JP6111800B2 - Battery electrode composition and battery - Google Patents

Description

  The present invention relates to a battery electrode composition and a battery applied to a lithium ion battery and the like. More specifically, the present invention relates to a battery electrode composition for producing a battery excellent in strength and adhesion to a current collector, and a battery using the same.

Electrode members of lithium ion batteries are used for electrode parts of batteries (including capacitors) used in, for example, electric vehicles, fuel cell vehicles, hybrid vehicles, household power storage facilities, electric tools, trains, small portable devices, etc. The In particular, its development has been remarkable in recent years.
The members constituting the lithium ion battery can be roughly divided into a positive electrode, a negative electrode, a separator, and an electrolytic solution. Among them, the electrode is made of a material such as a current collector, an active material, a binder, and a conductive additive, and greatly affects the performance of the entire battery.

The electrode is coated on a current collector using a metal foil or the like by applying a slurry in which a material containing an active material, a binder, a conductive additive, etc. is dispersed and mixed with a solvent using a coating machine. And then dried and wound up in an installed oven. Thereafter, slitting or pressing is performed as necessary.
The role of the binder in the electrode is to bind the active material particles, which are discrete particles, to maintain the shape as a coating film and to be in close contact with the current collector to ensure conductivity. If the binding between the active material particles is weak, that is, the coating film strength is weak, the film after electrode coating, that is, the electrode coating film cracks or cracks in the slit process or press process after electrode coating, etc. Problem arises.

If the adhesion between the coating film and the current collector is weak, problems such as peeling or lifting of the electrode coating film from the current collector occur in the slit process or pressing process after electrode coating. Furthermore, the electrode after coating must also have flexibility (flexibility), and if this is insufficient, cracking may occur at the winding of the coating machine outlet.
As a negative electrode, a carbon material is generally used as an active material, and an aqueous system containing carbon particles, a conductive additive, a binder, and a thickener in addition to the copper foil as a current collector. It is obtained by applying and drying the paint.

  Here, the thickener (in this specification, “thickener” is synonymous with “thickener”) is a water-based paint, and the binder generally uses an aqueous dispersion of a rubber-based resin. Since the viscosity of the coating is lowered, it is used for the purpose of adjusting (thickening) the viscosity to be suitable for coating. Furthermore, in the electrode coating film after coating and drying, it contributes to the strength of the coating film and the adhesion to the current collector together with the binder.

  As the binder for the carbon-based negative electrode, water-dispersed styrene butadiene rubber (hereinafter abbreviated as SBR) is usually used, and as the thickener, carboxymethyl cellulose (hereinafter abbreviated as CMC) is used. As a general method, a conductive auxiliary agent such as carbon black and carbon particles are added and uniformly dispersed in a CMC aqueous solution, and then an SBR aqueous dispersion is added to prepare an aqueous electrode paint.

When a defect such as cracking of the electrode coating or cracking occurs in the negative electrode manufactured in this way, there arises a problem that metal lithium is deposited in the defective part and breaks through the separator to cause a short circuit. In addition, when the adhesion between the electrode coating film and the current collector is weak, the internal resistance increases due to the electrode coating film peeling from the current collector during repeated charging and discharging, and the performance as a battery decreases.
In order to avoid this, the peel strength between the negative electrode mixture layer and the negative electrode current collector was increased by using a thickener composed of two types of carboxymethylcellulose having different viscosities and etherification degrees. A negative electrode plate is disclosed (for example, see Patent Document 1).

JP 2012-59488 A

However, in the case of the negative electrode plate in which the peel strength between the negative electrode mixture layer and the negative electrode current collector is increased, two types of different CMCs must be added to the negative electrode plate, which is troublesome.
In addition, an electrode that is cracked, cracked, or peeled off from the current collector is already a defective product if it can be clearly seen before it is assembled into a battery. In addition to the cases that can be clearly seen in this way, there are cases where there are minor damages that are not visible, or when the batteries are assembled in the process of being assembled into batteries, or are used as batteries for a long time. Therefore, there is a need for a strong electrode that does not cause cracking or peeling as much as possible in all possible situations.
Accordingly, an object of the present invention is to provide a composition for a battery electrode that has excellent strength of an electrode coating and adhesion to a current collector with a single thickening material without complicating the process, and a battery using the same. Is to provide.

As a result of intensive studies, the present inventor has improved the strength of the electrode coating and the adhesion with the current collector by using cellulose single nanofibers instead of CMC, compared to the case of using CMC. It has been found that a battery electrode composition and an electrode using the same can be obtained.
One aspect of the present invention is a battery electrode composition comprising a carbon-based active material, a conductive additive, a binder, and a thickener , wherein cellulose single nanofiber is used as the thickener, and the cellulose single nanofiber is used . the carboxyl group-terminated counterion, battery electrode composition which is one or two, characterized in Rukoto such only ions belonging to an ammonium ion, a.

Another aspect of the present invention is a battery comprising an electrode comprising the battery electrode composition according to any one of the above aspects.

  According to one aspect of the present invention, in a carbon-based lithium ion battery including a thickener, a cellulose single nanofiber is used as the thickener included in the battery electrode composition, so that, for example, CMC is used as the thickener. Thus, a battery electrode composition and a battery that are superior in the strength of the electrode coating film and the adhesion to the current collector can be obtained than in the case of using the above.

It is the schematic which shows an example of the electrode to which this invention is applied. It is the schematic which shows the measuring method of peeling adhesive strength in this invention.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, an electrode 10 of a lithium ion battery generally has a coating film 12 (hereinafter also referred to as an electrode coating film) 12 serving as an electrode film on a current collector 11 made of a metal foil or the like. It has a formed configuration. The electrode coating film 12 includes a carbon-based active material, a conductive additive, a binder, and a thickener.

In a negative electrode of a lithium ion battery, a combination using a carbon-based material as an active material, carbon black as a conductive additive, SBR as a binder, and CMC as a thickener is very common. In the present invention, cellulose single nanofiber is used as a thickening material instead of CMC.
Cellulose single nanofibers are nanofibers composed of cellulose derivatives that are completely separated from each other, and are obtained by catalytically oxidizing cellulose to TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical). It is something that can be done.

In this specification, the cellulose single nanofiber is a fibrous polysaccharide having a carboxyl group and is defined as a nanodispersion of TEMPO-oxidized cellulose.
In order to more specifically define the cellulose single nanofiber in the present invention, it will be described in detail with reference to production examples.
Examples of fibrous polysaccharides include cellulose fibers, chitin, and chitosan. In particular, cellulose fibers having a regular structural arrangement and a rigid skeleton are preferable. Wood pulp, non-wood pulp, cotton, bacterial cellulose, and the like can be used as cellulose that is a raw material for cellulose fibers.

Furthermore, the cellulose single nanofiber in the present invention has a fiber width of 2 nm to 50 nm and a length of 0.5 μm to 50 μm.
Within this range, dispersibility is improved because there are many sites capable of interacting with the active material, and electrochemical stability is improved because a conductive network between the active materials is formed. Furthermore, the entangled structure of cellulose fibers is excellent in swelling resistance to the electrolytic solution, and since the active material is captured, it is difficult to fall off, and good cycle characteristics as a battery can be obtained.

On the other hand, if the fiber width exceeds 50 nm, the ratio of the surface area to the total volume of the cellulose fibers becomes relatively small, and the number of sites capable of interacting with the active material is reduced, so that the active material cannot be efficiently dispersed.
On the other hand, if the length is less than 0.5 μm, the cellulose fibers cannot be sufficiently entangled with each other, which causes a decrease in the strength of the film. Furthermore, when the length exceeds 50 μm, the entanglement between the cellulose fibers increases, so that the fibers are difficult to disperse, and the precipitate is easily formed, so that the dispersion stability is lowered.

  The width and length of the fibers were determined by spreading fibers diluted to a solid content concentration of about 0.001% in a solvent such as water on a smooth substrate such as glass and drying them, using an atomic force microscope (Atomic Force Microscope, AFM), a transmission electron microscope (TEM), or the like.

  Moreover, it is desirable that the amount of carboxyl groups in the cellulose fiber is 0.5 mmol / g or more and 3.0 mmol / g or less with respect to the weight of cellulose. Cellulose fibers having an amount of carboxyl groups in this range have good dispersibility when subjected to a dispersion treatment, and sufficient interaction with the functional group of the active material is obtained, so that good dispersibility is obtained. Furthermore, a part of the carboxyl group is a carboxylate. For example, the cation serving as a counter ion of the carboxyl group includes alkali metal ions (lithium, sodium, potassium, etc.), alkaline earth metals (calcium, etc.), ammonium ions, organic oniums (various aliphatic amines, aromatic amines, diamines, etc.) Amines such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, benzyltrimethylammonium hydroxide, 2-hydroxyethyltrimethylammonium hydroxide, NR4OH (where R is an alkyl group or benzyl group, Or a phenyl group or a hydroxyalkyl group, and four Rs may be the same or different.) Ammonium hydroxide compound, phosphonium hydroxide compound such as tetraethylphosphonium hydroxide, oxohydroxide Um compounds include counterions such as hydroxide sulfonium compounds. It is also possible to form salts by mixing two or more of these.

  It is considered that the electrostatic repulsion increases by the ionization of the carboxyl group of the cellulose fiber, and the dispersibility of the cellulose fiber is maintained. Therefore, it is desirable to maintain a state in which a part of the carboxyl group is ionized. In addition, if a large amount of metal ions such as sodium ions are present as counter ions, there is a risk of electrodeposition or side reaction, which may not be preferable. At this time, these problems can be solved by using organic onium.

  As a method for introducing a carboxyl group into cellulose, several chemical treatment methods are currently reported. For example, when a molecularly dispersed water-soluble polysaccharide such as carboxymethylcellulose is used, the surface of the active material is covered with the water-soluble polysaccharide, and the internal resistance of the electrode increases, resulting in a decrease in battery characteristics. Therefore, in order to have a structure that is fibrous, has good dispersibility, and the active material can efficiently interact with the carboxyl groups of cellulose as in the present invention, highly crystalline cellulose that retains a rigid skeleton. It is desirable that a carboxyl group is introduced into the fiber and that the carboxyl group is present densely and regularly on the fiber surface.

Specifically, the following method is desirable.
That is, 2,2,6,6-tetramethyl-1-pipedinyloxy radical (TEMPO) is used as a catalyst, and an oxidizing agent such as sodium hypochlorite and bromide such as sodium bromide while adjusting pH. To process. According to this method, only the primary hydroxyl group at the cellulose C6 position existing on the surface of microfibril, which is the minimum fiber unit having crystallinity, is selectively oxidized to a carboxyl group due to the steric hindrance of TEMPO. Since the binding of microfibrils is weakened by electrostatic repulsion of the introduced carboxyl group, highly dispersed fibrous cellulose having high crystallinity can be obtained by mechanical treatment with low energy input. Furthermore, when this method is used, since the molecular weight reduction of the obtained cellulose fiber is suppressed, a high mechanical strength is maintained, so that excellent cycle characteristics can be obtained.

Hereinafter, a specific method of the chemical treatment for producing the cellulose single nanofiber in the present invention will be described.
Nitroxyl radical and sodium bromide are added to cellulose dispersed in water, and sodium hypochlorite aqueous solution is added with stirring at room temperature to oxidize the cellulose. An alkaline solution such as sodium hydroxide is added during the oxidation reaction, and the pH in the reaction system is controlled to 9-11. At this time, the hydroxyl group at the C6 position on the surface of the cellulose fiber is oxidized to a carboxyl group.

After the cellulose is oxidized, it is sufficiently washed with water, and the obtained cellulose dispersed in a fibrous form can be used as a constituent material of the dispersion. In addition, as an oxidizing agent, hypohalous acid or its salt, a halogenous acid or its salt can be used, and sodium hypochlorite is preferable. Examples of the bromide include lithium bromide, potassium bromide, sodium bromide and the like, and sodium bromide is preferable. By the above method, TEMPO oxidized cellulose having a carboxyl group is obtained.
In addition, the amount of carboxyl groups contained in cellulose is calculated by the following method.

  0.2 g of dry weight conversion of chemically treated cellulose is taken in a beaker, and 80 ml of ion exchange water is added. Thereto was added 5 ml of 0.01 M sodium chloride aqueous solution, and 0.1 M hydrochloric acid was added while stirring to adjust the whole to pH 2.8. Using an automatic titrator (AUT-701, manufactured by Toa DKK Co., Ltd.), 0.1M sodium hydroxide aqueous solution was injected at 0.05 ml / 30 seconds, and the conductivity and pH value were measured every 30 seconds. The measurement was continued until pH 11. A titration amount of sodium hydroxide was determined from the obtained conductivity curve, and the carboxyl group content was calculated.

  Since TEMPO-oxidized cellulose retains molecular weight to some extent, a dispersion obtained by entanglement of fibers has high viscosity characteristics even at a low concentration. In order to improve the coatability, the viscosity of the dispersion can be adjusted. As a method for adjusting the viscosity, in addition to appropriately selecting the type of the raw material cellulose and adjusting the concentration of the dispersion liquid, the cellulose subjected to the TEMPO oxidation treatment can be physically or chemically treated before the dispersion treatment. . Specifically, an alkali treatment exposed to an aqueous sodium hydroxide solution, an ultraviolet irradiation treatment that promotes β-elimination by ultraviolet irradiation, an enzyme treatment that promotes degradation by an enzyme, and the like.

  Incidentally, examples of the dispersion medium include water or a mixed solvent of water and an organic solvent. The organic solvent used here may be a water-soluble organic solvent that is uniformly miscible with water. For example, alcohols such as methanol, ethanol, 2-propanol (IPA), ketones such as acetone, methyl ethyl ketone (MEK), and the like. , Ethers such as 1,4-dioxane, tetrahydrofuran (THF), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetonitrile, ethyl acetate, etc. It is done. Any one of these may be used alone, or two or more mixed solvents may be used. When a mixed solvent of water and a water-soluble organic solvent is used as the dispersion medium, the blending ratio is appropriately determined in consideration of the type of the water-soluble organic solvent and the affinity between water and the water-soluble organic solvent.

  Further, the dispersion medium may contain a metal or the like. Metals such as gold, silver, platinum, palladium, ruthenium, iridium, rhodium, and osmium, as well as metals such as iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum Alternatively, alloys thereof, oxides, double oxides, carbides, or the like can be used. As a method for supporting the metal, in addition to mixing fine particles such as metal or metal oxide, a metal or metal oxide complex is formed in a dispersion of a fibrous polysaccharide having a carboxyl group dispersed in water or an aqueous solvent. By adding an agent, it can be deposited as metal particles. When this method is used, fine metal particles are uniformly immobilized on the fiber surface, so that the effect can be efficiently exhibited even with a small amount of metal.

  In the range where aggregation and precipitation do not occur, various additives and various resins containing a water-soluble polysaccharide in the dispersion medium are used for the purpose of increasing the electrostatic repulsion between fibers and controlling the viscosity of the dispersion. May be included. For example, chemically modified cellulose, carrageenan, xanthan gum, sodium alginate, agar, solubilized starch, antifoaming agent, water-soluble polymer, synthetic polymer and the like can be used. Alternatively, various solvents may be included in the dispersion medium in order to provide functionality such as coatability and wettability. As the solvent, alcohols, cellosolves, glycols, glycerin and the like can be used.

Moreover, in order to improve water resistance and electrolyte solution resistance, various dispersion agents may be included in the dispersion medium. For example, oxazoline, divinyl sulfone, carbodiimide, dihydrazine, dihydrazide, epichlorohydrin, glyoxal, organic titanium compound, organic zirconium compound, and the like can be used. Further, for the purpose of improving the reactivity, the pH can be adjusted by adding an acid or an alkali to the dispersion medium.
Cellulose single nanofibers produced in this way are excellent in dispersibility in water because the fibers are dispersed in the nano order by weakening hydrogen bonds in and between celluloses due to electrostatic repulsion of carboxyl groups. It is said that it does not disperse molecules like CMC and maintains a rigid fibrous form.

The present invention is characterized in that a cellulose single nanofiber is used as a thickening material instead of CMC in a lithium ion battery negative electrode using a carbon-based material as an active material, carbon black as a conductive additive, and SBR as a binder. .
As the cellulose single nanofiber used in the present invention, any of the above counter ion types can be appropriately selected, and two or more types can be mixed and used.

The cellulose single nanofiber used in the present invention is usually an aqueous solution or dispersion in which the appearance is colorless and transparent or slightly turbid, dissolved or dispersed in water. When the concentration is high, it may be gel (agar-like). What is necessary is just to dilute this with water so that it may become a desired density | concentration. What is necessary is just to select suitably the density | concentration and usage-amount of a cellulose single nanofiber from the target viscosity of a coating material, and the target composition ratio in an electrode after drying.
The reason why the coating strength and the adhesion with the current collector are improved by using cellulose single nanofibers as the thickening material than when CMC is used is that, according to the inventor's consideration, Thus, it is considered to be due to the characteristics of cellulose single nanofiber that the fibers are dispersed in the nano order without molecular dispersion and keep a rigid fiber shape.

Next, the manufacturing method of the carbon type negative electrode coating material which uses a cellulose single nanofiber for a thickener is demonstrated.
First, a stock solution of cellulose single nanofiber is charged into a suitable container. The concentration of the undiluted solution varies depending on the production method of cellulose single nanofibers, the type of counter ion, the average molecular weight (molecular chain length), etc., but it is adjusted to the range that can be handled as an aqueous solution, aqueous dispersion, or gel. 1% to 5% by weight. This is diluted by adding water to a concentration suitable for coating production. More specifically, the concentration of the stock solution is determined from the target viscosity of the paint and the target composition ratio in the electrode after drying.

When diluted and stirred to obtain a uniform aqueous solution or aqueous dispersion, a conductive aid such as carbon black is added and stirred until uniform. The input amount is determined from the target composition ratio in the electrode after drying. A carbon-based active material is added to this and stirred until it becomes more uniform. The input amount of the active material is also determined from the target composition ratio in the electrode after drying. Finally, an SBR aqueous dispersion is added as a binder. The amount of the SBR aqueous dispersion added is determined from the concentration of the SBR aqueous dispersion and the target composition ratio in the electrode after drying.
The coating material thus manufactured is a viscous slurry having a viscosity suitable for coating, and the viscosity is, for example, 1000 to 100,000 Pa · s.

Next, the manufacturing method of the electrode in this invention is demonstrated.
The carbon-based negative electrode paint of the present invention produced as described above can be obtained by coating on a current collector such as a copper foil and drying. The roll-shaped current collector foil is unwound from the unwinding part of the coating machine, and coating is performed in the coating part. The coating method is not particularly limited, but a roll coater, air knife coater, blade coater, rod coater, reverse coater, bar coater, comma coater, dip squeeze coater, die coater, gravure coater, micro gravure coater, silk screen coater, etc. should be used. In particular, a die coating method using a die coater is preferable.

  The drying method is not particularly limited, but in addition to natural drying, hot air, far-infrared rays, microwaves, and the like can be used, and drying is performed in an oven that is integrated and installed at the back of the coating machine (coater). It is common. After drying, it is wound up in a roll shape at the winding section of the coating machine. From unwinding to winding is preferably performed continuously in a series of flows.

Next, a method for measuring the peel adhesion strength of the electrode thus produced will be described.
The peel adhesion strength is a value obtained by measuring an excess weight (peeling force) when an electrode peels using a tensile tester. There are two cases in which the electrode is peeled off: the case where the coating film is broken in the coating film (so-called cohesive failure) and the case where the coating film itself is not broken and the whole coating film is peeled off from the current collector. In the present invention, the former is expressed as coating film strength, and the latter is expressed as adhesion to the current collector.

  The peel adhesion strength is measured as the strength including both of them. That is, peeling occurs at the weaker of the two. In which case the peeling occurred can be determined by observing the peeled state. In this method, only one strength, which was weak, is known, and it is not known how strong the other was. However, since the measured value of the peel adhesive strength indicates that the strength of the both is greater than the obtained measured value, it can be used as a value indicating the overall strength of the electrode. This is because the weakest part determines the strength of the entire electrode.

As shown in FIG. 2, the measurement is performed according to the 90-degree peeling method of JIS K6854-1 “Adhesive—Peeling Bond Strength Test Method”.
That is, the surface of the electrode 10 (which is coated only on one side) on which the electrode paint is not applied (the surface on the side where the current collector 11 is exposed) has a sufficient weight with respect to the peel adhesion strength. The double-sided tape 2 is used to affix the metal surface 1 having a flat surface. With the coating surface (electrode coating film 12) of the electrode 10 on top and the metal base 1 disposed on the lower side of the electrode 10, a commercially available adhesive tape 3 (width 12 mm) on the electrode coating film 12 of the electrode 10 In this case, the pressure-sensitive adhesive tape 3 is firmly pressed onto the electrode coating film 12 so that there are no bubbles or gaps. One end of the adhesive tape 3 is connected to one end of a wire 4 having a length of 600 mm or more, and the other end of the wire 4 is sandwiched between grips 5 disposed above the metal base 1 of the tensile tester.

  At this time, when one end of the wire 4 is fixed to the grip 5 disposed above the metal table 1 of the tensile tester and the other end of the wire 4 is hung from the metal table 1, The position on the metal table 1 where the wire 4 is perpendicular to the metal table 1 (hereinafter referred to as the center of the metal table 1) and the central portion in the longitudinal direction of the adhesive tape 3 coincide. And when the adhesive tape 3 is pulled up to the center position of the metal base 1, the metal base 1 is positioned so that the wire 4 is perpendicular to the coating surface of the electrode coating film 12.

  Then, the tensile tester is set to operate at a moving speed of 50 mm / min, and the tensile tester is operated. In the test, the wire 4 is continuously pulled with reference to the central portion in the longitudinal direction of the adhesive tape 3 until peeling from the central portion by 50 mm or more at least on one side in the longitudinal direction. That is, the wire 4 is continuously pulled until a range of 100 mm or more in the longitudinal direction on both sides of the center portion in the longitudinal direction of the adhesive tape 3 is peeled from the electrode coating film 12. 2 shows that the electrode coating film 12 itself is divided into two parts from the end of the adhesive tape 3 on the side where the wire 4 is connected to the center in the longitudinal direction of the adhesive tape 3 by operating the tensile tester. The peeled state (the state in which the coating film peeling described later has occurred) is shown.

  Each test piece under different conditions, that is, the electrode 10 is tested in the same procedure, and the length of both sides of the adhesive tape 3 is 50 mm on one side with respect to the central portion in the longitudinal direction, and the total longitudinal central portion is the center. The average value of the measured load values of the tester is obtained over the peel length of 100 mm in the direction. This operation is performed three times for each electrode 10, and the average value of the three times is obtained.

  When both the coating strength and the adhesive strength with the current collector exceed the adhesive strength between the coating surface of the electrode coating 12 and the adhesive tape 3, the electrode coating 12 does not peel inside the adhesive tape 3 Only peels from the coating surface of the electrode coating 12. In this state, the measured value of the peel adhesion strength merely measures the adhesive force between the coating film surface and the pressure-sensitive adhesive tape 3, and the actual coating film strength and the adhesion force with the current collector cannot be measured. However, in many cases, the adhesive strength of the adhesive tape 3 is sufficiently large with respect to the comparative evaluation area of the comparatively compared coating strength and adhesion strength with the current collector, so that the adhesive tape 3 peels off. In such a case, it may be determined that the coating strength and the adhesion with the current collector are sufficiently large. Therefore, in the peel adhesion strength test according to the method of the present invention, when the electrode coating 12 itself breaks in the electrode coating 12 (coating peeling), when the entire electrode coating 12 peels from the current collector 11 (base There are three cases when the material is peeled off) and the electrode coating 12 of the adhesive tape 3 is peeled off.

Hereinafter, specific measurement examples will be described based on examples.
Example 1
Each material was charged so that the weight ratio of the solid content after drying of the carbon-based active material: conductive auxiliary agent: binder: thickener was 92: 7: 1: 1, and mixed by stirring to obtain a negative electrode coating material. . Sodium-type cellulose single nanofiber was used as a thickener. This paint was applied onto a metal foil and dried with a hot air circulating constant temperature dryer to obtain a negative electrode. The peel adhesion strength of the obtained electrode was measured using a tensile tester. The results are shown in Table 1. In Table 1, the solid content weight ratio represents the solid content weight ratio of the thickener.

(Example 2)
The same procedure as in Example 1 except that each material was charged so that the weight ratio of the solid content after drying of the carbon-based active material: conductive aid: binder: thickener was 92: 7: 1: 1.5. The peel adhesion strength of the obtained electrode was measured. The results are shown in Table 1.
(Example 3)
Obtained in the same manner as in Example 1 except that each material was charged so that the weight ratio of the solid content after drying of the carbon-based active material: conductive aid: binder: thickener was 92: 7: 1: 2. The peel adhesion strength of the obtained electrode was measured. The results are shown in Table 1.

Example 4
The same procedure as in Example 1 except that each material was charged so that the weight ratio of the solid content after drying of the carbon-based active material: conductive additive: binder: thickener was 92: 7: 1: 0.8. The peel adhesion strength of the obtained electrode was measured. The results are shown in Table 1.
(Example 5)
The peel adhesion strength of the electrode obtained in the same manner as in Example 1 was measured except that ammonium-type cellulose single nanofiber was used as the thickener. The results are shown in Table 1.

(Comparative Example 1)
The peel adhesion strength of the electrode obtained in the same manner as in Example 1 was measured except that CMC was used as the thickener. The results are shown in Table 1.

  As is apparent from Table 1, when cellulose single nanofiber (sodium type) is used as the thickener, it is more than twice as long as the solid weight ratio is the same as in Comparative Example 1 using conventional CMC. It can be seen that the peel adhesion strength is improved (Example 1). Further, even when the solid content weight ratio is small, the peel adhesion strength is stronger than that of Comparative Example 1 (Example 2). Furthermore, when the solid content weight ratio is increased from Example 1, the peel adhesion strength is improved to the same level as the adhesive force of the adhesive tape 3 (Example 3), and further increasing the adhesive force of the adhesive tape, The peel adhesive strength shows a substantially constant value (tape peel strength is measured) (Example 4).

Even when ammonium type cellulose single nanofiber is used, the peel adhesion strength is improved by about 1.5 times or more when the solid content weight ratio of the thickener is the same as in Comparative Example 1 using conventional CMC. (Example 5).
In this example, since peeling of the base material did not occur, the adhesion between the current collector 11 and the electrode coating film 12 was stronger than the coating film strength in Examples 1, 2, 5 and Comparative Example 1, and was carried out. Examples 3 and 4 indicate that the adhesive strength of the adhesive tape 3 was stronger. This may be evaluated that the adhesion force between the current collector 11 and the electrode coating film 12 has a sufficient strength in evaluating the strength of the entire electrode 10.

DESCRIPTION OF SYMBOLS 1 Metal base 2 Double-sided tape 3 Adhesive tape 4 Wire 5 Grasp 10 Electrode (current collector 11 + electrode coating film 12)
11 Current collector 12 Electrode coating

Claims (2)

A battery electrode composition comprising a carbon-based active material, a conductive additive, a binder, and a thickener,
Using cellulose single nanofiber as the thickener ,
The cellulose single terminal carboxyl group counterion nanofibers, one or two battery electrode composition characterized Rukoto such only ions belonging to the ammonium ion. A battery comprising an electrode comprising the battery electrode composition according to claim 1 .

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