JP7198170B2 - Positive electrode active material for all-solid lithium-ion battery, method for producing positive electrode active material for all-solid-state lithium-ion battery, and all-solid lithium-ion battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a positive electrode active material for an all-solid lithium ion battery, a method for producing a positive electrode active material for an all-solid lithium-ion battery, and an all-solid lithium-ion battery.

2. Description of the Related Art In recent years, with the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones, the development of batteries used as power sources for these devices has been emphasized. Among these batteries, lithium batteries are attracting attention because of their high energy density. High energy density and improved battery characteristics are also required for lithium secondary batteries used in large-scale applications such as power sources for vehicles and load leveling.

However, in the case of lithium-ion batteries, most of the electrolytes are organic compounds, and even if flame-retardant compounds are used, the risk of fire cannot be completely eliminated. In recent years, all-solid-state lithium-ion batteries with a solid electrolyte have been attracting attention as a candidate to replace such liquid-type lithium-ion batteries.

As a positive electrode active material for all-solid-state lithium ion batteries, there is a demand for a single-particle positive electrode active material for the reasons that it is less likely to crack when pressed in cell fabrication, and that it is easy to coat due to its smooth surface. Conventionally, a positive electrode active material such as LiCoO ₂ obtained by mixing an oxide of Co ₃ O ₄ and a Li source and firing the mixture is close to a single particle and serves as a positive electrode with less cracking during pressing. For this reason, especially in an all-solid-state battery using an oxide-based solid electrolyte, the use of this material has become mainstream.

On the other hand, ternary positive electrode active materials such as Ni--Co--Mn and Ni--Co--Al having the same layered R3-m crystal structure use a hydroxide precursor as a starting material by a coprecipitation method. However, in such a starting material, since the particles of the original hydroxide are small, even if kneading with the Li source and firing are performed, the positive electrode active material is formed with secondary particles in which fine primary particles are aggregated. Therefore, it is difficult to form single particles.

Here, as a conventional technique for producing a positive electrode active material, for example, Non-Patent Document 1 discloses a technique for producing a single-particle NiCoMn-based positive electrode active material using a coprecipitated hydroxide precursor. According to the literature, it is described that a spinel structure like an oxide of LiMn is more likely to grow grains than a layered structure like an oxide of NiCoMn even if fired at the same temperature. Then, Li corresponding to Mn in the composition of NiCoMn is added, first fired at 1000 ° C. to prepare a spinel-oxide intermediate, after that, the missing Li is added to the intermediate and heated at 900 ° C. It is described that a single-particle positive electrode can be obtained by firing.

Further, as a conventional method for producing a high-strength positive electrode active material, for example, Patent Document 1 discloses a first firing step of firing a first mixture containing a lithium compound and a transition metal compound containing nickel and manganese. and a second firing step of firing a second mixture obtained by further adding a lithium compound to the precursor particles obtained in the first firing step. The content is less than 0.5 in molar ratio with respect to the total amount of transition metals, and the content of lithium in the second mixture is 0.9 or more and 1.1 or less in molar ratio with respect to the total amount of transition metals. A method for manufacturing a positive electrode active material for a battery is disclosed.

JP 2017-157548 A

Journal of Materials Chemistry A, 2018, 6, 12344-12352

Ni—Co—Mn-based positive electrode active materials for lithium ion batteries are known to improve battery characteristics and the like by having a high Ni content of 0.8 or more in a composition ratio of Ni/Ni+Co+Mn. However, the positive electrode active material described in Non-Patent Document 1 and Patent Document 1 has a transition metal composition of Ni:Co:Mn=1:1:1 and a low Ni composition ratio.

In addition to high strength, the positive electrode active material for lithium ion batteries also has good output characteristics when used in batteries. Here, for example, if the positive electrode active material for a lithium ion battery contains a phase such as NiO that does not contribute to movement of Li ions during charging and discharging, the battery capacity may significantly decrease. On the other hand, if the positive electrode active material for lithium ion batteries can be controlled to have a single phase, the effect of improving the battery capacity can be expected.

In view of such problems, an object of the embodiments of the present invention is to provide a positive electrode active material for an all-solid-state lithium-ion battery that has a high Ni composition ratio, a single phase, and high strength.

In one embodiment of the present invention, the composition formula: Li _a Ni _b Co _{c Mnd} O ₂
(wherein 1.0≦a≦1.10, 0.8≦b≦0.9, 0.05≦c≦0.19, 0.01≦d≦0.1, and b+c+d=1. )
and has an average particle diameter D50 of 2 μm or more, a particle strength of 300 MPa or more, a single phase belonging to the space group R3-m with a layered rock salt structure, and a single particle ratio of 80% or more. It is a cathode active material for an all-solid-state lithium-ion battery.

In one embodiment, the positive electrode active material for an all-solid-state lithium ion battery of the present invention has an average particle size D50 of 2 μm or more and 6 μm or less and a particle strength of 300 MPa or more and 800 MPa or less.

In another embodiment of the present invention, step 1 of preparing a NiCoMn-based metal hydroxide produced by a coprecipitation method, Li is the total molar ratio of Ni, Co and Mn in the NiCoMn-based metal hydroxide Step 2 of adding a lithium salt to the NiCoMn-based metal hydroxide so that the molar ratio is 20% or less and performing primary firing at 850 ° C. or higher, and the powder obtained after the primary firing is added to the step Lithium salt was further added so that the total molar ratio of Li, together with the lithium salt added in 2, was equal to or higher than the total molar ratio of Ni, Co and Mn in the NiCoMn-based metal hydroxide, and the temperature was 780 ° C. It is a manufacturing method of the positive electrode active material for all-solid-state lithium ion batteries according to the embodiment of the present invention, including the step 3 of secondary firing as described above.

In one embodiment of the method for producing a positive electrode active material for an all-solid-state lithium ion battery of the present invention, the coprecipitation method comprises adding aqueous ammonia and sodium hydroxide to an aqueous solution of a mixture of nickel salt, cobalt salt and manganese salt. This is a method for obtaining a NiCoMn-based metal hydroxide.

In still another embodiment of the present invention, an all-solid lithium ion comprising a positive electrode layer, a negative electrode layer and a solid electrolyte layer, and having the positive electrode active material for an all-solid lithium ion battery according to the embodiment of the present invention in the positive electrode layer Battery.

According to the embodiments of the present invention, it is possible to provide a positive electrode active material for an all-solid-state lithium-ion battery that has a high Ni composition ratio, a single phase, and high strength.

FIG. 4 is a projection view of particles for explaining the degree of envelopment of particles; It is a figure which shows the example of the envelopment degree of the particle measured using the dry particle image analyzer: Morphologi G3 (manufactured by Malvern Panalytical). 4 is an XRD chart of each positive electrode active material obtained in Example 1 and Comparative Example 1. FIG.

(Structure of positive electrode active material)
A positive electrode active material for an all _- solid lithium ion battery according to an embodiment of the present invention has a _{composition formula : LiaNibCocMndO2}
(wherein 1.0≦a≦1.10, 0.8≦b≦0.9, 0.05≦c≦0.19, 0.01≦d≦0.1, and b+c+d=1. ).

In the positive electrode active material for an all-solid lithium ion battery according to the embodiment of the present invention, if the Li composition is less than 1.0, the amount of lithium is insufficient and it is difficult to maintain a stable crystal structure, and if it exceeds 1.10, the There is a possibility that the discharge capacity of an all-solid-state lithium-ion battery produced using the positive electrode active material may be lowered.

The composition of the positive electrode active material can be measured by an inductively coupled plasma-optical emission spectrometer (ICP-OES) and ion chromatography.

The average particle diameter D50 of the positive electrode active material for all-solid lithium ion batteries according to the embodiment of the present invention is controlled to 2 μm or more. With such a configuration, the contact area between the solid electrolyte and the positive electrode active material is increased, and the conductivity of Li ions between the positive electrode active material and the solid electrolyte is improved. The average particle diameter D50 may be 2.5 µm or more, or may be 3 µm or more. In addition, the average particle diameter D50 may be 6 μm or less, 5 μm or less, 4.5 μm or less, 3.5 μm or less, or 3 μm or less. good.

The average particle size D50 of the positive electrode active material for all solid state lithium ion batteries according to the embodiment of the present invention can be measured with a particle size measuring device such as MT3300EXII manufactured by Microtrac.

The particle strength of the positive electrode active material for all-solid lithium ion batteries according to the embodiment of the present invention is controlled to 300 MPa or more. In batteries using conventional electrolytes, even if the particles crack during pressing, the highly fluid electrolyte seeps into the gaps, but in all-solid-state batteries, the solid electrolyte does not enter the gaps created by the cracks. Therefore, the conductive path is interrupted there, resulting in a decrease in output. On the other hand, by using the positive electrode active material for an all-solid-state lithium ion battery according to the embodiment of the present invention, a high-strength and hard-to-crack positive electrode can be obtained, thereby making it possible to produce a high-output all-solid-state battery. Become. The particle strength of the positive electrode active material is preferably 350 MPa or more, more preferably 400 MPa or more. Although the upper limit of the particle strength of the positive electrode active material is not particularly limited, it may be, for example, 800 MPa or less, 700 MPa or less, or 600 MPa or less.

The particle strength of the positive electrode active material for all-solid-state lithium ion batteries according to the embodiment of the present invention can be measured using a microcompression tester MCT-211 manufactured by Shimadzu Corporation as follows. That is, place the dispersed powder sample on the sample stage, aim at the center of one secondary particle with an average particle size of D50 size with a microscope, press an indenter with a diameter of 20 μm at a load rate of 0.532 mN / sec, and break it. is measured at N=10, and the average value is taken as the particle strength of each sample.

A positive electrode active material for an all-solid-state lithium ion battery according to an embodiment of the present invention has a single phase belonging to the space group R3-m and has a layered rock salt structure. The layered rock salt structure has a structure in which transition metals and lithium are regularly arranged to form a two-dimensional plane, and lithium diffuses two-dimensionally. For this reason, if the positive electrode active material for an all-solid-state lithium ion battery according to the embodiment of the present invention is a single phase belonging to the space group R3-m having a layered rock salt structure, the movement of Li ions during charging and discharging Since there is no phase such as NiO that does not contribute, the effect of improving the battery capacity can be expected.

In general, the fact that the primary particles constituting the positive electrode active material have a layered rock salt structure can be analyzed and identified by a known method based on powder X-ray diffractometry. For example, in the X-ray diffraction pattern of the positive electrode active material, mainly the (003) plane near the diffraction angle (2θ) = 18.7°, the (101) plane near 36.6°, the (012) plane near 38.3° ) plane, (104) plane near 44.4°, (015) plane near 48.6°, (107) plane near 58.6°, (018) plane near 64.4°, 64.8 The existence of a layered rock salt structure is confirmed by detecting the diffraction peaks attributed to a total of nine space groups R3-m, the (110) plane near 68.0° and the (113) plane appearing near 68.0°. be done. When only these peaks are observed, it can be determined that the crystal is a single phase belonging to the space group R3-m, which has a layered rock salt structure.

Further, for example, when the primary particles constituting the positive electrode active material are not in a single phase, the X-ray diffraction pattern of the positive electrode active material has NiO peaks near 37.5°, 43.5°, and 63.5°. Observed.

The positive electrode active material for an all-solid-state lithium ion battery according to an embodiment of the present invention has a single particle ratio controlled to 80% or more. When the ratio of the single particles is 80% or more, the positive electrode active material has high strength, and the positive electrode active material is less likely to crack when pressed in the manufacturing process of the battery. The ratio of single particles of the positive electrode active material is preferably 85% or more, more preferably 90% or more, and even more preferably 95% or more.

The ratio of single particles of the positive electrode active material is obtained from the degree of envelopment of the particles. Here, the envelopment of a particle is measured based on the contour of the particle. Particle contours provide information about properties such as surface roughness in addition to detecting agglomerated particles. A concept called the convex hull perimeter is used to calculate the particle contour parameter. The convex hull perimeter is calculated from a virtual rubber band wrapped around the contour of the particle, as shown in FIG.

In FIG. 1, the particle A has a shape with almost no unevenness on the outer periphery, and the length of the virtual rubber band wrapped around the contour of the particle (peripheral length of the convex hull) is the length of the outer periphery of the particle A ( is approximately equal to the actual perimeter of particle A). On the other hand, particle B has an uneven outer periphery, and the length of the imaginary rubber band wrapped around the contour of particle (convex hull perimeter) is smaller than the outer perimeter of particle B (actual perimeter of particle B). Become. At this time, the “particle envelopment degree” is defined by the following equation. The smaller the unevenness around the particle, the closer the numerical value of the particle envelopment to 1.0.
Particle Envelope = Convex Hull Perimeter / Particle Actual Perimeter

Particle envelopment can be measured as follows. That is, about 10,000 powder particles are measured with a dry particle image analyzer: Morphologi G3 (manufactured by Malvern Panalytical). In the measurement, the powder particles of the positive electrode active material to be targeted are put into a sample cartridge, the powder particles of the positive electrode active material are dispersed on a glass plate, the projection image of the particles is taken, and the two-dimensional measurement of the powder particles is performed. get the shape. By analyzing the resulting two-dimensional shape, the envelopment of the particle is calculated and defined by the above-mentioned "convex hull perimeter/actual perimeter of the particle".

FIG. 2 shows an example of particle envelopment measured using a dry particle image analyzer: Morphologi G3 (manufactured by Malvern Panalytical). FIG. 2 shows the shape of six particles and the envelopment of each particle. In the order of particles C, D, E and F, G and H, the unevenness of the outer periphery of the particles gradually decreases, and the outline becomes smooth. Accordingly, it can be seen that the envelopment degree of the particles gradually approaches 1.0. In particular, particles E and F, and particles G and H in FIG. 2 are in the form of single particles, and the enveloping degree at this time is 0.98 or more. In the positive electrode active material for an all-solid lithium ion battery according to the embodiment of the present invention, a single particle is defined as having an envelopment degree of 0.98 or more as defined above.

(Method for producing positive electrode active material for all-solid-state lithium ion battery)
Next, a method for producing a positive electrode active material for an all-solid-state lithium ion battery according to an embodiment of the present invention will be described in detail. In the method for producing a positive electrode active material for an all-solid-state lithium-ion battery according to an embodiment of the present invention, first, a NiCoMn-based metal hydroxide produced by a coprecipitation method is prepared. The coprecipitation method is preferably a method of obtaining a NiCoMn-based metal hydroxide by adding aqueous ammonia to an aqueous solution of a mixture of nickel salt, cobalt salt and manganese salt and adding sodium hydroxide while stirring. In the coprecipitation method, it is preferable to control the pH of the reaction liquid to 10.5 to 11.5, the ammonium ion concentration to 10 to 25 g/L, and the liquid temperature to 50 to 65°C.

The NiCoMn-based metal hydroxide produced by the coprecipitation method is Ni _b Co _{c Mnd} (OH) ₂ (wherein 0.8≦b≦0.9, 0.05≦c≦0.19, 0 .01≤d≤0.1 and b+c+d=1).

Next, a lithium salt is added to the NiCoMn-based metal hydroxide. At this time, Li is added so that the molar ratio is 20% or less of the total molar ratio of Ni, Co and Mn in the NiCoMn-based metal hydroxide. For example, when the total molar ratio of Ni, Co and Mn in the NiCoMn-based metal hydroxide is 1.0, the lithium salt is added so that the molar ratio of Li is 0.2 or less.

Examples of the lithium salt added to the NiCoMn-based metal hydroxide include lithium carbonate and lithium hydroxide.

Next, the NiCoMn-based metal hydroxide to which the lithium salt is added is primarily sintered at 850° C. or higher to obtain powder. The heating temperature for the primary firing may be 900° C. or higher, or 1000° C. or higher. Also, the heating temperature for the primary firing may be 1100° C. or higher. The heating time for the primary firing can be appropriately set depending on the relationship with the heating temperature. For example, when the heating temperature is 850.degree. C. to 1100.degree.

Next, a lithium salt is further added to the powder obtained after the primary firing. At this time, the lithium salt is further added so that the total molar ratio of Ni, Co, and Mn in the NiCoMn-based metal hydroxide is equal to or greater than the total molar ratio of the lithium salt added to the NiCoMn-based metal hydroxide. For example, when the total molar ratio of Ni, Co, and Mn in the NiCoMn-based metal hydroxide is 1.0, and a lithium salt is added so that the molar ratio of Li is 0.2 before primary firing, here Then, a lithium salt is added so that the molar ratio of Li is 0.8 or more.

The lithium salt to be further added after the primary firing is preferably lithium hydroxide. Lithium hydroxide has a melting point of 462.degree. Therefore, Li of the added lithium hydroxide can react well with the powder after the primary firing by the secondary firing described later.

Next, the powder to which the lithium salt is further added as described above is subjected to secondary firing at 780° C. or higher. In this manner, a positive electrode active material for an all-solid lithium ion battery according to an embodiment of the present invention can be produced.

The heating temperature for the secondary firing is preferably 900° C. or lower, more preferably 850° C. or lower, because desorption of oxygen and volatilization of Li occur at a high temperature of 900° C. or higher. The heating time for the secondary firing can be appropriately set depending on the relationship with the heating temperature. For example, when the heating temperature is 780 to 850° C., it can be 4 to 12 hours.

In the method for producing a positive electrode active material for an all-solid lithium ion battery according to the embodiment of the present invention, as described above, the NiCoMn-based metal hydroxide obtained by the coprecipitation method is used as a raw material, and Li is a NiCoMn-based metal water. Lithium salt is added so that the total molar ratio of Ni, Co and Mn in the oxide is 20% or less, and primary firing is performed at 850° C. or higher. After the primary firing, Li is added to the NiCoMn-based metal hydroxide in the same molar ratio as the total molar ratio of Ni, Co, and Mn in the NiCoMn-based metal hydroxide in total with the lithium salt added to the NiCoMn-based metal hydroxide. Lithium salt is added so that By such two-step firing, a positive electrode active material having a single phase and high strength can be produced.

In the method for producing a positive electrode active material for an all-solid-state lithium ion battery according to the embodiment of the present invention, a cubic crystal that does not contain much Li is more prone to grain growth than a layered oxide containing Li. , By adding less than 20% of Li to the stoichiometric composition of Li at the time of primary firing and firing at 850 ° C. or higher, a cubic crystal oxide with a large particle size is produced, and the particles grown here are used as raw materials for the remaining Secondary firing is performed by adding Li. Thereby, a positive electrode active material having a single layered structure can be obtained. Also, in the manufacturing method using a mixed powder of single Ni oxide, Mn oxide and Co oxide as a raw material, non-uniformity in composition occurs. On the other hand, in the method for producing a positive electrode active material according to the embodiment of the present invention, the coprecipitated hydroxide raw material is in a state in which the transition metals of Ni, Mn and Co are uniformly mixed in one particle, There is also the advantage that non-uniformity of composition does not occur.

(All-solid-state lithium-ion battery with positive electrode active material for all-solid-state lithium-ion battery)
A positive electrode layer can be formed using the positive electrode active material for an all-solid-state lithium-ion battery according to the embodiment of the present invention, and an all-solid-state lithium-ion battery including a solid electrolyte layer, the positive electrode layer, and the negative electrode layer can be produced. For the negative electrode layer, those used as negative electrode active materials in lithium ion batteries can be used. The solid electrolyte layer is made of a solid electrolyte, preferably a sulfide-based glass-ceramic solid electrolyte and/or a sulfide-based glass solid electrolyte.

The following examples are provided for a better understanding of the invention and its advantages, but the invention is not limited to these examples.

As shown below, positive electrode active materials were prepared in Examples 1 to 8 and Comparative Examples 1 to 8, respectively, and their average particle diameter D50, particle strength, and particle structure were measured, and the positive electrode active materials were used. Battery characteristics of all-solid-state lithium-ion batteries were measured. Also, the contents of Li, Ni, Mn, and Co in the positive electrode active material were measured by an inductively coupled plasma-optical emission spectrometer (ICP-OES) and ion chromatography. From the analysis results, a, b, c, and d when the positive electrode active material was represented by the composition of Li _a Ni _b Co _{c Mnd} O ₂ were determined.

(Examples 1 to 8 and Comparative Examples 1 to 8)
A 1.5 mol/L aqueous solution of nickel sulfate, cobalt sulfate, and manganese sulfate was prepared, and a predetermined amount of each aqueous solution was weighed, and a mixed metal salt solution was added so that the ratio of Ni:Co:Mn would be the mol % ratio shown in Table 1. It was conditioned and placed in the reactor.

Next, ammonia water and a 20% by mass sodium hydroxide aqueous solution are added to the reaction vessel so that the pH of the mixed solution in the reaction vessel is 11.0 ± 0.5 and the ammonium ion concentration is 10 to 25 g / L. and coprecipitated Ni--Co--Mn composite hydroxide by a coprecipitation method.

In addition, nitrogen gas was introduced into the reactor to prevent oxidation of the coprecipitate produced in the reaction. The gas to be introduced into the reaction tank is not limited to the above nitrogen gas, as long as it does not promote oxidation, such as helium, neon, argon, and carbon dioxide gas.

After the coprecipitated precipitate was sucked and filtered, it was washed with pure water and dried at 120° C. for 12 hours. The composition of the Ni--Co--Mn composite hydroxide particles thus produced: Ni _b Co _c Mn _d (OH) ₂ was measured.

Next, lithium carbonate was added to the Ni--Co--Mn composite hydroxide particles. At this time, lithium carbonate was added so that the molar ratio of Li to the total molar ratio of Ni, Co, and Mn in the Ni—Co—Mn composite hydroxide particles is the ratio (%) shown in Table 1.

Next, the Ni—Co—Mn composite hydroxide particles to which lithium carbonate was added were subjected to primary firing at the heating temperature shown in Table 1 for 10 hours.

Next, lithium hydroxide was further added to the powder obtained after the primary firing. At this time, lithium hydroxide was added so that the molar ratio of Li to the total molar ratio of Ni, Co and Mn in the Ni—Co—Mn composite hydroxide particles is the ratio (%) in Table 1. .

Next, the Ni—Co—Mn composite hydroxide particles to which lithium carbonate was added were subjected to secondary firing at the heating temperature shown in Table 1 for 4 hours. Thus, a positive electrode active material was produced.

-Structure of positive electrode active material-
Whether or not it is a single phase belonging to the space group R3-m with a layered rock salt structure was analyzed and identified by a known method based on the powder X-ray diffraction method as follows. That is, in the X-ray diffraction pattern of the positive electrode active material, mainly the (003) plane near the diffraction angle (2θ) = 18.7°, the (101) plane near 36.6°, the (012) plane near 38.3° ) plane, (104) plane near 44.4°, (015) plane near 48.6°, (107) plane near 58.6°, (018) plane near 64.4°, 64.8 The existence of a layered rock salt structure is confirmed by detecting the diffraction peaks attributed to a total of nine space groups R3-m, the (110) plane near ° and the (113) plane appearing near 68.0 °. do. Whether or not only these peaks were observed was judged to be a single phase belonging to the space group R3-m having a layered rock salt structure.

-Single particle ratio-
The single particle ratio of the positive electrode active material was measured as follows. First, about 10,000 powder particles are measured with a dry particle image analyzer: Morphologi G3 (manufactured by Malvern Panalytical). In the measurement, the powder particles of the positive electrode active material to be targeted are put into a sample cartridge, the powder particles of the positive electrode active material are dispersed on a glass plate, the projection image of the particles is taken, and the two-dimensional measurement of the powder particles is performed. got the shape. By analyzing the obtained two-dimensional shape, the enveloping degree of the particles was calculated as follows.
Particle envelopment=perimeter of convex hull/actual perimeter of particle At this time, particles with an envelopment of 0.98 or more were defined as single particles, and the ratio of the number of particles was defined as the single particle ratio.

-Average particle size D50-
The average particle diameter D50 of the positive electrode active material was measured by MT3300EXII manufactured by Microtrac.

-Particle strength-
The particle strength of the positive electrode active material was measured using a microcompression tester MCT-211 manufactured by Shimadzu Corporation as follows. First, the dispersed powder sample was placed on the sample stage. Next, aim at the center of one secondary particle with an average particle size of D50 size with a microscope, press an indenter with a diameter of 20 μm at a load rate of 0.532 mN / sec, and measure the strength at N = 10 when broken, The average value was taken as the particle strength of each sample.

Table 1 shows the test conditions and evaluation results for Examples 1 to 8 and Comparative Examples 1 to 8.

(Evaluation results)
In Examples 1 to 8, the average particle diameter D50 is 2 μm or more, the particle strength is 300 MPa or more, the single phase belongs to the space group R3-m with a layered rock salt structure, and the ratio of single particles is 80. % or more was obtained.
In Comparative Examples 1 to 8, a positive electrode active material for an all-solid lithium ion battery having a particle strength of less than 300 MPa or a positive electrode active material for an all-solid lithium ion battery without a single phase was obtained.

FIG. 3 shows XRD charts of the positive electrode active materials obtained in Example 1 and Comparative Example 1. As shown in FIG. In Example 1, no NiO peaks were observed, and in Comparative Example 1, NiO peaks were observed near 37.5°, 43.5°, and 63.5°.

Claims (5)

_{Composition formula : LiaNibCocMndO2 _}
(wherein 1.0≦a≦1.10, 0.8≦b≦0.9, 0.05≦c≦0.19, 0.01≦d≦0.1, and b+c+d=1. )
is represented by
All-solid lithium having an average particle diameter D50 of 2 μm or more, a particle strength of 300 MPa or more, a single phase belonging to the space group R3-m having a layered rock salt structure, and a single particle ratio of 80% or more. Positive electrode active material for ion batteries. The positive electrode active material for an all solid lithium ion battery according to claim 1, wherein the average particle diameter D50 is 2 µm or more and 6 µm or less, and the particle strength is 300 MPa or more and 800 MPa or less. Step 1 of preparing a NiCoMn-based metal hydroxide produced by a coprecipitation method;
Lithium salt is added to the NiCoMn-based metal hydroxide so that the molar ratio of Li to the total molar ratio of Ni, Co and Mn in the NiCoMn-based metal hydroxide is 20% or less. Step 2 of primary firing;
The total molar ratio of Li to the powder obtained after the primary firing, together with the lithium salt added in step 2, is equal to or greater than the total molar ratio of Ni, Co, and Mn in the NiCoMn-based metal hydroxide. 3. The method for producing a positive electrode active material for an all-solid lithium ion battery according to claim 1 or 2, further comprising a step 3 of adding a lithium salt and secondary firing at 780° C. or higher so that the mixture becomes . The all-solid lithium ion according to claim 3, wherein the coprecipitation method is a method of adding ammonia water and sodium hydroxide to an aqueous solution of a mixture of nickel salt, cobalt salt and manganese salt to obtain a NiCoMn-based metal hydroxide. A method for producing a positive electrode active material for a battery. A positive electrode layer, a negative electrode layer and a solid electrolyte layer,
An all-solid lithium ion battery comprising the positive electrode active material for an all-solid lithium ion battery according to claim 1 or 2 in the positive electrode layer.

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