Separator for alkaline battery, method for producing the same, and battery

• US 8,865,336 B2
• Filed: 12/07/2007
• Issued: 10/21/2014
• Est. Priority Date: 12/20/2006
• Status: Expired due to Fees

• Current Assignee: Kuraray Company Limited
• Original Assignee: Kuraray Company Limited
• Inventors: Hayakawa, Tomohiro, Inada, Shinya, Hayashi, Hideo, Kawai, Hiroyuki, Nishiyama, Masakazu
• Primary Examiner(s): Enin-Okut, Edu E
• Application Number:
  US12/517,840
• Publication Number:
  US 20100310921A1
• Time in Patent Office: 2,510 Days
• Field of Search: 429/129, 429/142, 429/144, 429/145, 264/176.1, 264/205, 264/638, 264/639
• US Class Current: 429/144
• CPC Class Codes: H01M 50/403 Manufacturing processes of separators, membranes or diaphragms
• CPC Class Codes: H01M 50/414 Synthetic resins, e.g. thermoplastics or thermosetting resins
• CPC Class Codes: H01M 50/429 Natural polymers
• CPC Class Codes: H01M 50/4295 Natural cotton, cellulose or wood
• CPC Class Codes: H01M 50/44 Fibrous material
• CPC Class Codes: H01M 50/449 having a layered structure
• CPC Class Codes: H01M 50/489 Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10S 977/948 Energy storage/generating using nanostructure, e.g. fuel cell, battery

Abstract

Provided is a separator for alkaline batteries which can not only prevent batteries from internal short circuit by inhibiting the dendrite formation at anode, but also enables to have a low electrical resistance. The separator for alkaline batteries comprises a composite sheet in which a base layer comprising a wet-type nonwoven material formed from alkaline resistant fibers is covered with a nanofiber layer comprising a modified polyvinyl alcohol fiber which has a fiber diameter of 10 to 1000 nm and a liquid absorption amount by fibers of 4.0 to 40.0 g/g after immersion in a 35% aqueous solution of KOH.

Claims

1. A separator for alkaline batteries having a composite sheet comprising:

a continuous polyvinyl alcohol nanofiber layer formed from a polyvinyl alcohol polymer modified with at least one modifying component and having a fiber diameter of 10 to 1000 nm, the nanofiber layer having a liquid absorption amount by fibers of 4.0 to 40.0 g/g after immersion in a 35% aqueous solution of KOH, wherein the at least one modifying component is an unsaturated carboxylic acid, an unsaturated carboxylic acid derivative, an unsaturated sulfonic acid, an unsaturated sulfonic acid derivative, a borane acid complex, a borane complex, a borane complex derivative, a vinyl ester, an amine, an acrylamide, a methacrylamide, an allyl alcohol, or vinyl pyrrolidone; and

a base layer joined to the nanofiber layer, the base layer comprising a wet-type nonwoven material made of alkaline resistant fibers and having a density of 0.1 to 0.4 g/cm³, wherein the alkaline resistant fiber is at least one alkaline resistant fiber selected from the group consisting of an alkaline resistant synthetic fiber and an alkaline resistant cellulose fiber;

the alkaline resistant synthetic fiber excluding a polyvinyl alcohol polymer modified with an unsaturated carboxylic acid; and

the alkaline resistant cellulose fiber being a fibrillated fiber having a refining degree in a CSF value of 0 to 700 mL.

2. The separator for alkaline batteries as claimed in claim 1, wherein the modified polyvinyl alcohol polymer comprises an unsaturated carboxylic acid as the modifying component.

3. The separator for alkaline batteries as claimed in claim 1, wherein the base layer further comprises a polyvinyl alcohol binder.

4. The separator for alkaline batteries as claimed in claim 1, wherein the composite sheet has a peeling strength for separating the nanofiber layer from the base layer of 10 to 100 g/30 mm.

5. The separator for alkaline batteries as claimed in claim 1, wherein the composite sheet has a rate of change in air permeability of 30 to 300% between before and after immersion of a 35% aqueous solution of KOH.

6. The separator for alkaline batteries as claimed in claim 1, wherein the nanofiber layer has a thickness of 0.5 to 30 μ

m, and the base layer has a thickness of 3 to 70 times higher than that of the nanofiber layer.

7. The separator for alkaline batteries as claimed in claim 1, wherein the nanofiber layer has a basis weight of 0.1 to 10 g/m², and the base layer has a basis weight of 2 to 35 times higher than that of the nanofiber layer.

8. The separator for alkaline batteries as claimed in claim 1, wherein the nanofiber layer has a density of 0.2 to 0.7 g/cm³, and the ratio of the density of the base layer relative to that of the nanofiber layer is (base layer density)/(nanofiber layer density)=0.2 to 0.9.

9. The separator for alkaline batteries as claimed in claim 1, wherein the composite sheet has a liquid absorption amount by fibers of 1.0 to 3.0 g/g after immersion in a 35% aqueous solution of KOH.

10. A method for producing the separator for alkaline batteries recited in claim 1, comprising

(A) preparing a spinning solution by dissolving a modified polyvinyl alcohol polymer in a solvent which is capable of dissolving the polymer, and

(B) forming polyvinyl alcohol nanofibers from the solution using an electro spinning method thereby forming a nanofiber layer onto a base layer to produce a composite sheet.

11. A battery comprising the separator for alkaline batteries of claim 1.

12. A battery, comprising the separator for alkaline batteries of claim 2.

13. A battery, comprising the separator for alkaline batteries of claim 3.

14. A battery, comprising the separator for alkaline batteries of claim 4.

15. A battery, comprising the separator for alkaline batteries of claim 5.

16. A battery, comprising the separator for alkaline batteries of claim 6.

17. A battery, comprising the separator for alkaline batteries of claim 7.

18. A battery, comprising the separator for alkaline batteries of claim 8.