WO2012128274A1 - Electrode for non-aqueous electrolyte secondary battery, and process for producing same - Google Patents

Electrode for non-aqueous electrolyte secondary battery, and process for producing same Download PDF

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Publication number
WO2012128274A1
WO2012128274A1 PCT/JP2012/057131 JP2012057131W WO2012128274A1 WO 2012128274 A1 WO2012128274 A1 WO 2012128274A1 JP 2012057131 W JP2012057131 W JP 2012057131W WO 2012128274 A1 WO2012128274 A1 WO 2012128274A1
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active material
electrolyte secondary
secondary battery
electrode
interval
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PCT/JP2012/057131
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French (fr)
Japanese (ja)
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正信 竹内
学 滝尻
喜田　佳典
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三洋電機株式会社
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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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/574—Devices or arrangements for the interruption of current
    • H01M50/581—Devices or arrangements for the interruption of current in response to temperature
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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 non-aqueous electrolyte secondary battery electrode that can improve safety and reliability without reducing the energy density of the non-aqueous electrolyte secondary battery electrode, and a method for manufacturing the same.
  • Nonaqueous electrolyte secondary batteries are widely used as power sources for portable devices as small, lightweight, and high energy density batteries.
  • Patent Document 1 shows that at least one of a positive electrode active material layer and a negative electrode active material layer is mixed with PTC powder whose electric resistance increases as the temperature rises. Yes.
  • the PTC powder is mixed with the active material layer, it is necessary to sufficiently add the carbon conductive agent to the active material layer so as not to cause deterioration in characteristics during normal operation.
  • it is necessary to mix a sufficient amount of PTC powder in order to obtain the electrical resistance increasing effect over the entire active material layer.
  • there is a problem in that the energy density of the electrode decreases because the amount of carbon conductive agent and PTC powder not involved in the battery capacity increases.
  • Patent Document 2 discloses disposing a conductive intermediate layer that changes to a high resistance during overcharging between a positive electrode current collector and an active material-containing layer.
  • the method disclosed herein requires a step of disposing a conductive intermediate layer and a step of providing an active material-containing layer thereon, and there is a problem that the manufacturing process becomes complicated.
  • Patent Document 3 shows that the adhesion between the active material layer and the aluminum foil is improved by using an aluminum foil whose surface on the positive electrode layer side is roughened. However, further improvements are necessary to improve the safety of the nonaqueous electrolyte secondary battery.
  • JP-A-2005-123185 JP 2000-164206 A Japanese Patent Laid-Open No. 9-22699
  • the present invention provides an electrode for a non-aqueous electrolyte secondary battery in which an active material layer is formed on a metal foil, and at least a part of the surface on which the active material layer is formed is roughened as the metal foil. And a PTC layer filled with a PTC powder and a binder having a property of increasing electric resistance with increasing temperature in at least a part of the concave portion of the metal foil having a roughened surface. In addition, an active material layer is formed on the PTC layer.
  • the metal foil having a roughened surface refers to a metal foil having irregularities formed on the surface of the metal foil by a method of roughening the surface of the metal foil.
  • Examples of the metal foil roughening method used in the present invention include a plating method, a vapor phase growth method, an etching method, and a polishing method.
  • Examples of the plating method include an electrolytic plating method and an electroless plating method.
  • Examples of the vapor phase growth method include a sputtering method, a CVD method, and a vapor deposition method.
  • Examples of the polishing method include sandpaper polishing and polishing by blasting.
  • FIG. 1 schematically shows a cross-sectional structure of an electrode according to the present invention.
  • the metal foil 3 having a roughened surface has irregularities formed on the surface.
  • a PTC layer 2 containing PTC powder 13 and a binder is formed in the recess, and the active material layer 1 is formed thereon.
  • the average value of the distance of the convex part tip which the surface is roughened and the metal foil 3 adjoins is a value close
  • the resistance of the PTC layer increases and the short circuit current is cut off as the temperature rises. Therefore, the safety of the battery can be improved.
  • the current from the active material is concentrated on the contact surface between the active material layer and the core. For this reason, a desired effect can be obtained with a smaller amount of added PTC powder by forming a PTC layer whose electrical resistance increases with increasing temperature between the active material layer and the core as in the present invention. . Therefore, safety and reliability can be improved without reducing the energy density of the electrode for the nonaqueous electrolyte secondary battery.
  • the method of measuring the particle size of the active material, the PTC powder, and the binder is preferably a laser diffraction method, and the method of measuring the particle size of the carbon conductive agent is preferably observation with an electron microscope.
  • the average roughening interval R sm on the surface of the metal foil can be obtained by a method defined as the average length R sm of the contour curve element in JIS B0601-2001.
  • the average roughening interval R sm obtained by the method defined as the average length of the contour curve element in JIS B0601-2001 on the surface of the metal foil is 0.05 ⁇ m or more and 3.0 ⁇ m or less.
  • the average roughening interval R sm is less than 0.05 ⁇ m, bubbles accumulate in the roughened concave portion of the metal foil surface, making it difficult for the PTC powder particles to enter.
  • Examples of the method for producing the non-aqueous electrolyte secondary battery electrode include the following methods.
  • an active material, a carbon conductive agent, a binder, and PTC powder are mixed in a solvent to prepare a slurry. This is applied onto the surface of the metal foil whose surface has been roughened and dried.
  • the particle sizes of 10%, 50%, and 90% accumulated from the fine particle side of the volume-based cumulative particle size distribution obtained by laser diffraction method or observation with an electron microscope are D 10 , D 50, and D 90 , respectively.
  • the particle diameter (D 50 ) of the PTC powder and the emulsion particles as the binder is an average roughness determined by the method defined as the average length of the contour curve element in JIS B0601-2001 on the surface of the metal foil.
  • the particle size of the conductive carbon material (D 10) and particle size of the active material (D 10) is it must be greater than the average roughened distance R sm metal foil surface.
  • the emulsion particles enter and the PTC layer 2 is self-formed.
  • PTC powder smaller than the average roughening interval R smm on the surface of the metal foil and the binder enter and the PTC layer 2 is self-formed.
  • the active material layer 1 and the PTC layer 2 are formed almost simultaneously by one application, and the manufacturing process of the electrode is simplified. Therefore, production cost reduction and productivity improvement can be expected.
  • a slurry containing PTC powder may be formed in advance, and after applying the slurry onto the surface of the metal foil whose surface has been roughened, an active material slurry containing an active material and a carbon conductive agent may be applied.
  • the carbon conductive agent may not be added.
  • the PTC layer 2 as described above may be provided on either or both of the positive and negative electrodes, but more preferably on the positive electrode side.
  • Lithium-containing transition metal oxides that are commonly used as positive electrode active materials for non-aqueous electrolyte secondary batteries have lower conductivity than graphite, which is commonly used as negative electrode active materials, and are conductive in the active material layer. Most of the properties depend on the carbon conducting agent. For this reason, the current path between the core and the active material layer is limited to the portion where the carbon conductive agent exists. For the reasons described above, it is considered that the effect of the PTC layer 2 can be further enhanced by using it for a positive electrode with low active material conductivity.
  • the PTC powder may contain a barium titanate added with an alkaline earth metal such as Sr, Pb or the like, or at least one selected from Cr, Ce, Mn, La, Y, Nb, and Nd. Good. Further, high density polyethylene or low density polyethylene and a mixture thereof can be used. Furthermore, the composition ratio of Ti and Ba of barium titanate can be adjusted as appropriate.
  • PTC powder using barium titanate as a main component is preferably used. This is because barium titanate has a large specific gravity, so that the PTC powder is easily filled in the concave portion of the metal foil whose surface is roughened. Moreover, since barium titanate has conductivity, there is an advantage that it is not necessary to mix a carbon conductive agent separately.
  • the particle diameter (D 50 ) is larger than the average roughening interval R sm on the surface of the metal foil. It is preferable to add a small carbon conductive agent to the PTC layer.
  • the volume of the carbon conductive agent exceeds the volume of the PTC powder, an increase in electrical resistance due to temperature rise cannot be obtained sufficiently. Therefore, the volume of 1: 1 (PTC powder: carbon conductive agent) or less with respect to the PTC powder. More preferably, a carbon conductive agent smaller than the average roughening interval R sm on the surface of the metal foil is mixed.
  • the particle size (D 50) is larger than the average roughening interval R sm of the surface of the metal foil having a volume ratio of 1: 0.1 (PTC powder: carbon conductive agent) or more. ) Must contain a small carbon conducting agent.
  • a carbon conductive agent having a particle diameter (D 50 ) smaller than the average roughening interval R smm and a carbon conductive agent having a particle diameter (D 50 ) larger than 2 in the slurry is more desirable to include a type of carbon conductive agent.
  • Both the carbon conductive agent and the PTC powder smaller than the average roughening interval R smm are filled in the concave portion whose surface is roughened, and functions as a PTC layer.
  • the carbon conductive agent larger than the average roughening interval R smm exists only in the active material layer, and can increase the conductivity in the active material layer.
  • the excess PTC powder which was not filled in the recessed part with which the surface was roughened and some carbon conductive agents of a small particle may exist in an active material layer.
  • the carbon conductive agent smaller than the average roughening interval R sm and the large carbon conductive agent, the PTC layer during normal use and the conductivity in the active material layer
  • the metal foil used in the present invention generally, an aluminum foil is used for the positive electrode and a copper foil is used for the negative electrode. However, nickel foil or the like can also be used.
  • the positive electrode active material include lithium-containing transition metal composite oxides containing transition metals such as cobalt, nickel, and manganese. Specifically, lithium cobaltate, lithium nickel cobalt manganese composite oxide, lithium nickel manganese composite oxide, lithium iron phosphate having an olivine structure, lithium manganate having a spinel structure, and the like can be given. These positive electrode active materials can be used alone or in combination.
  • the negative electrode active material is not particularly limited as long as it is used as a negative electrode active material for a non-aqueous electrolyte secondary battery.
  • the negative electrode active material include carbon materials such as graphite and coke, metals that can be alloyed with lithium such as tin oxide, metallic lithium, and silicon, and alloys thereof.
  • an electrode for a non-aqueous electrolyte secondary battery that can improve safety and reliability without reducing the energy density of the electrode.
  • FIG. 1 is a diagram schematically showing a cross-sectional structure of an electrode according to Example 1 of the present invention.
  • FIG. 2 is an SEM photograph showing a cross section of the positive electrode according to Example 1 of the present invention.
  • FIG. 3 is an SEM photograph showing a cross section of the positive electrode according to Example 2 of the present invention.
  • FIG. 4 is a diagram schematically showing a cross-sectional structure of an electrode according to Example 2 of the present invention.
  • Example 1 90 parts by mass of a lithium nickel cobalt manganese composite oxide having a particle size (D 10 ) of 9 ⁇ m as a positive electrode active material, 3 parts by mass of graphite having a particle size (D 10 ) of 3 ⁇ m as a carbon conductive agent, and a particle size as PTC powder 5 parts by mass of barium titanate having a (D 50 ) of 0.15 ⁇ m and 2 parts by mass of polyvinylidene fluoride as a binder were mixed, and an appropriate amount of N-methyl-2-pyrrolidone was added to prepare an active material slurry. This active material slurry was applied onto an aluminum foil 7 having an average surface roughening interval R sm of 2.4 ⁇ m and dried.
  • R sm average surface roughening interval
  • the particle sizes of the active material, the PTC powder, and the binder were determined by a laser diffraction method, and the particle size of the carbon conductive agent was determined by observation with an electron microscope. This was cut into a predetermined electrode size, rolled using a roller, a positive electrode lead was attached, and used as a positive electrode.
  • FIG. 1 schematically shows a cross-sectional structure of an electrode according to Example 1 of the present invention.
  • this figure is the schematic diagram which showed the structure of the electrode of this invention more clearly, and does not necessarily show the structure of an exact electrode. More precisely, refer to the cross-sectional SEM photograph of the electrode plate in FIG.
  • Reference numeral 1 denotes an active material layer including an active material powder 11 and a carbon conductive agent 4 made of graphite having a particle size (D 10 ) of 3 ⁇ m.
  • 2 represents the PTC layer 2 filled in the concave portion of the metal foil whose surface is roughened, and the PTC layer 2 contains the PTC powder 13.
  • the PTC layer 6 and the active material layer 5 can be simultaneously produced in one process, it is possible to contribute to improvement in productivity and cost reduction.
  • the PTC layer 6 since the PTC layer 6 is provided, when a nail is inserted from the outside or when a short circuit occurs when a foreign matter is mixed inside, the concave portion of the roughened metal foil is filled with a rise in temperature. Further, since the resistance of the PTC layer 6 is increased and the short-circuit current is interrupted, the safety of the battery can be improved. Furthermore, the current from the active material is concentrated on the contact surface between the active material layer and the metal foil.
  • Example 2 89 parts by mass of lithium nickel cobalt manganese composite oxide having a particle size (D 10 ) of 9 ⁇ m as the positive electrode active material, and 1 mass of carbon conductive agent having a particle size (D 50 ) of 0.05 ⁇ m as the first carbon conductive agent 3 parts by weight of graphite having a particle diameter (D 10 ) of 3 ⁇ m as the second carbon conductive agent, 5 parts by weight of barium titanate having a particle diameter (D 50 ) of 0.15 ⁇ m as the PTC powder, and the binder 2 parts by mass of polyvinylidene fluoride was mixed, and an appropriate amount of N-methyl-2-pyrrolidone was added to prepare a slurry.
  • This slurry was applied onto an aluminum metal foil 10 having an average surface roughening interval R sm of 2.4 ⁇ m and dried.
  • a cross-sectional SEM photograph of the electrode plate produced in this way is shown in FIG. From FIG. 3, it was confirmed that the PTC layer 9 filled with the PTC powder, the binder, and the small-sized carbon conductive agent 1 was formed in the concave portion of the metal foil whose surface was roughened.
  • carbon conductive agent 1 smaller than average roughening interval R sm and carbon conductive agent 2 larger, the conductivity and active material layer of PTC layer 9 during normal use 8 can be improved together.
  • the PTC layer 9 in the concave portion of the metal foil whose surface is roughened can more effectively cut off the current due to the increase in electric resistance when the battery temperature rises, without suppressing the decrease in the energy density of the battery, It is considered that an electrode with improved desired safety and reliability can be provided.
  • FIG. 4 is a view schematically showing the cross-sectional structure of the electrode according to Example 2 of the present invention.
  • this figure is the schematic diagram which showed the structure of the electrode of this invention more clearly, and does not necessarily show the structure of an exact electrode. More precisely, refer to the cross-sectional SEM photograph of the electrode plate in FIG.
  • Reference numeral 1 denotes an active material layer 11 and an active material layer 1 and 2 including a carbon conductive agent 4 made of graphite having a particle size (D 10 ) of 3 ⁇ m.
  • a PTC layer filled in a concave portion of a metal foil whose surface is roughened 2 and the PTC layer 2 may contain a carbon conductive agent 12 having a particle size (D 50 ) of 0.05 ⁇ m.
  • the present invention can be expected to be developed for a driving power source for mobile information terminals such as mobile phones, notebook computers, and PDAs, and a driving power source for high output such as HEV and electric tools.

Abstract

The purpose of the present invention is to provide an electrode for a non-aqueous electrolyte secondary battery, of which the energy density is not deteriorated, and which has improved safety and reliability. An electrode for a non-aqueous electrolyte secondary battery, which comprises an active material layer formed on a metal foil, and which is characterized in that the metal foil to be used is a metal foil in which at least a portion of a surface having the active material layer formed thereon is roughened, a PTC layer is provided in at least some of recessed parts of the surface-roughened metal foil, and the active material layer is arranged on the PTC layer, wherein a PTC powder having such a property that the electric resistance is increased with increasing temperature and a binder are filled in the PTC layer.

Description

非水電解質二次電池用電極及びその製造方法Nonaqueous electrolyte secondary battery electrode and method for producing the same
　本発明は、非水電解質二次電池用電極のエネルギー密度を低下させずに、安全性及び信頼性の向上を図ることができる非水電解質二次電池用電極及びその製造方法に関するものである。 The present invention relates to a non-aqueous electrolyte secondary battery electrode that can improve safety and reliability without reducing the energy density of the non-aqueous electrolyte secondary battery electrode, and a method for manufacturing the same.
　非水電解質二次電池は、小型、軽量、高エネルギー密度の電池として、携帯機器の電源などに広く利用されている。この種の電池の安全性向上の取り組みとして、特許文献１では、正極活物質層もしくは負極活物質層の少なくとも一方に、温度上昇に伴い電気抵抗が上昇するＰＴＣ粉末を混合させることが示されている。しかし、ＰＴＣ粉末を活物質層に混合する方法では、正常動作時の特性低下を引き起こさないように炭素導電剤を活物質層に十分に添加する必要がある。また、活物質層全体にわたって、電気抵抗上昇効果を得るためには、十分な量のＰＴＣ粉末を混合する必要がある。このような結果、電池容量に関与しない炭素導電剤とＰＴＣ粉末の添加量が多くなるため、電極のエネルギー密度が低下するという問題があった。 Nonaqueous electrolyte secondary batteries are widely used as power sources for portable devices as small, lightweight, and high energy density batteries. As an effort to improve the safety of this type of battery, Patent Document 1 shows that at least one of a positive electrode active material layer and a negative electrode active material layer is mixed with PTC powder whose electric resistance increases as the temperature rises. Yes. However, in the method in which the PTC powder is mixed with the active material layer, it is necessary to sufficiently add the carbon conductive agent to the active material layer so as not to cause deterioration in characteristics during normal operation. Moreover, in order to obtain the electrical resistance increasing effect over the entire active material layer, it is necessary to mix a sufficient amount of PTC powder. As a result, there is a problem in that the energy density of the electrode decreases because the amount of carbon conductive agent and PTC powder not involved in the battery capacity increases.
　特許文献２では、正極の集電体と活物質含有層の間に、過充電時に高抵抗体へ変化する導電性中間層を配置することが開示されている。しかし、ここに開示されている方法では導電性中間層を配置する工程と、その上に活物質含有層を設ける工程が必要であり、製造工程が複雑化するという問題があった。 Patent Document 2 discloses disposing a conductive intermediate layer that changes to a high resistance during overcharging between a positive electrode current collector and an active material-containing layer. However, the method disclosed herein requires a step of disposing a conductive intermediate layer and a step of providing an active material-containing layer thereon, and there is a problem that the manufacturing process becomes complicated.
　また、電池容量に関与しない過充電時に高抵抗体へ変化する導電性中間層を形成しているため、電極のエネルギー密度が低下するという問題があった。 In addition, there is a problem that the energy density of the electrode is lowered because a conductive intermediate layer that changes to a high resistance body is formed during overcharge that is not related to the battery capacity.
　一方で、特許文献３では、正極層側の面が粗面化されたアルミニウム箔を用いることにより、活物質層とアルミニウム箔間の密着性が改善されることが示されている。しかしながら、非水電解質二次電池の安全性向上のためには更なる改良が必要であった。 On the other hand, Patent Document 3 shows that the adhesion between the active material layer and the aluminum foil is improved by using an aluminum foil whose surface on the positive electrode layer side is roughened. However, further improvements are necessary to improve the safety of the nonaqueous electrolyte secondary battery.
特開２００５－１２３１８５号公報JP-A-2005-123185 特開２０００－１６４２０６号公報JP 2000-164206 A 特開平９－２２６９９号公報Japanese Patent Laid-Open No. 9-22699
　本発明は、前記非水電解質二次電池用電極のエネルギー密度を低下させずに、安全性及び信頼性を向上することが可能となる非水電解質用電極及びその製造方法を提供することを課題とする。 It is an object of the present invention to provide a nonaqueous electrolyte electrode that can improve safety and reliability without reducing the energy density of the nonaqueous electrolyte secondary battery electrode, and a method for manufacturing the same. And
　前記目的を達成するために本発明は、金属箔上に活物質層を形成した非水電解質二次電池用電極において、金属箔として、活物質層を形成する表面の少なくとも一部が粗化された金属箔を用いるとともに、表面が粗化された金属箔の少なくとも一部の凹部内に、温度上昇に伴い電気抵抗が上昇する特性を有するＰＴＣ粉末と結着剤が充填されたＰＴＣ層を備えると共に、ＰＴＣ層上に活物質層を形成することを特徴とする。 In order to achieve the above object, the present invention provides an electrode for a non-aqueous electrolyte secondary battery in which an active material layer is formed on a metal foil, and at least a part of the surface on which the active material layer is formed is roughened as the metal foil. And a PTC layer filled with a PTC powder and a binder having a property of increasing electric resistance with increasing temperature in at least a part of the concave portion of the metal foil having a roughened surface. In addition, an active material layer is formed on the PTC layer.
　ここで、表面が粗化された金属箔とは、金属箔の表面の粗化処理方法により、金属箔の表面に凹凸部が形成されたものを云う。 Here, the metal foil having a roughened surface refers to a metal foil having irregularities formed on the surface of the metal foil by a method of roughening the surface of the metal foil.
　本発明に使用する金属箔の粗化処理方法としては、例えば、めっき法、気相成長法、エッチング法及び研磨法などが挙げられる。めっき法としては、電解めっき法及び無電解めっき法が挙げられる。気相成長法としては、スパッタリング法、ＣＶＤ法、蒸着法などが挙げられる。また、研磨法としては、サンドペーパーによる研磨やブラスト法にやる研磨などが挙げられる。 Examples of the metal foil roughening method used in the present invention include a plating method, a vapor phase growth method, an etching method, and a polishing method. Examples of the plating method include an electrolytic plating method and an electroless plating method. Examples of the vapor phase growth method include a sputtering method, a CVD method, and a vapor deposition method. Examples of the polishing method include sandpaper polishing and polishing by blasting.
　図１に本発明に係る電極の断面構造を模式的に示す。ここで、表面が粗化された金属箔３は、その表面に凹凸が形成されている。この凹部内にＰＴＣ粉末１３と結着剤を含むＰＴＣ層２が形成されており、その上に活物質層１が形成されている。 FIG. 1 schematically shows a cross-sectional structure of an electrode according to the present invention. Here, the metal foil 3 having a roughened surface has irregularities formed on the surface. A PTC layer 2 containing PTC powder 13 and a binder is formed in the recess, and the active material layer 1 is formed thereon.
　尚、表面が粗化され金属箔３の隣り合う凸部先端と凸部先端の距離の平均値がＲｓｍに近い値である。 In addition, the average value of the distance of the convex part tip which the surface is roughened and the metal foil 3 adjoins is a value close | similar to R sm .
　前記ＰＴＣ層を有することにより、外部から釘がさされた場合や、内部に異物が混入した際に短絡が生じた場合に、温度上昇とともに、前記ＰＴＣ層の抵抗が上昇し、短絡電流を遮断するため、電池の安全性を向上することができる。 By having the PTC layer, when a nail is inserted from the outside or when a short circuit occurs when a foreign substance is mixed inside, the resistance of the PTC layer increases and the short circuit current is cut off as the temperature rises. Therefore, the safety of the battery can be improved.
　電池極板において、活物質からの電流は、活物質層と芯体との接触面に集中する。このため、本発明のように活物質層と芯体との間に、温度上昇に伴い電気抵抗が上昇するＰＴＣ層を形成させることにより、より少ないＰＴＣ粉末の添加量で所望の効果が得られる。よって、非水電解質二次電池用電極のエネルギー密度を低下させずに、安全性及び信頼性を向上することができる。 In the battery electrode plate, the current from the active material is concentrated on the contact surface between the active material layer and the core. For this reason, a desired effect can be obtained with a smaller amount of added PTC powder by forming a PTC layer whose electrical resistance increases with increasing temperature between the active material layer and the core as in the present invention. . Therefore, safety and reliability can be improved without reducing the energy density of the electrode for the nonaqueous electrolyte secondary battery.
　ここで、活物質及びＰＴＣ粉末、結着剤の粒径の測定法はレーザー回折法が好ましく、炭素導電剤の粒径の測定法は電子顕微鏡の観察が好ましい。また、金属箔表面の平均粗化間隔Ｒｓｍは、ＪＩＳ　Ｂ０６０１－２００１で輪郭曲線要素の平均長さＲｓｍとして規定されている方法により求めることができる。 Here, the method of measuring the particle size of the active material, the PTC powder, and the binder is preferably a laser diffraction method, and the method of measuring the particle size of the carbon conductive agent is preferably observation with an electron microscope. Further, the average roughening interval R sm on the surface of the metal foil can be obtained by a method defined as the average length R sm of the contour curve element in JIS B0601-2001.
　前記金属箔表面のＪＩＳ　Ｂ０６０１－２００１で輪郭曲線要素の平均長さとして規定されている方法により求められる平均粗化間隔Ｒｓｍは０．０５μｍ以上３．０μｍ以下であることが好ましい。前記平均粗化間隔Ｒｓｍが０．０５μｍ未満であると、金属箔表面の粗化された凹部に気泡が溜まりＰＴＣ粉末粒子が入り込むことが困難となる。 It is preferable that the average roughening interval R sm obtained by the method defined as the average length of the contour curve element in JIS B0601-2001 on the surface of the metal foil is 0.05 μm or more and 3.0 μm or less. When the average roughening interval R sm is less than 0.05 μm, bubbles accumulate in the roughened concave portion of the metal foil surface, making it difficult for the PTC powder particles to enter.
　一方、前記平均粗化間隔Ｒｓｍが３．０μｍ以上の場合、活物質の一部が金属箔の表面が粗化された凹部内に埋まる可能性があり、ＰＴＣ層が形成できない箇所が生じるため、本発明の効果が効率的に発揮されないことがある。 On the other hand, when the average roughening interval R sm is 3.0 μm or more, there is a possibility that a part of the active material may be buried in the concave portion where the surface of the metal foil is roughened, resulting in a place where a PTC layer cannot be formed. The effects of the present invention may not be exhibited efficiently.
　前記のような、非水電解質二次電池用電極を作成する方法は、例えば、以下の方法が挙げられる。 Examples of the method for producing the non-aqueous electrolyte secondary battery electrode include the following methods.
　まず、活物質と、炭素導電剤と、結着剤と、ＰＴＣ粉末を溶媒中で混合してスラリーを作製する。これを、表面が粗化された金属箔の表面上に塗布し、乾燥させる。この際、レーザー回折法もしくは、電子顕微鏡の観察によって求められる、体積基準累積粒度分布の微粒側から累積１０％、累積５０％および累積９０％の粒径をそれぞれＤ１０、Ｄ５０およびＤ９０としたとき、ＰＴＣ粉末及び、結着剤としてのエマルジョン粒子の粒径（Ｄ５０）は、金属箔表面のＪＩＳ　Ｂ０６０１－２００１で輪郭曲線要素の平均長さとして規定されている方法により求められる平均粗化間隔Ｒｓｍよりも小さく、炭素導電剤の粒径（Ｄ１０）と活物質の粒径（Ｄ１０）は金属箔表面の平均粗化間隔Ｒｓｍよりも大きい必要がある。これらの条件を満たす場合に図１の模式図で示すように、表面が粗化された金属箔の凹部内に、金属箔表面の平均粗化間隔Ｒｓｍよりも小さいＰＴＣ粉末及び、結着剤、特に、エマルジョン粒子が入り込みＰＴＣ層２が自己形成される。なお、溶媒に対し溶解性のある結着剤を用いた場合にも同様に、金属箔表面の平均粗化間隔Ｒｓｍよりも小さいＰＴＣ粉末と結着剤が入り込みＰＴＣ層２が自己形成される。以上の方法によれば、一度の塗布で活物質層１とＰＴＣ層２が略同時に形成され、電極の製造工程が簡易となるため、生産コスト削減及び生産性の向上が期待できる。 First, an active material, a carbon conductive agent, a binder, and PTC powder are mixed in a solvent to prepare a slurry. This is applied onto the surface of the metal foil whose surface has been roughened and dried. At this time, the particle sizes of 10%, 50%, and 90% accumulated from the fine particle side of the volume-based cumulative particle size distribution obtained by laser diffraction method or observation with an electron microscope are D 10 , D 50, and D 90 , respectively. In this case, the particle diameter (D 50 ) of the PTC powder and the emulsion particles as the binder is an average roughness determined by the method defined as the average length of the contour curve element in JIS B0601-2001 on the surface of the metal foil. smaller than reduction interval R sm, the particle size of the conductive carbon material (D 10) and particle size of the active material (D 10) is it must be greater than the average roughened distance R sm metal foil surface. When these conditions are satisfied, as shown in the schematic diagram of FIG. 1, a PTC powder smaller than the average roughening interval R sm on the surface of the metal foil and a binder in the concave portion of the metal foil whose surface is roughened In particular, the emulsion particles enter and the PTC layer 2 is self-formed. Similarly, when a binder that is soluble in the solvent is used, PTC powder smaller than the average roughening interval R smm on the surface of the metal foil and the binder enter and the PTC layer 2 is self-formed. . According to the above method, the active material layer 1 and the PTC layer 2 are formed almost simultaneously by one application, and the manufacturing process of the electrode is simplified. Therefore, production cost reduction and productivity improvement can be expected.
　但し、ＰＴＣ粉末を含有するスラリーを予め形成し、そのスラリーを表面が粗化された金属箔の表面上に塗布した後、活物質と炭素導電剤を含む活物質スラリーを塗布しても良い。 However, a slurry containing PTC powder may be formed in advance, and after applying the slurry onto the surface of the metal foil whose surface has been roughened, an active material slurry containing an active material and a carbon conductive agent may be applied.
　また、黒鉛等の電子伝導性が高い活物質の場合には、前記炭素導電剤を添加しなくても良い。 Further, in the case of an active material having high electron conductivity such as graphite, the carbon conductive agent may not be added.
　前記のようなＰＴＣ層２は、正負極両方もしくは、いずれか一方に設ければよいが、正極側に形成することがより望ましい。非水電解質二次電池用の正極活物質として一般的に用いられるリチウム含有遷移金属酸化物は、負極活物質として一般的に用いられている黒鉛よりも導電性が低く、活物質層内の導電性のほとんどを炭素導電剤に依存している。このため、芯体と活物質層間の電流経路が、炭素導電剤が存在している部分に限定されている。以上のような理由から、活物質の導電性が低い正極に使用した方がＰＴＣ層２の効果をより高めることができるものと考えられる。 The PTC layer 2 as described above may be provided on either or both of the positive and negative electrodes, but more preferably on the positive electrode side. Lithium-containing transition metal oxides that are commonly used as positive electrode active materials for non-aqueous electrolyte secondary batteries have lower conductivity than graphite, which is commonly used as negative electrode active materials, and are conductive in the active material layer. Most of the properties depend on the carbon conducting agent. For this reason, the current path between the core and the active material layer is limited to the portion where the carbon conductive agent exists. For the reasons described above, it is considered that the effect of the PTC layer 2 can be further enhanced by using it for a positive electrode with low active material conductivity.
　前記ＰＴＣ粉末としては、チタン酸バリウムにＳｒ等アルカリ土類金属や、Ｐｂ等を添加したものや、Ｃｒ，Ｃｅ，Ｍｎ，Ｌａ，Ｙ，Ｎｂ，Ｎｄから選択される少なくとも一種を含有してもよい。また、高密度ポリエチレンもしくは低密度ポリエチレン及びその混合体を用いることができる。さらに、チタン酸バリウムのＴｉとＢａとの組成比を適宜調整することができる。 The PTC powder may contain a barium titanate added with an alkaline earth metal such as Sr, Pb or the like, or at least one selected from Cr, Ce, Mn, La, Y, Nb, and Nd. Good. Further, high density polyethylene or low density polyethylene and a mixture thereof can be used. Furthermore, the composition ratio of Ti and Ba of barium titanate can be adjusted as appropriate.
　但し、チタン酸バリウムを主成分として用いたＰＴＣ粉末を用いることが好ましい。これは、チタン酸バリウムは比重が大きいために、表面が粗化された金属箔の凹部内にＰＴＣ粉末が充填されやすいためである。また、チタン酸バリウムは導電性を有するために、別途炭素導電剤を混合しなくてもよいという利点もある。 However, PTC powder using barium titanate as a main component is preferably used. This is because barium titanate has a large specific gravity, so that the PTC powder is easily filled in the concave portion of the metal foil whose surface is roughened. Moreover, since barium titanate has conductivity, there is an advantage that it is not necessary to mix a carbon conductive agent separately.
　さらに、ＰＴＣ粉末の導電性を補い、ＰＴＣ層が存在することによる通常使用時における内部抵抗の増大を抑制するために、金属箔表面の平均粗化間隔Ｒｓｍよりも粒径（Ｄ５０）が小さい炭素導電剤をＰＴＣ層中に添加することが好ましい。 Furthermore, in order to supplement the conductivity of the PTC powder and suppress the increase in internal resistance during normal use due to the presence of the PTC layer, the particle diameter (D 50 ) is larger than the average roughening interval R sm on the surface of the metal foil. It is preferable to add a small carbon conductive agent to the PTC layer.
　尚、ＰＴＣ粉末の体積に対し炭素導電剤の体積が超えると、温度上昇に伴う電気抵抗上昇が十分得られなくなるため、ＰＴＣ粉末に対し、１：１（ＰＴＣ粉末：炭素導電剤）以下の体積割合で金属箔表面の平均粗化間隔Ｒｓｍよりも小さな炭素導電剤を混合することが更に好ましい。 In addition, if the volume of the carbon conductive agent exceeds the volume of the PTC powder, an increase in electrical resistance due to temperature rise cannot be obtained sufficiently. Therefore, the volume of 1: 1 (PTC powder: carbon conductive agent) or less with respect to the PTC powder. More preferably, a carbon conductive agent smaller than the average roughening interval R sm on the surface of the metal foil is mixed.
　一方、ＰＴＣ粉末として高密度ポリエチレンや低密度ポリエチレンを使用することができる。その場合は、ＰＴＣ層の導電性を確保するために、１：０．１（ＰＴＣ粉末：炭素導電剤）以上の体積割合の金属箔表面の平均粗化間隔Ｒｓｍよりも粒径（Ｄ５０）が小さい炭素導電剤を含むことが必要である。 On the other hand, high-density polyethylene or low-density polyethylene can be used as the PTC powder. In that case, in order to ensure the conductivity of the PTC layer, the particle size (D 50) is larger than the average roughening interval R sm of the surface of the metal foil having a volume ratio of 1: 0.1 (PTC powder: carbon conductive agent) or more. ) Must contain a small carbon conducting agent.
　前記非水電解質二次電池用電極を作製する際にスラリー中に平均粗化間隔Ｒｓｍよりも粒径（Ｄ５０）が小さな炭素導電剤と粒径（Ｄ５０）が大きな炭素導電剤の２種類の炭素導電剤を含んでいることがより望ましい。平均粗化間隔Ｒｓｍよりも小さな炭素導電剤とＰＴＣ粉末は、共に表面が粗化された凹部内に充填されて、ＰＴＣ層として機能する。一方、平均粗化間隔Ｒｓｍよりも大きな炭素導電剤は、活物質層中にのみ存在し、活物質層中の導電性を高めることができる。なお、表面が粗化された凹部内に充填されなかった余剰なＰＴＣ粉末及び、小粒子の炭素導電剤の一部が活物質層中に存在してもよい。 When producing the electrode for a non-aqueous electrolyte secondary battery, a carbon conductive agent having a particle diameter (D 50 ) smaller than the average roughening interval R smm and a carbon conductive agent having a particle diameter (D 50 ) larger than 2 in the slurry. It is more desirable to include a type of carbon conductive agent. Both the carbon conductive agent and the PTC powder smaller than the average roughening interval R smm are filled in the concave portion whose surface is roughened, and functions as a PTC layer. On the other hand, the carbon conductive agent larger than the average roughening interval R smm exists only in the active material layer, and can increase the conductivity in the active material layer. In addition, the excess PTC powder which was not filled in the recessed part with which the surface was roughened and some carbon conductive agents of a small particle may exist in an active material layer.
　前記のように平均粗化間隔Ｒｓｍよりも小さな炭素導電剤と大きな炭素導電剤の２種類の炭素導電剤を混合することで、通常使用時のＰＴＣ層及び、活物質層中の導電性と、電池温度上昇時の電気抵抗上昇による電流遮断を両立させることができる。これにより、より一層本発明の効果を高めることができる。 As described above, by mixing the two types of carbon conductive agents, the carbon conductive agent smaller than the average roughening interval R sm and the large carbon conductive agent, the PTC layer during normal use and the conductivity in the active material layer In addition, it is possible to achieve both current interruption due to an increase in electrical resistance when the battery temperature rises. Thereby, the effect of the present invention can be further enhanced.
（その他の事項）
（１）本発明に使用する金属箔としては、一般的に、正極にはアルミニウム箔、負極には銅箔が用いられる。但し、ニッケル箔なども使用できる。
（２）正極活物質としては、コバルト、ニッケル、マンガン等の遷移金属を含むリチウム含有遷移金属複合酸化物が挙げられる。具体的には、コバルト酸リチウム、リチウムニッケルコバルトマンガン複合酸化物、リチウムニッケルマンガン複合酸化物、オリビン構造を有するリン酸鉄リチウム、スピネル構造を有するマンガン酸リチウム等が挙げられる。これらの正極活物質は単独で用いることもできるし、混合して用いることができる。
（３）負極活物質としては、非水電解液二次電池の負極活物質として用いるものであれば特に限定されるものではない。負極活物質としては、例えば、グラファイト、コークス等の炭素材料、酸化スズ、金属リチウム、珪素等のリチウムと合金化し得る金属及びそれらの合金等が挙げられる。 (Other matters)
(1) As the metal foil used in the present invention, generally, an aluminum foil is used for the positive electrode and a copper foil is used for the negative electrode. However, nickel foil or the like can also be used.
(2) Examples of the positive electrode active material include lithium-containing transition metal composite oxides containing transition metals such as cobalt, nickel, and manganese. Specifically, lithium cobaltate, lithium nickel cobalt manganese composite oxide, lithium nickel manganese composite oxide, lithium iron phosphate having an olivine structure, lithium manganate having a spinel structure, and the like can be given. These positive electrode active materials can be used alone or in combination.
(3) The negative electrode active material is not particularly limited as long as it is used as a negative electrode active material for a non-aqueous electrolyte secondary battery. Examples of the negative electrode active material include carbon materials such as graphite and coke, metals that can be alloyed with lithium such as tin oxide, metallic lithium, and silicon, and alloys thereof.
　本発明によれば、電極のエネルギー密度を低下させずに、安全性及び信頼性を向上することが可能な非水電解質二次電池用電極を提供することができる。 According to the present invention, it is possible to provide an electrode for a non-aqueous electrolyte secondary battery that can improve safety and reliability without reducing the energy density of the electrode.
図１は、本発明に係る実施例１に係る電極の断面構造を模式的に示した図である。FIG. 1 is a diagram schematically showing a cross-sectional structure of an electrode according to Example 1 of the present invention. 図２は、本発明の実施例１に係る正極の断面を示すＳＥＭ写真である。FIG. 2 is an SEM photograph showing a cross section of the positive electrode according to Example 1 of the present invention. 図３は、本発明の実施例２に係る正極の断面を示すＳＥＭ写真である。FIG. 3 is an SEM photograph showing a cross section of the positive electrode according to Example 2 of the present invention. 図４は、本発明に係る実施例２に係る電極の断面構造を模式的に示した図である。FIG. 4 is a diagram schematically showing a cross-sectional structure of an electrode according to Example 2 of the present invention.
　以下、本発明を下記形態に基づいてさらに詳細に説明するが、本発明は以下の形態に何ら限定されるものではなく、その要旨を変更しない範囲において適宜変更して実施することが可能なものである。 Hereinafter, the present invention will be described in more detail based on the following embodiments, but the present invention is not limited to the following embodiments, and can be appropriately modified and implemented without departing from the scope of the present invention. It is.
（実施例１）
　正極活物質として、粒径（Ｄ１０）が９μｍのリチウムニッケルコバルトマンガン複合酸化物を９０質量部、炭素導電剤として粒径（Ｄ１０）が３μｍの黒鉛を３質量部、ＰＴＣ粉末として粒径（Ｄ５０）が０．１５μｍのチタン酸バリウムを５質量部、結着剤としてポリフッ化ビニリデン２質量部を混合して、Ｎ－メチル－２－ピロリドンを適量加え、活物質スラリーを作製した。この活物質スラリーを、表面の平均粗化間隔Ｒｓｍが２．４μｍのアルミニウム箔７上に塗布して乾燥した。尚、活物質及びＰＴＣ粉末、結着剤の粒径はレーザー回折法により求め、炭素導電剤の粒径は電子顕微鏡の観察によって求めた。これを所定の電極サイズに切り取り、ローラーを用いて圧延し、正極リードを取り付け、正極として用いた。 Example 1
90 parts by mass of a lithium nickel cobalt manganese composite oxide having a particle size (D 10 ) of 9 μm as a positive electrode active material, 3 parts by mass of graphite having a particle size (D 10 ) of 3 μm as a carbon conductive agent, and a particle size as PTC powder 5 parts by mass of barium titanate having a (D 50 ) of 0.15 μm and 2 parts by mass of polyvinylidene fluoride as a binder were mixed, and an appropriate amount of N-methyl-2-pyrrolidone was added to prepare an active material slurry. This active material slurry was applied onto an aluminum foil 7 having an average surface roughening interval R sm of 2.4 μm and dried. The particle sizes of the active material, the PTC powder, and the binder were determined by a laser diffraction method, and the particle size of the carbon conductive agent was determined by observation with an electron microscope. This was cut into a predetermined electrode size, rolled using a roller, a positive electrode lead was attached, and used as a positive electrode.
　図１に本発明に係る実施例１に係る電極の断面構造を模式的に示した図を示す。尚、注釈ではあるが、この図は本発明の電極の構造をよりわかりやすく示した模式図であり、必ずしも正確な電極の構造を示しているとは限らない。より正確には、図２の極板の断面ＳＥＭ写真を参照されたし。１は活物質粉末１１と粒径（Ｄ１０）が３μｍの黒鉛からなる炭素導電剤４を備えた活物質層である。２は、表面が粗化された金属箔の凹部内に充填されたＰＴＣ層２を表し、そのＰＴＣ層２には、ＰＴＣ粉末１３が含まれている。 FIG. 1 schematically shows a cross-sectional structure of an electrode according to Example 1 of the present invention. In addition, although it is remarks, this figure is the schematic diagram which showed the structure of the electrode of this invention more clearly, and does not necessarily show the structure of an exact electrode. More precisely, refer to the cross-sectional SEM photograph of the electrode plate in FIG. Reference numeral 1 denotes an active material layer including an active material powder 11 and a carbon conductive agent 4 made of graphite having a particle size (D 10 ) of 3 μm. 2 represents the PTC layer 2 filled in the concave portion of the metal foil whose surface is roughened, and the PTC layer 2 contains the PTC powder 13.
　また、図２に作製した極板の断面ＳＥＭ写真を示す。粗化された金属箔の凹部内にＰＴＣ粉末と結着剤が充填されたＰＴＣ層６が形成されていることが確認された。 Moreover, the cross-sectional SEM photograph of the electrode plate produced in FIG. 2 is shown. It was confirmed that the PTC layer 6 filled with the PTC powder and the binder was formed in the concave portion of the roughened metal foil.
　このように、１回の工程でＰＴＣ層６と活物質層５を同時に作製することができるので、生産性の向上とコスト削減に寄与することができる。また、ＰＴＣ層６を有することから外部から釘がさされた場合や、内部に異物が混入した際に短絡が生じた場合に、温度上昇とともに、粗化された金属箔の凹部内に充填されたＰＴＣ層６の抵抗が上昇し、短絡電流を遮断するため、電池の安全性を向上させることができる。更に、活物質からの電流は、活物質層と金属箔との接触面に集中する。このため、本発明のように活物質層と芯体との間に、温度上昇に伴い電気抵抗が上昇するＰＴＣ層を形成させることにより、より少ない量で所望の効果が得られるため、電池のエネルギー密度の低下を抑制することができるものと考えられる。 Thus, since the PTC layer 6 and the active material layer 5 can be simultaneously produced in one process, it is possible to contribute to improvement in productivity and cost reduction. In addition, since the PTC layer 6 is provided, when a nail is inserted from the outside or when a short circuit occurs when a foreign matter is mixed inside, the concave portion of the roughened metal foil is filled with a rise in temperature. Further, since the resistance of the PTC layer 6 is increased and the short-circuit current is interrupted, the safety of the battery can be improved. Furthermore, the current from the active material is concentrated on the contact surface between the active material layer and the metal foil. For this reason, since a desired effect can be obtained in a smaller amount by forming a PTC layer in which the electrical resistance increases as the temperature rises between the active material layer and the core as in the present invention, It is considered that the decrease in energy density can be suppressed.
（実施例２）
　正極活物質として、粒径（Ｄ１０）が９μｍのリチウムニッケルコバルトマンガン複合酸化物を８９質量部、第１の炭素導電剤として粒径（Ｄ５０）が０．０５μｍの炭素導電剤を１質量部、第２の炭素導電剤として粒径（Ｄ１０）が３μｍの黒鉛を３質量部、ＰＴＣ粉末として粒径（Ｄ５０）が０．１５μｍのチタン酸バリウムを５質量部、結着剤としてポリフッ化ビニリデンを２質量部混合して、Ｎ－メチル－２－ピロリドンを適量加え、スラリーを作製した。 (Example 2)
89 parts by mass of lithium nickel cobalt manganese composite oxide having a particle size (D 10 ) of 9 μm as the positive electrode active material, and 1 mass of carbon conductive agent having a particle size (D 50 ) of 0.05 μm as the first carbon conductive agent 3 parts by weight of graphite having a particle diameter (D 10 ) of 3 μm as the second carbon conductive agent, 5 parts by weight of barium titanate having a particle diameter (D 50 ) of 0.15 μm as the PTC powder, and the binder 2 parts by mass of polyvinylidene fluoride was mixed, and an appropriate amount of N-methyl-2-pyrrolidone was added to prepare a slurry.
　このスラリーを表面の平均粗化間隔Ｒｓｍが２．４μｍのアルミニウム金属箔１０上に塗布し乾燥した。このように作製した極板の断面ＳＥＭ写真を図３に示す。この図３より、表面が粗化された金属箔の凹部内にＰＴＣ粉末と結着剤と小粒子の炭素導電剤１が充填されたＰＴＣ層９が形成されていることが確認された。このように、平均粗化間隔Ｒｓｍよりも小さな炭素導電剤１と大きな炭素導電剤２の２種類の炭素導電剤を混合することで、通常使用時のＰＴＣ層９の導電性と活物質層８中の導電性とを共に向上させることができる。更に、表面が粗化された金属箔の凹部内のＰＴＣ層９により、電池温度上昇時の電気抵抗上昇による電流遮断をより効果的にできるため、電池のエネルギー密度の低下を抑制せずに、所望の安全性と信頼性を向上させた電極を提供できるものと考えられる。 This slurry was applied onto an aluminum metal foil 10 having an average surface roughening interval R sm of 2.4 μm and dried. A cross-sectional SEM photograph of the electrode plate produced in this way is shown in FIG. From FIG. 3, it was confirmed that the PTC layer 9 filled with the PTC powder, the binder, and the small-sized carbon conductive agent 1 was formed in the concave portion of the metal foil whose surface was roughened. Thus, by mixing two types of carbon conductive agents, carbon conductive agent 1 smaller than average roughening interval R sm and carbon conductive agent 2 larger, the conductivity and active material layer of PTC layer 9 during normal use 8 can be improved together. Furthermore, since the PTC layer 9 in the concave portion of the metal foil whose surface is roughened can more effectively cut off the current due to the increase in electric resistance when the battery temperature rises, without suppressing the decrease in the energy density of the battery, It is considered that an electrode with improved desired safety and reliability can be provided.
　また、図４に本発明に係る実施例２に係る電極の断面構造を模式的に示した図を示す。尚、注釈ではあるが、この図は本発明の電極の構造をよりわかりやすく示した模式図であり、必ずしも正確な電極の構造を示しているとは限らない。より正確には、図３の極板の断面ＳＥＭ写真を参照されたし。１は活物質粉末１１と粒径（Ｄ１０）が３μｍの黒鉛からなる炭素導電剤４を備えた活物質層１、２は表面が粗化された金属箔の凹部内に充填されたＰＴＣ層２を表し、そのＰＴＣ層２中に粒径（Ｄ５０）が０．０５μｍの炭素導電剤１２を含んでいることがある。 FIG. 4 is a view schematically showing the cross-sectional structure of the electrode according to Example 2 of the present invention. In addition, although it is remarks, this figure is the schematic diagram which showed the structure of the electrode of this invention more clearly, and does not necessarily show the structure of an exact electrode. More precisely, refer to the cross-sectional SEM photograph of the electrode plate in FIG. Reference numeral 1 denotes an active material layer 11 and an active material layer 1 and 2 including a carbon conductive agent 4 made of graphite having a particle size (D 10 ) of 3 μm. A PTC layer filled in a concave portion of a metal foil whose surface is roughened 2 and the PTC layer 2 may contain a carbon conductive agent 12 having a particle size (D 50 ) of 0.05 μm.
　本発明は、例えば携帯電話、ノートパソコン、ＰＤＡ等の移動情報端末の駆動電源や、ＨＥＶや電動工具といった高出力向けの駆動電源に展開が期待できる。 The present invention can be expected to be developed for a driving power source for mobile information terminals such as mobile phones, notebook computers, and PDAs, and a driving power source for high output such as HEV and electric tools.
１…正極活物質層
２…表面が粗化された金属箔の凹部内に充填されたＰＴＣ層
３…表面が粗化されたアルミニウム箔
４…炭素導電剤
５…正極活物質層
６…表面が粗化された金属箔の凹部内に充填されたＰＴＣ層
７…表面が粗化されたアルミニウム箔
８…正極活物質層
９…金属箔の凹部内に充填された炭素導電剤も同時に含んだＰＴＣ層
１０…表面が粗化された金属箔
１１…活物質粉末
１２…炭素導電剤 DESCRIPTION OF SYMBOLS 1 ... Positive electrode active material layer 2 ... PTC layer 3 filled in the recessed part of the metal foil with which the surface was roughened ... Aluminum foil 4 with the roughened surface ... Carbon conductive agent 5 ... Positive electrode active material layer 6 ... The surface is PTC layer 7 filled in the concave portion of the roughened metal foil 7... Aluminum foil 8 whose surface is roughened...... Positive electrode active material layer 9. Layer 10 ... metal foil 11 with roughened surface ... active material powder 12 ... carbon conductive agent

Claims (9)

  1. 　金属箔上に活物質層を形成した非水電解質二次電池用電極において、前記金属箔として、前記活物質層を形成する表面の少なくとも一部が粗化された金属箔を用いるとともに、前記表面が粗化された金属箔の少なくとも一部の凹部内に、温度上昇に伴い電気抵抗が上昇する特性を有するＰＴＣ粉末と結着剤が充填されたＰＴＣ層を備えると共に、前記ＰＴＣ層上に前記活物質層を備えたことを特徴とする非水電解質二次電池用電極。 In the electrode for a non-aqueous electrolyte secondary battery in which an active material layer is formed on a metal foil, a metal foil in which at least a part of the surface forming the active material layer is roughened is used as the metal foil, and the surface And a PTC layer filled with a PTC powder and a binder having a property of increasing electrical resistance as the temperature rises in at least a part of the recesses of the roughened metal foil, and the PTC layer is provided with the PTC layer on the PTC layer. An electrode for a non-aqueous electrolyte secondary battery comprising an active material layer.
  2. 　請求項１に記載された非水電解質二次電池用電極において、前記粗化された金属箔のＪＩＳ　Ｂ０６０１－２００１で輪郭曲線要素の平均長さとして規定されている方法により求められる平均粗化間隔Ｒｓｍが０．０５μｍ以上３．０μｍ以下であることを特徴とする非水電解質二次電池用電極。 2. The electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein an average roughening interval obtained by a method defined as an average length of a contour curve element in JIS B0601-2001 of the roughened metal foil. Rsm is 0.05 micrometer or more and 3.0 micrometers or less, The electrode for nonaqueous electrolyte secondary batteries characterized by the above-mentioned.
  3. 　請求項１または請求項２に記載の非水電解質二次電池用電極において、体積基準累積粒度分布の微粒側から累積１０％、累積５０％の粒径をそれぞれＤ１０、Ｄ５０としたとき、前記ＰＴＣ粉末の粒径（Ｄ５０）が前記平均粗化間隔Ｒｓｍより小さく、前記活物質層に含まれる活物質の粒径（Ｄ１０）が前記平均粗化間隔Ｒｓｍより大きいことを特徴とする非水電解質二次電池用電極。 In the non-aqueous electrolyte secondary battery according to claim 1 or claim 2, 10% cumulative from the fine side based on volume cumulative particle size distribution, when the 50% cumulative particle size was defined as D 10, D 50, respectively, The particle size (D 50 ) of the PTC powder is smaller than the average roughening interval R sm , and the particle size (D 10 ) of the active material contained in the active material layer is larger than the average roughening interval R sm. An electrode for a non-aqueous electrolyte secondary battery.
  4. 　請求項３に記載の非水電解質二次電池用電極において、前記活物質はリチウム含有遷移金属複合酸化物であるとともに、前記活物質層中には、前記平均粗化間隔Ｒｓｍよりも、前記粒径Ｄ１０が大きい炭素導電剤を含むことを特徴とする非水電解質二次電池用電極。 4. The electrode for a non-aqueous electrolyte secondary battery according to claim 3, wherein the active material is a lithium-containing transition metal composite oxide, and the active material layer includes the average roughening interval R sm. non-aqueous electrolyte secondary battery, which comprises a particle size D 10 of greater conductive carbon material.
  5. 　請求項４に記載の非水電解質二次電池用電極において、前記炭素導電剤として、前記平均粗化間隔Ｒｓｍよりも粒径（Ｄ５０）が小さい炭素導電剤と前記平均粗化間隔Ｒｓｍよりも粒径（Ｄ１０）が大きい炭素導電剤とを有し、前記平均粗化間隔Ｒｓｍよりも小さい炭素導電剤は前記ＰＴＣ層中に含まれ、前記平均粗化間隔Ｒｓｍよりも大きい炭素導電剤は前記活物質層中に含まれることを特徴とする非水電解質二次電池用電極。 In the non-aqueous electrolyte secondary battery according to claim 4, wherein the conductive carbon material, the average roughening interval R the particle size (D 50) is less conductive carbon material and than sm average roughening distance R sm And a carbon conductive agent having a particle size (D 10 ) larger than that of the average roughening interval R sm is included in the PTC layer and is larger than the average roughening interval R sm. A carbon conductive agent is contained in the active material layer, and the electrode for a non-aqueous electrolyte secondary battery.
  6. 　活物質と結着剤と金属箔を備えた非水電解質二次電池用電極の製造方法において、体積基準累積粒度分布の微粒側から累積１０％、累積５０％の粒径をそれぞれＤ１０、Ｄ５０としたとき、前記粗化された金属箔のＪＩＳ　Ｂ０６０１－２００１で輪郭曲線要素の平均長さとして規定されている方法により求められる平均粗化間隔Ｒｓｍよりも大きい粒径（Ｄ１０）を有する活物質粉末と、結着剤と、前記平均粗化間隔Ｒｓｍよりも小さい粒径（Ｄ５０）を有するＰＴＣ粉末を溶媒中に分散させた活物質スラリーを作製する工程と、前記活物質スラリーを前記表面が粗化された金属箔上に塗布する工程と、前記金属箔上の前記活物質スラリーを乾燥する工程とを有することを特徴とする非水電解質二次電池用電極の製造方法。 In the method for manufacturing an electrode for a non-aqueous electrolyte secondary battery including an active material, a binder, and a metal foil, a particle size of 10% cumulative and 50% cumulative from the fine particle side of the volume-based cumulative particle size distribution is D 10 , D 50 , the grain size (D 10 ) larger than the average roughening interval R sm obtained by the method defined as the average length of the contour curve element in JIS B0601-2001 of the roughened metal foil. An active material powder, a binder, and an active material slurry in which a PTC powder having a particle size (D 50 ) smaller than the average roughening interval R sm is dispersed in a solvent, and the active material A method for producing an electrode for a non-aqueous electrolyte secondary battery, comprising: applying a slurry onto the metal foil having a roughened surface; and drying the active material slurry on the metal foil. .
  7. 　請求項６に記載の非水電解質二次電池用電極の製造方法において、前記活物質としてリチウム含有遷移金属酸化物を含み、前記スラリー中に前記平均粗化間隔Ｒｓｍよりも粒径（Ｄ１０）が大きい前記炭素導電剤を含むことを特徴とする非水電解質二次電池用電極の製造方法。 The method for producing an electrode for a non-aqueous electrolyte secondary battery according to claim 6, wherein the active material contains a lithium-containing transition metal oxide, and the particle size (D 10) is larger than the average roughening interval R sm in the slurry. ) Containing a large amount of the carbon conductive agent. A method for producing an electrode for a non-aqueous electrolyte secondary battery.
  8. 　請求項６または請求項７に記載の非水電解質二次電池用電極の製造方法において、前記活物質としてリチウム含有遷移金属酸化物を含み、前記スラリー中に前記平均粗化間隔Ｒｓｍよりも粒径（Ｄ５０）が小さい炭素導電剤を含むことを特徴とする非水電解質二次電池用電極の製造方法。 The method for producing an electrode for a nonaqueous electrolyte secondary battery according to claim 6 or 7, wherein the active material contains a lithium-containing transition metal oxide, and the slurry has a grain size that is larger than the average roughening interval R sm. diameter (D 50) the production method of the nonaqueous electrolyte secondary battery, which comprises a small conductive carbon material.
  9. 　請求項６ないし請求項８のいずれか一項に記載の非水電解質二次電池用電極の製造方法において、前記スラリー中に前記平均粗化間隔Ｒｓｍよりも粒径（Ｄ５０）が小さい炭素導電剤と前記平均粗化間隔Ｒｓｍよりも粒径（Ｄ１０）が大きい炭素導電剤の２種類の前記炭素導電剤を含むことを特徴とする非水電解質二次電池用電極の製造方法。 The method of manufacturing a nonaqueous electrolyte secondary battery electrode according to any one of claims 6 to 8, wherein the average particle diameter than the roughened interval R sm (D 50) is smaller in said slurry carbon A method for producing an electrode for a non-aqueous electrolyte secondary battery, comprising two types of carbon conductive agents, a conductive agent and a carbon conductive agent having a particle diameter (D 10 ) larger than the average roughening interval R sm .
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