Cell assembly method, storage unit, and related vehicle battery packs

Abstract

To provide a cell assembly method, an electric energy storage unit, and a vehicle battery pack, which are formed by a simple mounting with a high cost effectiveness.SOLUTION: A method for assembling a cell which can be attached to a vehicle battery pack, contains: a step of laminating a plurality of electrodes (3 and 4) so that a tab (6) of each electrode each having the same polarity is positioned each other; a step of locating a first flat cell (2) and a second flat cell (2) so that the tab (6) having the same polarity is at least partially opposite each other, and is at least partially overlapped so as to be matched to an overlapped region (7) of each tab (6) which is positioned at a distal position to a main body (8); and a step of directly welding both of at least one terminal tab (6) belonged to the first flat cell (2) and a terminal tab (6) belonged to the second flat cell (2) so as to be matched to the overlapped region (7), respectively.SELECTED DRAWING: Figure 2

Description

Cross-reference to related applications

[0001] This patent application claims priority from Italian Patent Application No. 102020000026593 filed on November 6, 2020, the entire disclosure of which is incorporated herein by reference.

Technical Field

[0002] The present invention relates to the field of energy storage systems in the automotive sector, and more specifically to a method for assembling cells, an electrical energy storage unit, and a related vehicle battery pack.

Background Art

[0003] Lithium batteries, due to their high density, are increasingly being used to power electric vehicles in the automotive field. In particular, lithium polymer currently represents the state-of-the-art technology in the manufacture of high-capacity batteries from a chemical perspective.

[0004] Solutions are known that provide for the series and parallel interconnection of different cells (generally each with a voltage of 3.7 V) to obtain the total voltage and total energy density required for a vehicle battery pack.

[0005] Battery modules that supply power to smartphones and tablets commonly available on the market (and which are also becoming increasingly widespread in the automotive field) are composed of flat pouch batteries that have a very limited thickness compared to other dimensions. Two very large opposing surfaces (where heat dissipates almost completely) and four thin and elongated side surfaces are identified, and the positive and negative terminals of the cells are arranged on one or two opposing side surfaces.

[0006] Typically, the aforementioned terminals are used to electrically connect different cells in series or parallel. Specifically, each cell consists of multiple laminated electrode plates with alternating polarities (positive and negative). Each of these electrode plates includes a tab extending from the rest of the electrode plate, which is electrically connected by a first welding means to another tab of the same cell extending from an electrode plate of the same polarity, and subsequently connected by a second welding means to the cell's terminals (positive or negative, respectively), which are generally made of metal plates that are thicker and more rigid than the electrode tabs. [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the aforementioned welding is usually performed using a laser device (at an extremely low speed for welding thick materials) or an ultrasonic device (which requires frequent replacement of the sonotrode, especially in cases of heavy wear, and adjustment of the laser device each time it is replaced).

[0008] Furthermore, battery packs produced by the aforementioned manufacturing methods are still very expensive and bulky. [Means for solving the problem]

[0009] The object of the present invention is, in particular, to provide a cell assembly method, an electrical energy storage unit, and an associated vehicle battery pack that do not contain, at least partially, the above-mentioned drawbacks, and at the same time are simple and cost-effective to implement.

[0010] According to the present invention, a cell assembly method, an electrical energy storage unit, and an associated vehicle battery pack are provided as described in the appended claims.

[0011] These claims describe preferred embodiments of the present invention that form an essential part of this specification. [Brief explanation of the drawing]

[0012] Next, the present invention will be described with reference to the accompanying drawings illustrating some non-limiting and exemplary embodiments thereof. Specifically, [Figure 1] This is a schematic cross-sectional view of a portion of an electrical energy storage unit, comprising two cells electrically interconnected in series according to prior art. [Figure 2] This is a schematic cross-sectional view of a portion of an electrical energy storage unit comprising two cells electrically interconnected in series according to the present invention. [Figure 3] This is a schematic and perspective view of the first embodiment of the present invention. [Figure 4] This is a schematic and perspective view of a second embodiment according to the present invention. [Figure 5] Figure 3 shows a perspective view and schematic diagram of the vehicle battery pack that constitutes the storage unit. [Modes for carrying out the invention]

[0013] In Figure 1, U represents a typical electrical energy storage unit comprising at least two planar cells C, each belonging to the prior art, and each containing, in order, a plurality of positive E+ electrode plates and negative E- electrode plates, each enclosed inside its own pouch P, and stacked alternately with respect to one another and spaced apart by separator layers (which are also of a known type and therefore not shown). Each electrode plate E+, E- contains its own electrode tab T (in this case, located on both sides of the cell C, i.e., shown in Figure 1, all electrode tabs T having the same polarity, positive or negative), and this electrode tab T extends from the body B of the cell C (precisely defined by the stack of electrodes and separators).

[0014] In each of the cells C shown in Figure 1, the electrode tabs T are initially welded to each other by a weld W' that forms a bundle of tabs.

[0015] Next, such a bundle of tabs is further welded to the electrical terminal TR of the cell by welding W'', making each tab T much thicker.

[0016] Next, cells C are connected in series by contacting respective terminals TR having the same polarity. As is apparent from FIG. 1, the distance between the bodies B of two cells connected in series is on the order of centimeters, specifically, corresponds to a distance L' exceeding 3 cm.

[0017] In FIG. 2, reference numeral 1 generally indicates an electrical energy storage unit that can be installed in a vehicle battery pack (for vehicle movement) according to a first aspect of the present invention.

[0018] The electrical energy storage unit 1 includes at least two planar cells C connected in series with each other.

[0019] Each cell C includes a plurality of electrodes 3 and 4 (for example, a negative electrode and a positive electrode, respectively). Next, each electrode includes a respective terminal tab 6 that protrudes and extends from the body 8 of the cell 2.

[0020] It is advantageous for the terminal tabs 6 to be made integrally with or from the positive and / or negative electrodes, but this is not necessarily the case. Specifically, each terminal tab 6 is made integrally (from the current collector) with a current collector (usually coated with an active material) of the positive or negative electrode. More specifically, the current collector and the terminal tab extending from this current collector are made of copper for the anode and made of aluminum or zinc for the cathode.

[0021] Specifically, each planar cell 2 has a parallelepiped shape with a thickness extremely limited with respect to other dimensions. Thus, six faces corresponding to 2×2 are identified, of which, as shown in the non-limiting embodiments of FIGS. 3 and 4, two are very wide planes S', two are thin and elongated front faces S'', and two are thin and elongated lateral faces S''' (narrower than the front face S''').

[0022] Advantageously, the electrodes 3 and 4 are stacked relative to each other such that the tabs 6 of the same polarity (positive or negative electrode, and thus made of the same material) are aligned with each other (in the vertical direction). Specifically, the planar cells 2 are arranged such that the tabs 6 having the same polarity as each planar cell 2 (positive or negative electrode, and thus made of the same material) are at least partially opposed to each other. That is, the faces S''' (as shown in the non-limiting embodiment of FIG. 3) or the faces S'' (as shown in the non-limiting embodiment of FIG. 4) of two adjacent cells face each other (and in a parallel direction).

[0023] Advantageously, as shown in the non-limiting embodiments of FIGS. 2 to 5, the planar cells 2 are arranged such that the tabs 6 having the same polarity as two adjacent cells connected in series are at least partially overlapped to coincide with the overlapping region 7. More precisely, the overlapping region 7 between the tabs 6 of two adjacent cells 2 is at the distal position of each tab 6 with respect to each cell 2 and with respect to the body 8 of each cell 2.

[0024] Specifically, at least one terminal tab 6 belonging to the planar cell 2 and the terminal tab 6 belonging to an adjacent planar cell 2 are directly welded to each other by thermal welding, particularly preferably, so as to connect the two planar cells 2 in series, so as to coincide with the overlapping region 7. It is clear that the tabs 6 overlapped in the region 7 have the same polarity.

[0025] In some non-limiting cases, this welding is laser welding, specifically linear welding (along a direction parallel to the faces S'', S''' where the terminal tabs 6 to be welded protrude) or spot welding.

[0026] As shown in the non-limiting embodiment of FIG. 2, the distance between the bodies 8 of two cells 2 connected in series corresponds to the distance L'', is shorter than the distance L', preferably on the order of millimeters, specifically shorter than 25 mm, and more precisely shorter than 10 mm, which is advantageous but not necessarily so.

[0027] Preferably, as shown in the non-limiting embodiments of Figures 2 and 3, in the overlapping region (7), at least one terminal tab 6 of cell 2 is spaced between two terminal tabs 6 of the other cell 2, and / or vice versa.

[0028] According to some non-limiting embodiments, two or more (e.g., three or four) consecutive alignment tabs having the same polarity and belonging to the planar cell 2 are welded to each other before being welded to adjacent planar cell 2 tabs 6 having the same polarity.

[0029] According to the non-limiting embodiments of Figures 3 and 5, terminal tabs 6 having different (opposite) polarities in the same planar cell 2 protrude from both sides of the planar cell 2, specifically from the respective cell faces S'''. In this case, the planar cells 2 connected in series lie on the same plane and on the same longitudinal axis of symmetry.

[0030] In the non-limiting embodiment of Figure 4, terminal tabs 6 with different (opposite) polarities of the same planar cell 2 protrude from the same side of the planar cell 2, specifically from one of the faces S'' of each cell 2. In these cases, the planar cells 2 connected in series are on the same plane but not on the same longitudinal axis of symmetry. Specifically, these planar cells 2 are offset from each other along both directions belonging to the plane in which they are provided. More specifically, the cells 2 are equal in length and offset by half their length along the longitudinal direction of the storage unit 1. In this way, a unit 1 can be constructed with the cells arranged as a coil, as shown in Figure 4. Furthermore, since all the contacts in series are continuous on the same straight line, the structure of the safety structure for continuously detecting the voltage of each cell can be simplified.

[0031] The storage unit 1 is preferably equipped with a single external pouch 5 containing at least one pair of cells 2, but is not necessarily required.

[0032] According to a further aspect of the present invention, a vehicle battery pack 10 comprising at least one unit 1 is provided in accordance with the foregoing.

[0033] The battery pack 10 is advantageous, but not necessarily, to have multiple levels (layers) of unit 1, as shown in the non-limiting embodiment of Figure 5.

[0034] In some non-limiting cases, such as those shown in the upper layer of Figure 5, Unit 1 occupies the entire level of the battery pack and also includes three or more cells connected in series, as described. In this way, the advantages of the present invention are maximized.

[0035] In other non-limiting cases, such as shown in the second layer (starting from the top), one level includes multiple units 1 interconnected in series according to known techniques. Thus, the advantages of the present invention are partial but significant nonetheless.

[0036] The battery pack 10 further includes a safety system SS and a battery management unit (BMU), which are advantageously located on both sides of the battery pack 10, but are not necessarily required.

[0037] The battery pack 10 is more preferably, but not necessarily, equipped with a cooling system CS located on the wall of the battery pack 10 that is perpendicular to the level of the energy storage unit 1 (and on a wall other than the wall occupied by the system SS and the BMU).

[0038] A further aspect of the present invention provides a method for assembling a planar cell 2 that can be attached to a vehicle battery pack. Specifically, the method aims to manufacture an electrical energy storage unit 1.

[0039] Advantageously, the method includes the step of stacking planar cells 2 and a plurality of at least three electrodes 3 and 4 with alternating polarities, each of which electrodes 3 and 4 includes a terminal tab 6 extending from the body 8 of the cell 2. Specifically, the electrodes 3 and 4 are stacked such that tabs 6 having the same polarity are aligned with each other (perpendicularly).

[0040] The method further includes the step of arranging at least two planar cells 2 such that tabs 6 having the same polarity as each of the two planar cells 2 are at least partially opposite to each other and at least partially overlapping with the overlapping region 7 of each tab 6 that is distal to the body 8. That is, a tab 6 in cell 2 that is positive (or negative) is at least partially superimposed on a tab 6 in another cell 2 that is negative (or positive, depending on the type of connection, whether in series or parallel).

[0041] Specifically, the method provides a further step of directly welding together at least one terminal tab 6 belonging to a planar cell 2 and a terminal tab 6 belonging to an adjacent planar cell 2, which is connected in series with that cell 2. In detail, this welding step is performed so as to coincide with the overlapping region 7.

[0042] Preferably, terminal tabs 6 having the same polarity as cell 2 and terminal tabs 6 having the same polarity as other cells 2 are welded to each other such that at least one terminal tab 6 of the first cell 2 is spaced between two terminal tabs 6 of the second cell 2 and / or vice versa.

[0043] The method may be advantageous, but is not necessarily, to further include the step of pre-welding one or more terminal tabs 6 having the same polarity and belonging to the same planar cell 6.

[0044] In some non-limiting cases, terminal tabs 6 having the same polarity in a planar cell 2 are welded individually or in pairs to each terminal tab 6 having the same polarity in adjacent cells 2 connected in series.

[0045] The method is advantageous, but not necessarily, to include a further step of encapsulating at least the first and second cells in the same pouch 5.

[0046] In some non-specific cases, this welding step is performed by a welding apparatus with multiple prongs, the same number as the number of weld points between the tabs of different cells where the welding is performed.

[0047] In other non-specific cases, this welding step is performed by a laser welding device.

[0048] Therefore, it is advantageous, but not necessarily, for the electrical energy storage unit 1 not to include an intermediate metal terminal (e.g., terminal TR) between the tabs 6 of two adjacent cells 2 connected in series.

[0049] Therefore, in this specific assembly method, no intermediate metal terminals are used between the tabs 6 of two adjacent cells 2 connected in series.

[0050] While the above inventions refer particularly to very precise and exemplary embodiments, they should not be considered limited to such exemplary embodiments, as all variations, modifications, or simplifications covered by the appended claims, such as different forms of arrangement, different types of materials, and different geometric shapes, are included within their scope.

[0051] The methods, units, and apparatus described above offer numerous advantages.

[0052] Firstly, the present invention allows for the optimization of space utilization within a battery pack. Specifically, the space normally present between two series-connected cells, as highlighted by the difference between lengths L' and L'', can consequently be filled with active material or used to reduce the overall volume of the battery pack (in cases with hundreds of cells, optimizing the use of such space can have significant effects).

[0053] Furthermore, the present invention avoids the low speed of dual laser welding and the high installation and maintenance costs of dual ultrasonic welding, thereby saving time and eliminating waste.

[0054] A further advantage of the present invention lies in the fact that this structure allows for a reduction or simplification of the number of control units required within the battery pack.

[0055] Finally, the above method, unit, and battery pack reduce the total number of welds performed in the manufacture of the battery pack by almost half, thus also halving the relative error coefficient, which limits the possibility of waste during battery pack manufacturing. [Explanation of symbols]

[0056] 1 Storage Unit 2 cells 3 electrodes 4 electrodes 5 pouches 6 tabs 7 Welding points 8-cell main unit 10 Battery Packs U Storage Unit C cell E+ electrode E-electrode P Pouch T tab W' Welding location W'' Welding location L' Distance between cells L'' distance between cells B Cell Body TR terminal S' side S'' side S''' side BMU Battery Management Unit SS safety CS Cooling System

Claims

1. A method (10) for assembling cells that can be attached to a vehicle battery pack, wherein the method is A step of stacking a first planar cell (2) and a second planar cell (2) with alternating polarities to generate a plurality of at least three electrodes (3, 4) contained in each of them, wherein each of the electrodes (3, 4) includes a terminal tab (6) extending from the respective bodies (8) of the first planar cell (2) and the second planar cell (2), and the electrodes (3, 4) are stacked such that the terminal tabs (6) having the same polarity are aligned with each other, and the terminal tabs (6) are manufactured integrally with the electrodes (3, 4) or manufactured from the electrodes (3, 4), The steps of arranging the first planar cell (2) and the second planar cell (2) such that at least one terminal tab (6) of the first planar cell (2) and the terminal tab (6) of the second planar cell (2) having the same polarity as the terminal tab (6) of the first planar cell (2) are at least partially facing each other and at least partially overlapping in the overlapping region (7) of each terminal tab (6) which is distal to the body (8); A step of directly welding at least one terminal tab (6) belonging to the first planar cell (2) and the terminal tab (6) belonging to the second planar cell (2) to each other so as to coincide with the overlapping region (7), A method comprising the step of welding together terminal tabs (6) having the same polarity as the first planar cell (2) and each terminal tab (6) having the same polarity as the second planar cell (2), such that at least one terminal tab (6) of the first planar cell (2) is spaced between two of the terminal tabs (6) of the second planar cell (2) and / or vice versa.

2. Prior to the welding step, the step includes welding two or more terminal tabs (6) having the same polarity and belonging to the same first planar cell (2), or The method according to claim 1, further comprising the step of welding two or more terminal tabs (6) having the same polarity and belonging to the same second planar cell (2) prior to the welding step.

3. The method according to claim 1, wherein the terminal tabs (6) having the same polarity in the first planar cell (2) are welded individually or in pairs to the respective terminal tabs (6) having the same polarity in the second planar cell (2).

4. The method according to any one of claims 1 to 3, further comprising the step of sealing at least the first planar cell (2) and the second planar cell (2) in the same pouch (5) or casing.

5. The method according to any one of claims 1 to 4, wherein the welding step is performed by a welding apparatus having a plurality of prongs equal to the number of welding locations between the terminal tabs (6) of the first planar cell (2) and the second planar cell (2) on which the welding is performed.

6. The method according to any one of claims 1 to 5, wherein no intermediate metal terminal is used between the terminal tab (6) belonging to the first planar cell (2) and the terminal tab (6) belonging to the second planar cell (2).

7. An electrical energy storage unit (1) that can be attached to a vehicle battery pack (10), wherein the electrical energy storage unit (1) comprises at least a first planar cell (2) and a second planar cell (2), each including a plurality of at least three electrodes (3, 4), each of which includes a terminal tab (6) extending from the body (8) of the first planar cell (2) and the second planar cell (2), and the electrodes (3, 4) are stacked such that the terminal tabs (6) having the same polarity are aligned with each other. The terminal tab (6) is manufactured integrally with the electrodes (3, 4) or manufactured from the electrodes (3, 4), and the first planar cell (2) and the second planar cell (2) are arranged such that at least one terminal tab (6) of the first planar cell (2) and the terminal tab (6) of the second planar cell (2) having the same polarity as the terminal tab (6) of the first planar cell (2) face each other at least partially. The aforementioned electrical energy storage unit (1) The first planar cell (2) and the second planar cell (2) are arranged such that the terminal tabs (6) having the same polarity as the first planar cell (2) and the second planar cell (2) overlap at least partially with respect to the overlapping region (7) of each terminal tab (6) which is distal to the main body (8). At least one terminal tab (6) belonging to the first planar cell (2) and a terminal tab (6) belonging to the second planar cell (2) are directly welded to each other so as to coincide with the overlapping region (7). An electrical energy storage unit (1) characterized in that, in the overlapping region (7), at least one terminal tab (6) of the first planar cell (2) is spaced between two terminal tabs (6) of the second planar cell (2), and / or vice versa.

8. The electrical energy storage unit (1) according to claim 7, wherein adjacent tabs (6) having the same polarity and belonging to the first planar cell (2) are welded to one another.

9. The electrical energy storage unit (1) according to any one of claims 7 or 8, wherein the terminal tabs (6) having different polarities protrude from both sides of the first planar cell (2) and the second planar cell (2), and the first planar cell (2) and the second planar cell (2) are on the same plane and on the same longitudinal axis of symmetry.

10. The electrical energy storage unit (1) according to any one of claims 7 or 8, wherein the terminal tabs (6) having different polarities protrude from the same side of the first planar cell (2) and the second planar cell (2), and the first planar cell (2) and the second planar cell (2) are on the same plane but not on the same longitudinal axis of symmetry.

11. The electrical energy storage unit (1) according to claim 10, wherein the first planar cell (2) and the second planar cell (2) are arranged offset from each other along both directions belonging to the plane on which the first planar cell (2) and the second planar cell (2) are provided.

12. The electrical energy storage unit (1) according to claim 11, wherein the first planar cell (2) and the second planar cell (2) are of equal length and are offset by half the length of the first planar cell (2) and the second planar cell (2) along the longitudinal direction of the electrical energy storage unit (1).

13. A vehicle battery pack (10) comprising at least one electrical energy storage unit (1) according to any one of claims 7 to 12.

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