Method for manufacturing all-solid-state battery

Abstract

The purpose of the present invention is to provide a means for obtaining an all-solid-state battery having both excellent capacity and rapid charge characteristics. Provided is a method for manufacturing an all-solid-state battery in which a power generation element is sealed inside a battery exterior, the power generation element having: a positive electrode having a positive electrode active material layer containing a positive electrode active material and a first solid electrolyte; a negative electrode having a negative electrode active material layer containing a negative electrode active material; and a solid electrolyte layer that is interposed between the positive electrode and the negative electrode and contains a second solid electrolyte, the method for manufacturing the all-solid-state battery having: a chemical conversion step that includes a step for initially charging the power generation element in an inert gas atmosphere; and a step in which, after the chemical conversion step, the power generation element is decompressed and sealed inside the battery exterior body.

Description

TECHNICAL FIELD

[0001] The present application relates to a manufacturing method of an all-solid-state battery. BACKGROUND

[0002] In recent years, research and development of an all-solid-state battery using a solid electrolyte of an oxide system or a sulfide system in an electrolyte is prevailing. The solid electrolyte is a material constituted mainly of an ion conductor capable of conducting ions in a solid. Therefore, in the all-solid-state battery, there is an advantage that various problems caused by flammable organic electrolyte solution, which have been conventionally generated in a liquid system secondary battery using a nonaqueous electrolyte, are not generated in principle. In addition, when a high-potential and high-capacity positive electrode material and a high-capacity negative electrode material are generally used, a large improvement in output density and energy density of the battery can be achieved.

[0003] In a general all-solid-state battery, a structure in which a power generating element in which a positive electrode, a solid electrolyte layer, and a negative electrode are sequentially stacked is sealed in the inside of a battery outer body is adopted. In the manufacturing of the all-solid-state battery, in order to improve the performance of the battery, the power generating element is subjected to initial charging in an oxygen-containing environment, and then a process of vacuum sealing is performed (Japanese Patent Application Publication No. 2017-126422).

[0004] However, according to the research by the present inventors, it was found that, as described in Japanese Patent Application Publication No. 2017-126422, when the power generating element of the all-solid-state battery is subjected to initial charging in an oxygen-containing environment, the charge-discharge efficiency is sometimes reduced. On the other hand, it was confirmed that if the initial charging of the power generating element is performed under reduced pressure, sufficient rapid charging characteristics are sometimes not obtained. SUMMARY

[0005] Therefore, an object of the present application is to provide a means for obtaining an all-solid-state battery excellent in both capacity and rapid charging characteristics.

[0006] The present inventors have made intensive studies in order to solve the above-described problems. As a result, it was found that the above-described problems can be solved by performing initial charging in a non-active gas environment and then performing a process of sealing the battery element under reduced pressure, and thus the present application was completed.

[0007] That is, one embodiment of the present application is a method for manufacturing an all-solid-state battery that seals, inside a battery exterior body, an electricity generating element having: a positive electrode having a positive electrode active material layer containing a positive electrode active material and a first solid electrolyte; a negative electrode having a negative electrode active material layer containing a negative electrode active material; and a solid electrolyte layer containing a second solid electrolyte, which is interposed between the positive electrode and the negative electrode, the method for manufacturing an all-solid-state battery including: a chemical conversion step including a process of primary charging the electricity generating element in a non-active gas environment; and a process of sealing the electricity generating element in the inside of the battery exterior body under reduced pressure after the chemical conversion step. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a cross-sectional view schematically showing the entire structure of a laminated (internal parallel connection type) all-solid-state lithium secondary battery (laminated secondary battery) as one embodiment of the present application. DETAILED DESCRIPTION

[0009] One embodiment of the present application is a method for manufacturing an all-solid-state battery that seals, inside a battery exterior body, an electricity generating element having: a positive electrode having a positive electrode active material layer containing a positive electrode active material and a first solid electrolyte; a negative electrode having a negative electrode active material layer containing a negative electrode active material; and a solid electrolyte layer containing a second solid electrolyte, which is interposed between the positive electrode and the negative electrode, the method for manufacturing an all-solid-state battery including: a chemical conversion step including a process of primary charging the electricity generating element in a non-active gas environment; and a process of sealing the electricity generating element in the inside of the battery exterior body under reduced pressure after the chemical conversion step. According to the method for manufacturing an all-solid-state battery of the present embodiment, an all-solid-state battery excellent in both capacity and rapid charge characteristics can be obtained.

[0010] As described in Japanese Patent Application Publication No. 2017-126422, in the manufacture of an all-solid-state battery having a structure in which an electricity generating element in which a positive electrode, a solid electrolyte layer, and a negative electrode are sequentially laminated is sealed inside a battery exterior body, a process of primary charging the electricity generating element in an oxygen-containing environment and then vacuum sealing is performed. However, it has been confirmed that if the electricity generating element is primary charged in an oxygen-containing environment, the charge-discharge efficiency is sometimes reduced. It is considered that this is because the positive electrode active material, the negative electrode active material, the solid electrolyte, and the like are oxidized or deteriorated by primary charging in an oxygen-containing environment.

[0011] On the other hand, it was found that if the power generating element is subjected to the initial charging under reduced pressure, although the charge / discharge characteristics are improved, the resistance increases, and sometimes sufficient rapid charge characteristics cannot be obtained. In contrast, in the manufacturing method of the present application, the initial charging of the power generating element is performed in a non-active gas environment, and then the sealing is performed under reduced pressure. As a result, it was found that the increase in resistance is suppressed, and the rapid charge characteristics are improved.

[0012] In the reduced pressure (reducing) environment, at the contact portion of the positive electrode active material and the solid electrolyte, a side reaction of the solid electrolyte and the positive electrode active material (for example, reduction of the positive electrode active material based on the solid electrolyte) can proceed. As a result, it is considered that when the initial charging is performed under reduced pressure, a layer of a reaction product caused by the side reaction is formed on the surface of the particle of the positive electrode active material, resulting in a large increase in resistance. For example, in a positive electrode active material of a metal oxide, the metal oxide is reduced to form a metal layer on the surface of the particle of the positive electrode active material, and thus the resistance can increase. However, if the initial charging is performed in a non-active gas environment, a structural change layer is formed on the surface of the particle of the positive electrode active material at the time of the structural change accompanying the charging. The increase in resistance caused by the formation of this structural change layer is much less than the increase in resistance when the initial charging is performed in a reduced pressure environment, and by forming the structural change layer, further side reactions of the positive electrode active material and the solid electrolyte can be suppressed.

[0013] Further, the present inventors found that if the initial charging is performed in a non-active gas environment, even if the pressure is reduced, neither the capacity reduction nor the increase in resistance occurs. Moreover, it was found that by reducing the pressure in the inside of the battery outer body after the initial charging is performed in a non-active gas environment, the rapid charge characteristics can be improved. After the initial charging is performed in a non-active gas environment, by reducing the pressure in the inside of the battery outer body, the power generating element is uniformly subjected to atmospheric pressure constraint in the stacking direction of the battery until the end portion thereof. As a result, even in the case where the charge / discharge is performed at a high current density, dendrite short circuit accompanying non-uniform reaction is difficult to occur, and it is considered that the rapid charge characteristics can be improved.

[0014] Hereinafter, embodiments of the present application will be described with reference to the drawings. In addition, in the description of the drawings, the same symbols are attached to the same elements, and repetitive description is omitted. In addition, the dimensional ratios of the drawings are exaggerated for the convenience of explanation, and sometimes differ from the actual ratios.

[0015] Figure 1 is a cross-sectional view schematically showing the overall structure of a laminated (internal parallel connection type) all-solid-state lithium secondary battery (hereinafter, also simply referred to as "laminated secondary battery") as an embodiment of the present application. In addition, Figure 1 shows the cross section of the laminated secondary battery at the time of charging in a lithium deposition type all-solid-state battery. Figure 1The illustrated laminated secondary battery 10a has a structure in which a substantially rectangular power generating element 21, in which a charge / discharge reaction is actually performed, is sealed inside a laminated film 29 as a battery outer body. Here, the power generating element 21 has a structure in which a negative electrode, a solid electrolyte layer 17, and a positive electrode are laminated. The negative electrode has a structure in which a negative electrode current collector 11' and a negative electrode active material layer 13 composed of lithium metal, which is deposited on the surface of the negative electrode current collector 11', are laminated. Further, a negative electrode intermediate layer 14 is disposed in a manner so as to be adjacent to the surface of the negative electrode active material layer 13 opposite the solid electrolyte layer 17. The positive electrode has a structure in which a positive electrode active material layer 15 is disposed on the surface of a positive electrode current collector 11". Further, the negative electrode, the solid electrolyte layer, and the positive electrode are sequentially laminated in a manner such that the negative electrode intermediate layer 14 and the positive electrode active material layer 15 are opposite each other with the solid electrolyte layer 17 interposed therebetween. Thus, the adjacent negative electrode, solid electrolyte layer, and positive electrode constitute one single cell layer 19. Therefore, Figure 1 The illustrated laminated secondary battery 10a can be said to have a structure in which a plurality of single cell layers 19 are connected in parallel by being laminated. A negative electrode current collecting plate 25 and a positive electrode current collecting plate 27, which are in conduction with each electrode (negative electrode and positive electrode), are respectively mounted on the negative electrode current collector 11' and the positive electrode current collector 11". The negative electrode current collecting plate 25 and the positive electrode current collecting plate 27 have a structure in which they are led to the outside of the laminated film 29 in a manner so as to be sandwiched by the end portions of the laminated film 29. A constraint pressure is imparted to the laminated secondary battery 10a in the laminating direction of the power generating element 21 by a pressure applying member (not shown). Thus, the volume of the power generating element 21 is kept constant.

[0016] Hereinafter, the main constituent members of the all-solid-state battery of the present embodiment will be described.

[0017] [Current collector]

[0018] The current collector (negative electrode current collector, positive electrode current collector) has a function of mediating the movement of electrons from the electrode active material layer (negative electrode active material layer, positive electrode active material layer). The material constituting the current collector is not particularly limited. As the material constituting the current collector, for example, a metal such as aluminum, nickel, iron, stainless steel, titanium, copper, or the like, a resin having electrical conductivity can be used. The thickness of the current collector is also not particularly limited, and is, for example, 10 to 100 μm.

[0019] [Positive electrode active material layer]

[0020] The positive electrode active material layer contains a positive electrode active material and a solid electrolyte, and can contain a binder, a conductive aid, as necessary.

[0021] The positive electrode active material has a function of releasing lithium ions or the like at the time of charging and absorbing lithium ions or the like at the time of discharging. As the positive electrode active material, a metal oxide is preferable from the aspect of more significantly obtaining the effect of the present application. As the positive electrode active material, for example, layered rock salt type active materials such as LiCoO2, LiMnO2, LiNiO2, LiVO2, Li(Ni-Mn-Co)O2, and the like, spinel type active materials such as LiMn2O4, LiNi 0.5 Mn 1.5 O4, and the like, olivine type active materials such as LiFePO4, LiMnPO4, and the like, Si-containing active materials such as Li2FeSiO4, Li2MnSiO4, and the like, and the like metal oxides can be exemplified. In addition, as the metal oxides other than the above, for example, Li4Ti5O 12 Among them, a composite oxide containing lithium and nickel (lithium-nickel composite oxide) is preferable. The metal oxide containing nickel such as the lithium-nickel composite oxide is easily reduced from the nickel oxide to nickel when it is in contact with the solid electrolyte in a reducing environment such as under reduced pressure, and thus the deactivation of the positive electrode active material easily proceeds, and an increase in resistance easily occurs. Therefore, the effect of the present application can be more significantly obtained. As the lithium-nickel composite oxide, Li(Ni-Mn-Co)O2 and a substance in which a part of these transition metals is replaced with another element (hereinafter, also referred to simply as "NMC composite oxide") can be preferably used. The NMC composite oxide has a layered crystal structure in which a lithium atom layer and a transition metal (Mn, Ni, and Co are arranged in order) atom layer are alternately stacked with an oxygen atom layer therebetween, 1 atom of Li is contained per 1 atom of the transition metal M, and the amount of extracted Li is twice that of spinel lithium manganese oxide, that is, the supply capacity is twice, and thus a high capacity can be obtained.

[0022] As described above, the NMC composite oxide also includes a composite oxide in which a part of the transition metal elements is replaced with another metal element. As the another element at this time, Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr, Fe, B, Ga, In, Si, Mo, Y, Sn, V, Cu, Ag, Zn, and the like can be exemplified, Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr are preferable, Ti, Zr, P, Al, Mg, Cr are more preferable, and Ti, Zr, Al, Mg, Cr are further preferable from the viewpoint of improving the cycle characteristics.

[0023] From the perspective of high theoretical discharge capacity, the NMC composite oxide preferably has a composition represented by the general formula (1): LiaNibMncCodMxO2 (where a, b, c, d, and x are at least one element selected from 0.98≤a≤1.2, 0.6≤b≤0.9, 0<c≤0.4, 0<d≤0.4, 0≤x≤0.3, and b+c+d+x=1). Here, a represents the atomic ratio of Li, b represents the atomic ratio of Ni, c represents the atomic ratio of Mn, d represents the atomic ratio of Co, and x represents the atomic ratio of M. In addition, in the all-solid-state battery of this type, the positive electrode active material is particularly preferred to be an NMC composite oxide (high-nickel NMC composite oxide) that satisfies 0.8≤b≤0.9, 0<c≤0.2, 0<d≤0.2, and 0≤x≤0.2 in the above general formula (1). When the atomic ratio of Ni, b, is 0.8 or higher, the balance between capacity and lifespan characteristics is better, and therefore preferred. Furthermore, when the atomic ratio of Ni, b, is 0.9 or less, the generation of gases accompanying the electrode reaction can be reduced. Therefore, it is less likely to cause a decrease in cycle durability due to gas generation, which is preferable. In addition, since the atomic ratio of nickel is high, the effects of the present invention can be obtained more significantly. In this case, from the viewpoint of improving the balance between capacity and lifetime characteristics, it is more preferable that c and d are 0.05≤c≤0.2 and 0.03≤d≤0.2 in general formula (1).

[0024] The average particle size of the positive electrode active material is not particularly limited, but from the viewpoint of high output, it is preferably 1 to 100 μm, and more preferably 1 to 20 μm. In this specification, the average particle size is the median particle size (D50) measured by a particle size distribution measuring device using laser diffraction-scattering method.

[0025] The positive electrode active material layer also includes a solid electrolyte. Including a solid electrolyte in the positive electrode active material layer improves its ionic conductivity. Examples of solid electrolytes include sulfide solid electrolytes and oxide solid electrolytes. Furthermore, in this specification, a solid electrolyte refers to a material primarily composed of an ion conductor capable of ion conduction within a solid state, specifically one with a lithium-ion conductivity of 1×10⁻⁶ at room temperature (25°C). -5 For materials with a S / cm or higher, the lithium-ion conductivity is preferably 1×10⁻⁶. -4 The ionic conductivity is above S / cm. Here, the value of ionic conductivity can be determined by electrochemical impedance spectroscopy.

[0026] Furthermore, in this specification, the solid electrolyte contained in the positive electrode active material layer is referred to as the "first solid electrolyte," and the solid electrolyte contained in the solid electrolyte layer described later is referred to as the "second solid electrolyte." Therefore, the sequence of "first" and "second" is meaningless in itself; these terms are merely used to distinguish the locations where the solid electrolyte is present.

[0027] The solid electrolyte (first solid electrolyte) contained in the positive electrode active material layer is not particularly limited. From the viewpoint of exhibiting excellent lithium-ion conductivity and being able to further track the volume change of the electrode active material during charging and discharging, a sulfide solid electrolyte containing sulfur (S) is preferred. Furthermore, the sulfide solid electrolyte readily reduces the positive electrode active material under reduced pressure, thus further significantly improving the fast charging characteristics brought about by the method of the present invention. More preferably, the solid electrolyte contained in the positive electrode active material layer is a sulfide solid electrolyte containing Li, M, and S, wherein the M element is at least one element selected from the group consisting of P, Si, Ge, Sn, Ti, Zr, Nb, Al, Sb, Br, Cl, and I. More preferably, it is a sulfide solid electrolyte containing S, Li, and P.

[0028] Sulfide solid electrolytes can have a Li3PS4 framework, a Li4P2S7 framework, or a Li4P2S6 framework. Examples of sulfide solid electrolytes with a Li3PS4 framework include LiI-Li3PS4, LiI-LiBr-Li3PS4, and Li3PS4. Examples of sulfide solid electrolytes with a Li4P2S7 framework include Li-PS based solid electrolytes known as LPS. Furthermore, sulfide solid electrolytes can be made from Li... （4-x） Ge （1-x） P x S4 (where x satisfies 0 < x < 1) represents LGPS, etc. More specifically, examples include LPS (Li2S-P2S5), Li7P3S... 11 Li 3.2 P 0.96 S, Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 Alternatively, Li6PS5X (where X is Cl, Br, or I), etc. Furthermore, the description of "Li2S-P2S5" refers to a sulfide solid electrolyte made using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions. Among these, sulfide solid electrolytes have high ionic conductivity and low bulk modulus; therefore, from the viewpoint of being able to track the volume change of the electrode active material accompanying charge and discharge, LPS (Li2S-P2S5), Li6PS5X (where X is Cl, Br, or I), and Li7P3S are preferred. 11 Li 3.2 P 0.96 In the group consisting of S and Li3PS4.

[0029] Examples of solid electrolyte shapes include spherical, ellipsoidal, and other particulate or film-like forms. When the solid electrolyte is in particulate form, its average particle size (D50) is not particularly limited, but is preferably 0.01 μm or more and 40 μm or less, more preferably 0.1 μm or more and 20 μm or less, and even more preferably 0.1 μm or more and 10 μm or less.

[0030] In a preferred embodiment of the present invention, the positive electrode active material layer comprises a lithium-nickel composite oxide as the positive electrode active material, and a sulfide solid electrolyte comprises a solid electrolyte. The present invention prevents the side reaction in which the positive electrode active material, acting as an oxidant, is reduced by the solid electrolyte, acting as a reducing agent, under reduced pressure. The effects of the present invention can be obtained regardless of the type of positive electrode active material; in particular, the lithium-nickel composite oxide is easily reduced by the sulfide solid electrolyte, resulting in a high degree of improvement in capacity and fast charging efficiency.

[0031] In addition to the positive electrode active material and solid electrolyte mentioned above, the positive electrode active material layer may also contain at least one of conductive additives and binders.

[0032] Examples of conductive additives include, but are not limited to, metals such as aluminum, stainless steel (SUS), silver, gold, copper, and titanium, alloys or metal oxides containing these metals; carbon fibers (specifically, vapor-grown carbon fibers (VGCF), polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, rayon-based carbon fibers, activated carbon fibers, etc.), carbon nanotubes (CNTs), and carbon black (specifically, acetylene black, Ketjen black (registered trademark), furnace black, channel black, thermal lamp black, etc.). Materials in which the aforementioned metal materials are coated around particulate ceramic or resin materials by means of plating can also be used as conductive additives. From the viewpoint of electrical stability, it is preferable that these conductive additives contain at least one selected from the group consisting of aluminum, stainless steel, silver, gold, copper, titanium, and carbon; more preferably, at least one selected from the group consisting of aluminum, stainless steel, silver, gold, and carbon; and even more preferably, at least one carbon. These conductive additives can be used alone or in combination of two or more.

[0033] When the positive electrode active material layer contains a conductive additive, the content of the conductive additive in the positive electrode active material layer is not particularly limited, for example, it is 1 to 10% by mass, more preferably 2 to 8% by mass. If it is within such a range, a more robust electronic conduction pathway can be formed in the positive electrode active material layer, which can effectively help improve the battery characteristics.

[0034] There are no particular limitations on the binder used in the positive electrode active material layer, and any known binder may be used appropriately. Examples of binders include polyvinylidene fluoride (PVDF), compounds in which the hydrogen atoms of PVDF are replaced by other halogen elements, polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC). The content of the binder in the positive electrode active material layer is not particularly limited, and may be, for example, 0.1% to 10% by mass.

[0035] The thickness of the positive electrode active material layer varies depending on the structure of the target all-solid-state battery, and is preferably in the range of 0.1 to 1000 μm, more preferably 10 to 200 μm, and even more preferably 40 to 100 μm.

[0036] [Solid electrolyte layer]

[0037] The solid electrolyte layer lies between the positive electrode active material layer and the negative electrode active material layer, and contains a solid electrolyte (usually as the main component). The specific form of the solid electrolyte (second solid electrolyte) contained in the solid electrolyte layer is not particularly limited; the first solid electrolyte and its preferred form, as exemplified in the section on the positive electrode active material layer, can be used in the same way. The solid electrolyte contained in the solid electrolyte layer can be the same as or different from the solid electrolyte contained in the positive electrode active material layer.

[0038] The solid electrolyte contained in the solid electrolyte layer is preferably a sulfide solid electrolyte. Sulfide solid electrolytes are easily oxidized, therefore, the charge-discharge efficiency of an all-solid-state battery containing a sulfide solid electrolyte tends to decrease during the initial charge in an oxygen-containing environment. Therefore, the effects of the present invention can be further significantly achieved.

[0039] From the viewpoint of high ionic conductivity, LPS (Li2S-P2S5), Li6PS5X (where X is Cl, Br, or I), and Li7P3S are preferred. 11 Li 3.2 P 0.96 S and Li3PS4. Depending on the circumstances, solid electrolytes other than those mentioned above may also be used.

[0040] The content of solid electrolyte in the solid electrolyte layer relative to the total mass of the solid electrolyte layer is preferably in the range of 10 to 100% by mass, more preferably in the range of 50 to 100% by mass, and even more preferably in the range of 90 to 100% by mass.

[0041] In addition to the solid electrolyte, the solid electrolyte layer may also contain a binder. There are no particular limitations on the binder; any known binder may be used, such as the binder described in the positive electrode active material layer above. The content of the binder in the solid electrolyte layer is not particularly limited, and may be, for example, 1 to 10% by mass.

[0042] The solid electrolyte layer can be a form in which a solid electrolyte is supported on a porous body. In this case, a binder can be further supported on the porous body. There are no particular restrictions on the material of the porous body; previously known insights can be appropriately referenced.

[0043] The thickness of the solid electrolyte layer varies depending on the structure of the target all-solid-state battery, and is preferably in the range of 0.1 to 1000 μm, more preferably 10 to 100 μm.

[0044] [Negative Electrode Intermediate Layer]

[0045] In this type of all-solid-state battery, particularly in the case of lithium deposition type all-solid-state batteries, a negative electrode interlayer is preferably provided, having a surface adjacent to the solid electrolyte layer opposite the negative electrode current collector. The negative electrode interlayer is not particularly limited, but preferably contains at least one material selected from the group consisting of a metal material capable of alloying with lithium and a carbon material capable of absorbing lithium ions, and a binder. Furthermore, the negative electrode interlayer is preferably conductive as a whole. The volume resistivity of the negative electrode interlayer is not particularly limited, but is preferably 10 Ω·cm. 2 The volume resistivity is less than Ω·cm, more preferably less than 10 Ω·cm. In this specification, the volume resistivity of the negative electrode intermediate layer is the value measured using an electrode resistance measurement system (manufactured by Hioki Electric Co., Ltd., product name: RM2610).

[0046] The negative electrode interlayer preferably contains at least one metal material selected from those capable of alloying with lithium. By containing a metal material capable of alloying with lithium in the negative electrode interlayer, lithium metal can be deposited more uniformly on the current collector surface. Specific examples of metal materials capable of alloying with lithium include indium (In), aluminum (Al), silicon (Si), tin (Sn), magnesium (Mg), gold (Au), silver (Ag), zinc (Zn), and alloys containing at least one of them. Preferably, this metal material contains at least one selected from the group consisting of In, Al, Si, Sn, Mg, Au, Ag, and Zn; more preferably, it contains at least one selected from the group consisting of Ag, Mg, Zn, and Al; even more preferably, it contains at least one selected from Ag, Mg, and Zn; and particularly preferably, it contains Ag.

[0047] The negative electrode interlayer preferably replaces at least one material selected from the group consisting of metals capable of alloying with lithium, or, in addition to containing at least one material selected from the group consisting of metals capable of alloying with lithium, also contains at least one material selected from the group consisting of carbon materials capable of storing lithium ions. By containing a carbon material capable of storing lithium ions in the negative electrode interlayer, the precipitation and growth of lithium dendrites can be suppressed. Specific examples of carbon materials capable of storing lithium ions include carbon black (specifically, acetylene black, Ketjen black (registered trademark), furnace black, channel black, thermal black, etc.), carbon nanotubes (CNTs), graphite, hard carbon, etc. Preferably, the carbon material contains at least one material selected from carbon black, more preferably at least one material selected from acetylene black, Ketjen black (registered trademark), furnace black, channel black, and thermal black.

[0048] Furthermore, the negative electrode intermediate layer may include, in addition to at least one selected from the group consisting of a metal material capable of alloying with lithium and a carbon material capable of storing lithium ions, a metal material other than the aforementioned metal material capable of alloying with lithium (a metal material that does not alloy with lithium). Examples of metal materials that do not alloy with lithium include nickel (Ni) and copper (Cu). According to one embodiment, the negative electrode intermediate layer includes at least one selected from the group consisting of a carbon material capable of storing lithium ions and a metal material that does not alloy with lithium.

[0049] According to a preferred embodiment, the negative electrode intermediate layer comprises: at least one metal particle containing the aforementioned metal material capable of alloying with lithium, and at least one carbon particle containing the aforementioned carbon material capable of absorbing lithium ions. By using both metal particles and carbon particles to form the negative electrode intermediate layer, an all-solid-state battery with superior cycle characteristics can be obtained.

[0050] When using both carbon particles and metal particles, the mass ratio of carbon particles to metal particles (carbon particles:metal particles) is preferably 10:1 to 1:1, more preferably 5:1 to 2:1, and even more preferably 4:1 to 2.5:1. The volume ratio of carbon particles to metal particles (carbon particles:metal particles) is preferably 99:1 to 70:30, more preferably 95:5 to 75:25. When the ratio of carbon particles to metal particles (mass ratio or volume ratio) is within the above range, an all-solid-state battery with superior cycle characteristics can be obtained.

[0051] The negative electrode interlayer may further include an adhesive. There are no particular limitations on the type of adhesive; adhesives known in the art can be appropriately used. Examples of adhesives include polyvinylidene fluoride (PVDF), compounds in which the hydrogen atoms of PVDF are replaced by other halogen elements, polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC). Preferably, the adhesive includes polyvinylidene fluoride (PVDF), more preferably polyvinylidene fluoride (PVDF).

[0052] The binder content in the negative electrode interlayer is, for example, 8% or more and 20% or less of the total mass of the metal material, carbon material, and binder (100% by mass), preferably 10% or more and 18% or less, and more preferably 12% or more and 16% or less. When the binder content is within the above range, the precipitation and growth of lithium dendrites can be further suppressed.

[0053] The thickness of the negative electrode interlayer is not particularly limited, but is preferably 1~20μm, more preferably 2~15μm, and even more preferably 5~15μm. When the thickness of the negative electrode interlayer is within the above range, it is possible to simultaneously suppress the precipitation and growth of lithium dendrites and the reduction in energy density.

[0054] [Negative electrode active material layer]

[0055] The negative electrode active material layer contains a negative electrode active material. There are no particular limitations on the type of negative electrode active material; examples include carbon materials, metal oxides, and metal active materials. Additionally, lithium-containing metals can also be used as negative electrode active materials. Such negative electrode active materials are not particularly limited as long as they contain lithium; lithium-containing alloys can be used in addition to lithium metal. Examples of lithium-containing alloys include alloys of Li with at least one of In, Al, Si, Sn, Mg, Au, Ag, and Zn. The negative electrode active material preferably contains lithium metal or a lithium-containing alloy, and particularly preferably contains lithium metal. Since lithium metal is easily oxidized, during the initial charging in an oxygen-containing environment, oxidation of the lithium metal, which is the negative electrode active material, easily leads to deactivation, thereby easily reducing charge and discharge efficiency. Therefore, the battery capacity can be significantly improved further. Furthermore, if the negative electrode active material is lithium metal, it is particularly susceptible to the influence of pressure distribution; therefore, the short-circuit suppression effect generated by the pressure reduction process is greater, resulting in greater performance improvement.

[0056] The negative electrode active material layer may further contain a solid electrolyte as needed. There are no particular limitations on the specific form of the solid electrolyte contained in the negative electrode active material layer; the solid electrolyte and its preferred form exemplified in the positive electrode active material layer section can also be used. The content of the solid electrolyte in the negative electrode active material layer is preferably in the range of 1 to 60% by mass, and more preferably in the range of 10 to 50% by mass.

[0057] In addition to the aforementioned negative electrode active material and solid electrolyte, the negative electrode active material layer may also contain at least one of a binder and a conductive additive. The thickness of the negative electrode active material layer varies depending on the structure of the target all-solid-state battery, and is preferably in the range of 0.1 to 1000 μm, more preferably 40 to 100 μm.

[0058] Furthermore, when lithium metal or a lithium-containing alloy is used as the negative electrode active material, the all-solid-state battery of this type can be a so-called lithium deposition type battery, in which lithium metal, as the negative electrode active material, is deposited on the negative electrode current collector during charging. Therefore, in this method, the thickness of the negative electrode active material layer increases as charging progresses and decreases as discharging progresses. The negative electrode active material layer may not exist during complete discharge, but depending on the circumstances, a negative electrode active material layer composed of some degree of lithium metal may be provided during complete discharge. Furthermore, the thickness of the negative electrode active material layer (lithium metal layer) during complete charging is not particularly limited, and is typically 0.1 to 1000 μm.

[0059] <Manufacturing Methods of All-Solid-State Batteries>

[0060] One aspect of the present invention discloses a method for manufacturing an all-solid-state battery, which involves sealing a power generation element inside a battery casing. The power generation element comprises: a positive electrode having a positive active material layer comprising a positive active material and a first solid electrolyte; a negative electrode having a negative active material layer comprising a negative active material; and a solid electrolyte layer situated between the positive and negative electrodes and comprising a second solid electrolyte. The manufacturing method includes: a chemical conversion step comprising an initial charging step of the power generation element in an inactive gas environment; and a step of sealing the power generation element under reduced pressure inside the battery casing after the chemical conversion step. According to this manufacturing method, an all-solid-state battery with excellent capacity and fast-charging characteristics can be obtained. The following describes each step of the manufacturing method of this invention.

[0061] [Chemical conversion process (chemical conversion treatment process)]

[0062] The chemical conversion process includes the initial charging of a power generation element having a positive electrode, a solid electrolyte layer, and a negative electrode in an inactive gas environment.

[0063] The specific forms of the positive electrode, solid electrolyte layer, and negative electrode are as described above. There are no particular limitations on the methods for fabricating the positive electrode, solid electrolyte layer, and negative electrode, or on the methods for stacking them to fabricate a power generation element. The process of fabricating the positive electrode, solid electrolyte layer, and negative electrode, and stacking them to fabricate a power generation element, is preferably carried out in a non-reactive gas environment.

[0064] Examples of inactive gases include nitrogen and rare gases (helium, argon, xenon, neon), with argon being preferred. The inactive gas may contain impurities, but from the viewpoint of preventing adverse effects on the performance of the all-solid-state battery, the impurity content is less than 0.1% by volume, preferably less than 0.01% by volume, and more preferably less than 0.001% by volume. Examples of impurities include water, oxygen, nitrogen, and solvents. In this method, an inactive gas environment refers to an environment filled with inactive gases whose total impurity content is less than 0.1% by volume. In this method, the inactive gas environment is not particularly limited, but an inactive gas environment with a dew point below -60°C is preferred, and an inactive gas environment with a dew point below -68°C is even more preferred.

[0065] The initial charge refers to the first charge of a power generation element that has a positive electrode, a solid electrolyte layer, and a negative electrode. The initial charge can be performed, for example, by constant current charging, constant voltage charging, or a combination of constant current and constant voltage charging. There are no particular limitations on the current density during the initial charge, for example, it can be 0.1~5 mA / cm². 2 Preferably, it is 0.5~2mA / cm 2 When the particle size is within the above range, the surface modification (structural change) of the positive electrode active material particles can be carried out effectively, and the fast charge and discharge characteristics can be further improved.

[0066] There is no particular limitation on the upper limit voltage of the initial charge (charging termination voltage), which can be appropriately adjusted according to the types of positive and negative active materials used, for example, 3.6~4.3V, preferably 3.6~4.2V. When the upper limit voltage is above 3.6V, surface modification (structural change) of the particles of the positive active material is easier to achieve, thus further improving the fast charge and discharge characteristics. In addition, when the upper limit voltage is below 4.3V, especially below 4.2V, excessive deoxygenation from the positive active material and oxidation of the solid electrolyte can be suppressed. Therefore, in addition to excellent fast charging characteristics, higher capacity can also be obtained.

[0067] In a preferred embodiment, the initial charge includes constant voltage charging. For example, the initial charge includes constant voltage charging or constant current constant voltage charging. By including constant voltage charging or constant current constant voltage charging in the initial charge, the power generation element can be maintained at a constant voltage for a constant time, thus allowing sufficient surface modification of the particles of the positive electrode active material. As a result, the fast charging characteristics can be further improved. In addition, the holding time at the upper limit voltage during constant voltage charging or constant current constant voltage charging is not particularly limited, for example, it is 0.5 to 48 hours, preferably 1 to 36 hours. If the holding time at the upper limit voltage is within the above range, the surface modification of the particles of the positive electrode active material based on the chemical conversion process can be further carried out, thus further improving the fast charge and discharge characteristics. In a preferred embodiment, after constant current charging to the desired upper limit voltage, constant voltage charging is performed during the initial charge. At this time, the preferred methods of constant current charging and constant voltage charging are the same as described above.

[0068] There are no particular restrictions on the temperature conditions during the first charge, for example, 20 to 80°C, preferably 50 to 70°C.

[0069] In a power generation element that has undergone initial charging in a non-reactive gas environment, the surface modification of the positive electrode active material particles results in the formation of a stable structural change layer on the surface of the positive electrode active material particles, making it less prone to degradation. Therefore, in the power generation element from the initial charging to the depressurization sealing described later, it can be discharged, repeatedly charged and discharged, or placed after charging or discharging. Furthermore, the power generation element after initial charging in a non-reactive gas environment can be kept in an environment other than a non-reactive gas environment, such as under depressurization, or further charged and discharged in an environment other than a non-reactive gas environment. Preferably, all processes from initial charging to depressurization sealing described later are performed in the non-reactive gas environment during initial charging.

[0070] The chemical conversion process preferably also includes a step of discharging the charged power generation element after its initial charging. The effects of the chemical conversion treatment are only apparent during the initial charging. However, the positive and negative electrode active materials in the charged state possess high oxidizing and reducing powers, respectively. Therefore, during subsequent sealing operations, they may sometimes undergo side reactions with trace amounts of environmental impurities (moisture, nitrogen, etc.). Thus, by discharging the charged power generation element before sealing, side reactions can be suppressed. As a result, the battery capacity and fast-charging characteristics can be further improved.

[0071] The discharge process is preferably carried out in a non-reactive gas environment. There are no particular restrictions on the temperature conditions during discharge, for example, 20–80°C, preferably 50–70°C.

[0072] There are no particular restrictions on the current density during discharge, for example, 0.1~10 mA / cm². 2 Preferably 1~5 mA / cm 2 It is preferable to perform constant current discharge at the aforementioned current density. There are no particular limitations on the discharge termination voltage, for example, it can be 2.8~3.2V.

[0073] [Pressure Reduction and Sealing Process]

[0074] In the depressurization sealing process, after the chemical conversion process, the power generation element is depressurized and sealed inside the battery casing.

[0075] As a battery casing, for example, Figure 1 As shown, a bag-shaped housing using an aluminum-containing laminated film 29 that covers the power generation element is preferred. This laminated film can be, for example, a three-layer structure laminated film made by sequentially stacking PP, aluminum, and nylon, but is not limited to these. From the viewpoint of high output, excellent cooling performance, and suitability for batteries used in large devices such as EVs and HEVs, the laminated film is preferred. Furthermore, since the packing voltage applied to the power generation element from the outside can be easily adjusted, the battery casing is more preferably an aluminum-containing laminated film.

[0076] There are no particular limitations on the method for sealing the power generation element under reduced pressure inside the battery casing. For example, when the battery casing is a pouch-shaped laminated film, a method can be proposed where the power generation element is housed inside the laminated film, and the interior of the laminated film is depressurized using a known depressurization device. Then, a method can be proposed where the ends of the laminated film are sealed by heat welding or the like. There are no particular limitations on the vacuum level inside the battery casing during depressurization, and conventionally known methods can be appropriately adopted. As for the vacuum level, it is preferably 11.3 kPa or less, more preferably 6.3 kPa or less, even more preferably 2 kPa or less, and particularly preferably 1.3 kPa or less. There are no particular limitations on the temperature conditions during depressurization sealing, for example, 20 to 80°C.

[0077] The above describes one embodiment of the manufacturing method of the all-solid-state battery of the present invention. However, the present invention is not limited to the structure described in the above embodiment, and appropriate modifications can be made based on the description in the claims.

[0078] For example, as a type of battery in which the all-solid-state battery of the present invention is applied, a bipolar battery comprising a bipolar electrode having a positive active material layer electrically bonded to one side of a current collector and a negative active material layer electrically bonded to the opposite side of the current collector.

[0079] Furthermore, the secondary battery of this method does not necessarily have to be all-solid-state. That is, the solid electrolyte layer may further contain a conventionally known liquid electrolyte (electrolyte). There is no particular limitation on the amount of liquid electrolyte (electrolyte) that may be contained in the solid electrolyte layer, but it is preferable to have an amount that maintains the shape of the solid electrolyte layer formed by the solid electrolyte and prevents leakage of the liquid electrolyte (electrolyte).

[0080] In addition, the following embodiments are also included within the scope of the present invention: a method for manufacturing an all-solid-state battery according to the first aspect having the features of the second aspect; a method for manufacturing an all-solid-state battery according to the first or second aspect having the features of the third aspect; a method for manufacturing an all-solid-state battery according to any one of the first to third aspects having the features of the fourth aspect; a method for manufacturing an all-solid-state battery according to any one of the first to fourth aspects having the features of the fifth aspect; and a method for manufacturing an all-solid-state battery according to any one of the first to fifth aspects having the features of the sixth aspect.

[0081] Example

[0082] The present invention will now be described in more detail through examples. However, the scope of the present invention is not limited to the following examples. Furthermore, in the following examples and comparative examples, the glove box containing an argon environment with a dew point below -68°C is an environment filled with argon gas containing a total impurity content of less than 0.001% by volume. Additionally, the utensils and devices used in the glove box are thoroughly dried beforehand.

[0083] <Example of battery manufacturing for evaluation>

[0084] [Example 1]

[0085] (Fabrication of the positive electrode active material layer)

[0086] As a constituent material of the positive electrode active material layer, NMC composite oxide (LiNi) was prepared as the positive electrode active material. 0.8 Mn 0.1 Co 0.1 O2), sulfide solid electrolytes (Li6PS5Cl) as solid electrolytes, acetylene black as conductive additives, and styrene-butadiene rubber (SBR) as adhesives.

[0087] In a glove box with an argon atmosphere below -68°C, the positive electrode active material, solid electrolyte, conductive additive, and binder were weighed at a mass ratio of 72:24:3:1 and dispersed in xylene to prepare a positive electrode active material slurry. Next, the prepared positive electrode active material slurry was coated on both sides of a carbon-coated aluminum foil (serving as the positive electrode current collector) and dried to form a positive electrode active material layer (100 μm thick on one side), thus fabricating the positive electrode.

[0088] (Fabrication of the solid electrolyte layer)

[0089] In a glove box with an argon atmosphere below -68°C, a sulfide solid electrolyte (Li6PS5Cl) and a styrene-butadiene rubber (SBR) as a binder were weighed at a mass ratio of 97:3 and dispersed in xylene to prepare a solid electrolyte slurry. The resulting solid electrolyte slurry was coated onto a porous body with a thickness of 40 μm and dried to create a solid electrolyte layer (40 μm thick) supported on the porous body.

[0090] (Fabrication of the negative electrode intermediate layer)

[0091] In a glove box with an argon environment below -68°C, acetylene black (AB), silver (Ag) nanoparticles, and polyvinylidene fluoride (PVDF) as a binder were weighed at a mass ratio of 65:21:14 and dispersed in N-methylpyrrolidone to prepare a negative electrode interlayer slurry. The obtained negative electrode interlayer slurry was coated on both sides of a stainless steel foil serving as the negative electrode current collector and dried to obtain the negative electrode interlayer (10 μm thick on one side).

[0092] (Fabrication of a laminate consisting of a positive electrode, a solid electrolyte layer, a negative electrode intermediate layer, and a negative electrode current collector)

[0093] In a glove box with an argon environment below -68°C, the solid electrolyte layer and the negative electrode intermediate layer prepared above are sequentially arranged on both sides of the positive electrode, and then rolled to obtain a laminate in which the positive electrode active material layer, the solid electrolyte layer, the negative electrode intermediate layer and the negative electrode current collector are sequentially stacked on both sides of the positive electrode current collector.

[0094] (The fabrication of laminated batteries)

[0095] In a glove box with an argon atmosphere below -68°C, an aluminum positive electrode tab and a nickel-plated copper negative electrode tab are bonded to a carbon-coated aluminum foil (positive current collector) and a stainless steel foil (negative current collector) of the aforementioned laminate using an ultrasonic welding machine. This is then placed inside an aluminum laminate and sealed by heat-fusion of the openings in the laminate, thus obtaining a laminated battery. The interior of this laminated battery is filled with argon gas containing less than 0.001% by volume of impurities.

[0096] (Chemical transformation treatment)

[0097] The chemical conversion process is carried out while applying a constraint pressure of 3 MPa in the stacking direction of the laminated battery fabricated above using a pressurizing component. The chemical conversion process is conducted using a charge-discharge testing device (HJ-SD8, manufactured by Hokuto Electric Co., Ltd.) in a constant-temperature bath set to 60°C. The laminated battery is placed inside the constant-temperature bath, and after the battery temperature reaches a certain level, the chemical conversion process is performed at 1.0 mA / cm². 2 The battery was charged at a constant current density to a voltage of 4.3V. Then, it was charged at 2.0mA / cm². 2 The battery is discharged at a constant current density until the battery voltage reaches 3.0V.

[0098] (Pressure relief seal)

[0099] In a glove box with an argon environment at a dew point below -68°C, the laminated end of the chemically converted laminated battery is cut off to form an opening. The interior of the laminate is then sealed at 1.3 kPa using a vacuum packaging machine (TOSEI Corporation, TOSPACK) at 25°C to obtain an evaluation battery for the lithium deposition type all-solid-state battery of this embodiment.

[0100] [Example 2]

[0101] In the chemical conversion process, the charging termination voltage (upper limit voltage) of the constant current charging was changed to 4.2V. Otherwise, the evaluation battery of this embodiment was made using the same method as in Example 1.

[0102] [Example 3]

[0103] Except for the following chemical conversion treatment, the evaluation battery of this example was prepared using the same method as in Example 1:

[0104] (Chemical transformation treatment)

[0105] The chemical conversion process was carried out while applying a constraint pressure of 3 MPa in the stacking direction of the laminated battery fabricated above. The chemical conversion process was conducted using a charge-discharge testing apparatus (HJ-SD8, manufactured by Hokuto Electric Co., Ltd.) in a constant-temperature bath set to 60°C. The laminated battery was placed inside the constant-temperature bath, and after the battery temperature reached a certain level, the chemical conversion process was performed at 1.0 mA / cm². 2 The battery was charged at a constant current density to a voltage of 4.2V, followed by 24 hours of constant voltage charging at 4.2V. Then, it was charged at 2.0mA / cm². 2 The battery is discharged at a constant current density until the battery voltage reaches 3.0V.

[0106] [Example 4]

[0107] In the chemical conversion process, the charging termination voltage (upper limit voltage) of the constant current charging was changed to 3.6V. Otherwise, the evaluation battery of this embodiment was made using the same method as in Example 1.

[0108] [Comparative Example 1]

[0109] A positive electrode active material layer, a solid electrolyte layer, and a negative electrode intermediate layer were fabricated using the same method as in Example 1 to obtain a laminate of a positive electrode, a solid electrolyte layer, a negative electrode intermediate layer, and a negative electrode current collector. In the fabrication of the laminated battery in Example 1, the laminate was placed inside an aluminum laminate film, and the interior of the laminate film was sealed at 1.3 kPa using a vacuum packaging machine (TOSEI Corporation, TOSPACK) at 25°C. The laminated battery obtained in this way was then subjected to the same chemical conversion treatment as in Example 1 to produce an evaluation battery for this comparative example.

[0110] [Comparative Example 2]

[0111] The evaluation battery for this comparative example was manufactured using the same method as in Example 1, except that no pressure reduction sealing was performed in Example 1.

[0112] [Comparative Example 3]

[0113] In Example 1, a laminated battery was fabricated by sealing a laminated film into a conjugate formed by joining a positive electrode tab and a negative electrode tab under atmospheric conditions (20% oxygen by volume). Next, the aforementioned chemical conversion treatment was performed while applying a constraint pressure of 3 MPa in the lamination direction of the laminated battery using a pressurizing device. Then, in a glove box with an argon atmosphere at a dew point below -68°C, the laminated end of the chemically converted laminated battery was cut to form an opening. The interior of the laminated film was then sealed at 25°C using a vacuum packaging machine (TOSEI Corporation, TOSPACK) to a reduced pressure of 1.3 kPa, yielding the evaluation battery of this comparative example.

[0114] Evaluation of the charge and discharge characteristics of all-solid-state batteries

[0115] The evaluation batteries fabricated above were evaluated for their charge-discharge characteristics under the following conditions. The evaluation of the battery's charge-discharge characteristics was conducted using a charge-discharge testing apparatus (HJ-SD8, manufactured by Hokuto Electric Co., Ltd.). A constraint pressure of 3 MPa was applied in the stacking direction of the laminated batteries using a pressurizing component, while the test was performed in a constant-temperature bath set to 60°C. The batteries were placed inside the constant-temperature bath, and after the battery temperature stabilized, a charge-discharge test was conducted at 2.0 mA / cm². 2 Constant current charging was performed at a current density until the battery voltage reached 4.3V. Then, it was charged at 2.0mA / cm². 2The battery was discharged at a constant current density until the battery voltage reached 3.0V. The capacity per unit mass of active material (mAh / g) was calculated from the discharge capacity obtained after five repeats of this charge-discharge cycle and the mass of the active material contained in the positive electrode, and this capacity was taken as the rated capacity of the battery. The results are shown in Table 1 below. If the values ​​are 0 and Δ according to the following evaluation criteria, the battery can be used without problems:

[0116] 〇: 190mAh / g or higher,

[0117] △: 160mAh / g or higher and less than 190mAh / g

[0118] ×: Less than 160mAh / g.

[0119] Evaluation of the fast charging characteristics of all-solid-state batteries

[0120] For the batteries with a rated capacity of 160 mAh / g or higher used in the evaluation process described above, fast charging characteristics were evaluated under the following conditions. The fast charging characteristics of the batteries were evaluated using a charge-discharge test apparatus (HJ-SD8, manufactured by Hokuto Electric Co., Ltd.). A constraint pressure of 3 MPa was applied in the stacking direction of the laminated batteries using a pressurizing component, while the test was conducted in a constant-temperature bath set to 60°C. The batteries were placed in the constant-temperature bath, and after the battery temperature stabilized, a charge-discharge test was performed at 2.0 mA / cm². 2 Constant current charging was performed at a current density (equivalent to 0.1C) until the battery voltage reached 4.3V, which was used as the low-speed charging capacity. Then, charging was performed at 2.0mA / cm². 2 After constant current discharge to a battery voltage of 3.0V, the discharge is carried out at a current density of 20.0mA / cm. 2 The battery was charged at a constant current density (equivalent to 1C) to a voltage of 4.3V, which was taken as the fast charging capacity. The ratio (percentage) of the fast charging capacity to the low-speed charging capacity was taken as the fast charging characteristic (%). The results are shown in Table 1 below. According to the following evaluation criteria, if it is 0, it can be used without problems:

[0121] 〇: Fast charging capability is over 70%.

[0122] △: Fast charging capability is less than 70%.

[0123] ×: Short circuit during fast charging.

[0124] [Table 1]

[0125]

[0126] As shown in Table 1, the results indicate that, as in Examples 1-4, the method according to the present invention yields all-solid-state batteries with excellent rated capacity and fast-charging characteristics. On the other hand, the battery of Comparative Example 3, which underwent a chemical conversion process under atmospheric pressure, did not achieve sufficient rated capacity. Furthermore, the battery of Comparative Example 1, which underwent a chemical conversion process under reduced pressure, achieved sufficient rated capacity, but exhibited poor fast-charging characteristics. The battery of Comparative Example 2, which was not sealed under reduced pressure, experienced a short circuit during fast charging.

[0127] Symbol Explanation

[0128] 10a: Stacked secondary battery

[0129] 11': Negative current collector

[0130] 11”: Positive current collector

[0131] 13: Negative electrode active material layer

[0132] 14: Negative electrode intermediate layer

[0133] 15: Positive electrode active material layer

[0134] 17: Solid electrolyte layer

[0135] 19: Single cell layer

[0136] 21: Power generation components

[0137] 25: Negative current collector

[0138] 27: Positive current collector

[0139] 29: Laminated film.

Claims

1. A manufacturing method of an all-solid-state battery, the all-solid-state battery having an electricity generating element sealed in the inside of a battery outer body, the electricity generating element having: a positive electrode having a positive electrode active material layer containing a positive electrode active material and a first solid electrolyte; a negative electrode having a negative electrode active material layer containing a negative electrode active material; and a solid electrolyte layer containing a second solid electrolyte, which is interposed between the positive electrode and the negative electrode, the manufacturing method of the all-solid-state battery characterized by comprising: a chemical conversion step including a step of primary charging the electricity generating element in a non-active gas environment; and a step of sealing the electricity generating element in the inside of the battery outer body under reduced pressure after the chemical conversion step.

2. The manufacturing method of the all-solid-state battery according to claim 1, characterized in that the primary charging includes constant voltage charging.

3. The manufacturing method of the all-solid-state battery according to claim 1 or 2, characterized in that the chemical conversion step further includes a step of discharging after the primary charging of the electricity generating element.

4. The manufacturing method of the all-solid-state battery according to claim 1 or 2, characterized in that the positive electrode active material is a lithium-nickel composite oxide, and the first solid electrolyte is a sulfide solid electrolyte.

5. The manufacturing method of the all-solid-state battery according to claim 1 or 2, characterized in that the negative electrode active material contains lithium metal.

6. The manufacturing method of the all-solid-state battery according to claim 1 or 2, characterized in that the charging termination voltage of the primary charging is 3.6 to 4.2 V. ​ ​ ​ ​ ​ ​ ​

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