Secondary batteries

Abstract

This product provides a highly safe rechargeable battery with excellent vibration resistance. [Solution] The secondary battery of the embodiment includes a positive electrode, a negative electrode, and a separator, and comprises an electrode group having multiple layers of wound current-collecting tabs at both ends in the winding axis direction, an outer case housing the electrode group, at least one pair of metal members that sandwich the current-collecting tabs from the innermost to the outermost circumference in the winding of the current-collecting tabs and are arranged opposite to the stacking direction of the current-collecting tabs, and an insulating cover provided between the current-collecting tabs and the outer case. The insulating cover has a back member provided between the current-collecting tabs and the outer case in the winding axis direction, and has at least one pair of projections that protrude from the back member and are provided along the innermost circumference side of the current-collecting tabs on the metal members. A space is provided between the pair of projections.

Description

Technical Field

[0001] Embodiments of the present invention relate to secondary batteries.

Background Art

[0002] In recent years, secondary batteries such as lead-acid batteries and nickel-metal hydride batteries have been used as power sources typified by electric vehicles, hybrid vehicles, electric motorcycles, and forklifts. Recently, development towards the adoption of lithium-ion secondary batteries with high energy density has been active, and development has been carried out while considering long life, safety, and the like.

[0003] <00000> As one form of a general lithium-ion secondary battery (hereinafter referred to as a secondary battery), there is a secondary battery including an exterior case, an electrode group housed in the exterior case, current collector tabs provided at both ends of the electrode group, and conductive members of positive and negative electrodes joined to the current collector tabs. Such secondary batteries are used for various applications. For example, when mounted on a vehicle, the secondary battery vibrates due to the vibration during running. Along with this vibration, a load is applied to the joint portion between the current collector tab and the conductive member described above, and there is a risk that the current collector tab joined to the conductive member may be damaged.

[0004] In addition, secondary batteries are generally required to have a high capacity. As a means for increasing the capacity, in order to increase the mass of the electrode active material, it is conceivable to increase the dimensions of the electrode group or increase the number of windings of the electrode. However, with such means, the electrode group becomes heavy, so the load applied to the joint portion between the current collector tab and the conductive member described above increases according to the weight of the electrode group, and there is a risk that the current collector tab joined to the conductive member may be damaged along with the vibration described above.

[0005] Furthermore, with the increase in the capacity of secondary batteries, it is expected that the amount of gas generated from the electrode group will increase. For example, if the generated gas accumulates inside the secondary battery and the pressure inside the secondary battery rises, the secondary battery may rupture.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2015-92507 [Overview of the project] [Problems that the invention aims to solve]

[0007] The problem that this invention aims to solve is to provide a highly safe secondary battery with excellent vibration resistance. [Means for solving the problem]

[0008] To solve the above problems, the secondary battery of the embodiment includes a positive electrode, a negative electrode, and a separator, and comprises an electrode group having multiple layers of wound current-collecting tabs at both ends in the winding axis direction, an outer case housing the electrode group, at least one pair of metal members that sandwich the current-collecting tabs from the innermost to the outermost circumference in the winding of the current-collecting tabs and are arranged opposite to the stacking direction of the current-collecting tabs, and an insulating cover provided between the current-collecting tabs and the outer case. The insulating cover has a back member provided between the current-collecting tabs and the outer case in the winding axis direction, and has at least one pair of protrusions that protrude from the back member and are provided along the innermost circumference side of the current-collecting tabs on the metal members. A space is provided between the pair of protrusions. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic perspective view showing a secondary battery according to the first embodiment. [Figure 2] A schematic perspective view showing a secondary battery according to the first embodiment, disassembled into its individual components. [Figure 3] A schematic perspective view showing the area around the electrode group used in the secondary battery according to the first embodiment. [Figure 4] A cross-sectional view of the section along line II in Figure 3, viewed from the direction of the arrow. [Figure 5]A schematic perspective view showing an insulating cover used in a secondary battery according to the first embodiment. [Figure 6] A schematic perspective view showing a modified example 1 of the insulating cover used in a secondary battery according to the first embodiment. [Figure 7] A schematic perspective view showing a modified example 2 of the insulating cover used in a secondary battery according to the first embodiment. [Figure 8] Figure 3 shows cross-sectional views of the section along line II-II in Figure 3, viewed from the direction of the arrow, illustrating modified examples 1 and 2 of the insulating cover used in the secondary battery according to the first embodiment. [Figure 9] A schematic perspective view showing a third modified example of the insulating cover used in a secondary battery according to the first embodiment. [Figure 10] A third modified example of the insulating cover used in the secondary battery according to the first embodiment is shown in Figure 3, a cross-sectional view of the cross section along line II, viewed from the direction of the arrow. [Modes for carrying out the invention]

[0010] The secondary battery of this embodiment will be described below with reference to the drawings.

[0011] (First embodiment) A 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 according to the first embodiment, and Figure 2 is a schematic perspective view showing the secondary battery 1 according to the first embodiment disassembled into its components. As shown in Figures 1 and 2, the secondary battery 1 comprises an outer casing 3 and an electrode group 5. The outer casing 3 is, for example, cylindrical in shape with side walls and a bottom wall. The outer casing 3 has an internal cavity, and an opening 9 is provided on its top surface. For example, a lid member 7 is placed in the opening 9, and the outer casing 3 and the lid member 7 are made of a metal such as aluminum, aluminum alloy, iron, copper, or stainless steel. The secondary battery 1 only needs to have an outer casing 3 and an electrode group 5, and the bottom wall and opening 9 are not limited to a rectangular shape as in this embodiment, nor is the outer casing 3 limited to a cylindrical shape.

[0012] The electrode group 5 is housed in the internal cavity of the outer case 3. The electrode group 5 is manufactured, for example, by winding a separator (not shown) between the positive electrode 13 and the negative electrode 15 around an axis, and then press-molding the entire assembly into a flattened shape. The positive electrode 13 has a positive electrode current collector 13a and a positive electrode active material carrying portion (not shown) supported on one or both sides of the positive electrode current collector 13a. Here, the positive electrode current collector 13a is a metal foil. The positive electrode current collector 13a has 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 15a and a negative electrode active material carrying portion (not shown) supported on one or both sides of the negative electrode current collector 15a. Here, the negative electrode current collector 15a is a metal foil. The negative electrode current collector 15a includes a negative electrode current collector tab 70b as an uncoated portion of the negative electrode active material carrying area. In the wound electrode group 5, multiple layers of wound positive electrode current collector tabs 70a and negative electrode current collector tabs 70b are provided at both ends in the direction of the winding axis.

[0013] When current-collecting tabs 70a and 70b are provided at both ends in the winding axis direction, it is preferable that the current-collecting tabs 70a and 70b are sandwiched by at least one pair of metal members 16. Here, sandwiching means that the metal members 16 bundle and integrate multiple layers of current-collecting tabs 70a and 70b from the innermost to the outermost circumference in the winding of the current-collecting tabs 70a and 70b, and it is sufficient that at least a part of the metal members 16 is in contact with the innermost and outermost circumferences of the current-collecting tabs 70a and 70b. The pair of metal members 16 are each arranged facing each other in the stacking direction (X direction) of the current-collecting tabs 70a and 70b.

[0014] More preferably, the current collector tabs 70a and 70b are each preferably sandwiched by two pairs of metal members 16 as shown in FIG. 2. In this case, the first pair of metal members 16 and the second pair of metal members 16 are preferably provided in parallel with respect to the housing direction (Z direction) of the electrode group 5 into the exterior case 3. Thereby, for example, even when the weight of the electrode group 5 is increased as a means for increasing the capacity of the secondary battery 1, the current collector tabs 70a and 70b can be stably sandwiched by the metal members 16. Here, the case where the weight of the electrode group 5 is increased means the case where the dimensions of the electrode group are increased or the number of windings of the electrode is increased in order to increase the mass of the electrode active material.

[0015] The positive electrode 13 is manufactured by applying a slurry containing a positive electrode active material onto a positive electrode current collector 13a made of aluminum foil, aluminum alloy foil, or the like. Examples of the positive electrode active material include, but are not limited to, oxides, sulfides, and their polymers that can occlude and release lithium ions. Preferred positive electrode active materials include lithium manganese composite oxides, lithium nickel composite oxides, lithium cobalt composite oxides, and lithium iron phosphate.

[0016] The negative electrode 15 is manufactured by applying a slurry containing a negative electrode active material onto a negative electrode current collector 15a made of aluminum foil, aluminum alloy foil, or copper foil. Examples of the negative electrode active material include, but are not limited to, metal oxides, metal sulfides, metal nitrides, and carbon materials that can occlude and release lithium ions. Preferred negative electrode active materials include titanium oxides, lithium titanium oxides, niobium titanium oxides, niobium oxides, tungsten oxides, amorphous tin oxides, tin silicon oxides, silicon oxides, and silicon.

[0017] Inside the exterior case 3, the electrode group 5 is impregnated with an electrolytic solution (not shown). The electrolytic solution is injected, for example, from a liquid injection port 17 provided in the lid member 7, and the liquid injection port 17 is closed with a sealing plate 19 after the injection of the electrolytic solution. As the electrolytic solution, a non-aqueous electrolytic solution prepared by dissolving an electrolyte (for example, a lithium salt) in a non-aqueous solvent is used. The non-aqueous solvent may be used alone or in combination of two or more.

[0018] On the surface of the lid member 7, a gas discharge valve 21 is formed together with the liquid injection port 17. Note that the liquid injection port 17 and the gas discharge valve 21 may not be provided on the lid member 7. Further, on the surface of the lid member 7, for example, a pair of positive electrode external terminals 23a and negative electrode external terminals 23b are attached, and the external terminals 23a and 23b are formed of a conductive material such as metal. The external terminals 23a and 23b are disposed in close contact with the lid member 7 via an insulating gasket 29, and are further connected to a conductive member 31.

[0019] The conductive member 31 is joined to a metal member 16 sandwiching current collecting tabs 70a and 70b. For example, when there are two pairs of metal members 16 sandwiching the current collecting tabs 70a and 70b, at least one pair of metal members 16 is joined. In this way, it is preferable that the electrode group 5 is electrically connected to the external terminals 23a and 23b, but it may be directly joined to the current collecting tabs 70a and 70b. When the conductive member 31 is connected to the metal member 16, breakage of the current collecting tabs 70a and 70b during connection can be suppressed as compared with the case where the conductive member 31 is directly connected to the current collecting tabs 70a and 70b.

[0020] Furthermore, an internal insulating member 33 may be provided between the lid member 7 and the conductive member 31, and the lid member 7 and the conductive member 31 are electrically insulated.

[0021] In the present embodiment, the current collecting tabs 70a and 70b are electrically insulated from the exterior case 3 by an insulating cover 34 provided between the current collecting tabs 70a and 70b and the exterior case 3. The insulating cover 34 is fixed to the electrode group 5 by an insulating tape 36. A terminal insulator 35 may be provided between the external terminals 23a and 23b and the lid member 7, and the external terminals 23a and 23b and the lid member 7 are electrically insulated.

[0022] The insulating cover 34 is provided between the current collector tabs 70a and 70b and the outer case 3. The surrounding structure of the electrode group 5 when the current collector tabs 70a and 70b are covered by the insulating cover 34 will be explained with reference to Figure 3. The structure in which the current collector tabs 70a and 70b are covered by the insulating cover 34 will also be explained with reference to Figure 4. Figure 3 is a schematic perspective view showing the area around the electrode group 5 used in the secondary battery 1 according to the first embodiment, and Figure 4 is a cross-sectional view of the cross section along line II in Figure 3, viewed from the direction of the arrow.

[0023] As shown in Figures 3 and 4, in the winding axis direction (Y direction) of the current collector tabs 70a and 70b, the back member 42 of the insulating cover 34 is located between the current collector tabs 70a and 70b and the outer case 3. The insulating cover 34 also has at least one pair of projections 60 protruding from the back member 42, and the projections 60 are provided along the innermost circumference of the metal member 16 that holds the current collector tabs 70a and 70b. Here, it is sufficient that the projections 60 are provided in contact with a part of the innermost circumference of the metal member 16. Furthermore, a space 50 is provided between the pair of projections 60 provided on the insulating cover 34.

[0024] Here, we define S as the thickness of the pair of protrusions 60 in the stacking direction (X direction) of the current collector tabs 70a and 70b. The thicknesses S of the pair of protrusions 60 are preferably equal from the viewpoint of balancing the insulating cover 34 in the stacking direction (X direction) of the current collector tabs 70a and 70b and from the viewpoint of the moldability of the insulating cover 34, but they may be different.

[0025] The pair of protrusions 60 provided on the insulating cover 34 are positioned along the innermost circumference of the metal member 16 that holds the current collector tabs 70a and 70b. As a result, even if the secondary battery 1 vibrates due to vibrations during vehicle operation, the innermost circumference of the metal member 16 that holds the current collector tabs 70a and 70b is in contact with the pair of protrusions 60 of the insulating cover 34, thus suppressing the displacement of the current collector tabs 70a and 70b. Because the displacement of the current collector tabs 70a and 70b can be suppressed by the insulating cover 34, the load on the joint between the current collector tabs 70a and 70b and the conductive member 31 can be suppressed, and damage to the current collector tabs 70a and 70b joined to the conductive member 31 can be prevented.

[0026] This means that even if the weight of the electrode group 5 increases due to the increased capacity of the secondary battery 1, such as by increasing the size of the electrode group 5 or increasing the number of turns of the electrode group 5, the displacement of the current collector tabs 70a and 70b can be suppressed by the insulating cover 34. The load on the joint between the current collector tabs 70a and 70b and the conductive member 31 increases in proportion to the weight of the electrode group 5, but even in this case, the load on the joint between the current collector tabs 70a and 70b and the conductive member 31 can be suppressed, and damage to the current collector tabs 70a and 70b joined to the conductive member 31 can be prevented.

[0027] In this embodiment, a space 50 is provided between a pair of protrusions 60 on the insulating cover 34. This ensures that even when a high-capacity electrode group 5 is manufactured and a large amount of gas is generated from the electrode group 5, the generated gas can pass through the space 50 in the insulating cover 34, securing a gas path to the gas discharge valve 21. In particular, since the gas generated inside the electrode group 5 moves towards the current collector tabs 70a and 70b, providing the space 50 in the insulating cover 34 allows the gas that has moved towards the current collector tabs 70a and 70b to be properly moved to the gas discharge valve 21. As a result, even when a large amount of gas is generated inside the secondary battery 1 from the electrode group 5, the gas is properly discharged from the gas discharge valve 21, preventing the pressure inside the secondary battery 1 from rising and causing it to rupture.

[0028] Figure 5 is a schematic perspective view showing an insulating cover 34 used in a secondary battery 1 according to the first embodiment. As shown in Figure 5, the insulating cover 34 has not only a rear member 42 but also a side member 40 connected to the rear member 42. When the insulating cover 34 is installed inside the secondary battery 1, the side member 40 of the insulating cover 34 is provided between the current collector tabs 70a, 70b and the outer case 3 in the stacking direction (X direction) of the current collector tabs 70a, 70b.

[0029] In this embodiment, preferred positions for providing a pair of protrusions 60 in the insulating cover 34 will be described. As shown in Figures 3 and 5, if the height of the electrode group 5 in the storage direction (Z direction) of the electrode group 5 into the outer case 3 is 1.0A, then it is preferable that the protrusions 60 be provided in a region with a height of 0.5A, extending from the bottom portion 66 of the electrode group 5, which is the back side in the storage direction (Z direction), to the upper portion 68 on the opposite side. Here, the protrusion 60 provided in the region with a height of 0.5A will be called the first protrusion 60'. As shown in Figure 4, in the region with a height of 0.5A, the first protrusion 60' is provided along the metal member 16, and the metal member 16 that is in contact with the first protrusion 60' will be called the first metal member 16'. The thickness of the first protrusion 60' will be S'.

[0030] The first metal member 16' and the first projection 60' are preferably provided in a region with a height of 0.5A from the base portion 66, because the region with a height of 0.5A from the base portion 66 of the electrode group 5 is more susceptible to displacement of the current collecting tab 70 due to vibrations of the secondary battery 1 than the region with a height of 0.5A to 1.0A from the electrode group 5. As described later, a conductive member 31 may also be provided in the region with a height of 0.5A to 1.0A from the electrode group 5, and in this case as well, the region with a height of 0.5A from the base portion 66 of the electrode group 5 is more susceptible to displacement of the current collecting tab 70 due to vibrations of the secondary battery 1 than the region with a height of 0.5A to 1.0A from the electrode group 5.

[0031] Modification 1 of the insulating cover 34 will be described with reference to Figure 6. Figure 6 is a schematic perspective view showing Modification 1 of the insulating cover 34. In Modification 1 of the insulating cover 34, as shown in Figure 6, not only is a first projection 60' provided in a region of 0.5A extending from the bottom 66 to the top 68 of the electrode group 5, but a pair of projections 60 are also provided in a region from 0.5A to 1.0A, which are referred to as the second projection 60''.

[0032] Here, in the second projection 60'', the thickness in the stacking direction (X direction) of the current collector tabs 70a and 70b is defined as S''. The thicknesses (S'') of the pair of second projections 60'' are preferably equal from the viewpoint of balancing the insulating cover 34 in the stacking direction (X direction) of the current collector tabs 70a and 70b and from the viewpoint of the moldability of the insulating cover 34, but they may be different.

[0033] Furthermore, a second modification of the insulating cover 34 will be described with reference to Figure 7. Figure 7 is a schematic perspective view showing the second modification of the insulating cover 34. As shown in Figure 7, the second modification of the insulating cover 34 has a pair of first protrusions 60' and a pair of second protrusions 60'' integrated together.

[0034] Modifications 1 and 2 of the insulating cover 34 will be described with reference to Figure 8, showing the structure in which the current collector tabs 70a and 70b are covered by Modifications 1 and 2 of the insulating cover 34. Figure 8 is a cross-sectional view of Modifications 1 and 2 of the insulating cover 34, taken from the direction of the arrow along the line II-II in Figure 3.

[0035] As shown in Figure 8, the pair of second protrusions 60'' are provided along the innermost circumference of the metal member 16 that holds the current collector tabs 70a and 70b, similar to the first protrusions 60''. Here, the metal member 16 that is in contact with the second protrusions 60'' is referred to as the second metal member 16'', and the second protrusions 60'' only need to be provided in contact with a part of the innermost circumference of the second metal member 16''. Furthermore, a space 50 is provided between the pair of second protrusions 60'', similar to the pair of first protrusions 60'.

[0036] Modified versions 1 and 2 of the insulating cover 34 are provided with a second projection 60'' in addition to the first projection 60', and the pair of projections 60(60',60'') are provided along the innermost circumference of the metal member 16(16',16'') that holds the current collector tabs 70a,70b. As a result, for example, even if the secondary battery 1 vibrates due to vibrations during vehicle operation, the innermost circumference of the pair of metal member 16(16',16'') that holds the current collector tabs 70a,70b is in contact with the pair of projections 60(60',60'') of the insulating cover 34, so that the displacement of the current collector tabs 70a,70b can be suppressed by the insulating cover 34 over the entire height of 1.0A. Since the displacement of the current collector tabs 70a and 70b can be suppressed by the insulating cover 34, the load on the joint between the current collector tabs 70a and 70b and the conductive member 31 can be suppressed, and damage to the current collector tabs 70a and 70b joined to the conductive member 31 can be prevented.

[0037] This means that even if the weight of the electrode group 5 increases due to the increased capacity of the secondary battery 1, such as by increasing the size of the electrode group 5 or increasing the number of turns of the electrode group 5, the displacement of the current collector tabs 70a and 70b can be suppressed by the insulating cover 34 over the entire height of 1.0A. The load on the joint between the current collector tabs 70a and 70b and the conductive member 31 increases in proportion to the weight of the electrode group 5, but even in this case, the load on the joint between the current collector tabs 70a and 70b and the conductive member 31 can be suppressed, and damage to the current collector tabs 70a and 70b joined to the conductive member 31 can be prevented.

[0038] In this embodiment, a space 50 is provided between a pair of protrusions 60 (60', 60'') on the insulating cover 34. This ensures that even when a high-capacity electrode group 5 is manufactured and a large amount of gas is generated from the electrode group 5, the generated gas can pass through the space 50 in the insulating cover 34, securing a gas path to the gas discharge valve 21. In particular, since the gas generated inside the electrode group 5 moves towards the current collector tabs 70a, 70b, providing the space 50 in the insulating cover 34 allows the gas that has moved towards the current collector tabs 70a, 70b to be properly moved to the gas discharge valve 21. As a result, even when a large amount of gas is generated inside the secondary battery 1 from the electrode group 5, the gas is properly discharged from the gas discharge valve 21, preventing the pressure inside the secondary battery 1 from rising and causing it to rupture.

[0039] In the insulating cover 34 of Modification 1, the protrusions 60 (60', 60'') are provided separately along each metal member 16 (16', 16''), so the protrusions 60 (60', 60'') can suppress the displacement of the current collector tabs 70a, 70b with minimal volume, and the manufacturing cost of the protrusions 60 (60', 60'') can be reduced. On the other hand, in the insulating cover 34 of Modification 2, the protrusions 60 (60', 60'') are integrated, making the manufacturing of the protrusions 60 (60', 60'') easier.

[0040] Furthermore, in this embodiment, as described above, the conductive member 31 may be connected to the current collector tabs 70a and 70b via the metal member 16. When the conductive member 31 is connected to the metal member 16, the conductive member 31 is provided between the metal member 16 at the outermost periphery of the current collector tabs 70a and 70b and the side member 40 of the insulating cover 34, and the conductive member 31 maintains insulation from the outer case 3 by the side member 40 of the insulating cover 34.

[0041] When the conductive member 31 is connected to the metal member 16, the preferred location for providing the conductive member 31 will be described. As mentioned above, since the conductive member 31 is electrically connected not only to the metal member 16 but also to the external terminals 23a and 23b, it is preferable that the location for providing the conductive member 31 be close to the external terminals 23a and 23b from the viewpoint of current-carrying characteristics. Therefore, it is preferable that the conductive member 31 be provided in a region with a height of 0.5A to 1.0A from the bottom 66 to the top 68 of the electrode group 5, relative to a height of 1.0A. This allows electrical energy to be extracted from the electrode group 5 via the conductive member 31 at a location close to the external terminals 23a and 23b, thereby obtaining high current-carrying characteristics. However, the location for providing the conductive member 31 is not limited to these, and it is sufficient as long as the conductive member 31 is connected to the metal member 16.

[0042] Since the conductive member 31 is preferably provided in a region of height 0.5A to 1.0A, it is also preferable that the conductive member 31 and the metal member 16 are connected in a region of height 0.5A to 1.0A. Therefore, for example, in Modification 1 and Modification 2 of the insulating cover 34, the second metal member 16'' is in contact with the second projection 60'' provided in a region of height 0.5A to 1.0A, and it is further preferable that the conductive member 31 is connected to this second metal member 16''. Here, the structure around the current collector tabs 70a and 70b in a state where the conductive member 31 is connected to the second metal member 16'' will be described again with reference to Figure 8.

[0043] As shown in Figure 8, the conductive member 31 is positioned in contact with the second metal member 16'', and the second metal member 16'' is sandwiched between the conductive member 31 and the second projection 60''. Even without the second projection 60'', the displacement of the current collecting tabs 70a and 70b can be suppressed by the conductive member 31 by the contact between the second metal member 16'' and the conductive member 31. However, by sandwiching the second metal member 16'' between the conductive member 31 and the second projection 60'', the displacement of the current collecting tabs 70a and 70b can be further suppressed not only by the conductive member 31 but also by the second projection 60''. This reduces the load on the joint between the current collecting tabs 70a and 70b and the conductive member 31, and prevents damage to the current collecting tabs 70a and 70b joined to the conductive member 31.

[0044] In Modification 1 and Modification 2, it is preferable that the conductive member 31 is positioned in contact with the second metal member 16'', where the thickness of the conductive member 31 in the stacking direction (X direction) of the current collecting tabs 70a and 70b is defined as T. In Modification 1 and Modification 2, the second metal member 16'' is sandwiched between the conductive member 31 of thickness T and the second projection 60'' of thickness S''. However, it is possible that only the first projection 60'' of thickness S'' is in contact with the first metal member 16', in which case both the first metal member 16' and the second metal member 16'' need to be evenly supported by the conductive member 31 and the projection 60 (60', 60'').

[0045] Here, a third modification of the insulating cover 34 will be described with reference to Figure 9. Figure 9 is a schematic perspective view showing the third modification of the insulating cover 34. As shown in Figure 9, the third modification of the insulating cover 34 is provided with a pair of third protrusions 62 that protrude from the side member 40. As a result, the first metal member 16' is supported not only by the first protrusions 60' with a thickness S' but also by the third protrusions 62.

[0046] Regarding the third modification of the insulating cover 34, a structure in which the current collector tabs 70a and 70b are covered by the third modification of the insulating cover 34 will be described with reference to Figure 10. Figure 10 is a cross-sectional view of the third modification of the insulating cover 34, taken from the direction of the arrow, along line II in Figure 3.

[0047] As shown in Figure 10, the third projection 62 is provided opposite to the pair of first projections 60' via a pair of first metal members 16'. Here, the thickness of the third projection 62 in the stacking direction (X direction) of the current collecting tabs 70a and 70b is defined as U. When the second metal member 16'' of the insulating cover 34 is sandwiched between a conductive member 31 with thickness T and a second projection 60'' with thickness S'', it is preferable that the thickness U of the third projection 62 is equal to or greater than the thickness T of the conductive member 31. More preferably, the sum of the thickness S' of the first projection 60' and the thickness U of the third projection 62 (S'+U) is equal to the sum of the thickness T of the conductive member 31 and the thickness S'' of the second projection 60'' (T+S''). This allows both the first metal member 16' and the second metal member 16'' to be evenly supported in the height direction of the electrode group 5.

[0048] According to the secondary battery 1 of at least one embodiment described above, the pair of protrusions 60 provided on the insulating cover 34 are provided along the innermost circumference of the metal member 16 that holds the current collector tabs 70a and 70b. As a result, even if the secondary battery 1 vibrates due to vibrations during vehicle operation, for example, the innermost circumference of the metal member 16 that holds the current collector tabs 70a and 70b is in contact with the pair of protrusions 60 of the insulating cover 34, so that the displacement of the current collector tabs 70a and 70b can be suppressed by the insulating cover 34. This suppresses the load on the joint between the current collector tabs 70a and 70b and the conductive member 31, and prevents damage to the current collector tabs 70a and 70b that are joined to the conductive member 31.

[0049] This means that even if the weight of the electrode group 5 increases due to the increased capacity of the secondary battery 1, such as by increasing the size of the electrode group 5 or increasing the number of turns of the electrode group 5, the displacement of the current collector tabs 70a and 70b can be suppressed by the insulating cover 34. The load on the joint between the current collector tabs 70a and 70b and the conductive member 31 increases in proportion to the weight of the electrode group 5, but even in this case, the load on the joint between the current collector tabs 70a and 70b and the conductive member 31 can be suppressed, and damage to the current collector tabs 70a and 70b joined to the conductive member 31 can be prevented.

[0050] Furthermore, in the secondary battery 1 of this embodiment, a space 50 is provided between a pair of protrusions 60 on the insulating cover 34. This ensures that even if, for example, a high-capacity electrode group 5 is manufactured and a large amount of gas is generated from the electrode group 5, the generated gas can pass through the space 50 in the insulating cover 34, securing a gas path to the gas discharge valve 21. In particular, since the gas generated inside the electrode group 5 moves towards the current collector tabs 70a and 70b, providing the space 50 in the insulating cover 34 allows the gas that has moved towards the current collector tabs 70a and 70b to be properly moved to the gas discharge valve 21. As a result, even if a large amount of gas is generated inside the secondary battery 1 from the electrode group 5, the gas can be properly discharged from the gas discharge valve 21, preventing the internal pressure of the secondary battery 1 from rising and causing it to rupture. Therefore, according to this embodiment, a secondary battery 1 with excellent vibration resistance and high safety can be provided.

[0051] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0052] 1...Secondary battery, 3...Outer casing, 5...Electrode group, 7...Lid member, 9...Opening, 13...Positive electrode, 13a...Positive electrode current collector, 15...Negative electrode, 15a...Negative electrode current collector, 16...Metal member, 16'...First metal member, 16''...Second metal member, 17...Filling port, 19...Sealing plate, 21...Gas discharge valve, 23a...Positive electrode external terminal, 23b...Negative electrode external terminal, 29...Insulating gasket T, 31...conductive member, 33...internal insulating member, 34...insulating cover, 35...terminal insulator, 36...insulating tape, 40...side member, 42...back member, 50...space, 60...protrusion, 60'...first protrusion, 60''...second protrusion, 62...third protrusion, 66...bottom, 68...top, 70...current collector tab, 70a...positive electrode current collector tab, 70b...negative electrode current collector tab.

Claims

1. An electrode group comprising a positive electrode, a negative electrode, and a separator, and having multiple layers of wound current-collecting tabs at both ends in the direction of the winding axis, An outer case for housing the aforementioned electrode group, From the innermost to the outermost circumference in the winding of the current-collecting tab, at least one pair of metal members are arranged to clamp the current-collecting tab and are positioned opposite to the stacking direction of the current-collecting tab, The system comprises an insulating cover provided between the current collection tab and the outer casing, The insulating cover has a back member provided between the current collector tab and the outer casing in the winding axis direction, It has at least one pair of protrusions that protrude from the rear member and are provided along the innermost circumference of the current collector tab on the metal member, A secondary battery having a space between a pair of the aforementioned protrusions.

2. It comprises a pair of first metal members and a pair of first protrusions, The secondary battery according to claim 1, wherein the first metal member and the first projection are provided in a region with a height of 0.5A extending upward from the bottom edge of the electrode group, which is on the back side in the storage direction of the electrode group, with respect to the height of the electrode group of 1.0A in the storage direction of the electrode group into the outer case.

3. It comprises a pair of second metal members and a pair of second protrusions, The secondary battery according to claim 2, wherein the second metal member and the second projection are provided in a region of height 0.5A to 1.0A from the bottom to the top of the electrode group with respect to the height 1.0A.

4. The secondary battery according to claim 3, wherein the first projection and the second projection are integrally formed.

5. The insulating cover has a side member provided between the current collector tab and the outer case in the stacking direction of the current collector tab, The secondary battery according to claim 2 or 3, wherein a conductive member is provided between the metal member and the side member at the outermost periphery of the current collection tab.

6. The secondary battery according to claim 5, wherein the conductive member is provided in a region of height 0.5A to 1.0A from the bottom to the top of the electrode group with respect to the height 1.0A.

7. The insulating cover has a pair of third protrusions that protrude from the side member and are provided opposite to the pair of first protrusions via a pair of first metal members, The secondary battery according to claim 5, wherein the thickness of the third projection of the current collector tab in the stacking direction is equal to or greater than the thickness of the conductive member of the current collector tab in the stacking direction.

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