Accumulator, in particular an accumulator for an electric vehicle

Abstract

An accumulator (1), in particular an accumulator (1) for an electric vehicle, which comprises electrical cells (2), in which at least one conduit (4) of the heat exchange medium made of hyperelastic, flexible and electrically non-conductive material is arranged in the space between its electrical cells (2), wherein each electrical cell (2) of the accumulator (1 ) is in at least one planar or linear contact with the conduit (4).

Description

[0001] Accumulator, in particular an accumulator for an electric vehicle

[0002] Technical field

[0003] The present technical solution relates to an accumulator, especially an accumulator for an electric vehicle, which comprises electrical cells and which is provided with means for active temperature control of electrical cells.

[0004] Background art

[0005] Existing lithium-ion (Li-Ion) accumulators provide a range of advantages and generally good performance for numerous applications, including electric vehicles. However, they require a suitable temperature for optimal operation and efficient charging. This temperature is typically in the range of about 10 to 45 °C with an optimum in the range of about 15 to 35 °C.

[0006] At lower temperatures, the mobility of the charge carriers decreases and the electrolyte viscosity and internal resistance of the accumulator increases. If the accumulator is charged at a low temperature, growth of dendrites (filaments or crystals that form in the deposition phase of substances on the electrode) may occur in the electrical cells, as well as plating of the anode with metallic lithium or undesirable reactions of the electrolyte with lithium. These processes deteriorate the accumulator parameters and reduce its safety. In extreme cases, dendrites can connect both electrodes and cause an internal short circuit of the given electrical cell, which can even result in its ignition or explosion. For this reason, most lithium-ion accumulators are equipped with a management system (BMS), which reduces the current used to charge the accumulator at low temperatures or heats the accumulator with its own energy to a suitable temperature before charging begins. However, in both cases the time required to recharge the accumulator is extended by up to tens of minutes. Another disadvantage of heating the accumulator before recharging is that it accelerates degradation processes and accelerates the accumulator aging.

[0007] On the contrary, at higher temperatures, the viscosity of the electrolyte decreases and the drift mobility of ions increases. This can speed up the charging of the accumulator and increase the supplied electric current. In addition, however, there is also an increase in the self-discharge of the accumulator, when uncontrolled chemical reactions take place in its electrical cells, the by-product of which is heat, and therefore a further increase in the temperature of the accumulator occurs. Moreover, excessive heating of electrical cells results in an increase in the production of vapours from the lithium salt solvent in the electrolyte and an increase in internal pressure, which can even result in the accumulator ignition or explosion. At the same time, there is also corrosion of the electrodes and later the emission of active materials into the electrolyte and the formation of deposits. Therefore, when charging the accumulator at high temperatures, the BMS reduces the current used to charge the accumulator or stops charging completely, which results in an increase in the time needed to recharge the accumulator by up to tens of minutes. When the accumulator is exposed to high temperatures (due to ambient temperature or accumulator operation) for an extended period of time or repeatedly, the processes described above significantly reduce accumulator capacity, service life and safety.

[0008] For active cooling or heating of the accumulator or its electrical cells, conduits of heat exchange liquid are used which pass through the accumulator structure and are in contact with its electrical cells. These conduits are currently made of metallic materials and their disadvantage is that they are electrically conductive, and so they need to be insulated from the electrical cells of the accumulator by a suitable material, which is electrically non-conductive and at the same time does not prevent heat exchange. Another disadvantage is that they are rigid, and so they make it very difficult to replace individual electrical cells of the accumulator or to change the number of electrical cells in the accumulator. In addition, they occupy a large amount of space in the accumulator structure in combination with the insulating material and increase the dimensions of the accumulator. See, e.g., https: / / gravicgroup.com / wp- content / uploads / 2021 / 02 / Thermal_Management-Brochure-2020-web.pdf.

[0009] The object of the technical solution is to propose an accumulator, especially an accumulator for an electric vehicle, which would be provided with means for active temperature control of electrical cells that would eliminate the disadvantages of the background art. of technical solution

[0010] The object of the technical solution is achieved by an accumulator, in particular an accumulator for an electric vehicle, which comprises electrical cells and whose principle consists in that at least one conduit of the heat exchange medium made of hyperelastic, flexible and electrically non-conductive material is arranged in the space between its electrical cells, wherein each electrical cell of the accumulator is in at least one planar or linear contact with this conduit. The conduit of the heat exchange medium can serve to cool or to heat the electrical cells of the accumulator.

[0011] In the space between the electrical cells of the accumulator, two or more heat exchange medium conduits can be arranged, or two or more interconnected loops of one heat exchange medium conduit.

[0012] If the conduit of the heat exchange medium comprises multiple loops (interconnected or independent), or if multiple heat exchange medium conduits are arranged in one accumulator, these loops or conduits can be arranged one above the other in the direction of the longitudinal axis of at least some of the electrical cells in at least part of the accumulator.

[0013] A suitable hyperelastic, flexible and electrically non-conductive material of the conduit of the heat exchange medium is, for example, Teflon, rubber, silicone, polyurethane elastomer, etc.

[0014] Brief

[0015] In the enclosed drawing, Fig. 1 schematically shows a longitudinal crosssection of the accumulator according to the technical solution in the first exemplary embodiment, Fig. 2 shows a view from above into the internal space of the accumulator according to the technical solution in the exemplary embodiment according to Fig. 1 , Fig. 3 shows a longitudinal cross-section of the accumulator according to the technical solution in a different exemplary embodiment than Fig. 1 , Fig. 4 shows a longitudinal cross-section of the accumulator according to the technical solution in a different exemplary embodiment than Fig. 1 and Fig. 3, Fig. 5 shows a transverse cross-section of the accumulator according to Fig. 4, and finally, Fig. 6 shows a view from above into the internal space of the accumulator according to the technical solution in a different exemplary embodiment than Fig. 2.

[0016] Examples of embodiment of technical solution

[0017] The accumulator 1_, especially accumulator for an electric vehicle, according to the technical solution is provided with means for active cooling or heating of its electrical cells 2.

[0018] The accumulator 1. comprises electrical cells 2, which are housed in a box 3, preferably in a box 3 that is made of an electrically non-conductive material, e.g. plastic, or a suitable composite. A suitable material for the box 3 is, e.g., polyamide (recycled material can also be used), which has advantageous mechanical and chemical properties. In a variant of the accumulator shown in Figs.1 to 6, the electrical cells 2 are cylindrical and are mounted vertically in the box 3; however, the principle of the technical solution can be applied analogously to other designs of the accumulator 1. with a different shape of the electrical cells 2 and / or their different spatial arrangement. The electrical cells 2 are interconnected in a known manner, which will not be described further here, and the accumulator 1_ is provided with a known electronic control unit (not shown), which will not be described further here, as it is not relevant for understanding the principle of the technical solution. The electrical cells 2_may be electrical cells 2 of any known type, especially such as Li-Ion, LiFePO4, Li-Pol, NiMH, NiCd, etc.

[0019] In the space between the electrical cells 2 of the accumulator 1_, at least one conduit 4 of the heat exchange medium is arranged, wherein each electrical cell 2 of the accumulator 1. is in at least one planar or linear contact with the conduit 4. The conduit 4 of the heat exchange medium comprises one loop, which is in at least one contact with each electrical cell 2 of the accumulator (see, e.g., Fig. 1 and Fig. 2) or comprises multiple loops and each electrical cell 2 of the accumulator 1. is in at least one planar or linear contact with at least one loop of the conduit 4 of the heat exchange medium. The loops may be independent of each other and may be separately provided with means 41 for connection to a heat exchange circuit (not shown) (see, e.g., Fig. 6) or may be interconnected and provided with common means 41 for connection to a heat exchange circuit (not shown). In both variants of embodiment, when the conduit 4 of the heat exchange medium comprises at least two loops, at least some electrical cells 2 may be in at least one contact with at least two loops of the conduit 4, wherein the area of this contact may be different for each loop, for example, in the embodiment shown in Fig. 6, the electrical cells 2 in the centre of the accumulator 1_ are in contact with two loops of the conduit 4 of the heat exchange medium, with one loop being in planar contact and the other being in linear contact.

[0020] If the conduit 4 of the heat exchange medium comprises multiple loops (interconnected or independent), or if multiple conduits of the heat exchange medium 4 are arranged in one accumulator 1_, these loops or conduits 4 can be arranged one above the other in at least part of the accumulator 1. in the direction of the longitudinal axis of the electrical cells 2 (see, e.g., Figs. 3, 4 and 5). They can be arranged with respect to each other in such a manner that the heat exchange medium flows in them in the same direction or, more preferably, in the opposite direction.

[0021] The conduit of the heat exchange medium is made of electrically non- conductive hyperelastic and flexible material such as Teflon, rubber, silicone, polyurethane elastomer, etc. The advantage of these materials is the fact that they have high chemical resistance, resistance to high and low temperatures (up to -70 to 250 °C), excellent electrical insulation properties, sealing effects, resistance to ageing and very good sliding properties. This enables, for example, the use of more aggressive and at the same time more efficient heat exchange media. Furthermore, the use of these materials prevents the conductive interconnection of the individual electrical cells 2 and the short-circuiting of the accumulator 1_. Moreover, their hyperelasticity allows the size of the contact area of the heat transfer medium conduit 4 with the electrical cells 2 of the accumulator 1_ to be varied, wherein upon increasing the pressure of the heat exchange medium the volume of the conduit 4 and also the contact area between the conduit 4 and the surface of the electrical cell 2 increases, using the otherwise free space between the electrical cells 2, and wherein upon decreasing the pressure the volume of the conduit and also contact area decreases. Another advantage of this material is also the fact that due to its hyperelasticity and flexibility, it allows to reduce the distances between the individual electrical cells 2 of the accumulator 1_ and thus increase the volumetric charge capacity of the accumulator 1_. In addition, the hyperelasticity of this conduit 4 allows to lead this conduit 4 in a spiral around the circumference of at least one electrical cell 2 and to arrange two or more interconnected loops of this conduit 4 above each other (see Figs. 3, 4 and 5) without the need to interrupt the conduit and connect it via rigid connecting elements. Hyperelasticity is defined as the ability to deform elastically (i.e., recoverably) by 100 to 700 %.

[0022] The conduit 4 of the heat exchange medium allows cooling and heating of the electrical cells 2 of the accumulator 1. as required. The heat exchange medium may be any known liquid, such as water, a mixture of water and ethylene glycol, ethylene glycol, oil, etc., or gas, such as air, isobutane, etc.

[0023] Via the means 41_, the conduit 4 of the heat exchange medium of the accumulator 1_ is connectable to a known heat exchange circuit (not shown) with a heat exchanger / heat exchangers, a pump / compressor, or a heat exchange liquid reservoir, etc.

[0024] For independent heating of the electrical cells 2, the accumulator 1. may be provided with a separate heating element / elements, e.g., based on electric resistance heating.

[0025] The walls of the box 3 of the accumulator 1_ are preferably provided with an unillustrated layer of material impermeable to electromagnetic radiation, or such material is incorporated directly into the material of the box of the accumulator 1_. This prevents electromagnetic radiation to penetrate to the surroundings of the accumulator 1_.

Claims

Claims1. An accumulator (1 ), in particular an accumulator (1 ) for an electric vehicle, which comprises electrical cells (2), characterized in that at least one conduit (4) of the heat exchange medium made of hyperelastic, flexibile and electrically non-conductive material is arranged in the space between its electrical cells (2), wherein each electrical cell (2) of the accumulator (1 ) is in at least one planar or linear contact with the conduit (4).

2. The accumulator (1 ) according to claim 1 , characterized in that at least two conduits (4) of the heat exchange medium are arranged in the space between its electrical cells (2).

3. The accumulator (1 ) according to claim 1 , characterized in that at least two interconnected loops of the conduit (4) of the heat exchange medium are arranged in the space between its electrical cells (2).

4. The accumulator (1 ) according to claim 2 or 3, characterized in that at least two conduits (4) of the heat transfer medium or at least two loops of the conduit (4) of the heat transfer medium are arranged above each other along the longitudinal axis of at least some of the electrical cells (2) in at least part of the accumulator (1 ).

5. The accumulator (1 ) according to claim 1 , characterized in that the hyperelastic, flexible and electrically non-conductive material of the conduit (4) of the heat exchange medium is Teflon, rubber, silicone, polyurethane elastomer.

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