Method for producing lithium metal composite oxide

Abstract

A method for producing a lithium metal composite oxide, the method comprising a step for obtaining a fired product by firing an object to be treated using a firing device, the firing device is provided with an input part into which an object to be processed is input, a conveying part for conveying the object to be processed input from the input part, a cylindrical kiln main body, a discharge port for discharging the fired object, and a gas supply mechanism, and in the step, a low-dew-point gas having a dew point of 10 DEG C or less is supplied from the upstream side of a heating mechanism. The oxygen-containing gas is supplied downstream from the heating means, and the value represented by formula (A) is 0.0001 Nm3 / kg or more and 0.30 Nm3 / kg or less. Formula (A): the supply amount (Nm3 / hour) of the low dew point gas / the supply amount (kg / hour) of the object to be processed.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for producing a lithium metal complex oxide.

[0002] This application claims priority based on Japanese Patent Application No. 2023-067067 filed on April 17, 2023, and the contents thereof are hereby incorporated by reference. BACKGROUND

[0003] A method for producing a lithium metal complex oxide used as a positive electrode active material for a lithium secondary battery includes a step of mixing a metal complex compound as a precursor with a lithium compound and performing firing on the obtained mixture. Such a firing step is performed using a continuous firing furnace such as a tunnel furnace or a roller hearth furnace, or a flow-type firing furnace such as a rotary furnace.

[0004] Patent Literature 1 discloses a method for producing a positive electrode active material using a firing furnace provided with a gas supply system of two systems, with the aim of promoting a firing reaction.

[0005] PRIOR ART DOCUMENTS PATENT LITERATURE Patent Literature 1: JP-A-2019-75253 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION Flow-type firing furnaces have a problem that it is difficult to stably produce a lithium metal complex oxide.

[0007] An object of the present application is to provide a method for producing a lithium metal complex oxide that can be stably produced.

[0008] MEANS FOR SOLVING THE PROBLEMS The present application includes [1] to [7] below.

[0009] [1] A method for producing a lithium metal complex oxide, comprising a step of obtaining a fired product by firing a processed material using a firing device, wherein the processed material contains a mixture of a metal complex compound and a lithium compound, the firing device comprises: a feeding portion into which the processed material is fed; a conveying portion that conveys the processed material fed from the feeding portion; a cylindrical kiln main body; a discharge port that discharges the fired product; and a gas supply mechanism, the kiln main body comprises a heating mechanism, and in the step, a low-dew-point gas having a dew point of 10°C or lower is supplied from an upstream side of the heating mechanism, an oxygen-containing gas is supplied from a downstream side of the heating mechanism, the oxygen-containing gas is brought into countercurrent contact with the processed material to perform the firing, and a value represented by the following formula (A) is 0.0001 Nm 3 / kg or more and 0.30 Nm 3 / kg or less.

[0010] Formula (A): supply amount (Nm 3 / hour) of low dew point gas / supply amount (kg / hour) of treated object [2] The method for producing a lithium metal complex oxide according to [1], wherein the calcining device is a rotary furnace (may also be referred to as a rotary kiln).

[0011] [3] The method for producing a lithium metal complex oxide according to [1] or [2], wherein the proportion of Li contained in the lithium compound is 5 mass% or more and 50 mass% or less.

[0012] [4] The method for producing a lithium metal complex oxide according to [3], wherein the proportion of Li is 5 mass% or more and 30 mass% or less.

[0013] [5] The method for producing a lithium metal complex oxide according to any one of [1] to [4], wherein the value represented by the following formula (C) is 0.3 Nm 3 / kg or more and 1 Nm 3 / kg or less.

[0014] Formula (C): supply amount (Nm 3 / hour) of oxygen-containing gas / supply amount (kg / hour) of treated object [6] The method for producing a lithium metal complex oxide according to any one of [1] to [5], wherein the calcining device is provided with an exhaust port on the upstream side of the heating mechanism, and in the process, the calcining device is calcined while discharging the oxygen-containing gas in the calcining device from the exhaust port.

[0015] [7] The method for producing a lithium metal complex oxide according to any one of [1] to [6], wherein the lithium metal complex oxide is represented by the following composition formula (I).

[0016] Li[Li a (Ni （1-x-y） Co x M1 y ) 1-a ]O2…Composition Formula (I) (In the composition formula (I), M1 is at least one element selected from Mn, Fe, Cu, Ti, Mg, Ca, Al, Zn, Sn, Zr, W, Nb, B, Si, S, and P, and the composition formula (I) satisfies -0.1 ≤ a ≤ 0.2, 0 ≤ x ≤ 0.7, 0 < y ≤ 0.7, and x + y < 1.) Effects of the Invention According to the present invention, a method for producing a lithium metal complex oxide that can be stably produced can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 FIG. is a schematic cross-sectional view of a firing apparatus used in a method for manufacturing a lithium metal composite oxide according to one embodiment of the present embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] In the present application specification, hereinafter, the metal composite compound will be referred to as "MCC", the lithium metal composite oxide will be referred to as "LiMO", and the cathode active material for lithium secondary batteries will be referred to as "CAM".

[0019] "Ni" does not refer to nickel metal, but to nickel atoms. Similarly, "Co", "Li", etc. respectively refer to cobalt atoms, lithium atoms, etc.

[0020] When a numerical range is described, for example, as "1 - 10 μm" or "1~10 μm", it means a range from 1 μm to 10 μm, and refers to a numerical range including 1 μm as the lower limit value and 10 μm as the upper limit value.

[0021] Regarding the numerical ranges in this specification, the upper limit value and the lower limit value can be arbitrarily combined.

[0022] The numerical ranges of each physical property, composition, and manufacturing conditions can be arbitrarily combined.

[0023] <Method for Manufacturing LiMO> The present embodiment is a method for manufacturing LiMO including a step of firing a workpiece to obtain a fired product using a firing apparatus (hereinafter, sometimes referred to as step A). The above-mentioned firing apparatus includes: an input section for inputting the workpiece, a conveying section for conveying the workpiece input from the input section, a cylindrical furnace body, an outlet for discharging the fired product, and a gas supply mechanism, and the furnace body includes a heating mechanism.

[0024] In the above step A, a low dew point gas with a dew point of 10°C or lower is supplied from a position upstream of the heating mechanism. Thereby, the water vapor remaining near the supply section of the workpiece can be dehumidified and dried. As a result, it is difficult to generate condensed water, clogging near the supply section can be avoided, and stable production of LiMO can be achieved. Here, "upstream of the heating mechanism" means closer to the input section than the heating mechanism. For example, the low dew point gas can be supplied from a low dew point gas supply section 56 described later.

[0025] Reference Figure 1 The firing device used in the production method of LiMO will be described.

[0026] Figure 1 is a schematic cross-sectional view of the firing device used in the production method of LiMO of the present embodiment.

[0027] Figure 1 The firing device 50 indicated is provided with an input section 51, a conveyance section 58, a kiln main body 52, a discharge port 53, and a gas supply mechanism 60. The conveyance section 58 is provided with a conveyance mechanism 581 and a motor 582.

[0028] The processed object, after being input by the input section 51 and supplied to the conveyance section 58, is conveyed to the inside of the kiln main body 52 by the conveyance mechanism 581 of the conveyance section 58.

[0029] The conveyance section 58 is, for example, a screw feeder. The conveyance mechanism 581 is, for example, a conveyance screw.

[0030] The kiln main body 52 is an apparatus that performs firing of the processed object. The processed object conveyed to the kiln main body 52 is fired, and the resultant fired product is discharged from the discharge port 53.

[0031] As described above, the processed object moves in the direction of the discharge port 53 via the input section 51, the conveyance section 58, and the kiln main body 52, is heated in the inside of the kiln main body 52, and is finally discharged from the discharge port 53.

[0032] The kiln main body 52 is cylindrical, specifically, circular cylindrical, and is rotatable with the axis O as a rotation axis. The kiln main body 52 is provided with a heating mechanism 54. The processed object supplied to the inside of the kiln main body 52 is fired by the heating mechanism 54.

[0033] The firing device 50 is provided with the gas supply mechanism 60. The gas supply mechanism 60 is provided with an oxygen-containing gas supply section 601 that supplies an oxygen-containing gas to the inside of the kiln main body 52 from a more downstream side than the heating mechanism 54. The "more downstream side than the heating mechanism 54" means a side closer to the discharge port 53 than the heating mechanism 54.

[0034] In order to make the oxygen-containing gas flow in the kiln main body 52 in the direction opposite to the moving direction of the processed object, it is preferable that the firing device 50 be provided with an exhaust port 55 at a more upstream side than the heating mechanism 54, and that, in the process A, firing be performed while the oxygen-containing gas in the firing device 50 is discharged from the exhaust port 55. Figure 1 EG1).

[0035] ​If the processed object is fired inside the furnace main body 52, moisture is sometimes generated due to a reaction that occurs at the time of firing. As the reaction that generates moisture, for example, there are a dehydration reaction of lithium hydroxide or MCC, or an elimination reaction of water molecules when a lithium compound reacts with MCC. The generated moisture flows in the direction of the transport section 58 as water vapor along the convection gas. The water vapor that reaches the upstream side of the heating mechanism 54 dew condenses due to a decrease in temperature.

[0036] When the dew condensation water generated due to dew condensation comes into contact with the raw material supplied to the transport section 58, a lump of the raw material is generated, and thus the transport section 58 is clogged. Due to this, the supply of the raw material that follows is hindered, and thus there is a problem in that it is difficult to stably produce LiMO.

[0037] To solve this problem, a method of increasing the rotation speed of the motor 582 of the transport section 58 so as to make the speed of the supplied raw material constant can be cited, but in the case of assuming long-time operation, it is difficult to eliminate clogging.

[0038] In the present embodiment, by supplying a low-dew-point gas to a position where dew condensation is likely to occur, that is, the upstream side of the heating mechanism 54, it is possible to dehumidify and dry the water vapor that remains in the vicinity of the supply section of the processed object. As a result, it is possible to avoid clogging of the transport section 58, to stably supply the raw material, and thus to stably produce LiMO.

[0039] Specifically, the gas supply mechanism 60 has, in addition to the oxygen-containing gas supply section 601, a low-dew-point gas supply line 602 that supplies a low-dew-point gas.

[0040] The supply amounts of the oxygen-containing gas and the low-dew-point gas are controlled by the control section 61.

[0041] Here, the "low-dew-point gas" is a gas having a dew point of 10°C or less, and specifically, is oxygen, nitrogen, air, or a mixed gas of two or more of the above three, having a dew point of 10°C or less.

[0042] In addition, the "oxygen-containing gas" is a gas containing oxygen, and oxygen or a mixed gas of oxygen and nitrogen can be cited.

[0043] The dew point of the low-dew-point gas is preferably -10°C or less, and more preferably -20°C or less. By using a low-dew-point gas having a dew point in the above range, it is possible to more stably produce LiMO.

[0044] The low-dew-point gas is supplied to the low-dew-point gas supply section 56. In Figure 1In this embodiment, the low-dew-point gas supply part 56 is provided at the upper portion of the motor 582. However, it is not limited thereto as long as it is on the upstream side of the heating mechanism 54. For example, it can be provided on the circumference on the upstream side of the heating mechanism 54 of the kiln main body 52, or it can be provided at the central upper portion of the conveyance mechanism 581. Further, the low-dew-point gas supply part can be provided at two or more places.

[0045] As the firing device, a rotary furnace as a flow-type firing furnace is preferable. In the rotary furnace, the fixed portion of the kiln main body rotates while sliding. The sliding portion is likely to generate a gap, and thus a sealing gas supply part is provided as a standard for the purpose of sealing the sliding portion. The sealing gas supply part is provided in the vicinity of the sliding portion, and is typically provided on either or both of the upstream side and the downstream side of the heating mechanism of the kiln main body.

[0046] As described above, since the rotary furnace is provided with the sealing gas supply part as a standard, the manufacturing method of the present embodiment can be implemented by an operation of changing the sealing gas to the low-dew-point gas without modifying the firing device.

[0047] As the firing device, in addition to the rotary furnace, a rocking-type cylindrical furnace provided with a low-dew-point gas supply part and a supply mechanism can be used.

[0048] Further, the gas that is typically used as the sealing gas is a gas having a dew point of more than 10°C, and thus the low-dew-point gas introduced in the present embodiment is a gas different from the sealing gas.

[0049] By using the sealing gas supply part provided on the upstream side of the heating mechanism of the kiln main body as the low-dew-point gas supply part, the low-dew-point gas can be supplied from the upstream side of the heating mechanism.

[0050] Next, the above-described process A using the above-described firing device 50 will be described.

[0051] The kiln main body 52 is rotated while the treated object is supplied from the supply portion 51.

[0052] The firing device 50 moves the treated object from the supply portion 51 to the kiln main body 52 by the conveyance portion 58 while supplying the low-dew-point gas from the upstream side of the heating mechanism 54 and the oxygen-containing gas from the downstream side of the heating mechanism 54 in the process A of continuously firing the treated object.

[0053] The process A is performed under the condition that the value represented by the following formula (A) is 0.0001 to 0.30 Nm 3 / kg.

[0054] Formula (A): supply amount of low-dew-point gas (Nm 3Supply amount of low dew point gas (Nm3 / hour) < Supply amount of oxygen-containing gas (Nm3 / hour) The value represented by formula (A) is preferably 0.06 Nm 3 / kg or more, more preferably 0.065 Nm 3 / kg or more, further preferably more than 0.07 Nm 3 / kg. The value represented by formula (A) is preferably 0.25 Nm 3 / kg or less, more preferably 0.22 Nm 3 / kg or less. The value represented by formula (A) is, for example, 0.06 to 0.25 Nm 3 / kg, 0.065 to 0.22 Nm 3 / kg, or more than 0.07 Nm 3 / kg and 0.22 Nm 3 / kg or less.

[0055] If the value represented by formula (A) is the above lower limit value or more, a low dew point gas in an amount capable of dehumidifying and drying water vapor reaching the vicinity of the supply portion of the processed material is sufficiently supplied, and thus dewing is less likely to occur in the vicinity of the supply portion of the processed material, and the raw material can be stably supplied.

[0056] If the value represented by formula (A) is the above upper limit value or less, the supply of the oxygen-containing gas from the oxygen-containing gas supply portion 601 is less likely to become excessive, and the heating energy of the heating mechanism 54 is less likely to increase.

[0057] In the process A, the oxygen-containing gas is brought into countercurrent contact with the processed material to perform firing. The supply amount of the oxygen-containing gas preferably satisfies the following formula (X).

[0058] Formula (X): Supply amount of low dew point gas (Nm3 / hour) < Supply amount of oxygen-containing gas (Nm3 / hour) 3 3 By performing firing while discharging the oxygen-containing gas in the firing device 50 from the exhaust port 55, firing can be performed under a condition in which the oxygen-containing gas flows in the kiln main body 52 in a direction opposite to the moving direction of the processed material.

[0059] Under the condition satisfying formula (X), the gas containing water vapor can be discharged from the inside of the firing device 50 including the conveying portion 58 to the exhaust port 55 (EG1) in a short time. Figure 1 Thereby, the time during which the gas containing water vapor stays in the inside of the firing device 50 can be shortened, and water vapor is less likely to stay in the vicinity of the supply portion of the processed material.

[0060] As a result, since the clogging of the conveying portion 58 is avoided, the raw material can be stably supplied, and thus LiMO can be stably produced. ​​

[0061] In the process A, the amount of the oxygen-containing gas supplied to the kiln main body 52 is preferably such that the value represented by the following formula (C) is 0.3 to 1 Nm 3 / kg.

[0062] Formula (C): Amount of oxygen-containing gas supplied (Nm 3 / hour) / Amount of treated material supplied (kg / hour) The value represented by the above formula (C) is preferably 0.4 to 1 Nm 3 / kg, and more preferably 0.5 to 1 Nm 3 / kg.

[0063] If the value represented by the formula (C) is the above lower limit value or more, the dew point of the oxygen-containing gas in the kiln main body 52 rises, and dewing is less likely to occur, so that LiMO can be stably produced.

[0064] If the value represented by the formula (C) is the above upper limit value or less, the increase in the heating energy due to the increase in the amount of the oxygen-containing gas supplied for heating can be suppressed, and LiMO can be stably produced.

[0065] In the process A, the amount of the oxygen-containing gas supplied is preferably 0.5 Nm 3 / hour or more.

[0066] If the amount of the oxygen-containing gas supplied is the above lower limit value or more, the reaction of the treated material with the oxygen-containing gas can be sufficiently promoted. The upper limit value of the amount of the oxygen-containing gas supplied is, for example, 2 Nm 3 / hour. The amount of the oxygen-containing gas supplied is more preferably 0.5 to 2 Nm 3 / hour.

[0067] The firing temperature of the treated material is, for example, 650 to 900°C, preferably 660 to 850°C, and more preferably 670 to 800°C. When the firing temperature is 650°C or more, the growth of the particles of LiMO can be promoted, and LiMO having a firm crystal structure can be obtained. In addition, when the heating temperature is 900°C or less, the formation of cracks in the particles in LiMO can be prevented, the strength of LiMO can be maintained, and the evaporation of lithium ions from the surface of the particles contained in LiMO can be reduced.

[0068] The firing temperature in the present specification refers to the maximum temperature of the atmosphere in the kiln main body 52.

[0069] The holding time in the firing is preferably 1 to 50 hours. When the holding time in the firing is 1 hour or more, the development of the crystal becomes good. When the holding time in the firing is 50 hours or less, the evaporation of lithium ions is less likely to occur.

[0070] In the present specification, the retention time in the firing is defined as the time from when the object to be treated reaches the region where the heating mechanism 54 is provided to when the end of the region where the heating mechanism 54 is reached.

[0071] The inner diameter of the kiln body 52 is preferably 0.05 to 10 m, more preferably 0.07 to 5 m, and further preferably 0.09 to 2 m.

[0072] The filling rate of the object to be treated into the kiln body 52 is preferably 1 to 20%, more preferably 2 to 17%, and further preferably 3 to 15%.

[0073] The rotation speed of the kiln body 52 in the process A is preferably 0.003 to 0.5 rad / sec, more preferably 0.05 to 0.4 rad / sec, and further preferably 0.08 to 0.3 rad / sec.

[0074] (Object to be treated) The object to be treated contains a mixture of the MCC and the lithium compound.

[0075] The mixture of the MCC and the lithium compound is a substance obtained by mixing the MCC and the lithium compound without firing. The object to be treated can contain other materials as long as it mainly contains the mixture. For example, the object to be treated can contain a reaction product of the MCC and the lithium compound in addition to the mixture. The reaction product of the MCC and the lithium compound is a substance obtained by firing the MCC and the lithium compound.

[0076] The MCC is a compound that can produce LiMO by firing together with the lithium compound. The MCC is, for example, a metal composite oxide or a metal composite hydroxide.

[0077] The proportion of Li contained in the above-described lithium compound is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more. The proportion of Li contained in the lithium compound is preferably 50% by mass or less, more preferably 30% by mass or less, further preferably 25% by mass or less, and particularly preferably 20% by mass or less. The proportion of Li contained in the lithium compound can be, for example, 5 to 50% by mass, 5 to 30% by mass, 10 to 25% by mass, or 15 to 20% by mass.

[0078] Specifically, the above lithium compound can use at least one of lithium carbonate (Li proportion: 19 mass%), lithium nitrate (Li proportion: 5-10 mass%), lithium acetate (Li proportion: 7-11 mass%), lithium hydroxide (Li proportion: 16-30 mass%), lithium oxide (Li proportion: 46 mass%), lithium chloride (Li proportion: 16 mass%), and lithium fluoride (Li proportion: 27 mass%). Among them, since the reactivity with MCC is high, lithium hydroxide (Li proportion: 16-30 mass%) is preferred.

[0079] Lithium hydroxide easily generates water vapor at firing. However, if it is the above manufacturing method of LiMO, even in a case where lithium hydroxide is used as the lithium compound, LiMO can be stably produced.

[0080] The mixture of MCC and the lithium compound contains a large amount of attached water and crystal water, and thus easily generates water vapor. However, if it is the above manufacturing method of LiMO, even in a case where the mixture of MCC and the lithium compound is used, LiMO can be stably produced.

[0081] Note that the composition analysis of the lithium compound can be performed, for example, using an ICP emission spectrometry device (Optima 7300 manufactured by PerkinElmer Corporation) after dissolving the lithium compound in hydrochloric acid.

[0082] MCC preferably contains Ni and an element M1, and more preferably contains Ni, Co, and an element M1. The element M1 represents one or more elements selected from Mn, Fe, Cu, Ti, Mg, Ca, Al, Zn, Sn, Zr, W, Nb, B, Si, S, and P.

[0083] MCC is, for example, a metal complex hydroxide or a metal complex oxide containing Ni, Co, and Al.

[0084] In a case where the MCC is a metal complex hydroxide, the metal complex hydroxide can be manufactured, for example, by the continuous coprecipitation method described in JP-A-2002-201028. For example, it can be manufactured according to the following steps. First, an alkaline aqueous solution is added to a mixed solution containing a metal salt solution and a complexing agent at a temperature of a reaction tank of 20-80°C so as to reach a range of pH 9-13. Next, the obtained reaction precipitate is subjected to washing, dehydration, and drying to obtain a metal complex hydroxide. As the metal salt solution, a nickel sulfate aqueous solution, a cobalt sulfate aqueous solution, an aluminum sulfate aqueous solution, and the like can be exemplified, and as the complexing agent, ammonium sulfate and the like can be exemplified. The alkaline aqueous solution can use a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, and the like.

[0085] In the case where the MCC is a metal composite oxide, the metal composite oxide can be prepared by heating the metal composite hydroxide at 300 to 700°C.

[0086] The lithium compound and the MCC are mixed in consideration of the composition ratio of the final target object, to produce a mixture. Specifically, the amount of Li is preferably 0.98 or more, more preferably 1.04 or more, and further preferably 1.05 or more, relative to the total amount (molar ratio) of Li and elements other than oxygen atoms (e.g., Ni, Co, and element M1) contained in the MCC. The amount of Li is preferably 1.20 or less. The amount of Li can be, for example, 0.98 to 1.20, 1.04 to 1.20, or 1.05 to 1.20.

[0087] After the above-described process A, a main firing can be performed. At this time, the firing in process A is referred to as pre-firing, and the fired product obtained by process A is referred to as a pre-fired product. If the main firing is performed on the pre-fired product, a main fired product is obtained. The firing device used in the main firing is not particularly limited, and any one of a continuous stationary firing furnace or a continuous flow firing furnace can be used, for example. As the flow firing furnace, the firing device 50 can also be used. The temperature and the time in the main firing are, for example, 650 to 950°C and 3 to 50 hours.

[0088] The fired product can be washed, dehydrated, and dried as needed. Through the above processes, LiMO2is obtained.

[0089] [Method for measuring variation coefficient of stirring blade frequency] Whether the production method of LiMO2is capable of stable production is evaluated by measuring the variation coefficient of the frequency of the stirring blade.

[0090] The firing device 50 rotates the stirring blade by the motor 582, thereby conveying the treated object that is fed from the feeding portion 51.

[0091] If the desired raw material feeding speed (kg / h) can be maintained without changing or substantially changing the frequency of the stirring blade, it means that stable production is possible. In order to maintain the desired raw material feeding speed, the degree of variation of the frequency when the frequency is adjusted during operation is calculated as the "variation coefficient of the stirring blade frequency".

[0092] Specifically, the variation coefficient of the stirring blade frequency is calculated by the following equation.

[0093] Variation coefficient of stirring blade frequency = standard deviation of frequency of stirring blade of conveying mechanism 581 / average value of frequency of stirring blade of conveying mechanism 581 In the calculation of the variation coefficient of the stirring blade frequency, the standard deviation of the frequency after the treated object is retained in the inside of the kiln main body 52 is used.

[0094] If the value of the above-described variation coefficient is large, it means that the frequency is adjusted every time in operation in order to maintain the desired raw material supply speed, meaning unstable production.

[0095] In the present embodiment, if the value of the above-described variation coefficient is 0.035 or less, it is difficult to cause the risk of clogging during long-time operation, and it is evaluated as "stable production is possible".

[0096] <limo> The above LiMO has the following properties.

[0097] The LiMO preferably contains Li, Ni, and the above element M1, and more preferably contains Li, Ni, Co, and the above element M1. The LiMO is represented by, for example, the composition formula (I).

[0098] Li[Li a (Ni （1-x-y） Co x M1 y ) 1-a ]O2... Composition formula (I) (In the composition formula (I), M1 is the above element M1, and the composition formula (I) satisfies -0.1 ≤ a ≤ 0.2, 0 ≤ x ≤ 0.7, 0 < y ≤ 0.7, and x + y < 1.) From the viewpoint of obtaining a lithium secondary battery having a high cycle maintenance rate, a in the above composition formula (I) is more preferably -0.05 or more, and further preferably -0.01 or more. In addition, from the viewpoint of obtaining a lithium secondary battery having a higher initial coulombic efficiency, a is preferably 0.08 or less, and more preferably 0.05 or less.

[0099] The upper limit value and the lower limit value of a can be arbitrarily combined. a is, for example, -0.01 to 0.2, -0.05 to 0.08, or -0.01 to 0.05.

[0100] From the viewpoint of improving the cycle characteristics, x is preferably 0.01 or more, and more preferably 0.02 or more. From the viewpoint of obtaining a lithium secondary battery having a high charge capacity, x is preferably 0.5 or less, and more preferably 0.3 or less.

[0101] x is, for example, 0.01 to 0.5 or 0.02 to 0.3.

[0102] From the viewpoint of improving the cycle characteristics, y is preferably 0.01 or more, and more preferably 0.02 or more. From the viewpoint of obtaining a lithium secondary battery having a high charge capacity, y is preferably 0.5 or less, and more preferably 0.3 or less.

[0103] y is, for example, 0.01 to 0.5 or 0.02 to 0.3.

[0104] x + y is more than 0 and less than 1, preferably more than 0 and 0.7 or less, more preferably more than 0 and 0.3 or less, and further preferably more than 0 and 0.25 or less.

[0105] From the viewpoint of obtaining a lithium secondary battery having a high cycle maintenance rate, M1 is preferably one or more elements selected from the group consisting of Mn, Ti, Mg, Al, W, Nb, B, and Zr, and more preferably one or more elements selected from the group consisting of Mn, Al, W, Nb, B, and Zr.

[0106] Note that the composition analysis of LiMO can be performed, for example, using an ICP emission spectrometry device (Optima 7300, manufactured by PerkinElmer, Inc.) after dissolving LiMO in hydrochloric acid.

[0107] The crystal structure of LiMO is a layered structure, and more preferably a hexagonal crystal structure or a monoclinic crystal structure.

[0108] [Method for confirming crystal structure] The crystal structure of LiMO can be confirmed by observation using a powder X-ray diffractometer (e.g., Ultima IV, manufactured by Rigaku Corporation).

[0109] The hexagonal crystal structure belongs to any one of the space groups selected from the group consisting of P3, P31, P32, R3, P-3, R-3, P312, P321, P3112, P3121, P3212, P3221, R32, P3m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P61, P65, P62, P64, P63, P-6, P6 / m, P63 / m, P622, P6122, P6522, P6222, P6422, P6322, P6mm, P6cc, P63cm, P63mc, P-6m2, P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P63 / mcm, and P63 / mmc.

[0110] In addition, the monoclinic crystal structure belongs to any one of the space groups selected from the group consisting of P2, P21, C2, Pm, Pc, Cm, Cc, P2 / m, P21 / m, C2 / m, P2 / c, P21 / c, and C2 / c.

[0111] Among them, in order to obtain a lithium secondary battery having a high discharge capacity, the crystal structure is further preferably a hexagonal crystal structure belonging to the space group R-3m, or a monoclinic crystal structure belonging to C2 / m.

[0112] <cam> The above LiMO can be preferably used as a CAM.

[0113] <Secondary battery> An example of a lithium secondary battery when the above LiMO is used as a CAM has a positive electrode and a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode.

[0114] Further, an example of a lithium secondary battery has a positive electrode and a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a solid electrolyte disposed between the positive electrode and the negative electrode. With respect to the lithium secondary battery, the constitution, materials, and manufacturing method described in

[0104] to

[0181] of WO2022 / 113904A1 can be used.

[0115] Embodiment Next, the present application is described in more detail by embodiments.

[0116] <Composition analysis> The composition analysis of the LiMO and the lithium compound was performed using an ICP emission spectrometry device (Optima 7300, manufactured by PerkinElmer) after dissolving the LiMO or the lithium compound in hydrochloric acid.

[0117] <Stirring paddle frequency variation coefficient> The variation coefficient was measured as described in the above [Measurement method of variation coefficient of stirring paddle frequency].

[0118] <Embodiment 1> After adding water to a reaction tank equipped with a stirrer and an overflow pipe, an aqueous sodium hydroxide solution was added, and the liquid temperature (temperature of the reaction tank) was maintained at 50°C.

[0119] A mixed raw material solution was prepared by mixing an aqueous nickel sulfate solution, an aqueous cobalt sulfate solution, and an aqueous aluminum sulfate solution at a ratio of 0.88:0.09:0.03 in terms of the atomic ratio of Ni, Co, and Al.

[0120] Next, an aqueous ammonium sulfate solution was continuously added to the mixed raw material solution as a complexing agent in the reaction tank with stirring. An aqueous sodium hydroxide solution was added dropwise in a timely manner so that the pH of the mixed solution in the reaction tank became 11.6 (measurement temperature: 40°C), and a reaction precipitate 1 was obtained.

[0121] After washing the reaction precipitate 1, dehydration, isolation were performed using a centrifugal separator, and drying was performed at 105°C, whereby a metal composite hydroxide 1 containing Ni, Co, and Al was obtained.

[0122] The metal complex hydroxide 1 was heated in an atmosphere at 650°C for 5 hours, cooled to room temperature, and MCC1 as a metal complex oxide was obtained.

[0123] Lithium hydroxide was weighed in an amount of Li in a proportion of 1.10 with respect to the total amount of Ni, Co, and Al contained in MCC1 (molar ratio). MCC1 and the lithium hydroxide were mixed using a mortar to obtain a mixture 1.

[0124] The proportion of Li contained in the lithium hydroxide used was 16.5 mass %.

[0125] The mixture 1 was put into a flow-type calcining furnace (manufactured by NORITAKE CO., LIMITED, trade name: Desktop rotary kiln) corresponding to the calcining device 50. While supplying an oxygen-containing gas from the exhaust port side under conditions satisfying the relationship of formula (X) and exhausting the oxygen-containing gas from the exhaust port corresponding to the exhaust port 55, the oxygen-containing gas was brought into countercurrent contact with the mixture 1, and pre-calcination was performed at 680°C for 2 hours to obtain a pre-calcination product 1.

[0126] At this time, the value of formula (A) was 0.20 (Nm 3 / kg), and the value represented by formula (C) was 0.67 (Nm 3 / kg), and oxygen having a dew point of -23.6°C was supplied as a low-dew-point gas from the low-dew-point gas supply part.

[0127] The coefficient of variation at the time of pre-calcination was 0, and it was confirmed that LiMO could be stably produced.

[0128] Next, the obtained pre-calcination product 1 was put into a stationary-type batch calcining furnace (manufactured by Motoyama, trade name: Oxidizing atmosphere furnace SKA-3050F-SP), and main calcination was performed at 720°C for 5 hours in an oxygen atmosphere to obtain a main calcination product 1.

[0129] The obtained main calcination product 1 was washed, and then dehydrated, isolated using a centrifugal separator, and dried at 250°C in a nitrogen atmosphere to obtain LiMO-1.

[0130] Composition analysis of LiMO-1 was performed, and as a result, in formula (I), a = 0.02, x = 0.09, and y = 0.03, and the element M1 was Al.

[0131] <Example 2> Except that the value of formula (A) was changed to 0.07 (Nm 3 / kg), the pre-calcination product 2 was obtained in the same manner as in Example 1.

[0132] The coefficient of variation at the time of pre-burning was 0.034, and it was confirmed that LiMO could be stably produced.

[0133] LiMO-2 was obtained by the same method as in Example 1, except that the pre-burnt product 2 was used.

[0134] Composition analysis of LiMO2 was performed, and as a result, in the composition formula (I), a = 0.02, x = 0.09, y = 0.03, and the element M1 was Al.

[0135] "Comparative Example 1" Instead of supplying the low-dew-point gas, the value represented by formula (C) was changed to 1.72 (Nm 3 / kg, and otherwise, pre-burnt product 11 was obtained by the same method as in Example 1.

[0136] The coefficient of variation at the time of pre-burning was 0.058. The value of the coefficient of variation was large, and if the operation was continued, there was a high risk of clogging, so the pre-burning was stopped midway.

[0137] "Comparative Example 2" Instead of supplying the low-dew-point gas, the value represented by formula (C) was changed to 0.10 (Nm 3 / kg, and otherwise, pre-burnt product 12 was obtained by the same method as in Example 1.

[0138] The coefficient of variation at the time of pre-burning was 0.040. The value of the coefficient of variation was large, and if the operation was continued, there was a high risk of clogging, so the pre-burning was stopped midway.

[0139] As shown in the above results, it was confirmed that in the convection contact type of the burning method, in the case where the low-dew-point gas having a dew point of 10°C or less was supplied from the upstream side of the heating mechanism, and the burning was performed under the condition satisfying formula (A), clogging caused by condensation near the raw material supply portion was difficult to occur, and LiMO could be stably produced.

[0140] Explanation of Reference Numerals 50: burning apparatus, 51: input portion, 52: kiln main body, 53: discharge port, 54: heating mechanism, 55: exhaust port, 56: low-dew-point gas supply portion, 58: conveyance portion, 581: conveyance mechanism, 582: motor, 60: gas supply mechanism, 601: oxygen-containing gas supply portion, 602: low-dew-point gas supply line, 61: control portion.< / cam> < / limo>

Claims

1. A method for producing a lithium metal complex oxide, comprising a step of firing a treated object using a firing apparatus to obtain a fired object, wherein the treated object comprises a mixture of a metal complex compound and a lithium compound, the firing apparatus comprises a feeding portion into which the treated object is fed, a conveying portion that conveys the treated object fed from the feeding portion, a cylindrical kiln main body, a discharge port that discharges the fired object, and a gas supply mechanism, the kiln main body comprises a heating mechanism, in the step, a low-dew-point gas having a dew point of 10°C or lower is supplied from an upstream side of the heating mechanism, an oxygen-containing gas is supplied from a downstream side of the heating mechanism, the oxygen-containing gas is brought into countercurrent contact with the treated object to perform the firing, and the firing apparatus is a rotary furnace. The proportion of Li contained in the lithium compound is 5% by mass or more and 50% by mass or less. The proportion of Li is 5% by mass or more and 30% by mass or less. The firing apparatus comprises an exhaust port at the upstream side of the heating mechanism, and in the step, the firing is performed while the oxygen-containing gas in the firing apparatus is exhausted from the exhaust port. The lithium metal complex oxide is represented by the following composition formula (I), In the composition formula (I), M1 is at least one element selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Ca, Al, Zn, W, Nb, Sn, Zr, B, Si, S, and P, and the composition formula (I) satisfies -0.1 ≤ a ≤ 0.2, 0 ≤ x ≤ 0.7, 0 < y ≤ 0.7, and x + y < 1. ​ ​ The value represented by the following formula (A) is 0.0001 Nm 3 / kg or more and 0.30 Nm 3 / kg or less, Formula (A): Supply amount (Nm3 / hour) of low-dew-point gas / supply amount (kg / hour) of the object to be treated 3 Formula (A): Supply amount (Nm3 / hour) of low-dew-point gas / supply amount (kg / hour) of the object to be treated 2. The method for producing a lithium metal complex oxide according to claim 1, wherein ​ 3. The method for producing a lithium metal complex oxide according to claim 1 or 2, wherein, ​ 4. The method for producing a lithium metal complex oxide according to claim 3, wherein ​ 5. The method for producing a lithium metal complex oxide according to claim 1 or 2, wherein The value represented by the following formula (C) is 0.3 Nm 3 / kg or more and 1 Nm 3 / kg or less, Formula (C): Supply amount of oxygen-containing gas (Nm 3 / hour) / supply amount of the object to be treated (kg / hour) 6. The method for producing a lithium metal complex oxide according to claim 1 or 2, wherein, ​ 7. The method of producing a lithium metal complex oxide according to claim 1 or 2, wherein ​ Li[Li a (Ni （1-x-y） Co x M1 y ) 1-a ]O2… Composition formula (I) ​

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