WO2020008061A1

WO2020008061A1 - Composite electromagnetic shielding wall, battery packaging comprising such a wall, and method for producing such a wall

Info

Publication number: WO2020008061A1
Application number: PCT/EP2019/068163
Authority: WO
Inventors: Jean-Baptiste Cassard
Original assignee: Faurecia Systemes D'echappement
Priority date: 2018-07-05
Filing date: 2019-07-05
Publication date: 2020-01-09
Also published as: EP3818576A1; FR3083648A1; CN112689925A; FR3083648B1

Abstract

A composite electromagnetic shielding wall, battery packaging comprising such a wall, and method for producing such a wall. This composite electromagnetic shielding wall (14) comprises a substrate (20) made of dielectric material and a conductive layer (22) applied on said substrate (20). The conductive layer (22) has been deposited onto the substrate (20) by mould coating and comprises a conductive load (30) embedded in a resin matrix (32).

Description

Composite electromagnetic shielding wall, battery packaging comprising such a wall, and method for producing such a wall

The present invention relates to a composite electromagnetic shielding wall, of the type comprising a substrate made of dielectric material and a conductive layer attached to said substrate.

The invention also relates to a battery package comprising such a shielding wall.

The invention also relates to methods of producing such a shielding wall and such a battery package.

It is known to equip motor vehicles with electric motors and batteries to power these motors. Generally, the current supplied by such a battery to power an electric motor is conditioned by a high frequency switching converter to adapt the voltage of the current to the supply voltage of the motor. However, this converter generates very rapid variations in current, called edges, in the electric cables supplying the motor, as a result of which these electric cables and the battery produce electric and electromagnetic fields liable to disturb the functioning of the surrounding electronic equipment. .

To solve this problem, it is known to make a conductive battery packaging around the battery and its current distribution buses, and to shield each electric cable out of the battery packaging.

The current way of making battery packings is however not entirely satisfactory.

Indeed, to give battery packaging electromagnetic shielding properties, the solution most often adopted is to produce these metal packaging. However, this solution is not satisfactory, because it weighs down the vehicle.

An alternative solution consists in making at least part of the packaging in plastic material, and in shielding this part of the packaging by applying an aluminum foil to it or by spraying a conductive material onto said part of the packaging. . The fact of making this envelope conductive gives it this shielding property. This solution has an obvious advantage in weight compared to the first solution. However, packaging is much more complicated and expensive to produce. An object of the invention is thus to allow the production of electromagnetic shielding parts which are light and easy to produce. Another objective is that these armor pieces are inexpensive.

To this end, the invention relates to a composite electromagnetic shielding wall of the aforementioned type, in which the conductive layer has been deposited on the substrate by mold coating, the conductive layer comprising a conductive filler embedded in a resin matrix.

According to particular embodiments of the invention, the composite electromagnetic shielding wall also has one or more of the following characteristics, taken in isolation or according to any technically possible combination (s):

- The conductive filler comprises carbon nanotubes, in particular single-walled carbon nanotubes;

the concentration of the conductive filler in the conductive layer is less than 1.5% by weight, preferably less than 0.5% by weight, and is in particular between 0.01 and 0.1% by weight relative to the total weight of the conductive layer;

.- the resin matrix consists of a solvent-free resin mainly composed of unsaturated esters crosslinked using a styrene monomer associated with dicyclopentadiene or without association with dicyclopentadiene, the unsaturated esters being preferably chosen from: polyesters, vinylesters, acrylates, and methacrylates;

the conductive layer has a thickness of less than 500 μm, preferably between 50 and 250 μm, and in particular between 80 and 150 μm;

- The substrate has a thickness greater than 0.5 mm, preferably less than 15 mm, and even more preferably between 1 and 5 mm;

the conductive layer has a surface resistivity of less than 20 W / p, preferably less than 10 W / p, and even more preferably less than or equal to 5

The subject of the invention is also a battery package comprising at least one wall of composite electromagnetic shielding as defined above.

The subject of the invention is also a method for producing a composite electromagnetic shielding wall, comprising the following steps:

production, in a mold, of a substrate of dielectric material, and mold coating of said substrate with a coating material so as to form a conductive layer added to the substrate, said coating material comprising a conductive filler embedded in a resin matrix.

According to particular embodiments of the invention, the production process also has one or more of the following characteristics, taken in isolation or according to any technically possible combination (s):

- the mold coating of the substrate is carried out by means of a mold coating process by high pressure injection.

the concentration of the conductive filler in the coating material is less than 1.5% by weight, preferably less than 0.5% by weight and is in particular between 0.01 and 0.1% by weight relative to the total weight of the coating material;

the resin matrix consists of a solvent-free resin mainly composed of unsaturated esters crosslinked using a styrene monomer associated with dicyclopentadiene or without association with dicyclopentadiene, the unsaturated esters being preferably chosen from: polyesters , vinyl esters, acrylates, and methacrylates; and

- The composite electromagnetic shielding wall obtained is constituted by a composite electromagnetic shielding wall as defined above.

Finally, the subject of the invention is a process for producing a battery pack, comprising the following steps:

production of at least one composite electromagnetic shielding wall by means of a process as defined above, and

assembling the composite electromagnetic shielding wall thus produced with at least one other wall to form the battery pack.

Other characteristics and advantages of the invention will appear on reading the description which follows, given solely by way of example and made with reference to the appended drawings, in which:

FIG. 1 is a sectional view of a battery packaging according to a first embodiment of the invention, FIG. 2 is a sectional view of a battery pack according to a second embodiment of the invention,

- Figure 3 is a view of a detail marked II in Figure 1,

- Figure 4 is a schematic view of a first step in a process for producing the packaging of Figure 1,

- Figure 5 is a schematic view of a second step in the production process of the packaging of Figure 1, and

- Figure 6 is a schematic view of a third step in the production process of the packaging of Figure 1.

The battery package 10 shown in Figure 1 comprises a plurality of walls 12 which together surround a battery 16 by forming a closed enclosure around said battery 16. This battery package 10 is typically carried on board a vehicle automobile (not shown), the battery 16 being electrically connected to an electric motor (not shown) of this motor vehicle to supply it with electrical energy.

Each wall 12 is adapted to act as a barrier to electromagnetic waves and therefore constitutes an electromagnetic shielding wall. In addition, the walls 12 are connected to each other so as to ensure electrical continuity between the walls 12, so that the battery packaging 10 constitutes a Faraday cage around the battery 16. For this purpose, pins 18 of electrically conductive material connect the walls 12 to each other.

In the example shown, there are two walls 12, each wall 12 being shaped like a half-shell.

The walls 12 include at least one composite electromagnetic shielding wall 14.

With reference to FIG. 3, this composite electromagnetic shielding wall 14 comprises a substrate 20 made of dielectric material and a conductive layer 22 attached to said substrate 20.

The substrate of dielectric material 20 has a thickness e1 greater than 0.5 mm, preferably less than 15 mm, and even more preferably between 1 and 5 mm.

The substrate of dielectric material 20 is made of composite material comprising material fibers (not shown) embedded in a resin matrix (not shown). In particular, in the example shown, the substrate of dielectric material 20 is formed of a plurality of layers 24, 26, 28 of material composite superimposed and glued to each other, the material of each layer 24, 26, 28 preferably being identical to the material of each other layer 24, 26, 28 and comprising fibers of material (not shown) embedded in a resin matrix (not shown).

The material fibers used in the composition of each layer 24, 26, 28 and therefore constituting the material fibers of the substrate 20 preferably comprise fibers of glass, basalt, carbon, aramid, or high-weight polypropylene molecular (better known under the acronym HMPP for “high-modulus polypropylene”) and are advantageously constituted by such fibers. As a variant, the fibers of material entering into the composition of each layer 24, 26, 28 and therefore constituting the fibers of material of the substrate 20 comprise bio-sourced fibers such as flax or hemp fibers, and are advantageously constituted by such fibers.

The resin matrix entering into the composition of each layer 24, 26, 28 and therefore constituting the resin matrix of the substrate 20 preferably comprises a polyester resin and is advantageously constituted by such a resin. As a variant, the resin matrix entering into the composition of each layer 24, 26, 28 and therefore constituting the resin matrix of the substrate 20 comprises a vinyl ester or acrylic resin and is typically constituted by such a resin.

The layers 24, 26, 28 are here represented three in number. As a variant, the layers 24, 26, 28 are two in number, or their number is strictly greater than three. In another variant, the substrate 20 is formed of a single layer.

The conductive layer 22 has a thickness e2 of less than 500 μm, preferably between 50 and 250 μm, and in particular between 80 and 150 μm. It has a surface resistivity less than 20 W / p, preferably less than 10 W / p, and even more preferably less than or equal to 5 W / p.

The conductive layer 22 has been deposited on the substrate of dielectric material 20 by coating with a mold (better known under known under the English name "In-Mold Coating" or under the corresponding acronym IMC).

In particular, the conductive layer 22 and the substrate made of dielectric material 20 are copolymerized.

The conductive layer 22 comprises a conductive filler 30 embedded in a resin matrix 32.

The conductive filler 30 comprises carbon nanotubes, in particular single-walled carbon nanotubes, better known by the acronym SWCNT (from English “Single Wall Carbon Nanotube”). Preferably, the conductive filler 30 is formed by these carbon nanotubes.

Carbon nanotubes have, for example, a diameter to length ratio of between 1/50000 and 1/40000.

The concentration of the conductive filler 30 in the conductive layer 22 is less than 1.5% by weight, preferably less than 0.5% by weight, and is in particular between 0.1 and 0.01% by weight per relative to the total weight of the conductive layer 22.

The resin matrix 32 is made of a solvent-free resin mainly composed of unsaturated esters crosslinked using a styrene monomer associated with dicyclopentadiene or without association with dicyclopentadiene. These unsaturated esters are preferably chosen from: polyesters, vinylesters, acrylates, and methacrylates.

In the variant of Figure 1, a single wall 12 is constituted by such a composite electromagnetic shielding wall 14, the other wall 12 being constituted by a metal wall. In the variant of FIG. 2, each wall 12 is constituted by such a composite electromagnetic shielding wall 14, the pins 18 then being arranged so as to electrically connect to each other the conductive layers 22 of said electromagnetic shielding walls composite 14.

A process for producing the battery pack 10 will now be written, with reference to Figures 4 to 6.

This method comprises a first step (not shown) for producing the metal walls 12 of the battery pack 10, a second step for producing the composite electromagnetic shielding wall 14, and a third step (not shown) for assembling the walls 12, 14 to each other so as to form the battery pack 10.

The step for producing metal walls 12 is carried out by means of a conventional method for producing metal walls for electromagnetic shielding.

The step of producing the composite electromagnetic shielding wall 14 is carried out in parallel with the step of producing the metal walls 12.

This step of producing the composite electromagnetic shielding wall 14 comprises the production, in a mold 40, of the substrate 20 of dielectric material, and the coating in the mold of said substrate 20 with a coating material 42 so as to form the conductive layer 22 attached to the dielectric material substrate 20. The mold coating of the substrate of dielectric material 20 is in particular carried out by means of a mold coating process by high pressure injection, better known by the acronym IMC HPIP (coming from the English “In-Mold Coating High Pressure Injection Process ”).

To this end, the step of producing the composite electromagnetic shielding wall 14 comprises, as shown in FIG. 4, a first sub-step of depositing sheet-shaped molding compositions 44 (better known under the English name “ Sheet Molding Compound ", or under the corresponding acronym SMC) in mold 40, said mold 40 being at an operating temperature typically between 140 and 150 ° C.

Each sheet-shaped molding composition 44 includes material fibers (not shown) embedded in a resin matrix (not shown).

The material fibers used in the composition of each sheet 44 preferably comprise glass fibers, basalt, carbon, aramid, or high molecular weight polypropylene (better known by the acronym HMPP for “high-modulus” polypropylene ") and are advantageously constituted by such fibers. As a variant, the fibers of material entering into the composition of each layer 24, 26, 28 and therefore constituting the fibers of material of the substrate 20 comprise bio-sourced fibers such as flax or hemp fibers, and are advantageously constituted by such fibers.

The resin matrix used in the composition of each sheet 44 preferably comprises a polyester resin and is advantageously constituted by such a resin. As a variant, the resin matrix entering into the composition of each sheet 44 comprises a vinyl ester or acrylic resin and is typically constituted by such a resin.

This first sub-step is followed by a second sub-step, shown in FIG. 5, of compression of the molding compositions in the form of sheets 44. During this step, the mold 40 is closed and applies a high pressure, typically between 80 and 100 bars, on the sheets 44. Under the effect of this pressure, the sheets 44 merge and take the form of the mold 40, which produces the substrate made of dielectric material 20.

The number and the thickness of the sheets 44 are preferably adapted so that the substrate of dielectric material 20 has a thickness e1 greater than 0.5 mm, preferably less than 15 mm, and even more preferably between 1 and 5 mm. it is preferably checked before inserting the sheets 44 into the mold 40, typically by weighing the sheets 44 and comparing the weight thus obtained with a target weight constituted by the weight of the finished part, excluding deburring and any cuts.

The pressure is thus maintained for a duration less than or equal to the gel time of the resin matrix used in the composition of the sheets 44.

This second substep is followed by a third substep, shown in FIG. 6, of coating the substrate with dielectric material 20 in a mold. During this third substep, the pressure applied by the mold 40 is reduced, said mold 40 remaining closed, and the coating material 42 is injected at high pressure between the substrate made of dielectric material 20 and a wall 46 of the mold 40 The pressure maintained by the mold 40 is then between 40 and 50 bars, the injection pressure being between 200 and 400 bars. Under the effect of this pressure, the coating material 42 is distributed in the space between the substrate of dielectric material 20 and the wall 46 of the mold 40, and thus forms the conductive layer 22.

The injection of the coating material 42 is advantageously dosed so as to obtain a conductive layer 22 of thickness e2 less than 500 μm, preferably between 50 and 250 μm, and in particular between 80 and 150 μm.

The coating material 42 comprises a conductive filler embedded in a resin matrix.

The conductive filler preferably comprises carbon nanotubes, in particular single-walled carbon nanotubes, better known by the acronym SWCNT (from the English “Single Wall Carbon Nanotube”). Advantageously, the conductive filler consists of these carbon nanotubes.

The concentration of the conductive filler in the coating material 42 is less than 1.5% by weight, preferably less than 0.5% by weight, and is in particular between 0.1 and 0.01% by weight. in relation to the total weight of the coating material 42.

The resin matrix consists of a solvent-free resin mainly composed of unsaturated esters crosslinked using a styrene monomer associated with dicyclopentadiene or without association with dicyclopentadiene. These unsaturated esters are preferably chosen from: polyesters, vinylesters, acrylates, and methacrylates. The mold 40 is maintained in this configuration after the injection of the coating material 42 has stopped, at least for the time necessary for the polymerization of the resin matrix used in the composition of the coating material 42.

In particular, at the end of this sub-step, the conductive layer 22 and the substrate made of dielectric material 20 have copolymerized.

The third sub-step is followed by a fourth sub-step of opening the mold 40 and extracting the composite electromagnetic shielding wall 14 thus formed.

Thanks to the invention described above, a non-porous composite electromagnetic shielding wall 14 is obtained, having an excellent surface condition, with a very tenacious chemical bond between the substrate 20 and the conductive layer 22, in a single operation. Thus, the production of the battery pack 10 is particularly quick and easy. It is therefore possible to lighten the battery pack 10 at a lower cost.

This economic dimension of the composite electromagnetic shielding wall 14 is reinforced by the particularly low density of carbon nanotubes which it is necessary to incorporate into the conductive layer 22 to obtain the desired electromagnetic shielding effect, and by the thickness e2 particularly weak of the conductive layer 22.

Furthermore, the low density of carbon nanotubes in the coating material 42 has little impact on the viscosity of the coating material 42, which allows it to be well distributed in the mold 40 and that the thickness e2 of the conductive layer 22 or, therefore, relatively homogeneous.

Claims

1.- composite electromagnetic shielding wall (14), said wall (14) comprising a substrate (20) of dielectric material and a conductive layer (22) attached to said substrate (20), characterized in that the conductive layer (22 ) was deposited on the substrate (20) by mold coating, the conductive layer (22) comprising a conductive filler (30) embedded in a resin matrix (32).

2. A composite electromagnetic shielding wall (14) according to claim 1, in which the conductive load (30) comprises carbon nanotubes, in particular single-walled carbon nanotubes.

3.- composite electromagnetic shielding wall (14) according to claim 1 or 2, wherein the concentration of the conductive charge (30) in the conductive layer (22) is less than 1.5% by weight, preferably less than 0.5% by weight, and is in particular between 0.01 and 0.1% by weight relative to the total weight of the conductive layer (22).

4.- composite electromagnetic shielding wall (14) according to any one of the preceding claims, in which the resin matrix (32) consists of a solvent-free resin composed mainly of unsaturated esters crosslinked using a styrene monomer associated with dicyclopentadiene or without association with dicyclopentadiene, the unsaturated esters being preferably chosen from: polyesters, vinyl esters, acrylates, and methacrylates.

5.- composite electromagnetic shielding wall (14) according to any one of the preceding claims, in which the conductive layer (22) has a thickness (e2) of less than 500 μm, preferably between 50 and 250 μm, and in particular between 80 and 150 pm.

6.- composite electromagnetic shielding wall (14) according to any one of the preceding claims, in which the substrate (20) has a thickness (e1) greater than 0.5 mm, preferably less than 15 mm, and even more preferably between 1 and 5 mm.

7.- composite electromagnetic shielding wall (14) according to any one of the preceding claims, in which the conductive layer (22) has a surface resistivity less than 20 W / p, preferably less than 10 W / p, and even more preferably less than or equal to 5 W / p.

8.- Battery package (10) comprising at least one electromagnetic composite shielding wall (14) according to any one of the preceding claims.

9.- Method for producing a composite electromagnetic shielding wall (14), characterized in that said method comprises the following steps:

production, in a mold (40), of a substrate of dielectric material (20), and

mold coating of said substrate (20) with a coating material (42) so as to form a conductive layer (22) attached to the substrate (20), said coating material (42) comprising a conductive filler embedded in a matrix resin.

10. The production method according to claim 9, wherein the mold coating of the substrate (20) is carried out by means of a mold coating process by high pressure injection.

1 1 .- Production method according to claim 9 or 10, wherein the composite electromagnetic shielding wall (14) obtained is constituted by a wall (14) according to any one of claims 1 to 7.

12.- Method for producing a battery pack (10), comprising the following steps:

production of at least one composite electromagnetic shielding wall (14) by means of a method according to any one of claims 9 to 1 1, and

assembling the composite electromagnetic shielding wall (14) thus produced with at least one other wall (12) to form the battery pack (10).