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

Abstract

To provide a manufacturing method of a bipolar electrode laminate which is capable of making densities of a cathode active material layer and an anode active material layer desirable and reduces manufacturing steps, and a manufacturing method of a bipolar battery including manufacturing such a bipolar electrode laminate.SOLUTION: A method of manufacturing a bipolar electrode laminate successively comprising a first electrode active material layer, a current collector layer and a second electrode active material layer 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; depositing the first electrode mixture on a first face of the current collector layer to form a first electrode active material layer precursor and depositing the second electrode mixture on a second face of the current collector layer to form a second electrode active material layer precursor; pressing a laminate including the first electrode active material layer precursor, the current collector layer and the second electrode active material layer precursor; and solving the electrolyte component in the second electrode active material layer with a solvent after the pressing to generate an electrolytic solution.SELECTED DRAWING: Figure 1

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 technology]

[0002] BACKGROUND ART Conventionally, a bipolar electrode has been known which has 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, the method including the steps of: applying a first electrode mixture slurry to form a first active material layer in a first area on a first surface of a current collector; applying a second electrode mixture slurry to form a second active material layer in a second area on a second surface of the current collector that is inner than the first area; applying an electrical insulating agent slurry to form an end electrical insulating layer in a third area on the second surface of the current collector that is outer than the second area and adjacent to the second area; drying the first electrode mixture slurry, the second electrode mixture slurry, and the electrical insulating agent slurry; and 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 230323 Summary of the Invention [Problem to be solved by the invention]

[0005] In bipolar batteries, a high density positive electrode active material layer is desirable for achieving high capacity, while a low to medium density negative electrode active material layer is sometimes desirable for absorbing expansion and contraction of the negative electrode active material.

[0006] In manufacturing a bipolar battery, a layer for forming a positive electrode active material layer (hereinafter referred to as a positive electrode active material layer precursor in this disclosure) and a layer for forming a negative electrode active material layer (hereinafter referred to as a negative electrode active material layer precursor in this disclosure) may be made of different materials, and in such cases, these layers have different flexibility. Therefore, when the negative electrode active material layer precursor and the positive electrode active material layer precursor are dried and pressed, the softer one of them is preferentially compressed, and the negative electrode active material layer and the positive electrode active material layer formed by pressing may not have the desired density.

[0007] One possible method for solving this problem is to form a film of a positive electrode active material layer precursor on one surface of a positive electrode current collector layer, a film of a negative electrode active material layer precursor on one surface of a negative electrode current collector layer, and then press them together to form each electrode active material layer, and then bond the surfaces of the two current collector layers without the electrode active material layers together to produce a bipolar electrode. However, this method requires two pressing steps, which increases the number of manufacturing steps.

[0008] An object of the present disclosure is to provide a method for manufacturing a bipolar electrode stack that can achieve desired densities for the positive electrode active material layer and the negative electrode active material layer and that requires fewer manufacturing steps, and a method for manufacturing a bipolar battery that includes manufacturing such a bipolar electrode stack. [Means for solving the problem]

[0009] The present inventors have found that the above problems can be solved by the following means. <Aspect 1> A method for manufacturing a bipolar electrode stack having a first electrode active material layer, a current collector layer, and a second electrode active material layer in this order, the method comprising the steps of: providing a first electrode mixture comprising a first electrode active material and a first binder, and a second electrode mixture comprising a second electrode active material, a second binder, and an electrolyte component; depositing the first electrode mixture on a first surface of the current collector layer to form a first electrode active material layer precursor, and depositing the second electrode mixture on a second surface of the current collector layer to form a second electrode active material layer precursor; pressing a laminate 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 in a solvent to produce an electrolyte solution. <Aspect 2> 2. The method of embodiment 1, wherein the electrolyte component is a lithium salt. <Aspect 3> 3. The method of claim 1 or 2, wherein 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. <Aspect 4> A method for producing a bipolar battery, comprising producing the bipolar electrode stack by the method according to any one of aspects 1 to 3. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a method for manufacturing a bipolar electrode stack that can achieve the desired density for each of the positive electrode active material layer and the negative electrode active material layer and that requires fewer manufacturing steps, and a method for manufacturing a bipolar battery that includes manufacturing such a bipolar electrode stack. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing a laminate before the electrolyte component is dissolved in a solvent. [Figure 2] FIG. 2 is a cross-sectional view showing the bipolar electrode stack after the electrolyte components have been dissolved in a solvent. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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 present disclosure.

[0013] <<Method for manufacturing bipolar electrode laminate>> The disclosed method for manufacturing a bipolar electrode laminate having a first electrode active material layer, a current collector layer, and a second electrode active material layer in this order includes providing a first electrode composite including a first electrode active material and a first binder, and a second electrode composite including a second electrode active material, a second binder, and an electrolyte component; depositing the first electrode composite on a first surface of the current collector layer to form a first electrode active material layer precursor, and depositing the second electrode composite on a second surface of the current collector layer to form a second electrode active material layer precursor; pressing the laminate including the first electrode active material layer precursor, the current 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 produce an electrolyte solution.

[0014] The present inventors have found that, in the case of simultaneously forming a bipolar electrode laminate by pressing a laminate in which an electrode active material precursor is formed on both sides of a current collector layer, an electrolyte component is added to the electrode active material layer precursor for which a lower density is desired, and the laminate is pressed, and then a solvent is added to dissolve the electrolyte component, thereby making it possible to suppress densification of the electrode active material layer due to pressing.

[0015] Furthermore, according to the method of the present disclosure, by dissolving the electrolyte inside the battery case, the obtained solution can be used as it is as the electrolyte for the battery.

[0016] The method of the present disclosure for manufacturing a bipolar electrode laminate will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the laminate before dissolving the electrolyte component in a solvent. As shown in FIG. 1, the second electrode active material layer includes a second electrode active material 31 and an electrolyte component 32. FIG. 2 is a cross-sectional view showing the bipolar electrode laminate after dissolving the electrolyte component 32 in a solvent. As shown in FIG. 2, the electrolyte component 32 is dissolved by the solvent, producing an electrolyte solution 40. This prevents the second electrode active material layer from becoming densified by pressing. Note that the first binder and the second binder are omitted from the drawings.

[0017] <Provision of electrode mixture> The method of the present disclosure includes providing a first electrode mix including a first electrode active material and a first binder, and a second electrode mix including a second electrode active material, a second binder, and an electrolyte component.

[0018] (1st electrode composite material) The first electrode mix includes a first electrode active material and a first binder, and optionally a first thickener and a first conductive additive. The first electrode mix can be provided by mixing these materials.

[0019] The first electrode active material is a positive electrode active material or a negative electrode active material. Two materials having different potentials (charge / discharge potentials) at which predetermined ions are absorbed and released can be selected from known active materials, and the material exhibiting a more noble potential can be used as the positive electrode active material, and the material exhibiting a less noble potential can be used as the negative electrode active material described below.

[0020] As the positive electrode active material, known active materials may be used. For example, when a lithium ion battery is constructed, lithium cobalt oxide, lithium nickel oxide, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Various lithium-containing composite oxides such as O2, lithium manganate, and spinel-based lithium compounds can be used. Furthermore, lithium iron phosphate (LFP) can be used as an olivine-type positive electrode active material. The positive electrode active material may be, for example, particulate, and the size of the particulates is not particularly limited.

[0021] Known active materials may be used as the negative electrode active material. For example, when constructing a lithium ion battery, 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, lithium alloys, etc. may be used as the negative electrode active material. The negative electrode active material may be, for example, in the form of particles, and the size thereof is not particularly limited.

[0022] Examples of the first binder include butadiene rubber (BR)-based binders, butylene rubber (IIR)-based binders, styrene butadiene rubber (SBR)-based binders, acrylate butadiene rubber (ABR)-based binders, polyvinylidene fluoride (PVdF)-based binders, and polytetrafluoroethylene (PTFE)-based binders.

[0023] Examples of the first conductive additive include carbon materials such as acetylene black, ketjen black, and carbon nanotubes, and metal materials such as nickel, aluminum, stainless steel, etc. The conductive additive may be, for example, in the form of particles or fibers, and its size is not particularly limited.

[0024] The first thickener may include, but is not limited to, carboxymethyl cellulose.

[0025] (2nd electrode composite material) The second electrode mixture includes a second electrode active material, a second binder, and an electrolyte component. The second electrode mixture also optionally includes a second thickener and a second conductive additive. The second electrode mixture can be provided by mixing these materials.

[0026] The second electrode active material is a material, either a positive electrode active material or a negative electrode active material, that forms an electrode active material layer different from that of the first 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.

[0027] For the second electrode active material, reference can be made to the above description of the first electrode active material of the present disclosure.

[0028] For the second binder, reference may be made to the above description of the first binder of the present disclosure.

[0029] The electrolyte component can be any material that can function as an electrolyte for a bipolar battery. For example, when configuring a lithium ion battery, the electrolyte component can be a lithium salt. Examples of lithium salts include lithium bis(fluorosulfonyl)imide (LiFSI) and lithium trifluoromethanesulfonate (LiOTF).

[0030] For the second thickener and the second conductive aid, reference can be made to the above descriptions regarding the first thickener and the first conductive aid of the present disclosure.

[0031] <Formation of Electrode Active Material Layer Precursor> The method of the present disclosure includes depositing a first electrode composite on a first surface of a current collector layer to form a first electrode active material layer precursor, and depositing a second electrode composite on a second surface of the current collector layer to form a second electrode active material layer precursor. In this disclosure, the term "electrode active material precursor" refers to a layer that can be pressed to form an electrode active material layer.

[0032] (current collector layer) In this disclosure, the term "current collector layer" refers to a bipolar current collector layer, i.e., a current collector layer having a positive electrode active material layer formed on one side thereof and a negative electrode active material layer formed on the other side thereof.

[0033] The current collector layer may be in the form of a foil, plate, mesh, punched metal, foam, or the like. The current collector layer may be made of a metal foil or a metal mesh. Metal foil is particularly excellent in terms of ease of handling. The current collector layer may be made of multiple foils. When the current collector layer is made of multiple metal foils, some layer may be present between the multiple metal foils.

[0034] When the current collector layer is made of a metal, examples of the metal constituting the current collector layer include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel.

[0035] When the current collector layer is made of a plurality of metal foils, the current collector layer can be formed, for example, by bonding the metal foils together with an adhesive.

[0036] 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, or 1 mm or less, or 100 μm or less.

[0037] The method of forming a film of the electrode mixture on the surface of the current collector layer is, for example, a method of applying a paste of the electrode mixture and drying it, but is not limited to this.

[0038] <Pressing the laminate> The method of the present disclosure includes 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, using a roll press.

[0039] The pressure used to press the laminate 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 more, and may be 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.

[0040] <Dissolution of electrolyte components> The method of the present disclosure includes, after pressing, dissolving the electrolyte components in the second electrode active material layer with a solvent to produce an electrolyte solution.

[0041] Examples of solvents that can be used include carbonates, esters, ethers, nitriles, sulfones, and lactones. Examples include 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, dioxane, 1,3-dioxolane, diethylene glycol, dimethyl ether, ethylene glycol, acetonitrile, propionitrile, nitromethane, N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, and γ-butyrolactone.

[0042] The bipolar electrode stack produced by the method of the present disclosure has a first electrode active material layer, a current collector layer, and a second electrode active material layer in this order.

[0043] <First electrode active material layer> In the method of the present disclosure, 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.

[0044] 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.

[0045] 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.

[0046] The density can be calculated from the basis weight of the active material and the actual measured thickness.

[0047] The content of each component in the first electrode active material layer may be the same as in the conventional case.

[0048] The shape of the first electrode active material layer may be the same as that of a conventional electrode active material layer, but from the viewpoint of making it easier to construct a battery, the first electrode active material layer may be in the form of a sheet.

[0049] 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.

[0050] <Current collector layer> For the current collector layer, reference may be made to the above description regarding the current collector layer of the present disclosure.

[0051] <Second electrode active material layer> In the method of the present disclosure, the second electrode active material layer may be either 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.

[0052] 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.

[0053] 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.

[0054] The second electrode active material is calculated from the density of the second electrode active material layer precursor. layerThe increase in density may be 0.1% or more, 1.0% or more, 3.0% or more, 5.0% or more, 7.0% or more, 8.0% or more, 9.0% or more, or 9.5% or more, and may be 29.0% or less, 25.0% or less, 20.0% or less, 17.0% or less, 15.0% or less, 14.0% or less, 13.0% or less, 12.0% or less, 11.0% or less, or 10.0% or less.

[0055] The content of each component in the second electrode active material layer may be the same as in the past.

[0056] The shape of the second electrode active material layer may be the same as that of a conventional electrode active material layer, but from the viewpoint of making it easier to construct a battery, the second electrode active material layer may be in the form of a sheet.

[0057] 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.

[0058] <<Bipolar battery manufacturing method>> The disclosed method of manufacturing a bipolar battery includes manufacturing a bipolar electrode stack.

[0059] <Production of bipolar electrode laminate> For the method of manufacturing the bipolar electrode stack, reference may be made to the above description of the disclosed method of manufacturing the bipolar electrode stack.

[0060] <Storage in a battery case, etc.> A bipolar battery can be obtained by alternately stacking bipolar electrode laminates and separator layers, housing them in a battery case, and impregnating them with an electrolyte. Specifically, the bipolar electrode laminate and separator layers are housed in a battery case, and the battery case is filled with a solvent that dissolves the electrolyte component in the second electrode active material layer to produce an electrolyte solution. The bipolar electrode laminate and separator layers, as well as the electrolyte solution, are immersed in the electrolyte solution, and the bipolar electrode laminate and separator layers are sealed in the battery case, thereby obtaining the bipolar battery of the present disclosure.

[0061] The separator layer may be an electrically insulating nonwoven fabric or a porous film, such as a film made of a resin such as polyethylene (PE) or polypropylene (PP). [Example]

[0062] <<Fabrication of bipolar electrode laminate>> <Formation of current collector layer> Example 1 The aluminum foil and the copper foil were bonded together with an adhesive (main agent: olefin-based resin, curing agent: isocyanate-based), and the adhesive was subjected to a curing reaction to form a current collector layer.

[0063] <Formation of Positive Electrode Active Material Layer Precursor and Negative Electrode Active Material Layer Precursor> A positive electrode composite paste was obtained by mixing 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 (CNTs) as a conductive additive, and water as a solvent. The obtained positive electrode composite paste was applied to the aluminum foil surface of the current collector layer to form a positive electrode active material layer precursor. A negative electrode composite paste was also obtained by mixing graphite as a negative electrode active material, SBR as a binder, CMC as a thickener, CNTs as a conductive additive, lithium bis(fluorosulfonyl)imide (LiFSI) (Ionel, Nippon Shokubai Co., Ltd.) as an electrolyte component, and water as a solvent. The obtained negative electrode composite paste was applied to the copper foil surface of the current collector layer to form a negative electrode active material layer precursor. The positive electrode active material layer precursor and negative electrode active material layer precursor formed on the current collector layer were dried to obtain a laminate.

[0064] <Pressing the laminate> The resulting laminate was pressed at a linear pressure of 8 kN / cm.

[0065] <Dissolution of electrolyte components> The pressed laminate was washed with water to dissolve and remove the LiFSI, thereby producing a bipolar electrode laminate.

[0066] (Comparative Example 1) A bipolar electrode laminate was produced in the same manner as in Example 1, except that no electrolyte component was used in forming the negative electrode active material layer precursor, and no dissolution of the electrolyte component was carried out.

[0067] "evaluation" <density> 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 densities were calculated from the measured values ​​of the active material coating weight and thickness.

[0068] "result" The calculated density is shown in Table 1.

[0069] [Table 1]

[0070] As shown in Table 1, the method of the present disclosure was able to suppress an increase in density of the negative electrode active material layer due to pressing, and was able to selectively increase the density of the positive electrode active material layer. [Explanation of symbols]

[0071] 10 First electrode active material layer 11 First electrode active material 20 Current collector layer 30 Second electrode active material layer 31 Second electrode active material 32 Electrolyte components 40 Electrolyte 50 Separator 100 bipolar electrodes 1000 Bipolar Batteries

Claims

1. A method for manufacturing a bipolar electrode stack having a first electrode active material layer, a current collector layer, and a second electrode active material layer in this order, the method comprising the steps of: providing a first electrode mixture including a first electrode active material and a first binder, and a second electrode mixture including 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 current 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 current collector layer to form a second electrode active material layer precursor; pressing a laminate including the first electrode active material layer precursor, the current collector layer, and the second electrode active material layer precursor; and After the pressing, dissolving the electrolyte component in the second electrode active material layer with a solvent to produce an electrolyte solution. where: the difference between the density of the first electrode active material layer and the density of the first electrode active material layer precursor is 0.20 g / cc or more and 0.45 g / cc or less; and The difference between the density of the second electrode active material layer and the density of the second electrode active material layer precursor is 0.01 g / cc or more and 0.15 g / cc or less.

2. The method of claim 1 , wherein the electrolyte component is a lithium salt.

3. 10. The method of claim 1, wherein 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. The method described in claim 1, wherein the rate of increase from the density of the second electrode active material layer precursor to the density of the second electrode active material layer is 5.0% or more and 15.0% or less.

5. A method for producing a bipolar battery, comprising producing the bipolar electrode stack by the method of any one of claims 1 to 4.

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