US2935547A

US2935547A - Air-depolarized deferred action cell

Info

Publication number: US2935547A
Application number: US721029A
Authority: US
Inventors: Kordesch Karl
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1958-03-12
Filing date: 1958-03-12
Publication date: 1960-05-03
Anticipated expiration: 1977-05-03

Description

VOLTS May 3, 1960 K. KORDESCH AIR-DEPOLARTZED.DEFERRED ACTIONJELL Filed March 12, 1958 a 9 10 u l2 I 0 IO 20 3O 4O 5O 1 6O 7O 8O 90 I00 IIO I20 AMPERE HOURS l00-MA. SERVICE HOURS INVENTOR. KARL KORDESCH over periods of s'everal -months.

volve impregnatingporous carbon with a soltitioncon t-aining at least -o'ne heat-decomposable salt -or a "heavy metal such as iron, cobaltfinicltel'; manganese, chromium; copper, silver, -gold,"platini1m,vanadium; titanium, uranidecomposable salt of aluminum, the enurnerate'd-sa'lts acting as =oxidizing agents forcarbo'n. Following impregnation with above-described solution, the treated carbons are heated to decompose'the salts, thereby activating and catalyzing themp Following this treatment, the carbon steel :cap 514"serving as the top contact of the cell. top seal 16 of plastic tape closes the cell to the air, and prevents the entrance of moisture therein. length of the cathode is about -73 that of the cell con- The remaining of the container is a self-contained elecnited States Patetrt ratof surrounded'cathode'. A perforated cardboard washcellulose" 'is ramped around the outsideof "the sass-:-

er'24 holds the "zine'powder in place. A c'opp'e'riiv' spiral" surrounds the 'anode" particlesffand. mrep'gh the sides of the"container to serveas theano" coli'ccfi. H In theembodiment of the cell shownbn'Fig. L an elastic membrane 28' seals'the' cath'ode' at its lowefend, and'sei'v'esasa'gasvent afteractivatiom' v 2 Activation of the present cell maybe "accomplished by first removing the plastic tape seal 16, and then applying downward pressure onthe deformable membrane invention relates to ia ir-depolariied fieferred action' cell employingan alkaline -electrolyte in conjunction with a 'gelled -anodex' The main object of -this'iinvention-is'to provide an air-depolarized deferred action cell operable at goodcurrents, and satisfactory voltages, at "temperatu'resas low es C.

Anotherobjectofihe inventionis'to provide "a cell ofthe character described; which even"after -activation can have its energy withdrawn 'witho'ut appreciable loss These 'and other related' objects, features' 'and advantages-bf the'preseritcell constr'uction will-become more apparent 'as the -"clescription thereof proceedsg particularly When taken in conjunction with the accompanying draw fdrman'c'e of such a cell, an'd "of somecomparable" existing 1 l 'Referring'now-to' Fig.1, it will be*s"een--that""the cell of the invention comprises a plastic' con'tainer' 1'0 fabricatedfrompoly'ethylen'e *orinethyl m'ethacryla'te. Cen trally' -positioned" -'in this container "is a "tubula'r carbon cathode 1'2,- treated'by either of the processes disclosed in :the -U.S. --Pat'e'1its-' 2,615,932 a1id- 2,669,598, issued '*-on i October 28, 1952 andpFebruary 16, l954 t'o Ai Marko and K. Kdfde'sch.

um, thorium and the rare earths, and"at"least"one heat contains within its pores and at the-surface thereof' a spinel type cat'alyst consisting of an oxide of the heavy metal and of aluminum oxide (RC-A1 0 This-treatment will be'more fully described hereinafter.

Surrounding the top of cathode-1'2" is a copper coated As shown, the

28 with a pencil orany otherhard cylindricaltool introduced into-the cellthrou'gh the open end of-"the= carbo cathode 12, until the same meets the pin '31),tlius br'ea'king the wall 20,'which m'ay be scored tonlalteit more readily frangible, permitting electrolyte to flow, into=th eanode regions of the'cell when the cell is inverted. More 'f simply, the'pin 30 can be dispensed with, and a pencil or other'pointed instrumentirsed to apply the necessary pressure through the membrane 28 to break thefrangible wall 20. Themembrane 28"must be strong enough not to be puncturedduring breakage of the electrolytere taini-ng frangible wall -20; Y

Cathode fabrication "Ihecathodes'used in-the "cells of the invent-ion are prepared from a mixtur'econsisting of about 60- percent by 'weight ofprojectortype carbon, about 40'-percent by-* weight of soft pitch and about"1% percent by weight of fuel oil.-- Tubes having the desired dimensions are extruded'irom such-a mix-and baked at 1000 0. for' about6 hour's." After-this baking the tubes have a-porosity of between 20 and 33 percent, using water saturation method measurements. The tubes "are next heate'd in CO atmospherebetwe'e'n 850 C; to 950- C. for 'tw o hours 'to convert their hard and shiny skinto a surface having a darkblackappearance. In this condition-the carbon tubes are better able to absorbthe"catalyzing sm' lution in which they will be immersed. /Such a solution consists of an 0.1 molar solutionof aluminum nitrate and cobalt nitrate containing g. Al (NO -9H O and 2.9 g. Co(NO) -'6H O per liter. Generally one carbon cathode" requires about 3 "ml. of'solution. Best-results have been obtained by placing the carbon dioxide-treated carbon tubes, once cooled, in a container which is then 1 evacuated. After obtaining a vacuum of about 20 millimeters of mercury, the catalyzing solution is allowed to enter'thecontainen'and tosoak the electrodes. Upon restoring ethe air '-pressur'e,*the solution :is presse'cl-into the poresofathetubes. The tubes are then dried at C. for-two hours; and heated again to 850 CJ-fo'r two hours in carbon 'dioxideto decompose the metal nitrates' to oxides. After-this treatment a 'spinel of -the formula CoO-Al O- is formed from the catalyst mix--- ture'." The depositis observable 0n the-surface of the carbon tubes" 38"?3. blue deposit. After cooling the can" bon=' tubes 'ina carbon dioxide atmosphere, the vacuum operationand heating cycles' are repeated -to increase the activity of the carbon surface. A third cycle of treatment is not necessary, except for high current electrodes of a capacity of 100 milliamperes per centimeter squared, or more. I

For best results the carbon electrode tubes should be wet-proofed. This can be achieved by immersing the tubes in a 1.5 percent parafiin petroleum ether solution for about five minutes. Following this the electrodes are air dried by passing air through their center. Wet-proofing affects the polarization of the electrode, but too much wet-proofing is detrimental to electrode life, since it permits accumulation of hydrogen peroxide, which accelcrates carbon oxidation, and in some cases destroys the ture of equal parts of nitro-benzene and kerosene is applied to the inside of the tubular carbon electrode. The very dense inner surface of the electrode does not take up an appreciable amount in a short time. However, the vapors of the compounds mentioned travel to the active outer surface, and are adsorbed there to give the desired degree of repellency.

Other wet-proofing agents can be used in addition to parafiin and petroleum ether. Thus chloronaphthalene and dibenzylether may be used.

Anode construction To achieve the highest possible capacity in a given volume, a powder zinc anode is used. Thirty percent of the zinc particles in this powder should be between 20 and 30 mesh (Tyler) in size; 30 percent between 60 and 100 mesh; another 30 percent should be between 100 and 200 mesh, and the rest is through 200 mesh, This powder is first coated with sodium carboxymethyl cellulose in such a way that a zinc powder carboxymethyl cellulose-water gel is formed. The gel is pressed into thin rods, dried and crushed to a particle size of 12 to 20 mesh. This material is coarse enough to allow the electrolyte to penetrate between the particles. During activation with electrolyte, the carboxymethyl cellulose coating swells, and forms a homogeneous gel anode.

The zinc powder should be amalgamated with from 2 to 4 percent of mercury. Amalgamation is best carried out in a 5 percent ammonia solution by adding the necessary amount of mercury to zinc powder. Vigorous stirring facilitates fast and uniform amalgamation.

Amalgamated zinc powder is then washed once or twice with water, and dried in a vacuum at amoderate temperature to C.).

Suitably, pieces of binding straw extending from top seal 17 to the perforated cardboard washer 24, may be placed in the zinc particles on either side of the cathode, to allow the escape of air when the cell is inverted to get electrolyte in place.

Electrolyte Potassium hydroxide is the preferred electrolyte for the cells of the invention, especially in respect to low temperature service. Nine normal potassium hydroxide solution was found superior to six normal solution for such application.

Separator A suitable separator 40 for this cell is regenerated cellulose on a vinyl chloride-vinyl acetate copolymer film base in a two-ply layer. Other suitable separator materials are copolymers of vinyl chloride and acrilonitrile, parchment paper and caustic-resistant cellophane.

Polystyrene, Lucite, and similar plastic materials are best suitable as cell containers. For best results a plastic seal should be placed on top of the cell to prevent moisture from entering the same. Suitably such seals may be of the type disclosed and claimed in the co-pending application of P. A. Marsal, Serial No. 409,435, filed February 10, 1954.

Cell performance Fig. 2 shows the performance of a D-size cell of the type above described on a drain of milliamperes.

Curve of A represents the performance at the indicated drain of a deferred action cell of the invention discharged for eight hours daily on a five days per week continuous service basis. Curve B relates the same information after a delay over a three months period for the same cell. The difference between curves A and B then shows shelf losses in capacity after activation over the given period. The simple flat discharge curves at both periods of time should be noticed. It should be noted also that until nearly the total discharge of the cells occurs, the shelf loss in voltage is only a few millivolts. Curve C relates the performance of a standard D-size LeClanche type cell. Curve D relates the performance in the above indicated test of a D-size cell using MnO depolarizer mix in conjunction with a zinc anode. It should be obvious from a comparison of the curves of Fig. 2, that the cells of the invention have a greater capacity and a greater keeping quality than those of the other systems.

What is claimed is:

1. A deferred action air-depolarized cell comprising a cupped container, the lower part of said container forming an electrolyte-containing reservoir defined by the container walls and bottom at its upper extremity, and by a frangible separation wall, a centrally-apertured tubular cathode composed of activated and catalyzed carbon, having in the pores and at the surface thereof a spinel type catalyst consisting of an oxide of a heavy metal and of aluminum oxide, said cathode extending from immediately above said separation wall to above the top of said container, said cathode being maintained in place at its lower extremity by a centrally apertured insulating washer; an anode gel between said container walls and said cathode; a separator consisting of alkali resistant material between said cathode and anode material, a

2. The cell of claim 1 wherein said anode consists of amalgamated zinc powder coated with sodium carboxymethyl cellulose.

3. The cell of claim 1 wherein said cathode is about two-thirds the length of said cell container.

4. The cell of claim 1 wherein said electrolyte is 9N potassium hydroxide.

5. The cell of claim 1 wherein metallic wire serving as the anode collector thereof is composed of copper.

References Cited in the file of this patent UNITED STATES PATENTS 2,097,077 Oppenheim Oct. 26, 1937 2,615,932 Marko et al. Oct. 28, 1952 2,850,556 Hermitte Sept. 2, 1958 FOREIGN PATENTS 506,866 Belgium Nov. 30, 1951