JP2022185624A - Manufacturing method of laminated electrode body and manufacturing method of all-solid secondary battery - Google Patents

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 The present disclosure relates to a laminated electrode body having a solid electrolyte layer and a manufacturing method of an all-solid secondary battery.

In recent years, with the development of mobile electronic devices such as mobile phones and laptop computers, and the practical use of electric vehicles, the need for secondary batteries that are small and lightweight, and that have high capacity and high energy density is increasing. .

Conventionally, lithium secondary batteries, particularly lithium ion secondary batteries, have been used as secondary batteries that satisfy this need. However, lithium-ion secondary batteries contain an organic solvent, which is a combustible substance, as a non-aqueous electrolyte. In addition, with the development of the above-described devices and electric vehicles, the energy density of lithium ion secondary batteries has increased, and the amount of organic solvents, which are combustible substances, tends to increase. As a result, lithium ion secondary batteries are required to have much higher reliability.

Under these circumstances, an all-solid lithium secondary battery (all-solid secondary battery) that does not use an organic solvent has attracted attention. The all-solid secondary battery uses a molded body of a solid electrolyte that does not use an organic solvent, instead of a conventional organic solvent-based electrolyte.

Various improvements have been attempted for all-solid secondary batteries. Japanese Patent Laying-Open No. 2017-10816 (Patent Document 1) discloses a method for manufacturing an all-solid-state battery. The method for manufacturing this all-solid-state battery includes a first pressing step of pressing the positive electrode laminate, a second pressing step of pressing the negative electrode laminate, and a third pressing step of pressing the positive electrode laminate, the intermediate solid electrolyte layer and the negative electrode laminate. Including pressing process. At least one of the positive electrode laminate and the negative electrode laminate has a first or second solid electrolyte layer apart from the intermediate solid electrolyte layer. The pressing pressure of the third pressing step is higher than the pressing pressure of the first pressing step and the pressing pressure of the second pressing step. 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. Also, the press temperature is adjusted in each press step. That is, by adjusting the pressing pressure and pressing temperature in each pressing step and having the first or second solid electrolyte layer, short circuits are suppressed and an all-solid-state battery with a reduced internal resistance value is provided. .

As an example, WO2020/66323 discloses a method for manufacturing a flat all-solid-state battery in which an electrode laminate is produced by laminating a positive electrode and a negative electrode on a solid electrolyte layer.

JP 2017-10816 A WO2020/66323

However, in the manufacturing method of the all-solid-state battery of Patent Document 1, for example, when 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. Therefore, it is difficult to improve the bonding state between the second solid electrolyte layer and the negative electrode active material layer. As a result, the resistance at the interface between the second solid electrolyte layer and the negative electrode active material layer increases, which causes deterioration in the load characteristics of the battery.

On the other hand, Patent Document 2 discloses that an electrode laminate is produced by laminating a positive electrode and a negative electrode on a solid electrolyte layer. No suggestions are given.

Therefore, an object of the present disclosure is to provide a method for manufacturing a laminated electrode body with low internal resistance and a method for manufacturing an all-solid secondary battery with excellent load characteristics.

In order to solve the above problems, the present disclosure is configured as follows. That is, the method for manufacturing a laminated electrode body according to the present disclosure includes a solid electrolyte layer, a first electrode layer laminated on one main surface of the solid electrolyte layer, and a first electrode layer laminated on the other main surface of the solid electrolyte layer. It may be a method for manufacturing a laminated electrode body having two electrode layers. A step of pressing the sulfide-based solid electrolyte particles with a surface pressure of less than 120 MPa to form a first temporary molding layer for obtaining the solid electrolyte layer may be included. A step of disposing the first electrode mixture on one main surface of the first temporary molding layer may be included. A step of pressing the first electrode mixture with a surface pressure of less than 500 MPa to form a second temporary molding layer for obtaining the first electrode layer on one main surface of the first temporary molding layer may be included. A step of disposing a second electrode mixture for obtaining a second electrode layer on the other main surface of the first temporary molding layer may be included. A step of pressing the second electrode mixture, the first temporary molding layer and the second temporary molding layer with a predetermined surface pressure to form a laminated electrode body may be included.

In the step of forming the first temporary molding layer, the sulfide-based solid electrolyte particles may be pressed with a surface pressure of 30 MPa or more.

In the step of forming the second temporary molding layer, the first electrode mixture may be pressed with a surface pressure of 30 MPa or more.

The first electrode mixture may be a negative electrode mixture. The first electrode layer may be a negative electrode layer.

In the step of forming the laminated electrode body, the second electrode mixture, the first temporary molding layer and the second temporary molding layer may be pressed with a surface pressure of 1000 MPa or more.

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

According to the method for manufacturing a laminated electrode body according to the present disclosure, a laminated electrode body with low internal resistance can be formed. According to the method for manufacturing an all-solid secondary battery, it is possible to manufacture an all-solid secondary battery with excellent load characteristics.

FIG. 1 is a flow chart showing a method for manufacturing a laminated electrode body and an all-solid secondary battery according to the present disclosure. FIG. 2 is a schematic diagram showing a method of manufacturing a laminated electrode assembly according to the present disclosure. FIG. 3 is a schematic diagram showing a method of manufacturing a laminated electrode body. FIG. 4 is a schematic diagram showing a method of manufacturing a laminated electrode body. FIG. 5 is a schematic diagram showing a method of manufacturing a laminated electrode body. FIG. 6 is a schematic diagram showing a method of manufacturing a laminated electrode body. FIG. 7 is a schematic diagram showing a method of manufacturing a laminated electrode body. FIG. 8 is a schematic diagram showing a method of manufacturing a laminated electrode body. FIG. 9 is a schematic diagram showing a method of manufacturing a laminated electrode body. FIG. 10 is a cross-sectional view showing the structure of an all-solid secondary battery manufactured by the manufacturing method according to the present disclosure.

1 to 10, the manufacturing method of the laminated electrode body 1 and the all-solid secondary battery 10 according to the present disclosure will be specifically described below. FIG. 1 is a flow chart showing a method of manufacturing a laminated electrode body 1 and an all-solid secondary battery 10. As shown in FIG. First, the manufacturing method of the laminated electrode body 1 according to the present disclosure will be specifically described using FIGS. 2 to 9 while referring to FIG. As will be described later, the manufactured laminated electrode body 1 includes the solid electrolyte layer 23, the negative electrode layer (electrode layer) 33 laminated on one main surface of the solid electrolyte layer 23, and the other main surface of the solid electrolyte layer 23. has a positive electrode layer (electrode layer) 42 laminated on the main surface of the . Note that the method for manufacturing the laminated electrode body 1 according to the present disclosure can be suitably used for manufacturing the laminated electrode body 1 including the solid electrolyte layer 23 having a thickness of 120 μm or less, for example.

(Step 1 (S1))
As shown in FIG. 2, first, the pressure device 100 is prepared. The pressurizing device 100 includes a die 101 having a die hole 101a penetrating vertically, a lower punch 102 inserted from below the die hole 101a and sliding in the die hole 101a, and a die inserted from above the die hole 101a. and an upper punch 103 that slides in the die hole 101a. The die 101 is formed in a plate shape. The die 101a has a cylindrical opening extending from the upper surface to the lower surface of the die 101. As shown in FIG. Each of the lower punch 102 and the upper punch 103 is formed in a cylindrical shape along the shape of the opening of the mortar and pestle. The pressing device 100 presses the material filled in the die hole 101a by vertically sliding the lower punch 102 and the upper punch 103 using a press machine. The pressurizing device 100 is a powder molding die in this embodiment. The pressurizing device 100 is not limited to a powder molding die, and may be a tablet molding machine or the like as long as the laminated electrode body 1 can be molded by applying pressure with a predetermined surface pressure, which will be described later.

(Step 2 (S2))
As shown in FIG. 3, a lower punch 102 is inserted into the die hole 101a, and with the lower opening of the die hole 101a closed by the lower punch 102, the sulfide-based solid electrolyte particles 21 are filled from above the die hole 101a. do. Although not shown, the sulfide-based solid electrolyte particles 21 are filled into the die hole 101a from a hopper that moves parallel to the upper surface of the die 101 (hereinafter referred to as a negative electrode mixture 31 and a positive electrode mixture filled in the die hole 101a). 41 as well). The hopper moves above the die hole 101a when the sulfide-based solid electrolyte particles 21 are filled, and stands by at a location other than above the die hole 101a when the sulfide-based solid electrolyte particles 21 are not filled. The sulfide-based solid electrolyte particles 21 are, for example, 1 mg of sulfide-based solid electrolyte material (Li ₆ PS ₅ Cl). The sulfide-based solid electrolyte particles 21 are not particularly limited, and may be other sulfide-based solid electrolyte materials such as aldirodite type in terms of ion conductivity.

(Step 3 (S3))
As shown in FIG. 4, the sulfide-based solid electrolyte particles 21 are pressed (temporarily pressed) from above by an upper punch 103 with a surface pressure of less than 120 MPa to form a temporary molded layer 22 for obtaining a solid electrolyte layer 23 described later. Form. If this surface pressure is 120 MPa or more, cracks may occur in the temporary molding layer 22 . As a result, the internal resistance of the solid electrolyte layer 23 obtained from the temporary molding layer 22 becomes high. Moreover, the negative electrode layer 33 and the positive electrode layer 42 are likely to come into contact with each other, and an internal short circuit may occur in the all-solid secondary battery 10 . On the other hand, when the surface pressure is less than 120 MPa, cracking of the temporary molding layer 22 can be suppressed. As a result, it is possible to form the solid electrolyte layer 23 that has a low internal resistance and can suppress internal short circuits. However, if the surface pressure is too low, the shape of the temporary molding layer 22 cannot be maintained, and in (step 6) described later, the position of the temporary molding layer 22 may shift or part of the temporary molding layer 22 may fall off. Therefore, it is difficult to make the thickness of the solid electrolyte layer 23 uniform after pressurization. Non-uniformity in the thickness of the solid electrolyte layer 23 causes degradation of battery performance. From such a viewpoint, the surface pressure for pressing the sulfide-based solid electrolyte particles 21 is preferably 30 MPa or more, preferably 40 MPa or more, more preferably 50 MPa or more, and is less than 120 MPa, preferably less than 100 MPa, more preferably It should be less than 90 MPa.

(Step 4 (S4))
As shown in FIG. 5, a negative electrode mixture (electrode mixture) 31 is filled in the die hole 101a, and the negative electrode mixture 31 is applied to one main surface of the temporary molding layer 22, that is, the upper surface of the temporary molding layer 22 in the figure. to place. The negative electrode mixture 31 includes, for example, LTO (Li ₄ Ti ₅ O ₁₂ , lithium titanate), a sulfide-based solid electrolyte (Li ₆ PS ₅ Cl), and 129 mg of a mixture containing carbon nanotubes at a weight ratio of 50:41:9. The negative electrode mixture 31 is not particularly limited, and examples thereof include metal materials such as metallic lithium and lithium alloys, carbon materials such as graphite and low-crystalline carbon, SiO, LTO (Li ₄ Ti ₅ O ₁₂ , lithium titanate), etc., or an appropriate mixture thereof.

(Step 5 (S5))
As shown in FIG. 6 , the negative electrode mixture 31 placed on the upper surface of the temporary molding layer 22 is pressed (temporarily pressed) from above by an upper punch 103 with a surface pressure of less than 500 MPa, thereby obtaining a temporary mold for obtaining the negative electrode layer 33 . A molding layer 32 is formed. If the surface pressure is 500 MPa or more, cracks may occur in the temporary molded layer 32, or bonding between the solid electrolyte layer 23 and the positive electrode layer 42 may be impaired when the positive electrode mixture 41 is pressurized in (Step 8) described later. become insufficient. As a result, the internal resistance of the finally obtained laminated electrode body 1 becomes high. On the other hand, when the surface pressure is less than 500 MPa, cracking of the temporary molding layer 32 can be suppressed, and the solid electrolyte layer 23 and the positive electrode layer 42 can be bonded in a good state, so that the final product can be obtained. The internal resistance of the stacked electrode body 1 can be lowered. However, if the surface pressure is too low, the shape of the temporary molding layer 32 cannot be maintained, and in (step 6) described later, the position of the temporary molding layer 32 may shift or part of the temporary molding layer 32 may fall off. Therefore, it is difficult to make the thickness of the negative electrode layer 33 uniform after pressurization. Non-uniformity in the thickness of the negative electrode layer 33 causes deterioration in battery performance. From this point of view, the surface pressure for pressing the negative electrode mixture 31 is preferably 30 MPa or more, preferably 100 MPa or more, more preferably 150 MPa or more, and is less than 500 MPa, preferably less than 450 MPa, and more preferably less than 400 MPa. Better to

(Step 6 (S6))
As shown in FIG. 7, the temporary molding layer 22 and the temporary molding layer 32 are turned upside down. That is, the top and bottom are reversed so that the temporary molding layer 22 is arranged on the upper side in the figure and the temporary molding layer 32 is arranged on the lower side. The temporary molding layer 22 and the temporary molding layer 32 formed in (Step 6) may be taken out from the mortar hole 101a once, turned upside down, and placed in the mortar hole 101a again. Alternatively, the pressure device 100 itself may be turned upside down to turn the temporary molding layer 22 and the temporary molding layer 32 upside down. In this way, by inverting the temporary molding layer 22 and the temporary molding layer 32, the negative electrode mixture 31 remaining in the die hole 101a is brought into contact with the positive electrode mixture 41 in (step 7-1) described later. Since there is no short circuit, short circuits can be suppressed. In this case, the upper and lower punches 103 and 102 are also interchanged. Here, even if the pressurizing device 100 itself is turned upside down, the upper punch 103 is the upper punch and the lower punch 102 is the lower punch.

(Step 7-1 (S7-1))
As shown in FIG. 8, the positive electrode mixture (electrode mixture) 41 is filled in the die hole 101a, and on the other main surface of the temporary molded layer 22, that is, on the upper surface of the temporary molded layer 22 after being turned upside down, A positive electrode mixture (electrode mixture) 41 is placed. The positive electrode mixture 41 is, for example, lithium cobalt oxide having an average particle size of 5 μm, a sulfide-based solid electrolyte (Li ₆ PS ₅ Cl), and a conductive aid as positive electrode active materials used in a lithium-ion secondary battery. 92 mg of a mixture containing carbon nanotubes at a mass ratio of 70:26:4. The positive electrode material mixture 41 is not particularly limited, and may be, for example, lithium cobaltate, lithium nickelate, lithium manganate, spinel-type manganese composite oxide, olivine-type composite oxide, or the like. may be appropriately mixed.

(Step 8 (S8))
As shown in FIG. 9, the positive electrode mixture 41, the temporary molding layer 22, and the temporary molding layer 32 are pressed (main pressing) with a surface pressure of 1000 MPa or more. As a result, the temporary molding layer 22, the temporary molding layer 32, and the positive electrode mixture 41 are compressed, and the solid electrolyte layer 23, the negative electrode layer 33 laminated on one main surface of the solid electrolyte layer 23, and the solid electrolyte layer 23 are formed. A laminated electrode body 1 having a positive electrode layer 42 laminated on the other main surface can be formed. The laminated electrode body 1 can be removed from the die hole 101a by relatively moving the die 101 and the lower punch 102. As shown in FIG. In order to take out the laminated electrode body 1 from the die hole 101a, the die 101 and the upper punch 103 may be moved relative to each other. The upper and lower punches 103 and 102 are moved relative to the die 101 to remove the laminated electrode body 1 from the die hole 101a. This is preferable because it is possible to suppress the occurrence of cracks and chips in 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 being moved. Thus, the laminated electrode body 1 can be manufactured. In order to improve the packing property 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, the contact pressure is preferably high.

In addition, between (Step 7-1) and (Step 8), forming a temporary molding layer for obtaining a positive electrode layer (Step 7-2) can be included. That is, although not shown in the figure, the positive electrode mixture 41 arranged on the other main surface of the temporary molded layer 22 in (Step 7-1) is pressurized (temporarily pressed) to obtain a temporary molded layer for obtaining a positive electrode layer. may be formed. At this time, the surface pressure for pressurizing (temporary pressing) the positive electrode mixture 41 is 30 MPa or more, preferably 100 MPa or more, from the same viewpoint as the surface pressure for pressurizing (temporary pressing) the negative electrode mixture 31 described above. , more preferably 150 MPa or more, less than 500 MPa, preferably less than 450 MPa, more preferably less than 400 MPa.

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

Alternatively, the positive electrode mixture 41 may be placed in (Step 4), and the negative electrode mixture 31 may be placed in (Step 7-1). That is, the order in which the positive electrode mixture 41 and the negative electrode mixture 31 are arranged on the main surface of the temporary molding layer 22 may be changed. In this case, the surface pressure in (Step 7-2) may be applied as the surface pressure for obtaining the temporary molded layer 32 of the positive electrode mixture 41 in (Step 5). As the surface pressure for obtaining the temporary molded layer of the agent 31, the surface pressure in (Step 5) may be applied. However, depending on the types of the positive electrode active material and the negative electrode active material, in general, the negative electrode active material is harder than the positive electrode active material, and the negative electrode mixture 31 may be more difficult to fill than the positive electrode mixture 41. many. Therefore, in order to improve the filling property of the negative electrode mixture, it is preferable to compress the negative electrode mixture 31 in stages. That is, it is preferable to form the temporary molding layer 32 for obtaining the negative electrode layer 33 in (Step 4) and form the negative electrode layer 33 in (Step 8). Moreover, 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 efficiently formed. On the other hand, as in (Step 7-2), when forming a temporary molding layer for obtaining an electrode layer also on the other main surface of the temporary molding layer 22, 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.

Such a method for manufacturing the laminated electrode body 1 can make the thickness of each of the solid electrolyte layer 23, the negative electrode layer 33 and the positive electrode layer 42 uniform, and the thickness of the solid electrolyte layer 23, the negative electrode layer 33 and the positive electrode layer 42 can suppress cracks in each of Therefore, it is possible to form the laminated electrode body 1 having excellent interface bondability between the negative electrode layer 33 and the solid electrolyte layer 23 and interface bondability between the positive electrode layer 42 and the solid electrolyte layer 23 and low internal resistance.

Next, a method for manufacturing the all-solid secondary battery 10 will be described with reference to FIG. Here, the all-solid secondary battery 10 is a flat battery.

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

Specifically, first, a case is prepared. The case has an outer can 11 , a sealing can 12 and a gasket 13 .

The outer can 11 includes a circular bottom portion 11a and a cylindrical peripheral wall portion 11b formed continuously 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 vertical cross-sectional view. The outer can 11 is made of a metal material such as stainless steel, nickel, or iron. The shape of the outer can 11 is not limited to a cylindrical shape with a circular bottom portion 11a. For example, the outer can 11 may be shaped such that the bottom portion 11a is formed in a polygonal shape such as a square shape, and the peripheral wall portion 11b is formed in a polygonal tubular shape such as a square tubular shape matching the shape of the bottom portion 11a. Various changes can be made according to the size and shape of the body 1 and the all-solid secondary battery 10 . Therefore, the shape of the peripheral wall portion 11b includes not only a cylindrical shape but also a polygonal cylindrical shape such as a rectangular cylindrical shape. In addition, the shape of the laminated electrode body 1 is, for example, a polygonal columnar shape such as a columnar shape or a square columnar shape.

The sealing can 12 includes a circular flat portion 12a and a cylindrical peripheral wall portion 12b formed continuously from the outer circumference of the flat portion 12a. The opening of the sealed can 12 faces the opening of the outer can 11 . The sealing can 12 is made of a metal material such as stainless steel. In addition, the shape of the sealing can 12 is not limited to the cylindrical shape provided with the circular flat portion 12a. For example, the shape of the sealed can 12 may be such that the plane portion 12a is formed in a polygonal shape such as a square shape, and the peripheral wall portion 12b is formed in a polygonal tube shape such as a square tube shape matching the shape of the plane portion 12a. Various changes can be made according to the size and shape of the laminated electrode body 1 and the all-solid secondary battery 10 . Therefore, the shape of the peripheral wall portion 12b includes not only a cylindrical shape but also a polygonal cylindrical shape such as a rectangular cylindrical shape.

The gasket 13 is made of a low-moisture-permeable resin such as polypropylene resin, polyphenylene sulfide resin, or PFA resin. The gasket 13 is formed in a tubular shape along the inner peripheral surface of the peripheral wall portion 11 b of the outer can 11 and is arranged between the peripheral wall portion 11 b of the outer can 11 and the peripheral wall portion 12 b 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, polyphenylene sulfide resin or fluororesin such as PFA resin is preferably used. .

The outer can 11 and the sealing can 12 are caulked via a gasket 13 between the peripheral wall portion 11b of the outer can 11 and the peripheral wall portion 12b of the sealing can 12 after accommodating the laminated electrode body 1 in the internal space. Specifically, the exterior can 11 and the sealing can 12 are arranged such that the openings of the exterior can 11 and the sealing can 12 face each other, and the peripheral wall portion 11b of the sealing can 12 is inserted inside the peripheral wall portion 11b of the exterior can 11. After that, the peripheral wall portion 11b and the peripheral wall portion 12b are crimped via a gasket 13. As shown in FIG. In this manner, the outer can 20 and the sealing can 30 constitute a case that accommodates the laminated electrode body 1 in the internal space. The manufacturing method of the all-solid secondary battery 10 is not limited to this, as long as the laminated electrode assembly 1 can be housed in a case and manufactured so as to function as a secondary battery.

Thereby, the all-solid secondary battery 10 having excellent load characteristics can be manufactured.

Although the embodiments have been described above, the present disclosure is not limited to the above embodiments, and various modifications are possible without departing from the scope of the present disclosure.

Flat all-solid secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 3 were produced, and the internal resistance of each flat all-solid secondary battery was measured.

(Example 1)
A flat all-solid secondary battery of Example 1 was produced as follows. First, 9.6 mg of powder of a sulfide-based solid electrolyte (Li _5.4 PS _4.4 Cl _0.8 Br _0.8 ) having an average particle size of 0.7 μm was placed in a powder molding die and pressed using a press. Pressure molding was performed with a surface pressure of 70 MPa (0.7 tf/cm ² ) to form a temporary molding layer for obtaining a solid electrolyte layer. Next, lithium titanate (Li ₄ Ti ₅ O ₁₂ , negative electrode active material) having an average particle size of 2 μm and an average particle size of A 0.7 μm sulfide-based solid electrolyte (Li _5.4 PS _4.4 Cl _0.8 Br _0.8 ) and graphene (a conductive agent) are mixed at a mass ratio of 50:41:9. 101 mg of the negative electrode mixture prepared by the above method is placed and pressure-molded at a surface pressure of 300 MPa (3 tf/cm ² ) to obtain the negative electrode layer on one main surface of the temporary molded layer for obtaining the solid electrolyte layer. was formed. After the mold is turned upside down, the upper surface (the other main surface) of the temporary molding layer for obtaining the solid electrolyte layer turned upside down together with the mold is coated with a LiNbO3 coating layer _on the surface, and the average particle size is 5 μm LiCoO ₂ (positive electrode active material), a sulfide-based solid electrolyte (Li _7.0 PS _5.4 Cl _1.2 ) having an average particle size of 3 μm, carbon black and vapor grown carbon fiber (VGCF) were mixed at a mass ratio of 70:26.8:1.1:2.1 to prepare 73 mg of a positive electrode mixture. The temporary molding layer for obtaining the negative electrode layer, the temporary molding layer for obtaining the solid electrolyte layer, and the positive electrode mixture were compressed by performing pressure molding at a surface pressure of 1300 MPa (13 tf/cm ² ) to obtain 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% by mass. Finally, using a stainless steel sealing can and an outer can as a case, the laminated electrode body is accommodated between the sealing can and the outer can, and between the sealing can and the laminated electrode body and between the outer can and the laminated electrode. A flat all-solid secondary battery was assembled by placing a porous carbon sheet having a thickness of 0.1 mm between each of the bodies for sealing.

(Example 2)
73 mg of the positive electrode mixture prepared in Example 1 was placed on the upper surface (one main surface) of the temporary molding layer for obtaining the solid electrolyte layer prepared in Example 1, and a surface pressure of 300 MPa (3 tf/cm ² ) was applied. to form a temporary molded layer for obtaining a positive electrode layer on one main surface of the temporary molded layer for obtaining a solid electrolyte layer. After the mold was turned upside down, 101 mg of the negative electrode mixture prepared in Example 1 was placed on the upper surface (the other main surface) of the temporary molding layer for obtaining the solid electrolyte layer turned upside down together with the mold, and the pressure was 1300 MPa. By performing pressure molding with a surface pressure of (13 tf/cm ² ), the temporary molding layer for obtaining the positive electrode layer, the temporary molding layer for obtaining the solid electrolyte layer, and the negative electrode mixture are compressed to a thickness of 825 μm. , a solid electrolyte layer having a thickness of 110 μm, and a positive electrode layer having a thickness of 540 μm were integrated. Finally, a flat all-solid-state battery was assembled in the same manner as in Example 1.

(Comparative example 1)
101 mg of the negative electrode mixture prepared in Example 1 was placed in a powder molding die, and pressure molding was performed using a pressing machine at a surface pressure of 300 MPa (3 tf/cm ² ) to form a temporary molding layer for obtaining a negative electrode layer. formed. 9.6 mg of powder of a sulfide-based solid electrolyte (Li _5.4 PS _4.4 Cl _0.8 Br _0.8 ) having an average particle size of 0.7 μm on the upper surface of the temporary molding layer for obtaining the negative electrode layer was placed, pressure molding was performed at a surface pressure of 70 MPa (0.7 tf/cm ² ), and a temporary molding layer for obtaining a solid electrolyte layer was formed on one upper surface of the temporary molding 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 molding layer for obtaining the solid electrolyte layer, and pressure molding was performed at a surface pressure of 1300 MPa (13 tf/cm ² ), A laminated electrode body in which the negative electrode layer, the solid electrolyte layer, and the positive electrode layer are integrated by compressing the temporary molded layer for obtaining the negative electrode layer, the temporary molded layer for obtaining the solid electrolyte layer, and the positive electrode mixture. Obtained. Finally, a flat all-solid secondary battery was assembled in the same manner as in Example 1.

(Comparative example 2)
A flat all-solid secondary battery was assembled in the same manner as in Example 1 except that the surface pressure during formation of the temporary solid electrolyte layer was changed to 130 MPa (1.3 tf/cm ² ). .

(Comparative Example 3)
A flat all-solid secondary battery was assembled in the same manner as in Example 1 except that the pressure in forming the temporary molding layer for obtaining the negative electrode layer was changed to 600 MPa (6 tf/cm ² ). .

(Evaluation results)
An AC voltage of 1 kHz was applied to the flat all-solid secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 3 to measure the internal resistance. The evaluation results were as follows. The internal resistance of the flat all-solid secondary battery of Example 1 was 230Ω. The internal resistance of the flat all-solid secondary battery of Example 2 was 260Ω. The internal resistance of the flat all-solid secondary battery of Comparative Example 1 was 316Ω. The internal resistance of the flat all-solid secondary battery of Comparative Example 2 was 519Ω. The internal resistance of the flat all-solid secondary battery of Comparative Example 3 was 432Ω.

In the flat all-solid-state secondary batteries of Examples 1 and 2, the thickness of each of the solid electrolyte layer, the negative electrode layer, and the positive electrode layer was made uniform by pressure molding in an appropriate order of steps and an appropriate surface pressure. It was possible to suppress cracks in them. Therefore, the flat all-solid secondary battery of Comparative Example 1 in which the order of steps of the solid electrolyte layer, the negative electrode layer and the positive electrode layer is different, the temporary molded layer for obtaining the solid electrolyte layer, or the temporary molded layer for obtaining the negative electrode layer. Compared to the flat all-solid-state secondary batteries of Comparative Examples 2 and 3 in which the surface pressure during formation was too high, the internal resistance could be reduced. Therefore, the flat all-solid secondary batteries of Examples 1 and 2 were able to obtain better load characteristics than the batteries of Comparative Examples 1-3. It is considered that similar results can be obtained even when the above-mentioned (step 7-2) is provided in Examples 1 and 2.

1 laminated electrode body 10 all-solid secondary battery 11 outer can 11a bottom 11b peripheral wall 12 sealing can 12a flat surface 12b peripheral wall 13 gasket 21 sulfide-based solid electrolyte particles 22 temporary molding layer , 23 solid electrolyte layer 31 negative electrode mixture 32 temporary molding layer 33 negative electrode layer 41 positive electrode mixture 42 positive electrode layer 100 pressure device 101 die 101a die hole 102 lower punch 103 upper punch material

Claims (6)

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 and
A step of pressing the sulfide-based solid electrolyte particles with a surface pressure of less than 120 MPa to form a first temporary molding layer for obtaining the solid electrolyte layer;
disposing a first electrode mixture on one main surface of the first temporary molding layer;
pressing the first electrode mixture with a surface pressure of less than 500 MPa to form a second temporary molding layer for obtaining the first electrode layer on one main surface of the first temporary molding layer;
disposing a second electrode mixture for obtaining the second electrode layer on the other main surface of the first temporary molding layer;
and pressing the second electrode mixture, the first temporary molding layer, and the second temporary molding layer with a predetermined surface pressure to form the laminated electrode body. A method for manufacturing a laminated electrode body according to claim 1,
A method for manufacturing a laminated electrode body, wherein in the step of forming the first temporary molding layer, the sulfide-based solid electrolyte particles are pressed with a surface pressure of 30 MPa or more. 3. A method for manufacturing a laminated electrode body according to claim 1 or 2,
A method for manufacturing a laminated electrode body, wherein in the step of forming the second temporary molding layer, the first electrode mixture is pressed with a surface pressure of 30 MPa or more. A method for manufacturing a laminated electrode body according to any one of claims 1 to 3,
The first electrode mixture is a negative electrode mixture,
The first electrode layer is a method for manufacturing a laminated electrode body, which is a negative electrode layer. A method for manufacturing a laminated electrode body according to any one of claims 1 to 4,
A method of manufacturing a laminated electrode body, wherein in the step of forming the laminated electrode body, the second electrode mixture, the first temporary molding layer, and the second temporary molding layer are pressed with a surface pressure of 1000 MPa or more. A method for manufacturing an all-solid secondary battery,
A method for producing an all-solid secondary battery, comprising the step of housing the laminated electrode assembly produced by the method for producing a laminated electrode assembly according to any one of claims 1 to 5 in a case.

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