ELECTROCHEMICAL CELL ARCHITECTURE FOR AUTOMOBILE BATTERIES.

Abstract

The invention relates to an electrochemical cell comprising, on the one hand, a stack of sheets (2) each containing an assembly consisting of a positive electrode and a negative electrode, their associated current collector and at least one electrically insulating separator, said assembly being impregnated with an electrolyte and, on the other hand, an outer casing (1) enclosing said stack and through which said collectors protrude, characterized in that said casing is in the form of a rectangular parallelepiped provided, on two opposite sides, with at least one slot (10) laterally delimited by at least one straight edge (11) which is intended to fit into the corresponding slots of identical cell casings. Figure 1.

Description

Title of the invention: ELECTROCHEMICAL CELL ARCHITECTURE FOR AUTOMOBILE BATTERIES.

[0001] The invention relates, in general, to the field of electrical energy accumulators and is more particularly concerned with a specific architecture of electrochemical cell intended for batteries equipping motor vehicles.

[0002] Generally, an electric battery (for example, a so-called metal-ion battery) contains one or more electrochemical cells connected in parallel and / or in series. Such cells comprise a set of current collectors on which positive and negative electrodes are deposited on either side of at least one electrically insulating separator. This assembly is immersed in an electrolyte ensuring ionic conductivity between the electrodes through the separator. An external casing completes the cell, ensuring its watertightness and airtightness, and through which the current collectors pass, intended for connection with external electrical components.

[0003] Depending on their format, these cells are assembled inside the battery in different ways, but often symmetrically. However, it turns out that the cells, and especially those with a substantially planar configuration (such as prismatic cells or so-called "pouch" cells), are subject to significant mechanical stresses resulting from deformations that naturally appear over time.

[0004] These deformations take the form of internal swellings located at the center of the cell, where the structural resistance of the casing containing it is lowest. These deformations accelerate the aging of the cell and therefore tend to promote destructive phenomena that are all the more problematic for batteries containing a large number of cells, as is the case for batteries used in motor vehicles.

[0005] Furthermore, battery research and development is opening up new avenues for chemical processes that result in strong and unusual mechanical stresses on the cells. Thus, batteries using solid materials present a risk of delamination and therefore loss of electrical contact. Silicon anodes are accompanied by very high expansion (300%), while lithium anodes present a risk of dendrite formation due to a lack of homogeneity in mechanical stresses. The trend is therefore to moderate the internal mechanical constraints in batteries to make them more reliable and increase their lifespan.

[0006] Therefore, the invention sought a technical solution to avoid the occurrence of these deformations or at least to limit their harmful effects within the battery.

[0007] French patent FR3061610B1 describes a metal-ion electrochemical battery with a monopolar architecture, that is, one with a single electrochemical cell. The structure of this single cell is designed to allow the battery to be miniaturized and made flexible so that it can be integrated directly into objects, in particular, into electronic devices.

[0008] However, the monopolar architecture of this accumulator is neither suitable nor intended to manage globally the deformation problems of the numerous cells conditioned inside a motor vehicle battery.

[0009] In this context, the invention aims to solve the technical problems posed by previous batteries by proposing a specific architecture that allows for the optimal distribution of mechanical stress points between all the cells integrated into the battery.

[0010] This goal is achieved, according to the invention, by means of an electrochemical cell comprising, on the one hand, a stack of sheets containing, each, an assembly consisting of a positive electrode and a negative electrode, their associated current collector and at least one electrically insulating separator, said assembly being impregnated with an electrolyte and, on the other hand, an outer envelope enclosing said stack and through which said collectors protrude, characterized in that said envelope is in the form of a rectangular parallelepiped provided, on two opposite sides, with at least one slot delimited laterally by at least one straight edge which is intended to fit into the corresponding slots of identical cell envelopes.

[0011] According to an advantageous feature of the cell of the invention, the envelope comprises two straight edges on either side of the slot and the length of the bottom of the slots corresponds to the sum of the lengths of the straight edges.

[0012] Preferably, the lateral sides of the crenellations are chamfered and the straight edges are of the same length.

[0013] According to another advantageous feature of the cell of the invention, the stacking fills the entire interior space of the envelope.

[0014] According to yet another feature of the cell of the invention, the stacking sheets are arranged parallel to the thickness of the envelope.

[0015] According to a first embodiment of the cell of the invention, the stacking sheets are juxtaposed.

[0016] According to another embodiment of the cell of the invention, the stack consists of a single sheet folded over itself.

[0017] Another object of the invention is an electric battery containing a series of electrochemical cells as described above which are nested one inside the other in a staggered pattern.

[0018] Yet another object of the invention is a motor vehicle equipped with at least one electric battery as defined above.

[0019] Thus, in principle, the invention proposes a simple and effective solution to counter cell deformations and preserve the integrity and reliability of the battery over time.

[0020] The specific architecture of the cell of the invention brings a significant improvement to the overall mechanical structure of the battery pack.

[0021] This architecture also makes it possible to do without the use of added stiffening elements to keep the cells in contact with each other in case of deformations and stresses or displacements of the cells within the battery.

[0022] Thus, the interlocking of cells proposed by the invention constitutes a guarantee of mechanical maintenance of the assembly and makes it possible to avoid any disorder resulting from the relative displacement under stress of all the cells.

[0023] The homogenization of the mechanical forces and stresses exerted during cycling (alternating charging and discharging) also increases the safety and longevity of the cells and therefore that of the battery.

[0024] In addition, the invention makes it possible to optimize the compactness of the batteries and the volumetric density of the pack.

[0025] Furthermore, since the manufacture of traction batteries for electric vehicles involves the assembly of hundreds, or even thousands, of battery cells, the mechanical homogeneity resulting from the interlocking of these numerous cells is of crucial importance. Indeed, a single mechanical imbalance due to local deformation is enough to render the battery unusable. Consequently, the present invention contributes to preventing the risk of failure and improving battery quality in the long term.

[0026] Other features and advantages of the invention will become apparent from the following description, with reference to the accompanying figures, for which:

[0027] [Fig. 1] is a perspective view of a first embodiment of an electrochemical cell according to the invention.

[0028] [Fig.2] is a side view of the electrochemical cell of [Fig.1] from one side of the envelope having the slots.

[0029] [Fig.3] is a second lateral view of the electrochemical cell from [Fig.1] since one side of the envelope not having a slot.

[0030] [Fig.4] is a perspective view of a second embodiment of a cell electrochemical according to the invention.

[0031] [Fig.5] is a side view of the electrochemical cell of [Fig.4] from one side of the envelope containing two slots.

[0032] [Fig.6] is a partial top view of a battery pack containing a series of electrochemical cells according to the invention, of which only three are shown.

[0033] [Fig.7] is a top view of an assembly by nesting a first variant embodiment of cells according to the invention of which only three are represented.

[0034] [Fig.8] is a top view of an assembly by nesting a second variant embodiment of cells according to the invention of which only three are represented.

[0035] [Fig.9] is a top view of an assembly by nesting a third variant embodiment of cells according to the invention of which only three are represented.

[0036] [Fig. 10] is a top view of an interlocking assembly of a fourth variant of cell embodiment according to the invention, of which only three are shown.

[0037] [Fig. 11] is a top view of an interlocking assembly of a fifth variant of cell embodiment according to the invention, of which only three are shown.

[0038] [Fig. 12] is a top view of an interlocking assembly of a sixth variant of cell embodiment according to the invention, of which only three are shown.

[0039] For clarity, identical or similar elements are identified by identical reference signs throughout the figures.

[0040] Naturally, the embodiments of the cell of the invention schematically illustrated in the figures above and described below are given only by way of non-limiting examples. It is explicitly provided for in the scope of the invention that different embodiments can be proposed and combined to create others.

[0041] The invention relates to the field of electrical energy accumulators or batteries and is more particularly concerned with a new electrochemical cell architecture intended for the production of advanced batteries.

[0042] In a manner known per se and as illustrated by Figures 1 and 4, the electrochemical cells traditionally used in batteries comprise, on the one hand, A stack of sheets 2, each containing an assembly consisting of a positive electrode and a negative electrode, a current collector 21 associated with each electrode, and at least one electrically insulating separator. This assembly is impregnated with an electrolyte and is enclosed within an outer casing 1 through which the collectors 21 protrude for connection to supply power to electrical equipment.

[0043] The collectors 21 of the series of cells 1 housed in the battery pack are grouped outside the pack and the envelope 1 provides the packaging and the airtight conditioning of the electrode sheets 2 inside the pack.

[0044] However, it has been observed that cells, and especially those whose configuration is substantially planar (such as prismatic cells or so-called "pouch" cells), are the site of significant mechanical stresses resulting from deformations that appear naturally over time.

[0045] These deformations generally appear as internal swellings located in the center of the cell, in the area where the structural resistance of the cell membrane is weakest. These deformations accelerate cell aging and therefore tend to promote destructive processes.

[0046] Batteries used in motor vehicles, and in particular traction batteries in electric vehicles, contain a large number of cells. Consequently, deformations of the internal cells are problematic because they lead to battery damage. The invention aims to provide a solution to this problem by proposing a specific cell architecture that distributes stresses within the cell assembly inside the battery.

[0047] As illustrated in Figures 1 and 4, this architecture consists of constructing the cell envelope 1 in the form of a rectangular parallelepiped provided, on two opposite sides, with at least one slot 10 delimited laterally by at least one straight edge 11, which is designed to interlock in a staggered pattern with the corresponding slots of identical cell envelopes. Figures 1 to 5 represent cell embodiments in which each slot 10 is delimited by two straight edges 11 formed on either side of the slot 10. These cells interlock as illustrated by the assembly in [Fig. 6]. This slot 10 can be recessed, as shown in Figures 1 to 6 and 7 to 9, or protruding, as shown in Figures 10 and 11.

[0048] The envelope 1 can take the form of a thin box whose thickness is more or less small depending on the profile and dimensions of the stack of sheets 2 which is intended to be packaged in it.

[0049] More specifically, in the embodiments shown here in the figures, the length of the bottom 10a of the crenellations 10 corresponds to the sum of the lengths of the straight edges 11. In the preferred embodiment of figures 1 to 6, the length of the bottom 10a corresponds here to twice the length of the straight edges 11 so as to obtain a symmetrical assembly because the two straight edges 11 have the same length.

[0050] However, it is possible to provide, without departing from the scope of the invention, that the slots 10 and the straight edges 11 are asymmetrical and of different geometries and dimensions (length, width and, where applicable, thickness). Thus, Figures 7 to 10 represent various possible embodiments of the cell of the invention, which are nested three by three (the stacks of electrode sheets are not shown).

[0051] Furthermore, in the embodiment of figures 1 to 6, the lateral sides 10b of the crenellations 10 are chamfered, but the invention also covers variants in which the sides of the crenellations are straight and perpendicular to the straight edges 11 and still allow for an interlocking assembly of cells, as illustrated by figures 7 to 10.

[0052] The stack of sheets 2 fills the entire interior space of the envelope 1 of the cell and the sheets 2 are arranged parallel to the height (or thickness) of the envelope 1, as illustrated by Figures 1 to 4.

[0053] Figures 1 to 3 represent a first embodiment of the internal stacking of the cell of the invention in which all the sheets 2 of the stacking are juxtaposed and each of them has two symmetrical collectors 21. Figures 4 and 5 represent another embodiment of the internal stacking of the cell of the invention in which this stacking consists here of a single sheet 2 folded or rolled on itself and the stacking then has only two collectors 21.

[0054] The invention provides for adding, inside the casing 1 and on either side of the slots 10, additional electrode sheets 2a of smaller dimensions as illustrated by [Fig. 1] or narrower winding loops 2b as illustrated by [Fig. 4]. Thus, the invention also relates to a new form of electrode stacking that adapts to the shape of the cell casing 1.

[0055] Thus, thanks to the invention, it becomes possible to arrange the cells in the battery pack, horizontally or vertically, without risk of slippage between them. The areas of high mechanical stress are offset and are no longer directly opposite each other as is the case when the cells are perfectly aligned.

[0056] Under these conditions, the cells 1 are assembled (horizontally on the [Fig. 6]) in the battery 3 in a staggered, interlocking pattern, offset from one another by in relation to others. In this configuration, it is therefore possible to control the potential expansion of the volume of the envelopes likely to generate constraints.

[0057] The cell architecture according to the invention is global and includes all embodiment variants comprising all forms of electrochemical sheets including the assembly comprising the electrodes, current collectors, separator and electrolyte and is applicable both to substantially flat profile cells, of the pouch type and prismatic cells as well as to any electrochemical process used for the operation of the battery.

Claims

Demands

1. An electrochemical cell comprising, on the one hand, a stack of sheets (2) each containing an assembly consisting of a positive electrode and a negative electrode, their associated current collector, and at least one electrically insulating separator, said assembly being impregnated with an electrolyte, and, on the other hand, an outer casing (1) enclosing said stack and through which said collectors protrude, characterized in that said casing is in the form of a rectangular parallelepiped provided, on two opposite sides, with at least one slot (10) laterally delimited by at least one straight edge (11) intended to interlock with the corresponding slots of identical cell casings, the casing (1) comprising two straight edges (11) on either side of the slot (10), and the length of the bottom (10a) of the slots (10) corresponding to the sum of the lengths of the edges straight lines (11).

2. Electrochemical cell according to claim 1, characterized in that the lateral flanks (10b) of the slots (10) are chamfered.

3. Electrochemical cell according to any one of the preceding claims, characterized in that the straight edges (11) have the same length.

4. Electrochemical cell according to any one of the preceding claims, characterized in that said stacking of sheets (2, 2a, 2b) fills the entire interior space of the envelope (1).

5. Electrochemical cell according to any one of the preceding claims, characterized in that the sheets (2) of said stack are arranged parallel to the thickness of the envelope (1).

6. Electrochemical cell according to any one of the preceding claims, characterized in that the sheets (2) of the stack are juxtaposed.

7. Electrochemical cell according to any one of claims 1 to 5, characterized in that the stack consists of a single sheet (2) folded over itself.

8. Electric battery (3) containing a series of electrochemical cells according to any one of the preceding claims which are nested one inside the other in a staggered pattern.

9. Motor vehicle equipped with at least one electric battery (3) according to claim 8.

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