Electrode active material, battery, and manufacturing method for electrode active material

Abstract

To solve the problem in which an electrode active material having an O2 type structure has room for improvement in capacity at high potentials.SOLUTION: An electrode active material has at least one O2-like structure selected from an O2-type structure, a T#2-type structure, and an O6-type structure, and has the chemical structure: LiaNabNix-pCoy-qMnz-rMp+q+rO2 (where 0<a≤1.00, 0≤b≤0.20, 0.15<x<0.35, 0.15<y<0.45, 0.25<z<0.50, x+y+z=1, and 0≤p+q+r<0.17, where element M is one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W).SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present application discloses an electrode active material, a battery, and a method for manufacturing the electrode active material. [Background technology]

[0002] Known electrode active materials have an O2-like structure. As disclosed in Patent Document 1, an electrode active material having an O2-like structure can be obtained by ion-exchanging at least a portion of Na in a Na-containing oxide having a P2-type structure with Li. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-182420 Summary of the Invention [Problem to be solved by the invention]

[0004] Electrode active materials with an O2-like structure have room for improvement in terms of the ratio of capacity at high potential to the total capacity. [Means for solving the problem]

[0005] The present application discloses the following aspects as means for solving the above problems. <Aspect 1> An electrode active material, having at least one O2-like structure selected from the group consisting of an O2-type structure, a T#2-type structure, and an O6-type structure; Li a Na b Ni x-p Co y-q Mn z-r M p+q+rO2 (where 0 < a ≤ 1.00, 0 ≤ b ≤ 0.20, 0.15 < x < 0.35, 0.15 < y < 0.45, 0.25 < z < 0.50, 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) having a chemical composition represented by an electrode active material. <Aspect 2> The electrode active material according to Aspect 1, where 0.70 < a ≤ 1.00, an electrode active material. <Aspect 3> A method for manufacturing an electrode active material, comprising: obtaining a precursor; coating the surface of the precursor with a Na source to obtain a composite; subjecting the composite to a main firing to obtain a Na-containing oxide having a P2-type structure; and contacting the Na-containing oxide with an ion exchange material to ion-exchange at least a part of the Na contained in the Na-containing oxide with Li to obtain a Li-containing oxide having at least one O2-like structure among an O2-type structure, a T#2-type structure, and an O6-type structure, where the main firing temperature of the composite is 800°C or higher and 900°C or lower, where the main firing time of the composite is 1 hour or longer and 12 hours or shorter, where the Na-containing oxide is Na c Ni x-p Co y-q Mn z-r M p+q+r O2 (where 0 < c ≤ 1.00, 0.15 < x < 0.35, 0.15 < y < 0.45, 0.25 < z < 0.50, 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) having a chemical composition represented by a method for manufacturing an electrode active material.

Advantages of the Invention

[0006] The electrode active material of the present disclosure tends to have a high ratio of capacity at high potential to the total capacity. [Brief explanation of the drawings]

[0007] [Figure 1] 1 shows an example of the flow of a method for producing an electrode active material. [Figure 2] 1 shows a schematic diagram of an example of a battery configuration. [Figure 3] 1 shows X-ray diffraction patterns of electrode active materials according to Examples 1 to 3. [Figure 4] 1 shows X-ray diffraction patterns of electrode active materials according to Examples 4 and 5. [Figure 5] 1 shows an X-ray diffraction pattern of the electrode active material according to Comparative Example 1. [Figure 6] 1 shows X-ray diffraction patterns of electrode active materials according to Comparative Examples 2 to 5. [Figure 7] 1 shows an X-ray diffraction pattern of the electrode active material according to Comparative Example 6. [Figure 8] The graph shows the relationship between the Na content of the Na-containing oxide having a P2 structure and the ratio of the capacity at 3 V or higher to the total capacity of the electrode active material. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, one embodiment of the electrode active material etc. of the present disclosure will be described, but the electrode active material etc. of the present disclosure is not limited to the embodiment described below.

[0009] 1. Electrode active material The electrode active material according to one embodiment has an O2-like structure, either one or both of an O2-type structure and an O6-type structure, and Li a Na b Ni x-p Co y-q Mn z-r M p+q+rIt has a chemical composition represented by O2 (where 0 < a ≤ 1.00, 0 ≤ b ≤ 0.20, 0.15 < x < 0.35, 0.15 < y < 0.45, 0.25 < z < 0.50, 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).

[0010] 1.1 Crystal Structure The electrode active material according to one embodiment has at least one O2-like structure among the O2-type structure (belonging to the space group P63mc), the T♯2-type structure (belonging to the space group Cmca), and the O6-type structure (belonging to the space group R-3m, with the c-axis length being 2.5 nm or more and 3.5 nm or less, typically 2.9 nm or more and 3.0 nm or less, and different from the O3-type structure also belonging to the space group R-3m). The electrode active material may have an O2-like structure as the main phase.

[0011] In an electrode active material according to an embodiment, the crystallite size of the O2-like structure is not particularly limited. In an electrode active material according to an embodiment, a single crystallite may form a particle, or multiple crystallites may form a particle. In other words, an electrode active material according to an embodiment may be (1) an independently existing single-crystal particle, (2) an aggregate (secondary particle) of multiple single-crystal particles, (3) a polycrystalline particle including multiple crystallites, or (4) an aggregate (secondary particle) of multiple polycrystalline particles. In particular, when the electrode active material is a polycrystalline particle, particularly a spherical polycrystalline particle as described below, even higher performance as an electrode active material is likely to be ensured. As described below, an electrode active material according to an embodiment can be obtained by ion-exchanging at least a portion of Na in a Na-containing oxide having a P2-type structure with Li. Here, the P2-type structure is a hexagonal crystal system with a large diffusion coefficient of Na ions, which facilitates crystal growth in a specific direction. Therefore, crystallites having a P2 type structure usually have a crystal growth direction biased in a specific direction (for example, plate-like). When Na in P2 type crystallites whose crystal growth direction is biased in a specific direction is ion-exchanged with Li to obtain crystallites with an O2-like structure, the ends of the crystallites with the O2-like structure (the ends in the crystal growth direction) tend to become inlets and outlets for intercalation. In other words, when the electrode active material is a polycrystalline particle, the effects of increasing the number of inlets and outlets for intercalation contained in one particle, reducing reaction resistance, shortening the migration distance of lithium ions, reducing diffusion resistance, and reducing the amount of expansion and contraction of the particle as a whole during charge and discharge can be expected.

[0012] As described above, the crystallites of a Na-containing oxide having a P2 structure tend to be plate-shaped. That is, a Na-containing oxide having a P2 structure can be formed into plate-shaped particles, or small plate-shaped crystallites can be connected to each other to form spherical particles. In other words, a single electrode active material particle may be a plate-shaped single crystal particle as a whole, or a spherical polycrystalline particle. A spherical polycrystalline particle has multiple crystallites on its surface. When the electrode active material is a spherical polycrystalline particle, spheroidization reduces the degree of curvature and reduces the lithium ion conduction resistance. This, for example, improves the rate characteristics of the battery and increases the reversible capacity. In this application, "spherical particles" refers to particles with a circularity of 0.80 or more. The circularity of the particles may be 0.81 or more, 0.82 or more, 0.83 or more, 0.84 or more, 0.85 or more, 0.86 or more, 0.87 or more, 0.88 or more, 0.89 or more, or 0.90 or more. The circularity of the particles is 4πS / L 2 where S is the orthogonal projected area of ​​the particle, and L is the perimeter of the orthogonal projected image of the particle. The circularity of a particle can be determined by observing the appearance of the particle using a scanning electron microscope (SEM), transmission electron microscope (TEM), or optical microscope.

[0013] 1.2 Chemical composition The electrode active material according to one embodiment has an O2-like structure and a predetermined chemical composition, which makes it easy to increase the ratio of the capacity at a high potential to the total capacity. a Na b Ni x-p Co y-q Mn z-r M p+q+rO2 (where 0 < a ≤ 1.00, 0 ≤ b ≤ 0.20, 0.15 < x < 0.35, 0.15 < y < 0.45, 0.25 < z < 0.50, 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) has a chemical composition represented by the above. In the above chemical composition, a is greater than 0, and may be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, 0.60 or more, 0.70 or more, or greater than 0.70, and is less than or equal to 1.00, and may be less than 1.00, 0.90 or less, or 0.80 or less. In the above chemical composition, b is 0 or more, and may be 0.01 or more, 0.02 or more, or 0.03 or more, and is less than or equal to 0.20, and may be 0.15 or less, or 0.10 or less. In the above chemical composition, x is greater than 0.15, and may be 0.20 or more, and is less than 0.35, and may be 0.30 or less, 0.25 or less, or 0.20 or less. In the above chemical composition, y is greater than 0.15, and may be 0.20 or more, 0.25 or more, 0.30 or more, 0.35 or more, or 0.40 or more, and is less than 0.45, and may be 0.40 or less. z is greater than 0.25, and may be 0.30 or more, 0.35 or more, or 0.40 or more, and is less than 0.50, and may be 0.45 or less, or 0.40 or less. The element M has little contribution to charge and discharge. In this regard, in the above chemical composition, when p + q + r is less than 0.17, it is easy to ensure a high charge and discharge capacity. p + q + r may be 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, or 0.10 or less. On the other hand, when the element M is included, the O2-like structure is likely to be stabilized. In the above chemical composition, p + q + r is 0 or more, and may be 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, or 0.10 or more. The composition of O is approximately 2, but is not necessarily exactly 2.0 and is indefinite.

[0014] 1.3 Others The electrode active material according to one embodiment may be, for example, solid particles, hollow particles, or particles having voids. The particle size of the electrode active material is not particularly limited, but smaller sizes are considered to be more advantageous. For example, the average particle diameter (D50) of the electrode active material particles may be 0.1 μm or more and 10 μm or less, 1.0 μm or more and 8.0 μm or less, or 2.0 μm or more and 6.0 μm or less. The average particle diameter (D50) is the particle diameter (D50, median diameter) at 50% cumulative in a volume-based particle size distribution determined by a laser diffraction / scattering method.

[0015] The electrode active material according to one embodiment may be a positive electrode active material. The electrode active material according to one embodiment has an O2-like structure and the above-described predetermined chemical composition, which increases the proportion of the capacity at high potentials in the total capacity and facilitates improvement of the energy density. For example, in one embodiment, the proportion of the capacity at 3 V or higher in the total capacity may be 72.0% or more, 73.0% or more, 74.0% or more, or 75.0% or more. This proportion may be 85.0% or less, or 82.0% or less.

[0016] 2. Manufacturing method of electrode active material The electrode active material according to one embodiment can be produced, for example, by the following method. That is, as shown in FIG. 1, the method for producing the electrode active material according to one embodiment includes the steps of: S1: Obtaining precursors, S2: Coating the surface of the precursor with a Na source to obtain a composite; S3: calcining the composite to obtain a Na-containing oxide having a P2 type structure; and S4: bringing the Na-containing oxide into contact with an ion exchange material to ion-exchange at least a portion of the Na contained in the Na-containing oxide with Li, thereby obtaining a Li-containing oxide having at least one O2-like structure selected from the O2-type structure, the T#2-type structure, and the O6-type structure. The sintering temperature of the composite may be 800°C or higher and 900°C or lower, The main firing time of the composite may be 1 hour or more and 12 hours or less, where the Na-containing oxide is Na c Ni x-p Co y-q Mn z-r M p+q+r O2 (where 0 < c ≤ 1.00, 0.15 < x < 0.35, 0.15 < y < 0.45, 0.25 < z < 0.50, 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). More specifically, the S3 may be S3-1: subjecting the composite to pre-firing at a temperature of 300°C or more and less than 700°C for 2 hours or more and 10 hours or less, S3-2: subsequently to the pre-firing, subjecting the composite to main firing at a temperature of 800°C or more and 900°C or less for 1 hour or more and 12 hours or less, and S3-3: subsequently to the main firing, rapidly cooling the composite from a temperature T1 of 200°C or more to a temperature T2 of 100°C or less.

[0017] 2.1 Preparation of the precursor The precursor may contain at least one of Mn, Ni, and Co, or may contain Mn, Ni, and Co. The precursor may be a salt containing at least one of the elements Mn, Ni, and Co. For example, the precursor may be at least one of a carbonate, a sulfate, a nitrate, and an acetate. Alternatively, the precursor may be a compound other than a salt. For example, the precursor may be a hydroxide. The precursor may be a hydrate. The precursor may be a combination of multiple types of compounds. The precursor may have various shapes. For example, the precursor may be particulate, and may be spherical particles as described later. The particle diameter of the particles composed of the precursor is not particularly limited.

[0018] In S1, the precursor precipitate may be obtained by coprecipitation using an ion source capable of forming a precipitate in aqueous solution with transition metal ions and a transition metal compound containing at least one element selected from Mn, Ni, and Co. This facilitates the production of spherical particles as the precursor. The "ion source capable of forming a precipitate in aqueous solution with transition metal ions" may 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 may be the above salt or hydroxide containing at least one element selected from Mn, Ni, and Co. Specifically, in S11, the ion source and the transition metal compound may be prepared as separate solutions, and the respective solutions may be added dropwise and mixed to obtain the precursor precipitate. In this case, water, for example, is used as the solvent. Various sodium compounds may be used as bases, and aqueous ammonia or the like may be added to adjust the basicity. In the case of the coprecipitation method, for example, an aqueous solution of the transition metal compound and an aqueous solution of sodium carbonate are prepared, and the respective aqueous solutions are added dropwise and mixed to obtain the precursor precipitate. Alternatively, the precursor can be obtained by a sol-gel method, and in particular, by a coprecipitation method, spherical particles can be easily obtained as the precursor.

[0019] In S1, the precursor may contain element M. Element M is at least one element selected from B, Mg, Al, K, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W. These elements M have the function of stabilizing, for example, a P2-type structure or an O2-like structure. The method for obtaining a precursor containing element M is not particularly limited. When obtaining a precursor by coprecipitation in S1, for example, an aqueous solution of a transition metal compound containing at least one of Mn, Ni, and Co, an aqueous solution of sodium carbonate, and an aqueous solution of a compound of element M are prepared, and the respective aqueous solutions are added dropwise and mixed to obtain a precursor containing element M together with at least one element of Mn, Ni, and Co. Alternatively, in the manufacturing method of the present disclosure, element M may not be added in S1, and element M may be doped during the firing process described below.

[0020] 2.2 Preparation of the complex In S2, the surface of the precursor obtained in S1 is coated with a Na source to obtain a composite. The Na source may be a salt containing Na, such as a carbonate or a nitrate, or a compound other than a salt, such as sodium oxide or sodium hydroxide. In S2, the amount of Na source coated on the surface of the precursor may be determined taking into account the amount of Na lost during subsequent calcination. In S2, the coverage rate of the Na source relative to the surface of the precursor is not particularly limited. In S2, the method for coating the surface of the precursor with the Na source is not particularly limited. For example, the precursor and the Na source may be mixed in a mortar or a mixer, or the precursor may be brought into contact with a solution containing the Na source using a tumbling fluidized coating method, a spray drying method, or the like, and then dried.

[0021] In S2, the precursor may be coated with an M source together with a Na source. For example, in S2, the precursor obtained in S1 may be mixed with a Na source and an M source containing at least one element M selected from B, Mg, Al, K, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W 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 depending on the chemical composition of the Na-containing oxide after firing.

[0022] 2.3 Firing of the composite In S3, the composite obtained in S2 is calcined to obtain a Na-containing oxide having a P2-type structure. S3 may include the above S3-1, S3-2, and S3-3. By adjusting the conditions in S3-1, S3-2, and S3-3 according to the target chemical composition of the finally obtained O2-like structure, it is possible to adjust the shape (plate-like particles or spherical particles) of the P2-type Na-containing oxide obtained in S3, and to adjust the shape of the finally obtained O2-like structure. In particular, in S3, by setting the main calcination temperature of the composite to 800°C or higher and 900°C or lower and the main calcination time of the composite to 1 hour or higher and 12 hours or lower, it is possible to more appropriately generate an O2-like structure while maintaining the above chemical composition.

[0023] In step S3-1, the composite is pre-fired at a temperature of 300°C to less than 700°C for 2 to 10 hours. In step S3-1, the composite may be optionally molded and then pre-fired. The pre-fired temperature is lower than that of the main firing. If the pre-fired temperature in step S3-1 is insufficient, the P2 phase may not be sufficiently formed in the final Na-containing oxide. In step S3-1, the pre-fired temperature is 300°C to less than 700°C and the pre-fired time is 2 to 10 hours. This allows the composite to be sufficiently pre-fired, improving thermal uniformity and making it easier for the Na-containing oxide obtained through steps S3-2 and S3-3 (described later) to be suitable. The pre-fired 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 650°C. The pre-firing time may be 2 hours or more and 8 hours or less, 3 hours or more and 8 hours or less, 4 hours or more and 8 hours or less, 5 hours or more and 8 hours or less, or 5 hours or more and 7 hours or less. The pre-firing atmosphere is not particularly limited, and may be, for example, an oxygen-containing atmosphere.

[0024] In S3-2, following the pre-firing, the composite is subjected to main firing at a temperature of 800°C to 900°C for 1 hour to 12 hours. If the main firing temperature is too low, the P2 phase will not be formed, and if the main firing temperature is too high, an O3 phase or the like will likely form instead of the P2 phase. The temperature rise conditions from the pre-firing temperature to the main firing temperature are not particularly limited. In S3-2, the shape and crystallite size of the Na-containing oxide can be controlled by the main firing temperature and main firing time. If the main firing time is too short, the P2 phase will not be formed sufficiently. On the other hand, if the main firing time is too long, the P2 phase will likely grow excessively.

[0025] In step S3-3, following the main firing, the composite is rapidly cooled (cooled at a cooling rate of 20°C / min or more) from a temperature T1 of 200°C or higher to a temperature T2 of 100°C or lower. The preliminary firing and main firing are performed, for example, in a heating furnace. In step S3-3, for example, the composite is main fired in a heating furnace, then cooled to a temperature T1 of 200°C or higher in the heating furnace. After reaching temperature T1, the fired product is removed from the heating furnace and rapidly cooled outside the furnace to a temperature T2 of 100°C or lower. Temperature T1 may be any temperature of 200°C or higher, or any temperature of 250°C or higher. Temperature T2 may be any temperature of 100°C or lower, or any temperature of 50°C or lower, or may be the cooling end temperature. In the predetermined temperature range between temperature T1 and temperature T2, moisture is likely to penetrate between the layers of the P2-type structure due to atomic vibration, molecular motion, etc. When cooling the sintered composite (a Na-containing oxide having a P2 structure), it is believed that the amount of moisture that penetrates between the layers of the P2 structure can be reduced by shortening the time spent in this temperature range where moisture easily penetrates (i.e., by rapid cooling). In this regard, when cooling the sintered composite in step S3-3, for example, by allowing it to cool in a dry atmosphere outside the furnace from a temperature T1 of 200°C or higher to a temperature T2 of 100°C or lower, the cooling rate from temperature T1 to temperature T2 is high (e.g., 20°C / min or higher), making it difficult for moisture to penetrate between the layers of the P2 structure, thereby preventing the collapse of the P2 structure. As a result, Na can be efficiently ion-exchanged with Li in step S4.

[0026] By using S3, it is possible to produce a Na-containing oxide having a P2 type structure and a predetermined chemical composition. c Ni x-p Co y-q Mn z-r M p+q+rIt may have a chemical composition represented by O2 (where 0 < c ≤ 1.00, 0.15 < x < 0.35, 0.15 < y < 0.45, 0.25 < z < 0.50, 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 Na-containing oxide has such a chemical composition, the P2-type structure is likely to be maintained. In the above chemical composition, c is greater than 0, and may be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, 0.60 or more, 0.70 or more, or greater than 0.70, and is also less than or equal to 1.00, and may be less than 1.00, less than 0.90, less than 0.80, or less than 0.70. For x, y, z, and p + q + r, it is as described above. The composition of O is approximately 2, but is not necessarily exactly 2.0 and is indefinite.

[0027] 2.4 Ion Exchange In S4, an ion exchange material is brought into contact with the Na-containing oxide obtained by S1 to S3, and at least a part of the Na contained in the Na-containing oxide is ion-exchanged with Li to obtain a Li-containing oxide having an O2-like structure. For example, a Li compound is used as the ion exchange material. Specifically, lithium salts such as lithium nitrate and lithium halide may also be used as the ion exchange material. When the above ion exchange material is brought into contact with the Na-containing oxide, the ion exchange material may be in a molten state or a solid state. In particular, it is preferably in a molten state. That is, by mixing the Na-containing oxide having the above P2-type structure with the ion exchange material and heating to a temperature above the melting point of the ion exchange material, at least a part of the Na in the Na-containing oxide can be ion-exchanged with Li. The temperature in the ion exchange may be, for example, above the melting point of the above ion exchange material and less than or equal to 600 °C, less than or equal to 500 °C, less than or equal to 400 °C, or less than or equal to 300 °C. If the temperature in the ion exchange is too high, an O3-type structure, which is a stable phase rather than an O2-like structure, is likely to be formed. On the other hand, from the perspective of shortening the time required for ion exchange, the temperature in the ion exchange is preferably as high as possible.

[0028] 3.Battery As shown in FIG. 2 , 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. In the battery 100, for example, the positive electrode active material layer 10 may include the electrode active material of the present disclosure. The battery 100 may include a positive electrode current collector 40 and a negative electrode current collector 50. The battery 100 may be a solid-state battery or a liquid-based battery. A solid-state battery refers to a battery that includes a solid electrolyte and can tolerate the presence of a liquid. The battery 100 may also be an all-solid-state battery that is substantially free of liquid. The battery configuration may be the same as a conventional battery, except that the electrode active material of the present disclosure is used. Detailed description will be omitted here. [Example]

[0029] As described above, one embodiment of the electrode active material etc. has been described, but the technology of the present disclosure can be modified in various ways other than the above embodiment without departing from the gist thereof. Below, the technology of the present disclosure will be described in more detail while showing examples, but the technology of the present disclosure is not limited to the following examples.

[0030] 1. Preparation of Electrode Active Material 1.1 Example 1 1.1.1 Preparation of precursor particles (1) NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O were weighed to achieve the desired composition ratio (Ni:Co:Mn=2:4:4) and dissolved in distilled water to a concentration of 1.2 mol / L to obtain a first solution. In a separate container, Na2CO3 was dissolved in distilled water to a concentration of 1.2 mol / L to obtain a second solution. (2) 1000 mL of pure water was placed in a reaction vessel (with a baffle plate), and 500 mL of the first solution and 500 mL of the second solution were added dropwise thereto at a rate of about 4 mL / min. (3) After the dropwise addition was completed, the mixture was stirred at room temperature for 1 hour at a stirring speed of 150 rpm to obtain a product. (4) The product was washed with pure water, and the solid was separated into liquid using a centrifuge to recover the precipitate. (5) The obtained precipitate was dried overnight at 120°C, crushed in a mortar, and then subjected to air classification to remove coarse particles and fine particles, thereby obtaining precursor particles.

[0031] 1.1.2 Preparation of the complex (1) Na2CO3 and distilled water were weighed out so that the concentration was 1150 g / L, and then the mixture was stirred using a stirrer until completely dissolved to prepare an aqueous Na2CO3 solution. (2) The above Na2CO3 aqueous solution and the above precursor particles are mixed, and the composition after calcination described below is Na 0.8 Ni 0.2 Co 0.4 Mn 0.4 The components were weighed and mixed to obtain a slurry. (3) The above slurry was spray-dried to obtain a composite. Specifically, a spray dryer DL410 was used, with a slurry flow rate of 30 mL / min, an inlet temperature of 200°C, and a circulating air volume of 0.8 m. 3 The above slurry was dried by airflow at a flow rate of 1 / min and a spray pressure of 0.3 MPa, thereby coating the surface of the precursor particles with Na2CO3 and obtaining a composite.

[0032] 1.1.3 Firing of the composite The composite was placed in an alumina crucible and fired in an air atmosphere to obtain a Na-containing oxide having a P2 structure under the firing conditions (1) to (7) below. (1) The alumina crucible containing the composite is placed in a heating furnace in an air atmosphere. (2) The temperature inside the heating furnace is raised from room temperature (25°C) to 600°C in 115 minutes. (3) The temperature in the heating furnace is maintained at 600°C for 360 minutes to perform pre-baking. (4) After the preliminary firing, the temperature inside the heating furnace is raised to 900°C and then maintained at 900°C for 1 hour for main firing. (5) After the main firing, the temperature inside the heating furnace is lowered from the main firing temperature to 250°C, and the alumina crucible is removed from the heating furnace at 250°C and allowed to cool outside the furnace in a dry atmosphere until it reaches 25°C in 10 minutes.

[0033] The fired product after cooling was pulverized in a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2 type structure (P2 type particles). 0.8 Ni 0.2 Co 0.4 Mn 0.4 The particles were spherical and had the chemical composition shown in O2.

[0034] 1.1.4 Ion exchange (1) LiNO3 and LiCl were weighed out to a molar ratio of 50:50, and mixed with the above P2 type particles in a molar ratio that was 10 times the minimum Li amount required for ion exchange to obtain a mixture. (2) Using an alumina crucible, ion exchange was carried out at 280°C for 1 hour in an air atmosphere to obtain a product containing a Li-containing oxide. (3) The salt remaining in the product was washed with pure water, and solid-liquid separation was carried out by vacuum filtration to obtain a precipitate. (4) The obtained precipitate was dried overnight at 120°C to obtain the electrode active material particles according to Example 1. The electrode active material particles contained Li 0.67 Ni 0.2 Co 0.4 Mn 0.4 The particles were spherical and had the chemical composition shown in O2.

[0035] 1.2 Example 2 1.2.1 Preparation of precursor particles and composites In the same manner as in Example 1, precursor particles and a composite were obtained.

[0036] 1.2.2 Firing of the composite The composite was fired and allowed to cool in the same manner as in Example 1, except that the firing time was changed to 12 hours. The fired product after cooling was pulverized in a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2 type structure (P2 type particles). 0.8 Ni 0.2 Co 0.4 Mn 0.4 The particles were spherical and had the chemical composition shown in O2.

[0037] 1.2.4 Ion exchange Ion exchange was carried out in the same manner as in Example 1 except that the P2 type particles were used, thereby obtaining electrode active material particles according to Example 2. The electrode active material particles were Li 0.64 Ni 0.2 Co 0.4 Mn 0.4 The particles were spherical and had the chemical composition shown in O2.

[0038] 1.3 Example 3 1.3.1 Preparation of precursor particles and composites In the same manner as in Example 1, precursor particles and a composite were obtained.

[0039] 1.3.3 Firing of the composite The composite was fired and allowed to cool in the same manner as in Example 1, except that the firing temperature was changed to 800°C. The fired product after cooling was pulverized in a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2 type structure (P2 type particles). 0.8 Ni 0.2 Co 0.4 Mn 0.4 The particles were spherical and had the chemical composition shown in O2.

[0040] 1.3.4 Ion exchange Ion exchange was carried out in the same manner as in Example 1 except that the P2 type particles were used, thereby obtaining electrode active material particles according to Example 3. The electrode active material particles were Li 0.66 Ni 0.2 Co 0.4 Mn 0.4 The particles were spherical and had the chemical composition shown in O2.

[0041] 1.4 Example 4 1.4.1 Preparation of precursor particles Precursor particles were prepared in the same manner as in Example 1, except that the raw materials were mixed so as to have a composition ratio of Ni:Co:Mn=3:3:4.

[0042] 1.4.2 Preparation of the complex A composite was obtained in the same manner as in Example 1, except that the above precursor particles were used.

[0043] 1.4.3 Firing of the composite The composite was fired and cooled under the same conditions as in Example 1, except that the firing temperature of the composite was changed to 800°C. The fired product after cooling was pulverized in a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2 type structure (P2 type particles). 0.9 Ni 0.3 Co 0.3 Mn 0.4 The particles were spherical and had the chemical composition shown in O2.

[0044] 1.4.4 Ion exchange Ion exchange was carried out in the same manner as in Example 1 except that the P2 type particles were used, thereby obtaining electrode active material particles according to Example 4. The electrode active material particles were Li 0.64 Ni 0.3 Co 0.3 Mn 0.4 The particles were spherical and had the chemical composition shown in O2.

[0045] 1.5 Example 5 1.5.1 Preparation of precursor particles Precursor particles were prepared in the same manner as in Example 1, except that the raw materials were mixed so as to have a composition ratio of Ni:Co:Mn=1:1:1.

[0046] 1.5.2 Preparation of the complex A composite was obtained by spray drying in the same manner as in Example 1, except that the above precursor particles were used.

[0047] 1.5.3 Firing of the composite The composite was fired and cooled under the same conditions as in Example 1, except that the firing temperature of the composite was changed to 850°C. The fired product after cooling was pulverized in a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2 type structure (P2 type particles). 1.0 Ni 1 / 3Co 1 / 3 Mn 1 / 3 The particles were spherical and had the chemical composition shown in O2.

[0048] 1.5.4 Ion Exchange Ion exchange was carried out in the same manner as in Example 1 except that the P2 type particles were used, thereby obtaining electrode active material particles according to Example 5. The electrode active material particles were Li 0.58 Ni 1 / 3 Co 1 / 3 Mn 1 / 3 The particles were spherical and had the chemical composition shown in O2.

[0049] 1.6 Comparative Example 1 1.6.1 Preparation of precursor particles and composites Precursor particles and a composite were prepared in the same manner as in Example 4.

[0050] 1.6.2 Firing of the composite The composite was fired and allowed to cool under the same conditions as in Example 4, except that the firing temperature was changed to 1000°C, and the fired product after cooling was pulverized in a mortar in a dry atmosphere to obtain Na-containing oxide particles. 0.9 Ni 0.3 Co 0.3 Mn 0.4 The particles were spherical and had the chemical composition shown in O2.

[0051] 1.6.3 Ion exchange Ion exchange was carried out in the same manner as in Example 4, except that the above-mentioned Na-containing oxide particles were used, to obtain electrode active material particles according to Comparative Example 1. The electrode active material particles were Li 0.65 Ni 0.3 Co 0.3 Mn 0.4 The particles were spherical and had the chemical composition shown in O2.

[0052] 1.7 Comparative Example 2 1.7.1 Preparation of precursor Precursor particles were prepared in the same manner as in Example 1, except that the raw materials were mixed so as to have a composition ratio of Ni:Co:Mn=2:3:5.

[0053] 1.7.2 Preparation of the complex A composite was obtained by spray drying in the same manner as in Example 1, except that the above precursor particles were used.

[0054] 1.7.3 Firing of the composite The firing and cooling were carried out under the same conditions as in Example 1 except that the above composite was used, and the fired product after cooling was pulverized in a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2 type structure (P2 type particles). 0.7 Ni 0.2 Co 0.3 Mn 0.5 The particles were spherical and had the chemical composition shown in O2.

[0055] 1.7.4 Ion Exchange Ion exchange was carried out in the same manner as in Example 1 except that the P2 type particles were used, to obtain electrode active material particles according to Comparative Example 2. The electrode active material particles were Li 0.64 Ni 0.2 Co 0.3 Mn 0.5 The particles were spherical and had the chemical composition shown in O2.

[0056] 1.8 Comparative Example 3 1.8.1 Precursor preparation Precursor particles were prepared in the same manner as in Example 1, except that the raw materials were mixed so as to have a composition ratio of Ni:Co:Mn=1:4:5.

[0057] 1.8.2 Preparation of the complex A composite was obtained by spray drying in the same manner as in Example 1, except that the above precursor particles were used.

[0058] 1.8.3 Firing of the composite The firing and cooling were carried out under the same conditions as in Example 1 except that the above composite was used, and the fired product after cooling was pulverized in a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2 type structure (P2 type particles).0.6 Ni 0.1 Co 0.4 Mn 0.5 The particles were spherical and had the chemical composition shown in O2.

[0059] 1.8.4 Ion Exchange Ion exchange was carried out in the same manner as in Example 1 except that the P2 type particles were used, to obtain electrode active material particles according to Comparative Example 3. The electrode active material particles were Li 0.57 Ni 0.1 Co 0.4 Mn 0.5 The particles were spherical and had the chemical composition shown in O2.

[0060] 1.9 Comparative Example 4 1.9.1 Preparation of precursor Precursor particles were prepared in the same manner as in Example 1, except that the raw materials were mixed so as to have a composition ratio of Ni:Co:Mn=2:2:6.

[0061] 1.9.2 Preparation of the complex A composite was obtained by spray drying in the same manner as in Example 1, except that the above precursor particles were used.

[0062] 1.9.3 Firing of the composite The firing and cooling were carried out under the same conditions as in Example 1 except that the above composite was used, and the fired product after cooling was pulverized in a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2 type structure (P2 type particles). 0.6 Ni 0.2 Co 0.2 Mn 0.6 The particles were spherical and had the chemical composition shown in O2.

[0063] 1.9.4 Ion Exchange Ion exchange was carried out in the same manner as in Example 1 except that the P2 type particles were used, to obtain electrode active material particles according to Comparative Example 4. The electrode active material particles were Li 0.59 Ni 0.2 Co 0.2 Mn 0.6The particles were spherical and had the chemical composition shown in O2.

[0064] 1.10 Comparative Example 5 1.10.1 Precursor Preparation Precursor particles were prepared in the same manner as in Example 1, except that the raw materials were mixed so as to have a composition ratio of Ni:Co:Mn=1:3:6.

[0065] 1.10.2 Preparation of the complex A composite was obtained by spray drying in the same manner as in Example 1, except that the above precursor particles were used.

[0066] 1.10.3 Firing of the composite The firing and cooling were carried out under the same conditions as in Example 1 except that the above composite was used, and the fired product after cooling was pulverized in a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2 type structure (P2 type particles). 0.5 Ni 0.1 Co 0.3 Mn 0.6 The particles were spherical and had the chemical composition shown in O2.

[0067] 1.10.4 Ion Exchange Ion exchange was carried out in the same manner as in Example 1 except that the P2 type particles were used, thereby obtaining electrode active material particles according to Comparative Example 5. The electrode active material particles contained Li 0.57 Ni 0.1 Co 0.3 Mn 0.6 The particles were spherical and had the chemical composition shown in O2.

[0068] 1.11 Comparative Example 6 1.11.1 Precursor Preparation Precursor particles were prepared in the same manner as in Example 1, except that the raw materials were mixed so as to have a composition ratio of Ni:Co:Mn=3:2:5.

[0069] 1.11.2 Preparation of the complex A composite was obtained by spray drying in the same manner as in Example 1, except that the above precursor particles were used.

[0070] 1.11.3 Firing of the composite The firing and cooling were carried out under the same conditions as in Example 1 except that the above composite was used, and the fired product after cooling was pulverized in a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2 type structure (P2 type particles). 0.8 Ni 0.3 Co 0.2 Mn 0.5 The particles were spherical and had the chemical composition shown in O2.

[0071] 1.11.4 Ion Exchange Ion exchange was carried out in the same manner as in Example 1 except that the P2 type particles were used, to obtain electrode active material particles according to Comparative Example 6. The electrode active material particles were Li 0.66 Ni 0.3 Co 0.2 Mn 0.5 The particles were spherical and had the chemical composition shown in O2.

[0072] 1.12 Summary of conditions Table 1 below shows the conditions for producing the Na-containing oxide particles in Examples 1 to 5 and Comparative Examples 1 to 6. [Table 1]

[0073] 2. Coin Cell Fabrication Coin cells (CR2032) were fabricated using each electrode active material. The coin cell fabrication procedure is as follows. (1) The above electrode active material, acetylene black (AB) as a conductive additive, and polyvinylidene fluoride (PVdF) as a binder were weighed out in a mass ratio of electrode active material:AB:PVdF = 85:10:5, and dispersed and mixed in N-methyl-2-pyrrolidone to obtain a positive electrode composite slurry. The positive electrode composite slurry was coated on aluminum foil and vacuum dried overnight at 120°C to obtain a positive electrode, which is a laminate of a positive electrode active material layer and a positive electrode current collector. (2) An electrolyte solution was obtained by dissolving LiPF6 at a concentration of 1 M in a mixed solvent of trifluoropropylene carbonate (TFPC) and trifluoroethyl methyl carbonate (TFEMC) in a ratio of TFPC:TFEMC = 30 vol%:70 vol%. (3) Metallic lithium foil was prepared as the negative electrode. (4) A coin cell (CR2032) was fabricated using the positive electrode, electrolyte, and negative electrode.

[0074] 3. Evaluation Method 3.1 Crystal structure X-ray diffraction patterns were obtained for each electrode active material using a CuKα radiation source. FIG. 3 shows the X-ray diffraction patterns of the electrode active materials according to Examples 1 to 3. FIG. 4 shows the X-ray diffraction patterns of the electrode active materials according to Examples 4 to 5. FIG. 5 shows the X-ray diffraction pattern of the electrode active material according to Comparative Example 1. FIG. 6 shows the X-ray diffraction patterns of the electrode active materials according to Comparative Examples 2 to 5. FIG. 7 shows the X-ray diffraction pattern of the electrode active material according to Comparative Example 6. As shown in FIGS. 3 to 7, the electrode active materials according to Examples 1 to 5 and Comparative Examples 2 to 6 had an O2-like structure, while the electrode active material according to Comparative Example 1 had an O3-type structure.

[0075] 3.2 Electrochemical measurements Each coin cell was charged and discharged in a thermostatic chamber maintained at 25°C at a voltage range of 2.0 to 4.8 V and a 0.1 C rate (1 C = 220 mA / g), and the initial discharge capacity was measured. The percentage of the initial discharge capacity at 3 V or higher was calculated.

[0076] 4. Evaluation Results Table 2 below shows the transition metal composition, crystal structure, initial discharge capacity, and the percentage of the capacity at 3 V or higher in the total discharge capacity (total capacity) for each of the electrode active materials of Examples 1 to 5 and Comparative Examples 2 to 6. Note that for the electrode active material of Comparative Example 1, the target crystal structure was not obtained, so no results were obtained regarding the capacity of a coin cell. Furthermore, Figure 8 shows the relationship between the Na composition of the Na-containing oxide having a P2 structure and the percentage of the capacity at 3 V or higher in the total capacity of the electrode active material. [Table 2]

[0077] The results shown in Table 2 and FIG. 8 show that when an electrode active material satisfies the following requirements (1) and (2), the proportion of high potential capacity in the total capacity of the electrode active material increases. (1) The electrode active material has at least one O2-like structure selected from the group consisting of an O2-type structure, a T#2-type structure, and an O6-type structure. Although the T#2-type structure is not shown in the above examples, the T#2-type structure has almost the same crystalline structure as the O2-type structure and can be said to exhibit the same effects as the O2-type structure. (2) The electrode active material is Li a Na b Ni x-p Co y-q Mn z-r M p+q+rO2 (where 0 < a ≤ 1.00, 0 ≤ b ≤ 0.20, 0.15 < x < 0.35, 0.15 < y < 0.45, 0.25 < z < 0.50, 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) has a chemical composition represented by. In the above examples, the element M is not shown, but the element M has the effect of stabilizing the O2-like structure, and it can be said that a certain effect is exhibited even when the electrode active material contains the element M. Also, when manufacturing an electrode active material having an O2-like structure, in ion exchange, a part of Na may remain unsubstituted by Li, but even if a trace amount of Na is present in the electrode active material, it can be said that a certain effect is exhibited.

Explanation of Reference Signs

[0078] 100 Battery 10 Positive Electrode Active Material Layer 20 Electrolyte Layer 30 Negative Electrode Active Material Layer 40 Positive Electrode Current Collector 50 Negative Electrode Current Collector

Claims

1. An electrode active material, having at least one O2-like structure selected from the group consisting of an O2-type structure, a T#2-type structure, and an O6-type structure; Li ａ Na ｂ Ni ｘ－ｐ Co ｙ－ｑ Mn ｚ－ｒ M ｐ＋ｑ＋ｒ O ２ (wherein 0<a≦1.00, 0≦b≦0.20, 0.15<x<0.35, 0.15<y<0.45, 0.25<z<0.50, x+y+z=1, and 0≦p+q+r<0.17; and element 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). Electrode active material.

2. The electrode active material according to claim 1, 0.70<a≦1.00; Electrode active material.

3. A method for producing an electrode active material, Obtaining a precursor, coating the surface of the precursor with a Na source to obtain a composite; calcining the composite to obtain a Na-containing oxide having a P2 type structure; and bringing the Na-containing oxide into contact with an ion exchange material to ion-exchange at least a portion of the Na contained in the Na-containing oxide with Li, thereby obtaining a Li-containing oxide having at least one O2-like structure selected from an O2-type structure, a T#2-type structure, and an O6-type structure; The sintering temperature of the composite is 800°C or higher and 900°C or lower, The firing time of the composite is 1 hour or more and 12 hours or less, The Na-containing oxide is Na ｃ Ni ｘ－ｐ Co ｙ－ｑ Mn ｚ－ｒ M ｐ＋ｑ＋ｒ O ２ (wherein 0<c≦1.00, 0.15<x<0.35, 0.15<y<0.45, 0.25<z<0.50, x+y+z=1, and 0≦p+q+r<0.17; and element 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). Method for producing electrode active material.

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