Method for manufacturing battery cell and battery cell

Abstract

To suppress insufficient welding of a resin when manufacturing a battery cell.SOLUTION: A method for manufacturing a battery cell 1 includes stacking electrode sheets 3, 4 in a stacking direction, the electrode sheets 3, 4 including electrodes 32, 42 located in a container 10 and current collectors 31, 41 connected to the electrodes in the container and protruding outward from openings 12, 13 of the container, pressurizing and heating a resin 51 located between the stacked current collectors from an outer side toward a center side in the stacking direction, and melting the resin 51. The resin is filled in the through-hole, and the resin is welded between the current collectors to seal the opening of the container.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The technology disclosed herein relates to a battery cell manufacturing method and a battery cell. [Background technology]

[0002] Patent Document 1 describes a conventional laminated battery. The conventional laminated battery is a battery in which an electrode assembly is housed in an exterior member. The conventional laminated battery includes multiple current collector terminals extending from the electrode assembly to the exterior member. The multiple current collector terminals are stacked with a thermoplastic resin interposed therebetween. The peripheral edge of the exterior member is closed by welding the thermoplastic resin to the exterior member. In this conventional laminated battery, each of the multiple current collector terminals extends to the exterior member, and the multiple current collector terminals are not connected to each other within the exterior member. In this conventional laminated battery, the space within the exterior member can be used to expand the electrode assembly, which is advantageous for improving the energy density of the battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-272161 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional laminated batteries are manufactured by a heat-sealing process, in which overlapping thermoplastic resin layers at the periphery of the exterior member are welded together by pressing a hot plate, which serves as an energy supply source, against the overlapping layers.

[0005] However, if the number of current collectors is increased in a battery cell with a structure similar to that of a conventional laminated battery, a large number of laminated resin pieces must be welded together during battery cell manufacturing. When a large number of resin pieces are stacked, the resin pieces located toward the center of the stacking direction are farther away from the energy supply source. This can lead to insufficient energy being supplied to the resin pieces located toward the center, resulting in insufficient welding of the resin pieces located toward the center.

[0006] The technology disclosed herein prevents insufficient resin welding during battery cell manufacturing. [Means for solving the problem]

[0007] The technology disclosed herein relates to a method for manufacturing a battery cell. Stacking electrode sheets in a stacking direction, each electrode sheet having an electrode located in a container and a current collector connected to the electrode in the container and protruding outward from an opening of the container; Pressurizing and heating the resin located between the stacked current collectors from the outside toward the center in the stacking direction, The molten resin flows in the stacking direction through the through holes formed in the current collector and fills the through holes, and The resin is welded between the current collectors, and the opening of the container is sealed.

[0008] In a battery cell manufactured using this manufacturing method, each of the stacked current collectors protrudes outside the container through an opening in the container. The current collectors are connected to electrodes with the same polarity, for example. The current collectors are not connected to each other inside the container. This eliminates the need for space inside the container for connecting the current collectors. The electrodes of the battery cell can be expanded using the space inside the container. This increases the energy density of the battery cell.

[0009] The opening of the container is sealed with resin. The resin is, for example, a thermoplastic resin. During the manufacture of the battery cell, the resin located between the stacked current collectors is pressurized and heated from the outside toward the center in the stacking direction. For example, a hot plate that heats the resin is located on the outside in the stacking direction and supplies thermal energy from the outside toward the center. Due to attenuation, the thermal energy supplied to the resin located toward the center in the stacking direction tends to be lower than the thermal energy supplied to the resin located on the outside in the stacking direction.

[0010] Here, the current collector has through holes. Molten resin flows in the stacking direction through the through holes formed in the current collector. Thermal energy is carried by the resin flowing from the outside to the center in the stacking direction, thereby suppressing energy attenuation. Furthermore, because the molten resin passes through the through holes in the current collector, the heat transfer distance is substantially short, and the heat transfer path formed by the resin is continuous from the outside to the center in the stacking direction without being interrupted by the current collector. Thermal energy is sufficiently supplied to the resin located at the center in the stacking direction. All resin can be sufficiently welded to the current collector. This suppresses insufficient resin welding during battery cell manufacturing.

[0011] the electrode sheet has the resin pre-adhered to a first surface of the current collector in the stacking direction, and does not have the resin on a second surface opposite to the first surface in the stacking direction; When pressurized and heated in the stacking direction, the resin on the first surface may flow through the through holes toward the second surface and be fused to the current collector between the second surface and the current collector facing the second surface.

[0012] The electrode sheet has resin on only one side of the current collector. In a group of electrode sheets stacked in the stacking direction, the total thickness of the resin is thin. Because the heat transfer distance is short, sufficient heat energy is supplied to the resin in the center of the stacking direction when the resin is pressurized and heated.

[0013] Furthermore, the resin on the first surface flows through the through holes toward the second surface and is welded to the current collector between the second surface and the current collector facing the second surface. Even if the electrode sheet has resin on only one surface of the current collector, the resin is welded to the current collector on both sides of the current collector, thereby sealing the opening of the container.

[0014] The technology disclosed herein relates to a battery cell. a container for housing the electrodes; a plurality of current collectors connected to the electrodes in the container, the current collectors being stacked in a stacking direction and protruding to the outside of the container through an opening of the container; a resin that seals the opening of the container, the resin being welded to the current collector between the stacked current collectors, the current collector has a first surface, a second surface opposite to the first surface in the stacking direction, and at least one through-hole penetrating the current collector in the stacking direction at a location sandwiched between a first resin in contact with the first surface and a second resin in contact with the second surface, The through-hole is filled with a resin continuous to the first resin and the second resin.

[0015] In a battery cell manufactured using the above-described manufacturing method, the through-holes of the current collector are filled with resins that are continuous with the first and second resins. This prevents insufficient resin welding during battery cell manufacturing, and ensures stable battery cell quality.

[0016] the current collector has a raised portion that protrudes from an opening edge of the through hole on at least one of the first surface and the second surface, The protrusion may be embedded in the first resin or the second resin.

[0017] The protrusions embedded in the first resin or the second resin have an anchor effect, which increases the strength against peeling between the current collector and the resin welded to the current collector.

[0018] The protrusions may be burrs, for example, that occur when through-holes are formed in the current collector by machining. If burrs generated during machining become detached from the current collector, they can cause short circuits between electrodes inside the container. Burrs are generally removed from the current collector after the through-holes are formed. In contrast, in the battery cell manufacturing method described above, the burrs are embedded in the resin and do not contaminate the battery cell. This eliminates the need for a burr removal process in the battery cell manufacturing method. [Effects of the Invention]

[0019] The battery cell manufacturing method and the battery cell described above can prevent insufficient welding of resin during battery cell manufacturing. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view of a battery cell. [Figure 2] FIG. 2 shows part of the manufacturing procedure for the electrode sheet. [Figure 3] FIG. 3 shows part of the manufacturing procedure for the electrode sheet. [Figure 4] FIG. 4 is a perspective view showing the surface of a current collector in which through holes are formed. [Figure 5] The left diagram in FIG. 5 shows the container before the resin that seals the opening is welded, and the right diagram shows the container after the resin has been welded. [Figure 6] FIG. 6 is an enlarged cross-sectional view showing the welding interface between the current collector and the resin. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of a battery cell manufacturing method and a battery cell will be described with reference to the drawings. The battery cell manufacturing method and the battery cell described here are examples.

[0022] (Battery cell structure) FIG. 1 shows a schematic diagram of the overall structure of a battery cell 1. The battery cell 1 is a secondary battery. The battery cell 1 is, for example, a lithium-ion battery. The container 10 of the battery cell 1 is formed into a bag shape by folding one sheet of laminate material 11 or by overlapping two sheets of laminate material 11. The laminate material 11 has, for example, a three-layer structure in which a metal layer is sandwiched between resin layers. The metal layer is, for example, aluminum or stainless steel. The resin layer is, for example, polypropylene (PP) or polyethylene (PE). The container 10 is sealed with the power generating element 2 and electrolyte housed inside. The battery cell 1 is a so-called pouch-type battery.

[0023] The power generating element 2 has a first electrode sheet 3 and a second electrode sheet 4. The first electrode sheet 3 is, for example, a negative electrode sheet. The second electrode sheet 4 is, for example, a positive electrode sheet. The first electrode sheets 3 and the second electrode sheets 4 are alternately stacked. The number of first electrode sheets 3 and second electrode sheets 4 in the power generating element 2 is arbitrary. The power generating element 2 is an electrode laminate. Note that, hereinafter, the direction in which the first electrode sheets 3 and the second electrode sheets 4 are stacked may be referred to as the stacking direction.

[0024] The first electrode sheet 3 has a current collector 31. The current collector 31 is a thin plate or foil extending in a direction perpendicular to the stacking direction. A first end of the current collector 31, i.e., the left end in FIG. 1 , protrudes outside the container 10 through a first opening 12 of the container 10.

[0025] An active material is applied to a first surface and a second surface of a current collector 31 located inside the container 10. The first surface is the upper surface of the current collector 31 in FIG. 1, and the second surface is the lower surface of the current collector 31 in FIG. 1. The active material forms a first electrode 32. The current collector 31 is connected to the first electrode 32.

[0026] The first electrode sheet 3 has a separator 33. The separator 33 separates the first electrode 32 of the first electrode sheet 3 from a second electrode 42 (described later) of the second electrode sheet 4. The separator 33 is, for example, a porous material that is permeable to ionic substances. The separator 33 covers the surface of each of the two first electrodes 32 of the first electrode sheet 3. The area of ​​the separator 33 may be larger than the area of ​​the first electrode sheet 3.

[0027] The second electrode sheet 4 has a current collector 41. The current collector 41 is a thin plate or foil extending in a direction perpendicular to the stacking direction. A second end of the current collector 41, i.e., the right end in FIG. 1 , protrudes out of the container 10 through a second opening 13 of the container 10. The second opening 13 is an opening opposite to the first opening 12 in the direction perpendicular to the stacking direction. Note that the protruding direction of the current collector 41 is not limited to the opposite direction to the protruding direction of the current collector 31.

[0028] An active material is applied to a first surface and a second surface of a current collector 41 located inside the container 10. The active material forms a second electrode 42. The current collector 41 is connected to the second electrode 42.

[0029] As described above, the first electrode sheets 3 and the second electrode sheets 4 are stacked alternately. The first electrodes 32 and the second electrodes 42 are stacked in the stacking direction inside the container 10 with the separator 33 interposed therebetween.

[0030] The first opening 12 of the container 10 is sealed with resin 5. The resin 5 is located between the laminate material 11 and the current collector 31 and between the current collectors 31. Similarly, the second opening 13 is sealed with resin 5. The resin 5 is located between the laminate material 11 and the current collector 41 and between the current collectors 41.

[0031] The multiple current collectors 31 are not connected inside the container 10, but individually protrude outside the container 10. Similarly, the multiple current collectors 41 are not connected inside the container 10, but individually protrude outside the container 10. Because the connection space for the current collectors 31, 41 inside the container 10 can be eliminated, the areas of the first electrode 32 and the second electrode 42 can be increased accordingly. As a result, the energy density of the battery cell 1 can be increased.

[0032] (Electrode sheet manufacturing method) 2 and 3 show the manufacturing procedure of the electrode sheet. 2 and 3 show the manufacturing procedure of the first electrode sheet 3. The manufacturing procedure of the second electrode sheet 4 is the same as the manufacturing procedure of the first electrode sheet 3, except that the fifth step P5 of forming the separator 33, which will be described later, is omitted. In other words, through holes, which will be described later, are also formed in the current collector 41 of the second electrode sheet 4.

[0033] In the first step P1, a current collector 31 is prepared. If the first electrode sheet 3 is a negative electrode sheet, the current collector 31 is, for example, copper foil. The current collector 31 has a shape in which, for example, the length in the X direction is longer than the length in the Y direction. The X direction is the left-right direction on the paper in FIG. 2 or 3. The Y direction is a direction perpendicular to the X direction, and is the up-down direction on the paper in FIG. 2 or 3. This is because, as will be described later, the electrode sheet is cut in half in the X direction. However, cutting in half is not essential in the production of the electrode sheet.

[0034] In the second step P2, the active material 320 is applied to each of the first and second surfaces of the current collector 31. The active material 320 is applied to the center of the current collector 31 in the X direction.

[0035] In the third step P3, a plurality of through holes 34 are formed in the current collector 31. The through holes 34 penetrate the current collector 31 in the thickness direction (i.e., the Z direction) and open to the first and second surfaces of the current collector 31. The through holes 34 are formed on both sides of the active material 320 in the X direction, with a gap between them and the active material 320. A large number of through holes 34 are formed in the current collector 31, and the region where the through holes 34 are formed extends in the Y direction. The through holes 34 can be formed, for example, by rolling a roller with pins attached relatively over the surface of the current collector 31.

[0036] 4 illustrates a through-hole 34 formed in a current collector 31. Mechanical processing using a pin generates burrs 341 protruding from the opening edges of the through-holes 34 on the surface of the current collector 31. As will be described later, the burrs 341 become raised portions 341 that exert an anchor effect, and therefore the burrs 341 are not removed from the current collector 31. Here, a roller is rolled on each of the first surface and the second surface of the current collector 31. As a result, the burrs 341 are generated on each of the first surface and the second surface of the current collector 31.

[0037] The through-holes 34 may be formed before the active material 320 is applied to the current collector 31.

[0038] In the fourth step P4 of FIG. 3 , a resin 51 is applied to the first surface of the current collector 31. The resin 51 is applied to the area where the through-holes 34 are formed. The resin 51 forms the resin 5 that seals the openings 12 and 13 of the container 10. The resin 51 is a thermoplastic resin. The resin 51 is selected from, for example, unoriented polypropylene (CPP), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), biaxially oriented polypropylene (OPP), polyethylene terephthalate (PET), or biaxially oriented nylon (ONY). The resin 51 is not applied to the second surface of the current collector 31. After the application of the active material 320 and the resin 51 is completed, the current collector 31 is pressed, for example, by passing it through a pair of rollers. A first electrode 32 is formed on each of the first and second surfaces of the current collector 31. The resin 51 is also welded to the first surface of the current collector 31.

[0039] The order of the second step P2 of applying the active material 320 and the fourth step P4 of applying the resin 51 may be reversed. Furthermore, the application of the active material 320 and the application of the resin 51 may be performed simultaneously.

[0040] In a fifth process P5, a film 330 forming the separator 33 is attached to the current collector 31. The film 330 is attached to at least the main surface of the first electrode 32 on the first side of the current collector 31 and the main surface of the first electrode 32 on the second side. The main surface of the first electrode 32 is the surface facing the second electrode 42 with the separator 33 interposed therebetween.

[0041] In the fifth step P5, the separator 33 may be formed by applying a slurry to the current collector 31. The slurry is applied to at least the main surface of the first electrode 32 on the first side of the current collector 31 and the main surface of the first electrode 32 on the second side. After the application of the slurry, the slurry is dried to form the separator 33.

[0042] Once the first electrode 32, resin 51, and separator 33 are formed on the current collector 31 to complete the electrode sheet, the electrode sheet is cut in half in the X direction in a sixth step P6 (see the two-dot chain line). In this way, two first electrode sheets 3, 3 are produced.

[0043] (Battery cell manufacturing method) Next, a method for manufacturing the battery cell 1 will be described with reference to Fig. 5. Here, the method for manufacturing the battery cell 1 will be described using the welding of resin at the first opening 12 as an example, but the same applies to the welding of resin at the second opening 13.

[0044] First, a first electrode sheet 3 and a second electrode sheet 4 are prepared. As described above, the first electrode sheet 3 has a current collector 31, a first electrode 32, a separator 33, and a resin 51. The second electrode sheet 4 has a current collector 41, a second electrode 42, and a resin.

[0045] The first electrode sheets 3 and the second electrode sheets 4 are stacked alternately. The first electrodes 32 and the second electrodes 42 overlap with a separator 33 interposed therebetween. A power generating element 2 having a plurality of first electrode sheets 3 and a plurality of second electrode sheets 4 is formed.

[0046] As shown in the left diagram of FIG. 5 , resin 51 is located between the first end of current collector 31 of first electrode sheet 3 and first electrode 32. Resin 51 is welded only to the first surface of current collector 31. In power generating element 2, resin 51 is aligned in the stacking direction. Furthermore, resin is also located between the second end of current collector 41 of second electrode sheet 4 and second electrode 42.

[0047] After the power generating element 2 is formed, the laminate material 11 is placed over the power generating element 2. As shown in the left diagram of FIG. 5, the edges of the laminate material 11 are positioned corresponding to the resins 51 arranged in the stacking direction, and are positioned outside the outermost current collectors 31 in the stacking direction. In other words, the edges of the laminate material 11 are positioned above the uppermost current collector 31 and below the lowermost current collector 31 in the up-down direction in the left diagram of FIG. 3. The resin 51 may be provided on the edges of the laminate material 11.

[0048] Next, the resins 51 aligned in the stacking direction are welded together. Here, the resins 51 are hot-plate welded. Specifically, as shown by the white arrows in the left diagram of Figure 3, two hot plates 61, 61 located on the outside of the laminate material 11 pressurize and heat the resins 51 aligned in the stacking direction from the outside toward the center in the stacking direction.

[0049] Thermal energy from the two hot plates 61, 61 is transmitted from the outer side toward the center in the stacking direction through the laminate material 11, resin 51, and current collector 31, and the resin 51 melts due to the thermal energy. Here, as shown by the dashed arrow in the left diagram of FIG. 5 , the molten resin 51 on the first surface flows through the through holes 34 of the current collector 31 in the stacking direction and reaches from the first surface to the second surface. On the second surface, the resin 51 is welded to the current collector 31 between the second surface and the current collector 31 facing the second surface.

[0050] Thus, as shown in the right diagram of Figure 5, at the opening of the container 10 (here, the first opening 12), the spaces between the laminate material 11 and the current collectors 31, and the spaces between the current collectors 31, are sealed by the welded resin 5.

[0051] As described above, the current collector 31 has through-holes 34. The molten resin 51 flows in the stacking direction through the through-holes 34 formed in the current collector 31. Thermal energy is carried by the resin 51 flowing from the outside to the center in the stacking direction, suppressing energy attenuation. Furthermore, because the molten resin 51 passes through the through-holes 34, the actual heat transfer distance is short. Furthermore, the heat transfer path formed by the resin 51 is continuous from the outside to the center in the stacking direction without being interrupted by the current collector 31. Thermal energy is sufficiently supplied to the resin 51 located in the center in the stacking direction from the heat plate 61 on the outside in the stacking direction. All of the resin 51 can be sufficiently welded to the current collector 31 or the laminate material 11. This suppresses insufficient welding of the resin 51 during the manufacture of the battery cell 1.

[0052] Furthermore, the electrode sheet has resin 51 only on one side (here, the upper side) of the current collector 31. In a group of electrode sheets stacked in the stacking direction, the total thickness of resin 51 is thin. Because the heat transfer distance is short, thermal energy is sufficiently supplied to resin 51 at the center in the stacking direction. The quality of the manufactured battery cell 1 is stable. Note that the electrode sheet may have resin 51 only on the lower side of the current collector 31. Alternatively, the electrode sheet may have resin 51 on both sides of the current collector 31.

[0053] As shown enlarged in FIG. 6, burrs 341 on the current collector 31 are embedded in the resin 5. The burrs embedded in the resin 5, i.e., the protrusions 341, increase the resistance to peeling between the resin 5 and the current collector 31 due to an anchor effect. In FIG. 6, the resin above the current collector 31 corresponds to the first resin, and the resin below the current collector 31 corresponds to the second resin. Burrs 341 generated during the machining of the through-holes 34 are embedded in the resin 5 after the battery cell 1 is manufactured, and therefore do not fall off from the current collector 31. Because the burrs 341 do not contaminate the battery cell 1, the step of removing the burrs 341 from the current collector 31 can be omitted when manufacturing the electrode sheet. [Explanation of symbols]

[0054] 1 battery cell 10 containers 3. First electrode sheet 31 Current collector 32 1st electrode 34 Through hole 341 Burr (raised part) 4 Second electrode sheet 41 Current collector 42 2nd electrode 5. Resin 51 Resin

Claims

1. Stacking electrode sheets in a stacking direction, each electrode sheet having an electrode located in a container and a current collector connected to the electrode in the container and protruding outward from an opening of the container; Pressurizing and heating the resin located between the stacked current collectors from the outside toward the center in the stacking direction, The molten resin flows in the stacking direction through the through holes formed in the current collector and fills the through holes, and welding the resin between the current collectors and sealing the opening of the container; Battery cell manufacturing method.

2. The method for manufacturing a battery cell according to claim 1 , the electrode sheet has the resin pre-adhered to a first surface of the current collector in the stacking direction, and does not have the resin on a second surface opposite to the first surface in the stacking direction, When pressurized and heated in the stacking direction, the resin on the first surface flows toward the second surface through the through holes and is welded to the current collector between the second surface and the current collector facing the second surface. Battery cell manufacturing method.

3. a container for housing the electrodes; a plurality of current collectors connected to the electrodes in the container, the current collectors being stacked in a stacking direction and protruding to the outside of the container through an opening of the container; a resin that seals the opening of the container, the resin being welded to the current collector between the stacked current collectors, the current collector has a first surface, a second surface opposite to the first surface in the stacking direction, and at least one through-hole penetrating the current collector in the stacking direction at a location sandwiched between a first resin in contact with the first surface and a second resin in contact with the second surface, The through hole is filled with a resin continuous to the first resin and the second resin. Battery cell.

4. 4. The battery cell according to claim 3, the current collector has a protruding portion protruding from an opening edge of the through hole on at least one of the first surface and the second surface, The raised portion is embedded in the first resin or the second resin. Battery cell.

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