Method for producing lithium metal composite oxides

Abstract

To provide a manufacturing method that can produce positive electrode active material in high yield, resulting in a non-aqueous electrolyte secondary battery exhibiting excellent charge-discharge capacity. [Solution] The manufacturing method according to this disclosure includes a precursor mixing step of mixing lithium hydroxide powder and a precursor metal compound, and a calcination step of calcining the precursor mixture. The lithium hydroxide powder has a particle size distribution of 1 μm to 1000 μm, a first peak showing the maximum frequency of peak tops, and a second peak showing the maximum frequency of peak tops among peaks that show peak tops at particle sizes 50 μm or more away from the particle size, the ratio of the frequency of the second peak top to the frequency of the first peak top is 0.2 to 0.95, and the loose bulk density is 0.10 g / cm³. 3 More than 0.45g / cm 3 The following will be used: A precursor mixture with a loosened bulk density of 0.95 g / cm³. 3 Below, we will use materials where the ratio of packing density to loose bulk density is 1.10 or higher.

Description

[Technical Field]

[0001] This disclosure relates to a method for producing lithium metal composite oxides. [Background technology]

[0002] Lithium-ion secondary batteries are attracting attention as power sources for electronic devices such as AV equipment and personal computers. They are small, lightweight, have high energy density, high charge / discharge voltage, and large charge / discharge capacity.

[0003] Lithium-ion secondary batteries using layered or spinel-type lithium transition metal composite oxides as the positive electrode active material are gaining practical use as batteries with high energy density because they can achieve high voltages of around 4V. The main materials proposed are lithium cobalt composite oxide (LiCoO2), which is relatively easy to synthesize, lithium nickel composite oxide (LiNiO2), which uses nickel that is cheaper than cobalt, and lithium nickel cobalt manganese composite oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Examples include lithium manganese composite oxides (LiMn2O4) using O2 and manganese.

[0004] Such lithium metal composite oxides can generally be manufactured by mixing a lithium source with a metal source such as nickel and firing the mixture. Here, the positive electrode of a lithium-ion secondary battery is formed, for example, by mixing a positive electrode active material with a binder such as polyvinylidene fluoride (PVDF) and a solvent such as N-methyl-2-pyrrolidone (NMP) to make a positive electrode mixture paste, which is then applied to a current collector such as aluminum foil. At this time, if lithium is released from the lithium metal composite oxide in the positive electrode mixture paste, it may react with the water contained in the binder, etc., to produce lithium hydroxide.

[0005] When the production of lithium hydroxide increases in this way, lithium hydroxide reacts with the binder, causing the positive electrode active material paste to gel. The gelling of the positive electrode active material paste leads to poor operability and reduced yield in the manufacturing process. This tendency is particularly prominent when the lithium in the lithium transition metal composite oxide, which is the positive electrode active material, is excessive compared to the stoichiometric ratio of the transition metal, especially when the proportion of nickel in the transition metal is high.

[0006] Here, the liberation of lithium is considered to be derived from the lithium content not incorporated into the crystal lattice of the lithium metal composite oxide and from the lithium incorporated into the crystal lattice of the lithium metal composite oxide. When the lithium incorporated into the crystal lattice of the lithium metal composite oxide elutes, the resistance of the lithium metal composite oxide increases, which can reduce the charge-discharge efficiency.

[0007] In order to remove the lithium content not incorporated into the crystal lattice of the lithium metal composite oxide, for example, as disclosed in Patent Document 1, a water washing treatment is performed on the fired product.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] But when attempting to remove the lithium content by performing a water washing treatment on the lithium metal composite oxide as in Patent Document 1, the lithium incorporated into the crystal lattice undergoes ion exchange with protons, resulting in a lithium-deficient state on the surface of the lithium metal composite oxide or the surface of the lithium metal composite oxide becoming rock salt phase, thereby reducing the charge-discharge capacity of the lithium-ion secondary battery.

[0010] Depending on the properties of the lithium source and metal sources such as nickel, it may not be possible to densely fill the sheath with the precursor mixture during firing, which can deteriorate productivity. On the other hand, when the precursor mixture is densely filled in the sheath, oxygen and heat do not reach the internal precursor mixture sufficiently, the quality of the resulting lithium metal composite oxide deteriorates, and the charge-discharge capacity of the lithium-ion secondary battery decreases.

[0011] The present disclosure has been made in view of the above circumstances, and in a non-aqueous electrolyte secondary battery including a lithium-ion secondary battery, when used as a positive electrode active material, a lithium metal composite oxide in which the non-aqueous electrolyte secondary battery exhibits excellent charge-discharge capacity can be produced at a high yield. An object is to provide a method for producing a lithium metal composite oxide.

Means for Solving the Problems

[0012] The inventors of the present invention have intensively studied to solve the above-described problems. As a result, a precursor mixing step of mixing lithium hydroxide powder and a precursor metal compound containing at least a transition metal to obtain a precursor mixture, and a firing step of firing the precursor mixture to obtain a lithium metal composite oxide, are included. In the precursor mixing step, as the lithium hydroxide powder, in the particle size distribution obtained by performing dry measurement by the laser diffraction method, in the range of particle diameters of 1 μm or more and 1000 μm or less, the first peak showing the maximum value of the frequency value at the peak top, and among the peaks showing the peak top at a particle diameter separated by 50 μm or more from the particle diameter showing the peak top of the first peak, having a second peak showing the maximum value of the frequency value at the peak top, and the ratio of the frequency value at the peak top of the second peak to the frequency value at the peak top of the first peak (frequency value at the peak top of the second peak / frequency value at the peak top of the first peak) is 0.2 or more and 0.95 or less, and the loose bulk density is 0.10 g / cm 3 0.45 g / cm or more 3 and below, and the loose bulk density of the precursor mixture is 0.95 g / cm 3According to the manufacturing method of adjusting so that the ratio of the packing density to the loose bulk density (sheath packing density / loose bulk density) becomes 1.10 or more, when used as a positive electrode active material, it has been found that a lithium metal composite oxide in which a non-aqueous electrolyte secondary battery exhibits excellent charge and discharge capacity can be produced in a high yield. Specifically, the present disclosure provides the following.

[0013] (1) A precursor mixing step of mixing lithium hydroxide powder and a precursor metal compound containing at least a transition metal to obtain a precursor mixture, A firing step of firing the precursor mixture to obtain a lithium metal composite oxide, In the precursor mixing step, As the lithium hydroxide powder, in the particle size distribution obtained by dry measurement by the laser diffraction method, in the range of particle diameters of 1 μm or more and 1000 μm or less, a first peak in which the frequency value at the peak top shows the maximum value, and a peak top at a particle diameter 50 μm or more away from the particle diameter showing the peak top of the first peak Among the peaks showing the peak top, having a second peak in which the frequency value at the peak top shows the maximum value, and the ratio of the frequency value at the peak top of the second peak to the frequency value at the peak top of the first peak (frequency value at the peak top of the second peak / frequency value at the peak top of the first peak) is 0.2 or more and 0.95 or less, and the loose bulk density is 0.10 g / cm 3 or more and 0.45 g / cm 3 or less is used, The loose bulk density of the precursor mixture is 0.95 g / cm 3 or less, and the ratio of the packing density to the loose bulk density (sheath packing density / loose bulk density) is adjusted to be 1.1 or more A method for producing a lithium metal composite oxide.

[0014] (2) The lithium metal composite oxide has the general formula Li a Ni x Co y Mn z M w O αA method for producing a lithium metal composite oxide as described in (1), represented by the formula (wherein M is one or more elements other than Li, Ni, Co, Mn, and O, and 0.90 ≤ a ≤ 1.15, x + y + z + w = ​​1.00, and 1.60 ≤ α ≤ 2.40). [Effects of the Invention]

[0015] According to this disclosure, it is possible to provide a method for producing lithium metal composite oxides that can be produced in high yield when used as a positive electrode active material in non-aqueous electrolyte secondary batteries, including lithium-ion secondary batteries, resulting in non-aqueous electrolyte secondary batteries exhibiting excellent charge and discharge capacity. [Modes for carrying out the invention]

[0016] The embodiments of this disclosure will be described below, but this disclosure is not limited in any way by the description of the embodiments and can be implemented with appropriate modifications.

[0017] <Method for manufacturing lithium metal composite oxides> A method for producing a lithium metal composite oxide according to an embodiment of this disclosure includes a precursor mixing step of mixing lithium hydroxide powder with a precursor metal compound containing at least a transition metal to obtain a precursor mixture, and a calcination step of calcining the precursor mixture to obtain a lithium metal composite oxide. In the precursor mixing step, the lithium hydroxide powder has a particle size distribution obtained by dry measurement using laser diffraction, in which a first peak shows the maximum value at the peak top within a particle size range of 1 μm to 1000 μm, and a second peak shows the maximum value at the peak top among peaks with a particle size 50 μm or more away from the particle size showing the peak top of the first peak, the ratio of the frequency value at the peak top of the second peak to the frequency value at the peak top of the first peak (frequency value at the peak top of the second peak / frequency value at the peak top of the first peak) is 0.2 or more and 0.95 or less, and the loose bulk density is 0.10 g / cm³. 3 More than 0.45g / cm 3The following was used, and the loosened bulk density of the precursor mixture was 0.95 g / cm³. 3 The following adjustments are made so that the ratio of packing density to loose bulk density (sheath packing density / loose bulk density) is 1.10 or higher.

[0018] This manufacturing method increases the number of contact points between lithium compounds and precursor compounds in the precursor mixture, allowing the lithiation reaction to proceed more uniformly during firing. This reduces the amount of residual lithium in the lithium metal composite oxide and improves battery characteristics. Furthermore, by controlling the loose bulk density and packing density of the precursor mixture (a mixture of lithium hydroxide particle size distribution and precursor compounds) to predetermined values, the scattering of lithium hydroxide due to airflow in the firing furnace during firing can be suppressed. This reduces the deviation of the lithium metal composite oxide composition from the input metal ratio (reduction in lithium content). Moreover, since the resulting precursor mixture has a packing density higher than its loose bulk density, productivity is not compromised. This provides a method for producing lithium metal composite oxides that, when used as a positive electrode active material in non-aqueous electrolyte secondary batteries, including lithium-ion secondary batteries, exhibit excellent charge-discharge capacity, and can be produced in high yield.

[0019] Below, an example of a method for producing coated particles according to this embodiment will be described in detail for each step. However, steps other than the precursor mixing and calcination steps are not essential, and steps other than these two can be omitted. Furthermore, other steps may be included before or after each of the steps described below, as long as they do not hinder the effects of this disclosure.

[0020] Precursor preparation step: Prepare a precursor metal compound containing at least a transition metal. Precursor mixing step: A precursor mixture is prepared by mixing lithium hydroxide powder with a precursor metal compound. Firing process: The precursor mixture prepared in the precursor mixing process is fired. Water washing process: The lithium metal composite oxide obtained by firing in the main firing process is subjected to a water washing treatment. Drying process: The lithium metal composite oxide that has been washed with water is dried. Addition step: To the lithium metal composite oxide obtained in either the pre-calcination step or the drying step, an additive compound containing the additive element is added to obtain a mixture. Heat treatment step: The mixture obtained in the additive step is subjected to heat treatment to obtain coated particles.

[0021] [Precursor preparation process] First, a precursor metal compound containing at least a transition metal is prepared. The method for synthesizing the precursor metal compound is not particularly limited, but for example, a mixed aqueous solution containing an aqueous solution of a transition metal and various aqueous solutions of compounds containing other elements depending on the composition of the lithium metal composite oxide can be added dropwise to a reaction vessel that is being stirred with an alkaline aqueous solution such as an aqueous sodium hydroxide solution or an ammonia solution as the mother liquor, and the mixture is coprecipitation by a wet reaction while monitoring and controlling the pH to be within an appropriate range while adding sodium hydroxide, etc., to obtain hydroxides, oxides obtained by calcining hydroxides, carbonates, etc.

[0022] Furthermore, in the reaction for the synthesis of precursor metal compounds, it is preferable to create a nitrogen atmosphere in the reaction vessel using an inert gas, or more preferably nitrogen gas, from the time the alkaline aqueous solution which will serve as the mother liquor is prepared, and to keep the oxygen concentration in the reaction vessel system and solution as low as possible. By lowering the oxygen concentration, the oxidation of the co-precipitated hydroxide by residual oxygen exceeding a predetermined amount can be suppressed, and the formation of the precursor metal compound by crystallization can be promoted.

[0023] The aqueous solution of the transition metal is not particularly limited, but it is preferable to use an acidic aqueous solution, and more preferably an aqueous sulfuric acid solution (for example, an aqueous nickel sulfate solution in the case of a nickel compound). Furthermore, one or more transition metals can be used as the aqueous solution.

[0024] Specifically, transition metals that can be used include nickel, cobalt, manganese, titanium, niobium, tungsten, molybdenum, vanadium, chromium, iron, yttrium, ruthenium, and tantalum.

[0025] The nickel compound is not particularly limited, but one or more can be selected from, for example, nickel sulfate, nickel oxide, nickel hydroxide, nickel nitrate, nickel carbonate, nickel chloride, nickel iodide, and metallic nickel.

[0026] The cobalt compound is not particularly limited, but one or more selected from, for example, cobalt sulfate, cobalt oxide, cobalt hydroxide, cobalt nitrate, cobalt carbonate, cobalt chloride, cobalt iodide, and metallic cobalt can be used.

[0027] The manganese compound is not particularly limited, but for example, one or more selected from manganese sulfate, manganese oxide, manganese hydroxide, manganese nitrate, manganese carbonate, manganese chloride, manganese iodide, and metallic manganese can be used.

[0028] The titanium compound is not particularly limited, but for example, one or more selected from titanyl sulfate, titanium dioxide, titanium hydroxide, titanium nitrate, titanium carbonate, titanium chloride, titanium iodide, and metallic titanium can be used.

[0029] The niobium compound is not particularly limited, but one or more selected from, for example, niobium oxide, niobium chloride, lithium niobate, niobium iodide, etc., can be used.

[0030] The tungsten compound is not particularly limited, but one or more selected from, for example, tungsten oxide, sodium tungstate, ammonium paratungstate, hexacarbonyltungsten, tungsten sulfide, etc., can be used.

[0031] The iron compound is not particularly limited, but one or more selected from, for example, iron sulfate, iron oxide, iron hydroxide, iron nitrate, iron carbonate, iron chloride, iron iodide, and metallic iron can be used.

[0032] For transition metals, one or more elements selected from sulfates, oxides, hydroxides, nitrates, carbonates, chlorides, iodides, and metals may be used. In addition to transition metals, elements other than transition metals can also be used. While not particularly limited, elements other than transition metals include magnesium, aluminum, zinc, calcium, gallium, strontium, indium, tin, bismuth, zirconium, boron, and phosphorus.

[0033] The magnesium compound is not particularly limited, but one or more selected from, for example, magnesium sulfate, magnesium oxide, magnesium hydroxide, magnesium nitrate, magnesium carbonate, magnesium chloride, magnesium iodide, and metallic magnesium can be used.

[0034] The aluminum compound is not particularly limited, but examples include aluminum sulfate, aluminum oxide, aluminum hydroxide, aluminum nitrate, aluminum carbonate, aluminum chloride, aluminum iodide, sodium aluminate, and metallic aluminum.

[0035] The zirconium compound is not particularly limited, but for example, one or more selected from zirconium sulfate, zirconium oxide, zirconium nitrate, ammonium zirconium carbonate, zirconium chloride, zirconium iodide, and metallic zirconium can be used.

[0036] The zinc compound is not particularly limited, but one or more selected from, for example, zinc sulfate, zinc oxide, zinc hydroxide, zinc nitrate, zinc carbonate, zinc chloride, zinc iodide, and metallic zinc can be used.

[0037] In addition to transition metals, one or more elements selected from sulfates, oxides, hydroxides, nitrates, carbonates, chlorides, iodides, and metals may also be used.

[0038] The proportions of each compound should be adjusted so that the amounts of each element reach the desired ratio, taking into account the composition of the target lithium metal composite oxide.

[0039] The pH range of the liquid in the reaction vessel when synthesizing the precursor metal compound is not particularly limited and should be determined to obtain the desired shape, such as the secondary particle size and density. For example, a range of 10 to 13 is sufficient.

[0040] The precursor metal compound obtained by the wet reaction is preferably subjected to washing, dehydration, and drying.

[0041] Washing the precursor metal compound removes impurities such as sulfate, carbonate, and sodium that may have been incorporated into the aggregated particles or adhered to the surface during the reaction. For small amounts, washing can be performed using a Buchner funnel or by sending the reaction suspension through a press filter for washing and dehydration. While pure water, sodium hydroxide solution, sodium carbonate solution, etc., can be used for washing, pure water is preferred industrially.

[0042] [Precursor mixing step] A precursor mixture is prepared by mixing at least lithium hydroxide powder and the precursor metal compound prepared as described above in a predetermined ratio. The method of mixing is not particularly limited, but for example, at least the lithium hydroxide powder compound and the precursor metal compound may be mixed in powder form. In the case of using other components, they may be used as a solution or dispersion.

[0043] Here, the lithium hydroxide powder is measured dry by laser diffraction, and the resulting particle size distribution shows a first peak with the maximum value at the peak top in the particle size range of 1 μm to 1000 μm, and a second peak with the maximum value at the peak top among the peaks at particle sizes 50 μm or more away from the particle size showing the peak top of the first peak, and the ratio of the frequency value at the peak top of the second peak to the frequency value at the peak top of the first peak (frequency value at the peak top of the second peak / frequency value at the peak top of the first peak) is between 0.2 and 0.95, and the loose bulk density is 0.10 g / cm³. 3 More than 0.45g / cm 3 Use the following:

[0044] Furthermore, in this process, the bulk density of the loosened precursor mixture is 0.95 g / cm³. 3 The following adjustments are made so that the ratio of packing density to loose bulk density (packing density / loose bulk density) is 1.10 or higher.

[0045] By using lithium hydroxide powder and precursor mixtures with these characteristics, even when the precursor mixture is packed relatively densely into the sheath during the calcination process described later, a lithium metal composite oxide exhibiting high charge-discharge capacity can be obtained when used as a positive electrode active material for a lithium-ion secondary battery.

[0046] In lithium hydroxide powder, the ratio of the frequency value at the peak top of the second peak to the frequency value at the peak top of the first peak (frequency value at the peak top of the second peak / frequency value at the peak top of the first peak) is not particularly limited as long as it is between 0.2 and 0.95, but is preferably 0.25 or higher, 0.3 or higher, 0.35 or higher, or 0.4 or higher. On the other hand, the ratio of the frequency value at the peak top of the second peak to the frequency value at the peak top of the first peak of lithium hydroxide powder is preferably 0.94 or lower, 0.93 or lower, or 0.92 or lower.

[0047] The loosened bulk density of lithium hydroxide powder is 0.10 g / cm³. 3 More than 0.45g / cm 3 The following are not particularly limited, but for example, 0.12 g / cm³ 3 More than 0.15g / cm 3 More than 0.17g / cm 3 More than 0.20g / cm 3 More than 0.22g / cm 3 More than 0.25g / cm 3 The above is preferable. On the other hand, the loosened bulk density of lithium hydroxide powder is 0.44 g / cm³. 3 Below, 0.43g / cm 3 Below, 0.42g / cm 3 The following is preferable:

[0048] The loosened bulk density of the precursor mixture is 0.95 g / cm³. 3 The following are not particularly limited, but for example, 0.10 g / cm³ 3 More than 0.20g / cm 3 More than 0.30g / cm 3 More than 0.40g / cm 3 More than 0.50g / cm 3 More than 0.60g / cm 3 The above is preferable. On the other hand, the loosened bulk density of the precursor mixture is 0.94 g / cm³. 3 Below, 0.93g / cm 3 Below, 0.92g / cm 3 The following is preferable:

[0049] The ratio of the packing density to the loose bulk density of the precursor mixture (sheath packing density / loose bulk density) is not particularly limited as long as it is 1.10 or higher, but it is preferably 1.11 or higher, 1.12 or higher, or 1.13 or higher. On the other hand, the ratio of the packing density to the loose bulk density of the precursor mixture is preferably 1.7 or lower, 1.65 or lower, 1.60 or lower, 1.55 or lower, 1.50 or lower, 1.45 or lower, 1.40 or lower, or 1.35 or lower.

[0050] The mixing ratio of lithium hydroxide powder to the precursor metal compound is not particularly limited, but can be appropriately adjusted so that the amount of lithium and the total amount of each element are in the desired ratio, taking into consideration the composition of the target lithium metal composite oxide.

[0051] While lithium hydroxide is not particularly limited, either lithium hydroxide monohydrate (LiOH·H2O) or other lithium hydroxide hydrates, or anhydrous lithium hydroxide (LiOH), can be used, but the use of anhydrous lithium hydroxide (LiOH) is preferred.

[0052] Furthermore, when mixing lithium hydroxide powder and the precursor metal compound, elemental compounds may be added in predetermined proportions and mixed simultaneously. The type and proportion of elements to be added are not particularly limited and can be appropriately adjusted to achieve the desired proportions, taking into consideration the composition of the target lithium metal composite oxide.

[0053] The elements used are not particularly limited, as long as they are elements other than lithium and capable of constituting a lithium composite metal compound. Specifically, the elements can be selected according to the composition of the target lithium metal composite oxide. For example, transition metals such as nickel, cobalt, manganese, titanium, niobium, tungsten, molybdenum, vanadium, chromium, iron, yttrium, ruthenium, and tantalum can be used, while non-transition metal elements such as magnesium, aluminum, zinc, calcium, gallium, strontium, indium, tin, bismuth, zirconium, boron, and phosphorus can be used. The states of these elements are not particularly limited, but one or more can be selected from sulfates, oxides, hydroxides, nitrates, carbonates, chlorides, iodides, and metals.

[0054] [Firing process] The calcination process involves calcining the precursor mixture obtained in the precursor mixing process to obtain a lithium metal composite oxide. The calcination process may be carried out in two stages, a pre-calcination process and a main calcination process, or in a single main calcination process.

[0055] (Pre-firing process) The pre-calcination process involves calcining the precursor mixture at a lower temperature than the main calcination process described later, in order to form a pre-calcined product as a lithium metal composite oxide. In other words, this pre-calcination process lithifies the precursor mixture to form a lithium metal composite oxide containing at least lithium and a transition metal.

[0056] The main calcination process, described later, generally involves weighing lithium hydroxide powder, a precursor metal compound, and, if necessary, compounds of other elements, mixing them in a mixer, and then filling the resulting mixture into containers such as crucibles or saggars. However, particularly in the lithiumization reaction, as the mixture approaches the bottom of the container, it becomes difficult to discharge the generated gas to the outside and to diffuse the required oxygen concentration. As a result, it becomes difficult to control the uniformity of the reaction and the primary particle size. Therefore, it is preferable to perform pre-calcination to ensure the uniformity of the reaction and control the primary particle size, and to advance the lithiumization reaction of the precursor metal compound before the main calcination.

[0057] Therefore, in this pre-calcination process, it is preferable to incorporate a calcination method that particularly promotes the lithiumization reaction. Specifically, this includes a method that makes the mixture more susceptible to heat, facilitates the release of gases generated from lithium compounds, and diffuses gases with high oxygen partial pressure into the mixture (particles). For example, it is possible to achieve the desired properties by calcining a smaller amount of mixture.

[0058] In the pre-firing process, the mixture can be pre-fired by filling saggers or crucibles and firing them in a stationary furnace, roller hearth kiln, or pusher furnace, but it is preferable to fire the mixture while it is flowing. In such cases, a rotary kiln can be used as the apparatus.

[0059] The pre-firing temperature is not particularly limited, but is preferably 350°C or higher, 360°C or higher, 370°C or higher, 380°C or higher, or 390°C or higher. On the other hand, the pre-firing temperature is preferably 650°C or lower, 640°C or lower, 630°C or lower, 620°C or lower, or 610°C or lower.

[0060] The pre-firing time is not particularly limited as long as it is sufficient for the lithiumization reaction to proceed reliably and uniformly, but it is preferably, for example, 1 to 10 hours or 2 to 8 hours.

[0061] In this disclosure, the firing temperature refers to the highest temperature the object being heated reaches. The highest temperature is the temperature of the hottest part of the object being heated. The firing time refers to the time from when the firing temperature reaches a predetermined range until that range is maintained.

[0062] The atmosphere for pre-calcination is not particularly limited, and any oxidizing atmosphere that ensures the lithiumization reaction proceeds reliably and uniformly is acceptable. For example, it is preferable to use a decarboxylated oxidizing gas atmosphere with a carbon dioxide concentration of 30 ppm or less, or an oxygen atmosphere with an oxygen concentration of 80% by volume or more, 90% by volume or more, or 95% by volume or more.

[0063] The mixture, which has been pre-calcined in this way, will be subjected to a final calcination in a later step at a higher temperature to promote crystal and particle growth.

[0064] If the lithium metal composite oxide obtained in the pre-calcination process is in a lumpy state, it may be powdered using a disc mill or mortar and pestle. In addition, to ensure a uniform reaction in the main calcination process, the resulting pre-calcined mixed powder may be homogenized by mixing, and additives may be added during the mixing process.

[0065] (Main firing process) In the main firing process, crystal growth is carried out. The lithium metal composite oxide obtained in this main firing process is in the form of primary or secondary particles.

[0066] The firing temperature is not particularly limited as long as it is higher than the pre-firing temperature, and can be adjusted depending on the composition of the lithium metal composite oxide to be obtained. For example, the firing temperature is preferably 700°C or higher, 710°C or higher, 720°C or higher, 730°C or higher, 740°C or higher, or 750°C or higher. On the other hand, the firing temperature is preferably 1100°C or lower, 1070°C or lower, 1050°C or lower, 1020°C or lower, 1000°C or lower, 970°C or lower, 950°C or lower, 920°C or lower, 900°C or lower, 870°C or lower, 850°C or lower, 820°C or lower, or 800°C or lower. By keeping the firing temperature within the required range, a lithium metal composite oxide having the desired crystal structure can be obtained. In addition, it is possible to reduce unreacted components and prevent a decrease in the battery characteristics of a non-aqueous electrolyte secondary battery using the obtained lithium metal composite oxide as the positive electrode.

[0067] The firing time is not particularly limited and should be sufficient to form a composite oxide having the desired crystal structure. For example, 1 to 15 hours, 2 to 12 hours, or 2 to 10 hours are preferred.

[0068] The firing atmosphere is not particularly limited, but it is preferable to have an oxygen partial pressure that ensures reliable and uniform crystal growth and prevents the reduction of transition metals contained in the pre-fired material. Preferably, the atmosphere has a low moisture content and low carbon dioxide concentration. For example, it is preferable to use a decarboxylated oxidizing gas atmosphere with a carbon dioxide concentration of 30 ppm or less, or an oxygen atmosphere with an oxygen concentration of preferably 80% by volume or more, 85% by volume or more, 90% by volume or more, or 95% by volume or more.

[0069] In this firing process, there are no particular limitations on the firing method, but the material to be fired (precursor mixture or pre-fired material after a pre-firing process) can be filled into saggars or crucibles and fired in a static furnace, roller hearth kiln, or pusher furnace.

[0070] When firing precursor mixtures or pre-fired products obtained in the pre-firing process using saggars, the filling height when filling the saggars with the precursor mixtures or pre-fired products is not particularly limited, but is preferably 100 mm or more, 105 mm or more, 110 mm or more, 115 mm or more, 120 mm or more, 125 mm or more, 130 mm or more, or 135 mm or more. By having a filling height greater than or equal to the required value, the mass of the precursor mixture filled into one saggar can be increased, and productivity can be further improved by highly compressing the saggars with the loose bulk density of the precursor mixture. On the other hand, the filling height is preferably 140 mm or less, 135 mm or less, 130 mm or less, 125 mm or less, 120 mm or less, 115 mm or less, 110 mm or less, or 105 mm or less. If the packing height of the precursor mixture in the saggar is too high, the quality deteriorates during the firing process due to difficulties in gas diffusion at the bottom of the saggar and uneven reaction, which can lead to an increase in the amount of residual LiOH in the final lithium metal composite oxide and a decrease in battery capacity. However, by keeping the packing height below the required value, the deterioration of quality can be suppressed.

[0071] (Lithium metal composite oxide) In one embodiment, the lithium metal composite oxide obtained in the calcination process contains at least lithium and a transition metal, and is in the form of primary or secondary particulate matter.

[0072] The chemical composition of lithium metal composite oxide is not particularly limited, but it has a layered rock salt structure and has the general formula Li a Ni x Co y Mn z M w O α It is preferable to use a formula in which M is one or more elements other than Li, Ni, Co, Mn, and O, and is expressed as 0.90 ≤ a ≤ 1.15, x + y + z + w = ​​1.00, and 1.60 ≤ α ≤ 2.40.

[0073] In the general formula for lithium metal composite oxides, the value of a is not particularly limited as long as it is within the range of 0.90 ≤ a ≤ 1.2, but for example, 0.905 or more, 0.91 or more, 0.915 or more, 0.92 or more, 0.925 or more, 0.93 or more, 0.935 or more, 0.94 or more, 0.945 or more, 0.95 or more, 0.955 or more, 0.96 or more, 0.965 or more, 0.97 or more, 0.975 or more, 0.98 or more, 0.985 or more, 0.99 or more, 0.995 or more, 1 or more, 1.005 or more, 1.01 or more, 1.015 or more, 1.02 or more, 1.025 or more, 1.03 or more, 1.03 Preferably, the values ​​are 5 or higher, 1.04 or higher, 1.045 or higher, 1.05 or higher, 1.055 or higher, 1.06 or higher, 1.065 or higher, 1.07 or higher, 1.075 or higher, 1.08 or higher, 1.085 or higher, 1.09 or higher, 1.095 or higher, 1.1 or higher, 1.105 or higher, 1.11 or higher, 1.115 or higher, 1.12 or higher, 1.125 or higher, 1.13 or higher, 1.135 or higher, 1.14 or higher, 1.145 or higher, 1.15 or higher, 1.155 or higher, 1.16 or higher, 1.165 or higher, 1.17 or higher, 1.175 or higher, 1.18 or higher, 1.185 or higher, 1.19 or higher, or 1.195 or higher. On the other hand, the values ​​of a are 1.2 or less, 1.195 or less, 1.19 or less, 1.185 or less, 1.18 or less, 1.175 or less, 1.17 or less, 1.165 or less, 1.16 or less, 1.155 or less, 1.15 or less, 1.145 or less, 1.14 or less, 1.135 or less, 1.13 or less, 1.125 or less, 1.12 or less, 1.115 or less, 1.11 or less, 1.105 or less, 1.1 or less, 1.095 or less, 1.09 or less, 1.085 or less, 1.08 or less, 1.075 or less, 1.07 or less, 1.065 or less, 1.06 or less, 1.055 or less, 1. Preferably, the values ​​are 0.5 or less, 1.045 or less, 1.04 or less, 1.035 or less, 1.03 or less, 1.025 or less, 1.02 or less, 1.015 or less, 1.01 or less, 1.005 or less, 1 or less, 0.995 or less, 0.99 or less, 0.985 or less, 0.98 or less, 0.975 or less, 0.97 or less, 0.965 or less, 0.96 or less, 0.955 or less, 0.95 or less, 0.945 or less, 0.94 or less, 0.935 or less, 0.93 or less, 0.925 or less, 0.92 or less, 0.915 or less, 0.91 or less, 0.905 or less, and 0.90 or less.

[0074] In the general formula for lithium metal composite oxide, the value of x is not particularly limited, but for example, it can be 0 or greater, greater than 0, 0.001 or greater, 0.0015 or greater, 0.002 or greater, 0.0025 or greater, 0.003 or greater, 0.0035 or greater, 0.004 or greater, 0.0045 or greater, 0.005 or greater, 0.0055 or greater, 0.006 or greater, 0.0065 or greater, 0.007 or greater, 0.0075 or greater, 0.008 or greater, 0.0085 or greater, 0.009 or greater, 0.0095 or greater, 0.01 or greater, 0.015 or greater, 0.02 or greater, 0.025 or greater, 0.03 or greater, 0.035 or greater, 0.04 or greater. , 0.045 or higher, 0.05 or higher, 0.055 or higher, 0.06 or higher, 0.065 or higher, 0.07 or higher, 0.075 or higher, 0.08 or higher, 0.085 or higher, 0.09 or higher, 0.095 or higher, 0.1 or higher, 0.105 or higher, 0.11 or higher, 0.115 or higher, 0.12 or higher, 0.125 or higher, 0.13 or higher, 0.135 or higher, 0.14 or higher, 0.145 or higher, 0.15 or higher, 0.155 or higher, 0.16 or higher, 0.165 or higher, 0.17 or higher, 0.175 or higher, 0.18 or higher, 0.185 or higher, 0.19 or higher, 0.195 or higher, 0.2 or higher, 0.205 or higher, 0. 21 or higher, 0.215 or higher, 0.22 or higher, 0.225 or higher, 0.23 or higher, 0.235 or higher, 0.24 or higher, 0.245 or higher, 0.25 or higher, 0.255 or higher, 0.26 or higher, 0.265 or higher, 0.27 or higher, 0.275 or higher, 0.28 or higher, 0.285 or higher, 0.29 or higher, 0.295 or higher, 0.3 or higher, 0.305 or higher, 0.31 or higher, 0.315 or higher, 0.32 or higher, 0.325 or higher, 0.33 or higher, 0.335 or higher, 0.34 or higher, 0.355 or higher, 0.36 or higher, 0.365 or higher, 0.37 or higher, 0.375 Above, 0.38 or above, 0.385 or above, 0.39 or above, 0.395 or above, 0.4 or above, 0.405 or above, 0.41 or above, 0.415 or above, 0.42 or above, 0.425 or above, 0.43 or above, 0.435 or above, 0.44 or above, 0.445 or above, 0.45 or above, 0.46 or above, 0.465 or above, 0.47 or above, 0.475 or above, 0.48 or above, 0.485 or above, 0.49 or above, 0.495 or above, 0.5 or above, 0.505 or above, 0.51 or above, 0.515 or above, 0.52 or above, 0.525 or above, 0.53 or above, 0.535 or above, 0.54 or above, 0.545 or higher, 0.55 or higher, 0.555 or higher, 0.56 or higher, 0.565 or higher, 0.57 or higher, 0.575 or higher, 0.58 or higher, 0.585 or higher, 0.59 or higher, 0.595 or higher, 0.6 or higher, 0.605 or higher, 0.61 or higher, 0.615 or higher, 0.62 or higher, 0.625 or higher, 0.63 or higher, 0.635 or higher, 0.64 or higher, 0.645 or higher, 0.65 or higher, 0.655 or higher , 0.66 or higher, 0.665 or higher, 0.67 or higher, 0.675 or higher, 0.68 or higher, 0.685 or higher, 0.69 or higher, 0.695 or higher, 0.7 or higher, 0.705 or higher, 0.71 or higher, 0.715 or higher, 0.72 or higher, 0.725 or higher, 0.73 or higher, 0.735 or higher, 0.74 or higher, 0.745 or higher, 0.75 or higher, 0.755 or higher, 0.76 or higher, 0.765 or higher, 0.77 Above, 0.775 or above, 0.78 or above, 0.785 or above, 0.79 or above, 0.795 or above, 0.8 or above, 0.805 or above, 0.81 or above, 0.815 or above, 0.82 or above, 0.825 or above, 0.83 or above, 0.835 or above, 0.84 or above, 0.845 or above, 0.85 or above, 0.855 or above, 0.86 or above, 0.865 or above, 0.87 or above, 0.875 or above, 0.88 or above, 0. Preferably, the values ​​are 885 or higher, 0.89 or higher, 0.895 or higher, 0.9 or higher, 0.905 or higher, 0.91 or higher, 0.915 or higher, 0.92 or higher, 0.925 or higher, 0.93 or higher, 0.935 or higher, 0.94 or higher, 0.945 or higher, 0.95 or higher, 0.955 or higher, 0.96 or higher, 0.965 or higher, 0.97 or higher, 0.975 or higher, 0.98 or higher, 0.985 or higher, 0.99 or higher, and 0.995 or higher. On the other hand, the values ​​of x are 1 or less, 0.997 or less, 0.995 or less, 0.992 or less, 0.99 or less, 0.987 or less, 0.985 or less, 0.982 or less, 0.98 or less, 0.977 or less, 0.975 or less, 0.972 or less, 0.97 or less, 0.967 or less, 0.965 or less, 0.962 or less, 0.96 or less, 0.957 or less, 0.955 or less, 0 .952 or less, 0.95 or less, 0.947 or less, 0.945 or less, 0.942 or less, 0.94 or less, 0.937 or less, 0.935 or less, 0.932 or less, 0.93 or less, 0. 927 or less, 0.925 or less, 0.922 or less, 0.92 or less, 0.917 or less, 0.915 or less, 0.912 or less, 0.91 or less, 0.907 or less, 0.905 or less, 0.It is preferable that the value is 902 or less and 0.9 or less.

[0075] In the general formula for lithium metal composite oxide, the value of y is not particularly limited, but for example, it can be 0 or greater, greater than 0, 0.001 or greater, 0.0015 or greater, 0.002 or greater, 0.0025 or greater, 0.003 or greater, 0.0035 or greater, 0.004 or greater, 0.0045 or greater, 0.005 or greater, 0.0055 or greater, 0.006 or greater, 0.0065 or greater, 0.007 or greater, 0.0075 or greater, 0.008 or greater, 0.0085 or greater, 0.009 or greater, 0.0095 or greater, 0.01 or greater, 0.015 or greater, 0.02 or greater, 0.025 or greater, 0.03 or greater, 0.035 or greater, 0.04 or greater. , 0.045 or higher, 0.05 or higher, 0.055 or higher, 0.06 or higher, 0.065 or higher, 0.07 or higher, 0.075 or higher, 0.08 or higher, 0.085 or higher, 0.09 or higher, 0.095 or higher, 0.1 or higher, 0.102 or higher, 0.105 or higher, 0.107 or higher, 0.11 or higher, 0.112 or higher, 0.115 or higher, 0.117 or higher, 0.12 or higher, 0.122 or higher, 0.125 or higher, 0.127 or higher, 0.13 or higher, 0.132 or higher, 0.135 or higher, 0.137 or higher, 0.14 or higher, 0.142 or higher, 0.145 or higher, 0.147 or higher, 0.15 or higher, 0.152 Above, 0.155 or above, 0.157 or above, 0.16 or above, 0.162 or above, 0.165 or above, 0.167 or above, 0.17 or above, 0.172 or above, 0.175 or above, 0.177 or above, 0.18 or above, 0.182 or above, 0.185 or above, 0.187 or above, 0.19 or above, 0.192 or above, 0.195 or above, 0.197 or above, 0.2 or above, 0.202 or above, 0.205 or above, 0.207 or above, 0.21 or above, 0.212 or above, 0.215 or above, 0.217 or above, 0.222 or above, 0.225 or above, 0.227 or above, 0.23 or above, 0.232 or above , 0.235 or higher, 0.237 or higher, 0.24 or higher, 0.242 or higher, 0.245 or higher, 0.247 or higher, 0.25 or higher, 0.252 or higher, 0.255 or higher, 0.257 or higher, 0.26 or higher, 0.262 or higher, 0.265 or higher, 0.267 or higher, 0.27 or higher, 0.272 or higher, 0.275 or higher, 0.277 or higher, 0.28 or higher, 0.282 or higher, 0.285 or higher, 0.287 or higher, 0.29 or higher, 0.292 or higher, 0.295 or higher, 0.297 or higher, 0.3 or higher, 0.302 or higher, 0.305 or higher, 0.307 or higher, 0.31 or higher, 0.312 or higher, 0.Preferably, the values ​​are 315 or higher, 0.317 or higher, 0.32 or higher, 0.322 or higher, 0.325 or higher, 0.327 or higher, 0.33 or higher, 0.332 or higher, 0.335 or higher, 0.337 or higher, 0.34 or higher, 0.342 or higher, 0.345 or higher, 0.347 or higher, 0.352 or higher, 0.355 or higher, 0.357 or higher, 0.36 or higher, 0.362 or higher, 0.365 or higher, 0.367 or higher, 0.372 or higher, 0.375 or higher, 0.377 or higher, 0.38 or higher, 0.382 or higher, 0.385 or higher, 0.387 or higher, 0.39 or higher, 0.392 or higher, 0.395 or higher, and 0.397 or higher. On the other hand, the values ​​of y are 0.4 or less, 0.397 or less, 0.395 or less, 0.392 or less, 0.39 or less, 0.387 or less, 0.385 or less, 0.382 or less, 0.38 or less, 0.377 or less, 0.375 or less, 0.372 or less, 0.37 or less, 0.367 or less, 0.365 or less, 0.362 or less, 0.36 or less, 0.357 or less, 0.355 or less, 0.352 or less, 0.35 or less, 0.347 or less, 0.345 or less, 0.342 or less, 0.34 or less, 0.337 or less, 0.335 or less, 0.332 or less, 0.33 or less, 0.327 or less, 0.325 or less, 0.322 or less, 0.32 or less, 0.317 0.315 or less, 0.312 or less, 0.31 or less, 0.307 or less, 0.305 or less, 0.302 or less, 0.3 or less, 0.297 or less, 0.295 or less, 0.292 or less, 0.29 or less, 0.28 7 or less, 0.285 or less, 0.282 or less, 0.28 or less, 0.277 or less, 0.275 or less, 0.272 or less, 0.27 or less, 0.267 or less, 0.265 or less, 0.26 or less, 0.257 or less, 0 .255 or less, 0.252 or less, 0.25 or less, 0.247 or less, 0.245 or less, 0.242 or less, 0.24 or less, 0.237 or less, 0.235 or less, 0.232 or less, 0.23 or less, 0.227 or less Lower, 0.225 or less, 0.222 or less, 0.22 or less, 0.217 or less, 0.215 or less, 0.212 or less, 0.21 or less, 0.207 or less, 0.205 or less, 0.202 or less, 0.2 or less, 0.19 7 or less, 0.195 or less, 0.192 or less, 0.19 or less, 0.187 or less, 0.185 or less, 0.182 or less, 0.18 or less, 0.177 or less, 0.175 or less, 0.172 or less, 0.17 or less, 0.167 or less, 0.165 or less, 0.162 or less, 0.16 or less, 0.155 or less, 0.152 or less, 0.15 or less, 0.147 or less, 0.145 or less, 0.142 or less, 0.14 or less, 0.137 or less, 0.135 or less, 0.132 or less, 0.13 or less, 0.127 or less, 0.12 5 or less, 0.122 or less, 0.12 or less, 0.117 or less, 0.115 or less, 0.112 or less, 0.11 or less, 0.107 or less, 0.105 or less, 0.102 or less, 0.1 or less, 0.095 or less, 0.09 or less, 0.085 or less, 0.08 or less, 0.075 or less, 0.07 or less, 0 Preferably, the values ​​are 0.065 or less, 0.06 or less, 0.055 or less, 0.05 or less, 0.045 or less, 0.04 or less, 0.035 or less, 0.03 or less, 0.025 or less, 0.02 or less, 0.015 or less, 0.01 or less, 0.0095 or less, 0.009 or less, 0.0085 or less, 0.008 or less, 0.0075 or less, 0.007 or less, 0.0065 or less, 0.006 or less, 0.0055 or less, 0.005 or less, 0.0045 or less, 0.004 or less, 0.0035 or less, 0.003 or less, 0.0025 or less, 0.002 or less, 0.0015 or less, and 0.001 or less.

[0076] In the general formula for lithium metal composite oxides, the value of z is not particularly limited, but for example, it can be 0 or greater, greater than 0, 0.001 or greater, 0.0015 or greater, 0.002 or greater, 0.0025 or greater, 0.003 or greater, 0.0035 or greater, 0.004 or greater, 0.0045 or greater, 0.005 or greater, 0.0055 or greater, 0.006 or greater, 0.0065 or greater, 0.007 or greater, 0.0075 or greater, 0.008 or greater, 0.0085 or greater, 0.009 or greater, 0.0095 or greater, 0.01 or greater, 0.015 or greater, 0.02 or greater, 0.025 or greater, 0.03 or greater, 0.035 or greater, 0.04 or greater. , 0.045 or higher, 0.05 or higher, 0.055 or higher, 0.06 or higher, 0.065 or higher, 0.07 or higher, 0.075 or higher, 0.08 or higher, 0.085 or higher, 0.09 or higher, 0.095 or higher, 0.1 or higher, 0.102 or higher, 0.105 or higher, 0.107 or higher, 0.11 or higher, 0.112 or higher, 0.115 or higher, 0.117 or higher, 0.12 or higher, 0.122 or higher, 0.125 or higher, 0.127 or higher, 0.13 or higher, 0.132 or higher, 0.135 or higher, 0.137 or higher, 0.14 or higher, 0.142 or higher, 0.145 or higher, 0.147 or higher, 0.15 or higher, 0.152 Above, 0.155 or above, 0.157 or above, 0.16 or above, 0.162 or above, 0.165 or above, 0.167 or above, 0.17 or above, 0.172 or above, 0.175 or above, 0.177 or above, 0.18 or above, 0.182 or above, 0.185 or above, 0.187 or above, 0.19 or above, 0.192 or above, 0.195 or above, 0.197 or above, 0.2 or above, 0.202 or above, 0.205 or above, 0.207 or above, 0.21 or above, 0.212 or above, 0.215 or above, 0.217 or above, 0.222 or above, 0.225 or above, 0.227 or above, 0.23 or above, 0.232 or above , 0.235 or higher, 0.237 or higher, 0.24 or higher, 0.242 or higher, 0.245 or higher, 0.247 or higher, 0.25 or higher, 0.252 or higher, 0.255 or higher, 0.257 or higher, 0.26 or higher, 0.262 or higher, 0.265 or higher, 0.267 or higher, 0.27 or higher, 0.272 or higher, 0.275 or higher, 0.277 or higher, 0.28 or higher, 0.282 or higher, 0.285 or higher, 0.287 or higher, 0.29 or higher, 0.292 or higher, 0.295 or higher, 0.297 or higher, 0.3 or higher, 0.302 or higher, 0.305 or higher, 0.307 or higher, 0.31 or higher, 0.312 or higher, 0.Preferably, the values ​​are 315 or higher, 0.317 or higher, 0.32 or higher, 0.322 or higher, 0.325 or higher, 0.327 or higher, 0.33 or higher, 0.332 or higher, 0.335 or higher, 0.337 or higher, 0.34 or higher, 0.342 or higher, 0.345 or higher, 0.347 or higher, 0.352 or higher, 0.355 or higher, 0.357 or higher, 0.36 or higher, 0.362 or higher, 0.365 or higher, 0.367 or higher, 0.372 or higher, 0.375 or higher, 0.377 or higher, 0.38 or higher, 0.382 or higher, 0.385 or higher, 0.387 or higher, 0.39 or higher, 0.392 or higher, 0.395 or higher, and 0.397 or higher. On the other hand, the values ​​of z are 0.4 or less, 0.397 or less, 0.395 or less, 0.392 or less, 0.39 or less, 0.387 or less, 0.385 or less, 0.382 or less, 0.38 or less, 0.377 or less, 0.375 or less, 0.372 or less, 0.37 or less, 0.367 or less, 0.365 or less, 0.362 or less, 0.36 or less, 0.357 or less, 0.355 or less, 0.352 or less, 0.35 or less, 0.347 or less, 0.345 or less, 0.342 or less, 0.34 or less, 0.337 or less, 0.335 or less, 0.332 or less, 0.33 or less, 0.327 or less, 0.325 or less, 0.322 or less, 0.32 or less, 0.317 0.315 or less, 0.312 or less, 0.31 or less, 0.307 or less, 0.305 or less, 0.302 or less, 0.3 or less, 0.297 or less, 0.295 or less, 0.292 or less, 0.29 or less, 0.28 7 or less, 0.285 or less, 0.282 or less, 0.28 or less, 0.277 or less, 0.275 or less, 0.272 or less, 0.27 or less, 0.267 or less, 0.265 or less, 0.26 or less, 0.257 or less, 0 .255 or less, 0.252 or less, 0.25 or less, 0.247 or less, 0.245 or less, 0.242 or less, 0.24 or less, 0.237 or less, 0.235 or less, 0.232 or less, 0.23 or less, 0.227 or less Lower, 0.225 or less, 0.222 or less, 0.22 or less, 0.217 or less, 0.215 or less, 0.212 or less, 0.21 or less, 0.207 or less, 0.205 or less, 0.202 or less, 0.2 or less, 0.19 7 or less, 0.195 or less, 0.192 or less, 0.19 or less, 0.187 or less, 0.185 or less, 0.182 or less, 0.18 or less, 0.177 or less, 0.175 or less, 0.172 or less, 0.17 or less, 0.167 or less, 0.165 or less, 0.162 or less, 0.16 or less, 0.155 or less, 0.152 or less, 0.15 or less, 0.147 or less, 0.145 or less, 0.142 or less, 0.14 or less, 0.137 or less, 0.135 or less, 0.132 or less, 0.13 or less, 0.127 or less, 0.12 5 or less, 0.122 or less, 0.12 or less, 0.117 or less, 0.115 or less, 0.112 or less, 0.11 or less, 0.107 or less, 0.105 or less, 0.102 or less, 0.1 or less, 0.095 or less, 0.09 or less, 0.085 or less, 0.08 or less, 0.075 or less, 0.07 or less, 0 Preferably, the values ​​are 0.065 or less, 0.06 or less, 0.055 or less, 0.05 or less, 0.045 or less, 0.04 or less, 0.035 or less, 0.03 or less, 0.025 or less, 0.02 or less, 0.015 or less, 0.01 or less, 0.0095 or less, 0.009 or less, 0.0085 or less, 0.008 or less, 0.0075 or less, 0.007 or less, 0.0065 or less, 0.006 or less, 0.0055 or less, 0.005 or less, 0.0045 or less, 0.004 or less, 0.0035 or less, 0.003 or less, 0.0025 or less, 0.002 or less, 0.0015 or less, and 0.001 or less.

[0077] In the general formula for lithium metal composite oxide, the value of w is not particularly limited, but for example, it can be 0 or greater, greater than 0, 0.001 or greater, 0.0012 or greater, 0.0015 or greater, 0.0017 or greater, 0.0022 or greater, 0.0025 or greater, 0.0027 or greater, 0.003 or greater, 0.0032 or greater, 0.0035 or greater, 0.0037 or greater, 0.004 or greater, or 0.00 42 or higher, 0.0045 or higher, 0.0047 or higher, 0.005 or higher, 0.0052 or higher, 0.0055 or higher, 0.0057 or higher, 0.0062 or higher, 0.0065 or higher, 0.0067 or higher, 0.007 or higher, 0.0072 or higher, 0.0075 or higher, 0.0077 or higher, 0.0082 or higher, 0.0085 or higher, 0.0087 or higher , 0.009 or higher, 0.0092 or higher, 0.0095 or higher, 0.0097 or higher, 0.01 or higher, 0.012 or higher, 0.015 or higher, 0.017 or higher, 0.02 or higher, 0.022 or higher, 0.025 or higher, 0.027 or higher, 0.03 or higher, 0.032 or higher, 0.035 or higher, 0.037 or higher, 0.04 or higher, 0.042 or higher, 0.045 or higher, 0.047 or higher, 0. Preferably, the values ​​are 0.5 or higher, 0.052 or higher, 0.055 or higher, 0.057 or higher, 0.06 or higher, 0.062 or higher, 0.065 or higher, 0.067 or higher, 0.07 or higher, 0.072 or higher, 0.075 or higher, 0.077 or higher, 0.08 or higher, 0.082 or higher, 0.085 or higher, 0.087 or higher, 0.09 or higher, 0.092 or higher, 0.095 or higher, and 0.097 or higher.On the other hand, the values ​​of w are: 0.1 or less, 0.097 or less, 0.095 or less, 0.092 or less, 0.09 or less, 0.087 or less, 0.085 or less, 0.082 or less, 0.08 or less, 0.077 or less, 0.075 or less, 0.072 or less, 0.07 or less, 0.067 or less, 0.065 or less, 0.062 or less, 0.06 or less, 0.057 or less, 0.055 or less. Below, 0.052 or less, 0.05 or less, 0.047 or less, 0.045 or less, 0.042 or less, 0.04 or less, 0.037 or less, 0.035 or less, 0.032 or less, 0.03 or less Lower, 0.027 or less, 0.025 or less, 0.022 or less, 0.02 or less, 0.017 or less, 0.015 or less, 0.012 or less, 0.01 or less, 0.0097 or less, 0.009 5 or less, 0.0092 or less, 0.009 or less, 0.0087 or less, 0.0085 or less, 0.0082 or less, 0.008 or less, 0.0077 or less, 0.0075 or less, 0.0 072 or less, 0.007 or less, 0.0067 or less, 0.0065 or less, 0.0062 or less, 0.006 or less, 0.0057 or less, 0.0055 or less, 0.0052 or less, 0. Preferably, the values ​​are 0.005 or less, 0.0047 or less, 0.0045 or less, 0.0042 or less, 0.004 or less, 0.0037 or less, 0.0035 or less, 0.0032 or less, 0.003 or less, 0.0027 or less, 0.0025 or less, 0.0022 or less, 0.002 or less, 0.0017 or less, 0.0015 or less, 0.0012 or less, and 0.001 or less.

[0078] In the general formula, element M is not particularly limited as long as it is one or more elements other than Li, Ni, Mn, and O. For example, Co, Al, Ti, Mg, Zn, Nb, W, Mo, Sb, V, Cr, Ca, Fe, Ga, Sr, Y, Ru, In, Sn, Ta, Bi, Zr, B, etc., can be used. The type of element M should be selected according to the purpose of addition. Also, if element M contains multiple elements, the value of w represents the total amount of the multiple elements.

[0079] [Water washing process] The lithium metal composite oxide obtained in the main firing process may contain impurities such as unreacted lithium compounds and lithium compounds that appear on the particle surface from the crystalline structure during the pre-firing and main firing processes. If the amount of such lithium compounds is large, as mentioned above, the lithium hydroxide reacts with the binder, causing the positive electrode mixture paste to gel, leading to poor handling in the manufacturing process and a decrease in yield. In addition, the additive compounds used in the additive process described later may form oxides with lithium and the elements contained in the additive compound (hereinafter sometimes referred to as "additive elements"), but may not coat the lithium metal composite oxide. Therefore, washing with water is performed to remove or reduce lithium compounds as impurities.

[0080] The solution used for rinsing is not particularly limited; for example, acidic, neutral, or alkaline solutions can be used, but it is preferable to use neutral pure water. Depending on the physical properties of the lithium metal compound being washed, if removal with pure water extracts too much Li from the particle surface, a solution with an alkaline pH can also be used.

[0081] As described above, for the production of coated particles according to the embodiments of this disclosure, it is preferable to wash the lithium metal composite oxide obtained in the calcination process. On the other hand, if the lithium metal composite oxide is washed too much, the lithium contained in the crystal lattice of the lithium metal composite oxide may be removed too deeply, which may adversely affect conductivity.

[0082] If washing is not possible due to process design or other reasons, it can be substituted by increasing the amount of additive compound described later. The additive compound reacts with lithium not present in the crystal lattice to form a compound, thereby suppressing the formation of lithium hydroxide and inhibiting gelation when the cathode mixture is formed into a slurry.

[0083] [Drying process] In the drying process, the lithium metal composite oxide, which has been washed in the washing process, contains the water used for washing, so it is dehydrated and dried.

[0084] The specific drying method is not particularly limited. For example, it may be carried out in air, an oxygen atmosphere, an oxidizing atmosphere with carbon dioxide at 30 ppm or less (decarboxylation), an inert gas atmosphere such as argon gas, or in a vacuum. Heating may or may not be performed. The heating temperature is not particularly limited and may be, for example, 40-200°C, 60-180°C, or 80-160°C.

[0085] In one embodiment, after a water washing process, the lithium metal composite oxide undergoes a dewatering treatment and is then dried using a dryer or the like to reduce its water content to 1% by mass or less. This prevents the lithium metal composite oxide from forming a rock salt structure due to the presence of water, which can lead to deterioration of its quality.

[0086] Dehydration can be performed by solid-liquid separation of the slurry-like lithium metal composite oxide after the washing process. Specifically, solid-liquid separation can be performed using a filter cloth. Alternatively, filtration using a press filter or reduced-pressure filtration using a Buchner funnel can be performed.

[0087] [Addition process] The additive step is a process of adding an additive compound containing an additive element to a lithium metal composite oxide to obtain a mixture. The additive compound can be added to the wet lithium metal composite oxide before the drying step, or to the lithium metal composite oxide after the drying step.

[0088] Specifically, the additive elements used here are not particularly limited and can be selected from transition metals and non-transition metal elements. For example, transition metals include nickel, cobalt, manganese, titanium, niobium, tungsten, molybdenum, vanadium, chromium, iron, yttrium, ruthenium, and tantalum, while non-transition metal elements include magnesium, aluminum, zinc, calcium, gallium, strontium, indium, tin, bismuth, zirconium, boron, and phosphorus. The state of these elements is not particularly limited, but one or more can be selected from sulfates, oxides, hydroxides, nitrates, carbonates, chlorides, iodides, and metals.

[0089] [Heat treatment process] In the heat treatment process, a mixture of lithium metal composite oxide and additive compound is subjected to heat treatment to coat the surface of the lithium metal composite oxide with the additive element.

[0090] The heat treatment temperature is not particularly limited, but is preferably 200°C or higher, 210°C or higher, 220°C or higher, 230°C or higher, 240°C or higher, or 250°C or higher. On the other hand, the heat treatment temperature is preferably 500°C or lower, 490°C or lower, 480°C or lower, 470°C or lower, 460°C or lower, 450°C or lower, 440°C or lower, 430°C or lower, 420°C or lower, 410°C or lower, or 400°C or lower.

[0091] The heat treatment time is not particularly limited, but is preferably, for example, 1 to 15 hours, 2 to 12 hours, or 2 to 10 hours.

[0092] In this disclosure, the heat treatment temperature refers to the highest temperature the object being heated reaches. The highest temperature is the temperature of the hottest part of the object being heated. The heat treatment time refers to the time from when the heat treatment temperature reaches a predetermined range until that range is maintained. [Examples]

[0093] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0094] <Sample Preparation> Lithium metal composite oxide samples of Examples 1-3 and Comparative Example 1 were prepared according to the method described below.

[0095] [Example 1] (Preparation of precursor compounds) A metallic aqueous solution was obtained by mixing nickel sulfate aqueous solution, cobalt sulfate aqueous solution, and sodium aluminate aqueous solution so that the ratio (molar ratio) of Ni and Co was Ni:Co = 89:6. Separately from this mixed aqueous solution, a sodium aluminate aqueous solution was prepared so that the amount of Al was Al / (Ni+Co+Al)×100 = 5.0 mol%. In the reaction vessel, 10 L of pure water to which 300 g of sodium hydroxide aqueous solution and 500 g of ammonia aqueous solution had been added was prepared as the mother liquor. The reaction vessel was filled with nitrogen gas at a flow rate of 0.7 L / min to create a nitrogen atmosphere, and the reaction was carried out under a nitrogen atmosphere. The reaction vessel was purged with nitrogen gas and this was continued throughout the reaction.

[0096] Subsequently, while rotating the stirring blade at 1000 rpm, the mixed aqueous solution, sodium aluminate aqueous solution, sodium hydroxide aqueous solution, and ammonia water were simultaneously added dropwise at a predetermined rate. The amount of alkaline solution added was adjusted so that the pH would be 12.1. This wet reaction caused Ni, Co, and Al to crystallize and form aggregated particles, resulting in coprecipitation of Ni, Co, and Al, and obtaining a coprecipitate.

[0097] Subsequently, the slurry in the reactor was separated into solid and liquid phases, and then washed with pure water to reduce residual impurities. The resulting coprecipitate was then dried in an atmospheric environment at 100°C for 12 hours to obtain the precursor metal compound.

[0098] (Preparation of lithium hydroxide powder) Lithium hydroxide hydrate was dehydrated by vacuum drying in a vacuum dryer under reduced atmospheric pressure from atmospheric pressure to -50 Pa at 150°C for 5 hours. The loose bulk density of the obtained anhydrous lithium hydroxide was 0.57 g / cm³. 3 That was the case.

[0099] The obtained anhydrous lithium hydroxide was pulverized using a jet mill (PJM-280SP, manufactured by Nippon Pneumatic Mfg. Co., Ltd.) under the following conditions. (Operating conditions for the jet mill) • Input rate: 100 kg / hr ·Crushing pressure: 0.25MPa

[0100] The resulting lithium hydroxide powder had a loosened bulk density of 0.25 g / cm³. 3 In dry laser diffraction particle size distribution measurement (Seishin Corporation), the particle size at the peak top of the largest peak (second highest peak top) was 7.4 μm, the particle size at the peak top of the second highest peak (second highest peak top) was 122.2 μm, and the frequency ratio at the peak tops of the largest and second highest peaks was 0.43.

[0101] (Manufacturing of lithium metal composite oxides) The precursor compound obtained as described above and lithium hydroxide powder were weighed so that the ratio (molar ratio) of Li to the total amount of Ni, Co, and Al was Li / (Ni+Co+Al) = 1.035, and these were mixed using a mixer to prepare a precursor mixture. The loosened bulk density of the mixture was measured using a powder tester (Hosokawa Micron).

[0102] Next, the precursor mixture was degassed using a filling machine into saggars measuring 320mm x 320mm x 150mm (length x width x height) until the depressurization pressure reached -0.002 MPa. Each saggar was then filled over 20 seconds, and it was confirmed that the filling height was 130-140mm. The density at this point was defined as the saggar filling density.

[0103] Subsequently, the mixture was calcined in an electric furnace under an oxygen atmosphere (oxygen concentration: 97 vol%) at a maximum temperature of 740°C for 5 hours. After cooling, it was pulverized using a pulverizer to obtain a lithium metal composite oxide. In the obtained lithium metal composite oxide, the residual LiOH content according to the Warder method was approximately 1.18% by mass.

[0104] The obtained lithium metal composite oxide was added to pure water (water temperature 25°C) in a reaction vessel (capacity 10 L) and stirred for 10 minutes to prepare a slurry. Here, the ratio of lithium metal composite oxide to the amount of pure water (solid-liquid ratio) was adjusted to 1500 g / L. The obtained slurry was filtered using a Buchner funnel to obtain a lithium metal composite oxide cake. The moisture content of the cake was 5.3% by weight.

[0105] Tungsten oxide (WO3) powder was added to the obtained cake in a ratio of W / (Ni+Co+Al)×100 = 0.5 mol%, and mixed. The cake was then heat-treated at 100°C for 60 minutes using a vacuum drying apparatus to dry it. After cooling, the cake was pulverized in a pulverizer to obtain a lithium metal composite oxide sample.

[0106] [Example 2] A lithium metal composite oxide sample was obtained in the same manner as in Example 1, except that anhydrous lithium hydroxide prepared under the same conditions as in Example 1 was pulverized using a mascolloider (manufactured by Masuko Sangyo Co., Ltd.) under the following conditions. (Mascolloider operating conditions) • Sharpening stone size: Φ300mm • Input rate: 200 kg / hr • Clearance between upper and lower grinding wheels: 350 μm • Processing rotation speed: 1500 rpm

[0107] The obtained anhydrous lithium hydroxide powder had a loose bulk density of 0.30 g / cm³, and the particle size at the peak top of the largest peak (second highest peak top) in the volume-based particle size distribution measurement (Seishin Corporation) was 7.4 μm, the particle size at the peak top of the second highest peak was 332.5 μm, and the frequency ratio at the peak tops of the largest and second highest peaks was 0.65.

[0108] [Example 3] A lithium metal composite oxide sample was obtained in the same manner as in Example 1, except that anhydrous lithium hydroxide powder, prepared under the same conditions as in Example 1, was pulverized using a Mascolloider (manufactured by Masuko Sangyo Co., Ltd.) under the following conditions. (Mascolloider operating conditions) • Sharpening stone size: Φ300mm • Input rate: 200 kg / hr • Clearance between upper and lower grinding wheels: 580 μm • Processing rotation speed: 1500 rpm

[0109] The obtained anhydrous lithium hydroxide powder has a loose bulk density of 0.42 g / cm³. 3 In dry laser diffraction particle size distribution measurements (Seishin Corporation), the particle size at the peak top of the largest peak (second highest peak top) was 406.2 μm, the particle size at the peak top of the second highest peak (second highest peak top) was 7.4 μm, and the frequency ratio between the peak tops of the largest and second highest peaks was 0.91.

[0110] [Comparative Example 1] A lithium metal composite oxide sample was obtained in the same manner as in Example 1, except that anhydrous lithium hydroxide prepared under the same conditions as in Example 1 was pulverized using a mascolloider (manufactured by Masuko Sangyo Co., Ltd.) under the following conditions. (Mascolloider operating conditions) • Sharpening stone size: Φ300mm • Input rate: 200 kg / hr • Clearance between upper and lower grinding wheels: 800 μm • Processing rotation speed: 1500 rpm

[0111] The obtained anhydrous lithium hydroxide powder has a loose bulk density of 0.49 g / cm³. 3 In dry laser diffraction particle size distribution measurements (Seishin Corporation), the particle size at the peak top of the largest peak (second highest peak top) was 406.2 μm, the particle size at the peak top of the second highest peak (second highest peak top) was 7.4 μm, and the frequency ratio between the peak tops of the largest and second highest peaks was 0.81.

[0112] <Sample Evaluation> The samples from Examples 1-3 and Comparative Example 1 were evaluated according to the method described below. The results are shown below.

[0113] [Composition of precursor compounds and lithium metal composite oxide samples] 0.2 g of a precursor compound or lithium metal composite oxide sample was heated and dissolved in 25 mL of 20% hydrochloric acid solution. After cooling, the solution was transferred to a 100 mL volumetric flask, and pure water was added to prepare the adjusted solution. The constituent elements of this adjusted solution were quantified using ICP-AES [Optima8300, PerkinElmer Corporation] to confirm that the precursor compound and lithium metal composite oxide were in the correct charging ratio for each metal element.

[0114] [Measurement of loose bulk density] The loose bulk density of the anhydrous lithium hydroxide powder and precursor mixture was measured using a powder tester in accordance with JIS Z 8804-2:2002 "Methods for measuring the physical properties of powders - Part 2: Bulk density test".

[0115] [Dry-type laser particle size distribution measurement] Dry laser particle size distribution measurements were performed using a laser particle size distribution analyzer (LMS-2000e, Seishin Corporation) with air as the dispersion medium and an air pressure of 4 bar. The measurement results obtained were volume-based particle size distributions.

[0116] Eight measurements were taken, and measurement results with clearly different particle size distribution charts were excluded. (1) Measurement results where the relative magnitudes of the peak top values ​​of two or more peaks differ. (2) Measurement results with a peak at 1000 μm or higher (3) Measurement results with four or more peaks For the remaining measurement results, within the range of 1 μm to 1000 μm, the particle size at the peak top with the largest peak was defined as the particle size corresponding to the peak top of the first peak (hereinafter sometimes referred to as "particle size at the first peak top"), and the particle size at the peak top with the next largest peak was defined as the particle size corresponding to the peak top of the second peak (hereinafter sometimes referred to as "particle size at the second peak top"), and the average value for the particle size of each peak was used.

[0117] Furthermore, the ratio (second peak / first peak) of the frequency value at the particle size of the second peak top (hereinafter sometimes referred to as "frequency of the second peak top (%)") to the frequency value at the particle size of the first peak top (hereinafter sometimes referred to as "frequency of the first peak top (%)") was calculated.

[0118] [Measurement of moisture content] The water content (ppm) of the sample was determined based on the Karl Fischer method (coulometric titration), representing the amount of water generated up to 300°C.

[0119] [Measurement of residual lithium hydroxide amount] The amount of residual lithium hydroxide in each sample was measured and calculated based on the Warder method in neutralization titration. Specifically, 20 g of the sample's particle powder was added to 100 ml of water, stirred at room temperature for 20 minutes, and the solid components were filtered off. The supernatant obtained was then titrated with 0.2 N hydrochloric acid. On a pH curve plotted with titration volume (ml) on the x-axis and pH of the supernatant on the y-axis, the two points with the greatest slope were designated as the first and second titration points, starting with the point with the smallest titration volume. The values ​​were then calculated using a formula based on the titration volumes at these points.

[0120] [Battery characteristics of non-aqueous electrolyte secondary batteries] (Fabrication of coin cells using positive electrode active material) A 2032 type coin cell using a lithium metal composite oxide sample as the positive electrode active material was fabricated using the positive electrode, negative electrode, and electrolyte prepared by the following method.

[0121] ·Positive electrode Acetylene black and graphite were used as conductive agents in a ratio of acetylene black:graphite = 1:1 (by weight), and polyvinylidene fluoride was used as a binder. The sample as the positive electrode active material, conductive agent, and binder were blended in a ratio of positive electrode active material:conductive agent:binder = 90:6:4 (by weight), and a slurry of these was mixed with N-methylpyrrolidone and applied to aluminum foil. This was dried at 110°C to produce a sheet, and after punching out this sheet to a diameter of 15 mm, the density of the composite material was 3.0 g / cm³. 3 The material rolled in this manner was used as the positive electrode.

[0122] ·Negative electrode A 500 μm thick lithium foil, punched out to a diameter of 16 mm, was used as the negative electrode.

[0123] ·Electrolyte A mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) was prepared with a volume ratio of EC:DMC = 1:2. This mixture was then mixed with 1 M LiPF6, which served as the electrolyte, to create the electrolyte solution.

[0124] (Initial discharge capacity) Using the coin cells manufactured by the method described above, constant current charging was performed at a current density of 0.1C up to 4.30V (upper voltage) in a 25°C environment, followed by constant voltage charging until the current became 0.01C. The capacity at this time was defined as the initial charging capacity (mAh / g).

[0125] Next, after a 5-minute pause, constant current discharge was performed under the same conditions at a current density of 0.1C up to 3.00V, followed by a 5-minute pause to measure the initial discharge capacity (mAh / g).

[0126] The initial charge-discharge efficiency was calculated using the measured initial charge capacity and initial discharge capacity based on the following formula. Initial charge / discharge efficiency (%) = (Initial discharge capacity / Initial charge capacity) × 100

[0127] Table 1 shows the results of each of the tests described above.

[0128] [Table 1]

Claims

1. A precursor mixing step involves mixing lithium hydroxide powder with a precursor metal compound containing at least a transition metal to obtain a precursor mixture. The process includes a calcination step of calcining the precursor mixture to obtain a lithium metal composite oxide, In the precursor mixing step, The lithium hydroxide powder, when measured dry by laser diffraction, has a particle size distribution in which the value of the frequency at the peak top is maximized in the particle size range of 1 μm to 1000 μm, and a second peak has a peak top at a particle size 50 μm or more away from the particle size showing the peak top of the first peak, and the value of the frequency at the peak top is maximized. The ratio of the value of the frequency at the peak top of the second peak to the value of the frequency at the peak top of the first peak (value of the frequency at the peak top of the second peak / value of the frequency at the peak top of the first peak) is 0.2 or more and 0.95 or less, and the loose bulk density is 0.10 g / cm³. ３ 0.45g / cm or more ３ Using the following, The loosened bulk density of the aforementioned precursor mixture is 0.95 g / cm³. ３ The following adjustments are made so that the ratio of packing density to loose bulk density (sheath packing density / loose bulk density) is 1.10 or higher. A method for producing lithium metal composite oxides.

2. The lithium metal composite oxide has the general formula Li ａ Ni ｘ Co ｙ Mn ｚ M ｗ O α (where M is one or more elements other than Li, Ni, Co, Mn, and O, 0.90 ≦ a ≦ 1.15, x + y + z + w = 1.00, and 1.60 ≦ α ≦ 2.40). A method for producing a lithium metal composite oxide according to claim 1.

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