Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/04—Construction or manufacture in general
  • H01M10/0413—Large-sized flat cells or batteries for motive or stationary systems with plate-like electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/34—Gastight accumulators
  • H01M10/342—Gastight lead accumulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M6/00—Primary cells; Manufacture thereof
  • H01M6/42—Grouping of primary cells into batteries
  • H01M6/46—Grouping of primary cells into batteries of flat cells
  • H01M6/48—Grouping of primary cells into batteries of flat cells with bipolar electrodes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the present invention relates to multicell electric storage batteries, in particular lead acid batteries, and is concerned with that type of battery known as “sealed” or “recombinant” in which the gases produced within the battery during operation and charging, at least at relatively low charging rates, are induced to recombine in the battery and are therefore not vented to atmosphere.
• Recombinant lead acid electric storage batteries are known, but it is an object of the present invention to provide a battery structure which may be easily assembled and is easily adapted to batteries of different voltages or capacities.
• a multicell electric storage battery comprises two or more juxtaposed flat battery elements, each flat element comprising two or more cell elements disposed side by side and separated by cell element defining strips of electrolyte resistant polymer material, each cell element including a current conductor carrying active electrode material, the regions of active material being spaced from each other by the cell element defining strips, the polarity of the active material of each cell element being different to that of the or both adjacent cell elements of the same battery element, adjacent battery elements being disposed relative to each other such that the cell element defining strips of adjacent battery elements are in registry and the polarity of the active material of each cell element is different to that of the or both opposed cell elements of the or both adjacent battery elements, all the cell elements at one end of the battery elements of positive polarity having a terminal conductor disposed in the plane of the element and connected to the positive terminal of the battery and all the cell elements at the other end of the battery elements of negative polarity having a terminal conductor disposed in the plane of the element and connected to the negative terminal of the battery
• a perimeter strip of electrolyte resistant polymer material may be provided extending around the edge of each battery element, the perimeter strips of adjacent battery elements being in registry.
• the battery includes a plurality of frames of plastics material, each frame comprising a perimeter member and one or more cell element defining strips, the spaces defined by the peri meter member and the or each cell element defining strip each receiving a current conductor carrying active material, every alternate cell element defining strip having on one side a connector recess extending over a minor proportion of its length, the connector recesses on adjacent frames being in cell element defining strips that are offset from one another, the current conductors in the spaces on each side of each cell element defining strip being connected together by a connector which is received in the recess in the cell element defining strip.
• every alternate cell element defining strip has two connector recesses formed in it, and each connector recess is preferably formed adjacent the perimeter member.
• each cell element defining strip of each frame which overlies a connector recess in the cell element defining strips of the adjacent frame has ah elongate recess formed in it which communicates with the exterior of the perimeter member, the connector recess and the longitudinal recess being filled with a sealing material which seals the connector in the connector recess.
• the sealing material which may be epoxy resin or a hot melt adhesive thus seals the intercell connectors and substantially eliminates the possibility of intercell ionic leakage currents flowing around the connectors.
• the ratio of X to Y may be in the range 6:1 to 1:1 e.g. 5.5:1 to 1.5:1, or more preferably 4:1 to 1.5:1 where X is the total pore volume of the separators in the dry state and Y is the total pore volume of the positive and negative active materials in the dry fully charged state.
• the charging rate is desirably kept at not greater than C/15 and preferably less than C/20 e.g. C/20 to C/60.
• the volume of electrolyte is desirably in the range 0.8 (X+Y) to 0.99 (X+Y) and especially for automotive batteries and other batteries which are largely held in a condition close to fully charged, at least 0.9 (X+Y) or even at least 0.95 (X+Y). These values enable the active material to be utilized more efficiently than when lower amounts of electrolyte are used.
• While the cell element defining strips can be sealed to each other e.g. by ultrasonic or other welding or adhesive means, such sealing may not be essential since due to the high affinity of the separator for electrolyte (as evinced by its electrolyte absorption ratio) and the restricted amount of electrolyte in the battery, electro lyte leakage between juxtaposed cell element defining strips is severely retarded and electrolyte conductivity paths by this route may not be present to such an extent as to cause significant self discharge problems in automotive batteries in use.
• the electrolyte/active material ratio is desirably at least 0.05 e.g. at least 0.06 or at least 0.10 and is the ratio of H 2 SO 4 in grams to the lead in the positive and negative active material calculated as grams of lead. It is preferably in the range 0.10 to 0.60 especially 0.11 to 0.55 e.g. 0.20 to 0.50.
• the ratio of negative to positive active material on the basis of the weight of active material calculated as lead may be in the range 0.5:1 to 1.5:1 e.g. 0.6:1 to 1.4:1.
• ratios below 1:1 is contrary to what is conventional in recombinant batteries but we find that recombinant operation can be achieved at these ratios and they have the advantage of providing more posi ti ve active material for the same cell volume.
• the separator material is a compressible absorbent fibrous material having an electrolyte absorption ratio of at least 100 ⁇ e.g. 100 to 200& especially 110 to 170%. It is electrically non conducting and electrolyte-resistant.
• Electrolyte absorption ratio is the ratio, as a percentage, of the volume of electrolyte absorbed by the wetted portion of the separator material to the dry volume of that portion of the separator material which is wetted, when a strip of the dry separator material is suspended vertically above a body of aqueous sulphuric acid electrolyte of 1.270 SG containing 0.01% by weight sodium lauryl sulphonate with 1 cm of the lower end of the strip immersed in the electrolyte after a steady state wicking condition has been reached at 20oC at a relative humidity of less than 50%.
• the thickness of the separator material is measured with a micrometer at a loading of 10 kilopascals (1.45 psi) and a foot area of 200 square millimetres (in accordance with the method of British standard specification No. 3983).
• the dry volume of the test sample is measured by multiplying the width and length of the sample by its thickness measured as described.
• the separator material should have a wicking height of at least 5 cms on the above test, namely that the electrolyte should have risen to a height of at least 5 cms above the surface of the electrolyte into which the strip of separator material dips when the steady state condition has been reached, so that good electrolyte distribution is achieved in each cell.
• fibrous blotting paper-like materials made from fibres having diameters in the range 0.01 microns or less up to 10 microns, the average of the diameters of the fibres being less than 10 microns, and preferably less than 5 microns
• the weight to fibre density ratio namely the ratio of the weight of the fibrous material in grams/ square metre to the density in grams/cubic centimetre of the material from which the individual fibres are made preferably being at least 20 preferably at least 30 and especially at least 50.
• the higher electrochemical efficiency of the negative active material enables the negative electrode to effect recombination of the oxygen produced by the positive electrode even at the beginning of the charge cycle. Thus it may not be necessary to have an excess weight of negative active material compared to the positive active material. However recombinant operation of the battery may be facilitated by the use of a number of features in combination.
• one desirably provides that, under the charge and discharge conditions, under which the battery is designed to operate, the capacity of the negative electrodes in each cell will normally be in excess of that of the positive electrodes.
• the electrochemical efficiency of the negative electrodes is in general greater than that of the positive electrodes but it must be born in mind that the efficiency of the negative electrodes drops more rapidly than that of the positive electrodes both as the cells undergo increasing numbers of cycles of charge and discharge and as the temperature of operation is reduced below ambient (i.e. 25oC). Excess negative capacity may thus conveniently be ensured by providing an excess of negative active material (calculated as lead) compared to the positive active material in each cell.
• one provides a restricted amount of electrolyte as defined above and thirdly one provides a separator, desirably having a high electrolyte absorption ratio as also described and defined above, which is compressible, so as to conform closely to the surfaces of the electrodes, and which has wicking or capillary activity, whereby transmission of electrolyte and electrolytic conduction between the electrodes is facilitated and preserved independent of the orientation of the cell, whilst gas transmission through the open spaces in the separator is maintained so that adequate and rapid gas transmission between the electrodes is also ensured.
• a separator desirably having a high electrolyte absorption ratio as also described and defined above, which is compressible, so as to conform closely to the surfaces of the electrodes, and which has wicking or capillary activity, whereby transmission of electrolyte and electrolytic conduction between the electrodes is facilitated and preserved independent of the orientation of the cell, whilst gas transmission through the open spaces in the separator is maintained so that adequate and rapid gas transmission between the electrodes is also ensure
• the amount of electrolyte added is not highly critical since it is observed that if a slight excess of electrolyte is added above that required to saturate the porosity of the cell components the recombination mechanism is suppressed and electrolyte is lost by electrolysis until the electrolyte volume has reached the correct amount for the cell in question, i.e. the cell porosity has reached the correct degree of unsaturation, when the recombination mechanism comes into operation again and a steady state recombination condition related to the rate of charging which is used is established.
• the pack of battery elements is preferably located in a container with a lid sealed thereto and if desired end plates of electrolyte resistant polymer material may be located over the ends of the pack.
• the pack of battery elements, and the container if used, is desirably provided with gas venting means in the form of a pressure relief valve so that air cannot obtain access to the interior of the battery although excess gas generated therein can escape to atmosphere.
• the perimeter strips of the battery elements which will be juxtaposed to the lid or form the upper surface of the battery in use may be formed with filling apertures to permit electrolyte to be introduced into each cell.
• the electrolyte may be added by immersing the battery in a bath of electrolyte, evacuating it and optionally then transferring the saturated cells to the container.
• the cells may be located in the container in the dry state, the lid sealed on, the cells evacuated and the electrolyte injected into the cells preferably in an amount of (X+Y) or 1.1 (X+Y) to 1.2 (X+Y) or 1.5 (X+Y).
• the electrodes may be separate rectilinear plates e.g. cast grids, or cast or rolled sheets, slit and expanded to make expanded mesh grids or cast or rolled sheets punched to produce perforated grids.
• Figure 1 is a plan view of two frames for use in the battery
• Figure 2 is an underneath plan view of the two frames shown in Figure 1, showing an end grid element and a bipolar grid element in position;
• Figure 3 is an electron scanning photomicrograph of a preferred separator material at 1000 fold magnification
• Figure 4 is a view similar to Figure 7 at 4000 fold magnification
• Figure 5 is a transverse section through a battery in accordance with the invention showing all the frames, electrodes and separators of one cell.
• the battery is made from a number of frames, which in accordance with a preferred aspect of the present invention are formed in pairs as a one piece injection moulding of polypropylene connected by an integral hinge 10.
• Each frame is of rectangular shape having an outer perimeter member 12 defining a space which is spanned by five equispaced cell element defining strips 14 parallel to two of the sides of the perimeter member.
• the perimeter member and cell element defining strips together define six equally sized rectangular cell elements or active material support spaces.
• Each frame has external dimensions of about 250 mm by 200 and is 5 mm thick, whilst the perimeter member is about 7 mm wide and the cell element defining strips are 6 mm wide.
• the lower frame of the pair has in each of the two outer and the central cell element defining strips 14 a pair of connector recesses 16, each adjacent the perimeter member extending across the full width of the strips 14 and having an overall length of about 13 mm.
• Each connector recess comprises a relatively deep central groove 18 on either side of which is a somewhat shallower recess 20 whose length is about 10 mm.
• the upper frame as seen in Figure 1, has elongate recesses 22 communicating with the exterior of the perimeter member formed in its cell element defining strips in positions such that a recess 22 overlies each of the connector recesses 16, when the surfaces of the two frames seen in Figure 1 are placed in contact.
• Figure 2 shows the rear surface of the two frames of Figure 1, and as may be seen, that frame which has on one surface connector recesses 16 has on its other surface elongate recesses 22 and vice versa.
• the connector recesses and the elongate recesses are formed in strips 14 that are laterally offset from one another.
• Figure 2 whose shape corresponds to that of two active material support spaces, whose two halves are connected by two connector portions 28 whose size and position corresponds to that of the connector recesses, the two halves of the bipolar grids carrying positive and negative active material respectively.
• a battery is made up as follows: three bipolar electrode grids are placed on the lower frame seen in Figure 1, such that their connector portions are received in the connector recesses 16, and the polarity of the grids alternate across the width of the frame. The depth of the connector recess and the thickness of the electrode grids are such that the grids lie wholly within the space defined by the frame. A separate strip 27 of microfine glass fibre separator material of the type described above is then laid over each active material support space such that the surface of the perimeter member and the division elements are at the most only partially covered by the edges of the strips of separator material. The visible surfaces of the two frames shown in Figure 1 are then connected together, for instance by hotplate welding, retaining the electrode grids and separators between the two frames. If one imagines that the upper frame in Figure 1 is placed on the lower frame, the upper surface of the two frame stack will look like the upper frame shown in Figure 2.
• connector recesses are formed in the cell element defining strips of this surface of this frame in the other surface of which elongate recesses are not formed.
• Electrode grids are now placed in the active material support areas of this frame, but in this case a unipolar grid is placed in each of the two outer support areas, and two bipolar grids in the remaining four central areas. The polarity of these grids is again arranged to alternate across the width of the frame, and also to be of reverse polarity to the electrode grids of the adjacent frame to which they are opposed.
• Six strips of separator material are then placed over the electrode grids and a further frame is then secured to the stack. It will be appreciated that the lower surface of the further frame will look like the visible surface of the lower frame in Figure 2, and that its upper surface will be that of the lower frame in Figure 1.
• the process is now continued until a battery of the desired capacity is formed.
• the finished stack of frames has a top, bottom and two end walls, and two side walls may be provided by securing, e.g. welding, a plastics sheet to each of the sides of the stack.
• an outer container for the battery is not strictly necessary but is desirable to ensure that the plate assemblies are held pressed tightly together since this facilitates operation in a gas recombinant mode.
• Such a container 29 is shown in Figure 5, sealed by a lid 31.
• a sealant such as epoxy resin is injected into each recess 22. This passes down around the connectors 28 and fills the grooves 18, thus completely sealing adjacent cells from each other.
• Terminal connections are of course required for the battery, and for this purpose every alternate frame is provided with a connector recess 30 in each limb of the perimeter member parallel to the cell element defining strips in that surface in which the connector recesses are formed.
• Those electrode grids which are placed in the support areas adjacent the connector recesses are provided with a terminal projection 32 extending in the plane of the grids which is received in the recess 30 and passes out of the battery.
• the terminal projections may be sealed in the terminal recesses, for instance by means of epoxy resin, and are connected together by an external terminal strap to form a battery terminal.
• the separator material is highly absorbent blotting paper-like short staple fibre glass matting about 1 mm thick. As seen in. Figures 7 and 8 there are fibres 61 as thin as 0.2 microns and fibres 60 as thick as 2 microns in diameter, the average diameter of the fibres being about 0.5 microns.
• the material whilst highly absorbent still has a very large amount of open space between the individual fibres.
• the material when tested for its wicking and electrolyte absorption capabilities as described above absorbs electrolyte so that the liquid has wicked up to a height of 20 cms after 2 hours and this is the steady state condition. This 20 cms of material absorbs 113% of its own dry volume of electrolyte, and this is its electrolyte absorption ratio.
• the separator material weighs 200 grams/square metre and has a porosity of 90-95% as measured by mercury intrusion penetrometry. The density of the glass from which the fibres of the separator are made is 2.69 gr/cc the weight to fibre density ratio is thus 74.
• the battery is of "recombinant" type.
• the separators should be under a certain compressive pressure to assure that their capillarity or wicking action is brought into play whereby adequate supply of electrolyte is provided to the entire surface of the active material carried by the electrode grids.
• the battery should be designed to operate at superatmospheric pressure. The battery is therefore preferably filled with the appropriate amount of electrolyte at the time of manufacture, through a hole 33 in each cell which may either be formed in one of the frames, or which may be subsequently formed, for instance by drilling.
• Each cell is then fitted with a safety vent 35, designed to vent the cell at a pressure in excess of 1 bar, either in the filling hole, or in a separate hole.
• the safety vent is intended during normal operation of the battery not to function, but merely to act as a relief valve if the rate of evolution of gas should be greater than the maximum possible rate of recombination.
• the fact that the intercell connectors, constituted by the connector portions 28, extend over a minor proportion of the length of the cell element defining strips means that the maximum area available for intercell leakage currents is relatively small.
• the battery is of reduced electrolyte, "recombinant" type means that the electrolyte rarely if ever need be topped up, and that there is a reduced (or even zero) amount of free electrolyte available for the conduction of intercell leakage currents.
• the frames have been shown as formed in integral pairs, which construction slightly reduces the amount of welding required and means that only one mould is required instead of two moulds of different construction the frames may be formed as quite separate units. Instead of being connected by a heat-welded butt joint the frames may be connected by any suitable means, such as adhesive.
• One suitable universal paste composition comprises:
• Vanisperse CB (a lignosulphonate material)
• Batteries in. accordance with the invention find application in all those areas. where batteries are conventionally used. They may however be particuarly advantageous in those applications where their facility to be substantially maintenance-free and spill-resistant is required.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Cell Separators (AREA)
• Secondary Cells (AREA)
• Hybrid Cells (AREA)

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• 1980
  • 1980-05-08 IN IN545/CAL/80A patent/IN152648B/en unknown
  • 1980-05-08 WO PCT/GB1980/000083 patent/WO1980002473A1/en unknown
  • 1980-05-09 ES ES491332A patent/ES8104647A1/es not_active Expired
  • 1980-11-17 EP EP80900779A patent/EP0028227A1/de not_active Withdrawn

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