Production method of particle

Abstract

To provide a production method of a single particle including a lithium metal complex oxide which exhibits a Li site occupancy which is prevented from decreasing.SOLUTION: A production method of a single particle including a lithium-containing metal complex oxide includes: a precursor firing step of firing a precursor including a metal complex hydroxide at a temperature of 700 to 900°C for 3 to 8 hours to obtain a precursor fired product; a mixture step of mixing the precursor fired product with a lithium compound to obtain a mixed product; a first firing step of firing the mixed product at a temperature of 700 to 820°C; and a second firing step of firing the mixed product after the first firing step at a temperature of 900°C or higher. A firing time in the first firing step is longer in comparison with that in the second firing step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing particles. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 2018-125305 (Patent Document 1) proposes a manufacturing method for obtaining a positive electrode active material containing lithium transition metal oxide particles that consist of a single particle or a small number of primary particles that make up a secondary particle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-125305 Summary of the Invention [Problem to be solved by the invention]

[0004] The positive electrode active material obtained by the manufacturing method described in Patent Document 1 may have a relatively low Li site occupancy. When the Li site occupancy of the positive electrode active material is low, the capacity of the nonaqueous electrolyte secondary battery tends to be low.

[0005] An object of the present disclosure is to provide a method for producing single particles containing a lithium metal composite oxide in which a decrease in the Li site occupancy rate is suppressed. [Means for solving the problem]

[0006] [1] A method for producing particles, comprising: a precursor calcination step of calcining a precursor containing a metal composite hydroxide at a temperature of 700 to 900°C for 3 to 8 hours to obtain a precursor calcined product; a mixing step of mixing the calcined precursor with a lithium compound to obtain a mixture; a first firing step of firing the mixture at a temperature of 700 to 820°C; a second firing step of firing the mixture after the first firing step at a temperature of 900°C or higher; Including, the particles contain a metal composite oxide containing lithium, the particle is a single particle, The method for producing particles, wherein the firing time in the first firing step is longer than the firing time in the second firing step. [2] The method for producing particles according to [1], wherein the firing temperature in the first firing step is 750°C or higher. [3] The method for producing particles according to [1] or [2], wherein the firing time in the second firing step is 6 hours or less. [4] The method for producing particles according to any one of [1] to [3], wherein in the mixing step, the ratio of the total number of moles of lithium to the total number of moles of metal elements other than lithium in the mixture is in the range of 1.0 to 1.2. [5] The method for producing particles according to any one of [1] to [4], wherein the particles have an average particle size of 2.0 to 6.0 μm. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a method for producing single particles containing a lithium metal composite oxide in which a decrease in the Li site occupancy rate is suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic flow chart illustrating the method for producing particles of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Particle manufacturing method> The method for producing particles according to the present disclosure includes a precursor calcination step of calcining a precursor containing a metal composite hydroxide at a temperature of 700 to 900°C for 3 to 8 hours to obtain a calcined precursor, a mixing step of mixing the calcined precursor with a lithium (Li) compound to obtain a mixture, a first calcination step of calcining the mixture at a temperature of 700 to 820°C, and a second calcination step of calcining the mixture obtained after the first calcination step at a temperature of 900°C or higher. The particles contain a metal composite oxide containing Li. The particles are single particles. The calcination time in the first calcination step is longer than the calcination time in the second calcination step.

[0010] According to the particle manufacturing method of the present disclosure, it is possible to manufacture single particles containing a Li-containing metal composite oxide in which a decrease in the lithium site occupancy (hereinafter also referred to as the Li site occupancy) is suppressed. In the method for manufacturing single particles containing a Li-containing metal composite oxide, a mixture of a precursor and Li is often calcined at a relatively high calcination temperature (e.g., 900°C or higher). On the other hand, when the calcination temperature is high, metal ions [e.g., nickel (Ni) ions] tend to be easily reduced, causing cation mixing that occupies the Li site, and the lithium site occupancy tends to decrease. According to the particle manufacturing method of the present disclosure, calcining the precursor in the precursor calcination step and then calcining at a relatively high calcination temperature (e.g., 900°C or higher) for a relatively short time in the subsequent calcination step facilitates the manufacture of single particles in which cation mixing is suppressed.

[0011] Fig. 1 is a schematic flowchart showing a method for producing particles. The method for producing particles includes a precursor calcination step (A1) of obtaining a calcined precursor by calcining at a temperature of 700 to 900°C for 3 to 8 hours, a mixing step (A2) of mixing the calcined precursor with a Li compound to obtain a mixture, a first calcination step (A3) of calcining the mixture at a temperature of 700 to 820°C, and a second calcination step (A4) of calcining the mixture after the first calcination step at a temperature of 900°C or higher.

[0012] (particle) The particles can be, for example, a positive electrode active material used in an active material layer of a positive electrode of a non-aqueous electrolyte secondary battery (hereinafter also referred to as a battery) such as a lithium ion battery.

[0013] The particles contain a Li-containing metal composite oxide. The particles may consist solely of a Li-containing metal composite oxide. The Li-containing metal composite oxide may further contain Ni. A Li- and Ni-containing metal composite oxide may have a large specific capacity. The particles may contain at least one selected from the group consisting of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(NiCoMn)O2, Li(NiCoAl)O2, and LiFePO4. Here, for example, a notation such as "(NiCoMn)" in a composition formula such as "Li(NiCoMn)O2" indicates that the sum of the composition ratios in parentheses is 1. The composition of the Li-containing metal composite oxide can be determined, for example, by ICP (inductively coupled plasma) optical emission spectroscopy.

[0014] The particles may, for example, comprise a first layered metal oxide. The first layered metal oxide has the formula (1): Li a1 Ni 1-b1 M 1 b1 O2(1) [In formula (1), 1.0≦a1≦1.2, 0 <b1≦0.5であり、 M 1 is one or more elements selected from the group consisting of Co, Mn, Al, Zr, Ti, V, Cr, Fe, Cu, Zn, Mo, Sn, Ge, Nb, W, B, Mg, Na, K, Ba, Sr, Ca, and Si. is expressed by

[0015] The first layered metal oxide is preferably represented by formula (2): Li a1’ Ni 1-c1-d1 Co c1 Mn d1 M 1’ e1 O2(2) is expressed by [In formula (2), 1.00≦a1'≦1.20, 0≦c1≦0.25, 0≦d1≦0.25, 0≦e1≦0.10, M 1’ is one or more elements selected from the group consisting of Al, Zr, Ti, V, Cr, Fe, Cu, Zn, Mo, Sn, Ge, Nb, W, B, Mg, Na, K, Ba, Sr, Ca, and Si. is expressed by

[0016] The particles are single particles. The single particles can have any shape. The single particles can be, for example, spherical, cylindrical, blocky, etc. The particles can be formed from one single particle. The particles can also be formed by agglomeration of 2 to 10 single particles.

[0017] The number of single particles contained in the particles is measured in a scanning electron microscope (SEM) image of the particles. The number of single particles contained in the particles is measured in an SEM image with a magnification of 10,000 times.

[0018] In an SEM image of a particle, for example, if two single particles overlap, the particle at the back may not be visible. However, in this embodiment, the number of single particles visible in the SEM image is considered to be the number of single particles contained in the particle. The same applies to aggregated particles described below. A particle may, for example, be substantially composed of 1 to 10 single particles. A particle may, for example, be composed of 1 to 10 single particles. A particle may, for example, be composed of 1 to 5 single particles. A particle may, for example, be composed of 1 to 3 single particles. A particle may, for example, be composed of 1 single particle.

[0019] In this embodiment, a single particle refers to a particle in which no grain boundary is visible in an SEM image of the particle. The single particle may have an average particle diameter of, for example, 2.0 to 6.0 μm. In this specification, the average particle diameter of a single particle is the particle diameter D50 at which the cumulative frequency of the smaller particle diameters in a volume-based particle size distribution reaches 50%. The volume-based particle size distribution can be measured using a particle size distribution analyzer.

[0020] (precursor) The precursor includes a metal composite hydroxide. The precursor may consist solely of a metal composite hydroxide. The metal composite hydroxide may be a metal composite hydroxide containing Ni. The metal composite hydroxide may be a metal composite hydroxide containing Ni and manganese (Mn). The metal composite hydroxide may be a nickel-cobalt-manganese composite hydroxide (hereinafter also referred to as an NCM composite hydroxide) containing Ni, Mn, and cobalt (Co). The metal composite hydroxide is preferably an NCM composite hydroxide.

[0021] The NCM composite hydroxide may be, for example, a compound represented by the following formula (i): Ni 1-x-y-z Co x Mn y M z (i) [In formula (i), 0 <x<0.5、0<y<0.5、0≦z<0.05であり、 M is one or more elements selected from the group consisting of Al, Ti, Zr, B, Mg, Fe, Cu, Zn, Sn, Na, K, Ba, Sr, Ca, W, Mo, Nb, Si, V, Cr and Ge. The composition of the metal complex hydroxide can be determined by, for example, ICP emission spectrometry.

[0022] The precursor can be produced, for example, by a production method including a first crystallization step and a second crystallization step. In the first crystallization step, a raw metal aqueous solution is placed in a reaction vessel, and crystallization is carried out while stirring by supplying an aqueous ammonia solution and sodium hydroxide to the reaction vessel and adjusting the pH and ammonium ion concentration of the solution in the reaction vessel at a base liquid temperature of 25°C. Then, in the second crystallization step, the pH of the solution in the reaction vessel at a base liquid temperature of 25°C is changed and crystallization is carried out, thereby producing a precursor.

[0023] The raw metal aqueous solution is an aqueous solution containing the metals contained in the metal composite hydroxide, and is prepared by adding the metal element itself or a metal-containing compound (e.g., sulfate, nitrate, or carbonate) to water. The metal-containing compound may be, for example, a Ni-containing compound, a Mn-containing compound, or a Co-containing compound. The Ni-containing compound may be, for example, nickel sulfate (NiSO4), nickel nitrate [Ni(NO3)2], nickel carbonate (NiCO3), etc. The Mn-containing compound may be, for example, manganese sulfate (MnSO4), manganese nitrate [Mn(NO3)2], manganese carbonate (MnCO3), etc. The Co-containing compound may be, for example, cobalt sulfate (CoSO4), cobalt nitrate [Co(NO3)2], cobalt carbonate (CoCO3), etc.

[0024] When the precursor is an NCM composite hydroxide, the molar ratio of Ni, Mn, and Co (Ni:Mn:Co) in the raw metal aqueous solution may be, for example, 1-xy: 0≦x≦0.5: 0≦y≦0.5, 1-xy: 0.05≦x≦0.25: 0.05≦y≦0.25, or 1-xy: 0.1≦x≦0.2: 0.1≦y≦0.2. The metal content in the raw metal aqueous solution may be, for example, 0.5 to 2.0 mol / L.

[0025] The first crystallization step can be a step of supplying a raw metal aqueous solution and an aqueous ammonia solution to a reaction tank and carrying out crystallization by stirring the solution while maintaining the pH of the solution in the reaction tank at, for example, 12.0 to 13.5 and the ammonium ion concentration at, for example, 5.3 to 11.7 g / L at a liquid temperature of 25° C. The pH in the first crystallization step may be higher than the pH in the second crystallization step described below.

[0026] In the first crystallization step, the raw metal aqueous solution and the aqueous ammonia solution can be supplied to the reaction vessel so that the molar ratio of the raw metal aqueous solution to the aqueous ammonia solution is 1:1.

[0027] During stirring, while monitoring the pH and ammonium ion concentration at a liquid temperature of 25°C, the pH at a liquid temperature of 25°C can be adjusted to the above range by adding sodium hydroxide, and the ammonium ion concentration can be adjusted to the above range by adjusting the concentration of the aqueous ammonia solution being supplied. The pH can be adjusted by controlling the flow rate of sodium hydroxide using a pH controller.

[0028] In the first crystallization step, the liquid temperature of the solution may be, for example, 10 to 60° C. The first crystallization step may be carried out for, for example, 1 to 120 minutes. The first crystallization step may be carried out in a non-acidified atmosphere, for example, while flowing nitrogen gas or the like into a reaction vessel.

[0029] The second crystallization step can be a step of adjusting the pH of the solution after the first crystallization step to 9.7 to 12.0 at a standard liquid temperature of 25° C. in a reaction tank, and then stirring the solution while maintaining the pH. The ammonium ion concentration of the solution in the reaction tank in the second crystallization step can be the same as the ammonium ion concentration in the first crystallization step described above.

[0030] In the second crystallization step, the liquid temperature of the solution may be, for example, 10 to 60° C. The second crystallization step may be carried out for, for example, 120 to 1200 minutes. The second crystallization step may be carried out in a non-acidified atmosphere, for example, while flowing nitrogen gas or the like into a reaction vessel.

[0031] The second crystallization step can be terminated by stopping the supply of the raw metal aqueous solution and the ammonia aqueous solution. The solution in the reaction vessel is filtered, and the filtrate is washed with water and then dried to obtain a precursor containing a metal composite hydroxide. The precursor containing a metal composite hydroxide can be in the form of secondary particles (aggregated particles) formed by aggregating a plurality of (e.g., 50 or more) primary particles.

[0032] (Precursor firing process) A precursor containing a metal composite hydroxide is calcined at a temperature of 700 to 900°C for 3 to 8 hours. This makes it easier to shorten the time required for calcination at a relatively high temperature (e.g., 900°C or higher) in the subsequent calcination step, and tends to make it easier to suppress cation mixing. This is presumably because the size of the primary particles that make up the secondary particles, which are the calcined precursor, increases.

[0033] In the precursor calcination step, the temperature at which the precursor containing the metal composite hydroxide is calcined (hereinafter also referred to as precursor calcination temperature) may be, for example, 750°C or higher and 850°C or lower.

[0034] In the precursor calcination step, the time for calcining the precursor containing the metal composite hydroxide (hereinafter also referred to as precursor calcination time) may be, for example, 4 hours or more and 7 hours or less.

[0035] The precursor firing step can be carried out, for example, in an air atmosphere.

[0036] The calcined precursor contains a metal composite oxide, and may be composed solely of a metal composite oxide.

[0037] (Mixing process) The calcined precursor and the Li compound can be mixed, for example, so that the ratio of the total moles of Li to the total moles of metal elements other than Li in the resulting mixture is 1.0 to 1.2. Examples of the lithium compound include lithium hydroxide, lithium carbonate, and lithium oxide.

[0038] (First firing step and second firing step) After the mixture is fired in the first firing step, the mixture after the first firing step is further fired in the second firing step.

[0039] In the first firing step, the temperature at which the mixture is fired (hereinafter also referred to as the first firing temperature) is 700 to 820°C.

[0040] The first firing temperature is preferably 750° C. or higher. By setting the first firing temperature to 750° C. or higher, the fired precursor reacts sufficiently with Li, and Li present near the outer surface easily enters the interior of the particles, which makes it easier to simultaneously reduce the amount of lithium compound remaining on the particle surface (amount of residual alkali) and suppress cation mixing, and tends to make it easier to improve the battery capacity.

[0041] In the second firing step, the temperature at which the mixture after the first firing step is fired (hereinafter also referred to as the second firing temperature) is 900° C. or higher. The second firing temperature may be, for example, 950° C. or lower.

[0042] In the first firing step, the time for firing the mixture (hereinafter also referred to as the first firing time) is longer than the time for firing the mixture after the first firing step (hereinafter also referred to as the second firing time) in the second firing step described below. In the particle production method of the present disclosure, the precursor is fired in the precursor firing step, thereby increasing the number of primary particles that constitute the precursor secondary particles. This makes it easier to produce single particles and shortens the firing time at relatively high temperatures of 900°C or higher, at which cation mixing is likely to occur. This tends to suppress cation mixing and make it easier to produce single particles.

[0043] The ratio of the second baking time to the first baking time (second baking time / first baking time) may be, for example, 1 / 3 or more and 3 / 4 or less, or 1 / 2 or more and 3 / 4 or less.

[0044] In the first firing step, the time for firing the mixture (hereinafter also referred to as the first firing time) may be, for example, more than 6 hours, 7 hours or more, or 8 hours or more, or 9 hours or less.

[0045] In the second firing step, the time for firing the mixture after the first firing step (hereinafter also referred to as the second firing time) may be, for example, 6 hours or less. If the second firing time is 6 hours or less, single particles tend to be more easily produced. The second firing time may be, for example, 3 hours or more, or 4 hours or more.

[0046] After the second firing step, single particles containing a lithium-containing metal composite oxide are obtained. The particles obtained by the particle manufacturing method of the present disclosure are single particles containing a lithium metal composite oxide in which the decrease in the Li site occupancy rate is suppressed, so when used in a positive electrode active material layer, the decrease in battery capacity tends to be easily suppressed. Therefore, the particles obtained by the particle manufacturing method of the present disclosure are suitable for positive electrode active materials. [Example]

[0047] [Measuring average particle size] The particle size distribution of the particles produced in the examples and comparative examples was measured using a commercially available laser light diffraction / scattering particle size analyzer, and the average particle size (D50) was measured using the volume integrated value.

[0048] [Li seat occupancy rate] For the particles produced in the examples and comparative examples, calculations were made by performing Rietveld analysis on the X-ray diffraction patterns obtained by X-ray measurement using a commercially available X-ray diffractometer.

[0049] [Residual alkali content] A portion of the particles produced in the examples and comparative examples was taken and added with water to form a slurry, which was then neutralized by titration with hydrochloric acid to determine the amount of alkali, thereby determining the amount of lithium hydroxide (residual alkali) contained in the powder.

[0050] [Evaluation of particle morphology] The particles prepared in the examples and comparative examples were observed under a scanning electron microscope (SEM) at 10,000x magnification. When the SEM image of a particle confirmed that the particle consisted of 1 to 10 individual particles, the particle was judged to be a single particle. On the other hand, when the particle was confirmed to be a secondary particle consisting of 50 or more primary particles, the particle was judged to be an agglomerated particle.

[0051] Example 1 [Precursor manufacturing process] Pure water was placed in a 5 L reaction vessel, and nitrogen gas was introduced to maintain the oxygen concentration in the vessel at 1.0% by volume or less, followed by stirring at 500 rpm. After adjusting the solution in the reaction vessel to 30°C, an appropriate amount of 30 wt% aqueous sodium hydroxide solution was added and the pH was adjusted to 12.5 at a liquid temperature of 25°C. Hereinafter, the pH of the solution in the reaction vessel at a liquid temperature of 25°C before the start of crystallization will be referred to as the initial pH. Next, nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in water in a respective molar ratio (hereinafter referred to as the first molar ratio) of 80:10:10 to prepare a 1.5 mol / L aqueous solution of raw metals.

[0052] The prepared raw metal aqueous solution and ammonia aqueous solution were supplied in a timed manner so that the ratio was 1:1, and crystallization was carried out for 30 minutes under conditions where the pH was 12.5 at a liquid temperature of 25°C. Hereinafter, the pH of the solution in the reaction tank at a liquid temperature of 25°C after the start of crystallization until the pH at a liquid temperature of 25°C was changed will be referred to as the first pH. The pH was controlled by adjusting the flow rate of sodium hydroxide using a pH controller. During this time, the concentration of the supplied ammonia aqueous solution was adjusted so that the ammonium ion concentration in the reaction solution was maintained at 10 g / L.

[0053] After 30 minutes of crystallization, sulfuric acid was gradually added dropwise to the solution in the reaction tank so that the pH was adjusted to 11.0 at a liquid temperature of 25°C. After adjusting the pH, the supply of liquid to the reaction tank was resumed, and crystallization was continued for 8 hours. Hereinafter, the pH of the solution in the reaction tank at a liquid temperature of 25°C where crystallization was performed after changing the first pH will be referred to as the second pH. Thereafter, the supply of solution was stopped, and crystallization was terminated. After completion, the product was filtered, washed with water, and dried, in that order, to obtain a precursor consisting of a NiCoMn composite hydroxide.

[0054] [Precursor firing process] The precursor made of NiCoMn composite hydroxide was calcined in an air atmosphere at a temperature of 770°C for 5 hours to obtain a calcined precursor made of NiCoMn oxide.

[0055] [Mixing process] The calcined precursor and lithium hydroxide were mixed so that the ratio of the total number of moles of Li to the total number of moles of metal elements other than Li was 1.10, thereby obtaining a mixture.

[0056] [Firing process] The mixture was heated in an electric furnace in an oxidizing atmosphere at 780°C for 8 hours (first firing step), and then heated at 930°C for 4 hours (second firing step) to produce particles made of LiNiCoMn composite oxide. The results are shown in Table 1.

[0057] <Example 2> Particles made of LiNiCoMn composite oxide were produced in the same manner as in Example 1, except that the precursor firing temperature, first firing temperature, second firing temperature, first firing time, and second firing time were changed as shown in Table 1. The results are shown in Table 1.

[0058] Example 3 Particles made of LiNiCoMn composite oxide were produced in the same manner as in Example 1, except that the first molar ratio was set to 60:20:20, the second pH was adjusted to 11.0, and the precursor calcination temperature, first calcination temperature, second calcination temperature, precursor calcination time, first calcination time, and second calcination time were changed as shown in Table 1. The results are shown in Table 1.

[0059] Example 4 Particles made of LiNiCoMn composite oxide were produced in the same manner as in Example 1, except that the initial pH and the first pH were adjusted to 12.0 and the precursor firing temperature, second firing temperature, first firing time, and second firing time were changed as shown in Table 1. The results are shown in Table 1.

[0060] <Comparative Example 1> Particles made of LiNiCoMn composite oxide were produced in the same manner as in Example 1, except that the initial pH and the first pH were adjusted to 12.0 and the precursor calcination temperature was changed as shown in Table 1. The results are shown in Table 1.

[0061] <Comparative Example 2> Particles made of LiNiCoMn composite oxide were produced in the same manner as in Example 1, except that the initial pH and the first pH were adjusted to 12.0 and the precursor calcination temperature was changed as shown in Table 1. The results are shown in Table 1.

[0062] <Comparative Example 2> Particles made of LiNiCoMn composite oxide were produced in the same manner as in Example 1, except that the first molar ratio was changed to 60:20:20 and the precursor firing temperature was changed to that shown in Table 1. The results are shown in Table 1.

[0063] <Comparative Example 3> Particles made of LiNiCoMn composite oxide were produced in the same manner as in Example 1, except that the second pH was adjusted to 11.5 and the precursor firing temperature, first firing temperature, second firing temperature, first firing time, and second firing time were changed as shown in Table 1. The results are shown in Table 1.

[0064] <Comparative Example 4> Particles made of LiNiCoMn composite oxide were produced in the same manner as in Example 1, except that the first molar ratio was changed to 60:20:20 and the precursor firing temperature, first firing temperature, second firing temperature, and first firing time were changed as shown in Table 1. The results are shown in Table 1.

[0065] <Comparative Example 5> Particles made of LiNiCoMn composite oxide were produced in the same manner as in Example 1, except that the second pH was adjusted to 11.5 and the precursor firing temperature, first firing temperature, second firing temperature, first firing time, and second firing time were changed as shown in Table 1. The results are shown in Table 1.

[0066] <Comparative Example 6> Particles made of LiNiCoMn composite oxide were produced in the same manner as in Example 1, except that the first molar ratio was set to 60:20:20 and the mixing step and the firing step were carried out without carrying out the precursor firing step. The results are shown in Table 1.

[0067] <Comparative Example 7> Particles made of LiNiCoMn composite oxide were produced in the same manner as in Example 1, except that the first molar ratio was set to 60:20:20, the mixing step and the firing step were carried out without performing the precursor firing step, and the first firing time and second firing time were changed as shown in Table 1. The results are shown in Table 1.

[0068] [Table 1]

[0069] As shown in Table 1, in Examples 1 to 4, single particles containing lithium metal composite oxide were obtained in which the decrease in the Li site occupancy rate was suppressed compared to Comparative Examples 1 to 7. Furthermore, in Examples 1, 2, and 4 in which the first firing temperature was 750°C or higher, single particles containing lithium metal composite oxide were obtained in which the Li site occupancy rate was decreased and the amount of residual alkali was reduced.

Claims

1. A method for producing particles, comprising: a precursor calcination step of calcining a precursor containing a metal composite hydroxide at a temperature of 700 to 900°C for 3 to 8 hours to obtain a precursor calcined product; a mixing step of mixing the calcined precursor with a lithium compound to obtain a mixture; a first firing step of firing the mixture at a temperature of 700 to 820°C; a second firing step of firing the mixture after the first firing step at a temperature of 900°C or higher; Including, the particles contain a metal composite oxide containing lithium, the particle is a single particle, The method for producing particles, wherein the firing time in the first firing step is longer than the firing time in the second firing step.

2. The method for producing particles according to claim 1 , wherein the firing temperature in the first firing step is 750° C. or higher.

3. The method for producing particles according to claim 1 , wherein the second firing step is performed for a firing time of 6 hours or less.

4. 2. The method for producing particles according to claim 1, wherein in the mixing step, the ratio of the total number of moles of lithium to the total number of moles of metal elements other than lithium in the mixture is in the range of 1.0 to 1.

2.

5. The method for producing particles according to claim 1, wherein the particles have an average particle size of 2.0 to 6.0 μm.

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