Electrode active material, electrode, and battery

Abstract

To disclose a technology that can improve the cycle characteristics of a battery when the battery is constructed using an electrode active material having an O2 type structure.SOLUTION: When a cross section of an electrode active material according to the present disclosure is observed, the relationships 2.30≤A2 / A1≤44.00 and 0.50≤A3 / A1≤1.90 are satisfied, where 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.SELECTED DRAWING: Figure 3A

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, one having an O2-type structure (O: Octahedral) is known. As disclosed in Patent Documents 1 and 2, an electrode active material having an O2-type structure can be obtained by ion-exchanging at least a part of Na in a Na-containing oxide having a P2-type structure with Li.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is room for improvement in the rate characteristics of a battery using an electrode active material having an O2-type structure.

Means for Solving the Problems

[0005] As means for solving the above problems, this application discloses the following multiple aspects. <Aspect 1> An electrode active material, wherein when observing a cross-section of the electrode active material, the following relationships (1) and (2): 2.30 ≦ A2 / A1 ≦ 44.00 (1) 0.50 ≦ A3 / A1 ≦ 1.90 (2) A1: Area ratio of the O2-type structure in the cross-section A2: Area ratio of the O6-type structure in the cross-section A3: Area ratio of the T#2-type structure in the cross-section is satisfied, electrode active material. <Aspect 2> The electrode active material of Aspect 1, including at least one of Ni, Mn, and Co as constituent elements, electrode active material. <Aspect 3> The electrode active material of Aspect 2, Li a Na b Mn x-p Ni y-q Co z-r M p+q+r 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), having a chemical composition represented by electrode active material. <Aspect 4> Including the electrode active material of any one of Aspects 1 to 3, electrode. <Aspect 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 includes the electrode active material of any one of Aspects 1 to 3, battery.

Advantages of the Invention

[0006] 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

[0007]

Figure 1A

Figure 1B

Figure 1C

Figure 2

Figure 3A

Figure 3B

[0008] Hereinafter, although one embodiment of the electrode active material, the electrode, and the battery of the present disclosure will be described, the electrode active material, the electrode, and the battery of the present disclosure are not limited to the embodiments described below.

[0009] 1. Electrode Active Material When observing the cross-section of the electrode active material according to one embodiment, the following relationships (1) and (2): 2.30 ≦ A2 / A1 ≦ 44.00 (1) 0.50 ≦ A3 / A1 ≦ 1.90 (2) A1: Area ratio of the O2-type structure in the cross-section A2: Area ratio of the O6-type structure in the cross-section A3: Area ratio of the T#2-type structure in the cross-section are satisfied.

[0010] 1.1 Crystal Structure The electrode active material according to one embodiment has, as a crystal structure, at least an O2-type structure, an O6-type structure, and a T#2-type structure. An example of the O2-type structure is shown in FIG. 1A, an example of the O6-type structure is shown in FIG. 1B, and an example of the T#2-type structure is shown in FIG. 1C. 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 according to one embodiment is characterized by containing these three crystal structures in a predetermined ratio.

[0011] For the electrode active material according to one embodiment, it is important that the above relations (1) and (2) are satisfied when observing its cross section. That is, in the cross section of the electrode active material according to one embodiment, together with the O2-type structure, a predetermined amount of the O6-type structure and a predetermined amount of the T#2-type structure exist. According to the new findings of the present inventor, the electrode active material containing these three crystal structures in the ratios of the above relations (1) and (2) has excellent rate characteristics. It is considered that a synergistic effect is exerted on the charge-discharge reaction by the interaction of these three crystal structures. Regarding the above relation (1), A2 / A1 is 2.30 or more and 44.00 or less, and may be 2.40 or more, 2.50 or more, 2.60 or more, or 2.70 or more, and may be 43.00 or less, 42.00 or less, 41.00 or less, or 40.00 or less. Regarding the above relation (2), A3 / A1 is 0.50 or more and 1.90 or less, and may 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 may be 1.85 or less or 1.80 or less.

[0012] In addition to the O2-type structure, the O6-type structure, and the T#2-type structure, the electrode active material according to one embodiment may have other crystal structures. However, the fewer the other crystal structures, the easier it is to exhibit a more excellent effect. For example, when observing the cross section of the electrode active material according to one embodiment, the total area ratio of the O2-type structure, the O6-type structure, and the T#2-type structure in the cross section may 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.

[0013] The "cross section" of the electrode active material can be exposed, for example, by cutting a layer containing the electrode active material. The "area fraction" of each crystalline phase in the cross section of the electrode active material can be determined by ACOM-STEM measurement. Specifically, using a JEOL JEM-2800 instrument, electron diffraction patterns are obtained at each measurement point on the cross section by precession electron diffraction. The indexing and crystal orientation are calculated to visualize the distribution of crystalline structures in the cross section and calculate the area fraction of each crystalline structure. The beam diameter in this measurement is approximately 1.5 nm. In this case, an O6-type structure with a large lattice constant may be calculated as an O3-type structure, which also belongs to the space group R-3m. On the other hand, the amounts of O3-type and O6-type structures contained in the electrode active material can be determined in advance by XRD or other methods. That is, even if the electrode active material contains an O3-type structure, the area fractions of the O3-type and O6-type structures can be determined by referring to the results of ACOM-STEM measurement and XRD.

[0014] 1.2 Chemical composition An electrode active material according to an embodiment may contain, for example, at least one of Ni, Mn, and Co as a constituent element. More specifically, an electrode active material according to an embodiment may contain, as constituent elements, at least one of Mn, Ni, and Co, Li, and O. In particular, when the electrode active material contains, as constituent elements, at least Li, Mn, one or both of Ni and Co, and O, higher performance is likely to be obtained when the electrode active material contains, as constituent elements, at least Li, Mn, Ni, Co, and O.

[0015] The electrode active material according to one embodiment is Li a Na b Mn x-p Ni y-q Co z-r M p+q+rO2 (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) may have a chemical composition represented thereby. When the electrode active material has such a chemical composition, the desired crystal structure is easily maintained. In the above chemical composition, a is greater than 0, and may be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, or 0.60 or more, and is at most 1.00, and may be 0.90 or less, 0.80 or less, or 0.70 or less. In the above chemical composition, b is 0 or more, and may be 0.01 or more, 0.02 or more, or 0.03 or more, and is at most 0.20, and may be 0.15 or less, or 0.10 or less. Also, x is 0 or more, and may be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.50 or more, and is at most 1.00, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, or 0.50 or less. Also, y is 0 or more, and may be 0.10 or more, or 0.20 or more, and is at most 1.00, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, or 0.20 or less. Also, z is 0 or more, and may be 0.10 or more, 0.20 or more, or 0.30 or more, and is at most 1.00, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.30 or less. The element M has a small contribution to charge and discharge. In this regard, in the above chemical composition, since p + q + r is less than 0.17, a high charge and discharge capacity is easily ensured. p + q + r may be 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, or 0.10 or less. On the other hand, when the element M is included, the desired crystal structure is easily stabilized. In the above chemical composition, p + q + r is 0 or more, and may be 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, or 0.10 or more.The composition of O is approximately 2, but it is not necessarily exactly 2.0 and is indeterminate.

[0016] 1.3 Others As will be described later, the electrode active material according to one embodiment can be obtained by substituting Na of a Na-containing oxide having a P2-type structure with Li. Here, the P2-type structure is hexagonal, has a large diffusion coefficient of Na ions, and is likely to grow crystallographically 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 likely to grow crystallographically 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 may be obtained based on such plate-like Na-containing oxide particles, or may be obtained based on spherical Na-containing oxide particles. That is, the shape of the electrode active material may be plate-like particles or spherical particles. When the electrode active material is spherical particles, the reaction resistance is reduced by reducing the crystallite size, and the diffusion resistance inside the particles is likely to be reduced. Furthermore, when applied to a battery, it is considered that the degree of bending is reduced by spheroidization, and the lithium ion conduction resistance is reduced. As a result, for example, the rate characteristics are further improved, and the reversible capacity is likely to increase. In the present application, the "spherical particles" means particles having a circularity of 0.80 or more. The circularity of the particles may be 0.81 or more, 0.82 or more, 0.83 or more, 0.84 or more, 0.85 or more, 0.86 or more, 0.87 or more, 0.88 or more, 0.89 or more, or 0.90 or more. The circularity of the particles is 4πS / L 2 which is defined as follows. Here, S is the projected area of the particle, and L is the perimeter of the projected image of the particle. The circularity of the particles can be determined by observing the appearance of the particles with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an optical microscope.

[0017] The electrode active material according to one embodiment may 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, but it is considered advantageous that the size is smaller. For example, the average particle diameter (D50) of the particles of the electrode active material may be 0.1 μm or more and 10 μm or less, 1.0 μm or more and 8.0 μm or less, or 2.0 μm or more and 6.0 μm or less. Note that the average particle diameter (D50) is the particle diameter (D50, median diameter) at the integrated value of 50% in the volume-based particle size distribution by the laser diffraction / scattering method.

[0018] 2. Method for manufacturing electrode active material The electrode active material 1 can be manufactured, for example, by the following method. That is, the method for manufacturing the electrode active material according to one embodiment is S1: Obtaining a Na-containing transition metal oxide having a P2-type structure, and S2: Substituting at least a part of Na in the Na-containing oxide 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 and may include.

[0019] 2.1 S1 In S1, the Na-containing transition metal oxide having a P2-type structure is, for example, S11: Obtaining a precursor (for example, a precursor containing at least one element among Mn, Ni, and Co), S12: Coating the surface of the precursor with a Na source to obtain a composite, and S13: Firing the composite and can be manufactured through. Here, the S13 is S13-1: Performing pre-firing on the composite at a temperature of 300°C or more and less than 700°C for 2 hours or more and 10 hours or less, S13-2: Subsequently to the pre-firing, performing main firing on the composite at a temperature of 700°C or more and 1100°C or less for 30 minutes or more and 48 hours or less, and S13-3: Subsequently to the main firing, the composite may be rapidly cooled from a temperature T1 of 200°C or higher to a temperature T2 of 100°C or lower.

[0020] 2.1.1 Preparation of the precursor The precursor may contain at least Mn and at least one or both of Ni and Co, or may contain at least Mn, Ni, and Co. The precursor may be a salt containing at least one element 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 multiple types of compounds. The precursor may have various shapes. For example, the precursor may be particulate, and may be spherical particles as described later. The particle diameter of the particles composed of the precursor is not particularly limited. By adjusting the particle diameter of the particles composed of the precursor and adjusting the manufacturing conditions of the composite and the firing conditions of the composite described later, the ratio of the crystal phases contained in the finally obtained electrode active material can be controlled.

[0021] In S11, a transition metal ion, an ion source capable of forming a precipitate in an aqueous solution, and a transition metal compound containing at least one element among Mn, Ni, and Co may be used to obtain a precipitate as the above-mentioned precursor by a coprecipitation method. Thereby, spherical particles as the precursor can be easily obtained. The "transition metal ion and an ion source capable of forming a precipitate in an aqueous solution" may be, for example, at least one selected from sodium salts such as sodium carbonate and sodium nitrate, sodium hydroxide, and sodium oxide. The transition metal compound may be the above-mentioned salts, hydroxides, etc. containing at least one element among Mn, Ni, and Co. Specifically, in S11, after preparing the ion source and the transition metal compound as solutions respectively, a precipitate as the precursor may be obtained by dropping and mixing each solution. At this time, for example, water is used as the solvent. At this time, various sodium compounds may be used as the base, and an aqueous ammonia solution or the like may be added for adjusting the basicity. 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 a precipitate as the precursor is obtained by dropping and mixing each aqueous solution. Alternatively, it is also possible to obtain the precursor by a sol-gel method. In particular, according to the coprecipitation method, spherical particles as the precursor can be easily obtained.

[0022] In S11, the precursor may contain element M. Element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W. These elements M have, for example, a function of stabilizing a P2-type structure or an O2-type structure. The method for obtaining a precursor containing element M is not particularly limited. When obtaining a precursor by the coprecipitation method in S11, for example, an aqueous solution of a transition metal compound containing at least one of Mn, Ni, and Co, an aqueous solution of sodium carbonate, and an aqueous solution of a compound of element M are prepared, and by dropping and mixing each aqueous solution, a precursor containing element M together with at least one element among Mn, Ni, and Co is obtained. Alternatively, in the manufacturing method of the present disclosure, element M may not be added in S11, and may be doped with element M when performing Na-doped firing in S2 and S3 described later.

[0023] 2.1.2 Preparation of Composite In S12, the surface of the precursor obtained in S11 is coated with a Na source to obtain a composite. The Na source may be a salt containing Na such as carbonate or nitrate, or a compound other than 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 lost during the subsequent firing. In S12, the coating rate of the Na source on the surface of the precursor is not particularly limited. In S12, the method of coating the surface of the above-mentioned precursor with a Na source is not particularly limited. For example, the precursor and the Na source may be mixed using a mortar or a mixing device, or a solution containing the Na source may be brought into contact with the precursor using a rolling fluid coating method, a spray drying method, etc., and then dried. In particular, by coating the surface of the precursor with a Na source by the spray drying method, the coating rate of the Na source on the surface of the precursor increases, and it becomes easier to more appropriately adjust the crystallinity and shape (plate-like particles or spherical particles) of the P2-type Na-containing oxide obtained by S13 described later, and the ratio of each crystal structure contained in the finally obtained electrode active material can be more appropriately controlled.

[0024] In S12, the precursor may be coated with an M source together with the Na source. For example, in S12, the precursor obtained in S11, a Na source, and an M source containing at least one element M selected from B, Mg, Al, K, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W may be mixed to obtain a composite. The M source may be, for example, a salt containing the element M such as carbonate or sulfate, or a compound other than a salt such as oxide or hydroxide. The amount of the M source with respect to the precursor may be determined according to the chemical composition of the Na-containing oxide after firing.

[0025] 2.1.3 Firing of Composite In S13, by firing the complex obtained in S12, a Na-containing oxide having a P2-type structure is obtained. S13 may include the above S13-1, S13-2, and S13-3. In addition to the manufacturing conditions of the precursor and the manufacturing conditions of the complex described above, 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 by S13 can be adjusted, and the ratio of each crystal structure contained in the finally obtained electrode active material can be controlled.

[0026] In S13-1, the complex is subjected to pre-firing at a temperature of 300°C or higher and lower than 700°C for 2 hours or longer and 10 hours or shorter. In S13-1, after arbitrarily shaping the above complex, pre-firing may be performed. The pre-firing is performed at a temperature lower than the main firing. 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, since the pre-firing temperature is 300°C or higher and lower than 700°C and the pre-firing time is 2 hours or longer and 10 hours or shorter, sufficient pre-firing can be performed on the complex, the thermal uniformity is enhanced, and the Na-containing oxide obtained through S13-2 and S13-3 described later is likely to be appropriate. The pre-firing temperature may be 400°C or higher and lower than 700°C, 450°C or higher and lower than 700°C, 500°C or higher and lower than 700°C, 550°C or higher and lower than 700°C, or 550°C or higher and 650°C or lower. Also, the pre-firing time may be 2 hours or longer and 8 hours or shorter, 3 hours or longer and 8 hours or shorter, 4 hours or longer and 8 hours or shorter, 5 hours or longer and 8 hours or shorter, or 5 hours or longer and 7 hours or shorter. The pre-firing atmosphere is not particularly limited, and for example, an oxygen-containing atmosphere may be used.

[0027] In S13-2, following the above pre-firing, the composite is subjected to main firing at a temperature of 700°C or higher and 1100°C or lower for 30 minutes or longer and 48 hours or shorter. In S13-2, the main firing temperature of the composite may be 800°C or higher and 1000°C or lower. If the main firing temperature is too low, the P2 phase will not be formed. If the main firing temperature is too high, phases other than the P2 phase, such as the O3 phase, are likely to be formed. The temperature rising conditions from the pre-firing temperature to the main firing temperature are not particularly limited. In S13-2, the shape of the Na-containing oxide can be controlled by the main firing time. If the main firing time is too short, the formation of the P2 phase will be insufficient. On the other hand, if the main firing time is too long, the P2 phase will grow excessively and the particles are likely to coarsen into a plate shape.

[0028] In S13-3, following the above main firing, the composite is rapidly cooled (cooled at a temperature drop rate of 20°C / min or more) from a temperature T1 of 200°C or higher to a temperature T2 of 100°C or lower. The above pre-firing and main firing are performed, for example, in a heating furnace. In step S13-3, for example, after the main firing of the composite in the heating furnace, it is cooled to an arbitrary temperature T1 of 200°C or higher in the heating furnace, and after reaching the 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 may be an arbitrary temperature of 250°C or higher. The temperature T2 is an arbitrary temperature of 100°C or lower, and may be an arbitrary temperature of 50°C or lower, or may be the cooling end temperature. In a predetermined temperature range from the temperature T1 to the temperature T2, moisture easily penetrates between the layers of the P2-type structure due to atomic vibration, molecular motion, etc. When cooling the composite (Na-containing oxide having a P2-type structure) after the main firing, by shortening the time in the temperature range where such moisture easily penetrates (that is, rapidly cooling), it is considered that the amount of moisture penetrating between the layers of the P2-type structure decreases. In this regard, in step S13-3, when cooling the composite after the main firing, from an arbitrary temperature T1 of 200°C or higher to an arbitrary temperature T2 of 100°C or lower, for example, by performing cooling in a dry atmosphere outside the furnace, the cooling rate from the temperature T1 to the temperature T2 becomes high (for example, 20°C / min or more), it becomes difficult for moisture to penetrate between the layers of the P2-type structure, and the collapse of the P2-type structure can be suppressed. As a result, in S2, Na can be efficiently ion-exchanged with Li.

[0029] By S13, a Na-containing oxide having a P2-type structure and a predetermined chemical composition can be produced. The Na-containing oxide contains, as constituent elements, at least one transition metal element among at least Mn, Ni, and Co, Na, and O. In particular, when the constituent elements include at least Na, Mn, at least one of Ni and Co, and O, among these, when the constituent elements include at least Na, Mn, Ni, Co, and O, the performance of the positive electrode active material is more likely to be higher. The Na-containing oxide is Na c Mnx-p Ni y-q Co z-r M p+q+r It may have a chemical composition represented by O2. Here, 0 < c < 1.00, x + y + z = 1, and 0 ≦ p + q + r < 0.17. Also, M is at least one element selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W. When the Na-containing oxide has such a chemical composition, the P2-type structure is more likely to be maintained. In the above chemical composition, c is greater than 0, and may be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, or 0.60 or more, and less than 1.00, and may be 0.90 or less, 0.80 or less, or 0.70 or less. x is 0 or more, and may be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.50 or more, and 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, or 0.50 or less. Also, y is 0 or more, and may be 0.10 or more or 0.20 or more, and 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, or 0.20 or less. Also, z is 0 or more, and may be 0.10 or more, 0.20 or more, or 0.30 or more, and 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.30 or less. The element M has a small contribution to charge and discharge. In this regard, in the above chemical composition, when p + q + r is less than 0.17, a high charge and discharge capacity is likely to be ensured. p + q + r may be 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, or 0.10 or less. On the other hand, when the element M is included, the P2-type structure and the O2-type structure are likely to be stabilized. In the above chemical composition, p + q + r is 0 or more, and may be 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, or 0.10 or more. The composition of O is approximately 2, but is not necessarily exactly 2.0 and is indefinite.

[0030] 2.2 S2 In S2, at least a part of Na in the Na-containing oxide obtained by 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. For the ion exchange, for example, there are a method using an aqueous solution containing lithium halide and a method using a mixture of lithium halide and other lithium salts (for example, a molten salt). From the viewpoints that the P2-type structure is liable to be broken by the intrusion of water and the 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-described P2-type structure with the molten salt and heating to a temperature equal to or higher than the melting point of the molten salt, at least a part of Na in the Na-containing oxide can be replaced with Li by ion exchange. The lithium halide constituting the molten salt is preferably at least one of lithium chloride, lithium bromide, and lithium iodide. The other lithium salt constituting the molten salt is preferably lithium nitrate. By using a molten salt, the melting point becomes lower than when using lithium halide or other lithium salts alone, and ion exchange at a lower temperature becomes possible. The temperature in the ion exchange may be, for example, equal to or higher than the melting point of the above-described 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, an O3-type structure, which is a stable phase rather than an O2-type structure, is likely to be formed. On the other hand, from the viewpoint of shortening the time required for ion exchange, the temperature in the ion exchange is preferably as high as possible.

[0031] 3. Electrode The electrode according to one embodiment contains the electrode active material of the present disclosure. Components other than the electrode active material contained in the electrode are not particularly limited and can be appropriately determined according to the intended performance. The electrode according to one embodiment may contain the electrode active material of the present disclosure and at least one of an electrolyte, a conductive assistant, and a binder. Optionally, the electrode according to one embodiment may contain other additives. The content of each of the active material, electrolyte, conductive assistant, binder, etc. in the electrode may be appropriately determined according to the intended battery performance. For example, when the electrode includes a current collector and an active material layer, assuming the total solid content contained in the active material layer is 100% by mass, the content of the electrode active material may be 40% by mass or more and less than 100% by mass.

[0032] 3.1 Active Material The active material contained in the electrode may consist only of the electrode active material of the present disclosure, or may contain, together with the electrode active material, other active materials (other active materials). From the viewpoint of further enhancing the effects of the technology of the present disclosure, the proportion of other active materials in the total active material contained in the electrode may be small. For example, assuming the total active material contained in the electrode is 100% by mass, the content of the electrode active material of the present disclosure may be 50% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, or 99% by mass or more and 100% by mass or less. Any of the known active materials can be adopted as the other active materials that can be contained in the electrode.

[0033] 3.2 Electrolyte The electrode may contain an electrolyte together with the above-mentioned electrode active material. The electrolyte that can be included in the electrode may be a solid electrolyte, a liquid electrolyte, or a combination thereof. As the solid electrolyte, those known as solid electrolytes for batteries may be used. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, inorganic solid electrolytes are excellent in ionic conductivity and heat resistance. Examples of inorganic solid electrolytes include oxide solid electrolytes, sulfide solid electrolytes, and ionic-bonded inorganic solid electrolytes. In particular, when the electrode contains a sulfide solid electrolyte as the solid electrolyte, higher performance is more easily ensured. The sulfide solid electrolyte may contain, for example, at least Li, S, and P as constituent elements. Alternatively, the electrode may contain an ionic-bonded solid electrolyte as the solid electrolyte, for example, a solid electrolyte containing at least Li, Y, and a halogen (at least one of Cl, Br, I, and F) as constituent elements. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may be 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. Only one type of solid electrolyte may be used alone, or two or more types 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 those known as the composition of the electrolyte solution of a lithium-ion battery. The electrolyte solution may be obtained by dissolving a lithium salt in water or a non-aqueous solvent. Examples of non-aqueous solvents include various carbonate solvents. Examples of lithium salts include lithium amide salts and LiPF6, etc.

[0034] 3.3 Conductive Aid Examples of the 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 nanotube (CNT), and carbon nanofiber (CNF); and metal materials such as nickel, titanium, aluminum, and stainless steel. The conductive aid may be, for example, particulate or fibrous, and its size is not particularly limited. Only one type of conductive aid may be used alone, or two or more types may be used in combination.

[0035] 3.4 Binder Examples of the binders that can be included in the electrode include butadiene rubber (BR)-based binders, isobutylene 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, and the like. Only one type of binder may be used alone, or two or more types may be used in combination.

[0036] 3.5 Others In addition to the above components, the electrode may contain various additives, such as dispersants and lubricants.

[0037] 4. Battery The electrode active material of the present disclosure can be employed, for example, as the positive electrode active material of a battery. As shown in FIG. 2, a battery 100 according to 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.

[0038] 4.1 Positive Electrode Active Material Layer The positive electrode active material layer 10 contains at least the electrode active material of the present disclosure, and may further optionally contain an electrolyte, a conductive aid, a binder, and the like. The shape of the positive electrode active material layer 10 is not particularly limited, and for example, a sheet-like positive electrode active material layer 10 having a substantially flat surface may be used. The thickness of the positive electrode active material layer 10 is not particularly limited, and 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.

[0039] 4.2 Electrolyte layer The electrolyte layer 20 is disposed between the positive electrode active material layer 10 and the negative electrode active material layer 30. The electrolyte layer 20 contains at least an electrolyte. The electrolyte layer 20 may contain at least one of a solid electrolyte and a liquid electrolyte, and may further optionally contain a binder and the like. The contents of the electrolyte and the binder and the like in the electrolyte layer 20 are not particularly limited. Alternatively, the electrolyte layer 20 may have a separator or the like for holding the liquid electrolyte and preventing contact between the positive electrode active material layer 10 and the negative electrode active material layer 30. The thickness of the electrolyte layer 20 is not particularly limited, and 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.

[0040] As the electrolyte contained in the electrolyte layer 20, it may be appropriately selected from those exemplified as the electrolytes that can be contained in the above-described positive electrode active material layer 10 (electrode mixture) (solid electrolyte and / or liquid electrolyte). Also, regarding the binder that can be contained in the electrolyte layer 20, it may be appropriately selected from those exemplified as the binders that can be contained in the above-described positive electrode active material layer. Each of the electrolyte and the binder may be used alone as one kind, or two or more kinds may be used in combination. The separator may be a separator commonly used in batteries, and examples thereof include those made of resins such as polyethylene (PE), polypropylene (PP), polyester, and polyamide. The separator may have a single-layer structure or a multi-layer structure. Examples of the multi-layer structure separator include a separator having a two-layer structure of PE / PP, or a separator having a three-layer structure of PP / PE / PP or PE / PP / PE. The separator may 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.

[0041] 4.3 Negative Electrode Active Material Layer The negative electrode active material layer 30 contains at least a negative electrode active material. Further, the negative electrode active material layer 30 may optionally contain an electrolyte, a conductive assistant, a binder, various additives, and the like. The content of each component in the negative electrode active material layer 30 may be appropriately determined according to the intended battery performance. For example, assuming the 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, 60% by mass or more, or 70% by mass or more, and may also be 100% by mass or less, less than 100% by mass, 95% by mass or less, or 90% by mass or less. Alternatively, assuming the entire negative electrode active material layer 30 is 100% by volume, the negative electrode active material and optionally the electrolyte, the conductive assistant, and the binder may be contained in a total amount of 85% by volume or more, 90% by volume or more, or 95% by volume or more, and the balance may be voids or other components. The shape of the negative electrode active material layer 30 is not particularly limited, and for example, it may be in the form of a sheet having a substantially flat surface. The thickness of the negative electrode active material layer 30 is not particularly limited, and for example, it may be 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or more, and may also be 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less.

[0042] The negative electrode active material can adopt any of those known as the negative electrode active material of a battery. Among the known active materials, various substances with a potential (charge-discharge potential) for occluding and releasing carrier ions that is lower than that of the above-described positive electrode active material can be adopted. For example, silicon-based active materials such as Si, Si alloys, and silicon oxide; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium, lithium alloys, etc. can be adopted. 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 enhanced. The negative electrode active material may be used alone as only one type, or two or more types may be combined and used. The shape of the negative electrode active material may be a general shape as the negative electrode active material of a battery. For example, the negative electrode active material may be in the form of particles. The negative electrode active material particles may be primary particles or secondary particles in which a plurality of primary particles are aggregated. The average particle diameter (D50) of the negative electrode active material particles may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and may also be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. Alternatively, the negative electrode active material may be in the form of a sheet (foil-like, film-like) such as a lithium foil. That is, the negative electrode active material layer 30 may be composed of a sheet of the negative electrode active material.

[0043] Examples of the electrolyte that can be included in the negative electrode active material layer 30 include the above-described solid electrolyte, liquid electrolyte, or a combination thereof. The conductive assistant that can be included in the negative electrode active material layer 30 may be appropriately selected, for example, from among those exemplified as the conductive assistants that can be included in the above-described positive electrode active material layer 10 (electrode mixture 5). The binder that can be included in the negative electrode active material layer 30 may be appropriately selected, for example, from among those exemplified as the binders that can be included in the above-described positive electrode active material layer 10 (electrode mixture 5). The electrolyte, conductive assistant, and binder may each be used alone as only one type, or two or more types may be combined and used.

[0044] 4.4 Positive Electrode Current Collector As shown in FIG. 2, the battery 100 may include a positive current collector 40 that contacts the positive electrode active material layer 10. Any of the commonly used materials for the positive current collector of a battery can be adopted as the positive current collector 40. Further, the positive current collector 40 may have at least one shape selected from a foil shape, a plate shape, a mesh shape, a punching metal shape, a foam, and the like. The positive current collector 40 may be composed of a metal foil or a metal mesh. In particular, the metal foil is excellent in handleability and the like. The positive current collector 40 may be composed of a plurality of foils. Examples of the metal constituting the positive current collector 40 include at least one selected from Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, V, Mg, Pb, Ge, In, Sn, Zr, and stainless steel. In particular, from the viewpoint of ensuring oxidation resistance and the like, the positive current collector 40 may contain Al. The positive current collector 40 may have some coating layer on its surface for the purpose of adjusting resistance or the like. For example, the positive current collector 40 may have a carbon coating layer. Further, the positive current collector 40 may be a metal foil or a substrate on which the above metal is plated or vapor-deposited. Also, when the positive current collector 40 is composed of a plurality of metal foils, there may be some layer between the plurality of metal foils. The thickness of the positive current collector 40 is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or more, and may be 1 mm or less or 100 μm or less.

[0045] 4.5 Negative current collector As shown in FIG. 2, the battery 100 may include a negative electrode current collector 50 that contacts the negative electrode active material layer 30. Any of the commonly used materials for the negative electrode current collector of the battery can be adopted as the negative electrode current collector 50. Further, the negative electrode current collector 50 may be in the form of a foil, a plate, a mesh, a punching metal, a foam, or the like. The negative electrode current collector 50 may be a metal foil or a metal mesh, or may be a carbon sheet. In particular, the metal foil is excellent in handleability and the like. The negative electrode current collector 50 may be composed of a plurality of 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. In particular, from the viewpoints of ensuring reduction resistance and being difficult to alloy with lithium, the negative electrode current collector 50 may contain at least one metal selected from Cu, Ni, and stainless steel. The negative electrode current collector 50 may have some coating layer on its surface for the purpose of adjusting resistance or the like. For example, the negative electrode current collector 50 may have a carbon coating layer. The negative electrode current collector 50 may be an aluminum foil having a carbon coating layer. Further, the negative electrode current collector 50 may be a metal foil or a substrate on which the above metal is plated or vapor-deposited. Also, when the negative electrode current collector 50 is composed of a plurality of metal foils, there may be some layer between the plurality of metal foils. The thickness of the negative electrode current collector 50 is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or more, and may be 1 mm or less or 100 μm or less.

[0046] 4.6 Other Configurations In addition to the above configuration, the battery 100 may have a general configuration as a battery. For example, tabs, terminals, etc. The battery 100 may be such that each of the above configurations is housed inside the exterior body. Any of the exterior bodies known as battery exterior bodies can be adopted. Also, a plurality of batteries 100 may be arbitrarily electrically connected and arbitrarily stacked to form a battery pack. In this case, the battery pack may be housed inside a known battery case. Examples of the shape of the battery 100 include coin type, laminate type, cylindrical type, and square type. The battery 100 may be a secondary battery.

[0047] The battery 100 can be manufactured by applying known methods, except for using the above specific electrode active material. For example, it can be manufactured as follows. However, the manufacturing method of the battery 100 is not limited to the following method. For example, each layer may be formed by dry forming or the like. (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 or 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 to obtain a positive electrode. (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 or 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 to obtain a negative electrode. (3)Stack the layers so that the electrolyte layer (solid electrolyte layer or separator) is sandwiched between the negative electrode and the positive electrode to obtain a laminate having 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. Attach other members such as terminals to the laminate as necessary. (4) Place the laminate in a battery case. In the case of an electrolyte battery, fill the battery case with the electrolyte and immerse the laminate in the electrolyte, then seal the laminate in the battery case to obtain a secondary battery. In the case of an electrolyte battery, the negative electrode active material layer, separator, and positive electrode active material layer may contain the electrolyte at the stage of (3) above.

[0048] 5. Vehicle 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 an aspect as a vehicle having a battery, wherein the battery has a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, and the positive electrode active material layer contains the electrode active material of the present disclosure.

Examples

[0049] As described above, one embodiment of the electrode active material and the like has been described. However, the technology of the present disclosure can be variously modified other than the above embodiments without departing from the gist thereof. Hereinafter, the technology of the present disclosure will be described in more detail while showing examples, but the technology of the present disclosure is not limited to the following examples.

[0050] 1. Preparation of Electrode Active Material 1.1 Example 1 1.1.1 Preparation of Precursor (1) Weigh MnSO4·5H2O, NiSO4·6H2O, and CoSO4·7H2O so as to have the target composition ratio (Mn:Ni:Co = 5:2:3), and dissolve them in distilled water to a concentration of 1.2 mol / L to obtain a first solution. Also, dissolve Na2CO3 in distilled water in another container to a concentration of 1.2 mol / L to obtain a second solution. (2) Put 1000 mL of pure water into a reaction vessel (with a baffle), and drop 500 mL of the first solution and 500 mL of the second solution into it at a rate of about 4 mL / min each. (3) After the dropping was completed, the mixture was stirred at a stirring speed of 150 rpm at room temperature for 1 hour to obtain a product. (4) The product was washed with pure water and subjected to solid-liquid separation using a centrifuge to recover the precipitate. (5) The obtained precipitate was dried at 120 °C overnight, pulverized in a mortar, and then separated into coarse particles and fine particles by air classification. The fine particles were removed to obtain coarse particles as precursor particles.

[0051] 1.1.2 Preparation of the composite (1) Na2CO3 and distilled water were weighed to obtain a concentration of 1150 g / L, and then stirred using a stirrer until completely dissolved to prepare an aqueous Na2CO3 solution. (2) The above aqueous Na2CO3 solution and the above precursor particles were weighed and mixed so that the composition after firing described below was Na 0.8 Mn 0.5 Ni 0.2 Co 0.3 O2, and a slurry was obtained. (3) The above slurry was dried by spray drying to obtain a composite. Specifically, using a spray drying apparatus DL410, the above slurry was dried by air flow under the conditions of a slurry feeding rate of 30 mL / min, an inlet temperature of 200 °C, a circulating air volume of 0.8 m 3 / min, and a spray pressure of 0.3 MPa, so that the surface of the precursor particles was coated with Na2CO3 to obtain a composite.

[0052] 1.1.3 Firing of the composite The composite was placed in an alumina crucible and fired in an air atmosphere to obtain a Na-containing oxide having a P2-type structure. The firing conditions are as follows (1) to (7). (1) An alumina crucible containing the above composite was placed in a heating furnace in an air atmosphere. (2) The temperature inside the heating furnace was raised from room temperature (25 °C) to 600 °C in 115 minutes. (3) The inside of the heating furnace was held at 600 °C for 360 minutes for pre-firing. (4) After pre-firing, the temperature inside the heating furnace was raised to 900 °C and then held at 900 °C for 60 minutes for main firing. (5) After this firing, the temperature inside the heating furnace was decreased from the firing temperature to 250 °C, and then the alumina crucible was taken out of the heating furnace at 250 °C and allowed to cool in a dry atmosphere outside the furnace until it reached 25 °C in 10 minutes.

[0053] The fired product after cooling was pulverized using a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2-type structure (P2-type particles).

[0054] 1.1.4 Ion Exchange (1) LiNO3 and LiCl were weighed so as to have a molar ratio of 50:50, and mixed with the above P2-type particles at a molar ratio that is 10 times the minimum amount of Li required for ion exchange to obtain a mixture. (2) Using an alumina crucible, ion exchange was carried out at 280 °C for 1 h in an air atmosphere to obtain a product containing a Li-containing oxide. (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. (4) The obtained precipitate was dried at 120 °C overnight to obtain the electrode active material particles according to Example 1. The electrode active material particles were Li 0.63 Mn 0.5 Ni 0.2 Co 0.3 a Li-containing oxide represented by O2. Also, when the crystal phase contained in the electrode active material particles was confirmed by XRD, the electrode active material particles did not have an O3-type structure and had at least an O2-type structure.

[0055] 1.2 Example 2 An electrode active material was prepared 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 were Li 0.62 Mn 0.5 Ni 0.2 Co 0.3 a Li-containing oxide represented by O2. Also, when the crystal phase contained in the electrode active material particles was confirmed by XRD, the electrode active material particles did not have an O3-type structure and had at least an O2-type structure.

[0056] 1.3 Comparative Example 1 Fine particles were employed as the precursor particles 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 the composite, firing and ion exchange were carried out in the same manner as in Example 1 to prepare an electrode active material. The electrode active material particles were a Li-containing oxide represented by Li 0.64 Mn 0.5 Ni 0.2 Co 0.3 O2. Also, when the crystal phase contained in the electrode active material particles was confirmed by XRD, the electrode active material particles did not have an O3-type structure and had at least an O2-type structure.

[0057] 1.4 Comparative Example 2 An electrode active material was prepared 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 were a Li-containing oxide represented by Li 0.63 Mn 0.5 Ni 0.2 Co 0.3 O2. Also, when the crystal phase contained in the electrode active material particles was confirmed by XRD, the electrode active material particles did not have an O3-type structure and had at least an O2-type structure.

[0058] 1.5 Comparative Example 3 An electrode active material was prepared 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 were a Li-containing oxide represented by Li 0.62 Mn 0.5 Ni 0.2 Co 0.3 O2. Also, when the crystal phase contained in the electrode active material particles was confirmed by XRD, the electrode active material particles did not have an O3-type structure and had at least an O2-type structure.

[0059] 2. ACOM-STEM Measurement ACOM-STEM measurements were performed on the cross-sections of each electrode active material, and the area ratios of the O2-type structure, O6-type structure, and T#2-type structure in each cross-section were calculated. For the identification of the crystal phase, the electron diffraction images of each measurement point were compared with the known crystal structure information. In this measurement, since a beam diameter of about 1.5 nm was adopted, for the O6-type structure with a lattice constant exceeding 20 nm, it may be calculated as the O3-type structure. On the other hand, as described above, from the results of XRD, the content rate of the O3-type structure in each electrode active material is 0%. Therefore, in the ACOM-STEM measurement, the parts determined to have the O3 structure were regarded as the parts having the O6-type structure, and the area ratios were calculated.

[0060] 3. Fabrication of Coin Cells Coin cells (CR2032) were fabricated using each electrode active material. The fabrication procedure of the coin cells is as follows. (1) The above electrode active material, acetylene black (AB) as a conductive assistant, and polyvinylidene fluoride (PVdF) as a binder were weighed in a mass ratio of electrode active material:AB:PVdF = 85:10:5, dispersed and mixed in N-methyl-2-pyrrolidone to obtain a positive electrode composite slurry. The positive electrode composite slurry was coated on an aluminum foil and vacuum dried at 120 °C overnight to obtain a positive electrode, which is a laminate of a positive electrode active material layer and a positive electrode current collector. (2) LiPF6 was dissolved in a mixed solvent obtained by mixing trifluoropropylene carbonate (TFPC) and trifluoroethyl methyl carbonate (TFEMC) at a ratio of TFPC:TFEMC = 30 vol%:70 vol% at a concentration of 1 M to obtain an electrolytic solution. (3) A metallic lithium foil was prepared as the negative electrode. (4) Using the positive electrode, the electrolytic solution, and the negative electrode, a coin cell (CR2032) was fabricated.

[0061] 4. Evaluation of Charge-Discharge Characteristics of Coin Cells For each coin cell, it was charged and discharged at a voltage range of 2.0 to 4.8 V and a 0.1C rate (1C = 220 mA / g) in a thermostatic bath maintained at 25°C, and the discharge capacity at 0.1C was measured. Subsequently, after charging at a 0.1C rate, it was discharged at 3C to measure the discharge capacity at 3C. By obtaining the ratio of the discharge capacity at 3C to the discharge capacity at 0.1C, the rate characteristics of the coin cell were evaluated.

[0062] 5. Evaluation Results In Table 1 below, for each electrode active material, "A1: Area ratio of the O2-type structure in the cross-section of the electrode active material", "A2: Area ratio of the O6-type structure in the cross-section", "A3: Area ratio of the T#2-type structure in the cross-section", "A2 / A1" and "A3 / A1" are shown. Also, for each coin cell, "0.1C discharge capacity", "3C discharge capacity" and "Rate characteristics (3C discharge capacity / 0.1C discharge capacity)" are shown.

[0063] [Table 1]

[0064] Fig. 3A shows the ACOM-STEM measurement results for the cross-section of the electrode active material according to Example 1. Fig. 3B shows the ACOM-STEM measurement results for the cross-section of the electrode active material according to Comparative Example 1.

[0065] From the results shown in Table 1, Fig. 3A and 3B, it can be seen that the batteries using the electrode active materials according to Examples 1 and 2, where A2 / A1 is within a predetermined range and A3 / A1 is within a predetermined range, are superior in rate characteristics compared to the batteries using the electrode active materials according to Comparative Examples 1 to 3, where A2 / A1 is outside the predetermined range and A3 / A1 is outside the predetermined range.

[0066] 6. Summary From 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.

[0067] 2.30 ≦ A2 / A1 ≦ 44.00 (1) 0.50 ≦ A3 / A1 ≦ 1.90 (2) A1: Area ratio of the O2 type structure in the cross-section of the electrode active material A2: Area ratio of the O6 type structure in the cross-section of the electrode active material A3: Area ratio of the T#2 type structure in the cross-section of the electrode active material

Explanation of symbols

[0068] 100 Battery 10 Positive electrode active material layer 20 Electrolyte layer 30 Negative electrode active material layer 40 Positive electrode current collector 50 Negative electrode current collector

Claims

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

2. The electrode active material according to Claim 1, including at least one of Ni, Mn, and Co as constituent elements, electrode active material.

3. The electrode active material according to Claim 2, Li ａ Na ｂ Mn ｘ－ｐ Ni ｙ－ｑ Co ｚ－ｒ M ｐ＋ｑ＋ｒ O ２ (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) having a chemical composition represented by electrode active material.

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

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 includes the electrode active material according to any one of Claims 1 to 3, battery.

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