FR2569904A1 - METHOD FOR THE DETECTION OF LEAKS FROM NON-AQUEOUS ELECTROCHEMICAL CELLS - Google Patents

Abstract

PROCESS FOR THE DETECTION OF LEAKS FROM NON-AQUEOUS ELECTROLYTE ELECTROLYTE BATTERIES AND ALKALINE OR ALKALINO-EARTH ANODES. THE SUBSTANCES LEAKING FROM THESE BATTERIES FORM ACIDS WHEN THEY COME IN CONTACT WITH THE ATMOSPHERE AND THESE ACIDS ARE DETECTED BY APPLICATION TO THE SURFACE OF THE BATTERIES OF A COATING CONTAINING AN ACID-BASED INDICATOR IN AN APPROPRIATE CARRYING MATERIAL, PREFERREDLY. AN ADHESIVE.

Description

2 5 G t} (tO_} The present invention relates to a detection method

  leakage of an electrolyte from batteries or

  sealed electrolyte containers, which form acids

  contact with atmospheric humidity, the acid being detected by means of an acid-base indicator; the invention also relates to electrochemical cells obtained

by this process.

  Electrochemical cells, in which alkali / alkaline earth metals serve as an anode and which contain non-aqueous electrolytes additionally used

  of cathodic depolarizing, are taking more and more

  load-bearing capacity as primary cells and batteries

  industrial, military and consumer goods. These batteries provide high energy density, a wide operating temperature range and long service and storage life of up to 10 years. The long service and storage life necessitates hermetic manufacture of the batteries, generally with the use of a glass / metal seal to ensure insulation between the positive and negative terminals, and a hermetic seal of the cover to the case by appropriate means. such as laser, plasma welding or tungsten welding under inert atmosphere (TIG). Loss of battery electrolyte can shorten their service life, cause products

  corrosives such as sulfur dioxide, chlorine and chlorine acid

  in contact with atmospheric humidity, and create

  unsafe conditions in certain types of batteries.

  Indicators have already been used, with certain electrochemical systems and in particular in systems comprising an aqueous electrolyte, to prevent the electrolyte from leaking from a sealed cell. US Patent No. 4,222,745 describes a method for detecting anhydride leaks

  sulfurous in stacks, using potassium dichromate-

  sium absorbed on finely divided and mixed silica

with a polymer type adhesive.

  The subject of the present invention is a simple method and a simple device for detecting electrolyte leakage from cells or batteries, the

  leakage component reacts with atmospheric humidity

  to produce acidic compounds. The present invention also relates to

  a composition comprising a mixture of an acid indicator

  base or a mixture of indicators dissolved in a suitable adhesive material. The acid-base indicators change color in the presence of acid. The color change can take place in the visible wavelength region or in the ultraviolet region. A partial list of acid-base indicators, and the pH at which the change takes place

  colored, can be found in: "Text Book of Quantita-

  tive Inorganic Analysis ", A.I. Vogel, Longmans, England

3rd Edition - 1961, page 51.

  The adhesive material usually includes a

  organic binder, pigments (sometimes deleted) and a li-

  that carrier (sometimes deleted). The binder is a polymer

  of high molecular weight which may or may not be crosslinked.

  The pigments, which can be organic or inorganic, contribute mainly to the opacity, the color, the adhesion and in particular to the rheological properties of the coating in the fluid form. After application of a regular coating, the carrier liquid is removed, generally by heating or evaporation. We trigger

  then polymerization by heat, atmospheric oxygen

  spherical, water vapor or exposure to an electron beam or ultraviolet radiation, depending on the

binder.

  The adhesive materials are preferably cured

  at room temperature by exposure to atmospheric humidity

  or they can be hardened while hot. These ma-

  adhesive adhesives may initially be transparent, translucent or contain colored pigments, so as to

  create a color contrast between the color of the indicator

  tor and the object to which they are applied. The adhesive can be in the form of a paste, a glue lacquer,

  a cement or a resin of natural or synthetic origin

  tick. Natural adhesives include

  example of lacquers, such as the original shellac

  male, and resins, such as gum arabic of vegetable origin. Synthetic adhesives are represented by thermoplastic lacquers (air-dried thermoplastic), as copolymers of vinyl chloride and acetate.

  vinyl, acrylates, chlorinated rubber, polyamides, copoly-

  vinyl chloride or vinylidene and acrylonitrile

  trile, vinyl acetate nylon, cellulose esters, poly-

  esters and others. Synthetic adhesives can be

  represented by thermosetting substances, such as epo-

  xy, polyamides and others, and by silicones. We can

  find a partial list of synthetic resins used

  for coating, in the work entitled "Encyclo-

  Chemical Technology Pedal ", by Kirk- Othmer, 3rd

  edition, Volume 6, pages 428 and 459-462.

  The adhesive material can be used to protect

  manage an area susceptible to corrosion, for example

  hard, by forming a resistant surface film.

  In the preparation of the composition according to the

  vention, the indicator may be dissolved in an or-

  ganique of which one uses a quantity just sufficient to dissolve the indicator. In addition, the organic solvent must

  dissolve the adhesive polymer, without affecting its properties.

  The mixture of the indicator and the organic solvent is added.

  tee stirring with adhesive polymer. The restless period

  tion can vary from 0.5 to 10 hours to obtain a mixture

  homogeneous, depending on the viscosity of the adhesive polymer. The quan-

  tity of indicator generally ranges from about 0.1 to 400 parts by weight of indicator per 10,000 parts by weight

of adhesive polymer.

  The term "precursewr" used here designates a compound which, when it comes into contact with the humidity of the ambient air, generates an acid, for example acid

hydrochloric or other.

  The invention is illustrated with reference to certain acid base indicators. It is understood that we can

  use, in place of these indicators, any other com-

  posed which changes color when it comes into contact with an acidic substance. This color change can be

  bleaching or any other effect.

  The term "adhesive" designates any composition which

  can be used as a matrix for the substance undergone

  color change and which can be applied to the surface of an electrochemical cell, or to part of

  this, to form a coating that adheres well to the surface

  face, Leak detection of electrochemical cells

  non-aqueous is described below, The mixture, prepared com-

  describes me above, is applied appropriately on the battery or cell box, in places where there is a risk of it happening, for example near the soldering of the battery cover, at the electrolyte filling hole,

  on glass / metal seals and on safety vents.

  Acids such as hydrochloric acid, hydrobromic acid,

  sulfuric acid, sulfurous acid, nitric acid, ni- acid

  treuç and others, caused by a leak of battery precursor coming into contact with atmospheric humidity, cause a change in color of the indicator. As

  typical precursors in the stack include sub-

  stanzas such as thionyl chloride (SOC12), chloride

  phosphoryl (POC13), aluminum chloride (AlC13), chloro-

  lithium aluminum rure (LiAlC14), sulfuryl chloride (S02C12), sulfur dioxide (S02), sulfuric anhydride

  (S03}, aluminum bromide (AlBr3) and others.

  Some of the substances in the stack are 2 66t4

  precursors for more than one acid. For example, a solu-

  tion of lithium aluminum chloride (LiAlCl4) in the

  thionyl chloride, which serves as an electrolyte in pi-

  commercial lithium batteries and generates, on contact with atmospheric humidity, hydrochloric acid (HCl) and sulfurous acid (H2S03), according to the equations

SOC12 + 2H20. H2SO3 + 2HC1

  LiAlC14 + H20> LiCl + Al (OH) C12 + HCl Thanks to the nature of the indicator mixture, it can be applied to the battery and battery casing and to the glass and metal electrolyte containers in cells and batteries reserve, which can leak precursors generating acids in contact with

atmospheric humidity.

  The examples below describe particular uses of an indicator, its color change and the electrochemical systems used. These examples are given to illustrate the invention and they do not limit

the scope of it.

EXAMPLE 1

  Dissolve a red indicator powder of

  methyl (0.50 g) in 10 ml of acetone. We add this solution

  tion to 1000 g of a one-component thermoplastic lacquer

polyamide resin base.

  The resulting suspension is stirred for two hours. A yellow color mixture is obtained. We apply

  a thin film on a metal surface and let

  expensive.In the presence of thionyl chloride vapor, the film

yellow turns red.

EXAMPLE 2

  A mixture in accordance with Example 1 is applied to

  the cover of a lithium battery containing as electrolyte-

  te 1.2 M LiAlC14 in thionyl chloride. The battery

  leaks at the glass / metal joint. The color of the indicator of-

comes red.

EXAMPLE 3

  A white adhesive, such as RTV 112, is sprayed onto a metal surface as in Example 1.

  drying for 24 hours, we project onto this surface a.min-

  that extra layer of methyl red like in the e-

  xample 1. The color of the indicator layer turns red.

  age by exposure to thionyl chloride. White background

  makes the color change more pronounced.

EXAMPLE 4

  The mixture of Example 1 is applied to a

  heat sealing area of a glass ampoule which con-

  holds a 1.2 M LiAlCl4 electrolyte in chloride

  of thionyl. This bulb is part of a battery of re-

  serve. Leak in seal causes change

  color of the indicator, from yellow to red.

EXAMPLES 5 to 9

  Tests are carried out in which 2.5 g of each of the five indicators indicated in Table I are dissolved in 19 ml of acetone. We add this solution to

  1000 g of a resin composition defined in Example 1.

  Each of the resulting suspensions is stirred for two

  hours. A thin film is applied to each of the suspen-

  resulting on a metal surface, we leave

  dry and then exposed to thionyl chloride vapor.

  Table 1 summarizes for each indicator the color change that occurs in the presence of steam

thionyl chloride.

TABLE 1

  Example N0 Indicator Color change _.... at .. Methyl orange yellow to orange 6 Bromocresol green blue to colorless 7 Alizarin pink to colorless 8 Eosine red to yellow 9 Bromocresol red blue to colorless

EXAMPLES 10 to 15

  The mixture is applied according to examples 1 and 9 to metal surfaces which are exposed to

  fears of sulfuryl chloride. T1 Changes occur

  similar in color to those obtained in Examples 1 and 5 to 9 (as shown in Table 1), respectively.

EXAMPLES 16 to 21

  The mixtures according to Examples 1 and 5 to 9 are applied to metallic surfaces and exposed to sulfur dioxide (SO2>. Changes occur

  similar in color to those obtained in the examples

  ples 1 and 5 to 9 (as indicated in Table 1) respecti-

vement.

EXAMPLES 22 to 27

  The mixtures are applied according to the examples

  1 and 5 to 9 on the commercial Li / 0O2 battery case.

  In these batteries, the electrolyte is lithium DbroMure and acetonitrile, dissolved in sulfur dioxide

  liquid. A voluntary leak is created by drilling a small

  tit hole in the battery case, which causes the ChAn-

  indicator color scheme, similar to the changes in examples 1 and 5 to 9 (as shown

in Table 1), respectively.

EXAMPLE 28

  1.5 g of cresol red indicator are dissolved in 10 ml of acetone. This solution is added to 1000 g of a single component acrylic lacquer. The resulting suspension is stirred for 0.5 hour. A thin film of the resulting msuspension is applied to a metal surface, allowed to dry at room temperature and then

  is exposed to thionyl chloride vapor. The neck-

  their film turns from yellow to purple.

EXAMPLE 29

  We prepare a mixture similar to that of example

  ple 28 but using dm methyl orange indicator form.

  By exposure to thionyl chloride vapor, the coating

  their film turns from yellow to red.

EXAMPLES 30 to 34

  Samples are carried out in which 1.5 g of each of the four indicators indicated in Table 2 are dissolved in 10 ml of methyl ethyl ketone. This solution was added to 1000 g of the curing component of a

  two-component lacquer. The resin is based on biphenol-

  epichlorohydrin. The two components of the epoxy lacquer are mixed in the appropriate reports just before

  Mtilisation. We apply the puppension on a metallic surface.

  metal, let it dry at room temperature and

  exposed to thionyl chloride vapor.

  Table 2 shows that each film changes it.

  color in the presence of thio chloride vapor

nyle.

TABLE 2

  Example Nw _ n4içatemr Color change 30 Alizaeine purple to red (without salt) 31 Cresol red Yellow to purple 32 Thymol blue Yellow to red 34 Methyl red Orange to red

EXAMPLE 35

  1.5 g of methyl red indicator are dissolved in 5 ml of methyl isobutyl ketone. This solution is added to 750 g of a one-component lacquer, based on chloride.

  vinyl and vinyl acetate. The stirred mixture is stirred

  sulting for an hour. We apply a thin film of the

  resulting diaper on a metal surface, let

  expensive at room temperature and exposed to thionyl chloride vapor. The color of the film changes from red to purple.

EXAMPLE 36

  A mixture similar to that of example

  ple 35, using methyl orange as an indicator.

  By exposure to thionyl chloride vapors, the

  their film changes from orange to brown.

EXAMPLE 37

  A composition is prepared comprising a polyamide resin, as in Example 1, with 0.2 g of red

  methyl and 100 g of fine titanium dioxide per 1000 g of a-

  adhesive, we clearly distinguish the passage of color

  yellowish to light pink when a leak occurs.

  It is understood that modifications of detail can be made to the implementation of the following process.

  before the invention, without departing from the scope thereof.

Claims (11)

Claims   1. Method of detecting a leak of batteries or bat-   non-aqueous electrolyte products comprising alkali or alkaline earth metal anodes, substances leaking from electrolyte cells, batteries or receptacles for reserve cells or batteries generating acids on contact with atmospheric humidity, characterized in that '' it consists in applying to the surfaces of the batteries or   batteries a coating composed of an acid indicator-   base in an adhesive, this composition comprising pre-   ference 0.1 to 400 parts by weight of an acid indicator-   base for 10,000 parts by weight of adhesive.   2. Method according to claim 1, characterized in that the acid-base indicator is first dissolved in an organic solvent, which is dissolved in the adhesive, the   organic solvent preferably being acetone, methyl-   ethyl ketone, methyl isobutyl ketone or a mixture of these substances. 3. Method according to claim 1, characterized in that the acid-base indicator is chosen from methyl red, methyl orange, bromocresol green, alizarin, eosin, bromocresol red, fluorescein, thymol blue and cresol red.   4. Method according to claim 1, characterized in that the adhesive is a one-component side-separation lacquer, based on polyamide resin, resin   acrylic or vinyl chloride-acetate resin.   5. Method according to claim 1, characterized in that the adhesive is a two-component lacquer based on biphenol-epichlorohydrin resin or phenolic resin, 4 to 40 parts of methyl red indicator preferably being dissolved in 10 000 parts of a lacquer to a   single component based on polyamide resin.   6. Method according to claim 1, characterized   in that the adhesive is silicone rubber, this rubber   silicone rubber preferably being Mn polydimethylsilo-   xane. 7. PrQcedé sMivnt claim 1, earactérisé   in that 14 stack contains thionyl chloride, a-   sulfur dioxide, sulfuryl chloride, phosphoryl chloride or mixtures thereof, a non-aqueous solution   LiAlC14 0 or AlC13 or mixtures thereof, chlorine, mono-   bromine chloride, bromine, nitrous oxide, anhy-   sulfuric dride or sulfur dioxide dissolved in   a non-aqueous organic or inorganic solvent, a solution   tion of LiBr in a mixture of sulfur dioxide and a- ketonitrile.   8. Electrochemical cell with non-aqueous electrolyte con-   holding a substance that generates an acid when   comes in contact with atmospheric humidity, characteristic   in that the purface of the pile or part of it   this is coated with a substance, the color of which changes,   - in a suitable adhesive mat, the substance which changes   Age of color is preferably an acid-base indicator.   9. Electrochemical cell according to claim 8, characterized in that the adhesive matrix is a polymer   compatible with the substance that changes color.   10. Eleetrochemical cell according to claim 8   or 9, characterized in that the matrix is a thermal resin moplastic.   11. Electrochemical cell according to one of the claims   8 to 10, because it undergoes a   visible color change in the ultraviolet area.