Electrical power storage apparatus

A rechargeable, electrical power storage system employing an electrical power storage medium in the form of a slurry containing active metal particles and an electrolyte solution, which system includes one or more metal-air cells, each including outer electrode apparatus including air electrode apparatus and being configured to define a liquid permeable housing; a volume of the active metal particles arranged within the housing so as to define a static bed which is saturated with the electrolyte solution; inner electrode apparatus arranged within the housing so as to be surrounded by the static bed. The system also includes apparatus for circulating an electrolyte solution through the static bed so as to dissolve discharge products that form therein as the slurry becomes electrically discharged, and apparatus for removing the dissolved discharge products from the circulating electrolyte. The electrical power storage system may be used for powering an electric vehicle. An electrical energy system includes an electric utility having electricity generation apparatus and distribution lines, and rechargeable electrical power storage apparatus which provides energy to the electric utility, when required. The rechargeable electrical power storage apparatus may optionally also be used for the regeneration of slurry for replacement of electrically discharged slurry in the electrical power storage system of an electric vehicle.

FIELD OF THE INVENTION 
The present invention relates to rechargeable electric power storage 
apparatus. 
BACKGROUND OF THE INVENTION 
Over the years, various proposals have been made for electric powered 
vehicles. To date, for a number of reasons, electric vehicle systems have 
yet to become commercial for urban and highway applications. 
There have been proposals to employ zinc/air batteries for urban vehicle 
propulsion. An example is the following publication: 
Improved slurry zinc/air systems as batteries for urban vehicle propulsion, 
by P. C. Foller, Journal of Applied Electrochemistry 16 (1986), 527-543. 
Metal/air battery structures are described in the following publications: 
U.S. Pat. No. 4,842,963, entitled Zinc Electrode and Rechargeable Zinc-Air 
Battery; 
U.S. Pat. No. 4,147,839, entitled Electrochemical Cell with Stirred Slurry; 
U.S. Pat. No. 4,908,281, entitled Metal/air Battery with Recirculating 
Electrolyte; 
U.S. Pat. No. 3,847,671, entitled Hydraulically-Refuelable Metal-Gas 
Depolarized Battery System; 
U.S. Pat. No. 3,716,413, entitled Rechargeable Electrochemical Power 
Supply; 
U.S. Pat. No. 4,925,744, entitled Primary Aluminum-Air Battery; 
U.S. Pat. No. 4,341,847, which describes an electrochemical generator 
having two sedimentation-bed chambers fed in series with an electrolyte 
which contains particles; and 
U.S. Pat. No. 4,719,156, which describes a power storage system employing 
an aluminum-air cell in which solid discharge products are formed. The 
system includes means for recirculating electrolyte from the cell so as to 
flush out the solid discharge products therein. This is achieved by use of 
a precipitation chamber employing an impeller. Discharge product-free 
electrolyte is thereafter returned to the cell. 
Electrical energy storage systems are described in the following 
publications: 
U.S. Pat. No. 4,843,251 entitled Energy Storage and Supply Recirculating 
Electrolyte; 
Energy on Call by John A. Casazza et al, IEEE Spectrum June, 1976, pp 
44-47. 
U.S. Pat. No. 4,275,310, entitled Peak Power Generation; 
U.S. Pat. No. 4,124,805, entitled Pollution-Free Power Generating and Peak 
Power Load Shaving System; and 
U.S. Pat. No. 4,797,566, entitled Energy Storing Apparatus. 
Zinc-air batteries using a replaceable slurry are known. These obviate the 
problem of dendrite formation in batteries with bifunctional electrodes. 
Among disadvantages inherent in zinc-air batteries, however, is that the 
functional life and ease of rechargeability employing thereof is limited, 
due to the formation of non-electrically conductive zinc oxide within the 
slurry, upon electrical discharge thereof. 
Further system problems that occur with metal-air systems in general, are 
the generation thereby of excess heat, and the drying out of the 
metal-based electrolytic slurry. 
The following references describe zinc-air power storage systems including 
a zinc anode, an air electrode, and means for circulating an electrolyte 
liquid: 
U.S. Pat. No. 3,359,136 entitled Rechargeable Energy Conversion System; 
U.S. Pat. No. 3,505,113 entitled Rechargeable Energy Conversion Process; 
U.S. Pat. No. 3,708,345 entitled Electrochemical Energy Conversion System. 
This reference also teaches the use of a jet pump so as to scour zinc 
oxide discharge deposits from the anode. 
U.S. Pat. No. 3,666,561 entitled Electrolyte Circulating Battery; 
U.S. Pat. No. 4,842,963 entitled Zinc Electrode And Rechargeable Zinc-Air 
Battery. The described battery is electrically rechargeable and also 
includes means for filtering zinc oxide discharge products accumulating in 
the circulating electrolyte. Zinc is plated out during recharging of the 
battery. 
The following reference describe zinc-air power storage systems employing a 
continuously circulated slurry of zinc powder suspended in an electrolyte: 
U.S. Pat. No. 3,977,903 entitled Forced-Flow Electrochemical battery; 
U.S. Pat. No. 4,038,458 entitled Zinc-Air Electrochemical Cell; 
U.S. Pat. No. 4,126,733 entitled Electrochemical Generator Comprising An 
Electrode In The Form Of A Suspension; 
U.S. Pat. No. 4,341,847 entitled Electrochemical Zinc-Oxygen Cell; and 
U.S. Pat. No. 3,887,400 entitled Method And Apparatus For Electrochemically 
Producing An Electrical Current. 
A disadvantage inherent in above-listed patents describing the continuous 
recirculation of a zinc-containing electrolyte slurry is that, in order to 
provide a power storage system of sufficient capacity to power a vehicle, 
the overall weight of such a system would be so large and heavy as to 
render its use impractical. 
A further publication teaching the continuous circulation of a slurry of 
zinc powder and electrolyte is U.S. Pat. No. 3,981,747, entitled Process 
For Producing Electric Current By The Electrochemical Oxidation Of An 
Active Anodic Metal, Especially Zinc. Although this reference specifically 
teaches that continuous re-circulation of zinc particles and electrolyte 
slurry does not in itself prevent passivation of the zinc during 
discharge, the system described in this reference is, nonetheless, based 
on a continuous circulation of such a slurry, but wherein the 
precipitation of discharged zincate from solution is provided by the 
addition of a lightweight material, such as aluminum. 
The following additional references are also noted: 
U.S. Pat. No. 3,520,728 entitled Electrical Accumulator With A Metal 
Hydride Serving As The Cathodic Reactive Material Arranged In Suspension 
In The Electrolyte describes a slurry of metal hydride particles and an 
electrolyte which flows through an electrochemical cell. 
U.S. Pat. No. 3,554,810 entitled Metal-Oxygen Power Source describes a 
metal-air power source with a reversibly collapsible electrolyte storage 
means. 
U.S. Pat. No. 4,005,061 is directed to a method of recovering potassium 
hydroxide and zinc oxide from potassium zincate solutions by the addition 
thereto of an organic solvent. 
U.S. Pat. No. 4,283,466 is directed to a process for chemical reaction 
using flowing slurry. 
U.S. Pat. No. 4,521,497 describes an electrically rechargeable zinc-air 
battery having electrodes which are rotated so as to control dendrite 
growth. 
The teachings of the foregoing publications are incorporated herein by 
reference. 
SUMMARY OF THE INVENTION 
The present invention seeks to provide an improved, rechargeable, 
electrical power storage system having one or more metal-air cells each 
containing a volume of a slurry containing an electrolyte solution and a 
volume of active metal particles enclosed in the cell so as to form a 
static bed through which additional electrolyte solution is circulated. A 
particular advantage of this system is that the quantity of electrolyte 
and of active metal particles required to be contained by the system is 
considerably smaller than that required by prior art metal-air systems 
employing a slurry. Accordingly, the power storage capacity per unit 
weight of the overall system is much higher in the system of the present 
invention than in prior art systems. 
A further aim of the present invention is to provide an electrically 
powered vehicle utilizing the improved rechargeable power storage system 
of the invention. 
Yet a further aim of the present invention is to provide improved, 
rechargeable, electrical power storage apparatus which receives power from 
a utility and, when required, provides power thereto. The power storage 
apparatus may also be used for recharging electric vehicles. 
There is provided, therefore, in accordance with an embodiment of the 
invention, a rechargeable electrical power storage system employing an 
electrical power storage medium in the form of a slurry containing active 
metal particles and an electrolyte solution. The system includes one or 
more metal-air cells, each having outer electrode apparatus including air 
electrode apparatus and to define a liquid permeable housing; a volume of 
the active metal particles arranged within the housing so as to define a 
liquid permeable static bed, which is saturated with the electrolyte 
solution; and inner electrode apparatus arranged within the housing so as 
to be surrounded by the static bed. The system also includes apparatus for 
causing flow of the electrolyte solution through the housing and the 
static bed. 
In accordance with a further embodiment of the invention, there is provided 
electrically powered transport apparatus including an electrically powered 
vehicle having vehicle drive apparatus; and rechargeable electrical power 
storage apparatus, coupled to the vehicle drive apparatus. The power 
storage apparatus employs an electrical power storage medium in the form 
of a slurry containing active metal particles and an electrolyte solution. 
The power storage apparatus includes one or more metal-air cells, each 
having outer electrode apparatus including air electrode apparatus and 
being configured to define a liquid permeable housing; a volume of the 
active metal particles arranged within the housing so as to define a 
liquid permeable static bed which is saturated with the electrolyte 
solution; and inner electrode apparatus arranged within the housing so as 
to be surrounded by the static bed. There is also provided apparatus for 
causing flow of the electrolyte solution through the housing and the 
static bed. 
In accordance with yet a further embodiment of the invention, there is 
provided an electrical energy system including an electric utility having 
electricity generation apparatus and distribution lines; a plurality of 
electric vehicles, each having vehicle drive apparatus; a plurality of 
rechargeable electrical power storage units, each coupled to the vehicle 
drive apparatus of one of the electric vehicles, and employing an 
electrical power storage medium in the form of a slurry containing active 
metal particles and an electrolyte solution; and electrical power storage 
apparatus receiving electrical power from the electric utility and 
supplying electrical power to each of the rechargeable electrical power 
storage units and to the electric utility, when required. Each 
rechargeable electrical power storage unit has one or more metal-air 
cells, each including outer electrode apparatus including air electrode 
apparatus and being configured to define a liquid permeable housing; a 
volume of the active metal particles arranged within the housing so as to 
define a liquid permeable static bed which is saturated with the 
electrolyte solution; and inner electrode apparatus arranged within the 
housing so as to be surrounded by the static bed. There os also provided 
apparatus for causing flow of the electrolyte solution through the housing 
and the static bed. 
Further in accordance with an embodiment of the invention, the apparatus 
for causing flow of the electrolyte solution through the housing and the 
static bed includes apparatus for pumping the electrolyte solution 
therethrough. 
Additionally in accordance with an embodiment of the invention, there is 
provided apparatus for replacing the volume of the active metal particles 
and the electrolyte solution with a fresh volume of the active metal 
particles and fresh electrolyte solution, respectively, thereby recharging 
the one or more cells. 
Further in accordance with an embodiment of the invention, a discharge 
product forms within the slurry upon electrical discharge thereof, and the 
electrolyte solution is selected to react with the solid discharge product 
so as to cause dissolution thereof. 
Additionally in accordance with an embodiment of the invention, the 
apparatus for causing flow includes apparatus for removing electrolyte 
solution from the one or more cells; electrolyte solution storage 
apparatus located externally of the one or more cells; apparatus for 
providing electrolyte solution to the one or more cells from the 
electrolyte solution storage apparatus; and apparatus for providing the 
electrolyte solution removed from the one or more cells to the electrolyte 
solution storage apparatus, including apparatus for resupplying the 
removed electrolyte solution to the one or more cells. 
According to a preferred embodiment of the invention, there is also 
provided apparatus for removing the dissolved discharge product from the 
electrolyte solution downstream of the one or more cells. 
Additionally according to a preferred embodiment of the invention, the 
apparatus for removing includes apparatus for receiving electrolyte 
solution containing the dissolved discharge product; and apparatus, 
associated with the apparatus for receiving, for causing precipitation of 
the dissolved discharge product into a solid. 
Further according to a preferred embodiment of the invention, the apparatus 
for removing also includes apparatus for resupplying electrolyte solution 
from which dissolved discharge product has been removed to the apparatus 
for causing flow, and apparatus for preventing the reentry of the 
precipitated solid into the resupplied electrolyte solution. 
In accordance with a further embodiment of the invention, there is provided 
a method of extending the useful life of a rechargeable, electrical, 
metal-air, power storage system employing an electrical power storage 
medium in the form of a slurry containing active metal particles and an 
electrolyte solution, the method including the steps of enclosing a volume 
of the active metal particles in operative association with one or more 
air electrodes associated with a first current collector, thereby 
providing a static bed of the active metal particles; saturating the 
static bed of active metal particles with electrolyte solution; arranging 
a second current collector in operative association with the saturated 
static bed; and causing a flow of the electrolyte solution through the 
static bed, thereby prolonging the useful life of the power storage 
system. 
Additionally in accordance with the present embodiment of the invention, a 
solid discharge product forms within the slurry upon electrical discharge 
thereof, and the step of causing flow includes the step of causing the 
flow of an electrolyte solution selected to react with the solid discharge 
product so as to cause dissolution thereof. 
Further in accordance with the present embodiment of the invention, the 
step of causing flow includes the steps of removing electrolyte solution 
from the static bed; providing electrolyte solution to the static bed from 
electrolyte solution storage apparatus; and providing the electrolyte 
solution removed from the static bed to the electrolyte solution storage 
apparatus, so as to resupply the removed electrolyte solution to the 
static bed. 
Additionally in accordance with the present embodiment of the invention, 
the method also includes the step of removing the dissolved discharge 
product from the electrolyte solution downstream of the static bed. 
Further in accordance with the present embodiment of the invention, the 
step of removing includes the steps of receiving electrolyte solution 
containing the dissolved discharge product, and precipitating the 
dissolved discharge product into a solid. 
Additionally in accordance with the present embodiment of the invention, 
the step of removing further includes the steps of resupplying electrolyte 
solution from which dissolved discharge product has been removed to the 
static bed, and preventing the re-entry of the precipitated solid into the 
resupplied electrolyte solution.

DETAILED DESCRIPTION OF THE INVENTION 
Reference is now made to FIG. 1A which is a block diagram illustration of 
an electrical power storage system suitable for powering an electric 
vehicle, constructed and operative in accordance with the present 
invention. The system includes a multi-cell, rechargeable, metal-air 
battery 15, containing a slurry of active metal particles and an 
electrolyte solution, and which is suitable for powering an electric 
vehicle, such as shown and described below in conjunction with FIGS. 5-8C. 
Battery 15 includes a plurality of serially-connected cells 42, the 
precise structure of which is described below in detail in conjunction 
with FIGS. 2-4. 
Typically, battery 15 is specifically a zinc-air battery employing a slurry 
containing a mixture of zinc particles, alkaline potassium hydroxide 
solution and/or sodium hydroxide solution. 
As described in the Background of the Invention, a problem with zinc-air 
batteries is the formation of zinc oxide during the electrical discharge 
of the battery. 
In order to reduce the amount of zinc oxide in the slurry and thus prolong 
the useful life of the battery, the system of the present invention, as 
represented schematically in FIG. 1A, includes a "watering" system, 
referenced generally 11, for circulating an electrolyte solution through a 
"static bed" of the zinc particles contained in each of the individual 
battery cells 42. The static bed arrangement of the zinc particles is 
described in greater detail below in conjunction with FIG. 3. 
There is also provided an air flow system, referenced generally 12, whose 
function is described hereinbelow. 
Watering system 11 may also include "de-solubilizing" apparatus 14, shown 
in detail in FIG. 1B, for removing dissolved zinc oxide from the 
circulating electrolyte downstream of battery 15. 
Watering system 11 includes a reservoir 25 for an electrolyte solution, 
such as KOH and/or NaOH, with optional additives LiOH, sorbitol, silicon 
dioxide (that may also be present in the cell electrolyte), for example, a 
manifold 26, associated with battery 15, and a pump 20, which is operative 
to pump electrolyte from battery 15 to reservoir 25, thereby also causing 
the circulation of electrolyte from reservoir 25 to battery 15, via 
manifold 26. Water may be added to the electrolyte solution stored in 
reservoir 25, from a further reservoir, referenced 28. 
The zinc oxide formed in the static bed of active metal particles in each 
cell 42 is dissolved by the pumped circulation therethrough of the 
electrolyte solution. Circulated electrolyte containing dissolved zinc 
oxide exits battery 15 via an outlet conduit 29, and is recirculated by 
pumping apparatus 20. 
A typical volumetric flow rate at which the electrolyte solution may be 
circulated through cells 42 is in the range 0.01-0.2 ml per minute per 
Ampere hour. Although the concentration of dissolved zinc oxide in the 
electrolyte increases as the battery continues to be electrically 
discharged, the volume of electrolyte circulated through the battery is 
selected such that the performance of the battery is maintained at at 
least a predetermined level. 
It will be appreciated that the flow rate at which the electrolyte is 
circulated is lower the flow rates of prior art systems in which either an 
electrolyte solution only, or an entire slurry suspension, is circulated. 
The system of the present invention furthermore has an electrolyte 
requirement typically in the range 2-4 cc/Ahr, whereas a conventional 
metal-air system typically has an electrolyte requirement in the range of 
5-15 cc/Ahr. 
Accordingly, a particular advantage of the present system is that the 
quantity of electrolyte and of active metal particles required to be 
contained by the system is considerably smaller than than required by 
prior art metal-air systems employing a slurry. A battery constructed in 
accordance with the present invention typically has an energy density in 
the range 100-150 WH/Kg, compared with a much lower energy density of only 
60-80 WH/Kg of conventional metal-air batteries. 
Referring now particularly to FIG. 1B, de-solubilizing apparatus 14 
comprises a flow-through housing 16 having an inlet 18 and an outlet 22. 
Contained within housing 16, preferably in a removable element, such as in 
the form of a tray 17, is a precipitation material, indicated generally at 
24, which, when electrolyte containing dissolved zinc oxide flows in 
contact therewith, causes precipitation of the dissolved zinc oxide into 
solid form. 
Precipitation material 24 is typically retained between a pair of fine mesh 
filter elements, indicated schematically at 34 and 35, which also serve to 
prevent the washing through of the precipitated zinc oxide, while 
permitting the flow through the housing of the recirculated electrolyte. 
Tray 17 is configured for slidable insertion and removal, as indicated by 
respective arrows 36 and 38, via suitable tracks 39, and is also provided 
with suitable sealing means, such as a gasket 41, so as to prevent leakage 
of electrolyte from the housing 16. 
It will be appreciated that the removal of tray 17 facilitates replacement 
of a batch of used up or zinc oxidesaturated precipitation material with a 
fresh batch of precipitation material. 
According to one embodiment, the precipitation material reacts with the 
dissolved zinc oxide contained in the recirculated electrolyte solution so 
as to precipitate into zinc oxide. Typical suitable reactants are calcium 
hydroxide, barium hydroxide and strontium hydroxide. 
If the metal-air system of the invention is an aluminum-air system wherein 
the active metal particles in the slurry are aluminum based, the 
precipitation material could be aluminum hydroxide. 
According to an alternative embodiment of the invention, the precipitation 
material is a nucleation site material, such as may be constituted by any 
suitable fibrous, porous or absorbent material. Typical suitable 
nucleation site materials are cellulose fibers, titania, zirconia, porous 
polyamide, porous polypropylene, kaolin and kieselguhr. 
Reference is now made to FIG. 9A, which is a block diagram illustration of 
a system similar to that shown and described above in conjunction with 
FIG. 1A, except wherein desolubilizing apparatus 14 is constructed and 
operative according to an alternative embodiment of the invention. 
Referring now particularly to FIG. 9B, according to the present embodiment, 
apparatus 14 includes a flow-through housing 60 having an inlet 62 and an 
outlet 64. A first nozzle 66 is mounted in the housing so as to have a 
line of sight 68 intersecting with the line of sight 70 of a second nozzle 
72. 
Although only a single first nozzle 66 and a single second nozzle 72 are 
indicated in FIG. 9B, this is by way of example only, and it is not 
intended to indicate the actual number of nozzles that may be used in a 
particular system. Rather, reference to a single nozzle is intended to 
infer one or more similar nozzles, it being envisaged that any number of 
nozzles may be employed in any particular system constructed according to 
the teachings of the present invention. 
In the present example, therefore, first nozzle 66 is operative to receive 
from battery 15 (FIG. 9A) and via pump 20 a pressurized supply of 
circulated electrolyte containing dissolved zinc oxide that it is sought 
to remove from solution. Second nozzle 72 is operative to receive from a 
reservoir 74, via a suitable pump 76, a pressurized supply of deionized 
water. The nozzles are arranged, as described, such that their respective 
lines of sight intersect. 
When their respective pumps are operated, so as to direct towards each 
other a stream of droplets of deionized water and a stream of droplets of 
the electrolyte solution containing dissolved zinc oxide, solid zinc oxide 
is formed, so as to be deposited onto a mesh element 78, mounted in a 
removable tray-like element 80, similar to element 17 described above in 
conjunction with FIG. 1A. The remaining electrolyte solution is permitted 
to pass through the mesh element 78 and is recirculated to reservoir 25 
(FIG. 9A) as by means of a pump 83. 
Although the addition of deionized water causes dilution of the electrolyte 
solution being circulated through the battery cells, this is substantially 
offset by the evaporation of water from the cells. 
It will be appreciated that according to the embodiment of the invention 
wherein watering system 11 incorporates desolubilizing apparatus 14, as 
described above in conjunction with either of FIGS. 1B or 9B, a smaller 
overall volume of electrolyte is required to extend the life of battery 15 
for a given amount of usage, than in the embodiment wherein apparatus 14 
is not incorporated. 
With further reference to FIG. 1A, the air flow system 12 includes a blower 
31 for circulating cooling air for the battery 15, via parallel conduits 
32, and reaction air for the battery via a scrubber 33. The reaction air 
for the battery is passed through scrubber 33 in order to remove from the 
air deleterious acidic gases such as carbon dioxide. The reaction air is 
distributed to the battery cells 42 via a manifold 27, and exits the 
battery through an outlet port 37, through which the cooling air also 
exits the battery. 
Operation of the watering system 11 and of the air flow system 12 is 
governed by a battery controller 41. In particular, the battery controller 
41, which may be based on any suitable microcontroller, operates pumping 
apparatus 20 and blower 31 so as to maintain predetermined operating 
conditions of the battery. 
Battery 15 is mechanically rechargeable. Once it has become electrically 
discharged, it is recharged by removing the discharged slurry from cells 
42 through a slurry outlet 45, flushing the cells 42 with a suitable 
fluid, typically KOH or water, supplied from an offboard flushing fluid 
reservoir 80, and refilling with a charged batch of slurry from charged 
slurry storage facility, referenced 82. 
The flushing fluid may be supplied, for example, via manifold 26, while the 
charged slurry may be supplied via a manifold (not shown), which may be of 
any suitable construction, such as described and shown in U.S. Pat. No. 
3,847,671, entitled Hydraulically-Refuelable Metal-Gas Depolarized Battery 
System, the contents of which are incorporated herein by reference. 
Typically, the electrolyte solution in reservoir 25 is also replaced with 
a fresh volume of electrolyte, and the water in reservoir 28 is refilled. 
It will be appreciated by persons skilled in the art that, watering system 
11 is operative to render the electrical power storage system more 
economical by extending the functional life of the slurry so as to 
decrease the frequency of the required replenishment thereof. 
As described above, when the system of the invention is a zinc-air system, 
the circulation of a potassium hydroxide solution through the cells 42 is 
operative to remove discharged zinc oxide in solution. 
It will be appreciated that the circulation of an electrolyte solution 
through a static bed of active metal particles is advantageous not only in 
a zinc-air system, but in other metal-air systems as well, such as 
aluminum-air and iron-air systems. 
A known phenomenon of metal-air cells is that of heat generation and, 
consequently, the drying out of the slurry. Reservoir 25 (FIG. 1A) is 
located externally of the cells 42, and can be maintained, therefore, at a 
temperature lower than that of the cells 42. Accordingly, the provision of 
a liquid solution from relatively cool reservoir 25 and the circulation of 
the solution through the battery cells is operative to remove excess heat 
therefrom, thereby aiding in heat management of the battery. Drying out of 
the slurry is also prevented by the supply of water from reservoir 28 as 
described above. 
Additional metal-air systems in which it may be useful to circulate a 
liquid solution, typically an aqueous electrolyte solution, are 
aluminum-air and iron-air systems. In both of these systems circulation of 
such a solution helps to remove undesired excess heat from the cells, 
while in an aluminum-air system, the circulation of a liquid helps prevent 
drying out of the aluminum based slurry. 
It will be appreciated that where de-ionized water is used to obtain 
precipitation of the dissolved zinc oxide, as described above in 
conjunction with FIGS. 9A and 9B, the relatively cool temperature of the 
de-ionized water helps to dissipate the heat from the electrolyte solution 
which is itself operative to remove excess heat from the cells 42, as 
described above. 
Additionally, liquid reservoir 25 may contain a KOH solution and/or an NaOH 
solution, for example, and suitable additives, selected to increase the 
solubility of the solid byproducts within the slurry, may also be added to 
the solution. Suitable additives may be silicon dioxide, sorbitol, or 
lithium hydroxide, for example. These additives may also be present in the 
cell electrolyte. 
FIG. 2 is a pictorial representation of a single battery cell 42, whose 
construction is described in detail hereinbelow with reference to FIGS. 3 
and 4. 
Referring now to FIGS. 3 and 4, battery cell 42 includes a pair of frame 
members 43 (FIG. 3), typically formed of polypropylene, each supporting an 
associated outer electrode unit 44. 
Referring now more particularly to FIG. 4, each outer electrode unit 
includes an outer support frame 46, typically formed of polypropylene; an 
outer current collector 48, typically formed of nickel mesh; a gas 
electrode 50, typically an air electrode formed of a wet-proofed, 
catalyzed carbon layer formed on the nickel mesh; a normal separator 52, 
formed typically of nonwoven porous nylon, for preventing contact between 
the metal particles in the slurry and the gas electrode; and an inner 
support frame 54, similar to outer support frame 46. 
In assembled form, as illustrated in FIGS. 2 and 3, top and side sealing 
members, referenced respectively 55 and 57 (FIG. 2), cooperate with frame 
members 43 (FIG. 3) which support outer electrode units 44 so as to define 
an interior space, referenced generally 59 (FIG. 3), for storing a power 
storage slurry, such as described above, indicated generally by reference 
numeral 56 (FIG. 3). 
A central current collector 58 is mounted within the interior space 59 of 
the battery cell so as to be immersed in, and thus in electrically 
conductive contact with the slurry. The central current collector 58 is 
typically connected to a base member 30 which is secured to frame members 
43 (FIG. 3). 
Reference is now made to FIG. 5, which illustrates a typical electric car 
99, including a zinc-air battery system 100, such as either of the systems 
described and shown hereinabove in conjunction with FIGS. 1A or 9A. The 
car 99 and battery system 100 are preferably constructed so as to 
facilitate replacement of spent slurry by charged slurry at the battery 
recharging subsystem shown and described below in conjunction with FIG. 
12. 
Referring now also to FIG. 6, a zinc-air battery 101 forming part of system 
100, is typically located centrally along the longitudinal axis of the car 
99 (FIG. 5) and is mounted on frame rails 102. Provision is made for 
distilled water and/or electrolyte supply tubes 104 and a scrubbed air 
flow channel 106 within an air tight enclosure 108, which surrounds the 
battery cells 110. 
Enclosure 108 is typically covered by thermal and acoustic insulation 112. 
The structure of the individual battery cells is substantially as 
described above in conjunction with any of FIGS. 2-4 hereinabove. 
Reference is now made to FIGS. 7-8C which illustrate the general 
configuration of an electric van 119 useful in the present invention. As 
seen in FIG. 7, the van is provided with two zinc-air battery banks 120 
and 122 on opposite sides of the body. The van 119 and battery banks 120 
and 122 are preferably constructed so as to facilitate replacement of 
spent slurry by charged slurry at the battery recharging subsystem shown 
and described below in conjunction with FIG. 12. An auxiliary lead-acid 
battery 124 is preferably provided in addition. A power switching system 
126 (FIG. 8B) governs the supply of power to and from the various 
batteries. 
FIGS. 8A-8C also illustrate preferred locations of a 12 volt vehicle 
auxiliary battery 128, a traction motor and drive 130 (FIG. 8B), a cabin 
heater 132, and a Driving Management System 134. 
Reference is now made to FIG. 10, which illustrates in generalized block 
diagram form an electrical system constructed and operative in accordance 
with a further embodiment of the present invention and including an 
electrical utility having electricity generation apparatus and 
distribution lines, a plurality of electric vehicles, such as shown and 
described above in conjunction with FIGS. 5-8C, and electric power storage 
apparatus receiving electrical power from the electric utility and 
supplying electrical power to the plurality of electric vehicles and to 
the electric utility when required. 
Illustrated in FIG. 10 is an AC transmission line 210 which is arranged for 
power transfer via a power conversion unit 212 with a storage battery bank 
214 and with a bank of electrolytic cells 216. The electrolytic cells 216 
are operative to electrically charge an energy storage slurry, similar to 
that employed by cells 42 (FIGS. 1-4), but following partial discharge and 
comprising a mixture of zinc granules, zinc oxide, and alkaline potassium 
hydroxide solution, thereby storing energy therein. 
In the illustrated embodiment, discharged slurry is stored in a discharged 
slurry storage facility 218 and supplied to electrolytic cells 216 via 
suitable pumps (not shown). The charged slurry is received in a facility 
220 and then stored in storage battery 214 or supplied to electric 
vehicles 222. 
Discharged slurry is received at facility 218 from the electric vehicles 
222 and from storage battery 214. The storage battery 214 provides, when 
necessary or economical, electrical power to transmission line 210 via 
conversion unit 212. 
It will be appreciated by persons skilled in the art that the present 
invention, through the synergistic combination of two disparate 
activities, utility energy storage and electric vehicle operation, each of 
which is presently uneconomical, provides economical electrical utility 
off-peak power storage, surge protection, on-peak and super-peak demand 
power supply, spinning reserve and electric vehicle system. 
Reference is now made to FIG. 11, which illustrates the system of FIG. 10 
in greater detail. As shown in FIG. 11, the AC utility transmission line, 
here indicated by reference numeral 230, is coupled via a transformer 232 
to a power line conditioner 234 which includes high capacity AC to DC and 
DC to AC converters. Reactive and other line control apparatus 236, such 
as peak switching-in detectors may be associated with the power line 
conditioner 234. 
A DC output of conditioner 234 may be supplied via a slurry reconditioning 
control circuitry 238 to a slurry reconditioning facility 240. The DC 
output of conditioner 234 may also be supplied via a charge control unit 
242 to a bank of lead-acid batteries 244. 
Slurry reconditioning facility 240 is operative to provide charged slurry, 
via slurry pumping apparatus 246 to an electric vehicle refueling station 
248, for supply to electric vehicles. Facility 240 is also operative to 
supply charged slurry via slurry pumping apparatus 246 to a zinc-air 
battery 250. Charged slurry from facility 240 may also be stored in a 
charged slurry storage tank 252. 
Discharged slurry removed from electric vehicles is supplied from electric 
vehicle refueling station 248 to a discharged slurry storage tank 254 and 
is supplied at appropriate times to facility 240 by slurry pumping 
apparatus 246. Normally recharging of slurry is carried out by facility 
240 during off-peak times for utility supplied electricity. 
Electrical power may be drawn from battery 250 when needed, and supplied 
via discharge control circuitry 256, power line conditioner 234 and 
transformer 232 to the utility via power line 230. Normally power is 
supplied to the utility from battery 250 at times of peak power 
consumption. 
Electrical power may be drawn from battery 244 when needed, and supplied 
via discharge control circuitry 258, power line conditioner 234 and 
transformer 232 to the utility via power line 230. Normally power 
transfers between battery 244 and utility power line 230 take place in 
order to balance the impedance of the power line 230, to absorb short term 
peaks and shortfalls, typically having a time constant of less than 
one-half hour. 
Reference is now made to FIG. 12, which is a pictorial illustration of an 
electric vehicle refueling station, such as station 248 (FIG. 11). As 
shown in FIG. 12, the refueling station includes a plurality of drain 
units 260 which are operative to remove discharged slurry from electric 
vehicles 262. The vehicles 262 are typically of the sort shown in and 
described above in conjunction with FIGS. 5-8C, and employing the 
electrical power storage system shown and described above in conjunction 
with FIGS. 1-4. The discharged slurry is supplied to discharged slurry 
storage tank 254 (FIG. 11). 
Automatic moving platforms 264 may be provided for moving the electric 
vehicles 262 from the drain units 260 to charged slurry supply units 266, 
which supply charged slurry from charged slurry storage tank 252 to the 
electric vehicles 262. 
Reference is now made to FIG. 13, which illustrates a electrolytic 
reprocessing subsystem, which is indicated generally by reference numeral 
216 in FIG. 10. Discharged slurry, here of the composition: unreacted zinc 
granules, zinc oxide and alkaline potassium hydroxide solution, stored in 
tanks 274, is supplied to a bank of electrolytic baths 278, such as 
modified alkaline zinc plating baths with scrapers for periodically 
removing zinc deposits thereon. Baths 278 receive an electrical input from 
power conversion unit 212 (FIG. 10). 
Freshly generated zinc mixed with alkaline potassium hydroxide solution is 
pumped from electrolytic baths 278 to a zinc treatment facility 280, such 
as a classifier for particle sizing, which provides a purified zinc output 
to a storage tank 282. KOH is received from electrolytic baths 278 and is 
supplied to a holding tank 284. The contents of tanks 282 and 284 are 
supplied to a formulation tank 286 in which they are combined to provide a 
recharged slurry. The recharged slurry is stored in a storage tank 288. 
Reference is now made to FIG. 14, which describes the operation of the 
apparatus of FIG. 13, It is see that the discharged electrolyte slurry 
containing Zn, ZnO, potassium zincate, water and KOH has its concentration 
adjusted by the addition of KOH. Subsequently, the discharged electrolyte 
having a predetermined concentration undergoes separation and reduction, 
the KOH being removed to a KOH storage tank such as tank 286 (FIG. 13) and 
the solids being supplied to a zinc storage facility, such as tank 282 
(FIG. 13). The zinc is supplied to a reformulation facility such as tank 
284 (FIG. 13) in which KOH and other additives are added to the zinc to 
provide a regenerated slurry which is stored as in tank 288 (FIG. 13). 
Reference is now made to FIGS. 15, 16 and 17 which illustrate the general 
configuration of a zinc-air utility storage battery. It is noted that the 
battery comprises a multiplicity of cells 300, each containing, inter 
alia, an air electrode 301 and a current collector 303, connected in 
series. Air is supplied from the outside atmosphere by a blower 302 via a 
CO.sub.2 scrubber 304. 
Slurry is pumped to and from the cells 300 by any suitable means, such as 
pumps 306. Thermal management apparatus 308 is provided as is a water 
humidifier 310. Apparatus 308 is operative to ensure optimum operating 
temperatures for the battery irrespective of the local ambient temperature 
and deals with parasitic heat generated by the battery during discharge. 
Humidifier 310 is operative to control the humidity of the incoming air to 
the battery and prevents slurry dry-out. 
According to an alternative embodiment of the invention, a watering system 
311 (FIG. 17) may also be provided for removing discharge products from 
the cells 300, and for aiding the thermal and humidity management thereof. 
Watering system 311 is similar to watering system 11, shown and described 
above in conjunction with FIGS. 1A, 1B, 9A and 9B, and is therefore not 
described in detail herein. 
Reference is now made to FIGS. 18 and 19 which illustrate the function of 
the utility battery during respective charging and discharging operations. 
During charging, AC line power is supplied via a transformer 320, 
rectifier 322 and control unit 324 to the battery. 
During discharge, as illustrated in FIG. 19, power from the battery 300 is 
supplied via control unit 324, AC converting unit 336 and transformer 320 
to the AC line. 
It will be appreciated by persons skilled in the art that the present 
invention is not limited by what has been particularly shown and described 
hereinabove. Rather the scope of the present invention is defined only by 
the claims which follow: