Manufacturing method of lithium metal composite oxide

Abstract

To provide a manufacturing method that can further reduce the occurrence of differences between the metal composition of a lithium metal composite oxide and the raw material metal ratio due to volatilization of lithium element and corrosion of the furnace body by lithium hydroxide when manufacturing a lithium metal composite oxide in a two-stage firing process of preliminary firing and main firing.SOLUTION: The manufacturing method of a lithium metal composite oxide according to the present disclosure comprises a preliminary firing step of heating a precursor compound of a lithium metal composite oxide and a lithium compound at 500°C or higher and 650°C or lower to obtain a preliminary fired product, a pelletization step of manufacturing pellets of the preliminary fired product, and a firing step of firing the pellets at 700°C or higher and 1000°C or lower.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a lithium metal composite oxide. [Background technology]

[0002] Lithium-ion secondary batteries, which are small, lightweight, have high energy density, high charge / discharge voltage, and large charge / discharge capacity, and are attracting attention as power sources for electronic devices such as AV equipment and personal computers. Examples of useful positive electrode active materials for such lithium-ion secondary batteries include those with the formula Li a (Ni x Co y M z A positive electrode active material made of a lithium metal composite oxide (where M is a metal such as Mn, Mg, or Al) having a basic composition represented by the formula: 1.)O2 has been proposed.

[0003] Lithium metal composite oxides are usually obtained by preparing a metal composite hydroxide from a nickel compound, a cobalt compound, and a compound of a metal such as Mn, Mg, or Al, followed by calcining the metal composite hydroxide to obtain a precursor metal composite oxide, and then calcining a precursor mixture of the metal composite oxide and a lithium compound (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-198195 Summary of the Invention [Problem to be solved by the invention]

[0005] In the method disclosed in Patent Document 1, lithium and a metal composite hydroxide react to form a lithium metal composite oxide for the first time in the calcination step, and the bulkiness decreases to about 70% of the original value before and after the reaction. This decrease in bulkiness is a factor that reduces productivity.

[0006] Therefore, the inventors have focused on a method in which a metal composite hydroxide is used as a precursor, mixed with lithium hydroxide, and preliminarily calcined to form a lithium metal composite oxide, and then the calcination is performed. With this method, the lithium metal composite oxide is formed before the calcination, so there is almost no change in bulkiness before and after the calcination, and productivity is not impaired by changes in bulkiness.

[0007] However, in such a method for producing a lithium metal composite oxide that involves two firing steps, the lithium element, which has a low boiling point, volatilizes in the firing step, which can result in a discrepancy between the metal composition of the resulting lithium metal composite oxide and the raw material metal ratio.Furthermore, the pre-fired product melts during the firing step, and lithium hydroxide produced can corrode the furnace body.

[0008] The present disclosure has been made in view of the above circumstances, and aims to provide a manufacturing method that can further reduce the occurrence of a difference between the metal composition of the lithium metal composite oxide and the raw material metal ratio due to volatilization of lithium element and corrosion of the furnace body due to lithium hydroxide when manufacturing a lithium metal composite oxide through a two-stage firing process of pre-firing and main firing. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, they have found that a method for producing a lithium metal composite oxide, which includes a pre-calcination step of heating a precursor compound of the lithium metal composite oxide and a lithium compound at 500°C or higher and 650°C or lower to obtain a pre-calcined product, a pelletization step of producing pellets of the pre-calcined product, and a calcination step of calcining the pellets at 700°C or higher and 1000°C or lower, can further reduce the occurrence of a difference between the metal composition of the lithium metal composite oxide and the raw material metal ratio due to volatilization of lithium element, and corrosion of the furnace body due to lithium hydroxide, and have thus invented the method of the present disclosure. Specifically, the present disclosure provides the following:

[0010] (1) a pre-calcination step of heating a precursor compound of a lithium metal composite oxide and a lithium compound at 500°C or higher and 650°C or lower to obtain a pre-calcined product; a pelletizing step for producing pellets of the pre-fired material; and a firing step of firing the pellets at 700°C or higher and 1000°C or lower. A method for producing lithium metal composite oxide.

[0011] (2) The lithium metal composite oxide has the general formula Li a Ni 1-x-y-z Co x Mn y M z O 2+α (wherein M is an element other than Li, Ni, Co, Mn, and O, and 0.95≦a≦1.20, 0≦x≦0.4, 0≦y≦0.4, 0≦z≦0.1, −0.5≦α≦0.5, 1−xyz≧0.3) (1) A method for producing the lithium metal composite oxide.

[0012] (3) The average maximum length of the pellets is 1 mm or more and 350 mm or less. A method for producing a lithium metal composite oxide according to (1) or (2). [Effects of the Invention]

[0013] According to the present disclosure, when a lithium metal composite oxide is produced through a two-stage firing process of pre-firing and main firing, a production method can be provided that can further reduce the occurrence of a difference between the metal composition of the lithium metal composite oxide and the raw material metal ratio due to volatilization of lithium element, and corrosion of the furnace body due to lithium hydroxide. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described, but the present disclosure is not limited in any way to the description of the following embodiment and can be implemented with appropriate modifications.

[0015] <Method for producing lithium metal composite oxide> The method for producing a lithium metal composite oxide according to this embodiment includes a pre-calcination step of heating a precursor compound of a lithium metal composite oxide and a lithium compound at 500°C or higher and 650°C or lower to obtain a pre-calcined product, a pelletization step of producing pellets of the pre-calcined product, and a calcination step of calcining the pellets at 700°C or higher and 1000°C or lower.

[0016] According to this manufacturing method, the lithium hydroxide reacts with the hydroxide containing the transition metal in the pre-calcination step to form a lithium-metal composite oxide. Therefore, the bulkiness hardly changes in the calcination step at a high temperature, which improves the production efficiency of the calcination step. This is because if the bulkiness decreases in the calcination step at a higher temperature, the amount of raw material that can be loaded into the furnace will decrease accordingly.

[0017] In addition, in this highly productive manufacturing method, by pelletizing the pre-fired product formed in the pre-fired step, volatilization of lithium can be reduced in the firing step, which is performed at a higher temperature than in the pre-fired step. Furthermore, since the contact area of ​​the pellets with the furnace body is smaller than that of the powder, damage to the furnace body is reduced even when heated in the firing step at a higher temperature.

[0018] [Lithium metal composite oxide] The lithium metal composite oxide produced by the production method of this embodiment is not particularly limited as long as it contains a transition metal. For example, a Ni 1-x-y-z Co x Mn y M z O 2+α (wherein M is an element other than Li, Ni, Co, Mn, and O, and 0.95≦a≦1.20, 0≦x≦0.4, 0≦y≦0.4, 0≦z≦0.1, −0.5≦α≦0.5, 1−xyz≧0.3) is preferred.

[0019] In the general formula, the value of a may be 0.95 or more, 0.955 or more, 0.96 or more, 0.965 or more, 0.97 or more, 0.975 or more, or 0.98 or more. On the other hand, the value of a may be 1.20 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, 1.10 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, or 1.05 or less.

[0020] In the general formula, the value of x is not particularly limited as long as it is within the range of 0≦x≦0.4, and examples thereof include: more than 0, 0.001 or more, 0.0015 or more, 0.002 or more, 0.0025 or more, 0.003 or more, 0.0035 or more, 0.004 or more, 0.0045 or more, 0.005 or more, 0.0055 or more, 0.006 or more, 0.0065 or more, 0.007 or more, 0.0075 or more, 0.008 or more, 0.0085 or more, 0.009 or more, 0.0095 or more, 0.01 or more, 0.015 or more, 0.02 or more, 0.025 or more, 0.03 or more, 0.035 or more, 0.04 or more, 0.045 or more, 0.05 or more, 0.055 or more, 0.06 or more, 0.065 or more, 0.07 or more, 0.075 or more, 0.08 or more, 0.085 or more, 0.09 or more, 0.095 or more, 0.1 or more, 0.102 or more, 0.105 or more, 0.107 or more, 0.11 or more, 0.112 or more, 0.115 or more, 0.117 or more, 0.12 or more, 0.122 or more, 0.125 or more, 0.127 or more, 0.13 or more, 0.132 or more, 0.135 or more, 0.137 or more, 0.14 or more, 0.142 or more, 0.145 or more, 0.147 or more, 0.15 or more, 0.152 or more, 0.155 or more, 0.157 or more, 0.16 or more, 0.162 or more, 0.165 or more, 0.167 or more, 0.17 or more, 0.172 or more, 0.175 or more, 0.177 or more, 0.18 or more, 0.182 or more, 0.185 or more, 0.187 or more, 0.19 or more, 0.192 or more, 0.195 or more, 0.197 or more, 0.2 or more, 0.202 or more, 0.205 or more, 0.207 or more, 0.21 or more, 0.212 or more, 0.215 or more, 0.217 or more, 0.22 or more, 0.222 or more, 0.225 or more, 0.227 or more, 0.23 or more, 0.232 or more , 0.235 or more, 0.237 or more, 0.24 or more, 0.242 or more, 0.245 or more, 0.247 or more, 0.25 or more, 0.252 or more, 0.255 or more, 0.257 or more, 0.26 or more, 0.262 or more, 0.265 or more, 0.267 or more, 0.27 or more, 0.272 or more, 0.275 or more, 0.277 or more, 0.282 or more, 0.285 or more, 0.287 or more, 0.29 or more, 0.292 or more, 0.295 or more, 0.297 or more, 0.3 or more, 0.302 or more, 0.305 or more, 0.307 or more, 0.31 or more, 0.312 or more, 0.315 or more, 0.317 or more, 0.32 or more, 0.322 or more, 0.325 or more, 0.327 or more, 0.33 or more, 0.332 or more, 0.335 or more, 0.337 or more, 0.34 or more, 0.342 or more, 0.345 or more, 0.347 or more, 0.35 or more, 0.352 or more, 0.355 or more, 0.357 or more, 0.362 or more, 0.365 or more, 0.367 or more, 0.37 or more, 0.372 or more, 0.375 or more, 0.377 or more, 0.382 or more, 0.385 or more, 0.387 or more, 0.39 or more, 0.392 or more, 0.395 or more, 0.397 or more is preferred. On the other hand, the values ​​of x are 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, 0.367 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 Below, 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 or less, 0.315 or less, 0.3 12 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, 0.287 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, 0.225 or less, 0.222 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, 0.197 or less, 0.195 or less, 0.19 2 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, 0.125 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, 0.065 or less, 0 Preferably, it is 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, 0.0055 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, or 0.001 or less.

[0021] In the general formula, the value of y is not particularly limited as long as it is within the range of 0≦y≦0.4, and examples thereof include greater than 0, 0.001 or more, 0.0015 or more, 0.002 or more, 0.0025 or more, 0.003 or more, 0.0035 or more, 0.004 or more, 0.0045 or more, 0.005 or more, 0.0055 or more, 0.006 or more, 0.0065 or more, 0.007 or more, 0.0075 or more, 0.008 or more, 0.0085 or more, 0.009 or more, 0.0095 or more, 0.01 or more, 0.015 or more, 0.02 or more, 0.025 or more, 0.03 or more, 0.035 or more, 0.04 or more, 0.045 or more, 0.05 or more, 0.055 or more, 0.06 or more, 0.065 or more, 0.07 or more, 0.075 or more, 0.08 or more, 0.085 or more, 0.09 or more, 0.095 or more, 0.1 or more, 0.102 or more, 0.105 or more, 0.107 or more, 0.11 or more, 0.112 or more, 0.115 or more, 0.117 or more, 0.12 or more, 0.122 or more, 0.125 or more, 0.127 or more, 0.13 or more, 0.132 or more, 0.135 or more, 0.137 or more, 0.14 or more, 0.142 or more, 0.145 or more, 0.147 or more, 0.15 or more, 0.152 or more, 0.155 or more, 0.157 or more, 0.16 or more, 0.162 or more, 0.165 or more, 0.167 or more, 0.17 or more, 0.172 or more, 0.175 or more, 0.177 or more, 0.18 or more, 0.182 or more, 0.185 or more, 0.187 or more, 0.19 or more, 0.192 or more, 0.195 or more, 0.197 or more, 0.2 or more, 0.202 or more, 0.205 or more, 0.207 or more, 0.21 or more, 0.212 or more, 0.215 or more, 0.217 or more, 0.22 or more, 0.222 or more, 0.225 or more, 0.227 or more, 0.23 or more, 0.232 or more , 0.235 or more, 0.237 or more, 0.24 or more, 0.242 or more, 0.245 or more, 0.247 or more, 0.25 or more, 0.252 or more, 0.255 or more, 0.257 or more, 0.26 or more, 0.262 or more, 0.265 or more, 0.267 or more, 0.27 or more, 0.272 or more, 0.275 or more, 0.277 or more, 0.282 or more, 0.285 or more, 0.287 or more, 0.29 or more, 0.292 or more, 0.295 or more, 0.297 or more, 0.3 or more, 0.302 or more, 0.305 or more, 0.307 or more, 0.31 or more, 0.312 or more, 0.315 or more, 0.317 or more, 0.32 or more, 0.322 or more, 0.325 or more, 0.327 or more, 0.33 or more, 0.332 or more, 0.335 or more, 0.337 or more, 0.34 or more, 0.342 or more, 0.345 or more, 0.347 or more, 0.35 or more, 0.352 or more, 0.355 or more, 0.357 or more, 0.362 or more, 0.365 or more, 0.367 or more, 0.37 or more, 0.372 or more, 0.375 or more, 0.377 or more, 0.382 or more, 0.385 or more, 0.387 or more, 0.39 or more, 0.392 or more, 0.395 or more, 0.397 or more is preferred. On the other hand, the values ​​of y are 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, 0.367 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 less than, 0.34 less than, 0.337 less than, 0.335 less than, 0.332 less than, 0.33 less than, 0.327 less than, 0.325 less than, 0.322 less than, 0.32 less than, 0.317 less than, 0.315 less than, 0.312 less than, 0.31 less than, 0.307 less than, 0.305 less than, 0.302 less than, 0.3 less than, 0.299 less than, 0.297 less than, 0.295 less than, 0.292 less than, 0.2 87 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, it is 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, or 0.001 or less.

[0022] In the general formula, the value of z is not particularly limited as long as it is within the range of 0≦z≦0.1, and examples thereof include values ​​greater than 0, 0.001 or more, 0.0012 or more, 0.0015 or more, 0.0017 or more, 0.002 or more, 0.0022 or more, 0.0025 or more, 0.0027 or more, 0.003 or more, 0.0032 or more, 0.0035 or more, 0.0037 or more, 0.004 or more, 0.004 2 or more, 0.0045 or more, 0.0047 or more, 0.005 or more, 0.0052 or more, 0.0055 or more, 0.0057 or more, 0.006 or more, 0.0062 or more, 0.0065 or more, 0.0067 or more, 0.007 or more, 0.0072 or more, 0.0075 or more, 0.0077 or more, 0.008 or more, 0.0082 or more, 0.0085 or more, 0.0087 or more, 0.009 or more, 0.0092 or more, 0.0095 or more, 0.0097 or more, 0.01 or more, 0.012 or more, 0.015 or more, 0.017 or more, 0.02 or more, 0.022 or more, 0.025 or more, 0.027 or more, 0.03 or more, 0.032 or more, 0.035 or more, 0.037 or more, 0.04 or more, 0.042 or more, 0.045 or more, 0.047 or more, 0.0 It is preferable that the molecular weight is 5 or more, 0.052 or more, 0.055 or more, 0.057 or more, 0.06 or more, 0.062 or more, 0.065 or more, 0.067 or more, 0.07 or more, 0.072 or more, 0.075 or more, 0.077 or more, 0.082 or more, 0.085 or more, 0.087 or more, 0.09 or more, 0.092 or more, 0.095 or more, or 0.097 or more.On the other hand, the z value is 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, 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, 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, 0.0095 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, 0.0072 less than or equal to 0.007, less than or equal to 0.0067, less than or equal to 0.0065, less than or equal to 0.0062, less than or equal to 0.006, less than or equal to 0.0057, less than or equal to 0.0055, less than or equal to 0.0052, 0.00 It is preferable that the molecular weight is 5 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, or 0.001 or less.

[0023] In the general formula, the element M is not particularly limited as long as it is one or more elements other than Li, Ni, Co, Mn, and O, and examples that can be used include Al, Ti, Mg, Zn, Nb, W, Mo, Sb, V, Cr, Ca, Fe, Ga, Sr, Y, Ru, In, Sn, Ta, Bi, Zr, and B. The type of element M may be selected depending on the purpose of addition. When multiple elements are contained as element M, the value z represents the total amount of the multiple elements.

[0024] The form of the lithium metal composite oxide to be produced is not particularly limited, and may be, for example, particulate. The particles may be aggregated as primary particles to form secondary particles, or may exist as primary particles, or may be a mixture of secondary particles and primary particles.

[0025] The average particle size of the primary particles of the lithium metal composite oxide is not particularly limited, but is preferably, 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, the average particle size of the primary particles is preferably 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. By keeping the average particle size of the primary particles within the required range, the energy density can be increased and particle breakage and deterioration of rate characteristics due to cycling can be suppressed. The average particle size of the primary particles of the lithium metal composite oxide is calculated by observing electron micrographs at 3,000 to 20,000 magnifications using a field-emission scanning electron microscope (JSM-7100F, manufactured by JEOL Ltd.) at an acceleration voltage of 10 kV. Specifically, a field of view in which 100 or more primary particles with visible particle outlines are visible is randomly selected, and electron micrographs are taken of all particles with visible outlines within the above-mentioned range, with the magnification changed as necessary. The equivalent sphere diameter of the electron micrograph is then calculated using image processing software (e.g., ImageJ, etc.) to determine the particle size of the primary particles.

[0026] The average particle size (D50) of the lithium metal composite oxide is not particularly limited, but is preferably, 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. By having a D50 equal to or greater than the required value, the electrode density can also be improved. On the other hand, D50 is 25μm or less, 24.5μm or less, 24μm or less, 23.5μm or less, 23μm or less, 22.5μm or less, 22μm or less, 21.5μm or less, 21μm or less, 20.5μm or less, 20μm or less, 19.5μm or less, 19μm or less, 18.5μm or less, 18μm or less, 17.5μm or less, 17μm or less, 16.5μm or less, 16μm or less, 15.5μm or less, 15 Preferably, the D50 of the lithium metal composite oxide is 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. By ensuring that the D50 of the lithium metal composite oxide is equal to or less than the required value, the energy density of a nonaqueous electrolyte secondary battery using this lithium metal composite oxide can be increased, and particle breakage and deterioration of rate characteristics due to cycling can be suppressed. Note that D50 is measured on a volume basis by a wet laser method using a laser particle size distribution analyzer (Microtrac HRA, manufactured by Nikkiso Co., Ltd.).

[0027] The BET specific surface area of ​​the lithium metal composite oxide powder is 0.3 m 2 / g or more, but is not particularly limited, for example, 0.31 m 2 / g or more, 0.32m 2 / g or more, 0.33m 2 / g or more, 0.34m 2 / g or more, 0.35m 2 / g or more, 0.36m 2 / g or more, 0.37m 2 / g or more, 0.38m 2 / g or more, 0.39m2 / g or more, 0.4m 2 On the other hand, the BET specific surface area of ​​the lithium metal composite oxide powder is preferably 5 m 2 / g or less, 4.5m 2 / g or less, 4m 2 / g or less, 3.5m 2 / g or less, 3m 2 / g or less, 2.5m 2 / g or less, 2m 2 / g or less, 1.5m 2 / g or less, 1m 2 / g or less.

[0028] Specifically, the method for producing the lithium metal composite oxide according to this embodiment can include the following steps. Precursor preparation step: A precursor compound containing at least nickel is prepared. Mixing step: The precursor compound prepared in the precursor preparation step is mixed with a lithium compound to prepare a precursor mixture. Pre-firing step: The precursor mixture prepared in the precursor mixing step is fired. Calcination step: The precursor mixture is calcined in the calcination step. Water washing step: If necessary, the lithium metal composite oxide obtained by firing in the firing step is subjected to a water washing treatment.

[0029] [Precursor preparation step] First, a precursor compound containing at least nickel is synthesized. In one embodiment, the precursor compound can be obtained as an aggregate of primary particles. The synthesis method for the precursor compound is not particularly limited. For example, an aqueous solution containing a transition metal solution and various aqueous solutions of compounds containing other elements corresponding to the composition of the desired lithium metal composite oxide can be added dropwise to a reaction vessel in which an alkaline aqueous solution, such as a sodium hydroxide solution or an ammonia solution, is stirred as a mother liquor. While also adding sodium hydroxide, the pH is monitored and controlled to be within an appropriate range, and a wet reaction is used to co-precipitate the precursor compound, resulting in the production of, for example, a hydroxide, an oxide obtained by calcining the hydroxide, or a carbonate. The precursor preparation step is not essential, and a precursor compound prepared by a method other than the precursor preparation step can also be used in the method for producing a lithium metal composite oxide.

[0030] In the synthesis reaction, after preparing the aqueous alkaline solution to serve as the mother liquid, it is preferable to create a nitrogen atmosphere in the reaction tank using an inert gas, or industrially preferably nitrogen gas, to reduce the oxygen concentration in the reaction tank system and in the solution. If the oxygen concentration is too high, there is a risk that the coprecipitated hydroxide may be over-oxidized by a predetermined amount or more of remaining oxygen, or that the formation of aggregates by crystallization may be hindered.

[0031] The aqueous solution of the metal source is not particularly limited, but for example, an acidic aqueous solution is preferably used, and in the case of a nickel compound, it is more preferable to use an aqueous sulfuric acid solution such as an aqueous nickel sulfate solution. In addition, one or more kinds of aqueous solutions of the metal source can be used.

[0032] The nickel compound is not particularly limited, but for example, one or more selected from nickel sulfate, nickel oxide, nickel hydroxide, nickel nitrate, nickel carbonate, nickel chloride, nickel iodide, metallic nickel, and the like can be used.

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

[0034] The manganese compound is not particularly limited, but for example, one or more compounds selected from manganese sulfate, manganese oxide, manganese hydroxide, manganese nitrate, manganese carbonate, manganese chloride, manganese iodide, and manganese metal can be used.

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

[0036] The aluminum compound is not particularly limited, but examples thereof include aluminum sulfate, aluminum oxide, aluminum hydroxide, aluminum nitrate, aluminum carbonate, aluminum chloride, aluminum iodide, sodium aluminate, and metallic aluminum.

[0037] The iron compound is not particularly limited, but for example, one or more selected from iron sulfate, iron oxide, iron hydroxide, iron nitrate, iron carbonate, iron chloride, iron iodide, metallic iron, and the like can be used.

[0038] The niobium compound is not particularly limited, but for example, one or more compounds selected from niobium oxide, niobium chloride, lithium niobate, niobium iodide, and the like can be used.

[0039] The tungsten compound is not particularly limited, but for example, one or more compounds selected from tungsten oxide, sodium tungstate, ammonium paratungstate, tungsten hexacarbonyl, tungsten sulfide, and the like can be used.

[0040] The magnesium compound is not particularly limited, but for example, one or more compounds selected from magnesium sulfate, magnesium oxide, magnesium hydroxide, magnesium nitrate, magnesium carbonate, magnesium chloride, magnesium iodide, and metallic magnesium can be used.

[0041] The zirconium compound is not particularly limited, but for example, one or more compounds selected from zirconium sulfate, zirconium oxide, zirconium nitrate, ammonium zirconium carbonate, zirconium chloride, zirconium iodide, and metallic zirconium can be used.

[0042] As for other elements, one or more selected from sulfates, oxides, hydroxides, nitrates, carbonates, chlorides, iodides, metals, and the like can be used.

[0043] The mixing ratio of each compound may be adjusted so that the amount of each element is in a desired ratio, taking into consideration the composition of the desired lithium metal composite oxide.

[0044] The appropriate pH range for synthesizing the precursor compound is not particularly limited and can be determined so as to obtain the desired secondary particle size and shape, such as the degree of coarseness and density, and is generally in the range of about 10 to 13.

[0045] The precursor compound obtained by the wet reaction is preferably subjected to a washing treatment, dehydrated, and then dried.

[0046] By subjecting the precursor compound to a washing treatment, impurities such as sulfate groups, carbonate groups, and sodium that have been incorporated into the aggregated particles or attached to the surface during the reaction can be washed away. For small amounts of the washing, a Nutsche washing method using a Buchner funnel can be used, or a method in which the suspension after the reaction is sent to a press filter for washing and dehydration can be used. For example, pure water, an aqueous sodium hydroxide solution, an aqueous sodium carbonate solution, etc. can be used in the washing treatment, but pure water is preferred for industrial use. However, if a large amount of residual sulfate groups remains, an aqueous sodium hydroxide solution with its pH adjusted according to the amount of residual sulfate groups can also be used.

[0047] [Mixing process] The mixing step is a step of preparing a precursor mixture by mixing at least lithium hydroxide with the precursor compound obtained in the precursor preparation step, although the mixing step is not an essential step.

[0048] It is preferable to thoroughly mix the raw materials, such as lithium hydroxide and precursor compounds. If the mixing is insufficient, the ratio of lithium to other metals may vary depending on the location, which may result in insufficient battery performance. A general mixer can be used for mixing. For example, a shaker mixer, a Lödige mixer, a Julia mixer, a V blender, or the like can be used.

[0049] The ratio of each raw material is not particularly limited, and may usually be set in accordance with the element ratio in the lithium metal composite oxide to be produced. However, if there is an increase or decrease in these ratios in a later step, the ratio may be set taking such an increase or decrease into consideration.

[0050] [Pre-firing process] The pre-calcination step is a step in which the precursor mixture is calcined at 500° C. or higher and 650° C. or lower to form a pre-calcined product as a lithium metal composite oxide.

[0051] This pre-firing step allows the precursor mixture to be converted into a lithium metal composite oxide containing at least lithium and a transition metal.

[0052] The precursor compound contained in the precursor mixture may or may not contain nickel. When the precursor compound contains nickel, the nickel may be divalent or trivalent, but preferably contains divalent nickel. The content of divalent nickel is not particularly limited, but is preferably 1 at% or more, 2 at% or more, 5 at% or more, 10 at% or more, 15 at% or more, 20 at% or more, 25 at% or more, 30 at% or more, 35 at% or more, 40 at% or more, 45 at% or more, 50 at% or more, 55 at% or more, 60 at% or more, 65 at% or more, 70 at% or more, 75 at% or more, 80 at% or more, 85 at% or more, 90 at% or more, 95 at% or more, 97 at% or more, or 99 at% or more relative to the total amount of nickel of all valences. On the other hand, the content of divalent nickel may be 100 at% or less.

[0053] In the pre-calcination step, it is preferable to adopt a calcination method that promotes the lithiation of the lithium metal composite oxide. Specifically, a method can be mentioned in which the precursor mixture is made more susceptible to heat, gas generated from the lithium source is easily discharged, and gas with a high oxygen partial pressure is diffused into the precursor mixture (particles).

[0054] In the preliminary calcination step, the precursor mixture can be filled into a sagger or a crucible and calcined using a stationary furnace, a roller hearth kiln, a pusher furnace, or the like. Alternatively, a rotary kiln can be used in which the precursor mixture is calcined while being flowed.

[0055] The firing temperature in the pre-firing step is not particularly limited as long as it is 500°C or higher and 650°C or lower. By setting the firing temperature in the pre-firing step within the above range, the lithium hydroxide and the metal composite hydroxide in the precursor mixture can be reacted, and the generation of a different phase can be suppressed to obtain a lithium metal composite oxide. The firing temperature in the pre-firing step is preferably 510°C or higher, 520°C or higher, or 530°C. Furthermore, the firing temperature in the pre-firing step is preferably 640°C or lower, 630°C or lower, 620°C or lower, 610°C or lower, 600°C or lower, 590°C or lower, or 580°C or lower. Note that the firing temperature in the present disclosure is the maximum temperature when the object is heated. The maximum temperature refers to the temperature of the hottest part of the object being heated. The same definition applies hereinafter.

[0056] The gas atmosphere in the pre-baking step is not particularly limited as long as it is an oxidizing atmosphere that ensures the lithiation reaction and oxidation reaction to proceed. For example, it is preferable to use a decarbonated oxidizing gas atmosphere with a carbon dioxide concentration of 30 ppm or less, or an oxygen atmosphere with an oxygen concentration of 80 vol% or more, 90 vol% or more, or 95 vol% or more.

[0057] The baking time in the pre-baking step is not particularly limited as long as it is a time that allows the lithiation reaction to proceed, and is preferably, for example, 1 hour or more, 2 hours or more, or 3 hours or more. On the other hand, the baking time in the pre-baking step is preferably, for example, 10 hours or less, 9 hours or less, or 8 hours or less. The baking time refers to the time during which the maximum temperature is maintained within the above-mentioned temperature range. The same definition applies hereinafter.

[0058] [Pelletization process] The pelletizing step is a step of producing pellets from the pre-fired material.

[0059] Specifically, the pelletizing step may involve packing the powdery pre-fired material into a mold and applying pressure to produce the pellets.

[0060] The pressure during pressurization is not particularly limited, but is preferably 20 MPa or more, 21 MPa or more, 22 MPa or more, 23 MPa or more, 24 MPa or more, 25 MPa or more, 26 MPa or more, 27 MPa or more, 28 MPa or more, 29 MPa or more, 30 MPa or more, 31 MPa or more, 32 MPa or more, 33 MPa or more, 34 MPa or more, 35 MPa or more, 36 MPa or more, 37 MPa or more, 38 MPa or more, 39 MPa or more, or 40 MPa or more. On the other hand, the pressure during pressurization may be 500 MPa or less, 450 MPa or less, 400 MPa or less, 350 MPa or less, 300 MPa or less, 250 MPa or less, 200 MPa or less, 150 MPa or less, 120 MPa or less, 100 MPa or less, 90 MPa or less, 80 MPa or less, or 70 MPa or less.

[0061] When pressing, water, a solvent, a resin binder, etc. may be added to the pre-baked product to improve moldability.

[0062] The maximum length of the pellets is not particularly limited, and may be, for example, 1 mm or more, 2 mm or more, 3 mm or more, 4 mm or more, 5 mm or more, 6 mm or more, 7 mm or more, 8 mm or more, 9 mm or more, or 10 mm or more. On the other hand, the maximum length of the pellets may be 350 mm or less, 320 mm or less, 300 mm or less, 270 mm or less, 250 mm or less, 220 mm or less, 200 mm or less, 170 mm or less, 150 mm or less, 120 mm or less, 100 mm or less, 70 mm or less, 60 mm or less, 50 mm or less, 47 mm or less, 45 mm or less, 42 mm or less, 40 mm or less, 37 mm or less, 35 mm or less, 32 mm or less, or 30 mm or less. The term "maximum length" refers to the longest distance from one end of the pellet to the other end.

[0063] The density of the pellets is not particularly limited, but is preferably 2 g / cm 3 More than 2.1g / cm 3 More than 2.2g / cm 3 More than 2.3g / cm 3 More than 2.4g / cm 3 More than 2.5g / cm 3 More than 2.6g / cm 3More than 2.7g / cm 3 More than 2.8g / cm 3 More than 2.9g / cm 3 More than 3g / cm 3 On the other hand, the density of the pellets is preferably 5 g / cm or more. 3 Below, 4.9g / cm 3 Below 4.8g / cm 3 Below, 4.7g / cm 3 Below, 4.6g / cm 3 Below 4.5g / cm 3 Below, 4.4g / cm 3 Below, 4.3g / cm 3 Below, 4.2g / cm 3 Below, 4.1g / cm 3 Below, 4g / cm 3 It may be the following:

[0064] The shape of the pellets is not particularly limited, but may be, for example, spherical, spheroidal, cylindrical, discoidal, polyhedral, or the like.

[0065] The pelletizing step is not limited to the above-mentioned method as long as it is a method that can mold the pre-fired product.

[0066] [Firing process] The firing step is a step of firing the pellets obtained in the pelletizing step at a temperature of 700°C or higher and 1000°C or lower.

[0067] In this firing step, the lithium metal composite oxide formed in the pre-firing step is heated at a higher temperature to grow crystals, thereby obtaining a lithium metal composite oxide with higher crystallinity.

[0068] The firing temperature in the firing step is not particularly limited as long as it is 700°C or higher and 1000°C or lower, but is preferably, for example, 710°C or higher, 720°C or higher, or 730°C or higher. On the other hand, the firing temperature in the firing step is preferably 980°C or lower, 950°C or lower, 920°C or lower, 880°C or lower, 850°C or lower, 820°C or lower, 810°C or lower, 800°C or lower, 790°C or lower, or 780°C or lower. By keeping the firing temperature within the required range, it is possible to reduce unreacted portions and obtain a lithium metal composite oxide with high crystallinity, which in turn makes it possible to prevent a decrease in the battery characteristics of a nonaqueous electrolyte secondary battery using the obtained lithium metal composite oxide in the positive electrode.

[0069] The gas atmosphere in the firing step is not particularly limited, and may be a non-reducing atmosphere in which crystal growth occurs and the transition metal contained in the lithium-metal composite oxide is not reduced, preferably an atmosphere with a low moisture content and carbon dioxide concentration. For example, it is preferable to use a decarbonated oxidizing gas atmosphere with a carbon dioxide concentration of 30 ppm or less, or an oxygen atmosphere with an oxygen concentration of 80 vol% or more, 90 vol% or more, or 95 vol% or more.

[0070] The calcination time in the calcination step is not particularly limited as long as it is a time that allows crystal growth of the lithium metal composite oxide to proceed, and is preferably, for example, 1 hour or more, 2 hours or more, or 3 hours or more. On the other hand, the calcination time in the calcination step is preferably, for example, 15 hours or less, 14 hours or less, 13 hours or less, 12 hours or less, 11 hours or less, 10 hours or less, 9 hours or less, or 8 hours or less.

[0071] [Cleaning process] The method for producing a lithium metal composite oxide according to this embodiment may include a washing step. The washing step is a step of washing the lithium metal composite oxide obtained in the calcination step. In the lithium metal composite oxide obtained in the calcination step, carbonate ions are absorbed by the additive compound, suppressing the production of lithium carbonate, but a small amount of lithium carbonate may still be produced. In addition, unreacted lithium hydroxide and lithium compounds produced when lithium ions migrate from the crystals to the particle surface during the calcination process may be present. Therefore, in order to remove or reduce these impurities, the product may be washed with water and heat-treated and dried, for example. The washing step is not an essential step.

[0072] [Surface treatment process] The method for producing a lithium metal composite oxide according to this embodiment may include a surface treatment step. The surface treatment step is a step of performing a surface treatment on the lithium metal composite oxide obtained in the firing step or washing step. By adding and mixing a compound of a predetermined element to the lithium metal composite oxide obtained in the firing step or washing step and performing a heat treatment, the surfaces of the primary particles and / or secondary particles of the lithium metal composite oxide can be surface-treated with the compound of lithium and the added element. This can achieve effects such as reducing the amount of lithium compounds remaining on the particle surface, improving lithium ion conductivity, and reducing reaction resistance. Note that the surface treatment step is not an essential step.

[0073] The element compound added for the above-mentioned surface treatment can be, for example, one or more of an aluminum compound, a boron compound, a tungsten compound, a manganese compound, a cobalt compound, a phosphorus compound, a niobium compound, a strontium compound, an antimony compound, a zirconium compound, a titanium compound, and the like.

[0074] The heat treatment temperature is not particularly limited, but is preferably, for example, 200° C. or higher, 210° C. or higher, 220° C. or higher, 230° C. or higher, 240° C. or higher, or 250° C. 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.

[0075] The heat treatment time is not particularly limited, and is preferably, for example, 1 hour to 15 hours, 2 hours to 12 hours, or 2 hours to 10 hours.

[0076] <Nonaqueous electrolyte secondary battery> The nonaqueous electrolyte secondary battery according to the embodiment of the present disclosure includes a positive electrode containing the above-described lithium metal composite oxide as a positive electrode active material, and the nonaqueous electrolyte secondary battery is composed of a positive electrode, a negative electrode, and an electrolytic solution containing an electrolyte.

[0077] When manufacturing a positive electrode, a conductive agent and a binder are added to and mixed with the lithium metal composite oxide according to the embodiment of the present disclosure. The conductive agent is preferably, for example, acetylene black, carbon black, graphite, or the like. The binder is preferably, for example, polytetrafluoroethylene, polyvinylidene fluoride, or the like.

[0078] The negative electrode is not particularly limited, and examples thereof include negative electrode active materials such as lithium metal, graphite, and low-crystalline carbon materials, as well as one or more nonmetallic or metallic elements selected from Si, Al, Sn, Pb, Zn, Bi, and Cd, alloys containing them, or chalcogen compounds containing them.

[0079] The solvent for the electrolytic solution is not particularly limited, but may be, for example, an organic solvent containing one or more selected from carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate, and ethers such as dimethoxyethane.

[0080] As the electrolyte, in addition to lithium hexafluorophosphate (LiPF6), one or more selected from lithium salts such as lithium perchlorate and lithium tetrafluoroborate can be dissolved in a solvent and used.

[0081] Although specific examples of the embodiments of the present disclosure have been described above, modifications can be made as appropriate within the scope that does not impair the effects of the present invention. [Example]

[0082] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0083] In the examples, for convenience, firing (a process of firing pellets at 700° C. or higher and 1000° C. or lower) is sometimes referred to as "main firing" to distinguish it from pre-firing.

[0084] <Preparation of lithium metal composite oxide samples> Lithium metal composite oxide samples of Examples 1 and 2 and Comparative Examples 1 and 2 were prepared by the methods described below.

[0085] [Preparation of precursor compounds] First, a method for preparing the precursor compound used as a raw material for the lithium metal composite oxide in each of the examples and comparative examples will be described.

[0086] A mixed aqueous solution was obtained by mixing an aqueous nickel sulfate solution, a cobalt sulfate solution, and an aqueous manganese sulfate solution so that the molar ratio of Ni to Co to Mn was Ni:Co:Mn = 90:4:6. 10 L of pure water containing 300 g of sodium hydroxide solution and 500 g of ammonia water was prepared in advance in the reaction vessel as a mother liquid. The reaction vessel was filled with nitrogen gas at a flow rate of 0.7 L / min to create a nitrogen atmosphere, and the reaction was also carried out in a nitrogen atmosphere.

[0087] Thereafter, while rotating the stirring blade at 1000 rpm, the mixed aqueous solution, sodium hydroxide aqueous solution, and ammonia water were simultaneously added dropwise at a predetermined rate, and the amount of the alkaline solution added was adjusted so that the pH became 11.7. Through a crystallization reaction, Ni, Co, and Mn were crystallized and coprecipitated to form aggregated particles, thereby obtaining a coprecipitate.

[0088] After that, the slurry in the reactor was separated into solid and liquid, and then washed with pure water to reduce the remaining impurities. The coprecipitate cake was then dried at 100°C for 10 hours in an air environment to obtain the product with the formula Ni 0.90 Co 0.04 Mn 0.06 A nickel-cobalt-aluminum composite hydroxide represented by (OH)2 was obtained.

[0089] [Preparation of Pre-fired Product] The resulting metal composite hydroxide and anhydrous lithium hydroxide were weighed and mixed to obtain a precursor mixture with a molar ratio of Li / (Ni+Co+Mn) = 1.08. The resulting precursor mixture was filled into a sheath and pre-fired in an electric furnace under an oxygen atmosphere (oxygen concentration: 97 vol%) at 620°C for 2 hours to obtain a powdery pre-fired product.

[0090] The powder density of the precursor mixture obtained above was 1.00 g / cc and the angle of repose was 55.0 degrees, while the powder density of the pre-fired product was 1.92 g / cc and the angle of repose was 35.1 degrees.

[0091] Example 1 5 g of the pre-fired material was packed into a 15 mm diameter mold (made of SUS304), and a pressure of 64 MPa was applied using a hydraulic jack for 30 seconds. The pressure from the hydraulic jack was then released, and the molded pellets were removed from the mold. The density of the pellets calculated from the volume and mass (hereinafter sometimes referred to as the "density of the packed material before firing") was 3.16 g / cc.

[0092] The pellets were then placed in a crucible (placed on an alumina setter) and fired in an oxygen atmosphere (oxygen concentration: 99 vol%) at a maximum temperature of 750°C for 4 hours. The compact maintained its shape even after firing. The fired product was crushed and pulverized to obtain a lithium metal composite oxide sample.

[0093] Example 2 A lithium metal composite oxide sample was obtained in the same manner as in Example 1, except that a powder prepared by adding 2 mass % of water to the pre-calcined product and mixing it was used.

[0094] Comparative Example 1 The pre-fired product was filled into a crucible without being pelletized, and then fired in an oxygen atmosphere (oxygen concentration: 99 vol%) at a maximum temperature of 750°C for 4 hours, and the resulting fired product was pulverized to obtain a lithium metal composite oxide sample. In Comparative Example 1, the density of the sample when filled into the crucible was taken as the density of the sample filled before firing.

[0095] Comparative Example 2 The precursor mixture was filled into a crucible without being pelletized, and then maintained at 600°C (oxygen concentration: 99 vol%) for 2 hours. The temperature was then increased to 750°C without cooling, and then fired at the maximum temperature of 750°C for 4 hours. The resulting fired product was pulverized to obtain a lithium metal composite oxide sample. In Comparative Example 2, the density of the sample when filled into the crucible was taken as the packed density of the sample before firing.

[0096] <Sample evaluation> The obtained samples were evaluated by the following methods.

[0097] [Composition analysis of precursor compounds and lithium metal composite oxides] The compositions of the precursor compound and the lithium metal composite oxide were identified by the following method. 0.2 g of the precursor compound and lithium metal composite oxide sample were heated and dissolved in 25 ml of 20% hydrochloric acid solution, cooled, and then transferred to a 100 ml measuring flask. Pure water was added to prepare a liquid. The elements in the obtained liquid were quantified using ICP-AES (Optima 8300, manufactured by PerkinElmer Japan Co., Ltd.).

[0098] [Measurement of loose bulk density, powder angle of repose and packing density] The loose bulk density and the angle of repose of the powder of the lithium metal composite oxide sample were measured using a Powder Tester (manufactured by Hosokawa Micron Corporation).

[0099] The loose bulk density is 100cm 3 The powder sample was allowed to fall naturally into a cup with a capacity of 1000 ml, and the mass was weighed to calculate the packing density (g / cm 3 )

[0100] The angle of repose of a powder is the angle of the peak of the powder (angle of elevation) formed when a powder sample is allowed to fall naturally.

[0101] When the lithium metal composite oxide sample was pelletized before firing, the density of the packed material was determined by the density of the pellet (g / cm 3 ) If pellets are not made before firing, the volume is 100 cm 3 The powder sample is weighed so that it falls naturally into the crucible, and the density (g / cm) is calculated by measuring the mass at this time. 3 )

[0102] [Productivity evaluation] The productivity was evaluated based on the mass of the sample before the main firing in the firing furnace for the same firing time, taking into consideration the loose density of the lithium metal composite oxide sample before the main firing, the ease of pelletization based on the judgment of fluidity based on the angle of repose of the powder, the judgment of productivity based on the packing into the sheath, and the state of the sample before the main firing (the ratio of high powder density due to molding to sheath packing density due to packing into the sheath). Specifically, a three-level evaluation was performed based on the following criteria A to C. A: Meet all of the following requirements (1) to (3) B: Meet one or two of the following requirements (1) to (3): C: None of the following requirements (1) to (3) are met. (1) The loose bulk density of the powder before firing is 1.5 g / cm 3 More than 2.6g / cm 3 below (2) The angle of repose of the powder before firing is 20° or more and 45° or less. (3) The ratio of the density of the filler before sintering to the loose bulk density of the powder before sintering (hereinafter sometimes referred to as the "ratio of density before sintering") is 1.2 times or more and 2.5 times or less.

[0103] [Quality evaluation] After the main calcination, the Li / Me (referred to as M) of the precursor mixture of the precursor compound and the lithium compound and the Li / Me (referred to as N) of the lithium metal composite oxide after the main calcination were calculated by composition analysis. At this time, (M-N) / M was calculated, and the quality was evaluated on a three-level scale based on the following criteria A to C. A: (MN) / M is 0.03 or less B: (MN) / M is greater than 0.03 and less than 0.043 C:(MN) / M is greater than 0.043

[0104] Table 1 below shows the loose bulk density of the powder before sintering, the angle of repose of the powder before sintering, the packed density before sintering, the density ratio before sintering, the Li / Me ratio (MN) / M of the lithium metal composite oxide sample, the quality evaluation, and the productivity evaluation results.

[0105] [Table 1]

Claims

1. a pre-firing step of heating a precursor compound of the lithium metal composite oxide and a lithium compound at 500°C or higher and 650°C or lower to obtain a pre-firing product; a pelletizing step for producing pellets of the pre-fired material; and a firing step of firing the pellets at 700°C or higher and 1000°C or lower. A method for producing lithium metal composite oxide.

2. The lithium metal composite oxide has the general formula Li ａ Ni １－ｘ－ｙ－ｚ Co ｘ Mn ｙ M ｚ O ２＋α (wherein M is an element other than Li, Ni, Co, Mn, and O, and 0.95≦a≦1.20, 0≦x≦0.4, 0≦y≦0.4, 0≦z≦0.1, −0.5≦α≦0.5, 1−x−y−z≧0.3) The method for producing the lithium metal composite oxide according to claim 1 .

3. The average maximum length of the pellets is 1 mm or more and 350 mm or less. The method for producing the lithium metal composite oxide according to claim 1 or 2.

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