FR2830687A1 - Electrochemical generator such as battery or accumulator has casing with major part of its surface coated with a reticulated resin - Google Patents

Abstract

The generator (1) consists of a casing (2) with at least one current outlet terminal (3), with the major part of the casing's outer surface coated with a thin protective and adhesive layer of a reticulated resin (5) which can incorporate a mechanical reinforcing agent, a coloring or a heat conducting insulating material. The generator (1) consists of a casing (2) with at least one current outlet terminal (3), with the major part of the casing's outer surface coated with a thin protective and adhesive layer of a reticulated resin (5) which can incorporate a mechanical reinforcing agent, a coloring or a heat conducting insulating material. After application of the resin coating to the whole of the casing's outer surface with the exception of the terminal's electrical contact zone it is reticulated by UV light for a period of less than 8 seconds and with no physical contact with the resin.

Description

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Electrochemical generator with coating and coating method
The present invention relates to an electrochemical generator comprising a container coated with a protective material and to the method of coating this generator.

 In the remainder of this description, the term “electrochemical generator” will designate any system capable of transforming chemical energy into electrical energy and vice versa. It can be a battery (primary generator), an accumulator (secondary or rechargeable generator), a supercapacitor (symmetrical generator) or an electrolyser. Batteries and accumulators can contain an aqueous (acid, alkaline) or non-aqueous (organic) electrolyte. They can be, for example, lithium or nickel generators, or even a fuel cell. The electrochemical generators can be associated in battery by a series or parallel connection.

 In order to protect its external surface from attack by the environment, it has been envisaged to wrap the container of an electrochemical generator with a material serving as a barrier to these attacks. Degradation of the container (scratches, removal of material, ... can be due to mechanical aggressions occurring when assembling the generators in a battery or when entering a housing. When they are melodic, the containers must also be protected against corrosion and electrically insulated.

 Document JP-3,127,445 proposes covering the surface of an electrochemical element with an insulating resin with a low melting point, with the exception of the section carrying the terminals. The assembly thus formed is surrounded by a resin case provided with an opening for gases and containing a foam. The disadvantage of this embodiment is the size of the generator obtained: the volume energy is in this case very low.

 Document JP-5,013,058 shows an electrochemical generator surrounded by an envelope containing a molded resin. A tube communicates the elastic seal of the generator with the outside for the evacuation of gases. Again the resin surrounding the generator increases the total volume significantly.

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 Furthermore, the document JP-55 119 346 describes the production of a battery obtained by rolling several flat elements which are kept compressed and immersed in an insulating wax bath in order to form a coating film. The remaining gaps after removal of the compression means can then be filled. The coated elements are finally provided with a container and terminals. The film obtained in this way has poor mechanical strength. Its role is essentially to electrically isolate the elements and it cannot serve as protection. This is why the coated elements must be placed in a container.

 The present invention aims to eliminate the drawbacks of the prior art and, in particular to provide an electrochemical generator comprising a container provided with a coating which simultaneously provides protection and electrical insulation of the container without significantly increasing the weight. and / or the volume of the generator.

 The object of the present invention is an electrochemical generator comprising a container carrying at least one current output terminal, characterized in that the major part of the surface of said container is coated with a thin and adherent protective layer consisting of a crosslinked resin.

 The resin may for example be an epoxy resin, an acrylic polymer, etc. In a preferred embodiment, the resin contains an acrylic polymer. The resin may as well be single-component, which has the advantage of simplifying its implementation and of avoiding dosage errors. In addition, the management of supplies is lightened because there is only one referenced product.

 The resin may also contain additives. According to a first variant, the resin also contains a mechanical reinforcing agent. This increases the strength of the protective layer. In particular in the case where the container is metallic, a more solid coating makes it possible to avoid the defects in electrical insulation which would result from its degradation.

 According to the invention the protective layer is adherent to the surface of the container. There is therefore no air film between the outer surface of the container and the inner surface of the protective layer which significantly improves the thermal conduction on the surface of the generator compared to a coating which would simply be placed on the container. . To further increase conduction

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 thermal, the resin may also contain an electrically insulating and thermally conductive material according to a second variant. This material is for example a mineral filler such as mica. It is preferably used in powder form to facilitate its homogeneous distribution within the resin. The addition of such a material is intended to improve the thermal conduction of the coating in order to more efficiently dissipate the calories generated during the operation of the generator. This is particularly necessary when the generator is used in an electric vehicle.

 According to a third variant, the resin also contains colored pigments, for example titanium oxide for the white color. The resin is usually transparent or translucent. The presence of colored pigment makes it easier to control the absence of gaps in the coating while allowing a reading of the information carried directly on the container (designation, bar code, etc.). In fact, the control is carried out visually when the layer is colored, whereas a transparent layer requires special equipment, such as for example a UV lamp which makes it fluorescent.

 According to a fourth variant, the resin also contains a flame retardant material.

 According to other alternative embodiments, the resin may also contain one or more additives intended to facilitate the covering, such as in particular a crosslinking agent or a fluidity agent.

 In order to make the volume increase as insignificant as possible, the thickness of the protective layer is less than 0.3mm. However, to satisfactorily perform the desired functions, the layer must have a thickness at least equal to 0.10 mm. According to a preferred embodiment, the thickness of the protective layer is between 0.1 mm and 0.20 mm.

 Advantageously, most of the surface is understood to mean the surface formed by the entire outer surface of the container with the exception of the electrical contact zones of the terminals which serve to establish an electrical connection with the external device to be supplied. A generator with a metal container thus being perfectly electrically insulated from the external environment can be handled with less precautions than a non-insulated generator, which facilitates and makes faster and safer the operations of battery. The metal container can in particular be made of steel or aluminum.

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 The invention also aims to provide a method of coating an electrochemical generator with a protective material which is simpler, faster and less expensive than known methods.

 The present invention also relates to a method of manufacturing an electrochemical generator comprising a container, comprising the following steps: - a thin and adherent layer of a crosslinkable resin is deposited on most of the outer surface of said container, - subjecting said resin layer to a crosslinking treatment at ambient temperature without physical contact with said resin.

 The in situ crosslinking of a resin can be carried out by several techniques: crosslinking by radiation (visible light, infrared, ultraviolet), by heat, by a liquid (organic or inorganic solvent, water), etc. Some of these methods have drawbacks, such as for example crosslinking with a solvent, which results in physical contact between the resin and the chemical compound used. In fact, the handling of a solvent requires special precautions, in particular with regard to operator safety, and its elimination is carried out by methods which can be costly and / or complex. When applied to an electrochemical generator, crosslinking by heat may damage the internal components of the generator if the temperature reached is too high.

 Advantageously, the crosslinking treatment is carried out under ultraviolet radiation. After crosslinking, the coating obtained is hard and adheres to the container. The generator is thus perfectly protected from its environment, in particular against corrosion, which increases its service life.

 Preferably the duration of the crosslinking treatment is less than 8 seconds, and more preferably less than 5 seconds.

 A resin is used which is quickly crosslinkable under the effect of ultraviolet radiation. According to a preferred embodiment, the resin contains an acrylic polymer.

 According to a first variant, the resin also contains a crosslinking agent. This agent plays the role of a catalyst facilitating initiation and then accelerating the course of crosslinking.

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 In order to facilitate deposition of the resin on the container, the resin may also contain a flow agent intended to reduce its viscosity. According to a second variant, the resin also contains a fluidity agent. According to other alternative embodiments, the resin may also contain one or more additives chosen in particular from a mechanical reinforcing agent, a thermal conductive material, colored pigments, and a flame-retardant material.

 The viscosity of the resin is preferably between 100 μm. s and lOOOmPa. s under the operating conditions of the deposition, in particular at a temperature between 20 C and 50 C.

 The resin can be deposited by immersion, painting, spraying, etc. Advantageously, said resin is deposited by spraying or by immersion. A continuous protective layer of uniform thickness is obtained. In addition, the thickness of the resin layer is low and the presence of this coating does not significantly increase either the weight or the volume of the generator.

 The installation for implementing the method comprises a crosslinking zone for the resin comprising means for in situ crosslinking of the deposited resin, and means for holding and moving the generator. The holding and displacement means are capable of carrying out a rotational movement around the axis of symmetry of the generator and a translational movement along this axis.

 Thanks to the process of the invention, all areas of the container, even manually inaccessible, are coated. We can thus ensure the protection of almost the entire surface of the generator regardless of the complexity of the shape of the generator or the battery of which it is a part. The generator thus benefits from a safe electrical insulation which is essential during battery charging. It is fully protected against any external attack, whether mechanical or chemical.

 According to an alternative embodiment, said resin is deposited by spraying. The installation comprises a zone for depositing the resin comprising a reservoir containing the crosslinkable resin, means for spraying the resin on the external surface of the generator, and means for holding and moving said generator. The holding and displacement means are capable of simultaneously carrying out a rotational movement around the axis of symmetry of the generator and a translational movement along this axis.

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 According to another alternative embodiment, said resin is deposited by immersion. The installation comprises a zone for depositing the resin comprising a receptacle open at its upper part containing the crosslinkable resin, means for holding and moving the generator. The holding and displacement means are capable of carrying out a vertical translational movement along the axis of symmetry of the generator so as to introduce the generator into said container.

 Other characteristics and advantages of the present invention will appear during the following examples of embodiment, given by way of non-limiting illustration, and in the appended drawing in which the single figure represents - FIG. 1 represents a cutaway view of the electrochemical generator according to the invention, the container of which is covered with a protective layer, - Figure 2 shows the device for carrying out the spraying process according to the invention, - Figure 3 shows the device for carrying out the immersion process according to the invention.

 The generator 1 according to the invention shown in FIG. 1 comprises a metal container 2 provided with terminals 3 whose external surface constitutes a contact area 4 making it possible to establish an electrical connection with the device to be supplied. The surface of the container 2 is covered with a protective layer 5. The protective layer 5 is obtained from a single-component resin crosslinkable by U. V. which is a commercial product presented as a transparent material of viscosity 300-400ma. s at 20 C and whose dielectric strength is greater than 40kV / mm. Colored pigments are added to the resin.

 The protective layer 5 is produced using the installation shown in FIG. 2. The installation includes a deposition zone ZD and a crosslinking zone ZR. In the ZD deposition zone there is a resin reservoir 11, maintained under a pressure of 2.5 bars, which communicates with two spray nozzles 12 and 12 ′ facing each other at an angle of 450 each. compared to each other. The resin is brought into the nozzles 12 and 12 ′ by pipes 13 which keep it protected from any U.V emission during its journey. One or more generators 10 are placed on a support 14 animated by a rotational movement around an axis 15 and a translational movement along this axis 15 represented by the double arrow 16, the combination of which

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 gives the generators a helical movement. The crosslinking zone ZR comprises a U.V. 20 radiation generator associated with a high pressure lamp 21. A blower 22 connected directly to the lamp 21 makes it possible to limit its heating.

 After verifying that the viscosity of the resin is satisfactory and constant for a temperature between 25 ° C. and 40 ° C., an electrochemical generator is produced provided with a protective layer according to the invention in the following manner. The generators 10 are installed on the support 14 and set in rotation; the generators are kept in rotation throughout the duration of the manufacturing operations. The resin is placed in the tank 11 at a temperature of 30 C. Under the effect of the internal pressure of the tank 11, the resin is sent into the nozzle 12 which projects the sprayed resin 17 onto the generators 10 animated simultaneously by a translational movement according to arrow 16. The quantity of resin deposited is determined by adjusting the opening of the nozzles 12 and 12 '. The support 14 carrying the generators 10 in rotation performs a round trip in the deposit zone ZD. The spraying of the resin by the nozzle 12 is then stopped, and the resin is sent to the nozzle 12 '. The nozzle 12 'projects the sprayed resin 17' onto the generators 10 simultaneously moving along the arrow 16, in the same manner as above. The support 14 carrying the generators 10, still in rotation, performs a round trip in the deposition zone ZD, then the spraying of the resin by the nozzle 12 is stopped. The generators 10 are then uniformly covered with a layer of crosslinkable resin having a thickness of the order of 0.15 mm. The support 14 then moves towards the crosslinking zone ZR. The generators 10 in rotation are maintained under U.V. 23 radiation for a period of approximately 15 seconds in order to crosslink. Visually, it is observed that the layer of crosslinked resin obtained is continuous and adherent to the container. It is hard and smooth, uniform and regular in appearance. Its thickness is about 0.15mm.

 In a second test, operating conditions similar to those of the first test were applied, except that the support made two round trips in front of each spray nozzle and two round trips in front of the UV lamp. obtained are then uniformly covered with a layer of crosslinked resin having a thickness of the order of 0.20mm. By visual control, it is ensured that a continuous crosslinked resin layer is obtained which adheres to the container. The layer obtained is hard and smooth, uniform and regular in appearance.

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 In a third test, operating conditions similar to those of the first test were applied except that the support made only one round trip in the spraying area and a round trip in front of the UV lamp The generators are then covered with a layer of crosslinked resin having a thickness of the order of 0.1 mm. However, it can be seen that certain parts of the container are insufficiently covered.

 In Figure 3, there is shown an installation for another embodiment of a generator according to the invention. The deposition zone ZD 'comprises a container 30, open at its upper part, containing the resin 31. In the crosslinking zone ZR'is a device similar to that of FIG. 2, FIG. 3 showing only the UV lamp 21. The generator 32 is suspended by its terminals 33 from a support 34 which can move in the vertical direction represented by the arrow 35, and a horizontal translational movement along the arrow 36. The generator 32 is plunged vertically in the direction indicated by the arrow 35 to the level of its terminals 33 in the resin 31 contained in the container 30. After a short time, the generator 32 is withdrawn from the container 30 and set in rotation around its axis of symmetry 37. It is then brought into the crosslinking zone ZR 'by horizontal displacement of the support 34, and placed in front of the UV lamp 21 arranged vertically. This process leads to the production of a continuous crosslinked protective layer adhering to the container. The layer obtained is hard and smooth, uniform and regular in appearance. Its thickness is between 0.15mm and 0.20mm.

Claims (24)

1. Electrochemical generator comprising a container carrying at least one current output terminal, characterized in that the major part of the surface of said container is covered with a thin and adherent protective layer made of a crosslinked resin.  2. Generator according to claim 1, wherein said resin contains an acrylic polymer.  3. Generator according to one of claims 1 and 2, wherein said resin further contains a mechanical reinforcing agent.  4. Generator according to one of the preceding claims, wherein said resin further contains a colored pigment.  5. Generator according to one of the preceding claims, wherein said resin further contains a thermally conductive insulating material.  6. Generator according to one of the preceding claims, wherein said resin further contains a crosslinking agent.  7. Generator according to one of the preceding claims, wherein said resin further contains a flow agent.  8. Generator according to one of the preceding claims, in which the major part of the surface of the container is constituted by the whole of the external surface of said container with the exception of the electrical contact zone of said terminal.  9. A method of manufacturing an electrochemical generator comprising a container, comprising the following steps: - depositing a thin and adherent layer of a crosslinkable resin on most of the surface of said container, - subjecting said resin layer to a crosslinking treatment at room temperature without physical contact with said resin.  10. The method of claim 9, wherein said crosslinking treatment is carried out under ultraviolet radiation. <Desc / Clms Page number 10>  11. Method according to one of claims 9 and 10, wherein the duration of said crosslinking treatment is less than 8 seconds.  12. Method according to one of claims 9 to 11, wherein said resin is crosslinkable under the effect of ultraviolet radiation.  13. Method according to one of claims 9 to 12, wherein said resin contains an acrylic polymer.  14. Method according to one of claims 9 to 13, wherein said resin further contains a crosslinking agent.  15. Method according to one of claims 9 to 14, wherein said resin further contains a flow agent.  16. Method according to one of claims 9 to 15, wherein said resin further contains a mechanical reinforcing agent.  17. Method according to one of claims 9 to 16, wherein said resin further contains a colored pigment.  18. Method according to one of claims 9 to 17, wherein said resin further contains a thermally conductive insulating material.  19. Method according to one of claims 9 to 18, wherein the viscosity of said resin is between 1 OOmPa. s and 1000ma. s.  20. Method according to one of claims 9 to 19, wherein said resin is deposited by spraying.  21. Method according to one of claims 9 to 19, wherein said resin is deposited by immersion.  22. Installation for implementing the method according to one of claims 9 to 21, comprising a crosslinking zone of said resin comprising means for in situ crosslinking of said resin, and means for holding and moving said generator, said means being capable of carrying out a rotational movement around the axis of symmetry of said generator and a translational movement along said axis. <Desc / Clms Page number 11>  23. Installation for implementing the method according to claim 20, comprising a zone for depositing said resin comprising a reservoir containing said crosslinkable resin, means for spraying said resin on the external surface of said generator, and holding means and of displacement of said generator, said means being capable of simultaneously carrying out a rotational movement around the axis of symmetry of said generator and a translational movement along said axis.  24. Installation for implementing the method according to claim 21, comprising a zone for depositing said resin comprising a receptacle open at its upper part containing said crosslinkable resin, and means for holding and moving said generator, said means being capable of performing a vertical translational movement along the axis of symmetry of said generator so as to introduce said generator into said container.