Method for producing lithium composite oxide

Abstract

Provided are: a zigzag LiMnO2 type compound which can be produced on an industrial scale; and / or a method for producing same.　Provided is a method for producing a lithium composite oxide which is represented by the compositional formula LixMnO2 (0.80≤x≤1.20), which has a zigzag layer structure as a basic structure, and which has a domain having an α-NaFeO2 type layered structure. The method is characterized by having a step for heating a composition containing a manganese source that is dimanganese trioxide and / or manganese oxyhydroxide and one or more lithium sources selected from the group consisting of lithium carbonate, anhydrous lithium hydroxide and lithium hydroxide monohydrate in an inert gas atmosphere to an attainment temperature of 600-750ºC, and maintaining the attainment temperature for a period of 6 hours or less.

Description

Method for producing lithium composite oxide

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

[0002] Lithium composite oxide, specifically lithium cobalt oxide (LiCoO ２ ), lithium nickel oxide (LiNiO ２ ), lithium manganese oxide (LiMn ２ O ４ ) are widely used as positive electrode active materials for lithium secondary batteries distributed worldwide. Such lithium composite oxides are actively researched to improve their properties (higher capacity, higher output, cycle stability) and safety.

[0003] Regarding performance improvement through improvement of the characteristics of the positive electrode active material for lithium secondary batteries, for example, increasing capacity has been attracting attention. ２ The crystal structure is represented by a zigzag layer structure, and is α-NaFeO ２ A lithium composite oxide having domains with a layered structure has been disclosed (Patent Document 1).

[0004] Patent Documents 2 and 3 disclose LiMnO characterized by being composed of at least one of orthorhombic and monoclinic crystals. ２ In Patent Document 1, a compound of the type ZnSe-type was disclosed, and the discharge capacity of a lithium ion secondary battery fabricated using this compound was low at about 170 mAh / g. In contrast, Patent Document 1 discloses that the crystal structure was changed by a heat treatment process after mechanical milling, and the discharge capacity was improved to 260 mAh / g.

[0005] Japanese Patent No. 6956039 Japanese Patent Application Laid-Open No. 2003-007297 Japanese Patent Application Laid-Open No. 2002-145619

[0006] LiMnO disclosed in Patent Document 1 ２ LiMnO type compounds are lithium composite oxides that have high capacity and are cheaper than cobalt-based or nickel-based lithium composite oxides, but they have been thought to be able to be produced only by mechanical milling. Mechanical milling is a production method that requires complicated manufacturing steps and produces very small amounts. Therefore, the LiMnO２ Compounds of this type have been difficult to produce on an industrial scale.

[0007] In the present disclosure, the crystal structure is a zigzag layered structure, and is α-NaFeO ２ Lithium composite oxide having a domain of a zigzag layer structure (hereinafter referred to as "zigzag LiMnO ２ The present invention aims to provide at least one of a compound of the formula (II) (also referred to as a "type compound") that can be produced on an industrial scale and a method for producing the compound.

[0008] In the present disclosure, zigzag LiMnO ２ As a result, it was possible to obtain zigzag LiMnO, which was previously thought to be obtainable only by mechanical milling. ２ Furthermore, the zigzag LiMnO obtained by this method has ２ The present invention has been described in detail in the claims, and the gist of the present disclosure is as follows: [1] A method for producing a manganese compound of the composition formula Li ｘ MnO ２ (where 0.80≦x≦1.20), and has a zigzag layer structure as its parent structure, and is represented by α-NaFeO ２ [2] The inert atmosphere is an argon (Ar) atmosphere or a nitrogen (N ２ [3] The method for producing a lithium composite oxide according to the above [1], wherein the inert atmosphere is an argon (Ar) atmosphere. [4] The method for producing a lithium composite oxide according to the above [1], wherein the lithium composite oxide has a span value S obtained by formula (1) of more than 0 and 15.0 or less, and a BET specific surface area of ​​3.0 m ２ / g or more 20.0m ２ The method for producing a lithium composite oxide according to the above [1] or [2], wherein the lithium composite oxide has a surface area of ​​1000 nm or less, and S=(D ９０ -D １０ ) / D ５０ (1) (In formula (1), D １０ [μm], D ５０ [μm] and D ９０ [μm] respectively represent the cumulative 10% particle diameter, cumulative 50% particle diameter, and cumulative 90% particle diameter in the volume-based particle size distribution.) [5] The span value S obtained by the formula (1) is more than 0 and 15.0 or less, and the BET specific surface area is 3.0 m ２ / g or more 20.0m ２ / g or less, the composition formula Li ｘ MnO ２ (where 0.80≦x≦1.20), and has a zigzag layer structure as its parent structure, and is represented by α-NaFeO ２ A lithium composite oxide having a domain of a layer structure of the type S=(D ９０ -D １０ ) / D ５０ (1) (In formula (1), D １０ [μm], D ５０ [μm] and D ９０ The values ​​[μm] respectively represent the cumulative 10% particle size, the cumulative 50% particle size, and the cumulative 90% particle size in the volume-based particle size distribution.) [6] The lithium composite oxide according to [5], wherein in powder X-ray diffraction using CuKα radiation (1.5418 Å) as an X-ray source, the half-width of a diffraction peak having a peak top at 2θ=25±1.0° is 1.0 or more and 2.0 or less.

[0009] According to the present disclosure, the crystal structure is a zigzag layered structure, and is α-NaFeO ２ The present invention provides at least one of a lithium composite oxide having a domain of a type layer structure, which can be produced on an industrial scale, and a method for producing the same.

[0010] 1 is a schematic diagram showing a zigzag layered structure; FIG. 2 is a schematic diagram showing a layered structure (2a) and a rock salt structure (2b); FIG. 3 is a diagram showing XRD patterns of Examples 1 to 4 and Comparative Examples 1 to 3; FIG. 4 is a photograph of morphology observation by a scanning electron microscope (SEM) of Example 1 and Comparative Example 1; FIG. 5 is a photograph of morphology observation by a scanning electron microscope (SEM) of Examples 1, 3, 4, and Comparative Example 2; FIG. 6 is a diagram showing charge-discharge characteristics of Example 1 and Comparative Example 1; FIG. 7 is a diagram showing cycle characteristics of Example 1 and Comparative Example 1; FIG. 8 is a diagram showing charge-discharge characteristics of Examples 1, 3, and 4; FIG. 9 is a diagram showing cycle characteristics of Examples 1, 3, and 4.

[0011] Hereinafter, an embodiment for carrying out the present disclosure (hereinafter referred to as the "present embodiment") will be described in detail using an example. The present embodiment is an example for explaining the present disclosure, and is not intended to limit the present disclosure to the following content. The present disclosure includes any combination of the configurations and numerical values ​​disclosed in this specification, and also includes any combination of the numerical values ​​disclosed in this specification.

[0012] The production method of this embodiment is a production method characterized by comprising the steps of heating a composition containing at least one manganese source of dimanganese trioxide and manganese oxyhydroxide, and one or more lithium sources selected from the group consisting of lithium carbonate, lithium hydroxide anhydride, and lithium hydroxide monohydrate, in an inert atmosphere to an ultimate temperature of 600°C or higher and 750°C or lower, and maintaining the ultimate temperature for 6 hours or shorter.

[0013] In the manufacturing method of this embodiment, manganese trioxide (Mn ２ O ３ A composition containing at least one manganese source selected from the group consisting of manganese trioxide (MnOOH) and manganese oxyhydroxide (MnOOH) is used as the raw material composition. The oxidation number of the compound used as the manganese source must not change during heat treatment in an inert atmosphere. Furthermore, manganese must diffuse during heat treatment. Therefore, at least one of dimanganese trioxide and manganese oxyhydroxide, which have the same oxidation number as the manganese after heat treatment and do not have oxidizing or reducing ability, is used. Among these, dimanganese trioxide is preferred as the manganese source because it is easy to control the particle shape.

[0014] In the manufacturing method of this embodiment, lithium carbonate (Li ２ CO ３ ), lithium hydroxide anhydrous (LiOH), and lithium hydroxide monohydrate (LiOH.1H ２ A composition containing one or more lithium sources selected from the group consisting of (1) and (2), is used as the raw material composition. The compound used as the lithium source is a lithium compound that is highly reactive and allows lithium to easily diffuse during heat treatment in an inert atmosphere, and is required to have no oxidizing or reducing ability. Therefore, the lithium source may be one or more selected from the group consisting of lithium carbonate, lithium hydroxide anhydride, and lithium hydroxide monohydrate. Among these, lithium hydroxide monohydrate is preferred as the lithium source because it has high reactivity in the temperature range of the heat treatment and is less likely to be mixed with moisture even when handled in an air atmosphere.

[0015] The manganese source may be dimanganese trioxide and manganese oxyhydroxide, and the lithium source may be two or more selected from the group consisting of lithium carbonate, lithium hydroxide anhydrous, and lithium hydroxide monohydrate.

[0016] Zigzag LiMnO of this embodiment ２ The ratio of manganese to lithium in the compound is ２ The ratio of manganese to lithium in the manganese source and lithium source may be approximately the same as that in the composition of the type compound, for example, the lithium (Li) / manganese (Mn) substance ratio may be 0.8 to 1.2. The mixing ratio may be changed depending on the amounts of manganese and lithium in the manganese source and lithium source so as to achieve this substance ratio.

[0017] Zigzag LiMnO used in the manufacturing method of this embodiment ２ The method for producing the compound may be any method, but it is sufficient to mix a manganese source and a lithium source. The mixing method may be any method that makes the manganese source and the lithium source uniform, and may be at least one of dry mixing and wet mixing, with dry mixing being preferred.

[0018] In the manufacturing method of this embodiment, the temperature increase and heat treatment are performed in an inert atmosphere. Examples of the inert atmosphere include a nitrogen atmosphere and an argon atmosphere, and an argon atmosphere is preferable. This makes it more difficult for the oxidation number of manganese to change before and after the heat treatment.

[0019] In the manufacturing method of this embodiment, the temperature is raised to a target temperature of 600° C. or higher and 750° C. or lower. If the target temperature is lower than 600° C., a part of the manganese source will remain unreacted, and the zigzag LiMnO ２ On the other hand, when the temperature exceeds 750°C, zigzag LiMnO ２ The crystal growth of the type compound proceeds excessively, resulting in the zigzag LiMnO ２ The charge / discharge capacity of a lithium secondary battery using such a compound as a positive electrode active material is likely to decrease.

[0020] The rate of temperature rise to the target temperature is not particularly limited, but may be, for example, 10° C. / min or more and 20° C. / min or less to allow appropriate crystal growth. The rate of temperature rise may also be changed during the temperature rise.

[0021] In the manufacturing method of this embodiment, the temperature increase and heat treatment may be performed in a general-purpose firing furnace. After the temperature is increased to the target temperature, the temperature may be decreased to any desired temperature, for example, 100°C or less, or even room temperature (20±10°C). The temperature decrease rate is not particularly limited, but may be, for example, 4°C / min or more and 10°C / min or less to promote appropriate crystal growth. The temperature decrease rate may also be changed during the temperature decrease.

[0022] In the manufacturing method of this embodiment, the holding time at the reached temperature is 6 hours or less. If the holding time exceeds 6 hours, crystal growth is promoted more than necessary, and the zigzag LiMnO ２ However, lithium secondary batteries using such a compound as a positive electrode active material cannot achieve high capacity. Since a positive electrode active material exhibiting high capacity can be easily obtained, a short holding time is preferable, and is preferably 3 hours or less, more preferably 1 hour or less. The holding time may also be 0 hours (i.e., no holding at the reached temperature). Examples of holding times include 0 minutes to 6 hours, and 0 minutes to 3 hours.

[0023] The production method of this embodiment is a simple production method that simply involves heat-treating a composition containing a manganese source and a lithium source, so it is easy to apply general-purpose, large-scale equipment, and the production process is simple. Therefore, compared with the conventional mechanochemical method, large-scale production is possible and the production cost is lower, so it is very easy to apply to industrial production. Therefore, the zigzag LiMnO obtained by the production method of this embodiment ２ The zigzag LiMnO type compound is easy to produce industrially due to its manufacturing method. ２ It is a type compound.

[0024] Zigzag LiMnO of this embodiment ２ The compound has the formula Li ｘ MnO ２ (However, 0.80≦x≦1.20) where x is 0.80 or more, 0.90 or more, or 0.95 or more, and 1.20 or less, 1.10 or less, or 1.05 or less, and is preferably 0.80 or more and 1.20 or less, 0.90 or more and 1.10 or less, or 0.95 or more and 1.05 or less.

[0025] Zigzag LiMnO of this embodiment ２ The composition of the compound is determined by ICP measurement using a general inductively coupled plasma emission spectrometer (e.g., OPTIMA 5300DV, manufactured by PerkinElmer Japan) to quantify Li and Mn. Next, the concentration (mass%) of each element determined by ICP measurement is divided by the atomic weight of each element, and converted into the amount of substance to determine the content (mol) of each element, and the composition formula can be determined. Note that ICP measurement can be performed on a measurement solution prepared by dissolving a sample in a mixed aqueous solution of hydrochloric acid and hydrogen peroxide.

[0026] Zigzag LiMnO of this embodiment ２ The type compound has a zigzag layer structure as its parent structure, and is ２ By having such a structure, the resulting lithium secondary battery does not require an initial charge-discharge cycle for activation, and can exhibit high capacity from the initial cycle. Therefore, the orthorhombic LiMnO２ This is advantageous in that the energy cost can be reduced compared to the above.

[0027] A schematic diagram of the zigzag layered structure is shown in Figure 1. Schematic diagrams of the layered structure and the rock salt structure are shown in Figure 2 (2a) and (2b), respectively. From Figures 1 and 2, it can be seen that the zigzag layered structure is α-NaFeO ２ It can be seen that the layers in the layered structure grow alternately up and down in a regular pattern, forming a zigzag layered crystalline structure.

[0028] Furthermore, the zigzag LiMnO ２ The type compound has a span value S obtained by the following formula of more than 0 and not more than 15.0, and a BET specific surface area of ​​3.0 m ２ / g or more 20.0m ２ / g or less, the composition formula Li ｘ MnO ２ (where 0.80≦x≦1.20), and has a zigzag layer structure as its parent structure, and is represented by α-NaFeO ２ It is preferable that the lithium composite oxide has a domain of a zigzag LiMnO ２ Compared with the compound of the type S, it is easy to obtain a lithium secondary battery with higher output characteristics. ９０ -D １０ ) / D ５０ (In the formula, D １０ [μm], D ５０ [μm] and D ９０ [μm] respectively indicate the cumulative 10% particle size, the cumulative 50% particle size, and the cumulative 90% particle size in the volume-based particle size distribution.) Zigzag LiMnO of this embodiment ２ The span value of the zigzag LiMnO type compound is preferably greater than 0, and is preferably 15.0 or less, 12.5 or less, or 10.0 or less, and more preferably greater than 0 and 15.0 or less, greater than 0 and 12.5 or less, or greater than 0 and 10.0 or less. The span value is one of the indicators showing the spread of particle size distribution, and a smaller span value indicates a more uniform particle size distribution. ２When the span value of the compound is within this range, the compound is mixed with the conductive material uniformly, and conductive paths are easily formed, which tends to increase the electrical conductivity of the resulting lithium secondary battery.

[0029] Above D １０ [μm], D ５０ [μm] and D ９０ [μm] indicates the particle diameter when the cumulative value from the smallest particle side is 10 vol%, 50 vol%, and 90 vol%, respectively, and D １０ [μm]≦D ５０ [μm]≦D ９０ The relationship is [μm].

[0030] Zigzag LiMnO of this embodiment ２ D-type compounds １０ is preferably 1 μm or more and 10 μm or less or 5 μm or less, and more preferably 1 μm or more and 10 μm or less, or 1 μm or more and 5 μm or less.

[0031] Zigzag LiMnO of this embodiment ２ D-type compounds ５０ is preferably 5 μm or more or 8 μm or more, and 15 μm or less or 12 μm or less, and more preferably 5 μm or more and 15 μm or less, or 8 μm or more and 12 μm or less.

[0032] Zigzag LiMnO of this embodiment ２ D-type compounds ９０ is preferably 10 μm or more or 15 μm or more, and 50 μm or less or 30 μm or less, and more preferably 10 μm or more and 50 μm or less, or 15 μm or more and 30 μm or less.

[0033] In this embodiment, D １０ [μm], D ５０ [μm] and D ９０The diameter [μm] may be measured using a general laser diffraction / scattering particle size distribution measuring device (for example, MT3000II series, manufactured by MicrotracBEL) under the following conditions: Light source: Semiconductor laser Calculation mode: HRA Measurement time: 30 seconds Measurement approximation: Aspherical approximation Solvent: Water Refractive index of solvent: 1.33 Refractive index of powder sample: 2.46 ２ The particle size retention rate [%] of the type compound is preferably 20% or more, 50% or more, or 80% or more, and is preferably 100% or less, for example, 20% or more and 100% or less, 50% or more and 100% or less, or 80% or more and 100% or less. By achieving these particle size retention rates, collapse of secondary particles can be suppressed when preparing a positive electrode for a lithium secondary battery, and a conductive path between the positive electrode active material and the conductive material can be maintained. As a result, the electrical conductivity of the resulting lithium secondary battery is likely to be high.

[0034] In this embodiment, the particle size retention rate was measured by measuring the particle size of the zigzag LiMnO ２ The compound was added at 3 t / cm ２ When pellets were produced by uniaxial pressing at a pressure of ５０ This is a value showing the rate of change in particle size, and can be calculated by the following formula: Particle size retention rate [%] = (zigzag LiMnO ２ D-type compounds ５０ [μm]) / (zigzag LiMnO of this embodiment before uniaxial pressing ２ D-type compounds ５０ [μm]) × 100 Zigzag LiMnO of this embodiment after uniaxial pressing ２ D-type compounds ５０ indicates the zigzag LiMnO of this embodiment after uniaxial pressing. ２ The pellets of the compound were crushed in a mortar to obtain the zigzag LiMnO ２ The D ５０ is.

[0035] Zigzag LiMnO of this embodiment ２ The BET specific surface area of ​​the compound is 3.0 m ２ / g or more, and ２ / g or less or 15.0m ２ / g or less, and ２ / g or more 20.0m ２ / g or less, or 3.0m ２ / g or more 15.0m ２ When the BET specific surface area is within this range, the capacity of the resulting lithium secondary battery tends to be high.

[0036] In this embodiment, the BET specific surface area can be measured by a general measuring device (for example, MICROMETRICS Desorb III manufactured by Shimadzu Corporation) using a mixed gas of 30% nitrogen and 70% helium as the adsorption gas, according to the method specified in JIS Z8830.

[0037] The BET specific surface area was measured by pre-treating the zigzag LiMnO ２ The compound is placed in a glass cell for measuring the BET specific surface area, and the measurement is carried out after dehydration treatment at 150° C. for 30 minutes in a nitrogen flow atmosphere.

[0038] Zigzag LiMnO of this embodiment ２ In the powder X-ray diffraction pattern of the compound using CuKα radiation (1.5418 Å) as an X-ray source, the half-width (hereinafter also referred to simply as "FWHM") of the diffraction peak observed at 2θ=25±1.0° is preferably 1.0 or more or 1.2 or more, and is preferably 2.5 or less or 2.3 or less, such as 1.0 to 2.5 or 1.2 to 2.3. When the FWHM is within this range, the rate characteristics of the resulting lithium secondary battery tend to be improved.

[0039] In this embodiment, the FWHM can be determined from a powder X-ray diffraction (hereinafter also referred to as "XRD") pattern measured using a general X-ray measurement device (for example, a D2 PHASER manufactured by Bruker) under the following conditions: X-ray source: CuKα ray = 1.5418 Å Output: 1.6 kW (40 mA - 40 kV) Divergence slit: 1° Divergence vertical limiting slit: 10 mm Scattering slit: open Receiving slit: open Scan width: 0.04° (2θ / θ) Scan speed: 4° / min Measurement range: 10 to 90° (2θ / θ) The obtained XRD pattern is analyzed using the accompanying analysis software (PDXL2), and the integral width of the peak at 2θ = 25 ± 1.0° can be taken as the FWHM.

[0040] Zigzag LiMnO of this embodiment ２ The compound of the type can be used as a positive electrode active material for a lithium secondary battery.

[0041] The present disclosure will be described in more detail below with reference to examples, but the present disclosure should not be construed as being limited to these examples. Furthermore, the "samples" described below refer to zigzag LiMnO ２ The type compound is shown.

[0042] <Powder X-ray diffraction> The 2θ of the diffraction peaks of each plane of the sample was measured by XRD. Measurements were performed using an X-ray diffractometer (trade name: Bruker D2 PHASER (Cu Kα = 1.54184 Å)) under the following conditions: X-ray source: CuKα ray = 1.5418 Å; Output: 1.6 kW (40 mA - 40 kV); Divergence slit: 1°; Divergence vertical limiting slit: 10 mm; Scattering slit: Open; Receiving slit: Open; Scan speed: 4° / min; Scan width: 0.04° (2θ / θ); Measurement range: 10 to 90° (2θ / θ). The obtained XRD pattern was analyzed using the accompanying analysis software (PDXL2), and the integral width of the peak at 2θ = 25 ± 1.0° was taken as the FWHM of the sample.

[0043] <Particle size distribution> A particle size distribution measuring device (product name: MT3000II series, manufactured by MicrotracBEL) was used to measure the particle size distribution based on volume of the sample. The measurement was performed after adding an appropriate amount of pure water to the sample and subjecting it to ultrasonic dispersion for 5 minutes. The sample was dispersed using a sample circulator attached to the device, and the measurement was performed under the following conditions. Light source: Semiconductor laser Calculation mode: HRA Measurement time: 30 seconds Measurement approximation: Aspherical approximation Dispersion medium: Water Refractive index of dispersion medium: 1.33 Refractive index of sample: 2.46 The cumulative 10% particle diameter (D) in the particle size distribution based on volume of the sample was １０ ) [μm], cumulative 50% particle diameter (D ５０ ) [μm] and cumulative 90% particle diameter (D ９０ ) [μm] was calculated using the software provided with the device, and the span value S was determined according to the above-mentioned formula (1).

[0044] <Composition Analysis> The composition of the sample was determined by quantifying Li and Mn by ICP measurement using an inductively coupled plasma emission spectrometer (product name: OPTIMA5300DV, manufactured by PerkinElmer Japan).

[0045] The sample was dissolved in a mixed aqueous solution of hydrochloric acid and hydrogen peroxide, and the resulting solution was subjected to ICP measurement. The concentration (mass%) of each element determined by ICP measurement was divided by the atomic weight of each element, and converted to the amount of substance to determine the Li and Mn contents (mol) in the sample, from which the general formula of the sample's composition was determined.

[0046] <BET Specific Surface Area> 0.3 g of a sample was placed in a glass cell for measuring the BET specific surface area, and pretreated by dehydration treatment at 150° C. for 30 minutes in a nitrogen flow atmosphere.

[0047] The BET specific surface area of ​​the pretreated sample was measured using a BET measurement device (trade name: MICROMETRICS Desorb III, manufactured by Shimadzu Corporation) by the single-point method in accordance with 7.3 of JIS Z8830. For the measurement, a mixed gas of 30% by volume of nitrogen and 70% by volume of helium was used as the adsorption gas.

[0048] <Scanning Electron Microscope> The morphology of the obtained sample was observed using a scanning electron microscope (SEM) (trade name: JEOL JCM-6000, manufactured by JEOL).

[0049] <Electrode Preparation> The positive electrode active material, conductive material (acetylene black), and binder (PVdF) were weighed in a mass ratio of 80:10:10. The binder was dissolved in an organic solvent (N-methylpyrrolidone), and the positive electrode active material and conductive material were mixed with this to prepare a positive electrode ink. The obtained positive electrode ink was applied to a current collector (aluminum foil), dried in an air atmosphere at 60°C, and then dried under reduced pressure at 150°C for 12 hours to prepare an electrode.

[0050] <Preparation of Li Counter Electrode Battery> The electrode prepared by the above method was used as a positive electrode, and LiPF was placed in a solution of EC and DMC mixed in a volume ratio of 3:7 as an electrolyte. ６ A two-electrode electrochemical cell (Li counter electrode battery) was prepared using a solution in which the above compound was dissolved at a concentration of 1.0 M, a polyolefin porous membrane (product name: Celgard 2500, manufactured by Celgard) as a separator, and lithium foil as a negative electrode.

[0051] <Evaluation of cycle characteristics> A charge / discharge test of the Li counter electrode battery was carried out using a charge / discharge evaluation device (product name: TOSCAT-3100, manufactured by Toyo Systems Co., Ltd.) at a measurement temperature of 25°C, a voltage range of 4.8 V to 1.5 V, and a current density of 25 mA / g (Example 1 and Comparative Example 1) or 10 mA / g (Examples 1, 3, and 4).

[0052] <Measurement of Rate Characteristics> Using a charge / discharge device (product name: BTS2004W, manufactured by NAGANO Corporation), the rate characteristics of the Li counter electrode battery were evaluated.

[0053] Measurements were performed at a measurement temperature of 25 ° C., a voltage range of 2.0 V - 4.5 V, and a current density of 6 mA / g. Two cycles of charge / discharge tests were then performed at a voltage range of 2.0 V - 4.5 V, a current density of 0.03 C, and a current density of 0.3 C. One cycle was then performed, and the charge / discharge was performed at a current density of 0.3 C. As a result, the discharge capacities 0.03 C [mAh / g] and C0.3 C [mAh / g] at 0.03 C and 0.3 C were measured. The discharge capacity when charged and discharged at a current density of 6 mA / g was calculated as 1 C, which is the current value that can be charged and discharged in 1 hour. The current density at current values ​​of 0.03 C and 0.3 C was calculated.

[0054] Also, from the discharge curves at current densities of 0.03 C and 0.3 C, the average discharge voltage V ０．０３Ｃ [V] and V ０．３Ｃ [V] was calculated, and the rate characteristics were calculated using the following formula: ０．０３Ｃ [mWh / g] = C ０．０３Ｃ [mAh / g] x V ０．０３Ｃ [V] E ０．３Ｃ [mWh / g] = C ０．３Ｃ [mAh / g] x V ０．３Ｃ [V] R[%]=E ０．３Ｃ [mWh / g] / E ０．０３Ｃ [mWh / g] x 100 where E ０．０３Ｃ [mWh / g] and E ０．３Ｃ [mWh / g] represents the energy density of the Li counter electrode battery at 0.03 C and 0.3 C, respectively, and R [%] represents the rate characteristic.

[0055] Example 1 Manganese carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was calcined in an air atmosphere at 600°C for 12 hours to obtain Mn ２ O ３ The prepared Mn ２ O ３ and LiOH 1H ２ 0 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was mixed so that the ratio of lithium (Li) / manganese (Mn) was 1.0, and the mixture was pressed into a uniaxial press (Mini Press Set, manufactured by Riken Kiki Co., Ltd.) at 3 t / cm ２ The produced pellets were heated in an argon atmosphere to 700°C at a rate of 10°C / min, and when the temperature reached 700°C, the pellets were cooled to room temperature at a rate of 4°C / min without being held at this temperature, resulting in a zigzag LiMnO ２ The compound of the type was obtained.

[0056] Example 2 The zigzag LiMnO of this example was prepared in the same manner as in Example 1, except that it was held at 700°C for 1 hour after reaching 700°C. ２ The compound of the type was obtained.

[0057] Example 3 2.0 mol / dm －３ and 1.2 mol / dm manganese nitrate aqueous solution. －３ Manganese carbonate was obtained by mixing the manganese carbonate with an aqueous solution of ammonium bicarbonate. The manganese carbonate was calcined in an air atmosphere at 600°C for 12 hours to obtain Mn ２ O ３ The prepared Mn ２ O ３ and LiOH 1H ２ The resulting mixture was mixed with lithium (Li) / manganese (Mn) in a ratio of 1.0, and pellets were produced using the uniaxial press molding machine. The pellets were heated to 700°C in an argon atmosphere at a rate of 10°C / min, and then cooled to room temperature at a rate of 4°C / min without being held at 700°C. This resulted in the formation of zigzag LiMnO of this example. ２ The compound of the type was obtained.

[0058] Example 4 The zigzag LiMnO of this example was prepared in the same manner as in Example 3, except that in the heat treatment, after reaching 700°C, it was held at 700°C for 1 hour. ２ The compound of the type was obtained.

[0059] Example 5 2.0 mol / dm －３ Instead of a manganese nitrate aqueous solution of 2.0 mol / dm －３ The manganese sulfate aqueous solution was used, and the prepared Mn ２ O ３ and LiOH 1H ２ The zigzag LiMnO of this example was prepared in the same manner as in Example 3, except that the material ratio of 1:2.1 was changed to 1:2.1 and the temperature drop rate during the heat treatment was changed to 5°C / min. ２ The compound of the type was obtained.

[0060] Zigzag LiMnO of this example ２ The composition of the compound is LiMnO ２ and D １０ , D ５０ and D ９０ were 0.61 μm, 0.93 μm and 2.03 μm, respectively, the particle size retention was 99%, and the FWHM was 1.6°.

[0061] Comparative Example 1 In this comparative example, a lithium composite oxide was obtained by a method according to Comparative Example 2 of Japanese Patent Application No. 2020-089664. ２ O ３ 2.08 g and Li ２ CO ３ 1.00 g of the above was weighed out, placed in a mortar, and crushed and mixed, and pellets were produced using the uniaxial press molding machine. The pellets were fired in an argon atmosphere at 900°C for 12 hours. Next, LiMnO having a zigzag layer structure was ２ The mechanical milling was carried out using a ball mill at a rotation speed of 600 rpm for 36 hours. ２ It was decided.

[0062] Next, LiMnO having a rock salt structure ２ The zigzag LiMnO of this comparative example was heated to 700°C at a rate of 10°C / min in an argon atmosphere, and after reaching 700°C, was maintained for 12 hours and then cooled to room temperature at a rate of 10°C / min. ２ The compound of the type was obtained.

[0063] Comparative Example 2 The zigzag LiMnO of this comparative example was prepared in the same manner as in Example 3, except that the heat treatment temperature reached 800°C. ２ The compound of the type was obtained.

[0064] Comparative Example 3: The zigzag LiMnO of this comparative example was prepared in the same manner as in Example 1, except that the temperature was maintained for 12 hours after reaching 700°C during the heat treatment. ２ The compound of the type was obtained.

[0065] Comparative Example 4 Manganese carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was calcined in an air atmosphere at 700°C for 12 hours to obtain Mn ２ O ３ The prepared Mn ２ O ３ and lithium carbonate (Li ２ CO ３ (manufactured by Rare Metallic Co., Ltd.) were mixed in a mortar so that the Li / Mn molar ratio of the metal composition was 1.0. After mixing, the mixture was heated to 900°C at a rate of 10°C / min in an argon atmosphere, held at 900°C for 12 hours, and then cooled to room temperature at a rate of 10°C / min, thereby carrying out a heat treatment.

[0066] Next, mechanical milling was performed in the same manner as in Comparative Example 1 to obtain the zigzag LiMnO ２ The compound of the type was obtained.

[0067] D of the lithium composite oxide of this comparative example １０ , D ５０ and D ９０ were 0.43 μm, 0.58 μm and 8.18 μm, respectively, the grain size retention was 98%, and the FWHM was 2.5°.

[0068] Comparative Example 5 This comparative example was carried out by a method according to Example 1 of Japanese Patent Application No. 2023-065577, in which a zigzag LiMnO ２ The electrolytic manganese dioxide (MnO ２ ) was calcined at 600°C for 12 hours, and Mn ２ O ３ The prepared Mn ２ O ３ 662 g, lithium hydroxide monohydrate (LiOH·H ２338 g of the powder O) was mixed with 4000 mL of pure water to prepare 5 kg of slurry, which was then pulverized for 2 hours using a pulverizer (trade name: Dyno Mill Multilab type, manufactured by Shinmaru Enterprises).

[0069] Next, the slurry was spray-dried using a spray dryer (product name: SB39, manufactured by Pris Co.) under conditions of a 90-type nozzle spray pressure of 0.2 MPa, a solution rate of 3 kg / h, and a hot air inlet temperature of 220° C. After spray-drying, the mixture was heated to 700° C. at a rate of 10° C. / min in a nitrogen atmosphere, held at 700° C. for 2 hours, and then cooled to room temperature at a rate of 5° C. / min to obtain the zigzag LiMnO of this comparative example. ２ The compound of the type was obtained.

[0070] Zigzag LiMnO of this comparative example ２ The composition of the type compound is Li １．０１ MnO ２ and D １０ , D ５０ and D ９０ were 2.8 μm, 9.5 μm and 19.1 μm, respectively, the particle size retention was 10%, and the FWHM was 2.1°.

[0071] Zigzag LiMnO obtained in Example 5 and Comparative Example 4 ２ The evaluation results of the type compounds are shown in the table below.

[0072] Zigzag LiMnO of Examples 1 to 5 and Comparative Examples 1 to 4 ２ It was found that the XRD pattern of the zigzag LiMnO compound had strong peaks in the orthorhombic (010), (011), (200), and (021) planes and a weak peak in the monoclinic (001) plane. ２ The crystal structure of the type compound is a zigzag layer structure, and is α-NaFeO ２ It was confirmed that the zigzag LiMnO of Examples 1 to 4 and Comparative Examples 1 to 3 had a structure having domains of a layer structure. ２ The XRD pattern of the compound is shown in FIG.

[0073] In Comparative Example 1, the peak of the (110) plane is weak and broad, which is due to the α-NaFeO ２This means that the compound has a layered structure domain, and when the (110) plane peak is strong and clear in the XRD pattern, it is α-NaFeO ２ This means that there are relatively few domains of the layered structure.

[0074] The peak of the (110) plane in the XRD patterns of Examples 1 to 4 was broad, whereas the peak of the (110) plane was sharp in Comparative Examples 2 and 3. In other words, the crystal structure of Examples 1 to 4 was α-NaFeO ２ The number of domains of the type layer structure was as large as in Comparative Example 1, and the base structure was a zigzag layer structure, and the α-NaFeO ２ The crystal structure of Comparative Examples 2 and 3 is α-NaFeO ２ The domains of the regular layer structure were relatively few, and the crystal structure was close to the zigzag layer structure.

[0075] Zigzag LiMnO of Example 1 and Comparative Example 1 ２ The morphology of the compound was observed using a scanning electron microscope (SEM), and the results are shown in FIG.

[0076] Zigzag LiMnO of Examples 1, 3, and 4 and Comparative Example 2 ２ The results of morphological observation of the α-NaFeO type compound using a scanning electron microscope (SEM) are shown in Figure 5. It was found that in Comparative Example 2, where the heat treatment temperature was increased, the primary particles grew and coarse primary particles were present. ２ LiMnO having a layered structure domain ２ It is known that high capacity can be obtained by controlling the crystallinity, and Comparative Example 2 in which primary particles have grown is considered to be unsuitable for achieving high capacity.

[0077] Zigzag LiMnO of Example 1 and Comparative Example 1 ２ The zigzag LiMnO type compound was charged and discharged under the measurement conditions of a measurement temperature of 25° C., a voltage range of 4.8 V to 1.5 V, and a current density of 25 mA / g. The results of the cycle characteristic evaluation are shown in FIGS. 6 and 7. ２ The compound is a zigzag LiMnO ２However, the manufacturing method of Example 1 is simpler than the manufacturing method of Comparative Example 1 ("calcination" → "mechanical milling" → "heat treatment") in that it does not require mechanical milling and requires only one heat treatment in the manufacturing process.

[0078] Zigzag LiMnO of Examples 1, 3 and 4 ２ The zigzag LiMnO type compounds were charged and discharged at a temperature of 25° C. in a voltage range of 4.8 V to 1.5 V, and at a current density of 10 mA / g. The results of the cycle characteristic evaluation are shown in FIGS. 8 and 9. ２ The zigzag LiMnO compound of Example 1 ２ It was found that the compound exhibited high capacity similar to that of the type compound and also showed excellent cycle stability.

[0079] From Table 1, the zigzag LiMnO of Example 5 ２ It was found that the compound of the type exhibited superior rate characteristics compared to Comparative Example 4.

[0080] The entire contents of the claims, specification, abstract and drawings of Japanese Patent Application No. 2024-102168 filed on June 25, 2024 are hereby incorporated by reference as the disclosure of the specification of the present invention.

[0081] The zigzag LiMnO of the present disclosure ２ The method for producing the zigzag LiMnO compound is simpler than the conventional method. ２ The resulting zigzag LiMnO ２ The compound of the type can be used as a positive electrode active material for a lithium secondary battery.

Claims

1. A method for producing a manganese oxide-based catalyst, comprising the steps of heating a composition containing at least one manganese source selected from the group consisting of dimanganese trioxide and manganese oxyhydroxide, and at least one lithium source selected from the group consisting of lithium carbonate, lithium hydroxide anhydride, and lithium hydroxide monohydrate in an inert atmosphere to a temperature of 600°C to 750°C, and maintaining the temperature for 6 hours or less, using the composition of the composition formula Li ｘ MnO ２ (where 0.80≦x≦1.20), and has a zigzag layer structure as its parent structure, and is represented by α-NaFeO ２ A method for producing a lithium composite oxide having a domain with a layered structure.

2. The inert atmosphere is an argon (Ar) atmosphere or a nitrogen (N ２ 2. The method for producing a lithium composite oxide according to claim 1, wherein the atmosphere is a mixture of 1000 and 1500 kJ / cm2.

3. The method for producing a lithium composite oxide according to claim 1, wherein the inert atmosphere is an argon (Ar) atmosphere.

4. The lithium composite oxide has a span value S obtained by the formula (1) of more than 0 and not more than 15.0, and a BET specific surface area of ​​3.0 m ２ / g or more 20.0m ２ 3. The method for producing a lithium composite oxide according to claim 1, wherein the lithium composite oxide has a surface area of ​​1000 nm or less, and the surface area of ​​the lithium composite oxide is ... ９０ -D １０ ) / D ５０ (1) (In formula (1), D １０ [μm], D ５０ [μm] and D ９０ [μm] respectively indicate the cumulative 10% particle size, cumulative 50% particle size, and cumulative 90% particle size in the volume-based particle size distribution.) 5. The span value S obtained by formula (1) is greater than 0 and less than 15.0, and the BET specific surface area is 3.0 m ２ / g or more 20.0m ２ / g or less, the composition formula Li ｘ MnO ２ (where 0.80≦x≦1.20), and has a zigzag layer structure as its parent structure, and is represented by α-NaFeO ２ A lithium composite oxide having a domain of a layer structure of the type S=(D ９０ -D １０ ) / D ５０ (1) (In formula (1), D １０ [μm], D ５０ [μm] and D ９０ [μm] respectively indicate the cumulative 10% particle size, cumulative 50% particle size, and cumulative 90% particle size in the volume-based particle size distribution.) 6. The lithium composite oxide according to claim 5, wherein the half-width of a diffraction peak having a peak top at 2θ=25±1.0° in powder X-ray diffraction using CuKα radiation (1.5418 Å) as an X-ray source is 1.0 or more and 2.0 or less.

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