Cylindrical cell for an electric battery and method for manufacturing same

Abstract

The invention relates to an electric battery cylindrical cell for an electrically propelled vehicle, comprising a stack (10) wound on itself and successively consisting of - a first electrode sheet (1) of a first polarity; - a first insulating separator sheet (2); - a second electrode sheet (3) having a second polarity opposite the first polarity; - a second insulating separator sheet (4), wherein a portion (34) of the second electrode sheet (3) protrudes from the successive stack (10) in a longitudinal direction thereof such that the winding is substantially centered on the protruding portion (34) wound on itself.

Description

Cylindrical cell for electric battery and its manufacturing process Technical field of the invention

[0001] The present invention relates to the technical field of cylindrical cells for electric vehicle batteries. In particular, the invention relates to electrode sheets for such cylindrical cells. Technical background

[0002] More particularly, the present invention relates to a cylindrical battery cell, said cell comprising a casing and a roller housed in the casing, the roller delimiting a central volume around which the roller is formed by winding, the roller comprising electrodes of the cell.

[0003] Cylindrical cells are manufactured by winding around a rotating mandrel, a successive stack of at least: - a positive electrode sheet, - an insulating separator sheet, - a negative electrode sheet, - an insulating separator sheet.

[0004] The manufacture of such a cell requires high industrial precision in the sense that the volume of housing in the casing to receive the roller must be properly sized to allow the insertion of the roller into the casing and limit the movement of the roller in the casing to avoid the collapse of said roller in particular when its central volume is left empty of solid material.

[0005] "Collapse" means that the multilayer structure breaks down inside the casing, potentially causing misalignment of the electrodes (particularly the first and second electrode sheets mentioned above) and the separator (particularly the first and / or second separator sheets mentioned above). In other words, the multilayer structure unwinds from the inside, within the central volume.

[0006] Although current cells, when correctly sized and configured, generally provide satisfactory performance, they can still be improved. Indeed, changes in the dimensions and / or parameters of the electrodes alter the cell's charge / discharge behavior. Successive charge and discharge cycles cause the roller to move within the casing. Naturally, the central volume can vary accordingly, sometimes causing the roller to collapse within this central volume. Roller collapse reduces cell performance. In the worst-case scenario, roller collapse can lead to dramatic accidents, such as explosions or fires, particularly due to short circuits caused by direct contact between electrodes at opposite potentials (especially contact between the first and second electrode sheets mentioned above) due to misalignment of the sheets (i.e.,the first electrode sheet, the first separator sheet, the second electrode sheet and the second separator sheet) of the multilayer.

[0007] Thus, there is a need to improve the cylindrical cell to improve the retention of the roller in the casing, particularly with a view to limiting the occurrence of an accident such as that mentioned above.

[0008] The present invention aims to improve the retention of the roller in the casing.

[0009] To this end, it is proposed, firstly, a cylindrical electric battery cell for an electric propulsion vehicle comprising a winding around a winding axis of a successive stack along a stacking axis - of a first electrode sheet of a first polarity; - of a first insulating separator sheet; - of a second electrode sheet of a second polarity opposite to the first polarity; - of a second insulating separator sheet, a portion of the second electrode sheet protruding, along a longitudinal axis of the successive stacking, said longitudinal axis being substantially perpendicular to the stacking axis and to the winding axis, cell in which said portion protrudes from the successive stacking so that said portion is wound around itself around said winding axis.

[0010] Various additional features may be provided, alone or in combination: - the winding around the winding axis of the portion is at least two turns; - the second electrode sheet comprises a metal sheet extending along the longitudinal axis between a first end and a second end opposite the first end, this second electrode sheet being intended to be wound around the winding axis from the first end, the metal sheet comprising - at the first end, a transverse inactive portion without active material; - an active portion coated with an active material extending along the longitudinal axis between the transverse inactive portion and the second end, the protruding portion comprising said transverse inactive portion; - the transverse inactive portion has a length between 50mm and 250mm along the longitudinal axis;- the second electrode sheet is a negative electrode sheet.;

[0011] Secondly, a manufacturing process for the cylindrical cell presented above is proposed, this process comprising the following steps: - successive stacking along a stacking axis of a first electrode sheet of a first polarity; of a first insulating separator sheet; of a second electrode sheet of a second polarity opposite to the first polarity, of a second insulating separator sheet, a portion of the second electrode sheet protruding, along a longitudinal axis of the successive stacking, of the successive stacking, - winding of the successive stacking around a winding axis substantially perpendicular to the stacking axis and to the longitudinal axis starting from said protruding portion so that this winding is substantially centered on a winding around the winding axis of the protruding portion.

[0012] The winding of the protruding portion around the winding axis is, in one embodiment, at least two turns.

[0013] Other features and advantages of the invention will become clearer and more concrete upon reading the following description of embodiments, which is made with reference to the accompanying drawings in which:

[0014] the figure schematically illustrates a first successive stacking of leaves according to various modes of realization;

[0015] the figure schematically illustrates a second successive stacking of leaves according to various modes of embodiment;

[0016] The figure schematically illustrates a cylindrical cell according to various embodiments;

[0017] The figure schematically illustrates the steps of a manufacturing process for a cylindrical cell according to various embodiments. Detailed description of the invention

[0018] Referring to the diagram, a successive stacking is shown along a stacking axis of: - a first sheet of electrode of a first polarity, - a first sheet of insulating separator, - a second sheet of electrode of a second polarity opposite to the first polarity, and - a second sheet of insulating separator.

[0019] The stacking axis 5 designates the direction in which the aforementioned sheets 1-4 are superimposed or stacked relative to each other. The stacking axis 5 is perpendicular to the surfaces of the sheets 1-4. The stacking axis 5 passes through the sheets 1-4 in the direction of their superposition, that is, normal to their surface.

[0020] The second electrode sheet 3 comprises a metallic sheet 30 (or current collector) extending longitudinally along a longitudinal axis 7 of the successive stack 10 between a first end 31 and a second end 32 opposite the first end 31. The longitudinal axis 7 corresponds to the largest dimension of the sheets 1-4 of the successive stack 10, in the plane of these sheets. The second electrode sheet 3 is substantially rectangular in shape, delimited longitudinally along the axis 7 by a first transverse edge of end 31 and a second transverse edge of end 32 opposite and substantially parallel to the first transverse edge of end 31. The second electrode sheet 3 is intended to be wound around a winding axis 6 substantially perpendicular to the stacking axis 5 and to the longitudinal axis 7, starting from the first end 31. The longitudinal axis 7 of the successive stack 10 is substantially perpendicular to the winding axis 6 and to the stacking axis 5.

[0021] The metallic sheet 30 comprises, at its first end 31, a transverse inactive portion 34 devoid of active material and an active portion 33 coated with an active material extending longitudinally along the longitudinal axis 7 of the successive stack 10 between the transverse inactive portion 34 and the second end 32.

[0022] The second electrode sheet is, in one embodiment, a negative electrode sheet or anode. The second electrode sheet may comprise a copper metal sheet and an active anode material such as graphite or carbon.

[0023] The transverse inactive portion 34 of the second electrode sheet 3 extends, along the longitudinal axis 7 of the successive stack 10, at least partially beyond the successive stack 10, such that this portion 34 is wound upon itself around the winding axis 6. The portion 34 extends beyond the successive stack 10 such that the winding of the successive stack 10 around the winding axis 6, starting from the protruding portion 34, is substantially centered on a winding of the portion 34 around the winding axis 6, as illustrated in the figure. In other words, the transverse inactive portion 34 of the second electrode sheet 3 extends, in the successive stack 10, beyond the other sheets 1, 2, 4 along the longitudinal axis 7 (i.e., in the longitudinal direction of sheets 1-4).Therefore, when winding around a rotating mandrel the successive stack 10, the transverse inactive portion 34 of the second electrode sheet 3 is wound first around the winding axis 6, followed by the sheets 1-4 of the successive stack 10.

[0024] The second electrode sheet 3 extends along the longitudinal axis 7 (that is, in a longitudinal direction of the successive stack 10), meaning that it extends beyond the other sheets 1, 2, 4 of the successive stack 10 in its longitudinal direction. The longitudinal direction refers to the longest axis of the successive stack 10 or the direction in which this successive stack 10 is wound to form the cylindrical cell 11. More generally, the second electrode sheet 3 has, along the longitudinal axis 7 of the successive stack 10, an extension allowing this second electrode sheet 3 to extend beyond the alignment of the other sheets 1, 2, 4, creating a distinct projection in the lengthwise direction of the successive stack 10 or, more generally, in the direction of the longitudinal axis 7 of the successive stack 10.

[0025] By exceeding along the longitudinal axis 7, the inactive transverse portion 34 is advantageously pre-wound around the winding axis 6 before the winding of the successive stack 10 (or initiates the winding before the successive stack 10 follows) so as to form a core (or pillar) in the center of the resulting roll allowing to stiffen the central area of ​​the latter and thus avoid a collapse towards the inside of the cylindrical cell 11.

[0026] In one embodiment, the inactive transverse portion 34 has, along a longitudinal direction of the metal sheet or more generally along the longitudinal axis 7 of the successive stack 10, a length between 50 mm and 250 mm or between 100 mm and 600 mm. Such lengths advantageously allow (depending on the perimeter of the rotary mandrel used for winding the successive stack 10 around the winding axis 6) a predefined number of turns providing sufficient rigidity to the core of the cylindrical cell 11 of an electric battery for an electric vehicle.

[0027] In one embodiment, the winding of the transverse inactive portion 34 around the winding axis 6 is at least two turns. Making at least two turns around the winding axis 6 with the transverse inactive portion 34 advantageously avoids the presence of weak points along the entire inner perimeter of the roller and provides substantially uniform strength capable of resisting any force tending to deform the core or the central zone of the cylindrical cell 11.

[0028] Referring to Figure 1, steps of a process 12 for manufacturing the cylindrical cell 11 of an electric battery for an electric vehicle are shown. This process 12 includes a step 41 of successive stacking along the stacking axis 5 of a first electrode sheet 1 of a first polarity, a first insulating separator sheet 2, a second electrode sheet 3 as shown above of a second polarity opposite to the first polarity, and a second insulating separator sheet 4. The transverse inactive portion 34 of the second electrode sheet extends at least partially along the longitudinal axis 7 of the successive stack 10. In other words, the second electrode sheet 3 is arranged in the successive stack 10 such that its transverse inactive portion 34 extends beyond the other sheets 1, 2, 4 in the longitudinal direction of the successive stack 10.

[0029] The process 12 further comprises a step 42 of winding the successive stack 10 around the winding axis 6, which is substantially perpendicular to the stacking axis 5 and to the longitudinal axis 7, starting from the transverse inactive portion 34, such that this winding is substantially centered on a winding around the winding axis 6 of the transverse inactive portion 34 extending along the longitudinal axis 7. The successive stack 10 is, in fact, wound around its shortest axis or, more generally, around the winding axis 6, so that the resulting winding is substantially centered on a winding around the winding axis 6 of the transverse inactive portion 34.In one embodiment, this involves a radial winding of the successive stack 10 around a transverse axis parallel to the width of the successive stack 10, starting from the overhanging portion 34, so as to form a concentric spiral around this transverse axis.

[0030] During this winding step 42, the transverse inactive portion 34 extending beyond the longitudinal axis 7 of the successive stack 10 is advantageously wound first around the winding axis 6, followed by the sheets 1-4 of the successive stack 10. In other words, the transverse inactive portion 34 of the second electrode sheet 3 initiates the winding around the winding axis 6 before the successive stack 10 follows. This advantageously results in a reinforcement of the central zone of the roll, preventing its collapse.

[0031] In one embodiment, the inactive transverse portion 34 of the second electrode sheet 3 has, along the longitudinal axis 7, a length sufficient for it to be able to wind itself around the winding axis 6 at least twice (of course, taking into account a predefined perimeter of the rotating mandrel).

[0032] Winding the inactive transverse portion 34 around itself around the winding axis 6 by at least two turns advantageously ensures a substantially uniform stiffening over the entire inner perimeter of the roller capable of resisting a possible force tending to deform the central area of ​​the cylindrical cell 11.

[0033] In one embodiment, the manufacturing process 12 for the cylindrical cell 11 is based on a continuous approach, in which the sheets 1-4 are unwound simultaneously from their respective rolls and, as they advance, are stacked in real time with a portion 34 of the second sheet extending beyond the successive stack 10 along the longitudinal axis 7. Without a cutting or pre-assembly step, the successive stacking step 41 can be carried out during unwinding. The resulting successive stack 10 can then be immediately fed into a winding unit, around the winding axis 6, starting from the extending portion 34. The stacking and winding steps can thus be integrated into a single, seamless sequence.

[0034] It should be noted that the embodiments described above are also valid for a second electrode sheet 3 without a transverse inactive portion 34. Indeed, in an alternative embodiment illustrated in Figure 3, the metallic sheet 30 of the second electrode sheet 3 includes an active portion 33 coated with an active material extending longitudinally along the longitudinal axis 7 between the first end 31 and the second end 32. In other words, the metallic sheet 30 does not have a transverse inactive portion 34.

[0035] A portion 33' of the second electrode sheet 3 extends, along the longitudinal axis 7, beyond the successive stack 10, such that the winding around the winding axis 6, starting from the protruding portion 33', is substantially centered on a winding around itself around the winding axis 6 of the protruding portion 33' of the second electrode sheet 3. As described previously, this advantageously results in a stiffening of the central zone of the roll, preventing its collapse.

[0036] More generally, the portion 34,33' of the second electrode sheet 3 extending, along the longitudinal axis 7, from the successive stack 10 may include a transverse inactive portion 34 or be a portion 33' coated at least partially with an active material. The portion 34,33' of the second electrode sheet 3 extends from the successive stack 10, along the longitudinal axis 7, such that the winding around the winding axis 6 of this successive stack 10 is substantially centered on a winding of the portion 34,33'. More generally, the portion 34,33' extends from the successive stack 10 in a longitudinal direction thereof such that this portion 34,33' is wound around itself around the winding axis 6.

Claims

1. Cylindrical electric battery cell (11) for an electric vehicle comprising a winding around a winding axis (6) of a successive stack (10) along a stacking axis (5) of: - a first electrode sheet (1) of a first polarity; - a first insulating separator sheet (2); - a second electrode sheet (3) of a second polarity opposite to the first polarity; - a second insulating separator sheet (4), a portion (34, 33') of the second electrode sheet (3) extending, along a longitudinal axis (7) of the successive stack (10), said longitudinal axis (7) being substantially perpendicular to the stacking axis (5) and to the winding axis (6), cell in which said portion (34, 33') extends beyond the successive stack (10) such that said portion (34,33') is wound around itself around said winding axis (6).

2. Cylindrical cell (11) according to the preceding claim, characterized in that the winding on itself around the winding axis (6) of the portion (34,33') is at least two turns.

3. Cylindrical cell (11) according to claim 1 or 2, characterized in that the second electrode sheet (3) comprises a metallic sheet (30) extending along the longitudinal axis (7) between a first end (31) and a second end (32) opposite the first end (31), this second electrode sheet (3) being intended to be wound around the winding axis (6) from the first end (31), the metallic sheet (30) comprising - at the first end (31), a transverse inactive portion (34) devoid of active material; - an active portion (33) coated with an active material extending along the longitudinal axis (7) between the transverse inactive portion (34) and the second end (32), the protruding portion (34,33') comprising said transverse inactive portion (34).

4. Cylindrical cell (11) according to the preceding claim characterized in that the inactive transverse portion (34) has a length between 50mm and 250mm along the longitudinal axis (7).

5. Cylindrical cell (11) according to claim 3 or 4 characterized in that the second electrode sheet (3) is a negative electrode sheet.

6. Method (12) of manufacturing a cylindrical cell (11) according to any one of the preceding claims, this method (12) comprising the following steps:- successive stacking (41) along a stacking axis (5) of a first sheet (1) of electrode of a first polarity; of a first sheet (2) of insulating separator;of a second sheet (3) of electrode of a second polarity opposite to the first polarity, of a second sheet (4) of insulating separator, a portion (34,33') of the second sheet (3) of electrode protruding, along a longitudinal axis (7) of the successive stack (10), of the successive stack (10),- winding (42) on itself of the successive stack (10) around a winding axis (6) substantially perpendicular to the stacking axis (5) and to the longitudinal axis (7) from said protruding portion (34,33') so that this winding is substantially centered on a winding on itself around the winding axis (6) of the protruding portion (34,33').; 7. Manufacturing method (12) according to the preceding claim, characterized in that the winding around the winding axis (6) of the protruding portion (34,33') is at least two turns.

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