Electrodes for all-solid-state batteries and all-solid-state batteries

Abstract

The present invention provides an all-solid-state battery with excellent load characteristics and electrodes capable of forming the all-solid-state battery. [Solution] The electrode for an all-solid-state battery of the present invention comprises a molded body of an electrode mixture, the electrode mixture comprises an electrode material composite, the electrode material composite consists of a granule comprising an active material and a solid electrolyte, the solid electrolyte comprises a granular argyrodite-type sulfide-based solid electrolyte, and the granule has the following characteristics (1) and (2) when observed in cross-section of the molded body of the electrode mixture. (1) The primary particles of the active material are aggregated in groups of 10 or more, and there are gaps between the primary particles of the active material that are 0.5 μm or more and 5 μm or less. (2) The active material has a solid electrolyte containing the granular argyrodite-type sulfide solid electrolyte between the primary particles.

Description

[Technical Field]

[0001] This invention relates to an all-solid-state battery with excellent load characteristics and electrodes capable of constituting the all-solid-state battery. [Background technology]

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

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

[0004] Furthermore, with the continued development of devices utilizing lithium-ion batteries, there is a growing demand for even longer lifespans, higher capacity, and higher energy density lithium-ion batteries, as well as a greater demand for reliability in these batteries.

[0005] However, because the organic electrolyte used in lithium-ion batteries contains organic solvents, which are flammable substances, there is a possibility that the organic electrolyte may overheat if an abnormal situation such as a short circuit occurs in the battery. Furthermore, with the recent trend towards higher energy density in lithium-ion batteries and an increase in the amount of organic solvents in the organic electrolyte, there is an even greater demand for the reliability of lithium-ion batteries.

[0006] In light of the above circumstances, all-solid-state lithium batteries that do not use organic solvents (all-solid-state batteries) are attracting attention. All-solid-state batteries use a molded solid electrolyte that does not use organic solvents instead of conventional organic solvent-based electrolytes, and they offer high safety as there is no risk of abnormal heat generation from the solid electrolyte.

[0007] Furthermore, solid-state batteries are expected to contribute to the development of society while also providing peace of mind and safety, as they possess not only high safety but also high reliability, high environmental resistance, and a long lifespan, making them maintenance-free batteries. By providing solid-state batteries to society, it is possible to contribute to achieving three of the 17 Sustainable Development Goals (SDGs) established by the United Nations: 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 and human settlements inclusive, safe, resilient and sustainable).

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

[0009] Furthermore, Patent Document 1 describes a process for manufacturing the material for all-solid-state batteries by mixing a sulfide-based inorganic solid electrolyte powder with an electrode active material powder to form a mixed powder, and then press-molding this mixture to form a molded body. It states that through this manufacturing method, in the material for all-solid-state batteries, electron conduction paths are formed when multiple electrode active material particles are adjacent to each other, sulfide-based inorganic solid electrolyte is placed between the electrode active material particles, and the sulfide-based inorganic solid electrolyte particles are deformed and bonded together by press-molding, causing their particle shape to disappear and forming a continuous phase, thereby forming ion conduction paths. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2014-192061 (Claims, paragraphs

[0015] ,

[0016] ) [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] Incidentally, the application fields of all-solid-state batteries are currently expanding rapidly. For example, they are being considered for applications that require high current discharge values, and therefore, it is necessary to improve their load characteristics to meet these requirements.

[0012] The present invention has been made in view of the above circumstances, and aims to provide an all-solid-state battery with excellent load characteristics and an electrode capable of constituting the all-solid-state battery. [Means for solving the problem]

[0013] The electrode for an all-solid-state battery of the present invention comprises a molded body of an electrode mixture, the electrode mixture comprises an electrode material composite, the electrode material composite consists of granules comprising an active material and a solid electrolyte, and the solid electrolyte comprises a granular argyrodite-type sulfide-based solid electrolyte.

[0014] Furthermore, the all-solid-state battery of the present invention includes a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, wherein at least one of the positive electrode and the negative electrode is an electrode for the all-solid-state battery of the present invention.

[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 with excellent load characteristics and electrodes capable of constituting the all-solid-state battery. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a schematic plan view showing an example of a part of the molded body of the electrode mixture for the all-solid-state battery electrode of the present invention. [Figure 2]Figure 2 is a magnified view of the area enclosed by the dotted line in Figure 1. [Figure 3] Figure 3 is a schematic plan view showing another example of a part of the molded body of the electrode mixture for the all-solid-state battery electrode of the present invention. [Figure 4] Figure 4 is a schematic plan view showing another example of a part of the molded body of the electrode mixture for the all-solid-state battery electrode of the present invention. [Figure 5] Figure 5 is a schematic cross-sectional view showing an example of the all-solid-state battery of the present invention. [Figure 6] Figure 6 is a schematic plan view illustrating another example of the all-solid-state battery of the present invention. [Figure 7] Figure 7 is a cross-sectional view taken along line II in Figure 6. [Modes for carrying out the invention]

[0018] <Electrodes for all-solid-state batteries> The electrode for all-solid-state batteries of the present invention is used as the positive or negative electrode of an all-solid-state battery and comprises a molded body of an electrode mixture containing an electrode material composite. The electrode material composite consists of a granule containing an active material and a solid electrolyte, and the solid electrolyte contains a granular argyrodite-type sulfide-based solid electrolyte.

[0019] When an electrode mixture for an all-solid-state battery is manufactured by simply mixing an active material and a solid electrolyte to form a powder, and then press-molding it, the surface irregularities of the active material particles are generally relatively large. As a result, the solid electrolyte particles cannot properly conform to the irregular shape of the active material particles, a relatively large gap is created between the active material particles and the solid electrolyte particles. This limits the improvement of ion conductivity (lithium ion conductivity) within the molded electrode mixture. These factors have hindered the improvement of the load characteristics of all-solid-state batteries.

[0020] Therefore, in the electrode for all-solid-state batteries of the present invention, an electrode material composite, formed by pre-granulating an active material and an argyrodite-type sulfide-based solid electrolyte, is incorporated into the molded body of the electrode mixture. In this case, since the active material and the argyrodite-type sulfide-based solid electrolyte constitute the granules, the contact between the active material particles and the argyrodite-type sulfide-based solid electrolyte particles in the electrode material composite is better than in the case of a mixture in which only the active material particles and solid electrolyte particles are mixed. As a result, even when a solid electrolyte different from the solid electrolyte used in the electrode material composite is mixed together with the electrode material composite to form the molded body of the electrode mixture, the ionic conductivity within the molded body of the electrode mixture is good due to the action of the solid electrolyte in the electrode material composite. Therefore, in an all-solid-state battery (the all-solid-state battery of the present invention) using the electrode for all-solid-state batteries of the present invention having this molded body, it is possible to ensure excellent load characteristics.

[0021] Furthermore, the argyrodite-type sulfide-based solid electrolyte contained in the electrode material composite included in the electrode for the all-solid-state battery of the present invention is granular.

[0022] In the all-solid-state battery material described in Patent Document 1, as mentioned above, the sulfide-based inorganic solid electrolyte interposed between the particles of the electrode active material is a continuous phase in which the particle 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 when improving the load characteristics of the all-solid-state battery by increasing the ion conductivity inside the electrode, it is preferable that the solid electrolyte present between the active materials forms a continuous phase rather than granular (particle shape).

[0023] However, contrary to these expectations, our investigations have revealed that in electrode material composites comprising a granule containing an active material and an argyrodite-type sulfide-based solid electrolyte for all-solid-state batteries, the presence of the solid electrolyte in granular form is advantageous for improving the load characteristics of the all-solid-state battery. The reason for this is not entirely clear, but we speculate it may be as follows.

[0024] Argyrodite-type sulfide-based solid electrolytes are usually supplied in granular (particulate) form. Such granular argyrodite-type sulfide-based solid electrolytes are crystalline and have higher ionic conductivity than when they are amorphous. In electrodes for all-solid-state batteries, if the sulfide-based solid electrolyte present between the active materials becomes a continuous phase where the particles bind together and lose their original shape (granular), it is thought to be amorphous or have a very low degree of crystallinity, and it is presumed that the solid electrolyte will not be able to fully exhibit its inherent ionic conductivity.

[0025] In contrast, if the argyrodite-type sulfide-based solid electrolyte in the electrode material composite contained in the electrode for all-solid-state batteries can maintain its original granular state, it is thought that its degree of crystallinity is also maintained at a relatively high level. As a result, the ion conductivity of the granulated electrode material composite is increased, and it is presumed that high ion conductivity can be ensured in the electrode for all-solid-state batteries of the present invention, and that by using it, an all-solid-state battery with excellent load characteristics can be formed.

[0026] In the electrode for an all-solid-state battery of the present invention, the presence of an electrode material composite consisting of a granule containing an active material and an argyrodite-type sulfide-based solid electrolyte is confirmed by observing a cross-section of the molded electrode material using a scanning electron microscope (SEM) at 10,000x magnification, where it is observed that 10 or more primary particles of the active material are clustered together, and there are areas where the gaps between the primary particles of the active material are 5 μm or less, and further, in an image observed at 30,000x magnification, granular solid electrolyte (argyrodite-type sulfide-based solid electrolyte and other solid electrolytes which may be contained in the electrode material composite) 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 usually 0.5 μm or more, depending on the particle size of the solid electrolyte.

[0027] Furthermore, during the aforementioned observation, if the solid electrolyte (an argyrodite-type sulfide-based solid electrolyte, and other solid electrolytes that may be contained in the electrode material composite) present between the primary particles of the active material has a granular outline, then that solid electrolyte is considered granular. For example, if two solid electrolyte particles are in close contact and the interface between each particle is ambiguous, and assuming the shape of those particles is a circle in a plan view, then if more than 60% of the circumference can be observed, then it is considered to have a "granular outline."

[0028] Figures 1 and 2 show schematic diagrams illustrating an example of a part of the molded electrode mixture for the electrode of the all-solid-state battery of the present invention. Figure 1 is a plan view showing a part of the molded electrode mixture, and Figure 2 is an enlarged view of the area enclosed by the dotted line in Figure 1.

[0029] The area enclosed by the ellipse in Figure 1 is the electrode material composite 1, which consists of a granule of active material and argyrodite-type sulfide-based solid electrolyte (hereinafter also simply referred to as argyrodite-type solid electrolyte). The electrode material composite 1, together with solid electrolyte 2 added separately from the argyrodite-type solid electrolyte that constitutes the electrode material composite 1, and active material (primary particles of the active material) 3 added separately from the active material that constitutes the electrode material composite 1, forms a molded body of the electrode mixture. In the electrode material composite 1, more than 10 primary particles 1a of the active material are aggregated. However, the ellipse shown in Figure 1 includes some solid electrolyte 2 that is present around the electrode material composite 1 and does not constitute the electrode material composite 1, and some of the primary particles 1a of the active material that constitute the electrode material composite 1 protrude from the ellipse shown in Figure 1 (the same is true in Figures 3 and 4 described later). Also, the argyrodite-type solid electrolyte that constitutes the electrode material composite 1 is not shown in Figure 1 (the same is true in Figures 3 and 4 described later).

[0030] As shown in Figure 2, granular argyrodite-type sulfide-based solid electrolyte 1b is present in the gaps between the primary particles 1a of the active material in the electrode material composite 1.

[0031] Figures 3 and 4 schematically illustrate other examples of molded electrode composites for electrodes in the all-solid-state battery of the present invention. The molded electrode composite shown in Figure 3 is formed of an electrode material composite 1 and a solid electrolyte 2 (different from the argyrodite-type solid electrolyte that constitutes the electrode material composite 1). That is, all of the active material contained in the molded electrode composite shown in Figure 3 constitutes the electrode material composite 1. On the other hand, the molded electrode composite shown in Figure 4 is formed of an electrode material composite 1, a solid electrolyte 2 (added separately from the argyrodite-type solid electrolyte that constitutes the electrode material composite 1), and an active material (primary particles of the active material) 3 that is different from that which constitutes the electrode material composite 1.

[0032] Examples of electrodes for all-solid-state batteries include molded bodies (such as pellets) formed by molding an electrode mixture, and structures in which a layer (composite layer) made of molded electrode mixtures is formed on a current collector.

[0033] When the electrode for an all-solid-state battery is the positive electrode and is used in an all-solid-state primary battery, the active material of the electrode material composite contained in the molded body of the electrode mixture can be the same as the positive electrode active material conventionally known for use in non-aqueous electrolyte primary batteries. Specifically, for example, manganese dioxide; lithium-containing manganese oxide [for example, LiMn3O6, or a composite oxide having the same crystal structure as manganese dioxide (β-type, γ-type, or a structure in which β-type and γ-type are mixed, etc.) and having a Li content of 3.5% by mass or less, preferably 2% by mass or less, more preferably 1.5% by mass or less, particularly preferably 1% by mass or less], Li a Ti 5 / 3 Examples include 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; and nickel oxides such as NiO2.

[0034] In addition, when the electrode for 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 composite to be incorporated into the molded body of the electrode binder can be the same as the positive electrode active material conventionally used in non-aqueous electrolyte secondary batteries, that is, 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 ≦ 0.2, 0 ≦ v ≦ 0.1), layered compound represented by Li 1-x Co 1-r M r O2 (where 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, 0 ≦ x ≦ 1, 0 ≦ r ≦ 0.5), lithium cobalt composite oxide represented by Li 1-x Ni 1-r M r O2 (where 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, 0 ≦ x ≦ 1, 0 ≦ r ≦ 0.5), lithium nickel composite oxide represented by Li 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 is an olivine-type composite oxide. 2-x M 1-r N r Examples include pyrophosphate compounds represented by P2O7 (where 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, with 0≦x≦2 and 0≦r≦0.5). Only one of these may be used, or two or more may be used in combination.

[0035] In the case of a positive electrode for an all-solid-state battery used in an all-solid-state secondary battery, among the positive electrode active materials exemplified above, lithium cobalt composite oxide (A) represented by the following general formula (1) is preferably used.

[0036] Lisco 1-a-b-c Al a M 1 b M 2 c O2(1)

[0037] In the general formula (1), M 1 M is at least one element selected from the group consisting of Mg, Ni, and Na. 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 <a<0.1、0<b<0.1、a+b<0.1、0≦cである。

[0038] When lithium cobalt composite oxide (A) is used as a positive electrode active material for non-aqueous electrolyte secondary batteries using organic electrolytes, the contained Al and M 1This material increases the internal resistance of a battery through the action of additive elements such as lithium cobalt. However, in the case of non-aqueous electrolyte secondary batteries with an organic electrolyte, the electrolyte that transfers ions between the positive and negative electrodes is liquid (electrolyte), and since the original internal resistance is small, the increase in internal resistance due to lithium cobalt composite oxide (A) has almost no effect on the battery characteristics. On the other hand, in all-solid-state secondary batteries in which ion transfer between the positive and negative electrodes is performed by a solid electrolyte, it is expected that an increase in internal resistance due to the action of the positive electrode active material may cause a decrease in battery characteristics such as load characteristics.

[0039] However, contrary to these expectations, when lithium cobalt composite oxide (A) is used as the positive electrode active material for an all-solid-state secondary battery, it is possible to lower the internal resistance compared to, for example, when LiCoO2 is used as the positive electrode active material, thereby improving the load characteristics of the all-solid-state secondary battery.

[0040] When a battery using LiCoO2 as the positive electrode active material is charged, Co expands due to a change in valence. In batteries using organic electrolytes, even if a volume change in the positive electrode active material occurs due to this, the contact between the electrolyte and the positive electrode active material is not impaired because the electrolyte that transfers ions is liquid. On the other hand, in all-solid-state secondary batteries, the electrolyte that transfers ions within the positive electrode is solid (solid electrolyte), so when the positive electrode active material changes volume due to charging and discharging the battery, a gap is created between the positive electrode active material and the solid electrolyte, increasing the internal resistance of the positive electrode and, consequently, the internal resistance of the battery.

[0041] However, in the case of lithium cobalt composite oxide (A) represented by the general formula (1) above, even when charged, Al and element M 1 Because the expansion of Co is suppressed by this action, the total expansion amount (volume change) of the positive electrode active material is reduced. Therefore, by using a positive electrode for an all-solid-state battery in which lithium cobalt composite oxide (A) is the positive electrode active material, good contact between the lithium cobalt composite oxide (A) and the solid electrolyte 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 superior load characteristics.

[0042] In lithium cobalt composite oxide (A), Al is the element that is substituted at the Co site, M 1 These are elements that are substituted at the Li site, and both have the effect of reducing the amount of expansion of Co (the amount of expansion of lithium cobalt composite oxide (A)) during charging.

[0043] Lithium cobalt composite oxide (A) is composed of element M 1 The element should contain at least one of Mg, Ni, and Na, but Mg is preferred because its ionic radius is equivalent to that of the substituted Li, and it does not undergo a change in valence during charging and discharging.

[0044] In lithium cobalt composite oxide (A), from the viewpoint of minimizing the amount of expansion during charging, the amount of Al a is greater than 0 and less than 0.1, and element M 1 The amount b is greater than 0 and less than 0.1, and a+b is less than 0.1. Preferably, the amount a of Al is 0.005 or more, and element M 1 The amount b of is preferably 0.005 or more. Furthermore, the amount a of Al is preferably 0.08 or less, and the element M 1 The amount b is preferably 0.08 or less.

[0045] Lithium cobalt composite oxide (A) is composed of element M 2 It may contain or may not contain (the amount c may be 0), but element M 2 If the amount of is too high, for example, the amount of Co will decrease, and the capacity of lithium cobalt composite oxide (A) may decrease. Therefore, element M 2 The amount c is preferably 0.05 or less.

[0046] When the electrode for an all-solid-state battery is the negative electrode and is used in an all-solid-state primary battery, examples of the active material of the electrode material composite to be contained in the molded body of the electrode mixture include metallic lithium and lithium alloys (such as lithium-aluminum alloy and lithium-indium alloy).

[0047] Furthermore, when the electrode for an all-solid-state battery is the negative electrode and is used in an all-solid-state secondary battery, there are no particular restrictions on the active material of the electrode material composite to be contained in the molded body of the electrode mixture, as long as it is an active material that can intercept and release lithium ions and is conventionally known to be used in lithium secondary batteries. For example, as the negative electrode active material, one or more carbon-based materials capable of intercepting and releasing lithium, such as graphite, pyrolytic carbons, cokes, glassy carbons, calcined organic polymer compounds, mesocarbon microbeads (MCMB), and carbon fibers, can be used. Oxides may also be used as the negative electrode active material, for example, Li x Nb y TiM 6 a O [5y+4 / 2]+ δ(where M 6 This is at least one 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 ramsdelite structure represented by Li2Ti3O7, Li4Ti5O 12 Examples include spinel-type lithium titanium composite oxides represented by [formula], and one or more of these can be used. Elements such as Si, Sn, Ge, Bi, Sb, and In, as well as their compounds and alloys; nitrides or oxides containing transition metals such as Co, Ni, Mn, Fe, Cr, Ti, and W, which can be charged and discharged at low voltages close to lithium metal; or metallic lithium or lithium alloys (such as lithium-aluminum alloys and lithium-indium alloys) can also be used as negative electrode active materials.

[0048] The active material of the electrode material composite may have a reaction-suppressing 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 the positive electrode, it is preferable that the surface of the active material (positive electrode active material) is provided with a reaction-suppressing layer.

[0049] The reaction suppression layer should be composed of a material that has ionic conductivity and can suppress the reaction between the active material and the solid electrolyte. Examples of materials that can constitute 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, and Zr, more specifically, Nb-containing oxides such as LiNbO3, Li3PO4, Li3BO3, Li4SiO4, Li4GeO4, LiTiO3, LiZrO3, and Li2WO4. The reaction suppression layer may contain only one of these oxides, or two or more, and furthermore, multiple of these oxides may form a composite compound. Among these oxides, it is preferable to use an Nb-containing oxide, and more preferable to use LiNbO3.

[0050] The reaction-inhibiting layer is preferably present on the surface in an amount of 0.1 to 1.0 parts by mass per 100 parts by mass of the active material (matrix particles on which the reaction-inhibiting layer is formed). Within this range, the reaction between the active material and the solid electrolyte can be effectively suppressed.

[0051] Methods for forming a reaction-inhibiting layer on the surface of an active material include the sol-gel method, mechanofusion method, CVD method, PVD method, and ALD method.

[0052] The solid electrolyte of the electrode material composite contained in the molded body of the electrode mixture for all-solid-state batteries is mainly an argyrodite-type sulfide-based solid electrolyte, but it is also possible to use only argyrodite-type sulfide-based solid electrolytes for all of the solid electrolytes used.

[0053] Examples of argyrodite-type sulfide solid electrolytes include those represented by the following general formula (2), such as Li6PS5Cl, and those represented by the following general formula (3).

[0054] Li 7-x+y PS 6-x Cl x+y (2)

[0055] In the general equation (2) above, 0.05 ≤ y ≤ 0.9 and -3.0x + 1.8 ≤ y ≤ -3.0x + 5.7.

[0056] Li 7-p PS 6-p Cl q Br r (3)

[0057] In the general formula (3), p=q+r, 0 <p≦1.8、0.1≦q / r≦10.0である。

[0058] In electrodes for all-solid-state batteries, other solid electrolytes can be used in the electrode material composite in addition to argyrodite-type sulfide-based solid electrolytes. Examples of such other solid electrolytes include sulfide-based solid electrolytes other than argyrodite-type sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, oxide-based solid electrolytes, and the like.

[0059] Examples of sulfide-based solid electrolytes other than argyrodite-type sulfide-based solid electrolytes include glass-based particles such as Li2S-P2S5, Li2S-SiS2, Li2S-P2S5-GeS2, and Li2S-B2S3; and LGPS-based ones (Li 10 GeP2S 12 Examples include:

[0060] Examples of hydride-based solid electrolytes include LiBH4, solid solutions of LiBH4 and the alkali metal compounds listed below (for example, those with a molar ratio of LiBH4 to alkali metal compound of 1:1 to 20:1). Examples of alkali metal compounds in the solid solution include at least one selected from the group consisting of lithium halides (LiI, LiBr, LiF, LiCl, etc.), rubidium halides (RbI, RbBr, RbF, RbCl, etc.), cesium halides (CsI, CsBr, CsF, CsCl, etc.), lithium amide, rubidium amide, and cesium amide.

[0061] Examples of the halide-based solid electrolyte include monoclinic LiAlCl4, defective spinel-type or layered-structured LiInBr4, monoclinic Li 6-3m Y m X6 (where 0 < m < 2 and X = Cl or Br), etc. In addition, for example, known ones described in International Publication No. 2020 / 070958 and International Publication No. 2020 / 070955 can also be used.

[0062] Examples of the oxide-based solid electrolyte include 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 La 2 / 3-q TiO3, etc.

[0063] When using other solid electrolytes together with the argyrodite-type sulfide-based solid electrolyte in the electrode material composite, it is preferable that the proportion of the argyrodite-type sulfide-based solid electrolyte in the total amount of the solid electrolyte in the electrode material composite is 70% by mass or more. Further, since it is preferable that all of the solid electrolytes used in the electrode material composite are argyrodite-type sulfide-based solid electrolytes, the preferable upper limit value of the proportion of the argyrodite-type sulfide-based solid electrolyte in the total amount of the solid electrolyte in the electrode material composite is 100% by mass.

[0064] The argyrodite-type sulfide-based solid electrolyte contained in the electrode material composite contained in the molded body of the electrode binder, if it is granular, is not particularly limited in its shape. For example, if the primary particle diameter Rs measured by the following method satisfies the following values, it may have any shape such as spherical, ellipsoidal, plate-like, etc. Further, when the electrode material composite also contains other solid electrolytes other than the argyrodite-type sulfide-based solid electrolyte, it is preferable that the shape of the other solid electrolyte is also granular.

[0065] When Ra is the average particle diameter of the primary particles of the active material contained in the electrode material composite, and Rs is the average particle diameter of the primary particles of the solid electrolyte contained in the electrode material composite (including other solid electrolytes if the electrode material composite also contains solid electrolytes other than argyrodite-type solid electrolytes), the ratio Ra / Rs is preferably 2 or more, more preferably 4 or more, most preferably 6 or more, preferably 50 or less, more preferably 35 or less, and most preferably 18 or less. For example, Ra / Rs can be set within the ranges of 2-50, 2-35, 2-18, 4-50, 4-35, 4-18, 6-50, 6-35, and 6-18. When Ra / Rs satisfies the above values, the contact between the active material and the solid electrolyte in the electrode material composite becomes better, and the effect of improving the load characteristics of the all-solid-state battery becomes better.

[0066] Furthermore, the average particle diameter Ra of the primary particles of the active material in the electrode material composite is preferably 1 μm or more, more preferably 3 μm or more, most preferably 4 μm or more, preferably 25 μm or less, more preferably 15 μm or less, and most preferably 10 μm or less. For example, Ra can be set within the ranges of 1 to 25 μm, 1 to 15 μm, 1 to 10 μm, 3 to 25 μm, 3 to 15 μm, 3 to 10 μm, 4 to 25 μm, 4 to 15 μm, and 4 to 10 μm.

[0067] Furthermore, the average particle size Rs of the primary particles of the solid electrolyte in the electrode material composite is preferably 0.2 μm or more, more preferably 0.4 μm or more, preferably 3 μm or less, and more preferably 1.8 μm or less. For example, Rs can be set within the ranges of 0.2 to 3 μm, 0.2 to 1.8 μm, 0.4 to 3 μm, and 0.4 to 1.8 μm.

[0068] The average particle diameter of the primary particles of the active material contained in the electrode material composite is determined as follows: Ten particles of the active material whose contours can be confirmed are selected from an image of the cross-section of the molded electrode composite in the electrode for an all-solid-state battery, observed at 2000x magnification using a SEM, and the longest diameter of the selected particles is measured using the two-point method. The average value (number mean) of the longest diameters of all measured particles is then taken as the average particle diameter of the primary particles of the active material.

[0069] Furthermore, the average particle size of the primary particles of the solid electrolyte contained in the electrode material composite is determined by the same method as the average particle size of the primary particles of the active material contained in the electrode material composite, except that the magnification used for observation with the SEM is changed to 30,000 times.

[0070] The composition of the active material and the argyrodite-type solid electrolyte in the electrode material composite is preferably such that the content of the argyrodite-type solid electrolyte is 2.5 parts by mass or more, more preferably 8 parts by mass or more, preferably 60 parts by mass or less, and more preferably 40 parts by mass or less, when the content of the active material is 100 parts by mass. For example, the content of the argyrodite-type solid electrolyte can be set within the ranges of 2.5 to 60 parts by mass, 2.5 to 40 parts by mass, 8 to 60 parts by mass, or 8 to 40 parts by mass. With such a component composition, an electrode for an all-solid-state battery can be formed that has a good balance between capacity and ionic conductivity.

[0071] The electrode material composite is manufactured by granulating particles of the active material and particles of an argyrodite-type sulfide-based solid electrolyte. There are no particular restrictions on the granulation method, and known methods can be applied, but 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, adjusting a known mixer to generate van der Waals forces and electrostatic forces due to collision and shearing actions between materials is a desirable method for adjusting the stress acting during granulation.

[0072] The particles of the argyrodite-type sulfide-based solid electrolyte used to form the electrode material composite are measured using a particle size distribution analyzer (such as the "MT-3300EXII" particle size distribution analyzer manufactured by Microtrac Bell Co., Ltd.) and are the average particle diameter [the value of the 50% diameter in the volume-based integrated fraction when calculating the integrated volume from small particles (D 50 The particle size is typically around 0.2 to 3 μm. Therefore, an argyrodite-type sulfide-based solid electrolyte of this size is granulated to form the electrode material composite, and then, within the molded body of the electrode mixture formed using this electrode material composite, granulation of the active material particles and argyrodite-type sulfide-based solid electrolyte particles can be carried out by selecting conditions that can satisfy the primary particle size Rs.

[0073] The molded body of the electrode mixture for all-solid-state batteries may also contain an active material in addition to the electrode material composite. The same active materials exemplified earlier for constituting the electrode material composite can be used as such. However, when an active material is included separately from the electrode material composite, it is preferable that the proportion of the active material in the electrode material composite, out of the total 100% by mass of the active material in the electrode material composite and the active material not constituting the electrode material composite, be 60% by mass or more. Note that the molded body of the electrode mixture does not necessarily need to use an active material separately from the electrode material composite, and the preferred upper limit for the proportion of the active material in the electrode material composite, out of the total 100% by mass of the active material in the electrode material composite and the active material not constituting the electrode material composite, is 100% by mass.

[0074] Furthermore, the content of active material in the electrode mixture (active material contained in the electrode material composite, and active material used separately from the electrode material composite as needed) is preferably 55 to 75% by mass. Note that the active material content here includes the amount of the reaction-inhibiting layer if the active material has a reaction-inhibiting layer.

[0075] The molded body of the electrode composite for the electrode of an all-solid-state battery may also contain a solid electrolyte in addition to the solid electrolyte contained in the electrode material composite. Examples of such solid electrolytes include the same 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 that were previously exemplified as usable in the electrode material composite. The solid electrolyte used separately from the electrode material composite may be of the same type as that contained in the electrode material composite, or of a different type. 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.

[0076] The content of solid electrolytes in the electrode mixture (solid electrolytes contained in the electrode material composite, and solid electrolytes used separately from the electrode material composite as needed) is preferably 25 to 50% by mass.

[0077] The molded electrode mixture for all-solid-state batteries may contain conductive additives such as carbon black and graphene, as needed. When conductive additives are included in the molded electrode mixture, the content in the electrode mixture is preferably 2 to 10% by mass.

[0078] The molded body of the electrode mixture for all-solid-state batteries may or may not contain a resin binder. Examples of resin binders include fluororesins such as polyvinylidene fluoride (PVDF). However, since the resin binder acts as a resistive component in the molded body of the electrode mixture, it is desirable to keep its amount as small as possible. Therefore, it is preferable that the molded body of the electrode mixture does not contain a resin binder, or if it is included, the content in the electrode mixture is 0.5% by mass or less. It is more preferable that the content of the resin binder in the electrode mixture is 0.3% by mass or less, and even more preferable that it is 0% by mass (i.e., does not contain a resin binder).

[0079] When a current collector is used in the electrodes for a solid-state battery, the current collector can be made of metal foil, perforated metal, mesh, expanded metal, foamed metal, carbon sheet, etc. When a metal current collector is used, if the electrode is the positive electrode of the solid-state battery, aluminum or stainless steel current collectors are preferred, and if the electrode is the negative electrode of the solid-state battery, copper or nickel current collectors are preferred.

[0080] The electrode mixture can be formed, for example, by compressing the electrode mixture, which is prepared by mixing the electrode material composite and solid electrolyte with conductive additives and binders as needed, using pressure molding or the like. An electrode for an all-solid-state battery consisting solely of the electrode mixture mixture can be manufactured by this method.

[0081] In the case of electrodes for all-solid-state batteries having a current collector, they can be manufactured by bonding a molded electrode mixture formed by the method described above to a current collector, such as by pressing it against the current collector.

[0082] Alternatively, an electrode mixture containing an electrode mixture may be prepared by mixing the electrode mixture with a solvent, and this mixture may be applied to a substrate such as a current collector or a solid electrolyte layer that faces the electrode. After drying, a press treatment may be performed to form a molded body of the electrode mixture.

[0083] For the solvent in the electrode mixture-containing composition, it is preferable to select one that does not easily degrade the solid electrolyte. In particular, since sulfide-based solid electrolytes and hydride-based solid electrolytes undergo chemical reactions with even trace amounts of water, it is preferable to use nonpolar aprotic solvents such as hydrocarbon solvents like hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene. It is especially preferable to use an ultra-dehydrated solvent with a water content of 0.001% by mass (10 ppm) or less. In addition, fluorine-based solvents such as "Bartrell®" from Mitsui DuPont Fluorochemicals, "Zeolora®" from Nippon Zeon Corporation, and "Novec®" from Sumitomo 3M Corporation, as well as non-aqueous organic solvents such as dichloromethane and diethyl ether, can also be used.

[0084] The thickness of the molded electrode mixture (in the case of an electrode with a current collector, the thickness of the molded electrode mixture per side of the current collector; the same applies hereinafter) is usually 50 μm or more, but from the viewpoint of increasing the battery capacity, it is preferable to have a thickness of 200 μm or more. In addition, the thickness of the molded electrode mixture is usually 3000 μm or less.

[0085] In the case of electrodes for all-solid-state batteries manufactured by forming an electrode mixture layer on a current collector using an electrode mixture-containing composition containing a solvent, the thickness of the electrode mixture layer (thickness per side of the current collector) is preferably 50 to 1000 μm.

[0086] <All-solid-state battery> The all-solid-state battery of the present invention comprises a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, wherein at least one of the positive electrode and the negative electrode is the electrode for the all-solid-state battery of the present invention as described above.

[0087] Figure 5 shows a schematic cross-sectional view illustrating an example of the all-solid-state battery of the present invention. The all-solid-state battery 10 shown in Figure 5 has an outer casing formed by an outer casing 50, a sealing casing 60, and a resin gasket 70 interposed between them, within which 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 are sealed.

[0088] 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 come into contact with the sealing can 60, thereby sealing the opening of the outer can 50 and creating a sealed structure inside the battery.

[0089] Stainless steel can be used for the outer casing and sealing can. Polypropylene, nylon, etc. can be used as gasket materials, and if heat resistance is required due to the battery application, fluororesins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) or polyphenylene ether can be used. PPE Heat-resistant resins with melting points exceeding 240°C, such as polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), and polyetheretherketone (PEEK), can also be used. Furthermore, when batteries are applied to applications requiring heat resistance, glass hermetic seals can be used for sealing.

[0090] Figures 6 and 7 also show schematic diagrams illustrating other examples of the all-solid-state battery of the present invention. Figure 6 is a plan view of the all-solid-state battery, and Figure 7 is a cross-sectional view taken along line II of Figure 6.

[0091] The all-solid-state battery 100 shown in Figures 6 and 7 houses an electrode body 200 consisting of a positive electrode, a solid electrolyte layer, and a negative electrode within a laminate film casing 500 made of two metal laminate films. The laminate film casing 500 is sealed by heat-sealing the upper and lower metal laminate films at its outer periphery. In Figure 7, to avoid complexity in the drawing, the individual layers constituting the laminate film casing 500, as well as the positive electrode, negative electrode, and solid electrolyte layer constituting the electrode body, are not shown separately.

[0092] The positive electrode of the electrode body 200 is connected to the positive electrode external terminal 300 inside the battery 100, and although not shown in the diagram, the negative electrode of the electrode body 200 is also connected to the negative electrode external terminal 400 inside the battery 100. The positive electrode external terminal 300 and the negative electrode external terminal 400 have one end extended to the outside of the laminate film casing 500 so that they can be connected to external devices.

[0093] In the case of an all-solid-state battery in which the electrode for all-solid-state batteries of the present invention is used as the positive electrode, the negative electrode may be the electrode for all-solid-state batteries of the present invention, or it may be a negative electrode other than the electrode for all-solid-state batteries of the present invention. Examples of negative electrodes other than the electrode for all-solid-state batteries of the present invention include an electrode (negative electrode) having the same configuration as the electrode for all-solid-state batteries of the present invention except that a negative electrode active material that can be used in the electrode material composite is used in place of the electrode material composite; a negative electrode consisting only of foil of various alloys that function as negative electrode active materials (such as lithium-aluminum alloy and lithium-indium alloy) or metallic lithium, or a negative electrode in which the foil is laminated as an active material layer on a current collector; and so on.

[0094] Furthermore, in the case of an all-solid-state battery in which the electrode for all-solid-state batteries of the present invention is used as the negative electrode, the positive electrode may be the electrode for all-solid-state batteries of the present invention, or it may be a positive electrode other than the electrode for all-solid-state batteries of the present invention. Examples of positive electrodes other than the electrode for all-solid-state batteries of the present invention include electrodes (positive electrodes) having the same configuration as the electrode for all-solid-state batteries of the present invention, except that the positive electrode active material that can be used in the electrode material composite is used in place of the electrode material composite.

[0095] The solid electrolyte constituting the solid electrolyte layer of an all-solid-state battery can be one or more of the following types of 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, as previously exemplified for use in the positive electrode. However, to improve battery characteristics, it is preferable to include a sulfide-based solid electrolyte, and more preferable to include an argyrodite-type sulfide-based solid electrolyte.

[0096] The solid electrolyte layer may have a porous material, such as a resin nonwoven fabric, as a support.

[0097] The solid electrolyte layer can be formed by methods such as compressing the solid electrolyte by pressure molding; or by applying a solid electrolyte layer-forming composition, prepared by dispersing the solid electrolyte in a solvent, onto a substrate, positive electrode, or negative electrode, drying it, and then performing pressure molding such as a press treatment as needed.

[0098] When selecting a solvent for a composition that forms a solid electrolyte layer, it is desirable to choose one that does not easily degrade the solid electrolyte, and it is preferable to use the same solvents as those previously exemplified for a positive electrode mixture composition containing a solid electrolyte.

[0099] The thickness of the solid electrolyte layer is preferably 100 to 300 μm.

[0100] The positive and negative electrodes can be used in batteries in the form of a laminated electrode body, which is formed by stacking solid electrolyte layers, or a wound electrode body, which is formed by winding this laminated electrode body.

[0101] Furthermore, when forming the electrode body, it is preferable to pressure-molde 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.

[0102] The all-solid-state battery of the present invention can be applied to the same applications as conventionally known all-solid-state batteries (all-solid-state primary batteries or all-solid-state secondary batteries). [Examples]

[0103] The present invention will be described in detail below based on examples. However, the following examples are not intended to limit the present invention.

[0104] (Example 1) <Fabrication of composite electrode materials for positive electrodes> LiCo with an average particle size of 5 μm and a layer of LiNbO3 on its surface. 0.98 Al 0.01 Mg 0.01A composite electrode material for the positive electrode was prepared by granulating primary O2 particles (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 positive electrode material composite was 20 parts by mass of argyrodite-type sulfide-based solid electrolyte per 100 parts by mass of positive electrode active material. 0.98 Al 0.01 Mg 0.01 The amount of the layer made of LiNbO3 on the surface of O2 is LiCo 0.98 Al 0.01 Mg 0.01 The ratio was 1 part by mass per 100 parts by mass of O2. Furthermore, during the granulation of the positive electrode active material and the argyrodite-type sulfide-based solid electrolyte, the mixing conditions in the mixer were adjusted to generate van der Waals forces and electrostatic forces due to collision and shearing between the materials.

[0105] <Fabrication of the positive electrode> The positive electrode material composite, the same argyrodite-type sulfide solid electrolyte used in the positive electrode material composite, and acetylene black (conductive additive) were mixed in a mass ratio of 20:5:1 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 molding was performed using a press machine to produce a positive electrode consisting of a cylindrical positive electrode mixture molded body.

[0106] <Formation of the solid electrolyte layer> Next, 9.6 mg of the same sulfide-based solid electrolyte used in the production of the positive electrode was placed on top of the positive electrode mixture molded body in the powder molding die, and pressure molding was performed using a press machine to form a solid electrolyte layer on the positive electrode mixture molded body, thereby obtaining a laminate of the positive electrode and the solid electrolyte layer.

[0107] <Fabrication of laminated electrode bodies> Lithium titanate (Li4Ti5O 12A negative electrode active material (average particle size: 1.3 μm), the same argyrodite-type sulfide solid electrolyte used in the positive electrode electrode material composite, and graphene (conductive additive) were mixed in a mass ratio of 6:5:1 and thoroughly kneaded to prepare the negative electrode 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 molding was performed using a press machine to form a negative electrode consisting of a molded negative electrode mixture on top of the solid electrolyte layer, 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 (molded positive electrode mixture), solid electrolyte layer, and negative electrode (molded negative electrode mixture) in the laminated electrode body were 750 μm, 100 μm, and 930 μm, respectively.

[0108] Furthermore, multiple laminated electrode bodies were fabricated, and the cross-section of the positive electrode mixture molded body of some of them was observed using SEM. By the method described above, it was confirmed that an electrode material composite consisting of granules was present in the positive electrode mixture molded body, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material composite was granular. In addition, in the electrode material composite, the average particle diameter Ra of the primary particles of the positive electrode active material was 5 μm, and the average particle diameter Rs of the primary particles of the argyrodite-type sulfide-based solid electrolyte was 0.6 μm, resulting in a Ra / Rs value of 8.3.

[0109] <Assembly of all-solid-state batteries> A solid-state battery with a diameter of approximately 9 mm was fabricated by placing a laminated electrode body consisting of a positive electrode, a solid electrolyte layer, and a negative electrode inside a stainless steel sealing can fitted with a polypropylene annular gasket, with the negative electrode facing inward, then covering it with a stainless steel outer can, and finally crimping the open end of the outer can inward to seal it.

[0110] (Example 2) Lithium titanate (Li4Ti5O) with an average particle size of 1.3 μm 12A composite electrode material for the negative electrode was prepared by granulating primary particles (negative 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 negative electrode material composite was 100 parts by mass of negative electrode active material and 40 parts by mass of argyrodite-type sulfide-based solid electrolyte. Furthermore, during the granulation of the negative electrode active material and the argyrodite-type sulfide-based solid electrolyte, the mixing conditions in the mixer were adjusted to generate van der Waals forces and electrostatic forces due to collision and shearing action between the materials.

[0111] A laminated electrode body was prepared in the same manner as in Example 1, except that a negative electrode composite was used, which was prepared by mixing the aforementioned negative electrode material composite, the same argyrodite-type sulfide-based solid electrolyte used in the aforementioned negative electrode material composite, and graphene (conductive additive) in a mass ratio of 8:2:1 and kneading thoroughly. An all-solid-state battery was then prepared in the same manner as in Example 1, except that this laminated electrode body was used.

[0112] Furthermore, multiple laminated electrode bodies were fabricated, and the cross-sections of the positive electrode mixture molded body and the negative electrode mixture molded body of some of them were observed using SEM. By the method described above, it was confirmed that electrode material composites consisting of granules were present in the positive electrode mixture molded body and the negative electrode mixture molded body, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material composite of the positive electrode mixture molded body and the argyrodite-type sulfide-based solid electrolyte in the electrode material composite of the negative electrode mixture molded body were granular. In addition, in the electrode material composite of the positive electrode mixture molded body, the average particle diameter Ra of the primary particles of the positive electrode active material was 5 μm, and the average particle diameter Rs of the primary particles of the argyrodite-type sulfide-based solid electrolyte was 0.6 μm, and the Ra / Rs value was 8.3. Furthermore, in the electrode material composite within the negative electrode composite molded body, the average particle size Ra of the primary particles of the negative electrode active material was 1.3 μm, and the average particle size Rs of the primary particles of the argyrodite-type sulfide-based solid electrolyte was 0.6 μm, resulting in a Ra / Rs value of 2.2.

[0113] (Example 3) A positive electrode electrode material composite was prepared in the same manner as in Example 1, except that the amount of the alligatorite-type sulfide-based solid electrolyte was changed to 48 parts by mass with respect to 100 parts by mass of the positive electrode active material. Then, a laminated electrode body was prepared in the same manner as in Example 1, except that the positive electrode mixture prepared by mixing the positive electrode electrode material composite and acetylene black (conductive assistant) at a mass ratio of 26:1 and kneading well was used. A all-solid-state battery was prepared in the same manner as in Example 1, except that this laminated electrode body was used.

[0114] Note that a plurality of laminated electrode bodies were prepared, and for a part of them, the cross section of the positive electrode mixture molded body was observed by SEM. By the above method, it was confirmed that there is an electrode material composite composed of granulated bodies in the positive electrode mixture molded body, and that the alligatorite-type sulfide-based solid electrolyte in the electrode material composite is granular. Further, in the electrode material composite, the average particle diameter Ra of the primary particles of the positive electrode active material was 5 μm, the average particle diameter Rs of the primary particles of the alligatorite-type sulfide-based solid electrolyte was 0.6 μm, and the value of Ra / Rs was 8.3.

[0115] (Example 4) The positive electrode active material was changed to primary particles of LiCo 0.98 Al 0.01 Mg 0.01 O2 (the amount of the layer composed of LiNbO3 on the surface of LiCo 0.98 Al 0.01 Mg 0.01 O2 was changed to 1 part by mass with respect to 100 parts by mass of LiCo 0.98 Al 0.01 Mg 0.01 O2). A positive electrode electrode material composite was prepared in the same manner as in Example 1, except for this change. A laminated electrode body was prepared in the same manner as in Example 1, except that this positive electrode electrode material composite was used. A all-solid-state battery was prepared in the same manner as in Example 1, except that this laminated electrode body was used.

[0116] Furthermore, multiple laminated electrode bodies were fabricated, and the cross-section of the positive electrode mixture molded body of some of them was observed using SEM. By the method described above, it was confirmed that an electrode material composite consisting of granules was present in the positive electrode mixture molded body, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material composite was granular. In addition, in the electrode material composite, the average particle diameter Ra of the primary particles of the positive electrode active material was 3 μm, and the average particle diameter Rs of the primary particles of the argyrodite-type sulfide-based solid electrolyte was 0.6 μm, resulting in a Ra / Rs value of 5.

[0117] (Example 5) A positive electrode material composite was prepared in the same manner as in Example 1, except that the amount of argyrodite-type sulfide solid electrolyte was changed to 37 parts by mass per 100 parts by mass of positive electrode active material. Then, a stacked electrode body was prepared in the same manner as in Example 1, except that a positive electrode mixture prepared by mixing the same argyrodite-type sulfide solid electrolyte used in the positive electrode material composite with acetylene black (conductive additive) in a mass ratio of 24:5:1 and kneading it well was used. An all-solid-state battery was prepared in the same manner as in Example 1, except that this stacked electrode body was used.

[0118] Furthermore, multiple laminated electrode bodies were fabricated, and the cross-section of the positive electrode mixture molded body of some of them was observed using SEM. By the method described above, it was confirmed that an electrode material composite consisting of granules was present in the positive electrode mixture molded body, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material composite was granular. In addition, in the electrode material composite, the average particle diameter Ra of the primary particles of the positive electrode active material was 5 μm, and the average particle diameter Rs of the primary particles of the argyrodite-type sulfide-based solid electrolyte was 0.6 μm, resulting in a Ra / Rs value of 8.3.

[0119] (Example 6) The positive electrode active material is LiCo with an average particle size of 5 μm and a layer of LiNbO3 on its surface. 0.3 Ni 0.7 Primary particles of O2 (LiCo 0.3 Ni 0.7 The amount of the layer made of LiNbO3 on the surface of O2 is LiCo 0.3 Ni 0.7An electrode material composite for a positive electrode was produced in the same manner as in Example 1, except that it was changed to 1 part by mass with respect to 100 parts by mass of O2. A laminated electrode body was produced in the same manner as in Example 1, except that this electrode material composite for a positive electrode was used. A all-solid-state battery was produced in the same manner as in Example 1, except that this laminated electrode body was used.

[0120] A plurality of laminated electrode bodies were produced. For a part of them, the cross section of the positive electrode mixture molded body was observed by SEM, and it was confirmed that an electrode material composite composed of granulated bodies was present in the positive electrode mixture molded body and that the argyrodite-type sulfide-based solid electrolyte in the electrode material composite was granular by the above method. Further, in the electrode material composite, the average particle diameter Ra of the primary particles of the positive electrode active material was 5 μm, the average particle diameter Rs of the primary particles of the argyrodite-type sulfide-based solid electrolyte was 0.6 μm, and the value of Ra / Rs was 8.3.

[0121] (Example 7) The positive electrode active material was LiNi having an average particle diameter of 5 μm and having a layer made of LiNbO3 on the surface 1 / 3 Co 1 / 3 Mn 1 / 3 O2 primary particles (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 The amount of the layer made of LiNbO3 on the surface of O2 was changed to 1 part by mass with respect to 100 parts by mass of LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2: An electrode material composite for a positive electrode was produced in the same manner as in Example 1, except that it was changed to 1 part by mass with respect to 100 parts by mass of O2. A laminated electrode body was produced in the same manner as in Example 1, except that this electrode material composite for a positive electrode was used. A all-solid-state battery was produced in the same manner as in Example 1, except that this laminated electrode body was used.

[0122] Furthermore, multiple laminated electrode bodies were fabricated, and the cross-section of the positive electrode mixture molded body of some of them was observed using SEM. By the method described above, it was confirmed that an electrode material composite consisting of granules was present in the positive electrode mixture molded body, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material composite was granular. In addition, in the electrode material composite, the average particle diameter Ra of the primary particles of the positive electrode active material was 5 μm, and the average particle diameter Rs of the primary particles of the argyrodite-type sulfide-based solid electrolyte was 0.6 μm, resulting in a Ra / Rs value of 8.3.

[0123] (Example 8) Algyrodite-type sulfide-based solid electrolyte, Li with an average particle size of 0.6 μm 10 GeP2S 12 Except for the change, a positive electrode material composite was prepared in the same manner as in Example 1, and using this positive electrode material composite, the solid electrolyte added separately from the positive electrode material composite was Li with an average particle size of 0.6 μm. 10 GeP2S 12 The positive electrode mixture was prepared in the same manner as in Example 1, except that it was changed to Li with an average particle size of 0.6 μm. Then, using this positive electrode mixture, the solid electrolyte used in the solid electrolyte layer and the negative electrode mixture was changed to Li with an average particle size of 0.6 μm. 10 GeP2S 12 A laminated electrode body was fabricated in the same manner as in Example 1, except for a change, and an all-solid-state battery was fabricated in the same manner as in Example 1, except for using this laminated electrode body.

[0124] Furthermore, multiple laminated electrode bodies were fabricated, and the cross-section of the positive electrode mixture molded body of some of them was observed using SEM. By the method described above, it was confirmed that an electrode material composite consisting of granules was present in the positive electrode mixture molded body, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material composite was granular. In addition, in the electrode material composite, the average particle diameter Ra of the primary particles of the positive electrode active material was 5 μm, and the average particle diameter Rs of the primary particles of the argyrodite-type sulfide-based solid electrolyte was 0.6 μm, resulting in a Ra / Rs value of 8.3.

[0125] (Example 9) Algyrodite-type sulfide-based solid electrolyte, Li with an average particle size of 0.6 μm 4.9 PS 4.2 Cl 0.9 Br 0.9 Except for the change, a positive electrode material composite was prepared in the same manner as in Example 1, and using this positive electrode material composite, the solid electrolyte added separately from the positive electrode material composite was Li with an average particle size of 0.6 μm. 4.9 PS 4.2 Cl 0.9 Br 0.9 The positive electrode mixture was prepared in the same manner as in Example 1, except that it was changed to Li with an average particle size of 0.6 μm. Then, using this positive electrode mixture, the solid electrolyte used in the solid electrolyte layer and the negative electrode mixture was changed to Li with an average particle size of 0.6 μm. 4.9 PS 4.2 Cl 0.9 Br 0.9 A laminated electrode body was fabricated in the same manner as in Example 1, except for a change, and an all-solid-state battery was fabricated in the same manner as in Example 1, except for using this laminated electrode body.

[0126] Furthermore, multiple laminated electrode bodies were fabricated, and the cross-section of the positive electrode mixture molded body of some of them was observed using SEM. By the method described above, it was confirmed that an electrode material composite consisting of granules was present in the positive electrode mixture molded body, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material composite was granular. In addition, in the electrode material composite, the average particle diameter Ra of the primary particles of the positive electrode active material was 5 μm, and the average particle diameter Rs of the primary particles of the argyrodite-type sulfide-based solid electrolyte was 0.6 μm, resulting in a Ra / Rs value of 8.3.

[0127] (Example 10) A laminated electrode body was fabricated in the same manner as in Example 1, except that the negative electrode active material was changed to graphite with an average particle size of 15 μm. An all-solid-state battery was then fabricated in the same manner as in Example 1, except that this laminated electrode body was used.

[0128] Furthermore, multiple laminated electrode bodies were fabricated, and the cross-section of the positive electrode mixture molded body of some of them was observed using SEM. By the method described above, it was confirmed that an electrode material composite consisting of granules was present in the positive electrode mixture molded body, and that the argyrodite-type sulfide-based solid electrolyte in the electrode material composite was granular. In addition, in the electrode material composite, the average particle diameter Ra of the primary particles of the positive electrode active material was 5 μm, and the average particle diameter Rs of the primary particles of the argyrodite-type sulfide-based solid electrolyte was 0.6 μm, resulting in a Ra / Rs value of 8.3.

[0129] (Comparative Example 1) The same LiCo material used in Example 1, having a layer of LiNbO3 on its surface. 0.98 Al 0.01 Mg 0.01 A positive electrode mixture was prepared by mixing primary O2 particles (positive electrode active material), the same argyrodite-type sulfide-based solid electrolyte used in Example 1, and acetylene black (conductive additive) in a mass ratio of 17:8:1. An all-solid-state battery was fabricated in the same manner as in Example 1, except that this positive electrode mixture was used. In Comparative Example 1, the positive electrode active material and solid electrolyte were not granulated.

[0130] (Comparative Example 2) The positive electrode active material is LiCo with an average particle size of 3 μm and a layer of LiNbO3 on its surface. 0.98 Al 0.01 Mg 0.01 Primary particles of O2 (LiCo 0.98 Al 0.01 Mg 0.01 The amount of the layer made of LiNbO3 on the surface of O2 is LiCo 0.98 Al 0.01 Mg 0.01 An all-solid-state battery was prepared in the same manner as in Comparative Example 1, except that the O2 content was changed to 1 part by mass per 100 parts by mass.

[0131] (Comparative Example 3) The positive electrode active material is LiCo with an average particle size of 5 μm and a layer of LiNbO3 on its surface. 0.3 Ni 0.7 Primary particles of O2 (LiCo 0.3 Ni 0.7The amount of the layer made of LiNbO3 on the surface of O2 is LiCo 0.3 Ni 0.7 An all-solid-state battery was prepared in the same manner as in Comparative Example 1, except that the O2 content was changed to 1 part by mass per 100 parts by mass.

[0132] (Comparative Example 4) An all-solid-state battery was fabricated in the same manner as in Comparative Example 1, except that the negative electrode active material was changed to graphite with an average particle size of 15 μm.

[0133] (Comparative Example 5) A composite material for the positive electrode was prepared in the same manner as in Example 1, except that the mixing of the positive electrode active material and the argyrodite-type sulfide-based solid electrolyte was carried out under conditions of stress sufficient to induce a mechanochemical reaction. A laminated electrode body was prepared in the same manner as in Example 1, except that this composite material for the positive electrode 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.

[0134] Furthermore, multiple laminated electrode bodies were fabricated, and the cross-section of the positive electrode composite molded body of some of them was observed using SEM to confirm that the argyrodite-type sulfide-based solid electrolyte in the electrode material composite could not maintain its granular shape and had become a continuous phase of solid electrolyte. In addition, the average particle size Ra of the primary particles of the positive electrode active material in the aforementioned electrode material composite was 5 μm.

[0135] The load characteristics of the all-solid-state batteries in the examples and comparative examples were evaluated by the following method.

[0136] For each solid-state battery in the examples and comparative examples, constant current charging was performed at a current of 0.05C until the voltage reached 2.6V, followed by constant voltage charging until the current reached 0.01C, and then discharged at a current of 0.05C until the voltage reached 1.5V. The initial capacity was then measured.

[0137] For each battery after initial capacity measurement, the 1C discharge capacity was measured by charging and discharging under the same conditions as during the initial capacity measurement, except that the discharge current was changed to 1C. Then, the capacity retention rate was calculated by dividing the 1C discharge capacity of each battery by its initial capacity and expressed as a percentage, and the load characteristics of each battery were evaluated.

[0138] The evaluation results described above, along with the configuration of the electrode material composite in the positive electrode (positive electrode composite molded body) and the electrode material composite in the negative electrode (negative electrode composite molded body) (Example 2 only) for the all-solid-state battery, are shown in Table 1. In Table 1, the capacity retention rate during load characteristic evaluation is shown as a relative value with the value of Comparative Example 1 set to 100.

[0139] [Table 1]

[0140] As shown in Table 1, the all-solid-state batteries of Examples 1 to 10, which used electrodes having a molded body of an electrode material composite comprising an electrode material composite consisting of granules of an active material and an argyrodite-type sulfide-based solid electrolyte, wherein the argyrodite-type sulfide-based solid electrolyte is in granular form, showed higher capacity retention rates during load characteristic evaluation and superior load characteristics compared to the batteries of Comparative Examples 1 to 4, which used electrodes having a molded body of an electrode material composite that did not contain the electrode material composite, and the battery of Comparative Example 5, which used an electrode having a molded body of an electrode material composite containing an electrode material composite in which the argyrodite-type sulfide-based solid electrolyte had lost its granular form and become a continuous phase.

[0141] In particular, the all-solid-state battery of Example 2, in which electrodes having molded bodies of electrode mixtures containing the electrode material composite were used as both the positive and negative electrodes, exhibited superior load characteristics compared to the batteries of Examples 1, 3 to 10, in which only the positive electrode had a molded body of electrode mixtures containing the electrode material composite.

[0142] This application can also be implemented in forms other than those described above, without departing from its spirit. The embodiments disclosed herein are examples and are not limiting. The scope of this application shall be interpreted in accordance with the claims attached, which take precedence over the description in the above specification, and all modifications within the scope equivalent to the claims shall be included in the claims. [Explanation of symbols]

[0143] 1 Electrode material composite 1a, 3 Primary particles of the active material 1b Argyrodite-type sulfide solid electrolytes 2 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 Laminate film outer casing

Claims

1. An electrode for an all-solid-state battery, comprising a molded body of an electrode mixture, The electrode mixture comprises an electrode material composite, The electrode material composite consists of a granular material containing an active material and a solid electrolyte. The solid electrolyte comprises a granular argyrodite-type sulfide-based solid electrolyte, An electrode for an all-solid-state battery in which the granulated material has the following characteristics (1) and (2) when observed in cross-section of the molded body of the electrode mixture. (1) The primary particles of the active material are aggregated in groups of 10 or more, and there are locations where the gaps between the primary particles of the active material are 0.5 μm or more and 5 μm or less. (2) The active material has a region where a solid electrolyte containing the granular argyrodite-type sulfide solid electrolyte is present between the primary particles of the active material.

2. The electrode for an all-solid-state battery according to claim 1, wherein the gaps between the primary particles of the active material are 0.5 μm or more and 4 μm or less.

3. The electrode for an all-solid-state battery according to claim 1, wherein the gaps between the primary particles of the active material are 0.5 μm or more and 3 μm or less.

4. The electrode for an all-solid-state battery according to claim 1, wherein, when a plurality of solid electrolytes containing the granular argyrodite-type sulfide-based solid electrolyte are in close contact, assuming that the planar shape of each particle in contact with the others is a circle, a range of 60% or more of the circumference of the virtual outer circle of each particle can be confirmed as an actual contour line.

5. An all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, An all-solid-state battery characterized in that at least one of the positive electrode and the negative electrode is an electrode for an all-solid-state battery according to any one of claims 1 to 4.

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