Manufacturing method of solid state battery

Abstract

To provide a manufacturing method of a solid state battery in which dimensional control is easy.SOLUTION: A manufacturing method of a solid state battery 1 includes: a negative electrode-side sheet member forming step S40 of forming a negative electrode-side sheet member 400; a positive electrode-side sheet member forming step S30 of forming a positive electrode-side sheet member 300; and an integration pressing step S9 of stacking and integrating the negative electrode-side sheet member 400 and the positive electrode-side sheet member 300. The negative electrode-side sheet member forming step S40 includes: a negative electrode-side solid electrolyte layer transfer step S6 of pressing and transferring a negative electrode-side solid electrolyte layer SE3 to at least a negative electrode current collector foil 221; and a negative electrode-side sheet member cutting step S7 of cutting a sheet-like member obtained by the transfer. The positive electrode-side sheet member forming step S30 includes a positive electrode pressing step S3. A first solid electrolyte layer SE1 is provided on a surface of the positive electrode-side sheet member 300 facing the negative electrode-side solid electrolyte layer SE3, and the negative electrode-side solid electrolyte layer SE3 contains less binder than the first solid electrolyte layer SE1.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a solid-state battery. [Background technology]

[0002] In recent years, research and development into secondary batteries that contribute to energy efficiency has been conducted to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] A method for automatically manufacturing secondary batteries with high productivity involves unwinding materials for positive electrode layers and negative electrode layers using rolls and cutting the materials in a stacked state. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 1999-288733 Summary of the Invention [Problem to be solved by the invention]

[0005] When manufacturing a secondary battery having multiple layers including a solid electrolyte layer, a method for manufacturing a solid battery that allows easy dimensional control is required. [Means for solving the problem]

[0006] (1) The present invention provides a method for manufacturing a solid-state battery (e.g., solid-state battery 1), the method comprising: an anode-side sheet member forming step (e.g., anode-side sheet member forming step S40) for forming an anode-side sheet member (e.g., anode-side sheet member 400) including at least an anode current collector (e.g., anode current collector foil 221) and an anode-side solid electrolyte layer (e.g., anode-side solid electrolyte layer SE3); a cathode-side sheet member forming step (e.g., cathode-side sheet member forming step S30) for forming a cathode-side sheet member (e.g., cathode-side sheet member 300) including at least a cathode current collector (e.g., cathode current collector foil 321) and a cathode active material layer (e.g., cathode active material layer 31); and an integration step (e.g., integration press step S9) for stacking and integrating the anode-side sheet member and the cathode-side sheet member, the positive electrode side sheet member forming step includes a positive electrode pressing step (e.g., a positive electrode pressing step S3) of pressing the positive electrode current collector and the positive electrode active material layer, and a first solid electrolyte layer (e.g., a first solid electrolyte layer SE1) is provided on a surface of the positive electrode side sheet member facing the negative electrode side solid electrolyte layer prior to the integrating step, and the negative electrode side solid electrolyte layer has a lower binder content than the first solid electrolyte layer.

[0007] (2) The maximum value of the pressing pressure in the positive electrode pressing step is preferably at least equal to or greater than the maximum value of the pressing pressure in the negative electrode solid electrolyte layer transferring step.

[0008] (3) The positive electrode sheet member is preferably pressed two or more times.

[0009] (4) The positive electrode sheet member preferably has a thickness in the stacking direction greater than that of the negative electrode sheet member.

[0010] (5) It is preferable to have, before the integration step, a second solid electrolyte layer transfer step (e.g., second solid electrolyte layer transfer step S4) of laminating and transferring a second solid electrolyte layer (e.g., second solid electrolyte layer SE2) having a higher binder content than the anode-side solid electrolyte layer between the anode-side solid electrolyte layer and the first solid electrolyte layer.

[0011] (6) The negative electrode sheet member preferably includes a negative electrode active material layer (for example, the negative electrode active material layer 21).

[0012] (7) It is preferable to have an intermediate layer transferring step (e.g., intermediate layer transferring step S5) of laminating and transferring an intermediate layer (e.g., intermediate layer 5) onto a negative electrode layer (e.g., negative electrode layer 2) including the negative electrode current collector. [Effects of the Invention]

[0013] According to the above (1), since the amount of binder in the anode-side solid electrolyte layer is smaller than that in the first solid electrolyte layer, the anode-side sheet member having the anode-side solid electrolyte layer is easy to cut, which makes it easy to cut the anode-side sheet member and then laminate and transfer it onto the cathode-side sheet member, making it easy to control the dimensions to the desired design dimensions.

[0014] According to the above (2), the positive electrode sheet member contains more binder than the negative electrode sheet member, and therefore can be pressed at a higher pressure than the negative electrode sheet member. This makes it possible to efficiently manufacture the solid state battery 1 by transporting the positive electrode sheet member without cutting it and integrating it with the cut negative electrode sheet member.

[0015] According to the above (3), the positive electrode sheet member contains a larger amount of binder than the negative electrode sheet member, so that multiple pressings are possible. By performing multiple pressings, the electrode becomes dense and can be formed to have a high energy density.

[0016] According to the above (4), in order to increase the energy density, the positive electrode side sheet member is formed thick and contains a large amount of the positive electrode active material layer 31. Therefore, the positive electrode side sheet member can be transported without cutting and integrated with the negative electrode side sheet member obtained by cutting, thereby enabling the solid state battery 1 to be manufactured efficiently.

[0017] According to the above (5), by including the second solid electrolyte layer between the anode-side solid electrolyte layer and the first solid electrolyte layer SE1, it becomes easier to stably attach the anode-side solid electrolyte layer, which has a relatively small amount of binder, to the first solid electrolyte layer via the second solid electrolyte layer.

[0018] According to the above (6), it is possible to provide a solid-state battery with high energy density.

[0019] According to the above (7), when the solid state battery 1 is a lithium metal battery, it becomes possible to deposit lithium metal uniformly, and the interface between the intermediate layer and the solid electrolyte layer can be stabilized. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view of a solid-state battery according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram showing a manufacturing system for a solid-state battery according to an embodiment of the present invention. [Figure 3] FIG. 1 is a diagram showing a part of a solid-state battery manufacturing system according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram showing a flow of a method for manufacturing a solid-state battery according to the present embodiment. [Figure 5] 3A to 3C are diagrams illustrating positions at which each layer constituting the solid state battery of the present embodiment is cut. [Figure 6A] 4A and 4B are diagrams illustrating the dimensional accuracy of layers constituting the positive electrode side sheet member of the present embodiment. [Figure 6B] 4A and 4B are diagrams illustrating the dimensional accuracy of layers constituting the negative electrode side sheet member of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] [Solid battery] As shown in FIG. 1, the solid-state battery 1 manufactured by the manufacturing method according to the present invention is an all-solid-state battery having an electrode 10 in which an anode layer 2, a solid electrolyte layer 4, and a cathode layer 3 are stacked in this order. In this embodiment, the structure in which the anode layer 2, the solid electrolyte layer 4, the cathode layer 3, the solid electrolyte layer 4, and the anode layer 2 are stacked in this order as shown in FIG. 1 will be described as the stacked structure of the solid-state battery 1. However, the structure of the solid-state battery 1 is not limited to the above. The solid-state battery 1 may have a configuration that can be used in solid-state batteries, such as an exterior body, in addition to the electrode 10 shown in FIG. 1.

[0022] The solid electrolyte layer 4 in the solid battery 1 has at least a first solid electrolyte layer SE1 arranged on the cathode layer 3 side and an anode-side solid electrolyte layer SE3 arranged on the anode layer 2 side. The solid electrolyte layer 4 may also have a second solid electrolyte layer SE2 arranged adjacent to the first solid electrolyte layer SE1. In this embodiment, the solid electrolyte layer 4 will be described as consisting of the above three layers. An intermediate layer 5 may be optionally arranged between the anode layer 2 and the solid electrolyte layer 4.

[0023] The solid state battery 1 is not particularly limited, but may be a lithium ion solid state secondary battery or a lithium metal secondary battery.

[0024] (negative electrode layer) The negative electrode layer 2 has a negative electrode active material layer 21 and a negative electrode current collector layer 22. The negative electrode active material layer 21 is not particularly limited and can be made of a material that can be used as a negative electrode active material for the solid-state battery 1. Examples of the negative electrode active material that makes up the negative electrode active material layer 21 include silicon-based active materials such as lithium metal, lithium alloys, Si, and Si alloys, and lithium titanate (Li4Ti5O 12 transition metal oxides such as TiO2, Nb2O3 and WO3, metal sulfides, metal nitrides, carbon materials such as graphite, soft carbon and hard carbon, metallic indium, etc.

[0025] The negative electrode active material layer 21 may contain materials that can be contained in the negative electrode active material layer 21 of the solid battery 1 in addition to the above. Examples of such materials include a solid electrolyte, a conductive additive, and a binder. Examples of the solid electrolyte include the same solid electrolyte as that contained in the solid electrolyte layer 4 described below. Examples of the conductive additive include carbon black, natural graphite, carbon fiber, and carbon nanotubes. Examples of the binder include a nitrile polymer, a polyester polymer, an acrylic acid polymer, a cellulose polymer, a styrene polymer, a styrene-butadiene polymer, a vinyl acetate polymer, a urethane polymer, and a fluoroethylene polymer.

[0026] The negative electrode current collector layer 22 is not particularly limited, but may be made of copper, nickel, stainless steel, or the like. Examples of the shape of the negative electrode current collector layer 22 include a foil, a plate, a mesh, a nonwoven fabric, and a foam. In this embodiment, the negative electrode current collector layer 22 is made of a negative electrode current collector foil 221 as a negative electrode current collector.

[0027] (solid electrolyte layer) The solid electrolyte layer 4 is formed between the anode layer 2 and the cathode layer 3. In this embodiment, the solid electrolyte layer 4 has a structure in which a first solid electrolyte layer SE1 arranged in contact with the cathode layer 3, a second solid electrolyte layer SE2, and an anode-side solid electrolyte layer SE3 arranged on the anode layer 2 side are stacked in this order.

[0028] The first solid electrolyte layer SE1 is disposed in contact with the positive electrode active material layer 31 of the positive electrode layer 3. The solid electrolyte constituting the first solid electrolyte layer SE1 is not particularly limited, and may be any material that can be used as an electrolyte in a solid-state battery. Examples include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, and lithium-containing salts, and polymer solid electrolytes such as polyethylene oxide. One type of the above solid electrolytes may be used, or two or more types may be used in combination.

[0029] The first solid electrolyte layer SE1 contains a binder in addition to the solid electrolyte material. The binder may be the same as the binder that can be contained in the negative electrode active material layer 21. The content of the binder in the first solid electrolyte layer SE1 relative to the total mass of the first solid electrolyte layer SE1 is equal to or greater than the content of the binder in the second solid electrolyte layer SE2 relative to the total mass of the second solid electrolyte layer SE2. The upper limit of the content of the binder in the first solid electrolyte layer SE1 is, for example, 25 mass %. The content of the binder in the first solid electrolyte layer SE1 is preferably 10 to 30 mass %. This allows the first solid electrolyte layer SE1 to easily extend following the positive electrode layer 3 when the positive electrode layer 3 is pressed. Furthermore, the pressing pressure in the transfer pressing step described below can be reduced.

[0030] The first solid electrolyte layer SE1 may contain, in addition to the solid electrolyte material and binder, materials that can be used in the solid electrolyte layer of a solid-state battery.

[0031] The thickness of the first solid electrolyte layer SE1 (the length of each layer in the stacking direction) is preferably thinner than the thickness of the second solid electrolyte layer SE2. The thickness of the first solid electrolyte layer SE1 is preferably, for example, 3 to 15 μm.

[0032] The second solid electrolyte layer SE2 is an arbitrarily disposed layer and is disposed adjacent to the first solid electrolyte layer SE1. The solid electrolyte material constituting the second solid electrolyte layer SE2 is not particularly limited and may be the same as the solid electrolyte material constituting the first solid electrolyte layer SE1. Like the first solid electrolyte layer SE1, the second solid electrolyte layer SE2 may contain a binder or the like in addition to the solid electrolyte material. The content of the binder in the second solid electrolyte layer SE2 is equal to or less than the content of the binder in the first solid electrolyte layer SE1. The content of the binder in the second solid electrolyte layer SE2 is preferably 10 to 30 mass %. This improves the energy density of the solid battery 1. The second solid electrolyte layer SE2 may contain a support. The support may be a three-dimensional structure such as a mesh, a woven fabric, a nonwoven fabric, an embossed body, a punched body, an expanded body, or a foamed body. The second solid electrolyte layer SE2 may not contain the support.

[0033] The thickness of the second solid electrolyte layer SE2 (the length of each layer in the stacking direction) is preferably greater than the thickness of the first solid electrolyte layer SE1. The thickness of the second solid electrolyte layer SE2 (the length of each layer in the stacking direction) is also preferably greater than the thickness of the anode-side solid electrolyte layer SE3, which will be described later. The thickness of the second solid electrolyte layer SE2 is preferably, for example, 10 to 50 μm.

[0034] The anode-side solid electrolyte layer SE3 is disposed on the anode layer side. The anode-side solid electrolyte layer SE3 is disposed adjacent to the anode layer 2. When the solid-state battery 1 has an intermediate layer 5 as shown in FIG. 1 , the anode-side solid electrolyte layer SE3 may be disposed adjacent to the intermediate layer 5.

[0035] The solid electrolyte material constituting the anode-side solid electrolyte layer SE3 is not particularly limited and can be the same as the solid electrolyte material constituting the first solid electrolyte layer SE1. The content of the binder in the anode-side solid electrolyte layer SE3 is preferably 1.3 to 8.7 mass %. In terms of volume %, the content of the binder in the anode-side solid electrolyte layer SE3 is preferably 2.7 to 10 volume %. The content of the binder in the anode-side solid electrolyte layer SE3 is lower than the content of the binder in the first solid electrolyte layer SE1.

[0036] The thickness of the negative electrode side solid electrolyte layer SE3 (the length of each layer in the stacking direction) is preferably thinner than the thickness of the second solid electrolyte layer SE2. The thickness of the negative electrode side solid electrolyte layer SE3 is preferably 3 to 8.5 μm, for example.

[0037] (positive electrode layer) The positive electrode layer 3 has a positive electrode active material layer 31 and a positive electrode current collector layer 32. In this embodiment, the positive electrode layer 3 has a configuration in which two positive electrode active material layers 31 are stacked on both sides of one positive electrode current collector layer 32. However, the configuration of the positive electrode layer 3 is not limited to the above, and the positive electrode layer 3 may have a configuration in which one positive electrode active material layer 31 is stacked on one side of one positive electrode current collector layer 32.

[0038] The positive electrode active material layer 31 is not particularly limited and can be made of a material that can be used as a positive electrode active material for a solid-state battery. Examples of the positive electrode active material that makes up the positive electrode active material layer 31 include LiCoO2, LiNiO2, LiCo x Ni y Mn z O2 (x+y+z=1), LiVO2, LiCrO2, etc., layered positive electrode active material particles, LiMn2O4, Li(Ni 0.25 Mn 0.75Examples of such positive electrode active materials include spinel-type positive electrode active materials such as LiCoPO, LiMnPO, and LiFePO; solid solution oxides (LiMnO-LiMO (M=Co, Ni, etc.)); conductive polymers such as polyaniline and polypyrrole; sulfides such as LiS, CuS, Li-Cu-S compounds, TiS, FeS, MoS, and Li-Mo-S compounds; and mixtures of sulfur and carbon. The positive electrode active material may be one of the above materials, or may be composed of two or more of the above materials.

[0039] The positive electrode active material layer 31 may contain a binder or the like. The binder content of the positive electrode active material layer 31 is preferably 0.5 to 5 mass %. It may be preferably 2.56 mass %. The thickness of the positive electrode active material layer 31 (the length in the stacking direction of each layer) is preferably 80 to 100 μm, for example. This can improve the battery capacity of the solid state battery 1.

[0040] As shown in Fig. 5, an insulating frame 6 may be provided on the outer periphery of the positive electrode active material layer 31. The insulating frame 6 can prevent short circuits in the solid state battery 1 and improve the strength. The insulating frame 6 is arranged so as to cover the side surfaces of the two positive electrode active material layers 31 formed on both sides of the positive electrode current collector layer 32 when the solid state battery 1 is completed. The material for the insulating frame 6 is not particularly limited, but examples thereof include insulating oxides such as alumina, resins such as polyvinylidene fluoride (PVDF), and rubbers such as styrene-butadiene rubber (SBR).

[0041] The positive electrode current collector layer 32 is not particularly limited, and can be made of, for example, aluminum, stainless steel, conductive carbon (graphite, carbon nanotubes, etc.), etc. Examples of the shape of the positive electrode current collector layer 32 include foil, plate, mesh, nonwoven fabric, and foam. In this embodiment, the positive electrode current collector layer 32 is made of a positive electrode current collector foil 321 as a positive electrode current collector.

[0042] (middle class) The intermediate layer 5 is disposed between the anode layer 2 and the solid electrolyte layer 4. For example, when the solid battery 1 is a lithium metal battery, the intermediate layer 5 has the function of uniformly depositing lithium metal. Therefore, the interface between the intermediate layer 5 and the solid electrolyte layer 4 is stabilized. When the solid battery 1 is a lithium metal secondary battery having the intermediate layer 5, the solid battery 1 may be an anode-free battery in which the anode active material layer 21 is not present during the initial charge. In this case, a lithium metal layer is formed as the anode active material layer 21 after the initial charge / discharge.

[0043] The material constituting the intermediate layer 5 is not particularly limited, and examples thereof include metals capable of forming an alloy with lithium and amorphous carbon. Examples of metals capable of forming an alloy with lithium include tin (Sn), silicon (Si), zinc (Zn), magnesium (Mg), gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), and antimony (Sb). The metal capable of forming an alloy with lithium may be nanoparticles. Examples of amorphous carbon include carbon blacks such as acetylene black, furnace black, and ketjen black, coke, and activated carbon. The amorphous carbon may be graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), CNT (carbon nanotube), fullerene, or graphene. The intermediate layer may contain a binder in addition to the above materials.

[0044] A manufacturing system 100 for manufacturing the above-described solid-state battery 1 will be described. FIG. 2 shows the manufacturing system 100 for the solid-state battery 1 of this embodiment. The manufacturing system 100 includes a first positive electrode transfer roller 310, a second positive electrode transfer roller 320, an intermediate layer transfer roller 370 (see FIG. 3), a negative electrode transfer roller 330 (see FIG. 3), a negative electrode sheet member laminating roller 340, a positive electrode press device 350, and an integration press device 360. The positive electrode sheet member 300 is continuously delivered in one direction by the rollers described above to manufacture the solid-state battery 1. Note that FIG. 1 shows the areas that are pressed or transfer-pressed in the positive electrode press step S3, the second solid electrolyte layer transfer step S4, the intermediate layer transfer step S5, the negative electrode solid electrolyte layer transfer step S6, and the integration press step S9 as an integration step, which will be described later.

[0045] The positive electrode side sheet member 300 is a sheet-like member obtained by laminating a positive electrode active material layer 31 on a positive electrode current collector foil 321 that constitutes the positive electrode current collector layer 32. The positive electrode side sheet member 300 constitutes the positive electrode layer 3 of the solid state battery 1 after production. The positive electrode side sheet member 300 is fed by rollers (not shown) and conveyed so as to extend continuously from the base end to the terminal end of the production line for the solid state battery 1.

[0046] The first positive transfer roller 310, the second positive transfer roller 320, the intermediate layer transfer roller 370, the negative transfer roller 330, and the negative sheet member laminating roller 340 each comprise a pair of rotating rollers. The first positive transfer roller 310, the second positive transfer roller 320, the intermediate layer transfer roller 370, and the negative transfer roller 330 perform transfer pressing by sandwiching a sheet such as a substrate to be transferred and a sheet provided with a solid electrolyte layer to be transferred between the pair of rollers and passing them while applying pressure. The negative sheet member laminating roller 340 positions the sandwiched sheet as it passes.

[0047] The positive electrode press device 350 and the integration press device 360 ​​are each composed of a pair of rotating rollers, similar to the transfer roller, and are devices that sandwich the positive electrode side sheet member 300, on which a solid electrolyte layer or the like is laminated depending on the process, between the pair of rollers and pass it through while applying pressure, thereby densifying the positive electrode side sheet member 300.

[0048] 2, these rollers are arranged in the following order from upstream along the feeding direction of the positive electrode side sheet member 300: the first positive electrode side transfer roller 310, the positive electrode press device 350, the second positive electrode side transfer roller 320, the negative electrode side sheet member laminating roller 340, and the integration press device 360. When the solid state battery 1 has a second solid electrolyte layer SE2, the second positive electrode side transfer roller 320 is disposed between the positive electrode press device 350 and the negative electrode side sheet member laminating roller 340.

[0049] The intermediate layer transfer roller 370 and the negative electrode side transfer roller 330 are positioned away from the delivery line L of the positive electrode side sheet member 300, and perform transfer pressing of the intermediate layer 5 or the negative electrode side solid electrolyte layer SE3. Thereafter, as will be described later, the formed intermediate layer 5 and negative electrode layer 2 are conveyed to the upper or lower side of the positive electrode side sheet member 300, merge with the delivery line L of the positive electrode side sheet member 300, and are laminated by the negative electrode side sheet member lamination roller 340.

[0050] A method for manufacturing the solid-state battery 1 using the manufacturing system 100 for the solid-state battery 1 will now be described. The method for manufacturing the solid-state battery 1 includes a cathode-side sheet member forming step S30 and an anode-side sheet member forming step S40. The cathode-side sheet member forming step S30 is a step for forming a cathode-side sheet member 300 including at least a cathode current collector foil 321 (a cathode current collector layer) and a cathode active material layer 31, and includes a cathode-side sheet member feeding step S1, a first solid electrolyte layer transferring step S2, a cathode pressing step S3, and a second solid electrolyte layer transferring step S4, which will be described later. The anode-side sheet member forming step S40 is a step for forming an anode-side sheet member including at least anode current collector foil 221 (a cathode current collector) and an anode-side solid electrolyte layer SE3, and includes an intermediate layer transferring step S5, an anode-side solid electrolyte layer transferring step S6, and an anode-side sheet member cutting step S7, which will be described later.

[0051] First, the positive electrode side sheet member 300, which is formed by coating and laminating a positive electrode active material on the positive electrode current collector foil 321 constituting the positive electrode current collector layer 32, is conveyed and sent out by conveying rollers (not shown) (positive electrode side sheet member feeding step S1).

[0052] 5, in the positive electrode side sheet member 300, an insulating frame 6 is formed on the positive electrode current collector foil 321 along the design dimensions of the completed solid state battery 1. The insulating frame 6 is arranged in a frame shape, and the positive electrode active material layer 31 is intermittently coated and arranged within the frame.

[0053] Next, the first solid electrolyte layer SE1 is transferred to the positive electrode side sheet member 300 by the first positive electrode side transfer roller 310 (first solid electrolyte layer transfer step S2). The first solid electrolyte layer transfer step S2 includes an alignment step S21 and a transfer press step S22. In the alignment step S21, the first solid electrolyte layer SE1 is aligned on the positive electrode side sheet member 300 so as to be positioned within a range guided by a guide roller (not shown). In the transfer press step S22, the slurry constituting the first solid electrolyte layer SE1 is passed over the positive electrode side sheet member 300 while being pressed by the first positive electrode side transfer roller 310, which serves as a transfer roller, to perform transfer press. The pressure at this time can be, for example, 50 to 500 MPa at room temperature (e.g., 10 to 35°C). Preferably, it may be 100 MPa at 25°C.

[0054] Next, the cathode side sheet member 300 onto which the first solid electrolyte layer SE1 has been transferred is pressed by a cathode press device 350 (cathode press step S3). This cathode press step S3 densifies the cathode. To achieve densification, the press pressure is about 800 to 1200 MPa at 25 to 100 degrees. The densified laminate of the cathode side sheet member 300 and the first solid electrolyte layer SE1 is transported downstream along the delivery line L.

[0055] After the positive electrode pressing step S3, the second positive electrode transfer roller 320 transfers the second solid electrolyte layer SE2 onto the positive electrode sheet member 300 onto which the first solid electrolyte layer SE1 has been transferred and pressed (second solid electrolyte layer transferring step S4). The second solid electrolyte layer transferring step S4 includes an alignment step S41 and a transfer pressing step S42. In the alignment step S41, the second solid electrolyte layer SE2 is positioned on the positive electrode sheet member 300 onto which the first solid electrolyte layer SE1 has been transferred so as to be disposed within a range guided by a guide roller (not shown). In the transfer pressing step S42, the slurry constituting the second solid electrolyte layer SE2 is passed over the positive electrode sheet member 300 while being pressed by the second positive electrode transfer roller 320 as a transfer roller, thereby performing transfer pressing. The pressure at this time can be 50 to 500 MPa at room temperature (e.g., 10 to 35°C). Preferably, it may be 150 MPa at 25°C.

[0056] Meanwhile, a negative electrode-side sheet member 400 is prepared at a position away from the delivery line L. First, as shown in the upper part of FIG. 3, an intermediate layer 5 is transferred onto the negative electrode layer 2 composed of the negative electrode active material layer 21 laminated on the negative electrode current collector foil 221 by an intermediate layer transfer roller 370 (intermediate layer transfer step S5). Then, as shown in the lower part of FIG. 3, a negative electrode-side solid electrolyte layer SE3 is transferred onto the intermediate layer 5 by an negative electrode-side transfer roller 330 to form the negative electrode-side sheet member 400 (negative electrode-side solid electrolyte layer transfer step S6). Through this procedure, the intermediate layer 5 is disposed between the negative electrode active material layer 21 and the negative electrode-side solid electrolyte layer SE3.

[0057] The intermediate layer transfer step S5 includes an intermediate layer positioning step S51 and an intermediate layer transfer press step S52. In the intermediate layer positioning step S51, the slurry constituting the intermediate layer 5 is positioned on the negative electrode active material layer 21 so as to be disposed within a range guided by a guide roller (not shown). In the intermediate layer transfer press step S52, the intermediate layer 5 is passed over the negative electrode active material layer 21 while being pressed by an intermediate layer transfer roller 370 serving as a transfer roller, thereby performing intermediate layer transfer press, in which the intermediate layer 5 is transferred to the negative electrode active material layer 21. The pressure at this time can be 50 to 800 MPa at room temperature (e.g., 10 to 35°C), and more preferably within a range of 300 MPa or more and 800 MPa or less at 25°C.

[0058] The anode-side solid electrolyte layer transfer step S6 includes an anode-side solid electrolyte layer positioning step S61 and an anode-side solid electrolyte layer transfer press step S62. In the anode-side solid electrolyte layer positioning step S61, the slurry constituting the anode-side solid electrolyte layer SE3 is positioned on the intermediate layer 5 so as to be placed within a range guided by a guide roller (not shown). In the anode-side solid electrolyte layer transfer press step S62, the anode-side solid electrolyte layer SE3 is passed over the intermediate layer 5 while being pressed by the anode-side transfer roller 330 serving as a transfer roller, thereby performing anode active material layer transfer press, in which the anode-side solid electrolyte layer SE3 is transferred to the intermediate layer 5. This results in a sheet-like member 400a in which the anode layer 2, the intermediate layer 5, and the anode-side solid electrolyte layer SE3 are laminated. The pressure at this time can be 600 to 800 MPa at room temperature (e.g., 10 to 35°C).

[0059] Regarding pressure, the pressing pressure in the positive electrode pressing step S3 is not only the maximum pressure applied to the positive electrode side sheet member 300, but also the maximum pressure applied in the entire manufacturing method of the solid state battery 1. The positive electrode side sheet member 300 is pressed at high pressure to increase the energy density and densify the electrode. The maximum pressing pressure in the positive electrode pressing step S3 is equal to or greater than the maximum pressing pressure applied to the negative electrode side sheet member 400.

[0060] The pressures applied during the transfer in the first solid electrolyte layer transfer step S2 and the second solid electrolyte layer transfer step S4 are lower than the pressing pressure in the positive electrode pressing step S3. The pressures applied during the transfer in the first solid electrolyte layer transfer step S2 and the second solid electrolyte layer transfer step S4 are lower than the pressing pressure in the negative electrode solid electrolyte layer transfer step S6.

[0061] Because the first solid electrolyte layer SE1 and the second solid electrolyte layer SE2 contain a relatively large amount of binder, the pressing pressure during transfer can be reduced. Furthermore, by setting the transfer pressing pressure as low as possible, the amount of stretching of the first solid electrolyte layer SE1 and the second solid electrolyte layer SE2 due to the transfer pressing can be reduced. Therefore, room for stretching of the first solid electrolyte layer SE1 and the second solid electrolyte layer SE2 can be left in the subsequent integration pressing step S9, etc., and the first solid electrolyte layer SE1 can be stretched in accordance with the positive electrode layer 3. This improves the bonding strength of the first solid electrolyte layer SE1 to the positive electrode active material layer 31.

[0062] As shown in FIG. 6A, the positive electrode layer 3 (positive electrode current collector layer 32 and positive electrode active material layer 31), the first solid electrolyte layer SE1, and the second solid electrolyte layer SE2 of the positive electrode side sheet member 300 are densified in the positive electrode pressing step S3 and the integration pressing step S9, and are therefore pressed with high pressure so as to achieve the designed dimensions during the pressing step.

[0063] After the anode-side solid electrolyte layer transfer step S6, the resulting continuous sheet-like member 400a, in which the anode layer 2, intermediate layer 5, and anode-side solid electrolyte layer SE3 are stacked, is cut with a cutter while supported by a payout roll that pays out the member to be transferred in the anode-side solid electrolyte layer transfer step S6 (anode-side sheet member cutting step S7). The sheet-like member 400a is cut to the design dimensions of the anode layer 2 of the solid-state battery 1. As shown in FIG. 5, to prevent short circuits, the sheet-like member 400a is cut to a size slightly smaller than the size to which the cathode-side sheet member 300 is cut in the cutting step S10, which will be described later, to form the anode-side sheet member 400.

[0064] As shown in FIG. 6B, the negative electrode layer 2, the intermediate layer 5, and the negative electrode-side solid electrolyte layer SE3 have finer particles and are softer than the positive electrode layer 3 and the like, and are therefore cut to fit the design dimensions in the negative electrode-side sheet member cutting step S7.

[0065] As shown in FIGS. 2 and 4 , the negative electrode-side sheet member 400 cut to the design dimensions is conveyed to the positive electrode-side sheet member 300 so as to merge with the delivery line L of the positive electrode-side sheet member 300, and is laminated on the positive electrode-side sheet member 300. At this time, prior to the integration pressing step S9 described below, a first solid electrolyte layer SE1 is provided on the lower layer side of the surface of the positive electrode-side sheet member 300 facing the negative electrode-side solid electrolyte layer SE3, and a second solid electrolyte layer SE2 is provided thereon. The negative electrode-side sheet member 400 is then placed on top of the first solid electrolyte layer SE1 and the second solid electrolyte layer SE2 in a cut state on the positive electrode-side sheet member 300. Specifically, the negative electrode-side sheet member 400 onto which the negative electrode-side solid electrolyte layer SE3 has been transferred is conveyed and laminated by the negative electrode-side sheet member laminating roller 340 on top of the positive electrode-side sheet member 300 onto which the first solid electrolyte layer SE1 and the second solid electrolyte layer SE2 have been transferred (negative electrode-side sheet member laminating step S8). In laminating the negative electrode side sheet member, the negative electrode side sheet member 400 cut to the design dimensions is positioned on the positive electrode side sheet member 300 onto which the first solid electrolyte layer SE1 and the second solid electrolyte layer SE2 have been transferred so that it is positioned within a range guided by guide rollers (not shown).

[0066] In this stacked state, the positive electrode side sheet member 300 and the negative electrode side sheet member 400 are pressed by the integration press device 360 ​​to integrate the electrode 10 (integration press step S9). In this way, the positive electrode side sheet member 300 is pressed two or more times, including the transfer step and the pressing step. Immediately before the integration press step S9, the thickness of the negative electrode side sheet member 400 and the positive electrode side sheet member 300 in the stacking direction is greater than the thickness of the negative electrode side sheet member 400. The pressure at this time is, for example, approximately 500 to 900 MPa at 25 to 100 degrees. The integration press step S9 integrates the positive electrode side sheet member 300 and the negative electrode side sheet member 400, and simultaneously densifies the first solid electrolyte layer SE1, the second solid electrolyte layer SE2, and the negative electrode side solid electrolyte layer SE3. Comparing the pressing pressure in the integration pressing step S9 and the positive electrode pressing step S3, the pressing pressure in the positive electrode pressing step S3 is greater than the pressing pressure in the integration pressing step S9.

[0067] After the integration pressing step S9, the formed electrode 10 is cut with a rotary cutter (cutting step S10).

[0068] The transfer of the first solid electrolyte layer SE1 in the first solid electrolyte layer transfer step S2, the pressing of the positive electrode-side sheet member 300 in the positive electrode pressing step S3, the transfer of the second solid electrolyte layer SE2 in the second solid electrolyte layer transfer step S4, the lamination of the negative electrode-side sheet member 400 before integration in the negative electrode-side sheet member lamination step S8, and the integration pressing in the integration pressing step S9 are performed on both sides of the positive electrode-side sheet member 300 delivered in the positive electrode-side sheet member delivery step S1. This results in a solid state battery 1 in which the layers are symmetrically stacked on both the top and bottom surfaces, as shown in FIG. 1 .

[0069] As described above, the first solid electrolyte layer transfer step S2, the second solid electrolyte layer transfer step S4, the positive electrode pressing step S3, the negative electrode side sheet member lamination step S8, and the integration pressing step S9 are successively performed on the positive electrode side sheet member 300 fed in the positive electrode side sheet member feeding step S1. The negative electrode side sheet member forming step S40 is performed at a position separated from the positive electrode side sheet member 300, but the formed negative electrode side sheet member 400 is arranged to merge with the positive electrode side sheet member 300, and the manufacturing method for the solid state battery 1 is performed in a continuous series of steps.

[0070] According to this embodiment, the following effects are achieved. (1) A method for manufacturing a solid-state battery 1 includes an anode-side sheet member forming step S40 for forming an anode-side sheet member 400 including at least an anode current collector foil 221 and an anode-side solid electrolyte layer SE3, a cathode-side sheet member forming step S30 for forming a cathode-side sheet member 300 including at least a cathode current collector foil 321 and a cathode active material layer 31, and an integration pressing step S9 for stacking and integrating the anode-side sheet member 400 and the cathode-side sheet member 300. The anode-side sheet member forming step S40 includes an anode-side solid electrolyte layer transferring step S6 for pressing at least the anode current collector foil 221 and the anode-side solid electrolyte layer SE3 to obtain an anode-side laminate, and an anode-side sheet member cutting step S7 for cutting the laminate, and the cathode-side sheet member forming step S30 includes a cathode pressing step S3 for pressing at least the cathode current collector foil 321 and the cathode active material layer 31. Prior to the integration press step S9, a first solid electrolyte layer SE1 is provided on the surface of the positive electrode side sheet member 300 facing the negative electrode side solid electrolyte layer SE3, and the negative electrode side solid electrolyte layer SE3 has a smaller binder content than the first solid electrolyte layer SE1. Because the amount of binder in the anode-side solid electrolyte layer SE3 is smaller than that in the first solid electrolyte layer SE1, it is easy to cut the anode-side sheet member 400 having the anode-side solid electrolyte layer SE3. This makes it easy to cut the anode-side sheet member 400 and then laminate and transfer it onto the cathode-side sheet member 300, making it easier to control the dimensions to the desired design dimensions.

[0071] (2) According to this embodiment, the maximum value of the pressing pressure in the positive electrode pressing step S3 is set to be at least equal to or greater than the maximum value of the pressing pressure in the negative electrode solid electrolyte layer transferring step S6. The positive electrode sheet member 300 contains more binder than the negative electrode sheet member 400, and therefore can be pressed at a higher pressure than the negative electrode sheet member 400. This allows the positive electrode sheet member 300 to be transported without being cut and integrated with the cut negative electrode sheet member 400, thereby enabling the solid state battery 1 to be manufactured efficiently.

[0072] (3) According to this embodiment, the positive electrode sheet member 300 is pressed two or more times. The positive electrode sheet member 300 contains more binder than the negative electrode sheet member 400, so multiple pressings are possible. By pressing multiple times, the electrode becomes dense and can be formed to have a high energy density.

[0073] (4) According to this embodiment, the positive electrode side sheet member 300 is configured to have a greater thickness in the stacking direction than the negative electrode side sheet member 400. The positive electrode side sheet member 300 is formed thick and contains a large amount of the positive electrode active material layer 31 in order to increase the energy density. Therefore, the positive electrode side sheet member 300 can be transported without cutting and integrated with the negative electrode side sheet member 400 obtained by cutting, thereby enabling the solid state battery 1 to be manufactured efficiently.

[0074] (5) According to this embodiment, the method includes a second solid electrolyte layer transfer step S4, which is performed before the integration press step S9, of laminating and transferring a second solid electrolyte layer SE2, which has a higher binder content than the anode-side solid electrolyte layer SE3, between the anode-side solid electrolyte layer SE3 and the first solid electrolyte layer SE1. By including the second solid electrolyte layer SE2 between the anode-side solid electrolyte layer SE3 and the first solid electrolyte layer SE1, the anode-side solid electrolyte layer SE3, which has a relatively small binder content, and the first solid electrolyte layer SE1 can be easily stably attached via the second solid electrolyte layer SE2.

[0075] (6) According to this embodiment, the negative electrode side sheet member 400 is configured to include the negative electrode active material layer 21. This makes it possible to provide a solid state battery 1 with high energy density.

[0076] (7) According to this embodiment, the process includes an intermediate layer transfer step S5 of laminating and transferring the intermediate layer 5 onto the negative electrode layer 2 including the negative electrode current collector foil 221. This makes it possible to deposit lithium metal uniformly when the solid state battery 1 is a lithium metal battery, and to stabilize the interface between the intermediate layer 5 and the solid electrolyte layer 4.

[0077] The present invention is not limited to the above-described embodiment, and includes modifications and improvements within the scope of achieving the object of the present invention. For example, in the above-described embodiment, the negative electrode-side sheet member 400 includes a laminate of the negative electrode current collector foil 221, the negative electrode active material layer 21, the intermediate layer 5, and the negative electrode-side solid electrolyte layer SE3, but the negative electrode active material layer 21 and the intermediate layer 5 may not be included. [Explanation of symbols]

[0078] 1 solid state battery 21 Negative electrode active material layer 31 Positive electrode active material layer SE1 1st solid electrolyte layer SE2 2nd solid electrolyte layer SE3 Negative side solid electrolyte layer 400 negative electrode side sheet member S3 Positive electrode pressing process S5 Intermediate layer transfer process S6 Negative electrode solid electrolyte layer transfer process S7: Cutting process of negative electrode sheet material S9 Integration press process (integration process) S40 Negative electrode side sheet member forming process S30 Positive electrode sheet member forming process

Claims

1. A method for manufacturing a solid-state battery, comprising: a negative electrode-side sheet member forming step of forming a negative electrode-side sheet member including at least a negative electrode current collector and a negative electrode-side solid electrolyte layer; a positive electrode side sheet member forming step of forming a positive electrode side sheet member including at least a positive electrode current collector and a positive electrode active material layer; an integration step of stacking and integrating the negative electrode side sheet member and the positive electrode side sheet member, The negative electrode side sheet member forming step includes: a negative electrode-side solid electrolyte layer transferring step of pressing and transferring the negative electrode-side solid electrolyte layer to at least the negative electrode current collector; a negative electrode-side sheet member cutting step of cutting the sheet-like member obtained by the transfer, The positive electrode side sheet member forming step includes: a positive electrode pressing step of pressing at least the positive electrode current collector and the positive electrode active material layer, a first solid electrolyte layer is provided on a surface of the positive electrode-side sheet member facing the negative electrode-side solid electrolyte layer before the integration step; the negative electrode solid electrolyte layer has a binder content smaller than that of the first solid electrolyte layer.

2. The method for manufacturing a solid state battery according to claim 1 , wherein the maximum value of the pressing pressure in the positive electrode pressing step is at least equal to or greater than the maximum value of the pressing pressure in the negative electrode solid electrolyte layer transferring step.

3. The method for manufacturing a solid state battery according to claim 1 , wherein the positive electrode side sheet member is pressed two or more times.

4. The method for manufacturing a solid state battery according to claim 1 , wherein the positive electrode side sheet member has a thickness in a stacking direction greater than that of the negative electrode side sheet member.

5. 2. The method for manufacturing a solid state battery according to claim 1, further comprising, prior to the integration step, a second solid electrolyte layer transfer step of laminating and transferring a second solid electrolyte layer, the second solid electrolyte layer having a higher binder content than the anode-side solid electrolyte layer, between the anode-side solid electrolyte layer and the first solid electrolyte layer.

6. The method for manufacturing a solid state battery according to claim 1 , wherein the negative electrode side sheet member includes a negative electrode active material layer.

7. The method for producing a solid-state battery according to claim 1 , further comprising an intermediate layer transfer step of laminating and transferring an intermediate layer onto the negative electrode layer including the negative electrode current collector.

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