Power storage device outer material, power storage device outer casing, and power storage device

Abstract

Provided are a power storage device outer material, a power storage device outer casing, and a power storage device, which feature excellent sealing strength at high temperatures and excellent barrier properties. This power storage device outer material 1 is characterized by comprising at least a base material layer 2, a barrier layer 4, and a heat-fusible resin layer 3, in that order from the outside to the inside, and characterized in that: the heat-fusible resin layer 3 is composed of a laminate of two or more layers including a first polyolefin layer 7, which is the innermost layer, and a second polyolefin layer 8, which is on the barrier layer 4 side; the first polyolefin layer 7 contains a polyolefin resin having a melting point of 155°C or less as a main component; and the second polyolefin layer 8 contains an elastomer-modified polyolefin resin having a melting point of 150°C or more in the amount of 10-70 mass% and a polyolefin resin having a melting point of 135°C or more in the amount of 10-60 mass%.

Description

Exterior material for power storage device, exterior case for power storage device, and power storage device

[0001] The present invention relates to a packaging material for an electricity storage device, and to an electricity storage device constructed using this packaging material.

[0002] In this specification and claims, the term "melting point" means the melting peak temperature measured by differential scanning calorimetry (DSC) in accordance with JIS K7121-1987, and the term "crystalline melting energy" means the heat of fusion (crystalline melting energy) measured by differential scanning calorimetry (DSC) in accordance with JIS K7122-1987.

[0003] In addition, in this specification and claims, the term "crystalline melting energy" refers to the highest crystalline melting energy value when there are two or more crystalline melting peak curves and two or three or more crystalline melting energies (ΔH1, ΔH2).

[0004] In addition, in this specification and claims, the term "melt flow rate (MFR)" means the melt flow rate measured in accordance with JIS K7210-1-2014.

[0005] In this specification, the term "aluminum" is used to include aluminum and its alloys.

[0006] Lithium ion secondary batteries are widely used as power sources for devices such as notebook computers, video cameras, mobile phones, and electric vehicles. These lithium ion secondary batteries have a battery body (a body including a positive electrode, a negative electrode, and an electrolyte) enclosed in a case. Known examples of the case material (exterior material) include an outer layer made of a heat-resistant resin film, an aluminum foil layer, and an inner layer made of a thermoplastic resin film, which are bonded together in this order.

[0007] The electricity storage device is configured by sandwiching the electricity storage device body between a pair of exterior materials, and sealing the peripheral edges of the pair of exterior materials by fusion bonding (heat sealing).

[0008] Among power storage devices such as lithium ion secondary batteries and all-solid-state batteries, all-solid-state batteries, which have an operating temperature of −40° C. to 90° C., are expected to be used in higher temperature environments, and therefore require good sealing strength even at high temperatures.

[0009] Patent Document 1 discloses a battery exterior packaging material 4 having a laminated structure of an outer layer 11 / a metal foil layer 10 / an inner layer 8, in which the inner layer 8 has, for example, a two-layer structure of a sealant layer 8b (the innermost layer) / a substrate layer 8a, or a three-layer structure of a sealant layer 8b / a substrate layer 8a / a sealant layer 8b. It also discloses that a predetermined propylene-based block copolymer is used for the substrate layer 8a, and a propylene-ethylene random copolymer is used for the sealant layer 8b.

[0010] JP 2013-157287 (Patent 6146953)

[0011] However, the substrate layer 8a of the inner layer 8 in this document is composed only of a propylene-based block copolymer. Therefore, the proportion of the elastomer component contained in the propylene-based block copolymer is high, which reduces the bond strength between the innermost sealant layer 8b or the sealant layer 8b on the metal foil layer 10 side and the substrate layer 8a at high temperatures, resulting in insufficient seal strength at high temperatures. Furthermore, the high proportion of the amorphous elastomer component increases moisture permeation, resulting in insufficient moisture barrier properties.

[0012] The present invention has been made in view of this technical background, and aims to provide an exterior material for an electricity storage device that has good sealing strength at high temperatures and also good moisture barrier properties, an exterior case for an electricity storage device, and an electricity storage device.

[0013] In order to achieve the above object, the present invention provides the following means.

[0014] [1] An exterior packaging material for an electricity storage device, in which at least a base material layer, a barrier layer, and a heat-sealable resin layer are laminated in this order from the outside to the inside, wherein the heat-sealable resin layer is made of a laminate of two or more layers including a first polyolefin layer as the innermost layer and a second polyolefin layer on the barrier layer side, the first polyolefin layer is mainly composed of a polyolefin resin having a melting point of 155°C or less, and the second polyolefin layer contains 10% by mass to 70% by mass of an elastomer-modified polyolefin resin having a melting point of 150°C or more and 10% by mass to 60% by mass of a polyolefin resin having a melting point of 135°C or more.

[0015] [2] The packaging material for an electricity storage device according to item 1, wherein the thickness ratio of the first polyolefin layer to the second polyolefin layer is from (10:90) to (40:60).

[0016] [3] The packaging material for an electricity storage device according to the above item 1 or 2, wherein the polyolefin resin of the second polyolefin layer has a crystalline melting energy of 60 J / g or more.

[0017] [4] The packaging material for an electricity storage device according to any one of items 1 to 3, wherein the elastomer-modified polyolefin resin has a crystalline melting energy of 60 J / g or more.

[0018] [5] The packaging material for an electricity storage device according to any one of items 1 to 4 above, wherein the heat-fusible resin layer has a crystalline melting energy of 70 J / g or more.

[0019] [6] The packaging material for an electricity storage device according to any one of items 1 to 5, wherein the polyolefin resin of the second polyolefin layer has an MFR of 2 g / 10 min or more and 20 g / 10 min or less.

[0020] [7] The packaging material for an electricity storage device according to any one of items 1 to 6, wherein the elastomer-modified polyolefin resin has an MFR of 1 g / 10 min or more and 10 g / 10 min or less.

[0021] [8] The packaging material for an electricity storage device according to any one of items 1 to 7, wherein the polyolefin resin of the second polyolefin layer is a polypropylene resin.

[0022] [9] The packaging material for an electricity storage device according to any one of items 1 to 8, wherein the elastomer-modified polyolefin resin is a resin composed of propylene and ethylene and / or butene.

[0023]

[10] The packaging material for an electricity storage device according to any one of items 1 to 9, further comprising an insulating resin layer between the barrier layer and the heat-sealable resin layer.

[0024]

[11] The packaging material for an electricity storage device according to the above item 10, wherein the insulating resin layer is made of a resin selected from polyethylene terephthalate, polyvinylidene chloride, polypropylene, and polyethylene.

[0025]

[12] The packaging material for an electricity storage device according to the above item 10 or 11, wherein a part of the heat-sealable resin layer is removed.

[0026]

[13] The exterior packaging material for an electricity storage device according to any one of items 1 to 12, wherein the residual thickness after the heat-sealing resin layer is heat-sealed under conditions of a heat sealing temperature of 200°C, a sealing pressure of 0.3 MPa, a sealing time of 3 seconds, and a sealing width of 5 mm is less than 70%.

[0027]

[14] The packaging material for an electrical storage device according to any one of items 1 to 13, wherein the second polyolefin layer contains 40% by mass or less of a polyolefin-modified elastomer having a melting point of 90°C or higher.

[0028]

[15] The packaging material for an electricity storage device according to the preceding item 14, wherein the polyolefin-modified elastomer has a crystalline melting energy of 40 J / g or less.

[0029]

[16] The packaging material for an electricity storage device according to item 14 or 15 above, wherein the polyolefin-modified elastomer has an MFR of 0.5 g / 10 min or more and 7 g / 10 min or less.

[0030]

[17] The packaging material for an electricity storage device according to any one of items 1 to 16, wherein the heat-sealable resin layer is a laminate of three or more layers including a third polyolefin layer on the barrier layer side of the second polyolefin layer.

[0031]

[18] In the heat-sealable resin layer, a thickness ratio of the first polyolefin layer to the second polyolefin layer to the third polyolefin layer is (10:90:10) to (30:40:30). 17. The exterior packaging material for an electricity storage device according to claim 17.

[0032]

[19] An exterior case for an electricity storage device, comprising a molded article of the exterior material according to any one of items 1 to 18 above.

[0033]

[20] An electricity storage device comprising: an electricity storage device main body; and an exterior member made of the electricity storage device exterior material according to any one of items 1 to 18 and / or the electricity storage device exterior case according to item 19, wherein the electricity storage device main body is exterior-packaged with the exterior member.

[0034] According to the invention [1], the heat-sealable resin layer is a laminate of two or more layers including a first polyolefin layer as the innermost layer and a second polyolefin layer on the barrier layer side, the first polyolefin layer being primarily composed of a polyolefin resin having a melting point of 155°C or lower, and the second polyolefin layer containing 10% by mass to 70% by mass of an elastomer-modified polyolefin resin having a melting point of 150°C or higher and 10% by mass to 60% by mass of a polyolefin resin having a melting point of 135°C or higher. This allows the content of elastomer-modified polyolefin resin to be reduced by the amount of polyolefin resin, i.e., the content of the elastomer component, to be reduced, compared to when the second polyolefin layer is composed solely of elastomer-modified polyolefin resin, thereby improving the bond strength between the first and second polyolefin layers at high temperatures. This improves seal strength at high temperatures and also reduces moisture permeation, improving moisture barrier properties.

[0035] Furthermore, in a sulfur-based solid electrolyte battery, even if moisture from the outside air penetrates and the electrolyte in the main body of the electricity storage device reacts with the moisture from the outside air to generate hydrogen sulfide gas, it is possible to make it difficult for hydrogen sulfide gas to penetrate.

[0036] According to the inventions [2] to [9], the effect of the above [1] can be more fully ensured.

[0037] According to the invention

[10] , by having an insulating resin layer between the barrier layer and the heat-sealable resin layer, it is possible to provide an exterior packaging material for an electricity storage device having good insulating properties.

[0038] According to the invention

[11] , by configuring the insulating resin layer to be made of a resin selected from polyethylene terephthalate, polyvinylidene chloride, polypropylene, and polyethylene, it is possible to provide an exterior material for an electricity storage device having even better insulating properties.

[0039] According to the invention

[12] , by adopting a configuration in which a part of the heat-sealable resin layer is removed, it is possible to reduce the weight of the packaging material for an electricity storage device and further reduce costs.

[0040] According to the inventions

[13] to

[18] , the effect of the above [1] can be more fully ensured.

[0041] According to the invention

[19] , by using a molded article of the exterior material described in the preceding items 1 to 18, the bonding strength between the first polyolefin layer and the second polyolefin layer at high temperatures can be improved, and therefore an exterior case for an electricity storage device can be provided that has good sealing strength at high temperatures, reduced moisture permeation, and good moisture barrier properties.

[0042] Furthermore, in the case of a sulfur-based solid electrolyte battery, even if moisture from the outside air penetrates and the electrolyte in the main body of the electricity storage device reacts with the moisture from the outside air to generate hydrogen sulfide gas, it is possible to provide an outer case for the electricity storage device that is resistant to hydrogen sulfide gas penetration.

[0043] According to the invention

[20] , an electricity storage device is provided with a main body of an electricity storage device and an exterior member made of the exterior material for an electricity storage device described in any one of items 1 to 18 above and / or the exterior case for an electricity storage device described in item 19 above, and the electricity storage device main body is sheathed with the exterior member. This improves the bonding strength between the first polyolefin layer and the second polyolefin layer at high temperatures, and therefore provides an electricity storage device that has good seal strength at high temperatures, reduced moisture permeation, and good moisture barrier properties.

[0044] Furthermore, in a sulfur-based solid electrolyte battery, even if moisture from the outside air penetrates and the electrolyte in the main body of the electricity storage device reacts with the moisture from the outside air to generate hydrogen sulfide gas, it is possible to provide an electricity storage device that is less susceptible to hydrogen sulfide gas permeation.

[0045] Fig. 3 is a cross-sectional view showing one embodiment of an exterior material for an electricity storage device of the present invention. Fig. 4 is a cross-sectional view showing another embodiment of an exterior material for an electricity storage device of the present invention. Fig. 5 is a cross-sectional view showing one embodiment of an electricity storage device of the present invention. Fig. 6 is a perspective view showing the exterior material (planar), the electricity storage device main body, and the exterior case (a molded article formed into a three-dimensional shape) constituting the electricity storage device of Fig. 3 in a separated state before being heat-sealed.

[0046] (External packaging material for electricity storage device) The external packaging material 1 for an electricity storage device of the present embodiment is preferably used as an external packaging material for a lithium ion secondary battery, an all-solid-state battery, etc. This external packaging material 1 may be used as an external packaging material as is without being subjected to molding, or may be subjected to molding such as deep drawing or stretch molding and used as an external case 10 (see FIG. 4 ).

[0047] As shown in FIGS. 1 and 2 , the exterior packaging material 1 for an electricity storage device of this embodiment preferably has a configuration in which a base material layer (outer layer) 2 is laminated integrally onto one surface of a barrier layer 4 via a first adhesive layer 5, and a heat-fusible resin layer (inner layer) 3 is laminated integrally onto the other surface of the barrier layer 4 via a second adhesive layer 6.

[0048] (Heat-Fusible Resin Layer) The heat-fusible resin layer 3 of the present embodiment preferably has excellent chemical resistance even against highly corrosive electrolytes used in lithium-ion secondary batteries and the like, and also serves to impart heat-sealability to the exterior packaging material.

[0049] The heat-sealable resin layer 3 of this embodiment preferably has a crystalline melting energy (ΔH) of 70 J / g or more. By making the crystalline melting energy (ΔH) of the heat-sealable resin layer 3 70 J / g or more, the content ratio of polymer crystals in the heat-sealable resin layer 3 increases. This makes it difficult for the tensile stress to decrease at high temperatures, thereby improving the seal strength and moisture barrier properties. The crystalline melting energy (ΔH) of the heat-sealable resin layer 3 is preferably 70 J / g or more and 100 J / g or less. If it is 70 J / g or less, heat resistance decreases, and if it is 100 J / g or more, the amount of heat and sealing time required for heat sealing increase, resulting in a longer takt time.

[0050] In this embodiment, the thickness of the heat-sealable resin layer 3 is preferably set to 20 μm to 120 μm. By setting the thickness to 20 μm or more, it is possible to sufficiently prevent the occurrence of pinholes and the deterioration of sealing strength and insulation, and by setting the thickness to 120 μm or less, it is possible to reduce the amount of resin used and thereby reduce costs. In particular, it is particularly preferable that the thickness of the heat-sealable resin layer 3 be set to 30 μm to 80 μm.

[0051] The heat-fusible resin layer 3 of this embodiment is preferably produced by a molding method such as multilayer extrusion molding, inflation molding, or T-die cast film molding.

[0052] As shown in FIG. 1 , the heat-fusible resin layer 3 of this embodiment preferably has a two-layer laminate structure consisting of a first polyolefin layer 7 and a second polyolefin layer 8 laminated on the barrier layer 4 side of the first polyolefin layer 7, with the first polyolefin layer 7 being disposed as the innermost layer.

[0053] (First Polyolefin Layer) The first polyolefin layer 7 of this embodiment is preferably made mainly of a polyolefin resin having a melting point (Tm) of 155° C. or less.

[0054] The melting point (Tm) of the polyolefin resin of the first polyolefin layer 7 is preferably 155° C. or lower, which allows reliable sealing in a sealing time of 10 seconds or less at an appropriate sealing temperature of about 180° C. to 220° C. The melting point (Tm) of the polyolefin resin of the first polyolefin layer 7 is preferably 130° C. or higher and 155° C. or lower.

[0055] As the polyolefin resin for the first polyolefin layer 7, it is preferable to use high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, homopolypropylene, propylene-ethylene copolymer, propylene-butene copolymer, propylene-ethylene-butene copolymer, cyclic polyolefin, acid-modified polyolefin, acid-modified cyclic polyolefin, etc.

[0056] (Second Polyolefin Layer) The second polyolefin layer 8 of the present embodiment preferably contains 10% by mass or more and 70% by mass or less of an elastomer-modified polyolefin resin having a melting point (Tm) of 150°C or more, and 10% by mass or more and 60% by mass or less of a polyolefin resin having a melting point (Tm) of 135°C or more.

[0057] More preferably, the second polyolefin layer 8 contains an elastomer-modified polyolefin resin as a main component, and more preferably, the content of the elastomer-modified polyolefin resin is higher than the content of the polyolefin resin.

[0058] (Elastomer-modified polyolefin resin) The melting point (Tm) of the elastomer-modified polyolefin resin of this embodiment is preferably 150°C or higher, which can prevent a decrease in heat resistance of the seal strength. The melting point (Tm) of the elastomer-modified polyolefin resin of this embodiment is preferably 150°C or higher and 170°C or lower. By setting the melting point (Tm) to 170°C or lower, reliable sealing can be achieved in a relatively short time of 10 seconds or less at a moderate sealing temperature of about 180°C to 220°C.

[0059] The content of the elastomer-modified polyolefin resin in this embodiment is preferably 10% by mass or more and 70% by mass or less, which allows the elastomer component to be contained in a constant amount, maintaining impact resistance while increasing heat resistance. The content of the elastomer-modified polyolefin resin is more preferably 30% by mass or more and 60% by mass or less, and even more preferably 40% by mass or more and 60% by mass or less. If the content falls below the lower limit of the specified value, the impact strength will decrease.

[0060] As the elastomer-modified polyolefin resin of the present embodiment, it is preferable to use a propylene-ethylene block copolymer, a propylene-butene block copolymer, a propylene-ethylene-butene block copolymer, etc. Among these, it is preferable to use a resin composed of propylene and ethylene and / or butene.

[0061] The elastomer-modified polyolefin resin of this embodiment preferably has a crystalline melting energy (ΔH) of 60 J / g or more. By making the crystalline melting energy (ΔH) of the elastomer-modified polyolefin resin 60 J / g or more, the content ratio of polymer crystals in the heat-sealable resin layer 3 is increased. This makes it difficult for the tensile stress to decrease at high temperatures, thereby improving the seal strength and moisture barrier properties. The crystalline melting energy (ΔH) of the elastomer-modified polyolefin resin is preferably 60 J / g or more and 95 J / g or less. By making it 95 J / g or less, reliable sealing can be achieved in a relatively short time of 10 seconds or less at a moderate sealing temperature of approximately 180°C to 220°C.

[0062] The elastomer-modified polyolefin resin of this embodiment preferably has an MFR of 1 g / 10 min or more and 10 g / 10 min or less. By making the elastomer-modified polyolefin resin have an MFR of 1 g / 10 min or more, when the two overlapping heat-sealable resin layers melt and flow to become thinner during heat sealing, the resins easily diffuse into each other, ensuring reliable sealing. Furthermore, by making the elastomer-modified polyolefin resin have an MFR of 10 g / 10 min or less, the remaining thickness of the heat-sealable resin layer at the sealed area can be maintained at a certain level or more, preventing a decrease in insulation properties. The elastomer-modified polyolefin resin preferably has an MFR of 1 g / 10 min or more and 5 g / 10 min or less.

[0063] In the elastomer-modified polyolefin resin of this embodiment, the elastomer is not particularly limited, but it is preferable to use EPR (ethylene propylene rubber) or EBR (ethylene butene rubber).

[0064] In the elastomer-modified polyolefin resin of this embodiment, the content of the elastomer contained in the elastomer-modified polyolefin resin is preferably 10% by mass or more and 30% by mass or less, and more preferably 20% by mass or more and 30% by mass or less. By setting the content within this range, impact resistance can be imparted in addition to heat resistance of the seal strength when combined with a polyolefin resin to form a composition.

[0065] In the elastomer-modified polyolefin resin of this embodiment, the "elastomer modification" may be graft polymerization or other modification modes.

[0066] The elastomer-modified polyolefin resin of the present embodiment can be produced, for example, by the following reactor-made method. This is merely one example, and the resin is not particularly limited to those produced by such a production method.

[0067] First, a Ziegler-Natta catalyst, a co-catalyst, propylene, and hydrogen are supplied to a first reactor to polymerize homopolypropylene, and the resulting homopolypropylene containing unreacted propylene and Ziegler-Natta catalyst is transferred to a second reactor.

[0068] In the second reactor, propylene and hydrogen are further added to polymerize homopolypropylene, which is then transferred to the third reactor in the state containing unreacted propylene and the Ziegler-Natta catalyst.

[0069] In the third reactor, ethylene, propylene and hydrogen are further added to polymerize ethylene-propylene rubber (EPR) obtained by copolymerizing ethylene and propylene, thereby producing an elastomer-modified polyolefin resin.

[0070] The elastomer-modified polyolefin resin of this embodiment preferably has two or more crystallization peaks in a DSC (differential scanning calorimeter) measurement graph. If it has two crystallization peaks, it is preferable that the higher crystallization peak (crystallization temperature) is 90°C or higher and the lower crystallization peak (crystallization temperature) is 80°C or lower. If it has three or more crystallization peaks, it is preferable that the highest crystallization peak (crystallization temperature) is 90°C or higher and the lowest crystallization peak (crystallization temperature) is 80°C or lower.

[0071] (Polyolefin Resin of Second Polyolefin Layer) The melting point (Tm) of the polyolefin resin of the second polyolefin layer 8 is preferably 135°C or higher. By doing so, the tensile stress at high temperatures is less likely to decrease due to the higher melting point, and therefore the sealing strength at high temperatures can be improved. The melting point of the polyolefin resin of the second polyolefin layer 8 is preferably 135°C or higher and 170°C or lower.

[0072] The polyolefin resin content of the second polyolefin layer 8 is preferably 10% by mass or more. By including a specified amount or more of a highly heat-resistant polyolefin resin, the tensile stress at high temperatures is less likely to decrease, thereby improving the seal strength and moisture barrier properties. Furthermore, the polyolefin resin content of the second polyolefin layer 8 is preferably 60% by mass or less. By adding an elastomer-modified polyolefin resin as the main component in combination, impact resistance can be imparted in addition to heat resistance. The polyolefin resin content of the second polyolefin layer 8 is preferably 20% by mass or more and 50% by mass or less.

[0073] The polyolefin resin for the second polyolefin layer 8 is preferably high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, homopolypropylene, propylene-ethylene copolymer, propylene-butene copolymer, propylene-ethylene-butene copolymer cyclic polyolefin, acid-modified polyolefin, acid-modified cyclic polyolefin, etc. Among these, polypropylene resin is preferably used.

[0074] The polyolefin resin of the second polyolefin layer 8 preferably has a crystalline melting energy (ΔH) of 60 J / g or more. By making the crystalline melting energy (ΔH) of the polyolefin resin of the second polyolefin layer 8 60 J / g or more, the content ratio of polymer crystals in the heat-fusible resin layer 3 increases. This makes it difficult for the tensile stress to decrease at high temperatures, thereby improving the seal strength and moisture barrier properties. The crystalline melting energy (ΔH) of the polyolefin resin of the second polyolefin layer 8 is preferably 60 J / g or more and 110 J / g or less.

[0075] The polyolefin resin of the second polyolefin layer 8 preferably has an MFR of 2 g / 10 min or more and 20 g / 10 min or less. By making the polyolefin resin of the second polyolefin layer 8 have an MFR of 2 g / 10 min or more, it is possible to improve the mixability with other resins and, during heat sealing, the heat-sealable resin layer is more likely to melt, flow, and become thinner, thereby ensuring reliable sealing. Furthermore, by making the polyolefin resin of the second polyolefin layer 8 have an MFR of 20 g / 10 min or less, it is possible to maintain a certain level of residual thickness of the heat-sealable resin layer at the sealed portion, thereby preventing a decrease in insulation properties. The polyolefin resin of the second polyolefin layer 8 preferably has an MFR of 5 g / min or more and 10 g / min or less.

[0076] (Polyolefin-Modified Elastomer of Second Polyolefin Layer) The second polyolefin layer 8 of the present embodiment may contain 40% by mass or less of a polyolefin-modified elastomer having a melting point (Tm) of 90° C. or higher. The content of the polyolefin-modified elastomer is preferably 10% by mass or more and 30% by mass or less. This makes it possible to suppress whitening of the heat-sealable resin layer when the exterior material for an electricity storage device is molded, and to more effectively exhibit impact resistance.

[0077] The melting point (Tm) of the polyolefin-modified elastomer is preferably 90°C or higher, and by doing so, the tensile stress at high temperatures is less likely to decrease due to the high melting point of the polyolefin-modified elastomer, and therefore the sealing strength at high temperatures can be improved. The melting point (Tm) of the polyolefin-modified elastomer is preferably 90°C or higher and 155°C or lower.

[0078] The crystalline melting energy (ΔH) of the polyolefin-modified elastomer is preferably 40 J / g or less. By setting the crystalline melting energy (ΔH) of the polyolefin-modified elastomer to 40 J / g or less, compatibility with other resin components is improved and impact resistance can be imparted. The crystalline melting energy (ΔH) of the polyolefin-modified elastomer is preferably 10 J / g or more and 40 J / g or less. If it is less than 10 J / g, compatibility with other resin components decreases and the interfacial strength between the polyolefin portion and the elastomer portion decreases, which is not preferable.

[0079] The polyolefin-modified elastomer preferably has an MFR of 0.5 g / 10 min or more and 7 g / 10 min or less. By setting the MFR of the polyolefin-modified elastomer to 0.5 g / 10 min or more, dispersibility with other resins is improved, and the interlayer bond strength between the second polyolefin layer 8 and the first polyolefin layer 7 and the third polyolefin layer 9 of the heat-sealable resin layer 3 is increased. Furthermore, by setting the MFR of the polyolefin-modified elastomer to 7 g / 10 min or less, the molecular weight is large, resulting in high tensile stress at high temperatures. The MFR of the polyolefin-modified elastomer is preferably 0.5 g / 10 min or more and 5 g / 10 min or less.

[0080] (Thickness Ratio of First Polyolefin Layer to Second Polyolefin Layer) In this embodiment, the thickness ratio of the first polyolefin layer 7 to the second polyolefin layer 8 is preferably (10:90) to (40:60).

[0081] In this embodiment, the first polyolefin layer 7 preferably contains an antiblocking agent and a slip agent in addition to the polyolefin resin, and the second polyolefin layer 8 preferably contains a slip agent in addition to the polyolefin resin and the elastomer-modified polyolefin resin.

[0082] The anti-blocking agent is not particularly limited, but examples thereof include silica, aluminum silicate, etc. The slip agent is not particularly limited, but examples thereof include fatty acid amides such as erucic acid amide, stearic acid amide, oleic acid amide, etc., and waxes such as crystalline wax and polyethylene wax, etc.

[0083] In this way, the first polyolefin layer 7 contains an antiblocking agent and a slip agent, and the second polyolefin layer 8 contains a slip agent, thereby imparting excellent slip properties to the surface of the exterior packaging material 1, allowing for successful molding to a greater depth when molding the exterior packaging material 1, and also sufficiently suppressing whitening during molding.

[0084] (Three-Layer Laminated Structure of Heat-Fusable Resin Layer) As shown in FIG. 2 , the heat-fusible resin layer 3 of this embodiment may have a three-layer laminated structure in which a third polyolefin layer 9 is further laminated on the barrier layer 4 side of the second polyolefin layer 8.

[0085] The third polyolefin layer 9 may have the same structure as or a different structure from the first polyolefin layer 7. It is preferable that the third polyolefin layer 9 has the same structure as the first polyolefin layer 7.

[0086] When the third polyolefin layer 9 has a different structure from the first polyolefin layer 7, the third polyolefin layer 9 is not particularly limited as long as it can be adhered to the barrier layer 4 described below.

[0087] When the heat-fusible resin layer 3 has the above three-layer laminated structure, the thickness ratio of the first polyolefin layer 7, the second polyolefin layer 8 and the third polyolefin layer 9 is preferably (10:90:10) to (30:40:30).

[0088] (Insulating Resin Layer) In this embodiment, an insulating resin layer may be provided between the thermally adhesive resin layer 3 and the barrier layer 4 described below.

[0089] The resin constituting this insulating resin layer is preferably selected from the group consisting of polyethylene terephthalate, polyvinylidene chloride, polypropylene, and polyethylene.

[0090] By providing the insulating resin layer in this manner, it is possible to provide an electrical storage device packaging material 1 with good insulating properties. Furthermore, by using the above-mentioned resins that form the insulating resin layer, it is possible to provide an electrical storage device packaging material 1 with even better insulating properties.

[0091] In the present embodiment, when the insulating resin layer is provided, a configuration may be adopted in which a part of the heat-sealable resin layer 3 is removed. Specifically, a configuration may be adopted in which all or a part of the heat-sealable resin layer 3 is removed except for a portion that will become a heat-sealed portion 39 (see FIG. 3 ), which will be described later. By adopting a configuration in which a part of the heat-sealable resin layer 3 is removed in this manner, the weight of the packaging material 1 for an electricity storage device can be reduced, and costs can also be reduced.

[0092] In this embodiment, it is preferable that the thickness remaining rate after heat sealing the heat-sealing resin layer 3 under the conditions of a heat-sealing temperature of 200° C., a sealing pressure of 0.3 MPa, a sealing time of 3 seconds, and a sealing width of 5 mm is less than 70%. The above-mentioned remaining rate means the ratio of the thickness of the heat-sealing resin layer 3 after heat sealing to the thickness of the heat-sealing resin layer 3 before heat sealing.

[0093] When the residual rate is less than 70%, it is possible to provide an exterior packaging material 1 for an electricity storage device that has better sealing strength at high temperatures and also has better moisture barrier properties.

[0094] The method for laminating the sealant film constituting the heat-fusible resin layer 3 of this embodiment onto the barrier layer 4 described below is not particularly limited, but examples thereof include a dry lamination method and a sandwich lamination method (a method in which an adhesive film such as acid-modified polypropylene is extruded, sandwich-laminated between a metal foil and the sealant film, and then heat-laminated using a heated roll).

[0095] (Barrier Layer) The barrier layer 4 of this embodiment serves to impart gas barrier properties to the packaging material 1, preventing the penetration of oxygen and moisture.

[0096] The barrier layer 4 is not particularly limited, but examples thereof include aluminum foil, SUS foil (stainless steel foil), steel foil, and copper foil, and among these, it is preferable to use aluminum foil or SUS foil (stainless steel foil).

[0097] The thickness of the barrier layer 4 is preferably 20 μm to 100 μm. A thickness of 20 μm or more can prevent the occurrence of pinholes during rolling in the production of the metal foil, and a thickness of 100 μm or less can reduce stress during forming such as stretch forming and drawing, thereby improving formability.

[0098] It is preferable that at least the inner surface (the surface on the second adhesive layer 6 side) of the barrier layer 4 is subjected to a chemical conversion treatment. By performing such a chemical conversion treatment, corrosion of the metal foil surface by the contents (such as the electrolyte of a battery) can be sufficiently prevented. For example, the chemical conversion treatment is performed on the metal foil by the following process. That is, for example, a chemical conversion treatment can be performed on the surface of a metal foil that has been degreased by applying one of the following solutions to the surface: 1) an aqueous solution of a mixture containing phosphoric acid, chromic acid, and at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides; 2) an aqueous solution of a mixture containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, and at least one compound selected from the group consisting of chromic acid and chromium (III) salts; or 3) an aqueous solution of a mixture containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, at least one compound selected from the group consisting of chromic acid and chromium (III) salts, and at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides.

[0099] The chemical conversion coating has a chromium deposition amount (per side) of 0.1 mg / m ２ ~50 mg / m ２ is preferred, and particularly 2 mg / m ２ ~20 mg / m ２ is preferred.

[0100] (Base Material Layer) The base material layer 2 of this embodiment is preferably formed of a heat-resistant resin layer. The heat-resistant resin constituting this heat-resistant resin layer is a heat-resistant resin that does not melt at the heat-sealing temperature when the packaging material 1 is heat-sealed. As this heat-resistant resin, a heat-resistant resin having a melting point that is 10°C or more higher than the melting point of the thermoplastic resin constituting the heat-fusible resin layer 3 is preferably used, and a heat-resistant resin having a melting point that is 20°C or more higher than the melting point of the thermoplastic resin is particularly preferably used.

[0101] The heat-resistant resin layer (outer layer) is not particularly limited, but examples thereof include polyamide films such as nylon films, polyester films, etc., and stretched films thereof are preferably used. Among these, it is particularly preferred to use biaxially oriented polyamide films such as biaxially oriented nylon films, biaxially oriented polybutylene terephthalate (PBT) films, biaxially oriented polyethylene terephthalate (PET) films, or biaxially oriented polyethylene naphthalate (PEN) films as the heat-resistant resin layer. The nylon film is not particularly limited, but examples thereof include nylon 6 film, nylon 6,6 film, and MXD nylon film. The heat-resistant resin layer may be formed as a single layer, or may be formed as a multilayer structure consisting of, for example, a polyester film / polyamide film (e.g., a multilayer structure consisting of a PET film / nylon film).

[0102] The thickness of the base material layer 2 is preferably 2 μm to 50 μm. When a polyester film is used, the thickness is preferably 2 μm to 50 μm, and when a nylon film is used, the thickness is preferably 7 μm to 50 μm. By setting the thickness to equal to or greater than the above-mentioned preferable lower limit, sufficient strength for the exterior packaging material 1 can be ensured, and by setting the thickness to equal to or less than the above-mentioned preferable upper limit, stress during molding such as stretch molding and draw molding can be reduced, thereby improving formability.

[0103] (First Adhesive Layer) The first adhesive layer 5 of this embodiment is not particularly limited, but examples thereof include a polyurethane adhesive layer, a polyester polyurethane adhesive layer, and a polyether polyurethane adhesive layer.

[0104] The thickness of the first adhesive layer 5 is preferably set to 1 μm to 5 μm. In particular, from the viewpoint of making the exterior packaging material 1 thinner and lighter, it is particularly preferable that the thickness of the first adhesive layer 5 be set to 1 μm to 3 μm.

[0105] (Second adhesive layer) The second adhesive layer 6 in this embodiment is not particularly limited, and for example, the adhesives exemplified above as the first adhesive layer 5 can be used, but it is preferable to use a polyolefin-based adhesive that swells little with the electrolyte solution.

[0106] The thickness of the second adhesive layer 6 is preferably set to 1 μm to 5 μm. In particular, from the viewpoint of making the exterior packaging material 1 thinner and lighter, it is particularly preferable that the thickness of the second adhesive layer 6 be set to 1 μm to 3 μm.

[0107] As explained above, the heat-sealable resin layer 3 of this embodiment is composed of a laminate of two or more layers including the first polyolefin layer 7 as the innermost layer and the second polyolefin layer 8 on the barrier layer 4 side, the first polyolefin layer 7 being mainly composed of a polyolefin resin having a melting point of 155°C or less, and the second polyolefin layer 8 containing 10% by mass to 70% by mass of an elastomer-modified polyolefin resin having a melting point of 150°C or more and 10% by mass to 60% by mass of a polyolefin resin having a melting point of 135°C or more. Therefore, compared to a case in which the second polyolefin layer 8 is composed only of an elastomer-modified polyolefin resin, the content of the elastomer-modified polyolefin resin can be reduced by the amount of the polyolefin resin, i.e., the content of the elastomer component can be reduced, and the bond strength at high temperatures between the first polyolefin layer 7 and the second polyolefin layer 8 can be improved. As a result, the seal strength at high temperatures can be improved, and the amount of moisture permeation can be reduced, improving the moisture barrier property.

[0108] Furthermore, if moisture from the outside air permeates and the electrolyte of the main body of the electricity storage device is a sulfur-based solid electrolyte, even if hydrogen sulfide gas is generated by reacting with moisture from the outside air, it is possible to make it difficult for hydrogen sulfide gas to permeate.

[0109] (Outer Case for Electricity Storage Device) As shown in FIG. 4, an outer case for an electricity storage device (such as a battery case) 10 can be obtained by molding (deep drawing, stretch molding, etc.) the outer case material 1 of this embodiment.

[0110] The packaging material 1 of this embodiment can also be used as it is without being subjected to molding.

[0111] By configuring the outer case 10 for an electricity storage device to be made from a molded body of the exterior material 1 of this embodiment in this way, the bond strength between the first polyolefin layer 7 and the second polyolefin layer 8 at high temperatures can be improved, and therefore it is possible to provide an outer case 10 for an electricity storage device that has good sealing strength at high temperatures, reduced moisture permeation, and good moisture barrier properties.

[0112] Furthermore, even if moisture from the outside air passes through and hydrogen sulfide gas is generated by reacting with the moisture from the outside air when the electrolyte of the main body 31 of the electricity storage device is a sulfur-based solid electrolyte, it is possible to provide an outer case 10 for an electricity storage device that is resistant to hydrogen sulfide gas passing through.

[0113] (Electricity Storage Device) One embodiment of an electricity storage device 30 configured using the exterior packaging material 1 of the present embodiment is shown in Fig. 3. This electricity storage device 30 is a lithium ion secondary battery.

[0114] As shown in FIGS. 3 and 4, in this embodiment, an exterior member 15 is formed by an exterior case 10 obtained by molding the exterior material 1 and the planar exterior material 1 .

[0115] Thus, an approximately rectangular parallelepiped-shaped electricity storage device main body (electrochemical element, etc.) 31 is accommodated in the accommodation recess of the exterior case 10 obtained by molding the exterior material 1 of this embodiment, and the exterior material 1 of this embodiment is placed on top of the electricity storage device main body 31 with its heat-sealable resin layer 3 side facing inward (lower side) without being molded, and the peripheral portion of the heat-sealable resin layer 3 of the planar exterior material 1 and the heat-sealable resin layer 3 of the flange portion (sealing peripheral portion) 29 of the exterior case 10 are sealed and joined by heat sealing to form the electricity storage device 30.

[0116] The inner surface of the storage recess of the exterior case 10 is a heat-sealable resin layer 3 , and the outer surface of the storage recess is a base material layer (outer layer) 2 .

[0117] 3, reference numeral 39 denotes a heat-sealed portion where the peripheral edge of the exterior material 1 and the flange portion (sealing peripheral edge) 29 of the exterior case 10 are joined (welded) together. In the electricity storage device 30, the tip end of the tab lead connected to the electricity storage device main body 31 is led out of the exterior member 15, but is not shown in the figure.

[0118] The power storage device main body 31 is not particularly limited, but examples thereof include a battery main body and a capacitor main body.

[0119] The width of the heat-sealed portion 39 is preferably set to 0.5 mm or more. By setting the width to 0.5 mm or more, sealing can be performed reliably. In particular, the width of the heat-sealed portion 39 is preferably set to 3 mm to 15 mm.

[0120] In this embodiment, the exterior member 15 is configured to be composed of an exterior case 10 obtained by molding the exterior material 1 and a planar exterior material 1, but is not limited to this combination. For example, the exterior member 15 may be configured to be composed of a pair of planar exterior materials 1, or may be configured to be composed of a pair of exterior cases 10.

[0121] In this way, the energy storage device 30 comprises an energy storage device main body 31 and an exterior member 15 consisting of the exterior material 1 of this embodiment and / or the exterior case 10 for an energy storage device, and the energy storage device main body 31 is configured to be exteriorly sheathed by the exterior member 15. This improves the bonding strength between the first polyolefin layer 7 and the second polyolefin layer 8 at high temperatures, thereby providing an energy storage device 30 that has good sealing strength at high temperatures, reduced moisture permeation, and good moisture barrier properties.

[0122] Furthermore, even if moisture from the outside air permeates and hydrogen sulfide gas is generated by reacting with the moisture from the outside air when the electrolyte of the energy storage device main body 31 is a sulfur-based solid electrolyte, it is possible to provide an energy storage device 30 that is less permeable to hydrogen sulfide gas.

[0123] Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

[0124] Example 1 A chemical conversion treatment solution consisting of phosphoric acid, polyacrylic acid (acrylic resin), a chromium (III) salt compound, water, and alcohol was applied to both sides of a 40 μm thick aluminum foil 4 (a soft aluminum alloy foil of A8021 specified in JIS H4160), and then dried at 180° C. to form a chemical conversion coating. The chromium deposition amount of this chemical conversion coating was 10 mg / m per side. ２ It was.

[0125] Next, a 15 μm thick biaxially oriented nylon 6 film was dry laminated (bonded) to one side of the chemically treated aluminum foil 4 via a two-component curing urethane adhesive 5, and then a 12 μm thick biaxially oriented polyethylene terephthalate film was dry laminated (bonded) to the side of the biaxially oriented nylon 6 film opposite the aluminum foil 4 via a two-component curing urethane adhesive 5. That is, the base layer 2 had a two-layer structure of the biaxially oriented nylon 6 film and the biaxially oriented polyethylene terephthalate film.

[0126] Next, a first polyolefin layer 7 having a thickness of 16 μm (composed of 90 mass % of r-PP (random polypropylene, propylene-ethylene copolymer) (hereinafter referred to as resin A) having a melting point of 145° C., MFR of 7.5 g / 10 min, and crystalline melting energy of 84 J / g, and 10 mass % of h-PP (homopolypropylene) (hereinafter referred to as resin B) having a melting point of 164° C., MFR of 7.5 g / 10 min, and crystalline melting energy of 107 J / g), and a second polyolefin layer 8 having a thickness of 64 μm. The resin B (consisting of 30% by mass of resin B and 70% by mass of elastomer-modified polypropylene b-PP (propylene-ethylene block copolymer, EPR content 25% by mass) having a melting point of 165°C, an MFR of 2 g / 10 min, and a crystalline melting energy of 79 J / g (hereinafter referred to as resin C)) was co-extruded using a T-die so as to be laminated, thereby obtaining a heat-fusible resin layer 3 (first polyolefin layer 7 / second polyolefin layer 8) having a thickness of 80 μm, in which these two layers were laminated.

[0127] Next, the surface of the heat-fusible resin layer 3 on the side of the second polyolefin layer 8 was superimposed on the other surface of the dry-laminated aluminum foil 4 via a two-component curing maleic acid-modified polypropylene adhesive 6, and the resultant was dry-laminated by being sandwiched between a rubber nip roll and a laminating roll heated to 100°C and pressure-bonded, and then aged (heated) at 50°C for 5 days to obtain an exterior packaging material 1 for an electricity storage device having the configuration shown in FIG. 1.

[0128] The two-component curing maleic acid-modified polypropylene adhesive 6 used was an adhesive solution containing 100 parts by mass of maleic acid-modified polypropylene (melting point 80°C, acid value 10 mgKOH / g) as a base material, 8 parts by mass of an isocyanurate of hexamethylene diisocyanate (NCO content: 20% by mass) as a curing agent, and a solvent. The adhesive solution was applied in a solids amount of 2 g / m ２ The coating was applied to the other surface of the aluminum foil 4 so that the coating became equal to the thickness of the aluminum foil 4, and after heating and drying, the coating was placed on the surface of the heat-fusible resin layer 3 on the side of the second polyolefin layer 8.

[0129] Example 2 An exterior packaging material 1 for an electricity storage device having the configuration shown in FIG. 1 was obtained in the same manner as in Example 1, except that the first polyolefin layer 7 was configured so that the resin A was 100% by mass (the resin B was 0% by mass).

[0130] Example 3 An outer casing material for an electricity storage device 1 having the configuration shown in FIG. 1 was obtained in the same manner as in Example 1, except that the thickness of the first polyolefin layer 7 was 32 μm and the thickness of the second polyolefin layer 8 was 48 μm.

[0131] Example 4 An exterior packaging material for an electricity storage device 1 having the configuration shown in FIG. 1 was obtained in the same manner as in Example 1, except that the second polyolefin layer 8 was configured to contain 40 mass % of resin A and 60 mass % of resin C.

[0132] Example 5 A chemical conversion treatment solution consisting of phosphoric acid, polyacrylic acid (acrylic resin), a chromium (III) salt compound, water, and alcohol was applied to both sides of an aluminum foil 4 having a thickness of 40 μm, and then dried at 180° C. to form a chemical conversion film. The chromium deposition amount of this chemical conversion film was 10 mg / m per side. ２It was.

[0133] Next, a biaxially oriented nylon 6 film 2 having a thickness of 15 μm was dry laminated (attached) to one surface of the chemically treated aluminum foil 4 via a two-component curing urethane adhesive 5 .

[0134] Next, a first polyolefin layer 7 having a thickness of 8 μm (composed of 90 mass% of resin A and 10 mass% of resin B), a second polyolefin layer 8 having a thickness of 64 μm (composed of 30 mass% of resin A and 70 mass% of resin C), and a third polyolefin layer 9 having a thickness of 8 μm (composed of 90 mass% of resin A and 10 mass% of resin B) were co-extruded using a T-die so that the three layers were laminated in this order, thereby obtaining a heat-sealable resin layer 3 (first polyolefin layer 7 / second polyolefin layer 8 / third polyolefin layer 9) having a thickness of 80 μm formed by laminating these three layers.

[0135] Next, the surface of the heat-fusible resin layer 3 on the side of the third polyolefin layer 9 was superimposed on the other surface of the dry-laminated aluminum foil 4 via a two-component curing maleic acid-modified polypropylene adhesive 6, and the resultant was dry-laminated by being sandwiched between a rubber nip roll and a laminating roll heated to 100°C and pressure-bonded, and then aged (heated) at 50°C for 5 days to obtain an exterior packaging material 1 for an electricity storage device having the configuration shown in FIG. 2.

[0136] The two-component curing maleic acid-modified polypropylene adhesive 6 used was an adhesive solution containing 100 parts by mass of maleic acid-modified polypropylene (melting point 80°C, acid value 10 mgKOH / g) as a base material, 8 parts by mass of an isocyanurate of hexamethylene diisocyanate (NCO content: 20% by mass) as a curing agent, and a solvent. The adhesive solution was applied in a solids amount of 2 g / m ２ The coating was applied to the other surface of the aluminum foil 4 so that the coating became equal to the thickness of the aluminum foil 4 , and after heating and drying, the coating was placed on the surface of the heat-fusible resin layer 3 on the side of the third polyolefin layer 9 .

[0137] Example 6 An exterior material for an electricity storage device 1 having the configuration shown in FIG. 2 was obtained in the same manner as in Example 5, except that the thickness of the first polyolefin layer 7 was 16 μm, the thickness of the second polyolefin layer 8 was 48 μm, and the thickness of the third polyolefin layer 9 was 16 μm.

[0138] Example 7 An exterior packaging material for an electricity storage device 1 having the configuration shown in FIG. 2 was obtained in the same manner as in Example 6, except that the second polyolefin layer 8 was configured to contain 20 mass % of resin A, 60 mass % of resin C, and 20 mass % of a polypropylene-modified elastomer (propylene-ethylene copolymer, EPR content 60 mass %) having a melting point of 140° C., an MFR of 0.6 g / 10 min, and a crystalline melting energy of 24 J / g (hereinafter referred to as resin D).

[0139] Example 8 An exterior packaging material for an electricity storage device 1 having the configuration shown in FIG. 2 was obtained in the same manner as in Example 6, except that the second polyolefin layer 8 was configured to contain 49 mass % of resin A, 41 mass % of resin C, and 10 mass % of a polypropylene-modified elastomer (propylene-butene copolymer, EBR) having a melting point of 98°C, an MFR of 7 g / 10 min, and a crystalline melting energy of 40 J / g (hereinafter referred to as resin E).

[0140] Example 9 An exterior packaging material for an electricity storage device 1 having the configuration shown in FIG. 2 was obtained in the same manner as in Example 6, except that the second polyolefin layer 8 was configured to contain 40 mass % of resin A, 48 mass % of resin C, and 12 mass % of resin D.

[0141] Example 10 An exterior packaging material for an electricity storage device 1 having the configuration shown in FIG. 2 was obtained in the same manner as in Example 6, except that the second polyolefin layer 8 was configured to contain 40 mass % of resin A, 48 mass % of resin C, and 12 mass % of a polypropylene-modified elastomer (propylene-ethylene copolymer, EPR content 45 mass %) having a melting point of 138°C, an MFR of 6 g / 10 min, and a crystalline melting energy of 36 J / g (hereinafter referred to as resin F).

[0142] Example 11 An exterior material for an electricity storage device 1 having the configuration shown in FIG. 2 was obtained in the same manner as in Example 10, except that the thickness of the first polyolefin layer 7 was 24 μm, the thickness of the second polyolefin layer 8 was 32 μm, and the thickness of the third polyolefin layer 9 was 24 μm.

[0143] Comparative Example 1 An outer casing material for an electricity storage device 1 having the configuration shown in FIG. 2 was obtained in the same manner as in Example 5, except that the second polyolefin layer 8 was configured so that the resin C was 100% by mass.

[0144] Comparative Example 2 An exterior packaging material for an electricity storage device 1 having the configuration shown in FIG. 2 was obtained in the same manner as in Example 5, except that the first polyolefin layer 7 had a thickness of 12 μm, the second polyolefin layer 8 had a thickness of 56 μm, the third polyolefin layer 9 had a thickness of 12 μm, and the second polyolefin layer 8 contained 80 mass % of resin C and 20 mass % of resin E.

[0145] Comparative Example 3 An outer casing material for an electricity storage device 1 having the configuration shown in FIG. 2 was obtained in the same manner as in Comparative Example 2, except that the residual rate, which will be described later, was set to 40%.

[0146]

[0147]

[0148] In Tables 1 and 2, Resins A to F respectively represent the following resins and elastomers: "Resin A": r-PP (random polypropylene, propylene-ethylene copolymer) with a melting point of 145°C, MFR of 7.5 g / 10 min, and crystalline melting energy of 84 J / g; "Resin B": h-PP (homopolypropylene) with a melting point of 164°C, MFR of 7.5 g / 10 min, and crystalline melting energy of 107 J / g; "Resin C": elastomer-modified polypropylene b-PP (propylene-ethylene block copolymer, EPR content of 25% by mass) with a melting point of 165°C, MFR of 2 g / 10 min, and crystalline melting energy of 79 J / g; "Resin D": polypropylene-modified elastomer (propylene-ethylene copolymer, EPR content of 60% by mass) with a melting point of 140°C, MFR of 0.6 g / 10 min, and crystalline melting energy of 24 J / g. "Resin E": Polypropylene modified elastomer (propylene-butene copolymer, EBR) having a melting point of 98°C, MFR of 7 g / 10 min, and crystalline melting energy of 40 J / g. "Resin F": Polypropylene modified elastomer (propylene-ethylene copolymer, EPR content 45% by mass) having a melting point of 138°C, MFR of 6 g / 10 min, and crystalline melting energy of 36 J / g. The "melting point" of each resin above is the melting peak temperature (Tm) measured by differential scanning calorimetry (DSC) in accordance with JIS K7121-1987, and the "crystalline melting energy" of each resin is the heat of fusion (crystalline melting energy; ΔH) measured by differential scanning calorimetry (DSC) in accordance with JIS K7122-1987. All of these were measured under the following measurement conditions.

[0149] Temperature increase / decrease speed: 23°C to 210°C at a temperature increase / decrease rate of 10°C / min. Sample material: 5 mg was prepared. Container: Aluminum pan was used. Apparatus: Shimadzu Corporation's DSC-60A. The "residual rate" in Tables 1 and 2 means the ratio of the thickness of the heat-sealable resin layer 3 after heat sealing to the thickness of the heat-sealable resin layer 3 before heat sealing, when the heat-sealable resin layer 3 is heat-sealed under the following conditions.

[0150] Temperature: 200°C Pressure: 0.3 MPa Time: 3 seconds (6 seconds for Comparative Example 3 only) Seal width: 5 mm For each of the exterior packaging materials 1 for an electricity storage device obtained as described above, the seal strength and moisture permeation amount were measured and evaluated based on the following measurement and evaluation methods.

[0151] <Method for measuring seal strength> Two test pieces measuring 15 mm in width and 150 mm in length were cut out from the obtained packaging material 1, and then these two test pieces were overlapped so that the heat-fusible resin layers 3 of each test piece were in contact with each other. In this state, heat sealing was performed by heating on one side using a heat sealing device (TP-701-A) manufactured by Tester Sangyo Co., Ltd. under the following conditions: heat sealing temperature: 180°C, sealing pressure: 0.15 MPa (gauge display pressure), sealing time: 3 seconds, and seal width: 5 mm.

[0152] Next, for a pair of exterior packaging materials in which the heat-fusible resin layers 3 were heat-sealed together as described above, the exterior packaging materials (test specimens) were peeled at an angle of 90 degrees at a tensile speed of 100 mm / min using a Strograph (AGS-5kNX) manufactured by Shimadzu Access Co., Ltd. in accordance with JIS Z0238-1998, and the peel strength was measured, and this was defined as the seal strength (N / 15 mm width).

[0153] The seal strength was measured by holding the exterior packaging material (test specimen) at each of the temperatures of 25°C, 60°C and 90°C for 1 minute, and then measuring at each temperature.

[0154] A seal strength of 60 N / 15 mm width or more was deemed to be acceptable. A seal strength of 70 N / 15 mm width or more was desirable.

[0155] <Moisture Permeation Rate Measurement Method> Batteries (mock batteries) were prepared as follows using each of the exterior packaging materials 1 for electricity storage devices obtained as described above. First, the exterior packaging material 1 was cut to a size of 120 mm long x 100 mm wide. This cut exterior packaging material was then embossed using a mold consisting of a male mold and a female mold into a roughly rectangular parallelepiped shape with an open top, measuring 100 mm long x 80 mm wide x 2 mm deep, to prepare a molded case 10 having a flange portion 29 around the periphery (see FIG. 4). The embossing was performed so that the inner surface of the bottom of the roughly rectangular parallelepiped shape with an open top was made of an unstretched polypropylene film (inner layer) 3. Meanwhile, a cut product of the exterior packaging material 1 with a size of 120 mm long x 100 mm wide that was not embossed (hereinafter referred to as "planar exterior packaging material 1") was also prepared (see FIG. 4).

[0156] A simulated electrode was prepared by layering 30 μm thick soft aluminum foil, 100 μm thick polypropylene film, and 30 μm thick soft copper foil together and punching them out to a size of 95 mm long x 75 mm wide. Ten of these simulated electrodes were stacked to obtain an electricity storage device main body (simulation) 31 (see FIG. 4).

[0157] As shown in FIG. 3, the energy storage device main body 31 was loaded into the approximately rectangular parallelepiped embossed portion with the open top of the molding case 10, and then the molding case 10 and the planar exterior material 1 were overlapped with each other so that their inner layers 3 faced each other, and a metal hot plate heated to 200°C was applied to three of the four sides of the inner layer 3 of the planar exterior material 1 and the inner layer 3 of the flange portion 29 of the molding case 10 at a pressure of 0.3 MPa for three seconds to form a heat-sealed joint, thereby forming a heat-sealed portion 39, and then this was left in a dry room with a dew point of -60°C for 24 hours.

[0158] Next, in a dry room with a dew point of −60° C., 7.5 mL of an electrolyte (an electrolyte having a LiPF6 concentration of 1 mol / L obtained by adding LiPF6 to a carbonate mixture in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1:1) was injected dropwise into the inside of the heat-sealed assembly through an open portion on one side that had not yet been joined, using a syringe. Then, a metal hot plate heated to 200° C. was applied to the unjoined side of the heat-sealed assembly at a pressure of 0.3 MPa for 3 seconds under a reduced pressure of 0.086 MPa to perform heat-seal joining, thereby completing sealing and obtaining a battery (simulated battery) 30 shown in FIG. 3 .

[0159] The battery (simulated battery) obtained as described above was subjected to a moisture permeation measurement evaluation by measuring the amount of moisture in the electrolyte solution inside the simulated battery based on the following evaluation test method. The measurement results of the amount of moisture (ppm) in the electrolyte solution obtained were combined with the cross-sectional area (mm ) of the sealed portion calculated from the circumferential length of the simulated battery and the remaining thickness (mm) of the sealed portion. ２ ) to obtain the moisture permeability (ppm / mm ２ The results are shown in Tables 1 and 2.

[0160] <Method for measuring moisture permeation amount> For each example and comparative example, three samples (simulated batteries) were prepared and placed in a second thermo-hygrostat at 60°C and a humidity of 90%. After three weeks, the samples were removed, and 0.5 mL of the electrolyte solution was removed from each battery using a syringe. The moisture content of the electrolyte solution was measured using a Karl Fischer moisture meter ("AQ2250" manufactured by Hiranuma Sangyo Co., Ltd.).

[0161] In the results of Tables 1 and 2, the moisture content of the Examples was approximately 1 / 5 to 1 / 3 of the moisture content of the Comparative Examples. In the simulated batteries constructed using the packaging material 1 of each Example, no significant (substantial) increase in moisture was observed, confirming the excellent effect of the moisture barrier provided by the packaging material of the present invention.

[0162] <Evaluation> A seal strength of 60 N / 15 mm width or more at a temperature of 90° C. was rated "A", and a seal strength of less than 60 N / 15 mm width was rated "B".

[0163] As is clear from the table, Examples 1 to 11 were evaluated as "A," and good results were obtained for the seal strength at 90°C, i.e., at high temperatures. The seal strength was also good at 25°C and 60°C. Furthermore, Examples 1 to 11 had low moisture permeation amounts and good results for the moisture barrier properties.

[0164] In contrast, Comparative Examples 1 to 3, which deviate from the scope of the claims of the present invention, were evaluated as "B," resulting in insufficient seal strength at 90°C, i.e., at high temperatures. Note that Comparative Example 3 showed insufficient seal strength not only at 90°C but also at 60°C. Furthermore, Comparative Examples 1 to 3 also showed high moisture permeation rates and insufficient moisture barrier properties.

[0165] The packaging material for an electricity storage device of the present invention is used as a packaging material for electricity storage devices such as mobile storage batteries, in-vehicle storage batteries, regenerative energy recovery storage batteries, capacitors, and all-solid-state batteries.

[0166] The electricity storage device of the present invention is used as a mobile storage battery, an in-vehicle storage battery, a storage battery for regenerative energy recovery, a capacitor, an all-solid-state battery, or the like.

[0167] This application claims priority from Japanese Patent Application No. 2024-33292, filed on March 5, 2024, the disclosure of which is incorporated herein by reference in its entirety.

[0168] It should be understood that the terms and expressions used herein are used for the purpose of explanation and not for limiting interpretation, and do not exclude any equivalents of the features shown and described herein, but also allow various modifications within the claimed scope of the present invention.

[0169] DESCRIPTION OF SYMBOLS 1... Power storage device exterior material 2... Base material layer (outer layer) 3... Heat-sealable resin layer 4... Barrier layer 7... First polyolefin layer 8... Second polyolefin layer 9... Third polyolefin layer 10... Power storage device exterior case (molded body) 15... Exterior member 30... Power storage device 31... Power storage device main body

Claims

1. An exterior packaging material for an electricity storage device, comprising at least a base layer, a barrier layer, and a heat-sealable resin layer laminated in that order from outside to inside, wherein the heat-sealable resin layer is a laminate of two or more layers, including a first polyolefin layer as the innermost layer and a second polyolefin layer on the barrier layer side, wherein the first polyolefin layer is primarily composed of a polyolefin resin having a melting point of 155°C or less, and the second polyolefin layer contains 10% by mass to 70% by mass of an elastomer-modified polyolefin resin having a melting point of 150°C or more and 10% by mass to 60% by mass of a polyolefin resin having a melting point of 135°C or more.

2. The packaging material for an electrical storage device according to claim 1, wherein the thickness ratio of the first polyolefin layer to the second polyolefin layer is from (10:90) to (40:60).

3. The packaging material for an electricity storage device according to claim 1 or 2, wherein the crystalline melting energy of the polyolefin resin of the second polyolefin layer is 60 J / g or more.

4. The packaging material for an electricity storage device according to claim 1 or 2, wherein the elastomer-modified polyolefin resin has a crystalline melting energy of 60 J / g or more.

5. The packaging material for an electricity storage device according to claim 1 or 2, wherein the heat-fusible resin layer has a crystalline melting energy of 70 J / g or more.

6. The packaging material for an electricity storage device according to claim 1 or 2, wherein the polyolefin resin of the second polyolefin layer has an MFR of 2 g / 10 min or more and 20 g / 10 min or less.

7. The packaging material for an electricity storage device according to claim 1 or 2, wherein the elastomer-modified polyolefin resin has an MFR of 1 g / 10 min or more and 10 g / 10 min or less.

8. The packaging material for an electricity storage device according to claim 1 or 2, wherein the polyolefin resin of the second polyolefin layer is a polypropylene resin.

9. The packaging material for an electricity storage device according to claim 1 or 2, wherein the elastomer-modified polyolefin resin is a resin composed of propylene and ethylene and / or butene.

10. The packaging material for an electricity storage device according to claim 1 or 2, which has an insulating resin layer between the barrier layer and the heat-sealable resin layer.

11. The packaging material for an electricity storage device according to claim 10, wherein the insulating resin layer is made of a resin selected from the group consisting of polyethylene terephthalate, polyvinylidene chloride, polypropylene, and polyethylene.

12. The packaging material for an electricity storage device according to claim 10, wherein a portion of the heat-sealable resin layer is removed.

13. An exterior packaging material for a storage battery device according to claim 1 or 2, wherein the thickness remaining after the heat-sealing resin layer is heat-sealed under conditions of a heat sealing temperature of 200°C, a sealing pressure of 0.3 MPa, a sealing time of 3 seconds, and a sealing width of 5 mm is less than 70%.

14. An exterior packaging material for an electrical storage device according to claim 1 or 2, wherein the second polyolefin layer contains 40 mass % or less of a polyolefin-modified elastomer having a melting point of 90°C or higher.

15. The packaging material for an electricity storage device according to claim 14, wherein the crystalline melting energy of the polyolefin-modified elastomer is 40 J / g or less.

16. The packaging material for an electrical storage device according to claim 14, wherein the polyolefin-modified elastomer has an MFR of 0.5 g / 10 min or more and 7 g / 10 min or less.

17. An exterior packaging material for an electrical storage device according to claim 1 or 2, wherein the heat-sealable resin layer is a laminate of three or more layers including a third polyolefin layer on the barrier layer side of the second polyolefin layer.

18. The exterior packaging material for an electricity storage device according to claim 17, wherein in the heat-sealable resin layer, the ratio of thickness of the first polyolefin layer to the second polyolefin layer to the third polyolefin layer is (10:90:10) to (30:40:30).

19. An exterior case for an electricity storage device, comprising a molded article of the exterior material according to claim 1 or 2.

20. An electricity storage device comprising: an electricity storage device main body; and an exterior member consisting of the exterior material for an electricity storage device according to claim 1 or 2 and the exterior case for an electricity storage device according to claim 19, wherein the electricity storage device main body is exterior-covered by the exterior member.

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