Active material secondary particles, electrode mixture material, battery, and method for manufacturing active material secondary particles

Abstract

To disclose an active material with an O2-type structure, a high capacity, and a low resistance.SOLUTION: The active material secondary particles according to the present disclosure include a plurality of primary particles and a Li-ion conductive material. The primary particles have the O2-type structure. The particle diameter of the primary particles is 1.5 μm at a maximum. The primary particles are connected together through the Li-ion conductive material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present application discloses secondary active material particles, an electrode mixture, a battery, and a method for producing secondary active material particles. [Background technology]

[0002] Active materials for batteries having an O2 type structure are known. As disclosed in Patent Document 1, active materials having an O2 type structure are obtained by ion-exchanging at least a part of Na in a Na-containing oxide having a P2 type structure with Li. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-092824 A Summary of the Invention [Problem to be solved by the invention]

[0004] Active materials having an O2 type structure have room for improvement in terms of capacity and resistance. [Means for solving the problem]

[0005] The present application discloses the following aspects as means for solving the above problems. <Aspect 1> The secondary particles of the active material include a plurality of primary particles and a Li-ion conductive material; the plurality of primary particles have an O2 type structure; The particle size of the plurality of primary particles is 1.5 μm or less, The plurality of primary particles are bonded to each other via the Li ion conductive material. Active material secondary particles. <Aspect 2> The active material secondary particles of embodiment 1, A ratio M2 / M1 of a mass M2 of the Li-ion conductive material to a mass M1 of the primary particles is 0.01 or more and 0.20 or less. Active material secondary particles. <Aspect 3> The active material secondary particles according to embodiment 1 or 2, At least a portion of the plurality of primary particles are plate-like particles. Active material secondary particles. <Aspect 4> The active material secondary particles according to any one of aspects 1 to 3, The particle diameter of the active material secondary particles is 3 μm or more and 25 μm or less. Active material secondary particles. <Aspect 5> The active material secondary particles according to any one of aspects 1 to 4, The Li ion conductive material is an inorganic compound. Active material secondary particles. <Aspect 6> The active material secondary particles of embodiment 5, The inorganic compound is a Li-containing oxide. Active material secondary particles. <Aspect 7> An electrode mixture, The active material secondary particles according to any one of aspects 1 to 6, A solid electrolyte; 13. An electrode mixture comprising: <Aspect 8> 8. The electrode mixture of embodiment 7, The solid electrolyte includes a sulfide solid electrolyte. Electrode composite material. <Aspect 9> A battery having a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, The positive electrode active material layer contains the active material secondary particles according to any one of aspects 1 to 6. battery. <Aspect 10> 10. The battery of embodiment 9, comprising: The electrolyte layer includes a solid electrolyte. battery. <Aspect 11> A method for producing secondary particles of an active material, comprising the steps of: Combining a plurality of primary particles via a Li-ion conductive material to form secondary particles; Including, the plurality of primary particles have an O2 type structure; The particle diameter of the primary particles is 1.5 μm or less. A method for producing secondary particles of an active material. <Aspect 12> A method for producing active material secondary particles according to embodiment 11, comprising the steps of: preparing a solution in which the Li-ion conductive material is dissolved; and bringing the solution into contact with the plurality of primary particles and then drying the solution, thereby bonding the plurality of primary particles via the Li-ion conductive material to form secondary particles; A method for producing secondary particles of an active material comprising the steps of: Effect of the Invention

[0006] The active material secondary particles of the present disclosure have high capacity and low resistance. [Brief description of the drawings]

[0007] [Figure 1] 2 shows a schematic diagram of an example of the internal (cross-sectional) structure of a secondary particle of an active material. [Diagram 2] 1 shows an example of a flow of a method for producing secondary particles of an active material. [Diagram 3] 2 shows a schematic diagram of an example of the configuration of an electrode mixture. [Figure 4] 1 shows a schematic diagram of an example of a battery configuration. [Diagram 5] 1 is a SEM image of secondary particles of an active material according to Example 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An embodiment of the active material secondary particles, electrode mixture, battery, and method for producing active material secondary particles according to the present disclosure will be described below, but the active material secondary particles, electrode mixture, battery, and method for producing active material secondary particles according to the present disclosure are not limited to the embodiment described below.

[0009] 1. Active material secondary particles As shown in Fig. 1, an active material secondary particle 1 according to one embodiment includes a plurality of primary particles 1a and a Li-ion conductive material 1b. The primary particles 1a have an O2 type structure. The primary particles 1a have a particle diameter of 1.5 µm or less. The primary particles 1a are bonded to each other via the Li-ion conductive material 1b.

[0010] 1.1 Primary particles 1.1.1 Crystal structure The primary particle 1a according to an embodiment may have an O2 type structure and may have a crystal structure other than the O2 type structure. Examples of crystal structures other than the O2 type structure include a T♯2 type structure (belonging to the space group Cmca) formed when Li is deintercalated from the O2 type structure and an O6 type structure (belonging to the 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 also belonging to the space group R-3m). The primary particle 1a according to an embodiment may have an O2 type structure as a main phase, or may have a crystal structure other than the O2 type structure (for example, an O6 type structure) as a main phase. The primary particle 1a according to an embodiment may have a crystal structure serving as a main phase that changes depending on the charge / discharge state. The primary particle 1a according to an embodiment may be a single crystal consisting of one crystallite, or may be a polycrystal having multiple crystallites. In particular, when the primary particle 1a is a single crystal, the particle diameter described below is easily satisfied.

[0011] 1.1.2 Particle size There is room for improvement in the ion conduction path within the active material and between the active materials. In particular, when the O2 type active material is combined with a solid electrolyte, the resistance is likely to increase and sufficient capacity may not be exhibited. In response to this, fine primary particles 1a of the O2 type active material are used, and the primary particles 1a are bonded to each other via a Li ion conductive material 1b described later to form secondary particles, so that the ion conduction path within the active material and between the active materials is appropriately secured. For example, when the active material secondary particles 1 are combined with a solid electrolyte, the resistance is likely to be small and sufficient capacity is likely to be exhibited. According to the findings of the present inventors, such an effect can be exhibited significantly by the particle diameter of the multiple primary particles 1a being 1.5 μm or less. The smaller the particle diameter, the more significant the effect. The particle diameter may be more than 0 μm and 1.5 μm or less, more than 0 μm and 1.0 μm or less, or 0.1 μm or more and 0.5 μm or less.

[0012] The "particle diameter of the primary particles" refers to the "average particle diameter" of the multiple primary particles 1a constituting the active material secondary particle 1. The "average particle diameter" of the multiple primary particles can be determined by observing the appearance of the active material secondary particle 1 with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Specifically, a two-dimensional image of the active material secondary particle 1 is obtained with an SEM or the like, and the area of ​​each of any 10 primary particles among the multiple primary particles constituting the active material secondary particle 1 contained in the two-dimensional image is determined, and the area is converted into a circle to determine the circle-equivalent diameter of each primary particle, and the number average value of each circle-equivalent diameter is determined as the "average particle diameter."

[0013] 1.1.3 Shape The primary particles 1a according to an embodiment can be obtained by substituting Li for Na in a Na-containing oxide having a P2-type structure, as described later. Here, the P2-type structure is a hexagonal crystal system, has a large diffusion coefficient of Na ions, and is likely to grow crystals 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, the crystals tend to grow in a plate-like shape in a specific direction. Therefore, the Na-containing oxide having the P2-type structure tends to become a plate-like particle with a large aspect ratio in which the crystal growth direction is biased in a specific direction. The primary particles 1a according to an embodiment may be obtained based on such plate-like Na-containing oxide particles, or may be obtained based on spherical Na-containing oxide particles. That is, the shape of the primary particles 1a may be a plate-like particle, a spherical particle, or an indeterminate shape. According to the knowledge of the present inventor, when at least a part of the multiple primary particles 1a constituting the active material secondary particle 1 is a plate-like particle, the capacity is further improved and the resistance is likely to be reduced.

[0014] In the present application, the term "plate-like particle" refers to a particle having an aspect ratio of 1.5 or more and 10 or less. Here, the "aspect ratio" of the primary particle 1a is measured as follows. That is, a cross section of the active material secondary particle (when the secondary particle is contained in the positive electrode active material layer described later, it may be a cross section of the positive electrode active material layer) is observed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM) to identify the shape of the primary particle contained in the active material secondary particle. In the shape, the maximum Feret diameter is identified and regarded as the "major axis". In addition, in the shape, the largest diameter perpendicular to the "major axis" is regarded as the "minor axis". The ratio of the "major axis" to the "minor axis" (major axis / minor axis) is regarded as the "aspect ratio" of the primary particle 1a.

[0015] In addition, "spherical particles" refers to particles having a circularity of 0.80 or more. The circularity of the particles may be 0.81 or more, 0.82 or more, 0.83 or more, 0.84 or more, 0.85 or more, 0.86 or more, 0.87 or more, 0.88 or more, 0.89 or more, or 0.90 or more. The circularity of the particles is 4πS / L 2Here, S is the orthogonal projected area of ​​the particle, and L is the perimeter of the orthogonal projected image of the particle. The circularity of a particle can be determined by observing the appearance of the particle using a scanning electron microscope (SEM), transmission electron microscope (TEM), or optical microscope.

[0016] 1.1.4 Chemical composition The chemical composition of the primary particles 1a is not particularly limited as long as the O2 type structure is maintained. The primary particles 1a may contain, for example, at least one element selected from Mn, Ni, and Co, Li, and O as constituent elements. The primary particles 1a are particularly likely to achieve higher performance when they contain, as constituent elements, at least Li, Mn, one or both of Ni and Co, and O, and particularly when they contain, as constituent elements, at least Li, Mn, Ni, Co, and O.

[0017] Primary particle 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 ≤ 1.00, 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 primary particle 1a has such a chemical composition, the O2-type structure is likely to be maintained. In the above chemical composition, a 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 is at most 1.00, and may be 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, 0.40 or more, or 0.50 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, or 0.50 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, or 0.30 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, or 0.30 or less. The element M has a small contribution to charge and discharge. In this regard, in the above chemical composition, since p + q + r is less than 0.17, a high charge and discharge capacity is likely to be 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 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 0.10 or more.The composition of O is approximately 2, but is not necessarily exactly 2.0 and is variable.

[0018] 1.1.5 Other There is no particular limitation on the number of primary particles 1a contained in the active material secondary particle 1. In one embodiment, one active material secondary particle 1 may contain 2 or more, 5 or more, 10 or more, 50 or more, or 100 or more primary particles 1a, or may contain 10,000 or less, 5,000 or less, or 1,000 or less. In particular, when the number satisfies the secondary particle diameter described below, higher performance is likely to be exhibited.

[0019] 1.2 Li-ion conductive materials As described above, in the active material secondary particle 1, a plurality of primary particles 1a are bonded together via the Li-ion conductive material 1b. The Li-ion conductive material may be any material that can bond a plurality of primary particles 1a together and ensure Li-ion conductive paths between the primary particles 1a. The Li-ion conductive material 1b may be an inorganic compound or an organic compound, but high performance is particularly likely to be ensured when the Li-ion conductive material 1b is an inorganic compound. The active material secondary particle 1 may be substantially free of an organic compound (the content of the organic compound is less than 0.01% by mass).

[0020] 1.2.1 Li-ion conductive inorganic compounds The Li-ion conductive inorganic compound may be, for example, at least one selected from Li-containing oxides and Li-containing halides, and high performance is particularly likely to be ensured when the compound is a Li-containing oxide.

[0021] The Li-containing oxide 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, Li, and O. The Li-containing oxide may be an oxynitride containing N. More specifically, the Li-containing oxide may be Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, Li4Ti5O 12 , Li2Ti2O5, Li2ZrO3, LiNbO3, Li2MoO4, Li2WO4, LiPON, Li2O-LaO2, Li2O-ZnO2, etc. The Li-containing oxide may be one in which some elements are substituted with various doping elements.

[0022] The Li-containing halide may be, for example, at least one of various compounds exemplified as the halide solid electrolyte described later. The Li-containing halide may include, 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, at least one halogen element selected from the group consisting of Cl, Br, I and F, and Li. The Li-containing halide may 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. The Li-containing halide may also 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. The Li-containing halide may also be, for example, a complex halide of Li, Ti, Al and F.

[0023] 1.2.2 Shape The shape of the Li-ion conductive material 1b in the active material secondary particle 1 is not particularly limited. In the active material secondary particle 1 according to an embodiment, the Li-ion conductive material 1b can cover the surface of the primary particle 1a. In this case, the coverage (area ratio) of the Li-ion conductive material 1b with respect to the surface of the primary particle 1a may be, for example, 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more. When the Li-ion conductive material 1b is layered, the thickness of the layer may be, for example, 0.1 nm or more or 1 nm or more, and may be 1 μm or less, 100 nm or less, or 20 nm or less.

[0024] 1.3 Mass ratio of primary particles to Li-ion conductive material The mass ratio of the primary particles 1a and the Li-ion conductive material 1b in the active material secondary particles 1 is not particularly limited as long as the secondary particles can be maintained. According to the findings of the present inventors, when the ratio M2 / M1 of the mass M1 of the primary particles 1a contained in the active material secondary particles 1 to the mass M2 of the Li-ion conductive material 1b is 0.01 or more and 0.20 or less, better performance in terms of capacity and resistance is likely to be ensured while maintaining the secondary particles. The ratio M2 / M1 may be 0.03 or more and 0.18 or less, 0.05 or more and 0.16 or less, or 0.07 or more and 0.14 or less.

[0025] 1.4 Secondary particle size The particle diameter (secondary particle diameter) of the active material secondary particles 1 is not particularly limited. Effects relating to capacity and resistance can be exhibited regardless of the size of the active material secondary particles 1. According to the findings of the present inventors, when the particle diameter of the active material secondary particles 1 is 2 μm or more and 30 μm or less, 3 μm or more and 25 μm or less, or 5 μm or more and 20 μm or less, the active material secondary particles 1 are easily granulated and the Li conduction distance inside the active material secondary particles 1 is easily shortened.

[0026] The "particle diameter of the active material secondary particles" can be determined by observing the appearance of the active material secondary particles 1 with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Specifically, a two-dimensional image of the active material secondary particles 1 is obtained with an SEM or the like, the area of ​​the active material secondary particles 1 contained in the two-dimensional image is determined, the area is converted into a circle to determine the circle-equivalent diameter, and the circle-equivalent diameter is determined as the "particle diameter of the active material secondary particles".

[0027] 1.5 Other The active material secondary particles 1 may or may not have voids. Even if the active material secondary particles 1 have voids, as described above, by bonding the fine primary particles 1a together with the Li-ion conductive material 1b, sufficient ion conduction paths can be secured, and high performance can be secured.

[0028] 2. Method for producing secondary particles of active material The above-mentioned active material secondary particles 1 can be produced, for example, by the following method. That is, the method for producing the active material secondary particles 1 according to one embodiment includes bonding a plurality of primary particles 1a via a Li-ion conductive material 1b to form secondary particles. Here, the plurality of primary particles 1a have an O2 type structure, and the particle diameter of the plurality of primary particles 1a is 1.5 μm or less.

[0029] 2.1 An example of secondary particle formation The method of bonding a plurality of primary particles 1a via the Li-ion conductive material 1b to form secondary particles is not particularly limited. For example, as shown in FIG. 2, a solution 1bx in which the Li-ion conductive material 1b is dissolved is brought into contact with a plurality of primary particles 1a, whereby the plurality of primary particles 1a can be bonded via the Li-ion conductive material 1b to form secondary particles. That is, the method of manufacturing the active material secondary particles 1 according to one embodiment is as follows: Preparing a solution 1bx in which a Li-ion conductive material 1b is dissolved; and bringing the solution 1bx into contact with the plurality of primary particles 1a and then drying the solution 1bx to bond the plurality of primary particles 1a via the Li-ion conductive material 1b to form secondary particles; More specifically, the method for producing the active material secondary particles 1 according to one embodiment includes the steps of: S1: Obtaining a slurry including a plurality of primary particles 1a and a solution 1bx; S2: forming droplets from the slurry to obtain slurry droplets 1x containing a plurality of primary particles 1a and a solution 1bx; and S3: Drying the slurry droplets 1x in a heated gas flow to bond the plurality of primary particles 1a via the Li-ion conductive material 1b to form secondary particles; It may include.

[0030] 2.1.1 Solution 1bx When the surface of the primary particle 1a is coated with a Li-containing oxide containing Li and an element A other than Li, the solution 1bx may contain a lithium source and an A source. The element A may be at least one selected from B, C, Al, Si, P, S, Ti, La, Zr, Nb, Mo, Zn, and W. The solution 1bx may contain lithium ions as a lithium source. For example, a lithium compound such as LiOH, LiNO3, or Li2SO4 may be dissolved in a solvent to obtain the solution 1bx containing lithium ions as a lithium source. Alternatively, the solution 1bx may contain an alkoxide of lithium as a lithium source. The solution 1bx may also contain a peroxo complex of the element A as an A source. Alternatively, the solution 1bx may contain an alkoxide of the element A as an A source. For example, when a plurality of primary particles 1a are bonded to each other via lithium niobate, the solution 1bx may contain at least a lithium source and a niobium source. In this case, the solution 1bx may contain at least one of a phosphorus source and a boron source in addition to the lithium source and the niobium source. Alternatively, instead of the niobium source, at least one of a phosphorus source and a boron source may be contained. For example, by substituting a part of Nb in lithium niobate with P (or doping lithium niobate with P), the voltage resistance is easily improved. The molar ratio of the lithium source and the A source contained in the solution 1bx is not particularly limited. For example, the molar ratio Li / A may be 0.5 or more or 0.8 or more, and may be 2.0 or less or 1.5 or less. The solvent constituting the solution 1bx may be any one capable of dissolving the above-mentioned lithium source, etc., and either water or an organic solvent may be adopted.

[0031] 2.1.2 Slurry The term "slurry" refers to a suspension or a suspension containing primary particles 1a and a solution 1bx, and may have fluidity sufficient to form droplets. The slurry may have fluidity sufficient to form droplets using, for example, a spray nozzle or a rotary atomizer. The solid content concentration of the slurry may be determined according to the type of primary particles 1a, the type of solution 1bx, and the conditions for forming droplets (the type of device used for forming droplets). The solid content concentration of the slurry is not particularly limited, and may be, for example, 1 vol% or more, 5 vol% or more, 10 vol% or more, 20 vol% or more, 25 vol% or more, 30 vol% or more, 35 vol% or more, 40 vol% or more, 45 vol% or more, 50 vol% or more, or 70 vol% or less, 65 vol% or less, 60 vol% or less, 55 vol% or less, 50 vol% or less, 45 vol% or less, 40 vol% or less, 35 vol% or less, 30 vol% or less, 25 vol% or less, or 20 vol% or less. By adjusting the solid content concentration in the slurry, the particle size and other properties of the finally obtained active material secondary particles 1 can be controlled.

[0032] 2.1.3 Slurry dropletization The "dropletization" of the slurry means that the slurry containing a plurality of primary particles 1a and the solution 1bx is made into grains (droplets 1x) containing a plurality of primary particles 1a and the solution 1bx. In addition to the droplets 1x, other droplets such as grains containing only the solution 1bx may be generated. The method of making the slurry containing a plurality of primary particles 1a and the solution 1bx into droplets is not particularly limited. For example, the slurry may be sprayed to obtain slurry droplets. When spraying the slurry, a spray nozzle may be used. Examples of methods for spraying the slurry using a spray nozzle include, but are not limited to, a pressurized nozzle method and a two-fluid nozzle method. When spraying the slurry using a spray nozzle, the nozzle diameter is not particularly limited. The nozzle diameter may be, for example, 0.1 mm or more, 0.5 mm or more, or 1 mm or more, or 10 mm or less, 5 mm or less, or 1 mm or less. In addition, the spray speed of the slurry (the supply speed (liquid delivery speed) of the slurry to the spray nozzle) and the spray pressure are also not particularly limited. The spray speed and injection pressure may be adjusted depending on the viscosity and solid content concentration of the slurry, the nozzle dimensions, etc. By controlling the slurry delivery speed and injection pressure, the particle size and other factors of the finally obtained active material secondary particles 1 can be controlled.

[0033] As a method for turning the slurry into droplets, in addition to the above-mentioned method of spraying the slurry using a spray nozzle, for example, a method of supplying the slurry onto a rotating disk at a constant speed and turning it into droplets by centrifugal force can be exemplified. Alternatively, a method of turning the slurry into droplets by applying a high voltage to the surface of the slurry can also be adopted. In the manufacturing method according to one embodiment, for example, the slurry may be turned into droplets and dried by airflow using a spray dryer. The type of spray dryer is not particularly limited, and examples include a method using the above-mentioned spray nozzle and a method using a rotating disk.

[0034] 2.1.4 Slurry droplets As described above, the "slurry droplet" may include a particle (droplet 1x) containing a plurality of primary particles 1a and a solution 1bx, or a particle (other droplet) consisting of the solution 1bx. The size of the slurry droplet is not particularly limited. The diameter (sphere equivalent diameter) of the droplet 1x may be, for example, 0.1 μm or more, 0.5 μm or more, or 5.0 μm or more, or 5000 μm or less, 1000 μm or less, or 500 μm or less. The diameter of the slurry droplet can be measured, for example, using a two-dimensional image obtained by capturing an image of the slurry droplet. Alternatively, the droplet diameter can be estimated from the operating conditions of the device that forms the slurry droplet.

[0035] 2.1.5 Air drying "Air flow drying" refers to drying the slurry droplets while suspending them in a high-temperature air flow. "Air flow drying" can include not only drying but also an additional operation using a dynamic air flow. By continuously applying hot air to the slurry droplets during air flow drying, a force is continuously applied to the slurry droplets. By controlling the conditions of air flow drying, the particle size, etc. of the finally obtained active material secondary particles 1 can be controlled.

[0036] The temperature of the heating gas may be any temperature that can volatilize the solvent from the slurry droplets. For example, the temperature may be 100°C or higher, 110°C or higher, 120°C or higher, 130°C or higher, 140°C or higher, 150°C or higher, 160°C or higher, 170°C or higher, 180°C or higher, 190°C or higher, 200°C or higher, 210°C or higher, 220°C or higher, 230°C or higher, 240°C or higher, or 250°C or higher. Whether the surface of the primary particles 1a is covered with the solution 1bx is considered to vary greatly depending on the surface energy of the solution 1bx. By increasing the temperature of the heating gas to a high temperature, the solution 1bx also becomes hot, and the surface energy of the solution 1bx changes significantly, which may reduce the amount of the solution 1bx that can be fixed to the surface of the primary particles 1a. In other words, by controlling the temperature of the heating gas, the mass ratio of the primary particles 1a and the Li-ion conductive material 1b in the active material secondary particles 1 finally obtained can be controlled.

[0037] The supply amount (flow rate) of the heating gas can be appropriately set in consideration of the size of the device used, the supply amount of the slurry droplets, etc. For example, the flow rate of the heating gas is 0.10 m 3 / min or more, 0.15m 3 / min or more, 0.20m 3 / min or more, 0.25m 3 / min or more, 0.30m 3 / min or more, 0.35m 3 / min or more, 0.40m 3 / min or more, 0.45m 3 / min or more, or 0.50m 3 / min or more, and may be 5.00m 3 / min or less, 4.00m 3 / min or less, 3.00m 3 / min or less, 2.00m 3 / min or less, or 1.00m 3 The supply velocity (flow rate) of the heated gas can also be appropriately set in consideration of the size of the device used, the supply amount of the slurry droplets, etc. For example, the flow rate of the heated gas may be 1 m / sec or more or 5 m / sec or more, and may be 50 m / sec or less or 10 m / sec or less in at least a part of the system.

[0038] The treatment time (drying time) with the heated gas can also be appropriately set in consideration of the size of the device used, the supply amount of slurry droplets, etc. For example, the treatment time may be 5 seconds or less, or 1 second or less.

[0039] In the flash drying, a heated gas that is substantially inert to the primary particles 1a and the solution 1bx may be used. For example, an oxygen-containing gas such as air, an inert gas such as nitrogen or argon, or low-dew-point dry air may be used.

[0040] As a device for performing air flow drying, for example, a spray dryer can be used, but is not limited thereto.

[0041] 2.2 Production method of primary particles The primary particles 1a having an O2 type structure and a particle diameter of 1.5 μm or less can be produced, for example, by the following method. That is, the method for producing the primary particles 1a according to one embodiment is as follows: S11: Obtaining a precursor (e.g., a precursor including at least one element of Mn, Ni, and Co); S12: Coating the surface of the precursor with a Na source to obtain a composite; S13: Calcining the composite to obtain a Na-containing oxide having a P2 type structure; and S14: At least a part of the Na in the Na-containing oxide is ion-exchanged with Li to obtain primary particles 1a having an O2 type structure. Here, S13 is S13-1: Pre-firing the composite at a temperature of 300°C or higher and lower than 700°C for 2 hours or higher and 10 hours or lower; S13-2: Following the preliminary firing, the composite is subjected to a main firing at a temperature of 700° C. or more and 1100° C. or less for a period of 30 minutes to 48 hours or less; and S13-3: Following the main sintering, the composite may be rapidly cooled from a temperature T1 of 200° C. or higher to a temperature T2 of 100° C. or lower.

[0042] 2.2.1 Preparation of precursor The precursor may contain at least Mn and one or both of Ni and Co, or may contain at least Mn, Ni, and Co. The precursor may be a salt containing at least one element of Mn, Ni, and Co. For example, the precursor may be at least one of carbonate, sulfate, nitrate, and acetate. 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 types of compounds. The precursor may have various shapes. For example, the precursor may be particulate, or may be spherical particles as described later. The particle size of the particles made of the precursor is not particularly limited.

[0043] In S11, a precipitate as the precursor may be obtained by a co-precipitation method using an ion source capable of forming a precipitate in an aqueous solution with transition metal ions and a transition metal compound containing at least one element selected from Mn, Ni, and Co. This makes it easier to obtain spherical particles as the precursor. The "ion source capable of forming a precipitate in an aqueous solution with transition metal ions" 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 salt or hydroxide containing at least one element selected from Mn, Ni, and Co. Specifically, in S1, the ion source and the transition metal compound may be prepared as solutions, and the solutions may be dropped and mixed to obtain a precipitate as the precursor. In this case, for example, water is used as the solvent. In this case, various sodium compounds may be used as the base, and an aqueous ammonia solution or the like may be added to adjust the basicity. In the case of the co-precipitation method, for example, an aqueous solution of a transition metal compound and an aqueous solution of sodium carbonate are prepared, and the aqueous solutions are dropped and mixed to obtain a precipitate as the precursor. Alternatively, the precursor can be obtained by a sol-gel method, and in particular, by a coprecipitation method, spherical particles can be easily obtained as the precursor.

[0044] 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 a function of stabilizing, for example, a P2 type structure or an O2 type structure. The method of obtaining a precursor containing element M is not particularly limited. When the precursor is obtained 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 dropped and mixed to obtain a precursor containing element M together with at least one element of Mn, Ni, and Co. Alternatively, in the manufacturing method of the present disclosure, element M may not be added in S1, and element M may be doped when Na-doping baking is performed in S2 and S3 described later.

[0045] 2.2.2 Preparation of the complex In S12, the surface of the precursor obtained in S11 is coated with a Na source to obtain a composite. The Na source may be a salt containing Na, such as carbonate or nitrate, or a compound other than salt, such as sodium oxide or sodium hydroxide. In S12, the amount of the Na source coated on the surface of the precursor may be determined taking into account the amount of Na lost during the subsequent firing. In S12, 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 in a mortar or a mixer, or the precursor may be contacted with a solution containing a Na source using a tumbling fluidized coating method or a spray drying method, and then dried.

[0046] In S12, the precursor may be coated with an M source together with a Na source. For example, in S12, the precursor obtained in S1, a Na source, and an 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 may be mixed to obtain a composite. The M source may be, for example, a salt containing the 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 may be determined according to the chemical composition of the Na-containing oxide after firing.

[0047] 2.2.3 Firing of the composite In S13, the composite obtained in S12 is calcined to obtain a Na-containing oxide having a P2 type structure. S13 may include the above S13-1, S13-2, and S13-3.

[0048] In S13-1, the composite is pre-fired at a temperature of 300° C. or more and less than 700° C. for 2 hours or more and 10 hours or less. In S13-1, the composite may be optionally molded and then pre-fired. The pre-fire is performed at a temperature lower than that of the main firing. If the pre-fire in S13-1 is insufficient, the P2 phase may not be sufficiently generated in the finally obtained Na-containing oxide. In S13-1, the pre-fire temperature is 300° C. or more and less than 700° C., and the pre-fire time is 2 hours or more and 10 hours or less, so that the composite can be sufficiently pre-fired, the heat uniformity is improved, and the Na-containing oxide obtained through S13-2 and S13-3 described later is likely to be appropriate. The pre-firing temperature may be 400° C. or more and less than 700° C., 450° C. or more and less than 700° C., 500° C. or more and less than 700° C., 550° C. or more and less than 700° C., or 550° C. or more and less than 650° C. The pre-firing time may be 2 hours or more and less than 8 hours, 3 hours or more and less than 8 hours, 4 hours or more and less than 8 hours, 5 hours or more and less than 8 hours, or 5 hours or more and less than 7 hours. The pre-firing atmosphere is not particularly limited, and may be, for example, an oxygen-containing atmosphere.

[0049] In S13-2, following the above pre-firing, the composite is subjected to main firing at a temperature of 700°C to 1100°C for 30 minutes to 48 hours. In S13-2, the main firing temperature of the composite may be 800°C to 1000°C. If the main firing temperature is too low, the P2 phase is not generated, and if the main firing temperature is too high, the O3 phase and the like are likely to be generated instead of the P2 phase. The temperature rise condition from the pre-firing temperature to the main firing temperature is 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 generation of the P2 phase is insufficient. On the other hand, if the main firing time is too long, the P2 phase grows excessively and the particles become coarse. By adjusting the main firing time, the particle size of the primary particles 1a can be controlled to 1.5 μm or less.

[0050] In step S13-3, following the main firing, the composite is rapidly cooled (cooled at a temperature drop rate of 20°C / min or more) from a temperature T1 of 200°C or more to a temperature T2 of 100°C or less. The preliminary firing and main firing are performed, for example, in a heating furnace. In step S13-3, for example, after the main firing of the composite is performed in a heating furnace, it is cooled to an arbitrary temperature T1 of 200°C or more in the heating furnace, and after the temperature T1 is reached, the fired product is removed from the heating furnace and rapidly cooled outside the furnace to an arbitrary temperature T2 of 100°C or less. The temperature T1 may be an arbitrary temperature of 200°C or more, or an arbitrary temperature of 250°C or more. The temperature T2 may be an arbitrary temperature of 100°C or less, or an arbitrary temperature of 50°C or less, or may be the cooling end temperature. In a certain temperature range between the temperature T1 and the temperature T2, moisture is likely to penetrate between the layers of the P2 type structure due to atomic vibration, molecular motion, etc. When cooling the composite (Na-containing oxide having a P2 type structure) after the main firing, it is considered that the amount of moisture penetrating between the layers of the P2 type structure is reduced by shortening the time in which the temperature range in which moisture easily penetrates (i.e., by cooling quickly). In this regard, when cooling the composite after the main firing in step S13-3, for example, by cooling in a dry atmosphere outside the furnace from an arbitrary temperature T1 of 200°C or more to an arbitrary temperature T2 of 100°C or less, the cooling rate from temperature T1 to temperature T2 is high (for example, 20°C / min or more), moisture is less likely to penetrate between the layers of the P2 type structure, and the collapse of the P2 type structure can be suppressed. As a result, Na can be efficiently ion-exchanged with Li in S4.

[0051] By S13, a Na-containing oxide having a P2 type structure and a predetermined chemical composition can be produced. The Na-containing oxide contains at least one transition metal element selected from Mn, Ni, and Co, Na, and O as constituent elements. In particular, when the constituent elements contain at least Na, Mn, at least one of Ni and Co, and O, and especially when the constituent elements contain at least Na, Mn, Ni, Co, and O, the performance of the positive electrode active material is more likely to be improved. The Na-containing oxide contains 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 has 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, 0.40 or more, or 0.50 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, or 0.50 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, or 0.30 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, or 0.30 or less. The contribution of element M to charge and discharge is small. In this regard, in the above chemical composition, when p + q + r is less than 0.17, a high charge and discharge capacity is likely to be 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 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 0.10 or more. The composition of O is approximately 2, but is not necessarily exactly 2.0 and is indefinite.

[0052] 2.2.4 Ion exchange In S14, at least a part of Na in the Na-containing oxide obtained in S13 is ion-exchanged with Li to obtain primary particles 1a having an O2 type structure. For example, there are a method using an aqueous solution containing lithium halide and a method using a mixture of lithium halide and other lithium salts (for example, molten salt) for ion exchange. 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 molten salt is preferable among the above two methods. 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 equal to or higher than the melting point of the molten salt, at least a part of 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 the molten salt, the melting point becomes lower than when lithium halide or other lithium salt is used alone, and ion exchange can be performed at a lower temperature. The temperature in the ion exchange may be, for example, above the melting point of the molten salt and below 600°C, below 500°C, below 400°C, or below 300°C. If the temperature in the ion exchange is too high, the stable O3 structure is likely to be formed instead of the O2 structure. On the other hand, from the viewpoint of shortening the time required for the ion exchange, it is preferable that the temperature in the ion exchange is as high as possible.

[0053] 2.3 Other processes The manufacturing method of the active material secondary particle 1 according to an embodiment may include, for example, doping the primary particle 1a constituting the active material secondary particle 1 with Li. This can further increase the capacity of the active material secondary particle 1. For example, the primary particle 1a can be doped with Li by contacting the primary particle 1a with a reducing solution containing Li ions. The "reducing solution" means a solution having reducing properties, and may be, for example, a solution containing an electrophile. The reducing solution may be obtained by dissolving the electrophile and the Li source in a solvent. As the solvent, various organic solvents capable of dissolving the electrophile and the Li source may be used. As the electrophile, various substances that dissolve in the above-mentioned solvent may be used. The electrophile may be an aromatic organic compound. As the Li source, various substances that dissolve in the above-mentioned solvent to generate Li ions may be used. The Li source may be metallic lithium or a Li compound. The concentrations of the electrophile and Li ions contained in the reducing solution may be appropriately determined according to the desired doping amount. According to the findings of the present inventors, 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 doped in the Li-containing transition metal oxide. The molar ratio of the electrophile and Li ions contained in the reducing solution (electrophile / Li ions) is not particularly limited. The form of contact between the reducing solution and the primary particles 1a is not particularly limited. For example, the primary particles 1a may be immersed in the reducing solution, or the reducing solution may be sprayed onto the primary particles 1a. There is no particular limit to the temperature during contact, and the solution may be heated or not heated. The primary particles 1a may be immersed in the reducing solution and then stirred. There is no particular limit to the time for which the primary particles 1a are contacted with the reducing solution, and it may be appropriately determined according to the desired doping amount. The timing for doping the primary particles 1a with Li may be before or after the secondary particles are formed.

[0054] Furthermore, the method for producing the active material secondary particles 1 according to one embodiment may include pulverizing the Na-containing oxide having the P2 type structure or the primary particles 1a having the O2 type structure to obtain primary particles 1a having a particle diameter of 1.5 μm or less, and / or classifying the Na-containing oxide having the P2 type structure or the primary particles 1a having the O2 type structure to obtain primary particles 1a having a particle diameter of 1.5 μm or less. That is, the particle diameter of the primary particles 1a may be controlled by the firing conditions of the Na-containing oxide having the P2 type structure or the like, or may be adjusted by pulverization or classification.

[0055] 3. Electrode composite material The active material secondary particles 1 may, for example, constitute an electrode mixture together with other substances. For example, as shown in FIG. 3, an electrode mixture 5 according to an embodiment may contain the active material secondary particles 1 of the present disclosure and a solid electrolyte 2. The electrode mixture 5 according to an embodiment may optionally contain a conductive assistant, a binder, and other additives. The contents of the active material, electrolyte, conductive assistant, binder, and the like in the electrode mixture 5 may be appropriately determined according to the intended battery performance. For example, the content of the active material may be 40% by mass or more and less than 100% by mass, and the content of the solid electrolyte may be more than 0% by mass and 60% by mass or less, assuming that the entire solid content contained in the electrode mixture 5 is 100% by mass. The content of the active material in the electrode mixture 5 may be 50 mass% or more, 60 mass% or more, 70 mass% or more, or 80 mass% or more, or 90 mass% or less, and the content of the solid electrolyte may be 10 mass% or more, and 50 mass% or less, 40 mass% or less, 30 mass% or less, or 20 mass% or less. These lower and upper limits may be combined in any desired manner.

[0056] 3.1 Active material The active material contained in the electrode composite material 5 may consist only of the above-described active material secondary particles 1, or may contain, together with the active material secondary particles 1, other active materials (other active substances). From the viewpoint of further enhancing the effects of the technology of the present disclosure, the proportion of other active materials in the total active material contained in the electrode composite material 5 may be small. For example, assuming that the total amount of the active material contained in the electrode composite material 5 is 100% by mass, the content of the above-described active material secondary particles 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.

[0057] As the other active materials that can be contained in the electrode composite material 5, any known active materials can be adopted. The electrode composite material 5 may contain, as the other active material, for example, the primary particles 1a having the above-described O2-type structure in a state where they are not secondary particleized. Further, the electrode composite material 5 may contain, as the other active material, at least one selected from various lithium compounds other than the primary particles 1a, elemental sulfur, sulfur compounds, and the like. The lithium compound as the other active material 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 the other active material is 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-yM y Li-Mn spinel substituted with different elements having a composition represented by the formula: O4 (M is one or more selected from Al, Mg, Co, Fe, Ni, and Zn), etc.), lithium nickel cobalt aluminate (for example, Li 1±α Ni p Co q Al r O 2±δ (e.g., p+q+r=1), lithium titanate, lithium metal phosphate (e.g., LiMPO4, where M is one or more selected from Fe, Mn, Co, and Ni), and the like. In particular, when the other active material contains a Li-containing oxide containing at least one of Ni, Co, and Mn, Li, and O as a constituent element, higher performance is likely to be obtained. Alternatively, when the other active material contains a Li-containing oxide containing at least one of Ni, Co, and Al, Li, and O as a constituent element, higher performance is likely to be obtained. Only one type of other active material may be used alone, or two or more types may be used in combination. The shape of the other active material may be a general shape for an active material. The other active material may be, for example, particulate. The other active material may be solid or may have voids, for example, porous or hollow. The other active material may be primary particles, or may be secondary particles in which a plurality of primary particles are aggregated. 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 be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less.

[0058] 3.2 Electrolytes The electrode mixture 5 may contain an electrolyte together with the above-mentioned active material secondary particles 1. The electrolyte that may be contained in the electrode mixture 5 may be a solid electrolyte, a liquid electrolyte, or a combination thereof. In particular, as described above, when the electrode mixture 5 contains a solid electrolyte, the effect of the technology of the present disclosure becomes more remarkable.

[0059] 3.2.1 Solid electrolyte As the solid electrolyte, a known solid electrolyte for batteries may be used. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, the inorganic solid electrolyte has excellent ion conductivity and heat resistance. Examples of the inorganic solid electrolyte include an oxide solid electrolyte, a sulfide solid electrolyte, and an ion-bonded inorganic solid electrolyte. In particular, when the electrode mixture 5 contains a sulfide solid electrolyte as a solid electrolyte, higher performance is likely to be ensured. The sulfide solid electrolyte may contain at least Li, S, and P as constituent elements, for example. Alternatively, the electrode mixture 5 may contain an ion-bonded solid electrolyte as a solid electrolyte, and may contain, 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 diameter (D50) of the solid electrolyte may be, for example, 10 nm or more and 10 μm or less. The solid electrolyte may be used alone or in combination of two or more kinds.

[0060] The oxide solid electrolyte is lithium lanthanum zirconate, LiPON, Li 1+X Al X Ge 2-X It may be one or more selected from (PO4)3, Li-SiO-based glass, Li-Al-SO-based glass, etc. In addition, when an oxide solid electrolyte is combined with a liquid electrolyte, ion conductivity can be improved.

[0061] 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). In addition, when the sulfide solid electrolyte has a crystalline phase, examples of the crystalline phase include a Thio-LISICON type crystalline phase, a LGPS type crystalline phase, and an Argyrodite type crystalline phase. The sulfide solid electrolyte may be particulate. The average particle diameter (D50) of the sulfide solid electrolyte may be, for example, 10 nm or more and 100 μm or less.

[0062] The sulfide solid electrolyte may contain, for example, Li element, X element (X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S element. The sulfide solid electrolyte may further contain at least one of O element and halogen element. The sulfide solid electrolyte may contain S element as a main component of anion element.

[0063] Examples of sulfide solid electrolytes include 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, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li x MO y (wherein x and y are positive numbers, and M is any one of P, Si, Ge, B, Al, Ga, and In).

[0064] 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. may 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 with 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 with 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 with at least one of Na, K, Mg, Ca, and Zn. In the above general formula, a part of S may be substituted with a halogen (at least one of F, Cl, Br, and I). Alternatively, the sulfide solid electrolyte is Li 7-a PS 6-a X a (X is at least one of Cl, Br, and I, and a is a number of 0 or more and 2 or less). a may be 0, or may be greater than 0. In the latter case, a may be 0.1 or more, may be 0.5 or more, and may be 1 or more. Also, a may be 1.8 or less, may be 1.5 or less.

[0065] The ion-bonded solid electrolyte may contain at least one element selected from the group consisting of, for example, Mg, Ca, Sr, Ba, Zn, Sn, Al, Sc, Ga, Bi, Sb, Zr, Hf, Ti, Ta, Nb, W, Y, Gd, Tb and Sm. These elements may generate cations in water. The ion-bonded solid electrolyte material may further contain, for example, at least one halogen element selected from the group consisting of Cl, Br, I and F. These elements may generate anions in water. The ion-bonded 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. The ion-bonded 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 may contain Li, Ca, Y, Gd, Cl, and Br, or may contain 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 Cl6.

[0066] The ionically bonded solid electrolyte may be a halide solid electrolyte. The halide solid electrolyte has excellent ion conductivity. Examples of the halide solid electrolyte include those represented by the 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 contained in Groups 1 to 12 of the periodic table (excluding hydrogen) and (ii) all elements contained in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se). The metal element can form an inorganic compound with the halide ion and become a cation.

[0067] 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 at least one selected from the group consisting of, for example, Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0068] 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 also be applicable. 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 the formula. 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 the formula. 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 also be applicable. 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 the formula. 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 also be applicable. 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 yIn 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。

[0069] The ionically bonded solid electrolyte may be a complex hydride solid electrolyte. The complex hydride solid electrolyte may be composed of Li ions and complex ions containing H. The complex ion containing H may have, for example, an element M containing at least one of a nonmetallic element, a semimetallic element, and a metallic element, and H bonded to the element M. In addition, the complex ion containing H may have the element M as a central element and H surrounding the element M bonded to each other via a covalent bond. In addition, the complex ion containing H may be (M m H n ) α- In this case, m is any positive number, and n and α can be any positive number depending on m and the valence of the element M. The element M may be a nonmetallic element or a metallic element capable of forming a complex ion. For example, the element M may contain at least one of B, C, and N as a nonmetallic element, or may contain B. Also, for example, the 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 likely to be ensured. Specific examples of complex ions containing H include (CB9H 10 ) - , (C.B. 11 H 12 ) - , (B 10 H 10 ) 2- , (B 12 H 12 ) 2- , (BH4) - , (NH2) - , (AlH4) - , and combinations thereof. In particular, (CB9H 10 ) - , (C.B. 11H 12 ) - In other words, the complex hydride solid electrolyte may contain Li, C, B, and H.

[0070] 3.2.2 Liquid electrolyte The liquid electrolyte (electrolytic solution) is a liquid containing lithium ions as carrier ions. The electrolytic solution may be an aqueous electrolytic solution or a non-aqueous electrolytic solution. The composition of the electrolytic solution may be the same as that of the electrolytic solution of a lithium ion secondary battery known in the art. The electrolytic solution may be a solution in which a lithium salt is dissolved in water or a non-aqueous solvent. Examples of the non-aqueous solvent include various carbonate-based solvents. Examples of the lithium salt include lithium amide salt and LiPF6.

[0071] 3.3 Conductive additives Examples of the conductive assistant that may be included in the electrode mixture 5 include carbon materials such as vapor grown carbon fiber (VGCF), acetylene black (AB), ketjen black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF); and metal materials such as nickel, titanium, aluminum, and stainless steel. The conductive assistant may be, for example, particulate or fibrous, and the size thereof is not particularly limited. Only one type of conductive assistant may be used alone, or two or more types may be used in combination.

[0072] 3.4 Binder Examples of binders that can be included in the electrode mixture 5 include butadiene rubber (BR)-based binders, butylene rubber (IIR)-based binders, acrylate butadiene rubber (ABR)-based binders, styrene butadiene rubber (SBR)-based binders, polyvinylidene fluoride (PVdF)-based binders, polytetrafluoroethylene (PTFE)-based binders, polyimide (PI)-based binders, etc. Only one type of binder may be used alone, or two or more types may be used in combination.

[0073] 3.5 Other The electrode mixture 5 may contain various additives in addition to the above-mentioned components, such as a dispersant and a lubricant.

[0074] 4.Battery The active material secondary particles 1 can be employed, for example, as a positive electrode active material of a battery. As shown in Fig. 4, 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 contains the active material secondary particles 1 of the present disclosure.

[0075] 4.1 Cathode active material layer The positive electrode active material layer 10 includes at least the active material secondary particles 1 of the present disclosure, and may further include an electrolyte, a conductive assistant, a binder, and the like. Furthermore, the positive electrode active material layer 10 may include various other additives. In other words, the positive electrode active material layer 10 may be composed of the above-mentioned electrode mixture 5. The shape of the positive electrode active material layer 10 is not particularly limited, and may be, for example, 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 may be, for example, 0.1 μm or more or 1 μm or more, and may be 2 mm or less or 1 mm or less.

[0076] 4.2 Electrolyte layer The electrolyte layer 20 is disposed between the positive electrode active material layer 10 and the negative electrode active material layer 30. The electrolyte layer 20 includes at least an electrolyte. The electrolyte layer 20 may include at least one of a solid electrolyte and an electrolytic solution, and may further include a binder or the like. In particular, when the electrolyte layer 20 includes a solid electrolyte, higher performance is likely to be ensured. The content of the electrolyte and the 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 for holding the electrolytic solution and preventing 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, and may be 2 mm or less or 1 mm or less.

[0077] The electrolyte layer 20 may be composed of one layer or may be composed of multiple layers. For example, the electrolyte layer 20 may include a first layer disposed on the positive electrode active material layer 10 side and a second layer disposed on the negative electrode active material layer 30 side, and the first layer may include the first electrolyte, and the second layer may include the second electrolyte. The first electrolyte and the second electrolyte may be different from each other. The first electrolyte and the second electrolyte may each be at least one selected from the above-mentioned oxide solid electrolyte, sulfide solid electrolyte, and ionic solid electrolyte. For example, the first layer may include an ionic solid electrolyte, and the second layer may include at least one of an ionic solid electrolyte and a sulfide solid electrolyte.

[0078] The electrolyte contained in the electrolyte layer 20 may be appropriately selected from those exemplified as electrolytes that can be contained in the above-mentioned positive electrode active material layer 10 (electrode mixture 5) (solid electrolytes and / or liquid electrolytes). The binder that can be contained in the electrolyte layer 20 may also be appropriately selected from those exemplified as binders that can be contained in the above-mentioned positive electrode active material layer. Each of the electrolytes and binders may be used alone or in combination of two or more. The separator may be any separator that is commonly used in batteries, and examples of the separator include those made of resins such as polyethylene (PE), polypropylene (PP), polyester, and polyamide. The separator may have a single layer structure or a multilayer structure. Examples of the multilayer separator include a separator with a two-layer structure of PE / PP, or a separator with a three-layer structure of PP / PE / PP or PE / PP / PE. The separator may be made of a nonwoven fabric such as a cellulose nonwoven fabric, a resin nonwoven fabric, or a glass fiber nonwoven fabric.

[0079] 4.3 Negative electrode active material layer The negative electrode active material layer 30 includes at least a negative electrode active material. The negative electrode active material layer 30 may also include an electrolyte, a conductive assistant, a binder, various additives, and the like. The content of each component in the negative electrode active material layer 30 may be appropriately determined according to the intended battery performance. For example, 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 100% by mass or less, less than 100% by mass, 95% by mass or less, or 90% by mass or less, based on the entire solid content of the negative electrode active material layer 30 being 100% by volume. Alternatively, the negative electrode active material and optionally the electrolyte, the conductive assistant, and the binder may be included in a total amount of 85% by volume or more, 90% by volume or more, or 95% by volume or more, based on the entire negative electrode active material layer 30 being 100% by volume, and the remainder may be voids or other components. The shape of the negative electrode active material layer 30 is not particularly limited, and may be, for example, 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, and may be 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less.

[0080] The negative electrode active material may be any of those known as negative electrode active materials for batteries. Of the known active materials, various materials may be used that have a potential (charge / discharge potential) for absorbing and releasing carrier ions that is lower than the above-mentioned 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, lithium alloys, and the like may be used. Among them, when the negative electrode active material layer 30 contains Si as the negative electrode active material, the performance of the battery 100 is likely to be improved. Only one type of negative electrode active material may be used alone, or two or more types may be used in combination. The shape of the negative electrode active material may be any shape that is common as a negative electrode active material for batteries. For example, the negative electrode active material may be in the form of particles. The negative electrode active material particles may be primary particles, or may be secondary particles formed by agglomeration of a plurality of primary particles. The average particle diameter (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, and 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 a lithium foil. That is, the negative electrode active material layer 30 may be made of a sheet of the negative electrode active material.

[0081] Examples of the electrolyte that can be contained in the negative electrode active material layer 30 include the above-mentioned solid electrolyte, electrolytic solution, or a combination thereof. The conductive assistant that can be contained in the negative electrode active material layer 30 may be appropriately selected from, for example, those exemplified as the conductive assistant that can be contained in the above-mentioned positive electrode active material layer 10 (electrode mixture 5). The binder that can be contained in the negative electrode active material layer 30 may be appropriately selected from, for example, those exemplified as the binder that can be contained in the above-mentioned positive electrode active material layer 10 (electrode mixture 5). Each of the electrolyte, conductive assistant, and binder may be used alone or in combination of two or more kinds.

[0082] 4.4 Positive electrode current collector As shown in FIG. 4, the battery 100 may include a positive electrode current collector 40 in contact with the positive electrode active material layer 10. The positive electrode current collector 40 may be any of those commonly used as a positive electrode current collector for a battery. The positive electrode current collector 40 may have at least one shape selected from a foil shape, a plate shape, a mesh shape, a punched metal shape, and a foam. The positive electrode current collector 40 may be made of a metal foil or a metal mesh. In particular, a metal foil is excellent in terms of handling and the like. The positive electrode current collector 40 may be made of a plurality of foils. Examples of metals constituting the positive electrode current collector 40 include 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 oxidation resistance, the positive electrode current collector 40 may contain Al. The positive electrode collector 40 may have some kind of coating layer on its surface for the purpose of adjusting the resistance or the like. For example, the positive electrode collector 40 may have a carbon coating layer. The positive electrode collector 40 may be a metal foil or a substrate on which the above-mentioned metal is plated or vapor-deposited. When the positive electrode collector 40 is made of a plurality of metal foils, some kind of layer may be present between the plurality of metal foils. The thickness of the positive electrode collector 40 is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or more, and may be 1 mm or less or 100 μm or less.

[0083] 4.5 Negative electrode current collector As shown in FIG. 4, the battery 100 may include a negative electrode current collector 50 in contact with the negative electrode active material layer 30. The negative electrode current collector 50 may be any of those commonly used as a negative electrode current collector for a battery. The negative electrode current collector 50 may be in the form of a foil, a plate, a mesh, a punched metal, a foam, or the like. The negative electrode current collector 50 may be a metal foil or a metal mesh, or may be a carbon sheet. In particular, a metal foil is excellent in terms of ease of handling. The negative electrode current collector 50 may be made of a plurality of foils or sheets. The metal constituting the negative electrode current collector 50 may 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 difficult to alloy 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 an aluminum foil having a carbon coating layer. The negative electrode current collector 50 may also be a metal foil or a base material on which the above metal is plated or vapor-deposited. In addition, when the negative electrode current collector 50 is made of a plurality of metal foils, some kind of layer may be present between the plurality of metal foils. The thickness of the negative electrode current collector 50 is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or more, and may be 1 mm or less or 100 μm or less.

[0084] 4.6 Other configurations In addition to the above configuration, the battery 100 may have a general configuration for a battery. For example, a tab, a terminal, etc. The battery 100 may have each of the above configurations housed inside an exterior body. Any known exterior body for a battery can be used as the exterior body. In addition, a plurality of batteries 100 may be electrically connected in any way and stacked in any way to form an assembled battery. In this case, the assembled battery may be housed inside a known battery case. Examples of the shape of the battery 100 include a coin type, a laminate type, a cylindrical type, and a square type. The battery 100 may be a secondary battery.

[0085] The battery 100 can be manufactured by applying a known method, except for using the above-mentioned specific active material secondary particles 1. For example, it 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 or the like. (1) The active material secondary particles 1 constituting the positive electrode active material layer are dispersed in a solvent to obtain a positive electrode layer slurry. The solvent used in this case is not particularly limited, and water or various organic solvents can be used. The positive electrode layer slurry is applied to the surface of a 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, forming a positive electrode. (2) The negative electrode active material constituting the negative electrode active material layer is dispersed in a solvent to obtain a negative electrode layer slurry. The solvent used in this case is not particularly limited, and water or various organic solvents can be used. The negative electrode layer slurry 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, thereby forming a negative electrode. (3) The layers are laminated so that the electrolyte layer (solid electrolyte layer or separator) is sandwiched between the negative electrode and the positive electrode to obtain a laminate having the negative electrode current collector, the negative electrode active material layer, the electrolyte layer, the positive electrode active material layer, and the positive electrode current collector in this order. Other members such as terminals are attached to the laminate as necessary. (4) The laminate is housed in a battery case, and in the case of an electrolyte battery, the battery case is filled with electrolyte, and the laminate is immersed in the electrolyte and sealed in the battery case to form a secondary battery. In the case of an electrolyte battery, the electrolyte may be impregnated in the negative electrode active material layer, the separator, and the positive electrode active material layer at the above step (3).

[0086] 5. Vehicles The battery of the present disclosure has high capacity and low resistance due to the use of the active material secondary particles 1. Such a battery can be suitably used in at least one type of vehicle selected from, for example, a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and an electric vehicle (BEV). That is, the technology of the present disclosure also has an aspect of a vehicle having a battery, the battery having a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, and the positive electrode active material layer containing the active material secondary particles 1 of the present disclosure. EXAMPLES

[0087] As described above, one embodiment of the active material secondary particles and the like has been described, but the technology of the present disclosure can be modified in various ways other than the above embodiment without departing from the gist of the technology. The technology of the present disclosure will be described in more detail below while showing examples, but the technology of the present disclosure is not limited to the following examples.

[0088] 1. Preparation of Primary Particles 1.1 Preparation of precursor 1.1.1 Examples 1 to 7 and Comparative Examples 1 to 5 (1) MnSO4·5H2O, NiSO4·6H2O, and CoSO4·7H2O were weighed out to achieve the desired composition ratio (Mn:Ni:Co=5:2:3) and dissolved in distilled water to a concentration of 1.2 mol / L to obtain a first solution. In a separate container, Na2CO3 was dissolved in distilled water to a concentration of 1.2 mol / L to obtain a second solution. (2) 1000 mL of pure water was placed in a reaction vessel (with a baffle plate), and 500 mL of the first solution and 500 mL of the second solution were each added dropwise at a rate of about 4 mL / min. (3) After the dropwise addition was completed, the mixture was stirred at room temperature at a stirring speed of 150 rpm for 1 hour to obtain a product. (4) The product was washed with pure water, subjected to solid-liquid separation using a centrifuge, and the precipitate was collected. (5) The obtained precipitate was dried overnight at 120°C, crushed in a mortar, and then separated into coarse particles and fine particles by air classification. The fine particles were removed to obtain coarse particles as precursor particles.

[0089] 1.1.2 Example 8 Precursor particles were obtained in the same manner as in Examples 1 to 7 and Comparative Examples 1 to 5, except that the composition ratio of Mn, Ni, and Co in the precursor was adjusted to Mn:Ni:Co=4:2:4.

[0090] 1.1.3 Example 9 Precursor particles were obtained in the same manner as in Examples 1 to 7 and Comparative Examples 1 to 5, except that the composition ratio of Mn, Ni, and Co in the precursor was adjusted to Mn:Ni:Co=3:3:4.

[0091] 1.2 Preparation of the complex 1.2.1 Examples 1 to 9, Comparative Examples 1, 4 and 5 The above precursor particles and Na2CO3 are mixed and calcined to obtain a composition of Na 0.8 Mn 0.5 Ni 0.2 Co 0.3 The surfaces of the precursor particles were coated with Na2CO3, and a composite was obtained by mixing the two ingredients in a mortar so that the total amount of Na2CO3 was O2.

[0092] 1.2.2 Comparative Examples 2 and 3 (1) Na2CO3 and distilled water were weighed out so that the total concentration was 1,150 g / L, and then the mixture was stirred using a stirrer until it was completely dissolved, thereby preparing an aqueous Na2CO3 solution. (2) The above-mentioned Na2CO3 aqueous solution and the above-mentioned precursor particles are mixed together to obtain a composition after calcination, which will be described later. 0.8 Mn 0.5 Ni 0.2 Co 0.3 The components were weighed and mixed to obtain a slurry of O2. (3) The above slurry was air-dried by spray drying to obtain a composite. Specifically, a DL410 spray dryer 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 m 3 The above slurry was dried by air flow at a spray rate of 0.3 MPa and a flow rate of 100 / min, to coat the surfaces of the precursor particles with Na2CO3, thereby obtaining a composite.

[0093] 1.3 Firing of the composite The composite was placed in an alumina crucible and sintered in an air atmosphere to obtain a Na-containing oxide having a P2 structure under the following sintering conditions (1) to (7). (1) An alumina crucible containing the above composite is placed in a heating furnace in an air atmosphere. (2) The temperature inside the heating furnace is raised from room temperature (25°C) to 600°C in 115 minutes. (3) The temperature in the heating furnace is kept at 600°C for 360 minutes to perform pre-baking. (4) After the preliminary firing, the temperature inside the heating furnace is raised to 900°C and then held at 900°C for 60 minutes for main firing. (5) After the main firing, the temperature inside the heating furnace is lowered from the main firing temperature to 250°C, and the alumina crucible is removed from the heating furnace at 250°C and allowed to cool outside the furnace in a dry atmosphere until it reaches 25°C in 10 minutes.

[0094] The fired product after cooling was pulverized in a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2 type structure (P2 type particles).

[0095] 1.4 Ion exchange (1) LiNO3 and LiCl were weighed out to have a molar ratio of 50:50, and mixed with the above P2 type particles in a molar ratio that was 10 times the minimum Li amount required for ion exchange to obtain a mixture. (2) Using an alumina crucible, ion exchange was carried out in air at 280°C for 1 hour to obtain a product containing 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 primary particles of Li-containing oxide with an O2-type structure.

[0096] 2. Secondary particle formation (1) A Li source and a Nb source were dissolved in water to obtain a solution. (2) The above primary particles were mixed into the solution to obtain a slurry. (3) The slurry was sprayed and dried by spray drying, and further dried overnight at 120° C. to obtain intermediate particles containing primary particles and a Li-containing oxide (a composite oxide of Li and Nb) as a Li-ion conductive material. Here, the presence or absence of granulation of the intermediate particles and the particle size of the intermediate particles were controlled by adjusting the spray drying conditions (slurry delivery flow rate, slurry solid content rate, and spray air pressure).

[0097] 3. Li-doped (1) In a glove box (Ar atmosphere), biphenyl was mixed and dissolved in tetrahydrofuran (THF) to give a concentration of 1 mol / L to obtain a biphenyl solution. (2) Li foil was added to the biphenyl solution in the same mole as biphenyl, and the solution was stirred for 2 hours to obtain a reduced solution containing 1 mol / L Li ions. (3) The intermediate particles were added to the obtained reduction solution, immersed, and stirred for 24 hours. The amount of intermediate particles added was adjusted so that the ratio of the number of moles of dissolved Li ions to the number of moles of intermediate particles (Li / O2) was 0.35. (4) After stirring, the intermediate particles were washed with THF and subjected to solid-liquid separation by vacuum filtration. The obtained precipitate was dried overnight at 120°C to obtain active material particles for evaluation. The molar ratios of Mn, Ni, and Co contained in the active material particles are as shown in Tables 1 to 3 below. In addition, when the crystal phase contained in the active material particles was confirmed by XRD, the active material particles had an O2 type structure.

[0098] 4. Morphological Observation of Active Material Particles The morphology of the active material particles was observed by SEM. Tables 1 to 3 below show, for each of Examples 1 to 9 and Comparative Examples 1 to 5, "shape (plate-like, spherical, irregular) of the primary particles constituting the active material particles," "particle diameter of the primary particles," "whether or not the active material particles were granulated (converted into secondary particles)," "particle diameter if the active material particles are secondary particles," and "ratio M2 / M1 of mass M1 of the Li-ion conductive material to mass M1 of the primary particles." For reference, FIG. 5 shows an SEM image of the appearance of the active material particles of Example 6.

[0099] 5.Charge / Discharge Characteristics Evaluation (1) The above-mentioned active material particles, sulfide-based solid electrolyte, vapor grown carbon fiber (VGCF), PVdF-based binder, and butyl butyrate were stirred by an ultrasonic dispersing device to obtain a positive electrode slurry. Here, the mass ratio of active material particles:sulfide-based solid electrolyte:VGCF:PVdF-based binder was 81.1:15.9:2.4:0.6. The positive electrode slurry was applied by a blade method onto an Al foil as a positive electrode current collector foil, and the applied mixture was dried on a hot plate at 100°C for 30 minutes to form a positive electrode active material layer on the Al foil. (2) Anode active material lithium titanate (LTO), sulfide-based solid electrolyte, VGCF, PVdF-based binder, and butyl butyrate were stirred by an ultrasonic disperser to obtain anode slurry. Here, the mass ratio of anode active material:sulfide-based solid electrolyte:VGCF:PVdF-based binder was 72.1:22.7:1.7:3.5. The anode slurry was applied by a blade method onto Ni foil as anode current collector foil, and the coated foil was dried on a hot plate at 100°C for 30 minutes to form anode active material layer on the Ni foil. (3) A sulfide-based solid electrolyte, a PVdF-based binder, and butyl butyrate were stirred by an ultrasonic dispersion device to obtain a solid electrolyte slurry. Here, the mass ratio of the sulfide-based solid electrolyte to the PVdF-based binder was 99.4:0.6. The solid electrolyte slurry was applied onto an Al foil substrate by a blade method, and the resulting mixture was dried on a hot plate at 100°C for 30 minutes to obtain a peelable solid electrolyte layer. (4) The positive electrode active material layer and the solid electrolyte layer are laminated and pressed with a roll press at a pressure of 50 kN / cm and a temperature of 160°C. Then, the Al foil is peeled off from the solid electrolyte layer and a 1 cm 2 A positive electrode laminate was obtained by punching out the material into a size of 10 mm. (5) The negative electrode active material layer and the solid electrolyte layer were laminated and pressed with a roll press at a pressure of 50 kN / cm and a temperature of 160°C, and then the Al foil was peeled off from the solid electrolyte layer to obtain a negative electrode laminate. Further, an additional solid electrolyte layer was laminated on the solid electrolyte side of the negative electrode laminate and pre-pressed with a flat uniaxial press at a pressure of 100 MPa and a temperature of 25°C, after which the Al foil was peeled off from the solid electrolyte layer and a 1.08 cm 2 By punching out the laminated body having the additional solid electrolyte layer, a negative electrode laminate having the additional solid electrolyte layer was obtained. (6) The positive electrode laminate and a negative electrode laminate having an additional solid electrolyte layer were laminated so that their composite surfaces overlapped, and pressed with a flat uniaxial press at a pressure of 200 MPa and a temperature of 120°C to obtain a battery laminate. (7) The above battery stack was sandwiched between two restraint plates, and these two restraint plates were fastened with a fastener at a restraint pressure of 5 MPa to fix the distance between the two restraint plates, thereby obtaining a cell for evaluation. (8) The evaluation cells were charged at a constant current of 1 / 10C to 3.25V, then charged at a constant voltage of 3.25V to a cut-off current of 1 / 100C, and further discharged at a constant current of 1 / 10C to 0.45V, and then discharged at a constant voltage of 0.45V to a cut-off current of 1 / 100C, and the initial discharge capacity was measured. (9) Furthermore, the evaluation cell was charged at a constant current of 1 / 10C to 2.2V, and then charged at a constant voltage of 2.2V to a cut-off current of 1 / 100C to adjust the state of charge. A current equivalent to 3C was passed through the evaluation cell after adjusting the state of charge for 10 seconds, and the resistance was measured by dividing the voltage change before and after by the current value. The resistance value of Example 1 was set to 100, and the resistance values ​​of the other examples were normalized.

[0100] The following Tables 1 to 3 show the "initial discharge capacity" and "normalized resistance value" for each of the cells of Examples 1 to 9 and Comparative Examples 1 to 5.

[0101] [Table 1]

[0102] [Table 2]

[0103] [Table 3]

[0104] The results shown in Tables 1 to 3 reveal the following:

[0105] From the results of Examples 1 to 3 and Comparative Examples 1 to 4 in Table 1, it can be seen that the normalized resistance value increases significantly when the primary particle diameter is 2.0 μm or more. It is presumed that, although granulation itself is possible when the primary particle diameter is 2.0 μm or more, the diffusion distance inside the bulk of the primary particles becomes longer, which increases the diffusion resistance, reduces the reaction area, and increases the reaction resistance.

[0106] From the results of Examples 1 to 3 and Comparative Examples 2 to 3 in Table 1, the initial charge / discharge capacity is greater when the primary particles contain plate-like particles than when the primary particles contain spherical particles. Spherical particles may have voids inside, which may reduce the utilization rate of the active material inside.

[0107] From the results of Examples 1 to 3 and Comparative Examples 4 and 5 in Table 1, it can be seen that the normalized resistance value increases significantly when the primary particles are not converted into secondary particles. This is presumably due to an increase in diffusion resistance caused by an increase in the diffusion distance inside the bulk, an increase in reaction resistance caused by a decrease in the reaction area, and an increase in the diffusion resistance caused by a decrease in the tortuosity of Li diffusion in the electrode due to the lack of secondary particle conversion.

[0108] From the results of Comparative Example 5 in Table 1, it can be seen that when fine primary particles are used without being converted into secondary particles, the initial charge / discharge capacity decreases. This is presumably because the fine primary particles aggregate with voids during the electrode preparation process, making it difficult to secure Li-ion conduction paths inside the aggregates.

[0109] From the results of Examples 4 to 7 in Table 2, it is clear that the effect of converting primary particles into secondary particles via a Li-ion conductive material can be obtained regardless of the particle size of the secondary particles.

[0110] The results of Examples 8 and 9 in Table 3 show that the effects of converting primary particles into secondary particles via a Li-ion conductive material can be obtained regardless of the chemical composition of the primary particles having an O2 type structure.

[0111] 6. Summary From the above results, it can be said that the following secondary particles of active material can achieve both high capacity and low resistance.

[0112] The secondary particles of the active material include a plurality of primary particles and a Li-ion conductive material; the plurality of primary particles have an O2 type structure; The particle size of the plurality of primary particles is 1.5 μm or less, The plurality of primary particles are bonded to each other via the Li ion conductive material. Active material secondary particles. [Explanation of symbols]

[0113] 1 Active material secondary particles 1a primary particle 1b Li-ion conductive material 5 Electrode mixture 2 Solid electrolyte 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. The secondary particles of the active material include a plurality of primary particles and a Li ion conductive material; the plurality of primary particles have an O2 type structure; The particle diameter of the plurality of primary particles is 1.5 μm or less, The plurality of primary particles are bonded to each other via the Li ion conductive material. Active material secondary particles.

2. The active material secondary particles according to claim 1 , A ratio M2 / M1 of a mass M2 of the Li ion conductive material to a mass M1 of the primary particles is 0.01 or more and 0.20 or less. Active material secondary particles.

3. The active material secondary particles according to claim 1 , At least a portion of the plurality of primary particles are plate-like particles. Active material secondary particles.

4. The active material secondary particles according to claim 1 , The particle diameter of the active material secondary particles is 3 μm or more and 25 μm or less. Active material secondary particles.

5. The active material secondary particles according to claim 1 , The Li ion conductive material is an inorganic compound. Active material secondary particles.

6. The active material secondary particles according to claim 5 , The inorganic compound is a Li-containing oxide. Active material secondary particles.

7. An electrode mixture, The active material secondary particles according to any one of claims 1 to 6, A solid electrolyte; 13. An electrode mixture comprising:

8. The electrode mixture according to claim 7, The solid electrolyte includes a sulfide solid electrolyte. Electrode composite material.

9. A battery having a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, The positive electrode active material layer contains the active material secondary particles according to any one of claims 1 to 6. battery.

10. 10. The battery of claim 9, The electrolyte layer includes a solid electrolyte. battery.

11. A method for producing secondary particles of an active material, comprising the steps of: binding a plurality of primary particles via a Li ion conductive material to form secondary particles; Including, the plurality of primary particles have an O2 type structure; The particle diameter of the plurality of primary particles is 1.5 μm or less; A method for producing secondary particles of an active material.

12. A method for producing active material secondary particles according to claim 11, Preparing a solution in which the Li ion conductive material is dissolved; and bringing the solution into contact with the plurality of primary particles and then drying the solution to bond the plurality of primary particles via the Li ion conductive material to form secondary particles; A method for producing secondary particles of an active material comprising the steps of:

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