Note: Descriptions are shown in the official language in which they were submitted.
1 This application is a divislon of our copending
Canadian Patent Application 327,458 filed May ll, 1979. This
invention generally relates to electrochemical means and more
particularly to a rechargeable metal-hydrogen electromechanical
~attery of an improved type.
There are numerous designs for secondary rechargeable
electrochemical batteries. Most are directed specifically to
systems employing a metal oxide-to-metal couple, such as the
nickel oxide-cadmium couple or the silver oxide-zinc couple
More recently, however, metal-hydrogen secondary electrochemical
battery systems, such as U~S. patents as Patent No. 3~867,199,
Patent No. 3,990,91~ and Patent No. 3,565,691 have become increas-
ingly attractive from the standpoint of obtaining a relatively
high volumetric energy density and a laryer num~er o charge-
discharge cycles.
In order to provide the necessary high energy density
`and be commercially feasible, it is essential to have a secondary
rechargeable battery comprising a plurality of cells arranged in
a compact relationship. The cons-truction of such a battery is
complicated, however, when the anode of each cell must, during
operation, be freely accessible to hydrogen. Heretofore~ the
problems of construction have resulted in less than optimal com-
pactness and substantial expense.
It therefore would be highly desirable to provide a
high energy density rechargeable secondary electrochemical battery
of the metal-hydrogen type having simplified inexpensive construc-
tion permitting convenient assembly and efficient charging and
discharging with a maximum of compactness.
The improved rechargeable metal-hydrogen electromechan-
ical battery of the present invention satisfies the foregoing
--1--
~' .
~z~
1 needs. The battery is compact, highly efficien-t, has high energy
density and is of simplified inexpensive construction which per-
mits easy assembly, It includes a plurality of bipolar duplex
electrodes in series connection in a pile or stack enclosed in
liquid- and gas-tight sealing means which also provide for aecess
of hydrogen only to one ~ace of each anode,
Each duplex electrode consists of a cathode of porous
sintered nickel or silver plaque, an anode comprising a sheet of
catalyzed carbon particles adhered together with a hydrophobic
binder to wetproof the same and provided on one side thereof
with a metallic screen laminated there-to~ The bipolar electrodes
are stacked with a suitable bibulous separator therebetween so
as to contact the cathode of a given bipolar electrode and also
the anode of the next adjacen-t bipolar electrode in the staek.
The separator bears a sufficient quantity of liquid electrolyte
so as to form with the contacted anode and cathode an electro-
chemical eell in the stack and to impregna-te the anode and
eathode~
Intercell connection in the s-tack is through the elec-
trode interfacing, there being no intercell wires or the like~Normally, a porous metallic conduc-tive spacer is disposed against
the free surface of the metallic screen and the faeing surfaee
of the cathode from the same bipolar eleetrode in the stack so
as to allo~ ree access of hydrogen through the stack spacer and
only to the screen covered surface of each hydrogen anode, The
gaskets, plus terminal end plates otherwise completely seal the
battery.
1 With the described arrangement, no external or internal
wiring is necessary, no complicated piping is needed to provide
hydrogen pathways and, moreover, the components of the stack,
i.e., the duplex electrodes, separators, gaskets, end terminal
plates, etc., can be readily laid up one upon the other so as to
rapidly and efficiently form the battery of the invention and
provide it with compactness, economy and high energy density.
Further features of the present invention are set forth in the
following detailed description and accompanying drawings.
1 O DR~WINGS
Fig. 1 is a schematic exploded cross-section of a first
preferred embodiment of the improved metal-hydrogen battery o the
present invention;
Fig. 2 is a schematic s.ide elevation, partly broken
away~ of a second preferred embodiment of the improved metal-
hydrogen battery of the present invention;
r,~icJ. 3 is a schematic top plan view of the battery of
Fig. 2;
Fig. 4 is an enlarged fragmentary schematic cross-
section of the battery of Fig. 2; and
Eig. 5 is an enlarged detail of a portion of the spacershown in Fig. ~.
DETAILED DESCRIPTION
Fig. 1
Now referring more particularly to Fig. 1 of the
accompanying drawings, a first preferred embodiment of the
improved battery of the present invention is schematically shown
in exploded cross~section. As indicated in Fig. 1 battery 10
comprises a plurality of duplex bipolar electrodes 12 disposed
in stacked relation with separators 1~ therebetween and sealed in
1 said configuration by peripheral gasket means 16 and terminal
end plates 18. Each duplex electrode 12 comprises an anode 20
and a cathode 22 connected in back-to-back relationship by a
conductive metallic connector plate 24 or the like. Each anode
20 in turn can comprise the hydrogen electrode of the present
invention, such as is more particularly shown in Figs. 2 - 4, in
the form of a porous sheet of carbon particles which have been
catalyzed by platinum or palladium and which have been bonded
together with hydrophobic binder so as to wetproof the sheet
while retaining its porosity. Each cathode 22 may comprise a
nickel or silver porous sintered plaque or the like, such as is
more particularly shown in Figs. 2 - 4. Gaskets 16 and connector
24 may cooperate to provide means (not shown) for access of
hydrogen to only the side of each anocle 20 which does not face
separator 14. Gaskets 16 otherwise seal battery 10 completely
to prevent loss of liquid electrolyte 26 from separators 14. In
that regard, separators 14 preferab~y are bibulous and carry
sufficient electrolyte 26 to permeate both the cathode 22 and the
anode 20 with which each separator 14 is in direct contact.
Figs. 2 through 5
A more detailed orm of the improved battery of the
present invention is se-t forth in Figs. 2 - 5. Thus, Fig. 2
shows a battery 50 which comprises a housing 52 of, for example,
electrically insulative material such as plastic, coated metal,
glass, ceramic or the like within which the main components of
battery 50 are stacked. ~ousing 52 may be of any suitable size
and shape, depending on its uses. For example, as shown in Fig.
3, housing 52 may be cylindrical and of an overall si2e of 8.92
in. dia. x 4.15 in. height. Within housing 52 is disposed a
stac~ or pile 5~ of electrochemical components spaced inwardly
1 :Erom ~he sldewalls 56 of housing 52 so as to provide a peripheral
space 58. Space 58 is connected to hydrogen gas inlet 60 and
outlet 62 through housing sidewalls 56. Housing 52 also includes
a removable threaded lid 64 for easy access to the interior
thereof.
Referring more particularly to Fig~ 4, it is seen that
pile 54 comprises a plurality of stacked, horizontally extending
hollow ring-shaped gaskets 66. Gaskets 66 can be of any suitable
material such as rubber, epoxy resin-glass laminate or an
electrolyte resistant plastic such as termed NORDEL ~ a registered
trademark of E. I. du Pont de Nemours, Co., and are stacked
vertically one on another and sealed together, as by polychloro-
prene adhesive, at their contac-t points 68. Each gasket 66 has
the open central part in 69 completely sealed or bridged over
by a horizontally extending conductive metallic plate 70 of
copper, nickel, silver or the like. Plates 70 are sufficiently
large so that their perimeters fit into and are held in recesses
in ~3askets 66, as shown in Ficr. 4.
Certain of plates 70 are imperforate and bear cathodes
72 on the upper surface thereof in the form of flat plates
completely covering the exposed central portion of plate 70,
that is, that portion not in peripheral recess 71. Each cathode
72 preferably comprises a porous sintered plaque of either nickel
oxide or silver o~ide prepared in any suitable manner, such as is
known in the art. Other suitable cathode plates are as ~ollows:
lead oxide, cobalt oxide and manganese dioxide.
Gaskets 66 bearing imperforate plates 70 and cathodes
72 alternate vertically in stack 54 with gaskets 66 bearing
perforate plates 70 which are integral with or attached to the
periphery of conductive metallic screens 74 of nickel, silver, or
~12~
1 the li~e, disposed in central portion 69 and a:Efixed -to hydrogen
anodes 76 depending therefrom in portion 69~ Each anode 76
comprises a gas porous sheet 78 of carbon particles which have
been catalyzed by platinum or palladium and which have been
bonded together by selected hydrophobic binder, preferably by
poly-tetrafluoroethylene, or fluorinated ethylene-propylene, to
wetproof sheet 78 while retaining its gas porosity. Preferably,
the carbon particles of sheet 78 are activated carbon and are of
average particle size of about O.Ol to about 0.3 microns. The
concentration of hydrophobic binder, by weight, relative to the
weight of sheet 78, is usually about ten (lO) to about fifty (50)
percent, so as to completely wetproof the carbon particles of
sheet 78 but still permit sheet 78 to retain sufficient gas
porosity for proper operation. Pre~erably, such gas porosity .is
about 13 to about 3.~ cm3/sec/cm2. Catalysis of the carbon
particles can be achieved by any suitable means, such as
selecting a suitable salt of palladium or platinum, for example,
the nitrate of either metal, plac:ing it in a suitable solvent,
such as an aromatic, for example, acetone, and impregnating
sheet 78 therewith and without removing the solvent, then
reducing the salt to the metal, as by treatment with hydrazine
as follows: by reacting the impregnated sheet with an aqueous
solution of lO weiyht percent hydrazine. Preferably, the
impregnating solution has a concentration of about O.l to about
5, percent by weight, of the salt therein, so as to cause the
final concentration of cataly~ic metal in sheet 78 to be about
0.0005 to about O.l percent by weight. It will be understood
that, if desired, the catalyzing of the carbon particles can be
carried out before they are formed into sheet 78. Formation of
sheet 78 can, in any event, be carried out by any suitable
~z~
1 procedure, such as mixing of the ca~bon par-ticles with about 20
to about 60 percent by weight of the mixture of an aqueous
dispersion of TEF~ON ~3 ~42 emulsion containing about 48 percent,
by weigh-t, of polytetrafluoroe-thylene, extruding the mixture into
sheet form under 2,000 psi. pressure and dry.ing the resulting
sheet to remove the residual water.
Screen 74 adheres to sheet 78 by any suitable means,
such as by a coatiny (not shown) of selected hydrophobie material,
such as fluorinated ethylene-propylene copolymer (FEP) or poly-
vinylidene fluoride known as KYNAR ~ a r~gistered trademark ofPennsalt Chemicals Corporation, whieh has been applied only to
that side of sereen 74 which contacts sheet 78. The upper
surfaee of sheet 78, that is, the sur~aee 79, whieh is eovered
by screen 74, is exposed to hydrogen gas during operation o~
battery 50. Preferably a metallic eonduetive spaeer 80 whieh is
gas porous, for example, a fle~ible, spring-like perforated
eorrugated metallic sheet 82 of nic~el, stainless steel or the
like, as shown particularly in Fig. 5, is eleetrieally conneeted
to the upper surface 81 of sereen 74 and is eonfigured to
2~ electrically connect to the lower surface 83 of the plate 70 next
above it in staek 54, as shown particularly in Fig. 4. This
spaeer 80 eooperates with and is at the level of passageways 84
extending radially through and defined by selected adjoining
gaskets 66, as shown in Fig. 4. Passageways 84 thus extend
through the sidewall of gaskets 66 and into eontact with peripher-
al spaee 58 at the level of each screen 74 and spaeer 80 so as to
permit free flow of hydrogen from space 58 into contact with
only anodes 76, specifically only the upper surfaees 79 thereof
covered by screens 74. This is necessary for proper and
eff.icient operation of battery 50. Hydrogen, as previously
1 indicated, enters and exits housing 52 through piping 60 and 62.
The lower face of each anode 76 and the upper face of
each cathode 72 next adjacent thereto (below) are contacted by
and fully covered and sealed by a separator 86 which preferably
is of bibulous material and, in any event, contains a substantial
quantity of liquid electrolyte 88. Such electrolyte 88 may be,
for example, an alkali metal hydroxide such as potassium hydrox-
ide, sodium hydroxide or lithium hydroxide and the separator 86
material preferably is cotton or other cellulosic material in
waddingr batted or sheeted form, or a suitable plastic, or porous
inorganic fiber material. Gaskets 66 prevent leakage of electro-
lyte 88 from pile 54.
In each instance, the combination of separator 86 with
its electrolyte 88 in contac-t with an anode 76 and cathode 72
within the sealing means comprising gaskets 66 and imperforate
plates 70 and including means for providing hydrogen access to
the anode 76, that is, passa~eway 84, perforate plate 70, screen
74 and spacer 801 forms a separate one of the improved electro-
chemical cells 90, in accordance with the present invention. Such
2Q cells 90 are in stacked relationship in pile 54 and are series
connected without the use of external conductive bus bars, tabs,
wires or the like. Instead, current passes vertically -through
pile 54 from each imperforate conductive plate 70, cathode 72,
electrolyte 88, anode 76, screen 7~ (with its associated plate
70) and spacer 80 to the next imperforate plate 70 vertically in
54. It will be understood that perforate plates could be non-
conductive in which event the electrically conductive pathway
would be made from anode 76 through screen 74 and spacer 80 to
imperforate plate 70. Horizontally extending conductive
imperforate metal terminal end plates 92 of the appropriate
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1 polarity and fabricated of nickel, silver, stainless steel or
copper sheet, are provided on the ~op and the bottom of stack 54
in contact with compon~nts of the stack, speciEically an anode
76 a-t one end of stack 54 and a cathode 72 at the opposite end
of stack 54, so as to complete battery 50. Plates 92 are
electrically connected to conductor lines 94 leading from housing
52. End plates 92 need not be conductive provided that the end
electrodes in the pile 54 contain conductive tabs, lines, bus
bars or the like.
Duplex elec-trodes 96 can be considered to be, for the
purposes of the present invention, relative to battery 50, the
electrochemical components between adjacent separators 86. Thus,
in each instance, imperforate plate 70 with cathode 72 thereon,
spacex 80 contacting such plate 70, the next lower perforate
plate 70 t and screen 74 with depending anode 76 comprise duplex
electrode ~6. The two named plates 70, spacer 80 and screen 74
to~ether form the conductive connector holding anode 76 and
cathode 72 in back-to-back relationship. If desired, each
duplex electrode ~6 with its associated gaskets 66 can be ~ormed
into a separate unit and a plurality of these units can be
vertically stacked, with separators ~6 (containing electrolyte
88) placed therebetween to form pile 54.
Further features of the present invention are set forth
in the following specific examples.
EXAMPLE I
An improved hydrogen electrode in accordance with the
present invention was formed by mixing together 100 gm of activa-
ted carbon particles having an average particle size of 0.1 ~m and
~0 gm of an aqueous dispersion of a hydrophobic binder comprising
polytetrafluoroethylene in a concentration in the binder of 45~
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1 by weight. The resulting mixture was then ex-truded as a sheet
having the followlng climensions:25 cm x 25 cm. The sheet was
then air dried at 680Y for one hour, after which it was immersed
in an acetone solution containing 0.1% by weight of palladium
nitrate. The sheet was withdrawn from the acetone after two
seconds, after which the palladium nitrate which had been
deposed therein from the acetone solution was reduced to palladium
metal with hydrazine by the following procedure: the impregnated
sheet is reacted with an aqueous solution containing 10 weight
percent hydrazine. The reaction procedure resulted in a concen-
tration of 0.005~, by weight of the sheet, of palladium metal in
the sheet, The resulting finished sheet had a porosity of about
50%. A nickel screen having an average U.S. standard mesh size
of 70 x 70 was then coated on one side thereof with an aqueous
dispersion oE fluorinated ethylene-propylene polymer having a
concentration in the dispersion of about 30~ by weight. While
the coating was still tacky, the co~ted side of the screen was
attached to one side of the above-descr:ibed sheet under pressure
and dried în place to formly secure the screen to the sheet. An
improved hydrogen electrode was thus formed which was suitable
for use in the battery of the present invention. A plurality of
G-12 (epoxy-glass laminate) gaskets having the following shape
and size dimensions were used: 9.7 cm dia. x 189 cm thick. Each
gasket had a horizontally extending annular recess therein
sufficien-tly large to receive a nickel plate having the following
dimensions: 8.5 cm dia. x 0.013 cm thick. Certain of the nickel
plates were imperforate while others ot the nickel plates had a
central opening therein about 7.2 cm in size.
An improved battery of the present invention was
30 assembled by disposing on the upper surface of each imperforate
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1 plate a sintered nickel plaque cathode extending to the inner
periphery of each gasket, and having the following characteris- -
tics: 0.089 cm thickness, 7.5 cm diameter, and a porosity of
about 80% and other characteristics as follows: an impregnated
capacity of 0.065- 0.079 ampere hours per square centimeter of
plaque.
On the top of each such cathode was disposed a separa-
tor completely covering the top surface of the cathode and
comprising a fibrous cellulosic wadding having an average thick-
ness of about 0.05 cm and containing potassium hydroxide electro-
lyte in a concentrations of about 160~ by weight of the separator.
On the upper surface of this separator was then disposed
the anode hydrophobic sheet previously described and cut to size
so as to extend to the inner periphery of the gaskets with which
it was associated. In this regard, a ~asket containing one of
the perforate plates installed therein was then disposed on tha
upper surEace of the screen attached to the upper surface of the
anodic sheet. In each instance the sa:id periphery of the screen
contacted the solid portion of the plate. The gasket holding
this plate was vertically aligned on the gasket containing the
imperforate plate 70 and the horizontal contact points there-
between were sealed together by epoxy adhesive means. A
corrugated perforated nickel spacer plate was then placed over
and in contact with the upper surface of the perforate plate
and the described nickel screen. The spacer was of an average
thickness of about 0.19 cm. It was dimensioned to contact the
undersurface of an imperforate plate when that plate was disposed
in gasket means and placed next above the spacer in the stack.
This procedure was continued until the full desixed stack was
obtained. The bottommost imperforate plate served as a terminal
~21~
1 end plate while the uppermost imperforate plate served as a ter-
minal end plate of opposite polarity and did not have any compo~
nents disposed thereabove. At the level of each spacer the
adjacent gaskets were configured to provide passageways permitting
access of hydrogen from outside the stack into contact with the
spacer screen and adjacent side of the anode sheet. The stack
was ctherwise fully sealed so as to prevent liquid and gas access
therefrom. The full stack contained seven gaskets, three cells
in each instance comprising one oE the described cathodes, one of
the described anodes with a separator in contact therebetween and
one of the described screens and spacers. Each cell was physically
isolated by an imperforate plate at each end thereof. The cells
were series connected internally by means of the plates, spacers
and screens.
The stack had the followincl dimensions: 9.7 cm dia. x
1.35 cm height. The stack was disposed within a container of
stainless steel 316 having the following internal dimensions:
10.4 cm d,ia. x 10.16 cm height. This provided a peripheral
space in the container around the gaskets for free circulation
of hydrogen. The free volume in the container was about 760 cm3
The battery had the following electrical characteristics: when
preloaded with hydrogen gas to 10 psig, charged at the ten hour
rate, and then discharged at the four hour rate, the battery
delivered 1.~5 ampere hours at an average voltage of 3.7 volts.
This corresponds to an output of 4.6 watt-hours and stack speeific
energy of 0.05 watt hours per cm3.
As can be seen from the above, the battery was simple
to assemble from easily manufactured components and could be made
of any desired size and number of cells. The spacers therein were
dimensioned so as to effect springlike contact by the horizontal
-12-
1 conduc-tive pla-tes and other components to insure proper electrical
conductivity throughout -the stack. The electrolyte in each cell
wetted the porous faces of the adjoining cathode and anode for
full operation of the cell, while hydrogen gas had free access
to the opposite dry face of the anode. Accordingly, the battery
could perform through many charging and discharging cycles
without substantial loss of performance and yet could be manu-
factured rapidly, simply and inexpensively.
_~MPLE II
The procedure of Example I was carried out except that
the gaskets were of NORDEL ~ and had the following configuration
and size: 9.7 ~m dia. x 0.189 cm thick. Moreover, the conductive
plates were s:ilver of about 0.013 cm average thickness, the
spacers were of silver oE about 0.19 cm -thickness, -the hydrophobic
binder in the sheet anode was FEP fluoropolymer, the catalyst
was platinum in a concentration oE about 0.01~ by weight of said
sheet, the screen was silver of average U.S. standard mesh size
of 40 x 40, the separatOr had an average -thickness of 0.05 cm
and comprised an organic-inorganic fiber laminate and the electro-
lyte was sodium hydroxide. A 3 cell battery of the electro-
chemical cells formed from these components was laid up as
described in Example I to form a stack disposed in a housing of
stainless steel having a peripheral hydrogen space of about
760 cc. The battery had the following overall dimensions and
electrical characteristics: 9.7 cm dia. x 1.35 cm height; when
preloaded and cycled similarly to the battery of Example I, this
battery delivered 2.5 ampere hours at an average voltage o~ 3.~5
volts; 8.6 watt hours; .09 watt hours per cm3. This battery
gave about twice the output obtained ~rom that o~ Example I.
Various modi~ications, changes,alterations and additions
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~2~
1 can be made in the improved hydrogen electrode, electrochemical
cell and battery of the present invention and in the components
and parameters of each. A11 such modifications, changes, altera-
tions and additions as are within the scope of the above-
mentioned claims form part of the present invention.
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