JP2020161277A - All-solid-state secondary battery and method for manufacturing the same - Google Patents

Abstract

To provide an all-solid-state secondary battery having excellent charge/discharge cycle characteristics under a high-temperature environment, and a method for manufacturing the same.SOLUTION: An all-solid-state secondary battery of the present invention includes an electrode laminate including a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer. The positive electrode active material layer, the negative electrode active material layer and the solid electrolyte layer each contain a sulfide-based solid electrolyte, the negative electrode active material layer contains a resin binder, and the positive electrode active material layer does not substantially contain a resin binder.SELECTED DRAWING: Figure 1

Description

The present invention relates to an all-solid-state secondary battery having excellent charge / discharge cycle characteristics in a high temperature environment, and a method for manufacturing the same.

In recent years, with the development of portable electronic devices such as mobile phones and notebook personal computers and the practical application of electric vehicles, small and lightweight secondary batteries with high capacity and high energy density are required. It has become to.

Currently, non-aqueous secondary batteries that can meet this demand, especially lithium ion secondary batteries, use lithium-containing composite oxides such as lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ) as the positive electrode active material. , Graphite or the like is used as the negative electrode active material, and an organic electrolytic solution containing an organic solvent and a lithium salt is used as the non-aqueous electrolyte.

With the further development of non-aqueous secondary batteries, there is a demand for longer life, higher capacity, and higher energy density of non-aqueous secondary batteries, as well as longer life and higher energy density. The reliability of non-aqueous secondary batteries with higher capacity and higher energy density is also highly required.

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

Under the above circumstances, an all-solid-state secondary battery that does not use an organic solvent has also been studied (Patent Document 1 and the like). The all-solid-state secondary battery uses a molded body of a solid electrolyte that does not use an organic solvent instead of the conventional organic solvent-based electrolyte, and has high reliability without the risk of abnormal heat generation of the solid electrolyte. ing.

In the all-solid secondary battery, as described in Patent Document 1, a binder is contained in a layer containing a positive electrode active material (positive electrode active material layer) and a layer containing a negative electrode active material (negative electrode active material layer). In general, this binder is used to improve the bondability between the components of these layers and the adhesiveness between these layers and adjacent layers (current collector and solid electrolyte layer). ing.

On the other hand, in Patent Document 2, the positive electrode active material layer and the negative electrode active material layer are heat-treated under specific conditions without containing a binder (binder), and these layers and the current collector are combined. A technique has also been proposed in which the use of a binder suppresses a decrease in capacity and an increase in internal resistance by increasing the adhesiveness.

JP-A-2018-125260 International Publication No. 2011/064842

It is expected that the range of application to all-solid-state secondary batteries will expand further in the future, and in response to this, the characteristics particularly expected of all-solid-state secondary batteries, specifically the charge / discharge cycle characteristics in high-temperature environments, etc. Is required to increase.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an all-solid-state secondary battery having excellent charge / discharge cycle characteristics in a high temperature environment, and a method for manufacturing the same.

The all-solid secondary battery of the present invention is interposed between the positive electrode active material layer containing the positive electrode active material, the negative electrode active material layer containing the negative electrode active material, and the positive electrode active material layer and the negative electrode active material layer. The positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer each contain a sulfide-based solid electrolyte, and the negative electrode active material layer contains a resin binder. It is characterized in that the positive electrode active material layer contains substantially no resin binder.

Further, the all-solid secondary battery of the present invention includes a step of forming a negative electrode active material layer using a composition for forming a negative electrode active material layer containing a negative electrode active material, a sulfide-based solid electrolyte, and a resin binder. Manufactured by a production method including a step of forming a positive electrode active material layer using a composition for forming a positive electrode active material layer containing a positive electrode active material and a sulfide-based solid electrolyte and substantially free of a resin binder. be able to.

According to the present invention, it is possible to provide an all-solid-state secondary battery having excellent charge / discharge cycle characteristics in a high-temperature environment and a method for manufacturing the same.

It is sectional drawing which shows typically an example of the all-solid-state secondary battery of this invention.

The all-solid secondary battery of the present invention has a positive electrode active material layer containing a positive electrode active material and a sulfide-based solid electrolyte, a negative electrode active material layer containing a negative electrode active material and a sulfide-based solid electrolyte, and a sulfide-based solid. It includes an electrode laminate containing an electrolyte and having a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer. That is, in the all-solid-state secondary battery of the present invention, the positive electrode is composed of a positive electrode active material layer, and the negative electrode is composed of a negative electrode active material layer.

In the all-solid-state secondary battery of the present invention, the negative electrode active material layer contains a resin binder, while the positive electrode active material layer does not substantially contain a resin binder.

By applying an electrode laminate having a positive electrode active material layer that does not contain a resin binder, the charge / discharge cycle characteristics of an all-solid secondary battery in a high temperature environment can be enhanced. The resin binder acts as a resistance component, and when it is contained in the positive electrode active material layer, it is presumed that the internal resistance of the positive electrode active material layer is increased especially in a high temperature environment, and that the action increases as charging and discharging are repeated. Therefore, by forming the positive electrode active material layer so as not to contain a resin binder, problems that may occur due to the resin binder can be avoided, and the charge / discharge cycle characteristics of the all-solid secondary battery in a high temperature environment can be improved. ..

For example, when the solid electrolyte layer adjacent to the positive electrode active material layer contains a resin binder, a part of the resin binder contained for the solid electrolyte layer is part of the positive electrode active material layer in the manufacturing process of the laminated electrode body. May move to. Therefore, in the present specification, the fact that the positive electrode active material layer does not "substantially" contain the resin binder means that the resin binder is inevitably mixed in the positive electrode active material layer as described above. This means that the positive electrode active material layer does not contain the positively added resin binder.

As described above, in the present invention, the positive electrode active material layer does not contain the resin binder, while the negative electrode active material layer contains the resin binder. This does not reduce the charge / discharge cycle characteristics even if the negative electrode active material layer contains a resin binder. On the other hand, the inclusion of the resin binder improves the shape retention of the laminated electrode body and is an all-solid state. Since the productivity and reliability of the secondary battery are increased, the charge / discharge cycle characteristics in a high temperature environment can be improved.

The positive electrode active material layer of the all-solid-state secondary battery contains a positive electrode active material and a sulfide-based solid electrolyte.

As the positive electrode active material, an active material capable of storing and releasing lithium ions, which is similar to that used in conventionally known lithium ion secondary batteries, can be used. Specifically, LiM ¹ _x Mn _2-x O ₄ (where M ¹ is Li, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Fe, Co, Ni, Cu, Al, Sn. , Sb, In, Nb, Mo, W, Y, Ru and Rh, at least one element selected from the group consisting of, and represented by 0.01 ≦ x ≦ 0.5). Oxide, Li _a Mn _(1-ba) Ni _b M ² _c O _2-d F _f (However, M ² is Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn. , Zr, Mo, Sn, Ca, Sr and W, at least one element selected from the group consisting of 0.8 ≦ a1.2, 0 <b <0.5, 0 ≦ c ≦ 0.5. , D + f <1, −0.1 ≦ d ≦ 0.2, 0 ≦ f ≦ 0.1), LiCo _1-g M ³ _g O ₂ (where M ³ is Al, Mg , Ti, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba, at least one element selected from the group consisting of 0 ≦ g ≦ 0.5). Represented lithium cobalt composite oxide, LiNi _1-h M ⁴ _h O ₂ (where M ⁴ is Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn , Sb and Ba, at least one element selected from the group consisting of LiM ⁵ _1-m N _m PO ₄ (where M), a lithium nickel composite oxide represented by 0 ≦ h ≦ 0.5). ⁵ is at least one element selected from the group consisting of Fe, Mn and Co, and N is Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn and Sb. At least one element selected from the group consisting of and Ba, an olivine-type composite oxide represented by 0 ≦ m ≦ 0.5), and a lithium titanium composite oxide represented by Li ₄ Ti ₅ O ₁₂ . Etc., and only one of these may be used, or two or more thereof may be used in combination.

Examples of the sulfide-based solid electrolyte in the positive electrode active material layer include Li ₂ S-P ₂ S ₃ , Li ₂ S-P ₂ S ₅ , Li ₂ S-P ₂ S _3- P ₂ S ₅ , and Li ₂ S-SiS. ₂ , LiI-Li ₂ S-P ₂ S ₅ , LiI-Li ₂ S-SiS _2- P ₂ S ₅ , Li ₂ S-SiS ₂ -Li ₄ SiO ₄ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₃ PS _4- Li ₄ GeS ₄ , Li _3.4 P _0.6 Si _0.4 S ₄ , Li _3.25 P _0.25 Ge _0.76 S ₄ , Li _4-x Ge _1-x P Examples thereof include _x S ₄ , Li ₇ P ₃ S _11, and only one of these may be used, or two or more thereof may be used in combination.

The positive electrode active material layer can contain a conductive auxiliary agent. Examples of the conductive auxiliary agent for the positive electrode active material layer include carbon materials such as carbon black.

The positive electrode active material layer is formed by using a composition for forming a positive electrode active material layer which contains a positive electrode active material and a sulfide-based solid electrolyte and substantially does not contain a resin binder. The composition for forming a positive electrode active material layer may contain a conductive auxiliary agent, if necessary.

The composition for forming a positive electrode active material layer may be a dry mixture (mixed powder) in which powders of each constituent material are mixed, or a wet type in which powders of each constituent material are dispersed in a solvent. It may be a composition such as a slurry of. The form of the composition is not particularly limited as long as it is a composition that does not substantially contain a resin binder.

When the composition for forming the positive electrode active material layer is a mixed powder, it is subjected to pressure treatment (on a substrate such as a current collector or on a solid electrolyte layer adjacent to the positive electrode active material layer in the electrode laminate). The positive electrode active material layer can be formed by compressing by pressing treatment) or the like. When the composition for forming the positive electrode active material layer is a wet composition, it is applied on a base material such as a current collector or on a solid electrolyte layer adjacent to the positive electrode active material layer in the electrode laminate. The positive electrode active material layer can be formed through a step of drying the material and applying a pressure treatment as needed.

When the composition for forming the positive electrode active material layer is a wet composition, it is preferable to select a solvent that does not easily deteriorate the sulfide-based solid electrolyte. Since sulfide-based solid electrolytes undergo a chemical reaction with a very small amount of water, non-polar aprotic solvents such as hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene are used. Is preferable. In particular, it is more preferable to use a super dehydration solvent having a water content of 0.001% by mass (10 ppm) or less. In addition, fluorosolvents such as "Bertrel (registered trademark)" manufactured by Mitsui Dupont Fluorochemical, "Zeorolla (registered trademark)" manufactured by Nippon Zeon, and "Novec (registered trademark)" manufactured by Sumitomo 3M, as well as , Dichloromethane, diethyl ether and other non-aqueous organic solvents can also be used.

As for the composition of the positive electrode active material layer, the content of the positive electrode active material is preferably 50 to 90% by mass, and the content of the sulfide-based solid electrolyte is preferably 10 to 50% by mass. When the positive electrode active material layer contains a conductive auxiliary agent, the content thereof is preferably 0.1 to 10% by mass.

The thickness of the positive electrode active material layer is preferably 30 μm to 3 mm.

The negative electrode active material layer of the all-solid-state secondary battery contains a negative electrode active material, a sulfide-based solid electrolyte, and a resin binder.

As the negative electrode active material, an active material capable of storing and releasing lithium ions, which is similar to that used in conventionally known lithium ion secondary batteries, can be used. Specifically, for example, lithium ions such as graphite, pyrolytic carbons, cokes, glassy carbons, calcined bodies of organic polymer compounds, mesocarbon microbeads (MCMB), and carbon fibers can be stored and released. One or a mixture of two or more carbon-based materials is used. In addition, simple compounds containing elements such as Si, Sn, Ge, Bi, Sb, and In, compounds and alloys thereof; compounds capable of charging and discharging at low voltages close to lithium metals such as lithium-containing nitrides or lithium-containing oxides; lithium metals. Lithium / aluminum alloys; can also be used as the negative electrode active material.

As the sulfide-based solid electrolyte in the negative electrode active material layer, the same sulfide-based solid electrolytes as those exemplified above that can be used in the positive electrode active material layer can be used.

Examples of the resin binder in the negative electrode active material layer include fluororesins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE); acrylic resins; imide-based binders; and amide-based binders.

The negative electrode active material layer can contain a conductive auxiliary agent. Examples of the conductive auxiliary agent for the negative electrode active material layer include carbon materials such as carbon black.

The negative electrode active material layer is formed by using a composition for forming a negative electrode active material layer containing a negative electrode active material, a sulfide-based solid electrolyte, and a resin binder. The composition for forming the negative electrode active material layer may contain a conductive auxiliary agent, if necessary, and is a wet composition in which a powder, an emulsion or a liquid of each constituent material is dispersed or dissolved in a solvent. (Slurry, paste, etc.), which is applied on a base material such as a current collector or on a solid electrolyte layer adjacent to the negative electrode active material layer in the electrode laminate, dried, and pressure-treated as necessary. The negative electrode active material layer can be formed through the step of applying.

As for the solvent used in the composition for forming the negative electrode active material layer, it is desirable to select a solvent that does not easily deteriorate the sulfide-based solid electrolyte, like the solvent used in the composition for forming the positive electrode active material layer. As the solvent for the layer-forming composition, it is preferable to use various solvents exemplified above, and it is particularly preferable to use a super-dehydrating solvent having a water content of 0.001% by mass (10 ppm) or less.

As for the composition of the negative electrode active material layer, for example, the content of the negative electrode active material is preferably 50 to 90% by mass, the content of the sulfide-based solid electrolyte is preferably 10 to 50% by mass, and the resin. The binder content is preferably 0.1 to 10% by mass. When the negative electrode active material layer contains a conductive auxiliary agent, the content thereof is preferably 0.1 to 10% by mass.

The thickness of the negative electrode active material layer is preferably 30 μm to 3 mm.

The solid electrolyte layer of the all-solid secondary battery contains a sulfide-based solid electrolyte. As the sulfide-based solid electrolyte in the solid electrolyte layer, the same sulfide-based solid electrolytes as those exemplified above that can be used in the positive electrode active material layer can be used.

The solid electrolyte layer can be formed substantially without containing a resin binder. In this case, since there is no resin binder that acts as a resistance component in the solid electrolyte layer, it is possible to avoid an increase in the internal resistance due to the resin binder, and further improvement in the discharge characteristics of the all-solid secondary battery can be expected. The term "substantially" as used herein means that the resin binder was positively added except when the resin binder was unavoidably mixed in from the adjacent negative electrode active material layer to the solid electrolyte layer. It means that the solid electrolyte layer does not contain the resin binder.

On the other hand, the solid electrolyte layer may contain a resin binder. In this case, since the resin binder of the solid electrolyte layer also has the same function as the resin binder of the negative electrode active material layer, further improvement in productivity and reliability of the all-solid secondary battery can be expected.

When the solid electrolyte layer contains a resin binder, the resin binder can be the same as the various resin binders exemplified above as those that can be used for the negative electrode active material layer.

When the solid electrolyte layer contains a resin binder, the solid electrolyte layer is formed by using a sulfide-based solid electrolyte and a composition for forming a solid electrolyte layer containing a resin binder. The composition for forming a solid electrolyte layer is a wet composition (slurry, paste, etc.) in which powders, emulsions, or liquids of each constituent material are dispersed or dissolved in a solvent, and the composition can be peeled off from the substrate. , It can be formed by applying it on the positive electrode active material layer or the negative electrode active material layer, drying it, and applying a pressure treatment if necessary.

Further, in the case of the solid electrolyte layer in a mode that does not contain the resin binder, the same wet composition as described above may be used except that the resin binder is not contained, and the solid electrolyte layer may be formed in the same step as described above. In addition, a powder containing a sulfide-based solid electrolyte (in the case where the solid electrolyte layer is composed of only the sulfide-based solid electrolyte, the powder of the sulfide-based solid electrolyte) is subjected to positive electrode activity on a peelable substrate. It may be formed by compression on the material layer or the negative electrode active material layer by a pressure treatment or the like.

As for the solvent used in the composition for forming the solid electrolyte layer, it is desirable to select a solvent that does not easily deteriorate the sulfide-based solid electrolyte, like the solvent used in the composition for forming the positive electrode active material layer. As the solvent for the forming composition, it is preferable to use various solvents exemplified above, and it is particularly preferable to use a super-dehydrating solvent having a water content of 0.001% by mass (10 ppm) or less.

As for the composition of the solid electrolyte layer, the content of the sulfide-based solid electrolyte is preferably 50% by mass or more. Since the solid electrolyte layer may be composed of only the sulfide-based solid electrolyte, the preferable upper limit value of the sulfide-based solid electrolyte in the solid electrolyte layer is 100% by mass. When the solid electrolyte layer contains a resin binder, the content thereof is preferably 0.1 to 10% by mass.

In the production of the electrode laminate, the positive electrode active material layer is first formed on a base material such as a current collector, then the solid electrolyte layer is formed on the positive electrode active material layer, and then the negative electrode activity is formed on the solid electrolyte layer. Each layer may be formed in the order of forming the material layer. That is, in the electrode laminate used for the all-solid secondary battery, a step of forming a positive electrode active material layer on a base material such as a current collector and a step of forming a solid electrolyte layer on the formed positive electrode active material layer. It can be produced by a method having a step of forming a negative electrode active material layer on the formed solid electrolyte layer [hereinafter, this method is referred to as "the first aspect of the method for producing an electrode laminate"]. When an electrode laminate having a plurality of positive electrode active material layers and negative electrode active material layers is obtained by this method, a solid electrolyte layer is formed on the formed negative electrode active material layer, and the positive electrode active material layer is formed on the solid electrolyte layer. The operation of forming, forming the solid electrolyte layer on the positive electrode active material layer after formation, and then forming the negative electrode active material layer on the solid electrolyte layer may be sequentially performed.

Further, first, the negative electrode active material layer is formed on a base material such as a current collector, then the solid electrolyte layer is formed on the negative electrode active material layer, and then the positive electrode active material layer is formed on the solid electrolyte layer. Each layer may be formed with. That is, in the electrode laminate used for the all-solid secondary battery, a step of forming a negative electrode active material layer on a base material such as a current collector and a step of forming a solid electrolyte layer on the formed negative electrode active material layer. It can be produced by a method having a step of forming a positive electrode active material layer on the formed solid electrolyte layer [hereinafter, this method is referred to as "a second aspect of a method for producing an electrode laminate"]. When an electrode laminate having a plurality of positive electrode active material layers and negative electrode active material layers is obtained by this method, a solid electrolyte layer is formed on the formed positive electrode active material layer, and a negative electrode active material layer is formed on the solid electrolyte layer. The operation of forming the solid electrolyte layer on the negative electrode active material layer after the formation and then forming the positive electrode active material layer on the solid electrolyte layer may be sequentially performed.

Further, the solid electrolyte layer may be formed in advance on a peelable base material, and the formed solid electrolyte layer may be peeled off from the base material to be used for producing an electrode laminate. For example, a positive electrode active material layer or a negative electrode active material layer is further formed on the solid electrolyte layer formed on the base material, and then the whole is peeled off from the base material and is located on the base material side of the solid electrolyte layer. The active material layer as the opposite electrode may be formed on the opposite surface.

In any of the above methods for producing the electrode laminate, the positive electrode active material layer, the solid electrolyte layer and the negative electrode active material layer may be formed by each of the methods described above.

Further, it is preferable to pressurize the entire electrode laminate after forming each layer constituting the electrode laminate, but particularly when the positive electrode active material layer is formed last, compression at the time of formation may result in the formation of the electrode laminate. The entire electrode laminate can be pressurized.

The negative electrode active material layer contains a resin binder as an essential component, and is superior in shape stability to the positive electrode active material layer that does not contain a resin binder. Therefore, in the production of the electrode laminate, the method of forming the negative electrode active material layer before the positive electrode active material layer, that is, the second aspect of the method for producing the electrode laminate is more than the first aspect. It is also possible to increase the productivity of the electrode laminate and, by extension, the productivity of the all-solid-state secondary battery.

The electrode laminate obtained as described above is housed in an exterior body to form an all-solid-state secondary battery.

FIG. 1 shows a drawing schematically showing a cross section of an example of an all-solid-state secondary battery of the present invention. In the all-solid-state secondary battery 1 shown in FIG. 1, the electrode laminate formed by laminating the positive electrode 10 and the negative electrode 20 with the solid electrolyte layer 30 interposed therebetween is formed between the outer can 40 and the sealing can 50. It is enclosed in an outer body (a flat outer body called a coin-shaped or button-shaped outer body) formed by a resin gasket 60 interposed therein. In the all-solid secondary battery 1 shown in FIG. 1, the sealing can 50 is fitted into the opening of the outer can 40 via the gasket 60, and the opening end of the outer can 40 is tightened inward. As a result, the gasket 60 comes into contact with the sealing can 50, so that the opening of the outer can 40 is sealed and the inside of the battery is sealed. Then, the upper surface of the negative electrode 20 in the drawing is electrically connected by contacting the inner surface of the sealing can 50 which also serves as the negative electrode terminal, and the lower surface of the positive electrode 10 in the drawing is in contact with the inner surface of the outer can 40 which also serves as the positive electrode terminal. It is electrically connected.

In the case of an exterior body composed of an exterior can and a sealing can, the shape may be polygonal (triangle, quadrangle, pentagon, hexagon, heptagon, octagon) in plan view, and circular or octagon in plan view. It may be oval.

Stainless steel cans can be used for the outer can and the sealing can. In addition, polypropylene, nylon, etc. can be used as the material of the gasket, and if heat resistance is required in relation to the application of the battery, tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), etc. can be used. Heat resistance of fluororesin, polyphenylene ether (PEE), polysulphon (PSF), polyallylate (PAR), polyethersulfon (PES), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), etc. with a melting point of more than 240 ° C. Resin can also be used. Further, when the battery is applied to an application requiring heat resistance, a glass hermetic seal can be used for the sealing.

Further, as the exterior body of the all-solid-state secondary battery, a resin film or a sheet-like exterior body composed of a metal laminate film in which a resin film and a metal film (aluminum foil or the like) are laminated can also be used.

The all-solid-state secondary battery of the present invention can be applied to the same applications as the conventionally known secondary batteries, but in addition to having a solid electrolyte layer instead of the organic electrolytic solution, a high temperature environment Since it has excellent charge / discharge cycle characteristics underneath, it can be preferably used in applications that may be exposed to high temperatures.

Hereinafter, the present invention will be described in detail based on Examples. However, the following examples do not limit the present invention.

Example 1
<Formation of electrode laminate>
Using xylene (“super dehydrated” grade) as the solvent, graphite with an average particle size of 20 μm, a sulfide-based solid electrolyte (Li ₆ PS ₅ Cl), and an acrylic resin binder were mixed in a mass ratio of 50:47: 3. The mixture was mixed so that the solid content ratio was 50%, and the mixture was stirred with a sinky mixer for 10 minutes to prepare a uniform slurry.

This slurry is applied onto a base material (SUS current collector foil) using an applicator with a gap of 200 μm, vacuum dried at 120 ° C., and then pressure-molded to perform negative electrode activity on the base material. A material layer was formed.

The integrated product of the base material and the negative electrode active material layer is punched to a size of 10 mmφ and placed in a mold for pressure molding, and 0.050 g of a sulfide-based solid electrolyte (Li ₆ ) is placed on the negative electrode active material layer. PS ₅ Cl) was added and pressure molding was performed under the condition of 3 tons / cm ² , and a solid electrolyte layer was formed on the negative electrode active material layer.

LiNi _0.6 Co _0.2 Mn _0.2 O ₂ with an average particle size of 3 μm, a sulfide solid electrolyte (Li ₆ PS ₅ Cl), and carbon nanotubes as a conductive auxiliary agent [“VGCF” manufactured by Showa Denko Co., Ltd. (Product name)] was mixed at a mass ratio of 55:40: 5 to obtain a mixed powder for forming a positive electrode active material layer.

A positive electrode active material layer was formed by putting 0.020 g of the mixed powder onto the solid electrolyte layer in the mold for pressure molding and performing pressure molding under the condition of 10 tons / cm ² . Then, this was taken out from a mold, and an electrode laminated body was obtained. In the obtained electrode laminate, the thickness of each layer was a negative electrode active material layer: 200 μm, a solid electrolyte layer: 300 μm, and a positive electrode active material layer: 200 μm.

<Battery assembly>
The electrode laminate is laminated on the inner bottom surface of the stainless steel sealing can so that the current collector (SUS current collector foil) of the negative electrode is in contact with the inner bottom surface, and the Al current collector foil is further placed on the positive electrode of the electrode laminate. After arranging on the active material layer, it is covered with an outer can made of stainless steel and sealed, so that the upper and lower surfaces of the electrode laminate have negative electrode and positive electrode current collecting foils, respectively, as in FIG. A coin-shaped all-solid-state secondary battery having the above structure was manufactured.

Comparative Example 1
<Positive electrode active material layer>
Using xylene (“ultra-dehydrated” grade) as the solvent, 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. , Sulfurized solid electrolyte (Li ₆ PS ₅ Cl), carbon nanotubes as conductive aid ("VGCF" (trade name) manufactured by Showa Denko Co., Ltd.], and acrylic resin binder in a mass ratio of 50:44: 3. The ratio was 3, and the mixture was mixed with the solvent so that the solid content ratio was 50%, and stirred with a sinky mixer for 10 minutes to prepare a uniform slurry. This slurry was placed on a substrate (Al current collector foil). Was coated with an applicator, vacuum-dried at 120 ° C., and then pressure-molded to form a positive electrode active material layer.

<Solid electrolyte layer>
Using xylene (“ultra-dehydrated” grade) as the solvent, a sulfide-based solid electrolyte (Li ₆ PS ₅ Cl) with an average particle diameter of 1 μm, an acrylic resin binder, and a dispersant were mixed in a mass ratio of 100: 3: 1. The solvent was mixed with the above solvent so that the solid content ratio was 40%, and the mixture was stirred with a sinky mixer for 10 minutes to prepare a uniform slurry. This slurry was applied onto a base material (SUS foil) for peeling using an applicator, vacuum dried at 120 ° C., and then pressure-molded to form a solid electrolyte layer.

<Assembly of electrode laminate>
The negative electrode active material layer formed on the base material in the same manner as in Example 1, the positive electrode active material layer and the solid electrolyte layer were all punched to a size of 10 mmφ, and the solid electrolyte layer was peeled off from the base material. Al collector foil / positive electrode active material layer-solid electrolyte layer-negative electrode active material layer / SUS current collector foil are stacked in this order between the upper and lower pins made of SUS, placed in a cylinder made of SUS, and pressurized at 10 tons / cm ^2. As a result, an electrode laminate was obtained.

<Battery assembly>
A coin-type all-solid-state secondary battery was produced in the same manner as in Example 1 except that the electrode laminate was used.

Comparative Example 2
Graphite having an average particle diameter of 20 μm and a sulfide-based solid electrolyte (Li ₆ PS ₅ Cl) were mixed at a mass ratio of 50:50 to obtain a mixed powder.

A base material (SUS current collector foil) is punched into a mold for pressure molding to 10 mφ, 0.02 g of the mixed powder is put therein, and pressure molding is performed under the condition of 10 tons / cm ^2. This was done to form a negative electrode active material layer on the substrate.

A solid electrolyte layer and a positive electrode active material layer were sequentially formed on the negative electrode active material layer in the same manner as in Example 1 to obtain an electrode laminate. Then, a coin-shaped all-solid-state secondary battery was produced in the same manner as in Example 1 except that this electrode laminate was used.

The charge / discharge cycle characteristics of the coin-shaped all-solid-state secondary batteries of Examples and Comparative Examples were evaluated in a high temperature environment by the following method.

Each battery is charged with a constant current at a current value of 0.1 C until the voltage reaches 4.2 V under an environment of 100 ° C., and then at a voltage of 4.2 V until the current value reaches 0.05 C. The voltage was charged, and a constant current was discharged until the voltage became 2.7 V at a current value of 0.1 C, and the first cycle was charged and discharged (first charge and discharge). After that, constant current / constant voltage charging under the same conditions as above except that the current value during constant current charging was changed to 1C, and constant current discharge under the same conditions as above except that the current value was changed to 1C. The charge / discharge cycle, which is one cycle, is executed 100 cycles counting from the first charge / discharge, and the charge / discharge cycle characteristics are evaluated by the ratio of the discharge capacity of the 100th cycle to the discharge capacity of the second cycle (capacity retention rate). did. The results are shown in Table 1.

The battery of Example 1 in which the positive electrode active material layer did not contain the resin binder and the negative electrode active material layer contained the resin binder had a high capacity retention rate and excellent charge / discharge cycle characteristics.

On the other hand, the battery of Comparative Example 1 in which the resin binder was contained in both the positive electrode active material layer and the negative electrode active material layer resulted in a significant decrease in charge / discharge cycle characteristics. Further, the battery of Comparative Example 2 in which neither the positive electrode active material layer nor the negative electrode active material layer contained the resin binder was inferior in shape retention of the electrode laminate, and was charged and discharged as compared with the battery of Example 1. The cycle characteristics were inferior.

1 All-solid-state secondary battery 10 Positive electrode 20 Negative electrode 30 Solid electrolyte layer 40 Exterior can 50 Sealed can 60 Gasket

Claims (4)

An electrode laminate having a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer. It is an all-solid secondary battery equipped with
The positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer each contain a sulfide-based solid electrolyte.
An all-solid-state secondary battery, wherein the negative electrode active material layer contains a resin binder, and the positive electrode active material layer does not substantially contain a resin binder. The all-solid-state secondary battery according to claim 1, wherein the solid electrolyte layer contains a resin binder. The all-solid-state secondary battery according to claim 1, wherein the solid electrolyte layer does not substantially contain a resin binder. The method for manufacturing an all-solid-state secondary battery according to any one of claims 1 to 3.
A step of forming a negative electrode active material layer using a composition for forming a negative electrode active material layer containing a negative electrode active material, a sulfide-based solid electrolyte, and a resin binder.
An all-solid-state battery characterized by having a step of forming a positive electrode active material layer using a composition for forming a positive electrode active material layer containing a positive electrode active material and a sulfide-based solid electrolyte and not containing a resin binder. How to manufacture the next battery.

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