WO2013002055A1

WO2013002055A1 - Current collector and electrode for use in non-aqueous secondary cell, and non-aqueous secondary cell

Info

Publication number: WO2013002055A1
Application number: PCT/JP2012/065500
Authority: WO
Inventors: 虎太　直人; 里美長谷川; 智史有馬
Original assignee: シャープ株式会社
Priority date: 2011-06-29
Filing date: 2012-06-18
Publication date: 2013-01-03
Also published as: JPWO2013002055A1

Abstract

Provided is a current collector for use in a non-aqueous secondary cell, the current collector constituting the cathode and/or anode used in the non-aqueous secondary cell, and having an active material layer arranged thereon. In this current collector for use in a non-aqueous secondary cell, the current collector is constituted by: a resin film; and a conductive layer stacked on at least one face of the resin film, and able to contact the active material layer; the conductive layer being furnished with one or more areas of exposure of the resin film, in which the resin film and the active material layer are able to come into direct contact.

Description

Current collector and electrode for non-aqueous secondary battery, and non-aqueous secondary battery

The present invention relates to a current collector and electrodes for a non-aqueous secondary battery, and a non-aqueous secondary battery. More specifically, the present invention relates to a non-aqueous secondary battery current collector that can effectively use an active material layer formed thereon, an electrode using the current collector, and a non-aqueous system using the electrode The present invention relates to a secondary battery.

A lithium oxide secondary battery (hereinafter simply referred to as a non-aqueous secondary battery) using a metal oxide as a positive electrode, an organic electrolyte as an electrolyte, a carbon material such as graphite as a negative electrode, and a porous separator between the positive electrode and the negative electrode Since it was first commercialized in 1991, it has rapidly spread as a battery for portable devices such as mobile phones that are becoming smaller and lighter due to its high energy density.
In addition, lithium ion secondary batteries (large capacity batteries) having a large capacity for storing the generated electricity have been studied. As this large-capacity battery, an example in which a conventional battery is simply scaled up has been reported.

The positive electrode and the negative electrode usually include an active material layer containing a positive electrode active material or a negative electrode active material (hereinafter also simply referred to as an active material) on a current collector. A metal foil is usually used for the current collector.
By the way, the lithium ion secondary battery uses an organic electrolyte as an electrolyte. Therefore, it is desired to prevent accidents such as rupture and fire even under severe use conditions. The metal foil did not have a function to prevent such an accident. Therefore, International Publication WO2009 / 131184 (Patent Document 1) proposes to use a film-like or fibrous resin layer having a conductive layer on both sides as a current collector.
In the battery including the current collector, when abnormal heat generation occurs, the positive electrode and / or the negative electrode are damaged by the melting of the resin layer, and a short circuit between the positive electrode and the negative electrode is prevented. As a result, the temperature rise inside the battery can be suppressed.

International Publication WO2009 / 131184

From the current collector of Patent Document 1, a battery with improved safety can be obtained. By the way, the positive electrode or the negative electrode is obtained by forming an active material layer containing a positive electrode active material or a negative electrode active material on a current collector. From the viewpoint of long-term reliability, the active material layer peels off from the current collector, and in particular, it becomes difficult to collect the active material. Therefore, there has been a problem that the battery capacity decreases when the battery is charged and discharged.

Thus, according to the present invention, it is a current collector for a non-aqueous secondary battery that constitutes at least one of a positive electrode and a negative electrode used in a non-aqueous secondary battery, and on which an active material layer is placed,
The current collector is composed of a resin film and a conductive layer that is laminated on at least one surface of the resin film and can be in contact with the active material layer,
The conductive layer is provided with a current collector for a non-aqueous secondary battery including at least one exposed region of the resin film in which the resin film and the active material layer can be in direct contact with each other.

Further, according to the present invention, at least one of a positive electrode and a negative electrode is a nonaqueous secondary battery electrode, and the nonaqueous secondary battery current collector and the conductive layer of the nonaqueous secondary battery current collector There is provided an electrode for a nonaqueous secondary battery comprising an active material layer formed thereon.
Furthermore, according to the present invention, it includes a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, and an electrolyte, and at least one of the positive electrode and the negative electrode is the electrode for a non-aqueous secondary battery. A non-aqueous secondary battery is provided.

The inventors of the present invention have the effect that the presence of the exposed region of the resin film on the current collector has the effect of further improving the adhesion between the current collector and the active material layer compared to the current collector of the metal foil. I found.
Therefore, according to the present invention, the degree of decrease in the utilization factor of the active material can be reduced as compared with the conventional case. As a result, the current collector and the non-aqueous secondary battery electrode that can improve the battery cycle characteristics, and the battery cycle characteristics are improved. A non-aqueous secondary battery can be provided.
Furthermore, since the resin film is used for the current collector, when the positive electrode and the negative electrode are short-circuited by a foreign object, the resistance in the vicinity of the short-circuit can be increased by fusing the resin film with heat generated by the short-circuit. As a result, since a short circuit between the positive electrode and the negative electrode can be cut off, it is possible to provide a current collector that can improve battery safety, an electrode for a non-aqueous secondary battery, and a non-aqueous secondary battery with improved safety.

When the current collector for the non-aqueous secondary battery has one or more openings in the region where the active material layer can be placed, the adhesion between the current collector and the active material layer can be further improved, so that the battery cycle characteristics Can be provided.
When the non-aqueous secondary battery current collector has one or more openings with a maximum diameter of 1 to 1000 μm in the region where the active material layer can be placed, the adhesion between the current collector and the active material layer is further improved. Therefore, it is possible to provide a current collector that can further improve battery cycle characteristics.
When the opening portion has an area of 0.5 to 50.0% of the area of the conductive layer in plan view (however, when there are a plurality of opening portions, the total area), the current collector and the active material layer Since the adhesion can be further improved, a current collector that can further improve the battery cycle characteristics can be provided.

It is the schematic sectional drawing and schematic plan view of the electrical power collector of Example 1 by this invention. It is the schematic sectional drawing and schematic plan view of the electrical power collector of Example 2 by this invention. It is the schematic sectional drawing and schematic plan view of the electrical power collector of this invention. 4 is a graph showing battery cycle characteristics of Example 1, Example 2, and Comparative Example 1;

(1) Current collector for non-aqueous secondary battery The current collector for non-aqueous secondary battery of the present invention (hereinafter simply referred to as current collector) can be used for either or both of the positive electrode and the negative electrode. Examples of the non-aqueous secondary battery that can use the current collector of the present invention include a lithium ion secondary battery and a lithium metal secondary battery. Among these, a lithium ion secondary battery that can use the current collector of the present invention for both the positive electrode and the negative electrode is preferable.
The current collector of the present invention comprises a resin film and a conductive layer laminated on at least one surface thereof. The conductive layer may be laminated only on one side of the resin film, or may be laminated on both sides. This conductive layer is a layer in which an active material layer is placed on an electrode (positive electrode and / or negative electrode) and is in contact with the active material layer.

The thickness of the current collector is preferably in the range of 0.01 to 0.1 mm. When the thickness is less than 0.01 mm, the supportability of the active material layer may not be ensured sufficiently. If it is thicker than 0.1 mm, the volume ratio of the current collector to the secondary battery becomes large, so the battery capacity may not be increased. This thickness can be 0.01 mm, 0.02 mm, 0.03 mm, 0.05 mm, 0.08 mm and 0.1 mm. A more preferred thickness is in the range of 0.02 to 0.08 mm.
The current collector preferably has a sheet resistance of 0.1Ω / □ or less from the viewpoint of securing sufficient current collecting performance. The sheet resistance can be 0.01Ω / □, 0.03Ω / □, 0.05Ω / □, 0.08Ω / □, and 0.1Ω / □. A more preferable sheet resistance is 0.05Ω / □ or less.

(A) Resin film The resin film is not particularly limited as long as it is made of a resin material that hardly affects the battery reaction. From the viewpoint of imparting safety to the battery, a resin material that melts when the temperature rises is preferable. Examples of such a resin material include polyolefin resins such as polyethylene (PE) and polypropylene (PP) having a heat distortion temperature of 200 ° C. or less, and resin films such as polystyrene (PS).
As the resin film, a film produced by any method such as uniaxial stretching, biaxial stretching, and non-stretching can be used.

The thickness of the resin film can be appropriately adjusted in order to obtain a current collector having the above thickness. For example, the thickness is preferably in the range of 0.01 to 0.1 mm. When the thickness is less than 0.01 mm, the supportability of the active material layer may not be ensured sufficiently. If it is thicker than 0.1 mm, the volume ratio of the current collector to the secondary battery becomes large, so the battery capacity may not be increased. This thickness can be 0.01 mm, 0.015 mm, 0.03 mm, 0.05 mm, 0.08 mm and 0.1 mm. A more preferred thickness is in the range of 0.015 to 0.05 mm.

(B) Conductive layer The conductive layer on the positive electrode side is preferably a layer made of aluminum, titanium, nickel or the like, and the negative electrode side conductive layer is preferably a layer made of copper, nickel or the like.
The thickness of the conductive layer is not particularly limited as long as conductivity can be ensured, but is usually in the range of 0.002 to 0.01 mm. This thickness can be 0.002 mm, 0.004 mm, 0.0065 mm, 0.008 mm and 0.01 mm.
The method for forming the conductive layer is not particularly limited, and examples thereof include methods such as vapor deposition, sputtering, electrolytic plating, electroless plating, bonding, and combinations of these methods.

(C) Exposed region of resin film In the current collector of the present invention, the exposed region of the resin film is in contact with the active material layer placed on the current collector. This is because the adhesiveness between the resin film constituting the current collector and the active material layer is higher than the adhesiveness between the conductive layer constituting the current collector and the active material layer. In other words, the resin constituting the resin film has higher adhesiveness with the organic material contained in the active material layer than the metal constituting the conductive layer. In particular, it is more preferable that the resin layer of the current collector and the organic material in the active material layer contain the same component resin.

The exposed region of the resin film may be formed in any part of the current collector as long as it can contact the active material layer to be placed in the region. For example, as shown in the schematic cross-sectional views and the schematic plan views of FIGS. 1A and 1B and FIGS. 2A and 2B, an opening is formed in a region where the active material layer of the current collector can be placed. By forming the portion, the side surface of the through hole constituting the opening portion can be an exposed region. Furthermore, you may produce the exposed area | region of a resin film by removing only a conductive layer and not penetrating a hole. Examples of the form of such a current collector include the forms shown in the schematic cross-sectional views and schematic plan views of FIGS. 3 (a) and 3 (b) are a method of laminating a conductive layer having an opening formed in advance on a resin film, a method of etching a conductive layer using a mask having an opening corresponding to the opening, It can be formed by a method of stretching a laminate film composed of a conductive layer and a resin film layer.

1A and 1B and FIGS. 2A and 2B, 1 is a conductive layer, 2 is a resin film, 3 is an opening, 3a is a recess, 3b is a protrusion, and a is a depth of the recess. The height and the height of the convex part, b means the diameter of the uppermost end of the concave part and the lowest part of the convex part, and y and d mean the maximum diameter of the hole.
The planar shape of the opening is not particularly limited, and examples thereof include a circle, an ellipse, a triangle, a quadrangle, a pentagon, a hexagon, a polygon that is heptagon or more, a star, and an indefinite shape. Among these, from the viewpoint of easy formation, a circle and a quadrangle are preferable.

The opening portion preferably has a maximum diameter of 1 to 1000 μm. When the maximum diameter is less than 1 μm, the effect of improving the adhesion of the active material layer due to the exposed region at the opening may be reduced. When it is larger than 1000 μm, the area where the conductive layer is in contact with the active material layer becomes small, and thus the current collection efficiency may be lowered. The maximum diameter can be 1 μm, 5 μm, 8 μm, 10 μm, 20 μm, 30 μm, 50 μm, 200 μm, 300 μm, 400 μm, 600 μm, 800 μm and 1000 μm. A more preferable maximum diameter is 5 to 300 μm. The maximum length corresponds to the diameter when the planar shape is circular, and the diagonal length when the planar shape is square.

Furthermore, the area of the opening portion (however, when there are a plurality of the opening portions, the total area thereof) is preferably 0.5 to 50% of the area of the conductive layer in a plan view of the current collector. If it is less than 0.5%, the effect of improving the adhesion of the active material layer due to the exposed region at the opening may be reduced. If it exceeds 50%, the area where the conductive layer is in contact with the active material layer becomes small, and the current collection efficiency may be reduced. This area can take 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% and 50%. A more preferable area ratio is 1.0 to 30.0%.
In FIGS. 1 to 3, a plurality of exposed regions are provided, but the number is not particularly limited, and may be one or two or more. For example, it may be 0.1 to 20 / mm ² per unit area of the current collector in plan view. This number is 0.1 / mm ² , 0.5 / mm ² , 1 / mm ² , 2 / mm ² , 5 / mm ² , 10 / mm ² , 15 / mm ² and It can take 20 pieces / mm ² .

Further, the area of the exposed region (however, when there are a plurality of exposed areas) is preferably 0.1 to 30.0% of the area of the conductive layer in plan view. If it is less than 0.1%, the effect of improving the adhesion of the active material layer due to the exposed region may be reduced. When the content is more than 30.0%, the area where the conductive layer is in contact with the active material layer is small, and thus current collection efficiency may be reduced. This area can be 0.1%, 1%, 2%, 0.5%, 5%, 10%, 15%, 20%, 25% and 30%. A more preferable area ratio is 0.5 to 10.0%.

2A and 2B, the current collector has a three-dimensional structure region. The three-dimensional structure region means a region where one or more concave portions and / or convex portions are formed in a direction perpendicular to the plane of the current collector. The current collector may include only a concave portion, may include only a convex portion, or may include both a concave portion and a convex portion. Furthermore, when providing both, a recessed part and a convex part may be arranged alternately, and the area | region only of a recessed part and the area | region only of a convex part may be arranged.
The three-dimensional structure region preferably occupies half or more of the plane of the current collector including the three-dimensional structure region. By occupying more than half, the adhesiveness of the active material layer formed thereon can be improved. The upper limit of the ratio of the three-dimensional structure region occupying the plane of the current collector is the entire surface. However, since the current collector is provided with a terminal for taking out electricity at either end, the portion where the end is provided should be flat with a width in the range of 2 to 20 mm from the end. preferable. This width can be 2 mm, 6 mm, 10 mm, 14 mm, 18 mm and 20 mm. Therefore, it is preferable that the three-dimensional structure region occupies the plane of the current collector in the range of 1.0 to 10.0% from the viewpoint of the efficiency of the charge / discharge reaction and the necessity of the region for forming the terminal. . This range can take 1%, 3%, 5%, 7% and 10%.

The number of concave portions and convex portions in the three-dimensional structure region (the total number when both concave portions and convex portions are formed) is not particularly limited as long as the effect of the present invention is not impaired. For example, it can be 0.1 / mm ² or more per unit area of the three-dimensional structure region. The upper limit of the number is the number that can form a concave portion and a convex portion in the three-dimensional structure region, and is, for example, 20 pieces / mm ² or less. A more preferable number is in the range of 0.5 to 10 pieces / mm ² . This number can be 0.5 / mm ² , 1 / mm ² , 2 / mm ² , 3 / mm ² , 6 / mm ² , 8 / mm ^2, and 10 / mm ^2. . In FIGS. 2A and 2B, the exposed region of the resin film is formed by providing a through-hole of the current collector at the bottom of the concave portion and the apex of the convex portion, but all the concave and convex portions are formed. It is not necessary to provide a through hole in the part.
The planar shape of the concave and convex portions (the plane means the conductive layer forming surface of the resin film) is not particularly limited as long as the effect of the present invention is not impaired. Examples thereof include a circle (see FIG. 2B), an ellipse, a triangle, a quadrangle, a pentagon, a hexagon, a polygon with a heptagon or more, a star, and an indefinite shape. Among these, a circular shape and a quadrangular shape are preferable from the viewpoint of easy formation.

If the maximum length of the uppermost end of the concave portion and the maximum length of the lowermost end of the convex portion are too small, the effect of improving the conductivity will be small, and if it is too large, it will be difficult to form the active material layer uniformly. Therefore, it is preferably in the range of 1 to 1000 μm. This maximum length can be 1 μm, 5 μm, 10 μm, 20 μm, 50 μm, 100 μm, 200 μm, 400 μm, 500 μm, 600 μm, 800 μm and 1000 μm. A more preferred maximum length is in the range of 5 to 500 μm. The maximum length corresponds to, for example, the diameter when the planar shape is circular, and the length of the diagonal line when the planar shape is square.
The cross-sectional shapes of the concave portion and the convex portion are not particularly limited as long as the effects of the present invention are not impaired. For example, a triangle (see FIG. 2A), a quadrangle, a partial circle, and the like can be given. Here, when the concave portion and the convex portion are partial circles, a corrugated cross-sectional shape can be obtained by alternately arranging the concave portion and the convex portion.

If the depth of the concave portion and the height of the convex portion are too small, the effect of improving the adhesiveness is small, and if it is too large, it is difficult to form the active material layer uniformly. Accordingly, the range of 50 to 1000 μm is preferable. This height can be 50 μm, 100 μm, 200 μm, 400 μm, 500 μm, 600 μm, 800 μm and 1000 μm. A more preferred height is in the range of 100 to 500 μm.
The three-dimensional structure region can be formed by, for example, a pressing method using a male mold and a female mold, a punching processing method, a lath processing method, or the like. Note that the three-dimensional structure region may be formed either after the conductive layer is formed or before the formation.

(2) Electrode for non-aqueous secondary battery An electrode for non-aqueous secondary battery (hereinafter also simply referred to as electrode) includes the current collector and an active material layer formed on the current collector. Here, an electrode means a positive electrode, a negative electrode, or a positive electrode and a negative electrode. The active material layer is a positive electrode active material layer in the case of a positive electrode, and is a negative electrode active material layer in the case of a negative electrode.

(A) Positive electrode (i) Positive electrode active material layer As a positive electrode active material contained in a positive electrode active material layer, the oxide containing lithium is mentioned. Specifically, LiCoO ₂ , LiNiO ₂ , LiFeO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , and a part of transition metals in these oxides are replaced with other metal elements (Co, Ni, Fe, Mn, Al, Mg Etc.), oxides having an olivine structure represented by LiMPO ₄ (M is at least one element selected from Co, Ni, Mn, and Fe). Among these, a positive electrode active material using Mn and / or Fe is preferable from the viewpoint of cost.

Examples of the positive electrode active material include olivine type lithium iron phosphate (eg, LiFePO ₄ ) from the viewpoints of safety and charging voltage. Normally, as the temperature rises, the positive electrode active material releases oxygen and burns the electrolyte solution, generating more intense heat. However, LiFePO ₄ is preferable from the viewpoint of safety because all oxygen is bonded to phosphorus by a strong covalent bond, and the release of oxygen hardly occurs due to temperature rise. In addition, since it contains phosphorus, it can be expected to have an anti-inflammatory effect. Furthermore, since the charging voltage of olivine type lithium iron phosphate is about 3.5V, and charging is almost completed at 3.8V, there is a little margin to the voltage that causes the decomposition of the electrolyte. Therefore, even if there is electrode polarization in the specified load characteristics, charging is possible by increasing the charging voltage, which is more preferable.

When using a positive electrode active material whose charging voltage reaches 4 V or higher, the electrolytic solution is likely to be decomposed when the charging voltage is further increased. For this reason, when the polarization is large as described above, if the charging voltage is increased and charging is performed, cycle characteristics may be affected, which is not preferable. In addition, since the voltage of olivine type lithium iron phosphate increases rapidly at the end of charging, it is very easy to detect the fully charged state, and even when an assembled battery is used, the accuracy of voltage detection is not so required. It also has the advantage of.

(Ii) Other Additives In order to maintain the positive electrode active material layer as a layer, a binder may be included in addition to the positive electrode active material.
Examples of the binder include fluorine polymers such as polyvinylidene fluoride (PVDF), polyvinyl pyridine, and polytetrafluoroethylene, polyolefin polymers such as polyethylene and polypropylene, and styrene butadiene rubber. In particular, it is preferable that the resin of the binder and the resin layer used for the current collector have the same component in order to give a better tendency to the long-term cycle performance of the battery.

In addition, the positive electrode active material layer may contain a conductive material or a thickener.
As the conductive material, it is preferable to use a chemically stable material. Specific examples include carbonaceous materials such as carbon black, acetylene black, ketjen black, graphite (natural graphite, artificial graphite), carbon fiber, and conductive metal oxides.
Examples of the thickener include polyethylene glycols, celluloses, polyacrylamides, poly N-vinyl amides, poly N-vinyl pyrrolidones and the like.

The mixing ratio of the binder, the thickener, and the conductive material varies depending on the types of the binder, the thickener, and the conductive material to be mixed, but the binder is 1 to 50 with respect to 100 parts by weight of the positive electrode active material. About 0.1 parts by weight, thickener is about 0.1-20 parts by weight, and conductive material is about 0.1-50 parts by weight. When the amount of the binder is less than about 1 part by weight, the binding ability may be insufficient. When the amount of the binder is more than about 50 parts by weight, the amount of active material contained in the positive electrode is reduced, and the resistance or polarization of the positive electrode is increased. As a result, the discharge capacity may be reduced. Further, if the thickener is less than about 0.1 parts by weight, the thickening ability may be insufficient, and if it is more than about 20 parts by weight, the amount of the active material contained in the positive electrode decreases, and the positive electrode resistance or Polarization and the like may increase and the discharge capacity may decrease. Furthermore, if the conductive material is less than about 0.1 parts by weight, the resistance or polarization of the positive electrode may increase and the discharge capacity may decrease, and if it exceeds about 50 parts by weight, the amount of active material contained in the positive electrode will decrease. As a result, the discharge capacity as the positive electrode may be reduced.
The amount of the binder can be 1 part by weight, 2 parts by weight, 10 parts by weight, 20 parts by weight, 30 parts by weight, 40 parts by weight, and 50 parts by weight. 5 parts by weight, 8 parts by weight, 10 parts by weight, 13 parts by weight, 18 parts by weight and 20 parts by weight, and the amount of the conductive material is 0.1 parts by weight, 6 parts by weight, 10 parts by weight, 20 parts by weight. Part, 30 parts, 40 parts and 50 parts by weight can be taken.

(B) Negative electrode (i) Negative electrode active material layer As the negative electrode active material contained in the negative electrode active material layer, natural graphite, particulate (scalar or lump, fiber, whisker, spherical, crushed, etc.) artificial graphite Or highly crystalline graphite typified by graphitized products such as mesocarbon microbeads, mesophase pitch powder and isotropic pitch powder, and non-graphitizable carbon such as resin-fired charcoal. These negative electrode active materials may consist of only 1 type, and may consist of 2 or more types of mixtures. Also, alloy materials having a large capacity such as tin oxide and silicon-based negative electrode active materials can be used.

(Ii) Other Additives The negative electrode active material layer may contain other additives such as a binder, a conductive material, and a thickener as in the positive electrode active material layer. As these other additives, any of those described in the column of the positive electrode active material layer can be used. Further, similarly to the positive electrode active material layer, it is preferable that the resin of the binder and the resin layer used for the current collector have the same components because a tendency toward better long-term reliability of the battery can be obtained.

(C) Formation method The active material layer is formed by a known method such as, for example, a method of applying a paste containing an active material and optionally other additives onto a current collector and drying the obtained coating film. Can be formed. Further, it is possible to form a thick active material layer by repeating application and drying. Further, after drying, the electrode may be pressed to improve the workability of the electrode.
The active material layer may cover the entire surface of the current collector, or may cover the current collector region excluding the portion where the terminal is formed. Further, an active material layer may be formed on both sides of the current collector. Furthermore, two current collectors having an active material layer on one surface are formed, and the other surfaces of the two current collectors on which the active material layer is not formed are bonded to each other, whereby an electrode having an active material layer on both surfaces You may get

(3) Non-aqueous secondary battery The non-aqueous secondary battery includes a positive electrode, a negative electrode, a separator positioned between the positive electrode and the negative electrode, and an electrolyte.
(A) Electrode At least one of a positive electrode and a negative electrode is the said electrode for non-aqueous secondary batteries. Both the positive electrode and the negative electrode may be the non-aqueous secondary battery electrode.
As an electrode other than the electrode for the non-aqueous secondary battery, a known material is composed of a flat current collector (a metal foil, a laminate of a conductive layer and a resin film, etc.) and an active material layer formed thereon. The electrode is mentioned.

(B) Separator The separator can be appropriately selected from, for example, electrically insulating synthetic resin fibers, glass fibers, nonwoven fabrics such as natural fibers, woven fabrics, or microporous membranes. Of these, non-woven fabrics such as polyethylene, polypropylene, polyester, aramid resin, and cellulose resin, and microporous membranes are preferable from the viewpoint of quality stability and the like. Some of these synthetic resin non-woven fabrics and microporous membranes have a function in which the separator melts by heat and blocks between the positive and negative electrodes when the battery abnormally heats up. can do.

Although the thickness of a separator is not specifically limited, The thickness which can hold | maintain a required amount of electrolyte solution and prevents the short circuit of a positive electrode and a negative electrode should just be sufficient. For example, it is about 10 to 500 μm. This thickness can be 10 μm, 20 μm, 65 μm, 80 μm, 100 μm, 200 μm, 300 μm, 400 μm and 500 μm. A preferred thickness is about 20 to 80 μm. The separator is made of a material having an air permeability of 0.01 to 500 seconds / cm ³ because strength sufficient to prevent a short circuit inside the battery can be secured while maintaining a low battery internal resistance. preferable. The air permeability is 0.01 sec / cm ³ , 0.03 sec / cm ³ , 100 sec / cm ³ , 200 sec / cm ³ , 300 sec / cm ³ , 400 sec / cm ³ and 500 sec / cm ^3. Can take.
The shape and size of the separator are not particularly limited, and examples thereof include various shapes such as a rectangle such as a square or a rectangle, a polygon, and a circle.

(C) Electrolyte As the electrolyte, an electrolytic solution containing an organic solvent and an electrolyte salt is generally used.
Examples of the organic solvent include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and butylene carbonate, chain carbonates such as dimethyl carbonate (DMC), diethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate, γ- Lactones such as butyrolactone and γ-valerolactone, furans such as tetrahydrofuran and 2-methyltetrahydrofuran, ethers such as diethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, dioxane, Examples thereof include dimethyl sulfoxide, sulfolane, methyl sulfolane, acetonitrile, methyl formate, and methyl acetate. Two or more of these organic solvents may be mixed.

Examples of the electrolyte salt include lithium borofluoride (LiBF ₄ ), lithium phosphofluoride (LiPF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium trifluoroacetate (LiCF ₃ COO), lithium imide trifluoromethanesulfonate ( Examples thereof include lithium salts such as LiN (CF ₃ SO ₂ ) ₂ ). Two or more of these electrolyte salts may be mixed.
Moreover, it is also possible to use the gel electrolyte which hold | maintained the said electrolyte solution in the polymer matrix, and the electrolyte containing an ionic liquid.

(D) Others The battery may be held in a bag made of an outer can or a resin film.
For the outer can, it is preferable to use a metal can, that is, a material in which iron is nickel-plated. This is because it can be achieved at low cost in order to maintain the strength of the outer can. Other can materials may be, for example, stainless steel, aluminum or the like. The shape of the outer can may be any of a thin flat tube type, a cylindrical type, a rectangular tube type, etc., but in the case of a large lithium secondary battery, it is often used as an assembled battery, so it is a thin flat type or a square type. Is preferred.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
Example 1
LiFePO ₄ having an olivine structure as a positive electrode active material, acetylene black as a conductive material, CMC as a thickener, an aqueous binder as a binder, positive electrode active material: conductive material: thickener: binder = 100: 6: It was weighed so as to be 2: 2 (weight ratio). These raw materials were kneaded with water to prepare a positive electrode forming paste.
The positive electrode forming paste is applied to both surfaces of the positive electrode current collector shown in the schematic cross-sectional view of FIG. 1A and the schematic plan view of FIG. 1B, dried sufficiently, and then pressed. A positive electrode provided with an active material layer was obtained.
The positive electrode current collector of FIG. 1 was made of a laminate film having an opening portion made of 6.5 μm aluminum foil / 30 μm polyolefin resin layer / 6.5 μm aluminum foil (planar shape: rectangular having a length of 250 mm and a width of 150 mm). ).

The outline of the opening is as follows.
-Number of holes formed by hole processing constituting the opening portion: 18750 (the number per unit area is 0.5 / mm ² )
・ Maximum hole diameter: 250 μm
-Ratio of the area occupied by the total area of the opening portion in the plan view of the positive electrode current collector: 10.0%
Artificial graphite as a negative electrode active material, CMC as a thickener, and a water-based binder as a binder were weighed so that the negative electrode active material: thickener: binder = 98: 1: 1 (weight ratio). These raw materials were kneaded using water to produce a paste for forming a negative electrode. This paste was applied to both sides of a copper foil as a negative electrode current collector, sufficiently dried, and then pressed to obtain a negative electrode provided with a negative electrode active material layer (negative electrode coating part size width 205 mm × length 158 mm).

Aramid resin nonwoven fabric (Nippon Vilene Co., Ltd., hereinafter referred to as aramid resin layer) having a width of 205 mm, a length of 158 mm, and a thickness of 65 μm is used as a separator. Separator / positive electrode / separator / negative electrode / separator / positive electrode / separator / negative electrode / separator / positive electrode / separator / negative electrode / separator / negative electrode / separator / positive electrode / separator / negative electrode / separator / positive electrode / separator / negative electrode / separator / Positive electrode / separator / negative electrode / separator / positive electrode / separator /
By laminating in order of the negative electrode, a battery element was obtained. Further, a tab was welded to each positive electrode and negative electrode. The obtained battery element was inserted into a can.
As the electrolytic solution, a solution obtained by dissolving 1M LiPF ₆ in a solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 1: 1 was used. This electrolytic solution was poured into a can and kept under reduced pressure. Subsequently, after returning to atmospheric pressure, the outer periphery of the lid was sealed to produce a battery.

Example 2
As the positive electrode current collector, a laminate film having a structural region shown in FIG. 3 composed of 6.5 μm aluminum foil / 30 μm polyolefin resin layer / 6.5 μm aluminum foil was used (planar shape: rectangle having a length of 250 mm and a width of 150 mm). ).
-Opening shape of the conductive layer: Circle-Number of holes formed by hole processing constituting the opening: 1875 (the number per unit area is 0.05 / mm ² )
・ Maximum diameter of hole (opening): 100 μm
-Ratio of the area occupied by the total area of the opening portion in the plan view of the positive electrode current collector: 1.0%
The above paste was applied to both sides of the positive electrode current collector, sufficiently dried, and then pressed to obtain a positive electrode having a positive electrode active material layer (maximum thickness of 230 μm) on both sides (positive electrode coating part size). : Width 200 mm × length 150 mm).
A battery was produced in the same manner as in Example 1 except that the positive electrode was used.

Comparative Example 1
A battery was fabricated in the same manner as in Example 1 except that a 20 μm aluminum foil without holes was used as the positive electrode current collector.
The batteries of Examples 1 and 2 and Comparative Example 1 were evaluated by the following charge / discharge cycle test.

(Charge / discharge test)
Cycle test conditions Charging: constant current and constant voltage charging with a charging current of 3.0C and a termination voltage of 4.0V, 2 hours or a charging current of 10mA cutoff Discharge: constant current discharging with a discharge current of 3C, cutoff voltage of 2.0V cutoff The charge / discharge test was conducted under the above conditions. The discharge capacity was calculated based on the time for discharging to 2.0V.
The results of cycle evaluation are shown in FIG.

It was found that the battery cycle characteristics of the batteries of Examples 1 and 2 of the present invention were excellent.
This is because the non-aqueous secondary battery current collector of the present invention improves the adhesion between the current collector and the active material layer compared to the metal foil current collector due to the presence of the exposed region of the resin film. It is presumed that the reduction of the utilization rate due to the peeling of the active material, particularly the reduction of the current collecting performance of the active material can be suppressed over a long period of time.

1: conductive layer, 2: resin film, 3: opening portion, 3a: concave portion, 3b: convex portion, a: depth of concave portion and height of convex portion, b: top end of concave portion and bottom end of convex portion Diameter, y and d: maximum diameter of the hole

Claims

It is a current collector for a non-aqueous secondary battery that constitutes at least one of a positive electrode and a negative electrode used for a non-aqueous secondary battery and on which an active material layer is placed,
The current collector is composed of a resin film and a conductive layer that is laminated on at least one surface of the resin film and can be in contact with the active material layer,
The conductive layer is a current collector for a non-aqueous secondary battery that includes at least one exposed region of the resin film in which the resin film and the active material layer can be in direct contact.
The current collector for a non-aqueous secondary battery according to claim 1, wherein the current collector for a non-aqueous secondary battery has one or more opening portions in a region where the active material layer can be placed.
The non-aqueous secondary battery collector according to claim 1, wherein the non-aqueous secondary battery current collector has one or more openings having a maximum diameter of 1 to 1000 μm in a region where the active material layer can be placed. Electric body.
The non-aqueous system according to claim 2, wherein the opening portion has an area of 0.5 to 50% of the area of the conductive layer in plan view (provided that there are a plurality of the opening portions, the total area thereof). Secondary battery current collector.
The current collector for a non-aqueous secondary battery according to claim 1, wherein the exposed regions are provided at a number of 0.1 to 20 / mm 2 per unit area of the current collector in plan view.
The current collector for a non-aqueous secondary battery according to claim 1, wherein the exposed region has an area of 0.1 to 30.0% of an area of the conductive layer in plan view.
The non-aqueous secondary according to claim 1, wherein the current collector has a three-dimensional structure region in which one or more concave portions and / or convex portions are formed in a direction perpendicular to a plane of the current collector. Battery current collector.
The current collector for a non-aqueous secondary battery according to claim 7, wherein the three-dimensional structure region occupies the plane of the current collector in a range of 1.0 to 10.0%.
The current collector for a non-aqueous secondary battery according to claim 7, wherein the concave portions and the convex portions are provided at a number of 0.5 to 10 pieces / mm 2 per unit area of the three-dimensional structure region.
The non-aqueous secondary battery according to claim 7, wherein the concave portion has a maximum length at an uppermost end in a range of 1 to 1000 µm, and the convex portion has a maximum length at a lowermost end in a range of 1 to 1000 µm. Current collector.
The current collector for a non-aqueous secondary battery according to claim 7, wherein the concave portion has a depth in the range of 50 to 1000 µm, and the convex portion has a height in the range of 50 to 1000 µm.
It is an electrode for non-aqueous secondary batteries of at least one of a positive electrode and a negative electrode, and is formed on the conductive layer of the non-aqueous secondary battery current collector according to claim 1 and the non-aqueous secondary battery current collector. A non-aqueous secondary battery electrode comprising the active material layer.
A non-aqueous secondary battery comprising a positive electrode, a negative electrode, a separator positioned between the positive electrode and the negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode is an electrode for a non-aqueous secondary battery according to claim 12. Next battery.