JP2021150204A - All-solid-state lithium secondary battery and manufacturing method thereof - Google Patents

Abstract

To provide an all-solid-state lithium secondary battery that prevents a short circuit from occurring at the outer peripheral ends of a positive electrode and a negative electrode, and has a high capacity and a high energy density even when the thickness of a solid electrolyte layer is reduced.SOLUTION: An all-solid-state lithium secondary battery disclosed in the present application includes a laminated electrode body including a positive electrode, a negative electrode, and a solid electrolyte-containing sheet arranged between the positive electrode and the negative electrode, and the solid electrolyte-containing sheet includes an insulating porous base material and a solid electrolyte filled in the insulating porous base material, and the peripheral portion of the solid electrolyte-containing sheet covers the outer peripheral side surface of the positive electrode or the negative electrode. The thickness of the solid electrolyte-containing sheet is 5 to 200 μm.SELECTED DRAWING: Figure 1

Description

The present invention relates to a high-capacity all-solid-state lithium secondary battery using a solid electrolyte and a method for producing the same.

Currently, the organic electrolyte used in lithium-ion secondary batteries contains an organic solvent, which is a flammable substance. Therefore, when an abnormal situation such as a short circuit occurs in the battery, the organic electrolyte generates abnormal heat. there is a possibility. Further, with the recent increase in energy density of lithium ion secondary batteries and the increasing tendency of the amount of organic solvent in organic electrolytic solutions, the safety and reliability of lithium ion secondary batteries are further required.

Under the above circumstances, an all-solid-state lithium secondary battery that does not use an organic solvent is drawing attention. The all-solid-state lithium secondary battery uses a solid electrolyte molded product that does not use an organic solvent instead of the conventional organic solvent-based electrolyte, and there is no risk of abnormal heat generation of the solid electrolyte, resulting in high safety. I have.

Generally, in an all-solid-state lithium secondary battery, a laminated electrode body in which a solid electrolyte layer is arranged between a positive electrode and a negative electrode is used. The laminated electrode body can be prepared by applying a paint in which each constituent material (active material, solid electrolyte) is dispersed in a solvent to form a laminated film, or by filling a mold with powder of each constituent material as it is. It can be produced by a method of forming pellets by pressure molding or the like.

Currently, a coin-shaped solid electrolyte battery is being developed as a battery used in a small electronic device. For a coin-shaped battery, pellets of laminated electrode bodies are prepared and stored in a battery container. It is common to assemble batteries.

When the laminated electrode body of the coin-shaped battery is manufactured as pellets, the powder of each constituent material is pressure-molded in the mold, so that the whole is formed as a cylindrical laminated body, and the areas of the positive electrode and the negative electrode and the solid electrolyte layer. Is the same as the area of. Therefore, when the active material particles are desorbed from the end portion of the positive electrode or the negative electrode, there is a problem that the outer peripheral end portion of the positive electrode and the outer peripheral end portion of the negative electrode are in contact with each other and a short circuit is likely to occur. In particular, when an attempt is made to form a thin solid electrolyte layer regardless of the battery capacity in order to increase the capacity of the battery, the short circuit is more likely to occur.

In order to solve this problem, Patent Document 1 proposes a shape in which at least one of the positive electrode and the negative electrode is covered with a solid electrolyte layer. Although the problem of the short circuit can be prevented by adopting the laminated electrode body having the above configuration, in Patent Document 1, a method of later integrating the separately produced electrodes and the solid electrolyte layer is used. It is difficult to form a thin solid electrolyte layer.

On the other hand, Patent Documents 2 and 3 propose a method in which a powder of an active material or a solid electrolyte is charged and applied, and then pressurized to form a film. According to this method, the thickness of each layer can be adjusted relatively freely, so that the thickness of the solid electrolyte layer can be reduced, and a shape in which the outer peripheral surface of the electrode is covered with the solid electrolyte is produced. It is also possible.

Japanese Unexamined Patent Publication No. 2009-64644 Japanese Unexamined Patent Publication No. 2010-282803 Japanese Unexamined Patent Publication No. 2019-21428

However, the methods described in Patent Documents 2 and 3 only pressurize the coating film in the thickness direction, and do not impose any restrictions on the surface direction of the coating film. Therefore, when the solid electrolyte layer is formed on the outer peripheral surface portion of the positive electrode or the negative electrode in order to prevent the above-mentioned short circuit, it is difficult to adjust the thickness of the solid electrolyte layer on the outer peripheral surface portion.

Further, since the molded body of the solid electrolyte layer is brittle, when the solid electrolyte layer is formed on the outer peripheral surface of the positive electrode or the negative electrode, the solid electrolyte layer formed on the outer peripheral surface of the positive electrode or the negative electrode is easily detached at the time of battery production, and the positive electrode is formed. There is a possibility that a short circuit may occur due to contact between the outer peripheral end portion of the negative electrode and the outer peripheral end portion of the negative electrode.

The present application has been made to solve the above problems, and is an all-solid-state lithium secondary battery in which a short circuit is prevented from occurring at the outer peripheral ends of the positive electrode and the negative electrode, and the thickness of the solid electrolyte layer is reduced to increase the capacity. Is to provide.

The all-solid lithium secondary battery of the present invention includes a laminated electrode body including a positive electrode, a negative electrode, and a solid electrolyte-containing sheet arranged between the positive electrode and the negative electrode, and the solid electrolyte-containing sheet is insulated. The solid electrolyte-containing sheet contains the porous porous substrate and the solid electrolyte filled in the insulating porous substrate, and the peripheral edge portion of the solid electrolyte-containing sheet covers the outer peripheral side surface portion of the positive electrode or the negative electrode, and the solid. The thickness of the electrolyte-containing sheet is 5 to 200 μm.

Further, the method for manufacturing the all-solid-state lithium secondary battery of the present invention is the above-mentioned method for manufacturing the all-solid-state lithium secondary battery of the present invention, in which an electrode preparation step for preparing a positive electrode and a negative electrode and solid electrolyte particles are provided. A filling step of filling an insulating porous base material to prepare a solid electrolyte-containing sheet, a laminating step of laminating the positive electrode, the solid electrolyte-containing sheet, and the negative electrode in this order, and the solid electrolyte-containing sheet. The peripheral portion is folded back to the outer peripheral side of one of the laminated positive electrode or the negative electrode, and the peripheral portion of the solid electrolyte-containing sheet covers the outer peripheral side surface portion of the positive electrode or the negative electrode.

According to the present application, even if the thickness of the solid electrolyte layer is reduced, short circuits can be prevented from occurring at the outer peripheral ends of the positive electrode and the negative electrode, and an all-solid-state lithium secondary battery having a high capacity and a high energy density can be provided.

FIG. 1 is a cross-sectional view showing an example of an all-solid-state lithium secondary battery of the embodiment. FIG. 2 is a cross-sectional view showing an example of a process of manufacturing a laminated electrode body of the all-solid-state lithium secondary battery of the embodiment.

(All-solid-state lithium secondary battery)
Embodiments of the all-solid-state lithium secondary battery disclosed in the present application will be described. The all-solid lithium secondary battery of the present embodiment includes a laminated electrode body including a positive electrode, a negative electrode, and a solid electrolyte-containing sheet arranged between the positive electrode and the negative electrode. The insulating porous base material and the solid electrolyte filled in the insulating porous base material are contained, and the peripheral portion of the solid electrolyte-containing sheet covers the outer peripheral side surface portion of the positive electrode or the negative electrode. The thickness of the solid electrolyte-containing sheet is 5 to 200 μm.

In the all-solid-state lithium secondary battery of the present embodiment, since the solid electrolyte is filled in the insulating porous base material, a thin and uniform solid electrolyte layer can be formed. This makes it possible to provide an all-solid-state lithium secondary battery having a high capacity and a high energy density. Further, since the peripheral portion of the solid electrolyte-containing sheet covers the outer peripheral side surface portion of the positive electrode or the negative electrode, even if the solid electrolyte layer (solid electrolyte-containing sheet) is formed thinly, a short circuit occurs at the outer peripheral end portion of the positive electrode and the negative electrode. Occurrence can be prevented.

Further, since the thickness of the solid electrolyte-containing sheet is 200 μm or less, a certain degree of flexibility can be imparted to the solid electrolyte-containing sheet, whereby the peripheral portion of the solid electrolyte-containing sheet can be attached to the outer peripheral side surface portion of the positive electrode or the negative electrode. It can be bent, and the outer peripheral side surface portion of the electrode can be covered with the solid electrolyte-containing sheet by a simple method. Further, since the thickness of the solid electrolyte-containing sheet is 5 μm or more, the insulating porous base material can retain the solid electrolyte and secure the shape-retainability of the solid electrolyte-containing sheet, and can be laminated with the positive electrode and the negative electrode. A laminated electrode body can be reliably formed.

Hereinafter, the all-solid-state lithium secondary battery of the present embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of a coin-shaped all-solid-state lithium secondary battery of the present embodiment. In FIG. 1, the all-solid-state lithium secondary battery 10 contains a negative electrode 14, a positive electrode 15, and a solid electrolyte inside an exterior body composed of an outer can 11, a sealing can 12, and a gasket 13 interposed between them. A laminated electrode body made of the sheet 16 is enclosed. The solid electrolyte-containing sheet 16 contains an insulating porous base material (not shown) and a solid electrolyte filled in the insulating porous base material, and the peripheral portion 16a of the solid electrolyte-containing sheet 16 has a positive electrode. It is folded back to the 15 side and covers the outer peripheral side surface portion of the positive electrode 15. The peripheral edge portion 16a of the solid electrolyte-containing sheet 16 may be folded back toward the negative electrode 14 side to cover the outer peripheral side surface portion of the negative electrode 14.

The sealing can 12 is fitted to the opening of the outer can 11 via a gasket 13, and the opening end of the outer can 11 is tightened inward, whereby the gasket 13 comes into contact with the sealing can 12. The opening of the outer can 11 is sealed, and the inside of the outer body has a closed structure.

Next, each component of the all-solid-state lithium secondary battery of the present embodiment will be described.

<Solid electrolyte-containing sheet>
The solid electrolyte-containing sheet according to the all-solid-state lithium secondary battery of the present embodiment constitutes the solid electrolyte layer of the laminated electrode body, and is filled with the insulating porous base material and the insulating porous base material. Contains solid electrolytes and binders.

As described above, the thickness of the solid electrolyte-containing sheet is set to 5 μm or more so that the shape-retainability of the solid electrolyte-containing sheet can be ensured and the laminated electrode body can be reliably formed by laminating with the positive electrode and the negative electrode. It is preferably 10 μm or more. Further, in order to make the peripheral edge portion of the solid electrolyte-containing sheet bendable to the outer peripheral side surface portion of the positive electrode or the negative electrode, the thickness of the solid electrolyte-containing sheet is set to 200 μm or less, preferably 100 μm or less.

Further, in the laminated electrode body, in order to ensure ionic conductivity at the interface between the electrode and the solid electrolyte-containing sheet, it is preferable that the entire surface of the insulating porous base material is covered with the solid electrolyte layer. ..

[Solid electrolyte]
The solid electrolyte is not particularly limited as long as it has lithium ion conductivity, and for example, a sulfide-based solid electrolyte, a hydride-based solid electrolyte, an oxide-based solid electrolyte, and the like can be used.

As the sulfide-based solid electrolyte, for example, sulfides such as _{Li 2 S-P 2 S 5} , Li 2 S-SiS 2, Li 2 S-P 2 S 5 -GeS 2, Li 2 S-B 2 S 3 _{In addition to physical solid electrolyte glass, Li 10} GeP ₂ S ₁₂ (LGPS system) and Li ₆ PS ₅ Cl (algirodite system), which have been attracting attention in recent years as having high lithium ion conductivity, can also be used. can. Among these, an algyrodite-based solid electrolyte having particularly high lithium ion conductivity and high chemical stability is preferably used.

As the hydride-based solid electrolyte, for example, a solid solution of LiBH ₄ and the alkali metal compound of the following (e.g., molar ratio of LiBH ₄ and the alkali metal compound is 1: 1 to 20: 1 of solid solution), and the like .. Examples of the alkali metal compound in the solid solution include lithium halide (LiI, LiBr, LiF, LiCl), rubidium halide (RbI, RbBr, RbF, RbCl), cesium chloride (CsI, CsBr, CsF, CsCl) and lithium amide. , Rubidium amide, at least one selected from cesium amide.

Examples of the oxide-based solid electrolyte include Li ₇ La ₃ Zr ₂ O ₁₂ , LiTi (PO ₄ ) ₃ , LiGe (PO ₄ ) ₃ , LiLaTIO _{3, and the} like.

Among the above-exemplified solid electrolytes, it is more preferable to use a sulfide-based solid electrolyte having high lithium ion conductivity.

One type of the solid electrolyte can be used alone, but two or more types can be used in combination. The form of the solid electrolyte is preferably in the form of particles from the viewpoint of fillingability into the insulating porous substrate, but may be in a form other than the form of particles. When two or more of the above solid electrolytes are used in combination, each solid electrolyte may be mixed in a particulate form, each solid electrolyte may be mixed at the molecular level, or each solid may be mixed. The electrolyte may be present in the thickness direction of the solid electrolyte-containing sheet so that the respective solid electrolyte particles form different regions in layers.

The average particle size of the solid electrolyte particles is preferably 5 μm or less, preferably 2 μm, from the viewpoint of further enhancing the filling property into the pores of the insulating porous base material and ensuring good lithium ion conductivity. The following is more preferable. However, if the size of the solid electrolyte particles is too small, the handleability may be lowered, or a larger amount of binder may be required to increase the resistance value. Therefore, the average particle size of the solid electrolyte particles is preferably 0.3 μm or more, and more preferably 0.5 μm or more.

The average particle size of the solid electrolyte particles and other particles (positive positive active material particles, negative negative active material particles, etc.) referred to in the present specification is, for example, a laser scattering particle size distribution meter (for example, "LA-920" manufactured by HORIBA). It is the number average particle diameter measured by dispersing the particles in a medium that does not dissolve or swell these particles.

[Insulating Porous Substrate]
The insulating porous base material is not particularly limited as long as it can be filled and held with a solid electrolyte, but a non-woven fabric that is easy to handle and thin is preferable.

The porosity of the insulating porous base material is preferably 30% by volume or more, preferably 40% by volume or more, from the viewpoint of keeping the filling amount of the solid electrolyte above a certain level and ensuring good lithium ion conductivity. More preferably. However, if the porosity of the insulating porous base material is too large, the shape retention of the solid electrolyte-containing sheet may decrease. Therefore, from the viewpoint of further increasing the strength of the solid electrolyte-containing sheet, the porosity of the insulating porous base material is preferably 90% by volume or less, and more preferably 85% by volume or less.

As described above, since it is preferable to cover the entire surface of the insulating porous base material with the solid electrolyte layer, the thickness of the insulating porous base material is slightly thinner than the thickness of the above-mentioned solid electrolyte-containing sheet. It is preferable that the thickness of the solid electrolyte-containing sheet is in the range of 5 to 200 μm in a state where the entire surface of the insulating porous base material is covered with the solid electrolyte layer. Therefore, the thickness of the insulating porous substrate is preferably set to 3.5 to 195 μm, more preferably 8.5 to 137 μm.

When a non-woven fabric is used as the insulating porous base material, the fiber diameter of the fibrous material constituting the non-woven fabric as the base material is preferably 20 μm or less, and preferably 0.5 μm or more.

The material of the fibrous material constituting the non-woven fabric is not particularly limited as long as it does not react with lithium metal and has insulating properties. For example, polyolefins such as polypropylene and polyethylene; polystyrene; aramid; polyamideimide Resins such as polyimide; nylon; polyester such as polyethylene terephthalate (PET); polyarylate; cellulose and cellulose modified product; can be used. Inorganic materials such as glass, alumina, silica, and zirconia can also be used.

^{Further, the texture of the non-woven fabric is preferably 10 g / m 2} or less, preferably 8 g / m ² or less so that a sufficient amount of solid electrolyte particles can sufficiently secure lithium ion conductivity. Is more preferable, and from the viewpoint of ensuring sufficient strength, ^{it is preferably 3 g / m 2} or more, and more preferably 4 g / m ² or more.

[Binder]
The binder is preferably one that does not react with the solid electrolyte, and at least one resin selected from butyl rubber, chloropyrene rubber, acrylic resin, and fluororesin is preferably used.

Further, the content of the binder is preferably 0.5% by mass or more with respect to the total mass of the solid electrolyte and the binder from the viewpoint of further enhancing the shape retention of the solid electrolyte-containing sheet, and is 1% by mass. The above is preferable, and from the viewpoint of limiting the amount of the binder to some extent and suppressing the decrease in lithium ion conductivity, it is preferably 5% by mass or less, and preferably 3% by mass or less. ..

The method for producing the above-mentioned solid electrolyte-containing sheet is not particularly limited, but a slurry or the like is prepared by dispersing the solid electrolyte particles in a solvent together with a binder, and this is used as a wet insulating porous substrate (resin non-woven fabric, etc.). It is preferably manufactured in the step of filling the pores. As a result, the strength of the solid electrolyte-containing sheet is improved, and the production of a large-area solid electrolyte-containing sheet becomes easy.

The above slurry is prepared by adding solid electrolyte particles and a binder to a solvent and mixing them. It is preferable to select a solvent for the slurry that does not easily deteriorate the solid electrolyte. In particular, sulfide-based solid electrolytes and hydride-based solid electrolytes cause a chemical reaction with a very small amount of water, and are therefore represented by hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene. It is more preferable to use a non-polar aprotic aprotic solvent and use it as a super-dehydrating solvent having a water content of 0.001% by mass (10 ppm) or less.

Examples of the solvent include "Bertrel (registered trademark)" manufactured by Mitsui Dupont Fluorochemical, "Zeolola (registered trademark)" manufactured by Zeon Corporation, and "Novec (registered trademark)" manufactured by Sumitomo 3M. Fluorine-based solvents and non-aqueous organic solvents such as dichloromethane and diethyl ether can also be used.

As a method of filling the pores of the insulating porous base material with the slurry containing the solid electrolyte particles and the binder, a coating method such as a screen printing method, a doctor blade method, or a dipping method can be adopted.

After filling the pores of the insulating porous base material with the slurry, the solvent of the slurry is removed by drying, and if necessary, pressure molding is performed to obtain a solid electrolyte-containing sheet.

The method for producing the solid electrolyte-containing sheet is not limited to the wet method. For example, the pores of the insulating porous substrate are dry-filled with a mixture of solid electrolyte particles and binder particles, and then pressurized. A solid electrolyte-containing sheet may be produced by a molding method.

<Positive electrode>
The positive electrode is not particularly limited as long as it is a positive electrode used in a conventionally known lithium ion secondary battery, that is, a positive electrode containing an active material capable of storing and releasing Li ions. For example, as the positive electrode active material, LiM _x Mn _2-x O ₄ (where M is Li, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Fe, Co, Ni, Cu, Al, Spinel-type lithium manganese represented by 0.01 ≦ x ≦ 0.5), which is at least one element selected from the group consisting of Sn, Sb, In, Nb, Mo, W, Y, Ru and Rh. composite _{oxides, Li x Mn (1-yx} ) Ni y M z O (2-k) F l ( where, M is, Co, Mg, Al, B , Ti, V, Cr, Fe, Cu, Zn, It is at least one element selected from the group consisting of Zr, Mo, Sn, Ca, Sr and W, and is 0.8 ≦ x ≦ 1.2, 0 <y <0.5, 0 ≦ z ≦ 0. 5. Layered compound represented by k + l <1, −0.1 ≦ k ≦ 0.2, 0 ≦ l ≦ 0.1), LiCo _1-x M _x O ₂ (where M is Al, Mg, It is at least one element selected from the group consisting of Ti, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba, and is represented by 0 ≦ x ≦ 0.5). Lithium-cobalt composite oxide, LiNi _1-x M _x O ₂ (where M is Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and At least one element selected from the group consisting of Ba, a lithium nickel composite oxide represented by 0 ≦ x ≦ 0.5), LiM _1-x N _x PO ₄ (where M is Fe, At least one element selected from the group consisting of Mn and Co, N is a group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba. It is at least one element selected from, and examples thereof include an olivine type composite oxide represented by 0 ≦ x ≦ 0.5), a lithium titanium composite oxide represented by _{Li 4} Ti ₅ O _{12, and the like.} Only one of these may be used, or two or more thereof may be used in combination.

As the positive electrode, one having a structure in which a positive electrode mixture layer containing the positive electrode active material and a conductive auxiliary agent or a binder is formed on one side or both sides of a current collector can be used.

As the binder of the positive electrode, for example, a fluororesin such as polyvinylidene fluoride (PVDF) can be used, and as the conductive auxiliary agent of the positive electrode, for example, a carbon material such as carbon black can be used. The solid electrolyte used in the solid electrolyte-containing sheet may be used as the conductive auxiliary agent.

Further, as the current collector of the positive electrode, a metal foil such as aluminum, a punching metal, a net, an expanded metal, a foamed metal or the like can be used.

In producing the positive electrode, for example, a positive electrode mixture-containing paste or slurry in which a positive electrode active material, a conductive auxiliary agent, a binder or the like is dispersed in a solvent such as xylene is applied to a current collector, dried, and then dried. If necessary, a method of pressure molding such as calendering can be adopted. As the solvent, a super dehydration solvent having a water content of 0.001% by mass (10 ppm) or less is preferably used.

When a conductive porous base material such as punching metal is used for the positive electrode current collector, for example, the positive electrode mixture-containing paste, slurry, or the like is filled in the pores of the conductive porous base material. After drying, the positive electrode can be manufactured by a method of pressure molding such as calendering, if necessary. Since the positive electrode manufactured by such a method can secure a large strength, it is possible to hold a solid electrolyte-containing sheet having a larger area.

Further, instead of the above-mentioned positive electrode mixture-containing paste, slurry, etc., a positive electrode mixture containing a positive electrode active material, a conductive auxiliary agent, a binder, etc., and containing no solvent is dried in the pores of the conductive porous base material. The positive electrode may be manufactured by a method of filling and, if necessary, pressure molding such as calendering.

<Negative electrode>
The negative electrode is not particularly limited as long as it is a negative electrode used in a conventionally known lithium ion secondary battery, that is, a negative electrode containing an active material capable of storing and releasing Li ions. For example, as a negative electrode active material, carbon capable of storing and releasing lithium such as graphite, pyrolytic carbons, cokes, glassy carbons, calcined organic polymer compounds, mesocarbon microbeads (MCMB), and carbon fibers. One or a mixture of two or more of the system materials is used. In addition, simple substances containing elements such as Si, Sn, Ge, Bi, Sb, and In, compounds and alloys thereof; compounds that can be charged and discharged at a low voltage close to that of lithium metals such as lithium-containing nitrides or lithium-containing oxides; lithium metals. A lithium / aluminum alloy or the like can also be used as the negative electrode active material.

For the negative electrode, a negative electrode mixture obtained by appropriately adding a conductive auxiliary agent (carbon material such as carbon black, solid electrolyte, etc.) or a binder such as PVDF to the negative electrode active material is used as a core material of a molded body (negative electrode). A mixture layer) is used, or the above-mentioned various alloys or lithium metal foils are used alone or laminated on a current collector as a negative electrode agent layer.

When a current collector is used for the negative electrode, copper or nickel foil, punching metal, net, expanded metal, foamed metal, or the like can be used as the current collector.

When manufacturing a negative electrode having a negative electrode mixture layer, for example, a negative electrode mixture-containing paste or slurry in which a negative electrode active material, a binder, and a conductive auxiliary agent to be used as needed are dispersed in a solvent such as xylene. Can be applied to the current collector, dried, and then pressure-formed, such as by calendering, if necessary. As the solvent, a super dehydration solvent having a water content of 0.001% by mass (10 ppm) or less is preferably used.

When a conductive porous base material such as punching metal is used for the negative electrode current collector, for example, the negative electrode mixture-containing paste, slurry, or the like is filled in the pores of the conductive porous base material. After drying, the negative electrode can be manufactured by a method of pressure molding such as calendering if necessary. Since the negative electrode manufactured by such a method can secure a large strength, it is possible to hold a solid electrolyte-containing sheet having a larger area.

Further, instead of the above-mentioned negative electrode mixture-containing paste, slurry, etc., a negative electrode mixture containing a negative electrode active material, a binder, a conductive auxiliary agent, etc., and containing no solvent is placed in the pores of the conductive porous base material. The negative electrode may be manufactured by a method of filling by a dry method and, if necessary, performing pressure molding such as calendering.

<Exterior body>
As the material of the outer can and the sealing can constituting the outer body, for example, stainless steel or the like can be used. Further, polypropylene, nylon or the like can be used as the material of the gasket, and a heat-resistant resin having a melting point of more than 240 ° C. can be used when heat resistance is required in relation to the use of the battery. Examples of the heat-resistant resin include fluororesins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA); polyphenylene ether (PPE); polysulfone (PSF); polyallylate (PAR); and polyethersulfone (PES). ); Polyphenylene sulfide (PPS); Polyetheretherketone (PEEK) and the like can be used. Further, when the battery is applied to an application requiring heat resistance, a glass hermetic seal can be used for the sealing.

<Electrode body>
The positive electrode and the negative electrode can be used in the form of a laminated electrode body laminated via the solid electrolyte-containing sheet described above, or a wound electrode body obtained by winding the laminated electrode body.

When forming the laminated electrode body, the positive electrode, the negative electrode, and the solid electrolyte-containing sheet may be pressure-molded in a laminated state, and the interface between the positive electrode, the negative electrode, and the solid electrolyte-containing sheet may be joined and integrated. Further, instead of pressing and joining the positive electrode and the negative electrode and the solid electrolyte-containing sheet at once, one electrode and the solid electrolyte-containing sheet are joined first, and then the other side is placed on the opposite side of the solid electrolyte-containing sheet. The electrodes may be laminated and joined to form a laminated electrode body.

<Battery form>
The all-solid-state lithium secondary battery of the present embodiment has an outer body composed of an outer can, a sealing can, and a gasket as shown in FIG. 1, that is, generally a coin-type battery or a button-type battery. It is not limited to the so-called form, and for example, a can having an outer body made of a resin film or a metal-resin laminated film, a metal cylindrical or square tubular outer can, and an opening thereof. It may have an exterior body having a sealing structure for sealing.

(Manufacturing method of all-solid-state lithium secondary battery)
Next, an embodiment of the method for manufacturing an all-solid-state lithium secondary battery disclosed in the present application will be described. A preferred embodiment of the method for manufacturing an all-solid lithium secondary battery of the present embodiment is an electrode preparation step of preparing a positive electrode and a negative electrode and a solid electrolyte particle as an insulating porous base material as a manufacturing step of a laminated electrode body. A filling step of filling to prepare a solid electrolyte-containing sheet, a laminating step of laminating the positive electrode, the solid electrolyte-containing sheet, and the negative electrode in this order, and laminating the peripheral portion of the solid electrolyte-containing sheet. It is provided with a folding step of folding back to the outer peripheral side of one of the positive electrode or the negative electrode and covering the outer peripheral side surface portion of the positive electrode or the negative electrode with the peripheral edge portion of the solid electrolyte-containing sheet. Further, in the filling step, it is preferable to further fill the insulating porous base material with a binder.

By the above-mentioned method for manufacturing an all-solid-state lithium secondary battery, a laminated electrode body used for the all-solid-state lithium secondary battery disclosed above can be produced. After that, it may be housed in the above-mentioned exterior body by a usual method to form a closed structure.

Subsequently, a method for manufacturing the laminated electrode body will be described with reference to the drawings. However, the manufacturing method of the laminated electrode body is not limited to the manufacturing method shown below.

FIG. 2 is a cross-sectional view showing an example of a process of manufacturing a laminated electrode body of an all-solid-state lithium secondary battery. First, as shown in FIG. 2A, for example, the above-mentioned negative electrode 14, the solid electrolyte-containing sheet 16, and the positive electrode 15 are sequentially placed in the mold 20. At this time, the outer circumference of the solid electrolyte-containing sheet 16 is set to be larger than the outer circumference of the positive electrode 15. Further, the size of the negative electrode 14 is the same as that of the positive electrode 15. Next, as shown in FIG. 2B, by pressurizing the entire laminated negative electrode 14, the solid electrolyte-containing sheet 16 and the positive electrode 15 from above, the peripheral edge portion 16a of the solid electrolyte-containing sheet 16 is folded back toward the positive electrode 15. The peripheral edge portion 16a of the solid electrolyte-containing sheet 16 covers the outer peripheral side surface portion of the positive electrode 15, and the negative electrode 14, the solid electrolyte-containing sheet 16 and the positive electrode 15 are integrated. As a result, the laminated electrode body shown in FIG. 2C is obtained.

After that, if the laminated electrode body is housed in the outer body by a usual method to form a closed structure, an all-solid-state lithium secondary battery can be manufactured.

Hereinafter, the all-solid-state lithium secondary battery disclosed in the present application will be described in detail based on Examples. However, the following examples do not limit the all-solid-state lithium secondary battery disclosed in the present application.

(Example 1)
<Preparation of solid electrolyte-containing sheet>
Using xylene (“super-dehydrated” grade with a water content of 10 ppm or less) as the solvent, sulfide-based solid electrolyte (Li ₆ PS ₅ Cl) particles with an average particle diameter of 1 μm and acrylic resin binder (butyl-acrylic acid acrylate). The copolymer) was mixed with the above solvent at a mass ratio of 100: 3 and a solid content ratio of 40% by mass, and stirred with a sinky mixer for 10 minutes to prepare a uniform slurry. A PET non-woven fabric having a thickness of 38 μm and a basis weight of 8 g / m ² (“05TH-8” manufactured by Hirose Paper Co., Ltd.) was passed through this slurry, and then pulled up to apply the slurry to the PET non-woven fabric. Then, it was vacuum dried at 120 degreeC for 1 hour to obtain a solid electrolyte-containing sheet having a thickness of 50 μm. The thickness of the non-woven fabric in the produced solid electrolyte-containing sheet was 80% of the total thickness of the solid electrolyte-containing sheet. The proportion of the PET non-woven fabric in the solid electrolyte-containing sheet was 25% by volume, and the proportion of the binder was 2.9% by mass in the total mass of the solid electrolyte particles and the binder.

Finally, the produced solid electrolyte-containing sheet was punched into a circle having a diameter of 11 mm and used for producing a laminated electrode body.

<Preparation of positive electrode>
_{LiNi 0.6} Co _0.2 Mn _0.2 O ₂ with an average particle size of 3 μm in which an amorphous composite oxide of Li and Nb was formed on the surface using xylene (“ultra-dehydrated” grade with a water content of 10 ppm or less) as a solvent. , Sulfurized solid electrolyte (Li ₆ PS ₅ Cl) particles, carbon nanotubes as a conductive aid ["VGCF" (trade name) manufactured by Showa Denko Co., Ltd.], and acrylic resin binder (butyl acrylate-acrylic acid co-weight). The mixture) was mixed with the above solvent so that the mass ratio was 50:44: 3: 3 and the solid content ratio was 50% by mass, and the mixture was stirred with a sinky mixer for 10 minutes to prepare a uniform slurry. .. This slurry was applied onto an Al foil having a thickness of 20 μm using an applicator with a gap of 200 μm, and vacuum dried at 120 ° C. to obtain a positive electrode.

Finally, the produced positive electrode was punched into a circle having a diameter of 10 mm and used for producing a laminated electrode body.

<Manufacturing of negative electrode>
Using xylene (“super-dehydrated” grade with a water content of 10 ppm or less) as the solvent, graphite with an average particle diameter of 20 μm, sulfide-based solid electrolyte (Li ₆ PS ₅ Cl) particles, and acrylic resin binder (butyl acrylate). -Acrylic acid copolymer) with a mass ratio of 50:47: 3, mixed with the above solvent so that the solid content ratio is 50% by mass, and stirred with a sinky mixer for 10 minutes to make a uniform slurry. Was prepared. This slurry was applied onto a stainless steel foil having a thickness of 20 μm using an applicator with a gap of 200 μm, and vacuum dried at 120 ° C. to obtain a negative electrode.

Finally, the produced negative electrode was punched into a circle having a diameter of 10 mm and used for producing a laminated electrode body.

<Battery assembly>
First, as shown in FIG. 2A, the prepared negative electrode, solid electrolyte-containing sheet and positive electrode are placed in the mold so that the negative electrode mixture layer and the positive electrode mixture layer are arranged on the solid electrolyte-containing sheet side. bottom. At this time, the center point of the solid electrolyte-containing sheet and the center points of the negative electrode and the positive electrode were aligned and placed. Next, as shown in FIG. 2B, the peripheral portion of the solid electrolyte-containing sheet is pressed by pressing the entire laminated negative electrode, solid electrolyte-containing sheet, and positive electrode at ^{a pressure of 392 MPa (4 tf / cm 2) from above.} It was folded back to the positive electrode side to cover the outer peripheral side surface portion of the positive electrode with the peripheral edge portion of the solid electrolyte-containing sheet, and the negative electrode, the solid electrolyte-containing sheet and the positive electrode were integrated to obtain a laminated electrode body shown in FIG. 2C.

Finally, as shown in FIG. 1, the laminated electrode body was housed in a stainless steel exterior body to prepare an all-solid-state lithium secondary battery of Example 1.

(Comparative Example 1)
Solid electrolyte-containing sheet, positive electrode, a negative electrode, all punched into a circle having a diameter of 10 mm, laminated together respective center point, to produce a laminated electrode body is pressurized as a whole by a pressure of 392MPa (4tf / cm ^2). Finally, the all-solid-state lithium secondary battery of Comparative Example 1 was produced in the same manner as in Example 1.

<Evaluation of all-solid-state lithium secondary battery>
When the voltage of the prepared batteries of Example 1 and Comparative Example 1 was measured, 0.4 V was measured with the battery of Example 1, but the voltage could not be measured with Comparative Example 1. This is because in the laminated electrode body of Comparative Example 1, the solid electrolyte-containing sheet, the positive electrode, and the negative electrode are all formed to have the same size, and the solid electrolyte-containing sheet does not cover the outer peripheral side surface portion of the positive electrode or the negative electrode. It is probable that a short circuit occurred due to contact between the end portion and the outer peripheral end portion of the negative electrode. On the other hand, in the laminated electrode body of Example 1, the peripheral edge portion of the solid electrolyte-containing sheet is folded back toward the positive electrode side, and the peripheral edge portion of the solid electrolyte-containing sheet covers the outer peripheral side surface portion of the positive electrode. It is probable that the contact between the outer peripheral end portion and the outer peripheral end portion of the negative electrode was prevented and no short circuit occurred.

The all-solid-state lithium secondary battery disclosed in the present application can prevent short circuits from occurring at the outer peripheral ends of the positive electrode and the negative electrode even if the thickness of the solid electrolyte layer is reduced, and is a high-capacity, high-energy density all-solid-state lithium secondary battery. It can be preferably used as a power source for various electronic devices (particularly portable electronic devices such as mobile phones and notebook personal computers).

10 All-solid-state lithium secondary battery 11 Exterior can 12 Sealed can 13 Gasket 14 Negative electrode 15 Positive electrode 16 Solid electrolyte-containing sheet 16a Peripheral part 20 Mold

Claims (10)

An all-solid-state lithium secondary battery including a laminated electrode body including a positive electrode, a negative electrode, and a solid electrolyte-containing sheet arranged between the positive electrode and the negative electrode.
The solid electrolyte-containing sheet contains an insulating porous base material and a solid electrolyte filled in the insulating porous base material.
The peripheral portion of the solid electrolyte-containing sheet covers the outer peripheral side surface portion of the positive electrode or the negative electrode.
An all-solid-state lithium secondary battery characterized in that the thickness of the solid electrolyte-containing sheet is 5 to 200 μm. The all-solid-state lithium secondary battery according to claim 1, wherein the insulating porous base material is made of a non-woven fabric. The all-solid-state lithium secondary battery according to claim ² , wherein the non-woven fabric has a basis weight of 3 to 10 g / m 2. The all-solid-state lithium secondary battery according to any one of claims 1 to 3, wherein the entire surface of the insulating porous base material is covered with the solid electrolyte layer. The all-solid-state lithium secondary battery according to any one of claims 1 to 4, wherein the thickness of the insulating porous substrate is 3.5 to 195 μm. The all-solid-state lithium secondary battery according to any one of claims 1 to 5, wherein the solid electrolyte-containing sheet further includes a binder. The all-solid-state lithium secondary battery according to claim 6, wherein the content of the binder is 0.5 to 5% by mass with respect to the total mass of the solid electrolyte and the binder. The all-solid-state lithium secondary battery according to any one of claims 1 to 7, wherein the solid electrolyte has a particulate form and the average particle diameter of the solid electrolyte is 0.3 to 5 μm. The method for manufacturing an all-solid-state lithium secondary battery according to any one of claims 1 to 8.
The electrode preparation process for preparing the positive and negative electrodes,
A filling step of filling an insulating porous base material with solid electrolyte particles to prepare a solid electrolyte-containing sheet, and
A laminating step of laminating the positive electrode, the solid electrolyte-containing sheet, and the negative electrode in this order.
A folding step in which the peripheral edge portion of the solid electrolyte-containing sheet is folded back toward the outer peripheral side of one of the laminated positive electrode or the negative electrode, and the peripheral edge portion of the solid electrolyte-containing sheet covers the outer peripheral side surface portion of the positive electrode or the negative electrode. A method for manufacturing an all-solid-state lithium secondary battery, which comprises. The method for manufacturing an all-solid-state lithium secondary battery according to claim 9, wherein in the filling step, the insulating porous base material is further filled with a binder.

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