JP5891806B2 - Battery case packaging material and secondary battery - Google Patents

Description

  The present invention relates to a battery case packaging material for manufacturing a battery case of a secondary battery such as a lithium ion secondary battery.

  Secondary batteries such as lithium-ion secondary batteries are widely used as power sources for various electronic devices such as mobile phones, smartphones, notebook computers, etc., but these secondary batteries have secondary battery elements as battery cases. It has an enclosed structure. Such a battery case is made by deep drawing or overhanging from a sheet-like packaging material for a battery case in which a heat-resistant stretched resin film, an aluminum foil, and a thermoplastic unstretched resin film are laminated via an adhesive. (Patent Document 1, Patent Document 2).

JP 2007-42469 A JP 2000-123800 A

  However, when deep drawing or overhanging is applied to the battery case packaging material of Patent Documents 1 and 2, there is a problem that the possibility of cracking in the aluminum foil increases as the drawing amount increases.

  In addition, when the battery case packaging material after drawing or overhanging or the secondary battery prepared therefrom is stored in a high-temperature and high-humidity environment, between the first adhesive layer and the heat-resistant stretched resin film or aluminum layer. There was a problem of delamination.

  An object of the present invention is to solve the above-described problems of the conventional technology, and is a battery case packaging material in which a heat-resistant stretched resin film, an adhesive, an aluminum foil, and a thermoplastic unstretched resin film are laminated. Even if deep drawing or overhanging is applied, the aluminum foil does not crack, and after deep drawing or overhanging, it can be stored in a high-temperature and high-humidity environment without causing delamination. Is to provide.

  The present inventor stated that “there should be no cracks in the aluminum foil during deep drawing or overhanging of the battery case packaging” and “preserving in a high temperature and high humidity environment after deep drawing or overhanging. In order to achieve “to prevent delamination even at the same time”, the surface heat-resistant stretched resin film that is the outer side of the deep-drawn battery case and the aluminum foil that is the inner side are bonded. Curing treatment of an adhesive composition containing a polyester resin having a glass transition temperature of −20 to 45 ° C. and 10 to 70 parts by mass of a toluene diisocyanate curing agent with respect to 100 parts by mass of the polyester resin. The present inventors have found that it is only necessary to configure the product and have completed the present invention.

  That is, the present invention provides a battery case packaging material having a structure in which a heat-resistant stretched resin layer, a first adhesive layer, an aluminum layer, and a thermoplastic non-stretched resin layer are sequentially laminated. It is comprised from the hardening processed material of the adhesive composition containing the polyester resin which shows the glass transition temperature of 20-45 degreeC, and 10-70 mass parts toluene diisocyanate type hardening | curing agent with respect to 100 mass parts of polyester resins. A battery case packaging material is provided.

  The present invention also provides a secondary battery having a battery case formed by deep drawing or overhanging from the above battery case packaging material and a secondary battery element enclosed in the battery case.

  The packaging material for a battery case of the present invention having a structure in which a heat-resistant stretched resin layer, a first adhesive layer, an aluminum layer, and a thermoplastic unstretched resin layer are sequentially laminated has a first adhesive layer of -20 to 45. It is comprised from the hardening | curing process material of the adhesive composition containing the polyester resin which shows the glass transition temperature of degree C, and 10-70 mass parts toluene diisocyanate type hardening | curing agent with respect to 100 mass parts of polyester resins. For this reason, even if deep drawing or overhanging is applied to the battery case packaging material, the aluminum layer does not crack, and the battery case packaging material after deep drawing or overhanging is subjected to a high temperature and high humidity environment ( For example, delamination can be prevented from occurring even when stored at 60 ° C., 90% RH, 72 hours).

FIG. 1 is a cross-sectional view of the battery case packaging material of the present invention. FIG. 2 is a cross-sectional view of the battery case packaging material of the present invention.

  As shown in FIG. 1, the packaging material 10 for a battery case of the present invention has a structure in which a heat-resistant stretched resin layer 1, a first adhesive layer 2, an aluminum layer 3, and a thermoplastic unstretched resin layer 4 are sequentially laminated. Have. Moreover, as shown in FIG. 2, it is good also as a structure which laminated | stacked the aluminum layer 3 and the thermoplastic unstretched resin layer 4 with the 2nd adhesive bond layer 5. As shown in FIG.

  The battery case packaging material 10 of the present invention is characterized in that the first adhesive layer 2 has a glass transition temperature of −20 to 45 ° C., preferably 4 to 45 ° C., and 100 parts by mass of the polyester resin. It is comprised from the cured | curing processed material of the adhesive composition containing 10-70 mass parts, Preferably 15-50 mass parts, More preferably, 40-50 mass parts toluene diisocyanate type hardening | curing agent.

  If the softening point of the polyester resin is too low, the adhesion reliability at high temperatures tends to decrease, and if it is too high, the possibility of occurrence of poor adhesion tends to increase. Preferably it is 40-100 degreeC.

  In the present invention, the polyester resin having a predetermined glass transition temperature is used as the material for the first adhesive layer 2 between the heat-resistant stretched resin layer 1 and the aluminum layer 3 because the battery case packaging 10 is deep drawn. When the heat-resistant stretched resin layer 1 on the outer side of the battery case is stretched more strongly than the inner layer when processed or stretched, the aluminum layer 3 is stressed to cause cracks in the aluminum layer 3. This is because, in view of the fact that the first adhesive layer 2 is given a function of relaxing such stress.

  Furthermore, the reason why a polyester resin having a glass transition temperature of -20 to 45 ° C. is used as the polyester resin is that the battery case packaging material 10 has practically no problem in moldability (in other words, This is because it indicates an Erichsen value (JIS Z2247).

  If the weight average molecular weight of the polyester resin is too small, the adhesive strength tends to decrease. If the weight average molecular weight is too large, the solubility in a solvent tends to decrease. Moreover, since the hydroxyl value of the polyester resin tends to be difficult to proceed with crosslinking by the curing agent if it is too small, and tends to be hydrolyzed if it is too large, it is preferably 3 to 6, more preferably 4 to 5. is there. Further, if the softening point of the polyester resin is too low, the adhesion reliability at high temperature tends to be lowered, and if it is too high, adhesion failure tends to occur. Therefore, the softening point is preferably 30 to 110 ° C., more preferably 40 to 80. ° C. If the acid value of the polyester resin is too low, crosslinking by the curing agent tends to be difficult to proceed, and if it is too high, hydrolysis tends to occur, and thus it is preferably 1 to 5, more preferably 1 to 3.

  Examples of the diol component constituting the polyester resin include ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol and the like. These can be used alone or as a mixture of two or more diol components. Examples of the dibasic acid component include terephthalic acid, isophthalic acid, adipic acid, sebacic acid and the like. These can also be used as a dibasic acid component individually or in mixture of 2 or more types.

  Adjustment of the glass transition temperature of the polyester resin composed of such components is performed by changing each kind of the diol component or the dibasic acid component or their ratio, changing the weight average molecular weight of the polyester resin, or the like. be able to. For example, when trying to lower the glass transition temperature, increase the amount of 1,4-butanediol used as the diol component, increase the amount of adipic acid used as the dibasic acid component, or the weight average molecular weight of the polyester resin For example. Conversely, when trying to raise the glass transition temperature, increase the amount of neopentyl glycol used as the diol component, increase the amount of terephthalic acid used as the dibasic acid component, or increase the weight average molecular weight of the polyester resin. For example.

  The reason why the first adhesive layer 2 is composed of a cured product of an adhesive composition containing a toluene diisocyanate curing agent in addition to a polyester resin exhibiting a glass transition temperature of -20 to 45 ° C. is In order to prevent delamination between the first adhesive layer 2 and the heat-resistant stretched resin layer 1 or the aluminum layer 3 in a battery case packaging material stored in a high-temperature and high-humidity environment after drawing or overhanging. It is.

  The toluene diisocyanate curing agent itself can undergo an isocyanuration reaction, and if an active hydrogen functional group such as a hydroxyl group or a carboxyl group is present in the polyester resin, they can also undergo a urethanization reaction. . Preferable specific examples of such a toluene diisocyanate curing agent include adducts of toluene diisocyanate and trimethylolpropane.

  As described above, the blending amount of the toluene diisocyanate curing agent in the adhesive composition for forming the first adhesive layer 2 is 10 to 70 parts by mass, preferably 15 to 100 parts by mass with respect to 100 parts by mass of the polyester resin. Although it is 50 mass parts, More preferably, it is 40-50 mass parts, but when there is too little, there exists a tendency for the hardening defect of an adhesive composition to arise, and when too large, the softness | flexibility of the hardened | cured material of an adhesive composition will be impaired. In addition, the moldability of the adhesive composition tends to be lowered.

  The adhesive composition for forming the first adhesive layer 2 contains known tackifiers, various rubbers, cross-linking agents, cross-linking accelerators and the like within a range that does not impair the effects of the invention. Can do.

  If the thickness of the first adhesive layer 2 is too thin, it cannot be said that the stress relaxation ability is sufficient, and if it is too thick, the volume energy density tends to decrease, so it is preferably 2 to 5 μm, more preferably 3 ˜4 μm.

  The heat-resistant stretched resin layer 1 constituting the battery case packaging material 10 of the present invention is a layer for protecting the battery case so that the aluminum layer is not exposed even in a high temperature environment and protecting the battery from a drop impact. . For this reason, the heat-resistant stretched resin layer 1 preferably has a glass transition temperature of 30 to 100 ° C., more preferably 40 to 90 ° C., and a softening point of 200 to 280 ° C., more preferably in consideration of processability. Is a resin having a heat resistance of 210 to 270 ° C., and has a breaking strength (JIS P8112) of preferably 150 to 350 MPa and an impact resistance (JIS K8134) of preferably 30000 to show good impact resistance. It is formed from 80000 J / m resin.

  Examples of the heat resistant stretched resin layer 1 include stretched polyamide films such as stretched nylon films, stretched polyimide films, stretched polyester films, and the like. Among these, from the viewpoint of strength and elongation, a stretched polyamide film, specifically, a stretched nylon film can be preferably used. Here, the stretching treatment is preferably biaxial stretching treatment, more preferably 4-axial stretching treatment.

  If the thickness of the heat-resistant stretched resin layer 1 is too thin, the electronic performance tends to be impaired due to environmental temperature or drop impact, and if it is too thick, it tends to be difficult to mold into a sharp shape. It is 9-50 micrometers, More preferably, it is 15-30 micrometers.

  The aluminum layer 3 constituting the battery case packaging material 10 of the present invention is a layer for preventing water vapor and oxygen from entering the battery case and contributing to the shape retention of the battery case.

  Examples of such an aluminum layer 3 include aluminum foil formed by rolling, and a composite aluminum sheet formed by vapor deposition on a resin film base such as polyester or polyimide. From the viewpoint of productivity and cost, an aluminum foil formed by rolling can be preferably used. In the present invention, “aluminum” includes not only pure aluminum but also various aluminum alloys.

  If the thickness of the aluminum layer 3 is too thin, there is a tendency that non-negligible pinholes or cracks occur due to external force, and if it is too thick, the moldability of the battery case packaging material 10 tends to decrease. Therefore, it is preferably 15 to 150 μm, more preferably 20 to 80 μm.

  The thermoplastic unstretched resin layer 4 constituting the battery case packaging material 10 of the present invention insulates the electronic element in the battery case from the aluminum layer 3 of the packaging material, and also provides a heat sealing property to the packaging material. It is.

  The reason why this thermoplastic unstretched resin layer 4 is thermoplastic is to maintain the airtightness of the battery case and exhibit heat sealability, and the reason that it is unstretched is to ensure sufficient heat sealability. It is to do.

  If the glass transition temperature of the thermoplastic unstretched resin layer 4 is too low, the adhesive reliability at high temperatures tends to decrease, and if it is too high, the heat sealability tends to decrease. ° C, more preferably -20 to -15 ° C, and if the softening point is too low, the heat sealability tends to decrease, and if it is too high, the adhesion reliability at high temperatures tends to decrease. Preferably it is 130-180 degreeC, More preferably, it is 140-170 degreeC.

  Examples of the thermoplastic unstretched resin layer 4 include unstretched polyolefin films, such as polyethylene films, polypropylene films, polyethylene-polypropylene copolymer films, acids (such as maleic acid and acrylic acid), and esters (such as acrylics). An acid ester) -modified polypropylene film can be preferably mentioned. Among these, an unstretched polyolefin film is preferable, and an unstretched polypropylene film is particularly preferable.

  The reason why this thermoplastic unstretched resin layer 4 is thermoplastic is to maintain the airtightness of the battery case and exhibit heat sealability, and the reason that it is unstretched is to ensure sufficient heat sealability. It is to do.

  Moreover, since the layer thickness of the thermoplastic unstretched resin layer 4 is too thin, sufficient heat seal strength cannot be obtained, and if it is too thick, the volume energy density tends to decrease, preferably 10 to 70 μm. Preferably it is 20-50 micrometers.

  The battery case packaging material 10 of the present invention may be provided with a second adhesive layer 5 between the aluminum layer 3 and the thermoplastic unstretched resin layer 4 as shown in FIG. In this case, the second adhesive layer 5 may be formed of the same type of adhesive as the first adhesive layer 2, and other acrylic adhesives, ester adhesives, urethane adhesives, styrene / butadiene based adhesives. You may form from a thermoplastic elastomer adhesive agent etc. Among them, those formed from a styrene / butadiene-based thermoplastic elastomer adhesive are preferable from the viewpoint of resistance to electrolytic solution and waterproofness.

  If the thickness of the second adhesive layer is too thin, sufficient adhesive strength cannot be obtained, and if it is too thick, the volume energy density tends to decrease, so it is preferably 1 to 5 μm, more preferably 2 to 4 μm. .

  The battery case packaging material of the present invention can be manufactured using a known film forming method or dry lamination method. For example, the battery case packaging material of FIG. 1 is obtained by applying an adhesive composition containing a polyester resin having a predetermined glass transition temperature and a predetermined amount of a toluene diisocyanate-based curing agent to a heat-resistant stretched resin film. After drying at a temperature that does not cure, a pre-adhesive layer is formed, an aluminum foil is attached to the pre-adhesive layer, and then heated above the temperature at which the curing agent cures, heat-resistant stretched resin film and aluminum The foil can be bonded with a cured product of the adhesive composition, and then the thermoplastic resin is laminated on the aluminum foil as a thermoplastic unstretched resin layer by a melt extrusion method. Also, the battery case packaging material of FIG. 2 is similar to the battery case packaging material of FIG. 1, after the heat-resistant stretched resin film and the aluminum foil are bonded with the cured product of the adhesive composition, The second adhesive layer forming composition is applied to the thermoplastic unstretched resin film arranged so as to oppose it, or the second adhesive layer is formed while being melt-extruded, and laminated by the dry lamination method. Can be manufactured.

  The battery case packaging material of the present invention is a battery case in which cracking does not occur in the aluminum layer and delamination does not occur even in a high-temperature and high-humidity environment by known deep drawing or stretch forming (see Japanese Patent No. 3567230). Can be processed. Moreover, it is possible to prevent the occurrence of delamination even in a high temperature and high humidity environment. Moreover, a secondary battery suitable for practical use can be obtained by enclosing a secondary battery element such as a known lithium ion secondary battery element in the battery case.

  Hereinafter, the packaging material for battery cases of the present invention will be described more specifically according to examples. Reference Examples 1 to 8 evaluate the relationship between the glass transition temperature of the polyester resin and the Erichsen value (deep drawing amount [mm]) in the battery case packaging prepared without using the toluene diisocyanate curing agent. It is an example for.

Reference Examples 1-8
On one side of a 15 μm-thick four-axis stretched nylon film (ON, Unitika Ltd.), a polyester resin (UE series, Unitika Ltd.) toluene solution (polyester 15% by volume) shown in Table 1 is 3 μm dry thickness It applied so that it might become, and it was made to dry and formed the 1st adhesive layer, and it wound up on the roll so that the 1st adhesive layer might become the inside.

  In addition, about the used polyester resin, a dicarboxylic acid component, a diol component, a glass transition temperature, a weight average molecular weight, a softening point, a hydroxyl value, and an acid value are shown together in Table 1.

  A 35 μm-thick aluminum foil (8021-o material, Sumi Light Aluminum Foil Co., Ltd.) was applied to the adhesive layer of the sheet unwound from the obtained roll with a heat drum heated to 60 ° C. to a weight of 3.0 kg / cm. Lamination was performed while applying linear pressure, and the product was wound on a roll. Next, the aluminum layer of the sheet that has been unwound from the wound roll is opposed to a separately prepared 30 μm-thick unstretched polypropylene film (GLC, Mitsui Chemicals, Inc.), and second adhesive is provided between them. A styrene / butadiene / styrene (SBS) -based adhesive (Tuftec M1913, Asahi Kasei Co., Ltd.), which is an agent layer, is applied to a layer thickness of 3 μm and laminated by a dry lamination method to form a battery case packaging material. Obtained.

  In order to evaluate the moldability of the obtained packaging material for battery cases, an Erichsen test was conducted using an Erichsen tester (Coating Tester Co., Ltd.) according to JIS Z2247 except that the drawing speed was 1 mm / min. It was visually confirmed whether or not a crack occurred in the aluminum layer of the packaging material, and the amount of drawing (Ericsen value) [mm] where the crack occurred was shown in Table 1 and evaluated according to the following criteria. The Erichsen number is desired to be 9 mm or more practically.

  From the results shown in Table 1, when the glass transition temperature range of the polyester resin in Reference Examples 2 to 7 was “−20 to 45 ° C.”, the exelin value was 9 or more. On the other hand, of the weight average molecular weight, softening point, hydroxyl value, and acid value, the weight average molecular weight and hydroxyl value are further limited by the scope of the invention, assuming that the glass transition temperature is -20 to 45 ° C. It turns out that it can contribute to limiting. In that case, the preferable range of a weight average molecular weight is 20000-30000, and it turns out that the preferable hydroxyl value of a polyester resin is 3-6. In addition, about a softening point and an acid value, it turns out that a clear correlation with an Erichsen value is not observed.

Examples 1-4 and Comparative Examples 1-8
On one side of a 15 μm thick biaxially stretched nylon film (ON, Unitika Ltd.), with the polyester resin of Reference Example 6 (UE3500, Unitika Ltd.) showing the best moldability among Reference Examples 1-8 Applying a toluene solution (15% by volume of polyester) of a mixed adhesive containing 100 parts by mass of the polyester resin and the type and mass part of the curing agent shown in Table 2 to a dry thickness of 3 μm and drying. Then, an adhesive layer was formed and wound on a roll so that the adhesive layer was inside.

  A 35 μm-thick aluminum foil (8021-o material, Sumi Light Aluminum Foil Co., Ltd.) was applied to the adhesive layer of the sheet unwound from the obtained roll with a heat drum heated to 60 ° C. to a weight of 3.0 kg / cm. Lamination was performed while applying linear pressure, and the product was wound on a roll. This roll was heated in an oven at 160 ° C. for 48 hours to cure the adhesive layer.

  Next, the aluminum layer of the sheet that has been unwound from the wound roll is opposed to a separately prepared 30 μm-thick unstretched polypropylene film (GLC, Mitsui Chemicals, Inc.), and second adhesive is provided between them. A battery case packaging material is obtained by applying a styrene / butadiene / styrene (SBS) adhesive (Tuftec M1913, Asahi Kasei Co., Ltd.) to be a layer thickness of 3 μm and laminating by a dry lamination method. It was.

  In order to evaluate the moldability of the obtained battery case packaging material, an Erichsen test was conducted according to JIS Z2247 using an Erichsen tester except that the drawing speed was 1 mm / min, and the aluminum layer of the packaging material was cracked. Table 2 shows the amount of squeezing (Erichsen value) [mm] at which cracks occurred. The Erichsen number is desired to be 9 mm or more practically.

  Also, the battery case packaging material is stored for “72 hours in an atmosphere of 60 ° C. and 90% RH” or “72 hours in an atmosphere of 80 ° C. and 90% RH” to determine whether delamination occurs. Visual observation was made and the case where delamination did not occur was evaluated as good. On the other hand, the case where delamination occurred was evaluated as defective, and “x” is shown in Table 2.

  From the results of Table 2, in the case of battery case packaging materials of Examples 1 to 4 using a toluene diisocyanate curing agent, there is no problem in moldability, and a high temperature of “60 ° C., 90% RH, 72 hours storage”. It can be seen that delamination is prevented even under high humidity conditions. In particular, in the case of the packaging materials for battery cases of Examples 3 and 4 in which the toluene diisocyanate curing agent was used at a ratio of 40 to 50 parts by mass with respect to 100 parts by mass of the polyester resin, 80 ° C., 90% RH, 72 hours. It can be seen that delamination is prevented even under the condition of storage.

  On the other hand, from the results of Comparative Examples 1 to 8, when a xylene diisocyanate curing agent or a hexamethylene diisocyanate curing agent was used as the curing agent, the conditions were 60 ° C. or 80 ° C., 90% RH, 72 hours storage. It can be seen that delamination has occurred.

  In the case of the battery case packaging materials of Reference Examples 1 to 8, it is added here that the occurrence of delamination was unavoidable under the conditions of 60 ° C. or 80 ° C., 90% RH, and 72 hours storage. .

  The battery case packaging material of the present invention does not cause cracks in the aluminum layer even when the battery case packaging material is deep-drawn, and delamination does not occur even when stored in a high temperature and high humidity environment. Therefore, it is useful for a battery case of a lithium ion secondary battery.

1 Heat Resistant Stretched Resin Layer 2 First Adhesive Layer 3 Aluminum Layer 4 Thermoplastic Unstretched Resin Layer 5 Second Adhesive Layer 10 Battery Case Packaging

Claims (10)

In a battery case packaging material having a structure in which a heat-resistant stretched resin layer, a first adhesive layer, an aluminum layer, and a thermoplastic unstretched resin layer are sequentially laminated,
Curing of an adhesive composition in which the first adhesive layer contains a polyester resin exhibiting a glass transition temperature of −20 to 45 ° C. and 10 to 70 parts by mass of a toluene diisocyanate curing agent with respect to 100 parts by mass of the polyester resin. It consists of processed materials ,
The polyester resin has a hydroxyl value of 3-6 mgKOH / g and a weight average molecular weight in the range of 20000-30000,
The toluene diisocyanate curing agent is a battery case packaging material that is an adduct of toluene diisocyanate and trimethylolpropane .   The packaging material for battery cases according to claim 1, wherein the adhesive layer contains a polyester resin exhibiting a glass transition temperature of 4 to 45 ° C.   The packaging material for battery cases of Claim 1 or 2 containing 15-50 mass parts toluene diisocyanate type hardening | curing agent with respect to 100 mass parts of polyester resins.   The packaging material for battery cases of Claim 1 or 2 containing 40-50 mass parts toluene diisocyanate type hardening | curing agent with respect to 100 mass parts of polyester resins. The battery case packaging material according to any one of claims 1 to 4 , wherein the heat-resistant stretched resin layer is a stretched polyamide film, and the thermoplastic unstretched resin layer is an unstretched polyolefin film. The battery case packaging material according to claim 5 , wherein the stretched polyamide film is a stretched nylon film, and the unstretched polyolefin film is a nonstretched polypropylene film. The packaging material for battery cases according to any one of claims 1 to 6 , wherein the aluminum layer and the thermoplastic unstretched resin layer are laminated by a second adhesive layer. The packaging material for a battery case according to claim 7, wherein the second adhesive layer is formed from a styrene / butadiene-based thermoplastic elastomer adhesive. Secondary battery having a battery case packaging material according to any one of claims 1-8, a battery case formed by deep drawing or stretch forming, and a secondary battery element enclosed in the battery case. The secondary battery according to claim 9 , wherein the secondary battery element is a lithium ion secondary battery element.

Images