Secondary battery

Abstract

To solve a problem in which improvements in safety are limited against battery heat generation in a conventional secondary battery.SOLUTION: A secondary battery according to the present invention includes a battery case 10, an electrode body 11 arranged in the battery case 10, a current collecting terminal 21 provided in the battery case 10 and joined to a current collecting foil extending from the electrode body 11, an external terminal 22 which has an external terminal pin 22c that fits into a terminal mounting hole 21a provided in the current collecting terminal 21 and is connected to the current collecting terminal 21 from outside the battery case 10, and a thermal expansion member 24 provided between the external terminal 22 and the battery case 10.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a secondary battery using a non-aqueous electrolyte secondary battery, such as a lithium ion secondary battery, as an electrode assembly. [Background technology]

[0002] In a secondary battery, when an internal short circuit occurs, for example, when a sharp object such as a nail is stuck in the battery, a large current flows suddenly and Joule heat is generated inside the battery. In addition, the temperature inside the battery may rise if overcharging occurs for some reason. If the temperature inside the battery rises excessively due to such Joule heat or overcharging, the physical or chemical stability of the battery decreases, which is problematic. Therefore, in a secondary battery, in order to maintain the stability of the battery when a temperature rise occurs inside the battery, measures such as cutting off the current and suppressing the temperature rise are taken. An example of such measures is disclosed in Patent Document 1.

[0003] The secondary battery described in Patent Document 1 is a secondary battery comprising a battery case, an electrode body arranged in the battery case, and a current collecting terminal, wherein the electrode body and the current collecting terminal have a joint portion where they are connected to each other, and near the joint portion there is an overlap portion where the electrode body and the current collecting terminal overlap, and a thermal expansion material is arranged in the gap between the electrode body and the current collecting terminal in the overlap portion, and when the temperature inside the battery case rises and the thermal expansion material expands, the joint portion breaks and the current collecting terminal is separated from the electrode body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-130320 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the secondary battery described in Patent Document 1, a thermal expansion material is expanded inside the battery case to break the joints, which may cause damage or short-circuiting to the current collecting terminals or electrode body after the breakage, resulting in a problem that the improvement in safety is limited.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to improve safety against temperature rise in a battery. [Means for solving the problem]

[0007] One aspect of the secondary battery of the present invention comprises a battery case, an electrode body disposed within the battery, a current collecting terminal provided within the battery case and joined to a current collecting foil extending from the electrode body, an external terminal having an external terminal pin that fits into a terminal mounting hole provided in the current collecting terminal and connected to the current collecting terminal from outside the battery case, and a thermal expansion member provided between the external terminal and the battery case. Effect of the Invention

[0008] According to the secondary battery of the present invention, it is possible to improve safety against a rise in battery temperature caused by an overcurrent or the like. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a secondary battery according to a first embodiment. [Diagram 2] 2 is a first enlarged view of the peripheral area of ​​the terminal of the secondary battery of FIG. 1. FIG. [Diagram 3] 2 is a second enlarged view of the peripheral area of ​​the terminal of the secondary battery of FIG. 1. FIG. [Figure 4] 2 is an enlarged cross-sectional view of a peripheral area of ​​a terminal of the secondary battery of FIG. 1. [Diagram 5] 11 is an enlarged cross-sectional view of a peripheral area of ​​a terminal of a secondary battery according to a second embodiment. FIG. [Figure 6] 11 is an enlarged cross-sectional view of a peripheral area of ​​a terminal of a secondary battery according to a third embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In each drawing, the same elements are given the same reference numerals, and repeated explanations are omitted as necessary. In the following description, the horizontal direction of FIG. 1 is defined as the width direction X, the vertical direction is defined as the height direction Z, and the front-rear direction of the drawing is defined as the depth direction Y. The width direction X and the depth direction Y coincide with the horizontal direction when the secondary battery is housed in the stack case, and the height direction Z coincides with the vertical direction. The width direction X, the depth direction Y, and the height direction Z are perpendicular to each other.

[0011] First embodiment Fig. 1 shows a schematic diagram of a secondary battery 1 according to the first embodiment. Fig. 1 is a cross-sectional view of the secondary battery according to the first embodiment taken along near the center of a surface on which the power input / output terminals of the secondary battery are provided (or near the center in the depth direction Y of the secondary battery 1).

[0012] 1, the secondary battery 1 according to the first embodiment is configured by housing an electrode assembly 11 in a battery case 10. The secondary battery 1 according to the first embodiment also has current collecting terminals 21 and 31, external terminals 22 and 32, and bus bars 23 and 33 as components for inputting and outputting electric power from the electrode assembly 11.

[0013] The current collecting terminals 21, 31 are provided inside the battery case 10 and joined to current collecting foils (not shown) extending from the electrode body. The external terminals 22, 32 have external terminal pins that fit into terminal mounting holes provided in the current collecting terminals 21, 31, and are connected to the current collecting terminals 21, 31 from outside the battery case 10. The bus bars 23, 33 are components that are attached to a stack case in which multiple secondary batteries 1 are stored in a stacked state. The bus bars 23, 33 electrically connect the external terminals of two adjacent secondary batteries 1 out of the multiple stacked secondary batteries 1.

[0014] Moreover, the secondary battery 1 according to the first embodiment has smoke vent valves 12, 13 on the surface on which the external terminals 22, 32 are provided. The smoke vent valves 12, 13 open when the pressure inside the battery case 10 reaches or exceeds a preset specified pressure, thereby safely reducing the internal pressure of the battery case 10.

[0015] Here, since the secondary battery 1 according to embodiment 1 has a characteristic structure in the vicinity of the current collecting component and the external terminal, the structure in the vicinity of the current collecting component and the external terminal will be described in detail using an enlarged view of the terminal peripheral area A including the vicinity of one of the current collecting component and the external terminal (for example, the current collecting terminal 21 and the external terminal 22 on the left side of Figure 1).

[0016] Fig. 2 shows a first diagram in which the peripheral area of ​​the terminal of the secondary battery in Fig. 1 is enlarged, Fig. 3 shows a second diagram in which the peripheral area of ​​the terminal of the secondary battery in Fig. 1 is enlarged, and Fig. 4 shows a cross-sectional view in which the peripheral area of ​​the terminal of the secondary battery in Fig. 1 is enlarged. Figs. 2 and 3 are perspective views of the peripheral area A of the terminal before the external terminal 22 is fitted into the current collecting terminal 21. Fig. 4 is a cross-sectional view of the peripheral area A of the terminal as viewed from the same cross section as Fig. 1.

[0017] 2 to 4, the current collecting terminal 21 has a terminal mounting hole 21a, and is provided inside the battery case 10 such that at least the terminal mounting hole 21a is exposed to the outside of the battery case 10. The battery case 10 also has an external terminal fitting groove 14 into which an external terminal 22 and a thermal expansion member 24 are fitted. In the secondary battery 1 according to the first embodiment, the external terminal 22 and the thermal expansion member 24 are assembled such that the thermal expansion member 24 is sandwiched between the external terminal 22 and the battery case 10.

[0018] The external terminal 22 has an external terminal pin 22c on the surface (hereinafter referred to as the back surface) that faces the battery case 10 after being assembled to the battery case 10. The current collecting terminal 21 has a terminal mounting hole 21a at a position corresponding to the external terminal pin 22c. The external terminal 22 is assembled to the battery case 10 such that the external terminal pin 22c fits into the terminal mounting hole 21a provided in the current collecting terminal.

[0019] In the external terminal 22 according to the first embodiment, the surface on which the external terminal pins 22c are provided is the back surface, and the surface facing the back surface is the front surface. The external terminal 22 has a flat surface 22a and a sloped surface 22b formed on the front surface. The flat surface 22a is parallel to the back surface. The sloped surface 22b is at a predetermined angle with respect to the back surface so that the thickness of the end side of the external terminal 22 is thicker than that of the flat surface. When the secondary battery 1 is stored in a stack case provided with a bus bar 23 that electrically connects the external terminals of two adjacent secondary batteries 1 out of the multiple secondary batteries 1 stacked, the bus bar 23 comes into contact with the sloped surface 22b.

[0020] The external terminal pin 22c is provided so as to protrude from the surface of the back surface facing the flat surface 22a towards the current collecting terminal 21. The external terminal pin 22c is preferably provided at a position on the back surface of the external terminal 22 that is shifted above or below the center position in the height direction Z of the battery case 10, and more preferably above the center position (for example, on a side not subjected to the pressing force of the bus bar 23).

[0021] The thermal expansion member 24 is disposed at a position sandwiched between the external terminal 22 and the battery case 10 when the external terminal 22 is assembled to the battery case 10. The thermal expansion member 24 also has a retaining tab 24a sandwiched between a part of the inner wall of the terminal mounting hole 21a and a part of the outer periphery of the external terminal pin 22c. The thermal expansion member 24 is made of an elastic material, and the presence of the retaining tab 24a can increase the contact pressure between the external terminal pin 22c and the inner wall of the terminal mounting hole 21a.

[0022] 4, the external terminal pin 22c is provided with a slip-out prevention notch B provided at a position into which the thermal expansion member 24 fits. By fixing the thermal expansion member 24 so that it fits into the slip-out prevention notch B before assembling the external terminal 22 to the battery case 10, it is possible to prevent the thermal expansion member 24 from falling off the external terminal 22 during the process of assembling the external terminal 22 to the battery case 10, thereby improving workability.

[0023] The thermal expansion member 24 has insulating properties, thereby ensuring insulation between the external terminal 22 and the battery case 10. The thermal expansion member 24 is a resin material that expands irreversibly when heat is applied. For example, a material also called thermal expansion rubber or thermal expansion insulating rubber can be used for the thermal expansion member 24. The thermal expansion member 24 has high thermal conductivity before expansion, but expands and functions as an insulating material when heat exceeding a preset expansion start temperature is applied. The expansion rate of the thermal expansion member 24 can be set arbitrarily, but can be adjusted within a range of about 200% to 3000%.

[0024] In the secondary battery 1 according to the first embodiment, the smoke vent valve 12 is provided at a position adjacent to the external terminal 22. Here, the position adjacent to the external terminal 22 is a position within a distance range in which the heat of the smoke exhausted from the smoke vent valve 12 is sufficiently transmitted to the thermal expansion member 24.

[0025] Next, referring to FIG. 4, the behavior of the secondary battery 1 when the thermal expansion member 24 expands will be described. When the temperature of the secondary battery 1 rises due to an overcurrent or the like and the heat transferred to the thermal expansion member 24 exceeds the expansion threshold temperature, or when the internal pressure of the battery case 10 exceeds the smoke exhaust pressure set in the smoke exhaust valve 12, the thermal expansion member 24 expands and displaces the external terminal 22 in a direction away from the battery case 10. Then, with the displacement of the external terminal 22, the external terminal pin 22c comes out of the terminal mounting hole 21a, and the secondary battery 1 is insulated from other secondary batteries or the bus bar 23. At this time, the thermal expansion member 24 expands irreversibly, so that the secondary battery 1 is kept insulated from other members even if the temperature of the secondary battery 1 drops.

[0026] 4, the external terminal 22 has a sloped surface 22b, the external terminal pin 22c is provided on a surface facing the flat surface 22a, and the sloped surface 22b is subjected to a pressing force from the bus bar 23. Therefore, when the external terminal 22 is peeled off from the battery case 10, the external terminal 22 is peeled off from the battery case 10 so as to rotate about a fulcrum C set near the boundary between the flat surface 22a and the sloped surface 22b (external terminal separation direction in FIG. 4). With this operation, in the secondary battery 1 according to the first embodiment, the external terminal 22 does not fall off from the battery case 10 and the secondary battery 1 maintains an insulated state.

[0027] As described above, in the secondary battery 1 according to the first embodiment, the thermal expansion member 24 for peeling the external terminal 22 from the current collecting terminal 21 is provided outside the battery case 10. Furthermore, when the thermal expansion member 24 expands, the external terminal 22 comes off from the current collecting terminal 21 in a direction that does not affect the structure inside the battery case 10. In other words, in the secondary battery 1 according to the first embodiment, it is possible to maintain an insulated state by separating the external terminal 22 from the current collecting terminal 21 without affecting the structure inside the battery case 10, and therefore it is possible to achieve high safety.

[0028] In the secondary battery 1 according to the first embodiment, the external terminal 22 is connected to the current collector terminal 21 by fitting the external terminal pin 22c into the terminal mounting hole 21a so as to sandwich the thermal expansion member 24 between the battery case 10. At this time, in the secondary battery 1 according to the first embodiment, the external terminal 22 and the current collector terminal 21 are connected without a process involving heat generation such as welding or ultrasonic bonding, so that the expansion start temperature of the thermal expansion member 24 can be set lower than that of the expansion material used in Patent Document 1. In this way, by setting the expansion start temperature of the thermal expansion member 24 lower, it is possible to make the thermal expansion member 24 expand at an earlier timing in response to overheating of the secondary battery 1 or exhaust of smoke from the smoke exhaust valve 12, and to make the secondary battery 1 in an insulated state. As a result, the secondary battery 1 according to the first embodiment can further improve safety.

[0029] Embodiment 2 In the second embodiment, a different form of the anti-slip tab 24a of the thermal expansion member 24 will be described. Fig. 5 shows an enlarged cross-sectional view of the terminal peripheral area A of the secondary battery 2 according to the second embodiment. As shown in Fig. 5, in the secondary battery 2 according to the second embodiment, the anti-slip tab 24a is shorter than that of the thermal expansion member 24 according to the first embodiment. In this way, by shortening the length of the anti-slip tab 24a, it is possible to improve the ease of assembly.

[0030] Third embodiment In the third embodiment, another form of the anti-removal tab 24a of the thermal expansion member 24 will also be described. Fig. 6 shows an enlarged cross-sectional view of the terminal peripheral area A of the secondary battery 3 according to the third embodiment. As shown in Fig. 6, in the secondary battery 3 according to the third embodiment, the thermal expansion member 24 has a portion sandwiched between the bottom surface of the terminal mounting hole 21a and the tip of the external terminal pin 22c. By providing the thermal expansion member 24 in the portion sandwiched between the bottom surface of the terminal mounting hole 21a and the tip of the external terminal pin 22c in this manner, it becomes possible for the external terminal pin 22c to be more reliably and more quickly removed from the terminal mounting hole 21a when the thermal expansion member 24 expands.

[0031] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0032] 1 Secondary battery 10 Battery case 11 Electrode body 12 Smoke exhaust valve 13 Smoke exhaust valve 14 External terminal fitting groove 21 Current collector terminal 21a Terminal mounting hole 22 External terminal 22a flat surface 22b Slope surface 22c External terminal pin 23 Busbar 24 Thermal expansion members 24a Anti-slip tongue A Terminal Surrounding Area B Notch to prevent slipping out C fulcrum

Claims

1. A battery case; An electrode assembly disposed in the battery case; a current collecting terminal provided in the battery case and joined to a current collecting foil extending from the electrode body; an external terminal including an external terminal pin that fits into a terminal mounting hole provided in the current collecting terminal and is connected to the current collecting terminal from the outside of the battery case; a thermal expansion member provided between the external terminal and the battery case; A secondary battery having the above structure.

2. The secondary battery according to claim 1 , wherein the external terminal pin has a notch for preventing the thermal expansion member from coming off the external terminal pin and is provided at a position where the thermal expansion member fits.

3. 2 . The secondary battery according to claim 1 , wherein the thermal expansion member has a tab for preventing the external terminal pin from coming out of the terminal hole and being sandwiched between a part of an inner wall of the terminal hole and a part of an outer periphery of the external terminal pin.

4. 4. The secondary battery according to claim 3, wherein the anti-dislodgement tab further has a portion sandwiched between a bottom surface of the terminal mounting hole and the tip of the external terminal pin.

5. the external terminal has a back surface on which the external terminal pin is provided and a front surface opposite to the back surface, the front surface has a flat surface parallel to the back surface and a slope surface formed of a surface having a predetermined angle with respect to the back surface such that a thickness of an end side of the external terminal is thicker than that of the flat surface; The secondary battery according to claim 1 , wherein the external terminal pin is provided so as to protrude from a surface of the rear surface facing the flat surface toward the current collecting terminal.

6. 6. The secondary battery according to claim 5, wherein when the secondary battery is housed in a stack case in which a bus bar is provided to electrically connect the external terminals of two adjacent secondary batteries among the plurality of stacked secondary batteries, the bus bar comes into contact with the sloped surface.

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