WO2020255489A1 - Matériau d'anode, anode et élément de batterie - Google Patents

Matériau d'anode, anode et élément de batterie Download PDF

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WO2020255489A1
WO2020255489A1 PCT/JP2020/008758 JP2020008758W WO2020255489A1 WO 2020255489 A1 WO2020255489 A1 WO 2020255489A1 JP 2020008758 W JP2020008758 W JP 2020008758W WO 2020255489 A1 WO2020255489 A1 WO 2020255489A1
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negative electrode
active material
electrode active
carbon
carbon material
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PCT/JP2020/008758
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English (en)
Japanese (ja)
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将成 織田
尚平 寺田
誠之 廣岡
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株式会社日立製作所
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • 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 negative electrode material, a negative electrode, and a battery cell.
  • Lithium-ion secondary batteries are used in various applications such as mobile power sources for mobile phones and portable personal computers, drive power sources for electric vehicles and hybrid vehicles, and stationary power sources for power storage.
  • the use of lithium-ion secondary batteries has expanded to large-scale products, and the demand for improved energy density is increasing more than before.
  • the negative electrode active material in addition to graphite-based materials, silicon-based materials, lithium metal composite oxides and the like that cause an intercalation reaction, metal oxides that cause a conversion reaction such as Fe 2 O 3 are also known.
  • metal oxides that cause a conversion reaction such as Fe 2 O 3 are also known.
  • the negative electrode active material of the intercalation system lithium ions are inserted and removed between the layers in the crystal structure, and the reaction in the battery proceeds.
  • the conversion-type negative electrode active material a conversion reaction occurs in which lithium ions and metal oxides exchange metals with each other, and the reaction in the battery proceeds.
  • Conversion-type negative electrode active materials show a relatively high theoretical capacity and can reduce raw material costs, so they are expected to be put into practical use and spread.
  • the conversion-type negative electrode active material has problems in terms of reversibility and voltage characteristics during charging and discharging. Since the conversion reaction impairs the reversibility and output of the reaction due to the disproportionation of the compound itself, improvements are being made in the nanostructure of the negative electrode and the morphology of the negative electrode material.
  • Patent Document 1 discloses the following contents as a technique related to a conversion-type negative electrode active material.
  • a negative electrode active material for a power storage device which comprises at least one selected from the group of SiO 2 , B 2 O 3 and P 2 O 5 as an oxide notation composition, and Fe 2 O 3 .
  • cellulose derivatives such as carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, ethyl cellulose, hydroxymethyl cellulose, water-soluble polymers such as polyvinyl alcohol; polyimide resin, Thermocurable resins such as phenolic resin, epoxy resin, urea resin, melamine resin, unsaturated polyester resin, and polyurethane; vinylidene fluoride and the like can be mentioned. ”(See paragraph 0034).
  • a battery cell using a conversion-type negative electrode active material has a problem in reversibility of the reaction at the time of charging / discharging. Therefore, it is required to improve the capacity retention rate associated with the charging / discharging cycle and suppress the internal resistance. Generally, it is considered effective to make the negative electrode active material into fine particles as a measure for improving the capacity retention rate of the battery cell or suppressing the internal resistance.
  • the negative electrode active material, the conductive agent, the binder and the like are kneaded in a solvent to prepare a negative electrode mixture, if the negative electrode active material is excessively small fine particles, the fine particles of the negative electrode active material aggregate in the slurry. Is a problem.
  • the negative electrode active material is aggregated, it is not uniformly dispersed with the conductive agent or the like, and a part of the negative electrode active material is likely to be electrically isolated during charging / discharging of the battery cell. In such an improperly dispersed state, the charge / discharge cycle characteristics are deteriorated, the battery life is shortened, the internal resistance is increased, and the output is deteriorated.
  • a method of dispersing fine particles in a slurry As a method of dispersing fine particles in a slurry, a method of adding a dispersant is also known. However, even if the dispersant is added to the slurry, the viscosity of the slurry itself is not significantly reduced, so that a large dispersion force and stirring time are required to disperse the negative electrode active material, the conductive agent, and the like. With such a method, the dispersion state of the fine particles depends solely on the degree of stirring, so that the efficiency in the process and the certainty of dispersion are poor.
  • the present invention provides a negative electrode material capable of improving the capacity retention rate associated with the charge / discharge cycle and suppressing the internal resistance of the battery cell, a negative electrode using the negative electrode material, and a battery cell including the negative electrode material. The purpose.
  • a negative electrode material containing a carbon material and a negative electrode active material A negative electrode material in which the half width of the peak to which the photoelectron energy derived from the OH bond is assigned, which is obtained from the X-ray photoelectron spectrum, is 1.4320 eV or more.
  • a negative electrode material capable of improving the capacity retention rate associated with a charge / discharge cycle and suppressing the internal resistance of the battery cell, a negative electrode using the negative electrode material, and a battery cell including the negative electrode material. .. Issues, configurations and effects other than those described above will be clarified by the description of the following embodiments.
  • FIG. 1 It is sectional drawing of a battery cell. It is a perspective view of the electrode body included in a battery cell. It is an electron micrograph which observed the negative electrode material which concerns on Example 1.
  • FIG. It is an X-ray photoelectron spectroscopic spectrum of the negative electrode material which concerns on Example 1.
  • FIG. 2 It is an electron micrograph which observed the negative electrode material which concerns on Example 2.
  • FIG. 2 It is an X-ray photoelectron spectroscopic spectrum of the negative electrode material which concerns on Example 2.
  • FIG. 1 It is an X-ray photoelectron spectroscopic spectrum of the negative electrode material which concerns on Example 3.
  • the following description shows a specific example of the contents of the present invention.
  • the present invention is not limited to the following description, and various modifications and modifications by those skilled in the art can be made within the scope of the technical ideas disclosed in the present specification.
  • the present invention includes various modifications different from the embodiments.
  • the embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. It is possible to replace part of the configuration of one embodiment with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of the embodiment with another configuration.
  • a lithium ion secondary battery is an electrochemical device that creates a potential difference between electrodes by occlusion of lithium ions into and discharges from the electrodes, thereby storing or making available electrical energy.
  • the object of the present invention also includes a secondary battery called by a name different from that of the lithium ion secondary battery, for example, a lithium ion battery, a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery, and the like.
  • a secondary battery called by a name different from that of the lithium ion secondary battery, for example, a lithium ion battery, a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery, and the like.
  • the technical idea of the present invention can also be applied to a sodium ion secondary battery, a magnesium ion secondary battery, a calcium ion secondary battery, a zinc secondary battery, an aluminum ion secondary battery and the like.
  • the material When a material is selected and used from the material group illustrated below, the material may be used alone or in combination of a plurality of materials as long as it does not contradict the contents disclosed in the present specification. May be good. Further, materials other than the material group exemplified below may be used as long as they do not contradict the contents disclosed in the present specification.
  • FIG. 1 is a cross-sectional view of a battery cell.
  • FIG. 2 is a perspective view of an electrode body included in the battery cell.
  • the battery cell 1000 includes a positive electrode 100, a negative electrode 200, a separator 300, and an exterior body 500.
  • FIG. 1 shows a laminated laminated battery as an example of a battery cell using a negative electrode material.
  • the shape of the battery cell may be any of a tubular shape, a square shape, a button shape, and the like.
  • the positive electrode 100, the separator 300, and the negative electrode 200 are laminated in this order to form the electrode body 400.
  • a plurality of electrode bodies 400 are laminated and built in.
  • the electrode bodies 400 are laminated with the separator 300 sandwiched between the adjacent positive electrode 100 and the negative electrode 200.
  • the positive electrode 100 has a positive electrode mixture layer 110, a positive electrode current collector 120, and a positive electrode tab 130.
  • the positive electrode mixture layer 110 is formed on both sides of the flat plate-shaped positive electrode current collector 120.
  • the positive electrode tab 130 is provided at the end of the positive electrode current collector 120 as a flat plate-shaped projecting piece. As shown in FIG. 2, the positive electrode tab 130 is provided on one side of the center of one side of the positive electrode current collector 120 so as not to overlap the negative electrode tab 230 in the state where the electrode body 400 is formed.
  • the negative electrode 200 has a negative electrode mixture layer 210, a negative electrode current collector 220, and a negative electrode tab 230.
  • the negative electrode mixture layer 210 is formed on both sides of the flat negative electrode current collector 220.
  • the negative electrode tab 230 is provided at the end of the negative electrode current collector 220 as a flat plate-shaped projecting piece. As shown in FIG. 2, the negative electrode tab 230 is provided on one side of the center of one side of the negative electrode current collector 220 so as not to overlap the positive electrode tab 130 in the state where the electrode body 400 is formed.
  • the positive electrode current collector 120 and the negative electrode current collector 220, the positive electrode tab 130 and the negative electrode tab 230 can be bonded to each other by various methods such as spot welding and ultrasonic bonding.
  • the electrode bodies 400 may be electrically connected in parallel, or a part or all of them may be electrically connected in series.
  • the positive electrode tab 130 and the negative electrode tab 230 can be electrically connected to the positive electrode terminal and the negative electrode terminal 250 exposed to the outside of the exterior body 500.
  • the electrolytic solution is injected into the inner space where the electrode body 400 is housed.
  • the electrode body 400 housed in the exterior body 500 is held in a state of being immersed in the electrolytic solution.
  • the electrode body 400 and the electrolytic solution are sealed by the exterior body 500 and the like to prevent contact with moisture, air and the like.
  • the electrode body 400 can be sealed without injecting an electrolytic solution.
  • the laminated type laminated battery shown in FIG. 1 is provided with a bag-shaped laminated container as the exterior body 500.
  • the laminated container can be formed by laminating a multilayer film with a heat seal, an adhesive or the like.
  • the multilayer film can be formed by laminating various films such as polyethylene, polypropylene, polyamide, polyester and aluminum foil.
  • the exterior body 500 can also be provided as a metal can in the case of a tubular battery, a square battery, a button battery, or the like.
  • the metal can be formed by using, for example, an aluminum alloy, stainless steel, nickel-plated steel, or the like.
  • the illustrated battery cell 1000 is a laminated type in which electrode bodies 400 are stacked, but the battery cell 1000 may be a winding type in which a strip-shaped electrode body is spirally wound.
  • the positive electrode mixture layer 110 of the positive electrode 100 contains a positive electrode active material capable of storing and releasing lithium ions.
  • the positive electrode mixture layer 110 may contain a conductive agent for improving the conductivity of the positive electrode mixture layer 110, a binder for binding the positive electrode active material and the conductive agent, and the like. Further, the positive electrode mixture layer 110 may contain a solid electrolyte. When a solid electrolyte having high ionic conductivity is used for the positive electrode mixture layer 110, the ionic conductivity in the positive electrode can be improved.
  • the positive electrode active material is selected from a material group such as LiCo-based composite oxide, LiNi-based composite oxide, LiMn-based composite oxide, LiCoNiMn-based composite oxide, LiFeP-based composite oxide, and LiMnP-based composite oxide.
  • Specific examples of the positive electrode active material include LiCoO 2 , Li (Co, Mn) O 2 , Li (Ni, Mn) O 2 , LiMn 2 O 4 , Li 4 Mn 5 O 12 , Li (Co, Ni, Mn).
  • Examples thereof include O 2 , LiFePO 4 , LiCoPO 4 , LiNiPO 4 , LiMnPO 4 , LiMnVO 4 , LiFeBO 3 , LiMnBO 3 , Li 2 FeSiO 4 , Li 2 CoSiO 4 , and Li 2 MnSiO 4 .
  • the positive electrode active material an oxide obtained by substituting these transition metals with different elements or an oxide having a chemical ratio different from that of the chemical ratio can also be used.
  • the dissimilar element include Co, Ni, Mn, Fe, Cr, Zn, Ta, Al, Mg, Cu, Cd, Mo, Nb, W, Ru and the like.
  • the conductive agent is selected from a group of materials such as natural graphite, artificial graphite, carbon black, carbon nanofibers, carbon nanotubes, and conductive polymers.
  • carbon black include Ketjen black, acetylene black, thermal black, furnace black, and channel black.
  • carbon nanofibers include pitch-based carbon nanofibers and PAN-based carbon nanofibers.
  • the conductive polymer include polyacetylene, polyaniline, polyacene and the like.
  • the binder forming the positive electrode mixture layer 110 is selected from a material group such as polyvinylidene fluoride (PVDF), acrylic acid ester resin, and methacrylic acid ester resin.
  • PVDF polyvinylidene fluoride
  • acrylic acid ester resin acrylic acid ester resin
  • methacrylic acid ester resin methacrylic acid ester resin
  • the positive electrode current collector 120 a metal foil, a perforated foil, or the like can be used.
  • the positive electrode current collector 120 is selected from a group of materials such as aluminum and aluminum alloy.
  • the thickness of the positive electrode current collector 120 is preferably 10 nm to 1 mm, more preferably 1 to 100 ⁇ m from the viewpoint of achieving both mechanical strength and energy density.
  • the positive electrode tab 130 can be formed of the same material as the positive electrode current collector 120.
  • the negative electrode mixture layer 210 of the negative electrode 200 contains a negative electrode active material capable of storing and releasing lithium ions, and a carbon material having a function as a conductive agent for improving the conductivity of the negative electrode mixture layer 210.
  • the negative electrode mixture layer 210 is formed using a negative electrode material containing a carbon material and a negative electrode active material as a material.
  • the negative electrode mixture layer 210 may contain a binder or the like for binding the negative electrode active material or the carbon material. Further, the negative electrode mixture layer 210 may contain a solid electrolyte. When a solid electrolyte having high ionic conductivity is used for the negative electrode mixture layer 210, the ionic conductivity in the negative electrode can be improved.
  • a conversion-based metal oxide is preferably used as the negative electrode active material.
  • the conversion-based metal oxide means a metal oxide that undergoes a conversion reaction to reduce and generate a metal. In the conversion reaction between the metal oxide and lithium ion, a single metal is produced by the reduction of the metal oxide, and lithium oxide is produced by the oxidation of lithium.
  • the conversion-type metal oxide by reversibly causing a conversion reaction and its reverse reaction, lithium ions can be occluded when the secondary battery is discharged and released when the secondary battery is charged. According to the conversion-type metal oxide, a potential difference required for charging and discharging can be generated between the electrodes by such a redox reaction, an accompanying alloying reaction, or the like.
  • the carbon material is selected from a group of materials such as natural graphite, artificial graphite, carbon black, carbon nanofibers, other non-graphitized carbons, vapor-grown carbon fibers, fullerenes, graphene, and carbon nanotubes.
  • Examples of carbon black include Ketjen black, acetylene black, thermal black, furnace black, and channel black.
  • Examples of the carbon nanofibers include pitch-based carbon nanofibers and PAN-based carbon nanofibers.
  • the binder forming the negative electrode mixture layer 210 is selected from a material group such as styrene-butadiene rubber, polyvinylidene fluoride (PVDF), acrylic acid ester resin, and methacrylic acid ester resin.
  • a thickening resin such as carboxymethyl cellulose may be used in combination.
  • the negative electrode current collector 220 a metal foil, a perforated foil, or the like can be used.
  • the negative electrode current collector 220 is selected from a group of materials such as copper and copper alloy.
  • the thickness of the negative electrode current collector 220 is preferably 10 nm to 1 mm, more preferably 1 to 100 ⁇ m from the viewpoint of achieving both mechanical strength and energy density.
  • the negative electrode tab 230 can be formed of the same material as the negative electrode current collector 220.
  • the positive electrode mixture layer 110 is prepared by kneading a positive electrode active material with a conductive agent or a binder in a solvent to prepare a positive electrode mixture, and applying the prepared positive electrode mixture to a positive electrode current collector. It can be formed by drying the agent.
  • a negative electrode material or a binder containing a carbon material and a negative electrode active material is kneaded in a solvent to prepare a negative electrode mixture, and the prepared negative electrode mixture is applied to a negative electrode current collector.
  • the mixture layer formed on the current collector is pressure-molded by a roll press or the like so that the active material has a predetermined density.
  • the mixture layer can also be laminated on the current collector by repeating the steps from coating to drying.
  • the electrode on which the mixture layer is formed can be punched, cut, or the like.
  • Kneading of the mixture can be performed with various devices such as a planetary mixer, a discharge mixer, a butterfly mixer, a twin-screw kneader, a ball mill, and a bead mill.
  • a solvent for dispersing the active material or the like various solvents such as 1-methyl-2-pyrrolidone (NMP), water, and ⁇ -butyrolactone can be used depending on the electrode.
  • NMP 1-methyl-2-pyrrolidone
  • water water
  • ⁇ -butyrolactone can be used depending on the electrode.
  • a method of applying the mixture various methods such as a roll coating method, a doctor blade method, a dipping method, and a spray method can be used.
  • the separator 300 acts as a medium for conducting ions between the positive electrode 100 and the negative electrode 200 while preventing a short circuit between the electrodes.
  • the separator 300 is formed by using any one or a combination of an insulating microporous film having minute pores, a non-volatile electrolyte obtained by supporting an electrolytic solution on particles, and a solid electrolyte. it can.
  • the thickness of the separator 300 is preferably several nm to several mm from the viewpoint of achieving both electron insulation and energy density.
  • the microporous film is a cellulose resin such as cellulose, carboxymethyl cellulose or hydroxypropyl cellulose, a polyolefin resin such as polypropylene or a polyethylene-polypropylene copolymer, or a polyester resin such as polyethylene terephthalate, polyethylene naphthalate or polybutylene terephthalate. , Aramid, Polyethyleneimide, Polyethylene, Glass and the like.
  • a porous sheet, a non-woven fabric, or the like can also be used.
  • the non-volatile electrolyte a semi-solid electrolyte composed of an electrolytic solution in which an electrolyte salt is dissolved and supporting particles for supporting the electrolytic solution can be used.
  • the non-volatile electrolyte may contain a binder for binding the supported particles. According to the non-volatile electrolyte, the electrolyte is retained in the pores between the particles of the supported particles to mediate ionic conduction. Since the volatilization and flow of the electrolytic solution are suppressed, it is possible to obtain a battery in which leakage of the electrolytic solution and changes in composition are unlikely to occur.
  • the supported particles various particles having high insulating properties and insoluble in the electrolytic solution can be used.
  • Specific examples of the supported particles include inorganic particles of metal oxides such as ⁇ -alumina (Al 2 O 3 ), silica (SiO 2 ), zirconia (ZrO 2 ), and ceria (CeO 2 ).
  • a particulate solid electrolyte can also be used.
  • the solid electrolytes include sulfide-based solid electrolytes such as Li 10 Ge 2 PS 12 and Li 2 SP 2 S 5 , garnet-type solid electrolytes such as Li 7 La 3 Zr 2 O 12 , and La 2 / 3-x. It is selected from a group of materials such as a perovskite type solid electrolyte such as Li 3x TiO 3 and a NASICON type solid electrolyte.
  • ⁇ Separator forming method> When a non-volatile electrolyte is used for the separator 300, a method of compression-molding the supported particles into pellets, sheets, etc., a method of mixing the supported particles with binder powder, and forming into a highly flexible sheet, etc.
  • the supported particles and the binder can be kneaded in a solvent, formed into a sheet or the like, and dried to remove the solvent.
  • the separator 300 may be integrally formed with the electrode by kneading the supported particles and the binder in a solvent, coating the surface of the mixture layer, and drying the mixture.
  • the separator 300 uses a combination of a non-volatile electrolyte and a microporous membrane, the supported particles and the binder are kneaded in a solvent, and the obtained mixture is applied to the microporous membrane, and the coated mixture is used. It can be formed by a method of drying to remove the solvent. Alternatively, the separator 300 may be formed individually, or may be integrally formed with the electrode, and the separator 300 may be sandwiched between the electrode and the microporous film to form an electrode body.
  • the electrolytic solution may be filled between the particles of the supported particles after the supported particles are formed into a sheet or the like, or may be mixed with the supported particles before the supported particles are formed. Mixing the electrolyte with the supported particles gives a semi-solid non-volatile electrolyte.
  • the supported particles and the electrolytic solution are mixed by adding an organic solvent such as methanol, and the obtained slurry is spread on a petri dish or the like to distill off the organic solvent to obtain a powdery non-volatile electrolyte.
  • the electrolytic solution may be held not only in the separator 300 but also in the positive electrode mixture layer 110 and the negative electrode mixture layer 210.
  • the electrolytic solution is held between the particles of the active material and the conductive agent in the mixture layer, the ionic conductivity in the electrode is increased and a high discharge capacity can be obtained.
  • a method of retaining the electrolytic solution in the mixture layer a method of injecting the electrolytic solution into the exterior body 500 or a method of kneading the electrolytic solution with an active material, a conductive agent, etc. to prepare a mixture, and then preparing the mixture.
  • a method of coating the current collector to produce an electrode or the like can be used.
  • binder used for forming the non-volatile electrolyte layer examples include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer (P (VdF-HFP)), and styrene.
  • PTFE polytetrafluoroethylene
  • PVdF-HFP vinylidene fluoride-hexafluoropropylene copolymer
  • styrene -Butadiene rubber, polyalginic acid, polyacrylic acid and the like can be mentioned.
  • a porous sheet made of fluororesin is preferable.
  • the average particle size of the primary particles of the supported particles is preferably 1/100 to 1/2 of the thickness of the microporous membrane.
  • the electrolytic solution contains an electrolyte that serves as a carrier of electric charges and a solvent that disperses and dissolves the electrolyte.
  • Various additives may be added to the electrolytic solution for the purpose of improving the cycle characteristics and stability of the battery cell 1000, the flame retardancy of the electrolytic solution, and the like.
  • a solid electrolyte is used as the separator 300, it is not necessary to use an electrolytic solution. Instead of immersing the positive electrode 100, the negative electrode 200, etc. in the electrolytic solution, a solid electrolyte may be filled between these electrodes.
  • Electrolyte LiPF 6, LiBF 4, LiClO 4, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) , Lithium bis (pentafluoroethanesulfonyl) imide (LiBETI), lithium bisoxalate volate (LiBOB), lithium trifurate and the like are selected from various lithium salt material groups.
  • the solvent is a group of materials such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate, butylene carbonate, ⁇ -butyrolactone, phosphoric acid triester, trimethoxymethane, dioxolane, diethyl ether, and sulfolane. Is selected from.
  • the negative electrode material used for forming the negative electrode mixture layer 210 contains a solvothermally synthesized negative electrode active material and a carbon material that mainly functions as a conductive agent.
  • the carbon material and the dispersant are put in a solvent to form a network of the carbon material, and the negative electrode active material is precipitated around the carbon material. Produced by the method.
  • the conversion-type negative electrode active material is known as an active material having a high theoretical capacity.
  • graphite which has been generally used as a negative electrode active material, has a theoretical capacity of about 372 mAh / g.
  • some conversion-type negative electrode active materials exhibit a high capacity of 1000 mAh / g or more. Since the conversion-based negative electrode active material undergoes a multi-step redox reaction, it tends to obtain a high capacity as a whole.
  • the conversion-type negative electrode active material has a problem in the reversibility of the reaction during charging and discharging, and the coulomb efficiency (ratio of the amount of discharging and the amount of charging) and the capacity retention rate associated with the charging / discharging cycle are not always good. It has the drawback of. If the reversibility of the reaction is low, the amount of discharge decreases as charging and discharging are repeated, resulting in a battery cell having a short service life. Since the coulomb efficiency reaches a maximum value at the first charge / discharge and decreases as the charge / discharge is repeated, a negative electrode active material having at least a high initial coulomb efficiency is desired.
  • the initial Coulomb efficiency and charge / discharge cycle characteristics of the battery cell can be improved to some extent by making the primary particles of the negative electrode active material smaller. Since the smaller the particles of the negative electrode active material, the higher the reactivity, the smaller the primary particles of the negative electrode active material, the smaller the direct current resistance (DCR) of the battery cell tends to be.
  • DCR direct current resistance
  • the primary particles of the negative electrode active material are excessively small, the fine particles of the negative electrode active material will easily aggregate with each other when preparing a slurry-like negative electrode mixture.
  • the negative electrode active material is aggregated, it becomes difficult to disperse it uniformly with the conductive agent or the like, and the contact area between the negative electrode active material and the conductive agent becomes small in the produced negative electrode 200.
  • the negative electrode active material inside the agglomerate tends to be electrically isolated, so that the charging / discharging cycle characteristics deteriorate and the DC resistance during charging / discharging becomes high.
  • the negative electrode material when the negative electrode active material is sorbothermally synthesized, the carbon material and the dispersant are put in a solvent to form a network of the carbon material, and the negative electrode activity is formed around the carbon material. Since it is produced by a method of precipitating a substance, the primary particles of the negative electrode active material are in a state of being uniformly dispersed with respect to a conductive agent or the like, and are less likely to be electrically isolated during charging and discharging. As a result, the capacity retention rate associated with the charge / discharge cycle of the battery cell is improved, and the DC resistance during charge / discharge is suppressed. The reason why such a method for producing a negative electrode material is effective is not necessarily clear, but the following reasons can be considered.
  • the dispersant When a carbon material and a dispersant are added to the solvent during solvothermal synthesis, the dispersant binds to the surface of the carbon material and the carbon materials repel each other due to the action of the dispersant.
  • the carbon material does not agglomerate between particles or structures such as aggregates, but is evenly dispersed in the solvent. When the solvent is heated and pressurized, it approaches a critical state and exhibits both liquid and gaseous properties.
  • the raw material dissolves and the negative electrode active material begins to precipitate, and the dispersant begins to deteriorate. It is considered that the dispersant causes a dehydration reaction or the like to change the functional group.
  • the dispersant bonded to the surface of the carbon material is altered, it is considered that a three-dimensional network is formed by agglutination or connection between the carbon materials. It is considered that the altered dispersant exists on the surface of the carbon material and strengthens the network by the carbon material.
  • the negative electrode active material precipitates on the surface or gaps of the carbon material in the network during or after the formation of such a network, and crystal growth occurs. Since the negative electrode active material is dispersedly deposited in the network of the carbon material, the negative electrode active materials are less likely to aggregate with each other, and the contact between the fine particles of the individual negative electrode active materials and the carbon material is ensured. As a result, it is considered that the negative electrode active material is less likely to be electrically isolated during charging / discharging, the capacity retention rate associated with the charging / discharging cycle is improved, and the DC resistance during charging / discharging is suppressed.
  • the negative electrode material is produced by a method in which a carbon material and a dispersant are put in a solvent to form a network of carbon materials and a negative electrode active material is precipitated around the carbon material is determined by whether or not the negative electrode material is a negative electrode containing the carbon material. It can be confirmed by analyzing the surface of the material by X-ray Photoelectron Spectroscopy (XPS).
  • XPS X-ray Photoelectron Spectroscopy
  • the detection signal of photoelectrons derived from the 1s orbital of oxygen appears on the X-ray photoelectron spectroscopy spectrum due to the presence of functional groups containing these oxygen atoms. ..
  • the detection signals for these functional groups appear as overlapping peaks in the binding energy range of 530-534 eV. The overlap of such peaks means that a substance derived from a carbon material or a dispersant is present in the sample.
  • the negative electrode material is produced by a method in which a carbon material and a dispersant are put in a solvent to form a network of carbon materials, and a negative electrode active material is precipitated around the carbon material, an OH bond is formed.
  • the changes in the elements and electronic states that occur are observed as changes in the X-ray photoelectron spectral spectrum.
  • the hydroxyl groups present on the surface of the carbon material are detected by X-ray photoelectron spectroscopy because they easily cause a dehydration reaction when heated and pressurized in the presence of a dispersant during solvothermal synthesis. The photoelectron energy will change.
  • the method for producing the negative electrode material can be determined based on the half width of the peak derived from the OH bond, which is a measured value comparable between the samples.
  • the method for producing the negative electrode material can be determined based on the price range.
  • the half width of the peak to which the photoelectron energy derived from the OH bond is assigned is about 1.4319 eV or less when the carbon material does not undergo a dehydration reaction during solvothermal synthesis. On the other hand, if the carbon material undergoes a dehydration reaction or the like during solvothermal synthesis, it will be 1.4320 eV or more.
  • the negative electrode material shows a detection signal in the range of 530 to 534 eV of the coupling energy in the X-ray photoelectron spectroscopy obtained by the X-ray photoelectron spectroscopy, and the detected signal is waveform-separated to obtain OH.
  • the half-value width of the peak to which the photoelectron energy derived from the bond is assigned is 1.4320 eV or more
  • the negative electrode material is formed by putting a carbon material and a dispersant in a solvent to form a network of carbon materials, and the carbon material is used. It can be said that it was produced by a method of precipitating a negative electrode active material around the above.
  • the fact that the negative electrode material shows a peak to which the photoelectron energy derived from the OH bond is assigned means that a certain amount of hydroxyl groups are present in the carbon material or the like.
  • a polar hydroxyl group is present on the surface of the carbon material, it can be said that the carbon material and the dispersant having a polar functional group are in a state where they can easily interact with each other.
  • Such a state means that when the carbon material and the dispersant were added to the solvent, the carbon material and the dispersant were easily bonded, so it can be said that it was advantageous for the dispersion between the carbon materials.
  • the analysis of the negative electrode material by X-ray photoelectron spectroscopy can be performed using a scanning X-ray photoelectron spectroscopy device.
  • a scanning X-ray photoelectron spectrometer for example, "PHI5000 VersaProbe II" (manufactured by ULVAC-PHI) equipped with a neutralizing gun for neutralizing the charge of the sample can be used.
  • the X-ray source monochromatic AlK ⁇ rays or the like can be used.
  • a coarse-grained negative electrode material is compacted and fixed in a sample holder, dried and washed with dry air, an inert gas, etc. as necessary, and then the sample holder is scanned. It can be mounted on an X-ray photoelectron spectrometer.
  • the measurement of the X-ray photoelectron spectrum can be performed by irradiating the sample surface with preferably monochromatic X-rays while irradiating the sample with an electron beam from a neutralizing gun to neutralize the charge of the sample.
  • the X-ray photoelectron spectroscopic spectrum obtained by the analysis may be charge-corrected based on the peak derived from the 1s orbital of the carbon of the CH bond.
  • the full width at half maximum of the peak to which the photoelectron energy derived from the OH bond is assigned can be obtained by waveform-separating the detection signal appearing in the range of 530 to 534 eV.
  • the detection signal appearing in the range of 530 to 534 eV is fitted by the Gauss-Lorentz function to a peak whose peak center is near 530 eV, a peak whose peak center is near 532 eV, and a peak whose peak center is near 534 eV.
  • the half width of the peak to which the photoelectron energy derived from the OH bond is assigned is preferably 1.4320 eV or more, more preferably 1.44 V or more, and further preferably 1.45 V or more. It can be said that the larger the half-value width of this peak is, the more the elemental and electronic states of the OH bond existing on the surface of the carbon material are changed, and the dehydration reaction of the hydroxyl group is greatly advanced. .. If the hydroxyl groups on the surface of the carbon material undergo a dehydration reaction during the production of the negative electrode, the resistance on the surface of the carbon material becomes low, so that higher charge / discharge capacity, energy density, and lower internal resistance can be obtained. it can.
  • Examples of the negative electrode active material include iron oxide, molybdenum oxide, tin oxide, manganese oxide, cobalt oxide, germanium oxide, nickel oxide, indium oxide, gallium oxide, aluminum oxide, and magnesium oxide. Conversion-type metal oxides such as substances can be used.
  • the conversion-based metal oxide may be a composite oxide having a plurality of types of metals among these metals.
  • conversion-based metal oxides include Fe 2 O 3 , MoO 3 , SnO 2 , MnO, Co 3 O 4 , CoO, GeO 2 , NiO, In 2 O 3 , Ga 2 O 3, and the like. ..
  • iron oxide that produces iron and lithium oxide by a conversion reaction with lithium ions is more preferable, and iron (III) oxide (Fe 2 O 3 ) is particularly preferable.
  • Iron (III) oxide may be any of ⁇ -Fe 2 O 3 , ⁇ -Fe 2 O 3 , ⁇ -Fe 2 O 3, and the like. Further, iron (III) oxide may be elementally substituted with various different elements such as Al, Co, Mg, Ni, Mo, Sn, Mn, Ge, In and Ga.
  • Iron (III) oxide has good cycle characteristics when used as an active material, so it is effective in stably obtaining high Coulomb efficiency and capacity retention rate. Moreover, since the number of Clarke numbers is large, it can be stably obtained at low cost. In addition, since the amount of chemicals used can be suppressed for refining, the environmental load during manufacturing can be reduced. From the viewpoint of improving the capacitance and cycle characteristics, iron (III) oxide is preferably elementally substituted with one or more of Al, Co, Mg and Ni.
  • the negative electrode active material may have a solid structure or a hollow structure.
  • the negative electrode active material may have substantially all the primary particles contained in the negative electrode material having a solid structure or a hollow structure, or may be a hybrid of a solid structure and a hollow structure.
  • the primary particles having a hollow structure may have only open pores, or may have open pores and closed pores.
  • the primary particles of the negative electrode active material have a circular equivalent diameter measured by approximating a circle on an electron microscope image, preferably 10 ⁇ m or less, more preferably 500 nm or less, and further preferably 100 nm or less.
  • the equivalent circle diameter of the primary particles is preferably 1 nm or more. The smaller the equivalent circle diameter of the primary particles, the larger the specific surface area of the negative electrode active material, and the larger the contact area between the negative electrode active material and the carbon material or the electrolytic solution.
  • the primary particles expand and contract with charging and discharging, the stress is easily relaxed. Therefore, the Coulomb efficiency and the capacity retention rate can be increased.
  • Ketjen Black is particularly preferable. Ketjen black can be produced by incompletely burning and activating hydrocarbons, then granulating and drying. Ketjen Black has the characteristics that the particle size of the primary particles is small and the specific surface area is large due to the hollow structure, and it is excellent in the performance of imparting conductivity. When Ketjen Black is used as the carbon material, the negative electrode active material can be uniformly dispersed in the network formed by the fine particle carbon material during solvothermal synthesis. Further, since the particle size is small, it is possible to form a comprehensive conductive path while ensuring charge / discharge capacity and energy density.
  • the carbon material preferably has a circle-equivalent diameter measured by approximating a circle on an electron microscope image to be equal to or less than the average circle-equivalent diameter of the primary particles of the negative electrode active material.
  • the equivalent circle diameter of the carbon material is preferably 10 ⁇ m or less, more preferably 500 nm or less, still more preferably 100 nm or less.
  • the equivalent circle diameter of the carbon material is preferably 1 nm or more.
  • the shape and structure of the negative electrode active material and carbon material can be confirmed by observation using, for example, a scanning electron microscope (SEM).
  • SEM scanning electron microscope
  • the equivalent circle diameter of the primary particles of the negative electrode active material and the carbon material can be measured on the electron microscope image by imaging an electron microscope image containing a sufficient number of primary particles using an electron microscope such as SEM. ..
  • the magnification of the electron microscope can usually be 40 k times to 20 k times.
  • the conversion-based metal oxide used as the negative electrode active material can be synthesized by using the solvothermal synthesis method.
  • a method for producing the negative electrode active material will be described by taking a method of synthesizing iron (III) oxide as an example of the negative electrode active material.
  • the negative electrode active material can be produced by a production method including a reaction solution preparation step, a reaction step, a solid-liquid separation step, and a post-treatment step.
  • iron (II) chloride, iron (II) sulfate, or the like can be used as a metal ion source.
  • iron (II) chloride, iron (II) sulfate, or the like can be used as a metal ion source.
  • ammonium dihydrogen phosphate, diammonium hydrogen phosphate and the like can be used as an additive for promoting nucleation of the negative electrode active material.
  • sodium sulfate, lithium sulfate, or the like can be used as an anion source that promotes the formation of a hollow structure of the negative electrode active material.
  • the shape of the primary particles of the negative electrode active material, the particle size of the primary particles, etc. can be controlled by adjusting the concentrations of the metal ion source, the additive, the anion source, the temperature / time of the synthesis reaction, the stirring conditions, and the like. ..
  • concentrations of the metal ion source, the additive, the anion source can be controlled by adjusting the concentrations of the metal ion source, the additive, the anion source, the temperature / time of the synthesis reaction, the stirring conditions, and the like. ..
  • the crystal growth of the primary particles is suppressed, so that primary particles with a small particle size, primary particles with a hollow structure, and other shapes with a large surface area Primary particles tend to be easier to synthesize.
  • reaction solution preparation step a reaction solution in which the raw materials are dissolved and dispersed is prepared.
  • a carbon material and a dispersant are added to the reaction solution before the synthesis reaction.
  • the metal ion source, the additive for promoting nucleation, the anion source, the carbon material and the dispersant are weighed so as to have appropriate concentrations and concentration ratios, respectively, and these raw materials are made into various low viscosities. It can be prepared by dissolving and dispersing in a polar solvent.
  • the dispersant examples include cellulose derivatives such as carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, ethyl cellulose and hydroxymethyl cellulose, and water-soluble polymers such as polyvinyl alcohol, polyacrylic acid and polyethylene glycol or derivatives thereof. , Polyimide resin, phenol resin, epoxy resin, urea resin, melamine resin, unsaturated polyester resin, thermosetting resin such as polyurethane, polyvinylidene fluoride and the like can be used. As the dispersant, a material having a high affinity for a polar solvent is preferably used.
  • polar solvent examples include water, ethanolamine-based solvents such as N, N-dimethylformamide (DMF), diethanolamine, triethanolamine, and polyethanolamine, diethylene glycol, and triethylene glycol. Glycol-based solvent and the like can be used.
  • ethanolamine-based solvents such as N, N-dimethylformamide (DMF), diethanolamine, triethanolamine, and polyethanolamine, diethylene glycol, and triethylene glycol.
  • Glycol-based solvent and the like can be used.
  • the concentration of metal ions in the reaction solution depends on the morphology of the particles to be synthesized and the conditions of the synthesis reaction, but is, for example, 0.001 to 0.05 mol / L, preferably 0.005 to 0.02 mol / L. Can be done.
  • the concentration of the additive can be, for example, 0.0001 to 0.005 mol / L, preferably 0.0002 to 0.002 mol / L.
  • the concentration of the anion added as the anion source can be, for example, 0.0001 to 0.05 mol / L, preferably 0.0002 to 0.01 mol / L.
  • the concentration of the carbon material in the reaction solution can be adjusted according to the amount of metal oxide charged or the target yield of metal oxide.
  • the concentration of the carbon material can be 1 to 500% by mass, preferably 3 to 100% by mass, and more preferably 5 to 20% by mass with respect to the weight of the metal oxide to be synthesized.
  • the concentration of the dispersant in the reaction solution can be adjusted according to the amount of carbon material charged.
  • the concentration of the dispersant can be 1 to 500% by mass, preferably 3 to 100% by mass, and more preferably 5 to 75% by mass with respect to the weight of the metal oxide to be synthesized.
  • the reaction solution prepared in the reaction solution preparation step is subjected to a solvothermal reaction (hydrothermal reaction) under high temperature and high pressure to generate a negative electrode active material.
  • the solvothermal reaction is carried out over a predetermined time by charging the reaction solution into the reactor and maintaining it under a high pressure of a predetermined temperature.
  • a pressure-resistant reactor made of stainless steel, titanium alloy, Hastelloy, pressure-resistant glass, etc., which is equipped with a temperature control device and has an inner cylinder made of polytetrafluoroethylene, etc., can be used. it can.
  • a batch reactor such as an autoclave
  • a continuous reactor such as a pressure resistant reactor can be used.
  • the temperature of the synthesis reaction depends on the form of the particles to be synthesized and the concentration of the reaction solution, but for example, when water is used as a solvent, it can be 140 to 240 ° C, preferably 210 to 230 ° C.
  • the time of the synthesis reaction depends on the form of the particles to be synthesized and the concentration of the reaction solution, but for example, when water is used as a solvent, it can be 0.5 to 72 hours, preferably 24 to 60 hours.
  • the product produced by the solvothermal reaction is solid-liquid separated.
  • the product produced in the reaction solution that is, the negative electrode material composed of the negative electrode active material, the carbon material, etc., can be recovered by solid-liquid separation by an appropriate method such as filtration or centrifugation.
  • the solid-liquid separated product is washed and dried.
  • the product recovered from the reaction solution that is, the negative electrode material composed of the negative electrode active material, the carbon material, etc.
  • water such as ultrapure water, demineralized water, alcohols such as methanol and ethanol, and other organic solvents. Can be washed using an appropriate combination.
  • the product recovered from the reaction solution can be dried by an appropriate method such as vacuum drying, hot air drying, and cold air drying.
  • the primary particles of the negative electrode active material generated by the solvothermal reaction have a particle size distribution of one mountain frequency distribution. Therefore, the equivalent circle diameter and the like of the primary particles of the negative electrode active material can be obtained without classification by the solvothermal reaction controlled under appropriate conditions.
  • the negative electrode material produced by the solvothermal reaction may be classified as necessary as long as the dispersed state of the negative electrode active material and the carbon material is not significantly impaired. Further, the classified negative electrode materials may be used in combination with different particle size groups.
  • the negative electrode material obtained by the above manufacturing method can be used as the material for the negative electrode 200.
  • the negative electrode material can be kneaded with a binder in a solvent to prepare a negative electrode mixture.
  • the negative electrode mixture layer 210 can be formed by applying the prepared negative electrode mixture to the negative electrode current collector and drying the applied negative electrode mixture.
  • the negative electrode material obtained by the above manufacturing method can be used as a material for the battery cell 1000 including the positive electrode 100, the negative electrode 200, and the separator 300 by forming the negative electrode mixture layer 210.
  • battery cells include, for example, a power source for mobile bodies such as mobile phones and portable personal computers, a power source for electric vehicles, hybrid vehicles, railway vehicles, hybrid railway vehicles, ships, etc., a stationary power source for power storage, and the like. It can be used for various purposes.
  • the battery cell can also be used as an assembled battery by electrically connecting a plurality of cells to each other.
  • the negative electrode material forms a network of carbon material by putting a carbon material and a dispersant in a solvent, and the negative electrode activity is activated around the carbon material. Since it is produced by a method of precipitating a substance, the half width of the peak to which the photoelectron energy derived from the OH bond, which is obtained from the X-ray photoelectron spectrum, is assigned is 1.4320 eV or more. Since the negative electrode active material and the carbon material in the negative electrode are dispersed with high uniformity, the capacity retention rate during the charge / discharge cycle is improved, the DC resistance during charge / discharge is suppressed, and the service life is long. A secondary battery having a long output characteristic and good output characteristics can be obtained.
  • a negative electrode containing Fe 2 O 3 which is a conversion-type negative electrode active material, by forming a network of carbon materials by putting a carbon material and a dispersant in a solvent and precipitating a negative electrode active material around the carbon material.
  • a material was prepared, and the X-ray photoelectron spectrum, the capacity retention rate of the battery cell, and the DC resistance during discharge were evaluated.
  • the negative electrode material was synthesized by the following procedure using a hydrothermal synthesis method. First, 0.02 mol / L iron (III) chloride (FeCl 3 ), 0.0002 mol / L ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ), 0.0005 mol / L sodium sulfate (Na 2 SO). An aqueous solution in which 4 ) was dissolved was prepared. This aqueous solution was prepared by dissolving each raw material powder weighed in a dry room in 70 mL of ultrapure water. The theoretical yield of Fe 2 O 3 based on this charge is about 0.1 g.
  • Ketjen black (KB) (12.5% by mass based on the theoretical yield of Fe 2 O 3 ) was added as a carbon material to the aqueous solution in which each raw material powder was dissolved.
  • KB Ketjen black
  • PVA polyvinyl alcohol
  • the produced precipitate was dehydrated with a centrifuge, washed with ultrapure water three times, and further washed with ethanol three times. Then, it was vacuum dried at 60 degreeC for 10 hours or more to obtain a negative electrode material containing a carbon material and a negative electrode active material.
  • the negative electrode material obtained after drying was 0.1118 g. This yield was substantially the same as the total weight of the amount of Ketjen Black, which is a carbon material, and the amount of polyvinyl alcohol, which is a dispersant, with respect to the theoretical yield based on the amount charged: about 0.1 g.
  • FIG. 3 is an electron micrograph of the negative electrode material according to Example 1.
  • the negative electrode material according to the first embodiment has a structure in which the primary particles of the negative electrode active material 10 are dispersed around the carbon material 20.
  • the primary particles of the negative electrode active material 10 are highly uniformly dispersed on the surface and gaps of the carbon material 20 forming a three-dimensional network.
  • ⁇ XPS analysis> The prepared negative electrode material was subjected to XPS analysis in the following procedure, and the X-ray photoelectron spectroscopic spectrum was measured. From the result, the half width of the peak to which the photoelectron energy derived from the OH bond is assigned was obtained.
  • As the scanning X-ray photoelectron spectrometer "PHI5000 VersaProbeII" (manufactured by ULVAC-PHI) was used. The dried negative electrode material was spread on the carbon tape, and the sample holder to which the carbon tape was fixed was attached to the scanning X-ray photoelectron spectrometer.
  • the beam diameter of the X-rays is 100 ⁇ m
  • the detection angle of photoelectrons is 45 degrees with respect to the normal line perpendicular to the sample surface
  • the measurement area of the sample is 500 ⁇ m ⁇
  • the X-ray photoelectron spectroscopy spectrum was measured while irradiating an electron beam from a neutralizing gun to neutralize the charge of the sample. Since the binding energy on the X-ray photoelectron spectrum is affected by the charge-up caused by X-ray irradiation, it is based on the peak derived from the 1s orbit of the carbon of the CH bond after the measurement using the neutralizing gun. Charge-corrected.
  • the detection signal appearing in the range of 530 to 534 eV has a peak derived from an oxide bond having a peak center of about 530 eV and an overlapping peak having a peak center of about 532 eV.
  • FIG. 4 is an X-ray photoelectron spectroscopic spectrum of the negative electrode material according to Example 1.
  • a peak having a peak intensity of about 3000 c / s was obtained.
  • the half width of this peak was 1.4501 eV.
  • the negative electrode was produced by the following procedure.
  • the prepared negative electrode material and the binder were kneaded by adding 1-methyl-2-pyrrolidone (NMP) to prepare a slurry-like negative electrode mixture.
  • NMP 1-methyl-2-pyrrolidone
  • As the binder an acrylic binder was used.
  • the prepared negative electrode mixture was applied onto the current collector foil and dried to form a negative electrode mixture layer, and then the negative electrode mixture layer was pressed to a predetermined density to obtain a negative electrode.
  • a unipolar cell which is a lithium ion secondary battery, was produced by using the produced negative electrode and metallic lithium as a counter electrode.
  • the capacity of Fe 2 O 3 used as the negative electrode active material was assumed to be 1007 Ah / g, and the rate of 1000 Ah / g was set to 1C.
  • the unipolar cell was charged with a constant current of 0.2 C to a final voltage of 3 V, and then discharged with a constant current of 0.2 C to a final voltage of 0.05 V.
  • the combination of the charging process and the discharging process was set as one cycle, and charging and discharging were repeated up to 50 cycles to measure the capacity retention rate.
  • the capacity retention rate was calculated as the ratio (%) of the discharge capacity of each cycle to the discharge capacity of the fifth cycle.
  • the direct current resistance (DCR) of the unipolar cell at the time of discharge was measured using the unipolar cell after the capacity retention rate was measured.
  • a unipolar cell that has been repeatedly charged and discharged up to 50 cycles is charged with a constant current of 0.2C to a charge rate (State of Charge: SOC) of 50%, and then discharged with a constant current of 0.5C, 1C or 2C for 10 seconds. Then, the amount of change in voltage during that period was measured. Then, the amount of change in the measured voltage was plotted against the current value, and the slope (V / I) was calculated as the DC resistance value at the time of discharge.
  • Example 2 A negative electrode material was prepared in the same manner as in Example 1 except that 0.01 g of polyvinyl alcohol (10% by mass based on the theoretical yield of Fe 2 O 3 ) was added to the reaction solution as a dispersant. The X-ray photoelectron spectroscopy spectrum, the capacity retention rate of the battery cell, and the DC resistance during discharge were evaluated.
  • FIG. 5 is an electron micrograph of the negative electrode material according to the second embodiment.
  • the negative electrode material according to the second embodiment has a structure in which the primary particles of the negative electrode active material 10 are dispersed around the carbon material 20.
  • the primary particles of the negative electrode active material 10 are highly uniformly dispersed on the surface and gaps of the carbon material 20 forming a three-dimensional network.
  • the proportion of the negative electrode active material 10 covered with the carbon material 20 is increased.
  • FIG. 6 is an X-ray photoelectron spectroscopic spectrum of the negative electrode material according to Example 2.
  • a peak having a peak intensity of about 2900 c / s was obtained.
  • the half width of this peak was 1.4734 eV.
  • Example 3 A negative electrode material was prepared in the same manner as in Example 1 except that 0.05 g of polyvinyl alcohol (50% by mass based on the theoretical yield of Fe 2 O 3 ) was added to the reaction solution as a dispersant. The X-ray photoelectron spectroscopy spectrum, the capacity retention rate of the battery cell, and the DC resistance during discharge were evaluated.
  • FIG. 7 is an electron micrograph of the negative electrode material according to Example 3.
  • the negative electrode material according to the third embodiment has a structure in which the primary particles of the negative electrode active material 10 are dispersed around the carbon material 20.
  • the primary particles of the negative electrode active material 10 are highly uniformly dispersed on the surface and gaps of the carbon material 20 forming a three-dimensional network.
  • the proportion of the negative electrode active material 10 covered with the carbon material 20 is increased.
  • FIG. 8 is an X-ray photoelectron spectroscopic spectrum of the negative electrode material according to Example 3.
  • a peak having a peak intensity of about 2800 c / s was obtained.
  • the half width of this peak was 1.8448 eV.
  • a negative electrode material is prepared by a method in which Fe 2 O 3 , which is a conversion-type negative electrode active material, is precipitated in a solvent without using a dispersant, and then a powder of the negative electrode active material and a carbon material are mixed.
  • the X-ray photoelectron spectroscopy spectrum, the capacity retention rate of the battery cell, and the DC resistance during discharge were evaluated.
  • the negative electrode material according to Comparative Example 1 was synthesized by the following procedure using a hydrothermal synthesis method. First, in the same manner as in Example 1, 0.02 mol / L of iron chloride (III) (FeCl 3), ammonium dihydrogen phosphate of 0.0002mol / L (NH 4 H 2 PO 4), 0.0005mol / An aqueous solution in which L sodium sulfate (Na 2 SO 4 ) was dissolved was prepared. The theoretical yield of Fe 2 O 3 based on this charge is about 0.1 g.
  • an aqueous solution in which each raw material powder was dissolved was placed in an autoclave having a volume of 100 mL, and heated and pressurized at 220 ° C. for 48 hours to cause a hydrothermal reaction.
  • the produced precipitate was dehydrated with a centrifuge, washed with ultrapure water three times, and further washed with ethanol three times. Then, it was vacuum dried at 60 ° C. for 10 hours or more.
  • 0.0125 g of Ketjen black (12.5% by mass with respect to the theoretical yield of Fe 2 O 3 ) as a carbon material was added to the obtained dried product, and the mixture was sufficiently mixed to prepare a negative electrode material. Obtained.
  • FIG. 9 is an X-ray photoelectron spectroscopic spectrum of the negative electrode material according to Comparative Example 1.
  • a peak having a peak intensity of about 3100 c / s was obtained.
  • the half width of this peak was 1.4319 eV.
  • ⁇ Comparative example 2> After precipitating Fe 2 O 3 , which is a conversion-type negative electrode active material, in a solvent without using a dispersant, the powder of the negative electrode active material, a carbon material, and PVA as a binder are mixed and coated.
  • a negative electrode was prepared by drying and pressure molding, and the X-ray photoelectron spectral spectrum of the negative electrode mixture layer on the negative electrode, the capacity retention rate of the battery cell, and the DC resistance during discharge were evaluated.
  • the negative electrode material (negative electrode) according to Comparative Example 2 was produced by the following procedure.
  • the negative electrode active material prepared in the same manner as in Comparative Example 1 and the binder were kneaded by adding 1-methyl-2-pyrrolidone to prepare a slurry.
  • As the binder an acrylic binder was used.
  • 0.05 g of polyvinyl alcohol (50% by mass with respect to the theoretical yield of Fe 2 O 3 ) as a binder was added and kneaded to prepare a slurry-like negative electrode mixture.
  • the prepared negative electrode mixture was applied onto the current collector foil and dried to form a negative electrode mixture layer, and then the negative electrode mixture layer was pressed to a predetermined density to obtain a negative electrode.
  • the prepared negative electrode material (negative electrode) was subjected to XPS analysis in the same manner as in Comparative Example 1.
  • the prepared negative electrode material was placed on a carbon tape, and a sample holder to which the carbon tape was fixed was attached to a scanning X-ray photoelectron spectrometer. Then, the X-ray photoelectron spectroscopic spectrum was measured in the same manner as in Comparative Example 1. From the result, the half width of the peak to which the photoelectron energy derived from the OH bond is assigned was obtained.
  • FIG. 10 is an X-ray photoelectron spectroscopic spectrum of the negative electrode material according to Comparative Example 2.
  • a peak having a peak intensity of about 8200 c / s was obtained.
  • the half width of this peak was 1.4163 eV.
  • Table 1 shows the composition of the negative electrode material, the peak intensity of the peak to which the photoelectron energy derived from the OH bond obtained from the X-ray photoelectron spectrum is assigned, and the peak to which the photoelectron energy derived from the OH bond is assigned.
  • the results of the half-value width of the battery cell, the capacity retention rate after 50 cycles of the battery cell, and the DC resistance when the battery cell is discharged are shown.
  • the DC resistance at the time of discharge is a relative value with the DC resistance value at the time of discharge of Comparative Example 1 as 100%.
  • FIG. 11 is a diagram showing a comparison of the capacity retention rates of Examples 1 to 3 and Comparative Example 1.
  • FIG. 12 is a diagram showing a comparison of the capacity retention rates of Example 3 and Comparative Example 2.
  • Table 1 and FIG. 11 in Examples 1 to 3, a carbon material and a dispersant are put in a solvent to form a network of carbon materials, and a negative electrode active material is precipitated around the carbon material. Since it was produced, the capacity retention rate increased by about 16% or more as compared with Comparative Example 1 in which the powder of the negative electrode active material and the carbon material were mixed after synthesis. According to Examples 1 to 3, it was confirmed that the volume retention rate improved as the amount of the dispersant added increased. In particular, in Example 3, since the amount of the dispersant added was 50% by mass, the volume was hardly reduced.
  • Examples 1 to 3 are produced by a method in which a carbon material and a dispersant are put in a solvent to form a network of carbon materials, and a negative electrode active material is precipitated around the carbon materials. Compared with Comparative Example 1 in which the powder of the negative electrode active material and the carbon material were mixed, the DC resistance at the time of discharge showed a decrease of about 40%. According to Examples 1 to 3, it was confirmed that the DC resistance at the time of discharge was suppressed as the amount of the dispersant added was large.
  • PVA is used as a dispersant.
  • PVA can also be used as a binder as in Comparative Example 2 and Patent Document 1.
  • PVA is used as a binder, the dissociation between particles is suppressed, so that the capacity retention rate of the battery cell tends to be high.
  • Comparative Example 2 using PVA as a dispersant had a higher capacity retention rate.
  • FIG. 13 is an electron micrograph of the negative electrode material according to Example 3.
  • FIG. 14 is an electron micrograph of the negative electrode material according to Comparative Example 1.
  • the negative electrode material according to the third embodiment has a structure in which the primary particles of the negative electrode active material 10 are dispersed around the carbon material 20. The primary particles of the negative electrode active material 10 are finely dispersed throughout in the matrix formed by the negative electrode material itself.
  • the negative electrode material according to Comparative Example 1 forms an aggregate 30 made of the negative electrode active material as surrounded by a broken line.
  • the agglomerate 30 is formed by aggregating the primary particles of the negative electrode active material, and contains almost no carbon material.
  • the negative electrode active material forming the aggregate 30 and the carbon material are in a dispersed state in which they are largely separated from each other.
  • Examples 1 to 3 are in a highly uniform dispersed state as shown in FIG. 13, it is considered that the negative electrode active material is unlikely to be electrically isolated. It is considered that the conversion-type negative electrode active material tends to maintain high reversibility of the reaction even when charging and discharging are repeated, and such a dispersed state improves the capacity retention rate.
  • Examples 1 to 3 are in a highly uniform dispersed state as shown in FIG. 13, it is considered that a conductive path made of a carbon material can be easily secured. It is considered that the conversion-type negative electrode active material can be kept in a state where it can easily come into contact with the carbon material even when charging and discharging are repeated, and such a dispersed state suppresses the DC resistance during discharging. Be done.
  • the negative electrode material produced by a method in which a carbon material and a dispersant are put in a solvent to form a network of carbon materials and a negative electrode active material is precipitated around the carbon material PVA or the like is used as a binder.
  • PVA or the like is used as a binder.
  • Negative electrode active material 10
  • Carbon material 30 Aggregate 100
  • Positive electrode 110 Positive electrode mixture layer 120
  • Positive electrode current collector 130 Positive electrode tab 200
  • Negative electrode 210 Negative electrode mixture layer 220
  • Negative electrode current collector 230 Negative electrode tab 250
  • Negative electrode terminal 300 Separator 400

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  • Battery Electrode And Active Subsutance (AREA)

Abstract

La présente invention concerne un matériau d'anode qui peut améliorer le ratio de capacité dans des cycles de charge/décharge et réduire la résistance interne d'un élément de batterie, une anode comprenant ce matériau d'anode, et un élément de batterie comportant cette anode. Le matériau d'anode contient un matériau au carbone et un matériau actif d'anode, et a une demi-largeur d'une crête attribuée à l'énergie de photoélectrons qui est dérivée d'une liaison O-H et obtenue d'un spectre spectroscopique de photoélectrons de rayons X d'au moins 1,4320 eV. L'anode (200) comprend un matériau d'anode qui contient un matériau au carbone et un matériau actif d'anode, le matériau d'anode ayant une demi-largeur d'une crête attribuée à l'énergie de photoélectrons qui est dérivée d'une liaison O-H et obtenue d'un spectre spectroscopique de photoélectrons de rayons X d'au moins 1,4320 eV. L'élément de batterie (1000) comprend une cathode (100), l'anode (200), et des séparateurs (300).
PCT/JP2020/008758 2019-06-20 2020-03-02 Matériau d'anode, anode et élément de batterie WO2020255489A1 (fr)

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JP2024025553A (ja) * 2022-08-12 2024-02-26 三桜工業株式会社 全固体電池および全固体電池の製造方法

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