Method for producing electrode for all-solid-state battery and method for producing all-solid

Abstract

To provide an all-solid battery excellent in load characteristics, and to provide an electrode capable of constituting the all-solid battery.SOLUTION: The method for producing an electrode for all-solid-state batteries of the present invention is a method for producing an electrode for all-solid-state batteries having a molded body of an electrode mixture containing an active material, a solid electrolyte, and a conductive auxiliary agent, the method including: The molded body of the electrode mixture contains an electrode material formed of a granulated body containing at least a part of an active material and at least a part of a solid electrolyte, and a conductive auxiliary agent different from the electrode material, the electrode material contains a granular argyrodite-type sulfide-based solid electrolyte as the solid electrolyte, A ratio Ms / Mc of a total content Ms (% by mass) of a solid electrolyte to a content Mc (% by mass) of a conductive auxiliary agent in a total amount of a molded body of an electrode mixture is 6 to 17, and the method includes a step of granulating an active material and a solid electrolyte to form an electrode material made of the granulated body, and a step of forming a molded body of an electrode mixture using an electrode mixture including at least the electrode material and a conductive auxiliary agent.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state battery having excellent load characteristics and an electrode that can be used to form the all-solid-state battery. [Background technology]

[0002] In recent years, with the development of portable electronic devices such as mobile phones and laptop personal computers, and the practical application of electric vehicles, there has been a growing demand for small, lightweight batteries with high capacity and high energy density.

[0003] Currently, lithium batteries, particularly lithium ion batteries, that can meet this demand use an organic electrolyte solution containing an organic solvent and a lithium salt as the non-aqueous electrolyte.

[0004] Furthermore, with the further development of devices that use lithium-ion batteries, there is a demand for longer life, higher capacity, and higher energy density of lithium-ion batteries, as well as a high demand for the reliability of these longer life, higher capacity, and higher energy density lithium-ion batteries.

[0005] However, the organic electrolyte used in lithium-ion batteries contains flammable organic solvents, which can cause the organic electrolyte to generate excessive heat in the event of an abnormality such as a short circuit. Furthermore, with the recent trend toward higher energy density in lithium-ion batteries and an increasing amount of organic solvent in the organic electrolyte, there is a growing demand for greater reliability in lithium-ion batteries.

[0006] In light of the above, all-solid-state lithium batteries (all-solid-state batteries) that do not use organic solvents are attracting attention. All-solid-state batteries use a molded body of a solid electrolyte that does not use organic solvents instead of the conventional organic solvent-based electrolyte, and are highly safe as they do not involve the risk of abnormal heat generation by the solid electrolyte.

[0007] Furthermore, because all-solid-state batteries are not only highly safe but also highly reliable, environmentally resistant, and have a long lifespan, they are expected to be maintenance-free batteries that can continue to contribute to social development while also contributing to safety and security.By providing all-solid-state batteries to society, we can contribute to the achievement of Goal 12 (Ensure sustainable consumption and production patterns), Goal 3 (Ensure healthy lives and promote well-being for all at all ages), Goal 7 (Ensure access to affordable, reliable, sustainable, and modern energy for all), and Goal 11 (Make cities inclusive, safe, resilient, and sustainable).

[0008] Furthermore, various improvements have been attempted for all-solid-state batteries. For example, Patent Document 1 describes that the performance of all-solid-state batteries can be improved by using a material made of a granulated mixture of a sulfide-based inorganic solid electrolyte and an electrode active material.

[0009] In Patent Document 1, the all-solid-state battery material is manufactured by mixing a sulfide-based inorganic solid electrolyte powder with an electrode active material powder to form a mixed powder, which is then pressure-molded to form a molded body. This manufacturing method results in the all-solid-state battery material having a plurality of electrode active material particles adjacent to one another, forming an electron conduction path, the sulfide-based inorganic solid electrolyte being disposed between the electrode active material particles, and the pressure molding causing the sulfide-based inorganic solid electrolyte particles to deform and bond to one another, losing their particle shape and becoming a continuous phase, thereby forming an ion conduction path. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2014-192061 A (Claims, paragraphs

[0015] and

[0016] ) Summary of the Invention [Problem to be solved by the invention]

[0011] Incidentally, the application fields of all-solid-state batteries are currently expanding rapidly, and applications requiring discharge at a large current value are expected, for example. Therefore, there is a demand for improving the load characteristics to meet this demand.

[0012] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an all-solid-state battery having excellent load characteristics and an electrode that can be used to constitute the all-solid-state battery. [Means for solving the problem]

[0013] The method for producing an electrode for an all-solid-state battery of the present invention is a method for producing an all-solid-state ionization electrode having a molded body of an electrode mixture containing an active material, a solid electrolyte, and a conductive additive, wherein the molded body of the electrode mixture contains an electrode material consisting of granules containing at least a portion of the active material and at least a portion of the solid electrolyte, and the electrode material contains a granular argyrodite-type sulfide-based solid electrolyte as the solid electrolyte, and the ratio Ms / Mc of the total content of the solid electrolyte: Ms (mass%) to the content of the conductive additive: Mc (mass%) in the total amount of the molded body of the electrode mixture is 6 to 17, and the method comprises the steps of: granulating the active material and the solid electrolyte to form an electrode material consisting of the granules; and forming a molded body of the electrode mixture using the electrode mixture containing at least the electrode material and the conductive additive.

[0014] Furthermore, the method for producing an all-solid-state battery of the present invention is a method for producing an all-solid-state battery having a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, and is characterized by comprising the steps of: forming at least one of the positive electrode and the negative electrode by the method for producing an electrode for an all-solid-state battery of the present invention; and assembling an all-solid-state battery using the electrode obtained by the step.

[0015] The all-solid-state battery of the present invention includes a primary battery (all-solid-state primary battery) and a secondary battery (all-solid-state secondary battery). [Effects of the Invention]

[0016] According to the present invention, it is possible to provide an all-solid-state battery having excellent load characteristics and an electrode that can constitute the all-solid-state battery. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a plan view schematically illustrating an example of a part of a molded body of an electrode mixture included in the electrode for an all-solid-state battery of the present invention. [Figure 2] FIG. 2 is an enlarged view of the area surrounded by the dotted line in FIG. 1. [Figure 3] FIG. 2 is a plan view schematically illustrating another example of a part of a molded body of an electrode mixture included in an electrode for an all-solid-state battery of the present invention. [Figure 4] FIG. 2 is a plan view schematically illustrating another example of a part of a molded body of an electrode mixture included in an electrode for an all-solid-state battery of the present invention. [Figure 5] FIG. 1 is a cross-sectional view schematically illustrating an example of an all-solid-state battery of the present invention. [Figure 6] FIG. 2 is a plan view schematically illustrating another example of the all-solid-state battery of the present invention. [Figure 7] FIG. 7 is a cross-sectional view taken along line II in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0018] <Electrodes for all-solid-state batteries> The electrode for an all-solid-state battery of the present invention is used for the positive or negative electrode of an all-solid-state battery and comprises a molded body of an electrode mixture containing an active material, a solid electrolyte, and a conductive additive. Furthermore, at least a portion of the active material contained in the molded body of the electrode mixture and at least a portion of the solid electrolyte contained in the molded body of the electrode mixture are present in the molded body of the electrode mixture as an electrode material consisting of a granule containing these. The electrode material contains a granular argyrodite-type sulfide-based solid electrolyte as the solid electrolyte.

[0019] When a compact of an electrode mixture constituting an electrode material for an all-solid-state battery is produced, for example, by simply mixing an active material and a solid electrolyte to form a mixed powder and then subjecting it to a process such as pressure molding, the active material particles generally have relatively large surface irregularities, and the solid electrolyte particles are unable to conform well to these irregularities, resulting in relatively large gaps between the active material particles and the solid electrolyte particles, which places a certain limit on the improvement of ionic conductivity (lithium ion conductivity) within the compact of the electrode mixture. This has been a factor hindering the improvement of the load characteristics of all-solid-state batteries.

[0020] Therefore, in the electrode for an all-solid-state battery of the present invention, an electrode material formed by granulating an active material and an argyrodite-type sulfide-based solid electrolyte in advance is contained in a molded body of an electrode mixture. In this case, since the active material and the argyrodite-type sulfide-based solid electrolyte are configured as granules, the contact between the active material particles and the argyrodite-type sulfide-based solid electrolyte particles in the electrode material is better than in the case of a simple mixture of the active material and the solid electrolyte particles. Therefore, even when a solid electrolyte other than the electrode material is used together with the electrode material to form a molded body of an electrode mixture, the action of the solid electrolyte in the electrode material improves ionic conductivity within the molded body of the electrode mixture.

[0021] In order to improve the load characteristics of an all-solid-state battery, not only good ionic conductivity but also good electronic conductivity is required within the compact of the electrode mixture that constitutes the electrode. However, when an electrode material made of a granule containing an active material and a solid electrolyte is used, the amount of solid electrolyte present in the vicinity of the active material particles increases, making it difficult to improve the electronic conductivity between the active material particles, for example.

[0022] As a result of extensive research, the present inventors have found that even when an electrode material formed by previously granulating an active material and an argyrodite-type sulfide-based solid electrolyte is contained in a molded electrode mixture, if a conductive additive is contained in the molded electrode mixture and the total amount of solid electrolyte contained in the molded electrode mixture (the amount of solid electrolyte contained as the electrode material, or the total amount of solid electrolyte contained as the electrode material and the amount of solid electrolyte contained other than the electrode material) and the amount of conductive additive are adjusted within specific ranges, the electronic conductivity between active material particles can be improved and a decrease in electronic conductivity within the molded electrode mixture can be suppressed.

[0023] In the electrode for an all-solid-state battery of the present invention, the ionic conductivity and electronic conductivity in the molded body of the electrode mixture can be improved by the above-mentioned actions, and therefore an all-solid-state battery (the all-solid-state battery of the present invention) constructed using this electrode has excellent load characteristics.

[0024] The argyrodite-type sulfide-based solid electrolyte contained in the electrode material included in the electrode for an all-solid-state battery of the present invention is in a granular form.

[0025] In the all-solid-state battery material described in Patent Document 1, as described above, the sulfide-based inorganic solid electrolyte present between particles of the electrode active material is in a continuous phase in which the particulate shape has disappeared. Patent Document 1 states that a good ion conduction path is formed by the continuous phase of the sulfide-based inorganic solid electrolyte. Therefore, according to this description, it is expected that, even when increasing the ion conductivity inside the electrode and improving the load characteristics of the all-solid-state battery, it is preferable that the solid electrolyte present between the active materials forms a continuous phase rather than a granular (particulate) shape.

[0026] However, according to the investigations of the present inventors, contrary to such expectations, it has been found that in an electrode material made of granules containing an active material and an argyrodite-type sulfide-based solid electrolyte contained in an electrode for an all-solid-state battery, the presence of the solid electrolyte in a granular form is advantageous in improving the load characteristics of the all-solid-state battery. Although the reason for this is not clear, it is speculated that it may be as follows.

[0027] Argyrodite-type sulfide-based solid electrolytes are usually provided in a granular (particulate) form, but such granular argyrodite-type sulfide-based solid electrolytes are crystallized and have higher ionic conductivity than when in an amorphous state. When the sulfide-based solid electrolyte present between active materials in an electrode for an all-solid-state battery becomes a continuous phase in which the particles are bonded together and lose their original shape (granular), it is considered that the solid electrolyte has become amorphous or its crystallinity is very low, and it is considered that the solid electrolyte is unable to fully exhibit its inherent ionic conductivity.

[0028] In contrast, when the argyrodite-type sulfide-based solid electrolyte in the electrode material contained in the all-solid-state battery electrode can exist in a state in which it maintains its original granular shape, it is thought that the crystallinity is also maintained at a relatively high level, which increases the ionic conductivity of the electrode material, which is a granule. Therefore, it is presumed that high ionic conductivity can be ensured in the all-solid-state battery electrode of the present invention.

[0029] Furthermore, if the solid electrolyte present between the active material particles forms a continuous phase and the active material particles are enveloped in this continuous phase, the contact between the conductive additive contained in the electrode and the active material may become poorer, and the electronic conductivity in the electrode may become insufficient. However, in the electrode for an all-solid-state battery of the present invention, as described above, the relationship between the total amount of solid electrolyte contained in the molded body of the electrode mixture and the amount of conductive additive is adjusted to within a specific range, thereby improving the electronic conductivity in the molded body of the electrode mixture.

[0030] As described above, the electrode for an all-solid-state battery of the present invention can have higher ionic conductivity and electronic conductivity than, for example, an electrode in which the solid electrolyte between active material particles forms a continuous phase. Therefore, it is presumed that the use of this electrode can form an all-solid-state battery with excellent load characteristics.

[0031] An all-solid-state battery formed using the all-solid-state battery electrode of the present invention (all-solid-state battery of the present invention) can exhibit excellent load characteristics even after long-term storage, and can maintain high load characteristics even after being subjected to a certain degree of thermal history (about 85°C or less), for example.

[0032] In the all-solid-state battery electrode of the present invention, the presence of an electrode material formed from a granule containing an active material and an argyrodite-type solid electrolyte in a compact of an electrode mixture is confirmed by observing a cross-section of the compact of the electrode mixture at 10,000x magnification using a scanning electron microscope (SEM) where 10 or more primary particles of the active material are aggregated together and the gaps between the primary particles of the active material are 5 μm or less, and further observing a cross-section at 30,000x magnification where granular solid electrolyte (the argyrodite-type sulfide solid electrolyte and other solid electrolytes that the electrode material may contain) is present between the primary particles of the active material. The gaps between the primary particles of the active material are preferably 4 μm or less, more preferably 3 μm or less, and are typically 0.5 μm or more, depending on the particle size of the solid electrolyte.

[0033] During the above observation, if the solid electrolyte (the argyrodite-type sulfide-based solid electrolyte and other solid electrolytes that may be contained in the electrode material) present between the primary particles of the active material has a granular outline, the solid electrolyte is considered to be granular. For example, if two solid electrolyte particles are in close contact with each other and the interface between the particles is unclear, and the shape of the particles is assumed to be a circle in a plan view, the solid electrolyte is considered to have a granular outline if more than 60% of the circumference can be confirmed.

[0034] 1 and 2 are diagrams schematically showing an example of a molded body of an electrode mixture included in an electrode for an all-solid-state battery of the present invention. Fig. 1 is a plan view showing a part of the molded body of an electrode mixture, and Fig. 2 is an enlarged view of the area surrounded by a dotted line in Fig. 1.

[0035] The area enclosed by an ellipse in FIG. 1 represents the electrode material 1, which is a granule of an active material and an argyrodite-type sulfide-based solid electrolyte. The electrode material 1, together with a solid electrolyte 2 added separately from the argyrodite-type solid electrolyte constituting the electrode material 1, forms a compact of an electrode mixture. The electrode material 1 is composed of an aggregate of 10 or more primary particles 1a of the active material. However, the ellipse shown in FIG. 1 includes some solid electrolyte 2 that is present around the electrode material 1 and does not constitute the electrode material 1. Furthermore, some of the primary particles 1a of the active material that constitute the electrode material 1 extend beyond the ellipse shown in FIG. 1 (this also applies to FIGS. 3 and 4, which will be described later). The argyrodite-type solid electrolyte that constitutes the electrode material 1 is not shown in FIG. 1 (this also applies to FIGS. 3 and 4, which will be described later).

[0036] As shown in FIG. 2, granular argyrodite-type sulfide-based solid electrolyte 1b is present in the gaps between primary particles 1a of the active material in the electrode material 1.

[0037] 3 and 4 are diagrams schematically illustrating a portion of another example of an electrode mixture compact included in an electrode for an all-solid-state battery of the present invention. The electrode mixture compact shown in FIG. 3 is formed from an electrode material 1 and a solid electrolyte 2 (different from the argyrodite-type solid electrolyte constituting the electrode material 1). That is, all of the active materials contained in the electrode mixture compact shown in FIG. 3 constitute the electrode material 1. On the other hand, the electrode mixture compact shown in FIG. 4 is formed from the electrode material 1, the solid electrolyte 2 (added separately from the argyrodite-type solid electrolyte constituting the electrode material 1), and an active material (primary particles of the active material) 3 different from that constituting the electrode material 1.

[0038] Examples of electrodes for all-solid-state batteries include a molded body (pellet, etc.) obtained by molding an electrode mixture, and a structure in which a layer (mixture layer) made of a molded body of an electrode mixture is formed on a current collector.

[0039] When the electrode for the all-solid-state battery is a positive electrode and is used in an all-solid-state primary battery, the active material of the electrode material to be incorporated into the molded body of the electrode binder can be the same as the positive electrode active material used in a conventionally known non-aqueous electrolyte primary battery. Specifically, for example, manganese dioxide, lithium-containing manganese oxide [e.g., LiMn3O6 and composite oxides having the same crystal structure as manganese dioxide (such as β-type, γ-type, or a structure in which β-type and γ-type are mixed), and the content of Li is 3.5% by mass or less, preferably 2% by mass or less, more preferably 1.5% by mass or less, and particularly preferably 1% by mass or less], Li a Ti 5 / 3 Lithium-containing composite oxides such as O4 (4 / 3 ≦ a < 7 / 3); vanadium oxides; niobium oxides; titanium oxides; sulfides such as iron disulfide; graphite fluoride; silver sulfides such as Ag2S; nickel oxides such as NiO2: and the like can be mentioned.

[0040] Also, when the electrode for the all-solid-state battery is a positive electrode and is used in an all-solid-state secondary battery, the active material of the electrode material to be incorporated into the molded body of the electrode binder can be the same as the positive electrode active material used in a conventionally known non-aqueous electrolyte secondary battery, that is, the same as an active material capable of occluding and releasing Li (lithium) ions. Specifically, Li 1-x M r Mn 2-r O4 (where M is at least one element selected from the group consisting of Li, Na, K, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Zr, Fe, Co, Ni, Cu, Zn, Al, Sn, Sb, In, Nb, Ta, Mo, W, Y, Ru, and Rh, 0 ≦ x ≦ 1, 0 ≦ r ≦ 1), spinel-type lithium manganese composite oxide represented by Li r Mn (1-s-t) Ni s M t O (2-u) F v (where M is at least one element selected from the group consisting of Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr, and W, 0 ≦ r ≦ 1.2, 0 < s < 0.5, 0 ≦ t ≦ 0.5, u + v < 1, -0.1 ≦ u ≦ 0. II, 0 ≦ v ≦ 0.1), layered compound represented by Li1-x Co 1-r M r Lithium cobalt composite oxide represented by LiO2 (wherein M is at least one element selected from the group consisting of Al, Mg, Ti, V, Cr, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, Ba, Mn, Bi, Ca, F, P, Sr, W, Si, Ta, K, S, Er, and Na, and 0≦x≦1, 0≦r≦0.5), 1-x Ni 1-r M r Lithium nickel composite oxide represented by LiO2 (wherein M is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦1, 0≦r≦0.5), 1+s-x M 1-r N r PO4F s (wherein M is at least one element selected from the group consisting of Fe, Mn, and Co, and N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, V, and Ba, and 0≦x≦1, 0≦r≦0.5, 0≦s≦1), Li 2-x M 1-r N r Examples include pyrophosphate compounds represented by P2O7 (wherein M is at least one element selected from the group consisting of Fe, Mn, and Co, and N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, V, and Ba, and 0≦x≦2, 0≦r≦0.5), and these may be used alone or in combination of two or more.

[0041] In the case of an electrode for an all-solid-state battery used in an all-solid-state secondary battery, among the above-exemplified positive electrode active materials, a lithium cobalt composite oxide (A) represented by the following general formula (1) is preferably used.

[0042] Li a Co 1-b-c-d Al b M1 c M 2 d O 2+e (1)

[0043] In the general formula (1), M 1 is at least one element selected from the group consisting of Mg, Ni and Na, M 2 is at least one element selected from the group consisting of Mn, Fe, Cu, Zr, Ti, Bi, Ca, F, P, Sr, W, Ba, Nb, Si, Zn, Mo, V, Sn, Sb, Ta, Ge, Cr, K, S, and Er, and 0.9 <a<1.1 、0<b<0.1、0<c<0.1、b+c<0.1、0≦d、-0.5<e<0.5である。

[0044] When the lithium cobalt composite oxide (A) is used as a positive electrode active material for a non-aqueous electrolyte secondary battery using an organic electrolyte, the Al and M contained therein are 1 It is a material that increases the internal resistance of a battery through the action of added elements such as lithium cobalt complex oxide (A). However, in the case of nonaqueous electrolyte secondary batteries containing an organic electrolyte, the electrolyte that transfers ions between the positive electrode and the negative electrode is liquid (electrolyte), and therefore the original internal resistance is low, so the increase in internal resistance due to the lithium cobalt complex oxide (A) has almost no effect on the battery characteristics. On the other hand, in all-solid-state secondary batteries in which ions are transferred between the positive electrode and the negative electrode by a solid electrolyte, the increase in internal resistance due to the action of the positive electrode active material is expected to cause a deterioration in battery characteristics such as load characteristics.

[0045] However, contrary to this expectation, when the lithium-cobalt composite oxide (A) is used as the positive electrode active material of an all-solid-state secondary battery, it is possible to reduce the internal resistance compared to when, for example, LiCoO2 is used as the positive electrode active material, and it is possible to further improve the load characteristics of the all-solid-state secondary battery.

[0046] When a battery using LiCoO2 as the positive electrode active material is charged, the Co expands due to a change in valence. In batteries using organic electrolytes, even if this causes a volume change in the positive electrode active material, the electrolyte that transfers ions is liquid, so contact with the positive electrode active material is not impaired. On the other hand, in all-solid-state secondary batteries, the electrolyte that transfers ions within the positive electrode is solid (solid electrolyte). Therefore, when the positive electrode active material changes volume during battery charging and discharging, a gap forms between the positive electrode active material and the solid electrolyte, increasing the internal resistance of the positive electrode and, ultimately, the battery.

[0047] However, in the case of the lithium cobalt composite oxide (A) represented by the general formula (1), even in a charged state, Al and element M 1 The expansion of Co is suppressed by this action, and the amount of expansion (volume change) of the entire positive electrode active material is reduced. Therefore, by using a positive electrode for an all-solid-state battery that uses the lithium-cobalt composite oxide (A) as the positive electrode active material, good contact between the lithium-cobalt composite oxide (A) and the solid electrolyte in the positive electrode can be maintained even during charging and discharging, and the internal resistance can be kept low, resulting in an all-solid-state secondary battery with better load characteristics.

[0048] In lithium cobalt composite oxide (A), Al is an element that substitutes for the Co site, and M 1 are elements that are substituted for the Li site, and both have the effect of reducing the amount of expansion of Co (the amount of expansion of the lithium cobalt composite oxide (A)) during charging.

[0049] Lithium cobalt composite oxide (A) contains element M 1 The lithium ion battery may contain at least one element selected from Mg, Ni, and Na. However, Mg is preferred because it has an ionic radius equivalent to that of the Li that it substitutes and does not undergo a change in valence during charge and discharge.

[0050] In the lithium cobalt composite oxide (A), in order to minimize the expansion amount during charging, the amount b of Al is greater than 0 and less than 0.1, and the element M 1The amount c of Al is greater than 0 and less than 0.1, and b+c is less than 0.1. The amount b of Al is preferably 0.005 or more, and the amount of element M 1 The amount c of Al is preferably 0.005 or more. Furthermore, the amount b of Al is preferably 0.08 or less. 1 The amount c is preferably 0.08 or less.

[0051] Lithium cobalt composite oxide (A) contains element M 2 may or may not be contained (the amount d may be 0), but the element M 2 If the amount of element M is too large, for example, the amount of Co may become small, and the capacity of the lithium cobalt composite oxide (A) may become small. 2 The amount d is preferably 0.05 or less.

[0052] When the electrode for an all-solid-state battery is a negative electrode and is used in an all-solid-state primary battery, examples of the active material of the electrode material to be contained in the molded body of the electrode mixture include metallic lithium and lithium alloys (lithium-aluminum alloys, lithium-indium alloys, etc.).

[0053] Furthermore, when the electrode for an all-solid-state battery is a negative electrode and is used in an all-solid-state secondary battery, the active material of the electrode material to be contained in the molded body of the electrode mixture is not particularly limited as long as it is an active material capable of absorbing and releasing lithium ions that has been used in conventionally known lithium secondary batteries. For example, the negative electrode active material may be one or a mixture of two or more carbonaceous materials capable of absorbing and releasing lithium, such as graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads (MCMB), and carbon fibers. An oxide may also be used as the negative electrode active material, for example, Li x Nb y TiM 6 a O {5y+4 / 2}+δ (However, M 6is at least one element selected from the group consisting of V, Cr, Mo, Ta, Zr, Mn, Fe, Mg, B, Al, Cu, and Si, and is a composite oxide having a monoclinic crystal structure represented by 0≦x≦49, 0.5≦y<24, −5≦δ≦5, 0≦a≦0.3), titanium dioxide having an anatase structure, lithium titanate having a ramsdellite structure represented by Li2Ti3O7, Li4Ti5O 12 and spinel-type lithium-titanium composite oxides represented by the formula (1), among which one or more can be used. Simple substances, compounds, and alloys thereof containing elements such as Si, Sn, Ge, Bi, Sb, and In; compounds that can be charged and discharged at low voltages close to those of metallic lithium, such as nitrides or lithium-containing oxides containing lithium and transition metals such as Co, Ni, Mn, Fe, Cr, Ti, and W; or metallic lithium or lithium alloys (such as lithium-aluminum alloys and lithium-indium alloys) can also be used as the negative electrode active material.

[0054] The active material of the electrode material may have a reaction suppression layer on its surface to suppress the reaction between the active material and the solid electrolyte. In particular, when the electrode for an all-solid-state battery is a positive electrode, it is preferable that a reaction suppression layer is provided on the surface of the active material (positive electrode active material).

[0055] The reaction suppression layer may be made of any material that has ion conductivity and can suppress the reaction between the positive electrode active material and the solid electrolyte. Examples of materials that can form the reaction suppression layer include oxides containing Li and at least one element selected from the group consisting of Nb, P, B, Si, Ge, Ti, Zr, Ta, and W. More specifically, Nb-containing oxides such as LiNbO3, Li3PO4, Li3BO3, Li4SiO4, Li4GeO4, LiTiO3, LiZrO3, and Li2WO4 are examples. The reaction suppression layer may contain only one of these oxides, or two or more of them, or may even form a composite compound of two or more of these oxides. Among these oxides, Nb-containing oxides are preferred, and LiNbO3 is more preferred.

[0056] The reaction suppression layer is preferably present on the surface in an amount of 0.1 to 1.0 part by mass per 100 parts by mass of the active material (base particles that form the reaction suppression layer). This range allows for effective suppression of the reaction between the active material and the solid electrolyte.

[0057] Examples of methods for forming a reaction suppression layer on the surface of an active material include the sol-gel method, mechanofusion method, CVD method, PVD method, and ALD method.

[0058] An argyrodite-type sulfide-based solid electrolyte is used as the solid electrolyte of the electrode material to be contained in the electrode mixture compact of the all-solid-state battery electrode.

[0059] Examples of argyrodite-type sulfide-based solid electrolytes include those represented by the following general formula (2), such as Li6PS5Cl, and those represented by the following general formula (3).

[0060] Li 7-x+y PS 6-x Cl x+y (2)

[0061] In the general formula (2), 0.05≦y≦0.9, and −3.0x+1.8≦y≦−3.0x+5.7.

[0062] Li 7-p PS 6-p Cl q Br r (3)

[0063] In the general formula (3), p=q+r, 0 <p≦1.8、0.1≦q / r≦10.0である。

[0064] The solid electrolyte of the electrode material in the electrode for the all-solid-state battery can be other solid electrolytes in addition to the argyrodite-type sulfide-based solid electrolyte, such as sulfide-based solid electrolytes other than the argyrodite-type sulfide-based solid electrolyte, hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes.

[0065] Examples of sulfide solid electrolytes other than the argyrodite-type sulfide solid electrolyte include particles such as Li2S-P2S5, Li2S-SiS2, Li2S-P2S5-GeS2, and Li2S-B2S3-based glasses; those of the LGPS type (Li 10 GeP2S 12 etc.); and the like.

[0066] Examples of hydride solid electrolytes include, for example, LiBH4, solid solutions of LiBH4 and the following alkali metal compounds (for example, those with a molar ratio of LiBH4 to the alkali metal compound of 1:1 to 20:1). Examples of the alkali metal compound in the solid solution include at least one selected from the group consisting of lithium halides (such as LiI, LiBr, LiF, LiCl), rubidium halides (such as RbI, RbBr, RbF, RbCl), cesium halides (such as CsI, CsBr, CsF, CsCl), lithium amide, rubidium amide, and cesium amide.

[0067] Examples of halide solid electrolytes include, for example, monoclinic LiAlCl4, defective spinel-type or layered LiInBr4, monoclinic Li 6-3m Y m X6 (where 0 < m < 2 and X = Cl or Br), etc., and in addition, for example, known ones described in International Publication No. 2020 / 070958 and International Publication No. 2020 / 070955 can be used.

[0068] Examples of oxide solid electrolytes include, for example, Li2O-Al2O3-SiO2-P2O5-TiO2-based glass ceramics, Li2O-Al2O3-SiO2-P2O5-GeO2-based glass ceramics, garnet-type Li7La3Zr2O 12 , NASICON-type Li 1+O Al 1+O Ti 2-O (PO4)3, Li 1+p Al 1+p Ge 2-p (PO4)3, perovskite-type Li 3q La2 / 3-q Examples include TiO3.

[0069] When an argyrodite-type sulfide-based solid electrolyte and another solid electrolyte are used in the electrode material, the proportion of the argyrodite-type sulfide-based solid electrolyte in the total amount of solid electrolyte in the electrode material is preferably 70 mass% or more. Furthermore, since it is preferable that all of the solid electrolytes used in the electrode material are argyrodite-type sulfide-based solid electrolytes, the preferred upper limit of the proportion of the argyrodite-type sulfide-based solid electrolyte in the total amount of solid electrolyte in the electrode material is 100 mass%.

[0070] The argyrodite-type sulfide-based solid electrolyte contained in the electrode material contained in the molded body of the electrode mixture is not particularly limited in shape as long as it is granular. For example, the argyrodite-type sulfide-based solid electrolyte may have any shape such as a spherical shape, an ellipsoidal shape, or a plate shape as long as the primary particle diameter Rs measured by the method described below satisfies the following value:

[0071] When the average particle size of the primary particles of the active material contained in the electrode material is Ra and the average particle size of the primary particles of the solid electrolyte contained in the electrode material (including other solid electrolytes when the electrode material contains other solid electrolytes besides the argyrodite-type solid electrolyte), the ratio Ra / Rs is preferably 2 or more, more preferably 4 or more, and most preferably 6 or more, and is preferably 50 or less, more preferably 35 or less, and most preferably 18 or less. When Ra / Rs satisfies the above value, the contact between the active material and the solid electrolyte in the electrode material becomes better, and the effect of improving the load characteristics of the all-solid-state battery becomes better.

[0072] The average particle size Ra of the primary particles of the active material in the electrode material is preferably 1 μm or more, more preferably 3 μm or more, and most preferably 4 μm or more, and is preferably 25 μm or less, more preferably 15 μm or less, and most preferably 10 μm or less.

[0073] The average particle size Rs of the primary particles of the solid electrolyte in the electrode material is preferably 0.2 μm or more, more preferably 0.4 μm or more, and is preferably 3 μm or less, more preferably 1.8 μm or less.

[0074] The average particle size of the primary particles of the active material contained in the electrode material is a value determined as follows: A cross section of a molded body of an electrode mixture for an all-solid-state battery electrode is observed at 2000x magnification using an SEM. Ten active material particles with visible outlines are selected, and the longest diameter of the selected particles is measured using the two-point method. The average (number average) of the longest diameters of all the measured particles is defined as the average particle size of the primary particles of the active material.

[0075] The average particle size of the primary particles of the solid electrolyte contained in the electrode material is a value determined in the same manner as the average particle size of the primary particles of the active material contained in the electrode material, except that the magnification of the SEM observation is changed to 30,000 times.

[0076] Regarding the composition of the active material and argyrodite-type solid electrolyte in the electrode material, the content of the argyrodite-type solid electrolyte is preferably 2.5 parts by mass or more, more preferably 8 parts by mass or more, and preferably 60 parts by mass or less, and more preferably 40 parts by mass or less, per 100 parts by mass of the active material. With the electrode material having such a component composition, an electrode for an all-solid-state battery having a good balance between capacity and ionic conductivity can be formed.

[0077] The electrode material is produced by granulating particles of an active material and particles of an argyrodite-type sulfide-based solid electrolyte. There are no particular limitations on the granulation method, and known methods can be used. However, it is necessary to adjust the stress acting during granulation so that the argyrodite-type sulfide-based solid electrolyte maintains its granular shape after granulation. For example, a desirable method for adjusting the stress acting during granulation is to adjust a known mixer so that van der Waals forces and electrostatic forces are generated due to the collision and shear action between the materials.

[0078] The particles of the argyrodite-type sulfide-based solid electrolyte used to form the electrode material have an average particle diameter (50% diameter value in the volume-based integrated fraction when calculating the integrated volume from particles with small particle sizes (D 50 ) is usually about 0.2 to 3 μm. Therefore, an argyrodite-type sulfide-based solid electrolyte of such a size is granulated to form the electrode material, and then, in a compact of an electrode mixture formed using this electrode material, conditions are selected to satisfy the primary particle diameter Rs, and the active material particles and the argyrodite-type sulfide-based solid electrolyte particles are granulated together.

[0079] The electrode mixture molded body of the all-solid-state battery electrode contains a conductive additive. Examples of such conductive additives include highly crystalline carbon materials such as graphite (natural graphite, artificial graphite), graphene (single-layer graphene, multi-layer graphene), and carbon nanotubes; and low-crystalline carbon materials such as carbon black. One or more of these may be used.

[0080] The electrode mixture compact of an all-solid-state battery electrode can also contain a solid electrolyte separate from the solid electrolyte contained in the electrode material. Examples of such solid electrolytes include the various sulfide-based solid electrolytes (argyrodite-type sulfide-based solid electrolytes and other sulfide-based solid electrolytes), hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes exemplified above as usable for the electrode material. The solid electrolyte used separate from the electrode material may be the same type as that contained in the electrode material, or a different type. However, among the solid electrolytes exemplified above, sulfide-based solid electrolytes are more preferred due to their high lithium ion conductivity, and argyrodite-type sulfide-based solid electrolytes are even more preferred due to their particularly high lithium ion conductivity and high chemical stability.

[0081] The ratio Ms / Mc of the total content of solid electrolyte in the electrode mixture compact (the solid electrolyte contained in the electrode material and the solid electrolyte used separately from the electrode material as needed): Ms (mass%) to the content of conductive additive in the electrode mixture compact: Mc (mass%) is 6 or more, preferably 7 or more, from the viewpoint of increasing the electronic conductivity in the electrode mixture compact and enabling the formation of an all-solid-state battery with excellent load characteristics. However, if the value of Ms / Mc is too large, there is a risk that the load characteristics of the battery after long-term storage or after being subjected to thermal history at about 85°C or less may deteriorate. Therefore, the Ms / Mc ratio in the electrode mixture compact is 17 or less, preferably 14 or less.

[0082] The content of the conductive additive in the electrode mixture compact (Mc) is preferably 1.3 to 8.3 mass %, and the total content of the solid electrolyte (the solid electrolyte contained in the electrode material and the solid electrolyte used separately from the electrode material as needed) in the electrode mixture compact (Ms) is preferably 8 to 50 mass %.

[0083] The electrode mixture compact of the all-solid-state battery electrode can also contain an active material in addition to the electrode material. Such active materials can be the same as the various active materials exemplified above for constituting the electrode material. However, when an active material in addition to the electrode material is contained, the proportion of the active material in the electrode material is preferably 60% by mass or more, based on a total of 100% by mass of the active material in the electrode material and the active material not constituting the electrode material. It is not necessary to use an active material in addition to the electrode material in the electrode mixture compact, and the preferred upper limit of the proportion of the active material in the electrode material is 100% by mass, based on a total of 100% by mass of the active material in the electrode material and the active material not constituting the electrode material.

[0084] Furthermore, the content of the active material in the electrode mixture (the active material contained in the electrode material and the active material used separately from the electrode material as needed) is preferably 55% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 77% by mass or less, and particularly preferably 75% by mass or less. Note that, if the active material has a reaction suppression layer, the content of the active material here also includes the amount of the reaction suppression layer.

[0085] The molded body of the electrode mixture in the electrode for the all-solid-state battery may or may not contain a resin binder. Examples of the resin binder include fluororesins such as polyvinylidene fluoride (PVDF). However, since the resin binder acts as a resistance component even in the molded body of the electrode mixture, it is desirable that the amount of the resin binder be as small as possible. Therefore, the molded body of the electrode mixture does not contain a resin binder, or if it does contain one, it is preferable that the content of the resin binder in the electrode mixture is 0.5 mass% or less. The content of the resin binder in the electrode mixture is more preferably 0.3 mass% or less, and even more preferably 0 mass% (i.e., no resin binder is contained).

[0086] When a current collector is used in an electrode for an all-solid-state battery, the current collector can be made of a metal foil, punched metal, mesh, expanded metal, foamed metal, carbon sheet, etc. When a metal current collector is used, if the electrode for an all-solid-state battery is a positive electrode, it is preferably made of aluminum or stainless steel, and if the electrode for an all-solid-state battery is a negative electrode, it is preferably made of copper or nickel.

[0087] The compact of the electrode mixture can be formed, for example, by compressing an electrode mixture prepared by mixing the electrode material and the solid electrolyte with, as needed, a conductive additive, a binder, etc., by pressure molding, etc. An electrode for an all-solid-state battery consisting only of a compact of the electrode mixture can be produced by such a method.

[0088] In the case of an electrode for an all-solid-state battery having a current collector, it can be produced by bonding a molded body of the electrode mixture formed by the above-mentioned method to the current collector by, for example, pressure bonding.

[0089] Alternatively, the electrode mixture may be mixed with a solvent to prepare an electrode mixture-containing composition, which may then be applied to a substrate such as a current collector or a solid electrolyte layer that faces an electrode, dried, and then pressed to form a molded body of the electrode mixture.

[0090] The solvent for the electrode mixture-containing composition can be water or an organic solvent such as N-methyl-2-pyrrolidone (NMP). When a solid electrolyte is also included in the electrode mixture-containing composition, it is preferable to select a solvent that is less likely to deteriorate the solid electrolyte. In particular, sulfide-based and hydride-based solid electrolytes undergo chemical reactions with trace amounts of water, so nonpolar aprotic solvents such as hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, xylene, methanestyrene, and tetralin are preferred. Ultra-dehydrated solvents with a water content of 0.001% by mass (10 ppm) or less are particularly preferred. Fluorine-based solvents such as "Vertrel®" from DuPont-Mitsui Fluorochemicals, "Zeorolla®" from Zeon Corporation, and "Novec®" from Sumitomo 3M Company, as well as nonaqueous organic solvents such as dichloromethane, diethyl ether, and anisole can also be used.

[0091] The thickness of the electrode mixture compact (in the case of an electrode having a current collector, the thickness of the electrode mixture compact per one side of the current collector; the same applies hereinafter) is usually 50 μm or more, but from the viewpoint of increasing the capacity of the battery, it is preferably 200 μm or more. In addition, the thickness of the electrode mixture compact is usually 3000 μm or less.

[0092] In the case of an electrode for an all-solid-state battery manufactured by forming an electrode mixture layer made of a molded body of an electrode mixture on a current collector using an electrode mixture-containing composition containing a solvent, the thickness of the electrode mixture layer (thickness per surface of the current collector) is preferably 50 to 1000 μm.

[0093] <All-solid-state battery> The all-solid-state battery of the present invention has a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, and at least one of the positive electrode and the negative electrode is the all-solid-state battery electrode of the present invention.

[0094] A cross-sectional view schematically illustrating an example of an all-solid-state battery of the present invention is shown in Fig. 5. The all-solid-state battery 10 shown in Fig. 5 has a positive electrode 20, a negative electrode 30, and a solid electrolyte layer 40 interposed between the positive electrode 20 and the negative electrode 30 enclosed in an exterior body formed by an exterior can 50, a sealing can 60, and a resin gasket 70 interposed between them.

[0095] The sealing can 60 is fitted into the opening of the outer can 50 via a gasket 70, and the open end of the outer can 50 is tightened inward, causing the gasket 70 to abut against the sealing can 60, thereby sealing the opening of the outer can 50 and creating an airtight structure inside the element.

[0096] The outer can and the sealing can can be made of stainless steel or other materials. Materials such as polypropylene and nylon can be used for the gasket. If heat resistance is required for the battery's intended use, heat-resistant resins with melting points exceeding 240°C, such as fluororesins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyphenylene ether (PEE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), and polyetheretherketone (PEEK), can also be used. If the battery is intended for use in applications requiring heat resistance, a glass hermetic seal can also be used for the sealing.

[0097] 6 and 7 are diagrams showing schematic diagrams of other examples of the all-solid-state battery of the present invention. Fig. 6 is a plan view of the all-solid-state battery, and Fig. 7 is a cross-sectional view taken along line II in Fig. 6.

[0098] 6 and 7, an electrode assembly 200 consisting of a positive electrode, a solid electrolyte layer, and a negative electrode is housed in a laminate film exterior casing 500 made of two metal laminate films, and the laminate film exterior casing 500 is sealed at its outer periphery by heat-sealing the upper and lower metal laminate films. In order to avoid cluttering the drawing, Fig. 7 does not distinguish between the layers constituting the laminate film exterior casing 500 and the positive electrode, negative electrode, and separator constituting the electrode assembly.

[0099] The positive electrode of the electrode body 200 is connected to a positive electrode external terminal 300 inside the battery 100, and although not shown, the negative electrode of the electrode body 200 is also connected to a negative electrode external terminal 400 inside the battery 100. One end of the positive electrode external terminal 300 and the negative electrode external terminal 400 is drawn out to the outside of the laminate film exterior body 500 so that they can be connected to external devices, etc.

[0100] In the case of an all-solid-state battery using the electrode for an all-solid-state battery of the present invention as the positive electrode, the negative electrode may be the electrode for an all-solid-state battery of the present invention, or may be a negative electrode other than the electrode for an all-solid-state battery of the present invention. Examples of negative electrodes other than the electrode for an all-solid-state battery of the present invention include an electrode (negative electrode) having the same configuration as the electrode for an all-solid-state battery of the present invention except that a negative electrode active material usable for the electrode material is used instead of the electrode material; a negative electrode consisting only of various alloys (e.g., lithium alloys such as lithium-aluminum alloys and lithium-indium alloys) or metallic lithium foil that function as a negative electrode active material, or a negative electrode in which the foil is laminated as an active material layer on a current collector;

[0101] In the case of an all-solid-state battery using the electrode for an all-solid-state battery of the present invention as the negative electrode, the positive electrode may be the electrode for an all-solid-state battery of the present invention, or may be a positive electrode other than the electrode for an all-solid-state battery of the present invention. Examples of positive electrodes other than the electrode for an all-solid-state battery of the present invention include electrodes (positive electrodes) having the same configuration as the electrode for an all-solid-state battery of the present invention, except that a positive electrode active material that can be used for the electrode material is used instead of the electrode material.

[0102] The solid electrolyte constituting the solid electrolyte layer of an all-solid-state battery can be one or more of the various sulfide-based solid electrolytes (argyrodite-type sulfide-based solid electrolytes and other sulfide-based solid electrolytes) exemplified above as usable in electrodes for all-solid-state batteries, hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes. However, to improve battery characteristics, it is preferable to include a sulfide-based solid electrolyte, and it is more preferable to include an argyrodite-type sulfide-based solid electrolyte.

[0103] The solid electrolyte layer may have a porous body such as a resin nonwoven fabric as a support.

[0104] The solid electrolyte layer can be formed by a method of compressing a solid electrolyte by pressure molding or the like; or a method of applying a solid electrolyte layer-forming composition prepared by dispersing a solid electrolyte in a solvent onto a substrate, a positive electrode, or a negative electrode, drying the composition, and, if necessary, performing pressure molding such as pressing.

[0105] It is desirable to select a solvent that is unlikely to deteriorate the solid electrolyte as the solvent used in the solid electrolyte layer-forming composition, and it is preferable to use the same solvents as those exemplified above as the solvents for the electrode mixture-containing composition containing the solid electrolyte.

[0106] The thickness of the solid electrolyte layer is preferably 100 to 300 μm.

[0107] The positive electrode and the negative electrode can be used in a battery in the form of a laminated electrode body in which the positive electrode and the negative electrode are laminated with a solid electrolyte layer interposed therebetween, or in the form of a wound electrode body in which this laminated electrode body is wound.

[0108] When forming the electrode body, it is preferable to pressure-mold the positive electrode, negative electrode, and solid electrolyte layer in a stacked state, from the viewpoint of increasing the mechanical strength of the electrode body.

[0109] The all-solid-state battery of the present invention can be used in the same applications as conventionally known all-solid-state batteries (all-solid-state primary batteries or all-solid-state secondary batteries). Furthermore, the electrode for the all-solid-state battery of the present invention can constitute the all-solid-state battery of the present invention. [Example]

[0110] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0111] Example 1 <Preparation of positive electrode material> LiCo with an average particle size of 5 μm and a layer of LiNbO3 on the surface 0.98 Al 0.01 Mg 0.01 A cathode material was prepared by granulating primary particles of O2 (positive electrode active material) and an argyrodite-type sulfide-based solid electrolyte (Li6PS5Cl) with an average particle size of 0.6 μm. The component composition of the cathode material was 100 parts by mass of the positive electrode active material and 15.8 parts by mass of the argyrodite-type sulfide-based solid electrolyte. In addition, LiCo 0.98 Al 0.01 Mg 0.01 The amount of LiNbO3 layer on the surface of O2 is 0.98 Al 0.01 Mg 0.01 The ratio was 1 part by mass to 100 parts by mass of O2. Furthermore, when granulating the positive electrode active material and the argyrodite-type sulfide-based solid electrolyte, the mixing conditions in the mixer were adjusted so that van der Waals forces and electrostatic forces were generated due to the collision and shearing action between the materials.

[0112] <Preparation of positive electrode> The positive electrode material, the same argyrodite-type sulfide-based solid electrolyte as used in the positive electrode material, and acetylene black (conductive additive) were mixed in a mass ratio of 75.3:20.7:4.0 and thoroughly kneaded to prepare a positive electrode mixture. Next, 75 mg of the positive electrode mixture was placed in a powder molding die with a diameter of 7.5 mm and pressure-molded using a press to produce a cylindrical positive electrode mixture compact. The mass ratio of the positive electrode mixture compact was 65.0:31.0:4.0 (positive electrode active material: argyrodite-type sulfide-based solid electrolyte (total amount of that contained in the positive electrode material and that added separately from the positive electrode material; the same applies hereinafter to the component composition of the positive electrode mixture compact):conductive additive, with an Ms / Mc ratio of 7.8.

[0113] <Formation of solid electrolyte layer> Next, 9.6 mg of the same sulfide-based solid electrolyte as that used for producing the positive electrode was placed on the positive electrode mixture compact in the powder molding die, and pressure molding was performed using a press to form a solid electrolyte layer on the positive electrode mixture compact, thereby obtaining a laminate of the positive electrode and the solid electrolyte layer.

[0114] <Fabrication of laminated electrode body> Lithium titanate (Li4Ti5O 12 A negative electrode mixture was prepared by mixing the same argyrodite-type sulfide-based solid electrolyte as used in the positive electrode material (negative electrode active material, average particle diameter: 1.3 μm) with graphene (conductive additive) in a mass ratio of 6:5:1 and thoroughly kneading the mixture. Next, 100 mg of the negative electrode mixture was placed on top of the solid electrolyte layer in the powder molding die and pressure-molded using a press. A negative electrode was formed on the solid electrolyte layer by using a negative electrode mixture compact, thereby producing a laminated electrode body in which the positive electrode, solid electrolyte layer, and negative electrode were stacked. The thicknesses of the positive electrode (positive electrode mixture compact), solid electrolyte layer, and negative electrode (negative electrode mixture compact) in the laminated electrode body were 600 μm, 100 μm, and 900 μm, respectively.

[0115] A plurality of laminated electrode bodies were produced, and the cross section of the positive electrode mixture compact of some of them was observed by SEM, and it was confirmed by the above-mentioned method that the electrode material consisting of granules was present in the positive electrode mixture compact, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material was in a granular form.

[0116] <Assembly of all-solid-state batteries> A laminate of the positive electrode, solid electrolyte layer, and negative electrode was placed on the inner surface of a stainless steel sealed can fitted with a polypropylene ring gasket, and then a stainless steel outer can was placed over it.The open end of the outer can was then crimped inward to seal it, producing an all-solid-state battery with a diameter of approximately 9 mm.

[0117] Example 2 A positive electrode material was prepared in the same manner as in Example 1, except that the composition of the argyrodite-type sulfide-based solid electrolyte was changed to 16.9 parts by mass per 100 parts by mass of the positive electrode active material. Then, using this positive electrode material, a positive electrode made of a positive electrode mixture compact was prepared in the same manner as in Example 1, except that the component composition was changed to a mass ratio of positive electrode material: argyrodite-type sulfide-based solid electrolyte: acetylene black = 76.0:22.0:2.0. The component composition of this positive electrode mixture compact was a mass ratio of positive electrode active material: argyrodite-type sulfide-based solid electrolyte: conductive additive = 65.0:33.0:2.0, with an Ms / Mc of 16.5.

[0118] A laminated electrode body was produced in the same manner as in Example 1 except that this positive electrode was used, and an all-solid-state battery was produced in the same manner as in Example 1 except that this laminated electrode body was used.

[0119] A plurality of laminated electrode bodies were produced, and the cross section of the positive electrode mixture compact of some of them was observed by SEM, and it was confirmed by the above-mentioned method that the electrode material consisting of granules was present in the positive electrode mixture compact, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material was in a granular form.

[0120] Example 3 A positive electrode material was prepared in the same manner as in Example 1, except that the composition of the argyrodite-type sulfide-based solid electrolyte was changed to 15.3 parts by mass per 100 parts by mass of the positive electrode active material. Then, using this positive electrode material, a positive electrode made of a positive electrode mixture compact was prepared in the same manner as in Example 1, except that the component composition was changed to a mass ratio of positive electrode material: argyrodite-type sulfide-based solid electrolyte: acetylene black = 75.0:20.0:5.0. The component composition of this positive electrode mixture compact was a mass ratio of positive electrode active material: argyrodite-type sulfide-based solid electrolyte: conductive additive = 65.0:30.0:5.0, with an Ms / Mc of 6.0.

[0121] A laminated electrode body was produced in the same manner as in Example 1 except that this positive electrode was used, and an all-solid-state battery was produced in the same manner as in Example 1 except that this laminated electrode body was used.

[0122] A plurality of laminated electrode bodies were produced, and the cross section of the positive electrode mixture compact of some of them was observed by SEM, and it was confirmed by the above-mentioned method that the electrode material consisting of granules was present in the positive electrode mixture compact, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material was in a granular form.

[0123] Example 4 A positive electrode material was prepared in the same manner as in Example 1, except that the composition of the argyrodite-type sulfide-based solid electrolyte was changed to 9.9 parts by mass per 100 parts by mass of the positive electrode active material. Then, using this positive electrode material, a positive electrode made of a positive electrode mixture compact was prepared in the same manner as in Example 1, except that the component composition was changed to a mass ratio of positive electrode material: argyrodite-type sulfide-based solid electrolyte: acetylene black = 82.4:14.8:2.8. The component composition of this positive electrode mixture compact was a mass ratio of positive electrode active material: argyrodite-type sulfide-based solid electrolyte: conductive additive = 75.0:22.2:2.8, with an Ms / Mc of 7.9.

[0124] A laminated electrode body was produced in the same manner as in Example 1 except that this positive electrode was used, and an all-solid-state battery was produced in the same manner as in Example 1 except that this laminated electrode body was used.

[0125] A plurality of laminated electrode bodies were produced, and the cross section of the positive electrode mixture compact of some of them was observed by SEM, and it was confirmed by the above-mentioned method that the electrode material consisting of granules was present in the positive electrode mixture compact, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material was in a granular form.

[0126] Example 5 A positive electrode material was prepared in the same manner as in Example 1, except that the composition of the argyrodite-type sulfide-based solid electrolyte was changed to 47.7 parts by mass per 100 parts by mass of the positive electrode active material. Then, using this positive electrode material, a positive electrode made of a positive electrode mixture compact was prepared in the same manner as in Example 1, except that the component composition was changed to a mass ratio of positive electrode material:acetylene black of 96.0:4.0. The component composition of this positive electrode mixture compact was a mass ratio of positive electrode active material:argyrodite-type sulfide-based solid electrolyte:conductive additive of 65.0:31.0:4.0, with an Ms / Mc of 7.8.

[0127] A laminated electrode body was produced in the same manner as in Example 1 except that this positive electrode was used, and an all-solid-state battery was produced in the same manner as in Example 1 except that this laminated electrode body was used.

[0128] A plurality of laminated electrode bodies were produced, and the cross section of the positive electrode mixture compact of some of them was observed by SEM, and it was confirmed by the above-mentioned method that the electrode material consisting of granules was present in the positive electrode mixture compact, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material was in a granular form.

[0129] Example 6 A positive electrode material was prepared in the same manner as in Example 1, except that the composition of the argyrodite-type sulfide-based solid electrolyte was changed to 8 parts by mass per 100 parts by mass of the positive electrode active material. Then, using this positive electrode material, a positive electrode made of a positive electrode mixture compact was prepared in the same manner as in Example 1, except that the component composition was changed to a mass ratio of positive electrode material: argyrodite-type sulfide-based solid electrolyte: acetylene black = 70.2:25.8:4.0. The component composition of this positive electrode mixture compact was a mass ratio of positive electrode active material: argyrodite-type sulfide-based solid electrolyte: conductive additive = 65.0:31.0:4.0, with an Ms / Mc of 7.8.

[0130] A laminated electrode body was produced in the same manner as in Example 1 except that this positive electrode was used, and an all-solid-state battery was produced in the same manner as in Example 1 except that this laminated electrode body was used.

[0131] A plurality of laminated electrode bodies were produced, and the cross section of the positive electrode mixture compact of some of them was observed by SEM, and it was confirmed by the above-mentioned method that the electrode material consisting of granules was present in the positive electrode mixture compact, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material was in a granular form.

[0132] Comparative Example 1 The same LiCo as used in Example 1, with a layer of LiNbO3 on the surface. 0.98 Al 0.01 Mg 0.01 A positive electrode mixture was prepared by mixing primary particles of O2, the same argyrodite-type sulfide-based solid electrolyte as used in Example 1, and acetylene black (conductive additive) in a mass ratio of 65.0:31.0:4.0. An all-solid-state battery was fabricated in the same manner as in Example 1, except for using this positive electrode mixture.

[0133] Comparative Example 2 A positive electrode material was prepared in the same manner as in Example 1, except that the composition of the argyrodite-type sulfide-based solid electrolyte was changed to 17.1 parts by mass per 100 parts by mass of the positive electrode active material. Then, using this positive electrode material, a positive electrode made of a positive electrode mixture compact was prepared in the same manner as in Example 1, except that the component composition was changed to a mass ratio of positive electrode material: argyrodite-type sulfide-based solid electrolyte: acetylene black = 76.1:22.2:1.7. The component composition of this positive electrode mixture compact was a mass ratio of positive electrode active material: argyrodite-type sulfide-based solid electrolyte: conductive additive = 65.0:33.3:1.7, with an Ms / Mc of 19.5.

[0134] A laminated electrode body was produced in the same manner as in Example 1 except that this positive electrode was used, and an all-solid-state battery was produced in the same manner as in Example 1 except that this laminated electrode body was used.

[0135] A plurality of laminated electrode bodies were produced, and the cross section of the positive electrode mixture compact of some of them was observed by SEM, and it was confirmed by the above-mentioned method that the electrode material consisting of granules was present in the positive electrode mixture compact, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material was in a granular form.

[0136] Comparative Example 3 A positive electrode material was prepared in the same manner as in Example 1, except that the composition of the argyrodite-type sulfide-based solid electrolyte was changed to 14.9 parts by mass per 100 parts by mass of the positive electrode active material. Then, using this positive electrode material, a positive electrode made of a positive electrode mixture compact was prepared in the same manner as in Example 1, except that the component composition was changed to a mass ratio of positive electrode material: argyrodite-type sulfide-based solid electrolyte: acetylene black = 74.7:29.0:6.0. The component composition of this positive electrode mixture compact was a mass ratio of positive electrode active material: argyrodite-type sulfide-based solid electrolyte: conductive additive = 65.0:29.0:6.0, with an Ms / Mc ratio of 4.8.

[0137] A laminated electrode body was produced in the same manner as in Example 1 except that this positive electrode was used, and an all-solid-state battery was produced in the same manner as in Example 1 except that this laminated electrode body was used.

[0138] A plurality of laminated electrode bodies were produced, and the cross section of the positive electrode mixture compact of some of them was observed by SEM, and it was confirmed by the above-mentioned method that the electrode material consisting of granules was present in the positive electrode mixture compact, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material was in a granular form.

[0139] Comparative Example 4 An electrode material for a positive electrode was prepared in the same manner as in Example 2, except that the positive electrode active material and the argyrodite-type sulfide-based solid electrolyte were mixed under conditions in which a stress was applied to the extent that a mechanochemical reaction occurred. A laminated electrode body was prepared in the same manner as in Example 1, except that this positive electrode material was used. An all-solid-state battery was prepared in the same manner as in Example 1, except that this laminated electrode body was used.

[0140] A number of laminated electrode bodies were produced, and the cross sections of the positive electrode mixture compacts of some of them were observed using an SEM. It was confirmed that the argyrodite-type sulfide-based solid electrolyte in the electrode material was unable to maintain its granular shape and had become a continuous phase of the solid electrolyte.

[0141] The load characteristics of the all-solid-state batteries of the Examples and Comparative Examples were evaluated by the following method.

[0142] Each of the all-solid-state batteries of the Examples and Comparative Examples was charged at a constant current of 0.05 C until the voltage reached 2.6 V, then charged at a constant voltage of 0.01 C until the current reached 0.01 C, and then discharged at a current of 0.05 C until the voltage reached 1.5 V, and the initial capacity was measured.

[0143] After the initial characteristic evaluation, each battery was charged and discharged under the same conditions as when the initial capacity was measured, except that the discharge current was changed to 1 C. The 1 C discharge capacity of each battery was then divided by the initial capacity to determine the capacity retention rate, which was expressed as a percentage, and the load characteristics (initial load characteristics) of each battery were evaluated.

[0144] After measuring the initial capacity, each battery was stored in a thermostatic chamber at 85°C for two days, then removed and returned to room temperature. The 1C discharge capacity was measured under the same conditions as when evaluating the initial load characteristics. The 1C discharge capacity of each battery after storage was divided by the initial capacity to determine the capacity retention rate, and the post-storage load characteristics of each battery were evaluated.

[0145] The load characteristics after storage correspond to an accelerated test that serves as a guide to the quality of the load characteristics of an all-solid-state battery after long-term storage, and also serves as a guide to the load characteristics of an all-solid-state battery after being subjected to a thermal history of about 85°C.

[0146] The evaluation results are shown in Table 1 together with the Ms / Mc values ​​of the positive electrodes (positive electrode mixture molded bodies) of the all-solid-state batteries. In Table 2, the capacity retention rates during the load characteristic evaluation are shown as relative values ​​when the value of the initial load characteristic of the battery of Example 1 is set to 100.

[0147] [Table 1]

[0148] As shown in Table 1, the all-solid-state batteries of Examples 1 to 6, which contained an electrode material made of a granule of an active material and an argyrodite-type sulfide-based solid electrolyte, in which the argyrodite-type sulfide-based solid electrolyte was in granular form, and which used a positive electrode having a positive electrode mixture molded product with an appropriate Ms / Mc value, had good initial load characteristics and good load characteristics after storage, and were able to exhibit excellent load characteristics even after long-term storage or after being subjected to a thermal history of about 85°C.

[0149] In contrast, the battery of Comparative Example 1, which did not use an electrode material consisting of granules of a positive electrode active material and an argyrodite-type sulfide-based solid electrolyte, the battery of Comparative Example 3, which used a positive electrode having a positive electrode mixture molded product with an excessively small Ms / Mc value, and the battery of Comparative Example 4, which used a positive electrode having a positive electrode mixture molded product containing an electrode material in which the argyrodite-type sulfide-based solid electrolyte had lost its granular shape and become a continuous phase, had poor load characteristics not only after storage but also at the initial stage. Furthermore, the battery of Comparative Example 2, which used a positive electrode having a positive electrode mixture molded product with an excessively large Ms / Mc value, also had poor load characteristics after storage. [Explanation of symbols]

[0150] 1 Electrode material 1a, 3 Primary particles of active material 1b, 2 Argyrodite-type solid electrolyte 10, 100 solid-state battery 20 positive electrode 30 negative electrode 40 Solid electrolyte layer 50 outer cans 60 Sealed cans 70 Gasket 200 Electrode body 300 Positive external terminal 400 Negative external terminal 500 Laminated film exterior

Claims

1. A method for producing an electrode for an all-solid-state battery having a molded body of an electrode mixture containing an active material, a solid electrolyte, and a conductive additive, comprising: the compact of the electrode mixture contains an electrode material made of granules containing at least a part of the active material and at least a part of the solid electrolyte, and a conductive assistant different from the electrode material, the electrode material contains a granular argyrodite-type sulfide-based solid electrolyte as the solid electrolyte, a ratio Ms / Mc of the total content of the solid electrolyte: Ms (mass%) to the content of the conductive assistant: Mc (mass%) in the total amount of the molded body of the electrode mixture is 6 to 17; a step of granulating the active material and the solid electrolyte to form an electrode material comprising the granules; and forming a compact of the electrode mixture using an electrode mixture containing at least the electrode material and a conductive additive.

2. 2. The method for producing an electrode for an all-solid-state battery according to claim 1, wherein the granules are formed by granulating the active material and the solid electrolyte prior to forming the electrode mixture into a compact.

3. 3. The method for producing an electrode for an all-solid-state battery according to claim 1 or 2, wherein the granules are an aggregate of 10 or more primary particles of the active material, a granular solid electrolyte is present between the primary particles, and gaps of 0.5 to 5 μm are present between the primary particles.

4. 4. The method for producing an electrode for an all-solid-state battery according to any one of claims 1 to 3, wherein a content of the argyrodite-type sulfide-based solid electrolyte contained in the electrode material is 2.5 to 60 parts by mass per 100 parts by mass of the active material contained in the electrode material.

5. The method for producing an electrode for an all-solid-state battery according to any one of claims 1 to 4, wherein the electrode for an all-solid-state battery is used as a positive electrode of the all-solid-state battery.

6. The method for producing an electrode for an all-solid-state battery according to claim 5 , wherein a reaction suppression layer that suppresses a reaction between the active material and the solid electrolyte is formed on a surface of the active material.

7. A method for producing an all-solid-state battery having a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, comprising: forming at least one of the positive electrode and the negative electrode by the method for producing an electrode for an all-solid-state battery according to any one of claims 1 to 6; and assembling an all-solid-state battery using the electrode obtained by the above step.

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