Calender transport roll and calendering device for the production of electrodes for a battery cell

Description

[0001] The invention relates to a calender transport roller for a calendering device for the production of electrodes for a battery cell, according to claim 1.

[0002] To manufacture electrodes for battery cells, especially lithium-ion battery cells, flat conductor strips in the form of thin copper foil for the anode or aluminum foil for the cathode, or corresponding metal meshes, are coated on both sides with a composite material, leaving the edges of the conductor strip uncoated. After the composite is applied to the metallic conductor strip and, if necessary, the carrier solvent is removed, the now double-coated electrode strip is fed, usually in a roll-to-roll process, into a calendering unit. There, the coating is compacted by one or more pairs of rotating calender rollers to reduce or adjust the porosity and increase the electrical conductivity and energy density.

[0003] It is desirable to feed the electrode strip into the gap formed between the calender rollers as flat, precisely, and uniformly as possible, and to transport it out of the gap after passing through the calender rollers. Since the electrode strip is also coated in sections on the side facing the transport roller, it does not lie flat on the roller across its entire width. There is a height difference between the coated section and the adjacent uncoated edge sections, corresponding to the thickness of the one-sided coating, which is typically about 30 µm to 100 µm (with a total electrode strip thickness of approximately 80 µm to 200 µm). In comparison, the foil thickness of the conductor strip is only about 6 µm to 25 µm.

[0004] To prevent the formation of creases, distortions, or cracks in the uncoated edge areas, it is common practice to compensate for the height difference between coated and uncoated sections by manually applying adhesive tape to the calender transport roller. This requires very precise application of the tape, which must be removed and reapplied for each new electrode strip to be compacted in order to achieve the appropriate adjustment for different coating widths and thicknesses. This manual adjustment is very time-consuming and not always precise.

[0005] Documents WO2020 / 143971 A1 A1 and US 2018 / 226630 describe calender rollers with varying circumferences along the axial direction. Document JP S57 9667 describes a guide for strip-shaped articles with a mechanically adjustable radius.

[0006] The object of the present invention is therefore to provide a calender transport roller and a calendering device for the production of electrodes, with which a reduction in preparation time and an improvement in the accuracy and thus the quality of the compacted electrodes can be achieved.

[0007] According to a first aspect of the invention, a calender transport roller of the type mentioned at the outset is provided, wherein the transport roller has at least one adjustment section in its contact area and an expansion device is provided which changes the diameter of the transport roller in the adjustment section so that a height difference between a coated section of the electrode strip and an adjacent uncoated section of the electrode strip is compensated.

[0008] It should be noted that the contact area refers to the entire surface area of ​​the transport roller that is touched by the electrode strip or on which the electrode strip rests. This area extends axially over a large portion of the transport roller's width and can be larger than the adjustment section. The calender transport roller serves solely to transport the electrode strip to or from the calender rolls and is not itself a calender roll.

[0009] In the transport roller according to the invention, the diameter of the transport roller in the adjustment section can be selectively changed and set to a desired value, particularly mechanically (i.e., not by thermal expansion or the like), by means of the expansion device. This creates a step on the transport roller, compensating for a height difference between a coated section and an adjacent uncoated section of the electrode strip, thus ensuring a flat feed of the electrode strip to the calender rollers. This prevents undesirable stresses as well as the formation of creases, cracks, or distortions in the conductor strip in the uncoated sections of the electrode strip. The calender transport roller according to the invention therefore improves the quality of the manufactured electrodes, which are also easier to wind into coils after compaction.Furthermore, subsequent steps such as cutting the coils to size and, in particular, the cleanliness of the contour cut, which is done mechanically or by laser, are significantly facilitated by flat and wrinkle-free uncoated areas.

[0010] Compared to the previously common method of height adjustment using adhesive tape manually applied to the transport roller for each electrode strip, the solution according to the invention offers the advantage of shorter preparation time when setting up the calendering unit for a new electrode strip, while simultaneously avoiding inaccuracies caused by manual application. Furthermore, the problem of contamination of the transport roller by adhesive tape residue, which can remain after the tape is removed, is eliminated. The calender transport roller according to the invention can also be easily retrofitted into existing calendering units by simply replacing the transport roller, while the rest of the system remains unchanged.

[0011] In the adjustment section, several individual segments are arranged side by side in the axial direction of the transport roller, which can be expanded radially independently of their respective neighboring segments. This makes it particularly easy to adapt the transport roller to electrode strips with coated sections of varying widths by expanding as many segments as necessary to the larger diameter to fully support the uncoated section(s) of the electrode strip across their entire width.

[0012] The segments are designed in particular as rings or ring-like forms, whereby the segments may be slotted or divided into several ring sections in the circumferential direction.

[0013] Furthermore, the segments are preferably made of steel, especially stainless steel, which allows for particularly high precision in setting the desired diameter. Additionally, the transport roller can be radially covered outside the segments with a firm rubber material that can stretch slightly to create a particularly uniform surface.

[0014] A particularly user-friendly design can be achieved if a motor-driven expansion mechanism is provided that controls each segment individually, electrically, hydraulically or mechanically.

[0015] To optimally adapt the transport roller to different widths of the coated sections of the respective electrode strip, the width of some or all segments in the axial direction of the transport roller is advantageously no more than 2 mm. In particular, the segments have a width of only about 1 mm.

[0016] In the axial edge areas of the transport roller or the contact area, where there is usually no coating of the electrode strip, the segments can be made correspondingly wider.

[0017] To achieve particularly precise adjustment to varying coating heights, the segments are preferably designed so that the diameter of the transport roller in the adjustment section can be adjusted in increments between 10 µm and 30 µm. This allows the transport roller to be adjusted to different coating heights in increments of 5 µm to 15 µm. For expandable segments, the expansion increments must be specified accordingly. It may be sufficient if these fine increments are possible around a mean value of the coating height.

[0018] According to a third aspect of the invention, a calendering device for the production of electrodes for a battery cell, in particular for a lithium-ion battery cell, is provided. This device comprises at least one pair of calender rolls and at least one calender transport roller, as previously described. The transport roller conveys the electrode strip to a gap formed between the calender rolls. Particularly with this transport roller, which serves as the feed to the calender rolls, the precise and crease-free transport of the electrode strip is crucial for achieving high-quality electrodes. The calendering device according to the invention thus offers high flexibility and rapid adaptation to different electrode strips. Regarding the further advantages, reference is made here to the descriptions of the calender transport rollers according to the independent claims.

[0019] In a further development, a second calender transport roller according to the invention is provided in the calendering device, which is arranged in one direction of travel of the electrode strip immediately after the pair of calender rollers. In this way, the quality of the produced electrode can be improved even further, whereby the diameter of the second calender transport roller is, of course, adapted section by section to the height difference between coated and uncoated sections of the electrode strip after compaction of the coating.

[0020] Further features and advantages will become apparent from the following description of several preferred embodiments with reference to the accompanying drawings. These show: Figure 1 a schematic side view, partially cut away, of a calender transport roller according to a first embodiment of the invention, which transports an electrode strip; Figure 2a schematic top view of the calender transport roller made of Figure 1 ; Figure 3 a schematic side view, partially cut away, of a calender transport roller according to a second embodiment of the invention, which transports an electrode strip; Figure 4 a schematic side view, partially cut away, of a calender transport roller according to a third embodiment of the invention, which transports an electrode strip; Figure 5 a schematic side view, partially cut away, of a calender transport roller which does not have all the features of the invention and which transports an electrode strip; Figure 6 a schematic side view, partially cut away, of a calender transport roller according to Figure 5 , which transports an electrode strip; Figure 7a schematic side view, partially cut away, of a calender transport roller, not having all the features of the invention, which transports an electrode strip, according to; and Figure 8 a schematic view of a calendering device according to the invention.

[0021] The Figures 1 and 2 show a calender transport roller 10 according to a first embodiment of the invention, which is in a calendering device 1 (see Figure 8) is used for the production of electrodes for a battery cell, in particular a lithium-ion battery cell. The transport roller 10 serves to convey an electrode strip 12 to and from a pair of calender rollers 2. The electrode strip 12 has a planar conductor strip 14, which is a metal foil or a metal mesh unwound from a roll. Aluminum foil is used to produce a cathode, and copper foil to produce an anode. The foil thicknesses are between 6 µm and 25 µm.

[0022] The conductor tape 14 is coated on both sides, section by section, with a composite coating 16, the thickness of which is approximately 30 µm to 100 µm. The coating 16 is a suspension that is applied as a wet film and then dried. Alternatively, it can be applied by press application or as an extruded, viscous mass in a so-called solvent-free "dry coating process" or extrusion process. The width of the coating 16 is approximately 70 mm to 430 mm.

[0023] The coating 16 creates a height difference on the side facing the transport roller 10 between a coated section 18 of the electrode strip 12 and two adjacent uncoated sections 20 of the electrode strip 12 located in the edge region. The width of the uncoated edges of the electrode strip 12 is typically between 0.5 cm and 10 cm, here approximately 2 cm.

[0024] Please note that the figures are for illustrative purposes only and are not to scale.

[0025] In order to prevent mechanical deformation of the sensitive conductor tape 14 and the formation of wrinkles, cracks and warping in the uncoated sections 20, the electrode tape 12 must be enclosed by a gap 4 formed between the calender rollers 2 (see figure). Figure 8 ) are supplied as evenly as possible. For this purpose, the transport roller 10 has an adjustment section 24 on its outer surface in a contact area 22 that is touchable by the electrode strip 12, which in the embodiment according to the Figures 1 and 2 in axial direction A of the transport roller 10 extends over the entire contact area 22.

[0026] In the adjustment section 24, a plurality of individual segments 26 are arranged next to each other in the axial direction A of the transport roller 10, which can be expanded in the radial direction R of the transport roller 10 by means of a radially internal expansion device 28, by changing the diameter of the transport roller 10 in the adjustment section 24, for each individual segment 26 independently of the respective neighboring segment.

[0027] The segments 26 are made of stainless steel and are specifically designed in a ring shape, with the rings being slotted circumferentially or even divided into several ring sections. Radially, the segments 26 can additionally be covered with a firm rubber material that is slightly elastic.

[0028] The expansion device 28 comprises a motor-driven expansion mechanism that individually controls each segment 26 electrically, hydraulically, pneumatically, or mechanically. Since the expansion steps are preferably in the range of approximately 10 µm, precise mechanical control is required.

[0029] By widening the adjustment section 24 or individual segments 26 in sections, the transport roller 10 is adjusted to the electrode strip 12 to be transported in such a way that the height difference between the coated section 18 of the electrode strip 12 and the two adjacent uncoated sections 20 is compensated.

[0030] The width of each segment 26 in the axial direction A of the transport roller 10 is preferably only a few millimeters, particularly in the transition areas between the coated section 18 and the uncoated sections 20. In the central area, where the continuous coating 16 is present, the segments 26 can be correspondingly wider, as can be the radial outer edges of the adjustment section 24.

[0031] Figure 3 A second embodiment of the calender transport roller 10 is shown, wherein identical components bear the same reference numerals and only the differences to the embodiment described so far are discussed.

[0032] The transport roller 10 according to Figure 3 differs from that of the Figure 1The only difference is that the individual segments 26 in a central area of ​​the adjustment section 24 are narrower in the axial direction A, while in the edge area the segments 26 are somewhat wider.

[0033] Furthermore, in the illustrated embodiment, the electrode strip 12 has two coated sections 18, between which a further uncoated section 20 of the electrode strip 12 is provided. In order to avoid the formation of wrinkles and the like in this area as well, the segments 26 are widened here too, so that the height difference between the coated sections 18 and the intervening uncoated section 20 is compensated.

[0034] As from Figure 3 As can be seen, the width of the uncoated section 20, which lies between the coated sections 18, is approximately twice as large as the width of the uncoated sections 20 at the two edges of the electrode strip 12.

[0035] In Figure 4 A third embodiment of the calender transport roller 10 is shown, in which the adjustment section 24 does not extend over the entire contact area 22, but rather two adjustment sections 24 are provided in the axial direction A of the transport roller 10, each arranged near an axial end of the transport roller 10. The diameter of the transport roller 10 between the adjustment sections 24 is constant, thus defining the minimum width that the coating 16 may have.

[0036] Figure 5 Figure 10 shows a calender transport roller 10 that does not have all the features of the invention, and here again only the differences from the embodiments described so far are discussed. The calender transport roller 10 according to Figure 5 has an adjustment section 24 which extends in the axial direction A of the transport roller over its entire contact area 22.

[0037] However, in the adjustment section 24, not individual expandable segments are provided, but several prefabricated adjustment rings 30 with which the diameter of the transport roller 10 can be changed so that the height difference between the coated section 18 of the electrode strip 12 and the uncoated sections 20 is compensated.

[0038] The adjustment section 24 has a plurality of adjustment rings 30 which are arranged next to each other in the axial direction A of the transport roller 10.

[0039] The adjusting rings 30 are circumferentially closed and made of steel, in particular stainless steel. The adjusting rings 30 are arranged on a rigidly designed roller body 32 of the transport roller 10, in particular pushed onto it laterally.

[0040] The adjusting rings 30, which contact the electrode strip 12 or the conductor strip 14 in the uncoated sections 20, have a greater radial thickness than the adjusting rings 30, which support the coated section 18 of the electrode strip 12.

[0041] To adapt the transport roller 10 to the respective electrode strip 12, the appropriate adjusting rings 30 are selected from a large number of adjusting rings 30, which have different radial thicknesses. These rings are optimally matched to the electrode strip 12 to be transported. A complete set of adjusting rings 30 is available for this purpose, with radial thicknesses stepped in approximately 10 µm increments, and the rings appropriate to the coating 16 are selected. The roller body 32 has a uniform diameter, onto which adjusting rings 30 are mounted across the entire contact area 22.

[0042] Here too, the width of each adjusting ring 30 in the axial direction A of the transport roller 10 is in the range of a few millimeters, which makes it possible to adapt as precisely as possible to the width of the coating 16.

[0043] Figure 6 Figure 1 shows a calender transport roller 10 that does not have all the features of the invention, in which the adjustment to the height difference between the coated sections 18 and the adjacent uncoated sections 20 of the electrode strip 12 is effected by several adjusting rings 30 arranged in the adjusting section 24. Similar to the embodiment according to Figure 1. Figure 3 Here too, the electrode strip 12 has two coated sections 18, between which an uncoated section 20 is again provided. It is noticeable that the adjusting rings 30 are slightly narrower in their axial width than in the embodiment according to [reference to relevant figure]. Figure 5 , at least in a middle section of setting section 24.

[0044] A calender transport roller 10 according to another example. Since it does not have all the features of the invention, it is in Figure 7 shown. Here too, the height differences between the coated section 18 and the uncoated sections 20 are compensated for by adjusting rings 30. Similar to the embodiment according to Figure 4 , two adjustment sections 24 are provided, which are arranged near the axial ends of the transport roller 10. In a central part of the contact area 22, in which the coated section 18 of the electrode strip 12 is arranged, the roller body 32 serves directly as a contact surface for the electrode strip 12 or the coating 16.

[0045] In the embodiment shown, the roller body 32 has a uniform diameter; alternatively, however, it would also be conceivable that the central part of the roller body 32, which directly contacts the coating 16, has a larger diameter, and that the roller body 32 has a smaller diameter in the area of ​​the adjustment sections 24. Such a design offers the advantage that the adjustment rings 30 can be made thicker in the radial direction R, which is technically easier to implement.

[0046] Figure 8 Finally, a calendering device 1 according to the invention for the production of electrodes is shown, comprising a pair of calendering rollers 2 and two transport rollers 10, 10', wherein the transport roller 10 conveys the electrode strip 12 to the gap 4 formed between the calendering rollers 2.

[0047] Between the calender rollers 2, the coating 16 is compacted to reduce its porosity, resulting in an improved surface structure as well as improved conductivity and higher energy density.

[0048] The second transport roller 10' is arranged in the direction of travel L of the electrode strip 12 after the calender rollers 2 and transports the fully compacted electrode strip 12 further to a winding device in which the coated and compacted electrode strip 12 is wound into a coil (not shown in the figure).

[0049] The transport roller 10 according to Figure 3 differs from that of the Figure 1 The only difference is that the individual segments 26 in a central area of ​​the adjustment section 24 are narrower in the axial direction A, while in the edge area the segments 26 are somewhat wider.

[0050] Furthermore, in the illustrated embodiment, the electrode strip 12 has two coated sections 18, between which a further uncoated section 20 of the electrode strip 12 is provided. In order to avoid the formation of wrinkles and the like in this area as well, the segments 26 are widened here too, so that the height difference between the coated sections 18 and the intervening uncoated section 20 is compensated.

[0051] As from Figure 3 As can be seen, the width of the uncoated section 20, which lies between the coated sections 18, is approximately twice as large as the width of the uncoated sections 20 at the two edges of the electrode strip 12.

[0052] In Figure 4A third embodiment of the calender transport roller 10 is shown, in which the adjustment section 24 does not extend over the entire contact area 22, but rather two adjustment sections 24 are provided in the axial direction A of the transport roller 10, each arranged near an axial end of the transport roller 10. The diameter of the transport roller 10 between the adjustment sections 24 is constant, thus defining the minimum width that the coating 16 may have.

[0053] Figure 5 Figure 1 shows a fourth embodiment of a calender transport roller 10 according to the invention, whereby again only the differences to the embodiments described so far are discussed. The calender transport roller 10 according to Figure 5 has an adjustment section 24 which extends in the axial direction A of the transport roller over its entire contact area 22.

[0054] However, in the adjustment section 24, not individual expandable segments are provided, but several prefabricated adjustment rings 30 with which the diameter of the transport roller 10 can be changed so that the height difference between the coated section 18 of the electrode strip 12 and the uncoated sections 20 is compensated.

[0055] The adjustment section 24 has a plurality of adjustment rings 30 which are arranged next to each other in the axial direction A of the transport roller 10.

[0056] The adjusting rings 30 are circumferentially closed and made of steel, in particular stainless steel. The adjusting rings 30 are arranged on a rigidly designed roller body 32 of the transport roller 10, in particular pushed onto it laterally.

[0057] The adjusting rings 30, which contact the electrode strip 12 or the conductor strip 14 in the uncoated sections 20, have a greater radial thickness than the adjusting rings 30, which support the coated section 18 of the electrode strip 12.

[0058] To adapt the transport roller 10 to the respective electrode strip 12, the appropriate adjusting rings 30 are selected from a large number of adjusting rings 30, which have different radial thicknesses. These rings are optimally matched to the electrode strip 12 to be transported. A complete set of adjusting rings 30 is available for this purpose, with radial thicknesses stepped in approximately 10 µm increments, and the rings appropriate to the coating 16 are selected. The roller body 32 has a uniform diameter, onto which adjusting rings 30 are mounted across the entire contact area 22.

[0059] Here too, the width of each adjusting ring 30 in the axial direction A of the transport roller 10 is in the range of a few millimeters, which makes it possible to adapt as precisely as possible to the width of the coating 16.

[0060] Figure 6 Figure 1 shows a calender transport roller 10 according to a fifth embodiment of the invention, in which the adjustment to the height difference between the coated sections 18 and the adjacent uncoated sections 20 of the electrode strip 12 is effected by several adjusting rings 30 arranged in the adjusting section 24. Similar to the embodiment shown in Figure 1. Figure 3 Here too, the electrode strip 12 has two coated sections 18, between which an uncoated section 20 is again provided. It is noticeable that the adjusting rings 30 are slightly narrower in their axial width than in the embodiment according to [reference to relevant figure]. Figure 5 , at least in a middle section of setting section 24.

[0061] A calender transport roller 10 according to a sixth embodiment of the invention is in Figure 7 shown. Here too, the height differences between the coated section 18 and the uncoated sections 20 are compensated for by adjusting rings 30. Similar to the embodiment according to Figure 4 , two adjustment sections 24 are provided, which are arranged near the axial ends of the transport roller 10. In a central part of the contact area 22, in which the coated section 18 of the electrode strip 12 is arranged, the roller body 32 serves directly as a contact surface for the electrode strip 12 or the coating 16.

[0062] In the embodiment shown, the roller body 32 has a uniform diameter; alternatively, however, it would also be conceivable that the central part of the roller body 32, which directly contacts the coating 16, has a larger diameter, and that the roller body 32 has a smaller diameter in the area of ​​the adjustment sections 24. Such a design offers the advantage that the adjustment rings 30 can be made thicker in the radial direction R, which is technically easier to implement.

[0063] Figure 8 Finally, a calendering device 1 according to the invention for the production of electrodes is shown, comprising a pair of calendering rollers 2 and two transport rollers 10, 10', wherein the transport roller 10 conveys the electrode strip 12 to the gap 4 formed between the calendering rollers 2.

[0064] Between the calender rollers 2, the coating 16 is compacted to reduce its porosity, resulting in an improved surface structure as well as improved conductivity and higher energy density.

[0065] The second transport roller 10' is arranged in the direction of travel L of the electrode strip 12 after the calender rollers 2 and transports the fully compacted electrode strip 12 further to a winding device in which the coated and compacted electrode strip 12 is wound into a coil (not shown in the figure).

Claims

1. Calender transport roller for a calendering device (1) for the production of electrodes for a battery cell, in particular for a lithium-ion battery cell, which serves to convey an electrode strip (12) to or from a pair of calendering rollers (2), wherein the electrode strip (12) has a flat conductor strip (14) and a coating (16) applied in sections on at least the side facing the transport roller (10), wherein the transport roller (10) has a contact area (22) on its outer surface, which can be touched by the electrode strip (12), wherein the transport roller (10) in its contact area (22) has at least one adjustment section (24), and wherein a widening device (28) is provided which changes the diameter of the transport roller (10) in the adjustment section (24), in order to compensate for a height difference between a coated portion (18) of the electrode strip (12) and an adjacent uncoated portion (20) of the electrode strip (12), and characterized in that, in the adjustment section (24), a plurality of individual segments (26) are arranged next to one another in the axial direction (A) of the transport roller (10), which segments can be widened in the radial direction (R) of the transport roller (10) independently of the respective adjacent segment.

2. Calender transport roller according to Claim 1, characterized in that a motorized widening mechanism is provided which individually actuates the segments (26) electrically, hydraulically or mechanically.

3. Calender transport roller according to Claim 1 or 2, characterized in that a plurality of the segments (26) or all the segments (26) have a width of at most 2 mm in the axial direction (A) of the transport roller (10).

4. Calender transport roller according to one of the preceding claims, characterized in that the adjustment section (24) extends in the axial direction (A) of the transport roller (10) over its entire contact area (22).

5. Calender transport roller according to one of Claims 1 to 4, characterized in that a plurality of adjustment sections (24) are provided in the axial direction (A) of the transport roller (10), in particular at least two adjustment sections (24) which are arranged near the axial ends of the transport roller (10).

6. Calendering device for the production of electrodes for a battery cell, in particular for a lithium-ion battery cell, with at least one pair of calendering rollers (2) and at least one transport roller (10) according to one of the preceding claims, characterized in that the transport roller (10) transports the electrode strip (12) to a gap (4) formed between the calendering rollers (2).

7. Calendering device according to Claim 6, characterized in that a second transport roller (10') according to one of Claims 1 to 5 is provided, which is arranged immediately downstream of the pair of calendering rollers (2) in a running direction (L) of the electrode strip (12).