JP2017199632A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an activation error of a short circuit mechanism owing to a long-term use.SOLUTION: A power storage device 100 comprises a short circuit mechanism 10 which causes a short circuit between a positive electrode terminal 5 and a negative electrode terminal 7 when a pressure of an internal space of a case 1 exceeds a predetermined value. The short circuit mechanism 10 has: a deformable plate 20 electrically connected with one electrode terminal of the positive electrode terminal 5 and the negative electrode terminal 7 and insulated from the other electrode terminal; and a short circuit plate 30 electrically connected with the other electrode terminal. The deformable plate 20 can be deformed to go into a first or second state; the deformable plate becomes convex to the short circuit plate 30 in the first state and in the second state, the deformable plate is concave to the short circuit plate 30. When the pressure of the internal space of the case 1 exceeds the predetermined value, the deformable plate 20 goes into the second state from the first state and thus, the deformable plate 20 is brought into contact with the short circuit plate 30. The deformable plate 20 is formed by an aluminum alloy including iron of which the content is 0.5-2.0 wt.% to 100 wt.% of the whole.SELECTED DRAWING: Figure 1

Description

  The technology disclosed in this specification relates to a power storage device.

  The power storage device may be provided with a mechanism for short-circuiting between the positive electrode and the negative electrode when overcharge or the like occurs. For example, in the power storage device disclosed in Patent Document 1, a short-circuit mechanism is provided between a positive electrode terminal and a negative electrode terminal provided in a case. The short-circuit mechanism includes a deformation plate and a short-circuit plate that are arranged to face each other. The deformation plate is electrically connected to the positive electrode terminal and insulated from the negative electrode terminal. The short-circuit plate is electrically connected to the negative terminal. When the pressure in the internal space of the case exceeds a predetermined value due to overcharge or the like, the deformed plate is deformed and contacts the short circuit plate. Then, the negative electrode terminal and the positive electrode terminal are short-circuited.

JP 2013-235814 A

  The deformation plate of Patent Document 1 is formed by press-molding a metal plate material, and internal stress tends to remain on the deformation plate. For this reason, when the power storage device is used for a long period of time, the residual stress inside the deformable plate is relaxed over time, and the tensile strength of the deformable plate is reduced. As a result, the pressure at which the deformable plate is deformed decreases, and the deformable plate may be deformed before the pressure in the internal space of the case reaches a predetermined value. The present specification discloses a technique for preventing malfunction of the short-circuit mechanism due to long-term use.

  A power storage device disclosed in this specification includes an electrode assembly including a positive electrode and a negative electrode, a case that can store the electrode assembly and an electrolyte, and a case that is provided in the case and electrically connected to the positive electrode of the electrode assembly. A positive electrode terminal connected to the case, a negative electrode terminal provided on the case and electrically connected to the negative electrode of the electrode assembly, and when the pressure in the internal space of the case exceeds a predetermined value, the positive electrode terminal and the negative electrode A short-circuit mechanism for short-circuiting the electrode terminal. The short-circuit mechanism is electrically connected to one electrode terminal of the positive electrode terminal and the negative electrode terminal, insulated from the other electrode terminal, a short-circuit plate electrically connected to the other electrode terminal, It has. The deformable plate can be deformed into a first state that is convex with respect to the short-circuit plate and a second state that is concave with respect to the short-circuit plate. When the pressure in the internal space of the case exceeds the predetermined value, the deformable plate changes from the first state to the second state, and the deformable plate comes into contact with the short-circuit plate. The deformation plate is formed of an aluminum alloy containing iron of 0.5 wt% or more and 2.0 wt% or less when the whole is 100 wt%.

  In the above power storage device, the deformable plate is formed of an aluminum alloy containing 0.5 wt% or more and 2.0 wt% or less of iron. When the aluminum alloy is used, the residual stress generated in the deformed plate when the deformed plate is formed can be reduced. For this reason, there is little residual stress relieved with progress of time, and even if it passes for a long time, the working pressure which a deformation plate deforms does not fall easily. Therefore, the short-circuit mechanism can be prevented from malfunctioning even after a long period of time has elapsed since the manufacture of the power storage device.

Sectional drawing of the electrical storage apparatus which concerns on an Example. The figure which shows the state at the time of normal about the short circuit mechanism which concerns on an Example. The figure which shows the state short-circuited about the short circuit mechanism which concerns on an Example. The graph which shows the relationship between tensile strength and time about the iron containing aluminum alloy used for the deformation | transformation board which concerns on an Example.

  The main features of the embodiments described below are listed. The technical elements described below are independent technical elements and exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Absent.

(Characteristic 1) In the power storage device disclosed in the present specification, the deformation plate may be formed of an aluminum alloy containing 0.7 wt% or more and 1.7 wt% or less of iron when the entire plate is 100 wt%. Good. According to such a configuration, it is possible to further reduce the residual stress generated in the deformation plate when the deformation plate is formed. For this reason, even if a long time passes since manufacture of an electrical storage apparatus, it can prevent suitably that a short circuit mechanism malfunctions.

(Feature 2) In the power storage device disclosed in the present specification, the case may be formed of the aluminum alloy, and the case and the deformation plate may be integrally formed. According to such a structure, since a case and a deformation | transformation board can be shape | molded by the same shaping | molding process, a shaping | molding process can be reduced by that much.

(Characteristic 3) In the power storage device disclosed in the present specification, the deformation plate may be formed separately from the case. According to such a configuration, different materials can be used for the case and the deformable plate. For this reason, while using said aluminum alloy for a deformation | transformation board, another material suitable for a case can be used for a case.

  Hereinafter, a power storage device 100 according to an embodiment will be described with reference to the drawings. As shown in FIG. 1, the power storage device 100 includes a case 1, an electrode assembly 3 accommodated in the case 1, a positive electrode terminal 5 and a negative electrode terminal 7 fixed to the case 1. The electrode assembly 3 and the positive electrode terminal 5 are electrically connected, and the electrode assembly 3 and the negative electrode terminal 7 are electrically connected. In addition, the power storage device 100 includes a short-circuit mechanism 10 fixed to the case 1. The inside of the case 1 is injected with an electrolytic solution, and the electrode assembly 3 is immersed in the electrolytic solution.

  The case 1 is made of metal and is a substantially rectangular parallelepiped box-shaped member. The case 1 includes a main body 111 and a lid portion 112 fixed to the main body 111. The lid part 112 covers the upper part of the main body 111. Mounting holes 81 and 82 are formed in the lid portion 112. The positive electrode terminal 5 communicates with the inside and outside of the case 1 through the attachment hole 81, and the negative electrode terminal 7 communicates with the inside and outside of the case 1 through the attachment hole 82. The lid portion 112 is electrically connected to the positive electrode terminal 5. An insulating member 61 is disposed between the lid portion 112 and the negative electrode terminal 7. The insulating member 61 insulates the lid portion 112 from the negative electrode terminal 7.

  The electrode assembly 3 includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The electrode assembly 3 is configured by laminating a plurality of laminated bodies including a positive electrode, a negative electrode, and a separator. Each of the plurality of positive electrodes and each of the plurality of negative electrodes includes a current collecting member and an active material layer formed on the current collecting member. As the current collecting member, one used for the positive electrode is, for example, an aluminum foil, and one used for the negative electrode is, for example, a copper foil. The electrode assembly 3 includes a positive current collecting tab 51 provided for each positive electrode and a negative current collecting tab 52 provided for each negative electrode. The positive electrode current collecting tab 51 is formed on the upper end portion of the positive electrode. The negative electrode current collecting tab 52 is formed on the upper end portion of the negative electrode. The positive electrode current collecting tab 51 and the negative electrode current collecting tab 52 protrude above the electrode assembly 3. The plurality of positive electrode current collecting tabs 51 are combined into one and fixed to the positive electrode lead 53. The plurality of negative electrode current collecting tabs 52 are combined into one and fixed to the negative electrode lead 54.

  The positive electrode lead 53 is connected to the positive electrode current collecting tab 51 and the positive electrode terminal 5. The positive electrode current collecting tab 51 and the positive electrode terminal 5 are electrically connected via the positive electrode lead 53. The negative electrode lead 54 is connected to the negative electrode current collecting tab 52 and the negative electrode terminal 7. The negative electrode current collecting tab 52 and the negative electrode terminal 7 are electrically connected via the negative electrode lead 54.

  The short-circuit mechanism 10 will be described with reference to FIG. As shown in FIG. 2, the short-circuit mechanism 10 is provided on the lid portion 112 of the case 1. The short-circuit mechanism 10 includes a short-circuit plate 30 and a deformation plate 20. The short circuit board 30 is a metal member and has conductivity. The short-circuit plate 30 is formed in a substantially rectangular shape in plan view, and is disposed above the deformation plate 20. The short-circuit plate 30 is electrically connected to the negative electrode terminal 7. Insulating members 61 and 62 are disposed between the short-circuit plate 30 and the lid portion 112 of the case 1. The short-circuit plate 30 is supported on the lid portion 112 by insulating members 61 and 62. The insulating member 61 insulates the negative electrode terminal 7 from the lid portion 112 and also insulates one end of the short-circuit plate 30 from the lid portion 112. The insulating member 62 insulates the other end of the short-circuit plate 30 and the lid portion 112. For this reason, the short-circuit plate 30 is insulated from the lid portion 112. That is, the short-circuit plate 30 is insulated from the positive electrode terminal 5.

  The deformable plate 20 is formed by plastic processing (for example, press processing) a plate material having a constant plate thickness, and is a conductive diaphragm that is circular when viewed in plan. The deformation plate 20 is fixed to the lid portion 112 of the case 1 by welding or the like. The thickness of the deformable plate 20 is smaller than the thickness of the lid 112 and smaller than the thickness of the short-circuit plate 30. The deformation plate 20 is convex downward (concave toward the short-circuit plate 30) when the pressure in the case 1 is lower than a predetermined value. The outer peripheral portion of the deformation plate 20 is joined to the lid portion 112 of the case 1. For this reason, the pressure in the case 1 acts on the lower surface of the deformation plate 20. On the other hand, atmospheric pressure acts on the upper surface of the deformation plate 20. The deformation plate 20 is electrically connected to the lid portion 112. As described above, the lid portion 112 is electrically connected to the positive electrode terminal 5 and insulated from the negative electrode terminal 7. For this reason, the deformation plate 20 is electrically connected to the positive electrode terminal 5 and insulated from the negative electrode terminal 7.

  The deformation plate 20 is formed of an aluminum alloy containing iron (Fe). The iron-containing aluminum alloy used for the deformable plate 20 has an iron (Fe) content of 0.5 wt% or more and 2.0 wt% or less when the whole is 100 wt%, in particular 0.7 wt%. It is preferable that it is above and 1.7 wt% or less. A softening effect can be generated by setting the iron content to 0.5 wt% or more. On the other hand, when the iron content is 2.0 wt% or less, the corrosion resistance can be secured, and when the iron content is 1.7 wt% or less, the corrosion resistance can be further increased. The iron-containing aluminum alloy used for the deformable plate 20 may contain, for example, silicon (Si), copper (Cu), zinc (Zn), and inevitable impurities in addition to iron (Fe).

  With reference to FIG.2 and FIG.3, the structure by which the positive electrode terminal 5 and the negative electrode terminal 7 are short-circuited by the short circuit mechanism 10 is demonstrated concretely. As shown in FIG. 2, when the pressure in the case 1 is equal to or lower than a predetermined value, the deformable plate 20 is convex downward. That is, the deformable plate 20 is in a concave first state toward the short-circuit plate 30. As described above, the deformation plate 20 is electrically connected to the positive electrode terminal 5 and insulated from the negative electrode terminal 7. For this reason, an energization path via the short-circuit mechanism 10 is not formed between the positive electrode terminal 5 and the negative electrode terminal 7. When the pressure in the case 1 increases, the pressure acting on the lower surface of the deformation plate 20 increases. On the other hand, atmospheric pressure acts on the upper surface of the deformation plate 20. For this reason, when the pressure in the case 1 rises and reaches a predetermined value, as shown in FIG. 3, the deformable plate 20 is inverted and changes to a convex state upward. That is, the deformable plate 20 enters the second state that is convex toward the short-circuit plate 30. At this time, the upper surface of the deformation plate 20 contacts the short-circuit plate 30. The deformation plate 20 is electrically connected to the positive electrode terminal 5. On the other hand, the short-circuit plate 30 is electrically connected to the negative electrode terminal 7. For this reason, when the deformation | transformation board 20 and the short circuit board 30 contact, between the positive electrode terminal 5 and the negative electrode terminal 7, the electricity supply path via the deformation board 20 and the short circuit board 30 will be formed. That is, the positive electrode terminal 5 and the negative electrode terminal 7 are short-circuited. As a result, the current flowing through the electrode assembly 3 can be reduced.

  With reference to FIG. 4 and Table 1, the result of having measured the time-dependent change of the residual stress of the iron containing aluminum alloy used for the deformation | transformation board 20 is demonstrated. In the experiment, a test piece was manufactured by pressing the iron-containing aluminum alloy plate according to the example, and the test piece was left under a certain temperature environment (80 ° C. in the experiment) for a predetermined time, and then the test piece. A tensile test was performed on the test piece. Since the test piece is press-molded, a residual stress is generated inside. For this reason, when the test piece is left in a constant temperature environment, the residual stress remaining on the test piece is released. Here, if the residual stress remaining on the test piece is large, the tensile strength of the test piece increases. On the other hand, when the residual stress remaining on the test piece is small, the tensile strength of the test piece becomes low. Therefore, the greater the rate of decrease in the tensile strength of the test piece (the rate of decrease in the tensile strength after the lapse of the predetermined time with respect to the tensile strength before the lapse of the predetermined time), the more residual stress remaining on the test piece is released. It will be done. That is, when the decrease rate of the tensile strength of the test piece is large, it can be evaluated that the residual stress generated in the test piece during press working is large. On the other hand, when the decrease rate of the tensile strength of the test piece is small, the test piece is tested during press working. It can be evaluated that the residual stress generated in the piece is small. In the experiment, it was evaluated how the release of the residual stress of the test piece progressed over time by changing the time in which the test piece was left in a constant temperature environment and performing a tensile test. As an iron-containing aluminum alloy, when the whole is 100 wt%, iron (Fe) is 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, respectively. %, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, and 1.7 wt% were used. As a representative example, the results of an iron-containing aluminum alloy containing 0.7 wt% of iron are shown below. As the iron content increases, the softening effect increases. For this reason, among the above, the result about the iron-containing aluminum alloy containing the iron content of 0.7 wt% with the smallest iron content was shown, and the residual stress of the iron-containing aluminum alloy used in this example was evaluated. Moreover, the same test was done also about aluminum alloy A1050 as a comparative example. The aluminum alloy A1050 had an aluminum (Al) content of 99.50 wt% or more and 0.40 wt% or less of iron (Fe) or the like when the whole was 100 wt%.

  Table 1 shows the relationship between the tensile strength and time of the iron-containing aluminum alloy used in the experiment and the aluminum alloy A1050 according to the comparative example, and FIG. 4 is a graph of Table 1. As shown in Table 1 and FIG. 4, the tensile strength of the aluminum alloy A1050 of the comparative example decreased from 156 Mpa with the passage of time, and after 720 hours became 115.44 Mpa, a decrease of about 26%. On the other hand, the tensile strength of the iron-containing aluminum alloy used for the deformable plate 20 was 147.62 Mpa after 720 hours from 167 Mpa, a decrease of about 12%. From this result, it was found that the iron-containing aluminum alloy used for the deformed plate 20 had a lower rate of decrease in tensile strength over time than aluminum alloy A1050. That is, it was found that the iron-containing aluminum alloy used for the deformable plate 20 has a small compressive residual stress generated in the test piece during press molding, and the corresponding compressive residual stress is also reduced. That is, it can be said that the internal residual stress of the iron-containing aluminum alloy used for the deformable plate 20 is more relaxed.

  Next, the results of evaluating the corrosion resistance of the iron-containing aluminum alloy used for the deformable plate 20 will be described. In the experiment, a test piece of the iron-containing aluminum alloy according to the example was produced, and the test piece was left in a state of being immersed in 3.5 wt% saline under a constant temperature environment (80 ° C. in the experiment). After leaving for 50 hours, the presence or absence of a change in the surface roughness of the test piece was confirmed. If there is no change in the surface roughness of the test piece after being left as compared with the surface roughness of the test piece before being left, it can be evaluated that the test piece has secured corrosion resistance. As the iron-containing aluminum alloy, those containing 1.5 wt%, 1.7 wt%, and 2.0 wt% of iron were used. As a result, in all the test pieces of the iron-containing aluminum alloy used, no change in surface roughness was observed before and after being left. That is, it was found that the iron-containing aluminum alloy used for the deformable plate 20 can ensure corrosion resistance when the iron content is 2.0 wt% or less.

  Since the deformable plate 20 of the present embodiment is formed by the above-described iron-containing aluminum alloy, the residual stress generated during forming is small. When the deformed plate is formed using the aluminum alloy A1050 according to the comparative example, the residual stress generated at the time of forming is large. Therefore, the residual stress is relaxed with time, and the creep resistance is poor. For this reason, when the deformed plate formed using the aluminum alloy A1050 according to the comparative example passes for a long time, the mechanical strength of the deformed plate is greatly reduced due to relaxation of the residual stress, and the pressure in the internal space of the case becomes the set value. There is a risk of flipping before reaching. Since the deformable plate 20 of the present embodiment is formed using the above-described iron-containing aluminum alloy, even if the power storage device 100 is used for a long period of time, the mechanical strength of the deformable plate 20 is hardly lowered, and the short-circuit mechanism 10 is It becomes difficult to cause malfunction. Further, even when the deformed plate is formed using the aluminum alloy A1050 according to the comparative example, the residual stress can be relieved in advance by performing a heat treatment or the like after the press working. The number of steps (ie, heat treatment step) will increase. By using the above-described iron-containing aluminum alloy, the deformation plate 20 of the present embodiment can reduce the residual stress of the deformation plate 20 without performing a heat treatment or the like after forming. Therefore, by forming the deformable plate 20 using the above-described iron-containing aluminum alloy, it is possible to easily manufacture the power storage device 100 in which the short-circuit mechanism 10 is unlikely to malfunction even after a long period of time has elapsed since manufacture. .

  In the embodiment described above, the deformable plate 20 is formed separately from the lid portion 112 and then joined to the lid portion 112. For this reason, the deformation | transformation board 20 and the cover part 112 can be shape | molded using a different material. For example, the deformable plate 20 can be formed using the above-described iron-containing aluminum alloy, and the lid portion 112 can be formed using aluminum alloy A1050, aluminum alloy A3003, or the like. Aluminum alloy A3003 is an aluminum alloy containing 1.0 wt% or more and 1.5 wt% or less of manganese (Mn), and has a feature of high strength. Although it is necessary to select a material for the deformable plate 20 in consideration of deformation when the pressure in the internal space of the case exceeds a predetermined value, it is suitable to use a material that is hard to deform and has high strength. ing. When the deformable plate 20 and the lid portion 112 are formed separately, the power storage device 100 can be manufactured using materials suitable for the deformable plate 20 and the lid portion 112. Unlike the above-described embodiment, the lid portion 112 of the case 1 and the deformation plate 20 may be integrally formed. If the deformable plate 20 and the lid portion 112 are integrally formed, the processing steps during manufacturing and the joining step for joining the lid portion 112 and the deformable plate 20 can be reduced, and the deformable plate 20 can be formed more easily. .

  As mentioned above, although the specific example of the technique disclosed by this specification was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing.

1: Case 3: Electrode assembly 5: Positive electrode terminal 7: Negative electrode terminal 10: Short circuit mechanism 20: Deformation plate 30: Short circuit plate 61, 62: Insulating member 100: Power storage device 112: Lid

Claims (4)

An electrode assembly comprising a positive electrode and a negative electrode;
A case capable of storing the electrode assembly and the electrolyte;
A positive electrode terminal provided in the case and electrically connected to the positive electrode of the electrode assembly;
A negative electrode terminal provided in the case and electrically connected to the negative electrode of the electrode assembly;
A short-circuit mechanism for short-circuiting the positive electrode terminal and the negative electrode terminal when the pressure in the internal space of the case exceeds a predetermined value,
The short-circuit mechanism is electrically connected to one electrode terminal of the positive electrode terminal and the negative electrode terminal, electrically connected to the deformation plate insulated from the other electrode terminal, and electrically connected to the other electrode terminal. A short circuit board, and
The deformable plate is deformable into a first state that is convex with respect to the short-circuit plate and a second state that is concave with respect to the short-circuit plate,
When the pressure in the internal space of the case exceeds the predetermined value, the deformation plate is changed from the first state to the second state, the deformation plate is in contact with the short-circuit plate,
The deformation plate is formed of an aluminum alloy containing 0.5 wt% or more and 2.0 wt% or less of iron when the deformation plate is 100 wt% as a whole.   2. The power storage device according to claim 1, wherein the deformation plate is formed of an aluminum alloy containing iron of 0.7 wt% or more and 1.7 wt% or less when the whole is 100 wt%. The case is formed of the aluminum alloy,
The power storage device according to claim 1, wherein the case and the deformation plate are integrally formed. The power storage device according to claim 1, wherein the deformable plate is formed separately from the case.