Separating the web to supply electrodes to the battery stacker

Abstract

Techniques for reducing out-of-plane protrusions during separation of an electrode from a web are disclosed. In some embodiments, a feed roller feeds perforated web material from a roll, a breaking and positioning roller receives a portion of the perforated web material from the feed roller, and a servo motor varies the speed of at least one of the feed roller and the breaking and positioning roller, thereby generating a breaking force that is applied to the portion of the perforated web material to separate the portion in a predetermined shape of the electrode.

Description

[Technical Field]

[0001] This disclosure relates primarily to the manufacture of electrodes for battery stack production. In particular, this disclosure relates to the separation of electrodes from rolled material.

[0002] A web is a continuous roll of flexible material (such as paper, film, or foil) that is in the process of being formed, converted, or printed. The web is either cut into sheets during the manufacturing process or fed in continuous form to a converter or printer.

[0003] Some batteries are formed by stacking alternating cathode layers, insulating separator layers, and anode layers. In z-fold embodiments, the separator is a continuous layer that is folded back and forth (z-fold) between alternating anode and cathode layers to form the stack. In other embodiments, separate separator layers are used.

[0004] The battery design itself prevents the edges of the individual layers from being aligned to a common reference. To avoid malfunction, there must be no electrical contact between the anode and the adjacent cathode. To this end, the anodes and cathodes are typically unequal in size and centered relative to one another, leaving a physical boundary of approximately 3 mm between adjacent anode and cathode layers.

[0005] Because the separator layer is folded or placed between the electrodes, there is a certain tolerance for burrs and spikes that may protrude from the major surface of the electrode toward the opposing major surface of the separator. Such burrs and spikes may be caused by the process of separating the electrodes from the web. These undesirable manufacturing defects may contact and damage the flat surfaces of the separator material. SUMMARY OF THE DISCLOSURE

[0006] Using the methods and systems disclosed herein, electrodes can be separated from a stack by forming a break line and then applying pressure along the formed break line to break the electrode from the web material.

[0007] Because the separation force acts along the web's transport direction, it reduces the generation of undesirable burrs, spikes, and other major surface defects that extend vertically along the separation line and protrude into the planar surface, which can occur when the separation force acts on the material as a cutting force. For example, knives, punches, and lasers tend to create defects / debris that protrude from the plane of the electrode, while perforation and breaking techniques tend to create in-plane defects, debris, or sharp edges. Perforation and breaking techniques allow for perforations to be performed in a pre-processing step, and even at a different location than the separation and breaking steps. This can streamline the overall process and allow the perforated web to be cleaned and / or inspected prior to the separation step.

[0008] In addition to addressing burrs and spikes protruding from the flat surface of the electrode, the perforation pattern can be optimized to prevent the fractured edge from becoming the part of the electrode that protrudes most from the separated electrode. This can prevent irregular and / or sharp edges from contacting adjacent materials. Thus, the resulting fracture shape (i.e., irregular edges) can be optimized for interaction with the separator and battery density.

[0009] According to one aspect, a method for separating electrodes is provided. The method includes forming a break line between adjacent electrodes in a web, feeding the web to a separating device, and applying a force to the web using the separating device to separate the electrodes from the web along the formed break line. In some embodiments, forming the break line may occur at a location different from other steps, and the web material may be transported from that location to the separating device location. Applying the force may include moving a set of breaking and positioning rollers at a higher speed than a pair of feed rollers that feed the web material to the breaking and positioning rollers.

[0010] According to another aspect, a separation system for separating an electrode from a web is provided, the system comprising a feed roller adapted to feed a web material from a roll and a breaking and positioning roller adapted to receive a portion of the web material from the feed roller, the system further comprising a controllable motor adapted to vary the speed of at least one of the feed roller and the breaking and positioning roller, thereby generating a breaking force applied to a break line formed along the web material to separate the portion of the web material according to a predetermined shape of the electrode.

[0011] Additional aspects and advantages will become apparent from the following detailed description of the embodiments, which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0012] To easily identify a particular element or description of an operation, the most significant digit(s) in a reference number refers to the number of the figure in which that element is first introduced.

[0013] [Figure 1] FIG. 1 illustrates an isometric view of a z-fold stacker device according to one embodiment. [Figure 2] FIG. 1 is an isometric view of a web undergoing notching, perforation, and coating according to one embodiment. [Figure 3]1 illustrates an isometric view of a processed web being separated in one embodiment. [Figure 4] FIG. 4 is an enlarged isometric view of the separation device shown in FIG. 3. [Figure 5] FIG. 4 is an enlarged isometric view of the breaking and positioning rollers, vacuum conveyor, and picking device shown in FIG. 3. [Figure 6] FIG. 10 is a plan view of a portion of a dashed-line shaped perforation line with an enlarged view of the separation line. [Figure 7] FIG. 10 is a plan view of a portion of the wavy perforation line with an enlarged view of the separation line. [Figure 8] FIG. 10 is a plan view of a portion of a trapezoidal perforation line with an enlarged view of the separation line. [Figure 9] FIG. 10 is an isometric view of a separation device according to another embodiment. Detailed Description of the Embodiments

[0014] 1 shows a simplified diagram of a z-fold stacker apparatus 100 according to one embodiment. The z-fold stacker apparatus 100 includes a first electrode delivery system 102 for providing a first type of electrode material 104 (e.g., copper anode 106), a second electrode delivery system 108 for providing a second type of electrode material 110 (e.g., aluminum cathode 112), and a central assembly system 114 for providing a separator 116 for z-folding with the electrodes to form a battery stack 118. In the z-fold configuration, the separator 116 is not singulated into individual layers, but instead forms a single continuous layer that is folded back and forth between alternating electrodes (anodes and cathodes).

[0015] In the cell stack 118, the copper anodes 106 and aluminum cathodes 112 are typically mismatched in size and centered relative to one another (i.e., no common edge reference), with a 3 mm physical boundary between adjacent anode and cathode layers. The z-fold stacker apparatus 100 is designed to meet this centering specification, typically achieved to an accuracy of about 0.25 mm. The z-fold stacker apparatus 100 can accommodate a wide range of electrode sizes.

[0016] In an embodiment of the z-fold stacker apparatus 100, the first electrode delivery system 102 includes a first roll 120 of electrode material 104. As the electrode material 104 is drawn from the first roll 120 by a conveyor 122 or other transport mechanism, a separator 124 separates the electrode material 104 to form a first electrode 126 separated from the first roll 120.

[0017] Similarly, the second electrode delivery system 108 includes a second roll 128 of electrode material 110. As the electrode material 110 is drawn from the second roll 128 by a conveyor 130 or other transport mechanism, a separator 132 separates the electrode material 110 to form a second electrode 134 separated from the second roll 128.

[0018] The central assembly system 114 includes three eccentrically rotatable multi-faceted grippers, which are described in further detail below. First, however, each eccentrically rotatable multi-faceted gripper has a longitudinal axis that is offset from the axis of rotation, such that the eccentrically rotatable multi-faceted grippers move along a circular path while sequentially presenting different arcuate gripping surfaces to lateral material transport locations.

[0019] In this example of z-fold stacker apparatus 100, first eccentric rotatable multi-surface gripper 136 and second eccentric rotatable multi-surface gripper 138 function as pick and place devices that move electrodes from horizontal positions on top of their respective conveyors 122 and 130 to vertical positions where they can be transferred to a central eccentric rotatable multi-surface gripper 140 that also selectively engages a drape portion 142 of separator 116. Central eccentric rotatable multi-surface gripper 140 then places the material on top of battery stack 118.

[0020] In this embodiment, the separator 116 is fed along the same side as the first electrode 126, but at twice the speed—that is, twice the length of separator per length of electrode. The unconstrained portion of the separator (between the battery stack 118 and the electrode being picked) is held in tension by air pressure before being folded onto the battery stack 118 by the orbital motion of the central eccentrically rotatable multi-faceted gripper 140. The inherent flexibility of the material allows for picking and placing with a rolling motion in place while the central eccentrically rotatable multi-faceted gripper 140 maintains continuous orbital motion. Because the central assembly system 114 uses continuous rotational motion, the z-fold stacker apparatus 100 is capable of high throughput, high efficiency, and reduced forces and vibrations associated with reciprocating motion.

[0021] In some embodiments, to maintain overall factory throughput, completed stack assemblies are quickly removed and replaced with identical stack elevator assemblies by a linear shuttle perpendicular to the feed direction. This optional shuttle maximizes the efficiency of the stack assembly process. Downstream process steps (e.g., wrapping, taping, and other steps) can occur in parallel with the assembly of subsequent stacks.

[0022] FIG. 2 illustrates an example of processing an untreated electrode supply roll 200. As the electrode web material 202 unwinds from the untreated electrode supply roll 200, it is transported to a notching and perforation station (e.g., laser or punch, not shown). This station defines the shape of the individual electrodes, which may include notching the distal tabs 204 and punching perimeter lines of breakable holes 210, 212 perpendicular to the transport direction 208 of the electrode web material 202. Perforation is also referred to as forming a break line for the electrode. Each of the breakable holes 210, 212 may be a partial perforation in the web or a through-hole perforation that extends entirely through the web.

[0023] For each electrode, the perimeter line of the breakable holes 210, 212 includes a first line 210 toward the leading portion of the electrode web material 202 and a second line 212 toward the trailing portion of the electrode web material 202. Those skilled in the art will appreciate that each perimeter line of the breakable holes 212 can be created individually or simultaneously with other lines or tabs. In some embodiments, forming the break lines can also include laser ablating the web along the break lines. This can be done as a perforation step or in addition to a separate perforation step using a punch or the like.

[0024] After the notching and perforation steps, the uncoated, non-separated electrode 214 may be coated with an electrode graphite coating 216 (all except the distal tab 204) to form a coated, non-separated electrode 218. As shown in FIG. 2, the coating may cover the perforation lines. The coated, unseparated electrode 218 is then optionally re-spooled for feeding into the stacker apparatus 100 or immediately fed into the stacker system. In other embodiments, perforation may occur after coating. In still other embodiments, coating is optional (e.g., uncoated lithium foil). In some embodiments, the separator may be part of the stacker apparatus or stacker system.

[0025] During drilling of bare copper or aluminum foil (8 μm and 12 μm thick, respectively), the resulting burrs (spikes) are subsequently covered by a graphite coating process (on the order of 100 μm thick on either side). Any spikes from the drilling are therefore irrelevant, as they do not protrude beyond the top surface of the electrode, e.g., beyond the 10 μm specification.

[0026] In other embodiments, the perforations may be cleaned and inspected prior to electrode coating. This can ensure that all of the input material is good and does not have any protruding punch protrusions. For example, the perforated metal may be passed through a set of rollers that flatten any out-of-plane protrusions and realign (squash) them into a flat surface. This calendaring step may also be performed after coating in some embodiments.

[0027] 3 shows an example of a separation assembly for a processed electrode supply roll 300, which in some embodiments is first roll 120 (FIG. 1) or second roll 128 (FIG. 1). In this example, processed electrode supply roll 300 includes repooled, coated, unseparated electrodes 218 (FIG. 2). That is, pre-notched, perforated, coated, and unseparated material 302 is fed from processed electrode supply roll 300 to a separator 304, which in some embodiments is separator 124 (FIG. 1) or separator 132 (FIG. 1).

[0028] The separation device 304 includes a feed roller 306 that pulls the material 302 from the electrode feed roll 300, which may include a slack loop 308 to provide tension relief and allow the roll 300 to feed at a substantially constant feed rate. The feed rollers 306 may be positioned close to each other with the web material tightly pressed between them. Breaking and positioning rollers 318, 320 accelerate the unseparated electrode away from the trailing perforation line (not shown) and apply a breaking force to the material 302 along the conveying direction 312, thereby separating the coated electrode from the material 302 along the separation line. This reduces the chance of problematic burrs or spikes from flat surfaces compared to a cutting process.

[0029] The breaking and positioning rollers 318, 320 optionally include a set of independently driven rollers, such as a tab-side roller 318 and a flat-side roller 320. The tab-side roller 318 and the flat-side roller 320 may be driven independently of one another. The tab-side roller 318 and / or the flat-side roller 320 may each comprise a pair of rollers. In some embodiments, the upper and lower rollers on each side operate in coordination with one another, which may involve them operating at the same speed. Because these rollers 318, 320 are independently driven, they rotate at different speeds, which can twist and align the coated separation electrodes 322 exiting the separator 304 and entering the feed stack location 324. In this example, the feed stack location 324 includes a vacuum conveyor 326 that transports the coated separation electrodes 322 to a picking device 328, the subject of U.S. Provisional Patent Application No. 63 / 380,359, filed October 20, 2022. The picking device 328 may be adapted to pick up the separated electrode using a vacuum and transport it to the battery stack.

[0030] In other embodiments, the piercing and precise alignment of the separated electrodes may be accomplished by other mechanisms, such as cross-axis actuators that position rollers that grip the separated electrodes.

[0031] The separating device 304 may also include an air knife or a rotating brush in some embodiments. These optional components remove debris generated during separation.

[0032] FIG. 4 shows in more detail the separating device 304 during breaking of the coated separated electrodes 322 from the material 302 of the treated electrode supply roll 300 (FIG. 3).

[0033] The feed roller 306 sandwiches the electrode material 302 between an upper roller 306 and a lower roller (not shown), which may be driven by a controllable servo motor. In this example, the feed roller 306 nominally feeds the material 302 at the same speed as the breaking and positioning rollers 318, 320. However, as the coated, unseparated electrode 218 ( FIG. 2 ) is fed to the breaking and positioning rollers 318, 320, either the feed roller 306 or the breaking and positioning rollers 318, 320 change speed relative to the other roller. For example, the feed roller 306 may slow down, or the breaking and positioning rollers 318, 320 may speed up, thereby breaking the coated, separated electrode 322 at and / or along the perimeter of the breakable hole 212 ( FIG. 2 ) and establishing the separation line. In some embodiments, the upper and lower roller pairs are synchronized mechanically or with a control system to slow the feed roller 306.

[0034] In some embodiments, the speed of the feed roller 306 ranges from 50 to 950 mm per second, typically from 250 to 600 mm per second. The speed difference between the feed roller and the breaking and positioning rollers 318, 320 during the electrode separation process ranges from very small to 5 to 10 times the speed, depending on the implementation. In some embodiments, the breaking and positioning rollers 318, 320 operate at least 1.5 times the speed of the feed roller 306. In some embodiments, the breaking and positioning rollers operate at 2 to 5 times the speed of the feed roller when breaking and separating the electrodes. The acceleration from operating at the same speed as the feed roller to operating at the increased speed can occur within a time period of 0.1 to 1 second.

[0035] Experiments conducted to quantify the force and speed required to break the material have shown that the breaking force is on the order of a few pounds across the width. This width can be approximately 6 inches, resulting in approximately 0.1 pounds per inch. However, this force can be easily adjusted with the perforation pattern (see, for example, the patterns shown in Figures 6-8). It is believed that the breaking strength can be approximately three times the local web tension, or approximately one-third the breaking strength of an unperforated web. More generally, {Web supply tension + margin}<{Breaking force (with perforations)}<{Breaking force (without perforations) + margin} Here, the "breaking force" of non-perforated material is understood to be the yield force, not necessarily the breaking force. During breakage at the perforations, yielding (elongation) in other areas of the electrode should be avoided. Foil material may be perforated to break at a very low tension, which can be adjusted to be close to the yield tension of the entire web.

[0036] In some embodiments, the tab-side roller 318 and flat-side roller 320 are independent, allowing the break to begin at one end and gradually separate across the entire web. This also allows for precise alignment of the coated, separated electrodes 322 on a vacuum conveyor or other transport device. For example, if the web is misaligned relative to where the electrodes should be picked up, the tab-side roller 318 and / or flat-side roller 320 can be used to properly align the separated electrodes by increasing the speed of one of the rollers relative to the other.

[0037] As previously mentioned, the perforation break and precise alignment of the separated electrodes can also be performed by other mechanisms, such as cross-axis actuators that align rollers gripping the separated electrodes.

[0038] 5 shows in more detail the placement of the electrodes for the infeed stacking position 324. Breaking and positioning rollers 318, 320 advance the coated, separated electrodes 322 onto a vacuum conveyor 326 toward the transfer position 502. The vacuum conveyor 326 creates a positive air bleed to ensure that the coated, separated electrodes 322 float freely above the conveyor surface 504.

[0039] After the electrodes are separated and aligned on the vacuum conveyor 326, the pressure switches to vacuum to secure the separated electrodes to the conveyor surface 504. This can occur near or at the next stop while downstream electrodes are being picked (i.e., transported to the picking device). The transition from roller control to vacuum belt control is coordinated when the electrodes leave the grip of the rollers.

[0040] In some embodiments, the picking device 324 is adapted to lift the electrode using vacuum. This process may be coordinated with releasing the vacuum being applied by the conveyor 326, such that the conveyor begins to release the vacuum on the front of the electrode in the transport direction, and the picking device begins to apply vacuum to the same part of the electrode, and then this continues gradually until the conveyor 326 has completely stopped applying vacuum to any part of the electrode, so that the picking device 324 has applied vacuum to the entire electrode.

[0041] The breaking and positioning rollers 318, 320 then match the speed of the vacuum conveyor 326 in advancing the coated, separated electrode 322 for the next incremental movement toward the pick position 506 until the coated, separated electrode 322 leaves contact with the breaking and positioning rollers 318, 320. The breaking and positioning rollers 318, 320 then match their speed to that of the feed rollers (only one shown) 306 to engage the next coated, unseparated electrode 218. The breaking and positioning roller then accelerates to break the electrode along the perforations as the perforated end exits the feed roller, before matching the speed of the vacuum conveyor 326 again. The vacuum conveyor 326 then advances one increment to move the coated, separated electrode 322 from the transfer position 502 to the pick position 506.

[0042] Figures 6 to 8 are examples showing dashed, wavy, and trapezoidal perforation lines, respectively, and the resulting breakage, which can be used in different embodiments. While the electrode web material may be different in different embodiments, the experimental results underlying Figures 6 to 8 were obtained using uncoated aluminum material. In each example, the perforation lines are formed by multiple through-holes arranged linearly across the width of the web. Through-holes and non-through-hole sections are arranged alternately. The fracture characteristics of the perforation lines can be controlled by changing the size and spacing of the through-holes. The shape of the through-holes is not particularly limited and may be, for example, a perfect circle, an ellipse, an elongated hole, a thin wire, etc. Furthermore, partial cuts or slits on one or both sides may also be used.

[0043] During the experiment, the trapezoidal shape was most likely to tear, followed by the wave shape, and then the dashed shape, however, one skilled in the art will understand that these results may vary based on the web width, spacing of the perforations (i.e., non-perforated material), and perforation volume.

[0044] The perforation rate may also be varied to adjust the breaking strength of the web. Preferably, the perforations cover the majority of the web, but in some embodiments, they may be lower. The perforation rate may be anywhere between 10 and 99%. In some embodiments, the perforation rate is anywhere between 50 and 99%, in some embodiments, 70 to 98%, in some embodiments, 80 to 95%, and in some embodiments, 90 to 95% of the entire web at the break location. There is a balance between having enough perforations to allow a smooth breaking process and not having so many perforations that the web begins to fall apart before separation occurs.

[0045] When laser cutting coated electrodes, the electrode layer typically requires the greatest amount of cutting energy, while cutting the coating uses significantly less energy. The coating can then be removed even with reduced laser intensity, which, in some embodiments, is useful for reducing particles near the coating edge that crumble during fracture. By adjusting the laser intensity during drilling, the perforation line can include a combination of through-holes and score lines (e.g., a score line that penetrates only the coating). Thus, because the coating is completely cut and the foil is perforated, the fracture is metal-only, thereby reducing coating particles that would otherwise be generated. Because separation can be achieved using perforations (through-holes or partial holes), scores (one-sided or two-sided), and any combination thereof, this disclosure generally refers to any of these results as a "formed fracture line." In some embodiments, the electrode is drilled before any coating is applied, and no perforations or scores are made in the coating.

[0046] Figure 6 shows details of dashed perforations. Specifically, the top portion of Figure 6 shows dashed perforation lines 600 that may be used for perforation in some embodiments. The bottom portion of Figure 6 shows enlarged breaks 602 of separation lines 604 formed by breaking the dashed perforation lines 600, although each dash has a slightly different shape. This shape forms a relatively rectangular lateral protrusion 606 along the separation lines 604 where material 608 breaks from the web.

[0047] Figure 7 shows details of the wavy perforations. Specifically, the top portion of Figure 7 shows wavy perforation lines 700, and the bottom portion of Figure 7 shows an enlarged break 702 in a separation line 704 formed by breaking one type of wavy perforation line 700. This shape forms a relatively triangular-shaped lateral protrusion 706 along the separation line 704 where material 708 breaks from the web.

[0048] Figure 8 shows details of trapezoidal perforations. Specifically, the top portion of Figure 8 shows a trapezoidal perforation line 800, and the bottom portion of Figure 8 shows an enlarged break 802 in a separation line 804 formed by breaking one type of trapezoidal perforation line 800. This shape forms a relatively triangular-shaped lateral protrusion 806 along the separation line 804 where material 808 breaks from the web.

[0049] In the examples of Figures 6-8, the perforations are fairly uniform. In other embodiments, the perforations may be non-uniform. For example, some embodiments may include more perforations in areas where initial breakage is desired. In one example, the break initiation is provided as a triangular notch at the break end, so that one of the electrodes accelerates ahead of the other and then follows, initiating the breaking action at the notch and recentering the electrodes. Thus, instead of a linear breaking action along the conveying direction, other breaking directions are also possible. For example, a traveling break (e.g., see Figure 5, starting at one end and progressing across the electrode), a cutting break (e.g., see Figure 9, moving the electrode in a transverse direction), an impact surface acting approximately perpendicular to the web to impact the surface of the perforations and thereby initiate the breaking action, or a combination of these breaking configurations.

[0050] FIG. 9 illustrates a separation apparatus 900 according to another embodiment. The separation apparatus 900 is configured to facilitate lateral movement via a roller pair 902 that breaks the electrode along the formed break line. In the example separation apparatus 900, a linear stage 904 moves one end of the electrode 910 against a fixed roller 906 shown at the top of a feed conveyor 908. The roller pair 906 includes a spring-tensioned upper roller that applies a downward force to the top of the electrode 910, pinching the electrode against a fixed lower roller. In some embodiments, once breaking is complete, the linear stage 904 also performs fine lateral positioning of the electrode 910 before stacking.

[0051] In some embodiments, the impactor is positioned at the location where the break is initiated, which may be at or near the center of the web and / or electrode. The impactor extends upward from the plane of the web material. Rollers move the formed break line over the impactor, accelerating or decelerating the material so that any slack near the formed break line is tensioned, thereby forcing the perforation along the blunt side of the impactor. This blunt side creates a break in the perforation. For example, after the electrode enters the downstream roller pair, the pair accelerates the electrode, pulling it toward the impactor at its center near the formed break line, creating tension near the impactor. This initiates a break at the center of the electrode and propagates toward the edge until it is completely separated.

[0052] The impactor may include a convex surface. Other types of impactors may include an edge. Additionally, a separate impactor may be moved relative to the electrode (i.e., a chopping action) to effect the breakage.

[0053] Those skilled in the art will understand that many changes can be made to the details of the above-described embodiments without departing from the underlying principles of the invention, and the scope of the invention should therefore be determined only by the claims and their equivalents.

Claims

1. forming break lines between adjacent electrodes in the web; feeding the web to a separating device; and applying a force to the web with the separating device to break the electrodes from the web along the formed break lines; An electrode separation method comprising:

2. coating the web with a coating material before feeding the web to the separating device; The method of claim 1 further comprising:

3. 2. The method of claim 1, wherein applying the force comprises accelerating the electrode being broken from the web relative to the web along the formed break line.

4. 2. The method of claim 1, wherein the step of forming the break line occurs at a different location than the step of applying the force.

5. 10. The method of claim 1, wherein applying the force comprises applying a breaking force that is about one-third of the web breaking strength and about three times the local web tension.

6. 1. An electrode separation system for separating an electrode from a web, comprising: a feed roller for feeding the web material from a roll; a breaking and positioning roller that receives a portion of the web material from the supply roller; a controllable motor for varying the speed of at least one of the feed roller and the breaking and positioning roller, thereby generating a breaking force applied to a break line formed along the web material to separate a portion of the web material according to a predetermined shape of an electrode; An electrode separation system comprising:

7. a perforation device adapted to form break lines between adjacent electrodes in the web; The system of claim 6 further comprising:

8. a conveyor adapted to transport the electrodes after they have been separated; and a picking device adapted to pick the separated electrodes from the conveyor and transport them to the battery stack; The system of claim 6 further comprising:

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