JP2019220353A - Positive electrode active material for all-solid-state lithium ion battery, positive electrode for all-solid-state lithium ion battery, all-solid-state lithium ion battery, and method of producing positive electrode active material for all-solid-state lithium ion battery - Google Patents

Abstract

To provide a positive electrode active material for an all-solid-state lithium ion battery, having good rate characteristics when applied to an all-solid-state lithium ion battery.SOLUTION: A positive electrode active material for an all-solid-state lithium ion battery has a composition represented by LiNiCoMnMO(where, a+b+c+d=1, 1.0≤x≤1.1, 0<d/(a+b+c)≤0.1, and 0<α≤0.2 are satisfied, and M is Nb or comprises Nb and at least one selected from among Ti, Mg, Al, Zr, Mo, and W), has an S content of 100 mass ppm or less, and is aspherical particles. In the positive electrode active material, Ni, Co, Mn, and M other than Al are all uniformly dispersed in EDX measurement of a particle cross section.SELECTED DRAWING: None

Description

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

Currently used lithium ion batteries include, as a positive electrode active material, a layered compound LiMeO ₂ (Me is a cation selected to have an average of + III valence and always includes a redox cation), and a spinel compound LiMeQO ₄ (Q cation) is chosen to be the average at + IV-valent, olivine compound _{^{LiX 1 X 2 O 4 (X}} 1 is a cation selected such that + II valence, always includes a redox cation, X ² is (Cation selected to have a + V value), a fluorite-type compound Li ₅ MeO _{4, and the} like, and on the other hand, an electrolytic solution and other constituent requirements have been improved year by year so that the characteristics can be utilized.

However, in the case of a lithium ion battery, most of the electrolyte is an organic compound, and even if a flame-retardant compound is used, it cannot be said that there is no danger of causing a fire. As an alternative candidate for such a liquid-based lithium-ion battery (hereinafter, referred to as a liquid-based LIB), an all-solid-state lithium-ion battery (hereinafter, referred to as an all-solid-state LIB) having a solid electrolyte has attracted attention in recent years (Patent Document 1). etc). Among them, sulfides such as Li ₂ S—P ₂ S ₅ as solid electrolytes and all solid-state lithium ion batteries to which lithium halide is added are becoming mainstream.

Japanese Patent No. 5971109

The all-solid-state LIB has a significantly lower possibility of unexpected battery combustion than the liquid-type LIB, but has a drawback that current is difficult to be extracted. As a countermeasure, for example, the active material particles used in the positive electrode are reduced in size. For example, techniques have been developed in which a solid electrolyte is mixed in the positive electrode by about 20 to 30%, or the surface of the positive electrode active material particles is coated with LiNbO ₃ .

However, even if all of these technologies are used, it is difficult to expect that the conversion from liquid LIB to all solid LIB will proceed smoothly. As a cause of this, there was a defect as shown in the following example.
(1) When the application is a PC or mobile device application, in order to make the battery characteristics equal to the liquid LIB of the application, the solid electrolyte must be mixed 20 to 30% in the positive electrode, and the particle size is small. , Which is disadvantageous in terms of volumetric energy density.
(2) When the application is an EV or power equipment application, since the particle diameter of the positive electrode active material originally assumed in the liquid LIB for the application is small, it is attempted to obtain the same characteristics as the liquid LIB with all solid LIBs. Then, it is necessary to further reduce the particle diameter, and the thickness of the electrode must be reduced, which makes the production of the electrode difficult.

  Therefore, there is a possibility of operating in a high temperature region of 60 ° C. or higher where the risk of decomposition or vaporization of the LIB electrolyte is high, or in a low temperature region of −30 ° C. or lower where the risk of thickening or freezing of the LIB electrolyte is high. It is assumed that practical use of the all-solid-state LIB will start from the use.

  Here, a method for producing the above-mentioned layered compound among the positive electrode active materials that are assumed to be currently generally practiced will be described. As an example, it is assumed that Me is made of Ni, Co, and Mn. First, an aqueous solution of an alkali metal hydroxide such as sodium hydroxide, an aqueous solution of a substance that forms a complex with Me ions such as ammonia, and a sulfate aqueous solution in which Ni, Co, and Mn ions are dissolved are prepared. These aqueous solutions are simultaneously and individually placed in one reaction tank (the aqueous solution of the alkali metal hydroxide is used for pH control, so it may be performed intermittently in conjunction with the pH). At this time, hydroxide particles are generated to form a slurry, and the size and shape of the hydroxide particles are adjusted by the reaction pH, the reaction temperature, the addition rate of each raw material aqueous solution, and the like. The size of the particles of the positive electrode active material as the final product is the same as or slightly smaller than the hydroxide particles. Therefore, this adjustment is very important when following this manufacturing method. This slurry is filtered, washed with water, and dried to extract only hydroxide particles.

The hydroxide particles or thermal decomposition products serving oxide particles thereof are mixed such as Li ₂ CO ₃ or LiOH · H ₂ O, calcined at from 450 to 1,000 ° C.. The firing temperature is higher as the ratio of Ni to the total amount of (Ni, Co, Mn) (hereinafter referred to as Ni / Me ratio) is lower, and is lower as Ni / Me is higher. The firing temperature is Ni / Me. Those with a small value are in the air atmosphere, and the oxygen partial pressure is increased as Ni / Me is increased. After firing, it becomes a lump and is crushed in dry air to form a positive electrode active material.

  In the manufacturing method as described above, a positive electrode active material having a high volume energy density can be obtained because the inside of the particles is dense, but when this is used as an all-solid LIB, the current value that can be taken out is small. Had become something. Accordingly, an object of the present invention is to provide a positive electrode active material for an all-solid-state lithium-ion battery having good rate characteristics when applied to an all-solid-state lithium-ion battery.

  The present inventor has conducted various studies and found that a positive electrode active material for an all-solid-state lithium ion battery having a predetermined composition, having a controlled S content, particle cross-sectional shape, and dispersibility of a predetermined element is controlled. Have found that the above-mentioned problem is solved.

In the present invention the embodiment was completed the basis of the above _{findings, Li x Ni a Co b Mn} c M d O 2 + α (a + b + c + d = 1,1.0 ≦ x ≦ 1.1,0 <d / (a + b + c ) ≦ 0.1, 0 <α ≦ 0.2, and M is Nb or a composition represented by Nb and at least one selected from Ti, Mg, Al, Zr, Mo and W). An all-solid lithium ion having non-spherical particles with an S content of 100 mass ppm or less, and in which E, M, Ni, Co, and Mn other than Al are uniformly dispersed in EDX measurement of the particle cross section. It is a positive electrode active material for batteries.

  In the positive electrode active material for an all solid state lithium ion battery of the present invention, the content of S is 70 mass ppm or less in the embodiment.

  In another embodiment, the present invention is a positive electrode for an all-solid lithium-ion battery including the positive electrode active material for an all-solid lithium-ion battery of the present invention.

  In still another embodiment, the present invention is an all-solid lithium-ion battery including the positive electrode of the present invention, a negative electrode, and a solid electrolyte.

  In still another embodiment of the present invention, the M is Nb, a step of dissolving a nickel ingot, a cobalt ingot, and a manganese ingot in nitric acid to obtain a ingot dissolving solution; Adding a suspension of water to obtain a slurry before spraying, adding an aqueous niobium oxalate solution to the slurry before spraying and spray-drying to obtain a dry powder, and adding 775 to the dry powder in an oxygen-containing atmosphere in a dry state. It is a method for producing a positive electrode active material for an all-solid-state lithium ion battery of the present invention, which includes a step of firing at 950 ° C.

  In still another embodiment of the present invention, the M is composed of Nb and at least one selected from Ti, Mg, Al, Zr, Mo, and W, and the nickel metal, the cobalt metal, and the manganese metal are converted to nitric acid. Dissolving to obtain an ingot solution, adding the ingot solution to lithium carbonate suspension water to obtain a slurry before spraying, an aqueous solution of niobium oxalate and an aqueous solution of titanium diammonium oxalate in the slurry before spraying, Adding at least one selected from an aqueous solution of magnesium nitrate, an aqueous solution of aluminum nitrate, an aqueous solution of zirconyl oxynitrate, an aqueous solution of lithium molybdate, and an aqueous solution of ammonium paratungstate, and spray-drying to obtain a dry powder; All-solid lithium ion of the present invention including a step of firing at 775 to 950 ° C. in an oxygen-containing atmosphere in a dry state It is a method for producing a positive electrode active material for a pond.

  ADVANTAGE OF THE INVENTION According to this invention, the positive electrode active material for all-solid-state lithium-ion batteries which has favorable rate characteristics when applied to an all-solid-state lithium-ion battery can be provided.

(Positive electrode active material for all solid-state lithium ion batteries)
The positive electrode active material for an all-solid-state lithium ion battery according to the embodiment of the present invention includes Li _x Ni _a Co _b M _c M _d O _{2 + α} (a + b + c + d = 1, 1.0 ≦ x ≦ 1.1, 0 <d /(A+b+c)≦0.1, 0 <α ≦ 0.2, where M is Nb or is composed of Nb and at least one selected from Ti, Mg, Al, Zr, Mo and W) It has the following composition. In the following, the terms “positive electrode active material”, “positive electrode active material powder”, and “positive electrode active material particles” are used, but since the present invention is all in powder form, these terms all have the same meaning. Shall have.

  In the positive electrode active material for an all-solid-state lithium ion battery according to the embodiment of the present invention, the content of S is controlled to 100 ppm by mass or less. In the case of the liquid LIB, even if the solid particles are dense, the rate characteristics are good, and the surface has good battery characteristics even if, for example, about 500 to 11000 ppm of sulfate is present, but in the case of the all solid LIB, Even if there is a slight amount of sulfate on the surface, since the battery characteristics (capacity, cycle characteristics, rate characteristics) are significantly affected, the content of S is preferably as small as possible, specifically, 100 mass ppm or less. Is preferably controlled. The content of S is preferably 70 mass ppm or less, more preferably 50 mass ppm or less, and still more preferably 30 mass ppm or less.

  The positive electrode active material for an all solid lithium ion battery according to the embodiment of the present invention is a non-spherical particle. If the positive electrode active material particles are spherical, the inside of the particles becomes too dense, and when this is used as an all-solid LIB, there is a problem that the current value that can be taken out is small. On the other hand, since the positive electrode active material for an all-solid lithium ion battery according to the embodiment of the present invention is a non-spherical particle, it is particularly a spherical product, and is described in FIG. 7 of Japanese Patent No. 5971109 and paragraph 0145 of the specification. It has a feature that the rate characteristic is higher than that of a positive electrode active material having only such a non-dense portion. Here, “non-spherical particles” in the present invention means particles having a shape different from a spherical shape. For example, examples of the non-spherical particles include particles having a “distorted (distorted) shape” deformed from a true spherical shape, platelet-like particles, and rod-like particles. When the primary particles are aggregated to form secondary particles, the secondary particles are “non-spherical particles” in the present invention when the secondary particles are non-spherical. Such non-spherical particles can improve the contact between the particles and reduce the contact transfer resistance, particularly for lithium ions. The spherical / non-spherical shape of the particles can be determined by SEM observation.

  That is, the existence of the active material in the positive electrode of the all-solid LIB shows that the conventional spherical product has a dense particle, a long Li movement distance in the particle, and a positive electrode active material crystal lattice accompanying the Li insertion and desorption. In order to forcibly suppress the expansion and contraction of Li, the transfer of Li ions is particularly difficult in all solid LIB. On the other hand, by using non-spherical particles in the positive electrode active material according to the embodiment of the present invention, expansion and shrinkage due to movement of Li are prevented as much as possible, and even when particle destruction occurs at that time, Nb is always Nb. It can be controlled to be on the surface. Therefore, the rate characteristics of the all-solid-state lithium-ion battery using the positive electrode active material for an all-solid-state lithium-ion battery are improved.

It is said that by coating LiNbO ₃ on the surface of the positive electrode active material particles in the all solid state LIB, the battery characteristics are improved as compared with the case without the coating. This is because the energy gap at the positive electrode-electrolyte interface between a general oxide-based positive electrode active material and a sulfide-based solid electrolyte is large, but by interposing LiNbO ₃ having a crystal lattice relaxation effect between the positive electrode-electrolyte interface, The total energy gap is reduced. In the case of a spherical product, if Nb forms a solid solution inside the dense particles, it becomes difficult to suppress the energy gap. Therefore, the firing conditions after coating are adjusted so that LiNbO ₃ is solidified into the positive electrode active material. In general, firing is performed under conditions that do not dissolve and sufficiently form on the particle surface. However, it has been found that in the case of non-spherical particles, even if Nb is present inside the active material particles, the suppression of the energy gap is successful.

  Although the detailed mechanism is unknown, the non-spherical product has a projection on the particle surface unlike the spherical product and acts as an active material even when the particle is broken. It is possible that the presence of the substance has led to an improvement in battery characteristics. Similarly, it is preferable that Ti, Mg, Zr, Mo, and W are uniformly present in the particles. Al may be present in any form in the particle, but is preferably present in a non-uniform form whose position is limited to some extent from the viewpoint of securing electron conductivity.

  The positive electrode active material for an all-solid-state lithium ion battery according to the embodiment of the present invention has a cross section of E, M, Ni, Co other than Al in EDX measurement (energy dispersive X-ray spectrometry: measurement by energy dispersive X-ray analysis). All of Mn are uniformly dispersed.

(Lithium ion battery)
Using the all-solid-state lithium-ion battery positive electrode active material according to each embodiment of the present invention to produce an all-solid-state lithium-ion battery positive electrode, further using the all-solid-state lithium-ion battery positive electrode, a negative electrode, and a solid electrolyte To produce an all-solid-state lithium-ion battery.

(Method of 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. First, a nickel ingot, a cobalt ingot, and a manganese ingot (Ni ingot, Co ingot, Mn ingot) are prepared, and a solution dissolved in nitric acid (hereinafter also referred to as “ingot solution”) is prepared. . At this time, since hydrogen and nitrogen oxide (NO _x ) are generated, it is preferable to perform exhaust gas treatment using an appropriate exhaust gas treatment device and discharge the air to the atmosphere. Further, in the present invention, the “metal” is a metal that is hardened in a form that is easy to store metal, and indicates a metal lump, an ingot, a bar, or the like.

Next, the Li / (Ni + Co + Mn + M) molar ratio in the final product was determined by preparing a Li ₂ CO ₃ corresponding to the amount, the suspension is suspended in water of 1 to 10 times the mass fraction. Then, the above-mentioned metal solution is dropped into the suspension. At this time, the number of pipes of the base metal solution to be put into the suspension tank may be any number, but it is preferable to increase the number of pipes according to the scale of the suspension tank. Of course, a large number of pipes may be arranged on a small-scale layer by design and the metal solution may be divided and dropped. However, due to the complexity of equipment, in the following embodiment, a 200-L tank has an inner diameter of 3. 3 to 8 tubes each having a size of １２12 mm were prepared, and a base metal solution was dropped into the suspension tank at the same time from the outlets of these pipes while stirring. This produces a slurry. This slurry is referred to as “pre-spray slurry”.

  The obtained pre-spray slurry is filled in a relay tank, and an aqueous niobium oxalate solution is added with stirring, or a niobium oxalate aqueous solution or another M component (a titanium diammonium oxalate aqueous solution, a magnesium nitrate aqueous solution, an aluminum nitrate aqueous solution) is added. An aqueous solution, an aqueous solution of zirconyl oxynitrate, an aqueous solution of lithium molybdate, and an aqueous solution of ammonium paratungstate) are added after the respective charging ratios are determined. When it becomes sufficiently uniform, spray drying is performed. Spray drying may be performed in any form, but using a micro mist dryer manufactured by Fujisaki Electric Co., Ltd. can easily obtain a dried powder (hereinafter, sometimes referred to as “dried powder”) and control production. It is preferable because it can be easily performed. When using the micro mist dryer, the air flow rate and the heater output may be adjusted so that the inlet temperature is 150 to 350 ° C and the outlet temperature is 120 to 150 ° C. The obtained dried powder is filled in a sagger and fired.

  The sintering may be anything as long as it can uniformly heat the entire sagger and can appropriately adjust the sintering atmosphere.For example, a roller hearth kiln, a pusher kiln, a box furnace, a rotary furnace, or the like may be used. . Preferably, it is preferable to use a roller hearth kiln or a box furnace in which it is considered that impurities due to furnace body material peeling are small, and it is particularly preferable to use a roller hearth kiln because continuous production is easily possible. Good.

  As firing conditions, firing is performed at 775 to 950 ° C. in an oxygen-containing atmosphere in a dry state. More preferably, the temperature is preferably raised to 850 to 950 ° C. in dry air, immediately lowered to 750 to 800 ° C., and maintained for 14 to 20 hours. However, at the end of the holding time after cooling, the amount of nitrate decreases and the risk of oxygen deficiency increases. The positive electrode active material according to the embodiment can be manufactured. The flowing gas for adjusting the firing atmosphere may be directly introduced into the furnace. However, the gas is first preheated until the temperature in the firing furnace is slightly higher than the temperature in the furnace, and the gas is introduced into the furnace. If the temperature is sometimes designed to be a desired temperature, unnecessary gradients and variations in the temperature distribution in the firing furnace can be reduced more easily. Further, for example, it is preferable that a firing zone is set in a firing furnace and a shutter is provided at each firing zone boundary so that atmospheres in different firing zones are not mixed.

  After firing, the powder becomes a lump, and is crushed by a roll crusher and a pulverizer while maintaining a dry atmosphere from the firing to obtain a positive electrode active material powder. When a material (eg, cast iron, stainless steel, Hastelloy, etc.) containing a metal that may generate magnetism, such as Fe, is used for the manufacturing equipment, it is preferable that the material be subjected to magnetic separation after crushing to obtain a positive electrode active material powder. When dry air is used as the atmosphere in the dry state, the dew point of the dry air is preferably -30 ° C or less. More preferably, it is -40C or lower. Since the positive electrode active material according to the embodiment of the present invention has high hygroscopicity and easily generates surface oxygen defects, it is preferable to keep the oxygen-containing atmosphere in a dry state from baking to storage if possible. For example, if the positive electrode active material powder is placed in an appropriate aluminum laminate in dry air and sealed while keeping the dry air atmosphere, storage becomes easy.

Hereinafter, examples for better understanding of the present invention and its advantages will be provided, but the present invention is not limited to these examples.
(Example 1)
-Preparation of slurry-
First, a nickel ingot, a cobalt ingot, and a manganese ingot were prepared, and these three kinds of ingots were dissolved in nitric acid (55% aqueous solution) to obtain an ingot solution. At this time, the charge molar ratio was adjusted so that the molar ratio of Ni: Co: Mn in the base metal solution was 85: 12: 3 and the molar ratio of NO ₃ / (Ni + Co + Mn) was 3.28. It was adjusted. Further, since hydrogen and NO _x removal, was operated exhaust gas treatment device simultaneously. Heating was performed at a target temperature of 110 ° C. for 3 hours from the start of dissolution, and the dissolution reaction was continued. Total dissolution time was 24 hours. Separately, lithium carbonate was dispersed in water and stirred and mixed at 45 Hz to prepare a suspension. Next, a metal solution was dropped into the suspension at a rate of about 2 L / min to prepare a slurry containing Li, Ni, Co, and Mn. At the time of this dropping, three pipes each having a diameter of 10 mm were prepared, and a base metal solution was separately dropped into each of the pipes. Thus, a slurry before spraying was prepared.

To the slurry before spraying, an aqueous solution of niobium oxalate (manufactured by HC Starck) was added and dissolved so that the molar ratio of Nb / (Ni + Co + Mn) was 0.01. This was spray-dried with a micro mist dryer manufactured by Fujisaki Electric. The spray drying conditions were as follows: inlet temperature 280 ± 2 ° C., outlet temperature 160 ± 5 ° C., air supply to the drying tower 1.5 ± 0.1 m ³ / min, ratio of nozzle air flow rate to slurry flow rate (G / S) was adjusted to 2400 to control the heater output, the nozzle air flow rate, the amount of air supplied to the drying tower, and the slurry flow rate.

  The dried powder obtained by this spray drying was filled in an alumina sagger and fired. The filling height of the sagger was 1.5 cm. The firing pattern was as shown in Table 1. In this embodiment, a roller hearth kiln is used for the firing furnace, and a firing zone is set every hour. At the boundary of the firing zone, the shutter is basically closed except for when passing through the sagger and the atmosphere of each firing zone is introduced as much as possible. Kept the same as the gas.

  The atmosphere in which the massive fired material thus obtained was placed was switched from dry pure oxygen to dry air, and was crushed using a roll mill and a pulverizer in the dry air. Active material.

(Example 2)
A positive electrode active material was prepared in the same manner as in Example 1 except that the composition of the base metal solution was changed to Ni: Co: Mn = 90: 5: 5, and the temperature of (1) in Table 1 was set to 850 ° C. It was prepared and used as a positive electrode active material of Example 2.

(Example 3)
A positive electrode active material was prepared in the same manner as in Example 1 except that the time (15 hours) in (2) in Table 1 was set to 20 hours, and used as a positive electrode active material in Example 3.

(Example 4)
A positive electrode active material was produced in the same manner as in Example 1, except that an aqueous solution of titanium oxalate was added and dissolved in the slurry before spraying so that the molar ratio of Ti / (Ni + Co + Mn) became 0.02. Thus, a positive electrode active material of Example 4 was obtained.

(Example 5)
A positive electrode active material was prepared and implemented in the same manner as in Example 1, except that an aqueous solution of magnesium nitrate was further added and dissolved in the slurry before spraying so that the molar ratio of Mg / (Ni + Co + Mn) became 0.014. The positive electrode active material of Example 5 was used.

(Example 6)
A positive electrode active material was prepared and carried out in the same manner as in Example 1 except that an aqueous solution of aluminum nitrate was further added to and dissolved in the slurry before spraying so that the molar ratio of Al / (Ni + Co + Mn) became 0.015. The positive electrode active material of Example 6 was used.

(Example 7)
A positive electrode active material was prepared in the same manner as in Example 1, except that an aqueous solution of zirconyl oxynitrate was further added to and dissolved in the slurry before spraying so that the molar ratio of Zr / (Ni + Co + Mn) was 0.013. The positive electrode active material of Example 7 was used.

(Example 8)
A positive electrode active material was prepared in the same manner as in Example 1, except that an aqueous solution of lithium molybdate was added to the slurry before spraying so that the molar ratio of Mo / (Ni + Co + Mn) became 0.05, and the mixture was dissolved. The positive electrode active material of Example 8 was used.

(Example 9)
A positive electrode active material was prepared in the same manner as in Example 1, except that an aqueous solution of ammonium paratungstate was added to and dissolved in the slurry before spraying so that the molar ratio of W / (Ni + Co + Mn) was 0.1. The positive electrode active material of Example 9 was used.

(Comparative Example 1)
A reaction vessel having a nitrogen atmosphere was prepared, 3 L of pure water was added thereto, and the mixture was stirred. 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 so that Ni: Co: Mn = 0.85: 0.12: 0.03. A mixed sulfate aqueous solution was prepared and placed in the reaction tank 1. Further, an aqueous caustic soda solution was prepared in the reaction tank 2 so as to have a concentration of 3 mol / L. Further, an aqueous ammonia solution was prepared in the reaction tank 3 so as to have a concentration of 20% by mass.

  While maintaining the stirring of the reaction vessel, the solution was fed from the reaction tank 1 and the reaction tank 3 into the reaction vessel at a rate of 5 mL / min. At that time, an aqueous caustic soda solution was charged from the reaction tank 2 into the reaction vessel so that the pH became 11.0. At this time, the temperature of the liquid in the reaction vessel was adjusted to 50 ° C. This was continued for 3 hours to prepare a seed crystal slurry.

Next, the solution was fed from the reaction tank 1 and the reaction tank 3 into the reaction vessel at a rate of 5 mL / min while maintaining the stirring in the reaction vessel. At that time, an aqueous caustic soda solution was charged from the reaction tank 2 into the reaction vessel so that the pH became 10.5. At this time, the temperature of the liquid in the reaction vessel was adjusted to 50 ° C. When the liquid reaches 10 L, the circulating pump below the reaction vessel is operated, the liquid is sent to the concentration tank at a rate of 15 mL / min, only the liquid component is partially filtered in the concentration tank, and the filtered liquid is reacted. Returned to container. The circulation pump was stopped when the liquid in the reaction vessel became 3 L or less, and was activated when the liquid became 10 L again. These operations were continuously performed for 10 hours in a nitrogen atmosphere in both the reaction vessel and the concentration tank. Thus, Ni _0.85 Co _0.12 Mn _0.03 (OH) ₂ was produced by the crystallization method. This solution was filtered and washed with a filter press, and dried in air at 120 ° C. for 12 hours.

This Ni _0.85 Co _0.12 Mn _0.03 (OH) ₂ and LiOH · H ₂ O having a D90 of 20 μm or less are mixed in one atmosphere so that Li / (Ni + Co + Mn) becomes 1.01 in an atmosphere of 60% humidity. The bag was weighed, the bag was inflated, the opening was grasped by hand to prevent the powder from leaking, and the unclamped hand was placed on the bottom of the bag, and the bag was shaken with both hands to perform coarse mixing. All of the coarsely mixed powder (coarse mixed powder) was put into a Henschel mixer from the bag, mixed at 1500 rpm for 5 minutes, and the mixed powder (mixed powder) was filled in an alumina sagger. The filling height of the sagger was 1 cm. After using a roller hearth kiln as a firing furnace, dry oxygen is passed through the roller hearth kiln at 10 m ³ / min to form a dry oxygen atmosphere, and the alumina sagger is put in the roller hearth kiln and kept at 490 ° C. for 8 hours. The firing pattern was set so that the temperature was raised and the temperature was maintained at 700 ° C. for 4 hours, and the sagger was moved. The baking pattern was set so that this was cooled to room temperature at 5 ° C./min, and the sagger was moved. With respect to the massive fired product thus obtained, the atmosphere in which it was placed was changed from dry pure oxygen to dry air, and the fired material was crushed in the dry air using a roll mill and a pulverizer.

The powder after the disintegration was coated with LiNbO ₃ on the surface of the powder using a Li alkoxide and an Nb alkoxide by a conventional method, and the powder after the coating was subjected to magnetic separation to produce a positive electrode active material of Comparative Example 1.

(Comparative Example 2)
In the slurry before spraying of Example 1, the same mass of pure water as that of the aqueous solution of niobium oxalate added in Example 1 was added to the slurry before spraying without adding the aqueous solution of niobium oxalate, and the mixture was thoroughly stirred and homogenized. Example 1 was the same as Example 1 except that the powder obtained by pulverizing using a roll mill and a pulverizer was coated with LiNbO ₃ on the surface of the powder using Li alkoxide and Nb alkoxide by an ordinary method, and the coated powder was magnetically selected. Similarly, a positive electrode active material of Comparative Example 2 was produced.

(Evaluation)
Each evaluation was performed under the following conditions using the samples of each of the examples and comparative examples thus obtained.
-Evaluation of SEM and EDX-
Regarding the particle surface and particle cross section, JEM JSM-7000F type was used for SEM observation, and JXA-8500F type made by JEOL was used for EDX. Judgment of spherical / non-spherical shape by SEM (judgment of particle morphology) and presence / absence of spot of each element by EDX (state of presence of each element) were determined by a conventional method. The cross section was prepared by solidifying the positive electrode active material powder with a polymer and then performing cross sectioning with a cross section polisher.

-Evaluation of S (sulfur) content-
SO ₄ ^2- was measured by ICP and converted to S.

-Evaluation of battery characteristics (all-solid lithium-ion battery)-
Positive active materials of Examples and Comparative Examples, a _{LiI-Li 2 S-P 2} S 5, 7: weighed at a ratio of 3 to obtain a positive electrode mixture by mixing. Li-an In alloy into a mold having an inner diameter of _{40mm, LiI-Li 2 S-} P 2 S 5, the positive electrode mixture, filling the Al foil in this order, and pressed at 500 MPa. The pressed compact was restrained at 100 MPa using a metal jig to produce an all-solid lithium-ion battery. For this battery, the initial capacity (25 ° C., upper limit voltage of charge: 4.55 V, lower limit voltage of discharge: 2.5 V) obtained at a discharge rate of 0.05 C was measured, and then the high rate obtained at a discharge rate of 1 C was obtained. The capacity (25 ° C., upper limit voltage of charge: 4.55 V, lower limit voltage of discharge: 2.5 V) was measured, and the ratio of (high rate capacity) / (initial capacity) was defined as a percentage to obtain rate characteristics (%).
The evaluation conditions and results are shown in Tables 1 and 2.

Claims (6)

Li _x Ni _a Co _b M _c M _d O _{2 + α} (a + b + c + d = 1, 1.0 ≦ x ≦ 1.1, 0 <d / (a + b + c) ≦ 0.1, 0 <α ≦ 0.2, M Is Nb or a composition represented by Nb and at least one selected from Ti, Mg, Al, Zr, Mo and W)
S content is 100 mass ppm or less,
Non-spherical particles,
A positive electrode active material for an all-solid-state lithium ion battery in which M, Ni, Co, and Mn other than Al are uniformly dispersed in EDX measurement of a particle cross section.   The positive electrode active material for an all solid lithium ion battery according to claim 1, wherein the content of S is 70 mass ppm or less.   A positive electrode for an all-solid-state lithium-ion battery, comprising the positive-electrode active material for an all-solid-state lithium-ion battery according to claim 1.   An all-solid lithium-ion battery including the positive electrode according to claim 3, a negative electrode, and a solid electrolyte. M is Nb,
A process of dissolving nickel ingot, cobalt ingot, and manganese ingot in nitric acid to obtain a ingot solution;
A step of adding the base metal solution to lithium carbonate suspension water to obtain a slurry before spraying,
Adding an aqueous solution of niobium oxalate to the slurry before spraying, and spray-drying to obtain a dry powder, and
Baking the dried powder at 775 to 950 ° C. in an oxygen-containing atmosphere in a dry state,
The method for producing a positive electrode active material for an all-solid lithium ion battery according to claim 1, comprising: M comprises Nb and at least one selected from Ti, Mg, Al, Zr, Mo and W;
A process of dissolving nickel ingot, cobalt ingot, and manganese ingot in nitric acid to obtain a ingot solution;
A step of adding the base metal solution to lithium carbonate suspension water to obtain a slurry before spraying,
An aqueous solution of niobium oxalate and at least one selected from an aqueous solution of titanium diammonium oxalate, an aqueous solution of magnesium nitrate, an aqueous solution of aluminum nitrate, an aqueous solution of zirconyl oxynitrate, an aqueous solution of lithium molybdate, and an aqueous solution of ammonium paratungstate are added to the slurry before spraying. Adding and spray-drying to obtain a dry powder; and
Baking the dried powder at 775 to 950 ° C. in an oxygen-containing atmosphere in a dry state,
The method for producing a positive electrode active material for an all-solid lithium ion battery according to claim 1, comprising: