Rechargeable battery with zinc negative and dendrite barrier

• US 3,970,472 A
• Filed: 07/08/1975
• Issued: 07/20/1976
• Est. Priority Date: 07/08/1975
• Status: Expired due to Term

• Current Assignee: SAB NIFE AB
• Original Assignee: Mcgraw-Edison Company (Eaton Corporation PLC.)
• Inventors: Steffensen, John
• Primary Examiner(s): Skapars, Anthony
• Application Number:
  US05/593,965
• Time in Patent Office: 378 Days
• Field of Search: 136/30, 136/31, 136/145, 136/146, 136/143, 136/147, 136/131, 136/132, 136/102, 136/167
• US Class Current: 429/206
• CPC Class Codes: H01M 10/24 Alkaline accumulators
• CPC Class Codes: H01M 4/02 Electrodes composed of, or comprising, active material
• CPC Class Codes: H01M 50/40 Separators; Membranes; Diaphragms; Spacing elements inside cells
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A rechargeable battery having a zinc negative electrode, and a positive electrode preferably of nickel hydroxide, is provided with a novel dendrite barrier to prevent zinc spurs growing out of the zinc electrode during charge and shorting the battery. A novel separator pocket, which includes the barrier and is adapted to confine the zinc negative electrode against shape change, comprises an inner wrap of an absorbent film, an intermediate wrap of a microporous film, a next adjacent wrap of the flexible dendrite barrier, and an outer wrap pf a cellulosic film. This improved barrier is a porous, flexible sheet material comprising a substrate of a flexible, porous cloth woven from random fiber polypropylene in and through which is deposited a porous metal having a low hydrogen over-voltage to oxidize the zinc dendrites on contact in an alkaline electrolyte. The barrier in this multiple wrap allows free flow of ions and free escape of evolved hydrogen; and prevents any dendrites from passing therethrough and penetrating the outer cellulosic film.

In rechargeable batteries using zinc negative electrodes such as of pasted plates in an alkaline electrolyte, the zinc electrode limits the cycle life of the battery because of (1) an effective loss of zinc through shape change and through shedding and dissolution of the zinc in the electrolyte, and (2) a shorting of the battery electrodes by growth of zinc dendrites during charging.

Claims

1. In a rechargeable battery having an alkaline electrolyte, and zinc-negative and positive electrodes wherein dendrite growths from the zinc electrode during charge tend to short the battery:

a dendrite barrier across the entire face of the zinc electrode including a porous absorbent layer between the zinc electrode and the barrier and a confining separator layer across the outer face of the barrier capable of diffusing the electrolyte but not the dissolved zinc, said barrier comprising a cloth substrate of a porous flexible material, and porous metal deposited on and through said substrate of a low hydrogen over-voltage which on contact with a zinc dendrite reacts with the same to dissolve the dendrite and prevent the same from shorting the adjacent electrode.

2. The battery set forth in claim 1 wherein the barrier layer is a flexible wrap completely surrounding the zinc electrode.

3. The battery set forth in claim 2 wherein the confining layer is a cellulosic wrap completely surrounding the barrier wrap.

4. The battery set forth in claim 1 including a microporous layer between said absorbent layer and said barrier to distribute dendrites wherein said layers are successive wraps forming a multilayer separator pocket completely encapsulating the zinc electrode in a tight wrap relationship to retard shape change.

5. The battery set forth in claim 4 wherein the positive electrode is adjacent said separator pocket including a single absorbent layer of a separator material between the positive electrode and said pocket.

6. The battery set forth in claim 1 wherein said zinc-negative electrode comprises a plurality of perforated metal strip pockets seamed along the edges into a plate structure, said pockets being filled with zinc active material and being compressed to retain the active material in place and in close electrical contact with the perforated metal strips.

7. The battery set forth in claim 1 wherein said substrate of said barrier comprises a cloth woven of random fiber polypropylene.

8. The battery set forth in claim 1 wherein said barrier metal is a layer of fine nickel powder of irregularly-shaped particles integrated into a porous self-sustaining coating on said substrate.

9. The battery set forth in claim 8 including a porous plastic cement securing said nickel powder into a porous self-sustaining coating onto said substrate.

10. The battery set forth in claim 3 wherein said dendrite barrier is wholly confined by said wrap of cellulosic material without any current lead connection whereby the barrier is operative only by local action without external current flow between it and the battery electrodes.

11. A multilayer separator pocket for the zinc-negative electrode of an alkaline-electrolyte nickel-zinc cell comprising a first inner layer of a porous material adjacent to the zinc electrode to absorb electrolyte, a microporous separator layer against the absorbent layer to distribute dendrites, a flexible porous dendrite barrier layer against the microporous layer including a porous metal of low hydrogen over-voltage capable of dissolving dendrites on contact therewith in an alkaline electrolyte, and an outer confining cellulosic layer against said dendrite barrier capable of diffusing electrolyte but not dissolved zinc.

12. The separator pocket set forth in claim 11 wherein said dendrite barrier comprises a porous substrate of a woven cloth having a porous coating thereon and cemented thereto of a metal powder with a low hydrogen over-voltage.