ELECTRIC BATTERY WITH COOLING SYSTEM FOR HOLLOW ELECTROCHEMICAL CELL

Abstract

The invention relates to an electric battery comprising at least one casing (2) itself comprising at least one electrochemical cell (3), which electrochemical cell (3) having electrodes (4), one positive and the other negative, where said battery includes a homogeneous cooling system for said electrochemical cell (3), which is hollow and whose electrodes (4) are wound around a cooling channel (6) adapted to receive a heat transfer fluid for temperature control, in particular the cooling, of said electrochemical cell (3). The invention further relates to an electric or hybrid motor vehicle comprising at least one such battery. Figure 3

Description

Title of the invention: ELECTRIC BATTERY WITH COOLING SYSTEM FOR HOLLOW ELECTROCHEMICAL CELL

[0001] The invention relates to a battery containing at least one casing itself comprising at least one electrochemical cell comprising at least two electrodes, one positive, the other negative.

[0002] The invention further relates to an electric or hybrid motor vehicle, comprising at least one such battery.

[0003] The invention relates to the field of temperature control systems, particularly for cooling batteries, especially but not limited to batteries for electric or hybrid motor vehicles. For example, for any other use in a vehicle, truck, motorcycle, or other device, or for a power tool, or other device. And more particularly within the context of a specific internal structure of electrochemical cells. An "electrode" is a current collector on which active material is deposited.

[0004] Different methods of cooling batteries are known from the prior art: natural convection, forced air convection, forced liquid convection, liquid immersion.

[0005] Natural convection is not controlled, and greatly limits the vehicle's capabilities due to the risk of battery degradation, or even thermal runaway under certain common conditions (driving or charging).

[0006] Forced convection adds a degree of freedom to the previous method, by considerably increasing the airflow passing in contact with the battery cells, and thus the cooling performance.

[0007] Liquid convection follows the same principle as forced air convection, but with a liquid whose heat transfer fluid (or refrigerant) properties are more efficient, thus increasing cooling performance. However, electrical insulation requirements apply, and the mass and volume of the cooling system are therefore greater.

[0008] A technology called "immersion cooling" proposes to immerse or spray the batteries directly with a dielectric heat transfer fluid.

[0009] These systems have the drawback of having to adapt to a specific cell shape. However, cells are made in such a way that they offer a very limited cooling capacity, due to their internal geometry.

[0010] Conventional cylindrical cells can only be cooled on their cylindrical face, because the ends are used by electrical connections.

[0011] Prismatic cells are mainly cooled from the side opposite the battery tabs, providing a longitudinal thermal input to the plane of the electrodes, but not homogeneous because only from one side (whereas it is the approaches to the tabs that heat up the most)

[0012] Pouch cells require a heavy structure to compensate for their lack of a solid sheath. Adding a cooling system, which must be maintained on the cell walls despite its swelling, makes the exercise difficult and inefficient.

[0013] Regardless of the method used, temperature adjustment, particularly cooling, is always inhomogeneous because the cells have stacks or windings of electrodes, creating local areas more or less exposed to the cooling system, which then attempts to overcompensate for this defect with an excessive power requirement (beyond current realistic performance levels). This leads, in particular, to a divergence between the actual state of the cell and the BMS (Battery Management System) model, causing very strong thermal and mechanical gradients within the cells themselves, which significantly accelerates degradation phenomena and can even lead to thermal runaways or premature dendritic short circuits.

[0014] Electric vehicle technology is closely linked to battery optimization. One of the main difficulties encountered by cells is their geometric inhomogeneity, causing gradients in thermal, electrochemical, and mechanical behavior, which can lead to cell destruction by thermal runaway or dendritic short circuit.

[0015] The objective of the present invention is to overcome these drawbacks by proposing the use of cells with a substantially toroidal geometry, that is, cells of any cross-section but hollowed out, having a cavity in their center, in order to design a suitable temperature control system, particularly for cooling, offering homogeneous cooling performance within the cell, thus making it possible to exceed current performance levels, particularly in fast charging power, while maintaining or even improving the mass and volume energy density of the battery pack. While cooling is the most common temperature control method, preheating the battery can also be achieved using the heat transfer fluid.

[0016] To achieve this objective, the invention proposes a battery containing at least one casing itself comprising at least one electrochemical cell, which electrochemical cell comprises at least two electrodes, one positive, the other negative.

[0017] According to the invention, said battery comprises a homogeneous cooling system for said electrochemical cell which is hollow and whose electrodes are wound around a cooling channel suitable for receiving a heat transfer fluid for temperature adjustment or cooling of said electrochemical cell.

[0018] According to this topology, each turn formed by the electrodes around this channel offers longitudinal thermal conduction to the plane of the electrodes with respect to the perimeter of the channel, thus thanks to the invention, the electrodes can be cooled continuously, in a homogeneous manner.

[0019] Advantageously, said electrodes are each connected to a connection tab, and the cooling channel contains a tube suitable for conveying said heat transfer fluid and distant from said connection tabs of said electrodes.

[0020] Thus it is easy to connect each cell of a battery to a cooling network, and to isolate the latter from the electrical network.

[0021] In a particular embodiment, said electrodes are each connected to a connecting tab, and which tabs are inside said cooling channel and insulated from said heat transfer fluid.

[0022] This configuration allows the central channel of the cells to be used to establish connections, both with a cooling circuit by means of the tubes, and with an electrical circuit outside the tubes but using available space in this central channel, using the tube as a busbar.

[0023] Advantageously, said cooling channel extends around a straight axis.

[0024] This arrangement makes production easy and economical.

[0025] Advantageously, said electrodes are spirally arranged flat in the shape of an Archimedes screw around said cooling channel.

[0026] This geometry ensures the homogeneity of current and heat flows within each electrode.

[0027] Advantageously, said electrodes are spirally arranged in a substantially flat manner, for example with a helix angle of less than 20°. In a particular embodiment, they are angularly offset from one another around said straight axis, forming a double helix.

[0028] Thus the two electrodes are balanced, and benefit from the same cooling flow.

[0029] Advantageously, in a first embodiment, the spiral of said electrodes is cylindrical at least on the inside; the external shape depends on the shape of the housing designed to house the electrodes; in examples that are by no means exhaustive, this external shape can be cylindrical or prismatic. Here, this electrochemical cell is called "toric-cylindrical" when its external shape is cylindrical.

[0030] This arrangement allows the use of inexpensive cylindrical housings, and the cooling channel to be lined with a cylindrical tube positioned as close as possible to, in particular in contact with, the electrodes.

[0031] Advantageously, in a second embodiment, the spiral of said electrodes is cylindrical on the inside and square or rectangular on the outside. This electrochemical cell is referred to herein as "toric-cylindrical-flat faces".

[0032] This arrangement allows the use of prismatic housings which allow optimal use of the available storage volume in the battery, and to line the cooling channel with a cylindrical tube positioned as close as possible, in particular in contact, to the electrodes.

[0033] Advantageously, in a third embodiment, the spiral of said electrodes is composed of a rectangular band formed in a spiral, and is square or rectangular on the inside, and square or rectangular on the outside. This electrochemical cell is herein called "toric-cubic" or "toric-prismatic".

[0034] This arrangement allows the use of prismatic housings which allow optimal use of the available storage volume in the battery, and the filling of the cooling channel with a tube of any cross-section, or even the juxtaposition of electrical conductors to a cylindrical tube.

[0035] In a particular, non-limiting embodiment, the external shape of said electrochemical cell, projected onto a plane perpendicular to said straight axis, corresponds to the internal profile of said packaging housing of said electrochemical cell. While the illustrated examples concern cylindrical or prismatic shapes with a rectangular base, any other shape is possible: triangular, hexagonal, octagonal, or other, not necessarily regular.

[0036] Thus the compactness of the battery is ensured, and the available space is used to the best of its ability.

[0037] The invention further relates to an electric or hybrid motor vehicle, comprising at least one such battery.

[0038] 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 a motor vehicle according to the invention, which includes a battery according to the invention, electrically connected to energy storage means controlled by control means; this battery includes a cooling system with internal tubes to the electrochemical cells of the battery, this system cooperating with temperature adjustment means, including cooling, also controlled by these control means; [Fig.2] schematically illustrates, in perspective, a battery according to the invention, as already represented in [Fig.1], this battery comprises a plurality of juxtaposed housings, each containing such an electrochemical cell; purely didactic and non-limitingly, some housings are cylindrical, others are prismatic and arranged in a staggered pattern with the former, so as to provide external spaces between the housings usable for secondary cooling, by air or otherwise; the internal tubes of the electrochemical cells of the battery, each inserted in a cooling channel of the substantially toroidal electrochemical cell, are connected to tubing leading to the cooling means; each electrochemical cell has two connection tabs, their connection to the energy storage means is not shown here; [Fig.3] schematically illustrates in perspective a housing shown in transparency in dashed line, containing an electrochemical cell which has two low slope helical electrodes separated by half a pitch in this non-limiting example, each equipped at the top with its connection tab; the electrodes, one shown in solid line, the other in dashed line, are clear in the center to provide the cooling channel, shown here empty; [Fig.4] schematically illustrates, in side view, the same way, the housing of [Fig.3], here equipped with an axial tube inserted into the cooling channel and represented in dashed line; [Fig.5] schematically illustrates, similarly to [Fig.3], only the electrodes and their cooling channel; [Fig.6] schematically illustrates, similarly to [Fig.4], only the electrodes and their cooling channel; [Fig.7] schematically illustrates, both in top view and side view, a revolution of a helical electrode, with the central recess forming a cooling channel; [Fig.8] schematically illustrates, in perspective, two electrodes, here represented with a different outer diameter for didactic purposes to better distinguish them, offset here by half a step in this non-limiting example, and wrapped around a tube inserted in the cooling channel; - [Fig.9] schematically illustrates, in perspective, only one of the two electrodes, in a first variant where the spiral that forms it is of the toric-cylindrical type: cylindrical on the outside and on the inside; - [Fig. 10] schematically illustrates, in perspective, only one of the two electrodes, in a second variant where the spiral which forms it is of the so-called toric-cylindrical-flat-faces type: the spiral is cylindrical on the inside and square or rectangular on the outside; - [Fig. 11] schematically illustrates, in perspective, only one of the two electrodes, in a third variant where the spiral which forms it is of the so-called toric-prismatic type: the internal and external shapes are both rectangular, in particular square; - [Fig. 12] schematically illustrates, in perspective, a cylindrical case, containing an electrochemical cell whose exterior is also cylindrical, and equipped with a cylindrical tube inserted into the cooling channel provided in the center of the electrodes; - [Fig. 13] schematically illustrates, in perspective, a cylindrical case, containing an electrochemical cell whose exterior is also cylindrical, and equipped with a square section tube inserted into the cooling channel provided in the center of the electrodes; - [Fig. 14] schematically illustrates, in longitudinal section, a battery comprising four identical elements whose casings are aligned, and a tube circulating in a zig-zag in the channels provided at the axis of each of the electrochemical cells.

[0039] As seen in [Fig.1], the invention relates to a motor vehicle 100, which includes at least one electric battery 1, which is electrically connected by connection means 130 to energy storage means 120, which are controlled by vehicle 100 control means 110.

[0040] The electric battery 1 according to the invention comprises at least one casing 2, which itself includes at least one electrochemical cell 3. This electrochemical cell 3 has at least two electrodes 4, one positive and the other negative. More particularly, and without limitation, each electrode 4 has a current collector on which active material is deposited and is connected to a connection tab 5, as shown in [Fig. 3] and [Fig. 4]. The electrodes are preferably separated by a separator not shown in the figures and are immersed in an electrolyte and may include various additives. [Fig. 2] shows an electric battery 1 with a juxtaposition of such casings 2, which is shown for purely didactic purposes. Naturally, and as shown in [Fig. 14], the battery 1 may include at least one row of cells of the same type, traversed by the same cooling tube 7 circulating in series, in a zig-zag, entering once at the top, once at the bottom, into successive cells, instead of a tube with branches as illustrated in [Fig.2].

[0041] According to the invention, and as seen in particular in [Fig.3], [Fig.4], [Fig.5], [Fig.6], this electric battery 1 comprises a homogeneous cooling system for the electrochemical cell 3 which is hollow and whose electrodes 4 are wound around a cooling channel 6 suitable for receiving a heat transfer fluid for temperature adjustment, in particular cooling, of the electrochemical cell 3.

[0042] This electric battery 1 more particularly comprises an electrochemical cell cooling system with tubes 7, suitable for conveying the heat transfer fluid, inside the electrochemical cells 3 of the electric battery 1, as seen in [Fig.2], [Fig.4], [Fig.8] and [Fig.12]. This system cooperates, via a tube 70, with cooling means 130, such as a radiator coupled to a circulation pump, also controlled by the vehicle control means 110 of the vehicle 100.

[0043] In a particular embodiment, the tube 7 is distant from the electrode connection tabs 5.

[0044] In another particular embodiment, the electrode connection tabs 5 are inside the cooling channel 6 and insulated from the heat transfer fluid.

[0045] More specifically, the cooling channel 6 extends around a straight axis D.

[0046] The invention aims to limit thermal gradients within an electrochemical cell of a battery. Rapid charging generates a great deal of heat, with high power, and no cooling system is currently able to provide adequate cooling power, leading to efforts to optimize heat flow in order to reduce the size of cooling systems.

[0047] The various electrode technologies for batteries all exhibit thermal homogeneity defects, whether they are flat stacks, Z-stacks, cylindrical windings, or prismatic windings. Indeed, their stacked or wound nature creates a hierarchy of successive layers, each with its own specific thermal conditions. The windings or layers near the middle do not have access to the same cooling power as the outer layers.

[0048] Temperature causes accelerated degradation of electrochemical cells (batteries). Furthermore, internal gradients (within a cell itself) also exacerbate these effects. Moreover, strong thermal gradients This causes a divergence between the hottest and coldest points, which distorts the estimation of the model integrated into the battery management system (BMS) for balancing. As a result, the estimation of the cell's actual state is erroneous and can lead to overuse, causing thermal runaway or an internal short circuit due to dendrite formation.

[0049] According to a preferred embodiment of the invention, the electrochemical cell 3 is of toroidal type, and the cooling system is adapted to this toroidal shape to ensure homogeneous cooling performance in the cell.

[0050] According to the invention, a new type of electrode winding, spiral, and in particular double flat spiral, makes it possible to optimize the symmetry of the cell with respect to the chosen cooling solution.

[0051] Advantageously, the electrodes 4 are spirally arranged flat in the shape of an Archimedes screw around the cooling channel 6, as seen in [Fig.3], [Fig.4], [Fig.5], [Fig.6], [Fig.7], [Fig.8], [Fig.9], [Fig.10], [Fig.11],

[0052] More particularly in a particular non-limiting embodiment, the electrodes 4 are spirally arranged substantially flat with a helix angle of less than 20°, and are angularly offset from each other around the straight axis D by forming a double helix, as seen in [Fig.3], [Fig.4], [Fig.5], [Fig.6], [Fig.8].

[0053] Naturally the electrodes can, depending on the applications, be spiraled with other values ​​of helix angle, and be or not angularly offset, and with various angular offsets.

[0054] The invention thus uses the shape of the cells to optimize thermal conductivity during cooling. This new topology offers advantages over current solutions.

[0055] Instead of being wound, stacked, or folded as in the prior art, thus creating inner and outer zones in the electrodes, the electrodes are now spiraled so that each layer of the electrode receives a similar cooling power, and to optimize the heat transfer factor, no longer perpendicular to the electrodes but in their plane. Different materials can be used for the current collectors. Copper and aluminum current collectors are efficient thermal conductors, without any limitations.

[0056] This electrode topology reduces thermal inhomogeneities by eliminating the windings or stacking that create internal and external electrode layers, and by providing each turn of the winding with the same cooling performance. Due to this new geometry, the electrode layers offer superior heat transfer performance compared to known technologies. Thus, internal thermal gradients are drastically reduced, which greatly limits exposure to the risk of thermal runaway or internal short circuit.

[0057] More specifically, the electrodes are made in the form of flat spirals, particularly cylindrical or similar shapes. Their Archimedean spiral shape is similar to the helices of the DNA molecule. These flat spirals are coreless and therefore have a hole in their middle. And, even more specifically, these electrodes are double helical, like a DNA molecule, or like the double helix staircase of the Château de Chambord.

[0058] Thus the shape of these cells is substantially toroidal, and each cell can therefore accommodate a heat transfer fluid conduit in its center, away from the tabs or tabs of electrical connection.

[0059] More particularly, the double helix shape of the electrodes is used to introduce a heat transfer fluid conduit, formed by the cooling channel 6, into the center of the toroidal cylinder in order to cool the entire cell homogeneously.

[0060] As shown in [Fig. 3], [Fig. 4], [Fig. 5], [Fig. 6], [Fig. 8], [Fig. 9], a first advantageous variant comprises hollow cells 3, of a so-called toroidal-cylindrical shape, the spiral being cylindrical both externally and internally. The heat transfer fluid tube 7 can be introduced into the cooling channel 6 formed by the cylindrical extrusion of the cells. It therefore has a circular cross-section. The cells 3 can be aligned along this axis to benefit from the same flow in either direction of the battery pack.

[0061] As seen in [Fig.10], a second variant concerns 4 hollow cells, of toric-cylindrical-flat-face type: the spiral is cylindrical inside and square or rectangular outside to optimize the empty volumes during assembly; the external shape can also be rectangular, but then bringing a slight inhomogeneity linked to the variations in length along the transverse axis.

[0062] As shown in [Fig. 1 1], a third variant concerns hollow cells 3, of toroidal-cubic (or toroidal-prismatic) type, the spiral of which is composed of a rectangular band formed in a spiral. Both the internal and external shapes are square (or rectangular). The heat transfer fluid tube 7 can be inserted into the square extrusion of the cells. It therefore has a square (or rectangular) cross-section. The cells can be aligned along this axis to benefit from the same flow in either direction of the battery pack.

[0063] Yet another variant concerns cells 3 whose external shape, projected onto a plane perpendicular to the axis D of the spiral, or double spiral, corresponds to a particular internal profile of the housing 2 for the electrochemical cell 3, called the "casing," for example polygonal, or otherwise. It is understood that the electric battery 1 consists of a juxtaposition of such housings 2 or casings. containing the cells 3, and it may be advantageous to establish, between these casings 2, a circulation of heat transfer fluid. The same electric battery 1 can then contain either casings 2 of the same shape, for example cylindrical with toroidal-cylindrical cells, or casings 2 of different shape, for example as seen in [Fig. 1], a staggered alternation of cylindrical casings 2 with toroidal-cylindrical cells and prismatic casings 2 with toroidal-cubic (or toroidal-prismatic) cells, or other, so as to use the empty spaces between the casings 2 for additional cooling.

[0064] The possible variants are also related to the various output topologies of the tabs 5 or tabs to the outside of the casings 2. It is therefore possible to imagine countless ways of arranging and electrically connecting the current collectors to the external tabs or tabs: either at the ends, or on a cylindrical surface in the case of a cylindrical casing 2, or on a lateral surface in the case of a prismatic casing 2, at two different heights with a contact ring or tab, or even inside the toroidal cavity itself.

[0065] The shapes of casings 2, cell shapes 3, and tab positions 5 can be combined to best adapt the design of the electric battery 1 to its intended location within the vehicle 100. An additional advantage is the possibility of taking advantage of irregular volumes that are generally underutilized within a vehicle.

[0066] This cooling method is innovative yet simple to implement. This topology allows for much more efficient channeling of the heat flow than in the prior art, thus offering new perspectives for fast charging, which is limited by thermal dynamics and its limitations.

[0067] These electrode shapes offer many advantages in terms of thermal and mechanical properties, and are adaptable to cylindrical or prismatic external geometries depending on the casing chosen.

[0068] Moreover, battery chemistries are moving towards high expansion technologies; the spiral (spring) shape offers new flexibility to the electrodes, which until now have tended to degrade with their over-stressed expansion.

[0069] In summary, the invention offers significant advantages:

[0070] - possible undersizing of the cooling system;

[0071] - possibility of designing cells as long as desired without constraint of Thermal gradient. Therefore, a gain in volumetric energy density;

[0072] - thermal and mechanical improvement without any loss of energy density.

Claims

Demands

1. Electric battery (1) containing at least one housing (2) itself comprising at least one electrochemical cell (3), which electrochemical cell (3) comprising at least two electrodes (4), one positive, the other negative, characterized in that said electric battery (1) comprises a homogeneous cooling system for said electrochemical cell (3) which is hollow and whose electrodes (4) are wound around a cooling channel (6) suitable for receiving a heat transfer fluid for temperature adjustment or cooling of said electrochemical cell (3), said electrodes (4) being spiraled flat in the form of an Archimedes screw around said cooling channel (6).

2. Electric battery (1) according to claim 1 characterized in that said electrodes (4) are each connected to a connection tab (5), and in that said cooling channel (6) contains a tube (7) suitable for conveying said heat transfer fluid and distant from said connection tabs (5) of said electrodes (4).

3. Electric battery (1) according to claim 1 characterized in that said electrodes (4) are each connected to a connecting tab (5), which tabs (5) are inside said cooling channel (6) and insulated from said heat transfer fluid.

4. Electric battery (1) according to any one of claims 1 to 3 characterized in that said cooling channel (6) extends around a straight axis (D).

5. Electric battery (1) according to claim 4 characterized in that said electrodes (4) are spirally flat with a helix angle of less than 20°.

6. Electric battery (1) according to claim 5 characterized in that the spiral of said electrodes (4) is cylindrical on the outside and inside.

7. Electric battery (1) according to claim 5 characterized in that the spiral of said electrodes (4) is cylindrical on the inside and square or rectangular on the outside.

8. Electric battery (1) according to claim 5 characterized in that the spiral of said electrodes (4) is composed of a rectangular band formed in a spiral, and is square or rectangular on the inside, and square or rectangular on the outside.

9. Electric or hybrid motor vehicle (100), comprising at least one electric battery (1) according to any one of claims 1 to 8.

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