Electrochemical energy storage and methods for its production

Abstract

Electrochemical energy storage device (1), containing 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, so 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 connected by a material bond, so that at least one connection point (3) is formed, characterized by the fact that The contact area of ​​the materially bonded connection points (3) is larger the higher the internal resistance of the respective electrochemical cell (11, 12) is.

Description

[0001] The invention relates to an electrochemical energy storage device comprising a cell arrangement with at least two electrochemical cells, each having a positive and a negative pole, and with a first cell connector by which the positive poles of the electrochemical cells are metallurgically connected, and with a second cell connector by which the negative poles of the electrochemical cells are metallurgically connected. Such electrochemical energy storage devices with parallel-connected electrochemical cells serve to provide a higher output current and a higher capacity than a single electrochemical cell can supply.

[0002] Electrochemical cells connected in parallel age faster than individual cells because some cells charge or discharge more extensively under electrical load, and the charge is balanced by the other cells. This results in equalizing currents between the electrochemical cells. Consequently, inhomogeneities remain in the discharge and charging behavior, causing some cells to be subjected to greater stress. These inhomogeneities are caused, firstly, by differences in the internal resistance of the electrochemical cells, resulting from manufacturing tolerances. Secondly, varying temperatures within the cell array can affect the internal resistance. Finally, contact resistances at the connection points and the conductor resistance of the cell connectors can also cause inhomogeneities in discharge and charging behavior.

[0003] US Patent 2010 / 0092854 A1 discloses a solution to this problem by using cell connectors with variable conductor cross-sections. Electrochemical cells with lower internal resistance are connected in sections of the cell connector with higher electrical resistance. 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, so that the individual cells are subjected to similar charging or discharging currents.

[0004] 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 therefore aims to reduce the aging of the electrochemical cells in a cell arrangement of an electrochemical energy storage device.

[0005] A cell connector is known from DE 10 2019 128 492 A1. The cell connector has several contact areas, each of which can be used to connect a cell terminal of a cell terminal group. Furthermore, the cell connector has connecting areas that link adjacent contact areas together. The cell connector is to be improved with regard to material consumption during its manufacture and / or with regard to its weight. To this end, it is proposed that the cross-sectional area of ​​the current conductor in one connecting area be smaller than the cross-sectional area of ​​another connecting area.

[0006] EP 2 416 405 A1 discloses a battery module that achieves improved performance, system reliability, and system safety. The battery module is designed such that the fusible links associated with a single battery are the last connection to melt in the event of a short circuit.

[0007] The following description includes, among others, an energy storage device according to claim 1, an energy storage device according to claim 2, a method according to claim 16, and a method according to claim 17. Potentially advantageous embodiments are found in the dependent claims.

[0008] According to one aspect of the invention, an electrochemical energy storage device is disclosed. The electrochemical energy storage device can be configured and designed 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 appliance, in particular a power tool.

[0009] 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 about 4 and about 40 electrochemical cells. In other embodiments of the invention, the cell arrangement can contain between about 40 and about 90 electrochemical cells. In still other embodiments of the invention, the cell arrangement can contain between about 80 and about 110 electrochemical cells. In yet other embodiments of the invention, the cell arrangement can contain between about 4 and about 10 electrochemical cells.

[0010] In some embodiments of the invention, at least two electrochemical cells are connected in parallel. This parallel connection allows for an increase in the output current and / or capacity of the electrochemical energy storage device. For this purpose, the electrochemical energy storage device can include 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 include a second cell connector, to which the negative terminals of the electrochemical cells are metallurgically connected. Both the first and the second cell connector 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 homogeneously constructed or fully or partially coated, which can reduce the contact resistance and / or provide corrosion protection.

[0011] 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 again be connected in series.

[0012] 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 bond is formed. This metallurgical bond can be formed, for example, by soldering, welding, or gluing. The two parts are thus connected at the bond 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 bond. Larger contact areas lead to lower contact resistance, and smaller contact areas lead to higher contact resistance.

[0013] 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.

[0014] In some embodiments of the invention, the contact area of ​​the metallurgical connections 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 device can be extended.

[0015] In some embodiments of the invention, the first cell connectors are connected to the positive 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 bonded connection points between the second cell connector and the negative terminals of the electrochemical cells varies depending on the internal resistance 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 bonded connection points between the first cell connector and the positive terminals of the electrochemical cells varies depending on the internal resistance 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 bonded connections between the second cell connector and the negative terminals of the electrochemical cells varies depending on the internal resistance of the respective electrochemical cell. Furthermore, the contact area of ​​the bonded connections between the second cell connector and the negative terminals of the electrochemical cells varies depending on the internal resistance of the respective electrochemical cell.

[0016] 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.

[0017] In some embodiments of the invention, 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 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.

[0018] Notwithstanding the designation as 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 tab," 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 tab" is used in the following description and in the claims; this is intended to always include the aforementioned alternatives.

[0019] 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 simplified manufacturing, as an identical joining process can always be used, and depending on the internal resistance, only a suitable solder lug needs to be selected or the number adjusted.

[0020] In some embodiments of the invention, the electrochemical cell can be selected from 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, so inhomogeneities lead to accelerated aging of individual cells, significantly reducing the overall lifespan of the energy storage device. Such energy storage devices therefore particularly benefit from the proposed adjustment of the contact resistances.

[0021] 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.

[0022] 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.

[0023] In some embodiments of the invention, at least one metallurgical connection can be created by soldering. In other embodiments of the invention, at least one metallurgical connection can be created 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 metallurgical connection can be created by press contacting. This avoids an impermissible heat input into the electrochemical cells.

[0024] In some embodiments of the invention, direct contact can be made 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.

[0025] 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 expansions, 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.

[0026] 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 connections. 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 contact 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, enable fine-tuning of the contact resistance after an optimized contact area of ​​the metallurgical connections has been selected for each electrochemical cell.

[0027] In some embodiments of the invention, a metallurgical connection can have a contact resistance between approximately 50 µΩ and approximately 400 µΩ. If the contact area of ​​the metallurgical connections is influenced by their number, the aforementioned value is to be understood as the total contact resistance of all connections of a positive or negative terminal of an electrochemical cell. This range of values ​​enables a high degree of homogenization of the resistances of the parallel-connected cells and thus a homogenization of the current load.

[0028] In some embodiments of the invention, the contact area of ​​the material-bonded connection points can be between approximately 0.5 mm 2 and about 1 cm 2 This allows for rapid manufacturing and the adjustment of the contact resistance within a wide range of values.

[0029] According to another aspect, a method for manufacturing an electrochemical energy storage device is disclosed. For this purpose, at least two electrochemical cells are first provided, each having a positive 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.

[0030] The method further comprises the step of metallurgically connecting the positive terminals of the electrochemical cells to a first cell connector, thereby forming at least one connection point. Furthermore, the negative terminals of the electrochemical cells are connected to a second cell connector, thereby 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 metallurgically connecting the positive and negative terminals to the first and second cell connectors. The contact area of ​​the metallurgical 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 connection points 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 produced with the same or approximately the same area, with the contact points at the other terminal being varied in size to equalize the internal resistances.

[0031] In some embodiments of the invention, the contact surfaces of the metallurgical connections can be selected such that, for each electrochemical cell, the sum of its internal resistance, the resistance of the metallurgical connections, and the resistance of the first and second cell connectors is constant. In other embodiments of the invention, the contact surfaces of the metallurgical connections can be selected such that, for each electrochemical cell, the sum of its internal resistance, the resistance of the metallurgical 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.

[0032] 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 achieve a higher operating temperature. In other embodiments, battery cells located at a greater distance from a cooling system or heat exchanger can achieve a higher operating temperature. A higher operating temperature can lead to a lower internal resistance.

[0033] In some embodiments of the invention, the internal resistance of each electrochemical cell can be determined taking into account the individual operating temperature. The operating temperature can be measured on a prototype or determined in simulation calculations.

[0034] The invention will now be explained in more detail with reference to figures, without limiting the general concept of the invention. This will show Fig. 1 the supervision of an electrochemical energy storage device according to a first embodiment of the invention. Fig. Figure 2 shows a top view of an electrochemical energy storage device according to a second embodiment of the invention. Fig. Figure 3a shows a top view and top view of an electrochemical energy storage device according to a third embodiment in the prior art. Fig. Figure 3b shows a top view and top view of an electrochemical energy storage device in a third embodiment of the invention. Fig. Figure 4 shows a top view of an electrochemical energy storage device according to a fourth embodiment of the invention. Fig. Figure 5 shows a top view of an electrochemical energy storage device according to a fifth embodiment of the invention. Fig. Figure 6 shows a top view of an electrochemical energy storage device according to a sixth embodiment of the invention. Fig. Figure 7 shows a top view of an electrochemical energy storage device according to a seventh embodiment of the invention.

[0035] Based on the Fig. Section 1 describes a first embodiment of an electrochemical energy storage device in more detail. 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.

[0036] 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 poles. In the Fig. In the top view shown, the positive poles 111, 121, 131, 141, 151 and 161 are visible. The opposite negative poles are shown in Fig. 1 of the respective electrochemical cells are covered and therefore not visible.

[0037] 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 terminals 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 22.

[0038] 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. For example, the metallic material can 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.

[0039] In the illustrated embodiment, the first and second cell connectors 21 and 22 are designed with a substantially rectangular base shape. In other embodiments of the invention, the shape of the cell connectors can also have a different geometry. As shown in Fig. As can be seen in Figure 1, at least the first cell connector 21 has a plurality of recesses which accommodate the housings of the electrochemical cells, so that the positive poles can be connected to the top of the cell connector 21 via associated solder lugs 4 in a material-bonded manner.

[0040] 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 electrical resistance are further reduced for the third and sixth electrochemical energy storage devices 13 and 16.

[0041] 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 mounting 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 result in a lower internal resistance for the second and fifth electrochemical energy storage devices 12 and 15.

[0042] All of these 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 lifespan of the individual electrochemical cells; in other words, the electrochemical cells in the cell array age at different rates.

[0043] As from Fig. As can be seen further 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.

[0044] In Fig. 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 made by resistance welding, in particular by resistance projection welding according to item 23 of EN ISO 4063.

[0045] In Fig. Figure 1 shows that the metallurgical connection points 3 are each designed as point connections and each form a contact area 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 connection points 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 thus the number of spot welds, can be selected such that the sum of the 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 for each electrochemical cell, or lies within predefined tolerances. This homogenizes the current load on the individual electrochemical cells during charging and discharging, ensuring they exhibit uniform aging behavior.

[0046] Based on the Fig. Section 2 describes in more detail an electrochemical energy storage device according to a second embodiment. Identical components of the invention are identified by the same reference numerals, so the following description is limited to the essential differences.

[0047] As from Fig. As can be seen in Figure 2, the connection points 3 are designed such that the contact area of ​​the material-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 Fig. In the embodiment shown in Figure 2, the contact area was increased by using weld points or weld spots 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.

[0048] Based on the Fig. Section 3 explains a third embodiment of the invention in more detail. Identical components of the invention are again designated with the same reference numerals. It shows Fig. 3a an electrochemical energy storage device according to the state of the art. Fig. Figure 3b shows an electrochemical energy storage device according to the present invention. The lower part of the image shows a view and the upper part a top view.

[0049] How Fig. Figure 3 shows that the electrochemical cells 11, 12, 13 and 14 are according to Fig. Three prismatic cells, meaning they essentially have the basic shape of a cuboid. The positive poles 111, 121, 131, and 141 on one side, and the negative poles 112, 122, 132, and 142 on the other, are arranged at opposite points on one side of the casing of the prismatic electrochemical cells. How Fig. Figure 3 shows that 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 therefore 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, as well as the positive terminals 131 and 141 of the third and fourth electrochemical cells 13 and 14.

[0050] The connection is again made by means of a material bond via connection points 3, which can be produced, for example, by soldering, gluing or welding.

[0051] How Fig. Figure 3a shows that, according to the state of the art, essentially identical connection points 3 with identical contact area and therefore also with identical contact resistance are present. Fig. Figure 3b shows the solution according to the invention, in which the contact area of ​​the material-bonded 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, 3b according to Fig. 3 are manufactured by laser welding. The contact area of ​​the joints 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 joint 3a with a correspondingly larger contact area.

[0052] Like the lower part of the image from Fig. As shown in Figure 3b, an optional fourth cell connector 24 can 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, in order to further homogenize the current distribution within the cell arrangement 10. It is of course known to those skilled in the art that the fourth cell connector 24 can optionally also be used in combination with the connections shown in Figure 3b. Fig. 1 or Fig. The two round cells shown can be used. This can also be demonstrated using... Fig. The laser welding processes described in 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.

[0053] Based on the Fig. Section 4 explains in more detail the interconnection of two pouch cells. The pouch cells are also described according to... Fig. The 4 cells are connected in such a way that two parallel cells are connected in series to increase both the current and the voltage of the electrochemical energy storage device.

[0054] As already demonstrated by Fig. As explained in Figure 1, the increase in the contact area in the fourth embodiment is achieved by increasing the number of metallurgical 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.

[0055] Based on the Fig. Section 5 describes a fifth embodiment of the present invention in more detail. Identical components of the invention are identified by the same reference numerals, so the following description is limited to the essential differences.

[0056] As from Fig. As can be seen in Figure 5, the angle between the solder lug 4 and the longitudinal extent 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 extent of the cell connector 21, which leads 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.

[0057] With reference to Fig. Section 6 describes a sixth embodiment of an electrochemical energy storage device. Identical components of the invention are designated with the same reference numerals, so that the description is limited to the essential differences.

[0058] 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 larger or smaller 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 poles. In the Fig. In the 6-digit top view, the positive poles 111, 121, 131, 141, 151 and 161 are visible. The opposite negative poles are shown in Fig. 1 of the respective electrochemical cells are covered and therefore not visible.

[0059] 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 and capacity of the electrochemical energy storage device. For this purpose, the positive terminals 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 located in Fig. 6 is concealed 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. For example, the metallic material can 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.

[0060] In the illustrated embodiment, the first cell connector 21 has a substantially rectangular base shape, to which a connection area 210 of smaller width is attached. As shown Fig. 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.

[0061] To simplify assembly, an identical joining process can be used 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 described above in conjunction with the Fig. 1, Fig. 2 and Fig. 3 explained.

[0062] With reference to Fig. Section 7 describes a seventh embodiment of an electrochemical energy storage device. Identical components of the invention are designated with the same reference numerals, so that the description is limited to the essential differences.

[0063] In the seventh embodiment, single-sided connected cylindrical cells are used, in which the positive and negative poles 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 to each other. The linear cell arrangement 10 has at least one first and one second cell connector 21 and 22, which are connected in Fig. 7 are arranged on opposite sides of the linear cell arrangement 10.

[0064] The positive terminals 111, 121, 131, 141, 151, and 161 are connected to the first cell connector 21. The negative terminals 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 larger or smaller and may range from approximately 2 to approximately 8 or from 1 to approximately 5.

[0065] Naturally, the invention is not limited to the embodiments described. The foregoing description is therefore not to be considered limiting, but rather explanatory. The following claims are to be understood as meaning 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 meaning that a named feature must be present in every embodiment of the invention. Insofar as the claims and the foregoing description define "first" and "second" embodiments, this designation serves to distinguish between two similar embodiments without establishing a hierarchy. The foregoing description is to be understood as meaning that the described first to seventh embodiments can be combined with one another to obtain further embodiments of the invention.

Claims

[1] Electrochemical energy storage device (1) containing 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, so 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 connected by a material bond, so that at least one connection point (3) is formed, characterized by , that The contact area of ​​the materially bonded connection points (3) is larger the higher the internal resistance of the respective electrochemical cell (11, 12) is. [2] Electrochemical energy storage device (1) containing 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) to 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) to which the negative poles (112, 122) of the electrochemical cells (11, 12) are connected via at least one solder lug (4), characterized by , that The cross-sectional area of ​​the conductor of the solder lugs (4) is larger the higher the internal resistance of the respective electrochemical cell (11, 12) is. [3] Energy storage device according to claim 2, characterized by , 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 by , 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 connected 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 one of claims 1 or 4, characterized by , that the contact area of ​​the material-bonded connection points (3) is increased by the fact that a plurality of material-bonded connection points (3) are made. [6] Energy storage device according to claim 5, characterized by , that the majority of material-bonded connection points (3) is between 2 and about 12 or between about 3 and about 10. [7] Energy storage device according to one of claims 1 or 4 to 6, characterized by , that the contact area of ​​the material-bonded joints (3) is increased by the fact that one material-bonded joint (3) has a greater length and / or width than another material-bonded joint (3). [8] Energy storage device according to one of claims 1 or 4 to 7, characterized by , that the material-joined joints (3) are produced by soldering or resistance projection welding and / or laser welding and / or resistance spot welding and / or press contacting. [9] Energy storage device according to one of claims 1 or 4 to 8, characterized by , that the material-bonded joints (3) have a contact resistance which is between about 50 µΩ and about 400 µΩ. [10] Energy storage device according to one of claims 1 or 4 to 9, characterized by , that the contact area of ​​the material-bonded joints (3) is between approximately 0.5 mm 2 and about 1 cm 2 amounts. [11] Energy storage device according to one of claims 2 or 3, characterized by , that the angle between the solder lug (4) and the respective cell connector (21, 22) is chosen according to the internal resistance of the electrochemical cell (11, 12). [12] Energy storage device according to claim 4, characterized by , 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 materially bonded connection points (3). [13] Energy storage device according to claim 4 and one of claims 5 to 10, characterized by , 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 materially bonded connection points (3). [14] Energy storage device according to any one of claims 1 to 13, characterized by, that the electrochemical cells (11, 12) are selected from at least one primary cell and / or at least one secondary cell. [15] Energy storage device according to claim 14, characterized by , 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. [16] 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 pole (111, 121) and a negative pole (112, 122), and Materially bonded connection of the positive poles (111, 121) of the electrochemical cells (11, 12) with a first cell connector (21), so that at least one connection point (3) is formed, and Materially bonded connection of the negative poles (112, 122) of the electrochemical cells (11, 12) with a second cell connector (22), so that at least one connection point (3) is formed, characterized by , that an internal resistance of each electrochemical cell (11, 12) is determined and The contact area of ​​the materially bonded connection points (3) is made larger the higher the internal resistance of the respective electrochemical cell (11, 12) is. [17] 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 pole (111, 121) and a negative pole (112, 122), and Material-bonded connection of 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 Material-bonded connection of 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 by , that an internal resistance of each electrochemical cell (11, 12) is determined and The cross-sectional area of ​​the conductor of the solder lugs (4) is chosen to be larger the higher the internal resistance of the respective electrochemical cell (11, 12) is. [18] Method according to claim 17, characterized by , 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. [19] Method according to claim 16, characterized by, that the material-bonded joints (3) have a contact resistance which is between about 50 µΩ and about 400 µΩ. [20] Method according to one of claims 16 or 19, characterized by , that the contact area of ​​the material-bonded joints (3) is between approximately 0.5 mm 2 and about 1 cm 2 amounts. [21] Method according to claim 16 or any one of claims 19 to 20, characterized by , that the material-joined joints (3) are produced by soldering or resistance projection welding and / or laser welding and / or resistance spot welding and / or press contacting. [22] Method according to any one of claims 16 to 21, characterized by, that the contact area of ​​the material-bonded connection points (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 material-bonded connection points (3) and the resistance of the first and second cell connectors (21, 22) is constant or lies within predefinable tolerances. [23] Method according to any one of claims 16 to 22, characterized by , that the internal resistance of each electrochemical cell (11, 12) is determined taking into account the later installation position and / or the individual operating temperature.

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