Electrode active material, electrode, and battery

Abstract

The invention provides an electrode active material, an electrode and a battery. When a battery is configured using the electrode active material of the present disclosure, the rate characteristics of the battery are easily improved. An electrode active material according to the present disclosure satisfies the relationships 2.30 < = A2 / A1 < = 44.00 and 0.50 < = A3 / A1 < = 1.90 when a cross-section thereof is observed. Wherein A1 is the area ratio of the O2-type structure in the cross section, A2 is the area ratio of the O6-type structure in the cross section, and A3 is the area ratio of the T # 2-type structure in the cross section.

Description

Technical Field

[0001] This application discloses an electrode active material, an electrode, and a battery. Background Art

[0002] As an active material for a battery, a substance having an O2-type structure (O: Octahedral) is known. As disclosed in JP-A-2010-092824 and JP-A-2022-085829, an electrode active material having an O2-type structure is obtained by ion-exchanging at least a part of the Na ions of a Na-containing oxide having a P2-type structure with Li. Summary of the Invention

[0003] There is room for improvement in the rate characteristics of a battery using an electrode active material having an O2-type structure.

[0004] As a means for solving the above problems, this application discloses the following multiple aspects.

[0005] <Aspect 1>

[0006] An electrode active material,

[0007] when observing a cross-section of the electrode active material, the following relationships (1) and (2) are satisfied:

[0008] 2.30 ≤ A2 / A1 ≤ 44.00 (1)

[0009] 0.50 ≤ A3 / A1 ≤ 1.90 (2)

[0010] A1: the area ratio of the O2-type structure in the cross-section,

[0011] A2: the area ratio of the O6-type structure in the cross-section,

[0012] A3: the area ratio of the T#2-type structure in the cross-section.

[0013] <Aspect 2>

[0014] The electrode active material according to Aspect 1,

[0015] contains at least one of Ni, Mn, and Co as a constituent element.

[0016] <Aspect 3>

[0017] The electrode active material according to Aspect 2,

[0018] has a structure composed of Li a Na b Mn x-p Niy-q Co z-r M p+q+r A chemical composition represented by O2 (where 0 < a ≤ 1.00, 0 ≤ b ≤ 0.20, x + y + z = 1 and 0 ≤ p + q + r < 0.17, and the element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W).

[0019] <Mode 4>

[0020] An electrode comprising the electrode active material described in any one of Modes 1 to 3.

[0021] <Mode 5>

[0022] A battery having a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer,

[0023] wherein the positive electrode active material layer contains the electrode active material described in any one of Modes 1 to 3.

[0024] When a battery is constructed using the electrode active material of the present disclosure, the rate characteristics of the battery are likely to be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Hereinafter, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the drawings, where like reference numerals denote like elements.

[0026] Figure 1A An example of an O2-type structure is shown.

[0027] Figure 1B An example of an O6-type structure is shown.

[0028] Figure 1C An example of a T#2-type structure is shown.

[0029] Figure 2 An example of the structure of a battery is schematically shown.

[0030] Figure 3A The ACOM-STEM measurement results of the cross-section of the electrode active material for Example 1 are shown.

[0031] Figure 3B The ACOM-STEM measurement results of the cross-section of the electrode active material for Comparative Example 1 are shown. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, an embodiment of the electrode active material, electrode, and battery of the present disclosure will be described, but the electrode active material, electrode, and battery of the present disclosure are not limited to the embodiment described below.

[0033] 1. Electrode active material

[0034] In the case of observing the cross-section of the electrode active material of one embodiment, the following relationships (1) and (2) are satisfied:

[0035] 2.30 ≤ A2 / A1 ≤ 44.00 (1)

[0036] 0.50 ≤ A3 / A1 ≤ 1.90 (2)

[0037] A1: The area ratio of the O2-type structure in the cross-section,

[0038] A2: The area ratio of the O6-type structure in the cross-section,

[0039] A3: The area ratio of the T#2-type structure in the cross-section.

[0040] 1.1 Crystal structure

[0041] The electrode active material of one embodiment has at least an O2-type structure, an O6-type structure, and a T#2-type structure as crystal structures. Figure 1A Shows an example of the O2-type structure, Figure 1B Shows an example of the O6-type structure, Figure 1C Shows an example of the T#2-type structure. The O2-type structure belongs to the space group P63mc. The O6-type structure belongs to the space group R-3m. The T#2-type structure belongs to the space group Cmca. The electrode active material of one embodiment is characterized by containing these three crystal structures in a predetermined ratio.

[0042] In the case of observing the cross-section of the electrode active material of one embodiment, it is important to satisfy the above relationships (1) and (2). That is, in the cross-section of the electrode active material of one embodiment, a predetermined amount of the O6-type structure and a predetermined amount of the T#2-type structure coexist with the O2-type structure. According to the new insight of the present inventor, the electrode active material containing these three crystal structures in the ratios of the above relationships (1) and (2) has excellent rate characteristics. It is considered that through the interaction of these three crystal structures, a synergistic effect can be exerted on the charge-discharge reaction. Regarding the above relationship (1), A2 / A1 is 2.30 or more and 44.00 or less, and can be 2.40 or more, 2.50 or more, 2.60 or more, or 2.70 or more, and can be 43.00 or less, 42.00 or less, 41.00 or less, or 40.00 or less. In addition, regarding the above relationship (2), A3 / A1 is 0.50 or more and 1.90 or less, and can be 0.60 or more, 0.70 or more, 0.80 or more, 0.90 or more, 1.00 or more, or 1.10 or more, and can be 1.85 or less or 1.80 or less.

[0043] In addition to the O2-type structure, O6-type structure, and T#2-type structure, the electrode active material of one embodiment may also have other crystal structures. However, it is easier to exhibit more excellent effects when the amount of these other crystal structures is as small as possible. For example, when observing the cross-section of the electrode active material of one embodiment, the total area ratio of the O2-type structure, O6-type structure, and T#2-type structure in the cross-section may also be 80% or more and 100% or less, 85% or more and 100% or less, 90% or more and 100% or less, 95% or more and 100% or less, 97% or more and 100% or less, or 99% or more and 100% or less.

[0044] The "cross-section" of the electrode active material can be exposed, for example, by cutting the layer containing the electrode active material. The "area ratio" of each crystal phase in the cross-section of the electrode active material can be determined by ACOM-STEM measurement. Specifically, using JEM-2800 manufactured by JEOL Ltd., the electron diffraction pattern of each measurement site of the cross-section is obtained by precession electron diffraction method, indexed, and the crystal orientation is calculated, thereby visualizing the distribution of the crystal structure in the cross-section and calculating the area ratio of each crystal structure. Here, the beam diameter in this measurement is about 1.5 nm. In this case, for the O6-type structure with a large lattice constant, it may be calculated as the O3-type structure belonging to the same space group R-3m. On the other hand, the amounts of the O3-type structure and O6-type structure contained in the electrode active material can be determined in advance by XRD or the like. That is, even if it is assumed that the electrode active material contains the O3-type structure, the area ratios of the O3-type structure and O6-type structure can be determined by referring to the results of XRD in combination with the results of ACOM-STEM measurement.

[0045] 1.2 Chemical composition

[0046] The electrode active material of one embodiment may also contain at least one of Ni, Mn, and Co as a constituent element. More specifically, the electrode active material of one embodiment may also contain at least one selected from at least one of Mn, Ni, and Co, Li, and O as constituent elements. The electrode active material is particularly likely to have higher performance when it contains at least Li, Mn, one or both of Ni and Co, and O as constituent elements. In particular, when it contains at least Li, Mn, Ni, Co, and O as constituent elements.

[0047] The electrode active material of one embodiment may also have a composition represented by Li a Na b Mn x-p Ni y-q Co z-r M p+q+rA chemical composition represented by O2 (where 0 < a ≤ 1.00, 0 ≤ b ≤ 0.20, x + y + z = 1, and 0 ≤ p + q + r < 0.17, and the element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W). When the electrode active material has such a chemical composition, it is easy to maintain the expected crystal structure. In the above chemical composition, a > 0, it can be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, or 0.60 or more, and is 1.00 or less, it can be 0.90 or less, 0.80 or less, or 0.70 or less. In the above chemical composition, b is 0 or more, it can be 0.01 or more, 0.02 or more, or 0.03 or more, and is 0.20 or less, it can be 0.15 or less, or 0.10 or less. In addition, x is 0 or more, it can be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.50 or more, and is 1.00 or less, it can be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, or 0.50 or less. In addition, y is 0 or more, it can be 0.10 or more, or 0.20 or more, and is 1.00 or less, it 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. In addition, z is 0 or more, it can be 0.10 or more, 0.20 or more, or 0.30 or more, and is 1.00 or less, it 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. The element M contributes little to charge and discharge. In this regard, in the above chemical composition, by making p + q + r less than 0.17, it is easy to ensure a high charge and discharge capacity. p + q + r can also 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, by including the element M, the expected crystal structure is easily stabilized. In the above chemical composition, p + q + r is 0 or more, and can also 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 limited to exactly 2.0 and is not fixed.

[0048] 1.3 Others

[0049] As described later, the electrode active material of one embodiment can be obtained by replacing Na in a Na-containing oxide having a P2-type structure with Li. Here, the P2-type structure is hexagonal, the diffusion coefficient of Na ions is large, and it is easy to crystallize and grow in a specific direction. In particular, when at least one of Mn, Ni, and Co is included as the transition metal element constituting the P2-type structure, it is easy to grow in a plate shape in a specific direction. Therefore, the Na-containing oxide having a P2-type structure usually becomes plate-like particles with a large aspect ratio in which the crystal growth direction is biased in a specific direction. The electrode active material can be obtained based on such plate-like Na-containing oxide particles, or can also be obtained based on spherical Na-containing oxide particles. That is, the shape of the electrode active material can be plate-like particles or spherical particles. When the electrode active material is spherical particles, the reaction resistance decreases due to the reduction of the crystallite size, and the diffusion resistance inside the particles easily decreases. Furthermore, when applied to a battery, it is considered that the tortuosity decreases due to spheroidization, and the lithium ion conduction resistance decreases. Thereby, for example, the rate performance is further improved, and the reversible capacity is likely to be large. Furthermore, in the present application, "spherical particles" means particles having a roundness of 0.80 or more. The roundness of the particles can also 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 roundness of the particles is defined by 4πS / L 2 . Here, S is the projected area of the particles, and L is the perimeter of the projected image of the particles. The roundness of the particles can be obtained by observing the appearance of the particles with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an optical microscope.

[0050] The electrode active material of one embodiment can be, for example, solid particles, hollow particles, or particles having voids. The size of the particles of the electrode active material is not particularly limited, and it is considered that a small size is advantageous. For example, the average particle diameter (D50) of the particles of the electrode active material can also 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. Furthermore, the average particle diameter (D50) refers to the particle diameter (D50, median diameter) at the cumulative value of 50% in the volume-based particle size distribution obtained by the laser diffraction / scattering method.

[0051] 2. Manufacturing method of electrode active material

[0052] The electrode active material 1 can be manufactured, for example, by the following method. That is, the manufacturing method of the electrode active material of one embodiment can also include:

[0053] S1: Obtaining a Na-containing transition metal oxide having a P2-type structure; and

[0054] S2: At least a part of Na in the Na-containing oxide is replaced with Li by ion exchange to obtain a Li-containing oxide having an O2-type structure, an O6-type structure, and a T#2-type structure.

[0055] 2.1S1

[0056] In S1, a Na-containing transition metal oxide having a P2-type structure can be manufactured, for example, via the following steps:

[0057] S11: Obtain a precursor (for example, a precursor containing at least one element among Mn, Ni, and Co);

[0058] S12: Coat the surface of the precursor with a Na source to obtain a composite; and

[0059] S13: Bake the composite.

[0060] Herein, S13 may include:

[0061] S13-1: Perform pre-baking on the composite at a temperature of 300°C or higher and less than 700°C for 2 hours or more and 10 hours or less;

[0062] S13-2: Immediately after the pre-baking, perform formal baking on the composite at a temperature of 700°C or higher and 1100°C or lower for 30 minutes or more and 48 hours or less; and

[0063] S13-3: Immediately after the formal baking, rapidly cool the composite from a temperature T1 of 200°C or higher to a temperature T2 of 100°C or lower.

[0064] 2.1.1 Fabrication of the Precursor

[0065] The precursor may contain at least Mn and one or both of Ni and Co selected therefrom, or may contain at least Mn, Ni, and Co. The precursor may also be a salt containing 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 various compounds. The precursor may be in various shapes. For example, the precursor may be particulate, or may be spherical particles as described later. The particle size of the particles composed of the precursor is not particularly limited. By adjusting the particle size of the particles composed of the precursor and adjusting the manufacturing conditions of the composite and the baking conditions of the composite, the ratio of the crystal phases contained in the finally obtained electrode active material can be controlled.

[0066] In S11, an ion source capable of forming a precipitate with transition metal ions in an aqueous solution and a transition metal compound containing at least one element among Mn, Ni, and Co can also be used, and a precipitate as the above precursor can be obtained by a coprecipitation method. Thus, spherical particles as the precursor can be easily obtained. The "ion source capable of forming a precipitate with transition metal ions in an aqueous solution" can also be, for example, at least one selected from sodium salts such as sodium carbonate and sodium nitrate, sodium hydroxide, sodium oxide, etc. The transition metal compound can be the above salts and / or hydroxides containing at least one element among Mn, Ni, and Co. Specifically, in S11, the ion source and the transition metal compound can also be made into solutions respectively, and then a precipitate as the precursor can be obtained by dropping / mixing the respective solutions. At this time, water can be used as the solvent, for example. At this time, various sodium compounds can be used as the base, and an aqueous ammonia solution, etc. can also be added to adjust the alkalinity. In the case of the coprecipitation method, for example, an aqueous solution of a transition metal compound and an aqueous solution of sodium carbonate are prepared, and the respective aqueous solutions are dropped and mixed to obtain a precipitate as the precursor. Alternatively, the precursor can also be obtained by a sol-gel method. In particular, according to the coprecipitation method, spherical particles as the precursor can be easily obtained.

[0067] In S11, the precursor can also contain element M. Element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W. These elements M have, for example, the function of stabilizing the P2-type structure and the O2-type structure. The method for obtaining the precursor containing element M is not particularly limited. In the case of obtaining the precursor by the coprecipitation method in S11, for example, by preparing 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, and dropping and mixing the respective aqueous solutions, a precursor containing element M together with at least one element among Mn, Ni, and Co can be obtained. Alternatively, in the manufacturing method of the present disclosure, element M can also be doped during the Na-doping firing in S2 and S3 described later without adding element M in S11.

[0068] 2.1.2 Fabrication of the composite

[0069] In S12, the surface of the precursor obtained through S11 is coated with a Na source to obtain a composite. The Na source can be a Na-containing salt such as a carbonate or a nitrate, or a compound other than a salt such as sodium oxide or sodium hydroxide. In S12, the amount of the Na source coated on the surface of the precursor may be determined in consideration of the amount of Na disappearance during the subsequent firing. In S12, there is no particular limitation on the coating rate of the Na source on the precursor surface. In S12, there is no particular limitation on the method of coating the surface of the above-mentioned precursor with the Na source. For example, the precursor and the Na source can be mixed using a mortar or a mixing device, or a solution containing the Na source can be brought into contact with the precursor and then dried using a rolling flow coating method, a spray drying method, etc. In particular, when the surface of the precursor is coated with the Na source by the spray drying method, the coating rate of the Na source on the precursor surface increases, and it is easier to more appropriately adjust the crystallinity and shape (plate-like particles or spherical particles) of the P2-type Na-containing oxide obtained through S13 described below, and the ratio of each crystal structure contained in the finally obtained electrode active material can be more appropriately controlled.

[0070] In S12, the M source can also be used to coat the precursor together with the Na source. For example, in S12, the precursor obtained through S11, the 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 can be mixed to obtain a composite. The M source can be, for example, a salt containing the element M such as a carbonate or a sulfate, or a compound other than a salt such as an oxide or a hydroxide. The amount of the M source relative to the precursor may be determined according to the chemical composition of the Na-containing oxide after firing.

[0071] 2.1.3 Firing of the composite

[0072] In S13, the composite obtained through S12 is fired to obtain a Na-containing oxide having a P2-type structure. S13 may also include the above-mentioned S13-1, S13-2, and S13-3. In addition to the above-mentioned precursor manufacturing conditions and composite manufacturing conditions, by adjusting the firing conditions in S13-1, S13-2, and S13-3, the crystallinity and shape (plate-like particles or spherical particles) of the P2-type Na-containing oxide obtained through S13 can be adjusted, and the ratio of each crystal structure contained in the finally obtained electrode active material can be controlled.

[0073] In S13-1, the composite is pre-fired at a temperature of more than 300°C and less than 700°C for 2 hours or more and 10 hours or less. In S13-1, the pre-firing can also be carried out on the basis of arbitrarily forming the above composite. The pre-firing is carried out at a temperature lower than the formal firing temperature. If the pre-firing in S13-1 is insufficient, the formation of the P2 phase may be insufficient in the finally obtained Na-containing oxide. In S13-1, by the pre-firing temperature being more than 300°C and less than 700°C, and the pre-firing time being 2 hours or more and 10 hours or less, sufficient pre-firing can be carried out on the composite, the thermal uniformity is improved, and the Na-containing oxide obtained through the subsequent S13-2 and S13-3 is likely to become a suitable oxide. The pre-firing 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. In addition, the pre-firing time can 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. For example, it can also be an oxygen-containing atmosphere.

[0074] In S13-2, following the above pre-firing, the composite is formally fired at a temperature of 700°C or more and 1100°C or less for 30 minutes or more and 48 hours or less. In S13-2, the formal firing temperature of the composite can also be 800°C or more and 1000°C or less. If the formal firing temperature is too low, the P2 phase is not formed. If the formal firing temperature is too high, it is easy to form phases such as O3 instead of the P2 phase. The temperature rising conditions from the pre-firing temperature to the formal firing temperature are not particularly limited. In S13-2, the shape of the Na-containing oxide can be controlled by the formal firing time. If the formal firing time is too short, the formation of the P2 phase becomes insufficient. On the other hand, if the formal firing time is too long, the P2 phase grows excessively, and the particles are likely to coarsen in a plate shape.

[0075] In S13-3, following the above-mentioned formal firing, the composite is rapidly cooled (at a cooling rate of 20°C / minute or more) from a temperature T1 of 200°C or higher to a temperature T2 of 100°C or lower. The above-mentioned pre-firing and formal firing are carried out, for example, in a heating furnace. In process S13-3, for example, after the formal firing of the composite in the heating furnace, it is cooled in the heating furnace to an arbitrary temperature T1 of 200°C or higher. After reaching this temperature T1, the fired product is taken out of the heating furnace and rapidly cooled outside the furnace to an arbitrary temperature T2 of 100°C or lower. The temperature T1 is an arbitrary temperature of 200°C or higher, and can also be an arbitrary temperature of 250°C or higher. The temperature T2 is an arbitrary temperature of 100°C or lower, can be an arbitrary temperature of 50°C or lower, or can also be the cooling end temperature. In a predetermined temperature range between the temperature T1 and the temperature T2, moisture easily intrudes into the interlayer of the P2-type structure due to atomic vibration, molecular motion, etc. It is considered that when cooling the composite (Na-containing oxide having a P2-type structure) after formal firing, by making the time in the temperature range where such moisture easily intrudes short (i.e., rapid cooling), the amount of moisture intruding into the interlayer of the P2-type structure becomes less. Regarding this point, in process S13-3, when cooling the composite after formal firing, from an arbitrary temperature T1 of 200°C or higher to an arbitrary temperature T2 of 100°C or lower, for example, it is cooled in a dry atmosphere outside the furnace, and the cooling rate between the temperature T1 and the temperature T2 becomes rapid (for example, 20°C / minute or more), and moisture is difficult to intrude into the interlayer of the P2-type structure, and damage to the P2-type structure, etc. can be suppressed. As a result, in S2, Na can be effectively ion-exchanged with Li.

[0076] Through S13, a Na-containing oxide having a P2-type structure and a predetermined chemical composition can be manufactured. The Na-containing oxide contains at least one transition metal element selected from Mn, Ni, and Co, Na, and O as constituent elements. In particular, in the case of containing at least Na, Mn, at least one of Ni and Co, and O as constituent elements, and in the case of containing at least Na, Mn, Ni, Co, and O as constituent elements, the performance of the positive electrode active material is likely to be further improved. The Na-containing oxide may also have a structure composed of Na c Mn x-p Ni y-q Co z-r M p+q+rThe chemical composition represented by O2. Here, 0 < c < 1.00, x + y + z = 1 and 0 ≤ p + q + r < 0.17. In addition, M is at least one element selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W. When the Na-containing oxide has such a chemical composition, it is easier to maintain the P2-type structure. In the above chemical composition, c is greater than 0, and can be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, or 0.60 or more, and less than 1.00, and can be 0.90 or less, 0.80 or less, or 0.70 or less. x is 0 or more, can be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.50 or more, and is 1.00 or less, and can be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, or 0.50 or less. In addition, y is 0 or more, can be 0.10 or more, or 0.20 or more, 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. In addition, z is 0 or more, can be 0.10 or more, 0.20 or more, or 0.30 or more, 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. The element M contributes little to charge and discharge. In this regard, in the above chemical composition, by making p + q + r less than 0.17, it is easy to ensure a high charge and discharge capacity. p + q + r can also 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, by including the element M, the P2-type structure and the O2-type structure are easily stabilized. In the above chemical composition, p + q + r is 0 or more, and can also 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 limited to exactly 2.0 and is not fixed.

[0077] 2.2S2

[0078] In S2, at least a part of the ions of Na in the Na-containing oxide obtained in S1 is ion-exchanged with Li to obtain a Li-containing oxide having an O2-type structure, an O6-type structure, and a T#2-type structure. In the ion exchange, for example, there are a method of using an aqueous solution containing lithium halide and a method of using a mixture of lithium halide and other lithium salts (such as a molten salt). From the viewpoints that the P2-type structure is easily damaged by the intrusion of water and crystallinity, among the above two methods, the method using a molten salt is preferred. That is, by mixing the Na-containing oxide having the above P2-type structure and the molten salt and heating to a temperature above the melting point of the molten salt, at least a part of Na in the Na-containing oxide can be replaced with Li by ion exchange. The lithium halide constituting the molten salt is preferably at least one of lithium chloride, lithium bromide, and lithium iodide. The other lithium salt constituting the molten salt is preferably lithium nitrate. By using a molten salt, compared with the case of using lithium halide or other lithium salts alone, the melting point is lowered, and ion exchange can be carried out at a lower temperature. The temperature in the ion exchange can be, for example, above the melting point of the above molten salt and 600 °C or lower, 500 °C or lower, 400 °C or lower, or 300 °C or lower. If the temperature in the ion exchange is too high, it is easy to form an O3-type structure as a stable phase instead of an O2-type structure. On the other hand, from the viewpoint of making the time taken for ion exchange a short time, the temperature in the ion exchange can be as high as possible.

[0079] 3. Electrode

[0080] An electrode of one embodiment contains the electrode active material of the present disclosure described above. The components other than the electrode active material contained in the electrode are not particularly limited and can be appropriately determined according to the target performance. An electrode of one embodiment may also contain the electrode active material of the present disclosure described above and at least one selected from an electrolyte, a conductive additive, and a binder. An electrode of one embodiment may optionally contain other additives. The contents of the active material, electrolyte, conductive additive, binder, etc. in the electrode can be appropriately determined according to the target battery performance. For example, in the case where the electrode contains a current collector and an active material layer, based on the total solid components contained in the active material layer being 100% by mass, the content of the electrode active material can also be 40% by mass or more and less than 100%.

[0081] 3.1 Active Material

[0082] The active material contained in the electrode may be composed only of the electrode active material of the present disclosure described above, or may contain, together with the electrode active material, other active materials (other active substances) in addition to the electrode active material. From the viewpoint of further improving the technical effect of the present disclosure, the proportion of the other active material in the total active material contained in the electrode may be small. For example, taking the total active material contained in the electrode as 100% by mass, the content of the electrode active material of the present disclosure described above may also be 50% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, or 99% by mass or more and 100% by mass or less. The other active materials that can be contained in the electrode may be any substances known as active materials.

[0083] 3.2 Electrolyte

[0084] The electrode may contain an electrolyte together with the above-described electrode active material. The electrolyte that can be contained in the electrode may be a solid electrolyte, a liquid electrolyte, or a combination thereof. As the solid electrolyte, it is sufficient to use a substance known as a solid electrolyte for a battery. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, the inorganic solid electrolyte has excellent ion conductivity and heat resistance. As the inorganic solid electrolyte, for example, oxide solid electrolytes, sulfide solid electrolytes, and ionic inorganic solid electrolytes can be cited. In particular, when the electrode contains a sulfide solid electrolyte as the solid electrolyte, it is easy to ensure higher performance. The sulfide solid electrolyte may also contain, for example, at least Li, S, and P as constituent elements. Alternatively, the electrode may contain an ionic solid electrolyte as the solid electrolyte. For example, it may contain a solid electrolyte containing at least Li, Y, and a halogen (at least one of Cl, Br, I, and F) as constituent elements. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may also be in the form of particles. The average particle diameter (D50) of the solid electrolyte may be, for example, 10 nm or more and 10 μm or less. The solid electrolyte may be used alone as only one kind, or two or more kinds may be used in combination. The liquid electrolyte (electrolyte solution) is a liquid containing lithium ions as carrier ions. The electrolyte solution may be an aqueous electrolyte solution or a non-aqueous electrolyte solution. The composition of the electrolyte solution may be the same as the composition known for the electrolyte solution of a lithium-ion battery. The electrolyte solution may also be an electrolyte solution in which a lithium salt is dissolved in water or a non-aqueous solvent. As the non-aqueous solvent, for example, various carbonate-based solvents can be cited. As the lithium salt, for example, lithium amide salts, LiPF6, etc. can be cited.

[0085] 3.3 Conductive Additive

[0086] Examples of conductive aids that can be included in the electrode include carbon materials such as vapor-grown carbon fiber (VGCF), acetylene black (AB), Ketjen black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF); and metal materials such as nickel, titanium, aluminum, and stainless steel. The conductive aid can also be, for example, particulate or fibrous, and its size is not particularly limited. The conductive aid can be used alone as only one type, or two or more types can be used in combination.

[0087] 3.4 Binder

[0088] Examples of binders that can be included in the electrode include butadiene rubber (BR)-based binders, isobutyl rubber (IIR)-based binders, acrylate butadiene rubber (ABR)-based binders, styrene butadiene rubber (SBR)-based binders, polyvinylidene fluoride (PVdF)-based binders, polytetrafluoroethylene (PTFE)-based binders, polyimide (PI)-based binders, etc. The binder can be used alone as only one type, or two or more types can be used in combination.

[0089] 3.5 Others

[0090] In addition to the above components, the electrode can also contain various additives, such as dispersants and lubricants.

[0091] 4. Battery

[0092] For example, the electrode active material of the present disclosure can be used as the positive electrode active material of a battery. As Figure 2 shown, a battery 100 of an embodiment has a positive electrode active material layer 10, an electrolyte layer 20, and a negative electrode active material layer 30. The positive electrode active material layer 10 contains the electrode active material of the present disclosure described above.

[0093] 4.1 Positive Electrode Active Material Layer

[0094] The positive electrode active material layer 10 contains at least the electrode active material of the present disclosure described above, and may optionally contain an electrolyte, a conductive aid, a binder, etc. The shape of the positive electrode active material layer 10 is not particularly limited. For example, the positive electrode active material layer 10 can also be a sheet-like positive electrode active material layer having a substantially planar shape. The thickness of the positive electrode active material layer 10 is not particularly limited. For example, it can be 0.1 μm or more or 1 μm or more, and can be 2 mm or less or 1 mm or less.

[0095] 4.2 Electrolyte Layer

[0096] The electrolyte layer 20 is disposed between the positive electrode active material layer 10 and the negative electrode active material layer 30. The electrolyte layer 20 contains at least an electrolyte. The electrolyte layer 20 may contain at least one of a solid electrolyte and a liquid electrolyte, and may optionally contain a binder or the like. The contents of the electrolyte and the binder or the like in the electrolyte layer 20 are not particularly limited. Alternatively, the electrolyte layer 20 may also have a separator or the like, which prevents the contact between the positive electrode active material layer 10 and the negative electrode active material layer 30 while retaining the liquid electrolyte. The thickness of the electrolyte layer 20 is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or more, and may be 2 mm or less or 1 mm or less.

[0097] As the electrolyte contained in the electrolyte layer 20, it can be appropriately selected from the electrolytes (solid electrolytes and / or liquid electrolytes) exemplified as the electrolytes that can be contained in the above positive electrode active material layer 10 (electrode binder). In addition, regarding the binder that can be contained in the electrolyte layer 20, it can be appropriately selected from the binders exemplified as the binders that can be contained in the above positive electrode active material layer. The electrolyte and the binder can each be used alone as only one kind, or two or more kinds can be used in combination. The separator may be a separator commonly used in batteries. For example, a separator made of a resin such as polyethylene (PE), polypropylene (PP), polyester, and polyamide can be cited. The separator may be a single-layer structure or a multi-layer structure. As the multi-layer structure separator, for example, a two-layer structure separator of PE / PP, or a three-layer structure separator of PP / PE / PP or PE / PP / PE can be cited. The separator may also be made of a non-woven fabric such as a cellulose non-woven fabric, a resin non-woven fabric, or a glass fiber non-woven fabric.

[0098] 4.3 Negative Electrode Active Material Layer

[0099] The negative electrode active material layer 30 contains at least a negative electrode active material. In addition, the negative electrode active material layer 30 may optionally contain an electrolyte, a conductive assistant, a binder, various additives, etc. The content of each component in the negative electrode active material layer 30 can be appropriately determined according to the target battery performance. For example, based on the total solid components of the negative electrode active material layer 30 being 100% by mass, the content of the negative electrode active material can be 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, and can be 100% by mass or less, less than 100% by mass, 95% by mass or less, or 90% by mass or less. Alternatively, based on the entire negative electrode active material layer 30 being 100% by volume, the negative electrode active material and the optionally included electrolyte, conductive assistant, and binder can together contain 85% by volume or more, 90% by volume or more, or 95% by volume or more, and the remaining portion can be either voids or other components. The shape of the negative electrode active material layer 30 is not particularly limited. For example, it can also be a sheet having a substantially planar shape. The thickness of the negative electrode active material layer 30 is not particularly limited. For example, it can be 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or more, and can be 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less.

[0100] Any of the known negative electrode active materials for a battery can be used as the negative electrode active material. Among the known active materials, various substances with a potential (charge-discharge potential) for occluding and releasing carrier ions lower than that of the above-mentioned positive electrode active material can be used. For example, silicon-based active materials such as Si, Si alloys, and silicon oxides; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium, lithium alloys, etc. can be used. Among them, when the negative electrode active material layer 30 contains Si as the negative electrode active material, the performance of the battery 100 is likely to be improved. The negative electrode active material can be used alone as only 1 type, or 2 or more types can be used in combination. The shape of the negative electrode active material is the general shape of the negative electrode active material for a battery. For example, the negative electrode active material can also be in the form of particles. The negative electrode active material particles can be primary particles or secondary particles formed by aggregating multiple primary particles. The average particle diameter (D50) of the negative electrode active material particles can be, for example, 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 also be in the form of a sheet (foil-like, film-like) such as a lithium foil. That is, the negative electrode active material layer 30 can also be composed of sheets of the negative electrode active material.

[0101] As the electrolyte that can be included in the negative electrode active material layer 30, for example, the above-mentioned solid electrolyte, liquid electrolyte, or a combination thereof can be cited. The conductive assistant that can be included in the negative electrode active material layer 30 can be appropriately selected, for example, from the conductive assistants exemplified as the conductive assistants that can be included in the above-mentioned positive electrode active material layer 10 (electrode mixture 5). The binder that can be included in the negative electrode active material layer 30 can be appropriately selected, for example, from the binders exemplified as the binders that can be included in the above-mentioned positive electrode active material layer 10 (electrode mixture 5). The electrolyte, conductive assistant, and binder can each be used alone as only one kind, or two or more kinds can be used in combination.

[0102] 4.4 Positive electrode current collector

[0103] As Figure 2 shown, the battery 100 can also include a positive electrode current collector 40 in contact with the positive electrode active material layer 10. The positive electrode current collector 40 can be any of the general positive electrode current collectors of a battery. In addition, the positive electrode current collector 40 can have at least one shape selected from a foil shape, a plate shape, a net shape, a perforated metal shape, and a foam body, etc. The positive electrode current collector 40 can be composed of a metal foil or a metal net. In particular, the processability of the metal foil is excellent. The positive electrode current collector 40 can also be composed of multiple foils. As the metal constituting the positive electrode current collector 40, at least one selected from Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, V, Mg, Pb, Ge, In, Sn, Zr, and stainless steel, etc. can be cited. In particular, from the viewpoint of ensuring oxidation resistance, etc., the positive electrode current collector 40 can also contain Al. For the purpose of adjusting the resistance, etc., the positive electrode current collector 40 can have a certain coating on its surface. For example, the positive electrode current collector 40 can have a carbon coating. In addition, the positive electrode current collector 40 can be a metal foil, or can be a current collector obtained by plating or vapor-depositing the above-mentioned metal on a substrate. In addition, when the positive electrode current collector 40 is composed of multiple metal foils, a certain layer can also be provided between these multiple metal foils. The thickness of the positive electrode current collector 40 is not particularly limited. For example, it can be 0.1 μm or more or 1 μm or more, and can be 1 mm or less or 100 μm or less.

[0104] 4.5 Negative electrode current collector

[0105] As Figure 2As shown, the battery 100 may also include a negative electrode current collector 50 in contact with the negative electrode active material layer 30. The negative electrode current collector 50 may be any of the common ones used as the negative electrode current collector of the battery. In addition, the negative electrode current collector 50 may be in the form of a foil, a plate, a mesh, a perforated metal, a foam, etc. The negative electrode current collector 50 may be a metal foil or a metal mesh, or may also be a carbon sheet. In particular, the processability of the metal foil is excellent. The negative electrode current collector 50 may also be composed of multiple foils or sheets. Examples of the metal constituting the negative electrode current collector 50 include at least one selected from Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, V, Mg, Pb, Ge, In, Sn, Zr, and stainless steel, etc. In particular, from the viewpoints of ensuring reducibility resistance and being less likely to alloy with lithium, the negative electrode current collector 50 may also contain at least one metal selected from Cu, Ni, and stainless steel. For the purpose of adjusting resistance, etc., the negative electrode current collector 50 may have a certain coating on its surface. For example, the negative electrode current collector 50 may have a carbon coating. The negative electrode current collector 50 may be an aluminum foil with a carbon coating. In addition, the negative electrode current collector 50 may be a metal foil, or may also be a current collector obtained by plating or vapor-depositing the above metal on a substrate. In addition, when the negative electrode current collector 50 is composed of multiple metal foils, there may also be a certain layer between these multiple metal foils. The thickness of the negative electrode current collector 50 is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or more, and may be 1 mm or less or 100 μm or less.

[0106] 4.6 Other Constitutions

[0107] In addition to the above constitution, the battery 100 may also include the common constitutions of a battery. For example, electrode tabs and terminals, etc. The battery 100 may also be a battery in which the above respective constitutions are housed inside an outer package. The outer package may be any of the known ones used as the outer package of the battery. In addition, multiple batteries 100 may be arbitrarily electrically connected or arbitrarily stacked to form a battery pack. In this case, the battery pack may also be housed inside a known battery case. Examples of the shape of the battery 100 include coin type, laminated type, cylindrical type, and square type, etc. The battery 100 may also be a secondary battery.

[0108] In addition to using the above specific electrode active materials, the battery 100 may be manufactured by applying known methods. For example, it may be manufactured as follows. However, the manufacturing method of the battery 100 is not limited to the following method. For example, each layer may also be formed by dry forming, etc.

[0109] (1)Disperse the electrode active material and the like that constitute the positive electrode active material layer in a solvent to obtain a slurry for the positive electrode layer. The solvent used in this case is not particularly limited, and water and various organic solvents can be used. Apply the slurry for the positive electrode layer to the surface of the positive electrode current collector using a doctor blade or the like, and then dry it to form a positive electrode active material layer on the surface of the positive electrode current collector, thereby manufacturing a positive electrode.

[0110] (2)Disperse the negative electrode active material and the like that constitute the negative electrode active material layer in a solvent to obtain a slurry for the negative electrode layer. The solvent used in this case is not particularly limited, and water and various organic solvents can be used. Apply the slurry for the negative electrode layer to the surface of the negative electrode current collector using a doctor blade or the like, and then dry it to form a negative electrode active material layer on the surface of the negative electrode current collector, thereby manufacturing a negative electrode.

[0111] (3)Stack the layers in such a way that the electrolyte layer (solid electrolyte layer or separator) is sandwiched between the negative electrode and the positive electrode to obtain a laminate having a negative electrode current collector, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector in this order. Install other components such as terminals on the laminate as needed.

[0112] (4)Accommodate the laminate in a battery case, fill the electrolyte in the battery case in the case of an electrolyte battery, immerse the laminate in the electrolyte, and seal the laminate in the battery case to manufacture a secondary battery. Furthermore, in the case of an electrolyte battery, the negative electrode active material layer, the separator, and the positive electrode active material layer may also contain the electrolyte in the stage of (3) above.

[0113] 5. Vehicle

[0114] The battery of the present disclosure has excellent rate characteristics by using the electrode active material. Such a battery can be suitably used, for example, in at least one vehicle selected from a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a battery electric vehicle (BEV). That is, the technology of the present disclosure also has the following aspect: a vehicle having a battery, the battery having a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, and the positive electrode active material layer containing the electrode active material of the present disclosure described above.

[0115] As described above, one embodiment of the electrode active material and the like has been described, but the technology of the present disclosure can be variously modified beyond the above embodiment without departing from its gist. Hereinafter, examples are shown to explain the technology of the present disclosure in more detail, but the technology of the present disclosure is not limited to the following examples.

[0116] 1. Fabrication of Electrode Active Material

[0117] 1.1 Example 1

[0118] 1.1.1 Preparation of Precursors

[0119] (1) MnSO4·5H2O, NiSO4·6H2O, and CoSO4·7H2O were weighed in such a way as to achieve the target composition ratio (Mn:Ni:Co = 5:2:3), and were dissolved in distilled water to a concentration of 1.2 mol / L to obtain the first solution. In addition, in another container, Na2CO3 was dissolved in distilled water to a concentration of 1.2 mol / L to obtain the second solution.

[0120] (2) 1000 mL of pure water was added to the reaction vessel (with baffle plates), and 500 mL of the first solution and 500 mL of the second solution were respectively added dropwise thereto at a rate of about 4 mL / minute.

[0121] (3) After the addition was completed, the mixture was stirred at a stirring speed of 150 rpm at room temperature for 1 hour to obtain the product.

[0122] (4) The product was washed with pure water, and solid-liquid separation was carried out using a centrifuge to recover the precipitate.

[0123] (5) The obtained precipitate was dried overnight at 120 °C, pulverized with a mortar, and classified into coarse particles and fine particles by air classification. The fine particles were removed to obtain the coarse particles as precursor particles.

[0124] 1.1.2 Preparation of Composite

[0125] (1) Na2CO3 and distilled water were weighed to a concentration of 1150 g / L, and were stirred with a stirrer until completely dissolved to prepare an aqueous Na2CO3 solution.

[0126] (2) In such a way that the composition after firing described below becomes Na 0.8 Mn 0.5 Ni 0.2 Co 0.3 O2, the above-mentioned aqueous Na2CO3 solution and the above-mentioned precursor particles were weighed and mixed to obtain a slurry.

[0127] (3) The above slurry was subjected to pneumatic drying by spray drying to obtain a composite. Specifically, using a spray drying device DL410, under the conditions of a slurry feeding rate of 30 mL / minute, an inlet temperature of 200 °C, a circulating air volume of 0.8 m 3 / minute, and a spray pressure of 0.3 MPa, the above slurry was subjected to pneumatic drying. Thus, the surface of the precursor particles was coated with Na2CO3 to obtain a composite.

[0128] 1.1.3 Firing of Composite

[0129] The composite was placed in an alumina crucible and fired in an air atmosphere to obtain a Na-containing oxide having a P2-type structure. The firing conditions are as shown in the following (1) to (7).

[0130] (1) An alumina crucible containing the above composite was placed in a heating furnace in an air atmosphere.

[0131] (2) The temperature in the heating furnace was raised from room temperature (25 °C) to 600 °C over 115 minutes.

[0132] (3) The heating furnace was maintained at 600 °C for 360 minutes for pre-firing.

[0133] (4) After pre-firing, the temperature in the heating furnace was raised to 900 °C and then maintained at 900 °C for 60 minutes for main firing.

[0134] (5) After main firing, the temperature in the heating furnace was lowered from the main firing temperature to 250 °C. The alumina crucible was taken out of the heating furnace at 250 °C and cooled outside the furnace in a dry atmosphere, reaching 25 °C in 10 minutes.

[0135] The cooled fired product was pulverized in a dry atmosphere using a mortar to obtain Na-containing oxide particles having a P2-type structure (P2-type particles).

[0136] 1.1.4 Ion exchange

[0137] (1) LiNO3 and LiCl were weighed in a molar ratio of 50:50 and mixed with the above P2-type particles in a molar ratio 10 times the minimum Li amount required for ion exchange to obtain a mixture.

[0138] (2) Using an alumina crucible, ion exchange was carried out at 280 °C in an air atmosphere for 1 hour to obtain a product containing a Li-containing oxide.

[0139] (3) The salts remaining in the product were washed with pure water and solid-liquid separation was carried out by vacuum filtration to obtain a precipitate.

[0140] (4) The obtained precipitate was dried at 120 °C overnight to obtain the electrode active material particles of Example 1. These electrode active material particles are Li 0.63 Mn 0.5 Ni 0.2 Co 0.3 O2-expressed Li-containing oxide. In addition, the crystal phase contained in these electrode active material particles was confirmed by XRD, and as a result, these electrode active material particles do not have an O3-type structure and have at least an O2-type structure.

[0141] 1.2 Example 2

[0142] An electrode active material was produced in the same manner as in Example 1, except that the firing temperature of the composite was changed from 900 °C to 800 °C. The electrode active material particles are a Li 0.62 Mn 0.5 Ni 0.2 Co 0.3 O₂-containing Li oxide. In addition, the crystal phase contained in the electrode active material particles was confirmed by XRD. As a result, the electrode active material particles did not have an O3-type structure and had at least an O2-type structure.

[0143] 1.3 Comparative Example 1

[0144] As precursor particles, fine particles were used instead of coarse particles. The fine particles and Na₂CO₃ powder were weighed so as to form Na 0.8 Mn 0.5 Ni 0.2 Co 0.3 O₂, and then mixed in a mortar to obtain a composite. Using this composite, firing and ion exchange were carried out in the same manner as in Example 1 to produce an electrode active material. The electrode active material particles are a Li 0.64 Mn 0.5 Ni 0.2 Co 0.3 O₂-containing Li oxide. In addition, the crystal phase contained in the electrode active material particles was confirmed by XRD. As a result, the electrode active material particles did not have an O3-type structure and had at least an O2-type structure.

[0145] 1.4 Comparative Example 2

[0146] An electrode active material was produced in the same manner as in Comparative Example 1, except that the firing temperature of the composite was changed from 900 °C to 800 °C. The electrode active material particles are a Li 0.63 Mn 0.5 Ni 0.2 Co 0.3 O₂-containing Li oxide. In addition, the crystal phase contained in the electrode active material particles was confirmed by XRD. As a result, the electrode active material particles did not have an O3-type structure and had at least an O2-type structure.

[0147] 1.5 Comparative Example 3

[0148] An electrode active material was produced in the same manner as in Example 1, except that the firing temperature of the composite was changed from 900 °C to 1000 °C. The electrode active material particles are a Li 0.62 Mn 0.5 Ni 0.2 Co 0.3A Li-containing oxide represented by O2. In addition, the crystal phase contained in the electrode active material particles was confirmed by XRD. As a result, the electrode active material particles did not have an O3-type structure and had at least an O2-type structure.

[0149] 2. ACOM-STEM measurement

[0150] The cross-section of each electrode active material was subjected to ACOM-STEM measurement, and the area ratios of the O2-type structure, O6-type structure, and T#2-type structure in the cross-section were calculated. The crystal phase was identified by comparing the electron diffraction images at each measurement point with the known crystal structure information. Furthermore, in this measurement, a beam diameter of about 1.5 nm was used. Therefore, for the O6-type structure with a lattice constant exceeding 20 nm, it was sometimes calculated as an O3-type structure. On the other hand, as described above, according to the XRD results, the content rate of the O3-type structure in each electrode active material was 0%. Therefore, in the ACOM-STEM measurement, the part judged to have an O3 structure was regarded as the part having an O6-type structure, and the area ratio was calculated.

[0151] 3. Fabrication of coin cell

[0152] Coin cells (CR2032) were fabricated using each electrode active material. The fabrication procedure of the coin cells is as described below.

[0153] (1) The above-mentioned electrode active material, acetylene black (AB) as a conductive additive, and polyvinylidene fluoride (PVdF) as a binder were weighed so that the mass ratio of the electrode active material: AB: PVdF = 85: 10: 5, and they were dispersed and mixed in N-methyl-2-pyrrolidone to obtain a positive electrode mixture slurry. The positive electrode mixture slurry was coated on an aluminum foil and vacuum-dried at 120 °C overnight, whereby a positive electrode, which is a laminate of a positive electrode active material layer and a positive electrode current collector, was obtained.

[0154] (2) Propylene carbonate trifluoride (TFPC) and ethyl methyl carbonate trifluoride (TFEMC) were mixed at a ratio of TFPC: TFEMC = 30 vol%: 70 vol% to obtain a mixed solvent, and LiPF6 was dissolved in the mixed solvent at a concentration of 1 M to obtain an electrolyte solution.

[0155] (3) A lithium metal foil was prepared as the negative electrode.

[0156] (4) Using the positive electrode, the electrolyte solution, and the negative electrode, a coin cell (CR2032) was fabricated.

[0157] 4. Evaluation of charge-discharge characteristics of coin cell

[0158] For each coin cell, charge and discharge were performed in a thermostat maintained at 25 °C in a voltage range of 2.0 to 4.8 V at a rate of 0.1 C (1 C = 220 mA / g), and the discharge capacity at 0.1 C was measured. Subsequently, after charging at a rate of 0.1 C, discharge was performed at 3 C, and the discharge capacity at 3 C was thereby measured. The rate characteristics of the coin cell were evaluated by obtaining the ratio of the discharge capacity at 3 C to the discharge capacity at 0.1 C.

[0159] 5. Evaluation Results

[0160] In Table 1 below, for each electrode active material, the "area ratio of the A1:O2 type structure in the cross-section of the electrode active material", "area ratio of the A2:O6 type structure in the cross-section", "area ratio of the A3:T#2 type structure in the cross-section", "A2 / A1", and "A3 / A1" are shown. In addition, for each coin cell, the "0.1 C discharge capacity", "3 C discharge capacity", and "rate characteristics (3 C discharge capacity / 0.1 C discharge capacity)" are shown.

[0161] Table 1

[0162]

[0163] Figure 3A Shows the ACOM-STEM measurement results for the cross-section of the electrode active material of Example 1. In addition, Figure 3B Shows the ACOM-STEM measurement results for the cross-section of the electrode active material of Comparative Example 1.

[0164] From Table 1, Figure 3A and Figure 3B As shown by the results, the batteries using the electrode active materials of Example 1 and Example 2 with A2 / A1 within a predetermined range and A3 / A1 within a predetermined range have excellent rate characteristics compared to the batteries using the electrode active materials of Comparative Examples 1 to 3 with A2 / A1 outside the predetermined range and A3 / A1 outside the predetermined range.

[0165] 6. Summary

[0166] Based on the above results, it can be said that by constructing a battery using an electrode active material that satisfies the following relationships (1) and (2), the rate characteristics of the battery can be improved.

[0167] 2.30 ≤ A2 / A1 ≤ 44.00 (1)

[0168] 0.50 ≤ A3 / A1 ≤ 1.90 (2)

[0169] The area ratio of the A1:O2 type structure in the cross-section of the electrode active material,

[0170] The area ratio of the A2:O6 structure in the cross-section of the electrode active material,

[0171] The area ratio of the A3:T#2 structure in the cross-section of the electrode active material.

Claims

1. An electrode active material, when observing the cross-section of the electrode active material, the following relationships (1) and (2) are satisfied: 2.30 ≤ A2 / A1 ≤ 44.00 (1) 0.50 ≤ A3 / A1 ≤ 1.90 (2) A1: The area ratio of the O2-type structure in the cross-section, A2: The area ratio of the O6-type structure in the cross-section, A3: The area ratio of the T#2-type structure in the cross-section.

2. The electrode active material according to claim 1, comprising at least one of Ni, Mn, and Co as a constituent element.

3. The electrode active material according to claim 2, Having a chemical composition represented by Li a Na b Mn x-p Ni y-q Co z-r M p+q+r O2, Among them, 0 < a ≤ 1.00, 0 ≤ b ≤ 0.20, x + y + z = 1 and 0 ≤ p + q + r < 0.17, and the element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W.

4. An electrode comprising the electrode active material according to any one of claims 1 to 3.

5. A battery having a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, wherein the positive electrode active material layer comprises the electrode active material according to any one of claims 1 to 3.

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