Positive electrode active material particle, method for manufacturing positive electrode active material particle, and lithium ion battery

Abstract

To disclose a positive electrode active material particle having the O2-type structure, and having excellent rate characteristics and capacity.SOLUTION: A positive electrode active material particle of the present disclosure has the O2-type structure, has a spherical shape and has a chemical composition represented by LiaNabMnx-pNiy-qCoz-rMp+q+rO2 (wherein 1.0<a<1.30, 0≤b≤0.20, x+y+z=1, and 0≤p+q+r≤0.15, 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).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present application discloses positive electrode active material particles, a method for manufacturing positive electrode active material particles, and a method for manufacturing a lithium ion battery. [Background technology]

[0002] Positive electrode active materials for lithium ion batteries are known to have an O2-type structure. As disclosed in Patent Document 1, a positive electrode active material having an O2-type structure is obtained by ion-exchanging at least a portion of Na in a sodium-containing transition metal oxide having a P2-type structure with Li. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-186937 Summary of the Invention [Problem to be solved by the invention]

[0004] There is room for improvement in the rate characteristics and capacity of positive electrode active materials having an O2-type structure. [Means for solving the problem]

[0005] The present application discloses the following aspects as means for solving the above problems. <Aspect 1> Positive electrode active material particles, It has an O2 type structure, Li a Na b Mn x-p Ni y-q Co z-r M p+q+rO2 (where 1.0 < a < 1.30, 0 ≤ b ≤ 0.20, x + y + z = 1, and 0 ≤ p + q + r ≤ 0.15, 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), and spherical, cathode active material particles. <Aspect 2> The cathode active material particles of Aspect 1, the particle surface is composed of a plurality of crystallites, cathode active material particles. <Aspect 3> A method for producing cathode active material particles, obtaining Na-containing transition metal oxide particles having a P2-type structure, and by contacting the Na-containing transition metal oxide particles with an ion exchange material, at least a part of the Na in the Na-containing transition metal oxide particles is replaced with Li to obtain Li-containing transition metal oxide particles having an O2-type structure, including the ion exchange material contains lithium hydroxide and a lithium salt, production method. <Aspect 4> The production method of Aspect 3, the Na-containing transition metal oxide particles are spherical, and the Li-containing transition metal oxide particles are spherical, production method. <Aspect 5> The production method of Aspect 3 or 4, the Na-containing transition metal oxide particles are Na c Mn x-p Ni y-q Co z-r M p+q+r ]>having a chemical composition represented by O2 (0 < c < 0.70, x + y + z = 1, and c0 ≤ p + q + r ≤ 0.15, 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), production method. <Aspect 6> In the production method according to any one of aspects 3 to 5, Obtaining precursor particles; coating the surface of the precursor particles with a Na salt to obtain coated particles; and and calcining the coated particles to obtain the Na-containing transition metal oxide particles. Manufacturing method. <Aspect 7> The manufacturing method of embodiment 6, and coating 40% or more by area of ​​the surface of the precursor particles with the Na salt to obtain the coated particles. The precursor particles are spherical. Manufacturing method. <Aspect 8> A lithium ion battery having a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, the positive electrode active material layer contains the positive electrode active material particles of embodiment 1 or 2; Lithium-ion battery. [Effects of the Invention]

[0006] The positive electrode active material particles of the present disclosure have excellent rate characteristics and capacity. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a SEM photograph showing an example of the external shape of positive electrode active material particles. [Figure 2] 1 shows an example of the flow of a method for producing positive electrode active material particles. [Figure 3] 1 shows an example of a flow of a method for producing Na-containing transition metal oxide particles having a P2 type structure. [Figure 4] 1 shows a schematic diagram of an example of the configuration of a lithium ion battery. [Figure 5] 1 shows an example of firing conditions for obtaining Na-containing transition metal oxide particles having a P2 type structure. [Figure 6A] 1 is a SEM photograph showing the external shape of a positive electrode active material particle according to Example 1. FIG. [Figure 6B]It is a SEM photograph showing the external appearance shape of the positive electrode active material particles according to Example 2. [Figure 6C] It is a SEM photograph showing the external appearance shape of the positive electrode active material particles according to Comparative Example 1. [Figure 6D] It is a SEM photograph showing the external appearance shape of the positive electrode active material particles according to Comparative Example 2. [Figure 6E] It is a SEM photograph showing the external appearance shape of the positive electrode active material particles according to Reference Example 1. [Figure 7] It shows the X-ray diffraction pattern of the positive electrode active material particles. [Figure 8A] It shows the first charge-discharge curve of the cell according to Example 1. [Figure 8B] It shows the first charge-discharge curve of the cell according to Example 2. <opposite [Figure 8C] It shows the first charge-discharge curve of the cell according to Comparative Example 1. [Figure 8D] It shows the first charge-discharge curve of the cell according to Comparative Example 2. [Figure 8E] It shows the first charge-discharge curve of the cell according to Reference Example 1. [Figure 9] It shows the rate characteristics of each cell.

BEST MODE FOR CARRYING OUT THE INVENTION

[0008] 1. Positive electrode active material particles Fig. 1 shows an example of the external appearance shape of the positive electrode active material particles according to one embodiment. The positive electrode active material particles according to one embodiment have an O2-type structure and contain Li a Na b Mn x-p Ni y-q Co z-r M p+q+r O2 (where 1.0 < a < 1.30, 0 ≤ b ≤ 0.20, x + y + z = 1, and 0 ≤ p + q + r ≤ 0.15, 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), and are spherical.

[0009] 1.1 Crystal structure of positive electrode active material particles The positive electrode active material particles according to one embodiment have at least an O2-type structure (belonging to the space group P63mc) as a crystal structure. The positive electrode active material particles may have an O2-type structure as well as a crystal structure other than the O2-type structure. Examples of crystal structures other than the O2-type structure include a T#2-type structure (belonging to the space group Cmca) formed when Li is inserted and removed from the O2-type structure, and an O6-type structure (belonging to the space group R-3m, with a c-axis length of 2.5 nm to 3.5 nm, typically 2.9 nm to 3.0 nm, and different from the O3-type structure also belonging to the space group R-3m). The positive electrode active material particles may have an O2-type structure as a main phase, or may have a crystal structure other than the O2-type structure as a main phase. The crystal structure of the positive electrode active material particles as a main phase may change depending on the charge / discharge state.

[0010] The positive electrode active material particles according to one embodiment may be single crystals consisting of a single crystallite, or polycrystalline having multiple crystallites. As shown in FIG. 1, the surface of the positive electrode active material particles may be composed of multiple crystallites. When the surface of the positive electrode active material particles has multiple crystallites, grain boundaries exist on the surface of the positive electrode active material particles. Here, the grain boundaries may serve as inlets and outlets for intercalation. Specifically, when the positive electrode active material particles have multiple crystallites on their surfaces, the following effects can be expected: Increased number of inlets and outlets for intercalation reduces reaction resistance; The lithium ion migration distance is shortened, reducing diffusion resistance; The absolute amount of expansion and contraction during charge and discharge is reduced, making cracks less likely to occur.

[0011] The size of the crystallites constituting the positive electrode active material particles according to one embodiment may be large or small. However, smaller crystallite sizes result in more grain boundaries, making it easier to achieve the above-mentioned advantageous effects. For example, when the diameter of the crystallites constituting the positive electrode active material particles is less than 1 μm, higher performance is likely to be obtained. The "crystallite" and "crystallite diameter" can be determined by observing the surface of the positive electrode active material particles using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). That is, when observing the surface of a positive electrode active material particle and a single closed region surrounded by grain boundaries is observed, the region is considered to be a "crystallite." The maximum Feret diameter of the crystallite is determined and considered to be the "crystallite diameter." If the particle is composed of a single crystal, the particle itself can be considered a single crystallite, and the maximum Feret diameter of the particle is the "crystallite diameter." Alternatively, the crystallite diameter can be determined using EBSD or XRD. For example, the crystallite diameter can be determined from the half-width of the diffraction line in the XRD pattern based on the Scherrer equation. When the crystallite diameter of the positive electrode active material particles is determined by any of these methods to be less than 1 μm, higher performance is likely to be obtained.

[0012] The crystallites of the positive electrode active material particles according to one embodiment may have a first surface exposed on the particle surface, and the first surface may be planar. The surface of the positive electrode active material particles may have a structure in which a plurality of planes are connected. When producing the positive electrode active material particles, crystallites having planar first surfaces can be easily obtained by growing the crystallites on the particle surface until one crystallite and another crystallite are connected to each other.

[0013] 1.2 Chemical composition of positive electrode active material particles The positive electrode active material particles according to one embodiment include Li a Na b Mn x-p Ni y-q Co z-r M p+q+rIt has a chemical composition represented by O2. Here, 1.00 < a < 1.30, 0 ≤ b ≤ 0.20, x + y + z = 1, and 0 ≤ p + q + r ≤ 0.15. 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. Conventionally, the positive electrode active material particles having an O2-type structure had a Li composition ratio of 1.00 or less (a above is 1.00 or less), and there was room for improvement in capacity. In contrast, the positive electrode active material particles of the present disclosure have an O2-type structure and a Li composition ratio exceeding 1.00 (a above exceeds 1.00), and have excellent capacity (as described above, both the conventional positive electrode active material particles and the positive electrode active material particles of the present disclosure may include other crystal structures together with the O2-type structure). Such positive electrode active material particles containing an excess of Li can be produced by a new method by the present inventor. The method for producing the positive electrode active material particles will be described later.

[0014] In the above chemical composition, a may be greater than 1.00, 1.02 or greater, 1.04 or greater, 1.06 or greater, 1.08 or greater, 1.10 or greater, 1.12 or greater, 1.14 or greater, or 1.16 or greater, and may be 1.30 or less, 1.28 or less, 1.26 or less, 1.24 or less, 1.22 or less, or 1.20 or less. In the above chemical composition, b may be 0 or greater, 0.01 or greater, 0.02 or greater, or 0.03 or greater, and may be 0.20 or less, 0.15 or less, or 0.10 or less. In the above chemical composition, x may be 0 or greater, 0.10 or greater, 0.20 or greater, 0.30 or greater, 0.40 or greater, or 0.50 or greater, and may be 1.00 or less, 0.90 or less, 0.80 or less, 0.70 or less, or 0.60 or less. In the above chemical composition, y may be 0 or more, 0.10 or more, or 0.15 or more, and may be 1.00 or less, 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, or 0.20 or less. In the above chemical composition, z may be 0 or more, 0.10 or more, 0.20 or more, or 0.25 or more, and may be 1.00 or less, 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 0.35 or less. Many M elements do not contribute to charge and discharge. In this regard, a high charge and discharge capacity is easily ensured by having p + q + r be 0.15 or less. p + q + r may be 0.10 or less, 0.05 or less, or even 0. The composition of O is approximately 2, but is not necessarily exactly 2.0 and is variable.

[0015] 1.3 Shape of positive electrode active material particles The positive electrode active material particles according to one embodiment are spherical. When spherical positive electrode active material particles are included in the positive electrode active material layer of a lithium ion secondary battery, crystallite growth is more likely to be suppressed and the crystallites are more likely to be small, compared with when non-spherical positive electrode active material particles (e.g., plate-like particles) are included. That is, when the positive electrode active material particles are spherical, the reaction resistance is reduced due to the reduction in crystallite size, and the diffusion resistance within the active material is likely to be reduced. Furthermore, it is believed that the degree of curvature is reduced by the spheroidization, thereby reducing the lithium ion conduction resistance within the layer that constitutes the positive electrode active material layer. As a result, spherical positive electrode active material particles are likely to have superior rate characteristics compared to non-spherical positive electrode active material particles. Such spherical positive electrode active material particles can be manufactured by a new method developed by the present inventors. A method for manufacturing positive electrode active material particles will be described later. The term "spherical" means that the circularity is 0.80 or more. The circularity of the positive electrode active material 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. 2 where S is the orthogonal projection area of ​​the particle, and L is the perimeter of the orthogonal projection image of the particle. The circularity of the positive electrode active material particles can be determined by observing the appearance or the cross-sectional shape of the particles using a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an optical microscope.

[0016] The positive electrode active material particles according to one embodiment may be solid particles, hollow particles, or particles having voids. When the positive electrode active material particles are hollow particles or particles having voids, it is considered possible to fill the hollows or voids with a liquid. For example, the electrolyte solution may penetrate not only the outer surface of the positive electrode active material particles but also the interior thereof, which tends to increase the contact area between the particles and the electrolyte solution.

[0017] 1.4 Positive electrode active material particle size The size of the positive electrode active material particles according to an embodiment is not particularly limited. For example, the diameter D of the positive electrode active material particles according to an embodiment may be 0.1 μm to 10 μm, 0.5 μm to 8.0 μm, or 1.0 μm to 6.0 μm. The diameter D of the positive electrode active material particles refers to the circle-equivalent diameter when the external appearance or cross-sectional shape of the positive electrode active material particles is observed using an SEM or the like. When there are multiple positive electrode active material particles, the diameter D of the positive electrode active material particles is the number-average value of the circle-equivalent diameters of the multiple positive electrode active material particles.

[0018] 2. Method for producing positive electrode active material particles Positive electrode active material particles containing excess Li can be produced, for example, by the following method. As shown in Figure 2, a method for producing positive electrode active material particles according to one embodiment includes obtaining Na-containing transition metal oxide particles having a P2-type structure (step S1), and contacting the Na-containing transition metal oxide particles with an ion exchange material to replace at least a portion of the Na in the Na-containing transition metal oxide particles with Li, thereby obtaining Li-containing transition metal oxide particles having an O2-type structure (step S2). Here, the ion exchange material contains lithium hydroxide and a lithium salt.

[0019] 2.1 Process S1 In step S1, Na-containing transition metal oxide particles having a P2-type structure are obtained. Here, the shape of the Li-containing transition metal oxide particles having an O2-type structure is determined by the shape of the Na-containing transition metal oxide particles having a P2-type structure. In a production method according to one embodiment, the Na-containing transition metal oxide particles are spherical, and the Li-containing transition metal oxide particles are also spherical. That is, when producing Li-containing transition metal oxide particles having an O2-type structure and being spherical, it is preferable to obtain Na-containing transition metal oxide particles having a P2-type structure and being spherical in step S1.

[0020] The Na-containing transition metal oxide particles having a P2-type structure can be produced, for example, by the method shown in Fig. 3. That is, the production method according to one embodiment includes obtaining precursor particles (step S11), coating the surfaces of the precursor particles with a Na salt to obtain coated particles (step S12), and calcining the coated particles to obtain Na-containing transition metal oxide particles having a P2-type structure (step S13).

[0021] 2.1.1 Process S11 In step S11, precursor particles are obtained. The precursor particles may be a salt containing at least one transition metal element selected from Mn, Ni, and Co. The precursor particles may be, for example, at least one of carbonate, sulfate, nitrate, acetate, and hydroxide. Specifically, the precursor particles may be a salt represented by MeCO3 (where Me is at least one transition metal element selected from Mn, Ni, and Co), a salt represented by MeSO4, a salt represented by Me(NO3)2, a salt represented by Me(CH3COO)2, or a compound represented by Me(OH)2. These may also be hydrates. In addition to the transition metal element Me, the precursor particles may also contain at least one element M selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W.

[0022] The precursor particles may also be spherical. The definition of "spherical" is as described above. When the precursor particles are spherical, the shape of the Na-containing transition metal oxide particles or the Li-containing transition metal oxide particles (positive electrode active material particles) can also be spherical. The size of the spherical precursor particles is not particularly limited. The spherical precursor particles can be obtained by a solution method such as a co-precipitation method or a sol-gel method. Specifically, in the case of the co-precipitation method, an aqueous solution of MeSO4 and an aqueous solution of Na2CO3 are prepared, and each aqueous solution is dropped and mixed to obtain a precipitate. The precipitate is a spherical precursor particle represented by MeCO3. A carbonate containing Me and M may be obtained as the precursor particle by dissolving a sulfate or the like of M in the aqueous solution of MeSO4.

[0023] 2.1.2 Process S12 In step S12, the surfaces of the precursor particles are coated with a Na salt to obtain coated particles. A manufacturing method according to one embodiment may include coating 40% or more of the surface of the precursor particles with a Na salt to obtain coated particles. Here, the precursor particles may be spherical. When the precursor particles are spherical and the coverage of the Na salt with respect to the precursor particles is 40% or more by area, spherical P2-type particles or spherical O2-type particles are easily obtained. The coated particles may be obtained by coating 50% or more, 60% or more, or 70% by area of ​​the surface of the precursor particles with a Na salt. Examples of Na salts include carbonates and nitrates.

[0024] Various methods can be used to coat the surface of precursor particles with Na salt. To finally obtain spherical O2-type positive electrode active material particles, for example, tumbling fluidized coating or spray drying can be used. That is, a coating solution containing dissolved Na salt is prepared, and the entire surface of the precursor particles is brought into contact with the coating solution, or the coating solution is dried at the same time as or after the contact. By adjusting the coating conditions (temperature, time, number of times, etc.), for example, 40% or more of the surface area of ​​the precursor particles can be coated with Na salt. According to the findings of the present inventors, if the coverage rate of Na salt is low, abnormal growth of P2-type crystals is likely to occur on the surface of the coated particles when the coated particles are calcined, resulting in plate-shaped Na-containing transition metal oxide particles, but it is difficult to obtain spherical Na-containing transition metal oxide particles. If the coverage rate of Na salt is high, the crystallites of the P2-type crystals can be reduced when the coated particles are calcined, and the shape of the coated particles is likely to become spherical, corresponding to the shape of the precursor particles. The amount of Na salt coated on the coated particles may be sufficient to obtain a P2-type structure (a sufficient amount of Na is doped).

[0025] 2.1.3 Process S13 In step S13, the coated particles are calcined to obtain Na-containing transition metal oxide particles having a P2-type structure. The Na-containing transition metal oxide particles may be plate-shaped or spherical, but as described above, spherical particles tend to exhibit better performance. When the Na-containing transition metal oxide particles are plate-shaped, the O2-type positive electrode active material obtained thereafter will also be plate-shaped. On the other hand, when the Na-containing transition metal oxide particles are spherical, the O2-type positive electrode active material obtained thereafter will also be spherical.

[0026] The firing temperature in step S13 may be any temperature at which a P2 type structure is formed. If the firing temperature is too low, Na doping will not occur and it will be difficult to obtain a P2 type structure. On the other hand, if the firing temperature is too high, an O3 type structure will likely be formed instead of a P2 type structure. The firing temperature may be, for example, 700°C or higher and 1100°C or lower, or 800°C or higher and 1000°C or lower.

[0027] The calcination time in step S13 may be adjusted appropriately depending on the desired shape of the Na-containing transition metal oxide particles. As described above, if the coverage rate of the Na salt on the coated particles is low, abnormal growth of P2-type crystals is likely to occur on the surface of the coated particles when the coated particles are calcined, resulting in plate-shaped Na-containing transition metal oxide particles. On the other hand, if the coverage rate of the Na salt on the coated particles is high, small P2-type crystallites are likely to form on the surface of the particles when the coated particles are calcined. By growing P2-type crystallites along the surface of the particles so as to connect one P2-type crystallite to another, spherical Na-containing transition metal oxide particles can be obtained. If the calcination time is too short, Na doping will not occur, and the desired P2-type structure will not be obtained. On the other hand, if the calcination time is too long, excessive growth of the P2-type structure will result in plate-shaped particles. As far as the inventors have confirmed, spherical Na-containing transition metal oxide particles are likely to be obtained when the firing time is 30 minutes or more and 3 hours or less, and plate-shaped Na-containing transition metal oxide particles are likely to be obtained when the firing time is longer than this.

[0028] The firing atmosphere in step S13 is not particularly limited, and may be, for example, an oxygen-containing atmosphere such as air atmosphere or an inert gas atmosphere.

[0029] The Na-containing transition metal oxide particles obtained through the above steps S11 to S13 may contain, as constituent elements, at least one transition metal element selected from Mn, Ni, and Co, Na, and O. In particular, when the constituent elements contain at least Na, Mn, at least one of Ni and Co, and O, and especially when the constituent elements contain at least Na, Mn, Ni, Co, and O, the performance of the positive electrode active material particles is likely to be further improved. The Na-containing transition metal oxide particles may contain Na c Mn x-p Ni y-q Co z-r M p+q+rIt may have a chemical composition represented by O2. Here, 0 < c < 0.70, x + y + z = 1, and 0 ≤ p + q + r ≤ 0.15. 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 transition metal oxide particles have such a chemical composition, the P2-type structure is more likely to be maintained. In the above chemical composition, c may be greater than 0, 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. In the above chemical composition, x may be 0 or more, 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.50 or more, and may be 1.00 or less, 0.90 or less, 0.80 or less, 0.70 or less, or 0.60 or less; y may be 0 or more, 0.10 or more, or 0.15 or more, and may be 1.00 or less, 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; z may be 0 or more, 0.10 or more, 0.20 or more, or 0.25 or more, and may be 1.00 or less, 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 0.35 or less. Many of M do not contribute to charge and discharge. In this regard, when p + q + r is 0.15 or less, it is easy to ensure a high charge and discharge capacity. p + q + r may be 0.10 or less, 0.05 or less, or 0.

[0030] 2.2 Step S2<000G341>In step S2, by bringing an ion exchange material into contact with the above Na-containing transition metal oxide particles, at least a part of Na in the Na-containing transition metal oxide particles is replaced with Li to obtain Li-containing transition metal oxide particles having an O2-type structure. Here, the ion exchange material contains lithium hydroxide and a lithium salt.

[0031] Ion exchange can be performed, for example, using an aqueous solution containing a lithium salt or using a molten lithium salt. Of the two methods, the method using a molten lithium salt is preferred because the P2-type structure is easily broken by water penetration and from the viewpoint of crystallinity. That is, by mixing the sodium-containing transition metal oxide particles having the P2-type structure with the lithium salt and then heating the mixture to a temperature equal to or higher than the melting point of the lithium salt, and bringing the molten lithium salt into contact with the sodium-containing transition metal oxide particles, at least a portion of the sodium in the sodium-containing transition metal oxide particles can be replaced with lithium by ion exchange.

[0032] Here, in step S2, it is important to use lithium hydroxide together with a lithium salt as an ion exchange material. By using a Li source with a high Li concentration during ion exchange, the ion exchange reaction can be promoted, and the Li composition ratio in the Li-containing transition metal oxide particles having an O2-type structure exceeds 1.0 (the above a exceeds 1.0). By using lithium hydroxide together with a lithium salt, this effect can be easily achieved.

[0033] In step S2, the type of lithium salt constituting the ion exchange material is not particularly limited. In one embodiment, the lithium salt constituting the ion exchange material may contain at least one lithium halide selected from the group consisting of lithium chloride, lithium bromide, and lithium iodide. In particular, when lithium chloride is used, better performance is likely to be ensured. In one embodiment, the lithium salt constituting the ion exchange material may contain lithium nitrate. In one embodiment, the lithium salt constituting the ion exchange material may be a mixed salt of the above-mentioned lithium halide and lithium nitrate. Lithium halide and lithium nitrate have low melting points, allowing ion exchange at lower temperatures.

[0034] In step S2, the ratio of lithium hydroxide to lithium salt contained in the ion exchange material is not particularly limited. In an ion exchange material according to one embodiment, the ratio of lithium hydroxide to the total (100 mol%) of lithium hydroxide and lithium salt may be 10 mol% to 90 mol%, 20 mol% to 80 mol%, 40 mol% to 75 mol%, 50 mol% to 70 mol%, or 55 mol% to 65 mol%. This lowers the melting point of the ion exchange material, making it more optimal as an ion exchange material. In an ion exchange material according to one embodiment, the molar ratio of lithium hydroxide may be higher than the molar ratio of lithium salt. In step S2, the ion exchange material may consist of only lithium hydroxide and lithium salt, or may contain any optional components in addition to lithium hydroxide and lithium salt.

[0035] In step S2, the ion exchange temperature may be, for example, above the melting point of the ion exchange material and below 600°C, 500°C, 400°C, or 300°C. If the ion exchange temperature is too high, the stable O3 structure is likely to be formed rather than the O2 structure. On the other hand, from the viewpoint of shortening the time required for ion exchange, it is preferable that the temperature for ion exchange be as high as possible. The ion exchange time is not particularly limited, but may be, for example, from 10 minutes to 10 hours, from 30 minutes to 7 hours, or from 1 hour to 5 hours. As far as the inventors have confirmed, positive electrode active material particles having an O2 crystal structure are more likely to be produced at an ion exchange temperature of from 270°C to 320°C and for an ion exchange time of from 1 hour to 8 hours.

[0036] 3. Lithium-ion battery The cathode active material particles of the present disclosure can be used as the cathode active material of a lithium-ion battery. FIG. 4 schematically illustrates the configuration of a lithium-ion battery 100 according to one embodiment. As illustrated in FIG. 4, the lithium-ion battery 100 includes a cathode active material layer 20, an electrolyte layer 30, and an anode active material layer 40. The cathode active material layer 20 includes the cathode active material particles of the present disclosure. In the lithium-ion battery 100, at least one of the cathode active material layer 20, the electrolyte layer 30, and the anode active material layer 40 may contain a solid electrolyte. Furthermore, the lithium-ion battery 100 may be a solid-state battery. A solid-state battery is one in which the electrolyte having carrier ion conductivity is primarily composed of a solid electrolyte. However, a liquid component may be included in part. Alternatively, the lithium-ion battery 100 may be an all-solid-state battery substantially free of liquid components. Alternatively, the lithium-ion battery 100 may be a liquid-based battery containing an electrolytic solution. 4, the lithium-ion battery 100 may include a positive electrode current collector 10 in contact with the positive electrode active material layer 20. The lithium-ion battery 100 may also include a negative electrode current collector 50 in contact with the negative electrode active material layer 40.

[0037] 3.1 Positive electrode current collector The positive electrode current collector 10 can be any of those commonly used as positive electrode current collectors for lithium-ion batteries. The positive electrode current collector 10 may have at least one shape selected from foil, plate, mesh, punched metal, and foam. The positive electrode current collector 10 may be made of metal foil or metal mesh. Metal foil is particularly easy to handle. The positive electrode current collector 10 may be made of multiple foils. Examples of metals constituting the positive electrode current collector 10 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, the positive electrode current collector 10 may contain Al to ensure oxidation resistance. The positive electrode current collector 10 may have a coating layer on its surface for purposes such as adjusting resistance. For example, the positive electrode current collector 10 may have a carbon coating layer. The positive electrode current collector 10 may also be a metal foil or a substrate plated or vapor-deposited with the above-mentioned metal. When the positive electrode current collector 10 is made of multiple metal foils, some layer may be present between the multiple metal foils. The thickness of the positive electrode current collector 10 is not particularly limited. For example, it may be 0.1 μm or more and 1 mm or less, with a lower limit of 1 μm or more and an upper limit of 100 μm or less.

[0038] 3.2 Cathode active material layer The positive electrode active material layer 20 includes at least the positive electrode active material particles of the present disclosure as the positive electrode active material. The positive electrode active material layer 20 may also include an electrolyte. The electrolyte may be a solid electrolyte, a liquid electrolyte, or a combination of a solid electrolyte and a liquid electrolyte. The positive electrode active material layer 20 may also include one or both of a conductive additive and a binder. The positive electrode active material layer 20 may also include an electrolyte and one or both of a conductive additive and a binder. The positive electrode active material layer 20 may also include an electrolyte, a conductive additive, and a binder. The positive electrode active material layer 20 may also include various additives. The contents of the positive electrode active material, electrolyte, conductive additive, binder, and the like in the positive electrode active material layer 20 may be determined appropriately depending on the desired performance. For example, the content of the positive electrode active material (the total of the positive electrode active material particles of the present disclosure and other positive electrode active materials) may be 40% by mass or more, 50% by mass or more, or 60% by mass or more, or 100% by mass or less, or 90% by mass or less, where the entire positive electrode active material layer 20 (total solid content) is taken as 100% by mass. The shape of the positive electrode active material layer 20 is not particularly limited, and may be, for example, a sheet-like positive electrode active material layer 20 having a substantially flat surface. The thickness of the positive electrode active material layer 20 is not particularly limited, and may be, for example, 0.1 μm or more or 1 μm or more, and 2 mm or less or 1 mm or less.

[0039] 3.2.1 Cathode active material The positive electrode active material layer 20 may contain only the positive electrode active material particles of the present disclosure as the positive electrode active material. Alternatively, the positive electrode active material layer 20 may contain, in addition to the positive electrode active material particles of the present disclosure, a different type of positive electrode active material (another positive electrode active material). From the viewpoint of further enhancing the effects of the technology of the present disclosure, the content of the other positive electrode active material in the positive electrode active material layer 20 may be small. For example, when the total positive electrode active material contained in the positive electrode active material layer 20 is taken as 100% by mass, the content of the positive electrode active material derived from the positive electrode active material particles 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.

[0040] Other positive electrode active materials may be any known positive electrode active material for lithium ion batteries. Among known active materials, a material with a relatively noble potential (charge / discharge potential) for absorbing and releasing lithium ions may be used as the positive electrode active material, and a relatively base material may be used as the negative electrode active material. The other positive electrode active material may be, for example, at least one selected from various lithium-containing compounds, elemental sulfur, and sulfur compounds. The lithium-containing compound as the positive electrode active material may be a lithium-containing oxide containing at least one element M, Li, and O. The element M may be, for example, at least one selected from Mn, Ni, Co, Al, Mg, Ca, Sc, V, Cr, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, Bi, Fe, and Ti, or at least one selected from the group consisting of Mn, Ni, Co, Al, Fe, and Ti. More specifically, the lithium-containing oxides include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium cobalt manganese oxide, and lithium nickel cobalt manganese oxide (Li 1±α Ni x Co y Mn z O 2±δ(For example, 0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1)), a spinel-type lithium compound (Li 1+x Mn 2-x-y M y O4 (where M is one or more selected from Al, Mg, Co, Fe, Ni, and Zn), such as a hetero-element substituted Li-Mn spinel with a composition represented by it), lithium nickel cobalt aluminate (for example, Li 1±α Ni p Co q Al r O 2±δ (For example, p + q + r = 1)), lithium titanate, lithium metal phosphate (such as LiMPO4, where M is one or more selected from Fe, Mn, Co, and Ni), etc. may be at least one selected from these. Other cathode active materials may include, as constituent elements, at least one of Ni, Co, and Mn, Li, and a lithium-containing oxide containing O. Alternatively, other cathode active materials may include, as constituent elements, at least one of Ni, Co, and Al, Li, and a lithium-containing oxide containing O. Only one kind of other cathode active material may be used alone, or two or more kinds may be used in combination.

[0041] The shape of other cathode active materials may be a general shape as a cathode active material of a lithium-ion battery. Other cathode active materials may be, for example, particulate. Other cathode active materials may have voids and may be, for example, porous or hollow. Other cathode active materials may be primary particles or secondary particles aggregated from a plurality of primary particles. The average particle diameter D50 of other cathode active materials may be, for example, 1 nm or more and 500 μm or less, the lower limit may be 5 nm or more or 10 nm or more, and the upper limit may be 100 μm or less, 50 μm or less, or 30 μm or less. Incidentally, the average particle diameter D50 is the particle diameter (median diameter) at the integrated value of 50% in the volume-based particle size distribution determined by the laser diffraction / scattering method.

[0042] 3.2.2 Protective Layer An ion-conductive protective layer may be formed on the surface of the positive electrode active material (the above-described positive electrode active material particles of the present disclosure or other positive electrode active materials). That is, the positive electrode active material layer 20 may include a composite of the positive electrode active material and a protective layer, and at least a portion of the surface of the positive electrode active material in the composite may be covered with a protective layer. This, for example, makes it easier to suppress reactions between the positive electrode active material and other battery materials (such as the sulfide solid electrolyte described below). The ion-conductive protective layer may include various ion-conductive compounds. The ion-conductive compound may be, for example, at least one selected from ion-conductive oxides, ion-conductive halides, and the like.

[0043] The ion-conductive oxide may contain, for example, at least one element selected from B, C, Al, Si, P, S, Ti, La, Zr, Nb, Mo, Zn, and W, Li, and O. The ion-conductive oxide may also be an oxynitride containing N. More specifically, the ion-conductive oxide may be Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, or Li4Ti5O. 12 , Li2Ti2O5, Li2ZrO3, LiNbO3, Li2MoO4, Li2WO4, LiPON, Li2O-LaO2, Li2O-ZnO2, etc. The ion-conductive oxide may be one in which some elements are substituted with various doping elements.

[0044] The ion-conductive halide may be, for example, at least one of the various compounds exemplified as halide solid electrolytes described below. The ion-conductive halide may contain, for example, at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sn, Al, Sc, Ga, Bi, Sb, Zr, Hf, Ti, Ta, Nb, W, Y, Gd, Tb, and Sm, at least one halogen element selected from the group consisting of Cl, Br, I, and F, and Li. The ion-conductive halide may contain at least one element selected from the group consisting of Ti, Al, Gd, Ca, Zr, and Y, at least one element selected from the group consisting of Cl, Br, I, and F, and Li. The ion-conductive halide may also contain at least one element selected from the group consisting of Ti and Al, at least one element selected from the group consisting of Cl, Br, I, and F, and Li. The ion-conductive halide may also be, for example, a complex halide of Li, Ti, Al, and F.

[0045] The coverage (area ratio) of the protective layer with respect to the surface of the positive electrode active material may be, for example, 70% or more, 80% or more, or 90% or more. The thickness of the protective layer may be, for example, 0.1 nm or more and 100 nm or less, with a lower limit of 1 nm or more and an upper limit of 20 nm or less.

[0046] 3.2.3 Electrolytes The positive electrode active material layer 20 may contain an electrolyte. The electrolyte that may be contained in the positive electrode active material layer 20 may be a solid electrolyte, a liquid electrolyte, or a combination of a solid electrolyte and a liquid electrolyte.

[0047] 3.2.3.1 Solid electrolyte The solid electrolyte may be any known solid electrolyte for lithium-ion batteries. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, inorganic solid electrolytes have excellent ionic conductivity and heat resistance. Examples of inorganic solid electrolytes include oxide solid electrolytes, sulfide solid electrolytes, and ionically bonded inorganic solid electrolytes. Among inorganic solid electrolytes, sulfide solid electrolytes, especially sulfide solid electrolytes containing at least Li, S, and P as constituent elements, have high performance. Among inorganic solid electrolytes, ionically bonded solid electrolytes, especially solid electrolytes containing at least Li, Y, and a halogen (at least one of Cl, Br, I, and F) as constituent elements, have high performance. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may be particulate. The average particle diameter (D50) of the solid electrolyte may be, for example, 10 nm or more and 10 μm or less. The average particle diameter D50 referred to in this application is the particle diameter (median diameter) at 50% of the cumulative value in the volume-based particle size distribution determined by a laser diffraction / scattering method. The ionic conductivity of the solid electrolyte at 25°C is, for example, 1×10 -5 S / cm or more, 1×10 -4 S / cm or more, or 1×10 -3 The solid electrolyte may be used singly or in combination of two or more.

[0048] The oxide solid electrolyte is lithium lanthanum zirconate, LiPON, Li 1+X Al X Ge 2-X It may be one or more selected from (PO4)3, Li-SiO-based glass, Li-Al-SO-based glass, etc. Furthermore, when an oxide solid electrolyte is combined with a liquid electrolyte, ionic conductivity can be improved.

[0049] The sulfide solid electrolyte may be a glass-based sulfide solid electrolyte (sulfide glass), a glass-ceramic-based sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. The sulfide glass is amorphous. The sulfide glass may have a glass transition temperature (Tg). When the sulfide solid electrolyte has a crystalline phase, examples of the crystalline phase include a Thio-LISICON-type crystalline phase, an LGPS-type crystalline phase, and an Argyrodite-type crystalline phase.

[0050] The sulfide solid electrolyte may contain, for example, Li, X (X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. The sulfide solid electrolyte may further contain at least one of O and a halogen element. The sulfide solid electrolyte may also contain S as a main anion element.

[0051] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-GeS2, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-LiI-LiBr, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (where m and n are positive numbers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is any one of P, Si, Ge, B, Al, Ga, and In).

[0052] The composition of the sulfide solid electrolyte is not particularly limited. For example, xLi2S·(100 - x)P2S5 (70 ≤ x ≤ 80), yLiI·zLiBr·(100 - y - z)(xLi2S·(1 - x)P2S5) (0.7 ≤ x ≤ 0.8, 0 ≤ y ≤ 30, 0 ≤ z ≤ 30), etc. may be mentioned. Alternatively, the sulfide solid electrolyte has a composition represented by the general formula: Li 4-x Ge 1-x P x S4 (0 < x < 1). In the above general formula, at least a part of Ge may be substituted with at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the above general formula, at least a part of P may be substituted with at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the above general formula, a part of Li may be substituted with at least one of Na, K, Mg, Ca, and Zn. In the above general formula, a part of S may be substituted with a halogen (at least one of F, Cl, Br, and I). Alternatively, the sulfide solid electrolyte is Li 7-a PS 6-a X a (X is at least one of Cl, Br, and I, and a is a number of 0 or more and 2 or less). a may be 0, or may be greater than 0. In the latter case, a may be 0.1 or more, may be 0.5 or more, and may be 1 or more. Also, a may be 1.8 or less, and may be 1.5 or less.)

[0053] The ionically bonded solid electrolyte may contain, for example, at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sn, Al, Sc, Ga, Bi, Sb, Zr, Hf, Ti, Ta, Nb, W, Y, Gd, Tb, and Sm. These elements can generate cations in water. The ionically bonded solid electrolyte material may further contain, for example, at least one halogen element selected from the group consisting of Cl, Br, I, and F. These elements can generate anions in water. The ionically bonded solid electrolyte may contain at least one element selected from the group consisting of Gd, Ca, Zr, and Y, at least one element selected from the group consisting of Cl, Br, I, and F, and Li. The ionically bonded solid electrolyte may also contain Li and Y, and at least one element selected from the group consisting of Cl, Br, I, and F. More specifically, the ionic solid electrolyte may contain Li, Y, Cl, and Br, or may contain Li, Ca, Y, Gd, Cl, and Br, or may contain Li, Zr, Y, and Cl. Even more specifically, the ionic solid electrolyte may be Li3YBr2Cl4, Li 2.8 Ca 0.1 Y 0.5 Gd 0.5 Br2Cl4 and Li 2.5 Y 0.5 Zr 0.5 It may be at least one of Cl6.

[0054] The ionically bonded solid electrolyte may be a halide solid electrolyte. The halide solid electrolyte has excellent ion conductivity. Examples of the halide solid electrolyte include a halide solid electrolyte represented by the formula (1): Li α M β X γ (A) It may have a composition represented by Here, α, β, and γ are each independently values greater than 0, M is at least one selected from the group consisting of metal elements other than Li and metalloid elements, and X is at least one selected from the group consisting of Cl, Br, and I. Note that the "metalloid element" may be at least one selected from the group consisting of B, Si, Ge, As, Sb, and Te. Further, the "metal element" may include (i) all elements contained in Groups 1 to 12 of the periodic table (excluding hydrogen) and (ii) all elements contained in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se). The metal element can form an inorganic compound with a halide ion and become a cation.

[0055] In formula (A), M may contain Y (i.e., yttrium). The halide solid electrolyte containing Y is Li a Me b Y c It may have a composition represented by X6 (where a + mb + 3c = 6, c > 0, Me is at least one selected from the group consisting of metal elements and metalloid elements other than Li and Y, and m is the valence of Me). Me may be at least one selected from the group consisting of, for example, Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0056] The halide solid electrolyte may have a composition represented by formula (A1): Li 6-3d Y d X6. In formula (A1), X is one or more elements selected from the group consisting of Cl, Br, and I. d may satisfy 0 < d < 2, or d may be 1. The halide solid electrolyte may have a composition represented by formula (A2): Li 3-3δ Y 1+δ Cl6. In formula (A2), 0 < δ ≦ 0.15 may hold. The halide solid electrolyte may have a composition represented by formula (A3): Li 3-3δ Y 1+δIt may have a composition represented by Br6. In formula (A3), 0 < δ ≦ 0.25 may also be applicable. The halide solid electrolyte has the formula (A4): Li 3-3δ+a Y 1+δ-a Me a Cl 6-x-y Br x I y and may have a composition represented by the formula. In formula (A4), Me may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, and Zn. In formula (A4), for example, -1 < δ < 2, 0 < a < 3, 0 < (3 - 3δ + a), 0 < (1 + δ - a), 0 ≦ x ≦ 6, 0 ≦ y ≦ 6, and (x + y) ≦ 6 are satisfied. The halide solid electrolyte has the formula (A5): Li 3-3δ Y 1+δ-a Me a Cl 6-x-y Br x I y and may have a composition represented by the formula. In formula (A5), Me may be at least one selected from the group consisting of Al, Sc, Ga, and Bi. In formula (A5), -1 < δ < 1, 0 < a < 2, 0 < (1 + δ - a), 0 ≦ x ≦ 6, 0 ≦ y ≦ 6, and (x + y) ≦ 6 may also be applicable. The halide solid electrolyte has the formula (A6): Li 3-3δ-a Y 1+δ-a Me a Cl 6-x-y Br x I y and may have a composition represented by the formula. In formula (A6), Me may be at least one selected from the group consisting of Zr, Hf, and Ti. In formula (A6), -1 < δ < 1, 0 < a < 1.5, 0 < (3 - 3δ - a), 0 < (1 + δ - a), 0 ≦ x ≦ 6, 0 ≦ y ≦ 6, and (x + y) ≦ 6 may also be applicable. The halide solid electrolyte has the formula (A7): Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x-y Br x I yIn formula (A7), Me may be at least one selected from the group consisting of Ta and Nb. In formula (A7), -1<δ<1, 0 <a<1.2、0<(3-3δ-2a)、0<(1+δ-a)、0≦x≦6、0≦y≦6、かつ、(x+y)≦6であってもよい。

[0057] The ionic solid electrolyte may be a complex hydride solid electrolyte. The complex hydride solid electrolyte may be composed of Li ions and complex ions containing H. The complex ions containing H may have, for example, an element M containing at least one of a nonmetal element, a semimetal element, and a metal element, and H bonded to the element M. In addition, the complex ions containing H may have the element M as a central element and H surrounding the element M bonded to each other via a covalent bond. In addition, the complex ions containing H may be composed of (M m H n ) α- In this case, m is any positive number, and n and α can be any positive number depending on m and the valence of element M. Element M may be any nonmetallic element or metallic element capable of forming a complex ion. For example, element M may contain at least one of B, C, and N as a nonmetallic element, or may contain B. Furthermore, for example, element M may contain at least one of Al, Ni, and Fe as a metallic element. In particular, when the complex ion contains B or when it contains C and B, higher ionic conductivity is likely to be ensured. Specific examples of complex ions containing H include (CBH 10 ) - , (CB 11 H 12 ) - , (B 10 H 10 ) 2- , (B 12 H 12 ) 2- , (BH4) - , (NH2) - , (AlH4) - , and combinations thereof. In particular, (CB9H 10 ) - , (CB 11H 12 ) - In other words, the complex hydride solid electrolyte may contain Li, C, B, and H.

[0058] 3.2.3.2 Liquid electrolyte The liquid electrolyte (electrolytic solution) is a liquid containing lithium ions as carrier ions. The electrolytic solution may be an aqueous electrolytic solution or a non-aqueous electrolytic solution. The composition of the electrolytic solution may be the same as known compositions of electrolytic solutions for lithium ion secondary batteries. The electrolytic solution may be one in which a lithium salt is dissolved in water or a non-aqueous solvent. Examples of non-aqueous solvents include carbonate-based solvents. Examples of carbonate-based solvents include fluoroethylene carbonate (FEC), ethylene carbonate (EC), dimethyl carbonate (DMC), and propylene carbonate (PC). Examples of lithium salts include LiPF6, LiTFSI, and LiFSI.

[0059] 3.2.4 Conductive additives Examples of conductive additives that can be contained in the positive electrode active material layer 20 include carbon materials such as vapor grown carbon fiber (VGCF), acetylene black (AB), ketjen black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF); and metal materials such as nickel, titanium, aluminum, and stainless steel. The conductive additive may be, for example, particulate or fibrous, and its size is not particularly limited. Only one type of conductive additive may be used alone, or two or more types may be used in combination.

[0060] 3.2.5 Binder Examples of binders that can be contained in the positive electrode active material layer 20 include butadiene rubber (BR)-based binders, butylene rubber (IIR)-based binders, acrylate butadiene rubber (ABR)-based binders, styrene butadiene rubber (SBR)-based binders, polyvinylidene fluoride (PVdF)-based binders, polytetrafluoroethylene (PTFE)-based binders, polyimide (PI)-based binders, etc. Only one type of binder may be used alone, or two or more types may be used in combination.

[0061] 3.2.6 Other The positive electrode active material layer 20 may contain various additives in addition to the above components, such as a dispersant and a lubricant.

[0062] The positive electrode active material layer 20 can be manufactured by applying a known method. For example, the positive electrode active material layer 20 can be easily formed by dry or wet molding a positive electrode composite containing the positive electrode active material particles and the like of the present disclosure. The positive electrode active material layer 20 may be molded together with the positive electrode current collector 10 or may be molded separately from the positive electrode current collector 10.

[0063] 3.3 Electrolyte layer The electrolyte layer 30 is disposed between the positive electrode active material layer 20 and the negative electrode active material layer 40. The electrolyte layer 30 contains at least an electrolyte. The electrolyte layer 30 may contain one or both of a solid electrolyte and a liquid electrolyte (electrolytic solution), and may further contain a binder and various additives. The contents of the electrolyte and binder in the electrolyte layer 30 are not particularly limited. Alternatively, the electrolyte layer 30 may include a separator or the like for retaining the electrolytic solution and preventing contact between the positive electrode active material layer 20 and the negative electrode active material layer 40. The thickness of the electrolyte layer 30 is not particularly limited and may be, for example, 0.1 μm or more and 2 mm or less, with a lower limit of 1 μm or more and an upper limit of 1 mm or less.

[0064] The electrolyte layer 30 may consist of one layer or multiple layers. For example, the electrolyte layer 30 may include a first layer disposed on the positive electrode active material layer 20 side and a second layer disposed on the negative electrode active material layer 40 side, where the first layer may contain a first electrolyte and the second layer may contain a second electrolyte. The first electrolyte and the second electrolyte may be different from each other. The first electrolyte and the second electrolyte may each be at least one selected from the oxide solid electrolyte, sulfide solid electrolyte, and ionic solid electrolyte described above. For example, the first layer may contain an ionic solid electrolyte, and the second layer may contain at least one of an ionic solid electrolyte and a sulfide solid electrolyte.

[0065] The electrolyte contained in the electrolyte layer 30 may be appropriately selected from the examples (solid electrolytes and / or liquid electrolytes) of the electrolytes that can be contained in the positive electrode active material layer 20 described above. The binder that can be contained in the electrolyte layer 30 may also be appropriately selected from the examples of the binders that can be contained in the positive electrode active material layer 20 described above. Each of the electrolytes and binders may be used alone or in combination of two or more. The separator may be any separator commonly used in secondary batteries, such as 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 multi-layer separators include a two-layer structure of PE / PP, or a three-layer structure of PP / PE / PP or PE / PP / PE. The separator may be made of a nonwoven fabric such as a cellulose nonwoven fabric, a resin nonwoven fabric, or a glass fiber nonwoven fabric.

[0066] 3.4 Negative electrode active material layer The negative electrode active material layer 40 includes at least a negative electrode active material. The negative electrode active material layer 40 may also optionally include an electrolyte, a conductive additive, a binder, various additives, and the like. The content of each component in the negative electrode active material layer 40 may be appropriately determined depending on the desired battery performance. For example, the total solid content of the negative electrode active material layer 40 is taken as 100% by mass, and 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, or may be 100% by mass or less, less than 100% by mass, 95% by mass or less, or 90% by mass or less. Alternatively, the total content of the negative electrode active material layer 40, taken as 100% by volume, may be 85% by volume or more, 90% by volume or more, or 95% by volume or more, and the remainder may be voids or other components. The shape of the negative electrode active material layer 40 is not particularly limited and may be, for example, a substantially flat sheet. The thickness of the negative electrode active material layer 40 is not particularly limited and may be, for example, 0.1 μm to 2 mm, with a lower limit of 1 μm, 10 μm, or 30 μm, and an upper limit of 1 mm, 500 μm, or 100 μm.

[0067] 3.4.1 Negative electrode active material The negative electrode active material contained in the negative electrode active material layer 40 may be any of those known as negative electrode active materials for lithium ion batteries. Among known active materials, various materials may be used that have a potential (charge / discharge potential) at which they absorb and release predetermined carrier ions that is lower than that of the positive electrode active material. The negative electrode active material may be at least one selected from, 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, and the like. Only one type of negative electrode active material may be used alone, or two or more types may be used in combination. The negative electrode active material may have any shape commonly used for negative electrode active materials for lithium ion batteries. 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 formed by agglomeration of multiple primary particles. The average particle diameter (D50) of the negative electrode active material particles may be, for example, 1 nm or more and 500 μm or less, with a lower limit of 5 nm or more or 10 nm or more and an upper limit of 100 μm or less, 50 μm or less, or 30 μm or less. Alternatively, the negative electrode active material layer 40 may be made of a sheet-like (foil-like, film-like) active material such as lithium foil.

[0068] 3.4.2 Other The electrolyte that can be contained in the anode active material layer 40 may be appropriately selected from the examples (solid electrolytes and / or liquid electrolytes) of the electrolytes that can be contained in the cathode active material layer 20 described above. The conductive additive that can be contained in the anode active material layer 40 may be appropriately selected from the examples of the conductive additive that can be contained in the cathode active material layer 20 described above. The binder that can be contained in the anode active material layer 40 may be appropriately selected from the examples of the binders that can be contained in the cathode active material layer 20 described above. Each of the electrolyte, conductive additive, and binder may be used alone or in combination of two or more.

[0069] The negative electrode active material layer 40 may contain various additives in addition to the above components, such as a dispersant and a lubricant.

[0070] The negative electrode active material layer 40 can be manufactured by applying a known method. For example, the negative electrode active material layer 40 can be easily formed by dry or wet molding a negative electrode composite containing the above-mentioned various components. The negative electrode active material layer 40 may be molded together with the negative electrode current collector 50, or may be molded separately from the negative electrode current collector 50.

[0071] 3.5 Negative electrode current collector The negative electrode current collector 50 can be any of those commonly used as negative electrode current collectors for lithium-ion batteries. The negative electrode current collector 50 may be in the form of a foil, plate, mesh, punched metal, foam, or the like. The negative electrode current collector 50 may be a metal foil or metal mesh, or a carbon sheet. Metal foil is particularly advantageous in terms of ease of handling. The negative electrode current collector 50 may be composed of multiple foils or sheets. Examples of metals 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 less likely 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 kind of coating layer on its surface for the purpose of adjusting the resistance, etc. 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. The negative electrode current collector 50 may also be a metal foil or a substrate on which the above metal is plated or vapor-deposited. When the negative electrode current collector 50 is made of multiple sheets of metal foil, some kind of layer may be present between the multiple sheets of metal foil. The thickness of the negative electrode current collector 50 is not particularly limited. For example, it may be 0.1 μm or more and 1 mm or less, with a lower limit of 1 μm or more and an upper limit of 100 μm or less.

[0072] 3.6 Other Configurations In addition to the above components, the lithium-ion battery 100 may also include typical battery components. For example, tabs and terminals. The lithium-ion battery 100 may have the above components housed inside an exterior body. Any known battery exterior body can be used as the exterior body. Furthermore, multiple lithium-ion batteries 100 may be electrically connected and stacked in any desired manner to form an assembled battery. In this case, the assembled battery may be housed inside a known battery case. The lithium-ion battery 100 may also include other obvious components, such as necessary terminals. The lithium-ion battery 100 may have, for example, a coin type, a laminate type, a cylindrical type, or a rectangular type. The lithium-ion battery 100 may also be a secondary battery.

[0073] 4. Lithium-ion battery manufacturing method The lithium ion battery 100 can be manufactured by applying a known method. For example, the lithium ion battery 100 can be manufactured as follows. However, the manufacturing method of the lithium ion battery 100 is not limited to the following method, and each layer may be formed by, for example, dry molding or the like. (1) A positive electrode active material constituting a positive electrode active material layer is dispersed in a solvent to obtain a positive electrode slurry. The solvent used in this case is not particularly limited, and water or various organic solvents can be used. The positive electrode slurry is then applied to the surface of a positive electrode current collector or an electrolyte layer (described later) using a doctor blade or the like, and then dried to form a positive electrode active material layer on the surface of the positive electrode current collector or the electrolyte layer, thereby forming a positive electrode. Here, the positive electrode active material layer may be press-molded. (2) The negative electrode active material constituting the negative electrode active material layer is dispersed in a solvent to obtain a negative electrode slurry. The solvent used in this case is not particularly limited, and water or various organic solvents can be used. The negative electrode slurry is then applied to the surface of the negative electrode current collector or the electrolyte layer described below using a doctor blade or the like, and then dried to form a negative electrode active material layer on the surface of the negative electrode current collector or the electrolyte layer, thereby forming a negative electrode. Here, the negative electrode active material layer may be press-molded. (3) The layers are stacked so that the electrolyte layer is sandwiched between the negative electrode and the positive electrode, thereby obtaining 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. The electrolyte layer may be obtained, for example, by molding an electrolyte mixture containing an electrolyte and a binder, or by press molding. Here, the laminate may be further press-molded. Other members such as terminals may be attached to the laminate as necessary. When an electrolytic solution is used, a separator may be used in the electrolyte layer. (4) The laminate is housed in a battery case and sealed to obtain a lithium ion battery.

[0074] 5. How to increase the capacity of a lithium-ion battery The technology of the present disclosure also has an aspect as a method for increasing the capacity of a lithium ion battery. That is, the method for increasing the capacity of a lithium ion battery of the present disclosure is characterized by using the above-described positive electrode active material particles of the present disclosure in a positive electrode active material layer of the lithium ion battery.

[0075] 6. Vehicles with lithium-ion batteries As described above, when a positive electrode active material layer of a lithium-ion battery is formed using the positive electrode mixture of the present disclosure, an increase in the capacity of the lithium-ion battery can be expected. Such a lithium-ion battery can be suitably used in at least one type of vehicle selected from, for example, a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and an electric vehicle (BEV). That is, the technology of the present disclosure also has an aspect of a vehicle having a lithium-ion battery, the lithium-ion battery having a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, and the positive electrode active material layer containing the positive electrode active material particles of the present disclosure. [Example]

[0076] As described above, one embodiment of the positive electrode active material layer, the lithium ion secondary battery, and the manufacturing method thereof according to the present disclosure has been described, but the technology of the present disclosure can be modified in various ways other than the above embodiment without departing from the gist thereof. Below, the technology of the present disclosure will be described in more detail with reference to examples, but the technology of the present disclosure is not limited to the following examples.

[0077] 1. Preparation of Precursor Particles MnSO4·5H2O, NiSO4·6H2O, and CoSO4·7H2O were weighed to achieve the desired composition ratio and dissolved in distilled water to a concentration of 1.2 mol / L to obtain the first solution. In a separate container, Na2CO3 was dissolved in distilled water to a concentration of 1.2 mol / L to obtain the second solution. Next, 500 mL of each of the first and second solutions was added dropwise at a rate of approximately 4 mL / min to a reaction vessel containing 1000 mL of pure water. After the addition, the mixture was stirred at room temperature for 1 hour at a stirring speed of 150 rpm. The precipitate was washed with pure water and subjected to solid-liquid separation using a centrifuge. The resulting precipitate was dried overnight at 120°C, crushed in a mortar, and then air-classified to remove fine particles, yielding mixed salt particles (precursor particles) containing Mn, Ni, and Co. The precursor particles were spherical with a circularity of 0.80.

[0078] 2. Preparation of Na-containing transition metal oxide particles with P2-type structure 2.1 Spherical (Examples 1 and 2 and Comparative Example 1) After weighing out Na2CO3 and distilled water to a concentration of 150 g / L, the mixture was stirred using a stirrer until completely dissolved to prepare an aqueous Na2CO3 solution. The precursor particles were mixed into the aqueous Na2CO3 solution to form a slurry. After drying, the Na2CO3 and the precursor particles were mixed into a Na 0.7 Mn 0.5 Ni 0.2 Co 0.3 The resulting slurry was dried by spray drying. Specifically, a spray drying apparatus DL410 was used, with a slurry delivery rate of 30 mL / min, an inlet temperature of 200°C, and a circulating air volume of 0.8 m 3 / min and a spray air pressure of 0.3 MPa, 90 area % of the surface of the precursor particles was coated with Na2CO3 to obtain coated particles.

[0079] The coated particles were fired in an electric furnace using an alumina crucible in an air atmosphere. Specifically, the coated particles were subjected to the "first heating step," "pre-firing step," "second heating step," "main firing step," "in-furnace cooling step," and "out-furnace cooling step" as shown in Table 1 below and FIG. 5. The "in-furnace cooling step" refers to a cooling step in an electric furnace, and the "out-furnace cooling step" refers to a step of cooling in the air outside the electric furnace. Thereafter, the particles were pulverized in a mortar in a dry atmosphere to obtain a Na-containing transition metal oxide (Na 0.7 Mn 0.5 Ni 0.2 Co 0.3 The Na-containing transition metal oxide was spherical particles with a circularity of 0.82.

[0080] 2.2 In the case of plate-like form (Reference Example 1 and Comparative Example 2) Na2CO3 and the above precursor particles were mixed 0.7 Mn 0.5 Ni 0.2 Co 0.3 The materials were weighed in a dry atmosphere to have a composition of 02, and mixed in a mortar to obtain a mixture. The mixture was fired in an electric furnace using an alumina crucible under an air atmosphere. Specifically, the mixture was subjected to the "first heating step," "pre-firing step," "second heating step," "main firing step," "in-furnace cooling step," and "out-furnace cooling step" as shown in Table 1 and Figure 5 below. Thereafter, the mixture was pulverized in a mortar in a dry atmosphere to obtain a Na-containing transition metal oxide (Na 0.7 Mn 0.5 Ni 0.2 Co 0.3 O2) was obtained. The Na-containing transition metal oxide was in the form of plate-like particles.

[0081] [Table 1]

[0082] 3. Preparation of active materials with O2-type structures 3.1 Example 1 and Reference Example 1 LiOH and LiCl were weighed out to a molar ratio of 65:35, and mixed with P2-type spherical particles (Example 1) or P2-type plate-like particles (Reference Example 1) in a molar ratio 10 times the minimum Li amount required for ion exchange to obtain a mixture. The mixture was fired in an alumina crucible at 300°C for 4 hours in an air atmosphere to obtain a fired product. The salt remaining in the fired product was washed with pure water, and solid-liquid separation was performed by vacuum filtration to obtain a precipitate. The precipitate was dried overnight at 120°C to obtain positive electrode active material particles having an O2-type structure.

[0083] 3.2 Example 2 LiOH and LiNO3 were weighed out to a molar ratio of 60:40 and mixed with P2-type spherical particles at a molar ratio 10 times the minimum Li amount required for ion exchange to obtain a mixture. The mixture was fired in an alumina crucible at 300°C for 1 hour in an air atmosphere to obtain a fired product. The salt remaining in the fired product was washed with pure water, and solid-liquid separation was performed by vacuum filtration to obtain a precipitate. The precipitate was dried overnight at 120°C to obtain positive electrode active material particles with an O2-type structure.

[0084] 3.3 Comparative Examples 1 and 2 LiCl and LiNO3 were weighed out to a molar ratio of 50:50 and mixed with P2-type spherical particles (Comparative Example 1) or P2-type plate-like particles (Comparative Example 2) at a molar ratio 10 times the minimum Li amount required for ion exchange to obtain a mixture. The mixture was fired in an alumina crucible at 280°C for 1 hour in an air atmosphere to obtain a fired product. The salt remaining in the fired product was washed with pure water, and solid-liquid separation was performed by vacuum filtration to obtain a precipitate. The precipitate was dried overnight at 120°C to obtain positive electrode active material particles having an O2-type structure.

[0085] 3.4 Supplementary information on ion exchange conditions The ion exchange conditions for Examples 1 and 2, Comparative Examples 1 and 2, and Reference Example 1 are summarized in Table 2 below.

[0086] [Table 2]

[0087] 4. Observation of the external shape of positive electrode active material particles 6A to 6E show SEM images of the positive electrode active material particles of Examples 1 and 2, Comparative Examples 1 and 2, and Reference Example 1. FIG. 6A shows Example 1, FIG. 6B shows Example 2, FIG. 6C shows Comparative Example 1, FIG. 6D shows Comparative Example 2, and FIG. 6E shows Reference Example 1. As shown in FIGS. 6D and 6E, when plate-shaped P2-type particles were used, the positive electrode active material particles having an O2-type structure obtained after ion exchange were also plate-shaped. On the other hand, as shown in FIGS. 6A to 6C, when spherical P2-type particles were used, the positive electrode active material particles having an O2-type structure obtained after ion exchange were also spherical. The circularity of the positive electrode active material particles of Example 1 was 0.83, the circularity of the positive electrode active material particles of Example 2 was 0.81, and the circularity of the positive electrode active material particles of Comparative Example 1 was 0.85. The plate-shaped O2-type positive electrode active material particles were substantially composed of a single crystallite. On the other hand, the surface of the spherical O2-type positive electrode active material particles was composed of multiple crystallites, each of which had a diameter of less than 1 μm and had a first surface exposed on the particle surface, and the first surface was planar.

[0088] 5. Crystal structure of positive electrode active material particles X-ray diffraction measurements were performed on the positive electrode active material particles of each of Examples 1 and 2, Comparative Examples 1 and 2, and Reference Example 1. The results are shown in Figure 7. As shown in Figure 7, all of the positive electrode active material particles had an O2-type crystal structure.

[0089] 6. Elemental analysis of positive electrode active material particles Elemental analysis by ICP was carried out on the positive electrode active material particles of each of Examples 1 and 2, Reference Example 1, and Comparative Examples 1 and 2. The results are shown in Table 3 below.

[0090] [Table 3]

[0091] 7. Preparation of Cell for Evaluation Coin cells were produced using the positive electrode active material particles of each of Examples 1 and 2, Comparative Examples 1 and 2, and Reference Example 1. The coin cells were produced according to the following procedure. (1) Positive electrode active material particles, acetylene black (AB) as a conductive additive, and polyvinylidene fluoride (PVdF) as a binder were weighed out in a mass ratio of positive electrode active material particles:AB:PVdF = 85:10:5, and dispersed and mixed in N-methyl-2-pyrrolidone to obtain a positive electrode composite slurry. The positive electrode composite slurry was coated onto aluminum foil and vacuum dried overnight at 120°C to obtain a positive electrode, which is a laminate of a positive electrode active material layer and a positive electrode current collector. (2) TDDK-217 (manufactured by Daikin Corporation) was prepared as the electrolyte. (3) Metallic lithium foil was prepared as the negative electrode. (4) A coin cell (CR2032) was fabricated using the positive electrode, electrolyte, and negative electrode.

[0092] 8.Charge / Discharge Characteristics Evaluation In a thermostatic bath maintained at 25°C, the cells were charged at 0.1C (1C = 270 mA / g for Examples 1 and 2 and Reference Example 1, and 1C = 220 mA / g for Comparative Examples 1 and 2) in the voltage range of 2.0-4.8V, and then discharged at 0.5C, 1C, or 3C, and the discharge capacity at each rate was measured. The results of the initial charge-discharge curves are shown in Figures 8A to 8E. Figure 8A is Example 1, Figure 8B is Example 2, Figure 8C is Comparative Example 1, Figure 8D is Comparative Example 2, and Figure 8E is Reference Example 1. The rate characteristics of each cell are shown in Figure 9.

[0093] 9. Evaluation Results The results shown in Table 3, FIGS. 6A to 6E, FIG. 7, FIGS. 8A to 8E, and FIG. 9 reveal the following. (1) As shown in Table 3 and FIG. 7, the positive electrode active material particles according to Examples 1 and 2 and Reference Example 1 have an O2-type structure and contain an excessive amount of Li (1.0 < a). On the other hand, the positive electrode active material particles according to Comparative Examples 1 and 2 have an O2-type structure and contain a small amount of Li (a < 0.7). For Examples 1 and 2 and Reference Example 1, since lithium hydroxide was used in combination with a lithium salt as the ion exchange material, ion exchange was promoted, and it is considered that Li-excess positive electrode active material particles were obtained. (2) As shown in FIGS. 8A to 8E, the cells according to Examples 1 and 2 and Reference Example 1 have better initial charge capacity and initial discharge capacity than the cells according to Comparative Examples 1 and 2. It is considered that the cells according to Examples 1 and 2 and Reference Example 1 have a higher initial charge capacity because the amount of Li that can be supplied to the negative electrode during the first charge is larger than that of the cells according to Comparative Examples 1 and 2. Further, when a < 0.7 as in Comparative Examples 1 and 2, it is considered that the elements whose valence changes during Li insertion (discharge) into the positive electrode active material are Ni, Mn, and Co. On the other hand, in the case of the Li-excess positive electrode active material where 1.0 < a as in Examples 1 and 2 and Reference Example 1, it is considered that oxygen contributes in addition to Ni, Mn, and Co. Therefore, it is considered that the cells according to Examples 1 and 2 and Reference Example 1 have a higher initial discharge capacity than the cells according to Comparative Examples 1 and 2. (3) As shown in FIG. 9, it can be seen that the cells according to Examples 1 and 2 have a smaller difference between the capacity at low-rate discharge and the capacity at high-rate discharge than the cells according to Reference Example 1, and can maintain a large capacity even during high-rate discharge. That is, the cells according to Examples 1 and 2 are superior in rate characteristics to the cells according to Reference Example 1. The spherical positive electrode active material particles according to Examples 1 and 2 (FIGS. 6A and 6B) are considered to have suppressed growth of crystallites, smaller crystallites, reduced reaction resistance, and reduced diffusion resistance inside the active material compared to the plate-like positive electrode active material particles according to Reference Example 1 (FIG. 6E). Further, it is considered that the degree of bending is reduced by spheroidization, and the lithium ion conduction resistance in the layer constituting the positive electrode is reduced. As a result, it is considered that the rate characteristics are improved.

[0094] Supplementary Furthermore, in the above examples, the cathode active material particles having a specific chemical composition were exemplified, but the chemical composition of the cathode active material particles of the present disclosure is not limited thereto. For example, the cathode active material particles may contain other element M other than Ni, Mn, and Co for the purpose of stabilizing the crystal structure or the like. The element M is as described above.

[0095] Also, in the above examples, the case of manufacturing the cathode active material particles at a specific ion exchange temperature and ion exchange time was exemplified, but the ion exchange temperature and ion exchange time are not limited thereto. As far as the present inventors have confirmed, cathode active material particles having an O2-type crystal structure are more appropriately easily manufactured at an ion exchange temperature of 270 ° C or higher and 320 ° C or lower and an ion exchange time of 1 hour or longer and 8 hours or shorter.

[0096] 11. Summary From the above examples, it can be said that the cathode active material particles satisfying the following requirements (1) to (3) have excellent rate characteristics and capacity. (1) The cathode active material particles have an O2-type structure. (2) The cathode active material particles are Li a Na b Mn x-p Ni y-q Co z-r M p+q+r It has a chemical composition represented by O2 (where 1.0 <a <: 1.30, 0 ≦ b ≦ 0.20, x + y + z = 1, and 0 ≦ p + q + r ≦ 0.15, 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). (3) The cathode active material particles are spherical.

[0097] Also, from the above examples and reference examples, it can be said that the Li-excess type O2-type cathode active material particles can be manufactured by a method satisfying, for example, the following requirement (4). (4) A method for producing positive electrode active material particles includes obtaining Na-containing transition metal oxide particles having a P2-type structure, and contacting the Na-containing transition metal oxide particles with an ion exchange material to replace at least a portion of the Na in the Na-containing transition metal oxide particles with Li, thereby obtaining Li-containing transition metal oxide particles having an O2-type structure, wherein the ion exchange material contains lithium hydroxide and a lithium salt. [Explanation of symbols]

[0098] 100 Lithium-ion batteries 10 Positive electrode current collector 20 Cathode active material layer 30 Electrolyte layer 40 Negative electrode active material layer 50 Negative electrode current collector

Claims

1. Positive electrode active material particles, It has an O2 type structure, Li ａ Na ｂ Mn ｘ－ｐ Ni ｙ－ｑ Co ｚ－ｒ M ｐ＋ｑ＋ｒ O ２ (wherein 1.0<a<1.30, 0≦b≦0.20, x+y+z=1, and 0≦p+q+r≦0.15, 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), and It is spherical, Positive electrode active material particles.

2. The positive electrode active material particles according to claim 1 , The particle surface is composed of multiple crystallites. Positive electrode active material particles.

3. A method for producing positive electrode active material particles, comprising: Obtaining Na-containing transition metal oxide particles having a P2 type structure, and and bringing the Na-containing transition metal oxide particles into contact with an ion exchange material to replace at least a portion of the Na in the Na-containing transition metal oxide particles with Li, thereby obtaining Li-containing transition metal oxide particles having an O2-type structure. the ion exchange material comprises lithium hydroxide and a lithium salt; Manufacturing method.

4. The manufacturing method according to claim 3, The Na-containing transition metal oxide particles are spherical, and The Li-containing transition metal oxide particles are spherical. Manufacturing method.

5. The manufacturing method according to claim 3, The Na-containing transition metal oxide particles ｃ Mn ｘ－ｐ Ni ｙ－ｑ Co ｚ－ｒ M ｐ＋ｑ＋ｒ O ２ (wherein 0<c<0.70, x+y+z=1, and 0≦p+q+r≦0.15, 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). Manufacturing method.

6. The manufacturing method according to any one of claims 3 to 5, Obtaining precursor particles; coating the surface of the precursor particles with a Na salt to obtain coated particles; and and calcining the coated particles to obtain the Na-containing transition metal oxide particles. Manufacturing method.

7. The manufacturing method according to claim 6, and coating 40% or more by area of ​​the surface of the precursor particles with the Na salt to obtain the coated particles. The precursor particles are spherical. Manufacturing method.

8. A lithium ion battery having a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, The positive electrode active material layer contains the positive electrode active material particles according to claim 1 or 2. Lithium-ion battery.

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