JP2006054097A - Electrode material composition enclosing body for lithium secondary battery, manufacturing method and preservation method of the same, and electrode material dispersion liquid for lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode material composition for lithium secondary battery excellent in a handling property capable of obtaining an excellent property as an electrode activator, capable of effectively preparing a painting slurry with an excellent uniform dispersion property and painting property on a current collector or the like. <P>SOLUTION: The electrode material composition enclosing body for the lithium secondary battery formed by enclosing an electrode material composition for the lithium secondary battery is formed by impregnating an organic solvent dissolving poly(vinylidene fluoride) by 3% or more in the electrode material for the lithium secondary battery. As the organic solvent is impregnated, it is excellent in a handling property without any problem of powder scattering. When preparing the painting slurry, since the PVdF soluble organic solvent is impregnated in advance, the painting slurry having good affinity with other materials and an excellent dispersion property can be prepared by a dispersion treatment within a short time. Since the spaces between electrode material fine powders are filled by the organic solvent preventing inclusion of air, generation of bubble at the preparation of painting slurry is eliminated and the slurry is excellent in a bubble removing property. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inclusion body of an electrode material composition for a lithium secondary battery, a production method thereof, a storage method, and an electrode material dispersion for a lithium secondary battery. Specifically, the electrode material composition for a lithium secondary battery, which is excellent in handleability and excellent in easy dispersibility and easy defoaming property of powder when preparing an electrode material dispersion for electrode preparation, is enclosed. Encapsulated body and method for producing the same, storage method of electrode material composition for lithium secondary battery, and electrode material dispersion for lithium secondary battery prepared using the sealed electrode material composition for lithium secondary battery About.

  2. Description of the Related Art In recent years, lithium secondary batteries having a high energy density have attracted attention as electric products become lighter and smaller.

  As a positive electrode material (positive electrode active material) for a lithium secondary battery, a lithium transition metal composite oxide is known. On the other hand, carbonaceous materials are known as negative electrode materials (negative electrode active materials).

  A positive electrode and a negative electrode for a lithium secondary battery have a dispersion (hereinafter referred to as “coating slurry”) in which the active material is dispersed in a liquid medium such as water or an organic solvent such as N-methylpyrrolidone (NMP) together with a binder. Is applied on a current collector and dried.

Patent Document 1 describes an electrode manufacturing method in which a dispersion liquid of an electrode material is prepared using water as a dispersion medium, and this is applied onto a current collector and dried. Patent Documents 2 and 3 describe an electrode manufacturing method in which a dispersion of an electrode material is prepared using NMP as a dispersion medium, and this is applied onto a current collector and dried.
JP 2001-332261 A JP-A-62-090863 JP-A-5-6766

  In recent years, with the rapid expansion of the application of lithium secondary batteries to portable devices such as notebook computers and mobile phones, lithium secondary batteries have high performance such as high power and high output. Is demanded, and at the same time, high productivity is demanded. For this reason, even in the electrode production process, in order to produce a high-quality electrode with high productivity, it is excellent in its own handling property, and a large amount of coating slurry can be efficiently prepared in a short time. There is a demand for an electrode material (positive electrode or negative electrode active material) that is excellent in the uniform dispersibility of the coating slurry and the coating property to the current collector, and that can stably maintain this property over a long period of time.

  That is, since the electrode material is usually in the form of fine powder, there is a problem of powder skipping when the electrode material package is opened and the electrode material is taken out, and the handling property is poor. Also, when this electrode material is made into a coating slurry, the dispersibility in the dispersion medium and the familiarity with the binder are poor, and it takes a long time for the dispersion treatment, or in the case of significant precipitation of the binder. There is also a problem. Furthermore, since the electrode material encloses air between the fine powders, foaming problems due to the release of this air from the electrode material during the mixing process during coating slurry preparation (defoaming treatment during coating slurry preparation) However, the defoaming property is poor and bubbles continue to come out forever.)

  In the case of a coating slurry with poor uniform dispersibility, defoaming and stability of the electrode material, when this is applied to a current collector and dried to produce an electrode, the coating property is poor, and the formed coating is repelled by bubbles. (Foaming marks) and undispersed pulverization are observed. And with such a coating film, the electrode excellent in the characteristic cannot be produced.

In particular, in the case of a lithium transition metal composite oxide as a positive electrode material, when it comes into contact with carbon dioxide in the atmospheric gas during storage, excess Li becomes lithium carbonate (Li ₂ CO ₃ ) through moisture. Lithium carbonate). In particular, in the case of a lithium nickel composite oxide, Li is extracted from the inside and carbonation occurs easily. In the lithium secondary battery using the electrode produced using such a lithium transition metal composite oxide, the lithium carbonate produced becomes a resistive film. It decomposes into lithium and generates gas, causing battery swelling and battery performance degradation.

  For this reason, the electrode material is excellent in handleability, dispersibility during preparation of the coating slurry, preparation efficiency of the coating slurry, uniform dispersibility of the prepared coating slurry, defoaming property, stability, etc. Furthermore, the lithium transition metal composite oxide of the positive electrode material is required to be hardly carbonated.

  Therefore, the present invention is excellent in handling properties, can obtain excellent characteristics as an electrode active material, and efficiently prepares a coating slurry excellent in uniform dispersibility, applicability to a current collector, and the like. It aims at providing the enclosure of the electrode material composition for lithium secondary batteries which can supply the electrode material composition for lithium secondary batteries which can be manufactured.

  The present invention also provides a method for stably storing such an electrode material composition for a lithium secondary battery, and dispersion of an electrode material for a lithium secondary battery as a coating slurry using the electrode material composition for a lithium secondary battery. The purpose is to provide a liquid.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have improved the handleability by encapsulating a lithium secondary battery electrode material impregnated with a specific organic solvent, and applying it. The present invention has been completed by finding that the uniform dispersibility, slurry characteristics, applicability to the current collector, and stability thereof during slurry preparation are improved and that the efficiency of preparation of the applied slurry is improved.

That is, the gist of the present invention is as follows.
A lithium secondary battery electrode material composition comprising an electrode material composition for lithium secondary battery impregnated with an organic solvent having a solubility of polyvinylidene fluoride of 3% or more in an electrode material for a lithium secondary battery. An inclusion body of an electrode material composition,
Exist.

Another gist of the present invention is as follows:
An electrode material for a lithium secondary battery in which an electrode material composition for a lithium secondary battery obtained by impregnating an organic solvent having a solubility of polyvinylidene fluoride of 3% or more into an electrode material for a lithium secondary battery is encapsulated A method for producing an inclusion body of the composition;
Exist.

Another gist of the present invention is as follows.
A lithium secondary battery electrode material composition obtained by impregnating a lithium secondary battery electrode material with an organic solvent having a polyvinylidene fluoride solubility of 3% or more is stored in the form of an enclosure. Method for storing electrode material composition for secondary battery,
Exist.

Yet another subject matter of the present invention is as follows:
An electrode material dispersion for forming an electrode active material layer on a current collector by applying and drying on the current collector in the production of an electrode for a lithium secondary battery, which is enclosed in the encapsulant of the present invention. An electrode material dispersion for lithium secondary batteries, wherein the electrode material composition for lithium secondary batteries is mixed with at least polyvinylidene fluoride as a binder,
Exist.

  Hereinafter, an organic solvent having a solubility of 3% or more of polyvinylidene fluoride (PVdF) used in the present invention may be referred to as a “PVdF soluble solvent”.

  The electrode material composition for a lithium secondary battery encapsulated in the encapsulant of the electrode material composition for a lithium secondary battery according to the present invention is easy to handle, dispersibility when preparing the coating slurry, and preparation efficiency of the coating slurry. Excellent uniform dispersion, defoaming and stability of coated slurry.

  That is, the conventional fine powder electrode material has a problem of powder skipping, but the electrode material composition of the present invention is impregnated with a PVdF soluble solvent and thus has no problem of powder skipping and is excellent in handleability. . Also, when coating slurry is made, it is pre-impregnated with PVdF soluble solvent, so it is easy to blend with other materials, has excellent dispersibility, and prepares uniform coating slurry in a short dispersion process. Can do. In addition, the space between the electrode material fine powders is filled with a PVdF soluble solvent and air inclusion is prevented, so there is little foaming during the preparation of the coating slurry, and excellent defoaming properties.

  By using such an electrode material composition for a lithium secondary battery as an inclusion body, it is possible to block the air and prevent scattering of the solvent gas, and to transport and transport it suitably, and to store the electrode material composition stably. Will be able to.

  The slurry applied to the current collector is dried with an application slurry prepared with the electrode material composition for a lithium secondary battery encapsulated in the encapsulant of the present invention and excellent in uniform dispersibility, defoaming and stability. When producing an electrode, it is possible to form a high-quality coating film free from bubble repellency and undispersed crushing, and thus an electrode having excellent electrode characteristics can be produced.

  Further, by impregnating the electrode material with a PVdF soluble solvent, the surface of the electrode material can be prevented from coming into contact with air. As a result, for example, in the above-described lithium transition metal composite oxide, Carbonization is suppressed, and excellent effects such as gas generation reduction, low resistance maintenance, and high capacity maintenance are obtained.

  The electrode material composition for a lithium secondary battery encapsulated in the encapsulant of the electrode material composition for a lithium secondary battery according to the present invention is obtained by impregnating an electrode material in advance with an organic solvent suitable for preparing a coating slurry. Therefore, in use, a binder and a conductive material can be mixed and easily formed into a coating slurry without performing a pretreatment such as drying.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not specified by these contents.

[Electrode material (active material)]
The electrode material for a lithium secondary battery in the present invention is not limited as long as the effect of the present invention is exhibited, and may be a positive electrode material or a negative electrode material.

[Positive electrode material: lithium transition metal composite oxide]
As the positive electrode material (positive electrode active material), a lithium transition metal composite oxide is preferably used. Examples of the lithium transition metal composite oxide include a lithium nickel composite oxide, a lithium cobalt composite oxide, and a lithium manganese composite oxide, but also a lithium transition metal oxide material such as a spinel type lithium manganate compound. good.

From the viewpoint of lithium secondary battery characteristics when used as a positive electrode active material, lithium transition metal composite oxides represented by the following general formula (I) are particularly preferable.
_{Li a A b D c O 2} ... (I)
(In the formula (I), a represents a number of 0.45 ≦ a ≦ 1.2, b represents a number of 0.95 ≦ b ≦ 1.05, and c represents 0 ≦ c ≦ 0.1. A represents a number, and A represents one or more selected from the group consisting of Ni, Mn, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, Nb, Sn, Ta and V, Of these, Ni and Co are preferable. D represents one or more selected from the group consisting of B, P, S, Bi, Si, Sb, Ca, Zr and C.)

  In the said general formula (I), it is preferable that Ni or Co is contained as transition metal A 0.3 mol or more with respect to 1 mol of all the transition metals A.

The lithium transition metal composite oxide is particularly preferably a lithium nickel composite oxide in that it has a high capacity, a high rate, and a long life when used in a lithium secondary battery. As lithium nickel composite oxide, the basic composition is represented by LiNiO ₂ , Li ₂ NiO ₂ , LiNi ₂ O _4, Li ₂ Ni ₂ O _4, etc., and a part of these nickels is replaced with other elements And the like. Among these lithium nickel composite oxides, those represented by the following general formula (II) are particularly preferable in the present invention because they are highly reactive to CO _{2 and} many substances are unstable in the air. . That is, with such a lithium nickel oxide, a carbonation prevention effect is effectively exhibited by impregnating the PVdF soluble solvent and suppressing contact with air.
_{Li a Ni d M e O 2} ... (II)
(In the formula (II), a is a number from 0.9 to 1.2, d is a number from 0.3 to 1.2, and the sum of d + e is a number from 0.9 to 1.2, M represents one or more elements selected from the group consisting of B, Mg, Al, Ca, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, and Ga.

Specific examples of the lithium nickel composite oxide represented by the above general formula (II) include the following. These are preferable because they have a high capacity, a high rate and excellent cycle life when used in lithium secondary batteries.
Li _a Ni _1-x Co _y Al _z O ₂ (0 ≦ x ≦ 0.7, x = y + z),
_{LiNi 1-x Mn y Co z} O 2 (0 ≦ x ≦ 0.7, x = y + z),
Li _a Co _1-x Q _x O ₂ (0 ≦ x ≦ 0.7, Q = at least one selected from Ni, Mn, and Al)

  In the electrode material composition for a lithium secondary battery according to the present invention, one of these lithium transition metal composite oxides may be used alone or as a mixture of two or more as the positive electrode material. Further, these composite oxides may be used as a core material and surface treatment or surface coating may be performed.

  The form of the lithium transition metal complex oxide is not particularly limited, but is generally a powder.

  The lithium transition metal composite oxide may exist as a primary crystal particle or as a secondary particle formed by agglomeration of primary crystal particles, but in the present invention, primary crystal particles agglomerate to form secondary particles. It is preferable to use what is doing.

The lower limit of the specific surface area of the lithium transition metal composite oxide powder is usually 0.1 m ² / g or more, preferably 0.3 m ² / g or more, more preferably 0.5 m ² / g or more, and the upper limit is Usually, it is 7 m ² / g or less, preferably 6 m ² / g or less, more preferably 5 m ² / g or less. When the specific surface area is less than this lower limit, the electric resistance of the powder is high, and the rate characteristics when it is made into a battery are likely to deteriorate. When the upper limit is exceeded, there are many reaction surfaces, the battery charge / discharge cycle and the resistance increase during battery storage are remarkably increased, and the life tends to be reduced.

  In the present invention, the specific surface area of the lithium transition metal composite oxide powder is measured by a BET method (nitrogen surface area method) based on ASTM D3037 using a BET type powder specific surface area measuring device.

  In addition, the average particle diameter (median diameter) of the lithium transition metal composite oxide powder according to the present invention has a lower limit of usually 0.3 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, and an upper limit is usually It is 40 μm or less, preferably 30 μm or less, more preferably 20 μm or less. When the average particle size is less than this lower limit, when the positive electrode active material layer is formed, the number of powders is large, so that the normal amount of the binder tends to cause film peeling. When the upper limit is exceeded, the coating film is likely to be drawn by thinning the positive electrode active material layer to obtain a high rate.

  In the present invention, the particle size distribution is measured using a laser diffraction / scattering type particle size distribution measuring device, specifically, a Horiba Seisakusho (model: LA920, LA910, LA500) or the like.

  The lithium transition metal composite oxide as the positive electrode material can be prepared by a usual method and used for the impregnation step with a PVdF soluble solvent. That is, the particulate matter obtained by mixing raw materials, granulating / drying steps is returned to room temperature after firing, and then subjected to pulverization and classification steps (however, pulverization and classification are not necessarily essential). The impregnation process is performed under the necessary atmosphere control. In particular, in the case of a lithium nickel composite oxide that deteriorates when it comes into contact with moisture or carbon dioxide, it is preferably subjected to an impregnation step under low humidity and / or low carbon dioxide concentration atmosphere management.

  Many transition metal composite oxides exhibit alkalinity of pH 11 or higher in water, while PVdF is in contact with alkali for a long time to cause gelation. Therefore, the moisture concentration of lithium transition metal composite oxide and PVdF soluble solvent used in the impregnation process Is preferably 1% by weight or less. In particular, in the case of a lithium nickel composite oxide that deteriorates upon contact with moisture or carbon dioxide, the moisture concentration is more preferably 500 ppm or less. Therefore, it is important to manage the lithium transition metal composite oxide subjected to the PVdF soluble solvent impregnation step so that such a low moisture concentration can be maintained.

[Negative electrode material: Carbonaceous material]
Any negative electrode material (negative electrode active material) can be used as long as it can electrochemically occlude and release lithium ions. Usually, it is a carbonaceous material that can occlude and release lithium in terms of safety. Is used.

  Carbonaceous material types include natural or artificial graphite, pitch carbides, carbides such as phenolic resin and cellulose, pitch-based carbon fibers, PAN-based carbon fibers, graphitized materials such as mesophase spherules, furnace black, Examples include acetylene black and graphitized products thereof. Moreover, after covering these carbonaceous materials with organic substances, such as pitch, it baked and what formed the amorphous carbon compared with these carbonaceous materials on the surface can be used suitably.

These carbonaceous materials preferably have a d-value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method of 0.335 to 0.340 nm. What is 337 nm is more preferable. The ash content is preferably 1% by weight or less, more preferably 0.5% by weight or less, and particularly preferably 0.1% by weight or less. The crystallite size (Lc) determined by X-ray diffraction by the Gakushin method is preferably 30 nm or more, more preferably 50 nm or more, and particularly preferably 100 nm or more. Further, in the Raman spectrum analysis using argon laser beam, the intensity _{I A} of the peak _{P A} is detected in the range of 1580～1620Cm ^-1, the intensity of the peak _{P B} detected in the range of 1350 ^-1 I intensity ratio _I a / _{I B} of _B is preferably not more than 0 and 0.5 or less, the peak half width of _{P a} is 26cm ^-1 or less, especially 25 cm ^-1 or less.

  As the powder physical properties, the median diameter determined by the powder laser diffraction / scattering method is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, particularly preferably 7 μm or more, and usually 100 μm or less, preferably 50 μm. Below, it is more preferably 40 μm or less, particularly preferably 30 μm or less.

  When the median diameter is less than the above lower limit, the specific surface area becomes large and easily reacts with the electrolytic solution. When the median diameter exceeds the above upper limit, when the slurry is applied and applied to the current collector, striations occur and the active material has a uniform thickness. Formation of the layer becomes difficult.

Further, the BET specific surface area is usually 0.5 m ² / g or more, preferably 0.7 m ² / g or more, more preferably 1.0 m ² / g or more, and particularly preferably 1.5 m ² / g or more. usually 25.0 m ² / g or less, preferably 20.0 m ² / g or less, more preferably 15.0 m ² / g or less, particularly preferably 10.0 m ² / g or less.

[PVdF soluble solvent]
In the electrode material composition for a lithium secondary battery according to the present invention, the PVdF soluble solvent impregnated in an electrode material such as a lithium transition metal composite oxide as a positive electrode material or a carbon material as a negative electrode material is polyvinylidene fluoride ( PVdF) has a solubility (25 ° C.) of 3% or more.

  When the solubility of PVdF is 3% or more, there is an advantage that PVdF can be easily dissolved and PVdF does not reprecipitate when a PVdF / NMP solution in which PVdF is dissolved in advance is added.

  Usually, PVdF having a molecular weight of about 1000 to 10000 added as a binder when preparing a coating slurry is dissolved in NMP. When the electrode material is mixed with the PVdF / NMP solution added at the time of preparing the coating slurry, if the electrode material is impregnated with an organic solvent having a solubility of PVdF of 3% or more, the compatibility between the electrode material and PVdF is good. Both can be mixed smoothly. Moreover, precipitation of PVdF at the time of mixing can be suppressed. In an organic solvent having a solubility of PVdF of less than 3%, PVdF may be precipitated when the ratio of solid content / organic solvent is lowered.

  The lower limit of the solubility of PVdF in the PVdF soluble solvent is 3% or more, preferably 5% or more. If the solubility of PVdF, which is a PVdF soluble solvent, is below this lower limit, the dispersibility may be impaired during the preparation of the coating slurry. The higher the solubility of PVdF in the PVdF-soluble solvent, the better. However, no organic solvent exceeding the solubility of PVdF of 20% is found, and the upper limit of this solubility is usually 20% or less.

  In the present invention, the method for measuring the solubility of PVdF as an organic solvent is as follows.

(Measurement method of solubility)
20 g of PVdF and 100 g of organic solvent are stirred for 24 hours at room temperature, and the insoluble matter is fractionated on a filter by vacuum filtration. The weight of the filter is measured in advance, and the whole filter is subjected to ventilation drying at 120 ° C. for 3 hours and then weighed to obtain the insoluble matter weight. The initial PVdF weight (20 g) minus the insoluble content weight is the dissolved content weight, and the solubility is expressed as a ratio to the organic solvent weight (100 g).

Examples of such PVdF-soluble solvents include organic solvents with high polarity, and specific examples include the following.
N-methylpyrrolidone (NMP), dimethylformamide, dimethyl sulfoxide, γ-butyllactone (GBL), acetone, methyl ethyl ketone, acetylacetone, cyclohexanone, acetic anhydride, methyl acetate, methyl acrylate, dimethyl carbonate, γ-propiolactone, dimethyl Among acetamide, hexamethylphosphoamide, diethyltriamine, tetrahydrofuran, dioxane, ethylene oxide, and propylene oxide, NMP is widely used when actually producing electrodes, and is preferable because it can be used as it is for producing electrodes.

  These PVdF-soluble solvents may be used alone or in combination of two or more.

  The purity of the PVdF-soluble solvent used is preferably as high as possible, and is preferably 95% by weight or more, particularly 97% by weight or more, and particularly preferably 98% by weight or more. In particular, the water concentration in the PVdF-soluble solvent is preferably kept low, as described above, due to the deterioration of the lithium transition metal composite oxide and the gelation of PVdF, and is preferably 1% or less, particularly 500 ppm or less, especially 300 ppm or less. It is preferable that Since it will be in contact with a strongly alkaline positive electrode material for a long time, there are some positive electrodes from which Li elutes if there is a large amount of moisture, and the PVdF solution gels due to Li elution, which is not preferable.

[Impregnation of PVdF soluble solvent into electrode material]
The lower limit of the weight ratio of the electrode material to the PVdF soluble solvent is usually 40:60, preferably 50:50, more preferably 60:40, and the upper limit is usually 99: 1, preferably 95: 5, more preferably 90. : 10. If this ratio is less than the above lower limit, the PVdF soluble solvent is larger than the electrode material. Therefore, separation and sedimentation of the electrode material in the PVdF soluble solvent is likely to occur. If the ratio exceeds the upper limit, the PVdF soluble solvent is present on the electrode material surface. Since there is a surface that does not adsorb, the effect of improving the dispersibility during preparation of the coating slurry and the effect of preventing lithium carbonation described above cannot be sufficiently obtained.

  The method for impregnating the electrode material with the PVdF soluble solvent is not particularly limited, and a predetermined amount of the PVdF soluble solvent may be added to the electrode material and mixed. Although there is no restriction | limiting in particular as the addition method of a PVdF soluble solvent, when there is little quantity of a PVdF soluble solvent with respect to an electrode material, it is easy to add the mist-like or droplet PVdF soluble solvent, stirring dry powder of an electrode material Can be mixed uniformly.

  There are no particular restrictions on the container used for impregnation, and a container for encapsulation at the time of product shipment may be used, and impregnation may be performed in this container. It may be put in a container. When the PVdF soluble solvent is mixed with the electrode material in a separate container and the slurry is put into the enclosure, the PVdF soluble solvent may be further added to the enclosure.

  For impregnation, a stirrer, a mixer, etc. are used, but the material is Teflon (trade name) or stainless steel coated with Teflon (trade name), iron, etc. It is preferred to use a constructed container.

  In the impregnation step, it is preferable to include a decompression step. That is, it is preferable to perform the impregnation treatment in a reduced pressure state because the PVdF-soluble solvent easily reaches every corner of the electrode material. In addition, when the pressure reduction process is performed and then the pressure is returned to normal pressure, it is possible to replace the inside pores of the electrode material with a solvent, and gas is generated from the electrode material when preparing the coating slurry. Can be prevented and has excellent defoaming properties. However, you may enclose with the gas suitable as atmospheric gas as it is, without a pressure reduction process. In this case, a certain amount of gas can be vented during storage and transportation. The impregnation-treated product without the decompression step may be put into the enclosure, and then the whole may be in a decompressed state. In this case, it is important to suppress the degree of vacuum so that the solvent does not volatilize.

[Other ingredients]
The electrode material composition for a lithium secondary battery according to the present invention may contain a binder and / or a conductive material in addition to an electrode material impregnated with a PVdF soluble solvent. That is, for example, a lithium transition metal composite oxide as a positive electrode active material (or a carbonaceous material as a negative electrode active material) is a positive electrode mixture (or negative electrode mixture) mixed with a binder and a conductive material. May be.

  As binders, resins such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, polymethyl methacrylate, polyethylene; rubbers such as styrene butadiene rubber, acrylonitrile butadiene rubber, ethylene propylene rubber, fluorine rubber; polyvinyl acetate, polyvinyl Examples thereof include polymer substances such as alcohol (PVA) and carboxymethyl cellulose (CMC). PVdF, polyvinyl acetate, and carboxymethyl cellulose (CMC) are preferable.

  Any conductive material known to be used in lithium secondary batteries can be used. For example, carbon black such as ketjen black and acetylene black, graphite and the like, preferably acetylene black can be used.

  When the binder and the conductive material are blended, the content ratio of the binder and the conductive material in the electrode material composition of the present invention is preferably a ratio suitable for the formation of the electrode active material layer. The ratio of the electrode material to the total of the material, the binder and the conductive material is usually 50% by weight or more, preferably 70% by weight or more, particularly preferably 80% by weight or more, and usually 98.9% by weight or less, preferably It is 97% by weight or less, particularly preferably 96% by weight or less. Below this lower limit, it is difficult to sufficiently secure battery characteristics such as the capacity of a battery manufactured using the same, and when exceeding the upper limit, mechanical strength as an electrode can be secured, and a good cycle life can be obtained. It will also be difficult.

  When a binder is blended, the binder is usually 0.1% by weight or more, preferably 3% by weight or more, particularly preferably 5% by weight, based on the total of the electrode material, binder and conductive material. These are usually 20% by weight or less, preferably 15% by weight or less, and particularly preferably 10% by weight or less. The ratio of the binder to the electrode material is usually 10% by weight or less, preferably 5% by weight or less, and usually 0.5% by weight or more. When the ratio of the binder is too small, it is difficult to ensure the mechanical strength as an electrode, and when it is too large, it is difficult to sufficiently secure battery characteristics such as battery capacity and conductivity.

  When a conductive material is blended, the conductive material is usually 1% by weight or more, preferably 2% by weight or more, particularly preferably 3% by weight or more based on the total of the electrode material, the binder and the conductive material. Usually, it is 20% by weight or less, preferably 10% by weight or less, particularly preferably 5% by weight or less. The ratio of the conductive material to the electrode material in the electrode material composition is usually 20% by weight or less, preferably 15% by weight or less, more preferably 10% by weight or less, and usually 0.5% by weight or more, preferably 1%. % By weight or more, more preferably 3% by weight or more, and particularly preferably 5% by weight or more. When the proportion of the conductive material is too small, it is difficult to obtain a good cycle life, and when it is too large, the battery capacity per volume tends to decrease.

  When a binder and a conductive material are blended in the electrode material composition, when the electrode material composition is prepared by impregnating the electrode material with a PVdF soluble solvent, these predetermined amounts may be added and mixed together. good. As described above, by mixing the binder and the conductive material in the electrode material composition, the step of mixing the binder and the conductive material when preparing the coating slurry can be omitted or simplified. In particular, by blending PVdF as a binder, or a polymer compound such as PVA or CMC, it is possible to improve the familiarity between the materials at the time of preparing the coating slurry and to improve the dispersibility. By making this binder the same type as the binder used when preparing the coating slurry, the dispersibility can be further improved. Note that a binder such as PVdF may be previously dissolved in a PVdF soluble solvent, and the impregnation treatment described above may be performed with a PVdF soluble solvent containing the binder.

[Encapsulated body of electrode material composition for lithium secondary battery]
Since the electrode material composition for a lithium secondary battery according to the present invention includes an organic solvent (dangerous material in the Fire Service Act), it is necessary to enclose it during storage and transportation.

  The encapsulant of the present invention formed by encapsulating the electrode material composition for a lithium secondary battery will be described below.

<Encapsulated container>
Examples of the enclosing container include an aluminum laminated bag, a stainless steel container, a plastic container, and a glass container. Among these, an aluminum laminated bag, a stainless steel container, and a plastic container are preferable in that they are not easily damaged. In the case of a stainless steel container, it is preferable that the inside is coated with a polymer having corrosion resistance to the PVdF soluble solvent according to the present invention, such as Teflon (trade name).

  There is no restriction | limiting in particular about the magnitude | size (capacity | capacitance) of an enclosure container, Usually, it is about 500mL-100L. The shape of the enclosing container is not particularly limited, but is preferably a self-supporting container such as a bottomed and covered cylinder or a rectangular tube container, and an aluminum-laminated bag is also preferable.

<Sealing method>
Although there is no restriction | limiting in particular also about the sealing method, It is preferable to employ | adopt the following methods according to enclosure containers.

  In the case of an aluminum laminated bag, the upper opening of the bag is fused with heat.

  Seal stainless steel cans with bottle caps. Alternatively, a pail-type drum can in which the lid and the main body are brought into close contact with a sealant (preferably made of polytetrafluoride) may be used.

  Seal the plastic container with a bottle cap. In the case of a plastic bottle or a stainless steel can, it may be further packed in an aluminum laminated bag.

  The degree of sealing is such that airtightness can be obtained, and the degree of airtightness is usually about 0.8 to 1.2 atm (0.08 to 0.12 MPa).

  As the pre-encapsulation treatment, the treatment may not be performed at normal pressure, or may be evacuated.

As the encapsulated gas species, inert gas, dry air, especially N ₂ gas is preferable because it is economical and does not contain oxygen, so that the safety during transportation of the PVdF soluble solvent is enhanced.

  As described above, the sealed gas pressure is about 0.8 to 1.2 atmospheres (0.08 to 0.12 MPa). Among these, normal pressure is preferable in terms of enhancing safety during transportation. In the case of an aluminum laminated bag, a slightly positive pressure is sufficient because it can be seen whether there is leakage from the atmosphere. A negative pressure is preferable because penetration of the PVdF soluble solvent into the pores in the particle of the electrode material proceeds and the defoaming property becomes even better.

  Regarding the enclosed atmosphere gas, it is particularly preferable to adopt the following conditions.

(Dew point)
The dew point is preferably −30 ° C. or lower. When the dew point exceeds −30 ° C., lithium carbonate is liable to occur particularly in a lithium transition metal composite oxide mediated by water, which is not preferable.

(Oxygen concentration)
The lower limit of the oxygen concentration is usually 1 ppm or more, preferably 10 ppm or more, and the upper limit is usually 1% or less. Below this lower limit, the economic merit is thin, and above the upper limit, the oxidation of the PVdF soluble solvent tends to proceed.

(Ozone concentration)
The lower limit of the ozone concentration is usually 1 ppm or more, preferably 10 ppm or more, and the upper limit is usually 100 ppm or less, preferably 80 ppm or less, more preferably 50 ppm or less. When this upper limit is exceeded, oxidation of the PVdF soluble solvent tends to proceed and the risk tends to increase.

(CO2 concentration)
In particular, in the case of a lithium transition metal composite oxide that requires low humidity and low carbonic acid concentration, the lower limit of the carbon dioxide concentration is usually 30 ppm or more, preferably 20 ppm or more, more preferably 10 ppm or more, and the upper limit is usually 200 ppm or less, preferably 150 ppm. Hereinafter, it is more preferably 100 ppm or less. If it is less than this lower limit, it is not economical in terms of purification of the enclosed gas, and if it exceeds the upper limit, carbonation of lithium in the lithium transition metal composite oxide tends to occur.

[Production of electrodes]
The electrode material composition for a lithium secondary battery encapsulated in the encapsulant of the electrode material composition for a lithium secondary battery according to the present invention is used as an electrode active material for producing an electrode for a lithium secondary battery.

  In this case, first, a binder, a conductive material, and further a necessary amount of a solvent are added to the electrode material composition for a lithium secondary battery taken out from the encapsulant of the present invention, and the mixture is stirred and mixed to prepare a coating slurry. To do. Here, when the electrode material composition contains a binder and / or a conductive material in advance, the addition of the binder and / or the conductive material is unnecessary or the amount added can be reduced. Further, when the amount of the PVdF soluble solvent contained in the electrode material composition is a sufficient amount as a solvent for preparing the coating slurry, the addition of the solvent is unnecessary. When the amount of the PVdF soluble solvent contained in the electrode material composition is insufficient as the amount of solvent for preparing the coating slurry, the insufficient amount of solvent may be added.

  What was mentioned above can be used as a binder and a electrically conductive material, and the mixing ratio with the electrode material is as having mentioned above as another compounding component of the electrode material composition of this invention.

  Here, as the solvent used for preparing the coating slurry, an organic solvent capable of dissolving or dispersing the binder is usually used. For example, ether solvents such as ethylene oxide and tetrahydrofuran; ketone solvents such as methyl ethyl ketone and cyclohexanone; ester solvents such as methyl acetate and methyl acrylate; amine solvents such as diethyltriamine and N, N-dimethylaminopropylamine; N -Aprotic polar solvents such as methylpyrrolidone, dimethylformamide and dimethylacetamide; and water, but not limited to these. These may be used alone or in a combination of two or more in any combination and ratio.

  The amount of solvent during preparation of the coating slurry varies depending on the amount of binder and conductive material added, but also includes the PVdF soluble solvent in the organic solvent composition and the solvent in the binder solution used as the binder. The total amount of the solvent is preferably 30% by weight or more, particularly 50% by weight or more, and 150% by weight or less, particularly 100% by weight or less, based on the electrode material. When the amount of the solvent is less than the above lower limit, a coating slurry having excellent coating properties cannot be obtained, and when it is more than the above upper limit, it takes a long time to dry after coating, which is not preferable in any case.

  The coated slurry thus obtained is applied to a current collector and dried, and if necessary, a consolidation process using a uniaxial press or a roll press is performed to form an electrode active material layer on the current collector to form lithium. A secondary battery electrode can be obtained.

  Examples of the material of the positive electrode current collector include aluminum, stainless steel, and nickel-plated steel. Among these, aluminum, particularly aluminum foil is preferable. The thickness of the positive electrode current collector is usually 1 μm or more, preferably 5 μm or more, and usually 1000 μm or less, preferably 500 μm or less, particularly preferably 100 μm or less.

  The thickness of the positive electrode active material layer formed on the positive electrode current collector is about 1 to 70 μm.

  As a material of the negative electrode current collector, a metal material such as copper, nickel, stainless steel, nickel-plated steel, or a carbon material such as carbon cloth or carbon paper is used. Among these, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, etc., and in the case of a carbon material, a carbon plate, a carbon thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are particularly preferred because they are currently used in industrialized products. In addition, you may form a thin film suitably in mesh shape. When a metal thin film is used as the negative electrode current collector, the preferred thickness range is the same as the range described above for the positive electrode current collector.

  The thickness of the negative electrode active material layer formed on the negative electrode current collector is usually 1 to 70 μm.

[Production of lithium secondary battery]
A lithium secondary battery can be suitably produced using the electrodes (positive electrode and negative electrode) produced by the above method.

  The lithium secondary battery includes a positive electrode capable of inserting and extracting lithium, a negative electrode capable of inserting and extracting lithium, and a nonaqueous electrolyte using a lithium salt as an electrolytic salt. Further, a separator for holding a nonaqueous electrolyte may be provided between the positive electrode and the negative electrode. In order to effectively prevent a short circuit due to contact between the positive electrode and the negative electrode, it is desirable to interpose a separator in this way.

  What was produced by the above-mentioned method about both a negative electrode and a positive electrode can also be used, and it is also possible to produce using the conventional electrode material for any one of a negative electrode and a positive electrode.

  As the electrolyte, for example, known organic electrolytes, polymer solid electrolytes, gel electrolytes, inorganic solid electrolytes, and the like can be used. Among them, organic electrolytes are preferable. The organic electrolytic solution is configured by dissolving a solute (electrolyte) in an organic solvent.

  Here, the type of the organic solvent is not particularly limited. For example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, chlorinated hydrocarbons, ethers, amines, esters, amides. A phosphoric acid ester compound or the like can be used. Typical examples are dimethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, vinylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 4-methyl-2-pentanone, 1,2-dimethoxyethane. 1,2-diethoxyethane, γ-butyrolactone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, benzonitrile, butyronitrile, valeronitrile 1,2-dichloroethane, dimethylformamide, dimethyl sulfoxide, trimethyl phosphate, triethyl phosphate and the like, and these can be used alone or in combination of two or more.

  The organic solvent described above preferably contains a high dielectric constant solvent in order to dissociate the electrolytic salt. Here, the high dielectric constant solvent means a compound having a relative dielectric constant of 20 or more at 25 ° C. Among the high dielectric constant solvents, it is preferable that ethylene carbonate, propylene carbonate, and compounds in which hydrogen atoms thereof are substituted with other elements such as halogen or alkyl groups are contained in the electrolytic solution. The proportion of the high dielectric constant solvent in the electrolytic solution is preferably 20% by weight or more, more preferably 30% by weight or more, and most preferably 40% by weight or more. If the content of the high dielectric constant solvent is less than the above range, desired battery characteristics may not be obtained.

The type of the electrolytic salt is not particularly limited, and any conventionally known solute can be used. Specific examples include LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCl, LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiN (SO ₂ CF ₃ ) _2. , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiN (SO ₃ CF ₃ ) _{2 and the} like. Any one of these electrolytic salts may be used alone, or two or more thereof may be used in any combination and ratio.

  Electrolytic salts such as lithium salts are usually contained in the electrolyte so as to be 0.5 mol / L or more, preferably 0.75 mol / L or more, usually 1.5 mol / L or less, preferably 1.25 mol / L or less. Let Even if this concentration is less than 0.5 mol / L or more than 1.5 mol / L, the electrical conductivity may be lowered, and the battery characteristics may be adversely affected.

It should be noted that the organic electrolyte solution is an additive that forms a good film that enables efficient charge and discharge of lithium ions on the negative electrode surface, such as gas such as CO ₂ , N ₂ O, CO, and SO ₂ and polysulfide S _x ^2−. May be added at an arbitrary ratio.

Even when a polymer solid electrolyte is used, the type thereof is not particularly limited, and any known crystalline / amorphous inorganic substance can be used as the solid electrolyte. Examples of the crystalline inorganic solid electrolyte include LiI, Li ₃ N, Li _{1 + x} J _x Ti _2-x (PO ₄ ) ₃ (J = Al, Sc, Y, La), Li _0.5-2x RE _{0. .5 + x} TiO ₃ (RE = La, Pr, Nd, Sm) and the like. Examples of the amorphous inorganic solid electrolyte include oxide glasses such as 4.9LiI-34.1Li ₂ O-61B ₂ O ₅ and 33.3Li ₂ O-66.7SiO ₂ . Any one of these may be used alone, or two or more may be used in any combination and ratio.

  When the above-described organic electrolyte is used as the electrolyte, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit between the electrodes. The material and shape of the separator are not particularly limited, but those that are stable with respect to the organic electrolyte used, have excellent liquid retention properties, and can reliably prevent short-circuiting between electrodes are preferable. Preferable examples include microporous films, sheets, nonwoven fabrics and the like made of various polymer materials. Specific examples of the polymer material include polyolefin polymers such as nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, and polybutene. In particular, from the viewpoint of chemical and electrochemical stability, which is an important factor for separators, polyolefin polymers are preferable. From the viewpoint of self-occluding temperature, which is one of the purposes of use of separators in batteries, polyethylene is preferred. Is particularly desirable.

  When using a separator made of polyethylene, it is preferable to use ultra-high molecular weight polyethylene from the viewpoint of maintaining high-temperature shape, and the lower limit of the molecular weight is preferably 500,000 or more, more preferably 1,000,000 or more, most preferably 1,500,000 or more. It is. On the other hand, the upper limit of the molecular weight is preferably 5 million or less, more preferably 4 million or less, and most preferably 3 million or less. This is because if the molecular weight is too large, the fluidity becomes too low, and the pores of the separator may not close when heated.

  The lithium secondary battery is manufactured by assembling the positive electrode, the negative electrode, the electrolyte, and the separator used as necessary into an appropriate shape. Furthermore, other components such as an outer case can be used as necessary.

  The shape of the lithium secondary battery is not particularly limited, and can be appropriately selected from various shapes generally employed according to the application. Examples of commonly used shapes include a cylinder type with a sheet electrode and separator in a spiral shape, a cylinder type with an inside-out structure combining a pellet electrode and a separator, and a coin type with stacked pellet electrodes and a separator. Can be mentioned. The method for assembling the battery is not particularly limited, and can be appropriately selected from various commonly used methods according to the shape of the target battery.

  EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of a following example, unless the summary is exceeded.

Example 1
35 g of NMP is added to 90 g of lithium nickel composite oxide (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) having a specific surface area of 1.0 m ² / g and a tap density of 1.6 g / cm ³ , and a lithium nickel composite The oxide is impregnated with NMP. This is sealed and held in a stainless steel can (Teflon inner flash) for one day and night in air at 0.5 atm, and the NMP impregnation proceeds sufficiently. This is taken out, 5 g of acetylene black and 40 g of PVdF (12 wt% NMP solution) are added as a conductive material, and after stirring and dispersing with a three-one motor, vacuum defoaming is performed for 5 minutes to obtain a coating slurry.

Comparative Example 1
Lithium nickel composite oxide (LiNi _1/3 Mn _1/3 Co _1/3 O having a specific surface area of 1.0 m ² / g and a tap density of 1.6 g / cm ³ that has been stored in an aluminum bag without solvent. ₂ ) Collect 90g. To this, 35 g of NMP, 5 g of acetylene black as a conductive material, and 40 g of PVdF (12 wt% NMP solution) are added, and after stirring and dispersing with a three-one motor, vacuum deaeration is performed for 5 minutes to obtain a coating slurry.

Example 2
30 g of NMP is added to 95 g of artificial graphite powder, and the graphite powder is impregnated with NMP. This is sealed and held in a stainless steel can (Teflon inner flash) for one day and night in air at 0.5 atm, and the NMP impregnation proceeds sufficiently. This is taken out, 40 g of PVdF (12 wt% NMP solution) and 20 g of NMP are added, and after stirring and dispersing with a three-one motor, vacuum defoaming is performed for 5 minutes to obtain a coating slurry.

The following are used as a current collector, and the coating slurry produced in Examples 1 and 2 and Comparative Example 1 is applied to form a coating film of an electrode active material.
Current collector used for coating slurry of Example 1 and Comparative Example 1: Aluminum expanded metal Current collector used for coating slurry of Example 2: Copper foil having a thickness of 18 μm

  The results shown in Table 1 are obtained when each coating slurry and the handling property, stability, coating property, and the like at the time of preparation thereof are evaluated by the following methods.

(Powder skipping)
When the coating slurry is prepared, “x” indicates that there is a problem of scattering of the powder of the electrode material, and “◯” indicates that there is no problem.

(Ease of dissemination)
When preparing a coating slurry, the electrode material is easy to disperse and easily disperse, “◯”, and the electrode material is difficult to disperse and does not disperse easily is “x”.

(Air barrier property)
Regarding the lithium nickel composite oxide, “○” means that contact with air during storage is suppressed and there is no problem of carbonation, and “x” means that a part of the lithium nickel composite oxide is carbonated.

(Reduction of coating slurry preparation time)
“◎” indicates that the electrode material is excellent in dispersibility and the preparation time is remarkably shortened, “◯” indicates that the preparation time is shortened, and “x” indicates that the preparation time is long.

(Stability)
“◯” indicates that the coating slurry is excellent in uniform dispersion stability and maintains a uniform dispersion state even after the preparation slurry has been prepared, and “×” indicates that the dispersibility decreases with time.

(Applicability)
The coating film formed by applying the coating slurry to the current collector is “O” if there is no foam repelling or undispersed crushing and excellent film uniformity. The case where there is a pulverized dispersion and the film is inferior in uniformity is indicated as “x”.

  The electrode material composition for a lithium secondary battery encapsulated in the encapsulant according to the present invention and the electrode material dispersion for the lithium secondary battery using the same are capable of producing a high-performance electrode with high productivity. In addition, it can be effectively used for the production of electrodes for lithium secondary batteries such as portable devices such as notebook computers and mobile phones, and its industrial value is extremely large.

Claims (9)

  A lithium secondary battery electrode material composition comprising an electrode material composition for lithium secondary battery impregnated with an organic solvent having a solubility of polyvinylidene fluoride of 3% or more in an electrode material for a lithium secondary battery. An enclosure of an electrode material composition.   The encapsulated body of an electrode material composition for a lithium secondary battery according to claim 1, wherein the electrode material for a lithium secondary battery is a lithium transition metal composite oxide.   The encapsulated body of an electrode material composition for a lithium secondary battery according to claim 1, wherein the electrode material for a lithium secondary battery is a negative electrode material for a lithium secondary battery.   The encapsulant of an electrode material composition for a lithium secondary battery according to claim 3, wherein the negative electrode material for a lithium secondary battery is a carbonaceous material.   The electrode for a lithium secondary battery according to any one of claims 1 to 4, wherein a weight ratio of the electrode material for the lithium secondary battery and the organic solvent is 40:60 to 99: 1. Inclusion body of material composition.   The encapsulated body of an electrode material composition for a lithium secondary battery according to any one of claims 1 to 5, wherein the organic solvent is N-methylpyrrolidone.   An electrode material for a lithium secondary battery in which an electrode material composition for a lithium secondary battery obtained by impregnating an organic solvent having a solubility of polyvinylidene fluoride of 3% or more into an electrode material for a lithium secondary battery is encapsulated A method for producing an inclusion body of a composition.   A lithium secondary battery electrode material composition obtained by impregnating a lithium secondary battery electrode material with an organic solvent having a polyvinylidene fluoride solubility of 3% or more is stored in the form of an enclosure. A storage method for an electrode material composition for a secondary battery.   An electrode material dispersion for forming an electrode active material layer on a current collector by applying and drying the current collector for producing a lithium secondary battery electrode, comprising: An electrode material dispersion for a lithium secondary battery, comprising at least polyvinylidene fluoride as a binder mixed with the electrode material composition for a lithium secondary battery sealed in the enclosure according to item 1. .