WO2024225150A1 - 二次電池用正極活物質および二次電池 - Google Patents

二次電池用正極活物質および二次電池 Download PDF

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WO2024225150A1
WO2024225150A1 PCT/JP2024/015360 JP2024015360W WO2024225150A1 WO 2024225150 A1 WO2024225150 A1 WO 2024225150A1 JP 2024015360 W JP2024015360 W JP 2024015360W WO 2024225150 A1 WO2024225150 A1 WO 2024225150A1
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positive electrode
lithium metal
composite oxide
metal composite
active material
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French (fr)
Japanese (ja)
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晋 張
元治 斉藤
光宏 日比野
健祐 名倉
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Panasonic Intellectual Property Management Co Ltd
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Panasonic Intellectual Property Management Co Ltd
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Priority to JP2025516762A priority Critical patent/JPWO2024225150A1/ja
Priority to EP24796903.3A priority patent/EP4704183A1/en
Priority to CN202480028372.7A priority patent/CN121058101A/zh
Publication of WO2024225150A1 publication Critical patent/WO2024225150A1/ja
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This disclosure relates to a positive electrode active material for a secondary battery and a secondary battery.
  • Secondary batteries especially lithium-ion secondary batteries, have high output and high energy density, and are therefore expected to be used in small consumer applications, power storage devices, and as power sources for electric vehicles.
  • a composite oxide of lithium and a transition metal e.g., cobalt
  • cobalt transition metal
  • Patent Document 1 discloses a positive electrode active material containing a lithium transition metal composite oxide having a crystal structure belonging to the space group Fm - 3m and represented by the composition formula Li1 + xNbyMezApO2 (Me is a transition metal including Fe and/or Mn , 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 0.5, 0.25 ⁇ z ⁇ 1, A is an element other than Nb and Me, and 0 ⁇ p ⁇ 0.2, excluding Li1 +pFe1 - qNbqO2 where 0.15 ⁇ p ⁇ 0.3, 0 ⁇ q ⁇ 0.3).
  • Patent Document 1 high capacity is possible by controlling the composition (i.e., adding Nb). However, the effect of improving capacity is insufficient, and there is still room for improvement.
  • one aspect of the present disclosure relates to a positive electrode active material for a secondary battery, comprising a lithium metal composite oxide having a rock-salt type crystal structure that can be assigned to the space group Fm-3m, the lithium metal composite oxide containing at least Li and Mn, and having a D50 in the volume-based cumulative particle size distribution of the lithium metal composite oxide of 0.05 ⁇ m or more and 10 ⁇ m or less.
  • Another aspect of the present disclosure relates to a secondary battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator interposed between the positive electrode and the negative electrode, the positive electrode including the positive electrode active material for secondary batteries.
  • This disclosure makes it possible to realize a secondary battery with high energy density.
  • FIG. 1 is a schematic perspective view of a secondary battery according to an embodiment of the present disclosure, with a portion cut away. 1 is a graph showing particle size distributions of the lithium metal composite oxides used in Examples 7 to 10 and Comparative Example 3.
  • the embodiments of the present disclosure are described using examples, but the present disclosure is not limited to the examples described below.
  • specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present disclosure are obtained.
  • the expression "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less.”
  • any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined as long as the lower limit is not equal to or greater than the upper limit.
  • one of the materials may be selected and used alone, or two or more of the materials may be used in combination.
  • containing includes the terms “containing,” “consists essentially of,” and “consists of.”
  • Secondary batteries include at least lithium ion batteries, non-aqueous electrolyte secondary batteries such as lithium metal secondary batteries, and all-solid-state batteries that use solid electrolytes.
  • the positive electrode active material for secondary batteries includes a lithium metal composite oxide (hereinafter also referred to as "lithium metal composite oxide (Fm)”) having a rock-salt type crystal structure that can be assigned to the space group Fm-3m.
  • the lithium metal composite oxide (Fm) has a crystal structure based on a rock-salt structure that belongs to the space group Fm-3m, and has a crystal structure similar to the rock-salt structure represented by NaCl, for example. In such a crystal structure, oxygen atoms are arranged at the anion site, and Li atoms and metal atoms other than Li can be irregularly arranged at the cation site.
  • the lithium metal composite oxide (Fm) contains at least Li and Mn.
  • the lithium metal composite oxide (Fm) based on the rock salt structure Li 1+x Mn 1-x O 2 is expected to exhibit high capacity.
  • the raw material mixture contains lithium compounds and manganese compounds.
  • lithium metal composite oxide (Fm) when mass-producing lithium metal composite oxide (Fm), it is necessary to synthesize it efficiently by calcining the raw material mixture.
  • the particles of lithium metal composite oxide (Fm) synthesized by calcination are usually very hard and lumpy.
  • the particle size of the lithium metal composite oxide (Fm) synthesized by ball milling tends to be small. As a result, the surface area contributing to the electrode reaction in the positive electrode active material is large, and side reactions also become large. As a result, when used as a positive electrode active material in a secondary battery, the cycle characteristics are likely to deteriorate.
  • the average particle size (meaning the median diameter D50 in the cumulative particle size distribution based on volume) of the lithium metal composite oxide (Fm) is preferably 0.05 ⁇ m or more or 0.1 ⁇ m or more, but it is difficult to control the particle size within the above range when synthesized by ball milling.
  • lithium metal composite oxide (Fm) By pulverizing the lithium metal composite oxide (Fm) synthesized by calcination, lithium metal composite oxide (Fm) having the desired particle size distribution can be obtained, and lithium metal composite oxide (Fm) with an average particle diameter D50 of 0.05 ⁇ m or more can be obtained.
  • this lithium metal composite oxide (Fm) As the positive electrode active material, a secondary battery with high discharge capacity and little deterioration of cycle characteristics can be realized.
  • the lithium metal composite oxide (Fm) has a cumulative particle size distribution based on volume of D50 of 0.05 ⁇ m or more and 10 ⁇ m or less.
  • the particle size distribution D50 can be controlled to the above range by pulverizing the high-hardness lithium metal composite oxide (Fm) obtained by firing the raw material mixture under appropriate conditions. Increasing D50 makes it easier to increase the electrode capacity.
  • D50 is 0.05 ⁇ m or more, preferably 0.1 ⁇ m or more, and more preferably 0.15 ⁇ m or more.
  • D50 may be 0.2 ⁇ m or more.
  • D50 is 10 ⁇ m or less, preferably 1 ⁇ m or less, and more preferably 0.8 ⁇ m or less, 0.6 ⁇ m or less, or 0.5 ⁇ m or less.
  • the upper and lower limits of D50 can be combined in any combination.
  • D90 particle size at which the cumulative volume, calculated from the smallest particle size, is 90% of the total
  • D90 particle size at which the cumulative volume, calculated from the smallest particle size, is 90% of the total
  • the particle size D90 is preferably 1 ⁇ m or more, and more preferably 2 ⁇ m or more.
  • the particle size D90 is preferably 10 ⁇ m or less, and more preferably 8 ⁇ m or less.
  • the upper and lower limits of D90 mentioned above can be combined in any combination.
  • a laser diffraction particle size measuring device e.g., Malvern Panalytical's "Mastersizer 3000"
  • a sample of the positive electrode active material is dispersed in 4 mL of an aqueous solution of sodium hexametaphosphate. Dispersion is performed by ultrasonic treatment for 1 minute. The entire amount of the sample is placed in the device and measured.
  • the concentration of the aqueous solution of sodium hexametaphosphate is 0.02 to 1 mass%.
  • the lithium metal composite oxide (Fm) synthesized by calcination is subjected to a pulverization process using a ball mill or the like, the peak in the volumetric particle size distribution shifts to the smaller particle size side, and the peak in the volumetric particle size distribution splits, and two peaks can be observed.
  • the longer the time required for the pulverization process the higher the peak height on the side with smaller particle sizes and the lower the peak height on the side with larger particle sizes.
  • the average particle diameter (median diameter D50 in the cumulative particle size distribution based on volume) of the lithium metal composite oxide (Fm) can be measured using the lithium metal composite oxide (Fm) particles observed in a scanning electron microscope (SEM) image (hereinafter simply referred to as a "cross-sectional SEM image") of a cross section in the thickness direction of the positive electrode.
  • the particles observed in the cross-sectional SEM image of the positive electrode may be cross-sections of particles.
  • the average particle diameter D50 (and D90) can be determined from the cumulative particle size distribution of 100 or more lithium metal composite oxide (Fm) particles (particle cross-sections) arbitrarily selected from the cross-sectional SEM image. An example of a procedure for determining the average value of D50 from a cross-sectional SEM image is described below.
  • a positive electrode to be measured is prepared.
  • a positive electrode comprises a positive electrode collector and a positive electrode active material layer formed on the surface of the positive electrode collector.
  • Such a positive electrode active material layer and the positive electrode collector are cut simultaneously along the thickness direction of the positive electrode to form a cross section.
  • a thermosetting resin may be filled in the positive electrode active material layer and cured.
  • a cross section sample of the positive electrode active material layer may be obtained by a CP (cross section polisher) method, an FIB (focused ion beam) method, or the like.
  • the positive electrode to be measured is taken from a secondary battery with a depth of discharge (DOD) of 90% or more.
  • the voltage of a battery in a fully charged state corresponds to the end of charge voltage.
  • the voltage of a battery in a fully discharged state corresponds to the end of discharge voltage.
  • a cross-section sample of the positive electrode (positive electrode active material layer) is observed by SEM. Observation by SEM is performed, for example, at a magnification of 500 to 3000 times.
  • the cross-sectional SEM image is taken so that a region having a length of 30 ⁇ m or more (preferably 40 ⁇ m or more) in the surface direction of the positive electrode active material layer is observed.
  • image analysis software e.g., ImageJ
  • image analysis software e.g., ImageJ
  • the cross-sectional SEM image can be binarized so that the lithium metal composite oxide (Fm) particles are black (or white) and the rest are white (or black).
  • elemental analysis may be performed on the cross-sectional SEM image using EDX (energy dispersive X-ray spectroscopy) or EPMA (electron probe microanalyzer).
  • a mapping image of the lithium metal composite oxide (Fm) may then be obtained from the analysis data.
  • a cumulative particle size distribution on a volume basis may be derived and D50 may be calculated based on each of 100 or more arbitrarily selected lithium metal composite oxide (Fm) particles (particle cross sections).
  • the volume-based cumulative particle size distribution obtained from 100 or more lithium metal composite oxide (Fm) particles (particle cross sections) randomly selected from a cross-sectional SEM image will be similar to the volume-based cumulative particle size distribution obtained from the lithium metal composite oxide (Fm) raw material powder of an electrode or the lithium metal composite oxide (Fm) powder separated and recovered from the positive electrode by disassembling a completed battery.
  • the volume-based cumulative particle size distribution of the raw material powder or the powder separated and recovered from the positive electrode can be obtained, for example, by converting the volume-based cumulative particle size distribution measured by a laser diffraction/scattering type particle size distribution measuring device.
  • the lithium metal composite oxide (Fm) may contain an element M other than Li and Mn.
  • Such an element M may be any electropositive element other than hydrogen, and may be a metal element (including so-called metalloid elements).
  • the lithium metal composite oxide (Fm) may be a lithium transition metal composite oxide containing at least three types of metals.
  • the element M may be, for example, at least one element selected from the group consisting of Ti, Fe, Ge, Si, Ga, Ni, Co, Sn, Cu, Nb, Mo, Bi, V, Cr, Y, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ag, Ru, Ta, W, La, Ce, Pr, Gd, Sm, Eu, Yb, Dy, Al, and Er.
  • the lithium metal composite oxide (Fm) may contain any two or more elements selected from the above group as the element M.
  • the lithium metal composite oxide (Fm) contains the element M, it is preferable that the main component of the metal element other than Li is Mn.
  • the number of Mn atoms b in the lithium metal composite oxide (Fm) may be the largest among the number of atoms of metals other than Li in the lithium metal composite oxide (Fm).
  • the number of Mn atoms may be greater than the total number of atoms c of metal elements other than Li and Mn.
  • the ratio (b/c) of the number of Mn atoms b to the number of atoms c of metal elements other than Li and Mn in the lithium metal composite oxide (Fm) is, for example, 1 or more and 15 or less, preferably 1 or more and 12 or less, may be greater than 1 and 12 or less, or may be 2 or more and 12 or less.
  • the lithium metal composite oxide (Fm) preferably contains at least Ti as the element M.
  • the lithium metal composite oxide (Fm) containing Ti as the element M can exhibit a particularly high capacity.
  • Ti can exist in the form of Ti 4+ with an empty d orbital. In that case, it is believed that a highly symmetrical, more stable, and high-capacity rock-salt crystal structure is formed. In addition, it is believed that such a rock-salt structure is less likely to become unstable even after repeated charging and discharging.
  • Mn/Ti When the lithium metal composite oxide (Fm) contains Ti, the ratio of the number of Mn atoms to the number of Ti atoms in the lithium metal composite oxide: Mn/Ti may be 4 or more, 5 or more, or 6 or more, and preferably 7 or more. In addition, Mn/Ti may be 70 or less, 30 or less, and preferably 15 or less.
  • the lithium metal composite oxide (Fm) may contain fluorine (F). Fluorine can substitute oxygen atoms at the anion site in the above crystal structure. This stabilizes the crystal structure and provides a higher capacity even when the lithium metal composite oxide (Fm) is in a Li-excess state. Furthermore, the average discharge potential increases due to the substitution of fluorine atoms.
  • the Li-excess state refers to a state in which the number of Li atoms in the lithium metal composite oxide (Fm) is greater than the total number of atoms of metal elements other than Li.
  • Li-excess lithium metal composite oxide In Li-excess lithium metal composite oxide (Fm), the arrangement of Li in the cation sites is irregular, and the bonding state of Li is varied. Therefore, the voltage distribution associated with Li release is wide. For this reason, it may be difficult to use the tail part on the low potential side of the voltage distribution as capacitance. However, by introducing fluorine atoms, the voltage distribution associated with Li release shifts to the high potential side, making it easier to use the tail part as capacitance. This further increases the available capacity.
  • Fm Li-excess lithium metal composite oxide
  • the lithium metal composite oxide (Fm) may be represented by a composition formula LiaMnbMcOdFe , where 1 ⁇ a ⁇ 1.4, 0.5 ⁇ b ⁇ 0.9, 0 ⁇ c ⁇ 0.4, 1.33 ⁇ d ⁇ 2, 0 ⁇ e ⁇ 0.67 , and 1.7 ⁇ d+e ⁇ 2.2 are satisfied.
  • the lithium metal composite oxide (Fm) containing Ti can be represented by the composition formula Li a Mn b Ti c1 M 2 c2 O d Fe e .
  • M 2 is the element M other than Ti, and 1 ⁇ a ⁇ 1.4, 0.3 ⁇ b ⁇ 0.9, 0 ⁇ c1 ⁇ 0.5, 0 ⁇ c2 ⁇ 0.25, 0 ⁇ e ⁇ 0.7, 1.7 ⁇ d+e ⁇ 2 are satisfied.
  • 1 ⁇ a ⁇ 1.4, 0.5 ⁇ b ⁇ 0.9, 0.02 ⁇ c1 ⁇ 0.4, 0 ⁇ e ⁇ 0.67, 1.7 ⁇ d+e ⁇ 2.2 are satisfied.
  • d+e is often 2 or less, and may be 1.94 or less, 1.9 or less, or 1.8 or less.
  • some of the oxygen atoms in the anion site may be replaced with fluorine atoms. This stabilizes the state of excess Li (a>1) and results in a high capacity.
  • the average discharge potential increases, further increasing the available capacity.
  • the fluorine-free lithium metal composite oxide (Fm) can be represented by a composition formula LiaMnbMcOd , where 1 ⁇ a ⁇ 1.4, 0.5 ⁇ b ⁇ 0.75, 0 ⁇ c ⁇ 0.35, and 1.6 ⁇ d ⁇ 2 are satisfied.
  • the content of the elements that make up the lithium metal composite oxide (Fm) can be measured using an inductively coupled plasma atomic emission spectrometer (ICP-AES), an electron probe microanalyzer (EPMA), or an energy dispersive X-ray analyzer (EDX), etc.
  • ICP-AES inductively coupled plasma atomic emission spectrometer
  • EPMA electron probe microanalyzer
  • EDX energy dispersive X-ray analyzer
  • the lithium metal composite oxide (Fm) synthesized by applying high shear force to the raw material mixture using a stirring device such as a ball mill at the laboratory level has a very large specific surface area.
  • the lithium metal composite oxide (Fm) synthesized by firing even if it is a particle or powder obtained by crushing agglomerated particles, does not have a history due to a high shear force that causes a solid-phase reaction to proceed. Therefore, the specific surface area of the lithium metal composite oxide (Fm) synthesized by firing is, for example, 0.13 m 2 /g or more and less than 13.2 m 2 /g, and may be 6 m 2 /g to 10 m 2 /g.
  • the specific surface area is within the above range, it is advantageous in that the filling rate of the lithium metal composite oxide (Fm) in the positive electrode can be increased and side reactions can be easily suppressed. If the specific surface area is excessively large, the surface state becomes unstable and it may be difficult to suppress side reactions.
  • the specific surface area can be measured using lithium metal composite oxide (Fm) as raw material powder before it becomes a positive electrode, or it can be measured using lithium metal composite oxide (Fm) separated from the positive electrode. Either method will give roughly similar measurement results.
  • the specific surface area of the lithium metal composite oxide (Fm) is measured after taking 0.20 g to 0.25 g of a sample of the lithium metal composite oxide (Fm), placing the sample in a measurement cell consisting of a glass tube for measuring the specific surface area, and drying and degassing the measurement cell. Drying and degassing is performed for at least one hour at a pressure of 6.67 Pa and a temperature of 250°C ⁇ 5°C. The mass of the sample in the measurement cell is then measured to the order of 0.1 mg. The amount of nitrogen adsorption of the sample at a temperature of -196°C is then measured using a specific surface area measuring device.
  • an automatic specific surface area/pore distribution measuring device "Tristar II 3020" manufactured by Shimadzu Corporation is used as the measuring device. From the measurement results of the amount of adsorption, the specific surface area of the lithium metal composite oxide (Fm) is determined by the BET multipoint method in the partial pressure (relative pressure) range of 0.001 to 0.2.
  • the method for producing the lithium metal composite oxide (Fm) is not limited, it is preferable to obtain the lithium metal composite oxide (Fm) by calcining a raw material mixture of elements constituting the lithium metal composite oxide (Fm). Calcination promotes the growth of crystals similar to the rock salt structure belonging to the space group Fm-3m, and a lithium metal composite oxide with a large crystallite size is obtained. The crystallite size may then be controlled to a desired range by performing a pulverization process.
  • the raw materials for the elements that make up the lithium metal composite oxide may be selected from Mn compounds, compounds of element M, lithium compounds, fluorine compounds, titanium compounds, and the like.
  • the types and mixing ratios of the raw materials may be appropriately selected according to the desired composition described above.
  • Mn compounds include Mn oxides such as MnO2 and Mn2O3 , and manganese salts such as lithium manganate.
  • compounds of element M include M salts such as oxides, oxyfluorides, and hydroxides.
  • lithium compounds include lithium oxides such as Li2O , and lithium salts such as lithium carbonate ( Li2CO3 ), LiOH, and lithium manganate ( LiMnO2 ).
  • fluorine compounds include fluorine salts such as lithium fluoride (LiF).
  • titanium compounds include titanium oxides such as TiO2 , and titanium salts such as lithium titanate.
  • the atmosphere in which the raw material mixture is fired may vary depending on the composition of the lithium metal composite oxide (Fm) to be obtained and the type of raw material, but may be, for example, an oxidizing atmosphere (e.g., in air or in the presence of oxygen). It is desirable to circulate the atmospheric gas.
  • Fm lithium metal composite oxide
  • the firing temperature of the raw material mixture may vary depending on the composition of the lithium metal composite oxide (Fm) to be obtained and the type of raw material, but may be, for example, 700°C or higher, and is preferably 900°C or higher and 1300°C or lower.
  • the aggregated particles may be pulverized to the desired aspect ratio or circularity.
  • a stirring device capable of applying a large shear force to the particles such as a ball mill or a bead mill, may be used.
  • the raw material mixture may be sintered while stirring the raw material mixture.
  • the raw material mixture may be sintered while stirring using a sintering furnace equipped with a fluidized bed.
  • particles that are nearly spherical may be used as part of the raw material.
  • a manganese compound or a manganese titanium composite compound that is nearly spherical may be used as the raw material.
  • the secondary battery includes, for example, a positive electrode, a negative electrode, an electrolyte, and a separator as described below.
  • the positive electrode comprises a positive electrode current collector and a positive electrode mixture layer formed on the surface of the positive electrode current collector and containing a positive electrode active material.
  • the positive electrode for secondary batteries described above is used as the positive electrode.
  • the positive electrode mixture layer can be formed, for example, by applying a positive electrode slurry in which a positive electrode mixture containing a positive electrode active material, a binder, etc. is dispersed in a dispersion medium to the surface of the positive electrode current collector and drying it. The coating film after drying may be rolled as necessary.
  • the positive electrode mixture layer may be formed on one surface of the positive electrode current collector or on both surfaces.
  • the positive electrode mixture layer contains a positive electrode active material as an essential component, and may contain optional components such as a binder, a thickener, a conductive agent, and a positive electrode additive.
  • a binder such as a binder, a thickener, a conductive agent, and a positive electrode additive.
  • Known materials can be used as the binder, thickener, and conductive agent.
  • the positive electrode active material includes the above-mentioned lithium metal composite oxide (Fm) having a crystal structure similar to the rock salt structure belonging to the space group Fm-3m.
  • the lithium metal composite oxide (Fm) is, for example, a secondary particle formed by the aggregation of multiple primary particles.
  • the particle size of the primary particles is generally 0.01 ⁇ m to 1 ⁇ m.
  • the lithium metal composite oxide (Fm) may be mixed with other known lithium metal oxides to be used as the positive electrode active material.
  • other known lithium metal oxides include lithium transition metal composite oxides such as LiaCoO2 , LiaNiO2 , LiaMnO2 , LiaCobNi1 - bO2 , LiaCobM1 -bOc , LiaNi1 - bMbOc , LiaMn2O4 , LiaMn2 - bMbO4 , LiMePO4 , and Li2MePO4F .
  • M is at least one selected from the group consisting of Na, Mg, Sc , Y , Mn , Fe , Co , Ni, Cu, Zn, Al, Cr, Pb, Sb, and B.
  • Me contains at least a transition element (e.g., contains at least one selected from the group consisting of Mn, Fe, Co, and Ni), where 0 ⁇ a ⁇ 1.2, 0 ⁇ b ⁇ 0.9, and 2.0 ⁇ c ⁇ 2.3.
  • the value a which indicates the molar ratio of lithium, increases or decreases with charge and discharge.
  • the shape and thickness of the positive electrode current collector can be selected from the same shape and range as the negative electrode current collector.
  • Examples of materials for the positive electrode current collector include stainless steel, aluminum, aluminum alloy, and titanium.
  • the negative electrode may, for example, include a negative electrode current collector and include a negative electrode active material layer formed on the surface of the negative electrode current collector.
  • the negative electrode active material layer can be formed, for example, by applying a negative electrode slurry in which a negative electrode mixture containing a negative electrode active material, a binder, etc. is dispersed in a dispersion medium to the surface of the negative electrode current collector and drying it. The coating film after drying may be rolled as necessary. That is, the negative electrode active material may be a mixture layer.
  • a lithium metal foil or a lithium alloy foil may be attached to the negative electrode current collector.
  • the negative electrode active material layer may be formed on one surface of the negative electrode current collector or on both surfaces.
  • the negative electrode active material layer contains a negative electrode active material as an essential component, and may contain a binder, a conductive agent, a thickener, etc. as optional components. Known materials can be used as the binder, conductive agent, and thickener.
  • Anode active materials include materials that electrochemically absorb and release lithium ions, lithium metal, and lithium alloys. Carbon materials and alloy-based materials are used as materials that electrochemically absorb and release lithium ions. Examples of carbon materials include graphite, graphitizable carbon (soft carbon), and non-graphitizable carbon (hard carbon). Among these, graphite is preferred because of its excellent charge/discharge stability and low irreversible capacity. Alloy-based materials include those that contain at least one metal that can form an alloy with lithium. For example, a lithium ion conductive phase and a composite material in which a silicon phase is dispersed in the lithium ion conductive phase may be used.
  • a non-porous conductive substrate such as metal foil
  • a porous conductive substrate such as a mesh, net, or punched sheet
  • materials for the negative electrode current collector include stainless steel, nickel, nickel alloys, copper, and copper alloys.
  • the electrolyte may be a liquid electrolyte (electrolytic solution), a gel electrolyte, or a solid electrolyte.
  • the liquid electrolyte is, for example, an electrolytic solution containing a non-aqueous solvent and a salt dissolved in the non-aqueous solvent.
  • the concentration of the salt in the electrolytic solution is, for example, 0.5 mol/L or more and 2 mol/L or less.
  • the electrolytic solution may contain a known additive.
  • the gel electrolyte contains a salt and a matrix polymer, or a salt, a non-aqueous solvent, and a matrix polymer.
  • a matrix polymer for example, a polymer material that absorbs the non-aqueous solvent and gels is used. Examples of the polymer material include fluororesin, acrylic resin, polyether resin, and polyethylene oxide.
  • solid electrolyte for example, a material known in all-solid-state lithium-ion secondary batteries (e.g., oxide-based solid electrolyte, sulfide-based solid electrolyte, halide-based solid electrolyte, etc.) is used.
  • oxide-based solid electrolyte e.g., oxide-based solid electrolyte, sulfide-based solid electrolyte, halide-based solid electrolyte, etc.
  • a liquid non-aqueous electrolyte is prepared by dissolving a salt in a non-aqueous solvent.
  • the salt is an electrolyte salt that ionizes in the electrolyte, and may include, for example, a lithium salt.
  • the electrolyte may include various additives.
  • the electrolyte is usually used in liquid form, but may also have its fluidity restricted by a gelling agent or the like.
  • non-aqueous solvents examples include cyclic carbonates, chain carbonates, cyclic carboxylates, and chain carboxylates.
  • cyclic carbonates examples include propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC).
  • chain carbonates include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).
  • cyclic carboxylates include ⁇ -butyrolactone (GBL), and ⁇ -valerolactone (GVL).
  • chain carboxylates examples include methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), and ethyl propionate (EP).
  • the non-aqueous solvents may be used alone or in combination of two or more.
  • lithium salts of chlorine-containing acids LiClO4 , LiAlCl4 , LiB10Cl10 , etc.
  • lithium salts of fluorine-containing acids LiPF6 , LiPF2O2 , LiBF4 , LiSbF6 , LiAsF6 , LiCF3SO3 , LiCF3CO2 , etc.
  • lithium salts of fluorine-containing acid imides LiN( FSO2 ) 2 , LiN( CF3SO2 ) 2 , LiN ( CF3SO2 ) (C4F9SO2 ), LiN( C2F5SO2 ) 2 , etc. )
  • lithium halides LiCl, LiBr, LiI, etc.
  • the lithium salt may be used alone or in combination of two or more kinds.
  • the concentration of the lithium salt in the electrolyte may be 1 mol/L or more and 2 mol/L or less, or 1 mol/L or more and 1.5 mol/L or less.
  • the lithium salt concentration is not limited to the above.
  • a separator is interposed between the positive electrode and the negative electrode.
  • the separator has high ion permeability and has appropriate mechanical strength and insulation.
  • a microporous thin film, a woven fabric, a nonwoven fabric, etc. can be used.
  • polyolefin such as polypropylene and polyethylene is preferable.
  • a secondary battery is a structure in which an electrode group in which positive and negative electrodes are wound with a separator interposed therebetween and a non-aqueous electrolyte are housed in an exterior body.
  • a wound type electrode group other types of electrode groups may be used, such as a stacked type electrode group in which positive and negative electrodes are stacked with a separator interposed therebetween.
  • the secondary battery may be in any type, such as a cylindrical type, a square type, a coin type, a button type, a laminate type, etc.
  • FIG. 1 is a schematic perspective view, with a portion cut away, of a prismatic secondary battery according to an embodiment of the present disclosure.
  • the battery includes a bottomed rectangular battery case 4, an electrode group 1 and a non-aqueous electrolyte (not shown) housed in the battery case 4.
  • the electrode group 1 includes a long strip-shaped negative electrode, a long strip-shaped positive electrode, and a separator interposed therebetween.
  • the negative electrode current collector of the negative electrode is electrically connected to a negative electrode terminal 6 provided on a sealing plate 5 via a negative electrode lead 3.
  • the negative electrode terminal 6 is insulated from the sealing plate 5 by a resin gasket 7.
  • the positive electrode current collector of the positive electrode is electrically connected to the back surface of the sealing plate 5 via a positive electrode lead 2.
  • the positive electrode is electrically connected to the battery case 4, which also serves as a positive electrode terminal.
  • the periphery of the sealing plate 5 is fitted into the open end of the battery case 4, and the fitting portion is laser welded.
  • the sealing plate 5 has an injection hole for the non-aqueous electrolyte, which is closed by a seal plug 8 after injection.
  • the structure of the secondary battery may be cylindrical, coin, button, or the like, with a metal battery case, or may be a laminated battery with a battery case made of a laminate sheet that is a laminate of a barrier layer and a resin sheet.
  • the type, shape, etc. of the secondary battery are not particularly limited.
  • the lithium metal composite oxide has a rock-salt type crystal structure that can be assigned to the space group Fm-3m, The lithium metal composite oxide contains at least Li and Mn, The lithium metal composite oxide has a volume-based cumulative particle size distribution D50 of 0.05 ⁇ m or more and 10 ⁇ m or less.
  • Technique 2 2. The positive electrode active material for a secondary battery according to claim 1, wherein a ratio b/c of the number of Mn atoms b to the number of atoms c of metal elements other than Li and Mn in the lithium metal composite oxide is 1 or more and 15 or less.
  • Technique 3 3.
  • the lithium metal composite oxide is represented by the composition formula Li a Mn b Mc O d Fe ,
  • M contains at least one element other than Li and Mn, and satisfies 1 ⁇ a ⁇ 1.4, 0.5 ⁇ b ⁇ 0.9, 0 ⁇ c ⁇ 0.4, 1.33 ⁇ d ⁇ 2, 0 ⁇ e ⁇ 0.67, and 1.7 ⁇ d+e ⁇ 2.
  • the lithium metal composite oxide contains at least Ti as the M.
  • a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator interposed between the positive electrode and the negative electrode;
  • the positive electrode of the secondary battery includes the positive electrode active material for the secondary battery according to any one of the first to seventh aspects.
  • the obtained lithium metal composite oxide (Fm) aggregate particles were pulverized under various conditions using a planetary ball mill to obtain lithium metal composite oxides (Fm) with different average particle sizes D50.
  • Example 1 the aggregate particles of the lithium metal composite oxide (Fm) were put into a planetary ball mill (Fritsch Premium-Line P7, rotation speed: 300 rpm, container: 45 mL, ball: ⁇ 3 mm ZrO2 ball) and treated in an air atmosphere at room temperature for 1 hour.
  • the ball mill treatment time was changed from 1 hour in Example 1 to 2 hours, 3 hours, 6 hours, 12 hours, and 24 hours, respectively.
  • Example 7 the rotation speed of the planetary ball mill was changed to 150 rpm.
  • the ball mill processing time was 3 hours in Example 7, 6 hours in Example 8, 12 hours in Example 9, and 24 hours in Example 10.
  • the particle size distribution of the lithium metal composite oxide (Fm) after the pulverization process was measured using a laser diffraction/scattering particle size measuring device, and the average particle size D50 and particle size D90 at which the cumulative particle volume was 50% and 90%, respectively, were determined.
  • An aqueous solution of sodium hexametaphosphate was used as the dispersion medium.
  • the X-ray diffraction pattern of the lithium metal composite oxide (Fm) after the crushing process was measured and analyzed.
  • the number and peak positions of the XRD peaks confirmed that the rock salt type crystal structure can be assigned to the space group Fm-3m.
  • the composition of the lithium metal composite oxide (Fm) in all of Examples 1 to 10 was identified as Li 1.21 Mn 0.61 Ti 0.175 O 1.78 .
  • the obtained lithium metal composite oxide (Fm), acetylene black, and polyvinylidene fluoride were mixed in a solid content mass ratio of 7:2:1, and a positive electrode slurry was prepared using N-methyl-2-pyrrolidone (NMP) as a dispersion medium.
  • NMP N-methyl-2-pyrrolidone
  • the positive electrode slurry was applied onto a positive electrode current collector made of aluminum foil, and the coating was dried and compressed, and then cut to the specified electrode size to obtain a positive electrode.
  • a non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt to a mixed solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a predetermined volume ratio.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DMC dimethyl carbonate
  • test cell A test cell was prepared using the above positive electrode and a negative electrode counter electrode made of lithium metal foil.
  • the above positive electrode and the negative electrode counter electrode were arranged opposite each other via a separator to form an electrode body, and the electrode body was housed in a coin-shaped outer can. After an electrolyte was injected into the outer can, the outer can was sealed to obtain a coin-shaped test secondary battery.
  • Li 2 MnO 4 having a spinel structure and an average particle diameter D50 of 15 to 17 ⁇ m was prepared as the positive electrode active material, and acetylene black and polyvinylidene fluoride were mixed with this in a solid content mass ratio of 7:2:1, and a positive electrode slurry was prepared using N-methyl-2-pyrrolidone (NMP) as a dispersion medium.
  • NMP N-methyl-2-pyrrolidone
  • the composition of the lithium metal composite oxide (Fm) was Li 1.21 Mn 0.61 Ti 0.175 O 1.78 , and that it was a rock salt type crystal structure that can be assigned to the space group Fm-3m.
  • This lithium metal composite oxide (Fm) powder was mixed with acetylene black and polyvinylidene fluoride in a solid content mass ratio of 7:2:1, and N-methyl-2-pyrrolidone (NMP) was used as a dispersion medium to prepare a positive electrode slurry.
  • NMP N-methyl-2-pyrrolidone
  • the average particle diameters D50 and D90 of the resulting lithium composite oxide (Fm) powder were measured in the same manner as in Example 1.
  • the average particle diameter D50 was 0.83 ⁇ m, and D90 was 20 ⁇ m.
  • measurement and analysis of the X-ray diffraction pattern confirmed that the resulting lithium composite oxide (Fm) had a rock-salt type crystal structure that could be assigned to the space group Fm-3m.
  • Table 1 The evaluation results are shown in Table 1.
  • Table 1 the discharge capacity C1 value of each secondary battery is shown together with the average particle diameters D50 and D90 of the positive electrode active material (lithium metal composite oxide (Fm)) used.
  • A1 to A10 correspond to Examples 1 to 10, respectively, and B1 and B2 correspond to Comparative Examples 1 and 2, respectively.
  • FIG. 2 shows the volumetric particle size distribution and cumulative particle size distribution of the lithium metal composite oxide (Fm) synthesized in Examples 7 to 10 and Comparative Example 3.
  • B3 corresponds to the comparative example.
  • the lithium metal composite oxide of Comparative Example 3 (B3) which was synthesized by ball mill processing without carrying out a sintering process of the raw material mixture, has a particle size distribution in the range exceeding 10 ⁇ m, and the particle size distribution is broad.
  • D90 is larger than that of the lithium metal composite oxides of Examples 1 to 10 synthesized by sintering.
  • the positive electrode active material for secondary batteries according to the present disclosure can provide secondary batteries with high energy density.
  • the secondary batteries according to the present disclosure are useful as main power sources for mobile communication devices, portable electronic devices, etc.

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PCT/JP2024/015360 2023-04-28 2024-04-18 二次電池用正極活物質および二次電池 Ceased WO2024225150A1 (ja)

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