Method for manufacturing bipolar electrode laminate and method for manufacturing bipolar battery

Abstract

The present disclosure provides a method for manufacturing a bipolar electrode laminate and a method for manufacturing a bipolar battery, wherein a positive electrode active material layer and a negative electrode active material layer can each have a desired density, and the number of manufacturing steps is small. A method for manufacturing a bipolar electrode laminate according to the present disclosure includes: providing a first electrode mixture containing a first electrode active material and a first binder, and a second electrode mixture containing a second electrode active material, a second binder, and an electrolyte component; forming a first electrode active material layer precursor by forming a film of a first electrode mixture on a first surface of the current collector layer, and forming a second electrode active material layer precursor by forming a film of a second electrode mixture on a second surface of the current collector layer; pressing a laminate comprising the first electrode active material layer precursor, a current collector layer, and a second electrode active material layer precursor; and generating an electrolyte solution by dissolving an electrolyte component in the second electrode active material layer with a solvent after pressing.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a bipolar electrode stack and a method for manufacturing a bipolar battery. Background Art

[0002] Conventionally, there is known a bipolar electrode including a positive electrode active material layer on one surface of a current collector and a negative electrode active material layer on the other surface.

[0003] For example, Patent document 1 discloses a method for manufacturing a bipolar electrode, which comprises: a process of applying a first electrode mixture slurry for forming a first active material layer on a first area on a first surface of a current collector; a process of applying a second electrode mixture slurry for forming a second active material layer on a second area on the inner side of the first area on the second surface of the current collector; a process of applying an electrical insulating agent slurry for forming an end electrical insulating layer on a third area on the outer side of the second area on the second surface of the current collector and connected to the second area; a process of drying the first electrode mixture slurry, the second electrode mixture slurry and the electrical insulating agent slurry; and a process of simultaneously pressing the dried first electrode mixture slurry, the second electrode mixture slurry and the electrical insulating agent slurry to form the first active material layer, the second active material layer and the end electrical insulating layer.

[0004] Prior art literature

[0005] Patent Document 1: International Publication No. 2019 / 230323 Summary of the invention

[0006] In a bipolar battery, in order to achieve a high capacity, the positive electrode active material layer is preferably high in density, while in order to absorb the expansion and contraction of the negative electrode active material, the negative electrode active material layer is preferably low to medium in density.

[0007] In the manufacture of bipolar batteries, the layer for forming the positive electrode active material layer (hereinafter referred to as the positive electrode active material layer precursor in this disclosure) and the layer for forming the negative electrode active material layer (hereinafter referred to as the negative electrode active material layer precursor in this disclosure) are sometimes composed of different materials, in which case, these layers have different softness. Therefore, when the negative electrode active material layer precursor and the positive electrode active material layer precursor are dried and pressed, the softer ones among them are compressed preferentially, and the expected density is sometimes not obtained in the negative electrode active material layer and the positive electrode active material layer formed by pressing.

[0008] As a method for solving this problem, the following method is considered: a film of a positive electrode active material layer precursor is formed on one surface of a positive electrode collector layer, and a film of a negative electrode active material layer precursor is formed on one surface of a negative electrode collector layer, and then each electrode active material layer is formed by pressing them separately, and a bipolar electrode is manufactured by making the surfaces of the two collector layers without forming the electrode active material layer face each other and bonding them. However, in this method, two pressing steps are required, and the manufacturing steps become more.

[0009] The present disclosure aims to provide a method for manufacturing a bipolar electrode stack and a method for manufacturing a bipolar battery including a process for manufacturing such a bipolar electrode stack, wherein the method can make the positive electrode active material layer and the negative electrode active material layer have a desired density and has a small number of manufacturing processes.

[0010] The inventors of the present disclosure have found that the above-mentioned problems can be solved by the following means.

[0011] <Scheme 1>

[0012] A method for manufacturing a bipolar electrode stack, wherein the bipolar electrode stack sequentially comprises a first electrode active material layer, a current collector layer, and a second electrode active material layer, the method comprising the following steps:

[0013] Providing a first electrode mixture and a second electrode mixture, wherein the first electrode mixture contains a first electrode active material and a first binder, and the second electrode mixture contains a second electrode active material, a second binder, and an electrolyte component;

[0014] forming a film of the first electrode mixture on the first surface of the current collector layer to form a first electrode active material layer precursor, and forming a film of the second electrode mixture on the second surface of the current collector layer to form a second electrode active material layer precursor;

[0015] pressing a stacked body including the first electrode active material layer precursor, the current collector layer, and the second electrode active material layer precursor; and

[0016] After the pressing, the electrolyte component in the second electrode active material layer is dissolved with a solvent to generate an electrolyte solution.

[0017] <Solution 2>

[0018] According to the method of embodiment 1, the electrolyte component is a lithium salt.

[0019] <Scheme 3>

[0020] According to the method of embodiment 1 or 2, the first electrode active material layer is a positive electrode active material layer, and the second electrode active material layer is a negative electrode active material layer.

[0021] <Scheme 4>

[0022] A method for producing a bipolar battery comprises the step of producing a bipolar electrode stack by the method for producing a bipolar electrode stack according to any one of aspects 1 to 3.

[0023] According to the present disclosure, a method for manufacturing a bipolar electrode stack and a method for manufacturing a bipolar battery including the steps of manufacturing such a bipolar electrode stack can be provided, wherein the method for manufacturing a bipolar electrode stack can make the positive electrode active material layer and the negative electrode active material layer have the desired density and has fewer manufacturing steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a cross-sectional view showing the stacked body before the electrolyte component is dissolved in a solvent.

[0025] Figure 2 It is a cross-sectional view showing a bipolar electrode stack after the electrolyte components are dissolved in a solvent.

[0026] Description of Reference Numerals

[0027] 101st electrode active material layer

[0028] 11.1st electrode active material

[0029] 20 collector layer

[0030] 30 Second electrode active material layer

[0031] 31 Second electrode active material

[0032] 32 electrolyte ingredients

[0033] 40 electrolyte

[0034] 50 Diaphragm

[0035] 100 bipolar electrodes

[0036] 1000 Bipolar Batteries DETAILED DESCRIPTION

[0037] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the disclosed gist.

[0038] 《Method for producing a bipolar electrode stack》

[0039] The method disclosed herein for manufacturing a bipolar electrode stack having, in sequence, a first electrode active material layer, a collector layer, and a second electrode active material layer comprises the following steps: providing a first electrode mixture and a second electrode mixture, the first electrode mixture containing a first electrode active material and a first binder, and the second electrode mixture containing a second electrode active material, a second binder, and an electrolyte component; forming a film of the first electrode mixture on a first surface of the collector layer to form a first electrode active material layer precursor, and forming a film of the second electrode mixture on a second surface of the collector layer to form a second electrode active material layer precursor; pressing the stack comprising the first electrode active material layer precursor, the collector layer, and the second electrode active material layer precursor; and after pressing, dissolving the electrolyte component in the second electrode active material layer with a solvent to generate an electrolyte solution.

[0040] The present inventors have discovered that when a stack having electrode active material precursor films formed on both sides of a current collector layer is pressed to form a bipolar electrode stack, an electrolyte component is added to the electrode active material layer precursor whose density is to be reduced and pressed, and then a solvent is added to dissolve the electrolyte component, thereby suppressing the high density of the electrode active material layer caused by pressing.

[0041] Furthermore, according to the method of the present disclosure, by dissolving the electrolyte in the battery case, the obtained solution can be used as an electrolytic solution of the battery as it is.

[0042] The method of manufacturing a bipolar electrode stack according to the present disclosure will be described with reference to the drawings. Figure 1 is a cross-sectional view showing the stacked body before the electrolyte components are dissolved by a solvent. Figure 1 As shown, the second electrode active material layer contains a second electrode active material 31 and an electrolyte component 32 . Figure 2 3 is a cross-sectional view showing a bipolar electrode stack after the electrolyte component 32 is dissolved in a solvent. Figure 2 As shown, the electrolyte component 32 is dissolved in a solvent to generate an electrolyte solution 40. This can suppress the density of the second electrode active material layer due to pressing. In addition, in the drawings, the first binder and the second binder are omitted.

[0043] <Provision of Electrode Mixture>

[0044] The method disclosed herein includes the following steps: providing a first electrode mixture and a second electrode mixture, wherein the first electrode mixture contains a first electrode active material and a first binder, and the second electrode mixture contains a second electrode active material, a second binder, and an electrolyte component.

[0045] (First electrode mixture)

[0046] The first electrode mixture contains a first electrode active material and a first binder. In addition, the first electrode mixture optionally contains a first thickener and a first conductive aid. The first electrode mixture can be provided by mixing these materials.

[0047] The first electrode active material is a positive electrode active material or a negative electrode active material. Two materials with different potentials (charge and discharge potentials) for absorbing and releasing predetermined ions can be selected from among the known active materials, and the material showing a high potential is used as the positive electrode active material, and the material showing a low potential is used as the negative electrode active material described later.

[0048] As the positive electrode active material, a known active material may be used. For example, when a lithium ion battery is constructed, lithium cobalt oxide, lithium nickel oxide, LiNi oxide, or the like may be used as the positive electrode active material. 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , lithium manganate, spinel lithium compounds and other lithium-containing composite oxides. In addition, lithium iron phosphate (LFP) can be used as an olivine-type positive electrode active material. The positive electrode active material can also be in the form of particles, and its size is not particularly limited.

[0049] As the negative electrode active material, a known active material may be used. For example, in the case of a lithium ion battery, as the negative electrode active material, silicon-based active materials such as silicon, silicon alloys, and silicon oxide; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium or lithium alloys, etc. may be used. The negative electrode active material may also be in the form of particles, and the size thereof is not particularly limited.

[0050] Examples of the first adhesive include butadiene rubber (BR) adhesives, butyl rubber (IIR) adhesives, styrene butadiene rubber (SBR) adhesives, acrylic butadiene rubber (ABR) adhesives, polyvinylidene fluoride (PVdF) adhesives, and polytetrafluoroethylene (PTFE) adhesives.

[0051] Examples of the first conductive agent include carbon materials such as acetylene black, Ketjen black, and carbon nanotubes, and metal materials such as nickel, aluminum, and stainless steel. The conductive agent may be in the form of particles or fibers, and its size is not particularly limited.

[0052] Examples of the first thickener include carboxymethyl cellulose, but the first thickener is not limited thereto.

[0053] (Second electrode mixture)

[0054] The second electrode mixture contains a second electrode active material, a second binder and an electrolyte component. In addition, the second electrode mixture optionally contains a second thickener and a second conductive aid. By mixing these materials, a second electrode mixture can be provided.

[0055] The second electrode active material is a material that forms an electrode active material layer different from the first electrode active material among the positive electrode active material and the negative electrode active material. That is, if the first electrode active material is a positive electrode active material, the second electrode active material is a negative electrode active material, and if the first electrode active material is a negative electrode active material, the second electrode active material is a positive electrode active material.

[0056] Regarding the second electrode active material, reference can be made to the above description regarding the first electrode active material of the present disclosure.

[0057] Regarding the second adhesive, reference can be made to the above description regarding the first adhesive of the present disclosure.

[0058] The electrolyte component may be any substance that can function as an electrolyte of a bipolar battery. For example, in the case of a lithium ion battery, the electrolyte component may be a lithium salt. Examples of the lithium salt include lithium bis(fluorosulfonyl)imide (LiFSI), lithium trifluoromethanesulfonate (LiOTF), and the like.

[0059] Regarding the second thickener and the second conductive aid, reference can be made to the above description regarding the first thickener and the first conductive aid of the present disclosure.

[0060] <Formation of Electrode Active Material Layer Precursor>

[0061] The method disclosed herein comprises the following steps: forming a film of a first electrode mixture on a first surface of a current collector layer to form a first electrode active material layer precursor, and forming a film of a second electrode mixture on a second surface of the current collector layer to form a second electrode active material layer precursor. Furthermore, in the present disclosure, "electrode active material precursor" refers to a layer that can form an electrode active material layer by pressing.

[0062] (Current Collector Layer)

[0063] In the present disclosure, the “current collector layer” refers to a bipolar current collector layer, that is, a current collector layer having a positive electrode active material layer formed on one surface thereof and a negative electrode active material layer formed on the other surface thereof.

[0064] The collector layer can be in the form of foil, plate, mesh, perforated metal, foam, etc. The collector layer can also be made of metal foil or metal mesh. In particular, metal foil has excellent handleability. The collector layer can also be made of multiple foils. In addition, when the collector layer is made of multiple metal foils, some other layers can also be provided between the multiple metal foils.

[0065] When the current collector layer is composed of metal, examples of the metal constituting the current collector layer include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and the like.

[0066] When the current collector layer is composed of a plurality of metal foils, the current collector layer can be formed by bonding the metal foils together with an adhesive, for example.

[0067] The thickness of the current collector layer is not particularly limited, and may be, for example, 0.1 μm or more or 1 μm or more, and 1 mm or less or 100 μm or less.

[0068] As a method of forming a film of the electrode mixture on the surface of the current collector layer, a method of applying a paste of the electrode mixture and drying it can be exemplified, but the method is not limited to this.

[0069] <Pressing of laminated body>

[0070] The method disclosed herein includes the step of pressing a laminate including a first electrode active material layer precursor, a current collector layer, and a second electrode active material layer precursor. For example, the pressing may be performed using a roll press.

[0071] The pressure for pressing the stack may be 1 kN / cm or more, 3 kN / cm or more, 5 kN / cm or more, 6 kN / cm or more, or 7 kN / cm or less, 15 kN / cm or less, 13 kN / cm or less, 11 kN / cm or less, 10 kN / cm or less, or 9 kN / cm or less.

[0072] <Dissolution of Electrolyte Components>

[0073] The method disclosed herein includes the step of dissolving the electrolyte component in the second electrode active material layer with a solvent to generate an electrolyte solution after pressing.

[0074] As the solvent, carbonates, esters, ethers, nitriles, sulfones, lactones, etc. can be used. For example, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxyethane ... Alkanes, 1,3-dioxolane, diethylene glycol, dimethyl ether, ethylene glycol, acetonitrile, propionitrile, nitromethane, N,N-dimethylformamide, dimethyl sulfoxide, cyclopentane, γ-butyrolactone, etc.

[0075] The bipolar electrode stack produced by the method disclosed herein includes a first electrode active material layer, a current collector layer, and a second electrode active material layer in this order.

[0076] <First Electrode Active Material Layer>

[0077] In the method disclosed herein, the first electrode active material layer may be a positive electrode active material layer or a negative electrode active material layer, but is preferably a positive electrode active material layer. In this case, the first electrode active material and the first electrode mixture may be a positive electrode active material and a positive electrode mixture, respectively.

[0078] The density of the first electrode active material layer may be 2.00 g / cc or more, 2.05 g / cc or more, or 2.10 g / cc or more, and may be 2.25 g / cc or less, 2.20 g / cc or less, or 2.15 g / cc or less.

[0079] The difference between the density of the first electrode active material layer and the density of the first electrode active material layer precursor may be 0.20 g / cc or more, 0.25 g / cc or more, or 0.30 g / cc or more, and may be 0.45 g / cc or less, 0.40 g / cc or less, or 0.35 g / cc or less.

[0080] The density can be a value calculated from the weight per unit area of ​​the active material and the measured value of its thickness.

[0081] The content of each component in the first electrode active material layer may be the same as in the related art.

[0082] The shape of the first electrode active material layer may be the same as in the related art. From the viewpoint of being able to more easily construct a battery, the first electrode active material layer may be in a sheet shape.

[0083] The thickness of the first electrode active material layer is not particularly limited. For example, it may be 0.1 μm or more and 2 mm or less. The lower limit may be 1 μm or more, and the upper limit may be 1 mm or less.

[0084] <Current Collector Layer>

[0085] Regarding the current collector layer, reference can be made to the above description regarding the current collector layer of the present disclosure.

[0086] <Second Electrode Active Material Layer>

[0087] In the method disclosed herein, the second electrode active material layer may be a positive electrode active material layer or a negative electrode active material layer, but is preferably a negative electrode active material layer. In this case, the second electrode active material and the second electrode mixture may be a negative electrode active material and a negative electrode mixture, respectively.

[0088] The density of the second electrode active material layer may be 1.00 g / cc or more, 1.05 g / cc or more, or 1.10 g / cc or more, and may be 1.25 g / cc or less, 1.20 g / cc or less, or 1.15 g / cc or less.

[0089] The difference between the density of the second electrode active material layer and the density of the second electrode active material layer precursor may be 0.01 g / cc or more, 0.05 g / cc or more, or 0.08 g / cc or more, and may be 0.20 g / cc or less, 0.15 g / cc or less, or 0.12 g / cc or less.

[0090] The rate of increase from the density of the second electrode active material layer precursor to the density of the second electrode active material can be greater than 0.1%, greater than 1.0%, greater than 3.0%, greater than 5.0%, greater than 7.0%, greater than 8.0%, greater than 9.0% or greater than 9.5%, and can be less than 29.0%, less than 25.0%, less than 20.0%, less than 17.0%, less than 15.0%, less than 14.0%, less than 13.0%, less than 12.0%, less than 11.0% or less than 10.0%.

[0091] The content of each component in the second electrode active material layer may be the same as in the related art.

[0092] The shape of the second electrode active material layer may be the same as in the conventional case. From the viewpoint of being able to more easily construct a battery, the second electrode active material layer may be in a sheet shape.

[0093] The thickness of the second electrode active material layer is not particularly limited. For example, it may be 0.1 μm or more and 2 mm or less. The lower limit may be 1 μm or more, and the upper limit may be 1 mm or less.

[0094] 《Method for manufacturing bipolar battery》

[0095] The method of manufacturing a bipolar battery disclosed herein includes manufacturing a bipolar electrode stack.

[0096] <Manufacturing of Bipolar Electrode Stack>

[0097] Regarding the method for producing the bipolar electrode stack, reference can be made to the above description regarding the method for producing the bipolar electrode stack of the present disclosure.

[0098] <Storage in Battery Case, etc.>

[0099] The bipolar electrode stack and the separator layer are alternately stacked, then housed in a battery case, and impregnated with an electrolyte, thereby obtaining a bipolar battery. Specifically, the bipolar electrode stack and the separator layer are housed in a battery case, and a solvent that dissolves the electrolyte component in the second electrode active material layer is filled in the battery case to generate an electrolyte, the bipolar electrode stack and the separator layer are immersed in the electrolyte, and the bipolar electrode stack, the separator layer and the electrolyte are sealed in the battery case, thereby obtaining the bipolar battery of the present disclosure.

[0100] The separator layer may be an electrically insulating nonwoven fabric or a porous film. Examples of the porous film include films made of resins such as polyethylene (PE) and polypropylene (PP).

[0101] [Example]

[0102] 《Production of bipolar electrode stack》

[0103] <Formation of Current Collector Layer>

[0104] (Example 1)

[0105] The aluminum foil and the copper foil are bonded together via an adhesive (main agent: olefin resin, curing agent: isocyanate), and the adhesive is cured to form a current collector layer.

[0106] <Formation of Positive Electrode Active Material Layer Precursor and Negative Electrode Active Material Layer Precursor>

[0107] Lithium iron phosphate (LFP) as a positive electrode active material, styrene butadiene rubber (SBR) as a binder, carboxymethyl cellulose (CMC) as a thickener, carbon nanotubes (CNT) as a conductive aid, and water as a solvent are mixed to obtain a positive electrode mixture paste. The obtained positive electrode mixture paste is applied on the aluminum foil surface of the above-mentioned collector layer to form a positive electrode active material layer precursor. In addition, graphite as a negative electrode active material, SBR as a binder, CMC as a thickener, CNT as a conductive aid, lithium bis(fluorosulfonyl)imide (LiFSI) (made by Nippon Catalyst, IONEL) as an electrolyte component, and water as a solvent are mixed to obtain a negative electrode mixture paste. The obtained negative electrode mixture paste is applied on the copper foil surface of the above-mentioned collector layer to form a negative electrode active material layer precursor. The positive electrode active material layer precursor and the negative electrode active material layer precursor formed on the collector layer are dried to obtain a laminate.

[0108] <Pressing of laminated body>

[0109] The obtained laminate was pressed at a linear pressure of 8 kN / cm.

[0110] <Dissolution of Electrolyte Components>

[0111] The pressed laminate was washed with water to dissolve and remove LiFSI. Thus, a bipolar electrode laminate was produced.

[0112] (Comparative Example 1)

[0113] A bipolar electrode stack was produced in the same manner as in Example 1, except that no electrolyte component was used and no dissolution of the electrolyte component was performed in the formation of the negative electrode active material layer precursor.

[0114] "evaluate"

[0115] <density>

[0116] The densities of the positive electrode active material layer precursor and the positive electrode active material layer, and the negative electrode active material layer precursor and the negative electrode active material layer were measured. The density was calculated from the actual measured values ​​of the weight per unit area of ​​the active material and its thickness.

[0117] "result"

[0118] Table 1 shows the calculation results of the density.

[0119] Table 1

[0120]

[0121] As shown in Table 1, in the method of the present disclosure, it is possible to suppress the increase in density of the negative electrode active material layer due to pressing, and to selectively increase the density of the positive electrode active material layer.

Claims

1. A method for manufacturing a bipolar electrode stack, wherein the bipolar electrode stack comprises a first electrode active material layer, a current collector layer, and a second electrode active material layer in sequence, the method comprising the following steps: Providing a first electrode mixture and a second electrode mixture, wherein the first electrode mixture contains a first electrode active material and a first binder, and the second electrode mixture contains a second electrode active material, a second binder, and an electrolyte component; forming a film of the first electrode mixture on the first surface of the current collector layer to form a first electrode active material layer precursor, and forming a film of the second electrode mixture on the second surface of the current collector layer to form a second electrode active material layer precursor; pressing a stacked body including the first electrode active material layer precursor, the current collector layer, and the second electrode active material layer precursor; and After the pressing, the electrolyte component in the second electrode active material layer is dissolved with a solvent to generate an electrolyte solution.

2. The method for producing a bipolar electrode stack according to claim 1, The electrolyte component is a lithium salt.

3. The method for producing a bipolar electrode stack according to claim 1, The first electrode active material layer is a positive electrode active material layer, and the second electrode active material layer is a negative electrode active material layer. 4 . A method for producing a bipolar battery, comprising the step of producing a bipolar electrode stack by the method for producing a bipolar electrode stack according to claim 1 .

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