Battery cell

Abstract

To improve durability of a current collector.SOLUTION: A battery cell 1 includes a case 10 that houses a plurality of electrodes, and a plurality of current collectors 31 and 41 that are respectively connected to the plurality of electrodes in the case 10 and have protruding portions 31a and 41a that protrude to the outside of the case 10 through an opening of the case 10 in a state of being stacked in a stacking direction, wherein the battery cell 1 includes first joining portions 8 and 9 at which the current collectors 31 and 41 are joined so as to be electrically connected to each other at the protruding portions 31a and 41a, and the protruding portions 31a and 41a include: And second joint parts 6 and 7 joined to each other via a resin layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed herein relates to 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. At the periphery of the exterior member, a thermoplastic resin is interposed between the multiple current collector terminals and the exterior member, and the thermoplastic resin is welded to the current collector terminals and the exterior member, thereby closing the periphery of the exterior member. In this conventional laminated battery, the multiple current collector terminals are not joined to each other within the exterior member, but are each extended to the outside of the exterior member and joined to each other outside the exterior member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-195393 Summary of the Invention [Problem to be solved by the invention]

[0004] When multiple collector terminals are pulled out of the exterior member and joined to each other outside the exterior member as described above, the individual collector terminals tend to be easily damaged around the joints between the collector terminals, which could impair the electrical connection between the battery cell and the outside.

[0005] The present invention has been made in view of the above points, and has as its object to improve the durability of the periphery of the joint between the current collectors. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention comprises a container that houses a plurality of electrodes, and a plurality of current collectors that are respectively connected to the plurality of electrodes within the container and stacked in a stacking direction, and have protrusions that protrude outside the container through an opening of the container, wherein the plurality of current collectors have first joints that are joined at the protrusions so as to be electrically connected to each other, and second joints that are joined at the protrusions via a resin layer.

[0007] As a result, the protruding portion of the current collector that protrudes outside the container is also joined by the second joint portion, thereby improving durability. [Effects of the Invention]

[0008] In the present invention, the durability of the periphery of the electrically connected portion of the current collector can be improved, and the reliability of the connection between the battery and the outside can be improved. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional side view of a battery cell. [Figure 2] FIG. 2 is a plan view of the battery cell with the container 10 removed. [Figure 3] FIG. 3 is a partial plan view showing an example of the second joint portion of the current collector. [Figure 4] FIG. 4 is a partial plan view showing another example of the second joint region of the current collector. [Figure 5] FIG. 5 is a partial plan view showing another example of the second joint region of the current collector. [Figure 6] FIG. 6 is a partial plan view showing another example of the second joint region of the current collector. [Figure 7] FIG. 7 is a partial plan view showing another example of the second joint region of the current collector. [Figure 8] FIG. 8 is a partial perspective view showing another example of the second joint region of the current collector. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The battery cells and methods for manufacturing the battery cells described here are examples.

[0011] (Overall battery cell configuration) The battery cell 1 has a power generating element 2 and a container 10. Figures 1 and 2 show the overall structure of the battery cell 1. The battery cell 1 is a secondary battery. The battery cell 1 may be, for example, a lithium ion battery. The battery cell 1 may be, for example, a nickel-metal hydride battery.

[0012] The container 10 is made of a laminate material 11. The container 10 is made by folding one sheet of the laminate material 11 in half and welding three sides together to form a bag. The container 10 may also be made by, for example, overlapping two sheets of the laminate material 11 together and welding four sides together to form a bag.

[0013] The laminate material 11 has a three-layer structure in which a metal layer is sandwiched between resin layers. The metal layers may be, for example, aluminum or stainless steel. The resin layers may be, for example, a heat-sealable resin. The resin layers may be, for example, polypropylene (PP) or polyethylene (PE). The container 10 is sealed with the power generating element 2 and electrolyte contained therein. The battery cell 1 is a so-called pouch-type battery.

[0014] 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 power generating element 2 has the first electrode sheets 3 and the second electrode sheets 4 alternately stacked one on top of the other. 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. 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. In other words, the stacking direction is the direction perpendicular to the main surfaces of the first electrode sheet 3 and the second electrode sheet 4.

[0015] The first electrode sheet 3 has a current collector 31. The current collector 31 is a thin plate extending in a direction perpendicular to the stacking direction. For example, when the first electrode sheet 3 is a negative electrode sheet, the current collector 31 may be made of copper or nickel. For example, when the first electrode sheet 3 is a positive electrode sheet, the current collector 31 may be made of aluminum. A first end of the current collector 31, that is, the left end in FIG. 1, protrudes outside the container 10 through a first opening 12 of the container 10. In FIG. 1, the width of the first end is the same as the width of the current collector 31. The width of the first end may be smaller than the width of the current collector 31, for example.

[0016] An active material is applied to at least one of the upper and lower surfaces of the 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. The active material may be, for example, a carbon material when the first electrode 32 is a negative electrode. The carbon material may be, for example, graphite or non-graphitizable carbon. The active material may be, for example, a silicon-based material. The silicon-based material may be, for example, silicon oxide or elemental silicon. The active material may be, for example, a mixture of a carbon material and a silicon-based material. The active material may be, for example, a transition metal oxide. The transition metal oxide may be, for example, lithium titanate (Li4Ti5O 12 The active material may be, for example, lithium metal.

[0017] The first electrode sheet 3 has a separator 33. The separator 33 separates the first electrode 32 of the first electrode sheet 3 from the second electrode 42 (described later) of the second electrode sheet 4. The separator 33 is, for example, a porous material through which an ionic substance can permeate. The separator 33 may be made of, for example, a polyolefin material. 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.

[0018] 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. The current collector 41 may be made of, for example, copper or nickel when the second electrode sheet 4 is a negative electrode sheet. The current collector 41 may be made of, for example, aluminum when the second electrode sheet is a positive electrode sheet. The second end portion of the current collector 41, that is, the right end portion in FIG. 1, protrudes outside the container 10 from the second opening 13 of the container 10.

[0019] In FIG. 1, the width of the second end portion is the same as the width of the current collector 41. The width of the second end portion may be, for example, smaller than the width of the current collector 41. 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 of the protruding direction of the current collector 31. For example, the current collector 31 and the current collector 41 may protrude in the same direction from positions shifted from each other in the same opening of the container 10.

[0020] An active material is applied to at least one of the upper surface and the lower surface of the current collector 41 located inside the container 10. The active material forms the second electrode 42. The current collector 41 is connected to the second electrode 42. The active material is, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (for example, Lix NiO2; 0 < x ≤ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≤ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), lithium phosphate having an olivine structure (e.g., Li x FePO4; 0 < x ≤ 1, Li x Fe 1-y Mn y PO4; 0 < x ≤ 1, 0 < y ≤ 1, Li x CoPO4; 0 < x ≤ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (e.g., V2O5), LiNi x Co y M z O2 (x + y + z = 1, x ≥ 0.8, M consists of Mn and Al), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) may also be used.

[0021] The electrolyte may contain an organic solvent, a lithium salt, and an additive. The organic solvent may be, for example, one or more of ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane (DME), and acetonitrile, used in any proportion.

[0022] The lithium salt may be, for example, lithium salts such as lithium perchlorate (LiClO), lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium hexafluoroarsenic (LiAsF), lithium trifluoromethanesulfonate (LiCFSO), lithium bis(trifluorosulfonyl)imide (LiTFSI), and lithium bis(fluorosulfonyl)imide (LiFSI), or mixtures thereof.

[0023] The additive may be, for example, vinylene carbonate (VC), ethylene sulfite (ES), fluoroethylene carbonate (FEC), lithium bis(oxalate)borane (LiBOB).

[0024] 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.

[0025] The first opening 12 of the container 10 is sealed with a sealing resin 5. The sealing 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 a sealing resin 5. The sealing resin 5 is located between the laminate material 11 and the current collector 41 and between the current collectors 41.

[0026] The multiple current collectors 31 are not connected to each other inside the container 10, but are connected to each other at protrusions 31a that protrude outside the container 10, as will be described later. Similarly, the multiple current collectors 41 are not connected to each other inside the container 10, but are connected to each other at protrusions 41a that protrude outside the container 10. Therefore, the area required to connect the current collectors 31 and 41 to each other inside the container 10 can be eliminated, and 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.

[0027] The current collectors 31 and 41 have first joints 8 and 9 on their protrusions 31a and 41a. The current collectors 31 and 41 are electrically connected to each other by the first joints 8 and 9. The first joints 8 and 9 may be formed by, for example, spot welding. In FIG. 1 , the thicknesses of the current collectors 31 and 41 and the sealing resin 5 are exaggerated for convenience, and the current collectors 31 and 41 are depicted as being significantly bent at the first joints 8 and 9. However, in reality, the current collectors 31 and 41 may be joined to each other with only a slight bending.

[0028] The current collectors 31 and 41 have second joints 6 and 7 around the first joints 8 and 9 of the protrusions 31a and 41a. In other words, the current collectors 31 and 41 are joined to each other via the second joints 6 and 7. That is, the first joints 8 and 9 are located within the openings 6a and 7a formed by the second joints 6 and 7. Furthermore, in the areas surrounding the first joints 8 and 9, the current collectors 31 and 41 are joined to each other via the second joints.

[0029] The second bonding portions 6 and 7 may be, for example, a welding resin layer. For example, the same welding resin layer as the sealing resin 5 may be used for the second bonding portions 6 and 7, or a different welding resin layer may be used. The second bonding portions 6 and 7 are not limited to a welding resin layer, but may also be, for example, an adhesive layer or a pressure-sensitive adhesive layer. This improves the durability of the periphery of the first bonding portions 8 and 9 of the current collectors 31 and 41, and improves the reliability of the connection between the battery cell and the outside.

[0030] 3, the second joints 6 and 7 may be located, for example, on at least a portion of the periphery of the protrusions 31a and 41a of the current collectors 31 and 41. This reduces the possibility of the protrusions 31a and 41a of the current collectors 31 and 41 being broken due to cracking from the periphery. Here, the periphery of the protrusions 31a and 41a of the current collectors 31 and 41 refers to the region from the outer periphery of the protrusions 31a and 41a to 20% of the width of the protrusions 31a and 41a.

[0031] 4, the second joints 6 and 7 do not have to be located on at least a portion of the outer periphery of the protrusions 31a and 41a of the current collectors 31 and 41. In other words, the opening regions 6a and 7a of the protrusions 31a and 41a of the current collectors 31 and 41 are connected to the outside through the outer periphery of the protrusions 31a and 41a. This allows gas to escape from the container 10 by following the shape of the second joints 6 and 7, and the direction of gas escape can be controlled by the arrangement of the second joints 6 and 7.

[0032] 5, the second joints 6 and 7 may be located, for example, on the edges of the protruding portions 31a and 41a of the current collectors 31 and 41, along the direction from the periphery of the container 10 toward the protruding ends of the protruding portions 31a and 41a. In other words, the second joints 6 and 7 do not have to be located on the outer circumferential sides of the protruding portions 31a and 41a that face the sealing resin 5. In this case, too, the direction in which the gas is ejected can be controlled by the arrangement of the second joints 6 and 7.

[0033] 1, the second joints 6 and 7 may be located not only between the current collectors 31 and 41 but also on the current collectors 31 and 41. This can improve the durability of the protrusions 31a and 41a of the current collectors 31 and 41.

[0034] (Battery cell manufacturing method) Next, we will explain the manufacturing method of the battery cell 1. Here, we will explain the manufacturing method of the battery cell 1 using the welding of resin in the first opening 12 and the joining of the current collector 31 as an example, but the welding of resin in the second opening 13 and the joining of the current collector 41 are similar.

[0035] 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, and a separator 33. The second electrode sheet 4 has a current collector 41 and a second electrode 42.

[0036] 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 the separators 33 interposed therebetween. Thus, the 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).

[0037] Here, a sealing resin 5 is previously welded to the upper and / or lower surfaces of the current collector 31 that are located on the periphery of the container 10. Also, a second bonding portion 6 is welded to the protruding portion 31a of the current collector 31 in an area excluding the opening area 6a.

[0038] The sealing resin 5 is a thermoplastic resin, specifically selected from, for example, pure polypropylene (CPP), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), biaxially oriented polypropylene (OPP), polyethylene terephthalate (PET), and biaxially oriented nylon (ONY).

[0039] The second bonding portion 6 may be made of the same resin as the sealing resin 5, or may be made of a resin with a relatively higher melting point, such as biaxially oriented polypropylene (OPP), polyethylene terephthalate (PET), or biaxially oriented nylon (ONY). By using different resin materials for the sealing resin 5 and the second bonding portions 6 and 7, the degree of freedom in selecting the respective resin materials can be easily increased.

[0040] Furthermore, flame-retardant resins such as polyvinyl chloride, polyphenylene oxide, polyvinylidene fluoride, and tetrafluoroethylene, as well as flame-retardant materials obtained by mixing bromine-based flame retardants, phosphorus-based flame retardants, inorganic flame retardants, etc. into various resins may be used for the second joint 6. This makes it difficult for the fire to spread from the current collectors 31 and 41 to the outside in the event of a short circuit and fire inside the battery.

[0041] After the power generating element 2 is formed, the laminate material 11 is placed over the power generating element 2. The sealing resin 5 is also welded to the edges of the laminate material 11. Alternatively, for example, the sealing resin 5 may not be provided on the edges of the laminate material 11. In this case, the edges are welded by the resin material contained in the laminate material 11.

[0042] Next, the sealing resins 5 aligned in the stacking direction are welded to each other. Specifically, for example, the sealing resins 5 aligned in the stacking direction are pressurized and heated from the outside toward the center in the stacking direction by two hot plates (not shown) positioned on the outside of the laminating material 11 (i.e., the second step).

[0043] The thermal energy from the two hot plates is transmitted from the outside toward the center in the stacking direction through the laminate material 11, the sealing resin 5, and the current collector 31, and adjacent sealing resins 5 in the stacking direction, or the sealing resin 5 and the current collector 31, are welded together by the thermal energy, and the spaces between the laminate material 11 and the current collector 31, and between the current collectors 31, are sealed by the welded sealing resin 5 at the opening of the container 10 (here, the first opening 12) (i.e., the third step).

[0044] Furthermore, similar to the sealing with the sealing resin 5, the protruding portion 31a of the current collector 31 and the second bonding portion 6 are bonded by heating and pressure (i.e., the fourth step). Note that such bonding may be performed prior to or simultaneously with the bonding of the laminate material 11 and the current collector 31.

[0045] Thereafter, the first joint portion 8 is joined to the protruding portion 31a of the current collector 31 by spot welding or the like (i.e., the fifth step). The joining of the first joint portion 8 may also be performed prior to the joining of the laminate material 11 and the current collector 31, or prior to the joining of the protruding portion 31a of the current collector 31 and the second joint portion 6. The joining of the first joint portion 8 to the protruding portion 31a of the current collector 31 may be performed by, for example, laser welding.

[0046] (Other matters) The second joints 6 and 7 are not limited to the entire area excluding the opening areas 6a and 7a of the protrusions 31a and 41a of the current collector 31 as described above, but may be provided in an area including at least a portion of the periphery of the protrusions 31a and 41a, or an area including the edge extending from the periphery of the container 10 toward the protruding ends of the protrusions 31a and 41a, as shown in Figures 3 to 5, for example.

[0047] 6, the sealing resin 5 may extend from the periphery of the container 10 toward the protruding portions of the current collectors 31 and 41, and function as the second bonding portions 6 and 7. In this case, as shown in FIG.

[0048] In addition, when the sealing resin 5 and the second bonding portion 7(6) are made of different resin materials and a gap is provided between them, for example, as shown in Fig. 7, the boundary between the sealing resin 5 and the second bonding portion 7(6) may be interdigitated like comb teeth, so that the sealing resin 5 or the second bonding portion 7(6) is always interposed between the peripheral edge of the container 10 and the first bonding portion 9(8) when viewed in the direction indicated by arrow A in the figure. Furthermore, as shown in Fig. 8, for example, the gap (boundary) between the sealing resin 5 and the second bonding portion 7(6) may be shifted from each other in each layer, so that the sealing resin 5 or the second bonding portion 7(6) is always interposed between the peripheral edge of the container 10 and the first bonding portion 9(8) when viewed in the direction indicated by arrow B in the figure. This prevents the current collector 41 (31) from having only the protruding portion 41a (31a) when viewed in the direction indicated by the arrows A and B, thereby making the current collector 41 (31) less susceptible to damage. [Explanation of symbols]

[0049] 1 battery cell 2 Power generation elements 3. First electrode sheet 4 Second electrode sheet 5 Sealing resin 6 Second joint 6a Opening area 7 Second joint 7a Opening area 8 1st joint 9 1st joint 10 containers 11 Laminated materials 12 First opening 13 Second opening 31 Current collector 31a Protrusion 32 1st electrode 33 Separator 41 Current collector 41a Protrusion 42 2nd electrode

Claims

1. a container containing a plurality of electrodes; a plurality of current collectors connected to the plurality of electrodes in the container, stacked in a stacking direction, each current collector having a protrusion that protrudes to the outside of the container through an opening of the container; Equipped with a first joint portion at the protruding portion where the current collectors are joined so as to be electrically connected to each other, and a second joint portion at the protruding portion where the current collectors are joined to each other via a resin layer.

2. 10. The battery cell of claim 1, The battery cell is characterized in that the second joint portion surrounds the first joint portion.

3. 10. The battery cell of claim 1, The battery cell is characterized in that the second joint portion is located on at least a portion of the periphery of the protruding portion of the current collector.

4. 10. The battery cell of claim 1, a second joint portion located on an edge portion of the protruding portion of the current collector along a direction from a peripheral edge portion of the container toward a protruding end portion of the protruding portion.

5. 10. The battery cell of claim 1, The battery cell, wherein the second joint portion includes any one of a welding resin layer, an adhesive layer, and a pressure-sensitive adhesive layer.

6. 6. The battery cell of claim 5, The container further includes a thermoplastic resin layer at a peripheral portion thereof for welding the plurality of current collectors, The battery cell is characterized in that the welding resin layer is a thermoplastic resin layer that extends from the peripheral edge of the container toward the protruding portion of the current collector.

7. 6. The battery cell of claim 5, The battery cell is characterized in that the welding resin layer is a flame-retardant resin layer.

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