Flat all-solid battery and method for manufacturing the same

Abstract

The flat all-solid battery disclosed in the present application has a battery container consisting of an outer packaging can and a sealing can, and a stacked body consisting of a positive electrode, a solid electrolyte layer, and a negative electrode, the stacked body is contained in the battery container, and a flexible conductive porous component consisting of a graphite molded body is arranged between the stacked body and the inner bottom surface of the outer packaging can or the inner bottom surface of the sealing can. In addition, the flat all-solid battery can be provided with the conductive porous component between the stacked body and the inner bottom surface of the sealing can and between the stacked body and the inner bottom surface of the outer packaging can.

Description

Technical Field

[0001] The present invention relates to a flat all-solid battery having excellent reliability and productivity and a method for manufacturing the same. Background Art

[0002] 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, there is an increasing demand for small, lightweight, high-capacity, and high-energy-density secondary batteries.

[0003] At present, in non-aqueous secondary batteries that can meet this requirement, especially lithium-ion secondary batteries, the positive electrode active material used is lithium-containing composite oxides such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), and the negative electrode active material used is graphite, etc., and as a non-aqueous electrolyte, an organic electrolyte containing an organic solvent and a lithium salt is used.

[0004] Furthermore, as the application equipment of non-aqueous secondary batteries further develops, non-aqueous secondary batteries are required to have a longer life, higher capacity, and higher energy density. At the same time, non-aqueous secondary batteries with longer life, higher capacity, and higher energy density are also required to have higher reliability.

[0005] However, the organic electrolyte used in lithium-ion secondary batteries contains an organic solvent as a flammable substance, so when the battery is short-circuited or other abnormal conditions occur, there is a possibility that the organic electrolyte will generate abnormal heat. In addition, with the trend of high energy density of non-aqueous secondary batteries and the increase in the amount of organic solvent in the organic electrolyte in recent years, the reliability of non-aqueous secondary batteries is further required.

[0006] In this case, all-solid-state secondary batteries that do not use organic solvents are also being studied (Patent Documents 1, 2, etc.). All-solid-state secondary batteries use a molded body of a solid electrolyte that does not use an organic solvent to replace the conventional organic solvent-based electrolyte, and there is no concern about abnormal heating of the solid electrolyte, and they have high reliability.

[0007] Among secondary batteries, flat batteries such as coin-shaped batteries and button-shaped batteries are known. In such flat batteries, a gasket is provided between the outer packaging can and the sealing can, and an outer casing is used by caulking the open end of the outer packaging can inward. However, the research of the present inventors has shown that in batteries such as all-solid batteries having electrodes (granular electrodes) composed of a molded body of an electrode mixture containing an active material, when an outer casing such as the above is used, cracks are easily generated in the electrodes, especially the electrode (negative electrode) on the sealing can side.

[0008] If cracks occur in the electrode, the capacity will decrease, which will damage the reliability of the battery. In addition, when manufacturing a large number of batteries, if the proportion of batteries with low reliability increases, the productivity of the battery decreases. Therefore, when using a flat outer package as described above to form an all-solid battery, it is necessary to suppress the generation of electrode cracks during manufacturing.

[0009] In contrast, it has been proposed that by disposing an elastic body whose surface is covered with a conductor between the outer packaging can (positive electrode can) and the positive electrode and between the sealing can (negative electrode can) and the negative electrode, the stress between the positive electrode can and the negative electrode can be alleviated and the electrode rupture can be prevented (Patent Document 3).

[0010] In addition, some people have proposed that, although there is no caulking process, in a planar-mounted solid battery, by arranging a current collecting component such as a carbon sheet and an anisotropic conductive rubber sheet that is elastic and contains a conductive material between at least one of the positive electrode and the negative electrode and the storage component, physical damage such as rupture of the battery body including the positive electrode layer, the solid electrolyte layer and the negative electrode layer can be suppressed (Patent Document 4).

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: Japanese Patent Application Publication No. 2005-56827

[0014] Patent Document 2: Japanese Patent Application Publication No. 2015-56326

[0015] Patent Document 3: Japanese Patent Application Laid-Open No. 11-144761

[0016] Patent Document 4: International Publication No. 2012 / 141231 Summary of the invention

[0017] Problems to be solved by the invention

[0018] However, even when the above elastic materials are used, desired characteristics may not always be obtained depending on the conditions during battery assembly, and further research on the materials, manufacturing methods, etc. is necessary.

[0019] The present application has been made in view of the above circumstances, and provides a flat all-solid-state battery with excellent reliability and productivity.

[0020] Methods for solving problems

[0021] The flat all-solid-state battery disclosed in the present application includes a battery container consisting of an outer packaging can and a sealing can, and a stack formed by stacking a positive electrode, a solid electrolyte layer and a negative electrode. The stack is accommodated in the battery container, and a flexible conductive porous component composed of a graphite molded body is arranged between the stack and the inner bottom surface of the outer packaging can or the inner bottom surface of the sealing can.

[0022] In addition, the manufacturing method of the flat all-solid battery disclosed in the present application is a manufacturing method of a flat all-solid battery including a battery container consisting of an outer packaging can and a sealing can and a stacked body consisting of a positive electrode, a solid electrolyte layer and a negative electrode, including a step of placing a conductive porous component and the above-mentioned stacked body on the inner bottom surface of a sealing can equipped with an annular gasket to form an assembly, and a step of covering the outer packaging can on the above-mentioned assembly and sealing it by caulking; the above-mentioned conductive porous component is arranged between the above-mentioned stacked body and the inner bottom surface of the above-mentioned outer packaging can or the inner bottom surface of the above-mentioned sealing can , the above-mentioned conductive porous component is a conductive porous sheet composed of fibers of carbon material or a flexible conductive porous sheet composed of a graphite molded body, the above-mentioned gasket has a bottom portion sandwiched between the open end of the above-mentioned sealing can and the inner bottom surface of the above-mentioned outer packaging can, and the above-mentioned assembly is constructed in the following manner: in the above-mentioned assembly, when the height from the inner bottom surface of the above-mentioned sealing can to the end of the bottom portion of the above-mentioned gasket on the outer packaging can side is set to t (mm), and the total thickness of the above-mentioned stack and the above-mentioned conductive porous component is set to a (mm), -0.25≦at≦0.18.

[0023] Effects of the Invention

[0024] According to the present application, a flat all-solid-state battery having excellent reliability and productivity can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic cross-sectional view showing an example of a conventional flat all-solid-state battery.

[0026] Figure 2 This is a cross-sectional image of the edge of the electrode on the outer can side of a conventional flat all-solid-state battery, taken non-destructively using an X-ray CT device.

[0027] Figure 3 This is a schematic cross-sectional view showing an example of a flat all-solid-state battery according to the present embodiment.

[0028] Figure 4 This is a schematic cross-sectional view showing an example of a sealed can equipped with a gasket.

[0029] Figure 5This is a schematic cross-sectional view showing an example of an assembly in which a conductive porous member on the sealing can side, an electrode stack, and a conductive porous member on the outer can side are stacked in this order on the inner bottom surface of the sealing can. DETAILED DESCRIPTION

[0030] The embodiment of the flat all-solid battery disclosed in the present application is described. The flat all-solid battery of the present embodiment includes a battery container composed of an outer packaging can and a sealing can, and a stacked body composed of a positive electrode, a solid electrolyte layer, and a negative electrode, the stacked body is contained in the battery container, and a conductive porous member (a flexible conductive porous sheet composed of a graphite molded body) is arranged between the stacked body and the inner bottom surface of the outer packaging can or the inner bottom surface of the sealing can.

[0031] When a compressive force is applied to the conductive porous member in the thickness direction, the conductive porous member can absorb the compressive force by being compressed, thereby weakening the force acting on the electrode.

[0032] Furthermore, the conductive porous member can maintain good conduction between the stack and the battery container by repeatedly compressing and restoring the stack in response to expansion and contraction of the stack produced during battery charge and discharge.

[0033] In the battery industry, flat batteries whose height is larger than their diameter are called coin batteries or button batteries, but there is no clear difference between coin batteries and button batteries. The flat all-solid battery of this embodiment includes any one of coin batteries and button batteries.

[0034] Hereinafter, the flat all-solid-state battery of the present embodiment will be described with reference to the drawings, while being compared with a conventional flat all-solid-state battery.

[0035] Figure 1 This is a schematic cross-sectional view showing an example of a conventional flat all-solid-state battery. Figure 1 The flat all-solid battery 100 shown is composed of a stacked body formed by stacking a positive electrode 30, a solid electrolyte layer 50 and a negative electrode 40, which is contained in a battery container composed of an outer packaging can 10, a sealing can 20 and a gasket 60. The sealing can 20 is embedded in the opening of the outer packaging can 10 via the gasket 60, and the open end 11 of the outer packaging can 10 is tightened inwardly by caulking, so that the gasket 60 abuts against the sealing can 20, so that the opening of the outer packaging can 10 is sealed, and a closed structure is formed inside the battery. In addition, by caulking the open end 11 of the outer packaging can 10, the bottom surface 61 of the gasket 60 is compressed by the open end 21 of the sealing can 20, thereby realizing a firm closed structure.

[0036] exist Figure 1In the case of a flat battery having the structure shown in the figure, the edge portion of the electrode facing the battery container (outer can or sealing can) is caulked inwardly by caulking the open end of the outer can toward the inside, for example Figure 1 A large stress is applied to the position surrounded by the circle in the figure. Therefore, if there is a solid electrolyte layer that is difficult to deform between the positive electrode and the negative electrode instead of a separator that is easily compressed, the electrode is prone to rupture due to the above stress. In particular, when the above electrode is difficult to deform like a molded body (particles, etc.) of an electrode mixture containing an active material, the problem of electrode rupture is more likely to occur.

[0037] Figure 2 Displayed Figure 1 The flat battery structure shown in the figure was imaged non-destructively using an X-ray CT device. Figure 1 From the cross-sectional image of the area surrounded by a circle in the figure, it can be confirmed that the electrode ( Figure 1 A crack 70 is generated in the positive electrode 30).

[0038] In addition, although it varies depending on the shape of the battery container, the electrode ( Figure 1 A large stress is applied to the edge of the sealed can side of the negative electrode 40 in the positive electrode. Therefore, if a solid electrolyte layer that is difficult to deform is present between the positive electrode and the negative electrode instead of a separator that is easily compressed, cracks are likely to occur in the electrode on the sealed can side due to the above stress.

[0039] Therefore, in the flat all-solid-state battery of the present embodiment, a conductive porous component is arranged between a stack consisting of a positive electrode, a solid electrolyte layer and a negative electrode (hereinafter sometimes referred to as an "electrode stack") and the inner bottom surface of the outer packaging can or the inner bottom surface of the sealing can, which can reduce the force acting on the electrode due to compression and also function as a current collector.

[0040] Figure 3 It is a schematic cross-sectional view of the flat all-solid-state battery according to this embodiment. Figure 3 In Figure 1 Common elements are given the same reference numerals to avoid repeated description. Figure 4 and Figure 5 The same is true.

[0041] Figure 3 In the flat all-solid-state battery 1 shown, conductive porous components (flexible conductive porous sheets composed of graphite molded bodies) 80, 80 are respectively arranged between the stack composed of the positive electrode 30, the solid electrolyte layer 50 and the negative electrode 40 and the inner bottom surface of the outer packaging can 10 and the inner bottom surface of the sealing can 20.

[0042] In the flat all-solid battery of this embodiment, the stress applied to the electrode on the sealing can side when the outer packaging can is caulked is mainly relieved by the above-mentioned conductive porous component arranged on the inner bottom surface side of the sealing can, so that the occurrence of cracks in the electrode on the sealing can side can be suppressed. Therefore, by using the above-mentioned conductive porous component, a highly reliable flat all-solid battery can be provided, and the productivity of the flat all-solid battery can be improved.

[0043] In addition, in a flat all-solid battery, depending on the shape of the battery container, when the open end of the outer can is caulked inward, the electrode ( Figure 1 In the positive electrode 30), especially Figure 1 Furthermore, if the electrode on the outer can side is difficult to deform like a molded body (granules, etc.) of an electrode mixture containing an active material, the problem of cracking is more likely to occur in the electrode on the outer can side.

[0044] However, in the flat all-solid battery of the present embodiment, the stress applied to the electrode on the outer can side when the outer can is caulked is mainly alleviated by the above-mentioned conductive component arranged on the inner bottom surface side of the outer can, thereby suppressing the occurrence of cracks in the electrode on the outer can side.

[0045] Therefore, if Figure 3 As shown, in the present embodiment, it is preferred that a conductive porous component is also arranged between the stack consisting of the positive electrode, the solid electrolyte layer and the negative electrode and the inner bottom surface of the outer packaging can. This can suppress the occurrence of cracks in the electrode on the outer packaging can side, thereby improving the reliability and productivity of the battery.

[0046] It should be noted that Figure 3 This is a diagram showing an example of a flat all-solid battery according to the present embodiment, and it should not be understood that the flat all-solid battery according to the present embodiment is limited to Figure 3 A battery having the structure shown.

[0047] For example, the conductive porous member may be disposed only between the electrode stack and the inner bottom surface of the outer can. However, it is generally believed that the electrode on the sealing can side is more likely to crack, so the conductive porous member is preferably disposed at least between the electrode stack and the inner bottom surface of the sealing can.

[0048] In addition, if the flat all-solid-state battery is repeatedly charged and discharged, the electrode stack repeatedly expands and contracts due to the volume change of the positive electrode active material and / or the negative electrode active material, and there is a problem that the conduction between the electrode stack and the outer packaging can and the sealing can cannot be well maintained, and the electrode on the outer packaging can side or the sealing can side is easily cracked due to the squeezing force from the battery container when the electrode stack expands.

[0049] In the flat all-solid battery of this embodiment, the conductive porous components disposed on both sides of the electrode stack are compressed or restored in shape according to the expansion / contraction of the electrode stack, thereby reducing the force acting on the electrodes and maintaining good conduction between the electrode stack and the outer packaging can and the sealing can. As a result, the reliability of the battery can be improved.

[0050] It should be noted that the conductive porous member has the function of preventing the above-mentioned problem even if it is arranged only on one side of the electrode stack, but the above-mentioned function can be more reliably achieved by arranging it on both sides of the electrode stack.

[0051] Figure 3 In the flat solid battery 1 shown in the figure, an example of an electrode stack is arranged in such a manner that the positive electrode 30 is on the outer packaging can 10 side and the negative electrode 40 is on the sealing can 20 side, but the flat all-solid battery of this embodiment is not subject to Figure 3 The above-mentioned form can be limited to, for example, the electrode stack can be arranged so that the positive electrode is on the sealing can side and the negative electrode is on the outer can side.

[0052] In addition, in the flat all-solid battery of this embodiment, an electrode stack having multiple layers of positive electrodes and / or negative electrodes and a solid electrolyte layer between each positive electrode and negative electrode may also be used. Figure 3 Similarly to the case shown, the electrode on the sealing can side and the electrode on the outer can side of the electrode of the outermost layer of the electrode stack may be electrodes of different polarities, or the electrode on the sealing can side and the electrode on the outer can side may be electrodes of the same polarity. Here, in the case of a battery using an electrode stack having multiple layers of positive and / or negative electrodes, the electrode on the sealing can side means the electrode closest to the sealing can, and the electrode on the outer can side means the electrode closest to the outer can.

[0053] Next, the constituent components and assembly steps of the flat all-solid-state battery of this embodiment will be described respectively.

[0054] <Conductive porous parts>

[0055] The conductive porous member used in the flat all-solid battery of this embodiment can be any member that is compressed when a compressive force is applied in the thickness direction, so that the compressive force can be appropriately absorbed and the shape can be fully restored when there is no compressive force. Preferably, it is a conductive porous sheet composed of carbon fiber or a flexible conductive porous sheet composed of a graphite molded body. Because they have excellent compressive force absorption capacity and excellent conductivity, and can be compressed and restored in shape according to the expansion / contraction of the electrode stack, they can maintain a good contact state with both the electrode stack and the battery container.

[0056] Furthermore, even when a solid electrolyte that easily reacts with other constituent materials in the battery, such as a sulfide-based solid electrolyte, is used, the conductive porous sheet can stably maintain its function.

[0057] It should be noted that when a conductive foam substrate made of metal such as copper and aluminum is used as the above-mentioned conductive porous component, although it is compressed when a squeezing force is applied in the thickness direction and can appropriately absorb the squeezing force, it cannot restore its shape when there is no squeezing force. Therefore, it is difficult to maintain good conductivity with the battery container according to the expansion / contraction of the electrode stack.

[0058] Examples of the conductive porous sheet composed of fibers of a carbon material include carbon felt, and woven or nonwoven fabrics of carbon nanotube fibers.

[0059] In the conductive porous sheet composed of fibers of a carbon material, the fibers constituting the sheet preferably have a fiber diameter of 1 nm to 1 μm.

[0060] Furthermore, the thickness of the conductive porous sheet composed of the fibers of the carbon material is preferably 0.1 to 1 mm, and more preferably 0.5 mm or less.

[0061] Furthermore, the basis weight of the conductive porous sheet composed of carbon fiber is preferably 5 to 200 g / m 2 .

[0062] On the other hand, from the viewpoints of compressibility and restorability, the conductive porous member is more preferably a conductive porous sheet composed of a graphite compact and having flexibility.

[0063] As the conductive porous sheet, one obtained by molding graphite into a sheet-like shape without using a binder is preferred, and expanded graphite is more preferably used because it is excellent in flexibility and compression / restoration properties.

[0064] As the sheet material composed of a graphite molded body, preferably used is a flexible graphite sheet "PERMA-FOIL (trade name)" manufactured by Toyo Tanso Co., Ltd., a soft graphite sheet "GRAFOIL (trade name)" manufactured by NeoGraf Corporation, or the like.

[0065] In order to achieve excellent compressibility and resilience, the thickness of the sheet composed of the graphite molded body is preferably set to 0.03 mm or more, more preferably 0.05 mm or more, and particularly preferably 0.07 mm or more. On the other hand, in order to prevent an increase in electrical resistance, it is preferably 0.5 mm or less, more preferably 0.3 mm or less, and particularly preferably 0.2 mm or less.

[0066] In order to achieve excellent conductivity, the apparent density of the sheet composed of the graphite molded body is preferably set to 0.5 g / cm 3 More preferably, it is 0.7 g / cm 3 On the other hand, in order to achieve excellent flexibility, it is preferably set to 1.7 g / cm 3 Below, more preferably set to 1.4 g / cm 3 the following.

[0067] In order to reduce the force acting on the electrode and at the same time maintain good conduction between the electrode stack and the battery container, the area of ​​the conductive porous sheet composed of the fibers of the carbon material and the conductive porous sheet having flexibility composed of the graphite molded body is preferably set to 70% or more of the area of ​​the opposite electrode, more preferably 80% or more, and particularly preferably 90% or more. On the other hand, if the area of ​​the portion extending from the electrode becomes larger, the dead angle around the electrode stack increases, resulting in a decrease in battery capacity, so the area of ​​the conductive porous sheet is preferably set to 130% or less of the area of ​​the opposite electrode, more preferably 120% or less, and particularly preferably 110% or less.

[0068] If the conductive porous sheet satisfies the above-mentioned physical properties, stress applied to the electrodes on the sealing can side and the outer can side due to caulking during formation of the battery container can be sufficiently alleviated, thereby satisfactorily suppressing cracking of the electrodes.

[0069] Furthermore, even when the battery is repeatedly charged and discharged, the conductive porous sheet is repeatedly compressed and restored according to the volume change of the electrode stack, so that the conduction between the electrode stack and the outer can and the sealing can can be well maintained.

[0070] <Positive electrode>

[0071] As the positive electrode of the flat all-solid-state battery of this embodiment, an electrode obtained by molding a positive electrode mixture containing a positive electrode active material (positive electrode mixture molded body), an electrode having a structure having a layer of a positive electrode mixture containing a positive electrode active material on one or both sides of a collector (positive electrode mixture layer), etc. can be used.

[0072] The positive electrode active material can use an active material that can absorb / release lithium ions similar to the materials used in conventionally known lithium ion secondary batteries. Specifically, LiM 1 x Mn 2-x O4 (where M 1is at least one element selected from the group consisting of Li, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Fe, Co, Ni, Cu, Al, Sn, Sb, In, Nb, Mo, W, Y, Ru and Rh, 0.01≦x≦0.5) represented by a spinel lithium manganese composite oxide, Li a Mn (1-b-a) Ni b M 2 c O 2-d F f (Among them, M 2 is at least one element selected from the group consisting of Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr and W, 0.8≦a≦1.2, 0<b<0.5, 0≦c≦0.5, d+f<1, -0.1≦d≦0.2, 0≦f≦0.1), a layered compound, LiCo 1-g M 3 g O2 (where M 3 is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba, 0≦g≦0.5) represented by lithium cobalt composite oxide, LiNi 1-h M 4 h O2 (where M 4 is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba, 0≦h≦0.5) represented by lithium nickel composite oxide, LiM 5 1-m N m PO4 (where M 5 is at least one element selected from the group consisting of Fe, Mn and Co, N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba, 0≦m≦0.5) represented by an olivine-type composite oxide, Li4Ti5O 12 The lithium-titanium composite oxides and the like shown above may be used alone or in combination of two or more.

[0073] In the case of a positive electrode composed of a positive electrode mixture molded body or a positive electrode having a positive electrode mixture layer, the positive electrode mixture (positive electrode mixture layer) may contain a conductive aid and a binder while containing a positive electrode active material, or may contain a solid electrolyte instead of the conductive aid and / or the binder, or may contain a solid electrolyte while containing a conductive aid and a binder.

[0074] As the solid electrolyte used in the positive electrode, the same solid electrolytes as those exemplified below as the substances present between the positive electrode and the negative electrode can be used.

[0075] As a binder for the positive electrode, for example, a fluororesin such as polyvinylidene fluoride (PVDF) can be used, and as a conductive additive for the positive electrode, for example, a carbon material such as carbon black can be used.

[0076] When a current collector is used in the positive electrode, a substrate composed of a metal material such as aluminum, nickel, stainless steel, titanium, etc. can be used as the current collector. Examples include sheets composed of foils, punched metals, meshes, expanded metals, foamed substrates, and fibrous materials made of the above-mentioned metal materials.

[0077] Alternatively, the positive electrode may be formed by filling the voids of a sheet composed of the foamed substrate and the fibrous material with the positive electrode mixture.

[0078] As the composition of the positive electrode mixture of the positive electrode, for example, the positive electrode active material is preferably 50 to 90 mass %, the conductive aid is preferably 0.1 to 10 mass %, the binder is preferably 0.1 to 10 mass %, and when a solid electrolyte is used, the solid electrolyte is preferably 10 to 50 mass %.

[0079] In the case where the positive electrode is formed of a positive electrode mixture molded body, its thickness is preferably 0.15 to 4 mm. On the other hand, in the case of a positive electrode having a positive electrode mixture layer formed on the surface of the collector, the thickness of the positive electrode mixture layer (the thickness of each side of the collector when the positive electrode mixture layer is provided on both sides of the collector) is preferably 30 to 300 μm.

[0080] <Negative electrode>

[0081] As the negative electrode of the flat all-solid battery of the present embodiment, as long as it is the negative electrode used in the lithium ion secondary battery known in the past, that is, the negative electrode containing the active material that can absorb / release lithium ions, there is no particular limitation. For example, as the negative electrode active material, a mixture of one or more carbon materials that can absorb / release lithium, such as graphite, pyrolytic carbon, coke, glassy carbon, sintered bodies of organic polymer compounds, secondary carbon microbeads (MCMB), carbon fibers, etc., is used. In addition, simple substances, compounds and alloys thereof, lithium-containing nitrides or lithium-containing oxides, etc., which can be charged and discharged at low voltages close to lithium metal, or lithium metal, lithium / aluminum alloys, can also be used.

[0082] The negative electrode uses an electrode (negative electrode mixture molded body) obtained by molding a negative electrode mixture in which a conductive aid (carbon materials such as carbon black, solid electrolytes that can constitute a solid electrolyte layer as described later) and binders such as PVDF are appropriately added to the negative electrode active material; an electrode having a layer of a negative electrode mixture containing a negative electrode active material (negative electrode mixture layer) on one or both sides of a collector; an electrode composed of the above-mentioned various alloys, lithium metal foils alone, or foils thereof stacked on a collector as a negative electrode layer; etc.

[0083] When a current collector is used in the negative electrode, a substrate composed of a metal material such as copper, nickel, stainless steel, titanium, etc. can be used as the current collector. Examples include sheets composed of foils, punched metals, meshes, expanded metals, foamed substrates, and fibrous materials of the above-mentioned metal materials.

[0084] The negative electrode may be formed by filling the gaps in a sheet composed of the foamed substrate and the fibrous material with the negative electrode mixture.

[0085] As the composition of the negative electrode mixture of the negative electrode, for example, the negative electrode active material is preferably 40 to 80% by mass, and the binder is preferably 0.1 to 10% by mass; in addition, when a conductive aid is used, the conductive aid is preferably 0.1 to 10% by mass; when a solid electrolyte is used, the solid electrolyte is preferably 10 to 60% by mass.

[0086] In the case where the negative electrode is formed of a negative electrode mixture molded body, its thickness is preferably 0.15 to 4 mm. On the other hand, in the case of a negative electrode having a negative electrode mixture layer formed on the surface of the current collector, the thickness of the negative electrode mixture layer (the thickness of each side of the current collector when the negative electrode mixture layer is provided on both sides of the current collector) is preferably 10 to 100 μm.

[0087] <Solid electrolyte layer>

[0088] The solid electrolyte constituting the solid electrolyte layer of the flat all-solid battery of this embodiment may be a hydride-based solid electrolyte, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or the like, and only one of them may be used or two or more thereof may be used in combination.

[0089] Specific examples of hydride-based solid electrolytes include LiBH4, solid solutions of LiBH4 and the following alkali metal compounds (e.g., substances in which the molar ratio of LiBH4 to the alkali metal compound is 1:1 to 20:1), etc. As the alkali metal compound in the above solid solution, at least one selected from the group consisting of lithium halides (LiI, LiBr, LiF, LiCl, etc.), rubidium halides (RbI, RbBr, RbF, RbCl, etc.), cesium halides (CsI, CsBr, CsF, CsCl, etc.), lithium amides, rubidium amides, and cesium amides can be listed.

[0090] Specific examples of sulfide-based solid electrolytes include Li2S-P2S3, Li2S-P2S5, Li2S-P2S3-P2S5, Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-SiS2-P2S5, Li2S-SiS2-Li4SiO4, Li2S-SiS2-Li3PO4, Li3PS4-Li4GeS4, Li 3.4 P 0.6 Si 0.4 S4, Li 3.25 P 0.25 Ge 0.76 S4, Li 4-x Ge 1-x P x S4、Li7P3S 11 etc., preferably using an argyrodite-type solid electrolyte represented by a general formula such as Li6PS5X (X: Cl, Br or I).

[0091] As a specific example of oxide-based solid electrolytes, Li7La3Zr2O 12 , LiTi(PO4)3, LiGe(PO4)3, LiLaTiO3, etc.

[0092] The solid electrolyte layer can be formed by heating and pressurizing a solid electrolyte powder, applying a solid electrolyte layer-forming composition prepared by dispersing a solid electrolyte in a solvent on a substrate, and peeling it off from the substrate after drying.

[0093] Furthermore, the solid electrolyte layer may use a core material such as a resin mesh as necessary.

[0094] The thickness of the solid electrolyte layer is preferably 100 to 200 μm.

[0095] <Other components>

[0096] The outer packaging tank and sealing tank constituting the battery container of the flat all-solid battery of the present embodiment can use stainless steel parts, etc. In addition, the material of the gasket can use polypropylene, nylon, etc. In addition, when heat resistance is required due to the use of the battery, fluororesins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyphenylene ether (PPE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), polyetheretherketone (PEEK) and other heat-resistant resins with a melting point exceeding 240°C can also be used. In addition, when the battery is used for applications requiring heat resistance, its seal can also be sealed with glass airtight.

[0097] <Assembly process>

[0098] The flat all-solid battery of the present embodiment can be assembled, for example, through the following steps.

[0099] The electrode and solid electrolyte layer can be prepared by either a dry method or a wet method. In order to prevent the reaction between the water contained in the solvent (dispersion medium) used to form the slurry used in the wet method and the solid electrolyte, it is preferably prepared by a dry method.

[0100] The positive electrode can be produced by the following steps: the positive electrode active material and other constituent materials constituting the positive electrode mixture such as a solid electrolyte and a conductive aid are fully mixed in a container, and pressure-molded to obtain a molded body of the positive electrode mixture.

[0101] The negative electrode can be produced similarly to the positive electrode by thoroughly mixing the negative electrode active material and other constituent materials of the negative electrode mixture such as a solid electrolyte and a conductive aid in a container, and press-molding to produce a negative electrode mixture molded body.

[0102] The solid electrolyte layer can be produced by heating and pressure-molding a solid electrolyte powder as necessary to produce a solid electrolyte molded body.

[0103] The electrode stack can be produced by the following steps: sequentially stacking the positive electrode (a molded body of the positive electrode mixture), the solid electrolyte layer (a molded body of the solid electrolyte), and the negative electrode (a molded body of the negative electrode mixture), and then pressurizing them for integration. Alternatively, the positive electrode and the negative electrode can be separately stacked on the solid electrolyte layer.

[0104] In addition, in order to simplify the process, the following process can also be used: after making a molded body of a positive electrode mixture (or a molded body of a negative electrode mixture), a solid electrolyte powder is placed on the above molded body and pressed to form a molded body in which one electrode and a solid electrolyte layer are integrated, and a mixture of another electrode is placed on the above solid electrolyte layer and pressed to form a molded body (electrode stack) in which a positive electrode, a solid electrolyte layer and a negative electrode are integrated. In this case, after making a molded body of a solid electrolyte, a molded body of a positive electrode mixture can be made on one side of the above molded body, and a molded body of a negative electrode mixture can be made on the other side.

[0105] The prepared electrode stack is inserted into Figure 4 The inner side of the sealed can 20 with the annular gasket 60 is formed as shown in FIG. Figure 5 The assembly is shown as a stacked body formed by stacking the conductive porous component 80 on the sealing can side, the electrode stack (negative electrode 40, solid electrolyte layer 50, positive electrode 30), and the conductive porous component 80 on the outer can side in this order on the inner bottom surface of the sealing can 20. It should be noted that Figure 5The display shows the reverse state.

[0106] The gasket 60 may be a preformed component embedded in the sealing can 20 , or may be directly formed on the surface of the sealing can 20 by insert molding or other methods.

[0107] By putting the outer packaging can 10 on the above-mentioned assembly and caulking the open end 11, the bottom portion 61 of the gasket 60 is compressed by the open end 21 of the sealing can 20 and the conductive components 80, 80 are compressed by the inner bottom surfaces of the sealing can 20 and the outer packaging can 10. Figure 3 The flat all-solid-state battery shown.

[0108] Here, when the open end 11 of the outer packaging can 10 is caulked, in order to fully exert the sealing effect of the gasket 60 and the above-mentioned effect of the conductive porous components 80, 80 by appropriately compressing the bottom portion 61 of the gasket 60 and appropriately compressing the conductive porous components 80, 80, it is desired to construct the above-mentioned assembly in a manner that satisfies the following conditions.

[0109] In the above-mentioned assembly, if the height from the inner bottom surface of the sealing can 20 to the bottom surface 61 of the gasket 60 (the portion sandwiched between the opening end 21 of the sealing can 20 and the inner bottom surface of the outer can 10) on the outer can side is t (mm) ( Figure 4 ), the total thickness of the electrode stack and the conductive porous members 80, 80 is set to a (mm) ( Figure 5 ), in order to make it easier to seal by caulking, it is desirable to make the values ​​of t and a not differ greatly. Specifically, it is preferably set to -0.25≦at≦0.18(mm), and at is more preferably -0.2(mm) or more, further preferably -0.15(mm) or more, and particularly preferably -0.1(mm) or more.

[0110] On the other hand, at is more preferably 0.15 (mm) or less, further preferably 0.12 (mm) or less, and particularly preferably 0.1 (mm) or less.

[0111] As at increases, the degree of compression of the conductive porous member increases, which may reduce the stress relaxation effect during caulking. Therefore, it is desirable to set the thickness of each component such as the conductive porous member according to the value of at.

[0112] When at≧0, it is considered that when the open end 11 of the outer can 10 is caulked, first, the conductive porous members 80, 80 are compressed, and the total thickness a of the electrode stack and the conductive porous members 80, 80 (in this case, a is substantially equal to the distance between the inner bottom surface of the outer can 10 and the inner bottom surface of the sealing can 20) decreases to a value substantially the same as t, thereby compressing the bottom surface 61 of the gasket 60. Therefore, when the total thickness of the conductive porous members 80, 80 is set to b (mm), if b is not made larger than at to some extent, the conductive porous members 80, 80 will be excessively compressed, and there is a concern that the conductive porous members 80, 80 cannot withstand the stress during caulked.

[0113] Therefore, it is preferably b≧3.5×(at), more preferably b≧4×(at), and particularly preferably b≧5×(at).

[0114] On the other hand, if the thickness of the conductive porous members 80 , 80 is too thick, it is necessary to adjust the thickness of the electrode stack to reduce the capacity of the electrode, so it is preferable to set b≦10×(at).

[0115] In addition, when at<0, it is considered that when the open end 11 of the outer packaging can 10 is caulked, first, the bottom portion 61 of the gasket 60 is compressed, and the height t from the inner bottom surface of the sealing can 20 to the end of the bottom portion 61 of the gasket 60 on the outer packaging can side (in this case, t is substantially equal to the distance between the inner bottom surface of the outer packaging can 10 and the inner bottom surface of the sealing can 20) decreases to a value substantially the same as a, so that the conductive porous members 80, 80 are compressed. Therefore, when the thickness of the bottom portion 61 of the gasket 60 in the height direction is s (mm) ( Figure 4 ), if s is not made larger than ta to a certain extent, the gasket 60 will be over-compressed, and cracks will appear on the bottom surface 61 of the gasket 60 during caulking, thereby reducing the sealing performance and causing concern about a short circuit between the open end 21 of the sealing can 20 and the inner bottom surface of the outer packaging can 10.

[0116] Therefore, it is preferably s≧2×(ta), more preferably s≧3×(ta), and particularly preferably s≧5×(ta).

[0117] On the other hand, if the thickness s of the bottom surface portion 61 of the gasket 60 is too thick, compression may be insufficient during caulking, which may result in loss of sealing performance. Therefore, it is preferably set to s≦15×(ta).

[0118] Specifically, the thickness s of the bottom surface portion 61 of the gasket 60 is preferably 0.1 mm or more, more preferably 0.2 mm or more, and is preferably 1 mm or less, more preferably 0.8 mm or less.

[0119] The flat all-solid battery of this embodiment can be used in the same applications as conventionally known secondary batteries, but has a solid electrolyte instead of an organic electrolyte solution, and thus has excellent heat resistance and can be preferably used in applications exposed to high temperatures.

[0120] In addition, in the flat all-solid battery of the present embodiment, an example is given of a battery in which a gasket is provided between the outer packaging can and the sealing can, and the battery is sealed by caulking the open end of the outer packaging can. However, the flat all-solid battery disclosed in the present application is not limited to this method, and for example, it also includes a battery in which a gasket is not used and the outer packaging can and the sealing can are joined to each other to be sealed.

[0121] Example

[0122] Hereinafter, the flat all-solid-state battery disclosed in the present application will be described in detail based on examples, but the following examples are not intended to limit the flat all-solid-state battery disclosed in the present application.

[0123] (Example 1)

[0124] <Production of positive electrode>

[0125] LiNi with an average particle size of 3 μm as the positive electrode active material 0.33 Co 0.33 Mn 0.33 O2, a sulfide solid electrolyte (Li6PS5Cl) having an argyrodite-type structure, and carbon nanotubes (Showa Denko Co., Ltd. "VGCF" (trade name)) as a conductive aid were mixed at a mass ratio of 65:30:5, and fully kneaded to prepare a positive electrode mixture. Next, 75 mg of the above positive electrode mixture was placed in a powder molding metal mold, and pressure molding was performed using a press to produce a positive electrode consisting of a positive electrode mixture molded body with a thickness of 0.85 mm.

[0126] <Formation of solid electrolyte layer>

[0127] Next, 24 mg of the sulfide solid electrolyte was added to the positive electrode mixture compact in the powder molding die, and pressure molding was performed using a press to form a solid electrolyte layer with a thickness of 0.4 mm on the positive electrode mixture compact.

[0128] <Production of negative electrode>

[0129] As the negative electrode active material, Li4Ti5O 12, the sulfide solid electrolyte and the carbon nanotubes are mixed in a mass ratio of 55:40:5, fully kneaded, and a negative electrode mixture is prepared. Next, 122 mg of the negative electrode mixture is added to the solid electrolyte layer in the powder molding metal mold, and a press is used to perform pressure molding to form a negative electrode consisting of a negative electrode mixture molded body with a thickness of 2.05 mm on the solid electrolyte layer, thereby producing an electrode stack with a diameter of 6.4 mm and a thickness of 3.3 mm formed by stacking a positive electrode, a solid electrolyte layer, and a negative electrode.

[0130] <Battery Assembly>

[0131] Two flexible graphite sheets "PERMA-FOIL (product name)" (thickness: 0.1 mm, apparent density: 1.1 g / cm) manufactured by Toyo Tanso Co., Ltd. were prepared by molding expanded graphite into sheets without using a binder. 3 ) was punched into a sample of the same size as the electrode stack, and one of them was placed on the inner bottom of a stainless steel sealed can with a polypropylene ring gasket embedded in it. Next, the electrode stack was stacked on the graphite sheet, with the negative electrode on the graphite sheet side, and another graphite sheet was further placed on it to form a Figure 5 The assembly shown.

[0132] At this time, the total thickness b of the two graphite sheets, the total thickness a of the electrode stack and the above-mentioned graphite sheets, the thickness s in the height direction of the bottom portion of the gasket, and the height t from the inner bottom surface of the sealing can to the end of the bottom portion of the gasket on the outer packaging can side are b = 0.2 (mm), a = 3.5 (mm), s = 0.5 (mm), and t = 3.65 (mm), respectively.

[0133] After covering the above-mentioned assembly with a stainless steel outer packaging can, the open end of the outer packaging can is sealed inwardly, thereby producing a flat all-solid battery with a diameter of about 7 mm, in which the above-mentioned graphite sheet is respectively arranged between the inner bottom surface of the sealing can and the above-mentioned stacked body and between the inner bottom surface of the outer packaging can and the above-mentioned stacked body.

[0134] The distance between the inner bottom surface of the sealed outer can and the inner bottom surface of the sealed can is 3.47 mm. In addition, the compression rate of the gasket bottom surface portion obtained by calculation is 36%, and the compression rate of the graphite sheet is 15%.

[0135] (Example 2)

[0136] An assembly was formed in the same manner as in Example 1 except that three samples were prepared by punching the above-mentioned flexible graphite sheets, two of which were arranged between the inner bottom surface of the sealing can and the negative electrode of the electrode stack, and the remaining one was arranged on the positive electrode of the electrode stack.

[0137] In this assembly, b=0.3 (mm), a=3.6 (mm), s=0.5 (mm), and t=3.65 (mm).

[0138] The following operation was carried out in the same manner as in Example 1 to produce a flat all-solid battery. The distance between the inner bottom surface of the sealed outer packaging can and the inner bottom surface of the sealing can was 3.51 mm. In addition, the compression rate of the gasket bottom surface was calculated to be 28%, and the compression rate of the graphite sheet was 30%.

[0139] (Example 3)

[0140] The same procedures as in Example 1 were followed except that the thickness of the flexible graphite sheet was changed from 0.1 mm to 0.2 mm to form an assembly. The same procedures as in Example 1 were followed to produce a flat all-solid-state battery.

[0141] In the above assembly, b = 0.4 (mm), a = 3.7 (mm), s = 0.5 (mm), t = 3.65 (mm). In the manufactured battery, the distance between the inner bottom surface of the sealed outer can and the inner bottom surface of the sealing can is 3.52 mm. In addition, the compression rate of the gasket bottom surface obtained by calculation is 26%, and the compression rate of the graphite sheet is 45%.

[0142] (Example 4)

[0143] The thickness of the solid electrolyte layer was changed from 0.4 mm to 0.35 mm, and the same operation as in Example 1 was performed to produce an electrode stack with a thickness of 3.25 mm. In addition, the thickness of the flexible graphite sheet was changed from 0.1 mm to 0.07 mm, and an assembly was formed using the electrode stack. The same operation as in Example 1 was performed to produce a flat all-solid battery.

[0144] In the above assembly, b = 0.14 (mm), a = 3.39 (mm), s = 0.5 (mm), t = 3.65 (mm). In the manufactured battery, the distance between the inner bottom surface of the sealed outer can and the inner bottom surface of the sealing can is 3.37 mm. In addition, the compression rate of the gasket bottom surface obtained by calculation is 56%, and the compression rate of the graphite sheet is 14%.

[0145] (Example 5)

[0146] The thickness of the flexible graphite sheet was changed from 0.07 mm to 0.3 mm. The same operation as in Example 4 was performed to form an assembly. The same operation as in Example 4 was then performed to produce a flat all-solid-state battery.

[0147] In the above assembly, b = 0.6 (mm), a = 3.85 (mm), s = 0.5 (mm), t = 3.65 (mm). In the manufactured battery, the distance between the inner bottom surface of the sealed outer can and the inner bottom surface of the sealing can is 3.54 mm. In addition, the compression rate of the gasket bottom surface obtained by calculation is 22%, and the compression rate of the graphite sheet is 52%.

[0148] (Example 6)

[0149] The thickness of the flexible graphite sheet is changed from 0.1 mm to 0.2 mm, and the graphite sheet is arranged only between the inner bottom surface of the sealing can and the electrode stack. Otherwise, the same operation is performed as in Example 1 to form an assembly. The following operation is performed in the same manner as in Example 1 to make a flat all-solid-state battery.

[0150] In the above assembly, b = 0.2 (mm), a = 3.5 (mm), s = 0.5 (mm), t = 3.65 (mm). In the manufactured battery, the distance between the inner bottom surface of the sealed outer can and the inner bottom surface of the sealing can is 3.47 mm. In addition, the compression rate of the gasket bottom surface obtained by calculation is 36%, and the compression rate of the graphite sheet is 15%.

[0151] (Example 7)

[0152] The same procedures as in Example 1 were followed except that a conductive sheet having a thickness of 0.2 mm and made of carbon fiber nonwoven fabric was used instead of the above-mentioned flexible graphite sheet to form an assembly. The same procedures as in Example 1 were followed to produce a flat all-solid-state battery.

[0153] In the above assembly, b = 0.4 (mm), a = 3.7 (mm), s = 0.5 (mm), t = 3.65 (mm). In the manufactured battery, the distance between the inner bottom surface of the sealed outer can and the inner bottom surface of the sealing can is 3.48 mm. In addition, the compression rate of the gasket bottom surface obtained by calculation is 34%, and the compression rate of the carbon nonwoven fabric is 55%.

[0154] (Comparative Example 1)

[0155] The thickness of the solid electrolyte layer was changed from 0.4 mm to 0.6 mm, and the same operation as in Example 1 was performed to produce an electrode stack with a thickness of 3.5 mm. In addition, the above-mentioned flexible graphite sheet was not used, and the negative electrode and the positive electrode of the above-mentioned electrode stack were directly contacted with the inner bottom surface of the sealing can and the inner bottom surface of the outer packaging can, respectively, and the same operation as in Example 1 was performed to produce a flat all-solid battery.

[0156] In the manufactured battery, the distance between the inner bottom surface of the sealed outer can and the inner bottom surface of the sealing can was 3.49 mm. In addition, the compression rate of the gasket bottom surface portion obtained by calculation was 32%.

[0157] (Comparative Example 2)

[0158] Instead of the above-mentioned flexible graphite sheet, a copper foam substrate (porosity: 97%) with a thickness of 1 mm is arranged between the inner bottom surface of the sealing can and the negative electrode of the electrode stack, and an aluminum foam substrate (porosity: 97%) with a thickness of 1 mm is arranged on the positive electrode of the electrode stack. Except for this, the same operation as Example 1 is performed to form an assembly.

[0159] In this assembly, b=2 (mm), a=5.3 (mm), s=0.5 (mm), and t=3.65 (mm).

[0160] The following operation was carried out in the same manner as in Example 1 to produce a flat all-solid battery. The distance between the inner bottom surface of the sealed outer packaging can and the inner bottom surface of the sealing can was 3.51 mm. In addition, the compression rate of the gasket bottom surface obtained by calculation was 28%, and the compression rate of the foam substrate was 90%.

[0161] Table 1 shows the dimensional relationship between the assemblies used in Examples 1 to 7 and Comparative Examples 1 and 2.

[0162] [Table 1]

[0163] a b s t at b / (at) s / (at) Example 1 3.5 0.2 0.5 3.65 -0.15 -- 3.3 Example 2 3.6 0.3 0.5 3.65 -0.05 -- 10 Example 3 3.7 0.4 0.5 3.65 0.05 8 -- Example 4 3.39 0.14 0.5 3.65 -0.26 -- 1.92 Example 5 3.85 0.6 0.5 3.65 0.2 3 -- Example 6 3.5 0.2 0.5 3.65 -0.15 -- 3.3 Example 7 3.7 0.4 0.5 3.65 0.05 8 -- Comparative Example 1 3.5 0 0.5 3.65 -0.15 -- 3.3 Comparative Example 2 5.3 2 0.5 3.65 1.65 1.21 --

[0164] <Confirmation of cracks in electrode stack>

[0165] Ten batteries of Examples 1 to 7 and Comparative Examples 1 to 2 were produced, and each of the produced flat all-solid batteries was observed using an X-ray CT apparatus to confirm whether cracks occurred in the electrode stack.

[0166] In the flat all-solid batteries of Examples 1 to 4, since a flexible conductive porous sheet made of a graphite molded body is arranged between the inner bottom surface of the sealing can and the inner bottom surface of the outer packaging can and the electrode stack, no cracks were confirmed in the electrode stack in any of the batteries produced.

[0167] In addition, in the flat all-solid battery of Example 7, since a carbon fiber nonwoven fabric was used as the conductive porous member, no cracks were observed in the electrode stack in any of the batteries produced.

[0168] On the other hand, the flat all-solid battery of Example 5 is also similar to the batteries of Examples 1 to 4, in which the above-mentioned conductive porous sheet is arranged between the inner bottom surface of the sealing can and the inner bottom surface of the outer packaging can and the electrode stack. However, in 4 batteries, cracks were confirmed in the negative electrode or the positive electrode. This is believed to be caused by the following reasons: the value of at exceeds 0.18 (mm), so the degree of compression of the flexible graphite sheet becomes greater, and the effect of relieving the stress during caulking decreases.

[0169] In the flat all-solid battery of Example 6, the conductive porous sheet was placed only between the inner bottom surface of the sealing can and the electrode stack. As a result, cracks were observed in the positive electrode of one battery.

[0170] The above-mentioned conductive porous sheet can prevent the electrode from breaking to some extent by being arranged only on one side of the electrode stack. However, as can be seen from the comparison between Example 1 and Example 6, the electrode can be more reliably prevented from breaking by being arranged on both sides of the electrode stack.

[0171] In addition, in the flat all-solid battery of Comparative Example 2, which uses a metal foam substrate instead of a flexible graphite sheet as a conductive porous component, the stress of compressing the above-mentioned foam substrate is also relieved, so that no cracks in the electrode stack are confirmed in any of the batteries produced.

[0172] On the other hand, in the flat all-solid battery of Comparative Example 1 in which the electrode stack is in direct contact with the inner bottom surface of the sealing can and the inner bottom surface of the outer packaging can, for all the batteries produced, the edge portion of the negative electrode facing the sealing can or the like Figure 1 and Figure 2 Cracks were observed in the edge of the positive electrode facing the outer can.

[0173] <Battery Characteristics Evaluation>

[0174] For the batteries of Examples 1 to 7 and Comparative Example 2 in which the rupture of the electrode stack was confirmed, 5 batteries in which no rupture was confirmed were selected, and 100 cycles of charge and discharge were repeated under the following conditions at a temperature of 100°C. The average value of the ratio of the discharge capacity of the 100th cycle to the discharge capacity of the 2nd cycle (capacity retention rate) was calculated to evaluate the cycle characteristics.

[0175] The charging is set to a constant current-constant voltage charging which is a combination of constant current charging at a current value of 0.2C until the battery voltage reaches 3.1V and constant voltage charging at a voltage of 3.1V until the current value reaches 0.02C. The discharging is set to a constant current discharging at a current value of 0.2C until the battery voltage reaches 1.2V.

[0176] The above evaluation results are shown in Table 2 together with the results of confirming cracks in the electrode stack.

[0177] [Table 2]

[0178] Batteries with ruptures in electrodes (units) Capacity maintenance rate (%) Example 1 0 94 Example 2 0 96 Example 3 0 98 Example 4 0 83 Example 5 4 77 Example 6 1 84 Example 7 0 87 Comparative Example 1 10 -- Comparative Example 2 0 10

[0179] In the batteries of Examples 1 to 3 and Examples 6 to 7 in which -0.25≦at≦0.18 (mm) was set when the assembly was formed, the sealing function by caulking was fully exerted, and the batteries had a high capacity retention rate.

[0180] In the battery of Example 4, at<-0.25, and the compression ratio of the gasket was too high, so it is considered that the sealing performance was reduced and the capacity retention rate was reduced compared with the batteries of Examples 1 to 3.

[0181] In the battery of Example 5, at>0.18, and the compression ratio of the conductive porous sheet was too high, so it is considered that the function of coping with expansion and contraction of the electrode stack was reduced compared with the batteries of Examples 1 to 3, and the capacity retention rate was reduced.

[0182] In the battery of Example 6, no conductive porous sheet is arranged between the inner bottom surface of the outer packaging can and the electrode stack. Therefore, compared with the batteries of Examples 1 to 3, the contact resistance on the positive electrode side increases and the uniformity of the charge and discharge reaction decreases. It is believed that the capacity retention rate decreases compared with Examples 1 to 3.

[0183] In the battery of Example 7, since carbon fiber nonwoven fabric is used as the conductive porous sheet, it is believed that the recovery property of the conductive porous sheet is reduced compared with the batteries of Examples 1 to 3, so the contact resistance increases, the uniformity of the charge and discharge reaction decreases, and the capacity retention rate decreases compared with Examples 1 to 3.

[0184] However, compared with the battery of Comparative Example 2 which uses a metal foam substrate having almost no recovery property after compression as a conductive porous component, any of the batteries in the embodiments has a high capacity retention rate, which confirms the effect of using a conductive porous sheet composed of carbon material fibers or a flexible conductive porous sheet composed of a graphite molded body as a conductive porous component.

[0185] Without departing from the scope of its purpose, the present invention can also be implemented in ways other than the above. The embodiments disclosed in this application are only some examples and are not limited to these examples. Compared with the description of the above specification, the scope of the present invention is interpreted preferentially by the description of the claims, and all changes within the scope of the claims are included in the claims.

[0186] Explanation of symbols

[0187] 1. 100: flat all-solid-state battery, 10: outer packaging can, 11: opening end, 20: sealing can, 21: opening end, 30: positive electrode, 40: negative electrode, 50: solid electrolyte layer, 60: gasket, 61: bottom portion, 70: rupture, 80: conductive porous component.

Claims

1. A flat all-solid battery having a battery container consisting of an outer packaging can and a sealing can, and a laminated body consisting of a positive electrode, a solid electrolyte layer and a negative electrode, The stacked body is accommodated in the battery container, The positive electrode is composed of a molded body of a positive electrode mixture containing a positive electrode active material and a solid electrolyte, or has a layer of a positive electrode mixture containing a positive electrode active material and a solid electrolyte on one or both sides of a current collector. The negative electrode is composed of a molded body of a negative electrode mixture containing a negative electrode active material, or has a layer of a negative electrode mixture containing a negative electrode active material on one or both sides of a current collector. A flexible conductive porous member made of expanded graphite is disposed between the stacked body and the inner bottom surface of the outer can or the inner bottom surface of the sealing can. 2 . The flat all-solid battery according to claim 1 , wherein the conductive porous member is disposed between the stacked body and the inner bottom surface of the sealing can and between the stacked body and the inner bottom surface of the outer can, respectively. 3 . The flat all-solid-state battery according to claim 2 , wherein the electrode on the sealing can side is formed of a molded body of an electrode mixture containing an active material. 4 . The flat all-solid battery according to claim 3 , wherein the molded body of the electrode mixture does not contain a binder. 5 . The flat all-solid battery according to claim 1 , wherein the conductive porous member has a thickness of 0.03 to 0.5 mm.

6. The flat all-solid battery according to any one of claims 1 to 4, wherein the apparent density of the conductive porous member is 0.5 to 1.7 g / cm 3 . 7 . The flat all-solid-state battery according to claim 1 , wherein the laminate contains a sulfide-based solid electrolyte.

8. A method for manufacturing a flat all-solid battery, which is a method for manufacturing a flat all-solid battery having a battery container consisting of an outer packaging can and a sealing can and a laminated body consisting of a positive electrode, a solid electrolyte layer and a negative electrode, comprising: a step of placing a conductive porous member and the laminated body on the inner bottom surface of a sealed can to which a ring-shaped gasket is attached to form an assembly; and A step of sealing the assembly by covering the assembly with an outer packaging can and caulking the can; The positive electrode is composed of a molded body of a positive electrode mixture containing a positive electrode active material and a solid electrolyte, or has a layer of a positive electrode mixture containing a positive electrode active material and a solid electrolyte on one or both sides of a current collector. The negative electrode is composed of a molded body of a negative electrode mixture containing a negative electrode active material, or has a layer of a negative electrode mixture containing a negative electrode active material on one or both sides of a current collector. The conductive porous member is disposed between the stacked body and the inner bottom surface of the outer can or the inner bottom surface of the sealing can. The conductive porous member is a flexible conductive porous sheet composed of expanded graphite. The gasket has a bottom surface sandwiched between the open end of the sealing can and the inner bottom surface of the outer packaging can. The assembly is configured as follows: in the assembly, when the height from the inner bottom surface of the sealing can to the end of the bottom surface of the gasket on the outer packaging can side is t in mm and the total thickness of the stack and the conductive porous component is a in mm, -0.25≦a-t≦0.

18. 9 . The method for manufacturing a flat all-solid battery according to claim 8 , wherein the conductive porous member is disposed between the stacked body and the inner bottom surface of the sealing can and between the stacked body and the inner bottom surface of the outer can, respectively.

Images