Method for manufacturing coated particles

Abstract

To provide a method for producing coated particles that, when used as a positive electrode active material for non-aqueous electrolyte secondary batteries, including lithium-ion secondary batteries, result in non-aqueous electrolyte secondary batteries exhibiting excellent charge / discharge capacity, electrical resistance, and cycle characteristics. [Solution] The manufacturing method according to the present disclosure comprises an addition step of adding a boron-containing additive compound to a lithium metal composite oxide to obtain a mixture, and a heat treatment step of applying heat treatment to the mixture to obtain coated particles, wherein in the heat treatment step, the sulfate ion concentration in the mixture before heat treatment is 1200 ppm or more and 5000 ppm or less, and the amount of sulfate ions relative to the amount of boron (SO4 / B) is 0.1 (mol / mol) or more and 1.0 (mol / mol) or less.

Description

[Technical Field]

[0001] This disclosure relates to a method for producing coated particles. [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 lithium hydroxide is produced in large quantities in this way, it reacts with the binder, causing the positive electrode mixture paste to gel. This gelation of the positive electrode mixture paste leads to poor handling during the manufacturing process and a decrease in yield. This tendency is particularly pronounced when the lithium in the lithium transition metal composite oxide, which is the positive electrode active material, is in excess of the stoichiometric ratio to the transition metal, especially when the proportion of nickel in the transition metal is high.

[0006] Here, lithium liberation can be attributed to either lithium that was not incorporated into the crystal lattice of the lithium metal composite oxide, or lithium that was incorporated into the crystal lattice of the lithium metal composite oxide. When lithium incorporated into the crystal lattice of the lithium metal composite oxide dissolves, the resistance of the lithium metal composite oxide increases, which can reduce the charge-discharge efficiency.

[0007] To remove lithium that was not incorporated into the crystal lattice of the lithium metal composite oxide, the calcined product is subjected to a water washing treatment, as disclosed in, for example, Patent Document 1.

[0008] Furthermore, in order to suppress the elution of lithium incorporated into the crystal lattice of lithium metal composite oxides, the material is coated with an oxygen-containing boron compound, as disclosed in, for example, Patent Document 2. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2005-97087 [Patent Document 2] Japanese Patent Publication No. 2019-114560 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, according to our findings, when lithium metal composite oxides are subjected to a water washing treatment to remove lithium, as described in Patent Document 1, the lithium incorporated into the crystal lattice undergoes ion exchange with protons, causing the surface of the lithium metal composite oxide to become lithium-deficient or undergo rock salt phase formation, which reduces the charge / discharge capacity of lithium-ion secondary batteries and increases their initial resistance.

[0011] Furthermore, as described in Patent Document 2, coating a lithium metal composite oxide with a boron compound containing oxygen has some effect in preventing the dissolution of lithium from the crystal lattice of the lithium metal composite oxide into the electrolyte and improving the cycle characteristics, but there is still room for further improvement in cycle characteristics.

[0012] This disclosure has been made in view of the above circumstances, and aims to provide a method for producing coated particles that, when used as a positive electrode active material for non-aqueous electrolyte secondary batteries, including lithium-ion secondary batteries, result in non-aqueous electrolyte secondary batteries exhibiting excellent charge / discharge capacity, electrical resistance, and cycle characteristics. [Means for solving the problem]

[0013] The present inventors have diligently conducted research to solve the above-mentioned problems. As a result, they have found that by using coated particles obtained by a manufacturing method comprising an addition step of adding a boron-containing additive compound to a lithium metal composite oxide to obtain a mixture, and a heat treatment step of heat treatment of the mixture to obtain coated particles, wherein in the heat treatment step, the sulfate ion concentration in the mixture before heat treatment is 1200 ppm or more and 5000 ppm or less, and the amount of sulfate ions relative to the amount of boron (SO4 / B) is 0.1 (mol / mol) or more and 1.0 (mol / mol) or less, as a positive electrode active material for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery using these particles exhibits excellent charge / discharge capacity, electrical resistance, and cycle characteristics. Specifically, this disclosure provides the following.

[0014] (1) Additive step of adding an additive compound containing boron to a lithium metal composite oxide to obtain a mixture, A heat treatment step of subjecting the mixture to heat treatment to obtain coated particles, In the heat treatment step, the sulfate ion concentration in the mixture before heat treatment is 1200 ppm or more and 5000 ppm or less, and the amount of sulfate ions relative to the amount of boron (SO4 / B) is 0.1 (mol / mol) or more and 1.0 (mol / mol) or less Method for producing coated particles

[0015] (2) The lithium metal composite oxide has a layered rock salt structure and is represented by 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, 1.6 ≦ α ≦ 2.4). The method for producing coated particles according to (1).

[0016] (3) The temperature of the heat treatment is 200°C or more and 500°C or less. The method for producing coated particles according to (1) or (2).

Advantages of the Invention

[0017] According to the present disclosure, when used as a positive electrode active material of a non-aqueous electrolyte secondary battery, coated particles can be provided in which the non-aqueous electrolyte secondary battery exhibits excellent charge and discharge capacity, electrical resistance, and cycle characteristics.

Embodiments for Carrying Out the Invention

[0018] [[ID=:40]] Hereinafter, embodiments of the present disclosure will be described. However, the present disclosure is not limited to the description of the following embodiments and can be implemented with appropriate modifications.

[0019] ≪Method for Producing Coated Particles≫ The method for producing coated particles according to this embodiment comprises an addition step of adding a boron-containing additive compound to a lithium metal composite oxide to obtain a mixture, and a heat treatment step of heat-treating the mixture to obtain coated particles, wherein in the heat treatment step, the sulfate ion concentration in the mixture before heat treatment is 1200 ppm or more and 5000 ppm or less, and the amount of sulfate ions relative to the amount of boron (SO4 / B) is 0.1 (mol / mol) or more and 1.0 (mol / mol) or less.

[0020] Thus, the sulfate ion concentration in the mixture before heat treatment is between 1200 ppm and 5000 ppm, and the sulfate ion ratio (SO4 / B) relative to the boron is between 0.1 (mol / mol) and 1.0 (mol / mol). As a result, lithium compounds are formed by sulfate ions and boron near the grain boundaries of the lithium metal composite oxide, resulting in areas where each is coated and areas where it is not. In addition, the concentration of each ion and the coating state of the formed lithium compound can be appropriately controlled. Consequently, cracking from the grain boundaries inside the secondary particles during charging and discharging of secondary batteries using this as the positive electrode active material can be suppressed. Furthermore, ionic conductivity and corrosion resistance to electrolytes can be specifically improved. In addition, on the surface of the lithium metal composite oxide, boron reacts with excess lithium to form lithium borate, reducing the residual lithium that induces gelation. Furthermore, the coating of lithium sulfate, formed by the reaction of sulfate ions and lithium, moderately extracts lithium from the crystalline structure near the surface of the lithium metal composite oxide due to boron, thereby improving battery capacity. In addition, by suppressing the amount of lithium extracted in this way, the crystalline structure of the positive electrode active material near the surface of the lithium metal composite oxide is stabilized, while the coating of lithium sulfate and lithium borate specifically improves ionic conductivity and corrosion resistance to the electrolyte.

[0021] The following describes in detail an example of a method for producing coated particles according to this embodiment, step by step, but the addition step The processes other than the heat treatment process are not mandatory, and processes other than these two can be omitted. Furthermore, to the extent that they do not impair the effects of this disclosure, processes other than those described below may be included before and after each of the processes described below.

[0022] Precursor preparation step: Prepare a precursor complex compound containing at least a transition metal. Precursor mixing step: The precursor complex compound and the lithium compound are mixed to prepare a mixture. Pre-calcination step: The mixture prepared in the precursor mixing step is pre-calcined. Main calcination process: The mixture prepared in the precursor mixing process or the pre-calcined material calcined in the pre-calcination process is calcined. 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: A mixture is obtained by adding a boron-containing additive compound to the lithium metal composite oxide obtained in either the pre-calcination step or the drying step. Heat treatment step: The mixture obtained in the additive step is subjected to heat treatment to obtain coated particles.

[0023] [Precursor preparation process] First, a precursor complex compound containing at least a transition metal is prepared. The method for synthesizing the precursor complex 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 complex 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.

[0024] Furthermore, in the reaction for the synthesis of the precursor complex compound, 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 the 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 complex compound by crystallization can be promoted.

[0025] 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.

[0026] Specifically, transition metals that can be used include nickel, cobalt, manganese, titanium, niobium, tungsten, molybdenum, vanadium, chromium, iron, yttrium, ruthenium, and tantalum.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] In addition to transition metals, one or more elements selected from sulfates, oxides, hydroxides, nitrates, carbonates, chlorides, iodides, and metals may also be used.

[0040] 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.

[0041] The pH range of the liquid in the reaction vessel when synthesizing the precursor complex 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.

[0042] The precursor complex compound obtained by the wet reaction is preferably subjected to washing, dehydration, and drying.

[0043] Washing the precursor complex 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. The degree of washing can also be controlled to leave a specific amount of these impurities. For small amounts, washing can be performed using a Buchner funnel (Nutsche washing) or by feeding the reaction suspension through a press filter for water washing and dehydration. While pure water, sodium hydroxide solution, sodium carbonate solution, etc., can be used for washing, pure water is preferred industrially.

[0044] [Precursor mixing step] The precursor complex compound and lithium compound prepared as described above are mixed in a predetermined ratio to prepare a mixture. The mixing may be done by wet mixing, in which the precursor complex compound and lithium compound are each prepared as an aqueous solution and these solutions are mixed in a predetermined ratio, or by dry mixing, in which the precursor complex compound powder and lithium compound powder are weighed in a predetermined ratio and mixed. Alternatively, one may be a solution and the other a powder.

[0045] The lithium compound is not particularly limited, and various lithium salts can be used. Specifically, as the lithium compound, one or more selected from, for example, anhydrous lithium hydroxide, lithium hydroxide hydrate, lithium nitrate, lithium carbonate, lithium acetate, lithium bromide, lithium chloride, lithium citrate, lithium fluoride, lithium iodide, lithium lactate, lithium oxalate, lithium phosphate, lithium pyruvate, lithium sulfate, and lithium oxide can be used. Among these, it is preferable to use one or more selected from anhydrous lithium hydroxide, lithium hydroxide hydrate, and lithium sulfate.

[0046] The mixing ratio of the lithium compound and the precursor complex 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 complex oxide.

[0047] Furthermore, when mixing the lithium compound and the precursor composite compound, compounds of any element may be added in a predetermined proportion 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 proportion, taking into consideration the composition of the target lithium metal composite oxide.

[0048] 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.

[0049] [Pre-firing process] The pre-calcination process involves calcining the raw material 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 raw material mixture to form a lithium metal composite oxide containing at least lithium and a transition metal.

[0050] The main calcination process, described later, generally involves weighing lithium compounds, precursor complex compounds, and compounds of other elements as needed, mixing them in a mixer, and then filling the resulting mixed powder into containers such as crucibles or saggars. However, particularly in the lithiumation reaction, as the mixed powder 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 lithiumation reaction of the precursor complex compounds before the main calcination.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] In this disclosure, the firing temperature is the highest temperature the object being heated reaches. The highest temperature refers to 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. The definitions of firing temperature and firing time will be the same hereafter.

[0056] 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.

[0057] 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.

[0058] If the lithium metal composite oxide obtained by pre-calcination 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.

[0059] [Firing Process] In this firing process, crystal growth is further promoted. The lithium metal composite oxide obtained by this firing process is in the form of primary or secondary particles.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] (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.

[0064] 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 Nix 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 ≤ 1.20, x + y + z + w = ​​1.00, and 1.60 ≤ α ≤ 2.40.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] In the general formula, element M is not particularly limited as long as it is one or more elements other than Li, Ni, Co, Mn, and O. For example, 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.

[0071] [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, the additive compounds used in the additive process described later may form oxides with lithium and elements contained in the additive compounds (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 these impurities.

[0072] 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.

[0073] 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.

[0074] In cases where cleaning is not possible due to process design or other reasons, it is possible to substitute this by increasing the amount of additive compound added. 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 the gelation of the cathode mixture.

[0075] [Drying process] The lithium metal composite oxide, which has been washed in the water washing process, contains the water used for washing, so it is dehydrated and dried.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] [Addition process] This process involves adding a boron-containing additive compound to a lithium metal composite oxide to obtain a mixture.

[0080] The elemental compounds added for the surface treatment described above can be, for example, one or more selected from boron compounds, phosphorus compounds, and sulfur compounds.

[0081] Examples of boron compounds that can be used include boric acid, lithium tetraborate, sodium tetraborate, sodium perborate, diboron trioxide, and boric acid trifluoride.

[0082] [Heat treatment process] In the heat treatment process, a mixture of lithium metal composite oxide and additive compound is heat-treated to obtain coated particles. In this heat treatment process, the sulfate ion concentration in the mixture before heat treatment is between 1000 ppm and 5000 ppm, and the amount of sulfate ions relative to the amount of boron (SO4 / B) is between 0.1 (mol / mol) and 1.0 (mol / mol).

[0083] Thus, in the method for producing coated particles of this embodiment, the mixture before heat treatment contains 1000 ppm or more of sulfate ions. The source of these sulfate ions is not particularly limited; sulfates can be used as a metal source such as a transition metal or a lithium source, or compounds containing sulfate ions, such as sulfuric acid, can be added at each step.

[0084] The sulfate ion concentration in the mixture before heat treatment is not particularly limited as long as it is between 1200 ppm and 5000 ppm, but is preferably, for example, 1250 ppm or more, 1300 ppm or more, 1350 ppm or more, 1400 ppm or more, 1450 ppm or more, 1500 ppm or more, 1550 ppm or more, 1600 ppm or more, 1650 ppm or more, 1700 ppm or more, 1750 ppm or more, 1800 ppm or more, or 1850 ppm or more. On the other hand, the sulfate ion concentration in the mixture before heat treatment is preferably 4750 ppm or less, 4500 ppm or less, 4250 ppm or less, 4000 ppm or less, 3750 ppm or less, 3500 ppm or less, 3250 ppm or less, 3000 ppm or less, 2750 ppm or less, or 2500 ppm or less.

[0085] The concentration of boron in the mixture before heat treatment is not particularly limited, but is preferably, for example, 100 ppm or more, 150 ppm or more, 200 ppm or more, 250 ppm or more, 300 ppm or more, 400 ppm or more, 500 ppm or more, 600 ppm or more, or 700 ppm or more. By having a boron concentration of the required amount or more, the effect of improving battery characteristics by the boron coating described above can be further enhanced. On the other hand, the concentration of boron in the mixture before heat treatment is preferably 1800 ppm or less, 1700 ppm or less, 1600 ppm or less, 1500 ppm or less, 1400 ppm or less, 1300 ppm or less, 1200 ppm or less, 1100 ppm or less, or 1000 ppm or less. If the boron concentration is below the required amount, during heat treatment, lithium may be extracted more than necessary from the lithium metal composite oxide, forming lithium borate. This can lead to deterioration of the crystal structure in the lithium metal composite oxide and a decrease in battery performance.

[0086] The amount of sulfate ions (SO4 / B) relative to the amount of boron in the mixture before heat treatment is not particularly limited as long as it is between 0.1 (mol / mol) and 1.0 (mol / mol), but is preferably, for example, 0.13 (mol / mol) or more, 0.18 (mol / mol) or more, or 0.20 (mol / mol) or more. On the other hand, the amount of sulfate ions (SO4 / B) relative to the amount of boron in the mixture before heat treatment is preferably 0.95 (mol / mol) or less, 0.90 (mol / mol) or less, 0.80 (mol / mol) or less, 0.70 (mol / mol) or less, 0.60 (mol / mol) or less, 0.50 (mol / mol) or less, 0.40 (mol / mol) or less, or 0.30 (mol / mol) or less.

[0087] 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.

[0088] 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.

[0089] 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. The definitions of heat treatment temperature and heat treatment time are the same hereafter.

[0090] [Coated particles] The characteristics of the coated particles produced by the manufacturing method according to this embodiment will be described below.

[0091] (Lithium metal composite oxide) Lithium metal composite oxides contain at least lithium and nickel, and are in the form of primary or secondary particulate matter. Other characteristics are the same as those described in the section on manufacturing methods.

[0092] (covering layer) The coating layer is a layer that covers all or part of the surface of the lithium metal composite oxide described above.

[0093] This coating layer is composed of layers containing boron.

[0094] The average particle diameter of the coated particles (primary particle diameter in the case of primary particles, secondary particle diameter in the case of secondary particles, sometimes abbreviated as D50) is not particularly limited, but may be, for example, 80 nm or more, 100 nm or more, 120 nm or more, 150 nm or more, 170 nm or more, 200 nm or more, 250 nm or more, 300 nm or more, 350 nm or more, 400 nm or more, or 450 nm or more. On the other hand, for D50, the following ranges apply: 25 μm or less, 24.5 μm or less, 24 μm or less, 23.5 μm or less, 23 μm or less, 22.5 μm or less, 22 μm or less, 21.5 μm or less, 21 μm or less, 20.5 μm or less, 20 μm or less, 19.5 μm or less, 19 μm or less, 18.5 μm or less, 18 μm or less, 17.5 μm or less, 17 μm or less, 16.5 μm or less, 16 μm or less, 15.5 μm or less, The particle size can be 15 μm or less, 14.5 μm or less, 14 μm or less, 13.5 μm or less, 13 μm or less, 12.5 μm or less, 12 μm or less, 11.5 μm or less, 11 μm or less, 10.5 μm or less, 10 μm or less, 9.5 μm or less, 9 μm or less, 8.5 μm or less, 8 μm or less, 7.5 μm or less, 7 μm or less, 6.5 μm or less, 6 μm or less, 5.5 μm or less, 5 μm or less, or 4.5 μm or less. D50 is measured by volume-based wet laser method using a laser particle size distribution analyzer (Microtrac HRA, manufactured by Nikkiso Co., Ltd.).

[0095] The sulfate ion concentration in the coated particles is not particularly limited, but is preferably, for example, 1200 ppm or more, 1250 ppm or more, 1300 ppm or more, 1350 ppm or more, 1400 ppm or more, 1450 ppm or more, 1500 ppm or more, 1550 ppm or more, 1600 ppm or more, 1650 ppm or more, 1700 ppm or more, 1750 ppm or more, 1800 ppm or more, or 1850 ppm or more. On the other hand, the sulfate ion concentration in the coated particles is preferably 5000 ppm or less, 4750 ppm or less, 4500 ppm or less, 4250 ppm or less, 4000 ppm or less, 3750 ppm or less, 3500 ppm or less, 3250 ppm or less, 3000 ppm or less, 2750 ppm or less, or 2500 ppm or less.

[0096] The concentration of boron in the coated particles is not particularly limited, but is preferably, for example, 100 ppm or more, 150 ppm or more, 200 ppm or more, 250 ppm or more, 300 ppm or more, 400 ppm or more, 500 ppm or more, 600 ppm or more, or 700 ppm or more. By having a boron concentration above the required amount, the effect of improving battery characteristics by the boron coating described above can be further enhanced. On the other hand, the concentration of boron in the coated particles is preferably 1800 ppm or less, 1700 ppm or less, 1600 ppm or less, 1500 ppm or less, 1400 ppm or less, 1300 ppm or less, 1200 ppm or less, 1100 ppm or less, or 1000 ppm or less.

[0097] The amount of sulfate ions (SO4 / B) relative to the amount of boron in the coated particles is not particularly limited, but is preferably, for example, 0.10 (mol / mol) or more, 0.13 (mol / mol) or more, 0.15 (mol / mol) or more, 0.18 (mol / mol) or more, or 0.20 (mol / mol) or more. On the other hand, the amount of sulfate ions (SO4 / B) relative to the amount of boron in the coated particles is preferably 1.0 (mol / mol) or less, 0.95 (mol / mol) or less, 0.90 (mol / mol) or less, 0.80 (mol / mol) or less, 0.70 (mol / mol) or less, 0.60 (mol / mol) or less, 0.50 (mol / mol) or less, 0.40 (mol / mol) or less, or 0.30 (mol / mol) or less.

[0098] The amount of residual LiOH in the coated particles is not particularly limited, but is preferably, for example, 0.40% by mass or less, 0.35% by mass or less, or 0.30% by mass or less. By controlling the amount of residual LiOH in this way, gelation can be suppressed when preparing the slurry during electrode fabrication. The amount of residual LiOH in the coated particles may be 0% by mass or more.

[0099] Such lithium metal composite oxides can be used as positive electrode active materials in non-aqueous electrolyte secondary batteries, including lithium secondary batteries. [Examples]

[0100] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0101] <Preparation of coated particle samples> Coated particle samples for Examples 1-8 and Comparative Examples 1-3 were prepared using the methods described below.

[0102] [Preparation of Precursor Compound 1] A mixed aqueous solution was obtained by mixing nickel sulfate aqueous solution, cobalt sulfate aqueous solution, and manganese sulfate aqueous solution so that the ratio (molar ratio) of Ni, Co, and Mn was Ni:Co:Mn = 89:5:6. In the reaction vessel, 10 L of pure water to which 20 g of 6N sodium hydroxide aqueous solution and 120 g of 25% by mass aqueous ammonia was added was prepared as the mother liquor, and nitrogen gas was continuously injected into the reaction vessel at a flow rate of 0.7 mL / min during the reaction.

[0103] Subsequently, the reaction solution temperature was maintained at 40°C while rotating the stirring blade at 950 rpm. The mixed aqueous solution and the mother liquor were simultaneously added dropwise using metering pumps, and the amount of alkaline solution added was adjusted to achieve a pH of 11.3 to carry out the crystallization reaction. During the crystallization reaction, the slurry solution in the reaction vessel was filtered through a filtration device in piping installed from the bottom of the reaction vessel to the outside, and then refluxed to the top of the reaction vessel in a circulating filtration process. Sampling was performed as needed, and the reaction continued by adding raw materials dropwise until the average particle size reached 11.0 μm. After that, the addition of raw materials was stopped, and the reaction slurry was collected.

[0104] After recovering the reaction slurry, solid-liquid separation was performed, followed by washing with a 6N sodium hydroxide solution and then with pure water to reduce residual impurities. The resulting coprecipitation, which was in a cake-like state, was dried at 90°C for 12 hours under atmospheric conditions to obtain a precursor complex compound sample. The D50 of the obtained precursor complex compound was 10.5 μm. The amount of sulfate ions contained was 7330 ppm.

[0105] [Preparation of Precursor Complex Compound 2] A mixed aqueous solution was obtained by mixing nickel sulfate aqueous solution, cobalt sulfate aqueous solution, and manganese sulfate aqueous solution so that the molar ratio of Ni, Co, and Mn was Ni:Co:Mn = 89:5:6. In the reaction vessel, 10 L of pure water to which 20 g of 6N sodium hydroxide aqueous solution and 125 g of 25% by mass aqueous ammonia was added was prepared as the mother liquor, and nitrogen gas was continuously injected into the reaction vessel at a flow rate of 0.7 mL / min during the reaction.

[0106] Subsequently, the reaction solution temperature was maintained at 40°C while rotating the stirring blade at 980 rpm. The mixed aqueous solution and the mother liquor were simultaneously added dropwise using metering pumps, and the amount of alkaline solution added was adjusted to achieve a pH of 11.1 to carry out the crystallization reaction. During the crystallization reaction, the slurry solution in the reaction vessel was filtered through a filtration device in piping installed from the bottom of the reaction vessel to the outside, and then refluxed to the top of the reaction vessel in a circulating filtration process. Sampling was performed as needed, and the reaction was continued by adding raw materials dropwise until the average particle size reached 11.0 μm. After that, the addition of raw materials was stopped, and the reaction slurry was collected.

[0107] After recovering the reaction slurry, solid-liquid separation was performed, followed by washing with a 6N sodium hydroxide solution and then with pure water to reduce residual impurities. The resulting coprecipitation, which was in a cake-like state, was then dried at 90°C for 12 hours under atmospheric conditions to obtain a precursor complex compound sample. The D50 of the obtained precursor complex compound was 10.7 μm. The amount of sulfate ions contained was 13025 ppm.

[0108] [Example 1] Precursor compound 1 was packed into a sagger and subjected to calcination in a standing furnace under an atmospheric environment (oxygen concentration: 21 vol%) at 430°C for 5 hours to obtain precursor compound 1 after removing impurities as appropriate.

[0109] The obtained precursor complex compound 1, anhydrous lithium hydroxide, lithium sulfate, zirconium oxide, and aluminum hydroxide were weighed and mixed so that the molar ratios were Li / (Ni+Co+Mn)=1.040, Zr / (Ni+Co+Mn+Al+Zr)=0.35, Al / (Ni+Co+Mn+Al+Zr)=1.55, and the total sulfate ions from the additives were 19680 ppm.

[0110] Subsequently, the material was heat-treated at 570°C for 3 hours under an oxygen atmosphere (oxygen concentration: 97% by volume), and then further calcined at 780°C for 6 hours under an oxygen atmosphere (oxygen concentration: 97% by volume). The resulting calcined material was pulverized to obtain lithium nickel composite oxide powder. At this time, the amount of sulfate ions was 27010 ppm.

[0111] The obtained lithium nickel composite oxide powder and pure water adjusted to a liquid temperature of 25°C were mixed in a ratio of 1300 g / L to prepare a slurry. After stirring for 10 minutes, the slurry was dehydrated to obtain a cake-like compound. The filtrate obtained during dehydration had a sulfate ion concentration of 26,470 ppm.

[0112] Subsequently, the cake-like compound was dried in a vacuum dryer at 75°C for 2 hours and then at 120°C for 10 hours. At this time, the amount of sulfate ions contained in the cake-like compound was 1891 ppm.

[0113] After drying, boric acid was added to the lithium metal composite oxide as a boron compound to a boron content of 900 ppm and mixed. The mixture was then heat-treated at 300°C for 3 hours under an oxygen atmosphere (oxygen concentration: 97 vol%) to obtain coated particle samples. The residual LiOH content obtained by the Warder method was 0.29 mass%.

[0114] [Example 2] Precursor compound 1 was packed into a sagger and subjected to calcination in a standing furnace under an atmospheric environment (oxygen concentration: 21 vol%) at 430°C for 5 hours to obtain precursor compound 1 after removing impurities as appropriate.

[0115] Precursor complex compound 1, lithium sulfate, anhydrous lithium hydroxide, zirconium sulfate, and aluminum hydroxide were weighed and mixed so that the molar ratios were Li / (Ni+Co+Mn)=1.040, Zr / (Ni+Co+Mn+Al+Zr)=0.35, Al / (Ni+Co+Mn+Al+Zr)=1.55, and the total sulfate ions from the additives were 14912 ppm.

[0116] Subsequently, the material was heat-treated at 570°C for 3 hours under an oxygen atmosphere (oxygen concentration: 97% by volume), and then further calcined at 780°C for 6 hours under an oxygen atmosphere (oxygen concentration: 97% by volume). The resulting calcined material was pulverized to obtain lithium nickel composite oxide powder. At this time, the amount of sulfate ions was 26891 ppm.

[0117] The obtained lithium nickel composite oxide powder and pure water adjusted to a liquid temperature of 25°C were mixed in a ratio of 1300 g / L to prepare a slurry. After stirring for 10 minutes, the slurry was dehydrated to obtain a cake-like compound. The filtrate obtained during dehydration had a sulfate ion concentration of 26,353 ppm.

[0118] Subsequently, the cake-like compound was dried in a vacuum dryer at 75°C for 2 hours and then at 120°C for 10 hours. At this time, the amount of sulfate ions contained in the cake-like compound was 1882 ppm.

[0119] After drying, boric acid was added to the lithium metal composite oxide as a boron compound to a boron content of 900 ppm and mixed. The mixture was then heat-treated at 300°C for 3 hours under an oxygen atmosphere (oxygen concentration: 97 vol%) to obtain coated particle samples. The residual LiOH content obtained by the Warder method was 0.31 mass%.

[0120] [Example 3] Precursor compound 1 was packed into a sagger and subjected to calcination in a standing furnace under an atmospheric environment (oxygen concentration: 21 vol%) at 430°C for 5 hours to obtain precursor compound 1 after removing impurities as appropriate.

[0121] Precursor complex compound 1, lithium sulfate, anhydrous lithium hydroxide, zirconium oxide, and cobalt sulfate were weighed and mixed in molar ratios such that Li / (Ni+Co+Mn)=1.040 (where the denominator is the metal element from precursor complex compound 1), Zr / (Ni+Co+Mn+Zr)=0.3, Co / (Ni+Co+Mn+Zr)=0.4, and the total sulfate ions from the additives were 17187 ppm.

[0122] Subsequently, the material was heat-treated at 570°C for 3 hours under an oxygen atmosphere (oxygen concentration: 97% by volume), and then further calcined at 780°C for 6 hours under an oxygen atmosphere (oxygen concentration: 97% by volume). The resulting calcined material was pulverized to obtain lithium nickel composite oxide powder. At this time, the amount of sulfate ions was 27617 ppm.

[0123] The obtained lithium nickel composite oxide powder and pure water adjusted to a liquid temperature of 25°C were mixed in a ratio of 1300 g / L to prepare a slurry. After stirring for 10 minutes, the slurry was dehydrated to obtain a cake-like compound. The filtrate obtained during dehydration had a sulfate ion concentration of 27065 ppm.

[0124] Subsequently, the cake-like compound was dried in a vacuum dryer at 75°C for 2 hours and then at 120°C for 10 hours. At this time, the sulfate ion content of the cake-like compound was 1933 ppm.

[0125] After drying, boric acid was added to the lithium metal composite oxide as a boron compound to a boron content of 900 ppm and mixed. The mixture was then heat-treated at 300°C for 3 hours under an oxygen atmosphere (oxygen concentration: 97 vol%) to obtain coated particle samples. The amount of residual LiOH obtained by the Warder method was 0.31 mass%.

[0126] [Example 4] Precursor compound 1 was packed into a sagger and subjected to calcination in a standing furnace under an atmospheric environment (oxygen concentration: 21 vol%) at 430°C for 5 hours to obtain precursor compound 1 after removing impurities as appropriate.

[0127] Precursor complex compound 1, lithium sulfate, anhydrous lithium hydroxide, and titanyl sulfate were weighed and mixed so that the molar ratios were Li / (Ni+Co+Mn)=1.040, Ti / (Ni+Co+Mn+Ti)=0.8, and the total sulfate ions from the additives were 12398 ppm.

[0128] Subsequently, the material was heat-treated at 570°C for 3 hours under an oxygen atmosphere (oxygen concentration: 97% by volume), and then further calcined at 780°C for 6 hours under an oxygen atmosphere (oxygen concentration: 97% by volume). The resulting calcined material was pulverized to obtain lithium nickel composite oxide powder. At this time, the amount of sulfate ions was 27888 ppm.

[0129] The obtained lithium nickel composite oxide powder and pure water adjusted to a liquid temperature of 25°C were mixed in a ratio of 1300 g / L to prepare a slurry. After stirring for 10 minutes, the slurry was dehydrated to obtain a cake-like compound. The filtrate obtained during dehydration had a sulfate ion concentration of 27,330 ppm.

[0130] Subsequently, the cake-like compound was dried in a vacuum dryer at 75°C for 2 hours and then at 120°C for 10 hours. At this time, the amount of sulfate ions contained in the cake-like compound was 1952 ppm.

[0131] After drying, boric acid was added to the lithium metal composite oxide as a boron compound to a boron content of 900 ppm and mixed. The mixture was then heat-treated at 300°C for 3 hours under an oxygen atmosphere (oxygen concentration: 97 vol%) to obtain coated particle samples. The amount of residual LiOH obtained by the Warder method was 0.28 mass%.

[0132] [Example 5] In Example 1, coated particle samples were obtained in the same manner as in Example 1, except that the amount of boron in the boric acid added to the dried lithium metal composite oxide was 600 ppm and mixed. The amount of residual LiOH obtained by the Warder method was 0.23% by mass.

[0133] [Example 6] In Example 1, coated particle samples were obtained in the same manner as in Example 1, except that the amount of boron in the boric acid added to the dried lithium metal composite oxide was 1400 ppm and mixed. The amount of residual LiOH obtained by the Warder method was 0.36% by mass.

[0134] [Example 7] Precursor complex compound 2 was packed into a sagger and subjected to calcination by heat treatment in a standing furnace at 430°C for 5 hours in an air atmosphere (oxygen concentration: 21 vol%).

[0135] The calcined precursor complex compound 2, along with lithium sulfate, anhydrous lithium hydroxide, titanyl sulfate, and cobalt hydroxide, were weighed and mixed so that the molar ratios were Li / (Ni+Co+Mn)=1.040 (where the denominator is the metal element from precursor complex compound 2), Ti / (Ni+Co+Mn+Ti)=0.8, Co / (Ni+Co+Mn+Ti)=0.4, and the total sulfate ions from the additives were 12398 ppm.

[0136] Subsequently, the material was heat-treated at 570°C for 3 hours under an oxygen atmosphere (oxygen concentration: 97 vol%), and then further calcined at 780°C for 6 hours under an oxygen atmosphere (oxygen concentration: 97 vol%). The resulting calcined material was pulverized to obtain lithium nickel composite oxide powder. At this time, the amount of sulfate ions was 34298 ppm.

[0137] The obtained lithium nickel composite oxide powder and pure water adjusted to a liquid temperature of 25°C were mixed in a ratio of 1300 g / L to prepare a slurry. After stirring for 10 minutes, the slurry was dehydrated to obtain a cake-like compound. The filtrate obtained during dehydration had a sulfate ion concentration of 33612 ppm.

[0138] Subsequently, the cake-like compound was dried in a vacuum dryer at 75°C for 2 hours and then at 120°C for 10 hours. At this time, the amount of sulfate ions contained in the cake-like compound was 2401 ppm.

[0139] After drying, boric acid was added to the lithium metal composite oxide as a boron compound to a boron content of 900 ppm and mixed. The mixture was then heat-treated at 300°C for 3 hours under an oxygen atmosphere (oxygen concentration: 97 vol%) to obtain coated particle samples. The amount of residual LiOH obtained by the Warder method was 0.30 mass%.

[0140] [Example 8] In Example 7, coated particle samples were obtained in the same manner as in Example 6, except that the amount of boron in the boric acid added to the dried lithium metal composite oxide was 300 ppm and mixed. The amount of residual LiOH obtained by the Warder method was 0.24% by mass.

[0141] [Comparative Example 1] Precursor compound 1 was packed into a sagger and subjected to calcination by heat treatment in a standing furnace at 430°C for 5 hours in an air atmosphere (oxygen concentration: 21 vol%).

[0142] The calcined precursor complex compound 1, anhydrous lithium hydroxide, zirconium oxide, and aluminum hydroxide were weighed and mixed so that the molar ratios were Li / (Ni+Co+Mn)=1.040, Al / (Ni+Co+Mn+Zr+Al)=1.55, and Zr / (Ni+Co+Mn+Zr+Al)=0.35.

[0143] Subsequently, the material was heat-treated at 570°C for 3 hours under an oxygen atmosphere (oxygen concentration: 97% by volume), and then further calcined at 70°C for 6 hours under an oxygen atmosphere (oxygen concentration: 97% by volume). The resulting calcined material was pulverized to obtain lithium nickel composite oxide powder. At this time, the sulfate ion concentration was 8838 ppm.

[0144] The obtained lithium nickel composite oxide powder and pure water adjusted to a liquid temperature of 25°C were mixed in a ratio of 1300 g / L to prepare a slurry. After stirring for 10 minutes, the slurry was dehydrated to obtain a cake-like compound. The filtrate obtained during dehydration had a sulfate ion concentration of 8861 ppm.

[0145] Subsequently, the cake-like compound was dried in a vacuum dryer at 75°C for 2 hours and then at 120°C for 10 hours. At this time, the sulfate ion content of the cake-like compound was 1149 ppm.

[0146] After drying, boric acid was added to the lithium metal composite oxide as a boron compound to a boron content of 900 ppm and mixed. The mixture was then heat-treated at 300°C for 3 hours under an oxygen atmosphere (oxygen concentration: 97 vol%) to obtain coated particle samples. The amount of residual LiOH obtained by the Warder method was 0.42 mass%.

[0147] [Comparative Example 2] In Example 3, coated particle samples were obtained in the same manner as in Example 3, except that boric acid was not added to the dried lithium metal composite oxide. The amount of residual LiOH obtained by the Warder method was 0.21% by mass.

[0148] <Rating> The obtained samples were evaluated using the following method.

[0149] [Compositional analysis of precursor compounds and lithium nickel complex oxides] The compositions of the precursor complex and lithium nickel complex oxide were determined by the following method: 0.2 g of the sample was heated and dissolved in 25 ml of 20% hydrochloric acid solution, cooled, and transferred to a 100 ml volumetric flask. Pure water was added to prepare the adjusted solution. The elements of the obtained adjusted solution were quantified using ICP-AES (Optima 8300, PerkinElmer Japan Co., Ltd.).

[0150] [Analysis of the composition of the filtrate] 50 ml of filtrate collected during the washing process was filtered using a syringe fitted with an MS syringe filter with a hole diameter of 0.45 μm. 50 μl of the filtered filtrate was dispensed, 100 μl of Sc standard solution was used as an internal standard, and the volume was increased to 50 ml using 0.05 N dilute hydrochloric acid to prepare the analytical solution. The elements in each sample were quantified using ICP-OES (Avio550MAX, PerkinElmer Japan Co., Ltd.) in the resulting analytical solution. The composition of the filtrate was calculated based on the amount of lithium metal composite oxide sample used in one wash during the washing process.

[0151] [Measurement of residual lithium hydroxide amount] The amount of residual lithium hydroxide (LiOH) in each sample was measured and calculated based on the Warder method in neutralization titration. Specifically, 20 g of the sample 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.

[0152] [Battery characteristics of non-aqueous electrolyte secondary batteries] (Fabrication of coin cells using positive electrode active material) A 2032 type coin cell using a positive electrode active material was fabricated using a positive electrode, negative electrode, and electrolyte prepared by the following method.

[0153] ·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.

[0154] ·Negative electrode A 500 μm thick lithium foil, punched out to a diameter of 16 mm, was used as the negative electrode.

[0155] ·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.

[0156] (Initial charging capacity and initial charge / discharge efficiency) Using the coin cells manufactured by the method described above, constant current charging was performed at a current density of 18 mA / g (equivalent to 0.1 C) up to 4.30 V (upper voltage) in a 25°C environment, followed by constant voltage charging until the current became 1.8 mA / g. The capacity at this time was defined as the initial charging capacity (mAh / g).

[0157] Next, after a 5-minute pause, constant current discharge was performed under the same conditions at a current density of 18 mA / g up to 3.00 V, followed by a 5-minute pause to measure the initial discharge capacity (mAh / g). This entire process, including the measurement of the initial discharge capacity, was defined as the charge-discharge cycle under condition A.

[0158] 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

[0159] (Cycle maintenance rate) The manufactured coin cells were subjected to 104 charge-discharge cycles under the following conditions at a temperature of 60°C. A current density of 180 mA / g was defined as 1C. During charging, constant current charging was performed until the cutoff voltage was reached, and then constant voltage charging was performed until the current reached 1.8 mA / g. Cycles 1, 2, and 104: After charging with a constant current of 0.2C until it reaches 4.3V, charge with a constant voltage until it reaches 0.01C. 5-minute break Constant current discharge of 0.2C up to 3.0V 5-minute break Cycles 3-103: Charge at a constant current of 0.5C until 4.3V, then charge at a constant voltage until 0.01C. 5-minute break 1C constant current discharge up to 3.0V 5-minute break Using the measured discharge capacity for the second cycle and the measured discharge capacity for the 104th cycle, the cycle maintenance rate at 60°C was calculated based on the following formula. Cycle maintenance rate (%) = (Discharge capacity at 104th cycle / Discharge capacity at 2nd cycle) × 100

[0160] (Initial reaction resistance) The initial reaction resistance was measured using the manufactured coin cells under the following conditions at a temperature of 25°C. • Cycle 1: After charging with a constant current of 0.1C until 4.3V, charge with a constant voltage until 0.01C. 5-minute break Constant current discharge up to 2.5V at 0.1C 5-minute break Cycle 2: After charging with a constant current of 0.1C until 4.3V, charge with a constant voltage until 0.01C. Impedance measurements were performed using cells that had completed their second charging cycle, under the following conditions at a temperature of 25°C. These results were defined as the impedance measurement results for the second cycle (reaction resistance for the second cycle (initial reaction resistance)). Frequency range: 300kHz to 0.01Hz (76 points) Amplitude: 10mV

[0161] Table 1 shows the results of each of the tests described above.

[0162] [Table 1]

Claims

1. An additive step is to add a boron-containing additive compound to a lithium metal composite oxide to obtain a mixture, The process includes a heat treatment step of applying heat treatment to the mixture to obtain coated particles, In the heat treatment step, the sulfate ion concentration in the mixture before heat treatment is 1200 ppm or more and 5000 ppm or less, and the amount of sulfate ions relative to the amount of boron (SO ４ / B) is between 0.1 (mol / mol) and 1.0 (mol / mol). A method for producing coated particles.

2. The lithium metal composite oxide has a layered rock salt structure, and its general formula is Li ａ Ni ｘ Co ｙ Mn ｚ M ｗ O α (In the formula, 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) A method for producing coated particles according to claim 1.

3. The temperature of the heat treatment is between 200°C and 500°C. A method for producing coated particles according to claim 1 or 2.

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