Multi-layer flexible battery interconnects and methods of making same

Abstract

A multi-layer flexible battery interconnect for interconnecting batteries in a battery pack and a method for making the same are provided. The multi-layer flexible battery interconnect is comprised of an insulating layer and two conductive layers stacked together and disposed between the insulating layers. One conductive layer is thicker than the other conductive layer. The thinner conductive layer includes a flexible tab for connecting to the battery and, in some instances, includes a voltage sensing trace. The thin thickness of these flexible tabs ensures the quality of the weld and reduces energy usage during welding. The battery cell contacts to which these flexible tabs are welded can be significantly thicker. Additionally, the reduced thickness allows for the incorporation of fusible links into the flexible tabs. At the same time, the two conductive layers collectively carry current within the interconnect, and the thicker layers enhance the overall current carrying capacity. The two conductive layers can be welded to ensure electrical connection and mechanical support.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]

[0001] This application claims the benefit under 35 U.S.C. Section 119(e) of U.S. Provisional Application No. 63 / 237,333, filed August 16, 2021 (Docket No. CLNK018P), and U.S. Provisional Application No. 63 / 165,582, filed March 24, 2021 (Docket No. CLNK016P), the entire disclosures of both provisional applications being incorporated herein by reference for all purposes. [Background technology]

[0002]

[0002] Rechargeable battery cells and battery packs assembled with these cells represent a promising technology for providing energy storage for mobile (e.g., electric vehicles) and stationary (e.g., grid) applications. In order to increase market penetration, the cost of battery cells and other pack components must be reduced. Although cells (e.g., lithium-ion cells and other types of cells) are currently the most expensive components in a battery pack, cell costs are expected to decrease in the future due to economies of scale, new materials, and improved designs. In addition, battery cell performance and lifetime will improve, which should lead to new heavy-duty applications. This trend will place greater emphasis on the cost, performance, and reliability of other components in the battery pack, especially the battery interconnects. In addition, new and efficient methods of assembling battery packs using these components will be required.

[0003]

[0003] Many conventional battery packs are assembled using bulky metal plates with complex designs and features. These metal plates interconnect individual battery cells and carry electrical current between the cells and / or the terminals of the battery pack. Special fuses and / or connector wires are used to connect these plates to the battery cells, for example to protect the individual cells from overcurrent and thermal runaway. These fuses are fragile and can break under stress and vibration conditions commonly encountered during operation of the pack. Furthermore, each plate is typically a separate component, and multiple plates are often required for large battery packs. This separate assembly increases the cost and complexity of the battery pack and can adversely affect the safety and robust performance of the battery pack. Summary of the Invention

[0004]

[0004] A multi-layer flexible battery interconnect for interconnecting batteries in a battery pack and a method for making the same are provided. The multi-layer flexible battery interconnect is comprised of an insulating layer and two conductive layers stacked together and disposed between the insulating layers. One conductive layer is thicker than the other conductive layer. The thinner conductive layer includes a flexible tab for connecting to the battery, and in some examples includes a voltage sensing trace. The thin thickness of these flexible tabs ensures the quality of the weld and reduces energy usage during welding. The contacts of the battery cells to which these flexible tabs are welded can be significantly thicker. Additionally, the thin thickness allows fusible links to be incorporated into the flexible tabs. At the same time, the two conductive layers collectively carry current within the interconnect, and the thicker layers enhance the overall current carrying capacity. The two conductive layers can be welded to ensure electrical connection and mechanical support. [Brief description of the drawings]

[0005] [Figure 1A] FIG. 1A is a schematic top view of a cylindrical battery cell showing center and end contacts of the cell, according to some examples. [Figure 1B] FIG. 1B is a schematic cross-sectional side view of the cylindrical battery cell of FIG. 1A, according to some examples. [Figure 1C] FIG. 1C is a schematic top view of a battery pack including multiple battery cells and interconnects, according to some examples. [Figure 1D] FIG. 1D is a schematic top view of a battery pack with additional example interconnections. [Figure 1E] FIG. 1E is a schematic top view of a battery pack with additional example interconnections. [Figure 2A-2B] Figure 2A is a schematic perspective view and partial cross-sectional view of a multi-layer flexible battery interconnect, according to some examples, and Figure 2B is a schematic perspective view of a portion of the multi-layer flexible battery interconnect of Figure 2A, focusing on the flexible tabs for connecting to the center contacts of the cells. [Figure 2C] FIG. 2C is a schematic perspective view of the multi-layer flexible battery interconnect of FIG. 2A with one insulating layer removed to reveal the different conductive layers of the interconnect. [Figure 2D] FIG. 2D is a schematic perspective view of a portion of the multi-layer flexible battery interconnect of FIG. 2C, focusing on the flexible tabs for connecting to the center contacts of the cells. [Figure 2E] FIG. 2E is a schematic cross-sectional view of a portion of a multi-layer flexible battery showing one bus bar formed by two conductive layers and sealed between two insulating layers. [Diagram 3] FIG. 3 is a schematic top view of a multi-layer flexible battery interconnect illustrating the distance between different types of flexible tabs, according to some examples. [Figure 4A] FIG. 4A is a schematic cross-sectional side view of a battery pack showing four battery cells interconnected by a multi-layer flexible battery interconnect, according to some examples. [Figure 4B] FIG. 4B is a schematic cross-sectional side view of a battery pack showing four battery cells interconnected by a multi-layer flexible battery interconnect, according to some examples. [Figure 4C] FIG. 4C is a schematic cross-sectional side view of a battery pack showing four battery cells interconnected by a multi-layer flexible battery interconnect, according to some examples. [Figure 4D] FIG. 4D is a schematic cross-sectional side view of a battery pack showing four battery cells interconnected by a multi-layer flexible battery interconnect, according to some examples. [Figure 5A] FIG. 5A is a schematic cross-sectional side view of a battery cell and a multi-layer flexible battery interconnect prior to forming electrical connections to the cell, according to some examples. [Figure 5B] FIG. 5B is a schematic top view of the multi-layer flexible battery interconnect of FIG. 5A showing one example of a center contact flexible tab. [Figure 5C] FIG. 5C is a schematic cross-sectional side view of a battery cell and a multi-layer flexible battery interconnect after forming electrical connections to the battery, according to some examples. [Figure 5D] FIG. 5D is a schematic cross-sectional side view of a battery cell and a multi-layer flexible battery interconnect after forming electrical connections to the battery, according to some examples. [Figure 5E] FIG. 5E is a schematic top view of a multi-layer flexible battery interconnect showing one example of end-point contact flexible tabs. [Figure 6A] FIG. 6A is a schematic top view of voltage traces of a multi-layer flexible battery interconnect, according to some examples. [Figure 6B] FIG. 6B is a schematic top view of voltage traces of a multi-layer flexible battery interconnect, according to some examples. [Figure 6C] FIG. 6C is a schematic top view of voltage traces of a multi-layer flexible battery interconnect, according to some examples. [Figure 6D] FIG. 6D is a schematic top view of voltage traces of a multi-layer flexible battery interconnect, according to some examples. [Figure 6E]FIG. 6E is a schematic cross-sectional side view of a multi-layer flexible battery interconnect with battery cells and voltage traces, according to some examples. [Figure 6F] FIG. 6F is a schematic cross-sectional side view of a multi-layer flexible battery interconnect including battery cells, signal traces, and sensors connected to the signal traces, according to some examples. [Figure 7A] FIG. 7A is a schematic top view of four prismatic cells showing the desired series connection of these cells. [Figure 7B] FIG. 7B is a schematic top view of the four prismatic cells of FIG. 7A showing a first conductive layer of a multi-layer flexible battery interconnect disposed over and interconnecting the cells. [Figure 7C] FIG. 7C is a schematic top view of the four prismatic cells of FIG. 7A showing the first and second conductive layers of a multi-layer flexible battery interconnect disposed over and interconnecting the cells. [Figure 7D] FIG. 7D is a schematic top view of the four prismatic cells of FIG. 7A, showing the overall interconnects disposed above the cells. [Figure 8] FIG. 8 is a process flow diagram corresponding to a method of manufacturing a multi-layer flexible battery interconnect, according to some examples. [Figure 9] FIG. 9 is a process flow diagram corresponding to another method of manufacturing a multi-layer flexible battery interconnect. [Figure 10A] FIG. 10A is a schematic diagram of the various components and assemblies used to fabricate a multi-layer flexible battery interconnect. [Figure 10B] FIG. 10B is a schematic diagram of the various components and assemblies used to fabricate a multi-layer flexible battery interconnect. [Figure 10C] FIG. 10C is a schematic diagram of the various components and assemblies used to fabricate a multi-layer flexible battery interconnect. [Figure 10D]FIG. 10D is a schematic diagram of the various components and assemblies used to fabricate a multi-layer flexible battery interconnect. [Figure 10E] FIG. 10E is a schematic diagram of the various components and assemblies used to fabricate a multi-layer flexible battery interconnect. [Figure 10F] FIG. 10F is a schematic diagram of the various components and assemblies used to fabricate a multi-layer flexible battery interconnect. [Figure 11A-11B] Figure 11A is a schematic cross-sectional view of a battery pack assembly including a battery and an interconnect circuit with a specially configured connection portion connected to the battery, according to some examples, and Figure 11B is a schematic enlarged cross-sectional view of a portion of the battery pack assembly of Figure 11A, showing an example of a connection portion. [Figure 11C] FIG. 11C is a schematic top view of a portion of the battery pack assembly of FIG. 11B. [Figure 12A] FIG. 12A is a schematic top view of a portion of a battery pack assembly showing tab openings of a conductor tab, according to some examples. [Figure 12B] FIG. 12B is a schematic cross-sectional view of a portion of the battery pack assembly of FIG. 12A illustrating tab openings of conductor tabs according to some examples. [Figure 13A] FIG. 13A is a schematic cross-sectional view of a battery pack assembly before and after forming an electrical connection between a conductor tab of an interconnect circuit and a battery, according to some examples. [Figure 13B] FIG. 13B is a schematic cross-sectional view of a battery pack assembly before and after forming an electrical connection between a conductor tab of an interconnect circuit and a battery, according to some examples. [Figure 13C] FIG. 13C is a schematic cross-sectional close-up of two conductor necks showing different examples of partial openings in the conductor neck that provide flexibility to the conductor neck when making a connection to the battery. [Figure 13D]FIG. 13D is a schematic cross-sectional close-up of two conductor necks showing different examples of partial openings in the conductor neck that provide flexibility to the conductor neck when making a connection to the battery. [Figure 14A] FIG. 14A is a schematic top view of a conductor of an interconnect circuit for use in a battery pack assembly, showing a partial opening of a conductor neck operable as a fusible link. [Figure 14B] FIG. 14B is a schematic cross-sectional view of the conductor of FIG. 14A showing a partial opening of the conductor neck. [Figure 14C] FIG. 14C is an enlarged schematic cross-sectional view of the conductor of FIG. 14A, identifying various features of the partial opening of the conductor neck. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006]

[0040] The following detailed description of examples of the present disclosure will be better understood when read in conjunction with the accompanying drawings. As used herein, an element or step described in the singular and followed by the word "a" or "an" should be understood as not excluding a plurality of said elements or steps, unless such exclusion is expressly stated. Furthermore, references to "one example" are not intended to be interpreted as excluding the existence of additional examples that also incorporate the recited features. Furthermore, unless expressly stated to the contrary, examples that "include" or "have" an element or elements having a particular characteristic may include additional elements that do not have that characteristic. Introduction

[0007]

[0041] Many modern battery packs contain multiple cells that must be interconnected. For example, a typical battery pack used in an electric vehicle has thousands of battery cells, such as cylindrical battery cells, more specifically 18650 cells, 21700 cells, 4680 cells, etc. The success of many battery applications often depends on robust, reliable, and inexpensive interconnects between the battery cells in such packs. As mentioned above, some conventional interconnects use rigid metal plates, called busbars, to connect to the cell contacts. Although these busbars can carry large currents and provide some mechanical support, these busbars are expensive to manufacture. For example, manufacturing the busbars requires unique tooling for each battery module, which can be expensive. Additionally, these busbars are expensive and difficult to connect to the battery cell terminals. The rigidity of these busbars prevents the relative motion of the battery cells and plates, which can break the electrical connection between these components. Finally, the thickness of these busbars also limits the thermal performance of the pack cooling plate / system, resulting in a suboptimal specific energy (e.g., reduced range in electric vehicle applications).

[0008]

[0042] Multilayer flexible battery interconnects are specially configured to provide reliable electrical connections and can often be easier to manufacture, connect to cell terminals, and attach to a battery pack than conventional interconnects. Multilayer flexible battery interconnects also provide current fusing capabilities, which are described further below. Unlike conventional printed circuits, which are generally limited to low current applications due to the thin thickness of the conductive layers, multilayer flexible battery interconnects can be configured to provide a full range of current carrying capabilities without affecting the ability to weld to the battery contacts. For example, the thickness of the printed conductive elements is limited by the capabilities of the mask and etch, which generally are not suitable for high aspect ratio features or thick conductors. Additionally, the long etching times required for thicker layers increase the manufacturing costs of flexible circuits. At the same time, many modern battery cells and packs can operate at currents of at least 50 A and even greater than 100 A, such as during fast charging or fast discharging of the pack. This necessitates the use of thick conductive layers (e.g., at least 200 micrometers, or even at least 500 micrometers thick) to provide sufficient electrical conductivity.

[0009]

[0043] It should be noted that thick conductive layers present various challenges. First, thick conductive layers (e.g., having a thickness greater than 200 micrometers) are difficult to weld or otherwise attach to a battery cell. The thicker the conductive layer, the more energy is required to form the weld, and the more heat is dissipated to the battery cell. At the same time, many cell components (e.g., separators, electrolytes, etc.) are heat sensitive and cannot withstand high temperatures (e.g., temperatures greater than 70° C.). Furthermore, thick conductive layers present various challenges when forming fuse / fusible links from these conductors. Fusible links control and sever the electrical connection to the battery cell when the current flowing through the link exceeds a certain threshold, which is controlled in part by the dimensions of the fusible link. For example, etching thick conductors makes it difficult to achieve narrow traces with uniform width. For etching, the minimum width-to-thickness ratio (referred to herein as the "aspect ratio") is typically 4 or even 5 to avoid the excessive undercutting that accompanies etching. For example, if a 200 micrometer thick conductor is etched to form a fusible link, the resulting width must be at least 700-800 micrometers, which may be too long for most fusing applications / types of battery cells. Furthermore, forming a fusible link that does not contact other components is usually not possible with etching, since the backside must be protected from the etchant. Any physical contact with the fusible link (except with the rest of the conductor) is undesirable and will interfere with the thermal properties and overall performance of the fusible link.

[0010]

[0044] The multi-layer flexible battery interconnects described herein address various deficiencies of the conventional interconnects mentioned above. In some examples, the multi-layer flexible battery interconnects include two insulating layers (e.g., a first insulating layer and a second insulating layer) and two conductive layers (e.g., a first conductive layer and a second conductive layer). One conductive layer (e.g., the first conductive layer) is thicker than the other (e.g., the second conductive layer). The two conductive layers form a stack, which is at least partially insulated by an insulating layer and sealed between the insulating layers. The thinner conductive layer includes a flexible tab that extends to the outside of the stack and even to the outside of the insulating layer. In particular, the second conductive layer has a flexible tab (of the same thickness) that allows for forming an electrical connection (e.g., welding) to the battery cell without requiring significant energy / heat to the battery cell because it is thinner. The thin conductive layer also ensures the quality of the laser welding. For example, the thickness of the top can of a typical cylindrical battery cell is 0.3 millimeters or 0.4 millimeters. If the thickness of the conductive layer is the same or thicker than the thickness of the can, the weld performance will be reduced. Therefore, welding a thinner conductive layer to a thicker battery will produce a higher quality weld.

[0011]

[0045] Additionally, various fusible links can be incorporated directly into the flexible tab. The first conductive layer is thick, which helps provide additional current carrying capabilities through the interconnect. In some examples, the first conductive layer is at least twice as thick as the second conductive layer. Thus, the first conductive layer may be the primary current carrier within the multi-layer flexible battery interconnect. The thickness of the first conductive layer can be adjusted to modify these current carrying capabilities of the multi-layer flexible battery interconnect without changing the thickness of the second conductive layer (and the thickness of the flexible tab).

[0012]

[0046] For purposes of this disclosure, the term "interconnect" is used interchangeably with "interconnect circuit," the term "conductive layer" is used interchangeably with "conductor" or "conductor layer," and the term "insulating layer" is used interchangeably with "insulator."

[0013]

[0047] In some examples, the multi-layer flexible battery interconnects can be used to electrically interconnect a set of battery cells having terminals on the same side of the cells. The cells can be cylindrical cells (e.g., 18650 cells, 21700 cells, 4680 cells, etc.) as shown generally in Figures 1A and 1B, or prismatic cells as shown in Figure 7A and described below. In particular, Figure 1A is a schematic top view of a cylindrical battery cell 192 showing a first contact 194 (also referred to as a center contact) and a second contact 195 (also referred to as an edge contact) according to some examples. Figure 1B is a schematic cross-sectional side view of the cylindrical battery cell 192 of Figure 1A according to some examples.

[0014]

[0048] FIG. 1C is a schematic top view of a battery pack 190 comprising a plurality of battery cells 192 and a multi-layer flexible battery interconnect 100 forming a connection to each battery cell 192, according to some examples. The multi-layer flexible battery interconnect 100 is shown in the form of an electrical diagram illustrating one example of a connection in a battery pack 190. In particular, in this example of FIG. 1C, the multi-layer flexible battery interconnect 100 comprises a first bus 101 and a second bus 102. Each bus is formed by two or more conductive layers, as described further below. One of these conductive layers (e.g., the thinner one) also forms a flexible tab 142 that is connected to a first contact 194 and a second contact 195 of the battery cell 192. The connection is made by a contact pad 145 located at the end of the flexible tab 142. In this example, the first / center contact 194 of the left row of battery cells 192 is connected to the flexible tab 142 of the first bus 101. The first / center contact 194 of the center row of battery cells 192 is also connected to the flexible tab 142 of the first bus 101. Thus, all cells 192 of the left and center rows are connected in parallel. The second / edge contact 195 of the middle row of battery cells 192 is connected to the flexible tab 142 of the second bus 102. Thus, the first bus 101 and the second bus 102 are connected in series by the middle row of battery cells 192. It should be noted that each flexible tab 142 of the second bus 102 is connected to two adjacent cells 192 of the middle row, more specifically, to the second / edge contact 195 of the two adjacent cells 192 of the middle row. This double edge contact is possible because the second / edge contact 195 of the two adjacent cells 192 are located adjacent to each other and can be achieved using the same contact pad 145. In this example, the connections to the first / center contact 194 are individual because these contacts are surrounded by the second / edge contact 195. Finally, the second / edge contacts 195 of the battery cells 192 in the right row are also connected to the flexible tabs 142 of the second bus 102. Thus, all of the cells 192 in the right row and the center row are connected in parallel.

[0015]

[0049] FIG. 1D is a schematic top view of a battery pack 190 in which battery cells 192 are interconnected with another example of the multi-layer flexible battery interconnect 100. The connection scheme is the same as FIG. 1C. The difference is in the position of the flexible tabs 142 forming the double-edge contacts. With reference to FIG. 1C, the flexible tabs 142 forming the double-edge contacts to the left and right columns of battery cells 192 are mutually aligned along the X-axis. Now with reference to FIG. 1D, the flexible tabs 142 forming the double-edge contacts to the left and right columns of battery cells 192 are shifted by the battery pitch along the Y-axis. For the purposes of this disclosure, the term "battery pitch" is defined as the distance between the centers of two adjacent batteries arranged in the same row. For cylindrical cells, the battery pitch is equal to the diameter of the cell plus the gap between two cells in the same row.

[0016]

[0050] FIG. 1E is a schematic top view of a battery pack 190 in which battery cells 192 are interconnected with yet another example of a multi-layer flexible battery interconnect 100. Again, the connection scheme is the same as in FIG. 1C. However, the multi-layer flexible battery interconnect 100 of FIG. 1E has more flexible tabs 142 to provide redundant edge contacts. Specifically, each battery cell 192 has two different flexible tabs 142 connected to its second / edge contact 195. This redundancy helps ensure that all cells remain connected without significant penalties in weight or cost. [Example of interconnect circuit and battery pack]

[0017]

[0051] 2A is a schematic perspective view of a multi-layer flexible battery interconnect 100 for interconnecting battery cells 192 in a battery pack 190, according to some examples. Referring to the cross-sectional view in FIG. 2A, the multi-layer flexible battery interconnect 100 includes a first insulating layer 110, a second insulating layer 120, a first conductive layer 130, and a second conductive layer 140. The first conductive layer 130 is disposed between the first insulating layer 110 and the second insulating layer 120 and directly contacts the first insulating layer 110. The second conductive layer 140 is disposed between each of the first conductive layer 130 and the second insulating layer 120 and directly contacts each of them. Furthermore, the first conductive layer 130 is thicker than the second conductive layer 140, i.e., T FCL >T SCL Most of first insulating layer 110, first conductive layer 130, and second conductive layer 140 are not visible in the perspective view of FIG.

[0018]

[0052] Referring to the perspective view of FIG. 2A, the second conductive layer 140 includes flexible tabs 142. The flexible tabs 142 are used to make electrical connections to the battery cells 192, for example as shown diagrammatically in FIG. 2B. For example, FIG. 2B shows two flexible tabs 142. The top tab is configured to connect to an edge contact (schematically shown with dashed lines) of the battery cell 192 and may be referred to as an edge contact flexible tab 149. The bottom tab is configured to connect to a center contact of the battery cell 192 and may be referred to as a center contact flexible tab 148. Note that these two flexible tabs 142 (center contact flexible tab 148 and edge contact flexible tab 149) are part of different buses (and different portions of the second conductive layer 140).

[0019]

[0053] The first conductive layer 130 is electrically connected to the second conductive layer 140, for example by direct interfacing and / or by welding. More specifically, the first conductive layer 130 and the second conductive layer 140 form a stack (as shown in the cross-sectional view of FIG. 2A) called a conductive stack. The second conductive layer 140, more specifically the flexible tab 142 of the second conductive layer 140, connects to the battery cell 192 and serves to carry the current between the battery cell 192 and the conductive stack. However, within the conductive stack, the current is mainly carried by the thicker first conductive layer 130. In fact, the current carrying capacity is determined by the relative cross-sectional areas of the first conductive layer 130 and the second conductive layer 140, which are proportional to the thickness of the layers.

[0020]

[0054] In some examples, the first conductive layer 130 is at least twice as thick, more specifically at least three times thicker than the second conductive layer 140. In the same or other examples, the first conductive layer 130 has a thickness of at least 300 micrometers, or even at least 350 micrometers, while the second conductive layer 140 has a thickness of less than 200 micrometers, or even less than 150 micrometers. For example, the first conductive layer 130 has a thickness of 400 micrometers, and the second conductive layer 140 has a thickness of 125 micrometers. As discussed above, the large thickness of the first conductive layer 130 allows for a large current to flow through the multilayer flexible battery interconnect 100, such as at least 50 A, or even more than 100 A. Additionally, the large thickness of the first conductive layer 130 allows for the use of less conductive materials, such as aluminum (compared to copper, which is twice as conductive but is significantly more expensive and has a much higher specific gravity). At the same time, the smaller thickness of the second conductive layer 140 allows the flexible tab 142 to be welded to the battery cell 192 without using significant energy (and therefore without heating the battery cell 192).

[0021]

[0055] In some examples, the first conductive layer 130 has a uniform thickness throughout the boundary of the first conductive layer 130. For example, the first conductive layer 130 can be formed from the same metal sheet. Different (separate) portions of the first conductive layer 130 (forming different buses of the same multi-layer flexible battery interconnect 100) can be formed from the same metal sheet. In the same or other examples, the second conductive layer 140 has a uniform thickness throughout the boundary of the second conductive layer 140.

[0022]

[0056] In some examples, the first conductive layer 130 and the second conductive layer 140 are formed from the same material, for example, aluminum. Using aluminum instead of copper also helps to lower the minimum achievable fuse current rating, since aluminum has a higher resistivity and a lower melting temperature compared to copper. Thus, forming a fusible link in an aluminum conductive layer may allow for more precise control of the fusible parameters. Alternatively, the first conductive layer 130 and the second conductive layer 140 are formed from different materials. For example, the first conductive layer 130 is formed from aluminum and the second conductive layer 140 is formed from copper. In general, the first conductive layer 130 and the second conductive layer 140 need to be sufficiently conductive (e.g., 100 .mu.m) to achieve a current through the foil with low power losses. 6 More than 10 S / m or even 7 The conductive material may be any conductive material having a conductivity greater than 0.05 S / m.

[0023]

[0057] In some examples, the first conductive layer 130 and the second conductive layer 140 may include a surface sub-layer or coating to provide low electrical contact resistance and / or improve corrosion resistance. The surface sub-layer may aid in forming electrical interconnections using techniques / materials including, but not limited to, soldering, laser welding, resistance welding, ultrasonic welding, bonding with a conductive adhesive, or mechanical pressure. Surface sublayers that provide a suitable surface for these connection methods include, but are not limited to, tin, lead, zinc, nickel, silver, palladium, platinum, gold, indium, tungsten, molybdenum, chromium, copper, alloys thereof, organic solderability preservatives (OSPs), or other conductive materials. Additionally, the surface sublayer may be applied by sputtering, plating, cold welding, or other means. In some examples, the thickness of the surface sublayer may range from 0.05 micrometers to 10 micrometers, more specifically 0.1 micrometers to 2.5 micrometers. Additionally, in some examples, adding a coating of OSP on top of the surface sublayer may help prevent the surface sublayer itself from oxidizing over time. Surface sublayers may be used when the base sublayers of the first conductive layer 130 and the second conductive layer 140 include aluminum or its alloys. Without protection, exposed surfaces of aluminum tend to form insulating native oxides. Oxides form easily in the presence of oxygen or moisture. In this case, the sub-surface layer can be made resistant to the in-diffusion of oxygen and / or moisture to provide a long-term stable surface. For example, zinc, silver, tin, copper, nickel, chromium, or gold plating can be used as a surface layer on an aluminum-containing base layer.

[0024]

[0058] 2A and 2B, in some examples, the first conductive layer 130 and the second conductive layer 140 are welded together at a number of weld locations 109 that are separated from one another. For example, the weld locations 109 are formed by laser welding, although other types of welding (e.g., ultrasonic welding, resistance welding) are within the scope. These weld locations 109 serve to conduct electrical current between the first conductive layer 130 and the second conductive layer 140. Additionally, these weld locations 109 serve to maintain the orientation of the first conductive layer 130 and the second conductive layer 140 and to support the layers relative to one another. Additional support for the first conductive layer 130 and the second conductive layer 140 can be provided by the first insulating layer 110 and the second insulating layer 120, for example, which extend beyond the conductive stack and are laminated directly onto each other to form an envelope-like structure around the conductive stack, as shown in FIG. 2E and described below with reference to this figure.

[0025]

[0059] It should be noted that the flexible tab 142 extends beyond the boundaries of the conductive stack, and more specifically, beyond the boundaries of the first conductive layer 130. The flexible tab 142 also extends beyond the boundaries of the first insulating layer 110 and the second insulating layer 120 to form an electrical connection with the battery cell 192. More specifically, various openings are formed in the first insulating layer 110 and the second insulating layer 120 to access the flexible tab 142. These openings are aligned with the contacts of the battery cell 192, allowing the flexible tab 142 to protrude into the openings. More specifically, when connected to the battery cell 192, the flexible tab 142 protrudes into the openings formed in the first insulating layer 110 (facing the battery cell 192). The openings in the second insulating layer 120 are used to access the flexible tab 142 while forming an electrical connection between the flexible tab 142 and the battery cell 192.

[0026]

[0060] In some examples, the openings in the first insulating layer 110 and the second insulating layer 120 are formed prior to laminating these insulating layers to their respective conductive layers, as described further below. The openings may be formed using techniques including, but not limited to, punching, flat bed die cutting, match metal die cutting, male / female die cutting, rotary die cutting, laser cutting, laser ablation, water jet cutting, machining, or etching.

[0027]

[0061] The thickness of one or both of the first insulating layer 110 and the second insulating layer 120 may be between 1 micrometer and 500 micrometers, more specifically between 10 micrometers and 125 micrometers. In some examples, the first insulating layer 110 and the second insulating layer 120 each include an adhesive sublayer disposed on at least one surface facing the corresponding conductive layer, e.g., for lamination to the conductive layer and to each other. These adhesive sublayers can also be used to directly laminate the first insulating layer 110 and the second insulating layer 120 (across the conductive layer boundary), as described below with reference to FIG. 2E. In some examples, the surface of the first insulating layer 110 facing the battery cells 192 includes an adhesive sublayer for adhering to these battery cells 192.

[0028]

[0062] The first insulating layer 110 and the second insulating layer 120 provide electrical insulation and mechanical support to the first conductive layer 130 and the second conductive layer 140. In some examples, the first insulating layer 110 and the second insulating layer 120 may be first processed in sheet or roll form and then laminated to the conductive layer using, for example, an adhesive material. The first insulating layer 110 and the second insulating layer 120 may include (or be formed from) polyimide (PI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), ethyl vinyl acetate (EVA), polyethylene (PE), polyvinyl fluoride (PVF), polyamide (PA), or polyvinyl butyral (PVB).

[0029]

[0063] 2A and 2B, in some examples, the second insulating layer 120 includes weld openings 122. Each of the plurality of weld locations 109 is disposed within one of the weld openings 122. These weld openings 122 allow for welding after the first conductive layer 130 and the second conductive layer 140 are laminated between the first insulating layer 110 and the second insulating layer 120.

[0030]

[0064] 2C and 3, in some examples, the flexible tab 142 comprises a first set of tabs 143 extending in a first direction (along the X-axis) and a second set of tabs 144 extending in a second direction opposite the first direction. The first set of tabs 143 is used to form an electrical connection to the battery cells 192 located in one row, and the second set of tabs 144 is used to form an electrical connection to the battery cells 192 located in an adjacent row. It should be noted that the first set of tabs 143 and the second set of tabs 144 can be formed by any type of flex tab 142. For example, FIG. 2C identifies the first set of tabs 143 and the second set of tabs 144 of a center contact flex tab 148, while FIG. 3 identifies the first set of tabs 143 and the second set of tabs 144 of an edge contact flexible tab 149. The first set of tabs 143 and the second set of tabs 144 are used simply to distinguish the location of the tabs on the same bus.

[0031]

[0065] FIG. 3 illustrates various types of tabs and their relative positions within the multi-layer flexible battery interconnect 100. Note that this tab arrangement corresponds to the schematic example shown in FIG. 1C and described above. Specifically, the multi-layer flexible battery interconnect 100 comprises a first bus 101 and a second bus 102. Each of the first bus 101 and the second bus 102 comprises (or is formed by) a first conductive layer 130 and a second conductive layer 140 with a flexible tab 142. It should be noted that the conductive components of the first bus 101 and the second bus 102 are not directly connected to each other. However, these conductive components can be interconnected via the battery cells 192. The first bus 101 and the second bus 102 share a first insulating layer 110 and a second insulating layer 120 that can be used for mechanical support of the first bus 101 and the second bus 102 relative to each other.

[0032]

[0066] 3, the first bus 101 and the second bus 102 have different types of flexible tabs 142. Specifically, the flexible tabs 142 of the second conductive layer 140 forming the first bus 101 are configured to connect to the first / center contacts 194 of the battery cells. Meanwhile, the flexible tabs 142 of the second conductive layer 140 forming the second bus 102 are configured to connect to the second / edge contacts 195 of the battery cells 192 and are referred to as edge contact flexible tabs 149. In some examples, each edge contact flexible tab 149 is configured to connect to the edge contacts 195 of two adjacent battery cells 192.

[0033]

[0067] As shown in Figure 3, one edge contact flexible tab 149 and one center contact flexible tab 148 are connected to each battery cell 192. In some examples described above with reference to Figure 1D, two edge contact flexible tabs and one center contact flexible tab 148 are connected to each battery cell 192. In either case, both the edge contact flexible tabs 149 and the center contact flexible tabs 148 extend on the same row of battery cells 192 to form an interdigitated assembly. Note that both the edge contact flexible tabs 149 and the center contact flexible tabs 148 have first and second sets of tabs 143 and 144 that extend in different directions.

[0034]

[0068] Various spacings between flexible tabs 142 (within the same or different sets, and / or within the same or different buses) are shown in Figure 3. In some examples, the first set of tabs 143 are offset relative to the second set of tabs 144 by half the battery pitch of the battery pack 190. This offset applies to the center contact flexible tabs 148 and the edge contact flexible tabs 149.

[0035]

[0069] 3, in some examples, any two adjacent tabs in the first tab set 143 are spaced apart by the battery pitch of the battery pack 190. Also, any two adjacent tabs in the second tab set 144 are spaced apart by the battery pitch of the battery pack 190.

[0036]

[0070] 3 , in some examples, any two adjacent edge contact flexible tabs 149 are spaced apart by the battery pitch or twice the battery pitch of the battery pack 190. More specifically, any two adjacent tabs in the first tab set 143 are spaced apart by the battery pitch or twice the battery pitch of the battery pack 190. Similarly, any two adjacent tabs in the second tab set 144 are spaced apart by the battery pitch or twice the battery pitch of the battery pack 190.

[0037]

[0071] 2B shows a central contact flexible tab 148 including a contact pad 145 and a fusible link 146 that connects and supports the contact pad 145 to the remainder of the second conductive layer 140. The contact pad 145 is configured to connect to the central contact 195 of one of the batteries 192. Furthermore, the second insulating layer 120 includes a contact opening 123 such that at least a majority of the fusible link 146 and the contact pad 145 protrude into the contact opening 123. Thus, the fusible link 146 is not affected by the thermal mass of the second insulating layer 120 (although the fusible link 146 may be at least partially supported by the first insulating layer 110). Furthermore, the contact opening 123 provides access to the contact pad 145 when welding the contact pad 145 to the first / central contact 194 of the battery cell 192.

[0038]

[0072] 2B and 5A, 5B, and 5E, in some examples, the second insulating layer 120 includes a support tab 124 that at least partially defines the contact opening 123. A portion of the contact pad 145 is bonded to the support tab 124. The support tab 124 supports the contact pad 145 at least prior to forming an electrical connection to the battery cell 192. In some examples, the contact pad 145 is separated from the support tab 124 while forming this electrical connection. Alternatively, the contact pad 145 remains bonded to the support tab 124 even after the electrical connection is formed, as shown, for example ...

[0039]

[0073] 2B and 5A, 5B, and 5E, in some examples, the second insulating layer 120 includes a flexible slit 125 that extends along the interface between the support tab 124 and the remainder of the second insulating layer 120. The flexible slit 125 aids in out-of-plane bending (XY plane) of the support tab 124, for example, when the contact pad 145 faces a battery cell and forms an electrical connection to the cell.

[0040]

[0074] 5A and 5B, in some examples, at least a portion of the fusible link 146 is adhered to the first insulating layer 110. For example, the first insulating layer 110 includes a link support tab 114 that extends beyond the edge formed by the first insulating layer 110 and the second insulating layer 120. It should be noted that one surface of the fusible link 146 is adhered to the first insulating layer 110 while the other surface of the fusible link 146 is exposed, thereby reducing the effect of the insulating layer on the performance of the fusible link 146.

[0041]

[0075] 2B and 5E, in some examples, the edge contact flexible tab 149 includes a contact pad 145 and a flexible neck 147. The flexible neck 147 connects and supports the contact pad 145 to the remainder of the edge contact flexible tab 149. Unlike the fusible link 146, the flexible neck 147 is much wider and does not provide a current control function. However, the flexible neck 147 can support current from two battery cells 192 when the contact pads 145 of the edge contact flexible tab 149 are connected to the respective edge contacts 195. Overall, in some examples, the contact pads 145 are configured to connect to the edge contacts 195 of two adjacent batteries 192 simultaneously. These connections are shown diagrammatically as weld zones in FIG. 5E.

[0042]

[0076] 5E, in some examples, the second insulating layer 120 includes contact openings 123. Flexible neck 147 and most of the contact pads 145 protrude into the contact openings 123. The contact openings 123 allow for out-of-plane flexing (XY plane) of the contact pads 145 as edge contact flexible tabs 149 form connections with the battery cells 192. Additionally, the contact openings 123 allow for access to the contact pads 145 while forming these connections.

[0043]

[0077] 2E, in some examples, the first insulating layer 110 and the second insulating layer 120 are directly bonded to one another and form a boundary around a portion of the first conductive layer 130 and the second conductive layer 140. This feature helps to maintain the orientation of the first conductive layer 130 and the second conductive layer 140 before they are welded together. Additionally, this feature seals the conductive layer portions from the environment, preventing, for example, electrical shorts and / or corrosion.

[0044]

[0078] In some examples, a thicker conductive layer is disposed between the battery cell and the thinner conductive layer, thereby providing access to the thinner conductive layer (i.e., from the opposite side of the battery cell). With reference to FIGS. 4A and 4B, the first conductive layer 130 is thicker than the second conductive layer 140. The second conductive layer 140 can be accessed through the weld openings 122 in the second insulating layer 120, for example, to weld the second conductive layer 140 to the first conductive layer 130. In some examples, this welding is performed at the same time that the flexible tabs 142 are welded to the battery cells 192. In particular, FIG. 4A shows edge contact flexible tabs 149, each connected to two adjacent battery cells 192. FIG. 4B shows center contact flexible tabs 148, each connected to one or more battery cells 192.

[0045]

[0079] In some examples, a thinner conductive layer is placed between the battery cell and the thicker conductive layer, so that the flexible tab (which is part of the thinner conductive layer) is placed closer to the battery cell. In other words, the flexible tab needs to have a smaller out-of-plane bend to reach the battery cell. With reference to Figures 4C and 4D, the first conductive layer 130 is thinner than the second conductive layer 140. In this example, the flexible tab 142 is part of the first conductive layer 130. Figure 4C shows edge contact flexible tabs 149, each connected to two adjacent batteries 192. Figure 4D shows center contact flexible tabs 148, each connected to one or more battery cells 192.

[0046]

[0080] As discussed above, the flexible tab 142 is positioned flush with the remainder of the conductive layer prior to forming an electrical connection to the battery cell. FIG. 5A is a schematic side cross-sectional view of a battery cell 192 and multi-layer flexible battery interconnect 100 prior to forming an electrical connection to the battery cell 192. In this example, the connection will be made to a center contact 195 of the battery cell 192. FIG. 5B is a schematic top view of the multi-layer flexible battery interconnect 100 of FIG. 5A. The flexible tab 142, referred to in this example as center contact flexible tab 148, is supported by the support tab 124. More specifically, a portion of the contact pad 145 of the flexible tab 142 is adhered to the support tab 124.

[0047]

[0081] 5C and 5D are schematic cross-sectional side views of the battery cell 192 and the multi-layer flexible battery interconnect 100 after electrical connections to the battery cell 192 have been made. Specifically, the contact pad 145 is bent out of plane and protrudes into an opening in the first insulating layer 110. Another opening in the second insulating layer 120 provides access to the contact pad 145 during this operation. The contact pad 145 is in direct contact with the center contact 195 of the battery cell 192 and is welded to the center contact 195 at this location. The support tab 124 may remain attached to the contact pad 145. In some examples shown in FIG. 5D, the support tab 124 is separated from the remainder of the second insulating layer 120. [Voltage trace example]

[0048]

[0082] 6A-6D are schematic top views of voltage traces 150 of a multi-layer flexible battery interconnect 100, according to some examples. For example, the voltage traces 150 can be used to monitor the voltage at each bus bar of the multi-layer flexible battery interconnect 100. In other words, each voltage trace 150 is connected to a different bus bar and used to monitor the voltage at that bus bar. Specifically, FIG. 6A shows that the voltage traces 150 are part of the second conductive layer 140. More specifically, each voltage trace 150 is monolithic with a corresponding portion of the second conductive layer 140 and forms the same bus bar.

[0049]

[0083] In some examples, the voltage traces 150 (or other components of the second conductive layer 140) are formed from a material that may not be suitable for some applications (e.g., forming connections to connector terminals). For example, the voltage traces 150 are formed from aluminum, which is not easily soldered. In these examples, the multi-layer flexible battery interconnect 100 includes transition traces 152, for example as shown in FIGS. 6B-6D. The transition traces 152 can be formed from a different material (e.g., copper) than the voltage traces 150 (e.g., aluminum). Each voltage trace 150 can have a corresponding transition trace 152. However, in some examples, the number of voltage traces 150 and transition traces 152 can vary (e.g., unused traces, multiple transition traces 152 connected to one voltage trace 150, etc.). The transition traces 152 can overlap the voltage traces 150 and can be welded to the voltage traces 150 (e.g., in the manner in which the second conductive layer 140 is welded to the first conductive layer 130). 6B-6D 。 Transition trace 152 may then be connected to terminal 155 of connector 154.

[0050]

[0084] 6C and 6D, in some examples, multiple options are available for interconnecting the transition traces 152 and the voltage traces 150. For example, an insulating layer 156 is disposed between the transition traces 152 and the voltage traces 150. In some examples, the insulating layer 156 can be one of the first insulating layer 110 or the second insulating layer 120. Furthermore, the transition traces 152 and the voltage traces 150 can overlap to form a many-to-many grid, for example, as shown diagrammatically in FIGS. 6C and 6D. In other words, each transition trace 152 overlaps multiple voltage traces 150. Also, each voltage trace 150 overlaps multiple transition traces 152. For example, FIGS. 6C and 6D show the transition traces 152 and the voltage traces 150 extending at right angles to each other, such that each transition trace 152 overlaps all the voltage traces 150.

[0051]

[0085] This isolation, overlap, and orientation of the transition traces 152 and the voltage traces 150 allows for different connection options. Specifically, in FIG. 6C, the left transition trace 152 is connected to the top voltage trace 150, the middle transition trace 152 is connected to the middle voltage trace 150, and the right transition trace 152 is connected to the bottom voltage trace 150. In FIG. 6D, the left transition trace 152 is connected to the bottom voltage trace 150, the middle transition trace 152 is connected to the top voltage trace 150, and the right transition trace 152 is connected to the middle voltage trace. Note that one transition trace 152 can be connected to multiple voltage traces 150. Similarly, multiple transition traces 152 can be connected to the same voltage trace 150. One skilled in the art will recognize the various overlap and connection options.

[0052]

[0086] FIG. 6E is a schematic cross-sectional side view of a multi-layer flexible battery interconnect 100 including a battery cell 192 and a voltage trace 150, according to some examples. Here, the voltage trace 150 is disposed as a separate layer (separate from other conductive layers) in the multi-layer flexible battery interconnect 100, e.g., stacked with other components. For example, a second insulating layer 120 is disposed between at least a portion of the voltage trace 150 and the second conductive layer 140. The second insulating layer 120 includes an opening through which the voltage trace 150 can connect with one of the bus bars formed by the conductive layers. FIG. 6E also shows a third insulating layer 160 that isolates the voltage trace 150 from the environment and supports the voltage trace 150 against the second insulating layer 120.

[0053]

[0087] 6F is a schematic cross-sectional side view of a multi-layer flexible battery interconnect 100 including a battery cell 192, a signal trace 158, and a sensor 159 connected to the signal trace 158, according to some examples. Various examples of the sensor 159 are within the scope, such as a thermocouple, a humidity sensor, a pressure sensor, etc. In some examples, the sensor 159 directly connects to one of the conductive layers, for example, the second conductive layer 140, as shown in FIG. 6F. [Example of interconnection of rectangular cells]

[0054]

[0088] Although the above examples of multi-layer flexible battery interconnects 100 are described in connection with cylindrical battery cells, many of the described features are also applicable to prismatic battery cells. FIG. 7A is a schematic top view of four prismatic battery cells 192 and illustrates the desired series connection of these batteries. Specifically, each battery cell 192 includes a first contact 194 and a second contact 195. Although FIG. 7A illustrates the alternating inversion positions of the prismatic battery cells 192 and the series connection of these cells, various other orientations and connections are within scope.

[0055]

[0089] FIG. 7B is a schematic top view of the four prismatic cells 192 of FIG. 7A and shows the second conductive layer 140 of the multi-layer flexible battery interconnect 100 disposed over and interconnecting the cells 192. The second conductive layer 140 is shown separately to illustrate the various features of this layer. Those skilled in the art will recognize that the second conductive layer 140 is part of the multi-layer flexible battery interconnect 100, which includes other components such as the first conductive layer 130, the first insulating layer 110, and the second insulating layer 120. The second insulating layer 120 is not shown. Those skilled in the art will also recognize that the second insulating layer 120 is disposed between the prismatic battery cells 192 and the second conductive layer 140 and includes openings aligned with the first contact 194 and the second contact 195 of each cell.

[0056]

[0090] FIG. 7C is a schematic top view of the four prismatic cells 192 of FIG. 7A , showing the first conductive layer 130 and the second conductive layer 140 of the multi-layer flexible battery interconnect 100 that are disposed over and interconnect the cells. The first conductive layer 130 is thicker than the second conductive layer 140. Thus, only the second conductive layer 140 is directly welded to the first contacts 194 and the second contacts 195 of the cells. Furthermore, the footprint of the first conductive layer 130 is smaller than the footprint of the second conductive layer 140. The second conductive layer 140 extends beyond the first conductive layer 130, particularly over the battery contacts. This feature allows the second conductive layer 140 to be welded to these battery contacts without interference from the first conductive layer 130. As the second conductive layer 140 is a thinner layer, less energy is required for welding, thereby avoiding excessive temperatures at the battery contacts. At the same time, the first conductive layer 130 provides additional electrical conductivity between the battery contacts without directly connecting to those contacts.

[0057]

[0091] FIG. 7D is a schematic top view of the four prismatic cells 192 of FIG. 7A, showing the entire multi-layer flexible battery interconnect 100 disposed on the cells. Specifically, FIG. 7D shows various openings in the first insulating layer 110, which are used to make various connections. An internal weld opening 118 is disposed on both the first conductive layer 130 and the second conductive layer 140, and is used to weld the two conductive layers together. An external weld opening 119 is disposed on the second conductive layer 140 (but not on the first conductive layer 130), and is used to weld the second conductive layer 140 to a battery contact. [Example of manufacturing a multi-layer flexible battery interconnect]

[0058]

[0092] 8 is a process flow diagram corresponding to a method 800 of manufacturing a multi-layer flexible battery interconnect 100, according to some examples. Various examples of the multi-layer flexible battery interconnect 100 are described above.

[0059]

[0093] In some examples, the method 800 includes patterning (block 810) the first insulating layer 110. An example of the first insulating layer 110 is shown in FIG. 10A. For example, various openings 117 can be formed in a continuous base film to obtain the first insulating layer 110. These openings 117 provide access to the flexible tabs 142 in the multi-layer flexible battery interconnect 100.

[0060]

[0094] Returning to FIG. 8, in some examples, the method 800 includes patterning the first conductive layer 130 (block 812). One example of the first conductive layer 130 is shown in FIG. 10B. For example, separate portions of the first conductive layer 130 can be formed from a continuous base metal foil to produce the first conductive layer 130. Each of these portions represents a different bus of the multilayer flexible battery interconnect 100 (e.g., FIG. 10B showing three different portions). In some examples, the first conductive layer 130 is supported on a temporary substrate (e.g., also used to pattern the first conductive layer 130) at least before the first conductive layer 130 is laminated to the first insulating layer 110. Once the first conductive layer 130 becomes the first insulating layer 110, the first insulating layer 110 provides support to the separate portions of the first conductive layer 130.

[0061]

[0095] Returning to FIG. 8, in some examples, the method 800 includes laminating the first conductive layer 130 to the first insulating layer 110 (block 814). For example, the first insulating layer 110 may include an adhesive surface to which the first conductive layer 130 adheres. An example of a subassembly including the first conductive layer 130 and the first insulating layer 110 is shown in FIG. 10C. As discussed above, the first insulating layer 110 provides support to the isolated portions of the first conductive layer 130.

[0062]

[0096] Returning to FIG. 8, in some examples, the method 800 includes patterning the second insulating layer 120 (block 820). One example of the second insulating layer 120 is shown in FIG. 10D. For example, various openings can be formed in a continuous base film to obtain the second insulating layer 120. Some openings 127 provide access to the flexible tabs 142 in the multi-layer flexible battery interconnect 100. Other openings are weld openings 122 and are used to weld the first conductive layer 130 to the second conductive layer 140 as described above.

[0063]

[0097] Returning to FIG. 8, in some examples, the method 800 includes patterning the second conductive layer 140 (block 822). One example of the second conductive layer 140 is shown in FIG. 10E. For example, separate portions of the second conductive layer 140 can be formed from a continuous base metal foil to produce the second conductive layer 140. Each of these portions represents a different bus of the multi-layer flexible battery interconnect 100. Additionally, each portion includes a flexible tab 142 for making an electrical connection to a battery cell. In some examples, the second conductive layer 140 is supported on a temporary substrate (e.g., also used for patterning) at least before the second conductive layer 140 is laminated to the second insulating layer 120.

[0064]

[0098] Returning to Figure 8, in some examples, the method 800 includes laminating the second conductive layer 140 to the second insulating layer 120 (block 824). For example, the second insulating layer 120 may include an adhesive surface to which the second conductive layer 140 adheres. An example of a subassembly comprising the second conductive layer 140 and the second insulating layer 120 is shown in Figure 10F. The second conductive layer 140 supports the separated portions of the second conductive layer 140 after this lamination operation.

[0065]

[0099] Returning to FIG. 8, in some examples, the method 800 includes laminating (block 830) a stack including the first conductive layer 130 and the second conductive layer 140. The first conductive layer 130 may be pre-laminated to the first insulating layer 110, while the second conductive layer 140 may be pre-laminated to the second insulating layer 120. Thus, the first insulating layer 110 and the second insulating layer 120 are also part of this lamination stack. For example, as shown, for example, in FIG. 2E, the portions of the first insulating layer 110 and the second insulating layer 120 that extend beyond the first conductive layer 130 and the second conductive layer 140 may adhere to each other during this operation. The combination of the first insulating layer 110, the first conductive layer 130, the second conductive layer 140, and the second insulating layer 120 may be referred to as a primary stack.

[0066]

[0100] 8, in some examples, the method 800 includes welding (block 832) the first conductive layer 130 to the second conductive layer 140. As described above with reference to Figures 2A and 2B, the second insulating layer 120 includes a plurality of weld openings 122 that are used to access the second conductive layer 140 and weld the second conductive layer 140 to the first conductive layer 130, thereby forming the weld locations 109. For example, laser welding may be used for this purpose.

[0067]

[0101] If the multi-layer flexible battery interconnect 100 includes voltage or signal traces provided as separate layers, for example as shown generally in Figures 6E and 6F, the method 800 may include patterning the third insulating layer 160 (block 840), patterning the voltage traces 150 (block 842), and forming an additional stack (block 844) by laminating the voltage traces 150 to the third insulating layer 160. The method 800 then proceeds to laminate this additional stack to the primary stack (block 850) and, in some examples, welding the voltage traces 150 to one of the conductive layers, for example the second conductive layer 140, which may be thinner and may be disposed near the voltage traces 150 on top of the first conductive layer 130 (block 852).

[0068]

[0102] FIG. 9 is a process flow diagram corresponding to another method 900 of manufacturing a multi-layer flexible battery interconnect 100. Some operations of the method 900 may be similar to corresponding operations of the method 800 described above. In some examples, the method 900 includes patterning the first insulating layer 110 (block 910), as represented by block 810 and similar to the operations described above. The method 900 includes patterning the first conductive layer 130 (block 912), as represented by block 812 and similar to the operations described above. The method 900 proceeds to laminating the first insulating layer 110 to the first conductive layer 130 (block 914), as represented by block 814 and similar to the operations described above. Additionally, the method 900 proceeds to patterning the second conductive layer 140 (block 920), as represented by block 822 and similar to the operations described above. The method 900 then proceeds to laminate (block 923) a stack including the first insulating layer 110, the first conductive layer 130, and the second conductive layer 140. Note that the second insulating layer 120 is not part of this stack. The second insulating layer 120 will be added later. If the second conductive layer 140 can be supported against the first insulating layer 110 and the first conductive layer 130 using a portion of the second conductive layer 140 that extends beyond the boundary of the first conductive layer 130 and is adhered to the first insulating layer 110, e.g., a portion of the flexible tab 142 that overlaps the first insulating layer 110, the method 900 includes patterning the second insulating layer 120 (block 930) (similar to the operations represented by block 820 and described above), followed by laminating the second insulating layer 120 into a stack including the first insulating layer 110, the first conductive layer 130, and the second conductive layer 140 (block 934), and welding the first conductive layer 130 and the second conductive layer 140 together (block 940). [Example of battery pack connection]

[0069]

[0103] FIG. 11A is a schematic diagram of a battery pack assembly 1100 according to some examples. The battery pack assembly 1100 includes an interconnect circuit 1110 and a battery 1150. Although FIG. 11A shows only one battery 1150, one skilled in the art would understand that the same interconnect circuit 1110 can be used to connect multiple batteries, for example, to interconnect the batteries and / or to connect to other components of the battery pack assembly 1100 (e.g., an inverter). The interconnect circuit 1110 includes a conductor 1120 and a first insulating layer 1111. The conductor 1120 may also be referred to as a conductive element. In some examples, the first insulating layer 1111 provides support to the conductor 1120. For example, the interconnect circuit 1110 can include multiple conductors, and the first insulating layer 1111 supports the conductors relative to each other (e.g., to prevent shorting and to guide the conductors to a desired location). The first insulating layer 1111 may also be used to insulate the conductors 1120 from other components, such as the battery 1150. In some examples, the interconnect circuit 1110 includes a second insulating layer 1112 such that at least a portion of the conductors 1120 is located between the first insulating layer 1111 and the second insulating layer 1112. An insulating layer may also be referred to as a dielectric layer or simply a dielectric. Various examples of dielectrics and conductive elements are described above.

[0070]

[0104] In some examples, the first insulating layer 1111 includes a first insulating layer opening 1113 that is used to allow a portion of the conductor 1120 to protrude when connecting to, for example, the battery 1150. Similarly, the second insulating layer 1112 may include a second insulating layer opening 1114 that is used to access, for example, the conductor 1120. For example, the second insulating layer opening 1114 may be used to access a portion of the conductor 1120 through the first insulating layer opening 1113 to make electrical contact, for example, with the battery 1150.

[0071]

[0105] In some examples, the conductor 1120 comprises a conductor trace 1128, a conductor neck 1126, and a conductor tab 1122, with the conductor neck 1126 disposed between and connecting the conductor trace 1128 and the conductor tab 1122. The conductor trace 1128 extends from the first insulating layer opening 1113 and is used to make another electrical connection to the conductor 1120. The conductor tab 1122 is mechanically and electrically connected (e.g., welded) to the battery 1150, as described further below. The conductor neck 1126 provides flexibility to the conductor tab 1122, for example, allowing the conductor tab 1122 to be positioned out of plane relative to the conductor trace 1128. For example, FIG. 11A shows the conductor tab 1122 extending beyond the opposite side of the first insulating layer 1111 relative to the conductor trace 1128. In this example, the conductor neck 1126 protrudes through the first insulating layer opening 1113. Further, in some examples, the conductor neck 1126 allows the battery 1150 to move (e.g., to a certain extent) relative to the rest of the interconnect circuit 1110 without breaking the connection between the conductor tab 1122 and the battery 1150.

[0072]

[0106] In some examples, the battery 1150 includes a battery case 1154, a battery cap 1152, and a battery cap insulator 1156. One of ordinary skill in the art would understand that the battery 1150 includes additional components (e.g., electrodes, electrolyte) not shown in FIG. 11A. The battery cap insulator 1156 supports the battery cap 1152 against the battery case 1154 and insulates the battery cap 1152 from the battery case 1154. In some examples, the battery case 1154 can act as one terminal of the battery 1150 while the battery cap 1152 can act as another terminal. Although FIG. 11A shows the conductor 1120 connected to the battery cap 1152, one of ordinary skill in the art would understand that in other examples, the conductor 1120 can be connected to the battery case 1154, for example, to a shoulder of the battery case 1154 that extends around the battery cap 1152 and over the battery cap insulator 1156.

[0073]

[0107] In some examples, the conductor tab 1122 includes a connection portion 1124 that has a thickness that is less than the thickness of the remainder of the conductor tab 1122, as shown, for example, in Figures 11A and 11B. In other examples, the conductor tab 1122 includes one or more tab openings 1130, as shown, for example, in Figures 12A and 12B. The conductor tab 1122 is welded to the battery 1150 around the connection portion 1124 or the one or more tab openings 1130. Each of these examples is described in more detail below.

[0074]

[0108] As mentioned above, FIGS. 11A and 11B show an example of a battery pack assembly 1100 in which the conductor tab 1122 includes a connection portion 1124 having a thickness that is less than the thickness of the remaining portion of the conductor tab 1122. For example, the conductor 1120 is formed from the same metal sheet, in which case all components of the conductor 1120 (e.g., the conductor trace 1128, the conductor neck 1126, and the conductor tab 1122) have the same thickness. Thus, the thickness of the conductor tab 1122 may be selected based on reasons related to the current carrying properties of other components of the conductor 1120, such as the conductor trace 1128. In some examples, the main thickness of the conductor 1120 is at least 100 micrometers, or even at least 200 micrometers. Welding such a thick sheet to the battery 1150 requires significant heating of the conductor 1120 and the battery 1150, which may be undesirable, at least from the battery's perspective. For example, the battery 1150 includes various components (e.g., insulators, separators, electrolytes) that may be sensitive to high temperatures. By forming an electrical connection to the battery 1150 using a connecting portion 1124 having a much thinner thickness, high temperature exposure when welding the connecting portion 1124 to the battery 1150 can be substantially reduced.

[0075]

[0109] In some examples, the thickness of the connection portion 1124 is at least two times, or three times, or even four times smaller than the thickness of the remaining portion of the conductor tab 1122. In some examples, the connection portion 1124 is circular, for example as shown in FIG. 11C. For example, the shape (and size) of the connection portion 1124 may be the same as the battery part to which the connection portion 1124 is welded. For example, the connection portion 1124 welded to the battery cap 1152 may have a circular footprint. In some examples, the connection portion 1124 is smaller than the area of ​​the battery part to which it is welded. More specifically, the size of the connection portion 1124 may be determined by the welding requirements, for example, the size of the weld nugget. In the same or other examples, the remaining portion of the conductor tab 1122 forms an edge shoulder 1123 surrounding the connection portion 1124. Note that the thickness of the edge shoulder 1123 is the same as the main thickness of the conductor 1120 and is larger than the thickness of the connection portion 1124.

[0076]

[0110] 12A and 12B illustrate an example of a battery pack assembly 1100 in which the conductor tab 1122 includes one or more tab openings 1130. Similar to the connection portion 1124 described above, the tab openings 1130 can reduce the power required to weld the conductor tab 1122 to the battery 1150. For example, the tab openings 1130 include sidewalls that increase the surface area of ​​the conductor tab 1122 available for welding.

[0077]

[0111] In some examples, each of the one or more tab openings 1130 has an elongated shape, as shown, for example, generally in Figure 12A. More specifically, the elongated shape extends perpendicular to the conductor neck 1126, and more specifically, to a central axis of the conductor neck 1126. As shown in Figure 12A, the conductor neck 1126 extends along the X-axis, while the elongated shape of the tab opening 1130 extends along the Y-axis.

[0078]

[0112] 12B, in some examples, the conductor tab 1122 further comprises a weld nugget 1134 disposed within each of the one or more tab openings 1130 and in direct contact with the battery 1150. The weld nugget 1134 increases the interface area between the conductor tab 1122 and the battery 1150 by utilizing more of the sidewalls 1133 of the tab openings 1130. In some examples, the conductor tab 1122 is welded to the battery 1150 using a resistance welder, a laser welder, and / or an ultrasonic welder. However, other attachment forms (e.g., conductive adhesives) are within scope.

[0079]

[0113] 13A, in some examples, the interconnect circuit 1110 is provided as a substantially planar structure disposed on the battery 1150. More specifically, prior to forming a connection to the battery 1150, the conductor tab 1122 of each conductor 1120 is substantially flush with other components of the conductor 1120 (and other conductors), such as the conductor trace 1128 and the conductor neck 1126. When connecting to the battery 1150, each conductor neck 1126 is bent such that the conductor tab 1122 protrudes through the first insulating layer 1111 to reach the battery 1150. For example, a press fixture as shown in FIG. 13A can be used for this purpose. It should be noted that this conductor neck bending operation can be performed simultaneously for dozens or even hundreds of these conductor necks, e.g., the same interconnect circuit 1110 can be used to connect to multiple batteries of the same battery pack. Additionally, the thickness of the conductor necks 1126 (e.g., greater than 100 micrometers, or even greater than 200 micrometers) can be a significant factor in determining the force required to simultaneously bend these multiple conductor necks to form a connection with the battery. Finally, the material used for the conductors 1120 (e.g., aluminum) can have a significant flexural modulus, resulting in a high resistance to bending. All these factors indicate that a large force is required to bend the conductor necks 1126 when forming a connection to the battery 1150, which is shown diagrammatically in FIG. 13B. Large forces require heavy equipment and may damage some components of the overall assembly (e.g., especially if misaligned).

[0080]

[0114] For example, FIG. 13B shows a conductor neck 1126 that extends beyond the end of the first insulating layer 1111 and protrudes through the first insulating layer opening 1113. The conductor neck 1126 includes a first bend 1131 adjacent to the conductor trace 1128 and a second bend 1132 adjacent to the conductor tab 1122. These bends are further shown in FIG. 13C and FIG. 13. In some examples, the conductor neck 1126 includes one or more first partial openings 1141 at the first bend 1131 and / or one or more second partial openings 1142 at the second bend 1132. In particular, FIG. 13C shows an example in which five first partial openings 1141 are disposed on an inner radius of the first bend 1131. FIG. 13D shows another example in which seven first partial openings 1141 are disposed on an outer radius of the first bend 1131. In some examples, the first partial opening 1141 may be disposed on both sides of the first bend 1131. Similarly, the second partial opening 1142 may be disposed on the inner radius of the second bend 1132, on the outer radius of the second bend 1132, or both. Additionally, any number of partial openings is within the scope (e.g., 1, 2, 3, 4, etc.). Increasing the number of partial openings may help improve the flexibility of the conductor neck 1126 while keeping the cross-section of each partial opening relatively small. It should be noted that increasing the cross-sectional area of ​​the partial openings increases the resistance of the conductor neck 1126 and decreases the mechanical strength of the conductor neck 1126. In some examples, the first partial opening 1141 comprises one or more slits extending across (between opposing edges) the conductor neck 1126. In more specific examples, the multiple slits have a depth of between about 10% and 40%, more specifically between 15% and 35%, or even between 20% and 30% of the total thickness of the conductor neck 1126.

[0081]

[0115] In some examples, the conductor neck 1126 can operate as a fusible link, for example, as shown in Figures 14A-14C. Specifically, the conductor neck 1126 includes one or more partial openings 1160 disposed away from the conductor trace 1128 and the conductor tab 1122. For example, the partial openings 1160 are disposed on a portion of the conductor neck 1126 having a constant width (W1), for example, as shown in Figure 14A. Each of the one or more partial openings 1160 has a controlled depth and a controlled width such that the conductor neck 1126 can operate as a fusible link. The depth (D) and width (W2) of each opening 1160 in combination with the width (W1) of the conductor neck 1126, the thickness (T) of the conductor neck 1126, and the material of the conductor neck 1126 define the resistance and current rating of the fusible link. In other words, each opening 1160 corresponds to the smallest cross-section of the conductor neck 1126. The cross-sectional area and length are controlled by various parameters listed above, e.g., cross-sectional area=W1*(TD), while the cross-sectional length is the same as the width (W2) of the opening 1160. In some examples, each of the one or more sub-openings 1160 extends across the conductor neck 1126. [Conclusion]

[0082]

[0116] The methods and apparatus described herein can be extended to the interconnection of electronic devices in general, including but not limited to integrated circuits, resistors, capacitors, inductors, solar cells, and other electronic components and / or power sources.

[0083]

[0117] It should be understood that the above description is for illustrative purposes, not limiting. For example, the above-described examples (and / or aspects thereof) can be used in combination with each other. Moreover, many modifications can be made to adapt a particular situation or material to the teachings presented herein. The dimensions, types of materials, orientations of the various components, and numbers and locations of the various components described herein are intended to define parameters of some examples, but are in no way limiting, and are merely examples. Many examples and modifications within the spirit and scope of the claims will become apparent to those skilled in the art upon reviewing the above description.

Claims

1. 1. A multi-layer flexible interconnect for interconnecting batteries in a battery pack, comprising: A first insulating layer; A second insulating layer; a first conductive layer disposed between the first insulating layer and the second insulating layer and in direct contact with the first insulating layer; a second conductive layer disposed between and in direct contact with the first conductive layer and the second insulating layer; Equipped with the first conductive layer has a thickness of at least 300 micrometers; the first insulating layer and the second insulating layer are directly adhered to one another to form a boundary around a portion of the first conductive layer and the second conductive layer to maintain the orientation of the first conductive layer and the second conductive layer relative to one another; Multi-layer flexible interconnect.

2. The first conductive layer and the second conductive layer are welded at a plurality of welding positions spaced apart from each other. The multi-layer flexible interconnect of claim 1 .

3. The second insulating layer has a weld opening, Each of the plurality of weld locations is disposed within one of the weld openings. The multi-layer flexible interconnect of claim 2.

4. The first conductive layer has a uniform thickness throughout the boundary of the first conductive layer; the second conductive layer has a uniform thickness across the boundary of the second conductive layer; The multi-layer flexible interconnect of claim 1 .

5. At least one of the first conductive layer and the second conductive layer includes a flexible tab, each tab including a contact pad for connecting to the first conductive layer and the second conductive layer, the tab protruding beyond the boundary of the first insulating layer and the second insulating layer. The multi-layer flexible interconnect of claim 1 .

6. At least one of the first insulating layer and the second insulating layer is made of polyethylene. The multi-layer flexible interconnect of claim 1 .

7. The first insulating layer and the second insulating layer are both made of polyethylene. The multi-layer flexible interconnect of claim 1 .

8. The polyethylene of the first insulating layer forms a first adhesive sublayer facing the second insulating layer; the polyethylene of the second insulating layer forms a second adhesive sublayer facing and directly adhering to the first insulating layer, thereby forming a boundary around the first conductive layer and a portion of the second conductive layer; The multi-layer flexible interconnect of claim 7.

9. The first adhesive sublayer is further adhered to the first conductive layer; The second adhesive sublayer is further adhered to the second conductive layer. The multi-layer flexible interconnect of claim 8.

10. The first insulating layer has a weld opening exposing a portion of the first conductive layer. The multi-layer flexible interconnect of claim 1 .

11. Further comprising a third conductive layer and a third insulating layer; the third conductive layer is disposed between the second insulating layer and the third insulating layer, the third insulating layer isolating the third conductive layer from the environment and supporting the third conductive layer relative to the second insulating layer; The multi-layer flexible interconnect of claim 1 .

12. The third conductive layer is made of aluminum. The multi-layer flexible interconnect of claim 11.

13. The first conductive layer having a thickness of at least 350 micrometers. The multi-layer flexible interconnect of claim 1 .

14. The first conductive layer and the second conductive layer have the same thickness. The multi-layer flexible interconnect of claim 1 .

15. The first conductive layer and the second conductive layer have different thicknesses. The multi-layer flexible interconnect of claim 1 .

16. Further comprising a connector having a terminal connected to the first conductive layer and the second conductive layer. The multi-layer flexible interconnect of claim 1 .

17. The terminals of the connector are connected to the first conductive layer and the second conductive layer using transition traces having a different composition than the first conductive layer and the second conductive layer.

20. The multi-layer flexible interconnect of claim 16.

18. At least one of the first conductive layer and the second conductive layer is formed from aluminum. The multi-layer flexible interconnect of claim 1 .

19. The method of claim 1, wherein the first conductive layer and the second conductive layer are both formed from aluminum. The multi-layer flexible interconnect of claim 1 .

20. The multi-layer flexible interconnect is configured to support a current of greater than 100 A. The multi-layer flexible interconnect of claim 1 .

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