Method for manufacture of battery pouch terminals

The present invention relates to a method and apparatus for the bending of battery terminals in preparation for the ultrasonic welding together of a stack of battery terminals with an interconnect member to form a battery pack.

Rechargeable energy storage systems for motor vehicles are assembled by electrically connecting together a plurality of individual battery cells. For example, lithium-ion battery cells typically include a soft housing pouch having a positive terminal and a negative terminal extending outwardly from the pouch. These battery cells are stacked in a battery case to bring the positive terminals together and the negative terminals together, thereby creating a stack of terminals to make a parallel electrical connection between the individual cells. Each terminal must have a precise bent shape in order to properly connect with the adjacent terminals and enable the subsequent ultrasonic welding together of the terminal stacks.

It would be desirable to provide a new and improved method for precise and economical bending of the battery pouch terminals in a manner that safeguards against injury to the pouches and prevents the inadvertent flow of electric current between the positive and negative terminals during the manufacturing operations.

A method is provided for manufacturing battery pouches for the subsequent welding together of a stack of battery terminals with an interconnect member to form a battery pack. According to the method, a plurality of pouches containing energy storage medium and having positive terminals and negative terminals extending therefrom are supported side by side in a pouch supporting fixture and lids are lowered to clamp the pouches against movement. The terminals are clamped against movement by clamping the terminals at the bases thereof. Then the end portions of the terminals are bent by die mechanisms to provide an offset shape in each terminal by which when the pouches are stacked adjacent one another, the positive terminals will contact one another and the negative terminals will contact one another. The clamping and bending are performed in a way that prevents the flow of electrical current between the positive and negative terminals.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

The present invention will become more fully understood from the detailed description and the accompanying drawings.

FIG. 1 is an end view of a battery pack of and having parts broken away to show the plurality of individual battery pouches supported in a battery housing and the shape of the terminals that are to be ultrasonically welded to ane interconnect bar.

FIG. 2 is a perspective view of the battery pack and an ultrasonic welding device for welding battery terminals to an interconnect bar.

FIG. 3 is a perspective view of an apparatus for automated bending of the terminals that project from the individual battery pouches.

FIG. 4 is a partial fragmentary view of FIG. 3 showing the open position of a nesting fixture for holding an individual pouch and supporting the terminals thereof.

FIG. 5 is a view similar to FIG. 6 but shows the nesting fixture in the closed position supporting the pouch and the terminals for bending.

FIG. 6 is a section view taken in the direction of Arrows 6 - 6 of FIG. 5 .

FIGS. 7A , 7 B, and 7 C show a set of terminal bending dies and the progression of their operation.

FIGS. 8A , 8 B, and 8 C show another set of terminal bending dies and the progression of their operation.

FIGS. 9A , 9 B, and 9 C show a third set of terminal bending dies and their progressive operation.

The following description of certain exemplary embodiments is exemplary in nature and is not intended to limit the invention, its application, or uses.

Referring to FIG. 1 , it is seen that a battery pack or module, generally indicated at 8 , has a plurality of individual battery cell pouches 10 , 12 , 14 , 16 , 18 , and 20 are stacked within a battery case 26 having a lid 28 . Each of these battery cell pouches is a flexible bag-like container of lithium ion or other energy storage medium. The pouches are constructed of a relatively flexible material such as foil. The pouches are supported and separated in their stacked positions of FIG. 1 by support frames 22 , as well insulators, heat exchangers, and other structures that are not shown in the drawing.

The battery cell pouch 16 is typical and includes a positive terminal 38 A that extends out of the pouch 16 . Also, as shown in FIG. 2 , a negative terminal 40 A extends out of the pouch 16 . The positive terminal 38 A is typically copper with a nickel coating and has a thickness of 0.2 mm. The negative terminal 40 A is typically made of aluminum and has a thickness of approximately 0.2 mm. Thus, it will be understood that each battery cell pouch has both a negative terminal and a positive terminal that projects outwardly of the foil pouch.

As best seen in FIG. 1 , the positive terminals 38 A, 38 B and 38 C of the individual pouches 16 , 18 and 20 pass through an opening 46 in the lid 28 . The positive terminals 38 A, 38 B, and 38 C of the three pouches are juxtaposed together to create a terminal stack 44 to be welded to an interconnect member or board 50 . The interconnect member 50 is generally U-shaped with a base 52 and upstanding legs 54 and 56 . As seen in FIG. 2 , the base 52 has stakes 60 and 62 struck downward therefrom which will be imbedded in the case of the battery so that the interconnect member 50 is fixed upon the case. Likewise as seen in FIG. 2 , the negative terminal 40 A of the pouch 16 is juxtaposed with negative terminal 40 B of pouch 18 and negative terminal 40 C of pouch 20 to create a negative terminal stack 55

Referring again to FIG. 1 , the positive terminal 38 A can be considered the innermost of the terminals of the terminal stack 44 in the sense that the terminal 38 A is the closest to the leg 54 of the interconnect member 50 . The terminal 38 A has a lateral bend 38 AA by which the terminal 38 A reaches over to contact with the terminal 38 B. The terminal 38 C can be considered the outermost of the terminals of the terminal stack 44 in the sense that the terminal 38 C is the furthest away from the leg 54 of the interconnect member 50 . The terminal 38 C has a lateral bend 38 CC by which the terminal 38 C reaches over to contact with the terminal 38 B. The terminal 38 B has a return lateral bend 38 BB.

Thus, as seen in FIG. 1 , the terminals 38 A, 38 B, and 38 C are loosely stacked together with 38 A being the innermost terminal of the terminal stack 44 and closest to the interconnect member 50 , the terminal 38 C being the outermost terminal the furthest from the interconnect member 50 , and terminal 38 B being the center terminal in the stack 44 and sandwiched between the terminals 38 A and 38 C.

As seen in FIGS. 1 and 2 , the ultrasonic welding will be performed by an ultrasonic weld mechanism that includes an anvil 80 and a sonotrode horn 82 . The anvil 80 and the sonotrode horn 82 are mounted on a multi-axis manipulating mechanism, not shown, by which the anvil 80 and horn 82 can be lowered to the position shown in FIG. 1 where an anvil surface 85 of the anvil 80 is located adjacent the interconnect board vertical leg 54 and the horn 82 is located adjacent but spaced from the outermost terminal 38 C of the terminal stack 44 . The anvil 80 is moved rightwardly in the direction of arrow 84 into supporting contact with the vertical leg 54 so that the anvil 80 will support the interconnect board 50 against movement. The horn 82 will be moved leftwardly in the direction of arrow 86 to bring serrated gripping fingers 90 of the sonotrode horn 82 into contact with the outermost terminal 38 C of the terminal stack 44 .

After the leftward movement of the horn 82 into contact with the terminal stack 44 , the sonotrode horn 82 will be cycled at 10,000 cycles per second to vibrate the serrated fingers 90 which in turn will vibrate the terminal stack 44 against the interconnect board vertical leg 54 . This vibration is continued at a certain pressure and for a certain time until the individual terminals 38 A, 38 B, and 38 C of the terminal stack 44 are ultrasonically welded to each other and the innermost of the terminals 38 A is welded to the interconnect board vertical leg 54 .

It will be understood that during the high speed vibration of the terminal stack 44 by the sonotrode horn 82 , the lateral portions 38 AA, 38 BB, and 38 CC of the terminals will flex slightly so that the vibratory energy is absorbed within the terminal tabs and not transmitted downwardly into the individual battery pouches.

After the making of the ultrasonic weld between the terminal tabs 38 A, 38 B, and 38 C and the interconnect board 50 , the horn 82 and anvil 80 will be moved away from one another and a multi-access manipulating mechanism will relocate the anvil 80 and horn 82 to the location of the next to be welded together terminal stack and interconnect board.

Referring to FIG. 3 , it is seen that a tab bending apparatus generally indicated at 100 includes three pouch supporting fixtures 102 , 104 and 106 that are mounted side by side on a machine base. These pouch supporting fixtures will support the individual battery pouches 16 , 18 and 20 . The tab bending fixture 100 also includes three tab bending fixtures 110 , 112 and 114 that are mounted side by side on the machine base. These tab bending fixtures will bend the terminals of the pouches, as will be described hereinafter.

Referring to FIG. 4 , the pouch supporting fixture 102 is shown and includes generally a pouch nesting fixture 115 and a lid 116 that will close into the nesting fixture 115 to hold the pouch 16 . The nesting fixture 115 slides on a pair of rails 118 and 119 that are best seen in FIG. 3 . In FIG. 3 the pouch nesting fixture 115 is slid to its rightward open position permitting the pouch 16 to be loaded and unloaded from the pouch nesting fixture 115 .

The pouch nesting fixture 115 includes a lower terminal support or clamp 120 that underlies and supports the positive terminal 38 A and a lower terminal support or clamp 122 that underlies and supports the negative terminal 40 A. These lower terminal supports 120 and 122 are constructed of plastic or other dielectric material so that there will not be an electrical short between the positive and negative terminals 38 A and 40 A.

The lid 116 of the pouch supporting fixture 102 is mounted on a stationary mounting plate 128 by a pneumatic cylinder 130 that will extend and retract to raise and lower the lid 116 relative to the nesting fixture 115 . Telescoping guide rods 134 and 136 also act between the mounting plate 128 and the lid 116 to stabilize the lid 116 and prevent its rotation about the axis of the pneumatic cylinder 130 . In FIG. 4 , the lid 116 is shown at its raised position. In FIGS. 5 and 6 , the lid 116 has been lowered by the pneumatic cylinder 130 so that the pouch 16 is supported between the nesting fixture 115 and the lid 116 as is shown in FIG. 6 . In particular, it is seen that the nesting fixture 115 supports the lower surface and the sides of the somewhat flexible pouch 16 . And as seen in FIG. 6 , a peripheral flange 16 A of the pouch 16 has been captured between the nesting fixture 115 and the lid 116 to lend further support to the pouch 16 .

FIGS. 4 and 5 also show that upper clamps 144 and 146 are provided on the lid 116 to cooperate with the lower clamps 120 and 122 in clamping and supporting the terminal tabs 38 A and 40 A. In particular, as best seen in FIG. 7A , the clamp 144 includes a jaw 150 , made of a dielectric material. The jaw 150 is attached to a block 152 by screws 154 and the block 152 slides up and down a bolt 158 attached to lid 116 . A coil compression spring 160 encircles the bolt 158 and bears upon the block 152 so that the jaw 150 is pushed downwardly by the spring 160 .

As seen in FIG. 4 , the jaw 150 is poised above the lower clamp 120 when the lid 116 is at its raised position of FIG. 4 . When the lid 116 is lowered to the position of FIGS. 5 and 7A , the jaw 150 engages with the terminal 38 A and the spring 160 begins to yield and thereby provide a clamping force that is determined by the spring constant of the spring 160 .

Referring again to FIG. 3 , it will be appreciated that the three tab bending fixtures 110 , 112 and 114 are operated in unison in order to simultaneously bend the terminals of the three pouches 16 , 18 and 20 that are supported as described above in the pouch supporting fixtures 102 , 104 , and 106 .

As seen in FIG. 3 , the bending fixture 110 has a stationary upright support 161 that is part of the machine base and will movably support bending dies for bending the terminals 38 A and 40 A. A first vertical track 162 is mounted vertically on the upright support 161 . A track follower 166 rides on the vertical track 162 and mounts a die arm 168 that extends toward the pouch supporting fixture 102 and mounts a lower die 170 . A pneumatic cylinder 172 will raise and lower the die arm 168 . Another track follower 176 rides on the vertical track 162 and mounts an upper die arm 178 that extends toward the pouch supporting fixture 102 and mounts an upper die 180 . A pneumatic cylinder 182 will raise and lower the upper die arm 178 and upper die 180 .

A second vertical track 186 is mounted vertically on the upright support 161 . A track follower 188 rides on the vertical track 186 and mounts a lower die arm 190 that extends toward the pouch supporting fixture 102 and mounts a lower die 192 . A pneumatic cylinder, not shown, will raise and lower the lower die arm 190 . Another track follower 196 rides on the vertical track 186 and mounts an upper die arm 200 that extends toward the pouch supporting fixture 102 and mounts an upper die 202 . A pneumatic cylinder 204 will raise and lower the upper die arm 200 and upper die 202 .

Referring to FIG. 7A , it is seen that the jaw 150 of the upper clamp 144 has been lowered toward the lower clamp 120 so that a base portion 203 of the terminal 38 A is clamped and the an portion 205 of the terminal 38 A is projecting beyond the clamps 144 and 120 and is positioned between the lower die 170 and the upper die 180 . The upper die 180 and lower die 170 will be closed toward one another in order to accomplish the bending of the terminal 38 A to the shape shown in FIG. 1 . In particular, FIG. 7B shows that the upper die 180 is lowered into contact with the terminal 38 A. Then, as shown in FIG. 7C the lower die 170 is raised and will bend the terminal 38 A into conformance with the cavity shapes 170 A and 180 A provided respectively on the lower die 170 and upper die 180 . Thus, the terminal 38 A of the pouch 16 will have been bent to provide the desired lateral offset 38 AA as shown in FIG. 1 . By clamping the terminal 38 A between the clamps 144 and 120 , the bending forces that are applied to the terminal 38 A will not be transmitted into the pouch 16 .

After the positive terminal 38 A has been bent, the negative terminal 40 A will be bent by lowering the lower die 192 and raising the upper die 202 . The lower die 192 and the upper die 202 have the same cavity shapes as the lower die 170 and upper die 180 so that the negative terminal 40 A will be bent to the same shape as the positive terminal 38 A. It will be understood that the positive terminal 38 A are not bent at the same time as the negative terminal 40 A in order to prevent the occurrence of an electrical short between the positive and negative terminals.

FIGS. 8A , 8 B and 8 C show the sequence of operation for the bending dies of the bending fixture 112 for bending the positive terminal 38 B of the pouch 18 . The positive terminal 38 B of the pouch 18 has been clamped between an upper clamp 206 and a lower clamp 208 and projects between upper die 210 and lower die 212 . In FIG. 8B , the upper die 210 has been lowered to contact the terminal 38 B. In FIG. 8C the lower die 212 has been raised and accordingly the terminal 38 B is bent into the shape of the cavities 210 A and 212 A provided respectively on the upper die 210 and lower die 212 . Thus, it is seen that the terminal 38 B has been provided with the offset 38 BB as shown in FIG. 1 .

FIGS. 9A , 9 B, and 9 C show the sequence of operation for the bending dies of the bending fixture 114 for bending the positive terminal 38 C of the pouch 20 . The terminal 38 C of the pouch 20 has been clamped between the upper clamp 216 and a lower clamp 218 and projects between upper die 220 and lower die 222 . In FIG. 9B the lower die 222 has been raised. In FIG. 9C the upper die 220 has been lowered and accordingly the terminal 38 C is bent into the shape of the cavities 220 A and 222 A provided respectively on the upper and lower dies 220 and 222 . Thus, it is seen that the terminal 38 C of the pouch 20 has been provided with the offset 38 CC as shown in FIG. 1 .

Thus, it is seen that the invention provides a new and improved method and apparatus for the bending of terminals for the manufacture of a battery pack by the ultrasonic welding of battery cell terminals to an interconnect board. The method and apparatus enables the automated bending of both the positive and negative terminals in a sequence of operation that prevents the occurrence of short circuits between the terminals. In addition, during the bending, the terminals and the flexible pouches are supported and also the terminals are supported and clamped in a manner to prevent the transmission of bending force into the pouches during the bending operation.

The foregoing description of the invention is merely exemplary in nature and, thus, variations thereof are intended to be within the scope of the invention.