GB2574023A

GB2574023A - Method of construction of an elongated bipolar plate battery

Info

Publication number: GB2574023A
Application number: GB1808408.7A
Authority: GB
Inventors: Murray-Smith Robert
Original assignee: Robert Murray Smith
Current assignee: Robert Murray Smith
Priority date: 2018-05-23
Filing date: 2018-05-23
Publication date: 2019-11-27
Also published as: GB201808408D0

Abstract

An elongated flat battery having a series of connected cells that are formed from a lamination of elongated tapes /layers. The lamination is formed from two sets of laminating tapes each comprising a carrier tape 1 bonded to a narrower electrode tape 2 which is covered by an elongated separator/spacer 6 that is narrower than and bonded to the carrier tape; wherein the laminated tapes have slots punched through the tapes that separate the electrode tape into plates, and allow electrolyte to be introduced into the cells, as an alternative to the use of a specific conduit. The spacers of two sets of laminated tapes are placed together, wherein the slots are offset from each other, and the carrier tapes are bonded together to form the elongated battery. A sealing plug 7 seals the slots isolating the cells electrolyte and/or gases. The spacer is preferably non-electrically conductive and act as fluid reservoirs e.g. cellulose, absorbent ceramics, fumed silicas; and may be a reservoir for the electrolyte. Electrode tape is preferably electrically conductive e.g. prolytic graphite, carbon, aluminium, zinc, gold; and preferably coated with electrochemically active materials. Carrier tape is preferably non-conductive, non-reactive and non-pervious to the electrolyte e.g. polyimide, polyethylene.

Description

Method Of Construction Of An Elongated Bipolar Plate Battery

BACKGROUND OF THE INVENTION

The present invention relates to electrochemical cells, and in particular to bipolar plates for use in electrochemical cells and a method for making bipolar plate batteries which provide substantial advantages, e.g., are structured to be effectively filled with controlled amounts of electrolyte and/or effectively limit, preferably substantially prevent, the liquid and/or gaseous components from one bipolar cell from interfering with the functioning of another bipolar cell and/or to maintain the desired spacing between electrodes.

The conventional battery is a multi-cell structure. Each cell generally comprises a set of vertical positive and negative plates formed of layers of electrochemically active pastes. An electrolyte is interposed between the positive and negative plates.

Modern attempts to produce light-weight batteries, especially in the aircraft, electric car and vehicle fields, have placed their emphasis on producing thinner plates from lighter weight materials. The thinner plates allow the use of more plates for a given volume, thus increasing the power density.

Higher voltages are provided in a bipolar battery including bipolar plates capable of through-plate conduction to serially connected electrodes or cells. The bipolar plates must be impervious to electrolyte and be electrically conductive to provide a serial connection between electrodes.

U.S. Pat. Nos. 4,708,918 and 4,861,689 discuss various aspects of bipolar plates and batteries.

One problem which has presented itself in considering bipolar plate batteries or bipolar batteries is the addition of electrolyte to the assembled battery. Such a bipolar battery includes a plurality of bipolar cells, each of which include a negative electrode, a positive electrode, a separator between the electrodes to separate the electrode and hold electrolyte, and a fluid impervious, electrically conductive bipolar plate adjacent each electrode. Thus, each bipolar plate may be considered to be a part of two bipolar cells. The thickness of such bipolar cells is often significantly less than the thickness of conventional monopolar cells. Such reduced thickness makes filling each of the bipolar cells, which are to be isolated against fluid flow one from the other, with a controlled amount of electrolyte quite difficult, particularly at fill rates to satisfy commercial production schedules and/or using commercially available equipment. A second problem presented is to effectively limit the liquid and/or gaseous components from one bipolar cell from interfering with the functioning of another bipolar cell. Such cell to cell interference can result in a reduction in the overall efficiency of the bipolar battery, or even in battery failure.

Another problem with bipolar batteries is that of maintaining the spacing between positive and negative electrodes. Maintaining the interelectrode spacing provides substantial performance advantages. For example, substantially uniform spacing between the positive and negative electrodes provides for a substantially uniform current distribution and flow between the bipolar cells and electrode pairs which are included in the assembled bipolar battery. Such spacing is particularly important in sealed maintenance free oxygen recombinant batteries. However, as the dimensions of the bipolar plate surfaces associated with the positive and negative electrodes increase, particularly the surface area dimension, the more difficult it becomes to maintain proper interelectrode spacing. It is often useful to make such surfaces relatively large in order to provide a bipolar battery with the desired capacity.

The present invention addresses these and other problems and concerns as will become apparent hereinafter.

SUMMARY OF THE INVENTION

The present batteries include a plurality of bipolar cells, each of which preferably includes a negative electrode; a positive electrode; a separator means between the electrodes to separate the electrodes, and hold an amount of electrolyte as an electrolyte reservoir; and a fluid impervious, electrically non conductive matrix surrounding and encapsulating the aforesaid structures.

The present invention is structured such that the bipolar plate itself is elongated along the plane. Bipolar plates as known in the art generally consist of the anode and cathode division as existing in plane to the plate. It is this arrangement that leads to many of the problems associated with bipolar plates, that is: expensive manufacture, leakage of electrolyte though the plate and problematic sealing of the overall battery pack. By extending the bipolar plate along the plane such the anode and cathode division occurs substantially at the midpoint of the pfate perpendicufar to the pfate surface that most of these problems can be overcome and many of the advantages of the bipolar plate arrangement realised.

The present invention provides substantial advantages. For example, the present batteries can be effectively and rapidly provided with a controlled amount of electrolyte despite the quite limited dimensions of the bipolar cells of the batteries. This electrolyte filling operation is preferably accomplished utilizing commercially available equipment. The present invention also provides for maintaining the spacing, preferably the substantially uniform spacing, between the positive and negative electrodes of the bipolar batteries. Maintaining such spacing is important for maintaining a substantially uniform current distribution and flow between the bipolar cells and the electrode pairs, e.g., the positive and negative electrode on either side of each bipofar pfate of the assembfed batteries. In addition, the present invention can effectively limit, preferably substantially prevent, the liquid and/or gaseous components from one bipolar cell from interfering with the functioning of another bipolar cell. The present battery elements are relatively easy to manufacture and provide for substantial battery performance benefits.

In one broad aspect of the present invention, an assembled bipolar battery comprises a plurality of means for introducing electrolyte into the plurality of bipolar cells of the battery. Each of these means acts to introduce electrolyte into a different one of the bipolar cells. Preferably, each of these means includes a conduit, more preferably a different conduit, which is in fluid communication with the one of the bipolar cells into which the means acts to introduce electrolyte. Since each bipolar cell preferably has its own individual filling conduit, the amount of electrolyte introduced into each individual cell can be very precisely controlled. Each cell is provided with the desired amount, preferably the same amount, of electrolyte. Also, the chances of electrolyte and/or evolved gases and/or entrained acid mists moving from one cell to another cell during use of the battery are substantiaffy reduced or ehminated. If efectrofyte or gases do ffow between bipofar ceffs, current losses or even cell failure can result.

In another broad aspect of the invention, a bipolar battery is provided with at least one spacer element, preferably at least one spacer element for each bipolar cell. Each of the spacer elements is associated or in contact with, preferably secured to, a carrier tape and is located at least partially away from the periphery of the carrier tape. The spacer element acts to maintain the spacing between bipolar cell electrodes, and/or between the associated plate and an adjacent plate. The spacer element may be considered to be also associated with the adjacent plate. Such a spacer element, which preferably contacts, and more preferably is secured to, the adjacent bipolar plate, provides a structure in which the distance or separation between adjacent plates, e.g., bipolar plates, and between adjacent electrodes is substantially maintained, preferably so that the closest distance between any point on a plate or an electrode and the adjacent plate or electrode, respectively, is substantially uniform. Using such spacer elements, the thickness of each bipolar cell of the battery is preferably maintained substantially uniform. More preferably, the thicknesses of all the bipolar cells are maintained substantially uniform and are substantially equal. Preferably the spacer element is non electrically conductive so that no current flows from plate to plate through the spacer element or elements. The use of the spacer element in combination with the bipolar plate allows the use of relatively thin bipolar plates, such as in the range of about 20 micrometers to 80 micrometers which feature is particularly important for achieving low internal resistance batteries. In addition, the spacer elements allow each cell to withstand differential pressure transients which the bipolar battery can reach during battery operation, particularly charging. The spacer element also acts as an electrolyte reservoir.

The several embodiments of the present invention may be employed alone or together, as desired. For example, an assembled battery may include a plurality of means to introduce electrolyte into individual bipolar cells, means to limit gaseous and liquid components from one ceff from interfering with the functioning of another cell, a plurality of spacer elements, as defined herein, and battery elements, as described herein. The spacer elements are preferably configured, particularly when the present means for introducing electrolyte are employed, so that electrolyte can flow substantially freely around such elements so that the entire bipolar cell is provided with electrolyte, as desired. In other words, the spacer elements preferably are configured so as to not substantially restrict the flow of electrolyte into or across the bipolar cell and/or restrict the removal of air during filling with electrolyte, and/or deleteriously produce pockets of gas during battery charging and operation.

One important feature of the present invention is the provision of a plurality of electrolyte addition means. Each of such means preferabfy acts to introduce electrolyte into a different one of the bipolar cells of the assembled bipolar battery. For example, a 12 volt bipolar battery including six (6) two (2) volt bipolar cells includes six (6) electrolyte addition means.

In one particularly useful embodiment, each electrolyte addition means includes a conduit which is in fluid communication with one, and preferably only one, of the bipolar cells into which such means acts to introduce electrolyte.The conduits are preferably also used to evacuate the cells prior to introducing electrolyte therein. This cycle of evacuation-electrolyte addition may be repeated more than one time, e.g., two (2) to four (4) and preferably two (2) or three (3) times, in order to get the proper amount of electrolyte into the cell. The use of vacuum facilitates a more uniform distribution of electrolyte in the cell and the wetting out of both the positive and negative active electrode materials, e.g., the pores of such materials, as well as the separator means. The cell is often considered filled with electrolyte even though only a fraction, preferably about 70% to about 95%, of the available void volume of the separator means and the active electrode materials are filled with electrolyte. Once electrolyte addition has been accomplished, the conduits are sealed, preferably individually sealed. In this sealed condition, each of the conduits within the battery acts as a fluid pressure/equalization compartment or reservoir, e.g., for oxygen in a recombinant battery, for the individual cell with which it is in fluid communication. This advantageously provides a degree of ffexibifity in the operation of the individuaf bipofar ceff, for exampfe, by providing a fluid pressure buffer compartment.

The opening into the individual cell from the conduit may be oriented in any suitable manner with respect to the general direction of flow in the conduit. For example, this opening may be parallel to the general direction of flow in the conduit. However, it is preferred that the opening into the cell be substantially perpendicular to the general direction of flow in the conduit. Such orientation provides for effective removal through the conduit of the vapor being replaced or displaced by the liquid electrolyte and, overall, provides for effective and efficient electrolyte addition. A a flow guide, or splash director, can be provided, e.g., in the conduit, to direct the electrolyte from the conduit into the cell.

In another important feature of the present invention, an assembled battery is provided with a plurality of spacer elements. Each bipolar cell is preferably provided with at least one of these spacer elements. Relatively large cells may advantageously employ a plurality of such spacer elements, e.g., up to about 10 and preferably up to about 6 spacer elements, to maintain plate/plate and/or electrode/electrode spacing.

Such spacer elements are preferably non-electrically conductive and act as fluid reservoirs. Such spacer elements preferably have a maximum thickness substantially equal to the thickness of the bipolar cell, e.g., from one surface of one plate to the facing surface of the adjacent plate. In a particularly useful embodiment, the spacer elements are configured so as to allow substantially free or unrestricted flow of electrolyte into substantially all parts of the cell space, i.e., the positive and negative active material and the separator means, and/or to not substantially restrict the removal of air during filling with electrolyte and/or to not deleteriously produce pockets of gas during battery charging and operation.

The spacer element or elements are in contact with, and preferably secured to, at least one carrier tape, and more preferably in contact with, and still more preferably secured to, both plates making up a bipolar cell. Such securement can involve mechanical interlocking, or physical or chemical bonding.

Typical materials for the spacer elements can include, but are not limited to cellulose, cross linked cellulose, cellulose polypropylene mixes, adsorbant ceramics,fumed silicas, etc

In another important feature of the present invention is the disposition of the electrode material on a carrier tape. The said disposition can be continuous or intermittent.

Such electrode elements are preferably electrically conductive and can be made from, for example but not exhaustively, graphite, pyrolytic graphite, graphitic paper, carbon cloth, carbon fibre, aluminiun, zinc, nickel, gold, etc.

In a particularly useful embodiment, the electrode elements are configured such that a layered approach is taken. That is the electrode material can perform as a current collector and said current collector can be over-coated with a variety of electrochemically active materials, for example, but not exhaustively nickel hydroxide, iron oxide, lead oxide, activated carbon, etc. Any suitable process may be employed to apply the coating onto the substrate. The primary criterion for such processing is that an effective coating results.

In a particularly useful embodiment, the electrode elements are configured so that they can be applied as a continuous tape to the carrier tape material.

The carrier tape is preferably of a non conductive, non reactive materiaf stabfe within the appropriate electrochemical environment that the resultant cell is designed to operate in. Examples of which would be polyimide, polyamide, acrylic, polyethylene and mixed materials of such such that the carrier tape is essentially non conductive and non pervious to the aforesaid electrolyte solution.

In a particularly useful embodiment, the carrier tapes are configured so that they are precoated with an adhesive to assist in affixing the electrode tape the adhesive been selected so that it is impervious to the conditions of the electrochemical cell in which the adhesive is to function.

Examples

An example of the proposed construction technique would be to use a tape conversion process whereby a carrier tape is unrolled and a suitable prepared electrode material tap is applied to the adhesive surface of the carrier tape. The combined dual tape is the punched through both layers such that a slot of desired width is cut sufficient to separate the electrode tape into sections of sufficient length that bipolar plates are formed.

Any suitable process may be employed to apply the tapes and to cut the slots. The primary criterion for such processing is that an effective joining results and the slots are cut sufficient to separate the electrode materials one from the other and that the two tapes are affixed essentially along the same midline axis.

The tape is then further layered with a separator material as described above. Any suitable process may be employed to apply the separator. The primary criterion for such processing is that the materials are affixed such that the midline of all the tapes are essentially along the same line and that there is a sufficient width of carrier tape remaining that is uncovered in the longitudinal axis.

Further to this processing two completed tape lengths are applied one to another such that one is reversed 90 degrees in that the two electrode surfaces are facing each other and the tapes are then cojoined in a way that the slots are off stepped by one half of the length of the distance between the centre to centre measurements of the aformentioned cut slots.

It is not a necessity of the current invention that the electrode tapes or coated electrode tapes be of the same material. If they are of the same material they can be regarded as a symmetric device and if they are of different materials they can be regarded as an asymmetric device.

Once affixed the two tapes form the bipolar battery arrangement. Prior to electrolyte filling the slots on one side of the tape are ealed with an appropriate sealer. For example but not restricted to, polydimethyl siloxane, acrylate glues, resins or other bonding agents.

In a particularly useful embodiment, filling channels are provided and in this case both sides would preferably be sealed prior to electrolyte filling. The channels being sealed with a separate sealing tab post the filling operation.

In another embodiment, electrolyte filling occurs through the slotted cuts that remain unsealed. These slots are sealed after electrolyte filling has taken place.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1 is a plan view of one half of a tape constructed without filling channels where slots are used for filling

FIG 2 is a plan view of one half of the tape with filling channels shown

FIG 3 is a plan view of one half of the tape with filling channels and separator shown

FIG 4 is a cross section of a finished tape.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG 1 Shows a plan view of one half of a tape constructed without filling channels where slots are used for filling. The carrier tape (1) has electrode tape (2) fixed thereupon such that essentially the median line of the longitudinal axis of both tapes are overlaid. Post this process the holes (3) are punched through both sets of tape simultaneously.

FIG 2 Shows a plan view of one half of the tape with filling channels (4) shown in position. In a preferred embodiment these filling channels (4) are constructed from folded paper and arranged such that they are central to the as formed cell chambers and preferabty projecting into the cell chamber slightly. Provided for sealing are sealing tabs (5) which can be constructed from the same tape as carrier tape (1) but castellated in order to form the fold over sealing tabs (5)

FIG 3 Shows a plan view of one half of the tape with filling channels (4), sealing tabs (5) and separator (6) shown. The separator (6) is overlaid the previous constructed tape whether or not the filling channels (4) or sealing tabs (5) have been applied. The decision to apply filling channels (4) or sealing tabs (5) being a process decision and no way affecting the scope of the invention.

FIG 4 Shows a cross section of a finished tape where sealing plug (7) has been applied to slot (3) on both sides of the tape. Depending on construction decisions sealing plug (7) is applied to one side of the tape prior to electrolyte insertion and to the other side of the tape post filling, or apphed to both sides prior to filling if filling channels (4) are present in which case sealing tabs (5) are closed post filling procedures.

All the figures together show a bipolar plate arrangement where the junction between anode and cathode has been moved from the centre of the plane of plate as is traditional to a point mid way between the plate and perpendicular to the plane of the plate with the carrier tape forming an effective case and cell seal such that migration of liquid or gas electrolyte is minimised while retaining the positive aspects of the bipolar plate arrangement.

Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.

Claims

Method Of Construction Of An Elongated Bipolar Plate Battery CLAIMS

1. A method for making a bipolar plate battery comprising:

providing a first sheet of material having a first bonding face and a first outer face;

providing a second sheet of material having a second bonding face and a second outer face such that the second layer of material is less wide than the first sheet of material;

providing a third sheet of material having a third inner face and a third outer face such that the third sheet of material is wider than the second sheet of material but less wide than the first sheet of material;

creating a layered structure of at feast one of said first bonding face and said second bonding face and at least one of second outer face and third inner face;

bonding said first and second bonding faces together; and creating slotted gaps through first and second sheets overlaying third sheet such that the third inner face is bonded to the first bonding face and in contact with the second outer face.

The cutting of slots through the said formed sheets along the linear axis of the formed sheets and that the long axis of the slot is ninety degrees to the longitudinal axis.

The overlaying of two such formed sheets such that the respective third outer faces of the formed sheets are in contact and that the remaining area of the first bonding faces are simultaneously in contacts and that the said slots are offset from from the other.

Bonding of the two such layers via the remaining unbonded area of the first bonding faces such that a series of strip cells are formed

Sealing of the said slot.

Injecting fluid between said bonded two formed sheets thereby causing the two formed sheets to project outward and thereby form a series connection of cells.

2. The method of claim 1 wherein injecting fluid further comprises:

placing said first and second formed sheets into a die having sealed an open slot of first or second formed sheet; and injecting fluid between said first and second formed sheets and thereafter sealing the remaining open slot.

3. The method of claim 1 wherein injecting fluid between said first and second sheet includes forming a flow channel between said first and formed sheet contiguous with each formed cell and providing a means of closure for the formed channels.

4. A method for making a current collector:

whereby the second sheet has had applied an active material prior to bonding to the first bonding face of the first sheet.

5. The method of claim 1 wherein the second sheet of both formed sheets may be of the same material.

6. The method of claim 1 wherein the second sheet of both formed sheets may be of a different material.

7. The method of claim 1 wherein the first sheet of both formed sheets may be of the same material.

8. The method of claim 1 wherein the first sheet of both formed sheets may be of a different material.

9. The method of claim 1 wherein the third sheet of both formed sheets may be of the same materiaf.

10. The method of claim 1 wherein the third sheet of both formed sheets may be of a different material.

11. The method of claim 1 wherein the bonding faces of the sheets may have had an adhesive previously applied.

12. The method of claim 1 wherein the bonding faces of the sheets may not have had an adhesive previously applied and a suitable adhesive is applied as part of the process.