JP7061454B2 - Resin collector for lithium-ion secondary battery and lithium-ion secondary battery - Google Patents

Description

The present invention relates to a resin collector for a lithium ion secondary battery and a lithium ion secondary battery.

Lithium-ion secondary batteries have been widely used in various applications in recent years as small-sized and high-capacity secondary batteries. Metal foils are used as current collectors constituting positive and negative electrodes, and an active material layer is formed on the surface thereof. Lithium-ion secondary batteries having an arranged structure are known. Among them, as a lithium-ion secondary battery that can achieve both high output and light weight, a resin current collector is used for each of the positive electrode and the negative electrode, and a bipolar lithium-ion secondary battery in which the current collector and the active material layer are laminated in series. Batteries are known (Patent Document 1 etc.).

However, the resin current collector used in the bipolar lithium-ion secondary battery described in Patent Document 1 may lack adhesion to the active material layer, and the volume change of the active material during charging / discharging and the entire battery may occur. When a stress is applied to the battery, such as when an impact is applied to the battery, defects such as peeling may occur at the interface and the resistance value at the interface may increase, resulting in deterioration of cycle characteristics and long-term durability. There was a problem that there was.

Japanese Unexamined Patent Publication No. 2012-150905

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a resin current collector for a lithium ion secondary battery capable of obtaining a lithium ion secondary battery having excellent long-term reliability. It is one of the purposes.

The present inventors have reached the present invention as a result of repeated diligent research.
That is, the present invention is characterized by comprising a conductive non-porous resin layer and a conductive porous resin layer laminated on the conductive non-porous resin layer, which is a resin collection for a lithium ion secondary battery. Electric body; a lithium ion secondary battery containing this.

According to the present invention, it is possible to provide a resin current collector for a lithium ion secondary battery having excellent long-term reliability.

FIG. 1 is a schematic view showing an example of a resin current collector for a lithium ion secondary battery of the present invention. FIG. 2 is a diagram schematically showing an example of electrodes constituting the lithium ion secondary battery of the present invention.

Hereinafter, the present invention will be described in detail.
The resin collector for a lithium ion secondary battery of the present invention comprises a conductive non-porous resin layer and a conductive porous resin layer laminated on the conductive non-porous resin layer.

The configuration of the resin current collector for a lithium ion secondary battery of the present invention is shown with reference to FIG.
FIG. 1 is a schematic view showing an example of a resin current collector for a lithium ion secondary battery of the present invention.
As shown in FIG. 1, the resin collector 10 for a lithium ion secondary battery has a conductive non-porous resin layer 100 and a conductive porous resin layer 200 laminated on the conductive non-porous resin layer 100. It consists of. The conductive porous resin layer 200 is a non-woven fabric in which conductive resin fibers 210 are entangled.

The conductive porous resin layer constituting the resin collector for a lithium ion secondary battery of the present invention is preferably a woven fabric, a non-woven fabric or a knitted fabric of conductive resin fibers, and the conductive resin fibers are the first. It preferably contains a conductive filler and a first non-conductive resin.
On the other hand, the conductive non-porous resin layer constituting the resin collector for a lithium ion secondary battery of the present invention preferably contains a second conductive filler and a second non-conductive resin.
In the present specification, the conductive filler constituting the conductive resin fiber is distinguished as the first conductive filler, and the conductive filler constituting the conductive non-porous resin layer is distinguished as the second conductive filler. Similarly, the non-conductive resin constituting the conductive resin fiber is referred to as the first non-conductive resin, and the non-conductive resin constituting the conductive non-porous resin layer is distinguished as the second non-conductive resin.
It is preferable that the first conductive filler and the second conductive filler, and the first non-conductive resin and the second non-conductive resin are the same, respectively.

First, a conductive porous resin layer constituting the resin current collector for a lithium ion secondary battery of the present invention will be described.

The conductive porous resin layer constituting the resin current collector for a lithium ion secondary battery of the present invention is arranged on the active material layer side in the lithium ion secondary battery.
By arranging the conductive porous resin layer on the active material layer side, the active material layer can be arranged on the conductive porous resin layer. When the active material layer is arranged on the conductive porous resin layer, a part of the active material constituting the active material layer invades the pores and voids of the conductive porous resin layer, so that the current collector and the active material are activated. The contact with the material layer is improved, and the active material layer is less likely to be peeled from the surface of the current collector. That is, the durability is improved.
The conductive porous resin layer is preferably a substantially flat plate-shaped layer (also referred to as a porous sheet) having pores on its surface and / or inside thereof. The structure of the pores may be one that penetrates the conductive porous resin layer, or may be one that stays on the surface or inside of the conductive porous resin layer.
Examples of the form of the porous sheet having pores on the surface and / or the inside include a mesh shape (woven fabric, non-woven fabric, knitted fabric, etc.) and a sponge shape having closed cells (sheet-shaped resin foam, etc.).

The form of the porous sheet having pores on the surface and / or inside is preferably mesh-like from the viewpoint of interfacial resistance and the like, and more preferably a woven fabric of conductive resin fibers or a non-woven fabric.
Two or more of the above-mentioned porous sheets may be laminated and used, and the types of the laminated porous sheets may be the same or different.

The conductive resin fiber is a fiber having conductivity formed from a polymer material, for example, a conductive resin fiber made of a conductive polymer (polyacetylene, polyaniline, polythiophene, etc.) having conductivity, or a conductive resin fiber. Examples thereof include conductive resin fibers using a non-conductive resin (first non-conductive resin) as a base material and adding a conductive filler (first conductive filler) as needed. From the viewpoint of adhesive strength with the conductive non-porous resin layer, the conductive resin fiber is preferably a conductive resin fiber using the first non-conductive resin as a base material and adding the first conductive filler.

The first non-conductive resin used as the base material of the conductive resin fiber includes polyolefins [polyethylene, polypropylene, polymethylpentene, polycycloolefin), vinylidene fluoride, polytetrafluoroethylene, and polar groups in these polyolefins. Thermoplastic resins such as introduced modified polyolefins, etc.], polyethylene resins [polyethylene terephthalate, etc.] and acrylic resins [polymethyl acrylate and polymethyl methacrylate), etc., and mixtures thereof can be preferably used, and synthetic rubber (styrene butadiene rubber, etc.) can be used. And polyacrylonitrile etc.), epoxy resin, silicone resin, engineering plastic such as polyether nitrile and the like can also be used.
Among them, as the non-conductive resin, polyolefin is preferable, polyethylene, polypropylene, modified polyolefin and a mixture thereof are more preferable, and a mixture containing modified polyolefin as an essential component is particularly preferable.

Polyolefin has a very wide potential window, is stable against both positive and negative potentials, and is lightweight, so that it is possible to increase the power density of the battery and it has excellent durability against the electrolytic solution used. Is preferable.
Further, when modified polyolefin is used as an essential component as the first non-conductive resin to be the base material of the conductive resin fiber, the polar functional group in the modified polyolefin interacts with the first conductive filler described later. , It functions as a dispersant for dispersing the first conductive filler, and is preferable because it has good conductivity.

Preferred modified polyolefins include polyethylene, polypropylene or copolymers thereof having a polar functional group introduced therein, and polar functional groups include a carboxyl group and a 1,3-dioxo-2-oxapropylene group. Examples thereof include a hydroxyl group, an amino group, an amide group and an imide group.

Modified polyolefins in which a polar functional group is introduced into polyethylene, polypropylene or a copolymer thereof are commercially available as dispersants and compatibilizers for resins, and are commercially available as Yumex series manufactured by Sanyo Kasei Kogyo Co., Ltd. and Admer manufactured by Mitsui Chemicals Co., Ltd. It is available as a series.

The conductive resin fiber using the non-conductive resin as a base material is a conductive fiber made of a conductive resin composition containing the first non-conductive resin and the first conductive filler (for example, Japanese Patent Application Laid-Open No. 2001). -Fiber containing conductive carbon described in JP-A-271218, JP-A-48-10324, etc.), the surface of the synthetic fiber obtained by spinning the first non-conductive resin by a known method is a metal described below. A coating layer made of a conductive polymer or a conductive resin composition is provided on the surface of the conductive fiber coated with the above and the synthetic fiber obtained by spinning the first non-conductive resin by a known method. Examples thereof include fibers, and among them, conductive resin fibers made of a first conductive resin composition containing a first non-conductive resin and a first conductive filler are preferable.
As a method of coating the surface of the fiber with metal, a known sputtering method, a vapor deposition method, or the like can be used, and as a method of further providing a coating layer on the surface of the fiber, a solution of a material forming the coating layer or the like can be used. Can be used, such as a method of applying.

The first conductive resin composition can be obtained, for example, by mixing the first non-conductive resin and the first conductive filler by a known method. The first conductive filler to be mixed with the first non-conductive resin includes conductive carbon fillers [graphite, carbon black, acetylene black, ketjen black, furnace black, channel black, thermal lamp black and single layer or multilayer. Carbon nanotubes, etc.] and metals (aluminum, gold, silver, copper, iron, platinum, chromium, tin, indium, antimony, titanium, nickel, alloys thereof, etc.) and the like.
These conductive fillers may be used alone or in combination of two or more.
From the viewpoint of corrosion resistance, aluminum, stainless steel, carbon and nickel are preferable, and carbon is more preferable.
Further, as the first conductive filler, a ceramic particle or a resin particle coated with the metal shown above by plating or the like can also be used.

The shape of the first conductive filler is not particularly limited, and known shapes such as particles, powders, fibers, plates, lumps, cloths, and meshes can be appropriately selected. For example, when it is desired to impart conductivity over a wide range, it is preferable to use a particulate conductive filler. On the other hand, if it is desired to further improve the conductivity in a specific direction (for example, the thickness direction or the in-plane direction perpendicular to the thickness direction), a material having a certain directionality such as a fibrous shape is used. It is preferably used alone or in combination with particulate matter.

When the first conductive filler is in the form of particles, powder or lumps, the average particle size of the primary particles is not particularly limited, but is preferably 0.01 to 10 μm, preferably 0.01. It is more preferably about 1 μm.
In the present specification, the "particle size" means the maximum distance L among the distances between arbitrary two points on the contour line of the particles, and the value of the "average particle size" is a scanning type. Using an observation means such as an electron microscope (SEM) or a transmission type electron microscope (TEM), a value calculated as an average value of particle diameters of particles observed in several to several tens of fields shall be adopted.
The "particle diameter" and "average particle diameter" of the particles other than the first conductive filler are also measured in the same manner as the "particle diameter" and "average particle diameter" of the first conductive filler described above. can do.

When the first conductive filler is fibrous, its average fiber length is not particularly limited, but is preferably 0.1 to 100 μm.
In the present specification, the average fiber length is calculated as the average value of the fiber lengths observed in several to several tens of fields using an observation means such as a scanning electron microscope or a transmission electron microscope. The value shall be adopted.
When the first conductive filler is fibrous, its average diameter is not particularly limited, but is preferably 0.01 to 1 μm. The "average fiber length" of the fibrous material other than the first conductive filler can be measured in the same manner as the "average fiber length" of the first conductive filler described above.

The content of the first conductive filler contained in the first conductive resin composition containing the first non-conductive resin and the first conductive filler is the first from the viewpoint of conductivity and the like. Based on the total weight of the non-conductive resin and the first conductive filler, it is preferably 3 to 80% by mass, more preferably 5 to 60% by mass.

The first conductive resin composition includes, in addition to the first non-conductive resin and the first conductive filler, as long as it does not impair the conductivity and the strength of the first conductive resin composition. It may contain a resin other than the first non-conductive resin and other additives. Examples of other additives include known resin additives such as colorants, ultraviolet absorbers, flame retardants and plasticizers. The content of these additives can be adjusted according to the function of the additives and the like.

When the first conductive resin composition contains a modified polyolefin as the first non-conductive resin, the content of the modified polyolefin is based on the total weight of the first non-conductive resin and the first conductive filler. 1 to 25% by mass is preferable.

The first conductive resin composition obtained by mixing the first non-conductive resin and the first conductive filler includes a predetermined amount of the first conductive filler, the first non-conductive resin, and necessary. The other additives and the like used in the above are mixed and kneaded using a known device such as a kneader, an internal mixer, a Banbury mixer and a roll type kneading device, and the first conductive filler is added to the first non-conductive resin. It can be obtained by a method of dispersion.

The order of adding each component during mixing and kneading is not particularly limited. For example, the first non-conductive resin and the first conductive filler are mixed in advance, and a different kind of first non-conductive resin is further mixed. May be mixed, or the first non-conductive resin and the conductive filler may be mixed at the same time.
At the time of kneading, the kneading device is used for kneading at a temperature equal to or higher than the melting point of the first non-conductive resin, and the temperature can be adjusted according to the type of the first non-conductive resin to be used, from 80 to 80. It is 200 ° C.

The first conductive resin composition obtained by the above method may be further pelletized or powdered by a pelletizer or the like.

Among the conductive resin fibers, the conductive resin fiber made of the conductive polymer or the first conductive resin composition is obtained by spinning the conductive polymer or the first conductive resin composition by a known method. A method in which a conductive polymer or a first conductive resin composition is melted by heat, extruded from a mouthpiece into a fibrous form, and then cooled and hardened (melt spinning method), has high conductivity. A method (wet spinning method) in which a molecule or a first conductive resin composition is dissolved in a low-volatile solvent and extruded from a mouthpiece into a coagulation bath to form a fibrous form, and a conductive polymer or the first. Known methods such as dissolving the conductive resin composition in a solvent that vaporizes with heat (low boiling point solvent, etc.) and extruding it from the base in a hot atmosphere to evaporate the solvent into a fibrous form (dry spinning method). Can be used.

When the conductive porous resin layer is a woven fabric made of conductive resin fibers, it can be obtained by making the conductive resin fibers into a woven fabric by a known method. The weaving method of the woven fabric is not particularly limited, and woven fabrics woven by plain weaving, twill weaving, satin weaving, pile weaving and the like can be used. Further, instead of the woven fabric, a knitted fabric made of conductive resin fibers may be used. The knitting method is not particularly limited, and knitting knitted by horizontal knitting, vertical knitting, round knitting, or the like can be used.

When the conductive porous resin layer is a nonwoven fabric made of conductive resin fibers, the nonwoven fabric is a wet method, a dry method, a melt blow method and a method using a conductive polymer or a first conductive resin composition. A fiber aggregate is produced by a known method such as a spunbond method, and if necessary, the fibers constituting the fiber aggregate are bonded to each other by a needle punch method, a spunlace method, a chemical bond method, a thermal bond method, a stitch bond method, etc. It can be produced by binding using a known method of.
The method for binding the fibers can be appropriately selected in consideration of the mechanical properties, chemical properties, allowable cost and applicability of the fiber material required for the final product, and is produced by using, for example, a conductive resin fiber. A method of making a non-woven fabric of a card web by a needle punch method, a method of making a non-woven fabric by a chemical bond method obtained by applying a heat-adhesive resin in the form of an aqueous solution to the card web and heating and drying the card web. On the other hand, a method of molding a web in which 10 to 40% of heat-meltable non-woven fabric is mixed using a hot roller, a thermal bond method described in Examples of JP-A-2001-271218, which treats the web under hot air. It can be obtained by a method of making a non-woven fabric or a method of making a non-woven fabric by a spunlace method in which the card web is dispersed in a high-pressure jet water stream and treated.

When the form of the conductive porous resin layer is mesh-like, the opening diameter (also referred to as opening) is preferably 50 μm or less from the viewpoint of the contact area between the active material and the current collector.
The opening diameter means the width per square formed by intersecting the vertical lines and the horizontal lines constituting the woven fabric, the knitted fabric, and the non-woven fabric, and has a width of 25.4 mm in the conductive porous resin layer. A method of calculating from the number of lines and the wire diameter inside, or magnifying the surface of the conductive porous resin layer with a scanning electron microscope, an optical microscope, etc., and at least 10 of the squares included in the visual field. It is obtained by the method of calculating the average value of the width.

When the form of the conductive porous resin layer is mesh-like, the aperture ratio (also referred to as pore opening ratio) is 30 from the viewpoint of the mechanical strength of the conductive porous resin layer and the prevention of leakage of active material during bending. It is preferably% or more and 50% or less.
The aperture ratio means the ratio of the area of the opening to the entire conductive porous resin layer, and is calculated from the above-mentioned opening diameter and the distance between the lines or the conductive porous resin layer with an optical microscope. It is obtained by a method of obtaining the area of the opening in the unit area by image analysis or the like by magnifying and observing by the above.

When the conductive porous resin layer is a woven fabric, a knitted fabric, or a non-woven fabric, the air permeability thereof is preferably 100 cf / m or more from the viewpoint of battery characteristics, retention of active material, and the like.
The air permeability of woven fabrics, knitted fabrics and non-woven fabrics is measured in accordance with JIS P8117 [paper and paperboard-air permeability and air permeability resistance test method (intermediate region) -Garley method].

When the morphology of the conductive porous resin layer is sponge-like with closed cells, the conductive sheet-like resin foam is a first conductive resin made of polyurethane foam, polystyrene foam, polyethylene foam, polypropylene foam, or the like. Examples thereof include a sheet-like resin foam in which a metal layer is provided on the surface of the composition by a method such as sputtering, electrodeposition, plating treatment and coating to make the composition conductive.

When a sheet-shaped resin foam having conductivity is used as the conductive porous resin layer, the porosity thereof is preferably 50% or more from the viewpoint of battery characteristics, retention of active material, and the like.
The porosity of the sheet-shaped resin foam is calculated by the following method.
[Measurement method of porosity]
The cross section of the sheet-shaped resin foam is magnified and observed with a scanning electron microscope, an optical microscope, or the like, and the obtained image is binarized by an image analysis device to obtain the total area of the void portion included in the visual field, and the void with respect to the entire observation cross section is obtained. The ratio of the total area of the parts is calculated, and the void ratio in the cross section is obtained. The cross section is changed in the thickness direction and the measurement is performed in the same manner for at least 10 cross sections, and the average value of the porosity in the measured cross section is obtained and used as the porosity of the sheet-shaped resin foam.

Next, a conductive non-porous resin layer used in the resin current collector for a lithium ion secondary battery of the present invention will be described.

The conductive non-porous resin layer has conductivity, has a substantially flat plate-shaped (also referred to as a sheet-like) layer having no pores on the surface and / or inside thereof, and has electrolyte impermeableness. Is preferable.
In the present invention, the electrolytic solution impermeable means that when the electrolytic solution is brought into contact with one surface of the conductive non-porous resin layer, the electrolytic solution does not seep out on the back surface thereof. However, by using a layer made of a non-porous sheet-like resin using a resin that does not swell with respect to the electrolytic solution, the electrolytic solution impermeable can be obtained.

The conductive non-porous resin layer preferably comprises a second conductive resin composition comprising a second conductive filler and a second non-conductive resin. The second conductive resin composition is the same as the conductive resin composition containing the first non-conductive resin and the first conductive filler exemplified in the above-mentioned conductive porous resin layer. From the viewpoint of impermeableness of the electrolytic solution and the like, the second non-conductive resin and the preferred ones as the second conductive filler are the same as those exemplified in the above-mentioned conductive porous resin layer.

The content of the second conductive filler contained in the second conductive resin composition containing the second non-conductive resin and the second conductive filler is the second content from the viewpoint of conductivity and the like. Based on the total weight of the non-conductive resin and the second conductive filler, it is preferably 5 to 90% by mass, more preferably 10 to 88% by mass.

The conductive non-porous resin layer is a sheet-like second conductive resin composition obtained by the same method as the method for producing the first conductive resin composition exemplified in the above-mentioned conductive porous resin layer. Can be obtained by molding into. As a method for forming into a sheet, known methods such as injection molding, compression molding, calender molding, slush molding, rotary molding, extrusion molding, blow molding, and film molding (casting method, tenter method, inflation method, etc.) are used. It can be selected according to the type of non-conductive resin and the like.

When the conductive porous resin layer is made of a woven fabric or a non-woven fabric of a conductive resin fiber made of the first conductive resin composition, the second conductive resin composition constituting the conductive non-porous resin layer can be used. The second conductive filler and the second non-conductive resin contained therein are the first conductive filler and the first non-conductive resin contained in the first conductive resin composition constituting the conductive resin fiber. It may be the same as or different from each other.
Among them, the first contained in the first conductive resin composition constituting the conductive resin fiber from the viewpoint of the adhesive strength and the interfacial resistance between the conductive porous resin layer and the conductive non-porous resin layer. What are the conductive filler and the first non-conductive resin, and the second conductive filler and the second non-conductive resin contained in the second conductive resin composition constituting the conductive non-porous resin layer? , It is preferable that they are the same.

The resin collector for a lithium ion secondary battery of the present invention can be obtained by laminating a conductive porous resin layer and a conductive non-porous resin layer and integrally molding them.

As a method of laminating the conductive porous resin layer and the conductive non-porous resin layer and integrally molding them, for example, the following method can be used.
(Laminating method 1)
The conductive porous resin layer and the conductive non-porous resin layer obtained by the above methods are laminated and heated and melted above the melting point of the conductive resin composition constituting the conductive non-porous resin layer. How to unite.
(Laminating method 2)
A heated melt or solution of the conductive resin composition constituting the conductive non-porous resin layer is applied onto one surface of the conductive porous resin layer obtained by the above method by a casting method or the like. A method for producing a conductive non-porous resin layer directly on a conductive porous resin layer.

In (Laminating Method 1), a step of laminating and integrating the conductive porous resin layer and the conductive non-porous resin layer separately prepared in advance may be performed, and the conductivity is continuously conductive. The process of producing the porous resin layer and the process of continuously producing the conductive non-porous resin layer are performed in parallel, and the conductive porous resin layer and the conductive non-porous resin layer are laminated and wound up. However, a step of integrating by means such as heating may be performed.

Of these, (lamination method 2) is preferable from the viewpoint of interfacial resistance between the conductive porous resin layer and the conductive non-porous resin layer.

The thickness of the resin collector for a lithium ion secondary battery of the present invention may be as long as it can maintain the strength, preferably 10 to 300 μm, more preferably 30 to 250 μm, and particularly preferably 50 to 150 μm. be. Within this range, it is preferable that the strength and conductivity of the process are ensured, the electrolytic solution is impermeable, and the output density of the battery can be increased by reducing the weight.

In the resin collector for a lithium ion secondary battery of the present invention, the thickness of the conductive porous resin layer is preferably 5 to 150 μm, more preferably 20 to 150 μm from the viewpoint of mechanical strength, interfacial resistance, and the like. It is 130 μm, particularly preferably 30 to 50 μm. The thickness of the conductive porous resin layer is measured by a laser film thickness meter.

In the resin collector for a lithium ion secondary battery of the present invention, the thickness of the conductive non-porous resin layer is preferably 5 to 150 μm, more preferably 5 to 150 μm, from the viewpoint of mechanical strength, electrolyte impermeableness, and the like. Is 10 to 120 μm, particularly preferably 20 to 100 μm. In the above molding method, the thickness of the conductive non-porous resin layer can be set in a preferable range by setting appropriate conditions. The thickness of the conductive non-porous resin layer is measured by a laser film thickness meter.

The lithium ion secondary battery of the present invention is a lithium ion secondary battery including the above-mentioned resin collector for a lithium ion secondary battery. Specifically, a positive electrode and a separator having a positive electrode active material layer formed on the above-mentioned resin collector for a lithium ion secondary battery, and a negative electrode active material on the above-mentioned resin collector for a lithium ion secondary battery. It has a cell cell in which a negative electrode formed by forming a layer is laminated. The cell may be made into a battery by connecting terminals for taking out current to both poles thereof and enclosing the cell together with the electrolytic solution in an outer container. In addition, a bipolar lithium-ion secondary battery in which multiple cell cells are stacked in series, terminals for extracting current are connected to the outermost bipolar current collectors, and the batteries are enclosed in an outer container together with the electrolytic solution. May be. In the case of a bipolar lithium-ion secondary battery, a resin collector for a lithium-ion secondary battery in which conductive porous resin layers are laminated on both sides of a conductive non-porous resin layer is used, and a positive electrode is used on one surface. A bipolar electrode is produced by forming an active material layer and forming a negative electrode active material layer on the other surface, and a plurality of these bipolar electrodes are laminated via a separator and sealed with an electrolytic solution mainly in an outer container. It can also be produced by doing so.

The electrode used in the lithium ion secondary battery of the present invention will be described with reference to FIG.
FIG. 2 is a diagram schematically showing an example of electrodes constituting the lithium ion secondary battery of the present invention.
The electrode 1 constituting the lithium ion secondary battery is a resin for a lithium ion secondary battery composed of a conductive non-porous resin layer 100 and a conductive porous resin layer 200 laminated on the conductive non-porous resin layer 100. An active material layer 300 made of an active material 310 is formed on the current collector 10.
Since a part of the active material 310 constituting the active material layer 300 is in contact with the conductive resin fiber 210 constituting the conductive porous resin layer 200, the contact between the current collector and the active material layer becomes good. Since the active material layer is less likely to peel off from the surface of the current collector, durability is improved.

The electrode used in the lithium ion secondary battery of the present invention has a positive electrode active material layer or a negative electrode active material layer on a conductive porous resin layer constituting the resin current collector for the lithium ion secondary battery of the present invention. ..
The positive electrode active material layer and the negative electrode active material layer have an active material slurry in which the positive electrode active material or the negative electrode active material is dispersed in a solvent described later or an electrolytic solution described later in the resin current collector for a lithium ion secondary battery. It can be obtained by applying and drying each on a conductive porous resin layer.
The active material slurry can be applied to the conductive porous resin layer by using an arbitrary coating device such as a bar coater or a brush, and after the application, further drying and heating press or the like are performed as necessary. The drying temperature and drying time are not particularly limited. The drying may be performed under atmospheric pressure or reduced pressure.
The coating amount of the active material (thickness of the active material layer) is not particularly limited and can be adjusted according to the capacity of the battery to be manufactured, etc., but the coating amount is such that the thickness of the active material layer is 10 to 1000 μm. Is preferable, and the coating amount is more preferably 50 to 500 μm.
By applying the active material slurry on each of the conductive porous resin layers, the contact area between the active material particles and the current collector can be increased and the interfacial resistance can be suppressed to a low level, and the surface of the current collector and the active material layer can be suppressed. Durability is improved by improving the adhesion with. Further, even when the viscosity of the active material slurry is high, the active material particles enter into the pores, which facilitates the application of the active material slurry and has the effect of stably forming the active material layer. Play.

The active material layer (positive electrode active material layer and negative electrode active material layer) constituting the lithium ion secondary battery of the present invention is preferably a positive electrode active material or a non-bonded body containing the negative electrode active material. The non-binding body means that the active materials constituting the active material layer are not fixed to each other by a binder (also referred to as a binder).
The active material layer in a conventional lithium ion battery is manufactured by applying a slurry in which an active material and a binder are dispersed in a solvent to the surface of a current collector or the like, and heating and drying the active material layer. Is in a state of being hardened by a binder. At this time, the active materials are fixed to each other by the binder, and the positions of the active materials are fixed to each other. When the active material layer is hardened by the binder, the active material layer hardened by the binder may be cracked due to expansion / contraction during charging / discharging, or the active material layer may be released from the surface of the current collector. It may peel off or fall off.

On the other hand, when the active material layer is a non-bound body containing a positive electrode active material or a negative electrode active material, the components in the active material layer are not bound to each other and their positions are not fixed. Therefore, the active material layer does not crack or peel off due to expansion / contraction during charging / discharging. Therefore, deterioration of cycle characteristics can be suppressed, which is preferable.

Examples of the positive electrode active material and the negative electrode active material used in the lithium ion secondary battery of the present invention include the following.

Examples of the positive electrode active material include LiMn ₂ O ₄ , LiMnO ₂ , LiCoO ₂ , LiNiO ₂ , Li (Ni—Mn—Co) O ₂ , and a material in which a part of these transition metals is replaced with another element. Lithium-transition metal composite oxides, lithium-transition metal phosphate compounds, lithium-transition metal sulfate compounds, transition metal oxides (eg MnO ₂ and V ₂ O ₅ ), transition metal sulfides (eg MoS ₂ and TiS ₂ ) ) And conductive polymers (eg, polyaniline, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene and polyvinylcarbazole) and the like. In some cases, two or more kinds of positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material from the viewpoint of capacity and output characteristics.

Examples of the negative electrode active material include metals (Si and Sn, etc.), metal alloys (for example, lithium-tin alloys, lithium-silicon alloys, lithium-aluminum alloys, lithium-aluminum-manganese alloys, etc.), and metal oxides (TIO, Ti ₂ ). O ₃ , TiO ₂ , SiO ₂ , SiO and SnO ₂ , etc.), composite oxides of lithium and transition metals (Li _4/3 Ti _5/3 O ₄ and Li ₇ MnN, etc.), Li, carbon materials [graphite (graphite ( Natural graphite, artificial graphite), carbon black, amorphous carbon, high molecular compound calcined material (for example, phenol resin, furan resin, etc. calcined and carbonized), coke (for example, pitch coke, needle coke, petroleum coke, etc.) , Activated carbon, carbon fiber (carbon fiber), soft carbon, hard carbon, etc.] and conductive polymers (for example, polyacetylene, polypyrrole, etc.) and the like.

The average particle size of the active material is not particularly limited, but is preferably 1 to 100 μm, more preferably 1 to 20 μm from the viewpoint of increasing the capacity of the battery, reactivity, and cycle durability.

As the positive electrode active material and the negative electrode active material used in the lithium ion secondary battery of the present invention, at least a part of the surface of the active material is coated with a coating resin and, if necessary, a coating agent containing a conductive auxiliary agent. Is preferable.

As the conductive auxiliary agent contained in the coating agent, the same conductive filler as described above can be used. One type of these conductive aids may be used alone, or two or more types may be used in combination.
Among them, from the viewpoint of electrical stability, aluminum, stainless steel, carbon, silver, gold, copper, titanium and mixtures thereof are preferable, and silver, gold, aluminum, stainless steel and carbon are particularly preferable. Is carbon. The content of the conductive auxiliary agent is not particularly limited as long as the conductivity of the active material layer can be improved to a desired degree, but is preferably 0.5 to 15 mass based on the total weight of the solid content contained in the active material layer. %, More preferably 1 to 10% by mass.

The shape (form) of the conductive auxiliary agent is not limited to the particle form, and may be a form other than the particle form, or may be a form practically used as a so-called filler-based conductive resin composition such as carbon nanotubes. good.

The average particle size of the conductive auxiliary agent is not particularly limited, but is preferably about 0.01 to 10 μm from the viewpoint of the electrical characteristics of the battery.

As the coating resin contained in the coating agent, a polymer containing a vinyl monomer as an essential constituent monomer is preferable. Since the polymer containing the vinyl monomer as an essential constituent monomer has flexibility, the volume change of the electrode can be alleviated and the expansion of the electrode can be suppressed by coating the active material with the polymer.

In particular, it is preferable to include a vinyl monomer (b1) having a carboxyl group and a vinyl monomer (b2) represented by the following general formula (1) as the vinyl monomer.
CH ₂ = C (R ¹ ) COOR ² (1)

In the formula (1), R ¹ is a hydrogen atom or a methyl group, and R ² is a linear alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 4 to 36 carbon atoms.

Examples of the vinyl monomer (b1) having a carboxyl group include monocarboxylic acids having 3 to 15 carbon atoms such as (meth) acrylic acid, crotonic acid, and cinnamic acid; (anhydrous) maleic acid, fumaric acid, and (anhydrous) itaconic acid. Examples thereof include dicarboxylic acids having 4 to 24 carbon atoms such as citraconic acid and mesaconic acid; and trivalent to tetravalent or higher valent polycarboxylic acids having 6 to 24 carbon atoms such as aconitic acid. Among these, (meth) acrylic acid is preferable, and methacrylic acid is particularly preferable.

In the vinyl monomer (b2) represented by the general formula (1), R ¹ represents a hydrogen atom or a methyl group. R ¹ is preferably a methyl group.

^R2 is a linear alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 4 to 36 carbon atoms. Specific examples of R ² include methyl group, ethyl group, propyl group, 1-alkylalkyl group (1-methylpropyl group (sec-butyl group), 1,1-dimethylethyl group (tert-butyl group)), 1 -Methylbutyl group, 1-ethylpropyl group, 1,1-dimethylpropyl group, 1-methylpentyl group, 1-ethylbutyl group, 1-methylhexyl group, 1-ethylpentyl group, 1-methylheptyl group, 1-ethylhexyl Group, 1-methyloctyl group, 1-ethylheptyl group, 1-methylnonyl group, 1-ethyloctyl group, 1-methyldecyl group, 1-ethylnonyl group, 1-butyleicosyl group, 1-hexyloctadecyl group, 1- Octylhexadecyl group, 1-decyltetradecyl group, 1-undecyltridecyl group, etc.), 2-alkylalkyl group (2-methylpropyl group (iso-butyl group), 2-methylbutyl group, 2-ethylpropyl group, etc.) , 2,2-dimethylpropyl group, 2-methylpentyl group, 2-ethylbutyl group, 2-methylhexyl group, 2-ethylpentyl group, 2-methylheptyl group, 2-ethylhexyl group, 2-methyloctyl group, 2 -Ethylheptyl group, 2-methylnonyl group, 2-ethyloctyl group, 2-methyldecyl group, 2-ethylnonyl group, 2-hexyloctadecyl group, 2-octylhexadecyl group, 2-decyltetradecyl group, 2-undecyl group. Tridecyl group, 2-dodecylhexadecyl group, 2-tridecylpentadecyl group, 2-decyl octadecyl group, 2-tetradecyl octadecyl group, 2-hexadecyl octadecyl group, 2-tetradecyleikosyl group, 2-hexa Decyleicosyl group, etc.) 3-34-alkylalkyl group (3-alkylalkyl group, 4-alkylalkyl group, 5-alkylalkyl group, 32-alkylalkyl group, 33-alkylalkyl group and 34-alkylalkyl group Etc.), as well as propylene oligomer (7 to 11 mer), ethylene / propylene (molar ratio 16/1 to 1/11) oligomer, isobutylene oligomer (7 to 8 mer) and α-olefin (5 to 20 carbon atoms). ) A mixed alkyl group containing one or more branched alkyl groups such as an alkyl residue of oxoalcohol corresponding to an oligomer (4 to octamer) and the like.

Of these, a methyl group, an ethyl group, and a 2-alkylalkyl group are preferable from the viewpoint of liquid absorption and electrical characteristics of the electrolytic solution, and 2-ethylhexyl group and 2-decyltetradecyl group are more preferable. be.

The active material coated with the coating agent (hereinafter referred to as the coating active material) is, for example, a resin solution containing a coating resin (for coating) in a state where the active material is placed in a universal mixer and stirred at 10 to 500 rpm. (Resin solution) is added dropwise over 1 to 90 minutes, a conductive additive is further mixed, the temperature is raised to 50 to 200 ° C. with stirring, the pressure is reduced to 0.007 to 0.04 MPa, and then the mixture is held for 10 to 150 minutes. Can be obtained by doing. The solvent of the resin solution is not particularly limited as long as it can dissolve the coating resin, but N, N-dimethylformamide and the like can be preferably used.

The blending ratio of the active material coating resin and the conductive auxiliary agent is not particularly limited, but the active material coating resin (resin solid content weight): conductive auxiliary agent = 1: 0.2 to 1: 3 in terms of weight ratio. It is preferably 0.0.

The mixing ratio of the active material and the active material coating resin (resin solid content weight) is not particularly limited, but the weight ratio is active material: active material coating resin (resin solid content weight) = 1: 0.001. It is preferably ~ 1: 0.1.

The coating resin solution contains a coating resin and a solvent, but may be produced by mixing the coating resin and the conductive auxiliary agent in some cases. By further mixing the coating resin solution mixed in advance with the active material, the coating resin solution adheres to the surface of the active material, and the active material can be coated with the coating agent.

Further, when coating with the coating agent, the coating resin, the active material and the conductive auxiliary agent may be mixed at the same time and coated on the surface of the active material with the coating agent containing the coating resin and the conductive auxiliary agent.

Further, when coating with a coating agent, a coating resin is mixed with the active material, a conductive auxiliary agent is further mixed, and the surface of the active material is coated with a coating agent containing the coating resin and the conductive auxiliary agent. May be good.

As the solvent used for the above-mentioned active material slurry, the same solvent as the solvent of the electrolytic solution used for the lithium ion secondary battery can be used, and carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate can be used. Can be preferably used. Further, 1-methyl-2-pyrrolidone, methylethylketone, N, N-dimethylformamide, dimethylacetamide, N, N-dimethylaminopropylamine, tetrahydrofuran and the like can also be used. The amount of the solvent used is not particularly limited, but is an amount such that the solid content concentration of the slurry is 40 to 80% by weight in consideration of ease of application to the current collector and the like.

As the electrolytic solution, the above-mentioned carbonates and lithium salts [Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiCF ₃ SO ₃ etc.] can be dissolved and an electrolytic solution can be used.

The electrolytic solution may further contain additives other than the above-mentioned components, for example, vinylene carbonate, methylvinylene carbonate, dimethylvinylene carbonate, phenylvinylene carbonate, diphenylvinylene carbonate, ethylvinylene carbonate, diethylvinylene carbonate, vinylethylene carbonate, etc. 1,2-Divinylethylene carbonate, 1-methyl-1-vinylethylenecarbonate, 1-methyl-2-vinylethylenecarbonate, 1-ethyl-1-vinylethylenecarbonate, 1-ethyl-2-vinylethylenecarbonate, vinylvinylene Carbonate, allylethylene carbonate, vinyloxymethylethylene carbonate, allyloxymethylethylene carbonate, acrylicoxymethylethylene carbonate, methacryloxymethylethylene carbonate, ethynylethylene carbonate, propargylethylene carbonate, ethynyloxymethylethylene carbonate, propargyloxyethylene carbonate, methylene Examples thereof include ethylene carbonate and 1,1-dimethyl-2-methyleneethylene carbonate.

If necessary, a conductive auxiliary agent or a binder can be further added to the active material slurry.
When a binder is added, examples of the binder include polymer compounds such as starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, polyvinylpyrrolidone, tetrafluoroethylene, styrene-butadiene rubber, polyethylene and polypropylene. The content of the binder is preferably less than 5% by weight, preferably 0% by weight, based on the weight of the active material, because the internal resistance increases by the amount of the added binder (that is, the active material layer is not formed). It is more preferable to be a binder).

When a conductive auxiliary agent is added to the active material slurry, the same conductive auxiliary agent as that contained in the above-mentioned coating agent can be used as the conductive auxiliary agent, preferably a fibrous conductive auxiliary agent, and more preferably carbon. It is a fiber. The content of the conductive auxiliary agent is preferably 0.5 to 15% by weight, more preferably 1 to 10% by weight, based on the weight of the active material from the viewpoint of battery performance.

As the separator arranged between the positive electrode active material layer and the negative electrode active material layer, a known separator generally used for lithium ion secondary batteries can be used, and vinylidene fluoride-hexafluoropropylene copolymer and polyolefin can be used. Porous film made of (polyethylene, polypropylene, etc.), multilayer film of porous film (for example, a laminate having a three-layer structure of polypropylene / polyethylene / polypropylene, etc.), synthetic fiber (polyester fiber, aramid fiber, etc.), and glass fiber. It is possible to use a polypropylene made of polypropylene, a known separator for a lithium ion secondary battery, or the like, which has ceramic fine particles such as silica, alumina, and titania adhered to the surface thereof.

The cell cell of the lithium ion secondary battery of the present invention has a structure in which a positive electrode, a separator and a negative electrode are laminated, but the outer peripheral portion of the positive electrode, the separator and the negative electrode has a structure sealed by a seal portion. The sealing portion has a function of preventing a short circuit at the end of the cell and preventing the electrolytic solution from leaking from the end of the cell.
As the material constituting the sealing portion, if it has insulating property, sealing property against falling off of solid electrolyte, sealing property against moisture permeation from the outside (sealing property), heat resistance under battery operating temperature, etc. Often, acrylic resin, urethane resin, epoxy resin, polyethylene resin, polypropylene resin, polyimide resin, rubber (ethylene-propylene-diene rubber, etc.) and the like can be used.
Further, an isocyanate-based adhesive, an acrylic resin-based adhesive, a cyanoacrylate-based adhesive, or the like may be used, or a hot melt adhesive (urethane resin, polyamide resin, polyolefin resin) or the like may be used.
Among them, polyethylene resin and polypropylene resin are preferably used as constituent materials of the insulating layer from the viewpoints of corrosion resistance, chemical resistance, ease of production (film formation), economy, etc., and mainly non-crystalline polypropylene resin. It is preferable to use a resin obtained by copolymerizing ethylene, propylene and butene as components.

As the outer container of the lithium ion secondary battery of the present invention, a known metal can case and a bag-shaped case using a laminated film containing aluminum can be used. As the laminating film, a three-layer structure laminating film or the like in which polypropylene, aluminum, and nylon are laminated in this order can be used. Among them, a laminated film is preferable from the viewpoint of high output, excellent cooling performance, light weight, and suitable use for a battery for large equipment.

The lithium ion secondary battery of the present invention has a positive electrode having a positive electrode active material layer formed on the above resin collector for a lithium ion secondary battery, a separator, and the above resin collector for a lithium ion secondary battery. It can be obtained by laminating a cell cell in which a negative electrode having a negative electrode active material layer formed in 1 is laminated by a known method, if necessary, and enclosing the negative electrode together with an electrolytic solution in an outer container.

Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto. In the following description, "part" indicates a part by weight.

<Production Example 1: Preparation of Conductive Porous Resin Layers (A1) to (A4)>
In a twin-screw extruder, polypropylene (trade name "SunAllomer (registered trademark) PL500A", manufactured by SunAllomer Ltd.) 83% by mass, acetylene black [Denka Black (registered trademark) HS-100, manufactured by Denka Co., Ltd., primary particles Average particle size: 36 nm] 12% by mass, and 5% by mass of dispersant (manufactured by Sanyo Kasei Kogyo Co., Ltd., trade name "Umex (registered trademark) 1001", anhydrous maleic acid-modified polypropylene), retained at 180 ° C., 100 rpm. It was melt-kneaded under the condition of 10 minutes, extruded into a gut shape without stretching operation, and cut to obtain a pellet-shaped material for a conductive porous resin layer (1-1). The amount of each of the above components represents a mixing ratio, and the total of polypropylene, acetylene black and the dispersant is 100% by mass.
The obtained conductive porous resin layer material (1-1) was spun, bonded and pressed under the same equipment and conditions as in Example 3 of JP-A-2001-271218, and the conductive porous material having a thickness of 90 μm was obtained. A conductive non-woven fabric (A1) which is a quality resin layer, a conductive non-woven fabric (A2) which is a conductive porous resin layer having a thickness of 120 μm, a conductive non-woven fabric (A3) which is a conductive porous resin layer having a thickness of 180 μm, Conductive nonwoven fabrics (A4) which are conductive porous resin layers having a thickness of 70 μm (in Table 1, (A1) to (A4) are described as “12% AB-PP / nonwoven fabric”) were obtained.

<Manufacturing Example 2: Fabrication of Conductive Porous Resin Layer (A5)>
In Production Example 1, 83% by mass of polypropylene (trade name "SunAllomer (registered trademark) PL500A", manufactured by SunAllomer Ltd.) is converted to 85% by mass of polyethylene (trade name "Novatec LL UJ960", manufactured by Nippon Polyethylene Co., Ltd.) and acetylene. Black [Denka Black (registered trademark) HS-100, manufactured by Denka Co., Ltd., average particle diameter of primary particles: 36 nm] is changed from 12% by mass to 10% by mass, and a conductive porous resin layer having a thickness of 80 μm. (A5) (in Table 1, (A5) is described as "10% AB-PE / nonwoven fabric") was obtained.

<Conductive porous resin layer (A6)>
A urethane foam [Sui-70-5005 manufactured by Salen Co., Ltd .: thickness 450 μm: electric conductivity 300 mS / cm] which was conductively treated by nickel plating was used as a conductive porous resin layer (A6).

<Production Example 3: Preparation of Conductive Non-porous Resin Layers (B1) to (B3)>
In a twin-screw extruder, polypropylene (trade name "SunAllomer (registered trademark) PL500A", manufactured by SunAllomer Ltd.) 75% by mass, acetylene black [Denka Black (registered trademark) HS-100, manufactured by Denka Co., Ltd., primary particles Average particle size: 36 nm] 20% by mass, and a dispersant (manufactured by Sanyo Kasei Kogyo Co., Ltd., trade name "Umex (registered trademark) 1001", anhydrous maleic acid-modified polypropylene) 5% by mass, retained at 180 ° C., 100 rpm. The material (2-1) for a conductive non-porous resin layer was obtained by melt-kneading under the condition of 10 minutes. By rolling the obtained conductive non-porous resin layer material (2-1) with a hot press machine, a conductive non-porous resin layer (B1) having a thickness of 50 μm and a thickness of 100 μm are non-conductive. The porous resin layer (B2) and the conductive non-porous resin layer (B3) having a thickness of 140 μm (in Table 1, (B1) to (B3) are referred to as “20% AB-PP / sheet”), respectively. Obtained.

<Production Example 4: Fabrication of Conductive Non-porous Resin Layer (B4)>
In Production Example 3, polypropylene (trade name "SunAllomer (registered trademark) PL500A", manufactured by SunAllomer Ltd.) was changed from 75% by mass to 25% by mass, and acetylene black [Denka Black (registered trademark) HS-100, Denka Co., Ltd. , Average particle size of primary particles: 36 nm] 20% by mass changed to 70% by mass of nickel powder (Type 255 manufactured by Vale), and a conductive non-porous resin layer (B4) with a thickness of 120 μm (in Table 1, (Table 1). B4) is described as "70% Ni particles-PP / sheet").

<Manufacturing Example 5: Preparation of Conductive Non-porous Resin Layer (B5)>
In Production Example 3, polypropylene (trade name "SunAllomer (registered trademark) PL500A", manufactured by SunAllomer Ltd.) was changed to polyethylene (trade name "Novatec LL UJ960", manufactured by Japan Polyethylene Corporation) to have a thickness of 100 μm. A conductive non-porous resin layer (B5) (in Table 1, (B5) is referred to as "20% AB-PE / sheet") was obtained.

<Manufacturing Example 6: Fabrication of Conductive Non-porous Resin Layer (B6)>
In Production Example 3, polypropylene (trade name "SunAllomer (registered trademark) PL500A", manufactured by SunAllomer Ltd.) was changed from 75% by mass to 55% by mass, and acetylene black [Denka Black (registered trademark) HS-100, Denka Co., Ltd. , Average particle size of primary particles: 36 nm] was changed from 20% by mass to 40% by mass, and the conductive non-porous resin layer (B6) with a thickness of 200 μm ((B6) in Table 1 was changed to “40%”. AB-PP / sheet ") was obtained.

<Production Example 7: Preparation of coating resin solution>
407.9 parts of N, N-dimethylformamide was charged into a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel and a nitrogen gas introduction tube, and the temperature was raised to 75 ° C. Next, a monomer compounded solution containing 242.8 parts of methacrylic acid, 97.1 parts of methyl methacrylate, 242.8 parts of 2-ethylhexyl methacrylate and 116.5 parts of DMF, and 2,2'-azobis (2,4-dimethylvalero). Initiator solution in which 1.7 parts of nitrile) and 4.7 parts of 2,2'-azobis (2-methylbutyronitrile) are dissolved in 58.3 parts of N, N-dimethylformamide are placed in a four-necked flask. Radical polymerization was carried out by continuously dropping the mixture with a dropping funnel over 2 hours while blowing nitrogen. After completion of the dropping, the reaction was continued at 75 ° C. for 3 hours. Then, the temperature was raised to 80 ° C. and the reaction was continued for 3 hours to obtain a copolymer solution having a resin concentration of 50%. 789.8 parts of N, N-dimethylformamide was added thereto to obtain a coating resin solution having a resin solid content concentration of 30% by weight.

<Production Example 8: Preparation of coated positive electrode active material>
1578 g of LiCoO ₂ powder was placed in a universal mixer, and 146 g of the resin solution (resin solid content concentration 30% by weight) prepared in Production Example 7 was added dropwise over 60 minutes in a state of stirring at room temperature and 150 rpm, and further 30 minutes. Stirred. Then, 44 g of acetylene black [manufactured by Denka Co., Ltd.] was mixed in 3 portions in a stirred state, the temperature was raised to 70 ° C. with stirring for 30 minutes, the pressure was reduced to 0.01 MPa, and the mixture was held for 30 minutes. By the above operation, 1666 g of the coated positive electrode active material was obtained.

<Example 1>
The non-woven fabric for the conductive porous resin layer (A1) produced in Production Example 1 and the conductive non-porous resin layer (B1) produced in Production Example 3 are laminated and heated to 120 ° C. while being rolled by a hot press machine. By rolling, a resin collector for a lithium ion secondary battery of the present invention having a thickness of 100 μm having two layers, a conductive porous resin layer and a conductive non-porous resin layer, was obtained. The thickness of (A1) after fusion was 50 μm, and the thickness of (B1) was 50 μm.

<Examples 2 to 6>
According to Table 1, resin current collectors for lithium ion secondary batteries of Examples 2 to 6 were obtained in the same manner as in Example 1.

The lithium-ion secondary battery for evaluation was manufactured and the charge / discharge cycle characteristics were evaluated by the following method.

<Manufacturing of lithium-ion secondary battery>
90 parts of the coated positive electrode active material prepared in Production Example 8, 5 parts of acetylene black [manufactured by Denka Co., Ltd.] and 5 parts of polyvinylidene fluoride are mixed, and 50 parts of N-methyl-2-pyrrolidone are further mixed to activate the positive electrode. A substance slurry was prepared. This slurry is coated on the conductive porous resin layer of the resin collector for a lithium ion secondary battery produced in Example 1 so that the coating amount (surface density) of the positive electrode active material is 2.5 mg / cm ² . Then, it was further heated to 80 ° C. under reduced pressure to form a coated positive electrode active material layer (thickness: 40 μm) on a resin current collector for a lithium ion secondary battery.
Next, a separator (made of polypropylene having a thickness of 25 μm) was laminated on the coated positive electrode active material layer. The obtained laminate was punched into a disk shape with a diameter of 15 mm, and the metal lithium punched into a disk shape with a diameter of 15 mm was stacked on a separator, stored in a coin cell container for evaluation, further injected with an electrolytic solution, and then sealed. It was stopped to produce a lithium ion secondary battery (V1) for evaluation. As an electrolytic solution, a solution prepared by dissolving 1M LiPF ₆ in a mixed solvent of ethylene carbonate and dimethyl carbonate (volume ratio 1: 1) was prepared.
Similarly for Examples 2 to 6, evaluation lithium ion secondary batteries (V2 to V6) were produced.

<Evaluation of charge / discharge cycle characteristics of lithium-ion secondary battery>
Using the charge / discharge measuring device "Battery Analyzer 1470" [manufactured by Toyo Technica Co., Ltd.], the evaluation lithium ion secondary battery (V1) is charged to a voltage of 4.3 V with a current of 0.1 C for 10 minutes. After the pause, the battery voltage was discharged to 3.0 V with a current of 0.1 C, and this charging and discharging was repeated. At this time, the battery capacity at the time of the first charge and the battery capacity at the time of the 200th cycle charge were measured, and the charge / discharge cycle characteristics (hereinafter, also referred to as cycle characteristics) were calculated from the following formulas. The value of the obtained charge / discharge cycle characteristics was 91%.
Charge / discharge cycle characteristics (%) = (battery capacity at the time of charging the 200th cycle / battery capacity at the time of initial charging) × 100
Similarly, the charge / discharge cycle characteristics of the evaluation lithium ion secondary batteries (V2 to V6) were evaluated. The results are shown in Table 1.
The larger the value of the charge / discharge cycle characteristic, the better the charge / discharge cycle characteristic, indicating that the charge / discharge cycle characteristic has excellent long-term reliability.

<Comparative Example 1>
Except that the resin collector for the lithium ion secondary battery produced in Example 1 was changed to the one in which the thickness of the conductive non-porous resin layer produced in Production Example 3 was changed to 180 μm (B7). A lithium ion secondary battery (H1) for comparative evaluation was produced in the same manner as in Example 1, and the charge / discharge cycle characteristics were measured and calculated in the same manner as in Example 1. The value of the obtained charge / discharge cycle characteristics was 80%.

Table 1 shows the results of charge / discharge cycle characteristics of the evaluation lithium ion secondary batteries (V1 to V6) and the comparative evaluation lithium ion secondary batteries (H1). As shown in Table 1, Examples 1 to 6 having a conductive porous resin layer have better charge / discharge cycle characteristics than Comparative Example 1 having no conductive porous resin layer, and have excellent long-term reliability. Had. From the above results, the resin collector for lithium ion secondary batteries having a conductive porous resin layer has excellent adhesive strength with the active material layer, and an increase in resistance value during a 200-cycle charge / discharge test is suppressed. it is conceivable that.

The battery using the resin collector for a lithium ion secondary battery of the present invention has excellent charge / discharge cycle characteristics. This is because the current collector has a conductive porous resin layer, which improves the adhesion to the active material layer, and the stress caused by the volume change of the active material during charging and discharging also causes defects such as peeling at the interface. It is thought that it became difficult.

Since the resin collector for a lithium ion secondary battery of the present invention has excellent charge / discharge cycle characteristics, the lithium ion secondary battery using the resin collector has excellent cycle characteristics, and in particular, a portable device such as a mobile phone and electricity. It is useful as a resin collector for lithium-ion secondary batteries used in automobiles and the like.

1 Electrode 10 Resin collector for lithium ion secondary battery 100 Conductive non-porous resin layer 200 Conductive porous resin layer 210 Conductive resin fiber 300 Active material layer 310 Active material

Claims (7)

With a conductive non-porous resin layer,
It is composed of a conductive porous resin layer laminated on the conductive non-porous resin layer .
A resin current collector for a lithium ion secondary battery , wherein the conductive porous resin layer is a woven fabric, a non-woven fabric, or a knitted fabric of conductive resin fibers . The resin collection for a lithium ion secondary battery according to claim 1 , wherein the conductive resin fiber comprises a first conductive resin composition comprising a first conductive filler and a first non-conductive resin. Electric body. The lithium ion II according to claim 1 or 2 , wherein the conductive non-porous resin layer comprises a second conductive resin composition comprising a second conductive filler and a second non-conductive resin. Resin collector for next battery. The conductive resin fiber comprises a first conductive resin composition comprising a first conductive filler and a first non-conductive resin.
The conductive non-porous resin layer comprises a second conductive resin composition comprising a second conductive filler and a second non-conductive resin.
The lithium ion II according to claim 1, wherein the first conductive filler and the second conductive filler, and the first non-conductive resin and the second non-conductive resin are the same. Resin collector for next battery. The resin current collector for a lithium ion secondary battery according to any one of claims 1 to 4 , wherein the conductive non-porous resin layer has a thickness of 5 to 150 μm. The resin current collector for a lithium ion secondary battery according to any one of claims 1 to 5 , wherein the conductive porous resin layer has a thickness of 5 to 150 μm. A lithium ion secondary battery comprising the resin collector for a lithium ion secondary battery according to any one of claims 1 to 6 .

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