Battery cell, and method for manufacturing battery cell

Abstract

To suppress insufficient welding of a resin when a battery cell is manufactured.SOLUTION: A battery cell 1 includes: a container 10; a plurality of current collectors 31 which projects to the outside of the container through an opening 12 of the container, in a state in which the current collectors are laminated in a lamination direction; a first resin 51 which seals the opening of the container, and is welded to the current collectors between the laminated current collectors; and a second resin 52 which seals the opening of the container, is welded to the current collectors between the laminated current collectors, is positioned on a side closer to the center side in the lamination direction than the first resin, and is thinner in the lamination direction than the first resin.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Patent Document 1 describes a conventional laminated battery. The conventional laminated battery is a battery in which an electrode body is housed in an exterior member. The conventional laminated battery includes a plurality of current collector terminals that are pulled out from the electrode body to the exterior member. The plurality of current collector terminals are overlapped with a thermoplastic resin interposed therebetween. The peripheral portion of the exterior member is closed by welding the thermoplastic resin to the exterior member. In this conventional laminated battery, each of the plurality of current collector terminals is pulled out to the outside of the exterior member, and the plurality of 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 body, which is advantageous for improving the energy density of the battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-272161 A 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 resins at the periphery of an exterior member are welded together by pressing a hot plate, which is an energy supply source, against the overlapping thermoplastic resins in the overlapping direction.

[0005] Here, when the number of current collectors is increased in a battery cell having the same structure as a conventional laminated battery, a large number of laminated resins must be welded together during the manufacture of the battery cell. If the number of laminated resins is large, the resins located at the center in the stacking direction are far away from the energy supply source. There is a risk that sufficient energy will not be supplied to the resins located at the center, resulting in insufficient welding of the resins located at 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 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 first resin that seals an opening of the container, the first resin being welded to the current collector between the stacked current collectors; and a second resin that seals the opening of the container, the second resin being welded to the current collector between the stacked current collectors, positioned toward the center in the stacking direction more than the first resin, and having a thickness in the stacking direction less than the first resin.

[0008] In the battery cell, 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. Inside the container, the current collectors are not connected to each other. The connection space between the current collectors inside the container is omitted. The electrodes of the battery cell can be expanded by using the space inside the container. This can increase the energy density of the battery cell.

[0009] The opening of the container is sealed with a first resin and a second resin. When manufacturing the battery cell, the first resin and the second resin are supplied with energy for welding. The first resin and the second resin are, for example, thermoplastic resins. The energy supplied to the first resin and the second resin is, for example, thermal energy. However, the energy for welding is not limited to thermal energy. The energy may be, for example, vibration energy. The interface between the first resin and the second resin supplied with the vibration energy is welded by frictional heat.

[0010] The current collector, the first resin, and the second resin are stacked in the stacking direction. An energy supply source, for example, a hot plate, is located on the outside of the stacking direction and supplies energy from the outside toward the center. The energy is transmitted to the second resin through the current collector and the first resin. Due to attenuation of the energy, the energy supplied to the second resin located on the center side of the stacking direction is lower than the energy supplied to the first resin located on the outside of the stacking direction.

[0011] Here, the second resin has a smaller thickness in the stacking direction than the first resin. Although the energy supplied to the second resin is low, the energy supplied per unit volume to the second resin is equivalent to the energy supplied per unit volume to the first resin. Since the energy corresponding to the volume is supplied to the second resin, the second resin can be sufficiently welded to the current collector or between resins. Since the energy corresponding to the volume is also supplied to the first resin, the first resin can also be stably and sufficiently welded to the current collector or between resins. Insufficient welding of the resin during the manufacture of the battery cell is suppressed.

[0012] The battery cell may further include a third resin that seals the opening of the container, the third resin being welded to the current collector between the stacked current collectors, being located between the first resin and the second resin in the stacking direction, being thinner in the stacking direction than the first resin, and being thicker in the stacking direction than the second resin.

[0013] The third resin is located between the first resin and the second resin in the stacking direction. Energy for welding is transmitted in the order of the first resin, the third resin, and the second resin.

[0014] The thickness of the third resin in the stacking direction is thinner than that of the first resin and thicker than that of the second resin. The energy supplied per unit volume to the third resin is equal to the energy supplied per unit volume to the second resin or the energy supplied per unit volume to the first resin. Since the energy corresponding to the volume is supplied to the first resin, the second resin, and the third resin, the first resin, the second resin, and the third resin can be stably and sufficiently welded to the current collector, or between the resins themselves.

[0015] The current collector may have a thickness in the stacking direction at a portion where the first resin and the second resin are welded, which is greater than the thickness at other portions.

[0016] For example, compared to resin, a metal current collector has a higher efficiency in transmitting energy for welding, such as heat or vibration. A metal current collector has a lower specific heat than resin. A metal current collector has a higher Young's modulus than resin. A current collector transmits energy for welding relatively easily. If the thickness of the current collector is thick at the location where the resin is welded, the thickness of the resin becomes thin, so that attenuation of energy is suppressed when the energy for welding is transmitted in the stacking direction. Suppressing energy attenuation is advantageous for supplying energy to the second resin in the center.

[0017] The second resin may have a lower melting point than the first resin.

[0018] If the melting point of the second resin is low, the second resin can be welded to the current collector or between the resins themselves even if the energy supplied to the second resin is low. A second resin with a low melting point can prevent the welded resin from being insufficiently welded.

[0019] The battery cell disclosed herein also includes 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 first resin that seals an opening of the container, the first resin being welded to the current collector between the stacked current collectors; and a second resin that seals the opening of the container, the second resin being welded to the current collector between the stacked current collectors, located closer to the center in the stacking direction than the first resin, and having a lower melting point than the first resin.

[0020] As described above, if the melting point of the second resin is low, the second resin can be welded even if the energy supplied to the second resin is low, and insufficient welding of the resin is suppressed.

[0021] The second resin may contain an additive that lowers the melting point.

[0022] The use of additives is effective in lowering the melting point of the resin.

[0023] The technology disclosed herein also relates to a method for manufacturing a battery cell, the method comprising the steps of: Stacking electrode sheets in a stacking direction, the electrode sheets 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; a first resin positioned between the stacked current collectors and a second resin positioned between the current collectors at a position closer to the center in the stacking direction than the first resin and having a smaller thickness in the stacking direction than the first resin, the first resin being pressurized and heated from the outside toward the center in the stacking direction; and The first resin and the second resin are welded between the current collectors, and the opening of the container is sealed.

[0024] When the electrode sheets are stacked in the stacking direction during the manufacture of the battery cell, the current collectors and the first and second resins between the current collectors are stacked in the stacking direction. The current collectors, the first and second resins are pressurized and heated from the outside toward the center in the stacking direction. Thermal energy is transferred to the second resin through the current collectors and the first resin.

[0025] The second resin has a smaller thickness in the stacking direction than the first resin. The thermal energy per unit volume supplied to the second resin is equal to the thermal energy per unit volume supplied to the first resin. The second resin can be sufficiently welded by the supplied thermal energy. Also, the first resin can be stably and sufficiently welded. Insufficient welding of the resin during the manufacture of the battery cell is suppressed.

[0026] The method for manufacturing a battery cell disclosed herein also includes: Stacking electrode sheets in a stacking direction, the electrode sheets 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; a first resin positioned between the stacked current collectors and a second resin positioned between the current collectors at a position closer to the center in the stacking direction than the first resin and having a melting point lower than that of the first resin, the first resin being pressurized and heated from the outside toward the center in the stacking direction; and The first resin and the second resin are welded between the current collectors, and the opening of the container is sealed.

[0027] The second resin has a lower melting point than the first resin. Even if the thermal energy supplied to the second resin is low, the second resin can be sufficiently welded by the supplied thermal energy. Also, the first resin, which has a high melting point, can be sufficiently welded because the supplied thermal energy is high. This prevents insufficient welding of the resin during battery cell manufacturing.

[0028] In the manufacturing method, when the first resin and the second resin are pressurized and heated, the second resin may be further heated through the current collector in contact with the second resin.

[0029] The second resin at the center side in the stacking direction is supplied with heat energy not only in the stacking direction but also through the current collector, so that the second resin at the center side in the stacking direction can be stably and sufficiently welded. Effect of the Invention

[0030] According to the battery cell and the manufacturing method of the battery cell, insufficient welding of the resin during manufacturing of the battery cell can be suppressed. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is a cross-sectional view of a battery cell. [Diagram 2] FIG. 2 is a perspective view of the power generating element housed in the container. [Diagram 3] The left image in FIG. 3 shows the container before the resin that seals the opening is welded, and the right image shows the container after the resin has been welded. [Figure 4] FIG. 4 shows the structure of a battery cell according to a modified example. [Diagram 5] FIG. 5 shows the structure of a battery cell according to a modified example. [Figure 6] The left diagram in FIG. 6 shows a battery cell according to a modified example before the resin has been welded, and the right diagram shows the battery cell after the resin has been welded. [Figure 7] FIG. 7 shows the structure of a battery cell according to a modified example. [Figure 8] FIG. 8 shows a method for manufacturing a battery cell according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, embodiments of a battery cell and a method for manufacturing the battery cell will be described with reference to the drawings. The battery cell and the method for manufacturing the battery cell described here are merely examples.

[0033] (Battery cell structure) FIG. 1 shows a schematic diagram of the overall structure of a battery cell 1. FIG. 2 shows a power generating element 2 housed in a container 10 of the 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 laminate material 11 or by overlapping two laminate materials 11. The laminate material 11 has, for example, a three-layer structure in which a metal layer is sandwiched between resin layers on both sides. 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 therein. The battery cell 1 is a so-called pouch-type battery.

[0034] 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 sheet 3 may be a positive electrode sheet and the second electrode sheet 4 may be a negative electrode sheet. The first electrode sheet 3 and the second electrode sheet 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. In the following, the direction in which the first electrode sheet 3 and the second electrode sheet 4 are stacked may be referred to as the stacking direction.

[0035] The first electrode sheet 3 has a current collector 31. The current collector 31 is a thin plate material extending in a direction perpendicular to the stacking direction. A first end of the current collector 31, that is, the left end in FIG. 1 , protrudes outside the container 10 from a first opening 12 of the container 10.

[0036] An active material is applied to the upper and lower surfaces of a current collector 31 located inside the container 10. The active material forms a first electrode 32. The current collector 31 is connected to the first electrode 32.

[0037] 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 surfaces of each of the two first electrodes 32 in the first electrode sheet 3. The area of ​​the separator 33 may be larger than the area of ​​the first electrode sheet 3.

[0038] The second electrode sheet 4 has a current collector 41. The current collector 41 is a thin plate material 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 from a second opening 13 of the container 10 to the outside 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. The protruding direction of the current collector 41 is not limited to the opposite direction to the protruding direction of the current collector 31.

[0039] An active material is applied to the upper and lower surfaces 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.

[0040] As described above, the first electrode sheets 3 and the second electrode sheets 4 are alternately laminated. The first electrodes 32 and the second electrodes 42 are stacked in the lamination direction inside the container 10 with the separator 33 interposed therebetween.

[0041] 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.

[0042] 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. Since the connection space for the current collectors 31, 41 inside the container 10 can be omitted, 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.

[0043] (Battery cell manufacturing method) 2 and 3, a method for manufacturing the battery cell 1 will be described. Here, the method for manufacturing the battery cell 1 will be described using the welding of resin in the first opening 12 as an example, but the same applies to the welding of resin in the second opening 13.

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

[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. As shown in Fig. 2, a power generating element 2 having a plurality of first electrode sheets 3 and a plurality of second electrode sheets 4 is formed (i.e., the first step).

[0046] Here, as shown in the left diagram of FIG. 2 or FIG. 3, resins 51 and 52 are welded in advance between the first end and the first electrode 32 in the current collector 31 of the first electrode sheet 3. The resins 51 and 52 are welded to the upper and lower surfaces of the current collector 31, respectively. The resins 51 and 52 extend along the surface of the current collector 31 in a direction perpendicular to the stacking direction. The resins 51 and 52 form the resin 5 that seals the first opening 12 of the container 10. In the power generating element 2, the resins 51 and 52 are aligned in the stacking direction. In addition, resin is welded between the second end and the second electrode 42 in the current collector 41 of the second electrode sheet 4.

[0047] The resins 51 and 52 are thermoplastic resins, and are selected from, for example, solid 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).

[0048] After the power generating element 2 is formed, the laminate material 11 is placed on the power generating element 2. As shown in the left diagram of FIG. 3, the edge of the laminate material 11 is located at a position corresponding to the resins 51 and 52 arranged in the stacking direction, and is located outside the outermost current collector 31 in the stacking direction. In other words, the edge of the laminate material 11 is located 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 is also welded to the edge of the laminate material 11. For example, the resin 51 does not need to be provided on the edge of the laminate material 11. In this case, the resin is welded by the resin material contained in the laminate material 11.

[0049] Next, the resins 51, 52 aligned in the stacking direction are welded to each other. Here, the resins 51, 52 are hot plate welded. Specifically, as shown by the white arrows in the left diagram of Fig. 3, two hot plates 61, 61 located on the outside of the laminate material 11 pressurize and heat the resins 51, 52 aligned in the stacking direction from the outside toward the center in the stacking direction (i.e., the second step).

[0050] Thermal energy from the two hot plates 61, 61 is transferred from the outside toward the center in the stacking direction through the laminate material 11, the resins 51, 52, and the current collector 31, and the resins 51, 52 adjacent to each other in the stacking direction are welded together by receiving the thermal energy. As shown in the right diagram of Fig. 3, at the opening (here, the first opening 12) of the container 10, the spaces between the laminate material 11 and the current collector 31 and the spaces between the current collectors 31 are sealed by the welded resin 5 (i.e., the third step).

[0051] Here, the battery cell 1 has a large number of first electrode sheets 3 and second electrode sheets 4. When the resins 51, 52 are welded, the resin 52 located at the center in the stacking direction is separated from the hot plates 61, 61. The thermal energy supplied to the resin 52 located at the center in the stacking direction attenuates while being transmitted through the large number of current collectors 31 and the large number of resins 51, and becomes lower than the thermal energy supplied to the resins 51 located on the outer sides in the stacking direction. The reduction in supplied energy may cause the resin 52 to be insufficiently welded.

[0052] In contrast, the resins 51 and 52 of the first electrode sheet 3 and the resin of the second electrode sheet 4 do not all have the same thickness in the stacking direction. The thickness T2 of the resin located at the center of the stacking direction, i.e., the second resin 52, is thinner than the thickness T1 of the resin located on the outside of the stacking direction, i.e., the first resin 51. The volume of the second resin 52 is relatively small. The second resin 52 is welded to the upper and lower surfaces of the current collector 31 located at the center of the stacking direction. The number of current collectors 31 to which the second resin 52 is welded is not limited to one, and the second resin 52 may be welded to multiple current collectors 31 located at the center of the stacking direction. In addition, the second resin 52 is not limited to being welded to both the upper and lower surfaces of the current collector 31, and the second resin 52 may be welded to the upper or lower surface of the current collector 31, and the first resin 51 may be welded to the lower or upper surface of the current collector 31.

[0053] The energy supplied per unit volume to the second resin 52 is equal to the energy supplied per unit volume to the first resin 51. Even if the energy supplied to the second resin 52 is relatively low, the second resin 52 can sufficiently weld the resins together. Even if the energy supplied to the first resin 51 is relatively high, the first resin 51 can stably weld the resins together without excessive melting. This prevents the resins 51, 52 from being insufficiently welded when manufacturing the battery cell 1.

[0054] 3, the manufactured battery cell 1 has the characteristic that, for the resin 5 sealing the first opening 12 or the second opening 13 of the container 10, the thickness (T1+T2) in the stacking direction of the resin 5 located at the center in the stacking direction is thinner than the thickness (T1+T1) in the stacking direction of the resin 5 located on the outer side in the stacking direction. A battery cell 1 having this structural characteristic can stabilize quality because insufficient welding of the resins 51, 52 during manufacturing is suppressed.

[0055] (Variation 1) Fig. 4 shows a modified example of the resin thickness. In the first electrode sheet 3 of Fig. 4, the thickness T2 of the second resin 52 located on the center side in the stacking direction is thinner than the thickness T1 of the first resin 51 located on the outside in the stacking direction. In addition, the thickness T3 of the third resin 53 located between the first resin 51 and the second resin 52 is thinner than the thickness T1 and thicker than the thickness T2. In other words, the thicknesses of the resins 51, 52, and 53 become thinner in stages from the outside to the center in the stacking direction.

[0056] The thermal energy for welding is transferred in the order of first resin 51, third resin 53, and second resin 52. The energy supplied per unit volume to third resin 53 is equal to the energy supplied per unit volume to second resin 52 or the energy supplied per unit volume to first resin 51. Energy commensurate with the volume is supplied to first resin 51, second resin 52, and third resin 53. The first resin 51, second resin 52, and third resin 53 can be sufficiently welded to each other.

[0057] The number of current collectors 31 to which third resin 53 is welded is set appropriately. Also, third resin 53 is not limited to being welded to both the upper and lower surfaces of current collector 31, and third resin 53 may be welded to the upper or lower surface of current collector 31, and first resin 51 or second resin 52 may be welded to the lower or upper surface of current collector 31.

[0058] (Variation 2) Fig. 5 shows a modified example of the form of the resin welded to the current collector. In the first electrode sheet 3 (and the second electrode sheet 4) shown in Fig. 3 or 4, the resins 51 and 52 are welded in advance to both sides of the current collector 31 (or the current collector 41). In contrast, in the first electrode sheet 3 (and the second electrode sheet 4) shown in Fig. 5, the first resin 54 and the second resin 55 are welded in advance only to one side of the current collector 31 (or the current collector 41). Also, the resin 54 is welded in advance only to one edge of the two edges of the laminate material 11.

[0059] Furthermore, the thickness T5 of the second resin 55 located on the central side in the stacking direction is thinner than the thickness T4 of the first resin 54 located on the outer side in the stacking direction.

[0060] Resins 54, 55 are welded to current collector 31 or laminate material 11, rather than to each other. When resins 54, 55 are welded, the energy supplied per unit volume to second resin 55 becomes equivalent to the energy supplied per unit volume to first resin 54. Second resin 55 can be sufficiently welded to current collector 31. Also, first resin 54 can be sufficiently welded to current collector 31 or laminate material 11. Welding of resins 54, 55 insufficient during manufacture of battery cell 1 is suppressed.

[0061] (Variation 3) Fig. 6 shows modified examples of the melting point of the resin. In the battery cell 1 of Fig. 3-5, the thicknesses of the resins 51-55 are changed. The resins 51-55 are the same type of resin, and have the same melting point.

[0062] 6 differs in melting points between resins 56 and 57. Specifically, the melting point of second resin 57 located at the center in the stacking direction is lower than the melting point of first resin 56 located at the outer side in the stacking direction.

[0063] Here, the first resin 56 having a relatively high melting point can be selected from, for example, biaxially oriented polypropylene (OPP), polyethylene terephthalate (PET), or biaxially oriented nylon (ONY). The melting point of the first resin 56 is, for example, in the range of 165-264°C.

[0064] The second resin 57 having a relatively low melting point can be selected from, for example, non-oriented polypropylene (CPP), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE). The melting point of the second resin 57 is in the range of 105-165°C.

[0065] In order to lower the melting point, an additive may be added to the second resin 57. Examples of additives include phthalate esters, phosphate esters, fatty acid esters, and polyesters. Epoxy and sulfonate amides may also be used.

[0066] When welding the resins 56, 57 shown in the left diagram of Fig. 6, the second resin 57, which has a low melting point, can be sufficiently welded even if the thermal energy supplied is low. Also, the first resin 56, which has a high melting point, can be sufficiently welded because the thermal energy supplied is high. This prevents the resins 56, 57 from being insufficiently welded when manufacturing the battery cell 1.

[0067] As shown in the right diagram of Fig. 6, the manufactured battery cell 1 has a feature in that, for the resin 5 sealing the first opening 12 or the second opening 13 of the container 10, the resin 5 located at the center in the stacking direction has a lower melting point than the resin 5 located on the outer side in the stacking direction. In other words, of the resin 5 welded to the current collector 31 between the current collectors 31, the resin 5 located at the center in the stacking direction contains resin 57 with a low melting point. A battery cell 1 having this structural feature can stabilize quality because insufficient welding of the resins 51, 52 is suppressed during manufacture.

[0068] 6, the thickness T1 of the second resin 57 in the stacking direction is the same as the thickness T1 of the first resin 56. The thickness of the second resin 57 in the stacking direction may be thinner than the thickness T1 of the first resin 56.

[0069] The number of current collectors 31 to which second resin 57 is welded is set appropriately. Second resin 57 is not limited to being welded to both the upper and lower surfaces of current collector 31, and second resin 57 may be welded to the upper or lower surface of current collector 31, and first resin 56 may be welded to the lower or upper surface of current collector 31.

[0070] (Variation 4) Fig. 7 shows a modified example of the shape of the current collector. The battery cell 1 in Fig. 3-6 has a structure that allows the second resins 52, 55, 57 located at the center in the stacking direction to be sufficiently welded together even if the energy supplied to the second resins 52, 55, 57 is low.

[0071] 3-5, the thickness of the second resin 52, 55 located at the center in the stacking direction is thin so that the energy supplied per unit volume to the second resin 52, 55 located at the center in the stacking direction is large. The melting point of the second resin 57 located at the center in the stacking direction is low so that the second resin 57 located at the center in the stacking direction is welded even if it receives a low energy.

[0072] 7 promotes energy transmission so that more energy is supplied to the second resin 52 located at the center in the stacking direction. Specifically, the battery cell 1 in Fig. 7 utilizes the fact that the current collector 31 made of metal has higher energy transmission efficiency than the resins 51 and 52.

[0073] The current collector 31 has thicknesses T6, T7 in the stacking direction at the locations where the resins 51, 52 are welded, which are greater than the thickness T8 at other locations. In other words, the current collector 31 has one or two protrusions 34 at the locations where the resins 51, 52 are welded. The resins 51, 52 are thinner by the amount that the thicknesses T6, T7 of the current collector 31 are greater. In the battery cell 1 of FIG. 7, the thickness T2 of the second resin 52 located at the center in the stacking direction is thinner than the thickness T1 of the first resin 51 located on the outer side in the stacking direction. Alternatively, the thickness of the second resin 52 may be the same as the thickness T1 of the first resin 51.

[0074] When the resins 51, 52 are welded, thermal energy from the hot plates 61, 61 is transferred to the second resin 52 through the first resin 51 and the current collector 31. The thickness of the current collector 31 is large, while the thickness of the first resin 51 is small. The metal current collector 31 has a relatively low specific heat, so attenuation of thermal energy until it reaches the second resin 52 is suppressed. The second resin 52 can receive thermal energy sufficient for welding. Insufficient welding of the resins 51, 52 is suppressed during the manufacture of the battery cell 1.

[0075] All of the current collectors 31 may have one protrusion 34, or all of the current collectors 31 may have two protrusions 34. The second resin 52 may be a resin having a lower melting point than the first resin 51.

[0076] (Variation 5) 8 shows a modified manufacturing method of the battery cell 1. Specifically, in this manufacturing method, when welding the resins 56, 57, not only the heat plates 61, 61 (i.e., the first heat sources 61, 61) located on the outer side in the stacking direction but also the second heat sources 62, 62 are used. The second heat sources 62, 62 are connected to the current collector 31 that contacts the second resin 57 located on the center side in the stacking direction. The current collector 31 has a longer protruding length than the other current collectors 31. The current collector 31 has a connection allowance for the second heat sources 62, 62. The number of current collectors 31 to which the second heat sources 62, 62 are connected is not limited to one, and may be multiple.

[0077] When the resins 56, 57 are welded, the first heat sources 61, 61 pressurize and heat the resins 56, 57 in the stacking direction as described above. The second heat sources 62, 62 supply thermal energy to the resin 57 through the current collector 31. The second resin 57 receives thermal energy from the first heat sources 61, 61 and the second heat sources 62, 62 as shown by the white arrows in FIG. 8. The second resin 57 can be welded sufficiently. Also, the first resin 56 can be welded sufficiently.

[0078] 8, the second resin 57 is a resin of a different type from the first resin 56, for example, a resin with a relatively low melting point. The second resin 57 may be the same type of resin as the first resin 56.

[0079] Furthermore, the thickness of the second resin 57 may be thinner than the thickness of the first resin 56, or may be the same as the thickness of the first resin 56.

[0080] (Other variations) Although hot plate welding is used in the above description, the resin may be welded by vibration welding, ultrasonic welding, or high frequency welding, for example. All of the above configurations allow for sufficient welding of the resin located toward the center of the stacking direction in various welding techniques, even if there is a loss of energy for welding.

[0081] The features of the above-mentioned configurations can be combined to the extent possible. [Explanation of symbols]

[0082] 1 Battery Cell 10 containers 12 First opening 13 Second Opening 31 Current collector 32 1st electrode 41 Current collector 42 2nd electrode 51, 54, 56 First resin 52, 55, 57 Second resin 53 Third Resin

Claims

1. 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 first resin that seals an opening of the container, the first resin being welded to the current collector between the stacked current collectors; a second resin that seals an opening of the container, the second resin being welded to the current collector between the stacked current collectors, positioned toward the center of the stacking direction more than the first resin, and having a thickness in the stacking direction less than the first resin.

2. 2. The battery cell according to claim 1, a third resin that seals an opening of the container, the third resin being welded to the current collector between the stacked current collectors, positioned between the first resin and the second resin in the stacking direction, having a thickness in the stacking direction that is thinner than the first resin and thicker than the second resin.

3. 2. The battery cell according to claim 1, the current collector has a thickness in the stacking direction at a portion where the first resin and the second resin are welded, the thickness being greater than the thickness at other portions.

4. 2. The battery cell according to claim 1, The second resin has a lower melting point than the first resin.

5. 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 first resin that seals an opening of the container, the first resin being welded to the current collector between the stacked current collectors; a second resin that seals an opening of the container, the second resin being welded to the current collector between the stacked current collectors, positioned closer to the center in the stacking direction than the first resin, and having a lower melting point than the first resin.

6. 6. The battery cell according to claim 5, A battery cell, wherein the second resin contains an additive that lowers its melting point.

7. Stacking electrode sheets in a stacking direction, the electrode sheets 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; a first resin positioned between the stacked current collectors and a second resin positioned between the current collectors at a position closer to the center in the stacking direction than the first resin and having a smaller thickness in the stacking direction than the first resin, the first resin being pressurized and heated from the outside toward the center in the stacking direction; and the first resin and the second resin are welded between the current collectors, and the opening of the container is sealed.

8. Stacking electrode sheets in a stacking direction, the electrode sheets 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; a first resin positioned between the stacked current collectors and a second resin positioned between the current collectors at a position closer to the center in the stacking direction than the first resin and having a melting point lower than that of the first resin, the first resin being pressurized and heated from the outside toward the center in the stacking direction; and the first resin and the second resin are welded between the current collectors, and the opening of the container is sealed.

9. The method for manufacturing a battery cell according to claim 7 or 8, a current collector that is in contact with the second resin and that is heated and pressurized to the first resin and the second resin, the second resin being further heated through the current collector that is in contact with the second resin.

Images