Active material of positive electrode and sodium-ion secondary battery.

Description

1 / 43 Active material of positive electrode and sodium-ion secondary battery. FIELD

[001] This application discloses a positive electrode active material and a sodium ion secondary battery. BACKGROUND

[002] PTL 1 and 2 disclose a Na-containing oxide with a P2-type structure and predetermined chemical composition. Na-containing oxides with a P2-type structure are used as active positive electrode materials in secondary sodium-ion batteries. LIST OF QUOTES Patent Literature

[003] [PTL 1] Publication of Unexamined Japanese Patent (Kokai) No. 2012-201588

[004] [PTL 2] Publication of Unexamined Japanese Patent (Kokai) No. 2017-045600 SUMMARY TECHNICAL PROBLEM

[005] Conventional positive electrode active materials with P2 type structure have room for improvement in terms of reversible capability. SOLUTION TO THE PROBLEM

[006] The present application, as a means to achieve the above objective, discloses the following plurality of aspects. Aspect 1

[007] A positively electrode active material comprising a Na-containing oxide, wherein the Na-containing oxide has a P2 type structure, the Na-containing oxide comprises, as constituent elements, Petition 870250091110, dated 06 / 10 / 2025, page 11 / 65 2 / 43 at least one element among Mn, Ni and Co; No; and O, an X-ray diffraction pattern of the oxide containing Na satisfies I1 / I2 <0.10, an X-ray diffraction pattern of the oxide containing Na satisfies I1 / I3 <0.70, h is the intensity of an X-ray diffraction peak originating from the 102 plane of the P2-type structure, h is the intensity of an X-ray diffraction peak originating from the 002 plane of the P2-type structure, eh is the intensity of an X-ray diffraction peak originating from the 100 plane of the P2-type structure. Aspect 2

[008] The active positive electrode material, according to Aspect 1, in which the X-ray diffraction pattern of the oxide containing Na satisfies 0.01 <li / l2<0,10 e padrão de difração de raios X do óxido contendo Na satisfaz 0,01 <li / l3<0,70. Aspect 3

[009] The active positive electrode material, according to Aspect 1 or 2, in which the X-ray diffraction pattern of the oxide containing Na satisfies 0.40° <HWi e HW1 is a half-width of the X-ray diffraction peak originating from the 102 plane of the P2-type structure. Aspect 4

[0010] The active positive electrode material, according to Aspect 3, where Petition 870250091110, dated 06 / 10 / 2025, page 12 / 65 3 / 43 The X-ray diffraction pattern of the oxide containing Na satisfies 0.40° < HWi < 1.00°. Aspect 5

[0011] The active positive electrode material, according to any of Aspects 1 to 4, in which the oxide containing Na has a chemical composition represented by NaaMnx-pNiy-qCOz-rMp+q+rO2 (where 0 < a < 1.00; x + y + z = 1; e0 <p + q + r<0,17, eo elemento M é pelo menos um selecionado entre B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo e W). Aspect 6

[0012] The active positive electrode material, according to any one of Aspects 1 to 5, wherein the oxide containing Na comprises, as constituent elements, at least Na, Mn, Ni, Co and O. Aspect 7

[0013] The active positive electrode material, according to any one of Aspects 1 to 4, wherein the oxide containing Na comprises, as constituent elements, at least Na, Mn, Fe and O. Aspect 8

[0014] A secondary sodium-ion battery comprising a layer of positive electrode active material, an electrolyte layer and a layer of negative electrode active material, wherein the layer of positive electrode active material comprises the positive electrode active material according to any one of Aspects 1 to 7. EFFECTS AND ADVANTAGES OF THE INVENTION

[0015] The active material of the positive electrode of the present invention Petition 870250091110, dated 06 / 10 / 2025, page 13 / 65 4 / 43 has a large reversible capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 shows an example of the flow of a manufacturing method for a Na-containing oxide with a P2 type structure.

[0017] Figure 2 shows schematically an example of a secondary sodium-ion battery configuration.

[0018] Figure 3 shows the X-ray diffraction pattern of each of Examples 1 to 3 and Comparative Example 1.

[0019] Figure 4 shows the X-ray diffraction pattern of each of Example 4 and Comparative Example 2. DESCRIPTION OF THE MODALITIES 1. Active material for positive electrode

[0020] The active positive electrode material, according to the embodiments, comprises a Na-containing oxide. The Na-containing oxide has a P2-type structure. The Na-containing oxide comprises, as constituent elements, at least one element among Mn, Ni, and Co; Na; and O. An X-ray diffraction pattern of the Na-containing oxide satisfies I1 / I2 <0.10. The X-ray diffraction pattern of the Na-containing oxide satisfies I1 / I3 <0.70. h is an X-ray diffraction intensity peak originating from the 102 plane of the P2-type structure. h is an X-ray diffraction peak intensity originating from the 002 plane of the P2-type structure. h is an X-ray diffraction peak intensity originating from the 100 plane of the P2-type structure. 1.1 Crystal structure

[0021] The sodium-containing oxide, according to the modalities, has at least one P2-type structure (belonging to the space group P63mc) as its crystal structure. The sodium-containing oxide may have a crystal structure other than P2-type, in addition to having a P2-type structure. Examples of crystal structures other than a P2-type structure include various crystal structures (such as the structure Petition 870250091110, dated 06 / 10 / 2025, page 14 / 65 5 / 43 of type 02) which are formed when Na is deintercalated from a P2 type structure. The oxide containing Na, according to the embodiments, can have a P2 type structure as the main phase. In the oxide containing Na, the crystalline structure that constitutes the main phase can change depending on the charge and discharge states. 1.1.1 X-ray diffraction peak intensity

[0022] The X-ray diffraction pattern of the Na-containing oxide according to the embodiments satisfies h / h <0.10 and I1 / I3 <0.70. h is an X-ray diffraction peak intensity originating from the 102 plane of the P2-type structure, h is an X-ray diffraction peak intensity originating from the 002 plane of the P2-type structure, and h is an X-ray diffraction peak intensity originating from the 100 plane of the P2-type structure.

[0023] Conventional P2-type positive electrode active materials exhibit a high X-ray diffraction peak intensity originating from the 102 plane and excellent crystallinity in all directions, including vertical, horizontal, and oblique directions. The Na-containing oxide, according to the embodiments, is synthesized under conditions not encountered in the prior art, where the X-ray diffraction peak intensity h originating from the 102 plane is reduced relative to the X-ray diffraction peak intensity I2 originating from the 002 plane and the X-ray diffraction peak intensity I3 originating from the 100 plane. Specifically, in the Na-containing oxide, according to the embodiments, the X-ray diffraction peak intensity for the 102 plane in the P2-type structure is reduced, and although the P2-type structure is maintained as a whole, the crystallinity in the oblique direction is reduced.According to the findings of the present inventors, Na-containing oxide with such a P2-type structure exhibits excellent reversibility compared to a conventional P2-type positive electrode active material. The low crystallinity of the 102 plane means that failures of... Petition 870250091110, dated 06 / 10 / 2025, page 15 / 65 6 / 43 Stacking faults are introduced into a specific crystalline plane of the P2-type crystal structure. In the Na-containing oxide according to the embodiments, it is presumed that stacking faults have some effect on increasing the reversible capacity of the positive electrode active material.

[0024] In an X-ray diffraction pattern of the Na-containing oxide according to the embodiments, the ratio h / h of the intensity of the X-ray diffraction peak h originating from the 102 plane of the P2-type structure to the intensity of the X-ray diffraction peak I2 originating from the 002 plane of the P2-type structure satisfies h / h < 0.10. Furthermore, in the X-ray diffraction pattern of the Na-containing oxide according to the embodiments, the ratio h / h of the intensity of the X-ray diffraction peak h originating from the 102 plane of the P2-type structure to the intensity of the X-ray diffraction peak h originating from the 100 plane of the P2-type structure satisfies h / h < 0.70. The above X-ray diffraction pattern may satisfy 0.01 <li / l2<0,10, 0,02 <li / l2<0,10 ou 0,03 <li / l2<0,10 e 0,01 <h / h <0,70, 0,05 <h / l3<0,70, 0,10 <h / h <0,70, 0,15 <h / h <0,70, 0,20 <h / h <0,70 ou 0,20 <h / l3<0,65. 1.1.2 Half-width of the X-ray diffraction peak

[0025] As described above, the oxide containing Na, according to the embodiments, exhibits low crystallinity for the 102 plane of the P2 type structure. For example, the X-ray diffraction pattern of the oxide containing Na, according to the embodiments, may satisfy 0.40° <HWi. O HW1 é a meia-largura do pico de difração de raios X originada do plano 102 da estrutura do tipo P2. A meia-largura do HW1 pode satisfazer 0,40° < HW1 < 1,00 °, 0,45° <HWi <1,00 °, 0,50° <HWi <1,00 °, 0,55° < HW1 < 1,00 °ou 0,60° < HW1 < 1.00 °. A meia-largura do pico de difração de raios X originada do plano 002 e a meia-largura do pico de difração de raios X originada do plano 100 da estrutura do tipo P2 não são particularmente limitadas. Petition 870250091110, dated 06 / 10 / 2025, page 16 / 65 7 / 43 1.1.3 Method for measuring the intensity of the X-ray diffraction peak and half-width

[0026] The X-ray diffraction pattern of the Na-containing oxide, X-ray diffraction peak intensity, and X-ray diffraction peak half-width in the present application refer to those acquired under the following conditions. Specifically, an X-ray diffraction pattern is acquired by subjecting the Na-containing oxide to a 2Θ / Θ scan using an X-ray diffractometer (Rigaku, Automated Multipurpose X-ray Diffractometer SmartLab), CuKa as the radiation source, and a tube voltage of 45 kV, tube current of 200 mA, step size of 0.02°, and scan speed of 1° / min. In the X-ray diffraction pattern, the X-ray diffraction peak originating from the 102 piano of the P2-type structure typically appears at 38.9° ± 0.5° (but may vary depending on the transition metal composition and the amount of Na).The X-ray diffraction peak originating from the 002 plane of the P2-type structure typically appears at 15.9° ± 0.5° (but may vary depending on the transition metal composition and the amount of Na). The X-ray diffraction peak originating from the 100 plane of the P2-type structure typically appears at 36° ± 0.5° (but may vary depending on the transition metal composition and the amount of Na). After subtracting the background value near the peaks from the X-ray diffraction pattern, oh / heo I1 / I3 above can be determined from the intensity of each of the X-ray diffraction peaks, and the halfwidth HW1 of the X-ray diffraction peak originating from the 002 plane is also determined. 1.1.4 Crystallite

[0027] The sodium-containing oxide, according to one embodiment, may be a single crystal consisting of a crystallite or it may be a polycrystal comprising a plurality of crystallites. For example, the sodium-containing oxide, according to one embodiment, may be composed of Petition 870250091110, dated 06 / 10 / 2025, page 17 / 65 8 / 43 a plurality of crystallites on its surface. In other words, the Na-containing oxide may have, on its surface, a structure in which the plurality of crystallites are interconnected. When the surface of the Na-containing oxide is composed of a plurality of crystallites, crystal grain boundaries are present on the surface. The crystal grain boundaries can be entry and exit points for intercalation. Specifically, when the Na-containing oxide is a polycrystal comprising a plurality of crystallites, expected effects include a decrease in reaction resistance due to the increased number of intercalation entry and exit points, a decrease in diffusion resistance due to the shorter migration distance of sodium ions, and the prevention of cracking due to the decrease in the absolute amounts of expansion and contraction during loading and unloading. The size of the crystallites can be large or small.However, it is considered that the smaller the crystallite size, the greater the number of crystal grain boundaries and the more easily the advantageous effects described above are displayed. For example, when the diameter of the crystallites constituting the Na-containing oxide is less than 1 μm, superior performance is easily obtained. Note that the crystallite and crystallite diameter can be determined by observing the surface of the Na-containing oxide with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Specifically, when a surface of a Na-containing oxide is observed and a closed region surrounded by crystal grain boundaries is observed, the region is considered a crystallite. The maximum Feret diameter of the crystallite is determined, and this is considered the crystallite diameter.If the sodium-containing oxide consists of a single crystal, the particle itself can be considered a crystallite, and the maximum Feret diameter of the particle is the crystallite diameter. Alternatively, the dia. Petition 870250091110, dated 06 / 10 / 2025, page 18 / 65 9 / 43 meter of the crystallite can be determined by EBSD or XRD. For example, the crystallite diameter can be determined based on the Scherrer equation from half the width of the diffraction line of the XRD pattern. In Na-containing oxide, when the crystallite diameter specified by either method is less than 1 μm, superior performance is easily obtained. A crystallite constituting the Na-containing oxide may have a first surface exposed on the oxide surface, and the first surface may be planar. Specifically, the surface of the Na-containing oxide may have a structure in which a plurality of planes are connected. As described below, when fabricating a Na-containing oxide, crystals with a planar first surface are easily obtained by growing crystals on the surface of a particle until one crystallite and another crystallite are connected to each other. 1.2 Chemical composition

[0028] The oxide containing Na, according to one embodiment, comprises, as constituent elements, at least one element among Mn, Ni and Co; Na; and O. In the oxide containing Na, particularly when at least Na, Mn, one or both Ni and Co, and O are included as constituent elements, especially when at least Na, Mn, Ni, Co and O are included as constituent elements, superior performance is easily obtained. Alternatively, when the oxide containing Na comprises, as constituent elements, at least Na, Mn, Fe and O, superior performance is easily obtained.

[0029] In one embodiment, the Na-containing oxide with a P2-type structure may have a chemical composition represented by NaaMnx. pNiy-qCOz-rMp+q+rO2 (where 0 < a <1.00; x + y + z=1; e0 <p + q + r<0,17, e o elemento M é pelo menos um selecionado dentre B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo e W). Quando o óxido contendo Na tem tal composição química, uma estrutura do tipo P2 é Petition 870250091110, dated 06 / 10 / 2025, p. 19 / 65 10 / 43 easily maintained. In the chemical composition above, a is greater than 0 and can be 0.10 or greater, 0.20 or greater, 0.30 or greater, 0.40 or greater, 0.50 or greater, or 0.60 or greater, and is 1.00 or less and can be 0.90 or less, 0.80 or less, or 0.70 or less. Furthermore, x is 0 or greater and can be 0.10 or greater, 0.20 or greater, 0.30 or greater, 0.40 or greater, or 0.50 or greater, and is 1.00 or less and can be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, or 0.50 or less. Furthermore, y is 0 or greater and can be 0.10 or greater, or 0.20 or greater, and is 1.00 or less and can 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. Additionally, z is 0 or greater and can be 0.10 or greater, 0.20 or greater, or 0.30 or greater, and is 1.00 or less and can 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 charging and discharging.In this sense, in the chemical composition above, because p + q + r is less than 0.17, high charge and discharge capacities are easily ensured: p + q + r can 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. Including the element M, a P2 type structure is easily stabilized. In the chemical composition above, p + q + r ≥ 0 or greater, and can be 0.01 or greater, 0.02 or greater, 0.03 or greater, 0.04 or greater, 0.05 or greater, 0.06 or greater, 0.07 or greater, 0.08 or greater, 0.09 or greater, or 0.10 or greater. The composition of O is approximately 2, but can be variable without being limited to exactly 2.0. 1.3 Format

[0030] The P2-type structure has a hexagonal crystal and a high diffusion coefficient of Na+ ions, and the crystals grow readily in a specific direction. Particularly, when a transition metal element that constitutes the P2-type structure includes at least one of Mn, Ni, and Co, the tabular crystals grow readily in a Petition 870250091110, dated 06 / 10 / 2025, page 20 / 65 11 / 43 specific direction. Therefore, a Na-containing oxide with a P2-type structure generally forms into tabular particles with a large aspect ratio, where the crystal growth direction is skewed in a specific direction. The Na-containing oxide, according to one embodiment, may consist of such tabular particles or spherical particles. When the Na-containing oxide is a spherical particle, the resistance to reaction decreases due to the decrease in crystallite size, and the resistance to diffusion within the particle is easily reduced. Furthermore, when applied to a secondary battery, the degree of curvature is considered to be reduced by spheroidization, and the resistance to sodium ion conduction decreases. As a result, for example, the rate characteristics are enhanced and the reversible capacity is easily increased. A “spherical particle” in the present application means a particle with a circularity of 0.80 or greater.The circularity of a spherical particle can be 0.81 or greater, 0.82 or greater, 0.83 or greater, 0.84 or greater, 0.85 or greater, 0.86 or greater, 0.87 or greater, 0.88 or greater, 0.89 or greater, or 0.90 or greater. The circularity of a particle is defined as 4kS / L², where S is the orthographic area of ​​the particle and L is the circumference of an orthographic image of the particle. The circularity of a particle can be determined by observing the exterior of the particle with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an optical microscope. In the case where the oxide consists of a plurality of particles, its circularity is measured as an average value, for example, as follows. (1) The particle size distribution of the particles is first measured. Specifically, a cumulative particle size of 10% D10 and a cumulative particle size of 90% D90 in a volume-based particle size distribution are determined by means of a laser diffraction / scattering method. Petition 870250091110, dated 06 / 10 / 2025, page 21 / 65 12 / 43 (2) The observation of the image of the exterior of the particles measured for particle distribution is carried out with a SEM, TEM or optical microscope, and from the particles contained in the image, 100 particles with an equivalent circle diameter (diameter of a circle with the same area as the orthographic area of ​​the particles) of D10 or more and D90 or less, which are determined in (1), are arbitrarily extracted. (3) The circularity of each of the 100 extracted particles is determined by image processing, and the average value of the same is considered as the “circularity of the particles”.

[0031] The sodium-containing oxide, according to one embodiment, may be a solid particle, a hollow particle, or a particle with a void. The particle size of the sodium-containing oxide is not particularly limited. However, a smaller size is considered advantageous. For example, the average particle size D50 of the sodium-containing oxide particles may be 0.1 m μ₀ or more and 10 μπ or less, 1.0 μπ or more and 8.0 μπ or less, or 2.0 m μπ or less and 6.0 μπ or less. The average particle size D50 is the cumulative particle size of 50% (D50, median diameter) in a volume-based particle size distribution, determined by a laser diffraction / scattering method. 1.4 Others

[0032] As described above, the active positive electrode material, according to the embodiments, possesses excellent reversible capability because it comprises the specific Na-containing oxide. As described above, in the Na-containing oxide, stacking faults are introduced in a specific crystalline plane, and there is a possibility that the stacking faults have led to an improvement in reversible capability. The active positive electrode material, according to the embodiments, may consist only of the Na-containing oxide or Petition 870250091110, dated 06 / 10 / 2025, page 22 / 65 13 / 43 may comprise sodium-containing oxide and other positive electrode active material (additional positive electrode active material). From the point of view of further enhancing the above effect, the proportion of additional positive electrode active material relative to the total positive electrode active material may be small. For example, when the total positive electrode active material is 100% by mass, the content of the sodium-containing oxide above may be 50% by mass or higher and 100% by mass or lower, 60% by mass or higher and 100% by mass or lower, 70% by mass or higher and 100% by mass or lower, 80% by mass or higher and 100% by mass or lower, 90% by mass or higher and 100% by mass or lower, 95% by mass or higher and 100% by mass or lower, or 99% by mass or higher and 100% by mass or lower. 2. Manufacturing method for active positive electrode material

[0033] The Na-containing oxide according to the above embodiment can be manufactured, for example, by the following method. As shown in Figure 1, the manufacturing method for the Na-containing oxide with a P2-type structure according to one embodiment comprises:

[0034] S1: obtain a precursor comprising at least one element among Mn, Ni and Co,

[0035] S2: cover a surface of the precursor with a Na source to obtain a composite, and

[0036] S3: Burn the composite to obtain a Na-containing oxide with a P2-type structure. S3 comprises

[0037] S3-1: subject the composite to pre-firing at a temperature of 300°C or higher and below 700°C for 2 h or more and 10 h or less,

[0038] S3-2: after pre-firing, subject the composite to a main firing at a temperature of 700°C or higher and 1100°C or Petition 870250091110, dated 06 / 10 / 2025, p. 23 / 65 14 / 43 smaller for 30 min or more and 48 h or less, and

[0039] S3-3: After the main firing, rapidly cool the composite from a temperature T1 of 200 °C or higher to a temperature T2 of 100 °C or lower. 2.1 S1

[0040] In S1, a precursor comprising at least one element among Mn, Ni, and Co is obtained. The precursor may comprise at least Mn and one or both of Ni and Co, or it may comprise at least Mn, Ni, and Co. The precursor may be a salt comprising at least one element among 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 a plurality of compound types. The precursor may have any of several shapes. For example, the precursor may be particulate or it may be spherical, as described below. The particle diameter of the particles comprising the precursor is not particularly limited.

[0041] In S1, a precipitate like the precursor above can be obtained by a coprecipitation method using an ion source that can form a precipitation with a transition metal ion in an aqueous solution and a transition metal compound comprising at least one element among Mn, Ni, and Co. As a result, spherical particles as a precursor are easily obtained. The ion source that can form a precipitation with a transition metal ion in an aqueous solution, for example, can be 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 a salt or hydroxide described above, comprising at least one element among Mn, Ni, and Co. Specifically, in S1, the Petition 870250091110, dated 06 / 10 / 2025, page 24 / 65 15 / 43 The ion source and the transition metal compound can each be formed in a solution, and the solutions can then be added and mixed to obtain a precursor precipitate. In this case, for example, water is used as a solvent. In this case, various sodium compounds can be used as a base, and an aqueous ammonia solution can be added to adjust the basicity. In the case of a coprecipitation method, the precipitate is obtained, for example, by preparing an aqueous solution of a transition metal compound and one of sodium carbonate, and mixing the aqueous solutions dropwise to obtain a precursor precipitate. Alternatively, the precursor can be obtained by a sol-gel method. In particular, according to a coprecipitation method, spherical particles as a precursor are easily obtained.

[0042] In S1, a precursor may comprise an element M. The 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. The method of obtaining the precursor comprising an element M is not particularly limited. When obtaining the precursor by a coprecipitation method in S1, for example, an aqueous solution of a transition metal compound comprising 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 dropwise added to mix the solutions and obtain a precursor comprising element M and at least one element of Mn, Ni, and Co. Alternatively, in the manufacturing method of the present invention, element M is not added in S1, and doping with element M can be carried out at the time of doping with Na and burning in S2 and S3 described below. 2.2 S2 Petition 870250091110, dated 06 / 10 / 2025, page 25 / 65 16 / 43

[0043] In S2, a surface of the precursor obtained via S1 is covered with a Na source to obtain a composite. The Na source can be a salt comprising Na, such as a carbonate or a nitrate, or it can be a compound other than a salt, such as sodium oxide or hydroxide. In S2, the amount of Na source covering the precursor surface only needs to be determined by taking into account the amount of Na lost during subsequent burning.

[0044] In S2, the coverage of the Na source relative to the precursor surface is not particularly limited. For example, in S2, the composite above can be obtained by covering 40% or more of the area, 50% or more of the area, 60% or more of the area, or 70% or more of the surface of the precursor above with a Na source. When the precursor obtained via S1 consists of spherical particles, and the composite obtained via S2 is obtained by covering 40% or more of the surface area of ​​the precursor with the Na source, a Na-containing oxide with a P2-type structure tends to form spherical particles in S3, described below. When the coverage of the Na source is small, P2-type crystals tend to grow abnormally on the surface of the composite when it is burned, and the Na-containing oxide tends to form tabular particles.When the coverage of the Na source is high, the P2-type crystals tend to be small when the composite is burned, and the Na-containing oxide tends to form spherical particles, which correspond to the shape of the precursor.

[0045] In S2, the method of coating the precursor surface with a Na source is not particularly limited. As described above, when covering 40% or more of the precursor surface with a Na source, the method includes several methods. Examples include a fluidized rolling coating method or a spray drying method. Specifically, a coating solution in which a Na source is dissolved is prepared, the coating solution is Petition 870250091110, dated 06 / 10 / 2025, page 26 / 65 17 / 43 placed in contact with the precursor surface and dried simultaneously or subsequently. By adjusting the coating conditions (such as temperature, time and count), for example, 40% or more of the precursor surface can be covered with a Na source.

[0046] In S2, the precursor can be coated with a Na source and an M source. For example, in S2, the precursor obtained via S1, a Na source, and an M source comprising 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 can be mixed to obtain a composite. The M source, for example, can be a salt comprising an element M, such as a carbonate or a sulfate, or it can be a compound other than a salt, such as an oxide or a hydroxide. The amount of the M source relative to the precursor is determined according to the chemical composition of the Na-containing oxide after combustion. 2.3 S3

[0047] In S3, the composite obtained via S2 is burned to obtain a Na-containing oxide with a P2-type structure. S3 comprises compounds S3-1, S3-2, and S3-3 above. 2.3.1 S3-1

[0048] In S3-1, the composite is subjected to a pre-fire at a temperature of 300°C or higher and below 700°C for 2 h or more and 10 h or less. In S3-1, the pre-fire can optionally be performed after molding the composite above. The pre-fire is carried out at a lower temperature than the main firing. When the pre-fire in S3-1 is insufficient, the formation of a P2 phase may be insufficient in the resulting Na-containing oxide. By setting the pre-fire temperature to 300°C or higher and below 700°C and the pre-fire time to 2 h or more and 10 h or less in S3-1, the composite can be subjected to sufficient pre-fire, and the X-ray diffraction pattern of the Na-containing oxide with a P2-type structure obtained via S3-2 and Petition 870250091110, dated 06 / 10 / 2025, p. 27 / 65 18 / 43 The S3-3 described below tends to satisfy I1 / I2 and I1 / I3 above. The pre-burn temperature can be 400°C or more and less than 700°C, 450°C or more and less than 700°C, 500°C or more and less than 700°C, 550°C or more and less than 700°C, or 550°C or more and 650°C or less. The pre-burn time can be 2 h or more and 8 h or less, 3 h or more and 8 h or less, 4 h or more and 8 h or less, 5 h or more and 8 h or less, or 5 h or more and 7 h or less. The pre-burn atmosphere is not particularly limited and can be, for example, an atmosphere containing oxygen. 2.3.2 S3-2

[0049] In S3-2, after the above pre-firing, the composite is subjected to a main firing at a temperature of 700°C or more and 1100°C or less for 30 minutes or more and 10 hours or less. In S32, the main firing temperature of the composite is 700°C or more and 1100°C or less, preferably 800°C or more and 1000°C or less. When the main firing temperature is too low, the P2 phase is not formed, and when the main firing temperature is too high, the O3 phase, not the P2 phase, is easily formed. The heating conditions from the pre-firing temperature to the main firing temperature are not particularly limited. The main firing time is not particularly limited and, for example, can be 30 minutes or more and 48 hours or less. The form of the Na-containing oxide can be controlled by the main firing time.As described above, when the coverage of the Na source in the composite is 40% by area or more in the method of the present invention, P2-type crystals with small crystals are easily formed during the firing of the composite. In the method of the present invention, by connecting one P2-type crystallite and another P2-type crystallite to each other and growing the P2-type crystals along the surface of a particle, the shape of the Na-containing oxide corresponds to the shape of... Petition 870250091110, dated 06 / 10 / 2025, page 28 / 65 19 / 43 precursor. For example, when the precursor consists of spherical particles, the Na-containing oxide can also form spherical particles. When the primary firing time is too short, the formation of the P2 phase is insufficient. When the primary firing time is too long, the P2 phase grows excessively, and tabular, rather than spherical, particles are formed. As far as the present inventors have confirmed, when the primary firing time is 30 min or more and 3 h or less, spherical particles of the Na-containing oxide are easily obtained. The resulting Na-containing oxide after primary firing may have a plurality of crystallites present on its surface and may have a structure in which the crystallites are connected. 2.3.3 S3-3

[0050] In S3-3, after the main firing above, the composite undergoes rapid cooling (cooled at a cooling rate of 20°C / min or more) from a temperature T1 of 200°C or more to a temperature T2 of 100°C or less. The pre-firing and main firing above are carried out, for example, in a heating furnace. In step S3-3, for example, the composite undergoes a main firing in a heating furnace and is then cooled to an arbitrary temperature Ti of 200°C or more in the heating furnace, and after reaching the temperature Ti, the fired product is removed from the heating furnace and undergoes rapid cooling outside the furnace to an arbitrary temperature T2 of 100°C or less. The temperature T1 is an arbitrary temperature of 200°C or more, and may be an arbitrary temperature of 250°C or more. Temperature T2 is an arbitrary temperature of 100°C or less, it could be an arbitrary temperature of 50°C or less, or it could be the cooling end temperature.Within a predetermined temperature range, from temperature T1 until it reaches temperature T2, moisture easily seeps between the layers of a structure. Petition 870250091110, dated 06 / 10 / 2025, p. 29 / 65 20 / 43 P2 type structure through atomic vibrations or molecular motion. When cooling the composite (Na-containing oxide with a P2 type structure) after the main firing, by shortening the time in the temperature range where this moisture infiltrates easily (i.e., rapid cooling), the amount of moisture infiltrated between the layers of the P2 type structure is considered to be reduced. In step S3-3, when cooling the composite after the main firing, allowing the composite to cool from an arbitrary temperature Ti of 200°C or more to an arbitrary temperature T2 of 100°C or less in a dry atmosphere outside the furnace, the cooling rate from temperature T1 to temperature T2 is rapid (e.g., 20°C / min or more), moisture does not easily infiltrate between the layers of the P2 type structure, and the collapse of the P2 type structure can be inhibited.As a result, the X-ray diffraction pattern of the Na-containing oxide with a P2-type structure obtained via S3-3 tends to satisfy I1 / I2 and I1 / I3 above.

[0051] According to the previous method, an oxide containing Na that has a P2 type structure, has a predetermined chemical composition and satisfies the h / he I1 / I3 requirements above can be manufactured. 3. Secondary sodium-ion battery

[0052] The positive electrode active material, according to the embodiment, comprises the specific oxide containing Na above. The positive electrode active material, for example, can be used as the positive electrode active material of a sodium-ion secondary battery. Figure 2 schematically shows a configuration of a sodium-ion secondary battery, according to an embodiment. As shown in Figure 2, the sodium-ion secondary battery 100, according to an embodiment, comprises a layer of positive electrode active material 10, a layer of electrolyte 20, and a layer of negative electrode active material 30, wherein the layer of positive electrode active material 10 comprises the active material of Petition 870250091110, dated 06 / 10 / 2025, page 30 / 65 21 / 43 positive electrode, according to the modality above. 3.1 Positive electrode active material layer

[0053] The active positive electrode layer 10 comprises at least the active positive electrode material according to the embodiment above and may optionally further comprise an electrolyte, a conductive auxiliary and a binder. In addition, the active positive electrode layer 10 may comprise various additives. The contents of the active positive electrode material, electrolyte, conductive auxiliary and binder in the active positive electrode layer 10 need only be determined appropriately according to the desired battery performance. For example, when the total (total solid content) of the active positive electrode layer 10 is 100% by mass, the content of the active positive electrode material may be 40% by mass or more, 50% by mass or more, or 60% by mass or more, and may be 100% by mass or less, or 90% by mass or less.The shape of the active material layer of the positive electrode 10 is not particularly limited and, for example, it may be a sheet-shaped active material layer of the positive electrode 10 with a substantially flat surface. The thickness of the active material layer of the positive electrode 10 is not particularly limited and, for example, may be 0.1 mm or more or 1 mm or more, and may be 2 mm or less or 1 mm or less. 3.1.1 Positive electrode active material

[0054] The active positive electrode material is as described above. Specifically, the active positive electrode material comprises a Na-containing oxide, and the Na-containing oxide has a P2-type structure, comprising at least one element among Mn, Ni, and Co; Na; and O, and satisfies the relationships according to h / h and I1 / I3. As described above, the active positive electrode material can consist only of the Na-containing oxide above. Petition 870250091110, dated 06 / 10 / 2025, page 31 / 65 22 / 43 or may comprise the above-mentioned Na-containing oxide and another positive electrode active material (an additional positive electrode active material). From the standpoint of further enhancing the effect according to the technique of the present invention, the proportion of the additional positive electrode active material to the total positive electrode active materials may be small. For example, when the total positive electrode active materials is 100% by mass, the content of the above-mentioned Na-containing oxide is 50% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, or 99% by mass or more and 100% by mass or less. 3.1.2 Electrolyte

[0055] The electrolyte that may be contained in the active material layer of positive electrode 10 may be a solid electrolyte, a liquid electrolyte (electrolyte solution), or a combination thereof. The solid electrolyte must be a known solid electrolyte for sodium-ion secondary batteries. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, an inorganic solid electrolyte possesses excellent ionic conductivity and heat resistance properties. Examples of inorganic solid electrolytes include at least one selected from oxides such as Na3Zr2PSI2OI2 and Na2O-1IAI2O3; hydrides and borides such as NaBHL, NaBioHw, NaCBgHw, NaCBnHi2, and NaBi2Cl2; Sulfides such as NasPS4, Na3SbS4, and Na2.8Sb0.88Wo.12S4, and fluorides such as NaPFe and NaBF4. The solid electrolyte, for example, can be particulate.The solid electrolyte can be of one type used alone, or it can be of two or more types used in combination. The electrolytic solution, for example, can... Petition 870250091110, dated 06 / 10 / 2025, page 32 / 65 23 / 43 understand sodium ions as carrier ions. The electrolyte solution can be an aqueous electrolyte solution or a non-aqueous electrolyte solution. The composition of the electrolyte solution needs to be just the same as that known as the composition of an electrolyte solution for secondary sodium-ion batteries. For example, a sodium salt dissolved at a predetermined concentration in a carbonate-based solvent can be used as the electrolyte solution. Examples of carbonate-based solvents include fluoroethylene carbonate (FEC), ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC). Examples of sodium salts include NaPFe. 3.1.3 Conducting aid

[0056] Examples of conductive auxiliary that may be contained in the active material layer of positive electrode 10 include carbon materials such as vapor-grown carbon fiber (VGCF), acetylene black (AB), ketone black (KB), carbon nanotubes (CNTs) and carbon nanofibers (CNFs); and metallic materials such as nickel, aluminum and stainless steel. The conductive auxiliary, for example, may be particulate or fibrous, and its size is not particularly limited. The conductive auxiliary may be of one type used alone or of two or more types used in combination. 3.1.4 Liquant

[0057] Examples of the binder that may be contained in the active material layer of positive electrode 10 include butadiene rubber (BR) based binders, butylene rubber (IIR) based binders, acrylate-butadiene rubber (ABR) based binders, styrene-butadiene rubber (SBR) based binders, polyvinylidene fluoride (PVdF) based binders, polytetrafluoroethylene (PTFE) based binders, and polyimide (PI) based binders. The binder may be of one type used alone or of two or more types used in combination. Petition 870250091110, dated 06 / 10 / 2025, p. 33 / 65 24 / 43 3.2 Electrolytic layer

[0058] The electrolyte layer 20 comprises at least one electrolyte. When the sodium-ion secondary battery 100 is a solid-state battery (it may be a battery comprising a solid electrolyte with a partially used liquid electrolyte in combination, or it may be a fully solid-state battery without liquid electrolyte), the electrolyte layer 20 comprises a solid electrolyte and may optionally comprise a binder. In this case, the contents of the solid electrolyte and the binder in the electrolyte layer 20 are not particularly limited. When the sodium-ion secondary battery 100 is an electrolyte solution battery, the electrolyte layer 20 comprises an electrolyte solution and may further comprise a separator to retain the electrolyte solution and prevent contact between the positive electrode active material layer 10 and the negative electrode active material layer 30.The thickness of the electrolyte layer 20 is not particularly limited and, for example, can be 0.1 mm or more or 1 mm or more and can be 2 mm or less or 1 mm or less.

[0059] The electrolyte contained in the electrolytic layer 20 only needs to be appropriately selected from those exemplified as an electrolyte that can be contained in the positive electrode active material layer 10 described above. The binder that can be contained in the electrolytic layer 20 only needs to be appropriately selected from those exemplified as a binder that can be contained in the positive electrode active material layer 10 described above. The electrolyte and the binder can be of one type, used alone, or they can be of two or more types, used in combination. The separator only needs to be any separator normally used in sodium-ion secondary batteries. Examples of these include those made of resins such as polyethylene (PE), polypropylene (PP), polyester, and polyamide. The separator can have a single-layer or multi-layer structure. Petition 870250091110, dated 06 / 10 / 2025, page 34 / 65 25 / 43 may have a multilayer structure. Examples of separators with a multilayer structure may include separators with a two-layer PE / PP structure and separators with a three-layer PP / PE / PP or PE / PP / PE structure. The separator may consist of a nonwoven fabric, such as cellulose nonwoven fabric, resin nonwoven fabric, or fiberglass nonwoven fabric. 3.3 Negative electrode active material layer

[0060] The negative electrode active material layer 30 comprises at least one negative electrode active material and may optionally comprise an electrolyte, a conductive auxiliary, and a binder. In addition, the negative electrode active material layer 30 may further comprise various additives. The content of each negative electrode active material, electrolyte, conductive auxiliary, and binder in the negative electrode active material layer 30 needs only to be properly determined according to the target battery performance. For example, when the total (total solid content) of the negative electrode active material layer 30 is 100% by mass, the content of the negative electrode active material may be 40% by mass or more, 50% by mass or more, or 60% by mass or more, and may be 100% by mass or less or 90% by mass or less.The shape of the negative electrode active material layer 30 is not particularly limited and, for example, may be a plate with a substantially flat surface. The thickness of the negative electrode active material layer 30 is not particularly limited and, for example, may be 0.1 mm or more or 1 mm or more and may be 2 mm or less or 1 mm or less.

[0061] Various materials with low electrical potential (charge and discharge potentials) for storing and releasing sodium ions, compared to the active positive electrode material of the present invention, Petition 870250091110, dated 06 / 10 / 2025, page 35 / 65 26 / 43 can be adopted as the negative electrode active material. The negative electrode active material, for example, can be an inorganic-based negative electrode active material, such as metallic sodium, it can be a negative electrode active material consisting of an organic compound, or it can be a combination thereof. The negative electrode active material can be of one type used alone or it can be of two or more types used in combination. The shape of the negative electrode active material need only be any of the general shapes of negative electrode active materials for batteries. For example, the negative electrode active material can be particulate. The particles of the negative electrode active material can be primary particles or they can be secondary particles from a plurality of agglomerated primary particles.The average particle diameter D50 of the negative electrode active material particles, for example, can be 1 nm or more, 5 nm or more, or 10 nm or more, and can be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. Alternatively, the negative electrode active material can be in sheet form (foil-like or membranous), such as a sodium foil. Specifically, the negative electrode active material layer 30 can consist of a sheet of negative electrode active material.

[0062] Examples of electrolytes that may be contained in the active material layer of negative electrode 30 include the solid electrolytes and electrolytic solutions above, and combinations thereof. Examples of conductive auxiliaries that may be contained in the active material layer of negative electrode 30 include the carbon materials and metallic materials above. The binder that may be contained in the active material layer of negative electrode 30 needs only to be selected appropriately, for example, from among those exemplified as a binder that may be contained in the active material layer of negative electrode 30. Petition 870250091110, dated 06 / 10 / 2025, page 36 / 65 27 / 43 positive 10 above. The electrolyte and the binder may be of one type used individually, or they may be of two or more types used in combination. 3.4 Positive electrode current collector

[0063] As shown in Figure 2, the sodium-ion secondary battery 100 can be provided with a positive electrode current collector 40 in contact with the active positive electrode material layer 10. Any general positive electrode current collector for batteries can be adopted as the positive electrode current collector 40. The positive electrode current collector 40 can be in the form of a sheet, laminar, mesh, perforated, or foam. The positive electrode current collector 40 can be composed of a metal sheet or a metal mesh. In particular, a metal sheet offers excellent handling. The positive electrode current collector 40 can consist of a plurality of sheets. Examples of metals that constitute the positive electrode current collector 40 include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel.Specifically, from the point of view of ensuring oxidation resistance, the positive electrode current collector 40 may comprise Al. The positive electrode current collector 40 may have some coating layer on its surface for resistance adjustment purposes. The positive electrode current collector 40 may be a metal sheet or substrate coated or vapor-deposited with a metal described above. When the positive electrode current collector 40 consists of a plurality of metal sheets, there may be some layer between the plurality of metal sheets. The thickness of the positive electrode current collector 40 is not particularly limited and, for example, may be 0.1 μπ or more and 1 μπ or more, and may be 1 mm or less or 100 μπ or less. Petition 870250091110, dated 06 / 10 / 2025, page 37 / 65 28 / 43 3.5 Negative electrode current collector

[0064] As shown in Figure 2, the sodium-ion secondary battery 100 can be provided with a negative electrode current collector 50 in contact with the negative electrode active material layer 30. Any general negative electrode current collector for batteries can be adopted as the negative electrode current collector 50. The negative electrode current collector 50 can be in the form of a sheet, laminar, mesh, perforated, or foam. The negative electrode current collector 50 can be a metal sheet or a metal mesh and, alternatively, it can be a carbon sheet. In particular, a metal sheet offers excellent handling. The negative electrode current collector 50 can consist of a plurality of sheets or plates. Examples of metals that constitute the negative electrode current collector 50 include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel.In particular, from the point of view of ensuring resistance to reduction, the negative electrode current collector 50 may comprise at least one metal selected from Cu, Ni, and stainless steel. The negative electrode current collector 50 may have a coating layer on its surface for resistance adjustment purposes. The negative electrode current collector 50 may be a metal sheet or a substrate coated or vapor-deposited with a metal described above. When the negative electrode current collector 50 consists of a plurality of metal sheets, there may be a layer between the plurality of metal sheets. The thickness of the negative electrode current collector 50 is not particularly limited and, for example, may be 0.1 μm or more or 1 μm or more, and may be 1 mm or less or 100 μm or less. 3.6 Additional Resources

[0065] The 100-valve sodium-ion secondary battery, in addition to the above configuration, can be supplied with any obvious configuration such as Petition 870250091110, dated 06 / 10 / 2025, page 38 / 65 29 / 43 Secondary battery, such as tabs or terminals. The above configurations of the 100 sodium-ion secondary battery can be housed within an outer casing. Any known outer casing can be adopted as the battery's outer casing. Furthermore, a plurality of 100 batteries can optionally be electrically connected and optionally stacked to form a battery pack. In this case, the battery pack can be housed within a known battery box. The 100 sodium-ion secondary battery can be supplied with other obvious configurations, such as the necessary terminals. Examples of 100 sodium-ion secondary battery shapes may include coin type, laminated type, cylindrical, and rectangular.

[0066] The 100-phase sodium-ion secondary battery can be manufactured using any known method, except that the specific positive electrode active material described above is used, and, for example, it can be manufactured as follows. However, the manufacturing method of the 100-phase sodium-ion secondary battery is not limited to the following method. For example, each layer can be formed by dry molding. (1) A positive electrode active material, constituting a layer of positive electrode active material, is dispersed in a solvent to obtain a fluid positive electrode layer paste. The solvent used in this case is not particularly limited, and water and various organic solvents may be used. The fluid positive electrode layer paste is then applied to the surface of a positive electrode current collector with a scraper blade, followed by drying, during which a layer of positive electrode active material is formed on the surface of the positive electrode current collector to obtain a positive electrode. (2) A negative electrode active material, constituting a negative electrode active material layer, is dispersed in a solvent to obtain a fluid negative electrode layer paste. Petition 870250091110, dated 06 / 10 / 2025, page 39 / 65 30 / 43 The solvent used in this case is not particularly limited, and water and various organic solvents can be used. The fluid paste of negative electrode layer is then applied to the surface of a negative electrode current collector using a scraper blade, followed by drying, during which a layer of active negative electrode material is formed on the surface of the negative electrode current collector to obtain a negative electrode. (3) The layers are laminated so that a layer of electrolyte (solid electrolyte layer or separator) is interposed between the negative electrode and the positive electrode, obtaining a laminated body composed of a negative electrode current collector, a layer of negative electrode active material, a layer of electrolyte, a layer of positive electrode active material and a positive electrode current collector, in this order. Additional members, such as terminals, are attached to the laminated body as needed. (4) The laminated body is housed in a battery case. In the case of a solution electrolyte battery, an electrolyte solution is placed in the battery case. The laminated body is immersed in the electrolyte solution and sealed in the battery case, thus obtaining a secondary battery. Note that, in the case of a solution electrolyte battery, the electrolyte solution may be contained in the negative electrode active material layer, in the separator, and in the positive electrode active material layer in step (3) above. 4. Method for increasing the reversible capacity of a secondary sodium-ion battery.

[0067] The technique of the present invention also presents an aspect of a method for increasing the reversible capacity of a secondary sodium-ion battery. Specifically, the method for increasing the reversible capacity of a secondary sodium-ion battery of the present invention is characterized by the use of the active material. Petition 870250091110, dated 06 / 10 / 2025, page 40 / 65 31 / 43 of the positive electrode of the present invention above in a layer of active material of the positive electrode of the secondary sodium-ion battery. 5. Vehicle comprising secondary sodium-ion battery

[0068] As mentioned above, the positive electrode active material of the present invention has excellent reversible capacity and is suitable as a positive electrode active material for sodium-ion secondary batteries. As a result, the sodium-ion secondary battery with such high reversible capacity, for example, can be suitably used in at least one type of vehicle selected from among hybrid vehicle (HEV), plug-in hybrid vehicle (PHEV) and electric vehicle (BEV). Specifically, the technique of the present invention presents an aspect of a vehicle comprising a sodium-ion secondary battery, wherein the sodium-ion secondary battery comprises a layer of positive electrode active material, an electrolyte layer and a layer of negative electrode active material, and the layer of positive electrode active material comprises the aforementioned positive electrode active material of the present invention. EXAMPLES

[0069] As described above, an embodiment for each of the active materials of the positive electrode and the sodium-ion secondary battery has been described. However, various modifications can be made to the above embodiments, within a range that does not depart from the spirit of the embodiments. The technique of the present invention will now be described in more detail with reference to the Examples. However, the technique of the present invention is not limited to the following Examples. 1. Production of active positive electrode material 1.1 Example 1 1.1.1 Production of precursor (1) MnSO4-5H2O, NiSO4 6H2O, and CoSO4 7H2O were weighed Petition 870250091110, dated 06 / 10 / 2025, page 41 / 65 32 / 43 of the components were diluted to a target compositional ratio and dissolved in distilled water at a concentration of 1.2 mol / L to obtain a first solution. In a separate container, Na2COs was dissolved in distilled water at a concentration of 1.2 mol / L to obtain a second solution. (2) 1000 mL of pure water were loaded into a reactor (with baffles), and 500 mL of the first solution and 500 mL of the second solution were added dropwise at a rate of about 4 mL / min. (3) After the drop-by-drop addition was complete, stirring was carried out at a stirring rate of 150 rpm at room temperature for 1 h to obtain a product. (4) The product was washed with pure water and subjected to solid-liquid separation with a centrifugal separator to recover a precipitate. (5) The resulting precipitate was dried overnight at 120°C and ground with a mortar, the fine particles were removed by air flow classification and the precursor particles were obtained. The precursor particles were spherical particles consisting of a composite salt comprising Mn, Ni and Co, with a circularity of 0.86. Composite production

[0070] (1) Na2COs and distilled water were weighed to 1150 g / L and then stirred until complete dissolution using a stirrer to produce an aqueous solution of Na2CO3.

[0071] (2) The above aqueous solution of Na2COs and the above precursor particles were weighed and mixed to obtain a composition of Nao,?Mno,5Nio,2 Coo,302 after the burning described below to obtain a fluid paste.

[0072] (3) The above fluid paste was air-dried by spray drying to obtain a composite. Specifically, using a Petition 870250091110, dated 06 / 10 / 2025, page 42 / 65 33 / 43 spray drying apparatus DL410, under the conditions of a fluid paste feed rate of 30 mL / min, an inlet temperature of 200°C, a circulating air volume of 0.8 m3 / min and a spray air pressure of 0.3 MPa, the above fluid paste was air-dried and the surfaces of the precursor particles were coated with Na2COs to obtain a composite. In the composite, 77% of the surface area of ​​the precursor particles was coated with Na2COs. 1.1.3 Composite firing

[0073] The composite was loaded into an alumina crucible and fired in an ambient air atmosphere to obtain a Na-containing oxide with a P2-type structure. The firing conditions were those described in items (1) to (7) below. (1) An alumina crucible containing the above composite was placed in a heating furnace in an ambient air atmosphere. (2) The temperature inside the heating furnace was raised from ambient temperature (25°C) to 600°C in 115 min. (3) The temperature inside the heating furnace was maintained at 600°C for 360 min and pre-firing was carried out. (4) After pre-firing, the temperature inside the heating furnace was raised from 600°C to 950°C in 140 min. (5) The temperature inside the heating furnace was maintained at 950°C for 60 min, and the main firing was carried out. (6) After the main firing, the temperature inside the heating furnace was reduced from 950°C to 250°C in 140 min. (7) The alumina crucible was removed from the heating furnace at 250°C and allowed to cool in a dry atmosphere outside the furnace to reach 25°C in 10 min.

[0074] The burnt product, after cooling, was crushed in an atmosphere Petition 870250091110, dated 06 / 10 / 2025, page 43 / 65 34 / 43 dried with the aid of a pestle to obtain oxide particles containing Na with a P2 type structure. Example 2

[0075] A composite was obtained in the same manner as in Example 1. The composite obtained was loaded into an alumina crucible and fired in an ambient air atmosphere, and the fired product, after cooling, was ground in a dry atmosphere to obtain a Na-containing oxide with a P2-type structure. The firing conditions are those described in (1) to (7) below. (1) An alumina crucible containing the above composite was placed in a heating furnace with an ambient air atmosphere. (2) The temperature inside the heating furnace was raised from ambient temperature (25°C) to 600°C in 115 min. (3) The interior of the heating furnace was maintained at 600°C for 360 min to carry out the pre-firing. (4) After pre-firing, the temperature inside the heating furnace was raised from 600°C to 925°C in 130 min. (5) The interior of the heating furnace was maintained at 925°C for 60 min to carry out the main firing. (6) After the main firing, the temperature inside the heating furnace was reduced from 925°C to 250°C in 135 min. (7) The alumina crucible was removed from the heating furnace at 250°C and allowed to cool in a dry atmosphere outside the furnace to reach 25°C in 10 min. 1.3 Example 3

[0076] A composite was obtained in the same manner as in Example 1. The composite obtained was loaded into an alumina crucible and fired in an ambient air atmosphere, and the fired product, after cooling, was ground in a dry atmosphere to obtain a Na-containing oxide with a P2-type structure. The firing conditions are as described. Petition 870250091110, dated 06 / 10 / 2025, page 44 / 65 35 / 43 in (1) to (7) below. (1) An alumina crucible containing the above composite was placed in a heating furnace with an ambient air atmosphere. (2) The temperature inside the heating furnace was raised from ambient temperature (25°C) to 600°C in 115 min. (3) The interior of the heating furnace was maintained at 600°C for 360 min to carry out the pre-firing. (4) After pre-firing, the temperature inside the heating furnace was raised from 600°C to 900°C in 120 min. (5) The interior of the heating furnace was maintained at 900°C for 60 min to carry out the main firing. (6) After the main firing, the temperature inside the heating furnace was reduced from 900°C to 250°C in 130 min. (7) The alumina crucible was removed from the heating furnace at 250°C and allowed to cool in a dry atmosphere outside the furnace to reach 25°C in 10 min. 1.4 Comparative Example 1

[0077] Precursor particles were obtained in the same manner as in Example 1. The precursor particles and Na2COs were weighed to obtain a composition of NaO,?MnO,5NiO,2COO,3O2. The weighed precursor and Na2COs were mixed using a mortar, obtaining a composite. In the composite, 24% of the surface area of ​​the precursor particles was covered with Na2CO3. The resulting composite was loaded into an alumina crucible and fired in an ambient air atmosphere, and the fired product after cooling was ground in a dry atmosphere to obtain an oxide containing Na with a P2 type structure. The firing conditions were those indicated in (1) to (7) below. (1) An alumina crucible containing the above composite was placed in a heating furnace with an ambient air atmosphere. Petition 870250091110, dated 06 / 10 / 2025, pages 45 / 65 36 / 43 (2) The temperature inside the heating furnace was raised from ambient temperature (25°C) to 600°C in 115 min. (3) The interior of the heating furnace was maintained at 600°C for 360 min to carry out the pre-firing. (4) After pre-firing, the temperature inside the heating furnace was raised from 600°C to 900°C in 120 min. (5) The interior of the heating furnace was maintained at 900°C for 720 min to carry out the main firing. (6) After the main firing, the temperature inside the heating furnace was reduced from 900°C to 250°C in 130 min. (7) The alumina crucible was removed from the heating furnace at 250°C and allowed to cool in a dry atmosphere outside the furnace to reach 25°C in 10 min. 1.5 Example 4 1.5.1 Production of precursor

[0078] (1) MnSO4-5H2O and FeSO^hLO were weighed to a target compositional ratio and dissolved in distilled water at a concentration of 1.2 mol / L to obtain a first solution. In a separate container, Na2COs was dissolved in distilled water at a concentration of 1.2 mol / L to obtain a second solution.

[0079] (2) 1000 mL of pure water were loaded into a reactor (with baffles), and 500 mL of the first solution and 500 mL of the second solution were added dropwise at a rate of about 4 mL / min.

[0080] (3) After the drop-by-drop addition was complete, stirring was carried out at a stirring rate of 150 rpm at room temperature for 1 h to obtain a product.

[0081] (4) The product was washed with pure water and subjected to solid-liquid separation with a centrifugal separator to recover a precipitate. Petition 870250091110, dated 06 / 10 / 2025, page 46 / 65 37 / 43

[0082] (5) The resulting precipitate was dried overnight at 120°C and ground with a mortar, the fine particles were removed by air flow classification and the precursor particles were obtained. The precursor particles were spherical particles consisting of a salt comprising Mn and Fe, and with a circularity of 0.86. 1.5.2 Production of composites

[0083] (1) Na2COs and distilled water were weighed to 1150 g / L and then stirred until complete dissolution using a stirrer to produce an aqueous solution of Na2COs.

[0084] (2) The above aqueous solution of Na2COs and the above precursor particles were weighed and mixed to obtain a composition of Nao,7Mno,5Feo,sO2 after the burning described below to obtain a fluid paste.

[0085] (3) The above fluid paste was air-dried by spray drying to obtain a composite. Specifically, using a DL410 spray drying apparatus, under the conditions of a fluid paste feed rate of 30 mL / min, an inlet temperature of 200°C, a circulating air volume of 0.8 m3 / min and a spray air pressure of 0.3 MPa, the above fluid paste was air-dried and the surfaces of the precursor particles were coated with Na2COs to obtain a composite. In the composite, 77% of the surface area of ​​the precursor particles was coated with Na2COs. 1.5.3 Composite firing

[0086] The composite was loaded into an alumina crucible and fired in an ambient air atmosphere, and the fired product, after cooling, was ground in a dry atmosphere to obtain a Na-containing oxide with a P2-type structure. The firing conditions were the same as conditions (1) to (7) of Example 3. Specifically, the heating inside the furnace (temperature increase from 25°C to 600°C in 115 Petition 870250091110, dated 06 / 10 / 2025, page 47 / 65 38 / 43 min), pre-firing inside the furnace (maintenance at 600°C for 360 min), heating inside the furnace (temperature increase from 600°C to 900°C in 120 min), main firing inside the furnace (maintenance at 900°C for 60 min), cooling inside the furnace (temperature reduction from 900°C to 250°C in 130 min) and external furnace cooling (temperature reduction from 250°C to 25°C in 10 min) to obtain a Na-containing oxide with a P2 type structure. 1.6 Comparative Example 2

[0087] The precursor particles were obtained in the same way as in Example 4. The precursor particles and Na2COs were weighed to obtain a composition of Nao,7Mno,5Feo,sO2. The weighed precursor and Na2COs were mixed using a mortar, obtaining a composite. In the composite, 26% of the surface area of ​​the precursor particles was covered with Na2CO3.The composite obtained was subjected, under the same conditions (1) to (7) of Comparative Example 1, to heating inside the furnace (increasing the temperature from 25°C to 600°C in 115 min), pre-firing inside the furnace (maintaining at 600°C for 360 min), heating inside the furnace (increasing the temperature from 600°C to 900°C in 120 min), main firing inside the furnace (maintaining at 900°C for 720 min), cooling inside the furnace (reducing the temperature from 900°C to 250°C in 130 min) and allowing to cool outside the furnace (reducing the temperature from 250°C to 25°C in 10 min), and the fired product after cooling was ground in a dry atmosphere to obtain a Na-containing oxide with a P2 type structure. 2. Evaluation of the active positive electrode material 2.1 Elementary Analysis

[0088] Elemental analysis was performed on the active positive electrode material in each of Examples 1 to 4 and in Comparative Examples 1 and 2 to identify its chemical composition. The results are presented in Table 1 below. Petition 870250091110, dated 06 / 10 / 2025, page 48 / 65 39 / 43 2.2 Identification of the crystal structure by X-ray diffraction measurement

[0089] For each of the positive electrode active materials of Examples 1 to 4 and Comparative Examples 1 and 2, an X-ray diffraction measurement was performed using CuKa as the radiation source to obtain an X-ray diffraction pattern. Figure 3 shows the X-ray diffraction pattern of each of Examples 1 to 3 and Comparative Example 1. Figure 4 shows the X-ray diffraction pattern of each of Example 4 and Comparative Example 2. As shown in Figures 3 and 4, all positive electrode active materials of Examples 1 to 4 and Comparative Examples 1 and 2 were found to have a P2-type structure belonging to the P63mc space group.Furthermore, as shown in Figure 3, it was found that, in the positive electrode active materials according to Examples 1 to 3, compared to the positive electrode active material according to Comparative Example 1, the X-ray diffraction peak intensities originating in the 102 plane were reduced and, therefore, stacking faults were introduced in the 102 plane. Additionally, as shown in Figure 4, it was found that, in the positive electrode active material according to Example 4, compared to the positive electrode active material according to Comparative Example 2, the X-ray diffraction peak intensity originating in the 102 plane was reduced and, therefore, stacking faults were introduced in the 102 plane.For each of Examples 1 to 4 and Comparative Examples 1 and 2, the ratio h / h of the X-ray diffraction peak intensity h originating from the 102 plane of the P2 type structure to the X-ray diffraction peak intensity h originating from the 002 plane of the P2 type structure, the ratio I1 / I3 of the X-ray diffraction peak intensity h to the X-ray diffraction peak intensity I3 originating from the 100 plane of the P2 type structure, and the half-width HW1 of the X-ray diffraction peak originating from the 102 plane are shown in Table 1 below. Petition 870250091110, dated 06 / 10 / 2025, page 49 / 65 40 / 43 3. Evaluation cell production

[0090] The active positive electrode material in each of Examples 1 to 4 and in Comparative Examples 1 and 2 was used to produce a coin cell. The procedure for producing the coin cell was as follows. (1) A positive electrode active material, acetylene black (AB) as a conducting auxiliary and polyvinylidene fluoride (PVdF) as a binder, was weighed to obtain a mass ratio of positive electrode active material: AB:PVdF = 85:10:5, and dispersed and mixed in N-methyl-2-pyrrolidone to obtain a fluid positive electrode mixture paste. The fluid positive electrode mixture paste was applied to an aluminum foil and vacuum dried overnight at 120°C to obtain a positive electrode that was a laminate of a layer of positive electrode active material and a positive electrode current collector. (2) An electrolytic solution in which NaPFe was dissolved in a mixed solvent of EC and DEC in a volume ratio of 1:1 to a concentration of 1 M was used. (3) A metallic sodium foil was prepared as a negative electrode. (4) The positive electrode, the electrolyte solution and the negative electrode were used to produce a coin cell (CR2032). 4. Evaluation of charge and discharge characteristics (1) Each of the coin-type cells from Examples 1 to 3 and Comparative Example 1 was charged and discharged in a voltage range of 1.0 to 4.5 V and at 0.1 °C (1 °C = 160 mA / g) in a thermostatic chamber maintained at 25 °C, and the reversible capacitance was measured. The results are shown in Table 1 below. (2) Each of the currency-type cells from Example 4 and Comparative Example 2 was loaded and unloaded in a range of Petition 870250091110, dated 06 / 10 / 2025, pages 50 / 65 41 / 43 voltage from 1.0 to 4.3 V and at 0.1°C (1°C = 190 mA / g) in a thermostatic chamber maintained at 25°C, and the reversible capacitance was measured. The results are shown in Table 1 below. 5. Evaluation results

[0091] For each of Examples 1 to 4 and Comparative Examples 1 and 2, the I1 / I2, I1 / I3 and 0 HW1 half-width values ​​identified from the X-ray diffraction pattern and the reversible capability of the evaluation cell are shown. Table 1 Chemical composition I1 / I2 11 / I3 HW1 [°] Reversible capacity [mAh / g] Example 1 NaO,65MnO,54NiO, 17Co0,29O2 0.06 0.63 0.61 174 Example 2 NaO,66MnO,54Ni 0.17Co0,29O2 0.05 0.35 0.87 179 Example 3 NaO,67MnO,54Ni 0.17Co0,29O2 0.03 0.24 0.92 185 Comparative Example 1 Na0.70Mn0.50Ni 0.19Co0.31O2 0.43 1.77 0.08 164 Example 4 NaO,71FeO,52Mn 0.48O2 0.10 0.60 0.71 209 Comparative Example 2 NaO,71FeO,52Mn 0.4802 0.14 0.74 0.36 175

[0092] As is clear from the results shown in Table 1, the active positive electrode materials, according to Examples 1 to 3, in which I1 / I2 and I1 / I3 are relatively small and the stacking faults in the 102 plane of the P2-type structure are relatively numerous, each has a higher reversible capacity than the active positive electrode material, according to Comparative Example 1, in which I1 / I2 and I1 / I3 are relatively large and the stacking faults in the 102 plane of the P2-type structure are relatively few. The same applies to Example 4 and Comparative Example 2, in which Petition 870250091110, dated 06 / 10 / 2025, pp. 51 / 65 42 / 43 the transition metal species differ from those in Examples 1 to 3 and Comparative Example 1. 6. Supplementary

[0093] Although the above examples illustrate cases where the precursor was obtained by a co-precipitation method, the precursor can be obtained by other methods. Furthermore, although the above examples illustrate cases where a Na source was applied to the precursor surfaces by spray drying to obtain a composite, the composite can be obtained by other methods. Additionally, although the Na-containing oxide has a P2-type structure, those with predetermined chemical compositions have been exemplified in the above examples, the chemical composition of the Na-containing oxide is not limited to this. Furthermore, the Na-containing oxide can be doped with an element M other than Mn, Ni, and Co. The element M is as described in the embodiments. 7. Conclusion

[0094] As described above, it can be said that in the active positive electrode material comprising a Na-containing oxide, when the Na-containing oxide satisfies the following requirements (1) to (4), the reversible capacity of the active positive electrode material is increased. (1) The oxide containing Na has a P2 type structure. (2) The oxide containing Na comprises, as constituent elements, at least one element among Mn, Ni and Co; Na; and O. (3) An X-ray diffraction pattern of the oxide containing Na satisfies I1 / I2 <0.10. (4) The X-ray diffraction pattern of the oxide containing Na satisfies I1 / I3 <0.70. Petition 870250091110, dated 06 / 10 / 2025, pages 52 / 65 43 / 43

[0095] Li is an X-ray diffraction peak intensity originating from the 102 plane of the P2-type structure, h is an X-ray diffraction peak intensity originating from the 002 plane of the P2-type structure, and oh is an X-ray diffraction peak intensity originating from the 100 plane of the P2-type structure. LIST OF REFERENCE SIGNS 100 secondary sodium-ion battery layer of active material of the positive electrode layer of electrolyte layer of active material of the negative electrode layer of active material of the positive electrode current collector of the negative electrode current collector of the negative electrode Petition 870250091110, dated 06 / 10 / 2025, pp. 53 / 65

Claims

1 / 2 CLAIMS 1. Active positive electrode material comprising a Na-containing oxide, characterized in that the Na-containing oxide has a P2 type structure, the Na-containing oxide comprises, as constituent elements, Mn; one or both of Co and Fe; and Na; and O, an X-ray diffraction pattern of the Na-containing oxide satisfies I1 / I2 <0.10, the X-ray diffraction pattern of the Na-containing oxide satisfies I1 / I3 <0.70, h is an intensity of an X-ray diffraction peak originating from the (102) plane of the P2 type structure, h is an intensity of an X-ray diffraction peak originating from the (002) plane of the P2 type structure, and h is an intensity of an X-ray diffraction peak originating from the (100) plane of the P2 type structure.

2. Active positive electrode material, according to claim 1, characterized in that the X-ray diffraction pattern of the Na-containing oxide satisfies 0.01 <li / l2 <0,10 e 0 padrão de difração de raios X do óxido contendo Na satisfaz 0,01 <li / l3 <0,70.

3. Positive electrode active material, according to claim 1 or 2, characterized in that the X-ray diffraction pattern of the Na-containing oxide satisfies 0.40° < HW1 and Petition 870250091110, dated 06 / 10 / 2025, page 7 / 65 2 / 2 where HWi is half the width of the X-ray diffraction peak originating from the (102) plane of the P2 type structure.

4. Active positive electrode material, according to claim 3, characterized in that the X-ray diffraction pattern of the Na-containing oxide satisfies 0.40° < HWi < 1.00°.

5. Active positive electrode material, according to any one of claims 1 to 4, characterized in that the Na-containing oxide has a chemical composition represented by NaaMnx-pNiy-qCOz-rMp+q+rO2 (where 0 < a < 1.00; x + y + z = 1; e0 <p + q + r<0,17, eo elemento M é pelo menos um selecionado entre B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo e W).

6. Active positive electrode material, according to any one of claims 1 to 5, characterized in that the Na-containing oxide comprises, as constituent elements, at least Na, Mn, Ni, Co and O.

7. Active positive electrode material, according to any one of claims 1 to 4, characterized in that the Na-containing oxide comprises, as constituent elements, at least Na, Mn, Fe and O.

8. Secondary sodium-ion battery, characterized in that it comprises a layer of positive electrode active material, an electrolyte layer, and a layer of negative electrode active material, wherein the layer of positive electrode active material comprises the positive electrode active material as defined in any one of claims 1 to 7. Petition 870250091110, dated 06 / 10 / 2025, page 8 / 65

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