Lithium nickel oxide and its manufacturing method

Abstract

To provide a method for producing a lithium nickel oxide capable of efficiently producing the lithium nickel oxide suppressing the spread of a particle size distribution and suppressing gelation in an electrode composition.SOLUTION: A method for producing a lithium nickel oxide comprises: heat-treating a lithium hydroperoxide at a temperature of 100°C or higher and lower than 300°C under reduced pressure to obtain lithium peroxide; heat-treating the lithium peroxide at a temperature of 300°C or higher and 500°C or lower to obtain lithium oxide; and heat-treating a mixture of the lithium oxide and a metal oxide containing nickel at a temperature of 500°C or higher and 800°C or lower to obtain a lithium nickel oxide.SELECTED DRAWING: Figure 2A

Description

Technical Field

[0001] The present disclosure relates to lithium nickel oxide and a method for producing the same.

Background Art

[0002] A secondary battery containing a lithium transition metal composite oxide having a layered structure as a positive electrode active material has a high operating voltage of 4 V and can obtain a large capacity, so it is widely used as a power source for electronic devices such as mobile phones, notebook computers, digital cameras, etc. or an in-vehicle battery. With the higher functionality of electronic devices and in-vehicle batteries, further higher capacity of secondary batteries is required. For example, in Patent Document 1, as a positive electrode active material capable of large-capacity charge and discharge, a lithium nickel composite oxide having a composition represented by Li2NiO 2+y (0 < y < 0.3) has been proposed. In Patent Document 2, Li2NiO2 that can be used alone or in combination with a conventional lithiated transition metal oxide material has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a positive electrode active material is combined with another positive electrode active material, it is required to prepare a positive electrode active material with a controlled particle size from the viewpoint of filling in the positive electrode. On the other hand, if pulverization is performed during the preparation of a positive electrode active material with a small average particle size, fine powder is mixed in, which makes gelation more likely to occur when preparing an electrode composition containing a solvent, and tends to make application difficult during electrode preparation. To address these problems, a lithium nickel oxide is required in which the spread of the particle size distribution is suppressed and gelation in the electrode composition is further reduced. One aspect of the present disclosure aims to provide a method for producing a lithium nickel oxide that can efficiently produce a lithium nickel oxide in which the spread of the particle size distribution is suppressed and gelation in the electrode composition is reduced. [Means for solving the problem]

[0005] The first aspect is a method for producing lithium nickel oxide, the method including: heat-treating lithium hydroperoxide under reduced pressure at a temperature of 100° C. or more and less than 300° C. to obtain lithium peroxide; heat-treating the lithium peroxide at a temperature of 300° C. or more and 500° C. or less to obtain lithium oxide; and heat-treating a mixture of the lithium oxide and a metal oxide containing nickel at a temperature of 500° C. or more and 800° C. or less to obtain lithium nickel oxide.

[0006] The second aspect is a method for producing lithium oxide, the method including: heat-treating lithium hydroperoxide under reduced pressure at a temperature of 100° C. or more and less than 300° C. to obtain lithium peroxide; and heat-treating the lithium peroxide at a temperature of 300° C. or more and 500° C. or less to obtain lithium oxide.

[0007] The third embodiment is a lithium transition metal compound powder. The lithium transition metal compound powder includes lithium nickel oxide. The lithium nickel oxide has a ratio of the number of moles of lithium to the total number of moles of metal elements other than lithium of 1.6 or more and 2.3 or less, a value obtained by dividing the 90% particle size D90 by the 10% particle size D10 in a cumulative particle size distribution based on volume is less than 5.8, and a 50% particle size D50 is 3 μm or more and 25 μm or less. Effect of the Invention

[0008] According to one aspect of the present disclosure, it is possible to provide a method for producing lithium nickel oxide that can efficiently produce lithium nickel oxide in which the spread of the particle size distribution is suppressed and gelation in the electrode composition is reduced. [Brief description of the drawings]

[0009] [Figure 1A] 1 is an example of a scanning electron microscope (SEM) image of the lithium oxide used in the production of Example 1. [Figure 1B] FIG. 1B is an example of an SEM image in which a part of the SEM image in FIG. 1A is further enlarged. [Figure 1C] 1 is an example of a SEM image of lithium oxide used in the production of Comparative Example 1. [Figure 1D] 1 is an example of a SEM image of lithium oxide used in the production of Comparative Example 2. [Figure 2A] 2 is an example of an SEM image of the lithium nickel oxide according to Example 1. [Figure 2B] 4 is an example of an SEM image of the lithium nickel oxide according to Example 2. [Figure 2C] 1 is an example of an SEM image of the lithium nickel oxide according to Example 3. [Figure 2D] 1 is an example of an SEM image of the lithium nickel oxide according to Comparative Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In this specification, the term "step" includes not only an independent step, but also a step that cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved. In addition, the content of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition. In this specification, the average particle size means the volume average particle size, unless otherwise specified, and is measured as the 50% particle size (D50) corresponding to the 50% cumulative volume from the small diameter side in the volume-based particle size distribution. In addition, the 90% particle size D90 and the 10% particle size D10 are particle sizes corresponding to the 90% and 10% cumulative volume in the volume-based cumulative particle size distribution, respectively. The volume-based cumulative particle size distribution is measured using a laser diffraction method. Hereinafter, the embodiments of the present invention will be described in detail. However, the embodiments shown below are examples of methods for producing lithium nickel oxide to embody the technical idea of ​​the present invention, and the present invention is not limited to the methods for producing lithium nickel oxide shown below.

[0011] Method for producing lithium nickel oxide The method for producing lithium nickel oxide includes a first step of heat-treating lithium hydroperoxide at a temperature of 100°C or more and less than 300°C under reduced pressure to obtain lithium peroxide, a second step of heat-treating the lithium peroxide at a temperature of 300°C or more and 500°C or less to obtain lithium oxide, and a third step of heat-treating a mixture of lithium oxide and a metal oxide containing nickel at a temperature of 500°C or more and 800°C or less to obtain lithium nickel oxide.

[0012] The method for producing lithium nickel oxide of the present embodiment can efficiently produce lithium nickel oxide having a desired volume average particle size, for example, 3 μm to 25 μm, preferably 4 μm to 20 μm, more preferably 4 μm to 11 μm, and a controlled particle size distribution. This is because, for example, the content of impurities such as lithium hydroxide in the lithium peroxide obtained in the first step can be sufficiently reduced, so that the purity of the lithium oxide obtained in the second step can be improved and sintering in the third step can be suppressed. In addition, by suppressing sintering in the third step, post-treatment such as pulverization is not required, and the generation of fine powder generated by these post-treatments is suppressed. Lithium nickel oxide in which the amount of fine powder having a nano-order particle size that is difficult to classify using a sieve or the like is reduced can suppress problems such as uneven coating during positive electrode production and gelation of the electrolyte.

[0013] First step In the first step, lithium hydroperoxide is heat-treated under reduced pressure at a temperature of 100°C or more and less than 300°C to obtain lithium peroxide. The lithium hydroperoxide may be prepared by a conventional method or may be appropriately selected from commercially available products. The lithium hydroperoxide may be a hydrate, for example, a monohydrate. The reduced pressure condition in the heat treatment may be, for example, 2000 Pa or less, preferably 1000 Pa or less, more preferably 200 Pa or less or 150 Pa or less. The lower limit of the pressure may be, for example, 10 Pa or more. By carrying out the heat treatment under reduced pressure conditions within the above range, the generation of lithium hydroxide generated as an impurity in the first step tends to be further reduced. The temperature of the heat treatment may be preferably 110°C or more, 120°C or more, or 140°C or more, and preferably 200°C or less, 180°C or less, or 160°C or less. By carrying out the heat treatment at a temperature within the above range, the generation of lithium hydroxide as an impurity tends to be further reduced. The time of the heat treatment may be, for example, 4 hours or more, preferably 8 hours or more. The heat treatment time may be, for example, 100 hours or less. When the heat treatment time is within the above range, the generation of lithium hydroxide as an impurity tends to be further reduced. The purity of the lithium peroxide obtained in the first step may be, for example, 91% by mass or more, and preferably 95% by mass or more.

[0014] By carrying out the first step under a predetermined reduced pressure, water generated when lithium peroxide is obtained from lithium hydroperoxide can be efficiently removed in a gaseous state. This can further reduce the generation of lithium hydroxide generated by the reaction of lithium peroxide with water. Therefore, the first step can be carried out by appropriately selecting the degree of reduced pressure and temperature at which the generated water can be vaporized and removed, and is not limited to the above-mentioned conditions. In addition, the first step is carried out under reduced pressure, but may be in a reduced pressure atmosphere containing an inert gas. Examples of the inert gas include rare gases such as nitrogen and argon.

[0015] The method for producing lithium nickel oxide may include a preparation step of preparing lithium hydroperoxide prior to the first step. The preparation step may include, for example, contacting lithium hydroxide with an oxidizing agent. The lithium hydroxide may be an anhydride or a hydrate. The lithium hydroxide may be, for example, a monohydrate. The purity of the lithium hydroxide may be, for example, 56% by mass or more, preferably 57% by mass or more. Examples of the oxidizing agent include hydrogen peroxide. By using hydrogen peroxide, it is possible to obtain lithium peroxide with fewer impurities. The molar ratio of the oxidizing agent to the lithium hydroxide may be 1.0 or more and 1.5 or less, preferably 1.1 or more and 1.4 or less, when the amount of change in oxidation number after the reaction of the oxidizing agent is -1. In addition, the contact of the lithium hydroxide with the oxidizing agent can be carried out, for example, by mixing an aqueous solution containing the oxidizing agent with lithium hydroxide and stirring as necessary. Thereafter, the resulting reaction product is subjected to solid-liquid separation to obtain lithium hydroperoxide. The concentration of the oxidizing agent solution used for the contact may be, for example, 20% by mass or more and 80% by mass or less, and preferably 30% by mass or more and 70% by mass or less. The temperature during the contact between the lithium hydroxide and the oxidizing agent may be, for example, 5° C. or more and 100° C. or less, and preferably 10° C. or more and 70° C. or less. The contact time may be, for example, 0.05 hours or more and 20 hours or less, and may be 0.1 hours or more and 1 hour or less.

[0016] Second process In the second step, the lithium peroxide obtained in the first step is heat-treated at a temperature of, for example, 300° C. or more and 500° C. or less to obtain lithium oxide. The temperature of the heat treatment in the second step is preferably 320° C. or more, 340° C. or more, or 360° C. or more, and preferably 460° C. or less, 440° C. or less, or 420° C. or less. When the heat treatment temperature is 500° C. or less, sintering of lithium oxide is more suppressed, and when the heat treatment temperature is 300° C. or more, the reaction proceeds sufficiently, so that the heat treatment is preferably performed at a temperature in the above range. The heat treatment time may be, for example, 1 hour or more, or 3 hours or more. The heat treatment time may be, for example, 100 hours or less. The heat treatment atmosphere may be, for example, an inert gas atmosphere, preferably a nitrogen atmosphere. By performing the heat treatment in the above atmosphere, the reaction between the obtained lithium oxide and the active gas can be more suppressed.

[0017] The lithium oxide obtained in the second step may be an aggregate of particles having an average particle size of, for example, 1 nm to 100 μm, preferably 10 nm to 30 μm. By using lithium oxide having a particle size within the above range, it tends to be easier to control the particle size during the production of lithium nickel oxide. The average particle size of lithium oxide is measured, for example, using a scanning electron microscope (SEM).

[0018] The purity of the obtained lithium oxide may be, for example, 90% by mass or more, and is preferably 95% by mass or more, or 98% by mass or more. When the lithium oxide contains less impurities such as lithium hydroxide, the sintering in the third step can be further reduced.

[0019] The second step may be carried out consecutively with the first step in the same heating device, or may be carried out sequentially after the first step in a separate heating device.

[0020] Third step In the third step, the mixture of lithium oxide and the metal oxide containing nickel is heat-treated at a temperature of 500° C. to 800° C. to obtain lithium nickel oxide. The metal oxide containing nickel may be nickel oxide (e.g., NiO) or a composite oxide containing nickel and other metal elements. Examples of other metal elements include cobalt (Co), manganese (Mn), aluminum (Al), calcium (Ca), zirconium (Zr), titanium (Ti), magnesium (Mg), tantalum (Ta), niobium (Nb), chromium (Cr), molybdenum (Mo), tungsten (W), iron (Fe), copper (Cu), silicon (Si), tin (Sn), bismuth (Bi), gallium (Ga), yttrium (Y), samarium (Sm), erbium (Er), cerium (Ce), neodymium (Nd), lanthanum (La), cadmium (Cd) and lutetium (Lu), and may be at least one selected from the group consisting of these. The other metal element may preferably be at least one selected from the group consisting of cobalt, manganese and copper, and more preferably may include at least cobalt. By including other metal elements as described above in the metal oxide containing nickel, the degree of synthesis of lithium nickel oxide tends to be high.

[0021] When the nickel-containing metal oxide contains other metal elements, the ratio of the total number of moles of metal elements other than nickel to the total number of moles of metal elements contained in the metal oxide may be, for example, 0.5 or less, preferably 0.2 or less, more preferably 0.1 or less. The lower limit of the ratio of the total number of moles of metal elements other than nickel to the total number of moles of metal elements may be, for example, 0.01 or more. When the nickel-containing metal oxide contains other metal elements within the above range, the charging capacity may be further improved when a secondary battery is formed by including lithium nickel oxide. In the nickel-containing metal oxide, the ratio of the total number of moles of at least one metal element selected from the group consisting of copper and iron to the total number of moles of metal elements may be, for example, 0.05 or less, preferably 0.02 or less, or less than 0.01. When the ratio of the total number of moles of at least one metal element selected from the group consisting of copper and iron is within the above range, it tends to be easy to detect when removing metal foreign matter that leads to battery short circuit in the obtained lithium nickel oxide.

[0022] The metal oxide containing nickel preferably has a low water content. The low water content may result in a better particle size distribution of the lithium nickel oxide obtained. The water content of the metal oxide containing nickel may be, for example, 5000 ppm or less, preferably 4000 ppm or less, 3000 ppm or less, 2000 ppm or less, or 1000 ppm or less. The lower limit of the water content is, for example, 100 ppm or more.

[0023] The volume average particle diameter (D50) of the nickel-containing metal oxide may be, for example, 3 μm or more and 25 μm or less, preferably 4 μm or more and 20 μm or less, and also preferably 4 μm or more and 11 μm or less. It is preferable that the nickel-containing metal oxide has a narrow particle size distribution. When the nickel-containing metal oxide has a volume average particle diameter within the above range, the lithium nickel oxide obtained tends to have a smaller volume average particle diameter. The nickel-containing metal oxide may have a value (D90 / D10) obtained by dividing the 90% particle diameter D90 by the 10% particle diameter D10 of 1 or more and 2.5 or less, preferably 1.2 or more, and also preferably 2.0 or less. When the nickel-containing metal oxide has a particle size distribution within the above range, the lithium nickel oxide obtained tends to have a narrower particle size distribution.

[0024] The mixture of lithium oxide and metal oxide containing nickel is obtained by mixing the lithium oxide obtained in the second step with the metal oxide containing nickel. The mixing method may be appropriately selected from commonly used dry mixing methods. Specific examples of the mixing method include a method using a mortar, a pestle, a stirring mixer, a V-type mixer, a W-type mixer, a ribbon mixer, a drum mixer, etc. The mixing atmosphere may be, for example, an inert gas atmosphere, and is preferably a nitrogen atmosphere. In addition, the mixing atmosphere is preferably a dry atmosphere, and the relative humidity in the mixing atmosphere may be, for example, 5% RH or less, and is preferably 1% RH or less. By performing the mixing under the above-mentioned atmosphere, the moisture contained in the mixture of lithium oxide and metal oxide containing nickel tends to be further reduced.

[0025] The mixture ratio of lithium oxide and metal oxide containing nickel in the mixture may be, for example, 1.5 or more and 2.5 or less, preferably 1.7 or more and preferably 2.3 or less, as the ratio of the number of moles of lithium contained in the lithium oxide to the total number of moles of metals contained in the metal oxide containing nickel. By setting the mixture ratio of lithium oxide and metal oxide containing nickel in the above range, a lithium nickel oxide with higher purity tends to be obtained.

[0026] The atmosphere in which the mixture is heat-treated may be an inert gas atmosphere, preferably a nitrogen atmosphere. The atmosphere in which the mixture is heat-treated may have an active gas content of, for example, 5% by volume or less, preferably 3% by volume or less, or 1% by volume or less. By performing heat treatment under the above-mentioned atmosphere, adhesion of multiple powders during heat treatment due to moisture or the like can be reduced, and the particle size of the lithium nickel oxide tends to be easier to control.

[0027] The temperature of the heat treatment of the mixture may be, for example, from 500° C. to 800° C., and preferably from 600° C. to 700° C. The time for the heat treatment of the mixture may be, for example, 3 hours or more, and preferably 5 hours or more, and the heat treatment time of the mixture may be, for example, 100 hours or less.

[0028] The method for producing lithium nickel oxide may further include a post-treatment step of subjecting the lithium nickel oxide obtained in the third step to a crushing treatment, classification treatment, or the like as necessary. When a crushing treatment is performed, it is preferable to perform the crushing treatment under conditions that suppress the generation of fine powder. Details of the lithium nickel oxide obtained by the production method of this embodiment are as described below.

[0029] Lithium transition metal compound powder The lithium transition metal compound powder of the present embodiment includes lithium nickel oxide. The lithium nickel oxide may have a ratio of the number of moles of lithium to the total number of moles of metal elements other than lithium of 1.6 or more and 2.3 or less, a value (D90 / D10) obtained by dividing the 90% particle size D90 by the 10% particle size D10 of less than 5.8, and a 50% particle size D50 of 3 μm or more and 25 μm or less.

[0030] The lithium transition metal compound powder has a relatively small 50% particle diameter D50 and a narrow particle size distribution, so that when the lithium transition metal compound powder is used as a positive electrode material for a non-aqueous electrolyte secondary battery, it can suppress coating unevenness during positive electrode production and improve the filling property in the positive electrode. The lithium transition metal compound powder can be efficiently produced, for example, by the above-mentioned method for producing lithium nickel oxide.

[0031] The lithium nickel oxide constituting the lithium transition metal compound powder may have a ratio of the number of moles of lithium to the total number of moles of metal elements other than lithium of, for example, 1.6 or more and 2.3 or less, preferably 1.7 or more or 1.8 or more, and preferably 2.1 or less or 2.05 or less. By having the ratio of the number of moles of lithium to the total number of moles of metal elements other than lithium in the above range, even in a battery using a negative electrode active material such as silicon oxide that has a large irreversible capacity during initial charging and discharging, the irreversible lithium ions tend to be more compensated for. In addition, the lithium nickel oxide may have a ratio of the total number of moles of metal elements other than lithium and nickel to the total number of moles of metal elements other than lithium of, for example, 0.5 or less, preferably 0.2 or less or 0.1 or less, and more preferably 0.05 or less. The lithium nickel oxide may have a ratio of the number of moles of oxygen element to the total number of moles of metal elements other than lithium of, for example, 1.6 or more and 2.3 or less, preferably 1.7 or more, and preferably 2.1 or less.

[0032] The lithium nickel oxide may have a composition represented by the following formula: Li x Ni y M 1-y O α

[0033] Here, 1.6≦x≦2.3, 0.5≦y≦1.0, and 1.6≦α≦2.3. M represents at least one selected from the group consisting of Co, Mn, Al, Ca, Zr, Ti, Mg, Ta, Nb, Cr, Mo, W, Fe, Cu, Si, Sn, Bi, Ga, Y, Sm, Er, Ce, Nd, La, Cd, and Lu. x is preferably 1.7≦x≦2.1, or 1.8≦x≦2.05. y is preferably 0.8≦y≦1, or 0.9≦y≦1, more preferably 0.95≦y≦1. α is preferably 1.7≦α≦2.1. M is preferably at least one selected from the group consisting of Co, Mn, and Cu, and more preferably may contain at least Co. When the nickel-containing metal oxide contains other metal elements within the above range, the charging capacity may be further improved when a secondary battery is formed by including lithium nickel oxide.

[0034] The lithium transition metal compound powder may have a D90 / D10 of preferably less than 5.8 or 5.5 or less. The lower limit of D90 / D10 may be, for example, 1.5 or more. When the lithium transition metal compound powder has a D90 / D10 within the above range, the packing property may be improved when mixed with other positive electrode active materials to form a positive electrode. In addition, the lithium transition metal compound powder may have a 50% particle diameter D50 of preferably 3 μm or more and 25 μm or less, 4 μm or more and 20 μm or less, or 4 μm or more and 11 μm or less. When the lithium transition metal compound powder has a 50% particle diameter D50 within the above range, the packing property tends to be improved when mixed with other positive electrode active materials to form a positive electrode. In addition, the lithium transition metal compound powder may have a D50 / D10 of, for example, 2.6 or less, preferably 2.3 or less. The lower limit of D50 / D10 may be, for example, 1.2 or more. When the D50 / D10 of the lithium transition metal compound powder is within the above range, gelation can be further reduced.

[0035] How lithium oxide is produced The method for producing lithium oxide of the present embodiment includes a first step of heat-treating lithium hydroperoxide at a temperature of 100° C. or more and less than 300° C. under reduced pressure to obtain lithium peroxide, and a second step of heat-treating the lithium peroxide at a temperature of 300° C. or more and 500° C. or less to obtain lithium oxide.

[0036] The method for producing lithium oxide can efficiently produce high-purity lithium oxide, which is an aggregate of particles having a desired average particle size of, for example, 1 nm to 100 μm, preferably 10 nm to 30 μm. This can be considered to be because, for example, the content of impurities such as lithium hydroxide in the lithium peroxide obtained in the first step can be sufficiently reduced, making it easy to improve the purity of the lithium oxide obtained in the second step.

[0037] The details of the first and second steps in the method for producing lithium oxide are similar to those of the first and second steps in the method for producing lithium nickel oxide. EXAMPLES

[0038] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0039] Example 1 Preparation of lithium oxide A 35% by mass aqueous solution of hydrogen peroxide and lithium hydroxide (LiOH·H2O) with a purity of 57% by mass were mixed so that the molar ratio of hydrogen peroxide to lithium hydroxide was 1.3, and the mixture was stirred at room temperature (25°C) for 0.5 hours. After stirring, the resulting slurry was filtered to separate the solid. The resulting solid was heat-treated at 150°C under reduced pressure (100 Pa) for 10 hours to obtain lithium peroxide (Li2O2) with a purity of 99% by mass. The resulting lithium peroxide was heat-treated at 380°C for 10 hours in a nitrogen atmosphere to obtain lithium oxide (Li2O) with a purity of 99% by mass. SEM images of the resulting lithium oxide are shown in Figures 1A and 1B.

[0040] Synthesis of lithium nickel oxide The obtained lithium oxide (Li2O) and nickel oxide (NiO) with a moisture content of 1000 ppm and D50 of 5.0 μm were weighed out so that the molar ratio of lithium to nickel (Li / Ni) was 2.0, and mixed in a nitrogen gas atmosphere with a humidity of 1% RH or less. The obtained mixture was heat-treated at 650°C for 10 hours in a nitrogen gas atmosphere to obtain lithium nickel oxide.

[0041] The composition of the obtained lithium nickel oxide was analyzed and found to be Li2NiO2. The volume-based particle size distribution of the obtained lithium nickel oxide was measured using a laser diffraction particle size distribution analyzer (Malvern; Mastersizer 3000), and found to be D10 2.8 μm, D50 6.2 μm, and D90 15.3 μm. An SEM image of the obtained lithium nickel oxide is shown in Figure 2A.

[0042] Example 2 Lithium nickel oxide was obtained in the same manner as in Example 1, except that the nickel oxide used was changed to nickel oxide having a water content of 400 ppm and a D50 of 8.3 μm.

[0043] The composition of the obtained lithium nickel oxide was analyzed and found to be Li2NiO2. The obtained lithium nickel oxide also had a D10 of 5.5 μm, a D50 of 10.3 μm, and a D90 of 19.0 μm. The SEM image of the obtained lithium nickel oxide is shown in Figure 2B.

[0044] Example 3 Lithium nickel oxide was obtained in the same manner as in Example 1, except that the nickel oxide used was changed to nickel oxide having a water content of 1700 ppm and a D50 of 20.8 μm.

[0045] The composition of the obtained lithium nickel oxide was analyzed and found to be Li2NiO2. The obtained lithium nickel oxide also had a D10 of 14.8 μm, a D50 of 22.4 μm, and a D90 of 34.3 μm. The SEM image of the obtained lithium nickel oxide is shown in Figure 2C.

[0046] Comparative Example 1 Lithium nickel oxide was obtained in the same manner as in Example 1, except that in the preparation of lithium oxide, the heat treatment of the solid after filtration was performed at normal pressure instead of reduced pressure. The purity of the lithium peroxide (Li2O2) obtained at the intermediate stage was 90 mass%, and the purity of the lithium oxide was 89 mass%. Also, an SEM image of the obtained lithium oxide is shown in FIG. 1C.

[0047] The composition of the obtained lithium nickel oxide was analyzed and found to be Li2NiO2. The obtained lithium nickel oxide also had a D10 of 11.0 μm, a D50 of 29.3 μm, and a D90 of 63.6 μm.

[0048] Comparative Example 2 Lithium nickel oxide was obtained in the same manner as in Example 1, except that lithium oxide having a purity of 99% by mass manufactured by Kojundo Chemical Co., Ltd. was used as the lithium oxide. An SEM image of the lithium oxide used is shown in FIG. 1D.

[0049] The composition of the obtained lithium nickel oxide was analyzed and found to be Li2NiO2. The obtained lithium nickel oxide also had a D10 of 3.9 μm, a D50 of 11.9 μm, and a D90 of 35.0 μm.

[0050] Comparative Example 3 The lithium nickel oxide obtained in Comparative Example 2 was subjected to a pulverization process to adjust the particle size distribution. The obtained lithium nickel oxide had a D10 of 1.7 μm, a D50 of 6.4 μm, and a D90 of 30.0 μm. An SEM image of the obtained lithium nickel oxide is shown in FIG. 2D.

[0051] [Table 1]

[0052] evaluation Pellet Density The pellet density of the lithium nickel oxides produced in Examples 1, 2, 3, Comparative Examples 2 and 3 was evaluated. The pellet density was measured using a positive electrode active material LNCM (LiNi 0.50 Co 0.20 Mn 0.30 A mixture was prepared by mixing lithium nickel oxide (O2) and lithium nickel oxide in a mass ratio of 0.80:0.20, and the mixture was weighed out to within 2.0000g (error range ±0.0005g). The mixture was pressed in a 20mm size mold with a presser of 25kN for 30 seconds to measure the reduction in height, and then the weight per volume was measured. The measurement results are shown in Table 2.

[0053] [Table 2]

[0054] The lithium nickel oxides of the Examples tended to have higher pellet density than the lithium nickel oxides of the Comparative Examples.

[0055] (Gelling characteristics of positive electrode mixture slurry) High Ni content positive electrode active material LNCM (LiNi 0.50 Co 0.20 Mn 0.30 O2) was used to prepare a positive electrode mixture slurry as follows, and the gelling characteristics of the positive electrode mixture slurry were evaluated.

[0056] (Preparation of Positive Electrode Mixture Slurry) A positive electrode mixture slurry was prepared by dispersing 93 parts by mass of a mixture of the positive electrode active material LNCM and lithium nickel oxide (mass ratio 0.98:0.02), 4 parts by mass of acetylene black as a conductive agent, a binder, and PVP (polyvinylpyrrolidone) in N-methyl-2-pyrrolidone (NMP).

[0057] (Gelling property evaluation) The viscosity of the positive electrode mixture slurry prepared above was measured immediately after the slurry preparation and 6 hours after the preparation using a B-type viscometer (Thermo Scientific; HAAKE Viscotester550). As shown in the following formula, the viscosity of the positive electrode mixture slurry 6 hours after preparation was divided by the viscosity immediately after preparation, and the result multiplied by 100 was taken as the gelation characteristic. (Slurry viscosity after 6 hours) x 100 / (Slurry viscosity immediately after preparation)

[0058] [Table 3]

[0059] It was confirmed that gelation was suppressed in the positive electrode mixture slurry using the lithium nickel oxide of Example 1, compared to the positive electrode mixture slurry using the lithium nickel oxide of Comparative Example 3 that had been subjected to a pulverization treatment.

Claims

1. heat-treating the lithium hydroperoxide under reduced pressure at a temperature of 140° C. or higher but lower than 300° C. to obtain lithium peroxide; heat-treating the lithium peroxide at a temperature of 300° C. or more and 500° C. or less to obtain lithium oxide; and heat-treating the mixture of lithium oxide and a metal oxide containing nickel at a temperature of 500° C. or higher and 800° C. or lower to obtain lithium nickel oxide.

2. 2. The method for producing lithium nickel oxide according to claim 1, wherein the heat treatment of the lithium peroxide is carried out in an inert gas atmosphere.

3. 3. The method for producing lithium nickel oxide according to claim 1, wherein the heat treatment of the lithium hydroperoxide is carried out at 2000 Pa or less.

4. heat-treating the lithium hydroperoxide at a temperature of 100° C. or higher and lower than 300° C. under a reduced pressure of 2000 Pa or lower to obtain lithium peroxide; heat-treating the lithium peroxide at a temperature of 300° C. or more and 500° C. or less to obtain lithium oxide; and heat-treating the mixture of lithium oxide and a metal oxide containing nickel at a temperature of 500° C. or higher and 800° C. or lower to obtain lithium nickel oxide.

5. The method for producing lithium nickel oxide according to claim 4, wherein the heat treatment of the lithium peroxide is carried out in an inert gas atmosphere.

6. The method for producing lithium nickel oxide according to any one of claims 1 to 5, wherein the water content in the metal oxide is 5000 ppm or less.

7. The method for producing lithium nickel oxide according to any one of claims 1 to 6, wherein the metal oxide has a ratio of the total mole number of metal elements other than nickel to the total mole number of metal elements of 0.1 or less.

8. The method for producing lithium nickel oxide according to any one of claims 1 to 7, wherein the heat treatment of the mixture of lithium oxide and the metal oxide containing nickel is carried out in an inert gas atmosphere.

9. The method for producing lithium nickel oxide according to any one of claims 1 to 8, wherein the metal oxide has a volume average particle size of 3 µm or more and 25 µm or less.

10. The method for producing lithium nickel oxide according to any one of claims 1 to 9, wherein the lithium nickel oxide has a volume average particle size of 3 µm or more and 25 µm or less.

11. heat-treating the lithium hydroperoxide under reduced pressure at a temperature of 140° C. or higher but lower than 300° C. to obtain lithium peroxide; and heat-treating the lithium peroxide at a temperature of 300° C. or higher and 500° C. or lower to obtain lithium oxide.

12. The method for producing lithium oxide according to claim 11, wherein the heat treatment of the lithium hydroperoxide is carried out at 2000 Pa or less.

13. The method for producing lithium oxide according to claim 11 or 12, wherein the heat treatment of the lithium peroxide is carried out in an inert gas atmosphere.

14. heat-treating the lithium hydroperoxide at a temperature of 100° C. or higher and lower than 300° C. under a reduced pressure of 2000 Pa or lower to obtain lithium peroxide; and heat-treating the lithium peroxide at a temperature of 300° C. or higher and 500° C. or lower to obtain lithium oxide.

15. The method for producing lithium oxide according to claim 14, wherein the heat treatment of the lithium peroxide is carried out in an inert gas atmosphere.

16. Lithium nickel oxide The lithium nickel oxide is a lithium transition metal compound powder in which the ratio of the number of moles of lithium to the total number of moles of metal elements other than lithium is 1.6 or more and 2.3 or less, the value obtained by dividing the 90% particle size D90 by the 10% particle size D10 in a volume-based cumulative particle size distribution is less than 5.8, and the 50% particle size D50 is 3 μm or more and 25 μm or less.

17. 17. The lithium transition metal compound powder according to claim 16, wherein the lithium nickel oxide has a composition represented by the following formula: Li ｘ Ni ｙ M １－ｙ O α Here, 1.6≦x≦2.3, 0.5≦y≦1.0, and 1.6≦α≦2.3, and M represents at least one selected from the group consisting of Co, Mn, Al, Ca, Zr, Ti, Mg, Ta, Nb, Cr, Mo, W, Fe, Cu, Si, Sn, Bi, Ga, Y, Sm, Er, Ce, Nd, La, Cd, and Lu.

18. 18. The lithium transition metal compound powder according to claim 16, wherein the lithium nickel oxide has a ratio of the total number of moles of metal elements other than lithium and nickel to the total number of moles of metal elements other than lithium of 0.1 or less.

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