Sulfide solid battery, printed circuit board with sulfide solid battery, and method for manufacturing sulfide solid battery

Abstract

To provide a novel sulfide solid-state battery sealed with an inorganic material, capable of being mounted on a printed circuit board using a soldering process, especially a reflow soldering process.SOLUTION: A sulfide solid-state battery 1000 of the present disclosure includes a battery laminate including one or more unit cells, and an inorganic coating layer 210 coating at least a portion around the battery laminate. The unit cell includes a positive electrode layer 30, 40, a solid electrolyte layer 12, and a negative electrode layer 20 which are laminated in this order. At least one of the positive layer, the solid electrolyte layer, and the negative electrode layer contains a sulfide solid electrolyte, and the inorganic coating layer comprises inorganic glass having a glass transition point of 260°C or more and 360°C or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a sulfide solid-state battery, a printed circuit board with a sulfide solid-state battery, and a method for manufacturing a sulfide solid-state battery.

Background Art

[0002] In recent years, various techniques for sealing batteries using resins have been disclosed (Patent Documents 1 to 3).

[0003] For example, Patent Document 3 discloses a sulfide solid-state battery having a battery laminate having two or more unit cells; and a resin layer covering the side surface of the battery laminate, wherein the unit cell is formed by laminating a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer in this order, and at least one of the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector layer has an extension portion extending outward from the other layers on the side surface of the battery laminate, and a gap is formed between the extension portions, and the ratio of the compression elastic modulus of the resin layer to the compression elastic modulus of the battery laminate is 0.4 or less.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] Depending on the use of the battery, the performance such as barrier properties and heat resistance may be insufficient in conventional sealing using a general resin.

[0006] In contrast, the present disclosure provides a novel sulfide solid-state battery encapsulated with an inorganic material.

[0007] Also, depending on the application of the battery, it may be preferable to mount the battery on a printed circuit board using a soldering process, particularly a reflow soldering process.

[0008] However, generally, sulfide solid-state batteries using a sulfide solid electrolyte are considered unsuitable for mounting on a printed circuit board using a soldering process because the sulfide solid electrolyte is weak against heat. In particular, as in the above prior art, in a sulfide solid-state battery encapsulated with a general resin, it is considered particularly unsuitable for mounting on a printed circuit board using a soldering process because the general resin is weak against heat.

[0009] In contrast, the present disclosure provides a sulfide solid-state battery that can be mounted on a printed circuit board using a soldering process, particularly a reflow soldering process.

Means for Solving the Problems

[0010] As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means, and have completed the present invention. That is, the present invention is as follows:

[0011] 〈Aspect 1〉 A battery laminate having one or more unit cells; and An inorganic coating layer covering at least a part of the periphery of the battery laminate having, the unit cell being formed by laminating a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in this order, at least one of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer containing a sulfide solid electrolyte, and the inorganic coating layer being composed of an inorganic glass having a glass transition point of 260°C or higher and 360°C or lower, a sulfide solid-state battery. 〈Aspect 2〉 The sulfide solid-state battery according to aspect 1, wherein the inorganic coating layer is coated with a resin coating layer made of a fluorine-based resin. <Aspect 3> A printed circuit board and a sulfide solid-state battery with a printed circuit board having the sulfide solid-state battery according to aspect 1 soldered thereto. <Aspect 4> A method for manufacturing a printed circuit board with a sulfide solid-state battery according to aspect 3, including soldering the sulfide solid-state battery to the printed circuit board by reflow soldering. <Aspect 5> A method for manufacturing a sulfide solid-state battery according to any one of aspects 1 to 3, including the following steps: (a) Preparing the battery laminate; and (b) Forming the inorganic coating layer on at least a part of the periphery of the battery laminate.

Advantages of the Invention

[0012] The present disclosure provides a novel sulfide solid-state battery sealed with an inorganic material and a method for manufacturing the same. In particular, the present disclosure provides a sulfide solid-state battery that can be mounted on a printed circuit board using a soldering process, particularly a reflow soldering process, and a method for manufacturing the same.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments for carrying out the present disclosure will be described in detail with reference to the drawings. However, the embodiments shown in the drawings are examples of the present disclosure and do not limit the present disclosure.

[0015] 《Sulfide Solid-State Battery》 The sulfide solid-state battery of the present disclosure has a battery laminate having one or more unit cells; and an inorganic coating layer covering at least a part of the periphery of the battery laminate. In addition, in the sulfide solid-state battery of the present disclosure, the unit cell is formed by laminating a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in this order, and at least one of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer contains a sulfide solid electrolyte, and the inorganic coating layer is composed of an inorganic glass having a glass transition point of 260°C or higher and 360°C or lower.

[0016] Regarding the present disclosure, the "glass transition point" can be evaluated by differential thermal analysis (DTA) measurement in accordance with JIS K 0129:2005. Specifically, for example, in the differential curve of the DTA curve obtained using α-alumina as a reference, the temperature at the center of the first endothermic peak (the intersection of the tangents at the first inflection point and the second inflection point) can be defined as the glass transition point (Tg).

[0017] Regarding the present disclosure, "around the battery laminate" refers to both surfaces in the stacking direction of each layer of the battery laminate and the peripheral edge in the plane direction of each layer of the battery laminate. Therefore, in the sulfide solid-state battery of the present disclosure, the inorganic coating layer covers at least a part of both surfaces in the stacking direction of each layer of the battery laminate and the peripheral edge in the plane direction of each layer of the battery laminate. For example, the inorganic coating layer may cover one or both of both surfaces in the stacking direction of each layer of the battery laminate, or may cover the whole or a part of the peripheral edge in the plane direction of each layer of the battery laminate. Also, for example, the inorganic coating layer may cover one or both of both surfaces in the stacking direction of each layer of the battery laminate and the whole or a part of the peripheral edge in the plane direction of each layer of the battery laminate.

[0018] The inventors of the present disclosure found that an inorganic glass having an appropriate glass transition temperature can cover at least a part of the periphery of the sulfide solid-state battery without significantly deteriorating the sulfide solid electrolyte, and thus conceived the sulfide solid-state battery of the present disclosure. In this regard, the inventors of the present disclosure heat-treated a positive electrode active material layer containing a lithium niobate-coated nickel-cobalt-manganese-based positive electrode active material and a Li2S-P2S5-based solid electrolyte, and confirmed that although the ionic conductivity of the solid electrolyte starts to decrease when the temperature exceeds 300°C, it is maintained when the temperature is 360°C or lower.

[0019] In the present disclosure, the inorganic coating layer covers at least a part of the periphery of the battery laminate. As a result, the sulfide solid-state battery of the present disclosure may not have an exterior such as a laminate film or a metal can. Therefore, the sulfide solid-state battery of the present disclosure can be made more compact than a conventional sulfide solid-state battery that requires an exterior such as an aluminum laminate film, thereby improving the energy density of the battery. However, the sulfide solid-state battery of the present disclosure may further have an exterior such as an aluminum laminate film in addition to the inorganic coating layer and an optional resin coating layer.

[0020] In addition, the present disclosure's inventors and the like found that in a soldering process at low to medium temperatures, soldering can be performed without significantly deteriorating the sulfide solid electrolyte, and that an inorganic glass having an appropriate glass transition temperature can cover at least a part of the periphery of the sulfide solid battery without significantly deteriorating the sulfide solid electrolyte and can withstand the heat of the soldering process, leading to the idea of the sulfide solid battery of the present disclosure. Unexpectedly, the sulfide solid battery of the present disclosure can be mounted on a printed circuit board using a soldering process, particularly a reflow soldering process.

[0021] Regarding the present disclosure, the "reflow soldering process" means a process of heating and melting a solder that has been previously applied at room temperature for soldering.

[0022] In the "reflow soldering process", a paste-like or cream-like solder is applied or printed on the necessary parts of the printed circuit board. Next, the object to be soldered is placed at a predetermined position on the printed circuit board. Finally, the entire printed circuit board is passed through a high-temperature reflow furnace to melt the solder and solder the object to be soldered and the printed circuit board. Here, examples of the heating method in the reflow furnace include the infrared method and the hot air method.

[0023] Incidentally, a process of flowing the molten solder between the object to be soldered and the printed circuit board for soldering is sometimes referred to as the "flow soldering process" with respect to the above "reflow soldering process". Naturally, the sulfide solid battery of the present disclosure can be mounted on a printed circuit board not only by the "reflow soldering process" but also by the "flow soldering process".

[0024] (Inorganic coating layer) The inorganic coating layer of the sulfide solid battery of the present disclosure is composed of an inorganic glass having a glass transition point of 260°C or higher and 360°C or lower. Here, this glass transition point may be 270°C or higher, 280°C or higher, 290°C or higher, 300°C or higher, 310°C or higher, 320°C or higher, 330°C or higher, 340°C or higher, or 350°C or higher, and may also be 350°C or lower, 340°C or lower, 330°C or lower, 320°C or lower, 310°C or lower, 300°C or lower, 290°C or lower, 280°C or lower, or 270°C or lower.

[0025] Examples of such inorganic glasses having a relatively low glass transition point include silicate glasses, borate glasses, bismuth silicate glasses, borosilicate glasses, vanadium oxide glasses, and phosphate glasses.

[0026] Examples of silicate glasses include those having SiO2-ZnO, SiO2-Li2O, SiO2-Na2O, SiO2-CaO, SiO2-MgO, SiO2-Al2O3, etc. as the main components. Examples of bismuth silicate glasses include those having SiO2-Bi2O3-ZnO, SiO2-Bi2O3-Li2O, SiO2-Bi2O3-Na2O, SiO2-Bi2O3-CaO, etc. as the main components. Examples of borate glasses include those having B2O3-ZnO, B2O3-Li2O, B2O3-Na2O, B2O3-CaO, B2O3-MgO, B2O3-Al2O3, etc. as the main components. Examples of borosilicate glasses include those having SiO2-B2O3-ZnO, SiO2-B2O3-Li2O, SiO2-B2O3-Na2O, SiO2-B2O3-CaO, etc. as the main components. Examples of vanadium oxide glasses include those having V2O5-B2O3, V2O5-B2O3-SiO2, V2O5-P2O5, V2O5-B2O3-P2O5, etc. as the main components. Examples of phosphate glasses include those having P2O5-Li2O, P2O5-Na2O, P2O5-CaO, P2O5-MgO, P2O5-Al2O3, etc. as the main components.

[0027] In addition to the components described above, these low glass transition point glasses may appropriately contain one or more of SiO2, ZnO, Na2O, B2O3, Li2O, SnO, BaO, CaO, Al2O3, etc. Here, the "main component" means that the above components are more than 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more of the weight of the inorganic glass.

[0028] The inorganic coating layer may optionally contain a filler, particularly an inorganic filler. Examples of such inorganic fillers include oxides (alumina (Al2O3), silica (SiO2), titania (TiO2), zirconia (ZrO2), and other CeO2, Y2O3, La2O3, LiAlO2, Li2O, BeO, B2O3, Na2O, MgO, P2O5, CaO, Cr2O3, Fe2O3, ZnO, etc.), porous composite ceramics (zeolite, sepiolite, palygorskite, etc.), nitrides (Si3N4, BN, AIN, TiN, Ba3N2, etc.), carbides (SiC, ZrC, B4C), carbonates (MgCO3, CaCO3, etc.), or sulfates (CaSO4, BaSO4, etc.), etc., but are not limited thereto.

[0029] Also, the material used for these inorganic fillers may be single or a mixture of two or more. The shape of the inorganic filler is not particularly limited and may be spherical, elliptical, fibrous, or scaly, etc.

[0030] The method for forming the inorganic coating layer is not particularly limited. For example, by methods such as the capillary underfill method, injection molding method, transfer molding method, or dipping molding method, the material of the inorganic coating layer softened by heating or in a liquid state is supplied around the battery laminate, and then this material is cooled and cured to form an inorganic coating layer on the side surface of the battery laminate. Also, the inorganic coating layer can be obtained by previously forming a sheet of this inorganic coating layer, sandwiching the battery laminate with this sheet, and heating the sheet together with the battery laminate to soften it.

[0031] (Resin coating layer) In the sulfide solid-state battery of the present disclosure, the inorganic coating layer may be coated with a resin coating layer composed of a fluororesin.

[0032] When the inorganic coating layer is coated with a resin coating layer composed of a fluororesin in this way, since the fluororesin has a relatively high gas barrier property, it is possible to better suppress the surrounding gas from reaching the battery laminate through the coating layer. The proportion of the fluororesin in the resin coating layer may be more than 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more.

[0033] Such a fluororesin may be any resin having fluorine atoms (F) in the structural unit (repeating unit). In particular, such a fluororesin may have a glass transition point of 260 °C or higher and 360 °C or lower. Here, this glass transition point may be 270 °C or higher, 280 °C or higher, 290 °C or higher, 300 °C or higher, 310 °C or higher, 320 °C or higher, 330 °C or higher, 340 °C or higher, or 350 °C or higher, and may also be 350 °C or lower, 340 °C or lower, 330 °C or lower, 320 °C or lower, 310 °C or lower, 300 °C or lower, 290 °C or lower, 280 °C or lower, or 270 °C or lower.

[0034] Such fluororesins may be, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), fluoropolyether (FPE), perfluoropolyether (PFPE), perfluoroalkoxyalkane (PFA), perfluoroethylene propene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), tetrafluoroethylene-perfluorodioxole copolymer (TFE / PDD), polyvinyl fluoride (PVF), etc.

[0035] The resin coating layer may optionally contain a filler, particularly an inorganic filler. For such inorganic fillers, reference can be made to the description in the inorganic coating layer.

[0036] The resin coating layer can be obtained by any method. For example, regarding the method for forming the resin coating layer, reference can be made to the descriptions in Patent Documents 1 to 3 and the above description regarding the inorganic coating layer.

[0037] 〈Types of Sulfide Solid Batteries〉 In the present disclosure, examples of the sulfide solid battery can include a solid lithium-ion battery, a solid sodium-ion battery, a solid magnesium-ion battery, and a solid calcium-ion battery. Among them, a solid lithium-ion battery and a solid sodium-ion battery are preferable, and particularly, a solid lithium-ion battery is preferable.

[0038] Also, the sulfide solid battery of the present disclosure may be a primary battery or a secondary battery, but among them, a secondary battery is preferably used. This is because a secondary battery can be repeatedly charged and discharged and is useful, for example, as an in-vehicle battery. Therefore, the sulfide solid battery of the present disclosure is preferably a solid lithium-ion secondary battery.

[0039] 〈Laminated Structure of Battery Stack〉 In the present disclosure, the battery stack has one or more unit cells, particularly two or more unit cells, and each unit cell is formed by laminating a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in this order. The positive electrode layer may have a positive electrode current collector layer and a positive electrode active material layer, and the negative electrode layer may have a negative electrode active material layer and a negative electrode current collector layer.

[0040] In the present disclosure, the battery stack may be a monopolar type battery stack or a bipolar type battery stack.

[0041] (Monopolar Type Battery Stack) When the battery laminate is a monopolar type battery laminate, two unit cells adjacent to each other in the stacking direction may have a monopolar configuration that shares a positive electrode current collector layer or a negative electrode current collector layer.

[0042] Therefore, for example, the battery laminate may be a laminate of two unit cells that share a negative electrode current collector layer. Specifically, it can have a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order (not shown).

[0043] Also, for example, the monopolar type battery laminate may be as shown in FIG. 1. Here, FIG. 1 is a cross-sectional view (FIGS. 1(a) and (b)) and a top view (FIG. 1(c)) showing an example of the sulfide solid battery of the present disclosure. FIG. 1(a) is a cross-sectional view of the portion indicated by “(a)” in FIG. 1(c), and FIG. 1(b) is a cross-sectional view of the portion indicated by “(b)” in FIG. 1(c).

[0044] Specifically, in the monopolar type battery laminate 110 shown in FIG. 1, with the solid electrolyte layer 11 as the center, a negative electrode active material layer 20, a solid electrolyte layer 12, a positive electrode active material layer 30, and a positive electrode current collector layer 40 are stacked in this order, and binder-rich solid electrolyte layers 91 and 92 are arranged as protective layers at locations where electron conduction should not occur.

[0045] In the sulfide solid battery 1000 of the present disclosure shown in this FIG. 1, electrical contact with the negative electrode active material layer 20 is achieved by the conductive portion 301 arranged on the left side of FIG. 1(a), and electrical contact with the positive electrode current collector layer 40 is achieved by the conductive portion 302 arranged on the right side of FIG. 1(a). Here, the conductive portions 301 and 302 can be obtained by applying a conductive paste to the side surface of the battery laminate 110.

[0046] In addition, in the battery 1000 of the present disclosure shown in FIG. 1, portions other than the conductive portions 301 and 302 among the surroundings of the battery laminate are covered with the inorganic coating layer 210. Such an inorganic coating layer can be obtained by any method. For example, an inorganic coating layer as shown in FIG. 1 can be obtained by previously forming a sheet of inorganic glass, sandwiching the battery laminate with this sheet, and heating the sheet together with the battery laminate to soften it, thereby coating the battery laminate with the sheet of inorganic glass.

[0047] (Bipolar battery laminate) When the battery laminate is a bipolar battery laminate, two unit cells adjacent in the stacking direction may have a bipolar configuration that shares a positive / negative current collector layer used as both a positive electrode and a negative electrode current collector layer.

[0048] Therefore, for example, the battery laminate may be a laminate of three unit cells that share a positive / negative current collector layer used as both a positive electrode and a negative electrode current collector layer. Specifically, it can have a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, a positive / negative current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, a positive / negative current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer in this order (not shown). Also, in this case, since the "positive / negative current collector layer" is used as both a positive electrode and a negative electrode current collector layer, it applies to either the "positive electrode current collector layer" or the "negative electrode current collector layer" as referred to in the present disclosure.

[0049] Also, for example, the bipolar battery laminate may be as shown in FIG. 2. Here, FIG. 2 is a cross-sectional view (FIGS. 2(a) and (b)) and a top view (FIG. 2(c)) showing an example of the sulfide solid battery of the present disclosure. FIG. 2(a) is a cross-sectional view of the portion indicated by "(a)" in FIG. 2(c), and FIG. 2(b) is a cross-sectional view of the portion indicated by "(b)" in FIG. 1(c).

[0050] Specifically, in the bipolar battery laminate shown in FIG. 2, on the roughened nickel foil 50 as the negative electrode current collector layer, a negative electrode active material layer 25, a solid electrolyte layer 15, a positive electrode active material layer 35, a positive / negative electrode current collector layer 60, a negative electrode active material layer 26, a solid electrolyte layer 16, a positive electrode active material layer 36, and an aluminum foil 45 as the positive electrode current collector layer are laminated.

[0051] In the solid battery 2000 of the present disclosure shown in this FIG. 2, the peripheral edge portion of the periphery of the battery laminate is coated with an inorganic coating layer 220. Such an inorganic coating layer can be obtained by any method. For example, the inorganic coating layer as shown in FIG. 2 can be obtained by pouring molten inorganic glass around the battery laminate placed in a mold in advance and then cooling to harden the inorganic glass.

[0052] 〈Restraint of Battery Laminate〉 The battery laminate of the sulfide solid battery of the present disclosure may be restrained in the stacking direction during use. According to this, during charge and discharge, the conductivity of ions and electrons inside each layer and between the layers of the battery laminate can be improved, and the battery reaction can be further promoted.

[0053] The restraining force in this case is not particularly limited. For example, it may be 1.0 MPa or more, 1.5 MPa or more, 2.0 MPa or more, or 2.5 MPa or more. The upper limit of the restraining force is not particularly limited. For example, it may be 50 MPa or less, 30 MPa or less, 10 MPa or less, or 5 MPa or less.

[0054] Any member can be used as each member used in the battery laminate. Hereinafter, each member used in the battery laminate will be described in detail. In order to easily understand the present disclosure, each member related to the battery laminate of the solid lithium-ion secondary battery will be described as an example. However, the sulfide solid battery of the present disclosure is not limited to the lithium-ion secondary battery and can be widely applied.

[0055] 〈Positive Electrode Layer〉 The positive electrode layer contains at least a positive electrode active material. During charging of the unit cell, lithium ions move from the positive electrode active material through the electrolyte layer to the negative electrode layer. Also, during discharging of the battery, lithium in the negative electrode layer is ionized and returned to the positive electrode active material. The form of the positive electrode layer may be any of the forms known as the positive electrode layer of a unit cell. For example, the positive electrode layer may include a positive electrode current collector layer and a positive electrode active material layer.

[0056] (Positive electrode current collector layer) Any of the common ones as the positive electrode current collector layer of a secondary battery can be adopted for the positive electrode current collector layer. The positive electrode current collector layer may be in the form of a foil, a plate, a mesh, a punched metal, a porous material, a foam, etc. The positive electrode current collector layer may be a metal foil or a metal mesh. In particular, a metal foil is excellent in handleability and the like. The positive electrode current collector layer may be composed of a plurality of metal foils. Examples of the metal constituting the positive electrode current collector layer include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and the like.

[0057] (Positive electrode active material layer) The positive electrode active material layer contains a positive electrode active material and may further optionally contain an electrolyte, a conductive assistant, a binder, etc. Further, the positive electrode active material layer may contain various other additives. The content of each of the positive electrode active material, electrolyte, conductive assistant, binder, etc. in the positive electrode active material layer may be appropriately determined according to the intended battery performance.

[0058] The positive electrode active material may be a known one as the positive electrode active material of a secondary battery and may be any material capable of supplying lithium to the negative electrode side during charging. For example, various lithium-containing composite oxides such as lithium cobaltate, lithium nickelate, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, lithium manganate, spinel-based lithium compounds, etc. can be used. Only one type of positive electrode active material may be used alone, or two or more types may be used in combination.

[0059] The electrolyte that can be included in the positive electrode active material layer may be a solid electrolyte, a liquid electrolyte (electrolyte solution), or a combination thereof.

[0060] As the solid electrolyte, those known as solid electrolytes for secondary batteries may be used. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, inorganic solid electrolytes are excellent in ionic conductivity and heat resistance.

[0061] Examples of inorganic solid electrolytes include lithium lanthanum zirconate, LiPON, Li 1+X Al X Ge 2-X (PO4)3, oxide solid electrolytes such as Li-SiO-based glass, Li-Al-S-O-based glass, etc.; sulfide solid electrolytes such as Li2S-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Si2S-P2S5, Li2S-P2S5-LiI-LiBr, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5-GeS2, etc. can be exemplified. In particular, sulfide solid electrolytes, especially those containing at least Li, S, and P as constituent elements, have high performance. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may be, for example, in the form of particles. Only one type of solid electrolyte may be used alone, or two or more types may be combined and used.

[0062] The electrolyte solution may contain, for example, lithium ions as carrier ions. The electrolyte solution may be, for example, a non-aqueous electrolyte solution. For example, as the electrolyte solution, a solution obtained by dissolving a lithium salt in a carbonate-based solvent at a predetermined concentration can be used. Examples of carbonate-based solvents include fluoroethylene carbonate (FEC), ethylene carbonate (EC), dimethyl carbonate (DMC), etc. Examples of lithium salts include hexafluorophosphate salts, etc.

[0063] Examples of the conductive aids that can be included in the positive electrode active material layer include carbon materials such as vapor grown carbon fiber (VGCF), acetylene black (AB), ketjen black (KB), carbon nanotube (CNT), and carbon nanofiber (CNF); and metal materials such as nickel, aluminum, and stainless steel. The conductive aids may be, for example, particulate or fibrous, and their size is not particularly limited. Only one type of conductive aid may be used alone, or two or more types may be used in combination.

[0064] Examples of the binders that can be included in the positive electrode active material layer include butadiene rubber (BR)-based binders, isobutylene rubber (IIR)-based binders, acrylate butadiene rubber (ABR)-based binders, styrene butadiene rubber (SBR)-based binders, polyvinylidene fluoride (PVdF)-based binders, polytetrafluoroethylene (PTFE)-based binders, polyimide (PI)-based binders, polyacrylic acid-based binders, and the like. Only one type of binder may be used alone, or two or more types may be used in combination.

[0065] (Others) In addition to the above configuration, the positive electrode layer may have a general configuration as a positive electrode of a secondary battery, for example, and may include tabs, terminals, and the like. The positive electrode layer can be manufactured by applying a known method. For example, the positive electrode active material layer can be easily formed by molding a positive electrode mixture containing the above various components in a dry or wet manner. The positive electrode active material layer may be molded together with the positive electrode current collector layer, or may be molded separately from the positive electrode current collector layer.

[0066] 〈Electrolyte layer〉 The electrolyte layer contains at least an electrolyte. The electrolyte layer may contain a solid electrolyte, and may further optionally contain a binder or the like. In this case, the content of the solid electrolyte and the binder or the like in the electrolyte layer is not particularly limited. Further, the electrolyte layer may contain various additives. Further, the electrolyte layer may contain a liquid component together with the solid electrolyte. Alternatively, the electrolyte layer may contain an electrolytic solution, and may further have a separator or the like for holding the electrolytic solution and preventing contact between the positive electrode and the negative electrode.

[0067] As the electrolyte contained in the electrolyte layer, it may be appropriately selected from those exemplified as the electrolytes that can be contained in the above-described positive electrode active material layer. Similarly, for the binder that can be contained in the electrolyte layer, it may be appropriately selected from those exemplified as the binders that can be contained in the above-described positive electrode active material layer. Each of the electrolyte and the binder may be used alone or in combination of two or more. The electrolyte layer can be easily formed, for example, by molding a dry or wet electrolyte mixture containing the above-described electrolyte and binder or the like.

[0068] On the other hand, when the electrolyte layer has an electrolytic solution or a separator, the separator may be a separator commonly used in secondary batteries. The separator may be made of a resin such as polyethylene (PE), polypropylene (PP), polyester, and polyamide, for example. The separator may have a single-layer structure or a multilayer structure. Examples of the multilayer structure separator include a two-layer structure separator of PE / PP, or a three-layer structure separator of PP / PE / PP or PE / PP / PE. The separator may be made of a non-woven fabric such as a cellulose non-woven fabric, a resin non-woven fabric, or a glass fiber non-woven fabric.

[0069] 〈Negative electrode layer〉 The negative electrode layer may include only the negative electrode current collector layer or may include a negative electrode active material layer and a negative electrode current collector layer. When the negative electrode layer includes only the negative electrode current collector layer, lithium ions that have migrated from the positive electrode during charging receive electrons and deposit as metallic lithium between the electrolyte layer and the negative electrode current collector layer. Further, when the negative electrode layer includes a negative electrode active material layer and a negative electrode current collector layer, lithium ions that have migrated from the positive electrode layer during charging receive electrons and are retained in the negative electrode active material of the negative electrode active material layer. Also, during discharge of the battery, lithium in the negative electrode layer ionizes and returns to the positive electrode layer.

[0070] (Negative electrode active material layer) The negative electrode active material layer contains at least a negative electrode active material and may further optionally contain an electrolyte, a conductive assistant, a binder, and the like. Further, the negative electrode active material layer may contain various other additives. The content of each of the negative electrode active material, electrolyte, conductive assistant, binder, etc. in the negative electrode active material layer may be appropriately determined according to the intended battery performance.

[0071] As the negative electrode active material, various substances having a potential (charge-discharge potential) for occluding and releasing lithium ions that is lower than that of the positive electrode active material of the present disclosure described above can be adopted. For example, silicon-based active materials such as Si, Si alloys, and silicon oxide; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium, lithium alloys, etc. can be adopted. The negative electrode active material may be used alone as a single type or may be used in combination of two or more types.

[0072] The shape of the negative electrode active material may be a common shape as the negative electrode active material of the battery. For example, the negative electrode active material may be in the form of particles. The negative electrode active material particles may be primary particles or secondary particles in which a plurality of primary particles are aggregated.

[0073] Examples of the electrolyte that can be included in the negative electrode active material layer include the above-described solid electrolyte, electrolyte solution, or a combination thereof. Examples of the conductive auxiliary agent that can be included in the negative electrode active material layer include the above-described carbon material and the above-described metal material. The binder that can be included in the negative electrode active material layer may be appropriately selected, for example, from those exemplified as the binder that can be included in the above-described positive electrode active material layer. Each of the electrolyte and the binder may be used alone as only one kind, or two or more kinds may be used in combination.

[0074] (Negative electrode current collector layer) The negative electrode layer may include a negative electrode current collector layer that contacts the negative electrode active material layer. Any of the general ones as the negative electrode current collector layer of the battery can be adopted. Further, the negative electrode current collector layer may be in the form of a foil, plate, mesh, punched metal, porous, or foam. The negative electrode current collector layer may be a metal foil or a metal mesh, or may be a carbon sheet. In particular, the metal foil is excellent in handleability and the like. The negative electrode current collector layer may be composed of a plurality of foils or sheets. Examples of the metal constituting the negative electrode current collector layer include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and the like. In particular, from the viewpoints of ensuring reduction resistance and being difficult to alloy with lithium, the negative electrode current collector layer may contain at least one metal selected from Cu, Ni, and stainless steel.

Examples

[0075] 〈Examples 1 and 2〉 In Examples 1 and 2, the gas barrier properties of an inorganic coating layer composed of inorganic glass (Example 1) and such an inorganic coating layer coated with a resin coating layer composed of a fluorine-based resin (Example 2) were evaluated.

[0076] (Method for producing inorganic coating layer) A low glass transition point glass (57V2O5 - 23TeO2 - 20P2O5 (mol%), glass transition point: 276 °C) and a binder (acrylic resin) were mixed at 95:5 (wt%), and a precursor film was formed by coating on an aluminum foil with a doctor blade having a coating gap of 100 μm. The formed precursor film was press-fired with a uniaxial press under the following conditions to produce the inorganic coating layer of Example 1.

[0077] Firing conditions: Uniaxial press, 10 kN, 276 °C, 5 minutes

[0078] (Method for producing an inorganic coating layer coated with a resin coating layer) Using a doctor blade with a coating gap of 50 μm, a fluororesin coating was applied onto the inorganic coating layer to produce the inorganic coating layer coated with the resin coating layer of Example 2.

[0079] (Evaluation of gas barrier property) A water vapor transmission test was conducted as follows to evaluate the gas barrier property: Test method: Conforming to JIS K 7129-4 (differential pressure method) Detector: Gas chromatograph Test gas: Water vapor (humidified atmosphere) Temperature and humidity: 40 ± 2 °C · 90 ± 5% (relative humidity) Differential pressure: 1 atm

[0080] Taking the water vapor transmission rate of the case of only the inorganic coating layer (Example 1) as the reference (1.0), the evaluation results are shown in Figure 3. As is clear from Figure 3, compared with the case of only the inorganic coating layer (Example 1), the inorganic coating layer coated with the resin coating layer (Example 2) was excellent in the defensive property against water vapor transmission, that is, the gas barrier property.

[0081] 〈Examples 3 and 4, and Comparative Example 1〉 In Examples 3 and 4, and Comparative Example 1, a cycle test was conducted to evaluate the durability of a sulfide solid-state battery coated with an inorganic coating layer composed of inorganic glass (Example 3), a sulfide solid-state battery coated with a resin coating layer and an inorganic coating layer composed of a fluororesin (Example 4), and a sulfide solid-state battery without these coating layers.

[0082] The sulfide solid-state battery (parallel laminated sulfide solid-state battery) was fabricated as follows.

[0083] (Fabrication of the positive electrode active material layer) In a polypropylene (PP) container, a polyvinylidene fluoride (PVdF)-based binder, a positive electrode active material (NCM LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2), a sulfide-based solid electrolyte (Li2S-P2S5-based glass ceramics), a conductive assistant (vapor-grown carbon fiber), and a solvent (butyl butyrate) were added and stirred with an ultrasonic disperser (UH-50 manufactured by SMT) for 30 seconds. Next, the polypropylene container was shaken with a shaker (TTM-1 manufactured by Shibata Scientific) for 3 minutes and further stirred with the ultrasonic disperser for 30 seconds to obtain a coating liquid for the positive electrode active material layer.

[0084] The obtained coating liquid for the positive electrode active material layer was coated on a stainless steel foil substrate by the blade method using an applicator, and after natural drying, it was dried on a hot plate at 100 °C for 30 minutes. Thereby, a transfer material A having a positive electrode active material layer on one surface of the stainless steel foil substrate was obtained.

[0085] (Fabrication of the negative electrode active material layer) In a polypropylene container, a polyvinylidene fluoride (PVdF)-based binder, a negative electrode active material (lithium titanate (LTO)), the above-mentioned sulfide-based solid electrolyte, and a solvent (butyl butyrate) were added and stirred with an ultrasonic disperser (UH-50 manufactured by SMT) for 30 seconds to obtain a coating liquid for the negative electrode active material layer.

[0086] The obtained coating liquid for the negative electrode active material layer was applied onto a stainless steel foil substrate by the blade method using an applicator, and after natural drying, it was dried on a hot plate at 100 °C for 30 minutes. Thereby, a transfer material B having a negative electrode active material layer on one surface of the stainless steel foil substrate was obtained.

[0087] (Fabrication of the solid electrolyte layer) Butyl butyrate and the above-mentioned sulfide-based solid electrolyte were added to a polypropylene container and stirred for 30 seconds using an ultrasonic disperser (UH-50 manufactured by SMT). Next, the polypropylene container was shaken for 30 minutes using a shaker (TTM-1 manufactured by Shibata Scientific), and further stirred for 30 seconds using an ultrasonic disperser to obtain a coating liquid for the solid electrolyte layer.

[0088] The obtained coating liquid for the solid electrolyte layer was applied onto a stainless steel foil substrate by the blade method using an applicator, and after natural drying, it was dried on a hot plate at 100 °C for 30 minutes. Thereby, a transfer material C having a solid electrolyte layer on one surface of the stainless steel foil substrate was obtained.

[0089] (Fabrication of the binder-rich solid electrolyte layer) Butyl butyrate and the above-mentioned sulfide-based solid electrolyte were added to a polypropylene container and stirred for 30 seconds using an ultrasonic disperser (UH-50 manufactured by SMT). Next, the polypropylene container was shaken for 30 minutes using a shaker (TTM-1 manufactured by Shibata Scientific), and further stirred for 30 seconds using an ultrasonic disperser to obtain a coating liquid for the binder-rich solid electrolyte layer (a solid electrolyte layer with a large amount of binder).

[0090] The obtained coating liquid for the binder-rich solid electrolyte layer was applied onto a stainless steel foil substrate by the blade method using an applicator, and after natural drying, it was dried on a hot plate at 100 °C for 30 minutes. Thereby, a transfer material D having a binder-rich solid electrolyte layer on one surface of the stainless steel foil substrate was obtained.

[0091] (Fabrication of the positive electrode current collector layer) Butyl butyrate and nickel powder were added to a polypropylene container and stirred for 30 seconds using an ultrasonic disperser (UH-50 manufactured by SMT). Next, the polypropylene container was shaken for 30 minutes using a shaker (TTM-1 manufactured by Shibata Scientific), and further stirred for 30 seconds using the ultrasonic disperser to obtain a coating liquid for the positive current collector layer.

[0092] The obtained coating liquid for the positive current collector layer was applied onto a stainless steel foil substrate by the blade method using an applicator, and after natural drying, it was dried on a hot plate at 100 °C for 30 minutes. Thereby, a transfer material E having a positive current collector layer on one surface of the stainless steel foil substrate was obtained.

[0093] (Fabrication of Sulfide Solid-State Battery Stack) Using the transfer materials A to E obtained as described above, a sulfide solid-state battery (parallel stacked type sulfide solid-state battery) as shown in FIG. 4 was fabricated. At that time, the transfer of each layer was performed under the following conditions, and the frame portion of the binder-rich solid electrolyte layer was fabricated by coating. Load: 10 kN Temperature: 135 °C Time: 10 seconds

[0094] Here, FIG. 4 is a cross-sectional view (FIGS. 4(a) and (b)) and a top view (FIG. 4(c)) showing an example of a sulfide solid-state battery. FIG. 4(a) is a cross-sectional view of the portion indicated by “(a)” in FIG. 4(c), and FIG. 4(b) is a cross-sectional view of the portion indicated by “(b)” in FIG. 4(c).

[0095] Specifically, in the monopolar type battery stack 1100 shown in FIG. 4, with the positive current collector layer 40 as the center, the positive electrode active material layer 30, the solid electrolyte layer 12, and the negative electrode active material layer 20 are laminated in this order, and binder-rich solid electrolyte layers 91 and 92 are arranged as protective layers at locations where electron conduction should not occur.

[0096] (Fabrication of Sulfide Solid-State Battery) In the fabrication of the battery sulfide solid battery of Example 3, portions other than the conductive parts 301 and 302 among the surroundings of the battery laminate were coated with the inorganic coating layer 210. Here, a sheet of this inorganic coating layer was formed in advance, the battery laminate was sandwiched with this sheet, and the sheet was heated together with the battery laminate to be softened, thereby obtained. Note that the sheet of the inorganic coating layer was manufactured as shown in Example 1.

[0097] In the fabrication of the battery sulfide solid battery of Example 4, on the inorganic coating layer obtained as in Example 3, using a doctor blade with a coating gap of 50 μm, a fluorine-based resin coating was applied to coat the inorganic coating layer with a resin coating layer.

[0098] On the other hand, in the fabrication of the sulfide solid battery of Comparative Example 1, neither the inorganic coating layer nor the resin coating layer was provided.

[0099] Thereafter, in the fabrication of the sulfide solid batteries of Example 3 and 4, and Comparative Example 1, conductive parts were provided to the sulfide solid battery laminate. Specifically, as shown in FIG. 4, electrical contact with the negative electrode active material layer 20 was achieved by the conductive part 301 disposed on the left side of FIG. 4(a), and electrical contact with the positive electrode current collector layer 40 was achieved by the conductive part 302 disposed on the right side of FIG. 4(a). Here, the conductive parts 301 and 302 were obtained by applying a conductive paste to the side surface of the battery laminate 110.

[0100] (Evaluation of battery cycle characteristics) For the sulfide solid batteries of Example 3 and 4, and Comparative Example 1 obtained above, cycle evaluations were measured. The measurements were performed at a constant current and constant voltage charge and discharge of 25°C and 0.33C within the range of 1.5 to 3.0V.

[0101] FIG. 5 shows the change in charge and discharge efficiency with the increase in the number of cycles with the charge and discharge efficiency of the first cycle being 100%. In the sulfide solid battery of Comparative Example 1 in which neither the inorganic coating layer nor the resin coating layer was provided, charge and discharge cycles could not be performed.

[0102] In contrast, as shown in FIG. 5, in the sulfide solid-state battery of Example 3 provided with the inorganic coating layer and the sulfide solid-state battery of Example 4 provided with both the inorganic coating layer and the resin coating layer, charge-discharge cycles could be performed up to at least the 10th cycle. Further, when comparing the sulfide solid-state battery of Example 3 and the sulfide solid-state battery of Example 4, the sulfide solid-state battery of Example 4 provided with both the inorganic coating layer and the resin coating layer had better cycle characteristics than the sulfide solid-state battery of Example 3 provided with the inorganic coating layer.

[0103] (Evaluation of solderability of battery) Regarding the sulfide solid-state batteries of Examples 3 and 4, they were fixed to a printed circuit board by reflow soldering in a reflow oven at a soldering temperature of about 250 °C using lead-free solder (glass transition point of about 220 °C). After the solder cooled and hardened, it was confirmed that the sulfide solid-state batteries of Examples 3 and 4 could be charged and discharged while being fixed to the printed circuit board.

Explanation of symbols

[0104] 11, 12, 15, 16 Solid electrolyte layer 20, 25, 26 Negative electrode active material layer 30, 35, 36 Positive electrode active material layer 40, 45 Positive electrode current collector layer 50 Negative electrode current collector layer 60 Positive electrode / negative electrode current collector layer 91, 92 Protective layer 210, 220 Inorganic coating layer 301, 302 Conductive part 1000, 1100, 2000 Sulfide solid-state battery

Claims

1. A battery laminate having one or more unit cells; and An inorganic coating layer covering both surfaces of each layer of the battery laminate in the stacking direction and a part of the periphery in the plane direction of each layer having, The unit cell is formed by stacking a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer in this order, At least one of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer contains a sulfide solid electrolyte, The inorganic coating layer is composed of an inorganic glass having a glass transition point of 260°C or higher and 360°C or lower, A negative electrode conductive part in electrical contact with the negative electrode active material layer and a positive electrode conductive part in electrical contact with the positive electrode active material layer are provided at a part of the periphery in the plane direction of each layer of the battery laminate, Among the surroundings of the battery laminate, the portions other than the negative electrode conductive part and the positive electrode conductive part are covered with the inorganic coating layer, whereby both surfaces of each layer of the battery laminate in the stacking direction and all of the peripheries in the plane direction of each layer of the battery laminate are covered with the negative electrode conductive part, the positive electrode conductive part, or the inorganic coating layer, A sulfide solid battery.

2. The sulfide solid battery according to claim 1, wherein the inorganic coating layer is covered with a resin coating layer composed of a fluorine-based resin.

3. The sulfide solid battery according to claim 1, which does not have an exterior body excluding the inorganic coating layer.

4. A printed circuit board having a printed circuit board and the sulfide solid battery according to claim 1 soldered to the printed circuit board.

5. A method for manufacturing a printed circuit board with a sulfide solid battery according to claim 4, including soldering the sulfide solid battery to the printed circuit board by reflow soldering.

6. A method for manufacturing a sulfide solid battery according to any one of claims 1 to 3, including the following steps: (a) Preparing the battery laminate having the negative electrode conductive part in electrical contact with the negative electrode active material layer and the positive electrode conductive part in electrical contact with the positive electrode active material layer; and (b) Forming the inorganic coating layer on both surfaces of each layer of the battery laminate in the stacking direction and on the portions of the peripheries in the plane direction of each layer of the battery laminate other than the negative electrode conductive part and the positive electrode conductive part. ​

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