FR2461363A1 - MECHANICALLY RESISTANT GLASS FOR USE IN GLASS-METAL JOINTS AND ELECTRICAL TERMINAL STRUCTURES OF LITHIUM ELECTROCHEMICAL CELLS - Google Patents

Abstract

THE INVENTION RELATES TO AN ELECTROCHEMICAL BATTERY TIGHTLY CLOSED WITH AT LEAST ONE METAL-GLASS-METAL SEAL. IN THE GASKET, THE GLASS IS A PART OF THE GROUP SHAPED ALUMINOSILICATE GLASSES, GLASSES INCLUDING ALUMINA AND OXIDES MORE STABLE THAN ALUMINA, AND GLASSES IN WHICH METAL OXIDE PARTICLES ARE INCORPORATED, IN SUFFICIENT QUANTITIES TO PREVENT SENSITIVELY THE FORMATION OF CRACKS IN THE GLASS, THE PARTICLES HAVING FREE FORMING ENERGIES PER ATOM-GRAM OF OXYGEN AT LEAST AS NEGATIVE AS THAT OF ALUMIN. THE INVENTION APPLIES IN PARTICULARLY TO ELECTROCHEMICAL LITHIUM BATTERIES.

Description

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  The present invention relates to

  metal and the electrical terminals used in

  chemicals and, in particular, batteries containing anodes of

  lithium and corrosive materials. -

  According to the prior art, glasses which are preferably used for the manufacture of glass-to-metal seals for electrochemical cells and capacitors requiring a serious seal, such as those described in US Pat. No. 4,053 692 and 3,646,405, are the glasses of the type called "borosilicate". These glasses include those designated by the trade names "Corning 7052" and "Fusite GC" and have the following general composition:

  Nature of the oxide Approximate percentage

matif SiO 2 70-75

B203 20

AI203 4-8

Na20 4-7

K20 6

  BaO 0-2 Borosilicate glasses have been and are still widely used for the manufacture of glass-to-metal joints because of their relatively low working temperatures and the good quality of glass-to-metal joints that can be achieved with them. Therefore, these glasses are used in a wide variety of applications using glass-to-metal joints. It has been discovered, however, that although these glass-to-metal seals are generally considered to be suitable for sealing the battery packs, in some cases, particularly when they are used as electrical terminals in batteries containing lithium anodes, these glass-to-metal joints suffer damage

  entailing leakage and possibly

  electricity, especially if the batteries are kept at a high temperature. These glasses are especially susceptible to damage when used in glass-to-metal battery gaskets containing lithium anodes and most importantly

  depolarizing electrolytes. corrosive fluids, such as chlorine

  thionyl chloride and sulfur dioxide. The glass-metal joints of the electrochemical cells are conventionally formed of external and internal metallic elements mutually separated by the

  glass and linked to it by fusion at the glass-glass interfaces.

  metal. Seals of this type are described in detail in US Pat. No. 4,053,692. Typically, the metal elements act as opposed terminals in the cells and are electrically connected to the electrodes disposed therein.

  inside the pile. The glass element placed between the

  The metal parts serve both as a seal and an electrical insulator. In lithium cells, the metal element used as the conductive associated with the lithium anode and the surrounding glass in the immediate vicinity attract lithium ions from the electrolytic solution. It appears that litium as well

  attracted enters the glass and makes it electrically conductive.

  The conductive glass then integrates with the conductive anode, which therefore extends into the glass, so that the width of the electrical insulator is gradually reduced. In addition, the glass in which lithium has penetrated occupies a larger volume than the initial glass, which causes the glass to break and, with some electrical terminal configurations, the glass separates from the metal to which it is bonded. This mechanical failure directly degrades the glass-to-metal joint and affects the rate at which the insulation

  Eliminates due to its replacement by conductive glass.

  Since the penetration of lithium into the glass creates an increase in volume towards the conductor associated with the facing cathode, a conductive bond through the initially insulating glass is established and results in a reduction in the capacitance of the

internal discharge battery.

  The object of the invention is to provide improved glass-metal seals for use in lithium electrochemical cells, the glass constituting the seals having improved resistance to the risk of deterioration,

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  even under excessive operating conditions.

  According to the invention, an electrochemical cell (in particular a lithium anode cell) comprises a metal-glass-metal seal assembly in which the insulating glass is either a glass filled with particles of aluminum oxides, or alumina (A1203), or other stable metal oxides, or an aluminosilicate-based or like-based glass, in which such

  particles are also dispersed.

  The aluminosilicate glasses contain relatively large amounts (about 15 to 35% by weight) of aluminum oxide, or alumina (Al 2 O 3), dissolved. The alumina found inside the aluminosilicate glasses partially takes the molecular structure of the glass by incorporating

  in the vitreous structure of pure silica and modifying it.

  Typical aluminosilicate glasses include those designated by the trade names "Corning 1720" and "Corning 1723", which have the following general compositions:

1723 1720

SiO2 57 60

A1203 15 17

B203 5 5

MgO 7 7-8 CaO 10 7-8

BaO 6 -

  Na20 - 1 It appeared that the aluminosilicate glass was more resistant to the intrusion of lithium ions and thus allowed to form glass-metal joints more stable than the borosilicate glasses described above. above. However, aluminosilicate glasses have so far not often been used

  in the manufacture of glass-to-metal joints for

  partly due to high temperatures (typically

  in the order of 1200 C) which are necessary for the work or softening

  lissement of the glass. The maximum temperature associated with equipment used for the continuous manufacture of glass-to-metal joints is approximately 1100C. Because of their high softening temperatures, low thermal expansion, and their suitability for tungsten and molybdenum, aluminosilicate glasses have mainly been used for high temperature applications. , including projection lamps, high temperature thermometers, combustion tubes and household objects for cooking intended for

  be used directly on flames, or other

heating systems. -

  Glasses containing only oxides such as alumina and oxides more stable than alumina (i.e. having free formation energies more negative than about -125 kcal / gram atom of oxygen ), such as calcium aluminate glass, which meet the requirements of thermal contraction, work and metal bonding which are suitable for glass-to-metal joints are generally identically susceptible to withstanding to be used as insulating glasses for durable electrical terminals, and are therefore

within the limits of the invention.

  The characteristics of resistance to deterioration

  aluminosilicate glasses and stable oxides can be further improved by inclusion or blending, in admixture, of particular metal oxide additives, especially aluminum oxide (alumina), in amounts sufficient to pocketing the appearance of harmful cracks, at least about 10% by weight. The inclusion of metal oxides such as alumina in existing borosilicate glasses which are used to form glass-to-metal joints has also been found to significantly reduce the deterioration of such glasses when

  Glass-to-metal joints are used in lithium batteries.

  The dispersion of hard particles of metal oxides

  such as alumina inside a glass can prevent the spread of cracks in the glass structure. It is assumed that if the embedded particles, which are more contractile than the glass, remain bound to the glass during contraction, the compressive stresses appearing in the glass around

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  each particle opposes the tension propagating the cracks at the end of an approaching crack. If the

  the glass surrounding the particle separates from it during the contrac-

  In this way, a cavity is formed between the glass and the particle and this cavity serves to stop the propagation of the crack by redistribution of the stresses in the glass. Metal oxide particles which contract in the same way as glass also succeed, if they are loosely bound to the surrounding glass, to stop the propagation of cracking by cavity formation, whereas, if they are strongly related to glass, they only prevent crack propagation if they are mechanically more resistant to cracking than

the glass itself.

  Metallic oxides other than alumina, which can be usefully incorporated in glass-metal glass forming glasses for lithium electrochemical cells

  to reduce the risk of deterioration of these joints,

  take the compounds whose formulas follow, namely CaO, BeO, BaO 2, MgO, SrO, BaO, CeO 2, Sc 2 O 3, Ce 2 O 3, ZrO 2, TiO 2 e Ti 2 O 3, etc. which have a high thermodynamic stability, even when used in corrosive environments of the type of that of a lithium battery. Suitable metal oxides generally have a free energy formation more negative than that of alumina

  (about -125 kcal / gram atom of oxygen) and are therefore thermo

  dynamically more stable than alumina. For the simplicity of

  manufacture, it will be preferred that the metal oxides be incor-

  pored in the glass in such a quantity that there is no increase in

  tation of the working temperature of the glass beyond 1100C. -

  We generally act on the inclusions of parti-

  alumina or other stable oxides by mixing mechanical

  appropriate quantities of glass and dry powder alumina, by pressing the mixture into a compact, friable formation of desired configuration and heating the formation so as to melt the glass particles together by local circulation between the still stiff particles. alumina. It is preferable to carry out, before the merger following a terminal set, a

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  sintering of the compact formation of glass (typically about 800 to 10,000 ° C for alumina and aluminosilicate glass

  and about 600 to 800 ° C for alumina and boron glass

  silicate) for a short time in order to reduce its porosity and to minimize the flow required to make a seal. We will also prefer to carry out, after the merger, a

  annealing the glass mixture to give it greater resistance

  mechanical stress and release the stresses existing in the glass for use in a glass-to-metal joint. During the formation of the metal-glass-metal joint, the preformed glass structure is placed between two metallic elements and heated to a sufficiently high temperature to soften the glass, a metal-glass-metal seal being then produced according to the known technique. manufacturing glass-to-metal joints. The temperature used

  to form the metal glass joints usually depends on the quantity

  The amount of alumina included is undissolved, with higher percentages of alumina requiring lower glass viscosity and a somewhat higher working temperature. In order to facilitate the relative movement of the alumina particles when the glass is flowing, the alumina particles will preferably be given a form free of asperities as much as possible. Preferred sizes

  particles are between 1 and 30 d in diameter.

  The glass-to-metal joints according to the invention comprise both suitable expansion joints and compression joints. In a suitably dilated joint, the selected aluminosilicate glass or alumina-loaded glass (or other stable particles) is used with a pure metal, or a metal alloy, having a coefficient of thermal expansion substantially identical when the glass is rigid. The metal used in the suitably-expanded joint usually receives, prior to assembly, a surface coating of its oxide so that an intimate and sealed bond between the oxide-based glass and the metal or metal alloy and its oxide can be achieved. In general, an outer compression seal is made of glass surrounded by an outer metal element whose expansion coefficient is sufficiently greater than that of the glass to compress the glass when the cooling continues after the glass has become rigid, but not large enough to cause inelastic stresses or cracks in the glass. An internal compression seal is obtained by placing the glass around a metal with a coefficient of expansion less than that of the glass.

  The joints according to the invention are found in particular

  especially useful for batteries containing lithium anodes.

  In addition to lithium, other applications involve anode materials for use in electrolyte batteries

  non-aqueous and comprising alkali metals and alkaline

  earthy, such as sodium, potassium, magnesium and calcium;

as well as aluminum.

  The cathodes used in the lithium cells consist of cathode-active material, such as silver chromate, carbon fluoride of the type (CFx) ny or carbon-based substrate for active materials of cathodes of the oxyhalide type, non-metallic oxides, or non-metallic halides. fluids. Such soluble active materials for cathodes include sulfur dioxide (SO2) and thionyl chloride (SOC12), as well as phosphorus oxychloride (POC 13), selenium oxychloride (SeOC12), sulfur trioxide ( S03), vanadium oxytrichloride

  (VOC13), chromium chloride (CrO2Ci2), sulfur oxychloride

  (N02Cl2), nitrile chloride (NO2Cl), nitrosyl chloride (NOC1), nitrogen peroxide (NO2), monochloride

  sulfur (S2C12), sulfur monobromide (S2Br2), and mixtures thereof.

  Other materials for active cathodes include MnOx (x being approximately 2), HgCrO4, HgO and, in general,

  halides, oxides, chromates and dichromates, permanent

  ganates, periodates, molybdates, vanadates and chal-

  metal cogenides, as well as their mixtures.

  Electrolytic solvents used in lithium batteries include organic solvents such as tetrahydrofuran, propylene carbonate, dimethyl sulfate, dimethyl sulfoxide, N-nitrosodimethylamine, γ-buryrolactone, dimethyl carbonate, methyl formate butyl formate, dimethoxyethane, acetonitrile and N, N-dimethylformamide. Saline electrolytes for these cells include light metal salts such as perchlorates, tetrachloroaluminates, tetrafluoroborates, halides,

  hexafluorophosphates, hexafluoroarsenates, and chloro

  borates. Examples of particular metals which can be used in these seals and are compatible with the various constituents of the batteries containing lithium anodes are given below. In suitable electrolytes, suitable metals in contact with lithium include copper, iron, steel, stainless steels of all types, nickel,

  titanium, tantalum, molybdenum, vanadium, niobium, -

  tungsten and metal alloys of the type defined by the

  trademarks "Kover", "Inconel" and "konel".

  Examples of metals and metal alloys that are stable at the cathode potential with sulfur dioxide include aluminum, titanium, vanadium tantalum,

  tungsten, niobium and molybdenum.

  Examples of metals compatible with silver chromate include titanium, tantalum, molybdenum, vanadium,

  chrome, tungsten and stainless steel.

  Examples of metals and metal alloys stable at the cathode potential with the highly oxidizing thionyl chloride include titanium, molybdenum, niobium, tantalum, tungsten, alloys known as "Kovar", "Inconel",

  onel ", nickel and stainless steel.

  The following examples illustrate manufacturing joints

  according to the invention which have been tested in lithium batteries, so that their stability can be clearly established. All parts are given by weight unless otherwise indicated. Since the following examples are for illustrative purposes only, it will be understood that the details

  in no way constitute limitations of the invention.

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EXAMPLE 1

  A certain amount of "1 micron" alumina abrasive of the "Buehier" type was heated to transform any

  trace of alumina hydrate in anhydrous alumina. We mixed the aluminum

  dried mine with "Corning 1723" aluminosilicate glass pulverized and dried in an amount sufficient to form a mixture containing 10% alumina. Elements in the form of washers, or "preforms", were compressed at 2.26 N / m and then sintered in the air

  between 850 and 1050C, the temperature increasing in stages progressively

  5 ° C every 10 minutes. We have assembled a metal terminal

  glass-metal by placing the element in the annular space between a cold-rolled (low-carbon) steel outer metal part and an inner molybdenum part to form an outer compression joint

  and an internal matched seal. The joints were manufactured

  under argon atmosphere by melting for 15 min at 12000C and annealing at 712 ° C for 15 min. The completed terminal was then mounted in a Li / SO2 cell of size "D" whose external metal piece is connected to the lithium anode. The cell was filled with an electrolyte consisting of a solution of 0.75 M lithium bromide in a mixture of 74% sulfur dioxide and 26% acetonitrile, then the cell was stored at 720C in

  a position such that the terminal was at the bottom.

  After 6 months of storage, there was no leakage of electro-

  and the electrical insulation did not fail.

  It is noted that a battery size "D" is a 33.3 mm diameter cylinder

and length 60.2 mm).

EXAMPLE 2

  A glass-to-metal seal was made following the procedure of Example 1, but using an external molybdenum metal member to form the matched seal. The seal was then placed in a sealed glass vial containing an electrolytic solution of the components given above containing 40% SO 2, the metal member of the seal being polarized by lithium. The vials thus formed were stored for 5 months at 72 ° C. At the end of the storage period, there was only slight corrosion indicating a minor attack. Borosilicate glass gaskets which had been subjected to similar tests had a similar

  significant corrosion after only 6 weeks of storage.

EXAMPLE 3

  A "Fusite" type borosilicate glass charged with 30.8% alumina was used to form suitable glass-to-metal joints with "Xovar" conductors. The inner metal part was polarized with lithium, and the joint was boiled in an electrolytic solution of thionyl chloride and 1M LiAlCl at reflux for 32 days. After this

  duration, only a slight blackening of the inner seal appeared.

  A similar structure seal using borosilicate glass type "Fusite" is charged with 57% alumina only showed

  large fractures when subjected to

gists.

  Of course, those skilled in the art will be able to

  giner, from the device whose description has just been

  given by way of illustration and in no way limiting,

  various variants and modifications that are not outside the scope of the

vention.

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Claims (8)

R E V E N D I C A T IO N S   1 - Electrochemical cell sealed by means of a metal-glass-metal seal, characterized in that the glass is a member of the group consisting of aluminosilicate glasses, glasses comprising alumina and oxides more stable than alumina, and glasses in which are incorporated particles of metal oxides in amounts sufficient to substantially   prevent cracks from forming in these glasses,   particles with free energies of formation, per gram atom   of oxygen, at least as negative as that of alumina.   2 - battery according to claim 1, characterized in that the glass contains particles of elements selected from CaO, BeO, Ba2O, MgO, SrO, BaO, CeO2, SC203, Ce203, ZrO2, TiO2 and Ti203.   3 - battery according to claim 1, characterized in   what the glass contains particles of alumina.   4 - battery according to claim 3, characterized in   what the glass is a borosilicate glass.   A cell according to claim 3 or 4, characterized in that the alumina particles are substantially free from roughness.   6 - battery according to claim 3, 4 or 5. characterized   in that the particles have diameters between 1 and microns.   7 - battery according to any one of the claims   1 to 6, characterized in that the particle content is at least %, by weight, of the glass.   8 - battery according to any one of the claims   1 to 7, characterized in that the inclusions of oxide particles   metallic materials do not increase by the working temperature of the glass beyond 1100 C.   9 - battery according to claim 1, characterized in that the glass which contains alumina and oxides more   stable that the alumina comprises calcium aluminate.   - Battery according to any one of the claims   1 to 9, characterized in that it comprises a lithium anode.   II - battery according to claim 10, characterized in that it contains, as a cathode depolarizer, sulfur dioxide or thionyl chloride. 12 - battery according to claim 11, characterized   in that the metal-glass-nimetal seal comprises a glass with alumina-   silicate or borosilicate, in which are incorporated, reason   of at least 10% by weight, alumina particles.