Secondary battery

Abstract

To provide a secondary battery capable of absorbing external force acting on a current collecting terminal inside the current collecting terminal without melting the current collecting terminal, thereby suppressing warpage deformation of a sealing body to which the current collecting terminal is joined.SOLUTION: A secondary battery 10 includes a case body 11 having an opening 111, a long sealing body 12 that seals the opening, an electrode body 2 contained within the case body and in which a positive electrode body 21 and a negative electrode body 22 are stacked with a separator 23 sandwiched between them, and positive and negative current collecting terminals 4 having a base portion 41 joined to both longitudinal end portions of the sealing body with an insulating member 3 interposed therebetween, a base adjacent portion 42 connected adjacent to the base portion and spaced from or in contact with the insulating member so as to be separable from the insulating member, and a lead portion 43 having an upper lead end 43a connected to the base adjacent portion and a lower lead end 43b joined to the electrode body, and the base adjacent portion or the upper lead end is provided with an easily deformable portion 44 formed so as to be able to deform without melting relative to the base portion and to displace the lower lead end in a longitudinal direction of the sealing body.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a secondary battery for use in hybrid vehicles, electric vehicles, and the like. [Background technology]

[0002] Conventionally, secondary batteries used in hybrid vehicles, electric vehicles, etc. may be provided with a current interruption mechanism to prevent excessive temperature rise due to overcharging, overdischarging, etc. For example, Patent Document 1 discloses a secondary battery equipped with a fuse mechanism as a current interruption mechanism, in which a cross-sectional reduced portion is provided near a fastening portion between a current collector terminal joined to an electrode body and a sealing body, and the cross-sectional reduced portion melts when the temperature rises due to an excessive current. However, the current interruption mechanism has a problem in that the cross-sectional reduced portion of the current collector terminal melts when the temperature rises, and the secondary battery cannot be reused unless the current collector terminal is replaced, etc.

[0003] Meanwhile, for example, Patent Document 2 discloses a mounting structure for a temperature sensor that contacts the upper surface of a battery cell (the upper surface of a sealing body) and monitors an excessive temperature rise of the battery cell. By mounting this temperature sensor, it is possible to prevent an excessive temperature rise of the battery cell, avoid melting of the current collecting terminal, and protect the battery cell. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US / A1 / 2013 / 0004831 publication [Patent Document 2] JP 2009-176601 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the past, when joining the end of the electrode body (the part not coated with the active material) to the current collecting terminal, an external force was applied to the current collecting terminal, and the current collecting terminal was deformed. This deformation of the current collecting terminal sometimes caused the sealing body to which the current collecting terminal was joined at both longitudinal ends to warp and deform in the vertical direction at its center.

[0006] In this regard, by increasing the rigidity of the current collecting terminal, it is possible to reduce the deformation of the current collecting terminal due to external forces. However, even if the rigidity of the current collecting terminal is increased, the rigidity of the sealing body is generally lower than the rigidity of the current collecting terminal, so that the external force acting on the current collecting terminal is transmitted almost directly to the sealing body to which the current collecting terminal is connected, resulting in the problem that warping deformation of the sealing body cannot be sufficiently suppressed.

[0007] The present disclosed technology has been made in consideration of such problems, and has an objective of providing a secondary battery that can absorb external forces acting on the current collecting terminal inside the current collecting terminal without melting the current collecting terminal, thereby suppressing warping deformation of the sealing body to which the current collecting terminal is joined. [Means for solving the problem]

[0008] (1) One aspect of the disclosed technique for solving the above problems is a secondary battery comprising: a case body having an opening; a long sealing body that seals the opening; an electrode body contained within the case body and in which a positive electrode body and a negative electrode body are stacked with a separator sandwiched between them; a base portion joined to both longitudinal end portions of the sealing body with an insulating member interposed therebetween; a base adjacent portion connected adjacent to the base portion and spaced from or in contact with the insulating member so as to be separable from the insulating member; and positive and negative current collecting terminals having lead portions, the base adjacent portion or the upper lead portions being connected to the base adjacent portion and the lower lead ends being joined to the electrode body, wherein the base adjacent portion or the upper lead ends are provided with easily deformable portions formed to deform without melting and to be able to displace the lower lead ends in the longitudinal direction of the sealing body.

[0009] (2) In the secondary battery described in (1), it is preferable that the upper surface of the sealing body has a sensor contact surface formed so as to be capable of contacting a temperature sensor that monitors the battery temperature, and that the easily deformable portion is formed so as to deform in the longitudinal direction of the sealing body with an amount of vertical displacement at the center of the sealing body within a predetermined reference value in response to an external force acting on the lower end of the lead in the longitudinal direction of the sealing body.

[0010] (3) In the secondary battery described in (1), it is preferable that the easily deformable portion is a thin-walled portion that is extended with a predetermined cross section in the short direction of the sealing body in the base adjacent portion and is formed at a position eccentric in the plate thickness direction.

[0011] (4) In the secondary battery described in (1), the easily deformable portion is preferably a curved portion extending with a predetermined cross section in the short direction of the sealing body at the base adjacent portion.

[0012] (5) In the secondary battery described in (1), it is preferable that the easily deformable portion is a width-reduced portion cut in the short direction of the sealing body from a width-wise end portion in the base adjacent portion at a position spaced from the insulating member.

[0013] (6) In the secondary battery described in any one of (1) to (4), it is preferable that the upper end of the lead is provided with a second easily deformable portion which is a thin-walled portion or a curved portion extending with a predetermined cross section in the longitudinal direction of the sealing body, or a width-reduced portion cut into the longitudinal direction of the sealing body from a width-direction end.

[0014] (7) In the secondary battery described in (1), the easily deformable portion is preferably a width-reduced portion cut into the upper end of the lead from a widthwise end in the longitudinal direction of the sealing body.

[0015] (8) In the secondary battery described in (1), the easily deformable portion is preferably a constriction portion cut into the upper end portion of the lead in the longitudinal and lateral directions of the sealing body. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view of a secondary battery according to one embodiment of the present invention. [Diagram 2] 2 is a schematic block diagram of a temperature monitoring system for the battery pack of the secondary battery shown in FIG. 1. [Diagram 3] 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. [Figure 4] 2 is a cross-sectional view taken along line A-A in FIG. 1. [Figure 5A] 2 is an enlarged cross-sectional view of a portion B in the secondary battery shown in FIG. 1 according to the first embodiment. [Figure 5B] FIG. 5B is an enlarged cross-sectional view of a modification of FIG. 5A. [Figure 5C] 5B is a view taken along the arrow D1 shown in FIG. 5A. [Figure 5D] FIG. 5B is a view taken along the arrow E1 shown in FIG. 5A. [Figure 6A] 2 is an enlarged cross-sectional view of a portion B in a second embodiment of the secondary battery shown in FIG. [Figure 6B] FIG. 6B is an enlarged cross-sectional view of a modification of FIG. 6A. [Figure 6C] FIG. 6B is a view taken along arrow D2 shown in FIG. 6A. [Figure 6D] FIG. 6B is a view taken along the arrow E2 shown in FIG. 6A. [Figure 7A] 1. FIG. 4 is an enlarged cross-sectional view of a portion B in a third embodiment of the secondary battery shown in FIG. [Figure 7B] FIG. 7B is an enlarged cross-sectional view of a modification of FIG. 7A. [Figure 7C] FIG. 7B is a view taken along arrow D3 shown in FIG. 7A. [Figure 7D] FIG. 7B is a view taken along the arrow E3 shown in FIG. 7A. [Figure 8A] 1. FIG. 4 is an enlarged cross-sectional view of a portion B in a fourth embodiment of the secondary battery shown in FIG. [Figure 8B] 8B is a view taken along the arrow D4 shown in FIG. 8A. [Figure 9A] 1. FIG. 4 is an enlarged cross-sectional view of a portion B in a fifth embodiment of the secondary battery shown in FIG. [Figure 9B] 9B is a view taken along the arrow D5 shown in FIG. 9A. [Figure 9C] 1. FIG. 4 is an enlarged perspective view of a portion B in a fifth embodiment of the secondary battery shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] <Overall description of this secondary battery> Next, the overall configuration of the secondary battery 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 a secondary battery according to one aspect of the present embodiment. FIG. 2 shows a schematic block diagram of a temperature monitoring system for a battery pack of the secondary battery shown in FIG. 1. FIG. 3 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. 4 shows a cross-sectional view taken along the line A-A shown in FIG. 1. In each figure, 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 vertical direction of the case. In some cases, the Z direction also indicates the plate thickness direction of the base adjacent portion.

[0018] 1 to 4, a secondary battery 10 according to an embodiment of the disclosed technique includes a case 1, an electrode assembly 2, and a current collecting terminal 4. 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).

[0019] Furthermore, thin-walled portions 111T are formed only on the inner walls on the short sides of opening 111 of case body 11. Therefore, both ends 12R in the longitudinal direction (X direction) of sealing body 12 are supported by step portions 111S formed at the lower ends of thin-walled portions 111T. However, opening 111 of case body 11 does not have thin-walled portions on the inner walls on the long sides, and thus, even if the central portion of sealing body 12 is displaced (warped) in the vertical direction (Z direction), this cannot be prevented.

[0020] Furthermore, on the upper surface of the sealing body 12, there is a sensor contact surface 12S formed so as to be able to come into contact with a temperature sensor 5 that monitors the battery temperature DJ. The temperature sensor 5 is connected to a control system 100, for example, as shown in Fig. 2. This control system 100 includes a battery pack 101 including the temperature sensor 5, a temperature monitoring unit 102, a battery control unit 103, a vehicle control unit 104, and a power control unit 105 connected to a power motor 106.

[0021] The battery pack 101 includes a plurality of connected secondary batteries (battery cells) 10 and a temperature sensor 5 that measures the battery temperature of at least one of the secondary batteries 10. The battery pack 101 supplies required power to a power motor 106 via a power control unit 105. The temperature sensor 5 is connected to a temperature monitoring unit 102. The temperature sensor 5 may be, for example, a thermistor or a thermocouple.

[0022] When the battery temperature DJ measured by the temperature sensor 5 exceeds a predetermined management temperature (e.g., 60 to 80°C) set lower than the battery upper limit temperature (e.g., 100 to 120°C) of the secondary battery 10, the temperature monitoring unit 102 sends an alarm signal to the battery control unit 103. The battery control unit 103 that receives the alarm signal sends a current suppression command or a current cutoff command to the battery pack 101. In addition, the vehicle control unit 104 that receives an abnormality signal of the battery temperature DJ from the battery control unit 103 controls the power motor 106 via the power control unit 105. Therefore, the secondary battery 10 is protected so that the battery temperature DJ does not exceed a predetermined battery upper limit temperature. Therefore, the secondary battery 10 does not need to have a fuse mechanism in the battery as in Patent Document 1. The battery upper limit temperature is usually set to be equal to or lower than the heat-resistant temperature of the electrode body 2 (e.g., the heat-resistant temperature of the separator 23).

[0023] The electrode body 2 is housed in the case body 11 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 parts 211 and 221 where the active materials KT1 and KT2 are not coated on one end 21K1 and 22K1 of the metal foils 21K and 22K, respectively, and active material coated parts 212 and 222 where the active materials KT1 and KT2 are coated on the metal foils 21K and 22K. The active material non-coated part 211 of the positive electrode body 21 and the active material non-coated part 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 parts 212 and 222 are formed on the other end 21K2 and 22K2 and the middle part 21K3 and 22K3 of the metal foils 21K and 22K.

[0024] For example, in a lithium ion secondary battery, the metal 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 metal 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.

[0025] The positive electrode current collector terminal 4A is made of, for example, aluminum, and the negative electrode current collector terminal 4B is made of, for example, copper. Usually, the tensile strength of the aluminum positive electrode current collector terminal 4A is smaller than the tensile strength of the copper negative electrode current collector terminal 4B, and the conductivity of the positive electrode current collector terminal 4A is smaller than the conductivity of the negative electrode current collector terminal 4B. Therefore, in order to equalize the strength and allowable current of the positive electrode current collector terminal 4A and the negative electrode current collector terminal 4B, the plate thickness of the positive electrode current collector terminal 4A is made larger than the plate thickness of the negative electrode current collector terminal 4B. The positive and negative current collector terminals 4 each have a base portion 41, a base adjacent portion 42, and a lead portion 43 that are integrally formed.

[0026] 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 the insulating member 3 interposed therebetween. The base adjacent portion 42 is adjacent to the base portion 41 and is spaced from or in contact with the insulating member 3 so as to be separable from the base portion 41. 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 43a located above the case, and is welded to the lead lower end 43b located below the case in a foil-collecting state of the metal foils 21K, 22K of the active material non-coated portions 211, 221 of the electrode body 2. When the electrode body 2 and the lead lower end 43b are welded to each other, the lead lower end 43b slides against the metal foils 21K, 22K in the middle of being collected, and an external force that displaces the lead lower end 43b in the longitudinal direction (X direction) of the sealing body 12 is likely to be generated.

[0027] The base portion 41 is connected to an external connection portion 45 located on the surface side of the sealing body 12 by, for example, a crimping pin 46 or the like. An insulating member 3 also serving as a sealant is interposed between the crimping pin 46 and 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 a battery pack 101 is constructed by connecting a plurality of the secondary batteries 10, a connecting bus bar (not shown) is connected to the external connection portion 45.

[0028] Further, the base adjacent portion 42 or the lead upper end 43a of the current collecting terminal 4 is provided with an easily deformable portion 44 formed to be able to deform without melting with respect to the base portion 41 and displace the lead lower end 43b in the longitudinal direction (X direction) of the sealing body 12. That is, the easily deformable portion 44 is formed so that, in response to an external force acting on the lead lower end 43b in the longitudinal direction (X direction) of the sealing body 12, the amount of displacement Q in the vertical direction (Z direction) at the center of the sealing body 12 is within a predetermined reference value (for example, about 10 to 20% of the plate thickness of the sealing body 12, or about 0.2 to 0.25 mm). The easily deformable portion 44 is formed in a shape that does not melt at least when the battery temperature DJ measured by the temperature sensor 5 is equal to or lower than a predetermined battery upper limit temperature DJ1.

[0029] This easily deformable portion 44 is preferentially deformed by an external force that displaces the lead lower end 43b in the longitudinal direction (X direction) of the sealing body 12, for example when the electrode body 2 and the lead lower end 43b are welded together, and can absorb the external force and reduce the displacement of the base portion 41 of the current collecting terminal 4. Therefore, it is possible to effectively suppress warping deformation of the sealing body 12, which is caused by the longitudinal center portion of the sealing body 12 to which the base portion 41 is joined to both longitudinal end portions 12R, being displaced in the up-down direction (Z direction).

[0030] As a result, the temperature sensor 5 can come into accurate contact with the sensor contact surface 12S formed on the upper surface 121 of the sealing body 12, improving the measurement accuracy of the temperature sensor 5. Then, based on the accurate temperature measurement results of the temperature sensor 5, the secondary battery 10 can be protected against overcharging or overdischarging without damaging the electrode body 2, the current collecting terminal 4, etc.

[0031] <First Example of the Secondary Battery> Next, a first embodiment of the secondary battery according to the disclosed technique will be described in detail with reference to the drawings. Fig. 5A shows an enlarged cross-sectional view of part B in the first embodiment of the secondary battery shown in Fig. 1. Fig. 5B shows an enlarged cross-sectional view of a modified example of Fig. 5A. Fig. 5C shows a view seen from the arrow D1 shown in Fig. 5A. Fig. 5D shows a view seen from the arrow E1 shown in Fig. 5A.

[0032] In the secondary battery 10A of the first embodiment, the easily deformable portion 44 is a thin-walled portion 44A that is extended in a predetermined cross section in the short-side direction (Y direction) of the sealing body 12 in the base adjacent portion 42 and is formed at a position eccentric in the plate thickness direction (Z direction) as shown in Figs. 5A to 5D. The thin-walled portion 44A is formed on one flat surface (here, the lower surface) of the flat base adjacent portion 42 by forming a groove having a U-shaped cross section on the other flat surface side (here, the upper surface side). However, this is not necessarily limited to this. For example, the thin-walled portion 44A may be formed on the lower surface side by forming a groove having a U-shaped cross section on the upper surface of the flat base adjacent portion 42. In this way, the thin-walled portion 44A is formed at a position that is eccentric in the plate thickness direction (Z direction) relative to the general portion of the base adjacent portion 42. Therefore, the neutral line of the thin-walled portion 44A during bending is eccentric up or down relative to the neutral line of the general portion of the base adjacent portion 42 during bending. Even if an external force acts on the lead lower end portion 43b parallel to the longitudinal direction (X direction) of the sealing body 12, the base adjacent portion 42 on the lead portion 43 side can be easily bent in the vertical direction starting from the thin-walled portion 44A.

[0033] Also, the minimum thickness t1 of the thin portion 44A is preferably about 30 to 50% of the thickness t0 of the general portion. In this case, the base adjacent portion 42 is more likely to bend in the up-down direction with respect to the base portion 41, starting from the thin portion 44A. This further reduces the amount of warpage deformation of the sealing body 12 due to an external force acting on the lead lower end portion 43b in the longitudinal direction (X direction) of the sealing body 12. The thin portion 44A may be formed as a groove having a V-shaped or W-shaped cross section.

[0034] 5A abuts against insulating member 3 so as to be separable therefrom, when an external force acts on lead lower end 43b in the longitudinal direction (X direction) of sealing body 12 toward the outside of the battery (to the right in the drawing), thin-walled portion 44A stretches to absorb the external force and reduce the amount of warpage deformation of sealing body 12. However, the reduction in the amount of warpage deformation of sealing body 12 is smaller than when the external force acts toward the inside of the battery (to the left in the drawing).

[0035] In this regard, the base adjacent portion 42b of the modified example shown in Fig. 5B is formed in a step shape downward from the base portion 41. Therefore, the base adjacent portion 42b is separated from the insulating member 3, so that even when an external force acting on the lead lower end portion 43b acts in the longitudinal direction (X direction) of the sealing body 12 toward the outside of the battery (to the right in the drawing), the base adjacent portion 42b is likely to bend in the vertical direction starting from the thin portion 44A, as in the case where the external force acts toward the inside of the battery (to the left in the drawing). Therefore, the amount of warpage deformation of the sealing body 12 against an external force acting on the lead lower end portion 43b in the longitudinal direction of the sealing body 12 (X direction: inside and outside the battery) can be further reduced.

[0036] The plate width dimension w3 in the longitudinal direction (X direction) of the sealing body 12 at the lead portion 43 is smaller than the plate width dimension w1 in the lateral direction (Y direction) of the sealing body 12 at the base portion 41. Therefore, when the lead portion 43 and the electrode body 2 are joined, the lead portion 43 is easily deformed, but the thin portion 44A can prevent or reduce the deformation of the lead portion 43 from propagating to the base portion 41. This reduces the width dimension of the active material non-coated portions 211, 221 of the electrode body 2 that are welded to the lead portion 43, thereby improving the battery capacity per unit volume.

[0037] Furthermore, because the lead portion 43 is bent toward the bottom of the case at the widthwise end of the base adjacent portion 42, a notch 42c for bending the lead portion 43 is formed in the base adjacent portion 42. The notch 42c makes the plate width dimension w2 in the short direction (Y direction) of the sealing body 12 in the thin portion 44A smaller than the plate width dimension w1 in the short direction (Y direction) of the sealing body 12 in the base portion 41. This makes the thin portion 44A more easily deformable, and the amount of warpage deformation of the sealing body 12 can be further reduced in response to an external force acting on the lead lower end portion 43b in the longitudinal direction (X direction) of the sealing body 12.

[0038] <Second embodiment of the present secondary battery> Next, a second embodiment of the secondary battery according to the disclosed technique will be described in detail with reference to the drawings. Fig. 6A shows an enlarged cross-sectional view of part B in the second embodiment of the secondary battery shown in Fig. 1. Fig. 6B shows an enlarged cross-sectional view of a modified example of Fig. 6A. Fig. 6C shows a view seen from the arrow D2 shown in Fig. 6A. Fig. 6D shows a view seen from the arrow E2 shown in Fig. 6A.

[0039] In the secondary battery 10B of the second embodiment, the easily deformable portion 44 is a curved portion 44B that is extended in a predetermined cross section in the short-side direction (Y direction) of the sealing body 12 on the base adjacent portion 42, as shown in Figs. 6A to 6D. The curved portion 44B shown in Fig. 6A is a curved portion that has an arc-shaped cross section and protrudes from one plane (here, the lower surface) of the flat plate-shaped base adjacent portion 42 in an out-of-plane direction (here, the downward direction). However, it is not necessary to be limited to this. For example, as shown in Fig. 6B, the curved portion 44B may be a curved portion that has an arc-shaped cross section and protrudes from the upper surface of the flat plate-shaped base adjacent portion 42 in an upward direction. In this case, the base adjacent portion 42b may be formed in a step shape downward from the base portion 41.

[0040] In this way, because the curved portion 44B is formed at a position offset in the up-down direction (Z direction) with respect to the general portion of the base adjacent portion 42, even if an external force acts on the lead lower end 43b parallel to the longitudinal direction (X direction) of the sealing body 12, the base adjacent portion 42 on the lead portion 43 side can be easily bent in the up-down direction starting from the curved portion 44B even with a small force. Also, the curved portion 44B expands and contracts in the longitudinal direction (X direction), so that the base adjacent portion 42 on the lead portion 43 side can be displaced parallel to the longitudinal direction (X direction) even with a small force.

[0041] Also, the minimum thickness t2 of the curved portion 44B is preferably about 30 to 50% of the thickness t0 of the general portion. In this case, the base adjacent portion 42 is likely to expand and contract in the horizontal direction (X direction) or bend in the vertical direction (Z direction) starting from the curved portion 44B with respect to the base portion 41. Therefore, the amount of warpage deformation of the sealing body 12 due to an external force acting on the lead lower end portion 43b in the longitudinal direction (X direction) of the sealing body 12 can be further reduced. The curved portion 44B may be formed into a waveform having a V-shaped or W-shaped cross section.

[0042] Furthermore, the plate width dimension w3 in the longitudinal direction (X direction) of the sealing body 12 at the lead portion 43 is smaller than the plate width dimension w1 in the lateral direction (Y direction) of the sealing body 12 at the base portion 41. Therefore, when the lead portion 43 and the electrode body 2 are joined, the lead portion 43 is easily deformed, but the curved portion 44B can prevent or reduce the deformation of the lead portion 43 from propagating to the base portion 41. This reduces the width dimension of the active material non-coated portions 211, 221 of the electrode body 2 that are welded to the lead portion 43, thereby improving the battery capacity per unit volume.

[0043] Furthermore, because the lead portion 43 is bent toward the bottom of the case at the widthwise end of the base adjacent portion 42, a notch 42c for bending the lead portion 43 is formed in the base adjacent portion 42. The notch 42c makes the sheet width dimension w2 in the short direction (Y direction) of the sealing body 12 at the curved portion 44B smaller than the sheet width dimension w1 in the short direction (Y direction) of the sealing body 12 at the base portion 41. This makes the curved portion 44B more easily deformable, and the amount of warpage deformation of the sealing body 12 can be further reduced in response to an external force acting on the lead lower end portion 43b in the longitudinal direction (X direction) of the sealing body 12.

[0044] <Third Example of the Secondary Battery> Next, a third embodiment of the secondary battery according to the embodiment of the disclosed technology will be described in detail with reference to the drawings. Fig. 7A shows an enlarged cross-sectional view of part B in the third embodiment of the secondary battery shown in Fig. 1. Fig. 7B shows an enlarged cross-sectional view of a modified example of Fig. 7A. Fig. 7C shows a view seen from the arrow D3 shown in Fig. 7A. Fig. 7D shows a view seen from the arrow E3 shown in Fig. 7A.

[0045] 7A to 7D, in the secondary battery 10C of the third embodiment, the easily deformable portion 44 is a reduced width portion 44C cut into the base adjacent portion 42 from the widthwise end portions 421 in the short direction (Y direction) of the sealing body 12. The reduced width portion 44C is formed in the widthwise center portion by forming U-shaped cutout portions 44C1 from both widthwise end portions 421 of the flat base adjacent portion 42. Since the lead portion 43 is bent at the widthwise end portions of the base adjacent portion 42, the cutout portions 44C2 forming the reduced width portion 44C also serve as cutout portions in the base adjacent portion 42 for bending the lead portion 43.

[0046] However, the shape is not necessarily limited to the above. For example, the width-reduced portion 44C may be formed on the other width-direction end side by forming a U-shaped notch portion 44C1 from one width-direction end portion 421 of the flat base-adjacent portion 42. Since the width-reduced portion 44C is formed on the base-adjacent portion 42 in this manner, even if an external force acts on the lead lower end portion 43b in parallel to the longitudinal direction (X direction) of the sealing body 12, the base-adjacent portion 42 on the lead portion 43 side can be easily bent in the vertical direction (Z direction) or the short-side direction (Y direction) of the sealing body 12 with a small force starting from the width-reduced portion 44C.

[0047] The minimum plate width dimension w2 of the reduced width portion 44C is preferably about 20 to 50% of the plate width dimension w1 of the general portion of the base portion 41. In this case, the base adjacent portion 42 on the lead portion 43 side is likely to bend in the up-down direction (Z direction) or the short-side direction (Y direction) of the sealing body 12 with respect to the base portion 41 starting from the reduced width portion 44C. This further reduces the amount of warpage deformation of the sealing body 12 due to an external force acting on the lead lower end portion 43b in the longitudinal direction (X direction) of the sealing body 12. The reduced width portion 44C may be formed, for example, by cutout portions 44C1 and 44C2 having a V-shaped cross section.

[0048] 7A abuts against insulating member 3 so as to be separable therefrom, when an external force acts on lead lower end 43b in the longitudinal direction (X direction) of sealing body 12 toward the outside of the battery (to the right in the drawing), width reduced portion 44C extends to absorb the external force and reduce the amount of warpage deformation of sealing body 12. However, the reduction in the amount of warpage deformation of sealing body 12 is smaller than when the external force acts toward the inside of the battery (to the left in the drawing).

[0049] In this regard, the base adjacent portion 42b of the modified example shown in FIG. 7B is formed in a step shape downward with respect to the base portion 41. Therefore, the width-reduced portion 44C of the easily deformable portion 44 is formed in the base adjacent portion 42b at a position separated from the insulating member 3. Therefore, even when an external force acting on the lead lower end portion 43b acts in the longitudinal direction (X direction) of the sealing body 12 toward the outside of the battery (rightward in the drawing), the base adjacent portion 42b is likely to bend in the vertical direction (Z direction) starting from the width-reduced portion 44C, as in the case where the external force acts toward the inside of the battery (leftward in the drawing). Therefore, the amount of warpage deformation of the sealing body 12 against an external force acting on the lead lower end portion 43b in the longitudinal direction of the sealing body 12 (X direction: inside and outside the battery) can be further reduced.

[0050] The plate width dimension w3 in the longitudinal direction (X direction) of the sealing body 12 at the lead portion 43 is smaller than the plate width dimension w1 in the lateral direction (Y direction) of the sealing body 12 at the base portion 41. Therefore, when the lead portion 43 and the electrode body 2 are joined, the lead portion 43 is easily deformed, but the width-reduced portion 44C can prevent or reduce the deformation of the lead portion 43 from propagating to the base portion 41. This reduces the width of the active material non-coated portions 211, 221 of the electrode body 2 that are welded to the lead portion 43, thereby improving the battery capacity per unit volume.

[0051] <Applications of the First, Second, and Third Embodiments of the Secondary Battery> Next, application examples of the first, second and third examples of the secondary battery according to the embodiment of the disclosed technology will be described in detail with reference to Figures 5A to 7D. The application examples are secondary batteries 10A1, 10A2, 10B1, 10B2, 10C1 and 10C2, which are the above-mentioned secondary batteries, and which are provided with a second easily deformable portion 47, which is a thin portion 47A or a curved portion 47B extending at a predetermined cross section in the longitudinal direction (X direction) of sealing body 12, or a width-reduced portion 47C cut from a width-direction end 431 in the longitudinal direction (X direction) of sealing body 12, at lead upper end 43a.

[0052] Here, the lead upper end 43a is provided with the second easily deformable portion 47, which is the thin-walled portion 47A or the curved portion 47B extending at a predetermined cross section in the longitudinal direction (X direction) of the sealing body 12, or the width-reduced portion 47C cut from the width-direction end 431 in the longitudinal direction (X direction) of the sealing body 12. Therefore, when an external force acts on the lead lower end 43b of the current collecting terminal 4 in the short-side direction (Y direction) of the sealing body 12, the second easily deformable portion 47 bends and displaces the lead lower end 43b in the short-side direction (Y direction) of the sealing body 12, thereby reducing the inclination displacement in which the base portion 41 is inclined with respect to the short-side direction (Y direction) of the sealing body 12. Therefore, in addition to the warpage deformation of the sealing body 12, the inclination deformation can be reduced, and the measurement accuracy of the temperature sensor 5 can be further improved.

[0053] In Figs. 5A to 7D, the second easily deformable portion 47 is formed in the same type of shape as the easily deformable portion 44, but this is not necessary and the second easily deformable portion 47 may be formed in a different type of shape from the easily deformable portion 44. Therefore, the shape may be appropriately selected according to the size, build, etc. of the secondary batteries 10A1, 10A2, 10B1, 10B2, 10C1, and 10C2. In addition, since the second easily deformable portion 47 is formed between the base adjacent portion 42 and the upper end of the electrode body 2, a necessary separation distance for the bending moment of the lead lower end 43b with respect to the second easily deformable portion 47 can be secured, and even if the external force when welding and joining to the electrode body 2 is small, the second easily deformable portion 47 can be easily deformed and the external force can be effectively absorbed. In addition, since the second easily deformable portion 47 is formed between the base adjacent portion 42 and the upper end of the electrode body 2, the empty space in the case 1 can be effectively utilized.

[0054] <Fourth Example of the Secondary Battery> Next, a fourth embodiment of the secondary battery according to the disclosed technique will be described in detail with reference to the drawings. Fig. 8A shows an enlarged cross-sectional view of part B in the fourth embodiment of the secondary battery shown in Fig. 1. Fig. 8B shows a view taken along the arrow D4 shown in Fig. 8A.

[0055] In the secondary battery 10E of the fourth embodiment, the easily deformable portion 44 is a width-reduced portion 44D cut into the lead upper end 43a from the width-direction end 431 in the longitudinal direction (X direction) of the sealing body 12, as shown in Figs. 8A and 8B. The width-reduced portion 44D is formed in the width-direction center by forming U-shaped cutout portions 44D1 and 44D2 from both width-direction ends 431 of the flat lead portion 43. However, it is not necessary to be limited to the above shape. For example, the width-reduced portion 44D may be formed on the other width-direction end side by forming a U-shaped cutout portion 44D1 from one width-direction end 431 of the flat lead portion 43.

[0056] In this way, since the width reduced portion 44D is formed in the lead upper end 43a, even if an external force acts on the lead lower end 43b in the longitudinal direction (X direction) or lateral direction (Y direction) of the sealing body 12 as a result of welding the lead lower end 43b to the electrode body 2, the lead lower end 43b can be easily bent in the longitudinal direction (X direction) or lateral direction (Y direction) of the sealing body 12 starting from the width reduced portion 44D. Therefore, in addition to warping deformation of the sealing body 12, tilt deformation can be reduced, and the measurement accuracy of the temperature sensor 5 can be further improved.

[0057] Also, the minimum plate width dimension w2 of the reduced width portion 44D is preferably about 20 to 50% of the plate width dimension w3 of the general portion of the lead portion 43. In this case, the lead lower end portion 43b is likely to bend in the longitudinal direction (X direction) or lateral direction (Y direction) of the sealing body 12 with respect to the base portion 41 starting from the reduced width portion 44D. Therefore, the warpage and tilt deformation of the sealing body 12 can be further reduced due to an external force acting on the lead lower end portion 43b in the longitudinal direction (X direction) and lateral direction (Y direction) of the sealing body 12. The reduced width portion 44D may be formed by, for example, V-shaped notches 44D1 and 44D2.

[0058] <Fifth Example of the Secondary Battery> Next, a fifth embodiment of the secondary battery according to the disclosed technique will be described in detail with reference to the drawings. Fig. 9A shows an enlarged cross-sectional view of part B in the fifth embodiment of the secondary battery shown in Fig. 1. Fig. 9B shows a view taken along the arrow D5 in Fig. 9A. Fig. 9C shows an enlarged perspective view of part B in the fifth embodiment of the secondary battery shown in Fig. 1.

[0059] In the secondary battery 10E of the fifth embodiment, the easily deformable portion 44 is a constriction portion 44E cut into the lead upper end portion 43a in the longitudinal direction (X direction) and the transverse direction (Y direction) of the sealing body 12, as shown in Figs. 9A to 9C. The constriction portion 44E is formed in the center of the width direction and the thickness direction by forming approximately U-shaped notches 44E1 and 44E2 from both width direction ends 431 and arc-shaped notches 44E3 and 44E4 from both thickness direction ends 432 of the plate-like lead portion 43. However, it is not necessary to be limited to the above shape. For example, the constriction portion 44E may be formed by V-shaped notches from both width direction ends 431 and both thickness direction ends 432.

[0060] In this way, since the neck portion 44E is formed in the lead upper end 43a, even when an external force acts on the lead lower end 43b in the longitudinal direction (X direction) and lateral direction (Y direction) of the sealing body 12 or in a twisting direction (W direction) rotating around an axis in the up-down direction (Z direction) due to welding of the lead lower end 43b and the electrode body 2, the lead lower end 43b can be easily deformed in the longitudinal direction (X direction), lateral direction (Y direction), or twisting direction (W direction) of the sealing body 12 starting from the neck portion 44E. Therefore, in addition to warping deformation of the sealing body 12, tilt deformation and twisting deformation can be reduced, and the measurement accuracy of the temperature sensor 5 can be further improved.

[0061] Furthermore, the minimum cross-sectional area s1 of the waist portion 44E is preferably about 20 to 50% of the cross-sectional area s0 of the general portion of the lead portion 43. In this case, the lead lower end 43b is more likely to deform in the longitudinal direction (X direction), lateral direction (Y direction), or twisting direction (W direction) of the sealing body 12, starting from the waist portion 44E, relative to the base portion 41. This makes it possible to further reduce warping, tilting, and twisting deformation of the sealing body 12 due to an external force acting on the lead lower end 43b in the longitudinal direction (X direction), lateral direction (Y direction), and twisting direction (W direction) of the sealing body 12.

[0062] <Modification> The above-described embodiment is merely an example, and does not limit the disclosed technology. Therefore, the disclosed technology can be improved and modified in various ways without departing from the scope of the invention. For example, in the present secondary battery 10 shown in FIG. 1, the base portion 41 of the current collector terminal 4 is connected to the external connection portion 45 located on the surface side of the sealing body 12 by, for example, a crimp pin 46 or the like. An insulating member 3, which also serves as a sealant, is interposed between the crimp pin 46 and the external connection portion 45 and the sealing body 12. However, this is not necessarily limited to this. For example, the current collector terminal 4 and the sealing body 12 may be connected to the insulating member 3 by insert molding. In this case, the base portion 41 of the current collector terminal 4 is inserted into the insulating member 3, and the base adjacent portion 42 is separated from the insulating member 3. Therefore, the easily deformable portion 44 of various forms in the above-described embodiments 1 to 5 can be formed on the base adjacent portion 42 separated from the insulating member 3 or the lead upper end portion 43a. [Explanation of symbols]

[0063] 1 case 2 Electrode body 3. Insulating materials 4 Current collector terminal 5 Temperature Sensor 10, 10A, 10B, 10C secondary battery 10D, 10E, 10A1 secondary battery 10A2, 10B1, 10B2 secondary battery 10C1, 10C2 secondary battery 11 Case body 12 Sealing body 12R Longitudinal both ends 12S Sensor contact surface 21 Cathode 22 Negative electrode 23 Separator 41 Base 42 Base adjacent part 43 Lead section 43a Lead top end 43b Lead bottom end 44, 47 Easy to deform part 44A, 47A Thin section 44B, 47B curved section 44C, 44D, 47C Width reduction part 44E Waist 111 Opening 121 Top surface 421, 431 Width direction end DJ battery temperature Q Displacement

Claims

1. A case body having an opening; a long sealing body that seals the opening; an electrode assembly housed in the case body and including a positive electrode body and a negative electrode body stacked with a separator sandwiched therebetween; positive and negative current collecting terminals each having a base portion connected to both longitudinal ends of the sealing body with an insulating member interposed therebetween, a base adjacent portion connected adjacent to the base portion and spaced from or in contact with the insulating member so as to be separable from the insulating member, and a lead portion having an upper end connected to the base adjacent portion and a lower end joined to the electrode body, The base adjacent portion or the upper end portion of the lead is provided with an easily deformable portion formed so as to be deformed without melting relative to the base portion and to be able to displace the lower end portion of the lead in the longitudinal direction of the sealing body. Secondary battery.

2. 2. The secondary battery according to claim 1, a sensor contact surface formed on an upper surface of the sealing body so as to be capable of contacting a temperature sensor that monitors the battery temperature; The easily deformable portion is formed so that, in response to an external force acting on the lower end of the lead in the longitudinal direction of the sealing body, a vertical displacement amount at the center of the sealing body is within a predetermined reference value. Secondary battery.

3. 2. The secondary battery according to claim 1, The easily deformable portion is a thin-walled portion that is provided at the base adjacent portion, extends with a predetermined cross section in the short direction of the sealing body, and is formed at a position eccentric in the plate thickness direction. Secondary battery.

4. 2. The secondary battery according to claim 1, The easily deformable portion is a curved portion extending in a lateral direction of the sealing body at a predetermined cross section in the base adjacent portion. Secondary battery.

5. 2. The secondary battery according to claim 1, The easily deformable portion is a width-reduced portion that is cut in the base adjacent portion at a position spaced from the insulating member from a width-direction end portion in the lateral direction of the sealing body. Secondary battery.

6. The secondary battery according to any one of claims 1 to 5, The upper end of the lead is provided with a second easily deformable portion which is a thin-walled portion or a curved portion extending in a predetermined cross section in the longitudinal direction of the sealing body, or a width-reduced portion cut into the longitudinal direction of the sealing body from a width-direction end. Secondary battery.

7. 2. The secondary battery according to claim 1, The easily deformable portion is a width-reduced portion cut into the upper end of the lead from the width direction end in the longitudinal direction of the sealing body. Secondary battery.

8. 2. The secondary battery according to claim 1, The easily deformable portion is a constriction portion cut into the upper end portion of the lead in the longitudinal and lateral directions of the sealing body. Secondary battery.

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