JP7291654B2 - secondary battery - Google Patents

Description

The present invention relates to secondary batteries.

As a secondary battery, there is already known one in which an opening of a case containing an electrode body together with an electrolytic solution is sealed with a lid. In this secondary battery, there is a mechanism that releases gas in the case when the internal pressure of the case rises excessively due to overcharging, etc., and a current interrupter that interrupts the current path from the electrode body to the external terminal. Some are provided (see Patent Document 1, for example).

The current interrupting device includes a first deformation plate provided on the negative terminal side and having a pressure receiving surface, a second deformation plate, and an energizing plate provided between the first deformation plate and the second deformation plate and electrically connected to the electrode body side. and a rod-shaped member that contacts the second deformation plate. The rod-like member is inserted through a through hole formed in the axial direction of the fastening member that connects the external terminal and the connecting member. When the pressure in the space inside the case rises above a predetermined level, the first deforming plate receives pressure on the pressure receiving surface and is displaced toward the current-carrying plate, and the projection provided on the first deforming plate hits the current-carrying plate. contact and break the current-carrying plate. Furthermore, the protrusion presses the second deformation plate to deform it so as to be inverted upward. As a result, the current path from the electrode body to the negative terminal is cut off. In addition, since the first space including the space provided between the first deformation plate and the current-carrying plate communicates with the external space through the through hole, the first space and the internal space of the battery (third space ), the malfunction of the current interrupting device due to an insufficient pressure difference is suppressed. In addition, the current interrupting device has a permeable membrane at the exit of the through hole to prevent foreign matter from entering the first space.

JP 2015-191825 A

However, in the above current interrupting device, the membrane provided at the exit of the through hole is broken by the rod-shaped member, so foreign matter is likely to enter through the hole created by the breaking. If foreign matter enters from the through-hole, there is a risk that the foreign matter will adhere to members such as the second deformable plate and corrode them. This problem is not limited to the structure that breaks the current-carrying plate like the above-described current interrupting device, but is generally a common problem in the protection mechanism that protects the electrode body when the internal pressure of the secondary battery rises. ing.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to operate a protection mechanism when the internal pressure of a battery rises excessively, and to operate the protection mechanism satisfactorily for a long period of time. The object is to provide a secondary battery that makes it possible.

A secondary battery that solves the above problems includes an electrode body in which a current collecting tab is formed, a case that accommodates the electrode body together with an electrolytic solution and has an opening, a lid that seals the opening, and the lid a current collecting portion provided in the portion and electrically connecting the current collecting tab and the external terminal; and a protection mechanism for generating a displacement portion that is provided in the internal pressure and is displaced according to the internal pressure to contact one of the external terminals to thereby generate a positive/negative short circuit with the other external terminal; and a communication path provided between the displacement member and another member to communicate with the space in which the displacement portion is displaced and the external space.

According to the above configuration, when the difference between the pressure in the space in which the displacement portion is displaced and the pressure in the internal space of the case reaches a predetermined pressure difference, when the displacement portion starts to be displaced toward the external terminal, the space of gas is pushed out into the communication passage. As a result, the pressure inside the space is always adjusted to the same pressure as the outside pressure, so that the displacement portion can be displaced to a predetermined position where the current flowing through the electrode body can be interrupted. In addition, since the communicating path is provided between the insulator and another member adjacent to the insulator, the path length, shape and layout of the communicating path can be easily changed, and the communicating path is formed in which foreign matter is less likely to enter. be able to. Therefore, it is possible to suppress corrosion or the like due to foreign matter adhering to the displacement portion, so that the protection mechanism can be operated satisfactorily for a long period of time.

In the above secondary battery, it is preferable that the communication path is formed by a groove formed in the bottom surface of the insulator and the lid.
According to the above configuration, since the communication path can be provided in a relatively wide range, it is possible to further increase the degree of freedom of the path length, shape, layout, and the like of the communication path.

In the secondary battery, it is preferable that the communication path is defined by a groove formed on the surface of the insulator and the external terminal.
According to the above configuration, the communication path can be configured to be less susceptible to deformation of the lid portion.

In the above secondary battery, it is preferable that the insulator and the lid portion have an uneven structure formed on the outer peripheral portion of the displacement portion.
According to the above configuration, since the uneven structure is provided on the outer peripheral portion of the displacement portion, it is possible to suppress the entry of foreign matter into the space.

In the above secondary battery, the communication path includes a first opening provided on the space side and a second opening provided on the opposite side of the first opening, It is preferable to further include a sealing portion that is provided in the portion and that can expand in response to an increase in pressure in the communication passage.

According to the above configuration, since the sealing portion is provided in the second opening, it is possible to enhance the effect of suppressing the entry of foreign matter. In addition, since the sealing portion can expand according to the pressure of the communication passage, it can receive the gas pushed out from the space with the expanded volume.

ADVANTAGE OF THE INVENTION According to this invention, when the internal pressure of a battery rises excessively, it can operate a protection apparatus reliably, and can operate a protection apparatus favorable for a long period of time.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the outline of a perspective structure about 1st Embodiment which actualized the secondary battery. The top view of the negative electrode current collection part in the same embodiment. FIG. 3 is a cross-sectional view of the negative electrode current collector taken along line 3-3 in FIG. 2; FIG. 3 is a cross-sectional view of the negative electrode current collector taken along line 4-4 in FIG. 2; FIG. 4 is a cross-sectional view of the negative electrode current collecting portion in the same embodiment, showing a state in which the displacement portion is displaced; Sectional drawing of the negative electrode current collection part of the secondary battery of 2nd Embodiment. The top view of the negative electrode current collection part of 2nd Embodiment. FIG. 4 is a cross-sectional view of a main part of a negative electrode current collector of a modified example; Sectional drawing of the negative electrode current collection part of a modification. The top view of the negative electrode current collection part of a modification. The top view of the negative electrode current collection part of a modification.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. An example in which the secondary battery is embodied as a lithium-ion secondary battery mounted in a vehicle such as an electric vehicle or a hybrid vehicle will be described below.

As shown in FIG. 1 , secondary battery 11 includes case 12 having an opening and lid 13 that seals the opening of case 12 . The case 12 and the lid portion 13 are made of a metal material. A positive electrode current collector 21 and a negative electrode current collector 20 are provided on the lid portion 13 . The secondary battery 11 constitutes an assembled battery by connecting the positive current collector 21 and the negative current collector 20 to another secondary battery 11 via a connecting member such as a bus bar.

An internal space 15 formed by the case 12 and the lid portion 13 accommodates an electrode body 14 and an electrolytic solution. The lid portion 13 is provided with a release portion 24 for releasing the gas in the internal space 15 according to the pressure in the internal space 15 and an injection hole 25 for injecting the electrolytic solution.

The electrode body 14 is a laminate in which a plurality of negative electrode plates 18 and a plurality of positive electrode plates 19 are alternately laminated with separators (not shown) interposed therebetween. The positive electrode plate 19 includes a base material made of a metal material such as aluminum or an aluminum alloy, and a positive electrode mixture provided on the base material. The positive electrode mixture contains a lithium-containing composite oxide that is a positive electrode active material, a binder, a conductive agent, and the like. A base material of the negative electrode plate 18 is provided with a positive electrode tab 19A (collecting tab) extending from an end portion thereof.

The negative electrode plate 18 includes a base material made of a metal material such as copper or nickel, and a negative electrode mixture provided on the base material. The negative electrode mixture includes, for example, carbon such as graphite, negative electrode active materials such as metallic lithium and lithium alloys, a binder, a conductive agent, and the like. A base material of the negative electrode plate 18 is provided with a negative electrode tab 18A (collecting tab) extending from an end portion thereof.

The negative electrode plate 18 and the positive electrode plate 19 are stacked with the positions of the negative electrode tab 18A and the positive electrode tab 19A aligned. A plurality of positive electrode tabs 19</b>A are gathered into a bundle to form a positive electrode tab group 23 . Moreover, the negative electrode tabs 18A of the plurality of negative electrode plates 18 are gathered in a bundle to form a negative electrode tab group 22. As shown in FIG. The positive electrode tab group 23 is electrically connected to the positive electrode collector 21 , and the negative electrode tab group 22 is electrically connected to the negative electrode collector 20 .

The configurations of the negative electrode collector 20 and the lid 13 will be described with reference to FIGS. 2 to 4. FIG.
As shown in FIG. 2 , the negative current collector 20 includes a negative external terminal 31 and an insulator 32 . The negative external terminal 31 and the insulator 32 are provided on the surface 13A side of the lid portion 13 . The insulator 32 is made of an insulating material such as resin, is interposed between the negative electrode external terminal 31 and the lid portion 13 , and insulates the lid portion 13 and the negative electrode external terminal 31 from each other.

The insulator 32 includes a bottom wall portion 32A (see FIG. 3) and side wall portions 32B. A through hole 36 is formed in the bottom wall portion 32A. The through hole 36 has a circular shape when viewed from the surface 13A side. The bottom wall portion 32</b>A and the side wall portion 32</b>B define a housing portion 33 that houses the negative electrode external terminal 31 .

As shown in FIG. 3 , the lid portion 13 has a displacement portion 40 at a position corresponding to the through hole 36 of the insulator 32 . The displacement portion 40 is a thinned region of the lid portion 13 and is formed in a circular shape having approximately the same size as the inner diameter of the through hole 36 . The displacement portion 40 has a concave shape protruding toward the electrode body 14 when the pressure in the internal space 15 is normal. Further, the negative external terminal 31 has an annular projecting portion 42 at a position opposed to the displacement portion 40 . The projecting portion 42 and the displacement portion 40 are separated from each other when the pressure in the internal space 15 is normal. A space 43 is formed by the displacement portion 40 and the bottom surface of the negative electrode external terminal 31 . The space 43 functions as a space in which the displacement part 40 can be displaced.

Hole portions 13B, 32C, and 31A are provided in the lid portion 13, the insulator 32, and the negative electrode external terminal 31, respectively. A rivet portion 35 is inserted through these holes 13B, 32C, and 31A. The rivet portion 35 connects the lid portion 13 , the insulator 32 and the negative external terminal 31 by crimping the tip portion thereof. An insulating portion 38 for insulating the lid portion 13 from the rivet portion 35 made of metal is provided in the hole portion 13B of the lid portion 13 . One end of the rivet portion 35 is connected to a conductive portion 37 electrically connected to the electrode body 14 , and the other end is in contact with the negative external terminal 31 . Thereby, the conductive portion 37 and the negative external terminal 31 are electrically connected via the rivet portion 35 . In addition, the positive electrode current collecting portion 21 has a configuration in which the insulator 32 is omitted and the positive electrode external terminal is in contact with the lid portion 13 . As a result, the lid portion 13 is at the same potential as the positive electrode.

As shown in FIG. 4, a groove portion 45 is provided in the bottom surface 32F of the insulator 32. As shown in FIG. The groove portion 45 is formed in a concave shape from the bottom surface 32F toward the opposite surface, and is open at the bottom surface 32F. The groove portion 45 is provided at a position that does not interfere with the rivet portion 35 . In this embodiment, the groove portion 45 extends linearly from the space 43 to reach the side wall portion 32B and opens at the outer surface 32D of the side wall portion 32B. Groove portion 45 configures communication path 46 that communicates space 43 with the external space of secondary battery 11 by sealing the opening on the bottom surface 32</b>F side with the surface of lid portion 13 . The communication path 46 has a first opening 46A communicating with the space 43 and a second opening 46B opening at the outer surface 32D of the side wall 32B. A protection mechanism 50 that protects the electrode body 14 is configured by the displacement portion 40 , the projecting portion 42 of the negative electrode external terminal 31 , and the communication path 46 .

Next, with reference to FIG. 5, the operation of the negative electrode collector 20 of the secondary battery 11 will be described. Since the space 43 is connected to the external space of the secondary battery 11 via the communication path 46, the pressure in the space 43 is maintained at the same pressure as the pressure in the external space. When the pressure in the internal space 15 is within the normal range, the pressure difference between the space 43 and the internal space 15 is smaller than the displacement start pressure at which the displacement portion 40 starts displacement.

When the pressure in the internal space 15 rises due to overcharging of the electrode body 14 or the like, and the pressure difference between the space 43 and the internal space 15 reaches the displacement start pressure at which the displacement portion 40 starts displacement (reversal), the displacement portion 40 starts to displace toward the negative external terminal 31 side. When the displacement portion 40 is displaced toward the negative external terminal 31 side, the space 43 is reduced. The space 43 is a closed space because the lid portion 13 , the insulator 32 , and the negative external terminal 31 are fixed to each other by the rivet portion 35 . Therefore, when the space 43 is not connected to the external space via the communication path 46, the pressure of the space 43 increases as the volume of the space 43 decreases. When the pressure difference between the space 43 and the internal space 15 falls below the displacement start pressure before the displacement portion 40 contacts the projecting portion 42 of the negative electrode external terminal 31, the displacement portion 40 stops the displacement operation.

In this embodiment, since the space 43 is connected to the external space via the communication path 46, as the volume of the space 43 is reduced, part of the gas in the space 43 is pushed out to the first opening 46A. It flows in, passes through the communication path 46, and is discharged from the second opening 46B to the external space. As a result, even when the displacement portion 40 starts to displace, the pressure difference between the space 43 and the internal space 15 is kept equal to or higher than the displacement starting pressure, and the displacement portion 40 protrudes toward the negative electrode external terminal 31 side. It is reversed and comes into contact with the projecting portion 42 of the negative external terminal 31 . As a result, a current flows through the lid portion 13 electrically connected to the positive electrode collector portion 21, and a positive/negative short circuit occurs. On the other hand, since the current does not flow through the electrode body 14, the electrode body 14 can be protected and gas generation accompanying the battery reaction can be suppressed. Further, since the discharge portion 24 is set to open after the displacement portion 40 is turned over, the gas in the internal space 15 is discharged to the external space via the discharge portion 24 .

Thus, in this embodiment, the communicating passage 46 is configured by the groove portion 45 formed in the insulator 32 . For example, when the insulator 32 is molded by an injection molding method, the grooves 45 can be easily formed by providing a projection for forming the grooves 45 in the molding die. Also, when the groove portion 45 is processed after the insulator 32 is molded, the groove portion 45 can be easily formed by cutting the bottom surface 32F of the insulator 32 or the like. Moreover, since the groove 45 can be formed at a position where it does not interfere with the rivet portion 35 on the bottom surface 32F of the insulator 32, the groove 45 having a long path length can be formed. If the path length of the communicating passage 46 is increased in this way, even if a chemical such as a snow-melting agent, water, or foreign matter such as dust enters the communicating passage 46, the mixed foreign matter moves inside the communicating passage 46, and the inner surface of the inner surface of the communicating passage 46 is removed. more chances of colliding with As a result, foreign matter is likely to remain in the communication path 46 , so that it is possible to suppress the foreign matter from reaching the space 43 . Furthermore, even if dew condensation occurs in the space 43 due to a change in temperature, water vapor in the space 43 can be discharged through the communication path 46, so that it is possible to prevent moisture from adhering to the displacement portion 40 for a long period of time. . As a result, adhesion of foreign matter to the displacement portion 40 can be suppressed, and the protection mechanism 50 can be operated satisfactorily for a long period of time.

Effects of the first embodiment will be described.
(1) Since the space 43 partitioned by the displacement portion 40 and the external space are connected by the communication path 46, the pressure inside the space 43 is always maintained at the same pressure as the external pressure. Therefore, while maintaining the pressure difference between the space 43 and the internal space 15 at the displacement start pressure, the displacement portion 40 can be displaced to a position where it contacts the projecting portion 42 of the negative electrode external terminal 31 . In addition, since the communicating path 46 is configured by the groove portion 45 formed in the insulator 32, the path length, shape and layout of the communicating path 46 can be easily changed, and the communicating path 46 is less likely to be mixed with foreign matter. can be done. As a result, it is possible to suppress corrosion or the like caused by foreign matter adhering to the displacement portion 40, so that the protection mechanism 50 can be operated satisfactorily for a long period of time.

(2) Since the communicating path 46 is provided between the insulator 32 and the lid portion 13 having a relatively large surface area, the degree of freedom of the path length, shape, layout, etc. of the communicating path 46 can be further increased.

(Second embodiment)
Next, a second embodiment will be described. The second embodiment is different from the first embodiment in that the negative electrode current collector 20 of the first embodiment is further provided with a configuration for suppressing the entry of foreign matter into the space 43 . In the following, configurations that are mainly different from those of the first embodiment will be described in detail, and for convenience of explanation, detailed descriptions of similar configurations will be omitted.

As shown in FIG. 6 , a convex portion 60 is formed on the outer peripheral portion of the displacement portion 40 of the lid portion 13 . The protrusion 60 is fitted into a recess 61 formed in the bottom surface 32</b>F of the insulator 32 .

As shown in FIG. 7, the convex portion 60 has an annular shape with a part cut away on the groove portion 45 side, and has a substantially C shape. The recess 61 has an annular shape surrounding the space 43 and communicates with the groove 45 . The projection 60 fits into the recess 61 without blocking the groove 45 connected to the space 43 . In addition, the convex portion 60 may have an interference with respect to the width of the concave portion 61, and the convex portion 60 and the concave portion 61 may be fitted to each other by an interference fit. Alternatively, the width of the projection 60 may be smaller than the width of the recess 61, and the projection 60 and the recess 61 may be fitted with a slight gap.

Due to the concave-convex structure consisting of the convex portion 60 provided on the outer peripheral portion of the displacement portion 40 and the concave portion 61 provided on the insulator 32, even if foreign matter such as water enters the small gap between the insulator 32 and the lid portion 13, , the intrusion into the space 43 can be suppressed.

According to the second embodiment, the following effects can be obtained in addition to the effects described in (1) and (2) of the first embodiment.
(3) Since the outer peripheral portion of the displacement portion 40 is provided with a concave-convex structure including the convex portion 60 formed on the lid portion 13 and the concave portion 61 formed on the insulator 32, adhesion of foreign matter to the displacement portion 40 is suppressed. be able to.

Each of the above embodiments can be implemented with the following modifications. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
- As shown in FIG. 8, the second opening 46B of the communication path 46 may be provided with a sealing portion 65 for suppressing entry of foreign matter. The sealing portion 65 expands outward in response to an increase in pressure in the communication path 46, can form a small space with the second opening 46B, and returns to its original state when the pressure in the communication path 46 decreases. return. According to this configuration, the sealing portion 65 can enhance the effect of suppressing the entry of foreign matter. Further, since the sealing portion 65 is expandable according to the pressure of the communication passage 46, the gas pushed out from the space 43 can be received in the small space formed by the expansion. Therefore, while maintaining the pressure difference between the space 43 and the internal space 15 at the displacement start pressure, the displacement portion 40 can be displaced to a position where it contacts the projecting portion 42 of the negative electrode external terminal 31 .

- The communication path 46 may be provided between the groove formed in the insulator 32 and another member adjacent to the insulator 32 . For example, as shown in FIG. 9 , the groove portion 45C is formed on the top surface 32E of the bottom wall portion 32A of the insulator 32 facing the negative external terminal 31 . 46 C of communication paths are comprised by this groove part 45C and the negative electrode external terminal 31. As shown in FIG. The communication path 46C has a first opening 46D that opens on the space 43 side and a second opening 46E that opens near the gap 34 between the side wall portion 32B of the insulator 32 and the negative electrode external terminal 31 . The gas that has flowed into the first opening 46D due to the displacement of the displacement portion 40 is discharged from the second opening 46E through the gap 34 to the external space. According to this aspect, even if the lid portion 13 is relatively thin and the pressure in the internal space 15 rises excessively and the lid portion 13 expands slightly, the communication path 46C prevents the influence of the deformation of the lid portion 13. Hard to accept. Therefore, the gas in the space 43 can be smoothly discharged. Also in this aspect, an uneven structure may be provided between the insulator 32 and the lid portion 13 as in the second embodiment.

- The groove portion 45 formed in the insulator 32 may have a shape other than a straight line. For example, as shown in FIG. 10, a groove 45D having an annular portion may be formed. The groove portion 45D may be connected to the space 43 and may be composed of a substantially annular portion provided on the outer peripheral portion of the displacement portion 40 and a linear portion. Further, as shown in FIG. 11, a groove portion 45E may be formed in a bellows-like shape that bends a plurality of times. By forming the grooves 45D and 45E formed in the insulator 32 in this manner, the communicating passage 46 can be made into which foreign matter is likely to enter.

- In 2nd Embodiment, the uneven|corrugated structure was comprised by the convex part 60 formed in the cover part 13, and the recessed part 61 formed in the insulator 32. FIG. Alternatively, the lid portion 13 may be provided with a concave portion and the insulator 32 may be provided with a convex portion.

- In each of the above-described embodiments, the protection mechanism 50 is provided in the negative electrode current collector 20 . Instead of or in addition to this, the protection mechanism 50 may be provided in the positive current collector 21 . That is, the positive current collector 21 may include the insulator 32 between the positive external terminal and the lid 13 .

- In each of the above-described embodiments, the electrode body 14 has been described by exemplifying the configuration including the electrode body 14 in which a plurality of electrode plates are laminated. Alternatively, the electrode body 14 may be configured by stacking and winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween. Moreover, both the positive electrode current collecting tab and the negative electrode current collecting tab of the electrode body 14 are not provided at one end of the electrode body 14 (the upper end in FIG. 1), but on both sides of the electrode body 14 (the 1, the left end and the right end) may be provided respectively.

- In the above embodiment, the case where the secondary battery 11 is a lithium-ion secondary battery has been exemplified. However, the secondary battery is not limited to this, and may be a secondary battery with other non-aqueous electrolyte, or a secondary battery with an aqueous electrolyte such as a nickel-hydrogen secondary battery.

- The secondary battery 11 may be used in mobile bodies other than vehicles (ships, aircraft, etc.), and may be used in various devices other than mobile bodies.

DESCRIPTION OF SYMBOLS 11... Secondary battery, 12... Case, 13... Cover part, 13A... Surface, 14... Electrode body, 15... Internal space, 18... Positive electrode plate, 19... Negative electrode plate, 20... Negative electrode collector, 21... Positive electrode collector Electric part 31 Negative electrode external terminal 32 Insulator 32A Bottom wall 32B Side wall 32D Outer surface 32E Surface 32F Bottom 35 Rivet 36 Through hole 37 Conductive Part 38... Insulating part 40... Displaced part 42... Protruding part 43... Space 45, 45C, 45D, 45E... Groove part 46, 46C... Communication path 46A, 46D... First opening 46B, 46E ... second opening, 50 ... protection mechanism, 60 ... convex portion, 61 ... concave portion, 65 ... sealing portion.

Claims (3)

an electrode body having a current collecting tab formed thereon;
a case containing the electrode body together with the electrolyte and having an opening;
a lid that seals the opening;
a collector provided on the lid and electrically connecting the collector tab and an external terminal;
a protection mechanism that generates a positive/negative short circuit via the lid when the internal pressure of the case sealed by the lid increases, the secondary battery comprising:
The current collector includes an insulator made of an insulating material and provided between the external terminal and the lid,
The protection mechanism is
a displacement part provided in the lid part and displaced according to the internal pressure to contact one of the external terminals to generate a positive/negative short circuit;
a communication path provided between the insulator and another member adjacent to the insulator and communicating the space in which the displacement portion is displaced and an external space;
A secondary battery, wherein the communication path is configured by a groove formed in the bottom surface of the insulator and the lid. an electrode body having a current collecting tab formed thereon;
a case containing the electrode body together with the electrolyte and having an opening;
a lid that seals the opening;
an external terminal;
a collector provided on the lid and electrically connecting the collector tab and the external terminal;
a protection mechanism that generates a positive/negative short circuit via the lid when the internal pressure of the case sealed by the lid increases, the secondary battery comprising:
The current collector includes an insulator made of an insulating material and provided between the external terminal and the lid,
The protection mechanism is
a displacement part provided in the lid part and displaced according to the internal pressure to contact one of the external terminals to generate a positive/negative short circuit;
a communication path provided between the insulator and another member adjacent to the insulator and communicating the space in which the displacement portion is displaced and an external space;
The communication path is defined by a groove formed in the upper surface of the insulator facing the bottom surface of the external terminal and the bottom surface of the external terminal, and the communication path extends along the longitudinal direction of the upper surface of the lid. exists
secondary battery. The secondary battery according to claim 1 or 2 , wherein the insulator and the lid portion have an uneven structure formed on an outer peripheral portion of the displacement portion.

Images