Composite active materials, batteries, and methods for manufacturing the same.

Abstract

A composite active material having high capacity and low resistance is disclosed. [Solution] The composite active material of the present disclosure comprises active material particles and a coating portion. The active material particles have an O2-type structure. The active material particles contain, as constituent elements, Li, at least one transition metal element from Mn, Ni, and Co, and O. The active material particles are plate-shaped. The coating portion covers at least a portion of the surface of the active material particles. The coating portion contains a sulfide solid electrolyte.

Description

[Technical Field]

[0001] This application discloses composite active materials, batteries, and methods for manufacturing the same. [Background technology]

[0002] Patent Document 1 discloses an electrode active material having an O2-type structure (O: Octahedral). The electrode active material having an O2-type structure is obtained by ion-exchanging at least a portion of the Na in a Na-containing oxide having a P2-type structure with Li. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-085829 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Electrode active materials with an O2-type structure have room for improvement in terms of capacitance and resistance. [Means for solving the problem]

[0005] This application discloses several embodiments as means for solving the above-mentioned problems. <Aspect 1> A composite active material having active material particles and a coated portion, The active material particles have an O2-type structure, The active material particles consist of the following constituent elements: Li and At least one transition metal element from Mn, Ni, and Co, O and, Includes, The active material particles are plate-shaped, The coating portion covers at least a part of the surface of the active material particles, The coating portion contains a sulfide solid electrolyte, Composite active material. <Aspect 2> The composite active material of Aspect 1, where the coating rate of the coating portion with respect to the surface of the active material particles is 50% or more, Composite active material. <Aspect 3> The composite active material of Aspect 1 or 2, where the active material particles have a protective layer on their surface, at least a part of the surface of the protective layer is coated by the coating portion, where the protective layer contains Li, B, P, and O as constituent elements, Composite active material. <Aspect 4> The composite active material of any one of Aspects 1 to 3, where the active material particles contain Li, Mn, Ni, Co, and O as constituent elements, Composite active material. <Aspect 5> The composite active material of any one of Aspects 1 to 4, where the active material constituting the active material particles is Li a Na b Mn x-p Ni y-q Co z-r M p+q+r and has a chemical composition represented by O2 (where 0 < a ≤ 1.40, 0 ≤ b ≤ 0.20, x + y + z = 1, and 0 ≤ p + q + r < 0.17, and the element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W), Composite active material. <Aspect 6> A battery having a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, where the positive electrode active material layer contains the composite active material of any one of Aspects 1 to 5, Battery. <Aspect 7> The battery of Aspect 6, where the electrolyte layer contains a solid electrolyte, Battery. <Aspect 8> A method for producing a composite active material, To obtain active material particles, and The surface of the active material particles is covered with a coating. Includes, The active material particles have an O2-type structure, The active material particles consist of the following constituent elements: Li and At least one transition metal element from Mn, Ni, and Co, O and, Includes, The active material particles are plate-shaped, The coating portion contains a sulfide solid electrolyte, A method for producing a composite active material. <Pattern 9> A method for manufacturing a battery, To produce a composite active material by the method of embodiment 8, At a minimum, the composite active material, the electrolyte, the conductive additive, and the binder are mixed to obtain an electrode composite material. Using the aforementioned electrode composite material, obtain a positive electrode active material layer. To obtain an electrolyte layer containing an electrolyte, and To obtain a negative electrode active material layer containing a negative electrode active material, A method for manufacturing batteries, including the invention of a battery. [Effects of the Invention]

[0006] The composite active material of this disclosure has high capacity and low resistance. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram schematically shows an example of the internal (cross-sectional) structure of a composite active material. [Figure 2] This is a schematic diagram illustrating a method for determining the aspect ratio of the cross-sectional shape of active material particles. [Figure 3] This shows an example of the stacking state of plate-shaped active material particles in an electrode. [Figure 4]This shows an example of a manufacturing process for a composite active material. [Figure 5] A schematic example of a battery configuration is shown. [Figure 6] This shows an example of a battery manufacturing process. [Figure 7] This is an SEM-EDX image of a cross-section of the composite active material according to Example 1. [Modes for carrying out the invention]

[0008] The following describes one embodiment of the composite active material, battery, and method for manufacturing the same as described herein, but the composite active material, battery, and method for manufacturing the same as described herein are not limited to the embodiment described below.

[0009] 1.Composite active material As shown in Figure 1, a composite active material 1 according to one embodiment comprises active material particles 1a and a coating portion 1b. The active material particles 1a have an O2-type structure. The active material particles 1a contain Li, at least one transition metal element from Mn, Ni, and Co, and O as constituent elements. The active material particles 1a are plate-shaped. The coating portion 1b covers at least a portion of the surface of the active material particles 1a. The coating portion 1b contains a sulfide solid electrolyte.

[0010] 1.1 Active material particles The active material particle 1a has an O2-type structure. Furthermore, the active material particle 1a contains Li, at least one transition metal element from Mn, Ni, and Co, and O as constituent elements. The active material particle 1a is also plate-shaped. As shown in Figure 1, the active material particle 1a according to one embodiment may have a protective layer 1ay on its surface. In other words, the active material particle 1a may have an internal active material portion 1ax and a protective layer 1ay covering at least a portion of the surface of the active material portion 1ax. The presence of the protective layer 1ay is optional. However, if the active material particle 1a has a protective layer 1ay on its surface, the resistance of the composite active material 1 is more easily and significantly improved. When the active material particle 1a has an active material portion 1ax and a protective layer 1ay, the active material portion 1ax has an O2-type structure and contains Li, at least one transition metal element from Mn, Ni, and Co, and O as constituent elements.

[0011] 1.1.1 Crystal structure of the active material The active material particle 1a has an O2-type structure (belonging to space group P63mc). If the active material particle 1a has an active material portion 1ax and a protective layer 1ay, the active material portion 1ax has an O2-type structure. In one embodiment, the active material particle 1a has an O2-type structure in the active material portion 1ax, and may also have a crystal structure other than the O2-type structure. Examples of crystal structures other than the O2-type structure include the T#2-type structure (belonging to space group Cmca) and the O6-type structure (belonging to space group R-3m, with a c-axis length of 2.5 nm to 3.5 nm, typically 2.9 nm to 3.0 nm, and different from the O3-type structure which also belongs to space group R-3m), which are formed when Li is deinserted from the O2-type structure. In one embodiment, the active material particle 1a has an O2-type structure as the main phase in the active material portion 1ax, or it may have a crystal structure other than the O2-type structure (for example, an O6-type structure) as the main phase. In one embodiment, the active material particle 1a may change its main phase crystal structure depending on its charge and discharge state. The active material portion 1ax of the active material particle 1a in one embodiment may be a single crystal consisting of one crystallite, or it may be a polycrystalline material having multiple crystallites.

[0012] 1.1.2 Chemical Composition of Active Material The active material particles 1a contain, as constituent elements, Li, at least one transition metal element selected from Mn, Ni, and Co, and O. In particular, when the active material particles 1a contain, as constituent elements, Li, Mn, and one or both of Ni and Co, and O, especially when they contain, as constituent elements, Li, Mn, Ni, Co, and O, higher performance is more likely to be obtained. When the active material particles 1a have an active material portion 1ax and a protective layer 1ay, the active material portion 1ax may contain, as constituent elements, Li, at least one transition metal element selected from Mn, Ni, and Co, and O, may contain Li, Mn, and one or both of Ni and Co, and O, or may contain Li, Mn, Ni, Co, and O. The active material particles 1a may contain other elements other than Li, Mn, Ni, Co, and O.

[0013] The active material constituting the active material particles 1a is Li a Na b Mn x-p Ni y-q Co z-r M p+q+rIt may have a chemical composition represented by O2 (where 0 < a ≤ 1.40, 0 ≤ b ≤ 0.20, x + y + z = 1, and 0 ≤ p + q + r < 0.17, and the element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W). When the active material portion 1ax has such a chemical composition, high performance is easily ensured, and the O2-type structure is easily maintained. In the above chemical composition, a may be greater than 0, and may be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, or 0.60 or more, and is at most 1.40, and may be 1.30 or less, 1.20 or less, 1.10 or less, 1.00 or less, 0.90 or less, 0.80 or less, or 0.70 or less. In the above chemical composition, b is 0 or more, and may be 0.01 or more, 0.02 or more, or 0.03 or more, and is at most 0.20, and may be 0.15 or less, or 0.10 or less. Also, x is 0 or more, and may be 0.10 or more, 0.20 or more, 0.30 or more, or 0.40 or more, and is at most 1.00, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, or 0.40 or less. Also, y is 0 or more, and may be 0.10 or more, or 0.20 or more, and is at most 1.00, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, or 0.20 or less. Also, z is 0 or more, and may be 0.10 or more, 0.20 or more, 0.30 or more, or 0.40 or more, and is at most 1.00, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, or 0.40 or less. The element M has little contribution to charge and discharge. In this regard, in the above chemical composition, when p + q + r is less than 0.17, a high charge-discharge capacity is easily ensured. p + q + r may be 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, or 0.10 or less. On the other hand, when the element M is included, the O2-type structure is easily stabilized.In the above chemical composition, p+q+r is 0 or greater, and may be 0.01 or greater, 0.02 or greater, 0.03 or greater, 0.04 or greater, 0.05 or greater, 0.06 or greater, 0.07 or greater, 0.08 or greater, 0.09 or greater, or 0.10 or greater. The composition of O is approximately 2, but is not fixed.

[0014] 1.1.3 Protective layer As shown in Figure 1, the active material particles 1a may have a protective layer 1ay on their surface. In this case, at least a portion of the surface of the protective layer 1ay may be covered by the coating portion 1b. In one embodiment, the protective layer 1ay may contain Li, B, P, and O as constituent elements. When the protective layer 1ay contains Li, B, P, and O as constituent elements, the resistance of the composite active material 1 is more easily improved. Alternatively, the protective layer 1ay may have a different chemical composition.

[0015] The protective layer 1ay may be made of a Li ion conductive material. That is, the protective layer 1ay may suppress direct contact between the active material portion 1ax of the active material particle 1a and the coating portion 1b described later, while also ensuring a Li ion conduction path between the active material portion 1ax and the coating portion 1b. The Li ion conductive material may be an inorganic compound or an organic compound, but high performance is particularly easily ensured when it is an inorganic compound. Furthermore, the protective layer 1ay may be substantially free of organic compounds (the organic compound content is less than 0.01% by mass).

[0016] When the protective layer 1ay is composed of an inorganic compound that conducts Li ions, the inorganic compound may be at least one selected from, for example, Li-containing oxides and Li-containing halides. In particular, when it is a Li-containing oxide, high performance is easily ensured when it contains Li, B, P, and O as constituent elements, as described above. When the protective layer 1ay contains Li, B, P, and O as constituent elements, the proportion of Li contained in the protective layer 1ay may be, for example, 20 mol% to 50 mol%. The proportion of P contained in the protective layer 1ay may be, for example, 5 mol% to 20 mol%. The molar ratio of B to P contained in the protective layer 1ay (B / P) may be, for example, 0.5 to 2.0. The molar ratio of Li to the total of P and B contained in the protective layer 1ay (Li / (P+B)) may be, for example, 0.3 to 1.2. The proportions of these elements can be determined, for example, by elemental analysis by SEM-EDX or ICP analysis. Furthermore, the proportion of oxygen contained in protective layer 1ay can be determined as the oxygen concentration, for example, by the heat melting method. The oxygen concentration of protective layer 1ay determined by the heat melting method may be, for example, 45% by weight or more and 60% by weight or less. The proportion of oxygen contained in protective layer 1ay may be, for example, 30 mol% or more and 60 mol% or less.

[0017] The Li-containing oxide constituting the protective layer 1ay may be an oxide containing Li and an element A other than Li. For example, the Li-containing oxide may contain at least one element A selected from B, C, Al, Si, P, S, Ti, La, Zr, Nb, Mo, Zn, and W, along with Li and O. In particular, higher performance is more easily ensured when element A includes B and P. The Li-containing oxide may also be an oxynitride containing N. More specifically, the Li-containing oxides include Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, and Li4Ti5O 12It may be at least one selected from Li2Ti2O5, Li2ZrO3, LiNbO3, Li2MoO4, Li2WO4, LiPON, Li-BPO, Li2O-LaO2, Li2O-ZnO2, etc. The Li-containing oxide may have some elements substituted by various doping elements.

[0018] The Li-containing halide constituting the protective layer 1ay may be, for example, at least one of the various compounds exemplified as halogen solid electrolytes described later. The Li-containing halide may, for example, include at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sn, Al, Sc, Ga, Bi, Sb, Zr, Hf, Ti, Ta, Nb, W, Y, Gd, Tb, and Sm, at least one halogen element selected from the group consisting of Cl, Br, I, and F, and Li. The Li-containing halide may also include at least one element selected from the group consisting of Ti, Al, Gd, Ca, Zr, and Y, at least one element selected from the group consisting of Cl, Br, I, and F, and Li. Furthermore, the Li-containing halide may include at least one element selected from the group consisting of Ti and Al, at least one element selected from the group consisting of Cl, Br, I, and F, and Li. In addition, the Li-containing halide may be, for example, a composite halide of Li, Ti, Al, and F.

[0019] The protective layer 1ay may cover part or all of the surface of the active material portion 1ax. For example, the protective layer 1ay may cover 70% or more, 80% or more, 90% or more, 95% or more, or 99% or more of the surface of the active material portion 1ax. The coverage rate of the protective layer 1ay over the active material portion 1ax can be determined by performing elemental analysis on the cross-section of the active material particles 1a (or composite active material 1).

[0020] The thickness of the protective layer 1ay may be, for example, 0.1 nm to 100 nm, or 1 nm to 50 nm. The thickness of the protective layer 1ay can be determined by observing the cross-section of the active material particle 1a using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0021] 1.1.4 Shape of active material particles The active material particles 1a are plate-shaped. As described later, the active material particles 1a can be obtained by substituting Na with Li in a Na-containing oxide having a P2-type structure. Here, the P2-type structure is hexagonal, has a large diffusion coefficient for Na ions, and is prone to crystal growth in a specific direction. In particular, when at least one of Mn, Ni, and Co is included as a transition metal element constituting the P2-type structure, it is prone to plate-shaped crystal growth in a specific direction. Therefore, Na-containing oxides having a P2-type structure tend to become plate-shaped particles with a large aspect ratio, in which the crystal growth direction is biased in a specific direction. The active material particles 1a according to one embodiment may be obtained from such plate-shaped Na-containing oxide particles.

[0022] In this application, the term "plate-shaped" for the active material particle 1a means that the predetermined cross-sectional shape of the active material particle 1a has an aspect ratio of 1.2 or greater. Here, the "aspect ratio" of the cross-sectional shape of the active material particle 1a is measured as follows: (1) Multiple composite active materials 1 are press-molded together with resin and metal powder to obtain a sample for cross-sectional observation (or, an electrode containing the composite active material 1 may be used as the sample for cross-sectional observation). The sample is then cross-sectionally processed using a cross-sectional preparation device (Hitachi ion milling device: IM4000II). The cross-section should be aligned with the direction of pressure applied during press molding. (2) The sample that has undergone cross-sectional processing is mounted on an FE-SEM to confirm the cross-section. (3) An elemental mapping analysis (oxygen, sulfur) of the cross-section of composite active material 1 is performed using EDX manufactured by Oxford Instruments, and elemental mappings of each element are obtained using EDX analysis software (AZtecLive) manufactured by Oxford Instruments. (4) The cross-sectional shape of the active material particles is determined from the obtained O Kα1 mapping region. (5) In the identified cross-sectional shape, the largest Ferret diameter is determined and considered to be the "major axis" of the active material particle 1a. For example, as shown in Figure 2, the major axis D in the cross-sectional shape of the active material particle 1a L Identify. (6) Among the line segments connecting two points on the outer circumference of the identified cross-sectional shape, the longest line segment perpendicular to the "major axis" identified in (5) is considered to be the "minor axis" of the active material particle 1a. For example, as shown in Figure 2, the minor axis D in the cross-sectional shape of the active material particle 1a S Identify. (7) The ratio of the specified "major axis" to the "minor axis" (major axis / minor axis) is considered to be the "aspect ratio" of the predetermined cross-sectional shape of the active material particle 1a, and if the "aspect ratio" is 1.2 or greater, the active material particle 1a is considered to be "plate-shaped". However, there is no particular upper limit to the aspect ratio. The aspect ratio may be, for example, 10.0 or less. In one embodiment, the aspect ratio may be 1.2 or more and 10.0 or less, 1.3 or more and 10.0 or less, 1.5 or more and 10.0 or less, 1.7 or more and 10.0 or less, or 2.0 or more and 10.0 or less, 2.5 or more and 10.0 or less, 3.0 or more and 10.0 or less, 3.5 or more and 10.0 or less, 4.0 or more and 10.0 or less, 4.5 or more and 10.0 or less, or 5.0 or more and 10.0 or less.

[0023] The particle size of the active material particles 1a is not particularly limited. The average particle size (D50) of the active material particles 1a may be 0.1 μm or more and 10 μm or less, 1.0 μm or more and 8.0 μm or less, 2.0 μm or more and 6.0 μm or less, or 2.0 μm or more and 4.0 μm or less. The average particle size (D50) is the particle size (D50, median diameter) at 50% of the cumulative value in the volume-based particle size distribution obtained by laser diffraction-scattering method. In one embodiment, the active material particles 1a may be positive electrode active material particles.

[0024] 1.2 Court Section When forming electrodes using active material particles, pressure may be applied to the electrodes for purposes such as densification. According to the inventors' findings, in electrodes using plate-shaped active material particles, when pressure is applied to the electrodes, the flat surfaces (broad surfaces) of the plate-shaped active material particles tend to stack together, as shown in Figure 3. As a result, it is not possible to apply pressure evenly to the electrodes, which can lead to insufficient interface formation between the active material particles and between the active material particles and other battery materials (electrolytes, etc.). Furthermore, active materials having an O2-type structure exhibit large volume changes in the high SOC region. Therefore, in batteries using active materials having an O2-type structure, the volume change of the active material in the high SOC region can lead to insufficient interface formation between the active material particles and between the active material particles and other battery materials (electrolytes, etc.). Insufficient interface formation in this way can cause interruptions in the Li ion conduction path, easily leading to a decrease in capacity and an increase in resistance.

[0025] In contrast, in this embodiment, in order to suppress interruptions in the Li ion conduction path at the interfaces between the active material particles and the interfaces between the active material particles and other battery materials, at least a portion of the surface of the active material particles 1a is covered with a coating portion 1b. Since the coating portion 1b contains a sulfide solid electrolyte, a Li ion conduction path is ensured at the interface between the active material particles 1a and the coating portion 1b. In an electrode using such a composite active material 1, the coating portion 1b is interposed between the active material particles 1a and between the active material particles 1a and other battery materials. Therefore, a Li ion conduction path is ensured by the coating portion 1b at the interfaces between the active material particles and the interfaces between the active material particles and other battery materials (electrolytes, etc.), making it easier to improve capacity and resistance.

[0026] 1.2.1 Sulfide solid electrolyte The coated portion 1b contains a sulfide solid electrolyte. The sulfide solid electrolyte may be a glass-based sulfide solid electrolyte (sulfide glass), a glass-ceramic-based sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. The sulfide glass is amorphous. The sulfide glass may have a glass transition temperature (Tg). If the sulfide solid electrolyte has a crystalline phase, examples of the crystalline phase include a thio-LISICON type crystalline phase, an LGPS type crystalline phase, and an argyrodite type crystalline phase.

[0027] The sulfide solid electrolyte may contain, for example, Li, X (where X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S as constituent elements. In one embodiment, the sulfide solid electrolyte may contain Li, S, and P as constituent elements. The sulfide solid electrolyte may further contain at least one of O and halogens as constituent elements. The sulfide solid electrolyte may also contain S as the main component of the anionic element.

[0028] Sulfide solid electrolytes include, for example, Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-GeS2, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-LiI-LiBr, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (where m and n are positive numbers. Z is either Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers. M is either P, Si, Ge, B, Al, Ga, or In). It may be at least one selected from these.

[0029] The composition of the sulfide solid electrolyte is not particularly limited. For example, xLi2S·(100 - x)P2S5 (70 ≤ x ≤ 80), yLiI·zLiBr·(100 - y - z)(xLi2S·(1 - x)P2S5) (0.7 ≤ x ≤ 0.8, 0 ≤ y ≤ 30, 0 ≤ z ≤ 30), etc. can be mentioned. Alternatively, the sulfide solid electrolyte has a composition represented by the general formula: Li 4-x Ge 1-x P x S4 (0 < x < 1). In the above general formula, at least a part of Ge may be substituted by at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the above general formula, at least a part of P may be substituted by at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the above general formula, a part of Li may be substituted by at least one of Na, K, Mg, Ca, and Zn. In the above general formula, a part of S may be substituted by a halogen (at least one of F, Cl, Br, and I). Alternatively, the sulfide solid electrolyte is Li 7-a PS 6-a X aThe composition may be represented as (where X is at least one of Cl, Br, and I, and a is a number between 0 and 2). a may be 0 or greater than 0. In the latter case, a may be 0.1 or greater, 0.5 or greater, or 1 or greater. Also, a may be 1.8 or less, or 1.5 or less.

[0030] The proportion of the sulfide solid electrolyte in the coated portion 1b may be, for example, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, or 99% by mass or more and 100% by mass or less.

[0031] 1.2.2 Other Ingredients The coated portion 1b may contain other components in addition to the sulfide solid electrolyte. The proportion of other components in the coated portion 1b may be, for example, 0% to 30% by mass, 0% to 20% by mass, 0% to 10% by mass, 0% to 5% by mass, or 0% to 1% by mass. The other components may be, for example, solid electrolytes other than sulfide solid electrolytes. Solid electrolytes other than sulfide solid electrolytes may be inorganic solid electrolytes or organic polymer electrolytes. Examples of inorganic solid electrolytes include oxide solid electrolytes and ionic inorganic solid electrolytes.

[0032] Oxide solid electrolytes include lithium lanthanum zirconate, LiPON, and Li 1+X Al X Ge 2-X (PO4)3, Li-SiO glass, Li-Al-SO glass, and one or more other materials may be selected from these.

[0033] The ionic solid electrolyte may contain, for example, at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sn, Al, Sc, Ga, Bi, Sb, Zr, Hf, Ti, Ta, Nb, W, Y, Gd, Tb, and Sm. These elements can generate cations in water. The ionic solid electrolyte material may also further contain, for example, at least one halogen element selected from the group consisting of Cl, Br, I, and F. These elements can generate anions in water. The ionic solid electrolyte may contain at least one element selected from the group consisting of Gd, Ca, Zr, and Y, at least one element selected from the group consisting of Cl, Br, I, and F, and Li. Alternatively, the ionic solid electrolyte may contain Li and Y, and at least one element selected from the group consisting of Cl, Br, I, and F. More specifically, the ionic solid electrolyte may contain Li, Y, Cl, and Br, or Li, Ca, Y, Gd, Cl, and Br, or Li, Zr, Y, and Cl. More specifically, the ionic solid electrolyte may be Li3YBr2Cl4, Li 2.8 Ca 0.1 Y 0.5 Gd 0.5 Br2Cl4 and Li 2.5 Y 0.5 Zr 0.5 It may be at least one of the Cl6 species.

[0034] The ionic solid electrolyte may be a halide solid electrolyte. Halide solid electrolytes have excellent ionic conductivity. For example, formula (A): Li α M β X γ ...(A) It may have a composition represented by [here, α, β, and γ are each independently a value greater than 0, M is at least one selected from the group consisting of metal elements other than Li and metalloid elements, and X is at least one selected from the group consisting of Cl, Br, and I. Note that the "metalloid element" may be at least one selected from the group consisting of B, Si, Ge, As, Sb, and Te. Also, the "metal element" may include (i) all elements (excluding hydrogen) contained in Groups 1 to 12 of the periodic table and (ii) all elements (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se) contained in Groups 13 to 16 of the periodic table. The metal element can form an inorganic compound with a halide ion and become a cation.]

[0035] In formula (A), M may contain Y (i.e., yttrium). The halide solid electrolyte containing Y is Li a Me b Y c It may have a composition represented by X6 (where a + mb + 3c = 6, c > 0, Me is at least one selected from the group consisting of metal elements and metalloid elements other than Li and Y, and m is the valence of Me). Me may be, for example, at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0036] The halide solid electrolyte may have a composition represented by formula (A1): Li 6-3d Y d X6. In formula (A1), X is one or more elements selected from the group consisting of Cl, Br, and I. d may satisfy 0 < d < 2, or d = 1. The halide solid electrolyte may have a composition represented by formula (A2): Li 3-3δ Y 1+δ Cl6. In formula (A2), 0 < δ ≦ 0.15 may hold. The halide solid electrolyte may have a composition represented by formula (A3): Li 3-3δ Y 1+δIt may have a composition represented by Br6. In formula (A3), 0 < δ ≦ 0.25 may be satisfied. The halide solid electrolyte has the formula (A4): Li 3-3δ+a Y 1+δ-a Me a Cl 6-x-y Br x I y and may have a composition represented by. In formula (A4), Me may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, and Zn. In formula (A4), for example, -1 < δ < 2, 0 < a < 3, 0 < (3 - 3δ + a), 0 < (1 + δ - a), 0 ≦ x ≦ 6, 0 ≦ y ≦ 6, and (x + y) ≦ 6 are satisfied. The halide solid electrolyte has the formula (A5): Li 3-3δ Y 1+δ-a Me a Cl 6-x-y Br x I y and may have a composition represented by. In formula (A5), Me may be at least one selected from the group consisting of Al, Sc, Ga, and Bi. In formula (A5), -1 < δ < 1, 0 < a < 2, 0 < (1 + δ - a), 0 ≦ x ≦ 6, 0 ≦ y ≦ 6, and (x + y) ≦ 6 may be satisfied. The halide solid electrolyte has the formula (A6): Li 3-3δ-a Y 1+δ-a Me a Cl 6-x-y Br x I y and may have a composition represented by. In formula (A6), Me may be at least one selected from the group consisting of Zr, Hf, and Ti. In formula (A6), -1 < δ < 1, 0 < a < 1.5, 0 < (3 - 3δ - a), 0 < (1 + δ - a), 0 ≦ x ≦ 6, 0 ≦ y ≦ 6, and (x + y) ≦ 6 may be satisfied. The halide solid electrolyte has the formula (A7): Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x-y Br x I yIt may have the composition shown in formula (A7). In formula (A7), Me may be at least one selected from the group consisting of Ta and Nb. In formula (A7), -1 < δ < 1, 0 <a<1.2、0<(3-3δ-2a)、0<(1+δ-a)、0≦x≦6、0≦y≦6、かつ、(x+y)≦6であってもよい。

[0037] Ionic solid electrolytes may also be complex hydride solid electrolytes. Complex hydride solid electrolytes may be composed of Li ions and complex ions containing H. A complex ion containing H may, for example, have an element M containing at least one of nonmetallic elements, metalloid elements, and metallic elements, and H bonded to element M. In addition, in a complex ion containing H, element M as the central element and H surrounding element M may be bonded to each other via covalent bonds. In addition, a complex ion containing H may have (M m H n ) α- It may also be represented as follows: In this case, m is any positive number, and n and α can be any positive number depending on m, the valence of element M, etc. Element M can be any nonmetallic or metallic element that can form a complex ion. For example, element M may contain at least one of B, C, and N as a nonmetallic element, or it may contain B. Also, for example, element M may contain at least one of Al, Ni, and Fe as a metallic element. In particular, when the complex ion contains B, or contains C and B, higher ionic conductivity is more easily ensured. A specific example of a complex ion containing H is (CB9H 10 ) - , (CB 11 H 12 ) - , (B 10 H 10 ) 2- , (B 12 H 12 ) 2- (BH4) - , (NH2) - (AlH4) - , and combinations thereof are examples. In particular, (CB9H 10 ) - , (CB 11H 12 ) - When using these or combinations thereof, it is easier to ensure higher ionic conductivity. That is, the complex hydride solid electrolyte may contain Li, C, B, and H.

[0038] 1.2.3 Coating rate The coating portion 1b covers at least a part of the surface of the active material particles 1a. It is considered that the higher the coating rate of the coating portion 1b with respect to the surface of the active material particles 1a, the higher the above-described interface forming ability, and the capacity and resistance are improved. The coating rate of the coating portion 1b with respect to the surface of the active material particles 1a may be, for example, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more. The upper limit of the coating rate is not particularly limited. The coating rate may be 100% or less. Note that the "coating rate" of the coating portion 1b with respect to the surface of the active material particles 1a is measured as follows. That is, (1) A plurality of composite active materials 1 are press-molded together with a resin and a metal powder to obtain a sample for cross-sectional observation (or an electrode containing the composite active material 1 may be used as a sample for cross-sectional observation). The sample is subjected to cross-sectional processing using a cross-sectional preparation apparatus (Hitachi ion milling apparatus: IM4000II). The cross-section shall be along the pressure application direction during press molding. (2) The sample subjected to cross-sectional processing is mounted on a FE-SEM to confirm the cross-section. (3) Element mapping analysis (oxygen, sulfur) of the cross-section of the composite active material 1 is performed using EDX manufactured by Oxford Instruments, and element mapping of each element is obtained using EDX analysis software (AZtecLive) manufactured by Oxford Instruments. (4) The outer peripheral length of the portion corresponding to the active material particles 1a is calculated from the mapping region of O Kα1. (5) The contact length of S Kα1 in contact with the portion corresponding to the active material particles identified from the mapping region of O Kα1 is calculated. (6) Based on the following formula, the coating rate of the coating portion 1b with respect to the surface of the active material particles 1a is specified. (Coverage %) = 100 × (Contact length of S Kα1 in contact with O Kα1) / (Perimeter length calculated from the mapping region of O Kα1) (7) Perform steps (3) to (6) above on 10 randomly selected composite active materials 1 and calculate the average coverage rate.

[0039] 1.2.4 Thickness The thickness of the coated portion 1b may be, for example, greater than 0 μm and 1.0 μm or less, or greater than 0 μm and 0.5 μm or less. The thickness of the coated portion 1b can be determined by elemental analysis of the cross-section of the composite active material 1, as described above.

[0040] 1.3 Others 1.3.1 Shape of the composite active material as a whole The composite active material 1 comprises the active material particles 1a and the coated portion 1b described above. The composite active material 1 may be particulate overall. Alternatively, multiple composite active materials 1 may aggregate to form secondary particles. The particle size of the composite active material 1 is not particularly limited. The average particle size (D50) of the composite active material 1 may be 0.1 μm or more and 10 μm or less, 1.0 μm or more and 8.0 μm or less, or 2.0 μm or more and 6.0 μm or less. The average particle size (D50) is the particle size (D50, median diameter) at 50% of the cumulative value in the volume-based particle size distribution obtained by laser diffraction-scattering. In one embodiment, the composite active material 1 may be a positive electrode active material.

[0041] 1.3.2 Volume ratio of active material particles to coating The volume ratio of active material particles 1a to coating portion 1b in the composite active material 1 is not particularly limited. For example, a higher resistance improvement effect is more easily ensured when the ratio V2 / V1 of the volume of coating portion 1b to the volume V1 of active material particles 1a contained in the composite active material 1 is 0.1 or more and 0.5 or less, or 0.1 or more and 0.3 or less.

[0042] 2. Method for producing composite active material The composite active material 1 described above can be manufactured, for example, by the following method. That is, as shown in Figure 4, the method for manufacturing the composite active material 1 according to one embodiment is: S1: To obtain active material particles 1a, and S2: Covering at least a portion of the surface of the active material particles 1a with the coating portion 1b. The active material particles 1a have an O2-type structure, and the active material particles 1a contain Li, at least one transition metal element from Mn, Ni, and Co, and O as constituent elements, the active material particles 1a are plate-shaped, and the coating portion 1b contains a sulfide solid electrolyte.

[0043] 2.1 S1 In S1, active material particles 1a having an O2-type structure, containing predetermined constituent elements, and being plate-shaped can be obtained, for example, by the following method. That is, as shown in Figure 4, S1 is S11: To obtain a precursor containing at least one transition metal element from Mn, Ni, and Co. S12: Mix the precursor and the Na source to obtain a mixture. S13: To obtain plate-shaped Na-containing oxide particles having a P2-type structure by calcining the above mixture, and S14: This may include obtaining Li-containing oxide particles having an O2-type structure by ion-exchanging at least a portion of the Na in the Na-containing oxide particles with Li.

[0044] 2.1.1 Preparation of Precursors The precursor contains at least one transition metal element from among Mn, Ni, and Co. The precursor may contain Mn and one or both of Ni and Co, or it may contain at least Mn, Ni, and Co. The precursor may be a salt containing at least one element from among Mn, Ni, and Co. For example, the precursor may be at least one of carbonates, sulfates, nitrates, and acetates. Alternatively, the precursor may be a compound other than a salt. For example, the precursor may be a hydroxide. The precursor may be a hydrate. The precursor may be a combination of multiple compounds. The precursor may be in various shapes. For example, the precursor may be particulate, or it may be spherical particles as described later. The particle size of the particles made up of the precursor is not particularly limited.

[0045] In S11, a precipitate as a precursor may be obtained by coprecipitation using an ion source capable of forming a precipitate with transition metal ions in aqueous solution and a transition metal compound containing at least one element from Mn, Ni, and Co. This makes it easier to obtain spherical particles as a precursor. The "ion source capable of forming a precipitate with transition metal ions in aqueous solution" may be at least one selected from, for example, sodium salts such as sodium carbonate and sodium nitrate, sodium hydroxide, and sodium oxide. The transition metal compound may be the above salts or hydroxides containing at least one element from Mn, Ni, and Co. Specifically, in S1, the precipitate as a precursor may be obtained by preparing solutions of the ion source and the transition metal compound separately, and then adding and mixing each solution dropwise. In this case, water may be used as the solvent. Various sodium compounds may be used as the base, and aqueous ammonia may be added to adjust the basicity. In the case of coprecipitation, for example, an aqueous solution of the transition metal compound and an aqueous solution of sodium carbonate are prepared, and the precipitate as a precursor is obtained by adding and mixing each aqueous solution dropwise. Alternatively, the precursor can be obtained by the sol-gel method.

[0046] In S11, the precursor may contain element M. Element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W. These elements M have functions such as stabilizing P2-type or O2-type structures. The method for obtaining a precursor containing element M is not particularly limited. When obtaining a precursor by coprecipitation in S1, for example, an aqueous solution of a transition metal compound containing at least one of Mn, Ni, and Co, an aqueous solution of sodium carbonate, and an aqueous solution of a compound of element M are prepared, and each aqueous solution is added dropwise and mixed to obtain a precursor containing element M along with at least one of Mn, Ni, and Co. Alternatively, in the manufacturing method of this disclosure, element M may not be added in S11, and element M may be doped in S12 and S13 as described below.

[0047] 2.1.2 Preparation of mixtures (complexes) In S12, the precursor obtained in S11 and the Na source are mixed to obtain a mixture. In S12, the surface of the precursor may be coated with the Na source to obtain a composite. The Na source may be a salt containing Na, such as a carbonate or nitrate, or a compound other than a salt, such as sodium oxide or sodium hydroxide. In S12, the amount of Na source relative to the precursor should be determined taking into account the amount of Na lost during subsequent calcination. In S12, when the surface of the precursor is coated with the Na source, the coverage rate of the Na source on the surface of the precursor is not particularly limited. In S12, the method of coating the surface of the precursor with the Na source is not particularly limited. For example, the precursor and the Na source may be mixed using a mortar and pestle or a mixing device, or the solution containing the Na source may be brought into contact with the precursor using a rolling flow coating method or a spray drying method, and then dried.

[0048] In S12, the precursor may be mixed with the Na source and the M source. For example, in S12, the precursor obtained in S1 may be mixed with the Na source and the M source containing at least one element M selected from B, Mg, Al, K, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W to obtain a mixture. The M source may be a salt containing element M, such as a carbonate or sulfate, or a compound other than a salt, such as an oxide or hydroxide. The amount of the M source relative to the precursor should be determined according to the chemical composition of the Na-containing oxide after calcination.

[0049] 2.1.3 Preparation of P2-type Na-containing oxide particles In S13, the mixture (composite) obtained in S12 is calcined to obtain a Na-containing oxide having a P2-type structure. S13-1: The mixture is pre-fired at a temperature of 300°C or higher but less than 700°C for a period of 1 hour or more but not more than 10 hours. S13-2: Following the pre-firing, the mixture is subjected to a main firing at a temperature of 700°C to 1100°C for 30 minutes to 48 hours, and S13-3: Following the above-mentioned firing, the composite is rapidly cooled from a temperature T1 of 200°C or higher to a temperature T2 of 100°C or lower. It may include [something].

[0050] In S13-1, the mixture (composite) is pre-fired at a temperature of 300°C or higher but less than 700°C for a period of 2 hours or more but less than 10 hours. In S13-1, the mixture may be arbitrarily molded before pre-fired. Pre-fired is performed at a temperature lower than that of the main firing. If the pre-fired in S13-1 is insufficient, the formation of the P2 phase in the final Na-containing oxide may be insufficient. In S13-1, by setting the pre-fired temperature to 300°C or higher but less than 700°C and the pre-fired time to 2 hours or more but less than 10 hours, the mixture can be sufficiently pre-fired, the uniformity of the heat is increased, and the Na-containing oxide obtained via S13-2 and S13-3 described below is more likely to be suitable. The pre-firing temperature may be between 400°C and 700°C, 450°C and 700°C, 500°C and 700°C, 550°C and 700°C, or 550°C and 650°C. The pre-firing time may be between 2 hours and 8 hours, 3 hours and 8 hours, 4 hours and 8 hours, 5 hours and 8 hours, or 5 hours and 7 hours. The pre-firing atmosphere is not particularly limited and may be, for example, an oxygen-containing atmosphere.

[0051] In S13-2, following the pre-sintering described above, the mixture (composite) is subjected to main firing at a temperature of 700°C to 1100°C for a period of 30 minutes to 48 hours. In S13-2, the main firing temperature may be 800°C to 1000°C. If the main firing temperature is too low, the P2 phase will not be formed, and if the main firing temperature is too high, other phases besides the P2 phase are likely to be formed. The heating conditions from the pre-sintering temperature to the main firing temperature are not particularly limited. In S13-2, the shape of the Na-containing oxide can be controlled by the main firing time. If the main firing time is too short, the formation of the P2 phase will be insufficient. In this embodiment, by setting the main firing time to a certain level or longer, the P2 phase grows and plate-shaped Na-containing oxide particles are obtained.

[0052] In step S13-3, the fired product after the main firing described above is rapidly cooled (cooled at a cooling rate of 20°C / min or more) from a temperature T1 of 200°C or higher to a temperature T2 of 100°C or lower. The above pre-firing and main firing are performed, for example, in a heating furnace. In step S13-3, for example, after the main firing of the mixture (composite) is performed in a heating furnace, it is cooled in the heating furnace to an arbitrary temperature T1 of 200°C or higher, and after reaching that temperature T1, the fired product is removed from the heating furnace and rapidly cooled outside the furnace to an arbitrary temperature T2 of 100°C or lower. Temperature T1 is any temperature of 200°C or higher, and may also be any temperature of 250°C or higher. Temperature T2 is any temperature of 100°C or lower, and may also be any temperature of 50°C or lower, and may also be the cooling completion temperature. In the predetermined temperature range between temperature T1 and temperature T2, moisture easily penetrates between the layers of the P2 type structure due to atomic vibrations, molecular motion, etc. When cooling the calcined product (Na-containing oxide having a P2-type structure) after the main calcination, it is thought that reducing the time spent in the temperature range where moisture easily penetrates (i.e., rapid cooling) will reduce the amount of moisture penetrating into the interlayers of the P2-type structure. In this regard, in step S13-3, when cooling the calcined product after the main calcination, if the cooling is performed in a dry atmosphere outside the furnace from an arbitrary temperature T1 of 200°C or higher to an arbitrary temperature T2 of 100°C or lower, the cooling rate from temperature T1 to temperature T2 becomes high (e.g., 20°C / min or higher), making it difficult for moisture to penetrate into the interlayers of the P2-type structure and suppressing the collapse of the P2-type structure. As a result, Na can be efficiently ion-exchanged for Li in S14.

[0053] S13 allows for the production of plate-shaped Na-containing oxide particles having a P2-type structure and a predetermined chemical composition. The Na-containing oxide particles contain, as constituent elements, at least one transition metal element from among Mn, Ni, and Co, as well as Na and O. In particular, when the constituent elements include at least Na, Mn, at least one of Ni and Co, and O, high performance is more easily ensured when the constituent elements include at least Na, Mn, Ni, Co, and O. Na-containing oxide particles are Na c Mnx-p Ni y-q Co z-r M p+q+r It may have a chemical composition represented by O2. Here, 0 < c < 1.00, x + y + z = 1, and 0 ≦ p + q + r < 0.17. Also, M is at least one element selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W. When the Na-containing oxide particles have such a chemical composition, the P2-type structure is more likely to be maintained. In the above chemical composition, c is greater than 0, and may be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, or 0.60 or more, and less than 1.00, and may be 0.90 or less, 0.80 or less, or 0.70 or less. x is 0 or more, and may be 0.10 or more, 0.20 or more, 0.30 or more, or 0.40 or more, and 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, or 0.40 or less. Also, y is 0 or more, and may be 0.10 or more or 0.20 or more, and 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, or 0.20 or less. Also, z is 0 or more, and may be 0.10 or more, 0.20 or more, 0.30 or more, or 0.40 or more, and 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, or 0.40 or less. The element M has a small contribution to charge and discharge. In this regard, in the above chemical composition, when p + q + r is less than 0.17, it is easy to ensure a high charge and discharge capacity. p + q + r may be 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, or 0.10 or less. On the other hand, when the element M is included, the P2-type structure and the O2-type structure are likely to be stabilized. In the above chemical composition, p + q + r is 0 or more, and may be 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, or 0.1 or more. The composition of O is approximately 2, but is indefinite.

[0054] 2.1.4 Ion exchange In step S14, Li-containing oxide particles having an O2-type structure are obtained by ion exchange of at least a portion of the Na in the Na-containing oxide particles obtained in step S13 with Li. For ion exchange, there are methods such as using an aqueous solution containing lithium halide and using a mixture of lithium halide and other lithium salts (e.g., a molten salt). From the viewpoint that the P2-type structure is easily broken by the intrusion of water and from the viewpoint of crystallinity, the method using a molten salt is preferred among the two methods above. That is, by mixing the Na-containing oxide having the above-mentioned P2-type structure with the molten salt and heating it to a temperature above the melting point of the molten salt, at least a portion of the Na in the Na-containing oxide can be replaced with Li by ion exchange. The lithium halide constituting the molten salt is preferably at least one of lithium chloride, lithium bromide, and lithium iodide. The other lithium salt constituting the molten salt is preferably lithium nitrate. By using a molten salt, the melting point becomes lower than when lithium halide or other lithium salts are used alone, and ion exchange becomes possible at lower temperatures. The temperature during ion exchange may be, for example, above the melting point of the molten salt and below 600°C, 500°C, 400°C, or 300°C. If the temperature during ion exchange is too high, the stable O3-type structure is more likely to form than the O2-type structure. On the other hand, from the viewpoint of minimizing the time required for ion exchange, it is desirable for the temperature during ion exchange to be as high as possible.

[0055] 2.1.5 Protective Coating A method for producing active material particles 1a according to one embodiment is, for example, S15: Covering at least a portion of the surface of the Li-containing oxide particles after ion exchange as described above, or the Li-containing oxide particles after further Li doping as described below, with a protective layer. It may also contain [a specific component]. This results in an active material particle 1a having an active material portion 1ax and a protective layer 1ay, as shown in Figure 1.

[0056] In S15, the method for coating at least a portion of the surface of the Li-containing oxide particles, which constitute the active material portion 1ax, with the protective layer 1ay is not particularly limited. For example, a coating solution can be prepared by dissolving the raw materials constituting the protective layer 1ay in a solvent, and the solvent can be volatilized and removed while the coating solution is in contact with the surface of the Li-containing oxide particles, or after contact, thereby coating at least a portion of the surface of the Li-containing oxide particles, which constitute the active material portion 1ax, with the protective layer 1ay. In one embodiment, a slurry may be prepared by mixing the Li-containing oxide particles and the coating solution, and then the slurry may be heated to volatilize the solvent, thereby obtaining active material particles 1a having an active material portion 1ax and a protective layer 1ay. For heating and drying the slurry, for example, spray drying may be used.

[0057] 2.1.6 Li-doping A method for producing active material particles 1a according to one embodiment is, for example, S16: Further doping of Li with Li to the Li-containing oxide particles after the ion exchange described above, It may also contain [a specific substance]. This may further increase its capacity as an active material.

[0058] In S16, for example, Li can be doped into Li-containing oxide particles by contacting them with a reducing solution containing Li ions. "Reducing solution" means a solution that has reducing properties, and may, for example, be a solution containing an electrophile. The reducing solution may be obtained, for example, by dissolving an electrophile and a Li source in a solvent. Various organic solvents capable of dissolving the electrophile and Li source can be used as the solvent. Various substances that dissolve in the above solvent can be used as the electrophile. The electrophile may be an aromatic organic compound. Various substances that dissolve in the above solvent to produce Li ions can be used as the Li source. The Li source may be metallic lithium or a Li compound. The concentration of the electrophile and Li ions contained in the reducing solution can be appropriately determined according to the desired doping amount. The greater the amount of Li ions contained in the reducing solution relative to the amount of Li-containing transition metal oxide contacted with the reducing solution, the greater the amount of Li doping to the Li-containing transition metal oxide tends to be. The molar ratio of electrophile to Li ions (electrophile / Li ions) contained in the reducing solution is not particularly limited. The form of contact between the reducing solution and the Li-containing oxide particles is not particularly limited. For example, the Li-containing oxide particles may be immersed in the reducing solution, or the reducing solution may be sprayed onto the Li-containing oxide particles. There are no particular restrictions on the temperature at contact; heating may be used or not. Alternatively, the Li-containing oxide particles may be immersed in the reducing solution and then stirred. There are no particular restrictions on the contact time between the Li-containing oxide particles and the reducing solution; it can be appropriately determined according to the desired doping amount. The timing of further doping the Li-containing oxide particles with Li may be before or after the application of the protective layer 1ay described above.

[0059] 2.2 S2 In step S2, at least a portion of the surface of the active material particles 1a obtained in step S1 is covered by a coating portion 1b containing a sulfide solid electrolyte. The method for coating the active material particles 1a with the sulfide solid electrolyte is not particularly limited. Step S2 can be performed using various coating devices.

[0060] In one embodiment, for example, the sulfide solid electrolyte may be coated onto the surface of the active material particles 1a by applying mechanical energy (e.g., shear force) to a mixture of active material particles 1a and a sulfide solid electrolyte. The coating of the sulfide solid electrolyte onto the surface of the active material particles 1a may be performed dry or wet. Specifically, the sulfide solid electrolyte can be coated onto the surface of the active material particles 1a by placing the mixture of active material particles 1a and a sulfide solid electrolyte in a container and applying a shear force to the mixture by rotating a rotor. Here, the coverage rate of the coating portion 1b on the surface of the active material particles 1a can be controlled by controlling the rotation speed of the rotor, the operating time, etc. As will be described later, in this embodiment, after manufacturing the composite active material 1, an electrode mixture can be obtained by mixing the composite active material 1 with a conductive additive, etc. In other words, the mixture in S2 includes, for example, active material particles 1a and a sulfide solid electrolyte, but does not include a conductive additive and a binder. The mixture in S2 may consist only of active material particles 1a and a sulfide solid electrolyte, or it may consist only of active material particles 1a, a sulfide solid electrolyte, and a dispersion medium (solvent and any additives).

[0061] 3. Electrode mixture The composite active material 1 can constitute an electrode mixture together with other substances, for example. For example, an electrode mixture according to one embodiment may include the composite active material 1, an electrolyte, a conductive additive, and a binder. The electrode mixture may also optionally contain other additives. The respective contents of the active material, electrolyte, conductive additive, and binder in the electrode mixture can be appropriately determined according to the desired battery performance. For example, if the total solid content in the electrode mixture is taken as 100% by mass, the content of the active material (active material derived from the composite active material 1 and any other active material) may be 40% by mass or more and less than 100% by mass, and the total content of the conductive additive, binder, and solid electrolyte may be greater than 0% by mass and 60% by mass or less. The active material content in the electrode mixture may be 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass or more, or 90% by mass or less. The total content of the conductive additive, binder, and solid electrolyte may be 10% by mass or more, or 50% by mass or less, 40% by mass or less, 30% by mass or less, or 20% by mass or less. These lower and upper limits may be combined in any way.

[0062] 3.1 Active material The active material contained in the electrode mixture may consist only of the above-mentioned composite active material, or it may contain other active materials (other active materials) together with the composite active material 1. From the viewpoint of further enhancing the effects of the technology of this disclosure, the proportion of other active materials in the total active material contained in the electrode mixture may be small. For example, if the total active material contained in the electrode mixture is taken as 100% by mass, the content of the active material derived from the above-mentioned composite active material 1 may be 50% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, or 99% by mass or more and 100% by mass or less.

[0063] Other active materials that can be included in the electrode composite material can adopt any of those known as active materials. The electrode composite material may contain at least one selected from various lithium compounds other than the active material particles 1a, elemental sulfur, sulfur compounds, etc. as other active materials. The lithium compound as other active materials may be a Li-containing oxide containing at least one element M, Li, and O. The element M may be, for example, at least one selected from Mn, Ni, Co, Al, Mg, Ca, Sc, V, Cr, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, Bi, Fe, and Ti, or at least one selected from the group consisting of Mn, Ni, Co, Al, Fe, and Ti. More specifically, the Li-containing oxide as other active materials may be lithium cobaltate, lithium nickelate, lithium manganate, lithium nickel cobaltate, lithium nickel manganate, lithium cobalt manganate, lithium nickel cobalt manganate (Li 1±α Ni x Co y Mn z O 2±δ (for example, 0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1), spinel-type lithium compounds (Li 1+x Mn 2-x-y M y O4 (M is one or more selected from Al, Mg, Co, Fe, Ni, and Zn), such as hetero-element-substituted Li-Mn spinel with a composition represented by this formula), lithium nickel cobalt aluminum oxide (for example, Li 1±α Ni p Co q Al r O 2±δThe other active material may be at least one selected from (for example, p+q+r=1), lithium titanate, metallic lithium phosphate (LiMPO4, etc., where M is one or more selected from Fe, Mn, Co, and Ni), etc. In particular, higher performance is more likely to be obtained when the other active material contains a Li-containing oxide as a constituent element, which includes at least one of Ni, Co, and Mn, Li, and O. Alternatively, higher performance is also more likely to be obtained when the other active material contains a Li-containing oxide as a constituent element, which includes at least one of Ni, Co, and Al, Li, and O. The other active material may be used alone or in combination of two or more. The shape of the other active material may be any shape that is common for active materials. The other active material may be particulate, for example. The other active material may be solid or have voids, for example, it may be porous or hollow. The other active material may be primary particles or secondary particles formed by the aggregation of multiple primary particles. The average particle size D50 of the other active materials may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and may also be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less.

[0064] 3.2 Electrolytes The electrode mixture may contain an electrolyte along with the composite active material 1 described above. The electrolyte that may be included in the electrode mixture may be a solid electrolyte, a liquid electrolyte, or a combination thereof. In particular, the effects of the technology of this disclosure become more pronounced when the electrode mixture contains a solid electrolyte.

[0065] 3.2.1 Solid electrolyte As the solid electrolyte, any known solid electrolyte for batteries may be used. The solid electrolyte mixed with the composite active material 1 in the electrode mixture may be of the same type as the sulfide solid electrolyte contained in the coating portion 1b of the composite active material 1, or it may be of a different type. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, inorganic solid electrolytes have excellent ionic conductivity and heat resistance. Examples of inorganic solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, and ionically bonded inorganic solid electrolytes. Details of sulfide solid electrolytes, oxide solid electrolytes, and ionically bonded inorganic solid electrolytes are as described above. In particular, higher performance is more easily ensured when the electrode mixture contains a sulfide solid electrolyte as the solid electrolyte. The sulfide solid electrolyte may, for example, contain at least Li, S, and P as constituent elements. Alternatively, the electrode mixture may contain an ionically bonded solid electrolyte as the solid electrolyte, for example, a solid electrolyte containing at least Li, Y, and a halogen (at least one of Cl, Br, I, and F) as constituent elements. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may be particulate. The average particle size (D50) of the solid electrolyte may be, for example, 10 nm or more and 10 μm or less. Only one type of solid electrolyte may be used alone, or two or more types may be used in combination.

[0066] 3.2.2 Liquid electrolyte The liquid electrolyte (electrolyte) is a liquid containing lithium ions as carrier ions. The electrolyte may be aqueous or non-aqueous. The composition of the electrolyte may be the same as that known for lithium-ion secondary battery electrolytes. The electrolyte may be a solution of lithium salt dissolved in water or a non-aqueous solvent. Examples of non-aqueous solvents include various carbonate-based solvents. Examples of lithium salts include lithium amide salts and LiPF6.

[0067] 3.3 Conductive additives Examples of conductive additives that may be included in electrode composites include carbon materials such as vapor-processed carbon fiber (VGCF), acetylene black (AB), Ketjenblack (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF); and metallic materials such as nickel, titanium, aluminum, and stainless steel. Conductive additives may be in particulate or fibrous form, and their size is not particularly limited. Conductive additives may be used alone or in combination of two or more types.

[0068] 3.4 Binder Examples of binders that may be included in electrode composites include butadiene rubber (BR) binders, butylene rubber (IIR) binders, acrylate butadiene rubber (ABR) binders, styrene butadiene rubber (SBR) binders, polyvinylidene fluoride (PVdF) binders, polytetrafluoroethylene (PTFE) binders, and polyimide (PI) binders. A single binder may be used alone, or two or more may be used in combination.

[0069] 3.5 Other In addition to the components listed above, the electrode mixture may also contain various additives, such as dispersants and lubricants.

[0070] 4. Method for manufacturing electrode composite material The electrode mixture described above can be manufactured, for example, by the following method. That is, a method for manufacturing the electrode mixture according to one embodiment may include at least mixing the composite active material 1, an electrolyte, a conductive additive, and a binder. The means for mixing the composite active material 1, the electrolyte, the conductive additive, and the binder are not particularly limited. For example, a method for manufacturing the electrode mixture may include dispersing the composite active material 1, the electrolyte, the conductive additive, and the binder in a solvent to obtain a slurry. Note that the method for mixing the composite active material 1, the electrolyte, the conductive additive, and the binder is completely different from the method of coating the active material particles 1a with a sulfide solid electrolyte when manufacturing the composite active material 1 described above. "Mixing" in the method for manufacturing the electrode mixture simply means homogenizing the dispersion state of the composite active material 1, the electrolyte, the conductive additive, and the binder.

[0071] 5.Battery The composite active material 1 can be used, for example, as the positive electrode active material of a battery. As shown in Figure 5, a battery 100 according to one embodiment has a positive electrode active material layer 10, an electrolyte layer 20, and a negative electrode active material layer 30. The positive electrode active material layer 10 includes the composite active material 1 of the present disclosure.

[0072] 5.1 Cathode active material layer The positive electrode active material layer 10 comprises at least the composite active material 1 described above, and may further contain an electrolyte, a conductive additive, a binder, etc. Furthermore, the positive electrode active material layer 10 may contain various other additives. In other words, the positive electrode active material layer 10 may be composed of the above-described electrode composite material. The shape of the positive electrode active material layer 10 is not particularly limited, and for example, it may be a sheet-like positive electrode active material layer 10 having a substantially flat surface. The thickness of the positive electrode active material layer 10 is not particularly limited, and for example, it may be 0.1 μm or more or 1 μm or more, or 2 mm or less or 1 mm or less.

[0073] 5.2 Electrolyte layer The electrolyte layer 20 is placed between the positive electrode active material layer 10 and the negative electrode active material layer 30. The electrolyte layer 20 contains at least an electrolyte. The electrolyte layer 20 may contain at least one of a solid electrolyte and an electrolyte solution, and may also optionally contain a binder or the like. In particular, higher performance is more easily ensured when the electrolyte layer 20 contains a solid electrolyte. The content of electrolyte and binder or the like in the electrolyte layer 20 is not particularly limited. Alternatively, the electrolyte layer 20 may have a separator or the like to hold the electrolyte solution and prevent contact between the positive electrode active material layer 10 and the negative electrode active material layer 30. The thickness of the electrolyte layer 20 is not particularly limited and may be, for example, 0.1 μm or more or 1 μm or more, or 2 mm or less or 1 mm or less.

[0074] The electrolyte layer 20 may consist of one layer or multiple layers. For example, the electrolyte layer 20 may comprise a first layer located on the positive electrode active material layer 10 side and a second layer located on the negative electrode active material layer 30 side, wherein the first layer contains a first electrolyte and the second layer contains a second electrolyte. The first electrolyte and the second electrolyte may be of different types. The first electrolyte and the second electrolyte may each be at least one selected from the oxide solid electrolyte, sulfide solid electrolyte and ionic solid electrolyte described above. For example, the first layer may contain an ionic solid electrolyte, and the second layer may contain at least one of the ionic solid electrolyte and sulfide solid electrolyte.

[0075] The electrolyte included in the electrolyte layer 20 may be appropriately selected from among the examples of electrolytes that can be included in the positive electrode active material layer 10 (electrode composite material) described above (solid electrolytes and / or liquid electrolytes). Similarly, the binder that can be included in the electrolyte layer 20 may be appropriately selected from among the examples of binders that can be included in the positive electrode active material layer described above. The electrolyte and binder may each be used individually or in combination of two or more types. The separator may be any separator commonly used in batteries, such as those made of polyethylene (PE), polypropylene (PP), polyester, and polyamide resins. The separator may have a single-layer structure or a multi-layer structure. Examples of multi-layer separators include a PE / PP two-layer separator, or a PP / PE / PP or PE / PP / PE three-layer separator. The separator may also be made of a nonwoven fabric such as cellulose nonwoven fabric, resin nonwoven fabric, or glass fiber nonwoven fabric.

[0076] 5.3 Negative electrode active material layer The negative electrode active material layer 30 contains at least negative electrode active material. The negative electrode active material layer 30 may also optionally contain an electrolyte, a conductive additive, a binder, and various other additives. The content of each component in the negative electrode active material layer 30 can be appropriately determined according to the desired battery performance. For example, taking the total solid content of the negative electrode active material layer 30 as 100% by mass, the content of the negative electrode active material may be 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, or it may be 100% by mass or less, less than 100% by mass, 95% by mass or less, or 90% by mass or less. Alternatively, taking the entire negative electrode active material layer 30 as 100% by volume, the negative electrode active material and optionally the electrolyte, conductive additive, and binder may together account for 85% by volume or more, 90% by volume or more, or 95% by volume or more, with the remainder being void or other components. The shape of the negative electrode active material layer 30 is not particularly limited and may, for example, be a sheet having a substantially flat surface. The thickness of the negative electrode active material layer 30 is not particularly limited and may be, for example, 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or more, or 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less.

[0077] Any known negative electrode active material can be used as the negative electrode active material for batteries. Among the known active materials, various materials can be used whose potential for intercalating and releasing carrier ions (charge / discharge potential) is lower than that of the positive electrode active material. For example, silicon-based active materials such as Si, Si alloys, and silicon oxide; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium and lithium alloys can be used. In particular, the performance of the battery 100 tends to improve when the negative electrode active material layer 30 contains Si as the negative electrode active material. The negative electrode active material may be used alone or in combination of two or more types. The shape of the negative electrode active material may be any shape that is common for negative electrode active materials in batteries. For example, the negative electrode active material may be particulate. The negative electrode active material particles may be primary particles or secondary particles formed by the aggregation of multiple primary particles. The average particle size (D50) of the negative electrode active material particles may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, or it may be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. Alternatively, the negative electrode active material may be in the form of a sheet (foil or film) such as lithium foil. That is, the negative electrode active material layer 30 may consist of a sheet of negative electrode active material.

[0078] Examples of electrolytes that may be included in the negative electrode active material layer 30 include the solid electrolyte, electrolyte solution, or a combination thereof as described above. Conductive additives that may be included in the negative electrode active material layer 30 may be appropriately selected from among the examples of conductive additives that may be included in the positive electrode active material layer 10 (electrode mixture 5) described above. Binders that may be included in the negative electrode active material layer 30 may be appropriately selected from among the examples of binders that may be included in the positive electrode active material layer 10 (electrode mixture 5) described above. Electrolytes, conductive additives, and binders may each be used individually or in combination of two or more types.

[0079] 5.4 Positive electrode current collector As shown in Figure 5, the battery 100 may include a positive electrode current collector 40 that contacts the positive electrode active material layer 10. Any of the common types of positive electrode current collectors for batteries can be used for the positive electrode current collector 40. The positive electrode current collector 40 may also have at least one shape selected from foil, plate, mesh, perforated metal, and foam. The positive electrode current collector 40 may have metal foil or metal mesh. Alternatively, the positive electrode current collector 40 may have a layer made of a resin composition containing resin and conductive material. Alternatively, the positive electrode current collector 40 may include a combination of two or more layers made of metal foil, metal mesh, and resin composition. The positive electrode current collector 40 may consist of multiple foils or sheets. The metal constituting the metal foil for the positive electrode current collector 40 can be at least one selected from Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, V, Mg, Pb, Ge, In, Sn, Zr, and stainless steel. In particular, the positive electrode current collector 40 may contain Al from the viewpoint of ensuring oxidation resistance. The positive electrode current collector 40 may have some kind of coating layer on its surface for the purpose of adjusting resistance, etc. For example, the positive electrode current collector 40 may have a carbon coating layer. The positive electrode current collector 40 may also be a metal foil or substrate on which the above metals are plated or deposited. Furthermore, if the positive electrode current collector 40 consists of multiple metal foils, there may be some kind of layer between the multiple metal foils. The thickness of the positive electrode current collector 40 is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or more, or 1 mm or less or 100 μm or less.

[0080] 5.5 Negative electrode current collector As shown in Figure 5, the battery 100 may include a negative electrode current collector 50 that contacts the negative electrode active material layer 30. Any of the negative electrode current collectors commonly used for batteries can be used as the negative electrode current collector 50. The negative electrode current collector 50 may be in the form of foil, plate, mesh, perforated metal, or foam. The negative electrode current collector 50 may have metal foil or metal mesh. Alternatively, the negative electrode current collector 50 may have a layer made of a resin composition containing resin and conductive material. Alternatively, the negative electrode current collector 50 may have a carbon sheet. Alternatively, the negative electrode current collector may include a combination of two or more of the following: metal foil, metal mesh, resin composition, and carbon sheet. The negative electrode current collector 50 may consist of multiple foils or sheets. The metal constituting the metal foil as the negative electrode current collector 50 can be at least one selected from Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, V, Mg, Pb, Ge, In, Sn, Zr, and stainless steel. In particular, from the viewpoint of ensuring reduction resistance and being less prone to alloying with lithium, the negative electrode current collector 50 may contain at least one metal selected from Cu, Ni, and stainless steel. The negative electrode current collector 50 may have some kind of coating layer on its surface for the purpose of adjusting resistance, etc. For example, the negative electrode current collector 50 may have a carbon coating layer. The negative electrode current collector 50 may be aluminum foil with a carbon coating layer. The negative electrode current collector 50 may also be a metal foil or substrate on which the above metals are plated or deposited. Furthermore, if the negative electrode current collector 50 consists of multiple metal foils, there may be some kind of layer between the multiple metal foils. The thickness of the negative electrode current collector 50 is not particularly limited. For example, the thickness may be 0.1 μm or more, or 1 μm or more, or 1 mm or less, or 100 μm or less.

[0081] 5.6 Other Configurations In addition to the above configuration, the battery 100 may have other configurations common to batteries, such as tabs and terminals. The battery 100 may have each of the above configurations housed inside an outer casing. Any known battery casing can be used. Furthermore, multiple batteries 100 may be electrically connected and stacked as desired to form a battery pack. In this case, the battery pack may be housed inside a known battery case. Examples of battery shapes include coin type, laminate type, cylindrical type, and prismatic type. The battery 100 may be a rechargeable battery. The battery 100 may be an all-solid-state battery that substantially does not contain a liquid electrolyte.

[0082] 6. Battery manufacturing method The battery 100 can be manufactured by applying known methods, except that the electrode mixture is obtained using the specific composite active material 1 described above. As shown in Figure 6, a method for manufacturing the battery 100 according to one embodiment is: S10: To produce the composite active material 1 by the method of the present disclosure described above, S20: At least, the composite active material 1, the electrolyte, the conductive additive, and the binder are mixed to obtain an electrode composite material. S30: Using the electrode composite material, obtain a positive electrode active material layer 10. S40: To obtain an electrolyte layer 20 containing an electrolyte, and S50: To obtain a negative electrode active material layer 30 containing the negative electrode active material. It may include the following. The order of S30, S40 and S50 is not particularly limited. In one embodiment, the battery 100 can be manufactured as follows. However, the manufacturing method of the battery 100 is not limited to the following method, and each layer may be formed by, for example, dry molding.

[0083] (1) A slurry for the positive electrode layer is obtained by dispersing the composite active material 1, etc., that constitutes the positive electrode active material layer in a solvent. The solvent used in this case is not particularly limited, and water or various organic solvents can be used. The slurry for the positive electrode layer is coated onto the surface of the positive electrode current collector using a doctor blade or the like, and then dried to form a positive electrode active material layer on the surface of the positive electrode current collector, which serves as the positive electrode. (2) The negative electrode active material and other materials constituting the negative electrode active material layer are dispersed in a solvent to obtain a slurry for the negative electrode layer. The solvent used in this case is not particularly limited, and water or various organic solvents can be used. The slurry for the negative electrode layer is applied to the surface of the negative electrode current collector using a doctor blade or the like, and then dried to form a negative electrode active material layer on the surface of the negative electrode current collector, which serves as the negative electrode. (3) The layers are stacked so that an electrolyte layer (solid electrolyte layer or separator) is sandwiched between the negative electrode and the positive electrode, and a laminate is obtained having the negative electrode current collector, negative electrode active material layer, electrolyte layer, positive electrode active material layer and positive electrode current collector in this order. Other members such as terminals are attached to the laminate as needed. (4) The laminate is housed in a battery case, and in the case of an electrolyte battery, the battery case is filled with electrolyte, the laminate is immersed in the electrolyte, and the laminate is sealed inside the battery case to form a secondary battery. In the case of an electrolyte battery, the negative electrode active material layer, separator and positive electrode active material layer may be made to contain the electrolyte at the stage of (3) above.

[0084] 7. Vehicles The battery of this disclosure has high capacity and low resistance due to the use of composite active material 1. Such a battery can be suitably used in at least one type of vehicle selected from, for example, hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs). That is, the technology of this disclosure also has an aspect as a vehicle having a battery, wherein the battery has a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, and the positive electrode active material layer contains the composite active material 1 of this disclosure. [Examples]

[0085] As described above, one embodiment of the composite active material, etc., has been explained, but the technology of this disclosure can be modified in various ways other than the above embodiment without departing from its gist. The technology of this disclosure will be described in more detail below with reference to examples, but the technology of this disclosure is not limited to the following examples.

[0086] 1. Preparation of active material for evaluation 1.1 Examples 1 and 2 The composite active materials according to Examples 1 and 2 were prepared using the following procedure.

[0087] 1.1.1 Preparation of Precursor Particles (1) MnSO4·5H2O, NiSO4·6H2O, and CoSO4·7H2O were weighed to the desired composition ratio (Mn:Ni:Co=4:2:4) and dissolved in distilled water to a concentration of 1.2 mol / L to obtain the first solution. In a separate container, Na2CO3 was dissolved in distilled water to a concentration of 1.2 mol / L to obtain the second solution. (2) 1000 mL of pure water was placed in a reaction vessel (with baffles), and 500 mL of the first solution and 500 mL of the second solution were added dropwise, each at a rate of approximately 4 mL / min. (3) After the dropwise addition was complete, the mixture was stirred at room temperature at a stirring speed of 150 rpm for 1 hour to obtain the product. (4) The product was washed with pure water, and solid-liquid separation was performed using a centrifuge to recover the precipitate. (5) The obtained precipitate was dried overnight at 120°C, then ground in a mortar and pestle, and coarse particles were removed by air classification to obtain precursor particles.

[0088] 1.1.2 Preparation of mixtures (complexes) The above-mentioned precursor particles and Na2CO3 were mixed using a mortar and pestle to coat the surface of the precursor particles with Na2CO3, thereby obtaining a mixture (composite).

[0089] 1.1.3 Preparation of P2-type Na-containing oxide particles The above mixture (composite) was placed in an alumina crucible and calcined under an atmospheric environment to obtain a Na-containing oxide having a P2-type structure. The calcination conditions were as follows (1) to (6). (1) Place an alumina crucible containing the above composite in a heating furnace in an atmospheric environment. (2) Heat the furnace from room temperature (25°C) to 600°C in 120 minutes. (3) Maintain the temperature inside the heating furnace at 600°C for 360 minutes to perform pre-firing. (4) After pre-firing, raise the temperature inside the furnace to 900°C in 100 minutes. (5) Maintain the temperature inside the heating furnace at 900°C for 120 minutes to perform the final firing. (6) After the main firing, the temperature inside the furnace is lowered from the main firing temperature to 250°C. At 250°C, the alumina crucible is removed from the furnace and allowed to cool outside the furnace in a dry atmosphere until it reaches 25°C in 10 minutes.

[0090] By crushing the calcined material after cooling in a dry atmosphere using a mortar, Na-containing oxide particles having a P2-type structure (P2-type particles) were obtained. These Na-containing oxide particles were plate-shaped particles with an aspect ratio of 1.2 or more in their cross-sectional shape.

[0091] 1.1.4 Ion exchange (1) LiNO3 and LiCl were weighed in a molar ratio of 50:50 and mixed with the above P2 type particles in a molar ratio that was 10 times the minimum amount of Li required for ion exchange to obtain a mixture. (2) Using an alumina crucible, ion exchange was performed at 280°C for 1 hour under an atmospheric atmosphere to obtain a product containing a Li-containing oxide. (3) The salt remaining in the product was washed with pure water, and solid-liquid separation was performed by vacuum filtration to obtain a precipitate. (4) The obtained precipitate was dried overnight at 120°C to obtain Li-containing oxide particles having an O2-type structure.

[0092] 1.1.5 Protective Coating (1) 4.52 g of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries) was dissolved in 191.8 g of deionized water. Next, boric acid (manufactured by Nacalai Tesque) was added and dissolved so that the molar ratio (B / P) was 1.0. Furthermore, lithium hydroxide monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries) was added and stirred so that the molar ratio (Li / (P+B)) was 1.00. This yielded a coating solution containing Li, P, and B sources. (2) The above-mentioned Li-containing oxide particles were mixed with the coating liquid to obtain a slurry. (3) The slurry was dried using a spray drying device to obtain a solid component. (4) The solid component was heat-treated at 200°C for 5 hours in an air atmosphere. This coated the surface of the active material particles with a protective layer. The protective layer contained Li, B, P, and O as constituent elements.

[0093] 1.1.6 Li-doping (1) In a glove box (Ar atmosphere), 9-fluorenone was mixed and dissolved in tetrahydrofuran (THF) to obtain a fluorenone solution. (2) Li foil was added to the fluorenone solution and stirred for 2 hours to obtain a reducing solution containing Li ions. (3) Li-containing oxide particles after protective coating were added to the obtained reducing solution and immersed in it, and the mixture was stirred for 24 hours. (4) The particles after stirring were washed with THF and solid-liquid separation was performed by vacuum filtration. The resulting precipitate was dried overnight at 120°C to obtain active material particles.

[0094] XRD analysis revealed that the crystalline phase contained in the active material particles had an O2-type structure. Furthermore, the active material particles were plate-shaped particles with an aspect ratio of 1.2 or greater in their cross-sectional shape. The method of cross-sectional observation was as described in the embodiments of this specification.

[0095] 1.1.7 Sulfide Solid Electrolyte Coating The above-mentioned active material particles and sulfide solid electrolyte (Li2S-P2S5-based sulfide solid electrolyte) were placed in a coating apparatus (Nobilta®, manufactured by Hosokawa Micron Corporation), and the apparatus was operated to generate shear force within the apparatus, thereby coating the surface of the active material particles with the sulfide solid electrolyte to obtain a composite active material for evaluation. Here, by changing the shear force, two types of composite active materials with different coating rates of sulfide solid electrolyte were obtained. In Example 1, the shear force was relatively increased, and in Example 2, the shear force was relatively decreased.

[0096] 1.2 Comparative Example 1 The plate-shaped active material particles were used directly for evaluation without applying a sulfide solid electrolyte coating.

[0097] 1.3 Comparative Example 2 Precursor particles were obtained in the same manner as in Examples 1 and 2. A mixture (composite) was obtained by subjecting the obtained precursor to the following treatment. (1) After weighing Na2CO3 and distilled water to a concentration of 1150 g / L, an aqueous solution of Na2CO3 was prepared by stirring with a stirrer until it was completely dissolved. (2) A slurry was obtained by mixing the above Na2CO3 aqueous solution with the above precursor particles. (3) The slurry described above was air-dried by spray drying to obtain a second mixture (second composite). Specifically, a spray dryer DL410 was used with a slurry delivery rate of 30 mL / min, an inlet temperature of 200°C, and a circulating air volume of 0.8 m³. 3 The slurry was air-dried under conditions of / min and a spray pressure of 0.3 MPa to coat the surface of the precursor particles with Na2CO3, thereby obtaining a mixture (composite).

[0098] The obtained mixture (composite) was pre-fired by raising the temperature under the same conditions as in Examples 1 and 2. After pre-fired, the temperature inside the heating furnace was raised to 800°C in 100 minutes, and the furnace was held at 800°C for 60 minutes for the main firing. Subsequently, it was cooled under the same conditions as in Examples 1 and 2 to obtain Na-containing oxide particles having a P2-type structure (P2-type particles). These Na-containing oxide particles were spherical particles with an aspect ratio of less than 1.2 in their cross-sectional shape.

[0099] Using the obtained spherical Na-containing oxide particles, ion exchange, protective layer coating, and Li doping were performed under the same conditions as in Examples 1 and 2 to obtain active material particles. XRD confirmed that the crystalline phase contained in the active material particles had an O2-type structure. Furthermore, the active material particles were spherical particles with an aspect ratio of less than 1.2 in their cross-sectional shape.

[0100] The obtained spherical active material particles were coated with a sulfide solid electrolyte under the same conditions as in Example 2 to obtain a composite active material for evaluation.

[0101] 1.4 Comparative Example 3 Spherical active material particles were used directly for evaluation without applying a sulfide solid electrolyte coating.

[0102] 2. Measurement of coverage Cross-sectional observation of the composite active material was performed to determine the coverage rate of the sulfide solid electrolyte on the surface of the active material particles. The method of cross-sectional observation was as described in the embodiments of this specification. Figure 7 shows an SEM-EDS image of the composite active material according to Example 1. From Figure 7, it can be seen that the composite active material according to Example 1 has plate-shaped active material particles coated with a sulfide solid electrolyte. Example 2 had a similar form, except that the coverage rate was different.

[0103] 3. Creating cells for evaluation (1) The evaluation active material, argyrodite-type sulfide solid electrolyte, vapor-grown carbon fiber (VGCF), and PVdF-based binder described above were weighed in a mass ratio of active material:sulfide solid electrolyte:VGCF:binder = 81:16:1:2. When a composite active material coated with sulfide solid electrolyte was used as the evaluation active material, the argyrodite-type sulfide solid electrolyte was added so that the mass ratio of the active material to the sulfide solid electrolyte (sulfide solid electrolyte in the coating + argyrodite-type sulfide solid electrolyte) was 81:16, taking into account the amount of sulfide solid electrolyte constituting the composite active material. A positive electrode slurry was obtained by dispersing and mixing each weighed component in DIBK. The positive electrode slurry was coated onto an Al foil, which was to be used as the positive electrode current collector foil, by the blade method, and this was dried on a hot plate to form a positive electrode active material layer on the Al foil. (2) Lithium titanate (LTO) as the negative electrode active material, argyrodite-type sulfide solid electrolyte, VGCF, and PVdF-based binder were weighed in a ratio of negative electrode active material:sulfide-based solid electrolyte:VGCF:binder = 72:23:3:2 and dispersed and mixed in butyl butyrate to obtain a negative electrode slurry. This negative electrode slurry was coated onto Ni foil as the negative electrode current collector foil by the blade method and dried on a hot plate to form a negative electrode active material layer on the Ni foil. (3) A solid electrolyte slurry was obtained by stirring an argyrodite-type sulfide solid electrolyte, a PVdF-based binder, and butyl butyrate using an ultrasonic dispersion device. The mass ratio of the argyrodite-type sulfide solid electrolyte to the PVdF-based binder was 99.4:0.6. The solid electrolyte slurry was coated onto an Al foil substrate using the blade method, and this was dried on a hot plate at 100°C for 30 minutes to obtain a peelable solid electrolyte layer. (4) The above positive electrode active material layer and solid electrolyte layer are laminated and pressed in a roll press machine at a press pressure of 50 kN / cm and a temperature of 160°C, after which the Al foil is peeled off from the solid electrolyte layer, and 1 cm 2 A positive electrode laminate was obtained by punching out the material to the specified size. (5) The above-mentioned negative electrode active material layer and solid electrolyte layer were laminated and pressed in a roll press machine at a press pressure of 50 kN / cm and a temperature of 160°C, after which the Al foil was peeled off from the solid electrolyte layer to obtain a negative electrode laminate. Furthermore, an additional solid electrolyte layer was laminated on the solid electrolyte side of the above negative electrode laminate and pre-pressed in a flat single-axis press machine at a press pressure of 100 MPa and a temperature of 25°C, after which the Al foil was peeled off from the solid electrolyte layer, and 1.08 cm 2 By punching out the material to the specified size, a negative electrode laminate having an additional solid electrolyte layer was obtained. (6) The positive electrode laminate and the negative electrode laminate having an additional solid electrolyte layer were stacked so that their composite material surfaces overlapped, and pressed in a planar single-axis press at a pressing pressure of 200 MPa and a temperature of 120°C to obtain a battery laminate. (7) The battery stack was sandwiched between two restraining plates, and these two restraining plates were fastened together with fasteners to fix the distance between them, thereby obtaining a cell for evaluation.

[0104] 4. Measurement of volume For the evaluation cells, charging and discharging were performed at a voltage range of 0.45-3.25V and a current of 0.1C (1C = 220mA / g) in a constant temperature bath maintained at 25°C, and the initial discharge capacity was measured.

[0105] 5. Measuring Resistance For the evaluation cells, they were charged at 0.1C (1C = 220mA / g) in a constant temperature bath maintained at 25°C at a voltage range of 0.45-3.25V, then discharged until the state of charge (SOC) reached 80%, and after reaching 80% SOC, discharged again at 3.0C for 10 seconds, and the 5s resistance value at 80% SOC was measured. Similarly, they were discharged until the SOC reached 50%, and after reaching 50% SOC, discharged again at 3.0C for 10 seconds, and the 5s resistance value at 50% SOC was measured.

[0106] 6. Evaluation Results Table 1 below shows the crystal structure, chemical composition, and particle shape of each active material for Examples 1 and 2 and Comparative Examples 1 to 3, as well as the presence or absence of a sulfide solid electrolyte coating (SSE coating) and the coverage rate of the sulfide solid electrolyte coating. Table 2 below shows the initial discharge capacity, 5s resistance values ​​at SOC 50%, and 5s resistance values ​​at SCO 80% for evaluation cells using each active material from Examples 1 and 2 and Comparative Examples 1 to 3. [Table 1] [Table 2]

[0107] The results shown in Tables 1 and 2 indicate the following: (1) From the results of Examples 1 and 2 and Comparative Example 1, when plate-shaped active material particles having an O2-type structure are coated with a sulfide solid electrolyte on their surface, high capacity is maintained and resistance is reduced. (2) From the results of Comparative Examples 2 and 3, the resistance of spherical active material particles having an O2-type structure is not reduced, but rather increased, even when a sulfide solid electrolyte coating is applied to its surface. Furthermore, the discharge capacity is reduced compared to plate-shaped active material particles having an O2-type structure.

[0108] In the above examples, evaluation active materials having a predetermined chemical composition were used as illustrations, but the chemical composition of the active material is not limited thereto. It is believed that similar effects will be achieved if the active material contains at least one transition metal element from among Mn, Ni, and Co as a constituent element.

[0109] 7. Summary Based on the above results, the following composite active materials can be said to have high capacity and low resistance.

[0110] A composite active material having active material particles and a coated portion, The active material particles have an O2-type structure, The active material particles consist of the following constituent elements: Li and At least one transition metal element from Mn, Ni, and Co, O and, Includes, The active material particles are plate-shaped, The coating portion covers at least a part of the surface of the active material particles, The coating portion contains a sulfide solid electrolyte, Composite active material. [Explanation of Symbols]

[0111] 1 Composite active material 1a Active material particles 1ax active material part 1ay protective layer 1b Court Section 100 batteries 10 Cathode active material layer 20 Electrolyte layer 30 Negative electrode active material layer 40 Positive electrode current collector 50 Negative electrode current collector

Claims

1. A composite active material having active material particles and a coated portion, The active material particles have an O2 type structure, The active material particles consist of the following constituent elements: Li and, At least one transition metal element from Mn, Ni, and Co, O and, Includes, The active material particles are plate-shaped, The coating portion covers at least a part of the surface of the active material particles, The coating portion contains a sulfide solid electrolyte, Composite active material.

2. A composite active material according to claim 1, The coverage rate of the coating portion on the surface of the active material particles is 50% or more. Composite active material.

3. A composite active material according to claim 1, The active material particles have a protective layer on their surface, At least a portion of the surface of the protective layer is covered by the coating portion, The protective layer comprises Li, B, P, and O as constituent elements. Composite active material.

4. A composite active material according to claim 1, The active material particles contain Li, Mn, Ni, Co, and O as constituent elements. Composite active material.

5. A composite active material according to claim 1, The active material constituting the active material particles is Li ａ Na ｂ Mn ｘ－ｐ Ni ｙ－ｑ Co ｚ－ｒ M ｐ＋ｑ＋ｒ O ２ (where 0 < a ≤ 1.40, 0 ≤ b ≤ 0.20, x + y + z = 1, and 0 ≤ p + q + r < 0.17, and element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W) has the chemical composition shown, Composite active material.

6. A battery comprising a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, The positive electrode active material layer includes the composite active material described in any one of claims 1 to 5. battery.

7. The battery according to claim 6, The electrolyte layer includes a solid electrolyte. battery.

8. A method for producing a composite active material, To obtain active material particles, and The surface of the active material particles is covered with a coating. Includes, The active material particles have an O2 type structure, The active material particles consist of the following constituent elements: Li and, At least one transition metal element from Mn, Ni, and Co, O and, Includes, The active material particles are plate-shaped, The coating portion contains a sulfide solid electrolyte, A method for producing a composite active material.

9. A method for manufacturing a battery, To produce a composite active material by the method described in claim 8, At a minimum, the composite active material, the electrolyte, the conductive additive, and the binder are mixed to obtain an electrode composite material. Using the aforementioned electrode composite material, obtain a positive electrode active material layer. To obtain an electrolyte layer containing an electrolyte, and To obtain a negative electrode active material layer containing a negative electrode active material, A method for manufacturing batteries, including the invention of a battery.

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