JP6419408B2 - Battery electrode composition and battery electrode binder composition - Google Patents

Description

  The present invention relates to a battery electrode composition and a battery electrode binder composition.

  In recent years, electronic devices have been increasingly miniaturized. Lithium ion or lithium ion secondary batteries or nickel metal hydride batteries that use a material that reversibly occludes and releases hydrogen are used for portable electronic devices such as mobile phones and laptop computers. It is becoming increasingly important as a central power source. Each of these secondary battery electrodes has a structure in which an active material is applied on a metal substrate (hereinafter referred to as a current collector), and is usually a polymer binder as a binder for binding the active material to the current collector. Is being used. This polymer binder is required to have a binding property with an active material, resistance to an electrolytic solution, stability in an electrochemical environment, and the like. Particularly in the case of lithium ion secondary batteries, conventionally, a fluorine-based polymer such as polyvinylidene fluoride is dissolved in a solvent such as N-methyl-2-pyrrolidone and used as a binder. There is a problem that segregation on the electrode surface tends to occur and the binding force is insufficient, and improvement is desired. For example, in Japanese Patent Application Laid-Open No. 04-51459 (Patent Document 1), by using a binder for an electrode made of a non-fluorine aqueous dispersion and a coating composition for an electrode, the segregation of the binder is suppressed and the binding force is good. It is possible to provide a simple electrode. However, there is a concern that the long-term stability of the paint such as viscosity may be insufficient due to the water-based coating composition. In addition, International Publication WO2004 / 107481 (Patent Document 2) discloses that a binder and a dispersant are combined in a specific polymerization method to improve the stability of the binder composition and the coating composition. Proposed.

Japanese Patent Laid-Open No. 04-51459

International Publication No. WO2004 / 107481

However, it cannot be said that the battery electrode composition containing the binder or the stability of the binder itself such as pH and viscosity is sufficient.
An object of the present invention is to provide a composition for battery electrodes that has little change over time such as viscosity over a long period of time. As a result, an object is to provide an electrode excellent in binding force and the like, and a battery having good battery characteristics.

  In order to solve the above-described problems, the battery electrode composition of the present invention comprises 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 1,2- It contains at least one selected from the group consisting of benzoisothiazolin-3-one.

  The composition for a battery electrode of the present invention has stable physical properties such as viscosity over a long period of time, and it is possible to obtain an electrode with extremely stable quality such as binding force. As a result, a battery having good battery characteristics can be obtained. can get.

  The composition for battery electrodes of the present invention comprises 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, and 1,2-benzisothiazolin-3-one. Contains one or more selected from the group.

Further, 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 1,2-benzisothiazolin-3-one, 2,2-dibromo- 3 -nitrilo It is preferable from the viewpoint of non-release of formaldehyde that it contains at least one selected from the group consisting of propionamide and 2-n-octyl 4-isothiazolin-3-one.

Furthermore, 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 1,2-benzisothiazolin-3-one, 2,2-dibromo - 3 - One selected from the group consisting of nitrilopropionamide, 2-n-octyl 4-isothiazolin-3-one, 2-bromo-2-nitropropane-1,3-diol, and 2,2-dibromo-2-nitroethanol It is more preferable to contain the above from a viewpoint of the long-term stability maintenance effect of the composition for battery electrodes.

  Although it does not specifically limit about the addition amount of the said compound, It is 0.00001-1 weight part with respect to solid content of the composition for battery electrodes, or 0.001-10 weight part with respect to solid content of the binder for battery electrodes. preferable. If the amount is less than 0.00001 parts by weight with respect to the battery electrode composition or less than 0.001 parts by weight with respect to the solid content of the battery electrode binder, the time-dependent stability effect of the battery electrode composition tends to be difficult to develop. When the amount exceeds 1 part by weight with respect to the battery electrode composition or the solid content of the battery electrode binder, the binding force tends to decrease, which is not preferable. 0.0001 to 0.1 parts by weight based on the solid content of the battery electrode composition, or 0.01 to 1 part by weight based on the solid content of the battery electrode binder is more preferable.

  In the present invention, as a method for containing the above-mentioned compound in the battery electrode composition, these may be added directly to the battery electrode composition, or a battery in which these substances are previously contained in a binder. Any method of adding the electrode binder composition to the battery electrode composition may be used.

  The binder used in the battery electrode composition of the present invention is not particularly limited, but styrene / butadiene rubber (SBR), acrylonitrile / butadiene rubber (NBR), methyl methacrylate / butadiene rubber (MBR), butadiene rubber (BR). ) And other water-based emulsions such as acrylic rubber latex containing (meth) acrylic acid ester as a main monomer, and one kind or two or more kinds can be used. Further, these copolymers are more preferably modified with a functional group-containing monomer such as an unsaturated carboxylic acid monomer from the viewpoint of the viscosity stability of the battery electrode composition.

  The composition for battery electrodes of this invention contains the active material and binder of each of a positive electrode and a negative electrode. The type of active material is not particularly limited. For example, in the case of a non-aqueous electrolyte secondary battery, graphite, carbon fiber, resin-fired carbon, linear graphite hybrid, coke, pyrolytic gas-layer-grown carbon, furfuryl alcohol resin Carbonaceous materials such as calcined carbon, polyacene organic semiconductors, mesocarbon microbeads, mesophase pitch carbon, graphite whiskers, pseudo-isotropic carbon, calcined natural materials, and pulverized products thereof, transitions such as MnO2 and V2O5 Examples include metal oxides, lithium-containing composite oxides such as LiCoO 2, LiMnO 2, and LiNiO 2, and one kind or a mixture of two or more kinds can be used.

  The composition for battery electrodes of the present invention has a binder content of 0.1 to 10 parts by weight (solid content), more preferably 1 to 7 parts by weight (solid content) with respect to 100 parts by weight (solid content) of the active material. Is preferably used. When the amount of the binder is less than 0.1 parts by weight, there is a tendency that a good binding force to a current collector or the like cannot be obtained. When the amount exceeds 10 parts by weight, the overvoltage is remarkably increased when assembled as a battery, and the battery characteristics. This is undesirable because it tends to adversely affect

  Various additives such as a water-soluble thickener may be added to the battery electrode composition of the present invention as necessary. For example, water-soluble thickeners such as carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, polyacrylic acid (salt), oxidized starch, phosphorylated starch, casein, hexametaphosphate soda, tripolyphosphate soda, pyrophosphate soda, Examples thereof include dispersants such as sodium polyacrylate, nonionic and anionic surfactants as latex stabilizers.

  The battery electrode composition of the present invention is applied to a current collector and dried to be used as a battery electrode. In addition, as a method for applying the battery electrode composition to the current collector, any coater head such as a reverse roll method, a comma bar method, a gravure method, an air knife method can be used. Machine, warm air dryer, infrared heater, far-infrared heater and the like can be used.

  Current collectors, separators, non-aqueous electrolytes, terminals, insulators, battery containers, etc. used when manufacturing batteries using the battery electrode composition of the present invention can be used without particular limitation. It is.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is changed. In the examples, parts and percentages indicating percentages are based on weight. In addition, various physical properties in the examples were evaluated by the following methods.

Preparation of copolymer latex A In a pressure resistant polymerization reactor, under a nitrogen atmosphere, 2 parts 1,3-butadiene, 4 parts styrene, 1.5 parts acrylonitrile, 1 part methyl methacrylate, 2 parts hydroxyethyl acrylate, 0.6 parts of acrylic acid, 1.9 parts of fumaric acid, 0.05 part of t-dodecyl mercaptan, 5 parts of cyclohexene, 0.6 part of sodium dodecylbenzenesulfonate and 100 parts of pure water were added and the temperature was raised to 50 degrees. Later, 1 part of potassium persulfate was added to initiate the polymerization. 3 hours after the start of the polymerization, 20 parts of 1,3-butadiene, 42 parts of styrene, 15 parts of acrylonitrile, 10 parts of methyl methacrylate, 0.45 part of t-dodecyl mercaptan, 0.2 part of sodium dodecylbenzenesulfonate, pure water 20 Part was added, the temperature of the polymerization reactor was raised to 60 degrees, and the polymerization was continued. The polymerization was stopped 12 hours after the initiation of polymerization, and the pH was adjusted to 7.5 with an aqueous sodium hydroxide solution. Thereafter, steam distillation was performed at 90 ° C. for 15 hours to remove unreacted monomers and other low-boiling compounds to obtain a copolymer latex A having a number average particle size of 160 nm and a gel content of 85%. .

<Examples 1-15>
Preparation of composition for negative electrode Natural graphite having an average particle diameter of 20 μm is used as a negative electrode active material, and 100 parts by weight of natural graphite is 1 part by weight of a carboxymethyl cellulose aqueous solution as a thickener and co-polymerized as a binder. 2 parts by weight of combined latex A in a solid content and the amount of the compound shown in Table 1 and Table 2 were added, and an appropriate amount of water was added and kneaded so that the total solid content would be 40%. Prepared.
Here, in Example 13, first, 0.2 parts by weight of 2-methyl-4-isothiazolin-3-one was added to 100 parts by weight of the solid content of the copolymer latex A, and the copolymer was sufficiently stirred. Polymer latex A ′ was prepared. Except for adding this copolymer latex A ′ instead of the copolymer latex A,
A negative electrode composition was prepared in the same manner as in Example 1.

Preparation of Negative Electrode Sheet Each negative electrode composition was applied to a 20 μm thick copper foil as a current collector, dried at 120 ° C. for 5 minutes, and then pressed at room temperature to form a negative electrode having a coating layer thickness of 80 μm. Obtained.

Preparation of copolymer latex B In a pressure resistant polymerization reactor, in a nitrogen atmosphere, 7 parts of butyl acrylate, 1 part of methyl methacrylate, 1 part of hydroxyethyl acrylate, 2 parts of itaconic acid, 2 parts of acrylic acid, ethylene glycol di After adding 0.5 parts of methacrylate, 0.3 parts of cyclohexene, 0.2 parts of sodium dodecylbenzenesulfonate and 100 parts of pure water and raising the temperature to 65 ° C., 0.8 parts of potassium persulfate is added to initiate polymerization. did. One hour after the start of polymerization, 50 parts of butyl acrylate, 13 parts of methyl methacrylate, 11 parts of styrene, 3 parts of acrylamide, 2 parts of hydroxyethyl acrylate, 5 parts of methacrylic acid, 2.5 parts of ethylene glycol dimethacrylate, t-dodecyl mercaptan 0 0.02 part, 0.5 part of sodium dodecylbenzenesulfonate and 20 parts of pure water were added, the temperature of the polymerization reactor was raised to 70 ° C., and the polymerization was continued. The polymerization was stopped 6 hours after the start of the polymerization, and the pH was adjusted to 7.5 with an aqueous sodium hydroxide solution. Thereafter, steam distillation was performed at 90 ° C. for 15 hours to remove unreacted monomers and other low-boiling compounds to obtain a copolymer latex B having a number average particle size of 230 nm and a gel content of 85%. .

<Examples 16 to 30>
Preparation of composition for positive electrode 100 parts by weight of LiCoO2 as a positive electrode active material, 5 parts by weight of acetylene black as a conductive agent, 1 part by weight of a carboxymethylcellulose aqueous solution as a thickener, and copolymer latex B as a binder 2 parts by weight of a solid content and the amount of the compound shown in Tables 3 and 4 were added, and an appropriate amount of water was added and kneaded so that the total solid content was 40% to prepare a positive electrode composition.
Here, in Example 28, first, 0.2 parts by weight of 2-methyl-4-isothiazolin-3-one was added to 100 parts by weight of the solid content of the copolymer latex B, and the copolymer was sufficiently stirred. Polymer latex B ′ was prepared. Except for adding this copolymer latex B ′ instead of the copolymer latex B,
A negative electrode composition was prepared in the same manner as in Example 16.

Preparation of positive electrode sheet Each positive electrode composition was applied to an aluminum foil having a thickness of 20 μm as a current collector, dried at 120 ° C. for 5 minutes, and then pressed at room temperature to obtain a positive electrode having a coating layer thickness of 80 μm. Obtained.

Change in viscosity of battery electrode composition over time (stability over time)
The viscosity immediately after production of the battery electrode composition obtained above and the B-type viscosity after 1 week at room temperature were measured with a TVB-10M manufactured by Toki Sangyo Co., Ltd. (60 rpm, No. 4 rotor), and the following: The time-dependent change value R of the viscosity of the battery electrode composition was determined from the formula, and the results are shown in Tables 1 to 4. In addition, about the composition for battery electrodes one week after standing at room temperature, it measured, after stirring sufficiently until the apparent viscosity became constant with the speed | rate which a bubble does not enter with a spatula.
R = | Viscosity after 1 week at room temperature−Viscosity immediately after production |

Measurement of binding force (180 ° peel strength) The electrode sheet obtained by the above method is cut into a strip of 7 cm x 2 cm, a 1 mm thick steel plate is bonded to the current collector side with double-sided tape, and the cellophane is applied to the coating layer side. Adhesive tape was affixed, and the stress when peeling in the 180 ° direction at a speed of 100 mm / min was measured with a tensile tester. The results are shown in Tables 1 to 4.

As shown in Tables 1 to 4, the battery electrode composition of the present invention has a small viscosity change with time and is excellent in viscosity stability. Moreover, it is excellent also in the binding force of the electrode obtained by apply | coating the composition for battery electrodes of this invention.
In the comparative examples, none of the compounds specified in the present application is contained, and it is clear that the viscosity stability is greatly inferior and the binding force is also inferior.

  In addition, although the said invention was provided as embodiment of illustration of this invention, this is only a mere illustration and must not be interpreted limitedly. Modifications of the present invention apparent to those skilled in the art are intended to be included within the scope of the following claims.

  As described above, the composition for a battery electrode of the present invention has a stable viscosity over a long period of time, and it is possible to obtain an electrode having a stable binding force. As a result, a battery having good battery characteristics is obtained, which is extremely useful.

Claims (8)

A composition for a lithium ion secondary battery electrode comprising a binder and 2-methyl-4-isothiazolin-3-one,
The binder is an acrylic rubber latex that is a copolymer of monomers containing methyl methacrylate (excluding those having an α, β-unsaturated nitrile monomer unit).
Composition for lithium ion secondary battery electrode. A composition for a lithium ion secondary battery electrode comprising a binder and 2-methyl-4-isothiazolin-3-one,
The binder is a conjugated diene rubber latex that is a copolymer of monomers containing methyl methacrylate .
Lithium ion secondary battery electrode composition (excluding those containing a chelate compound or α-methylstyrene dimer).   3. The lithium ion secondary battery according to claim 1, wherein the addition amount of the 2-methyl-4-isothiazolin-3-one is 0.025 to 2.5 parts by weight with respect to the solid content of the binder. Electrode composition.   2,2-dibromo-3-nitrilopropionamide, 2-n-octyl 4-isothiazolin-3-one, 2-bromo-2-nitropropane-1,3-diol, 2,2-dibromo-2-nitroethanol The composition for lithium ion secondary battery electrodes as described in any one of Claim 1 to 3 containing 1 or more types chosen from the group which consists of. A binder composition for a lithium ion secondary battery electrode comprising a binder and 2-methyl-4-isothiazolin-3-one,
The binder is an acrylic rubber latex that is a copolymer of monomers containing methyl methacrylate (excluding those having an α, β-unsaturated nitrile monomer unit).
A binder composition for a lithium ion secondary battery electrode. A binder composition for a lithium ion secondary battery electrode comprising a binder and 2-methyl-4-isothiazolin-3-one,
The binder is a conjugated diene rubber latex that is a copolymer of monomers containing methyl methacrylate .
Binder composition for lithium ion secondary battery electrodes (excluding those containing a chelate compound or α-methylstyrene dimer).   The lithium ion secondary battery according to claim 5 or 6, wherein the addition amount of the 2-methyl-4-isothiazolin-3-one is 0.025 to 2.5 parts by weight with respect to the solid content of the binder. Electrode binder composition.   2,2-dibromo-3-nitrilopropionamide, 2-n-octyl 4-isothiazolin-3-one, 2-bromo-2-nitropropane-1,3-diol, 2,2-dibromo-2-nitroethanol The binder composition for lithium ion secondary battery electrodes according to any one of claims 5 to 7, comprising one or more selected from the group consisting of: