ACTIVE MATERIAL FOR ELECTRODES, BATTERY AND METHOD FOR PRODUCEING ACTIVE MATERIAL FOR ELECTRODES

Abstract

The present application discloses an active electrode material, a battery, and a manufacturing process for an active electrode material. The active electrode material of the invention is characterized in that, in an X-ray diffraction pattern thereof, the half-width of a diffraction peak among the diffraction peaks attributable to an O2-type structure exhibiting a peak at 2θ = 64.8° to 65.4° is less than 0.79°.

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The present application discloses an active electrode material, a battery and a manufacturing process for an active electrode material. 2. Description of the state of the art

[0002] An active electrode material with an O2-type structure (O: octahedral) is known. As disclosed in Japanese patent application no. 2010-092824 (JP 2010-092824 A), an active electrode material with an O2-type structure is obtained by replacing at least some of the Na ions of a Na-containing transition metal oxide with a P2-type structure with Li ions. SUMMARY OF THE INVENTION

[0003] Conventional active electrode materials with an O2-type structure can be improved with regard to achieving both high capacitance and low resistance.

[0004] The present application discloses the following aspects as a means of solving the above-mentioned challenge: Aspect 1

[0005] Active material of the electrode with an O2-type structure, wherein in an X-ray diffraction pattern of the active material of the electrode a half-width of a diffraction peak among the diffraction peaks attributable to the O2-type structure, which has a peak maximum at 2θ = 64.8° to 65.4°, is less than 0.79°. Aspect 2

[0006] Active material of the electrode according to aspect 1, where the half-width can be 0.66° or less. Aspect 3

[0007] Active material of the electrode according to aspect 1 or 2, wherein the active material of the electrode may have a chemical composition that is defined by Li a N / a b Mn x-p Ni y-q Co z-r M p+q+rO2 is represented (where 0.70 < a ≤ 1.40, 0 ≤ b ≤ 0.20, x + y + z = 1, 0 ≤ p + q + r < 0.17 and 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). Aspect 4

[0008] A battery can have the active material of the electrode according to one of aspects 1 to 3. Aspect 5

[0009] Method for producing an active material of an electrode, comprising: Obtaining a sodium-containing transition metal oxide with a P2-type structure; Replacing at least part of the Na in the Na-containing transition metal oxide with Li by ion exchange to obtain a Li-containing transition metal oxide with an O2-type structure; and Bringing a reducing solution containing Li ions into contact with the Li-containing transition metal oxide in order to dope the Li-containing transition metal oxide with Li, wherein a duration during which the reducing solution is held in contact with the Li-containing transition metal oxide is 10 minutes or longer and 120 minutes or shorter; and a temperature at which the reducing solution is held in contact with the Li-containing transition metal oxide is 10°C or higher and 50°C or lower.

[0010] The active material of the electrode of the present invention has an O2-type structure and can achieve both high capacitance and low resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Features, advantages and technical and industrial significance of embodiments of the invention are described below with reference to the accompanying drawings, in which the same reference numerals denote the same elements, wherein Fig.1 shows an example of the process flow of a manufacturing procedure for an active material of the electrode; Fig. Figure 2 schematically shows an example of how to configure a battery; Fig. Three X-ray diffraction patterns of active materials of the electrode from Example 1, Comparative Example 1 and Comparative Example 3 are shown; and Fig. Figure 4 shows a relationship between the half-width of an X-ray diffraction peak and a normalized resistance value. DETAILED DESCRIPTION OF DESIGN FORMS 1. Active material of the electrode

[0012] An active material of the electrode according to one embodiment has an O2-type structure. In an X-ray diffraction pattern of the active material of the electrode, the half-width of a diffraction peak among the diffraction peaks attributable to the O2-type structure, which has a peak maximum at 2θ = 64.8° to 65.4°, is less than 0.79°. 1.1 Crystal structure

[0013] The active material of the electrode has an O2-type structure (belonging to the space group P63mc). In addition to the O2-type structure, the active material of the electrode may have other crystal structures. For example, the active material of the electrode may have a T#2-type structure (belonging to the space group Cmca) and / or an O6-type structure (belonging to the space group R-3m and having a c-axis length of 2.5 nm or longer and 3.5 nm or shorter, typically 2.9 nm or longer and 3.0 nm or shorter), which differs from an O3-type structure, also belonging to the space group R-3m). The active material of the electrode may have the O2-type structure as the main phase or a crystal structure other than the O2-type as the main phase. In particular, it is preferable to have the O2-type structure as the main phase.

[0014] When an X-ray diffraction pattern of the active material of the electrode is acquired according to the embodiment, this X-ray diffraction pattern includes diffraction peaks that can be attributed to the O2-type structure described above. A feature of the embodiment is that the half-width of a diffraction peak among the diffraction peaks that can be attributed to the O2-type structure, which exhibit a peak maximum at 2θ = 64.8° to 65.4°, is less than 0.79°.

[0015] The presence of a diffraction peak in the X-ray diffraction pattern of the electrode's active material, which can be attributed to the O2-type structure and exhibits a peak maximum or peak tip at 2θ = 64.8° to 65.4°, indicates that the lithium deficiency in this electrode's active material is low and that a large amount of lithium is present in its crystal structure. This will be described in more detail below. First, among the diffraction peaks attributable to the O2-type structure, the one with a peak maximum at 2θ = 64.8° to 65.4° is considered, for example, to correspond to the (110) plane of the O2-type structure. Here, the X-ray diffraction peak, which can be assigned to the (110) plane of the O2-type structure, shifts proportionally to the amount of Li in the active material of the electrode.In particular, the X-ray diffraction peak associated with the (110) plane of the O2-type structure exhibits a peak maximum near 2θ = 65° when the molar ratio of Li contained in the active material of the electrode (“a” in a chemical composition to be described later) is 1.0.

[0016] As will be described later, in a conventional method, the molar ratio of Li contained in an active electrode material with an O2-type structure (“a” in the chemical composition to be described later) is no more than 0.7 or less, and thus the capacitance potential of the active electrode material cannot be fully utilized. In contrast, in the embodiment, since the X-ray diffraction pattern of the active electrode material exhibits a diffraction peak attributable to the O2-type structure and a peak maximum at 2θ = 64.8° to 65.4°, it can be said that a large amount of Li has been incorporated into the active electrode material and that the molar ratio of Li contained in the active electrode material (“a” in the chemical composition to be described later) has been increased to above 0.7 (e.g., close to 1.0).Therefore, it is likely that the capacity of the active material of the electrode increases with the O2-type structure.

[0017] If, however, the intercalation state of Li in the O2-type structure becomes uneven or inconsistent, excessive Li intercalation is likely, so that, for example, Li is intercalated at a location that is not between layers of the O2-type structure, which probably leads to a higher resistance. If the intercalation state of Li in the O2-type structure becomes uneven, the aforementioned diffraction peak with a peak maximum at 2θ = 64.8° to 65.4° broadens, and its half-width increases. In contrast, in the embodiment, the half-width of the diffraction peak among the diffraction peaks attributable to the O2-type structure, which have a peak maximum at 2θ = 64.8° to 65.4°, is as small as less than 0.79°. Thus, in the active material of the electrode according to the embodiment, the uniformity or...The uniformity of the intercalation state of Li in the O2-type structure is high, and Li is less likely to be intercalated at a position not located between layers of the O2-type structure, so the active material of the electrode is likely to have low resistance. In particular, if the half-width is 0.66° or less, the resistance can be reduced even more significantly. The lower limit of the half-width is not particularly restricted. The half-width can be, for example, 0.58° or more, 0.60° or more, or 0.62° or more.

[0018] In the present application, “X-ray diffraction pattern” and “half-width of diffraction peak” refer to those obtained under the following conditions: Using an X-ray diffractometer (Rigaku Corporation, a fully automatic multi-purpose X-ray diffractometer “SmartLab”) with CuKα as the radiation source, the X-ray diffraction pattern is acquired by performing a 2θ / θ scan of the active material of the electrode at a tube voltage of 45 kV, a tube current of 200 mA, a step size of 0.02° and a scanning rate of 1° / min. In this X-ray diffraction pattern, a diffraction peak is determined which is due to the O2-type structure and has a peak maximum at 2θ = 64.8° to 65.4°, and after subtracting the value of a background near this diffraction peak, the half-width of this diffraction peak is determined.

[0019] In the active material of the electrode according to one embodiment, the crystallite size of the O2-type structure described above is not particularly limited. In the active material of the electrode according to one embodiment, a single crystallite can form a particle, or a plurality of crystallites can form a particle. In other words, the active material of the electrode according to one embodiment can be (1) a single crystal particle that exists independently; (2) an aggregate (secondary particle) of a plurality of single crystal particles; (3) a polycrystalline particle comprising a plurality of crystallites; or (4) an aggregate (secondary particle) of a plurality of polycrystalline particles. In particular, if the active material of the electrode is a polycrystalline particle, especially if it is a spherical particle to be described later, the size of the crystallites can be determined in more detail.Given the use of a spherical polycrystalline particle, it is likely that even higher performance of the electrode's active material will be ensured. As described later, the electrode's active material can be obtained according to one embodiment by ionizing at least a portion of the Na in a Li-containing oxide with a P2-type structure with Li. Here, the P2-type structure is a hexagonal system in which the diffusion coefficient of Na ions is high and crystals are likely to grow in a specific direction. Therefore, crystallites with the P2-type structure are typically those whose crystal growth direction is disproportionately strongly oriented in one particular direction (e.g., plate-like crystallites).If crystallites with an O2-type structure are obtained by replacing Na ions in P2-type crystallites, whose crystal growth direction is thus disproportionately oriented in one direction, with Li ions, the end portions or end sections of the O2-type crystallites (end portions in the aforementioned crystal growth direction) likely form inlet and outlet openings for intercalation. In other words, if the active material of the electrode is a polycrystalline particle, effects can be expected such as a decrease in reaction resistance as the number of inlet and outlet openings for intercalation within a particle increases, a decrease in diffusion resistance as the path length of the lithium ions becomes shorter, and a decrease in the overall expansion and contraction properties of the particles during charging and discharging.

[0020] As described above, the crystallites of the sodium-containing oxide with a P2-type structure likely adopt a plate-like shape. That is, the sodium-containing oxide with a P2-type structure can become a plate-like particle, but also a spherical particle if small plate-like crystallites are linked together. In other words, a particle of the electrode's active material can be either a plate-like single-crystal particle or a spherical polycrystalline particle. A spherical polycrystalline particle exhibits multiple crystallites on its surface. If the electrode's active material is a spherical polycrystalline particle, the bending angle is reduced due to its spherical shape, which appears to decrease the lithium-ion conduction resistance. Thus, for example, the battery is likely to exhibit improved charging characteristics and a higher reversible capacity.In the present application, "spherical particle" means a particle whose degree of roundness is 0.80 or higher. The degree of roundness of the particle may be 0.81 or higher, 0.82 or higher, 0.83 or higher, 0.84 or higher, 0.85 or higher, 0.86 or higher, 0.87 or higher, 0.88 or higher, 0.89 or higher, or 0.90 or higher. The degree of roundness of the particle is expressed as 4πS / L. 2 The roundness of the particle is defined as follows: Here, S is an orthogonal projection surface of the particle and L is the perimeter of an orthogonal projection image of the particle. The roundness of the particle can be obtained by observing its appearance under a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an optical microscope. 1.2 Chemical composition

[0021] The chemical composition of the electrode's active material is not particularly restricted, as long as the O2-type structure described above can be maintained and the half-width requirements described above are met. The electrode's active material can contain at least one element selected from Mn, Ni, Co, Li, and O. In particular, even higher performance is likely to be achieved if the components include Mn, at least one of Ni, Co, Li, and O, and especially if they include Li, Mn, Ni, Co, and O. However, if Li is almost completely released during charging, for example, the molar concentration of Li in the electrode's active material can approach zero. The electrode's active material can also contain Na as a component due to a manufacturing step described later.The active material of the electrode can contain a predetermined element M. The active material of the electrode can also contain other impurities. For example, the active material of the electrode can contain impurities resulting from the manufacturing step described later. In particular, the active material of the electrode can contain components (an aromatic compound, ether, etc.) resulting from a reducing solution.

[0022] The active material of the electrode according to one embodiment can have a chemical composition characterized by Li a N / a b Mn x-p Ni y - q Co z - r M p+q+rO2 is represented (where 0.70 < a ≤ 1.40, 0 ≤ b ≤ 0.20, x + y + z = 1, 0 ≤ p + q + r < 0.17 and M is at least one element selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W). In this chemical composition, a is greater than 0.70 and can be 0.75 or more, 0.80 or more, 0.85 or more, 0.90 or more, or 0.95 or more, and can be 1.40 or less, and can be 1.35 or less, 1.30 or less, 1.25 or less, 1.20 or less, 1.15 or less, 1.10 or less, 1.05 or less, or 1.00 or less. The compositional fraction of b is 0 or more and can exceed 0, and is 0.20 or less, and can be 0.15 or less, 0.10 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less.The compositional proportion of x is 0 or more and 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. The compositional proportion of y is 0 or more and 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. The compositional fraction of z is 0 or more and 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. Element M contributes little to charging and discharging.In this respect, a high charge-discharge capacity is likely if p + q + r in the chemical composition described above is less than 0.17. The composition fraction of p + q + r can be 0.15 or less, 0.13 or less, 0.11 or less, 0.09 or less, 0.07 or less, 0.06 or less, 0.05 or less, or 0.04 or less. On the other hand, the structure is likely to stabilize into an O₂-type structure if the element M is present. In this respect, in the chemical composition described above, p + q + r is 0 or more and can exceed 0, or be 0.01 or more, 0.02 or more, or 0.03 or more. While the composition fraction of O is close to 2, it is not limited to exactly 2.0 and is variable. In the chemical composition described above, if the valence of the element is M +n, a relationship 3.0 ≤ 4 (x - p) + 2 (y - q) + 3 (z - r) + n (p + q + r) ≤ 3.5 can be satisfied.This is conceived as the region in which the total valence of the metal in a Li-containing transition metal oxide is close to 3.33 valences (charge-neutral when 'a' is 0.67). During its synthesis, a Li-containing transition metal oxide with an O2-type structure passes through a state of a Na-containing transition metal oxide with a P2-type structure. A case in which the above relationship is satisfied corresponds to a case in which charge neutrality is achieved in a region where the compositional fraction of Na in this state is 0.5 or more and 1.0 or less. 1.3 Other

[0023] The active material of the electrode according to one embodiment can, for example, be solid particles, hollow particles, or particles with cavities. The size of the particles of the active material of the electrode is not particularly restricted; however, a smaller size is considered advantageous. For example, a mean particle diameter (D50) of the particles of the active material of the electrode can be 0.1 µm or larger and 10 µm or smaller, 1.0 µm or larger and 8.0 µm or smaller, or 2.0 µm or larger and 6.0 µm or smaller. The mean particle diameter (D50) is a particle diameter (D50, a mean diameter) at an integrated value of 50% in a volume-based particle size distribution obtained by a laser diffraction scattering method. The active material of the electrode according to one embodiment can be the active material of the positive electrode. 2. Manufacturing process for the active material of the electrode

[0024] As in Fig. Figure 1 shows a manufacturing process for an active material of the electrode according to one embodiment: Obtaining a Na-containing transition metal oxide with a P2-type structure (step S1); Replacing at least part of the Na in the Na-containing transition metal oxide with Li by ion exchange to obtain a Li-containing transition metal oxide with an O2-type structure (step S2); and Bringing a reducing solution containing Li ions into contact with the Li-containing transition metal oxide in order to dope the Li-containing transition metal oxide with Li (step S3). Here, the active electrode material described above can be produced according to one embodiment by controlling a contact duration and a contact temperature in step S3. For example, in the manufacturing process of an active electrode material according to one embodiment a duration during which the reducing solution is held in contact with the Li-containing transition metal oxide may be 10 minutes or longer and 120 minutes or shorter; and a temperature at which the reducing solution is held in contact with the Li-containing transition metal oxide, be 10 °C or higher and 50 °C or lower. 3.1 Step S1

[0025] In step S1, the Na-containing transition metal oxide with the P2-type structure can be obtained, for example, by obtaining a precursor containing Na and a transition metal element, optionally shaping this precursor and optionally carrying out a pre-firing and subsequently carrying out a main firing.

[0026] In step S1, the precursor can be obtained, for example, by mixing a transition metal source and a sodium source. The transition metal source can be, for example, a transition metal salt such as carbonate, sulfate, nitrate, or acetate, or a transition metal compound such as a transition metal hydroxide. The transition metal element can be at least one of Mn, Ni, and Co. The transition metal source can be a salt produced by Me(CO3) x represented (Me is at least one transition metal element consisting of Mn, Ni and Co, and x depends on the valence of Me), or a salt represented by Me(SO4)x is represented, or a salt represented by Me(NO3) x represented by Me(CH3COO) x , or be a compound formed by Me(OH) xThe sodium source can be, for example, a sodium salt such as carbonate or sulfate, or a sodium compound such as sodium oxide or sodium hydroxide. The amount of sodium source mixed relative to the transition metal source can be determined taking into account the amount of sodium lost during subsequent firing. In step S1, a surface of the particle formed by the transition metal source described above can be coated with the sodium source to obtain a coated particle as a precursor. Here, the coated particle can be obtained by coating at least a portion of the surface of the particle formed by the transition metal source described above with the sodium source.The coated particle can be obtained by coating 40 area % or more, 50 area % or more, 60 area % or more, or 70 area % or more of the surface of the particle formed by the transition metal source described above with the Na source.

[0027] In step S1, the precursor can be obtained, for example, by mixing an M source that contains the element M in addition to the transition metal source and the Na source. Here, the element M is at least one type selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W. The element M can further stabilize the P2-type and O2-type structures. The M source can be, for example, a salt such as nitrate, sulfate, carbonate, or acetate, or a compound other than a salt, such as a hydroxide. The amount of the M source in the precursor can be appropriately determined according to the desired composition of the Na-containing transition metal oxide after calcination.

[0028] In step S1, the precursor can be obtained, for example, by mixing a precipitate obtained using a transition metal compound and an ion source capable of forming a precipitate with a transition metal ion in aqueous solution, along with a sodium source and, optionally, an elemental metal source. Examples of ion sources capable of forming a precipitate with a transition metal ion include sodium salts such as sodium carbonate and sodium nitrate, sodium hydroxide, and sodium oxide. Examples of transition metal compounds include salts such as nitrate, sulfate, carbonate, and acetate, as well as hydroxides. In step S1, a precipitate can be obtained by separately dissolving the ion source and the transition metal compound, then dropping and mixing these solutions together.In this case, various sodium compounds can be used as the base, and an aqueous ammonia solution or the like can be added to adjust the basicity. More precisely, in step S1, the precipitate can be a precipitate containing at least one transition metal element from Mn, Ni, and Co. The precipitate can be obtained, for example, by a solution method such as a coprecipitation process or a sol-gel process. In the case of the coprecipitation process, a precipitate can be obtained, for example, by preparing an aqueous solution of Me(SO₄). xand an aqueous solution of Na₂CO₃ and droplets, and mixing these aqueous solutions. After collecting the precipitate, this precipitate can be mixed with a sodium source. The amount of sodium source to be mixed can be determined taking into account the amount of sodium lost during subsequent calcination. A surface of a particle formed by the precipitate can be coated with sodium salt to obtain a coated particle as a precursor. The coating ratio, etc., for the coated particle are as described above.

[0029] In step S1, the pre-firing of the precursor obtained as described above can be carried out at a temperature equal to or lower than that of the main firing. For example, the pre-firing can be carried out at a temperature of less than 700 °C. The pre-firing duration is not particularly limited. Alternatively, the pre-firing can be omitted.

[0030] In step S1, the main combustion of the precursor can be carried out at a temperature of, for example, 700 °C or higher and 1100 °C or lower. Preferably, the temperature is 800 °C or higher and 1000 °C or lower. If the main combustion temperature is too low, the sodium doping cannot be performed, and if the main combustion temperature is too high, a structure other than the P2-type structure is likely to form. The temperature increase condition from the pre-combustion temperature to the main combustion temperature is not particularly restricted. The main combustion duration is also not particularly restricted and can be, for example, 30 minutes or longer and 10 hours or less. The main combustion atmosphere is also not particularly restricted and can be, for example, an oxygen-containing atmosphere, such as ambient air, or an inert gas atmosphere.

[0031] In step S1, after the main firing described above, the sodium-containing transition metal oxide with a P2-type structure can be doped with the element M described above. That is, after a sodium-containing transition metal oxide with a P2-type structure, which does not contain the element M, has been synthesized, this oxide can be doped with the element M. The doping of the element M can be carried out, for example, by ion exchange.

[0032] The sodium-containing transition metal oxide obtained by step S1 can contain, for example, at least one type of element from Mn, Ni, and Co, Na, and O. In particular, if the components include at least Na, Mn, at least one of Ni and Co, and O, the performance of the active material of the positive electrode is likely to be even higher. More precisely, the sodium-containing transition metal oxide obtained by step S1 can have a chemical composition that is determined by Na c Mn x-p Ni y-q Co z-r M p+q+rO2 (where 0 < c ≤ 1.00, x + y + z = 1 and 0 ≤ p + q + r < 0.17 and the element M is at least one type chosen from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W). If the sodium-containing transition metal oxide has such a chemical composition, it is likely that the P2-type structure will be retained. 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 is 1.00 or less and can be 0.90 or less, 0.80 or less, or 0.70 or less. The compositional proportions of x, y, z, p, q and r as well as O can be the same as those mentioned above and are not described in more detail here. 2.2 Step S2

[0033] In step S2, at least a portion of the Na in the Na-containing transition metal oxide obtained in step S1 is exchanged with Li by ion exchange to obtain a Li-containing transition metal oxide with an O2-type structure. In step S2, at least a portion of the Na in the Na-containing transition metal oxide can be exchanged, for example, by ion exchange using a lithium salt. For instance, at least a portion of the Na can be exchanged by ion exchange by mixing the Na-containing transition metal oxide with a P2-type structure and a lithium salt, and then heating the mixture to a temperature equal to or higher than the melting point of the lithium salt to melt the lithium salt. The lithium salt can, for example, be a lithium halide. The lithium halide is preferably at least one of lithium chloride, lithium bromide, and lithium iodide. Alternatively, the lithium salt can be lithium nitrate.Or the lithium salt could be a mixed salt of lithium halide and lithium nitrate.

[0034] In step S2, element M can be doped during the ion exchange described above. The sodium-containing transition metal oxide described above can be doped with element M by, for example, heating and melting a salt containing element M and then bringing this salt into contact with the oxide. An example of a salt containing element M is a halide of element M. In step S2, a salt containing lithium and element M can be brought into contact with the sodium-containing transition metal oxide described above to carry out an ion exchange of at least some of the sodium from the sodium-containing transition metal oxide particles with lithium, thus doping element M. When using a salt containing lithium and element M (a mixed salt of lithium salt and element M or a compound salt of lithium and element M), the melting point of the salt may be lower than when using the lithium salt and the element M salt separately.In particular, when using a salt containing at least one of Al and Ga as element M and Li, the melting point is likely to be significantly lower. This lowers the temperature required for melting, allowing the ion exchange of Li and the doping of element M described above to be carried out at lower temperatures. The mixing ratio of lithium salt and element M salt is not particularly restricted. Specific examples of salts containing Li and element M include, for instance, salts containing Li, element M, and a halogen (mixed salts of lithium halide and element M halide, or halide compounds of Li and element M).

[0035] The temperature in step S2 (e.g., the heating temperature in the case where the lithium salt is brought into contact with the sodium-containing transition metal oxide particles and then ion exchange is carried out by heating and melting) can be, for example, 600 °C or less, 500 °C or less, 400 °C or less, 350 °C or less, 300 °C or less, 280 °C or less, 250 °C or less, 230 °C or less, 200 °C or less, 170 °C or less, or 150 °C or less, and room temperature or higher, or 100 °C or higher. If the temperature is too high, an O3-type structure, which is a stable phase, is likely to form instead of the O2-type structure. When melting the lithium salt, it should be heated to its melting point or above, as described above. The duration in step S2 (e.g.,The heating time (in the case where lithium salt is brought into contact with the sodium-containing transition metal oxide and ion exchange is then carried out by heating and melting) can be adjusted so that a large proportion of the sodium in the sodium-containing transition metal oxide particles is replaced by lithium. Assuming sufficient time for the lithium salt to melt, the duration in step S2 can be, for example, 10 minutes or more, or 60 minutes or more, and 12 hours or less, or 6 hours or less. The atmosphere in step S2 is not particularly restricted and can be, for example, an oxygen-containing atmosphere, such as ambient air, or an inert gas atmosphere. After the ion exchange, some type of post-treatment, such as washing, can be performed on the lithium-containing transition metal oxide with an O₂-type structure.

[0036] In step S2, the lithium-containing transition metal oxide of type O2 obtained by ion exchange can contain at least one element selected from Mn, Ni and Co, Li and O. In particular, if the elements include Mn, at least one of Ni and Co, Li and O, or especially if they include Li, Mn, Ni, Co and O, even higher performance is likely. The lithium-containing transition metal oxide of type O2 obtained by ion exchange can contain Na as a component due to the manufacturing step described above. The lithium-containing transition metal oxide of type O2 obtained by ion exchange can contain the element M described above. The lithium-containing transition metal oxide of type O2 obtained by ion exchange can contain other impurity elements.The chemical composition of the Li-containing transition metal oxide of the O2 type obtained by the ion exchange in step S2 can be changed by Li. a N / a b Mn x-p Ni y-q CO z-r M p+q+rO2 can be represented (where 0 < a ≤ 0.70, 0 ≤ b ≤ 0.20, x + y + z = 1 and 0 ≤ p + q + r < 0.17, and the element M is at least one type selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W). In this chemical composition, a 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. The mixing ratio of b is 0 or more and can exceed 0, and is 0.20 or less and can be 0.15 or less, 0.10 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less. The compositional proportions of x, y, z, p, q, and r, as well as O, can be the same as those mentioned above, and their description is omitted here. 3.3 Step S3

[0037] By performing steps S1 and S2 described above, a lithium-containing transition metal oxide with an O2-type structure can be obtained. However, as far as the inventor has determined, the amount of lithium contained in the lithium-containing transition metal oxide when only steps S1 and S2 are performed is likely to be insufficient, and an active electrode material that meets the requirements described above regarding the peak maximum position and full width at half maximum (FWHM) cannot be obtained. For example, the ion exchange described above reduces the molar ratio of lithium in the lithium-containing transition metal oxide (described as "a" above) to no more than 0.70 or less, thus failing to fully exploit the potential capacity of the active material of the positive O2-type electrode.

[0038] As a countermeasure, in step S3, the lithium-containing transition metal oxide obtained by step S2 described above is additionally doped with lithium in a step separate from the ion exchange, thereby increasing the molar ratio of lithium in the lithium-containing transition metal oxide ("a" as described above) to above 0.70. Specifically, in step S3, a reducing solution containing lithium ions is brought into contact with the lithium-containing transition metal oxide to further dope the lithium-containing transition metal oxide with lithium in a step separate from the ion exchange. "Reducing solution" refers to a solution with reducing properties and can, for example, be a solution containing an electrophile. The reducing solution can be obtained, for example, by dissolving an electrophile and a lithium source in a solvent.Various organic solvents capable of dissolving an electrophile and a Li source can be used as solvents.

[0039] The solvent forming the reducing solution can, for example, be an ether. In other words, the reducing solution can contain an ether. The ether is preferably, for example, at least one type selected from tetrahydrofuran, which may have a substituent (tetrahydrofuran, 2-methyltetrahydrofuran, etc.), dialkyl ethers (dibutyl ether, etc.), alkylene glycol dialkyl ethers (dimethoxyethane, etc.), etc.

[0040] Various substances that dissolve in the solvent described above can be used as electrophiles. For example, the electrophile in the reducing solution can be an aromatic compound. In other words, the reducing solution can contain an aromatic compound. If this aromatic compound has multiple benzene rings, the electron density within the structure decreases, and the electrons incorporated into the aromatic compound become more stable, resulting in a greater effect. Conversely, if this aromatic compound has an electron-withdrawing substituent, electrons are attracted to this group, the electron density within the benzene ring decreases, and the electrons incorporated into the aromatic compound become more stable, resulting in a greater effect."Electron-withdrawing group" refers to a group with a relatively high electronegativity, comprising a group containing halogen, oxygen, and / or nitrogen. In particular, the electron-withdrawing group may comprise at least one type selected from a halogen group, a carbonyl group, a nitro group, etc. The aromatic compound acting as the electrophile is preferably, for example, at least one type selected from biphenyl, which may have a substituent (e.g., biphenyl, 2-methylbiphenyl, etc.), fluorenone, which may have a substituent (e.g., 9-fluorenone, etc.), naphthalene, which may have a substituent (e.g., naphthalene, fluoronaphthalene, bromonaphthalene, nitronaphthalene, etc.), anthracene, which may have a substituent (e.g., anthracene, 9-bromothracene, etc.).), Tetracen, das einen Substituenten aufweisen kann, Pentacen, das einen Substituenten aufweisen kann, Tetraphenylcyclopentadienon, das einen Substituenten aufweisen kann usw.

[0041] Various substances that dissolve in the solvent described above and form lithium ions can be used as a lithium source. The lithium source can be metallic lithium or a lithium compound.

[0042] The concentrations of the electrophile and the Li ions in the reducing solution can be suitably determined according to the desired doping amount. For example, if the Li-containing transition metal oxide described above is immersed in the reducing solution, the molar ratio between the Li ions in the reducing solution and the Li-containing transition metal oxide being immersed in this reducing solution (Li ions / Li-containing transition metal oxide) can be 0.1 or higher, 0.2 or higher, 0.3 or higher, 0.4 or higher, 0.5 or higher, 0.6 or higher, 0.7 or higher, or 0.8 or higher, and 2.0 or less, 1.5 or less, 1.0 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, or 0.2 or less.In particular, if this molar ratio (Li ions / Li-containing transition metal oxide) is 0.2 or higher and 0.6 or lower, especially 0.3 or higher and 0.5 or lower, it is likely that an active material for the positive electrode with excellent performance will be obtained. The molar ratio between the electrophile and the Li ions contained in the reducing solution (electrophile / Li ions) is not particularly restricted and can be, for example, 0.5 or higher and 2.0 or lower, 0.7 or higher and 1.5 or lower, or 0.9 or higher and 1.1 or lower.

[0043] In step S3, for example, the lithium-containing transition metal oxide can be additionally doped with lithium by simply bringing it into contact with the reducing solution described above. The form of contact between the reducing solution and the lithium-containing transition metal oxide is not particularly restricted. For example, the lithium-containing transition metal oxide can be immersed in the reducing solution, or the reducing solution can be sprayed onto the lithium-containing transition metal oxide. As confirmed by the present inventor, the active electrode material described above can be produced according to one embodiment by controlling the contact duration and contact temperature of the lithium-containing transition metal oxide and the reducing solution in step S3.In particular, the duration for which the reducing solution is held in contact with the lithium-containing transition metal oxide can be 10 minutes or longer and 120 minutes or shorter, and the temperature at which the reducing solution is held in contact with the lithium-containing transition metal oxide can be 10 °C or higher and 50 °C or lower. For example, the "contact duration" is considered equivalent to the "immersion time" from the time the lithium-containing transition metal oxide is immersed in the reducing solution until the time it is withdrawn, and equivalent to the "spray time" in the case where the reducing solution is sprayed onto the lithium-containing transition metal oxide. The "contact temperature" is the "temperature of the reducing solution" that is brought into contact with the lithium-containing transition metal oxide.

[0044] In step S3, after Li doping, a washing or drying step can be performed using the reducing solution, if necessary. The washing or drying step can control the amount of impurities (the amount of impurities attributable to the reducing solution) contained in the active electrode material. 3rd battery

[0045] A battery according to one embodiment comprises the active electrode material of the invention as described above. The active electrode material of the invention can, for example, be used as the active material of the positive electrode of a lithium-ion battery. As described in Fig.As shown in Figure 2, a battery 100 according to one embodiment comprises a layer of active material for the positive electrode 10, an electrolyte layer 20, and a layer of active material for the negative electrode 30. For example, the layer of active material for the positive electrode 10 in the battery 100 can comprise the active material of the electrode of the invention. The battery 100 can include a current collector 40 for the positive electrode and a current collector 50 for the negative electrode. The battery 100 can be a solid-state battery or an aqueous battery. A solid-state battery refers to a battery that contains a solid electrolyte, although the presence of a liquid is acceptable. The battery 100 can be a solid-state battery that contains practically no liquid.The battery composition can be the same as that of a conventional battery, except that the active electrode material of the invention is used. A detailed description is omitted here.

[0046] While one embodiment of the active material of the electrode, etc., of the invention has been described above, various modifications to the active material of the electrode, etc., of the invention can be made within such a range that no deviation from the essential nature of the invention occurs. The technology of the invention is described in more detail below with reference to an exemplary embodiment, although the technology of the invention is not limited to the following exemplary embodiment. 1. Preparation of active material for electrodes 1.1 Coprecipitation synthesis of a transition metal source

[0047] MnSO₄·5H₂O, NiSO₄·6H₂O, and CoSO₄·7H₂O were weighed out in target proportions and dissolved in distilled water to a concentration of 1.2 mol / L to obtain a first liquid. In a separate container, Na₂CO₃ was dissolved in distilled water to a concentration of 1.2 mol / L to obtain a second liquid. Subsequently, 500 mL each of the first liquid and the second liquid were added dropwise to a reaction vessel to which 1000 mL of pure water had previously been added, at a rate of approximately 4 mL / min. After completion of the dropwise addition, the mixture was stirred for one hour at room temperature at a speed of 150 rpm. The precipitate was washed with pure water and separated into a solid and a liquid by centrifugal separator.The resulting precipitate was dried overnight at 120 °C and pulverized in a mortar, after which fine particles were removed by airflow classification. This yielded mixed salt particles (transition metal source) containing Mn, Ni, and Co. 1.2 Mixing the transition metal source and the Na source (Na coating)

[0048] Na₂CO₃ and distilled water were weighed to a concentration of 1150 g / L and then stirred until the former was completely dissolved to produce a Na₂CO₃-aqueous solution. The aforementioned mixed salt particles were mixed into the Na₂CO₃-aqueous solution to create a slurry. The Na₂CO₃ and the aforementioned mixed salt particles were mixed together so that, upon drying, they would form a composition of Na₂CO₃. 0,7 Mn 0,5 Ni 0,2 Co 0,3The resulting slurry was dried by spray drying. Specifically, using a DL410 spray drying device, the surfaces of the aforementioned mixed salt particles with Na2CO3 were dried under the conditions of a slurry feed rate of 30 ml / min, an inlet temperature of 200 °C, and a circulation airflow rate of 0.8 m³ / h. 3 / min and coated with a spray air pressure of 0.3 MPa to obtain precursor particles. 1.3 Burning of the precursor particles

[0049] In an ambient air atmosphere (humidity 50% or higher), the firing of precursor particles was carried out in an electric furnace using an alumina crucible. Specifically, the precursor particles underwent a "first temperature increase step," a "pre-firing step," a "second temperature increase step," a "main firing step," and a "furnace cooling step," as shown in Table 1 below. Afterward, the fired product was removed from the electric furnace at 250 °C and pulverized in a mortar in a dry atmosphere with a dew point of -30 °C or less to produce a sodium-containing transition metal oxide (Na₂O₂). 0,7 Mn 0,5 Ni 0,2 Co 0,3 O2) with the P2-type structure. Table 1 Step Starting temperature Final temperature Length of time Rate of temperature increase or cooling (°C) (°C) (min) (°C / min) First temperature increase step 25 600 115 5 Pre-burn step 600 600 360 0 Second temperature increase step 600 900 100 3 Main fire step 900 900 60 0 Cooling step in the oven 900 250 130 5 1.4 Ion exchange

[0050] LiNO3 and LiCI were weighed in a molar ratio of 50:50 and mixed with the aforementioned Na-containing transition metal oxide in such a molar ratio that the amount of Li was ten times the minimum amount required for ion exchange.

[0051] A mixture was thus obtained. It was then fired for one hour at 280 °C in an ambient air atmosphere (humidity 50% or higher) using an aluminum oxide crucible. The salt remaining after firing was washed with pure water and separated into a solid and a liquid fraction by vacuum filtration. The resulting precipitate was dried overnight at 120 °C to obtain a lithium-containing transition metal oxide with an O₂-type structure. 1.5 Li doping

[0052] In a glovebox (argon atmosphere), naphthalene was mixed and dissolved in tetrahydrofuran (THF) to a concentration of 1 mol / L to obtain a naphthalene solution. Li-film was added to this naphthalene solution in the same molar ratio as the naphthalene, and the mixture was stirred for two hours to obtain a reducing solution containing Li ions at a concentration of 1 mol / L. The aforementioned Li-containing transition metal oxide was added to and immersed in the resulting reducing solution, and stirring was carried out at the times and temperatures shown in Table 2 below. The molar ratio between the Li ions in the reducing solution and the Li-containing transition metal oxide being immersed in the reducing solution (Li ions / Li-containing transition metal oxide) was 0.4.After stirring, the lithium-containing transition metal oxide was washed with THF and separated into a solid and a liquid fraction by vacuum filtration. The resulting precipitate was dried overnight at 120 °C to obtain the active materials of the electrode (the aforementioned lithium-containing transition metal oxides, additionally doped with lithium) of Examples 1 to 3 and Comparative Examples 1 to 3. Table 2 Contact duration (min) Contact temperature (°C) Example 1 10 25 Example 2 60 25 Example 3 60 10 Example 4 60 50 Comparative example 1 10 0 Comparative example 2 1 25 Comparative example 3 1 -5 2. Determination of the chemical composition of the electrode's active material

[0053] The chemical compositions of the active materials of the electrode according to Examples 1 to 4 and Comparative Examples 1 to 3 were determined by ICP analysis. Each of the active materials of the electrode according to Examples 1 to 4 and Comparative Examples 1 to 3 had a chemical composition determined by Li x Mn 0,5 Ni 0,2 Co 0,3O2 was represented, i.e., it had the same proportions of transition metals, while differing in its proportion of Li. Table 3 below shows the proportions of Li (the value of X in the aforementioned chemical composition) of the active materials of the electrode according to Examples 1 to 4 and Comparative Examples 1 to 3, respectively. 3. Recording the X-ray diffraction pattern of the active material of the electrode

[0054] The active materials of the electrodes in Examples 1 to 4 and Comparison Examples 1 to 3 were subjected to X-ray diffraction measurements to obtain X-ray diffraction patterns, and the crystal structures of the respective active materials of the electrodes were determined. As a result, each active material of the electrodes exhibited an O2-type structure. In each X-ray diffraction pattern, the position of a peak maximum of an X-ray diffraction peak that can be assigned to the (110) plane of the O2-type structure was determined. A full width at half maximum (FWHM) of this X-ray diffraction peak that can be assigned to the (110) plane of the O2-type structure was determined after subtracting the background value. Table 3 below shows the positions of the peak maxima and the FWHM of the active materials of the electrodes in Examples 1 to 4 and Comparison Examples 1 to 3. Fig.Figure 3 shows the X-ray diffraction patterns of the active materials of the electrode of Example 1, Comparison Example 1 and Comparison Example 3. 4. Production and evaluation of the button cell

[0055] Button cells (CR2032) were manufactured using the active materials of the electrodes from Examples 1 to 4 and Comparative Examples 1 to 3. The manufacturing process for the button cell is as follows: (1) The electrode active material described above, acetylene carbon black (AB) as a conductivity enhancer, and polyvinylidene fluoride (PVdF) as a binder were mixed in a mass ratio of electrode active material : AB : PVdF = 85 : 10 : 5 and dispersed in N-methyl-2-pyrrolidone to obtain a slurry of composite material for the positive electrode. The slurry of composite material for the positive electrode was applied to an aluminum foil and vacuum-dried overnight at 120°C to obtain a positive electrode consisting of a laminate of positive electrode active material and a positive electrode current collector. (2) LiPF6 was dissolved to a concentration of 1 M in a mixed solvent obtained by mixing trifluoropropylene carbonate (TFPC) and trifluoroethyl methyl carbonate (TFEMC) in a ratio of TFPC : TFEMC = 30 vol% : 70 vol% to obtain an electrolyte solution. (3) A metal-lithium foil was produced as the negative electrode. (4) A button cell (CR2032) was produced using the positive electrode, the electrolyte solution and the negative electrode.

[0056] In a thermostatically controlled bath maintained at 25 °C, the button cell was charged and discharged within a voltage range of 2 to 4.8 V at a rate of 0.1 C (1 C = 240 mA / g). Subsequently, in the same thermostatically controlled bath maintained at 25 °C and at a state of 50% state of charge (SOC), a current corresponding to 3 C was applied for 10 seconds to measure the DCIR. Using one of the button cells from Examples 1 to 4 or Comparison Examples 1 to 3, which exhibited the lowest resistance value, as a standard (100), the resistance values ​​of the other button cells were normalized. The result is shown in Table 3 below. Fig. 4 shown. 5. Evaluation result Table 3 Li composition fraction (X) Position of the peak maximum (°) Half-width (°) Normalized resistance value Example 1 0,97 65,14 0,66 103 Example 2 0,98 65,04 0,62 100 Example 3 0,99 64,96 0,64 101 Example 4 0,98 65,08 0,62 100 Comparative example 1 0,97 65,02 0,79 186 Comparative example 2 0,96 65,24 0,95 277 Comparative example 3 0,96 65,20 1,03 353

[0057] As shown in Table 3 and Fig.As shown in Figure 3, the active materials of the electrode, which have an O2-type structure and exhibit a diffraction peak in the X-ray diffraction pattern of the active material (Examples 1 to 4 and Comparative Examples 1 to 3) that can be attributed to the O2-type structure and has a peak maximum at 2θ = 64.8° to 65.4°, can be considered highly capacitive due to doping with Li. An earlier application by the present applicant (Japanese patent application No. 2023-200071) also shows that the doping of a Li-containing transition metal oxide of the O2 type with additional Li after ion exchange further increases the capacitance of the active material of the electrode.

[0058] As shown in Table 3 and Fig.As shown in Figure 4, it can be seen that those active materials of the electrode that have the O2-type structure, for which the half-width of the diffraction peak in the X-ray diffraction pattern of the active material of the electrode is less than 0.79° among the diffraction peaks that are associated with the O2-type structure, which has a peak at 2θ = 64.8° to 65.4° (Examples 1 to 4), have a lower resistance than the comparison examples 1 to 3.

[0059] While the active material of the electrode with a specific chemical composition was illustrated in the embodiment described above, the chemical composition of the active material of the electrode is not limited to that described above. It is assumed that, if the peak maximum position and half-width described above are satisfied, the active material of the electrode can exhibit both high capacitance and low resistance, regardless of the types of transition metals from which the active material of the electrode is composed. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2010-092824

[0002] JP 2010-092824 A

[0002] JP 2023-200071

[0057]

Claims

[1] Active material of an electrode with an O2-type structure, wherein in an X-ray diffraction pattern of the active material of the electrode a half-width of a diffraction peak among the diffraction peaks attributable to the O2-type structure having a peak maximum at 2θ = 64.8° to 65.4° is less than 0.79°. [2] Active material of the electrode according to claim 1, wherein the half-width is 0.66° or less. [3] Active material of the electrode according to claim 1, wherein the active material of the electrode has a chemical composition characterized by Li a N / a b Mn x-p Ni y-q Co z-r M p+q+r O2 is represented (where 0.70 < a ≤ 1.40, 0 ≤ b ≤ 0.20, x + y + z = 1, 0 ≤ p + q + r < 0.17 and 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). [4] Battery comprising the active material of the electrode according to any one of claims 1 to 3. [5] Method for producing an active material of an electrode, comprising: Obtaining a sodium-containing transition metal oxide with a P2-type structure; Replacing at least part of the Na in the Na-containing transition metal oxide with Li by ion exchange to obtain a Li-containing transition metal oxide with an O2-type structure; and Bringing a reducing solution containing Li ions into contact with the Li-containing transition metal oxide in order to dope the Li-containing transition metal oxide with Li, wherein: a duration during which the reducing solution is held in contact with the Li-containing transition metal oxide is one minute or longer and 120 minutes or shorter; and a temperature at which the reducing solution is held in contact with the Li-containing transition metal oxide is 10°C or higher and 50°C or lower.

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