JP2020149867A - All-solid-state lithium secondary battery and manufacturing method therefor - Google Patents

Abstract

To provide an all-solid-state lithium secondary battery having a high energy density and a manufacturing method therefor.SOLUTION: An all-solid-state lithium secondary battery of the present invention has an electrode laminate in which every multiple layers of positive electrodes and negative electrodes are alternately laminated via a solid electrolyte layer, end portions of the positive electrodes are provided with a positive electrode conductive connection portion for electrically connecting the positive electrodes, end portions of the negative electrodes are provided with a negative electrode conductive connection portion for electrically connecting the negative electrodes, the positive electrode conductive connection portion and the negative electrode conductive connection portion contain at least particulate conductive material, the solid electrolyte layers are connected at the ends thereof by a solid electrolyte connection portion containing solid electrolyte, and the solid electrolyte connection portions are arranged between the positive electrode conductive connection portion and the end portion of the negative electrode, and between the negative electrode conductive connection portion and the end portion of the positive electrode, respectively.SELECTED DRAWING: Figure 1

Description

The present invention relates to a high energy density all-solid-state lithium secondary battery 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.

For example, Patent Document 1 proposes to construct a flat secondary battery by using a plurality of positive electrodes and a plurality of negative electrodes, respectively, and using an electrode laminate formed by stacking these with a separator interposed therebetween. ..

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 Documents 2 and 3 and the like). The all-solid-state secondary battery uses a molded body of a solid electrolyte instead of the conventional organic solvent-based electrolyte, and has high reliability without the risk of abnormal heat generation or ignition of the electrolyte.

Japanese Unexamined Patent Publication No. 2012-64366 JP-A-2017-40531 Japanese Unexamined Patent Publication No. 2017-168387

By the way, since the all-solid-state secondary battery does not use an organic electrolytic solution, it is possible to form all the power generation elements by printing, and the shape of each component can be given a degree of freedom.

However, for example, when an all-solid-state secondary battery is formed by using a plurality of positive electrodes and a plurality of negative electrodes and using an electrode laminate formed by stacking them with a solid electrolyte layer interposed therebetween, the positive electrodes are placed inside the exterior. Since it is necessary to secure a certain amount of space so that the tabs that connect the electrodes and the negative electrodes do not come into contact with the counter electrode and cause a short circuit, in order to reduce the total volume of the electrode laminate as much as possible and achieve high energy density. , It was necessary to devise the arrangement of each component.

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 lithium secondary battery having a high energy density and a method for producing the same.

The all-solid-state lithium secondary battery of the present invention has an electrode laminate in which a plurality of positive electrodes and a negative electrode are alternately laminated via a solid electrolyte layer, and the positive electrodes are electrically connected to each other at the end of the positive electrode. A positive electrode conductive connection portion is provided, and a negative electrode conductive connection portion for electrically connecting the negative electrodes is provided at an end portion of the negative electrode, and the positive electrode conductive connection portion and the negative electrode conductive connection portion are at least particles. The solid electrolyte layers are connected at the ends by the solid electrolyte connecting portion containing the solid electrolyte, and are connected between the positive electrode conductive connecting portion and the end of the negative electrode, and the negative electrode. It is characterized in that the solid electrolyte connecting portion is arranged between the conductive connecting portion and the end portion of the positive electrode, respectively.

The all-solid-state lithium secondary battery of the present invention has, for example, a negative electrode and a part of the negative electrode conductive connection, or a part of the negative electrode and the negative electrode conductive connection, a part of the positive electrode conductive connection, and a solid electrolyte connection. A layer (a) having a part of a portion, a solid electrolyte layer, a layer (b) having a part of a positive electrode conductive connection portion and / or a part of a negative electrode conductive connection portion, and a positive electrode and a positive electrode conductive connection portion. The positive electrode and the negative electrode are laminated with a layer (c) having a part of the positive electrode, a part of the positive electrode conductive connection part, a part of the negative electrode conductive connection part, and a part of the solid electrolyte connection part. However, the positive electrode is formed through a step of forming an electrode laminate in which a plurality of layers are alternately laminated via a solid electrolyte layer, and a step of applying a positive electrode forming composition containing a positive electrode active material and a solvent. Then, the negative electrode is formed through a step of applying a negative electrode forming composition containing a negative electrode active material and a solvent, and a solid electrolyte layer-forming composition and a solid electrolyte connecting portion forming composition containing a solid electrolyte and a solvent are formed. After forming the solid electrolyte layer and the solid electrolyte connecting portion, and applying a conductive connecting portion forming composition containing a particulate conductive material and a solvent, the positive electrode conductive connecting portion is formed. And, it can be manufactured by the manufacturing method of the present invention characterized by forming the negative electrode conductive connection portion.

According to the present invention, it is possible to provide an all-solid-state lithium secondary battery having a high energy density and a method for producing the same.

It is a drawing which shows an example of the cross section of the all-solid-state lithium secondary battery of this invention schematically. It is explanatory drawing of the manufacturing method of the all-solid-state lithium secondary battery of this invention. It is explanatory drawing of the manufacturing method of the all-solid-state lithium secondary battery of this invention. It is explanatory drawing of the manufacturing method of the all-solid-state lithium secondary battery of this invention. It is explanatory drawing of the manufacturing method of the all-solid-state lithium secondary battery of this invention. It is a top view which shows typically the electrode which concerns on the battery of the comparative example.

The all-solid-state lithium secondary battery of the present invention has an electrode laminate in which a plurality of positive electrodes and negative electrodes are alternately laminated via a solid electrolyte layer, and the positive electrodes are electrically connected to the ends of the positive electrodes. A positive electrode conductive connection portion is provided, and a negative electrode conductive connection portion for electrically connecting the negative electrodes is provided at the end of the negative electrode. The solid electrolyte layers are connected at the ends by the solid electrolyte connecting portion containing the solid electrolyte, and are connected between the positive electrode conductive connecting portion and the negative electrode end, and the negative electrode conductive connecting portion and the positive electrode end. A solid electrolyte connection portion is arranged between the two.

FIG. 1 shows a drawing schematically showing an example of a vertical cross section of the all-solid-state lithium secondary battery of the present invention. In the all-solid-state lithium secondary battery 1 shown in FIG. 1, a plurality of positive electrodes 5 and a plurality of negative electrodes 6 are alternately laminated via a solid electrolyte layer 7 to form an electrode laminate. Is sealed in the outer body formed by the outer can 2, the sealing can 3, and the resin gasket 4 interposed between them. In the all-solid-state lithium secondary battery 1, the sealing can 3 is fitted into the opening of the outer can 2 via the gasket 4, and the opening end of the outer can 2 is tightened inward, whereby the gasket is used. When the 4 comes into contact with the sealing can 3, the opening of the outer can 4 is sealed and the inside of the battery has a sealed structure.

The positive electrode 5 has a positive electrode conductive connection portion 51 at its end, and the positive electrodes 5 constituting the electrode laminate are electrically connected to each other by the positive electrode conductive connection portion 51. Further, the negative electrode 6 also has a negative electrode conductive connection portion 61 at its end, and the negative electrodes 6 constituting the electrode laminate are electrically connected by the negative electrode conductive connection portion 61. The positive electrode conductive connection portion 51 and the negative electrode conductive connection portion 61 are, for example, layered ones containing a particulate conductive material.

Further, the solid electrolyte layers 7 arranged between the positive electrode 5 and the negative electrode 6 are connected at the end by the solid electrolyte connecting portion 71 containing the solid electrolyte, and the positive electrode conductive connecting portion 51 and the negative electrode 6 are connected to each other. A solid electrolyte connecting portion 71 is arranged between the negative electrode conductive connecting portion 61 and the positive electrode 6, respectively.

In the electrode laminate according to the all-solid-state lithium secondary battery of the present invention, the positive electrodes are connected to each other at the positive electrode conductive connection portion containing the conductive material, and the negative electrodes are connected to each other at the negative electrode conductive connection portion containing the conductive material. A solid electrolyte connecting portion for connecting the solid electrolyte layers is interposed between the connecting portion and the negative electrode and between the negative electrode conductive connecting portion and the positive electrode. Therefore, the direct contact between the positive electrode conductive connection portion and the negative electrode and the direct contact between the negative electrode conductive connection portion and the positive electrode are prevented by the solid electrolyte connection portion, so that the occurrence of a short circuit due to the contact can be satisfactorily suppressed. .. Moreover, the positive electrode conductive connection portion and the negative electrode conductive connection portion can be formed into a layered structure containing a particulate conductive material. Therefore, it is easy to form the positive electrode conductive connection portion and the negative electrode conductive connection portion in close contact with the solid electrolyte connection portion interposed between the positive electrode and the counter electrode.

Therefore, in the all-solid-state lithium secondary battery of the present invention, it is generally adopted for connecting the positive electrodes and the negative electrodes in a normal battery including an electrode laminate having a plurality of positive electrodes and a plurality of negative electrodes. Compared with the case of using a metal foil or the like, a space for preventing contact between the conductive connection portion of one electrode and the other electrode in the exterior body (battery container) becomes unnecessary. This makes it possible to increase the energy density of the all-solid-state lithium secondary battery of the present invention.

As the positive electrode of the all-solid-state lithium secondary battery, a positive electrode mixture containing a positive electrode active material formed into layers can be used.

Examples of the positive electrode active material include LiM _x Mn _2-x O ₄ (where M is Li, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Fe, Co, Ni, Cu, Al, Sn, It is at least one element selected from the group consisting of Sb, In, Nb, Mo, W, Y, Ru and Rh, and is a spinel type lithium manganese composite oxidation represented by 0.01 ≦ x ≦ 0.5). _{things, Li x Mn (1-y} -x) Ni y M z O (2-k) F l ( although, M is, Co, Mg, Al, B , Ti, V, Cr, Fe, Cu, Zn, At least one element selected from the group consisting of Zr, Mo, Sn, Ca, Sr and W, 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) and a lithium titanium composite oxide represented by Li ₄ Ti ₅ O ₁₂ . Only one of these may be used, or two or more thereof may be used in combination.

The positive electrode mixture usually contains a solid electrolyte or a conductive auxiliary agent, and if necessary, a binder.

As the solid electrolyte contained in the positive electrode mixture, the same solid electrolyte as that contained in the solid electrolyte layer described later can be used. Further, when the positive electrode mixture contains a conductive auxiliary agent (a conductive auxiliary agent other than a solid electrolyte), a carbon material such as carbon black can be used as the conductive auxiliary agent. Further, when the positive electrode mixture contains a binder, for example, an acrylic polymer or a fluororesin such as polyvinylidene fluoride (PVDF) can be used as the binder.

When producing a positive electrode, for example, a positive electrode forming composition (paste, slurry, etc.) in which a positive electrode active material, a solid electrolyte or a conductive auxiliary agent, and a binder are dispersed in a solvent is used as a base material or a solid electrolyte layer. A method can be adopted in which the coating is applied on the surface, dried, and then pressure-formed, such as by pressing, if necessary.

The composition of the positive electrode mixture of the positive electrode is, for example, preferably 50 to 90% by mass of the positive electrode active material, 0.1 to 10% by mass of the conductive auxiliary agent, and 0.1 to 1% by mass of the binder. It is preferably 10% by mass, and when a solid electrolyte is used, the solid electrolyte is preferably 10 to 50% by mass. Further, the thickness of the positive electrode is preferably 30 to 200 μm.

The negative electrode of the all-solid lithium secondary battery includes a negative electrode active material, and if necessary, a solid electrolyte or a conductive auxiliary agent (a conductive auxiliary agent other than the solid electrolyte, such as a carbon material such as carbon black), PVDF, etc. A layered negative electrode mixture to which a binder or the like is appropriately added can be used.

As the negative electrode active material, for example, lithium such as graphite, thermally decomposed carbons, cokes, glassy carbons, calcined 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.

When manufacturing a negative electrode having a negative electrode mixture layer, for example, a negative electrode forming composition (paste) in which a negative electrode active material, a solid electrolyte used as necessary, a conductive auxiliary agent, a binder, etc. are dispersed in a solvent. , Slurry, etc.) is applied onto the base material or the solid electrolyte layer, dried, and then pressure-formed, such as by pressing, if necessary.

The positive electrode conductive connection portion of the positive electrode and the negative electrode conductive connection portion of the negative electrode contain particulate conductive materials, and for example, these particulate conductive materials can be formed into a layered form bound by a binder.

As the particulate conductive material that can be used for the positive electrode conductive connection and the negative electrode conductive connection, graphite (natural graphite; thermally decomposed carbons, mesophase carbon microbeads, carbon fibers and other easily graphitized carbon is graphite at 2800 ° C or higher. Chemicalized artificial graphite; etc.), thermally decomposed carbons, cokes, glassy carbons, calcined organic polymer compounds, mesophase carbon microbeads, particles of carbon materials such as activated carbon (carbon particles); Ti, Fe , Ni, Cu, Mo, Ta, W and other metals, and particles (metal particles) composed of alloys of these metals.

The binder that can be used for the positive electrode conductive connection and the negative electrode conductive connection is the same as the binder used for the positive electrode mixture layer and the negative electrode mixture layer of non-aqueous secondary batteries such as ordinary lithium ion secondary batteries. More specifically, fluororesins [PVDF, polytetrafluoroethylene (PTFE), etc.], styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyvinylpyrrolidone (PVP), acrylic resins (polyacrylic). Acid ester) and the like can be exemplified.

The positive electrode conductive connection portion and the negative electrode conductive connection portion may have the same configuration, or may have different configurations such as using different conductive materials or binders.

The composition of the positive electrode conductive connection portion and the negative electrode conductive connection portion is not particularly limited as long as the positive electrodes and the negative electrodes can be electrically connected to each other, but usually the content of the particulate conductive material is high. It is 85 to 99% by mass, and when a binder is used, its content is 1 to 15% by mass. The thickness of the positive electrode conductive connection portion and the negative electrode conductive connection portion is also not particularly limited, but may be a thickness that can sufficiently secure conductivity, and is usually about 5 to 200 μm.

For the positive electrode conductive connection portion and the negative electrode conductive connection portion, for example, a composition for forming a conductive connection portion (paste, slurry, etc.) in which a particulate conductive material and a binder are dispersed in a solvent is applied to the formation portion of the conductive connection portion. After being applied and dried, it can be formed by performing pressure molding such as press treatment if necessary.

As the solid electrolyte constituting the solid electrolyte layer of the all-solid-state lithium secondary battery, a hydride-based solid electrolyte, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, etc. can be used, and only one of these can be used. Also, two or more types may be used in combination.

Specific examples of the hydride-based solid electrolyte include a solid solution of LiBH ₄ , LIBH ₄ and the following alkali metal compound (for example, one having a molar ratio of LiBH ₄ to the alkali metal compound of 1: 1 to 20: 1). Can be mentioned. Examples of the alkali metal compound in the solid solution include lithium halide (LiI, LiBr, LiF, LiCl, etc.), rubidium halide (RbI, RbBr, RbiF, RbCl, etc.), and cesium halide (CsI, CsBr, CsF, CsCl, etc.). , At least one selected from the group consisting of lithium amide, rubidium amide and cesium amide.

Specific examples of the sulfide-based solid electrolyte 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 , Li ₂ S-SiS ₂ , LiI-Li ₂ SP 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 _x S ₄ , Li ₇ P ₃ S _{11 and the} like can be mentioned.

Specific examples of the oxide-based solid electrolyte include Li ₇ La ₃ Zr ₂ O ₁₂ , LiTi (PO ₄ ) ₃ , LiGe (PO ₄ ) ₃ , and LiLaTIO ₃ .

For the solid electrolyte layer, a composition for forming a solid electrolyte layer prepared by dispersing a solid electrolyte in a solvent is applied onto a base material, a positive electrode, and a negative electrode, dried, and if necessary, pressure molding such as press treatment is performed. It can be formed by doing.

As the solvent used in the composition for forming the solid electrolyte layer, it is preferable to select a solvent that does not easily deteriorate the solid electrolyte. In particular, sulfide-based solid electrolytes and hydride-based solid electrolytes cause chemical reactions 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 preferable to use a non-polar aprotic solvent. The solvent is preferably dehydrated, and the water content is preferably 0.01% (100 ppm) or less, more preferably 0.005% (50 ppm) or less in terms of mass ratio. It is particularly preferably 0.001% (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.

Further, as the solvent for the positive electrode forming composition, the negative electrode forming composition, and the conductive connecting portion forming composition, it is preferable to select a solvent that does not easily deteriorate the solid electrolyte, and the solid electrolyte layer forming composition. It is desirable to use the same solvents as those exemplified above as those that can be used in.

The thickness of the solid electrolyte layer is preferably 10 to 200 μm.

The solid electrolyte connection portion contains a solid electrolyte, and examples of the solid electrolyte include various solid electrolytes exemplified above as those that can form a solid electrolyte layer. The composition of the solid electrolyte connection portion may be the same as or different from that of the solid electrolyte layer, but it is more preferable that the composition is the same in consideration of battery productivity and the like.

The solid electrolyte connecting portion connecting each solid electrolyte layer in the electrode laminate is a step of applying a composition for forming a solid electrolyte connecting portion containing a solid electrolyte and a solvent to the formed portion of the solid electrolyte connecting portion and drying the composition. Can be formed through. As the solvent of the composition for forming the solid electrolyte connection portion, it is preferable to use the same solvent as the various solvents exemplified above as those that can be used for the composition for forming the solid electrolyte layer.

Further, when the solid electrolyte connecting portion has the same composition as the solid electrolyte layer, the solid electrolyte connecting portion may be formed by using the composition for forming the solid electrolyte layer.

The thickness of the solid electrolyte connection portion is not particularly limited, but is usually 10 to 1000 μm.

When manufacturing an all-solid lithium secondary battery, it has a negative electrode and a part of the negative electrode conductive connection, or a part of the negative electrode and the negative electrode conductive connection, a part of the positive electrode conductive connection, and a solid electrolyte connection. A layer (a) having a part of the positive electrode, a solid electrolyte layer, a layer (b) having a part of the positive electrode conductive connection portion and / or a part of the negative electrode conductive connection portion, and a positive electrode and a positive electrode conductive connection portion. The positive electrode and the negative electrode are laminated by laminating a layer (c) having a part of the positive electrode, a part of the positive electrode conductive connection portion, a part of the negative electrode conductive connection portion, and a part of the solid electrolyte connection portion. However, it is preferably produced by the production method of the present invention, which comprises a step of forming an electrode laminate in which a plurality of layers are alternately laminated via a solid electrolyte layer.

In the production method, the positive electrode is formed through a step of applying a positive electrode forming composition containing a positive electrode active material and a solvent, and the negative electrode forming composition containing a negative electrode active material and a solvent is applied. Through the steps of forming a negative electrode and applying a solid electrolyte layer forming composition and a solid electrolyte connecting portion forming composition containing a solid electrolyte and a solvent, the solid electrolyte layer and the solid electrolyte connecting portion are formed, and particles are formed. The positive electrode conductive connection portion and the negative electrode conductive connection portion are formed through a step of applying a composition for forming a conductive connection portion containing a conductive material and a solvent.

With the above method, the all-solid-state lithium secondary battery of the present invention can be produced with higher productivity.

The details of the process of forming the electrode laminate in the manufacturing method of the present invention will be described below with reference to the drawings. 2 to 5 are explanatory views of an example of the method for manufacturing the all-solid-state lithium secondary battery of the present invention, and the numbers in parentheses shown in FIGS. 2 to 5 mean the order of the steps of manufacturing the electrode laminate. are doing. Further, among the drawings shown with numbers in parentheses in FIGS. 2 to 5, the left side [in each figure (i)] is a plan view, and the right side [in each figure (ii)] is a cross section. The figures are shown respectively.

2 to 5 show a case where the layer (a), the layer (b), and the layer (c) are formed in this order in the manufacturing method of the present invention to prepare an electrode laminate.

First, a negative electrode 6 and a negative electrode conductive connecting portion 61 provided at the end of the negative electrode 6 are formed on a base material (for example, a negative electrode current collector 62) to form a layer (a) [(1) in FIG. ), (2) and (3) in FIG. When forming the negative electrode conductive connection portion 61 in the layer (a), the portion of the negative electrode conductive connection portion 61 in the layer (b) provided on the upper side in the drawing of the layer (a) can be formed at the same time.

It is preferable that the side surface of the electrode laminate included in the all-solid-state lithium secondary battery is included in the solid electrolyte (solid electrolyte layer 7) as shown in FIG. 1, and in this case, in FIG. 2 (3). As shown, the solid electrolyte layer 7 is formed on the outer peripheral portion of the layer (a).

Next, a layer (b) having a solid electrolyte layer 7 and a part of the negative electrode conductive connection portion 61 is formed on the layer (a) [FIG. 3 (4)].

Subsequently, on the layer (b), a layer (c) having a positive electrode 5, a part of the positive electrode conductive connection portion 51, a part of the negative electrode conductive connection portion 61, and a part of the solid electrolyte connection portion 71 is formed [c]. 4 (5), (6) and 5 (7). However, FIG. 5 (7) shows a state in which a layer (b) is further formed on the layer (c) formed in this procedure. ]. In this case, for example, the positive electrode 5 is formed on the layer (b) [(5) in FIG. 4], and then the positive electrode conductive connection portion 51 (a part thereof) is formed at the end of the positive electrode 5 [FIG. 4]. Along with the middle (6)], a negative electrode conductive connection 61 (a part thereof) is formed on the negative electrode conductive connection 61 of the layer (b), followed by the positive electrode 5, the positive electrode conductive connection 51, and the negative electrode conductive connection 61. The layer (c) can be formed by the procedure of forming the solid electrolyte layer 7 and the solid electrolyte connecting portion 71 [(7) in FIG. 5] on the outer periphery of the solid electrolyte layer 7. Although not shown in FIG. 5 (7), in this procedure, the solid electrolyte layer 7 may be formed on the outer periphery of the negative electrode conductive connection portion 61 in addition to the outer circumference of the positive electrode conductive connection portion 51.

Subsequently, a layer (b) having a solid electrolyte layer 7 and a part of the positive electrode conductive connection portion 51 and a part of the negative electrode conductive connection portion 61 is formed on the layer (c) [(7) in FIG. 5). ]. In this procedure, for example, the positive electrode conductive connection portion 51 (a part thereof) is formed on the positive electrode conductive connection portion 51 of the layer (c), and the negative electrode conductive connection portion 61 (a part thereof) is formed on the negative electrode conductive connection portion 61. Is subsequently formed, and then the solid electrolyte layer 7 is formed so as to leave the upper surfaces of the formed positive electrode conductive connection portion 51 and negative electrode conductive connection portion 61.

FIG. 5 (8) shows a layer having a negative electrode 6, a part of the positive electrode conductive connection portion 51, a part of the negative electrode conductive connection part 61, and a part of the solid electrolyte connection part 71 on the layer (b). It shows up to the middle of the process of forming (a). After that, the layer (a) is completed, and if necessary, the layers (b), the layer (c), the layer (a), and so on are sequentially formed to prepare an electrode laminate. ..

As shown in FIGS. 2 (1) to (3), the layer (a) having the outermost negative electrode of the electrode laminate is a part of the negative electrode conductive connection portion (more preferably a solid electrolyte layer) in addition to the negative electrode. ), But in the case of the layer (a) having a negative electrode other than the outermost one [in the case of the layer (a) formed in the steps after (8) in FIG. 5], the negative electrode conductive connection portion is included in addition to the negative electrode. A part of the positive electrode conductive connection part, and a part of the solid electrolyte connection part (more preferably, the solid electrolyte layer).

Further, as shown in FIG. 3 (4), the layer (b) adjacent to the layer (a) having the outermost negative electrode of the electrode laminate is a part of the negative electrode conductive connection portion other than the solid electrolyte layer. However, in the case of the layer (b) adjacent to the layer (c) having the outermost positive electrode of the electrode laminate, a part of the positive electrode conductive connection portion is included in addition to the solid electrolyte layer, and the outermost of the electrode laminate. In the case of the layer (a) having the electrodes and the layer (b) not adjacent to the layer (c), a part of the positive electrode conductive connection portion and a part of the negative electrode conductive connection portion are included in addition to the solid electrolyte layer.

Further, as shown in FIG. 5 (7), the layer (c) having a positive electrode other than the outermost portion of the electrode laminate is a part of the positive electrode conductive connection portion and one of the negative electrode conductive connection portions in addition to the positive electrode. In the case of the layer (c) having the outermost positive electrode of the electrode laminate, which includes a part and a part of the solid electrolyte connecting part (more preferably, the solid electrolyte layer), a part of the positive electrode conductive connecting part other than the positive electrode. (More preferably, a solid electrolyte layer) is included.

After forming each layer constituting the electrode laminate, pressure molding such as press processing may be performed if necessary.

In the method described with reference to FIGS. 2 to 5, the step of directly forming the layer (b) on the layer (a), the step of directly forming the layer (b) on the layer (c), and the step of directly forming the layer (b) on the layer (b). An electrode laminate is produced through a step of directly forming (a) and a step of directly forming a layer (c) on the layer (b) [referred to as an electrode laminate production step (A)]. In the production method of the present invention, the layer (a), the layer (b) and the layer (c) are individually formed, and after laminating the layers, pressure molding such as press processing is performed as necessary. As a result, an electrode laminate may be formed [referred to as an electrode laminate manufacturing step (B)].

However, in the case of the electrode laminate manufacturing step (A), the adhesion between the positive electrode and the solid electrolyte layer and the adhesion between the negative electrode and the solid electrolyte layer are higher than those in the electrode laminate manufacturing step (B), for example. It is high, and the resistance value between them is low, so that better battery characteristics can be expected to be ensured. Therefore, it is more preferable to manufacture the electrode laminate by the electrode laminate manufacturing step (A).

At the time of producing the electrode laminate, each component (positive electrode, negative electrode, conductive connection portion of positive electrode and negative electrode, solid electrolyte layer, and solid electrolyte connection portion) contains the constituent materials and solvent of these components. It is formed through the steps of applying each composition (positive electrode forming composition, negative electrode forming composition, conductive connecting portion forming composition, solid electrolyte layer forming composition and solid electrolyte connecting portion forming composition). .. At the time of application in this case, masking may be performed on the parts that do not need to be formed of each component.

The coating method of each of the above compositions is not particularly limited, and various known coating methods can be adopted, but spray coating is more preferable, and a laminated electrode body can be formed more efficiently. , Battery productivity is improved.

In the electrode laminate, both of the outermost electrodes may be positive electrodes or negative electrodes, and one of the outermost electrodes may be a positive electrode and the other may be a negative electrode. The outermost layer of the electrode laminate may be an electrode (positive electrode or negative electrode), or may be a layer other than the electrode (solid electrolyte layer, resin layer for insulation, etc.) depending on the type of exterior body. Good. For example, in the case of an all-solid-state lithium secondary battery having an exterior body composed of an exterior can, a sealing can, and a gasket as shown in FIG. 1, it is laminated with an exterior can or a sealing can that also serves as a positive electrode or negative electrode terminal. Since it is efficient that the outermost electrode of the electrode body is in direct contact with the electrode, the outermost layer of the electrode laminate is preferably an electrode, and one of the outermost layers of the electrode laminate is a positive electrode. It is more preferable that the other is a negative electrode.

The electrode laminate thus obtained is encapsulated inside the exterior body to obtain an all-solid-state lithium secondary battery. The exterior of the all-solid-state lithium secondary battery includes an exterior composed of an exterior can, a sealing can, and a gasket, as shown in FIG. 1, as well as an exterior composed of a resin film and a metal-resin laminated film. The body etc. can also be applied.

In the case of an exterior body composed of an outer can, a sealing can and a gasket, stainless steel or the like 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.

The all-solid-state lithium secondary battery of the present invention can be applied to the same applications as the conventionally known secondary batteries, but has excellent heat resistance because it has a solid electrolyte instead of the organic electrolyte. It can be preferably used for applications that are 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 <Composition for forming a positive electrode>
Using xylene as a solvent, LiNi _0.6 Co _0.2 Mn _0.2 O ₂ having an average particle size of 3 μm and an amorphous composite oxide of Li and Nb formed on the surface and an average particle size of 0.7 μm. Solid sulfide 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 85:10: 3: 2. The mixture was mixed so that the solid content ratio was 30%, and stirred with a sinky mixer for 10 minutes to prepare a uniform slurry. This slurry was used as a positive electrode forming composition.

<Composition for forming negative electrode>
Using xylene as a solvent, graphite having an average particle size of 20 μm, a sulfide solid electrolyte (Li ₆ PS ₅ Cl), and an acrylic resin binder have a mass ratio of 50:47: 3, and a solid content ratio of 50. The mixture was mixed so as to be%, and stirred with a sinky mixer for 10 minutes to prepare a uniform negative electrode slurry. This slurry was used as a composition for forming a negative electrode.

<Composition for forming a solid electrolyte layer>
Using xylene as a solvent, a sulfide-based solid electrolyte (Li ₆ PS ₅ Cl) having an average particle diameter of 0.7 μm, an acrylic resin binder, and a dispersant were mixed in a mass ratio of 100: 3: 1 and The mixture was mixed so that the solid content ratio was 40%, and stirred with a sinky mixer for 10 minutes to prepare a uniform slurry. This slurry was used as a composition for forming a solid electrolyte layer.

<Composition for forming a positive electrode conductive connection portion>
Using xylene as a solvent, spherical aluminum powder with an average particle size of 10 μm and an acrylic resin binder were mixed so that the mass ratio was 100: 1 and the solid content ratio was 40%, and the mixture was used with a sinky mixer. Stir for 10 minutes to prepare a uniform slurry. This slurry was used as a composition for forming a positive electrode conductive connection portion.

<Composition for forming a negative electrode conductive connection portion>
Using xylene as a solvent, copper powder having an average particle size of 6 μm and an acrylic resin binder were mixed so that the mass ratio was 100: 1 and the solid content ratio was 40%, and the mixture was mixed with a sinky mixer for 10 minutes. Stir to prepare a uniform slurry. This slurry was used as a composition for forming a negative electrode conductive connection portion.

Each composition was applied by the following procedure using a thin film laminated coating device (MTSVIIIS) equipped with an automatic coating weight measurement system manufactured by MTEC Smart, and dried to form an electrode laminate.

<Formation of electrode laminate>
On a circular SUS foil having a diameter of 8.15 mm and a thickness of 15 μm, the portion other than the negative electrode formed was arranged as masking so as to be covered with a SUS plate having a thickness of 0.5 mm. A negative electrode forming composition was applied onto the electrode and dried to form a negative electrode having a thickness of 90 μm [FIG. 2 (1)].

In order to form the negative electrode conductive connection portion at the end portion of the negative electrode, a SUS plate was arranged as masking so as to cover the portion other than the negative electrode conductive connection portion. A composition for forming a negative electrode conductive connection portion was applied from above and dried to form a negative electrode conductive connection portion having a thickness of 150 μm [FIG. 2 (2)].

In order to form a solid electrolyte layer around the negative electrode, a SUS plate was arranged as masking so as to cover a portion other than the solid electrolyte layer. A composition for forming a solid electrolyte layer was applied from above and dried to form a solid electrolyte layer having the same thickness as the negative electrode [FIG. 3 (3)].

Next, in order to further form a solid electrolyte layer on the negative electrode, a SUS plate was arranged as masking so as to cover only the negative electrode conductive connection portion. A composition for forming a solid electrolyte layer was applied from above and dried to form a solid electrolyte layer so as to be at the same height as the upper surface of the negative electrode conductive connection portion [FIG. 3 (4)].

Further, in order to form the positive electrode on the solid electrolyte layer, a SUS plate was arranged as masking so as to cover the portion other than the positive electrode formed. A positive electrode forming composition was applied from above and dried to form a positive electrode having a thickness of 100 μm [FIG. 4 (5)].

In order to form the positive electrode conductive connection at the end of the positive electrode opposite to the negative electrode conductive connection, a SUS plate was arranged as masking so as to cover the portion other than the positive electrode conductive connection. .. A composition for forming a positive electrode conductive connection portion was applied from above and dried to form a positive electrode conductive connection portion having the same thickness as the positive electrode. Further, a positive electrode conductive connection portion having a narrow width was formed on the positive electrode conductive connection portion having a thickness of 60 μm [FIG. 4 (6)].

In order to further form the negative electrode conductive connection portion on the negative electrode conductive connection portion, a SUS plate was arranged as masking so as to cover the rest. A composition for forming a negative electrode conductive connection portion was applied from above and dried to further form a negative electrode conductive connection portion having a thickness of 160 μm.

In order to form a solid electrolyte layer around the positive electrode conductive connection portion and to form a solid electrolyte connection portion between the positive electrode and the negative electrode conductive connection portion, a SUS plate was arranged as masking so as to cover the other portion. A composition for forming a solid electrolyte layer was applied from above and dried to form a solid electrolyte layer having a thickness of 100 μm and a solid electrolyte connection portion.

Next, in order to further form a solid electrolyte layer on the positive electrode, a SUS plate was arranged as masking so as to cover a portion other than the negative electrode conductive connection portion and the positive electrode conductive connection portion. The composition for forming the solid electrolyte layer was applied from above and dried to form the solid electrolyte layer with a thickness of 60 μm so as to be the same height as the negative electrode conductive connection portion and the positive electrode conductive connection portion [FIG. 5]. Medium (7)].

A negative electrode having the same size as the above is formed on the solid electrolyte layer in the same manner as described above, and then a negative electrode conductive connection is made on the negative electrode conductive connection portion in the same manner as described above so as to be in contact with the negative electrode. A positive electrode conductive connection portion is formed on the positive electrode conductive connection portion in the same manner as described above, and a solid electrolyte connection portion is formed between the negative electrode and the positive electrode conductive connection portion. This was repeated to form an electrode laminate having three layers each of a negative electrode and a positive electrode, a negative electrode (SUS foil) was arranged in the lowermost layer, and a positive electrode was arranged in the uppermost layer.

A circular aluminum foil having a diameter of 8.15 mm and a thickness of 15 μm was placed on the uppermost portion of the obtained electrode laminate, and then pressed at a pressure of 10 tons / cm ² to form a molded product.

The electrode laminate (molded body) was placed in a sealing can with the SUS foil of the negative electrode facing down, and an outer can was placed over the sealing can to seal the electrode, thereby producing a coin-shaped all-solid-state lithium secondary battery.

The size of the positive electrode in this all-solid-state lithium secondary battery [the lengths of R, a and b shown in FIG. 4 (6)] and the size of the negative electrode [the length of R, a and b shown in FIG. 5 (8)]. ] Is shown in Table 1.

In the battery of this embodiment, extra space is provided by arranging the solid electrolyte connection portion between the positive electrode conductive connection portion and the end portion of the negative electrode and between the negative electrode conductive connection portion and the end portion of the positive electrode, respectively. It was possible to increase the proportion of the active material layer by eliminating the problem, and it was possible to charge and discharge without causing a short circuit.

Comparative Example FIG. 6 shows a plan view schematically showing an electrode related to the battery of the comparative example (a battery having a conventional electrode laminate), and both surfaces of the metal foil 102 having the shape shown in FIG. 6 are active. In the case of a conventional electrode laminate in which the electrodes 100 on which the material layer 101 is formed are laminated, in order to join the uncoated portions 102a (tabs) of the metal foil to each other to realize a conductive connection between the positive electrode and the negative electrode, the above-mentioned It is necessary to secure a certain amount of space so that the tab does not come into contact with the counter electrode and cause a short circuit. It is also necessary to reduce the thickness of the active material layer by the thickness of the metal foil.

Table 1 also shows the sizes of the electrodes (lengths of R, a and b shown in FIG. 6), but as shown in Table 1, the outer diameters R of the active material layers of the positive electrode and the negative electrode are the same. Even so, a and b corresponding to the width must be made smaller than those in the embodiment. Therefore, the capacity of the electrode is reduced. Moreover, since the thickness of each active material layer is also reduced, the capacity of the battery of the comparative example is reduced to 87% of that of the battery of the example.

1 All-solid-state lithium secondary battery 2 Exterior can 3 Sealed can 4 Gasket 5 Positive electrode 51 Positive electrode Conductive connection part 6 Negative electrode 61 Negative electrode conductive connection part 7 Solid electrolyte layer 71 Solid electrolyte connection part

Claims (7)

An all-solid-state lithium secondary battery in which the positive electrode and the negative electrode have an electrode laminate in which a plurality of layers are alternately laminated via a solid electrolyte layer.
The end portion of the positive electrode is provided with a positive electrode conductive connection portion that electrically connects the positive electrodes to each other.
At the end of the negative electrode, a negative electrode conductive connection portion for electrically connecting the negative electrodes is provided.
The positive electrode conductive connection portion and the negative electrode conductive connection portion contain at least a particulate conductive material.
The solid electrolyte layers are connected at the end by a solid electrolyte connecting portion containing the solid electrolyte.
The all-solid-state lithium is characterized in that the solid electrolyte connection portion is arranged between the positive electrode conductive connection portion and the end portion of the negative electrode and between the negative electrode conductive connection portion and the end portion of the positive electrode, respectively. Secondary battery. The all-solid-state lithium secondary battery according to claim 1, wherein the positive electrode conductive connection portion and the negative electrode conductive connection portion contain carbon particles or metal particles. The all-solid-state lithium secondary battery according to claim 2, wherein the positive electrode conductive connection portion and the negative electrode conductive connection portion contain a binder. The all-solid-state lithium secondary battery according to any one of claims 1 to 3, wherein one of the outermost layers of the electrode laminate is composed of a positive electrode and the other is composed of a negative electrode. The all-solid-state lithium secondary battery according to any one of claims 1 to 4, wherein the solid electrolyte layer and the solid electrolyte connecting portion contain a sulfide-based solid electrolyte. The method for manufacturing an all-solid-state lithium secondary battery according to any one of claims 1 to 5.
A layer (a) having a negative electrode and a part of the negative electrode conductive connection part, or a part of the negative electrode and the negative electrode conductive connection part, a part of the positive electrode conductive connection part, and a part of the solid electrolyte connection part.
A layer (b) having a solid electrolyte layer and a part of a positive electrode conductive connection portion and / or a part of a negative electrode conductive connection portion,
A layer (c) having a positive electrode and a part of the positive electrode conductive connection portion, or having a part of the positive electrode and the positive electrode conductive connection portion, a part of the negative electrode conductive connection portion, and a part of the solid electrolyte connection portion. It has a step of laminating to form an electrode laminate in which a positive electrode and a negative electrode are alternately laminated with a plurality of layers via a solid electrolyte layer.
The positive electrode is formed through a step of applying a positive electrode forming composition containing a positive electrode active material and a solvent.
The negative electrode is formed through a step of applying a negative electrode forming composition containing a negative electrode active material and a solvent.
The solid electrolyte layer and the solid electrolyte connection portion are formed through the steps of applying the composition for forming the solid electrolyte layer and the composition for forming the solid electrolyte connection portion containing the solid electrolyte and the solvent.
An all-solid-state lithium secondary battery characterized in that the positive electrode conductive connection portion and the negative electrode conductive connection portion are formed through a step of applying a composition for forming a conductive connection portion containing a particulate conductive material and a solvent. Production method. A step of directly forming the layer (b) on the layer (a),
A step of directly forming the layer (b) on the layer (c),
The all-solid-state lithium according to claim 6, further comprising a step of directly forming the layer (a) on the layer (b) and a step of directly forming the layer (c) on the layer (b). How to manufacture a secondary battery.

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