Lithium-ion secondary battery electrode

Abstract

Provided is a lithium-ion secondary battery electrode in which there are fewer holes formed in a current collector foil made of aluminum or copper. This lithium-ion secondary battery electrode comprises a current collector foil made of aluminum or copper, and a solid composition that is formed on the current collector foil and contains an active material, a carbon material, and carboxymethyl cellulose, the lithium-ion secondary battery electrode being characterized by satisfying the conditions Y < 97 and Y < 3 × 10−60 × (1 / X20.22), where X (mass%) is the chlorine ion content of the solid composition, and Y (mass%) is the carbon material blending amount.

Description

Electrodes for lithium-ion secondary batteries

[0001] The present invention relates to an electrode for a lithium ion secondary battery.

[0002] In recent years, the lithium-ion battery market has boomed with the spread of electronic devices and environmentally friendly mobility. Lithium-ion batteries are equipped with anodes and cathodes containing active materials that allow lithium ions to reversibly enter and exit the battery, and an electrolyte that immerses them. The electrodes are manufactured by applying a slurry consisting of the active material, conductive material, and binder to a current collector plate made of aluminum foil or the like, drying it, and pressing it.

[0003] Patent Document 1 discloses a nonaqueous electrolyte secondary battery using LiNiO2 as a positive electrode active material, 100 parts by weight of powder of LiNiO2 mixed with 3 parts by weight of acetylene black and 7 parts by weight of a fluororesin binder, and suspending this in an aqueous carboxymethyl cellulose solution to form a paste. While stirring this paste, a mixed gas of carbon dioxide gas and air in a volume ratio of 1:1 is passed through the paste at a rate of 2 L / min until the pH of the paste reaches 11.0, 10.5, 10.0, 9.5, 9.0, or 7.0, respectively. Each of the obtained pastes is applied to both sides of a 30 μm thick aluminum foil, and the resulting electrode plate is dried and rolled to a thickness of 0.17 mm using a roller press, and then cut into a positive electrode plate having a width of 35 mm and a length of 250 mm.

[0004] The Patent Document 1 describes that if an alkaline component remains in the positive electrode active material as an unreacted product, the pH of the paste increases significantly, and as a result, when the paste is applied to an aluminum foil, the aluminum foil is corroded and hydrogen gas is generated at the interface between the foil and the active material layer, causing the active material to fall off or float up from the foil, thereby reducing the yield of the application process. However, the Patent Document 1 does not pay attention to the content of chloride ions in the paste applied to the aluminum foil.

[0005] Patent Document 2 discloses an electrode film including a coating film of a composite slurry containing a dispersion of specific carbon nanotubes, a binder resin, and an active material, and describes the use of carboxymethyl cellulose as the binder resin, but does not pay attention to the content of chloride ions in the composite slurry.

[0006] Patent Document 3 describes that carboxymethyl cellulose is produced by reacting cellulose contained in pulp with sodium hydroxide and monochloroacetic acid, and that the ammonium salt of carboxymethyl cellulose produced from carboxymethyl cellulose contains residual chloride ions along with sodium ions, and that using this as a binder in battery electrodes or a viscosity modifier for the electrolyte solution of secondary batteries reduces battery performance. However, the use of carboxymethyl cellulose in a paste to be applied to aluminum foil and the content of chloride ions in this paste are not noted.

[0007] Non-Patent Document 1 describes that carboxymethyl cellulose is produced by an etherification reaction between cellulose and monochloroacetic acid, and contains 12 to 15% of sodium chloride as an impurity, and is therefore further purified by a sulfuric acid purification method or a methanol purification method.

[0008] JP-A-8-69791 (Detailed description of the invention, Examples) JP-A-2023-98706 (Claims, Detailed description of the invention) JP-A-2010-70686 (Detailed description of the invention)

[0009] Watanabe Koichiro, Production Research, April 1, 1960, pp. 218-221

[0010] Electrodes for lithium ion secondary batteries are manufactured by preparing an electrode slurry containing an active material, a carbon material, and carboxymethyl cellulose, applying the slurry to a current collector foil made of aluminum foil or copper foil, drying it, and then pressing it. However, it has been found that during this process, a phenomenon that the performance of the electrode deteriorates often occurs.

[0011] The problem to be solved by the present invention is to provide an electrode for a lithium ion secondary battery in which few voids are formed in a current collecting foil made of aluminum or copper.

[0012] As a result of investigating the above phenomenon, the inventors have found that the cause is corrosion of the aluminum foil or copper foil, and have discovered that it is effective to control the chloride ion content and the amount of carbon material blended in a solid composition formed on a current collector foil made of aluminum or copper, thereby completing the present invention.

[0013] That is, the present invention provides an electrode comprising a current collecting foil made of aluminum or copper, and a solid composition formed on the current collecting foil, the solid composition containing an active material, a carbon material, and carboxymethyl cellulose, wherein when the chloride ion content in the solid composition is X (mass%) relative to the total amount of the solid composition, and the carbon material content is Y (mass%) relative to the total amount of the solid composition, Y<97 and Y<3×10 －６０ × (1 / X ２０．２２ ) The electrode for a lithium ion secondary battery is characterized by satisfying the following conditions.

[0014] The lithium ion secondary battery electrode of the present invention significantly suppresses corrosion of the current collector foil made of aluminum or copper, resulting in fewer voids, and therefore has excellent properties as an electrode for a lithium ion secondary battery.

[0015] <Solid Composition> In the present invention, a solid composition containing at least an active material, a carbon material, and carboxymethyl cellulose (also referred to herein as a "composite composition" or simply as a "composite") is used. As the active material, both a negative electrode active material and a positive electrode active material can be used.

[0016] As the negative electrode active material, metal oxide-based active material particles, silicon-based active material particles, and graphite can be used, and metal oxide-based negative electrode active material particles can be particularly preferably used.

[0017] As the metal oxide-based negative electrode active material particles, for example, titanium oxide can be used. The titanium oxide is not particularly limited as long as it can absorb and release lithium. Examples of titanium oxide include spinel-type lithium titanate, ramsdellite-type lithium titanate, titanium-containing metal composite oxide, and titanium dioxide (TiO) having a monoclinic crystal structure. ２ (B)) and anatase type titanium dioxide can be used.

[0018] The spinel-type lithium titanate includes Li ４＋ｘ Ti ５ O １２ (x varies in the range of -1≦x≦3 depending on the charge / discharge reaction). Ramsdellite-type lithium titanate includes Li ２＋ｙ Ti ３ O ７ (y varies in the range of -1≦y≦3 depending on the charge / discharge reaction). ２ (B) and anatase type titanium dioxide include Li １＋ｚ TiO ２ (z varies in the range of −1≦z≦0 depending on the charge / discharge reaction).

[0019] Examples of titanium-containing metal composite oxides include metal composite oxides containing Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, and Fe. Examples of metal composite oxides containing Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, Nb, and Fe include TiO ２ -P ２ O ５ , TiO ２ -V ２ O ５ , TiO ２ -P ２ O ５ -SnO ２ , TiO ２ -P ２ O ５ -MeO (Me is at least one element selected from the group consisting of Cu, Ni, Nb and Fe).

[0020] Such a metal composite oxide preferably has a microstructure with low crystallinity, in which a crystalline phase and an amorphous phase coexist, or in which an amorphous phase exists alone, which can further improve cycle performance.

[0021] Examples of the positive electrode active material include composite oxides of lithium and transition metals such as lithium-nickel composite oxide, lithium-cobalt composite oxide, lithium-manganese composite oxide, lithium-nickel-manganese composite oxide, lithium-nickel-cobalt composite oxide, lithium-nickel-aluminum composite oxide, lithium-nickel-cobalt-aluminum composite oxide, lithium-nickel-manganese-cobalt composite oxide, lithium-nickel-manganese-aluminum composite oxide, and lithium-nickel-cobalt-manganese-aluminum composite oxide; TiS ２ , FeS, MoS ２ transition metal sulfides such as MnO, V ２ O ５ , V ６ O １３ , TiO ２ and transition metal oxides such as those mentioned above, and olivine-type lithium phosphate oxides.

[0022] The olivine-type lithium phosphate contains, for example, at least one element selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B, Nb, and Fe, as well as lithium, phosphorus, and oxygen. These compounds may have some elements partially substituted with other elements to improve their properties.

[0023] A preferred positive electrode active material is a lithium-nickel composite oxide, and more preferably, the lithium-nickel composite oxide is represented by the formula: LiNi Ｘ M1 Ｙ M2 Ｚ O ２ (M1 and M2 are at least one metal element selected from the group consisting of Al, B, alkali metals, alkaline earth metals, and transition metals; 0.8≦ Ｘ ≦1.0, 0≦ Ｙ ≦0.2, 0≦ Ｚ≦0.2) These positive electrode active materials may be used singly or in combination of two or more.

[0024] The composite composition of the present invention contains a carbon material. The amount of the carbon material is preferably 0.09% by mass or more and 50% by mass or less, more preferably 0.09% by mass or more and 30% by mass or less, and even more preferably 0.09% by mass or more and 10% by mass or less, based on the total amount of solids contained in the composite composition.

[0025] As the carbon material, carbon nanotubes, carbon black, and graphite are used. Although carbon nanotubes, carbon black, and graphite can be used alone, it is preferable to use two or more of them in combination.

[0026] In particular, carbon nanotubes blended as the carbon material are preferably used in combination with carbon black and / or graphite, which will be described later. The blending amount of carbon nanotubes in the composite composition is preferably 5% by mass or more and 50% by mass or less, and more preferably 8% by mass or more and 30% by mass or less, based on the total amount of the carbon material.

[0027] The carbon nanotubes (CNTs) to be blended as the carbon material are preferably carbon nanotubes having a cylindrical shape formed by substantially winding one surface of graphite around it, and either single-walled carbon nanotubes, in which one surface of graphite is wound around one layer, or multi-walled carbon nanotubes, in which one surface of graphite is wound around two or more layers, can be used.

[0028] Examples of the form of carbon nanotubes include, but are not limited to, graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers, and these may be used alone or in combination of two or more types (hereinafter simply referred to as "at least one type").

[0029] The average outer diameter of the carbon nanotubes is preferably 1 nm or more and 30 nm or less, more preferably 2 nm or more and 15 nm or less, from the viewpoints of the viscosity, conductivity, and stability of the composite composition. Here, the average outer diameter of the carbon nanotubes refers to the arithmetic mean value of the outer diameters of a sufficient number n of carbon nanotubes measured using an image of a transmission electron microscope at a magnification of 100,000 times or more. The purity of the carbon nanotubes is preferably 90 to 100 mass%, particularly preferably 95 to 100 mass%. The purity of the carbon nanotubes is calculated based on the amount of impurities, with ash content measured in accordance with JIS K 1469 or JIS K 6218 being considered as an impurity.

[0030] In the present invention, the carbon black blended as the carbon material in the composite composition can be one produced by incomplete combustion of hydrocarbons such as heavy aromatic oils and gases. Acetylene black, produced by thermal decomposition of acetylene, is preferred. The graphite blended as the carbon material can be layered graphite having a turtle shell-like structure consisting of hexagonal plate-like crystals.

[0031] In the present invention, when the chloride ion content in the composite solid composition containing the active material, the carbon material, and the carboxymethyl cellulose is X (mass%) and the amount of the carbon material in the composite solid composition is Y (mass%), Y<97 and Y<3×10 －６０ × (1 / X ２０．２２ Here, the chloride ion content X is the chloride ion content relative to the total amount of the composite composition. The carbon material blend amount Y is the total amount of the carbon material blended relative to the total amount of the composite composition.

[0032] The inequality was empirically derived from the correlation between the chloride ion content X and the carbon material content Y in a composite composition to determine the conditions under which a good electrode for a lithium ion secondary battery can be obtained from a composite composition containing an active material, a carbon material, and carboxymethyl cellulose.

[0033] The present invention was achieved by controlling the balance between the content of chloride ions in the solid composition and the amount of carbon material blended in. If the content of chloride ions in the solid composition and the amount of carbon material blended in are outside the above-mentioned conditions, good electrode properties cannot be obtained.

[0034] One means for obtaining the electrode of the present invention is to use carboxymethyl cellulose with a controlled chloride ion content as the carboxymethyl cellulose to be blended when preparing the composite composition.

[0035] The carboxymethyl cellulose used in the present invention has a structure in which the hydroxyl groups in the glucose units constituting cellulose are substituted with carboxymethyl ether groups. Carboxymethyl cellulose may be in the form of a metal salt such as a sodium salt or an ammonium salt. The term "carboxymethyl cellulose" includes not only acid-type carboxymethyl cellulose but also carboxymethyl cellulose salts such as sodium salt and ammonium salt.

[0036] Carboxymethyl cellulose can be produced by etherifying cellulose in the presence of an alkali hydroxide such as sodium hydroxide or potassium hydroxide by adding an etherifying agent such as monochloroacetic acid or sodium monochloroacetate. The raw cellulose may be any of native cellulose, regenerated cellulose, fine cellulose, and microcrystalline cellulose from which the amorphous region has been removed.

[0037] Non-Patent Document 1 describes that carboxymethyl cellulose is produced by the etherification reaction of cellulose and monochloroacetic acid, and contains 12 to 15% salt as an impurity, and is therefore further purified by a sulfuric acid purification method or a methanol purification method. Therefore, commercially available carboxymethyl cellulose generally contains chloride ions derived from the production process, with the content being approximately 1,000 to 5,000 μg / g of the carboxymethyl cellulose solids. Therefore, it has been the norm for composite compositions containing commercially available carboxymethyl cellulose to contain a considerable amount of chloride ions.

[0038] The carboxymethyl cellulose used in the present invention can be obtained as carboxymethyl cellulose with a reduced chloride ion content by subjecting a normal carboxymethyl cellulose product to a special treatment.

[0039] The present invention can be suitably carried out by blending carboxymethyl cellulose having a reduced chloride ion content into the composite composition. Specifically, the chloride ion content of the carboxymethyl cellulose is preferably reduced to less than 200 μg / g, more preferably less than 100 μg / g. Here, the chloride ion content of the carboxymethyl cellulose refers to the chloride ion content relative to the mass of the carboxymethyl cellulose.

[0040] By using carboxymethyl cellulose with a reduced chloride ion content and adjusting the blending amount of the carbon material, the chloride ion content X (mass%) of the present invention and the blending amount Y (mass%) of the carbon material can be set to Y<97 and Y<3×10. －６０ × (1 / X ２０．２２ ) can be obtained.

[0041] The chloride ion content in the composite composition can be measured as follows: The composite layer is peeled off from the electrode, crushed, mixed with pure water, and treated in an ultrasonic cleaner for 5 minutes to prepare a suspension, which is then filtered to prepare an extract. TM IonPac TM AS22 was used, and 4.5 mM Na was used as the eluent. ２ CO ３ / 1.4mM NaHCO ３ The chloride ion concentration in the extract is measured using the following formula: The chloride ion content in the composite material composition is calculated from this value.

[0042] The amount of carbon material in the composite composition can be measured as follows: The composite layer is peeled off from the electrode, pulverized, and placed in a container, and then heated to 600°C in a nitrogen flow atmosphere using a Thermo Plus EVO2 (Rigaku Corporation) to dry. The heating temperature is then lowered to 400°C, the flow atmosphere gas is switched from nitrogen to air, and the mixture is heated to 1000°C for combustion. The weight loss before and after the operation of heating to 1000°C in the air atmosphere is taken as the amount of carbon material.

[0043] Another method for obtaining the electrode of the present invention is to adjust the amount of the carbon material blended when preparing the composite material composition.

[0044] In the present invention, even if a composite composition containing carboxymethyl cellulose is used, by using a composite composition with a significantly reduced chloride ion content, deterioration of battery performance is prevented and electrodes for lithium ion secondary batteries are produced with a high yield. The lithium ion secondary battery electrodes produced by the present invention have a reduced defective rate and are therefore advantageous for industrial production of lithium ion secondary batteries.

[0045] In the present invention, the electrode slurry can be prepared by adding at least the active material, the carbon material, the carboxymethyl cellulose, and the solvent to a disperser and mixing them. As the solvent, an organic solvent as well as water can be used.

[0046] When preparing the electrode slurry, in addition to the active material, carbon material, and carboxymethyl cellulose (salt), other components may be added and blended within the scope of the present invention. When preparing the electrode slurry, a dispersant for cellulose nanofibers, a binder for styrene butadiene copolymer (SBR), a preservative, a pH adjuster, a viscosity adjuster, an electrolyte, and the like may also be added and blended as desired.

[0047] <Dispersion> Examples of dispersers used in preparing the electrode slurry include homomixers, high-pressure homogenizers, ultra-high-pressure homogenizers, ultrasonic dispersion processors, planetary mixers, combimixes, kneaders, planetary mixers, kneaders, planetary mixers, kneaders, Henschel mixers, ball mills, bead mills, thin film rotary high-speed agitators, screw mixers, paddle mixers, disperser mixers, turbine mixers, propeller mixers, blenders, ultrasonic homogenizers, colloid mills, pebble mills, beaters, disk refiners, conical refiners, double disk refiners, and grinders. It is also preferable to use two or more types of dispersers in combination.

[0048] <Coating and Pressing> The prepared electrode slurry is applied to a current collector foil made of aluminum or copper, dried, and then pressed to produce an electrode for a lithium ion secondary battery. The thickness of the current collector foil made of aluminum or copper is preferably 4 μm or more. In particular, the thickness of the current collector foil made of aluminum is preferably 7 μm or more, more preferably 8 μm or more. Furthermore, the thickness of the current collector foil made of copper is preferably 5 μm or more, more preferably 6 μm or more. With a thickness in this range, both high output and quality stability as an electrode for a lithium ion secondary battery can be achieved. The amount of electrode slurry applied to the current collector foil, i.e., the basis weight, is 20 g / m ２ ~200g / m ２ is preferred, and 50 g / m ２ ~150g / m ２ is more preferred.

[0049] In the process of preparing an electrode by applying an electrode slurry to a current collector foil and drying it, if the composite material obtained from the electrode slurry contains a high content of chloride ions, the current collector foil made of aluminum or copper will corrode. Gases generated by this corrosion will cause voids in the foil, which will reduce the electrode density and lead to a decrease in battery performance. In the present invention, the occurrence of this problem can be prevented by controlling the chloride ion content in the composite material.

[0050] The prepared electrode slurry is applied to a current collector foil made of aluminum or copper, and during the drying process or subsequent storage, if gaps form between the current collector foil and the electrode composition containing the active material, the performance of the electrode will be reduced. Furthermore, if tears occur in the current collector foil during the pressing process, the performance of the electrode will be reduced. The present invention can prevent these problems.

[0051] In view of the above, another aspect of the present invention is a method for producing an electrode for a lithium ion secondary battery by applying an electrode slurry containing an active material, a carbon material, carboxymethyl cellulose, and a solvent to a current collector foil made of aluminum or copper, drying the slurry, and then pressing the coated foil, wherein, when the chloride ion content in the solid matter contained in the electrode slurry is X (mass%) and the blending amount of the carbon material in the electrode slurry is Y (mass%), Y<97 and Y<3×10 －６０ × (1 / X ２０．２２ ) is a method for producing an electrode for a lithium ion secondary battery.

[0052] Example 1 51.04 parts (parts by mass, hereinafter the same) of a negative electrode active material (LTO-2S, manufactured by Betelgeuse New Energy Materials Co., Ltd.), 1.53 parts of acetylene black, 1.02 parts of graphite, 1.02 parts of carbon nanotubes having an average outer diameter of 9.0 nm, and 0.77 parts of a purified product of carboxymethylcellulose sodium salt, CMC-B (chloride ion content 3.82 μg / g), were mixed with ion-exchanged water and subjected to a dispersion treatment using a bead mill. The mixture was then transferred to a planetary mixer, and 2.55 parts by solids mass of a 40% aqueous dispersion of styrene butadiene copolymer (SBR) and ion-exchanged water were added to the mixture so that the total amount was 100 parts. The mixture was mixed and subjected to a dispersion treatment using a bead mill. The mixture was then transferred to a planetary mixer, and SBR was added and kneaded to obtain an electrode slurry.

[0053] The obtained electrode slurry was applied to one side of an aluminum foil having a thickness of 20 μm using an applicator in a manner to give a basis weight of 50 g / m ２After that, it was dried for 5 minutes at 80° C. Then, it was pressed using a small roll press under the conditions of a load of 20 KN, a gap of 0 mm, and a feed rate of 0.5 m / min to obtain an electrode for a lithium ion secondary battery.

[0054] The chloride ion content of the solid composition was measured by peeling the composite layer from the electrode, mixing it with pure water, treating it with an ultrasonic cleaner for 5 minutes, obtaining a suspension, and filtering it to obtain an extract. TM IonPac TM AS22 was diluted with 4.5 mM Na as the eluent. ２ CO ３ / 1.4mM NaHCO ３ The chloride ion concentration in the extract was measured using a chlorine ion detector and calculated.

[0055] The carbon material content in the solid composition was determined by peeling the composite layer from the electrode, heating it to 40° C. to 600° C. in a nitrogen atmosphere, then lowering the heating temperature to 400° C., switching the atmospheric gas from nitrogen to air, and heating it to 1000° C. The weight loss when the atmosphere was switched to air and the mixture was heated to 1000° C. was taken as the amount of carbon material and converted to determine the content.

[0056] The obtained lithium ion secondary battery electrodes were evaluated as follows. The foil side on which the electrode was formed was photographed using an optical microscope (Keyence Corporation, model number: VHX-8000) with light shining from the foil side, and an image was obtained. This image was subjected to electronic data processing to extract image portions with a brightness of 240 to 255, which correspond to pores in the foil, and the number of such portions within a certain area range was counted. The counted number was converted to the number per φ30 mm circular area. This was performed at three different locations on the surface of the same composite material, and the average was taken. The following evaluation was made based on the magnitude of the average number obtained. The smaller the average value, the better the properties as an electrode.

[0057] Electrode evaluation ○: The number of parts showing voids in the foil is 100 or less △: The number of parts showing voids in the foil is 101 or more and 150 or less ▲: The number of parts showing voids in the foil is 151 or more and 200 or less ×: The number of parts showing voids in the foil is 201 or more

[0058] Examples 2 to 8 and Comparative Examples 1 to 3: Electrode slurries were prepared in the same manner as in Example 1, except that the components shown in Table 1 were blended. In Table 1, CMC-A represents a purified product of carboxymethylcellulose sodium salt (chloride ion content: 75.3 μg / g), CMC-B represents a purified product of carboxymethylcellulose sodium salt (chloride ion content: 3.82 mg / kg), and CMC-Z represents a commercially available product of carboxymethylcellulose sodium salt (chloride ion content: 1426 μg / g). The chloride ion content is the content relative to the respective carboxymethylcellulose sodium salts. The resulting electrode slurries were applied to aluminum or copper foils in the same manner as in Example 1, dried, and pressed to obtain electrodes for lithium ion secondary batteries. The resulting lithium ion secondary battery electrodes were evaluated in the same manner as in Example 1.

[0059] The compositions of the electrode slurries used in Examples 1 to 8 and Comparative Examples 1 to 3, the chloride ion content X (mass%) and the carbon material blending amount Y (mass%) in the solid composition constituting the produced electrodes, and the results of electrode evaluation are shown in Table 1. X and Y in Examples 1 to 8 were Y<97 and Y<3×10 －６０ × (1 / X ２０．２２ On the other hand, X and Y in Comparative Examples 1 to 3 satisfy the conditions Y<97 and Y<3×10 －６０ × (1 / X ２０．２２ When the chloride ion content X in the solid composition constituting the electrode and the carbon material content Y satisfy the conditions of the present invention, the aluminum foil or copper foil was a good electrode with few voids in the foil.

[0060]

[0061] As is clear from the results in Table 1, Examples 1 to 8, in which the relationship between the chloride ion content X in the solid composition and the carbon material content Y in the solid composition satisfied the conditions prescribed in the present invention, provided electrodes with significantly fewer voids formed in the aluminum or copper current collector foil, compared to Comparative Examples 1 to 3, in which the relationship between the chloride ion content X and the carbon material content Y did not satisfy the conditions prescribed in the present invention. On the other hand, in Comparative Examples 1 to 3, numerous protrusions with diameters of 0.5 to 1.0 mm were found on the surface of the current collector foil after the electrode slurry was applied and dried. This caused the formation of voids in the foil during the pressing process. It was presumed that the protrusions were formed due to gas generated by corrosion of the aluminum or copper.

[0062] Examples 11 to 17, Comparative Examples 11 to 16 The electrode slurries obtained with the compositions of Example 1 or Comparative Example 1 were applied to one side of aluminum or copper foils of various thicknesses using an applicator at various basis weights, and then dried for 5 minutes at 80° C. Next, this was pressed using a small roll press under conditions of a load of 20 KN, a gap of 0 mm, and a feed rate of 0.5 m / min to obtain electrodes for lithium ion secondary batteries.

[0063] The obtained lithium ion secondary battery electrodes were evaluated in the same manner as in Example 1. Table 2 shows the electrode preparation conditions and electrode evaluation results for Examples 11 to 17 and Comparative Examples 11 to 16. In Examples 11 to 17, an electrode slurry prepared with the same composition as in Example 1 was used. In Comparative Examples 11 to 16, an electrode slurry prepared with the same composition as in Comparative Example 1 was used. When the chloride ion content X and the carbon material blending amount Y in the solid composition constituting the electrode satisfied the conditions of the present invention, good electrodes with few voids in the foil were obtained for aluminum foil or copper foil of various thicknesses.

[0064]

[0065] The lithium ion secondary battery electrode of the present invention can be used as an electrode for a lithium ion secondary battery.

Claims

1. An electrode comprising a current collecting foil made of aluminum or copper and a solid composition formed on the current collecting foil, the solid composition containing an active material, a carbon material, and carboxymethyl cellulose, wherein when the chloride ion content of the solid composition is X (mass%) relative to the total amount of the solid composition and the carbon material content is Y (mass%) relative to the total amount of the solid composition, Y<97 and Y<3×10 －６０ × (1 / X ２０．２２ ) An electrode for a lithium ion secondary battery, characterized in that it satisfies the following conditions:

2. The electrode for a lithium ion secondary battery according to claim 1, wherein the amount of carboxymethyl cellulose blended is 0.3 to 2.0 mass % based on the total amount of the solid composition.

3. The electrode for a lithium ion secondary battery according to claim 1, wherein the amount of the carbon material is 50 mass % or less based on the total amount of the solid composition.

4. The electrode for a lithium ion secondary battery according to claim 1, wherein the carbon material contains carbon nanotubes.

5. The electrode for a lithium ion secondary battery according to claim 1, wherein the carbon material contains carbon nanotubes having a width of 1 to 30 nm.

6. The electrode for a lithium ion secondary battery according to claim 1, wherein the thickness of the current collecting foil is 4 μm or more.

7. An electrode for a lithium ion secondary battery according to claim 1, produced by applying a slurry composition containing an active material, a carbon material, carboxymethyl cellulose, and a solvent onto a current collecting foil made of aluminum or copper, drying the composition, and then pressing the composition.

8. The electrode for a lithium ion secondary battery according to claim 7, wherein the chloride ion content in the carboxymethyl cellulose blended in the slurry composition is less than 200 μg / g relative to the mass of the carboxymethyl cellulose.

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