Battery

Abstract

The invention relates to a battery comprising at least one electrochemical cell (2) and at least one heat pipe (1) having a housing (10) which contains a working medium, the housing (10) having an evaporation region (17) and a condensation region (19) which are connected to one another by a channel (18), the housing (10) containing a first film bag (15) or consisting of a first film bag (15), the first film bag (15) comprising at least a first and a second material layer (151, 152), one material layer (151) of which consists of a polymer and the other material layer (152) of which consists of a metal material, the electrochemical cell (2) being arranged in the housing (10) of the heat pipe (1).

Description

[0001] BATTERY

[0002] The invention relates to a battery with at least one electrochemical cell and a heat pipe with a housing which contains a working medium, wherein the housing has an evaporation region and a condensation region which are connected to one another by a channel.

[0003] From H. Behi et al.: "Thermal management analysis using heat pipe in the high current discharging of lithium-ion battery in electric vehicles", Journal of Energy Storage, Vol. 32, p. 101893, 2020, it is known that lithium-ion batteries for high-current applications, for example in electric vehicles, can be cooled using heat pipes. However, the known heat pipe has comparatively high thermal contact resistances between the battery cell and the heat pipe. This limits the cooling performance.

[0004] Based on the prior art, the invention is therefore based on the object of providing a battery with improved thermal management.

[0005] The object is achieved by a battery according to claim 1. Advantageous developments of the invention can be found in the subclaims.

[0006] According to one aspect of the invention, a battery with at least one electrochemical cell and at least one heat pipe is proposed. The electrochemical cell can, for example, be a lithium-ion accumulator, which is to be kept within a predeterminable temperature range during a charging or discharging cycle to extend its service life.

[0007] The electrochemical cell can have any known design and, for example, take the form of a round cell or a prismatic cell. In other embodiments of the invention, the electrochemical cell can be a pouch cell packaged in a foil bag. In some embodiments of the invention, the heat pipe housing and the pouch cell housing can be made of an identical or highly similar material.

[0008] According to one aspect of the invention, a heat pipe with a housing is proposed which contains a working medium. The housing can have an evaporation region and a condensation region which are connected to one another by at least one channel. Waste heat from an electronic or electrical component or a battery cell is fed to the heat pipe via the evaporation region. This leads to the evaporation of the working medium, which is then passed in gaseous form through the channel into the condensation region. There, the heat is released into the environment or into a cooling medium flowing around the heat pipe, whereby the working medium condenses again. The working medium liquefied in this way flows back into the evaporation region via the at least one channel. This process is repeated cyclically.The temperature range in which the heat pipe operates is determined by the choice of working medium and the pressure prevailing in the heat pipe and can be adapted to the intended use of the heat pipe.

[0009] In some embodiments of the invention it is proposed that the housing consists at least in sections of a first film bag or contains such a film bag. In some embodiments of the invention the housing can be made entirely from a film bag. The material of the film bag, which at least partially represents the wall of the housing, contains at least a first and at least a second material layer, wherein one material layer consists of a polymer and the other material layer consists of a metallic material. The first and second material layers can be fully connected to one another, for example by gluing or welding. In some embodiments of the invention the second material layer can be applied to the first material layer by means of a coating process.The coating method used may, for example, be coating by rolling, brushing, doctor blade coating, or printing. In other embodiments of the invention, the coating method may include a vacuum coating method, for example, a sputtering process or thermal vapor deposition.

[0010] The use of a film bag as a housing for the heat pipe has the advantage that the wall thickness is thinner, resulting in lower thermal resistance than would be the case with a dimensionally stable polymer. In addition, the heat pipe remains flexible, meaning that it can adapt to the shape of a body to be cooled or heated. This is particularly advantageous when battery cells, resistors or other heat-emitting components have a cylindrical basic shape or another shape with non-planar boundary surfaces. Of course, the use of the heat pipe is not restricted to these applications. Rectangular or cuboid-shaped components that require cooling or heating can also be brought into contact with the heat pipe, whereby the low wall thickness and the flexibility of the film bag can enable good thermal contact.In some embodiments, the battery can be designed as a pouch cell. The use of a flexible foil pouch as the heat pipe housing has the particular advantage that dynamic volume changes during loading and unloading of the pouch cell can be absorbed by the flexible foil pouch. In contrast to the prior art, where this task is performed by nonwovens with poor thermal conductivity, this ensures better heat dissipation or supply from the pouch cell.

[0011] Due to the two-layer construction of the film bag, in which at least one material layer contains or consists of a metallic material, the film bag is diffusion-tight, so that the gaseous working medium cannot escape from the heat pipe and no foreign gases can penetrate, thus ensuring a long service life and reliable operation over longer periods.

[0012] Furthermore, it was recognized that with higher heat input, the temperature and thus the internal pressure of the heat pipe can rise. The flexibility of the foil bag allows it to conform better to the heat source or heat sink, thus improving heat transfer. The heat pipe can therefore be viewed as a self-regulating system that reduces the effort required to regulate temperature. Furthermore, the heat pipe has the advantage of being lightweight, which expands its possible uses, particularly in mobile applications.

[0013] In some embodiments of the invention, the first film bag can further comprise a third material layer. The third material layer can be arranged such that the second material layer, which contains a metallic material, is enclosed on both sides by the first and third material layers. This can prevent mechanical damage to the second material layer, thus increasing the service life of the heat pipe.

[0014] In some embodiments of the invention, the film bag may further comprise a fourth material layer, which may contain a polymer or consist of a polymer. A plurality of polymer material layers in the film material, each of which may be fully bonded to one another, opens up the possibility of absorbing tensile forces in different directions, thus improving mechanical stability.

[0015] In some embodiments of the invention, the first, third, and / or fourth material layer can be selected from polyamide and / or polyethylene terephthalate and / or polyhexamethylene adipamide. These materials are characterized by good availability, high mechanical stability, and low thermal resistance.

[0016] In some embodiments of the invention, the second material layer can contain or consist of gold and / or aluminum and / or titanium and / or copper. The metallic material of the second material layer can contain a plurality of thin films arranged one above the other. For example, a thin layer of titanium can first be vapor-deposited onto the first material layer, after which a further layer of gold and / or aluminum and / or copper is applied. In some embodiments of the invention, the second material layer can contain an alloy. In some embodiments of the invention, the second material layer can have a high diffusion resistance and a high plastic deformability. The latter reduces microcracks.

[0017] In some embodiments of the invention, the channel can be divided into a steam channel and a condensate channel. Due to the spatial separation, the heat pipe does not necessarily have to be operated in the wet steam range, thus increasing the possible applications and / or the transferable thermal power.

[0018] In some embodiments of the invention, the channel may contain a capillary structure. This allows the liquid working medium to be returned from the condensation region to the evaporation region even against gravity, so that the heat pipe can be used regardless of its position.

[0019] In some embodiments of the invention, the housing can further contain at least one filling element. The filling element can be provided to prevent the film bag from collapsing, which can occur if the pressure inside the heat pipe is lower than the ambient pressure. Such operating states can occur in particular if the heat pipe is to be used at comparatively low temperatures and as a result the working medium only has a low pressure. In some embodiments of the invention, the pressure inside the housing can temporarily drop below the ambient pressure during manufacture of the heat pipe when the housing is evacuated in order to prevent contamination of the working medium. The filling element is thus designed and intended to counteract the air pressure acting on the housing from the outside with a restoring force which prevents the housing from collapsing completely.

[0020] In some embodiments of the invention, the filling element can have a dual function and, for example, simultaneously form a heat exchanger, which increases the area available for evaporation and / or condensation of the working medium within the heat pipe. In some embodiments of the invention, the filling element can form a capillary structure or consist of a capillary structure, so that the filling element not only increases the mechanical stability of the heat pipe, but also serves to recirculate the liquid working medium in the channel.

[0021] In some embodiments of the invention, the filling element can be selected from at least one leaf spring and / or at least one helical spring and / or at least one nonwoven fabric and / or at least one knitted fabric and / or at least one tube, at least one braid and / or at least one lattice structure. In some embodiments of the invention, a different filling element can be used in the condensation region and / or in the evaporation region and in the channel. This can improve the performance of the heat pipe.

[0022] In some embodiments of the invention, the filler element may contain or consist of a polymer, a metal, or an alloy. This can also improve the function of the heat pipe, for example, if a material with comparatively high thermal conductivity is used in the condensation region and / or evaporation region and a material with comparatively low thermal conductivity is used in the region of the channel(s).

[0023] In some embodiments of the invention, the first film bag can have a wall thickness of approximately 100 pm to approximately 200 pm. In other embodiments of the invention, the first film bag can have a wall thickness of approximately 50 pm to approximately 250 pm. Such a multi-layer film material has, on the one hand, sufficiently high mechanical strength and, on the other hand, has a low thermal resistance, so that the heat of the component to be cooled can be used efficiently to evaporate the working medium. In some embodiments of the invention, the electrochemical cell can be arranged in the housing of the heat pipe. This allows particularly efficient heat transfer by reducing heat transfer resistance.

[0024] In some embodiments of the invention, the electrochemical cell can be arranged in a second foil bag that is in contact with the first foil bag. This allows heat pipes and / or electrochemical cells to be easily replaced to repair the battery.

[0025] The invention will be explained in more detail below with reference to figures without limiting the general idea of ​​the invention.

[0026] Figure 1 shows a heat pipe in view.

[0027] Figure 2 shows a heat pipe in a first embodiment in section.

[0028] Figure 3 shows a heat pipe in a second embodiment in section.

[0029] Figure 4 shows a foil bag of a heat pipe in

[0030] cut .

[0031] Figure 5 shows a battery in a first embodiment.

[0032] Figure 6 shows a battery in a second embodiment.

[0033] Figure 7 shows a test setup for demonstrating the operation of the present invention. Figure 8 shows measured values ​​obtained with the test setup shown in Figure 7.

[0034] A heat pipe 1 is explained in more detail with reference to Figure 1. The heat pipe 1 has a housing 10, which according to one aspect of the invention is designed in the form of a first foil bag 15. The housing 10 has approximately the basic shape of a cuboid. In other embodiments of the invention, the housing 10 can also have a different shape.

[0035] In the illustrated embodiment, the housing 10 is made from a single film web, which has been folded over at the upper edge 105 so that there is no seam there. At the two side edges 101 and 102, which adjoin the upper edge 105 at approximately right angles, the upper and lower film webs are glued or welded together to form a gas-tight connection. The lower edge 103 is sealed in the same way by gluing or welding, so that the housing 10 defines a completely closed cavity 14.

[0036] Inside the heat pipe 1 or in its cavity 14 there is an evaporation area and a condensation area which are connected to one another by a channel. During operation, the outer side of the component to be cooled is brought into contact with the evaporation area of ​​the housing 10 of the heat pipe 1. Heat which penetrates through the wall of the film bag 15 into the cavity 14 of the heat pipe 1 causes the working fluid to evaporate there. The gaseous working fluid passes through the channel into the condensation area. There the working fluid condenses, giving off heat, and is transported back through the channel as a liquid to the evaporation area. In the case of a component to be heated, the outer side of the component to be heated is brought into contact with the condensation area of ​​the heat pipe.In some embodiments of the invention, the channel can be designed as a single cavity, so that the gas and liquid of the working medium are in equilibrium. In other embodiments of the invention, the channel can be divided to create at least one vapor channel and at least one condensate channel. In some embodiments of the invention, the channel can contain an optional capillary structure, which transports the liquid working medium into the evaporation region, even against gravity or counteracting acting acceleration forces.

[0037] Figure 2 shows a first embodiment of the heat pipe 1 in cross section. Identical components of the invention are provided with the same reference numerals, so that the following description is limited to the essential differences. As can be seen from Figure 2, the evaporation region 17 is arranged adjacent to the lower edge 103 in the housing 10 and extends from an upper side 11 to an opposite lower side 12. A channel 18 adjoins the evaporation region 17. Adjoining the channel 18 is the condensation region 19, which is thus arranged adjacent to the upper edge 105 in the housing 10. The heat pipe according to the first embodiment thus transports heat from its lower edge 103 to its upper edge 105.

[0038] As Figure 2 further shows, at least one filling element is located in the cavity 14 of the housing 10. In the illustrated embodiment, three different filling elements 171, 181, and 191 are shown.

[0039] The filling elements can consist of a polymer, a metal or an alloy. The filling elements can be selected from at least one leaf spring and / or at least one helical spring and / or at least one nonwoven material and / or at least one knitted fabric and / or at least one crocheted fabric and / or at least one tube and / or at least one lattice structure and / or at least one woven fabric. In other embodiments of the invention, a single filling element can be present inside the housing. In some embodiments of the invention, the filling element can only fill part of the housing. In some embodiments of the invention, a filling element can also be omitted.

[0040] The filler element(s) can perform individual functions within the heat pipe 1 or be provided with a multiple function. For example, the filler elements can prevent the housing 10 from collapsing due to external air pressure when the internal pressure inside the heat pipe is lower than the ambient pressure, for example because a working medium is filled in which only requires a low working pressure or because the interior of the housing 10 is evacuated during manufacture of the heat pipe 1 in order to prevent contamination of the working medium. In addition, the filler elements can improve the heat transfer from the outside of the housing 10 to the working medium, for example by improving the heat conduction within the housing 10 and / or by providing a larger surface for the evaporation of the working medium.In particular, the filling element 181 in the channel 18 can also exert capillary forces on a liquid working medium in order to return it from the condensation region 19 to the evaporation region 17.

[0041] A second embodiment of the heat pipe is explained in more detail with reference to Figure 3. According to the second embodiment, the evaporation region 17 is located adjacent to the top side 11 of the housing 10 and extends from the upper edge 105 to the lower edge 103.

[0042] In the same way, the condensation region 19 extends along the underside 12. The condensation region 19 also extends from the upper edge 105 to the lower edge 103. The channel 18 is again located between the condensation region and the evaporation region. The evaporation region 17, the channel 18 and the condensation region 19 can be provided with identical or different filling elements, as explained above. The second embodiment differs from the first embodiment described above in particular in that the heat is transported from the upper side 11 to the underside 12. The direction of the heat flow thus follows the normal vector of the largest base area of ​​the housing 10, whereas in the first embodiment described with reference to Figure 2 it runs orthogonal to this.Evaporation and condensation areas can also be swapped, so that the heat flow occurs against gravity and the condensate flow occurs with gravity.

[0043] Figure 4 shows the cross-section through the housing wall or the film bag 15. As can be seen from Figure 4, the film bag 15 in the present embodiment has four material layers 151, 152, 153, 154. The four material layers 151, 152, 153, 154 are fully bonded to one another.

[0044] The first material layer 151 has a thickness of approximately 12 μm and is made of polyethylene terephthalate. A second material layer 152 made of a metallic material, in the present example aluminum with a thickness of approximately 9 μm, is located thereon. A third material layer 153, which has a thickness of approximately 15 μm and is made of polyamide, is located on the second material layer 152. A fourth material layer 154, which is made of polyethylene and has a thickness of approximately 100 μm, is located on the third material layer 153.

[0045] The multi-layer structure of the film bag 15 can increase the service life of the heat pipe. The fourth material layer 154 forms a seal for the interior 14 of the housing 10. The third material layer 153 increases the mechanical strength to prevent damage to the film bag 15. The second material layer 152, made of a metallic material, serves as a vapor barrier, preventing the escape of the working fluid. The first material layer 151 serves as an outer protective layer to prevent damage to the second material layer 152.

[0046] Overall, the film bag 15 has a wall thickness of between approximately 100 μm and 200 μm. The individual material layers are bonded to one another over their entire surface, either by gluing or welding, or by directly depositing a material layer onto the preceding material layers, for example, by printing, doctoring, painting, or rolling. Alternatively, individual or all layers can also be deposited onto the preceding layer using a vacuum coating process.

[0047] It has been shown that the foil bag used has sufficiently low leakage rates to prevent the penetration of gaseous contaminants into the heat pipe and at the same time prevent the leakage of the working fluid, so that the heat pipe has a sufficiently long operating life.

[0048] A battery according to a first embodiment of the invention is explained with reference to Figure 5. Figure 5 shows an electrochemical cell 2, which may, for example, be a lithium-ion accumulator. In other embodiments of the invention, a different cell chemistry may also be used. The invention does not teach the use of a specific electrochemical cell as a solution principle.

[0049] The electrochemical cell 2 is located in a second foil pouch 25. In some embodiments of the invention, the second foil pouch 25 can be constructed similarly to the heat pipe, so that the electrochemical cell 2 is a pouch cell. In other embodiments of the invention, other designs can also be used, for example, with a housing made of a metal, an alloy, or a polymer.

[0050] The second foil bag 25 or the housing has passages through which the connection contacts 21 and 22 are led outwards, so that a charging current can be supplied to the electrochemical cell 2 or a useful current can be withdrawn.

[0051] The heat pipe 1 is located in a first foil bag 15, as described above. The first foil bag 15 and the second foil bag 25 are in contact with each other with at least a partial surface, so that the heat emitted or absorbed by the electrochemical cell 2 can penetrate the second and first foil bags 25 and 15 and be fed to the evaporation region 17 of the heat pipe 1.

[0052] In the case of heat dissipation, the heat dissipated by the heat pipe 15 is fed to a cooling medium 3. The cooling medium 3 can be gaseous or liquid. The cooling medium 3 can be, for example, an air stream, cooling water, or thermal oil.

[0053] By releasing heat from the condensation area 19 within the heat pipe 1 to the cooling medium 3, the working medium within the first foil bag 15 is liquefied again and fed again to the evaporation area 17 of the heat pipe 1.

[0054] A second embodiment of a battery is explained with reference to Figure 6. Identical components of the invention are provided with the same reference numerals, so that the following description is limited to the essential differences. As can be seen from Figure 6, the electrochemical cell 2 is located within the first foil bag 15. This enables particularly good heat transfer from the electrochemical cell 2 to the working fluid in the first foil bag 15. The cooling or heating of the electrochemical cell 2 can therefore take place with greater efficiency.

[0055] Figure 7 illustrates a test setup for the heat pipe in more detail. The heat pipe 1 is fixed at an angle of 20° to the horizontal. An electrical heating resistor 5 is located in the evaporation region 17, allowing a heat flow to be supplied to the evaporation region 17. Two first temperature sensors 41 measure the temperature of the evaporation region 17.

[0056] In the condensation zone 19, a thermal heat flow is dissipated, allowing the working medium to condense there. The condensate is subsequently returned through channel 18 to the evaporation zone 17. Two second temperature sensors 42 are also located in the condensation zone 19.

[0057] Figure 8 shows the measured values ​​of a comparison test which were obtained using the test setup shown in Figure 7. The temperature difference between the mean value of the temperature sensors 41 and the mean value of the temperature sensors 42 is shown in Kelvin on the ordinate. The time in hours is shown on the abscissa. The same thermal output is applied to all three comparison objects. Since the insulation is very good, it can be assumed that the same output is transported through all three comparison objects. The following therefore applies: the smaller the temperature difference, the lower the thermal resistance and consequently the better the heat transport capacity.Figure 8 shows three measurement curves for the three comparison objects, namely curve C shows the measured values ​​of a heat pipe according to the first embodiment of the invention shown in Figure 2, wherein the cavity 14 of the housing 10 contained filling elements 171, 181 and 191, but no working fluid. Curve B shows the measured values ​​of a solid aluminum plate which has approximately the same geometric dimensions as the housing 10 of the heat pipe. Curve A shows the measured values ​​of the heat pipe after it has been filled with working fluid.

[0058] An initial power of 5 watts was introduced into the evaporation zone 17 via the electrical heating resistor 5. After approximately 15 minutes, the electrical power was increased to 10 watts. After approximately another ten minutes, the power was increased to 15 watts.

[0059] As shown in curve C in Figure 8, a temperature difference between the evaporation region 17 and the condensation region 19 quickly develops on the heat pipe without a working medium, and this temperature difference rapidly increases with increasing heating power. The temperature difference on the aluminum plate is approximately 6 K at 15 watts of applied electrical power, which is about a factor of 6 higher than the temperature drop along the heat pipe (curve A) of approximately 1 K, as curve B shows. The temperature difference of the heat pipe without any working medium is approximately 30 K at the end of the test, as can be seen from curve C. The heat pipe without a working medium therefore has a significantly higher thermal resistance than the heat pipe with a working medium, which is reflected in a significantly higher temperature difference for the same applied power.A battery that constantly dissipates waste heat would overheat, whereas with the foil heat pipe filled with working fluid, it can be kept at a low temperature with the same heat dissipation due to the low thermal resistance. Even the aluminum plate used for comparison shows a temperature difference that is approximately six times greater than that of the heat pipe, which suggests that the heat transfer capacity is approximately six times worse than that of the heat pipe. Therefore, compared to the aluminum plate, the heat pipe can be expected to dissipate heat from electrical or electronic components very efficiently.

[0060] Of course, the invention is not limited to the embodiments shown. The above description is therefore not to be regarded as limiting, but as illustrative. The following claims are to be understood in such a way that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define "first" and "second" embodiments, this designation serves to distinguish between two similar embodiments without establishing a priority.

Claims

Claims 1. Battery with at least one electrochemical cell (2) and at least one heat pipe (1) with a housing (10) which contains a working medium, wherein the housing (10) has an evaporation region (17) and a condensation region (19) which are connected to one another by a channel (18), wherein the housing (10) contains a first film bag (15) or consists of a first film bag (15), wherein the first film bag (15) has at least a first and a second material layer (151, 152), of which one material layer (151) consists of a polymer and the other material layer (152) consists of a metallic material, characterized in that the electrochemical cell (2) is arranged in the housing (10) of the heat pipe (1).

2. Battery according to claim 1, characterized in that the first film bag further comprises a third material layer (153) and / or a fourth material layer (154), each of which contains or consists of a polymer.

3. Battery according to claim 1 or 2, characterized in that the first, third and / or fourth material layer (151, 153, 154) contain or consist of a thermoplastic.

4. Battery according to one of claims 1 to 3, characterized in that the second material layer (152) contains or consists of gold and / or aluminum and / or titanium and / or copper.

5. Battery according to one of claims 1 to 4, characterized in that the channel (18) is divided into a vapor channel and a condensate channel and / or that the channel contains a capillary structure.

6. Battery according to one of claims 1 to 5, characterized in that the housing (10) further contains at least one filling element (181).

7. Battery according to claim 6, characterized in that the filling element (181) is selected from at least one leaf spring and / or at least one helical spring and / or at least one nonwoven fabric and / or at least one knitted fabric and / or at least one tube and / or at least one lattice structure.

8. Battery according to claim 6 or 7, characterized in that the filling element (181) contains or consists of a polymer or a metal or an alloy.

9. Battery according to one of claims 1 to 8, characterized in that the first film bag (15) has a wall thickness of 100 pm to 200 pm or of 50 pm to 250 pm.

10. Battery according to one of claims 1 to 9, characterized in that the first, third and / or fourth material layer (151, 153, 154) are selected from polyamide and / or polyethylene and / or polyethylene terephthalate and / or polytetrafluoroethylene and / or polyvinylidene fluoride.

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