CA1228892A - Comb-type bipolar stack - Google Patents

Abstract

ABSTRACT
An electrode assembly is described which generally comprises a first electrode, a pair of second planar electrodes, a generally rectangular frame member for supporting each of the second electrodes substantially along three sides thereof, the rectangular frame member having a pair of spaced inwardly extending channels through which said second electrodes slide into and which mask the edges of said second electrodes along the three supported sides, and a laterally displaced integrally formed, inwardly facing elongate channel along an unsupported side of the second electrode which is adjacent to an external face of one of the second electrodes and shaped to receive one side of the first electrode while masking the adjacent second electrode along the unsupported side thereof, a generally elongated frame member coupled to the rectangular frame member between the second electrodes along the unsupported edge thereof, and conduit means associated with the elongated frame member for conveying fluid to the cavity between the second electrodes.

Description

lZ2889Z
IMPR~VED-COME~ BOILABLE
m e present invention relates generally to electrochemical systems, and particularly to an improved cell design in a ~etal-halogen battery stack.

EA~g~RCUND AN SUMMARY OF THE INVENTION
Electrochemical devices or systems of the type referred to herein include one or more of the metal-halogen battery systems, such as a zinc-chloride battery system. Thea metal-halogen battery systems generally are oonprised of three basic components, namely an electrode stack section, an electrolyte circulation subsystem, and a store subsystem. Ike electrode tack section typically includes a plurality of ox ifs connected together electrically in various series and parallel combinations to achieve a desired operating voltage and current at the battery terminals over a charge/discharge battery cycle. Each cell is comprised of a positive and negative electrode which are both in contact with an aqueous metal halide electrolyte. the electrolyte circulation subsystem operate to circulate the metal halide electrolyte from a reservoir through each of the cells in the electrode stack in order to replenish the metal and halogen electrolyte ionic components as they are oxidized or reduced in the cells during the battery cycle. In a closed, self-contained metal-halogen battery system, the storage subsystem is used to contain the halogen gas or liquid which is liberated from the cells during the charging of the battery system for subsequent return to the cells during the discharging of the battery system. In the zinc-chloride battery system, chlorine gas is liberated from the positive electrodes of the cells and stored in the form of chlorine hydrate. Chlorine hydrate is a solid which it formed by the store subsystem in a process analogous to the process of freezing water were chlorine is included in the ice crystal.
With reference to the general operation of a zinc-chloride

2 2~3~3~ Z
battery system, an electrolyte pump operates to circulate the aqueous zinc-chloride electrolyte from a reservoir to each of the positive or chlorine electrodes in the electrode stack. these chlorine electrodes are typically jade of porous graphite, and the electrolyte passe through the purify of the chlorine electrodes into a space between the chlorine electrodes and the opposing negative or Seneca electrodes. The electrolyte then flows up between the opposing electrodes or otherwise out of the cells in the electrode stack and back to the electrolyte reservoir or sup.
During the charging of the zinc-chloride battery system, zinc metal is deposited on the zinc electrode substrates and chlorine gas is liberated or generated at the chlorine electrode. The chlorine gas is collected in a suitable conduit, and then mixed with a chilled liquid to form chlorine hydrate. A gas pump is typically employed to draw the chlorine gas from the electrode stack and mix it with the chilled liquid, (i.e., generally either zinc-chloride electrolyte or water).
the chlorine hydrate is then deposited in a store container until the battery system is to be discharged.
During the discharging of the zinc-chloride battery system, the chlorine hydrate is decomposed by permitting the store temperature to increase, such as by circulating a warm liquid through the tore container. The chlorine gas thereby recovered is returned to the electrode stack via the electrolyte circulation subsystem, were it it reduced at the chlorine electrodes. Simultaneously, the zinc metal is dissolved off of the zinc electrode substrates, and power is available at the battery terminal Over the course of the zinc-chloride battery charge/discharge cycle, the concentration of the electrolyte varies a a result of the electrochemical reactions occurring at the electrodes in the jells of lZ2~3892 the electrode stack. At the beginning of charge, the con-cent ration of zinc chloride in the aqueous electrolyte may typically be 2.0 molar. As the charging portion of the cycle progresses, the electrolyte concentration will gradually decrease with the depletion of zinc and chloride ions from the electron lyre. When the battery system is fully charged, the electrolyte concentration will typically be reduced to 0.5 molar. Then, as the battery system is discharged, the electrolyte concern-traction will gradually swing upwardly and return to the original 2.0 molar concentration when the battery system is completely or fully discharged.

Further discussion of the structure and operation of zinc-chloride battery systems may be found in the following commonly assigned patents: Simmons US. Patent No. 3,713,888 entitled "Process For Electrical Energy Using Solid Halogen Hydrates"; Simmons US. Patent No. 3,809,578, entitled "Process For Forming And Storing Halogen Hydrate In A Battery"; Car et at. US. Patent No. 3,909,298 entitled "Batteries Comprising Vented Electrodes And Methods of Using Same"; Car US. Patent No. 4,100,332 entitled "Comb Type Bipolar Electrode Elements And Battery Stack Thereof". Such systems are also described in published reports prepared by the assignee herein, such as "Development of the Zinc-Chloride Battery for Utility Apply-cations", Interim Report EM-1417, May 1980, and "Development of the Zinc-Chloride Battery for Utility Applications", Interim Report EM-1051, April 1979, both prepared for the Electric Power Research Institute, Palo Alto, California.

According to one aspect of the invention there is provided an electrode assembly which has a first electrode and a pair of second electrodes disposed in substantially parallel spaced relation to one another and in substantially parallel spaced relation to the first electrode. A generally rectangular one piece first frame member defines a pair of spaced apart generally U-shaped and parallel channels, the channels extending substantially around three sides of the first frame member, each channel having an outer channel wall and having a common inner wall which defines a first masking mob/

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member. A second frame member is insertable carried in the first frame member and defines a second masking member in co-planar relationship with the first masking member. An electrode supporting structure is integrally formed on the first member and laterally displaced from and adjacent to the second frame member, the electrode supporting member having an elongated channel for slid ably receiving and masking one edge of the first electrode. The electrode supporting member is specially fixed relative to the second electrode while permitting sliding movement of the first electrode to accommodate position changes of the first electrode during assembly and during thermal expand soon and contraction thereof. The electrode supporting member provides masking between the first electrode and the adjacent one of the second electrodes such that the unmasked surface boundaries of the first electrode and the adjacent second electrode remain fixed relative to one another.

Another aspect of the invention resides in a comb type bipolar cell for a battery system having a circulating electrolyte, the cell having first and second bus members each being enclosed in a plastic frame around the edges and external face thereof. There is provided a plurality of spaced first electrodes extending from the first bus member, and a plurality of spaced second electrode structures from the second bus member, the first electrodes being interdigitated with the second electrode structures. There is provided a generally rectangular plastic housing which forms a compartment in combination with the first and second bus members substantially enclosing the first elect--troves and the second electrode structures. The housing includes a top section which has an electrolyte distribution manifold means for distribution of electrolyte to the second electrode structures, and the top section further has discharge manifold means for removal of the electrolyte from the compartment and means for isolating the distribution manifold from the disk charge manifold.

Yet another aspect of the invention resides in a comb type bipolar cell for a battery system having a circulating electrolyte, the cell including a frame structure and first - pa -mob/

~L2Z8892 and second bus members. A plurality of spaced first electrodes extend from the first bus member, and a plurality of spaced second electrodes extend from the second bus member and are interdigitated with the first electrodes. The first and second bus members have a generally planar opposed faces and are joined around the edges thereof to the frame structure thereby defining a compartment for containing the interdigitated first and second electrodes. The first and second bus bar members having top and bottom edges each provided with longitudinally extending, key defining grooves. The top and bottom edges are provided with injection molded, encapsulating edge structures forming an ionic seal by mechanically interlocking with the key defining grooves. The encapsulating edge structure provides the means by which the first and second bus members are joined to the frame structure.

An object of the present invention is to provide an improved cell design 3b -mob;
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:~ZZ8~92 which is based upon flat plate electrodes (i.e., electrodes not having a contoured faces).
It is another objective of the present invention to provide an improved cell design which incorporates low-cost electrode frames that may be injection molded to enhance manufacturability and which facilitates assembly of the battery stack.
It is a further objective of the prevent invention to provide an improved cell design which incorporates low-cost electrode frames that feature integral masking of both the interior and exterior of the positive and negative electrodes.
It is an additional objective of the present invention to provide an improved cell design which incorporates low-cost electrode frames which features an electrolyte feed tube providing a controlled flow of electrolyte to the positive electrodes.
It is a further objective of m e present invention to provide improved unit cell and battery stack design to provide a controlled flow of electrolyte that is uniform to all positive electrodes within the battery stack.
It is an objective of the present invention to provide an improved electrode frame design which Physically supports electrodes placed therein o as to prevent electrode bowing and to maintain the desired inter-electrode gap.
It is another objective of the present invention to provide an improved unit cell and battery stack design having excellent hydraulic integrity and ionic cell-to-cell isolation.
It is yet another objective of the present invention to provide an improved ox if design which it capable of filtering the electrolyte flow to a plurality of cells connected electrically in parallel.
It is still another objective of the present invention to provide a cell design which incorporates a substantially closed compartment which controls both the electrolyte flow to and from a plurality of cells.

In the comb-type bipolar cell design which tonically isolates adjacent cells, the ionic isolation is important in achieving uniform coulombic efficiency for each of the cells connected electrically in series. This cell design may also feature a housing or compartment means having a top section which includes the manifold means for controlling both the electrolyte flow into and out of each series connected cell.

Additional advantages and features for the present invention will become apparent from a reading of the detailed description of the preferred embodiments which make reference to the following set of drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure lo is a side elevation view of one embodiment of a zinc-chloride battery system according to the present invention.

Figure lo is a front elevation view of the battery system shown in Figure lay Figure 2 is a schematic diagram of the battery system shown in Figures lo and lo.

Figure 3 is a cutaway perspective view of the stack and electrolyte circulation subsystems for the hatter system shown in Figures 1 and 2.

Figure 4 is a schematic diagram of the electrolyte circulation subsystem shown in the Figures 2 and 3.

Figure 5 is a front elevation view of the stack and electrolyte mob/ ' 1~28~s92 circulation 6ub~stems Shown in Figure 3 with the end cap removed.
Figure 6 it a fragmentary plan view of the electrolyte distribution manifold for tube electrolyte circulation fiubsystem.
Figure 7 is a fragmentary cross-6ectional view of the manifold shown in Figure 10 taken along line 7-7.
Figure 8 is a graph comparing parasitic current values associated with two electrolyte circulation schemes, Figure 9 it an exploded perspective view of an electrode assembly which forms the basic building block of the battery tack shown in Figures 2 and 3.
Figure 10 is a fragmentary exploded view of an "open" sub module for a zinc-chloride battery tack.
Figure 11 it a perspective view of a comb assembly employed in the sub module shown in Figure 10.
Figure 12 it a cutaway perspective view of a closed" module for the zinc-chloride battery stack shown in Figures 2 and 3.
Figure 13 is a fragmentary top elevation view of the Eu~module shown in Figure 12.
Figure 14 is a cro~s-sectional view of the sub module shown in Figure 13 taken along lines 14-14.
Figure 15 is a cross-sectional view of the semidaily shown in Figure 13 taken along lines 15-15.
Figure 16 is a horizontal cross-sectional view of the sub module shown in Figure 13 taken along lines 16-16.
Figure 17 is a cutaway perspective view of a store subsystem employing a conventional decomposition heat exchanger.
Figure 18 is a schematic diagram of a self draining heat decomposition heat exchanger for a zinc-chloride battery stem Figure 19 is a cutaway perspective view of the store subsystem for the battery system shown in Figures 1 and 2.
Figure 20 is an alternative embodiment of a zinc-chloride battery system according to the present invention.
Figure 21 ill a high density arrangement of a plurality of battery sustains of the type shown in Figure 20.

Referring to Figures lo and lo, two elevation views of a zinc-chloride battery ~y6tem 10 in accordance with the present invention are shown. The various opponents of the battery system 10 are housed by two interconnected cylindrical vessels 12 and 14, which may best be illustrated by the fichematic diagram of Figure 2. The upper vessel or case 12 it used to contain the chlorine hydrate store subsystem generally designated by reference numeral 16. The lower vessel or case 14 is used to contain both the battery stack 18 and the electrolyte circulation Subsystem generally designated by reference numeral 20.
The cylindrical vessels 12 and 14 are supported by a battery rack structure 22r Ike vessels 12 and 14 are preferably made from fiberglass-reinforced plastic (FRY) with an internal polyvinyl chloride (PVC) liner bonded thereto which it chemically resistant or inert to the electrolyte and the other chemical entities present within these vessels. ill e vessel 12 and 14 are interconnected by four fluid exchange lines or conduits 24, 26~ 28 and 30~ and the direction of fluid flow through these lines are indicated by the appropriate arrows.
Additionally, the battery system 10 it provided with four refrigerant lines or conduit 32~ 34~ 36 and 38. Refrigerant lines 32 and 34 are used to supply a coolant to the tore subsystem 16 during the charging of the battery system for reducing the temperature inside vessel 12 to the appropriate level to form chlorine hydrate. Refrigerant lines 36 l~Z889Z
and 38 are used to supply a coolant Jo the jump or electrolyte reservoir 40 of the electrolyte circulation subsystem 20 to control the temperature of the zinc-chloride electrolyte.
Referring now to Figure 2 and 3, the electrolyte circulation subsystem 20 will now be described. ill e electrolyte circulation subsystem 20 includes an ovate electrolyte pump plan which is mounted to the front end cap 42 of the bottom vessel 14 below the electrolyte level in the sup 40. The electrolyte pump Pi is driven by an electric ion 44 which is magnetically coupled to the electrolyte pump. The electrolyte pump 42 it preferably of the centrifugal type manufactured by Ingersoll-Rand. ill e electrolyte pump 42 is adapted to draw electrolyte from the sup 40 trough a titanium protective screen filter 46, and discharge the electrolyte axially through a slip joint 48 into a unique center-feed electrolyte distribution manifold 50.
Ike manifold 50 it used to distribute electrolyte to each of the unit cells in the pair of sub modules 52 and 54 which comprise the battery stack 18. The manifold 50 not only uniformly distributes the electrolyte to each of the unit cells in the sub module 52 and 54, but also acts to control and suppress the flow of parasitic currents which flow in the electrolyte circulation subsystem. Parasitic currents are two æ electrical currents which flow in the conductive paths created by the network of electrolyte connection linking the cells. With the provision of the manifold 50, especially in combination with inlet and outlet crossed distribution tubes arrangements significant improvements in the suppression of parasitic currents have been achieved which will be discussed more fully below.
Referring to Figure 4, a schematic diagram of one embodiment of the electrolyte circulation subsystem 20 is shown, which particularly illustrates the flow of electrolyte through the manifold 50. Reference ~2Z889Z

may also be made to Figure 5 Rich illustrate a front end view of electrolyte circulation subsystem in a chutney with the swindles 52 and 54, and Figure 6 and 7 icky illustrate two views of ye manifold 50. The manifold 50 includes a central portion 56 Ng?rising a pair of concentric tubes, namely or tune 58 and outer tube 60. Inner tube 58 is in fluid cannunication with the electrolyte pump Pi at a first em 62 thereof and includes an Zen opposite end 64 which it fitted with an incline wire mesh electrolyte filter 66. Filter 56 includes a perforated protective outer jacket 68 and terminates at its distal end in a cap or plug 70. Electrolyte is pimped through inner tube 58 and passes out through filter 66 into outer tube 60. Outer tube 60 is fitted with an end cap 72 which includes a fluid conduit path 74 for conducting fluid around the inner end cap 70 and thence into conduit 76.
Conduit 76 is sealed a at end plate 78 and includes a pair of fittings 80 and 82 for bifurcating the electrolyte fluid path. Similarly, outer tube 60 includes a pair of fittings 84 and 86 at the end adjacent electrolyte pump Pi for providing yet another bifurcated fluid path.
Electrolyte is thus Ended out through filter 66 and into outer tube 60, whereupon half of the fluid it transmitted through tube 76 generally away from electrolyte pump Pi, while the other half is transmitted through outer tube 60 generally toward electrolyte pump Pi. At fittings 80-82 and at fittings 84-86 the electrolyte fluky is again split into four distribution paths for feeding individually both left and right halves of the two 6ubmodules 52 sod 54.
With specific reference to Figure 4, the crossed inlet distribution tubes arrangement may now be explained. It will be teen in Figure 4 that, for example, the distribution tube 88, which it connected to fitting 82, feeds the left half 90 of unideal 54, the left half being Et~ysically more rote Fran fitting 82 than the right ~LZZ8~9Z
half 92. Similarly, fitting 86 i coupled via distribution tube 94 to the right half 92 of ~ubTodule 54. pence the electrical circuit path between left and right paths of Eubmodule 54 are quite elongated and provide substantial resistance against parasitic current flow. For example, parasitic current flow between unit ox if feeder 96 and 98 must travel the entire distance through tube 88, fitting 82, tube 76, outer tube 60, fitting 86, and tube 94 in order to complete the shunt circuit. Although the length of this shunt circuit is substantial and the electrical resistance it therefore high, the fluid circuit thus described including the crossed inlet distribution tubes 88 and 94 provides remarkably little burden on electrolyte pump Pro pence electrolyte pump Pi can be of a lower horsepower with a resultant improvement of the overall efficiency of the system.
The outlet portion of the electrolyte circulation subsystem 20 in the embodiment of Figure 4 also employs the crossed outlet distribution tubes arrangement in order to increase the electrical resistance to parasitic current flow, in a similar wanner as described above with respect to crossed inlet distribution tubes 88 and 94. With reference to Figure 4 it will be seen that the left and right halves of each sub module, such as left and right halves 90 and 92 are cross-coupled to outlet tubes 100 and 102, respectively, in a fashion similar to the cross-coupled center feed inlet portion. Alternatively, the outlet portion of the electrolyte circulation subsystem 20 may employ a cascade canopy 104 as illustrated in Figures 3 and 5. In this alternative outlet arrangement each individual unit jell discharges through an outlet port 106 via discharge tube 108 and thence through orifices 110 onto the upper surface of the cascade canopy 104. The electrolyte then spills over the canopy 104, like rain water upon a shingled roof, spreading outwardly as it falls into sup 40, which I

12288~2 improves the abrasion of gaseous chlorine by the electrolyte during the discharge cycle.
The manifold 50, the inlet crossed distribution tubes arrangement and the outlet crossed collection tubes arrangement may broadly be viewed as different facets or building blocks of a more general principle or arrangement which may be called the center feed principle or arrangement, which is best explained by reference to prior art electrolyte distribution practices. In prior art zinc-chloride battery system, electrolyte is typically delivered to each unit cell in a sub module comprised of series-connected unit cells via a common header, such a continuous substantially manifold or distribution tube having relatively low electrolyte resistance from one end of the header to the other. This end feed arrangement allows relatively large parasitic currents to develop in virtually every inter-cell shunt circuit in the sub module. In contrast, the electrolyte distribution system illustrated in Figure 4 delivers electrolyte to a jingle 6ubmodule (such as ~ubmodule 54 for example) composed of series-connected unit cells by splitting the electrolyte flow in half, and delivering (or removing) each half-flow through a physically distinct header (for example tubes 60 and 76 in manifold 50, or inlet distribution tubes 88 and 94) having a relatively large resistance to parasitic current flow. m us, in comparison to the large parasitic currents existing between the commonly fed halves of the s~bmodule in the prior art and feed arrangement, all shunt circuits in Figure 4 existing between the separately fed (with electrolyte) halves of the module are dramatically reduced. Broadly speaking then the center feed arrangement may be said to encompass any electrolyte distribution scheme wherein the flow of electrolyte to a single 6ubmodule of series-connected unit jells it divided into two (or ore) roughly equal portions and thereafter segregated for distribution (or collection) through two separate, electrically isolated headers having a relatively large electrical resistance wherein each header supplies electrolyte to (or collects electrolyte from) a plurality of series-connected unit cell, and the parasitic current caused by inter-cell Shunt circuits between the separately fed portions of the semidaily are substantially reduced relative to an end feed electrolyte distribution arrangement.
The electrolyte circulation subsystem 20 of the battery system JO
disclosed herein was specifically designed 80 as to incorporate the foregoing center feed principle and to maximize the advantageous reduction in parasitic currents obtainable by utilizing a center feed arrangement.
The effectiveness of the above-described center feed electrolyte distribution arrangement is exemplified by reference to Figure 8. Figure 8 is a graphical representation of typical shunt or parasitic current values displayed along the ordinate as a function of the cell number displayed along the abscissa. For illustration purposes a battery having thirty unit cells connected electrically in series has been assumed, although it should be understood that the same advantageous results are obtainable in batteries having a different number of unit cells connected electrically in series. As related above, all of the cells in the battery are served by one electrolyte pump through a common supply and return manifolding. ill is common electrolyte manifolding provides an electrically conductive path through which current will pass when a voltage is present across the battery terminals and electrolyte circulation subsystem 20 including the battery stack is full of electrolyte. this shunt current reduces the effective current flowing through the cells during charge and causes cells in the battery to self discharge during discharge at different rates. In - l~Z88gZ
general, this results in faster depletion of zinc from the electrodes of cells in the center of the battery stack, and can cause measurable differences in the coulombic efficiency of cells within toe battery stack.
Rowing the r~sistivity of the electrolyte and the sizes of different portions of the electrolyte circulation subsystem 20, the effective electrical resistances of the various sections con be calculated. An equivalent electrical circuit model may when be constructed, if desired, in accordance with the teachings of US. Patent No. 4,371,825, issued on February 1, 1983 to Chit et at, entitled mud of Minimizing The Effects of Parasitic Currents".
Figure 8 is a graph comparing parasitic current values during charging which were calculated from such an - electrical circuit model. Figure 8 includes a curve 112 which represents the parasitic current distribution for a battery system having a prior art end-feed electrolyte distribution manifold, and a curve 114 which represents the parasitic current distribution for a battery system in accordance with the present invention having z center fee electrolyte distribution manifold. It is important to note that the total parasitic current flaw of curve 112 is not only greater than that for curve 114, but curve 114 indicates that the parasitic current distribution is considerably more uniform when the center-feed manifold is utilized. This benefit of the center- cod manifold is advantageous because it is not only defrayable to minimize parasitic current flow, but is is also desirable to have a uniform distribution ox the Parasitic currents across the battery stack in order to avow a substantially uniform coulombic efficiency for each of the unit cells in the battery stack.
Referring to Figure 9, an exploded view of a zinc-chlori~e l~Z8892 battery electrode afisembly 200 it one which forms the basic building block of the battery stack 18. Electrode assembly 200 generally comprises a pair of porous graphite positive or chlorine electrodes 202 and 204, a dense graphite negative or zinc electrode 206, and plastic frame member 208 and 210. the positive electrodes 202 and 204 are adapted to slide into channels 212 and 214, respectively, in the frame member 208 suck that the frame member supports these two electrodes along the top and bottom edges as well as along one of the side edges.
the frame member 208 operates to align the positive electrodes 202 and 204 in parallel and provides an internal cavity between these electrodes. The frame member 208 is also formed to nauseatingly receive the frame member 210 between the positive electrodes 202 and 204.
m e frame member 210 includes a plastic-feed tube 216 for conveying electrolyte from a unit cell manifold to the internal cavity between the positive electrodes 202 and 204. The frame member 208 is also formed with a channel 218 which is adapted to receive a side edge of the negative electrode 206 and align the negative electrode 206 in parallel with the positive electrode 202. Accordingly, it will be appreciated that the frame number 208 so Noes to align and separate the positive electrodes 202 and 204 from each other, and also to align and separate the negative electrode 206 from tube positive electrode 202.
The separation between the negative electrode 206 and the positive electrode 202 it referred to as the inter-electrode gap which may generally range from about 40 miss (lam) to about 250 miss (6mm) and is preferably about 129 miss (3.3mm).
m e frame member 208 also serves to control tube edge effects of the positive electrodes 202 and 204 by providing an integral masking or screening around the edges of the positive electrodes in order to modify the electrochemical activity along these edges. Generally speaking, 1 ~28~39;~
the channels ~l2,214 and 218 are formed such that the apparent surface area of the positive electrodes it staller in comparison with the apparent surface area of the negative electrodes. A more detailed discussion of massing edge effects may be found in the commonly assigned Car et at. US. Patent Jo. Allah, entitled method for Control of Edge Effects of Oxidant Electrode. ` `
. .
It should also be noted that fit e frame member 208 includes an orifice 220 at the top thereof for venting any undissolved chlorine gas which could otherwise be trapped in the internal cavity between the positive electrodes 202 and 204. Additionally, the frame member 208 is formed with a pair of opposing, vertically extending spacmg ribs 222 and 224. Ike ribs 222 and 224 restrain any tendency of the positive electrodes 202 and 204 to bow outwardly, and insure that the desired inter-electrode gap between the positive and negative electrodes is maintained. Ike integrity of this inter-electrode gap is im~ortar.t because it has been fount that with increased gaps on the order of 129 miss the electrical current density for the battery system may be significantly increased. Also such increased gaps permit Lowry zinc loadings on the negative electrodes, which in turn means that substantial cost savings can be achieved through the reduction in the number of electrodes required to store an equivalent mount of electrical energy.
m e feed tube 216 of the electrode assembly 200 is press fit into a socket which is formed into an upwardly extending nipple portion 226 of the frame member 210. Additionally, the bottom end of the feed tube 216 is trapped between an upwardly extending clip portion 228 Ed the support channel portion 230 of the frame somber 210. It Elude also be noted that the bottom end of the support channel portion 230 of the 1~889~
frame member 210 is shaped to mate with the bottom end of the internal separator portion 232 of the frame member 208. This contoured shaping at the bottom end karat in combination with a generally horizontally extending flange portion 234 of the frame number 210 at the top thereof to lock the frame member 210 to the frame ember 208.
With respect to the materials which may be used to construct the electrode assembly 20G, it it preferred that the positive electrodes 202 and 204 be constructed from Union Carbide Croup PG-60 or ~S-1697 graphite, or Ark Carbon Co. S-1029 or S-1517 graphite. With respect to the negative electrode 206, it is preferred that this electrode be constructed from Union Carbide Carp. EEL grade graphite or alternative grades such as PI or AIR graphite herein. With respect to the frame members 208 and 210 and the tube 216, these components (as well as the other plastic components to be described below may be constructed from any suitable electrically nonconductive material Bush is chemically resistant or inert to the electrolyte and other chemical entities with which they will come unto contact. While it it preferred that the frame members 208 and 210 be constructed from General Tire and Rubber Corp.
Boltaron try polyvinyl chloride or BY Goodrich Corp. coon (R) Polyvinyl-chloride and the tube 216 from Dupont Teflon (R) (polytetrafluoro-ethylene), other suitable plastic material may be employed such as Penlight Renoir (~) (polyvinylidene fluoride) or any of the other appropriate material described in Section 33 of ill e Development of the Zinc Chloride Battery For Utility Application, April 1979 report identified earlier.
Referring to Figure 10, an exploded view of an pen sub module 236 for a zinc-chloride battery stack it shown. ill e sub module 236 generally comprises a zinc termination Lomb assembly 238, a chlorine termination comb amiably 240, and one or more bipolar intermediate Lomb issue assemblies 242. Chile the ~ubmodule 236 i& shown with only one intermediate comb assembly 242, it should be appreciated that the s~bmodule may be expanded by merely providing for more intermediate Lomb assemblies. A how in Figure 10, the ~ubmodule 236 includes two unwept cells connected electrically in series. Each of three unit cells comprise a number of jingle cells (i.e., a positive electrode and an opposing negative electrode) connected electrically in parallel.
The intermediate comb assembly 242, which may best be seen with reference to Figure 11, includes an electrically conductive bus member 244 (i.e. constructed from dense graphite) which has two generally planar opposing face and a plastic frame 246 generally disposed around the edges of the bus member to provide an ionic Neal between adjacent unit jells. Frame 246 is preferably formed by injection lying PVC
about the edges of bus member 244. A pair of opposed longitudinally extending groove& 247 may be used to provide a mechanical interlock between this PVC encapsulation and the edges of bus member 244. A
plurality of positive electrode structures 248 are attached via a press or interference fit connection to one exterior face of the bus member 244, which is provided with spaced vertical grooves 2491 while a plurality of negative electrodes 250 are attached to the other face of the bus member in a similar fashion. Each of the positive electrode structures 248 are constructed in accordance with the electrode assembly 200 of Figure 9, and include the positive electrodes 202 and 204, and the plastic frame members 208 and 210. A unit cell electrolyte distribution manifold 252 is ultrasonically welded or otherwise secured to the top section of each frame 246 such that electrolyte may be conveyed to the feed tubes 216. Specifically, the nipples 226 extending from the top of the frame members 210 are inserted through holes in the bottom tray 254 of the manifold 252. These nipples 226 are then welded lZZ88~32 by thermal waging to the bottom tray 254 of the manifold 252 to provide a leak-proof connection.
In order that each unit ox if may be separately sealed, a plastic tray 256 a shown in Figure 10 is welded or otherwise secured to the bus bar frame 246 in a fluid tight connection. A return path for the electrolyte supplied to each of the unit cell is provided by a collection cup 258 and a discharge serpentine channel plate 260 which are adapted to receive the electrolyte flowing from the unit cell and direct this electrolyte to the reservoir or sup. As in the vase of the other plastic frame members or component the collection cup 258 and the discharge serpentine channel plate 260 are welded or otherwise secured (such as by Solvent bonding) to the tray 256 in a fluid tight connection.
As illustrated in Figure 11, the unit cell distribution manifold 252 also includes a top cover 262 which is secured to the bottom tray 254 by welding or solvent bonding. An important feature of the manifold 252 it the provision of a plastic perforated screen 264 which extends along the complete length of the manifold between the bottom tray 254 and the lap cover 262. The perforations in the screen 264 are selected to be suitably staller than the diameter of the opening in the nipples 226 of the frame member 210, so that any particles which could plug or obstruct fluid flow through the feed tubes 216 will be filtered by the screen 264. Ike screen 264 is preferably constructed from Renoir (R) and is preferably bent over in a generally U-shape. It should also be noted that the manifold 252 is also be provided with a suitable orifice 265 (fihcwn in Figure 12) for permitting any gas which could otherwise be trapped in the manifold to escape. The location of orifices 265 near the outside edges of the unit jell also assures that sufficient electrolyte flow will occur adjacent the outermost electrodes of the I

unit cell. 1~2~38~3~
In Figure 10, the aforementioned plastic components 252 through 264 are shown in an assembled state with reference to the chlorine termination Lomb assembly 240. The chlorine termination Lomb assembly 240 it similar in construction to the intermediate comb assembly 242 except that the chlorine termination Lomb assembly is nut provided with a plurality of negative electrodes 250 along one foe of the bus bar 244. however, the chlorine termination Lomb assembly 240 Includes a plurality of electrical terminal mounted to the bus bar 244 to facilitate external electrical connections to the sub module 236. These electrical terminals, generally designated by reference numeral 266, are illustrated with reference to the zinc termination comb assembly 238.
The zinc termination comb assembly 238 simply comprises a bus bar whose edges and external face are enclosed in a plastic frame and a plurality of negative electrodes attached on the internal face thereof. In an assembled state, the positive electrode structures 248 of the intermediate comb assembly 242 will be interdigitated with the negative electrodes 250 of the zinc termination comb assembly 238, and the negative electrodes 250 of the intermediate Lomb assembly 242 will be interdigitated with the positive electrode structures 248 of the chloride termination comb assembly 240. Accordingly, the positive electrode structures 248 of the intermediate comb assembly 242 and the negative electrodes 250 of the zinc termination Lomb assembly 238 will form one unit cell, and the negative electrodes 250 of the intermediate comb assembly 242 and the positive electrode structures 248 of the chlorine termination comb assembly 240 will form the other unit cell of the sub module 236.
Referring to Figure 12, a cutaway perspective view of the closed sub module 54 for the battery flack 18 of Figures 2 and 3 is I

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shown. The construction of the sub module 54 it similar to the Eubmodule 236 of Figure 10 in Several respect. The principal difference between these two 6ubmodules it that the submDdule 236 is generally open at the top thereof to allow chlorine gas ( well as any other gases) to be liberated from the unit oily; whereas, the sub module 54 is generally closed at the top thereof to control the flow of fluid from unit cells.
m e sub module 54 is comprised of twenty-four unit cells connected electrically in Eeriest IheEe unit ox ifs are generally designated by reference 300.
Referring additionally to Figures 13 through 16, several views of the zing termination unit ox if 300 for the ~ubnodule 54 are shown, which particularly illustrate the plastic top section 310 thereof. Ike top section it welded or otherwise sealable secured to a three tided tray section 311 to form a Substantially closed compartment for the unit cell. Ike top section 31G includes a 6upp1y port 312 which is connected to electrolyte distribution tube 88 via a unit cell feed tube 313. A
similar electrolyte connection may best be seen with reference to Figure

3, which how the supply port 314 of a unit cell 316 of the sub module 52 connected to the electrolyte distribution tube 318 via a feed tube 320.
m e top section 310 of the unit cell 300 also includes an outlet port 322 which is connected to the cascade canopy 324 via an outlet tube 326. As may bet be seen with respect to Figure 14, the top section further includes a generally horizontally extending top wall 328 which it integrally formed with a downwardly extending serpentine partition portion 330. m e serpentine partition portion 330 is used to form a erpentine-channel discharge manifold 332 in combination with a bottom cover plate 334 which is secured thereto in a generally fluid tight Neal. Ike opening 336 of the discharge manifold permit chlorine 1~28~39Z
gas and electrolyte to flow out of the unit jell 300 as may best be seen with reference to Figure 16.
me top Ejection 310 of the unit cell 300 additionally includes a unit jell feed manifold 338, Rich to generally cnprised of a to?
cover 340 and a bottom tray 342 secured thereto in fluid tight relationship. The top cover 340 includes an upper cylindrical portion 344 idyll is adapted to extend trough an orifice in the top wall 328 of the top section 310. me Swahili port 312 is adapted to slide over and be secured to the cylindrical portion 344. The top cover to also formed with elongated, da~wardly extending partition portions 346 and 348 which direct the flow of electrolyte through the manifold 338 in cooperation wit the bottom tray 342. Interposed between the to cover 340 and the bottom tray it a screen 350 for filtering the flow of electrolyte to the unit cell 300. Ire bottom tray 342 is formed with a plurality of holes 3S2 trough Rich the nipples 226 of electrode frames 208 extend in order to be welded to the bottom tray and permit electrolyte flow to the internal cavities between the chlorine or positive electrodes 202 and 204.
Referring collectively to Figures 3, 4, ~16, the uniformity of electrolyte distribution amongst all of the individual chlorine electrode pairs contained in electrode assemblies 200 of the battery system 10 may new be explained. As Ann in the Figures just mentioned, the electrolyte circulation ~ybsystem 20 of the battery system 10 is c~nprised of myriad large and small manifolds, serpentine and various size distribution tubes, all of which have been sized to present faker low hydraulic resistance to the amount of electrolyte designed to flaw there through in o~nparison to relatively high hydraulic resistance to fluky presented by each feed tube 216 (eye Figure 9) in the battery stack 18~ I account of the foregoing design, there exits substantially ~2~88~
equal hydraulic pressure in all us t jell manifolds 252 (fee Figure if) and in all serpentine-channel discharge manifolds of each ~ubmodule (Lee Figures 12 and 14)~ of not Roth 6ubmodules 52 and 54. Accordingly, wince the differential electrolyte pressure across each feed tube 216 is substantially the same, and wince all feed tube 216 in the battery tack 18 are of the tame length and inner diameter, all electrode assemblies 200 in each ~ubmcdule experience Substantially equal flow rates.
Similarly, wince the flow capacities of all manifolds and distribution tubes in electrolyte circulation subsystem 20 are relatively large in comparison to the flow rates they experience, the differential hydraulic pressure across any given feed tube 216, an therefore the electrolyte flow rate for the electrode assembly 200 it supplies, remains substantially uniform over time while the battery system 10 is charging or discharging.
Referring specifically now to Figure 15 the unit cell 300 is also Chicano to include a gas relief valve 354 Rich is secured to the top wall 328 in a fluid tight relationship. The relief valve 354 is used to selectively vent gay Fran the interior compartment of the unit cell 300 in response to ye electrolyte level in the unit cell. In particular, the relief valve 354 is advantageously used to vent any hydrogen gas which may be present in the unit cell compartment when the battery system 10 is in a charge standby mode.
he relief valve 354 is generally canprised of a conical-shaped housing 356 having a roughly cone-shaped hulk interior 357, and a buoyant float member 358. The housing 356 is formed with an orifice 360 at its top end for venting gas, and the relief valve 354 is formed at its bottom end with a pair of tang m~rbers 362 and 364 Rich may best be seen in Figure 16) for mechanically locking the relief valve to the lZ2889Z
top wall 328 in a nap fit connection. Ike float member 358 is Shaped to generally conform to the interior surface 366 of the housing 356, BY
that the float member will block the flow of fluid from the unit cell compartment when the float member it moved upwardly into sealing engagement with the housing by the prowar exerted on the float member by the electrolyte. Ike float member 358 also formed with an upwardly extending Tao portion 368 for guiding the upward movement of the float member into sealing engagement with the housing 356. Since the float member 358 preferably has a hollow interior, a bottom plate 370 is bonded to the cylindrical portion of the float member in order to trap a quantity of air wherein. It fulled alpha be noted that while the top wall 328 of the unit cell compartment is provided with an orifice 372 for communicatmg fluid to the relief valve 354, the orifice is made suitably smaller than the diameter of the float member 358 in order to prevent the float member from dropping into the discharge manifold 332 when the electrolyte level is low. Nevertheless, the orifice 372 must also be suitably shaped o as to permit venting even when the float member 358 has dropped to the point where it is resting upon the top wall 328.
when the electrolyte is being circulated through the battery system 10, such as during the charging or discharging of the battery system, the discharge manifolds 332 for each of the unit cells 300 will become filled with electrolyte and cause the float members 358 to Ye upwardly to the point were the float members 358 seal the orifices 360.
When, when the battery system is switched to a standby mode, for example at the end of charge or discharge, the electrolyte pump Pi will be turned off and electrolyte circulation will cease. this will cause the electrolyte level in the discharge manifolds 332 to drop to a point sufficient to reopen the orifices 360 by the downward movement of the 1228~Z
float mQnbers 35~. ye wrung at the orifices 360 will permit any gas prevent in the discharge infolds 332 or in the gas Space between tube plates 334 and the tops of the electrode frame member 208 to be vented Fran the unit jell c~npartment~ through the relief valves 354.
This automatic venting provision it especially important when the battery system 10 i placed in a standby mode after the battery system has been charged, a it will permit any hydrogen gas evolved at tube zinc or negative electrodes 206 during this time to be vented from the unit cell carpartm~ts. It Gould also be noted that the relief valve 354 is designed, through an appropriate choice of size and density for the float Norway 358, Jo as to not permit capillary attraction or surface tension of the electrolyte to hold the buoyant float meter 358 up in sealing engagement with the housing 356 after electrolyte circulation has ceased.
Referring to Figures 3 and 5, these Figures also illustrate a plastic sled 400 which is used to support the swindles 52 and 54 in the lower vessel 14. After the swindles 52 and 54 have been fully assembled with the various electrolyte distribution and collection c~ponents descried above connected thereto, the sled 400 is then slid into the visual 14 along an elongated rail 402.
Figure 3 also illustrates the electrical connections which are made to the su~Mdules 52 and 54. A set of four Err terminals 404 are provided such that one power terminal is connected to each end of the swaddles 52 and 54. Each of these payer terminals cerise a titanium clad copper rod 406 which is friction welded to a titanium bar 408. ye titanium bars 408 are attached to tube plurality of terminal posts 41 0 provided at each end of the sub module 52 and 54. Once Atwood to the sub modules 52 and 54, tube power terminals 404 are then preferably encased in a plastic (liquid potting resin) envelope that extends I

lZZ8892 outside of the vessel 14. The free ends of the power terminals 404 may then be connected to a suitable DO power source for charging the battery system 10 or a suitable load for discharging the battery system.
Figure 3 Allah illustrates a glass tune 412 which is used to house a suitable ultraviolet light source, shown in phantom at reference numeral alp. The glass tube 412 is adapted to extend outside of the vessel 14 to facilitate replacement of the ultraviolet light source 414.
m e ultraviolet light source is adapted to react any hydrogen gas which may be present in the gas spate in the vessel 14 with chlorine gas to form hydrogen chloride.
Referring again to Figure 2, the interaction between the store subsystem 16 of the vessel 12 and the battery stack 18 and electrolyte circulation subsystem 20 of vessel 14 will now be briefly described.
When the battery system 10 is in a charge mode, the battery stack 18 will generate a continuous supply of chlorine gas. The chlorine gas will be drawn from the vessel 14 to the vessel 12 by the gas/hydrate pump UP" via conduit 26. The pump Pi will then mix the chlorine gas with a chilled liquid (preferably water) in the vessel 12 to form chlorine hydrate. when the battery is in a discharge mode, valve nil will be opened to permit warm electrolyte from the sup 40 to be pumped through the hydrate decomposition heat exchanger ~HX2" located in vessel 12 via conduits 28 and 30. this will Q use the hydrate to gradually decompose and liberate a continuous supply of chlorine gas. when the valve ~V2~ is opened, the chlorine gas being liberated in the vessel 12 will then be transmitted back to the vessel 14 via conduit 24. This supply of chlorine gas is then injected into the electrolyte circulation subsystem 20 where the gas is dissolved in the electrolyte which is being distributed to the battery stack 18~ At the end of discharge, all of the chlorine hydrate will have been decomposed and the chlorine gas .....

1~28~9Z
returned and consumed in tube battery stack 18.
Figure 17 it a cutaway perspective view Showing the equipment arrangement inside the store subsystem 16 depicted in Figures 1 and 2.
Store 16 it contained within a short cylindrical case or vessel 12 and is preferably mounted above the tack vessel 14 as Shown in Figure 1.
Vessel 12 has an integral domed end 600 end is closed wit a domed cover 602 at the otter end Wabash it bolted to flange 604. In operation, vessel 12 is filled almost entirely wit liquid (preferably water), leaving a relatively small gas space 605 best shown by liquid level line 606 in Figure 2.
Component located within or on the Tore vessel 12 include gafi~hydrate pump Pi, filter package F, pressure control orifice 622, hydrate former heat exchanger Eel, and decomposition heat exchanger HX2. Various features and operating characteristics of these components may now be described.
Gas/hydrate pump Pi with its electric driving motor 608 attached is mounted on boss 610 of domed cover 602. Pump Pi is of plug in style construction with the motor armature magnetically-coupled to the pump shaft through a plastic pump cover 612, so that no motor or pump Shaft projects through the wall of store vessel 12. The pump Pi is an external or spur gear type pump manufactured by Ingersoll-Rand and built with plastic gears and housings and graphite bushings.
Pump Pi discharges through conical nozzle 614 directly into the gas space 605 at the top of vessel 12. Suction portion 616 of pump Pi plugs or couples directly into inlet fitting or coupling 618 rigidly mounted within the vessel 12. Gas from battery stack 18 provided via conduit 26 and liquid from the store 16 are fed into pump Pi through coupling 618. Chilled liquid (preferably water) is drawn 28~9~, thrush the coiled tube-in--tube heat exchanger Hal from the liquid or water reservoir 620 of vessel 12.
In order that hydrate crystals, also slurries in water reservoir 620, not be drown through heat exchanger Al and pump Pi, a separation leaf-type filler package ala is enploye~. Filter F is configured as a double-walled cylinder and submerged in water reservoir 620. Filter F is constructed of a heavy-gause PVC mesh on a rigid ring-like plastic frame, and covered with a sleeve of*reflon-felted clot, icky effectively prevents any hydrate crystals fry entering Tao spa ox between the cylinder walls of filter F.
Water enters heat exchanger Al from the space between the cylinder walls of filter F through an orifice 622 sized to allow the desired liquid flaw rate and maintain the internal pressure within heat exchanger Hal at approximately suction pressure of pump I which is preferably about 11 Asia.
feat exchanger Al as shown in a number of Tao accompanying drawings, is a simple tube-in-tube assembly, weaken preferably consists of two concentric titanium tubes rolled to form. a coil 624 as Cowan in Figure 17. ~igh-flux coating, cc~erci~lly available from Union Carbide corporation, is preferably deposited on the outer surface of the inner tube to drastically reduce the superheat required for refrigerant boiling by promoting nucleate boiling, thus effectively increasing toe heat trainer coefficient from two to ten-fold. Use of such a crating allows heat exchanger Hal to be made more compact than otherwise would be possible.
Refrigerant used in heat exchanger Al is prefe~ably*Freon 12, and is provided through refrigerant supply and return lines 32 and 34, which are shown passing through the domed old 600 of I
- * trade mark .-;

1~2~3~9z store vessel 12 by way of pressure-tight sealed bushings. As shown in Figures 2 and 17, refrigerant flow through the annuls portion of coil 624 of heat exchanger EKE, while the store liquid flows through the inner tube of coil 624.
The equipment packaged inside tore vowel 12 is preferably mounted on a self-locating support frame or sled (not shown) contoured to rest upon the curved inner surface of the vessel. Such a support frame allows heat exchanger Hal and HX2, package filter F, pressure control orifice 622, and the pump inlet coupling 618 to be erected outside of store vessel 12 Jo that they may be slipped inside as a complete assembly. The equipment packaged inside the store vessel 12 can then be held stationary with respect to store vessel 12 by various attachments of the equipment to the store vessel 12 such as the bushings for the two refrigerant lines 32 and 34 and the two bushings for lines 28 and 30 going to heat exchanger HX2 (see Figures 2 and 19). By utilizing such a support frame and system of attachment points, no assembly work need be accomplished inside of the store vessel 12.
he various configuration of decomposition heat exchangers HX2 shown in Figures 17, 19 and 20 are formed by bending a length of tubing (preferably 1/2 or 5/8 inch OLD. titanium tubing) into the desired shape or pattern. For reasons which will be shortly explained in detail, the coil pattern selected for the heat exchanger HX2 should allow electrolyte to drain from the heat exchanger HX2 when not in use. Figures 19 and 20 show two preferred coil patterns for heat exchanger HX2 designed to ensure such proper drainage. Experience has Shown, for example, that even the generally horizontal coil pattern for heat exchanger HX2 shown in Figure 17 does not effectively provide complete drainage of i22~3~92 electrolyte from heat exchanger EX2.
As mentioned earlier, the store vessel 12 itself it preferably made from FRY with a YVC liner bonded thereto. Since the temperature within tore vessel 12 is preferably maintained at approximately ten degrees C, which may be below ambient temperatures typically encountered in indoor installation of the battery system, thermal insulation it preferably placed about much of the external Eurface6 of the tore vessel to improve the overall system energy efficiency. In a preferred embodiment, a one and one-half inch layer of urethane foam designated by the numeral 628 covers approximately eighty percent of the exterior of vessel 12, and the foam in turn may be hovered by a thin one-eighth inch of FRY lay-up to protect it from damage.
In the battery system 10 of the present Invention, a preferred electrolyte is a two molar concentration of zinc-chloride (measured when the battery system 10 is fully discharged), having supporting (i.e., conductivity-improving) salts of about a four molar concentration of potassium chloride and about a one solar concentration of sodium chloride to increase overall battery system efficiency.
During the normal operation of the battery system 10, the electrolyte temperature in tack vessel 14 preferably maintained between about thirty and forty degrees C. Warm electrolyte from sup 40 continuously circulating through heat exchanger HX2 typically is not tooled during it passage through heat exchanger HX2 more than ten degrees C, and thus, precipitation of supporting salts in the electrolyte doer not normally occur at the time. However, whenever heat exchanger HX2 it turned off long enough for the electrolyte within the heat exchanger to cool to near the internal temperature maintained within the store, ~28~9Z
precipitation of supporting alto and the resultant clogging of decomposition heat exchanger HX2 would be a major problem if the highly salted electrolyte were allowed to remain in this heat exchanger a the lets highly salted electrolyte were allowed to do in earlier zinc-chloride battery ~y6tems.
Tub eliminate such problems, the zinc-chloride battery systems Cowan in the prior art have been redesigned Jo that the decomposition heat exchanger ~X2 it now self-draining during those periods of time when no flow of electrolyte is required there through. Tub do this without adding any appreciable additional cost, complexity, or control equipment (such as a control valve and/or pump) to the battery system, the battery system 10 is now designed so that heat exchanger ~X2 of the store subsystem 16 is located higher than the Bump 40 associated with the battery stack 18, Jo that electrolyte will drain from heat exchanger HX2 back to the snip 40 when electrolyte flaw there through is not required. This it preferably accomplished by placing tore vessel 12 completely above stack vessel 14 as shown in the latest battery system designs in Figures 1, 2 and 20.
Figure 18 is a schematic diagram of the self-draining heat exchanger concept with the tore 630 elevated above the level of electrolyte in the sup 40. A can be seen by referring to Figure 18, electrolyte pump Pi provides electrolyte to the stack 632.
During the discharge mode of the zinc-chloride battery cycle, pump Pi also provides electrolyte to heat exchanger EX2 through conduit 634 by opening decomposition control valve Al, which is normally closed during all other times of the battery cycle. me rate at which heat is provided to the liquid in tore 630 by heat exchanger HX2 determine the rate at which chlorine is liberated by the decomposition of chlorine hydrate in the store. Control valve Al may ~Z88~
be intermittently opened and closed during the discharge mode to modulate this heat transfer rate When the flaw of electrolyte is blocked my control valve n, electrolyte in heat exchanger drains into sup 40 through conduit 636. flus skilled in the art will appreciate Lotte if heat exchanger ~X2 it higher Jan jump 40 and is provided with sufficient slope and its tubing is of sufficient inner diameter, electrolyte will naturally drain there- from, especially since the aqueous electrolyte used in zinc~hloride battery systems has a consistency very Shea like plain water. however, to pro mote muck faster drainage of ye relatively small delimiter tubing Connally used in heat exchanger Eye a vent means 638 has buff added between the outlet of En> Pi and the inlet 640 ox heat exchanger I to allow gas to enter heat exchanger By to replace electrolyte as it drains therefrom. ye gas is preferably drawn, as spawn in Figure 18, from the gas space 642 of stack vessel 14. In battery systems employing a decnposition control valve Al located basically as shown in Figure 18, vent 638 must be placed downstream from the control valve Al.
Vent means 638 in the preferred embodiment of the zinc-chloride battery system of the present invention is a 1/16 inch diameter hole in conduit 634, and is connected to gas space 642 in tack vessel 14. owe skilled in the art will appreciate Lotte a larger or staller size hole could be used for the vent 638. While a 1/32 inch hole could be used for example, a 1/16 inch hole is deemed preferable since it is deemed less susceptible to clogging by any small particulate or foreign matter whiz might possibly be present in the electrolyte. An advantage of a slr~ll hole, such as a 1/16 inch diameter hole, over a considerably large hole such as a 5/16 inch diameter hole, it that its liquid volumetric capacity is lZZ8~92 insignificant in oomparisDn to the flow of electrolyte through the heat exchanger, 80 that any electrolyte flow through vent 638 back to the sup 40 represents a negligible energy loss to the battery system. Yet, the guy volumetric capacity of the vent 638 for such a foamily hole is Efficiently large to ensure fairly rapid drainage of the electrolyte from heat exchanger HX2 before the electrolyte therein cools efficiently to allow any significant precipitation of conductivity-Improving salt.
Figures 18, 19 and 20 how that a heat exchanger EX2 of the Eelf-draining type is preferably constructed of three parts: an inlet portion 640, an outlet portion 644, and a generally helical central portion 646 disposed between the inlet and outlet portions.
Central portion 646 preferably slopes substantially continuously downward from the inlet portion 640 to the outlet portion 644 in order to prevent any electrolyte from remaining in the central portion of heat exchanger HX2 when the electrolyte it to be drained therefrom.
The angle of the slope may be varied HO long as it is sufficient both to prevent electrolyte from remaining within heat exchanger HX2, and to allow relatively quick drainage of the electrolyte before it cools sufficiently to allow any significant precipitation. The optimal slope and configuration of heat exchanger ~X2 is dependent upon the room available therefore in tore vessel 12, the size and length of the tubing used therefore the length of the conduit inter connections between the heat exchanger and the sup 40 and electrolyte pump Pi, and the size of the hole or orifice for the vent 638. Variations in all of these design details are within the contemplated scope of the invention.
Vent means 638, rather than being continuously open to the gas space as is shown in Figure 18, could alternatively be opened and closed as needed through the Lee of a control valve. A simple hole in conduit 634 it deemed preferable to using control valve approach to venting since such a vent hole it less costly, simpler, and inherently automatic in operation.
A can be teen in Figure 18, owe electrolyte may remain in conduit 634 between d~co~p~ition control valve Ye and vent 638.
because conduit 634 it outside of store vessel 12, end it therefore subject to much higher ambient temperatures, precipitation of Belt therein is not a problem.
Another benefit of the basic self-draining heat exchanger arrangement Cowan in Figure 18 it that it tykes full advantage of the natural ncmentum of the electrolyte flowing through the heat exchanger HX2 to help promote rapid draining of heat exchanger HX2.
Figures 1 and 2 show a preferred embodiment of vent 638 and piping therefore Specifically, decomposition control valve Al and vent 638, which is shown schematically in Figure 2 as orifice 648, are located exterior to both tore and stack vessels 12 and 14.
Ike exterior location of conduit 24, 26, 28 and 30, valves Al and V2, and vent 638, as well as other equipment shown in Figures and 2, facilitate troubleshooting maintenance and repair of these items. Figures 19 and 20 each illustrate a preferred embodiment of an overall lay-out and coil pattern for a self-draining heat exchanger HX2. Tests of self-draining heat exchanger ~X2 arrangement described above with respect to Figure lo have Shown it to be very effective in preventing precipitation of salt in heat exchanger HX2 and the clogging problem resulting therefrom.
Figure 20 shows an alternative embodiment of the tore subsystem that is being designed for large commercial installations such as electrical utility load-leveling applications. The principles l~Z8892 of operation and construction techniques of the battery system shown in Figure 20 are basically the Blame as those shown for the battery system of Figure 1. the upright position of store vessel 12 in Figure 20, in conjunction with the reduction of the diameter of the tore vessel to match the diameter of the tack vessel 14, provides a considerably Gore compact tacking arrangement for multiple battery y6t~ms used in large applications like a commercial load-leveling battery plant. One such coquette tacking arrangement, which beneficially provides a rather high battery Ey~tem density per unit volume, is shown in Figure 21. To provide for an increased energy capacity, each individual battery system shown in Figure 20 has it battery tack 18 within the stack vessel 14 increased from 72 inches (as how in the battery tack of Figure 2) to 92 inches. Similarly, other components such as the three heat exchangers Al HX2 and EKE are increased in size to accommodate the increased energy capacity.
While it will be appreciated that toe preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

Claims (18)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An electrode assembly, comprising:
a first electrode;
a pair of planar second electrodes disposed in substantially parallel spaced relation to one another, said second electrodes having opposing inwardly facing interior surfaces and outwardly facing exterior surfaces;
a generally rectangular one piece first frame member, defining a pair of spaced apart generally U-shaped and parallel channels, said channel extending substantially around three sides of said first frame member, each channel having an outer channel wall and having a common inner wall which defines a first masking member;
a second frame member insertably carried in said first frame member and defining a second masking member in coplanar relationship with said first masking member;
said second frame member having a nipple at one end thereof and having a clip forming projection at the opposite end thereof;
a hollow tubular feed tube insertably carried at one end thereof in said nipple and retained at the other end thereof by said clip forming projection;
electrode supporting member integrally formed on said first frame member and laterally displaced adjacent said second frame member, said electrode supporting member having an elongated channel for receiving and masking one edge of said first electrode;
said second electrodes being slidably carried in said U-shaped channels and in sandwiching relationship with said second frame member, such that said first and second masking members substantially mask a peripheral portion of said interior surfaces thereof and such that said outer channel walls sub-stantially mask a peripheral portion of said exterior surfaces thereof;
wherein said first and second masking members mask a greater surface area than the surface area masked by said outer channel walls; and wherein said electrode supporting member defines a third masking member disposed adjacent to and substantially masking a peripheral portion of said exterior surface of one of said second electrodes.

2. The invention according to claim 1, wherein said first frame member also includes integral rib means for supporting the exterior faces of said second electrodes generally at the center thereof.

3. The invention of claim 2 wherein said rib means is substantially triangular in cross section and provides a flat supporting surface adjacent said second electrodes and provides a generally knife-edged outwardly facing portion for restraining said first electrode.

4. The invention according to claim 1, wherein said second electrodes are of relatively porous graphite.

5. The invention according to claim 1, wherein said second electrodes are rectangular and dimensioned such that said edges along said three supported sides are captivated within said U-shaped channels.

6. The invention according to claim 1, wherein said first electrode is of relatively dense graphite.

7. The invention of claim 1 wherein said first electrode is disposed in substantially parallel spaced relation to said second electrodes.

8. The invention according to claim 1, wherein said second electrodes define an internal cavity therebetween.

9. The invention of claim 1 wherein said second frame member is at least partially disposed between said second electrodes.

10. A comb-type bipolar cell for a battery system having a circulating electrolyte, comprising:
first and second bus members each being enclosed in a plastic frame around the edges and external face thereof;
a plurality of spaced first electrodes extending from said first bus member;
a plurality of spaced second electrode structures from said second bus member, said first electrodes being inter-digitated with said second electrode structures;
a generally rectangular plastic housing which forms a compartment in combination with said first and second bus members substantially enclosing said first electrodes and said second electrode structures, said housing including a top section; and said top section having electrolyte distribution manifold means for distribution of electrolyte to said second electrode structures and said top section further having dis-charge manifold means for removal of said electrolyte from said compartment and means for isolating said distribution manifold from said discharge manifold.

11. The invention of claim 10, wherein said first bus member is of relatively dense graphite.

12. The invention of claim 10, wherein said first and second bus members are of relatively dense graphite.

13. The invention of claim 10 wherein said first bus member has two generally planar opposing faces, each of said faces having a plastic frame disposed at least partially there around.

14. The invention of claim 13 wherein said plastic frame is formed by injection molding.

15. The invention of claim 13 wherein said second bus member has two generally planar opposing faces, each of said faces having a plastic frame disposed at least partially therearound.

16. The invention of claim 10 wherein said manifold means for distribution of electrolyte includes filter screen extending substantially the entire length of said manifold.

17. An electrode assembly comprising:
a first electrode;
a pair of second electrodes disposed in substan-tially parallel spaced relation to one another and in substan-tially parallel spaced relation to said first electrode;
a generally rectangular one piece first frame member defining a pair of spaced apart generally U-shaped and parallel channels, said channels extending substantially around three sides of said first frame member, each channel having an outer channel wall and having a common inner wall which defines a first masking member;
a second frame member insertably carried in said first frame member and defining a second masking member in coplanar relationship with said first masking member;
an electrode supporting structure integrally formed on said first member and laterally displaced from and adjacent to said second frame member, said electrode supporting member having an elongated channel for slidably receiving and masking one edge of said first electrode;
said electrode supporting member being spatially fixed relative to said second electrodes while permitting sliding movement of said first electrode to accomodate position changes of said first electrode during assembly and during thermal expansion and contraction thereof;
said electrode supporting member providing masking between said first electrode and the adjacent one of said second electrodes such that the unmasked surface boundaries of said first electrode and said adjacent second electrode remain fixed relative to one another.

18. A comb-type bipolar cell for a battery system having a circulating electrolyte, comprising:
a frame structure;
first and second bus members;

Claim 18 cont'd.

a plurality of spaced first electrodes extending from said first bus member;
a plurality of spaced second electrodes extending from said second bus member and being interdigitated with said first electrodes;
said first and second bus members having generally planar opposing faces and being joined around the edges thereof to said frame structure thereby defining a compartment for containing said interdigitated first and second electrodes;
said first and second bus members having top and bottom edges each provided with longitudinally extending, key defining grooves, and said top and bottom edges being provided with injection molded, encapsulating edge structures forming an ionic seal by mechanically interlocking with said key defining grooves;
said encapsulating edge structures providing the means by which said first and second bus members are joined to said frame structure.