JP2014060015A - Collector for secondary battery, method for manufacturing the same, and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a collector for a secondary battery, having a plating layer on a surface thereof, made of a resin, and capable of improving adhesion between a base material and the plating layer; a method for manufacturing the collector; and a secondary battery.SOLUTION: A collector for a secondary battery includes: a base material having a plurality of fine spaces inside thereof, having a structure where the fine spaces are communicated to be connected to the outermost surface, and made of a resin; a catalyst part formed after a surface of the base material including an internal surface of the fine spaces has been modified, and including Pd or Ag; and a plating layer formed on a surface of the catalyst layer and including Cu or Ni.

Description

  The present invention relates to a current collector for a secondary battery, a manufacturing method thereof, and a secondary battery.

  Secondary batteries are batteries that can be repeatedly charged and discharged, and lead storage batteries, lithium ion secondary batteries, nickel metal hydride storage batteries, nickel cadmium storage batteries, sodium sulfur batteries, redox flow batteries, and the like are known.

  In recent years, lithium ion secondary batteries are well known as secondary batteries. A lithium ion secondary battery is a secondary battery having a high charge / discharge capacity and capable of high output. Lithium ion secondary batteries are mainly used as power sources for portable electronic devices, and are expected to be used as power sources for electric vehicles that are expected to become popular in the future.

  In the lithium ion secondary battery, a lithium-containing metal composite oxide such as lithium cobalt composite oxide is mainly used as a positive electrode active material, and a carbon material is mainly used as a negative electrode active material. The positive and negative electrode plates are prepared by dispersing the active material, binder resin, and conductive additive in a solvent to form a slurry on a metal foil as a current collector. After forming the agent layer, it is produced by compression molding with a roll press.

  Since the current collector itself needs to have conductivity, metal foils such as copper and aluminum have been conventionally used as a current collector for lithium ion secondary batteries. In recent years, a reduction in the weight of the current collector has been studied for the purpose of reducing the weight of the battery.

  For example, in Patent Document 1, after conducting a conductive treatment on the surface of a resin film to form a conductive treatment layer having a resistance of 1.3 Ω / cm or less, a plating layer having a thickness of at least 0.3 μm or more per side is formed by electrolytic plating treatment. A secondary battery that has a resistance of an electrolytic plating layer of 40 mΩ / cm or less and further satisfies a formula that defines the relationship between the thickness and weight of a resin film, a conductive treatment layer, and a plating layer. Lightweight current collectors have been proposed.

  Patent Document 2 proposes a current collector for an alkaline battery, which is a three-dimensional nickel porous body in which the current collector is nickel-plated on a nonwoven fabric made of alkali-resistant fibers. Nickel plating is applied to a nonwoven fabric using an electrolytic plating method after imparting conductivity to the nonwoven fabric using at least one of a sputtering method and an electroless plating method.

  However, the adhesive force between the plating layer and the resin film or nonwoven fabric is weak when the electroplating treatment is performed after forming the conductive treatment layer on the surface of the resin film or nonwoven fabric as the current collector. Therefore, the plating layer and resin may be peeled off from the resin film or non-woven fabric during the battery charge / discharge cycle, or when the current collector is largely deformed during the battery manufacturing process. There is a risk that the film or the non-woven fabric will peel off.

Japanese Patent Laid-Open No. 2003-3224 JP 2008-117579 A

  The present invention has been made in view of such circumstances, and a secondary battery current collector that can improve the cycle characteristics of the secondary battery by improving the adhesion between the substrate and the plating layer. It is an object to provide a body, a manufacturing method thereof, and a secondary battery.

  As a result of intensive studies by the present inventors, the catalyst part is formed after the surface of the resin base material is modified, and the plating layer is formed on the surface of the catalyst part, whereby the adhesion between the base material and the plating layer is achieved. It was found that can be improved significantly.

  That is, the current collector for the secondary battery according to the present invention has a resin base material having a structure in which a large number of fine spaces are formed in the interior and the fine spaces are connected to the outermost surface, and the inner surface of the fine space. It has a catalyst part containing Pd or Ag formed after the surface of the base material containing is modified, and a plating layer containing Cu or Ni formed on the surface of the catalyst part.

  It is preferable that resin which comprises the said base material consists of 1 type selected from the group which consists of polypropylene, polyethylene, these mixtures, and these copolymers.

  Moreover, it is preferable that a base material is one chosen from a single layer porous film, a laminated porous film, a woven fabric, and a nonwoven fabric.

  The modification is preferably performed by ozone treatment.

  The secondary battery of this invention contains the said collector for secondary batteries.

  The method for producing a current collector for a secondary battery according to the present invention provides a base material preparation for preparing a resin base material having a structure in which a large number of fine spaces are connected and the fine spaces are connected to the outermost surface. An ozone treatment step in which the surface of the substrate is treated with ozone to form an ozone treatment substrate, and a catalyst part containing Pd or Ag by contacting a metal compound solution containing Pd or Ag on the surface of the ozone treatment substrate. A catalyst part providing step to form a catalyst part providing base, and a surface of the catalyst part providing base is contacted with an electroless plating solution containing Cu or Ni to form a plating layer containing Cu or Ni to form a plating layer provision group And a plating process step as a material.

  The ozone treatment process includes a first ozone treatment process in which the surface of the base material is treated with a first ozone solution containing a polar solvent excluding water to form a first ozone treatment base material, and the surface of the first ozone treatment base material is water. It is preferable to have the 2nd ozone treatment process processed with the 2nd ozone solution containing this as a 2nd ozone treatment base material.

  In addition, after the ozone treatment step and before the catalyst portion applying step, the surface of the ozone treatment substrate or the second ozone treatment substrate is brought into contact with a solution containing at least an alkali component and / or a surfactant to clean the surface. It is preferable to further have a surface cleaning step.

  Moreover, it is preferable to further have the electroplating process process which performs electroplating on the surface of a plating layer provision base material and increases the thickness of a plating layer after a plating process process.

  Since the current collector for a secondary battery of the present invention uses a resin base material, it can be made lighter than that of a metal base material. Moreover, since the resin base material has a structure in which a large number of fine spaces are connected inside and the fine spaces are connected to the outermost surface, the active material can be carried in the fine space of the current collector. Since the active material can be supported in the fine space of the current collector, the ratio of the amount of the active material installed in the vicinity of the current collector in the total amount of the active material increases. For this reason, in the entire active material, the moving distance of electrons between the active material and the current collector is shortened, so that the supported active material can be effectively used.

  Further, by supporting the active material on the current collector having the above structure, more active material can be supported than when the foil is used for the current collector. In addition, the supported active material can be used effectively.

  In addition, since the active material is carried in the fine space of the current collector, even if the active material expands and contracts as the battery is repeatedly charged and discharged, the current collector suppresses the expansion and shrinkage of the active material, and It is possible to suppress the separated active material from peeling off from the current collector. Therefore, the secondary battery having the current collector has improved durability and a long life.

  Further, the current collector for the secondary battery according to the present invention forms the catalyst part after modifying the surface of the resin base material, and forms the plating layer on the surface of the catalyst part. And the adhesion between the plating layer can be greatly improved. Therefore, the plating layer is hardly peeled off from the base material even in the charge / discharge cycle of the battery, and the plating layer and the base material are not easily peeled off even when the current collector is largely deformed. Therefore, the secondary battery having the current collector has improved durability and a long life.

  Since the secondary battery of this invention has the said collector for secondary batteries, it can be set as the battery which has favorable cycling characteristics.

  According to the method for producing a current collector for a secondary battery of the present invention, a current collector for a secondary battery can be easily produced.

It is a schematic diagram which shows the place where the active material was carry | supported by the collector for secondary batteries of this embodiment. It is a schematic diagram of the porous film extended | stretched to the uniaxial direction. It is a schematic diagram of the porous film extended | stretched to the biaxial direction. It is a schematic diagram of the collector for secondary batteries of this embodiment. It is a schematic cross section which shows typically the base material before and after each process of the manufacturing method of the collector for secondary batteries of this embodiment. It is a graph which shows the discharge capacity maintenance factor for every cycle of the model battery of Example 1, Comparative Example 1, and Comparative Example 2.

<Current collector for secondary battery>
The current collector for a secondary battery of the present invention has a resin base material, a catalyst portion, and a plating layer.

  The resin-made base material has a structure in which a large number of fine spaces are formed therein, and the fine spaces are connected to the outermost surface. The fine space communicates with each other and is connected to the outermost surface of the substrate, and penetrates from one surface of the substrate to the other surface. Since the current collector has a fine space penetrating the front and back, the current collector is more conductively connected to the front and back of the current collector so that no potential distribution occurs on the front and back of the current collector. Uniformity can be maintained. For example, the substrate preferably has a network-like three-dimensional structure.

  Since the resin base material has a fine space, the active material can be supported in the fine space. FIG. 1 is a schematic view showing a state where an active material is supported on the secondary battery current collector of the present embodiment. FIG. 1 shows that the active material 2 is carried in a fine space of the current collector 1. Although FIG. 1 shows that only the active material 2 is carried on the current collector 1, a conductive auxiliary agent or a binder may be carried in the fine space of the current collector 1.

  As shown in FIG. 1, the active material 2 is supported in a fine space in the current collector 1, and the ratio of the amount of the active material 2 disposed in the vicinity of the current collector 1 to the total amount of the active material 2 is Increased compared to the case where foil is used for the current collector. Therefore, when the active material 2 as a whole is viewed, the moving distance of electrons between the active material 2 and the current collector 1 becomes shorter than when a foil is used for the current collector. The capacity can be used effectively.

  The resin constituting the substrate may be any resin that can withstand the environment in the secondary battery. Specifically, the resin constituting the base material is preferably a resin that is durable to a solvent used in a slurry or an electrolytic solution and is heat resistant to heat applied during electrode formation. For example, the resin constituting the substrate is preferably a polyolefin resin. In particular, since the durability to a solvent is excellent, the resin constituting the base material is preferably made of one kind selected from the group consisting of polypropylene, polyethylene, a mixture thereof, and a copolymer thereof. Examples of resins that can be used include polypropylene, polyethylene, polyethylene / polypropylene, polyethylene / polypropylene / polyethylene, and polypropylene / polyethylene / polypropylene.

  The substrate is preferably one selected from a single-layer porous film, a laminated porous film, a woven fabric, and a non-woven fabric.

  The porous film may be stretched and made porous, or may be unstretched and made porous. When the current collector is required to have high mechanical strength, it is preferable to use a stretched porous film that has been stretched and made porous. The stretched porous film is particularly preferable in that when the resin is bent, a resin cut portion or the like hardly appears on the bent surface, and when used as a current collector, the secondary battery is not easily short-circuited.

  The stretched porous film may be stretched in a uniaxial direction or may be stretched in a multiaxial direction. For example, FIG. 2 shows a schematic diagram of a porous film stretched in a uniaxial direction. FIG. 2 is a schematic diagram of a polyolefin porous film, grade UP3074 manufactured by Ube Industries, Ltd. Moreover, the schematic diagram of the porous film extended | stretched to the biaxial direction is shown in FIG. FIG. 3 is a schematic diagram of a polyethylene porous film, grade V20 CFD, manufactured by Toray Tonen Functional Film GK. These porous films may be a single layer or a laminate of a plurality of sheets.

  The woven or non-woven fabric may be formed into a woven or non-woven fabric after forming a plating layer on the fibers constituting the woven or non-woven fabric. It may be formed. In the process of producing the woven or non-woven fabric, the plating layer may be peeled off from the fiber. Therefore, the plating layer is preferably formed after being formed into a woven or non-woven fabric shape.

  In particular, a commercially available secondary battery separator can be used as the resin base material. The separator for the secondary battery can hold the electrolyte for the secondary battery, is electrically insulating, and has ion permeability. Since it is confirmed that the secondary battery separator can be used in the secondary battery, the safety is high.

  As a commercially available secondary battery separator, in addition to the above-mentioned polyolefin porous film made by Ube Industries, grade UP3074, Toray Tonen Functional Film GK, polyethylene porous film, grade V20 CFD, uniaxial stretching made by Ube Industries, Ltd. Grades UP3093, UP3085, UP3146, UP3138, and biaxially stretched grades V25CGD, V25EKD, V20EHD, P25CH1, F16CK1, F20BMU, CP1902, XP2301, and other products manufactured by Sumitomo Chemical Co., Ltd. Biaxially stretched grade S258-4 and Asahi Kasei's biaxially stretched grades H6022 and ND525 can be suitably used.

  The current collector preferably has a thickness of 5 μm to 20 μm. Since the current collector for a secondary battery of the present invention can carry an active material in the fine space of the base material, the thickness of the current collector can be equal to the thickness of the electrode. When the thickness of the current collector is less than 5 μm, the amount of the current collector is small with respect to the active material, the electric resistance increases, and it is preferable in that the output of the battery is lowered when assembled as a battery, and the mechanical strength. Is too low and difficult to handle. On the other hand, if the thickness of the current collector is larger than 20 μm, the amount of the current collector relative to the active material is too large, and the weight energy density and volume energy of the battery when assembled as a battery It is not preferable in that the density is lowered.

  The catalyst part is formed after the surface of the base material including the inner surface of the fine space is modified, and contains Pd or Ag. Hereinafter, what is called a surface includes the inner surface of a fine space.

  The surface of the resin substrate is modified to give a polar group to the surface. For example, molecular chains such as double bonds are cleaved on the surface, and polar groups such as OH groups, CO groups, and COOH groups are generated on the surface. The modification is preferably performed by ozone treatment. When modified by ozone treatment, polar groups are imparted to the surface and pores of nano-level or less are formed on the surface of the resin base material.

  In other words, a modified layer having polar groups and pores is formed on the surface of the resin base material by performing the ozone treatment in this way. This reforming layer is easily penetrated by a catalyst solution containing Pd or Ag, and the catalyst portion containing Pd or Ag is formed by biting into the reforming layer. Therefore, the adhesion between the resin base material and the catalyst portion containing Pd or Ag is improved.

  The ozone treatment may be performed by bringing the surface of the resin base material into contact with the ozone solution, or may be performed by bringing gaseous ozone into contact with the surface of the resin base material.

  When the catalyst portion contains Pd or Ag, a reaction active point is imparted, so that a plating layer containing Cu or Ni is easily formed.

  The catalyst part is an aggregate of catalyst particles. The catalyst part may form a layer by continuous catalyst particles.

  The thickness of the catalyst part is preferably 10 nm or more and 200 nm or less. At this time, the thickness of the catalyst portion refers to the approximate thickness of the aggregate of catalyst particles. When the aggregate of catalyst particles forms a layer, the thickness of the catalyst portion refers to the thickness of the layer. If the thickness of the catalyst part is greater than 200 nm, the resistance of the entire current collector increases, and the battery output decreases when a current collector with a catalyst part thickness greater than 200 nm is assembled as a battery. When the thickness of the catalyst portion is smaller than 10 nm, it is not preferable that the thickness is greater than 200 nm. If the thickness of the catalyst portion is smaller than 10 nm, the adhesion between the resin base material and the plating layer decreases, the conductivity of the current collector decreases, and the resistance increases. When the battery is assembled as a battery, the battery output decreases, so that the thickness of the catalyst portion is less than 10 nm.

  The thickness of the plating layer is preferably 0.3 μm or more and 10 μm or less. When the thickness of the plating layer is larger than 10 μm, the amount of the current collector relative to the active material increases, and when the current collector with the thickness of the plating layer larger than 10 μm is assembled as a battery, the weight energy density or volume energy density of the battery is reduced. Since it falls, it is not preferable that the thickness of the plating layer is thicker than 10 μm. On the other hand, if the thickness of the plating layer is greater than 10 μm, the residual stress at the time of plating increases, so that the plating layer is cracked and the current collector is torn and resistance is increased. When the thickness of the plating layer is smaller than 0.3 μm, the amount of the current collector relative to the active material is small and the electric resistance increases, and when the current collector with the thickness of the plating layer smaller than 0.3 μm is assembled as a battery, Since the output is lowered, it is not preferable that the thickness of the plating layer is smaller than 0.3 μm.

  The conductivity of the plating layer is improved by containing Cu or Ni. When the electroconductivity of the plating layer is improved, the electrical resistance of the current collector is lowered, the electrical conductivity of the current collector is improved, and the battery output is improved when the current collector is assembled as a battery.

  FIG. 4 is a schematic diagram of a current collector for a secondary battery according to this embodiment. As shown in FIG. 4, the base material 30 includes a modified layer 31 on the surface of the base material, and the catalyst portion 40 is formed in the modified layer 31. In FIG. 4, the catalyst unit 40 is described as an aggregate of circular particles, but the aggregate may form a layer. A plating layer 50 is formed on the surface of the catalyst unit 40. The plating layer 50 is formed using the catalyst contained in the catalyst unit 40 as a nucleus and has a nanoanchor 51. When the plating layer 50 has the nano anchors 51, the plating layer 50 is more strongly bonded to the base material 30.

<Secondary battery>
The secondary battery of this invention has the said collector for secondary batteries. If it is set as the secondary battery which has the said collector for secondary batteries, a secondary battery will show favorable cycling characteristics. Moreover, the current collector for a secondary battery of the present invention can be used by being filled with an active material at a high density. Therefore, when an electrode having the current collector for a secondary battery is provided, the electric capacity of the secondary battery can be increased.

  In the secondary battery of the present invention, an electrolyte and, if necessary, a separator may be used as a battery component in addition to the positive electrode or the negative electrode having the above-described current collector for a secondary battery.

  The positive electrode or the negative electrode has an active material, a binder, and optionally a conductive aid.

  The active material is supported on the current collector by impregnating the current collector in a slurry obtained by adding a solvent to the dispersion of the active material, the conductive additive, and the binder, or by applying the slurry to the current collector. Can be done. Further, since the current collector has a three-dimensional structure, the active material can be immobilized in the current collector without using or using a small amount of binder. As the solvent for adjusting the viscosity, N-methyl-2-pyrrolidone (NMP), methanol, methyl isobutyl ketone (MIBK) and the like can be used.

  The active material is preferably in the form of a powder. The average particle diameter of the powder is preferably 5 μm or more and 50 μm or less, depending on the intended secondary battery. The smaller the average particle size, the higher the density of the active material that can be filled in the current collector. The active material may be a composite powder composed of active material coarse particles having a large average particle diameter and active material fine particles having a small average particle diameter. In that case, if the volume ratio of the active material coarse particles to the active material fine particles is 1.5 to 4 and the average particle size ratio of the active material coarse particles to the active material fine particles is 10 to 15, the bulk density can be further improved. The inventor has confirmed. More desirably, the average particle diameter ratio of the active material coarse particles to the active material fine particles is 11 to 14, and the volume ratio is 2 to 3. Specifically speaking, the average particle diameter of the active material particles is preferably 5 μm to 50 μm and the average particle diameter of the active material fine particles is preferably 0.5 μm to 5 μm.

  In the case of a lithium ion secondary battery, a lithium-containing metal composite oxide such as a lithium cobalt composite oxide, a lithium nickel composite oxide, or a lithium manganese composite oxide is used as the positive electrode active material. As the negative electrode active material, a carbon-based material capable of inserting and extracting lithium, a metal capable of alloying lithium, or an oxide thereof is used.

  The conductive auxiliary agent is added to increase the conductivity when the active material is fixed to the current collector via the binder. Carbon black, graphite, acetylene black (AB), ketjen black (KB), vapor grown carbon fiber (Vapor Carbon Carbon Fiber: VGCF), etc., which are carbonaceous fine particles, are used alone or in combination of two or more as conductive aids. Can be added. The amount of the conductive auxiliary agent used is not particularly limited. For example, the conductive auxiliary agent can be about 2% by mass to 10% by mass with respect to 100% by mass of the active material contained in the electrode. Although not particularly limited, it is more preferably about 3% by mass to 5% by mass.

  The binder plays a role of tethering these active materials and conductive assistants to the current collector. The binder is required to bind the active material and the conductive assistant to the current collector in as little amount as possible, and the amount is 100% by mass of the total of the active material, the conductive assistant and the binder. The content is desirably 0.5% by mass to 10% by mass, and is not particularly limited, but is preferably about 3% by mass to 6% by mass.

  The binder is not particularly limited, and any known binder resin can be used. As the binder resin, for example, a fluorine-containing resin such as polyvinylidene fluoride, polytetrafluoroethylene or fluororubber, a thermoplastic resin such as polypropylene or polyethylene, an imide resin such as polyimide or polyamideimide, or an alkoxysilyl group-containing resin may be used. it can. Moreover, you may use the solvent which can disperse | distribute an active material, without using binder resin.

  The separator separates the positive electrode and the negative electrode and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. As the separator, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramics can be used.

  As the electrolyte, an organic solvent-based electrolyte obtained by dissolving an electrolyte in an organic solvent called a non-aqueous electrolyte, a solid electrolyte containing an electrolyte solution, or the like can be used.

  For example, cyclic esters, chain esters, and ethers can be used as the organic solvent. Examples of cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma butyrolactone, and gamma valerolactone. Examples of chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers that can be used include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane, and the like.

As the electrolyte dissolved in the organic solvent, for example, a lithium salt such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ can be used.

For example, as an electrolytic solution, 0.5 mol / l to 1.7 mol / l of a lithium salt such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO _{3 in} a solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, and dimethyl carbonate. A solution dissolved at a certain concentration can be used.

  As the solid electrolyte, a gel electrolyte containing an electrolyte solution can be used.

Examples of the gel electrolyte include lithium sulfide, silicon sulfide, phosphorus sulfide and a composite thereof, lithium nitride, lithium iodide, LiPON (Li ₃ PO _4−x N _x ), Li _4−x Si _x P _1−x O. ₄ (0 ≦ x ≦ 1), Li _x La _{2−x / 3} TiO ₃ (x = 0.1 to 0.5), Li _{7 + x} La ₃ Zr ₂ O _{12+ (x / 2)} (−5 ≦ x ≦ 3, preferably −2 ≦ x ≦ 2), Li _{1 + x + y} (Al, Ga) _x (Ti, Ge, Zr) _2−x Si _y P _3−y O ₁₂ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) ), Li ₂ O-5Al ₂ O ₃ , Li ₂ O-11Al ₂ O ₃ , Li ₅ La ₃ (Nb, Ta) ₂ O ₁₂ , Li ₁₄ ZnGe ₄ O ₁₆ , Li ₉ SiAlO _8, or the like can be used. .

  A separator is sandwiched between the positive electrode and the negative electrode to form an electrode body. It is preferable to connect the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal that communicate with the outside using a current collecting lead or the like and then combine the electrode body with an electrolyte to form a secondary battery.

  The shape of the secondary battery is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, and a laminate shape can be employed.

<Method for producing current collector for secondary battery>
The manufacturing method of the collector for secondary batteries of this invention has a base material preparation process, an ozone treatment process, a catalyst part provision process, and a plating treatment process.

  If the outline of the manufacturing method of the current collector for a secondary battery of the present invention is shown in the drawing, it can be considered as shown in FIG. FIG. 5 is a schematic cross-sectional view schematically showing a base material before and after each step of the method for producing a current collector for a secondary battery of the present invention. In FIG. 5, (a) represents the base material before the ozone treatment. As shown in (a), organic contaminants 60 are present on the surface of the substrate 30. When ozone treatment is performed on the surface of the base material, organic contaminants 60 are removed from the surface of the base material 30 as shown in (b), and a modified layer 31 is formed on the surface of the base material 30 as shown in (c). Is done. After the catalyst portion applying step, the catalyst portion 40 is formed so as to bite into the reformed layer 31 as shown in (d). After the plating process, a plating layer 50 is formed on the catalyst portion 40 as shown in FIG. Since the plating layer 50 is formed using the catalyst as a nucleus, the nano-anchor 51 is formed. Since it is predicted that a nano-level anchor effect will appear, it seems that the adhesion strength at the interface between the plating layer 50 and the substrate 30 is maintained high.

  In the base material preparation step, a resin base material having a structure in which a large number of fine spaces are formed inside and the fine spaces are connected to the outermost surface is prepared. The base material made of resin is the same as that described in the current collector for secondary battery.

  In the ozone treatment step, the surface of the substrate is subjected to ozone treatment to obtain an ozone treatment substrate. The ozone treatment may be performed by bringing the surface of the resin base material into contact with the ozone solution, or may be performed by bringing gaseous ozone into contact with the surface of the resin base material. The treatment with the ozone solution includes a method of immersing the substrate in the ozone solution, a method of spraying the ozone solution onto the substrate, and the like. The method of immersing the substrate in the ozone solution is preferable because ozone is less likely to be detached from the ozone solution as compared with contact by spraying. In order to bring gaseous ozone into contact with the surface of the base material, the base material may be passed through the ozone generation cell or held in the ozone generation cell for a certain period of time.

  The ozone treatment process includes a first ozone treatment process in which the surface of the base material is treated with a first ozone solution containing a polar solvent excluding water to form a first ozone treatment base material, and the surface of the first ozone treatment base material is water. It is preferable to have the 2nd ozone treatment process processed with the 2nd ozone solution containing this as a 2nd ozone treatment base material.

  In the first ozone treatment step, the polar solvent can be an organic polar solvent or an inorganic polar solvent. Organic polar solvents include alcohols such as methanol, ethanol, isopropyl alcohol, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, hexamethylphosphoramide, formic acid, acetic acid, etc. Organic acids or a mixed solvent obtained by mixing these with water or an alcohol solvent can be used. In addition, examples of the inorganic polar solvent include inorganic acids such as nitric acid, hydrochloric acid, and hydrofluoric acid. An ozone solution is obtained by pressurizing and dissolving ozone in the solvent.

  The ozone concentration in the ozone solution greatly affects the activation of the surface of the base material, and the activation effect is seen from about 10 ppm, but if it is 20 ppm or more, the activation effect is dramatically increased, and organic matter The dirt of the is quickly decomposed. Therefore, it is desirable to use an ozone solution having an ozone concentration of 20 ppm or more as the first ozone solution used in the first ozone treatment step.

  If such a first ozone solution is used, the surface of the resin base material swells with the solvent, so that erosion by ozone is likely to proceed, and even if organic dirt is adhered to the surface of the resin base material, it is improved. A quality layer can be formed.

  However, when the first ozone solution using an organic or inorganic polar solvent as the solvent is used, there is a large variation during the treatment, and a portion having a low adhesion strength of the plating layer is locally generated or is locally eroded and smooth. There may be a problem that the quality is impaired. Therefore, it is preferable to perform the second ozone treatment step using a second ozone solution using water as a solvent. Since the organic contaminants have already been removed, the surface of the first ozone-treated substrate is eroded by the second ozone solution, and the unevenness of the surface of the first ozone-treated substrate is averaged to improve the surface smoothness. Further, the local erosion variation due to the first ozone solution is also averaged, and the adhesion strength of the plating layer is averaged.

  The second ozone solution used in the second ozone treatment step is preferably an ozone solution having an ozone concentration of 1 ppm to 20 ppm. If the ozone concentration of the second ozone solution is out of this range, it is difficult to solve the problem that a portion having a low adhesion strength of the plating layer is locally generated or that the smoothness is impaired due to local erosion. It becomes.

  In the first ozone treatment step and the second ozone treatment step, it is considered that an ozonide is formed by oxidation with ozone in an ozone solution, and polar groups such as an OH group, a CO group, and a COOH group are generated. In principle, the higher the treatment temperature in the ozone treatment step, the higher the reaction rate, but the higher the temperature, the lower the solubility of ozone in the ozone solution, and the ozone concentration in the ozone solution at a temperature exceeding 40 ° C. In order to set it to 40 ppm or more, it is necessary to pressurize the processing atmosphere to atmospheric pressure or more, and the apparatus becomes large. The processing temperature may be about room temperature.

  The contact time between the ozone solution and the surface of the substrate in the first ozone treatment step and the second ozone treatment step varies depending on the resin type, but is preferably 2 minutes to 30 minutes. If it is less than 2 minutes, even if the ozone concentration is set to 100 ppm, it will be difficult to achieve the effect of ozone treatment, and if it exceeds 30 minutes, the resin base material will deteriorate.

  After the ozone treatment step and before the catalyst portion application step, the surface of the ozone treatment substrate or the second ozone treatment substrate is brought into contact with a solution containing at least an alkali component and / or a surfactant to contact the surface cleaning substrate. It is desirable to further have a surface cleaning step. The alkaline component solubilizes the very surface of the modified layer of the substrate in water at the molecular level. At this time, more polar groups are exposed on the surface of the modified layer. Although there is no limitation in particular in the kind of alkali component, Sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. can be used.

  It is considered that the surfactant easily adsorbs the hydrophobic group to the polar group present in the modified layer. Therefore, the wettability of the modified layer can be improved. As the surfactant, a surfactant that can easily adsorb a hydrophobic group to at least one polar group composed of an OH group, a CO group, and a COOH group is used. Examples of the surfactant include sodium lauryl sulfate, potassium lauryl sulfate, sodium stearyl sulfate, potassium stearyl sulfate, polyoxyethylene dodecyl ether and the like.

  In the surface cleaning step, a cleaner conditioner solution that has been widely used conventionally as a solution containing an alkali component and a surfactant can be used. As the solvent of the cleaner conditioner solution containing the surfactant and the alkali component, it is desirable to use a polar solvent, and water can be typically used. However, in some cases, an alcohol solvent or a water-alcohol mixed solvent is used. It may be used.

  The concentration of the surfactant in the cleaner conditioner solution is preferably in the range of 0.01 g / L to 10 g / L. When the concentration of the surfactant is lower than 0.01 g / L, the amount of catalyst metal particles produced is reduced. When the surfactant concentration is higher than 10 g / L, excess surfactant remains as impurities in the reforming layer. The amount of particles produced decreases. In this case, the surface of the substrate may be washed with water to remove excess surfactant.

  The alkali component concentration in the cleaner conditioner solution is preferably 10 or more in terms of pH value. The effect can be obtained even if the pH value is less than 10, but since the number of polar groups to be expressed is small, it takes a long time to generate a predetermined amount of catalyst metal particles. When the pH value is 10 or more, the removal treatment of the surface embrittlement layer is accelerated.

  The contact time between the cleaner conditioner solution and the surface of the substrate is not particularly limited, but is preferably 1 minute or longer at 10 ° C. If the contact time is too short, the amount of surfactant adsorbed on the polar group may be insufficient. However, if the contact time becomes too long, the layer in which the polar group is exposed may dissolve. The contact time is preferably about 1 minute to 10 minutes. Moreover, the higher temperature is desirable, and the higher the temperature, the shorter the contact time. The temperature is preferably about 10 ° C to 70 ° C.

  Further, the cleaner conditioner solution can be brought into contact with the surface of the ozone-treated substrate by a method of immersing the substrate in the cleaner conditioner solution, a method of applying the cleaner conditioner solution to the substrate, or the like.

  Coupling that brings the surface of the surface cleaning substrate into contact with the coupling agent in order to increase the adhesion between the catalyst portion and the surface of the substrate after the surface cleaning step and before the catalyst portion applying step. You may further perform an agent processing process. A coupling agent is generally an organic compound having a functional group capable of chemically bonding both an inorganic material and an organic material. By bringing the coupling agent into contact with the surface of the surface-cleaning substrate, the surface of the surface-cleaning substrate and the catalyst part can be chemically bonded via the coupling agent. Can adhere firmly. As the coupling agent, commonly used coupling agents such as silane coupling agents, titanate coupling agents, aluminate coupling agents, and silazanes can be used.

  In the catalyst part applying step, a metal compound solution containing Pd or Ag is brought into contact with the surface of the ozone-treated base material to form a catalyst part containing Pd or Ag to be a catalyst part providing base material. Specifically, the modified layer on the surface of the ozone-treated substrate is brought into contact with a metal compound solution containing colloids and / or ions so that the colloids and / or ions are adsorbed on the modified layer, and the adsorbed ions and colloids are absorbed. The catalyst part is formed as nano-level fine metal particles by reduction. By bringing the modified layer into contact with the metal compound solution, the colloid or ions of the catalytic metal are adsorbed on the polar group existing on the surface of the modified layer and further on the pores. As the metal compound solution, an alkaline solution containing a metal complex ion or an acidic solution containing a metal colloid is known, and any of them can be used. The catalyst metal is a catalyst used when metal ions are reduced and precipitated in the plating process, and palladium (Pd) or silver (Ag) can be used.

  In order to bring the metal compound solution into contact with the surface of the modified layer, a method of applying the metal compound solution to the surface of the modified layer or immersing the base material in the metal compound solution can be used. When the metal compound solution is brought into contact with the modified layer, the metal compound solution can be diffused and penetrated from the surface of the modified layer into the substrate.

  In the plating treatment step, a plating layer containing Cu or Ni is formed by bringing an electroless plating solution containing Cu or Ni into contact with the surface of the catalyst portion-giving substrate to obtain a plating layer-giving substrate. In the plating process, the plating metal is deposited using the catalyst metal adsorbed on the modified layer as a nucleus.

  An electroplating process may be further performed after the plating process. After the plating process, it is possible to further perform electroplating on the surface of the plating layer. By performing the electroplating process, the plating layer can be made thicker.

  In addition, the conditions of the surface cleaning process, the catalyst part providing process, the plating process, and the electroplating process described above are not limited, and can be performed in the same manner as a conventional plating process.

  As mentioned above, although the collector of the secondary battery of the present invention, the manufacturing method thereof, and the embodiment of the secondary battery have been described, the present invention is not limited to the above embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
<Preparation of base material>
A polyolefin porous film, grade UP3074 manufactured by Ube Industries, Ltd. was prepared as a resin base material for the current collector.
<Manufacture of current collector>
A catalyst part and a plating layer were formed on the resin base material by the following procedure to obtain a current collector of Example 1.

(1) <Ozone treatment process>
The prepared base material was immersed in an ozone solution containing 40 ppm of ozone at 20 ° C. for 8 minutes.

(2) <Surface cleaning process>
The base material after the ozone treatment step was immersed in a cleaner conditioner solution (“OPC370 Condy Clean M” manufactured by Okuno Pharmaceutical Co., Ltd.) heated to 50 ° C. for 3 minutes. Further, it was immersed in H ₂ SO ₄ having a concentration of 0.5 mol / L heated to 30 ° C. for 1 minute.

(3) <Catalyst part providing step>
The substrate after the surface cleaning step was washed with water and dried, and then dissolved in 3 mol / L HCl so that PdCl ₂ was 0.1% by mass and SnCl ₂ was 5% by mass at 50 ° C. Then, it was immersed in 1 mol / L HCl as a Pd reducing solution at 30 ° C. for 6 minutes.

(4) <Plating process>
The base material after the catalyst part providing step was immersed in a Cu chemical plating bath kept at 30 ° C. for 20 minutes to precipitate a Cu plating layer. The thickness of the deposited Cu plating layer was 0.3 μm to 0.5 μm.

(5) <Heat treatment process>
The base material obtained above was heated at 150 ° C. for 60 minutes. By applying the heat treatment, the residual stress is removed, and the adhesion between the plating layer and the substrate can be increased.

<Preparation of negative electrode for lithium ion secondary battery>
A negative electrode for a lithium ion secondary battery was prepared using the current collector prepared in Example 1 as a negative electrode current collector.

A negative electrode active material was prepared as follows. SiO powder (manufactured by Sigma-Aldrich Japan, average particle size 5 μm) was heat-treated at 900 ° C. for 2 hours to prepare SiO _x powder having an average particle size of 5 μm. The obtained SiO _x powder is an aggregate of SiO _x particles, and the SiO _x particles have a structure in which fine Si particles are dispersed in a SiO ₂ matrix.

The slurry was adjusted as follows. This SiO _x powder, ketjen black (KB) as a conductive additive, graphite (MAG), and polyamideimide (PAI) as a binder resin were dissolved in N-methylpyrrolidone (NMP) as an organic solvent. Those were mixed with each other to prepare a slurry-like negative electrode mixture. As the PAI, Arakawa Chemical Industries, Ltd., trade name Composeran AI series, product number AI-301 was used. The composition ratio of each component (solid content) in the slurry was SiO _x : MAG: KB: PAI = 42: 40: 3: 15 (mass ratio).

  The slurry of Example 1 was impregnated with the slurry, and the current collector of Example 1 was filled with the slurry. The current collector filled with the slurry was dried at 80 ° C. for 15 minutes, and the organic solvent was volatilized and removed from the slurry. After drying, the electrode density was adjusted with a roll press.

  Next, the dried current collector filled with the slurry was heated at 200 ° C. for 2 hours in a vacuum drying furnace to cure the binder resin. Then, it cooled naturally and the negative electrode of Example 1 was obtained.

<Production of coin-type lithium ion secondary battery>
Evaluation in the half cell was performed using the negative electrode of Example 1 described above as the evaluation electrode and metal lithium as the counter electrode. 1 mol of LiPF ₆ / ethylene carbonate (EC) + diethyl carbonate (DEC) (EC: DEC = 1: 1 (volume ratio)) as an electrolyte and a coin-type model battery (CR 2032 type) in a dry room ) Was produced. The coin-type model battery was manufactured by stacking a spacer, a Li foil having a thickness of 500 μm as a counter electrode, a separator (trade name Celgard # 2400, manufactured by Celgard), and an evaluation electrode in this order and caulking to prepare a model battery of Example 1. .

(Comparative Example 1)
A current collector of Comparative Example 1 was prepared in the same manner as the current collector of Example 1 except that the ozone treatment step was not performed on the current collector of Example 1, and compared in the same manner as the model battery of Example 1. The model battery of Example 1 was produced.

(Comparative Example 2)
Instead of the current collector of Example 1, a copper foil was used as the current collector, and a slurry containing the negative electrode active material used in Example 1 was applied onto the copper foil with a doctor blade. The copper foil coated with the slurry was heated in the same manner as in Example 1 to obtain a negative electrode of Comparative Example 2, and a model battery of Comparative Example 2 was produced in the same manner as the model battery of Example 1.

<Cycle test>
A cycle test of the coin-type model batteries of Example 1, Comparative Example 1, and Comparative Example 2 was performed. The charge was CCCV charge (constant current constant voltage charge) at a 1/3 C rate and a voltage of 4.1 V at 65 ° C. The voltage was held for 1 hour. Discharge performed CC discharge (constant current discharge) at 2.9V and 1 / 3C rate.

  This charging / discharging was made into 1 cycle and repeated to 500 cycles. The initial discharge capacity was measured and used as the initial capacity. It calculated similarly from each discharge capacity of 100th, 200th, 300th, 500th cycle, and it was set as the discharge capacity of each cycle. The capacity maintenance rate was obtained by the following formula. Capacity maintenance rate = (discharge capacity of each cycle / initial discharge capacity).

  The results are shown in FIG. FIG. 6 is a graph showing the discharge capacity maintenance rate for each cycle of the model batteries of Example 1, Comparative Example 1 and Comparative Example 2.

  As seen in FIG. 6, in the model battery of Comparative Example 1 using the current collector of Comparative Example 1 that was not subjected to ozone treatment, the cycle characteristics were significantly reduced as compared to the model battery of Example 1. The cycle test result of the model battery of Comparative Example 1 was worse than the cycle test result of the model battery of Comparative Example 2 using a copper foil as a current collector. From this, it is presumed that in the model battery of Comparative Example 1, the copper plating layer was peeled off from the base material by repeating the cycle test, the amount of electronic conductivity of the current collector was lowered, and the discharge capacity was lowered. .

  The model battery of Example 1 was superior in cycle characteristics to the model battery of Comparative Example 2. In the negative electrode of Example 1, the negative electrode active material is filled in the fine space of the current collector. In the negative electrode of Example 1, the negative electrode active material is supported in the fine space of the current collector. Therefore, even when the negative electrode active material expands and contracts due to repeated charge and discharge of the battery, the supported negative electrode active material is It is presumed that it was possible to suppress peeling and dropping from the current collector.

  1: Current collector, 2: Active material, 30: Base material, 31: Modified layer, 40: Catalyst part, 50: Plating layer, 51: Nano anchor, 60: Organic soiling.

Claims (11)

A resin base material having a structure in which a large number of fine spaces are formed inside and the fine spaces are connected to the outermost surface;
A catalyst part containing Pd or Ag formed after the surface of the base material including the inner surface of the fine space is modified;
A plating layer containing Cu or Ni formed on the surface of the catalyst part;
A current collector for a secondary battery.   2. The current collector for a secondary battery according to claim 1, wherein the resin constituting the base material is one selected from the group consisting of polypropylene, polyethylene, a mixture thereof, and a copolymer thereof.   The current collector for a secondary battery according to claim 1, wherein the base material is one selected from a single-layer porous film, a laminated porous film, a woven fabric, and a non-woven fabric.   The current collector for a secondary battery according to claim 1, wherein the reforming is performed by ozone treatment.   The secondary battery which has the electrical power collector for secondary batteries of any one of Claims 1-4. A base material preparation step for preparing a resin base material having a structure in which a large number of fine spaces are formed inside and the fine spaces communicate with each other and connected to the outermost surface;
An ozone treatment step in which the surface of the substrate is ozone treated to form an ozone treated substrate;
A catalyst part providing step of bringing a metal compound solution containing Pd or Ag into contact with the surface of the ozone-treated base material to form a catalyst part containing Pd or Ag to form a catalyst part providing base material;
A plating treatment step in which an electroless plating solution containing Cu or Ni is brought into contact with the surface of the catalyst portion-giving substrate to form a plating layer containing Cu or Ni to form a plating layer-giving substrate;
The manufacturing method of the electrical power collector for secondary batteries which has this. The ozone treatment step is a first ozone treatment step in which the surface of the substrate is treated with a first ozone solution containing a polar solvent excluding water to form a first ozone treatment substrate;
And a second ozone treatment step of treating the surface of the first ozone-treated substrate with a second ozone solution containing water to form a second ozone-treated substrate. Body manufacturing method.   After the ozone treatment step and before the catalyst portion application step, the surface of the ozone treatment substrate or the second ozone treatment substrate is brought into contact with a solution containing at least an alkali component and / or a surfactant to clean the surface. The manufacturing method of the electrical power collector for secondary batteries of Claim 6 or 7 which further has the surface cleaning process used as a conversion base.   The secondary battery according to any one of claims 6 to 8, further comprising an electroplating treatment step for increasing the thickness of the plating layer by performing electroplating on the surface of the plating layer-applied substrate after the plating treatment step. Method for manufacturing a current collector.   The secondary battery according to any one of claims 6 to 9, wherein the resin constituting the base material is one selected from the group consisting of polypropylene, polyethylene, a mixture thereof, and a copolymer thereof. A method of manufacturing a current collector.   The said base material is one chosen from a single layer porous film, a lamination | stacking porous film, a woven fabric, and a nonwoven fabric, The manufacture of the collector for secondary batteries of any one of Claims 6-10. Method.

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