Rechargeable battery with zinc negative and dendrite barrier
First Claim
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.
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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.
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Citations
12 Claims
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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.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- 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.
Specification