WO2026033763A1 - Matériau d'électrode positive et mélange d'électrode positive et batterie rechargeable au lithium l'utilisant - Google Patents

Matériau d'électrode positive et mélange d'électrode positive et batterie rechargeable au lithium l'utilisant

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Publication number
WO2026033763A1
WO2026033763A1 PCT/JP2024/028563 JP2024028563W WO2026033763A1 WO 2026033763 A1 WO2026033763 A1 WO 2026033763A1 JP 2024028563 W JP2024028563 W JP 2024028563W WO 2026033763 A1 WO2026033763 A1 WO 2026033763A1
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WO
WIPO (PCT)
Prior art keywords
positive electrode
solid electrolyte
sulfide solid
sulfur
phosphorus
Prior art date
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Pending
Application number
PCT/JP2024/028563
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English (en)
Japanese (ja)
Inventor
大介 伊藤
晴美 高田
美咲 赤石
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Nissan Motor Co Ltd
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Nissan Motor Co Ltd
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Publication date
Application filed by Nissan Motor Co Ltd filed Critical Nissan Motor Co Ltd
Priority to PCT/JP2024/028563 priority Critical patent/WO2026033763A1/fr
Publication of WO2026033763A1 publication Critical patent/WO2026033763A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
    • H01M10/0562—Solid materials
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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 material, a positive electrode mixture using the same, and a lithium secondary battery.
  • Solid electrolytes are materials primarily composed of ionic conductors capable of ion conduction in a solid state. Therefore, all-solid-state lithium secondary batteries do not, in principle, encounter various problems caused by flammable organic electrolytes, as in conventional liquid-based lithium secondary batteries.
  • the use of high-potential, high-capacity positive electrode materials and high-capacity negative electrode materials generally leads to significant improvements in the output density and energy density of batteries.
  • elemental sulfur (S 8 ) has an extremely large theoretical capacity of approximately 1670 mAh/g and is advantageous in that it is low cost and abundantly available.
  • WO 2022/090757 discloses a positive electrode material for an electric device, comprising a composite material including a conductive material having pores, a solid electrolyte, and a positive electrode active material containing sulfur, wherein at least a portion of the solid electrolyte and at least a portion of the positive electrode active material are arranged on the inner surfaces of the pores so as to be in contact with each other.
  • a composite material having the above structure can be used as is as a positive electrode material, or that a solid electrolyte can be added to and mixed with the composite material, and if necessary, processed in a device such as a ball mill before being used as a positive electrode material.
  • the present invention therefore aims to provide a means for reducing the cell resistance of lithium secondary batteries.
  • the present inventors have conducted extensive research in light of the above-mentioned problems and have found that the above-mentioned problems can be solved by a positive electrode material that exhibits a predetermined profile in a spectrum determined by 31P solid-state nuclear magnetic resonance spectroscopy, thereby completing the present invention.
  • one aspect of the present invention relates to a cathode material comprising a porous carbon material and a sulfur- and phosphorus-containing sulfide solid electrolyte filled into the pores thereof, characterized in that , in a spectrum obtained by P solid-state nuclear magnetic resonance spectroscopy, the ratio (B/A) of the sum (B) of the integral (A) of the signal at 85.0 ⁇ 10 ppm to the integral (A) of the signal at a chemical shift other than 85.0 ⁇ 10 ppm is less than 0.32.
  • FIG. 1 is a cross-sectional view showing a schematic overall structure of a stacked-type (internal parallel connection type) lithium secondary battery (hereinafter also simply referred to as a "stacked-type secondary battery") according to one embodiment of the present invention.
  • stacked-type secondary battery internal parallel connection type lithium secondary battery
  • One aspect of the present invention is a cathode material in which the pores of porous carbon are filled with a sulfur- and phosphorus-containing sulfide solid electrolyte, and in a spectrum obtained by P solid-state nuclear magnetic resonance spectroscopy (NMR), the ratio (B/A) of the sum B of the integrals of signals present at chemical shifts other than 85.0 ⁇ 10 ppm to the integral A of the signal present at 85.0 ⁇ 10 ppm is less than 0.32.
  • the cathode material according to this aspect makes it possible to reduce the cell resistance in a lithium secondary battery.
  • the inventors conducted a predetermined mechanical milling process on a composite material in which a sulfur- and phosphorus-containing sulfide solid electrolyte was filled into the pores of porous carbon. Then, a solid electrolyte was added to prepare a positive electrode mixture. A lithium secondary battery was fabricated using the positive electrode mixture, and the cell resistance was measured. It was found that the resistance was significantly reduced compared to when the technology described in the above literature was used. Then, when the composite material after mechanical milling was analyzed using 31P solid-state NMR, it was found that the NMR spectrum had a predetermined profile, leading to the completion of the present invention.
  • the positive electrode material according to this embodiment is characterized in that, in a spectrum obtained by 31 P solid-state NMR, the ratio (B/A) of the sum B of the integrals of signals present at chemical shifts other than 85.0 ⁇ 10 ppm to the integral A of the signal present at 85.0 ⁇ 10 ppm is less than 0.32.
  • the signal present at 85.0 ⁇ 10 ppm is assigned to PS 4 3- . Therefore, this signal serves as an indicator of the presence of Li 3 PS 4 .
  • signals present at chemical shifts other than 85.0 ⁇ 10 ppm include, for example, those assigned to POS 3 3- , PO 2 S 2 3- , PO 3 S 3- , and PO 4 3- . Therefore, these signals are indicators of the presence of oxides such as Li3POS3 , Li3PO2S2 , Li3PO3S , and Li3PO4 . Therefore, a ratio (B/A) of less than 0.32 means that the amount of oxide is small relative to the amount of Li3PS4 . Li3PS4 has high lithium ion conductivity, but the lithium ion conductivity of the oxide is low. Therefore, it is presumed that application of the positive electrode material according to this embodiment to a lithium secondary battery will improve the lithium ion conductivity in the battery, resulting in a reduction in cell resistance.
  • a cathode material with a ratio (B/A) of less than 0.32 can be prepared by preparing a composite material (referred to as "composite material 2" in the cathode material manufacturing method described below) in which sulfur and a phosphorus-containing sulfide solid electrolyte are filled into the pores of porous carbon, and then subjecting the composite material alone to mechanical milling.
  • composite material preparation methods for filling the pores with the phosphorus-containing sulfide solid electrolyte include dispersing porous carbon in a solution of the phosphorus-containing sulfide solid electrolyte dissolved in a dehydrated solvent and then removing the solvent.
  • Another method for filling the pores with sulfur involves mixing the sulfur and porous carbon, then heating the mixture to melt the sulfur and impregnate the pores. While these methods are performed in an inert atmosphere, the inclusion of trace amounts of moisture or oxygen can oxidize a portion of the phosphorus-containing sulfide solid electrolyte, inevitably resulting in the aforementioned oxides. It is believed that mechanical milling of only the composite material containing such oxides results in the following mechanochemical reaction:
  • the above-mentioned International Publication No. 2022/090757 also discloses a composite material in which a sulfur- and phosphorus-containing sulfide solid electrolyte is filled into the pores of porous carbon (FIG. 3B and Example 1, etc.).
  • Li 6 PS 5 Cl is added to the composite material, and then mechanically milled using a ball mill, and the resulting material is used as a positive electrode material to produce an all-solid-state lithium secondary battery (Example 1, etc.), and there is no mention of performing mechanical milling on the composite material alone.
  • [sulfur] Sulfur can function as a positive electrode active material.
  • the sulfur preferably has an S8 structure and is preferably at least one selected from ⁇ -sulfur, ⁇ -sulfur, and ⁇ -sulfur.
  • the sulfur content is not particularly limited, but is preferably 50 to 90 mass%, more preferably 55 to 85 mass%, and even more preferably 60 to 80 mass%, relative to 100 mass% of the total mass of the positive electrode material. When the sulfur content is within the above range, a good balance between capacity and output characteristics can be achieved in the lithium secondary battery.
  • the phosphorus-containing sulfide solid electrolyte is a solid electrolyte containing at least lithium atoms, phosphorus atoms, and sulfur atoms.
  • Examples of such phosphorus-containing sulfide solid electrolytes include Li 2 S—P 2 S 5 , Li 2 S—P 2 S 5 , Li 2 S—P 2 S 5 -LiI, Li 2 S—P 2 S 5 -Li 2 O—LiI, Li 2 S— SiS 2 -P 2 S 5 -LiI, and Li 2 S—P 2 S 5 -Z m S n (where m and n are positive numbers, and Z is Ge, Zn, or Ga).
  • the expression "Li 2 S-P 2 S 5 " means a solid electrolyte obtained using a raw material composition containing Li 2 S and P 2 S 5 , and the same applies to other expressions.
  • the phosphorus-containing sulfide solid electrolyte may have, for example, a Li 3 PS 4 skeleton, a Li 4 P 2 S 7 skeleton, or a Li 4 P 2 S 6 skeleton.
  • Examples of phosphorus-containing sulfide solid electrolytes having a Li 3 PS 4 skeleton include LiI-Li 3 PS 4 , LiI-LiBr-Li 3 PS 4 , and Li 3 PS 4.
  • Examples of phosphorus-containing sulfide solid electrolytes having a Li 4 P 2 S 7 skeleton include Li-P-S-based solid electrolytes known as LPS (for example, Li 7 P 3 S 11 ).
  • the phosphorus-containing sulfide solid electrolyte for example, a solid electrolyte having an LGPS-type crystal structure (represented by Li (4-x) Ge (1-x) P x S 4 (x satisfies 0 ⁇ x ⁇ 1)) or a solid electrolyte having an argyrodite-type crystal structure (represented by Li 6 PS 5 X (X is Cl, Br, or I)) is also preferably used.
  • These phosphorus-containing sulfide solid electrolytes have high ionic conductivity and can effectively contribute to reducing internal resistance.
  • the phosphorus-containing sulfide solid electrolyte is preferably one having an LPS, LGPS, or argyrodite-type crystal structure, and more preferably one having an argyrodite-type crystal structure.
  • the content of the phosphorus-containing sulfide solid electrolyte is not particularly limited, but is preferably 5 to 35 mass%, more preferably 7 to 30 mass%, and even more preferably 10 to 25 mass%, relative to the total mass of the positive electrode material (100 mass%).
  • the content of the phosphorus-containing sulfide solid electrolyte is within the above range, a good balance between capacity and output characteristics can be achieved in the lithium secondary battery.
  • porous carbon refers to a carbon material that has pores and is composed primarily of carbon.
  • “composed primarily of carbon” refers to containing carbon atoms as the main component, and is a concept that encompasses both “consisting solely of carbon atoms” and “consisting essentially of carbon atoms.””Consisting essentially of carbon atoms” means that the inclusion of impurities in an amount of about 2 to 3 mass % or less is acceptable.
  • the shape of the porous carbon is not particularly limited, but particulate form is preferred.
  • porous carbon particles include activated carbon, carbon black (e.g., Ketjen Black®), (oil) furnace black, channel black, acetylene black, thermal black, and lamp black, as well as carbon particles (carbon supports) made from coke, natural graphite, and artificial graphite.
  • a ceramic or other mold may be mixed with a carbon raw material (e.g., resin), fired in an inert atmosphere, and then the mold dissolved in acid to synthesize a carbon material with a porous structure in which the shape of the mold has been transferred.
  • This carbon material can be used as porous carbon particles.
  • the pore size and pore volume of the resulting carbon material can be altered by appropriately adjusting the particle size of the mold and the blending ratio of the carbon raw materials.
  • the amount of porous carbon is not particularly limited, but is preferably 3 to 25% by mass, more preferably 5 to 20% by mass, and even more preferably 7 to 15% by mass, relative to the total mass of the positive electrode material (100% by mass).
  • the lithium secondary battery can achieve a good balance between capacity and output characteristics.
  • the positive electrode material according to the present embodiment is characterized in that, in a spectrum obtained by 31P solid-state nuclear magnetic resonance spectroscopy (NMR), the ratio (B/A) of the integral A of the signal present at 85.0 ⁇ 10 ppm to the sum B of the integrals of signals present at chemical shifts other than 85.0 ⁇ 10 ppm is less than 0.32.
  • the ratio (B/A) is determined by the method described in the Examples below. As described above, the ratio (B/A) is an indicator of the ratio of the amount of oxide to the amount of Li3PS4 , and the smaller this value, the more improved the lithium ion conductivity of the positive electrode material.
  • the ratio (B/A) is preferably 0.30 or less, more preferably 0.25 or less, even more preferably 0.23 or less, and most preferably 0.225 or less. While a smaller ratio (B/A) is preferable for reducing cell resistance, it is usually 0.05 or more because it is difficult to completely eliminate the oxides that inevitably form.
  • the value of the ratio (B/A) can be controlled by the processing conditions when the composite material 2 is subjected to mechanical milling in the manufacturing method of the positive electrode material described below. Specifically, the value of the ratio (B/A) can be reduced by increasing the load of the mechanical milling (for example, when using a ball mill, increasing the centrifugal acceleration and/or lengthening the processing time).
  • the positive electrode material according to this embodiment preferably has a molar ratio (P/C) of phosphorus (P) to carbon (C) of 0.025 or more, as determined by surface analysis using X-ray photoelectron spectroscopy.
  • the molar ratio (P/C) is determined by the method described in the Examples below.
  • the molar ratio (P/C) is an index indicating the amount of phosphorus-containing sulfide solid electrolyte present on the surface of the positive electrode material; a higher value indicates a greater amount of phosphorus-containing sulfide solid electrolyte present on the surface of the positive electrode material.
  • the molar ratio (P/C) is preferably 0.030 or more, more preferably 0.035 or more, and even more preferably 0.036 or more.
  • a larger molar ratio (P/C) is preferable to reduce cell resistance, but is typically 0.100 or less.
  • the molar ratio (P/C) can be controlled by the processing conditions when subjecting composite material 2 to mechanical milling. Specifically, the molar ratio (P/C) can be increased by increasing the load on mechanical milling (for example, by increasing the centrifugal acceleration and/or lengthening the processing time when using a ball mill).
  • the positive electrode material according to this embodiment preferably has a mass ratio ( PS4/C) of PS4 units to carbon (C) of 0.32 or more, as determined by surface analysis using X-ray photoelectron spectroscopy.
  • the mass ratio (PS4 / C) is determined by the method described in the Examples below.
  • the mass ratio ( PS4 /C) is an index indicating the amount of phosphorus-containing sulfide solid electrolyte present on the surface of the positive electrode material; a larger value indicates a larger amount of phosphorus-containing sulfide solid electrolyte present on the surface of the positive electrode material.
  • the mass ratio ( PS4 /C) is preferably 0.35 or more, more preferably 0.40 or more, even more preferably 0.45 or more, particularly preferably 0.46 or more, and most preferably 0.48 or more. It should be noted that a larger value of the mass ratio (PS 4 /C) is preferable for reducing cell resistance, but is usually a value of 1.00 or less.
  • the value of the mass ratio (PS 4 /C) can be controlled by the processing conditions when subjecting the composite material 2 to mechanical milling. Specifically, the value of the mass ratio (PS 4 /C) can be increased by increasing the load of mechanical milling (for example, when using a ball mill, increasing the centrifugal acceleration or lengthening the processing time).
  • the positive electrode material according to this embodiment can be produced by the following method. That is, another embodiment of the present invention is a method for producing a positive electrode material, comprising the steps of impregnating porous carbon with a solution containing a phosphorus-containing sulfide solid electrolyte and a solvent, and then removing the solvent to obtain a composite material 1 (hereinafter also referred to as "step (1)"), impregnating the composite material 1 with a sulfur melt to obtain a composite material 2 (hereinafter also referred to as "step (2)”), and mechanically milling the composite material 2 (hereinafter also referred to as "step (3)").
  • step (1) composite material 1
  • step (2) composite material 2
  • step (3) mechanically milling the composite material 2
  • step (1) porous carbon is impregnated with a solution containing a phosphorus-containing sulfide solid electrolyte and a solvent, and the solvent is then removed. This results in composite material 1, in which the phosphorus-containing sulfide solid electrolyte is filled into the pores of the porous carbon.
  • the phosphorus-containing sulfide solid electrolyte solution is prepared by dissolving the phosphorus-containing sulfide solid electrolyte in a solvent.
  • the solvent used in this process is not particularly limited, but from the standpoints of solubility, operability, safety, etc., a lower alcohol is preferred, and an alcohol having 1 to 4 carbon atoms is more preferred.
  • alcohols having 1 to 4 carbon atoms include methanol, ethanol, 1-propanol, 2-propanol, n-butanol, 2-butanol, and tert-butanol. Among these, from the standpoints of solubility, operability, safety, etc., methanol, ethanol, 1-propanol, and 2-propanol are preferred, with methanol and ethanol being more preferred, and ethanol being even more preferred.
  • the above-mentioned solvent preferably has a low water content; specifically, the water content of the solvent is preferably less than 0.2% by mass. More preferably, the water content of the solvent is 0.1% by mass or less, even more preferably 0.05% by mass or less, even more preferably 0.02% by mass or less, even more preferably 0.01% by mass or less, even more preferably 0.005% by mass or less, and particularly preferably 0.002% by mass or less.
  • the water content of the solvent can be measured, for example, by Karl Fischer coulometric titration.
  • the content of the phosphorus-containing sulfide solid electrolyte in the phosphorus-containing sulfide solid electrolyte solution is preferably 3 to 30 mass %, and more preferably 5 to 20 mass %. If the content of the phosphorus-containing sulfide solid electrolyte is within the above range, the desired amount of phosphorus-containing sulfide solid electrolyte can be filled into the pores of the porous carbon.
  • the phosphorus-containing sulfide solid electrolyte solution By adding porous carbon to a phosphorus-containing sulfide solid electrolyte solution and dispersing the porous carbon in the solution, the phosphorus-containing sulfide solid electrolyte solution can be impregnated into the porous carbon.
  • the solvent is then removed while stirring the dispersion.
  • the solvent is preferably removed under reduced pressure at a temperature of 70°C or less. This prevents decomposition of the phosphorus-containing sulfide solid electrolyte and prevents an increase in cell resistance.
  • step (2) the composite material 1 is impregnated with a sulfur melt. This results in a composite material 2 in which the sulfur- and phosphorus-containing sulfide solid electrolyte is filled into the pores of the porous carbon.
  • step (2) one method for impregnating the composite material 1 with the sulfur melt is to mix sulfur and porous carbon in advance, then heat-treat the mixture to melt the sulfur, and impregnate the porous carbon with the sulfur melt.
  • step (3) the composite material 2 is mechanically milled, thereby obtaining a positive electrode material.
  • Mechanical milling can be performed using a ball mill such as a planetary ball mill or an agitation ball mill.
  • a ball mill such as a planetary ball mill or an agitation ball mill.
  • a planetary ball mill is used, and milling balls and composite material 2 are placed in a milling pot, followed by mechanical milling at a predetermined rotation speed and time.
  • mechanical milling applies forces such as shear stress, friction, shear, impact, and compression to composite material 2, causing a mechanochemical reaction, which is thought to regenerate Li3PS4 , which has high lithium ion conductivity, from oxides that are inevitably produced during the production process of composite material 2.
  • Li3PS4 which has high lithium ion conductivity
  • the load (centrifugal acceleration [G] x processing time [min]) applied to composite material 2 is preferably 1000 to 7000 [G ⁇ min], and more preferably 2000 to 5000 [G ⁇ min].
  • the centrifugal acceleration [G] is preferably 10 to 100 [G], and more preferably 20 to 50 [G].
  • the processing time is preferably 10 to 600 [min], and more preferably 30 to 300 [min].
  • the cathode material may be used as it is as a material for the cathode active material layer, but it is preferable to add a solid electrolyte to the cathode material to form a cathode mixture and then use the resulting cathode mixture as a material for the cathode active material layer.
  • a sulfide solid electrolyte as the solid electrolyte for the cathode mixture, and to control the crystallite diameters of sulfur in the cathode mixture and the sulfide solid electrolyte within predetermined ranges.
  • the positive electrode mixture according to this embodiment essentially contains the above-mentioned positive electrode material and a sulfide solid electrolyte.
  • the sulfide solid electrolyte may be the same as or different from the phosphorus-containing sulfide solid electrolyte contained in the positive electrode material, but it is preferable that they are the same.
  • the sulfide solid electrolyte essentially contains the element S, preferably the element Li, the element M (where M is at least one element selected from the group consisting of P, Si, Ge, Sn, Ti, Zr, Nb, Al, Sb, Br, Cl, and I), and the element S, and more preferably the element S, the element Li, and the element P.
  • the sulfide solid electrolyte may have a Li 3 PS 4 skeleton, a Li 4 P 2 S 7 skeleton, or a Li 4 P 2 S 6 skeleton.
  • sulfide solid electrolytes having a Li 3 PS 4 skeleton include LiI-Li 3 PS 4 , LiI-LiBr-Li 3 PS 4 , and Li 3 PS 4 .
  • sulfide solid electrolytes having a Li 4 P 2 S 7 skeleton include Li-P-S solid electrolytes known as LPS.
  • Examples of sulfide solid electrolytes that may be used include LGPS, which is represented by Li (4-x) Ge (1-x) P x S 4 (where x satisfies 0 ⁇ x ⁇ 1). More specifically, examples include LPS (Li 2 S—P 2 S 5 ), Li 7 P 3 S 11 , Li 3.2 P 0.96 S, Li 3.25 Ge 0.25 P 0.75 S 4 , Li 10 GeP 2 S 12 , and Li 6 PS 5 X (wherein X is Cl, Br, or I).
  • LPS Li 2 S—P 2 S 5
  • Li 7 P 3 S 11 Li 3.2 P 0.96 S
  • Li 3.25 Ge 0.25 P 0.75 S 4 Li 10 GeP 2 S 12
  • Li 6 PS 5 X wherein X is Cl, Br, or I.
  • Li 2 S—P 2 S 5 refers to a sulfide solid electrolyte obtained using a raw material composition containing Li 2 S and P 2 S 5 , and the same applies to other descriptions.
  • sulfide solid electrolytes are preferably selected from the group consisting of LPS (Li 2 S-P 2 S 5 ), Li 6 PS 5 X (where X is Cl, Br, or I), Li 7 P 3 S 11 , Li 3.2 P 0.96 S, and Li 3 PS 4, from the viewpoint that they have high lithium ion conductivity and a low bulk modulus, and therefore can follow the volume changes of the electrode active material that accompany charge and discharge.
  • the sulfide solid electrolyte is preferably one having an argyrodite-type crystal structure, and more preferably Li 6 PS 5 X (where X is Cl, Br, or I) having an argyrodite-type crystal structure.
  • the sulfide solid electrolyte preferably has a particulate shape, such as a spherical or oval sphere.
  • the content of the positive electrode material is preferably 88% by mass or less, and more preferably 85% by mass or less.
  • the content of the positive electrode material is within this range, the cell resistance of the lithium secondary battery can be further reduced.
  • the content of the positive electrode material is preferably more than 50% by mass, more preferably 60% by mass or more, and even more preferably 70% by mass or more.
  • the crystallite diameters X and Y are determined by the method described in the Examples below.
  • the crystallite diameter X of the sulfide solid electrolyte is more preferably 25 nm or more, even more preferably 29 nm or more, and even more preferably 30 nm or more.
  • the crystallite diameter Y of the sulfur is more preferably less than 60 nm, even more preferably less than 56.9 nm, and particularly preferably less than 50 nm.
  • the crystallite diameters X and Y are within the above ranges, the lithium ion conductivity of the positive electrode mixture is further improved, thereby further reducing the cell resistance of the lithium secondary battery.
  • the sulfur crystallite diameter Y can be set to less than 60 nm.
  • a lithium secondary battery including a power generating element having a positive electrode having a positive electrode active material layer containing the above-mentioned positive electrode mixture, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode and containing a solid electrolyte.
  • FIG. 1 is a cross-sectional view schematically illustrating the overall structure of a stacked-type (internal parallel connection type) all-solid-state lithium secondary battery (hereinafter simply referred to as a "stacked-type secondary battery") according to one embodiment of the present invention.
  • the stacked-type secondary battery 10a shown in FIG. 1 has a structure in which a substantially rectangular power generating element 21, where the actual charge/discharge reactions take place, is sealed inside a laminate film 29, which is the battery outer casing.
  • the power generating element 21 has a structure in which a negative electrode, a solid electrolyte layer 17, and a positive electrode are stacked.
  • the negative electrode has a structure in which a negative electrode current collector 11' and a negative electrode active material layer 13 are disposed on the surface of the negative electrode current collector 11'.
  • the positive electrode has a structure in which a positive electrode active material layer 15 are disposed on the surface of the positive electrode current collector 11".
  • the negative electrode current collector 11', the negative electrode active material layer 13, the solid electrolyte layer 17, the positive electrode active material layer 15, and the positive electrode current collector 11" constitute a single cell layer 19. Therefore, the stacked secondary battery 10a shown in FIG. 1 can be said to have a configuration in which a plurality of unit cell layers 19 are stacked and electrically connected in parallel.
  • a pressure member (not shown) applies a restraining pressure to the stacked secondary battery 10a in the stacking direction of the power generating element 21. Therefore, the volume of the power generating element 21 is maintained constant.
  • the main components of the lithium secondary battery according to this embodiment are described below.
  • the current collectors (negative electrode current collector, positive electrode current collector) have the function of mediating the movement of electrons from the electrode active material layer (negative electrode active material layer, positive electrode active material layer).
  • the material that constitutes the current collectors There are no particular restrictions on the material that constitutes the current collectors. Examples of materials that can be used for the current collectors include metals such as aluminum, nickel, iron, stainless steel, titanium, and copper, as well as conductive resins. There are also no particular restrictions on the thickness of the current collectors, but an example is 10 to 100 ⁇ m.
  • the negative electrode active material layer contains a negative electrode active material.
  • the type of negative electrode active material is not particularly limited, but includes carbon materials, metal oxides, and metal active materials.
  • a lithium-containing active material such as lithium metal or a lithium-containing alloy may be used as the negative electrode active material.
  • lithium-containing alloys include alloys of Li with at least one of In, Al, Si, Sn, Mg, Au, Ag, and Zn.
  • the lithium secondary battery is preferably a so-called lithium deposition type in which lithium metal as the negative electrode active material is deposited on the negative electrode current collector during charging.
  • the layer of lithium metal deposited on the negative electrode current collector during this charging process constitutes the negative electrode active material layer. Therefore, the thickness of the negative electrode active material layer increases as the charging process progresses, and decreases as the discharging process progresses.
  • the negative electrode active material layer does not need to be present during full discharge, but in some cases, a negative electrode active material layer made of a certain amount of lithium metal may be present during full discharge.
  • the thickness of the negative electrode active material layer (thickness when fully charged in the case of a lithium deposition type) varies depending on the configuration of the intended lithium secondary battery, but is preferably within the range of 0.1 to 1000 ⁇ m, for example.
  • Solid electrolyte layer The solid electrolyte layer is interposed between the negative electrode and the positive electrode and contains a solid electrolyte (usually as a main component).
  • the solid electrolyte contained in the solid electrolyte layer is not particularly limited, and any solid electrolyte known in the art can be appropriately used, for example, a sulfide solid electrolyte or an oxide solid electrolyte.
  • the solid electrolyte content in the solid electrolyte layer is preferably 50% by mass or more and 100% by mass or less, and more preferably 90% by mass or more and 99% by mass or less.
  • the solid electrolyte layer may further contain a binder in addition to the solid electrolyte.
  • a binder in addition to the solid electrolyte.
  • binders known in the art can be used as appropriate. Examples include styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are substituted with other halogen elements), and carboxymethyl cellulose (CMC).
  • styrene-butadiene rubber tetrafluoroethylene
  • polyvinylidene fluoride are preferred, with tetrafluoroethylene and polyvinylidene fluoride being more preferred.
  • binders may be used alone or in combination of two or more.
  • the thickness of the solid electrolyte layer varies depending on the configuration of the desired lithium secondary battery, but is typically 0.1 to 1000 ⁇ m, and preferably 10 to 40 ⁇ m.
  • the positive electrode active material layer essentially contains the positive electrode mixture and may contain a binder and/or a conductive additive as necessary.
  • the positive electrode active material layer is typically disposed on the surface of a positive electrode current collector as shown in Fig. 1 , but if the positive electrode active material layer 15 itself has a certain degree of conductivity, it may also constitute a positive electrode without using a positive electrode current collector.
  • the content of the positive electrode mixture contained in the positive electrode active material layer is not particularly limited, but from the viewpoint of energy density, it is, for example, 50 to 100 mass% of the total mass of the positive electrode active material layer, preferably 70 to 99 mass% or less, and more preferably 80 to 99 mass% or less.
  • the binders that can be used in the positive electrode active material layer are the same as those described above for the solid electrolyte layer.
  • Conductive additives that can be used in the positive electrode active material layer include, but are not limited to, metals such as aluminum, stainless steel (SUS), silver, gold, copper, and titanium, alloys or metal oxides containing these metals, carbon fibers (specifically, vapor-grown carbon fibers (VGCF), polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, rayon-based carbon fibers, activated carbon fibers, etc.), carbon nanotubes (CNT), and carbon black (specifically, acetylene black, Ketjen Black (registered trademark), furnace black, channel black, thermal lamp black, etc.). Also usable as conductive additives are particulate ceramic materials or resin materials coated with the above-mentioned metal materials by plating or other methods. These conductive additives may be used alone or in combination. The concept of conductive additive does not include those that have pores but retain sulfur or a solid electrolyte within the pores.
  • the thickness of the positive electrode active material layer varies depending on the configuration of the intended lithium secondary battery, but is, for example, 0.1 to 1000 ⁇ m, preferably 30 to 300 ⁇ m, more preferably 50 to 200 ⁇ m, and even more preferably 70 to 150 ⁇ m.
  • the material constituting the current collector plates (25, 27) is not particularly limited, and known highly conductive materials conventionally used as current collector plates for secondary batteries can be used. Metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferred as constituent materials of the current collector plates. From the viewpoints of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferred, and aluminum is particularly preferred.
  • the positive current collector plate 27 and the negative current collector plate 25 may be made of the same material or different materials.
  • the current collectors (11", 11') and the current collector plates (27, 25) may be electrically connected via a positive electrode lead or a negative electrode lead.
  • materials used in known lithium ion secondary batteries can be similarly adopted.
  • the portion removed from the exterior is preferably covered with a heat-resistant, insulating heat-shrinkable tube or the like so as to prevent contact with peripheral devices or wiring, etc., resulting in electrical leakage and affecting products (e.g., automobile parts, particularly electronic devices, etc.).
  • Battery exterior material As the battery exterior material, a known metal can case can be used, or a bag-shaped case using an aluminum-containing laminate film 29 that can cover the power generating element as shown in FIG. 1 can be used.
  • the laminate film can be, for example, a three-layer laminate film formed by laminating PP, aluminum, and nylon in this order, but is not limited thereto.
  • a laminate film is desirable from the viewpoint of its high output and excellent cooling performance, making it suitable for use in batteries for large equipment such as EVs and HEVs.
  • an aluminum-containing laminate film is more preferable as the exterior material because it allows for easy adjustment of the collective pressure applied to the power generating element from the outside.
  • the lithium secondary battery according to this embodiment has a configuration in which multiple single cell layers are connected in parallel, resulting in high capacity and excellent cycle durability. Therefore, the lithium secondary battery according to this embodiment is suitable for use as a power source for driving EVs and HEVs.
  • the type of battery to which the positive electrode mixture of the present invention can be applied includes a bipolar battery that includes a bipolar electrode having a positive electrode active material layer electrically bonded to one surface of a current collector and a negative electrode active material layer electrically bonded to the opposite surface of the current collector.
  • the lithium secondary battery according to this embodiment does not have to be an all-solid-state type. That is, the solid electrolyte layer may further contain a conventionally known liquid electrolyte (electrolytic solution).
  • a conventionally known liquid electrolyte electrolyte (electrolytic solution).
  • the amount of liquid electrolyte (electrolytic solution) that can be contained in the solid electrolyte layer but it is preferable that the amount be such that the shape of the solid electrolyte layer formed by the solid electrolyte is maintained and leakage of the liquid electrolyte (electrolytic solution) does not occur.
  • Item 1 A positive electrode material comprising a sulfur- and phosphorus-containing sulfide solid electrolyte filled into the pores of porous carbon, wherein in a spectrum obtained by 31P solid-state nuclear magnetic resonance spectroscopy, the ratio (B/A) of the sum B of the integrals of signals present at chemical shifts other than 85.0 ⁇ 10 ppm to the integral A of the signal present at 85.0 ⁇ 10 ppm is less than 0.32;
  • Item 2 The positive electrode material according to Item 1, wherein the molar ratio of phosphorus (P) to carbon (C) (P/C) determined by surface analysis using X-ray photoelectron spectroscopy is 0.025 or more;
  • Item 3 The positive electrode material according to Item 1 or 2, wherein the mass ratio of PS4 units to carbon (C) ( PS4 /C) determined by surface analysis using X-ray photoelectron spectroscopy is 0.32 or more;
  • Item 4 A positive electrode mixture
  • Item 9 A method for producing a positive electrode material, comprising: impregnating porous carbon with a solution containing a phosphorus-containing sulfide solid electrolyte and a solvent, removing the solvent to obtain composite material 1; impregnating composite material 1 with a sulfur melt to obtain composite material 2; and mechanically milling composite material 2.
  • Example 1 Preparation of composite material 1
  • 1 g of particulate porous carbon Toyo Tanso Co., Ltd., Knobel (registered trademark) P(3)010
  • 1.5 g of an argyrodite-type phosphorus-containing sulfide solid electrolyte (Ampcera, Li6PS5Cl ) were placed in a flask.
  • composite material 2 (sulfur-phosphorus-containing sulfide solid electrolyte-carbon composite material) was obtained.
  • Example 2 The positive electrode material and positive electrode mixture of this example were obtained in the same manner as in Example 1 above, except that in the above (preparation of positive electrode material), mechanical milling was carried out at a centrifugal acceleration of 20 G for 180 minutes.
  • Example 3 The cathode material and cathode mixture of this example were obtained in the same manner as in Example 1 above, except that in the above (preparation of cathode material), mechanical milling was performed for 240 minutes at a centrifugal acceleration of 20 G; and in the above (preparation of cathode mixture), 1.68 g (84 parts by mass) of the cathode material and 0.32 g (16 parts by mass) of the solid electrolyte were mixed in a mortar.
  • ULVAC-PHI VersaProbe III X-ray source Monochromated Al K ⁇ ray (1486.6eV) 50W Photoelectron take-off angle: 45° (measurement depth: approximately 4 nm) Measurement area: 200 ⁇ m ⁇ Sample: In a glove box with an argon atmosphere having a dew point of ⁇ 68° C. or less, the positive electrode material or composite material 2 was fixed to a sample holder and introduced into the apparatus using a transfer vessel without being exposed to the atmosphere.
  • the element content was quantified using the relative sensitivity factor method from the peak area, and the molar ratio (P/C) of phosphorus (P) with a binding energy of 132 eV to carbon (C) with a binding energy of 284 eV on the surface was calculated. Furthermore, from the obtained XPS spectrum, the molar ratio of sulfur (S) with the same binding energy of 132 eV as the quantified carbon (C) and phosphorus (P) was used to calculate the mass ratio of PS4 units to carbon (C) ( PS4 /C) from the molar mass. These values are shown in Table 1 below.
  • An evaluation cell was prepared using the positive electrode mixture prepared in the above Examples and Comparative Examples.
  • the cell was prepared in a glove box in an argon atmosphere with a dew point of -68 ° C or less.
  • a stainless steel cylindrical convex punch (10 mm diameter) was inserted into one side of a Macor cylindrical tube jig (tube inner diameter 10 mm, outer diameter 23 mm, height 20 mm), and 80 mg of solid electrolyte (Ampcera, Li 6 PS 5 Cl) was inserted from the top of the cylindrical tube jig.
  • a cylindrical convex punch (also serving as a positive electrode current collector) was again inserted from above and pressed at a pressure of 300 MPa for 3 minutes to form a positive electrode active material layer having a diameter of 10 mm and a thickness of approximately 0.06 mm on one side of the solid electrolyte layer.
  • the lower cylindrical convex punch was removed, and a lithium foil (manufactured by Honjo Metals Co., Ltd., thickness 0.20 mm) punched to a diameter of 8 mm and an indium foil (manufactured by Nilaco Corporation, thickness 0.30 mm) punched to a diameter of 9 mm were stacked as negative electrodes.
  • the indium foil was inserted from the bottom of the cylindrical tube jig so that it was positioned on the side of the solid electrolyte layer.
  • a cylindrical convex punch also serving as a negative electrode current collector
  • an evaluation cell all-solid-state lithium secondary battery
  • the negative electrode current collector punch
  • lithium-indium negative electrode solid electrolyte layer
  • positive electrode active material layer positive electrode active material layer
  • positive electrode current collector punch
  • the evaluation cell was subjected to a charge/discharge test using a charge/discharge tester (HJ-SD8, manufactured by Hokuto Denko Corporation) in a thermostatic chamber set at 25 ° C.
  • HJ-SD8 manufactured by Hokuto Denko Corporation
  • the cell was placed in the thermostatic chamber, and after the cell temperature became constant, a constant current/constant voltage charge of 2.5 V at a current density of 1 C was performed with a cutoff current of 0.01 mA/cm 2 , followed by a constant current discharge to 0.5 V at the same current density.
  • the capacity value (mAh/g) per mass of the positive electrode active material was calculated from the charge/discharge capacity value at this time and the mass of the positive electrode active material (sulfur) contained in the positive electrode.
  • the capacity value calculated in this way was discharged at 0.03 C, 0.05 C, and 0.1 C for 10 seconds each at a 50% state of charge (SOC50%) relative to the capacity value calculated in this way (100%), and the direct current resistance (DCR) value was calculated from the voltage drop and current value at that time according to Ohm's law.
  • SOC50% 50% state of charge
  • DCR direct current resistance
  • the present invention makes it possible to reduce the cell resistance of a lithium secondary battery.

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Abstract

La présente invention aborde le problème de la fourniture d'un moyen qui est capable de réduire la résistance d'élément d'une batterie rechargeable au lithium. Le problème abordé par la présente invention est résolu par un matériau d'électrode positive qui est obtenu par remplissage de pores d'un carbone poreux avec du soufre et un électrolyte solide au sulfure contenant du phosphore, où dans un spectre obtenu par spectroscopie par résonance magnétique nucléaire à l'état solide 31P, le rapport (B/A) de la somme B de valeurs intégrales de signaux qui sont présents dans des déplacements chimiques autres que 85,0 ± 10 ppm à la valeur intégrale A d'un signal qui est présent à 85,0 ± 10 ppm est inférieur à 0,32.
PCT/JP2024/028563 2024-08-08 2024-08-08 Matériau d'électrode positive et mélange d'électrode positive et batterie rechargeable au lithium l'utilisant Pending WO2026033763A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2021057289A (ja) * 2019-10-01 2021-04-08 トヨタ自動車株式会社 リチウム硫黄電池
JP2022115375A (ja) * 2021-01-28 2022-08-09 日産自動車株式会社 電気デバイス用正極材料並びにこれを用いた電気デバイス用正極および電気デバイス
WO2022230163A1 (fr) * 2021-04-30 2022-11-03 日産自動車株式会社 Matériau d'électrode positive pour dispositif électrique, et électrode positive pour dispositif électrique et dispositif électrique l'utilisant
WO2022260056A1 (fr) * 2021-06-09 2022-12-15 株式会社Ｇｓユアサ Élément électrochimique tout solide et complexe soufre-carbone

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2021057289A (ja) * 2019-10-01 2021-04-08 トヨタ自動車株式会社 リチウム硫黄電池
JP2022115375A (ja) * 2021-01-28 2022-08-09 日産自動車株式会社 電気デバイス用正極材料並びにこれを用いた電気デバイス用正極および電気デバイス
WO2022230163A1 (fr) * 2021-04-30 2022-11-03 日産自動車株式会社 Matériau d'électrode positive pour dispositif électrique, et électrode positive pour dispositif électrique et dispositif électrique l'utilisant
WO2022260056A1 (fr) * 2021-06-09 2022-12-15 株式会社Ｇｓユアサ Élément électrochimique tout solide et complexe soufre-carbone

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