Manufacturing method for energy storage devices

Abstract

To provide a manufacturing method of a power storage device capable of suppressing warpage deformation of a sealing body, to which a collector terminal is joined, by reducing positional displacement, etc., of the collector terminal when joining an electrode foil and the collector terminal while improving a power storage capacity per case unit volume.SOLUTION: Provided is a manufacturing method of a power storage device 10 comprising: an electrode body 2 which is stored in a case 1 and in which a cathode body 21 and an anode body 22 including active material coated parts 212 and 222 and active material non-coated parts 211 and 221 are laminated on electrode foils 21K and 22K while interposing a separator 23 therebetween; and a collector terminal 4 including a base part 41 coupled to both end portions of the case 1 in a length direction and a lead part 43 to which the active material non-coated parts are joined in an overlapping state. The manufacturing method includes: an auxiliary bending step S1 of bending the active material non-coated parts in the overlapping state, adding a bending state to a boundary with the active material coated parts, and opening the active material non-coated parts; and a collector terminal joining step S2 of folding the active material non-coated parts again and joining them with the lead part after the auxiliary bending step.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The disclosed technology relates to a method for manufacturing a power storage device that can reduce the positional deviation of a current collecting terminal joined to an electrode body and suppress the warping deformation of a sealing body to which the current collecting terminal is coupled.

Background Art

[0002] Conventionally, when joining an electrode foil (non-active material coated portion) at the axial end of a stacked electrode body to a current collecting terminal, a joining tool (for example, a welding tip or an ultrasonic horn, etc.) presses the current collecting terminal and a plurality of electrode foils together, and often joins (resistance welding or ultrasonic joining) the current collecting terminal while overlapping the electrode foils. In that case, phenomena such as the current collecting terminal sliding with respect to the electrode foils during the overlapping process, and the joining portion of the current collecting terminal being displaced in the axial direction (lateral direction) of the electrode body have occurred. Therefore, a long case that houses the electrode body and to which the current collecting terminal is coupled is likely to undergo warping deformation in which the central portion in its longitudinal direction is displaced in the vertical direction. As a result, there has been a problem of reducing the measurement accuracy of a temperature sensor that monitors the battery temperature by contacting the upper surface of the case, for example.

[0003] In this regard, for example, in Patent Document 1, when joining an electrode foil and a current collecting terminal, a portion closer to the active material coated portion of the electrode body than the joined portion of the electrode foil is pressed from both sides in the stacking direction by pressing means, and the electrode foil and the current collecting terminal are joined in a state where the electrode foils are overlapped in advance. According to the above terminal joining method, since the electrode foils are overlapped in advance, the problem of the joining portion of the current collecting terminal being displaced in the axial direction is unlikely to occur. As a result, the warping deformation of the case to which the current collecting terminal is coupled can be suppressed, and for example, the measurement accuracy of a temperature sensor that contacts the upper surface of the case can be improved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] However, in this case, the electrode foil is pressed from both sides in the lamination direction by a pressing means, closer to the active material coated portion than the portion to be joined with the current collector terminal. Therefore, it is necessary to form the portion to be joined on the electrode foil in a position where the joining device does not interfere with the pressing means. For this reason, the portion to be joined on the electrode foil must be extended in a direction away from the active material coated portion of the electrode body. This is undesirable because it increases the case volume and leads to a decrease in the energy storage capacity per unit volume of the case.

[0006] The disclosed technology has been made in view of the above problems, and aims to provide a method for manufacturing an energy storage device that can improve the energy storage capacity per unit volume of the case, reduce misalignment of the current collector terminals when joining the electrode foil and the current collector terminals, and suppress warping deformation of the case to which the current collector terminals are joined. [Means for solving the problem]

[0007] (1) One aspect of the present invention for solving the above problems is a method for manufacturing an energy storage device comprising: a case; an electrode body in which a positive electrode body and a negative electrode body are laminated with a separator in between, each having a positive electrode body and a negative electrode body, each having an active material coated portion having an active material coated portion having an active material coated portion having an active material uncoated portion having one end of the electrode foil located on opposite sides in the longitudinal direction of the case where the active material is not coated; a base portion connected to both longitudinal ends of the case via insulating members; and positive and negative current collector terminals having lead portions to which the active material uncoated portions are joined in an overlapping state, the method comprising: a pre-bending step in which the active material uncoated portion is pressed with pressing tools from both sides in a direction perpendicular to the plane of the active material uncoated portion in an overlapping state to create a crease in the active material uncoated portion at the boundary with the active material coated portion, and then released; and a current collector terminal joining step in which, after the pre-bending step, the active material uncoated portion is bent again in an overlapping state and joined to the lead portion, Each of the aforementioned pressing tools has a pressing surface for pressing the uncoated portion of the active material and a vertical wall surface that stands upright relative to the pressing surface, and the intersection angle formed by the pressing surface and the vertical wall surface is an acute angle of 80 degrees or more and less than 90 degrees. This is a method for manufacturing energy storage devices.

[0008] (2) In the method for manufacturing an energy storage device described in (1), the preliminary bending step is a plurality It is preferable to fold the uncoated active material portions in an overlapping manner over several cycles. 。 [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view of an energy storage device manufactured by a manufacturing method according to one aspect of this embodiment. [Figure 2] Figure 1 is a schematic perspective view showing the state during the winding process, where the positive and negative electrodes of the electrode body are stacked with a separator in between and then wound. [Figure 3] This is a cross-sectional view AA shown in Figure 1. [Figure 4] This is an enlarged cross-sectional view of section B shown in Figure 1. [Figure 5] Figure 1 is a flowchart illustrating the manufacturing method of the energy storage device shown. [Figure 6A] Figure 4 shows a CC cross-section, which is a schematic cross-sectional view representing the stacked state of the electrode body before the preliminary bending process shown in Figure 5. [Figure 6B] Figure 6A is a schematic cross-sectional view when the uncoated active material portion is folded in an overlapping state, creating a crease in the uncoated active material portion at the boundary with the coated active material portion. [Figure 6C] Figure 6B shows a schematic cross-sectional view of the uncoated active material portion when it is released from its overlapping state. [Figure 7A] Figure 6C is a schematic cross-sectional view showing the current collection terminal set on the uncoated portion of the active material. [Figure 7B] Figure 7A is a schematic cross-sectional view showing the current collection terminals being joined by folding the uncoated active material portions into an overlapping state. [Figure 7C] Figure 7B is a schematic cross-sectional view showing the state after the bond between the uncoated active material portion and the current collector terminal has been completed. [Figure 8]This is a schematic cross-sectional view of the intermediate state in the manufacturing method of the comparative example of an energy storage device, where the bonding tool pressurizes the current collector terminal and the uncoated portion of the active material together, overlapping the uncoated portion of the active material while bonding it to the current collector terminal. [Modes for carrying out the invention]

[0010] <Description of this energy storage device> Next, the configuration of the energy storage device manufactured by the manufacturing method according to the embodiment of the disclosed technology described above will be explained in detail with reference to the drawings. Figure 1 shows a schematic cross-sectional view of an energy storage device manufactured by the manufacturing method according to one aspect of this embodiment. Figure 2 shows a schematic perspective view showing the state in the middle of winding, where the positive electrode and negative electrode of the electrode body shown in Figure 1 are stacked with a separator in between and then wound. Figure 3 shows the AA cross-sectional view shown in Figure 1. In Figures 1 and 3, the X direction indicates the longitudinal direction of the sealing body, the Y direction indicates the short direction of the sealing body, and the Z direction indicates the vertical direction of the case.

[0011] As shown in Figures 1 to 3, the energy storage device 10 manufactured by the manufacturing method according to the embodiment of the disclosed technology comprises a case 1, an electrode body 2, and a current collector terminal 4. Here, the case 1 comprises a bottomed rectangular tubular case body 11 having a rectangular opening 111, and a long, flat sealing body 12 that seals the opening 111. Both the case body 11 and the sealing body 12 are made of aluminum, but the sealing body 12 is made of a material that is softer and more easily deformable than the current collector terminal 4, due to the need to improve the opening performance of a safety valve (not shown). Note that the case 1 is not limited to the above shape.

[0012] In addition, in the opening 111 of the case body 11, a thin portion 111T is formed only on the inner wall on the short side. Therefore, both end portions 12R in the longitudinal direction (X direction) of the sealing body 12 are supported by a step portion 111S formed at the lower end of the thin portion 111T. However, there is no thin portion on the inner wall on the long side of the opening 111 of the case body 11, and even if the central portion of the sealing body 12 is displaced (warped) in the vertical direction (Z direction), it cannot be stopped. Further, on the upper surface 121 of the case 1 (sealing body 12), there is a sensor contact surface 12S formed so as to be able to contact a temperature sensor 5 for monitoring the battery temperature.

[0013] Further, the electrode body 2 is housed in the case 1 with the positive electrode body 21 and the negative electrode body 22 laminated with a separator 23 interposed therebetween. The positive electrode body 21 and the negative electrode body 22 each have an active material non-coated portion 211, 221 where the active materials KT1, KT2 are not coated on one end portions 21K1, 22K1 of the electrode foils 21K, 22K, and an active material coated portion 212, 222 where the active materials KT1, KT2 are coated on the electrode foils 21K, 22K. The active material non-coated portion 211 of the positive electrode body 21 and the active material non-coated portion 221 of the negative electrode body 22 are arranged to face each other in the longitudinal direction (X direction) of the sealing body 12. The active material coated portions 212, 222 are formed at the other end portions 21K2, 22K2 and the intermediate portions 21K3, 22K3 of the electrode foils 21K, 22K. Here, the electrode body 2 is laminated with the positive electrode body 21 and the negative electrode body 22 with a separator 23 interposed therebetween and wound in a flat shape, but the sheet-like positive electrode body 21 and the negative electrode body 22 may be laminated in a planar shape with a separator 23 interposed therebetween.

[0014] The power storage device 10 means all power storage devices capable of extracting electrical energy, and includes, for example, primary batteries, secondary batteries, electric double layer capacitors, etc. For example, in a lithium ion secondary battery, the electrode foil 21K of the positive electrode body 21 uses, for example, an aluminum foil, and the active material KT1 coated thereon is, for example, a lithium transition metal oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3It is possible to use, for example, O2, LiNiO2, etc. Also, the electrode foil 22K of the negative electrode body 22 can use, for example, a copper foil, and the active material KT2 coated thereon can use, for example, graphite, hard carbon, soft carbon, etc. Further, the separator 23 can use a porous sheet such as polypropylene or polyethylene. Note that a known non-aqueous electrolyte can be used as the electrolyte.

[0015] Also, the current collector terminal 4A of the positive electrode is made of, for example, aluminum, and the current collector terminal 4B of the negative electrode is made of, for example, copper. The positive and negative current collector terminals 4 (4A, 4B) each have a base portion 41, a base adjacent portion 42, and a lead portion 43 formed integrally. Further, the base portion 41 is coupled to the back surface sides of both end portions 12R in the longitudinal direction (X direction) of the sealing body 12 with an insulating member 3 interposed therebetween. Also, the base adjacent portion 42 is adjacent to the base portion 41 and is in contact with the insulating member 3 so as to be separable. The lead portion 43 is bent downward in the case (Z direction) from the base adjacent portion 42 at the position of the lead upper end portion 43a above the case, and is welded and joined to the lead lower end portion 43b below the case in a state where the electrode foils 21K, 22K of the active material non-coated portions 211, 221 of the electrode body 2 are overlapped (current collecting foil state).

[0016] Note that the base portion 41 is coupled to an external connection portion 45 located on the surface side of the sealing body 12 by, for example, a caulking pin 46, etc. An insulating member 3 also serving as a sealing material is interposed between the caulking pin 46 and the external connection portion 45 and the sealing body 12. The insulating member 3 can use, for example, a polyphenylene sulfide (PPS) resin. When a plurality of the power storage devices 10 are connected to the external connection portion 45, a connection bus bar (not shown) is connected thereto.

[0017] Furthermore, when welding the electrode body 2 and the lower lead end 43b together, the lower lead end 43b tends to slide against the electrode foils 21K and 22K during the foil collection process, generating an external force that displaces the lower lead end 43b in the longitudinal direction (X direction) of the sealing body 12. By reducing this external force, the warping deformation of the sealing body 12 (case 1), where the longitudinal center of the sealing body 12 (case 1), to which the base portion 41 is connected at both longitudinal ends 12R, is displaced in the vertical direction (Z direction), can be effectively suppressed. As a result, the temperature sensor 5 can make accurate contact with the sensor contact surface 12S formed on the upper surface 121 of the sealing body 12 (case 1), improving the measurement accuracy of the temperature sensor 5.

[0018] A method for manufacturing an energy storage device 10 that reduces the external force that displaces the lower end 43b of the lead in the longitudinal direction (X direction) of the sealing body 12 (case 1) when welding the electrode body 2 and the lower end 43b of the lead, is described below.

[0019] <Method of manufacturing this energy storage device> Next, a method for manufacturing the energy storage device 10 according to the embodiment of the disclosed technology described above will be explained in detail with reference to the drawings. Figure 4 shows an enlarged cross-sectional view of section B shown in Figure 1. Figure 5 shows a flowchart illustrating the method for manufacturing the energy storage device shown in Figure 1. Figure 6A shows a schematic cross-sectional view of the CC section shown in Figure 4, representing the stacked state of the electrode body before the preliminary bending process shown in Figure 5.

[0020] As shown in Figure 5, the manufacturing method of this energy storage device 10 includes a preliminary bending step S1 and a current collector terminal joining step S2. Here, as shown in Figures 4 and 6A, the electrode body 2 prior to the preliminary bending step S1 is formed linearly, with an electrode body portion 2H in which a separator 23 and the active material coated portion 222 of the negative electrode body 22 and the separator 23 and the active material coated portion 212 of the positive electrode body 21 are stacked in order, and an electrode body end portion 2T in which the uncoated active material portions 221 of the negative electrode body 22 are stacked in order with gaps in between. Note that the electrode body end portion 2T (not shown) of the positive electrode body 21, which faces the electrode body end portion 2T of the negative electrode body 22 in the longitudinal direction of the sealing body 12 (case 1), is formed linearly by stacking the uncoated active material portions 211 of the positive electrode body 21 in order with gaps in between.

[0021] Furthermore, Figure 6B shows a schematic cross-sectional view when the uncoated active material portion shown in Figure 6A is folded into an overlapping state, creating a crease in the uncoated active material portion at the boundary with the coated active material portion. Figure 6C shows a schematic cross-sectional view when the uncoated active material portion shown in Figure 6B is released from the overlapping state.

[0022] In the preliminary bending process S1, as shown in Figure 6B, the uncoated active material portions 211 and 221 are folded into an overlapping state (KS) using the pressing jig 6 to create a crease QP in the uncoated active material portions 211 and 221 at the boundary KR with the coated active material portions 212 and 222. Then, as shown in Figure 6C, the uncoated active material portions 211 and 221 are released. The pressing jig 6 comprises an upper pressing tool 6A and a lower pressing tool 6B, each having flat pressing surfaces 61 and 62 and vertical wall surfaces 63 and 64. The upper pressing tool 6A and the lower pressing tool 6B clamp the uncoated active material portions 211 and 221 from above and below, and the corners R1 and R2 of the upper pressing tool 6A and the lower pressing tool 6B create a crease QP in the uncoated active material portions 211 and 221 at the boundary KR with the coated active material portions 212 and 222.

[0023] Furthermore, the intersection angles θ1 and θ2 of the corners R1 and R2 between the pressing surfaces 61 and 62 and the vertical wall surfaces 63 and 64 are preferably formed at right angles, but they may also be formed at acute angles (for example, 80 degrees or more and less than 90 degrees). This is because forming the intersection angles θ1 and θ2 of the corners R1 and R2 at acute angles allows the corners R1 and R2 to contact the uncoated active material portions 211 and 221 of the boundary KR before contacting them, making it easier to create the crease QP. Also, when the corners R1 and R2 of the upper pressing tool 6A and the lower pressing tool 6B are formed in an arc shape, the arc radius is preferably less than 1 mm, and more preferably around 0.4 to 0.6 mm. This is because if the arc radius is 1 mm or more, the electrode foils 21K and 22K of the folded uncoated active material portions 211 and 221 may spring back, making it difficult to create a sufficient crease QP. Furthermore, when the upper pressing tool 6A and the lower pressing tool 6B clamp the uncoated active material portions 211 and 221 from above and below, the gap D1 between the pressing surfaces 61 and 62 is preferably slightly larger (for example, about 0.1 to 0.3 mm) than the total thickness D2 of the uncoated active material portions 211 and 221. This is to prevent the electrode foils 21K and 22K from being strongly pulled and breaking when the upper pressing tool 6A and the lower pressing tool 6B clamp the uncoated active material portions 211 and 221 from above and below.

[0024] Furthermore, after applying a crease QP to the uncoated active material portions 211 and 221 at the boundary KR with the active material coated portions 212 and 222, the uncoated active material portions 211 and 221 are opened as shown in Figure 6C. By opening the folded uncoated active material portions 211 and 221, they try to return to their original state by elastic force, thereby reducing the tensile residual stress of the electrode foils 21K and 22K in the uncoated active material portions 211 and 221, and making it less likely for the electrode foils 21K and 22K to break in the next current collector terminal joining process S2. Note that the uncoated active material portions 211 and 221 in the open state (KH) spring back as they try to return to their original state, but the crease QP at the boundary KR remains to a certain extent. In particular, the fold crease QP remains significantly in the uncoated active material portions 211 and 221 of the laminated upper and lower layers.

[0025] Furthermore, Figure 7A shows a schematic cross-sectional view when the current collector terminal is set on the uncoated active material portion shown in Figure 6C. Figure 7B shows a schematic cross-sectional view when the uncoated active material portion shown in Figure 7A is folded again to overlap and the current collector terminal is joined. Figure 7C shows a schematic cross-sectional view of the state in which the uncoated active material portion and the current collector terminal shown in Figure 7B have been joined.

[0026] In the current collector terminal joining process S2, after the preliminary bending process S1, as shown in Figure 7A, the lead portion 43 (lower end portion 43b of the lead) of the current collector terminal 4 is brought into contact with the open (KH) uncoated active material portions 211 and 221, where a crease QP remains at the boundary portion KR. Then, as shown in Figure 7B, the joining tool 7 is used to bend the uncoated active material portions 211 and 221 into an overlapping state and join them with the lower end portion 43b of the lead. The joining tool 7 comprises, for example, an upper pressurizer 7A and a lower pressurizer 7B, which have pressurizing surfaces 71 and 72 capable of resistance welding or ultrasonic welding. The upper pressurizer 7A and the lower pressurizer 7B are in an overlapping state (KS) where they sandwich the lower end portion 43b of the lead and the uncoated active material portions 211 and 221 from above and below. By applying an electric current or ultrasonic vibration, the uncoated active material portions 211 and 221 and the lead portion 43 (lower end portion 43b of the lead) are welded together.

[0027] Here, since a crease QP remains at the boundary KR between the uncoated active material portions 211 and 221 and the coated active material portions 212 and 222, when the upper pressurizer 7A and the lower pressurizer 7B fold the uncoated active material portions 211 and 221 again into an overlapping state (KS), the uncoated active material portions 211 and 221 can be easily folded starting from the crease QP. As a result, the breakage of the uncoated active material portions 211 and 221 can be reduced, and the external force that displaces the lower end portion 43b of the lead in the longitudinal direction (X direction) of the case can be reduced. By reducing this external force, the amount of displacement Q in the vertical direction (Z direction) of the longitudinal center of the sealing body 12 (case 1), to which the base portion 41 is connected at both longitudinal ends 12R, can be reduced, and the measurement accuracy of the temperature sensor 5 that monitors the battery temperature can be improved. Furthermore, since the creases QP of the uncoated active material portions 211 and 221 are formed at the boundary KR with the coated active material portions 212 and 222, the current collector terminals 4 can be joined near the boundary KR with the coated active material portions 212 and 222, thereby improving the energy storage capacity per unit volume of the case.

[0028] Therefore, the manufacturing method for the energy storage device 10 makes it possible to improve the energy storage capacity per unit volume of the case, reduce misalignment of the current collector terminal 4 when joining the electrode foils 21K and 22K to the current collector terminal 4, and suppress warping deformation of the case 1 to which the current collector terminal 4 is joined.

[0029] Furthermore, in the manufacturing method of this energy storage device 10, it is preferable that the preliminary bending step S1 shown in Figure 5 involves bending the uncoated active material portions 211 and 221 into an overlapping state (KS) multiple times. By bending the uncoated active material portions 211 and 221 multiple times, the crease QP formed at the boundary KR with the coated active material portions 212 and 222 can be retained more stably, and the external force that displaces the lower end portion 43b of the lead in the longitudinal direction (X direction) of the case in the current collector terminal joining step S2 can be further reduced, and the fracture of the uncoated active material portions 211 and 221 can also be reduced. Therefore, the amount of displacement Q of the longitudinal center of the sealing body 12 (case 1) to which the base portion 41 is joined at both longitudinal ends 12R can be reduced in the vertical direction (Z direction), and the measurement accuracy of the temperature sensor 5 that monitors the battery temperature can be further improved.

[0030] Furthermore, in the preliminary bending process S1, when bending the uncoated active material portions 211 and 221 into an overlapping state (KS) multiple times, it is even more preferable to gradually narrow the gap D1 between the pressurized surfaces 71 and 72 and gradually increase the bending angle of the uncoated active material portions 211 and 221. In this case, local elongation of the electrode foils 21K and 22K in the uncoated active material portions 211 and 221 can be reduced, and their breakage can be further avoided.

[0031] Figure 8 shows a schematic cross-sectional view of the intermediate state in the manufacturing method of the comparative example energy storage device 10B, in which the joining tool 7 pressurizes the current collection terminal 4 and the uncoated active material portions 211 and 221 together, overlapping the uncoated active material portions 211 and 221 while joining them to the current collection terminal 4. In this manufacturing method of the comparative example energy storage device 10B, the lower end portion 43b of the lead of the current collection terminal 4 is prone to sliding in the longitudinal direction (X direction) of the sealing body 12 (case 1) relative to the uncoated active material portions 211 and 221 while they are being bent, which increases the amount of displacement of the lower end portion 43b of the lead, and is therefore undesirable.

[0032] <Variation> The embodiments described in detail above are merely illustrative and do not limit the disclosed technology in any way. Therefore, the disclosed technology can be improved and modified in various ways without departing from its essence. For example, the pressing jig 6 used in the preliminary bending process S1 is different from the joining tool 7 used in the current collection terminal joining process S2, but it is not limited to this. For example, the joining tool 7 used in the current collection terminal joining process S2 may also be the pressing jig 6 used in the preliminary bending process S1. [Explanation of Symbols]

[0033] 1 case 2 Electrode body 3. Insulating material 4, 4A, 4B current collector terminal 10 Energy Storage Devices 21 Positive electrode 22 Negative electrode 23 Separator 21K, 22K electrode foil 21K1, 22K1 One end 41 Base section 43 Lead section 43b Lower end of lead 211, 221 Uncoated active material section 212, 222 Active material coating section KR boundary KT1, KT2 active material QP crease S1 Preliminary bending process S2 Current collector terminal joining process

Claims

1. The case and, An electrode body is formed by laminating a positive electrode body and a negative electrode body, each having an active material coated portion on the electrode foil and an active material uncoated portion on one end of the electrode foil located on opposite sides in the longitudinal direction of the case, with a separator in between. A method for manufacturing an energy storage device comprising positive and negative current collection terminals having a base portion connected to both longitudinal ends of the case via an insulating member, and a lead portion to which the uncoated portion of the active material is joined in an overlapping state, A preliminary bending step is performed by pressing the uncoated portion of the active material with pressing tools from both sides in a direction perpendicular to the plane of the uncoated portion of the active material while it is overlapping, thereby creating a crease in the uncoated portion of the active material at the boundary with the coated portion of the active material, and then releasing it. The process includes a current collector terminal joining step in which, after the preliminary bending step, the uncoated portion of the active material is bent again into an overlapping state and joined to the lead portion, Each of the aforementioned pressing tools has a pressing surface for pressing the uncoated portion of the active material, and a vertical wall surface that stands upright relative to the pressing surface. The intersection angle formed by the pressing surface and the vertical wall surface is an acute angle of 80 degrees or more and less than 90 degrees. A method for manufacturing energy storage devices.

2. In the method for manufacturing an energy storage device described in claim 1, The aforementioned preliminary bending process involves folding the uncoated active material portion into an overlapping state multiple times. A method for manufacturing energy storage devices.

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