Manufacturing method of power storage device

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 technique relates to a method for manufacturing an electricity storage device that can reduce misalignment of current collecting terminals joined to an electrode assembly and suppress warping deformation of a sealing body to which the current collecting terminals are joined. [Background technology]

[0002] Conventionally, when joining the electrode foil (active material non-coated portion) at the axial end of a laminated electrode body to a current collecting terminal, a joining tool (e.g., a welding tip or ultrasonic horn, etc.) often presses the current collecting terminal and multiple sheets of electrode foil together, and joins the electrode foil to the current collecting terminal while overlapping them (resistance welding or ultrasonic joining). In such cases, the current collecting terminal slides against the electrode foil in the middle of overlapping, causing a phenomenon in which the joint of the current collecting terminal is displaced in the axial direction (lateral direction) of the electrode body. For this reason, a long case that houses the electrode body and to which the current collecting terminal is joined is prone to warping deformation in which the longitudinal center is displaced in the up and down direction, resulting in a problem of, for example, reducing the measurement accuracy of a temperature sensor that contacts the top surface of the case to monitor the battery temperature.

[0003] In this regard, for example, Patent Document 1 discloses a terminal joining method in which, when joining an electrode foil and a current collecting terminal, a pressing means is used to press the electrode foil closer to the active material coated portion of the electrode body than the joined portion of the electrode foil from both sides in the lamination direction, and the electrode foil and the current collecting terminal are joined in a state in which 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 joint portion of the current collecting terminal being misaligned in the axial direction is unlikely to occur. As a result, it is possible to suppress warping deformation of the case to which the current collecting terminal is joined, and it is possible to improve the measurement accuracy of, for example, a temperature sensor that is brought into contact with the upper surface of the case. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-22203 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in this case, since the electrode foil is pressed by the pressing means from both sides in the stacking direction closer to the active material-coated portion than the joining portion to be joined to the current collecting terminal, it is necessary to form the joining portion of the electrode foil at a position where the joining tool does not interfere with the pressing means. Therefore, the joining portion of 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 reduces the storage capacity per unit volume of the case.

[0006] The present disclosed technology has been made in consideration of such problems, and has an objective of providing a manufacturing method for an electricity storage device that can improve the electricity storage capacity per unit volume of the case while reducing positional misalignment of the current collecting terminal when joining the electrode foil and the current collecting terminal, thereby suppressing warping deformation of the case to which the current collecting terminal is joined. [Means for solving the problem]

[0007] (1) One aspect of the disclosed technique for solving the above-mentioned problems is a method for manufacturing an electricity storage device including a case; an electrode body in which positive and negative electrode bodies are stacked with a separator sandwiched between them, the positive and negative electrode bodies being housed in the case and having an active material-coated portion in which an active material is coated on an electrode foil and an active material-uncoated portion in which the active material is not coated at one end of the electrode foil facing each other in the longitudinal direction of the case; and positive and negative current collecting terminals having a base portion joined to both longitudinal ends of the case via an insulating member and lead portions to which the active material-uncoated portions are joined in an overlapping state, the method including: a pre-bending step of folding the active material-uncoated portions into an overlapping state, forming a crease in the active material-uncoated portions at the boundary with the active material-coated portions, and then releasing the active material-uncoated portions; and a current collecting terminal joining step of folding the active material-uncoated portions again into an overlapping state after the pre-bending step, and joining the active material-uncoated portions to the lead portions.

[0008] (2) In the method for producing an electricity storage device described in (1), the pre-bending step preferably includes bending the active material non-coated portion into an overlapping state a plurality of times. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of an electricity storage device manufactured by a manufacturing method according to one aspect of the present embodiment. [Diagram 2] 2 is a schematic perspective view showing a state in the middle of winding the positive electrode body and the negative electrode body of the electrode assembly shown in FIG. 1, with a separator sandwiched between them. FIG. [Diagram 3] 2 is a cross-sectional view taken along the line AA in FIG. 1. [Figure 4] FIG. 2 is an enlarged cross-sectional view of a portion B shown in FIG. [Diagram 5] 2 is a flowchart showing a method for manufacturing the electricity storage device shown in FIG. 1. [Figure 6A] 6 is a schematic cross-sectional view taken along the CC cross section shown in FIG. 4, illustrating the laminated state of the electrode body before the preliminary bending step shown in FIG. 5. [Figure 6B] 6B is a schematic cross-sectional view of the non-coated portion of active material shown in FIG. 6A folded in an overlapping state to form a crease in the non-coated portion of active material at the boundary with the coated portion of active material. FIG. [Figure 6C] FIG. 6C is a schematic cross-sectional view of the active material non-coated portion shown in FIG. 6B when it is released from the overlapping state. [Figure 7A] FIG. 6D is a schematic cross-sectional view of a current collecting terminal set on the active material non-coated portion shown in FIG. 6C. [Figure 7B] FIG. 7B is a schematic cross-sectional view showing the active material non-coated portion shown in FIG. 7A being folded again into an overlapping state and a current collecting terminal being joined. [Figure 7C] FIG. 7C is a schematic cross-sectional view showing a state in which joining of the active material non-coated portion and the current collecting terminal shown in FIG. 7B is completed. [Figure 8] This is a schematic cross-sectional view of a state in the middle of a manufacturing method of an electricity storage device of a comparative example, in which a connector presses a current collecting terminal and an active material non-coated portion together to join the active material non-coated portion to the current collecting terminal while overlapping it. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Description of this energy storage device> Next, the configuration of the electricity storage device manufactured by the manufacturing method according to the embodiment of the disclosed technology will be described in detail with reference to the drawings. Fig. 1 shows a schematic cross-sectional view of an electricity storage device manufactured by the manufacturing method according to one aspect of the present embodiment. Fig. 2 shows a schematic perspective view of a state in the middle of winding in which the positive electrode body and the negative electrode body of the electrode body shown in Fig. 1 are stacked with a separator sandwiched therebetween and wound. Fig. 3 shows an AA cross-sectional view shown in Fig. 1. In Figs. 1 and 3, the X direction indicates the longitudinal direction of the sealing body, the Y direction indicates the lateral direction of the sealing body, and the Z direction indicates the up-down direction of the case.

[0011] An electricity storage device 10 manufactured by the manufacturing method according to the embodiment of the disclosed technique includes a case 1, an electrode assembly 2, and a current collecting terminal 4, as shown in Figs. 1 to 3. Here, the case 1 includes a case body 11 in the shape of a bottomed square cylinder 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 deformed than the current collecting terminal 4 because of the need to improve the opening performance of a safety valve (not shown). The case 1 is not limited to the above shape.

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

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

[0014] The present electricity storage device 10 refers to any electricity storage device capable of extracting electric energy, and includes, for example, a primary battery, a secondary battery, an electric double layer capacitor, etc. For example, in a lithium ion secondary battery, the electrode foil 21K of the positive electrode body 21 is, for example, an aluminum foil, and the active material KT1 applied thereto is, for example, a lithium transition metal oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 For example, a copper foil may be used as the electrode foil 22K of the negative electrode body 22, and for example, graphite, hard carbon, soft carbon, etc. may be used as the active material KT2 to be applied thereto. For example, a porous sheet of polypropylene, polyethylene, etc. may be used as the separator 23. For the electrolyte, a known non-aqueous electrolyte may be used.

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

[0016] The base portion 41 is coupled to an external connection portion 45 located on the front surface side of the sealing body 12 by, for example, a crimp pin 46 or the like. An insulating member 3 also serving as a sealant is interposed between the crimp pin 46 and the sealing body 12 and between the external connection portion 45 and the sealing body 12. For example, polyphenylene sulfide (PPS) resin can be used as the insulating member 3. When multiple electricity storage devices 10 are connected, a connecting bus bar (not shown) is connected to the external connection portion 45.

[0017] Furthermore, when electrode body 2 and lead lower end 43b are welded together, lead lower end 43b slides relative to electrode foils 21K and 22K in the middle of being collected, and an external force is likely to be generated that displaces lead lower end 43b in the longitudinal direction (X direction) of sealing body 12. By reducing this external force, it is possible to effectively suppress warpage deformation of sealing body 12 (case 1) in which the longitudinal center of sealing body 12 (case 1) where base portion 41 is joined to both longitudinal ends 12R is displaced in the up-down direction (Z direction). As a result, temperature sensor 5 can accurately contact sensor contact surface 12S formed on upper surface 121 of sealing body 12 (case 1), and the measurement accuracy of temperature sensor 5 can be improved.

[0018] A method for manufacturing an electricity storage device 10 that can reduce the external force that displaces the lead lower end 43b in the longitudinal direction (X direction) of the sealing body 12 (case 1) when the electrode body 2 and the lead lower end 43b are welded together will be described below.

[0019] <Method of manufacturing the present electricity storage device> Next, a method for manufacturing the electricity storage device 10 according to the embodiment of the disclosed technique will be described in detail with reference to the drawings. Fig. 4 shows an enlarged cross-sectional view of part B shown in Fig. 1. Fig. 5 shows a flow chart showing a method for manufacturing the electricity storage device shown in Fig. 1. Fig. 6A shows a schematic cross-sectional view of the CC cross-section shown in Fig. 4, showing the laminated state of the electrode body before the preliminary bending step shown in Fig. 5.

[0020] As shown in Fig. 5, the manufacturing method of the present electricity storage device 10 includes a preliminary bending step S1 and a current collecting terminal joining step S2. Here, as shown in Fig. 4 and Fig. 6A, the electrode body 2 before the preliminary bending step S1 has an electrode main body 2H in which the separator 23, 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 laminated in order, and an electrode body end 2T in which the active material non-coated portion 221 of the negative electrode body 22 are laminated in order with a gap therebetween, each of which is formed linearly. Note that the electrode body end 2T of the negative electrode body 22 and the electrode body end 2T (not shown) of the positive electrode body 21 facing each other in the longitudinal direction of the sealing body 12 (case 1) are formed linearly by laminating the active material non-coated portion 211 of the positive electrode body 21 in order with a gap therebetween.

[0021] Fig. 6B is a schematic cross-sectional view of the non-coated portion shown in Fig. 6A folded into an overlapping state to form a crease in the non-coated portion at the boundary with the active material-coated portion, and Fig. 6C is a schematic cross-sectional view of the non-coated portion shown in Fig. 6B released from the overlapping state.

[0022] In the preliminary bending step S1, as shown in Fig. 6B, the active material non-coated portions 211, 221 are folded into an overlapping state (KS) using a pressing tool 6 to form folds QP in the active material non-coated portions 211, 221 at the boundaries KR with the active material coated portions 212, 222, and then the active material non-coated portions 211, 221 are released as shown in Fig. 6C. The pressing tool 6 includes an upper pressing tool 6A and a lower pressing tool 6B having flat pressing surfaces 61, 62 and vertical wall surfaces 63, 64. The upper pressing tool 6A and the lower pressing tool 6B clamp the active material non-coated portions 211, 221 from above and below, and the corners R1, R2 of the upper pressing tool 6A and the lower pressing tool 6B create a fold QP in the active material non-coated portions 211, 221 at the boundary portion KR with the active material coated portions 212, 222.

[0023] The intersection angles θ1, θ2 of the corners R1, R2 between the pressing surfaces 61, 62 and the vertical wall surfaces 63, 64 are preferably formed as right angles, but may be formed as acute angles (for example, 80 degrees or more and less than 90 degrees). By forming the intersection angles θ1, θ2 of the corners R1, R2 as acute angles, the corners R1, R2 come into contact with the active material non-coated parts 211, 221 of the boundary part KR beforehand, and it becomes easier to make the fold QP. In addition, when the corners R1, 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 about 0.4 to 0.6 mm. If the arc radius is 1 mm or more, the electrode foils 21K, 22K of the folded active material non-coated parts 211, 221 may spring back, and the fold QP may not be made sufficiently. Furthermore, it is preferable that the gap D1 between the pressing surfaces 61, 62 when the upper pressing tool 6A and the lower pressing tool 6B sandwich the active material non-coated portions 211, 221 from above and below is slightly larger (for example, about 0.1 to 0.3 mm) than the total plate thickness D2 of the active material non-coated portions 211, 221. This is to prevent the electrode foils 21K, 22K from being pulled too hard and breaking when the upper pressing tool 6A and the lower pressing tool 6B sandwich the active material non-coated portions 211, 221 from above and below.

[0024] In addition, after forming the crease QP in the active material non-coated portions 211, 221 at the boundary KR with the active material coated portions 212, 222, the active material non-coated portions 211, 221 are opened as shown in Fig. 6C. By temporarily opening the folded active material non-coated portions 211, 221, the active material non-coated portions 211, 221 attempt to return to their original state by elastic force, so that the tensile residual stress of the electrode foils 21K, 22K in the active material non-coated portions 211, 221 can be reduced, and the electrode foils 21K, 22K can be made less likely to break in the next current collecting terminal joining step S2. Note that the active material non-coated portions 211, 221 in the open state (KH) spring back in an attempt 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 large in the upper and lower active material non-coated portions 211, 221 of the laminate.

[0025] Fig. 7A is a schematic cross-sectional view of the current collector terminal set on the non-coated part of the active material shown in Fig. 6C. Fig. 7B is a schematic cross-sectional view of the current collector terminal joined to the non-coated part of the active material shown in Fig. 7A by folding the non-coated part of the active material again into an overlapping state. Fig. 7C is a schematic cross-sectional view of the state in which the joining of the non-coated part of the active material and the current collector terminal shown in Fig. 7B is completed.

[0026] In the current collector terminal joining step S2, after the preliminary bending step S1, the lead portion 43 (lead lower end 43b) of the current collector terminal 4 is brought into contact with the active material non-coated portions 211, 221 in an open state (KH) with a crease QP remaining at the boundary KR as shown in Fig. 7A, and the active material non-coated portions 211, 221 are folded again into an overlapping state using a joining tool 7 as shown in Fig. 7B to be joined to the lead lower end 43b. The joining tool 7 includes, for example, an upper pressing tool 7A and a lower pressing tool 7B having pressing surfaces 71, 72 capable of resistance welding or ultrasonic welding. The upper pressure tool 7A and the lower pressure tool 7B sandwich the lead lower end 43b and the active material non-coated portions 211, 221 from above and below in an overlapping state (KS), and the active material non-coated portions 211, 221 and the lead portion 43 (lead lower end 43b) are welded together by passing an electric current or applying ultrasonic vibration, etc.

[0027] Here, the active material non-coated parts 211, 221 have folds QP remaining at the boundaries KR between the active material coated parts 212, 222. When the upper pressing tool 7A and the lower pressing tool 7B bend the active material non-coated parts 211, 221 again to the overlapping state (KS), the active material non-coated parts 211, 221 can be easily bent from the folds QP. This reduces breakage of the active material non-coated parts 211, 221 and reduces the external force that displaces the lead lower end 43b in the case longitudinal direction (X direction). By reducing this external force, the displacement amount Q of the longitudinal center of the sealing body 12 (case 1) where the base part 41 is joined to 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 improved. Furthermore, since the fold creases QP of the non-active material coated portions 211, 221 are formed at the boundaries KR with the active material coated portions 212, 222, the current collecting terminal 4 can be joined near the boundaries KR with the active material coated portions 212, 222, thereby improving the storage capacity per unit volume of the case.

[0028] Therefore, according to the present manufacturing method for the electricity storage device 10, it is possible to provide a manufacturing method for the electricity storage device 10 that can improve the storage capacity per unit volume of the case while reducing positional misalignment of the current collecting terminal 4 when joining the electrode foils 21K, 22K and the current collecting terminal 4, thereby suppressing warping deformation of the case 1 to which the current collecting terminal 4 is joined.

[0029] In the manufacturing method of the present electricity storage device 10, the preliminary bending step S1 shown in Fig. 5 is preferably performed by bending the active material non-coated parts 211, 221 into an overlapping state (KS) multiple times. By bending the active material non-coated parts 211, 221 multiple times, the fold crease QP formed at the boundary part KR with the active material coated parts 212, 222 can be more stably maintained, and the external force that displaces the lead lower end part 43b in the case longitudinal direction (X direction) in the current collecting terminal joining step S2 can be further reduced, and the breakage of the active material non-coated parts 211, 221 can also be reduced. Therefore, the displacement amount Q of the longitudinal center part of the sealing body 12 (case 1) in which the base part 41 is joined to 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] It is even more preferable that in the preliminary bending step S1, when bending the active material non-coated portions 211, 221 into the overlapping state (KS) multiple times, the gap D1 between the pressurized surfaces 71, 72 is gradually narrowed to gradually increase the bending angle of the active material non-coated portions 211, 221. In this case, local elongation of the electrode foils 21K, 22K in the active material non-coated portions 211, 221 can be reduced, and breakage can be further prevented.

[0031] 8 shows a schematic cross-sectional view of a state in the middle of a manufacturing method for electricity storage device 10B of the comparative example in which connector 7 presses current collecting terminal 4 and active material uncoated portions 211, 221 together to join active material uncoated portions 211, 221 to current collecting terminal 4 while overlapping them, in the manufacturing method for electricity storage device 10B of the comparative example. This manufacturing method for electricity storage device 10B of the comparative example is not preferable because lead lower end 43b of current collecting terminal 4 is likely to slip in the longitudinal direction (X direction) of sealing body 12 (case 1) relative to active material uncoated portions 211, 221 that are in the middle of being folded, increasing the amount of positional deviation of lead lower end 43b.

[0032] <Modification> The above-described embodiment is merely an example and does not limit the disclosed technology in any way. Therefore, the disclosed technology can be improved or modified in various ways without departing from the spirit of the technology. For example, the pressing jig 6 used in the preliminary bending process S1 is different from the connector 7 used in the current collector terminal joining process S2, but this is not necessary. For example, the connector 7 used in the current collector 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 materials 4, 4A, 4B current collector terminal 10. Energy storage devices 21 Cathode 22 Negative electrode 23 Separator 21K, 22K electrode foil 21K1, 22K1 One end 41 Base 43 Lead section 43b Lead bottom end 211, 221 Active material non-coated part 212, 222 Active material coating section KR boundary KT1, KT2 active material QP folding habits S1 Pre-bending process S2 Current collector terminal joining process

Claims

1. Case and an electrode body in which a positive electrode body and a negative electrode body are stacked with a separator sandwiched therebetween, the positive electrode body and the negative electrode body having an active material-coated portion in which an active material is coated on an electrode foil and an active material-uncoated portion in which the active material is not coated on one end of the electrode foil that faces each other in the longitudinal direction of the case; a positive and negative current collecting terminals having a base portion connected to both longitudinal ends of the case via an insulating member and a lead portion to which the active material non-coated portion is joined in an overlapping state, a pre-bending step of folding the non-coated portion of the active material in an overlapping state to form a crease in the non-coated portion of the active material at the boundary with the active material coated portion, and then releasing the non-coated portion; and a current collecting terminal joining step of folding the non-coated portion of the active material again into an overlapping state after the preliminary bending step and joining the non-coated portion of the active material to the lead portion. A method for manufacturing an electricity storage device.

2. The method for producing an electricity storage device according to claim 1, The preliminary bending step includes bending the non-coated portion of the active material into an overlapping state a plurality of times. A method for manufacturing an electricity storage device.

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