This disclosure generally relates to a battery stacker machine for stacking anodes, cathodes, and separator. The disclosure also relates to a method and a gripper for battery stacking. In particular, this disclosure relates to a rolling transfer of battery layers.
Prismatic batteries are formed by interleaving alternate layers of cathodes, insulating separators, and anodes. Accordingly, to form a stack, the separator is a continuous layer that is folded back and forth (z-fold) between the alternating anode and cathode layers. The battery design itself precludes aligning the edges of individual layers to a common datum. To avoid malfunction, there should be no electrical contact between an anode and an adjacent cathode. To that end, the anode and cathode are typically mismatched in size and center aligned to each other, such that a physical border of 1 to 2 mm exists between adjacent anode and cathode layers.
Conventional z-fold stacker mechanisms are limited in throughput by system architectures following a repeating place/clamp/fold sequence. With one transfer device per each electrode, these previous attempts included various clamping and retention techniques to hold the stack in place while another electrode is placed on top, which reduces throughput. Moreover, synchronization for each transfer device and a separator feed device has been challenging.
One example of a previous attempt is described in Patent Application Publication No. US2006/0051652 A1 of Samuels. The '652 publication describes an interleave machine to form a stack.
Another example is Korean Patent No. 101220981, which also describes a stacking device having a first vacuum transfer means for anodes and a second vacuum transfer means for cathodes. Each vacuum transfer means can pivot to fold the separator down onto the stack.
In one aspect, a method, performed by a battery stacker or by a gripper of a battery stacker, is disclosed for forming a battery electrode and separator stack. The method comprises applying, via an arcuate surface, a force to a battery layer to move it from a first location and flex it into a conforming position on the arcuate surface. The method further comprises, while the force maintains the battery layer flexed in the conforming position, rotating the arcuate surface with the battery layer into a second location. The method further comprises transferring the battery layer from the conforming position on the arcuate surface to a receiver surface, wherein the transferring comprises releasing the force applied via the arcuate surface.
In some embodiments, the receiver surface is another arcuate surface, and wherein the transferring comprises applying a force with the arcuate receiver surface to flex the layer into a conforming position on the receiver surface.
In some embodiments, the receiver surface is a battery electrode and separator stack comprising a substantially planar surface, and wherein the transferring comprises transferring the battery stack to an unflexed position.
The method may also include eccentrically rotating the arcuate surface so that it translates laterally and vertically relative to the receiver surface.
The method may also include applying the force by pulling a vacuum through apertures in the arcuate surface.
The method may also include the battery layer having a discrete electrode atop a continuous separator sheet.
The method may also include the battery layer having a discrete electrode atop a discrete separator sheet.
The method may also include applying the force by pulling a vacuum through apertures in a laterally reciprocating gripper.
The method may also include gradually applying, as a function of lateral position, positive pressure through apertures in the arcuate surface.
The method may also include the first location being a vertically oriented material-transfer position defined by the arcuate surface confronting another arcuate surface that acts as a pick-and-place device.
The method may also include performing the applying of the force, the rotating, and the transferring in connection with a first laterally reciprocating roller on a first side of the battery stacker, and the method further includes repeating the applying of the force, the rotating, and the transferring in connection with a second laterally reciprocating roller on a second side of the battery stacker.
The method may also include the applying of the force by pulling a vacuum through pores on the continuous separator sheet to flex the battery layer.
In one aspect, a battery stacker is disclosed. The stacker includes an arcuate surface configured for application of a force for pulling a battery layer from a first location and flexing into a conforming position on the arcuate surface, an axis about which the arcuate surface is rotatable while the force maintains the battery layer flexed in the conforming position so as to rotate the battery layer into a second location, and a receiver surface for receiving the battery layer in response to release of the force to transfer the battery layer from the conforming position on the arcuate surface to the receiver surface.
In some embodiments, the receiver surface may be another arcuate surface of a battery stacker, which may comprise means for applying a force on the battery layer. In some embodiments, the receiver surface may be identical or substantially identical to the arcuate surface from which the battery layer is transferred. In some embodiments, the receiver surface is a battery electrode and separator stack comprising a substantially planar surface.
The battery stacker may also include a rotatable multi-sided gripper including the arcuate surface. The rotatable multi-sided gripper may be eccentrically rotatable.
The battery stacker may also include left- and right-side eccentrically rotatable multi-sided grippers acting as pick-and-place devices.
The battery stacker may also be a z-fold stacker.
The battery stacker may also include the force as a vacuum force applied through apertures in the arcuate surface.
The battery stacker may also include the force being a first force and in which the arcuate surface is configured for application of a second force as a positive pressure applied though apertures in the arcuate surface.
In one aspect, a rotatable multi-sided gripper for transporting a battery layer is disclosed. The gripper comprises a body, including three mutually angularly spaced apparat arcuate gripper surfaces, and three mutually angularly spaced apparat truncated sides. Each arcuate gripper surface comprises means for applying a force on a battery layer positioned on the gripper surface for maintaining the battery layer in a conforming position on the arcuate surface.
In some embodiments, each arcuate gripper surface further comprises means for applying a second force as a positive pressure on the battery layer in order to release and/or transfer the battery layer to a receiver surface.
The disclosed embodiments exploit the physical flexibility of the materials to be stacked to perform material handoffs by means of a rolling action. There are four cases of rolling handoffs that may leverage the disclosed techniques: (1) transfer from a moving roller to a stationary plane; (2) transfer from a stationary plane to a moving roller; (3) transfer from a stationary roller to a moving plane; or (4) transfer from a moving plane to a stationary roller. The disclosed material transfer is made with no scrubbing, i.e., minimal relative motion between the roller and the plane.
Conventional z-fold stacker techniques typically use reciprocating motion (e.g., pick and place) to build a stack from discrete electrodes. Thus, in some embodiments, it is also desirable to use continuous rotary motion as an alternative to reciprocation.
Additional aspects and advantages will be apparent from the following detailed description of embodiments, which proceeds with reference to the accompanying drawings.
To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.
In battery stack 118, copper anode 106 and aluminum cathode 112 are typically mismatched in size and center aligned to each other (i.e., with no common edge datum), such that a physical border of 1 to 2 mm exists between adjacent anode and cathode layers. Z-fold stacker machine 100 is designed to meet this center alignment specification, typically to an accuracy of about 0.25 mm. Z-fold stacker machine 100 can accommodate a wide range of electrode sizes.
In the example of z-fold stacker machine 100, first electrode delivery system 102 includes a first roll 120 of electrode material 104. As electrode material 104 is pulled from first roll 120 by a conveyor 122 or other transport mechanism, a laser ablation device 124 cuts electrode material 104 to form first electrodes 126 that are singulated from first roll 120.
Likewise, second electrode delivery system 108 includes a second roll 128 of electrode material 110. As electrode material 110 is pulled from second roll 128 by a conveyor 130 or other transport mechanism, a laser ablation device 132 cuts electrode material 110 to form second electrodes 134 that are singulated from second roll 128.
Central assembly system 114 includes three eccentrically rotatable multi-sided grippers, which are explained in further detail below. Initially, however, each eccentrically rotatable multi-sided gripper has a longitudinal axis that is offset from an axis of rotation such that the eccentrically rotatable multi-sided gripper moves about a circular path while sequentially presenting different arcuate gripper surfaces to transverse material-transfer positions.
In this example of z-fold stacker machine 100, a first eccentrically rotatable multi-sided gripper 136 and a second eccentrically rotatable multi-sided gripper 138 act as pick-and-place devices that move electrodes from horizontal positions atop respective conveyor 122 and conveyor 130 to vertical positions where they are transferrable to a central eccentrically rotatable multi-sided gripper 140 that also selectively engages a draped section 142 of separator 116. Central eccentrically rotatable multi-sided gripper 140 then places the material atop battery stack 118.
In this embodiment, separator 116 is fed along the same side as first electrodes 126, but at twice the rate, i.e., twice the length of separator per length of electrode. The unconstrained portion of the separator (between battery stack 118 and the electrode being picked) is held in tension by air pressure before it is folded onto battery stack 118 by orbital motion of central eccentrically rotatable multi-sided gripper 140. The inherent flexibility of the materials enables picking and placing with a rolling action at predetermined locations while central eccentrically rotatable multi-sided gripper 140 maintains continuous orbital motion. Because central assembly system 114 employs continuous rotary motion, z-fold stacker machine 100 is capable of high throughput, high efficiency, and reduction of the high forces and vibrations associated with reciprocating motion.
As explained below, loading of layers from arcuate gripper surfaces and unloading them onto battery stack 118 is achieved with substantially no scrubbing. Scrubbing occurs when one layer at the top of a stack is pulled laterally (i.e., dragged or slipped) against a lower layer. For instance, in some embodiments, there is less than about 100 μm in terms of a change in distance from an initial point of contact of two layers to the final relative position of the layers. Skilled persons will appreciate, however, that different tolerances for scrubbing may be achieved using different battery layer materials and production specifications.
The continuous motion of the rotational components at a constant rotational velocity enables higher throughput. A targeted cycle time of 0.1 s (electrode to electrode) is about six times faster than a conventional system. This means that a stack of a typical quantity of 100 layers can be completed in 10 seconds instead of 60 seconds.
In some embodiments, to maintain the overall throughput of the factory, a completed stack assembly is rapidly removed and replaced by and identical stack elevator assembly by means of a linear shuttle transverse to the feed direction. This optional shuttle maximizes the utilization of the stacking process. Downstream process steps (e.g., wrapping, taping, and other steps) can then be done in parallel with building the subsequent stack.
Initially, in the example of
A first position 202 is established when first eccentrically rotatable multi-sided gripper 136 (
Concurrently, central eccentrically rotatable multi-sided gripper 140 has a first arcuate gripper surface 206 rotated downward and eccentrically moved toward draped section 142 as an idler roller 208 is adjusted to maintain tension on separator 116. As the two confronting arcuate gripper surfaces meet at a left-side material-transfer position 210, first electrode 204 is released from first eccentrically rotatable multi-sided gripper 136 and simultaneously pulled onto central eccentrically rotatable multi-sided gripper 140 (e.g., it vacuumed through the relatively porous draped section 142 underlying first electrode 204). Thus, first arcuate gripper surface 206 retains first electrode 204 and a secured portion 212 of separator 116. Also, a second arcuate gripper surface 214 holds a second electrode 216 in an upward intermediate right-side position 218 oriented 120° clockwise from left-side material-transfer position 210.
With first electrode 204 and secured portion 212 held by central eccentrically rotatable multi-sided gripper 140, a second position 220 is established as central eccentrically rotatable multi-sided gripper 140 continues to rotate downward and eccentrically toward battery stack 118. Accordingly, first electrode 204 and secured portion 212 pass through an intermediate left-side position 222, and second electrode 216 arrives at a top-most central position 224. A jet of air from an air knife, vacuum, or similar force is applied to a slack section 226 of separator 116 to direct it across a top 228 of battery stack 118, thereby imparting a z-fold bend in slack section 226 preparatory to placing first electrode 204 atop battery stack 118.
As central eccentrically rotatable multi-sided gripper 140 continues to rotate to a third position 230, first electrode 204 and secured portion 212 move further downward and rightward. Second electrode 216 moves closer to left-side material-transfer position 210.
In a fourth position 232, central eccentrically rotatable multi-sided gripper 140 is at a bottom-most central position 234 at which point first electrode 204 and secured portion 212 are released on top 228 of battery stack 118. A z-elevator (not shown) for battery stack 118 decrements downward as layers are added such that placement always occurs at the same elevation. As noted above, the release at bottom-most central position 234 is made with substantially no lateral movement so as to avoid scrubbing.
Once released, central eccentrically rotatable multi-sided gripper 140 continues rotating and moving toward second eccentrically rotatable multi-sided gripper 138 (
Finally, in an eighth position 246, second electrode 216 is released atop battery stack 118 without scrubbing. Third electrode 242 is rotated upward and eccentrically moved away from right-side material-transfer position 244, and a fourth electrode 248 (of the same type as first electrode 204) is moved into left-side material-transfer position 210 by first eccentrically rotatable multi-sided gripper 136 (
Body 312 has an offset longitudinal axis 318 that is spaced apart from pivot axis of rotation 310 to establish eccentric orbital motion that is guided by external planetary gear 304 in internal ring gear 302. A mounting block 320 houses internal ring gear 302 and provides a pneumatic inlet port 322 and a pneumatic outlet port 324.
Without truncated side 316, arcuate gripper surface 314 could form a three-sided body resembling a triangle with curved sides. In body 312, however, vertices of the triangle are truncated for clearance and reduced mass, since they perform no function related to stacking. The specific design of the truncated faces may be tailored to accommodate the tensioning on the unconstrained separator (i.e., tensioning on secured portion 212 and slack section 226 (
Arcuate gripper surfaces 314 include pneumatic gripper apertures 326 configured to apply vacuum and pressure (obtained from pneumatic inlet port 322 and pneumatic outlet port 324) to hold and release layers from two active arcuate gripper surfaces 314, as explained previously with reference to
In some embodiments, continuous negative and positive pressures are applied to ports. Delivery of these pressures, however, is made periodically automatically as a function of orbital position through fluid communication channels (not shown) in body 312 that align with fixed internal port locations (not shown) as central eccentrically rotatable multi-sided gripper 140 orbits.
To illustrate an example of retention and handoff forces applied during transfer of an electrode and separator section,
In eighth position 246, a first battery layer 502 (e.g., a graphite-coated copper or aluminum electrode) is flexed into a conforming position on a first arcuate gripper surface 504. The dashed arrow lines show the application of a vacuum force (negative pressure) that pulls first battery layer 502 onto first arcuate gripper surface 504. In this example, draped section 142 is not affected by the vacuum force, although in other embodiments draped section 142 may also be pulled toward first arcuate gripper surface 504 (see, e.g., fourth electrode 248 and the separator 116 in
In first position 202, an upper portion 506 of first arcuate gripper surface 504 applies a negative pressure while a bottom portion 508 applies a positive pressure (indicated by solid arrow lines). Concurrently, an upper portion 510 of a second arcuate gripper surface 512 applies no pressure and a bottom portion 514 applies negative pressure. Thus, central eccentrically rotatable multi-sided gripper 140 applies, via its second arcuate gripper surface 512, the negative force to pull the battery layer from its left-side material-transfer position 210 on first arcuate gripper surface 504 and flex it into a conforming position on second arcuate gripper surface 512.
In second position 220, the coordination of pressures thereby transfers the material from one surface to the other surface. First arcuate gripper surface 504 applies only a positive pressure 516 and second arcuate gripper surface 512 applies only a negative pressure 518. Positive pressure 516 from first arcuate gripper surface 504 also acts to facilitate a z-fold 520 in slack section 226 (
From second position 220, while the force of negative pressure 518 maintains the battery layer flexed in the conforming position, central eccentrically rotatable multi-sided gripper 140 rotates second arcuate gripper surface 512 with the battery layer into a second location (i.e., bottom-most central position 234,
Note that, in some embodiments, the opposite force (e.g., positive pressure) is optional. For instance, depending on the speed of rotation, releasing the force while rotating is sufficient for placing the electrode atop battery stack 118 because gravity is sufficient to separate the material from the arcuate surface.
As mentioned previously, eccentrically rotatable multi-sided gripper 328 includes arcuate gripper surfaces 314 for continuous rotary motion. One candidate shape of the surfaces for the continuous rotary motion system is based on a Reuleaux triangle 700, as shown in
Notably, however, there are two issues in a system based on a pure Reuleaux triangle. The first is that the orbital motion at the center of the triangle is not a simple circle, but combined segments of four ellipses. The second is that the action of the rotor on the electrodes at the sides of the square is not pure rolling that is free from scrubbing. For pure rolling, the linear distance travelled by the vertex along one side of the square must be equal to the length of the opposite arc as it is rolled along the opposite side. A difference results in scrubbing due to relative linear motion between the curved surface and the electrode to be picked or placed.
A first step in designing a modified Reuleaux triangle is to create a non-slip profile path for the centroid of the shape. The non-slip path would ensure pure rolling motion at the curved surface. This is accomplished by assuming that the rolling traversal distance equals the lateral motion of the Reuleaux triangle top vertex. This is similar to a non-slip wheel traversing a distance, with the specification being that the arc length contacting the ground during motion is equivalent to the axle lateral distance travelled.
This is not amenable nor practical for motion using standard gear driven transmission assemblies.
Accordingly,
In order to realize zero scrubbing, constant angular velocity gear motion, and proportional centroidal Θ counter-rotation during orbit,
In other embodiments, additional numbers of sides are also possible. Skilled persons will also appreciate that, instead of the previously described empirical approach, closed-form analytical techniques may also be employed to develop arcuate gripper surface shapes.
In a first position 2002, a first electrode 1904 is oriented horizontally atop a first vacuum roller 2004 where it can be lifted by a negative pressure applied by first gripper 1902 (
In a second position 2008, first electrode 1904 is released by first vacuum roller 2004 and shuttled atop stack 1804. Concurrently, second vacuum roller 2006 applies, via its arcuate surface, a vacuum force to second electrode 1908 to move it from its initial location and flex it into a conforming position on the arcuate surface.
A third position 2010 is then reached as follows. While the vacuum force maintains second electrode 1908 flexed in the conforming position, second vacuum roller 2006 rotates so that the arcuate surface retaining second electrode 1908 is moved into a second location (e.g., horizontal) that is transverse to the first location when second electrode 1908 was introduced.
To transition to a fourth position 2012, second vacuum roller 2006 releases its vacuum force while second gripper 1906 (
The method 2300 comprises applying 2302, via an arcuate surface, a force to a battery layer to move it from a first location and flex it into a conforming position on the arcuate surface. The applied force may in some embodiments be applied via vacuum, and in some embodiments it may be applied electrostatically. The arcuate surface may in some embodiments be located at a multi-sided gripper and/or in stacker machine.
In step 2304, while the force maintains the battery layer flexed in the conforming position, the method comprises transporting the arcuate surface with the battery layer to a receiver surface. The transporting may comprise rotating the arcuate surface, wherein the rotating may comprise eccentric rotation. The receiver surface is located at a second location different from the first location. In some embodiments, the receiver surface is angularly offset from the first location. In some embodiments the second location is transverse to the first location.
In step 2306, the method 2300 comprises transferring the battery layer from the conforming position on the arcuate surface to a receiver surface, wherein the transferring comprises releasing the force applied via the arcuate surface, and optionally applying an opposite force to provide the transfer. The transfer may in some embodiments be scrub-free or substantially scrub-free.
In some embodiments, the receiver surface is another arcuate surface. In some embodiments, the receiver surface is located on an electrode and separator stack and the transferring comprises depositing the battery layer into the battery electrode and separator stack.
The methods 2200, 2300 may also include eccentrically rotating the arcuate surface so that it translates laterally and vertically relative to the receiver surface.
In another embodiment, methods 2200, 2300 may also include applying of the force by pulling a vacuum through apertures in the arcuate surface.
In another embodiment, methods 2200, 2300 may also include the battery layer having a discrete electrode atop a continuous separator sheet.
In another embodiment, methods 2200, 2300 may also include the battery layer having a discrete electrode atop a discrete separator sheet.
In another embodiment, methods 2200, 2300 may also include applying of the force by pulling a vacuum through pores on the continuous separator sheet to flex the battery layer.
In another embodiment, methods 2200, 2300 may also include applying of the force by pulling a vacuum through apertures in a laterally reciprocating gripper.
In another embodiment, methods 2200, 2300 may also include applying of the optional force by gradually applying, as a function of lateral position, positive pressure applied through apertures in a laterally reciprocating roller.
In another embodiment, methods 2200, 2300 may also include the first location being a vertically oriented material-transfer position defined by the arcuate surface confronting another arcuate surface that acts as a pick-and-place device.
In another embodiment, methods 2200, 2300 may also include performing the applying of the force, the rotating, and the transferring and/or releasing in connection with a first laterally reciprocating roller on a first side of the battery stacker, and the method further includes repeating the applying of the force, the rotating, and the transferring and/or releasing in connection with a second laterally reciprocating roller on a second side of the battery stacker.
Skilled persons will appreciate that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. For example, the embodiments may be employed for other applications including unstacking, singulation, and pick-and-place uses. The scope of the present invention should, therefore, be determined only by claims and equivalents thereof.
This application claims priority of U.S. Provisional Application No. 63/380,359, filed Oct. 20, 2022, which the entirety thereof is incorporated herein by reference.
Number | Date | Country | |
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63380359 | Oct 2022 | US |