WO2018221263A1 - リチウムイオン二次電池用正極活物質複合体及びこれを用いた二次電池、並びにリチウムイオン二次電池用正極活物質複合体の製造方法 - Google Patents
リチウムイオン二次電池用正極活物質複合体及びこれを用いた二次電池、並びにリチウムイオン二次電池用正極活物質複合体の製造方法 Download PDFInfo
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- 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
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- 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
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- H01M4/64—Carriers or collectors
- H01M4/66—Selection of materials
- H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
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- H01M4/64—Carriers or collectors
- H01M4/70—Carriers or collectors characterised by shape or form
- H01M4/80—Porous plates, e.g. sintered carriers
- H01M4/806—Nonwoven fibrous fabric containing only fibres
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- H—ELECTRICITY
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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- 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
- the present invention relates to a positive electrode active material composite for a lithium ion secondary battery having a layered rock salt structure, a lithium ion secondary battery including this as a positive electrode material and having excellent high-temperature cycle characteristics, and a lithium ion secondary having a layered rock salt structure.
- the present invention relates to a method for producing a positive electrode active material composite for a secondary battery.
- lithium composite oxide has been used as a positive electrode active material capable of constituting a high output and high capacity lithium ion secondary battery.
- a lithium composite oxide has a layered crystal structure in which a lithium atomic layer and a transition metal atomic layer are alternately stacked via an oxygen atomic layer, and one lithium atom is included per one atom of the transition metal. It is also known to have a so-called layered rock salt structure.
- a lithium ion secondary battery using such a lithium composite oxide as a positive electrode active material charging / discharging is performed as lithium ions are desorbed and inserted into the lithium composite oxide, but usually the charge / discharge cycle is repeated.
- the battery capacity may be significantly reduced. This is considered to be caused by the fact that the transition metal component of the lithium composite oxide is eluted into the electrolytic solution during charging, so that the crystal structure is easily collapsed. In particular, the higher the temperature, the greater the amount of transition metal elution and the greater the effect on cycle characteristics.
- the transition metal component of the lithium composite oxide may elute into the surrounding electrolyte, which may reduce the thermal stability and impair safety.
- Patent Document 1 primary particles having an average particle diameter of 1 ⁇ m to 8 ⁇ m are aggregated to form secondary particles having an average particle diameter of 5 ⁇ m to 30 ⁇ m, and the porosity of the secondary particles is 30% or less.
- a lithium composite oxide is disclosed.
- Patent Document 2 discloses a lithium composite oxide having a true density of 4.40 to 4.80 g / cm 3 and having a high volumetric energy density and having appropriate voids in the positive electrode active material.
- an electrode active material having a lithium composite oxide of a core part and a lithium composite oxide of a shell part having a composition different from that of the core part is also described.
- the subject of this invention is providing the positive electrode active material composite for lithium ion secondary batteries which can improve a high temperature cycling characteristic effectively, when it uses as a positive electrode active material of a lithium ion secondary battery. .
- the present inventors have found that the lithium composite oxide particles and the lithium composite oxide secondary particles only on the surface of the lithium composite oxide secondary particles made of specific composite oxide particles.
- a specific lithium-based polyanion particle having a specific mass ratio when used as a positive electrode material of a lithium ion secondary battery, the reaction with the electrolytic solution is effectively suppressed and applied many times. It has been found that a positive electrode active material composite for a lithium ion secondary battery that does not cause a decrease in output even after a charge / discharge cycle is obtained.
- M 2 is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, S
- lithium composite oxide secondary particles (A) composed of one or more lithium composite oxide particles represented by the following formula (III) or (III) ′: Li g Mn h Fe i M 3 z PO 4 (III) (In the formula (III), M 3 represents Co, Ni, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd.
- a lithium-based polyanion particle (B) having carbon (c) supported on the surface thereof and a lithium composite oxide particle are combined,
- the amount of carbon (c) supported on the surface of the lithium-based polyanion particle (B) is 0.1% by mass or more and less than 18% by mass in 100% by mass of the lithium-based polyanion particle (B),
- the lithium polyanion particles (B) have an average particle size of 50 to 200 nm, Lithium having a mass ratio ((A) :( B)) of 95: 5 to 65
- the positive electrode active material composite for a lithium ion secondary battery of the present invention in the lithium ion secondary battery obtained by preventing the collapse of the crystal structure while using a layered rock salt structure and using this as a positive electrode material The high-temperature cycle characteristics can be effectively enhanced.
- lithium composite oxide secondary particles (A) composed of one or more lithium composite oxide particles represented by the following formula (III) or (III) ′: Li g Mn h Fe i M 3 z PO 4 (III) (In the formula (III), M 3 represents Co, Ni, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd.
- a lithium-based polyanion particle (B) having carbon (c) supported on the surface thereof and a lithium composite oxide particle are combined,
- the amount of carbon (c) supported on the surface of the lithium-based polyanion particle (B) is 0.1% by mass or more and less than 18% by mass in 100% by mass of the lithium-based polyanion particle (B),
- the lithium polyanion particles (B) have an average particle size of 50 to 200 nm,
- Lithium nickel composite oxide (so-called Li—Ni—Co—Mn oxide, hereinafter referred to as “NCM composite oxide”) particles represented by the above formula (I), and the above formula (II)
- the lithium nickel composite oxide (so-called Li—Ni—Co—Al oxide, hereinafter referred to as “NCA composite oxide”) particles are all particles having a layered rock salt structure.
- M 1 in the above formula (I) is Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb
- Ni, Co, and Mn are known to have excellent electron conductivity and contribute to battery capacity and output characteristics. From the viewpoint of cycle characteristics, it is preferable that a part of the transition element is substituted with another metal element M 1 . By substituting with these metal elements M 1 , the crystal structure of the NCM-based composite oxide represented by the formula (I) is stabilized. It is considered that the cycle characteristics can be realized.
- NCM composite oxide represented by the above formula (I) examples include LiNi 0.33 Co 0.33 Mn 0.34 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , Examples include LiNi 0.2 Co 0.4 Mn 0.4 O 2 , LiNi 0.33 Co 0.31 Mn 0.33 Mg 0.03 O 2 , and LiNi 0.33 Co 0.31 Mn 0.33 Zn 0.03 O 2 .
- LiNi 0.33 A composition having a small amount of Ni, such as Co 0.33 Mn 0.34 O 2 and LiNi 0.33 Co 0.31 Mn 0.33 Mg 0.03 O 2, is preferable.
- Li—NCM composite oxide particles represented by the above formula (I) are composed of a core-shell structure lithium composite oxide having a core portion (inside) and a shell portion (surface layer portion).
- Material secondary particles (A) Li-NCM composite oxide secondary particles (A) may be formed.
- the Li-NCM composite oxide secondary particles (A) formed with this core-shell structure it is easy to elute into the electrolyte and easily release oxygen that adversely affects safety, or a solid
- Li-NCM composite oxide particles having a high Ni concentration that easily react with the solid electrolyte are arranged in the core portion, and Li-NCM composite oxide particles having a low Ni concentration are arranged in the shell portion in contact with the electrolytic solution. Therefore, it is possible to further improve the suppression of deterioration of cycle characteristics and the securing of safety.
- the core part may be a single phase or may be composed of two or more phases having different compositions.
- the core part is composed of two or more phases
- a structure in which a plurality of phases are concentrically stacked and laminated, or a structure in which the composition changes transitionally from the surface of the core part toward the center part may be used.
- the shell part should just be formed in the outer side of a core part, may be 1 phase like a core part, and may be comprised by 2 or more phases from which a composition differs.
- the core portion )-(Shell part) is, for example, (LiNi 0.8 Co 0.1 Mn 0.1 O 2 )-(LiNi 0.2 Co 0.4 Mn 0.4 O 2 ), (LiNi 0.8 Co 0.1 Mn 0.1 O 2 )-(LiNi 1/3 Co 1 / 3 Mn 1/3 O 2), or (LiNi 0.8 Co 0.1 Mn 0.1 O 2) - (LiNi 0.33 Co 0.31 Mn 0.33 Mg 0.03 O 2) consisting of such particles.
- the Li—NCM composite oxide particles represented by the above formula (I) may be coated with a metal oxide, a metal fluoride, or a metal phosphate.
- a metal oxide e.g., a metal oxide represented by the above formula (I)
- metal fluoride e.g., a metal fluoride
- metal phosphate e.g., a metal phosphate
- Such coatings CeO 2, SiO 2, MgO , Al 2 O 3, ZrO 2, TiO 2, ZnO, RuO 2, SnO 2, CoO, Nb 2 O 5, CuO, V 2 O 5, MoO 3,
- La 2 O 3 , WO 3 , AlF 3 , NiF 2 , MgF 2 , Li 3 PO 4 , Li 4 P 2 O 7 , LiPO 3 , Li 2 PO 3 F, and LiPO 2 F 2 Two or more kinds, or these composites can be used.
- the average particle diameter of the primary particles of the NCM composite oxide represented by the above formula (I) is preferably 500 nm or less, and more preferably 300 nm or less.
- the lower limit of the average particle size of the primary particles is not particularly limited, but is preferably 50 nm or more from the viewpoint of handling.
- the average particle diameter of the NCM composite oxide secondary particles (A) formed by aggregation of the primary particles is preferably 25 ⁇ m or less, more preferably 20 ⁇ m or less.
- the average particle size of the secondary particles is 25 ⁇ m or less, a battery having excellent high-temperature cycle characteristics can be obtained.
- the lower limit of the average particle size of the secondary particles is not particularly limited, but is preferably 1 ⁇ m or more and more preferably 5 ⁇ m or more from the viewpoint of handling.
- the average particle size means an average value of measured values of the particle size (length of major axis) of several tens of particles in observation using an SEM or TEM electron microscope.
- the NCM-based composite oxide secondary particles (A) include only primary particles formed from secondary particles, and include lithium-based polyanion particles (B) and carbon derived from cellulose nanofibers ( It does not contain other components such as c1) or carbon derived from a water-soluble carbon material (c2).
- the primary that forms the core portion The average particle size as particles is preferably 50 nm to 500 nm, more preferably 50 nm to 300 nm.
- the average particle size of the core part formed by aggregation of the primary particles is preferably 1 ⁇ m to 25 ⁇ m, more preferably 1 ⁇ m to 20 ⁇ m.
- the average particle size as the primary particles of the Li—NCM composite oxide particles constituting the shell portion covering the surface of the core portion is preferably 50 nm to 500 nm, more preferably 50 nm to 300 nm.
- the layer thickness of the shell part formed by aggregation of such primary particles is preferably 0.1 ⁇ m to 5 ⁇ m, more preferably 0.1 ⁇ m to 2.5 ⁇ m.
- the internal porosity of the secondary particles (A) composed of the NCM composite oxide represented by the above formula (I) is determined by the expansion of the NCM composite oxide accompanying the insertion of lithium ions within the internal voids of the secondary particles. From the viewpoint of allowing it, 4 to 12% by volume is preferable in 100% by volume of the secondary particles of the NCM composite oxide, and 5 to 10% by volume is more preferable.
- M 2 in the above formula (II) is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi. And one or more elements selected from Ge.
- the NCA-based complex oxide represented by the above formula (II) is further superior in battery capacity and output characteristics than the NCM-based complex oxide represented by the formula (I).
- the NCA-based composite oxide represented by the above formula (II) include LiNi 0.33 Co 0.33 Al 0.34 O 2 , LiNi 0.8 Co 0.1 Al 0.1 O 2 , LiNi 0.8 Co 0.15 Al 0.03 Mg 0.03 O, for example. 2 , LiNi 0.8 Co 0.15 Al 0.03 Zn 0.03 O 2 and the like. Of these, LiNi 0.8 Co 0.15 Al 0.03 Mg 0.03 O 2 is preferable.
- the Li—NCA composite oxide particles represented by the above formula (II) may be coated with a metal oxide, a metal fluoride, or a metal phosphate.
- a metal oxide e.g., a metal oxide, a metal fluoride, or a metal phosphate.
- the metal components Ni, Al, Co from the Li—NCA composite oxide particles to the electrolyte solution.
- the elution of M 2 can be suppressed.
- Such coatings CeO 2, SiO 2, MgO , Al 2 O 3, ZrO 2, TiO 2, ZnO, RuO 2, SnO 2, CoO, Nb 2 O 5, CuO, V 2 O 5, MoO 3,
- La 2 O 3 , WO 3 , AlF 3 , NiF 2 , MgF 2 , Li 3 PO 4 , Li 4 P 2 O 7 , LiPO 3 , Li 2 PO 3 F, and LiPO 2 F 2 Two or more kinds, or these composites can be used.
- the internal porosity of the secondary particles is the same as that of the NCM composite oxide. That is, the average particle size of the primary particles of the NCA-based composite oxide represented by the above formula (II) is preferably 500 nm or less, more preferably 300 nm or less, and the NCA-based composite oxide composed of the primary particles.
- the average particle diameter of the secondary particles (A) is preferably 25 ⁇ m or less, more preferably 20 ⁇ m or less.
- the internal porosity of the NCA-based composite oxide secondary particles (A) composed of the NCA-based composite oxide represented by the above formula (II) is 4 to 12% by volume in 100% of the volume of the secondary particles. 5 to 10% by volume is more preferable.
- the lithium composite oxide secondary particles (A) of the present invention may contain both the NCM composite oxide represented by the above formula (I) and the NCA composite oxide represented by the above formula (II). Good.
- the mixed state forms secondary particles in which the primary particles of the NCM composite oxide represented by the above formula (I) and the primary particles of the NCA composite oxide represented by the above formula (II) coexist.
- secondary particles composed only of the NCM composite oxide represented by the above formula (I) and secondary particles composed only of the NCA composite oxide represented by the above formula (II) are mixed. Further, secondary particles in which the primary particles of the NCM composite oxide represented by the above formula (I) and the primary particles of the NCA composite oxide represented by the above formula (II) coexist.
- the ratio (mass of NCM type complex oxide and NCA type complex oxide when NCM type complex oxide represented by said formula (I) and NCA type complex oxide represented by said formula (II) coexist. %) May be adjusted as appropriate according to the required battery characteristics. For example, when importance is attached to the rate characteristics, it is preferable to increase the proportion of the NCM composite oxide represented by the above formula (I). Specifically, the NCM composite oxide and the NCA composite oxide are preferred.
- the proportion of the NCA-based composite oxide represented by the above formula (II) Specifically, for example, the NCM-based composite oxide and the NCA-based oxide are used.
- the secondary particles (A) composed of the NCM composite oxide represented by the above formula (I) and / or the NCA composite oxide represented by the above formula (II), NCM composite oxide particles and Since the lithium-based polyanion particles (B) or the NCA-based composite oxide particles and the lithium-based polyanion particles (B) are combined so as to cover the surface of the secondary particles, the NCM-based composite oxide The elution of the metal element contained in the particles or the NCA-based composite oxide particles can be suppressed.
- the lithium-based polyanion particle (B) is represented by the above formula (III) or (III) ′, and the former is a Li-containing particle, while the latter is a particle not containing Li, but both have an olivine structure.
- the lithium-based polyanion particle (B) represented by the formula (III) ′ has properties very similar to those of the lithium-based polyanion particle (B) represented by the formula (III) and has the same effect. Therefore, these particles including the particles represented by the formula (III) ′ are collectively referred to as “lithium-based polyanion particles (B)”.
- M 3 represents Co, Ni, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd.
- g, h, i, and z are 0 ⁇ g ⁇ 1.2, 0 ⁇ h ⁇ 1.2, 0 ⁇ i ⁇ 1.2, and 0 ⁇ z ⁇ 0.3.
- h ′, i ′, and z ′ in the above formula (III) ′ are 0 ⁇ h ′ ⁇ 1.2, 0 ⁇ i ′ ⁇ 1.2, 0 ⁇ z ′ ⁇ 0.3, and h ′.
- the number satisfying + i ′ ⁇ 0 and satisfying (Mn valence) ⁇ h ′ + (Fe valence) ⁇ i ′ + (M 3 valence) ⁇ z ′ 3 is shown.
- the lithium-based polyanion particles (B) represented by the above formula (III) 0.5 ⁇ g ⁇ 1.2 is preferable from the viewpoint of the average discharge voltage of the positive electrode active material composite for a lithium ion secondary battery, 0.6 ⁇ g ⁇ 1.1 is more preferable, and 0.65 ⁇ g ⁇ 1.05 is more preferable.
- the polyanion particle (B) represented by the formula (III) ′ is preferably 0.5 ⁇ h ⁇ 1.2, more preferably 0.6 ⁇ h ⁇ 1.1, and 0 More preferably, 65 ⁇ h ⁇ 1.05.
- the polyanion particle (B) represented by the formula (III) ′ is preferably 0.5 ⁇ h ′ ⁇ 1.2, and more preferably 0.6 ⁇ h ′ ⁇ 1.1. .
- lithium-based polyanion particles represented by the above formula (III) or (III) ′ having different compositions have a core-shell structure having a core part (inside) and a shell part (surface layer part).
- Lithium-based polyanion particles (B) may be formed.
- a lithium-based polyanion having a high Mn content that easily elutes from the lithium-based polyanion particles (B) into the electrolyte solution is disposed in the core portion.
- the shell part in contact with the electrolyte contains a lithium polyanion with a low Mn content, or a lithium polyanion with a high Co content, which is highly toxic to the human body and the environment, is placed in the core part to contact the electrolyte. Since it is possible to arrange a lithium-based polyanion having a low Co content in the part, it is possible to further improve the suppression of cycle characteristics due to the lithium-based polyanion particles and the securing of safety.
- the core part may be a single phase or may be composed of two or more phases having different compositions.
- the core part is composed of two or more phases
- a structure in which a plurality of phases are concentrically stacked may be used, or a structure in which the composition changes transitionally from the surface of the core part toward the center part may be used.
- the shell part should just be formed in the outer side of a core part, may be 1 phase like a core part, and may be comprised by 2 or more phases from which a composition differs.
- (core part)-(shell part) is, for example, (LiMnPO 4 )-(LiFePO 4 ), (LiCoPO 4 )-( Examples thereof include particles made of LiNiPO 4 ), (LiMnPO 4 ) — (LiNiPO 4 ), (LiCoPO 4 ) — (LiFePO 4 ), (LiMn 0.5 Co 0.5 PO 4 ) — (LiFePO 4 ), and the like.
- the average particle diameter of the lithium-based polyanion particles (B) represented by the above formula (III) or (III) ′ is intimately combined with the lithium composite oxide particles on the surface of the lithium composite oxide secondary particles (A). From the viewpoint of conversion, the thickness is 50 to 200 nm, preferably 70 to 150 nm.
- the electrical conductivity of the lithium-based polyanion particles (B) represented by the above formula (III) or (III) ′ when pressurized at 20 MPa at 25 ° C. is preferably 1 ⁇ 10 ⁇ 7 S / cm or more. More preferably, it is 1 ⁇ 10 ⁇ 6 S / cm or more.
- the lower limit value of the electrical conductivity of the lithium-based polyanion particle (B) is not particularly limited.
- the lithium-based polyanion particle (B) has carbon (c) supported on its surface.
- the supported amount of carbon (c) is 0.1% by mass or more and less than 18% by mass in 100% by mass of the total amount of lithium-based polyanion particles (B) on which carbon (c) is supported, and preferably 1 -11% by mass, more preferably 1-8% by mass.
- Mass of lithium composite oxide secondary particle (A) content and lithium polyanion particle (B) content (including carbon (c) loading) with carbon (c) supported on the surface The ratio ((A) :( B)) is preferably 95: 5 to 65:35, more preferably 90:10 to 70:30.
- the carbon (c) supported on the surface of the lithium-based polyanion particle (B) represented by the above formula (III) or (III) ′ is carbon (c1) derived from cellulose nanofiber described later or water-soluble. Carbon (c2) derived from a functional carbon material is preferred.
- the supported amount of carbon (c) in the lithium-based polyanion particles (B) is the total supported amount of carbon (c1) derived from cellulose nanofibers and carbon (c2) derived from a water-soluble carbon material. It corresponds to the carbon atom equivalent amount of the cellulose nanofiber or water-soluble carbon material as the carbon source.
- the cellulose nanofibers to be the carbon source (c1) supported on the surface of the lithium-based polyanion particles (B) are skeletal components that occupy about 50% of all plant cell walls and constitute such cell walls. It is a lightweight high-strength fiber that can be obtained by defibrating plant fibers to nano size, and carbon derived from cellulose nanofibers has a periodic structure. The fiber diameter of such cellulose nanofiber is 1 nm to 100 nm, and has good dispersibility in water.
- the cellulose molecular chains constituting the cellulose nanofibers have a periodic structure formed of carbon, they are carbonized and coupled with the polyanion particles, so that they are firmly supported on the surface of the lithium-based polyanion particles (B). As a result, it is possible to obtain a useful positive electrode active material composite for a lithium ion secondary battery that imparts electron conductivity to these polyanion particles and is excellent in cycle characteristics.
- the water-soluble carbon material as the carbon source (c2) supported on the surface of the lithium-based polyanion particle (B) is 0.4 g in terms of carbon atoms of the water-soluble carbon material in 100 g of water at 25 ° C. As described above, it means a carbon material that is preferably dissolved in an amount of 1.0 g or more. When carbonized, carbon is present on the surface of the lithium-based polyanion particle (B) as carbon.
- the water-soluble carbon material include one or more selected from saccharides, polyols, polyethers, and organic acids.
- monosaccharides such as glucose, fructose, galactose and mannose
- disaccharides such as maltose, sucrose and cellobiose
- polysaccharides such as starch and dextrin
- polyols and polyethers such as diol, propanediol, polyvinyl alcohol, and glycerin
- organic acids such as citric acid, tartaric acid, and ascorbic acid.
- glucose, fructose, sucrose, and dextrin are preferable, and glucose is more preferable from the viewpoint of enhancing the solubility and dispersibility in a solvent and effectively functioning as a carbon material.
- the amount of carbon (c) supported on the surface of the lithium-based polyanion particles (B) (when carbon (c) is carbon (c1) derived from cellulose nanofibers or carbon (c2) derived from a water-soluble carbon material) These carbon atom equivalent amounts) can be confirmed as the carbon amount measured using a carbon / sulfur analyzer for the lithium-based polyanion particles (B).
- the lithium-based polyanion particles (B) represented by the above formula (III) or (III) ′ of the present invention may be combined with primary particles of a lithium composite oxide, and the primary particles of the lithium composite oxide are aggregated.
- the lithium composite oxide secondary particles (A) thus formed may be directly composited.
- the method for producing a positive electrode active material composite for a lithium ion secondary battery according to the present invention compresses lithium-based polyanion particles (B) on which lithium composite oxide secondary particles (A) and carbon (c) are supported. What is necessary is just to provide the process of mixing and compounding, adding force and shear force.
- the process of mixing while applying a compressive force and a shearing force is preferably performed in a closed container equipped with an impeller.
- the processing time and / or the impeller peripheral speed during the mixing process while applying the compressive force and shearing force are as follows: lithium composite oxide secondary particles (A) and lithium-based polyanion particles (B) charged into the container It is necessary to adjust appropriately according to the total amount. For example, in the case where the process of mixing while applying the compressive force and the shearing force is performed for 5 to 90 minutes in a closed container equipped with an impeller rotating at a peripheral speed of 15 to 45 m / s, the lithium composite oxide 2 charged in the container is used.
- the total amount of the secondary particles (A) and the lithium-based polyanion particles (B) is preferably 0.1 per 1 cm 3 of an effective container (a container corresponding to a portion capable of accommodating a mixed object in a sealed container equipped with an impeller).
- the amount is 1 to 0.7 g, more preferably 0.15 to 0.4 g.
- the peripheral speed of such an impeller is preferably 15 to 45 m / s, more preferably 15 to 35 m / s, from the viewpoint of increasing the tap density of the obtained positive electrode active material composite for a lithium ion secondary battery.
- the mixing time is preferably 5 to 90 minutes, more preferably 10 to 80 minutes.
- the peripheral speed of the impeller means the speed of the outermost end of the rotary stirring blade (impeller), which can be expressed by the following formula (1), and is mixed while applying compressive force and shearing force.
- the processing time may vary depending on the peripheral speed of the impeller so that it becomes longer as the peripheral speed of the impeller is slower.
- Impeller peripheral speed (m / s) Impeller radius (m) x 2 x ⁇ x rotational speed (rpm) ⁇ 60 ... (1)
- Examples of the apparatus including a sealed container that can easily perform the compounding process while applying such compressive force and shear force include a high-speed shear mill, a blade-type kneader, and the like.
- Particle design equipment COMPOSI, mechanohybrid, high-performance fluidity mixer FM mixer (manufactured by Nihon Coke Kogyo Co., Ltd.) fine particle composite device mechanofusion, nobilta (manufactured by Hosokawa Micron), surface reformer miraro, hybridization system (Nara Machinery Co., Ltd.) Can be suitably used.
- the treatment temperature is preferably 5 to 80 ° C., more preferably 10 to 50 ° C.
- the treatment atmosphere is not particularly limited, but is preferably an inert gas atmosphere or a reducing gas atmosphere.
- the degree to which the lithium-based polyanion particles (B) were densely and uniformly dispersed and combined on the surface of the lithium composite oxide secondary particles (A) by the composite treatment while applying the compressive force and shear force is X It can be evaluated by linear photoelectron spectroscopy (XPS). Specifically, when the obtained positive electrode active material composite for a lithium ion secondary battery is irradiated with several keV of soft X-rays, it is inherent to the element constituting the part from the part subjected to the soft X-ray irradiation.
- Photoelectrons having an energy value of 2 are emitted, so that the peak intensity of Ni2p 3/2 emitted from the lithium composite oxide secondary particles (A) and the P2p and C1s emitted from the lithium-based polyanion particles (B)
- the area ratio of the material that is the surface of the positive electrode active material composite for a lithium ion secondary battery, that is, the lithium-based polyanion particles (B) are converted into lithium composite oxide secondary particles ( The extent to which A) is coated can be seen.
- the lithium-based polyanion particles (B) may contain trivalent Ni
- the lithium composite oxide secondary particles (A) are obtained from the peak intensity of Ni2p 3/2 of the lithium composite oxide secondary particles (A).
- This peak intensity ratio ((Ni2p 3/2 peak intensity) / (P2p peak intensity + C1s peak intensity)) is preferably 0.05 or less, more preferably 0.04 or less, and still more preferably 0.8. 03 or less.
- the surface of the obtained positive electrode active material composite for a secondary battery is a lithium-based polyanion that is composited with the composite oxide particles on the surface of the lithium composite oxide secondary particles (A).
- the particles (B) are densely covered.
- a water-insoluble carbon other than carbon (c1) derived from cellulose nanofibers is used as a carbon source.
- the powder (c3) may be mixed at the same time and combined with the lithium composite oxide secondary particles (A) and the lithium-based polyanion particles (B).
- the water-insoluble carbon powder (c3) is a carbon material different from the carbon (c2) derived from the water-soluble carbon material, and is water-insoluble (water at 25 ° C.) other than the carbon (c1) derived from cellulose nanofibers.
- the amount dissolved in 100 g is a carbon powder having conductivity of less than 0.4 g in terms of carbon atom of the water-insoluble carbon powder (c3).
- the composite of the water-insoluble carbon powder (c3) allows the positive electrode for a lithium ion secondary battery without deteriorating the battery characteristics when the positive electrode active material composite for a lithium ion secondary battery of the present invention is used as a secondary battery.
- Examples of the water-insoluble carbon powder (c3) include graphite, amorphous carbon (Ketjen black, acetylene black, etc.), nanocarbon (graphene, fullerene, etc.), conductive polymer powder (polyaniline powder, polyacetylene powder, polythiophene powder). , Polypyrrole powder, etc.) and the like.
- graphite, acetylene black, graphene, and polyaniline powder are preferable, and graphite is more preferable from the viewpoint of reinforcing the degree of complexation of the lithium composite oxide secondary particles (A) and the lithium-based polyanion particles (B).
- the graphite may be any of artificial graphite (scaly, massive, earthy, graphene) or natural graphite.
- the average particle size of the water-insoluble carbon powder (c3) is preferably 0.5 to 20 ⁇ m, more preferably 1.0 to 15 ⁇ m, from the viewpoint of compositing.
- the positive electrode active material composite for a lithium ion secondary battery of the present invention water that is mixed and combined at the same time when the lithium composite oxide secondary particles (A) and the lithium-based polyanion particles (B) are combined.
- the content of the insoluble carbon powder (c3) is preferably 0.5 to 17 parts by mass with respect to 100 parts by mass of the total amount of the lithium composite oxide secondary particles (A) and the lithium-based polyanion particles (B).
- the amount is more preferably 1 to 10 parts by mass, and further preferably 1 to 7 parts by mass.
- the total content of the water-insoluble carbon powder (c3) (((A) + (B)): ((c) + (c3))) is preferably 99.5: 0.5 to 85:15, more preferably 99: 1 to 90:10, and even more preferably 99: 1 to 93: 7.
- the positive electrode active material composite for a lithium ion secondary battery of the present invention is applied as a positive electrode material, and as a lithium ion secondary battery including the same, a positive electrode, a negative electrode, an electrolyte solution, a separator, or a positive electrode, a negative electrode, and a solid electrolyte are essential. If it is set as a structure, it will not specifically limit.
- the material structure is not particularly limited, and a known material structure can be used.
- a known material structure can be used.
- lithium metal, graphite, silicon-based (Si, SiO x ), carbon material such as lithium titanate or amorphous carbon can be used.
- two or more types of the above negative electrode materials may be used in combination, and for example, a combination of graphite and silicon can be used.
- the electrolytic solution is obtained by dissolving a supporting salt in an organic solvent.
- the organic solvent is not particularly limited as long as it is an organic solvent usually used for an electrolyte solution of a lithium ion secondary battery.
- An oxolane compound or the like can be used.
- the type of the supporting salt is not particularly limited, but an inorganic salt selected from LiPF 6 , LiBF 4 , LiClO 4 and LiAsF 6 , a derivative of the inorganic salt, LiSO 3 CF 3 , LiC (SO 3 CF 3 ) 2 and LiN (SO 3 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 and LiN (SO 2 CF 3 ) (SO 2 C 4 F 9 ), and organic salt derivatives It is preferable that it is at least 1 type of these.
- the separator plays a role of electrically insulating the positive electrode and the negative electrode and holding the electrolytic solution.
- a porous synthetic resin film particularly a polyolefin polymer (polyethylene, polypropylene) porous film may be used.
- the solid electrolyte electrically insulates the positive electrode and the negative electrode and exhibits high lithium ion conductivity.
- La 0.51 Li 0.34 TiO 2.94 Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 , Li 7 La 3 Zr 2 O 12 , 50Li 4 SiO 4 .50Li 3 BO 3 , Li 2.9 PO 3.3 N 0.46 , Li 3.6 Si 0.6 P 0.4 O 4 , Li 1.07 Al 0.69 Ti 1.46 (PO 4 ) 3 , Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 , Li 10 GeP 2 S 12 , Li 3.25 Ge 0.25 P 0.75 S 4 , 30Li 2 S ⁇ 26B 2 S 3 ⁇ 44LiI, 63Li 2 S ⁇ 36SiS 2 ⁇ 1Li 3 PO 4 , 57Li 2 S ⁇ 38SiS 2 ⁇ 5Li 4 SiO 4 , 70Li 2 S ⁇ 30P 2 S 5 , 50Li 2 S ⁇
- the shape of the lithium ion secondary battery having the above configuration is not particularly limited, and may be various shapes such as a coin shape, a cylindrical shape, a square shape, and an indefinite shape sealed in a laminate outer package. .
- the slurry A1 was filtered and dried to obtain a metal composite hydroxide mixture B1, and then 37 g of lithium carbonate was mixed with the mixture B1 by a ball mill to obtain a powder mixture C1.
- the obtained powder mixture C1 was calcined at 800 ° C. for 5 hours in an air atmosphere and pulverized, and then calcined at 800 ° C. for 10 hours in an air atmosphere as main firing, to obtain an NCM composite oxide (LiNi 1 / 3 Co 1/3 Mn 1/3 O 2 ) secondary particles A were obtained.
- the secondary particle A of the NCM complex oxide is referred to as NCM-A.
- NCM-B Production of secondary particles of NCM composite oxide
- secondary particles B of NCM composite oxide LiNi 1/3 Co 1/3 Mn 1/3 O 2
- the secondary particle B of the NCM complex oxide is referred to as NCM-B.
- NCA-based complex oxide secondary particles 370 g of lithium carbonate, 950 g of nickel carbonate, 150 g of cobalt carbonate, 58 g of aluminum carbonate, and 3 L of water were mixed so that the molar ratio of Li: Ni: Co: Al was 1: 0.8: 0.15: 0.05. After that, the mixture was mixed with a ball mill to obtain a powder mixture A2. The obtained powder mixture A2 was calcined by calcination at 800 ° C. for 5 hours in an air atmosphere, and then baked as 800 ° C.
- NCA-based composite oxide LiNi 0.8 Co 0.15 Al 0.05 O 2
- secondary particles C were obtained.
- the secondary particle C of the NCA-based composite oxide is referred to as NCA-A.
- the obtained slurry B3 was purged with nitrogen so that the dissolved oxygen concentration of the slurry B3 was 0.5 mg / L, and then 1688 g of MnSO 4 .5H 2 O and 834 g of FeSO 4 .7H 2 O were added to the total amount of the slurry B3.
- slurry C3 was obtained.
- the molar ratio of MnSO 4 and FeSO 4 added (manganese compound: iron compound) was 70:30.
- the obtained slurry C3 was put into an autoclave and subjected to a hydrothermal reaction at 170 ° C. for 1 hour.
- the pressure in the autoclave was 0.8 MPa.
- the produced crystal was filtered, and then washed with 12 parts by mass of water with respect to 1 part by mass of the crystal.
- the washed crystals were lyophilized at ⁇ 50 ° C. for 12 hours to obtain complex D3.
- 1000 g of the obtained composite D3 was collected, and 1 L of water was added thereto to obtain a slurry E3.
- the obtained slurry E3 was dispersed with an ultrasonic stirrer (T25, manufactured by IKA) for 1 minute to uniformly color the whole, and then spray dried (MDL-050M, manufactured by Fujisaki Electric Co., Ltd.). Then, it was subjected to spray drying to obtain a granulated body F3.
- the obtained granulated body F3 was calcined at 700 ° C. for 1 hour in an argon hydrogen atmosphere (hydrogen concentration: 3%), and lithium manganese phosphate containing 2.0% by mass of cellulose nanofiber-derived carbon was supported.
- LMP-A lithium iron manganese phosphate A
- Example 1 (NCM-A 70% + LMP-A 30%) complex a1] 350 g of NCM-A obtained in Production Example 1 and 150 g of LMP-A obtained in Production Example 4 were combined at 20 m / s (2600 rpm) for 10 minutes using Mechanofusion (AMS-Lab, manufactured by Hosokawa Micron). The positive electrode active material composite a1 for lithium ion secondary batteries formed by combining NCM and LMP-A was obtained.
- Example 2 (NCM-A 70% + LMP-B 30%) complex b1]
- a positive electrode active material composite b1 for a lithium ion secondary battery was obtained in the same manner as in Example 1 except that LMP-A was changed to LMP-B obtained in Production Example 5.
- Example 3 (NCM-A 90% + LMP-A 10%) complex c1]
- a positive electrode active material composite c1 for a lithium ion secondary battery was obtained in the same manner as in Example 1 except that NCM-A was changed to 450 g and LMP-A was changed to 50 g.
- Example 4 (NCM-A 90% + LMP-D 10%) complex d1]
- NCM-A was changed to 450 g
- LMP-A was changed to LMP-D obtained in Production Example 7, and the combined treatment amount was changed to 50 g.
- a positive electrode active material composite d1 was obtained.
- Example 5 (NCM-A 80% + LMP-A 20%) complex e1]
- a positive electrode active material composite e1 for a lithium ion secondary battery was obtained in the same manner as in Example 1, except that NCM-A was changed to 400 g and LMP-A was changed to 100 g.
- Example 6 (NCM-A 70% + LMP-E 30%) complex f1]
- a positive electrode active material composite f1 for a lithium ion secondary battery was obtained in the same manner as in Example 1, except that LMP-A was changed to LMP-E obtained in Production Example 8.
- Example 7 (NCM-A 70% + LMP-I 30%) complex g1]
- a positive electrode active material composite g1 for a lithium ion secondary battery was obtained in the same manner as in Example 1 except that LMP-A was changed to LMP-I obtained in Production Example 12.
- Example 8 (NCM-A70% + LMP-J30%) complex h1]
- a positive electrode active material composite h1 for a lithium ion secondary battery was obtained in the same manner as in Example 1 except that LMP-A was changed to LMP-J obtained in Production Example 13.
- Example 9 (NCM-A 70% + LMP-F 30%) complex i1]
- a positive electrode active material composite i1 for a lithium ion secondary battery was obtained in the same manner as in Example 1, except that LMP-A was changed to LMP-F obtained in Production Example 9.
- Example 10 (NCM-A 70% + LMP-F 30%) 99% + graphite 1% complex j1]
- Example 1 except that LMP-A was changed to LMP-F obtained in Production Example 9, and 5 g of graphite (manufactured by Nippon Graphite Co., Ltd., CGB10, average particle size 10 ⁇ m) was added to perform the composite treatment.
- the positive electrode active material composite j1 for lithium ion secondary batteries was obtained.
- Example 11 (NCM-A 70% + LMP-F 30%) 90% + graphite 10% composite k1]
- Example 1 except that LMP-A was changed to LMP-F obtained in Production Example 9, and 55 g of graphite (manufactured by Nippon Graphite Co., Ltd., CGB10, average particle size 10 ⁇ m) was added to perform the composite treatment.
- the positive electrode active material composite k1 for lithium ion secondary batteries was obtained.
- Example 12 (NCM-A 70% + LMP-F 30%) 99% + graphene 1% complex 11]
- Example 1 except that LMP-A was changed to LMP-F obtained in Production Example 9 and 5 g of graphene (XG sciences, xGNP, average particle size 30 ⁇ m) was added to perform the complexing treatment.
- the positive electrode active material composite l1 for lithium ion secondary batteries was obtained.
- Example 13 (NCM-A 70% + LMP-F 30%) 99% + acetylene black 1% complex m1]
- acetylene black manufactured by Denka, LI-100, average particle size of 50 nm
- Example 14 (NCM-A 70% + LMP-F 30%) 99% + polyaniline 1% complex n1]
- LMP-A was changed to LMP-F obtained in Production Example 9, and 5 g of polyaniline (manufactured by Sigma-Aldrich) was added to perform the complexing treatment, A positive electrode active material composite n1 for a secondary battery was obtained.
- Example 15 (NCM-B70% + LMP-A30%) complex o1]
- a positive electrode active material composite o1 for a lithium ion secondary battery was obtained in the same manner as in Example 1, except that NCM-A was changed to NCM-B obtained in Production Example 2.
- Example 16 (NCA-A 70% + LMP-A 30%) complex a2] 350 g of NCA-A obtained in Production Example 3 and 150 g of LMP-A obtained in Production Example 4 were combined at 20 m / s (2600 rpm) for 10 minutes using mechanofusion (AMS-Lab, manufactured by Hosokawa Micron). The positive electrode active material composite a2 for lithium ion secondary batteries formed by combining NCA and LMP-A was obtained.
- Example 17 (NCA-A 70% + LMP-B 30%) complex b2]
- a positive electrode active material composite b2 for a lithium ion secondary battery was obtained in the same manner as in Example 16, except that LMP-A was changed to LMP-B obtained in Production Example 5.
- Example 18 (NCA-A 90% + LMP-A 10%) complex c2]
- a positive electrode active material composite c2 for a lithium ion secondary battery was obtained in the same manner as in Example 16 except that NCA-A was changed to 450 g and LMP-A was changed to 50 g.
- Example 19 (NCA-A 90% + LMP-D 10%) complex d2]
- NCA-A was changed to 450 g
- LMP-A was changed to LMP-D obtained in Production Example 7, and the amount of complexation was changed to 50 g.
- a positive electrode active material composite d2 was obtained.
- Example 20 (NCA-A 80% + LMP-A 20%) complex e2]
- a positive electrode active material composite e2 for a lithium ion secondary battery was obtained in the same manner as in Example 16, except that NCA-A was changed to 400 g and LMP-A was changed to 100 g.
- Example 21 (NCA-A 70% + LMP-E 30%) complex f2]
- a positive electrode active material composite f2 for a lithium ion secondary battery was obtained in the same manner as in Example 16 except that LMP-A was changed to LMP-E obtained in Production Example 8.
- Example 22 (NCA-A 70% + LMP-I 30%) complex g2]
- a positive electrode active material composite g2 for a lithium ion secondary battery was obtained in the same manner as in Example 16 except that LMP-A was changed to LMP-I obtained in Production Example 12.
- Example 23 (NCA-A 70% + LMP-J 30%) complex h2]
- a positive electrode active material composite h2 for a lithium ion secondary battery was obtained in the same manner as in Example 16, except that LMP-A was changed to LMP-J obtained in Production Example 13.
- Example 24 (NCA-A 70% + LMP-F 30%) complex i2]
- a positive electrode active material composite i2 for a lithium ion secondary battery was obtained in the same manner as in Example 16 except that LMP-A was changed to LMP-F obtained in Production Example 9.
- Example 25 (NCA-A 70% + LMP-F 30%) 99% + graphite 1% complex j2]
- Example 16 is the same as Example 16 except that LMP-A was changed to LMP-F obtained in Production Example 9, and 5 g of graphite (manufactured by Nippon Graphite Co., Ltd., CGB10, average particle size: 10 ⁇ m) was added to perform the composite treatment. Similarly, the positive electrode active material composite j2 for lithium ion secondary batteries was obtained.
- Example 26 (NCA-A 70% + LMP-F 30%) 90% + graphite 10% composite k2] Except that LMP-A was changed to LMP-F obtained in Production Example 9, and 55 g of graphite (manufactured by Nippon Graphite Co., Ltd., CGB10, average particle size 10 ⁇ m) was added to perform a composite treatment, Example 16 and Similarly, the positive electrode active material composite k2 for lithium ion secondary batteries was obtained.
- Example 27 (NCA-A 70% + LMP-F 30%) 99% + graphene 1% complex 12] Except that LMP-A was changed to LMP-F obtained in Production Example 9, and graphene (manufactured by XG sciences, xGNP, average particle size 30 ⁇ m) 5 g was added and subjected to a composite treatment, Example 16 Similarly, the positive electrode active material composite l2 for lithium ion secondary batteries was obtained.
- Example 28 (NCA-A 70% + LMP-F 30%) 99% + acetylene black 1% complex m2]
- acetylene black manufactured by Denka, LI-100, average particle size of 50 nm
- Example 29 (NCA-A 70% + LMP-F 30%) 99% + polyaniline 1% complex n2]
- LMP-A was changed to LMP-F obtained in Production Example 9, and 5 g of polyaniline (manufactured by Sigma-Aldrich) was added to perform the complexing treatment, A positive electrode active material composite n2 for a secondary battery was obtained.
- Example 30 (NCM-A35% + NCA-A35% + LMP-A30%) complex o2]
- a positive electrode active material composite o2 for a lithium ion secondary battery was obtained in the same manner as in Example 1 except that 350 g of LMP-A was changed to a mixture of 175 g of LMP-A and NCA-A 175 g obtained in Production Example 3.
- NCA-A 70% + LMP-A 30% mixture p2
- NCA-A 350 g obtained in Production Example 3 and LMP-A 150 g obtained in Production Example 4 were mixed using a mortar for 5 minutes, and NCA-A and LMP-A were combined.
- NCA-A and LMP-A were combined.
- Example 12 (NCA-A 99.5% + LMP-A 0.5%) complex r2]
- a positive electrode active material composite r2 for a lithium ion secondary battery was obtained in the same manner as in Example 16 except that NCA-A was changed to 497.5 g and LMP-A was changed to 2.5 g.
- the Ni2p 3 / derived from LMP normalized from the Ni2p 3/2 peak of the positive electrode active material composite or the positive electrode active material mixture to the P2p peak of the positive electrode active material composite or the positive electrode active material mixture.
- the XPS peak intensity ratio (A) was determined by the following formula (2).
- the XPS peak intensity ratio (A) indicates that the smaller the value is, the more the composite particle surface is coated with LMP. The results are shown in Tables 1 and 2.
- XPS peak intensity ratio (A) (peak intensity of Ni2p 3/2 ) / ((P2p peak intensity) + (C1s peak intensity)) ...
- the slurry after stirring and kneading was dried at 80 ° C. for 12 hours using a hot air dryer to obtain a positive electrode active material composite for a lithium ion secondary battery, and then the obtained positive electrode active for a lithium ion secondary battery.
- the substance composite was subjected to X-ray photoelectron spectroscopy, and the XPS peak intensity ratio (B) was determined from the same calculation as in the above expression (2), and then the coating intensity ratio was determined according to the following expression (3).
- This coating strength ratio is smaller in value and closer to 1 indicates that the surface of the composite particle is more strongly coated with LMP.
- a result is shown in Table 1 and Table 2 with the manufacturing conditions of the positive electrode active material composite_body
- Coating intensity ratio (XPS peak intensity ratio (B)) / (XPS peak intensity ratio (A)) ... (3)
- the positive electrode slurry was applied to a current collector made of an aluminum foil having a thickness of 20 ⁇ m using a coating machine, and vacuum dried at 80 ° C. for 12 hours. Thereafter, it was punched into a disk shape of ⁇ 14 mm and pressed at 16 MPa for 2 minutes using a hand press to obtain a positive electrode. Next, a coin-type secondary battery was constructed using the positive electrode. A lithium foil punched to ⁇ 15 mm was used for the negative electrode.
- the electrolytic solution a solution obtained by dissolving LiPF 6 at a concentration of 1 mol / L in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 was used.
- a known one such as a polymer porous film such as polypropylene was used.
- These battery components were assembled and housed in a conventional manner in an atmosphere having a dew point of ⁇ 50 ° C. or lower to produce a coin-type secondary battery (CR-2032).
- the obtained secondary battery was charged. Specifically, constant current charging with a current of 170 mA / g and a voltage of 4.5 V was performed. Thereafter, the secondary battery was disassembled, and the taken out positive electrode was washed with dimethyl carbonate and then immersed in an electrolytic solution.
- an electrolytic solution As the electrolytic solution at this time, a solution obtained by dissolving LiPF 6 at a concentration of 1 mol / L in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 was used.
- the electrolyte solution in which the positive electrode was immersed was placed in a sealed container and allowed to stand at 70 ° C. for 1 week.
- the rate characteristic was evaluated using the secondary battery manufactured by evaluation of the amount of transition metal elution into the electrolytic solution. Specifically, a constant current charge at a current density of 34 mA / g and a voltage of 4.25 V, a constant current discharge at a current of 34 mA / g and a final voltage of 3.0 V, and the discharge capacity at a current density of 34 mA / g was determined. Furthermore, constant current charging was performed under the same conditions to obtain a constant current discharge with a current density of 510 mA / g and a final voltage of 3.0 V, and a discharge capacity at a current density of 510 mA / g was determined.
- Capacity ratio (%) (discharge capacity at a current density of 510 mA / g) / (Discharge capacity at a current density of 34 mA / g) ⁇ 100 ... (5)
- the lithium ion secondary battery using the positive electrode active material composite for a lithium ion secondary battery obtained in the example as the positive electrode active material is the lithium ion obtained in the comparative example. It can be seen that both the high-temperature cycle characteristics and the rate characteristics are excellent as compared with the lithium ion secondary battery using the positive electrode active material composite for the secondary battery or the positive electrode active material mixture for the lithium ion secondary battery as the positive electrode active material. Furthermore, as is clear from Table 3 or Table 4, a lithium ion secondary battery using the positive electrode active material composite for a lithium ion secondary battery obtained in Examples as a positive electrode active material was obtained in a comparative example.
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Abstract
Description
LiNiaCobMncM1 xO2・・・(I)
(式(I)中、M1はMg、Ti、Nb、Fe、Cr、Si、Al、Ga、V、Zn、Cu、Sr、Mo、Zr、Sn、Ta、W、La、Ce、Pb、Bi及びGeから選ばれる1種又は2種以上の元素を示す。a、b、c、xは、0.3≦a<1、0<b≦0.7、0<c≦0.7、0≦x≦0.3、かつ3a+3b+3c+(M1の価数)×x=3を満たす数を示す。)
又は、下記式(II):
LiNidCoeAlfM2 yO2・・・(II)
(式(II)中、M2はMg、Ti、Nb、Fe、Cr、Si、Ga、V、Zn、Cu、Sr、Mo、Zr、Sn、Ta、W、La、Ce、Pb、Bi及びGeから選ばれる1種又は2種以上の元素を示す。d、e、f、yは、0.4≦d<1、0<e≦0.6、0<f≦0.3、0≦y≦0.3、かつ3d+3e+3f+(M2の価数)×y=3を満たす数を示す。)
で表される1種以上のリチウム複合酸化物粒子からなるリチウム複合酸化物二次粒子(A)の表面のみにおいて、下記式(III)又は(III)':
LigMnhFeiM3 zPO4・・・(III)
(式(III)中、M3はCo、Ni、Ca、Sr、Y、Zr、Mo、Ba、Pb、Bi、La、Ce、Nd又はGdを示す。g、h、i、及びzは、0<g≦1.2、0≦h≦1.2、0≦i≦1.2、0≦z≦0.3、及びh+i≠0を満たし、かつg+(Mnの価数)×h+(Feの価数)×i+(M3の価数)×z=3を満たす数を示す。)
Mnh'Fei'M3 z'PO4・・・(III)'
(式(III)'中、M3は式(III)と同義である。h'、i'、及びz'は、0≦h'≦1.2、0≦i'≦1.2、0≦z'≦0.3、及びh'+i'≠0を満たし、かつ(Mnの価数)×h'+(Feの価数)×i'+(M3の価数)×z'=3を満たす数を示す。)
で表され、かつ表面に炭素(c)が担持されたリチウム系ポリアニオン粒子(B)と、リチウム複合酸化物粒子とが複合化してなり、
リチウム系ポリアニオン粒子(B)の表面における炭素(c)の担持量が、リチウム系ポリアニオン粒子(B)100質量%中に0.1質量%以上18質量%未満であり、
リチウム系ポリアニオン粒子(B)の平均粒径が50~200nmであり、
リチウム複合酸化物二次粒子(A)の含有量と、リチウム系ポリアニオン粒子(B)の含有量との質量比((A):(B))が、95:5~65:35であるリチウムイオン二次電池用正極活物質複合体を提供するものである。
本発明のリチウムイオン二次電池用正極活物質複合体は、下記式(I):
LiNiaCobMncM1 xO2・・・(I)
(式(I)中、M1はMg、Ti、Nb、Fe、Cr、Si、Al、Ga、V、Zn、Cu、Sr、Mo、Zr、Sn、Ta、W、La、Ce、Pb、Bi及びGeから選ばれる1種又は2種以上の元素を示す。a、b、c、xは、0.3≦a<1、0<b≦0.7、0<c≦0.7、0≦x≦0.3、かつ3a+3b+3c+(M1の価数)×x=3を満たす数を示す。)
又は、下記式(II):
LiNidCoeAlfM2 yO2・・・(II)
(式(II)中、M2はMg、Ti、Nb、Fe、Cr、Si、Ga、V、Zn、Cu、Sr、Mo、Zr、Sn、Ta、W、La、Ce、Pb、Bi及びGeから選ばれる1種又は2種以上の元素を示す。d、e、f、yは、0.4≦d<1、0<e≦0.6、0<f≦0.3、0≦y≦0.3、かつ3d+3e+3f+(M2の価数)×y=3を満たす数を示す。)
で表される1種以上のリチウム複合酸化物粒子からなるリチウム複合酸化物二次粒子(A)の表面のみにおいて、下記式(III)又は(III)':
LigMnhFeiM3 zPO4・・・(III)
(式(III)中、M3はCo、Ni、Ca、Sr、Y、Zr、Mo、Ba、Pb、Bi、La、Ce、Nd又はGdを示す。g、h、i、及びzは、0<g≦1.2、0≦h≦1.2、0≦i≦1.2、0≦z≦0.3、及びh+i≠0を満たし、かつg+(Mnの価数)×h+(Feの価数)×i+(M3の価数)×z=3を満たす数を示す。)
Mnh'Fei'M3 z'PO4・・・(III)'
(式(III)'中、M3は式(III)と同義である。h'、i'、及びz'は、0≦h'≦1.2、0≦i'≦1.2、0≦z'≦0.3、及びh'+i'≠0を満たし、かつ(Mnの価数)×h'+(Feの価数)×i'+(M3の価数)×z'=3を満たす数を示す。)
で表され、かつ表面に炭素(c)が担持されたリチウム系ポリアニオン粒子(B)と、リチウム複合酸化物粒子とが複合化してなり、
リチウム系ポリアニオン粒子(B)の表面における炭素(c)の担持量が、リチウム系ポリアニオン粒子(B)100質量%中に0.1質量%以上18質量%未満であり、
リチウム系ポリアニオン粒子(B)の平均粒径が50~200nmであり、
リチウム複合酸化物二次粒子(A)の含有量と、リチウム系ポリアニオン粒子(B)の含有量との質量比((A):(B))が、95:5~65:35である。
また、上記式(I)中のa、b、c、xは、0.3≦a<1、0<b≦0.7、0<c≦0.7、0≦x≦0.3、かつ3a+3b+3c+(M1の価数)×x=3を満たす数である。
上記式(I)で表されるNCM系複合酸化物としては、具体的には、例えばLiNi0.33Co0.33 Mn0.34O2、LiNi0.8Co0.1Mn 0.1O2、LiNi0.6Co0.2Mn 0.2O2、LiNi0.2Co0.4Mn0.4O2、LiNi0.33Co0.31Mn0.33Mg0.03O2、及びLiNi0.33Co0.31Mn0.33Zn0.03O2等が挙げられる。なかでも、放電容量を重視する場合には、LiNi0.8Co0.1Mn 0.1O2、LiNi0.6Co0.2Mn 0.2O2等のNi量の多い組成が好ましく、サイクル特性を重視する場合には、LiNi0.33Co0.33 Mn0.34O2、LiNi0.33Co0.31Mn0.33Mg0.03O2等のNi量の少ない組成が好ましい。
このコア-シェル構造を形成してなるLi-NCM系複合酸化物二次粒子(A)とすることによって、電解液に溶出しやすい上に安全性に悪影響を与える酸素を放出しやすい、或いは固体電解質において固体電解質と反応しやすいNi濃度の高いLi-NCM系複合酸化物粒子をコア部に配置し、電解液に接するシェル部にはNi濃度の低いLi-NCM系複合酸化物粒子を配置することができるので、サイクル特性の低下の抑制と安全性の確保をより向上させることができる。このとき、コア部は1相であってもよいし、組成の異なる2相以上で構成していてもよい。コア部を2相以上で構成する態様として、同心円状に複数の相が層状となって積層された構造でもよいし、コア部の表面から中心部に向けて遷移的に組成が変化する構造でもよい。
さらに、シェル部は、コア部の外側に形成されてなるものであればよく、コア部同様に1相であってもよいし、組成の異なる2相以上で構成していてもよい。
また、上記一次粒子が凝集して形成するNCM系複合酸化物二次粒子(A)の平均粒径は、好ましくは25μm以下であり、より好ましくは20μm以下である。かかる二次粒子の平均粒径が25μm以下であると、高温サイクル特性に優れた電池を得ることができる。なお、上記二次粒子の平均粒径の下限値は特に限定されないが、ハンドリングの観点から1μm以上が好ましく、5μm以上がより好ましい。
ここで、平均粒径とは、SEM又はTEMの電子顕微鏡を用いた観察における、数十個の粒子の粒径(長軸の長さ)の測定値の平均値を意味する。
なお、本明細書において、NCM系複合酸化物二次粒子(A)は、二次粒子を形成してなる一次粒子のみを含み、リチウム系ポリアニオン粒子(B)や、セルロースナノファイバー由来の炭素(c1)又は水溶性炭素材料由来の炭素(c2)等、その他の成分を含まない。
また、かかるコア部の表面を被覆するシェル部を構成するLi-NCM系複合酸化物粒子の一次粒子としての平均粒径は、好ましくは50nm~500nmであり、より好ましくは50nm~300nmであって、かかる一次粒子が凝集して形成するシェル部の層厚は、好ましくは0.1μm~5μmであり、より好ましくは0.1μm~2.5μmである。
上記式(II)中のM2は、Mg、Ti、Nb、Fe、Cr、Si、Ga、V、Zn、Cu、Sr、Mo、Zr、Sn、Ta、W、La、Ce、Pb、Bi及びGeから選ばれる1種又は2種以上の元素を示す。
また、上記式(II)中のd、e、f、yは、0.4≦d<1、0<e≦0.6、0<f≦0.3、0≦y≦0.3、かつ3d+3e+3f+(M2の価数)×y=3を満たす数である。
上記式(II)で表されるNCA系複合酸化物としては、具体的には、例えばLiNi0.33Co0.33Al0.34O2、LiNi0.8Co0.1Al0.1O2、LiNi0.8Co0.15Al0.03Mg0.03O2、LiNi0.8Co0.15Al0.03Zn0.03O2等が挙げられる。なかでもLiNi0.8Co0.15Al0.03Mg0.03O2が好ましい。
上記式(III)及び(III)'中、いずれもM3はCo、Ni、Ca、Sr、Y、Zr、Mo、Ba、Pb、Bi、La、Ce、Nd又はGdを示す。
また、上記式(III)中のg、h、i、及びzは、0<g≦1.2、0≦h≦1.2、0≦i≦1.2、0≦z≦0.3、及びh+i≠0を満たし、かつg+(Mnの価数)×h+(Feの価数)×i+(M3の価数)×z=3を満たす数を示す。
さらに、上記式(III)'のh'、i'、及びz'は、0≦h'≦1.2、0≦i'≦1.2、0≦z'≦0.3、及びh'+i'≠0を満たし、かつ(Mnの価数)×h'+(Feの価数)×i'+(M3の価数)×z'=3を満たす数を示す。
上記式(III)で表されるリチウム系ポリアニオン粒子(B)としては、リチウムイオン二次電池用正極活物質複合体の平均放電電圧の観点から、0.5≦g≦1.2が好ましく、0.6≦g≦1.1がより好ましく、0.65≦g≦1.05がさらに好ましい。また、式(III)'で表されるポリアニオン粒子(B)としては、同様の観点から、0.5≦h≦1.2が好ましく、0.6≦h≦1.1がより好ましく、0.65≦h≦1.05がさらに好ましい。また、式(III)'で表されるポリアニオン粒子(B)としては、同様の観点から、0.5≦h'≦1.2が好ましく、0.6≦h'≦1.1がより好ましい。
具体的には、例えばLiMnPO4、LiMn0.9Fe0.1PO4、LiMn0.8Fe0.2PO4、LiMn0.75Fe0.15Mg0.1PO4、LiMn0.75Fe0.19Zr0.03PO4、LiMn0.7Fe0.3PO4、LiMn0.6Fe0.4PO4、LiMn0.5Fe0.5PO4、Li1.2Mn0.63Fe0.27PO4、Li0.6Mn0.84Fe0.36PO4、Mn0.7Fe0.3PO4等が挙げられ、なかでもLiMn0.8Fe0.2PO4、Li1.2Mn0.63Fe0.27PO4、Li0.6Mn0.84Fe0.36PO4、又はMn0.7Fe0.3PO4が好ましい。
このコア-シェル構造を形成してなるリチウム系ポリアニオン粒子(B)とすることによって、リチウム系ポリアニオン粒子(B)から電解液に溶出しやすいMn含有量の多いリチウム系ポリアニオンをコア部に配置し、電解液に接するシェル部にはMn含有量の少ないリチウム系ポリアニオンを配置したり、或いは人体や環境に対する毒性の強いCo含有量の多いリチウム系ポリアニオンをコア部に配置し、電解液に接するシェル部にはCo含有量の少ないリチウム系ポリアニオンを配置したり等することが可能となるため、リチウム系ポリアニオン粒子に起因するサイクル特性の低下の抑制と安全性の確保をより向上させることができる。このとき、コア部は1相であってもよいし、組成の異なる2相以上で構成していてもよい。コア部を2相以上で構成する態様として、同心円状に複数の相が積層された構造でもよいし、コア部の表面から中心部に向けて遷移的に組成が変化する構造でもよい。
さらに、シェル部は、コア部の外側に形成されてなるものであればよく、コア部同様に1相であってもよいし、組成の異なる2相以上で構成していてもよい。
例えば、上記圧縮力及びせん断力を付加しながら混合する処理を、周速度15~45m/sで回転するインペラを備える密閉容器内で5~90分間行う場合、容器に投入するリチウム複合酸化物二次粒子(A)及びリチウム系ポリアニオン粒子(B)の合計量は、有効容器(インペラを備える密閉容器のうち、混合対象物を収容可能な部位に相当する容器)1cm3当たり、好ましくは0.1~0.7gであり、より好ましくは0.15~0.4gである。
かかるインペラの周速度は、得られるリチウムイオン二次電池用正極活物質複合体のタップ密度を高める観点から、好ましくは15~45m/sであり、より好ましくは15~35m/sである。また、混合時間は、好ましくは5~90分であり、より好ましくは10~80分である。
なお、インペラの周速度とは、回転式攪拌翼(インペラ)の最外端部の速度を意味し、下記式(1)により表すことができ、また圧縮力及びせん断力を付加しながら混合する処理を行う時間は、インペラの周速度が遅いほど長くなるように、インペラの周速度によっても変動し得る。
インペラの周速度(m/s)=
インペラの半径(m)×2×π×回転数(rpm)÷60
・・・(1)
上記混合の処理条件としては、処理温度が、好ましくは5~80℃、より好ましくは10~50℃である。処理雰囲気としては、特に限定されないが、不活性ガス雰囲気下、又は還元ガス雰囲気下が好ましい。
Ni:Co:Mnのモル比が1:1:1となるように、硫酸ニッケル六水和物 263g、硫酸コバルト七水和物 281g、硫酸マンガン五水和物 241g、及び水 3Lを混合した後、かかる混合液に25%アンモニア水を、滴下速度300ml/分で滴下して、pHが11の金属複合水酸化物を含むスラリーA1を得た。
次いで、スラリーA1をろ過、乾燥して、金属複合水酸化物の混合物B1を得た後、かかる混合物B1に炭酸リチウム37gをボールミルで混合して粉末混合物C1を得た。
得られた粉末混合物C1を、空気雰囲気下で800℃×5時間仮焼成して解砕した後、本焼成として空気雰囲気下で800℃×10時間焼成し、NCM系複合酸化物(LiNi1/3Co1/3Mn1/3O2)の二次粒子Aを得た。(二次粒子の平均粒径:10μm)
以後、上記NCM系複合酸化物の二次粒子AをNCM-Aと称する。
製造例1のNCM系複合酸化物(1)の製造において、硫酸ニッケル六水和物、硫酸コバルト七水和物、硫酸マンガン五水和物硫酸ニッケル六水和物の使用量を、それぞれ473g、169g、145g(Ni:Co:Mnのモル比=6:2:2)とし、金属複合水酸化物の混合物に混合した炭酸リチウムの代わりに水酸化リチウム一水和物 22gを混合した以外、製造例1と同様にして、NCM系複合酸化物(LiNi1/3Co1/3Mn1/3O2)の二次粒子Bを得た。(二次粒子の平均粒径:10μm)
以後、上記NCM系複合酸化物の二次粒子BをNCM-Bと称する。
Li:Ni:Co:Alのモル比が1:0.8:0.15:0.05となるように、炭酸リチウム370g、炭酸ニッケル950g、炭酸コバルト150g、炭酸アルミニウム58g、及び水3Lを混合した後、ボールミルで混合して粉末混合物A2を得た。得られた粉末混合物A2を、空気雰囲気下で800℃×5時間仮焼成して解砕した後、本焼成として空気雰囲気下で800℃×24時間焼成し、NCA系複合酸化物(LiNi0.8Co0.15Al0.05O2)の二次粒子Cを得た。(二次粒子の平均粒径:10μm)
以後、上記NCA系複合酸化物の二次粒子CをNCA-Aと称する。
LiOH・H2O 1272g、及び水4Lを混合してスラリーA3を得た。次いで、得られたスラリーA3を、25℃の温度に保持しながら3分間撹拌しつつ85%のリン酸水溶液1153gを35mL/分で滴下し、続いてセルロースナノファイバー(Wma-10002、スギノマシン社製、繊維径4~20nm)5892gを添加して、速度400rpmで12時間撹拌して、Li3PO4を含むスラリーB3を得た。
得られたスラリーB3に窒素パージして、スラリーB3の溶存酸素濃度を0.5mg/Lとした後、スラリーB3全量に対し、MnSO4・5H2O 1688g、FeSO4・7H2O 834gを添加してスラリーC3を得た。添加したMnSO4とFeSO4のモル比(マンガン化合物:鉄化合物)は、70:30であった。
次いで、得られたスラリーC3をオートクレーブに投入し、170℃で1時間水熱反応を行った。オートクレーブ内の圧力は0.8MPaであった。水熱反応後、生成した結晶をろ過し、次いで結晶1質量部に対し12質量部の水により洗浄した。洗浄した結晶を-50℃で12時間凍結乾燥して複合体D3を得た。
得られた複合体D3を1000g分取し、これに水1Lを添加して、スラリーE3を得た。得られたスラリーE3を超音波攪拌機(T25、IKA社製)で1分間分散処理して、全体を均一に呈色させた後、スプレードライ装置(MDL-050M、藤崎電機株式会社製)を用いてスプレードライに付して造粒体F3を得た。
得られた造粒体F3を、アルゴン水素雰囲気下(水素濃度3%)、700℃で1時間焼成して、2.0質量%のセルロースナノファイバー由来の炭素が担持されたリン酸マンガン鉄リチウムA(LiMn0.7Fe0.3PO4、炭素の量=2.0質量%、平均粒径:100nm)を得た。
以後、上記リン酸マンガン鉄リチウムAをLMP-Aと称する。
製造例4のリチウム系ポリアニオン粒子の製造において、スラリーA3に添加したセルロースナノファイバー5892gをグルコース125gに変更した以外、製造例4と同様にして、2.0質量%のグルコース由来の炭素が担持されたリン酸マンガン鉄リチウムB(LiMn0.7Fe0.3PO4、炭素の量=2.0質量%、平均粒径:100nm)を得た。
以後、上記リン酸マンガン鉄リチウムBをLMP-Bと称する。
製造例4のリチウム系ポリアニオン粒子の製造において、スラリーA3へのセルロースナノファイバーの添加量5892gを53028gに変更した以外、製造例4と同様にして、18.0質量%のセルロースナノファイバー由来の炭素が担持されたリン酸マンガン鉄リチウムC(LiMn0.7Fe0.3PO4、炭素の量=18.0質量%、平均粒径:100nm)を得た。
以後、上記リン酸マンガン鉄リチウムCをLMP-Cと称する。
製造例4のリチウム系ポリアニオン粒子の製造において、スラリーA3へのセルロースナノファイバーの添加量5892gを35352gに変更した以外、製造例4と同様にして、12.0質量%のセルロースナノファイバー由来の炭素が担持されたリン酸マンガン鉄リチウムD(LiMn0.7Fe0.3PO4、炭素の量=12.0質量%、平均粒径:100nm)を得た。
以後、上記リン酸マンガン鉄リチウムDをLMP-Dと称する。
製造例4のリチウム系ポリアニオン粒子の製造において、スラリーA3へのセルロースナノファイバーの添加量5892gを2946gに変更した以外、製造例4と同様にして、1.0質量%のセルロースナノファイバー由来の炭素が担持されたリン酸マンガン鉄リチウムE(LiMn0.7Fe0.3PO4、炭素の量=1.0質量%、平均粒径:100nm)を得た。
以後、上記リン酸マンガン鉄リチウムEをLMP-Eと称する。
製造例4のリチウム系ポリアニオン粒子の製造において、スラリーA3へのセルロースナノファイバーの添加量5892gを294gに変更した以外、製造例4と同様にして、0.1質量%のセルロースナノファイバー由来の炭素が担持されたリン酸マンガン鉄リチウムF(LiMn0.7Fe0.3PO4、炭素の量=0.1質量%、平均粒径:100nm)を得た。
以後、上記リン酸マンガン鉄リチウムFをLMP-Fと称する。
製造例4のリチウム系ポリアニオン粒子の製造において、スラリーA3へのセルロースナノファイバーの添加量5892gを147gに変更した以外、製造例4と同様にして、0.05質量%のセルロースナノファイバー由来の炭素が担持されたリン酸マンガン鉄リチウムG(LiMn0.7Fe0.3PO4、炭素の量=0.05質量%、平均粒径:100nm)を得た。
以後、上記リン酸マンガン鉄リチウムGをLMP-Gと称する。
製造例4のリチウム系ポリアニオン粒子の製造において、スラリーC3の水熱反応条件170℃×1時間を200℃×48時間に変更した以外、製造例4と同様にして、2.0質量%のセルロースナノファイバー由来の炭素が担持されたリン酸マンガン鉄リチウムH(LiMn0.7Fe0.3PO4、炭素の量=2.0質量%、平均粒径:500nm)を得た。
以後、上記リン酸マンガン鉄リチウムHをLMP-Hと称する。
製造例4のリチウム系ポリアニオン粒子の製造において、スラリーC3の水熱反応条件170℃×1時間を200℃×3時間に変更した以外、製造例4と同様にして、2.0質量%のセルロースナノファイバー由来の炭素が担持されたリン酸マンガン鉄リチウムI(LiMn0.7Fe0.3PO4、炭素の量=2.0質量%、平均粒径:150nm)を得た。
以後、上記リン酸マンガン鉄リチウムIをLMP-Iと称する。
製造例4のリチウム系ポリアニオン粒子の製造において、スラリーC3の水熱反応条件170℃×1時間を140℃×1時間に変更した以外、製造例4と同様にして、2.0質量%のセルロースナノファイバー由来の炭素が担持されたリン酸マンガン鉄リチウムJ(LiMn0.7Fe0.3PO4、炭素の量=2.0質量%、平均粒径:70nm)を得た。
以後、上記リン酸マンガン鉄リチウムJをLMP-Jと称する。
製造例4のリチウム系ポリアニオン粒子の製造において、スラリーC3の水熱反応条件170℃×1時間を140℃×10分間に変更した以外、製造例4と同様にして、2.0質量%のセルロースナノファイバー由来の炭素が担持されたリン酸マンガン鉄リチウムK(LiMn0.7Fe0.3PO4、炭素の量=2.0質量%、平均粒径:10nm)を得た。
以後、上記リン酸マンガン鉄リチウムKをLMP-Kと称する。
製造例4のリチウム系ポリアニオン粒子の製造において、スラリーA3にセルロースナノファイバーを添加しない以外、製造例4と同様にして、炭素が担持されていないリン酸マンガン鉄リチウムL(LiMn0.7Fe0.3PO4、炭素の量=0.0質量%、平均粒径:10nm)を得た。
以後、上記リン酸マンガン鉄リチウムLをLMP-Lと称する。
製造例1で得られたNCM-A350gと、製造例4で得られたLMP-A 150gを、メカノフュージョン(ホソカワミクロン社製、AMS-Lab)を用いて20m/s(2600rpm)で10分間の複合化処理を行い、NCMとLMP-Aとが複合化してなるリチウムイオン二次電池用正極活物質複合体a1を得た。
LMP-Aを製造例5で得られたLMP-Bに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体b1を得た。
NCM-Aを450gに、LMP-Aを50gに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体c1を得た。
NCM-Aを450gとし、LMP-Aを製造例7で得られたLMP-Dに変更し、その複合化処理量を50gとした以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体d1を得た。
NCM-Aを400gに、LMP-Aを100gに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体e1を得た。
LMP-Aを製造例8で得られたLMP-Eに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体f1を得た。
LMP-Aを製造例12で得られたLMP-Iに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体g1を得た。
LMP-Aを製造例13で得られたLMP-Jに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体h1を得た。
LMP-Aを製造例9で得られたLMP-Fに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体i1を得た。
LMP-Aを製造例9で得られたLMP-Fに変更し、さらにグラファイト(日本黒鉛社製、CGB10、平均粒径10μm)5gを添加して複合化処理を行った以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体j1を得た。
LMP-Aを製造例9で得られたLMP-Fに変更し、さらにグラファイト(日本黒鉛社製、CGB10、平均粒径10μm)55gを添加して複合化処理を行った以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体k1を得た。
LMP-Aを製造例9で得られたLMP-Fに変更し、さらにグラフェン(XG sciences社製、xGNP、平均粒径30μm)5gを添加して複合化処理を行った以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体l1を得た。
LMP-Aを製造例9で得られたLMP-Fに変更し、さらにアセチレンブラック(デンカ社製、LI-100、平均粒径50nm)5gを添加して複合化処理を行った以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体m1を得た。
LMP-Aを製造例9で得られたLMP-Fに変更し、さらにポリアニリン(シグマアルドリッチ社製)5gを添加して複合化処理を行った以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体n1を得た。
NCM-Aを製造例2で得られたNCM-Bに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体o1を得た。
製造例3で得られたNCA-A350gと、製造例4で得られたLMP-A 150gを、メカノフュージョン(ホソカワミクロン社製、AMS-Lab)を用いて20m/s(2600rpm)で10分間の複合化処理を行い、NCAとLMP-Aとが複合化してなるリチウムイオン二次電池用正極活物質複合体a2を得た。
LMP-Aを製造例5で得られたLMP-Bに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体b2を得た。
NCA-Aを450gに、LMP-Aを50gに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体c2を得た。
NCA-Aを450gとし、LMP-Aを製造例7で得られたLMP-Dに変更し、その複合化処理量を50gとした以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体d2を得た。
NCA-Aを400gに、LMP-Aを100gに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体e2を得た。
LMP-Aを製造例8で得られたLMP-Eに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体f2を得た。
LMP-Aを製造例12で得られたLMP-Iに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体g2を得た。
LMP-Aを製造例13で得られたLMP-Jに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体h2を得た。
LMP-Aを製造例9で得られたLMP-Fに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体i2を得た。
LMP-Aを製造例9で得られたLMP-Fに変更し、さらにグラファイト(日本黒鉛社製、CGB10、平均粒径10μm)5gを添加して複合化処理を行った以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体j2を得た。
LMP-Aを製造例9で得られたLMP-Fに変更し、さらにグラファイト(日本黒鉛社製、CGB10、平均粒径10μm)55gを添加して複合化処理を行った以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体k2を得た。
LMP-Aを製造例9で得られたLMP-Fに変更し、さらにグラフェン(XG sciences社製、xGNP、平均粒径30μm)5gを添加して複合化処理を行った以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体l2を得た。
LMP-Aを製造例9で得られたLMP-Fに変更し、さらにアセチレンブラック(デンカ社製、LI-100、平均粒径50nm)5gを添加して複合化処理を行った以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体m2を得た。
LMP-Aを製造例9で得られたLMP-Fに変更し、さらにポリアニリン(シグマアルドリッチ社製)5gを添加して複合化処理を行った以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体n2を得た。
LMP-A350gを、LMP-A175gと製造例3で得られたNCA-A175gの混合物に変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体o2を得た。
製造例1で得られたNCM-A350gと、製造例4で得られたLMP-A 150gとを、乳鉢を用いて、5分間の混合処理を行い、NCM-AとLMP-Aとが複合化することなく、単に混合してなるリチウムイオン二次電池用正極活物質混合物p1を得た。
LMP-Aを製造例15で得られたLMP-Lに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体q1を得た。
NCM-Aを497.5gに、LMP-Aを2.5gに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体r1を得た。
NCM-Aを250.0gに、LMP-Aを250.0gに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体s1を得た。
LMP-Aを製造例10で得られたLMP-Gに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体t1を得た。
LMP-Aを製造例6で得られたLMP-Cに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体u1を得た。
LMP-Aを製造例14で得られたLMP-Kに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体v1を得た。
LMP-Aを製造例11で得られたLMP-Hに変更した以外、実施例1と同様にして、リチウムイオン二次電池用正極活物質複合体w1を得た。
NCM-Aを製造例2で得られたNCM-Bに変更した以外、比較例1と同様にして、リチウムイオン二次電池用正極活物質混合物x1を得た。
製造例3で得られたNCA-A350gと、製造例4で得られたLMP-A 150gとを、乳鉢を用いて、5分間の混合処理を行い、NCA-AとLMP-Aとが複合化することなく、単に混合してなるリチウムイオン二次電池用正極活物質混合物p2を得た。
LMP-Aを製造例15で得られたLMP-Lに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体q2を得た。
NCA-Aを497.5gに、LMP-Aを2.5gに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体r2を得た。
NCA-Aを250.0gに、LMP-Aを250.0gに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体s2を得た。
LMP-Aを製造例10で得られたLMP-Gに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体t2を得た。
LMP-Aを製造例6で得られたLMP-Cに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体u2を得た。
LMP-Aを製造例14で得られたLMP-Kに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体v2を得た。
LMP-Aを製造例11で得られたLMP-Hに変更した以外、実施例16と同様にして、リチウムイオン二次電池用正極活物質複合体w2を得た。
比較例1、比較例9及び比較例10で得られたリチウムイオン二次電池用正極活物質混合物p1、リチウムイオン二次電池用正極活物質混合物x1、及びリチウムイオン二次電池用正極活物質混合物p2を除いた、全てのリチウムイオン二次電池用正極活物質複合体について、X線光電子分光法(XPS)を用いた複合体粒子表面に存在する元素を分析した。具体的には、正極活物資複合体もしくは正極活物質混合物のNi2p3/2のピークから、正極活物資複合体もしくは正極活物質混合物のP2pのピークに対して規格化したLMP由来のNi2p3/2のピークを差し引いた、差分XPSプロファイルにおけるNCM又はNCA由来のNi2p3/2のピーク強度と、正極活物資複合体もしくは正極活物質混合物におけるLMP由来のP2pのピーク強度及びC1sのピーク強度から、下記式(2)によりXPSピーク強度比(A)を求めた。このXPSピーク強度比(A)は、値が小さいほど複合体粒子表面がLMPに被覆されていることを示す。結果を表1及び表2に示す。
XPSピーク強度比(A)=(Ni2p3/2のピーク強度)/
((P2pのピーク強度)+(C1sのピーク強度))
・・・(2)
比較例1、比較例9及び比較例10で得られたリチウムイオン二次電池用正極活物質混合物p1、リチウムイオン二次電池用正極活物質混合物x1、及びリチウムイオン二次電池用正極活物質混合物p2を除いた、全てのリチウムイオン二次電池用正極活物質複合体について、複合体粒子に一定のせん断力を加えた後に複合体粒子表面に存在する元素を上記と同様にX線光電子分光法を用いてXPSピーク強度比を求め、せん断力を加える前後のXPSピーク強度比の比からNCM又はNCAへのLMPの被覆強度を評価した。
具体的には、得られたリチウムイオン二次電池用正極活物質複合体2gとN-メチル-2-ピロリドン10gを高速ミキサー(プライミクス社製フィルミックス40L型)を用い2000rpmで3分間攪拌混練した。これは、二次電池の製造プロセスでの集電体への正極スラリーの塗布工程を強調的に模擬したものであって、かかる塗布工程で正極活物質粒子に加えられるせん断力以上の力が加わっている。攪拌混練処理後のスラリーを、温風乾燥機を用いて80℃×12時間乾燥してリチウムイオン二次電池用正極活物質複合体を得た後、得られたリチウムイオン二次電池用正極活物質複合体にX線光電子分光法を行い、上記式(2)と同様の計算からXPSピーク強度比(B)を求めた後、下記式(3)により被覆強度比を求めた。この被覆強度比は、値が小さく、1に近いほど複合体粒子表面に強固にLMPが被覆されていることを示す。結果を、リチウムイオン二次電池用正極活物質複合体の製造条件と共に表1及び表2に示す。
被覆強度比=(XPSピーク強度比(B))/(XPSピーク強度比(A))
・・・(3)
実施例1~30、比較例1~17で得られたリチウムイオン二次電池用正極活物質複合体又はリチウムイオン二次電池用正極活物質混合物を正極材料として用い、リチウムイオン二次電池の正極を作製した。具体的には、得られたリチウムイオン二次電池用正極活物質複合体またはリチウムイオン二次電池用正極活物質混合物、アセチレンブラック、ポリフッ化ビニリデンを質量比90:5:5の配合割合で混合し、これにN-メチル-2-ピロリドンを加えて充分混練し、正極スラリーを調製した。正極スラリーを厚さ20μmのアルミニウム箔からなる集電体に塗工機を用いて塗布し、80℃で12時間の真空乾燥を行った。その後、φ14mmの円盤状に打ち抜いてハンドプレスを用いて16MPaで2分間プレスし、正極とした。
次いで、上記の正極を用いてコイン型二次電池を構築した。負極には、φ15mmに打ち抜いたリチウム箔を用いた。電解液には、エチレンカーボネート及びエチルメチルカーボネートを体積比3:7の割合で混合した混合溶媒に、LiPF6を1mol/Lの濃度で溶解したものを用いた。セパレータには、ポリプロピレンなどの高分子多孔フィルムなど、公知のものを用いた。これらの電池部品を露点が-50℃以下の雰囲気で常法により組み込み収容し、コイン型二次電池(CR-2032)を製造した。
その後、かかる二次電池を解体し、取り出した正極を炭酸ジメチルで洗浄後、電解液に浸した。このときの電解液は、エチレンカーボネート及びエチルメチルカーボネートを体積比3:7の割合で混合した混合溶媒に、LiPF6を1mol/Lの濃度で溶解したものを用いた。正極を浸した電解液を密閉容器に入れ、70℃で1週間静置した。
静置後、正極を取り出した電解液を0.45μmのディスミックフィルタで濾過し、硝酸により酸分解した。酸分解した電解液に含まれるNCM由来のMn、Ni、Co、又はNCA由来のAl、Ni、Coを、ICP発光分光法を用いて定量した。結果を表3及び表4に示す。
上記の電解液への遷移金属溶出量の評価で製造した二次電池を用いて、高温サイクル特性を評価した。具体的には、電流密度85mA/g、電圧4.25Vの定電流充電と、電流密度85mA/g、終止電圧3.0Vの定電流放電とし、電流密度85mA/g(0.5CA)における放電容量を求めた。さらに、同じ充放電条件の100サイクル繰り返し試験を行い、下記式(4)により容量保持率(%)を求めた。なお、充放電試験は全て45℃で行った。結果を表5及び表6に示す。
容量保持率(%)=
(100サイクル後の放電容量)/(1サイクル後の放電容量)×100
・・・(4)
上記の電解液への遷移金属溶出量の評価で製造した二次電池を用いて、レート特性を評価した。具体的には、電流密度34mA/g、電圧4.25Vの定電流充電と、電流34mA/g、終止電圧3.0Vの定電流放電とし、電流密度34mA/gにおける放電容量を求めた。さらに、同条件で定電流充電を行い、電流密度510mA/g、終止電圧3.0Vの定電流放電とし、電流密度510mA/gにおける放電容量を求めた。なお、充放電試験は30℃で行った。
得られた放電容量から、下記式(5)により容量比(%)を求めた。結果を表5及び表6に示す。
容量比(%)=(電流密度510mA/gにおける放電容量)/
(電流密度34mA/gにおける放電容量)×100
・・・(5)
さらに、表3又は表4から明らかなように、実施例で得られたリチウムイオン二次電池用正極活物質複合体を正極活物質として使用したリチウムイオン二次電池は、比較例で得られたリチウムイオン二次電池用正極活物質複合体又はリチウムイオン二次電池用正極活物質混合物を正極活物質として使用したリチウムイオン二次電池と比べ、電極から電解液への遷移金属の溶出量が少なく、耐久性においても優れていることがわかる。
Claims (10)
- 下記式(I):
LiNiaCobMncM1 xO2・・・(I)
(式(I)中、M1はMg、Ti、Nb、Fe、Cr、Si、Al、Ga、V、Zn、Cu、Sr、Mo、Zr、Sn、Ta、W、La、Ce、Pb、Bi及びGeから選ばれる1種又は2種以上の元素を示す。a、b、c、xは、0.3≦a<1、0<b≦0.7、0<c≦0.7、0≦x≦0.3、かつ3a+3b+3c+(M1の価数)×x=3を満たす数を示す。)
又は、下記式(II):
LiNidCoeAlfM2 yO2・・・(II)
(式(II)中、M2はMg、Ti、Nb、Fe、Cr、Si、Ga、V、Zn、Cu、Sr、Mo、Zr、Sn、Ta、W、La、Ce、Pb、Bi及びGeから選ばれる1種又は2種以上の元素を示す。d、e、f、yは、0.4≦d<1、0<e≦0.6、0<f≦0.3、0≦y≦0.3、かつ3d+3e+3f+(M2の価数)×y=3を満たす数を示す。)
で表される1種以上のリチウム複合酸化物粒子からなるリチウム複合酸化物二次粒子(A)の表面のみにおいて、下記式(III)又は(III)':
LigMnhFeiM3 zPO4・・・(III)
(式(III)中、M3はCo、Ni、Ca、Sr、Y、Zr、Mo、Ba、Pb、Bi、La、Ce、Nd又はGdを示す。g、h、i、及びzは、0<g≦1.2、0≦h≦1.2、0≦i≦1.2、0≦z≦0.3、及びh+i≠0を満たし、かつg+(Mnの価数)×h+(Feの価数)×i+(M3の価数)×z=3を満たす数を示す。)
Mnh'Fei'M3 z'PO4・・・(III)'
(式(III)'中、M3は式(III)と同義である。h'、i'、及びz'は、0≦h'≦1.2、0≦i'≦1.2、0≦z'≦0.3、及びh'+i'≠0を満たし、かつ(Mnの価数)×h'+(Feの価数)×i'+(M3の価数)×z'=3を満たす数を示す。)
で表され、かつ表面に炭素(c)が担持してなるリチウム系ポリアニオン粒子(B)と、リチウム複合酸化物粒子とが複合化してなり、
リチウム系ポリアニオン粒子(B)の表面における炭素(c)の担持量が、リチウム系ポリアニオン粒子(B)100質量%中に0.1質量%以上18質量%未満であり、
リチウム系ポリアニオン粒子(B)の平均粒径が50~200nmであり、
リチウム複合酸化物二次粒子(A)の含有量と、リチウム系ポリアニオン粒子(B)の含有量との質量比((A):(B))が、95:5~65:35であるリチウムイオン二次電池用正極活物質複合体。 - 前記リチウム系ポリアニオン粒子(B)の表面に担持してなる炭素(c)が、セルロースナノファイバー由来の炭素(c1)又は水溶性炭素材料由来の炭素(c2)である請求項1に記載のリチウムイオン二次電池用正極活物質複合体。
- リチウム複合酸化物二次粒子(A)の平均粒径が、1~25μmである請求項1又は2に記載のリチウムイオン二次電池用正極活物質複合体。
- 表面に炭素(c)が担持してなるリチウム系ポリアニオン粒子(B)の25℃での20MPa加圧時における粉体としての電気伝導率が、1×10-7S/cm以上である請求項1~3のいずれか1項に記載のリチウムイオン二次電池用正極活物質複合体。
- セルロースナノファイバー由来の炭素(c1)以外の水不溶性炭素粉末(c3)が、リチウム複合酸化物二次粒子(A)及び表面に炭素(c)が担持してなるリチウム系ポリアニオン粒子(B)と複合化してなり、
水不溶性炭素粉末(c3)の含有量が、リチウム複合酸化物二次粒子(A)及び表面に炭素(c)が担持してなるリチウム系ポリアニオン粒子(B)の合計量100質量部に対して0.5~17質量部である請求項1~4のいずれか1項に記載のリチウムイオン二次電池用正極活物質複合体。 - リチウムイオン二次電池用正極活物質複合体のX線光電子分光法(XPS)によるNi2p3/2のピークから、リチウムイオン二次電池用正極活物質複合体のP2pのピークに対して規格化したリチウム系ポリアニオン粒子由来のNi2p3/2のピークを差し引いた、差分XPSプロファイルにおけるリチウム複合酸化物粒子由来のNi2p3/2のピーク強度と、リチウムイオン二次電池用正極活物質複合体におけるLMP由来のP2pのピーク強度及びC1sのピーク強度から算出したピーク強度比((Ni2p3/2のピーク強度)/(P2pのピーク強度+C1sのピーク強度))が、0.05以下である請求項1~5のいずれか1項に記載のリチウムイオン二次電池用正極活物質複合体。
- 請求項1~6のいずれか1項に記載のリチウムイオン二次電池用正極活物質複合体を正極材料として含むリチウムイオン二次電池。
- リチウム複合酸化物二次粒子(A)、及び表面に炭素(c)が担持してなるリチウム系ポリアニオン粒子(B)を、圧縮力及びせん断力を付加しながら混合して複合化する工程を備える請求項1~6のいずれか1項に記載のリチウムイオン二次電池用正極活物質複合体の製造方法。
- リチウム複合酸化物二次粒子(A)、表面に炭素(c)が担持してなるリチウム系ポリアニオン粒子(B)、及びセルロースナノファイバー由来の炭素(c1)以外の水不溶性炭素粉末(c3)を、圧縮力及びせん断力を付加しながら混合して複合化する工程を備える請求項1~6のいずれか1項に記載のリチウムイオン二次電池用正極活物質複合体の製造方法。
- 複合化する工程が、周速度15~45m/sで回転するインペラを備える密閉容器内で行う工程である請求項8又は9に記載のリチウムイオン二次電池用正極活物質複合体の製造方法。
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JP7320418B2 (ja) | 2019-09-20 | 2023-08-03 | 太平洋セメント株式会社 | リチウムイオン二次電池用混合型正極活物質及びリチウムイオン二次電池用正極の製造方法 |
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US20200161632A1 (en) | 2020-05-21 |
CN110462896B (zh) | 2021-04-27 |
EP3633775B1 (en) | 2022-08-10 |
KR102102094B1 (ko) | 2020-04-17 |
WO2018220972A1 (ja) | 2018-12-06 |
KR20190120377A (ko) | 2019-10-23 |
EP3633775A4 (en) | 2021-03-03 |
US10868295B2 (en) | 2020-12-15 |
JPWO2018221263A1 (ja) | 2019-06-27 |
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JP6549807B2 (ja) | 2019-07-24 |
CN110462896A (zh) | 2019-11-15 |
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