阅读说明：本技术 蓄电装置用构件、其制造方法和蓄电装置 (Member for electricity storage device, method for producing same, and electricity storage device ) 是由 中林诚 阮红福 海田启司 奥村素宜 菊池卓郎 于 2018-03-20 设计创作，主要内容包括：本发明提供一种蓄电装置用构件。所述蓄电装置用构件包含主要由金属构成的基材和层叠在所述基材上的树脂层,其中所述树脂层含有交联含氟树脂。(The invention provides a member for an electric storage device. The member for an electricity storage device comprises a base material mainly composed of a metal and a resin layer laminated on the base material, wherein the resin layer contains a crosslinked fluorine-containing resin.)

1. A member for an electric storage device, comprising:

a base material mainly composed of a metal; and

a resin layer laminated on the substrate,

the resin layer contains a crosslinked fluorine-containing resin.

2. The member for a power storage device according to claim 1,

the fluorine-containing resin and the surface of the base material have a chemical bond therebetween.

3. The member for a power storage device according to claim 1 or 2,

the resin layer is a thermal adhesive layer.

4. The member for a power storage device according to claim 1, 2, or 3,

the resin layer contains a cloth or a filler, and

the resin layer has a linear thermal expansion coefficient of 1X 10^-7/K～40×10^-6/K。

5. The member for power storage devices according to any one of claims 1 to 4, further comprising a covering layer containing a fluorine-containing resin, wherein,

the cover layer is laminated on a surface of the resin layer opposite to the substrate,

the fluorine-containing resin contained in the cover layer is a non-crosslinked fluorine-containing resin or a fluorine-containing resin having a melting point lower than that of the crosslinked fluorine-containing resin.

6. The member for power storage devices according to any one of claims 1 to 5,

the cross-linked fluorine-containing resin is tetrafluoroethylene-hexafluoropropylene copolymer.

7. The member for a power storage device according to claim 5,

the fluorine-containing resin contained in the covering layer is tetrafluoroethylene-hexafluoropropylene copolymer.

8. The member for power storage devices according to any one of claims 1 to 7,

the peel strength between the resin layer and the base material is 0.1N/cm to 100N/cm.

9. The member for power storage devices according to any one of claims 1 to 8,

a ten-point average roughness (R) of the surface of the substrate in a region where the resin layers are laminated_Z) 0.001 to 10 μm.

10. The member for power storage devices according to any one of claims 1 to 9,

the component for the electric storage device is a tab lead or a case.

11. A method of manufacturing a member for a power storage device, the method comprising the steps of:

laminating a layer containing a fluorine-containing resin on a base material mainly composed of a metal, and

ionizing radiation is applied to the layer containing the fluorine-containing resin.

12. An electrical storage device, comprising:

a positive electrode;

a negative electrode;

an electrolyte;

a case that accommodates the positive electrode, the negative electrode, and the electrolyte; and

a lead wire of the pole ear is connected with the pole ear,

one end of the tab lead is exposed from the case and the other end is connected with the positive electrode or the negative electrode,

the case and the tab leads are thermally bonded to each other,

at least one of the case and the tab lead is the member for a power storage device according to any one of claims 1 to 9.

13. The power storage device according to claim 12, further comprising a thermoadhesive film interposed between the case and the tab lead, wherein,

the heat-adhesive film contains a non-crosslinked fluorine-containing resin or a fluorine-containing resin having a melting point lower than that of a crosslinked fluorine-containing resin.

Technical Field

The invention relates to a member for a power storage device, a method for manufacturing the same, and a power storage device. This application claims priority to japanese patent application No. 2017-110096, filed on 6/2 of 2017, the disclosure of which is incorporated herein by reference in its entirety.

Background

Lithium ion secondary batteries have been used as power sources for electronic devices. In addition to secondary batteries, other power storage devices such as electric double layer capacitors have been developed. For example, a secondary battery generally includes: a bag-like case made of an aluminum laminate film or the like; an electrode group including a positive electrode, a negative electrode, and the like, housed in the case; and a tab lead extending from the inside of the case to the outside (refer to patent document 1).

The tab lead is mainly composed of a metal base material responsible for transmitting electric power between the positive electrode or negative electrode of the electrode group and an external member. Typically, the pouch case further comprises a metal substrate in the form of a film. In order to electrically insulate the base material of the case from the base material of the tab lead, resin layers are respectively provided on the two base materials, and the two base materials are joined to each other with the resin layer interposed therebetween. The presence of these resin layers also makes it possible to seal the electrode group within the pouch-shaped case.

Typically, these resin layers are made of polyolefins such as polypropylene. These resin layers need to be sufficiently adhered to the metal substrate. However, for example, polyolefins have poor adhesion to metals. Therefore, in the tab lead or the like, when the base material and the polyolefin resin layer are laminated on each other, the acid-modified polyolefin is generally interposed between the base material and the polyolefin resin layer.

Disclosure of Invention

The present invention has been devised to solve the above problems. One aspect of the present invention is a member for an electricity storage device, comprising a base material mainly composed of a metal and a resin layer laminated on the base material, wherein the resin layer contains a crosslinked fluorine-containing resin.

Another aspect of the invention is a method of manufacturing a member for a power storage device, wherein the method includes the steps of: a layer containing a fluorine-containing resin is laminated on a base material mainly composed of a metal, and ionizing radiation is applied to the layer containing the fluorine-containing resin.

Another aspect of the invention is an electric storage device including a positive electrode; a negative electrode; an electrolyte; a case for accommodating the positive electrode, the negative electrode, and the electrolyte; and a tab lead having one end exposed from the case and the other end connected to the positive electrode or the negative electrode, wherein the case and the tab lead are thermally bonded to each other, and at least one of the case and the tab lead is the member for an electric storage device described above.

Drawings

Fig. 1 is a perspective view of a secondary battery according to a first embodiment of a power storage device of the present invention.

Fig. 2 is a partial sectional view of the secondary battery shown in fig. 1.

Fig. 3 is a partial cross-sectional view of a tab lead of a second embodiment of a member for an electricity storage device according to the present invention.

Fig. 4 is a partial sectional view of a secondary battery according to a third embodiment of the power storage device of the invention.

Detailed Description

[ problem to be solved by the present disclosure ]

The resin layer is required to have not only heat adhesiveness and adhesion to a substrate but also durability against an electrolytic solution, i.e., chemical resistance, heat resistance, flame retardancy, and strength, for example. When the chemical resistance or heat resistance of the resin layer is poor, adverse consequences may occur, including easy leakage of the electrolyte from, for example, a thermal bonding interface or an interface between the substrate and the resin layer. With the trend of applying a larger current and a higher voltage to an electric storage device such as an electric storage device for an electric vehicle, the demand for improvement in heat resistance and the like is also increasing.

The present invention has been devised in view of the above circumstances. The purpose of the present invention is to provide a member for an electrical storage device having good heat resistance and good flame retardancy, a method for manufacturing the member for an electrical storage device, and an electrical storage device including the member for an electrical storage device.

[ Effect of the present disclosure ]

The present invention can provide a member for an electric storage device including a resin layer having good heat resistance and good flame retardancy, a method of manufacturing the member for an electric storage device, and an electric storage device including the member for an electric storage device.

[ description of embodiments ]

A member for an electricity storage device according to one aspect of the present invention includes a base material mainly composed of a metal, and a resin layer laminated on the base material, wherein the resin layer contains a crosslinked fluorine-containing resin. The term "crosslinked" herein refers to a state in which a three-dimensional crosslinked structure is formed.

In a member for an electric storage device that includes a resin layer containing a crosslinked fluorine-containing resin and thus has good heat resistance and good chemical resistance, liquid leakage is reduced. In addition, the crosslinked fluorine-containing resin is excellent in flame retardancy. Therefore, the member for an electric storage device is excellent in, for example, heat resistance and flame retardancy of the resin layer, and is therefore suitable for an electric storage device intended to be used under high temperature and severe environment, such as an electric storage device for an electric vehicle. Further, the power storage device including the member for a power storage device is highly safe in an unpredictable abnormal situation such as heat generation. Here, the term "mainly composed of … (component)" means that the content of the component in all the components is the highest, preferably 50 mass% or more.

In the member for an electricity storage device, it is preferable that a chemical bond exists between the fluorine-containing resin and the surface of the base material. This configuration can improve the adhesion between the substrate and the resin layer, thereby making it possible to alleviate liquid leakage and ensure safety even in the case where an impact such as that caused by dropping is applied. Further, in manufacturing the member for a power storage device, neither roughening treatment of the base material nor use of an adhesive is required, so that productivity can be improved. "chemical bond" refers to any of covalent, ionic, and hydrogen bonds.

Preferably, the resin layer is a thermal adhesive layer. With this configuration, excellent thermal adhesiveness can be exhibited. The "thermal adhesive layer" herein refers to a layer bonded to another resin layer by a thermal bonding process. In the heat bonding treatment, the heat bonding layer, which is the resin layer of the member for the power storage device, can be softened to achieve heat bonding; or another resin layer to be bonded with the thermal bonding layer may be softened to achieve thermal bonding. In the latter case, the thermal adhesive layer of the member for an electrical storage device may remain substantially un-softened at the time of thermal bonding.

Preferably, the resin layer contains a cloth or a filler, and the resin layer has a linear thermal expansion coefficient of 1 × 10^-7/K～40×10^-6and/K. Such a configuration in which the resin layer contains the cloth or the filler can thereby lower the linear thermal expansion coefficient, thereby bringing the thermal expansion coefficient of the resin layer closer to that of the base material mainly composed of the metal. Thereby, for example, strain caused by a change in temperature is relieved, so that the peel strength, more specifically, the adhesion between layers can be further improved. When the substrate is temporarily adhered to the fluorine-containing resin layer by a technique such as pressing and then ionizing radiation is applied to the resultant to perform crosslinking, a very small gap may be formed, for example, between the substrate and the resin layer before the ionizing radiation is applied, due to a difference in linear thermal expansion coefficient. Thus, as described above, the resin layer contains the clothOr the filler and thus the resin layer has a coefficient of thermal expansion closer to that of the base material, the formation of a gap due to the difference in the linear thermal expansion coefficients can be alleviated. With the above-described configuration in which the resin layer contains cloth or filler, the tensile strength at break and the like can also be improved, whereby performance such as safety and durability can be improved. "coefficient of linear thermal expansion" herein refers to the length of an object that increases when the temperature increases by 1 ℃. Used herein is an average value of linear thermal expansion coefficients measured when the temperature is increased from 20 ℃ to 150 ℃. The "coefficient of linear thermal expansion" can be measured according to JIS-K-7197(2012) "test method for the coefficient of linear thermal expansion of plastics by thermal mechanical analysis".

Preferably, the member for an electricity storage device further includes a covering layer containing a fluorine-containing resin, the covering layer being laminated on a surface of the resin layer opposite to the substrate, and the fluorine-containing resin contained in the covering layer is a non-crosslinked fluorine-containing resin or a fluorine-containing resin having a melting point lower than that of the crosslinked fluorine-containing resin. With such a structure further including a coating layer containing a fluorine-containing resin, it is possible to maintain good heat resistance and good flame retardancy, and to improve heat adhesiveness.

Preferably, the crosslinked fluororesin is a tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Compared with other fluorine-containing resins, FEP has a low melting point and has high fluidity at about 300 ℃. Therefore, the use of FEP in the resin layer can lower the heat bonding temperature and can shorten the duration of the heat bonding treatment.

Preferably, the fluorine-containing resin contained in the cover layer is FEP. As described above, FEP is preferable among the fluorine-containing resins from the viewpoint of heat adhesiveness. The use of FEP in the cover layer can lower the heat bonding temperature and shorten the duration of the heat bonding process.

Preferably, the peel strength of the resin layer from the substrate is 0.1N/cm to 100N/cm. The adhesion between the substrate and the resin layer can be further improved by setting the peel strength between the resin layer and the substrate to 0.1N/cm or more. Further, the peel strength is used as an index of the degree of crosslinking of the fluorine-containing resin in the resin layer. When the peel strength is 0.1N/cm or more, it is indicated that crosslinking is formed to an extent suitable for further improvement of heat resistance and chemical resistance. Further, when the peel strength between the resin layer and the substrate is 100N/cm or less, it indicates that crosslinking is formed to such an extent that moderate softening occurs upon heating to improve the heat adhesiveness. "peel strength" herein means "measurement of peel strength of adhesive-bonded assembly" according to JIS-K-6854-2(1999) "part 2: 180 ° peel "test method.

Preferably, in the region where the resin layers are laminated, the ten-point average roughness (R) of the surface of the base material_Z) In the range of 0.001 to 10 μm. When the smoothness of the surface of the substrate in the region where the resin layers are laminated is high, the thickness of the resin layer is uniform, so that insulation breakdown and migration can be reduced. In addition, the thermal adhesiveness and chemical resistance can be improved. Further, when the smoothness of the substrate surface is high, roughening treatment such as etching is not required, so that productivity can be improved. "Ten-point average roughness (Rz)" herein means a value obtained by measurement according to JIS-B-0601(2001) in which the cutoff wavelength (. lamda.c) is 2.5mm and the evaluation length (. lamda.c) is 12.5 mm.

Preferably, the member for the power storage device is a tab lead or a case. When the member for an electric storage device is used as a tab lead and/or a case, the advantages of the present invention including good heat resistance and good flame retardancy can be further effectively exhibited.

A method of manufacturing a member for a power storage device according to an aspect of the present invention includes the steps of: a layer containing a fluorine-containing resin is laminated on a base material mainly composed of a metal, and ionizing radiation is applied to the layer containing the fluorine-containing resin.

With the ionizing radiation, a cross-link may be formed in the fluorine-containing resin in the irradiated layer, and a chemical bond may also be formed between the fluorine-containing resin and the metal or the like in the base material. Therefore, a member for an electric storage device including a resin layer having good heat resistance, good flame retardancy, and excellent adhesion to a substrate can be obtained by using the production method.

An electrical storage device according to an aspect of the present invention includes: a positive electrode; a negative electrode; an electrolyte; a case for accommodating the positive electrode, the negative electrode, and the electrolyte; and a tab lead having one end exposed from the case and the other end connected to the positive electrode or the negative electrode, wherein the case and the tab lead are thermally bonded to each other, and at least one of the case and the tab lead is the member for an electric storage device described above.

In the power storage device in which at least one of the case and the tab lead is the above-described member for a power storage device, the resin layer has good heat resistance and good flame retardancy. Therefore, the power storage device can maintain its high quality even when used in a severe environment including a high-temperature environment or under a high voltage and a high current, for example.

Preferably, the power storage device further comprises a thermoadhesive film interposed between the case and the tab lead, wherein the thermoadhesive film contains a non-crosslinked fluorine-containing resin or a fluorine-containing resin having a melting point lower than that of the crosslinked fluorine-containing resin. In the electricity storage device in which a heat-adhesive film containing a non-crosslinked fluorine-containing resin or a fluorine-containing resin having a melting point lower than that of the crosslinked fluorine-containing resin is interposed between the case and the tab lead, heat adhesiveness can be improved.

[ details of embodiments of the present invention ]

< first embodiment: secondary Battery 10>

Next, a secondary battery according to a first embodiment of the power storage device according to the present invention will be described in detail with reference to the appropriate drawings. A case and a tab lead of a secondary battery will also be described as embodiments of a member for an electric storage device according to the present invention.

The secondary battery 10 shown in fig. 1 and 2 includes: a plate-shaped positive electrode, a plate-shaped negative electrode, and an electrolyte (none of which are shown in the drawings), a case 11, and tab leads 12, 12'.

A positive electrode and a negative electrode (not shown) are stacked on each other with a separator interposed therebetween, whereby they form a stacked electrode group. The stacked electrode groups and the electrolyte are housed in a case 11 in a sealed manner. In the case 11, the stacked electrode group is immersed in an electrolyte. As described below, the housing 11 is formed of one or more laminated films. Two laminated films or one folded laminated film has a sealing portion 13 at the edge, and these sealing portions 13 are thermally bonded to each other to effect sealing. The tab lead 12 is provided in the following manner: one end of which is exposed from the case 11 and the other end of which is connected to a positive electrode housed in the case 11. The tab lead 12' is provided in the following manner: one end thereof is exposed from the case 11 and the other end thereof is connected to a negative electrode housed in the case 11. The intermediate portions of the tab leads 12, 12' are sandwiched between laminated films as the case 11. The intermediate portion is a portion where the tab leads 12, 12' are thermally bonded to the case 11.

Typically, the positive electrode and the negative electrode are each a laminate composed of: a current collector such as a metal foil; an active material layer containing an active material is laminated on a surface of the current collector. The positive electrode and the negative electrode are each generally plate-shaped, but may be different in shape.

The separator is typically a porous sheet that is electrically insulating. The separator is impregnated with an electrolyte.

The electrolytic solution may be a nonaqueous solvent in which an electrolyte salt is dissolved. Alternatively, the solvent in the electrolyte may be water.

(case 11)

As shown in fig. 2, a case 11 as an embodiment of a member for an electric storage device according to the present invention includes: a substrate 15; a resin layer 16 laminated on the inner side of the substrate 15; and an outer layer 17 laminated on the outer side of the base material 15. In other words, the case 11 is a laminated film formed by laminating the resin layer 16, the substrate 15, and the outer layer 17 in this order. As described above, the case 11 is a sealed container that houses the positive electrode, the negative electrode, the separator, and the electrolyte.

The substrate 15 has a film form and is typically a metal foil. More specifically, the base material 15 is mainly composed of metal. Examples of metals include aluminum, copper, and stainless steel. The substrate 15 may be substantially composed of a metal, but may contain an additive other than a metal.

Preferably, the ten-point average roughness (R) in the inner side surface of the substrate 15, more specifically, in the region of the laminated resin layer 16_Z) The upper limit of (B) is 10 μm, more preferably 5 μm. When the arithmetic average roughness (Ra) of the inner surface of the base material 15 is not more than the upper limit, the roughness may beInsulation breakdown and migration are mitigated, and thermal adhesion and chemical resistance can be improved. The lower limit of the arithmetic average roughness (Ra) is preferably 0.001. mu.m, more preferably 0.01. mu.m, still more preferably 0.1. mu.m, and particularly preferably 0.3. mu.m, and the roughness (R) is preferably averaged at ten points on the inner surface of the base material 15_Z) When the lower limit is not less than the above-described lower limit, adhesion to the resin layer 16 can be improved, for example.

The resin layer 16 is directly laminated on the inner side of the base material 15. The resin layer 16 is a layer containing a crosslinked fluorine-containing resin. The resin layer 16 may contain optional additional components in addition to the fluorine-containing resin. The resin layer 16 is a thermal adhesive layer having thermal adhesiveness.

The fluorine-containing resin refers to a resin in which at least one hydrogen atom bonded to a carbon atom in a main chain structural unit of a polymer chain is substituted with a fluorine atom or an organic group containing a fluorine atom (hereinafter, also referred to as a "fluorine atom-containing group"). The fluorine atom-containing group refers to a group in which at least one hydrogen atom in a linear, branched or cyclic organic group is substituted with a fluorine atom. Examples of the fluorine atom-containing group include fluoroalkyl groups, fluoroalkoxy groups and fluoropolyether groups.

"fluoroalkyl" refers to an alkyl group in which at least one hydrogen atom is replaced with a fluorine atom. Also included are "perfluoroalkyl groups". More specifically, "fluoroalkyl" comprises, for example, the following groups: an alkyl group in which all hydrogen atoms in the alkyl group are substituted with fluorine atoms, and an alkyl group in which all hydrogen atoms except one terminal hydrogen atom are substituted with fluorine atoms.

"fluoroalkoxy" refers to an alkoxy group in which at least one hydrogen atom is replaced by a fluorine atom. "Perfluoroalkoxy" is also included. More specifically, "fluoroalkoxy" includes, for example, the following groups: an alkoxy group in which all hydrogen atoms in the alkoxy group are substituted with fluorine atoms, and an alkoxy group in which all hydrogen atoms except one terminal hydrogen atom are substituted with fluorine atoms.

"fluoropolyether group" means a monovalent group having a plurality of oxyalkylene chains as a repeating unit and containing an alkyl group or a hydrogen atom at a terminal, wherein at least one hydrogen atom in the oxyalkylene chain and/or at least one hydrogen atom in the terminal alkyl group or the terminal hydrogen atom is substituted with a fluorine atom. The "fluoropolyether group" includes a "perfluoropolyether group" having a plurality of perfluoroalkoxyalkylene chains as a repeating unit.

The fluorine-containing resin is a polymer compound containing a fluorine atom in the molecule. Examples of the fluorine-containing resin include tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene- (perfluoroalkyl vinyl ether) copolymer (PFA), Polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluorodioxole copolymer (TFE/PDD), Polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-Ethylene Copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), (vinylidene fluoride) -hexafluoropropylene copolymer (VDF-HFP copolymer), and (vinylidene fluoride) -hexafluoropropylene-tetrafluoroethylene copolymer (VDF-HFP-TFE copolymer). Among these fluorine-containing resins, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene- (perfluoroalkylvinyl ether) copolymer (PFA), Polytetrafluoroethylene (PTFE), and tetrafluoroethylene-perfluorodioxole copolymer (TFE/PDD) are preferable, and FEP is more preferable. For example, the use of FEP can improve the heat adhesiveness as described above. One kind of these fluorine-containing resins may be used, or two or more kinds thereof may be used as a mixture.

The fluorine-containing resin in the resin layer 16 contains a crosslinking bond. More specifically, it is preferable that a carbon atom in the fluorine-containing resin main chain is bonded to another carbon atom in the fluorine-containing resin main chain through a covalent bond. When the fluorine-containing resin contains a crosslinking bond like this, good chemical resistance and good heat resistance can be exhibited.

In the case 11, a chemical bond is preferably present between the fluorine-containing resin in the resin layer 16 and the surface of the substrate 15. More specifically, it is preferable that the carbon atom in the fluorine-containing resin main chain is bonded to the atom on the surface of the substrate 15 by a covalent bond or an ionic bond. The atoms on the surface of the substrate 15 may be metal atoms or other atoms as a main component of the substrate 15. The resin layer 16 may contain a coupling agent, and the fluorine-containing resin may be chemically bonded to atoms on the surface of the substrate 15 by the coupling agent.

For example, the presence of a chemical bond between the fluorine-containing resin and the base material can be confirmed by X-ray photoelectron spectroscopy (XPS), also referred to as Electron Spectroscopy for Chemical Analysis (ESCA). The X-ray photoelectron spectroscopy involves measuring the energy distribution of photoelectrons released from a sample upon X-ray irradiation, and then subtracting the obtained value from the energy value of the irradiated X-ray, thereby calculating the binding energy of electrons. The value of the binding energy of an electron is inherent to, for example, an element and its electronic state, and therefore the presence of an element and a chemical bond in a sample can be confirmed from the value. In particular, using hard X-rays such as Spring-8, it is possible to analyze a depth of about 20nm, and thus, it is possible to analyze chemical bonds at the interface.

The melting point of the crosslinked fluorine-containing resin in the resin layer 16 is preferably in the range of 250 to 350 ℃, for example. When the melting point of the fluorine-containing resin is within this range, for example, both good heat adhesiveness and good heat resistance can be obtained.

The formation of crosslinks in the fluorine-containing resin in the resin layer 16 and the formation of chemical bonds between the resulting fluorine-containing resin and the surface of the substrate 15 can be carried out by generating fluorine radicals by applying ionizing radiation, for example, in an oxygen-free environment or in a state where the fluorine-containing resin is molten. The method of applying ionizing radiation will be described below in the section on the manufacturing method.

The lower limit of the peel strength between the resin layer 16 and the substrate 15 is preferably 0.1N/cm, more preferably 0.3N/cm, still more preferably 1N/cm, still more preferably 5N/cm, and particularly preferably 10N/cm. When the peel strength between the resin layer 16 and the substrate 15 is not less than the lower limit, the adhesion between the resin layer 16 and the substrate 15 can be further improved. As described above, the peel strength is related to the degree of crosslinking in the fluororesin. When the peel strength is not less than the lower limit, it is shown that sufficient crosslinking is formed in the fluorine-containing resin to further improve chemical resistance and heat resistance. The upper limit of the peel strength is preferably 100N/cm, more preferably 80N/cm. When the peel strength between the resin layer 16 and the substrate 15 is not more than the upper limit, the degree of crosslinking falls within a range suitable for improving the heat adhesiveness.

The lower limit of the content of the fluorine-containing resin in the resin layer 16 is preferably 50% by mass, more preferably 70% by mass, further preferably 90% by mass, and optionally particularly preferably 99% by mass. When the content of the fluorine-containing resin in the resin layer 16 is not less than the lower limit, chemical resistance and heat resistance can be further improved. The content of the fluorine-containing resin in the resin layer 16 may be 100% by mass, but in a structure in which the resin layer 16 contains a cloth or a filler described later, the content of the fluorine-containing resin is preferably not less than the lower limit value with respect to the total content of all components except the cloth and the filler in the resin layer 16.

Preferably, the resin layer 16 contains cloth or filler. The cloth may be defined as, for example, a textile product made of fibers, a cloth-like object, etc. Examples of the cloth include resin cloth, metal cloth, ceramic, glass cloth, and LCP cloth and glass cloth are preferable. Examples of the filler include resin fillers, metal fillers, ceramic fillers, and glass fillers. For example, in the case where the resin layer 16 thus contains cloth and/or a filler, more preferably, the resin layer 16 contains cloth, the heat resistance and the tensile strength can be improved. When the resin layer 16 contains cloth, the resin layer 16 may be formed by impregnating cloth with fluorine-containing resin.

The percentage content of the cloth or filler in the resin layer 16 may be, for example, 10 to 90 mass%. When the resin layer 16 contains cloth, the average thickness of the cloth may be in the range of 10% to 90% with respect to the average thickness of the resin layer 16.

Examples of additional components that may be included in the resin layer 16 include resins other than the crosslinked fluorine-containing resin, coupling agents, flame retardants, antioxidants, and plasticizers. Examples of the resin other than the crosslinked fluorine-containing resin include thermoplastic resins such as polyethylene and polypropylene.

The upper limit of the linear thermal expansion coefficient of the resin layer 16 may be, for example, 200 × 10^-6Preferably 40X 10,/K^-6K, more preferably 30X 10^-6and/K. When the linear thermal expansion coefficient of the resin layer 16 is so small, the peel strength and the like can be improved. This is because the difference in the thermal expansion coefficient between the resin layer 16 and the base material 15 mainly composed of metal is reduced. The linear thermal expansion coefficient of aluminum is 24X 10^-6K, the linear thermal expansion coefficient of copper is 17 x 10^-6and/K. For example, when the resin layer 16 contains cloth and/or filler, the amount of the filler can be reducedThe linear thermal expansion coefficient of the small resin layer 16. The lower limit of the linear thermal expansion coefficient of the resin layer 16 may be, for example, 10 × 10^-6and/K. Preferably, the lower limit of the linear thermal expansion coefficient of the resin layer 16 is 1 × 10^-7and/K. When the linear thermal expansion coefficient of the resin layer 16 is less than 1X 10^-7at/K, the workability of the resin layer 16 may be impaired. Such damage may be caused by an increase in the difference in the linear thermal expansion coefficient between the substrate 15 composed mainly of a metal and the resin layer 16.

The average thickness of the resin layer 16 is not particularly limited, and may be, for example, 1 μm to 200 μm. When the average thickness of the resin layer 16 is within this range, for example, a sufficient level of thermal adhesiveness and electrical insulation can be secured.

For example, the outer layer 17 serves as a protective layer that protects the outside of the substrate 15. Typically, the outer layer 17 is composed primarily of resin. Examples of the resin in the outer layer 17 include polyethylene terephthalate (PET) and polyamide. The resin in the outer layer 17 may be a resin having a melting point higher than that of the crosslinked fluorine-containing resin contained in the resin layer 16.

(Tab lead 12, 12')

As shown in fig. 2, the tab leads 12, 12' as one embodiment of the member for the power storage device according to the present invention include a base 18 and a resin layer 19 laminated on the base 18.

The substrate 18 has a belt-like shape. Typically, substrate 18 is a metal foil. More specifically, the substrate 18 is composed mainly of metal. Preferably, the base material 18 forming the tab lead 12 for the positive electrode is made of aluminum or an aluminum alloy. The tab lead 12 for the positive electrode may be subjected to a high potential, but when the base material 18 is thus made of aluminum or an aluminum alloy, the dissolution of the base material 18 in the electrolyte may be mitigated. As the base material 18 forming the tab lead 12' for the negative electrode, copper, nickel, aluminum, and alloys thereof may be suitable. Substrate 18 may consist essentially of a metal, but may contain, for example, additives other than metals. The structure of the tab lead 12 for a positive electrode may be the same as that of the tab lead 12' for a negative electrode, except for a suitable material of the base material 18 used.

The size of the substrate 18 is not particularly limited and may be appropriately selected according to the size and use of the secondary battery 10. The average thickness of the substrate 18 may be, for example, 0.05mm to 0.5 mm. The length of the substrate 18 may be, for example, 20mm to 100 mm. The width of the substrate 18 may be 2mm to 80 mm. The width of substrate 18 may be longer than the length of substrate 18.

Ten-point average roughness (R) in the central portion in the longitudinal direction of the base 18, in other words, in the region where the resin layer 19 is laminated_Z) May be the same as the above-described corresponding values of the base material 15 of the housing 11.

Both end portions of the base material 18, more specifically, one end 18a and the other end 18b of the base material 18 are not laminated with the resin layer 19. One end 18a of the base material 18 is exposed from the housing 11. The other end 18b of the base material 18 of the tab lead 12 for the positive electrode is connected to a positive electrode (not shown) through a wire 14. In the same manner, the other end 18b of the base material 18 of the tab lead 12' for a negative electrode is connected to a negative electrode (not shown) through the wire 14.

The resin layer 19 covers the entire center portion in the longitudinal direction of the base material 18 having a belt-like shape. More specifically, the resin layers 19 are laminated not only on both surfaces of the central portion of the base material 18 but also on both side surfaces of the central portion of the base material 18. Resin layer 19 is directly laminated on substrate 18. The resin layer 19 contains a crosslinked fluorine-containing resin. The resin layer 19 may contain optional additional components in addition to the fluorine-containing resin. The resin layer 19 is a thermal adhesive layer having thermal adhesiveness.

The crosslinked fluororesin contained in the resin layer 19 is the same as the above-described crosslinked fluororesin contained in the resin layer 16 of the case 11. Preferably, in the same manner as the case 11, there is a chemical bond between the crosslinked fluorine-containing resin contained in the resin layer 19 of the tab lead 12, 12 'and the surface of the base material 18 of the tab lead 12, 12'. Further, the preferable configuration of the resin layer 19 and the preferable configuration of the relationship between the resin layer 19 and the substrate 18 are also the same as the above-described preferable configuration of the resin layer 16 of the housing 11 and the above-described preferable configuration of the relationship between the resin layer 16 and the substrate 15.

The average thickness of the resin layer 19 of the tab leads 12, 12' may be, for example, 1 to 200 μm. When the average thickness of the resin layer 19 is within this range, for example, a sufficient level of thermal adhesiveness and electrical insulation can be secured.

As described above, in the secondary battery 10, one end of the tab lead 12, 12', more specifically, one end 18a of the base material 18, is disposed to be exposed from the case 11 and sealed by the case 11. More specifically, the tab leads 12, 12 'are disposed in such a manner that the resin layer 16 of the case 11 is in direct contact with the resin layer 19 of the tab leads 12, 12'. By providing the tab leads 12, 12 'in this manner, the resin layers 16 of the case 11 are thermally bonded to each other at the seal portions 13, and the respective resin layers 16 of the case 11 are thermally bonded to the resin layers 19 of the tab leads 12, 12'. This configuration enables the stacked electrode group composed of the positive electrode, the negative electrode, and the separator immersed in the electrolytic solution to be sealed in the case 11.

(advantages)

In the secondary battery 10, the resin layer 16 of the case 11 and the resin layer 19 of the tab leads 12, 12' each contain a crosslinked fluorine-containing resin, and thus have good heat resistance, good flame retardancy, and good chemical resistance. In addition, these resin layers all have high adhesion to the base material. Further, the resin layer 16 and the resin layer 19 to be subjected to thermal adhesion each have excellent thermal adhesion because they each contain a fluorine-containing resin, more specifically, the same kind of resin. For these reasons, in the secondary battery 10 including the case 11 and the tab leads 12, 12', liquid leakage can be reduced even under a severe environment, thereby ensuring excellent safety. The secondary battery 10 including the case 11 and the tab leads 12, 12' may be used for the same purposes as a conventional electric storage device, and may be particularly suitable for use with high current and high voltage, including uses such as an electric storage device for an electric vehicle.

< method for manufacturing Member for Electrical storage device (case 11 and Tab leads 12, 12') >

A method of manufacturing a member for a power storage device according to an embodiment of the present invention includes the steps of:

laminating a layer containing a fluorine-containing resin on a base material mainly composed of a metal; and

ionizing radiation is applied to the layer containing the fluorine-containing resin.

The ionizing radiation causes the fluorine-containing resin to crosslink to form a resin layer. In other words, this manufacturing method is suitable for manufacturing the case 11 and the tab leads 12, 12' of the secondary battery 10 described above.

(laminating step)

The laminating step includes laminating a layer containing a fluorine-containing resin on the base material. The lamination can be performed, for example, by the following method: a method of forming a layer containing a substantially non-crosslinked fluorine-containing resin by melt extrusion while laminating the layer on a surface of a base material; or a method of laminating a layer containing a substantially non-crosslinked fluorine-containing resin and a substrate together. Alternatively, powder coating using a fluororesin-containing powder may be used to laminate the layers containing a fluororesin.

(irradiation step)

The irradiation step is performed by applying ionizing radiation to a laminate composed of a base material and a layer containing a fluorine-containing resin, more specifically, to the surface of the layer containing a fluorine-containing resin. As in the case of the case 11, in the configuration in which the resin layer is formed only on one side, the application of the ionizing radiation may be performed only on the one side. In the configuration in which the resin layer is formed over the entire circumference, the ionizing radiation is applied to the entire circumference, as in the case of the tab lead 12.

The laminate placed in an oxygen-free atmosphere, more specifically, an atmosphere having an oxygen concentration of 100ppm or less and the fluorine-containing resin in a molten state is subjected to the application of ionizing radiation. By this step, a crosslink is formed in the fluorine-containing resin, and a chemical bond is formed between the fluorine-containing resin and the base material.

More preferably, the oxygen-free atmosphere has an oxygen concentration of 10ppm or less. When the oxygen concentration is too high, the main chain of the fluorine-containing resin may be cut when ionizing radiation is applied. Preferably, the fluorine-containing resin is melted at a temperature higher than the melting point of the fluorine-containing resin, and the temperature difference is 0 ℃ or more and less than 30 ℃. When the fluorine-containing resin is heated to a temperature of 30 ℃ or more above the melting point, thermal degradation of the fluorine-containing resin may be promoted, thereby impairing the material properties. Examples of methods of reducing the oxygen concentration include using an inert gas such as nitrogen or creating a vacuum.

Examples of ionizing radiation that may be used include: gamma rays, electron beams, X-rays, neutron beams, and high energy ion beams. Preferably, the dose of ionizing radiation is from 0.01kGy to 2000kGy, more preferably from 1kGy to 500 kGy. When the dose of the radiation is less than the lower limit, the crosslinking reaction in the fluorine-containing resin may not sufficiently proceed. In contrast, when the dose of radiation is higher than the upper limit, the fluorine-containing resin may be easily degraded, and the crosslinking reaction may excessively proceed to impair the thermal adhesiveness.

The process of manufacturing the case 11 includes laminating an outer layer 17 on one side of the base material 15. The lamination may be performed by a known method such as lamination. The outer layer may be laminated before or after the irradiation step.

< second embodiment: component for electric storage device (tab lead 22) >

The tab lead 22 as a second embodiment shown in fig. 3 includes: a base material 28, a resin layer 29 laminated on the base material 28, and a cover layer 30 laminated on the resin layer 29. The base material 28 is the same as the base material 18 of the tab leads 12, 12' of the secondary battery 10 shown in fig. 2.

On the substrate 28, a resin layer 29 and a cover layer 30 are laminated in this order. In other words, the cover layer 30 is laminated on the surface of the resin layer 29 opposite to the substrate 28. The tab lead 22 is different from the tab leads 12, 12' shown in fig. 2 in that a covering layer 30 is additionally laminated on the resin layer 29.

The resin layer 29 is directly laminated on the substrate 28. The resin layer 29 is a layer containing a crosslinked fluorine-containing resin. As the resin layer 29, the resin layer 19 of the tab lead 12, 12' shown in fig. 2 may be used as it is.

The cover layer 30 is directly laminated on the outer side of the resin layer 29. The cover layer 30 contains a fluorine-containing resin. The fluorine-containing resin contained in the cover layer 30 is a non-crosslinked fluorine-containing resin or a fluorine-containing resin having a melting point lower than that of the crosslinked fluorine-containing resin in the resin layer 29. Examples of the fluorine-containing resin having a melting point lower than that of the crosslinked fluorine-containing resin include a fluorine-containing resin which has not been subjected to crosslinking treatment. Specific examples include: FEP, PFA, PTFE and TFE/PDD which have not been subjected to crosslinking treatment, in other words, which have substantially no crosslinked structure. FEP and PFA are preferred, FEP being more preferred. Preferably, the melting point of the fluorine-containing resin is, for example, 250 to 350 ℃.

The lower limit of the content of the fluorine-containing resin in the covering layer 30 is preferably 50% by mass, more preferably 70% by mass, still more preferably 90% by mass, and optionally particularly preferably 99% by mass. The content of the fluorine-containing resin in the cover layer 30 may be 100 mass%. The average thickness of the cover layer 30 may be, for example, 1 μm to 200 μm.

For example, the cover layer 30 may be laminated by laminating a film or sheet containing a non-crosslinked fluorine-containing resin or a fluorine-containing resin having a melting point lower than that of the crosslinked fluorine-containing resin on the resin layer 29.

The covering layer 30 of the tab lead 22 is more easily softened or melted when heated than the resin layer 29 containing a crosslinked fluorine-containing resin, and is also thermally bonded well to the layer containing a fluorine-containing resin. In other words, the cover layer 30 functions as a good thermal adhesive layer. Therefore, when the tab lead 22 is used in place of the tab lead 12 in the secondary battery 10 shown in fig. 2, for example, the thermal bonding between the tab lead 22 and the case 11 can be further improved. Further, since the cover layer 30 is a layer containing a fluorine-containing resin, good chemical resistance, good flame retardancy, good heat resistance, and the like are ensured.

< third embodiment: secondary Battery 40>

As shown in fig. 4, a secondary battery 40 as a third embodiment includes a thermal adhesive film 41 interposed between a case 11 and a tab lead 12. This secondary battery 40 is the same as the secondary battery 10 shown in fig. 1 and 2 described above, except that a thermoadhesive film 41 is included. Therefore, the same reference numerals as those of the secondary battery 10 are used except for the thermoadhesive film 41, and the description thereof is omitted.

The thermoadhesive film 41 contains a non-crosslinked fluorine-containing resin or a fluorine-containing resin having a melting point lower than that of the crosslinked fluorine-containing resin contained in the resin layers 16, 19. Such a fluorine-containing resin film may be used as the thermal adhesive film 41. Examples of the fluorine-containing resin having a melting point lower than that of the crosslinked fluorine-containing resin include the above-described non-crosslinked fluorine-containing resin as an example of the fluorine-containing resin contained in the covering layer 30 of the tab lead 22 according to the second embodiment.

The heat-adhesive film 41 is more easily softened when heated than the resin layers 16, 19 containing a crosslinked fluorine-containing resin, and is also heat-adhered to the resin layers 16, 19 well. Therefore, in the secondary battery 40, the thermal bonding between the tab lead 12 and the case 11 can be further improved. Further, since the thermal adhesive film 41 contains a fluorine-containing resin, good chemical resistance, good flame retardancy, good heat resistance, and the like are ensured.

< other embodiment >

It is to be understood that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the constitution of the above embodiments, and includes any modifications and variations within the meaning and scope equivalent to the claims.

For example, the description in the above embodiment has been made with the secondary battery as an exemplary power storage device, but the present invention may be applied to a power storage device other than a secondary battery. Examples of the power storage device other than the secondary battery include an electric double layer capacitor.

In the secondary battery according to the above embodiment, both the case and the tab lead are members for the power storage device according to the present invention. However, one of the case and the tab lead may be a conventional one. In other words, the resin layer of one of the case and the tab lead may not contain the crosslinked fluorine-containing resin. In this case, the resin layer may be made of a known thermoplastic resin, such as a non-crosslinked fluorine-containing resin, polyolefin, polyphenylene sulfide, and/or polyether ether ketone. As an alternative configuration, a cover layer may be laminated on the surface of the resin layer of the case. Further, the member for a power storage device according to the present invention may further include a layer other than any one of the base material, the resin layer, and the cover layer.

The member for the power storage device according to the present invention is not limited to the case and the tab lead. For example, the member for a power storage device according to the present invention may be used as a package of a power storage device.