CH713316B1 - Battery, in particular button battery, and method of manufacture thereof. - Google Patents

Abstract

The present invention relates to a method of manufacturing a battery, in particular a button cell, comprising a first and a second part respectively defining the poles of the cell, the first part comprising a first surface (1) intended for be assembled with a second surface of the second part. The method successively comprises a step of depositing a silicatized layer (2) by reactive sandblasting on the first (1) and second surfaces and then a step of depositing a layer of adhesive (4) having a thickness of at least 30 µm on the first surface (1) and / or the second surface before assembly. In an advantageous variant, a deposit of an adhesion promoter is also provided between the two silicatized layers and the adhesive layer (4)

Description

Technical area

The present invention relates to a method of manufacturing batteries and, in particular, button batteries. It also relates to the battery resulting from the aforementioned manufacturing process.

Technological background

Button cells generally include a housing provided with a receptacle and a cover respectively forming the positive and negative poles of the battery. Conventionally, button cells are sealed with a preformed polymeric gasket positioned by compression between the container and the cover. This polymer seal provides galvanic isolation between the poles and forms a barrier between the electrolyte contained inside the cell and the external environment. Such an assembly is shown, for example, in GB 1,566,061.

This assembly with a preformed polymer seal has several disadvantages. The polymer seal has a certain permeability to water vapor and oxygen, which will contribute to the aging of the battery. Then, due to the purely mechanical connection between the housing and the gasket, sealing cannot be guaranteed under conditions of high humidity and also during prolonged storage of discharged batteries in the case of alkaline batteries. These specific conditions will therefore give rise to an electrolyte leak at the interface between the seal and the housing, in particular following an increase in the pressure inside the cell. Finally, the junctions with a preformed and compressed polymer seal between the container and the cover generally occupy a not insignificant space which will restrict the active volume of the cell containing the electrolyte.

To reduce the space allocated to the junction and reduce its permeability, a bonded seal instead of the preformed polymer seal is a promising solution. However, there remains the problem of adhesion between the adhesive layer and the surfaces to be assembled. In addition to the problem of adhesion, it is also necessary to ensure the galvanic insulation between the poles with an adhesive seal.

Summary of the invention

[0005] The present invention proposes a new method of manufacturing batteries making it possible to improve the adhesion between the substrates and the adhesive layer while ensuring galvanic insulation.

[0006] To this end, a manufacturing method as well as a battery according to the appended claims are proposed.

[0007] Thus, the invention relates to a method of manufacturing a battery, in particular a button battery, comprising a first part and a second part respectively defining the two poles of the battery, the first part comprising a first surface intended to be assembled with a second surface of the second part, this method being characterized that in that it successively comprises a step of depositing a silicatized layer by reactive sandblasting on each of the first and second surfaces, a step supplying an adhesive on the first surface covered with its silicatized layer or / and on the second surface covered with its silicatized layer and a step of assembling the first and second parts by forming, by means of said adhesive, a layer of adhesive between the first and second surfaces so as to obtain a battery casing which comprises an adhesive seal between its two poles.

[0008] In a preferred embodiment, the manufacturing process is characterized in that it further comprises, following the step of depositing a silicatized layer, a step of depositing, on each of the two layers silicatized deposited respectively on the first and second surfaces, of a layer of an adhesion promoter comprising silane groups chemically bonding with the silicatized layer.

[0009] The present invention therefore proposes to treat the surfaces to be assembled with a reactive sandblasting, also called silicatization, before carrying out a bonding to form an adhesive joint. This reactive sandblasting increases roughness and deposits an inorganic layer anchored in the surfaces intended to be bonded.

The adhesion promoter comprises silanes, which form a chemical bond with the silicatized layer, and other chemical functions selected according to the glue provided to react specifically with the glue deposited. A durable chemical bond is thus created between the assembly surfaces of the two parts of the case and the adhesive arranged between these surfaces, making it possible to ensure a strong bond and the sealing of the battery.

[0011] According to a preferred variant, the surfaces are assembled with a layer of adhesive having a minimum thickness that is substantially constant and controlled by means of a spacer in order to guarantee galvanic insulation between the parts to be assembled.

The manufacturing method according to the invention offers other advantages of ensuring the compactness of the assembly, of allowing assembly at room temperature therefore without impact on the battery, and of operating on different types of support (plastic, ceramic or metal).

The present invention also relates to a battery, in particular a button battery, comprising a first and a second part forming a housing of the battery and respectively defining the two poles of this battery, the first part comprising a first separate surface of a second surface of the second part by a contiguous zone, this stack being characterized in that the contiguous zone comprises a layer of adhesive interposed between two layers of silica respectively anchored in the first and second surfaces.

According to a preferred embodiment, the contiguous zone of the cell further comprises two layers of an adhesion promoter arranged respectively on the two layers of silica to chemically bond each of these two layers of silica with the layer of glue.

Brief description of the figures

The invention will be described below in more detail with the aid of the accompanying drawings, given by way of non-limiting examples, in which: FIG. 1 schematically represents the various layers deposited on a substrate, defining a bonding surface of part of the package, according to a variant of the method of the invention; Figures 2 and 3 respectively show a partial sectional view of two alternative arrangements of the contiguous zone between the container and the cover of the battery box after assembly; Figure 4 is a graph with the average fracture energies determined by the wedge cleavage test for different assemblies.

Detailed description of the invention

The present invention relates to a method of manufacturing a battery comprising two parts defining its poles. It relates more particularly to the steps implemented to ensure a sealed and insulating assembly between these two parts.

The present invention also relates to the battery resulting from this manufacturing process. It may be a button cell but the present invention is also applicable to other types of cells such as bag batteries.

In the context of the present invention, the respective surfaces of the two parts of the housing facing one another are assembled by gluing. According to the invention, they are previously treated by sandblasting and preferably functionalized to improve the strength of the assembly and also the tightness of the battery box. More precisely, and as shown diagrammatically in FIG. 1, the surface 1 of each part is first subjected to reactive sandblasting, also called silicatization, which consists in sandblasting the surface with grains of alumina coated with silica. Typically, the grains have an average size of between 10 μm and 100 μm, preferably between 20 μm and 40 μm. The sandblasting pressure and time conditions can easily be determined by those skilled in the art depending on the sandblasting equipment at their disposal.

Sanding increases the roughness and allows to deposit a layer of silica 2 which is firmly anchored to the surface 1 of the part of the treated housing. In a preferred variant, after the aforementioned reactive sandblasting, an adhesion promoter 3, which can also be qualified as a chemical coupling and functionalization agent, is deposited on the silica layer (ceramic layer) of each surface. This second step is recommended but not essential, as shown by the results of the tests presented below.

In an advantageous variant, the adhesion promoter comprises silanes whose alkoxyl functions are intended to form a chemical bond with the silicatized layer. It further comprises other organic functional groups such as, for example, acrylates, amines, epoxy, alkyl, acetoxy, aryl, glycol, mercapto, methacryl, vinyl, etc., intended to bind with the adhesive. The functionality must be selected to suit the chosen glue. Thus, for example, an adhesion promoter comprising acrylate groups is preferred when the glue is an acrylate glue. The adhesion promoter as well as the glue are also chosen according to their chemical compatibility with the materials used inside and outside the cell. According to the invention, the bond between the adhesion promoter and the adhesive can be one or more bonds chosen from strong bonds of the ionic or covalent bond type and from weak interactions of the Van der Waals interaction type, hydrogen bonds, etc. .

After depositing the adhesion promoter, an adhesive 4 is deposited on a surface or on the two surfaces intended (s) to be assembled. Acrylate glue has already been mentioned, but other glues can be used, in particular an epoxy glue or a polyurethane glue, to name but a few. Any type of glue, whether physically curing glues, chemical curing glues or pressure sensitive glues, can be used as long as the glues are chemically compatible with the materials used inside and out. exterior of the batteries. After deposition, the adhesion of the glue to the surfaces to be assembled is ensured by applying the curing conditions required according to the type of glue. For example, in the case of a chemically hardening adhesive, the (at least terminal) polymerization of the adhesive can take place at room temperature and in ambient air, in particular by exposure to light having a length of given wave. Ultimately, the anchoring of the silica layer in each assembly surface of the two parts of the case combined, on the one hand, with the chemical bonds between the silica layer and the adhesion promoter and, on the other hand, interactions between the adhesion promoter and the adhesive creates a strong and lasting bond between the adhesive and the surfaces.

To obtain a junction between the two parts which is electrically insulating, the adhesive layer has a thickness of minimum 30 μm and, preferably, minimum 50 μm. The thickness of the adhesive layer can be advantageously controlled by means of a spacer formed from an electrically insulating material. In particular, the spacer is formed by a plurality of balls or particles incorporated in the glue. The term “spacer” is understood here to mean both a set of distinct elements distributed in the adhesive joint, such as particles, and a continuous structure such as a mesh. The material of the spacer is preferably chosen from glasses, ceramics (carbides, nitrides, oxides, etc.), diamond, polymers and composites with an organic matrix. More particularly, there may be mentioned alumina as the choice of ceramic and Teflon, PEEK, PET and nylon as the choice of polymers.

Depending on the type of battery, the nature of the substrate may be different. Thus, generally for a button cell battery, the surfaces to be assembled are metallic and in particular made of steel coated or not with nickel, whereas for a bag battery, the surfaces to be assembled are plastic.

The bonded junction can be made at different places of the battery case. For example, Figures 2 and 3 show different arrangements of the bonded junction between the two parts which are the cover and the battery container. In FIG. 2, the bonded junction 5 between the cover 6 and the container 7 is positioned on the cylindrical periphery of the housing 8 with at the base of the cover 6 a polymer gasket 9 isolating the end of the cover from the container. In FIG. 3, according to a preferred variant, the bonded junction 5 between the cover 6 and the container 7 is positioned in a frustoconical zone in the upper part of the housing 8.

The advantages of the method according to the invention are now illustrated through the non-limiting examples described below.

Examples

The role of reactive sandblasting and of the adhesion promoter on adhesion and electrical conductivity were tested for two types of glue.

Experimental procedure

The tests were carried out on steel bars 430 0.5 mm or 0.8 mm thick for a length and a width of 4 cm and 1 cm respectively. Reactive sandblasting was performed with a CoJet Prep ™ microblasting machine using 3M ™ ESPE ™ CoJet Sand ™ sand having an average particle size of 30 µm. Comparative tests of conventional sandblasting, i.e. sandblasting aimed at creating roughness but without depositing a ceramic layer, were carried out with sand having a similar average particle size of 36.5 µm (F280 sand).

Two types of adhesion promoters were tested. One has silane and acrylate groups (ESPE ™ Sil from 3M ™ ESPE ™) and the other has silane and amine groups (Asusil from The Swatch Group R&D, Polymers division). Two types of glue were tested, namely an epoxy type glue (E610 from The Swatch Group R&D, Polymers division) and an acrylate type glue (APM Unocol 38 from APM Technica). In this latter adhesive is incorporated a spacer in the form of polymer particles having an average size of 50 μm.

Roughness measurements were carried out with an Altisurf 500 optical profilometer (ISO 4288/4287) at a measurement speed of 50 μm / s, at a rate of one measurement per 0.5 μm. Corner cleavage tests according to the ISO 15107 standard were also carried out to evaluate the adhesion between two glued bars. Two-point conductivity measurements were also performed with an HP 3478A multimeter on the bonded bars.

Results

Reactive sandblasting was carried out for 15 s under a pressure of 5 bar, these conditions being adapted to the equipment used. Compared to a substrate that has not been subjected to reactive sandblasting, an increase in the arithmetic mean deviation Ra of the roughness profile is observed from a value of 0.09 μm to a value of 0.43 μm.

The deposited layer is uniform. Its thickness is difficult to measure because the latter is anchored in the material, but according to the product data sheet, the components of the abrasive are anchored in the material at a depth of 15 µm.

The impact of the deposition of a silane layer on the roughness was tested with an adhesion promoter comprising acrylate functions. No significant influence was observed. For reactive sandblasting at 5 bar for 15 seconds, the arithmetic mean deviation Ra goes from 0.43 before deposition of the adhesion promoter to 0.4 after deposition. After depositing the adhesion promoter, the roughness is therefore maintained as shown diagrammatically in FIG. 1.

The role of the silicate layer, of the adhesion promoter and of the type of adhesive on the adhesion of the assembly was evaluated. Table 2 shows the various assemblies tested, their breaking energies measured with the wedge cleavage test and the conductivity measurements carried out on the bars assembled with an adhesive. The results of the wedge cleavage tests are also shown in Figure 4.

Compared to the reference samples having undergone conventional sandblasting optionally followed by the deposition of an adhesion promoter, it is observed that the sole silicatization of the surfaces without adhesion promoter already makes it possible to improve the adhesion of the adhesive on surfaces. The deposition of an adhesion promoter, correctly selected according to the adhesive, on the silicatized layer makes it possible overall to further improve adhesion. The effect is more or less marked depending on the type of promoter and the type of glue. Thus, for the epoxy glue, an improvement is observed when the adhesion promoter comprises silane and amine groups. For an acrylate glue, for which only the adhesion promoter with silane and acrylate groups was tested, a very marked improvement in adhesion is observed. This very good result is attributed to the presence of the acrylate groups of the adhesion promoter which react with the corresponding groups of the adhesive.

Concerning the conductivity, the tests confirm that the electrical insulation between the two assembled parts is well ensured for all the acrylate adhesives tested which contain a spacer making it possible to guarantee a substantially constant thickness of the adhesive layer of 50 μm.

Legend of figures

[0036] (1) Surface intended to be assembled, also referred to as the first surface (2) Silicatized layer, also called silica layer (3) Layer of the adhesion promoter (4) Layer of adhesive (5) Joint zone, also called glued junction or glued joint (6) Cover (7) Container (8) Housing (9) Silic polymer seal. : silicatisation Promo: promoter

Claims (17)

1. A method of manufacturing a battery, in particular a button battery, comprising a first part (6) and a second part (7) respectively defining the two poles of the battery, the first part comprising a first surface (1 ) intended to be assembled with a second surface (1) of the second part, this method being characterized that in that it successively comprises a step of depositing a silicatized layer (2) by reactive sandblasting on each of the first and second surfaces, a step of providing an adhesive on the first surface covered with its silicatized layer or / and on the second surface covered with its silicatized layer and a step of assembling the first and second parts by forming by means of said glue a layer of glue (4) between the first and second surfaces so as to obtain the stack which comprises an adhesive joint between its two poles, said layer of glue (4) having a thickness of at least 30 μm. 2. The manufacturing method according to claim 1, characterized in that it further comprises, following said step of depositing a silicatized layer (2), a deposition step, on each of the two silicatized layers deposited respectively on the first and second surfaces, a layer of an adhesion promoter (3) comprising silane groups chemically bonding with the silicate layer. 3. Manufacturing process according to claim 2, characterized in that the adhesion promoter (3) further comprises functional groups intended to bind with said adhesive layer (4) via one or more bonds selected in particular from the interactions. ionic or covalent type and weak intermolecular interactions such as Van der Waals forces or hydrogen bonds. 4. Manufacturing process according to any one of the preceding claims, characterized in that the glue is a physically curing glue, a chemical curing glue or a pressure sensitive glue. 5. Manufacturing process according to any one of the preceding claims, characterized in that the glue is an epoxy, acrylate or polyurethane glue. 6. Manufacturing process according to claim 5, characterized in that the adhesion promoter (3) comprises acrylate groups and is used in combination with the acrylate adhesive. 7. Manufacturing process according to claim 5, characterized in that the adhesion promoter (3) comprises amino groups and is used in combination with the epoxy adhesive. 8. Manufacturing process according to any one of the preceding claims, characterized in that the adhesive layer (4) has after assembly a substantially constant thickness which is controlled by means of a spacer. 9. Manufacturing process according to any one of the preceding claims, characterized in that each silicatized layer (2) is deposited by sandblasting the first and second surfaces with alumina particles covered with silica and having an average size of between 10 µm and 100 µm or, preferably, between 20 µm and 40 µm. 10. The manufacturing method according to any one of the preceding claims, characterized in that the silicatized layer (2) has an average thickness less than or substantially equal to 15 microns. 11. The manufacturing method according to any one of the preceding claims, characterized in that the first and second surfaces are defined by a metallic material forming a battery casing. 12. The manufacturing method according to any one of claims 1 to 10, characterized in that the first and second surfaces are defined by a synthetic material. 13. Battery, in particular button battery, comprising a first and a second part forming a housing of the battery and respectively defining the two poles of this battery, the first part comprising a first surface (1) separated from a second surface (1). ) of the second part by a contiguous zone (5), characterized in that the contiguous zone (5) comprises a layer of adhesive (4) interposed between two silicatized layers (2) respectively anchored in the first and second surfaces, said layer glue (4) having a minimum thickness of 30 µm. 14. Battery according to claim 13, characterized in that the contiguous zone (5) further comprises two layers of an adhesion promoter (3) arranged respectively on the two silicatized layers (2) to chemically bond each of these two. layers silicatized with the adhesive layer (4). 15. Battery according to claim 13 or 14, characterized in that the adhesive layer (4) has a substantially constant thickness of at least 50 microns. 16. Battery according to any one of claims 13 to 15, characterized in that a spacer is incorporated in the adhesive layer (4) to define its minimum thickness. 17. Battery according to claim 16, characterized in that the spacer is formed of beads or particles of insulating material.