CN117691306A - Traction battery pack with electrically connected battery cells and battery cell joining method - Google Patents

Abstract

The present disclosure provides "traction battery packs with electrically connected battery cells and battery cell joining methods." One method includes electrically connecting a first battery cell to a second battery cell by joining a first tab terminal of the first battery cell to a second tab terminal of the second battery cell. The method also includes compressing the first tab terminal and the second tab terminal after joining. A battery assembly includes a first tab terminal extending from a first housing of a first battery cell and a second tab terminal extending from a second housing of a second battery cell. The second tab terminal is directly connected to the first tab terminal. The method also includes an insulating layer enclosing the first and second tab terminals against the first and second housings.

Description

Traction battery pack with electrically connected battery cells and battery cell joining method

Cross-references to related applications

This application claims priority from U.S. Provisional Application No. 63/403445, filed on September 2, 2022 and incorporated herein by reference.

Technical field

The present disclosure relates generally to battery cells electrically connected to traction batteries, and in particular to pouch-type battery cells having tab terminals.

Background technique

Electric vehicles differ from conventional motor vehicles in that they are selectively driven using one or more electric motors powered by traction batteries. Instead of or in addition to internal combustion engines, electric motors can power electrified vehicles. A traction battery for an electric vehicle may include battery cells having a housing arranged in one or more arrays.

Contents of the invention

In some aspects, the technology described herein relates to a method that includes: to electrically connect a first battery cell to a second battery cell, engaging a first tab terminal of the first battery cell to a second battery cell. a second tab terminal of the battery cell; and after joining, compressing the first tab terminal and the second tab terminal.

In some aspects, the technology described herein relates to a method wherein joining includes soldering a first tab terminal to a second tab terminal.

In some aspects, the technology described herein relates to a method in which first and second tab terminals are disconnected from the bus bar after engagement and compression.

In some aspects, the technology described herein relates to a method further comprising: prior to joining the tab terminals of the second battery cell to the tab terminals of the first battery cell, first connecting the second battery cell to the tab terminal of the first battery cell. The tab terminals of the battery cell are folded over the tab terminals of the first battery cell.

In some aspects, the technology described herein relates to a method, wherein the first battery cell and the second battery cell are pouch battery cells.

In some aspects, the technology described herein relates to a method in which a first tab terminal extends from a first housing of a first battery cell and a second tab terminal extends from a second housing of a second battery cell. , wherein the first tab terminal and the second tab terminal are folded and compressed toward the first and second housings during compression.

In some aspects, the technology described herein relates to a method further comprising covering a first tab terminal and a second tab terminal with an insulating layer prior to compressing.

In some aspects, the technology described herein relates to a method wherein a first battery cell and a second battery cell are within a group of battery cells disposed along an axis, with an insulating layer at a first axial end of the group directly adhered to the casing of the battery cells at 1 and at the opposite second end of the set.

In some aspects, the technology described herein relates to a method that further includes pressing against an insulating layer during compression to force air out of a region between the insulating layer and first and second housings.

In some aspects, the technology described herein relates to a method in which the cross-sectional area of a first tab terminal is different from the cross-sectional area of a second tab terminal.

In some aspects, the technology described herein relates to a method further comprising: to electrically connect a third battery cell to a second battery cell, engaging a third tab terminal of the third battery cell to a third battery cell. A first tab terminal of a battery cell, the first tab terminal being joined to a second tab terminal by a first weld seam, the first tab terminal being joined to a second weld seam that is separate and distinct from the first weld seam. Third tab terminal.

In some aspects, the technology described herein involves a method wherein the first weld and the second weld are laser welds.

In some aspects, the technology described herein relates to a method in which a first tab terminal and a second tab terminal are connected in series with a third tab terminal, wherein the third tab terminal has a greater cross-sectional area than the first tab terminal The cross-sectional area is larger than the cross-sectional area of the second tab terminal.

In some aspects, the technology described herein relates to a battery assembly that includes: a first tab terminal extending from a first housing of a first battery cell; a second a tab terminal extending from the second housing of the second battery cell, the second tab terminal being directly connected to the first tab terminal; and an insulating layer abutting against the first The housing and the second housing enclose the first tab terminal and the second tab terminal.

In some aspects, the technology described herein relates to a battery assembly in which a first tab terminal and a second tab terminal are directly connected to each other by at least one weld.

In some aspects, the technology described herein relates to a battery assembly in which a first tab terminal and a second tab terminal are disconnected from a busbar.

In some aspects, the technology described herein relates to a battery assembly in which first and second tab terminals are folded and compressed against first and second housings when enclosed by an insulating layer.

In some aspects, the technology described herein relates to a battery assembly, wherein a first battery cell and a second battery cell are within a group of battery cells disposed along an axis, with an insulating layer in a first axial direction of the group. Adhering directly to the housing of the battery cell at one end and directly to the housing of the battery cell at an opposite second end of the set.

In some aspects, the technology described herein relates to a battery assembly, wherein the first battery cell and the second battery cell are pouch battery cells.

In some aspects, the technology described herein relates to a battery assembly in which a first tab terminal has a cross-sectional area that is different than a second tab terminal.

The embodiments, examples and alternatives of the preceding paragraphs, claims or the following description and drawings, including any of their various aspects or corresponding individual features, may be taken independently or in any combination. Features described in connection with one embodiment apply to all embodiments unless such features are incompatible.

Description of the drawings

The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The drawings accompanying the detailed description may be briefly described as follows:

Figure 1 shows a side view of an exemplary electrified vehicle.

Figure 2 shows an enlarged perspective view of the battery pack of the electric vehicle from Figure 2 and shows a number of arrays of battery packs in a highly schematic form.

3 shows a perspective view of a battery cell from one of the arrays in the battery pack of FIG. 2 .

Figure 4 shows a cross-sectional view taken along line 4-4 in Figure 2 prior to joining the tab terminals of the battery cells within the array.

Figure 5 shows a cross-sectional view of Figure 4 after the tab terminal has been folded.

6 illustrates a close-up view of a single tab terminal coupled to two additional tab terminals in accordance with another exemplary aspect of the present disclosure.

FIG. 7 shows the cross-sectional view of FIG. 5 after the tab terminals are engaged.

Figure 8 shows yet another exemplary embodiment in which tab terminals having different lengths are joined by welding seams.

FIG. 9 shows the cross-sectional view of FIG. 7 after the tab terminal is covered with an insulating layer.

Figure 10 shows the cross-sectional view of Figure 9 after the tab terminal has been compressed against the casing of the battery cell and held in the compressed position by the insulating layer.

Detailed ways

A battery pack assembly may include a housing assembly housing a plurality of battery cell arrays. Each of the arrays may include a plurality of battery cells. The battery cells are electrically connected together.

This disclosure details exemplary methods of electrically connecting battery cells together without the use of bus bars. The present disclosure also details battery assemblies that electrically connect battery cells together without the use of bus bars.

Referring to FIG. 1 , an electric vehicle 10 includes a battery pack 14 , an electric motor 18 and wheels 22 . The battery pack 14 powers an electric motor 18 that converts electrical power into mechanical power to drive the wheels 22 .

In the exemplary embodiment, the battery pack 14 is secured to the underbody 26 of the electric vehicle 10 . In other examples, battery pack 14 may be located elsewhere on electrified vehicle 10 .

The electrified vehicle 10 is a pure electric vehicle. In other examples, electrified vehicle 10 is a hybrid electric vehicle that selectively uses torque provided by an internal combustion engine (in lieu of or in addition to an electric motor) to drive the wheels. Generally speaking, electrified vehicle 10 may be any type of vehicle having a battery pack.

Referring now to FIG. 2 , the battery pack 14 includes a plurality of arrays 30 held within a housing assembly 34 . In the exemplary embodiment, housing assembly 34 includes housing cover 38 and housing tray 42 . Housing cover 38 is secured to housing tray 42 to provide an interior area 44 for housing array 30 .

Each of the arrays 30 includes a plurality of battery cells 50 (or simply "cells") disposed along the array axis. The battery cells 50 are stacked side by side relative to each other along the array axis. Battery cells 50 store and supply electricity.

Although a specific number of arrays 30 is shown in the various figures of this disclosure, the battery pack 14 may include any number of arrays 30 with any number of cells 50 .

Figure 3 shows one of the battery cells 50, which in this example is a prismatic pouch battery cell. The battery cell 50 includes first and second tab terminals 54 , 58 extending from the housing 62 . In the example, housing 62 is a multi-layer structure including aluminum film layers and polymer portions.

In the past, terminals have been bonded to bus bars to electrically connect battery cells. In the exemplary battery pack 14, the busbars electrically connected to the terminals are omitted. The first tab terminal 54 and the second tab terminal 58 are instead joined to tab terminals of other battery cells 50 within the array 30 to provide the desired electrical connection. The first tab terminal 54 and the second tab terminal 58 are disconnected from any bus bars.

Referring to FIG. 4 , the first tab terminals 54 extending from the battery cells 50 in the first group 66 are electrically connected to each other and to the first tab terminals 54 extending from the battery cells 50 in the second group 70 . The first tab terminals 54 of the first set 66 may be positive and the first tab terminals 54 of the second set 70 may be negative.

In the exemplary embodiment, in preparation for electrically connecting the first tab terminal 54 , the first tab terminal 54 is folded and positioned within the clamping member 74 of the clamping assembly 78 , as shown in FIG. 5 . Clamping member 74 helps strengthen first tab terminal 54 for engagement. The peripheral area of the housing 62 can also be folded together with the first tab terminal 54 . In some examples, these areas of housing 62 may be trimmed or trimmed to facilitate folding.

After folding, the clamping member 74 is then actuated to compress and hold together the first tab terminals 54 of the first set 66 and the second set 70 . Clamping members 74 hold the first tab terminals 54 together in a position suitable for engagement.

In this example, a weld joins the first tab terminal 54 . Specifically, laser welds join the tab terminals. In other examples, the first tab terminal 54 is joined in other ways, such as by spot welding. In other examples, the first tab terminal 54 is engaged in other ways, such as by clamping them together with a clamping member 74 that is held together with the tab terminal 54 .

While the clamping member 74 retains the first tab terminal 54, the laser welding machine's electrode 82 moves to a position and applies a laser weld to engage the first tab terminal 54 at the desired location. The laser weld may extend through any number of first tab terminals 54 . That is, a single laser weld may join two of the first tab terminals 54 , three of the first tab terminals 54 , or another number of the first tab terminals 54 . In an example, the four tab terminals 54 of the first set 66 may be soldered directly to the four tab terminals 54 of the set 70 to avoid the need to stagger the tab end locations. After joining (here by laser welding), the clamping member 74 can be withdrawn, as shown in Figure 6.

In some examples, the first tab terminals 54 of the battery cells 50 within the array 30 may have different cross-sectional areas. The cross-sectional area can be varied to suit the desired current carrying capacity. For example, referring to FIG. 7 , laser weld S' joins two of the first tab terminals 54A to the first tab terminal 54B such that the first tab terminal 54A is connected in series to the first tab terminal 54B. The width W of the first tab terminal 54A and the first tab terminal 54B is the same. However, the thickness of the first tab terminal 54A is different from the thickness of the first tab terminal 54B. Specifically, the thickness of the first tab terminal 54A is T and the thickness of the first tab terminal 54B is 2T. Therefore, the cross-sectional area of the first tab terminal 54B is twice that of the first tab terminal 54A. Varying the cross-sectional area helps ensure that first tab terminal 54B has sufficient current carrying capability. For the purposes of this disclosure, cross-sectional area is the axial cross-sectional area.

FIG. 7 shows the first tab terminal 54 after engagement and after the clamping member 74 has been withdrawn. In this example, three laser weld seams S join the first tab terminal 54 . When joined in this manner, the first group 66 is connected in series to the second group 70. It is worth noting that the first tab terminals 54 are electrically connected together without using any bus bars.

Referring again to FIG. 3 and with continued reference to FIGS. 4 and 5 , to facilitate proper positioning of the first tab terminals 54 during bonding, the array 30 may include battery cells 50 having first tab terminals 54 of different sizes. For example, the first tab terminals 54 of the battery cells 50 at the axial ends of the array 30 may be longer in direction L than the first tab terminals 54 closer to the axial middle of the array 30 . The longer first tab terminal 54 extends further from the associated housing 62 than the shorter first tab terminal 54 . In another example, tab terminal 54 may include a fold that enables adjustment of the length of tab terminal 54 .

Adjusting the length can help provide a weld location in the desired area. Referring to Figure 8, the first tab terminals 54C are of different lengths because it is desired to perform soldering with only two tab terminals 54C rather than with more than two tab terminals 54C. It may be desirable to solder through both tab terminals 54C to prevent burning through the tab terminals 54C during soldering. In the example of Figure 8, each weld S' engages two tab terminals 54C.

Referring to FIG. 9 , in the exemplary embodiment, after soldering, an insulating layer 90 is applied to the array 30 to cover the first tab terminals 54 . The insulating layer 90 may protect the first tab terminal 54 from contact with surrounding structures or other conductors. The insulating layer 90 may facilitate tight packaging of the array 30 within the housing assembly 34 . For example, the insulating layer 90 may allow one array 30 to be positioned within the housing assembly 34 in close proximity to another array 30 without the two arrays 30 being inadvertently electrically connected to each other.

The insulating layer 90 may be a tape or polyester film attached directly to the housing 62 of the battery cell 50 at the first and second axial ends of the array 30 . The polyester film can be secured to the housing with adhesive. In another example, insulating layer 90 may be a shrink wrap or adhesive film that does not include adhesive.

The insulating layer 90 may help maintain the first tab terminal 54 in a compressed position against the housing 62 . In some examples, plunger 94 may move in direction D to press insulating layer 90 and first tab terminal 54 against housing 62 , as shown in FIG. 10 . After the adhesive holding the insulating layer 90 has cured, the plunger 94 can be removed. The insulating layer 90 then holds the first tab terminal 54 tightly against the housing 62 .

Omitting the busbars and compressing the tab terminals can provide an array with a reduced packaging envelope compared to an array with busbars. The reduced packaging envelope can lead to higher density battery systems.

The preceding description is illustrative in nature and not restrictive. Changes and modifications to the disclosed examples that may become apparent to those skilled in the art do not necessarily depart from the essence of the disclosure. Therefore, the scope of protection given to this disclosure can only be determined by studying the following claims.

Claims (15)

1. A method, comprising:

in order to electrically connect a first battery cell to a second battery cell, a first tab terminal of the first battery cell is joined to a second tab terminal of the second battery cell; and

after the engagement, the first tab terminal and the second tab terminal are compressed.

2. The method of claim 1, wherein the bonding comprises welding the first tab terminal to the second tab terminal.

3. The method of claim 1, further comprising: the tab terminal of the second battery cell is folded over the tab terminal of the first battery cell prior to joining the tab terminal of the second battery cell to the tab terminal of the first battery cell.

4. The method of claim 1, wherein the first tab terminal extends from a first housing of the first battery cell and the second tab terminal extends from a second housing of the second battery cell, wherein the first tab terminal and the second tab terminal are folded and compressed toward the first housing and the second housing during the compressing, and optionally the method further comprises covering the first tab terminal and the second tab terminal with an insulating layer prior to the compressing.

5. The method of claim 4, wherein the first battery cell and the second battery cell are within a set of battery cells disposed along an axis, the insulating layer being directly adhered to a housing of a battery cell at a first axial end of the set of battery cells and directly adhered to a housing of a battery cell at an opposite second end of the set of battery cells.

6. The method of claim 4, further comprising pressing against the insulating layer during the compressing to force air out of a region between the insulating layer and the first and second housings.

7. The method of claim 1, further comprising: in order to electrically connect a third battery cell to the second battery cell, a third tab terminal of the third battery cell is joined to the first tab terminal of the first battery cell, the first tab terminal is joined to the second tab terminal with a first weld, the first tab terminal is joined to the third tab terminal with a second weld that is separate and distinct from the first weld, and optionally, wherein the first weld and the second weld are laser welds.

8. The method of claim 7, wherein the first tab terminal and the second tab terminal are connected in series with the third tab terminal, wherein a cross-sectional area of the third tab terminal is greater than a cross-sectional area of the first tab terminal and greater than a cross-sectional area of the second tab terminal.

9. A battery assembly, comprising:

a first tab terminal extending from a first housing of a first battery cell;

a second tab terminal extending from a second housing of a second battery cell, the second tab terminal being directly connected to the first tab terminal; and

an insulating layer, the insulating layer closing the first tab terminal and the second tab terminal against the first housing and the second housing.

10. The battery assembly of claim 9, wherein the first tab terminal and the second tab terminal are directly connected to each other by at least one weld.

11. The battery assembly of claim 9, wherein the first tab terminal and the second tab terminal are folded and compressed against the first housing and the second housing when enclosed by the insulating layer.

12. The battery assembly of claim 9, wherein the first battery cell and the second battery cell are within a set of battery cells disposed along an axis, the insulating layer being directly adhered to the housing of the battery cell at a first axial end of the set of battery cells and directly adhered to the housing of the battery cell at an opposite second end of the set of battery cells.

13. The method of claim 1 or the battery assembly of claim 11, wherein the first battery cell and the second battery cell are pouch battery cells.

14. The method of claim 1 or the battery assembly of claim 11, wherein a cross-sectional area of the first tab terminal is different than a cross-sectional area of the second tab terminal.

15. The method of claim 1 or the battery assembly of claim 11, wherein the first tab terminal and the second tab terminal are disconnected from a bus bar.