Classifications

• • 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
  • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• • 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
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • 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
  • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• • 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
  • H01M4/362—Composites
  • H01M4/364—Composites as mixtures
• • 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
  • H01M4/362—Composites
  • H01M4/366—Composites as layered products
• • 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
  • H01M4/386—Silicon or alloys based on silicon
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
• • 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
  • H01M4/58—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
  • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
  • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
• • 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
• • 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
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/027—Negative electrodes
• • 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
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/028—Positive electrodes
• • 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 disclosure relates to a non-aqueous electrolyte secondary battery.
• Patent Document 1 proposes an active material in which a surface layer containing a lithium sulfonate salt compound is formed on the surface of particles of lithium titanate containing Li 4 Ti 5 O 12 as a main component. Patent Document 1 describes that by using the active material as a negative electrode active material, it is possible to suppress a change in resistance of a battery before and after being charged and stored.
• Patent Document 1 In non-aqueous electrolyte secondary batteries, it is an important issue to improve charge-discharge cycle characteristics while ensuring high capacity. Conventional techniques including Patent Document 1 cannot sufficiently address such problems, and there is still much room for improvement.
• a non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and the positive electrode includes a lithium-containing composite oxide and a sulfonic acid compound present on the particle surface of the composite oxide.
• the sulfonic acid compound is a compound represented by formula (I)
• the negative electrode contains at least a silicon-containing material as a negative electrode active material, and the proportion of the silicon-containing material in the negative electrode active material is 3% by mass or more.
• the nonaqueous electrolyte secondary battery according to the present disclosure has high capacity and excellent charge/discharge cycle characteristics.
• FIG. 1 is a cross-sectional view of a non-aqueous electrolyte secondary battery that is an example of an embodiment.
• the present inventors conducted further studies and used a lithium-containing composite oxide with a specific sulfonic acid compound attached to the particle surface as the positive electrode active material, and also included silicon at a ratio of 3% by mass or more in the negative electrode active material. By incorporating these materials, they succeeded in improving charge-discharge cycle characteristics while ensuring high capacity. According to the non-aqueous electrolyte secondary battery according to the present disclosure, since deterioration of the positive electrode is suppressed, it is thought that charge/discharge cycle characteristics are improved. It is presumed that by increasing the capacity of the negative electrode by including a silicon-containing material in the negative electrode, the charge/discharge capacity of the battery is regulated by the negative electrode, and deterioration of the positive electrode is suppressed.
• ⁇ means a range including the upper and lower limits before and after " ⁇ ".
• non-aqueous electrolyte secondary battery a cylindrical battery in which a wound electrode body 14 is housed in a cylindrical outer can 16 with a bottom is exemplified.
• the non-aqueous electrolyte secondary battery according to the present disclosure may be, for example, a prismatic battery with a prismatic exterior can, a coin-shaped battery with a coin-shaped exterior can, and a laminate sheet including a metal layer and a resin layer.
• a pouch-type battery may be provided with an exterior body made up of.
• the electrode body is not limited to a wound type electrode body, and may be a laminated type electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated with separators interposed therebetween.
• FIG. 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery 10 that is an example of an embodiment.
• the nonaqueous electrolyte secondary battery 10 includes a wound electrode body 14, a nonaqueous electrolyte, and an outer can 16 that houses the electrode body 14 and the nonaqueous electrolyte.
• the electrode body 14 includes a positive electrode 11 , a negative electrode 12 , and a separator 13 , and has a wound structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 in between.
• the outer can 16 is a bottomed cylindrical metal container with an open end in the axial direction, and the opening of the outer can 16 is closed by a sealing member 17 .
• the sealing body 17 side of the battery is referred to as the upper side
• the bottom side of the outer can 16 is referred to as the lower side.
• the non-aqueous electrolyte has lithium ion conductivity.
• the non-aqueous electrolyte may be a liquid electrolyte (electrolyte solution) or a solid electrolyte.
• the liquid electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
• non-aqueous solvents include esters, ethers, nitriles, amides, and mixed solvents of two or more of these.
• nonaqueous solvents include ethylene carbonate (EC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents thereof.
• the non-aqueous solvent may contain a halogen-substituted product (for example, fluoroethylene carbonate) in which at least a portion of hydrogen in these solvents is replaced with a halogen atom such as fluorine.
• a halogen-substituted product for example, fluoroethylene carbonate
• a lithium salt such as LiPF6 is used as the electrolyte salt.
• the solid electrolyte for example, a solid or gel polymer electrolyte, an inorganic solid electrolyte, etc.
• an inorganic solid electrolyte materials known for use in all-solid lithium ion secondary batteries and the like (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used.
• the polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a nonaqueous solvent, a lithium salt, and a matrix polymer.
• the matrix polymer for example, a polymer material that absorbs a non-aqueous solvent and gels is used. Examples of polymer materials include fluororesins, acrylic resins, polyether resins, and the like.
• the positive electrode 11, the negative electrode 12, and the separator 13 that constitute the electrode body 14 are all long strip-shaped bodies, and are wound in a spiral shape so that they are alternately stacked in the radial direction of the electrode body 14.
• the negative electrode 12 is formed to be one size larger than the positive electrode 11 in order to prevent precipitation of lithium. That is, the negative electrode 12 is formed longer than the positive electrode 11 in the length direction and the width direction.
• the separators 13 are formed to be at least one size larger than the positive electrode 11, and for example, two separators 13 are arranged so as to sandwich the positive electrode 11 therebetween.
• the electrode body 14 has a positive electrode lead 20 connected to the positive electrode 11 by welding or the like, and a negative electrode lead 21 connected to the negative electrode 12 by welding or the like.
• Insulating plates 18 and 19 are arranged above and below the electrode body 14, respectively.
• the positive electrode lead 20 passes through the through hole of the insulating plate 18 and extends toward the sealing body 17, and the negative electrode lead 21 passes through the outside of the insulating plate 19 and extends toward the bottom of the outer can 16.
• the positive electrode lead 20 is connected by welding or the like to the lower surface of the internal terminal plate 23 of the sealing body 17, and the cap 27, which is the top plate of the sealing body 17 and electrically connected to the internal terminal plate 23, serves as a positive electrode terminal.
• the negative electrode lead 21 is connected to the bottom inner surface of the outer can 16 by welding or the like, and the outer can 16 serves as a negative electrode terminal.
• a gasket 28 is provided between the outer can 16 and the sealing body 17 to ensure airtightness inside the battery.
• the outer can 16 is formed with a grooved part 22 that supports the sealing body 17 and has a part of the side surface protruding inward.
• the grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the outer can 16, and supports the sealing body 17 on its upper surface.
• the sealing body 17 is fixed to the upper part of the outer can 16 by the grooved part 22 and the open end of the outer can 16 which is crimped to the sealing body 17 .
• the sealing body 17 has a structure in which an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are laminated in order from the electrode body 14 side.
• Each member constituting the sealing body 17 has, for example, a disk shape or a ring shape, and each member except the insulating member 25 is electrically connected to each other.
• the lower valve body 24 and the upper valve body 26 are connected at their respective central portions, and an insulating member 25 is interposed between their respective peripheral portions.
• the positive electrode 11, negative electrode 12, and separator 13 that make up the electrode body 14 will be explained in detail, particularly the positive electrode active material that makes up the positive electrode 11, and the negative electrode active material that makes up the negative electrode 12.
• the positive electrode 11 includes, for example, a positive electrode core 30 and a positive electrode mixture layer 31 provided on the surface of the positive electrode core 30.
• a metal foil such as aluminum that is stable in the potential range of the positive electrode 11, a film with the metal disposed on the surface, or the like can be used.
• the positive electrode mixture layer 31 contains a positive electrode active material, a conductive agent, and a binder, and is preferably provided on both surfaces of the positive electrode core 30 except for the portion to which the positive electrode lead 20 is connected.
• the positive electrode 11 is formed by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder to the surface of the positive electrode core 30, drying the coating film, and then compressing it to form the positive electrode mixture layer 31. It can be produced by forming on both sides of the positive electrode core body 30.
• Examples of the conductive agent included in the positive electrode mixture layer 31 include carbon black such as acetylene black and Ketjen black, graphite, carbon nanotubes (CNT), carbon nanofibers, and carbon materials such as graphene.
• Examples of the binder included in the positive electrode mixture layer 31 include fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resin, and polyolefin. . Further, these resins, carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide, etc. may be used in combination.
• the content of the conductive agent and the binder is, for example, 0.1% by mass to 5% by mass with respect to the mass of the positive electrode mixture layer 31, respectively.
• the positive electrode 11 includes a lithium-containing composite oxide and a sulfonic acid compound present on the particle surface of the composite oxide.
• the lithium-containing composite oxide with a sulfonic acid compound attached to the particle surface functions as a positive electrode active material.
• the sulfonic acid compound is a compound represented by formula (I). In the formula, A is a Group 1 or Group 2 element, R is a hydrocarbon group, and n is 1 or 2.
• the sulfonic acid compound represented by formula (I) (hereinafter sometimes simply referred to as “sulfonic acid compound”) reduces the reaction resistance at the positive electrode 11 and improves the output characteristics of the battery. Furthermore, with the reduction in resistance, it becomes possible to increase the depth of charging and discharging, making it possible to achieve higher capacity.
• the amount of the sulfonic acid compound present on the surface of the lithium-containing composite oxide is preferably 0.1% by mass or more and 1% by mass or less based on the mass of the lithium-containing composite oxide, from the viewpoint of increasing capacity. .
• the positive electrode active material may have as a main component composite particles that are lithium-containing composite oxides with a sulfonic acid compound attached to the particle surface, and may be substantially composed only of the composite particles. Note that the positive electrode active material may contain a composite oxide other than the composite particles or other compounds as long as the purpose of the present disclosure is not impaired.
• the lithium-containing composite oxide has a layered rock salt structure.
• the layered rock salt structure of the lithium-containing composite oxide include a layered rock salt structure belonging to space group R-3m, a layered rock salt structure belonging to space group C2/m, and the like. Among these, a layered rock salt structure belonging to space group R-3m is preferred from the viewpoint of high capacity and stability of crystal structure.
• the layered rock salt structure of the lithium-containing composite oxide includes a transition metal layer, a Li layer, and an oxygen layer.
• a lithium-containing composite oxide is a composite oxide containing metal elements such as Ni, Co, Al, and Mn in addition to Li.
• the metal elements constituting the lithium-containing composite oxide are, for example, Ni, Co, and M (M is at least one selected from the group consisting of Al, Mn, Fe, Ti, Si, Nb, Mo, W, and Zn). species element). Among these, it is preferable to contain at least one selected from Ni, Co, Al, and Mn.
• suitable composite oxides include composite oxides containing Ni, Co, and Al, and composite oxides containing Ni, Co, and Mn.
• the lithium-containing composite oxide preferably contains 80 mol% or more of Ni based on the total number of moles of metal elements excluding Li. Further, the effect of adding a sulfonic acid compound is more remarkable when a lithium-containing composite oxide with a high Ni content is used.
• the Ni content may be 87 mol% or more, or 90 mol% or more, based on the total number of moles of metal elements excluding Li.
• the upper limit of the Ni content is, for example, 95 mol%.
• An example of a suitable lithium-containing composite oxide is a composite oxide containing Ni, Co, and M, as described above.
• the content of Co is, for example, 0 mol % to 20 mol % with respect to the total number of moles of metal elements excluding Li.
• the content of M is, for example, 0 mol% to 20 mol% with respect to the total number of moles of metal elements excluding Li.
• Co may not be substantially added, but battery performance is improved by adding a small amount of Co.
• M includes at least one of Mn and Al.
• the content of elements constituting the lithium-containing composite oxide is measured using an inductively coupled plasma emission spectrometer (ICP-AES), an electron beam microanalyzer (EPMA), an energy dispersive X-ray analyzer (EDX), etc. be able to.
• ICP-AES inductively coupled plasma emission spectrometer
• EPMA electron beam microanalyzer
• EDX energy dispersive X-ray analyzer
• a lithium-containing composite oxide is, for example, a secondary particle formed by agglomerating a plurality of primary particles.
• the volume-based median diameter (D50) of the composite oxide is not particularly limited, but is, for example, 3 ⁇ m to 30 ⁇ m, preferably 5 ⁇ m to 25 ⁇ m.
• the D50 of the composite oxide means the D50 of the secondary particles.
• D50 means a particle size at which the cumulative frequency is 50% from the smallest particle size in the volume-based particle size distribution, and is also called the median diameter.
• the particle size distribution of the composite oxide (the same applies to the negative electrode active material) can be measured using a laser diffraction type particle size distribution measuring device (for example, MT3000II manufactured by Microtrac Bell Co., Ltd.) using water as a dispersion medium.
• a laser diffraction type particle size distribution measuring device for example, MT3000II manufactured by Microtrac Bell Co., Ltd.
• the average particle size of the primary particles constituting the lithium-containing composite oxide is, for example, 0.05 ⁇ m to 1 ⁇ m.
• the average particle diameter of the primary particles is calculated by averaging the diameters of the circumscribed circles of the primary particles extracted by analyzing a scanning electron microscope (SEM) image of a cross section of the secondary particles.
• the sulfonic acid compound present on the particle surface of the lithium-containing composite oxide is a compound represented by formula (I).
• A is a Group 1 or Group 2 element
• R is a hydrocarbon group
• n is 1 or 2.
• A is preferably a Group 1 element.
• Li or Na is more preferred, and Li is particularly preferred.
• R is preferably an alkyl group.
• the number of carbon atoms in the alkyl group is preferably 5 or less, more preferably 3 or less. From the viewpoint of reducing reaction resistance, etc., a suitable example of R is an alkyl group having 3 or less carbon atoms, and among them, a methyl group is preferable.
• a part of hydrogen bonded to carbon may be substituted with fluorine.
• n in formula (I) is preferably 1.
• sulfonic acid compounds include lithium methanesulfonate, lithium ethanesulfonate, lithium propanesulfonate, sodium methanesulfonate, sodium ethanesulfonate, magnesium methanesulfonate, lithium fluoromethanesulfonate, and the like.
• at least one selected from the group consisting of lithium methanesulfonate, lithium ethanesulfonate, and sodium methanesulfonate is preferred, and lithium methanesulfonate is particularly preferred.
• the sulfonic acid compound exists homogeneously over the entire particle surface of the lithium-containing composite oxide.
• the presence of the sulfonic acid compound on the particle surface of the lithium-containing composite oxide can be confirmed by Fourier transform infrared spectroscopy (FT-IR).
• FT-IR Fourier transform infrared spectroscopy
• a positive electrode active material containing lithium methanesulfonate has absorption peaks around 1238 cm ⁇ 1 , 1175 cm ⁇ 1 , 1065 cm ⁇ 1 , and 785 cm ⁇ 1 , for example.
• the peaks around 1238 cm ⁇ 1 , 1175 cm ⁇ 1 , and 1065 cm ⁇ 1 are peaks caused by SO stretching vibrations derived from lithium methanesulfonate.
• the peak around 785 cm ⁇ 1 is a peak resulting from CS stretching vibration derived from lithium methanesulfonate.
• positive electrode active materials containing sulfonic acid compounds other than lithium methanesulfonate can also be confirmed from the absorption peak derived from the sulfonic acid compound in the infrared absorption spectrum.
• the presence of the sulfonic acid compound on the particle surface of the lithium-containing composite oxide can also be confirmed by ICP, atomic absorption spectrometry, X-ray photoelectron spectroscopy (XPS), synchrotron radiation XRD measurement, TOF-SIMS, etc.
• a positive electrode active material that is an example of an embodiment can be manufactured by the following method. Note that the manufacturing method described here is just an example, and the method for manufacturing the positive electrode active material is not limited to this method.
• Metal oxides can be prepared by, for example, adding an alkaline solution such as sodium hydroxide dropwise to a solution of a metal salt containing Ni, Co, Al, Mn, etc. while stirring the solution, and adjusting the pH to an alkaline side (for example, 8.5 to 12. 5), a composite hydroxide containing metal elements such as Ni, Co, Al, Mn, etc. can be precipitated (co-precipitated), and the composite hydroxide can be synthesized by heat treatment.
• the heat treatment temperature is not particularly limited, but is, for example, 300°C to 600°C.
• lithium compound examples include Li 2 CO 3 , LiOH, Li 2 O 2 , Li 2 O, LiNO 3 , LiNO 2 , Li 2 SO 4 , LiOH ⁇ H 2 O, LiH, and LiF.
• the metal oxide and the lithium compound are mixed such that, for example, the molar ratio of the metal element in the metal oxide to Li in the lithium compound is 1:0.98 to 1:1.1. Note that when mixing the metal oxide and the lithium compound, other metal raw materials may be added as necessary.
• the mixture of metal oxide and lithium compound is fired, for example, in an oxygen atmosphere.
• the mixture may be fired through multiple heating processes.
• the firing step includes, for example, a first heating step in which the temperature is raised from 450° C. to 680° C. at a heating rate of 1.0° C./min to 5.5° C./min, and a first temperature raising step of 0.1° C./min to 3° C.
• a second heating step is included in which the temperature is raised to a temperature above 680°C at a heating rate of .5°C/min.
• the maximum temperature of the firing step may be set at 700° C. to 850° C., and may be maintained at this temperature for 1 hour to 10 hours.
• the fired product (lithium-containing composite oxide) is washed with water and dehydrated to obtain a cake-like composition.
• This cleaning step removes remaining alkaline components. Washing and dehydration can be performed by conventionally known methods.
• the cake-like composition is dried to obtain a powder-like composition.
• the drying step may be performed under a vacuum atmosphere.
• An example of drying conditions is a temperature of 150° C. to 400° C. for 0.5 hours to 15 hours.
• the sulfonic acid compound is added, for example, to the cake-like composition obtained in the washing step or the powder-like composition obtained in the drying step.
• a sulfonic acid solution may be added instead of or together with the sulfonic acid compound.
• the sulfonic acid compound may be added as an aqueous dispersion.
• the sulfonic acid solution is an aqueous solution of sulfonic acid.
• the concentration of sulfonic acid in the sulfonic acid solution is, for example, 0.5% to 40% by weight.
• the negative electrode 12 includes, for example, a negative electrode core 40 and a negative electrode mixture layer 41 provided on the surface of the negative electrode core 40.
• a metal foil such as copper that is stable in the potential range of the negative electrode 12, a film with the metal disposed on the surface, or the like can be used.
• the negative electrode mixture layer 41 contains a negative electrode active material and a binder, and is provided on both sides of the negative electrode core body 40 except for the portion to which the negative electrode lead 21 is connected.
• the negative electrode 12 is made by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to the surface of the negative electrode core 40, drying the coating film, and then compressing the negative electrode mixture layer 41 to the negative electrode core. It can be produced by forming it on both sides of 40.
• the negative electrode mixture layer 41 may further contain a conductive agent such as CNT.
• binder included in the negative electrode mixture layer 41 examples include styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethyl cellulose (CMC) or a salt thereof, polyacrylic acid (PAA) or a salt thereof ( PAA-Na, PAA-K, etc. (may also be partially neutralized salts), polyvinyl alcohol (PVA), and the like. These may be used alone or in combination of two or more.
• SBR styrene-butadiene rubber
• NBR nitrile-butadiene rubber
• CMC carboxymethyl cellulose
• PAA polyacrylic acid
• PAA-Na, PAA-K, etc. may also be partially neutralized salts
• PVA polyvinyl alcohol
• the negative electrode 12 includes at least a silicon-containing material as a negative electrode active material, and the proportion of the silicon-containing material in the negative electrode active material is 3% by mass or more. This is thought to suppress deterioration of the positive electrode, thereby improving charge/discharge cycle characteristics.
• the proportion of the silicon-containing material in the negative electrode active material is, for example, 3% by mass or more and 20% by mass or less.
• the silicon-containing material may be any material containing Si, and examples thereof include silicon alloys, silicon compounds, and composite materials containing Si. Among these, composite materials containing Si are preferred.
• the D50 of the composite material is generally smaller than the D50 of graphite.
• the volume-based D50 of the composite material is, for example, 1 ⁇ m to 15 ⁇ m. Note that one type of silicon-containing material may be used alone, or two or more types may be used in combination.
• Suitable silicon-containing materials are composite particles comprising an ion-conducting phase and a Si phase dispersed within the ion-conducting phase.
• the ion conductive phase is, for example, at least one selected from the group consisting of a silicate phase, a carbon phase, a silicide phase, and a silicon oxide phase.
• the silicide phase is a phase of a compound consisting of Si and an element more electropositive than Si, and examples thereof include NiSi, Mg 2 Si, TiSi 2 and the like.
• the Si phase is formed by dispersing Si in the form of fine particles.
• the ion conductive phase is a continuous phase composed of aggregation of particles finer than the Si phase.
• the average size of the Si phase is preferably 1 nm to 200 nm, more preferably 1 nm to 100 nm.
• the average size of the Si phase is calculated by taking a SEM image of a cross section of a particle of the silicon-containing material and averaging the diameters of the circumscribed circles of the Si phase extracted by image analysis.
• the average size of the Si phase may be, for example, 1 nm to 10 nm.
• the above composite material may have a conductive layer covering the surface of the ion conductive phase.
• the conductive layer is made of a material having higher conductivity than the ion conductive layer, and forms a good conductive path in the negative electrode mixture layer 41.
• the conductive layer is, for example, a carbon film made of a conductive carbon material.
• the conductive carbon material carbon black such as acetylene black and Ketjen black, graphite, amorphous carbon with low crystallinity (amorphous carbon), etc. can be used.
• the thickness of the conductive layer is preferably 1 nm to 200 nm, or 5 nm to 100 nm, taking into consideration ensuring conductivity and diffusivity of Li ions into the interior of the particles.
• the thickness of the conductive layer can be measured by observing the cross section of the composite material using a SEM or a transmission electron microscope (TEM).
• An example of a suitable composite material containing Si has a sea-island structure in which fine Si is substantially uniformly dispersed in an amorphous silicon oxide phase, and has the general formula SiO x (0 ⁇ x ⁇ 2) as a whole.
• This is a composite particle represented.
• the main component of silicon oxide may be silicon dioxide.
• the silicon oxide phase may be doped with Li.
• the content ratio (x) of oxygen to Si is, for example, 0.5 ⁇ x ⁇ 2.0, preferably 0.8 ⁇ x ⁇ 1.5.
• a suitable composite material containing Si is a composite particle having a sea-island structure in which fine Si is substantially uniformly dispersed in an amorphous silicate phase.
• the silicate phase contains, for example, at least one element selected from the group consisting of Group 1 and Group 2 elements of the periodic table.
• the silicate phase may further include B, Al, Zr, Nb, Ta, V, La, Y, Ti, P, Bi, Zn, Sn, Pb, Sb, Co, Er, F, and W. It may contain at least one selected element.
• a preferred silicate phase is a lithium silicate phase containing Li.
• the lithium silicate phase is, for example, a complex oxide phase represented by the general formula Li 2z SiO (2+z) (0 ⁇ z ⁇ 2).
• Li 4 SiO 4 is an unstable compound and exhibits alkalinity when reacting with water, so it may alter Si and cause a decrease in charge/discharge capacity.
• a suitable composite material containing Si is a composite particle having a sea-island structure in which fine Si is substantially uniformly dispersed in a carbon phase.
• the ion-conducting phase in at least a portion of the silicon-containing material is a carbon phase.
• the carbon phase is an amorphous carbon phase.
• the carbon phase may contain a crystalline phase component, it is preferable that the carbon phase contains more amorphous phase components.
• the amorphous carbon phase is composed of, for example, a carbon material having an average interplanar spacing of (002) planes of more than 0.34 nm as measured by X-ray diffraction.
• the composite material containing a carbon phase may have a conductive layer separate from the carbon phase, or may not have the conductive layer.
• the discharge capacity of the negative electrode active material is preferably 380 mAh/g or more. Thereby, the charge/discharge capacity of the battery is regulated by the negative electrode, and deterioration of the positive electrode is more significantly suppressed.
• the negative electrode 12 may further contain a carbon material as a negative electrode active material.
• the negative electrode 12 may include substantially only a carbon material and a silicon-containing material as the negative electrode active material. Note that a non-aqueous electrolyte secondary battery that uses a positive electrode 11 to which a sulfonic acid compound is applied and a negative electrode 12 that does not contain a silicon-containing material may have deteriorated charge-discharge cycle characteristics.
• the carbon material contained in the negative electrode mixture layer 41 is, for example, at least one selected from the group consisting of natural graphite, artificial graphite, soft carbon, and hard carbon.
• artificial graphite such as massive artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB), natural graphite such as flaky graphite, lumpy graphite, earthy graphite, or a mixture thereof.
• the volume-based D50 of the carbon material is, for example, 1 ⁇ m to 30 ⁇ m, preferably 5 ⁇ m to 25 ⁇ m.
• Soft carbon and hard carbon are classified as amorphous carbon in which the graphite crystal structure is not developed. More specifically, it means a carbon component having a d(002) plane spacing of 0.342 nm or more as determined by X-ray diffraction. Soft carbon is also called easily graphitizable carbon, and is carbon that is more easily graphitized by high-temperature treatment than hard carbon. Hard carbon is also called non-graphitizable carbon. Note that, in view of the configuration of the present invention, it is not necessary to clearly distinguish between soft carbon and hard carbon. Graphite and at least one amorphous carbon of soft carbon and hard carbon may be used together as the negative electrode active material.
• a porous sheet having ion permeability and insulation properties is used.
• porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics.
• Suitable materials for the separator 13 include polyolefins such as polyethylene and polypropylene, cellulose, and the like.
• the separator 13 may have a single layer structure or a multilayer structure. Further, a resin layer with high heat resistance such as aramid resin may be formed on the surface of the separator 13.
• a filler layer containing an inorganic filler may be formed at the interface between the separator 13 and at least one of the positive electrode 11 and the negative electrode 12.
• the inorganic filler include oxides and phosphoric acid compounds containing metal elements such as Ti, Al, Si, and Mg.
• the filler layer can be formed by applying a slurry containing the filler to the surface of the positive electrode 11, the negative electrode 12, or the separator 13.
• Example 1 [Preparation of positive electrode active material]
• the composite hydroxide represented by [Ni 0.90 Al 0.05 Mn 0.05 ](OH) 2 obtained by the coprecipitation method was calcined at 500°C for 8 hours to form an oxide (Ni 0.90 Al 0.05 Mn 0.05 O 2 ) was obtained.
• LiOH and the composite oxide were mixed so that the molar ratio of Li to the total amount of Ni, Al, and Mn was 1.03:1 to obtain a mixture.
• This mixture was fired from room temperature to 650°C at a heating rate of 2.0°C/min under an oxygen stream with an oxygen concentration of 95% (flow rate of 2 mL/min per 10 cm 3 and 5 L/min per 1 kg of mixture), and then heated.
• a lithium-containing composite oxide was obtained by firing from 650°C to 780°C at a rate of 0.5°C/min.
• a positive electrode mixture slurry is prepared using N-methyl-2-pyrrolidone (NMP) as a dispersion medium.
• NMP N-methyl-2-pyrrolidone
• a positive electrode mixture slurry is applied onto the positive electrode core made of aluminum foil, the coating film is dried and compressed, and then the positive electrode core is cut into a predetermined electrode size, and the positive electrode mixture is coated on both sides of the positive electrode core.
• a positive electrode on which the agent layer was formed was obtained. Note that an exposed portion in which the surface of the positive electrode core was exposed was provided in a part of the positive electrode.
• a negative electrode mixture slurry was prepared by mixing 100 parts by mass of a negative electrode active material, 1 part by mass of carboxymethyl cellulose (CMC), and 1 part by mass of styrene butadiene rubber (SBR), and adding an appropriate amount of water.
• CMC carboxymethyl cellulose
• SBR styrene butadiene rubber
• a negative electrode mixture slurry is applied onto the negative electrode core made of copper foil, the coating film is dried and compressed, and then the negative electrode core is cut into a predetermined electrode size, and the negative electrode mixture is coated on both sides of the negative electrode core.
• a negative electrode on which the agent layer was formed was produced. Note that an exposed portion in which the surface of the negative electrode core was exposed was provided in a part of the negative electrode.
• Non-aqueous electrolyte 1.2 mol of LiPF 6 was added to a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) mixed at a volume ratio of 3:3:4 (25°C).
• EC ethylene carbonate
• EMC ethyl methyl carbonate
• DMC dimethyl carbonate
• a non-aqueous electrolyte was prepared by dissolving the solution at a concentration of 1/liter.
• test cell (secondary battery) Attach an aluminum lead to the exposed part of the positive electrode and a nickel lead to the exposed part of the negative electrode, and create a wound electrode body by spirally winding the positive and negative electrodes through a polyolefin separator. did. Insulating plates were placed above and below the electrode body, and the electrode body was housed in an exterior can. The negative electrode lead was welded to the bottom of the bottomed cylindrical outer can, and the positive electrode lead was welded to the sealing body. An electrolytic solution was injected into the outer can, and the opening of the outer can was sealed with a sealing member via a gasket to produce a secondary battery as a test cell.
• Example 1 A test cell was prepared and evaluated in the same manner as in Example 1, except that lithium methanesulfonate was not added in the preparation of the positive electrode active material.
• Example 2-2 In producing the positive electrode active material, a test cell was produced in the same manner as in Example 2-1, except that the amount of lithium methanesulfonate added to the total mass of the lithium-containing composite oxide was 0.3% by mass, We conducted an evaluation.
• Example 2-3 In producing the positive electrode active material, a test cell was produced in the same manner as in Example 2-1, except that the amount of lithium methanesulfonate added to the total mass of the lithium-containing composite oxide was 0.5% by mass, We conducted an evaluation.
• Example 2-4 In preparing the positive electrode active material, a test cell was prepared in the same manner as in Example 2-1, except that the amount of lithium methanesulfonate added to the total weight of the lithium-containing composite oxide was 1% by mass, and the evaluation was carried out. went.
• Example 2-5> In the production of the positive electrode active material, sodium methanesulfonate was used instead of lithium methanesulfonate, and the amount of sodium methanesulfonate added was 0.5% by mass with respect to the total mass of the lithium-containing composite oxide. A test cell was prepared and evaluated in the same manner as in Example 2-1.
• Example 2-6> In producing the positive electrode active material, lithium ethanesulfonate was used instead of lithium methanesulfonate, and the amount of lithium ethanesulfonate added was 0.5% by mass with respect to the total mass of the lithium-containing composite oxide. A test cell was prepared and evaluated in the same manner as in Example 2-1.
• Example 2-1 A test cell was prepared and evaluated in the same manner as in Example 2-1, except that lithium methanesulfonate was not added in the preparation of the positive electrode active material.
• Example 2- except that in producing the positive electrode active material, lithium succinate was added instead of methanesulfonic acid, and the amount of lithium succinate added was 0.5% by mass with respect to the total mass of the lithium-containing composite oxide.
• a test cell was prepared and evaluated in the same manner as in Example 1.
• Example 2- except that in producing the positive electrode active material, lithium oxalate was added instead of methanesulfonic acid, and the amount of lithium oxalate added was 0.5% by mass with respect to the total mass of the lithium-containing composite oxide.
• a test cell was prepared and evaluated in the same manner as in Example 1.
• Example 3 In producing the positive electrode active material, a test cell was produced and evaluated in the same manner as in Example 1, except that in producing the negative electrode, the mixing ratio of artificial graphite and SiO was 85:15.
• Example 3 A test cell was prepared and evaluated in the same manner as in Example 3, except that lithium methanesulfonate was not added in the preparation of the positive electrode active material.
• Example 4 In producing the positive electrode active material, a test cell was produced and evaluated in the same manner as in Example 1, except that the mixing ratio of artificial graphite and SiO was 80:20 in producing the negative electrode.
• Example 4 A test cell was prepared and evaluated in the same manner as in Example 4, except that lithium methanesulfonate was not added in the preparation of the positive electrode active material.
• Example 5 A test cell was prepared and evaluated in the same manner as in Example 1, except that SiO was used as the negative electrode active material in the preparation of the positive electrode active material and the negative electrode.
• Example 5 A test cell was prepared and evaluated in the same manner as in Example 5, except that lithium methanesulfonate was not added in the preparation of the positive electrode active material.
• Example 6-1 A test cell was prepared and evaluated in the same manner as in Example 1, except that artificial graphite was used as the negative electrode active material in the preparation of the positive electrode active material and the negative electrode.
• the evaluation results of the test cells of Examples and Comparative Examples are shown in Tables 1 to 3.
• the capacity retention rate of the test cell of Example 1 is a relative value when the capacity retention rate of the test cell of Comparative Example 1 is set to 100.
• the capacity retention rates of the test cells of Examples 2-1 to 2-6 and Comparative Examples 2-2 and 2-3 are based on the capacity retention rate of the test cell of Comparative Example 2-1 as 100. It is a relative value.
• the capacity retention rates of the test cells of Examples 3, 4, 5, and Comparative Example 6-1 are the capacity retention rates of the test cells of Comparative Examples 3, 4, 5, and Comparative Example 6-2, respectively. This is a relative value when the value is set to 100.
• a larger capacity retention rate means better charge/discharge cycle characteristics.
• test cells of the examples all have better capacity retention rates than the test cells of the comparative example. From the results of the test cells of Examples 2-1 to 2-4 in Table 2, it can be seen that the charge/discharge cycle characteristics are most improved when the amount of methanesulfonic acid compound added is around 0.5% by mass. Further, the results of the test cells of Examples 2-3, 2-5, and 2-6 show that lithium methanesulfonate is preferable as the sulfonic acid compound. On the other hand, the test cells of Comparative Examples 2-2 and 2-3 in which lithium succinate or lithium oxalate was used instead of the sulfonic acid compound were compared to the test cells of Comparative Example 2-1 in which no acid salt was added to the positive electrode.
• Configuration 1 Comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte
• the positive electrode includes a lithium-containing composite oxide and a sulfonic acid compound present on the particle surface of the lithium-containing composite oxide,
• the sulfonic acid compound is a compound represented by formula (I)
• the negative electrode contains at least a silicon-containing material as a negative electrode active material, and the proportion of the silicon-containing material in the negative electrode active material is 3% by mass or more,
• a non-aqueous electrolyte secondary battery wherein the negative electrode active material has a discharge capacity of 380 mAh/g or more.
• Configuration 2 The non-aqueous electrolyte secondary battery according to configuration 1, wherein the A is a Group 1 element.
• Configuration 3 The non-aqueous electrolyte secondary battery according to configuration 1, wherein the A is Li.
• Configuration 4 The non-aqueous electrolyte secondary battery according to any one of configurations 1 to 3, wherein the R is an alkyl group.
• Configuration 5 The non-aqueous electrolyte secondary battery according to any one of configurations 1 to 3, wherein the R is a methyl group.
• Configuration 6 Any of configurations 1 to 5, wherein the amount of the sulfonic acid compound present on the surface of the lithium-containing composite oxide is 0.1% by mass or more and 1% by mass or less with respect to the mass of the lithium-containing composite oxide.
• Configuration 7 7.
• Configuration 8 The negative electrode further includes a carbon material as the negative electrode active material, 8.
• Configuration 9 9. The non-aqueous electrolyte secondary battery according to any one of configurations 1 to 8, wherein the silicon-containing material includes an ion-conducting phase and a Si phase dispersed in the ion-conducting phase.
• Configuration 10 The nonaqueous electrolyte secondary battery according to configuration 9, wherein the ion conductive phase is at least one selected from the group consisting of a silicate phase, a carbon phase, a silicide phase, and a silicon oxide phase.
• Configuration 11 11.
• the non-aqueous electrolyte secondary battery according to configuration 9 or 10 wherein the ion conductive phase contains at least one element selected from the group consisting of Group 1 and Group 2 elements.
• Configuration 12 The ion conductive phase is further selected from the group consisting of B, Al, Zr, Nb, Ta, V, La, Y, Ti, P, Bi, Zn, Sn, Pb, Sb, Co, Er, F and W.
• Configuration 13 The nonaqueous electrolyte secondary battery according to any one of configurations 9 to 12, wherein the ion conductive phase in at least a portion of the silicon-containing material is a carbon phase.
• Configuration 14 The non-aqueous electrolyte secondary battery according to any one of Structures 1 to 13, wherein the proportion of the silicon-containing material in the negative electrode active material is 3% by mass or more and 20% by mass or less.
• Non-aqueous electrolyte secondary battery 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 16 outer can, 17 sealing body, 18, 19 insulating plate, 20 positive electrode lead, 21 negative electrode lead, 22 grooved part, 23 internal terminal Plate, 24 lower valve body, 25 insulating member, 26 upper valve body, 27 cap, 28 gasket, 30 positive electrode core, 31 positive electrode mixture layer, 40 negative electrode core, 41 negative electrode mixture layer

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