JP2009283275A - Current collecting foil for secondary battery, and method for manufacturing thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current collecting foil for a secondary battery in which peeling-off of a carbon thin film layer is suppressed. <P>SOLUTION: The current collecting foil A as the current collector of the secondary battery is equipped with a metal foil body 1 having conductivity and the carbon thin film layer 3 film-formed on the metal foil body 1. A metal intermediate layer 2 that is brought into close contact with each of the metal film body 1 and the carbon thin film layer 3 is formed between the metal foil body 1 and the carbon thin film layer 3. Preferably, the formation of the intermediate layer 2 is carried out by metal deposition using a metal material for deposition composed of a prescribed species of metal. Here, the metal deposition is carried out under a condition wherein an internal stress of the metal intermediate layer 2 consisting of the metal species acts as a tensile stress. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a current collector foil used as an electrode current collector that is a constituent element of an electrode body in a secondary battery such as a lithium ion battery, and a method for manufacturing the same.

  In recent years, lithium ion batteries, nickel metal hydride batteries, and other secondary batteries have become increasingly important as power sources for vehicles or as power sources for personal computers and portable terminals. In particular, a lithium secondary battery such as a lithium ion battery that is lightweight and has a high energy density is expected to be preferably used as a high-output power source mounted on a vehicle.

  In a lithium ion battery, charging / discharging is performed by exchanging lithium ions between a positive electrode made of a positive electrode active material and a negative electrode made of a negative electrode active material. In this type of secondary battery, typically, an electrode active material (electrode active material layer) made of a material that easily absorbs and releases lithium ions is held on the surface of an electrode current collector made of a conductive member ( Formed) electrode body. For example, a lithium composite oxide containing lithium and one or more metal elements is suitably used as a material for the positive electrode active material. Carbon-based materials such as graphite carbon and amorphous carbon are preferably used as the negative electrode active material. In addition, a sheet-like or foil-like member mainly composed of aluminum or aluminum alloy is preferably used as the positive electrode current collector, and a sheet-like or foil-like member mainly composed of copper or the like as the negative electrode current collector.

In manufacturing a lithium secondary battery including an electrode body having such a structure, a thin film layer is formed between the surface of the electrode current collector and the electrode active material layer, whereby the surface of the electrode current collector, the electrode active material, In some cases, the internal resistance of the battery is lowered by improving the electrical conductivity between the two. For example, Patent Document 1 describes a battery in which a carbon thin film layer is formed between a positive electrode current collector made of aluminum and a positive electrode active material layer for the purpose of improving conductivity. Patent documents 2 and 3 are mentioned as similar prior art.
Japanese Patent Laid-Open No. 11-250900 Japanese Patent Laid-Open No. 10-106585 JP 2002-352796 A

  When the electrode current collector is a foil-like current collector (current collector foil) composed of a metal foil such as aluminum or copper, a thin film layer such as carbon is formed on the surface for the purpose of improving conductivity, preventing corrosion, etc. In general, the coefficient of thermal expansion of the current collector material (metal) is larger than that of the thin film material (carbon). Therefore, when the thin film layer is formed (during film formation), the thermal stress is restored to room temperature. Occurs. As a result, the thin film layer is subjected to compressive stress, and wrinkles may occur in the current collector foil.

  Further, in a current collector foil made of, for example, an aluminum foil, if a carbon thin film layer is formed on the surface of the current collector foil, the adhesion between aluminum and carbon is low, and the carbon thin film layer may be peeled off from the aluminum foil. . In Patent Document 1, a coating layer (corresponding to a carbon thin film layer) is formed on the etched aluminum foil surface to improve the adhesion between them. However, in this method, it is possible to improve the adhesion at the time of producing the current collector foil. However, in an actual use environment, a defect portion such as a pinhole is likely to be generated in the carbon thin film layer. As a result, an aluminum oxide film is formed, and as a result, the coating layer may be peeled off.

  Therefore, the present invention has been made in view of the problems of the secondary battery current collector foil provided with the carbon thin film layer, and its main purpose is for a secondary battery in which peeling of the carbon thin film layer is suppressed. It is to provide a current collector foil. Another object is to provide a method for suitably producing such a current collector foil for a secondary battery. Moreover, the other objective is to provide secondary batteries, such as a lithium ion battery provided with the current collection foil for such secondary batteries.

  In order to achieve the above object, the present invention provides a current collector foil used as an electrode current collector of a secondary battery. The current collector foil for a secondary battery includes a conductive metal foil and a carbon thin film layer formed on the metal foil. And between the said metal foil body and the said carbon thin film layer, the metal intermediate | middle layer which adhere | attaches both this metal foil body and a carbon thin film layer is formed.

  In the current collector foil for a secondary battery having such a configuration, a metal intermediate layer that is in close contact with both the metal foil body and the carbon is formed between the metal foil body and the carbon thin film layer. For this reason, in the current collector foil for the secondary battery, the metal foil body and the carbon thin film layer are kept in close contact with each other via the metal intermediate layer, and the peeling of the carbon thin film layer from the metal foil body is suppressed. Can be done. Thereby, by using the secondary battery current collector foil of this configuration, it is possible to provide a highly durable lithium ion battery or other secondary battery that maintains good battery performance over a long period of time.

  One form of the secondary battery current collector foil to which the present invention can be suitably applied is a current collector foil used as a positive electrode current collector of a lithium ion battery. That is, in a preferred embodiment of the positive electrode current collector foil according to the present invention, the metal intermediate layer is composed of a metal species that does not dissolve under the positive electrode potential when the lithium ion battery is charged. The metal species is one or more selected from the group consisting of Ti (titanium), Nb (niobium), Ta (tantalum), Zr (zirconium), Hf (hafnium), and W (tungsten). It is particularly preferred that

  The positive electrode of a lithium ion battery is anodicly polarized during charging (potential applied to the electrode in the positive direction so that an oxidation reaction takes place) to become a high potential, and is cathode-polarized during discharging (to the electrode so that a reduction reaction takes place). When the potential is applied in the negative direction, the potential becomes low. For example, the electrode potential (positive electrode potential) of the positive electrode containing lithium cobaltate as the positive electrode active material can fall within a range of 2.5 V to 4.5 V with reference to metal lithium through a charge / discharge cycle. Thus, when exposed to a high potential environment exceeding 4 V on the basis of lithium, some metals may corrode and be eluted into the electrolyte.

  The metal species constituting the metal intermediate layer (preferably one or more selected from the group consisting of Ti, Nb, Ta, Zr, Hf, and W) are excellent in corrosion resistance. Even when the metal species are in contact with the electrolyte and exposed to the positive electrode potential during charging, the metal species are not easily ionized and do not dissolve. Therefore, for example, when a lithium ion battery using such a positive electrode current collector foil is used and a defective portion is generated in the carbon thin film layer formed on the surface of the positive electrode current collector foil, the metal species is contained in the electrolyte solution. And the metal foil covered with the metal intermediate layer made of the metal species can avoid contact with the electrolytic solution. As a result, there is no possibility that the metal foil is eluted (corroded) into the electrolytic solution and the battery performance is lowered, and a highly reliable (or highly durable) battery can be constructed.

  One of the other forms of the secondary battery current collector foil to which the present invention can be suitably applied is a current collector foil used as a negative electrode current collector of a lithium ion battery. In a preferred embodiment of the negative electrode current collector foil according to the present invention, the metal intermediate layer is alloyed with a metal species that does not dissolve under a negative electrode potential during discharge of a lithium ion battery, or with lithium under a negative electrode potential during charging. It consists of metal species that do not. The metal species is preferably Cu and / or Ni.

  The negative electrode of a lithium ion battery is anodicly polarized during discharge to become a high potential, and is negatively polarized during charging to a low potential. For example, the electrode potential (negative electrode potential) of a negative electrode containing carbon (graphite) as a negative electrode active material can be within a range of 0 V to 3.0 V with respect to metallic lithium through a charge / discharge cycle. If the negative electrode potential rises during discharge of the secondary battery, depending on the metal, there is a risk of corrosion and elution into the electrolyte. On the other hand, when the negative electrode potential decreases during charging, there is a possibility that some metals may be alloyed with reduced metallic lithium.

  The metal species constituting the metal intermediate layer (preferably Cu and / or Ni) are not easily ionized even when exposed to the negative electrode potential during discharge in contact with the electrolytic solution, and do not elute into the electrolytic solution. . For this reason, when a lithium ion battery using such a negative electrode current collector foil is used and a defective portion is generated in the carbon thin film layer formed on the surface of the negative electrode current collector foil, the metal species is contained in the electrolyte. The metal foil body which does not elute and is covered with the metal intermediate layer made of the metal species can escape contact with the electrolytic solution. As a result, the possibility that the metal intermediate layer and / or the metal foil body may elute into the electrolyte solution and the battery performance is deteriorated can be eliminated. Further, even when the negative electrode current collector foil is exposed to the negative electrode potential during charging in a state where it is in contact with the electrolytic solution, the metal species of the metal intermediate layer is, for example, metallic lithium reduced at a defective portion of the carbon thin film layer. Reacts with and does not alloy. As a result, there is no possibility that the lithium ion exchanged between the positive and negative electrodes decreases and the battery performance deteriorates, and a highly reliable (or highly durable) battery can be constructed.

  According to this invention, the secondary battery provided with the electrode body which consists of one of the current collector foils for secondary batteries disclosed here is provided. Since such a secondary battery includes the electrode body having the above-described effects as at least one electrode, the carbon thin film layer may be peeled off from the current collector foil, or the metal intermediate layer or the metal foil body may be dissolved. However, it can maintain good battery performance over a long period of time.

  Such a secondary battery is suitable as a battery mounted on a vehicle such as an automobile. That is, the present invention provides a vehicle including the secondary battery disclosed herein (including an assembled battery to which a plurality of secondary batteries are connected). In particular, such a secondary battery is a lithium secondary battery (typically a lithium ion battery) that is lightweight and has a high energy density, and is used as a power source (typically a hybrid vehicle or an electric vehicle). A vehicle (for example, an automobile) provided as a power source of the vehicle is preferable.

  Moreover, this invention provides the method of manufacturing the current collection foil used as an electrode electrical power collector of a secondary battery in order to implement | achieve the said objective. This manufacturing method includes preparing a metal foil body having conductivity, forming a metal intermediate layer made of a metal in close contact with both the metal foil body and a thin film made of carbon on the surface of the metal foil body, And forming a carbon thin film layer on the surface of the metal intermediate layer.

  In the secondary battery current collector foil obtained by such a manufacturing method, the metal foil body and the carbon thin film layer are in close contact with each other through the metal intermediate layer, and the carbon thin film layer peels off from the metal foil body. Can be suppressed. Moreover, the secondary battery provided with the electrode body made of the current collector foil for the secondary battery dissolves the metal species and / or the metal foil body constituting the metal intermediate layer when used (charge / discharge). Thus, elution into the electrolytic solution or alloying with metallic lithium is prevented, so that good battery performance can be maintained. That is, the present invention provides a method for producing a high-performance, high-durability secondary battery (lithium ion battery or the like), characterized by using the current collector foil obtained by the production method of the present invention. The

  In a preferred embodiment of the current collector foil manufacturing method disclosed herein, the metal intermediate layer is formed by metal vapor deposition using a metal material for vapor deposition made of a predetermined metal species, wherein the metal vapor deposition is It implements on the conditions from which the internal stress of the said metal intermediate layer formed from this metal seed | species becomes a tensile stress.

  According to this method, a metal intermediate layer of a predetermined metal type is formed with a uniform thickness on the surface of the metal foil body by metal deposition (film formation), and the internal stress of the formed metal intermediate layer is reduced. Even if the carbon thin film layer formed on the surface of the metal intermediate layer has a compressive stress by performing the film formation under the condition of tensile stress, the compressive stress is It is relieved by the tensile stress it has. As a result, the internal stress received as a whole of the current collector foil is offset, and wrinkles and the like can be prevented from occurring in the current collector foil.

  Preferably, the metal vapor deposition is performed by sputtering vapor deposition, and the sputtering gas pressure is set so that the internal stress of the metal intermediate layer to be formed becomes a tensile stress. In sputter deposition, typically, a deposition metal material made of a desired metal species for forming a thin film in a vacuum chamber is set as a target, and an ionized rare gas element (typically argon) is used as a target. In this method, the target atoms struck from the target surface and deposited on the substrate are deposited. This method is capable of (i). The target atom has a large energy, (ii). It is possible to produce a film with a strong adhesion (adhesion) to the substrate, (iii). Comparison with high melting point materials The film can be formed easily, and (iv) has an advantage that the film thickness can be controlled only by adjusting the execution time. Further, in such sputter deposition, the internal stress of the metal intermediate layer can be adjusted only by changing the gas pressure condition of the rare gas element (sputter gas), and the internal stress can be easily adjusted to the tensile stress.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification, and matters necessary for carrying out the present invention (for example, a method for producing an electrode active material, a method for preparing a paste-like composition containing an electrode active material, General techniques relating to the construction of lithium secondary batteries and other batteries, etc.) can be understood as design matters for those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

  The secondary battery current collector foil disclosed herein includes a conductive metal foil body, a carbon thin film layer formed on the metal foil body, and the metal foil body and the carbon thin film layer. And a metal intermediate layer formed on the substrate. The metal foil may be a metal material that is usually used as an electrode current collector in a conventional secondary battery, that is, a metal material having good conductivity (for example, aluminum, nickel, copper, iron, or these It is possible to preferably use an alloy made of an alloy containing as a main component. The secondary battery current collector foil disclosed herein can be used as either a positive electrode or a negative electrode current collector by selecting the metal foil body. Moreover, the electrode body which consists of the said collector foil for secondary batteries can be preferably utilized as an electrode with which a secondary battery (for example, lithium secondary battery) of various forms is equipped. As a preferred embodiment of the secondary battery constructed using the electrode comprising the current collector foil for the secondary battery according to the present invention, a secondary battery (for example, a lithium secondary battery) having a wound electrode body can be mentioned. . In this embodiment, a metal foil body made of aluminum (aluminum or an alloy containing aluminum as a main component) is used as a positive electrode metal foil body, and a metal foil body made of copper (copper or an alloy containing copper as a main component) is used as a negative electrode. A positive electrode current collector foil or a negative electrode current collector foil obtained by providing a metal foil body for use and providing a metal intermediate layer and a carbon thin film layer on each metal foil body can be preferably used.

  Hereinafter, although not intended to be particularly limited, each of the collections for a positive electrode body and a negative electrode body of a lithium secondary battery (typically a lithium ion battery) mainly using a metal foil body made of aluminum and copper. The present invention will be described in detail by taking the case of manufacturing an electric foil as an example. FIG. 1 is a cross-sectional view showing a laminated structure of the secondary battery current collector foil A according to an embodiment. FIG. 2 is a longitudinal sectional view showing the structure of the lithium ion battery 100 according to one embodiment. FIG. 3 is a side view schematically showing an example of a vehicle (automobile) provided with the lithium ion battery 100.

  In the method for producing a current collector foil for a lithium ion battery disclosed herein, first, as a metal foil body serving as a conductive base material, for example, a metal foil body made of aluminum having a thickness of about 10 μm to 30 μm (here, an aluminum foil) And copper (copper foil here) is prepared. An aluminum metal foil is preferably used as a component of the positive electrode current collector foil, and a copper metal foil is preferably used as a component of the negative electrode current collector foil.

  Next, a metal intermediate layer made of a predetermined metal species is formed on each of the metal foil bodies.

  Preferred metal species for the metal intermediate layer formed on the surface of the aluminum metal foil are both good affinity with the metal foil and affinity with carbon, and are strong with both the metal foil and carbon. It is a metal species that has the property of being able to adhere to. In the positive electrode current collector foil, preferred metal species for the metal intermediate layer formed on the surface of the aluminum metal foil include titanium group transition metals such as Ti, Zr, and Hf. Other preferred metal species include vanadium group transition metals such as Nb and Ta. Or W is mentioned as another preferable metal seed | species. In addition to the above properties, these metal species have a property (corrosion resistance to the electrolyte) that does not dissolve even when placed under a positive electrode potential during charging of a lithium ion battery (even when exposed to the electrolyte under the potential). Since it has, it is preferable. This corrosion resistance is such that, for example, it does not dissolve in the electrolyte even under a positive electrode potential containing lithium cobaltate as a positive electrode active material (for example, in the range of 2.5 V to 4.5 V with respect to metal lithium per charge / discharge cycle). Refers to nature.

  On the other hand, a preferable metal species for the metal intermediate layer formed on the surface of the copper metal foil is Cu and / or Ni. In addition to the high adhesion described above, these metal species do not dissolve under the negative electrode potential during lithium ion battery discharge (corrosion resistance to the electrolyte), or alloy with lithium under the negative electrode potential during charging. It is preferable because it has a property that does not. That is, these metal species can be dissolved or alloyed even under a negative electrode potential (range of 0 V to 3.0 V with reference to metal lithium per charge / discharge cycle) containing carbon (graphite) as a negative electrode active material. It has a chemically stable property to the extent that it does not.

  As a method for forming such a metal intermediate layer on the surface of the metal foil body, a known metal vapor deposition method, for example, physical vapor deposition method (PVD method, for example, sputtering (sputter deposition) method), chemical vapor deposition method (CVD method, for example, plasma). CVD method) and the like can be preferably employed. In particular, a vapor deposition method by a sputtering method is preferable. The sputter deposition method is a rare gas element (sputtering) that is ionized and accelerated by applying a high voltage to discharge a metal material for deposition made of a predetermined metal species to be applied as a thin film in a vacuum chamber. Target atoms are knocked out by striking the target with a gas, typically argon), or by directly sputtering gas ions with the target with an ion gun, and the target atoms knocked out from the target surface This is a method of forming a thin film by depositing on the substrate. Examples of the sputtering deposition method include direct current sputtering, high-frequency sputtering, magnetron sputtering, ion beam sputtering, and the like depending on the method of ionizing the sputtering gas. In the current collector foil for the secondary battery according to the present invention, any of the above sputtering deposition methods may be used.For example, the magnetron sputtering method is advantageous in that the gas pressure of the sputtering gas can be controlled over a wide range. Preferably employed. In addition, formation of the metal intermediate | middle layer by such a vapor deposition method is implemented by using the general commercial vacuum vapor deposition apparatus of a batch processing system or a continuous processing system. In addition, such a vacuum deposition apparatus may be equipped with a function capable of performing an accompanying process such as an ashing process in the same vacuum chamber. In this case, it is preferable because, for example, an ashing process using argon or the like can be performed on the surface of the metal foil body before sputtering deposition. This is because an ashing treatment for about 1 to 5 minutes is effective in cleaning the rolling oil and the like adhering to the surface of the aluminum metal foil.

  The internal stress of the metal intermediate layer (sputtered thin film layer) formed by the sputtering deposition method is greatly affected by sputtering conditions, particularly sputtering gas pressure conditions and film thickness. Therefore, in order to form the metal intermediate layer with a predetermined film thickness, the internal stress may be controlled by adjusting the sputtering gas pressure condition. The sputtering gas pressure threshold varies depending on the target metal species, but when forming a film with a constant film thickness, typically argon gas is used as the sputtering gas, this sputtering gas pressure is a certain value (threshold). When it raises above, the internal stress of the sputtered thin film formed tends to become a tensile stress. This tendency is considered to be because if the sputtering gas pressure is high, the target particles (ions) are likely to be greatly scattered due to an increase in the frequency (probability) of collision with the sputtering gas particles (ions), and the oblique incident component on the substrate increases. It has been. On the contrary, when the sputtering gas pressure is lowered, the internal stress tends to be a compressive stress. This tendency is that if the sputtering gas pressure is low, the average free path of the target particles (ions) becomes longer, and the particles that reach the base material (metal foil body) contain more target particles with higher energy. This is thought to be because the target particles enter the sputtered thin film to form a dense film.

  As such sputtering gas pressure conditions, for example, when forming a metal intermediate layer made of Ti having a film thickness of about 50 nm to 300 nm on an aluminum metal foil body using argon gas (Ar gas) as a sputtering gas, the film formation rate If the sputtering gas pressure (Ar gas pressure) is 0.3 Pa or higher (particularly preferably 0.5 Pa or higher), the film temperature is returned to room temperature. A preferable metal intermediate layer is formed in which the internal stress is tensile stress. When the Nb metal intermediate layer is formed under the same conditions, a preferable sputtering gas pressure is 1.0 Pa or more (particularly preferably 1.06 Pa or more). Similarly, a preferable sputtering gas pressure when forming the Ta metal intermediate layer is 3.0 Pa or more. Further, the sputtering gas pressure is 0.80 Pa or more (particularly preferably 1.0 Pa or more) in the Zr metal intermediate layer, the sputtering gas pressure is 0.8 Pa or more in the Hf metal intermediate layer, and 2. in the W metal intermediate layer. A sputtering gas pressure of 0 Pa or higher is preferable.

  Further, when a Cu (copper) metal intermediate layer is formed on a copper metal foil within a range of a film thickness of 50 nm to 300 nm by a sputter deposition method, a preferable sputtering gas pressure condition is that the sputtering gas is Ar gas, When the film formation rate is 0.1 nm / s to 10 nm / s, it is 0.25 Pa or more. Under this sputtering gas pressure condition, a preferable metal intermediate layer having a tensile stress when returned to room temperature can be formed.

  Further, when the Ni metal intermediate layer is formed under the same conditions, a sputtering gas pressure of 0.25 Pa or more is preferable.

  From the above, when a metal intermediate layer made of a predetermined metal species is formed by sputtering deposition on an aluminum metal foil or a copper metal foil, argon is used depending on the desired film thickness and the metal species. The sputtering gas pressure condition of a rare gas such as a gas is adjusted, and the internal stress of the metal intermediate layer is controlled to be inclined from the compressive stress to the tensile stress.

  The thickness of the metal intermediate layer formed in this way is not less than a thickness that can uniformly cover the predetermined range of the metal foil body, and is formed on the metal intermediate layer (deposited). According to the thickness of the carbon thin film layer, the thickness is preferably a thickness that can maintain a tensile stress that can sufficiently relax the compressive stress of the carbon thin film layer. For example, when the thickness of the carbon thin film layer is about 30 nm to 100 nm, the preferable thickness of the metal intermediate layer is 10 nm to 100 nm.

  Further, the range (region) where the metal intermediate layer is formed on the surface of the metal foil body is the region where the carbon thin film layer is to be formed, that is, the active material layer containing an electrode active material described later is the metal foil. It is preferable to set so as to at least include a region to be formed (applied) on the body (the surface of the current collector foil). For example, when the active material layer is formed only on one side of the metal foil (a part or the whole of the one side), the metal intermediate layer is preferably formed on the entire side of the one side. On the other hand, when the active material is formed on both surfaces of the metal foil (a part or the entire surface of the both surfaces), the metal intermediate layer is preferably formed over the entire surface of the both surfaces. As described above, a metal foil body having a metal intermediate layer having a predetermined thickness is obtained in this way.

  Next, the carbon thin film layer formed on the surface of the metal intermediate layer will be described. The carbon thin film layer is preferably a carbon thin film containing substantially no organic component, and a carbon thin film consisting essentially of carbon is particularly preferred. The structure of such a carbon thin film is not particularly limited, and may be, for example, amorphous, graphite, or a structure in which these are mixed.

  As a method for forming such a carbon thin film layer on the surface of the metal intermediate layer, similarly to the method for forming the metal intermediate layer, a known vapor deposition method, for example, a physical vapor deposition method such as sputter vapor deposition, or a chemical such as plasma CVD. A vapor deposition method can be preferably employed. Here, when the carbon thin film layer is formed by sputtering deposition using carbon as a target, it is performed in an atmosphere of a sputtering gas (typically argon) in a reduced pressure of about 0.01 Pa to 100 Pa. It is preferably 0.01 to 1.0 Pa. The carbon thin film layer deposited at such a low sputtering gas pressure can take a dense film structure. However, the carbon thin film layer deposited under the sputtering gas pressure condition receives a compressive stress as an internal stress when the film forming temperature (deposition temperature) is returned to room temperature.

  The thickness of the carbon thin film layer may be a thickness that can uniformly cover the metal foil body on which the metal intermediate layer is formed, and may be in the range of 5 nm to 2000 nm. Usually, the thickness of the carbon film is preferably about 50 nm to 100 nm. The thickness of the carbon thin film layer can be arbitrarily controlled by adjusting vapor deposition conditions such as vapor deposition time.

  Further, the region on the surface of the metal intermediate layer where the carbon thin film layer is formed includes at least a region where the active material layer containing the electrode active material is formed as described above, and the region formed on the surface of the metal foil body. It is preferable not to exceed the region of the metal intermediate layer.

  As an example of such a manufacturing method, argon ashing is performed on an aluminum metal foil body under a reduced pressure condition (vacuum degree) of 0.3 Pa, an applied voltage of 600 V, an arc current of 60 A, and a vacuum chamber temperature of 150 ° C. for 3 minutes. Processing was carried out. Thereafter, the surface of the metal foil body is changed to Ti with a vacuum degree of 0.67 Pa, sputtering gas is argon gas, sputter deposition is performed for 30 minutes under the discharge conditions and the temperature in the vacuum chamber (film formation temperature). A metal intermediate layer of 100 nm was formed thereon. Next, a carbon thin film having a thickness of 70 nm is formed on the surface of the metal intermediate layer by performing sputter deposition for 3 minutes under a vacuum of 0.3 Pa, the sputter gas, the discharge conditions, and the film formation temperature. A layer was formed.

  The secondary battery current collector foil A manufactured by such a manufacturing method has a laminated structure as shown in FIG. FIG. 1 is a view showing an aspect in which a metal intermediate layer 2 and a carbon thin film layer 3 are sequentially laminated on one side surface of a metal foil body 1. In the secondary battery current collector foil A, the metal foil body 1 and the carbon thin film layer 3 are strongly adhered to each other through the metal intermediate layer 2 formed between the metal foil body 1 and the carbon thin film layer 3. is doing. For this reason, peeling from the metal foil body 1 of the carbon thin film layer 3 can be suppressed.

  Further, the internal stress of the carbon thin film layer 3 generated when the film is cooled from the film forming temperature to room temperature is a compressive stress, but the internal stress of the metal intermediate layer 2 generated in the same process is canceled out because it is a tensile stress. The compressive stress of the carbon thin film layer 3 is relaxed. As a result, generation of wrinkles in the metal foil body 1 due to the compressive stress can be prevented, and deterioration of battery performance accompanying generation of wrinkles can be prevented.

  The carbon thin film layer 3 is formed on the surface of the metal intermediate layer 2 in a region that does not deviate from the region of the metal intermediate layer 2 formed on the metal foil body 1. In addition, the metal species constituting the metal intermediate layer 2 is chemically inactive even if it is exposed to a charge / discharge reaction of a lithium ion battery and does not dissolve in the electrolyte or alloy with metal lithium. It is. For this reason, even if a defect occurs in the carbon thin film layer 3, it is possible to avoid the metal foil body 1 from coming into contact with the electrolytic solution by the metal intermediate layer 2 existing immediately below. As a result, it is possible to prevent a decrease in battery performance due to dissolution or deterioration of the metal intermediate layer and / or the metal foil body.

  Next, a construction (assembly) method of the lithium ion battery 100 will be described with reference to FIG. The construction method of the lithium ion battery 100 may be the same as the conventional construction method, and is not particularly limited. An example is shown below.

The electrode body 10 has a positive electrode active material on the surface of the current collector foil A for secondary batteries (hereinafter simply referred to as “positive electrode current collector foil A ₁ ”) using an aluminum metal foil body 1 (see FIG. 1). The above-described secondary battery current collector foil A (hereinafter simply referred to as “negative electrode current collector foil A”) using a positive electrode sheet 11 having a layer, a long sheet-like separator (not shown), and a copper metal foil 1. ₂ ”)) and a negative electrode sheet 12 having a negative electrode active material layer on the surface thereof.

Positive electrode collector foil A ₁ positive electrode sheet 11 positive electrode active material layer is formed on, and the negative electrode current collector foil A ₂ negative electrode sheet 12 on which the anode active material layer formed on the laminated while sandwiching between the sheet-like separator The electrode body 10 is manufactured by superimposing and winding this around the shaft core 13. In each of the positive electrode sheet 11 and the negative electrode sheet 12, the active material layer is not applied to one end portion (that is, one end portion in the width direction of the sheet) along the winding direction. The foils A ₁ and A ₂ are exposed. The exposed portions are wound so as to be opposed to both ends of the wound electrode body 10 in the axial direction.

As the positive electrode active material, one type or two or more types of materials conventionally used in lithium ion batteries can be used without any particular limitation. Preferable examples include lithium transition metal oxides such as LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ . Further, a lithium composite oxide in which a part of the transition metal in these lithium transition metal oxides is substituted with at least one other metal element may be used. In addition to the lithium oxide, the positive electrode active material includes a conductive material (for example, acetylene black) for improving electronic conductivity, a binder such as polytetrafluoroethylene and carboxymethylcellulose as a binder or thickener. included. To these mixtures, a solvent or water is added as a solvent and kneaded to prepare a paste. The resulting positive electrode paste was uniformly applied to the surface of the carbon thin film layer 3 of the positive electrode current collector foil A ₁ is formed, drying the coating material in a suitable drying means. After drying, an appropriate press treatment may be performed as necessary to appropriately adjust the thickness and density of the positive electrode active material layer. In this way, the positive electrode sheet 11 having the positive electrode active material layer is produced.

On the other hand, the negative electrode sheet 12, in the same manner as the positive electrode sheet 11, the negative electrode active material was prepared into a paste, the negative electrode paste obtained on the surface of the carbon thin film layer 3 of the negative electrode collector foil A ₂ is formed A negative electrode sheet 12 having a negative electrode active material layer is prepared by uniformly applying and drying. As the negative electrode active material, one or two materials conventionally used in lithium ion batteries can be used without particular limitation. Examples thereof include carbon-based materials such as graphite carbon and amorphous carbon, lithium transition metal oxides, lithium transition metal nitrides, and the like, and carbon-based materials are particularly preferable. The negative electrode active material includes a binder such as styrene butadiene rubber and carboxymethyl cellulose in addition to the main components such as the carbon-based material. These mixtures are also prepared in the negative electrode paste by adding a solvent or water.

  Suitable sheet-like separators used between the positive and negative electrode sheets 11 and 12 include those made of a porous polyolefin resin. When a solid electrolyte or a gel electrolyte is used as the electrolyte, a separator may not be necessary (that is, in this case, the electrolyte itself can function as a separator).

  When the shaft core 13 is used, for example, various polymer materials exhibiting resistance to the electrolyte to be used may be selected as appropriate.

Attaching a positive electrode current collector foil A ₁ and the positive electrode current collector terminal 40 exposed at one axial end of the electrode body 10 (joined). Further, the exposed negative electrode current collector foil A ₂ and the negative electrode current collector terminal 50 at the other end of the electrode body 10 are attached (joined). As a joining method, for example, various welding methods such as an ultrasonic welding method are suitably employed. For example, each end of the electrode body 10 in the axial direction is sandwiched between a horn and an anvil of a welding apparatus by a predetermined width, and ultrasonic welding is performed.

As the constituent material of the positive electrode current collector terminal 40 is preferably a positive electrode current collector foil A ₁ and the same kind of metal material (preferably aluminum). On the other hand, as the material of the negative electrode current collector terminal 50 is preferably a negative electrode current collector foil A ₂ and the same kind of metallic material (preferably copper).

  Next, the electrode body 10 in which the current collecting terminals 40 and 50 are attached to both ends in the axial direction is accommodated in the battery container 20 having at least one of the openings. In the lithium ion battery 100 shown in FIG. 2, the electrode body 10 is accommodated such that the axial direction is along the vertical direction so that the positive electrode current collecting terminal 40 protrudes from the opening 21.

Next, an electrolytic solution in which various lithium salts (for example, LiPF ₆ ) containing fluorine as a constituent element are dissolved in a nonaqueous solvent such as ethylene carbonate or diethyl carbonate is poured into the battery container 20.

  Finally, the opening 21 of the battery container 20 is closed with a lid 30 having a perforated center. The positive electrode current collector terminal 40 is inserted through the hole in the center of the lid body 30 and fixed from the upper surface of the lid body 30 with a nut 31. The peripheral edge of the opening 21 and the edge of the lid 30 are welded.

  The material of the battery container 20 and the lid 30 is not limited, but a metal material such as aluminum, stainless steel, nickel-plated steel, etc., which is lightweight and has good thermal conductivity is preferable. Further, the shape of the battery container 20 may be any of a rectangular parallelepiped square shape (box shape), a cylindrical shape, and the like. In the case where the battery container 20 is rectangular, the electrode body 10 may be crushed from the side surface direction and stored in a flat shape. The battery container 20 of the lithium ion battery 100 shown in FIG. 2 is a closed-bottomed cylindrical body, and only the positive electrode current collecting terminal 40 protrudes from the battery container 20, but both ends are open. Then, a cylindrical battery in which the positive and negative current collecting terminals protrude from the respective opening end portions may be used.

  The lithium ion battery 100 is constructed as described above.

  Since a secondary battery (for example, a lithium ion battery) provided with the secondary battery current collector foil A according to the present invention can maintain good battery performance as described above, a motor (in particular, a motor mounted on a vehicle such as an automobile ( It can be suitably used as a power source for an electric motor. Therefore, as schematically shown in FIG. 3, the present invention provides a vehicle (typically an automobile, particularly a hybrid) including such a secondary battery (including an assembled battery to which a plurality of secondary batteries are connected) 100 as a power source. An automobile equipped with an electric motor such as an automobile, an electric automobile, and a fuel cell automobile) C is provided.

It is typical sectional drawing which shows the laminated structure of the collector foil A for secondary batteries which concerns on one Embodiment. It is a longitudinal cross-sectional view which shows typically the structure of the lithium secondary battery 100 which concerns on one Embodiment. It is a side view which shows typically an example of the vehicle (automobile) provided with the secondary battery which concerns on this invention.

Explanation of symbols

A Current collecting foil for secondary battery A ₁ Positive current collecting foil A ₂ Negative current collecting foil C Vehicle (automobile)
DESCRIPTION OF SYMBOLS 1 Metal foil body 2 Metal intermediate layer 3 Carbon thin film layer 10 Electrode body 11 Positive electrode sheet 12 Negative electrode sheet 20 Battery container 40 Positive electrode current collection terminal 50 Negative electrode current collection terminal 100 Lithium ion battery (secondary battery)

Claims (10)

A current collector foil used as an electrode current collector of a secondary battery,
A conductive metal foil and a carbon thin film layer formed on the metal foil;
A current collector foil for a secondary battery, wherein a metal intermediate layer is formed between the metal foil body and the carbon thin film layer so as to be in close contact with both the metal foil body and the carbon thin film layer.   2. The secondary battery current collector according to claim 1, wherein the metal intermediate layer is used as a positive electrode current collector of a lithium ion battery, which is made of a metal species that does not dissolve under a positive electrode potential during charging of the lithium ion battery. Electric foil.   The current collector foil for a secondary battery according to claim 2, wherein the metal species is one or more selected from the group consisting of Ti, Nb, Ta, Zr, Hf, and W.   The metal intermediate layer is composed of a metal species that does not dissolve under a negative electrode potential during discharge of a lithium ion battery, or a metal species that does not alloy with lithium under a negative electrode potential during charging. The current collector foil for a secondary battery according to claim 1, which is used as a current collector.   The current collector foil for a secondary battery according to claim 4, wherein the metal species is Cu and / or Ni.   A secondary battery comprising the secondary battery current collector foil according to claim 1.   A vehicle comprising the secondary battery according to claim 6. A method for producing a current collector foil used as an electrode current collector of a secondary battery, comprising:
Preparing a conductive metal foil;
Forming on the surface of the metal foil body a metal intermediate layer made of metal that is in close contact with both the metal foil body and the thin film made of carbon; and forming a carbon thin film layer on the surface of the metal intermediate layer;
A method for producing a current collector foil for a secondary battery.   The formation of the metal intermediate layer is performed by metal vapor deposition using a metal material for vapor deposition made of a predetermined metal species, where the internal stress of the metal intermediate layer formed from the metal species is tensile. The manufacturing method of Claim 8 implemented on the conditions used as stress.   The manufacturing method according to claim 9, wherein the metal deposition is performed by sputter deposition, wherein the sputtering gas pressure is set so that an internal stress of the formed metal intermediate layer becomes a tensile stress.

Images