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

Abstract

The invention relates to active material secondary particles, an electrode mixture, a battery, and a method for producing active material secondary particles. Disclosed is an active material having an O2-type structure and having high capacity and low resistance. An active material secondary particle according to the present disclosure includes a plurality of primary particles and a Li ion conductive material. The plurality of primary particles have an O2-type structure. The plurality of primary particles have a particle diameter of 1.5 [mu] m or less. The plurality of primary particles are bonded to each other via the Li ion conductive material.

Description

Technical Field

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

[0002] As a battery active material, a battery active material having an O2 type structure is known. As disclosed in Patent Document 1, an active material having an O2 type structure can be obtained by exchanging at least a portion of Na in an oxide containing Na having a P2 type structure with Li.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-092824 Summary of the invention

[0006] Problems to be solved by the invention

[0007] Active materials with O2-type structures still have room for improvement in capacity and resistance.

[0008] Means for solving problems

[0009] The present application discloses the following multiple solutions as means for solving the above-mentioned problems.

[0010] <Option 1>

[0011] The active material secondary particle comprises a plurality of primary particles and a Li ion conductive material, wherein 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, and the plurality of primary particles are bonded to each other via the Li ion conductive material.

[0012] <Option 2>

[0013] The active material secondary particle according to claim 1, wherein a ratio M2 / M1 of a mass M2 of the Li ion conductive material to a mass M1 of the primary particle is 0.01 or more and 0.20 or less.

[0014] <Option 3>

[0015] The active material secondary particle according to aspect 1 or 2, wherein at least a part of the plurality of primary particles are plate-like particles.

[0016] <Option 4>

[0017] The active material secondary particle according to any one of aspects 1 to 3, wherein the particle diameter of the active material secondary particle is 3 μm or more and 25 μm or less.

[0018] <Option 5>

[0019] The active material secondary particle according to any one of aspects 1 to 4, wherein the Li ion conductive material is an inorganic compound.

[0020] <Option 6>

[0021] The active material secondary particle according to claim 5, wherein the inorganic compound is an oxide containing Li.

[0022] <Option 7>

[0023] An electrode composite material comprising the active material secondary particles according to any one of Embodiments 1 to 6, and a solid electrolyte.

[0024] <Option 8>

[0025] The electrode composite according to Scheme 7, wherein the solid electrolyte comprises a sulfide solid electrolyte.

[0026] <Option 9>

[0027] A battery comprising a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, wherein the positive electrode active material layer comprises the active material secondary particle according to any one of Embodiments 1 to 6.

[0028] <Option 10>

[0029] The battery according to claim 9, wherein the electrolyte layer contains a solid electrolyte.

[0030] <Plan 11>

[0031] A method for producing active material secondary particles, comprising: combining a plurality of primary particles via a Li ion conductive material to form secondary particles, the plurality of primary particles having an O2 type structure, and the particle size of the plurality of primary particles being 1.5 μm or less.

[0032] <Plan 12>

[0033] The method for producing active material secondary particles according to claim 11 comprises: 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 combining the plurality of primary particles via the Li ion conductive material to form secondary particles.

[0034] Effects of the Invention

[0035] The active material secondary particles disclosed herein have high capacity and low resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 An example of the internal (cross-sectional) structure of an active material secondary particle is schematically shown.

[0037] Figure 2 An example of the flow of a method for producing active material secondary particles is schematically shown.

[0038] Figure 3 An example of the structure of an electrode composite material is schematically shown.

[0039] Figure 4 An example of a battery configuration is schematically shown.

[0040] Figure 5 This is a SEM image of the active material secondary particles involved in Example 6.

[0041] Description of Reference Numerals

[0042] 1 Active material secondary particles

[0043] 1a Primary particles

[0044] 1b Li ion conductive material

[0045] 5 Electrode composite materials

[0046] 2 Solid Electrolyte

[0047] 100 Batteries

[0048] 10 Positive electrode active material layer

[0049] 20 Electrolyte layer

[0050] 30 Negative electrode active material layer

[0051] 40 positive electrode collector

[0052] 50 Negative electrode collector DETAILED DESCRIPTION

[0053] An embodiment of the active material secondary particles, electrode composites, batteries, and methods for producing active material secondary particles disclosed herein is described below. The active material secondary particles, electrode composites, batteries, and methods for producing active material secondary particles disclosed herein are not limited to the embodiment described below.

[0054] 1. Active material secondary particles

[0055] like Figure 1As shown, 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 plurality of primary particles 1a have an O2 type structure. The particle size of the plurality of primary particles 1a is 1.5 μm or less. The plurality of primary particles 1a are bonded to each other via the Li ion conductive material 1b.

[0056] 1.1 Primary particles

[0057] 1.1.1 Crystal structure

[0058] The primary particle 1a involved in one embodiment has an O2-type structure and may have a crystal structure other than the O2-type structure. As a crystal structure other than the O2-type structure, for example, a T#2-type structure (belonging to the space group Cmca) formed when Li is inserted and separated in the O2-type structure, an O6-type structure (belonging to the space group R-3m, with a c-axis length of 2.5nm or more and 3.5nm or less, typically 2.9nm or more and 3.0nm or less, which is different from the O3-type structure also belonging to the space group R-3m) and the like can be cited. The primary particle 1a involved in one embodiment may have an O2-type structure as the main phase, and may also have a crystal structure other than the O2-type structure (for example, an O6-type structure) as the main phase. The crystal structure that becomes the main phase of the primary particle 1a involved in one embodiment may change according to its charge and discharge state. The primary particle 1a involved in one embodiment may be a single crystal composed of one microcrystal, or may be a polycrystalline having multiple microcrystals. In particular, in the case of a single crystal, it is easy to satisfy the particle size described later.

[0059] 1.1.2 Particle size

[0060] For O2-type active materials, there is still room for improvement in the ion conduction paths within and between active materials. In particular, when an O2-type active material is combined with a solid electrolyte, the resistance is sometimes easy to increase and it is difficult to fully exert the capacity. In this regard, by using fine primary particles as the primary particles 1a of the O2-type active material, and combining the primary particles 1a with each other via the Li ion conductive material 1b described later to form secondary particles, the ion conduction paths within and between active materials can be properly ensured. For example, when the active material secondary particles 1 are combined with a solid electrolyte, the resistance is easy to decrease and it is easy to fully exert the capacity. According to the knowledge of the inventors, such an effect can be significantly exerted by having a particle size of multiple primary particles 1a of less than 1.5μm. The smaller the particle size, the more significant this effect becomes. The particle size may be greater than 0μm and less than 1.5μm, greater than 0μm and less than 1.0μm, or greater than 0.1μm and less than 0.5μm.

[0061] Furthermore, the "particle size of the primary particles" refers to the "average particle size" of the plurality of primary particles 1a constituting the active material secondary particles 1. The "average particle size" of the plurality of primary particles can be determined by observing the appearance of the active material secondary particles 1 using 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 using SEM or the like, and the areas of any 10 primary particles of the plurality of primary particles constituting the active material secondary particles 1 contained in the two-dimensional image are determined, and the areas are converted into circles to determine the circle equivalent diameter of each primary particle, and the arithmetic mean of the circle equivalent diameters is determined as the "average particle size".

[0062] 1.1.3 Shape

[0063] The primary particles 1a involved in one embodiment can be obtained by replacing Na of an oxide containing Na with a P2-type structure with Li as described later. Among them, the P2-type structure is a hexagonal system, the diffusion coefficient of Na ions is large, and it is easy 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, it is easy to grow crystals into plates in a specific direction. Therefore, the oxide containing Na with a P2-type structure is easy to become a plate-like particle with a large aspect ratio in which the growth direction of the crystal is biased toward a specific direction. The primary particles 1a involved in one embodiment can be obtained based on such plate-like oxide particles containing Na, or can be obtained based on spherical oxide particles containing Na. That is, the shape of the primary particles 1a can be plate-like particles, spherical particles, or indefinite shapes. According to the knowledge of the inventors, when at least a part of the multiple primary particles 1a constituting the active material secondary particles 1 is a plate-like particle, the capacity is further improved and the resistance is easy to become smaller.

[0064] Furthermore, in the present application, "plate-like particles" refer to particles having an aspect ratio of greater than 1.5 and less than 10. Among them, the "aspect ratio" of the primary particle 1a is measured as described below. That is, a scanning electron microscope (SEM) or a transmission electron microscope (TEM) is used to observe the cross section of the active material secondary particle (when the secondary particle is included in the positive electrode active material layer described later, it may be the cross section of the positive electrode active material layer) to determine the shape of the primary particle contained in the active material secondary particle. In this shape, the largest Feret diameter is determined and regarded as the "major diameter". In addition, in this shape, the largest diameter orthogonal to the "major diameter" is regarded as the "minor diameter". The ratio of the "major diameter" to the "minor diameter" (major diameter / minor diameter) is regarded as the "aspect ratio" of the primary particle 1a.

[0065] In addition, "spherical particles" refer to particles with a circularity of 0.80 or more. The circularity of the particles can 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 2 Definition. Wherein, S is the orthographic projection area of ​​the particle, and L is the perimeter of the orthographic projection image of the particle. The circularity of the particle can be obtained by observing the appearance of the particle using a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an optical microscope.

[0066] 1.1.4 Chemical composition

[0067] The chemical composition of the primary particle 1a is not particularly limited as long as the O2 type structure is maintained. The primary particle 1a may contain, for example, at least one element of Mn, Ni, and Co, Li, and O as constituent elements. Among them, when the primary particle 1a contains at least Li, Mn, one or both of Ni and Co, and O as constituent elements, in particular, when it contains at least Li, Mn, Ni, Co, and O as constituent elements, higher performance is easily obtained.

[0068] The primary particle 1a may have a a Na b Mn x-p Ni y-q Co z-r M p+q+rA chemical composition represented by O2 (wherein 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, it is easy to maintain the O2 type structure. In the above chemical composition, a is greater than 0, and can be greater than 0.10, greater than 0.20, greater than 0.30, greater than 0.40, greater than 0.50 or greater than 0.60, and is less than 1.00, and can be less than 0.90, less than 0.80 or less than 0.70. In the above chemical composition, b is greater than 0, and can be greater than 0.01, greater than 0.02 or greater than 0.03, and is less than 0.20, and can be less than 0.15 or less than 0.10. In addition, 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 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. In addition, y is 0 or more, and may be 0.10 or more, or 0.20 or more, and is 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. In addition, z is 0 or more, and may be 0.10 or more, 0.20 or more, or 0.30 or more, and is 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. Element M contributes little to charge and discharge. From this point of view, in the above chemical composition, it is easy to ensure a high charge and discharge capacity by having p+q+r be less than 0.17. p+q+r may be less than 0.16, less than 0.15, less than 0.14, less than 0.13, less than 0.12, less than 0.11 or less than 0.10. On the other hand, by including element M, the O2 type structure is easily stabilized. In the above chemical composition, p+q+r is greater than 0, and may be greater than 0.01, greater than 0.02, greater than 0.03, greater than 0.04, greater than 0.05, greater than 0.06, greater than 0.07, greater than 0.08, greater than 0.09 or greater than 0.10. The composition of O is approximately 2, and is not limited to exactly 2.0, but is indefinite (variable).

[0069] 1.1.5 Others

[0070] The number of primary particles 1a contained in the active material secondary particle 1 is not particularly limited. 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, and may contain 10,000 or less, 5,000 or less, or 1,000 or less primary particles 1a. In particular, when the number of secondary particle diameters described later is satisfied, higher performance can be easily achieved.

[0071] 1.2 Li ion conductive material

[0072] As described above, in the active material secondary particle 1, a plurality of primary particles 1a are bonded to each other via the Li ion conductive material 1b. The Li ion conductive material can be used as long as it can bond a plurality of primary particles 1a to each other and can ensure a Li ion conductive path between the primary particles 1a. The Li ion conductive material 1b can be an inorganic compound or an organic compound. In particular, in the case of an inorganic compound, it is easy to ensure high performance. In addition, 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).

[0073] 1.2.1 Li-ion conductive inorganic compounds

[0074] The Li ion conductive inorganic compound may be, for example, at least one selected from an oxide containing Li and a halide containing Li. In the case of an oxide containing Li, high performance can be easily ensured.

[0075] As for the oxide containing Li, an oxide containing Li and an element A other than Li can be cited. For example, it can contain elements A, Li, and O, wherein the element A is at least one selected from B, C, Al, Si, P, S, Ti, La, Zr, Nb, Mo, Zn, and W. The oxide containing Li can be an oxynitride containing N. More specifically, the oxide containing Li can be selected from Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, Li4Ti5O 12 At least one of Li2Ti2O5, Li2ZrO3, LiNbO3, Li2MoO4, Li2WO4, LiPON, Li2O-LaO2, Li2O-ZnO2, etc. The oxide containing Li may be a product in which a part of the elements is replaced by various doping elements.

[0076] The halide containing Li may be, for example, at least one of the various compounds exemplified as the halide solid electrolyte described later. The halide containing Li may include, for example, at least one element selected from 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 Cl, Br, I and F, and Li. The halide containing Li may include at least one element selected from Ti, Al, Gd, Ca, Zr and Y, at least one selected from Cl, Br, I and F, and Li. In addition, the halide containing Li may include at least one element selected from Ti and Al, at least one element selected from Cl, Br, I and F, and Li. In addition, the halide containing Li may be, for example, a composite halide of Li, Ti, Al and F.

[0077] 1.2.2 Shape

[0078] 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 involved in one embodiment, the Li ion conductive material 1b may be coated on the surface of the primary particle 1a. In this case, the coverage rate (area rate) of the Li ion conductive material 1b relative 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. In the case where 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.

[0079] 1.3 Mass ratio of primary particles to Li-ion conductive material

[0080] The mass ratio of the primary particles 1a to 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 knowledge of the present inventors, when the ratio M2 / M1 of the mass M2 of the Li ion conductive material 1b contained in the active material secondary particles 1 to the mass M1 of the primary particles 1a is 0.01 or more and 0.20 or less, it is easy to ensure better capacity and resistance performance 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.

[0081] 1.4 Secondary particle size

[0082] There is no particular limitation on the particle size (secondary particle size) of the active material secondary particle 1. The effect of capacity and resistance can be exerted independently of the size of the active material secondary particle 1. According to the knowledge of the inventors, when the particle size of the active material secondary particle 1 is 2 μm or more and 30 μm or more and 25 μm or more and 20 μm or more, the active material secondary particle 1 is easily granulated, and the Li conduction distance inside the active material secondary particle 1 is easily shortened.

[0083] It should be noted that the “particle size of the active material secondary particle” can be determined by observing the appearance of the active material secondary particle 1 using 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 using SEM or the like, the area of ​​the active material secondary particle 1 included in the two-dimensional image is determined, the area is converted into a circle, the circle equivalent diameter is determined, and the circle equivalent diameter is determined as the “particle size of the active material secondary particle”.

[0084] 1.5 Others

[0085] The active material secondary particle 1 may or may not have voids. Even if the active material secondary particle 1 has voids, as described above, sufficient ion conduction paths can be ensured by bonding fine primary particles 1a to each other via the Li ion conductive material 1b, thereby ensuring high performance.

[0086] 2. Method for producing active material secondary particles

[0087] The above-mentioned active material secondary particles 1 can be manufactured, for example, by the following method. That is, the manufacturing method of the active material secondary particles 1 according to one embodiment includes: combining a plurality of primary particles 1a via a Li ion conductive material 1b to form secondary particles. The plurality of primary particles 1a have an O2 type structure, and the particle size of the plurality of primary particles 1a is 1.5 μm or less.

[0088] 2.1 An example of secondary particleization

[0089] There is no particular limitation on the method of combining the plurality of primary particles 1a via the Li ion conductive material 1b to form secondary particles. Figure 2As shown, by bringing a solution 1bx in which a Li ion conductive substance 1b is dissolved into contact with a plurality of primary particles 1a, the plurality of primary particles 1a can be combined to form secondary particles via the Li ion conductive substance 1b. That is, a method for producing an active material secondary particle 1 according to an embodiment may include: preparing a solution 1bx in which a Li ion conductive substance 1b is dissolved; and bringing the solution 1bx into contact with a plurality of primary particles 1a and drying the solution 1bx, thereby combining the plurality of primary particles 1a to form secondary particles via the Li ion conductive substance 1b. More specifically, a method for producing an active material secondary particle 1 according to an embodiment may include the following steps. S1: obtaining a slurry containing a plurality of primary particles 1a and a solution 1bx; S2: making the slurry droplet-like, obtaining a slurry droplet 1x containing a plurality of primary particles 1a and a solution 1bx; and S3: drying the slurry droplet 1x in a heated gas flow, thereby combining the plurality of primary particles 1a to form secondary particles via the Li ion conductive substance 1b.

[0090] 2.1.1 Solution 1bx

[0091] In the case where the surface of the primary particle 1a is coated with an oxide containing Li and an element A other than Li, the solution 1bx may contain a lithium source and an A source. As the element A, at least one selected from B, C, Al, Si, P, S, Ti, La, Zr, Nb, Mo, Zn and W can be listed. The solution 1bx may contain lithium ions as a lithium source. For example, by dissolving a lithium compound such as LiOH, LiNO3, Li2SO4 in a solvent, a solution 1bx containing lithium ions as a lithium source can be obtained. Alternatively, the solution 1bx may contain a lithium alkoxide as a lithium source. In addition, the solution 1bx may 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, in the case where 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 a lithium source and a niobium source. Alternatively, at least one of a phosphorus source and a boron source may be included instead of the niobium source. For example, by replacing a portion of Nb in lithium niobate with P (or doping lithium niobate with P), the withstand voltage is easily improved. There is no particular limitation on the molar ratio of the lithium source and the A source contained in the solution 1bx. For example, the molar ratio Li / A may be greater than 0.5 or greater than 0.8, and may be less than 2.0 or less than 1.5. As long as the solvent constituting the solution 1bx can dissolve the above-mentioned lithium source, etc., water and an organic solvent may be used.

[0092] 2.1.2 Slurry

[0093] The so-called "slurry" is a suspension or suspension containing primary particles 1a and solution 1bx, as long as it has a fluidity that can be dropletized. The slurry can have a fluidity that can be dropletized using a nozzle or a rotary atomizer, for example. The solid content concentration of the slurry can be determined according to the type of primary particles 1a, the type of solution 1bx, and the conditions for dropletization (the type of device for dropletization). The solid content concentration in the slurry is not particularly limited, for example, it can be more than 1 volume %, more than 5 volume %, more than 10 volume %, more than 20 volume %, more than 25 volume %, more than 30 volume %, more than 35 volume %, more than 40 volume %, more than 45 volume %, more than 50 volume %, can be less than 70 volume %, less than 65 volume %, less than 60 volume %, less than 55 volume %, less than 50 volume %, less than 45 volume %, less than 40 volume %, less than 35 volume %, less than 30 volume %, less than 25 volume % or less than 20 volume %. By adjusting the solid content concentration in the slurry, the particle size of the active material secondary particles 1 finally obtained can be controlled.

[0094] 2.1.3 Dropletization of slurry

[0095] The so-called "dropletization" of the slurry means that the slurry containing multiple primary particles 1a and the solution 1bx is made into particles (droplets 1x) containing multiple primary particles 1a and the solution 1bx. In addition, other droplets such as particles containing only the solution 1bx can be generated together with the droplets 1x. There is no particular limitation on the method of dropletizing the slurry containing multiple primary particles 1a and the solution 1bx. For example, the slurry can be sprayed to obtain slurry droplets. In the case of spraying the slurry, a nozzle can be used. As a method of spraying the slurry using a nozzle, a pressurized nozzle method, a two-fluid nozzle method, etc. can be listed, but they are not limited to these. In the case of spraying the slurry using a nozzle, there is no particular limitation on the nozzle diameter. The nozzle diameter can be, for example, 0.1 mm or more, 0.5 mm or more, or 1 mm or less, 10 mm or less, 5 mm or less, or 1 mm or less. In addition, the spraying speed of the slurry (relative to the slurry supply speed (liquid delivery speed) of the nozzle) and the injection pressure are not particularly limited. The spraying speed and injection pressure can be adjusted according to the viscosity of the slurry, the solid content concentration, the nozzle size, etc. By controlling the slurry feeding speed and injection pressure, the particle size of the active material secondary particles 1 finally obtained can be controlled.

[0096] As a method for dropletizing the slurry, in addition to the above-mentioned method of spraying the slurry using a nozzle, for example, a method of supplying the slurry at a certain speed on a rotating disc and using centrifugal force to drop it can also be exemplified. Alternatively, a method of applying a high voltage to the surface of the slurry to drop it can also be adopted. In the manufacturing method involved in one embodiment, for example, a spray dryer can be used to drop the slurry and air flow drying. There is no particular limitation on the method of the spray dryer, and the method using the above-mentioned nozzle, the method using a rotating disc, etc. can be listed.

[0097] 2.1.4 Slurry droplets

[0098] As described above, the "slurry droplets" may include particles (droplets 1x) containing multiple primary particles 1a and solution 1bx and particles (other droplets) composed of solution 1bx. The size of the slurry droplets is not particularly limited. The diameter (spherical equivalent diameter) of the droplet 1x may be, for example, greater than 0.1 μm, greater than 0.5 μm, or greater than 5.0 μm, and may be less than 5000 μm, less than 1000 μm, or less than 500 μm. The diameter of the slurry droplets can be measured, for example, by using a two-dimensional image obtained by photographing the slurry droplets. Alternatively, the droplet diameter can also be estimated from the operating conditions of the device that forms the slurry droplets.

[0099] 2.1.5 Airflow drying

[0100] The so-called "airflow drying" means drying the slurry droplets while floating them in a high-temperature airflow. "Airflow drying" is not just drying, but also includes the accompanying operations generated by the use of dynamic airflow. Airflow drying is used to continuously blow hot air on the slurry droplets, thereby continuously applying force to the slurry droplets. By controlling the conditions of airflow drying, the particle size of the active material secondary particles 1 obtained in the end can be controlled.

[0101] The temperature of the heating gas may be any temperature that allows the solvent to volatilize from the slurry droplets. For example, it 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. In addition, it is considered that whether the surface of the primary particle 1a is covered with the solution 1bx varies greatly depending on the surface energy of the solution 1bx. By making the temperature of the heating gas high, the solution 1bx also becomes high, and the surface energy of the solution 1bx varies greatly, and the amount of the solution 1bx that can be fixed (fixed) on the surface of the primary particle 1a may be reduced. That is, by controlling the temperature of the heating gas, the mass ratio of the primary particle 1a to the Li ion conductive material 1b in the active material secondary particle 1 finally obtained can be controlled.

[0102] The amount (flow rate) of the heating gas supplied can be appropriately set in consideration of the size of the device used and the amount of slurry droplets supplied. For example, the flow rate of the heating gas can be 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 / minute or more, or 0.50m 3 / minute or more, in addition, it can 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 / minute or less. The gas supply speed (flow rate) of the heating gas can also be appropriately set in consideration of the size of the device used and the supply amount of the slurry droplets. For example, the flow rate of the heating gas can be 1 m / sec or more or 5 m / sec or less, and can be 50 m / sec or less or 10 m / sec or less in at least a portion of the system.

[0103] The treatment time (drying time) using the heated gas can also be appropriately set in consideration of the size of the device used, the amount of slurry droplets supplied, etc. For example, the treatment time may be 5 seconds or less, or 1 second or less.

[0104] In the air flow drying, a heating gas that is substantially inactive to the primary particles 1a and the solution 1bx can be used, for example, an oxygen-containing gas such as air, an inert gas such as nitrogen or argon, a dry gas with a low dew point, or the like can be used.

[0105] As an apparatus for performing airflow drying, for example, a spray dryer can be used, but the invention is not limited to this.

[0106] 2.2 Method for producing primary particles

[0107] The primary particles 1a having an O2 type structure and a particle size 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 may include:

[0108] S11: obtaining a precursor (for example, a precursor containing at least one element of Mn, Ni and Co);

[0109] S12: coating the surface of the precursor with a Na source to obtain a composite;

[0110] S13: calcining the composite to obtain an oxide containing Na having a P2 type structure; and

[0111] S14: Ions of at least a portion of Na in the Na-containing oxide are exchanged with Li, thereby obtaining primary particles 1a having an O2 type structure.

[0112] Wherein, the S13 may include:

[0113] S13-1: pre-sintering 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;

[0114] S13-2: After the preliminary calcination, the composite is subjected to main calcination at a temperature of 700° C. to 1100° C. for 30 minutes to 48 hours; and

[0115] S13-3: Following the main firing, the composite body is rapidly cooled from a temperature T1 of 200°C or higher to a temperature T2 of 100°C or lower.

[0116] 2.2.1 Preparation of precursor

[0117] The precursor may contain at least Mn, and one or both of Ni and Co, and 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 compounds. The precursor may be in various shapes. For example, the precursor may be in the form of particles, or may be spherical particles as described later. There is no particular limitation on the particle size of the particles formed by the precursor.

[0118] In S11, an ion source capable of forming a precipitate with transition metal ions in an aqueous solution and a transition metal compound containing at least one element of Mn, Ni and Co can be used to obtain a precipitate as the above-mentioned precursor by a coprecipitation method. Thus, spherical particles as a precursor can be easily obtained. "An ion source capable of forming a precipitate with transition metal ions in an aqueous solution" can be, for example, at least one selected from sodium salts such as sodium carbonate and sodium nitrate, sodium hydroxide and sodium oxide. The transition metal compound can be the above-mentioned salt, hydroxide, etc. containing at least one element of Mn, Ni and Co. Specifically, in S1, after the ion source and the transition metal compound are made into solutions respectively, each solution is dripped and mixed to obtain a precipitate as a precursor. At this time, as a solvent, for example, water is used. At this time, as an alkali, various sodium compounds can be used, and in addition, an ammonia solution can be added to adjust the alkalinity. In the case of the coprecipitation method, for example, an aqueous solution of a transition metal compound and an aqueous solution of sodium carbonate can be prepared, and each aqueous solution is dripped and mixed to obtain a precipitate as a precursor. Alternatively, a sol-gel method can also be used to obtain a precursor. In particular, according to the coprecipitation method, spherical particles as a precursor can be easily obtained.

[0119] 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, for example, have the function of stabilizing the P2 type structure and the O2 type structure. There is no particular limitation on the method for obtaining the precursor containing element M. In the case where the precursor is obtained by the coprecipitation method 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 dripped and mixed to obtain a precursor containing at least one element of Mn, Ni and Co while also containing element M. Alternatively, in the manufacturing method of the present disclosure, element M is not added in S1, and element M may be doped during Na-doping sintering in S2 and S3 described later.

[0120] 2.2.2 Fabrication of the complex

[0121] In S12, the surface of the precursor obtained by S11 is coated with a Na source to obtain a composite. The Na source can be a salt containing Na such as a carbonate, a nitrate, or a compound other than a salt such as sodium oxide, sodium hydroxide, etc. In S12, the amount of the Na source coated on the surface of the precursor can be determined by considering the part where Na disappears during subsequent calcination. In S12, the coverage rate of the Na source on the surface of the precursor is not particularly limited. In S12, the method for coating the surface of the above-mentioned precursor with a Na source is not particularly limited. For example, the precursor and the Na source can be mixed using a mortar or a mixing device, or a solution containing a Na source can be contacted with the precursor and then dried using a tumbling flow coating method or a spray drying method.

[0122] In S12, the precursor may be coated with an M source together with a Na source. For example, in S12, the precursor obtained by S1, the Na source, and the M source containing at least one element M selected from B, Mg, Al, K, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W 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 a sulfate, or a compound other than a salt such as an oxide or a hydroxide. The amount of the M source relative to the precursor may be determined according to the chemical composition of the oxide containing Na after sintering.

[0123] 2.2.3 Firing of the composite

[0124] In S13, the composite obtained in S12 is calcined to obtain an oxide containing Na and having a P2 type structure. S13 may include the above-mentioned S13-1, S13-2 and S13-3.

[0125] In S13-1, the composite is pre-fired at a temperature of 300°C to 700°C for 2 hours to 10 hours. In S13-1, the pre-fired can be performed after the composite is arbitrarily formed. The pre-fired is performed at a temperature lower than that of the main calcination. If the pre-fired in S13-1 is insufficient, the formation of the P2 phase in the finally obtained Na-containing oxide may become insufficient. In S13-1, by setting the pre-fired temperature to 300°C to 700°C and the pre-fired time to 2 hours to 10 hours, the composite can be sufficiently pre-fired, the thermal uniformity is improved, and the Na-containing oxide obtained by the later-described S13-2 and S13-3 can easily become a suitable oxide. The pre-firing temperature may be 400°C to less than 700°C, 450°C to less than 700°C, 500°C to less than 700°C, 550°C to less than 700°C, or 550°C to less than 650°C. In addition, the pre-firing time may be 2 hours to 8 hours, 3 hours to 8 hours, 4 hours to 8 hours, 5 hours to 8 hours, or 5 hours to 7 hours. The pre-firing atmosphere is not particularly limited, and may be, for example, an oxygen-containing atmosphere.

[0126] In S13-2, following the above-mentioned pre-calcination, the main calcination is performed for the composite at a temperature of 700°C to 1100°C for 30 minutes to 48 hours. In S13-2, the main calcination temperature of the composite can be 800°C to 1000°C. If the main calcination temperature is too low, the P2 phase is not generated. If the main calcination temperature is too high, the O3 phase is easily generated instead of the P2 phase. There is no particular limitation on the heating conditions from the pre-calcination temperature to the main calcination temperature. In S13-2, the shape of the oxide containing Na can be controlled by the main calcination time. If the main calcination time is too short, the generation of the P2 phase becomes insufficient. On the other hand, if the main calcination time is too long, the P2 phase grows excessively and the particles become coarse. By adjusting the main calcination time, the particle size of the primary particle 1a can be controlled to be less than 1.5μm.

[0127] In S13-3, following the above-mentioned main calcination, the composite is rapidly cooled (cooled at a temperature drop rate of 20°C / min or more) from a temperature T1 of more than 200°C to a temperature T2 of less than 100°C. The above-mentioned preliminary calcination and main calcination are performed, for example, in a heating furnace. In step S13-3, for example, after the main calcination of the composite is performed in a heating furnace, it is cooled to an arbitrary temperature T1 of more than 200°C in the heating furnace. After reaching the temperature T1, the calcined product is taken out of the heating furnace and rapidly cooled outside the furnace to an arbitrary temperature T2 of less than 100°C. Temperature T1 is an arbitrary temperature of more than 200°C, and can be an arbitrary temperature of more than 250°C. Temperature T2 is an arbitrary temperature of less than 100°C, and can be an arbitrary temperature of less than 50°C, and can be the cooling end temperature. In the specified temperature range from temperature T1 to temperature T2, moisture easily penetrates into the interlayers of the P2 type structure due to atomic vibration or molecular motion. It is believed that by shortening the time when the composite body (Na-containing oxide having a P2-type structure) after the main firing is cooled to such a temperature region where water easily penetrates (i.e., performing rapid cooling), the amount of water penetrating into the interlayers of the P2-type structure is reduced. In this regard, in step S13-3, when the composite body after the main firing is cooled, for example, by cooling in a dry atmosphere outside the furnace from an arbitrary temperature T1 above 200°C to an arbitrary temperature T2 below 100°C, the cooling rate from temperature T1 to temperature T2 becomes high (e.g., 20°C / min or more), and it becomes difficult for water to penetrate into the interlayers of the P2-type structure, which can suppress the collapse of the P2-type structure. As a result, Na can be effectively ion-exchanged for Li in S4.

[0128] By using S13, it is possible to manufacture an oxide containing Na having a P2 type structure and a prescribed chemical composition. The oxide containing Na contains at least one transition metal element among Mn, Ni and Co, Na, and O as constituent elements. Among them, when at least Na, Mn, at least one of Ni and Co, and O are contained as constituent elements, in particular, when at least Na, Mn, Ni, Co, and O are contained as constituent elements, the performance of the positive electrode active material is likely to be further improved. The oxide containing Na may have a composition consisting of Na c Mn x-p Ni y-q Co z-r M p+q+rThe chemical composition represented by O2. Wherein, 0<c<1.00, x+y+z=1 and 0≤p+q+r<0.17. In addition, 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. In the case where the oxide containing Na has such a chemical composition, it is easy to further maintain the P2 type structure. In the above chemical composition, c is greater than 0, and can be greater than 0.10, greater than 0.20, greater than 0.30, greater than 0.40, greater than 0.50 or greater than 0.60, and is less than 1.00, and can be less than 0.90, less than 0.80 or less than 0.70. 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 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. In addition, y is 0 or more, and may be 0.10 or more, or 0.20 or more, and is 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. In addition, z is 0 or more, and may be 0.10 or more, 0.20 or more, or 0.30 or more, and is 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. Element M has a small contribution to charge and discharge. From this aspect, in the above chemical composition, by making p+q+r less than 0.17, it is easy to ensure a high charge and discharge capacity. p+q+r can be less than 0.16, less than 0.15, less than 0.14, less than 0.13, less than 0.12, less than 0.11 or less than 0.10. On the other hand, by including the element M, the P2 type structure and the O2 type structure are easily stabilized. In the above chemical composition, p+q+r is greater than 0, and can be greater than 0.01, greater than 0.02, greater than 0.03, greater than 0.04, greater than 0.05, greater than 0.06, greater than 0.07, greater than 0.08, greater than 0.09 or greater than 0.10. The composition of O is approximately 2, and is not limited to exactly 2.0, but is indefinite.

[0129] 2.2.4 Ion exchange

[0130] In S14, at least a portion of the Na in the oxide containing Na obtained by S13 is ion-exchanged with Li to obtain a primary particle 1a having an O2 type structure. In ion exchange, for example, there is a method using an aqueous solution containing lithium halide, and a method using a mixture of lithium halide and other lithium salts (such as a molten salt). From the viewpoint that the P2 type structure is easily destroyed by the intrusion of water and the viewpoint of crystallinity, the method using a molten salt is preferred among the above two methods. That is, by mixing the above-mentioned oxide containing Na with the P2 type structure with the molten salt, heating to a temperature above the melting point of the molten salt, at least a portion of the Na in the oxide containing Na 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 salts constituting the molten salt are preferably lithium nitrate. By using a molten salt, the melting point is lowered compared to the case where lithium halide or other lithium salts are 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, an O3 type structure as a stable phase is easily generated instead of an O2 type structure. On the other hand, from the viewpoint of shortening the time spent on ion exchange, the temperature in the ion exchange may be as high as possible.

[0131] 2.3 Other processes

[0132] The method for manufacturing the active material secondary particle 1 according to one embodiment may, for example, include: doping the primary particle 1a constituting the active material secondary particle 1 with Li. As a result, the capacity of the active material secondary particle 1 can be further increased. For example, by contacting the primary particle 1a with a reducing solution containing Li ions, the primary particle 1a can be doped with Li. The so-called "reducing solution" means a solution having reducing properties, for example, a solution containing an electrophilic agent. The reducing solution may, for example, be a solution obtained by dissolving an electrophilic agent and a Li source in a solvent. The solvent may be various organic solvents capable of dissolving an electrophilic agent and a Li source. The electrophilic agent may be various substances that are soluble in the above-mentioned solvents. The electrophilic agent may be an aromatic organic compound. The Li source may be various substances that are dissolved in the above-mentioned solvents to generate Li ions. The Li source may be metallic lithium or a Li compound. The concentration of the electrophilic agent and the Li ions contained in the reducing solution may be appropriately determined according to the target doping amount. According to the knowledge of the present inventors, the more Li ions contained in the reducing solution relative to the amount of transition metal oxide containing Li in contact with the reducing solution, the easier it is to increase the doping amount of Li relative to the transition metal oxide containing Li. There is no particular limitation on the molar ratio of the electrophilic agent contained in the reducing solution to the Li ions (electrophilic agent / Li ions). There is no particular limitation on the contact method between the reducing solution and the primary particles 1a. For example, the primary particles 1a can be immersed in the reducing solution, or the reducing solution can be sprayed on the primary particles 1a. There is no particular limitation on the temperature during contact, and it can be heated or not. In addition, the primary particles 1a can be immersed in the reducing solution and then stirred. There is no particular limitation on the time for contacting the primary particles 1a with the reducing solution, and it can be appropriately determined according to the target doping amount. The timing of doping Li with the primary particles 1a can be before or after the secondary particles are formed.

[0133] In addition, the method for producing the active material secondary particles 1 according to one embodiment may include: crushing the above-mentioned oxide containing Na with a P2-type structure and the primary particles 1a having an O2-type structure to obtain the primary particles 1a having a particle size of 1.5 μm or less; and / or classifying the above-mentioned oxide containing Na with a P2-type structure and the primary particles 1a having an O2-type structure to obtain the primary particles 1a having a particle size of 1.5 μm or less. That is, the particle size of the primary particles 1a can be controlled by the calcination conditions of the above-mentioned oxide containing Na with a P2-type structure, etc., and can also be adjusted by crushing or classification.

[0134] 3. Electrode composite materials

[0135] The active material secondary particles 1 can, for example, form an electrode composite material together with other materials. Figure 3As shown, the electrode composite 5 involved in one embodiment may include the active material secondary particles 1 of the present disclosure described above, and the solid electrolyte 2. The electrode composite 5 involved in one embodiment may optionally include a conductive additive, a binder and other additives. The respective contents of the active material, electrolyte, conductive additive and binder in the electrode composite 5 can be appropriately set according to the target battery performance. For example, when the solid component contained in the electrode composite 5 is set to 100% by mass as a whole, the content of the active material can be 40% by mass or more and less than 100% by mass, and the content of the solid electrolyte can be greater than 0% by mass and less than 60% by mass. The content of the active material in the electrode composite 5 can be 50% by mass or more, 60% by mass or more, 70% by mass or more or 80% by mass or more, and can be 90% by mass or less, and the content of the solid electrolyte can be 10% by mass or more, and can be 50% by mass or less, 40% by mass or less, 30% by mass or less or 20% by mass or less. These lower and upper limits can be combined arbitrarily.

[0136] 3.1 Active substances

[0137] The active material contained in the electrode composite 5 may include only the above-mentioned active material secondary particles 1, or may include active materials other than the above-mentioned active material secondary particles 1 while including the active material secondary particles 1. From the viewpoint of further improving the effect of the technology disclosed in the present invention, the proportion of other active materials in the overall active material contained in the electrode composite 5 may be a small amount. For example, when the overall active material contained in the electrode composite 5 is set to 100 mass%, the content of the above-mentioned active material secondary particles 1 may be 50 mass% or more and 100 mass% or less, 60 mass% or more and 100 mass% or less, 70 mass% or more and 100 mass% or less, 80 mass% or more and 100 mass% or less, 90 mass% or more and 100 mass% or less, 95 mass% or more and 100 mass% or less, or 99 mass% or more and 100 mass% or less.

[0138] As for other active materials that may be contained in the electrode composite 5, any known active materials may be used. In the electrode composite 5, as other active materials, for example, the above-mentioned primary particles 1a having an O2 type structure may be included in a state that has not yet been converted into secondary particles. In addition, in the electrode composite 5, as other active materials, at least one selected from various lithium compounds, elemental sulfur and sulfur compounds other than the primary particles 1a may be included. The lithium compound as other active material may be an oxide containing Li 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 Mn, Ni, Co, Al, Fe and Ti. More specifically, the oxide containing Li as other active materials may be selected from 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 lithium compounds (composed of Li 1+x Mn 2-x-y M y O4 (M is one or more selected from Al, Mg, Co, Fe, Ni and Zn) represented by a different element substitution Li-Mn spinel, etc.), lithium nickel cobalt aluminum oxide (such as Li 1±α Ni p Co q Al r O 2±δ(for example, p+q+r=1)), lithium titanate, lithium metal phosphate (LiMPO4, etc., M is one or more selected from Fe, Mn, Co and Ni), etc. In particular, when other active materials include Li-containing oxides containing at least one of Ni, Co and Mn, and Li, and O as constituent elements, higher performance is easily obtained. Alternatively, when other active materials include Li-containing oxides containing at least one of Ni, Co and Al, and Li, and O as constituent elements, higher performance is easily obtained. Other active materials may be used alone or in combination of two or more. The shape of other active materials can be any shape that is generally used as an active material. Other active materials may be, for example, in the form of particles. Other active materials may be solid or have voids, for example, may be porous or hollow. Other active materials may be primary particles or secondary particles formed by the agglomeration (aggregation) of multiple primary particles. The average particle size D50 of 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.

[0139] 3.2 Electrolytes

[0140] The electrode composite 5 may contain an electrolyte while containing the above-mentioned active material secondary particles 1. The electrolyte that may be contained in the electrode composite 5 may be a solid electrolyte, a liquid electrolyte, or a combination thereof. In particular, as described above, when the electrode composite 5 contains a solid electrolyte, the effect produced by the technology disclosed in the present invention becomes more significant.

[0141] 3.2.1 Solid Electrolyte

[0142] As a solid electrolyte, a solid electrolyte known as a solid electrolyte for a battery can be used. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, the ion conductivity and heat resistance of the inorganic solid electrolyte are excellent. As an inorganic solid electrolyte, for example, oxide solid electrolytes, sulfide solid electrolytes, and ionic inorganic solid electrolytes can be listed. In particular, when the electrode composite 5 includes a sulfide solid electrolyte as a solid electrolyte, it is easy to ensure higher performance. The sulfide solid electrolyte may, for example, contain at least Li, S, and P as constituent elements. Alternatively, the electrode composite 5 may include an ionic solid electrolyte as a solid electrolyte, for example, a solid electrolyte containing at least Li, Y, and 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 in the form of particles. The average particle size (D50) of the solid electrolyte may be, for example, greater than 10 nm and less than 10 μm. The solid electrolyte may be used alone or in combination of two or more.

[0143] The oxide solid electrolyte may be selected from lithium lanthanum zirconate, LiPON, Li 1+X Al X Ge 2-X (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.

[0144] The sulfide solid electrolyte may be a glass-based sulfide solid electrolyte (sulfide glass), a glass-ceramic sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. Sulfide glass is amorphous. 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 Thio-LISICON type crystalline phase, LGPS type crystalline phase, and Argentum type crystalline phase. The sulfide solid electrolyte may be in the form of particles. The average particle size (D50) of the sulfide solid electrolyte may be, for example, 10 nm or more and 100 μm or less.

[0145] 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, In), and S element. In addition, the sulfide solid electrolyte may further contain at least one of O element and halogen element. In addition, the sulfide solid electrolyte may contain S element as the main component of the anion element.

[0146] The sulfide solid electrolyte can be, for example, selected from 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 (wherein m and n are positive numbers. Z is any one of Ge, Zn, and Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (wherein x and y are positive numbers. M is any one of P, Si, Ge, B, Al, Ga, and In.)

[0147] There is no particular limitation on the composition of the sulfide solid electrolyte, and examples thereof include xLi2S·(100-x)P2S5(70≤x≤80), yLiI·zLiBr·(100-yz)(xLi2S·(1-x)P2S5)(0.7≤x≤0.8, 0≤y≤30, 0≤z≤30), etc. Alternatively, the sulfide solid electrolyte may have a general formula: Li 4-x Ge 1-x P x The composition represented by S4 (0<x<1). In the above general formula, at least a part of Ge can be replaced by at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V and Nb. In the above general formula, at least a part of P can be replaced by at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V and Nb. In the above general formula, a part of Li can be replaced by at least one of Na, K, Mg, Ca and Zn. In the above general formula, a part of S can be replaced by halogen (at least one of F, Cl, Br and I). Alternatively, the sulfide solid electrolyte may have a Li 7-a PS 6-a X a (X is at least one of Cl, Br and I, and a is a number greater than or equal to 0 and less than or equal to 2). a may be 0 or greater than 0. In the latter case, a may be greater than or equal to 0.1, greater than or equal to 0.5, or greater than or equal to 1. In addition, a may be less than or equal to 1.8, or less than or equal to 1.5.

[0148] The ionic solid electrolyte may, for example, contain at least one element selected from Mg, Ca, Sr, Ba, Zn, Sn, Al, Sc, Ga, Bi, Sb, Zr, Hf, Ti, Ta, Nb, W, Y, Gd, Tb and Sm. These elements can generate cations in water. In addition, the ionic solid electrolyte material may, for example, further contain at least one halogen element selected from Cl, Br, I and F. These elements can generate anions in water. The ionic solid electrolyte may contain at least one selected from Gd, Ca, Zr and Y, at least one selected from Cl, Br, I and F, and Li. In addition, the ionic solid electrolyte contains Li and Y, and may contain at least one selected from Cl, Br, I and F. More specifically, the ionic solid electrolyte may contain Li and Y and Cl and Br, may contain Li and Ca and Y and Gd and Cl and Br, or may contain Li and Zr and Y and Cl. More specifically, the ionic solid electrolyte may be Li3YBr2Cl4, Li 2.8 Ca 0.1 Y 0.5 G 0.5 Br2Cl4, and Li 2.5 Y 0.5 Zr0.5 At least one of Cl6.

[0149] The ionic solid electrolyte may be a halide solid electrolyte. The halide solid electrolyte has excellent ion conductivity. As a halide solid electrolyte, for example, it may have a halide solid electrolyte represented by formula (A):

[0150] Li α M β X γ ···(A)

[0151] The composition represented by . Wherein, α, β and γ are each independently a value greater than 0, M is at least one selected from metal elements and semi-metal elements other than Li, and X is at least one selected from Cl, Br and I. Furthermore, the "semi-metal element" may be at least one selected from B, Si, Ge, As, Sb and Te. In addition, the "metal element" may include (i) all elements contained in the first to twelfth groups of the periodic table (however, excluding hydrogen) and (ii) all elements contained in the thirteenth to sixteenth groups of the periodic table (however, excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S and Se.). The metal element forms an inorganic compound together with the halide ion and can become a cation.

[0152] In formula (A), M may include Y (ie, yttrium). The halide solid electrolyte including Y may have a a Me b Y c A composition represented by X6 (wherein a+mb+3c=6, c>0, Me is at least one selected from metal elements and semi-metal elements other than Li and Y, and m is the valence of Me). Me can be, for example, at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta and Nb.

[0153] The halide solid electrolyte may have a structure represented by formula (A1): Li 6-3d Y d The composition represented by X6. In formula (A1), X is one or more elements selected from Cl, Br and I. d may satisfy 0<d<2, and may be d=1. The halide solid electrolyte may have a composition represented by formula (A2): Li 3-3δ Y 1+δ The composition represented by Cl6. In formula (A2), 0<δ≤0.15. The halide solid electrolyte may have a composition represented by formula (A3): Li 3-3δ Y 1+δ The composition represented by Br6. In formula (A3), 0<δ≤0.25 may be satisfied. The halide solid electrolyte may have a composition represented by formula (A4): Li 3-3δ+a Y 1+δ-a Mea Cl 6-x-y Br x I y In formula (A4), Me may be at least one selected from 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 may have a composition represented by formula (A5): Li 3-3δ Y 1+δ-a Me a Cl 6-x-y Br x I y In formula (A5), Me may be at least one selected from 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. The halide solid electrolyte may have a composition represented by formula (A6): Li 3-3δ- a Y 1+δ-a Me a Cl 6-x-y Br x I y In formula (A6), Me may be at least one selected from 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. The halide solid electrolyte may have a composition represented by formula (A7): Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x-y Br x I y The composition represented by the formula (A7) may be at least one selected from Ta and Nb. In the formula (A7), -1<δ<1, 0<a<1.2, 0<(3-3δ-2a), 0<(1+δ-a), 0≤x≤6, 0≤y≤6, and (x+y)≤6.

[0154] The ionic solid electrolyte may be a complex hydride (complex hydride) solid electrolyte. The complex hydride solid electrolyte may be composed of Li ions and complex ions containing H. The complex ions containing H may, for example, have an element M containing at least one of a non-metallic element, a semi-metallic element, and a metal element, and H bound to the element M. In addition, in the case of the complex ion containing H, the element M as the central element and the H surrounding the element M may be bound to each other via covalent bonds. In addition, the complex ion containing H may be composed of (M m Hn ) α- Indicated. In this case, m is an arbitrary positive number, and n and α can be arbitrary positive numbers according to m, the valence of the element M, etc. The element M only needs to be a non-metallic element or a metal element that can form a complex ion. For example, the element M may contain at least one of B, C and N as a non-metallic element, and may contain B. In addition, for example, the element M may contain at least one of Al, Ni and Fe as a metal element. In particular, when the complex ion contains B, or contains C and B, it is easy to ensure higher ion conductivity. As a specific example of a complex ion containing H, (CB9H 10 ) - , (CB 11 H 12 ) - ,(B 10 H 10 ) 2- ,(B 12 H 12 ) 2- 、(BH4) - 、(NH2) - 、(AlH4) - , and combinations thereof. In particular, when using (CB9H 10 ) - , (CB 11 H 12 ) - , or a combination thereof, it is easy to ensure higher ion conductivity. That is, the complex hydride solid electrolyte may contain Li, C, B and H.

[0155] 3.2.2 Liquid Electrolytes

[0156] The liquid electrolyte (electrolyte) is a liquid containing lithium ions as carrier ions. The electrolyte may be an aqueous electrolyte or a non-aqueous electrolyte. The composition of the electrolyte may be the same as the composition known as the composition of the electrolyte of a lithium ion secondary battery. The electrolyte may be a product of dissolving a lithium salt in water or a non-aqueous solvent. As a non-aqueous solvent, for example, various carbonate-based solvents may be listed. As a lithium salt, for example, lithium amide salts, LiPF6, etc. may be listed.

[0157] 3.3 Conductive additives

[0158] As the conductive additive that can be included in the electrode composite material 5, for example, 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 can be listed. The conductive additive can be, for example, in the form of particles or fibers, and its size is not particularly limited. The conductive additive can be used alone or in combination of two or more.

[0159] 3.4 Adhesives

[0160] As the binder that can be included in the electrode composite material 5, for example, there can be listed 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. The binders can be used alone or in combination of two or more.

[0161] 3.5 Others

[0162] The electrode composite material 5 may contain various additives in addition to the above-mentioned components, such as a dispersant, a lubricant, and the like.

[0163] 4. Battery

[0164] The active material secondary particles 1 can be used as a positive electrode active material of a battery, for example. Figure 4 As shown, a battery 100 according to one embodiment includes a positive electrode active material layer 10, an electrolyte layer 20, and a negative electrode active material layer 30. The positive electrode active material layer 10 includes the active material secondary particle 1 of the present disclosure.

[0165] 4.1 Positive electrode active material layer

[0166] The positive electrode active material layer 10 contains at least the above-mentioned active material secondary particles 1 of the present disclosure, and may further optionally contain an electrolyte, a conductive aid, a binder, etc. Furthermore, the positive electrode active material layer 10 may also contain various additives. In other words, the positive electrode active material layer 10 may be composed of the above-mentioned electrode composite material 5. There is no particular limitation on the shape of the positive electrode active material layer 10, for example, it may be a sheet-shaped positive electrode active material layer 10 with a roughly flat surface. There is no particular limitation on the thickness of the positive electrode active material layer 10, for example, it may be greater than 0.1 μm or greater than 1 μm, and may be less than 2 mm or less than 1 mm.

[0167] 4.2 Electrolyte layer

[0168] The electrolyte layer 20 is arranged between the positive electrode active material layer 10 and the negative electrode active material layer 30. The electrolyte layer 20 contains at least an electrolyte. The electrolyte layer 20 may contain at least one of a solid electrolyte and an electrolyte solution, and may further optionally contain a binder, etc. In particular, when the electrolyte layer 20 contains a solid electrolyte, it is easy to ensure higher performance. There is no particular limitation on the content of the electrolyte and the binder, etc. in the electrolyte layer 20. Alternatively, the electrolyte layer 20 may have a diaphragm (separator) for preventing the positive electrode active material layer 10 from contacting the negative electrode active material layer 30 while maintaining the electrolyte solution. There is no particular limitation on the thickness of the electrolyte layer 20, for example, it may be 0.1 μm or more or 1 μm or more, or it may be 2 mm or less or 1 mm or less.

[0169] The electrolyte layer 20 may be composed of one layer or a plurality of layers. For example, the electrolyte layer 20 may include: a first layer configured on the positive electrode active material layer 10 side, and a second layer configured on the negative electrode active material layer 30 side, the first layer may include a first electrolyte, and the second layer may include a second electrolyte. The first electrolyte and the second electrolyte may be different types 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.

[0170] As the electrolyte contained in the electrolyte layer 20, it is sufficient to select appropriately from the electrolyte (solid electrolyte and / or liquid electrolyte) exemplified as the electrolyte that can be contained in the above-mentioned positive electrode active material layer 10 (electrode composite material 5). In addition, for the binder that can be contained in the electrolyte layer 20, it is sufficient to select appropriately from the binder exemplified as the binder that can be contained in the above-mentioned positive electrode active material layer. Electrolytes and binders can be used alone or in combination of two or more. The diaphragm (separator) can be a diaphragm commonly used in batteries, for example, diaphragms composed of resins such as polyethylene (PE), polypropylene (PP), polyester and polyamide can be listed. The diaphragm can be a single-layer structure or a multi-layer structure. As a multi-layer structure diaphragm, for example, a 2-layer structure diaphragm of PE / PP, or a 3-layer structure diaphragm of PP / PE / PP or PE / PP / PE can be listed. The diaphragm can be composed of non-woven fabrics such as cellulose non-woven fabrics, resin non-woven fabrics, and glass fiber non-woven fabrics.

[0171] 4.3 Negative electrode active material layer

[0172] The negative electrode active material layer 30 contains at least a negative electrode active material. In addition, the negative electrode active material layer 30 may optionally contain an electrolyte, a conductive aid, a binder, and various additives. The content of each component in the negative electrode active material layer 30 can be appropriately determined according to the target battery performance. For example, when the solid content of the negative electrode active material layer 30 is set to 100% by mass, the content of the negative electrode active material may be 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, and may be 100% by mass or less, less than 100% by mass, 95% by mass or less, or 90% by mass or less. Alternatively, when the negative electrode active material layer 30 is set to 100% by volume, it may contain a total of 85% by volume or more, 90% by volume or more, or 95% by volume or more of a negative electrode active material and optional electrolytes, conductive aids, and binders, and the remainder may be voids or other components. The shape of the negative electrode active material layer 30 is not particularly limited, for example, it may be a sheet with 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 less, or 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less.

[0173] As for the negative electrode active material, any material known as the negative electrode active material of the battery can be used. Among the known active materials, various materials whose potential for absorbing and releasing ions (charge and discharge potential) is lower than that of the above-mentioned positive electrode active materials can be used. 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, etc. can 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 easily improved. The negative electrode active material can be used alone or in combination of two or more. The shape of the negative electrode active material can be any shape as the general shape of the negative electrode active material of the battery. For example, the negative electrode active material can be in the form of particles. The negative electrode active material particles can be primary particles or secondary particles formed by the agglomeration (aggregation) of multiple primary particles. The average particle size (D50) of the negative electrode active material particles may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, 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, film) such as lithium foil. That is, the negative electrode active material layer 30 may be composed of a sheet of the negative electrode active material.

[0174] As the electrolyte that can be contained in the negative electrode active material layer 30, for example, the above-mentioned solid electrolyte, electrolyte solution or a combination thereof can be listed. The conductive aid that can be contained in the negative electrode active material layer 30, for example, can be appropriately selected from the conductive aids exemplified as the conductive aids that can be contained in the above-mentioned positive electrode active material layer 10 (electrode composite material 5). The binder that can be contained in the negative electrode active material layer 30, for example, can be appropriately selected from the binders exemplified as the binders that can be contained in the above-mentioned positive electrode active material layer 10 (electrode composite material 5). The electrolyte, the conductive aid, and the binder can be used alone or in combination of two or more.

[0175] 4.4 Positive electrode collector

[0176] like Figure 4 As shown, the battery 100 may include a positive electrode collector 40 in contact with the positive electrode active material layer 10. As for the positive electrode collector 40, any positive electrode collector generally used as a positive electrode collector of a battery can be used. In addition, the positive electrode collector 40 may have at least one shape selected from foil, plate, mesh, punched metal, and foam. The positive electrode collector 40 may be composed of a metal foil or a metal mesh. In particular, the metal foil has excellent handling properties. The positive electrode collector 40 may be composed of a plurality of foils. As the metal constituting the positive electrode collector 40, 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 can be listed. In particular, from the viewpoint of ensuring oxidation resistance, the positive electrode collector 40 may contain Al. The positive electrode collector 40 may have some coating on its surface for the purpose of adjusting resistance, etc. For example, the positive electrode current collector 40 may have a carbon coating. In addition, the positive electrode current collector 40 may be a product obtained by plating or vapor-depositing the above-mentioned metal on a metal foil or a substrate. In addition, when the positive electrode current collector 40 is composed of a plurality of metal foils, some layers may be provided between the plurality of metal foils. The thickness of the positive electrode current collector 40 is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or less, and may be 1 mm or less or 100 μm or less.

[0177] 4.5 Negative Electrode Collector

[0178] like Figure 4As shown, the battery 100 may include a negative electrode collector 50 in contact with the negative electrode active material layer 30. As for the negative electrode collector 50, any negative electrode collector generally used as a negative electrode collector of a battery can be used. In addition, the negative electrode collector 50 may be in the form of a foil, a plate, a mesh, a punched metal, a foam, etc. The negative electrode collector 50 may be a metal foil or a metal mesh, or may be a carbon sheet. In particular, the metal foil has excellent handling properties. The negative electrode collector 50 may be composed of a plurality of foils and sheets. As the metal constituting the negative electrode collector 50, 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 can be listed. In particular, from the viewpoint of ensuring reduction resistance and the viewpoint of being difficult to alloy with lithium, the negative electrode collector 50 may contain at least one metal selected from Cu, Ni, and stainless steel. The negative electrode current collector 50 may have some coating on its surface for the purpose of adjusting resistance, etc. For example, the negative electrode current collector 50 may have a carbon coating. The negative electrode current collector 50 may be an aluminum foil having a carbon coating. In addition, the negative electrode current collector 50 may be a product of plating or vapor-depositing the above-mentioned metal on a metal foil or a substrate. In addition, when the negative electrode current collector 50 is composed of a plurality of metal foils, there may be some layers between the plurality of metal foils. There is no particular limitation on the thickness of the negative electrode current collector 50. For example, it may be greater than 0.1 μm or greater than 1 μm, and may be less than 1 mm or less than 100 μm.

[0179] 4.6 Other components

[0180] In addition to the above-mentioned structures, the battery 100 may also include structures that are common to batteries. For example, pole pieces, terminals, etc. The battery 100 may be a product in which the above-mentioned structures are housed inside an outer packaging body. As for the outer packaging body, any outer packaging body known as an outer packaging body of a battery can be adopted. In addition, a plurality of batteries 100 can be electrically connected arbitrarily, and can be overlapped arbitrarily to form a battery pack. In this case, the battery pack can be accommodated inside a known battery casing. As the shape of the battery 100, for example, a coin type, a laminate type, a cylindrical type, and a square type can be listed. The battery 100 may be a secondary battery.

[0181] The battery 100 can be manufactured by applying a known method, except for using the specific active material secondary particles 1 described above. 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 can be formed by dry molding, for example.

[0182] (1) The active material secondary particles 1 and the like 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 the positive electrode collector using a scraper or the like, and then dried to form a positive electrode active material layer on the surface of the positive electrode collector to prepare a positive electrode.

[0183] (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 collector using a scraper or the like, and then dried to form a negative electrode active material layer on the surface of the negative electrode collector to prepare a negative electrode.

[0184] (3) The layers are stacked in such a way that the electrolyte layer (solid electrolyte layer or separator) is sandwiched between the negative electrode and the positive electrode to obtain a stacked body having a negative electrode collector, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer and a positive electrode collector in this order. Other components such as terminals are installed on the stacked body as needed.

[0185] (4) The stacked body is housed in a battery case, and in the case of an electrolyte battery, the battery case is filled with an electrolyte, the stacked body is immersed in the electrolyte, and the stacked body is sealed in the battery case, thereby preparing a secondary battery. In the case of an electrolyte battery, the negative electrode active material layer, the separator, and the positive electrode active material layer may contain an electrolyte at the stage (3) above.

[0186] 5. Vehicles

[0187] The battery disclosed in the present invention has high capacity and low resistance by using the active material secondary particles 1. Such a battery can be preferably used in a vehicle selected from at least one of a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV) and a pure electric vehicle (BEV). That is, the technology disclosed in the present invention also has the following aspects: a vehicle, which is a vehicle having a battery, wherein the battery has a positive electrode active material layer, an electrolyte layer and a negative electrode active material layer, and the positive electrode active material layer contains the active material secondary particles 1 disclosed above.

[0188] Example

[0189] As described above, one embodiment of the active material secondary particles, etc., has been described, but the technology of the present disclosure can be variously modified outside the above embodiment without departing from the scope of its purpose. The following examples are shown to explain the technology of the present disclosure in more detail, but the technology of the present disclosure is not limited to the following examples.

[0190] 1. Preparation of primary particles

[0191] 1.1 Preparation of precursor

[0192] 1.1.1 Examples 1 to 7, Comparative Examples 1 to 5

[0193] (1) MnSO4·5H2O, NiSO4·6H2O, and CoSO4·7H2O were weighed to obtain a target 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 addition, Na2CO3 was dissolved in distilled water in another container to a concentration of 1.2 mol / L to obtain a second solution.

[0194] (2) 1000 mL of pure water was placed in a reaction container (with baffles), and 500 mL of the first solution and 500 mL of the second solution were added dropwise thereto at a rate of about 4 mL / min.

[0195] (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.

[0196] (4) The product is washed with pure water, separated into solid and liquid using a centrifuge, and the precipitate is recovered.

[0197] (5) The obtained precipitate was dried at 120° C. overnight, crushed in a mortar, and separated into coarse particles and fine particles by air flow classification. The fine particles were removed to obtain coarse particles as precursor particles.

[0198] 1.1.2 Example 8

[0199] 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.

[0200] 1.1.3 Example 9

[0201] 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.

[0202] 1.2 Fabrication of the complex

[0203] 1.2.1 Examples 1 to 9, Comparative Examples 1, 4 and 5

[0204] The above-mentioned precursor particles and Na2CO3 are weighed so that the composition after sintering described below becomes Na 0.8 Mn 0.5 Ni 0.2 Co 0.3O2 was mixed using a mortar, thereby coating the surfaces of the precursor particles with Na2CO3 to obtain a composite.

[0205] 1.2.2 Comparative Examples 2 and 3

[0206] (1) Na 2 CO 3 and distilled water were weighed to give a concentration of 1150 g / L, and then stirred with a stirrer until the mixture was completely dissolved, thereby preparing a Na 2 CO 3 aqueous solution.

[0207] (2) The Na2CO3 aqueous solution and the precursor particles are weighed and mixed so that the composition after calcination described below becomes Na 0.8 Mn 0.5 Ni 0.2 Co 0.3 O2, thereby obtaining a slurry.

[0208] (3) The slurry was dried by spray drying to obtain a composite. Specifically, a spray drying device DL410 was used at a slurry feeding rate of 30 mL / min, an inlet temperature of 200°C, and a circulating air volume of 0.8 m 3 The slurry was air-dried under the conditions of 0.5047 W / min and a spray pressure of 0.3 MPa, thereby coating the surfaces of the precursor particles with Na2CO3 to obtain a composite.

[0209] 1.3 Firing of the composite

[0210] The composite was placed in an alumina crucible and sintered in air atmosphere to obtain an oxide containing Na and having a P2 type structure. The sintering conditions were as described below (1) to (7).

[0211] (1) An alumina crucible containing the above-mentioned composite is placed in a heating furnace in an air atmosphere.

[0212] (2) The temperature in the heating furnace was raised from room temperature (25°C) to 600°C over 115 minutes.

[0213] (3) The temperature in the heating furnace is maintained at 600° C. for 360 minutes for preliminary calcination.

[0214] (4) After the preliminary firing, the temperature in the heating furnace was raised to 900°C and maintained at 900°C for 60 minutes for the main firing.

[0215] (5) After the main firing, the temperature in the heating furnace was lowered from the main firing temperature to 250°C, and the alumina crucible was taken out of the heating furnace at 250°C and allowed to cool outside the furnace in a dry atmosphere to 25°C in 10 minutes.

[0216] The fired product after cooling was pulverized using a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2-type structure (P2-type particles).

[0217] 1.4 Ion Exchange

[0218] (1) LiNO 3 and LiCl were weighed to a molar ratio of 50:50, and mixed with the above-mentioned P2 type particles at a molar ratio of 10 times the minimum amount of Li required for ion exchange to obtain a mixture.

[0219] (2) Using an alumina crucible, ion exchange was performed in an air atmosphere at 280° C. for 1 hour to obtain a product containing an oxide containing Li.

[0220] (3) The salt remaining in the product was washed with pure water, and the solid and liquid were separated by vacuum filtration to obtain a precipitate.

[0221] (4) The obtained precipitate was dried at 120° C. overnight to obtain primary particles of an oxide containing Li having an O2 type structure.

[0222] 2. Secondary particle

[0223] (1) A Li source and a Nb source are dissolved in water to obtain a solution.

[0224] (2) The above-mentioned primary particles are mixed in the solution to obtain a slurry.

[0225] (3) The slurry was sprayed and dried by spray drying, and then dried overnight at 120° C. to obtain intermediate particles including primary particles and Li-containing oxides (composite oxides of Li and Nb) as Li ion conductive materials. The conditions of spray drying (slurry liquid feeding flow rate, slurry solid content, and spraying air pressure) were adjusted to adjust the presence or absence of granulation of the intermediate particles and the particle size of the intermediate particles.

[0226] 3. Li doping

[0227] (1) In a glove box (Ar atmosphere), biphenyl was mixed in tetrahydrofuran (THF) to a concentration of 1 mol / L and dissolved to obtain a biphenyl solution.

[0228] (2) Li foil in an amount equal to the mole of biphenyl was added to the biphenyl solution and stirred for 2 hours to obtain a reducing solution containing 1 mol / L of Li ions.

[0229] (3) The intermediate particles A were added to the obtained reducing solution, and the mixture was immersed and stirred for 24 hours. The amount of the intermediate particles was adjusted so that the ratio of the molar number of dissolved Li ions to the molar number of the intermediate particles (Li / O2) was 0.35.

[0230] (4) The stirred intermediate particles were washed with THF and solid-liquid separation was performed by vacuum filtration. The obtained precipitate was dried at 120°C overnight to obtain active material particles for evaluation. The molar ratios of Mn, Ni and Co contained in the active material particles are shown in Tables 1 to 3 below. In addition, the crystal phase contained in the active material particles was confirmed by XRD, and the results showed that the active material particles had an O2 type structure.

[0231] 4. Observation of the morphology of active material particles

[0232] The morphology of the active material particles was observed using SEM. In the following Tables 1 to 3, for each of Examples 1 to 9 and Comparative Examples 1 to 5, the "shape of the primary particles constituting the active material particles (plate-like, spherical, or irregular shape)", "the particle size of the primary particles", "the presence or absence of granulation (secondary particle formation) of the active material particles", "the particle size of the active material particles when they are secondary particles", and "the ratio M2 / M1 of the mass M2 of the Li ion conductive material to the mass M1 of the primary particles" are shown. In addition, for reference, Figure 5 : A SEM image of the appearance of the active material particles of Example 6 is shown.

[0233] 5. Evaluation of charge and discharge characteristics

[0234] (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 dispersion device to obtain a positive electrode slurry. 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 coated on Al foil as a positive electrode collector foil by a doctor blade method, and dried on a hot plate at 100°C for 30 minutes to form a positive electrode active material layer on the Al foil.

[0235] (2) Lithium titanate (LTO) as a negative electrode active material, sulfide-based solid electrolyte, VGCF, PVdF-based binder and butyl butyrate were stirred using an ultrasonic dispersion device to obtain a negative electrode slurry. The mass ratio of negative electrode active material: sulfide-based solid electrolyte: VGCF: PVdF-based binder was 72.1:22.7:1.7:3.5. The negative electrode slurry was applied to Ni foil as a negative electrode collector foil using a doctor blade method, and dried on a hot plate at 100°C for 30 minutes to form a negative electrode active material layer on the Ni foil.

[0236] (3) A sulfide-based solid electrolyte, a PVdF-based binder, and butyl butyrate were stirred using an ultrasonic dispersion device to obtain a solid electrolyte slurry. The mass ratio of the sulfide-based solid electrolyte to the PVdF-based binder was 99.4:0.6. The solid electrolyte slurry was coated on an Al foil as a substrate using a doctor blade method and dried on a hot plate at 100°C for 30 minutes to obtain a peelable solid electrolyte layer.

[0237] (4) The positive electrode active material layer and the solid electrolyte layer were stacked and pressed with a roll press at a pressure of 50 kN / cm and a temperature of 160° C. The Al foil was peeled off from the solid electrolyte layer and punched into 1 cm 2 size, thereby obtaining a positive electrode stack.

[0238] (5) The negative electrode active material layer and the solid electrolyte layer are stacked, and after pressing with a roller press at a pressing pressure of 50 kN / cm and a temperature of 160°C, the Al foil is peeled off from the solid electrolyte layer to obtain a negative electrode stack. Furthermore, an additional solid electrolyte layer is stacked on the solid electrolyte side of the negative electrode stack, and pre-pressed with a flat uniaxial press at a pressing pressure of 100 MPa and a temperature of 25°C, the Al foil is peeled off from the solid electrolyte layer, and punched into 1.08 cm 2 , thereby obtaining a negative electrode stack having an additional solid electrolyte layer.

[0239] (6) The positive electrode laminate and the negative electrode laminate having an additional solid electrolyte layer were stacked with their surfaces overlapping, and pressed using a flat uniaxial press at a pressing pressure of 200 MPa and a temperature of 120° C. to obtain a battery laminate.

[0240] (7) The battery stack was sandwiched between two restraining plates, and the two restraining plates were fastened using a fastening tool at a restraining pressure of 5 MPa to fix the distance between the two restraining plates, thereby obtaining a battery cell for evaluation.

[0241] (8) The battery cells for evaluation were charged at a constant current of 1 / 10C to 3.25V, then charged at a constant voltage of 3.25V to a final current of 1 / 100C, then discharged at a constant current of 1 / 10C to 0.45V, then discharged at a constant voltage of 0.45V to a final current of 1 / 100C, and the initial discharge capacity was measured.

[0242] (9) Furthermore, the battery cells for evaluation were charged at a constant current of 1 / 10C to 2.2V, and then charged at a constant voltage of 2.2V to a final current of 1 / 100C, thereby adjusting the charging state. A current equivalent to 3C was passed through the battery cells for evaluation whose charging state was adjusted for 10 seconds, and the voltage change before and after was divided by the current value to measure the resistance value. The resistance value of Example 1 was set to 100, and the resistance values ​​of the other examples were normalized.

[0243] In Tables 1 to 3 below, “initial discharge capacity” and “normalized resistance value” are shown for each battery cell of Examples 1 to 9 and Comparative Examples 1 to 5.

[0244]

Table 1

[0245] (Table 1)

[0246]

[0247]

Table 2

[0248] (Table 2)

[0249]

Table 3

[0250] (Table 3)

[0251]

[0252] The following contents can be understood from the results shown in Tables 1 to 3.

[0253] 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 size is 2.0 μm or more. It is speculated that when the primary particle size is 2.0 μm or more, although granulation itself can be performed, the diffusion distance inside the bulk of the primary particles becomes longer, the diffusion resistance increases, the reaction area decreases, and the reaction resistance increases.

[0254] From the results of Examples 1 to 3 and Comparative Examples 2 to 3 in Table 1, it can be seen that the initial charge-discharge capacity increases when the primary particles include plate-like particles compared to the case where the primary particles include spherical particles. Spherical particles sometimes have voids inside them, which may reduce the utilization rate of the active material inside.

[0255] 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. It is speculated that the diffusion resistance increases due to the increase in diffusion resistance caused by the increase in diffusion distance inside the bulk, the increase in reaction resistance caused by the decrease in reaction area, and the decrease in curvature of Li diffusion in the electrode without secondary particle formation, which increases the diffusion resistance.

[0256] From the results of Comparative Example 5 in Table 1, it can be seen that the initial charge and discharge capacity decreases when the fine primary particles are used without being converted into secondary particles. It is speculated that this is because the fine primary particles have gaps and aggregate in the electrode production process, making it difficult to ensure the Li ion conduction path inside the aggregate.

[0257] From the results of Examples 4 to 7 in Table 2, it is understood that the effect of converting primary particles into secondary particles via the Li ion conductive material can be obtained regardless of the particle size of the secondary particles.

[0258] From the results of Examples 8 and 9 in Table 3, it can be seen that the effect of converting primary particles into secondary particles via the Li ion conductive material can be obtained regardless of the chemical composition of the primary particles having an O2 type structure.

[0259] 6. Summary

[0260] From the above results, it can be said that according to the following active material secondary particles, both high capacity and low resistance can be achieved.

[0261] The active material secondary particle comprises a plurality of primary particles and a Li ion conductive material, wherein 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, and the plurality of primary particles are bonded to each other via the Li ion conductive material.

Claims

1. An active material secondary particle comprising a plurality of primary particles and a Li ion conductive material, The plurality of primary particles have an O2 type structure, a particle size of the plurality of primary particles is 1.5 μm or less, and the plurality of primary particles are bonded to each other via the Li ion conductive material.

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

3. The active material secondary particle according to claim 1 or 2, wherein: At least a part of the plurality of primary particles are plate-like particles.

4. The active material secondary particle according to any one of claims 1 to 3, wherein The particle size of the active material secondary particles is 3 μm or more and 25 μm or less.

5. The active material secondary particle according to any one of claims 1 to 4, wherein The Li ion conductive material is an inorganic compound.

6. The active material secondary particle according to claim 5, wherein: The inorganic compound is an oxide containing Li.

7. An electrode composite material comprising: the active material secondary particles according to any one of claims 1 to 6, and a solid electrolyte.

8. The electrode composite material according to claim 7, wherein: The solid electrolyte includes a sulfide solid electrolyte. 9 . A battery comprising a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, wherein the positive electrode active material layer comprises the active material secondary particle according to claim 1 .

10. The battery according to claim 9, wherein The electrolyte layer includes a solid electrolyte.

11. A method for producing active material secondary particles, comprising: Multiple primary particles are combined into secondary particles through Li ion conductive materials. The plurality of primary particles have an O2 type structure, and a particle size of the plurality of primary particles is 1.5 μm or less.

12. The method for producing active material secondary particles according to claim 11, comprising: preparing a solution for dissolving the Li ion conductive material; and The solution is brought into contact with the plurality of primary particles and then dried, so that the plurality of primary particles are bonded via the Li ion conductive material to form secondary particles.

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