Secondary battery

Abstract

Provided is a secondary battery that is excellent in vibration resistance.　A secondary battery according to an embodiment comprises: an exterior can that has a bottom wall and a side wall and has an opening; an electrode group that is formed by winding an electrode member, has a flat cross-sectional shape, and has a pair of curved parts; a lid member that is disposed in the opening of the exterior can; and an electrode group retainer that is provided between the electrode group and the lid member. The electrode group is housed so that one of apexes of the curved parts faces the opening of the outer can. The electrode group retainer has at least one pair of protrusions protruding toward the curved parts. The tips of the protrusions are in contact with at least a portion of the curved parts, with the apexes being interposed therebetween, and spaces including the apexes are provided between the tips.

Description

Secondary battery

[0001] An embodiment of the present invention relates to a secondary battery.

[0002] In recent years, secondary batteries such as lead-acid batteries and nickel-hydrogen batteries have been used as power sources typified by electric vehicles, hybrid vehicles, electric motorcycles, forklifts and the like. Recently, development toward the adoption of lithium ion secondary batteries with high energy density has become active, and development is being carried out while giving consideration to long life, safety and other aspects.

[0003] A common lithium ion secondary battery (hereinafter referred to as a secondary battery) is sometimes manufactured by housing an electrode group including electrode members in an outer can having an opening, and disposing a lid member at the opening of the outer can. In some cases, an electrode group retainer is provided between the electrode group and the lid member inside the outer can.

[0004] In such a secondary battery, external impacts such as vibration may be applied to the secondary battery, and these impacts may cause displacement of the electrode group inside the secondary battery. Here, the external impact is, for example, vibration caused by traveling of a vehicle equipped with the secondary battery. If the electrode group inside the secondary battery is not sufficiently restrained by the electrode group retainer or the like at that time, the displacement of the electrode group may cause fracture of a part of the electrode group. The fracture of a part of the electrode group may lead to increased resistance, reduced capacity, and even short circuit of the secondary battery.

[0005] International Publication No. 2022 / 118432, Japanese Patent Laid-Open No. 2024-135176

[0006] The problem to be solved by the present invention is to provide a secondary battery excellent in vibration resistance.

[0007] To solve the above problems, the secondary battery of the embodiment comprises an outer casing having a bottom wall and side walls and an opening; an electrode group formed by winding electrode members and having a flattened cross-sectional shape and a pair of curved portions; a lid member positioned at the opening of the outer casing; and an electrode group retainer provided between the electrode group and the lid member. The electrode group is housed with one of the apex portions of the curved portion facing the opening of the outer casing, and the electrode group retainer has at least one pair of protruding portions projecting toward the curved portion, the tips of the protruding portions abutting with at least a part of the curved portion with the apex portion in between, and a space including the apex portion is provided between the tips.

[0008] A schematic perspective view of the secondary battery of the first embodiment. A schematic perspective view of the secondary battery of the first embodiment disassembled into its components. A schematic perspective view of the electrode group holder used in the secondary battery of the first embodiment. A cross-sectional view of the area around the electrode group holder of the first embodiment, viewed from the direction of the arrow along the line I-I in Figure 1. A schematic perspective view of the electrode group holder used in the secondary battery of the second embodiment. A schematic perspective view of a modified example of the electrode group holder used in the secondary battery of the second embodiment. A schematic perspective view of the electrode group holder used in the secondary battery of the third embodiment. A cross-sectional view of the area around the electrode group holder of the third embodiment, viewed from the direction of the arrow along the line I-I in Figure 1.

[0009] The secondary battery 1 of this embodiment will be described below with reference to the drawings.

[0010] (First Embodiment) The secondary battery 1 of the first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic perspective view showing the secondary battery 1 of the first embodiment, and Figure 2 is a schematic perspective view showing the secondary battery 1 of the first embodiment disassembled into its components.

[0011] As shown in Figures 1 and 2, the secondary battery 1 comprises an outer casing 3 and an electrode group 5 housed inside the outer casing 3. The outer casing 3 is, for example, cylindrical in shape with a bottom wall 3a and side walls 3b, and has an opening 9. A lid member 7 having, for example, a first through hole 20 is placed in this opening 9, and the outer casing 3 and lid member 7 are made of a metal such as aluminum, aluminum alloy, iron, copper, or stainless steel. The lid member 7 is, for example, rectangular in shape with a long side 12 and a short side 14.

[0012] The electrode group 5 is manufactured, for example, by winding an electrode member (not shown) including a positive electrode 13 and a negative electrode 15 around an axis, and then press-molding the entire assembly into a flattened cross-sectional shape, and has a pair of curved portions 5a. The electrode group 5 has apex portions 5b at the top of these curved portions 5a, with one apex portion 5b facing the opening 9 of the outer container 3 and the other apex portion 5b facing the bottom wall 3a of the outer container 3, in which case the electrode group 5 is housed.

[0013] The positive electrode 13 has a positive electrode current collector (not shown) and a positive electrode active material carrying portion (not shown) supported on the positive electrode current collector. The positive electrode current collector includes a positive electrode current collector tab 70a as an uncoated portion of the positive electrode active material carrying portion. On the other hand, the negative electrode 15 has a negative electrode current collector (not shown) and a negative electrode active material carrying portion (not shown) supported on the negative electrode current collector. The negative electrode current collector includes a negative electrode current collector tab 70b as an uncoated portion of the negative electrode active material carrying portion. Hereinafter, the positive electrode current collector tab 70a and the negative electrode current collector tab 70b may be collectively referred to as the current collector tab 70.

[0014] In this embodiment, the electrode group 5 is a wound body, and at least one end of the electrode group 5 is provided with multiple layers of current-collecting tabs 70 leading out from the positive electrode 13 and the negative electrode 15. In this embodiment, the positive electrode current-collecting tab 70a leads out in the opposite direction to the lead-out direction of the negative electrode current-collecting tab 70b, and current-collecting tabs 70 are provided at both ends of the electrode group 5 in the winding axis direction, leading out in a direction perpendicular to the direction (Z direction) in which the electrode group 5 is housed in the outer casing 3. However, the lead-out directions of the positive electrode current-collecting tab 70a and the negative electrode current-collecting tab 70b are not limited to these. For example, both current-collecting tabs 70 may lead out in the same direction, and a current-collecting tab 70 may be provided at one end of the electrode group 5.

[0015] In this embodiment, when a wound electrode group 5 is used and current-collecting tabs 70 wound at both ends in the direction of the winding axis are provided, it is preferable that the tips of the current-collecting tabs 70 are clamped by two or more metal members 16. Here, clamping means that the metal members 16 bundle and integrate multiple layers of current-collecting tabs 70, and it is sufficient that at least a part of the metal members 16 is in contact with one surface and the other surface of the current-collecting tab 70. This allows the current-collecting tabs 70 to be stably clamped by the metal members 16, for example, when the weight of the electrode group 5 is increased as a means of increasing the capacity of the secondary battery 1. Here, increasing the weight of the electrode group 5 refers to increasing the size of the electrode group 5 or increasing the number of windings of the electrodes in order to increase the mass of the electrode active material in the electrode group 5. The number of metal members 16 placed on each of the current-collecting tabs 70 at both ends of the electrode group 5 is not limited to these, and it is preferable that at least one of the current-collecting tabs 70 at both ends of the electrode group 5 is sandwiched between one or more metal members 16.

[0016] In the secondary battery 1 of this embodiment, an electrode group retainer 33 made of an insulating material is provided between the electrode group 5 and the lid member 7. Here, the electrode group retainer 33 may be provided as a pair, separated on the positive electrode 13 side and the negative electrode 15 side, or it may be provided as a single unit without separation. In the secondary battery 1 of Figure 2, the electrode group retainer 33 is provided as a single unit on the positive electrode 13 side and the negative electrode 15 side.

[0017] The electrode group retainer 33 may have a second through hole 50, in which case it is preferable that the position of the first through hole 20 of the lid member 7 and the second through hole 50 of the electrode group retainer 33 coincide in the direction (Z direction) of storing the electrode group 5 into the outer can 3. Terminals 23 are placed in the first through hole 20 of the lid member 7 and the second through hole 50 of the electrode group retainer 33. The terminals 23 are made of a conductive material such as metal and are placed in close contact with the lid member 7 via an insulating gasket 29.

[0018] The terminal 23 may be further connected to a conductive member 31. Here, the conductive member 31 has a first substrate portion 31a provided between the electrode group 5 and the electrode group retainer 33, and a second substrate portion 31b provided between the electrode group 5 and the side wall 3b of the outer casing 3, and connected to the first substrate portion 31a. In this embodiment, the conductive member 31 has two second substrate portions 31b for each first substrate portion 31a, but the number of second substrate portions 31b is not limited to these.

[0019] It is preferable that the conductive member 31 is joined to the metal member 16 that holds the current-collecting tab 70, thereby electrically connecting the electrode group 5 to the terminal 23. When the conductive member 31 is joined to the metal member 16, compared to when the conductive member 31 is directly joined to the current-collecting tab 70, the tearing of the current-collecting tab 70 during joining can be suppressed.

[0020] In the secondary battery 1 of this embodiment, the lid member 7 is provided with a liquid injection port 17 along with a gas discharge valve 21, but it is not necessary to provide it.

[0021] In this embodiment, the current collector tab 70 is electrically insulated from the outer casing 3 by an insulating cover 34 provided between the current collector tab 70 and the outer casing 3. The insulating cover 34 may be fixed to the electrode group 5 by insulating tape 36. The terminal insulator 35 may be provided between the terminal 23 and the lid member 7, thereby electrically insulating the terminal 23 and the lid member 7.

[0022] The electrode group holder 33 used in the secondary battery 1 of this embodiment will be described with reference to Figures 3 and 4. Figure 3 is a schematic perspective view showing the electrode group holder 33 used in the secondary battery 1 of the first embodiment, and Figure 4 is a cross-sectional view of the area around the electrode group holder 33, viewed from the direction of the arrow along the line I-I in Figure 1.

[0023] As shown in Figures 3 and 4, the electrode group holder 33 first has a base portion 38 provided opposite the lid member 7, and has at least one pair of protruding portions 40 that project toward the curved portion 5a of the electrode group 5. Here, in the electrode group holder 33 of the first embodiment, there is one pair of protruding portions 40. The tip portions 40a of these protruding portions 40 abut against at least a part of the curved portion 5a of the electrode group 5. Furthermore, as shown in Figure 4, a space 42 including the apex portion 5b of the electrode group 5 is provided between the tip portions 40a of the protruding portions 40.

[0024] In the secondary battery 1 of this embodiment, the electrode group retainer 33 has a pair of protrusions 40, and the tip 40a of the protrusions 40 abuts against at least a part of the curved portion 5a of the electrode group 5. This abutment between the protrusions 40 and the electrode group 5 restrains the electrode group 5 in the height direction (Z direction) of the secondary battery 1. As a result, even if the electrode group 5 is displaced in the height direction (Z direction), the electrode group 5 is pressed down by the protrusions 40 in the same direction as the displacement (Z direction), so the displacement of the electrode group 5 in the Z direction can be sufficiently suppressed. Therefore, even if external shocks such as vibrations are applied to the secondary battery 1, the displacement of the electrode group 5 can be suppressed by the electrode group retainer 33 having a pair of protrusions 40, and a secondary battery 1 with excellent vibration resistance can be provided. As a result, the secondary battery 1 of this embodiment can suppress partial breakage of the electrode group 5 due to displacement of the electrode group 5, as well as an increase in resistance, a decrease in capacity, and short circuits of the secondary battery 1 due to breakage of the electrode group 5.

[0025] Furthermore, in this embodiment, a space 42 including the vertex 5b of the electrode group 5 is provided between the tip portions 40a of the protruding portions 40. This ensures that even if excessive gas generation occurs in the electrode group 5 inside the secondary battery 1, the space 42 provides a path for the gas to move to the gas discharge valve 21. This makes it possible to provide a secondary battery 1 that guarantees safety.

[0026] As described above, in the secondary battery 1 of this embodiment, an insulating cover 34 may be provided in the width direction (X direction) of the secondary battery 1. In this case, the electrode group 5 is constrained by the insulating cover 34 in the X direction, but as in this embodiment, the electrode group 5 is also constrained by the protruding portion 40 of the electrode group retainer 33 in the height direction (Z direction) of the secondary battery 1, so that the electrode group 5 is sufficiently constrained in both the width direction (X direction) and the height direction (Z direction) of the secondary battery 1. As a result, even if external shocks such as vibrations are applied to the secondary battery 1, the displacement of the electrode group 5 can be suppressed by the electrode group retainer 33 and the insulating cover 34, and a secondary battery 1 with excellent vibration resistance can be provided.

[0027] The electrode group holder 33 of this embodiment will be described further. The tip portion 40a of the protruding portion 40 of the electrode group holder 33 abuts against at least a part of the curved portion 5a of the electrode group 5, and it is preferable that it has a chamfered portion 40b along the outer surface of the curved portion 5a. This chamfered portion 40b ensures a sufficient contact area between the chamfered portion 40b and the electrode group 5, and thus the electrode group 5 can be sufficiently restrained.

[0028] Furthermore, as mentioned above, in the event of excessive gas generation from the electrode group 5 inside the secondary battery 1, it is preferable that the substrate portion 38 of the electrode group retainer 33 is not provided in a position that overlaps with the gas discharge valve 21 in the housing direction (Z direction) of the electrode group 5, from the viewpoint of ensuring a path for the gas to move to the gas discharge valve 21. Specifically, in the electrode group retainer 33 of this embodiment, a part of the substrate portion 38 is cut out in a position that overlaps with the gas discharge valve 21 in the Z direction, thereby appropriately ensuring a path for the gas to move to the gas discharge valve 21.

[0029] Furthermore, as shown in Figure 4, it is preferable that the protrusion 40 of the electrode group holder 33 is provided parallel to the side wall 3b of the outer container 3. Here, parallel to the side wall 3b of the outer container 3 means the same as parallel to the storage direction (Z direction) of the electrode group 5. As described above, the protrusion 40 of the electrode group holder 33 restrains the electrode group 5 in the height direction (Z direction). Therefore, even if the electrode group 5 is displaced in the height direction (Z direction), the electrode group 5 is pressed down by the protrusion 40 in the same direction as the displacement direction (Z direction), so the displacement of the electrode group 5 in the Z direction can be sufficiently suppressed.

[0030] Next, the specific location where the protrusion 40 is provided will be explained with reference to Figure 4. When the lid member 7 is rectangular in shape with a long side 12 and a short side 14, one of the protrusions 40 is provided in a region of 0.05L to 0.3L, extending from one end to the other end of the lid member 7, relative to the length of the short side 14 of the lid member 7, which is 1.0L. Here, the center R of the protrusion 40 in the thickness direction (Z direction) of the short side 14 of the secondary battery 1 is located within the region of 0.05L to 0.3L. Furthermore, the other protrusion 40 is provided symmetrically to the other protrusion 40 on a line Q that passes through the vertex 5b of the electrode group 5 and is parallel to the long side 12 of the lid member 7.

[0031] Here, by providing one side of the protrusion 40 in a region of 0.05L or more, the protrusion 40 can properly contact the curved portion 5a of the electrode group 5 while maintaining sufficient strength of the protrusion 40. If the region is less than 0.05L, the distance in the Z direction between the substrate portion 38 of the electrode group holder 33 and the curved portion 5a of the electrode group 5 becomes greater, requiring the length of the protrusion 40 in the Z direction to be increased accordingly, which may result in insufficient strength of the protrusion 40. Furthermore, by providing one side of the protrusion 40 in a region of 0.3L or less, a sufficient space 42 including the apex portion 5b can be provided, and a sufficient space 42 can secure a path for the gas to move to the gas discharge valve 21.

[0032] Next, the position of the protruding portion 40 of the electrode group retainer 33 will be explained. As mentioned above, from the viewpoint of arranging the terminals 23, it is preferable that the first through-hole 20 of the lid member 7 and the second through-hole 50 of the electrode group retainer 33 coincide in the Z direction, and it is preferable that the protruding portion 40 of the electrode group retainer 33 be positioned closer to the center of the lid member 7 than the first through-hole 20 of the lid member 7. This is because, as mentioned above, the terminals 23 may be further connected to a conductive member 31, and in this case, the first substrate portion 31a of the conductive member 31 overlaps with the electrode group retainer 33, so there is no space to provide the protruding portion 40 at the position where the terminals 23 are arranged. On the central side of the position where the terminals 23 are arranged, the substrate portion 38 of the electrode group retainer 33 is provided facing the electrode group 5, and there is space to provide the protruding portion 40, so the protruding portion 40 can be appropriately provided at a position that contacts the electrode group 5.

[0033] In this embodiment, the electrode group holder 33 is provided with a pair of protrusions 40, but in this case, it is preferable that a pair of protrusions 40 be provided at the center of the electrode group holder 33, as shown in Figure 3. By providing a pair of protrusions 40 at the center of the electrode group holder 33, the protrusions 40 come into contact with the center of the electrode group 5, and the entire electrode group 5 can be uniformly restrained by the protrusions 40.

[0034] In the secondary battery 1 of the first embodiment described above, the electrode group holder 33 has a pair of protrusions 40 that project toward the curved portion 5a of the electrode group 5. The tips 40a of these protrusions 40 abut against at least a part of the curved portion 5a of the electrode group 5. This contact between the protrusions 40 and the electrode group 5 allows the electrode group 5 to be restrained in the height direction (Z direction) of the secondary battery 1. As a result, even if the electrode group 5 is displaced in the height direction (Z direction), the electrode group 5 is pressed down by the protrusions 40 in the same direction as the displacement (Z direction), so the displacement of the electrode group 5 in the Z direction can be sufficiently suppressed. Therefore, even if external shocks such as vibrations are applied to the secondary battery 1, the displacement of the electrode group 5 can be suppressed by the electrode group holder 33 having a pair of protrusions 40, and a secondary battery 1 with excellent vibration resistance can be provided. As a result, the secondary battery 1 of this embodiment can suppress partial breakage of the electrode group 5 due to displacement of the electrode group 5, as well as an increase in resistance, a decrease in capacity, and short circuits of the secondary battery 1 due to the breakage of the electrode group 5.

[0035] Furthermore, in this embodiment, a space 42 including the vertex 5b of the electrode group 5 is provided between the tip portions 40a of the protruding portions 40. This ensures that even if excessive gas generation occurs in the electrode group 5 inside the secondary battery 1, the space 42 provides a path for the gas to move to the gas discharge valve 21. This makes it possible to provide a secondary battery 1 that guarantees safety.

[0036] (Second Embodiment) A modified example (electrode group holder 43) of the electrode group holder 33 used in the secondary battery 1 of the second embodiment will be described with reference to Figure 5. Figure 5 is a schematic perspective view showing the electrode group holder 43 used in the secondary battery 1 of the second embodiment. The differences between the electrode group holder 43 of the second embodiment and the electrode group holder 33 of the first embodiment are that the electrode group holder 43 is provided with two pairs of protrusions 40 and the position in which the protrusions 40 are provided.

[0037] The position of the protrusions 40 of the electrode group holder 43 will now be explained. Here, if the electrode group holder 43 is rectangular in shape with a long side 22 and a short side 24, the first pair of protrusions 40 are provided symmetrically with respect to the second pair of protrusions 40' on a line P that passes through the center point T of the electrode group holder 43 and is parallel to the short side 24 of the electrode group holder 43. It is preferable from the viewpoint of moldability and strength of the electrode group holder 33 that the first pair of protrusions 40 and the second pair of protrusions 40' are provided symmetrically with respect to line P.

[0038] Furthermore, as shown in Figure 6, the electrode group retainer 43 of this embodiment may be provided in pairs, separated on the positive electrode 13 side and the negative electrode 15 side. Figure 6 is a schematic perspective view showing a modified example 2 (electrode group retainer 53) of the electrode group retainer 43 used in the secondary battery 1 of the second embodiment. As described above, if excessive gas generation occurs in the electrode group 5 inside the secondary battery 1, it is preferable not to provide the base portion 38 of the electrode group retainer 33 in a position that overlaps with the gas discharge valve 21 in the housing direction (Z direction) of the electrode group 5, from the viewpoint of securing a path for the gas to move to the gas discharge valve 21. However, the base portion 38 of the electrode group retainer 33 may be provided in an area of ​​60% or less of the area of ​​the gas discharge valve 21. In this embodiment, by not providing the electrode group retainer 53 in a position that overlaps with the gas discharge valve 21 in the Z direction, and instead providing a pair separated on the positive electrode 13 side and the negative electrode 15 side, a path for the gas to move to the gas discharge valve 21 can be appropriately secured. Specifically, the first pair of protrusions 40 are connected to the first substrate portion 38a, and the second pair of protrusions 40' are connected to the second substrate portion 38b. The first substrate portion 38a and the second substrate portion 38b are provided facing the lid member 7.

[0039] In the secondary battery 1 of the second embodiment, the electrode group retainer 43 has two pairs of protrusions 40 that project toward the curved portion 5a of the electrode group 5. The tips 40a of these protrusions 40 abut against at least a part of the curved portion 5a of the electrode group 5, thereby restraining the electrode group 5 in the height direction (Z direction) of the secondary battery 1. By providing two pairs of protrusions 40, the contact area between the electrode group 5 and the protrusions 40 is increased, so the electrode group 5 can be restrained more sufficiently compared to the case where a pair of protrusions 40 are provided. As a result, even if the electrode group 5 is displaced in the height direction (Z direction), the electrode group 5 is pressed down by the protrusions 40 in the same direction as the displacement (Z direction), so the displacement of the electrode group 5 in the Z direction can be sufficiently suppressed. Therefore, even if external shocks such as vibrations are applied to the secondary battery 1, the displacement of the electrode group 5 can be suppressed by the electrode group retainer 33 having a pair of protrusions 40, and a secondary battery 1 with excellent vibration resistance can be provided. As a result, the secondary battery 1 of this embodiment can suppress partial breakage of the electrode group 5 due to displacement of the electrode group 5, as well as an increase in resistance, a decrease in capacity, and short circuits of the secondary battery 1 due to the breakage of the electrode group 5.

[0040] (Third Embodiment) A modification 3 (electrode group holder 63) of the electrode group holder 33 used in the secondary battery 1 of the third embodiment will be described with reference to Figure 7. Figure 7 is a schematic perspective view showing the electrode group holder 63 used in the secondary battery 1 of the third embodiment. As shown in Figure 7, the difference between the electrode group holder 63 of the third embodiment and the electrode group holder 33 of the first embodiment and the electrode group holder 43 of the second embodiment is that the electrode group holder 63 has a proximity plate portion 65. Here, Figure 7 shows the electrode group holder 63 with two pairs of protrusions 40, but it is sufficient to have at least one pair or more protrusions 40, and it may be one pair or three pairs.

[0041] The proximity plate portion 65 of the electrode group holder 63 will be further described with reference to Figure 8. Figure 8 is a cross-sectional view of the area around the electrode group holder 63 of the third embodiment, viewed from the direction of the arrow along the line I-I in Figure 1. As shown in Figure 8, the proximity plate portion 65 is provided along the outer surface of the curved portion 5a of the electrode group 5, and the protruding portion 40 protrudes from the proximity plate portion 65 and comes into contact with the electrode group 5.

[0042] In the secondary battery 1 of the third embodiment, the electrode group retainer 63 has a proximity plate portion 65, and since the distance in the Z direction between the proximity plate portion 65 and the curved portion 5a of the electrode group 5 is short, the volume of the protruding portion 40 can be minimized. By minimizing the volume of the protruding portion 40 inside the outer casing 3, it becomes possible to increase the volume of the electrode group 5 inside the outer casing 3. As a result, in order to increase the mass of the electrode active material in the electrode group 5, the dimensions of the electrode group 5 can be increased or the number of electrode windings can be increased, making it possible to increase the capacity of the electrode group 5. Therefore, by constraining the electrode group 5 in the height direction (Z direction) of the secondary battery 1 with the protruding portion 40 while minimizing the volume of the protruding portion 40, it is possible to provide a secondary battery 1 that is highly resistant to vibration and has a high capacity.

[0043] Furthermore, in this embodiment, in addition to providing a space 42 including the vertex 5b of the electrode group 5 between the tip portions 40a of the protruding portion 40, a space 42' is also provided between the proximity plate portion 65 and the substrate portion 38. As a result, even if excessive gas generation occurs in the electrode group 5 inside the secondary battery 1, both the space 42 and the space 42' ensure a path for the gas to move to the gas discharge valve 21. This makes it possible to provide a secondary battery 1 that guarantees safety.

[0044] According to the secondary battery 1 of at least one embodiment described above, the electrode group retainer 33 has a pair of protruding portions 40 protruding toward the curved portion 5a of the electrode group 5. A tip end portion 40a of each protruding portion 40 is in contact with at least a part of the curved portion 5a of the electrode group 5. The contact portion between the protruding portions 40 and the electrode group 5 can restrain the electrode group 5 in the height direction (Z direction) of the secondary battery 1. Thus, even when the electrode group 5 is displaced in the height direction (Z direction) of the electrode group 5, the electrode group 5 is pressed against the protruding portions 40 in the same direction (Z direction) as the displacement direction, whereby the displacement of the electrode group 5 in the Z direction can be sufficiently suppressed. Therefore, even when an external impact such as vibration is applied to the secondary battery 1, the displacement of the electrode group 5 can be suppressed by the electrode group retainer 33 having the pair of protruding portions 40, and the secondary battery 1 excellent in vibration resistance can be provided. Thereby, the secondary battery 1 of the present embodiment can suppress breakage of a part of the electrode group 5 caused by displacement of the electrode group 5, increase in resistance and decrease in capacity of the secondary battery 1 caused by breakage of the electrode group 5, and further short circuit and the like.

[0045] Furthermore, in the present embodiment, a space portion 42 including the apex portion 5b of the electrode group 5 is provided between the tip end portions 40a of the protruding portions 40. With this configuration, even if excessive gas generation occurs in the electrode group 5 inside the secondary battery 1, the space portion 42 can secure a movement path for gas to the gas discharge valve 21. Thereby, the secondary battery 1 with ensured safety can be provided.

[0046] Although several embodiments of the present invention have been described above, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions and alterations can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention recited in the claims and the equivalents thereof.

[0047] 1...Secondary battery, 3...Outer casing, 3a...Bottom wall, 3b...Side wall, 5...Electrode group, 5a...Bent section, 5b...Apex section, 7...Lid member, 9...Opening, 12...Long side, 13...Positive electrode, 14...Short side, 15...Negative electrode, 16...Metal member, 17...Filling port, 20...First through hole, 21...Gas discharge valve, 22...Long side, 23...Terminal, 24...Short side, 29...Insulating gasket, 31...Conductive member, 31a...First substrate Part, 31b...Second substrate part, 34...Insulating cover, 35...Terminal insulator, 36...Insulating tape, 38...Substrate part, 38a...First substrate part, 38b...Second substrate part, 40...Protruding part, 40'...Protruding part, 40a...Tip part, 40b...Chamfered part, 42...Space part, 42'...Space part, 50...Second through hole, 65...Proximity plate part, 70...Current collector tab, 70a...Positive electrode current collector tab, 70b...Negative electrode current collector tab.

Claims

1. A secondary battery comprising: an outer casing having a bottom wall and side walls and an opening; an electrode group formed by winding electrode members and having a flattened cross-sectional shape and a pair of curved portions; a lid member positioned at the opening of the outer casing; and an electrode group retainer provided between the electrode group and the lid member, wherein the electrode group is housed with one of the apex portions of the curved portion facing the opening of the outer casing; the electrode group retainer has at least one pair of protrusions projecting toward the curved portion; the tips of the protrusions abut with at least a portion of the curved portion on either side of the apex, and a space including the apex is provided between the tips.

2. The secondary battery according to claim 1, wherein the protrusion is provided parallel to the side wall.

3. The secondary battery according to claim 1, wherein the lid member is rectangular in shape with a long side and a short side, one of the protrusions is provided in a region of 0.05L to 0.3L from one end to the other of the lid member with respect to the length of the short side of 1.0L, and the other of the protrusions is provided symmetrically with respect to a line passing through the vertex and parallel to the long side.

4. The secondary battery according to claim 1, wherein the lid member has a through hole in which terminals are arranged, and the protrusion is positioned on the central side of the lid member relative to the through hole.

5. The secondary battery according to claim 1, wherein the electrode group holder is rectangular in shape with a long side and a short side, and has two pairs of protrusions, and the two pairs of protrusions are arranged symmetrically along a line passing through the center point of the electrode group holder and parallel to the short side.

6. The electrode group retainer has a first substrate portion connected to one of the two pairs of protrusions and a second substrate portion connected to the other of the two pairs of protrusions, and the first substrate portion and the second substrate portion are provided facing the lid member, the secondary battery according to claim 5.

7. The electrode group retainer has a proximity plate portion provided along the outer surface of the curved portion, and the protruding portion protrudes from the proximity plate portion, as described in claim 1.

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