Welding to seal an electrolyte fill hole for a battery cell, and associated battery cell
A novel welding pattern for electrochemical battery cells addresses the issue of incomplete seals by reducing overlap zones, improving seal reliability and reducing leakage risks through a specific laser welding process.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- AUTOMOTIVE CELLS CO SE
- Filing Date
- 2024-12-17
- Publication Date
- 2026-06-19
AI Technical Summary
Existing welding processes for sealing electrolyte fill holes in electrochemical battery cells result in incomplete or non-uniform seals, leading to potential leakage and reduced efficiency due to the complexity of laser welding and the need for precise overlap zones that weaken the seal.
A new welding pattern is employed that includes a pre-weld segment deviating from the tangent axis to the disc plate, followed by a complete circle and a post-weld segment extending back to the disc plate edge, reducing the overlap area while ensuring a complete seal, using a laser beam to weld the disc plate to the cover plate.
The new welding pattern enhances the reliability of the seal by minimizing the risk of leakage and maintaining airtightness, while being easier to implement and less prone to failure compared to traditional methods.
Smart Images
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Abstract
Description
Title of the invention: Sealing welding of an electrolyte fill hole for a battery cell, and associated battery cell
[0001] The present invention relates to a welding sealing process for an electrolyte filling hole in an electrochemical battery cell.
[0002] An electrochemical battery cell, and in particular a lithium ion cell, comprises a casing containing at least one cathode and one anode separated by a separator.
[0003] In an electrochemical battery cell, the cathode and the anode each comprise a porous active material and a current collector.
[0004] An electrolytic solution, allowing ion exchange between the cathode and the anode, impregnates the cathode and the anode, as well as the separator.
[0005] During the battery manufacturing process, the electrolyte solution is injected into the cell through a fill hole, usually located on the top surface of the battery cell. The fill hole is sealed after the filling process, and the battery cell is made airtight to prevent any fluid exchange with the external environment. Therefore, sealing the electrolyte fill hole is one of the main challenges in the production of high-performance electrochemical battery cells.
[0006] Among other things, partial or non-uniform sealing of the filling hole may result in leakage of the electrolyte solution, which may damage the battery cell and reduce its overall efficiency.
[0007] Therefore, sealing the electrolyte filling hole is one of the key steps in the manufacture of electrochemical cells.
[0008] The sealing step includes welding a disc plate, for example using a laser beam. The step may first include inserting a plug positioned on the edges of the fill hole. Next, the disc plate is placed over the outlet of the fill hole so as to completely cover it, and held in contact with the upper cover plate of the battery cell. The laser beam is then used on the edges of the disc plate and on the portion of the upper cover plate surrounding the disc plate to make it airtight by welding.
[0009] Currently, a specific weld bead design is widely used given the technical challenges of this process, such as the complexity of using the laser and the precision required for an airtight seal. The design, such as illustrated in [Fig. 1], comprises a first line of pre-weld beads extending from the disc plate to a first edge of the disc plate, following the axis tangent to the disc plate at the first point of the edge. Next, a complete circle surrounds the disc plate. Finally, a second line, following the first line, extends away from the circle.
[0010] However, this design has a significant overlap zone where melting and resolidification occur twice. This overlap zone is necessary to ensure complete sealing of the disc plate, but it is also one of the main causes of failures due to leakage, as it weakens the seal.
[0011] One of the objectives of the invention is therefore to propose a more reliable welding process for sealing at least one electrochemical cell, the process being easy to implement and allowing a more reliable sealing of the electrolyte filling hole.
[0012] The invention describes a process for manufacturing an electrochemical cell, the process comprising:
[0013] a. the supply of at least one dry assembly comprising:
[0014] - at least one cathode comprising a porous cathode active material;
[0015] - at least one anode comprising a porous anode active material; and
[0016] - a cell housing comprising a top cover plate with a filling hole
[0017] at least one cathode and at least one anode being inserted into at least one cell housing, the cell housing being at least partially metallic,
[0018] b. filling the respective cell casing with an electrolytic solution through the filling hole,
[0019] c. the arrangement of a disc plate on the upper cover plate in order to cover the filling hole,
[0020] d. welding an edge of the disc plate to a portion of the upper cover plate surrounding the disc plate using a laser beam that follows a specific pattern comprising:
[0021] - at least one cathode comprising a porous cathode active material;
[0022] - a pre-weld segment from a weld bead starting point away from the disc plate to a first edge point of the disc plate, the pre-welded segment deviating from the axis tangent to the disc plate at the first edge point;
[0023] - a complete circle of a main weld bead covering all edges of the disc plate until it reaches the first edge point again;
[0024] - a post-weld segment extending from the first edge point to a point of end of weld bead away from the disc plate, the post-weld segment deviating from the axis tangent to the disc plate at the first edge point.
[0025] Taking into account such a welding scheme makes it possible to obtain a sufficient overlap area to ensure complete sealing of the filling hole, while reducing the surface area of the overlap area, thus reducing the risks of failure and leakage due to weakening of the seal.
[0026] According to other advantageous aspects of the invention, the welding process of at least one electrochemical cell comprises one or more of the following features, taken individually or in any technically feasible combination:
[0027] - in step d, the pre-welding segment and the post-welding segment form respectively an arc of a circle;
[0028] - at step d, the arcs of circles defined by the pre-welding and post-welding segments welding follows a circle whose radius is between 1.15 and 2.6 times smaller than the radius of the disc plate;
[0029] - at step d, the arcs of circles defined by the pre-welding and post-welding segments welding represents 10% to 20% of the total of a circle;
[0030] - in step d, the pre-weld segment comprises an arc of a circle departing from the tangent axis to the disc plate at the first edge point, from a starting point of the weld bead away from the disc plate to a straight line following the aforementioned axis to the first edge point; the post-weld segment includes a straight line following the tangent axis to the disc plate at the first edge point, from the first edge point to an arc of a circle departing from the aforementioned axis to an end point of the weld bead;
[0031] - the length of the straight lines defined by the pre-welding and post-welding segments welding represents between 25% and 75% of the total length of the pre-welding and post-welding segments;
[0032] - the pre-weld segment is a straight line extending from the starting point of the weld bead away from the disc plate to the first edge point of the disc plate, the straight line being inclined at an angle strictly less than 90° to the axis tangent to the disc plate at the first edge point; the post-weld segment is a straight line extending from the first edge point of the disc plate to the arrival point of the weld bead;
[0033] - the pre-welding segment and the post-welding segment are carried out symmetrically around an axis passing through the center of the disc plate and the first edge point;
[0034] - in step c, a plug is inserted into the filling hole before positioning the disc plate;
[0035] - the upper cover plate includes a circular recess with the filling hole in its center and complementary to the shape of the disc plate, the depth of the recess ensuring a flat surface of the upper cover plate when the disc plate is positioned.
[0036] The invention also relates to an electrochemical cell obtained by the sealing process according to any one of the preceding embodiments.
[0037] The invention will be better understood upon reading the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings, in which:
[0038] [Fig-1] Fig. 1 is a top view of the welding pattern according to the current state of the technique;
[0039] [Fig.2] The [Fig.2] is a flowchart of the process according to the invention;
[0040] [Fig. 3] Fig. 3 is a 3D view of an example electrochemical cell on which the process of [Fig.2] is implemented;
[0041] [Fig.4] The [Fig.4] is an example dry assembly on which the process of the [Fig.2] is being implemented.
[0042] [Fig.5] The [Fig.5] is a cross-sectional view of the electrochemical cell of the [Fig.3] along a plane transverse to the length of the electrochemical cell, including the electrolyte filling hole;
[0043] [Fig.6] The [Fig.6] is a top view of the welding pattern according to a first embodiment;
[0044] [Fig.7] Fig.7 is a top view of the welding pattern according to a second method of implementation;
[0045] [Fig.8] The [Fig.8] is a top view of the welding pattern according to a third embodiment.
[0046] The process 10 according to the invention is described with reference to [Fig.2].
[0047] The process 10 is intended to seal an electrolyte filling hole 15 for produce an electrochemical cell 17.
[0048] For example, the electrochemical cell 17 is a lithium ion cell.
[0049] To this end, the process 10 includes a supply step 101, a filling step 102, a positioning step 103 and a sealing step 104.
[0050] Supply step 101 includes the supply of at least one dry assembly 18.
[0051] A dry assembly example 18 is illustrated in [Fig.4].
[0052] In this example, a dry assembly 18 includes an electrode stack and a cell housing 20. The electrode stack includes at least one cathode 22 comprising a porous active material of cathode 22A and a cathode terminal 22B, at least one anode 25 comprising a porous active material of anode 25A and an anode terminal 25B.
[0053] The dry assembly 18 is a so-called "dry" assembly, insofar as neither of the active materials of cathode 22A and anode 25A has yet been impregnated with an electrolytic solution 35 at the beginning of the supply step 101.
[0054] In this example, the cathode 22 and the anode 25 are separated by a separator 30, the active material of the cathode 22A facing the active material of the anode 25A.
[0055] The cathode 22 and the anode 25 are each spaced apart from the separator 30.
[0056] The separator 30 is configured to allow controlled ion exchange between the cathode 22 and the anode 25 and to prevent an electrical short circuit between them.
[0057] The dry assembly 18 further includes a cathode current collector 22C and an anodic current collector 25C to ensure electrical contact with another electrochemical cell 17 and / or an external electrical circuit.
[0058] The cathode current collector 22C is in direct contact with the active material of the cathode 22A.
[0059] The anodic current collector 25C is in direct contact with the active material of the anode 25A.
[0060] The cathode 22 and the anode 25, and here the separator 30, are inserted into the cell housing 20.
[0061] The cell housing 20 is at least partially made of metal.
[0062] The cell housing 20 defines a receiving volume. The cathode 22 and the anode 25, and here the separator 30, are fully inserted into the receiving volume.
[0063] The cell housing 20 is designed such that at least two metallic areas of the cell housing 20 frame the dry assembly 18 after its insertion inside it.
[0064] The shape of the cell housing 20 is preferably chosen according to an external shape of the dry assembly 18.
[0065] The cell housing 20 is advantageously prismatic, advantageously parallelepiped as shown in [Fig.3]. In this case, the cell housing 20 comprises at least two parallel faces.
[0066] The upper face of the cell housing 20 is an upper cover plate 32, mounted after the insertion of the cathode 22, the anode 25 and the separator 30, to facilitate installation.
[0067] The cell housing 20 preferably comprises, more preferably consists of, aluminum.
[0068] One or more pairs of cathodes 22 and anodes 25 can be inserted into the same cell housing 20.
[0069] The number of cathode 22 and anode 25 pairs inserted in the same cell housing 20 depends, for example, on the voltage and power to be supplied by a battery formed with the electrochemical cell(s) 17 produced after the welding process 10.
[0070] A plurality of dry assemblies 18 can be inserted in parallel into a plurality of housings 20, particularly when the process 10 is carried out on an industrial scale. In this case, all the dry assemblies 18 can be identical and all the cell housings 20 can be identical.
[0071] The filling step 102 includes dosing the electrolytic solution 35 inside each of the cell housings 20.
[0072] The filling step 102 is carried out using dosing means (not shown).
[0073] Preferably, the dosing means includes a precision pump. This allows for precise control of the initial weight of the electrolytic solution 35 in the cell housing 20.
[0074] The electrolytic solution 35 is designed to allow ion exchange in and between the cathode 22, the anode 25 and the separator 30.
[0075] The electrolytic solution 35 can be any known electrolytic solution. For example, the electrolytic solution 35 can comprise a non-aqueous lithium salt and a non-aqueous solvent.
[0076] The electrolytic solution 35 is inserted into the respective cell housing through the filling hole 15, located on the upper cover plate 32
[0077] Next, at positioning step 103, a plug 45 is preferably inserted into the filling hole 15, as illustrated in [Fig.4].
[0078] The plug 45 has, for example, a body such that it has a shape of revolution around a central axis XX' passing through the filling hole 15, when it is inserted into the filling hole 15.
[0079] The stopper 45 is made of an elastically deformable material, preferably having the following properties:
[0080] # chemical compatibility with the electrolyte, i.e. the absence of reaction chemical interaction with the electrolyte;
[0081] # a high elastic elongation, that is to say preferably greater than 50%;
[0082] # a significantly lower rigidity than that of the upper cover plate 32,
[0083] # a higher thermal resistance, that is to say, preferably, that it must resist a thermal shock from exposure to 200 degrees Celsius for 5 seconds.
[0084] The cap 45 covers the edge of the filling hole 15 and ensures a first airtight seal.
[0085] A disc plate 50 is then positioned on the upper cover plate 32, with the filling hole 15 at its center on the X-X' axis. The disc plate 50 has a diameter greater than the diameter of the filling hole 15 so as to cover the entire filling hole 15.
[0086] The upper cover plate 32 preferably includes a circular recess 52 centered on the axis XX' around the filling hole 15 and complementary to the shape of the disc plate 50, the depth of the recess 52 ensuring a flat surface of the upper cover plate when the disc plate is positioned. The disc plate 50 is thus stably positioned in its axial and radial directions for the subsequent sealing step 104.
[0087] The disc plate 50 is preferably made of the same material as the upper cover plate 32, i.e. a metallic material such as aluminium.
[0088] Finally, the sealing step 104 includes welding the edges of the disc plate with the surrounding part of the upper cover plate 32, using a laser beam 55. For example, the laser beam melts the metal parts together on a circular shape over a molten section 56 of about 150 pm to 300 pm.
[0089] According to a first embodiment shown in [Fig. 5], a welding model A specific procedure is followed. Starting from a point on the weld bead 58 located away from the disc plate 50, a pre-weld segment 59 is performed on the upper cover plate 32, in the form of a circular arc 60, until it reaches a first edge point 62 on the disc plate 50. The circular arc 60 deviates from the tangent axis to the disc at the first edge point and follows a circle with a radius, for example, between 1.5 mm and 3.5 mm, i.e., 1.15 to 2.6 times smaller than the radius of the disc plate. Without limitation, the length of the circular arc 60 is between 2.3 mm and 5.5 mm and represents 10% to 20% of the total circle.
[0090] Next, a complete circle 65 of the main weld bead is made following the edges of the disc plate 50, until it again reaches the first edge point 62. Finally, a post-weld segment 67 is preferably made symmetrically with respect to the pre-weld segment 59, around an axis passing through the center of the disc plate 50 and the first edge point 62, making an arc of a circle 70 until reaching an end point of the weld bead 72.
[0091] Following this welding pattern, an overlap zone 73 is drawn where melting and then solidification occur twice. This overlap zone 73 ensures complete welding of the edges of the disc plate 50. However, the dimensions of the overlap zone 73 are slightly reduced compared to a generally applied pattern comprising straight lines tangent to the first edge point 62 instead of arc segments of the pre-weld bead and the weld bead. post-welding. As an indication, a reduction of 25% to 75% of the surface area covered by the overlap zone is obtained compared to the generally applied model.
[0092] Thus, such a welding pattern is particularly advantageous because the overlap zone 73, although essential to guarantee an airtight seal, is one of the main causes of leakage failure.
[0093] In addition, in order to optimize the dimensions of the overlap zone 73, a second embodiment is disclosed, as illustrated in [Fig.6], and differs slightly from the first embodiment.
[0094] According to this second embodiment, the pre-weld segment 59 mentioned in the first embodiment comprises an arc of a circle 74 departing from the axis tangent to the disc plate at the level of the first edge point 62, from a starting point of the weld bead 76 away from the disc plate to a straight line 78 following the aforementioned axis to the first edge point.
[0095] With regard to the post-weld segment 67 mentioned in the first embodiment, it is preferably carried out symmetrically with respect to the pre-weld segment 59, around an axis passing through the center of the disc plate 50 and the first edge point 62. It comprises a straight line 80 following the axis tangent to the disc plate 50 at the level of the first edge point 62, from the first edge point to an arc of a circle 82 departing from the aforementioned axis to an end point of the weld bead 84 away from the disc plate 50.
[0096] By way of non-limitation, the straight segments 78 or 80 have a length between 0.75 and 2.25 mm, representing 25% to 75% of the length of the pre-weld segments 59 or post-weld segments 67.
[0097] This welding scheme makes it possible to increase the overlap area 86 compared to the first embodiment, while reducing it slightly compared to a generally applied model comprising straight lines tangent to the first edge point 62. The airtight property ensured by the sealing is advantageously optimized.
[0098] A third embodiment, illustrated in [Fig.7], is disclosed and differs slightly from the first embodiment.
[0099] According to this third embodiment, the pre-weld segment 59 mentioned in the first embodiment is a straight line 88 extending from a starting point of the weld bead 89 away from the disc plate 50 to the first edge point 62 of the disc plate. The straight line 88 is inclined at an angle strictly less than 90° to the axis tangent to the disc plate 50 at the first edge point 62.
[0100] The post-weld segment 67 mentioned in the first embodiment is a straight line 90 extending from the first edge point 62 to an end point of the weld bead 91. It is carried out symmetrically with respect to the pre-weld segment 59, around an axis passing through the center of the disc plate 50 and the first edge point 62.
Claims
Demands
1. A process (10) for manufacturing an electrochemical cell (17), the process (10) comprising: a. supplying at least one dry assembly (18) comprising: - at least one cathode (22) comprising a porous cathode active material (22A); - at least one anode (25) comprising a porous anode active material (25A); and - a cell housing (20) comprising a top cover plate (32) with a filling hole (15), the at least one cathode (22) and the at least one anode (25) being inserted into the at least one cell housing (20), the cell housing being at least partially metallic, b. filling the respective cell housing (20) with an electrolytic solution (35) through the filling hole (15), c. the arrangement of a disc plate (50) on the upper cover plate (32) in order to cover the filling hole (15),d. welding the edge of the disc plate (50) with a portion of the upper cover plate (32) surrounding the disc plate (50) using a laser beam (55) which follows a specific pattern comprising: - a pre-weld segment (59) from a starting point of the weld bead (58, 76, 89) away from the disc plate (50) to a first edge point (62) of the disc plate (50), the pre-weld segment (59) moving away from the tangent axis to the disc plate (50) at the first edge point (62); - a complete circle (65) of main weld bead covering all the edges of the disc plate (50) until reaching the first edge point (62) again; - a post-weld segment (67) from the first edge point (62) to a weld bead end point (72, 84, 91) away from the disc plate (50),the post-weld segment (67) deviating from the axis tangent to the disc plate (50) at the level of the first edge point (62).
2. Process (10) according to claim 1, wherein in step d, the pre-welding segment (59) and the post-welding segment (67) respectively form an arc of a circle (60, 70).
3. Process (10) according to claim 2, wherein in step d, the arcs of circles (60, 70) defined by the pre-weld (59) and post-weld (67) segments follow a circle with a radius between 1.15 and 2.6 times smaller than the radius of the disc plate (50).
4. Process (10) according to claims 2 or 3, wherein at step d, the arcs of circles (60, 70) defined by the pre-welding and post-welding segments represent 10% to 20% of the total of a circle.
5. A process (10) according to claim 1, wherein in step d: - the pre-weld segment (59) comprises a circular arc (74) extending from the axis tangent to the disc plate (50) at the first edge point (62), from a starting point of the weld bead (76) away from the disc plate (50) to a straight line (78) following the aforementioned axis to the first edge point (62). - the post-weld segment (67) comprises a straight line (80) following the axis tangent to the disc plate (50) at the first edge point (62), from the first edge point (62) to a circular arc (82) extending from the aforementioned axis to an end point of the weld bead (84).
6. Process (10) according to claim 6, wherein, at step d, the length of the straight lines (78, 80) defined by the pre-welding (59) and post-welding (67) segments represents between 25% and 75% of the total length of the pre-welding and post-welding segments (59, 67).
7. Process (10) according to any one of the preceding claims, wherein in step d: - the pre-weld segment (59) is a straight line (88) extending from the starting point of the weld bead (89) away from the disc plate (50) to the first edge point (62) of the disc plate (50), the straight line (88) being inclined at an angle strictly less than 90° to the tangent axis to the disc plate at the first edge point (62); - the post-weld segment (67) is a straight line (90) extending from the first edge point (62) of the disc plate (50) to the end point of the weld bead (91).
8. Process (10) according to any one of the preceding claims, wherein the pre-welding segment (59) and the post-welding segment (67) are carried out symmetrically around an axis passing through the center of the disc plate (50) and the first edge point (62).
9. Process (10) according to any one of the preceding claims, wherein, in step c, a plug (45) is inserted into the filling hole (15) before positioning the disc plate (50).
10. A process (10) according to any one of the preceding claims, wherein the upper cover plate (32) comprises a circular recess (52) with the filling hole (15) in its center and complementary to the shape of the disc plate (50), the depth of the recess (52) ensuring a flat surface of the upper cover plate (32) when the disc plate (50) is positioned.
11. Electrochemical cell (17) obtainable by process (10) according to any one of claims 1 to 10.