IL26126A - Sealed rechargeable battery cell - Google Patents

Description

SEALED RECHARGEABLE BATTERY CELL This invention relates to sealed rechargeable batteries operating with alkaline electrolyte and developing excess internal gas pressure during the invention relates to such nickel cadmium although in its broad aspects the invention is of in other types of rechargeable practical lifications of the invention will be described in connection with sealed nickel cadmium battery As protection against damage by rupture of the cell casing under developed excessive internal gas nickel cadmium cells have been sealed with a flexible which is punctured or ruptured under predetermined excessive internal pressure by an overlying casing pro ectio Once the thin diaphragm of such sealed cell is ruptured by internal gas each quent charging operation converts some of the cell electrolyte into vapor or of which escapes through the ruptured diaphragm into the exterior Such increasing loss of electrolyte by successive charging operations and also by evaporation in standby condition gradually reduces the charging capacity of the cell until it has to be discarded and replaced by a new Among the the invention are sealed rechargeable of foregoing type which will suppress loss of cell electrolyte after rupture of its protective diaphragm by excessive internal In accordance with the the casing part of such cell adjoining the exterior surface with its rupturable diaphragm is provided with a vent opening which is positively sealed escape of gas or vapor prevents their escape through the Ruptured diaphragm to the exterior The foregoing and other objects the invention will be best understood from the following description and exemplifications thereof by reference to the drawings wherein 1 is a vertical and partially diagrammatic view of one example of a sealed cell of the and are views similar to showing modified arrangements for a sealed cell of the type shown in is a top view of the cell seen in 3 is a vertical view similar to 1 of a modified form of valve arrangement for a cell of the and 4 is a view similar to 1 of another form of rechargeable cell exemplifying the Although the invention is applicable to other type of sealed rechargeable battery it has been evolved and is of special value in connection with sealed rechargeable cells of the nickel cadmium the principles of the invention will herein described in connection with nickel cadmium battery Most rechargeable sealed battery cells are made with sintered electrode plates containing in their pores the respective active electrode such sealed cells may also operate with In all rechargeable the positive electrode mass consists of nickel hydroxide which when full charged is converted into nickel hydroxide having nickel in a higher oxidation The discharged negative electrode mass of such consists of hydroxide which when fully charged is converted into metallic The negative electrode of should have more capacity than the positive for causing all oxygen developed during charging to be absorbed by the negative The principles of the invention are of value not only sealed nickel cadmium battery cells operating with an electrode assembly the pores of which are not fully filled with but also to a sealed cell of the invention having an electrode assembly all pores and spaces of which are filled and saturated with electrolyte and held in engagement with or fitting within the surrounding cell casing quality of a sealed nickel cadmium eable cell is determined by its ability to be repeatedly charged and to retain the same charge and charge characteristics for a lon useful in a great many charge and discharge With normal quality controls applied to the manufacture of sealed nickel cadmium some of the may develop excess internal while being Such excessive pressure developed in the sealed cell may cause bulgin of the strong metallic and may also cause dangerous bursting of the cell meet this such sealed cells been provided with a puncturable thin metallic once the puncturable of such sealed cell is subsequent charging operations will conver some of the cell content into vapor or gas part of which escapes the ruptured diaphragm into the exterior As a a cell with a ruptured sealing diaphragm keeps losing electrolyte in ssive charging Such loss of electrolyte the charging capacity of the cell until it becomes useless or althoug its electrode assembly retains its full usefulness for a long period except for the lack of In accordance with the the casin part of a sealed cadmium adjoining the exterior surface of its puncturable o rupturable diaphragm is provided a vent openin which is normally closed and keeps sealed the interior of the cell casing and prevents escape of electrolyte vapor gases even if its thin rupturable diaphragm has been broken by excessive internal gas The normally closed vent opening is arranged to permit its valve means to open the gas only in response to the internal gas pressure reaching a predetermined raised level beyond which the casing would be bulging or cause to burst the 1 and 2 show one form of a sealed rechargeable battery cell exemplifying the It comprises an electrode assembly 13 which may consist of one or more pairs of superposed positive electrode plates and negative electrode plates with an interposed porous insulating separator The electrode assembly has its pores impregnated with alkaline The cell show has only one pair of superposed electrode plates with an interposed separator 16 coiled along a common central axis 12 into an electrode assembly 13 fitting or engaging with its surface surroundin tubular casing The tubular casing 21 has a bottom wall 22 and an upper open end surrounded by a generally tubular casin junction region Within the casing junction region 23 is held a metallic cover wall 31 having a rim 32 which is joined by an electrically insulating seal 24 to the surrounding casing junction region The insulating seal 24 is shown formed by a relatively thick collar 24 of insulating for a which is held compressed by the surrounding casing junction 23 against the adjoining edge and opposite rim surfaces o rim The casing junction 23 has an inward casing shoulder 25 and an casing edge region 26 which compress the overlapping side walls of insulating 24 against the opposite surfaces of cover rim 32 provide a insulating seal between The casing 21 and cover wall 31 are formed of strong metal such as rolled steel sheet material coated with an coating such as a thin nickel A thin rupturable metallic diaphragm extends and overlaps the entire inwardly facing surface of wall 31 and also its rim 3 The rupturable diaphragm 36 has a region 37 overlapping and surrounding the edge and adjoining rim surfaces of cover Mm so when the plastic insulating collar of is compressed by the junction region 23 the overlapping rim portions 37 of the thin gas diaphragm will be tightly clamped against the embraced edge and rim surfaces of cover rim 32 positively establish and maintain gas tight insulating seal between the cover rim and the surrounding casing junction region 23 and their interposed plastic nsulating collar The central portion of cover 31 has an inwardly extending metallic of for pointed end held immediately adjacent underlyin portio of flexible diaphragm so that it is when it is flexed upwardly by excessive internal casing gas or releasing the excess pressure In the form puncture projection 34 has mounting tail portion whic is as by electric to overlying metal cover All pores and spaces of the electrode assembly 13 ma be impregnated with As one good results are obtained with a thi rupturable diaphragm 36 a s metal such as nickel or plated For in the of having dimensions of a good results are with a steel cover 31 of inch thickness and rupturable thin diaphragm 32 of inch coiled electrode assembly may wrapped in a insulating material which insulates it from surrounding metallic casing The positive and negative cell electrode plates and connected by flexible metallic connector tabs to exposed metallic casin terminals electrode tab 17 from the positive electrode 14 passes through a slit in an upper of metal cover 31 and its overlapping rupturable metal diaphragm The negative electrode tab 18 passes through a slit of a similar bottom insulating sheet and its tab end is joined by electrode welds to underlying central portion of metallic casing bottom The electrode assembly 13 has an axially extending central passage of sufficient width to permit insertion through its upper open of elongated weldin electrode agains bottom casing wall for the welds In accordance with the to protect rechargeable cell of the type described above against continuous progressive deterioration through loss of electrolyte after diaphragm rupture by excessive internal pressure the cell casing is provided with a closed vent which normally prevents escape of gas or vapor through the ruptured but permits escape of gases in to a predetermined rise of internal gas for above 180 psi per square shows one cell exemplifying the The intermediate or central portion of cover wall 31 has a ven opening 43 bounded by rim The vent opening 43 is normally closed by valve member which is held pressed against the ven opening rim 44 by an overlying metallic terminal wall In the form the valve member 46 is formed a elasticaliy yieldable organic polyme body which corrosion by alkaline electrolyte of such As they include such as neoprene butyl rubber and alkaline resistant fluorocarbon such as poly as copolymers of tetrafluoroethylene and hexafluoropropylene as and resistant polymera in the Modern Plastic 1963 iaaue and subsequent In anothe the valve member may formed of a spherical member or ball metal or a alkali resistant strong plastic body of fluorocarbon for The intermediate wall portion of casing terminal wall constitutes a compressing beam which is separated by two longitudinal slits the side wall regions thereof for enabling independent shaping and elastically deforming this terminal beam 47 to apply predetermined sealing forces compress the valve member with a predetermined sealing agains the engaged sealin surface of vent opening rim 44 cell casing vent wall elastically deformed casing wall portion 47 engaging the valve 46 has a central inwardly deformed wall region and is properly chosen and dimensioned in order to cause its elastic deformation to provide the predetermined pressure forces with which compresses the movable valve against the sealing surface of vent opening rim The terminal is metallically connected to positive cell terminal tab terminal is established through the electric connections between metallic terminal wall rim 48 and the underlying metallic cover rim of which is connected by electric weld the underlying tab end of positive cell tab A thin coating of plastic or resinous material may be applied to the surface of vent opening rim 44 is in pressure sealing with valve ball 46 deforming such plastic coating of vent 45 by th applied sealing pressure of valve ball 46 and establish a sealing engagement For good results obtained by coating the sealing surfaces of the vent opening rim 44 with an adhering thin layer resistant plastic such as the above identified fluorocarbon Other resistant resins may be used fo such adhering plastic sealing for the heat resistant special also such vinylchloride and polymers for in Modern Plastic and 1964 shows another form vent valve arrangement for such A vent cover wall has a similar vent opening with a vent rim The upper end of vent has an inwardly tapering surface shaped for engagement with a valve ball which is pressed into sealing engagement therewith by terminal wall which is otherwise similar to terminal wall 47 of 1 and Such a hermetic seal is cribed in the MSA TECH published information obtainable from Technology Utilization Propulsion 4800 Oak Grove Reference shows a modification of the Valve arrangemen of wherein the uppe rim surface has secured thereto a thin layer of resisting such as the fluorocarbon and other resins identified If while charging the cell of and 2 of excessive internal pressure a predetermined level is developed within the cell instance exceeding 180 its thin metal diaphragm 35 deflected and ruptured by overlying cover tooth so diaphragm permits excess gases to escape in the space underlyin metallic cover with its closed vent opening If the excess internal pressure remains above the predetermined maximum for example above 180 the compressed gases lift the valve member from its sealing engagement with the vent opening rim 44 and permit the excess pressure to escape into the exterior through the ven slits of the outer metallic terminal wall After escape of the excess pressure reduces the internal pressure to a predetermined for example 180 the elastic restoring forces of the metallic terminal wall 47 retur and compress the valve with the predetermined pressure forces into sealing engagement with the vent opening rim 44 condition of the vent wall opening gases developed in the cell casing 21 will be to pass into the space the ruptured metal diaphragm 36 underlying the vent cover wall l and its sealed vent openin I in a subsequent charging operation a predetermined excess internal gas pressure is example above 180 they will again wall member 46 from its sealing from its vent opening rim 44 for releasing excess pressure The valve member will return to the sealed condition when the internal gas pressure has been lowered to the predetermined upper 3 another example of a sealed cell of invention having rupturable diaphragm combined with a cove having a normally closed vent valve which releases predetermined excess internal gas pressure after rupture of its cell has an electrode assembly which may be identical to that of held within a sealed caeing having a tubular metallic casing 21 with a similar casing junction 23 at its open A wall 51 with a similar intermediate or central vent opening has a puncture tooth The cover wall 51 with its rim 52 are overlapped in a similar way by a similar rupturable 61 its diaphragm rim An insulating collar 57 to insulating collar 24 o is held compressed by the surrounding casing junction wall 23 against the edge and opposite rim surfaces of cover wall rim 52 and the overlappin diaphragm portions 37 of its rapturable diaphragm The cover wall vent opening 53 is normally material as fche fluorocarbon resin for described The surface rim 62 of the plastic sealing sheet 61 is affixed to the facing cover wall rim Except for its flat rim the major area of the metallic cover 51 is deformed into an upwardl facin convex structure holding radially stretched thereon the overlying main region of its resin sealing shee The intermediate or central portion of the sealing sheet 61 is held stretched in tight sealin engagement with the underlying main convex surface of metal cover 51 surrounding its central vent opening Radially spaced from the intermediate or central portion of sealing sheet overlying the cover vent opening radially stretched resin cover shee has one or a plurality of arcuately spaced vent openings which are held sealed by the underlying portions of metal 51 against which plasti sealing sheet 61 is held in stretched sealing engagement The combination of the convexed shaped vented metallic cover wall 51 with its complementary stretched plastic sealing sheet 61 secured to the metal cover rim 52 is while the entire area of the metal cover 51 and the plastic sealing Sheet 61 and their rims 62 are still in flat planar This makes it possible to affix the rim 62 of the still unstretched plastic 61 to the underlying of metal cover rim 52 while they are both in flat After so affixing the unstretched plastic sheet rim 62 to metal cover and plastic sheet assembly are subjected to the deforming operation in which their main central region is deformed outwardly into the convex shape in Pigv 3 in which the overlying plastic sealing sheet 61 is radially elastically stretched for establishing tight and positive sealing engagement thereof with the central metal cover vent opening 53 and for also sealing the radially displaced plastic sheet vent openings 63 of plastic sealing sheet 61 the underlying solid surface of convex metal cover wall The rupture tooth 54 and its vent opening 53 are in a metal 51 while still in the flat conditio and before the plastic sheet rim 62 has been affixed to metal cover rim In the cell of the rim 37 of the rupturable metal diaphragm 36 overlaps the side edges of both the metallic wall rim 52 and the plastic rim 62 of the etretchable sheet However the rupturable diaphragm 37 may overlap only the surface of the metallic cover rim 52 as in the cell of 1 and An outer strong metallic terminal wall 67 has a main central region raised above its rim 68 which is coextensive with and overlies and is compressed against the underlying overlapping rims 52 and 62 of the inner metallic cover wall 51 and the overlapping stretched sealing sheet 61 which keeps the underlying cell space sealed under normal operating A thick insulating collar 57 of suitable such as is held compressed in sealing engagement with the overlapped edge surfaces of the inner metallic cover rim 52 and its affixed plastic sheet rim 62 and also against the adjoining surfaces of the superposed metallic cover rim sheet rim 62 and terminal wall rim 68 to provide between them insulating seals with the surrounding casing region The raised portion of metallic terminal wall 67 has or a plurality of vent openings 69 for passing excess pressure gases pelled from the casing interior through the opened vent opening Insulating collar 57 may have integrally therewith the upper insulating separator layer or sheet 64 corresponding to the upper insulating sheet 19 of the cell of the of 3 may be identical with that of and If during charging predetermined excess internal for example 180 develops in the cell of the rupturable diaphragm 36 will be wardly deformed and ruptured by overlying cover tooth 54 for discharging the excess pressure gases into underlying If the internal gas pressure remains above the predetermined upper for example above 180 the compressed gases acting through metallic cover vent opening 53 on the overlying sealing portion of stretched sealing sheet 61 and the central portion of ing sheet 61 will lifted from its sealing engagement with the cover wall vent opening 53 also open its normally sealed vent openings and cause the compressed gases to escape throug into the overlying space fromWhich the escape through ent openings 69 of outer metallic terminal wall Although fluorocarbon resin bodies are known for their unique selected areas of such fluorocarbon bodied may treated along their junction surfaces for securing strong cemented junctions between such treated fluorocarbon body junction as with epoxy to metallic o other structures to which they are to be Such treatments of junction surfaces of fluorocarbon bodies and the affixing their so treated surfaces to surfaces of metallic ceramic and plastic structures is well know in the Reference is to the following publications describing bonding of carbon bodies to structural materials ADHESIVE August article of Bonding Fluorocarbon Plastic to Structural by PRODUCT September article High A New by An example of a process for affixing the surface of the rim 62 of a polytetrafluoroethylene plastic sheet 61 to the facing metal cover rim 52 will now circular fluorocarbon sheet 61 has its exposed surfaces except its bonded paraffin coating The so differentially coated sheet 61 or at least its uncoated Mm exposed for two minutes to etching or treatment with a dispersion of sodium naphthalene available the trade name which dispersion is slightly agitated during the the etching the plastic sheet is immersed in fresh water for thirty seconds followed by rinsing with hot running wate for three The so treated and rinsed plastic sheet is then rinsed with d enatured alcohol followed by drying and removing the paraffins Thereafter the treated sheet 61 is placed cover 51 with the treated sheet rim surface 62 facing the cover rim and the two aligned facing rim surfaces are affixed or o each other with an epoxy Suitable resistant for forming bonds are described in by Lee and Copyrigh 1957 by Hill Company and by 1958 by Reinhold Publishing Table of the book gives data on epoxy resin Also in Modern issue of pages and the references given 4 shows a sealed cell which is similar to of 3 except for the modifications described The electrode assembly the tubular casing 21 with its casing junction metallic cover wall 71 with its metallic cover its flexible diaphragm outer identical with or similar to corresponding elements of wall 71 has a vent opening and a puncture tooth 74 identical with elements 53 and 54 of A plastic sealing shee 81 the same characteristics as sheet 61 of Fi has an upper rim section 82 and a lower sheet section 83 overlying the opposite rim surfaces of cover rim 72 and also its coyer Both plastic sheet rim sections 82 and 83 or only the lower sheet rim section 83 are affixed in the same way to facing surface of cover rim The plastic sheet overlapped metal cover rim 72 has a plurality of arcuately distributed openings the overlapping plastic sections 82 and 83 are also affixed to each other by plastic portions compressed into positioned in and filling these cover openings Alternatively the metal rim 72 may be coextensive with the rim 68 of the outer terminal wall and both the upper and lower plastic rim sections 82 and 83 are secured to each other and to the upper and lower rim surface of cover by the plastic junctions filling the openings of the cover wall rim 72 and also with cement to opposite overlying metal rim surfaces The flexible diaphragm 36 overlaps with its rim 37 the two plastic rim sections 83 and the metal cover rim 72 held The metal cover 71 has a downwardly displaced wall portion which the end of the positive electrode tab 17 is affixed by electric welds as in the cell of 2 or insufficientOCRQuality

Claims (1)

The principles underlying the inventio described in connection with specific exemplifications ill suggest other modifications and applications thereof. It is accordingly desired that the appended claims shall not be limited to specific examples shown or described herein, HAVING NO particularly described and ascertained' the nature of a¾r said invention and in wha manner the same is to be performed, we declare that what we claim is :- t ,

1. In a sealed rechargeable batter cell : an electrode assembly of at least two opposite - polarity electrodes and associated electrolyte which develop gas pressure when charged, a sealed enclosure comprising a strong tubula metallic casing and a strong cover wall enclosing said assembly and connected to said two electrodes, respectively, said cover wall haviftg a vent opening and an inwardl projecting pointed tooth and a peripheral cover rim affixed with a gas-tight insulating seal to the surrounding tubular casing junction region near the open tubular casing end, a thin flexible metallic diaphragm overlapping the entire interior surface and the rim edge of said cover wall for flexure against and being punctured . by said tooth by gas pressure within said enclosure, a continuous plastic insulating collar surrounding said- cover rim and havin inner and outer collar flanges overlapping the rim edge and adjoining interior and exterior radial rim areas of said cover rim and also the rim of said diaphragm overlapping said cover wall rimfi a movable valve body in gas-tight sealing engagement with vent wall portions of aaid, vent, wall defining said vent opening, . and pressure means for holding said,valve body with predetermined pressure in said tight sealing engagement with said vent opening wall portion* . said pressure means being responsive to predetermined internal {fas pressure on said valve body for releasing said valve body from said sealing engagement and releasing internal gases through said valve opening. 2> In a sealed rechargeable battery cell an electrode assembly of at least two opposite-polarity electrodes and associated electrolyte which develop gas pressure when charged, a sealed enclosure comprising a strong tubular metallic casing and a strong cover wall enclosin said assembly and connected to said two electrodes, respectively* said cover wall havin a vent opening, an inwardly projecting pointed tooth and a peripheral cover rim. affixed with a gas-tight insulating seal to the surrounding tubular casing junction region near the open 0 22 tubular casing end, a continuous plastic insulating collar surrounding said cover rim and having inner and outer collar flanges overlapping the rim edge and adjoining interior and exterior radial rim areas of said cover rim, a thin flexible metallic diaphragm overlapping the entire interior surface and the rim edge and rim surfaces of said cover wall for flexure agains and being punctured b said tooth by gas pressures within said enclosure, an adjoining strong outer metallic vent wall overlapping the outer side and rim of said cover wall and having a vent opening for discharging gases discharged from the casing interior upon rupture of said diaphragm, a movable valve body in gas-tight sealing engagement with vent wall portions of said vent wall defining said vent opening, and means for holding said valve body with predetermined pressure in said tight sealing engagement with said vent openin wall portion and responsive to predetermined excessive internal gas pressure for breaking its sealing engagement and releasing excess pressure gases through said vent opening.