JP5448555B2 - Negative electrode for lithium ion secondary battery, lithium ion secondary battery using the same, slurry for preparing negative electrode for lithium ion secondary battery, and method for producing negative electrode for lithium ion secondary battery - Google Patents

Negative electrode for lithium ion secondary battery, lithium ion secondary battery using the same, slurry for preparing negative electrode for lithium ion secondary battery, and method for producing negative electrode for lithium ion secondary battery Download PDF

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JP5448555B2
JP5448555B2 JP2009110614A JP2009110614A JP5448555B2 JP 5448555 B2 JP5448555 B2 JP 5448555B2 JP 2009110614 A JP2009110614 A JP 2009110614A JP 2009110614 A JP2009110614 A JP 2009110614A JP 5448555 B2 JP5448555 B2 JP 5448555B2
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negative electrode
active material
electrode active
lithium ion
ion secondary
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JP2010262754A (en
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健 西村
道宏 島田
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古河電気工業株式会社
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product
    • Y02P70/54Manufacturing of lithium-ion, lead-acid or alkaline secondary batteries

Description

  The present invention relates to a negative electrode for a lithium ion secondary battery, and more particularly to a negative electrode for a lithium ion secondary battery having a high capacity and a long life.

  Conventionally, lithium ion secondary batteries using graphite as a negative electrode active material have been put into practical use. Also, a negative electrode is formed by kneading a negative electrode active material, a conductive aid such as carbon black, and a resin binder to prepare a slurry, and applying and drying on a copper foil. Yes.

  On the other hand, with the aim of increasing the capacity, negative electrodes for lithium ion secondary batteries using metals, particularly silicon alloys, as negative electrode active materials have been developed. Silicon alloyed by occlusion of lithium ions expands in volume up to about 4 times that of silicon before occlusion, so a negative electrode using a silicon-based alloy as a negative electrode active material expands and contracts during a charge / discharge cycle. repeat.

  Therefore, a negative electrode for a non-aqueous electrolyte secondary battery that grows carbon nanofibers on the surface of a silicon-based active material, relaxes strain due to expansion and contraction of negative electrode active material particles by its elastic action, and improves cycle characteristics. It is disclosed (see, for example, Patent Document 1).

JP 2006-244984 A

  However, a conventional negative electrode that forms a negative electrode by applying and drying a slurry of a negative electrode active material, a conductive additive, and a binder, binds the negative electrode active material and the current collector with a resin binder. The bonding strength of the resin is weak. In addition, a powdered negative electrode active material is used. Therefore, during charge and discharge, the negative electrode active material is pulverized, the negative electrode active material is peeled off, the negative electrode is cracked, the conductivity between the negative electrode active materials is reduced, and the capacity is reduced. Therefore, there are problems that the cycle characteristics are poor and the life of the secondary battery is short.

  In addition, the invention described in Patent Document 1 binds the negative electrode active material and the current collector with a resin, and the cycle characteristics cannot be sufficiently prevented from being deteriorated. In addition, the productivity was poor due to the formation process of carbon nanofibers.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to obtain a negative electrode for a lithium ion secondary battery that realizes a high capacity and a long life and is excellent in productivity.

In order to achieve the above-described object, the first invention includes a metal current collector, and a negative electrode active material and a conductive additive bonded on the current collector with a binder. the negative active material is observed including a negative electrode active material of the wire-shaped, through the metal nanoparticles, the negative active material and the current collector or the negative electrode active material and the conductive aid is bonded by a metal bond The negative electrode active material includes at least one material selected from the group consisting of silicon, tin, antimony, aluminum, lead, and arsenic, or an alloy thereof, and the conductive additive includes carbon, copper, A negative electrode for a lithium ion secondary battery comprising at least one substance selected from the group consisting of tin, zinc, nickel, and silver, or an alloy thereof . The “binder” described in the first invention broadly means a substance that binds the negative electrode active material and the conductive additive on the current collector, and includes not only the resin binder 9 described later. The concept includes the metal nanoparticles 25 described later.
In the first invention, the average particle diameter of primary particles of the metal nanoparticles is preferably 2 to 100 nm. Moreover, it is preferable that the quantity of the metal of the said metal nanoparticle is 2 to 40 weight% with respect to the metal powder of the said conductive support agent.

  The wire-shaped negative electrode active material has a length of 0.1 μm to 2 mm, and the negative electrode active material preferably has an outer diameter of 4 nm to 1000 nm. The wire-shaped negative electrode active material is partially linear. Or it is preferable that one part is a crimped shape, and it is preferable that the said conductive support agent contains a wire-shaped conductive support agent, and also has sufficient space | gap which absorbs the volume expansion of a negative electrode active material.

  The binder is a metal nanoparticle, and the negative electrode active material and the current collector or the negative electrode active material and the conductive additive are bonded through a metal bond through the metal nanoparticle. It is preferable.

  Further, the metal nanoparticles are nanoparticles of at least one metal selected from the group consisting of copper, tin, zinc, nickel and silver, and the average particle size of primary particles is 2 nm to 100 nm, The bond is formed by sintering the metal nanoparticles, and has a void surrounded by part or all of the current collector, the negative electrode active material, the conductive additive, and the metal nanoparticles. preferable.

  A second invention is a lithium ion secondary battery using the negative electrode for the lithium ion secondary battery.

A third invention is an anode active material, a conductive additive, a slurry is a binder comprising a mixture, the negative electrode active material, see it contains a negative electrode active material of the wire shape, the binder Includes metal nanoparticles, and the negative electrode active material includes at least one substance selected from the group consisting of silicon, tin, antimony, aluminum, lead, and arsenic, or an alloy thereof, and the conductive additive includes carbon. A slurry for preparing a negative electrode for a lithium ion secondary battery , comprising at least one substance selected from the group consisting of copper, tin, zinc, nickel, and silver, or an alloy thereof .

According to a fourth aspect of the present invention, there is provided a kneading step of preparing a slurry by kneading a negative electrode active material, a conductive additive, and a binder, an application step of applying the slurry to a current collector, and the collector applied with the slurry. comprising the step of drying the collector and the negative electrode active material, see contains a negative electrode active material of the wire shape, the binder comprises a metal nanoparticle, the current collector is made of metal, The negative electrode active material includes at least one material selected from the group consisting of silicon, tin, antimony, aluminum, lead, and arsenic, or an alloy thereof, and the conductive additive includes carbon, copper, tin, zinc, A method for producing a negative electrode for a lithium ion secondary battery , comprising at least one substance selected from the group consisting of nickel and silver, or an alloy thereof .

Also, after pre-Symbol drying step, further comprising a sintering step of heating the current collector under an inert atmosphere of 1/2 or less of the temperature of the melting point (absolute temperature) of the bulk of the metal of the metal nanoparticles It is preferable.

  The feature of the present invention is that the negative electrode contains a negative electrode active material in a wire shape (= linear shape, linear shape), and a particulate negative electrode active material may or may not be blended. . In addition, the conductive assistant may be in the form of a wire, a particle, a chain of particles to form a structure, or a simple mixture thereof. It may be.

  According to the present invention, a negative electrode for a lithium ion secondary battery that achieves a high capacity and a long life and is excellent in productivity can be obtained.

(A)-(c) The figure which shows the negative electrode 1, the negative electrode 2, and the negative electrode 4 for lithium ion secondary batteries which concern on the 1st Embodiment of this invention. The figure which shows the granulated body 13 which concerns on the 1st Embodiment of this invention. The figure which shows the mixer 15 which concerns on the 1st Embodiment of this invention. The figure which shows the coater 21 which concerns on the 1st Embodiment of this invention. (A)-(c) The figure which shows the negative electrode 23, the negative electrode 29, and the negative electrode 31 which concern on the 2nd Embodiment of this invention. (A), (b) TEM photograph of silicon linear body manufactured by CVD method. (A), (b) The SEM photograph of the silicon | silicone linear body manufactured by CVD method. (A), (b) The other SEM photograph of the silicon | silicone linear body manufactured by CVD method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Each drawing schematically shows each component, and does not represent an actual scale.

  The negative electrode 1 according to this embodiment will be described. FIG. 1A shows the negative electrode 1. The negative electrode 1 has a conductive additive 7, a negative electrode active material 5, a binder 9, and voids 10 on a current collector 3. The binder 9 binds the current collector 3, the negative electrode active material 5, and the conductive additive 7.

  The current collector 3 is a foil made of at least one metal selected from the group consisting of copper, nickel, and stainless steel. Each may be used alone or may be an alloy of each. The thickness is preferably 4 μm to 35 μm, and more preferably 8 μm to 18 μm.

  The negative electrode active material 5 is a wire-shaped linear body of at least one material selected from the group consisting of silicon, tin, antimony, aluminum, lead, and arsenic. Each of these may be used alone, or an alloy or oxide of each may be used. Specifically, silicon monoxide, titanium silicide, phosphorus-doped silicon, tin iron alloy, tin cobalt alloy, antimony tin alloy, tin silver alloy, indium antimony alloy, or the like can be used. In addition, the linear body is also called a nanowire, a nanorod, a nanowhisker, a nanotube (hollow), a nanofiber, a nanobelt or the like if the outer diameter is 100 nm or less.

  The thickness of the negative electrode active material layer formed by the negative electrode active material 5, the conductive auxiliary agent 7, the binder 9, and the voids 10 is 5 to 60 μm, preferably 10 to 25 μm.

  Moreover, the length of the negative electrode active material 5 is preferably 0.1 μm to 2 mm. The outer diameter of the negative electrode active material 5 is preferably 4 nm to 1000 nm, more preferably 25 nm to 200 nm. If the length of the negative electrode active material 5 is 0.1 μm or more, the length is sufficient to increase the productivity of the negative electrode active material 5, and if the length of the negative electrode active material 5 is 2 mm or less, the slurry Is easy to apply. Moreover, when the outer diameter of the negative electrode active material 5 is thicker than 4 nm, the synthesis is easy, and when the outer diameter is thinner than 1000 nm, the negative electrode active material can be prevented from being pulverized. The measuring method of the outer diameter and length of the negative electrode active material was performed by image analysis using SEM.

  The negative electrode active material 5 may include a linear shape, a curved shape, or a crimped shape that is bent three-dimensionally. When the linear negative electrode active material 5 is produced, it may be obtained as a mixture of a linear shape, a curved shape, or a crimped shape, but it is not necessary to separate these shapes using a special method. These shapes may be used alone or as a mixture.

  As an example, a TEM photograph and an SEM photograph of a silicon linear body manufactured by a CVD method are shown. FIG. 6 shows a shape in which silicon that is linear or substantially linear is bent. The maximum outer diameter is about 1000 nm. FIG. 7 is a mixture of substantially straight silicon and curved silicon. The outer diameter is about 10 nm to 200 nm. In FIG. 8, the silicon is bent three-dimensionally and the shape of the silicon is single. The outer diameter is about 20 nm to 150 nm.

  The conductive assistant 7 is a powder made of at least one conductive material selected from the group consisting of carbon, copper, tin, zinc, nickel, and silver. A single powder of carbon, copper, tin, zinc, nickel, or silver may be used, or a powder of each alloy may be used. For example, general carbon black such as furnace black and acetylene black can be used.

  The binder 9 is a resin binder, and a fluororesin such as polyvinylidene fluoride (PVdF) and styrene butadiene rubber (SBR) or a rubber-based organic material can be used.

  The negative electrode 1 is not in a state where the negative electrode active material 5 and the conductive auxiliary agent 7 are densely packed with the binder 9 and the slurry is applied to the current collector 3 and dried. The void 10 is a space surrounded by part or all of the current collector 3, the negative electrode active material 5, and the conductive additive 7, and occupies about 10% to 80% with respect to the volume of the negative electrode 1. The role of the gap 10 is to allow the electrolytic solution to permeate and allow lithium ions to pass through, and to absorb the volume change of the negative electrode active material 5 that accompanies charging / discharging and from the current collector 3 of the negative electrode active material 5 and the conductive additive 7 This is to prevent peeling and occurrence of cracks in the negative electrode 1 in advance.

  Moreover, as shown in FIG.1 (b), not only the wire-shaped negative electrode active material 5 but the particulate negative electrode active material 6 may be included. The negative electrode active material 6 is formed of the same material as the material listed as the negative electrode active material 5, and is a powder or nanoparticle negative electrode active material. The average particle size of the primary particles is about 10 nm to 2 μm. As the negative electrode active material 6, the same material as the negative electrode active material 5 may be used, or a different material may be used. Furthermore, the negative electrode active material 6 may use graphite. The primary particles are particles that are the smallest unit of particles and are not further divided, and are particles that are not aggregated.

  Regarding the average particle diameter of the negative electrode active material 6, the conductive auxiliary agent 7, the metal nanoparticles 25 and the conductive auxiliary agent 27, which will be described later, the fine particles are usually present in an aggregated state. Point to. For particle measurement, image information of an electron microscope (SEM) and a volume-based median diameter of a dynamic light scattering photometer (DLS) are used in combination.

  The average particle diameter of the negative electrode active material 6 and the metal nanoparticles 25 described later is obtained by confirming the particle shape in advance using an SEM image, obtaining the particle diameter by image analysis (for example, A image manufactured by Asahi Kasei Engineering), And measured by DLS (for example, DLS-8000 manufactured by Otsuka Electronics Co., Ltd.). If the fine particles are sufficiently dispersed and not agglomerated, almost the same measurement results can be obtained with SEM and DLS.

  The average particle size of the conductive auxiliary agent 7 and the conductive auxiliary agent 27 described later also refers to the average particle size of the primary particles. Even when the structure shape is highly developed such as acetylene black, the average particle diameter can be defined by the primary particle diameter here, and the average particle diameter can be obtained by image analysis of the SEM photograph.

  Moreover, as shown in FIG.1 (c), you may use both the particulate-form conductive support agent 7 and the wire-shaped conductive support agent 8. FIG. The conductive assistant 8 is a wire made of a conductive substance, and the conductive substances listed in the conductive assistant 7 can be used. As the conductive additive 8, a linear body having an outer diameter of 300 nm or less, such as carbon fiber, carbon nanotube, copper nanowire, or nickel nanowire, can be used. By using the wire-shaped conductive auxiliary agent 8, the electrical connection with the negative electrode active materials 5, 6 and the current collector 3 can be easily maintained and the current collecting performance is improved, and the negative electrode 1 in the porous film shape is fibrous. A substance increases and it becomes difficult to produce a crack in the negative electrode 1. The conductive auxiliary agent 8 may use the same conductive material as the conductive auxiliary agent 7 or a different substance. For example, it is conceivable to use copper powder as the particulate conductive aid 7 and use vapor grown carbon fiber (VGCF) as the wire-shaped conductive aid 8. In addition, you may use only the wire-shaped conductive support agent 8 without adding the particulate-form conductive support agent 7. FIG.

  The length of the conductive auxiliary agent 8 is preferably 0.1 μm to 2 mm. The outer diameter of the conductive auxiliary agent 8 is preferably 4 nm to 1000 nm, more preferably 25 nm to 200 nm. If the length of the conductive additive 8 is 0.1 μm or more, the length is sufficient to increase the productivity of the conductive additive 8, and if the length is 2 mm or less, the slurry can be easily applied. is there. Moreover, when the outer diameter of the conductive auxiliary agent 8 is thicker than 4 nm, the synthesis is easy, and when the outer diameter is thinner than 1000 nm, the kneading of the slurry is easy. The measuring method of the outer diameter and length of the conductive material 8 was performed by image analysis using SEM.

  In addition, as shown in FIG. 2, the surface of the particles of the negative electrode active material 5 may be covered with a conductive material 11. Furthermore, as shown in FIG. 2, the negative electrode active material 5 coated with the conductive material 11 and the conductive additive 7 may be granulated, and the negative electrode active material 5 may be used as the granulated body 13. In addition, the negative electrode active material which comprises the granulated body 13 may be a mixture of the wire-shaped negative electrode active material 5 and the particulate negative electrode active material 6, and the conductive auxiliary agent which comprises the granulated body 13 is a particle It may be a mixture of the conductive aid 7 having a shape and the conductive aid 8 having a wire shape. The diameter of the granulated body 13 is preferably 0.2 μm to 10 μm.

  Examples of the conductive material 11 include carbon, copper, tin, zinc, nickel, silver, and alloys thereof.

  Coating of the negative electrode active material 5 with the conductive material 11 can be performed using a CVD method, a liquid phase method, a firing method, or a dry method. Moreover, it can also coat | cover by the mechanical alloying method using a ball mill etc. According to these methods, the conductive material 11 can be coated on at least a part of the surface of the particles of the negative electrode active material 5.

  The granulated body 13 can be produced by using dry and wet general granulation methods. For example, in the dry process, the mechanical alloying method in which compression and shearing force is applied, or the powders are rapidly moved together in an air current. There is a hybridization method for collision. Furthermore, in the wet process, an electroless plating method or a spray drying method can be used alone or in combination. For example, the negative electrode active material 5 is dry-coated with a carbon-based conductive material 11 to form a composite, and the conductive material 11 and the binder 9 are dispersed in water so that the suspension has a predetermined size. There is a method of granulation by spray drying. In addition, there is a method in which after the negative electrode active material 5 is dispersed in a copper sulfate solution, copper is deposited on the surface of the negative electrode active material 5 using a reducing agent such as sodium borohydride to form a conductive material coating. is there. In addition, there is a method in which the negative electrode active material is dispersed in an aqueous polyvinyl alcohol solution (PVA aqueous solution), and then PVA is fired in an inert atmosphere and coated with carbon.

  Examples of the carbon coating method include the following methods. The negative electrode active material and a 10% aqueous polyvinyl alcohol solution are kneaded and then fired at 700 ° C. for 3 hours in an inert atmosphere (vacuum, nitrogen atmosphere, argon atmosphere, etc.). Carbon in the polyvinyl alcohol is carbonized, oxygen and hydrogen are vaporized as water, and the negative electrode active material is coated with carbon to improve conductivity.

  Next, the manufacturing method of the negative electrode 1 is demonstrated. As shown in FIG. 3, a slurry raw material 19 is put into a mixer 15 and kneaded to form a slurry 17. The slurry raw material 19 is the negative electrode active material 5, the conductive additive 7, the binder 9, a thickener, a solvent, and the like.

  In the solid content in the slurry 17, the negative electrode active material 5 includes 25 to 90 wt%, the conductive auxiliary agent 7 includes 5 to 70 wt%, and the binder 9 includes 1 to 10 wt%. For example, the negative electrode active material 5 is 60% by weight, the conductive additive 7 is 33% by weight, the binder 9 is 2% by weight, and the thickener is 5% by weight.

  As the mixer 15, a general kneader used for preparing a slurry can be used, and an apparatus capable of preparing a slurry called a kneader, a stirrer, a disperser, a mixer, or the like may be used. Moreover, as a thickener, it is suitable to use polysaccharides, such as carboxymethylcellulose and methylcellulose, as a 1 type, or 2 or more types of mixture. Moreover, water can be used as a solvent.

  Next, as shown in FIG. 4, slurry 17 is applied to one surface of current collector 3 using coater 21. The coater 21 can use a general coating apparatus that can apply slurry to a current collector, and is, for example, a coater using a roll coater or a doctor blade.

  Then, in order to dry at about 70 degreeC and adjust thickness, the negative electrode 1 is obtained through a roll press. Further, the gap 10 can be controlled by the size and blending ratio of the negative electrode active materials 5 and 6 and the conductive assistants 7 and 8 which are the main components of the slurry raw material 19, and when the thickness is adjusted by a roll press. A desired size and amount can be set by adjusting the rolling reduction and the thickness of the slurry 17.

  Next, a method for producing a lithium ion secondary battery using the negative electrode 1 of the present invention will be described.

  First, a positive electrode active material, a conductive additive, a binder, and a solvent are mixed to prepare a positive electrode active material composition. The composition of the positive electrode active material is directly applied on a metal current collector such as an aluminum foil and dried to prepare a positive electrode. It is also possible to manufacture a positive electrode by casting the composition of the positive electrode active material on a separate support, and then laminating the film obtained by peeling from the support on a metal current collector.

As the positive electrode active material, any lithium-containing metal oxide that is generally used can be used. For example, LiCoO 2 , LiMn x O 2x , LiNi 1-x Mn x O 2x (X = 1, 2), Ni 1-xy Co x Mn y O 2 (0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5), etc., more specifically, LiMn 2 O 4, it is a LiMnO 2, LiNiO 2, LiFeO 2 , LiFePO 4, Li 2 FePO 4 F, V 2 O 5, TiS and MoS 2 and compounds capable redox lithium.

  Carbon black is used as a conductive additive, and vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVdF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE) and the like are used as a binder. A mixture and a styrene butadiene rubber-based polymer are used, and N-methylpyrrolidone (NMP), acetone, water and the like are used as a solvent. At this time, the contents of the positive electrode active material, the conductive additive, the binder, and the solvent are at levels that are normally used in lithium ion secondary batteries.

  Any separator can be used as long as it has a function of insulating electronic conduction between the positive electrode and the negative electrode and is usually used in a lithium ion secondary battery. In particular, it is preferable that the thickness is as low as about 20 microns from the viewpoint of the high capacity of the battery because of its low resistance to ion migration of the electrolyte. A typical separator is a three-layer laminate film of polypropylene (PP) / polyethylene (PE) / polypropylene (PP) microporous film, and PP and PE are thermoplastic resins of about 170 ° C. and about 130 ° C., respectively. The degree of polymerization and the like are designed so that the melting point becomes. When the temperature inside the battery exceeds 130 ° C., the PE film melts, the micropores are clogged and lithium ions cannot permeate, and the battery reaction can be stopped.

Examples of the electrolyte include propylene carbonate, ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, butylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyloxolane, N , N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate , dipropyl carbonate, LiPF 6 dibutyl carbonate, in a solvent or a mixed solvent thereof and the like diethylene glycol or dimethyl ether, LiBF 4, L SbF 6, LiAsF 6, LiClO 4 , LiCF 3 SO 3, Li (CF 3 SO 2) 2 N, LiC 4 F 9 SO 3, LiAlO 4, LiAlCl 4, LiN (C x F 2x + 1 SO 2) (C y F 2y + 1 SO 2) (however, x, y are natural numbers), LiCl, can be used by dissolving a mixture of one or thereof two or more of the electrolyte comprising a lithium salt such as LiI.

  A separator is disposed between the positive electrode and the negative electrode as described above to form a battery structure. When such a battery structure is wound or folded and placed in a cylindrical battery case or a rectangular battery case, an electrolyte is injected to complete a lithium ion secondary battery.

  Further, after the battery structure is laminated in a bicell structure, it is impregnated with an organic electrolyte, and the resultant product is put in a pouch and sealed to complete a lithium ion polymer battery.

  The volume of the negative electrode active material 5 changes due to insertion / extraction of lithium. However, since the negative electrode active material 5 has a wire shape having a submicron or nano level outer diameter, even if the negative electrode active material 5 undergoes a volume change. Further, pulverization of the negative electrode active material 5 does not occur. For example, when silicon absorbs lithium, the volume expands up to 4 times, but even if the wire diameter of silicon increases, the curvature of the curved portion changes, or the length of the wire changes, the void 10 In this space, the negative electrode is prevented from being broken (the active material is peeled off or dropped from the current collector). Regarding the life characteristics, it is particularly important not to cause cracks in the negative electrode.

  According to the first embodiment, since a silicon-based alloy is used as the negative electrode active material, the capacity can be increased as compared with a conventional negative electrode using a carbon-based material as the negative electrode active material.

  Further, according to the first embodiment, since the wire-shaped negative electrode active material is used, even if the volume change of the negative electrode active material is large, the negative electrode active material is absorbed into the gap with the thickness and length of the one-dimensional negative electrode active material. The As a result, problems such as pulverization of the negative electrode active material, generation of cracks in the negative electrode film, peeling and dropping of the negative electrode active material and the current collector, and decrease in conductivity between the negative electrode active materials are suppressed, and the life of the negative electrode is suppressed. Becomes longer.

  In addition, according to the first embodiment, since the negative electrode for a lithium ion secondary battery is manufactured by the manufacturing method of applying and drying the slurry, a vacuum system is not necessary, and the negative electrode can be manufactured continuously, thereby improving productivity. Excellent.

Next, a second embodiment will be described.
FIG. 5 is a diagram illustrating the negative electrode 23, the negative electrode 29, and the negative electrode 31 according to the second embodiment. In the following embodiment, the same number is attached | subjected to the element which fulfill | performs the same aspect as the negative electrode 1 concerning 1st Embodiment, and the duplicate description is avoided.

  As shown in FIG. 5A, the negative electrode 23 according to the second embodiment is different from the negative electrode 1 according to the first embodiment in that metal nanoparticles 25 are used instead of the binder 9.

  The metal nanoparticles 25 are nanoparticles of at least one metal selected from the group consisting of copper, tin, zinc, nickel, and silver, and the average particle size of the primary particles is preferably 2 nm to 100 nm. By sintering in an inert atmosphere, the metal nanoparticles 25 form a metal bond in the vicinity of the contact point between the current collector 3, the negative electrode active material 5, and the conductive additive 7, and the negative electrode active material 5 and the conductive additive 7. Are joined to the current collector 3. In addition, strong voids 28 are formed in the negative electrode due to the sintering of the metal nanoparticles 25, and it plays a role of suppressing the penetration of the electrolytic solution and the volume change of the negative electrode active material, and suppressing the generation of cracks in the negative electrode.

  The metal nanoparticles 25 can be manufactured more easily if the average particle size of the primary particles is 2 nm or more, and can be sintered at a lower temperature if the average particle size of the primary particles is 100 nm or less. is there.

  Since the metal nanoparticles 25 have a very large surface area compared to the weight, the ratio of atoms present on the surface is increased and the melting point is lowered. For example, although the melting point of gold is 1337K, there is a report that the melting point of gold nanoparticles having a diameter of 5 nm is about 1100K, which is about 200K lower. Therefore, by using the metal nanoparticles 25, the surface of the metal nanoparticles 25 becomes active and can be sintered even at a temperature of 1/2 or less of the melting point of the metal of the bulk body. 3. The negative electrode active material 5 or the conductive additive 7 is bonded by a metal bond.

  Further, as shown in FIG. 5B, a conductive auxiliary agent 27 may be used instead of the conductive auxiliary agent 7. The conductive auxiliary agent 27 is a powder made of at least one metal selected from the group consisting of copper, tin, zinc, nickel, and silver. A single powder of copper, tin, zinc, nickel, or silver may be used, or a powder of each alloy may be used. The average particle diameter of the conductive auxiliary agent 27 is preferably 1 μm to 10 μm. If the average particle size of the primary particles of the conductive additive 7 is 1 μm or more, the negative electrode 29 having a strong and larger void 28 that does not crack in the negative electrode 29 even when the negative electrode active material 5 expands is more sure. Can be formed. When the average particle diameter of the conductive auxiliary agent 27 is 10 μm or less, the slurry is kneaded more uniformly, and an electrode having a uniform thickness is obtained.

  Further, as shown in FIG. 5C, a carbon material 33 may be further added to the conductive auxiliary agent 27, and the negative electrode 31 has a gap 28. The amount of the carbon material 33 to be added is preferably 10 to 70% by weight of the total of the negative electrode active material 5, the conductive additive 27 and the metal nanoparticles 25. As the carbon material 33 to be added, general carbon black such as furnace black, acetylene black and carbon fiber can be used.

  The conductive additive 27 and the negative electrode active material 5 are connected by metal bonds through the metal nanoparticles 25, and a porous structure film having many voids 28 is formed on the current collector 3. Moreover, the metal bond formed by the sintered 25 is higher in strength than the organic material of the binder 9, and the negative electrode 23, the negative electrode 29, and the negative electrode 31 are less prone to cracking and have excellent cycle characteristics.

  The amount of metal of the metal nanoparticles 25 is preferably 2 to 40% by weight with respect to the metal powder of the conductive additive 27 before sintering. Within the above range, a suitable porous structure having a sufficient gap 28 can be formed. The void 28 can be adjusted by the particle size, wire diameter, and composition ratio of the raw material blended in the slurry, and is also suitable for adjusting the thickness by passing the negative electrode after applying and drying the slurry through a roll press. A porous structure can be formed.

  The negative electrode 23, the negative electrode 29, and the negative electrode 31 are the same except that the metal nanoparticles 25 are used instead of the binder 9, and the conductive assistant 27 and the carbon material 33 are used instead of the conductive assistant 7 as necessary. 1 in the same process. In addition to the powder, the metal nanoparticles 25 may be blended in the slurry 17 in a suspension state for the purpose of preventing oxidation and kneaded by the mixer 15. In the suspension containing the metal nanoparticles 25, an antioxidant or a reducing agent may be added to a solvent such as water or alcohol.

  Moreover, in the manufacturing method of the negative electrode 23, the negative electrode 29, and the negative electrode 31, after application | coating and drying of a slurry, it has a sintering process under inert atmosphere (vacuum, nitrogen, argon, etc.). The sintering temperature is preferably not more than half the melting point (absolute temperature) of the metal used for the metal nanoparticles 25 in the bulk. If copper nanoparticles are used for the metal nanoparticles 25, the melting point of copper in the bulk is 1357K, so the sintering temperature is 678K (= 405 ° C.). Further, the sintering temperature is preferably 350 ° C. or lower, and more preferably 200 ° C. to 300 ° C. practically.

  If only the conductive auxiliary agent 27 is sintered without adding the metal nanoparticles 25, it is not sintered unless the temperature is raised. On the other hand, when only the metal nanoparticles 25 are sintered without adding the conductive additive 27, a dense film with few voids can be obtained.

  In the second embodiment, a particulate negative electrode active material 6 may be added in addition to the wire shaped negative electrode active material 5, or a wire shaped conductive aid may be used instead of the particulate conductive aid 7. The agent 8 may be used, or a mixture of the particulate conductive additive 7 and the wire-shaped conductive additive 8 may be used.

  According to the second embodiment, in addition to the effects obtained in the first embodiment, the current collector 3 and the conductive auxiliary agent 7 and the conductive auxiliary agent 27 are bonded by metal bonds via the metal nanoparticles 25. Since the negative electrode 23, the negative electrode 29, and the negative electrode 31 form a porous structure having a large number of voids 28, even when the volume change of the negative electrode active material is large, strain accompanying the volume change is absorbed, and the negative electrode film cracks. Does not enter and the peeling between the negative electrode active material and the current collector is suppressed, and the life of the negative electrode is further long.

  In addition, according to the second embodiment, the current collector 3, the conductive assistant 7, the conductive assistant 27, and the negative electrode active material 5 are connected by metal bonds through the metal nanoparticles, so that the internal resistance of the electrode film And the charge / discharge characteristics at a high rate are improved.

  As mentioned above, although preferred embodiment of the negative electrode for lithium ion secondary batteries concerning this invention was described referring an accompanying drawing, this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

1, 2 ......... Negative electrode 3 ......... Current collector 4 ......... Negative electrode 5 ......... Wire-shaped negative electrode active material 6 ......... Particulate negative electrode active material 7 ......... Particulate conductive auxiliary agent 8 ……… Wire-shaped conductive aid 9 ……… Binder 10 ……… Void 11 ……… Conductive material 13 ……… Granulated material 15 ……… Mixer 17 ……… Slurry 19 ……… Slurry Raw material 21 ......... Coater 23 ......... Negative electrode 25 ......... Metal nanoparticles 27 ......... Metal conductive aid 28 ......... Void 29 ......... Negative electrode 31 ......... Negative electrode 33 ......... Carbon material

Claims (12)

  1. A metal current collector,
    On the current collector, a negative electrode active material bonded with a binder and a conductive additive,
    The negative electrode active material, see contains a negative electrode active material of the wire shape,
    Via the metal nanoparticles, the negative electrode active material and the current collector or the negative electrode active material and the conductive additive are bonded by a metal bond,
    The negative electrode active material includes at least one substance selected from the group consisting of silicon, tin, antimony, aluminum, lead and arsenic or an alloy thereof;
    The negative electrode for a lithium ion secondary battery, wherein the conductive auxiliary agent includes at least one substance selected from the group consisting of carbon, copper, tin, zinc, nickel, and silver, or an alloy thereof .
  2. 2. The negative electrode for a lithium ion secondary battery according to claim 1, wherein an average particle diameter of primary particles of the metal nanoparticles is 2 to 100 nm.
  3. 2. The negative electrode for a lithium ion secondary battery according to claim 1, wherein the amount of the metal of the metal nanoparticles is 2 to 40% by weight based on the metal powder of the conductive additive.
  4.   The length of the wire-shaped negative electrode active material is 0.1 μm to 2 mm, and the outer diameter of the negative electrode active material is 4 nm to 1000 nm. The lithium ion secondary battery according to claim 1, Negative electrode.
  5.   The negative electrode for a lithium ion secondary battery according to claim 1, wherein at least a part of the wire-shaped negative electrode active material has a crimped shape.
  6.   The negative electrode for a lithium ion secondary battery according to claim 1, wherein at least a part of the wire-shaped negative electrode active material is linear.
  7.   The negative electrode for a lithium ion secondary battery according to claim 1, wherein the conductive additive includes a wire-shaped conductive additive.
  8. The metal nanoparticles are nanoparticles of at least one metal selected from the group consisting of copper, tin, zinc, nickel and silver, and the average particle size of primary particles is 2 nm to 100 nm,
    The metal bond is formed by sintering the metal nanoparticles;
    2. The lithium ion secondary battery according to claim 1 , wherein the current collector, the negative electrode active material, the conductive additive, and the metal nanoparticles have a void surrounded by part or all of the current collector, the negative electrode active material, the conductive auxiliary agent, and the metal nanoparticles. Negative electrode.
  9.   The lithium ion secondary battery using the negative electrode for lithium ion secondary batteries of any one of Claims 1-8.
  10. A slurry in which a negative electrode active material, a conductive additive, and a binder are mixed,
    The negative electrode active material, see contains a negative electrode active material of the wire shape,
    The binder comprises metal nanoparticles;
    The negative electrode active material includes at least one substance selected from the group consisting of silicon, tin, antimony, aluminum, lead and arsenic or an alloy thereof;
    For producing a negative electrode for a lithium ion secondary battery, wherein the conductive additive contains at least one substance selected from the group consisting of carbon, copper, tin, zinc, nickel, and silver, or an alloy thereof . Slurry.
  11. A kneading step of kneading a negative electrode active material, a conductive additive and a binder to prepare a slurry;
    An application step of applying the slurry to a current collector;
    A drying step of drying the current collector coated with the slurry;
    Comprising
    The negative electrode active material, see contains a negative electrode active material of the wire shape,
    The binder comprises metal nanoparticles;
    The current collector is made of metal;
    The negative electrode active material includes at least one substance selected from the group consisting of silicon, tin, antimony, aluminum, lead, and arsenic, or an alloy thereof.
    Production of a negative electrode for a lithium ion secondary battery, wherein the conductive additive contains at least one substance selected from the group consisting of carbon, copper, tin, zinc, nickel, and silver, or an alloy thereof. Method.
  12. After pre-Symbol drying step, and characterized by further comprising a sintering step of heating the negative electrode in an inert atmosphere of 1/2 or less of the temperature of the melting point (absolute temperature) of the bulk of the metal of the metal nanoparticles The manufacturing method of the negative electrode for lithium ion secondary batteries of Claim 11.
JP2009110614A 2009-04-30 2009-04-30 Negative electrode for lithium ion secondary battery, lithium ion secondary battery using the same, slurry for preparing negative electrode for lithium ion secondary battery, and method for producing negative electrode for lithium ion secondary battery Expired - Fee Related JP5448555B2 (en)

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US9780365B2 (en) 2010-03-03 2017-10-03 Amprius, Inc. High-capacity electrodes with active material coatings on multilayered nanostructured templates
US9172088B2 (en) 2010-05-24 2015-10-27 Amprius, Inc. Multidimensional electrochemically active structures for battery electrodes
US8450012B2 (en) 2009-05-27 2013-05-28 Amprius, Inc. Interconnected hollow nanostructures containing high capacity active materials for use in rechargeable batteries
US9373838B2 (en) * 2009-09-29 2016-06-21 Georgia Tech Research Corporation Electrodes, lithium-ion batteries, and methods of making and using same
EP2550698A4 (en) * 2010-03-22 2015-04-08 Amprius Inc Interconnecting electrochemically active material nanostructures
DE102010062006A1 (en) * 2010-11-26 2012-05-31 Robert Bosch Gmbh Nanofibers comprising anode material for a lithium-ion cell
KR101978726B1 (en) * 2011-06-03 2019-05-15 가부시키가이샤 한도오따이 에네루기 켄큐쇼 Power storage device and method of manufacturing the same
JP5525003B2 (en) * 2012-05-07 2014-06-18 古河電気工業株式会社 Anode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery using the same
WO2014021691A1 (en) * 2012-08-03 2014-02-06 (주)오렌지파워 Cathode material, cathode assembly, secondary battery, and method for manufacturing same
JP2016522552A (en) * 2013-07-31 2016-07-28 エルジー・ケム・リミテッド Negative electrode active material for secondary batteries with improved life characteristics
US20170309913A1 (en) * 2014-11-14 2017-10-26 Hitachi, Ltd. Negative Electrode Active Material for Lithium Ion Secondary Battery and Lithium Ion Secondary Battery

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JP4212263B2 (en) * 2000-09-01 2009-01-21 三洋電機株式会社 Negative electrode for lithium secondary battery and method for producing the same
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JP2008091135A (en) * 2006-09-29 2008-04-17 Nikko Kinzoku Kk Active material for lithium ion secondary battery negative electrode, and the battery negative electrode
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