JP2014075191A - Electrode for nonaqueous secondary battery and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery having high safety with high capacity.SOLUTION: Disclosed is an electrode as a positive electrode or a negative electrode used for a nonaqueous secondary battery. The electrode includes: an active material layer; and a current collector group composed of at least two current collectors laminated in the thickness direction of the active material layer via the active material layer. At least one current collector in the current collector group is constituted of a resin film and a conductive layer laminated on at least one surface, and all current collectors or current collectors except one current collector in the current collector group have one or more of openings.

Description

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

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 (for example, Japanese Patent Application Laid-Open No. 2001-118565 (patent) Literature 1)). For this current collector, a metal foil is usually used.

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 ignition even under severe use conditions. The metal foil did not have a function to prevent such an accident. Therefore, in WO2009 / 131184 (Patent Document 2), it is proposed 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 due to melting of the resin layer, and the current at the abnormal portion is partially cut off. As a result, the temperature rise inside the battery can be suppressed.

JP 2001-118565 A WO2009 / 131184

  The current collector of Patent Document 2 can provide a battery with improved safety. By the way, a positive electrode or a 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. The positive electrode active material or the negative electrode active material in the active material layer is charged and discharged. Therefore, it is desired to use it more effectively. In particular, in a large-capacity battery, a configuration has been proposed in which the capacity is ensured by increasing the thickness of the active material layer, and in a portion away from the current collector of the thick active material layer, the positive electrode active material or the negative electrode active material is charged and discharged. May not contribute to the reaction. In that case, the ratio of the actual capacity to the theoretical capacity is low, and the desired capacity may not be obtained.

Thus, according to the present invention, an electrode as a positive electrode or a negative electrode used in a non-aqueous secondary battery,
The electrode includes an active material layer, and a current collector group including at least two current collectors stacked via the active material layer in the thickness direction of the active material layer,
At least one current collector in the current collector group is composed of a resin film and a conductive layer laminated on at least one surface thereof, and all the current collectors or one sheet in the current collector group A non-aqueous secondary battery electrode is provided in which the current collector other than the above has one or more openings.
According to the invention, there is provided a cell comprising a positive electrode, a negative electrode, and a separator containing an electrolyte positioned between the positive electrode and the negative electrode, wherein at least one of the positive electrode and the negative electrode is for the non-aqueous secondary battery. A non-aqueous secondary battery characterized by being an electrode is provided.

  According to the electrode for a non-aqueous secondary battery of the present invention, since the electrode includes a plurality of current collectors, the active material layer can be made thicker, and therefore a high-capacity non-aqueous secondary battery can be provided. In addition, since at least one current collector in the current collector group includes a resin film and a conductive layer, the current collector melts in the event of abnormal heat generation, so that the electrode is damaged and the current at the abnormal location is reduced. It is possible to provide a highly safe non-aqueous secondary battery that can be shut off.

In addition, when the two outermost current collectors in the current collector group include a resin film and a conductive layer, it is possible to provide a non-aqueous secondary battery with high capacity and higher safety. .
Furthermore, when the weight per unit area of the active material contained in the active material layer is 15 to 100 mg / cm ² × the number of the current collectors, the non-aqueous secondary battery has a higher capacity and higher safety. Can be provided.
In addition, when at least one current collector in the current collector group includes a three-dimensional structure region having one or more concave portions and / or convex portions, the current collector is compared with an electrode using a flat current collector. An active material present at a site away from the electric body can also be efficiently used for the charge / discharge reaction. Therefore, since the theoretical capacity and the actual capacity can be close to each other, the non-aqueous secondary battery electrode and the non-aqueous secondary battery that can obtain a larger actual capacity than the conventional capacity can be provided with the same amount of active material.

  Further, a plurality of cells are provided in the stacking direction of the positive electrode, the separator, and the negative electrode, and the positive electrode in one cell is adjacent to the positive electrode of another cell and / or the negative electrode in one cell is adjacent. When also serving as the negative electrode of another cell, a non-aqueous secondary battery with higher energy density can be provided.

2 is a schematic cross-sectional view of a positive electrode of Example 1. FIG. It is an example of the schematic principal part top view and sectional drawing of a collector provided with the three-dimensional structure area. It is an example of the schematic principal part top view and sectional drawing of a collector provided with the three-dimensional structure area | region and opening.

(Electrode for non-aqueous secondary battery)
The electrode includes an active material layer and a current collector group composed of at least two current collectors stacked via the active material layer in the thickness direction of the active material layer. 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.

(1) Current collector group The current collector group can be used as a positive electrode and negative electrode current collector group. The current collector group can be used for either the positive electrode or the negative electrode, or may be used for both. Examples of the non-aqueous secondary battery using the current collector group include a lithium ion secondary battery and a lithium metal secondary battery. Among these, the lithium ion secondary battery which can use a collector group for both a positive electrode and a negative electrode is preferable.
The number of current collectors constituting the current collector group is at least two. The upper limit of the number of current collectors is not particularly limited as long as the current can be collected, but is preferably 2 to 3 sheets.
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 material 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. A more preferred thickness is in the range of 0.02 to 0.05 mm.
The current collector preferably has a sheet resistance of 0.1Ω / □ or less from the viewpoint of ensuring sufficient current collecting performance. A more preferable sheet resistance is 0.05Ω / □ or less.

At least one current collector in the current collector group is composed of a resin film and a conductive layer laminated on at least one surface thereof.
(A) Resin film and conductive layer The resin film is not particularly limited, but it is preferable to use a film of a resin material that is thermally deformed when the temperature rises from the viewpoint of providing safety to the battery. Examples of such a resin material include polyolefin resins such as polyethylene (PE) and polypropylene (PP), polystyrene (PS), and the like having a heat distortion temperature of 150 ° C. or lower.
As the resin film, a resin film produced by any method such as uniaxial stretching, biaxial stretching, or non-stretching can be used.

  The thickness of the resin film is preferably in the range of 0.01 to 0.1 mm. When the thickness is less than 0.01 mm, sufficient support of the active material may not be ensured. 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. A more preferred thickness is in the range of 0.015 to 0.05 mm.

The positive electrode side conductive layer is preferably an aluminum, titanium or nickel layer, and the negative electrode side conductive layer is preferably a copper or nickel layer.
Although the thickness of a conductive layer will not be specifically limited if electroconductivity is securable, Usually, it is the range of 0.002-0.01 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.
The current collectors including the resin film and the conductive layer are preferably the two outermost sheets in the current collector group. Abnormal heat generation mainly occurs on the electrode surface (for example, short circuit between the positive electrode and the negative electrode), so if the current collector near the electrode surface has a resin film and a conductive layer, abnormal heat generation is more effective. Can be suppressed.

(B) Openings All current collectors in the current collector group or current collectors other than one current collector have one or more openings. By forming an opening, even if a plurality of current collectors are provided, it is possible to prevent the diffusion of lithium ions from the active material between the current collectors, thereby preventing batteries with better charge / discharge efficiency. Is possible. The number of openings is preferably in the range of 1 to 1000 / cm ² per unit area of the current collector. 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 heptagon or more polygon, a star, and an indefinite shape. Among these, from the viewpoint of easy formation, a circle and a quadrangle are preferable. If the maximum length of the opening is too small, the effect of preventing lithium ion diffusion is reduced, and if it is too large, the strength of the current collector may be reduced. Therefore, it is preferably in the range of 1 to 1000 μm, more preferably in the range of 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.

(C) Three-dimensional structure region At least one current collector in the current collector group may include a three-dimensional structure region having one or more concave portions and / or convex portions. By providing the current collector with a three-dimensional structure region, an electrode with high charge / discharge efficiency can be provided even if the active material layer is thickened.
The three-dimensional structure region preferably occupies half or more of the current collector surface including the three-dimensional structure region. By occupying more than half, the active material in the active material layer formed thereon can be efficiently used for the charge / discharge reaction. The upper limit of the ratio of the three-dimensional structure region to the current collector surface is the entire surface. However, since the current collector is provided with a terminal for taking out electricity at either end, it is preferable that the current collector is flat with a width in the range of 2 to 20 mm. Therefore, it is preferable that the three-dimensional structure region occupies the current collector surface in the range of 80 to 98% from the viewpoint of charge / discharge efficiency and the necessity of the region for forming the terminal.

The three-dimensional structure region means a region where one or more concave portions and / or convex portions are formed on the current collector. Moreover, the current collector may be provided with only a concave portion, may be provided with only a convex portion, or may be provided with 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 concave portion and the convex portion may be arranged, for example, as shown in the schematic plan view of the main part of FIG. 2A and the schematic cross-sectional view of the main part of FIG.

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 1 piece / cm ² or more per unit area. The upper limit of the number is the number of concave portions and convex portions that can be formed in the three-dimensional structure region, and is, for example, 2000 pieces / cm ² or less. A more preferable number is in the range of 1 to 1000 / cm ² .
The planar 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 circle (see FIG. 2A), an ellipse, a triangle, a quadrangle, a pentagon, a hexagon, a polygon more than a heptagon, a star, an indeterminate form, and the like can be given. Among these, from the viewpoint of easy formation, a circle and a quadrangle are preferable.

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 large, the effect of improving the conductivity will be small, and if it is too small, it will be difficult to form the active material layer uniformly. Therefore, it is preferably in the range of 1 to 1000 μm, more preferably 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. 2B), 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 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 50 to 1000 μm, and more preferably in the range of 150 to 750 μm.

Furthermore, as shown in the schematic cross-sectional view of the main part in FIG. 3A and the schematic plan view of the main part in FIG. Good. Note that the openings may be formed at locations other than FIGS. 3A and 3B as long as it is possible to prevent the diffusion of lithium ions from the active material between the current collectors.
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. The three-dimensional structure region may be formed either after the conductive layer is formed or before it is formed, but can be appropriately selected according to the method for forming the conductive layer.

(2) Configuration of electrode The electrode includes at least two current collectors and an active material layer. Since the electrode of the present invention includes a plurality of current collectors, it is possible to prevent the presence of an active material that does not contribute to charge / discharge even when the coating weight of the active material is increased. For example, the weight per unit area of the active material contained in the active material layer can be 15 to 100 mg / cm ² × the number of the current collectors.
For example, when there are two current collectors, the electrode has a stacked structure of active material layer / current collector / active material layer / current collector, active material layer / current collector / active material layer / current collector in the stacking direction. It may have a laminated structure of body / active material layers.
Note that when the active material layer is partitioned into a plurality of layers by the current collector, each of the partitioned active material layers may have the same thickness or a different thickness.

(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.

(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 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 part 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 may be small. By decreasing, the discharge capacity as the positive electrode may be reduced.

(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 (scale-like, lump-like, fibrous, whisker-like, 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 mix 2 or more types. 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.

(C) Forming method For example, the electrode is formed by applying a paste containing an active material and optionally other additives on the current collector, and then placing the other current collector on the coating film. It can form by the method of drying, apply | coating a paste on another electrical power collector, repeating the procedure of drying the obtained coating film, and finally pressing.
As a method other than the above,
(I) A coated film is formed on both sides of the current collector to obtain a double-sided coated current collector. Separately, a coated film is formed on one side of the current collector to obtain a single-sided coated current collector. A method of placing and pressing a double-sided coated current collector on the uncoated surface of the coated current collector,
(Ii) A method of forming a coating film on an uncoated surface of a single-sided coated current collector, placing an uncoated surface of another single-sided coated current collector on the formed coating film, and pressing it;
(Iii) A coating film is formed on the uncoated surface of the single-sided coated current collector, the uncoated current collector is placed on the formed coating film, and the coated film is applied to the uncoated surface of the uncoated current collector. Forming and pressing method,
(Iv) A method in which a current collector group is arranged in a mold of a predetermined size, the mold is filled with paste, the paste is dried, taken out from the mold, or pressed without being taken out, and the like.
Further, the active material layer itself can be thickened by repeating the application and drying of the paste. Furthermore, after drying, you may press for an electrode characteristic improvement.
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, by forming two current collectors having an active material layer on one side and bonding the surfaces of the two current collectors where the active material layer is not formed, electrodes having an active material layer on both sides are formed. May be obtained.

(3) Nonaqueous secondary battery A nonaqueous secondary battery has a cell provided with a positive electrode, a negative electrode, a separator located 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, and either one 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 10-1000 micrometers, Preferably it is about 20-50 micrometers. Moreover, it is preferable that the material constituting the separator has an air permeability of 1 to 500 seconds / cm ³ because strength sufficient to prevent a battery internal short circuit can be secured while maintaining a low battery internal resistance.

  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. Furthermore, when laminated together with the positive electrode and the negative electrode, it is preferably larger than the positive electrode, and in particular, it is preferably a similar shape slightly larger than the positive electrode and slightly smaller than the negative electrode.

(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; -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, and dioxane Dimethyl sulfoxide, sulfolane, methyl sulfolane, acetonitrile, methyl formate, methyl acetate and the like. 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 trifluoromethanesulfonate imido ( 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 which consists of an ionic liquid.

(D) Cell The battery may include a plurality of cells in the stacking direction of the positive electrode, the separator, and the negative electrode. In this case, the positive electrode in one cell can also serve as the positive electrode of another cell and / or the negative electrode of another cell in which the negative electrode in one cell is adjacent. By serving also, the space for newly providing the positive electrode and / or the negative electrode can be reduced, so that a battery having a higher energy density can be provided.
Furthermore, it is preferable that the current collector on the outermost surface of the current collector group constituting the electrode is a current collector provided with the resin film and the conductive layer. If this electrode is used, when abnormal heat generation occurs inside the battery, the current interruption function due to electrode breakage due to fusing of the resin film can be expressed more effectively, providing a safer battery it can.

(E) 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, for example, 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. As another material, for example, a can made of stainless steel, aluminum, or the like may be used. 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. Preferably there is.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.
Example 1
In this example, a battery including the positive electrode shown in the schematic cross-sectional view of FIG. 1 was produced. In FIG. 1, A and C are upper and lower positive electrode current collectors, B is a central positive electrode current collector, and D is a positive electrode active material layer. Note that the upper and lower current collectors have a three-dimensional structure and an opening, but are omitted in FIG. 1 for simplicity of illustration.
100 parts by weight of LiFePO ₄ as a positive electrode active material, 10 parts by weight of a conductive material (Denka Black manufactured by Denki Kagaku Kogyo), 10 parts by weight of PVDF (KF polymer (registered trademark) manufactured by Kureha Co., Ltd.) as a binder, A paste for forming a positive electrode active material layer was prepared using N-methyl-2-pyrrolidone (hereinafter referred to as NMP).
For the upper and lower positive electrode current collectors A and C of the positive electrode, a laminate film formed by laminating 6.5 μm thick aluminum foil / 20 μm thick polyolefin resin layer / 6.5 μm thick aluminum foil is used as the lowest point of the concave portion and the convex portion. What was processed into a three-dimensional shape so that an opening was formed at the apex of the plate (planar shape: rectangle with a length of 250 mm and a width of 150 mm) was used. 3A shows a part of a schematic cross-sectional view of the main part of the positive electrode current collector, and FIG. 3B shows a part of the schematic plan view of the main part. An outline of the three-dimensional structure region and the opening will be described below.
・ Total number of concave and convex portions: 73500 (number per unit area is 200 / cm ² )
-Planar shape of recesses and projections: circles-Plane shape of openings: cross-sectional shapes of circles, recesses and projections: triangles-Depth of recesses and height of projections: 200 μm
・ Diameter of the uppermost end of the concave portion and the lowermost end of the convex portion: 300 μm
・ Aperture diameter: 200 μm
-The range of 5 mm in width from the end in the length direction in plan view is a flat surface having no concave portions, convex portions, or openings. The central positive electrode current collector B was a flat plate-shaped 20 μm thick aluminum foil.

3 (a) and 3 (b), 1 is a resin film, 2 is a conductive layer, 3 is a recess, 4 is a protrusion, 5 is an opening, a is the depth of the recess and the height of the protrusion, and b is a recess. The diameter of the uppermost end and the lowermost end of the convex part, c is the distance between the lowest point of the nearest concave part and the apex of the convex part, and d is the diameter of the opening.
The positive electrode paste was applied to both surfaces of the positive electrode current collectors A to C, the applied positive electrode current collectors A to C were laminated, sufficiently dried, and then pressed to provide a positive electrode active material layer. A positive electrode was obtained (positive electrode coating part size: length 200 mm × width 150 mm, average active material weight per unit area: about 110 mg / cm ² ).

Next, 100 parts by weight of Chinese natural graphite (average particle size 15 μm, d002 = 0.3357 nm, BET specific surface area 3 m ² / g) as negative electrode active material, 12 parts by weight of PVDF as binder, and solvent A paste for forming a negative electrode active material layer was prepared using NMP. 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: length 205 mm × Width 158 mm).

  A non-woven fabric of aramid resin having a length of 205 mm, a width of 158 mm, and a thickness of 36 μm (manufactured by Japan Vilene Co., Ltd., heat shrinkage rate of 1.0% or less at 200 ° C., hereinafter referred to as an aramid resin layer) is used as a separator. Negative electrode, negative electrode / 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 A battery element was obtained by stacking in the order of / negative electrode / separator / positive electrode / separator / negative electrode / separator / positive electrode / separator / negative electrode / separator / positive electrode / separator / negative electrode. Further, a tab was welded to each positive electrode (three positive electrode current collectors) and the negative electrode, and the obtained battery element was inserted into a can.

The heat shrinkage rate was determined as follows. First, two points were attached on the resin film with an interval of 50 mm or more, and the distance between the two points was measured using a caliper. Then, after heat-processing for 15 minutes at 200 degreeC, the same distance between points was measured again and the thermal contraction rate was calculated | required from the measured value before and behind heat processing. Based on this method, the distance between three or more points was measured for each of the longitudinal direction and the transverse direction of the resin film, and the average value of the thermal shrinkage rate calculated from each measurement result was determined for the longitudinal and lateral thermal shrinkage rates. And the larger value of either vertical or horizontal was determined as the final heat shrinkage rate. At this time, for each of the longitudinal direction and the lateral direction of the resin film, at least two points within 10% from the end of the resin film and one point around 50% from the end of the resin film are measured for the distance between the points. Selected as a location.
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, held under reduced pressure and returned to atmospheric pressure, and then the outer periphery of the lid was sealed to produce a battery.

Comparative Example 1
Three-dimensional shape processing and openings are formed on a laminate film made by laminating 6.5 μm thick aluminum foil / 20 μm thick polyolefin resin layer / 6.5 μm thick aluminum foil used as upper and lower positive electrode current collectors. The procedure was the same as in Example 1 except that no.

Comparative Example 2
A laminate film formed by laminating 6.5 μm-thick aluminum foil / 20 μm-thick polyolefin resin layer / 6.5 μm-thick aluminum foil is used as the central positive electrode current collector without using the upper and lower positive electrode current collectors. The same procedure as in Example 1 was performed except that a three-dimensional shape was used so that an opening was formed at the apex of the convex portion. However, the active material weight per unit area of the positive electrode was made equal to that of the positive electrode of Example 1.

(Battery characteristics evaluation)
The batteries of Example 1 and Comparative Examples 1 and 2 were evaluated by the following charge / discharge test.

(Charge / discharge test)
Test conditions Charging: Charged at constant current and constant voltage at a charging current of 0.2 C and a final voltage of 3.5 V, and terminated after charging for 20 hours or after the charging current decayed to 0.02 C. Discharge: Discharge current of 0.2 C, 0.5 C 1C was discharged at a constant current, and the discharge was completed after reaching a final voltage of 2.0 V. The charge / discharge test was performed under the above conditions. Based on the discharge time to 2.0 V, the discharge capacity at discharge currents of 1.0 C and 0.2 C was calculated. Table 1 below shows the discharge capacity at 0.2 C and the ratio of the discharge capacity at 1.0 C to the discharge capacity.

  From Table 1, the discharge capacity at 0.2 C and the ratio of the discharge capacity (1.0 C capacity / 0.2 C capacity) were larger than the other batteries in Example 1, and the three-dimensional shape processing and opening formation were performed. It was found that the arrangement of the applied upper and lower positive electrode current collectors is effective for improving battery characteristics.

(Battery safety evaluation)
The battery of Example 1 after the charge / discharge test was evaluated by the following nail penetration test.

(Nail penetration test)
After the above charge / discharge test, the battery was fully charged and the behavior in a nail penetration test using a 2.5 mmφ nail was observed. As a result, it was confirmed that there was no expansion, rupture, or ignition of the battery. There was found.

A and C: upper and lower positive electrode current collectors, B: central positive electrode current collector, D: positive electrode active material layer, 1: resin film, 2: conductive layer, 3: concave portion, 4: convex portion, 5: opening, a: Depth of concave portion and height of convex portion, b: Diameter of the uppermost end of the concave portion and the lowermost end of the convex portion, c: Distance in plan view between the lowest point of the nearest concave portion and the apex of the convex portion, d : Diameter of opening

Claims (6)

It is an electrode as a positive electrode or a negative electrode used for a non-aqueous secondary battery,
The electrode includes an active material layer, and a current collector group including at least two current collectors stacked via the active material layer in the thickness direction of the active material layer,
At least one current collector in the current collector group is composed of a resin film and a conductive layer laminated on at least one surface thereof, and all the current collectors or one sheet in the current collector group An electrode for a non-aqueous secondary battery, wherein the current collector other than 1 has one or more openings.   2. The electrode for a non-aqueous secondary battery according to claim 1, wherein two outermost current collectors in the current collector group include the resin film and a conductive layer. The electrode for a non-aqueous secondary battery according to claim 1 or 2, wherein the weight per unit area of the active material contained in the active material layer is 15 to 100 mg / cm ² × the number of the current collectors.   The non-aqueous secondary according to any one of claims 1 to 3, wherein at least one current collector in the current collector group includes a three-dimensional structure region having one or more concave portions and / or convex portions. Battery electrode.   It has a cell provided with a positive electrode, a negative electrode, and the separator containing the electrolyte located between the said positive electrode and the said negative electrode, At least one of the said positive electrode and the said negative electrode is a non-aqueous system as described in any one of Claims 1-4 A non-aqueous secondary battery, which is an electrode for a secondary battery.   A plurality of the cells are provided in the stacking direction of the positive electrode, the separator, and the negative electrode, and the positive electrode in one cell is adjacent to the positive electrode of another cell and / or the negative electrode in one cell is adjacent. The nonaqueous secondary battery according to claim 5, which also serves as a negative electrode of the cell.