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WO2015146899A1 - Matériau carboné d'électrode négative pour batterie rechargeable au lithium, électrode négative pour batterie au lithium, et batterie rechargeable au lithium - Google Patents

Matériau carboné d'électrode négative pour batterie rechargeable au lithium, électrode négative pour batterie au lithium, et batterie rechargeable au lithium Download PDF

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WO2015146899A1
WO2015146899A1 PCT/JP2015/058706 JP2015058706W WO2015146899A1 WO 2015146899 A1 WO2015146899 A1 WO 2015146899A1 JP 2015058706 W JP2015058706 W JP 2015058706W WO 2015146899 A1 WO2015146899 A1 WO 2015146899A1
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carbon material
negative electrode
lithium secondary
secondary battery
lithium
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Japanese (ja)
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騫 程
田村　宜之
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NEC Corp
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NEC Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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 invention relates to a negative electrode carbon material for a lithium secondary battery, a negative electrode for a lithium secondary battery, and a lithium secondary battery.
  • Lithium secondary batteries have been widely put into practical use as batteries for small electronic devices such as notebook computers and mobile phones because of their advantages such as high energy density, low self-discharge and excellent long-term reliability. In recent years, advanced functions of electronic devices and use in electric vehicles have progressed, and development of lithium secondary batteries with higher performance has been demanded.
  • carbon materials are generally used as negative electrode active materials for lithium secondary batteries, and various carbon materials have been proposed for improving battery performance.
  • Carbon materials include high crystalline carbon such as natural graphite and artificial graphite, low crystalline carbon such as graphitizable carbon (soft carbon) and non-graphitizable carbon (hard carbon), and amorphous carbon (amorphous). Carbon) is known. It is known that graphite, which is highly crystalline carbon, is excellent in reactivity with Li ions and has a capacity close to the theoretical capacity value. On the other hand, highly crystalline carbon easily reacts with propylene carbonate (PC), which is frequently used as a solvent for the electrolytic solution, thereby causing deterioration in charge rate characteristics due to deterioration of the electrolytic solution.
  • PC propylene carbonate
  • Low crystalline carbon and amorphous carbon have a theoretical capacity value that is higher than the theoretical capacity value of graphite, but the reactivity with Li ions is low and long-time charging is required. Lower. On the other hand, the reactivity with PC is low, and the deterioration of the electrolytic solution is small. Therefore, a composite carbon material combining graphite and amorphous carbon (including low crystalline carbon) has been proposed.
  • Patent Document 1 discloses a negative electrode active material in which amorphous carbon is adhered to the surface of graphite particles.
  • the graphite particles are oxidized to generate oxygen-containing functional groups on the surface of the graphite particles, and the surface of the graphite particles is roughened. It is disclosed.
  • Patent Document 1 discloses a method in which air oxidation is performed at a temperature of 200 ° C. to 700 ° C., and heat treatment is performed at 300 ° C. to 700 ° C. after alkali is attached to the surface of the graphite particles.
  • the negative electrode made of a carbon material has a reduced input characteristic and life when the amount of reaction with Li ions increases.
  • the tendency of graphite is remarkable, and the capacity at a high rate is small.
  • low crystalline carbon materials such as soft carbon and hard carbon have higher input characteristics than graphite, but their initial capacity is smaller than that of graphite. Therefore, there is a demand for a negative electrode material that has a large amount of reaction with Li ions, has better input characteristics and cycle life, and is inexpensive.
  • An object of the present invention is to solve the above-described problems, that is, a negative electrode carbon material from which a lithium secondary battery with improved charge rate characteristics as an index of input characteristics and cycle life can be obtained, and the same are used.
  • the object is to provide a negative electrode for a lithium secondary battery and a lithium secondary battery.
  • low crystalline carbon such as pitch coke is used instead of graphite, and a material in which pores are formed on the surface by heat treatment in an oxidizing atmosphere is used as the negative electrode material.
  • a negative electrode carbon material for a lithium secondary battery comprising a low crystalline carbon material having pores formed on the surface thereof, wherein the pore size is in the range of 20 nm to 1 ⁇ m.
  • a negative electrode carbon material for a secondary battery is provided.
  • the negative electrode for lithium secondary batteries containing said negative electrode carbon material is provided.
  • a lithium secondary battery including the negative electrode is provided.
  • the embodiment of the present invention it is possible to provide a negative electrode carbon material from which a lithium secondary battery with improved charge rate characteristics can be obtained, and a negative electrode for a lithium secondary battery and a lithium secondary battery using the same.
  • a negative electrode carbon material for a lithium secondary battery according to an embodiment of the present invention is made of a low crystalline carbon material, a carbon material called so-called soft carbon or hard carbon, and has a predetermined pore on the surface, thereby reducing the normal low-carbon material.
  • the holes include those formed in a groove shape.
  • This low crystalline carbon material having pores includes a crystalline graphite-like structure (a graphene laminated structure, hereinafter referred to as a graphene layer), and at least a plurality of pores are formed in the graphene layer on the surface side.
  • holes are formed in a plurality of graphene layers from the surface to the inside. These vacancies can pass lithium ions (Li ions) and function as a Li ion path (Li path) into the graphene layer.
  • Li path Li ion path
  • the Li path into the graphene layer of Li ions is almost limited to the path from the edge surface side of the graphene layer, and further to the back of the graphene layer (the center in the plane direction of the graphene layer) As the distance is long, and the amount of reaction with lithium increases, the charge rate characteristics deteriorate.
  • the graphene layer plane (basal surface) has holes that function as the Li path, so the Li path increases, and The path to the back of the graphene layer is shortened. As a result, the charge rate characteristics of the lithium secondary battery can be improved.
  • Such vacancies are preferably also formed in the graphene layer plane inside the surface-side graphene layer, and more preferably at least from the surface layer toward the inside. Holes can be formed in all graphene layers constituting the low crystalline carbon material. In addition, holes can be formed so as to penetrate a plurality of graphene layers. By forming such vacancies, a Li path reaching the inside in the stacking direction of the graphene layer (direction perpendicular to the graphene layer plane) is formed, and the charge rate characteristics can be further improved.
  • the pores in the plane of the graphene layer inside can be observed with an electron microscope such as TEM or SEM by cutting the low crystalline carbon material by various methods to obtain a cross section.
  • the opening size of these vacancies is not particularly limited as long as lithium ions can pass therethrough and the characteristics of the carbon material are not greatly deteriorated by vacancy formation, but it is preferably 20 nm or more, preferably 50 nm or more. More preferably, it is more preferably 100 nm or more. Further, from the viewpoint of not deteriorating the characteristics of the carbon material, the opening size is preferably 1 ⁇ m or less, more preferably 800 nm or less, and even more preferably 500 nm or less.
  • the “opening size” means the maximum length (maximum opening size) of the opening, and corresponds to the diameter of a circle having the smallest area that can accommodate the outline of the opening.
  • the opening size (minimum opening size) corresponding to the diameter of the circle with the largest area that can exist inside the outline of the hole opening is also preferably 20 nm or more, and more preferably 50 nm or more. More preferably, it is more preferably 100 nm or more.
  • the number density of holes having such an opening size is preferably in the range of 1 to 50 / ⁇ m 2 . It is preferable that pores having a number density in this range are formed at least in the surface layer. If the number density of vacancies is too low, a sufficient charge rate characteristic improvement effect cannot be obtained, and conversely, if the number density of vacancies is too high, the specific surface area becomes too large and side reactions during charge and discharge are likely to occur. Charge / discharge efficiency may decrease.
  • the number density of holes is selected from 10 1 ⁇ m ⁇ 1 ⁇ m areas on the surface of an electron microscope image of the surface of a low crystalline carbon material, and the number of holes having an opening size of 20 nm or more in each area is counted.
  • the vacancies are preferably formed over the entire surface of the carbon material, and more preferably uniformly distributed.
  • the interval between the plurality of holes is preferably in the range of 100 nm to 1 ⁇ m.
  • graphitizable carbon is preferable, and among them, petroleum pitch coke, coal pitch coke, mesophase pitch coke, etc. More preferably, pitch coke is used.
  • Pitch coke is obtained by charging soft pitch into a delayed coker and dry-distilling (carbonizing), and then calcining with a rotary kiln to form calcined pitch coke.
  • artificial graphite can be obtained by heat-treating these pitch cokes at 1500 ° C. or higher, particularly 2000 to 3300 ° C. In the present invention, pitch coke obtained at a lower cost than artificial graphite is used.
  • heat treatment is performed in an oxidizing atmosphere in the present invention.
  • the heat treatment in an oxidizing atmosphere is performed at a temperature lower than the ignition temperature of low crystalline carbon. If it ignites, temperature control becomes impossible by combustion of a carbon material, and it becomes difficult to form a desired hole.
  • the ignition temperature varies depending on the composition of the low crystalline carbon, the heat treatment temperature can usually be selected from the range of 350 to 800 ° C. under normal pressure.
  • the heat treatment time is in the range of about 30 minutes to 24 hours.
  • the oxidizing atmosphere include oxygen, carbon dioxide, and air. Also, the oxygen concentration and pressure can be adjusted as appropriate.
  • the opening size, number density, and distribution of pores can be controlled by heat treatment conditions such as heat treatment temperature, heat treatment time, and oxidizing atmosphere.
  • the vacancies thus formed on the surface of the carbon material are different from the voids inherent to the low crystalline carbon (voids between primary particles, defects, voids and cracks near the edges). Even when ordinary low crystalline carbon having voids is used for the negative electrode, the charge rate characteristics of the lithium secondary battery are low. Also, a treatment for roughening the surface of the low crystalline carbon (for example, a treatment of irradiating ultrasonic waves after immersing the low crystalline carbon in an alkaline solution) may be performed, and the low crystalline carbon after such treatment may be used for the negative electrode. The charge rate characteristics of lithium secondary batteries are low.
  • the chemical activation and gas activation methods used in the production of activated carbon expand the voids created by carbonization, open closed pores, and add more pores in the voids. Even if such normal activation treatment is performed on low crystalline carbon, it is difficult to obtain a lithium secondary battery having desired charge rate characteristics.
  • the highly crystalline graphene layer is preferentially oxidized, and the amorphous structure portion serves as a protective layer for protecting the graphene layer.
  • pores isolated from each other are formed on the surface of the carbon material. When graphite is oxidized, it does not become such a hole isolated from each other but forms a continuous groove (channel), which is clearly different.
  • lithium since it is possible to form vacancies in the surface layer without significantly degrading the structure of the low crystalline carbon, lithium does not significantly impair the battery characteristics due to the inherent characteristics of the low crystalline carbon.
  • the charge rate characteristics of the secondary battery can be improved.
  • the low crystalline carbon material after the vacancy formation according to the present embodiment example can have a structure and physical properties corresponding to the low crystalline carbon of the raw material.
  • the plane distance d 002 of the (002) plane of the low crystalline carbon material according to the present embodiment is preferably 0.350 nm or less, and more preferably 0.347 nm or less.
  • the surface spacing d 002 is greater than the typical graphite is usually, 0.340 nm or more.
  • This interplanar distance d 002 can be obtained by an X-ray diffraction method (X-Ray Diffraction: XRD).
  • the graphene layer contained in the low crystalline carbon material is much smaller in size than graphite.
  • the size of the graphene layer is represented by an average network size (the number of hexagonal meshes) based on a benzene ring obtained by the Diamond method.
  • the low crystalline carbon material according to the present embodiment is smaller than the raw low crystalline carbon material. Is also characterized in that the average mesh size increases. In the present invention, the average mesh size is preferably 60 or more.
  • a particulate material can be used from the viewpoint of filling efficiency, mixing property, moldability, and the like.
  • the particle shape include a spherical shape, an elliptical spherical shape, and a scale shape (flakes).
  • a general spheroidizing treatment may be performed.
  • the average particle size of the low crystalline carbon material according to the present embodiment is preferably 1 ⁇ m or more, more preferably 2 ⁇ m or more, and further preferably 5 ⁇ m or more from the viewpoint of suppressing side reactions during charging and discharging to suppress a decrease in charging and discharging efficiency.
  • it is preferably 40 ⁇ m or less, more preferably 35 ⁇ m or less, and even more preferably 30 ⁇ m or less from the viewpoints of input / output characteristics and electrode production (smoothness of the electrode surface).
  • the average particle diameter means the particle diameter (median diameter: D 50 ) at an integrated value of 50% in the particle size distribution (volume basis) by the laser diffraction scattering method.
  • the BET specific surface area (based on measurement at 77 K by the nitrogen adsorption method) of the low crystalline carbon material according to the present embodiment example is 10 m 2 / from the point of suppressing side reactions at the time of charge and discharge and suppressing a decrease in charge and discharge efficiency. Less than g is preferable, and 5 m 2 / g or less is more preferable. On the other hand, from the viewpoint of obtaining sufficient input / output characteristics, the BET specific surface area is preferably 0.5 m 2 / g or more, and more preferably 1 m 2 / g or more.
  • the low crystalline carbon material according to this embodiment preferably has a discharge capacity of 240 mAh / g or more in charge / discharge at a lithium potential of 0 to 2 V, and a charge / discharge efficiency of 75% or more.
  • charging / discharging efficiency means the value shown in at least initial charging / discharging at room temperature.
  • the low crystalline carbon material according to the present embodiment has a feature that the discharge capacity is increased by the formation of a lithium path as compared with the raw low crystalline carbon material.
  • the low crystalline carbon material according to the present embodiment may form a metal that can be alloyed with Li or its oxide on the surface and in the pores.
  • This metal or metal oxide can react with lithium and is electrochemically active in charging / discharging of a lithium secondary battery.
  • a metal or metal oxide at least one metal selected from the group consisting of Si, Ge, Sn, Pb, Al, Ga, In, and Mg, or an oxide thereof can be used.
  • Such a metal or metal oxide is preferably formed around the pores formed in the low crystalline carbon material.
  • the reaction capacity can be increased by forming such a metal or metal oxide.
  • the metal or metal oxide since the metal or metal oxide is formed around the vacancies, the metal or metal oxide can be strongly bonded to the graphene layer around the vacancies compared to other sites, and there are Li reaction sites that are excellent in reversibility.
  • the reaction volume can be increased.
  • Examples of such a metal or metal oxide forming method include CVD, sputtering, electrolytic plating, electroless plating, and hydrothermal synthesis.
  • the content of metal or metal oxide in the negative electrode carbon material according to the present embodiment is preferably 0.1 to 30% by mass with respect to the low crystalline carbon material. If the content is too small, sufficient content effects cannot be obtained. If the content is too large, the volume or shrinkage of the metal or metal oxide during charge / discharge is large, and the low crystalline carbon material deteriorates. It becomes easy.
  • the low crystalline carbon material according to this embodiment can be coated with amorphous carbon.
  • the amorphous carbon can suppress the side reaction between the low crystalline carbon material and the electrolytic solution, the charge / discharge efficiency can be improved, and the reaction capacity can be increased.
  • the low crystalline carbon material in which the metal which can be alloyed with the above-mentioned lithium (Li), or its oxide was formed in the surface can also be coat
  • amorphous carbon does not mean only a material that is not completely crystalline, but means a material that has a lower degree of crystallinity (graphitization degree) than a raw material low-crystalline carbon material. . In general, it is a material with extremely low crystallinity called amorphous carbon. Further, it is a material that can be formed by the following method.
  • Examples of the method for coating amorphous carbon on the low crystalline carbon material include hydrothermal synthesis, CVD, and sputtering.
  • the amorphous carbon coating by the hydrothermal synthesis method can be performed, for example, as follows. First, powder of a low crystalline carbon material in which pores are formed is immersed in a carbon precursor solution and mixed. It is treated in a hydrothermal reactor at 180 ° C. for 3 hours, and then vacuum filtered to separate the powder. Next, the separated powder is heat-treated in an inert atmosphere. The powder agglomerates are then pulverized to the desired particle size. Also, amorphous carbon is coated on the low crystalline carbon material before forming vacancies, and then heat-treated in an oxidizing atmosphere to form continuous vacancies in amorphous carbon and low crystalline carbon. You can also.
  • the carbon precursor solution various sugar solutions can be used, and an aqueous sucrose solution is particularly preferable.
  • the sucrose concentration of this aqueous solution can be set to 0.1 to 6M, and the immersion time can be set to 1 minute to 24 hours.
  • the heat treatment can be performed at 400 to 1200 ° C. for 0.5 to 24 hours in an inert atmosphere such as nitrogen or argon.
  • a negative electrode carbon material for a lithium secondary battery obtained by heat-treating pitch coke at a temperature selected from the range of 350 to 800 ° C. in an oxidizing atmosphere
  • the (002) plane spacing d 002 is 0.340 or more and 0.350 nm or less
  • the intensity ratio of the D peak reflecting irregularity to the G peak reflecting the graphite structure in Raman spectroscopy (I D / I G
  • a negative electrode carbon material for a lithium secondary battery having a ratio of less than 0.8 and a mass fraction of the graphene laminated structure of 66% or more is provided. It is preferable to use calcined pitch coke as the pitch coke.
  • the mass fraction of the graphene stacked structure is preferably 70% or more.
  • the negative electrode carbon material of the present embodiment example preferably has various characteristics similar to those of the above-described embodiment example, and can be subjected to the same amorphous carbon coating treatment as that of the above-described embodiment example.
  • the initial capacity and the initial efficiency are not necessarily improved.
  • the Li path increases, and the graphene layer has As a result of the shorter path leading to the back, the charge rate characteristics of the lithium secondary battery can be advantageously improved.
  • the low crystalline carbon material described above can be applied to the negative electrode active material of a lithium ion secondary battery, and the lithium ion secondary battery having improved charge rate characteristics by using this low crystalline carbon material as the negative electrode active material. Can be provided.
  • a negative electrode for a lithium ion secondary battery can be prepared, for example, by forming a negative electrode active material layer including a negative electrode active material made of this low crystalline carbon material and a binder on a negative electrode current collector.
  • This negative electrode active material layer can be formed by a general slurry coating method.
  • a negative electrode can be obtained by preparing a slurry containing a negative electrode active material, a binder, and a solvent, applying the slurry onto a negative electrode current collector, drying, and pressing as necessary.
  • Examples of the method for applying the negative electrode slurry include a doctor blade method, a die coater method, and a dip coating method.
  • a negative electrode can be obtained by forming a thin film of aluminum, nickel, or an alloy thereof as a current collector by a method such as vapor deposition or sputtering.
  • the binder for the negative electrode is not particularly limited, but polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene.
  • NMP N-methyl-2-pyrrolidone
  • water carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, and polyvinyl alcohol can be used as a thickener.
  • the content of the binder for the negative electrode is preferably in the range of 0.1 to 30 parts by mass with respect to 100 parts by mass of the negative electrode active material, from the viewpoints of binding force and energy density that are in a trade-off relationship.
  • the range of 0.5 to 25 parts by mass is more preferable, and the range of 1 to 20 parts by mass is more preferable.
  • the negative electrode current collector is not particularly limited, but copper, nickel, stainless steel, molybdenum, tungsten, tantalum and an alloy containing two or more of these are preferable from the viewpoint of electrochemical stability.
  • Examples of the shape include foil, flat plate, and mesh.
  • the lithium ion secondary battery by embodiment of this invention contains the said negative electrode, a positive electrode, and electrolyte.
  • a positive electrode for example, a slurry containing a positive electrode active material, a binder, and a solvent (and a conductive auxiliary material if necessary) is prepared, applied to the positive electrode current collector, dried, and pressurized as necessary.
  • a positive electrode active material layer can be formed on the positive electrode current collector.
  • lithium complex oxide lithium iron phosphate, etc.
  • the lithium composite oxide include lithium manganate (LiMn 2 O 4 ); lithium cobaltate (LiCoO 2 ); lithium nickelate (LiNiO 2 ); and at least part of the manganese, cobalt, and nickel portions of these lithium compounds.
  • lithium composite oxides may be used individually by 1 type, and 2 or more types may be mixed and used for them.
  • the average particle diameter of the positive electrode active material for example, a positive electrode active material having an average particle diameter in the range of 0.1 to 50 ⁇ m can be used from the viewpoint of reactivity with the electrolytic solution, rate characteristics, and the like.
  • a positive electrode active material having a particle diameter in the range of 1 to 30 ⁇ m, more preferably an average particle diameter in the range of 5 to 25 ⁇ m can be used.
  • the average particle diameter means the particle diameter (median diameter: D 50 ) at an integrated value of 50% in the particle size distribution (volume basis) by the laser diffraction scattering method.
  • the binder for the positive electrode is not particularly limited, but the same binder as that for the negative electrode can be used. Among these, polyvinylidene fluoride is preferable from the viewpoint of versatility and low cost.
  • the content of the binder for the positive electrode is preferably in the range of 1 to 25 parts by mass with respect to 100 parts by mass of the positive electrode active material from the viewpoint of the binding force and energy density which are in a trade-off relationship. The range of 2 to 10 parts by mass is more preferable.
  • binders other than polyvinylidene fluoride (PVdF) vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer rubber, polytetrafluoroethylene, polypropylene, Examples include polyethylene, polyimide, and polyamideimide.
  • NMP N-methyl-2-pyrrolidone
  • the positive electrode current collector is not particularly limited, but from the viewpoint of electrochemical stability, for example, aluminum, titanium, tantalum, stainless steel (SUS), other valve metals, or alloys thereof are used. Can be used. Examples of the shape include foil, flat plate, and mesh. In particular, an aluminum foil can be suitably used.
  • a conductive auxiliary material may be added for the purpose of reducing the impedance.
  • the conductive auxiliary material include carbonaceous fine particles such as graphite, carbon black, and acetylene black.
  • a nonaqueous electrolytic solution in which a lithium salt is dissolved in one or two or more nonaqueous solvents can be used.
  • cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC); Dimethyl carbonate (DMC), Chain carbonates such as diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and dipropyl carbonate (DPC); aliphatic carboxylic acid esters such as methyl formate, methyl acetate and ethyl propionate; ⁇ -lactones such as ⁇ -butyrolactone Chain ethers such as 1,2-ethoxyethane (DEE) and ethoxymethoxyethane (EME); and cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofur
  • non-aqueous solvents include dimethyl sulfoxide, 1,3-dioxolane, dioxolane derivatives, void muamide, acetamide, dimethyl void muamide, acetonitrile, propionitrile, nitromethane, ethyl monoglyme, phosphate triester, trimethoxymethane , Sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethyl ether, 1,3-propane sultone, anisole, N-methylpyrrolidone An aprotic organic solvent such as can also be used.
  • lithium salt dissolved in the nonaqueous solvent is not particularly limited, for example LiPF 6, LiAsF 6, LiAlCl 4 , LiClO 4, LiBF 4, LiSbF 6, LiCF 3 SO 3, LiCF 3 CO 2, Li (CF 3 SO 2 ) 2 , LiN (CF 3 SO 2 ) 2 , and lithium bisoxalatoborate are included.
  • These lithium salts can be used individually by 1 type or in combination of 2 or more types.
  • a polymer electrolyte may be used instead of the non-aqueous electrolyte solution.
  • a separator can be provided between the positive electrode and the negative electrode.
  • a porous film, a woven fabric, or a nonwoven fabric made of a polyolefin such as polypropylene or polyethylene, a fluororesin such as polyvinylidene fluoride, polyimide, or the like can be used.
  • Battery shapes include cylindrical, square, coin type, button type, and laminate type.
  • a laminate type it is preferable to use a laminate film as an exterior body that accommodates a positive electrode, a separator, a negative electrode, and an electrolyte.
  • the laminate film includes a resin base material, a metal foil layer, and a heat seal layer (sealant).
  • the resin base material include polyester and nylon
  • examples of the metal foil layer include aluminum, an aluminum alloy, and a titanium foil.
  • the material for the heat welding layer include thermoplastic polymer materials such as polyethylene, polypropylene, and polyethylene terephthalate.
  • the resin base material layer and the metal foil layer are not limited to one layer, and may be two or more layers. From the viewpoint of versatility and cost, an aluminum laminate film is preferable.
  • the positive electrode, the negative electrode, and the separator disposed between them are accommodated in an outer container made of a laminate film or the like, and an electrolyte is injected and sealed.
  • a structure in which an electrode group in which a plurality of electrode pairs are stacked can be accommodated.
  • Example 1 Pitch coke having an average particle size of 10 ⁇ m was heat-treated in air at 480 ° C. for 1 hour to obtain a carbon material having pores.
  • the SEM image of pitch coke before heat treatment is shown in FIG. 1 (a is 2000 times, b is 10,000 times), and the SEM image after heat treatment is shown in FIG. It can be seen that pores having a diameter of 20 nm to 1 ⁇ m are formed in the pitch coke after the heat treatment.
  • the XRD pattern of the carbon material before and after heat treatment is shown in FIG. In FIG. 3, the air-oxidized pitch coke is shown with the baseline raised.
  • Table 1 shows the average mesh size. As shown in Table 1, it can be seen that the surface spacing, the average number of layers, and the weight fraction are hardly changed by the heat treatment, but the average mesh size is increased. This is probably because very small graphene disappeared by heat treatment and the average mesh size increased.
  • Example 2 A carbon material having pores was obtained in the same manner as in Example 1 except that the heat treatment temperature was 600 ° C.
  • Example 2 A heat treatment was performed in the same manner as in Example 1 except that the atmosphere in Example 1 was changed to nitrogen and the heat treatment temperature was set to 800 ° C.
  • the potential of the working electrode with respect to the counter electrode was charged to 0 V (Li was inserted into the working electrode), and discharged to 1.5 V (Li was desorbed from the working electrode).
  • the current value at the time of charging / discharging was set to 1C as a current value for flowing the discharge capacity of the working electrode in one hour.
  • the first cycle charge / discharge is 0.1C constant current charge-0.025C constant current charge-0.1C discharge
  • the second cycle charge / discharge is 0.1C constant current charge-0.1C discharge.
  • the fourth cycle was 10 C constant current charge-0.1 C discharge.
  • initial discharge capacity discharge capacity at the first cycle
  • initial efficiency discharge capacity at the first cycle / charge capacity at the first cycle
  • 1C / 0.1C charge rate characteristics discharge capacity at the third cycle
  • Discharge capacity at 2nd cycle Discharge capacity at 2nd cycle
  • 10C / 0.1C charge rate characteristics discharge capacity at 4th cycle / discharge capacity at 2nd cycle
  • Comparative Example 3 Flakes of pitch coke (average maximum diameter of 15 ⁇ m) were used as the carbon material of Comparative Example 3.
  • a battery was prepared in the same manner as above except that the coating amount of the negative electrode was 100 g / m 2, and the initial discharge capacity, initial efficiency, and charge rate characteristics (1C / 0.1C, 4C / 0.1C, 6C / 0.1C 10C / 0.1C). The results are shown in Table 3.
  • flaky pitch coke also becomes a carbon material excellent in initial discharge capacity, initial efficiency, and charge rate characteristics by heat treatment in an oxidizing atmosphere.
  • Comparative Example 4 Flaked calcined pitch coke was used as the carbon material of Comparative Example 4. This pitch coke is obtained by heat-treating raw coal at 1000 to 1500 ° C. in a nitrogen atmosphere, and this carbon material has relatively higher crystallinity than ordinary pitch coke (corresponding to Comparative Examples 1 and 3). .
  • Comparative Example 5 The carbon material of Comparative Example 4 was heat-treated at 600 ° C. for 1.5 hours in an atmosphere of 100% N 2 to obtain the carbon material of Comparative Example 5.
  • a battery was prepared in the same manner as above except that the coating amount of the negative electrode was 50 g / m 2, and the initial discharge capacity and the initial efficiency were measured.
  • the results are shown in Table 4.
  • Each carbon material was measured by Raman spectroscopic analysis, and the intensity ratio (I D / I G ) of the D peak reflecting irregularity with respect to the G peak reflecting the graphite structure was obtained.
  • the interplanar interplanar spacing d 002 of each carbon material and the mass fraction Ps of the graphene laminated structure were determined from the XRD pattern. The results are summarized in Table 4.
  • FIG. 5 shows charge / discharge curves of batteries using the carbon materials of Example 4 and Comparative Example 4.
  • Example 4 From the results of Comparative Example 4 and Example 4, it can be seen that the air oxidation of high-capacity soft carbon reduces the initial capacity and initial efficiency, but greatly improves the rate characteristics. This is because the carbon material of Comparative Example 4 had a surplus capacity derived from pitch coke nanocavities, but it was considered that such nanocavities burned due to air oxidation and the capacity was reduced. Although the heat treatment itself shows an increase in the overall crystallinity as a decrease in the I D / IG ratio (Example 4 and Comparative Example 5), Example 4 in which the nanocavities are reduced by the oxidation treatment is a graphene stack. It also leads to an increase in the mass fraction of the structure.
  • Comparative Example 5 where heat treatment was similarly performed in a nitrogen atmosphere, the capacity was further reduced, which was due to an increase in the interplanar spacing d002 . In the air oxidation, the surface distance d002 does not increase. Further, as shown in FIG. 4, the rate characteristics of the comparative example 4 and the comparative example 5 are almost the same, and the rate characteristics are not improved even by simple heat treatment. Thus, the low crystalline carbon material can be made into a negative electrode active material having excellent rate characteristics by heat treatment in an oxidizing atmosphere.

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Abstract

　Selon l'invention, afin de fournir un matériau carboné d'électrode négative qui permet d'obtenir une batterie rechargeable au lithium présentant de meilleures caractéristiques de taux de charge, on utilise un matériau carboné faiblement cristallin sur la surface duquel sont formés des pores, en particulier, un matériau carboné d'électrode négative pour une batterie rechargeable au lithium comprenant du coke de brai, les pores présentant une ouverture comprise entre 20 nm et 1 µm. Les pores peuvent être formés par traitement thermique du coke de brai dans une atmosphère oxydante.
PCT/JP2015/058706 2014-03-26 2015-03-23 Matériau carboné d'électrode négative pour batterie rechargeable au lithium, électrode négative pour batterie au lithium, et batterie rechargeable au lithium Ceased WO2015146899A1 (fr)

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KR20200089448A (ko) * 2019-01-17 2020-07-27 주식회사 엘지화학 이차전지용 음극 활물질, 이를 포함하는 음극 및 이의 제조방법
EP3761410A4 (fr) * 2018-04-06 2021-04-21 Lg Chem, Ltd. Matériau actif de cathode, procédé de préparation de matériau actif de cathode, cathode comprenant un matériau actif de cathode, et batterie secondaire comprenant une cathode
US11349125B2 (en) 2016-10-06 2022-05-31 Nec Corporation Spacer included electrodes structure and its application for high energy density and fast chargeable lithium ion batteries
US11682766B2 (en) 2017-01-27 2023-06-20 Nec Corporation Silicone ball containing electrode and lithium ion battery including the same
EP4318673A4 (fr) * 2021-03-30 2025-08-27 Ningde Amperex Technology Ltd Matériau d'électrode négative et appareil électrochimique le contenant, et dispositif électronique

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US11349125B2 (en) 2016-10-06 2022-05-31 Nec Corporation Spacer included electrodes structure and its application for high energy density and fast chargeable lithium ion batteries
US11682766B2 (en) 2017-01-27 2023-06-20 Nec Corporation Silicone ball containing electrode and lithium ion battery including the same
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EP4318673A4 (fr) * 2021-03-30 2025-08-27 Ningde Amperex Technology Ltd Matériau d'électrode négative et appareil électrochimique le contenant, et dispositif électronique

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