JP2016129113A - Heat-bonding insulative resin film and power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-bonding insulative resin film which shows a superior endurance against a tensile force resulting from the expansion of an exterior member owing to the rise in internal pressure of a power storage device such as a laminate type lithium ion secondary battery.SOLUTION: A heat-bonding insulative resin film comprises three layers, namely a lead member adhesion layer 1 adhering to a lead member 4 of a power storage device 6, an exterior member adhesion layer 3 adhering to an exterior member 5 of the power storage device 6, and an insulator layer 2 interposed between the lead member adhesion layer 1 and the exterior member adhesion layer 3. In the heat-bonding insulative resin film, the proportion of a thickness T2 of the insulator layer 2 to a total thickness T which is the sum of a thickness T1 of the lead member adhesion layer 1, the thickness T2 of the insulator layer 2, and a thickness T3 of the exterior member adhesion layer 3 is set to 10-45%.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a heat-welded insulating resin film that insulates between a lead member and an exterior member in a sealing portion of a power storage device such as a laminated lithium ion secondary battery, an electric double layer capacitor, or a lithium ion capacitor and prevents a short circuit, and The present invention relates to a power storage device using the heat-welded insulating resin film.

  In recent years, in the field of lithium ion secondary batteries, along with the widespread use of thin portable electronic devices such as smartphones and tablet terminals, it has become thinner and lighter in place of the conventional square metal can type lithium ion secondary batteries. Efforts are being made to develop laminate-type lithium ion secondary batteries that are advantageous in the field of commercialization.

  This laminated lithium ion secondary battery is generally formed by laminating a negative electrode, a separator, and a positive electrode that are formed into a thin plate in order, and a lead member (electrode terminal) is attached to the laminate. (Generally, an aluminum laminate film) is housed together with the electrolytic solution, and the opening is sealed by heat sealing in a state in which the lead member is pulled out from the opening.

  In addition, in the sealed portion where the opening from which the lead member is drawn is sealed, heat is not generated between the lead member and the exterior member so that the lead member and the exterior member are not brought into contact with each other due to overheating during heat sealing. It is set as the structure which prevented generation | occurrence | production of the short circuit by the overheating at the time of heat sealing by interposing a welding insulation resin film and sealing via this heat welding insulation resin film.

  Conventionally, what is shown, for example in patent document 1 is known as such a heat welding insulation resin film. This heat-welded insulating resin film of Patent Document 1 (in the invention described in Patent Document 1, a lead sealant film) is composed of a lead member adhesive layer (inner layer), an insulating layer (intermediate layer), and an exterior member adhesive layer (outer layer). The intermediate layer is made of a material with a higher melting point than the other layers, so that the insulating layer does not dissolve during heat sealing, and the insulating layer is retained and reliably short-circuited. It is.

JP 2008-192451 A

  However, the laminate type lithium ion secondary battery has a problem that due to its characteristics, gas is generated inside with deterioration over time, the internal pressure is increased due to the generation of this gas, and the exterior member expands. Although the problem of short circuit has been solved, there are still problems in terms of durability, and it may endure without being able to withstand the tensile force generated by expansion, and this heat-welded insulating resin film may break. In some cases, the sealing of the exterior member is broken, and problems such as rupture of the power storage device and leakage of the electrolytic solution may occur.

  The present invention was made in view of the current situation as described above, and uses a heat-welded insulating resin film that exhibits excellent durability against tensile force generated by expansion of the exterior member, and this heat-welded insulating resin film, It is an object of the present invention to provide a highly safe power storage device in which occurrence of problems such as rupture and electrolyte leakage in a power storage device such as a laminated lithium ion secondary battery or a lithium ion capacitor is reduced as much as possible.

  The gist of the present invention will be described with reference to the accompanying drawings.

  A lead member adhesive layer 1 that adheres to the lead member 4 of the power storage device 6 such as a laminate type lithium ion secondary battery, an electric double layer capacitor, or a lithium ion capacitor, and an exterior member adhesive layer that adheres to the exterior member 5 of the power storage device 6 3 and a heat-welded insulating resin film consisting of three layers, an insulating layer 2 interposed between the lead member adhesive layer 1 and the exterior member adhesive layer 3, and the thickness T1 of the lead member adhesive layer 1 and the insulation Thermal welding, wherein the ratio of the thickness T2 of the insulating layer 2 to the total thickness T, which is the sum of the thickness T2 of the layer 2 and the thickness T3 of the exterior member adhesive layer 3, is set to 10% to 45% It relates to an insulating resin film.

  Moreover, the said total thickness T was set to 50 micrometers-200 micrometers, It concerns on the heat welding insulation resin film of Claim 1 characterized by the above-mentioned.

  The insulating layer 2 is made of a resin having a tensile strength in a tensile test based on JIS-Z-1702-1994 of 70 MPa or less. This relates to the heat-welded insulating resin film described.

  The insulating layer 2 is a heat-welded insulating resin film according to any one of claims 1 to 3, wherein the insulating layer 2 is a polypropylene resin, an acid-modified polypropylene resin, or a polyethylene resin. is there.

  Further, the present invention relates to a power storage device characterized in that the heat-welded insulating resin film according to any one of claims 1 to 4 is provided between the lead member 4 and the exterior member 5.

  Since the present invention is configured as described above, the durability against the tensile force generated by the expansion action of the exterior member is improved, and it does not break even if it is pulled by the tension action due to the expansion of the exterior member due to the internal pressure increase in the power storage device. Thermal seal insulation with excellent practicality that can maintain the sealed state of the exterior member well, thus preventing the storage device from rupturing or leaking electrolyte, and realizing a highly safe power storage device It becomes a resin film.

  Moreover, in the present invention, the thickness T2 of the insulating layer with respect to the total thickness T, which is simply the sum of the thicknesses of the lead member adhesive layer, the insulating layer, and the exterior member adhesive layer, is 10% without changing the material of the insulating layer. Since the durability can be easily improved with an extremely simple configuration which is set to a thickness of ˜45%, it becomes an epoch-making heat-welded insulating resin film which can be realized very easily.

  Moreover, in invention of Claims 2-4, durability of an insulating layer improves further and it becomes a heat welding insulation resin film excellent in practicality further.

  Further, in the invention according to claim 5, even when the exterior member expands due to an increase in internal pressure due to deterioration, the sealing of the exterior member is not broken, and thus problems such as rupture of the power storage device and leakage of the electrolyte occur. It becomes an excellent power storage device with high safety.

It is explanatory drawing which shows the use condition of a present Example. It is AA explanatory sectional drawing in FIG. It is explanatory perspective view which shows a present Example. The detailed result of the 180 degree peel strength test in a present Example is shown.

  An embodiment of the present invention which is considered to be suitable will be briefly described with reference to the drawings showing the operation of the present invention.

  The ratio of the thickness T2 of the insulating layer 2 to the total thickness T of the heat-welded insulating resin film 7 (thickness T1 of the lead member adhesive layer 1 + thickness T2 of the insulating layer 2 + thickness T3 of the exterior member adhesive layer 3) is set to be small (thin). Specifically, by setting to 10% to 45%, for example, the tensile force generated by the expansion action of the power storage device 6 such as a laminated lithium ion secondary battery or a lithium ion capacitor of the heat-welded insulating resin film 7 is set. Durability is improved, and even if the expansion action occurs, the heat-welded insulating resin film 6 is not broken, and a good sealing state is maintained, and it is possible to cause problems such as rupture of the power storage device and leakage of the electrolyte. Can be suppressed. Specifically, the following mechanism is considered.

  The present inventors have repeatedly conducted various verification experiments on breakage of the heat-welded insulating resin film 7 due to expansion of the exterior member 5 due to an increase in internal pressure of the power storage device 6 such as a laminated lithium ion secondary battery or a lithium ion capacitor, As a result of ascertaining that the insulating layer 2 that is an intermediate layer of the welded insulating resin film 7 is ruptured and further studying the factors that cause the insulating layer 2 to break, the thickness T2 of the insulating layer 2 is determined to be the total thickness. It came to the conclusion that setting thicker than T is one of the breakage factors.

  That is, if the insulating layer 2 is sufficiently thicker than the other layers (the lead member adhesive layer 1 and the exterior member adhesive layer 3), the breaking point is large, and the stress generated by the tensile force of the exterior member 5 is concentrated on the insulating layer 2. Therefore, it was considered that the insulating layer 2 could not withstand this concentrated stress and was broken.

  Therefore, the present inventors reduced the ratio of the thickness T2 of the insulating layer 2 to the total thickness T of the heat-welded insulating resin film 7 (insulating layer 2) in order to alleviate the stress concentration on the insulating layer 2. In order to reduce the breaking point and to disperse the stress to other layers, the durability of the insulating layer 2 is relatively improved, and the durability of the heat-welded insulating resin film 7 as a whole is reduced. Found to improve.

  Furthermore, conventionally, the insulating layer 2 is considered to be harder than the adhesive layers such as the lead member adhesive layer 1 and the exterior member adhesive layer 3, thereby having lower durability against elongation stress than the other layers. By adopting a soft material for the insulating layer 2 (for example, a resin having a tensile strength of 70 MPa or less (preferably 60 MPa or less) in a tensile test based on JIS-Z-1702-1994), the durability of the insulating layer 2 is improved. It has also been found that the property can be further improved.

  Specific embodiments of the present invention will be described with reference to the drawings.

  In this embodiment, the thermal welding insulation used to insulate the lead member 4 (tab lead) and the exterior member 5 (laminate film) in the lead lead portion 8 of the laminate type lithium ion secondary battery 6 as shown in FIG. It relates to a resin film.

  Specifically, as shown in FIGS. 2 and 3, the lead member adhesive layer 1 that adheres to the lead member 4 of the laminated lithium ion secondary battery 6 and the outer member 5 of the laminated lithium ion secondary battery 6 adhere to each other. The insulating member 2 is composed of three layers, an insulating layer 2 interposed between the lead member adhering layer 1 and the outer member adhering layer 3, and the thickness T2 of the insulating layer 2 is set to 10% to 45% of the total thickness T, that is, the total thickness T that is the sum of the thickness T1 of the lead member adhesive layer 1, the thickness T2 of the insulating layer 2, and the thickness T3 of the exterior member adhesive layer 3 It is.

  More specifically, the total thickness T is set to a range of 50 μm to 200 μm.

  The lead member adhesive layer 1 and the exterior member adhesive layer 3 employ an acid-modified polypropylene resin, and the insulating layer 2 employs a polypropylene resin, an acid-modified polypropylene resin, or a polyethylene resin. The lead member adhesive layer 1 and the exterior member adhesive layer 3 are not limited to those described above, and can be appropriately adopted as long as they exhibit equivalent performance.

  Furthermore, the insulating layer 2 has a configuration in which a low hardness (soft material) is adopted. Specifically, the tensile strength in a tensile test based on JIS-Z-1702-1994 is 70 MPa or less (preferably 60 MPa). The following is adopted.

  Hereinafter, the configuration example 1 to the configuration example 3 configured by the above-described configuration requirements of the present embodiment and the comparative example 1 in which conditions other than the configuration requirements of the present embodiment are set are shown below.

<Configuration example 1>
In the configuration example 1, the total thickness T is set to 74 μm, and the ratio of the thickness T2 of the insulating layer 2 to the total thickness T is set to about 40%. Specifically, the thickness T1 of the lead member adhesive layer 1, the thickness T2 of the insulating layer 2, and the thickness T3 of the exterior member adhesive layer 3 were T1 / T2 / T3 = 22 μm / 30 μm / 22 μm, respectively.

  Further, the insulating layer 2 is configured to employ a polypropylene resin (specifically, a random polypropylene resin).

  Furthermore, the random polypropylene resin used for the insulating layer 2 has a tensile strength of 70 MPa in a tensile test based on JIS-Z-1702-1994.

<Configuration example 2>
In the configuration example 2, the total thickness T is set to 74 μm, and the ratio of the thickness T2 of the insulating layer 2 to the total thickness T is set to about 40%. Specifically, the thickness T1 of the lead member adhesive layer 1, the thickness T2 of the insulating layer 2, and the thickness T3 of the exterior member adhesive layer 3 were T1 / T2 / T3 = 22 μm / 30 μm / 22 μm, respectively.

  Further, the insulating layer 2 has a configuration employing a polypropylene resin (specifically, a homopolypropylene resin).

  Furthermore, the homopolypropylene resin used for the insulating layer 2 was one having a tensile strength of 60 MPa in a tensile test based on JIS-Z-1702-1994.

<Configuration example 3>
In the configuration example 3, the total thickness T is set to 74 μm, and the ratio of the thickness T2 of the insulating layer 2 to the total thickness T is set to about 32%. Specifically, the thickness T1 of the lead member adhesive layer 1, the thickness T2 of the insulating layer 2, and the thickness T3 of the exterior member adhesive layer 3 were T1 / T2 / T3 = 25 μm / 24 μm / 25 μm, respectively.

  Further, the insulating layer 2 has a configuration employing a polypropylene resin (specifically, a homopolypropylene resin).

  Furthermore, the homopolypropylene resin used for the insulating layer 2 was one having a tensile strength of 60 MPa in a tensile test based on JIS-Z-1702-1994.

<Comparative example>
In the comparative example, the total thickness T was set to 74 μm, and the ratio of the thickness T2 of the insulating layer 2 to the total thickness T was set to about 54%. Specifically, the thickness T1 of the lead member adhesive layer 1, the thickness T2 of the insulating layer 2, and the thickness T3 of the exterior member adhesive layer 3 were T1 / T2 / T3 = 17 μm / 40 μm / 17 μm, respectively.

  Further, the insulating layer 2 has a configuration employing a polypropylene resin (specifically, a homopolypropylene resin).

  Furthermore, the homopolypropylene resin used for the insulating layer 2 was one having a tensile strength of 60 MPa in a tensile test based on JIS-Z-1702-1994.

Table 1 below shows a list of the configuration conditions of the configuration examples 1 to 3 and the comparative example.

  The durability of each of the configuration examples 1 to 3 and the comparative example configured as described above was confirmed.

  Specifically, the durability was confirmed by measuring the peel strength of the heat-welded insulating resin film by a 180 degree peel strength test.

  The test method will be described. The sample is a laminate film (this book) similar to the exterior member 5 in which each heat-welded insulating resin film 7 of Configuration Examples 1 to 3 and Comparative Example is formed into a strip shape having a width of 5 mm. In the examples, the aluminum laminate film is used to wrap the laminated film at the bent side end portion, and the overlapping portions where the heat-welded insulating resin film 7 and the laminate film overlap each other (200 ° C., 5 seconds). Then, the heat-welded insulating resin film 7 and the laminate film were welded and cut into a direction perpendicular to the folding direction of the laminate film to form a strip shape having a width of 5 mm.

  Moreover, the peeling tester used the precision universal testing machine (EZ-L) by Shimadzu Corporation, and set the peeling rate to 5 mm / min-100 mm / min, and measured the peeling strength in each case. In addition, the measurement was performed 3 times per 1 condition per sample.

Table 2 below shows the measurement results. Detailed results are shown in FIG.

  As shown in Table 2, when the tensile strength (durability) of the comparative example is 100%, the durability of the configuration example 1 is 130%, the durability of the configuration example 2 is 150%, and the durability of the configuration example 3 180%, an improvement in durability was confirmed in all examples.

  Moreover, from the structural example 1 and the structural example 2, it has also confirmed that durability was improved more when the hardness of the insulating layer 2 was soft.

  In addition, in the 180 degree peel strength test, the structural example 2 and structural example 3 which were relatively good results were further subjected to a durability test in a form close to the actual use state.

Specifically, the lead member 4 is inserted and disposed in the lead lead-out portion 8 of the exterior member 5 (in this embodiment, the positive electrode material, the negative electrode material, and the electrolytic solution are not inserted), heat sealed, and the actual laminate type Air is injected into the exterior member 5 of the sample formed in the same form as the exterior of the lithium ion secondary battery 6, the internal pressure in the exterior member 5 is increased to 5 kgf / cm ² , and this state is continued for 30 seconds. A leak test was conducted to confirm the state of the heat-welded insulating resin film 7 when a load was applied (damaged state or presence or absence of leakage of the exterior member 5). The leak test was conducted for each of the examples, comparative examples, and 5 samples.

Table 3 below shows the leak test results.

  As shown in Table 3, Structural Example 2 and Structural Example 3 that showed good durability in the 180-degree peel test were conducted in a leak test that simulated the expansion action of an actual laminated lithium ion secondary battery. Also showed good results.

  Thus, in this example, the thickness T2 of the insulating layer 2 with respect to the total thickness T of the heat-welded insulating resin film 7 (thickness T1 of the lead member adhesive layer 1 + thickness T2 of the insulating layer 2 + thickness T3 of the exterior member adhesive layer 3). Is set to 10% to 45%, preferably 30% to 35%, and the material of the insulating layer 2 has a hardness of 70 MPa or less in tensile strength in a tensile test in accordance with JIS-Z-1702-1994. Preferably, by adopting a material having a thickness of 60 MPa or less, the durability against the tensile force generated by the expansion action of the laminated lithium ion secondary battery 6 of the heat-welded insulating resin film 7 is improved, and even if the expansion action occurs. Without being broken, the sealed state of the lead lead-out portion 8 (opening portion) of the laminated lithium ion secondary battery 6 is satisfactorily maintained, and the occurrence of leakage of the electrolyte is suppressed as much as possible. It becomes innovative thermal welding insulating resin film excellent in practicality capable.

  Note that the present invention is not limited to this embodiment, and the specific configuration of each component can be designed as appropriate.

DESCRIPTION OF SYMBOLS 1 Lead member adhesive layer 2 Insulating layer 3 Exterior member adhesive layer 4 Lead member 5 Exterior member 6 Power storage device

Claims (5)

  A lead member adhesive layer that adheres to a lead member of a power storage device such as a laminate-type lithium ion secondary battery, an electric double layer capacitor, or a lithium ion capacitor; an exterior member adhesive layer that adheres to an exterior member of the power storage device; and the lead member In the heat-welded insulating resin film comprising three layers of an adhesive layer and an insulating layer interposed between the exterior member adhesive layer, the lead member adhesive layer thickness T1, the insulating layer thickness T2, and the exterior member adhesive layer A heat-welded insulating resin film, wherein the ratio of the thickness T2 of the insulating layer to the total thickness T, which is the sum of the thickness T3, is set to 10% to 45%.   The heat-welded insulating resin film according to claim 1, wherein the total thickness T is set to 50 μm to 200 μm.   3. The heat according to claim 1, wherein the insulating layer is made of a resin having a tensile strength of 70 MPa or less in a tensile test based on JIS-Z-1702-1994. Welding insulation resin film.   4. The heat-welded insulating resin film according to claim 1, wherein the insulating layer is one of a polypropylene resin, an acid-modified polypropylene resin, and a polyethylene resin.   5. A power storage device, wherein the heat-welded insulating resin film according to claim 1 is provided between a lead member and an exterior member.

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