JP6103222B2 - Power storage device - Google Patents

Description

  The present invention relates to a power storage device.

  A vehicle such as an EV (Electric Vehicle) or a PHV (Plug in Hybrid Vehicle) is equipped with a secondary battery such as a lithium ion battery as a power storage device that stores power supplied to an electric motor serving as a prime mover. The secondary battery has an electrode assembly in which a negative electrode obtained by applying a negative electrode active material to a metal foil and a positive electrode obtained by applying a positive electrode active material to a metal foil are insulated with a separator and laminated in layers. The case of the secondary battery contains an electrode assembly and an electrolytic solution, and a pressure release valve (gas discharge valve) for releasing the pressure inside the case to the outside of the case is provided on the wall surface of the case.

  Since aluminum has a property of decreasing in strength as the temperature rises, when an aluminum pressure relief valve is employed as in the secondary battery described in Patent Document 1, the pressure relief valve increases as the case temperature rises. The strength of the will decrease. As a result, in the secondary battery described in Patent Document 1, when the case becomes hot, the pressure release valve may operate at a pressure extremely lower than the preset operating pressure. Therefore, the secondary battery described in Patent Document 2 employs a pressure release valve formed of a clad material of a strong metal material such as nickel and aluminum. According to such a secondary battery described in Patent Document 2, the pressure relief valve caused by temperature change is achieved by improving the strength of the pressure relief valve with a high-strength metal material while ensuring the conductivity in the pressure relief valve with aluminum. The fluctuation of the operating pressure can be suppressed.

JP 2011-181214 A JP 2001-126682 A

  By the way, in a pressure relief valve formed of a clad material, there is a possibility that warpage may occur or peel off due to a difference in thermal expansion coefficient of each metal constituting the clad material, and there is room for improvement in this respect.

  The present invention has been made paying attention to such problems existing in the prior art, and its purpose is to suppress the fluctuation of the operating pressure of the pressure release valve due to the temperature change of the case, while reducing the pressure. An object of the present invention is to provide a power storage device that can suppress warping and peeling with an open valve.

A power storage device for solving the above problems includes a case in which an electrode assembly and an electrolytic solution are accommodated, and has a pressure release valve on a wall surface of the case for releasing the pressure in the case to the outside of the case. is made of aluminum, the wall surface of the case having a pressure relief valve, the part of the surface of the at least pressure relief valve Ri anodized layer there, the pressure relief valve has a cleavage groove, the anodized The layer is in a portion including the cleavage groove, and the ratio between the thickness of the pressure relief valve and the thickness of the anodized layer in the cleavage groove is 2: 1 .

  The anodized layer is unlikely to change in strength due to temperature changes. According to the above configuration, the strength of the pressure release valve can be ensured even when the temperature of the case rises, and fluctuations in the operating pressure of the pressure release valve due to the temperature change of the case can be suppressed. Furthermore, according to the said structure, since a pressure release valve is not formed with a clad material, it can also suppress that a pressure release valve generate | occur | produces or peels.

Since the cleavage groove portion of the pressure release valve is thin, the strength is likely to decrease due to the temperature change of the case. For this reason, in the pressure release valve in which the cleavage groove is formed, the fluctuation of the operating pressure of the pressure release valve due to the temperature change of the case may become more remarkable. According to the said structure, the fall of the intensity | strength by the temperature change of a case becomes difficult to produce in a cleavage groove. Therefore, even if it is the pressure relief valve in which the cleavage groove was formed, it can suppress that an operating pressure fluctuates due to the temperature change of a case.

Examples of the portion where the anodized layer is formed include the entire surface on the pressure release valve.
According to the said structure, the intensity | strength of the pressure release valve itself can be ensured more, and the fluctuation | variation of the operating pressure of the pressure release valve resulting from the temperature change of a case can be suppressed more.

Anodized layer, it is also possible that form on both sides of the wall surface of the case with a pressure relief valve.
According to the said structure, the intensity | strength of the pressure release valve itself can be ensured more, and the fluctuation | variation of the operating pressure of the pressure release valve resulting from the temperature change of a case can be suppressed more.

  An example of the power storage device is a secondary battery.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that curvature and peeling arise with a pressure release valve, suppressing the fluctuation | variation of the operating pressure of the pressure release valve resulting from the temperature change of a case.

The perspective view which shows the external appearance of a secondary battery. The top view which shows the surface of a pressure release valve. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. The graph which shows the relationship between the temperature of a case, and a working pressure about the pressure release valve in which the alumite process layer was formed, and the pressure release valve in which the alumite process layer was not formed.

Hereinafter, an embodiment embodying a power storage device will be described with reference to FIGS.
As shown in FIG. 1, in a secondary battery 10 as a power storage device, an electrode assembly 12 is accommodated in a case 11. The case 11 also contains an electrolyte solution together with the electrode assembly 12. The case 11 includes a bottomed cylindrical case main body 13 and a flat lid 14 that closes an opening 13 a into which the electrode assembly 12 is inserted into the case main body 13. In a state where the case body 13 and the lid body 14 are assembled as the case 11, the front surface 14 a of the lid body 14 is a surface located outside the case 11, and the back surface 14 b of the lid body 14 is located inside the case 11. It is a surface to be located. And in case 11, the outer peripheral part in the back surface 14b of the cover body 14 and the opening part 13a of the case main body 13 become the junction part 14c joined mutually. Both the case main body 13 and the lid body 14 are made of aluminum. In addition, the secondary battery 10 of this embodiment is a rectangular battery whose appearance is a rectangular shape because the case body 13 has a bottomed rectangular tube shape and the lid body 14 has a rectangular flat plate shape. Moreover, the secondary battery 10 of this embodiment is a lithium ion battery.

  The electrode assembly 12 includes a positive electrode, a negative electrode, and a separator that insulates the positive electrode from the negative electrode. The positive electrode is configured by applying a positive electrode active material to both surfaces of a positive metal foil (aluminum foil). The negative electrode is configured by applying a negative electrode active material to both surfaces of a negative electrode metal foil (copper foil). The electrode assembly 12 has a stacked structure in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked and a separator is interposed between the electrodes. In addition, a positive electrode terminal 15 and a negative electrode terminal 16 are electrically connected to the electrode assembly 12. Each part of the positive electrode terminal 15 and the negative electrode terminal 16 is exposed to the outside of the case 11 from the lid body 14. Further, a ring-shaped insulating ring 17 a for insulating from the case 11 is attached to the positive terminal 15 and the negative terminal 16, respectively.

  Further, the case 11 is cleaved when the pressure in the case 11 reaches an open pressure, which is a predetermined pressure, so that the pressure in the case 11 does not increase too much. A pressure release valve 20 is provided for opening the valve. In this embodiment, the pressure release valve 20 is located on the lid body 14 as a wall surface of the case 11. The opening pressure of the pressure release valve 20 is set to a pressure at which the case 11 itself and the joint 14c between the case main body 13 and the lid body 14 can be broken before cracks or breakage can occur. The pressure release valve 20 has a thin plate-like valve body 21 that is thinner than the plate thickness of the lid body 14. The valve body 21 is located at the bottom of a recess 22 that is recessed in the surface 14 a of the lid body 14 and is formed integrally with the lid body 14. That is, in the pressure release valve 20, the surface 21 a on the valve body 21 is a part of the surface 14 a of the lid body 14 of the case 11, and the back surface 21 b (FIG. 3) on the valve body 21 is the back surface of the lid body 14. 14b. Further, the pressure release valve 20 is made of aluminum like the case 11.

  As shown in FIG. 2, the pressure relief valve 20 of this embodiment has a track-shaped periphery in which two parallel straight portions 26 and 27 are connected by arc portions 28 and 29. The valve body 21 of the pressure release valve 20 is connected to the periphery of the pressure release valve 20 and has a track shape like the pressure release valve 20. Moreover, the surface 21a of the valve body 21 has a cleavage groove. The cleavage groove includes an intersecting groove 31, a plurality of arc-shaped grooves 32 and 33 along the arc portions 28 and 29, and a plurality of linear grooves 34 and 35 along the straight portions 26 and 27. The intersecting groove 31 includes two straight grooves 36 and 37 that intersect at an intersecting portion P as a cleavage starting point. In this embodiment, the intersecting grooves 31, the arc-shaped grooves 32 and 33, and the linear grooves 34 and 35 are all V-shaped grooves.

  As shown in FIG. 2, on the surface 21 a of the valve body 21, assuming virtual straight lines Y <b> 1 and Y <b> 2 along the intersecting grooves 31, a plurality of virtual straight lines Y <b> 1 and Y <b> 2 and a plurality of peripheral edges of the pressure release valve 20 are surrounded. Regions S1, S2, S3 and S4 are assumed. The region S1 and the region S2 are regions including the straight line portions 26 and 27, and are point-symmetric with respect to the intersection point of the virtual straight line Y1 and the virtual straight line Y2. The region S3 and the region S4 are regions including the arc portions 28 and 29, and are point-symmetric with respect to the intersection of the virtual straight line Y1 and the virtual straight line Y2.

  As shown in FIG. 1, the lid 14 of the case 11 has anodized layers 24 and 25 on both the front surface 14a and the back surface 14b. In the case 11 of this embodiment, the joining portion 14c on the back surface 14b of the lid body 14 and the outer peripheral portion on the front surface 14a of the lid body 14 do not have the alumite treatment layers 24 and 25, and these portions are excluded. Anodized layers 24 and 25 are provided on the entire surface 14 a and back surface 14 b of the lid 14.

  As shown in FIG. 3, in this embodiment, an alumite treatment layer 24 is also provided on the entire surface 21 a of the valve body 21 of the pressure release valve 20. Here, on the surface 21 a of the valve body 21, the alumite treatment layer 24 is present in the cleavage groove on the surface 21 a of the valve body 21 and the portion other than the cleavage groove on the surface 21 a of the valve body 21. The cleavage groove on the surface 21a of the valve body 21 has an alumite treatment layer 24 over the entire groove surface. Although FIG. 3 shows the anodized layer 24 in the straight groove 36, the groove surfaces of the other straight grooves 37, arc-shaped grooves 32 and 33, and straight grooves 34 and 35, which are other cleavage grooves, An anodized layer 24 is provided. Further, the pressure release valve 20 has an alumite treatment layer 25 on the entire back surface 21 b of the valve body 21 which is a part of the back surface 14 b of the lid 14 of the case 11. In the valve body 21 of the pressure release valve 20, the thickness excluding the anodized layers 24 and 25 on the front surface 21a and the back surface 21b is such that the thickness W2 of the valve body 21 in the cleavage groove portion is in a portion other than the cleavage groove. It is thinner than the thickness W1 of the valve body 21. And thickness W3 of the alumite process layers 24 and 25 in the surface 21a and the back surface 21b of the valve body 21 of the pressure release valve 20 is thinner than thickness W1 or thickness W2, for example. For example, the thickness W2 and the thickness W3 have a relationship in which the ratio of the thickness W2 to the thickness W3 is 2: 1.

  Next, the operation of this embodiment will be described with reference to FIG. FIG. 4 shows data of experiments conducted by the present applicant for the pressure release valve 20 in which the anodized layers 24 and 25 are formed and the pressure release valve 20 in which the anodized layers 24 and 25 are not formed. FIG.

  As shown in FIG. 4, in the present embodiment in which the front surface 21 a and the rear surface 21 b of the valve body 21 of the pressure release valve 20 are subjected to alumite treatment, the operating pressure is unlikely to decrease even if the temperature of the case 11 increases. This is because the strength of the pressure release valve 20 can be ensured even if the temperature of the case 11 rises due to the properties of the anodized layers 24 and 25 that are less likely to change in strength due to temperature changes. In this embodiment, even when the case 11 becomes high temperature, the pressure release valve 20 can be operated with an operating pressure that is hardly different from a preset operating pressure.

  On the other hand, when the surface 21a and the back surface 21b of the valve body 21 of the pressure release valve 20 are not subjected to an alumite treatment, the degree of decrease in the strength of the pressure release valve 20 due to the temperature rise of the case 11 is caused by the property of aluminum. Compared to For this reason, when case 11 becomes high temperature, there exists a possibility that the pressure relief valve 20 may operate | move with the operating pressure in which the fall degree from the preset operating pressure is large compared with this embodiment.

Next, a method for forming the alumite treatment layers 24 and 25 on the lid 14 of the case 11 will be mainly described as a method for manufacturing the secondary battery 10.
Before subjecting the lid 14 of the case 11 to the alumite treatment, first, a cleavage groove such as a cross groove 31, arc-shaped grooves 32 and 33, and linear grooves 34 and 35 is formed on the surface 21 a of the valve body 21 of the pressure release valve 20. To do. After the formation of the cleavage groove, the alumite treatment on the lid 14 and the pressure release valve 20 of the case 11 is started. In the alumite treatment, masking is applied to the outer peripheral portion of the back surface 14b of the lid body 14 that functions as the joint portion 14c of the case 11 with the case body 13 and the outer peripheral portion of the front surface 14a of the lid body 14. The alumite treatment is performed by electrolyzing the lid 14 of the aluminum case 11 with the pressure release valve 20 integrally formed in a treatment bath such as dilute sulfuric acid or oxalic acid. Anodized layers 24 and 25 are formed on the front surface 14 a and the back surface 14 b of the lid 14 of the case 11 and the front surface 21 a and the back surface 21 b of the valve body 21 of the pressure release valve 20. When the formation of the anodized layers 24 and 25 is completed, the opening 13a of the case main body 13 of the case 11 and the outer peripheral portion of the back surface 14b of the lid body 14 are joined by, for example, laser welding. Thereby, the case main body 13 and the cover body 14 of the case 11 are joined by the joining part 14c.

Therefore, according to the present embodiment, the following effects can be obtained.
(1) Since the pressure release valve 20 has the alumite treatment layers 24 and 25 on the entire surface 21a and back surface 21b of the valve body 21, the operating pressure of the pressure release valve 20 due to the temperature change of the case 11 is reduced. Variations can be suppressed. Furthermore, since the clad material is not employed for the valve body 21 of the pressure release valve 20, it is possible to suppress the warp or peeling of the pressure release valve 20.

  (2) In the valve body 21 of the pressure release valve 20, since the thickness W2 of the cleavage groove portion is thinner than the thickness W1 of the other portions, the cleavage groove portion in the valve body 21 has strength due to the temperature change of the case 11. Decline is likely to occur. For this reason, in the pressure release valve 20 in which the cleavage groove is formed, the fluctuation of the operating pressure of the pressure release valve 20 due to the temperature change of the case 11 may become more remarkable. According to the present embodiment, since the alumite treatment layer 24 is also present in the cleavage groove in the valve body 21 of the pressure release valve 20, it is difficult for the strength to decrease due to the temperature change of the case 11 in the cleavage groove. Therefore, even if it is the pressure release valve 20 in which the cleavage groove was formed, it can suppress that an operating pressure fluctuates due to the temperature change of the case 11.

  (3) Outer peripheral portion of the front surface 14a of the lid body 14 and outer peripheral surface of the rear surface 14b among the front surface 14a and the rear surface 14b of the lid body 14 of the case 11 and the front surface 21a and the rear surface 21b of the valve body 21 of the pressure release valve 20 In order to perform the alumite treatment on the portion other than the portion, alumite treatment layers 24 and 25 are formed on most of both surfaces of the lid 14 of the case 11. Thereby, for example, the portion to be masked can be reduced as compared with the case where the alumite treatment layers 24 and 25 are formed only on one surface of the lid 14 of the case 11. It can be simplified.

  (4) When anodizing the lid 11 of the case 11 and the pressure release valve 20, masking is applied to the outer peripheral portion of the back surface 14 b of the lid 14 that functions as a joint 14 c between the lid 14 and the case body 13. Therefore, the anodized layers 24 and 25 are not formed on the outer peripheral portion of the back surface 14 b of the lid body 14. For this reason, when the case main body 13 and the lid body 14 of the case 11 are welded, the alumite treatment layers 24 and 25 become foreign matters, and the joint of the joint portion 14c between the case main body 13 and the lid body 14 of the case 11 is weak. It is suppressed.

  (5) After forming a cleavage groove such as a cross groove 31, arc-shaped grooves 32, 33, and linear grooves 34, 35 on the surface 21a of the valve body 21 of the pressure relief valve 20, the lid 14 of the case 11 and the pressure relief. Anodizing the valve 20 is performed. If a cleavage groove is formed on the surface 21a of the valve element 21 of the pressure relief valve 20 after the alumite treatment, the alumite treatment layers 24 and 25 at the formation portion of the cleavage groove may be peeled off. It can suppress that such a problem arises.

The above-described embodiment can be modified as follows.
○ Even if the anodized layer 24 is formed on the outer peripheral portion of the surface 14a of the lid 14 of the case 11 and the influence on the bonding of the bonding portion 14c is small, masking of the outer peripheral portion of the surface 14a of the lid 14 is performed. May be omitted.

  The lid 14 of the case 11 may have anodized layers 24 and 25 at the joint 14c with the case main body 13. However, in order to prevent the bonding of the bonding portion 14c from being lowered by the anodized layers 24 and 25, it is desirable to form the anodized layers 24 and 25 in a part of the bonding portion 14c.

  The cover body 14 of the case 11 may be configured not to have the alumite treatment layers 24 and 25 in a wider range than the outer peripheral portion of the front surface 14 a of the cover body 14 of the case 11 and the outer peripheral portion of the back surface 14 b of the cover body 14. For example, the front surface 21a and the back surface 21b of the valve body 21 of the pressure release valve 20 have anodized layers 24 and 25, and the portions other than the pressure release valve 20 in the front surface 14a and the back surface 14b of the lid body 14 of the case 11 It is good also as a form which does not have the alumite process layers 24 and 25. In short, it is only necessary to have the alumite treatment layers 24 and 25 on the front surface 14a and the back surface 14b of the lid body 14 of the case 11 and at least on the portion including the front surface 21a and the back surface 21b of the valve body 21 of the pressure release valve 20. .

  The pressure release valve 20 may have anodized layers 24 and 25 on part of the front surface 21a and the back surface 21b on the valve body 21. However, in order to suppress the fluctuation of the operating pressure of the pressure release valve 20 due to the temperature change of the case 11 as much as possible, most of the surface 21a and the back surface 21b on the valve body 21 of the pressure release valve 20 is an alumite treatment layer. It is desirable to have 24,25.

The shape of the pressure release valve 20 may be a shape other than the track shape such as a circular shape.
O The shape and location of the cleavage groove of the pressure release valve 20 may be changed.
O The cross-sectional shape of the cleavage groove of the pressure release valve 20 may be changed.

  The pressure release valve 20 may be a separate part from the lid 14 of the case 11, and the pressure release valve 20 may be joined to the lid 14 of the case 11. The joining is performed by, for example, laser welding. Even in such a configuration, the pressure release valve 20 is made of aluminum.

The valve body 21 of the pressure release valve 20 may have a cleavage groove on the back surface 21b.
(Circle) the valve body 21 of the pressure release valve 20 may have the alumite process layers 24 and 25 only in the cleavage groove | channel of the surface 21a and the back surface 21b. In such a form, when the pressure release valve 20 has a cleavage groove on the surface 21a of the valve body 21, the surface 21a of the valve body 21 has the anodized layer 24 only in the cleavage groove. Further, in the form in which the pressure release valve 20 has the cleavage groove on the back surface 21b of the valve body 21, the back surface 21b of the valve body 21 has the alumite treatment layer 25 only in the cleavage groove.

  O Formation of the cleavage groove of the valve body 21 of the pressure release valve 20 may be omitted. In this embodiment, the alumite treatment layers 24 and 25 are formed on at least a part of the front surface 21a and the rear surface 21b of the pressure relief valve 20 on the front surface 14a and the rear surface 14b of the lid body 14 of the case 11.

  The lid 14 of the case 11 may have anodized layers 24 and 25 only on one of the front surface 14a and the back surface 14b. When the pressure in the case 11 increases, a tensile stress acts on the surface 21 a of the valve body 21 of the pressure release valve 20. For this reason, it is desirable that the surface 14 a of the lid body 14 including the surface 21 a of the valve body 21 of the pressure release valve 20 has the anodized layer 24.

  The pressure release valve 20 may be formed on the wall surface of the case body 13 of the case 11. In this embodiment, if there are anodized layers 24 and 25 on at least a part of the surface 21a and the back surface 21b on the valve body 21 of the pressure release valve 20 on the surface and the back surface of the wall surface of the case main body 13 of the case 11, anodizing treatment is performed. The formation range of the layers 24 and 25 can be freely set.

○ The shape of the case 11 may be changed. For example, the case 11 may be cylindrical.
The electrode assembly 12 is not limited to the laminated type, but may be a wound type in which a belt-like positive electrode and a belt-like negative electrode are wound and laminated in layers.

  The secondary battery 10 is a lithium ion secondary battery, but is not limited thereto, and may be another secondary battery. In short, any ion may be used as long as ions move between the positive electrode active material layer and the negative electrode active material layer and transfer charge. Further, a capacitor may be used as the power storage device.

  (Circle) the secondary battery 10 may be mounted in a motor vehicle as a vehicle power supply device, and may be mounted in an industrial vehicle. Further, the present invention may be applied to a stationary power storage device.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery, 11 ... Case, 12 ... Electrode assembly, 13 ... Case main body, 14 ... Lid body, 14a ... Surface of (lid body), 14b ... Back surface (of lid body), 20 ... Pressure release valve, 21 ... Valve, 21a ... (Valve) front surface, 21b ... (Valve) rear surface, 24, 25 ... Anodized layer, 31 ... Cross groove, 32, 33 ... Arc-shaped groove, 34, 35 ... Linear groove , 36, 37 ... straight grooves.

Claims (4)

In a power storage device comprising a case in which an electrode assembly and an electrolytic solution are accommodated, and having a pressure release valve on the wall surface of the case for releasing the pressure in the case to the outside of the case,
The pressure relief valve is made of aluminum;
It said wall of said case having a pressure relief valve, the part of the surface on at least the pressure release valve Ri anodized layer there,
The pressure relief valve has a cleavage groove;
The anodized layer is in a portion including the cleavage groove,
The power storage device , wherein the ratio of the thickness of the pressure release valve and the thickness of the anodized layer in the cleavage groove is 2: 1 . The power storage device according to claim 1, wherein the alumite treatment layer is on the entire surface of the pressure release valve. The anodized layer has a power storage device according to claim 1 or claim 2 on both surfaces of the wall surface of the casing with the pressure release valve. The power storage device according to any one of claims 1 to 3 , wherein the power storage device is a secondary battery.