WO2024024976A1

WO2024024976A1 - Bus bar, manufacturing method of same, and power storage device

Info

Publication number: WO2024024976A1
Application number: PCT/JP2023/027871
Authority: WO
Inventors: 浩徳川崎; 真之助後藤
Original assignee: イビデン株式会社
Priority date: 2022-07-29
Filing date: 2023-07-28
Publication date: 2024-02-01
Also published as: JP2024018703A; JP7518133B2

Abstract

Provided is a bus bar that can be protected from high temperatures and flames from a battery cell in a time of abnormality of a battery. A bus bar (1) is obtained by a bus bar main body (5) containing an electroconductive material being covered by an insulating covering film (10) that is formed on the surface thereof and includes a first layer (11) containing an insulating material of which an expansion initiation temperature is a predetermined temperature or higher, and a second layer (12) that is formed on the surface of the first layer (11) and that contains a resin that melts at a temperature lower than the predetermined temperature.

Description

Bus bar and its manufacturing method, and power storage device

The present invention relates to a bus bar, a method for manufacturing the same, and a power storage device in which a plurality of battery cells or battery modules are connected by a bus bar.

Various electronic devices, electric vehicles or hybrid vehicles driven by electric motors, storage batteries, etc. are equipped with power storage devices in which multiple battery cells are connected in series or in parallel with bus bars. In addition, lithium ion secondary batteries, which are capable of higher capacity and higher output than lead-acid batteries, nickel-metal hydride batteries, etc., are mainly used as battery cells.

However, if excessive current is applied to the battery cells during charging and discharging, the busbars used for connection may generate heat, and in some cases may emit flames. When such a battery abnormality occurs, the bus bar is also exposed to similar high temperatures and flames, causing damage to the bus bar itself or causing high heat to adjacent battery cells via the bus bar. Therefore, in Patent Document 1, the busbar is covered with a mica sheet.

Japanese Patent Application Publication No. 2020-528650

However, Patent Document 1 is a measure to suppress the heat generation of the bus bar itself, and does not focus on protecting the bus bar from high temperatures and flames from the battery cells when the battery is abnormal. Moreover, since mica contains water of crystallization, when exposed to high temperatures or flames during battery abnormalities, it expands and releases water of crystallization, making it structurally unstable.

Further, in Patent Document 1, it is necessary to wrap the mica sheet around the bus bar. Busbars may have a complicated shape due to spatial restrictions on the location where battery cells are installed, and when the busbar has a complicated shape, it is difficult to wrap the mica sheet to every corner of the busbar. If the mica sheet has uneven winding or gaps, the desired effects described above cannot be sufficiently obtained.
Furthermore, it is also assumed that the adhesive surface of the mica sheet may peel off at high temperatures.

Therefore, an object of the present invention is to provide a bus bar that can protect the bus bar from high temperatures and flames from the battery cells when the battery is abnormal. In addition, we provide a method for manufacturing busbars that does not require wrapping work like mica sheets, causes uneven winding, gaps between sheets, and peeling of sheets, and can easily accommodate complex shapes. The purpose is to A further object of the present invention is to provide a power storage device that connects a plurality of battery cells or battery modules using such a bus bar and exhibits high safety even in abnormal situations.

The above object of the present invention is achieved by the following configuration [1] regarding the bus bar.

[1] A bus bar used in a power storage device including a battery cell,
The busbar body containing conductive material is
a first layer formed on the surface of the bus bar body and containing an insulating material whose expansion start temperature is equal to or higher than a predetermined temperature; and a first layer formed on the surface of the first layer and containing a resin that melts below the predetermined temperature. A busbar characterized by being coated with an insulating coating consisting of two layers.

Further, preferred embodiments of the present invention regarding the bus bar relate to the following [2] to [10].

[2] The bus bar according to [1], wherein the insulating material contains a foaming agent and a binder.
[3] The busbar according to [2], wherein the foaming agent is at least one of an ammonium salt, an amino compound, and a chlorinated paraffin.
[4] The busbar according to [2] or [3], wherein the binder is at least one of a synthetic resin emulsion, an alkyd, a vinyl chloride resin, a urethane resin, and an epoxy resin.
[5] The bus bar according to any one of [2] to [4], wherein the insulating material further contains a carbonizing agent.
[6] The bus bar according to [5], wherein the carbonizing agent is at least one of carbohydrates and polyhydric alcohols.
[7] The busbar according to [5], wherein the foaming agent is ammonium polyphosphate, the binder is a urethane resin, and the carbonizing agent is a polyhydric alcohol.
[8] The busbar according to any one of [1] to [7], wherein the predetermined temperature is 300°C.
[9] The busbar according to any one of [1] to [7], wherein the thickness of the insulating coating is 0.3 mm or more.
[10] The busbar according to [8], wherein the insulating coating has a thickness of 0.3 mm or more.

Further, the above object of the present invention is achieved by the following configuration [11] related to the bus bar manufacturing method.

[11] A method for manufacturing a bus bar used in a power storage device including a battery cell, comprising:
After applying a first coating liquid containing an insulating material whose expansion start temperature is a predetermined temperature or higher on the surface of a bus bar body containing a conductive material, the first coating liquid is dried to form a first layer;
A method for manufacturing a bus bar, comprising applying a second coating liquid containing a resin that melts at a temperature lower than the predetermined temperature to the surface of the first layer, and then drying the liquid to form a second layer.

Further, preferred embodiments of the present invention relating to the bus bar manufacturing method relate to the following [12] to [16].

[12] The method for manufacturing a bus bar according to [11], wherein the insulating material contains a foaming agent and a binder.
[13] The method for manufacturing a bus bar according to [12], wherein the insulating material further contains a carbonizing agent.
[14] The method for manufacturing a busbar according to any one of [11] to [13], wherein the predetermined temperature is 300°C.
[15] The method for manufacturing a busbar according to any one of [11] to [13], characterized in that the coating liquid is applied so that the film thickness after drying is 0.3 mm or more.
[16] The method for manufacturing a bus bar according to [14], characterized in that the coating liquid is applied so that the film thickness after drying is 0.3 mm or more.

Further, the above object of the present invention is achieved by the following configurations [17] to [20] related to the power storage device.

[17] A power storage device in which a plurality of battery cells or battery modules are connected by the bus bar according to any one of [1] to [7].
[18] A power storage device in which a plurality of battery cells or battery modules are connected by the bus bar according to [8].
[19] A power storage device in which a plurality of battery cells or battery modules are connected by the bus bar according to [9].
[20] A power storage device in which a plurality of battery cells or battery modules are connected by the bus bar according to [10].

The busbar of the present invention includes a first layer that is formed on the surface of the busbar body and includes an insulating material whose expansion start temperature is a predetermined temperature or higher, and a first layer that is formed on the surface of the first layer and melts below the predetermined temperature. It is coated with an insulating coating composed of a second layer containing resin. Therefore, during normal use of the battery, the stable insulation performance of the second layer functions to prevent short circuits with the battery cells and other components. When an abnormality occurs in the battery, the second layer melts and disappears, exposing the first layer, and the insulating material expands and, more preferably, carbonizes, so it is protected from the high temperatures and flames from battery cells that have experienced thermal runaway. Ru.

In addition, the busbar manufacturing method of the present invention simplifies the manufacturing process because it is only necessary to apply each of the coating liquids forming the first layer and the second layer to the busbar body. Regardless, the insulation coating can be formed uniformly without any gaps.

Furthermore, since the power storage device of the present invention connects a plurality of battery cells and battery modules using such a bus bar, it exhibits high safety even in abnormal situations.

FIG. 1 is an exploded perspective view showing a state in which an example of the bus bar of the present invention is attached to a battery cell. FIG. 2 is a cross-sectional view of the embodiment of the bus bar taken along the line AA in FIG. FIG. 3 is a graph showing the back surface temperature (° C.) during flame irradiation in Examples and Comparative Examples. FIG. 4 is a graph showing the results of measuring the film thickness (mm) of the insulating coating before and after flame irradiation in Examples and Comparative Examples. FIG. 5 is a drawing-substitute photograph taken after flame irradiation of the insulation coating of each sample of Example 1 and Comparative Example 1, and FIG. 5(A) is that of Example 1, and FIG. 5(B) is that of Example 1. Comparative Example 1 is shown. FIG. 6 is a photograph substituted for a drawing taken of the side surface of the sample of Example 1 after irradiation with flame. FIG. 7 is a sectional view showing an example of the power storage device of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and can be implemented with arbitrary changes within the scope of the gist of the present invention.

[Busbar]
FIG. 1 is an exploded perspective view showing a state in which a bus bar 1 according to the present embodiment is attached to a battery cell 110. As shown in FIG. 1, the busbar body 5 made of a conductive material is, for example, a Z-shaped metal plate member as a whole, and an electrode 111 of a battery cell 110 is inserted into a connection hole 6a at one end. Then, the terminal cap 112 is covered and fixed. Further, adjacent battery cells (not shown) and external equipment (not shown) are connected to the connection hole 6b at the other end of the busbar body 5. Then, a portion (surface) of the busbar main body 5 excluding the connection holes 6a and 6b is covered with an insulating coating 10, which will be described later, to form the busbar 1.

Although not shown in the drawings, the bus bar body 5 can have various shapes depending on the installation location of the battery cells 110, such as an I-shape as a whole or an irregular shape with a curved part.

If the busbar main body 5 has a shape having a bent part 5a or a curved part (not shown) like the Z-shape shown in FIG. It is assumed that the winding operation takes time to prevent uneven winding or gaps from occurring in the bent portion 5a or the curved portion, or gaps may occur due to vibration, or the adhesive may peel off. However, as will be described later, in this embodiment, such a problem does not occur because the insulating film 10 is formed by coating using a predetermined coating liquid.

Next, FIG. 2 is a cross-sectional view of the bus bar 1 taken along the line AA in FIG. 1. Although not shown, there is a battery cell 110 on the lower side of FIG. 2, and when the battery is abnormal, high temperature and flame are generated due to heat transfer from the battery cell 110. For this reason, the busbar body 5 is coated with a predetermined insulating coating 10. Note that, as shown in the figure, the insulating coating 10 can be formed on the side surfaces (thick part) and the top and bottom surfaces of the busbar body 5 so as to cover the entire surface thereof, but at least the surface facing the battery cells 110 (here It may be formed only on the lower surface).

As illustrated, the insulating coating 10 includes, in order from the surface of the bus bar body 5, a first layer 11 containing an insulating material whose expansion start temperature is a predetermined temperature or higher, and a resin that melts below the predetermined temperature. The second layer 12 is laminated.

Even under normal conditions, the temperature of the bus bar 1 is approximately 100° C. when energized (during normal use of the battery). The expansion start temperature is set at a predetermined temperature at which the first layer 11 does not expand during normal use of the battery, specifically, for example, 300°C or higher (the expansion start temperature of the insulating material included in the first layer 11 is 300°C or higher). ), or 350°C or higher (the expansion start temperature of the insulating material included in the first layer 11 is 350°C or higher), or 400°C or higher (the expansion start temperature of the insulating material included in the first layer 11 is 400°C or higher). It is better to do so.

When the first layer 11 starts to expand at a high temperature higher than the predetermined temperature, air is taken into the first layer 11 and an air layer is formed, so that the generated high heat is transmitted to the bus bar 1. suppressed, and the insulation performance is improved. Furthermore, melting of the bus bar 1 itself (that is, damage to the bus bar 1 due to high heat) can be effectively suppressed.
In addition, in order to effectively improve the heat insulation performance, it is preferable that the expansion coefficient of the first layer 11 is as large as possible, and the expansion coefficient is preferably 10% or more, and 13% or more with respect to the volume before expansion. More preferably, it is 15% or more.

In the bus bar 1 of this embodiment, the bus bar body 5 containing a conductive material is covered with the first layer 11 containing an insulating material whose expansion start temperature is higher than a predetermined temperature, so that during normal use of the battery, the bus bar body 5 includes a conductive material. (approximately 100°C at most), it functions as an insulating material to ensure insulation from other parts and equipment around the bus bar 1, but when the battery is abnormal (at least 300°C or higher), By expanding the first layer 11, the contact distance with the conductive portion becomes larger, and the risk of short circuit can be lowered.

In addition, in consideration of further improvement in insulation, it is preferable that the insulating material used for the first layer 11 contains a foaming agent and a binder, and more specifically, the insulating material used for the first layer 11 is Preferably, it is a foamed resin. Note that when the insulating material contains a foaming agent and a binder, air is effectively taken into the foamed foam, so that effective heat insulation properties can be expected.

There is no particular restriction on the type of insulating material whose expansion start temperature is 300°C or higher as the predetermined temperature, but in the case where the insulating material contains a foaming agent, the foaming agent may include ammonium salts, amino compounds, and chlorine. It is preferable to use at least one of the converted paraffins, and a combination of at least some of these may be used. Examples of ammonium salts include ammonium phosphate, ammonium polyphosphate, and melamine phosphate. Examples of amino compounds include dicyanamide, urea, and melamine.

In addition, when the insulating material contains a binder, the binder may be a synthetic resin emulsion (water-based), alkyd (solvent-based), vinyl chloride resin (solvent-based), urethane resin (solvent-based), or epoxy resin (solvent-based). It is preferable to use at least one of these, and a combination of at least some of these may be used.

Further, examples of the urethane resin as a binder include urethane prepolymers. A urethane prepolymer is obtained by reacting a polyol compound with an excess polyisocyanate compound, and has an isocyanate group at the end of the molecule.

Examples of the polyol compounds constituting the urethane prepolymer include polyether polyols, polyester polyols, and the like. The weight average molecular weight of these is usually 300 to 5,000 (preferably 500 to 3,000).

Further, examples of the polyisocyanate compound include aliphatic, alicyclic, or aromatic polyisocyanates used in the production of general polyurethanes. Specifically, for example, tetramethylene diisocyanate, hexamethylene diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, meth Examples include xylylene diisocyanate and 4,4'-diphenylmethane diisocyanate.

The reaction ratio between the polyol compound and the polyisocyanate compound may be set so that the isocyanate groups in the polyisocyanate compound are in excess of the hydroxyl groups in the polyol compound, and (NCO/OH) is 1.2 to 2. It is preferable to set it to about .2.

Note that the above foaming agent can also function as a carbonized layer forming agent. The carbonized layer forming agent herein refers to a component that promotes carbonization of the above-mentioned foamed resin, which is a carbonization component. After the foamed resin is foamed, the surrounding area is set to an inert gas atmosphere to carbonize the carbon in the resin to form a carbonized layer, which has the effect of stopping further combustion. The compound having such an effect is preferably ammonium polyphosphate, which is one of the above-mentioned ammonium salts and has a large inert gas generating effect. Nitrogen gas is generated from ammonium groups in ammonium polyphosphate, effectively blocking contact with oxygen in the air.

As mentioned above, the expansion start temperature of the insulating material included in the insulating coating 10 is a predetermined temperature or higher, for example, 300° C. or higher, but the flame retardant effect against high temperatures and flames from battery cells that have experienced thermal runaway is limited. In order to further increase the temperature, the expansion start temperature is preferably 550°C or lower, 540°C or lower, or 530°C or lower. In particular, when the insulating material contains a foaming agent, a more effective flame retardant effect can be expected due to the formation of a carbonized layer as described above, but if the expansion start temperature is too high, the sufficiently foamed surface layer There is a risk that a carbonized layer may not be formed properly and a more effective flameproofing effect may not be obtained. Therefore, the expansion start temperature of the insulating material included in the insulating coating 10 is preferably in the range of, for example, 300° C. or more and 550° C. or less.

As will be described later, a coating solution is used to form the first layer 11, but ammonium polyphosphate decomposes in the coating solution if left for a long time, generates ammonia gas, and deteriorates over time. There is a risk that the performance of forming a carbonized layer will deteriorate. Therefore, in order to prevent this change over time, it is preferable to thinly coat the material with a water-resistant resin and microcapsule it.

Furthermore, it is preferable that the first layer 11 further contains a carbonizing agent. Note that the carbonizing agent is preferably at least one of carbohydrates and polyhydric alcohols, and may be a combination of at least some of these. The first layer 11 further includes a carbonizing agent in addition to the above-described foaming agent and binder, so that, for example, the foaming agent (also carbonization forming agent) is ammonium polyphosphate and the carbonization agent is polyhydric alcohol. In this case, when the temperature of the first layer 11 reaches 250 to 300°C, ammonium polyphosphate as a reaction catalyst decomposes, and the polyhydric alcohol as a carbonizing agent decomposes with the generated phosphate. A carbonized layer can be formed more effectively by the dehydration action.

In addition, in parallel with this reaction, ammonium polyphosphate, which is a foaming agent, further decomposes, generating ammonia gas, water vapor, carbon dioxide gas, etc., and by significantly expanding the carbonized layer formed, the heat insulating layer to form.

In addition to the above-mentioned foaming agent, binder (resin), and carbonizing agent, the first layer 11 also contains various additives (for example, inorganic particles, Examples of other additives include flame retardants, dispersants, color pigments (titanium oxide, etc.), and extender pigments.

Subsequently, the total content of the foaming agent and the binder in the first layer 11 is preferably 0.5 to 1.8 kg/m ² of the total amount of the coating, and is 0.5 to 0.7 kg/m ² . It is more preferable. If the total content of the blowing agent and binder, as well as the carbonizing agent, is less than the respective lower limit values listed above, sufficient heat resistance against abnormal high temperatures and flames will not be obtained. Even if it exceeds this, no further improvement in heat resistance can be expected.

Furthermore, the thickness of the first layer 11 is preferably 0.3 mm or more, more preferably 0.4 mm or more. As shown in the test examples described below, if the thickness of the first layer 11 is less than 0.3 mm, sufficient heat resistance against high temperatures and flames during battery abnormalities cannot be obtained. Note that there is no upper limit to the thickness of the first layer 11, but even if it becomes thicker than necessary, no further improvement in heat resistance can be expected, and rather problems may occur in the film quality such as cracks in the first layer 11. 2.0 mm is appropriate as the upper limit of the film thickness of the first layer 11.

Subsequently, the second layer 12 includes a resin that melts below a predetermined temperature. Therefore, there is no particular restriction as long as the resin has a melting point or glass transition point below a predetermined temperature. Note that the predetermined temperature here needs to be set in accordance with the predetermined temperature at which the insulating material included in the first layer 11 starts to expand. That is, for example, if the expansion start temperature of the insulating material contained in the first layer 11 is 300°C or higher, the melting temperature of the resin contained in the second layer 12 may be less than 300°C; When the expansion start temperature of the insulating material contained in the first layer 11 is 350°C or higher, the melting temperature of the resin contained in the second layer 12 may be less than 350°C.
In other words, in order for the bus bar 1 according to the present embodiment to have the effects, the expansion start temperature of the insulating material included in the first layer 11 must be higher than the melting temperature of the resin included in the second layer 12. There needs to be.

As mentioned above, even during normal use of the battery, the bus bar 1 reaches a high temperature of about 100°C, so the resin contained in the second layer 12 should be a resin with a melting point or glass transition point of 100°C or higher. The temperature is preferably 150°C or higher, more preferably 200°C or higher, and even more preferably 200°C or higher.

Moreover, since the second layer 12 becomes the outermost layer of the insulating coating 10 which is a laminate, it is preferable that the second layer 12 has a high heat resistance temperature. Specifically, considering availability and handling, examples of resins that melt at temperatures below 300°C include polyethylene (PE), polypropylene (PP), vinyl chloride (PVC), AS resin (SAN), and ABS resin. (ABS), vinylidene chloride resin (PVDC), polyamide (PA), polyacetal (POM), polybutylene terephthalate (PBT), fluororesin (PTFE), phenolic resin (PF), melamine resin (MF), urea resin (UF) ), polyurethane (PUR), epoxy resin (EP), unsaturated polyester resin (UP), nylon 6 (PA6), nylon 66 (PA66), and the like.

Further, the second layer 12 may contain other materials, but there are no particular limitations as long as they do not interfere with the effects of the bus bar 1 according to the present embodiment as shown below. Specifically, for example, flame retardants, colorants, inorganic fillers, etc. can be included.
However, the resin contained in the second layer 12 that melts below a predetermined temperature is the main component in the second layer 12, that is, 50% by mass or more, preferably 60% by mass or more, more preferably 60% by mass or more of the total amount of the second layer 12. It is preferably 70% by mass or more.

The thickness of the second layer 12 is not particularly limited, but in consideration of ensuring insulation, durability, film quality, etc., it is 0.01 to 2.0 mm, preferably 0.1 to 1.0 mm. 0 mm is appropriate.

As described above, the busbar 1 of the present embodiment includes the first layer 11 that is formed on the surface of the busbar body and includes an insulating material whose expansion start temperature is a predetermined temperature or higher, and the first layer 11 that is formed on the surface of the first layer 11. A second layer 12 containing a resin that melts below the predetermined temperature is coated with an insulating coating 10 made of a laminate. Therefore, during normal use of the battery, the stable insulation performance of the second layer 12 functions to prevent short circuits with the battery cells 110 and other components. When the battery is abnormal, the second layer 12 melts and disappears, the first layer 11 is exposed, and the insulating material 10 expands (if the insulating material 10 is a foamed resin, it foams and expands). ), more preferably carbonized, so that it is protected from high temperatures and flames from the battery cells 110 that have experienced thermal runaway.

[Busbar manufacturing method]
To manufacture the bus bar 1, first, an insulating material that expands at least the above-mentioned expansion start temperature is higher than a predetermined temperature, for example, 300° C. or higher, preferably a foaming agent and a binder, more preferably a carbonizing agent, and, if necessary, Accordingly, other additives are weighed, added to the thinner as a dispersion medium, and thoroughly mixed to prepare the first coating liquid. Subsequently, the area around the connection holes 6a and 6b (see FIG. 1) in the busbar body 5 is masked, and the first coating liquid is applied, and then the coating film is dried to form the inside of the insulating coating 10 according to the present embodiment. The first layer 11 is formed.
Furthermore, before forming the first layer 11, an undercoat material for anti-corrosion purposes is applied to the surface of the bus bar body 5 using a brush to a predetermined thickness, and then the coating film is dried and an undercoat material is applied. A coating film may be formed, and the first layer 11 may be formed on the undercoat coating film.

The first coating amount is adjusted so that the film thickness after drying (that is, the film thickness of the first layer 11) is 0.3 mm or more, preferably 0.4 mm or more.

Here, the drying mentioned above includes not only the hardening treatment of the coating film by heat treatment, but also the hardening treatment of the coating film by natural drying at room temperature. Further, during drying, the insulating material may be heated to a temperature at which it does not foam and expand, for example, to about 100° C. in order to accelerate the curing process.

Then, a resin that melts at least below the above-mentioned predetermined temperature, for example, below 300°C, and other additives as necessary are weighed, added to thinner as a dispersion medium, and thoroughly mixed to form a second coating liquid. Prepare. Then, the second coating liquid is applied to the surface of the first layer 11 and the coating film is dried to form the second layer 12 in the insulating coating 10 according to the present embodiment. is formed on the surface of the busbar body 5, and the busbar 1 is completed.

There are no restrictions on the method of applying both the first coating liquid and the second coating liquid, and there are various methods such as applying with a brush, roll coater, spray, etc., or dipping the bus bar body 5 in each coating liquid. This method is possible.

In addition, the method of winding the mica sheet as in Patent Document 1 requires a winding operation, and the winding operation is particularly time-consuming in order to prevent uneven winding or gaps from occurring at the bent portion 5a or the curved portion. . Furthermore, it is assumed that a gap may be created due to vibration or the like, or that the adhesive may peel off. However, in the present invention, such a problem does not occur because the first layer 11 and the second layer 12 are formed by coating.

Note that the conductivity of the bus bar 1 decreases when it generates heat, which may reduce the performance of battery cells and battery packs (battery modules) to which it is applied. In the method of forming the insulating coating 10 (i.e., the first layer 11 and the second layer 12) by applying the first coating liquid and the second coating liquid, the insulating coating 10 is thinly coated. Due to the effective heat dissipation of the bus bar 1 during normal use of the battery, deterioration in the performance of the battery cells and the battery module as a whole can be reduced.

Furthermore, since the insulating coating 10 can be made thinner, the volume occupied by the entire busbar 1 does not become too large, and the battery space within the battery pack can be effectively utilized, contributing to an increase in the capacity of the battery pack.

[Power storage device]
As shown in FIG. 7, power storage device 100 includes a plurality of battery cells 110 housed in a battery case 120. Adjacent battery cells 110 are connected by the bus bar 1.

The bus bar 1 is coated with the above-mentioned insulating coating 10, so that even if a certain battery cell 110 causes thermal runaway, the bus bar 1 can be protected, and the chain of thermal runaway to the adjacent battery cell 110 via the bus bar 1 can be prevented. can be prevented.
Therefore, since the power storage device of the present embodiment connects a plurality of battery cells 110 and modules (not shown) through such a bus bar 1, it exhibits high safety even in the event of an abnormality.

In order to verify the effect of the insulating material of the first layer 11, which is one of the components of the bus bar 1 according to the present embodiment, the following test was conducted.

(Examples 1 to 4)
Apply SK Taica Coat undercoat (for rust prevention) to one side of an aluminum plate with a side of 100 mm and a thickness of 2 mm to a thickness of about 0.05 mm using a brush and let it dry. Ta. Then, on the formed undercoat film, "Taika Coat" manufactured by SK Kaken Co., Ltd. is applied as an insulating film using a scraper to a film thickness shown in Table 1 ("Insulating film thickness (mm)" column). (See "Before Flame Irradiation") to prepare samples.

(Comparative Examples 1 to 3)
In Comparative Example 1, mica tape with a thickness of 0.11 mm manufactured by Nippon Mica Seisakusho Co., Ltd. was adhered in double layers to one side of the same aluminum plate as in the example as an insulating material, and a total thickness of 0.22 mm was applied. A sample was prepared by forming an insulating film.
In Comparative Example 2, a sheet of "D680A" manufactured by Okabe Mica Co., Ltd. with a thickness of 0.3 mm was used as the lower layer and the same mica tape (thickness: 0.11 mm) was layered and adhered as the upper layer, and the total thickness was 0.52 mm. A sample was prepared by forming an insulating film.
In Comparative Example 3, a 0.5 mm thick sheet of "D680A" manufactured by Okabe Mica Co., Ltd. and the same mica tape (0.11 mm thick) as an upper layer were stacked and adhered to form an insulating coating with a total thickness of 0.72 mm. A sample was prepared by forming a

(Heat resistance test)
The sample was stood up, and a flame was irradiated from a burner at a distance of 100 mm from the surface on which the insulating film was formed, and the size of the flame was adjusted so that the temperature was 1100°C. Then, the temperature (° C.) of the surface of the sample opposite to the surface on which the insulating film was formed (back surface) was measured.

Additionally, the thickness (mm) of the insulating coating before and after flame irradiation was measured using a dial gauge, and the expansion rate (%) was determined.

Table 1 summarizes the structure of the insulating coating of each sample of the example and comparative example, as well as the measurement results of the expansion coefficient and back surface temperature. Further, the back surface temperature (° C.) during flame irradiation is shown in FIG. 3, and the film thickness (mm) of the insulating coating before and after flame irradiation is shown in graph form in FIG. 4, respectively.

As shown in Table 1, FIG. 3, and FIG. 4, each sample of Examples 1 to 4 has a change in film thickness before and after flame irradiation, that is, thermal expansion, compared to each sample of Comparative Examples 1 to 3. It can be seen that the ratio is large and the back surface temperature is low, indicating that it has excellent heat insulation properties. Further, the thickness of the insulating film is preferably 0.3 mm or more, and more preferably 0.4 mm or more.

Further, FIG. 5 shows photographs of the insulation coatings of the samples of Example 1 ((A) in the same figure) and Comparative Example 1 ((B) in the same figure) taken after flame irradiation. As shown in FIG. 5(A), in the sample of Example 1, the insulating coating was foamed and further carbonized, so that the entire surface became black.

Figure 6 is a photograph taken of the side surface of the sample of Example 1 after irradiation with flame, and it shows that the insulation film remains on the surface of the aluminum plate, and the black part on it foams and carbonizes, forming a layered structure. There is.

Although various embodiments have been described above, it goes without saying that the present invention is not limited to such examples. It is clear that those skilled in the art can come up with various changes or modifications within the scope of the claims, and these naturally fall within the technical scope of the present invention. Understood. Further, each of the constituent elements in the above embodiments may be arbitrarily combined without departing from the spirit of the invention.

Note that this application is based on a Japanese patent application (Japanese Patent Application No. 2022-122199) filed on July 29, 2022, and the contents thereof are incorporated as a reference in this application.

1 Busbar 5

Busbar bodies

6a, 6b Connection hole 10 Insulating coating 11 First layer 12 Second layer 100 Power storage device 110 Battery cell 111 Electrode 120 Battery case

Claims

A bus bar used in a power storage device including a battery cell,
The busbar body containing conductive material is
a first layer formed on the surface of the bus bar body and containing an insulating material whose expansion start temperature is equal to or higher than a predetermined temperature; and a first layer formed on the surface of the first layer and containing a resin that melts below the predetermined temperature. A busbar characterized by being coated with an insulating coating consisting of two layers.
The busbar according to claim 1, wherein the insulating material includes a foaming agent and a binder.
The busbar according to claim 2, wherein the blowing agent is at least one of an ammonium salt, an amino compound, and a chlorinated paraffin.
The bus bar according to claim 2, wherein the binder is at least one of a synthetic resin emulsion, an alkyd, a vinyl chloride resin, a urethane resin, and an epoxy resin.
The bus bar according to claim 2, wherein the insulating material further includes a carbonizing agent.
The bus bar according to claim 5, wherein the carbonizing agent is at least one of carbohydrates and polyhydric alcohols.
The bus bar according to claim 5, wherein the foaming agent is ammonium polyphosphate, the binder is a urethane resin, and the carbonizing agent is a polyhydric alcohol.
The bus bar according to any one of claims 1 to 7, wherein the predetermined temperature is 300°C.
The bus bar according to any one of claims 1 to 7, wherein the thickness of the insulating coating is 0.3 mm or more.
The bus bar according to claim 8, wherein the thickness of the insulating coating is 0.3 mm or more.
A method for manufacturing a bus bar used in a power storage device including a battery cell, the method comprising:
After applying a first coating liquid containing an insulating material whose expansion start temperature is a predetermined temperature or higher on the surface of a bus bar body containing a conductive material, the first coating liquid is dried to form a first layer;
A method for manufacturing a bus bar, comprising applying a second coating liquid containing a resin that melts at a temperature lower than the predetermined temperature to the surface of the first layer, and then drying the liquid to form a second layer.
12. The method of manufacturing a bus bar according to claim 11, wherein the insulating material includes a foaming agent and a binder.
13. The bus bar manufacturing method according to claim 12, wherein the insulating material further includes a carbonizing agent.
The method for manufacturing a busbar according to any one of claims 11 to 13, wherein the predetermined temperature is 300°C.
The method for manufacturing a bus bar according to any one of claims 11 to 13, characterized in that the coating liquid is applied so that the film thickness after drying is 0.3 mm or more.
15. The bus bar manufacturing method according to claim 14, wherein the coating liquid is applied so that the film thickness after drying is 0.3 mm or more.
A power storage device in which a plurality of battery cells or battery modules are connected by the bus bar according to any one of claims 1 to 7.
A power storage device in which a plurality of battery cells or battery modules are connected by the bus bar according to claim 8.
A power storage device in which a plurality of battery cells or battery modules are connected by the bus bar according to claim 9.
A power storage device in which a plurality of battery cells or battery modules are connected by the bus bar according to claim 10.