WO2008001535A1 - électrode négative pour une batterie secondaire à électrolyte non aqueux - Google Patents

électrode négative pour une batterie secondaire à électrolyte non aqueux Download PDF

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Publication number
WO2008001535A1
WO2008001535A1 PCT/JP2007/058082 JP2007058082W WO2008001535A1 WO 2008001535 A1 WO2008001535 A1 WO 2008001535A1 JP 2007058082 W JP2007058082 W JP 2007058082W WO 2008001535 A1 WO2008001535 A1 WO 2008001535A1
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Prior art keywords
particles
active material
negative electrode
material layer
metal material
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PCT/JP2007/058082
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English (en)
Japanese (ja)
Inventor
Hitohiko Ide
Takeo Taguchi
Shinji Ishii
Kiyotaka Yasuda
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Mitsui Mining & Smelting Co., Ltd.
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Application filed by Mitsui Mining & Smelting Co., Ltd. filed Critical Mitsui Mining & Smelting Co., Ltd.
Publication of WO2008001535A1 publication Critical patent/WO2008001535A1/fr

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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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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 for a non-aqueous electrolyte secondary battery such as a lithium secondary battery.
  • the present applicant has previously described an active material comprising a pair of current collecting surface layers whose surfaces are in contact with an electrolytic solution, and particles of an active material having a high ability to form a lithium compound, interposed between the surface layers.
  • a negative electrode for a non-aqueous electrolyte secondary battery provided with a layer has been proposed (see Patent Document 1).
  • the active material layer of the negative electrode is infiltrated with a metal material having a low lithium compound forming ability, and active material particles are present in the infiltrated metal material. Since the active material layer has such a structure, the negative electrode is less likely to fall off even if it becomes fine due to expansion and contraction of the particles due to charge / discharge. As a result, the use of this negative electrode has the advantage of increasing the battery's lifetime.
  • Patent Document 1 US2006-115735A1
  • an object of the present invention is to provide a negative electrode for a non-aqueous electrolyte secondary battery whose performance is further improved as compared with the above-described conventional negative electrode.
  • the present invention includes an active material layer containing particles of an active material, and at least a part of the surface of the particles has a low ability to form a potassium compound, is coated with a metal material !, and Negative electrode for non-aqueous electrolyte secondary battery in which voids are formed between the particles coated with a metal material Because
  • the present invention provides a negative electrode for a non-aqueous electrolyte secondary battery characterized by being less than the amount.
  • the present invention provides a suitable method for producing the negative electrode for a non-aqueous electrolyte secondary battery
  • the multi-layer coating film thus formed has a low lithium compound forming ability! Then, it is immersed in a plating bath containing a metal material to perform electroplating, and at least a part of the surface of each particle is coated with the metal material, and the particles coated with the metal material are coated with each other.
  • the present invention provides a method for producing a negative electrode for a non-aqueous electrolyte secondary battery in which voids are formed therebetween.
  • the present invention provides, as another preferred method for producing the negative electrode for a non-aqueous electrolyte secondary battery, forming a first coating film using a first slurry containing active material particles,
  • the multi-layer coating film thus formed has a low lithium compound forming ability! Then, it is immersed in a plating bath containing a metal material to perform electrolytic plating, so that at least a part of the surface of the particle is coated with the metal material, and a gap is formed between the particles coated with the metal material.
  • a plating bath containing a metal material to perform electrolytic plating so that at least a part of the surface of the particle is coated with the metal material, and a gap is formed between the particles coated with the metal material.
  • FIG. 1 is a schematic diagram showing a cross-sectional structure of a first embodiment of a negative electrode for a non-aqueous electrolyte secondary battery according to the present invention.
  • FIG. 2 (a) and FIG. 2 (e) are process diagrams showing a method for producing the negative electrode shown in FIG.
  • FIG. 3 is a schematic view showing a cross-sectional structure of a second embodiment of the negative electrode for a non-aqueous electrolyte secondary battery of the present invention.
  • FIG. 1 shows a schematic diagram of a cross-sectional structure of an embodiment of a negative electrode for a non-aqueous electrolyte secondary battery of the present invention.
  • the negative electrode 10 of the present embodiment includes a current collector 11 and an active material layer 12 formed on at least one surface thereof. Note that FIG. 1 shows a state where the active material layer 12 is formed only on one surface of the current collector 11 for the sake of convenience! Although the active material layer is formed on both surfaces of the current collector, the active material layer 12 is formed on both surfaces of the current collector. It may be.
  • the active material layer 12 includes active material particles 12a.
  • the active material layer 12 is formed, for example, by applying a slurry containing active material particles 12a.
  • the active material include silicon materials, tin materials, aluminum materials, and germanium materials.
  • the soot-based material for example, an alloy containing tin, conoretate, carbon, and at least one of nickel and chromium is preferably used. In order to improve the capacity density per weight of the negative electrode, a silicon-based material is particularly preferable.
  • the silicon-based material a material that can occlude lithium and contains silicon, for example, silicon alone, an alloy of silicon and a metal element, silicon oxide, or the like can be used. These materials can be used alone or in combination.
  • the metal element include one or more elements selected from the group force consisting of Cu, Ni, Co, Cr, Fe, Ti, Pt, W, Mo, and Au. Of these metal elements, Cu, Ni, and Co are preferred. In particular, Cu and Ni are desirable because of their excellent electronic conductivity and low ability to form lithium compounds.
  • lithium may be occluded in the active material having silicon-based material strength.
  • a particularly preferable silicon-based material is silicon or silicon oxide having a high point of occlusion of lithium.
  • the active material layer 12 at least a part of the surface of the particle 12a is covered with a metal material having a low lithium compound forming ability.
  • the metal material 13 is a material different from the constituent material of the particles 12a. Voids are formed between the particles 12a coated with the metal material. That is, the metal material covers the surface of the particle 12a in a state in which a gap is secured so that the non-aqueous electrolyte containing lithium ions can reach the particle 12a.
  • metal materials 13 is conveniently represented as a thick line surrounding the periphery of the particle 12a. “Lithium compound formation ability is low” means that lithium does not form an intermetallic compound or solid solution, or even if lithium is formed, the amount of lithium is very small or very unstable.
  • the metal material 13 is preferably present over the entire thickness direction of the active material layer 12. It is preferable that the active material particles 12 a exist in the matrix of the metal material 13. As a result, even if the particles 12a expand and contract due to charging / discharging, the particles 12a are less likely to fall off. In addition, since the overall electronic conductivity of the active material layer 12 is ensured through the metal material 13, the electrically isolated active material particles 12a are generated, particularly in the deep part of the active material layer 12. Generation of the active material particles 12a is effectively prevented. This is particularly advantageous when a material that is a semiconductor and has poor electron conductivity, such as a silicon-based material, is used as the active material. The presence of the metal material 13 on the surface of the active material particles 12a over the entire thickness direction of the active material layer 12 can be confirmed by electron microscope mapping using the material 13 as a measurement target.
  • the metal material 13 covers the surfaces of the particles 12a continuously or discontinuously.
  • the metal material 13 continuously covers the surfaces of the particles 12a, it is preferable to form fine voids in the coating of the metal material 13 so that a nonaqueous electrolytic solution can flow.
  • the metal material 13 discontinuously covers the surface of the particle 12a, the non-aqueous electrolyte is supplied to the particle 12a through a portion of the surface of the particle 12a that is not covered with the metal material 13. .
  • the metal material 13 may be deposited on the surfaces of the particles 12a by, for example, electrolytic plating according to the conditions described later.
  • a gap is formed between the particles 12 a coated with the metal material 13.
  • This space serves as a distribution path for the non-aqueous electrolyte containing lithium ions.
  • the non-aqueous electrolyte easily reaches the active material particles 12a due to the presence of the voids, so that the overcharge voltage in the initial charge can be lowered.
  • generation of lithium dendrites on the surface of the negative electrode is prevented.
  • the generation of dendrite causes a short circuit between the two poles.
  • the ability to reduce the overvoltage is also advantageous in terms of preventing decomposition of the non-aqueous electrolyte. This is because the irreversible capacity increases when the non-aqueous electrolyte is decomposed. Furthermore, the ability to reduce overvoltage is positive. It is also advantageous from the point that the pole becomes damaged.
  • the voids formed between the particles 12a also serve as a space for relieving the stress caused by the volume change of the active material particles 12a due to charge and discharge.
  • the increase in the volume of the active material particles 12a whose volume has been increased by charging is absorbed by the voids. As a result, it is difficult for the fine particles of the particles 12a to be generated, and significant deformation of the negative electrode 10 is effectively prevented.
  • the amount of active material in the active material layer 12 is inclined in the thickness direction of the active material layer 12. Specifically, when the active material layer 12 is virtually divided into two in the thickness direction, the quantity of the particles 12a on the side closer to the negative electrode surface of the two divided active material layers It is less than the amount of particles 12a on the far side.
  • the amount here is a force that means weight. There is no essential difference even if this is replaced by volume.
  • the active material layer closer to the negative electrode surface is referred to as “surface-side active material layer”, and the active material layer farther from the negative electrode surface is referred to as “current collector-side active material layer”.
  • the particle size D value of the particles 12a in the surface-side active material layer 12S From the particle size D value of the particles 12a in the current collector-side active material layer 12C
  • the amount of the particles 12a in the surface side active material layer 12S is smaller than the amount of the particles 12a in the current collector side active material layer 12C.
  • the particle diameter of the particles 12a may be continuously changed in the thickness direction of the active material layer 12, or may be changed stepwise. Specifically, the particle size of the particles 12a may increase continuously from the surface side of the active material layer 12 toward the current collector side, or may increase stepwise.
  • the amount of the particles 12a in the surface-side active material layer 12S depends on the degree of filling. May exceed the amount of particles 12a in 12C. Therefore, attention should be paid to the degree of filling of the particles 12a in the surface side active material layer 12S.
  • the amount of the particles 12a in the surface side active material layer 12S is smaller than the amount of the particles 12a in the current collector side active material layer 12C.
  • the electrode is placed on the surface of the active material layer 12 and in the vicinity thereof. Even if the reaction occurs unevenly, the active material layer 12 does not collapse because the amount of the particles 12a is small. As a result, even if the active material repeatedly expands and contracts due to charge and discharge, it is possible to effectively prevent the active material from dropping off significantly on the surface of the active material layer and in the vicinity thereof. Thereby, the cycle characteristics can be improved.
  • the amount of particles 12a in the surface-side active material layer 12S is preferably 20 to 95%, particularly 40 to 90%, of the amount of particles 12a in the current collector-side active material layer 12C.
  • the force depending on the type of particle 12a is preferably 0.7 to 0.8 g / cm 3 .
  • the amount of the particles 12a in the collector-side active material layer 12C which is preferably 0.7 to 0.8 g / cm 3 , is 0.8 to 1.2 gZcm 3 , particularly 0.9 to 1.2 gZcm 3 . It is preferable that The amount of the particles 12a in each of the surface side active material layer 12S and the current collector side active material layer 12C can be determined, for example, by the following method.
  • the amount of the active material particles 12a in the entire active material layer 12 is measured using an ICP emission analyzer.
  • the surface-side active material layer 12S and the current-collector side active material layer 12C of the active material particles 12a Find the distribution ratio of quantities. From the measured active material layer 12 of the total amount of active material particles 12a and the distribution ratio of the amount of active material particles 12a in each layer, the surface active material layer 12S and the current collector side active material layer 1 2C respectively Find the amount of particles 12a.
  • the particle size of the particles 12a contained in the active material layer 12 is such that the particle size of the particles 12a in the surface side active material layer 12S is smaller than the particle size of the particles 12a in the current collector side active material layer 12C.
  • the D value is 0.1 to 8 ⁇ m, particularly 1 to 5 ⁇ m in any layer.
  • the particle 12a has a maximum particle size of 30 m or less, particularly preferably 10 m or less.
  • the particle size is measured by laser diffraction scattering particle size distribution measurement and electron microscope observation (SEM observation).
  • the metal material 13 is distributed substantially uniformly over the thickness direction of the active material layer 12.
  • the amount of particles 12a in the surface-side active material layer 12S is smaller than the amount of particles 12a in the current-collector-side active material layer 12C.
  • Particles in layer 12S 12aZ metal material 13 weight ratio Is smaller than the weight ratio of the particles 12aZ metal material 13 in the current collector active material layer 12C.
  • the weight ratio of the particles 12aZ metal material 13 in the surface-side active material layer 12S is 20 to 90%, particularly 50 to 85% of the weight ratio of the particles 12aZ metal material 13 in the current collector-side active material layer 12C. It is preferable that This weight ratio can be measured using an energy dispersive X-ray analyzer (EDX) for the longitudinal section of the active material layer 12.
  • EDX energy dispersive X-ray analyzer
  • the average thickness of the metal material 13 covering the surface of the active material particles 12a is preferably 0.05 to 2 / ⁇ ⁇ , more preferably 0.1 to 0.25 / zm. / !, thin! /. That is, the metal material 13 covers the surface of the active material particles 12a with a minimum thickness. This prevents the dropout due to the particles 12a from expanding and contracting due to charge and discharge to be pulverized while increasing the energy density.
  • the “average thickness” is a value calculated based on a portion of the surface of the active material particle 12 a that is actually covered with the metal material 13. Accordingly, the portion of the surface of the active material particles 12a not covered with the metal material 13 is not used as the basis for calculating the average value.
  • the active material layer 12 preferably has a predetermined plating bath applied to the coating film obtained by applying a slurry containing particles 12a and a binder onto a current collector and drying the slurry. It is formed by carrying out the electrolytic plating used and depositing the metal material 13 on the surface of the particles 12a.
  • the plating solution is sufficiently permeated into the coating film.
  • the conditions for depositing the metal material 13 by electrolytic plating using the plating solution are appropriate.
  • the plating conditions include the composition of the mating bath, the pH of the plating bath, and the current density of the electrolysis.
  • the pH of the plating bath it is preferable to adjust it to 7.1 to L 1.
  • the metal material 13 for plating it is preferable to use a copper pyrophosphate bath.
  • nickel for example, an alkaline nickel bath is preferably used.
  • the active material layer 12 is thickened.
  • the voids can be easily formed over the entire thickness direction of the layer.
  • the metal material 13 is deposited on the surface of the active material particles 12a and the metal material 13 is less likely to be deposited between the particles 12a, the voids between the particles 12a are successfully formed. This is also preferable.
  • the bath composition, electrolysis conditions and pH are preferably as follows.
  • the metal material covering the active material particles 12a tends to be thick, and it may be difficult to form desired voids between the particles 12a.
  • a P ratio exceeding 12 is used, the current efficiency is deteriorated and gas generation is likely to occur, so that production stability may be lowered.
  • a copper pyrophosphate bath having a P ratio of 6.5 to 10.5 is used as a more preferable copper pyrophosphate bath, the size and number of voids formed between the active material particles 12a and This is very advantageous for the flow of the water electrolyte.
  • the bath composition, electrolysis conditions and pH are preferably as follows.
  • the void ratio in the active material layer 12 formed by the various methods described above is preferably about 15 to 45% by volume, and more preferably about 20 to 40% by volume.
  • the porosity is measured by the following steps (1) to (7)
  • the weight per unit area of the coating film formed by applying the slurry is measured, and the weight of the particles 12a and the weight of the binder are calculated from the blending ratio of the slurry.
  • the thickness of the active material layer 12 is obtained by SEM observation of the cross section of the negative electrode
  • the volume of the active material layer 12 per unit area is calculated from the thickness of the active material layer 12.
  • the respective volumes are calculated from the weight of the particles 12a, the weight of the binder, the weight of the plating metal species, and the respective mixing ratios.
  • the void volume is calculated by subtracting the volume of the particles 12a, the volume of the binder, and the volume of the metal species from the volume of the active material layer 12 per unit area.
  • the thickness of the active material layer 12 is preferably 10 to 40 / ⁇ ⁇ , more preferably 15 to 30 ⁇ m, and still more preferably 18 to 25 ⁇ m.
  • the metal material 13 is deposited in the active material layer 12 and has a low ability to form a lithium compound, and the metal material 13 has conductivity. Examples thereof include copper, nickel, iron, cobalt, and these metals. An alloy etc. are mentioned.
  • the metal material 13 is preferably a material having high ductility because the surface coating of the particles 12a is not easily broken even when the active material particles 12a expand and contract. It is preferable to use copper as such a material.
  • a thin surface layer (not shown) may be formed on the surface of the active material layer 12. Further, the negative electrode 10 may not have such a surface layer.
  • the thickness of the surface layer is as thin as 0.25 ⁇ m or less, preferably 0.1 ⁇ m or less.
  • the lower limit of the thickness of the surface layer 14 is not limited.
  • the negative electrode 10 is thin and has the surface layer 14 or the surface layer 14.
  • a secondary battery is assembled using the negative electrode 10, and the battery is initially charged.
  • the overvoltage when performing can be lowered.
  • the reduction of lithium leads to the generation of dendrites that cause a short circuit between the two electrodes.
  • the surface layer covers the surface of the active material layer 12 continuously or discontinuously.
  • the surface layer has a large number of fine voids (not shown) that are open to the surface and communicate with the active material layer 12. It is preferable to have. It is preferable that the fine voids exist in the surface layer so as to extend in the thickness direction of the surface layer. The fine voids allow the non-aqueous electrolyte to flow. The role of the fine voids is to supply a non-aqueous electrolyte into the active material layer 12.
  • the fine voids are the ratio of the area covered with the metal material 13, that is, the coverage is 95% or less, particularly 80% or less, particularly 60% or less. Such a size is preferable.
  • the surface layer is composed of a metal compound having a low lithium compound forming ability.
  • This metal material may be the same as or different from the metal material 13 present in the active material layer 12.
  • the surface layer may have a structure of two or more layers having two or more different metal material forces. Considering the ease of production of the negative electrode 10, the metal material 13 present in the active material layer 12 and the metal material constituting the surface layer 14 are preferably the same type.
  • the current collector 11 in the negative electrode 10 may be the same as that conventionally used as the current collector of the negative electrode for a non-aqueous electrolyte secondary battery. It is preferable that the current collector 11 is composed of a metal material having a low lithium compound forming ability as described above. Examples of such metal materials are as already described.
  • the current collector it is preferably made of copper, nickel, stainless steel or the like. Also, it is possible to use a copper alloy foil represented by Corson alloy foil. Further, as the current collector, a metal foil having a normal tensile strength (JIS C 2318) of preferably 500 MPa or more, for example, a copper film layer formed on at least one surface of the aforementioned Corson alloy foil can be used. Furthermore, it is also preferable to use a current collector having a normal elongation CFIS C 2318) of 4% or more. This is because, when the tensile strength is low, stress is generated due to the stress when the active material expands, and when the elongation is low, the current collector may crack.
  • JIS C 2318 normal tensile strength
  • the thickness of the current collector 11 is not critical in this embodiment. Considering the balance between maintaining the strength of the negative electrode 10 and improving the energy density, it is preferably 9 to 35 / ⁇ ⁇ . In addition, when using a copper foil as the current collector 11, it is preferable to perform a chromate treatment or an antifungal treatment using an organic compound such as a triazole compound and an imidazole compound.
  • a two-layer coating film is formed on the current collector 11 using two different types of slurry containing active material particles and a binder, and then the electrolytic plating is applied to the coating film. Done.
  • a current collector 11 is prepared as shown in FIG. Then, a first slurry containing active material particles 12a is applied onto the current collector 11 to form a first coating film 15a.
  • the slurry contains a binder and a diluting solvent in addition to the active material particles.
  • the slurry may also contain a small amount of conductive carbon material particles such as acetylene black and graphite.
  • the active material particles 12a have a silicon-based material strength, it is preferable that the conductive carbon material is contained in an amount of 1 to 3% by weight with respect to the weight of the active material particles 12a.
  • the content of the conductive carbon material is less than 1% by weight, the viscosity of the slurry is lowered and the sedimentation of the active material particles 12a is promoted, so that it is difficult to form a good coating film 15 and uniform voids. Become. If the conductive carbon material content exceeds 3% by weight, the conductive carbon material Plating nuclei concentrate on the surface, making it difficult to form a good coating.
  • binder styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyethylene (PE), ethylene propylene monomer (EPDM), or the like is used.
  • a diluting solvent N-methylpyrrolidone, cyclohexane or the like is used.
  • the amount of the active material particles 12a in the slurry is preferably about 30 to 70% by weight.
  • the amount of the binder is preferably about 0.4 to 4% by weight.
  • a dilute solvent is added to these to form a slurry.
  • the first coating film 15a After the first coating film 15a is formed, it may be dried if necessary. However, from the viewpoint of maintaining the adhesion between the first coating film 15a and the second coating film 15b described later, it is preferable that the first coating film 15a is not completely dried.
  • a second slurry is applied on the first coating film 15a to form a second coating film 15b.
  • the components contained in the second slurry are the same as those in the first slurry. Accordingly, the active material particles contained in the second slurry are the same type as the active material particles contained in the first slurry. However, the particles contained in the second slurry are smaller in size than the particles of the active material contained in the first slurry. In this way, the multi-layered coating film 15 composed of the first coating film 15a and the second coating film 15b is formed.
  • the formed coating film 15 has a large number of minute spaces between the particles 12a.
  • the current collector 11 on which the coating film 15 is formed is immersed in a plating bath containing a metal material having a low ability to form a lithium compound. By dipping in the plating bath, the plating solution enters the minute space in the coating film 15 and reaches the interface between the coating film 15 and the current collector 11. Under this condition, electrolytic plating is performed to deposit metal species on the surface of the particles 12a (hereinafter, this plating is also referred to as penetration plating). The penetration is performed by using the current collector 11 as a force sword, immersing the counter electrode as the anode in the plating bath, and connecting both electrodes to the power source.
  • the deposition of the metal material by the penetration adhesion proceeds by applying one side force of the coating film 15 to the other side. Specifically, as shown in FIGS. 2 (c) to (e), the interfacial force between the coating film 15 and the current collector 11 is electrolyzed so that the deposition of the metal material 13 proceeds toward the coating film surface. Make a mess.
  • the surface of the active material particles 12a can be successfully coated with the metal material 13, and the metal material 13 is coated with the metal material 13.
  • Voids can be successfully formed between the particles 12a.
  • the porosity of the voids can be easily set within the preferred range described above.
  • the conditions of penetration for depositing the metal material 13 include the composition of the plating bath, the pH of the plating bath, and the current density of electrolysis. Such conditions are as described above.
  • the penetration staking is terminated when the metal material 13 is deposited in the entire thickness direction of the coating film 15.
  • a surface layer (not shown) can be formed on the upper surface of the active material layer 12. In this way, the desired negative electrode is obtained as shown in FIG. 2 (e).
  • the negative electrode 10 thus obtained is suitably used as a negative electrode for a non-aqueous electrolyte secondary battery such as a lithium secondary battery.
  • the positive electrode of the battery is prepared by suspending a positive electrode active material and, if necessary, a conductive agent and a binder in an appropriate solvent to produce a positive electrode mixture, applying this to a current collector, drying it, and then rolling it. It is obtained by pressing, cutting and punching.
  • the positive electrode active material conventionally known positive electrode active materials such as lithium-containing metal composite oxides such as lithium nickel composite oxide, lithium manganese composite oxide, and lithium cobalt composite oxide are used.
  • a positive electrode active material at least LiCoO
  • Lithium transition metal composite oxide containing both Zr and Mg and a mixture of lithium transition metal composite oxide having a layered structure and containing at least both Mn and Ni are also preferably used. Can do.
  • the use of a positive active material can be expected to increase the end-of-charge voltage without deteriorating charge / discharge cycle characteristics and thermal stability.
  • the average value of the primary particle size of the positive electrode active material is 5 ⁇ m or more and 10 ⁇ m or less, and the weight average molecular weight of the binder used for the positive electrode is preferably 350, in view of the balance between packing density and reaction area.
  • the polyvinylidene fluoride is preferably 2,000,000 or less. This is because it can be expected to improve the discharge characteristics in a low temperature environment.
  • a synthetic resin nonwoven fabric a polyolefin such as polyethylene or polypropylene, a porous film of polytetrafluoroethylene, or the like is preferably used.
  • a porous polyolefin film manufactured by Asahi Kasei Chemicals; N9420G
  • a separator in which a polyolefin film is formed on one or both sides of the polyolefin microporous membrane.
  • the separator preferably has a puncture strength of 0.2N 7 111 to 0.49 NZwm and a tensile strength in the winding axis direction of 40 MPa to 150 MPa. Even when a negative electrode active material that expands and contracts greatly with charge and discharge is used, damage to the separator can be suppressed, and the occurrence of internal short circuit can be suppressed.
  • the non-aqueous electrolyte is a solution obtained by dissolving a lithium salt as a supporting electrolyte in an organic solvent.
  • Lithium salts include LiCIO, LiAlCl, LiPF, LiAsF, LiSbF, LiBF, LiSCN,
  • Examples include LiCl, LiBr, Lil, LiCF SO, LiC F SO and the like.
  • Examples of organic solvents include
  • Examples include ethylene carbonate, jetino carbonate, dimethylol carbonate, propylene carbonate, butylene carbonate, and the like. Especially for the whole non-aqueous electrolyte
  • a high dielectric constant solvent with a relative dielectric constant of 30 or more such as cyclic carbonic acid ester derivatives having a halogen atom such as 1,3 dioxolan-2-one or 4-trifluoromethyl-1,3-dioxolan-2-one. It is also preferable. This is because it is difficult to be decomposed due to its high resistance to reduction.
  • the above-mentioned high dielectric constant solvent, dimethyl carbonate, jetyl carbon Also preferred is an electrolyte mixed with a low-viscosity solvent having a viscosity of 1 mPa ⁇ s or less, such as a sodium salt or methylethyl carbonate.
  • the content of fluorine ions in the electrolytic solution is within the range of 14 mass ppm or more and 1290 mass ppm or less.
  • the electrolyte solution contains an appropriate amount of fluorine ions, a coating film such as lithium fluoride derived from the fluorine ions is formed on the negative electrode, which can suppress the decomposition reaction of the electrolyte solution in the negative electrode.
  • FIG. 3 the same members as those in FIGS. 1 and 2 are denoted by the same reference numerals.
  • the active material particles 12a included in the surface-side active material layer 12S and the active material particles 12a included in the current collector-side active material layer 12C there is no difference in the type and particle size. However, there is a difference between the number of active material particles 12a included in the surface-side active material layer 12S and the number of active material particles 12a included in the current collector-side active material layer 12C. There is. Specifically, the number of particles 12a included in the surface side active material layer 12S is smaller than the number of particles 12a included in the current collector side active material layer 12C.
  • the amount of particles 12a in the surface-side active material layer 12S is smaller than the amount of particles 12a in the current collector-side active material layer 12C.
  • the number of particles 12a may be continuously changed over the thickness direction of the active material layer 12, or may be changed stepwise. Specifically, the number of particles 12a may increase continuously or stepwise from the surface side of the active material layer 12 toward the current collector side. Also with the negative electrode 10 having such a structure, the same effects as the negative electrode of the embodiment shown in FIG.
  • the particles 12a included in the surface-side active material layer 12S are drawn as if they were independent of each other and there was no contact between the particles. This is due to the two-dimensional observation. In reality, each particle is in contact with other particles directly or through a metal material 13.
  • the negative electrode 10 of the present embodiment can be manufactured by a method similar to that of the negative electrode shown in FIG.
  • a first slurry containing active material particles 12a is applied onto the current collector 11 to form a first coating film 15a.
  • a second slurry is applied on the first coating film 15a to form a second coating film 15b.
  • the viscosity of the second slurry can be increased by adding a thickener thereto.
  • the amount of thickener in the second slurry is preferably 0.01 to 1% by weight, particularly 0.05 to 0.5% by weight, depending on the type.
  • the concentration of the active material particles 12a in the second slurry can also be made lower than the concentration of the active material particles 12a in the first slurry as shown in FIG.
  • the negative electrode 10 in the form can be successfully manufactured
  • the present invention has been described based on the preferred embodiments thereof, the present invention is not limited to the above-described embodiments. It is not limited to the state.
  • a specific means for reducing the amount of the particles 12a in the surface-side active material layer 12S to be smaller than the amount of the particles 12a in the current collector-side active material layer 12C is limited to the embodiment shown in FIGS. I can't. Examples of other means include a combination of the embodiment shown in FIG. 1 and the embodiment shown in FIG.
  • the particle size of the particles 12a in the surface side active material layer 12S is made smaller than the particle size of the particles 12a in the current collector side active material layer 12C, and the number of particles 12a included in the surface side active material layer 12S is The number can be smaller than the number of particles 12a included in the current collector side active material layer 12C.
  • a current collector made of an electrolytic copper foil having a thickness of 18 m was acid-washed at room temperature for 30 seconds. After the treatment, it was washed with pure water for 15 seconds.
  • a first slurry containing Si particles was applied to the current collector to a thickness of 10 m to form a first coating film.
  • the average particle size D of Si particles was 2.8 m.
  • the average particle diameter D is a
  • the second slurry was applied to a thickness of 10 m to form a second coating film.
  • the composition of the second slurry was similar to the composition of the first slurry.
  • the average particle diameter D of the Si particles was 1.7 m. In this way, a coating film having a multilayer structure was formed.
  • the current collector on which the coating film was formed was immersed in a copper pyrophosphate bath having the following bath composition, and by electrolysis, copper penetrated into the coating film to form an active material layer. did.
  • the electrolysis conditions were as follows. DSE was used for the anode. A DC power source was used as the power source.
  • the average particle diameter D of the Si particles was 2.5 m.
  • the average particle size D of Si particles was the same as that of the Si particles in the first slurry.
  • Example 2 Using these two types of slurries, a first coating film was formed on the current collector by the same operation as in Example 1, and a second coating film was formed thereon. The thickness of the first coating film was 10 m, and the thickness of the second coating film was 10 m. Thereafter, the same operation as in Example 1 was performed to obtain a negative electrode having the structure shown in FIG.
  • the weight of Cu and the weight of Si per unit area of the entire active material layer were measured using an ICP emission spectrometer.
  • a longitudinal section of the active material layer was cut out, and the distribution ratio of Cu and Si in the surface side active material layer and the current collector side active material layer was measured by an energy dispersive X-ray analyzer (EDAX-made Pegasus system). From these measurement results, the weight of Cu and the weight of Si per unit area were determined for each of the surface side active material layer and the current collector side active material layer.
  • the results are shown in Table 1.
  • the measurement conditions using an energy dispersive X-ray analyzer are as follows. 'Acceleration voltage 5kV
  • lithium secondary batteries were manufactured using the negative electrodes obtained in the examples and comparative examples. LiCo Ni Mn O was used as the positive electrode. As electrolyte, ethylene carbonate and
  • the example has a high capacity retention rate at the 150th cycle and excellent cycle characteristics.
  • the capacity retention rate at the 100th cycle is high in the comparative example, but the capacity retention rate is low at the 150th cycle after further cycles. It's half way down.

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Abstract

La présente invention concerne une électrode négative (10) destinée à être utilisée dans une batterie secondaire à électrolyte non aqueux et qui comprend une couche de matière active (12) contenant une particule (12a) d'une matière active. Au moins une partie de la surface de la particule (12a) est recouverte d'un matériau métallique (13) ayant une faible capacité à former un composé lithium. Un vide est créé entre les particules (12a) qui sont recouvertes du matériau métallique (13). Lorsque la couche de matière active (12) est hypothétiquement divisée en deux parties égales dans le sens de l'épaisseur, la quantité de la particule (12a) dans une partie située plus près de la surface de l'électrode négative est plus petite que celle dans une partie située plus loin de la surface de l'électrode négative.
PCT/JP2007/058082 2006-06-30 2007-04-12 électrode négative pour une batterie secondaire à électrolyte non aqueux WO2008001535A1 (fr)

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JP2006-182803 2006-06-30
JP2007069876A JP2008034346A (ja) 2006-06-30 2007-03-19 非水電解液二次電池用負極
JP2007-069876 2007-03-19

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8034483B2 (en) 2007-03-29 2011-10-11 Tdk Corporation Anode and lithium-ion secondary battery

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Publication number Priority date Publication date Assignee Title
JPH11242954A (ja) * 1997-01-28 1999-09-07 Canon Inc 電極構造体、二次電池及びそれらの製造方法
JP2000012091A (ja) * 1998-06-23 2000-01-14 Fuji Photo Film Co Ltd 非水二次電池とその製造方法
JP2002231224A (ja) * 2001-01-30 2002-08-16 Sanyo Electric Co Ltd リチウム二次電池用電極及びその製造方法並びにリチウム二次電池
JP2004241329A (ja) * 2003-02-07 2004-08-26 Mitsui Mining & Smelting Co Ltd 非水電解液二次電池用負極
JP2004296412A (ja) * 2003-02-07 2004-10-21 Mitsui Mining & Smelting Co Ltd 非水電解液二次電池用負極活物質の製造方法
JP2005285581A (ja) * 2004-03-30 2005-10-13 Sanyo Electric Co Ltd リチウム二次電池用負極及びリチウム二次電池

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11242954A (ja) * 1997-01-28 1999-09-07 Canon Inc 電極構造体、二次電池及びそれらの製造方法
JP2000012091A (ja) * 1998-06-23 2000-01-14 Fuji Photo Film Co Ltd 非水二次電池とその製造方法
JP2002231224A (ja) * 2001-01-30 2002-08-16 Sanyo Electric Co Ltd リチウム二次電池用電極及びその製造方法並びにリチウム二次電池
JP2004241329A (ja) * 2003-02-07 2004-08-26 Mitsui Mining & Smelting Co Ltd 非水電解液二次電池用負極
JP2004296412A (ja) * 2003-02-07 2004-10-21 Mitsui Mining & Smelting Co Ltd 非水電解液二次電池用負極活物質の製造方法
JP2005285581A (ja) * 2004-03-30 2005-10-13 Sanyo Electric Co Ltd リチウム二次電池用負極及びリチウム二次電池

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8034483B2 (en) 2007-03-29 2011-10-11 Tdk Corporation Anode and lithium-ion secondary battery

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