Resin current collector and laminated battery

Abstract

To provide a resin collector having an improved gas barrier property while utilizing a merit of the resin collector such as a light weight and a processing property or the like, and provide a lamination battery having such as a resin collector.SOLUTION: A resin collector 100 of the present disclosure, includes: a conductive resin layer 10 that contains a base material resin 1 and a conductive filler 2 that is scattered into the base material resin 1; and a fluorine-based resin layer 20 that is laminated to the conductive resin layer 10. Also, the use in the lamination battery of this resin collector, a collector of at least one end surface of the lamination battery is the resin collector 100 of the present disclosure, and the conductive resin layer 10 is contacted to the other layer constructing the lamination battery, and the fluorine-based resin layer 20 is arranged so as to be directed to the side opposite to the other layer constructing the lamination battery.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a resin current collector and a laminated battery having a resin current collector, particularly a sulfide solid state laminated battery having a resin current collector. [Background technology]

[0002] In recent years, it has been proposed to use a resin current collector for a laminated battery (Patent Documents 1 and 2).

[0003] For example, Patent Document 2 discloses an all-solid-state lithium ion secondary battery that includes a solid electrolyte, a positive electrode, and a negative electrode, with the positive electrode and the negative electrode each including a resin current collector, and the resin current collector including a base material made of a polymer material, a conductive filler, and a dispersant. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-038426 [Patent Document 2] Japanese Patent Publication No. 2020-087922 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have found that although resin current collectors have advantages such as light weight and ease of processing, depending on the application, their gas barrier properties are poor compared to metal current collectors such as aluminum foil, stainless steel foil, and copper foil.

[0006] In response to this, the present disclosure aims to solve the above problems while taking advantage of the advantages of resin current collectors, such as light weight and ease of processing. [Means for solving the problem]

[0007] The present inventors have conducted extensive research and found that the above problems can be solved by the following means, and have completed the present invention. That is, the present invention is as follows:

[0008] <Aspect 1> a conductive resin layer including a base resin and a conductive filler dispersed in the base resin; and a fluorine-based resin layer laminated on the conductive resin layer; A resin current collector having the above structure. <Aspect 2> A stacked battery having one or more unit batteries, a current collector on at least one end surface of the stacked battery is the resin current collector according to aspect 1; and the conductive resin layer of the resin current collector is in contact with other layers constituting the laminated battery, and the fluorine-based resin layer of the resin current collector is disposed facing away from the other layers constituting the laminated battery; Stacked battery. <Aspect 3> 3. The stacked battery according to aspect 2, wherein at least one of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer constituting the unit battery contains a sulfide solid electrolyte. [Effects of the Invention]

[0009] The present disclosure provides a resin current collector that has improved gas barrier properties while taking advantage of the advantages of resin current collectors, such as light weight and processability, and a laminated battery that includes such a resin current collector. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a resin current collector according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view showing an example of a conventional resin current collector. [Figure 3] FIG. 3 is a cross-sectional view showing an example of a stacked battery according to the present disclosure. [Figure 4]FIG. 4 is a diagram showing the relationship between the number of cycles and the charge / discharge efficiency for the sulfide solid laminate batteries of Example 1 and Comparative Example 1. [Figure 5] FIG. 5 is a diagram showing the evaluation results of the water vapor permeability of the resin current collectors used in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the embodiments shown in the drawings are merely examples of the present disclosure and are not intended to limit the present disclosure.

[0012] <Resin current collector> The resin current collector of the present disclosure has a conductive resin layer containing a matrix resin and a conductive filler dispersed in the matrix resin, and a fluorine-based resin layer laminated on the conductive resin layer.

[0013] According to such a resin current collector of the present disclosure, in a stacked battery having one or more unit batteries, the current collector on at least one end surface of the stacked battery is the resin current collector of the present disclosure, the conductive resin layer of the resin current collector of the present disclosure is in contact with other layers that constitute the stacked battery, and the fluororesin layer of the resin current collector of the present disclosure is arranged so as to face the opposite side to the other layers that constitute the stacked battery. This makes it possible to take advantage of the advantages of the resin current collector, such as light weight and processability, while providing improved gas barrier properties due to the fluororesin layer, and thereby providing the stacked battery with excellent durability.

[0014] Specifically, for example, as shown in FIG. 1 , a resin current collector 100 of the present disclosure includes a base resin 1 and a conductive resin layer 10 containing conductive filler 2 dispersed in the base resin 1, and a fluororesin layer 20 laminated on the conductive resin layer 10. Furthermore, when using such a resin current collector of the present disclosure, as shown in FIG. 3 , in a stacked battery 1000 having one or more unit cells, the current collector on at least one end surface of the stacked battery 1000 is the resin current collector 100 of the present disclosure, and the conductive resin layer 10 of the resin current collector 100 of the present disclosure is in contact with another layer 50 constituting the stacked battery 1000, and the fluororesin layer 20 of the resin current collector 100 of the present disclosure is disposed so as to face the opposite side from the other layer 50 constituting the stacked battery 1000. In such a stacked battery, the fluororesin layer of the resin current collector provides excellent gas barrier properties, thereby enabling the stacked battery to have excellent durability.

[0015] In contrast, as shown in Fig. 2, a conventional resin current collector 200 does not have a fluorine-based resin layer like the resin current collector of the present disclosure, and is composed only of a base resin 1 and a conductive resin layer 10 containing conductive filler 2 dispersed in the base resin 1. Therefore, the present inventors have found that such conventional resin current collectors lack gas barrier properties, and as a result, the durability of stacked batteries obtained using such resin current collectors is poor.

[0016] (Conductive resin layer) The conductive resin layer constituting the resin current collector of the present disclosure includes a matrix resin and a conductive filler dispersed in the matrix resin. This resin current collector layer may be any conductive layer known for resin current collectors. For example, the descriptions in Patent Documents 1 and 2 can be referenced for resin current collector layers. The conductive resin layer may also be a single layer or a laminate of two or more conductive resin sublayers.

[0017] The matrix resin may be any thermoplastic resin or thermosetting resin, such as polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polycycloolefin (PCO), polyethylene terephthalate (PET), polyethernitrile (PEN), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), epoxy resin, silicone resin, or a mixture thereof. From the viewpoint of electrical stability, the matrix resin is preferably polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), or polycycloolefin (PCO), more preferably polyethylene (PE), polypropylene (PP), or polymethylpentene (PMP), or a mixture thereof.

[0018] The conductive filler can be selected from any material having electrical conductivity. From the viewpoint of suppressing ion permeation within the current collector, the conductive filler is preferably a material that does not have conductivity with respect to the ions used as the charge transfer medium. Specifically, the conductive filler may be, but is not limited to, a carbon material, aluminum, gold, silver, copper, iron, platinum, chromium, tin, indium, antimony, titanium, nickel, etc. These conductive fillers may be used alone or in combination of two or more. Furthermore, an alloy material such as stainless steel (SUS) may be used as the conductive filler. From the viewpoint of corrosion resistance, the conductive filler is preferably aluminum, stainless steel, a carbon material, or nickel, more preferably a carbon material. Furthermore, these conductive fillers may be formed by coating a ceramic material or a resin material with the above-mentioned metal by plating or the like.

[0019] The conductive resin layer may optionally contain, in addition to the matrix resin and conductive filler, a dispersant for dispersing the conductive filler in the matrix resin. The conductive resin layer may also optionally contain other components, such as a colorant, an ultraviolet absorber, or a plasticizer. The total amount of components other than the matrix resin and conductive filler added may be 0.001 parts by weight or more, 0.01 parts by weight or more, 0.1 parts by weight or more, or 1 part by weight or more, or 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, 5 parts by weight or less, or 3 parts by weight or less, per 100 parts by weight of the conductive resin layer.

[0020] (Fluorine-based resin layer) In the resin current collector of the present disclosure, a fluororesin layer is laminated on a conductive resin layer. In the resin current collector of the present disclosure, the fluororesin has relatively high gas barrier properties, and therefore, when the resin current collector of the present disclosure is used as a current collector on the end surface of a stacked battery, it is possible to prevent ambient gas from passing through the resin current collecting layer of the present disclosure and reaching the battery stack.

[0021] The proportion of the fluororesin in the fluororesin layer may be more than 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more. Components other than the fluororesin in the fluororesin layer may include any other resin such as those listed for the base resin of the conductive resin layer, as well as colorants, ultraviolet absorbers, plasticizers, etc. Components other than the fluororesin in the fluororesin layer may include conductive fillers such as those listed for the conductive filler in the conductive resin layer, and insulating fillers such as oxides, nitrides, carbides, carbonates, or sulfates.

[0022] The fluorine-based resin may be any resin having a fluorine atom (F) in the structural unit (repeating unit).

[0023] Examples of such fluorine-based resins include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), fluoropolyether (FPE), perfluoropolyether (PFPE), perfluoroalkoxyalkane (PFA), perfluoroethylenepropene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), tetrafluoroethylene-perfluorodioxole copolymer (TFE / PDD), and polyvinyl fluoride (PVF).

[0024] The fluororesin layer may have a lower water vapor permeation rate than the conductive resin layer, for example, when subjected to a water vapor permeation test as follows: Test method: JIS K 7129-4 compliant (differential pressure method) Detector: Gas chromatograph Test gas: Water vapor (humidified atmosphere) Temperature and humidity: 40±2°C, 90±5% (relative humidity) Differential pressure: 1atm

[0025] 《Stacked battery》 The stacked battery of the present disclosure is a stacked battery having one or more unit batteries, wherein a current collector on at least one end face of the stacked battery is the resin current collector of the present disclosure, the conductive resin layer of the resin current collector is in contact with other layers constituting the stacked battery, and the fluororesin layer of the resin current collector is disposed so as to face the opposite side from the other layers constituting the stacked battery.

[0026] That is, as shown in FIG. 3 , this stacked battery is a stacked battery 1000 having one or more unit cells, in which the current collector on at least one end surface of the stacked battery 1000 is a resin current collector 100 of the present disclosure, and the conductive resin layer 10 of the resin current collector 100 of the present disclosure is in contact with another layer 50 constituting the stacked battery 100, and the fluorine-based resin layer 20 of the resin current collector 100 of the present disclosure is disposed facing away from the other layer 50 constituting the stacked battery 1000. In such a stacked battery, the fluorine-based resin layer provides excellent gas barrier properties, thereby achieving excellent durability. The stacked battery of the present disclosure may be further packaged with a laminate film, such as an aluminum laminate film, as an exterior packaging.

[0027] The one or more unit batteries constituting the laminated battery of the present disclosure may be any battery. Examples of the unit battery include a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a calcium ion battery. Of these, the unit battery is preferably a lithium ion battery or a sodium ion battery, and more preferably a lithium ion battery.

[0028] When the unit battery is a sulfide solid-state battery, that is, a solid-state battery in which at least one of the positive electrode layer, solid electrolyte layer, and negative electrode layer constituting the unit battery contains a sulfide solid electrolyte, the sulfide solid electrolyte is likely to react with moisture, and therefore the performance of the unit battery is relatively likely to deteriorate in an environment where moisture is present.

[0029] In contrast, the resin current collector of the present disclosure can provide improved gas barrier properties due to the fluorine-based resin layer, and therefore can be used particularly well when combined with a sulfide solid battery.

[0030] Therefore, in the laminated battery of the present disclosure, the unit battery is preferably a sulfide solid battery, i.e., a solid battery in which at least one of the positive electrode layer, solid electrolyte layer, and negative electrode layer constituting the unit battery contains a sulfide solid electrolyte. Furthermore, this unit battery may be a lithium ion sulfide solid battery, a sodium ion sulfide solid battery, a magnesium ion sulfide solid battery, a calcium ion sulfide solid battery, or the like. Among these, this unit battery is preferably a lithium ion sulfide solid battery or a sodium ion sulfide solid battery, and more preferably a lithium ion sulfide solid battery.

[0031] The sulfide solid laminate battery of the present disclosure may be a primary battery or a secondary battery, but is preferably a secondary battery. This is because secondary batteries can be repeatedly charged and discharged and are useful, for example, as automotive batteries. Therefore, the sulfide solid laminate battery of the present disclosure is preferably a lithium-ion sulfide solid secondary battery.

[0032] In the laminated battery of the present disclosure, the unit battery is formed by laminating a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in this order. The positive electrode layer may have a positive electrode current collector layer and a positive electrode active material layer, and the negative electrode layer may have a negative electrode active material layer and a negative electrode current collector layer.

[0033] The stacked battery of the present disclosure may be a monopolar type battery stack or a bipolar type battery stack.

[0034] (Monopolar battery stack) When the battery stack is a monopolar battery stack, two unit batteries adjacent in the stacking direction may have a monopolar configuration in which they share a positive electrode current collector layer or a negative electrode current collector layer.

[0035] Therefore, for example, the battery stack may be a stack of two unit batteries that share a negative electrode current collector layer, and specifically may have a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer, in this order.

[0036] (Bipolar battery stack) When the battery stack is a bipolar battery stack, two unit batteries adjacent in the stacking direction may have a bipolar configuration in which they share a positive electrode / negative electrode current collector layer that is used as both the positive electrode and negative electrode current collector layers.

[0037] Therefore, for example, a battery stack may be a stack of three unit batteries that share a positive electrode / negative electrode current collector layer used as both a positive electrode and a negative electrode current collector layer, and specifically may have, in this order, a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, a positive electrode / negative electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, a positive electrode / negative electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer. In this case, the "positive electrode / negative electrode current collector layer" is used as both a positive electrode and a negative electrode current collector layer, and therefore corresponds to either a "positive electrode current collector layer" or a "negative electrode current collector layer" as used in the present disclosure.

[0038] (Restraint of stacked batteries) The stacked battery of the present disclosure may be constrained in the stacking direction during use, which improves ionic and electronic conductivity within and between the layers of the battery stack during charging and discharging, thereby further accelerating the battery reaction.

[0039] In this case, the restraining force is not particularly limited and may be, for example, 1.0 MPa or more, 1.5 MPa or more, 2.0 MPa or more, or 2.5 MPa or more. The upper limit of the restraining force is not particularly limited and may be, for example, 50 MPa or less, 30 MPa or less, 10 MPa or less, or 5 MPa or less. [Example]

[0040] Example 1 (Preparation of positive electrode active material layer) A polyvinylidene fluoride (PVDF) binder (Kureha Corporation), a positive electrode active material, a sulfide solid electrolyte (Li2S-P2S5-based glass ceramics), a conductive additive (vapor-grown carbon fiber (VGCF), Showa Denko K.K.), and a solvent were added to a polypropylene (PP) container, and the resulting mixture was stirred for 30 seconds using an ultrasonic disperser (SMT UH-50). Next, the resulting mixture was shaken in a shaker (Shibata Scientific TTM-1) for 3 minutes, and then further stirred for 30 seconds using the ultrasonic disperser to obtain a coating solution.

[0041] The obtained coating liquid was applied onto a stainless steel (SUS) foil by the blade method using an applicator, and after natural drying, it was dried on a hot plate at 100°C for 30 minutes to obtain a transfer material for a positive electrode active material layer having a positive electrode active material layer on one surface of the stainless steel foil.

[0042] (Preparation of negative electrode active material layer) A polyvinylidene fluoride binder (manufactured by Kureha Corporation), a negative electrode active material (lithium titanate (LTO)), the above sulfide solid electrolyte, and a solvent were added to a propylene container, and the resulting mixture was stirred for 30 seconds using an ultrasonic disperser (UH-50 manufactured by SMT) to obtain a coating solution.

[0043] The obtained coating liquid was applied onto a stainless steel foil by the blade method using an applicator, and after natural drying, it was dried on a hot plate at 100°C for 30 minutes to obtain a negative electrode active material layer on one surface of the stainless steel foil.

[0044] (Fabrication of solid electrolyte layer) Butyl butyrate and the sulfide solid electrolyte were added to a propylene container and stirred for 30 seconds with an ultrasonic disperser (UH-50 manufactured by SMT Co., Ltd.). Next, the resulting mixture was shaken in a shaker (TTM-1 manufactured by Shibata Scientific Co., Ltd.) for 30 minutes, and further stirred for 30 seconds with the ultrasonic disperser to obtain a coating solution.

[0045] The obtained coating liquid was applied onto a stainless steel foil by the blade method using an applicator, and after natural drying, it was dried on a hot plate at 100°C for 30 minutes to obtain a transfer material for a solid electrolyte layer having a solid electrolyte layer on one surface of the stainless steel foil.

[0046] (Creating a resin collector) A fluororesin coating was applied onto the conductive resin layer using a doctor blade with a coating gap of 50 μm to obtain a resin current collector of fluororesin layer / conductive resin layer.

[0047] (Fabrication of a sulfide solid-state laminated battery for evaluation) The transfer material for the solid electrolyte layer was placed on the negative electrode active material layer on the surface of the stainless steel foil, pressed, and then the stainless steel foil of the transfer material for the solid electrolyte layer was peeled off. This resulted in a laminate of the solid electrolyte layer / negative electrode active material layer / stainless steel foil. The resulting laminate was punched out to a size larger than the positive electrode active material layer obtained above.

[0048] Next, the transfer material for the positive electrode active material layer was placed on the solid electrolyte layer of the obtained solid electrolyte layer / negative electrode active material layer / stainless steel foil laminate, pressed, and the stainless steel foils on both sides were peeled off, thereby obtaining a laminate having a structure of the positive electrode active material layer / solid electrolyte layer / negative electrode active material layer.

[0049] Next, conductive resin layers were bonded to both sides of the obtained laminate of positive electrode active material layer / solid electrolyte layer / negative electrode active material layer to obtain the sulfide solid laminate battery of Example 1 having a structure of resin current collector / positive electrode active material layer / solid electrolyte layer / negative electrode active material layer / resin current collector. Here, the resin current collector was arranged so that the conductive resin layer of the resin current collector was in contact with the positive electrode active material layer and the negative electrode active material layer, and the fluorine-based resin layer of the resin current collector faced the side opposite to the positive electrode active material layer and the negative electrode active material layer. Therefore, the sulfide solid laminate battery of Example 1 had a laminate structure of fluorine-based resin layer / conductive resin layer / positive electrode active material layer / solid electrolyte layer / negative electrode active material layer / conductive resin layer / fluorine-based resin layer.

[0050] The obtained sulfide solid laminated battery of Example 1 was used as the evaluation battery of Example 1. All of the operations up to this point were carried out in a dry room environment.

[0051] Comparative Example 1 An evaluation battery of Comparative Example 1 was obtained in the same manner as in Example 1, except that a single conductive resin layer without a fluorine-based resin layer was used as the resin current collector.

[0052] "evaluation" (Cycle characteristics of stacked battery) Cycle evaluation was performed in the atmosphere on the evaluation batteries of Example 1 and Comparative Example 1. The measurement was performed by charging and discharging at a constant current and constant voltage within the range of 1.5 to 3.0 V at 25° C. and 0.33 C.

[0053] The change in charge-discharge efficiency with the increase in the number of cycles, where the charge-discharge efficiency at the first cycle is taken as 100%, is shown in Fig. 4. As is clear from Fig. 4, the sulfide solid laminate battery of Example 1, which had a fluorine-based resin layer on each conductive resin layer on both sides, had superior cycle characteristics compared to the sulfide solid laminate battery of Comparative Example 1, which had no fluorine-based resin layer.

[0054] (Gas barrier property evaluation) The gas barrier properties were evaluated for the resin current collector used in Example 1, i.e., a resin current collector having a laminated structure of a fluorine-based resin layer / a conductive resin layer, and the resin current collector used in Comparative Example 1, i.e., a single conductive resin layer.

[0055] Specifically, a water vapor permeation test was carried out as follows to evaluate the gas barrier properties: Test method: JIS K 7129-4 compliant (differential pressure method) Detector: Gas chromatograph Test gas: Water vapor (humidified atmosphere) Temperature and humidity: 40±2°C, 90±5% (relative humidity) Differential pressure: 1atm

[0056] The evaluation results are shown in Figure 5, with the water vapor permeation amount of the resin current collector consisting only of a conductive resin layer (Comparative Example 1) set as the reference (1.0). As is clear from Figure 5, the water vapor permeation amount of the resin current collector consisting only of a conductive resin layer body In comparison with the case of Comparative Example 1, the fluorine-based resin layer and Conductive resin layer The resin current collector (Example 1) made of this material had excellent protection against water vapor permeation, that is, excellent gas barrier properties. [Explanation of symbols]

[0057] 1 Base resin 2. Conductive filler 10 Conductive resin layer 20 Fluorine-based resin layer 50 Parts of the laminated battery other than the resin current collector of the present disclosure 100 Resin current collector of the present disclosure. 200 Conventional resin current collector. 1000 Stacked battery of the present disclosure

Claims

1. a conductive resin layer including a base resin and a conductive filler dispersed in the base resin; and a fluorine-based resin layer laminated on the conductive resin layer; and The fluororesin layer does not contain a conductive filler as a component other than the fluororesin. Resin current collector (excluding those also used as packaging material for film batteries).

2. a conductive resin layer including a base resin and a conductive filler dispersed in the base resin; and a fluorine-based resin layer laminated on the conductive resin layer; and The proportion of the fluorine-based resin in the fluorine-based resin layer is 99% by mass or more. Resin current collector (excluding those also used as packaging material for film batteries).

3. 1. A packaged stacked battery comprising: a stacked battery having one or more unit batteries; and a laminate film as an exterior packaging for packaging the stacked battery, The current collector on at least one end surface of the stacked battery is the resin current collector according to claim 1 or 2, and the conductive resin layer of the resin current collector is in contact with other layers constituting the laminated battery, and the fluorine-based resin layer of the resin current collector is disposed facing away from the other layers constituting the laminated battery; Stacked battery with exterior.

4. At least one of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer constituting the unit battery is sulfide.

4. The packaged laminated battery according to claim 3, containing a polymer solid electrolyte.

5. 4. The packaged laminated battery according to claim 3, wherein the laminate film is an aluminum laminate film.

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