Spinel-type lithium manganate composition and manufacturing method thereof

Abstract

To provide at least one of a spinel-type lithium manganate composition that is suitable as a positive electrode active material for LIBs and has excellent output characteristics at the beginning of charge / discharge cycles and long-term stability in charge / discharge cycles even at high temperatures, and a manufacturing method thereof.SOLUTION: To provide a composition which contains a composite oxide containing lithium and molybdenum, and a spinel-type lithium manganate, and which has a specified peak in a powder X-ray diffraction pattern.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a spinel-type lithium manganese oxide composition and a method for producing the same.

Background Art

[0002] Spinel-type lithium manganese oxide has been studied as a positive electrode active material for lithium-ion secondary batteries. However, spinel-type lithium manganese oxide causes manganese elution during charge and discharge. Various studies have been conducted to suppress manganese elution.

[0003] For example, in Patent Document 1, it has been reported that by adding an inorganic phosphorus compound to spinel-type lithium manganese oxide, manganese elution is suppressed, and as a result, the storage stability at high temperatures is improved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the composition containing the inorganic phosphorus compound and spinel-type lithium manganese oxide disclosed in Patent Document 1, manganese elution still occurred during charge and discharge. Therefore, a lithium-ion secondary battery (hereinafter also referred to as "LIB") provided with this as a positive electrode active material had low output characteristics at the initial stage of the charge-discharge cycle and long-term stability of the charge-discharge cycle.

[0006] An object of the present disclosure is to provide at least one of a spinel-type lithium manganese oxide composition suitable as a positive electrode active material for LIB and a method for producing the same, which is excellent in output characteristics (hereinafter also referred to as "output characteristics") at the initial stage of the charge-discharge cycle and long-term stability of the charge-discharge cycle (hereinafter also referred to as "storage characteristics") even at high temperatures. [Means for Solving the Problems]

[0007] In the present disclosure, we focused on and investigated the suppression of manganese elution during charge and discharge in a spinel-type lithium manganese oxide composition at high temperatures. As a result, it has been found that by compounding a lithium salt containing a specific transition metal element with spinel-type lithium manganese oxide, manganese elution is suppressed, and thereby the output characteristics and storage characteristics are further improved.

[0008] That is, the present invention is as described in the claims, and the gist of the present disclosure is as follows. [1] A composite oxide containing lithium and molybdenum, and a composition containing spinel-type lithium manganese oxide and having at least the peaks shown in the following table in the powder X-ray diffraction pattern.

[0009] [Table 1]

[0010] [2] The composition according to [1], wherein the spinel-type lithium manganese oxide is represented by the general formula Li 1+X Mn 2-X―Y M Y O4 (where 0.02 ≤ X ≤ 0.20, 0.05 ≤ Y ≤ 0.30, and M is at least one of Mg and Al). [3] The composition according to [1] or [2] having an inorganic phosphorus compound. [4] The composition according to any one of [1] to [3], wherein the half-value width in the (400) plane is more than 0.000° and 0.2° or less. [5] A method for producing the composition according to any one of [1] to [4], comprising a mixing step of mixing a manganese source and a lithium source to obtain an LMO precursor, a firing step of firing the LMO precursor obtained in the mixing step, and a step of compounding a Li-Mo composite oxide with the LMO obtained in the firing step. [6] A method for manufacturing the composition according to any one of [1] to [4], comprising a mixing step of mixing a manganese source, a lithium source, and a Li-Mo composite oxide to obtain an LMO precursor, and a firing step of firing the LMO precursor. [7] A positive electrode active material for a lithium ion secondary battery having the composition according to any one of [1] to [4]. Positive electrode active material. [8] A positive electrode having the positive electrode active material for a lithium ion secondary battery according to [7]. [9] A lithium ion secondary battery having the positive electrode according to [8]. [Advantages of the Invention]

[0011] According to the present disclosure, at least one of a spinel-type lithium manganese oxide composition suitable as a positive electrode active material and a method for manufacturing the same, which are excellent in output characteristics and storage characteristics, can be provided. [Embodiments for Carrying Out the Invention]

[0012] Hereinafter, an example of an embodiment of the present disclosure will be shown and described. In addition, each configuration and parameter disclosed in this specification can be combined arbitrarily, and the upper and lower limits of the values disclosed in this specification can be combined arbitrarily.

[0013] This embodiment contains a composite oxide containing lithium and molybdenum (hereinafter, also referred to as "Li-Mo composite oxide"), and spinel-type lithium manganese oxide (hereinafter, also referred to as "LMO"), and is a composition (hereinafter, also referred to as "the composition of this embodiment") having at least the peaks shown in the following table in the powder X-ray diffraction pattern.

[0014] [Table 2]

[0015] The composition of this embodiment contains a Li-Mo composite oxide. By containing the Li-Mo composite oxide, a LIB provided with the composition of this embodiment as a cathode active material exhibits excellent output characteristics and storage characteristics. The Li-Mo composite oxide is not particularly limited as long as it is a composite oxide containing Li and Mo, and examples thereof include at least one of lithium molybdate and lithium molybdate fluoride, such as Li2MoO4, Li2MoO3, LiMoO2, Li4MoO5, and Li4Mo5O 17 and one or more selected from the group of Li3MoO2F2 are preferred, and Li2MoO4 is more preferred.

[0016] The composition of this embodiment is a composition containing spinel-type lithium manganate (LMO), and more specifically, a composition containing LMO as a main component, that is, a so-called spinel-type lithium manganate composition.

[0017] One of the reasons for the improvement in the output characteristics and storage characteristics of the LIB provided with the composition of this embodiment as a cathode active material is that in the composition of this embodiment, a synergistic effect is considered to occur due to the coexistence of the Li-Mo composite oxide and LMO. That is, LMO functions as a cathode active material and causes the desorption and insertion of Li ions. On the other hand, the Li-Mo composite oxide has functions of Li ion conductivity and suppression of Mn elution from the surface of LMO. Therefore, when these coexist, it is considered that the elution of Mn ions from LMO is suppressed without inhibiting the desorption and insertion of Li ions from LMO, and furthermore, the Li-Mo composite oxide captures the eluted Mn ions. As a result, the poisoning of Mn ions on the anode is suppressed, and it is considered that the output characteristics and storage characteristics of the LIB provided with the composition of this embodiment as a cathode active material are improved.

[0018] The LMO contained in the composition of this embodiment has the general formula Li 1+X Mn 2-X―Y M Y O4 (where 0.02 ≦ X ≦ 0.20, 0.05 ≦ Y ≦ 0.30, and M is at least one of Mg and Al). It is preferably LMO represented by the general formula Li1+X Mn 2-X―Y M Y O4 (where 0.05 ≤ X ≤ 0.15, 0.05 ≤ Y ≤ 0.10, and M is at least one of Mg and Al) is more preferably LMO. Further, in the general formula Li 1+X Mn 2-X―Y M Y O4, M is preferably Mg. When LMO is LMO represented by the general formula Li 1+X Mn 2-X―Y M Y O4, that is, when it is a substituted spinel, the LIB provided with the composition of the present embodiment as a positive electrode active material is likely to exhibit excellent output characteristics and storage characteristics even at high temperatures.

[0019] The composition of the present embodiment may contain an inorganic phosphorus compound. Thereby, the elution of manganese (M n) is further suppressed, and the storage characteristics are further improved.

[0020] The inorganic phosphorus compound is preferably a phosphate, for example, Li3PO4, H3PO4, LiPO3, Na3PO 4、 NaH2PO4, Na2HPO4, K3PO4, KH2PO4, K2HPO4, Mg3(PO4)2, MgHPO4, Mg(H2PO4)2, NH4H2PO4, and one or more selected from the group of (NH4)2HPO4 can be mentioned. In the charge and discharge of the LIB provided with the composition of the present embodiment as a positive electrode active material, since the precipitation of impurities is less likely to occur, the inorganic phosphorus compound is preferably Li3PO4.

[0021] In the composition of the present embodiment, LMO, the Li-Mo composite oxide, and the inorganic phosphorus compound may be contained in a state where a synergistic effect between LMO and the Li-Mo composite oxide occurs. For example, LMO, the Li-Mo composite oxide, and the inorganic phosphorus compound are contained as particles, and at least one of the particles of the Li-Mo composite oxide and the inorganic phosphorus compound adheres to the particle surface of LMO, etc. can be mentioned.

[0022] In the composition of the present embodiment, the LMO, Li-Mo composite oxide, and inorganic phosphorus compound may be identified by comparing the powder X-ray diffraction (hereinafter also referred to as "XRD") pattern measured under the following conditions using a general X-ray measuring device (for example, Ultima IV, manufactured by Rigaku Corporation) with the XRD pattern of JCPDS (hereinafter also referred to as the "reference pattern").

[0023] Target (light source): CuKα (λ = 1.5405 Å) Output: 1.6 kW (40 mA - 40 kV) Filter: Kβ filter Divergence slit: 1° Divergence vertical limiting slit: 10 mm Scattering slit: Open Receiving slit: Open Scanning mode: Continuous Scan speed: 4.000° / min Sampling width: 0.04° (2θ / θ) Integration times: 1 time Measurement range: 10 - 90° (2θ / θ) No. 35 - 782 (LiMn2O4) can be cited as the reference pattern of LMO.

[0024] As the reference patterns of the inorganic phosphorus compounds, No. 25 - 1030 (Li3PO4), 44 - 0782 (H3PO4), 26 - 1177 (LiPO3), 27 - 0771 (Na3PO4), 11 - 0636 (NaH2PO4), 35 - 0735 (Na2HPO4), 20 - 0921 (K3PO4), 5 - 0385 (KH2PO4), 25 - 0639, 82 - 0522, (K2HPO4), 25 - 1373, 33 - 0876 (Mg3(PO4)2), 46 - 0375 (MgHPO4·xH2O), 1 - 0781 (Mg(H2PO4)2), 6 - 0125 (NH4H2PO4), and 20 - 0084 ((NH4)2HPO4) can be cited respectively.

[0025] As reference patterns of the Li-Mo composite oxide, No. 12-0763 (Li2MoO4), 21-0515 (Li2MoO3), 42-1127 (LiMoO2), 21-0509 (Li4MoO5), and 25-0492 (Li4Mo5O 17 ) may be mentioned.

[0026] The compositions of LMO, the Li-Mo composite oxide, and the inorganic phosphorus compound contained in the composition of this embodiment may be determined from the measurement results of ICP and the XRD pattern, respectively. That is, by ICP measurement using a general inductively coupled plasma optical emission spectrometer (for example, ICP-AES, manufactured by PerkinElmer Japan), Li, Mn, Al, Mg, and P are quantified. Next, the concentration (mass%) of each element obtained by ICP measurement is divided by the atomic weight of each element and converted into the amount of substance to obtain the content (mol) of each element. The ICP measurement may be performed on the measurement solution by dissolving the composition of this embodiment in a hydrochloric acid-hydrogen peroxide mixed aqueous solution, and if necessary, the composition of this embodiment may be dissolved by pressurized acid decomposition or the like.

[0027] Among the results of the obtained ICP measurement, the content (mol) of Mo is regarded as being derived from the Li-Mo composite oxide, and the content (mol) of P is regarded as being derived from the inorganic phosphorus compound. Based on the calculation according to the composition formulas of the used Li-Mo composite oxide and inorganic phosphorus compound, the content of Li contained therein can be calculated.

[0028] The value obtained by subtracting the total content of Li calculated from the Li in the results of the ICP measurement is regarded as the Li content of LMO. Furthermore, using the obtained Li content of LMO and the contents of Mn, Al, and Mg in the results of the ICP measurement, the general formula of LMO, Li 1+X Mn 2-X―Y M Y O4, and the composition of LMO contained in the measurement sample may be specified.

[0029] The mass ratio (mass%) of the Li-Mo composite oxide is obtained by multiplying the concentration (mass%) of Mo obtained by ICP by the molecular weight of the used Li-Mo composite oxide with respect to the atomic weight of Mo.

[0030] The mass ratio (mass %) of the inorganic phosphorus compound is determined by multiplying the concentration of P (mass %) obtained by ICP by the molecular weight of the inorganic phosphorus compound used with respect to the atomic weight of P.

[0031] The mass ratio of LMO is determined by subtracting the mass ratios of the above Li-Mo composite oxide and inorganic phosphorus compound from 100 mass% when the mass of the composition of this embodiment is 100 mass%.

[0032] The amount (mass %) of the Li-Mo composite oxide contained in the composition of this embodiment is 0.1 mass% or more or 0.2 mass% or more, and may be 10 mass% or less or 7 mass% or less. 0.1 mass% or more and 10 mass% or less, or 0.2 mass% or more and 7 mass% or less is preferable.

[0033] The amount (mass %) of the inorganic phosphorus compound contained in the composition of this embodiment is 0 mass% or more, and may be 20 mass% or less or 15 mass% or less. 0 mass% or more and 20 mass% or less, or 0 mass% or more and 15 mass% or less is preferable.

[0034] The amount (mass %) of LMO contained in the composition of this embodiment is 70.0 mass% or more or 75.0 mass% or more, and may be 99.9 mass% or less or 99.8 mass% or less. 70.0 mass% or more and 99.9 mass% or less, or 75.0 mass% or more and 99.8 mass% or less is preferable.

[0035] The composition of this embodiment may contain at least one of sulfate (SO4 2- ) and a boron compound as an impurity.

[0036] LMO may be LMO obtained from a manganese compound produced in the presence of sulfate (SO4 2- ) as a starting material. In this case, the composition of this embodiment may contain sulfate (SO4 2- ). Therefore, with respect to the mass of the composition of this embodiment, sulfate (SO4 2-The mass ratio of 2- (hereinafter also referred to as "sulfate content") is 0 mass% or more, or 0.01 mass% or more, and is 1.2 mass% or less, or 1.0 mass% or less. It is preferably 0 mass% or more and 1.2 mass% or less, or 0.01 mass% or more and 1.0 mass% or less. On the other hand, the sulfate content may be 0 mass%, that is, the composition of the present embodiment does not contain sulfate (SO4

[0037] The sulfate content is the concentration (mass%) of sulfur (S) element measured by ICP measurement, multiplied by the molecular weight ratio of sulfate ion (SO4 2- ) to the atomic weight of sulfur (S), and then converted to the concentration (mass%) of SO4 2- .

[0038] As a starting material for LMO, a boron compound may be used. In this case, the composition of the present embodiment may contain a boron compound. Therefore, the mass ratio of the boron compound to the total mass of the composition and impurities of the present embodiment (hereinafter also referred to as "boron compound content") is 0 mass ppm or more, and is 13000 mass ppm or less, or 10000 mass ppm or less. It is preferably 0 mass ppm or more and 13000 mass ppm or less, or 0 mass ppm or more and 10000 mass ppm or less.

[0039] The boron compound content is a value obtained by converting the boron contained in the composition of the present embodiment into the content of boron oxide (B2O3). That is, the boron compound content is obtained by multiplying the concentration (mass ppm) of boron (B) element measured by ICP measurement by the molecular weight ratio of boron oxide (B2O3) to the atomic weight of boron (B) and converting it to the concentration (mass ppm) of the boron compound.

[0040] In the composition of the present embodiment, the mass may be obtained from the weighed value of the composition. Therefore, the sulfate content and the boron compound content are external numbers of the mass of the composition of the present embodiment, and the mass of the composition of the present embodiment when impurities such as sulfate are added may exceed 100 mass%.

[0041] The composition of this embodiment has at least the XRD peaks shown in the following table in the XRD pattern. By containing the Li-Mo composite oxide and LMO in a state where the composition of this embodiment exhibits such XRD peaks, the LIB provided with the composition of this example as a cathode active material exhibits excellent output characteristics and storage characteristics even at high temperatures.

[0042]

Table 3

[0043] It is more preferable that the composition of this embodiment has at least the peaks shown in the following table in the XRD pattern.

[0044]

Table 4

[0045] Since peaks with a relative intensity of less than 1% are regarded as measurement noise, the XRD pattern of the composition of this embodiment may include peaks with a relative intensity of less than 1%.

[0046] The XRD pattern of the composition of this embodiment may be measured under the above conditions.

[0047] For the lattice plane spacing and area intensity of the XRD peaks in the XRD pattern, the XRD pattern obtained by general powder X-ray diffraction measurement analysis software (for example, PDXL2: manufactured by Rigaku) may be analyzed. Also, for the relative intensity, the ratio of the integrated intensity of each peak to the integrated intensity of the XRD peak with a lattice plane spacing d(Å)=2.05±0.1Å may be obtained and regarded as the relative intensity.

[0048] The composition of this embodiment preferably has a half-value width (hereinafter, also simply referred to as "half-value width") on the (400) plane that is greater than 0.000°, 0.005° or more, or 0.10° or more, and may be 0.20° or less, 0.1° or less, 0.15° or less, or 0.08° or less. It is preferably greater than 0.000° and less than 0.20°, greater than 0.000° and less than 0.1°, between 0.10° and 0.15°, or between 0.005° and 0.08°. When the half-value width is within the above range, the elution of manganese (Mn) from the composition is suppressed, and a LIB provided with the composition of this example as a positive electrode active material is likely to exhibit excellent storage characteristics even at high temperatures.

[0049] The half-value width is obtained by analyzing the XRD pattern with general powder X-ray diffraction measurement analysis software, determining the integrated width of the XRD peak having a peak top at a lattice plane spacing d (Å) = 2.05 ± 0.1, and correcting the instrumental error by subtracting the half-value width of a standard substance (α-type quartz powder, manufactured by NIST) from the obtained integrated width. The value thus obtained is taken as the half-value width.

[0050] To facilitate use as a positive electrode active material, the average particle size of the composition of this embodiment is 0.1 μm or more, 0.5 μm or more, or 1 μm or more, and may be 40 μm or less, 30 μm or less, or 25 μm or less. It is preferably between 0.1 μm and 40 μm, between 0.5 μm and 30 μm, or between 1 μm and 25 μm.

[0051] The average particle size of the composition of this embodiment is the average particle size of the secondary particles. Using a general laser diffraction / scattering device (for example, MT3000II series, manufactured by MicrotracBEL), it is the particle size corresponding to the 50% volume diameter (hereinafter, also referred to as "D50") in the cumulative volume particle size distribution curve obtained under the following conditions.

[0052] Light source: Semiconductor laser Refractive index of particles: 2.20 Measurement approximation: Non-spherical approximation Dispersion medium: Ethanol The average particle size of the composition is equal to or greater than the average secondary particle size of LMO and the Li-Mo composite oxide, and further, is a value exceeding the average secondary particle size of LMO and the Li-Mo composite oxide.

[0053] The BET specific surface area of the composition of this embodiment is 0.2 m 2 / g or more, or 0.3 m 2 / g or more, and is also 2.0 m 2 / g or less, or 1.5 m 2 / g or less, and preferably is 0.2 m 2 / g or more and 2.0 m 2 / g or less, or 0.3 m 2 / g or more and 1.5 m 2 / g or less.

[0054] The BET specific surface area can be measured by a general measuring device (for example, Macsorb, manufactured by MOUNTECH) using a mixed gas of 30% nitrogen - 70% helium as the adsorption gas and by the one-point method defined in 7.3 of JIS Z8830.

[0055] The BET specific surface area may be measured after putting the composition of this embodiment into a glass cell for BET specific surface area measurement as a pretreatment and performing dehydration treatment at 150 °C for 20 minutes in a nitrogen flow atmosphere.

[0056] The pH of the composition of this embodiment is 9.00 or more, or 9.50 or more, and is also 12.0 or less, or 11.5 or less, and preferably is 9.00 or more and 12.0 or less, or 9.50 or more and 11.5 or less.

[0057] In this embodiment, pH is a value measured by a method according to the 5.9.2 water method of JIS K1467.

[0058] Next, the manufacturing method of the composition of this embodiment will be described.

[0059] The composition of the present embodiment is obtained by at least one of a production method having a mixing step of mixing a manganese source and a lithium source to obtain an LMO precursor, a firing step of firing the LMO precursor obtained in the mixing step, and a step of complexing the LMO obtained in the firing step with a Li-Mo composite oxide (hereinafter, also referred to as the "complexing method"), and a production method having a mixing step of mixing a manganese source, a lithium source, and a Li-Mo composite oxide to obtain an LMO precursor, and a firing step of firing the LMO precursor obtained in the mixing step (hereinafter, also referred to as the "firing method"). <Complexing method> The complexing in the present embodiment refers to an operation of physically mixing the LMO obtained in the firing step and the Li-Mo composite oxide to form an integral composition.

[0060] The production method of the composition of the present embodiment includes a mixing step, a firing step, and a complexing step.

[0061] In the mixing step, a manganese source and a lithium source are mixed to obtain an LMO precursor. As long as the manganese source and the lithium source are uniformly mixed, the mixing method may be either wet mixing or dry mixing. From the perspective of the cost related to drying after the mixing step, dry mixing is preferred. The starting materials in the mixing step include a manganese source and a lithium source, and may also include one or more selected from the group of metal sources, inorganic phosphorus compounds, and additives described below.

[0062] The manganese source is not particularly limited as long as it is a compound containing manganese (Mn). For example, at least one of manganese oxides and manganese organic acid salts can be mentioned, and one or more selected from the group of MnO2, Mn3O4, Mn2O3, and manganese acetate can be mentioned. Further, at least one of MnO2 and Mn3O4 can be mentioned, and further, MnO2 can be mentioned.

[0063] The MnO₂ may be MnO₂ obtained by electrolytic deposition, or may be MnO₂ obtained by a chemical reaction. MnO₂ obtained by a chemical reaction is likely to have a small crystallite size and a large half-value width of the (400) plane. Therefore, when used as an electrode active material, insertion and extraction of Li from the active material easily occur, and the initial capacity is likely to be large.

[0064] The lithium source is not particularly limited as long as it is a compound containing lithium (Li). For example, one or more lithium salts selected from the group consisting of lithium carbonate, lithium hydroxide, lithium nitrate, lithium chloride, lithium iodide, and lithium oxalate may be mentioned. At least one of lithium carbonate and lithium hydroxide is preferable, and lithium carbonate is more preferable.

[0065] In the mixing step, a metal source containing at least one of a magnesium source and an aluminum source may be mixed.

[0066] Examples of the magnesium source include one or more selected from the group consisting of magnesium hydroxide, magnesium oxide, and magnesium carbonate. At least one of magnesium hydroxide and magnesium oxide is preferable.

[0067] Examples of the aluminum source include one or more selected from the group consisting of aluminum hydroxide, aluminum oxyhydroxide, and aluminum oxide. At least one of aluminum hydroxide and aluminum oxide is preferable.

[0068] In the mixing step, an inorganic phosphorus compound may be mixed, and an inorganic phosphorus compound equivalent to the inorganic phosphorus compound contained in the composition of the above-described embodiment may be used.

[0069] In the mixing step, other additives may be included as necessary. Examples of the additive include a boron compound. The boron compound functions as a flux during firing and makes it easy for the primary particle size of LMO to increase. As a result, when the composition of the present embodiment is used as a positive electrode active material for a LIB, a LIB showing excellent storage characteristics is easily obtained.

[0070] The boron compound is a compound of boron, and examples thereof include one or more selected from the group consisting of H3BO3, B2O3, and Li2O·nB2O3 (n is 1 or more and 5 or less), and H3BO3 is preferred.

[0071] The mixing amount of the manganese source is 70% by mass or more, or 75% by mass or more, and 90% by mass or less, or 85% by mass or less, based on the total mass of the starting materials, and 70% by mass to 90% by mass, or 75% by mass to 85% by mass is preferred.

[0072] The mixing amount of the lithium source is 15% by mass or more, or 17% by mass or more, and 25% by mass or less, or 23% by mass or less, based on the total mass of the starting materials, and 15% by mass to 25% by mass, or 17% by mass to 23% by mass is preferred.

[0073] The mixing amount of the magnesium source and the aluminum source is 0% by mass or more, or 2.0% by mass or more, and 6.0% by mass or less, or 5.0% by mass or less, based on the total mass of the starting materials, and 0% by mass to 6.0% by mass, or 2.0% by mass to 5.0% by mass is preferred.

[0074] The total mixing amount of the magnesium source and the aluminum source is 1.0% by mass or more, or 2.0% by mass or more, and 6.0% by mass or less, or 5.0% by mass or less, based on the total mass of the starting materials, and 1.0% by mass to 6.0% by mass, or 2.0% by mass to 5.0% by mass is preferred.

[0075] The mixing amount of the inorganic phosphorus compound is 0% by mass or more, or 1.0% by mass or more, and 5.0% by mass or less, or 4.5% by mass or less, based on the total mass of the starting materials, and 0% by mass to 5.0% by mass, or 1.0% by mass to 4.5% by mass is preferred.

[0076] The mixing amount of the boron compound is 0% by mass or more, or 0.2% by mass or more, based on the total mass of the starting materials, and is also 1.0% by mass or less, or 0.8% by mass or less. 0% by mass or more and 1.0% by mass or less, or 0.2% by mass or more and 0.8% by mass or less are preferred.

[0077] The firing step is a step of obtaining LMO by firing the LMO precursor obtained in the mixing step. The firing temperature in the firing step is 750 °C or higher, or 780 °C or higher, and is also 970 °C or lower, or 950 °C or lower. 750 °C or higher and 970 °C or lower, or 780 °C or higher and 950 °C or lower are preferred. If the firing temperature is less than 750 °C, the (400) half-value width of the obtained LMO becomes large. That is, when the crystallite diameter of the obtained LMO decreases, manganese (Mn) is likely to elute when the composition of the present embodiment is used as a positive electrode active material for LIB, and the charge-discharge capacity of LIB, and the output characteristics and storage characteristics at high temperatures decrease. If the firing temperature exceeds 970 °C, the oxygen deficiency of the obtained LMO increases, and thereby the charge-discharge capacity of LIB provided with the obtained composition as a positive electrode active material for LIB, and the output characteristics and storage characteristics at high temperatures decrease.

[0078] The firing time of the firing step may be appropriately set according to the amount of the LMO precursor to be fired, the performance of the firing furnace, etc. However, in order to reduce the cost related to production, it is 3 hours or more, or 4 hours or more, and is also 12 hours or less, or 10 hours or less. 3 hours or more and 12 hours or less, or 4 hours or more and 10 hours or less are preferred.

[0079] The firing atmosphere is not particularly limited as long as it does not inhibit the reaction for generating LMO. For example, an air atmosphere or a high-concentration oxygen atmosphere (including a pure oxygen atmosphere) can be mentioned. A preferable oxygen concentration is 18% by volume or more, and it can be 100% by volume or less, or 60% by volume or less. 18% by volume or more and 100% by volume or less, or 18% by volume or more and 60% by volume or less are preferable. Further, the constituent components other than oxygen are not particularly limited as long as the atmosphere does not inhibit the reaction for generating LMO. For example, one or more selected from the group consisting of helium, nitrogen, argon, and carbon dioxide can be mentioned.

[0080] After the firing step, it is preferable to wash the obtained LMO with water. Thereby, boron and the like are removed, and a LIB showing excellent storage characteristics even at high temperatures can be obtained when the composition of the present embodiment is used as a positive electrode active material for LIB.

[0081] For the water washing, for example, it is preferable to perform water washing so that the boron compound content of the LMO after water washing is 0 mass ppm or more and 13000 mass ppm or less, or 10000 mass ppm or less, and it is preferable to perform it so that it becomes 0 mass ppm or more and 13000 mass ppm or less, 0 mass ppm or more, or 10000 mass ppm or less.

[0082] The boron compound content of the LMO contained in the LMO after water washing can be 0 wtppm, that is, the LMO may not contain a boron compound.

[0083] In order to remove the moisture adhering to the LMO after water washing, drying may be performed. The pressure during drying includes normal pressure or reduced pressure, and normal pressure is preferable. Further, the drying atmosphere is not particularly limited as long as the crystal structure and composition of the LMO do not change. For example, one or more selected from the group consisting of an air atmosphere, a high-concentration oxygen atmosphere (including a pure oxygen atmosphere), a nitrogen atmosphere, and an argon atmosphere can be mentioned, and an air atmosphere is preferable.

[0084] The drying temperature is preferably 60°C or more and 200°C or less, and the drying time is preferably 1 hour or more and 48 hours or less.

[0085] The average particle diameter of the secondary particles of LMO (hereinafter also referred to as "average secondary particle diameter") is 3.0 μm or more, or 5.0 μm or more, and is 40 μm or less, 30 μm or less, or 25 μm or less, and it is preferably 3.0 μm or more and 40 μm or less, 5.0 μm or more and 30 μm or less, or 5.0 μm or more and 25 μm or less. Thereby, when the composition of the present embodiment is used as a positive electrode active material for LIB, the filling property of the positive electrode active material is improved, and the lithium diffusion distance in the LMO particles is reduced, so that a LIB showing excellent output characteristics even at high temperatures can be obtained.

[0086] The average particle diameter of the primary particles of LMO (hereinafter also referred to as "average primary particle diameter") is 0.50 μm or more, or 1.0 μm or more, and is 15 μm or less, or 10 μm or less, and it is preferably 0.5 μm or more and 15 μm or less, or 1.0 μm or more and 10 μm or less.

[0087] In addition, for LMO, the average primary particle diameter is less than or equal to the average secondary particle diameter, and further, the average primary particle diameter is less than the average secondary particle diameter.

[0088] Here, the "secondary particles" are particles in which primary particles are aggregated, and the "primary particles" are independent crystal particles.

[0089] The average secondary particle diameter of LMO is a particle corresponding to D50 measured by the laser diffraction / scattering method of the above general particle size distribution measuring device.

[0090] The average primary particle diameter of LMO is the average diameter of the primary particles of LMO measured by scanning electron microscope-energy dispersive X-ray analysis (hereinafter also referred to as "SEM-EDS"), and this is a value obtained by analyzing the SEM observation image or elemental mapping obtained under the following conditions using a general SEM-EDS (for example, FE-SEM JSM-7600F, manufactured by JEOL Ltd.).

[0091] Accelerating voltage: 5 kV Observation magnification: 2000 times to 5000 times When taking element mapping, the following elements may be mapped.

[0092] Mapped element: Manganese (Mn) For the obtained SEM observation image or element mapping, the average primary particle size may be determined using general image analysis software (e.g., ImageJ).

[0093] The composite process is a process of compositing the obtained LMO with a Li-Mo composite oxide in the firing process.

[0094] As the Li-Mo composite oxide, a commercially available product (e.g., product name: lithium molybdate (Li2MoO4), manufactured by Mitsuwa Chemical Co., Ltd.) can be used.

[0095] The average secondary particle size of the Li-Mo composite oxide is 0.050 μm or more, 0.25 μm or more, or 0.50 μm or more, and is also 30 μm or less, 25 μm or less, or 20 μm or less, and 0.050 μm or more and 30 μm or less, 0.25 μm or more and 25 μm or less, or 0.50 μm or more and 20 μm or less is preferable.

[0096] The average secondary particle size of the Li-Mo composite oxide can be the D50 measured by the laser diffraction / scattering method of the above general particle size distribution measuring device.

[0097] In addition, the average secondary particle size of the Li-Mo composite oxide may be less than or equal to the average particle size of the composition, and further may be less than the average particle size.

[0098] In order to adjust the average secondary particle size of the Li-Mo composite oxide, it may be pulverized.

[0099] The pulverization method is arbitrary, and examples include pulverization using one or more selected from the group consisting of a hammer mill, a ball mill, a jet mill, a pin mill, and a screen mill. Since high density can be achieved when used as the positive electrode of LIB, the pulverization is preferably pulverization using a jet mill.

[0100] The compounding of the Li-Mo composite oxide with LMO can be carried out such that the amount of the Li-Mo composite oxide is 0.10% by mass or more, 0.20% by mass or more, or 0.30% by mass or more with respect to LMO, and is 12% by mass or less, 7.5% by mass, or 5.0% by mass or less. It is preferably 0.10% by mass or more and 12% by mass or less, 0.20% by mass or more and 7.5% by mass or less, or 0.30% by mass or more and 5.3% by mass or less.

[0101] The method for compounding the Li-Mo composite oxide with LMO may be any method of mixing while applying at least one of the forces of compression, shear, and impact. For example, a method of applying a shear force to LMO and the Li-Mo composite oxide and mixing them, or a wet method in which a solution containing the Li-Mo composite oxide is mixed with LMO and then dried to remove the solvent can be mentioned. Since the cost related to the drying of the solvent is not incurred, the dry method is preferred.

[0102] Since the particles of the composition of this embodiment obtained in the compounding step are likely to be consolidated with each other during firing, crushing may be performed to obtain the target particle size.

[0103] The method of crushing is not particularly limited, but crushing by shear force is preferred in order to suppress the generation of fine powder.

[0104] In order to remove coarse particles, the composition of this embodiment obtained in the compounding step preferably undergoes at least one of classification by the specific gravity of the solvent, classification by wind force, and classification by a sieve. Classification by a sieve with good recovery rate of the composition is preferred.

[0105] The mesh size of the sieve used for classification by a sieve is 10 μm or more or 20 μm or more, and is 200 μm or less or 150 μm or less. It is preferably 10 μm or more and 200 μm or less, or 20 μm or more and 150 μm or less.

[0106] Drying may be performed to remove the moisture adhering to the composition after the compounding step. The pressure during drying may be normal pressure or reduced pressure, with normal pressure being preferred. Also, the drying atmosphere is not particularly limited as long as it does not change the crystal structure and composition of LMO. For example, one or more selected from the group of air atmosphere, high-concentration oxygen atmosphere (including pure oxygen atmosphere), nitrogen atmosphere, and argon atmosphere may be mentioned, and an air atmosphere is preferred.

[0107] The drying temperature is preferably 60°C or higher and 200°C or lower, and the drying time is preferably 1 hour or longer and 48 hours or shorter. <Firing method> The firing method is a manufacturing method having a mixing step of mixing a manganese source, a lithium source, and a Li-Mo composite oxide to obtain an LMO precursor, and a firing step of firing the LMO precursor obtained in the mixing step. In the mixing step, by mixing a Li-Mo composite oxide in addition to the manganese source and the lithium source, the Li-Mo composite oxide melts during firing. Thereby, it becomes easier for the Li-Mo composite oxide to be coated more uniformly on the LMO surface.

[0108] The Li-Mo composite oxide used in the mixing step may be the same as the Li-Mo composite oxide used in the compounding step of the compounding method. The Li-Mo composite oxide used in the firing method preferably has a melting point lower than the firing temperature, preferably 970°C or lower or 950°C or lower. Thereby, it becomes easier to be coated uniformly on the LMO surface. Also, the melting point of the Li-Mo composite oxide used in the firing method is preferably 500°C or higher, or 600°C or higher. When the melting point is 500°C or higher, it becomes easier for the Li-Mo composite oxide to be uniformly mixed into the LMO precursor by dry mixing. Examples of the melting point of the Li-Mo composite oxide include 500°C or higher and 970°C or lower, or 600°C or higher and 950°C or lower. A preferable Li-Mo composite oxide is lithium molybdate (melting point: 705°C).

[0109] In the mixing step, a method similar to the compounding method may be used as long as it is other than mixing a Li-Mo composite oxide in addition to the manganese source and the lithium source.

[0110] In the mixing process, the mixing ratio of the Mn source and the Li source is preferably 55% or more, or 60% or more, calculated as {amount of Mn substance (mol) in the Mn source / (amount of Mn substance (mol) in the Mn source + amount of Li substance (mol) in the Li source)} × 100. When the mixing ratio of the Mn source and the Li source is within this range, it is easier to obtain LMO that exhibits a higher discharge capacity. The mixing ratio of the Mn source and the Li source is preferably 75% or less, or 70% or less. When the mixing ratio of the Mn source and the Li source is within this range, the storage characteristics are more likely to be improved. Examples of the mixing ratio of the Mn source and the Li source include 55% or more and 75% or less, or 60% or more and 70% or less.

[0111] The mixing ratio of the Mn source and the Li-Mo composite oxide is preferably 70% or more, or 80% or more, calculated as {amount of Mn substance (mol) in the Mn source / (amount of Mn substance (mol) in the Mn source + amount of Mo substance (mol) in the Li-Mo composite oxide)} × 100. When it is 70% or more, it is easier to obtain a cathode active material with a higher capacity. Also, the mixing ratio of the Mn source and the Li-Mo composite oxide is preferably 99.9% or less, or 99.8% or less. When it is 99.9% or less, the storage characteristics are higher. Examples of the mixing ratio of the Mn source and the Li-Mo composite oxide include 70% or more and 99.9% or less, or 80% or more and 99.8% or less.

[0112] In the mixing process, the particle size ratio of the Mn source and the Li-Mn composite oxide is preferably small. As (D50 of the Li-Mo composite oxide / D50 of the Mn source), it is preferably 5.0 or less, and more preferably 4.0 or less. When it is within this range, the Li-Mo composite oxide is mixed in a highly dispersed state and is more likely to be uniformly coated on the LMO surface. The particle size ratio may be 0.0001 or more or 0.001 or more, and examples include 0.0001 or more and 5.0 or less, or 0.001 or more and 4.0 or less.

[0113] In the firing process, the LMO precursor obtained in the mixing process may be fired. As a result, the conversion of the LMO precursor to LMO and the compounding of LMO and the Li-Mo composite oxide proceed in parallel. Therefore, the composition of the present embodiment can be obtained without requiring a compounding step.

[0114] The firing process may be carried out by a firing method similar to the compounding method.

[0115] The firing method may include a step of compounding the Li-Mo composite oxide with the composition obtained in the firing process. The firing method can obtain the composition of the present embodiment without having a compounding step. However, in order to increase the Li-Mo composite oxide on the LMO surface and make it difficult to suppress the elution of manganese during use as an active material, it may have a compounding step.

[0116] The composition of the present embodiment can be used as a positive electrode active material for LIB.

[0117] The method for producing the positive electrode of LIB may be a known production method using the composition of the present embodiment. For example, the composition of the present embodiment, a conductive material (for example, a carbon material such as Denka black), and a binder solution (for example, an N-methyl-2-pyrrolidone solution of polyvinylidene fluoride) are mixed to obtain a positive electrode mixture slurry, and this is applied to a current collector and dried.

[0118] The cell used for battery evaluation is not particularly limited as long as it can evaluate the cycle characteristics described later. For example, any one selected from the group of screw cells, coin cells, and laminate cells can be mentioned, and a laminate cell is preferred.

[0119] The method for producing the laminate cell may be a known production method. For example, the obtained positive electrode, negative electrode (for example, artificial graphite), and electrolyte (for example, a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio 1:1) containing 1 mol / dm of LiPF6 3A solution in which 1% by mass of vinylene carbonate is dissolved) and a separator (for example, product name: Ceramic Coated Wet Separator SH716E14 for Lithium Ion Secondary Batteries, manufactured by Shenzhen Senior Technology Material) are used, and a manufacturing method can be mentioned.

Example

[0120] Next, the present disclosure will be described with specific examples, but the present disclosure is not construed as being limited to these examples.

[0121] <Measurement of XRD Pattern> The XRD pattern of the sample was obtained under the following conditions using a powder X-ray diffractometer (Ultima IV, manufactured by Rigaku).

[0122] X-ray source: CuKα ray (wavelength λ = 1.5405 Å) Output: 1.6 kW (40 mA - 40 kV) Filter: Kβ filter Divergence slit: 1° Divergence vertical limiting slit: 10 mm Scattering slit: Open Receiving slit: Open Scanning mode: Continuous Scan speed: 4.000° / min Sampling width: 0.04° (2θ / θ) Integration times: 1 time Measurement range: 10 - 90° (2θ / θ) The lattice plane spacing and the integrated intensity were obtained by analyzing the XRD pattern obtained using analysis software for powder X-ray diffraction measurement (PDXL2, manufactured by Rigaku). The relative intensity was determined as the ratio (%) of the integrated intensity of each peak to the integrated intensity of the lattice plane spacing with a lattice plane spacing d (Å) = 2.05 as the reference.

[0123] The full width at half maximum (FWHM) on the (400) plane was obtained by analyzing the XRD pattern using the above-mentioned analysis software for powder X-ray diffraction measurement (PDXL2), considering the XRD peak with a peak top at the lattice plane spacing d(Å) = 2.05 as the peak of the (400) plane, and determining its integral width. The instrumental error was corrected by subtracting the FWHM of the standard substance (α-type quartz powder, manufactured by NIST) from the obtained integral width, and the resulting value was taken as the FWHM.

[0124] <ICP measurement> The composition of the sample was determined by quantifying Li, Mn, Al, Mg, B, S, and P through ICP measurement using an inductively coupled plasma optical emission spectrometer (ICP-AES, manufactured by PerkinElmer Japan). The measurement was performed on the measurement solution prepared by dissolving the measurement sample in an aqueous hydrochloric acid-hydrogen peroxide mixed solution. The content (mol) of each element in the measurement sample was obtained by dividing the concentration (mass%) of each element determined by ICP measurement by the atomic weight of each element and converting it to the amount of substance.

[0125] <Identification of composition> The composition of the sample was determined from the ICP measurement results and the XRD pattern. That is, by comparing the obtained XRD pattern with the JCPDS card, LMO, Li-Mo composite oxide, and inorganic phosphorus compound contained in the measurement sample were identified.

[0126] Among the results of the ICP measurement, Mo was considered to be derived from the Li-Mo composite oxide, and P was considered to be derived from the inorganic phosphorus compound, and the Li content contained in these was calculated. The value obtained by subtracting the total calculated Li content from the Li in the ICP measurement results was taken as the Li content of LMO.

[0127] Using the obtained Li content of LMO and the contents of Mn, Al, and Mg in the ICP measurement results, the general formula of LMO, Li 1+X Mn 2-X―Y M Y O4 was considered, and the composition of LMO contained in the measurement sample was specified.

[0128] <Contents of sulfate and boron compound> Sulfate (SO4 2-) content was determined by multiplying the sulfur (S) concentration (% by mass) obtained by ICP measurement by the molecular weight ratio of SO4 2- / S. On the other hand, the content of the boron compound (B2O3) was determined by multiplying the boron (B) concentration (ppm by mass) obtained by ICP measurement by the molecular weight ratio of B2O3 / B.

[0129] <Measurement of BET specific surface area> 1.0 g of the sample was placed in a glass cell for BET specific surface area measurement and pretreated by dehydration at 150 °C for 20 minutes in a nitrogen flow atmosphere.

[0130] Using a BET measuring device (Macsorb, manufactured by MOUNTECH), the BET specific surface area of the pretreated sample was measured by the one-point method according to 7.3 of JIS Z8830. During the measurement, a mixed gas of 30 vol% nitrogen - 70 vol% helium was used as the adsorption gas.

[0131] <Measurement of pH> The JIS-pH of the composition was measured according to the water method defined in 5.9.2 of JIS K1467.

[0132] <Measurement of average secondary particle diameter> Using a particle size distribution measuring device (MT3000II series, manufactured by MicrotracBEL), D50 was taken as the average secondary particle diameter from the volume frequency distribution curve obtained under the following conditions. The measurement was carried out after irradiating the slurry obtained by mixing the measurement sample with the dispersion medium (ethanol) with ultrasonic waves for 3 minutes.

[0133] Light source: Semiconductor laser Refractive index of particles: 2.20 Measurement approximation: Non-spherical approximation Dispersion medium: Ethanol <Measurement of average primary particle diameter> Using a field emission scanning electron microscope (FE-SEM JSM-7600F, manufactured by JEOL Ltd.), SEM observation images of the sample were obtained under the following conditions.

[0134] Accelerating voltage: 5 kV Observation magnification: 2000 times - 5000 times In the obtained SEM observation image, 30 ± 10 primary particles whose contours were observed continuously were extracted. The longest diameter of each primary particle was regarded as the primary particle diameter, and the average value thereof was taken as the average primary particle diameter of the sample.

[0135] <Measurement of Output Characteristics> 4.7 g of a positive electrode active material, 0.15 g of acetylene black (Denka Black, manufactured by Denka Co., Ltd.), 1.5 g of a 10 mass% polyvinylidene fluoride / N-methyl-2-pyrrolidone solution (0.15 g of polyvinylidene fluoride), and 1.23 mL of N-methyl-2-pyrrolidone (spinel-type lithium manganate:acetylene black:polyvinylidene fluoride = 94:3:3 by mass ratio) were mixed with a rotation-revolution mixer (AR-310, manufactured by Shin Kee Co., Ltd.) to prepare a positive electrode mixture. The obtained positive electrode mixture was applied to an aluminum foil, dried at 120°C for 20 minutes, punched out into a length of 60 mm × width of 30 mm with a Thomson blade, and roll-pressed so that the density of the positive electrode mixture became 2.5 ± 0.1 g / cm 3 After roll-pressing, the upper end portion of the positive electrode mixture coating portion with a length of 10 mm × width of 30 mm was peeled off, vacuum-dried at 120°C for 2 hours or more, and an aluminum tab was spot-welded. The coating amount was adjusted so that the amount of the positive electrode active material became 15.0 ± 0.3 mg / cm 2

[0136] For the negative electrode, 4.0 g of artificial graphite, 2.1 g of a 10 mass% polyvinylidene fluoride / N-methyl-2-pyrrolidone solution (0.21 g of polyvinylidene fluoride), and 3.2 mL of N-methyl-2-pyrrolidone (graphite:polyvinylidene fluoride = 95:5 by mass ratio) were mixed with a rotation-revolution mixer to prepare a negative electrode mixture. The obtained negative electrode mixture was applied to a copper foil, dried at 120°C for 20 minutes, punched out into a length of 62 mm × width of 32 mm with a Thomson blade, and roll-pressed so that the density of the negative electrode mixture became 1.5 g / cm 3 After roll-pressing, the upper end portion of the negative electrode mixture coating portion with a length of 10 mm × width of 32 mm was peeled off, vacuum-dried at 120°C for 5 hours, and a nickel tab was spot-welded. The coating amount was adjusted so that the amount of graphite became 5.5 mg / cm 2

[0137] ​​A positive electrode, a negative electrode, an electrolyte solution in which LiPF6 is dissolved at 1 mol / dm³ in a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio 1:1) 3 and 1% by mass of vinylene carbonate, 0.24 mL of the electrolyte solution, and a separator (trade name: Ceramic Coated Wet Separator SH716E14 for Lithium Ion Secondary Battery, manufactured by Shenzhen Senior Technology Material) were used to fabricate a single-layer laminated cell.

[0138] Using the fabricated battery, at 24°C, constant current constant voltage charging - constant current discharging was performed at a current of 4.5 mA between a cell voltage of 4.2 V and 3.0 V for 3 cycles, and the discharge capacity of the 3rd cycle was taken as the initial capacity.

[0139] <Measurement of Output Characteristics and Storage Characteristics> Next, at 60°C, between a cell voltage of 4.2 V and 3.0 V, constant current constant voltage charging - constant current discharging was performed for 100 cycles at a current of 0.2 C (discharge rate of 0.2 hours) for the 1st, 10th, 20th, 50th, and 100th cycles with respect to the initial capacity, and at a current of 1 C (discharge rate of 1 hour) for the other cycles with respect to the initial capacity. The discharge capacity of the 1st cycle and the discharge capacity of the 2nd cycle were calculated by the following formula (1) and taken as the output characteristics (%). Also, the value calculated by the following formula (2) from the discharge capacity of the 100th cycle and the discharge capacity of the 1st cycle was taken as the storage characteristics (%). (Output Characteristics (%)) = (Discharge Capacity of the 2nd Cycle (mAh / g)) / (Discharge Capacity of the 1st Cycle (mAh / g)) × 100 Formula (1) (Storage Characteristics (%)) = (Discharge Capacity of the 100th Cycle (mAh / g)) / (Discharge Capacity of the 1st Cycle (mAh / g)) × 100 Formula (2) Note that the end condition of constant voltage charging was the point when the charging current decayed to 1 / 20 of that during constant current charging. Synthesis Example 1 Into a reaction vessel containing 7.3 L of pure water at 80°C, while stirring at a rotation speed of 370 rpm using a stirring blade and bubbling with air, an aqueous solution of manganese sulfate at 2.0 mol / L and an aqueous solution of sodium hydroxide at 20% by mass were supplied.

[0140] In bubbling, the air supply rate was set to 0.5 L / min. Also, the supply rate of the manganese sulfate aqueous solution was 12 g / min (0.565 L / hour), and the supply rate of the 20 mass% sodium hydroxide aqueous solution was 7 g / min (0.347 L / hour). The production of the manganese oxide slurry was started under the above conditions. Also, the supply of the 20 mass% sodium hydroxide aqueous solution was carried out so that the pH of the manganese oxide slurry during synthesis became 7.5 ± 0.5. The supply of the raw materials was stopped when 16 L of the manganese sulfate aqueous solution was supplied.

[0141] The reaction was carried out in a continuous manner, that is, the supply of raw materials, the reaction, and the discharge of the product were carried out simultaneously. The residence time of the added manganese sulfate aqueous solution was adjusted to be 11 hours as (reaction liquid volume [L] / raw material supply rate [L / hour]). The "raw material supply rate" indicates the sum of the supply rates of the manganese sulfate aqueous solution and the sodium hydroxide aqueous solution, and was 0.912 L / hour. Here, the "reaction liquid volume" is the liquid volume in the reaction tank and was 10 L. The obtained manganese oxide slurry was filtered using a Nutsche filter paper (product name: quantitative filter paper No. 5C, manufactured by ADVANTEC). Then, it was dried in a forced-air constant-temperature dryer (product name: DRS420DB, manufactured by ADVANTEC) at 110 °C for 15 hours in an air atmosphere to obtain the Mn3O4 powder of Synthesis Example 1. Synthesis Example 2 100 g of the Mn3O4 obtained in Synthesis Example 1, 28.6 g of lithium carbonate, 5.16 g of aluminum hydroxide, 0.451 g of boric acid, and 730 g of zirconia balls with a diameter of 10 mm were put into a 500 ml plastic wide-mouth bottle, and dry pulverization and mixing were carried out at a rotation speed of 250 rpm for 60 minutes using a pot mill (product name: POT MILL ROTATOR PM-001, manufactured by AS ONE) to obtain a mixed powder.

[0142] 134.21 g of the obtained mixed powder was filled into an alumina crucible and fired in an electric furnace (product name: electric muffle furnace FUW253PB, manufactured by ADVANTEC, volume 31 L) under the following firing conditions.

[0143] Firing atmosphere: Air circulation atmosphere (flow rate: 8 L / min) Firing temperature: 930 °C Holding time at 930 °C: 6 hours Heating rate: 100 °C / hour After firing, the temperature was lowered to 700 °C at a cooling rate of 20 °C / hour, and then annealed by holding at that temperature for 24 hours. After the annealing treatment, the temperature was lowered from 700 °C to room temperature (25 °C) at a cooling rate of 100 °C / hour, and then the fired powder was crushed with a hammer crusher (product name: NH-34S, manufactured by Sanjo Industry Co., Ltd.) to obtain a crushed powder.

[0144] 100 g of the crushed powder was dispersed in 300 mL of pure water to form a slurry, and then filtered using a Nutsche filter paper (product name: quantitative filter paper No. 5C, manufactured by ADVANTEC). Then, it was dried in a forced-air constant-temperature dryer (product name: DRS420DB, manufactured by ADVANTEC) in an air atmosphere at 120 °C for 20 hours to obtain a dried powder. The dried powder was crushed with a rotary crusher (product name: NR-04A, manufactured by Sanjo Industry Co., Ltd.), and then classified with a vibrating sieve using a sieve with an aperture of 32 μm for 5 minutes, and the powder passing through the sieve was collected to obtain the LMO powder of Synthesis Example 2. Synthesis Example 3 (Grinding of Lithium Molybdate) Lithium molybdate (Li2MoO4, product name: Lithium molybdate, manufactured by Fujifilm Wako Pure Chemical Corporation) was ground with a jet mill (product name: Nano Grinding Mill NJ-50, manufactured by Tokuju Works) until the secondary particle size reached 2.4 μm to obtain the Li-Mo composite oxide powder of Synthesis Example 3.

[0145] Example 1 1577 g of electrolytic manganese dioxide, 369 g of lithium carbonate, 53 g of magnesium hydroxide, 2.8 g of boric acid (boron addition amount to manganese: 500 wtppm), and 63 g of trilithium phosphate were added to pure water to obtain a slurry with a solid content concentration of 20 mass%. Using a grinder (Dyno Mill, manufactured by Shinmaru Enterprise Co., Ltd.), the obtained slurry was ground and mixed for 3 hours to obtain a raw material slurry. The D50 of the mixed powder in the raw material slurry was 0.6 μm.

[0146] Using a spray dryer (manufactured by Pulis Co.), the raw material powder was spray-dried under the following conditions to remove the solvent (water), and spherical granular dry particles with a D50 of 10 μm were obtained.

[0147] Spray pressure: 0.3 MPa Supply rate: 3000 g / hour Inlet temperature: 200 °C Outlet temperature: 120 °C 200 g of the granular dry particles were placed in a box furnace, and the temperature was raised from room temperature to the firing temperature and fired. The firing conditions are shown below.

[0148] Firing atmosphere: Air circulation atmosphere (flow rate: 5 L / min) Firing temperature: 850 °C Firing time: 6 hours Heating rate: 100 °C / hour After firing, the temperature was lowered from the firing temperature to the annealing temperature and annealed under the following conditions.

[0149] Annealing temperature: 600 °C Annealing time: 24 hours Cooling rate: 20 °C / hour After annealing, the temperature was lowered to room temperature at a cooling rate of 100 °C / hour, and the fired product was recovered. The recovered fired product and pure water were mixed to form a slurry, and after stirring and filtering for 1 hour, it was dried in an air atmosphere at 120 °C to recover the precursor composition.

[0150] The precursor composition and lithium molybdate (Li2MoO4, average secondary particle diameter 18.6 μm. Product name: Lithium molybdate, manufactured by Mitsuwa Chemical Co., Ltd.) were weighed so that the precursor composition was 98.6% by mass and lithium molybdate was 1.4% by mass, and then they were mixed in an agate mortar to obtain the composition of this example. The main XRD peaks of the composition of this example are shown below.

[0151]

Table 5

[0152] As a result of XRD measurement and composition analysis, the pattern was equivalent to the XRD pattern consisting of JCPDS card No. 35-782 (LiMn2O4), No. 25-1030 (Li3PO4), and No. 53-0670 (Li2MoO4). The composition of this example was a composition consisting of LMO, Li3PO4, and Li2MoO4 represented by the general formula Li 1.10 Mn 1.84 Mg 0.06 O4.

[0153] The composition of this example had an average secondary particle diameter of 9.0 μm and an average primary particle diameter of 1.2 μm.

[0154] The composition of this example had an LMO content of 94.9% by mass, a Li3PO4 content of 3.7% by mass, and a Li2MoO4 content of 1.4% by mass.

[0155] In the composition of this example, for convenience, the mass was taken as the total mass of LMO, Li3PO4, and Li2MoO4. Therefore, the sulfate content and the boron content were external numbers to the mass of the composition of this embodiment, and the mass of the composition of this example when these were added exceeded 100% by mass.

[0156] In the composition of this example, the sulfate content was 0.35% by mass and the boron compound content was 1610 ppm by mass.

[0157] Example 2 The LMO powder of Synthesis Example 2 and the Li-Mo composite oxide powder of Synthesis Example 3 were weighed so that the LMO powder was 98.0% by mass and the Li-Mo composite oxide powder was 2.0% by mass, and then these were mixed in an agate mortar. After mixing, vibration sieving treatment was performed for 5 minutes using an electromagnetic vibrating sieve equipped with a sieve with an opening of 40 μm, and the powder passing through the sieve was collected to obtain the composition of this example. The main XRD peaks of the composition of this example are shown below.

[0158]

Table 6

[0159] As a result of XRD measurement and composition analysis, the XRD pattern was equivalent to the XRD pattern consisting of JCPDS card No. 35-782 (LiMn2O4) and No. 53-0670 (Li2MoO4). From this, the composition of this example has the general formula Li 1.09 Mn 1.81 Al 0.10 It was confirmed that the composition was composed of LMO represented by O4 and Li2MoO4.

[0160] The composition of this example had an average secondary particle diameter of 14.7 μm and an average primary particle diameter of 5.6 μm. Also, the content of LMO was 97.6% by mass and the content of Li2MoO4 was 2.4% by mass.

[0161] In the composition of this example, the sulfate content was 0.35% by mass and the boron compound content was 67 ppm by mass.

[0162] Note that in the composition of this example, the mass was taken as the total mass of LMO and Li2MoO4. Therefore, when the mass of the composition of this embodiment was added, the mass of the composition of this example exceeded 100% by mass for the sulfate content and boron content.

[0163] Example 3 A composition of this example was obtained in the same manner as in Example 2, except that the precursor composition was 97.0% by mass and lithium molybdate was 3.0% by mass. The main XRD peaks of the composition of this example are shown below.

[0164]

Table 7

[0165] As a result of XRD measurement and composition analysis, the XRD pattern is equivalent to the XRD pattern consisting of JCPDS card No. 35-782 (LiMn2O4) and No. 53-0670 (Li2MoO4). Also, the composition of this example has the general formula Li 1.09 Mn 1.81 Al 0.10 It was confirmed that the composition is composed of LMO and Li2MoO4 represented by O4.

[0166] The composition of this example had an average secondary particle diameter of 14.7 μm and an average primary particle diameter of 5.5 μm. Also, the content of LMO was 96.6 mass% and the content of Li2MoO4 was 3.4 mass%.

[0167] In the composition of this example, the sulfate content was 0.36 mass% and the boron compound content was 74 mass ppm.

[0168] Note that in the composition of this example, the mass was taken as the total mass of LMO and Li2MoO4. Therefore, when the mass of the composition of this embodiment is added, the sulfate content and the boron content exceed 100 mass% of the mass of the composition of this embodiment.

[0169] Example 4 5 g of Mn3O4 obtained in Synthesis Example 1, 1.456 g of lithium carbonate, 0.258 g of aluminum hydroxide, 0.0226 g of boric acid, and 0.0297 g of lithium molybdate of Synthesis Example 3 were pulverized in a mortar for 20 minutes to obtain a mixed powder.

[0170] The obtained mixed powder was filled into an alumina crucible and fired under the following firing conditions.

[0171] Firing atmosphere: Air flow atmosphere (flow rate: 8 L / min) Firing temperature: 930 °C Firing time: 6 hours Heating rate: 100 °C / hour After firing, the temperature was decreased to 700 °C at a rate of 20 °C / hour, and then annealed by holding at that temperature for 24 hours. After the annealing treatment, the temperature was decreased from 700 °C to room temperature (25 °C) at a rate of 100 °C / hour, and then the fired powder was recovered to obtain a fired powder.

[0172] The fired powder was subjected to a vibrating sieve treatment for 5 minutes using a sieve with an opening of 40 μm, and the powder passing through the sieve was recovered to obtain the powder of this example. The main XRD peaks of the composition of this example are shown below.

[0173]

Table 8

[0174] As a result of XRD measurement and composition analysis, the XRD pattern was equivalent to the XRD pattern consisting of JCPDS card No. 35-782 (LiMn2O4) and No. 53-0670 (Li2MoO4). Also, the composition of this example has the general formula Li 1.09 Mn 1.81 Al 0.10 It was confirmed that the composition is composed of LMO and Li2MoO4 represented by O4.

[0175] The composition of this example had an average secondary particle diameter of 23.1 μm and an average primary particle diameter of 4.9 μm. Also, the content of LMO was 99.3 mass% and the content of Li2MoO4 was 0.7 mass%.

[0176] In the composition of this example, the sulfate content was 0.86 mass% and the boron compound content was 426 mass ppm.

[0177] Note that in the composition of this example, the mass was taken as the total mass of LMO and Li2MoO4. Therefore, when the mass of the composition of this example was added to the mass of the composition of this embodiment, the sulfate content and the boron content exceeded 100 mass%.

[0178] Example 5 A composition of this example was obtained in the same manner as in Example 4, except that the addition amount of lithium molybdate was 0.119 g. The main XRD peaks of the composition of this example are shown below.

[0179]

Table 9

[0180] As a result of XRD measurement and composition analysis, the XRD pattern was equivalent to the XRD pattern consisting of JCPDS card No. 35-782 (LiMn2O4) and No. 53-0670 (Li2MoO4). The composition of this example was confirmed to be a composition consisting of LMO represented by the general formula Li 1.09 Mn 1.81 Al 0.10 O4 and Li2MoO4.

[0181] The composition of this example had an average secondary particle diameter of 18.3 μm and an average primary particle diameter of 4.7 μm. Also, the content of LMO was 97.6 mass% and the content of Li2MoO4 was 2.4 mass%.

[0182] In the composition of this example, the sulfate content was 0.80 mass% and the boron compound content was 421 mass ppm.

[0183] Note that in the composition of this example, the mass was taken as the total mass of LMO and Li2MoO4. Therefore, when the mass of the composition of this embodiment was added, the mass of the composition of this embodiment exceeded 100 mass%.

[0184] Comparative Example 1 The precursor composition obtained in the same manner as in Example 1 was used as the composition of this comparative example.

[0185] The main XRD peaks of the composition of this comparative example are shown below.

[0186]

Table 10

[0187] As a result of XRD measurement and composition analysis, the pattern was equivalent to the XRD pattern composed of JCPDS card No. 35-782 (LiMn2O4) and No. 25-1030 (Li3PO4). The composition of this comparative example had the general formula Li 1.10 Mn 1.84 Mg 0.06 and was a composition composed of LMO represented by O4 and Li3PO4.

[0188] The composition of this comparative example had an average secondary particle diameter of 9.0 μm and an average primary particle diameter of 1.2 μm.

[0189] The composition of this comparative example had an LMO content of 96.3% by mass and an Li3PO4 content of 3.7% by mass.

[0190] Note that in the composition of this comparative example, for convenience, the mass is regarded as the total mass of LMO, Li-Mo composite oxide, and inorganic phosphorus compound. Therefore, the sulfate content and boron content are external numbers to the mass of the composition of this embodiment, and the mass of the composition of this embodiment when these are added may exceed 100% by mass.

[0191] In the composition of this comparative example, the sulfate content was 0.35% by mass and the boron compound content was 1610 ppm by mass.

[0192] Table 11 shows the physical properties of the starting materials of the compositions of the examples and comparative examples, and Table 12 shows the battery performance of the LIBs using the compositions as the positive electrode active materials.

[0193]

Table 11

[0194]

Table 12

[0195] From Table 12, for Comparative Example 1, the compositions of Examples 1 to 5 were excellent in storage characteristics and output characteristics.

Claims

1. A composition comprising a composite oxide containing lithium and molybdenum, and a lithium manganese spinel oxide, and having at least the peaks shown in the following table in a powder X-ray diffraction pattern. 【Table 1】

2. The spinel-type lithium manganese oxide has the general formula Li １＋Ｘ Mn ２－Ｘ―Ｙ M Ｙ O ４ The composition according to claim 1, represented by the formula: (wherein 0.02≦X≦0.20, 0.05≦Y≦0.30, and M is at least one of Mg and Al).

3. The composition according to claim 1 or claim 2, comprising an inorganic phosphorus compound.

4. The composition according to claim 1 or 2, wherein the half width on the (400) plane is more than 0.000° and not more than 0.1°.

5. 3. A method for producing the composition according to claim 1, comprising: a mixing step of mixing a manganese source and a lithium source to obtain an LMO precursor; a calcination step of calcining the LMO precursor obtained in the mixing step; and a step of compounding the LMO obtained in the calcination step with a Li-Mo composite oxide.

6. 3. A method for producing the composition according to claim 1, comprising: a mixing step of mixing a manganese source, a lithium source, and a Li-Mo composite oxide to obtain an LMO precursor; and a calcination step of calcining the LMO precursor.

7. A positive electrode active material for a lithium ion secondary battery comprising the composition according to claim 1 or 2.

8. A positive electrode comprising the positive electrode active material for a lithium ion secondary battery according to claim 7.

9. A lithium ion secondary battery comprising the positive electrode according to claim 8.

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