel direction to the flat plane of the flat cell, thus forming an electrode group.

4. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein the cathode comprises a cathode plate having a cathode active material layer formed on one or both sides of a cathode current-collecting body, the anode comprises an anode plate having an anode active material layer formed on one or both sides of an anode current-collecting body, and the thickness of the active material layer coated on one side of each of the cathode and anode current-collecting bodies is 0.03 mm to 0.40 mm.

5. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein the cathode comprises a cathode plate having a cathode active material layer formed on both sides of a cathode current-collecting body, the anode comprises an anode plate having an anode active material layer formed on both sides of an anode current-collecting body, each terminal thereof has each active substance layer formed on only one side, and each exposed cathode current-collecting body is brought into contact with the cathode case while each exposed anode current-collecting body is brought into contact with the anode case.

6. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein a carbon material having a developed graphite structure wherein the distance of face d₀₀₂ is 0.338 nm or less is used as the anode, and a solution comprising lithium borofluoride as a supporting electrolyte dissolved in ethylene carbonate and γ

-butyrolactone as major solvent is used as the non-aqueous electrolyte.

7. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein the ratio by volume of ethylene carbonate to γ

-butyrolactone is from 0.3 to 1.0.

8. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein the concentration of the supporting electrolyte in the non-aqueous electrolyte is 1.3 to 1.8 mol/l.

9. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein stainless steel prepared by adding 0.1 to 0.3% niobium, 0.1 to 0.3% titanium and 0.05 to 0.15% aluminum to ferrite-based stainless steel containing 28.50 to 32.00% chromium and 1.50 to 2.50% molybdenum is used as the cathode case also serving as a cathode terminal, or as a constituent member for a metallic part brought directly into contact with the cathode active material.

10. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein stainless steel prepared by adding 0.8 to 0.9% niobium, 0.05 to 0.15% titanium and 0.20 to 0.30% copper to ferrite-based stainless steel containing 20.00 to 23.00% chromium and 1.50 to 2.50% molybdenum is used as the cathode case also serving as a cathode terminal, or as a constituent member for a metallic part brought directly into contact with the cathode active material.

11. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein a metal net is provided between the cathode case and/or the anode case and the electrode group.

12. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein a non-metal thermal insulator is provided between the cathode case and/or the anode case and the separator.

13. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein the opening of the insulating gasket is sealed through caulking by compressing said cathode case in the directions of diameter and height, a cutting is provided in the side of the cathode case, and the width of the cutting is 0.1 π

to 0.9 π

rad in terms of central angle to the circumference of the cathode case, and the depth of the cutting is 5 to 30% of the height of the cathode case.

14. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein the opening of the insulating gasket is sealed through caulking by compressing said cathode case in the directions of diameter and height, and one or two grooves are formed in the lengthwise direction of an opening-sealed portion R in the cathode case, to constitute a thin-plate portion.

15. The flat non-aqueous electrolyte secondary cell according to claim 14, wherein the thickness of the thin-plate portion by groove processing is in the range of 0.07 mm to 0.15 mm.

16. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein the anode case has at least one or more shattering grooves having a concave shape in section.

17. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein the shattering grooves having a concave shape in section are formed on the external surface of the anode case.

18. The flat non-aqueous electrolyte secondary cell according to claim 1, wherein unevenness or protrusion is provided in the inside of the cathode case and/or the anode case.