JP7278999B2 - Method for manufacturing secondary battery and secondary battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a secondary battery having a current collecting structure and a manufacturing method thereof .

Secondary batteries such as lithium ion secondary batteries and alkaline secondary batteries have a current collecting structure for extracting current from the electrode body and supplying current from the outside to the electrode body (for example, , see Patent Document 1). The current collecting structure includes a current collecting terminal made of a metal material electrically connected to the electrode body, and an external terminal provided outside the case of the secondary battery. The collector terminal and the external terminal are electrically joined by crimping each other or the like. As a result, a current path consisting of the electrode body, collector terminal, and external terminal is formed.

JP 2018-147681 A

When the current collecting terminal and the external terminal are made of different metal materials, electrolytic corrosion may occur due to water vapor or the like entering the gap between the current collecting terminal and the external terminal.
The present invention has been made in view of such circumstances, and an object of the present invention is to suppress electrolytic corrosion in the current collecting structure of a secondary battery.

A secondary battery that solves the above problems is made of an external terminal made of a metal material and made of a metal material different from the external terminal, one end of which is electrically connected to an electrode body, and the other end of which is connected to the external terminal. and a current collecting structure including a current collecting terminal crimped to the terminal and a bus bar made of the same metal material as the external terminal and in contact with the external terminal, wherein the current collecting structure is attached to the current collecting terminal. A crimped portion is accommodated in a recess formed in at least one of the bus bar and the external terminal, and a seal portion is further provided for suppressing entry of moisture into the recess.

According to the above configuration, the infiltration of moisture into the crimped portion of the current collector terminal and the contact portion of the external terminal is suppressed. Therefore, electric corrosion of the contact portion is suppressed.
In the secondary battery, the sealing portion may be made of resin or elastomer and accommodated inside the recess.

According to the above configuration, since the seal portion is made of resin or elastomer, it deforms along the shapes of the current collector terminal and the external terminal inside the recess, so that the crimped portion of the current collector terminal and the contact portion of the external terminal are deformed. Sealability can be improved.

In the above secondary battery, the sealing portion may be a cap that is a resin molded product or an elastomer molded product, and attached to the crimped portion inside the recess.
According to the above configuration, since the seal portion is a cap that is attached to the caulked portion, it is possible to easily perform the attachment work of the seal portion.

The secondary battery further includes an insulating portion provided between the external terminal and a lid portion that seals an opening of a case that accommodates the electrode assembly, and the sealing portion is provided at a tip of the insulating portion. may be provided to abut against the bus bar outside the external terminal.

According to the above configuration, the seal portion prevents moisture from entering the concave portion by contacting the bus bar outside the external terminal. According to this, the material, shape, etc. of the seal portion are not restricted by the collector terminal or the external terminal, and the degree of freedom in design can be increased.

ADVANTAGE OF THE INVENTION According to this invention, the electrical corrosion in the current collection structure of a secondary battery can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing a perspective structure of a first embodiment embodying a secondary battery; Sectional drawing of the negative electrode current collection part of the same embodiment. Sectional drawing of the negative electrode current collection part in 2nd Embodiment which actualized the secondary battery. Sectional drawing of the negative electrode current collection part in 3rd Embodiment which actualized the secondary battery. The figure which expanded the principal part of the negative electrode current collection part in 3rd Embodiment. Sectional drawing of the negative electrode current collection part in a modification. Sectional drawing of the negative electrode current collection part in a modification.

(First embodiment)
An embodiment of a secondary battery will be described with reference to FIGS. 1 and 2. FIG. In this embodiment, 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.

As shown in FIG. 1 , secondary battery 11 includes case 12 , lid 13 , and electrode body 14 . The case 12 and the lid portion 13 are made of a metal material. Case 12 has an opening, and lid 13 seals the opening. 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 gas discharge valve 24 for discharging the gas in the internal space 15 according to the pressure in the internal space 15 and a liquid injection port 25 for injecting the electrolytic solution.

In addition, the lid portion 13 is provided with a positive current collecting portion 21 and a negative current collecting portion 20 which are current collecting structures. The positive current collector 21 of the secondary battery 11 is connected to the negative current collector 20 of the adjacent secondary battery 11 via a busbar 26 . Also, the negative electrode current collector 20 of the secondary battery 11 is connected to the positive electrode current collector 21 of the adjacent secondary battery 11 via a bus bar 26 . An assembled battery is configured by connecting two or more secondary batteries 11 via the bus bar 26 in this way. Although only two secondary batteries 11 are shown in FIG. 1 , the assembled battery may be composed of three or more secondary batteries 11 .

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 as 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 copper (Cu) and a negative electrode mixture provided on the base material. The negative electrode mixture includes, for example, a negative electrode active material such as a carbon material, 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 configuration of the negative electrode current collector 20 will be described with reference to FIG. The negative electrode current collecting portion 20 includes a current collecting terminal 30 , a first insulating portion 31 , a second insulating portion 32 , and an external terminal 33 . In this embodiment, the collector terminal 30 is made of copper, like the base material of the negative electrode plate 18 . Also, the external terminals 33 and the busbars 26 are made of aluminum. Note that the collector terminal 30 may be an alloy containing copper as a main component (content of 50% by mass or more). Also, the external terminals 33 and the busbars 26 may be made of an alloy containing aluminum as a main component (content of 50% by mass or more).

The first insulating portion 31 is made of an insulating material such as resin, has a cylindrical shape, and has a through hole 310 inside. The first insulating portion 31 is provided inside a through hole 131 provided in the lid portion 13 . Also, the second insulating portion 32 and the external terminals 33 are provided on the surface 130 side of the lid portion 13 . The second insulating portion 32 is made of an insulating material such as resin, is interposed between the external terminal 33 and the lid portion 13 , and insulates the external terminal 33 and the lid portion 13 . A through hole 320 is provided in the second insulating portion 32 .

The external terminal 33 has a concave portion 331 that is a counterbore for preventing the collector terminal 30 from protruding toward the busbar 26 . The recess 331 is open at the surface 330 and has a circular shape when viewed from the surface 330 side. A through hole 332 is provided in the bottom surface of the recess 331 . The external terminal 33 is arranged such that the through hole 332 is aligned with the through hole 320 of the second insulating portion 32 , the through hole 310 of the first insulating portion 31 , and the through hole 131 of the lid portion 13 . A portion of the surface 330 of the external terminal 33 is joined to the busbar 26 by welding or the like. The opening of recess 331 is wholly or partially covered by bus bar 26 .

The collector terminals 30 are provided in the through holes 332 of the external terminals 33 , the through holes 320 of the second insulating portion 32 , and the through holes 310 of the first insulating portion 31 . One end of the current collector terminal 30 protrudes into the internal space 15 defined by the case 12 and the lid portion 13 . One end of the collector terminal 30 is connected to a connection member 34 electrically connected to the electrode body 14 . The collector terminal 30 has a crimped portion 301 at the other end. The crimped portion 301 is a substantially disc-shaped portion having an outer diameter larger than the inner diameter of the through hole 332 and is arranged in the recessed portion 331 of the external terminal 33 . A portion of the crimped portion 301 is crimped to the external terminal 33 . A gap 50 is provided between the inner side surface 333 of the recess 331 of the external terminal 33 and the crimped portion 301 . The collector terminal 30 and the external terminal 33 form a current path between the electrode assembly 14 and the busbar 26 .

The positive electrode current collector 21 has substantially the same configuration as the negative electrode current collector 20 . However, the current collecting terminal (not shown) differs from the negative electrode current collecting portion 20 in that it is made of aluminum or an aluminum-based material like the base material of the positive electrode plate 19 . In other words, the external terminal (not shown) of the positive electrode collector 21, the collector terminal, and the bus bar 26 are made of the same material or material of the same component system.

As described above, in the negative electrode collector 20, the collector terminal 30 and the external terminal 33 are made of different materials. The standard potential of aluminum forming the external terminal 33 (approximately −1.68 V vs. SHE) is lower than the standard potential of copper forming the collector terminal 30 (approximately 0.34 V). If moisture containing an electrolyte is present at a portion where different metals are in contact, a current may flow due to the potential difference between them, and a material with a lower standard potential may be corroded, which is called electrolytic corrosion. In other words, in the configuration of this embodiment, moisture in the air that flows in between the external terminal 33 and the bus bar 26 may cause electric corrosion to progress from the contact portion 39 of the external terminal 33 that contacts the collector terminal 30 . have a nature. Also, the greater the potential difference, the faster the rate of progress of electrolytic corrosion. On the other hand, in the positive electrode current collector 21, since the current collector terminals, the external terminals, and the bus bar 26 are all made of aluminum, electrolytic corrosion does not occur.

Therefore, in the present embodiment, the recess 331 is filled with the sealing portion 40 made of resin or elastomer. The seal portion 40 mainly fills the gap 50 between the collector terminal 30 and the inner side surface 333 of the recess 331 . As the resin, a moisture-curable resin, a thermosetting resin, a photo-curable resin, an anaerobic-curable resin, a two-liquid-curable resin, or the like can be used. After the collector terminal 30 is crimped to the external terminal 33 , the concave portion 331 is filled with a fluid resin before curing. For example, when a moisture-curable resin is used, the resin is filled into the concave portion 331 and then cured by the moisture contained in the air. In the case of using a photo-curing resin, after the resin is filled in the concave portion 331, it is cured by irradiating it with light of a predetermined wavelength. When a thermosetting resin is used, the recess 331 is filled with the resin, and then the resin is cured by heating with a heating device. When using a two-liquid curable resin, the concave portion 331 is filled with a mixture of two types of resin. After filling the recess 331 with the seal portion 40 , the bus bar 26 is welded to the external terminal 33 .

The operation of the negative electrode current collector 20 of this embodiment will be described.
Since the surface of the collector terminal 30 and the surface of the external terminal 33 are flush or substantially flush, rattling between the bus bar 26 and the external terminal 33 can be suppressed. Therefore, the shock given to the secondary battery 11 by the vibration of the vehicle is alleviated.

Since the space between the external terminal 33 and the bus bar 26 is not sealed, air containing moisture flows into the recess 331 . Since the seal portion 40 is filled in the concave portion 331 so as to seal the inlet portion of the contact portion 39 between the external terminal 33 and the current collector terminal 30 , it suppresses the entry of moisture into the contact portion 39 . Therefore, water, which serves as a medium for transferring electrons, does not intervene in the contact portion 39 between the external terminal 33 and the collector terminal 30, thereby suppressing the occurrence of electric corrosion.

Effects of the first embodiment will be described.
(1) The sealing portion 40 is arranged inside the concave portion 331 of the external terminal 33 of the negative electrode current collecting portion 20 . This prevents moisture from entering the crimped portion 301 of the current collector terminal 30 and the contact portion 39 of the external terminal 33 . Therefore, electric corrosion of the contact portion 39 can be suppressed.

(2) In the first embodiment, the sealing portion 40 is provided by filling the inside of the concave portion 331 with resin. According to this, the uncured resin flows inside the concave portion 331 along the shapes of the collector terminal 30 and the external terminal 33, and also flows into small gaps. Therefore, it is possible to improve the sealing performance at the crimped portion 301 of the collector terminal 30 and the contact portion 39 of the external terminal 33 .

(Second embodiment)
Next, a second embodiment will be described. 2nd Embodiment differs in the structure of the seal|sticker part from the structure of the seal|sticker part 40 of 1st Embodiment. 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.

FIG. 3 is a cross-sectional view of the negative electrode current collector 20. As shown in FIG. A surface 300 of the collector terminal 30 and a bottom surface 334, which is a part of the bottom surface of the recess 331, are the same or substantially the same because they are processed by FSW (Friction Stir Welding) or the like. Therefore, the crimped portion 301 of the collector terminal 30 and the external terminal 33 can be easily joined.

The seal portion 41 is a molded product made of resin or elastomer, and differs from the first embodiment in that it is a cap that covers the caulked portion 301 . As the resin material, the resin material of the first embodiment may be used, and the type is not particularly limited. Examples of elastomers include fluororubbers (FKM, FEPM, etc.), silicone rubbers (VMQ, FVMQ, etc.), and ethylene/propylene rubbers (EPM, EPDM, etc. can be used). Further, in the present embodiment, the surface 330 of the external terminal 33 is positioned closer to the busbar 26 than the surface 300 of the collector terminal 30 is.

The seal portion 41 has a disk shape, and its outer diameter is slightly larger than the inner diameter L1 of the opening of the recess 331 . In addition, a housing portion 410 is provided in the sealing portion 41 on the collector terminal 30 side. The accommodation portion 410 is formed in a concave shape and accommodates a part of the crimped portion 301 of the current collector terminal 30 . The inner diameter of the accommodating portion 410 is smaller than the outer diameter of the crimped portion 301 .

After forming the caulked portion 301 , the seal portion 41 is provided at the opening of the recess 331 . At this time, since the outer diameter of the seal portion 41 is larger than the inner diameter L1 of the opening of the recess 331, the seal portion 41 is provided in the recess 331 in an interference fit. Thereby, the seal portion 41 tightly seals the opening of the recess 331 . This can prevent moisture from entering the contact portion 39 between the external terminal 33 and the collector terminal 30 .

In addition, since the inner diameter of the accommodating portion 410 is smaller than the outer diameter of the crimped portion 301, the crimped portion 301 is accommodated in the accommodating portion 410 in an interference fit state. In this way, since the seal portion 41 is fixed not only to the opening of the recess 331 but also to the current collector terminal 30, the seal portion 41 may be displaced from the opening due to vibration or the like during running of the vehicle. It is possible to suppress the occurrence of a gap between 41 and the opening.

According to the second embodiment, the following effects can be obtained in addition to the effects described in (1) of the first embodiment.
(3) Since the seal portion 41 is a cap that is attached to the crimped portion 301, the work of attaching the seal portion 41 to the crimped portion 301 can be easily performed.

(Third embodiment)
Next, a third embodiment will be described. The configuration of the seal portion of the third embodiment differs from the configuration of the seal portion 40 of the first embodiment. 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.

In this embodiment, the second insulating portion 51 is made of resin or elastomer. The second insulating portion 51 is interposed between the external terminal 33 and the lid portion 13, and has substantially the same configuration as the second insulating portion 32 of the first embodiment, but differs in that it functions as a sealing portion.

As shown in FIG. 4 , the second insulating portion 51 includes a bottom wall portion 511 and side wall portions 512 . The side wall portion 512 is provided along the edge of the bottom wall portion 511 so as to surround the bottom wall portion 511 . A seal portion 513 provided at the tip of the side wall portion 512 is pressed against the bus bar 26 . That is, the height of the side wall portion 512 is greater than the distance between the lid portion 13 and the bus bar 26, and the seal portion 513 is bent.

FIG. 5 is an enlarged view of the main portion 5 around the tip portion of the seal portion 513 in FIG. A thickness L2 of seal portion 513 may decrease toward the contact surface with bus bar 26 . Since the seal portion 513 is tapered in this manner, the pressure is concentrated on the seal portion 513, the load applied to the seal portion 513 is increased, and the sealing performance is improved.

Thus, in this embodiment, the side wall portion 512 of the second insulating portion 51 functions as a sealing portion, and the sealing portion 513 of the second insulating portion 51 is in close contact with the busbar 26 . This suppresses penetration of moisture into the inside of the second insulating portion 51 . As a result, it is possible to prevent moisture from entering the contact portion 39 between the external terminal 33 and the collector terminal 30 .

According to the third embodiment, the following effects can be obtained.
(4) Outside the external terminal 33 of the negative electrode current collector 20 , the recess 331 was sealed with the sealing portion 513 of the second insulating portion 51 . According to this, the seal portion 513 is less likely to be restricted by the current collector terminal 30 and the external terminal 33 in terms of its shape and the like, so that the degree of freedom in design can be increased.

Each of the above embodiments can be implemented with the following modifications. Each of the above-described embodiments and the following modifications can be implemented in combination with each other within a technically consistent range.
- In each of the above embodiments, the recess 331 is provided in the external terminal 33 . Alternatively, as shown in FIG. 6 , a recess 261 for accommodating the crimped portion 301 may be provided on the busbar 26 side. In this embodiment, the recessed portion 261 is filled in advance with the seal portion 41 made of resin or elastomer before hardening, and the caulked portion 301 is accommodated in the recessed portion 261 . Moreover, both the external terminal 33 and the bus bar 26 may be provided with recesses and these recesses may face each other. These configurations can also prevent moisture from entering the contact portion 39 between the collector terminal 30 and the external terminal 33 .

- In each of the above-described embodiments, the surface 300 of the collector terminal 30 is a flat surface. Alternatively, the central portion of the current collecting terminal 30 may be elevated, and the surface may be inclined from the central portion to the edge of the caulked portion 301 . Further, as shown in FIG. 7 , when the bus bar 26 has the escape hole 263 , the collector terminal 30 may be provided with the projecting portion 302 . In addition, FIG.6 and FIG.7 shows the modification of 1st Embodiment filled with resin or an elastomer. Moreover, when using the seal portion 41 which is a resin molded product, it is formed in a shape that matches the shape of the projecting portion 302 .

- In 2nd Embodiment, the sealing part 41 was taken as the structure provided with the accommodating part 410. FIG. Alternatively, the seal portion 41 may be disc-shaped without the accommodating portion 410 . In this aspect, the collector terminal 30 may have a height that does not come into contact with the seal portion 41 fitted in the opening of the recess 331 .

- In 3rd Embodiment, the sealing part 513 of the side wall part 512 of the external terminal 33 was made into the taper shape. Alternatively, sidewall 512 may have a constant thickness from proximal to distal.
- In the third embodiment, the bus bar 26 may be formed with a groove into which the seal portion 513 of the second insulating portion 51 is fitted. According to this, the sealing performance between the seal portion 513 and the bus bar 26 can be improved.

In each of the above-described embodiments, the electrode body 14 of the secondary battery 11 has a laminated structure in which a plurality of negative electrode plates 18 and a plurality of positive electrode plates 19 are alternately laminated via separators. Alternatively, the electrode assembly 14 may have a wound structure in which a long positive electrode plate and a long negative electrode plate are flatly wound with a long separator interposed therebetween.

- In each of the above embodiments, the secondary battery 11 was described as a lithium ion secondary battery including a positive electrode mixture containing a lithium-containing composite oxide and a negative electrode mixture containing a carbon material. is not limited to The sealing structure using the respective sealing portions described above can be applied to at least one of the negative electrode collector portion 20 and the positive electrode collector portion 21 as long as the materials of the external terminal 33 and the collector terminal 30 are different.

- In each of the above-described embodiments, the recess 331 is covered with the busbar 26 , but the recess 331 does not necessarily have to be covered with the busbar 26 . For example, if the sealing portion 40 of the first embodiment has excellent weather resistance and water resistance, the concave portion 331 may not be covered with the busbar 26 . Further, if the seal portion 41 of the second embodiment can prevent moisture from entering the contact portion 39, the concave portion 331 does not have to be covered with the bus bar 26. FIG. The bus bar 26 may be joined to the external terminal 33, and its configuration may be other than the configuration shown in FIG.

- The current collection structure is not limited to the configuration described in each of the above embodiments. For example, the bus bar 26 and the current collecting structure may be connected by bolts. Also, the external terminal 33 and the second insulating portions 32, 51 may have shapes other than those shown in FIGS. In the first embodiment, it suffices if there is a concave portion 331 or the like that can be filled with resin around the crimped portion 301 . Alternatively, even if there is no recessed portion 331 or the like, it is sufficient if there is a space for curing the resin around the crimped portion 301 . 2nd Embodiment should just have the recessed part 331 grade|etc., which can fit the sealing part 41 which is a cap. Alternatively, even if there is no recess 331 or the like, it is sufficient if there is a space that allows the seal portion 41 to be fitted onto the caulked portion 301 . In the third embodiment, the structure of the current collecting structure is not particularly limited as long as the sealing portion 513 can contact the bus bar 26 outside the external terminal 33 .

- The secondary battery 11 may be used in vehicles such as electric vehicles, hybrid vehicles, gasoline vehicles, and diesel vehicles, and other moving bodies. Alternatively, it may be a secondary battery for household stationary use or industrial stationary use.

DESCRIPTION OF SYMBOLS 11... Secondary battery 12... Case 13... Cover part 14... Electrode body 20... Negative electrode collector part 21... Positive electrode collector part 26... Bus bar 30... Current collector terminal 32, 51... Second insulating part 33... External terminal 40, 41, 513... Seal part 331... Recessed part

Claims (3)

an external terminal made of a metal material;
a collecting terminal made of a metal material different from that of the external terminal, one end of which is electrically connected to an electrode body and the other end of which is crimped to the external terminal;
A method for manufacturing a secondary battery including a current collecting structure made of the same metal material as the external terminal and including a bus bar in contact with the external terminal,
The other end of the current collecting terminal is crimped onto the external terminal to provide a crimped portion in a recess formed in the external terminal ,
A fluid resin is filled between the concave portion and the caulking portion, and the resin is cured to form a sealing portion that suppresses intrusion of moisture into the concave portion.
A method for manufacturing a secondary battery. an external terminal made of a metal material;
a collecting terminal made of a metal material different from that of the external terminal, one end of which is electrically connected to an electrode body and the other end of which is crimped to the external terminal;
A current collecting structure made of the same metal material as the external terminal and including a bus bar in contact with the external terminal,
The current collecting structure is
the crimped portion of the current collector terminal is accommodated in a recess formed in at least one of the bus bar and the external terminal;
further comprising a seal portion that suppresses ingress of moisture into the recess,
The seal portion is a resin molded product or an elastomer molded product , and is a cap that covers an upper surface of the crimped portion on the bus bar side , and is attached to the crimped portion inside the recess.
secondary battery. an external terminal made of a metal material;
a collecting terminal made of a metal material different from that of the external terminal, one end of which is electrically connected to an electrode body and the other end of which is crimped to the external terminal;
A current collecting structure made of the same metal material as the external terminal and including a bus bar in contact with the external terminal,
The current collecting structure is
the crimped portion of the current collector terminal is accommodated in a recess formed in at least one of the bus bar and the external terminal;
further comprising a seal portion that suppresses ingress of moisture into the recess,
further comprising an insulating portion provided between the external terminal and a lid portion that seals an opening of a case that houses the electrode body,
The sealing portion is provided at a tip of the insulating portion and abuts against the bus bar outside the external terminal.
secondary battery.

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