JP2012094344A - Method for manufacturing electrode plate for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode plate for nonaqueous electrolyte secondary battery, which does not cause breakage, wrinkle, and so on in manufacturing, thereby manufacturing the electrode plate with an excellent manufacturing yield, the manufactured electrode plate being excellent in a battery characteristic.SOLUTION: A method for manufacturing an electrode plate for nonaqueous electrolyte secondary battery, comprises: a preparation step for preparing a collector made of aluminum foil with a purity of 99% or more; a step for forming a precursor including at least electrode active substance particles and a chemical compound containing metal element, on the collector having been prepared in the preparation step; and a step for heating the chemical compound containing metal element in the precursor at equal to or more than a temperature at which the chemical compound containing metal element becomes metallic oxide.

Description

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

  Non-aqueous electrolyte secondary batteries have a high energy density and high voltage, and the phenomenon that the battery capacity gradually decreases when the battery is charged before it is completely discharged at the time of charging / discharging, so-called memory effect. Since it does not exist, it is used in various fields such as portable devices, notebook computers, and portable devices.

Currently, as a measure to prevent global warming, efforts to reduce CO ₂ emissions are being carried out on a global scale. By reducing the dependence on oil and allowing it to travel with a low environmental load, it can greatly reduce CO ₂ emissions. There is an urgent need to develop and promote next-generation clean energy vehicles represented by plug-in hybrid vehicles and electric vehicles that can contribute. If non-aqueous electrolyte secondary batteries can be used as the driving force for these next-generation clean energy vehicles, there is no need to rely on gasoline, which can greatly contribute to CO ₂ reduction and greatly prevent global warming. Can contribute. On the other hand, in order for non-aqueous electrolyte secondary batteries to be used as the driving force for next-generation clean energy vehicles, the performance of each part that constitutes the battery, such as an electrode plate, is improved and these parts are improved. It is necessary to produce with high accuracy and high yield.

  Currently, various proposals of non-aqueous electrolyte secondary batteries include a positive electrode plate, a negative electrode plate, a separator, and a non-aqueous electrolyte solution. The positive electrode plate is generally provided with an electrode active material layer in which positive electrode active material particles are fixed on the current collector surface. Moreover, as a negative electrode plate, what is equipped with the electrode active material layer by which a negative electrode active material particle adheres to the collector surface is common. Aluminum foil is widely used as a current collector.

  In order to produce the electrode plate which is the positive electrode plate or the negative electrode plate, first, the electrode active material particles which are the positive electrode active material particles or the negative electrode active material particles, the resin binder, or further, a conductive agent or other as required The material is kneaded and / or dispersed in a solvent to prepare a slurry-like electrode active material layer forming liquid. Then, the electrode active material layer forming liquid is applied to the surface of the current collector, then dried to form a coating film on the current collector, and pressed to form an electrode plate having the electrode active material layer (for example, Patent Document 1 or Patent Document 2).

  At this time, the electrode active material particles contained in the electrode active material layer forming liquid is a particulate metal compound dispersed in the liquid, and as such, is coated on the surface of the current collector and dried. Even if it is pressed, it is difficult to adhere to the surface of the current collector, and it will peel off from the current collector immediately. Therefore, when forming the electrode active material layer, a resin binder is added to the electrode active material layer forming liquid, and the electrode active material particles are fixed on the current collector by the resin binder, and the electrode active material The particles are fixed to each other.

JP 2006-310010 A JP 2006-107750 A

  However, since the electrode plate formed by the method proposed in Patent Document 1 and Patent Document 2 described above, the electrode active material particles, the current collector, and the electrode active material particles are fixed with a resin binder, There is a problem that the impedance of the electrode active material layer becomes large and the output characteristics cannot be improved.

  In order to solve such problems, there is an attempt to replace all or part of the resin binder with a metal oxide, that is, to fix the electrode active material particles, the current collector and the electrode active material particles to each other with the metal oxide. Has been made. By using a metal oxide instead of the resin binder, the impedance of the electrode active material layer can be reduced by the amount of using the metal oxide, thereby improving the output characteristics.

  As a method for producing an electrode plate fixed with a metal oxide, for example, (1) a current collector made of aluminum foil is coated with a precursor containing at least electrode active material particles and a metal element-containing compound. And (2) a step of heating at or above a temperature at which the metal element-containing compound in the precursor becomes a metal oxide. According to the method, in the process of changing the metal element-containing compound contained in the precursor into a metal oxide by pyrolysis or the like, the electrode active material particles contained in the precursor, and the precursor It is convenient because the current collector and the electrode active material particles below can be fixed by metal oxides.

  However, when the electrode plate is formed by the above method, it is necessary to heat at a temperature higher than the temperature at which the metal element-containing compound becomes a metal oxide. When the current collector is an aluminum foil, The current collector becomes soft or causes a decrease in strength, thereby causing breakage, wrinkles and the like.

  The present invention has been made in view of such a situation, and when a current collector made of aluminum foil is used, an electrode plate can be manufactured with high yield without causing breakage or wrinkles during the manufacturing. And the main subject is providing the manufacturing method of the electrode plate for non-aqueous-electrolyte secondary batteries with the high battery characteristic of the electrode plate manufactured.

  The manufacturing method of the present invention for solving the above problems includes a preparation step of preparing a current collector made of aluminum foil having a purity of 99% or more, and at least an electrode active material on the current collector prepared in the preparation step The method includes a step of forming a precursor containing particles and a metal element-containing compound, and a step of heating at or above a temperature at which the metal element-containing compound in the precursor becomes a metal oxide.

  According to the method for producing an electrode plate for a non-aqueous electrolyte secondary battery of the present invention, firstly, a precursor containing a metal element-containing compound is used, and this is heated to form a metal oxide. Therefore, the electrode active material particles and each of the electrode active material particles and the current collector can be fixed by the metal oxide derived from the metal element-containing compound. Therefore, it is possible to provide an electrode plate having a low impedance and excellent output characteristics as compared with a conventional electrode plate in which these are fixed using only a resin binder.

  Secondly, according to the method of manufacturing the electrode plate for a non-aqueous electrolyte secondary battery, since the current collector made of aluminum foil having a purity of 99% or more is used, the current collector becomes soft during heating. Does not cause a drop in strength. Therefore, an electrode plate free from breakage and wrinkles can be manufactured with high yield.

(Method for producing electrode plate for non-aqueous electrolyte secondary battery)
Hereinafter, the manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries of this invention is demonstrated in detail.

  The method of the present invention comprises (1) a step of preparing a current collector made of an aluminum foil having a purity of 99% or more (hereinafter sometimes referred to as “preparation step”), and (2) on the current collector. A step of forming a precursor containing at least electrode active material particles and a metal element-containing compound (hereinafter sometimes referred to as “precursor formation step”), and (3) a metal element-containing compound in the precursor And a step of heating at a temperature equal to or higher than the temperature at which the metal oxide becomes a metal oxide (hereinafter sometimes referred to as “heating step”). Hereinafter, these steps will be described in detail.

(1) Preparation Step In the method of the present invention, the preparation step is a step of preparing a current collector made of an aluminum foil having a purity of 99% or more.

  In the method of the present invention, whether or not the current collector prepared in the preparation step is a current collector made of aluminum foil having a purity of 99% or more is confirmed by ICP-MS (inductively coupled plasma mass spectrometer). be able to.

The thickness of the current collector is not particularly limited, but in the case of a current collector used for manufacturing a positive electrode plate, it is preferably about 3 to 150 μm, and the current collector used for manufacturing a negative electrode plate Is preferably about 3 to 100 μm.
(2) Precursor formation step In the method of the present invention, the precursor formation step includes at least the electrode active material particles and the metal element-containing compound on the current collector prepared in the preparation step, and after this step The process of forming the precursor which should become an electrode active material layer through the heating process performed is said.

  In the precursor formation step in the present invention, it is only necessary that a desired precursor can be formed on the current collector, and the formation method is not particularly limited, and various methods are appropriately selected. Can be used. For example, a printing method, spin coating, dip coating, bar coating, spray coating and the like can be mentioned. In addition, when the surface of the current collector is porous, has a large number of irregularities, or has a three-dimensional structure, it can be applied manually other than the above method. . Hereinafter, the positive electrode plate and the precursor for producing the negative electrode plate will be specifically described.

(Precursor for producing positive electrode plate)
In the case of producing a positive electrode plate of a non-aqueous electrolyte secondary battery by the method of the present invention, as the electrode active material particles contained in the precursor, conventionally known various positive electrode active material particles that can be charged and discharged are used. It can be appropriately selected and used, and is not particularly limited. Examples of such positive electrode active material particles include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFeO ₂ , Li ₄ Ti ₅ O ₁₂ , LiFePO ₄ , LiNi _1/3 Mn _1/3 Co _1/3 O _2. And positive electrode active material particles such as lithium transition metal composite oxides such as LiNi _0.80 Co _0.15 Al _0.05 O ₂ .

Among these positive electrode active material particles, LiMn ₂ O ₄ can be particularly preferably used. Since LiMn ₂ O ₄ has particularly high rate characteristics among various positive electrode active materials, the rate characteristics can be improved and the charge / discharge speed can be increased.

  Further, these positive electrode active material particles may be primary particles or secondary particles. Further, the particle diameter is not particularly limited, and those having an arbitrary size can be appropriately selected and used.

  In addition, when the positive electrode plate is produced by the method of the present invention, the metal element-containing compound contained in the precursor is any one selected from a lithium element-containing compound and cobalt, nickel, manganese, iron, or titanium. One or more metal element-containing compounds containing a metal element can be preferably used. The metal element-containing compound may be an inorganic metal element-containing compound that does not contain carbon in the compound, or may be an organometallic element-containing compound that contains carbon in the compound. Good. In the present invention and the present specification, the inorganic metal element-containing compound and the organic metal-containing compound may be simply referred to as a metal element-containing compound.

  In addition, examples of the metal element-containing compound include chlorides, nitrates, sulfates, perchlorates, acetates, phosphates, bromates, and the like of other metal elements such as lithium element and cobalt. Among them, in the present invention, chloride, nitrate, and acetate are preferably used because they are easily available as general-purpose products. In particular, nitrate is preferably used because of its good film-forming property for a wide variety of positive electrode current collectors.

For example, as a metal element-containing compound for producing LiCoO ₂ as a metal oxide, a Li element-containing compound and a Co element-containing compound can be used in combination as main raw materials, and other raw materials as necessary Can also be used in combination. Examples of the Li element-containing compound include lithium citrate tetrahydrate, lithium perchlorate trihydrate, lithium acetate dihydrate, lithium nitrate, and lithium phosphate. Examples of the compound include cobalt (II) chloride hexahydrate, cobalt (II) formate dihydrate, cobalt (III) acetylacetonate, cobalt (II) acetylacetonate dihydrate, cobalt acetate (II ) Tetrahydrate, cobalt (II) oxalate dihydrate, cobalt (II) nitrate hexahydrate, cobalt (II) ammonium chloride hexahydrate, sodium cobalt (III) nitrite, and cobalt sulfate ( II) The heptahydrate etc. are mentioned. The combination ratio (Li: Co = X: 1) of the Li element-containing compound and the Co element-containing compound used as the main raw material is not particularly limited, but is preferably 1 ≦ X <2, and preferably 1 ≦ X ≦ 1. 2 is more preferable.

Further, as the metal element-containing compounds to produce LiNiO ₂ as the metal oxide, Li-element-containing compound, and a Ni element-containing compound can be used in combination as the main raw material, and further, other ingredients as needed Can also be used in combination. Examples of the Li element-containing compound are the same as in the case of producing LiCoO ₂ described above. Examples of the Ni element-containing compound include nickel chloride (II) hexahydrate and nickel acetate (II) tetrahydrate. , Nickel (II) perchlorate hexahydrate, nickel (II) bromide trihydrate, nickel (II) nitrate hexahydrate, nickel (II) acetylacetonate dihydrate, hypophosphorous acid Examples thereof include nickel (II) acid hexahydrate and nickel (II) sulfate hexahydrate. The combination ratio (Li: Ni = X: 1) of the Li element-containing compound and Ni element-containing compound used as the main raw material is not particularly limited, but is preferably 1 ≦ X <2, and preferably 1 ≦ X ≦ 1. 2 is more preferable.

In addition, as a metal element-containing compound for generating LiMn ₂ O ₄ as a metal oxide, a Li element-containing compound and a Mn element-containing compound can be used in combination as main raw materials. These raw materials can also be used in combination. Examples of the Li element-containing compound are the same as in the case of producing LiCoO ₂ described above, and examples of the Mn element-containing compound include manganese acetate (III) dihydrate and manganese nitrate (II) hexahydrate. Products, manganese (II) sulfate pentahydrate, manganese (II) oxalate dihydrate, manganese (III) acetylacetonate, and the like. The combination ratio (Li: Mn = X: 1) of the Li element-containing compound and the Mn element-containing compound used as the main raw material is not particularly limited, but is preferably 0.5 ≦ X <1, 0.5 ≦ More preferably, X ≦ 0.6.

Further, as the metal element-containing compounds to produce LiFeO ₂ as the metal oxide, Li-element-containing compound, and a Fe element-containing compound can be used in combination as the main raw material, and further, other ingredients as needed Can also be used in combination. Examples of the Li element-containing compound are the same as in the case of producing LiCoO ₂ described above. Examples of the Fe element-containing compound include iron (II) chloride tetrahydrate, iron (III) citrate, and acetic acid. Examples include iron (II), iron (II) oxalate dihydrate, iron (III) nitrate nonahydrate, iron (II) lactate trihydrate, and iron (II) sulfate heptahydrate. . The combination ratio (Li: Fe = X: 1) of the Li element-containing compound and the Fe element-containing compound used as the main raw material is not particularly limited, but is preferably 1 ≦ X <2, and preferably 1 ≦ X ≦ 1. 2 is more preferable.

In addition, as a metal element-containing compound for producing Li ₄ Ti ₅ O ₁₂ as a metal oxide, a Li element-containing compound and a Ti element-containing compound can be used in combination as main raw materials, and if necessary, Other raw materials can also be used in combination. Examples of the Li element-containing compound are the same as in the case of producing LiCoO ₂ described above, and examples of the Ti element-containing compound include titanium tetrachloride and titanium acetylacetonate. The combination ratio (Li: Ti = X: 1) of the Li element-containing compound and the Ti element-containing compound used as the main raw material is not particularly limited, but is preferably 1 ≦ X <2, preferably 1 ≦ X ≦ 1. 2 is more preferable.

  The compounding ratio of the electrode (positive electrode) active material particles and the metal element-containing compound contained in the precursor for producing the positive electrode plate is not particularly limited, but the metal element-containing compound is a metal that undergoes a heating process. Since it becomes an oxide and the electrode (positive electrode) active material particles and the electrode (positive electrode) active material particles and the current collector are fixed by this metal oxide, when the content of the metal oxide is too small, There is a possibility that the fixing force cannot be increased to a desired level, or that the impedance cannot be decreased to a desired level. Therefore, in the state where the precursor finally becomes the positive electrode active material layer, the mass ratio of the metal oxide when the mass ratio of the electrode (positive electrode) active material particles is 100 parts by mass is 1 part by mass or more. It is preferable to adjust the blending ratio of the electrode (positive electrode) active material particles and the metal element-containing compound contained so as to be 100 parts by mass or less.

  Here, in forming the precursor for producing the positive electrode plate, the electrode active material particles described above and the metal element-containing compound are mixed in a solvent to obtain a coating solution, which is used on the positive electrode current collector. In the case of forming a precursor by coating, any solvent can be used as long as it can dissolve the metal element-containing compound, and a conventionally known solvent can be appropriately selected and used. it can. For example, water, lower alcohols such as NMP (N-methyl-2-pyrrolidone), methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, 2-butanol, t-butanol, acetylacetone, diacetyl And ketones such as benzoylacetone, ketoesters such as ethyl acetoacetate, ethyl pyruvate, ethyl benzoylacetate and ethyl benzoylformate, toluene, ethylene glycol, diethylene glycol, polyethylene glycol, and mixed solvents thereof.

  In addition, when the metal element-containing compound is dissolved in the solvent as described above, the total ratio of one or more metal element-containing compounds added to the solvent is 0.01 to 5 mol / L, especially 0.1 to 2 mol / L is preferred. By setting the concentration to 0.01 mol / L or more, the positive electrode current collector and the positive electrode active material layer generated from the precursor on the surface of the current collector can be satisfactorily adhered, and the electrode (positive electrode) The active material particles can be fixed. In addition, by setting the concentration to 5 mol / L or less, it is possible to maintain a good viscosity enough to apply the coating liquid onto the surface of the positive electrode current collector, thereby forming a uniform coating film. can do.

  Furthermore, when using the above coating liquid, you may mix | blend the organic substance which is a conductive material or the viscosity modifier of a coating liquid, and another additive in the said coating liquid.

  The thickness of the precursor is not particularly limited, but is generally about 15 to 300.

(Precursor for forming negative electrode plate)
On the other hand, the electrode active material particles contained in the precursor in the case of producing a negative electrode plate of a nonaqueous electrolyte secondary battery by the method of the present invention include, for example, titanium cobalt oxide, manganese, iron, cobalt Examples thereof include materials capable of occluding and releasing lithium ions, such as nitrides and composite oxides containing lithium and titanium elements (for example, Li ₄ Ti ₅ O ₁₂ , Li ₂ Ti ₃ O ₇ ). Especially, in this invention, a lithium titanium complex oxide with a high rate characteristic can be used conveniently.

  In addition, in the case of producing a negative electrode plate by the method of the present invention, the metal element-containing compound contained in the precursor includes metal element chloride, nitrate, acetate, perchlorate, phosphate, bromate Examples thereof include metal salts such as salts, and hydrates of these metal salts. Among them, chlorides, nitrates, and acetates are easily available as general-purpose products, and chlorine ions, nitrate ions, and acetate ions can be easily eliminated from the precursor by heating in the heating process described later. Since it can be used, it can be particularly preferably used.

  More specifically, for example, when the metal element is copper, copper chloride, copper nitrate, copper acetate, copper acetate (II) monohydrate and the like can be mentioned, and when the metal element is nickel Can include nickel chloride, nickel nitrate, nickel acetate, nickel (II) nitrate hexahydrate, nickel acetate (II) tetrahydrate, and the like. When the metal element is lithium, lithium chloride , Lithium nitrate, lithium acetate, lithium acetate trihydrate and the like.

  The blending ratio of the electrode (negative electrode) active material particles and the metal element-containing compound contained in the precursor for producing the negative electrode plate is not particularly limited, but is the same reason for producing the positive electrode plate. Thus, in a state where the precursor finally becomes the negative electrode active material layer, the mass ratio of the metal oxide when the mass ratio of the electrode (negative electrode) active material particles is 100 parts by mass is 1 part by mass or more. It is preferable to adjust the blending ratio of the electrode (negative electrode) active material particles and the metal element-containing compound contained so as to be 100 parts by mass or less.

  Also, the precursor for producing the negative electrode plate is the same as in the case of the positive electrode plate described above, and the precursor can be formed by coating this on the negative electrode current collector. As the solvent used in the above, the same solvent as that for the positive electrode plate can be used. In that case, the ratio of the total amount of the one or more metal element-containing compounds added to the solvent is preferably 0.01 to 20 mol / L, particularly preferably 0.1 to 10 mol / L. By setting the concentration to 0.01 mol / L or more, the negative electrode current collector and the negative electrode active material layer produced from the precursor on the current collector surface can be satisfactorily adhered, and the negative electrode active material particles Adhesion to the current collector can be sufficiently achieved. In addition, by setting the concentration to 20 mol / L or less, it is possible to maintain a satisfactory viscosity to the extent that the coating solution can be satisfactorily applied to the surface of the negative electrode current collector, and form a uniform coating film. be able to.

  The thickness of the precursor is not particularly limited, but is generally about 15 to 300 μm.

(3) Heating step In the method of the present invention, the heating step refers to the current collector on which the precursor after the precursor forming step (2) is formed, and the metal element-containing compound in the precursor is a metal oxide. The process of heating at a temperature equal to or higher than

The heating temperature is not particularly limited as long as it is equal to or higher than the temperature at which the metal element-containing compound in the precursor becomes a metal oxide. For example, in the production of a positive electrode plate, the metal element-containing compound contained in the precursor Are Li (CH ₃ COO) · 2H ₂ O and Mn (CH ₃ COO) ₂ · 4H ₂ O, the heating temperature is about 400 ° C., and the metal is heated by heating at that temperature. element-containing compound is thermally decomposed, LiMn ₂ O ₄ becomes a metal oxide, by the LiMn ₂ O _4, the positive electrode active material particles and the current collector, and fixing of the positive electrode active material particles with each other is achieved.

  For example, in the production of the negative electrode plate, when the metal element-containing compound contained in the precursor is copper nitrate, the heating temperature is about 270 ° C., and the metal element is heated by heating at the temperature. Copper nitrate which is a contained compound becomes copper oxide, and the negative electrode active material particles, the current collector, and the negative electrode active material particles are fixed to each other by the copper oxide.

  Further, the heating method is not particularly limited as long as it is a heating method or a heating apparatus that can be heated at a temperature equal to or higher than the temperature at which the metal element-containing compound becomes a metal oxide. For example, a method of using any one of a hot plate, an oven, a heating furnace, an infrared heater, a halogen heater, a hot air blower, etc., or a combination of two or more can be mentioned.

  Further, the heating atmosphere in the heating step is not particularly limited, and may be appropriately determined in consideration of the material used for manufacturing the positive electrode plate and the negative electrode plate, the heating temperature, the oxygen potential of the metal element-containing compound, and the like. it can. For example, an air atmosphere is preferable in that a special atmosphere adjustment is not necessary and the heating process can be easily performed. In particular, in the present invention, since the aluminum foil is used as the current collector, the heating step can be preferably performed because there is no possibility that the aluminum foil is oxidized even if the heating step is performed in an air atmosphere.

  Although the method of the present invention has been described with a focus on a production method in which a resinous binder is not contained as the best embodiment, this does not prohibit the inclusion of a resinous binder. For example, a resin binder is contained in the precursor, or the electrode plate after the heating step is immersed in an immersion tank filled with a resin mixture prepared by mixing a resin binder with an NMP solvent or the like. Thus, the electrode plate formed by the method of the present invention can contain a resin binder. Even when a resin binder is contained, it goes without saying that the input / output characteristics are improved and the battery capacity is increased by the amount of the metal oxide.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. Hereinafter, unless otherwise specified, parts or% is based on mass.

Example 1
Li (CH ₃ COO) · 2H ₂ O [molecular weight: 102.02]: 2 g and Mn (CH ₃ COO) ₂ · 4H ₂ O [molecular weight: 245.09]: 10 g added to methanol: 12 g The raw material liquid for mixing and forming a metal oxide was used. Next, 10 g of the above raw material liquid: 10 g of positive electrode active material particles having an average particle diameter of 4 μm: LiMn ₂ O ₄ : 10 g, acetylene black (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.): 1.2 g, carbon fiber (Showa Denko) (VGCF) 0.25g, resin hydroxyethyl cellulose 0.2g dissolved in pure water 9.8g, 15g thickener aqueous solution and solvent methanol were mixed, and 8000rpm with Excel Auto Homogenizer (Nippon Seiki Seisakusho Co., Ltd.). The positive electrode active material layer forming liquid was prepared by kneading for 15 minutes at a rotational speed of.

Next, the positive electrode active material layer forming liquid prepared above is applied to the surface of an aluminum foil (current collector 1) having a thickness of 15 μm and an aluminum purity of 99.7%. The electrode mass of the material layer was applied to one side of the current collector with an applicator in such an amount that the electrode mass was 82 g / m ² to form a coating film for forming an electrode active material layer. Subsequently, the coating film was pressed using a roll press machine (manufactured by Sank Metal Co., Ltd .: mechanical type 1 ton) under the conditions of applied pressure: 0.1 ton / cm and pressing speed of 10 mm / second. Thereafter, the current collector with the electrode active material layer-forming coating film formed thereon was placed in a normal temperature electric furnace (muffle furnace, Denken, P90) and heated from room temperature to 450 ° C. over 20 minutes. Thus, a positive electrode plate for a non-aqueous electrolyte secondary battery in which a positive electrode active material layer was laminated on the current collector was obtained. And the said positive electrode plate was taken out from the electric furnace, and it was left until it became room temperature, and the positive electrode plate 1 of Example 1 with which the positive electrode active material layer was laminated | stacked on the positive electrode collector was obtained.

(Example 2)
A positive electrode plate of Example 2 was obtained in the same manner as in Example 1 except that instead of the current collector 1, an aluminum foil having an aluminum purity of 99.2% was used.

(Example 3)
A positive electrode plate of Example 2 was obtained in the same manner as in Example 1 except that instead of the current collector 1, an aluminum foil having an aluminum purity of 99.0% was used.

(Comparative Example 1)
A positive electrode plate of Comparative Example 1 was obtained in the same manner as in Example 1 except that instead of the current collector 1, an aluminum foil having an aluminum purity of 96.5% was used.

(Comparative Example 2)
The same positive electrode active material particles and conductive material as in Example 1 were kneaded with a PVDF binder dispersed in an NMP solvent, coated on the current collector 1 and heated to 120 ° C. to volatilize the NMP solvent. Thus, a positive electrode plate of Comparative Example 2 was obtained.

(Comparative Example 3)
The same positive electrode active material particles and conductive material as in Example 1 were kneaded in an aqueous solvent in which CMC was dissolved, and an electrode slurry was prepared using SBR as a binder. After coating this electrode slurry on the current collector 1, the positive electrode plate of Comparative Example 3 was obtained by heating to 120 ° C. to volatilize the aqueous solvent.

<Evaluation of yield>
Twenty positive electrode plates of Examples 1 to 3 and Comparative Examples 1 to 3 were cut into 10 cm square and rolled until the electrode density was 2.4 g / cm ³ . The non-defective product was inspected by confirming whether or not the edge portion of the current collector of the 20 positive electrode plates after rolling was broken and the occurrence of wrinkles. Each yield is shown in Table 1. The yield is a value obtained by dividing the number of non-defective products by the number of test samples of 20, and the non-breaking edge portion and the occurrence of wrinkles were defined as non-defective products.

<Production of tripolar coin cell>
Lithium hexafluorophosphate (LiPF ₆ ) is added as a solute to a mixed solvent of ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio = 1: 1), and the concentration of LiPF _{6 as} the solute is 1 mol. The non-aqueous electrolyte was prepared by adjusting the concentration to be / L. Using the examples and comparative examples prepared as described above as the positive electrode plate as the working electrode, the metal lithium plate as the counter electrode plate and the reference electrode plate, the non-aqueous electrolyte prepared above as the electrolyte, The assembly was subjected to the following charge / discharge test.

(Charge test)
The test cells of each Example and Comparative Example were charged with a constant current at a constant current (charge rate: 0.2 C) under a 25 ° C. environment until the voltage reached 4.3V. After the voltage reaches 4.3V, the current (charge rate: 0.2C) is reduced to 5% or less so that the voltage does not exceed 4.3V, and charging is performed at a constant voltage. The battery was fully charged and rested for 10 minutes. Here, the above-mentioned “0.2C” means a current value (current value reaching the discharge end voltage) at which the constant current discharge is performed using the tripolar coin cell and the discharge is completed in 5 hours.

(Discharge test)
Thereafter, the test cells of each of the fully charged Examples and Comparative Examples were kept at a constant current until the voltage was changed from 4.3 V (full charge voltage) to 3.0 V (discharge end voltage) in an environment of 25 ° C. (Discharge rate: 0.2 C) Constant current discharge, cell voltage (V) on the vertical axis, discharge time (h) on the horizontal axis, a discharge curve is created, and the discharge capacity (mAh) of the working electrode is obtained. The discharge capacity (mAh / g) per unit active material mass of the working electrode was converted.

(Rate characteristics test)
Subsequently, a constant current discharge test at a constant current (discharge rate: 1 C, discharge end time: 1 hour) was performed on the test cells of each Example and Comparative Example, and the discharge capacity of the working electrode at the 1 C rate was determined. It was converted to discharge capacity per active material mass (mAh / g). Next, a constant current discharge test of 30 times constant current (discharge rate 30C, discharge end time: 2 minutes) is performed based on the constant current discharge test at 1C rate, and the discharge capacity (mAh) of the working electrode at 30C rate is calculated. It calculated | required and converted into the discharge capacity per unit active material mass (mAh / g). Then, the discharge capacity maintenance rate at 30 C rate relative to the discharge capacity with 1 C rate current applied was calculated. Table 1 shows the results.

(Cycle test)
After confirming the capacity, a cycle test in which CC + CV charge and CC discharge were repeated at a charge / discharge rate of 1 C was performed, and the cycle number in which the discharge capacity was less than 80% of the initial discharge capacity was defined as the cycle life in this test. The results are also shown in Table 1.

  As can be seen from the above table, the current collector made of aluminum foil having a purity of 99% or more was used, and the electrode active material particles and the current collector, and the electrode active material particles were fixed with a metal oxide. Examples are excellent in all evaluation items of yield, rate characteristics, and cycle characteristics. On the other hand, the yield of Comparative Example 1 having a purity of less than 99% was poor, and the electrode active material particles, the current collector, and the electrode active material particles were fixed to each other by PVDF or SBR resin instead of the metal oxide. It was confirmed that Comparative Examples 2 and 3 were inferior in battery characteristics.

Claims (1)

A preparation step of preparing a current collector made of aluminum foil having a purity of 99% or more;
Forming a precursor containing at least electrode active material particles and a metal element-containing compound on the current collector prepared in the preparation step;
Heating at a temperature at which the metal element-containing compound in the precursor becomes a metal oxide or higher,
The manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries which has this.