Secondary batteries

Abstract

To provide a secondary battery with superior performance. [Solution] This secondary battery comprises a battery element to which leads are connected, a container housing the battery element, a lid covering the container and the battery element housed in the container, and a first insulating portion sealing the container and the lid. The lid has a first conductive member having an opening, and a second conductive member attached to the first conductive member via a second insulating portion so as to cover the opening and connected to the leads through the opening. The lid is provided with a first joining region and a second joining region where the first conductive member and the second conductive member are mechanically joined, respectively. In the first joining region, the first conductive member and the second conductive member are electrically joined, and in the second joining region, the first conductive member and the second conductive member are electrically insulated. The second joining strength between the first conductive member and the second conductive member in the second joining region is higher than the first joining strength between the first conductive member and the second conductive member in the first joining region.

Description

Technical Field

[0001] The present disclosure relates to a secondary battery in which battery elements are housed in a container.

Background Art

[0002] A variety of electronic devices such as mobile phones have become widespread, and there is a demand for miniaturization, weight reduction, and long life of such electronic devices. Therefore, as a power source, it is small and lightweight.

[0003] A secondary battery includes an electrolytic solution together with a positive electrode and a negative electrode. When gas is generated due to a decomposition reaction of the electrolytic solution or the like, the secondary battery has a safety mechanism for breaking the current path from the battery element to the external terminal as necessary in order to suppress the occurrence of problems caused by the gas (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, various studies have been made to improve the performance of secondary batteries. However, there is still room for improvement in the performance of secondary batteries.

[0006] Therefore, a secondary battery having more excellent performance is desired.

Means for Solving the Problems

[0007] A secondary battery according to one embodiment of the present disclosure comprises a battery element to which leads are connected, a container housing the battery element, a lid covering the container and the battery element housed in the container, and a first insulating portion sealing the container and the lid. The lid has a first conductive member having an opening, and a second conductive member attached to the first conductive member via a second insulating portion so as to cover the opening and connected to the leads through the opening. The lid is provided with a first joining region and a second joining region to which the first conductive member and the second conductive member are mechanically joined, respectively. In the first joining region, the first conductive member and the second conductive member are electrically joined, and in the second joining region, the first conductive member and the second conductive member are electrically insulated. The second joining strength between the first conductive member and the second conductive member in the second joining region is higher than the first joining strength between the first conductive member and the second conductive member in the first joining region. [Effects of the Invention]

[0008] According to one embodiment of the secondary battery of this disclosure, when the pressure inside the container rises due to gas generation, the current path from the battery element to the first conductive member via the second conductive member is interrupted. As a result, the progress of the battery reaction is stopped, and safety is ensured.

[0009] Furthermore, the effects of this disclosure are not necessarily limited to those described herein, but may include any of the series of effects related to this disclosure described later. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a cross-sectional view showing an example of the overall configuration of a secondary battery according to the first embodiment of this disclosure. [Figure 2] Figure 2 is a cross-sectional view showing an example of the upper part of the secondary battery shown in Figure 1. [Figure 3] Figure 3 is a plan view showing an example of the configuration of the safety valve mechanism of the secondary battery shown in Figure 1. [Figure 4] Figure 4 is a cross-sectional view showing an enlarged portion of the battery element configuration shown in Figure 1. [Figure 5A]FIG. 5A is a first cross-sectional view for explaining the operation of the safety valve mechanism shown in FIG. 2. [Figure 5B] FIG. 5B is a second cross-sectional view for explaining the operation of the safety valve mechanism shown in FIG. 2. [Figure 6] FIG. 6 is a plan view showing a configuration example of a safety valve mechanism as a first modification of the first embodiment of the present disclosure. [Figure 7] FIG. 7 is a plan view showing a configuration example of a safety valve mechanism as a second modification of the first embodiment of the present disclosure. [Figure 8A] FIG. 8A is a cross-sectional view showing a configuration example of a safety valve mechanism as a third modification of the first embodiment of the present disclosure. [Figure 8B] FIG. 8B is a plan view showing a configuration example of the safety valve mechanism of the secondary battery shown in FIG. 8A. [Figure 8C] FIG. 8C is a first cross-sectional view for explaining the operation of the safety valve mechanism shown in FIG. 8A. [Figure 8D] FIG. 8D is a second cross-sectional view for explaining the operation of the safety valve mechanism shown in FIG. 8A. [Figure 9A] FIG. 9A is a plan view showing a configuration example of a connection part as a fourth modification of the first embodiment of the present disclosure. [Figure 9B] FIG. 9B is a cross-sectional view showing a configuration example of a connection part as a fifth modification of the first embodiment of the present disclosure. [Figure 9C] FIG. 9C is a plan view showing a configuration example of a connection part as a sixth modification of the first embodiment of the present disclosure. [Figure 10] FIG. 10 is a cross-sectional view showing a configuration example of a safety valve mechanism of a secondary battery as a second embodiment of the present disclosure. [Figure 11A] FIG. 11A is a first cross-sectional view for explaining the operation of the safety valve mechanism shown in FIG. 10. [Figure 11B] FIG. 11B is a second cross-sectional view for explaining the operation of the safety valve mechanism shown in FIG. 10. [Figure 12] It is a block diagram showing the configuration of an application example (battery pack) of a secondary battery.

Mode for Carrying Out the Invention

[0011] Hereinafter, with reference to the drawings, a detailed description will be given of an embodiment of the present disclosure. The order of description is as follows. 1. First Embodiment (Secondary Battery) 1-1. Overall Configuration 1-2. Detailed Configuration of the Safety Valve Mechanism 1-3. Detailed Configuration of the Battery Element 1-4. Operation 1-5. Manufacturing Method 1-6. Action and Effect 1-7. Variation 2. Second Embodiment (Secondary Battery) 3. Applications of the Secondary Battery

[0012] <<1. First Embodiment (Secondary Battery)>> First, the secondary battery according to the first embodiment of the present disclosure will be described.

[0013] In this embodiment, a cylindrical secondary battery having a cylindrical outer appearance will be exemplified and described. However, the secondary battery of the present disclosure is not limited to a cylindrical secondary battery, and may be a secondary battery having an outer appearance of a shape other than a cylindrical shape.

[0014] The charge-discharge principle of the secondary battery is not particularly limited. Hereinafter, the case where the battery capacity is obtained by utilizing the occlusion and release of electrode reactants will be described. This secondary battery includes an electrolyte together with a positive electrode and a negative electrode.

[0015] The type of electrode reactant is not particularly limited. Specifically, it is a light metal such as an alkali metal and an alkaline earth metal. The alkali metal includes lithium, sodium, potassium, etc., and the alkaline earth metal includes beryllium, magnesium, calcium, etc.

[0016] In the following example, we will consider the case where lithium is the electrode reactant. A secondary battery that obtains battery capacity by utilizing the intercalation and deintercalation of lithium is a so-called lithium-ion secondary battery. In this lithium-ion secondary battery, lithium is intercalated and deintercalated in an ionic state.

[0017] <1-1. Overall Structure> Figure 1 shows a cross-sectional view of a secondary battery according to the first embodiment. In this secondary battery, as shown in Figure 1, the battery element 20 is housed inside a cylindrical battery case 11. The symbol CP represents the central axis of this secondary battery.

[0018] In the following, the direction in which the battery elements 20 are housed inside the battery can 11, that is, the height direction of the cylindrical battery can 11, is defined as the Z direction, and the radial direction of the cylindrical battery can 11 is defined as the R direction.

[0019] More specifically, in the secondary battery shown in Figure 1, for example, a pair of insulating plates 12 and 13 and a battery element 20 are housed inside a cylindrical battery case 11. A safety valve mechanism 30 is attached to the battery case 11. The battery case 11 is sealed, for example, by a battery cover 14. However, the secondary battery may further include one or more of the following inside the battery case 11: a thermal resistance element (also called a PTC element) and a reinforcing member. The battery can 11 is a specific example corresponding to one embodiment of the "container" in this disclosure. Furthermore, the structure formed by combining the battery cover 14 and the safety valve mechanism 30 (described later) is a specific example corresponding to one embodiment of the "lid" in this disclosure.

[0020] [Battery can] The battery can 11 is a hollow container extending in the Z direction, with its lower end in the Z direction closed and its upper end in the Z direction open. One end of the battery can 11 in the Z direction is the open end 11N. The battery can 11 contains one or more types of metallic materials, such as iron, aluminum, and their alloys. The surface of the battery can 11 may be plated with one or more types of metallic materials, such as nickel.

[0021] [insulating board] Each of the insulating plates 12 and 13 is, for example, a dish-shaped plate having a surface perpendicular to the central axis CP, which is the winding center of the battery element 20, i.e., a surface perpendicular to the Z direction in Figure 1. The pair of insulating plates 12 and 13 are arranged to sandwich the battery element 20 in the Z direction and to extend along a surface perpendicular to the Z direction.

[0022] [Crimped structure] The open end 11N of the battery can 11 is crimped to the battery cover 14 and the safety valve mechanism 30 via a gasket 15. As a result, a bent portion 11P is formed in the battery can 11 that defines the open end 11N. The combined portion of the battery cover 14 and the safety valve mechanism 30 is one specific example corresponding to one aspect of the "cover portion" of this disclosure.

[0023] With the battery elements 20 and the like housed inside the battery can 11, the open end 11N of the battery can 11 is sealed by the battery cover 14. The battery can 11 has a crimping structure 11R formed near the open end 11N. The crimping structure 11R is a structure in which a bent portion 11P defining the open end 11N, the battery cover 14 and the safety valve mechanism 30 are crimped together via a gasket 15. In addition, a constricted portion 11S is provided between the bent portion 11P and the insulating plate 12, in which a part of the battery can 11 protrudes inward.

[0024] [Battery cover] The battery cover 14 is a cover member that closes the open end 11N of the battery can 11. The battery cover 14 may be made of the same material as the forming material of the battery can 11. However, the battery cover 14 may contain a different forming material than the forming material of the battery can 11.

[0025] In particular, the battery cover 14 preferably contains stainless steel. This is because the physical strength of the crimping structure 11R is ensured in accordance with the physical strength of the battery cover 14, thereby suppressing the detachment of the battery cover 14 and leakage of electrolyte even when the internal pressure of the battery can 11 rises. Specific examples of stainless steel include SUS304 and SUS430.

[0026] The protrusion 14T in the central region of the battery cover 14 protrudes upward (+Z direction), for example. As a result, the peripheral region of the battery cover 14, which is the region other than the central region, is in contact with the safety valve mechanism 30, for example. A through hole H14 is provided in the protrusion 14T of the battery cover 14. By providing the through hole H14, if gas is generated inside the battery can 11 and the internal pressure of the battery can 11 rises, the third conductive member 33 is more likely to rupture, as will be described later. Note that there may be only one through hole H14 or there may be multiple through holes H14.

[0027] [gasket] The gasket 15 is a sealing member that seals the gap between the bent portion 11P and the battery cover 14. The gasket 15 is interposed between the bent portion 11P of the battery can 11 and the battery cover 14.

[0028] The gasket 15 contains one or more types of insulating materials, and specific examples of these insulating materials are polymer materials such as polybutylene terephthalate (PBT) and polypropylene (PP). By using these insulating polymer materials as the gasket 15, the battery can 11 and the battery cover 14 are electrically isolated from each other, while the gap between the folded portion 11P and the battery cover 14 is sufficiently sealed. The gasket 15 is a specific example corresponding to one embodiment of the "first insulating part" of this disclosure.

[0029] [Safety valve mechanism] The safety valve mechanism 30 is located inside the battery cover 14 in the Z direction. The safety valve mechanism 30 is a mechanism that releases the internal pressure of the battery can 11 by releasing the sealed state of the battery can 11 as needed when the internal pressure of the battery can 11 rises. The cause of the rise in internal pressure of the battery can 11 is gas generated due to the decomposition reaction of the electrolyte during charging and discharging. In addition, the internal pressure of the battery can 11 may rise due to external heating. The detailed configuration of the safety valve mechanism 30 will be described later (see Figures 2, 3, and 5 below).

[0030] [Battery element] The battery element 20 is housed inside the battery can 11 and contains an electrolyte solution, which is a liquid electrolyte, along with the positive electrode 21 and the negative electrode 22.

[0031] In the example shown in Figure 1, the battery element 20 is a so-called wound electrode body. That is, in the battery element 20, the positive electrode 21 and the negative electrode 22 are stacked with a separator 23 in between, and the positive electrode 21, the negative electrode 22, and the separator 23 are wound together. The electrolyte is impregnated into the positive electrode 21, the negative electrode 22, and the separator 23, respectively.

[0032] At the center of the battery element 20, a space is formed, i.e., a central space 20C, which is created when winding the positive electrode 21, negative electrode 22, and separator 23. A center pin 24 is inserted into the central space 20C. However, the center pin 24 may be omitted.

[0033] A positive electrode lead 25 is connected to the positive electrode 21. A negative electrode lead 26 is connected to the negative electrode 22. The positive electrode lead 25 contains one or more types of conductive materials, such as metal materials. A specific example of the metal material constituting the positive electrode lead 25 is aluminum. The positive electrode lead 25 is electrically connected to the battery cover 14 via a safety valve mechanism 30. The negative electrode lead 26 contains one or more types of conductive materials, such as metal materials. A specific example of the metal material constituting the negative electrode lead 26 is nickel. The negative electrode lead 26 is electrically connected to the battery can 11.

[0034] The detailed configuration of the battery element 20, namely the positive electrode 21, negative electrode 22, separator 23, and electrolyte, will be described later (see Figure 4).

[0035] <1-2. Detailed Configuration of the Safety Valve Mechanism> Figure 2 shows a part of the cross-sectional configuration of the secondary battery shown in Figure 1, more specifically showing the safety valve mechanism 30 and its vicinity. Figure 3 is a plan view showing an enlarged example of the configuration of the safety valve mechanism 30. The structure formed by combining the safety valve mechanism 30 and the battery cover 14 described above is a specific example corresponding to one embodiment of the "cover portion" of this disclosure.

[0036] As shown in Figures 2 and 3, the safety valve mechanism 30 includes a first conductive member 31, a second conductive member 32, a third conductive member 33, and a sealing portion 16. However, the third conductive member 33 is omitted from the description in Figure 3. The first conductive member 31 is a specific example corresponding to one embodiment of the "first conductive member" of this disclosure, and the second conductive member 32 is a specific example corresponding to one embodiment of the "second conductive member" of this disclosure. Furthermore, the sealing portion 16 is a specific example corresponding to one embodiment of the "second insulating portion" of this disclosure.

[0037] The third conductive member 33 is a disc-shaped metal member centered on a central axis CP, extending along a horizontal plane perpendicular to the Z direction, for example. The third conductive member 33 includes an upper surface 33TS facing the battery cover 14 and a lower surface 33BS opposite to the upper surface 33TS. The upper surface 33TS of the third conductive member 33 abuts against the lower surface 14BS of the battery cover 14. The third conductive member 33 is partially detachable in response to an increase in the internal pressure of the battery can 11. As shown in Figure 2, the third conductive member 33 includes a valve portion 33V in the central region of the safety valve mechanism 30 that is detachable in response to an increase in the internal pressure of the battery can 11. The third conductive member 33 has a groove portion 33U arranged in an annular shape in plan view, surrounding the valve portion 33V. That is, the valve portion 33V is defined by the groove portion 33U. When the third conductive member 33 ruptures, the valve portion 33V may partially rupture due to a partial fracture of the groove portion 33U, or the entire valve portion 33V may rupture due to a complete fracture of the groove portion 33U. The third conductive member 33 contains one or more types of conductive materials, such as metal materials, and specific examples of such metal materials include aluminum and aluminum alloys. The planar shape of the third conductive member 33 is not particularly limited, but specifically it may be circular. This "planar shape" refers to a shape along a horizontal plane perpendicular to the Z direction, and the definition of planar shape described here will be the same hereafter. Furthermore, the third conductive member 33 may have a stepped structure, as described later for the first conductive member 31.

[0038] The first conductive member 31 is an annular member provided so as to surround the central axis CP along a horizontal plane perpendicular to the Z direction, as shown in Figure 3. The first conductive member 31 has an opening 31K that penetrates in the Z direction at a position that overlaps with the central space 20C of the battery element 20 in the Z direction. The opening 31K is a vent for releasing gas generated inside the battery can 11 to the outside. The planar shape of the opening 31K is not particularly limited, but specifically it is circular, for example. The first conductive member 31 has a stepped structure including, for example, a first seat portion 311, a second seat portion 312, and a flange portion 313, in the R direction in order from a position close to the central axis CP. The first seat portion 311, the second seat portion 312, and the flange portion 313 are each formed in an annular shape in plan view. In the example of Figure 3, the center positions of the first seat portion 311, the second seat portion 312, and the flange portion 313 coincide with the position of the central axis CP. The upper surface 311TS of the first seat portion 311 and the upper surface 312TS of the second seat portion 312 each include portions extending parallel to horizontal planes perpendicular to the Z direction (see Figure 2). The upper surface of the flange portion 313 is joined to the lower surface 33BS of the third conductive member 33 (see Figure 2). The first conductive member 31 includes one or more types of metallic materials, such as pure iron, pure aluminum, and alloys containing at least one of iron and aluminum.

[0039] The second conductive member 32 includes a main body portion 321 and a connecting portion 322. The main body portion 321 is a disc-shaped member provided in a position that overlaps with the opening 31K in the Z direction, as shown in Figure 3. That is, the main body portion 321 of the second conductive member 32 is provided so as to cover the opening 31K of the first conductive member 31. The peripheral edge of the main body portion 321 overlaps with the vicinity of the opening 31K in the Z direction and is attached to the first conductive member 31 via the sealing portion 16. Specifically, the peripheral edge of the main body portion 321 is positioned to face a part of the upper surface 311TS of the first seat portion 311 with the sealing portion 16 in between, and the peripheral edge of the main body portion 321 and a part of the upper surface 311TS of the first seat portion 311 are joined by the sealing portion 16. The connecting portion 322 is, for example, a strip-shaped metal foil. Therefore, the thickness of the connecting portion 322 is thinner than the thickness of the main body portion 321. The connecting portion 322 is joined to the upper surface 321TS of the main body portion 321 and the upper surface 312TS of the second seat portion 312, respectively. The main body portion 321 and the connecting portion 322 contain one or more types of metallic materials, such as pure iron, pure aluminum, and alloys containing at least one of iron and aluminum. The constituent materials of the main body portion 321 and the constituent materials of the connecting portion 322 may be the same type or different types. Furthermore, as shown in Figure 3, the sealing portion 16 is provided in an annular shape so as to surround the opening 31K in a plan view. The sealing portion 16 may be made of a thermoplastic insulating resin such as polypropylene or polyethylene. In addition, the main body portion 321 of the second conductive member 32 is connected to the positive electrode lead 25 through the opening 31K.

[0040] As shown in Figures 2 and 3, the safety valve mechanism 30 is provided with a first bonding region AR1 and a second bonding region AR2, to which the first conductive member 31 and the second conductive member 32 are mechanically joined, respectively. The first conductive member 31 is located, for example, on the opposite side of the central axis CP from the second conductive member 32 in the radial direction (R direction). In the first bonding region AR1, the first conductive member 31 and the second conductive member 32 are electrically connected, while in the second bonding region AR2, the first conductive member 31 and the second conductive member 32 are electrically insulated. More specifically, in the first bonding region AR1, the main body portion 321 is electrically and mechanically joined to the first conductive member 31 via the connecting portion 322. That is, the upper surface 321TS of the main body portion 321 is electrically and mechanically joined to the connecting portion 322, and the upper surface 312TS of the second seat portion 312 of the first conductive member 31 is electrically and mechanically joined to the connecting portion 322. The upper surface 321TS of the main body 321 and the connecting portion 322 can be joined by methods such as laser welding, ultrasonic welding, or resistance welding. Similarly, the upper surface 312TS of the second seat portion 312 of the first conductive member 31 can be joined to the connecting portion 322 by methods such as laser welding, ultrasonic welding, or resistance welding. In the first joining region AR1, the lower surface 321BS of the main body 321 is mechanically joined to the upper surface 311TS of the first seat portion 311 via the sealing portion 16. In the second joining region AR2, the lower surface 321BS of the main body 321 is also mechanically joined to the upper surface 311TS of the first seat portion 311 via the sealing portion 16. Here, the lower surface 321BS of the main body 321 and the sealing portion 16 can be joined by, for example, heat welding or by bonding using an adhesive.

[0041] In the safety valve mechanism 30, the second bonding strength between the first conductive member 31 and the second conductive member 32 in the second bonding region AR2 is higher than the first bonding strength between the first conductive member 31 and the second conductive member 32 in the first bonding region AR1. The first bonding strength here refers to the maximum strength among the following four: the bonding strength between the main body 321 and the connecting portion 322, the bonding strength between the second seat portion 312 and the connecting portion 322, the bonding strength between the main body 321 and the first seat portion 311, and the breaking strength of the connecting portion 322. In this embodiment, the bonding strength between the main body 321 and the first seat portion 311 is the maximum strength. Therefore, if an external force is applied to the first joint region AR1 such that the main body 321 separates from the first seat 311, at least one of the following will occur: separation of the connecting portion 322 from the main body 321, separation of the connecting portion 322 from the second seat 312, and fracture of the connecting portion 322. The joint strength is determined by measuring the pressing force per unit area when the sealing portion 16 ruptures by pressing the main body 321 in the +Z direction (the direction from the bottom of the battery can 11 of the secondary battery toward the open end 11N, i.e., upward). That is, the joint strength can be calculated by dividing the pressing force on the main body 321 when the sealing portion 16 ruptures by the area of ​​the overlapping portion. Furthermore, by checking which part of the circumferential direction of the sealing portion 16 has ruptured, it is possible to identify parts with relatively weak joint strength and parts with relatively strong joint strength. In the secondary battery of this embodiment, the first bonding strength of the portion of the sealing portion 16 that occupies the first bonding region AR1 is lower than the second bonding strength of the portion of the sealing portion 16 that occupies the second bonding region AR2. Therefore, the sealing portion 16 is designed to crack in the first bonding region AR1. Furthermore, in this embodiment, as shown in Figures 1 to 3, in the radial direction (R direction) perpendicular to the Z direction, the width 16W2 of the sealing portion 16 in the second bonding region AR2 is wider than the width 16W1 of the sealing portion 16 in the first bonding region AR1. Therefore, the bonding strength between the main body portion 321 and the first seat portion 311 via the sealing portion 16 in the second bonding region AR2 is stronger than the bonding strength between the main body portion 321 and the first seat portion 311 via the sealing portion 16 in the first bonding region AR1.In this embodiment, as shown in Figure 3, for example, the center position of the circular inner edge 16E1 of the sealing portion 16 and the center position of the circular outer edge 16E2 of the sealing portion 16 are different. In the example in Figure 3, the center position of the inner edge 16E1 of the sealing portion 16 coincides with the position of the central axis CP, but the center position of the outer edge 16E2 of the sealing portion 16 is shifted to the left of the plane of the paper from the position of the central axis CP. Also, the center position of the main body portion 321 and the center position of the opening 31K coincide with the position of the central axis CP. For this reason, as shown in Figures 1 to 3, in the radial direction (R direction) perpendicular to the Z direction, the width 16W1 of the sealing portion 16 in the first joining region AR1 is the smallest among the widths 16W in all regions of the sealing portion 16. Consequently, the bonding strength between the main body portion 321 and the first seat portion 311 via the sealing portion 16 in the first joining region AR1 is lower than the bonding strength between the main body portion 321 and the first seat portion 311 via the sealing portion 16 in regions other than the first joining region AR1. Therefore, for example, if a biasing force is applied to the main body 321 in the +Z direction due to an increase in pressure inside the battery can 11, the separation of the main body 321 from the first seat portion 311 of the second conductive member 32 will first occur in the first bonding region AR1.

[0042] <1-3. Detailed Configuration of Battery Components> Figure 4 shows a magnified view of a portion of the cross-sectional configuration of the battery element 20 shown in Figure 1. As described above, the battery element 20 includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte.

[0043] [Positive electrode] As shown in Figure 4, the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B.

[0044] The positive electrode current collector 21A has a pair of surfaces on which the positive electrode active material layer 21B is provided. The positive electrode current collector 21A contains a conductive material such as a metal material, a specific example of which is aluminum.

[0045] In the example shown in Figure 4, the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A. The positive electrode active material layer 21B contains one or more types of positive electrode active materials capable of intercalating and deintercalating lithium. However, the positive electrode active material layer 21B may be provided on only one side of the positive electrode current collector 21A on the side where the positive electrode 21 faces the negative electrode 22. Furthermore, the positive electrode active material layer 21B may also contain a positive electrode binder and a positive electrode conductive agent. The method for forming the positive electrode active material layer 21B is not particularly limited, but specifically, it may be a coating method.

[0046] The positive electrode active material contains a lithium compound. This lithium compound is a compound that contains lithium as a constituent element, and more specifically, a compound that contains lithium along with one or more transition metal elements as constituent elements. This is because a high energy density can be obtained. However, the lithium compound may further contain one or more other elements, i.e., elements other than lithium and the transition metal elements.

[0047] The types of lithium compounds are not particularly limited, but specifically include lithium composite oxides having a layered rock salt crystal structure, lithium composite oxides having a spinel crystal structure, and lithium phosphate compounds having an olivine crystal structure. A specific example of a lithium composite oxide having a layered rock salt crystal structure is LiNiO 2 、 LiRing 0.8 Co 0.15 Al 0.05 Examples include LiCoO2. A specific example of a lithium composite oxide having a spinel-type crystal structure is LiMn2O4. Specific examples of lithium phosphate compounds having an olivine-type crystal structure are LiFePO4 and LiMnPO4.

[0048] In particular, the positive electrode active material preferably contains a lithium phosphate compound having an olivine-type crystal structure. This is because the crystal structure of lithium phosphate compounds having an olivine-type crystal structure is thermally stable, making it less likely for thermal runaway caused by overcharging and internal short circuits to occur in secondary batteries. Furthermore, because the crystal structure of lithium phosphate compounds having an olivine-type crystal structure is robust, the battery capacity does not easily decrease even after repeated charging and discharging of secondary batteries.

[0049] The positive electrode binder contains one or more of the following: synthetic rubber and polymer compounds. Synthetic rubber is styrene-butadiene rubber, while polymer compounds are polyvinylidene fluoride.

[0050] The positive electrode conductive agent contains one or more types of conductive materials, such as carbon materials, and the carbon materials include graphite, carbon black, acetylene black, and Ketjenblack. However, the conductive materials may also be metallic materials and polymer compounds.

[0051] [Negative electrode] As shown in Figure 4, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B.

[0052] The negative electrode current collector 22A has a pair of surfaces on which the negative electrode active material layer 22B is provided. The negative electrode current collector 22A contains a conductive material such as a metal material, a specific example of which is copper.

[0053] Here, the negative electrode active material layer 22B is provided on both sides of the negative electrode current collector 22A and contains one or more types of negative electrode active materials capable of intercalating and deintercalating lithium. However, the negative electrode active material layer 22B may be provided on only one side of the negative electrode current collector 22A on the side where the negative electrode 22 faces the positive electrode 21. Furthermore, the negative electrode active material layer 22B may further contain a negative electrode binder and a negative electrode conductive agent. Details regarding the negative electrode binder and negative electrode conductive agent are the same as the details regarding the positive electrode binder and positive electrode conductive agent. The method for forming the negative electrode active material layer 22B is not particularly limited, but specifically, it may be one or more types from among coating, gas phase, liquid phase, thermal spraying, and firing (sintering).

[0054] The negative electrode active material includes one or both of the following: carbon materials and metallic materials. This is because a high energy density can be obtained. Carbon materials include easily graphitizable carbon, poorly graphitizable carbon, and graphite (natural graphite and artificial graphite). Metallic materials are materials that contain one or more metallic elements and metalloid elements capable of forming alloys with lithium as constituent elements. Specific examples of these metallic and metalloid elements include one or both of silicon and tin. However, metallic materials may be elements, alloys, compounds, mixtures of two or more of these, or materials containing two or more of these phases. Specific examples of metallic materials are TiSi2 and SiO2. x (0 <x≦2または0.2<x<1.4)などである。

[0055] [Separator] As shown in Figure 4, the separator 23 is an insulating porous membrane interposed between the positive electrode 21 and the negative electrode 22. The separator 23 allows lithium ions to pass through while preventing a short circuit between the positive electrode 21 and the negative electrode 22. The separator 23 contains a polymer compound such as polyethylene.

[0056] [Electrolyte] The electrolyte contains a solvent and an electrolyte salt. The solvent is a non-aqueous solvent (organic solvent) such as carbonate ester compounds, carboxylic acid ester compounds, and lactone compounds. An electrolyte containing one or more of the following, and containing a non-aqueous solvent, is a so-called non-aqueous electrolyte. However, the solvent may be an aqueous solvent. The electrolyte salt contains one or more of the following light metal salts, such as lithium salts. The electrolyte salt content is not particularly limited, but it is preferably 0.3 mol / kg to 3 mol / kg relative to the solvent, because this provides high ionic conductivity.

[0057] <1-4. Operation> Figures 5A and 5B are explanatory diagrams illustrating the operation of the secondary battery in this embodiment, specifically its behavior when the internal pressure rises, and represent the cross-sectional configuration corresponding to Figure 2. Below, the operation during charging and discharging will be described, followed by the operation when the internal pressure rises. In this case, Figure 2 will be referred to along with Figure 5 as needed.

[0058] [Operation during charging and discharging] During charging, lithium is released from the positive electrode 21 of the battery element 20, and this lithium is absorbed into the negative electrode 22 via the electrolyte. Conversely, during discharging, lithium is released from the negative electrode 22 of the battery element 20, and this lithium is absorbed into the positive electrode 21 via the electrolyte. During both charging and discharging, lithium is absorbed and released in an ionic state.

[0059] [Operation when internal pressure rises] During charging and discharging of the secondary battery, if the internal pressure of the battery case 11 rises, the safety valve mechanism 30 is activated to prevent the secondary battery from rupturing or being damaged. In the secondary battery of this embodiment, the safety valve mechanism 30 is configured such that the current path from the battery case 20 to the battery cover 14 is interrupted when the internal pressure of the battery case 11 housing the battery element 20 rises, causing a separation between the first conductive member 31 and the second conductive member 32.

[0060] Specifically, during normal operation of the secondary battery, as shown in Figure 2, in the first junction region AR1, the main body 321 is joined to the first seat portion 311 via the sealing portion 16 and is electrically connected to the second seat portion 312 via the connecting portion 322. Therefore, the opening 31K of the first conductive member 31 is closed by the second conductive member 32.

[0061] In contrast, if gas is generated inside the battery can 11 due to side reactions such as the decomposition reaction of the electrolyte, this gas accumulates in the space inside the battery can 11, that is, the space sealed by the battery can 11 and the safety valve mechanism 30, causing the internal pressure of the battery can 11 to rise. When the internal pressure of the battery can 11 reaches a certain level, as shown in Figure 5A, the sealing portion 16 that seals the main body portion 321 and the first seat portion 311 partially ruptures so that the main body portion 321 separates from the first seat portion 311 in the first bonding region AR1. As a result, the space inside the battery can 11 and the space between the first conductive member 31 and the third conductive member 33 of the safety valve mechanism 30 communicate through the opening 31K. At this time, a part of the main body portion 321 separates from the sealing portion 16 in the first bonding region AR1, and at the same time, the connecting portion 322 breaks. As a result, the electrical connection between the main body 321, which is connected to the positive electrode lead 25, and the first conductive member 31 is broken, and the current path inside the secondary battery is interrupted. Thus, the battery reaction stops. Furthermore, as the internal pressure of the battery can 11 rises, as shown in Figure 5B, a part of the groove 33U of the third conductive member 33 breaks, and the valve 33V partially opens. This creates an opening 33K in the third conductive member 33, and the gas release path using the openings 31K, 33K, and through hole H14 is opened. Thus, the gas generated inside the battery can 11 is released to the outside of the secondary battery via the openings 31K, 33K, and through hole H14.

[0062] Furthermore, if the internal pressure of the secondary battery increases further, the bent portion 11P will deform, and the crimped structure 11R will break. As a result, the battery cover 14 will detach from the battery case 11, and gas will be released to the outside of the secondary battery.

[0063] <1-5. Manufacturing method> [Fabrication of the positive electrode] First, a positive electrode mixture is prepared by mixing the positive electrode active material with a positive electrode binder and a positive electrode conductive agent as needed. Next, the positive electrode mixture is dispersed in a solvent to prepare a paste-like positive electrode mixture slurry. The type of solvent is not particularly limited and may be an aqueous solvent or a non-aqueous solvent (organic solvent). Subsequently, the positive electrode mixture slurry is applied to both sides of the positive electrode current collector 21A to form a positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B is compressed and molded using a roll press or the like. In this case, the positive electrode active material layer 21B may be heated, or the compression molding of the positive electrode active material layer 21B may be repeated multiple times. As a result, a positive electrode active material layer 21B is formed on both sides of the positive electrode current collector 21A, and the positive electrode 21 is manufactured.

[0064] [Fabrication of the negative electrode] A negative electrode active material layer 22B is formed on both sides of the negative electrode current collector 22A using the same procedure as described above for the positive electrode 21. Specifically, a negative electrode mixture is formed by mixing the negative electrode active material with a negative-positive electrode binder and a negative electrode conductive agent. Then, the negative electrode mixture is dispersed in a solvent to form a paste-like negative electrode mixture slurry. Details regarding the solvent are as described above. Next, the negative electrode active material layer 22B is formed by applying the negative electrode mixture slurry to both sides of the negative electrode current collector 22A. Finally, the negative electrode active material layer 22B is compressed and molded using a roll press or the like. Details regarding the compression molding are as described above. As a result, a negative electrode active material layer 22B is formed on both sides of the negative electrode current collector 22A, and the negative electrode 22 is manufactured.

[0065] [Assembly of rechargeable batteries] First, the positive electrode lead 25 is connected to the positive electrode current collector 21A of the positive electrode 21 using a welding method or the like. Similarly, the negative electrode lead 26 is connected to the negative electrode current collector 22A of the negative electrode 22 using a welding method or the like. Next, the positive electrode 21 and the negative electrode 22 are stacked on top of each other via a separator 23 to form a laminate, and then the resulting laminate is wound to form a wound body having a central space 20C. This wound body has the same configuration as the battery element 20, except that the positive electrode 21, the negative electrode 22, and the separator 23 are not impregnated with electrolyte. Next, a center pin 24 is inserted into the central space 20C of the wound body.

[0066] Next, after preparing the battery can 11, the winding body is placed inside the battery can 11 together with the insulating plates 12 and 13, with the insulating plates 12 and 13 facing each other via the winding body. In this case, the positive electrode lead 25 is connected to the safety valve mechanism 30 using a welding method or the like, and the negative electrode lead 26 is connected to the battery can 11 using a welding method or the like.

[0067] Next, the electrolyte is injected into the battery case 11, impregnating the wound material with the electrolyte. This impregnates the positive electrode 21, the negative electrode 22, and the separator 23 with the electrolyte, thus creating the battery element 20. Subsequently, the battery cover 14 and the safety valve mechanism 30 are housed inside the battery case 11 together with the gasket 15. The safety valve mechanism 30 is prepared in advance by joining the second conductive member 32 to the first conductive member 31 via a sealing portion 16, as shown in Figure 2 and other figures.

[0068] Finally, as shown in Figure 1, the open end 11N of the battery can 11 is crimped to the battery cover 14 and the safety valve mechanism 30 via the gasket 15. This forms the bent portion 11P and the crimped structure 11R. As a result, the battery can 11 is closed by the battery cover 14, and the assembly of the secondary battery is completed.

[0069] [Stabilization of secondary batteries] The assembled secondary battery is then charged and discharged. Various conditions such as ambient temperature, number of charge / discharge cycles, and charge / discharge conditions can be set arbitrarily. This causes a film to form on the surface of the negative electrode 22, etc., and the state of the secondary battery is electrochemically stabilized. As a result, a cylindrical secondary battery with the battery elements 20 and other components sealed inside the battery case 11 is completed.

[0070] <1-6. Mechanism and Effects> In the secondary battery of this embodiment, the safety valve mechanism 30 is configured such that the current path from the battery element 20 to the battery cover 14 is interrupted when the internal pressure of the battery can 11 housing the battery element 20 increases, causing a separation between the first conductive member 31 and the second conductive member 32. Specifically, the safety valve mechanism 30 is provided with a first bonding region AR1 and a second bonding region AR2, to which the first conductive member 31 and the second conductive member 32 are mechanically joined. In the first bonding region AR1, the first conductive member 31 and the second conductive member 32 are electrically joined, while in the second bonding region AR2, the first conductive member 31 and the second conductive member 32 are electrically insulated. Here, the second bonding strength between the first conductive member 31 and the second conductive member 32 in the second bonding region AR2 is higher than the first bonding strength between the first conductive member 31 and the second conductive member 32 in the first bonding region AR1. Therefore, according to the secondary battery of this embodiment, when the pressure inside the battery can 11 rises above a predetermined value due to gas generation, the mechanical connection between the first conductive member 31 and the second conductive member 32 in the first junction region AR1 is dissolved, and the electrical connection between the first conductive member 31 and the second conductive member 32 in the first junction region AR1 is also dissolved. Consequently, the current path from the battery element 20 to the first conductive member 31 via the second conductive member 32 is interrupted. As a result, the progress of the battery reaction is stopped, and safety is ensured.

[0071] In the secondary battery of this embodiment, the internal space of the battery case 11, which houses the battery element 20 containing the electrolyte, is sealed by a sealing portion 16 made of an insulating resin or the like. Thus, since the structure of the secondary battery of this embodiment does not involve sealing the internal space of the battery case 11 that houses the battery element 20 with a connecting portion 322, the connecting portion 322 can be made of a thin metal foil.

[0072] In contrast, as described in Patent Document 1 above, when the internal pressure of the battery can rises, a metal plate is deformed to secure a gas release path and interrupt the current path. However, relatively high pressure is required to deform the metal plate, and considering the safety of the battery, it is desirable to stop the battery reaction at a lower internal pressure in the battery can. To this end, it is conceivable to make the metal plate thinner, but work hardening when the metal plate is thinned makes it difficult for the metal plate to deform. Furthermore, work hardening when the metal plate is thinned increases the brittleness of the metal plate, making it more susceptible to cracking when subjected to impact during normal use. In Patent Document 1 above, since the internal space of the battery can is sealed by such a metal plate, if a crack occurs in the metal plate, there is a possibility that the electrolyte may leak to an unintended area even though the current path is not interrupted. For this reason, in the secondary battery of Patent Document 1 above, the set value of the internal pressure at which the current path is interrupted must be set relatively high.

[0073] In the secondary battery of this embodiment, the first junction region AR1 is provided with a connection portion 322 responsible for interrupting the current path and a main body portion 321 responsible for sealing the internal space of the battery can. That is, in the secondary battery of this embodiment, the current path is interrupted by the rupture of the connection portion 322, while a gas release path is formed by the partial release of the bond between the main body portion 321 and the second conductive member 32 via the sealing portion 16. Therefore, even if a crack occurs in the connection portion 322 for any reason by making it thinner, the electrolyte will not leak to areas other than the predetermined area. Furthermore, by selecting the physical properties of the insulating resin material constituting the sealing portion 16, the strength of the bond between the main body portion 321 and the second conductive member 32 via the sealing portion 16 can be adjusted. Thus, in the secondary battery of this embodiment, the set value of the internal pressure at which the current path is interrupted can be set regardless of the physical properties of the connection portion 322. Therefore, compared to the secondary battery of Patent Document 1 described above, it is possible to set a lower set value of the internal pressure at which the current path is interrupted. In other words, with the secondary battery of this embodiment, the battery reaction can be stopped at a stage where the internal pressure of the battery case is lower, thereby improving safety.

[0074] <1-7. Variations> The configuration of the secondary battery can be modified as appropriate, as described below. However, any two or more of the variations described below may be combined with each other.

[0075] [Variation 1-1] Figure 6 is a plan view showing an example of the configuration of a safety valve mechanism 30A as a first modified example (modification 1-1) of the first embodiment. In the above embodiment, as shown in Figure 3, for example, by making the center position of the circular inner edge 16E1 of the sealing portion 16 and the center position of the circular outer edge 16E2 of the sealing portion 16 different, the width 16W1 of the sealing portion 16 in the first bonding region AR1 is made narrower than the width 16W2 of the sealing portion 16 in the second bonding region AR2. However, in the secondary battery of this embodiment, the safety valve mechanism 30A shown in Figure 6 can also be adopted. In the safety valve mechanism 30A of Figure 6, in a plan view, both the center position of the circular inner edge 16E1 of the sealing portion 16 and the center position of the circular outer edge 16E2 of the sealing portion 16 coincide with the position of the central axis CP. In addition, the sealing portion 16 of the safety valve mechanism 30A is provided with a notch 16C in the part corresponding to the first bonding region AR1. Therefore, similar to the safety valve mechanism 30 of the first embodiment (Figure 3), in the safety valve mechanism 30A, the width 16W1 of the sealing portion 16 in the first bonding region AR1 is narrower than the width 16W2 of the sealing portion 16 in the second bonding region AR2. Consequently, the bonding strength between the main body portion 321 and the first seat portion 311 via the sealing portion 16 in the first bonding region AR1 is lower than the bonding strength between the main body portion 321 and the first seat portion 311 via the sealing portion 16 in regions other than the first bonding region AR1. Thus, a secondary battery equipped with the safety valve mechanism 30A can obtain the same effects as a secondary battery equipped with the safety valve mechanism 30 of the first embodiment.

[0076] [Variation 1-2] Figure 7 is a plan view showing an example of the configuration of a safety valve mechanism 30B as a second modified example (modification 1-2) of the first embodiment. In the safety valve mechanism 30 of the above embodiment, all parts of the sealing portion 16 are formed from the same type of material. In contrast, in the safety valve mechanism 30B of Figure 7, the bonding strength of the first portion 161 corresponding to the first joining region AR1 of the sealing portion 16 is weaker than the bonding strength of the parts of the sealing portion 16 other than the first portion 161. During the manufacturing stage, for example, by selectively changing the heating temperature and applied pressure to the sealing portion 16 when joining the main body portion 321 and the first seat portion 311, it is possible to form the first portion 161 with relatively low bonding strength. In the safety valve mechanism 30B as well, the bonding strength between the main body portion 321 and the first seat portion 311 via the sealing portion 16 in the first joining region AR1 is lower than the bonding strength between the main body portion 321 and the first seat portion 311 via the sealing portion 16 in areas other than the first joining region AR1. Therefore, a secondary battery equipped with the safety valve mechanism 30B can obtain the same effects as a secondary battery equipped with the safety valve mechanism 30 of the first embodiment described above.

[0077] [Modifications 1-3] Figure 8A is a cross-sectional view showing an example of the configuration of a safety valve mechanism 30C as a third modified example (modification 1-3) of the first embodiment. Figure 8B is a plan view showing an example of the configuration of the safety valve mechanism 30C shown in Figure 8A. Note that Figure 8A corresponds to a cross-section in the direction of the arrow along line VIII-VIII shown in Figure 8B. In the safety valve mechanism 30 of the above embodiment, the connection part 322 connects the main body part 321 and the second seat part 312 in the first joining region AR1, thereby achieving an electrical connection between the first conductive member 31 and the second conductive member 32, and when the internal pressure of the battery can 11 rises, the connection part 322 breaks to interrupt the current path. In contrast, in the safety valve mechanism 30C of Figures 8A and 8B, a terminal 323 is provided in place of the connection part 322 in the second conductive member 32 in the first joining region AR1. The terminal 323 is attached, for example, near the end face of the main body 321, and under normal use, is biased toward the upper surface 311TS of the seat portion 311 of the first conductive member 31 and is in contact with the upper surface 311TS. The terminal 323 includes one or more types of metallic materials, such as pure iron, pure aluminum, and alloys containing at least one of iron and aluminum.

[0078] Figures 8C and 8D are explanatory diagrams illustrating the behavior of a secondary battery having the safety valve mechanism 30C shown in Figures 8A and 8B when the internal pressure rises. The operation when the internal pressure rises will be described below. In a secondary battery having the safety valve mechanism 30C, the current path from the battery element 20 to the battery cover 14 is interrupted when the internal pressure of the battery can 11 housing the battery element 20 rises, causing a separation between the first conductive member 31 and the second conductive member 32.

[0079] Specifically, during normal operation of the secondary battery, as shown in Figure 8A, in the first junction region AR1, the main body 321 is joined to the first seat portion 311 via the sealing portion 16 and is electrically connected to the first seat portion 311 via the terminal 323. For this reason, the opening 31K of the first conductive member 31 is closed by the second conductive member 32.

[0080] In contrast, if gas is generated inside the battery can 11 due to side reactions such as the decomposition reaction of the electrolyte, this gas accumulates inside the battery can 11, causing the internal pressure of the battery can 11 to rise. When the internal pressure of the battery can 11 reaches a certain level, as shown in Figure 8C, the sealing portion 16 that seals the main body portion 321 and the first seat portion 311 partially ruptures so that the main body portion 321 separates from the first seat portion 311 in the first junction region AR1. As a result, the space inside the battery can 11 and the space between the first conductive member 31 and the third conductive member 33 of the safety valve mechanism 30 communicate through the opening 31K. At this time, as a part of the main body portion 321 separates from the sealing portion 16 in the first junction region AR1, the terminal 323 also separates from the first seat portion 311. Therefore, the conductivity between the main body portion 321 connected to the positive electrode lead 25 and the first conductive member 31 is released, and the current path inside the secondary battery is interrupted. Therefore, the battery reaction stops. Furthermore, as the internal pressure of the battery can 11 increases, a part of the groove 33U of the third conductive member 33 ruptures, as shown in Figure 8D, and the valve 33V partially opens. As a result, an opening 33K is formed in the third conductive member 33, and a gas release path using the openings 31K, 33K, and through-hole H14 is opened. Therefore, the gas generated inside the battery can 11 is released to the outside of the secondary battery via the openings 31K, 33K, and through-hole H14.

[0081] In the safety valve mechanism 30C, which is a modified example 1-3, the external shape of the terminal 323 can be arbitrarily selected. Specifically, the external shape of the terminal 323 shown in Figures 8A to 8D is approximately cylindrical, but it may be spherical, hemispherical, conical, or prismatic, for example.

[0082] [Modifications 1-4] Figure 9A is a plan view showing an example of the configuration of a connecting portion 322A as a fourth modified example (modification 1-4) of the first embodiment. In the safety valve mechanism 30 of the above embodiment, a connecting portion 322 having a strip-shaped planar form is used as shown in Figure 3, but the shape of the connecting portion of this disclosure is not limited thereto. For example, as shown in Figure 9A, the connecting portion 322A may have a constricted portion with a notch K322 provided on a part of its outer edge. In the example of the connecting portion 322A shown in Figure 9A, two notches K322 are provided. The positions of the two notches K322 should roughly coincide with the positions of the outer edge of the main body portion 321 of the first conductive member 31 in the Z direction. With the connecting portion 322A, it is easier to break at the two notches K322, so the breaking strength can be made lower compared to the connecting portion 322.

[0083] [Variations 1-5] Figure 9B is a cross-sectional view showing an example of the configuration of the connecting portion 322B as a fifth modified example (modification 1-5) of the first embodiment. In the connecting portion 322A of modification 1-4 described above, a notch K322 is provided on the outer edge in a plan view, but the shape of the connecting portion of this disclosure is not limited thereto. For example, as shown in Figure 9B of the connecting portion 322B, a groove V322 may be provided on a part of the surface. The position of the groove V322 should roughly coincide with the position of the outer edge of the main body portion 321 of the first conductive member 31 in the Z direction. With the connecting portion 322B, fracture is more likely to occur at the groove V322, so the fracture strength can be made lower compared to the connecting portion 322.

[0084] [Variations 1-6] Figure 9C is a plan view showing an example configuration of a connection portion 322C as a sixth modified example (modification 1-6) of the first embodiment. In the connection portion 322A of modification 1-4 described above, a notch K322 is provided on the outer edge in a plan view, but the shape of the connection portion of this disclosure is not limited thereto. For example, as shown in Figure 9C, the connection portion 322C may have one or more holes H322. In the example of the connection portion 322C shown in Figure 9C, four holes H322 are provided. The positions of the four holes H322 should roughly coincide with the positions of the outer edge of the main body portion 321 of the first conductive member 31 in the Z direction. With the connection portion 322C, fracture is more likely to occur near the four holes H322, so the fracture strength can be made lower compared to the connection portion 322.

[0085] [Variations 1-7] In the secondary battery of the first embodiment, a through hole H14 is provided in the battery cover 14. However, as in the secondary battery of Modification 1-7 of this disclosure, it is not necessary to provide a through hole H14 in the protrusion 14T of the battery cover 14.

[0086] <<2. Second Embodiment (Secondary Battery)>> Next, with reference to Figure 10, a secondary battery of a second embodiment of the present disclosure will be described. In the first embodiment described above, a cylindrical secondary battery equipped with a battery case 11 having a crimping structure 11R was illustrated and described. In contrast, the secondary battery of this embodiment is a secondary battery with a so-called beadless structure, which does not have a crimping structure. Figure 10 shows the cross-sectional configuration of the secondary battery of the second embodiment.

[0087] As shown in Figure 10, in this embodiment of the secondary battery, the battery casing 11 does not have a crimped structure. The battery casing 11 is a container having a cylindrical wall portion 11W including an open end 11N at its upper end, and a bottom portion 11B that closes the lower end of the wall portion 11W. The wall portion 11W extends in the Z direction without including a constricted portion 11S or a bent portion 11P. The lower surface of, for example, an annular plate-shaped member 17 is joined to the open end 11N of the battery casing 11. The upper surface of the plate-shaped member 17 is joined to the battery lid 14 via a sealing portion 18. The battery lid 14 is a flat, disc-shaped member that does not include any protrusions. The sealing portion 18 can be made of, for example, a thermoplastic insulating resin such as polypropylene or polyethylene. A safety valve mechanism 30 is joined to the battery lid 14, sandwiched between the battery lid 14 and the insulating plate 12. Here, the sealing portion 18 is a specific example corresponding to one embodiment of the "first insulating portion" of this disclosure.

[0088] The third bonding strength between the battery can 11 and the battery cover 14 by the sealing portion 18 should be higher than the first bonding strength between the first conductive member 31 and the second conductive member 32 in the first bonding region AR1.

[0089] In this embodiment of the secondary battery, the same behavior as in the secondary battery of the first embodiment is observed. Specifically, when the internal pressure of the battery case 11 housing the battery element 20 increases, a separation occurs between the first conductive member 31 and the second conductive member 32, interrupting the current path from the battery element 20 to the battery cover 14.

[0090] Specifically, during normal operation of the secondary battery, as shown in Figure 10, in the first junction region AR1, the main body 321 is joined to the first seat portion 311 via the sealing portion 16 and is electrically connected to the second seat portion 312 via the connecting portion 322. For this reason, the opening 31K of the first conductive member 31 is closed by the second conductive member 32.

[0091] In contrast, if gas is generated inside the battery can 11 due to side reactions such as the decomposition reaction of the electrolyte, this gas accumulates inside the battery can 11, causing the internal pressure of the battery can 11 to rise. When the internal pressure of the battery can 11 reaches a certain level, as shown in Figure 11A, the sealing portion 16 that seals the main body portion 321 and the first conductive member 31 partially ruptures so that the main body portion 321 separates from the first conductive member 31 in the first bonding region AR1. As a result, the space inside the battery can 11 and the space between the safety valve mechanism 30 and the battery cover 14 are connected through the opening 31K. Therefore, the gas generated inside the battery can 11 is released into the space between the safety valve mechanism 30 and the battery cover 14 via the opening 31K. Also, when the main body portion 321 separates from the first conductive member 31 in the first bonding region AR1, the connecting portion 322 ruptures. Therefore, the electrical connection between the main body 321, which is connected to the positive electrode lead 25, and the first conductive member 31 is broken, and the current path inside the secondary battery is interrupted. As a result, the battery reaction stops.

[0092] Subsequently, if the internal pressure of the secondary battery increases further, the battery cover 14 detaches from the plate-shaped member 17 joined to the battery case 11, as shown in Figure 11B, thereby releasing gas to the outside of the secondary battery. Figures 11A and 11B are explanatory diagrams illustrating the behavior of the secondary battery in this embodiment when the internal pressure rises, and represent the cross-sectional configuration corresponding to Figure 11.

[0093] Thus, since the secondary battery of this embodiment is also equipped with a safety valve mechanism 30, the same effects as the secondary battery of the first embodiment described above can be obtained.

[0094] <<3. Applications of rechargeable batteries>> Next, I will explain the applications (examples of use) of the secondary batteries mentioned above.

[0095] The uses of secondary batteries are not particularly limited. Secondary batteries used as power sources are the primary or auxiliary power sources for electronic devices and electric vehicles. A primary power source is a power source that is used preferentially regardless of the availability of other power sources. An auxiliary power source is a power source used in place of the primary power source, or a power source that can be switched to from the primary power source.

[0096] Specific examples of secondary battery applications are as follows: Electronic devices such as video cameras, digital still cameras, mobile phones, notebook computers, headphone stereos, portable radios, and portable information terminals; backup power supplies and storage devices such as memory cards; power tools such as electric drills and electric saws; battery packs installed in electronic devices; medical electronic devices such as pacemakers and hearing aids; electric vehicles (including hybrid vehicles); and power storage systems such as household or industrial battery systems that store power in preparation for emergencies. In these applications, one secondary battery may be used, or multiple secondary batteries may be used.

[0097] The battery pack may use individual cells or a battery pack. An electric vehicle is a vehicle that operates (drives) using a secondary battery as its power source, and may also be a hybrid vehicle equipped with a power source other than the secondary battery. In a household power storage system, household electrical appliances can be used by utilizing the electricity stored in the secondary battery, which is the power storage source.

[0098] Here, we will specifically explain one example of a secondary battery application. The configuration of the application example described below is merely an example and can be modified as needed.

[0099] Figure 12 shows the block configuration of the battery pack. The battery pack described here is a single rechargeable battery pack (a so-called soft pack) and is installed in electronic devices such as smartphones.

[0100] As shown in Figure 12, this battery pack comprises a power supply 51 and a circuit board 52. The circuit board 52 is connected to the power supply 51 and includes a positive terminal 53, a negative terminal 54, and a temperature detection terminal 55.

[0101] The power supply 51 includes one rechargeable battery. In this rechargeable battery, the positive lead is connected to the positive terminal 53, and the negative lead is connected to the negative terminal 54. Since the power supply 51 can be connected to the outside via the positive terminal 53 and the negative terminal 54, it can be charged and discharged. The circuit board 52 includes a control unit 56, a switch 57, a thermal resistance element (PTC element) 58, and a temperature detection unit 59. However, the PTC element 58 may be omitted.

[0102] The control unit 56 includes a central processing unit (CPU) and memory, and controls the operation of the entire battery pack. This control unit 56 detects and controls the usage status of the power supply 51 as needed.

[0103] Furthermore, when the voltage of the power supply 51 (secondary battery) reaches the overcharge detection voltage or over-discharge detection voltage, the control unit 56 disconnects the switch 57 to prevent charging current from flowing through the current path of the power supply 51. For example, the overcharge detection voltage is 4.2V ± 0.05V, and the over-discharge detection voltage is 2.4V ± 0.1V.

[0104] Switch 57 includes a charge control switch, a discharge control switch, a charging diode, and a discharging diode, and switches the connection between the power supply 51 and external equipment according to the instructions of the control unit 56. This switch 57 includes a field-effect transistor (MOSFET) using a metal oxide semiconductor, and the charge / discharge current is detected based on the ON resistance of switch 57.

[0105] The temperature detection unit 59 includes a temperature detection element such as a thermistor and measures the temperature of the power supply 51 using the temperature detection terminal 55, and outputs the temperature measurement result to the control unit 56. The temperature measurement result measured by the temperature detection unit 59 is used when the control unit 56 performs charge / discharge control in the event of abnormal heat generation, and when the control unit 56 performs correction processing when calculating the remaining capacity.

[0106] Although the present disclosure has been described above with reference to one embodiment and one example, the configuration of the present disclosure is not limited to the configuration described in the one embodiment and one example, and can be modified in various ways.

[0107] Specifically, the explanation described the case where the element structure of the battery element is a wound type, but the element structure of the battery element is not particularly limited, and other element structures such as a stacked type in which the electrodes (positive electrode and negative electrode) are stacked, and a zigzag-fold type in which the electrodes (positive electrode and negative electrode) are folded are also acceptable.

[0108] Furthermore, while we have described the case where the electrode reactant is lithium, the electrode reactant is not particularly limited. Therefore, as mentioned above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0109] The effects described herein are illustrative only, and therefore the effects of this technology are not limited to those described herein. Accordingly, other effects may be obtained with respect to this technology. [Explanation of symbols]

[0110] 11...Battery can, 11N...Open end, 11P...Bent part, 11R...Crimped structure, 12,13...Insulating plate, 14...Battery cover, 14BS...Bottom surface, 15...Gasket, 16,18...Sealing part, 20...Battery element, 20C...Center space, 21...Positive electrode, 22...Negative electrode, 23...Separator, 24...Center pin, 25...Positive electrode lead, 26...Negative electrode lead, 30...Safety valve mechanism, 31...First conductive member, 31K...Opening, 311...First seat part, 312...Second seat part, 313...Flange part, 32...Second conductive member, 33...Third conductive member, AR1...First bonding region, AR2...Second bonding region.

Claims

1. A battery element to which leads are connected, A container for housing the aforementioned battery element, A lid that covers the container and the battery element housed in the container, A first insulating portion that seals the container and the lid Equipped with, The aforementioned lid portion is A first conductive member having an opening, A second conductive member is attached to the first conductive member via a second insulating portion so as to cover the opening and is connected to the lead through the opening. It has, The lid portion is provided with a first joining region and a second joining region where the first conductive member and the second conductive member are mechanically joined, respectively. In the first bonding region, the first conductive member and the second conductive member are electrically connected. In the second junction region, the first conductive member and the second conductive member are electrically insulated. The second bonding strength between the first conductive member and the second conductive member in the second bonding region is higher than the first bonding strength between the first conductive member and the second conductive member in the first bonding region. Secondary battery.

2. The second conductive member includes a main body and a connecting portion. In the first bonding region, the main body is electrically and mechanically bonded to the first conductive member via the connecting portion. In the second bonding region, the main body is mechanically bonded to the first conductive member via the second insulating portion. The secondary battery according to claim 1.

3. In the first bonding region, the main body is mechanically bonded to the second conductive member via the second insulating portion. The secondary battery according to claim 2.

4. The thickness of the connecting portion is thinner than the thickness of the main body portion. The secondary battery according to claim 2 or claim 3.

5. The connecting portion includes at least one of a constricted portion, a hole, and a groove. A secondary battery according to any one of claims 2 to 4.

6. The first conductive member includes a main body and a connecting portion. In the first bonding region, the main body is mechanically bonded to the second conductive member via the second insulating portion, and the connecting portion is biased toward the second conductive member and in contact with the second conductive member. The secondary battery according to claim 1.

7. The third joint strength between the container and the lid, provided by the first insulating portion, is higher than the first joint strength. A secondary battery according to any one of claims 1 to 6.

8. A battery element to which leads are connected, A container for housing the aforementioned battery element, A lid that covers the container and the battery element housed in the container, A first insulating portion that seals the container and the lid Equipped with, The aforementioned lid portion is A first conductive member having an opening, A second conductive member is attached to the first conductive member via a second insulating portion so as to cover the opening and is connected to the lead through the opening. It has, The increase in internal pressure of the container causes a separation between the first conductive member and the second conductive member, thereby interrupting the current path from the battery element to the lid. Secondary battery.

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