Electrochemical energy store and method for the production thereof

Abstract

The invention relates to an electrochemical energy store (1), containing a cell assembly (10) having at least two electrochemical cells (11, 12) each of which has a positive pole (111, 121) and a negative pole (112, 122); a first cell connector (21) to which the positive poles (111, 121) of the electrochemical cells (11, 12) are integrally bonded such that at least one connection point (3) is formed; and a second cell connector (22) to which the negative poles (112, 122) of the electrochemical cells (11, 12) are integrally bonded such that at least one connection point (3) is formed, wherein a contact surface of the integrally bonded connection points (3) increases as the internal resistance of the respective electrochemical cell (11, 12) and / or a line resistance of the first cell connector (21) and / or a line resistance of the second cell connector (22) increases. The invention also relates to a method for producing such an electrochemical energy store (1).

Description

[0001]FRIESE GOEDEN Patent Attorneys PartGmbB Widenmayerstraße 49 80538 Munich Our reference: 31998 PWO GO Applicant: Fraunhofer-Gesellschaft eV ───────────────────────────────────────────────────────────────── Electrochemical energy storage and process for its production The invention relates to an electrochemical energy storage device comprising a cell arrangement with at least two electrochemical cells, each having a positive pole and a negative pole, and with a first cell connector to which the positive poles of the electrochemical cells are metallurgically connected, as well as with a second Cell connector, with which the negative poles of the electrochemical cells are metallurgically connected.Electrochemical energy storage systems with parallel-connected electrochemical cells serve to provide a higher output current and capacity than a single electrochemical cell can deliver. Electrochemical cells connected in parallel age faster than single cells because some cells charge or discharge more extensively under electrical load, and the charge is balanced by the other cells. This results in balancing currents between the electrochemical cells. Consequently, inhomogeneities remain in the discharge and charge behavior, causing some cells to be subjected to greater stress. These inhomogeneities are caused, on the one hand, by differences in the internal resistance of the electrochemical cells, resulting from manufacturing tolerances. Furthermore, varying temperatures within the cell array can influence the internal resistance.Finally, contact resistances at the joints and the conductor resistance of the cell connectors can cause inhomogeneities in the discharge and charging behavior. US Patent 2010 / 0092854 A1 discloses a solution to this problem: the cell connectors are designed with variable conductor cross-sections. Electrochemical cells with lower internal resistance are connected in sections of the cell connector with higher electrical resistance, while electrochemical cells with higher internal resistance are connected in sections of the cell connector with lower conductor resistance. As a result, the sum of the internal resistance of the electrochemical cells and the respective electrical resistance of the cell connectors is approximately constant, ensuring that the individual cells are subjected to similar charging and discharging currents.This known battery has the disadvantage that the cell connectors either have to be manufactured individually for each battery or the adaptation to the individual internal resistances of the electrochemical cells is insufficient. Based on the prior art, the invention is therefore based on the objective of reducing the aging of the electrochemical cells in a cell arrangement of an electrochemical energy storage device. The following description describes, inter alia, an energy storage device according to claim 1, an energy storage device according to claim 2, a method according to claim 14, and a method according to claim 15. Potentially advantageous embodiments are found in the dependent claims. According to one aspect, an electrochemical energy storage device is disclosed. The electrochemical energy storage device can be configured and intended to provide electrical energy.The electrochemical energy storage device can be used in a stationary manner, for example, to supply one or more buildings with electrical energy. In other embodiments of the invention, the electrochemical energy storage device can be part of a vehicle or a ship and serve, for example, as a traction battery. In yet other embodiments of the invention, the electrochemical energy storage device can be part of an electrical device, in particular a power tool. The electrochemical energy storage device can contain a cell arrangement of at least two electrochemical cells. In some embodiments of the invention, the cell arrangement can contain between approximately 4 and approximately 40 electrochemical cells. In yet other embodiments of the invention, the cell arrangement can contain between approximately 40 and approximately 90 electrochemical cells.In other embodiments of the invention, the cell arrangement can contain between approximately 80 and approximately 110 electrochemical cells. In yet other embodiments of the invention, the cell arrangement can contain between approximately 4 and approximately 10 electrochemical cells. In some embodiments of the invention, at least two electrochemical cells are connected in parallel. By connecting them in parallel, the output current and / or the capacity of the electrochemical energy storage device can be increased. For this purpose, the electrochemical energy storage device can contain at least one first cell connector to which the positive terminals of the electrochemical cells are metallurgically connected. Furthermore, the electrochemical energy storage device can contain a second cell connector to which the negative terminals of the electrochemical cells are metallurgically connected.Both the first and second cell connectors can be made of a metal or an alloy. In some embodiments of the invention, the first and / or second cell connector can contain or consist of copper and / or aluminum and / or silver. The first and / or second cell connector can be homogeneous or be wholly or partially coated with a material that reduces contact resistance and / or provides corrosion protection. In some embodiments of the invention, the electrochemical cells can be connected in series to increase the output voltage of the electrochemical energy storage device. In some embodiments of the invention, several strings of parallel-connected electrochemical cells can be connected in series.In some embodiments of the invention, the positive terminals and / or the negative terminals of the electrochemical cells can be connected to the respective cell connector in such a way that at least one metallurgical connection is formed. This metallurgical connection can be established, for example, by soldering, welding, or gluing. The two parts are thus connected at the connection point by fusion and / or by intermolecular or chemical bonding forces, optionally via additives. The contact resistance between the respective terminal of the electrochemical cell and the respective cell connector results from the contact area of ​​the metallurgical connection. Larger contact areas lead to lower contact resistance, and smaller contact areas lead to higher contact resistance.In some embodiments of the invention, the contact resistance of the metallurgical joint can be influenced by selectively controlling the microstructure and the (intermetallic) phases through the selection of welding parameters and / or by combining welding processes. In this way, the current flow through a plurality of parallel electrochemical cells can be homogenized, so that cell aging proceeds uniformly and the lifetime of the electrochemical energy storage device can be extended. In some embodiments of the invention, ultrasound-assisted laser welding can be used. In some embodiments of the invention, the contact area of ​​the metallurgical joints can be larger the higher the internal resistance of the respective electrochemical cell.Conversely, the contact area of ​​the metallurgical connections is chosen to be smaller the lower the internal resistance of the respective electrochemical cell. Thus, electrochemical cells with low internal resistance are connected to the cell connectors with a higher contact resistance, and electrochemical cells with comparatively high internal resistance are connected to the cell connectors with a lower contact resistance. In this way, the current flow through a plurality of parallel electrochemical cells can be homogenized, so that cell aging proceeds uniformly and the service life of the electrochemical energy storage system can be extended.In some embodiments of the invention, the contact area of ​​the metallurgical connections can be larger the higher the conductivity of the first cell connector and / or the conductivity of the second cell connector of the respective electrochemical cell. Conversely, the contact area of ​​the metallurgical connections is chosen to be smaller the lower the conductivity of the first cell connector and / or the conductivity of the second cell connector of the respective electrochemical cell. Thus, electrochemical cells with low conductivity within the cell arrangement are connected to the cell connectors with a higher contact resistance, and electrochemical cells with comparatively high conductivity within the cell arrangement are connected to the cell connectors with a lower contact resistance.In this way, the current flow through a plurality of parallel electrochemical cells can be homogenized, so that cell aging proceeds uniformly and the service life of the electrochemical energy storage device can be extended. In some embodiments of the invention, the first cell connectors are connected to the positive terminals of the electrochemical cells in such a way that all connection points have the same or approximately the same contact area. In this case, the contact area of ​​the metallurgical connection points between the second cell connector and the negative terminals of the electrochemical cells varies depending on the internal resistance and / or the conduction resistance of the first cell connector and / or the conduction resistance of the second cell connector of the respective electrochemical cell.In other embodiments of the invention, the second cell connectors are connected to the negative terminals of the electrochemical cells such that all connection points have the same or approximately the same contact area. In this case, the contact area of ​​the metallurgical connection points between the first cell connector and the positive terminals of the electrochemical cells varies depending on the internal resistance and / or the conduction resistance of the first cell connector and / or the conduction resistance of the second cell connector of the respective electrochemical cell.In other embodiments of the invention, the first cell connectors are connected to the positive terminals of the electrochemical cells such that the contact area of ​​the metallurgical connection points between the second cell connector and the negative terminals of the electrochemical cells varies depending on the internal resistance and / or the conduction resistance of the first cell connector and / or the conduction resistance of the second cell connector of the respective electrochemical cell. Furthermore, the contact area of ​​the metallurgical connection points between the second cell connector and the negative terminals of the electrochemical cells varies depending on the internal resistance and / or the conduction resistance of the first cell connector and / or the conduction resistance of the second cell connector of the respective electrochemical cell.In some embodiments of the invention, the first cell connector and the positive terminals of the electrochemical cells can be connected via at least one solder lug. In some embodiments of the invention, the second cell connector and the negative terminals of the electrochemical cells can be connected via at least one solder lug. In yet other embodiments of the invention, both the positive and negative terminals can be connected to the respective cell connectors via their respective solder lugs. The conductor cross-section of the solder lugs can be larger the higher the internal resistance of the respective electrochemical cell. Conversely, the conductor cross-section of the solder lugs is chosen to be smaller the lower the internal resistance of the respective electrochemical cell.Thus, electrochemical cells with low internal resistance are connected to the cell connectors with a higher contact resistance, and electrochemical cells with comparatively high internal resistance are connected to the cell connectors with a lower contact resistance. In this way, the current flow through a multiple of parallel electrochemical cells can be homogenized, resulting in uniform cell aging and extending the lifespan of the electrochemical energy storage device. Despite being called a "solder tab," the connecting element between the respective electrochemical cell and the cell connector can also be made by welding or bonding, for example, spot welding, press contacting, resistance spot welding, resistance projection welding, laser welding, or friction welding.Notwithstanding the designation as a "solder lug," the connecting element between the respective electrochemical cell and the cell connector can also be at least one bond wire. For the sake of readability, the term "solder lug" is used in the following description and in the claims; this is intended to always include the aforementioned alternatives. In some embodiments of the invention, the conductor cross-section of the solder lugs can be adapted to the internal resistance of the respective electrochemical cell by adjusting the number of solder lugs and / or their width and / or thickness. This allows for simple manufacturing, since an identical joining process can always be carried out, and only a suitable solder lug needs to be selected or the number adjusted depending on the internal resistance.In some embodiments of the invention, the electrochemical cell can be selected from at least one fuel cell and / or at least one primary cell and / or at least one secondary cell. In some embodiments of the invention, a secondary cell can be selected from a lithium iron phosphate cell, a lithium ceramic cell, a lithium polymer cell, a nickel manganese cobalt cell, a metal sulfur cell, a sodium ion cell, a metal air cell, and / or a redox flow cell. These electrochemical cells are typically used for high storage capacities and / or high currents and / or high output voltages, such that inhomogeneities lead to accelerated aging of individual cells, resulting in a significant reduction in the overall lifespan of the energy storage system. Such energy storage systems therefore particularly benefit from the proposed adjustment of the contact resistances.In some embodiments of the invention, the contact area of ​​the material-bonded connections can be increased by providing a plurality of material-bonded connections. In some embodiments of the invention, the plurality of material-bonded connections can be between 1 and approximately 12. In other embodiments of the invention, the plurality of material-bonded connections can be between 2 and approximately 10. In still other embodiments of the invention, the plurality of material-bonded connections can be between 1 and 6. Thus, by repeatedly applying a single tool, the contact resistance of the respective electrochemical cell to the cell connector can be quickly and easily adjusted.In some embodiments of the invention, the contact area of ​​the material-bonded joints can be increased by having one material-bonded joint have a greater length and / or width than another material-bonded joint. For example, round joints can have a larger radius or diameter. Elongated joints, which are produced, for example, by laser welding, can be designed with a larger or smaller longitudinal extent while maintaining a constant width, so that the contact resistance can be easily adapted to the internal resistance of the respective cell. In some embodiments of the invention, at least one material-bonded joint can be produced by soldering.In other embodiments of the invention, at least one material-bonded connection can be produced by resistance projection welding, laser welding, and / or resistance spot welding. Resistance projection welding is understood to be a welding process according to EN ISO 4063, item 23. In yet other embodiments of the invention, at least one material-bonded connection can be produced by press contacting. This avoids impermissible heat input into the electrochemical cells. In some embodiments of the invention, direct contact can be established between the respective positive or negative terminal and the first or second cell connector. Thus, no further components are arranged between the respective terminal of the electrochemical cell and the respective cell connector. This avoids additional contact points and increases operational reliability.In other embodiments of the invention, a solder lug can be arranged between the respective pole of the electrochemical cell and the first and / or second cell connector. The solder lug can absorb vibrations and / or thermal expansion, thus increasing operational reliability. Notwithstanding the designation as a "solder lug," a connection between the electrochemical cell and the solder lug, or between the solder lug and the cell connector, can also be made by welding, gluing, or press-fitting. In some embodiments of the invention, the angle between the solder lug and the respective cell connector can be selected according to the internal resistance of the electrochemical cell and / or the contact area of ​​the metallurgical connection points. This results in a longer or shorter current path on the respective cell connector.The length of the current path influences the electrical resistance between the electrochemical cell and a terminal of the electrochemical energy storage device. Therefore, the length of the current path, or the angle between the solder lug and the respective cell connector, can either be used solely to influence the contact resistance or, as a further parameter, to allow for fine-tuning of the contact resistance after an optimized contact area of ​​the metallurgical connection points has been selected for each electrochemical cell. In some embodiments of the invention, a metallurgical connection point can have a contact resistance ranging from approximately 50 µΩ to approximately 400 µΩ.If the contact area of ​​the metallurgical connections is influenced by their number, the stated value is to be understood as the sum of the contact resistances of all connections of a positive or negative terminal of an electrochemical cell. This range of values ​​allows for a high degree of homogenization of the resistances of the parallel-connected cells and thus a homogenization of the current load. In some embodiments of the invention, the contact area of ​​the metallurgical connections can range from approximately 0.5 mm² to approximately 1 cm². This enables rapid manufacturing and allows the contact resistance to be adjusted within a wide range of values. According to another aspect, a method for manufacturing an electrochemical energy storage device is disclosed. For this purpose, at least two electrochemical cells are initially provided, each having a positive terminal and a negative terminal.At least two electrochemical cells are connected in parallel. For this purpose, at least one first cell connector and at least one second cell connector are used. The method further comprises the step of connecting the positive terminals of the electrochemical cells to a first cell connector, forming at least one connection point. Furthermore, the negative terminals of the electrochemical cells are connected to a second cell connector, forming at least one connection point. In some embodiments of the invention, the internal resistance of each electrochemical cell can also be determined. This can be done before the positive and negative terminals are connected to the first and second cell connectors. The contact area of ​​the connection points can then be made larger the higher the internal resistance of the respective electrochemical cell.Conversely, this means that the contact area of ​​the metallurgical connections is made smaller the lower the internal resistance of the respective electrochemical cell. In some embodiments, this can apply both to the contact points between the respective positive terminals and the first cell connector, and to the respective contact points between the negative terminals and the second cell connector. In other embodiments of the invention, contact points at one terminal of the electrochemical cells can also be made with the same or approximately the same area, with the contact points at the other terminal being varied in size to match the internal resistances.In some embodiments of the invention, the contact surfaces of the metal-bonded connections can be selected such that, for each electrochemical cell, the sum of its internal resistance, the resistance of the metal-bonded connections, and the resistance of the first and second cell connectors is constant. In other embodiments of the invention, the contact surfaces of the metal-bonded connections can be selected such that, for each electrochemical cell, the sum of its internal resistance, the resistance of the metal-bonded connections, and the resistance of the first and second cell connectors lies within predefinable tolerances. These tolerances can be, for example, less than approximately ±40 µΩ, less than approximately ±20 µΩ, or less than approximately ±5 µΩ.Even if the internal resistance of the electrochemical cells is constant, in some embodiments of the invention the contact areas and / or the number of metal-bonded connections can vary depending on the installation position of the respective electrochemical cell within the energy storage device in order to compensate for the increasing electrical resistance of the first and second cell connectors with increasing distance. Electrochemical cells located further away from a terminal of the cell assembly can then have larger contact areas and / or a greater number of metal-bonded connections, and electrochemical cells located closer to a terminal of the cell assembly can have smaller contact areas and / or a fewer number of metal-bonded connections.In some embodiments of the invention, the internal resistance of each electrochemical cell can be determined taking into account its eventual installation position. For example, cells located at the center of an electrochemical energy storage device can reach a higher operating temperature. In other embodiments, battery cells located at a greater distance from a cooling system or heat exchanger can reach a higher operating temperature. A higher operating temperature can lead to a lower internal resistance. Thus, not only can production tolerances be determined, but also changes in internal resistance due to the eventual operating temperature of the electrochemical cells. In some embodiments of the invention, the internal resistance of each electrochemical cell can be determined taking into account its individual operating temperature. The operating temperature can be measured on a prototype or determined through simulation calculations.The invention will now be explained in more detail with reference to the figures, without limiting the general concept of the invention. Figure 1 shows a top view of an electrochemical energy storage device according to a first embodiment of the invention. Figure 2 shows a top view of an electrochemical energy storage device according to a second embodiment of the invention. Figure 3a shows a top view and a side view of an electrochemical energy storage device according to a third embodiment of the prior art. Figure 3b shows a top view and a side view of an electrochemical energy storage device in a third embodiment of the invention. Figure 4 shows a top view of an electrochemical energy storage device according to a fourth embodiment of the invention. Figure 5 shows a top view of an electrochemical energy storage device according to a fifth embodiment of the invention.Figure 6 shows a top view of an electrochemical energy storage device according to a sixth embodiment of the invention. Figure 7 shows a top view of an electrochemical energy storage device according to a seventh embodiment of the invention. A first embodiment of an electrochemical energy storage device is explained in more detail with reference to Figure 1. The electrochemical energy storage device contains a cell arrangement 10 with at least two electrochemical cells. In the illustrated embodiment, six electrochemical cells 11, 12, 13, 14, 15, and 16 are shown. However, the invention does not teach the use of exactly six electrochemical cells as the solution principle. Rather, the number can be greater or lesser in different embodiments of the invention. In the illustrated embodiment, the electrochemical cells 11, 12, 13, 14, 15, and 16 are designed as cylindrical cells with a cylindrical base shape.The two opposing base surfaces of the cylindrical cells can be used as the positive and negative poles. In the top view shown in Figure 1, the positive poles 111, 121, 131, 141, 151, and 161 are visible. The opposite negative poles are obscured by the respective electrochemical cells in Figure 1 and are therefore not visible. The electrochemical cells 11, 12, 13, 14, 15, and 16 are connected in parallel in the electrochemical energy storage device 1 to increase the output current of the electrochemical energy storage device. For this purpose, the positive poles 111, 121, 131, 141, 151, and 161 are connected by a first cell connector 21. The negative poles of the electrochemical cells are accordingly connected by a second cell connector 22. The first and second cell connectors 21 and 22 contain a metallic material capable of conducting electricity. This metallic material can be selected from a metal or an alloy.The metallic material can, for example, contain or consist of copper and / or aluminum and / or silver. The first and second cell connectors 21 and 22 can have a homogeneous structure or a multilayer structure. In particular, the cell connectors 21 and 22 can be coated. A coating can contain or consist of a metal, an alloy, a polymer, or a ceramic. In the illustrated embodiment, the first and second cell connectors 21 and 22 have a substantially rectangular base shape. In other embodiments of the invention, the shape of the cell connectors can also have a different geometry. As can be seen from Figure 1, at least the first cell connector 21 has a plurality of recesses that accommodate the housings of the electrochemical cells, so that the positive terminals can be connected to the top surface of the cell connector 21 via associated solder lugs 4.The first cell connector 21 has a connection area 210. The second cell connector 22 has a connection area 220. Connection areas 210 and 220 form the connection contacts of the cell arrangement 10. If only one cell arrangement 10 is present in the electrochemical energy storage device 1, connection areas 210 and 220 also form the connection contacts of the electrochemical energy storage device; that is, a charging and / or discharging current is supplied to or discharged from the electrochemical energy storage device and thus to the cell arrangement 10 via connection areas 210 and 220. This means that the current supplied by the first electrochemical energy storage device 11 and the fourth electrochemical energy storage device 14 has to travel a longer path on the first cell connector 21 before it reaches connection area 210.The electrical resistance of the first cell connector 21 is therefore greater for the first and fourth electrochemical energy storage devices 11 and 14 than for the adjacent second and fifth electrochemical energy storage devices 12 and 15. The electrical path, and thus the electrical resistance, is further reduced for the third and sixth electrochemical energy storage devices 13 and 16. Furthermore, the electrochemical energy storage devices may exhibit different internal resistances due to manufacturing tolerances. Finally, the second and fifth electrochemical energy storage devices 12 and 15, due to their central installation position, may have poorer heat dissipation and thus a higher operating temperature than the outer electrochemical energy storage devices 11, 13, 14, and 16. This higher operating temperature may also lead to a lower internal resistance for the second and fifth electrochemical energy storage devices 12 and 15.All the aforementioned effects result in the parallel-connected electrochemical cells not being subjected to a uniform load from the charging and discharging current. This leads to equalizing currents, which affect the service life of the individual electrochemical cells; that is, the electrochemical cells in the cell arrangement age differently. As can be further seen in Figure 1, the electrochemical cells are each connected to the first cell connector 21 by means of an optional solder lug 4. Regardless of their designation, the solder lugs can be connected to the first cell connector 21 on the one hand and to the respective positive terminal of the electrochemical cells on the other hand not only by soldering, but also by welding or gluing. It should be noted that the solder lugs 4 are optional. In other embodiments of the invention, the positive terminals of the electrochemical cells can also be connected directly to the first cell connector 21.Figure 1 further illustrates that the connection between the respective positive terminal of the electrochemical cells and the first cell connector 21 or the optional solder lug 4 is material-bonded. A material-bonded connection is understood to be a connection in which parts are joined to one another by fusion and by intermolecular or chemical bonding forces, optionally via additives. Solders or adhesives are particularly suitable as additives. In some embodiments of the invention, the material-bonded connection can be achieved by resistance welding, in particular by resistance projection welding according to item 23 of EN ISO 4063. Figure 1 shows that the material-bonded connection points 3 are each designed as point welds and each form a contact surface between the joined parts.The solder lugs 4 of the third and sixth electrochemical cells are connected by two weld points, the solder lugs 4 of the second and fifth electrochemical cells 12 and 15 are each connected by four weld points, and the solder lugs 4 of the first and fourth electrochemical cells 11 and 14 are each connected by six weld points. Thus, the contact area of ​​the metallurgical connections is larger the higher the internal resistance or the conduction resistance caused by the length of the first cell connector 21. The size of the contact area, and therefore the number of spot welds, can be chosen such that for each electrochemical cell the sum of its internal resistance, the contact resistance of the metallurgical connections 3, and the resistance of the first and second cell connectors 21 and 22 is constant or lies within predefinable tolerances. This ensures that, during charging or discharging,The discharge homogenizes the current load of the individual electrochemical cells, so that they exhibit the same aging behavior. An electrochemical energy storage device according to a second embodiment is explained in more detail with reference to Figure 2. Identical components of the invention are designated with the same reference numerals, so that the following description is limited to the essential differences. As can be seen from Figure 2, the connection points 3 are again designed such that the contact area of ​​the materially bonded connection points is larger the higher the internal resistance or the resistance of the first and second cell connectors 21 and 22 for the respective electrochemical cell. In the embodiment shown in Figure 2, the increase in the contact area was achieved by using welds or weld points with a larger radius or diameter.This increases the contact area, thus reducing the contact resistance. Therefore, by adjusting the diameter or radius of the weld points, it is also possible to homogenize the current flow within the cell arrangement 10. This can also be done analogously for weld points that are not round, but, for example, polygonal. A third embodiment of the invention is explained in more detail with reference to Figure 3. Identical components of the invention are again designated with the same reference numerals. Figure 3a shows an electrochemical energy storage device according to the prior art. Figure 3b shows an electrochemical energy storage device according to the present invention. The lower part of each figure shows a view, and the upper part a top view. As Figure 3 shows, the electrochemical cells 11, 12, 13, and 14 are prismatic cells, i.e., they essentially have the basic shape of a cuboid.The positive terminals 111, 121, 131, and 141, on the one hand, and the negative terminals 112, 122, 132, and 142, on the other, are arranged at opposite points on one side of the housing of the prismatic electrochemical cells. As shown in Figure 3, two electrochemical cells are connected in parallel to increase the current of the electrochemical energy storage device. Furthermore, two parallel-connected electrochemical cells are connected in series to increase the voltage of the electrochemical energy storage device 1. Three cell connectors are thus used. The first cell connector 21 connects the two positive terminals 111 and 121 of the first electrochemical cell 11 and the second electrochemical cell 12. The second cell connector 22 connects the negative terminals 132 and 142 of the third and fourth electrochemical cells 13 and 14.The third cell connector 23 connects the negative terminals 112 and 122 of the first and second electrochemical cells 11 and 12, and the positive terminals 131 and 141 of the third and fourth electrochemical cells 13 and 14. The connection is again made by metallurgical bonding via connection points 3, which can be produced, for example, by soldering, gluing, or welding. As Figure 3a shows, according to the prior art, essentially identical connection points 3 with identical contact areas and thus also identical contact resistances are present. Figure 3b shows the solution according to the invention, in which the contact area of ​​the metallurgical connection points 3 is larger the higher the internal resistance of the respective electrochemical cell. Thus, connection points 3a with a large contact area are present, and connection points 3b with a smaller contact area. The connection points 3a and 3b according to Figure 3 are produced by laser welding.The contact area of ​​the connection points thus has a width defined by the diameter of the laser beam and a length defined in the feed direction of the laser beam. To increase the contact area, the laser beam can therefore be switched on for a longer time at a constant feed rate, resulting in a longer connection point 3a with a correspondingly larger contact area. As the lower part of Figure 3b shows, an optional fourth cell connector 24 can also be used, which connects the two outer electrochemical cells 11 and 14 via the connection points 3a. In this way, the coldest electrochemical cells with the highest internal resistance can also be connected to each other with low resistance, thus further homogenizing the current distribution within the cell arrangement 10.It is of course common knowledge to those skilled in the art that the fourth cell connector 24 can optionally also be used in combination with the cylindrical cells shown in Figure 1 or Figure 2. Likewise, the laser welding process explained with reference to Figure 3 can also be used for contacting cylindrical cells. Those skilled in the art are free to combine the described embodiments to obtain further embodiments not explicitly shown in the drawings. The connection of two pouch cells is explained in more detail with reference to Figure 4. The pouch cells according to Figure 4 are also connected such that two parallel-connected cells are connected in series with each other in order to increase both the current and the voltage of the electrochemical energy storage device.As already explained with reference to Figure 1, the increase in the contact area in the fourth embodiment is achieved by increasing the number of material-bonded connections as the internal resistance of the respective electrochemical cell increases. In the illustrated embodiment, the inner electrochemical cells 12 and 13 have a higher temperature because they are located further away from an externally flowing cooling medium. The higher temperature results in a lower internal resistance, which is compensated for by a smaller number of connections 3 at the negative terminal 122 and the positive terminal 131. A fifth embodiment of the present invention is explained in more detail with reference to Figure 5. Identical components of the invention are designated with the same reference numerals, so the following description is limited to the essential differences.As can be seen in Figure 5, the angle between the solder lug 4 and the longitudinal extension of the cell connector 21 is selected differently for each installation position of the electrochemical cells. This feature has the effect of increasing the length of the current path when the solder lug 4 is rotated away from the connection area 210. Conversely, the current path, and thus the electrical resistance of the cell connector 21, is shortened when the solder lug points towards the connection area 210. In this way, the electrical resistance can be adjusted by selecting the angle between the solder lug 4 and the longitudinal extension of the cell connector 21, leading to a homogenization of the current load on the electrochemical cells. In some embodiments of the invention, this can be the sole measure for homogenizing the current load.In other embodiments of the invention, the contact area of ​​the material-bonded connection points can additionally be varied, as described above. With reference to Figure 6, a sixth embodiment of an electrochemical energy storage device is explained. Identical components of the invention are designated with the same reference numerals, so that the description is limited to the essential differences. The electrochemical energy storage device comprises a cell arrangement 10 with at least two electrochemical cells. In the illustrated embodiment, six electrochemical cells 11, 12, 13, 14, 15, and 16 are shown. However, the invention does not teach the use of exactly six electrochemical cells as the solution principle. Rather, the number can be greater or lesser in different embodiments of the invention.In the illustrated embodiment, the electrochemical cells 11, 12, 13, 14, 15, and 16 are designed as cylindrical cells with a cylindrical base shape. The two opposite base surfaces of the cylindrical cells can be used as the positive and negative terminals. In the top view shown in Figure 6, the positive terminals 111, 121, 131, 141, 151, and 161 are visible. The opposite negative terminals are obscured by the respective electrochemical cells in Figure 1 and are therefore not visible. The electrochemical cells 11, 12, 13, 14, 15, and 16 are connected in parallel in the electrochemical energy storage device 1 in order to increase the output current and the capacity of the electrochemical energy storage device. For this purpose, the positive poles 111, 121, 131, 141, 151 and 161 are connected to a first cell connector 21.The negative terminals of the electrochemical cells are accordingly connected to a second cell connector, which is concealed in Figure 6 and therefore not visible. The first cell connector 21 contains a metallic material capable of conducting electricity. The metallic material can be selected from a metal or an alloy. The metallic material can, for example, contain or consist of copper and / or aluminum and / or silver. The first cell connector 21 can have a homogeneous structure or a multilayer structure. In particular, the cell connector 21 can be coated. A coating can contain or consist of a metal, an alloy, a polymer, a ceramic, or carbon. In the illustrated embodiment, the first cell connector 21 has a substantially rectangular base shape, to which a connection area 210 of a smaller width is attached.As can be seen in Figure 6, at least the first cell connector 21 has a plurality of recesses that accommodate the housings of the electrochemical cells, so that the positive terminals can be connected to the top of the cell connector 21 via associated solder lugs 4. The conductor cross-section of the solder lugs 4 is larger the higher the internal resistance or the electrical resistance of the cell connector 21 of the respective electrochemical cell (11, 12, 13, 14, 15, 16). In the illustrated embodiment, the conductor cross-section of the solder lugs 4 is varied by adjusting the width while maintaining a constant thickness. Alternatively or additionally, the thickness of the solder lugs 4 can also be varied, or only the thickness can be varied.To simplify assembly, an identical joining process can be carried out between the respective positive terminals 111, 121, 131, 141, 151, and 161 of the electrochemical cells 11, 12, 13, 14, 15, and 16 and the solder lugs, so that the resistance is adjusted solely by the conductor cross-section of the solder lugs 4. Alternatively, the contact area of ​​the joining points can also be adjusted as a further parameter for optimization, as explained above in conjunction with Figures 1, 2, and 3. With reference to Figure 7, a seventh embodiment of an electrochemical energy storage device is described. Identical components of the invention are designated with the same reference numerals, so that the description is limited to the essential differences. In the seventh embodiment, single-ended cylindrical cells are used, in which the positive and negative terminals are arranged on the same end face of the cylindrical cell.In the illustrated embodiment, the positive poles 111, 121, 131, 141, 151, and 161 and the negative poles 112, 122, 132, 142, 152, and 162 are arranged concentrically. The linear cell arrangement 10 has at least one first and one second cell connector 21 and 22, which are arranged on opposite sides of the linear cell arrangement 10 in Fig. 7. The positive poles 111, 121, 131, 141, 151, and 161 are connected to the first cell connector 21. The negative poles of the electrochemical cells are accordingly connected to the second cell connector 22. Solder lugs 4 are used for this purpose, which in the illustrated embodiment have identical width and thickness. In the illustrated embodiment, the conductor cross-section of the solder lugs 4 is varied by adjusting the number of parallel solder lugs 4 used.In the illustrated embodiment, one solder lug 4 is used for a high-resistance connection and three solder lugs 4 for a low-resistance connection. In other embodiments of the invention, the number of solder lugs 4 can also be greater or lesser and may range from approximately 2 to approximately 8 or from 1 to approximately 5. Naturally, the invention is not limited to the illustrated embodiments. The preceding description is therefore not to be considered limiting, but rather explanatory. The following claims are to be understood as stating that a named feature is present in at least one embodiment of the invention. This does not preclude the presence of further features. The following claims are not to be understood as stating that a named feature must be present in every embodiment of the invention.Features described together may also individually contribute to the success of the invention and may be present in some embodiments on their own. Where the claims and the preceding description define "first" and "second" embodiments, this designation serves to distinguish between two similar embodiments without establishing a hierarchy. The preceding description is to be understood as meaning that the described first through seventh embodiments can be combined to obtain further embodiments of the invention.

Claims

Claims 1. Electrochemical energy storage device (1) comprising a cell arrangement (10) with at least two electrochemical cells (11, 12), each having a positive pole (111, 121) and a negative pole (112, 122), and a first cell connector (21) with which the positive poles (111, 121) of the electrochemical cells (11, 12) are metallurgically connected, such that at least one connection point (3) is formed, and a second cell connector (22) with which the negative poles (112, 122) of the electrochemical cells (11, 12) are metallurgically connected, such that at least one connection point (3) is formed, characterized in that the contact area of ​​the connection points (3) is larger the higher the internal resistance of the respective electrochemical cell (11, 12) and / or the conduction resistance of the first cell connector. (21) and / or a conduction resistance of the second cell connector (22). 2.Electrochemical energy storage device (1) comprising a cell arrangement (10) with at least two electrochemical cells (11, 12), each having a positive pole (111, 121) and a negative pole (112, 122), and a first cell connector (21) with which the positive poles (111, 121) of the electrochemical cells (11, 12) are connected via at least one solder lug (4), and a second cell connector (22) with which the negative poles (112, 122) of the electrochemical cells (11, 12) are connected via at least one solder lug (4), characterized in that a conductor cross-section of the solder lugs (4) is the larger. the higher the internal resistance of the respective electrochemical cell (11, 12) and / or the conduction resistance of the first cell connector (21) and / or the conduction resistance of the second cell connector (22).

3. Energy storage device according to claim 2, characterized in that the conductor cross-section of the solder lugs (4) is adapted to the internal resistance of the respective electrochemical cell (11, 12) by the number of solder lugs and / or their width and / or their thickness.

4. Energy storage device according to claim 1, characterized in that the respective pole (112, 122, 111, 121) of the electrochemical cells (11, 12) is connected to the first and / or second cell connector (21, 22) via at least one solder lug (4), which is metallurgically bonded to the respective pole (112, 122, 111, 121) of the electrochemical cells (11, 12) and / or to the first and / or second cell connector (21, 22), so that at least one connection point (3) is formed. 5.Energy storage device according to any one of claims 1 to 4, characterized in that the electrochemical cells (11, 12) are selected from at least one fuel cell and / or at least one primary cell and / or at least one secondary cell.

6. Energy storage device according to claim 5, characterized in that the secondary cell is selected from a lithium iron phosphate cell and / or a lithium ceramic cell and / or a lithium polymer cell and / or a nickel manganese cobalt cell and / or a metal sulfur cell and / or a sodium ion cell and / or a metal air cell and / or a redox flow cell.

7. Energy storage device according to any one of claims 1 to 6, characterized in that the contact surface of the materially bonded connection points (3) is thereby 8. Energy storage device according to claim 7, characterized in that the plurality of material-bonded connection points (3) is between 2 and about 12 or between about 3 and about 10.

9. Energy storage device according to any one of claims 1 to 8, characterized in that the contact area of ​​the material-bonded connection points (3) is increased in that one material-bonded connection point (3) has a greater length and / or width than another material-bonded connection point (3).

10. Energy storage device according to any one of claims 1 to 9, characterized in that the material-bonded connection points (3) are produced by soldering or resistance projection welding and / or laser welding and / or resistance spot welding and / or press contacting. 11.Energy storage device according to any one of claims 2 to 10, characterized in that the angle between the solder lug (4) and the respective cell connector (21, 22) is selected according to the internal resistance of the electrochemical cell (11, 12) and / or the contact area of ​​the metallurgical connections (3).

12. Energy storage device according to any one of claims 1 to 11, characterized in that the metallurgical connections (3) have a contact resistance of between approximately 50 µΩ and approximately 400 µΩ.

13. Energy storage device according to any one of claims 1 to 12, characterized in that the contact area of ​​the metallurgical connections (3) is between approximately 0.5 mm. 2 and about 1 cm 2 14. Method for producing an electrochemical energy storage device (1) comprising the following steps: Providing at least two electrochemical cells (11, 12), each having a positive terminal (111, 121) and a negative terminal (112, 122), and connecting the positive terminals (111, 121) of the electrochemical cells (11, 12) to a first cell connector (21) so that at least one connection point (3) is formed, and connecting the negative terminals (112, 122) of the electrochemical cells (11, 12) to a second cell connector (22) so that at least one connection point (3) is formed, characterized in that an internal resistance of each electrochemical cell (11, 12) is determined and a contact area of ​​the materially connected connection points (3) is made larger the higher the internal resistance of the respective electrochemical cell (11, 12) and / or a conduction resistance of the first cell connector (21) and / or a conduction resistance of the second cell connector (22). 15.Method for manufacturing an electrochemical energy storage device (1) comprising the following steps: providing at least two electrochemical cells (11, 12), each having a positive pole (111, 121) and a negative pole (112, 122), and connecting the positive poles (111, 121) of the electrochemical cells (11, 12) to a first cell connector (21) via at least one solder lug (4), and connecting the negative poles (112, 122) of the electrochemical cells (11, 12) to a second cell connector (22) via at least one solder lug (4), characterized in that an internal resistance of each electrochemical cell (11, 12) is determined and a conductor cross-section of the solder lugs (4) is chosen to be larger the higher the internal resistance of the respective electrochemical cell (11, 12) and / or a.

16. Method according to claim 15, characterized in that the conductor cross-section of the solder lugs (4) is adapted to the internal resistance of the respective electrochemical cell (11, 12) by the number of solder lugs and / or their width and / or their thickness.

17. Method according to claim 14, characterized in that the metallurgical connection points (3) have a contact resistance which is between about 50 µΩ and about 400 µΩ.

18. Method according to one of claims 14 or 17, characterized in that the contact area of ​​the metallurgical connection points (3) is between about 0.5 mm². 2 and about 1 cm 219. A method according to claim 14 or any one of claims 17 to 18, characterized in that the metallurgical joints (3) are produced by soldering or resistance projection welding and / or laser welding and / or resistance spot welding and / or press contacting.

20. A method according to any one of claims 14 to 19, characterized in that the contact area of ​​the metallurgical joints (3) and / or the conductor cross-section of the solder lugs (4) is selected such that for each electrochemical cell (11, 12) the sum of its internal resistance, the resistance of the metallurgical joints (3) and the resistance of the first and second cell connectors (21, 22) is constant or lies within predefinable tolerances.

21. A method according to any one of claims 14 to 20, characterized in that the internal resistance of each electrochemical cell is selected in such a way that the internal resistance of each electrochemical cell (11, 12) is determined by the number of cells in the cell (3) and the number of cells in the cell (3) is determined by the number of cells in the cell (3) and the number of cells in the cell (4) is determined by the number of cells in the cell (11, 12 ... mixing cell (11, 12) is determined taking into account the later installation position and / or the individual operating temperature.

Images