Method for producing monocell of battery and method for producing battery

Abstract

To provide a method for producing a monocell for a planar battery with sufficient stiffness for easy handling, without requiring lamination.SOLUTION: From a first foil, the shape of a coated portion of a first electrode is partially cut out along a cut-out lane. The first foil is inserted between separator sheets, where at least one pair of alignment openings in the separator sheets are mutually aligned to each other and aligned to an alignment opening in the first foil. A second foil is then placed on or under a first assembly, and an alignment opening in the second foil is aligned to the alignment openings in the first assembly. From a second assembly 28, a monocell is cut out according to a predefined shape.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to batteries, and more particularly to batteries including a plurality of stacked battery cells. [Background technology]

[0002] A battery cell contains two or more electrodes separated by a separator sheet. Cells can be manufactured by various manufacturing techniques, including winding, folding, and stacking. According to stacking techniques, multiple monocells are stacked together, with each monocell containing a first electrode (usually a cathode) inserted between two separator sheets. The separator sheets are thermally or adhesively bonded along the periphery of the cathode and then cut to form pockets with the same shape and dimensions as the anode. These pockets containing cathodes are then alternately stacked with anodes and placed in a metal container, with tabs extending from the electrodes welded together for connection to the battery's contacts. The container is filled with liquid electrolyte before final sealing. Alternatively, stacked cells may be integrated into an aluminum laminate pouch. A general advantage of stacked cell batteries is that they can be manufactured in a variety of shapes, as the cell shape is not limited to a specific format.

[0003] Each pair of cathode-containing pocket and anode forms a monocell, and therefore the battery contains multiple stacked monocells. However, as the size of the battery decreases, it becomes more difficult to control the position of the cathode between the separator layers. As a result, precision and efficiency decrease as the cell size decreases. Furthermore, handling and alignment of individual monocells become more difficult as the size decreases.

[0004] An improved assembly method has been developed in which monocells are fabricated by placing a cathode sheet cut to the desired cell shape between continuous rolls of separator sheets, placing an anode sheet above or below it, laminating the sheets together under heat and pressure, and then cutting the monocell to the desired shape. This increases the rigidity of the monocell and allows for faster processing.

[0005] However, not all types of separator sheets can be easily laminated together, and the pressure and heat used in lamination can damage the separator and electrodes, causing undesirable results such as short circuits or poor electrolyte adsorption when the monocell is assembled into a battery. Summary of the Invention

[0006] The present invention relates to a method for manufacturing a monocell for a battery according to the appended claims. According to the method, a cutout pattern is produced in a first coated metal foil, a second coated metal foil, and a pair of separator sheets. The first foil is used to manufacture a first electrode, and the second foil is used to manufacture a second electrode of the monocell. The first electrode may be the cathode and the second electrode may be the anode, or vice versa. The invention is summarized below for the first case (first electrode is the cathode and second electrode is the anode), but the terms cathode and anode may be reversed.

[0007] The shape of the cathode coating portion is partially cut out from the cathode foil along the cutting lane. This cutting is partial in the sense that the coating portion remains attached to the foil at a predetermined location on the cathode tab. The cutting pattern in the first foil additionally includes alignment openings, while the cutting patterns in the anode foil and the paired separator sheet also include respective alignment openings. The cathode foil is inserted between the separator sheets, where at least one pair of alignment openings in the separator sheets are aligned with each other and with the alignment openings in the cathode foil. The paired separator sheets are then joined along the cutting lane to form a first assembly including a pocket containing the coated cathode portion. The anode foil is then placed above or below the first assembly, with the alignment openings in the anode foil aligned with the alignment openings in the first assembly. The anode foil is then attached to the first assembly to obtain a second assembly. A monocell is cut out from the second assembly according to a predetermined shape.

[0008] By leaving the coated cathode portion initially attached to the foil and providing respective alignment openings, proper positioning of the cathode foil between the pair of separator sheets is possible. By attaching the anode foil to the first assembly, a monocell can be formed that is sufficiently rigid for easy handling without requiring lamination. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows a monocell suitable for battery fabrication by stacking techniques. [Figures 2a-2d] 2a to 2d show the four parts of the monocell shown in FIG. [Figure 3a-3b] 1 shows cutting patterns for a cathode foil, an anode foil, and two separator sheets according to a first embodiment of the present invention. [Figure 4a-4b]1 shows cutting patterns for a cathode foil, an anode foil, and two separator sheets according to a first embodiment of the present invention. [Figure 5a-5b] 1 shows cutting patterns for a cathode foil, an anode foil, and two separator sheets according to a first embodiment of the present invention. [Figure 6] FIG. 1 shows how the cut foils and sheets shown in FIGS. 3 to 5 are assembled to form a monocell according to a first embodiment. [Figure 7] FIG. 1 shows how the cut foils and sheets shown in FIGS. 3 to 5 are assembled to form a monocell according to a first embodiment. [Figure 8] FIG. 8 shows how a monocell is cut from the assembly obtained by the assembly steps shown in FIG. [Figure 9] 10 illustrates a slight variation of the embodiment shown in FIGS. 3 to 8. [Figures 10a-10c] 1 shows applicable cutting patterns for continuous foils and separator sheets for applying the method of the present invention in a continuous production line. [Figure 11a-11b] 4 shows cutting patterns for a cathode foil and an anode foil according to a second embodiment of the present invention. [Figure 12a-12b] 4 shows cutting patterns for a cathode foil and an anode foil according to a second embodiment of the present invention. [Figure 13a-13b] 1 shows an assembly of a monocell according to a second embodiment. [Figures 14a-14c] 10 illustrates an alternative set of cutting patterns applicable to the method of the present invention where additional alignment openings are provided. DETAILED DESCRIPTION OF THE INVENTION

[0010] FIG. 1 shows a monocell 1 suitable for fabricating a battery using the lamination method described above. The battery includes a number of overlapping components, shown separately in FIGS. 2a-2d. At the bottom of the monocell is one of several electrodes. In this exemplary case, an anode 2 is shown in FIG. 2a, but it could also be the cathode. The anode is formed from a coated metal foil including a coated electrode portion 3 and an uncoated tab 4. The anode coating can be a graphite coating, in the case of a rechargeable lithium-ion battery. The tab 4 is integral with the anode foil; that is, the tab is the uncoated portion of the foil that extends out from the coated portion 3. The anode is cut into a "D" shape; however, this is merely one exemplary monocell shape. Other shapes are possible.

[0011] A pocket 11 is located on top of the anode 2. The pocket 11 contains first and second separator sheets between which the cathode is inserted. Cathode 5 is shown in FIG. 2c. Cathode 5 is formed from a metal foil having a coated portion 6 and an uncoated tab 7. The cathode coating may contain lithium cobalt oxide or other lithium-based active components in rechargeable lithium-ion batteries. Separator sheets 8 and 9, shown separately in FIGS. 2b and 2d, are attached to each other along the periphery of the coated cathode portion 6 in attachment lane 10, shown dotted in FIG. 1. Cathode tab 7 includes a portion 7a that is positioned between separator sheets 8 and 9 and a portion 7b that extends out of pocket 11 and will be positioned adjacent to anode tab 4 in the assembled monocell. The periphery of coated portion 3 of anode 2 corresponds to the periphery of the cathode-containing pocket 11.

[0012] In accordance with the present invention, a monocell 1, as shown in Figure 1, is assembled from individual sheets of material that are pre-cut according to a specific pattern and then aligned and assembled. The present invention is described for a D-shaped monocell, but is applicable to any monocell shape.

[0013] A first embodiment is shown in Figures 3 to 5. Figure 3a shows a rectangular cathode foil 14. This foil is a metal foil coated with a cathode coating over its entire surface, except for a strip 16 along one edge of the foil. That is, the strip 16 is formed from bare metal foil. The cathode foil 14 therefore includes a coated portion 15 and an uncoated portion 16. From this foil, the coated cathode portion 6 is partially cut out by removing the coated foil material at a cut-out lane 17 that surrounds the shape of the coated portion 6, as shown in Figure 3b. In addition, an alignment opening 18 is cut out of the uncoated strip 16 of foil material, resulting in a cutout that includes the cut-out lane 17 and the alignment opening 18. The alignment opening completely covers a predetermined surface area of ​​the anode tab 4 at its predetermined location and extends to the left of the anode tab location. The coated cathode portion 6 remains attached to the foil at a predetermined location 19, which is the designated location of the cathode tab.

[0014] Figure 4a shows a rectangular anode foil 20 comprising equal portions of coated 21 and uncoated strips 22. From this foil, alignment openings 23a are cut in the uncoated strips 22, as shown in Figure 3b.

[0015] The left edges of both alignment openings 18 and 23a are positioned the same distance from the predetermined anode tab location, which allows for final alignment as described further herein.

[0016] In addition to alignment opening 23a, tab opening 23b is cut from anode foil 20 opposite the intended anode tab location. The width of tab opening 23b is equal to the combined width of cathode tab 7 and the gap between tabs 4 and 7 of a monocell. More generally, tab opening 23b is sized to cover at least a predetermined surface area of ​​portion 7b of cathode tab 7 extending out of pocket 11 at that predetermined location of portion 7b.

[0017] FIG. 5a shows a rectangular separator sheet 25. As shown in FIG. 5b, alignment openings 26 are cut in the separator sheet 25. The height of the openings 26 is equal to the height of the anode tabs 4, and the width of the openings 26 is equal to the combined width of adjacent tabs 4 and 7, including the gap between said tabs, and the width of the alignment openings 23a in the anode foil. Two separator sheets 25 are cut in this manner, i.e., with alignment openings 26 of equal size. These sheets 25 are made of materials that can adhere to each other under the influence of heat and / or light. For example, a polyethylene sheet and a polypropylene sheet can be heated and bonded to each other in this manner. All cutting steps to create the tear lanes and openings may be performed, for example, by laser cutting.

[0018] Following these cutting steps, the separator sheets 25 and cathode foils 14 are superimposed in the manner shown in FIG. 6. In the superimposed image, the separator sheets 25 are shown in perspective. The cathode foil 14 is placed between two separator sheets 25, with the equally sized openings 26 of the separator sheets 25 aligned with one another. The left edges of the alignment openings 18 are aligned with the left edges of the alignment openings 26. When the cathode foils 14 and the separator sheets 25 are aligned in this manner, the separator sheets contact each other along the tear lanes 17. When the separator sheets are pressed and heated, for example by a physical heater or laser, they bond in areas corresponding to the tear lanes 17, forming an assembly 27. The tear lanes 17 now become the attachment lanes 10 shown in FIG. 1. The assembly 27 includes pockets 11 that contain the coated cathode portions 6. The coated cathode portion 6 is secured by the bond between the pair of separator sheets 25 in the attachment lane 10 and is sandwiched between the separator sheets 25 while remaining attached to the cathode foil 14 at the cathode tab locations 19.

[0019] Referring to FIG. 7 , the cut anode foil 20 is then placed under the separator sheet and cathode foil assembly 27. The left edge of alignment opening 23 a is aligned with the left edges of alignment openings 18 and 26 in assembly 27. The overlay image in FIG. 7 shows the separator sheet as well as the cathode and anode foils in perspective to visualize the alignment of openings 18, 23 a, and 26. The anode foil 20 is then attached by a suitable adhesive to the pocket containing the cut-out coated portion 6 of the cathode, thereby forming a further assembly 28. The monocell 1 is then cut from assembly 28 along cut lines 29 shown in FIG. 8 , for example by laser cutting.

[0020] By partially cutting out the cathode, i.e., by leaving the cathode attached to the foil 14 at the tab location 19 prior to bonding of the separator layers 25, and by providing alignment openings 18, 26 that allow for proper alignment of the cathode foil 14 with the separator sheet 25, proper positioning of the cathode between the separator sheets is assured, regardless of the cathode's size. Alignment openings 23a in the anode foil further allow for proper alignment of the electrodes relative to one another. The placement of openings 18, 23a, 26 relative to the predetermined tab locations further permits cutting out the monocell along a single cut line 29 after assembling the various foils and sheets. Because all components of the monocell are adhered, a highly rigid monocell is obtained that is easy to handle without requiring lamination of multiple constituent layers.

[0021] A slight variation of the above-described embodiment will be described with reference to FIG. 9 . This figure shows an alternative cutout pattern for the cathode foil 14. The cathode foil now includes alignment openings 18 a and tab openings 18 b. The tab openings 18 b are integral with the tear-off lanes 17 and, in their predetermined positions, cover a predetermined surface area of ​​the anode tab 4. The cutout patterns for the anode foil 20 and separator sheet 25 are similar to those of the previous embodiment. The only difference from the previous embodiment is that the alignment openings 18 a in the cathode foil 14 are physically separated from the tab openings 18 b. This illustrates the more general principle of this embodiment: both foils 14, 20 and both separator sheets 25 are provided with matching alignment openings that allow the foils and sheets to be superimposed and aligned by aligning the respective alignment openings along at least one edge of the opening (the left edge in the illustrated embodiment).

[0022] Tab openings 18b, 23b are not provided for alignment purposes, but to allow the final assembly to be cut out in a single cutting step resulting in the required monocell shown in Figure 1. To this end, tab opening 18b in cathode foil 14 must cover at least a predetermined surface area of ​​anode tab 4 at its predetermined position, and tab opening 23b in anode foil 20 must cover at least a predetermined surface area of ​​cathode tab portion 7b extending out of pocket 11 at its predetermined position.

[0023] 3-7 is therefore a special case in which the alignment opening 18a and the tab opening 18b in the cathode foil 14 form a single continuous opening 18. This opening 18 may be referred to as an "alignment opening" even though it serves the dual function of alignment and allowing the monocell to be cut out in a single cutting step.

[0024] According to one embodiment, the cathode and anode foils and the separator sheets may have alignment openings 18a, 23a, 26, but no tab openings, so that the assembly 28 must be cut along cutting line 29, followed by cutting out the tab-shaped portions of the cathode and anode foils, to obtain the required monocell.

[0025] Similarly, the alignment openings 26 in the separator sheet 25 may have the same shape and size as the alignment openings 18a, 23a in these foils, and the shape and location of the tabs may not be a consideration. In that case, to obtain the required monocell, after cutting the assembly 28 along the cutting lines 29, the remaining separator sheet portions between the tabs must be cut away.

[0026] The method of the present invention is suitable for producing multiple monocells and batteries in a continuous process. Figures 10a-10c show repeating cut patterns in a continuous roll of cathode foil 14 (Figure 10a), anode foil 20 (Figure 10b), and two separator sheets 25 (Figure 10c). Each of the cut patterns described above is repeated at regular distances from each other, allowing for the continuous alignment and assembly of the various components in the manner described above.

[0027] A further embodiment is shown in Figures 11 and 12. These figures show the cut patterns for the cathode foil 14 and the anode foil 20. The cut pattern for the separator sheet 25 is the same as in the previous embodiment: namely, the cut openings 26. The rectangular cathode foil 14 and the anode foil 20 shown in Figures 11a and 12a are now fully coated; that is, there are no uncoated metal strips along either side of the foil. Therefore, the coating is locally removed in the areas corresponding to the tabs. This is shown in Figures 11b and 12b, which show the cathode tab area 40 and the anode tab area 41, respectively. The localized removal of the coating can be achieved by laser ablation. The cut patterns for the cathode foil 14 and the anode foil 20 are the same as in the first embodiment: namely, the cut lines 17 and the alignment openings 18 (combined alignment and tab openings) in the cathode foil 14, and the alignment openings 23a and tab openings 23b in the anode foil 20. The removal of the coating in the tab area can occur before or after the cutting operation. Figure 13a shows how the cathode foil is inserted between and aligned with two separator sheets to obtain a first assembly 27. Figure 13B shows how the first assembly is aligned with the anode foil to obtain a second assembly 28 before cutting out the monocell along the same cutting line 29 as shown in Figure 8.

[0028] 14A and 14B show an embodiment in which additional openings are provided on the opposite side of the electrodes. In the illustrated case, this is a mirror copy 18' of the first alignment opening 18, and mirror copies 23a', 26' of alignment openings 23a, 26. These additional openings are included purely for alignment purposes and do not form part of the final cut monocell. The presence of these openings improves alignment prior to joining the separator sheets and adhering the anode foil to the first assembly.

[0029] The present invention is applicable to rechargeable and non-rechargeable flat batteries of any practically feasible shape and size. A flat battery according to the present invention can be obtained by stacking monocells produced by the method according to any embodiment of the present invention into a container, connecting the tabs of the first and second electrodes of the monocells to their respective battery contacts, and closing and sealing the container.

Claims

1. A method for manufacturing a monocell (1) for a flat battery, comprising the steps of: The monocell includes first and second electrodes (5, 2), each electrode including a coated metal foil portion (6, 3) and an uncoated metal tab (7, 4), the coated foil portion and the tab having a predetermined position relative to each other and a predetermined shape and surface area, the first electrode (5) sandwiched between two separator sheets (8, 9) attached to each other along an attachment lane (10) extending along the periphery of the coated foil portion (6) of the first electrode except for the position (19) of the tab (7) of the first electrode, the separator sheets (8, 9) forming a pocket (11) into which the coated foil portion (6) of the first electrode is inserted, a portion (7b) of the tab (7) of the first electrode extending out of the pocket (11), and the second electrode (2) attached to the pocket (11); The method comprises: - providing first and second metal foils (14, 20), each foil including a coating containing the chemical components of the first and second electrodes, respectively; - partially cutting out the coated foil portion (6) of the first electrode in the first foil (14) according to a predetermined shape by removing foil material in cutting lanes (17) extending along the periphery of said shape, the coated foil portion (6) of the first electrode remaining attached to the first foil (14) at the predetermined locations (19) of the tabs (7) of the first electrode (5); - cutting first alignment openings (18, 18a) in said first foil (14); - cutting second alignment openings (23a) in said second foil (20); - providing first and second separator sheets (25) and cutting at least a pair of registration openings (26) in each of said first and second separator sheets; - inserting the cut first foil (14) between the first and second separator sheets (25) so that the separator sheets (25) face each other along the tear-off lane (17) and aligning the pair of registration openings (26) of the separator sheets with each other and with the first registration openings (18, 18a) in the first foil (14); thereafter, adhering the separator sheets (25) together along the cutting lanes (17) to obtain a first assembly (27) comprising the pockets (11) containing the partially cut-out coated foil portions (6) of the first electrodes (5); - aligning the second foil (20) with the first assembly (27) such that the second alignment openings (23a) in the second foil (20) are aligned with the pair of alignment openings (26) in the separator sheet (25) and with the first alignment openings (18, 18a) in the first foil (14); - then attaching said second foil (20) to said first assembly (27) to obtain a second assembly (28); - cutting said second assembly (28) along cutting lines (29) that follow the contours of said attachment lanes (10) and said tabs (7, 4); A method comprising:

2. - before inserting the first foil (14) between the separator sheets (25), cutting a first tab opening (18b) in the first foil, the first tab opening covering at least a predetermined surface area of ​​the tab (4) of the second electrode (2) at the predetermined position; - before aligning the second foil (20) with the first assembly (27), cutting a second tab opening (23b) in the second foil, the second tab opening covering at least the predetermined surface area of ​​the portion (7b) of the first tab (7) extending out of the pocket (11) at the predetermined position of the portion (7b) of the first tab; The method of claim 1 , comprising:

3. The method of claim 2, wherein the alignment opening and the tab opening (18b) in the first foil form a single continuous opening (18).

4. 2. The method of claim 1, wherein one of the pair of alignment openings (26) in the separator sheet (25) covers the predetermined surface area of ​​the tab (4) of the second electrode (2) and of the portion (7b) of the tab of the first electrode (5) that extends out of the pocket (11).

5. 2. The method of claim 1, wherein the first and second foils (14, 20) are rectangular foils having a coated portion (15, 21) and an uncoated strip (16, 22) along one side of the foil, and the tear-off lane (17) and the first and second alignment openings (18, 18a, 23a) are formed such that the tabs (7, 4) of the monocell are formed from the material of the uncoated strip (16, 22) and the coated electrode portions (6, 3) of the monocell are formed from the coated portion (15, 21) of the foil.

6. 2. The method of claim 1, wherein the first and second foils (14, 20) are fully coated foils, and the method comprises the additional step of removing the coating of the respective foils at the predetermined location on the tab (7, 4) in an area (40, 41) corresponding to at least the predetermined surface area of ​​the tab (7, 4).

7. 2. The method of claim 1, wherein the alignment openings (18, 18a, 23a, 26) in the first and second foils (14, 20) and the separator sheet (25) are rectangular in shape.

8. Manufacturing a plurality of monocells (1) according to the method of claim 1; stacking the monocells in a container; connecting the tabs (7, 4) of the first and second electrodes (5, 2) of the monocell to respective battery contacts; closing and sealing said container; A method for manufacturing a battery by

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