Connection part intended for electrically connecting a first metal surface to a second metal surface in an electrochemical element, and associated element, method and process

Abstract

The part (12) comprises a metal body having a first portion (32) for electrical connection to the first metal surface and a second portion (34) for electrical connection to the second metal surface. The first electrical connection portion (32) has an attachment face (44) intended to be welded respectively to a metal surface and an opposite face (46) for the application of a welding power. The opposite face (46) for the application of a welding power has at least one anti-reflective region, characterised in that the anti-reflective region is formed by a metal coating (56) deposited on the face (46) for the application of the welding power.

Description

[0001] DESCRIPTION

[0002] TITLE: Connection piece for electrically connecting a first metal surface to a second metal surface in an electrochemical element, associated element, method and process

[0003] The present invention relates to a connection part for electrically connecting a first metal surface to a second metal surface in an electrochemical element, the connection part comprising a metal body having a first electrical connection part to the first metal surface and a second electrical connection part to the second metal surface, at least one of the first electrical connection part and the second electrical connection part having a fixing face intended to be welded respectively on the first metal surface or on the second metal surface and an opposite face for applying welding power, the opposite face for applying welding power having at least one anti-reflective region.

[0004] Such an electrical connection part is intended to be fixed in particular by laser welding between two parts in an electrochemical element, for example a lithium-ion accumulator.

[0005] The connection part is in particular intended to be welded onto metal surfaces made of copper, aluminum, or stainless steel of connection elements, such as a tab and / or an electrode strip of an electrochemical harness, an output terminal, a busbar, a latch, etc.

[0006] In laser transparency welding, part of the laser beam is reflected and does not contribute to the welding energy. For example, when using an infrared wavelength (approximately 1070 nm), only about 5% of the laser beam energy for copper and 10% of the laser beam energy for aluminum is actually transmitted to the material to be welded to initiate the weld pool.

[0007] To overcome this problem, the welding energy applied to this part is significantly increased and can be at the maximum technical limits of the laser (particularly in terms of power), leaving no room for adjustment to the welding process.

[0008] Furthermore, the risk of burning peripheral parts remains high, due to the significant energy required. Conventionally, to reduce the applied power, it is known to form the portion intended to be welded of the connection part from a co-laminated part comprising a layer of stainless steel on the copper layer, as described in FR2974451.

[0009] The stainless steel layer absorbs more of the energy emitted by the laser during transparency welding, making it easier to laser weld the two copper layers under the stainless steel layer.

[0010] This soldering solution, which is made possible by the stainless steel layer laminated onto the copper, guarantees the passage of high currents (for example, greater than 100A) through the copper connection once the soldering has been carried out.

[0011] In FR2974451, the co-rolled parts are reduced to the ends intended to be welded, thus limiting the cost of stainless steel.

[0012] However, such a solution can still be improved to reduce manufacturing costs. In addition, co-lamination is sometimes complicated to implement, especially on small surfaces.

[0013] An aim of the invention is to propose a connection part guaranteeing the passage of high currents, fixed by laser welding on at least one element, while reducing the manufacturing cost and simplifying the welding process.

[0014] To this end, the invention relates to a connection part of the aforementioned type, characterized in that the anti-reflective region is formed from a metallic coating deposited on the face of application of the welding power.

[0015] The connection part according to the invention may comprise one or more of the following characteristics, taken in isolation or in any possible combination: the anti-reflective region has a roughness Ra of between 10 micrometers and 40 micrometers according to standard NF EN ISO 21920-3; the connection part is made of copper; the deposited coating is made of stainless steel or nickel; the thickness of the deposited coating is between 50 micrometers and 200 micrometers; at least one of the first electrical connection part and the second electrical connection part has a groove, the anti-reflective region being arranged in the groove; at least one of the first electrical connection part and the second electrical connection part comprises at least two distinct anti-reflective regions;the or each anti-reflective region is in the form of a strip with a longitudinal extent advantageously between 10 mm and 50 mm and a transverse extent advantageously between 1 mm and 10 mm; at least one of the first electrical connection part and the second electrical connection part defines a gas passage orifice, the two anti-reflective regions being arranged on either side of the gas passage orifice;

[0016] The invention also relates to an electrochemical element comprising: a first metal surface; a second metal surface; a connection part as defined above electrically connecting the first metal surface to the second metal surface, the fixing face having at least one weld on at least one of the first metal surface and the second metal surface, the weld extending opposite the anti-reflective region.

[0017] The electrochemical element according to the invention may comprise one or more of the following characteristics, taken in isolation or in any technically possible combination: the first metal surface is defined on an electrical power output terminal, the second metal surface being defined in an electrochemical beam comprising at least one electrode; the face for applying a welding power comprises an anti-reflective region only opposite the second metal surface.

[0018] The invention also relates to a manufacturing method comprising the following steps: providing a metal body having a first electrical connection part to a first metal surface of an electrochemical element and a second electrical connection part to a second metal surface of the electrochemical element, at least one of the first electrical connection part and the second electrical connection part having a fixing face intended to be welded respectively to the first metal surface or to the second metal surface and an opposite face for applying a welding power; depositing a metal coating on the or each opposite face to form at least one anti-reflective region.The manufacturing method according to the invention may comprise the following characteristic: the deposition of the metallic anti-reflective coating is carried out by dynamic gas projection of metallic particles, in particular particles of stainless steel, nickel or / and nickel alloy, the temperature of the gas preferably being lower than the melting temperature of the metallic particles.

[0019] The invention also relates to a method for connecting a first metal surface to a second metal surface in an electrochemical element, the method comprising the following steps: providing a connection part as defined above; applying a welding power to the or each anti-reflective region to carry out the welding between the first metal surface and / or the second metal surface and the connection part opposite the anti-reflective region.

[0020] The connection method according to the invention may comprise the following characteristic: the application of the welding power is carried out by emitting a laser beam directed onto the anti-reflective region.

[0021] The invention will be better understood on reading the following description, given solely as a non-limiting example, and made with reference to the appended drawings, in which:

[0022] [Fig. 1] Figure 1 is a simplified view, taken in section along a vertical plane, of an electrochemical element comprising a first metal connection part according to the invention;

[0023] [Fig. 2] Figure 2 is an enlarged view of Figure 1, illustrating in more detail the positioning of the connecting piece;

[0024] [Fig. 3] Figure 3 is a schematic view of a metal body intended to receive a metal coating by deposition;

[0025] [Fig.4] Figure 4 is a schematic view of a connection part according to the invention, after deposition of the coating;

[0026] [Fig. 5] Figure 5 is a schematic sectional view of a laser welding step in a method of connecting the connection part according to the invention;

[0027] [Fig. 6] Figure 6 is a view similar to Figure 2, in a variant where the electrochemical element is a prismatic element;

[0028] [Fig. 7] Figure 7 is a schematic view of another connection piece according to the invention, in the variant where the electrochemical element is a prismatic element. A first electrochemical element 10 according to the invention, provided with a connection piece 12 according to the invention is shown schematically in Figure 1.

[0029] In this example, the electrochemical element 10 is a cylindrical element 14.

[0030] Alternatively, as will be described later with reference to Figure 5, the electrochemical element 10 is a prismatic element, or a pocket.

[0031] The electrochemical element 10 is for example of the lithium-ion type.

[0032] The electrochemical element 10 comprises, in the example of FIG. 1, a bundle 16 of electrodes of opposite polarities.

[0033] The bundle of electrodes 16 comprises an alternation of electrodes of a first polarity, for example negative, and electrodes of a second polarity, for example positive, and a separator separating each pair of electrodes of opposite polarities facing each other.

[0034] In this example, the electrode bundle 16 is wound around a central axis AA' and forms a coil.

[0035] Advantageously, the electrochemical element 10 further comprises a container 20 containing the bundle of electrodes 16 and the connection part 12, and a cover 22, closing the container 20 upwards. The electrochemical element 10 advantageously comprises a flat connection 24 arranged at the foot of the bundle of electrodes 16, an electrically conductive shaped part 26, electrically connected to the flat connection 24 and a bottom wall 28 fixed under the shaped part 26 to close the container 20 downwards.

[0036] The electrochemical element 10 further comprises terminals 18A, 18B carried by the cover 22.

[0037] Terminals 18A, 18B are output terminals configured to provide electrical power when electrochemical element 10 is discharging, and to receive electrical power when electrochemical element 10 is charging.

[0038] Advantageously, terminal 18A is connected to the or each electrode of first polarity and terminal 18B is connected to the or each electrode of second polarity.

[0039] In this example, the first polarity terminal 18A is mounted through the cover 22 while being electrically insulated therefrom by a seal 30 (visible in FIG. 2). The first polarity terminal 18A is connected to electrodes of a first polarity of the electrode bundle 16 by means of a connection piece 12 according to the invention.

[0040] The planar connection 24 is electrically connected to electrodes of a second polarity opposite to the first polarity in the electrode bundle 16. The conductive shaped part 26 electrically connects the planar connection 24 to the bottom wall 28.

[0041] The planar connection 24 and the conductive shaped part 26 are made of a conductive material such as copper, aluminum, aluminum alloy or stainless steel.

[0042] The bottom wall 28 is electrically connected to the container 20, itself being electrically connected to the cover 22.

[0043] The second polarity electrode 18B is directly mounted on the cover 22, being in electrical contact with the cover 22. The or each second polarity electrode is electrically connected to the second polarity terminal 18B via the flat connection 24, the conductive shaped part 26, the bottom wall 28, the container 20 and the cover 22.

[0044] As visible in Figure 2, the connection part 12 extends here between a first metal surface defined by the terminal 18A and a second metal surface 23 defined on the bundle 16. In particular, it mechanically and electrically connects one or more electrodes of first polarity of the bundle 16 and the terminal 18A.

[0045] With reference to figures 2 to 4, the connection part 12 has a first part 32 for electrical connection to the harness 16, welded to the harness 16 and a second part 34 for connection to the terminal 18A, fixed to the terminal 18A, for example by welding.

[0046] The connecting piece 12 comprises a thin metal body 36.

[0047] The metal body 36 is for example formed from copper or a copper alloy. Examples of material forming the metal body 36 are Cua1 type copper (Cu-ETP) having a minimum of 99.9% by mass of copper, Cub1 type copper (Cu-DHP), having a minimum of 99.9% by mass of copper, with a residual presence of phosphorus, or Cud type copper (CU-OF), which is deoxidized, and which has a minimum of 99.95% by mass of copper.

[0048] Alternatively, the metal body 36 is made of aluminum or aluminum alloy.

[0049] The thickness of the metal body 36 is for example less than 2 mm, and is in particular between 200 μm and 2 mm, preferably between 300 μm and 600 μm.

[0050] In the example shown in Figure 2, the metal body 36 is folded. Here, it has an intermediate portion 38 located between the connecting portions 32, 34, defining a plurality of successive folds 40. In the example shown in Figures 2 and 4, the folds 40 extend transversely relative to a longitudinal axis C-C' of the connecting part 12. In the example visible in Figure 3, the first portion 32 comprises, on one side, a face 44 for fixing to the metal surface 23 and, on the other side, a face 46 for applying welding power. It defines a through-orifice 42 for the passage of gases, opening into the two faces 44, 46 and at least one groove 48 formed in the application face 46 and forming a relief in the fixing face 44.

[0051] The gas passage orifice 42 is provided through the first part 32. It is intended for the passage of gases coming from the electrode bundle 16, in particular gases generated during a thermal runaway phenomenon.

[0052] The fixing face 44 is intended to be welded to the metal surface 23 of the electrode bundle 16.

[0053] The application face 46 is located opposite the fixing face 44 and is intended to receive the welding power, in particular by applying a beam from a welding laser.

[0054] In the example visible in Figure 3, two grooves 48 are provided in the application face 46 of the first part 32.

[0055] The two grooves 48 are advantageously arranged on either side of the orifice 42, along an axis B-B' perpendicular to the longitudinal axis C-C' of the connection part 12.

[0056] Advantageously, each groove 48 is formed by stamping. In this case, each groove 48 creates, on the fixing face 44, a boss configured to protrude towards the metal surface 23 of the electrode bundle 16. This allows better electrical contact between the fixing face 44 and the electrode bundle 16.

[0057] Each groove 48 here extends over more than 80%, in particular over 100% of the width of the connecting part 32 taken along the axis B-B'. The longitudinal extent of the groove 48, taken along the axis B-B', is advantageously between 10 mm and 50 mm.

[0058] The transverse extent of each groove 48 taken along the axis C-C' is generally less than the transverse extent of the gas passage orifice 42, taken along the same axis C-C'. This transverse extent is advantageously between 1 mm and 10 mm.

[0059] The depth of the groove 48 is advantageously between 0.3 mm and 1.2 mm.

[0060] The application face 46 advantageously comprises at least one anti-reflective region 52.

[0061] In Figure 4, the fixing face 46 comprises, in each groove 48, an associated anti-reflective region 52, which advantageously covers the entire groove 48. Thus, in the example of Figure 4, the first electrical connection part 32 comprises two distinct anti-reflective regions, each located in a groove 48.

[0062] Each anti-reflective region 52 is intended, after application of the fixing face 44 on the metal surface 23 of the electrode bundle 16, to receive the welding power, for example by being illuminated by a laser beam 54, visible in FIG. 5, providing the welding light power.

[0063] The application face 46 thus receives the welding power from an external source via the anti-reflective region 52. This power is then transmitted by thermal conduction through the metal body 36 to the fixing face 44 and into the metal surface 23 of the beam 16.

[0064] Each anti-reflective region 52 consists of a metal coating 56 deposited on the application face 46 in the groove 48. In the example shown in FIGS. 4 and 5, the metal coating 56 extends at least in each groove 48, but preferably without covering the entire application face 46.

[0065] The thickness of the metal coating 56 is advantageously between 50 and 200 micrometers.

[0066] The metal coating 56 is for example formed from stainless steel.

[0067] Examples of material forming the deposited metal coating 56 are 316L stainless steel, 304L stainless steel or 630 stainless steel.

[0068] The 56 metallic coating has a roughness Ra of between 10 micrometers and 40 micrometers according to standard NF EN ISO 21920-3.

[0069] As will be seen below, the metallic coating 56 advantageously results from the deposition without fusion of metallic particles projected against the application face 46.

[0070] The first part 32 of the metal body 36 is fixed to the metal surface 23 of the bundle 16 by at least one weld bead 58 connecting the fixing face 44 and the metal surface 23 of the bundle 16.

[0071] The weld bead 58 is produced by melting metal from the metal body 36 and the metal surface 23 of the beam 16 in a contact zone and by solidifying the contact zone.

[0072] As illustrated by figure 5, the weld bead 58 obtained advantageously has a width L less than its depth P.

[0073] The or each weld bead 58 extends opposite an anti-reflective region 52, opposite the metal coating 56.

[0074] A method of manufacturing a connecting part 12 will now be described.

[0075] Initially, a metal body 36 is provided, the metal body 36 advantageously comprising at least one groove 48 as described previously. A metal anti-reflective coating 56 is deposited on the application face 46, in particular in each groove 48.

[0076] This deposition is preferably carried out by dynamic projection of metallic particles carried by a gas brought to a temperature lower than the melting temperature of the particles (designated by the English term “Cold Spray”).

[0077] Metal particles include steel particles. The particle size, for example, ranges from 5 pm to 80 pm on average in number.

[0078] The gas used for dynamic gas projection is, for example, helium, air or nitrogen.

[0079] The gas is preferably projected together with the metal particles through a nozzle which accelerates the mixture to a speed advantageously greater than the speed of sound.

[0080] The deposition carried out by dynamic gas projection at a temperature below the melting temperature of the particles forms the metallic coating 56 on the or each anti-reflective region 52, by deformation of the metallic particles resulting from the conversion of their kinetic energy after their contact with the application face 46.

[0081] Alternatively, the deposition of the metallic anti-reflective coating 56 is carried out by electrochemical deposition.

[0082] A method of electrically connecting a first metal surface of a terminal 18A to an electrode bundle 16 within an electrochemical element 10, via a connection part 12 according to the invention, will now be described.

[0083] Initially, an 18A terminal and a 16 electrode harness are provided.

[0084] Then, a connecting piece 12 as described above is provided.

[0085] The second part 34 of the connection piece 12 is fixed to a metal surface of the terminal 18A, in particular by ultrasonic welding.

[0086] The attachment between the second part 34 of the connection piece 12 and the terminal 18A is for example carried out away from the electrode bundle 16, thus avoiding any risk of damage to the electrode bundle 16.

[0087] Then, the fixing face 44 of the first part 32 of the connection piece 12 is brought into contact with the metal surface 23 of the electrode bundle 16. The relief formed on the fixing face 44 opposite each groove 48 is inserted into the electrode bundle 16, guaranteeing a significant contact area between the fixing face 44 and the metal surface 23.

[0088] Then, as illustrated by FIG. 5, a laser beam 54 is brought opposite the or each anti-reflective region 52. The laser beam 54 is directed and focused on the or each anti-reflective region 52. The laser beam 54 advantageously emits infrared light, in particular at a wavelength between 900 nm and 1200 nm, preferably between 1050 nm and 1100 nm.

[0089] The laser beam 54 is for example provided by a Nd:YAG type laser (neodymium-doped yttrium-aluminium garnet).

[0090] Due to the metallic composition of the anti-reflective region 52, the reflection of the laser beam 54 on the application face 46 is reduced, and the absorption of the energy of the laser beam 54 through the metallic body 36 and the metallic surface 23 of the beam 16 is increased.

[0091] Thus, a weld pool is formed through the entire thickness of the metal body 36, and partially through the metal surface 23 of the bundle 16 to which the metal body 36 is to be welded. The weld pool brings molten metal from the metal body 36 into contact with molten metal from the metal surface 23 of the bundle 16.

[0092] When the solder bath cools, a solid 58 weld bead is thus produced.

[0093] Thus, the weld between the metal body 36 at the first part 32 and the metal surface 23 of the bundle 16 is particularly robust.

[0094] In a variant, illustrated by FIG. 6, the electrochemical element 10 is a prismatic element. The bundle 16 of electrodes comprises a stack of planar electrodes having electrical connection tabs 60A, 60B. The tabs 60A of the electrodes of first polarity are preferably grouped on one side of the prismatic element, while the tabs 60B of the electrodes of second polarity are grouped on another side of the prismatic element.

[0095] In this example, as illustrated by figure 7, the connection part 12 advantageously has a Y shape.

[0096] The connecting piece 12 connects each group of tabs 60A, 60B to a terminal 18A.

[0097] In the example visible in Figure 7, the first electrical connection part 32 comprises a first branch 61 and a second branch 62.

[0098] The first branch 61 and the second branch 62 each have an application face 46 having an anti-reflective region. In this example, the application faces 46 of each of the first branch 61 and the second branch 62 are entirely covered with a metal coating 56 intended to receive the welding power. The first branch 61 and the second branch 62 each have a fixing face 44 opposite the application face 46, the fixing faces 44 of the first branch 61 and the second branch 62 being connected to the tabs 60A.

[0099] The second part 34 electrically connects the connection piece 12 to the terminal 18A. The second part 34 is advantageously offset vertically relative to the first part 32 by a height, for example, of between 0.3 mm and 1.2 mm.

[0100] In another variant (not shown), the metal coating 56 constituting the anti-reflective region 52 is made of nickel or nickel alloy or is made of stainless steel.

[0101] Thanks to the invention which has just been described, during laser welding, the or each anti-reflective region 52 maximizes the absorption of the power received from the laser, in a localized manner on the connection part 12.

[0102] It is therefore not necessary to use the laser at its maximum power, thus reducing the risks and associated energy costs. Similarly, it is not necessary to use a green laser (with a wavelength approximately equal to 500 nm), which is an expensive piece of equipment.

[0103] In particular, adjacent surfaces are subjected to a lower power of laser beam 54, which prevents their damage.

[0104] In addition, the connection part 12 is produced in a very simple manner, while reducing the quantity of material used when depositing the metal coating 56.

[0105] The use of a coating deposited on the application face 44 instead of a co-laminated layer also simplifies the production of the part 12 and guarantees thermal contact between the coating and the metal body 36 for the transmission of thermal power by conduction.

[0106] The presence of an anti-reflective region 52 therefore preserves the basic material of the metal body 36, here copper, thus guaranteeing the passage of strong currents

[0107] The installation of such a connection part 12 in an electrochemical element 10 therefore ensures the passage of high currents between the terminal 18A and the electrode bundle 16 by laser welding, while greatly reducing the manufacturing cost and simplifying the manufacturing process.

Claims

CLAIMS 1. A connecting piece (12) for electrically connecting a first metal surface to a second metal surface in an electrochemical element (10), the connecting piece (12) comprising a metal body (36) having a first portion (32) for electrical connection to the first metal surface and a second portion (34) for electrical connection to the second metal surface, at least one of the first portion (32) for electrical connection and the second portion (34) for electrical connection having a fixing face (44) for being welded respectively to the first metal surface or to the second metal surface and an opposite face for applying a welding power (46), the opposite face for applying a welding power (46) having at least one anti-reflective region (52),characterized in that the anti-reflective region (52) is formed of a metallic coating deposited on the welding power application face (46)., 2. Connection part (12) according to claim 1, in which the anti-reflective region (52) has a roughness Ra of between 10 micrometers and 40 micrometers according to standard NF EN ISO 21920-3.

3. A connecting piece (12) according to any preceding claim, wherein the connecting piece (12) is made of copper.

4. Connecting part (12) according to any one of the preceding claims, in which the coating (56) deposited is made of stainless steel or nickel.

5. Connection part (12) according to any one of the preceding claims, in which the thickness of the coating (56) deposited is between 50 micrometers and 200 micrometers.

6. A connecting piece (12) according to any preceding claim, wherein at least one of the first electrical connection portion (32) and the second electrical connection portion (34) has a groove (48), the anti-reflective region (52) being disposed in the groove (48).

7. Connecting part (12) according to any one of the preceding claims, in which at least one of the first connecting part (32) electrical and the second electrical connection part (34) comprises at least two distinct anti-reflective regions (52).

8. Connecting piece (12) according to claim 7, in which the or each anti-reflective region (52) is in the form of a strip with a longitudinal extent advantageously between 10 mm and 50 mm and a transverse extent advantageously between 1 mm and 10 mm.

9. Connection part (12) according to one of claims 7 or 8, in which at least one of the first electrical connection part (32) and the second electrical connection part (34) defines a gas passage orifice (42), the two anti-reflective regions (52) being arranged on either side of the gas passage orifice (42).

10. Electrochemical element (10), comprising: - a first metallic surface; - a second metal surface; - a connecting piece (12) according to any one of the preceding claims, electrically connecting the first metal surface to the second metal surface, the fixing face (44) having at least one weld on at least one of the first metal surface and the second metal surface, the weld extending opposite the anti-reflective region (52).

11. Electrochemical element (10) according to claim 10, wherein the first metal surface is defined on an electrical power output terminal (18A), the second metal surface being defined in an electrochemical beam (16) comprising at least one electrode.

12. Electrochemical element (10) according to claim 10 or 11, wherein the welding power application face (46) comprises an anti-reflective region (52) only opposite the second metal surface.

13. Method of manufacturing a connecting part (12) according to one of claims 1 to 9, the method comprising the following steps: - providing a metallic body (36) having a first part (32) for electrical connection to a first metallic surface of an electrochemical element (10) and a second part (34) for electrical connection to a second surface metallic surface of the electrochemical element (10), at least one of the first electrical connection part (32) and the second electrical connection part (34) having a fixing face (44) intended to be welded respectively on the first metallic surface or on the second metallic surface and an opposite face for applying (46) a welding power, - depositing a metallic coating (56) on the or each opposite face (46) to form at least one anti-reflective region (52).

14. Method according to claim 13, in which the deposition of the metallic anti-reflective coating (56) is carried out by dynamic gas projection of metallic particles, in particular particles of stainless steel, nickel or / and nickel alloy, the temperature of the gas preferably being lower than the melting temperature of the metallic particles.

15. A method of connecting a first metal surface to a second metal surface in an electrochemical element (10), the method comprising the following steps: - providing a connecting part (12) according to any one of claims 1 to 9, - applying a welding power to the or each anti-reflective region (52) to produce the weld between the first metal surface and / or the second metal surface and the connecting part (12) opposite the anti-reflective region (52).

16. The method of claim 15, wherein the application of the welding power is carried out by emitting a laser beam (54) directed onto the anti-reflective region (52).

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