Secondary battery

Abstract

To provide a highly safe secondary battery provided with a current interrupt mechanism capable of quickly interrupting currents as the battery temperature rises without waiting for the gas pressure in the battery to rise above the working pressure of a safety valve.SOLUTION: A secondary battery 10 includes a battery case 1, an electrode body 2 housed in the battery case while being restricted, and a current collector terminal 4 fixed to the battery case via an insulating resin member 3 and connected to the electrode body. The secondary battery also includes a current interrupt mechanism 7 configured such that when the battery temperature rises above a predetermined temperature, a connection 5 connecting the electrode body and the current collector terminal is separated by the biasing force P of a spring member 6 biasing the current collector terminal and placed into a de-energized state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a secondary battery. [Background technology]

[0002] In general, if a sealed secondary battery is overcharged or a short circuit occurs in the electrode body, the temperature inside the battery rises, generating gas and causing an increase in the battery's internal pressure. Therefore, a safety mechanism is generally provided that opens a safety valve to release the internal battery pressure when the internal battery pressure rises above a predetermined value (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-117750 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the operating pressure required to open the safety valve is usually very high, around 1.4 MPa, and when the safety valve is activated, high-pressure gas and electrolyte are released from the opening of the safety valve to the outside of the battery, which can easily damage other nearby secondary batteries and control devices.

[0005] The disclosed technology has been made in consideration of such problems, and aims to provide a highly safe secondary battery equipped with a current interruption mechanism that can quickly interrupt current as the battery temperature rises, without waiting for the gas pressure inside the battery to rise above the operating pressure of the safety valve. [Means for solving the problem]

[0006] (1) One aspect of the disclosed technology for solving the above problem is a secondary battery comprising a battery case, an electrode body housed in the battery case in a constrained state, and a current collector terminal fixed to the battery case via an insulating resin member and connected to the electrode body, wherein when the battery temperature rises above a predetermined temperature, the connection between the electrode body and the current collector terminal is severed by the biasing force of a spring member that biases the current collector terminal, thereby establishing a non-conductive state.

[0007] (2) In the secondary battery described in (1), it is preferable that when the insulating resin member melts or softens, the current-breaking mechanism moves the current-collector terminal due to the spring force of the spring member, causing the connection portion to stretch locally and be cut, thereby becoming non-conductive.

[0008] (3) In the secondary battery described in (2), the connection portion is a tab portion on which the electrode foil of the electrode body is laminated, and the tab portion preferably has a notch groove and / or perforations formed along the moving direction of the collector terminal or along an inclined line inclined relative to the moving direction.

[0009] (4) In the secondary battery described in (1), the connection portion comprises a terminal-side connection portion connected to the current collector terminal and an electrode-side connection portion connected to the electrode foil of the electrode body, the terminal-side connection portion and the electrode-side connection portion are joined by a low-melting-point joining member having a melting point lower than that of the insulating resin member, the current collector terminal comprises an easily deformable portion between the terminal-side connection portion and a case fixing portion fixed to the battery case via the insulating resin member, and the current interruption mechanism is preferably configured such that, when the low-melting-point joining member melts or softens, the easily deformable portion is deformed by the biasing force of the spring member, and the terminal-side connection portion and the electrode-side connection portion are separated, resulting in a non-conductive state.

[0010] (5) In the secondary battery described in (1), the current collecting terminal is fixed to the battery case via a laminated insulating resin member in which a low-melting-point resin member having a melting point lower than that of the insulating resin member is sandwiched between the insulating resin members while surrounding the current collecting terminal, and it is preferable that when the low-melting-point resin member melts or softens, the current interruption mechanism is configured such that the connection portion is severed by the biasing force of the spring member, thereby bringing the current interruption mechanism into a non-conductive state. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view of a secondary battery according to one aspect of the present embodiment. [Figure 2] 2 is a partial cross-sectional view of an electrode body in the secondary battery shown in FIG. 1. [Figure 3] 2 is a cross-sectional view taken along the line AA in FIG. 1. [Figure 4] 2 is an enlarged perspective view of a tab portion of the electrode body in part B shown in FIG. 1. FIG. [Figure 5A] 2 is an enlarged cross-sectional view of the current interruption mechanism at part B shown in FIG. 1. FIG. [Figure 5B] FIG. 5B is an enlarged cross-sectional view of the current-blocking mechanism shown in FIG. 5A during operation. [Figure 6] 1. FIG. 4 is a schematic cross-sectional view of the secondary battery shown in FIG. 1 in a state where a current-blocking mechanism according to Modification 1 is activated. [Figure 7A] 1. FIG. 4 is an enlarged cross-sectional view of a portion B shown in FIG. 1, illustrating a current-blocking mechanism according to a second modified example. [Figure 7B] FIG. 7B is an enlarged cross-sectional view of the current-blocking mechanism shown in FIG. 7A during operation. [Figure 8A] 1. FIG. 4 is an enlarged cross-sectional view of a portion B shown in FIG. 1, illustrating a current-blocking mechanism according to a third modified example. [Figure 8B] 8B is an enlarged cross-sectional view of the current-blocking mechanism shown in FIG. 8A during operation. FIG. [Figure 9A] 1. FIG. 4 is an enlarged cross-sectional view of a portion C shown in FIG. [Figure 9B] FIG. 9B is an enlarged cross-sectional view of the state in which the current interruption mechanism shown in FIG. 9A is activated. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Description of this secondary battery> Next, the configuration of a secondary battery according to one aspect of the embodiment of the disclosed technology will be described in detail with reference to the drawings. FIG. 1 shows a schematic cross-sectional view of a secondary battery according to one aspect of the present embodiment. FIG. 2 shows a partial cross-sectional view of an electrode body in the secondary battery shown in FIG. 1. FIG. 3 shows a cross-sectional view taken along line AA in FIG. 1. FIG. 4 shows an enlarged perspective view of the tab portion of the electrode body at part B shown in FIG. 1. FIG. 5A shows an enlarged cross-sectional view of the current-blocking mechanism at part B shown in FIG. 1. FIG. 5B shows an enlarged cross-sectional view of the current-blocking mechanism shown in FIG. 5A during operation. The X direction indicates the longitudinal direction of the battery case, the Y direction indicates the vertical direction of the battery case, and the Z direction indicates the width direction (short direction) of the battery case.

[0013] 1 to 5B, the secondary battery 10 includes a battery case 1, an electrode assembly 2 housed in the battery case 1 in a constrained state, and a current collecting terminal 4 fixed to the battery case 1 via an insulating resin member 3 and connected to the electrode assembly 2. The secondary battery 10 also includes a current interruption mechanism 7 that, when the battery temperature rises above a predetermined temperature, disconnects a connection 5 connecting the electrode assembly 2 and the current collecting terminal 4 by a biasing force P of a spring member 6 that biases the current collecting terminal 4, thereby bringing the battery into a non-conductive state.

[0014] Here, the current interrupt mechanism 7 includes a positive electrode current interrupt mechanism 7a in which the connection portion 5 connecting the positive electrode body 2 and the positive electrode current collecting terminal 4 is separated by the biasing force P of the spring member 6 that biases the positive electrode current collecting terminal 4, thereby bringing the device into a non-conductive state, and a negative electrode current interrupt mechanism 7b in which the connection portion 5 connecting the negative electrode body 2 and the negative electrode current collecting terminal 4 is separated by the biasing force P of the spring member 6 that biases the negative electrode current collecting terminal 4, thereby bringing the device into a non-conductive state, but either the positive electrode current interrupt mechanism 7a or the negative electrode current interrupt mechanism 7b may be used. However, by providing both the positive electrode current interrupt mechanism 7a and the negative electrode current interrupt mechanism 7b, current can be interrupted quickly regardless of where a short circuit occurs within the electrode body 2.

[0015] As shown in FIGS. 1 and 3 , the battery case 1 includes a case body 11 in the shape of a rectangular cylinder with a bottom 11c extending in the longitudinal direction (X direction), and a lid 12 that seals an opening 111 formed at the upper end of the case body 11 in the vertical direction (Y direction). The case body 11 is composed of a pair of long side walls 11a, a pair of short side walls 11b, and a bottom 11c, each of which is formed in a flat rectangular shape. Terminal through-holes 121 are formed at both ends of the lid 12 in the longitudinal direction (X direction). An external terminal 41 of the current collector terminal 4 is inserted through the terminal through-hole 121 with its tip protruding outside the battery and fixed to the lid 12 via an insulating resin member 3. The insulating resin member 3 can be made of, for example, polyphenylene sulfide (PPS) resin. The lid 12 is formed with an inlet 122 for injecting the electrolyte into the battery case 1 and a safety valve 123 that opens when the pressure inside the battery case 1 rises above a predetermined value. The inlet 122 is sealed after the electrolyte is injected. The material of the battery case 1 is not particularly limited, but aluminum or stainless steel, for example, can be used. When connecting multiple secondary batteries 10, a connecting bus bar (not shown) is connected to the external terminal 41.

[0016] As shown in FIGS. 1 and 2 , the electrode body 2 is formed by stacking sheet-like positive electrode bodies 21 and negative electrode bodies 22 in a planar manner with a sheet-like separator 23 sandwiched between them. However, the electrode body 2 is not limited to this configuration. For example, the electrode body 2 may be formed by stacking strip-like positive electrode bodies 21 and negative electrode bodies 22 with a strip-like separator 23 sandwiched between them and wound flat. The positive electrode body 21 has a positive electrode active material layer 21K in which a positive electrode foil 21H is coated with a positive electrode active material KT1 or the like. The negative electrode body 22 has a negative electrode active material layer 22K in which a negative electrode foil 22H is coated with a negative electrode active material KT2 or the like. Here, the positive electrode active material layer 21K and the negative electrode active material layer 22K are coated on both sides of the electrode foils 21H and 22H, respectively, but they may be coated on only one side.

[0017] In a lithium ion secondary battery, which is an example of the secondary battery 10, the electrode foil 21H of the cathode body 21 is made of, for example, aluminum foil, and the cathode active material KT1 coated thereon is, for example, lithium transition metal oxide (LiNi1 / 3 Co 1 / 3 Mn 1 / 3 The electrode foil 22H of the negative electrode body 22 may be made of, for example, copper foil, and the negative electrode active material KT2 coated thereon may be made of, for example, graphite, hard carbon, soft carbon, or the like. The separator 23 may be made of, for example, a porous sheet of polypropylene resin or polyethylene resin. The electrolyte may be a known non-aqueous electrolyte. The positive electrode current collector terminal 4 may be made of, for example, aluminum, and the negative electrode current collector terminal 4 may be made of, for example, copper.

[0018] As shown in FIG. 3, the electrode body 2 is preferably pressed inward (in the direction of arrow Q) by pressing seats 112 formed on the long side walls 11a on both sides of the case body 11 in the width direction (Z direction), and is thus constrained to the battery case 1. When a plurality of secondary batteries 10 are stacked to form a battery pack, the electrode body 2 may be constrained to the battery case 1 by pressing adjacent long side walls 11a against each other. The connection portion 5 connecting the electrode body 2 to the current collecting terminal 4 can be formed, for example, as shown in FIG. 4, by a tab portion 2T formed by stacking electrode foils 21H, 22H partially extending in the longitudinal direction (X direction) at the longitudinal end (X direction) of the electrode foil 21H (22H), but is not necessarily limited to this. Modified examples will be described later.

[0019] 1, 5A, and 5B, an end of the connection portion (tab portion 2T) 5 is connected by a weld 422 or the like to a side surface of an internal terminal 42 of the current collecting terminal 4. The internal terminal 42 extends downward from a case-fixed portion 4K, which is fixed to the battery case 1 (lid 12) via an insulating resin member 3. A triangular receiving portion 421 is preferably formed on the side surface of the internal terminal 42 of the current collecting terminal 4. The receiving portion 421 abuts against a lower end portion 2TK of the connection portion (tab portion 2T) 5 near the internal terminal 42. When the battery temperature rises above a predetermined temperature, the connection portion (tab portion 2T) 5 softens, and the tip of the receiving portion 421 bites into the connection portion (tab portion 2T) 5 due to the biasing force P of the spring member 6 that biases the current collecting terminal 4, causing a crack. This crack can grow and separate the connection portion (tab portion 2T) 5.

[0020] When the connection portion (tab portion 2T) 5 is severed, it is preferable to use the biasing force P of the spring member 6 to bend or displace the lower end of the current collecting terminal 4 in a direction away from the electrode body 2. In this case, the crack generated in the connection portion (tab portion 2T) 5 is allowed to grow further, and the connection portion (tab portion 2T) 5 can be rapidly severed. Here, the spring member 6 that biases the current collecting terminal 4 is mounted in a compressed state between a spring seat 43 formed at a position eccentric to the electrode body 2 at the lower end of the internal terminal 42 and the bottom 11c of the case body 11. If the spring member 6 is made of a conductive material, an insulating sheet 431 is interposed between the spring member 6 and the spring seat 43 of the current collecting terminal 4. The spring member 6 is formed of two cylindrical spring members, but this is not necessarily limited to this. The spring member 6 may be made of, for example, elastic rubber, as long as it can separate the connection portion 5 that connects the electrode body 2 and the current collecting terminal 4 with its biasing force P when the battery temperature rises above a predetermined temperature. The spring member 6 may also be a tension spring member.

[0021] As described above, the secondary battery 10 includes the current interruption mechanism 7. When the battery temperature rises above a predetermined temperature, the connection 5 connecting the electrode assembly 2 and the current collecting terminal 4 is severed by the biasing force P of the spring member 6 that biases the current collecting terminal 4, thereby bringing the battery into a non-conductive state. Therefore, when the battery temperature rises suddenly due to a short circuit or the like in the electrode assembly 2, the connection 5 connecting the electrode assembly 2 and the current collecting terminal 4 is severed and brought into a non-conductive state without waiting for the gas pressure inside the battery to rise above a predetermined value. Therefore, the secondary battery 10 can quickly interrupt the current as the battery temperature rises. As a result, the safety valve 123 is prevented from opening, and high-pressure gas, electrolyte, etc. are not released outside the battery, providing a highly safe secondary battery 10.

[0022] Since the secondary battery 10 has a compressed spring member 6 interposed between the current collecting terminal 4 and the bottom 11c of the battery case 1, it can be assembled, for example, using the following procedure. The current collecting terminal (external terminal 41) 4 and the lid 12 are insert-molded to be fixed to the insulating resin member 3. The current collecting terminal (internal terminal 42) 4 and the connection portion (tab portion 2T) 5 of the electrode body 2 are joined by welding or the like. Thereafter, the spring member 6 is attached to the spring seat 43 of the current collecting terminal 4. Then, while correcting the opening 111 of the case body 11 in the opening direction, the electrode body 2, the current collecting terminal 4, and the spring member 6 are inserted into the case body 11, and while holding the spring member 6 in a compressed state, the lid 12 and the case body 11 are welded to seal the case. The secondary battery 10 can be assembled using the above procedure.

[0023] Furthermore, the battery case 1 of the present secondary battery 10 is not limited to the above-described form as long as the interior of the battery case 1 is watertight. For example, the battery case may include a rectangular cylindrical case body having openings at both ends in the longitudinal direction (X direction) and a pair of lids that seal both openings. In this case, the positive electrode current collector terminal and the negative electrode current collector terminal may be fixed to separate lids via insulating resin members.

[0024] The current interrupt mechanism 7 of the secondary battery 10 is only required to be such that when the battery temperature rises above a predetermined temperature, the connection portion 5 connecting the electrode body 2 and the current collecting terminal 4 is separated by the biasing force P of the spring member 6 biasing the current collecting terminal 4, thereby bringing the current interrupt mechanism 7 into a non-conductive state. Therefore, the current interrupt mechanism 7 can be modified in various ways depending on the configuration of the connection portion 5, the current collecting terminal 4, etc. Representative modifications are described below. In the description of each modification, items common to those described above are designated by the same reference numerals, and, as a rule, their description will be omitted.

[0025] (Current interruption mechanism of modified example 1) Fig. 6 is a schematic cross-sectional view of the secondary battery shown in Fig. 1 in a state where the current-breaking mechanism of Modification 1 is activated. As shown in Figs. 1 and 6, in this secondary battery 10B, the current-breaking mechanism 7B of Modification 1 moves the current-collecting terminal 4 due to the biasing force P of the spring member 6 when the insulating resin member 3 that secures the current-collecting terminal 4 to the battery case 1 melts or softens, causing the connecting portion (tab portion 2T) to locally stretch and break, resulting in a non-conductive state. In this case, when the battery temperature rises to the melting temperature of the insulating resin member 3 (e.g., about 290°C when the insulating resin member 3 is made of PPS resin) or a softening temperature close to that temperature (e.g., about 270°C to 280°C), the battery current can be quickly interrupted without waiting for the gas pressure inside the battery to rise above a predetermined value at which the safety valve 123 ruptures.

[0026] Here, the current collecting terminal 4 moves outward from the battery due to the biasing force P of the spring member 6, so there is no need to ensure extra space within the battery case 1 for the movement of the current collecting terminal 4, and the volumetric efficiency of the secondary battery 10B can be improved. As a result, the volumetric efficiency of the secondary battery 10B can be improved while quickly interrupting current as the temperature rises, thereby providing a highly efficient and safe secondary battery 10B. Note that if a bus bar is connected to the external terminal 41, the bus bar needs to be formed so that it can deform as the current collecting terminal 4 moves outward from the battery. Note that the spring member 6 may be a tension spring, which moves the current collecting terminal 4 inward from the battery, thereby cutting off the connection portion (tab portion 2T).

[0027] (Current interruption mechanism of modified example 2) 7A shows an enlarged cross-sectional view of the current interruption mechanism of Variation 2 at portion B shown in FIG. 1 . FIG. 7B shows an enlarged cross-sectional view of the current interruption mechanism shown in FIG. 7A during operation. As shown in FIGS. 1 , 7A, and 7B, in a current interruption mechanism 7C of Variation 2 in the secondary battery 10C, the connection portion 5 is a tab portion 2T formed by stacking electrode foils 21H and 22H of the electrode body 2. The tab portion 2T is provided with a notched groove 51 and / or a perforation 52 formed along a moving direction of the current collecting terminal 4 or an inclined line 23T inclined relative to the moving direction. Here, the notched groove 51 is formed at the lower end of the tab portion 2T, and the perforation 52 is formed continuously from the tip of the notched groove 51 to the upper end of the tab portion 2T. However, only the notched groove 51 or only the perforation 52 may be provided. The notched groove 51 is preferably, for example, a V-shaped notched groove 51 formed at the lower end of the tab portion 2T, closer to the current collecting terminal 4. The perforations 52 are preferably, for example, micro-holes that penetrate the connection portion (tab portion 2T) 5 and are continuously formed at a predetermined pitch.

[0028] Here, the tab portion 2T preferably has a notched groove 51 and / or a perforation 52 formed along an inclined line 23T whose tip 231T is inclined at an acute angle toward the electrode body 2 with respect to the moving direction of the current collecting terminal 4. In other words, the moving direction (Y direction) of the current collecting terminal 4 and the inclined line 23T preferably intersect at an acute intersection angle θ. In this case, the spring member 6 is interposed between the spring seat 43 formed on the lower end of the current collecting terminal 4 and the bottom 11c of the battery case 1. Therefore, when the insulating resin member 3 that secures the current collecting terminal 4 to the battery case 1 melts or softens, the current collecting terminal 4 moves in the vertical direction (Y direction) in which the biasing force P of the spring member 6 acts. However, because the tab portion 2T is formed from the electrode foils 21H, 22H with thin plate thicknesses, the biasing force P of the spring member 6 tears the tab portion 2T left and right along the inclined line 23T, starting from the notched groove 51 or the perforation 52, making it easier to cut. Another advantage is that the notched groove 51 and / or the perforation 52 formed along the inclined line 23T make it easy for the separated upper tab portion 21T and lower tab portion 22T to separate even if the movement of the current collecting terminal 4 is small.

[0029] As described above, according to the current interrupt mechanism 7C of the second variation of the secondary battery 10C, the tab portion 2T includes the notched groove 51 and / or the perforation 52 formed along the movement direction of the current collector terminal 4 or along the inclined line 23T inclined relative to the movement direction. Therefore, when the current collector terminal 4 is moved by the biasing force P of the spring member 6, the tab portion 2T locally extends from the notched groove 51 and / or the perforation 52, resulting in more rapid separation and a non-conductive state. Therefore, the secondary battery 10C can interrupt current more quickly as the battery temperature rises. As a result, the safety valve 123 is prevented from opening, preventing high-pressure gas, electrolyte, and the like from being released outside the battery, resulting in a highly safe secondary battery 10C.

[0030] (Current interrupt mechanism of modified example 3) 8A shows an enlarged cross-sectional view of the current interruption mechanism of Variation 3 at portion B shown in FIG. 1. FIG. 8B shows an enlarged cross-sectional view of the current interruption mechanism shown in FIG. 8A during operation. As shown in FIGS. 1, 8A, and 8B, in this secondary battery 10D, connection portion 5D includes terminal-side connection portion 53 connected to current collecting terminal 4 and electrode-side connection portion 54 connected to electrode foils 21H and 22H of electrode body 2. Current collecting terminal 4 and terminal-side connection portion 53 are joined by welded portion 422 or the like, and electrode foils 21H and 22H and electrode-side connection portion 54 are joined by welded portion 541 or the like. Terminal-side connection portion 53 and electrode-side connection portion 54 are formed, for example, as right-angled trapezoids, with tip portion 551 inclined toward electrode body 2 relative to the direction of movement of current collecting terminal 4 and inclined surface 55S coinciding.

[0031] Furthermore, the terminal-side connecting portion 53 and the electrode-side connecting portion 54 are joined by a low-melting-point joining member 55 (for example, lead-free solder with a melting temperature of about 217°C or leaded solder with a melting temperature of about 183°C) having a lower melting point than the insulating resin member 3 (for example, PPS resin with a melting temperature of about 290°C). The low-melting-point joining member 55 may be an adhesive as long as it is formed to a predetermined thickness and is a conductive joining member.

[0032] The current collecting terminal 4 also includes an easily deformable portion 423 in the internal terminal 42 between the terminal-side connection portion 53 and the case-fixed portion 4K fixed to the battery case 1 via the insulating resin member 3. The easily deformable portion 423 is formed, for example, by dividing the internal terminal 42 into upper and lower halves and protruding in a U-shape from the side surfaces of the separated divided end portions 42a and 42b in the longitudinal direction (X direction). The case-fixed portion 4K is connected to the internal terminal 42 above the upper divided end portion 42a. The terminal-side connection portion 53 is connected to the internal terminal 42 below the lower divided end portion 42b. In the current interruption mechanism 7D of the third modification, when the low-melting-point bonding member 55 melts or softens, the easily deformable portion 423 is deformed by the biasing force P of the spring member 6, and the terminal-side connection portion 53 and the electrode-side connection portion 54 are separated, resulting in a non-conductive state.

[0033] In this case, if the low-melting-point joining member 55 is lead-free solder, when the battery temperature rises to the melting temperature of the lead-free solder (approximately 217°C) or a softening temperature close to that temperature (e.g., approximately 210°C to 215°C), the terminal-side connecting portion 53 and the electrode-side connecting portion 54 are separated by the biasing force P of the spring member 6, resulting in a non-conductive state. Here, the low-melting-point joining member 55 has a tip end 551 formed along an inclined surface 55S that slopes toward the electrode body 2. Therefore, even if the deformation amount of the easily deformable portion 423 is small, the terminal-side connecting portion 53 and the electrode-side connecting portion 54 are easily separated in the vertical direction by the biasing force P of the spring member 6, and quickly become non-conductive. Note that, in the internal terminal 42 of the current collecting terminal 4, the upper divided end 42a and the lower divided end 42b, to which the easily deformable portion 423 is connected, are preferably connected by a connecting member 55T made of the same material as the low-melting-point joining member 55. In this case, the connecting member 55T does not melt or soften at a temperature before the low melting point joining member 55 melts or softens, so the easily deformable portion 423 can be maintained in an undeformed state.

[0034] As described above, according to the present secondary battery 10D, the connection portion 5D includes a terminal side connection portion 53 connected to the current collecting terminal 4 and an electrode side connection portion 54 connected to the electrode foils 21H, 22H of the electrode body 2, and the terminal side connection portion 53 and the electrode side connection portion 54 are joined by a low-melting point joining member 55 having a melting point lower than that of the insulating resin member 3, and the current collecting terminal 4 includes an easily deformable portion 423 in the internal terminal 42 between the terminal side connection portion 53 and the case fixing portion 4K fixed to the battery case 1 via the insulating resin member 3, and when the low-melting point joining member 55 melts or softens, the easily deformable portion 423 is deformed by the spring force P of the spring member 6, and the terminal side connection portion 53 and the electrode side connection portion 54 are separated, resulting in a non-conductive state. Therefore, the battery current can be interrupted at a lower temperature by simply raising the battery temperature to the melting temperature or softening temperature of the low-melting point joining member 55, without waiting for the battery temperature to rise to the melting temperature of the insulating resin member 3. Furthermore, the terminal-side connecting portion 53 and the electrode-side connecting portion 54 are separated at the specific position joined by the low-melting point joining member 55, allowing for more stable and rapid current interruption.

[0035] (Current interrupt mechanism of modification 4) 9A shows an enlarged cross-sectional view of the current interruption mechanism of Variation 4 at portion C shown in FIG. 1. FIG. 9B shows an enlarged cross-sectional view of the current interruption mechanism shown in FIG. 9A in an activated state. As shown in FIGS. 1, 9A, and 9B, in this secondary battery 10E, the current collecting terminal 4 is fixed to the battery case 1 via a laminated insulating resin member 3E in which a low-melting-point resin member 32 having a lower melting point than the insulating resin members 31 (31a, 31b) is sandwiched between the insulating resin members 31 (31a, 31b) while surrounding the current collecting terminal 4.

[0036] The laminated insulating resin member 3E has a first insulating resin member 31 (31a) fixed to the lid 12 and a second insulating resin member 31 (31b) fixed to the external terminal 41, and an annular low-melting-point resin member 32 laminated to a predetermined thickness between them. The first insulating resin member 31 (31a) and the second insulating resin member 31 (31b) can be made of, for example, polyphenylene sulfide (PPS) resin, and the low-melting-point resin member 32 can be made of, for example, polypropylene (PP) resin.

[0037] Furthermore, in the current interruption mechanism 7E of the fourth modification, when the low-melting-point resin member 32 melts or softens, the biasing force P of the spring member 6 separates the connection portion 5, thereby bringing the current interruption mechanism 7E into a non-conductive state. The connection portion 5 can be configured, for example, as shown in FIG. 4 , by a tab portion 2T formed by stacking strips of electrode foil 21H (22H) extending in the longitudinal direction (X direction) at the longitudinal end of the electrode foil 21H (22H). The connection portion (tab portion 2T) 5 may be provided with a notched groove 51 and / or a perforation 52, as shown in FIG. 7A . More preferably, the connection portion 5 may be provided with a notched groove 51 and / or a perforation 52 formed along an inclined line 23T whose tip 231T is inclined toward the electrode body 2 with respect to the direction of movement of the current collecting terminal 4.

[0038] In this case, when the battery temperature rises to the melting temperature of the low-melting-point resin member 32 (approximately 170°C when the low-melting-point resin member 32 is made of polypropylene (PP) resin) or its softening temperature (e.g., approximately 150°C to 160°C), as shown in FIG. 9B , the current collecting terminal (external terminal 41) 4 fixed to the battery case 1 (lid 12) moves toward the outside of the battery due to the biasing force P of the spring member 6, thereby severing the connection portion (tab portion 2T) 5 and interrupting the battery current. Therefore, the battery current can be interrupted at a lower temperature without waiting for the battery temperature to rise to the melting point of the insulating resin member 31 (31a, 31b) (approximately 290°C when made of PPS resin). Furthermore, because the external terminal 41 moves toward the outside of the battery, there is no need to secure extra space within the battery case 1, which can improve the volumetric efficiency of the secondary battery 10E.

[0039] As described above, in the present secondary battery 10E, the current collecting terminal 4 is fixed to the battery case 1 via a laminated insulating resin member 3E in which the low-melting-point resin member 32, which has a lower melting point than the insulating resin members 31 (31a, 31b), is sandwiched between the insulating resin members 31 (31a, 31b) while surrounding the current collecting terminal 4. Furthermore, in the current interrupt mechanism 7E of the fourth modification, when the low-melting-point resin member 32 melts or softens, the biasing force P of the spring member 6 separates the connection portion (tab portion 2T) 5, thereby establishing a non-conductive state. This allows the battery current to be interrupted more quickly at the lower melting or softening temperature of the low-melting-point resin member 32, without waiting for the battery temperature to rise to the melting temperature of the insulating resin members 31 (31a, 31b). As a result, the safety valve 123 is prevented from opening, and high-pressure gas, electrolyte, and the like are not released to the outside of the battery, providing a highly safe secondary battery 10E.

[0040] Preferably, the portion where the lid 12 is fixed to the first insulating resin member 31 (31a) and the portion where the external terminal 41 is fixed to the second insulating resin member 31 (31b) are formed with annular roughened surfaces 411, 124 having an arithmetic mean roughness of 30 to 500 nm, for example, to ensure watertightness with the insulating resin members 31 (31a, 31b). The roughened surfaces 411, 124 may also be formed on the portion where the external terminal 41 is fixed to the insulating resin member 3 at part C shown in FIG. 1 and the portion where the lid 12 is fixed to the insulating resin member 3. The above-described embodiment is merely illustrative and does not limit the disclosed technology in any way. Therefore, various improvements and modifications are possible within the spirit and scope of the disclosed technology. [Explanation of symbols]

[0041] 1 Battery case 2 Electrode body 2T tab part 3, 3E Insulating resin material 4 Current collector terminal 4K case fixing part 5, 5D connection part 6 Spring member 7, 7B, 7C, 7D, 7E Current interrupt mechanism 10, 10B, 10C, 10D, 10E secondary battery 21H, 22H electrode foil 23T slope line 31, 31a, 31b insulating resin member 32 Low-melting-point resin materials 51 Notched groove 52 perforations 53 Terminal side connection part 54 Electrode side connection part 55 Low melting point joining material 231T tip 423 Easily deformable part

Claims

1. A battery case and an electrode assembly housed in the battery case in a constrained state; a current collecting terminal fixed to the battery case via an insulating resin member and connected to the electrode body, When the battery temperature rises above a predetermined temperature, the connection between the electrode body and the current collector terminal is cut off by the biasing force of a spring member that biases the current collector terminal, thereby establishing a non-conductive state. Secondary battery.

2. 2. The secondary battery according to claim 1, When the insulating resin member melts or softens, the current-blocking mechanism moves the current-collecting terminal due to the biasing force of the spring member, causing the connection portion to stretch locally and be cut off, resulting in a non-conductive state. Secondary battery.

3. 3. The secondary battery according to claim 2, the connection portion is a tab portion on which the electrode foil of the electrode body is laminated, The tab portion has a notched groove and / or a perforation formed along the moving direction of the current collecting terminal or along an inclined line inclined with respect to the moving direction. Secondary battery.

4. 2. The secondary battery according to claim 1, the connection portion includes a terminal-side connection portion connected to the current collecting terminal and an electrode-side connection portion connected to the electrode foil of the electrode body, the terminal-side connecting portion and the electrode-side connecting portion are joined by a low-melting-point joining material having a melting point lower than that of the insulating resin material, the current collecting terminal has an easily deformable portion between the terminal-side connection portion and a case fixing portion fixed to the battery case via the insulating resin member, When the low-melting-point joining member melts or softens, the current-breaking mechanism deforms the easily deformable portion due to the biasing force of the spring member, and the terminal-side connecting portion and the electrode-side connecting portion are separated, resulting in a non-conductive state. Secondary battery.

5. 2. The secondary battery according to claim 1, the current collecting terminal is fixed to the battery case via a laminated insulating resin member in which a low-melting-point resin member having a melting point lower than that of the insulating resin member is sandwiched between the insulating resin members while surrounding the current collecting terminal, When the low-melting-point resin member melts or softens, the current-breaking mechanism separates the connection portion due to the biasing force of the spring member, thereby bringing the current-breaking mechanism into a non-conductive state. Secondary battery.

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