JP2012028006A - Electrode plate for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which: although higher safety is requested as a lithium secondary battery has higher capacity, a mixture layer of a conventional electrode plate used for the lithium secondary battery falls.SOLUTION: The present invention relates to an electrode plate 4 for lithium secondary battery which has an electrode mixture layer, including a binder and an electrode active material, on a collector 1. The electrode mixture layer is sectioned into an inside region 2 and end regions 3, and a binding property of the end regions 3 is increased by making a weight ratio of the binder based upon the electrode active material larger in the end regions 3 than in the inside region 2, so that falling of mixture during cutting is suppressed. The weight ratio of the binder based upon the electrode active material is small in the inside region 2 of the electrode plate 4, so the lithium secondary battery using the electrode plate 4 has superior cycle characteristics. Further, the electrode plate 4 prevents mixture falling, so the lithium secondary battery using the electrode plate 4 is also superior in safety.

Description

  The present invention relates to an electrode plate for a non-aqueous electrolyte secondary battery.

  2. Description of the Related Art In recent years, electronic devices have become rapidly portable and cordless, and there is an increasing demand for secondary batteries that are small and lightweight and have high energy density as power sources for driving these devices. In addition to small-sized consumer applications, there is a demand for large-sized secondary batteries that require long-term durability and safety, such as for power storage and electric vehicles, and technological development has been accelerated. Under such circumstances, non-aqueous electrolyte secondary batteries have high voltage and high energy density, and are therefore expected to be used for electronic devices, for power storage, and for electric vehicle power supplies.

A nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator interposed between them, and a nonaqueous electrolyte. In a lithium secondary battery that is put into practical use (an example of a nonaqueous electrolyte secondary battery), A microporous membrane made of polyolefin is mainly used for the separator, and a liquid nonaqueous electrolyte (nonaqueous electrolyte) in which a lithium salt such as LiBF ₄ or LiPF ₆ is dissolved in an aprotic organic solvent is used for the nonaqueous electrolyte. Yes. In addition, a lithium cobalt oxide (for example, LiCoO ₂ ) that has a high potential with respect to lithium, is excellent in safety, and is relatively easy to synthesize is used as the positive electrode active material, and various carbons such as graphite are used as the negative electrode active material. Agents are used.

  Such a lithium secondary battery has a problem that metal powder and other foreign matters generated during the manufacturing process are mixed in the battery, and an internal short circuit is induced by breaking through the separator, thereby impairing safety. Have.

  There are various factors that generate the metal powder and foreign matter. For example, in the cutting process at the time of manufacturing a lithium secondary battery, a mixture layer such as a burr of a current collector generated at both edges of the electrode plate is used. For example, cutting scraps due to dropping off.

  As a method for producing a lithium secondary battery, usually, an electrode coating liquid prepared by kneading and dispersing an electrode active material, a binder and a solvent is first applied to one or both sides of a wide current collector. After drying, the sheet is rolled to a predetermined thickness, and an original sheet of a wide electrode plate wound in a long shape is manufactured. Then, it moves to a cutting process, and the raw material of the wide electrode plate is cut into a plurality of narrow electrode plates having a predetermined dimension by a plurality of cutting blades arranged in a slitter device. Thereby, a plurality of wound hoops are obtained. For cutting from the wide electrode plate to the narrow electrode plate, a cutting blade such as a shear method or a gang method is usually used.

  In order to solve the problems of the current collector burrs and cutting chips generated on the cross-sections of both edge portions of the electrode plate after cutting, a method of cutting using laser light has been proposed (see Patent Document 1). ). According to this proposal, since the electrode plate is cut by a high-density heat source of laser light, the electrode plate is blown by high heat. As a result, it is stated that there is no generation of burrs in the current collector that occurs in the cross-sections at both edges of the electrode plate, and that an internal short circuit can be prevented.

Further, for the purpose of improving the problem of burrs and cutting chips, a method of covering the peripheral edge portion of the electrode plate including the cut surface with a heat-fusible resin is exemplified (see Patent Document 2).
Furthermore, for the purpose of suppressing burrs, there is exemplified a method in which after cutting into a plurality of narrow electrode plates with a cutting blade, only the respective edge portions of the narrow electrode plates are pressed with a pressing roll ( (See Patent Document 3).

Japanese Patent Laid-Open No. 61-66364 JP-A-5-190200 JP 2008-176939 A

  However, in the cutting method using laser light as proposed in Patent Document 1, burrs and cutting scraps on the cut surface of the electrode plate are reduced, but the unevenness of the cut surface due to heat melting and the wrinkles generated at the time of heat melting are reduced. Due to dirt and the like, there was a new problem regarding the processing method.

  Moreover, even if the technique proposed in Patent Document 2 is used, only the burrs and cutting chips on the cut surface are covered with the binder, and the sharp burrs and cutting chips are not suppressed. It was difficult to sufficiently prevent the occurrence of an internal short circuit.

Furthermore, even if the method proposed in Patent Document 3 is used, it is only difficult to suppress burrs on the cut surface, and it is difficult to suppress the generation of cutting waste due to the dropping of the mixture.
In these Patent Documents 2 and 3, safety cannot be ensured due to the generation of cutting waste, and even if the mixture dropping at the time of cutting is suppressed by increasing the amount of binder, there is a problem that the cycle characteristics deteriorate at the same time. To do.

  On the other hand, the present invention solves the above-described conventional problems, and provides an electrode plate for a nonaqueous electrolyte secondary battery that suppresses mixture dropping at the time of cutting and is excellent in safety and cycle characteristics. Objective.

  In order to achieve the above object, an invention according to claim 1 of the present invention is an electrode plate for a nonaqueous electrolyte secondary battery having an electrode mixture layer containing a binder and an electrode active material on a current collector. The electrode mixture layer is divided into an inner region and an end region, and the weight ratio of the binder based on the polar active material is larger in the end region than in the inner region. To do.

  The invention according to claim 2 of the present invention is the electrode plate for a nonaqueous electrolyte secondary battery according to claim 1, wherein the weight ratio of the binder based on the polar active material is the end region. Then, it is not less than 2 times and not more than 5 times the inner region, and the boundary between the inner region and the end region is not less than 0.5 mm and not more than 10 mm from the end of the electrode plate.

  Furthermore, the invention according to claim 3 of the present invention is the electrode plate for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the binder is a fluorine-based binder, acrylic rubber, modified acrylic rubber. Styrene-butadiene rubber, acrylic polymer or vinyl polymer, or a mixture or copolymer of two or more thereof.

  The invention described in claim 4 of the present invention is the electrode plate for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the active material is cobalt, manganese, nickel, chromium. It is a composite metal oxide of lithium and one or more metals selected from iron and vanadium.

  On the other hand, the invention according to claim 5 of the present invention is a non-aqueous electrolyte secondary battery using the electrode plate for non-aqueous electrolyte secondary battery according to any one of claims 1 to 4. It is characterized by comprising.

  According to the electrode plate for a non-aqueous electrolyte secondary battery of the present invention, the weight ratio of the binder based on the polar active material is sufficiently large in the end region, so that the synthetic dropout at the time of cutting is prevented and safety is ensured. Excellent in properties. In addition, since the weight ratio of the binder in the inner region is sufficiently small, the ion migration of the electrode plate is not hindered and the cycle characteristics are excellent.

The expanded perspective view of the positive electrode plate in Embodiment 1 of this invention Enlarged perspective view of a wide positive electrode plate in the same embodiment Enlarged perspective view of the negative electrode plate in the same embodiment

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a positive electrode plate which is an example of an electrode plate for a nonaqueous electrolyte secondary battery according to the present invention. The direction of the upper and lower surfaces of the positive electrode plate 4 will be described as the thickness direction, the depth direction of the positive electrode plate 4 as the length direction, and the direction perpendicular to the length direction and the thickness direction will be described as the width direction.

  In FIG. 1, the positive electrode plate 4 is configured by providing positive electrode mixture layers for storing electricity on both surfaces of a current collector 1 which is a terminal for taking out electricity. The positive electrode mixture layer is divided into an end region 3 having a width A from both ends in the width direction of the positive electrode plate 4 and an inner region 2 between the end regions 3 depending on the difference in the components. In the end region 3, the width A is 0.5 mm to 10 mm, and the weight ratio of the binder based on the positive electrode active material of the positive electrode mixture layer is based on the positive electrode active material in the inner region 2. It is larger than the weight ratio of the binder.

The positive electrode plate 4 is obtained by cutting the wide positive electrode plate 40 shown in FIG. 2 into a plurality of pieces in the width direction along a cutting line C in the length direction.
FIG. 3 shows the negative electrode plate 5. This negative electrode plate 5 has the same configuration as that of the positive electrode plate 4 and is obtained by cutting a wide negative electrode plate.

Next, a method for producing the positive electrode plate 4 and the negative electrode plate 5 will be specifically described.
As for the positive electrode plate 4, a positive electrode active material and a binder, and optionally a conductive agent, an increase in the number of both sides of the current collector 1 made of an aluminum foil, a lath processed or etched foil having a thickness of 10 μm to 60 μm. A paste prepared by kneading and dispersing a viscous agent in a solvent is applied, dried, and rolled to provide a positive electrode mixture layer that becomes the inner region 2 and the end region 3.

As the positive electrode active material, for example, a lithium-containing transition metal compound that can accept lithium ions as a guest is used. For example, a composite metal oxide of at least one metal selected from cobalt, manganese, nickel, chromium, iron, and vanadium and lithium is used. For _{example, LiCoO 2, LiMnO 2, LiNiO} 2, LiCo x Ni (1-x) O 2 (0 <x <1), LiCrO 2, αLiFeO 2, LiVO 2 and the like are used.

  The binder is not particularly limited as long as it can be kneaded and dispersed in a solvent. For example, a fluorine binder, acrylic rubber, modified acrylic rubber, styrene-butadiene rubber (SBR), acrylic A polymer or vinyl polymer is used alone, or two or more kinds of mixtures or copolymers are used. Examples of the fluorine-based binder include polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, a dispersion of a polytetrafluoroethylene binder, an ethylene-vinyl alcohol copolymer, carboxymethyl cellulose, Methyl cellulose or the like is used.

  As described above, a conductive agent can be added to the positive electrode active material and the binder in the inner region 2 and the end region 3 as necessary. As the conductive agent, acetylene black, graphite, carbon fiber, etc. are used alone. Or a mixture of two or more types is preferred.

  The thickening agent is not particularly limited as long as it is an agent having viscosity as an aqueous solution such as polyethylene oxide (PEO) or polyvinyl alcohol (PVA), but a cellulose resin such as carboxymethyl cellulose (CMC) and its modification. The body is preferable from the viewpoint of dispersibility and thickening of the mixture paint.

  As the solvent, a solvent in which a binder can be dissolved is used. In the case of an organic binder, N-methyl-2-pyrrolidone, N, N-dimethylformamide, tetrahydrofuran, dimethylacetamide, dimethyl sulfoxide, hexa An organic solvent such as methylsulfuramide, tetramethylurea, acetone, or methyl ethyl ketone is preferably used alone or a mixed solvent thereof. In the case of an aqueous binder, water or warm water is preferred.

  The mixing ratio of the positive electrode active material, the conductive agent and the binder in the positive electrode mixture applied to the inner region 2 is 80 to 97% by weight for the positive electrode active material, 1 to 20% by weight for the conductive agent, and the binder. The amount is in the range of 2-5% by weight.

  In the positive electrode mixture applied to the end region 3, the mixing ratio of the positive electrode active material and the conductive agent is made equal to that of the inner region 2, and only the mixing ratio of the binder is made larger than that of the inner region 2. Specifically, the weight ratio based on the positive electrode active material is 2 to 5 times that of the inner region 2 in the end region 3.

Thus, in the edge part area | region 3, the mixture omission at the time of cutting can be suppressed by making only the compounding ratio of a binder into 2 times or more of the inner side area | region 2.
In addition, by setting the blending ratio of the binder in the end region 3 to 5 times or less that of the inner region 2, the coating of the binder on the positive electrode active material is suppressed, Li ion migration is not inhibited, and the electrolyte solution Therefore, the influence of cycle characteristics can be suppressed.

  The method for preparing the paste mixture by kneading and dispersing the positive electrode active material, the binder, and a conductive agent added as necessary in a solvent is not particularly limited. For example, a planetary mixer, a homomixer, A pin mixer, kneader, homogenizer, or the like can be used. These can be used alone or in combination. In addition, various dispersants, surfactants, stabilizers, and the like can be added as necessary during the kneading dispersion of the paste mixture.

  The process of applying and drying the mixture on the current collector 1 is not particularly limited, and the paste mixture mixed and dispersed as described above is used, for example, by using several types of slit die coaters. The end region 3 whose boundary with the inner region 2 is 0.5 mm or more and 10 mm or less from the end portion is applied separately from the inner region 2. Thereafter, it is preferable to perform drying close to natural drying, but considering productivity, it is preferable to dry at a temperature of 70 ° C. to 300 ° C. for 5 hours to 1 minute. By coating the end region 3 whose boundary with the inner region 2 is 0.5 mm or more from the end portion separately from the inner region 2, it is possible to suppress the dropping of the mixture during cutting.

  Further, in the inner region 2, the air in the electrode plate is difficult to escape, but by separately applying the inner region 2 and the end region 3, the permeability of the electrolyte solution in the inner region 2 is deteriorated by a large amount of binder. Therefore, since the amount of the electrolytic solution does not decrease, deterioration of cycle characteristics can be suppressed.

  In the rolling step, it is preferable to perform rolling several times at a linear pressure of 102 to 204 N / cm (1000 to 2000 kgf / cm) or to change the linear pressure at each time until a predetermined thickness is obtained by a roll press.

  Next, the wide positive electrode plate 40 obtained as described above is cut into a predetermined size in a cutting step. The cutting blade used here is either a shear blade method or a gang blade method. There is no problem.

  The negative electrode plate 5 is coated with a negative electrode active material, a binder, and, if necessary, a paste-like mixture obtained by kneading and dispersing a conductive additive and a thickener in an organic solvent, and then dried. In addition, it is prepared by applying and drying the other surface of the current collector 1 and then rolling it.

The current collector 1 of the negative electrode plate 5 is made of a copper foil, a lathed foil, or an etched foil, and has a thickness in the range of 5 μm to 50 μm.
Although it does not specifically limit as a negative electrode active material, For example, the carbon agent material, coke, and pitch which are obtained by baking an organic polymer compound (A phenol binder, polyacrylonitrile, cellulose, etc.) are baked. As the shape of the carbon agent material obtained by this, artificial graphite or natural graphite, a spherical shape, a scale shape, or a lump shape can be used.

The mixing ratios of the negative electrode active material and the binder are 93 to 99% by weight for the negative electrode active material and 1 to 5% by weight for the binder, respectively.
In the negative electrode mixture applied to the end region 3, the mixing ratio of the negative electrode active material and the conductive agent is made equal to that of the inner region 2, and only the mixing ratio of the binder is based on the weight ratio based on the active material. The inner region 2 is 2 times or more and 5 times or less. Others can be manufactured in the same manner as the positive electrode plate 4.

Here, a lithium secondary battery using the above-described positive and negative electrode plates 4 and 5 will be described.
The lithium secondary battery includes a separator sandwiched between the positive electrode plate 4 and the negative electrode plate 5 and an electrolyte filled between the positive and negative electrode plates 4 and 5 and the separator.

  The separator is not particularly limited as long as it is a composition that can withstand the range of use of the lithium secondary battery, but a microporous film of an olefin resin such as polyethylene or polypropylene is generally used singly or in combination. And it is preferable as an aspect. The thickness of the separator is not particularly limited, but is 10 to 25 μm.

Moreover, for the electrolytic solution, it is possible to use various lithium compounds such as LiPF ₆ and LiBF ₄ as an electrolyte salt. Further, ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), or methyl ethyl carbonate (MEC) can be used alone or in combination as a solvent. In addition, vinylene carbonate (VC), cyclohexylbenzene (CHB), or a modified product thereof is used as a solvent to form a good film on the positive and negative electrode plates 4 and 5 or to ensure stability during overcharge. It is done.

  Hereinafter, specific embodiments of the present invention will be described in more detail with reference to the drawings.

The slurry applied to the inner region 2 is 100 parts by weight of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ powder as the positive electrode active material, 2.5 parts by weight of acetylene black as the conductive agent, and polyfluoride as the binder. It was produced by kneading 3 parts by weight of vinylidene chloride (PVDF) and a dispersion medium.

Furthermore, 100 parts by weight of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ powder as the positive electrode active material and 2.5 parts by weight of acetylene black as the conductive agent were bound to the slurry applied to the end region 3. It was prepared by kneading 6 parts by weight of polyvinylidene fluoride (PVDF) as an agent and a dispersion medium.

  The inner region 2 and the end region 3 are formed in a state in which the positive electrode plate mixture slurry thus prepared is cut into a positive electrode plate 4 having a width of 54 mm in a later process using several types of slit die coaters. Thus, the end region 3 whose boundary with the inner region 2 is 10 mm from the end after cutting was applied to the current collector 1 separately from the inner region 2. Thereafter, the current collector 1 was dried to produce a wide positive electrode plate 40 shown in FIG.

The wide positive electrode plate 40 is rolled with a flat plate roll press so that the mixture density is 3.00 g / cm ³ and the thickness is 150 μm in the width direction, and a positive electrode plate 4 having a width of 54 mm is obtained using a cutting device in a cutting process. It was. In addition, in the cutting process, Table 1 shows the number of the mixture dropouts in the length direction 1000 m of the positive electrode plate 4.

  On the other hand, the slurry applied to the inner region 2 is 100 parts by weight of graphite as a negative electrode active material, 1 part by weight of carboxymethyl cellulose as a thickener, 1 part by weight of styrene-butadiene rubber (SBR) as a binder, and dispersed. It was produced by kneading the medium.

  Furthermore, 100 parts by weight of graphite as a negative electrode active material, 1 part by weight of carboxymethyl cellulose as a thickener, 2 parts by weight of styrene-butadiene rubber (SBR) as a binder, and slurry applied to the end region 3; It was produced by kneading the dispersion medium.

  These slurries are applied to both sides of a 10 μm-thick copper foil, which is a long current collector 1, dried in the same manner as the positive electrode plate 4, and rolled so that the mixture density is 1.52 g / cc and the thickness is 156 μm. And it cut | judged to width 56mm using the slitter apparatus at the cutting process, and the negative electrode plate 5 was obtained.

  The positive electrode plate 4 and the negative electrode plate 5 produced as described above are combined, and current collecting leads are welded to the exposed regions of the current collectors 1 of the positive electrode plate 4 and the negative electrode plate 5. % Of a 20 μm polyethylene separator is sandwiched between the positive electrode plate 4 and the negative electrode plate 5 and wound into a spiral shape to form an electrode plate group. This group is made of stainless steel bottom as a battery case with a thickness of 25 μm. A cylindrical lithium secondary battery having a battery can outer diameter of 18 mm and a height of 65 mm was prepared by being housed in a cylindrical container. The characteristics evaluation of these batteries will be described later together with the batteries of other examples and comparative examples.

  The above lithium secondary battery was charged at 0.3 C in a 20 ° C. atmosphere and charged and discharged three times at 1 C to 3 V. After that, the lithium secondary battery was 4.2 V at 0.3 C in a 25 ° C. atmosphere. The charge / discharge cycle of charging to 1 V and discharging to 3 V at 1 C was repeated a plurality of times. Table 1 shows the capacity at the 500th cycle as a percentage when the capacity at the first cycle in an atmosphere of 25 ° C. is 100%.

  A positive electrode plate 4 was obtained in the same manner as in Example 1 except that the boundary between the inner region 2 and the end region 3 was changed to 5 mm from the end when Example 1 was carried out. .

  When Example 1 was carried out, a positive electrode plate 4 was obtained in the same manner as Example 1 except that the boundary between the inner region 2 and the end region 3 was 0.5 mm from the end, and Example 3 was obtained. It was.

When Example 1 was carried out, 100 parts by weight of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ powder was used as the positive electrode active material, and 2 acetylene blacks were used as the conductive agent. A positive electrode plate 4 was obtained in the same manner as in Example 1 except that it was prepared by kneading 5 parts by weight, 15 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and a dispersion medium. It was set to 4.

When Example 2 was performed, the slurry applied to the end region 3 was 100 parts by weight of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ powder as the positive electrode active material, and 2 acetylene blacks as the conductive agent. A positive electrode plate 4 was obtained in the same manner as in Example 2 except that it was prepared by kneading 5 parts by weight, 15 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and a dispersion medium. It was set to 5.

When Example 3 was performed, the slurry applied to the end region 3 was 100 parts by weight of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ powder as the positive electrode active material, and 2 acetylene blacks as the conductive agent. A positive electrode plate 4 was obtained in the same manner as in Example 3 except that it was prepared by kneading 5 parts by weight, 15 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and a dispersion medium. It was set to 6.

Comparative Example 1

  Except that the end region 3 was eliminated when Example 1 was carried out, a positive electrode plate 4 was obtained in the same manner as Example 1 to obtain Comparative Example 1.

Comparative Example 2

When Comparative Example 1 was performed, the slurry applied to the current collector plate 1 was 100 parts by weight of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ powder as the positive electrode active material and 2 acetylene blacks as the conductive agent. A positive electrode plate 4 was obtained in the same manner as in Comparative Example 1 except that it was prepared by kneading 5 parts by weight, 6 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and a dispersion medium. 2.

Comparative Example 3

  When Example 1 was carried out, a positive electrode plate 4 was obtained in the same manner as Example 1 except that the boundary between the inner region 2 and the end region 3 was set to 0.3 mm from the end, and a comparative example was obtained. It was set to 3.

Comparative Example 4

  When Example 1 was carried out, a positive electrode plate 4 was obtained in exactly the same manner as Example 1 except that the boundary between the inner region 2 and the end region 3 was set to 12 mm from the end, and Comparative Example 4 and did.

Comparative Example 5

When Example 1 was carried out, the slurry applied to the end region 3 was 100 parts by weight of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ powder as the positive electrode active material and 2 acetylene blacks as the conductive agent. 0.5 parts by weight, 18 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and a dispersion medium were prepared by kneading.

  The end region 3 whose boundary with the inner region 2 is 7 mm from the end in a state where the mixture slurry for the positive electrode plate thus produced is cut in a later process using several types of slit die coaters, The wide positive electrode plate 40 was produced by coating separately from the region 2 and then drying.

Except for these, a positive electrode plate 4 was obtained in the same manner as in Example 1 to obtain Comparative Example 5.
―Evaluation of mix omission―
In Comparative Example 1, when the amount of the binder in the end region 3 was small, the adhesion between the mixture and the current collector 1 was lowered, and the mixture was dropped. Further, as in Comparative Example 3, when the width A of the end region 3 is 0.3 mm, that is, when the boundary between the inner region 2 and the end region 3 is 0.3 mm from the end, the end region Since the breakage starts from the inner region 2 on the inner side than 3, it is not possible to prevent the mixture from falling off. From the above results, the amount of the binder in the end region 3 is twice or more that of the inner region 2 in terms of the weight ratio based on the positive electrode active material, and the boundary between the inner region 2 and the end region 3 extends from the end. It is desirable to be 0.5 mm or more.
-Battery evaluation-
The cycle characteristics are desirably 80% or more in terms of practical use as a lithium secondary battery, and the cycle characteristics in each example were 80% or more, all being good.

  In Comparative Examples 2 and 5, since there were many binders, the positive electrode active material was coated to inhibit Li ion migration, and the permeability of the electrolytic solution was deteriorated, so that the cycle characteristics were deteriorated. In Comparative Example 4, since the boundary between the inner region 2 and the end region 3 is 12 mm from the end, and the amount of the binder in the end region 3 is large, in the inner region 2 where the air in the positive electrode plate 4 is difficult to escape. The permeability of the electrolyte was deteriorated by a large amount of the binder, and the cycle characteristics were deteriorated because the amount of the electrolyte was reduced. In the positive electrode plate 4 of the example, since the boundary between the inner region 2 and the end region 3 is 10 mm or less from the end, the air escape is good and the electrolyte permeability is high, so that the cycle characteristics are excellent. Yes. From the above results, the amount of the binder in the end region 3 is 5 times or less that of the inner region 2 in terms of the weight ratio of the positive electrode active material, and the boundary between the inner region 2 and the end region 3 extends from the end. It is desirable to be 10 mm or less.

本発明は、上述した正極板４だけでなく、負極板５にも適用でき、同様の効果が生じる。

The present invention can be applied not only to the positive electrode plate 4 described above but also to the negative electrode plate 5, and the same effect is produced.

  From the above results, in the electrode plate for a non-aqueous electrolyte secondary battery of the present invention, the weight ratio of the binder based on the polar active material is sufficiently large in the end region, so that the synthetic omission at the time of cutting is eliminated. Can be prevented. In addition, in the nonaqueous electrolyte secondary battery using this electrode plate, the weight ratio of the binder in the inner region of the electrode plate is sufficiently small and ion migration is not inhibited, so that the cycle characteristics are excellent, and the electrode plate synthesis Since it can be prevented from falling off, it is excellent in safety.

By the way, in the said Example, although demonstrated as what has a positive mix layer on both surfaces of the electrical power collector 1, it is not limited to both surfaces, A single side may be sufficient.
Moreover, in the said Example, although the lithium secondary battery was demonstrated as an example of a nonaqueous electrolyte secondary battery, it is not limited to this, A nickel hydride battery, a fuel cell, or a ceramic capacitor may be sufficient.

  The nonaqueous electrolyte secondary battery using the electrode plate for a nonaqueous electrolyte secondary battery according to the present invention is useful as a power source for portable equipment and the like because of its high capacity and high power battery safety and cycle characteristics. is there.

DESCRIPTION OF SYMBOLS 1 Current collector 2 Inner area | region 3 End part area | region 4 Positive electrode plate 5 Negative electrode plate 40 Wide positive electrode plate

Claims (5)

An electrode plate for a non-aqueous electrolyte secondary battery having an electrode mixture layer containing a binder and an electrode active material on a current collector,
The electrode mixture layer is divided into an inner region and an end region,
An electrode plate for a non-aqueous electrolyte secondary battery, wherein a weight ratio of a binder based on a polar active material is larger in the end region than in the inner region. The weight ratio of the binder based on the polar active material is not less than 2 times and not more than 5 times the inner region in the end region,
2. The electrode plate for a nonaqueous electrolyte secondary battery according to claim 1, wherein a boundary between the inner region and the end region is 0.5 mm or more and 10 mm or less from an end of the electrode plate.   The binder is a fluorine-based binder, acrylic rubber, modified acrylic rubber, styrene-butadiene rubber, acrylic polymer or vinyl polymer, or a mixture or copolymer of two or more of these. The electrode plate for nonaqueous electrolyte secondary batteries according to claim 1 or 2.   The polar active material is a composite metal oxide of at least one metal selected from cobalt, manganese, nickel, chromium, iron and vanadium and lithium, according to any one of claims 1 to 3. The electrode plate for a nonaqueous electrolyte secondary battery as described. A non-aqueous electrolyte secondary battery comprising the non-aqueous electrolyte secondary battery electrode plate according to claim 1.

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