JP2013045558A - Electrode and electric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode capable of simultaneously achieving increased liquid absorption property and improved adhesion thereof.SOLUTION: In an electrode (4), an active material layer (6) containing CMC is arranged on a collector (5) and an electrolyte layer is arranged on a side opposite to a collector side of the active material layer (6). The active material layer (6) includes at least two or more active material layers containing CMC having an etherification degree different from each other, and the active material layer containing CMC having a relatively high etherification degree is arranged on an electrolyte layer side while the active material layer containing CMC having a relatively low etherification degree is arranged on the collector (5) side.

Description

  The present invention relates to an electrode and an electrical device such as a secondary battery.

  Examples of the electrode mixture responsible for the adhesion of the electrode in the negative electrode include styrene butadiene rubber (SBR) as an aqueous binder and carboxymethyl cellulose (hereinafter referred to as “CMC”) as a thickener. Some of these electrode mixtures are mixed with a negative electrode active material to form a negative electrode active material layer, and this negative electrode active material layer is placed on a negative electrode current collector (see Patent Document 1). In this product, the adhesion of the negative electrode is enhanced by lowering the degree of etherification of CMC.

JP-A-4-342966

  By the way, the present inventors have newly found that the characteristics required for the negative electrode and the positive electrode are different between the separator side and the current collector side. That is, according to the knowledge of the present inventors, it is required that the electrode has high liquid absorbency on the separator side and that the electrode has good electrode adhesion on the current collector side. For this reason, as in the technique of Patent Document 1 described above, if the degree of etherification of the CMC is only lowered to increase the adhesion of the entire electrode, the liquid absorbency of the entire electrode is lowered, and the battery is inserted. The output characteristics will deteriorate.

  Then, this invention aims at providing the electrode which can aim at coexistence with improving the liquid absorptivity of an electrode and improving the adhesiveness of an electrode.

  The electrode of the present invention is an electrode in which an active material layer containing CMC is disposed on a current collector and an electrolyte layer is disposed on the side of the active material layer opposite to the current collector side. Furthermore, in the electrode of the present invention, the active material layer includes at least two active material layers containing CMC having different degrees of etherification, and the active material layer containing CMC having a relatively high degree of etherification is included in the active material layer. An active material layer containing CMC having a relatively low degree of etherification is arranged on the current collector side on the electrolyte layer side.

   According to the present invention, the active material layer containing CMC having a relatively low degree of etherification improves the adhesion of the electrode, and the active material layer containing CMC having a relatively high degree of etherification has input / output characteristics. It is possible to improve the electrode, and by including these active material layers in the active material layer, it is possible to improve both the liquid absorbency of the electrode and the adhesion of the electrode.

1 is a schematic view of a laminated battery according to a first embodiment of the present invention. It is the sectional view on the AA line of FIG. It is an expansion schematic of negative electrode 4 of a 1st embodiment. It is the expansion schematic of the negative electrode 4 of 2nd Embodiment. It is an expansion schematic of the negative electrode 4 of 3rd Embodiment. It is an expansion schematic of the negative electrode 4 of 4th Embodiment. It is an expansion schematic of negative electrode 4 of a 5th embodiment. It is the expansion schematic of the negative electrode 4 of 6th Embodiment. It is an expansion schematic of the negative electrode 4 of 7th Embodiment. It is a characteristic view of the electrode intensity | strength and discharge rate of an Example and a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the dimension ratio of drawing has the location exaggerated on account of description, and the location differs from the actual ratio.

(First embodiment)
First, the lithium ion secondary battery 1 of this embodiment is demonstrated. FIG. 1 is a schematic perspective view of a lithium ion secondary battery 1, and FIG. 2 is a cross-sectional view taken along line AA of FIG.

  As shown in FIGS. 1 and 2, in a lithium ion secondary battery 1, a power generation element 2 having a substantially rectangular thin plate in which a charge / discharge reaction actually proceeds is sealed inside a laminate film 14 that is a battery exterior material. Has a structure. Specifically, the power generation element 2 is housed and sealed by joining a peripheral part (peripheral part) by thermal fusion using a polymer-metal composite laminate film as a battery exterior material. . Here, the polymer-metal composite laminate film generally has a three-layer structure in which a metal film is sandwiched between polymer films (resin films).

  Such a stacked battery 1 is referred to as a “laminated battery” in order to be distinguished from a can battery. A can-type battery is one in which two electrodes are wound and housed in a hard cylindrical metal outer frame like a commercially available AA battery or AA battery. On the other hand, the laminate type battery is a battery in which the power generation element is sealed by joining the peripheral portion (peripheral portion) of the power generation element 2 having a substantially rectangular thin plate shape by heat fusion. Hereinafter, the lithium ion secondary battery 1 is referred to as a “laminated battery”. Alternatively, it is simply called “battery”.

  The power generation element 2 has a configuration in which a negative electrode 4, a separator 12, and a positive electrode 8 are stacked in this order. Here, the negative electrode 4 is obtained by disposing negative electrode active material layers 6 and 6 on both sides of a rectangular thin plate-like negative electrode current collector 5. Similarly, the positive electrode 8 is obtained by disposing positive electrode active material layers 10 and 10 on both sides of a rectangular thin plate-shaped positive electrode current collector 9. The separator 12 is mainly formed from a porous thermoplastic resin. Since the separator 12 holds the electrolytic solution, an electrolyte layer is formed integrally with the separator 12.

  Thereby, the adjacent negative electrode 4, the separator 12, and the positive electrode 8 comprise one single cell layer 13 (single cell). Therefore, it can be said that the laminate type battery 1 of the present embodiment has a configuration in which the single battery layers 13 are stacked to be electrically connected in parallel. Further, a seal portion (insulating layer) for insulating between the adjacent negative electrode current collector 5 and positive electrode current collector 9 may be provided on the outer periphery of the unit cell layer 13. In the outermost layer negative electrode current collector 5 located in both outermost layers of the power generation element 2, the negative electrode active material layer 6 is disposed only on one side. Note that the arrangement of the negative electrode and the positive electrode is reversed from that in FIG. 2 so that the outermost positive electrode current collector is positioned in both outermost layers of the power generation element 2, and the positive electrode is provided only on one side of the outermost positive electrode current collector. An active material layer may be disposed.

  The negative electrode current collector 5 and the positive electrode current collector 9 are attached with high voltage tabs 15 and 16 that are electrically connected to the respective electrodes (negative electrode and positive electrode), and are led out of the laminate film 14 so as to be sandwiched between the ends of the laminate film 14. I am letting. The high voltage tabs 15 and 16 are ultrasonically welded to the negative electrode current collector 5 and the positive electrode current collector 9 of each electrode via a positive electrode terminal lead (not shown) and a negative electrode terminal lead (not shown) as necessary. Or it may be attached by resistance welding. Here, the battery 1 shown in FIGS. 1 and 2 has four sides when viewed from above, and the high-power tabs 15 and 16 are led out to the outside from two parallel sides of the two. 16 may be derived to the outside from only one side.

  As another form of the lithium ion secondary battery, a bipolar electrode in which a positive electrode active material layer is formed on one surface of a current collector and a negative electrode active material layer is formed on the other surface through a separator. A stacked bipolar secondary battery can be mentioned. The battery 1 and the bipolar secondary battery are basically the same except that the electrical connection state (electrode structure) in both batteries is different.

  A battery having a predetermined voltage is obtained by laminating and storing the laminated battery 1 configured as described above in a metal battery case, and connecting the plurality of laminated laminated batteries 1 in series using each high voltage tab. A pack is composed. Furthermore, an assembled battery having a predetermined voltage is configured by electrically combining a plurality of battery packs, and this assembled battery is mounted on a transportation facility such as an electric vehicle or a hybrid vehicle.

  The present inventors have newly found that the characteristics required for the negative electrode and the positive electrode are different between the separator side and the current collector side. That is, according to the knowledge of the present inventors, it is required that the electrode has high liquid absorbency on the separator side and that the electrode has good electrode adhesion on the current collector side.

  In this regard, there are styrene butadiene rubber (SBR), which is an aqueous binder (binder), and CMC, which is a thickener, as an electrode mixture that is responsible for the adhesion of the electrode in the negative electrode. There is a conventional device in which these electrode mixtures are mixed with a negative electrode active material to form a negative electrode active material layer, and this negative electrode active material layer is placed on a negative electrode current collector.

  However, the inventor's knowledge is not described at all in the conventional apparatus. For this reason, as in the conventional device, if the degree of etherification of CMC is only lowered to improve the adhesion of the whole negative electrode, the liquid absorption of the whole negative electrode is lowered, and the input / output of the laminated battery 1 is reduced. The characteristics will deteriorate.

  Therefore, in the present embodiment, the negative electrode active material layer 6 (active material layer) containing CMC is disposed on the negative electrode current collector 5 (current collector), and the negative electrode current collector 5 side of the negative electrode active material layer 6 and Is a negative electrode 4 (electrode) provided with a separator 12 (electrolyte layer) on the opposite side, and the negative electrode active material layer 6 includes at least two active material layers containing CMC having different degrees of etherification, and is etherified. A negative electrode active material layer containing CMC having a relatively high degree of CMC is arranged on the separator 12 side, and a negative electrode active material layer containing CMC having a relatively low degree of etherification is arranged on the negative electrode current collector 5 side.

This will be described with reference to FIG. 3. FIG. 3 is an enlarged schematic view of the negative electrode 4 and the separator 12 of the first embodiment.
As shown in FIG. 3, the negative electrode active material layer 6 includes a negative electrode active material layer 21 containing CMC having a relatively high degree of etherification, and a negative electrode active material layer 22 containing CMC having a relatively low degree of etherification. And two negative electrode active material layers. Hereinafter, the negative electrode active material layer containing CMC having a relatively high degree of etherification is referred to as “first negative electrode active material layer”, and the negative electrode active material layer containing CMC having a relatively low degree of etherification is referred to as “second negative electrode”. It is called “active material”. Among these, the first negative electrode active material layer 21 is disposed on the surface of the negative electrode active material layer 6, and the second negative electrode active material layer 22 is disposed on the negative electrode current collector 5 side. Specifically, the degree of etherification of CMC contained in the first negative electrode active material layer 21 is specifically 1.2, and the degree of etherification of CMC contained in the second negative electrode active material layer 22 is specifically 0.6.

  Here, CMC is produced by substituting a part of the hydroxyl group of cellulose with a carboxyl group, and an ether bond is formed when the carboxyl group is substituted. The degree of substitution is called “the degree of etherification”.

  There is the following relationship between the degree of etherification of CMC and the physical properties of the negative electrode active material layer containing CMC. That is, when the degree of etherification of CMC is increased, the viscosity of the negative electrode active material layer containing CMC is decreased, and the hardness of the negative electrode active material layer is decreased (softened). On the other hand, when the degree of etherification of CMC is lowered, the viscosity of the negative electrode active material layer containing CMC is increased, and the hardness of the negative electrode active material layer is increased (hardened). In other words, when the degree of etherification of CMC is increased, the negative electrode active material layer containing CMC has high liquid absorption, low Li ion migration resistance, and excellent input / output characteristics. On the other hand, when the degree of etherification of CMC is lowered, the negative electrode active material layer containing CMC is excellent in adhesion to the negative electrode current collector.

  Here, “liquid absorption” of the negative electrode 4 means a property that the electrolytic solution enters the inside of the negative electrode active material layer 6, and “high liquid absorption” means electrolysis inside the negative electrode active material layer 6. It means that the liquid can easily enter. The “input / output characteristics” are characteristics of the laminated battery 1 as a whole including the negative electrode active material layer 6 containing CMC, and are expressions that combine input characteristics and output characteristics. Here, “input characteristics” are charging characteristics of the laminate-type battery 1, and “output characteristics” are discharge characteristics of the laminate-type battery 1. “Excellent input characteristics” means that the laminated battery 1 can be easily charged, specifically, can be charged to full charge in a short time. “Excellent output characteristics” means that the laminate-type battery 1 is easily discharged, specifically, can be discharged for a long time with a large current.

  The “adhesiveness” of the negative electrode 4 refers to a property that the negative electrode active material layer 6 in a laminated state does not peel from the negative electrode current collector 5. “Excellent adhesion” means that the negative electrode active material layer 6 does not easily peel from the negative electrode current collector 5.

  Therefore, the negative electrode 4 having high input / output characteristics is obtained by disposing the first negative electrode active material layer 21 on the negative electrode surface layer (separator 12 side) where charge / discharge reaction easily occurs. In addition, by disposing the second negative electrode active material layer 22 on the negative electrode current collector 5 side, the negative electrode 4 having excellent adhesion to the negative electrode current collector 5 is obtained.

  Here, the function and effect of the first embodiment will be described.

  In the first embodiment, the negative electrode active material layer 6 (active material layer) containing CMC is placed on the negative electrode current collector 5 (current collector), and the negative electrode current collector 5 side of the negative electrode active material layer 6 Is a negative electrode 4 (electrode) provided with a separator 12 (electrolyte layer) on the opposite side, and the negative electrode active material layer 6 has two negative electrode active material layers containing CMC having different degrees of etherification (at least two or more). ) And the first electrode active material layer 21 (active material layer containing CMC having a relatively high degree of etherification) on the separator 12 side, and the second electrode active material layer 22 (CMC having a relatively low degree of etherification) Active material layer) is disposed on the negative electrode current collector 5 side. In particular, the portion where the adhesion of the negative electrode 4 is required is the interface between the negative electrode current collector 5 and the negative electrode active material layer 6. According to the first embodiment, the adhesion of the negative electrode 4 can be improved by providing the second negative electrode active material layer 22 at this interface. Further, according to the first embodiment, the negative electrode 4 having high liquid absorption is provided by providing the first negative electrode active material layer 21 in the negative electrode active material layer 6 on the separator 12 side that requires high input / output characteristics. A surface can be obtained.

  In the first embodiment, as shown in FIG. 3, the first and second negative electrode active material layers 21 and 22 have the same thickness W1 and W2. However, the present invention is not limited to this. It is not something. The ratio between the thickness W1 of the first negative electrode active material layer 21 and the thickness W2 of the second negative electrode active material layer 22 may be arbitrary. A second embodiment described below specifies this ratio.

(Second Embodiment)
FIG. 4 is an enlarged schematic view of the negative electrode 4 of the second embodiment. The same parts as those in FIG. 3 of the first embodiment are denoted by the same reference numerals.

  In the second embodiment, on the premise of the first embodiment of FIG. 3, the thickness W3 of the first negative electrode active material layer 21 is further made larger than the thickness W4 of the second negative electrode active material layer 22. In other words, the thickness W4 of the second negative electrode active material layer 22 is made thinner than the thickness W3 of the first negative electrode active material layer 21. This is because the second negative electrode active material layer 22 may be thin as long as it does not peel from the negative electrode current collector 5 (so long as the peel strength can be secured). Preferably, the thickness W3 of the first negative electrode active material layer 21 is four times thicker than the thickness W4 of the second negative electrode active material layer 22.

  In particular, the adhesion of the negative electrode 4 is required because the interface between the negative electrode current collector 5 and the negative electrode active material layer 6 is mainly used, and therefore the second electrode active material layer 22 is formed near the interface even if it is thin. It only has to exist. On the contrary, the higher the thickness W3 of the first electrode active material layer 21 present on the separator 12 side, the better the input / output characteristics. According to the second embodiment, the thickness W3 of the first negative electrode active material layer 21 (active material layer containing CMC having a relatively high degree of etherification) is set to the second negative electrode active material layer 22 (relative etherification degree). Therefore, the input / output characteristics of the laminated battery 1 can be further enhanced while ensuring the minimum adhesion of the negative electrode 4.

(Third embodiment)
FIG. 5 is an enlarged schematic view of the negative electrode 4 of the third embodiment. The same parts as those in FIG. 4 of the second embodiment are denoted by the same reference numerals.

  In the third embodiment, on the premise of the second embodiment of FIG. 4, the first negative electrode active material layer 21 is further replaced with third and fourth two electrode active material layers 21 a containing CMC having different degrees of etherification, 21b. That is, the third negative electrode active material layer 21a is a negative electrode active material layer containing CMC having a relatively high degree of etherification. On the other hand, the fourth negative electrode active material layer 21b has an ether lower than the degree of etherification of CMC contained in the third negative electrode active material layer 21a and higher than the degree of etherification of CMC contained in the second negative electrode active material layer 22. A negative electrode active material layer containing a degree of CMC is obtained. Then, the third negative electrode active material layer 21a is disposed on the separator 12 side, and the fourth negative electrode active material layer 21b is disposed on the second negative electrode active material layer 22 side. Specifically, the degree of etherification of CMC contained in the third negative electrode active material layer 21a is 1.2, the degree of etherification of CMC contained in the fourth negative electrode active material layer 21b is 0.8, The degree of etherification of CMC contained in the negative electrode active material layer 22 is set to 0.6. That is, in the third embodiment, the negative electrode active material layer 6 includes three negative electrode active material layers containing CMC having different degrees of etherification, and a negative electrode active material layer containing CMC having a relatively high degree of etherification ( 21a) is disposed on the separator 12 side, and a negative electrode active material layer (22) containing CMC having a relatively low degree of etherification is disposed on the negative electrode current collector side 5.

  FIG. 5 shows a case where the total thickness (W5 + W6) of the third and fourth negative electrode active material layers 21a and 21b is the same as the thickness W3 of the first negative electrode active material layer 21 of the second embodiment. However, it is not limited to this. The ratio of the thicknesses of the three negative electrode active material layers 21a, 21b, and 22 may be arbitrary.

  According to 3rd Embodiment, there exists an effect similar to 1st Embodiment. That is, according to the third embodiment, by providing the negative electrode active material layer (22) containing CMC having a relatively low degree of etherification at the interface between the negative electrode current collector 5 and the negative electrode active material layer 6, the negative electrode 4 can be improved. According to the third embodiment, the negative electrode active material layer (21a) containing CMC having a relatively high degree of etherification is provided on the negative electrode active material layer on the separator 12 side that requires high input / output characteristics. The surface of the negative electrode 4 having high liquid absorption can be obtained.

(Fourth and fifth embodiments)
6 and 7 are enlarged schematic views of the negative electrode 4 of the fourth and fifth embodiments. The same parts as those in FIG. 3 of the first embodiment are denoted by the same reference numerals.

  In the fourth embodiment, as shown in FIG. 6, the second negative electrode active material layer 22 is further formed on the end in the surface direction of the first negative electrode active material layer 21 (the end in the left-right direction in FIG. 6) on the premise of the first embodiment. The extended portion 22b extending from the separator 12 to the separator 12 is provided. The extended portion 22b is provided in the second negative electrode active material layer 22 for the following reason. That is, since the end portion 21c in the plane direction of the first negative electrode active material layer 21 is easily peeled off from the second negative electrode active material layer 22, the negative electrode active material layer having relatively high adhesion only to the end portion 21c in the plane direction that is easy to peel off. The extended portion 22b of the second negative electrode active material layer 22 is disposed.

  On the other hand, in the fifth embodiment, the thickness W8 of the surface end 22a of the second negative electrode active material layer 22 is set to be greater than the thickness W7 of the surface end 21c of the first negative electrode active material layer 21 as shown in FIG. It is thickened. In 5th Embodiment, what made thickness W7 of the surface direction edge part 21c of the 1st negative electrode active material layer 21 into zero is equivalent to 4th Embodiment.

  According to the fourth and fifth embodiments, the second negative electrode active material layer 22 (CMC having a relatively low degree of etherification) having excellent adhesion at the end in the surface direction of the negative electrode active material layer 6 (active material layer). The active material layer contained) is sufficiently present as the thickness W8, or the negative electrode active material layer 6 (active material layer) has an end in the surface direction of the second negative electrode active material layer 22 (CMC having a relatively low degree of etherification). (W7 = 0), it is possible to further improve the adhesion at the end in the surface direction of the negative electrode 4.

(Sixth and seventh embodiments)
8 and 9 are enlarged schematic views of the negative electrode 4 of the sixth and seventh embodiments. The same parts as those in FIG. 3 of the first embodiment are denoted by the same reference numerals.

  In the sixth embodiment, as shown in FIG. 8, on the premise of the first embodiment, the first negative electrode active material layer 21 is further provided at the end in the surface direction of the second negative electrode active material layer 22 (the end in the left-right direction in FIG. 8). To the negative electrode current collector 5 is provided with an extending portion 21d. The extension part 21d is provided in the first negative electrode active material layer 21 for the following reason. That is, when the electrolytic solution is injected after the power generation element 2 is covered with the battery outer packaging material, the end portions 21c and 22a in the surface direction of the negative electrode active material layers 21 and 22 penetrate into the negative electrode active material layer. It becomes the entrance to do. Therefore, the extended portion 21d of the first negative electrode active material layer 21 that is a negative active material layer having a relatively high liquid absorption property is disposed at the end in the surface direction that is the electrolyte infiltration inlet.

  On the other hand, in the seventh embodiment, as shown in FIG. 9, the thickness W9 of the surface end 21c of the first negative electrode active material layer 21 is greater than the thickness W10 of the surface end 22a of the second negative electrode active material layer 22. It is thickened. In the seventh embodiment, the thickness W9 of the surface direction end 22a of the second negative electrode active material layer 22 is zero, which corresponds to the sixth embodiment.

  According to the sixth and seventh embodiments, the first negative electrode active material layer 21 (CMC having a relatively high degree of etherification) having excellent liquid absorbency at the end in the surface direction of the negative electrode active material layer 6 (active material layer). Is present as the thickness W9, or the negative electrode active material layer 6 (active material layer) has a first negative electrode active material layer 21 (CMC having a relatively high degree of etherification) at the end in the surface direction. (W10 = 0) containing only the active material layer), the liquid absorbency of the negative electrode 4 is improved, and the electrolyte can be easily impregnated into the negative electrode active material layer 6.

  In order to confirm the effects of the first to third embodiments, three examples and three comparative examples were manufactured.

<Preparation of positive electrode slurry / positive electrode>
LiMn 2 O 4 (average particle diameter 20 μm, acetylene black as a conductive additive and polyvinylidene fluoride (PVDF) as a binder were mixed in a mass ratio of 86: 6: 8 as a positive electrode active material to obtain a positive electrode slurry. A positive electrode slurry was applied to both sides of a plate-like current collector (thickness 20 μm), dried with hot air at 130 ° C., and then rolled to form a sheet.The thickness of the positive electrode (positive electrode plate) was 262 μm. .

<Preparation of negative electrode slurry / negative electrode>
Graphite (average particle diameter: 10 μm) as the negative electrode active material, SBR as the binder and CMC as the thickener were mixed at a mass ratio of 97: 2: 1 to obtain a negative electrode slurry. A negative electrode slurry was applied to both sides of a copper plate-like current collector (thickness 10 μm), dried with hot air at 130 ° C., and then roll-rolled to form a sheet. The thickness of the negative electrode (negative electrode plate) was 122 μm.

  At that time, three types (1.2, 0.6, and 0.8) of negative electrode slurries were prepared using CMC having different degrees of etherification. Hereinafter, negative electrode slurries containing CMCs having etherification degrees of 1.2, 0.6, and 0.8 are referred to as negative electrode slurries A, B, and C. Moreover, let the negative electrode active material layer containing each CMC whose etherification degree is 1.2, 0.6, and 0.8 be the negative electrode active material layers A, B, and C.

<Description of Examples>
[Example 1]
The negative electrode slurry B was applied onto the negative electrode current collector, and the negative electrode slurry A was applied onto the negative electrode slurry B with a doctor blade to obtain a negative electrode. This was roll-rolled in a drying furnace at 100 ° C. after sufficiently evaporating water to form a sheet. Regarding the thickness on one side with respect to the negative electrode current collector, the negative electrode active material layer A was 30 μm and the negative electrode active material layer B was 30 μm. Example 1 corresponds to the first embodiment of FIG.

[Example 2]
The negative electrode slurry B was applied onto the negative electrode current collector, and the negative electrode slurry A was applied onto the negative electrode slurry B with a doctor blade to obtain a negative electrode. This was roll-rolled in a drying furnace at 100 ° C. after sufficiently evaporating water to form a sheet. Regarding the thickness on one side with respect to the negative electrode current collector, the negative electrode active material layer A was 50 μm and the negative electrode active material layer B was 10 μm. Example 2 corresponds to the second embodiment of FIG.

[Example 3]
The negative electrode slurry B was applied onto the negative electrode current collector, and the negative electrode slurry A was applied onto the negative electrode slurry B with a doctor blade to obtain a negative electrode. This was roll-rolled in a drying furnace at 100 ° C. after sufficiently evaporating water to form a sheet. Regarding the thickness on one side with respect to the negative electrode current collector, the negative electrode active material layer A was 10 μm and the negative electrode active material layer B was 50 μm.

[Comparative Example 1]
The negative electrode slurry A was applied onto the negative electrode current collector with a doctor blade to obtain a negative electrode electrode. This was roll-rolled in a drying furnace at 100 ° C. after sufficiently evaporating water to form a sheet. About the one-side thickness with respect to a negative electrode electrical power collector, the negative electrode active material layer A was 60 micrometers.

[Comparative Example 2]
The negative electrode slurry B was coated on the negative electrode current collector with a doctor blade to obtain a negative electrode. This was roll-rolled in a drying furnace at 100 ° C. after sufficiently evaporating water to form a sheet. About the one-side thickness with respect to a negative electrode electrical power collector, the negative electrode active material layer B was 60 micrometers.

[Comparative Example 3]
The negative electrode slurry C was coated on the negative electrode current collector with a doctor blade to obtain a negative electrode. This was roll-rolled in a drying furnace at 100 ° C. after sufficiently evaporating water to form a sheet. Regarding the thickness of one side of the negative electrode with respect to the current collector, the negative electrode active material layer C was set to 60 μm.

  The obtained positive electrode (positive electrode plate) was punched out so that the electrode part size was 34 mm × 24 mm, and an aluminum high voltage tab was joined by ultrasonic welding. Further, the obtained negative electrode (negative electrode plate) was punched out so that the electrode part size was 36 mm × 26 mm, and a high-voltage nickel tab was joined by ultrasonic welding.

<Production of battery>
A polyethylene microporous membrane (thickness = 25 μm) was prepared as a separator. Further, as the electrolytic solution, a mixed electrolytic solution of ethylene carbonate (EC) and diethylene carbonate (DEC) (EC: DEC = 1: 1 volume ratio) holding 1.0 M LiPF6 electrolyte was used.

  Three negative electrodes (negative electrode plates) including the negative electrode active material layer prepared and prepared above, four separators, two positive electrodes (positive electrode plates), and negative electrode active material layers are arranged on both upper and lower sides. Then, a negative electrode, a separator, a positive electrode, a separator,... Were stacked in the same order as shown in FIG.

  The obtained power generation element was housed in a bag made of a polymer-aluminum composite laminate film, which is a battery exterior material, and the electrolytic solution prepared above was injected. Under vacuum conditions, the opening of the polymer-aluminum composite laminate film bag was sealed so that the high voltage tabs connected to both electrodes were led out, and the test battery was completed.

<Aging process>
The test battery produced above was subjected to aging treatment at 45 ° C. for 6 days.

<Evaluation of test cell>
Each test battery was charged in the air at 25 ° C. for 13 hours by the constant current constant voltage method (CCCV, current: 0.1 C, voltage: 4.2 V). Next, after a 10-minute pause, discharge treatment was performed to 2.5 V by a constant current method (CC, current: 0.1 C).

  Subsequently, after a further 10 minutes of rest, the battery was charged for 3 hours by a constant current constant voltage method (CCCV, current: 1 C, voltage: 4.2 V), and the charge capacity was measured. Then, it discharged to 2.5V with constant current (CC, electric current: 0.2C), measured the discharge capacity, and was taken as 0.2C capacity. Further, after resting for 10 minutes, the battery was charged for 3 hours by a constant current constant voltage method (CCCV, current: 1 C, voltage: 4.2 V), and the charge capacity was measured. Then, it discharged to 2.5V with constant current (CC, electric current: 3C), measured the discharge capacity, and was set as 3C capacity. The discharge rate characteristics were calculated using the 3C capacity as the numerator and the previous 0.2C capacity as the denominator to obtain the 3C / 0.2C discharge rate.

  The discharge rate characteristic results thus obtained are shown in the following Table 1 together with the electrode strength results.

As the electrode strength in Table 1, a tape peeling test was performed on the electrode before battery assembly. In order to make Table 1 easier to understand, the results of Table 1 are shown as two-dimensional data in FIG. As can be seen from FIG. 10, according to the three examples, both the discharge rate characteristics and the peel strength can be improved as compared with the comparative example.

  In the embodiment, the case where the negative electrode active material layer is formed by mixing CMC with the negative electrode active material to form a negative electrode active material layer on the negative electrode current collector has been described. However, the CMC is mixed with the positive electrode active material. The present invention can also be applied to the case where a positive electrode active material layer is formed in a layer shape and this positive electrode active material layer is placed on a positive electrode current collector. In this case, a positive electrode active material layer containing CMC is disposed on the positive electrode current collector, and a positive electrode active material layer is disposed on the opposite side of the positive electrode current collector side from the positive electrode current collector side. The material layer includes at least two positive electrode active material layers containing CMC having different degrees of etherification, and the positive electrode active material layer containing CMC having a relatively high degree of etherification is disposed on the electrolyte layer side. A positive electrode active material layer containing a relatively low CMC is used as a positive electrode disposed on the positive electrode current collector side.

  In the embodiment, a lithium ion secondary battery using a laminate film as an exterior material is illustrated as an electrical device, but the present invention is not limited thereto. The present invention can also be applied to a metal plate as an exterior material, other types of secondary batteries, and further primary batteries. Further, it can be applied not only to batteries but also to electrochemical capacitors such as electric double layer capacitors.

1 Laminated battery 4 Negative electrode (electrode)
5 Negative electrode current collector (current collector)
6 Negative electrode active material layer (active material layer)
12 Separator 21 First Negative Electrode Active Material Layer 21c Surface End 21d Extension 22 Second Negative Active Material Layer 22a Surface End 22b Extension

Claims (5)

An electrode in which an active material layer containing CMC is placed on a current collector and an electrolyte layer is placed on the side opposite to the current collector side of the active material layer,
The active material layer includes at least two active material layers containing CMC having different degrees of etherification,
An active material layer containing CMC having a relatively high degree of etherification is disposed on the electrolyte layer side, and an active material layer containing CMC having a relatively low degree of etherification is disposed on the current collector side. electrode.   The active material layer containing CMC having a relatively high degree of etherification is made thicker than the active material layer containing CMC having a relatively low degree of etherification. The electrode as described.   The thickness of the end portion in the surface direction of the active material layer containing CMC having a relatively low degree of etherification is larger than the thickness of the end portion in the surface direction of the active material layer containing CMC having a relatively high degree of etherification. Or extending an active material layer containing CMC having a relatively low degree of etherification to the electrolyte layer at an end in the surface direction of the active material layer containing CMC having a relatively high degree of etherification. The electrode according to claim 1 or 2.   The thickness of the active material layer containing CMC having a relatively high degree of etherification is thicker than the thickness of the active material layer containing CMC having a relatively low degree of etherification. Or an active material layer containing CMC having a relatively high degree of etherification is extended to the current collector at an end in the surface direction of the active material layer containing CMC having a relatively low degree of etherification. The electrode according to claim 1 or 2, characterized by the above-mentioned.   An electrical device comprising the electrode according to any one of claims 1 to 4.