Method for manufacturing a stacked electrode body and method for manufacturing an all-solid-state secondary battery

Abstract

To provide a manufacturing method of a laminated electrode body with a low internal resistance and a manufacturing method of an all-solid secondary battery excellent in load characteristic.SOLUTION: Sulfide solid electrolyte particles are compressed with a surface pressure less than 120 MPa to form a first temporary molding layer for obtaining a solid electrolyte layer. A first electrode mixture is arranged on one principal surface of the first temporary molding layer, the first electrode mixture is compressed with a surface pressure less than 1000 MPa to form a second temporary molding layer for obtaining a first electrode layer on one principal surface of the first temporary molding layer. A second electrode mixture for obtaining a second electrode layer is arranged on the other principal surface of the first temporary molding layer, and the second electrode mixture, the first temporary molding layer and the second temporary molding layer are compressed a the prescribed surface pressure to form a laminated electrode body. The laminated electrode body with a low internal resistance can be manufactured by suppressing a crack on each layer and making the thickness of each layer uniform. An all-solid secondary battery excellent in load characteristic can be manufactured by storing the laminated electrode body in a case.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a laminated electrode body having a solid electrolyte layer and a method for manufacturing an all-solid-state secondary battery. [Background technology]

[0002] In recent years, with the development of portable electronic devices such as mobile phones and notebook computers, and the practical application of electric vehicles, the need for small, lightweight, high-capacity, and high-energy-density secondary batteries has increased.

[0003] Traditionally, lithium-ion batteries, in particular, have been used to meet this need. However, lithium-ion batteries contain organic solvents, which are flammable substances, as a non-aqueous electrolyte. Furthermore, with the development of the aforementioned devices and electric vehicles, lithium-ion batteries have become more energy dense, and the amount of organic solvents, which are flammable substances, is also increasing. As a result, lithium-ion batteries are required to be even more reliable.

[0004] In this context, all-solid-state lithium secondary batteries (all-solid-state secondary batteries) that do not use organic solvents are attracting attention. All-solid-state secondary batteries use a molded solid electrolyte that does not use organic solvents, instead of the conventional organic solvent-based electrolyte.

[0005] Various improvements have been attempted to improve all-solid-state rechargeable batteries. Japanese Patent Publication No. 2017-10816 (Patent Document 1) discloses a method for manufacturing an all-solid-state battery. This method includes a first pressing step for pressing a positive electrode stack, a second pressing step for pressing a negative electrode stack, and a third pressing step for pressing the positive electrode stack, an intermediate solid electrolyte layer, and a negative electrode stack. At least one of the positive electrode stack and the negative electrode stack has a first or second solid electrolyte layer in addition to the intermediate solid electrolyte layer. The pressing pressure in the third pressing step is higher than the pressing pressure in the first and second pressing steps. Before the intermediate solid electrolyte layer is pressed in the third pressing step, it is not pressed with a pressure exceeding the pressing pressure in the third pressing step. Furthermore, the pressing temperature is adjusted in each pressing step. In other words, by adjusting the pressing pressure and pressing temperature in each pressing step, and by having a first or second solid electrolyte layer, an all-solid-state battery is provided that suppresses short circuits and reduces internal resistance.

[0006] International Publication No. 2020 / 66323 discloses, as an example, a method for manufacturing a flat-type all-solid-state battery, in which an electrode stack is fabricated by stacking a positive electrode and a negative electrode, respectively, on a solid electrolyte layer. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2017-10816 [Patent Document 2] International Publication No. 2020 / 66323 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, in the manufacturing method of the all-solid-state battery described in Patent Document 1, for example, if the second solid electrolyte layer is omitted, the solid electrolyte constituting the intermediate solid electrolyte layer is pressed onto the surface of the negative electrode active material layer. As a result, it is difficult to achieve a good bonding state between the second solid electrolyte layer and the negative electrode active material layer. Consequently, the resistance at the interface between the second solid electrolyte layer and the negative electrode active material layer increases, which is a factor in degrading the load characteristics of the battery.

[0009] On the other hand, Patent Document 2 discloses the fabrication of an electrode laminate by stacking a positive electrode and a negative electrode on a solid electrolyte layer, but it does not offer any specific suggestions for forming a laminated electrode with low internal resistance.

[0010] Therefore, the object of this disclosure is to provide a method for manufacturing a laminated electrode body with low internal resistance, and a method for manufacturing an all-solid-state secondary battery with excellent load characteristics. [Means for solving the problem]

[0011] To solve the above problems, this disclosure is configured as follows. That is, the method for manufacturing a laminated electrode body according to this disclosure may be a method for manufacturing a laminated electrode body having a solid electrolyte layer, a first electrode layer laminated on one main surface of the solid electrolyte layer, and a second electrode layer laminated on the other main surface of the solid electrolyte layer. The method may include a step of forming a first temporary layer for obtaining the solid electrolyte layer by pressurizing sulfide-based solid electrolyte particles at a surface pressure of less than 120 MPa. The method may include a step of placing a first electrode mixture on one main surface of the first temporary layer. The method may include a step of forming a second temporary layer for obtaining the first electrode layer by pressurizing the first electrode mixture at a surface pressure of less than 500 MPa on one main surface of the first temporary layer. The method may include a step of placing a second electrode mixture for obtaining the second electrode layer on the other main surface of the first temporary layer. The method may include a step of forming a laminated electrode body by pressurizing the second electrode mixture, the first temporary layer, and the second temporary layer at a predetermined surface pressure.

[0012] In the process of forming the first pre-formed layer, the sulfide-based solid electrolyte particles may be pressurized with a surface pressure of 30 MPa or more.

[0013] In the step of forming the second green compact layer, the first electrode mixture may be pressed at a surface pressure of 30 MPa or more.

[0014] The first electrode mixture may be a negative electrode mixture. The first electrode layer may be a negative electrode layer. <000008%>

[0015] In the step of forming the laminated electrode body, the second electrode mixture, the first green compact layer, and the second green compact layer may be pressed at a surface pressure of 1000 MPa or more.

[0016] The method for manufacturing an all-solid-state secondary battery according to the present disclosure may include a step of housing the laminated electrode body manufactured by the above-described method for manufacturing a laminated electrode body inside a case.

Advantages of the Invention

[0017] According to the method for manufacturing a laminated electrode body of the present disclosure, a laminated electrode body with low internal resistance can be formed. According to the method for manufacturing an all-solid-state secondary battery, an all-solid-state secondary battery excellent in load characteristics can be manufactured.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a flowchart showing a method for manufacturing a laminated electrode body and an all-solid-state secondary battery according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing a method for manufacturing a laminated electrode body according to the present disclosure. [Figure 3] FIG. 3 is a schematic diagram showing a method for manufacturing a laminated electrode body. [Figure 4] FIG. 4 is a schematic diagram showing a method for manufacturing a laminated electrode body. [Figure 5] FIG. 5 is a schematic diagram showing a method for manufacturing a laminated electrode body. [Figure 6] FIG. 6 is a schematic diagram showing a method for manufacturing a laminated electrode body. [Figure 7] FIG. 7 is a schematic diagram showing a method for manufacturing a laminated electrode body. [Figure 8] FIG. 8 is a schematic diagram showing a method for manufacturing a laminated electrode body. [Figure 9] Figure 9 is a schematic diagram showing a method for manufacturing a multilayer electrode. [Figure 10] Figure 10 is a cross-sectional view showing the structure of an all-solid-state secondary battery manufactured by the manufacturing method according to this disclosure. [Modes for carrying out the invention]

[0019] The manufacturing methods for the laminated electrode body 1 and the all-solid-state secondary battery 10 according to this disclosure will be described in detail below with reference to Figures 1 to 10. Figure 1 is a flowchart showing the manufacturing methods for the laminated electrode body 1 and the all-solid-state secondary battery 10. First, the manufacturing method for the laminated electrode body 1 according to this disclosure will be described in detail with reference to Figure 1, using Figures 2 to 9. The manufactured laminated electrode body 1 has a solid electrolyte layer 23, a negative electrode layer (electrode layer) 33 laminated on one main surface of the solid electrolyte layer 23, and a positive electrode layer (electrode layer) 42 laminated on the other main surface of the solid electrolyte layer 23, as will be described later. The manufacturing method for the laminated electrode body 1 according to this disclosure can be suitably used to manufacture a laminated electrode body 1 including a solid electrolyte layer 23 having a thickness of, for example, 120 μm or less.

[0020] (Step 1 (S1)) As shown in Figure 2, first, the pressurizing device 100 is prepared. The pressurizing device 100 comprises a die 101 having a die hole 101a that penetrates vertically, a lower punch 102 that is inserted from below the die hole 101a and slides inside the die hole 101a, and an upper punch 103 that is inserted from above the die hole 101a and slides inside the die hole 101a. The die 101 is formed in a plate shape. The die hole 101a is formed as a cylindrical opening from the top surface to the bottom surface of the die 101. The lower punch 102 and the upper punch 103 are each formed in a cylindrical shape that conforms to the opening shape of the die punch. The pressurizing device 100 pressurizes the material filled in the die hole 101a by sliding the lower punch 102 and the upper punch 103 in the vertical direction using a press machine. In this embodiment, the pressurizing device 100 is a powder molding die. The pressurizing device 100 is not limited to powder molding dies, but may also be a tablet molding machine or the like, as long as it can pressurize and form the laminated electrode body 1 at a predetermined surface pressure, as described later.

[0021] (Step 2 (S2)) As shown in Figure 3, the lower punch 102 is inserted into the die cavity 101a, and with the lower opening of the die cavity 101a closed by the lower punch 102, sulfide-based solid electrolyte particles 21 are filled into the die cavity 101a from above. The sulfide-based solid electrolyte particles 21 are filled into the die cavity 101a from a hopper that moves parallel to the upper surface of the die 101 (the same applies to the negative electrode mixture 31 and positive electrode mixture 41 filled into the die cavity 101a hereafter). The hopper moves above the die cavity 101a when filling with sulfide-based solid electrolyte particles 21, and waits in a location other than above the die cavity 101a when not filling with sulfide-based solid electrolyte particles 21. The sulfide-based solid electrolyte particles 21 are, for example, 1 mg of sulfide-based solid electrolyte material (Li6PS5Cl). The sulfide-based solid electrolyte particles 21 are not particularly limited and may be other sulfide-based solid electrolyte materials such as argyrodites, from the viewpoint of ionic conductivity.

[0022] (Step 3 (S3)) As shown in Figure 4, sulfide-based solid electrolyte particles 21 are pressed (pre-pressed) from above by an upper punch 103 at a surface pressure of less than 120 MPa to form a pre-formed layer 22 for obtaining the solid electrolyte layer 23 described later. If this surface pressure is 120 MPa or higher, cracks may occur in the pre-formed layer 22. As a result, the internal resistance of the solid electrolyte layer 23 obtained from the pre-formed layer 22 becomes high. Also, the negative electrode layer 33 and the positive electrode layer 42 become more likely to come into contact, which may cause an internal short circuit in the all-solid-state secondary battery 10. On the other hand, if the surface pressure is less than 120 MPa, cracks in the pre-formed layer 22 can be suppressed. As a result, a solid electrolyte layer 23 with low internal resistance and suppression of internal short circuits can be formed. However, if this surface pressure is too low, the shape of the pre-formed layer 22 cannot be maintained, and in step 6 described later, the position of the pre-formed layer 22 may shift or a part of the pre-formed layer 22 may fall off, making it difficult to achieve a uniform thickness of the solid electrolyte layer 23 after pressurization. Non-uniformity in the thickness of the solid electrolyte layer 23 can cause a decrease in battery performance. From this viewpoint, the surface pressure applied to the sulfide-based solid electrolyte particles 21 should be 30 MPa or more, preferably 40 MPa or more, more preferably 50 MPa or more, and less than 120 MPa, preferably less than 100 MPa, and more preferably less than 90 MPa.

[0023] (Step 4 (S4)) As shown in Figure 5, the negative electrode mixture (electrode mixture) 31 is filled into the die cavity 101a, and the negative electrode mixture 31 is placed on one main surface of the temporary molded layer 22, that is, on the upper surface of the temporary molded layer 22 in the figure. The negative electrode mixture 31 is, for example, LTO(Li4Ti5O) used as a negative electrode active material in lithium-ion secondary batteries. 12 This is a 129 mg mixture containing lithium titanate, a sulfide-based solid electrolyte (Li6PS5Cl), and carbon nanotubes in a weight ratio of 50:41:9. The negative electrode mixture 31 is not particularly limited and can include, for example, metallic materials such as metallic lithium and lithium alloys, carbon materials such as graphite and low-crystallinity carbon, and SiO2, LTO (Li4Ti5O2). 12 It may also be lithium titanate, etc., or a mixture of these as appropriate.

[0024] (Step 5 (S5)) As shown in Figure 6, the negative electrode mixture 31 placed on the upper surface of the temporary molded layer 22 is pressed (temporarily pressed) from above by the upper punch 103 with a surface pressure of less than 500 MPa to form a temporary molded layer 32 for obtaining the negative electrode layer 33. If this surface pressure is 500 MPa or higher, cracks may occur in the temporary molded layer 32, or the bonding between the solid electrolyte layer 23 and the positive electrode layer 42 may become insufficient when the positive electrode mixture 41 is pressed in (step 8) described later. As a result, the internal resistance of the final laminated electrode body 1 becomes high. On the other hand, if this surface pressure is less than 500 MPa, cracks in the temporary molded layer 32 can be suppressed, and the bonding between the solid electrolyte layer 23 and the positive electrode layer 42 can be made good, so the internal resistance of the final laminated electrode body 1 can be made low. However, if this surface pressure is too low, the shape of the temporary molded layer 32 cannot be maintained, and in step 6 described later, the temporary molded layer 32 may shift position or a part of the temporary molded layer 32 may fall off, making it difficult to achieve a uniform thickness of the negative electrode layer 33 after pressurization. Non-uniformity in the thickness of the negative electrode layer 33 can cause a decrease in battery performance. From this viewpoint, the surface pressure applied to pressurize the negative electrode mixture 31 should be 30 MPa or more, preferably 100 MPa or more, more preferably 150 MPa or more, and less than 500 MPa, preferably less than 450 MPa, and more preferably less than 400 MPa.

[0025] (Step 6 (S6)) As shown in Figure 7, the temporary molding layers 22 and 32 are inverted vertically. That is, they are inverted vertically so that the temporary molding layer 22 is positioned at the top and the temporary molding layer 32 is positioned at the bottom in the figure. Alternatively, the temporary molding layers 22 and 32 created in (Step 6) may be removed from the die cavity 101a, inverted vertically, and then placed back into the die cavity 101a. Alternatively, the pressurizing device 100 itself may be inverted vertically to invert the vertical orientation of the temporary molding layers 22 and 32. By inverting the vertical orientation of the temporary molding layers 22 and 32 in this way, the negative electrode mixture 31 remaining in the die cavity 101a will not come into contact with the positive electrode mixture 41 in (Step 7-1) described later, thus suppressing a short circuit. In this case, the upper punch 103 and the lower punch 102 are also swapped vertically. In this explanation, even when the pressurizing device 100 itself is inverted vertically, the upper part of the figure will be referred to as the upper punch 103 and the lower part as the lower punch 102.

[0026] (Step 7-1 (S7-1)) As shown in Figure 8, the positive electrode mixture 41 is filled into the die cavity 101a, and the positive electrode mixture 41 is placed on the other main surface of the temporary molded layer 22, that is, on the upper surface of the temporary molded layer 22 after inversion. The positive electrode mixture 41 is, for example, a 92 mg mixture containing lithium cobalt oxide with an average particle size of 5 μm, a sulfide-based solid electrolyte (Li6PS5Cl), and carbon nanotubes as a conductive additive in a mass ratio of 70:26:4, used as a positive electrode active material in lithium-ion secondary batteries. The positive electrode mixture 41 is not particularly limited and may be, for example, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, spinel-type manganese composite oxide, olivine-type composite oxide, etc., or a mixture of these as appropriate.

[0027] (Step 8 (S8)) As shown in Figure 9, the positive electrode mixture 41, the temporary molded layer 22, and the temporary molded layer 32 are pressed with a surface pressure of 1000 MPa or more (main press). This compresses the temporary molded layer 22, the temporary molded layer 32, and the positive electrode mixture 41, forming a laminated electrode body 1 having a solid electrolyte layer 23, a negative electrode layer 33 laminated on one main surface of the solid electrolyte layer 23, and a positive electrode layer 42 laminated on the other main surface of the solid electrolyte layer 23. The laminated electrode body 1 can be removed from the die cavity 101a by moving the die 101 and the lower punch 102 relative to each other. Alternatively, the laminated electrode body 1 can be removed from the die cavity 101a by moving the die 101 and the upper punch 103 relative to each other. Furthermore, it is preferable to remove the laminated electrode body 1 from the die cavity 101a by moving the upper punch 103 and lower punch 102 relative to the die 101 while the laminated electrode body 1 is sandwiched between them, as this can suppress cracking and chipping of the laminated electrode body 1. Alternatively, the die 101 may be divided and the laminated electrode body 1 may be removed from the die 101 without moving it. In this way, the laminated electrode body 1 can be manufactured. It is preferable that the surface pressure be high in order to improve the packing of each of the solid electrolyte layer 23, the negative electrode layer 33, and the positive electrode layer 42, that is, to reduce the porosity.

[0028] Furthermore, between (step 7-1) and (step 8), a step (7-2) may be included in which a temporary molded layer for obtaining the positive electrode layer is formed. That is, although not specifically shown in the figures, the positive electrode mixture 41, which is placed on the other main surface of the temporary molded layer 22 in (step 7-1), may be pressed (temporarily pressed) to form a temporary molded layer for obtaining the positive electrode layer. In this case, the surface pressure used to press (temporarily press) the positive electrode mixture 41 is preferably 30 MPa or more, more preferably 100 MPa or more, more preferably 150 MPa or more, and less than 500 MPa, more preferably less than 450 MPa, more preferably less than 400 MPa, from the same viewpoint as the surface pressure used when pressing (temporarily pressing) the negative electrode mixture 31 described above.

[0029] In this case, in step 8, the temporary molded layer for obtaining the positive electrode layer 42, the temporary molded layer 22, and the temporary molded layer 32 are pressed with a surface pressure of 1000 MPa or more (main press). As a result, the temporary molded layer 22, the temporary molded layer 32, and the temporary molded layer for obtaining the positive electrode layer 42 are compressed, and a laminated electrode body 1 can be formed having a solid electrolyte layer 23, a negative electrode layer 33 laminated on one main surface of the solid electrolyte layer 23, and a positive electrode layer 42 laminated on the other main surface of the solid electrolyte layer 23.

[0030] Alternatively, the positive electrode mixture 41 may be placed in (Step 4) and the negative electrode mixture 31 in (Step 7-1). In other words, the order in which the positive electrode mixture 41 and the negative electrode mixture 31 are placed on the main surface of the temporary molded layer 22 may be reversed. In this case, the surface pressure in (Step 7-2) may be applied as the surface pressure to obtain the temporary molded layer 32 of the positive electrode mixture 41 in (Step 5), and the surface pressure in (Step 5) may be applied as the surface pressure to obtain the temporary molded layer of the negative electrode mixture 31 in (Step 7-2). However, depending on the types of positive and negative electrode active materials, the negative electrode active material is generally harder than the positive electrode active material, and the negative electrode mixture 31 is often more difficult to fill than the positive electrode mixture 41. Therefore, in order to improve the filling ability of the negative electrode mixture, it is preferable to compress and mold the negative electrode mixture 31 in stages. In other words, it is preferable to form the temporary molded layer 32 for obtaining the negative electrode layer 33 in (Step 4) and form the negative electrode layer 33 in (Step 8). Furthermore, since no temporary molding layer for obtaining the positive electrode layer 42 is formed on the other main surface of the temporary molding layer 22, the laminated electrode body 1 can be formed efficiently. On the other hand, if a temporary molding layer for obtaining the electrode layer is formed on the other main surface of the temporary molding layer 22, as in (step 7-2), either the negative electrode mixture 31 or the positive electrode mixture 41 may be placed on the main surface of the temporary molding layer 22 first.

[0031] This method for manufacturing the laminated electrode body 1 allows for uniform thickness of the solid electrolyte layer 23, the negative electrode layer 33, and the positive electrode layer 42, and suppresses cracking of each of the solid electrolyte layer 23, the negative electrode layer 33, and the positive electrode layer 42. Therefore, it is possible to form a laminated electrode body 1 with excellent bonding properties at the interface between the negative electrode layer 33 and the solid electrolyte layer 23, as well as at the interface between the positive electrode layer 42 and the solid electrolyte layer 23, and with low internal resistance.

[0032] Next, the manufacturing method of the all-solid-state secondary battery 10 will be explained with reference to Figure 10. In this case, the all-solid-state secondary battery 10 is a flat-type battery.

[0033] (Step 9 (S9)) The laminated electrode body 1 manufactured in step 8 described above is housed inside the case.

[0034] Specifically, first, prepare the case. The case consists of an outer can 11, a sealing can 12, and a gasket 13.

[0035] The outer casing 11 comprises a circular bottom portion 11a and a cylindrical peripheral wall portion 11b that is continuously formed from the outer circumference of the bottom portion 11a. The peripheral wall portion 11b is provided so as to extend substantially perpendicularly to the bottom portion 11a in a longitudinal cross-sectional view. The outer casing 11 is made of a metal material such as stainless steel, nickel, or iron. The shape of the outer casing 11 is not limited to a cylindrical shape with a circular bottom portion 11a. For example, the shape of the outer casing 11 may be such that the bottom portion 11a is formed in a polygonal shape such as a square, and the peripheral wall portion 11b is formed in a polygonal cylindrical shape such as a square tube that matches the shape of the bottom portion 11a, and can be changed in various ways depending on the size and shape of the laminated electrode body 1 and the all-solid-state secondary battery 10. Therefore, the shape of the peripheral wall portion 11b includes not only cylindrical shapes but also polygonal cylindrical shapes such as square tubes. The shape of the laminated electrode body 1 is, for example, a cylindrical shape, a rectangular prism shape, or a polygonal prism shape.

[0036] The sealing can 12 comprises a circular flat portion 12a and a cylindrical peripheral wall portion 12b that is continuously formed from the outer circumference of the flat portion 12a. The opening of the sealing can 12 faces the opening of the outer can 11. The sealing can 12 is made of a metal material such as stainless steel. The shape of the sealing can 12 is not limited to a cylindrical shape with a circular flat portion 12a. For example, the shape of the sealing can 12 may be formed with the flat portion 12a in a polygonal shape such as a square, and the peripheral wall portion 12b may be formed in a polygonal cylindrical shape such as a square tube that matches the shape of the flat portion 12a, and can be changed in various ways depending on the size and shape of the laminated electrode body 1 and the all-solid-state secondary battery 10. Therefore, the shape of the peripheral wall portion 12b includes not only a cylindrical shape but also polygonal cylindrical shapes such as a square tube.

[0037] The gasket 13 is formed from a low-moisture-permeability resin such as polypropylene resin, polyphenylene sulfide resin, or PFA resin. The gasket 13 is formed in a cylindrical shape along the inner surface of the peripheral wall portion 11b of the outer can 11 and is positioned between the peripheral wall portion 11b of the outer can 11 and the peripheral wall portion 12b of the sealing can 12. The gasket 13 is not particularly limited as long as it can insulate the outer can 11 and the sealing can 12, but from the viewpoint of moisture permeability and heat resistance, fluororesins such as polyphenylene sulfide resin or PFA resin are preferably used.

[0038] The outer casing 11 and the sealing casing 12 are crimped together via a gasket 13 between the peripheral wall portion 11b of the outer casing 11 and the peripheral wall portion 12b of the sealing casing 12 after the laminated electrode body 1 has been placed inside the internal space. Specifically, the outer casing 11 and the sealing casing 12 are placed with their openings facing each other, the peripheral wall portion 11b of the sealing casing 12 is inserted inside the peripheral wall portion 11b of the outer casing 11, and then crimped together via a gasket 13 between the peripheral wall portions 11b and 12b. In this way, the outer casing 20 and the sealing casing 30 form a case that houses the laminated electrode body 1 inside the internal space. Note that the manufacturing method of the all-solid-state secondary battery 10 is not limited to this; it is sufficient if the laminated electrode body 1 can be housed in a case and manufactured to function as a secondary battery.

[0039] As a result, the all-solid-state secondary battery 10 with excellent load characteristics can be manufactured.

[0040] As described above, the embodiments have been explained. However, the present disclosure is not limited to the above embodiments, and various modifications are possible without departing from the gist thereof.

Examples

[0041] Hereinafter, flat all-solid-state secondary batteries of Example 1 and Example 2, and Comparative Examples 1 to 3 were fabricated, and the internal resistance of each flat all-solid-state secondary battery was measured.

[0042] (Example 1) The flat all-solid-state secondary battery of Example 1 was fabricated as follows. First, 9.6 mg of a sulfide-based solid electrolyte (Li 5.4 PS 4.4 Cl 0.8 Br 0.8 ) with an average particle diameter of 0.7 μm was placed in a powder molding die, and pressure molding was performed at a surface pressure of 70 MPa (0.7 tf / cm 2 ) using a press machine to form a temporary molding layer for obtaining a solid electrolyte layer. Next, on the upper surface (one main surface) of the temporary molding layer for obtaining a solid electrolyte layer, 101 mg of a negative electrode mixture prepared by mixing lithium titanate (Li4Ti5O 12 , negative electrode active material) with an average particle diameter of 2 μm, a sulfide-based solid electrolyte (Li 5.4 PS 4.4 Cl 0.8 Br 0.8 ) with an average particle diameter of 0.7 μm, and graphene (conductive assistant) in a mass ratio of 50:41:9 was placed, and pressure molding was performed at a surface pressure of 300 MPa (3 tf / cm 2 ) to form a temporary molding layer for obtaining a negative electrode layer on one main surface of the temporary molding layer for obtaining a solid electrolyte layer. After inverting the die upside down, on the upper surface (the other main surface) of the temporarily molded layer for obtaining the solid electrolyte layer inverted together with the die, LiCoO2 (positive electrode active material) with an average particle diameter of 5 μm having a coating layer of LiNbO3 formed on its surface, and a sulfide-based solid electrolyte (Li 7.0 PS 5.4 Cl 1.2A 73 mg positive electrode mixture, prepared by mixing carbon black and vapor-grown carbon fiber (VGCF) in a mass ratio of 70:26.8:1.1:2.1, was placed. A preliminary molded layer for obtaining the negative electrode layer, a preliminary molded layer for obtaining the solid electrolyte layer, and the positive electrode mixture were subjected to 1300 MPa (13 tf / cm²). 2 By compressing the material under pressure molding with a surface pressure of ), a laminated electrode body was obtained in which a negative electrode layer having a thickness of 830 μm, a solid electrolyte layer having a thickness of 110 μm, and a positive electrode layer having a thickness of 550 μm were integrated. The ratio of the weight of the coating layer to the total weight of the positive electrode active material powder including the coating layer was 2 mass%. Finally, a flat-type all-solid-state secondary battery was assembled by using a stainless steel sealing can and outer can as a case, housing the laminated electrode body between the sealing can and the outer can, and sealing the assembly by placing a porous carbon sheet with a thickness of 0.1 mm between the sealing can and the laminated electrode body, and between the outer can and the laminated electrode body.

[0043] (Example 2) 73 mg of the positive electrode mixture prepared in Example 1 was placed on the upper surface (one main surface) of the pre-formed layer used to obtain the solid electrolyte layer prepared in Example 1, and pressure was applied at 300 MPa (3 tf / cm²). 2 Pressurized molding was performed with a surface pressure of ) to form a temporary molded layer for obtaining the positive electrode layer on one main surface of the temporary molded layer for obtaining the solid electrolyte layer. After inverting the mold, 101 mg of the negative electrode mixture prepared in Example 1 was placed on the upper surface (the other main surface) of the temporary molded layer for obtaining the solid electrolyte layer, which was inverted along with the mold, and pressed at 1300 MPa (13 tf / cm²). 2 By performing pressure molding with a surface pressure of ), a temporary molded layer for obtaining the positive electrode layer, a temporary molded layer for obtaining the solid electrolyte layer, and the negative electrode mixture were compressed to obtain a laminated electrode body in which a negative electrode layer with a thickness of 825 μm, a solid electrolyte layer with a thickness of 110 μm, and a positive electrode layer with a thickness of 540 μm were integrated. Finally, a flat-type all-solid-state battery was assembled in the same manner as in Example 1.

[0044] (Comparative Example 1) 101 mg of the negative electrode mixture prepared in Example 1 was placed in a powder molding die and pressed using a press machine at 300 MPa (3 tf / cm²).2 A temporary molded layer for obtaining the negative electrode layer was formed by pressure molding with a surface pressure of ). On the upper surface of the temporary molded layer for obtaining the negative electrode layer, a sulfide-based solid electrolyte (Li) with an average particle size of 0.7 μm was placed. 5.4 PS 4.4 Cl 0.8 Br 0.8 9.6 mg of the powder is placed at 70 MPa (0.7 tf / cm²). 2 Pressure molding was performed with a surface pressure of ) and a temporary molded layer for obtaining the solid electrolyte layer was formed on one upper surface of the temporary molded layer for obtaining the negative electrode layer. Furthermore, 73 mg of the positive electrode mixture prepared in Example 1 was placed on the upper surface of the temporary molded layer for obtaining the solid electrolyte layer and pressed at 1300 MPa (13 tf / cm²). 2 By performing pressure molding with a surface pressure of ), a temporary molded layer for obtaining the negative electrode layer, a temporary molded layer for obtaining the solid electrolyte layer, and the positive electrode mixture were compressed to obtain a laminated electrode body in which the negative electrode layer, solid electrolyte layer, and positive electrode layer were integrated. Finally, a flat-type all-solid-state secondary battery was assembled in the same manner as in Example 1.

[0045] (Comparative Example 2) The surface pressure used when forming the pre-molded layer of the solid electrolyte is 130 MPa (1.3 tf / cm²). 2 The flat-type all-solid-state secondary battery was assembled in the same manner as in Example 1, with the other steps being the same.

[0046] (Comparative Example 3) The pressure used when forming the pre-formed layer to obtain the negative electrode layer is 600 MPa (6 tf / cm²). 2 The flat-type all-solid-state secondary battery was assembled in the same manner as in Example 1, with the other steps being the same.

[0047] (Evaluation results) The internal resistance of the flat-type all-solid-state secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 3 was measured by applying an AC voltage of 1 kHz. The evaluation results were as follows: The internal resistance of the flat-type all-solid-state secondary battery of Example 1 was 230 Ω. The internal resistance of the flat-type all-solid-state secondary battery of Example 2 was 260 Ω. The internal resistance of the flat-type all-solid-state secondary battery of Comparative Example 1 was 316 Ω. The internal resistance of the flat-type all-solid-state secondary battery of Comparative Example 2 was 519 Ω. The internal resistance of the flat-type all-solid-state secondary battery of Comparative Example 3 was 432 Ω.

[0048] The flat-type all-solid-state secondary batteries of Examples 1 and 2 were manufactured by pressure molding with an appropriate process sequence and appropriate surface pressure, resulting in uniform thickness of the solid electrolyte layer, negative electrode layer, and positive electrode layer, and suppression of cracking. Therefore, compared to the flat-type all-solid-state secondary battery of Comparative Example 1, which had a different process sequence for the solid electrolyte layer, negative electrode layer, and positive electrode layer, and the flat-type all-solid-state secondary batteries of Comparative Examples 2 and 3, which had excessively high surface pressure when forming the temporary molding layer for obtaining the solid electrolyte layer or the temporary molding layer for obtaining the negative electrode layer, the internal resistance was reduced. As a result, the flat-type all-solid-state secondary batteries of Examples 1 and 2 were able to obtain superior load characteristics compared to the batteries of Comparative Examples 1 to 3. It is also believed that similar results could be obtained in Examples 1 and 2 even if the above-mentioned (Step 7-2) was included. [Explanation of symbols]

[0049] 1 Stacked electrode body, 10 All-solid-state secondary battery, 11 Outer casing, 11a Bottom, 11b Peripheral wall, 12 Sealing casing, 12a Flat surface, 12b Peripheral wall, 13 Gasket, 21 Sulfide-based solid electrolyte particles, 22 Pre-formed layer, 23 Solid electrolyte layer, 31 Negative electrode mixture, 32 Pre-formed layer, 33 Negative electrode layer, 41 Positive electrode mixture, 42 Positive electrode layer, 100 Pressurizing device, 101 Die, 101a Die hole, 102 Lower punch, 103 Upper punch material

Claims

1. A method for manufacturing a laminated electrode body having a solid electrolyte layer, a first electrode layer laminated on one main surface of the solid electrolyte layer, and a second electrode layer laminated on the other main surface of the solid electrolyte layer, A step of forming a first pre-formed layer for obtaining the solid electrolyte layer by pressurizing sulfide-based solid electrolyte particles with a surface pressure of less than 120 MPa, A step of placing the first electrode mixture on one main surface of the first temporary molded layer, A step of pressurizing the first electrode mixture with a surface pressure of less than 500 MPa to form a second temporary layer for obtaining the first electrode layer on one main surface of the first temporary layer, A step of placing a second electrode mixture for obtaining the second electrode layer on the other main surface of the first temporary molded layer, The process includes a step of forming the laminated electrode body by pressurizing the second electrode mixture, the first temporary molded layer, and the second temporary molded layer with a predetermined surface pressure, The first electrode mixture includes at least lithium titanate (Li) as the negative electrode active material. ４ Ti ５ O １２ It is a negative electrode mixture containing ), A method for manufacturing a laminated electrode body, wherein the first electrode layer is a negative electrode layer.

2. A method for manufacturing a laminated electrode body according to claim 1, In the step of forming the first pre-formed layer, the sulfide-based solid electrolyte particles are pressurized with a surface pressure of 30 MPa or more. In the step of forming the second pre-formed layer, the first electrode mixture is pressurized with a surface pressure of 30 MPa or more and less than 500 MPa. A method for manufacturing a laminated electrode, wherein, in the step of forming the laminated electrode body, the second electrode mixture, the first temporary molded layer, and the second temporary molded layer are pressurized with a surface pressure of 1000 MPa or more.

3. A method for manufacturing an all-solid-state secondary battery, A method for manufacturing an all-solid-state secondary battery, comprising the step of housing the laminated electrode body manufactured by the method for manufacturing a laminated electrode body according to claim 1 or 2 inside a case.

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