Electrochemical cell with grooves to facilitate disassembly and tooling for such disassembly

Abstract

An electrochemical cell (2) for storing electrical energy, having a metallic casing with an outer wall, and having a cell axis (A), the outer wall comprising at least one groove extending locally in a local extension direction inclined with respect to a cell axis, the local extension direction forming an angle (θ1) between 40° and 80° with respect to the cell axis, helical when the electrochemical cell is cylindrical, and an assembly comprising a tool for disassembling an electrochemical cell, the disassembly tool comprising a rotating part mounted for rotation about an axis, one or two grippers mounted on a radially oriented slide, each gripper being configured to grasp an upper portion of the outer wall and pull it radially outwards. Abstract figure: Fig. 1

Description

Title of the invention: Electrochemical cell with grooves facilitating disassembly and tooling for such disassembly

[0001] The present invention relates to an electrochemical cell for storing electrical energy, particularly the treatment it undergoes at the end of its life. The present invention also relates to an assembly comprising electrochemical cells and a tool for disassembling electrochemical cells.

[0002] The battery of an electric vehicle comprises electrochemical cells grouped together in a set called in the trade 'battery pack'.

[0003] The most common traction batteries on electric vehicles are Lithium-Ion type electrochemistry batteries. Among these, there are several types, namely for example NMC (Nickel Manganese Cobalt), LFP (Lithium Iron Phosphate / LifePO4) and others.

[0004] Each electrochemical cell contains chemical elements contained hermetically within a cell envelope.

[0005] The electrochemical cell of interest here is contained in a relatively rigid metallic casing. The electrochemical cells of interest here may have a cylindrical or prismatic shape.

[0006] When the battery pack is removed from the motor vehicle, it can be directed to a second life and in this case the battery pack is not disassembled at this stage.

[0007] When the battery pack has reached the end of its life, it is disassembled, and in addition it is desirable to disassemble the electrochemical cells individually.

[0008] The central subject of the present invention is the unit disassembly of electrochemical cells.

[0009] At the time of disassembly, the electrochemical cell of interest here still contains electrical energy. Of course, it is necessary to avoid short-circuiting the positive and negative terminals of the cell.

[0010] Furthermore, mechanical damage which can lead to thermal runaway of the cell must be avoided.

[0011] The electrochemical cell contains electrochemical elements housed in its protective metallic casing which serves as a sealed enclosure for the electrochemical elements, where applicable including a liquid electrolyte.

[0012] When the electrochemical cell is cylindrical, it contains an internal part called a 'coil' housed within the metal casing that protects the coil. The coil houses or contains the electrochemical elements.

[0013] The difficulty is to be able to remove the metal casing without damaging the reel or more generally the elements contained in the metal casing.

[0014] In known practice, the upper cover of the cell is crimped by means of a rolled rim of the metal casing.

[0015] If we try to loosen the rolled rim in question, we will inevitably deform the main body of the metal casing and consequently affect the integrity of the cell.

[0016] The inventors sought to propose a solution for removing the metal casing without risking damage to its contents.

[0017] To this end, an electrochemical cell for storing electrical energy is proposed, having a metallic envelope with an outer wall, and having a cell axis, the outer wall comprising at least one groove extending locally along a local extension direction inclined with respect to a cell axis, the local extension direction forming an angle between 40° and 80° with respect to the cell axis.

[0018] Thanks to these features, the presence of the groove makes it possible to tear the metal casing and peel it away from the outside without risking damage to its contents. More specifically, it is possible to grasp the top of the metal casing where the groove forms an acute angle with the upper surface of the cell.

[0019] Advantageously, the metal casing tears at the location of the groove which has a lower mechanical resistance than the other areas of the outer wall of the metal casing.

[0020] Put another way, the groove forms a fusible groove capable of giving way and tearing when the metal casing is peeled outwards.

[0021] The groove extends continuously from top to bottom, without interruption, which ensures a continuous breaking process from step to step.

[0022] It is noted that the metallic casing is sufficiently rigid. The metallic casing is a self-supporting structure that allows it to retain its shape, even when flaps of skin are pulled during the peeling process.

[0023] According to one embodiment, two grooves are provided opposite each other with respect to the cell axis.

[0024] Advantageously, it is then possible to grasp the top of the metal casing in two places where each groove makes an acute angle with the upper plane of the cell and symmetrically spread apart the grasping organs, which causes the 'peeling' of the metal casing.

[0025] According to one embodiment, the metal casing is cylindrical in shape and the groove extends helically. This is a very common form factor and is particularly well suited to the implementation of the present invention.

[0026] According to one embodiment, two diametrically opposed grooves are provided. In this configuration, two interlaced helices are provided.

[0027] This type of groove can be easily produced on machining equipment such as a turning machine, with two diametrically opposed cutting tools in axial translation and a concomitant rotation of the metal casing.

[0028] According to one embodiment, the metal casing is prismatic in shape and the groove extends linearly obliquely in sections on each of the four lateral faces. The present invention can indeed be applied to a prismatic form factor.

[0029] According to one embodiment, two adjacent grooves are provided framing an outer wall strip having a width of at most 5 mm.

[0030] It may be easier to tear a narrow strip than a wide strip of the outer sheath, the remaining part of the sheath can then be removed by applying a twist which tends to increase the diameter of the remaining part.

[0031] The present invention also relates to an assembly comprising a tool for disassembling an electrochemical cell as defined above, the disassembly tool comprising: - a rotating part mounted to rotate about an axis, - at least one gripper (51, 52) mounted on a carriage, the carriage being mounted to slide in a radial direction guide, the gripper being configured to grasp an upper portion of the outer wall and pull it radially outwards.

[0032] The clamp can thus grasp the upper portion of the metal casing near the groove, on the acute angle side, and can exert an outward pull which allows the peeling of the metal casing to begin.

[0033] Advantageously, the gripper comprises a movable jaw. A fixed jaw is provided opposite the movable jaw. The movable jaw and the fixed jaw are mounted on the carriage mentioned above, which is itself mounted to slide in a radial guide rail.

[0034] Pulling is continuous until the groove breaks all the way to the bottom of the cell.

[0035] Optionally, the rotating part, where applicable the motorized chuck, may be provided to be equipped with a vertical movement or to have a pusher to lift the cell as the outer wall and peel assemblies are made.

[0036] For each clamp, at least one of the clamp elements, fixed or mobile, is made of insulating material.

[0037] This prevents the creation of an electrical short circuit when the clamp contracts the upper part of the cell. In particular, the part of the clamp that contacts the positive pole (the positive terminal) of the cell is made of electrically insulating material.

[0038] According to one embodiment, the disassembly tool comprises two diametrically opposed grippers, each mounted on a carriage mounted to slide in a radial direction slide, each gripper being configured to grasp an upper portion of the outer wall and pull it radially outwards.

[0039] Advantageously, we then have a pull of the grippers opposite each other with a balancing of the forces.

[0040] According to one embodiment, the rotating part is a motorized chuck in which the movement of spreading the clamps / jaws and the rotational movement of the chuck are synchronized.

[0041] This allows us to minimize the stresses experienced by the body of the metal casing. The breaking force of the fusible grooves in the slots is substantially the same from the top to the bottom of the cell.

[0042] The present invention also relates to a battery pack comprising a plurality of electrochemical cells as defined above.

[0043] The present invention also relates to an electric or hybrid vehicle, comprising a battery pack as defined above.

[0044] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which: - [Fig. 1] schematically illustrates the general principle of disassembling the outer casing of an electrochemical battery cell; - [Fig.2] represents a perspective view of an example of an electrochemical cell, cylindrical in shape and with helical grooves; - [Fig.3] shows an elevation view of another example of an electrochemical cell, with a double groove; - [Fig.4] schematically represents a perspective view of another example of an electrochemical cell, of prismatic shape; - [Fig.5] illustrates a detailed cross-sectional view of an example of a metal envelope wall; - [Fig.6] illustrates a perspective view of an example of a disassembly tool, shown before the start of disassembly; - [Fig.7] is analogous to [Fig.6], and illustrates a perspective view of the disassembly tool, shown during disassembly. - [Fig-8] represents a detailed perspective view showing the pincers mounted on trolleys, and configured to grasp the upper portion of the metal casing.

[0045] In the various figures, the same reference numerals designate identical or similar elements. For the sake of clarity, some elements are not necessarily shown to scale. It should be noted that the chemical elements contained within the electrochemical cells have not been shown in the figures.

[0046] An electric or hybrid vehicle includes a battery pack. Said battery pack comprises a plurality of electrochemical cells, arranged or not in groups in a sub-assembly called a module.

[0047] The present invention relates to the recycling of electrochemical cells at the end of the life of the battery pack (or end of the life of the module).

[0048] Each electrochemical cell must be disassembled so that its components can be recycled, including copper, aluminum, lithium, cobalt and so on.

[0049] For example, electrochemical cells are based on Lithium-Ion type electrochemistry. However, it should be noted that the present invention can be applied to any electrochemical variant of electrochemical cells for traction batteries of electric vehicles.

[0050] It should be noted that in a battery pack, the number of electrochemical cells can range from 20 to 2000, without excluding a larger number. The battery pack is generally installed in the floor area of ​​the vehicle.

[0051] The height H2 of the electrochemical cell 2 along the Z-axis can be between 3 cm and 10 cm. In a cylindrical version, its diameter D2 can be between 2 cm and 5 cm.

[0052]

[0053] The electrochemical cells 2 of interest here may have a cylindrical shape or a prismatic shape.

[0054] Each electrochemical cell 2 comprises a metallic envelope 7 with an outer wall 71.

[0055] Each electrochemical cell 2 comprises two electrical terminals. More specifically, the electrochemical cell 2 comprises a positive terminal generally located on the top of the cell. The electrochemical cell 2 comprises a negative terminal which may be arranged as the main body of the cell, namely the metal casing itself, or a specific terminal located on the side of the cell.

[0056] In the prismatic version shown in [Fig.4], the two terminals, positive 25 and negative 26, are located on the upper face of the cell.

[0057] The metal casing 7 has a structure that is sufficiently rigid to be self-supporting and to support the weight of the elements it includes.

[0058] Whether the cell is prismatic or cylindrical, a cell axis designated A can be defined. The cell axis A extends from top to bottom, that is to say vertically with respect to a classic situation of the cell placed on its base with the positive terminal on top, passing through the center of the cell.

[0059] When the cell is prismatic in shape, i.e. parallelepiped, it has six faces, a lower face forming the base and an upper face equipped with the terminals.

[0060] In addition, the cell comprises four lateral faces on which oblique grooves will be formed as will be seen below.

[0061] The metal casing 7 can be made of steel alloy or aluminum alloy.

[0062] The outer wall 71 comprising at least one groove 3, the depth of the groove, as illustrated in [Fig.5], can be between 20% and 50% of the thickness in the current section of the wall of the metal casing.

[0063] In the illustrated example, the groove profile noted 30 is triangular but it could be in the form of a cup or in any other form.

[0064] The standard wall thickness, denoted El, can be between 0.3 µm and 1.5 mm. If the casing is made of steel, the lower end of the range, i.e., between 0.3 and 0.6 mm, is chosen. If the casing is made of aluminum, the upper end of the range is chosen.

[0065] The depth of the groove E2 can be between 0.15 and 0.5 mm, the depth being in proportional relationship with the thickness El.

[0066] The groove 3 extends locally along a local extension direction W, which is inclined with respect to the cell axis.

[0067] Advantageously, the local extension direction W forms an angle 01 between 40° and 80° with respect to the cell axis A.

[0068] Thanks to this inclination, it will be possible, by pulling on a portion of the metal casing, to detach it from the rest of the cell, and to continue with a break of the groove, to peel the metal casing continuously from top to bottom.

[0069] Figure 1 shows the detached part of the outer envelope, identified as 74.

[0070] It is noted that the peeling by rupture of the metallic casing is all the more It's easy to see that angle 01 is close to 85°.

[0071] Depending on the geometric characteristics, an optimum can be found for the angle 01 between 70° and 80°, if we take into account the effort to be produced to tear the groove and the time required to 'peel' the whole cell.

[0072] At least for the cylindrical version of the cell, it is intended that the outer casing will crimp the cover 21. For this purpose, a crimping by turning inwards, also called a rolled rim, is carried out.

[0073] This crimping operation of the lid is carried out after the grooving operation. Consequently, as can be seen in [Fig.2], the two diametrically opposed grooves 31, 32 are found on the rolled edge and in particular its upper part at references 31a and 32a.

[0074] The same configuration can be found on the prismatic shape of the electrochemical cell.

[0075] As illustrated in [Fig. 3], two adjacent grooves 33, 34 can be provided framing an outer wall strip 35. The strip in question is narrow. The width of the strip 35 to be torn can be at most 5 mm.

[0076] Turning to figures 6 to 8, we now discuss the disassembly tool 1. The disassembly tool 1 comprises a rotating part 4 mounted for rotation about an axis denoted X.

[0077] When a cell 2 is installed on the rotating part 4, there is coincidence between the axes X and A.

[0078]

[0079] The disassembly tool 1 includes two clamps 51, 52 configured to clamp the upper portion of the metal casing, preferably on the side of the acute angle delimited by the groove.

[0080] The gripper is mounted on a carriage 5. The carriage 5 is mounted to slide in a radial guide rail R2. The carriage 5 is designed to move away from the X-axis, i.e., to move backward after the gripper has grasped the upper portion of the metal casing. The gripper is mounted on the carriage 5.

[0081] In other words, each clamp is configured to pull radially outwards the upper portion of the outer wall.

[0082] At [Fig.7], in the middle of the peeling process, each gripper pulls a flap 74,75 of the metallic sheath.

[0083] For each clamp, at least one of the clamp elements, fixed or mobile, is made of insulating material.

[0084] For example, the movable jaw 52 which comes into contact with the cover 21 of the cell is made of rigid plastic, or of metal coated with an insulating plastic coating.

[0085] It is noted that in figures 6 to 8, the disassembly tool 1 includes two clamps 51, 52, whereas in the figure, the disassembly tool 1 includes only one clamp, but it can still work correctly.

[0086] According to one option, the rotating part 4 is a motorized chuck. Thus, the cell can be rotated at the same time as the grippers pull the tearing metal casing outwards.

[0087] Advantageously, the spreading movement of the clamps / jaws and the rotational movement of the chuck are synchronized.

[0088] This is all the more relevant when using a single clamp with a single groove on the cell, because in this case the cantilevered traction effects can be minimized by the synchronized rotation of the chuck.

[0089] Of course, the distance between the clamps as well as the height position of the rotating part can be adapted according to the diameter D2 of the cell and the height H2 of the cell to be disassembled.

[0090] The inventors also noted that when the cell is immersed in a dielectric coolant, there is wall layer turbulence at the location of the grooves 3, which generates an improvement in the heat transfer coefficient.

[0091] The reel housed in the metal casing can contain, for example, a stack of various sheets wound spirally around the cell axis.

[0092] It should be noted that the number of grooves can be greater than 2, for example 3 grooves or 4 grooves.

[0093] Thanks to a controlled groove depth, the inventors were able to verify that this does not cause substantial weakening of the metal casing.

Claims

Demands

1. Electrochemical cell (2) for electrical energy storage, having a metallic envelope (7) with an outer wall (71), and having a cell axis (A), the outer wall comprising at least one groove (3) extending locally in a local extension direction (W) inclined with respect to the cell axis, the local extension direction forming an angle (01) between 40° and 85° with respect to the cell axis.

2. Electrochemical cell (2) according to claim 1, wherein two grooves (31,32) opposite each other are provided with respect to the cell axis (A).

3. Electrochemical cell (2) according to claim 1, characterized in that the metal casing is cylindrical in shape and the groove extends helically.

4. Electrochemical cell (2) according to claim 3, wherein two diametrically opposed grooves (31,32) are provided.

5. Electrochemical cell (2) according to claim 1, wherein two adjacent grooves (33,34) are provided framing an outer wall strip having a width of at most 5 mm.

6. Assembly comprising a disassembly tool (1) for an electrochemical cell according to any one of claims 1 to 5, the disassembly tool comprising: - a rotating part (4) mounted for rotation about an axis, - at least one gripper (51,52) mounted on a carriage (5), the carriage being mounted to slide in a radial direction guide (R2), the gripper being configured to grasp an upper portion of the outer wall and pull it radially outwards.

7. Assembly according to claim 6, wherein the disassembly tool comprises two diametrically opposed grippers (51,52), each mounted on a carriage mounted to slide in a radial direction slide, each gripper being configured to grasp an upper portion of the outer wall and pull it radially outwards.

8. Assembly according to any one of claims 6 to 7, wherein the rotating part is a motorized chuck and wherein the spreading movement of the grippers / jaws and the rotational movement of the chuck are synchronized.

9. Battery pack comprising a plurality of electrochemical cells (2), according to any one of claims 1 to 8.

10. Electric or hybrid vehicle, comprising a battery pack according to claim 9.