JP2003151555A - Coating composite for negative electrode, negative- electrode board, its manufacturing method, and non- aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composite, which can form a negative-electrode active-material layer, in which exfoliation of the active material layer by the pressing face cannot occur easily at press processing, while excelling in flexibility and adhesion, the negative-electrode board using the coating composite concerned, the manufacturing method of the negative-electrode board concerned, and the non-aqueous electrolyte secondary battery using this negative-electrode board. SOLUTION: This coating composite for negative electrodes contains negative- electrode active material and a rubber system adhesion material whose glass transition temperature is 0 to 120 deg.C. By applying this coating composite for negative electrodes to a collector, and by manufacturing the negative-electrode board performing press processing, the secondary battery is assembled using the negative-electrode board concerned.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating material for forming a negative electrode active material layer of a non-aqueous electrolyte secondary battery typified by a lithium-ion secondary battery, and a negative electrode plate produced using the coating material. The present invention relates to a method for manufacturing the negative electrode plate and a non-aqueous electrolyte secondary battery incorporating the negative electrode plate.

[0002]

2. Description of the Related Art In recent years, electronic devices and communication devices have been rapidly reduced in size and weight, and secondary batteries used as power sources for driving these devices are also required to be reduced in size and weight. . Therefore, a non-aqueous electrolyte secondary battery having a high energy density and a high voltage, typically a lithium ion secondary battery, has been proposed in place of the conventional alkaline storage battery.

An electrode plate for a positive electrode (a positive electrode plate) of a non-aqueous electrolyte secondary battery uses a composite oxide such as lithium manganate or lithium cobalt oxide as a positive electrode active material, and uses such a positive electrode active material and a binder. (Binder) and suitable wetting agent (solvent)
It is prepared by dispersing or dissolving in a slurry to prepare a coating composition in the form of a slurry, and coating the coating composition on a current collector made of a metal foil to form a positive electrode active material layer.

On the other hand, the negative electrode plate (negative electrode plate) of the non-aqueous electrolyte secondary battery uses a carbonaceous material such as carbon capable of storing cations such as lithium ions released from the positive electrode active material layer during charging. Used as an active material, such a negative electrode active material and a binder (binder) are dispersed or dissolved in an appropriate wetting agent (solvent) to prepare a slurry coating composition, and the coating composition is prepared. It is prepared by coating on a current collector made of a metal foil to form a negative electrode active material layer.

Then, a terminal for taking out a current is attached to each of the positive electrode plate and the negative electrode plate, and a separator for preventing a short circuit is sandwiched between both electrode plates and wound up,
The secondary battery is assembled by sealing in a container filled with the non-aqueous electrolyte solution.

The binder for preparing the active material coating solution in the above-mentioned coating type electrode plate is chemically stable with respect to the non-aqueous electrolytic solution, does not elute into the electrolytic solution, and It must be one that can be dissolved in some solvent and can be applied thinly on a substrate.

Further, the coated and dried active material layer has flexibility so as not to cause peeling, falling off, cracking, etc. in the process of assembling the battery, and has good adhesiveness with the current collector. It is required to be excellent.

[0008] Further, when the coating type electrode plate is produced, in order to improve the adhesion, density, homogeneity and the like of the active material layer with respect to the current collector, the active material coating liquid is usually applied on the current collector. After forming a coating film by coating on, a press treatment is performed. However, when press processing such as roll press or sheet press (flat plate press) is performed, the coating film is taken off on the pressing surface, that is, a part of the coating film adheres to the pressing surface and peels off from the current collector. If they are taken off, product defects may occur. In particular, when a binder having high tackiness is used in order to form an active material layer having sufficient adhesion to the current collector while suppressing the amount of the binder to a small amount so as not to deteriorate the battery performance, However, the frequency of removal of the active material layer by the press surface during press working increases, resulting in a poor yield.

[0009]

SUMMARY OF THE INVENTION The present invention has been accomplished in view of the above circumstances, and a first object thereof is to have excellent flexibility and adhesion to a current collector, and to provide a press surface during press working. Another object of the present invention is to provide a coating composition capable of forming a negative electrode active material layer in which the removal of the active material layer by the method is difficult.

A second object of the present invention is to provide a negative electrode plate having an active material layer which has a good yield in the manufacturing process and is excellent in flexibility and adhesion.

A third object of the present invention is to provide a method for producing a negative electrode plate in which it is difficult for the active material layer to be removed by the pressing surface when the active material layer is pressed.

A fourth object of the present invention is to provide a non-aqueous electrolyte secondary battery assembled using the above negative electrode plate.

[0013]

First, a negative electrode active material layer coating composition according to the present invention (negative electrode coating composition) has at least a negative electrode active material and a glass transition temperature of 0 to 120 ° C.
It is characterized in that it contains the rubber binder.

Regarding the conditions under which the active material layer is removed by the pressing surface when the active material layer is pressed, the following condition 1 or condition 2 is considered to hold. -Condition 1: (cohesive force of active material layer) <(adhesive force between pressed surface and active material layer) -Condition 2: (adhesive force between active material layer and current collector)
<(Adhesive force between pressed surface and active material layer) Here, in order to simply increase the cohesive force of the active material layer and the adhesive force of the active material layer to the current collector, it is necessary to increase the amount of the binder. However, in that case, it is difficult to actually increase the amount of the binder because the battery performance is deteriorated and a trade-off between performance and workability is made.

Under these restrictions, in order to reduce the active material layer removal without increasing the amount of the binder, it is necessary to weaken the adhesive force between the pressing surface and the active material layer.

Here, paying attention to the glass transition temperature of the rubber resin, the rubber resin having a low glass transition temperature generally tends to have high adhesiveness and tackiness at room temperature. On the contrary, a rubber-based resin having a high glass transition temperature does not exhibit so much tackiness at room temperature.

Since the roll pressing is usually carried out at room temperature, if a material showing weak tackiness at room temperature is selected as the binder, the adhesive force between the pressing surface and the active material layer becomes weak and the active material layer is removed. It is possible to reduce the damage. In addition, the active material layer is at room temperature or higher (50 to 14
Since it is heated to 0 ° C), if a material showing sufficient adhesiveness and tackiness at that temperature is selected as the binder, the obtained active material layer will have sufficient cohesive force and adhesiveness with the current collector. To have.

In the step of forming the active material layer, the temperature conditions as described above are passed, so that the binder for the active material layer has sufficient adhesiveness and tackiness under the temperature conditions during coating and drying. It is considered that a binder having weak adhesiveness and tackiness should be used during press working. In the present invention, a rubber binder having a glass transition temperature of 0 to 120 ° C. is used as a material satisfying such requirements.

By using a rubber binder having a glass transition temperature of 0 to 120 ° C., the flexibility and the adhesion to the current collector are excellent, and the active material layer is removed by the pressing surface during pressing. Since it is possible to form a difficult negative electrode active material layer, it is possible to produce a high quality negative electrode plate in which the active material layer does not drop off or cracks during battery assembly or in a battery with a high yield.

The negative electrode coating composition according to the present invention contains 0.5% of the rubber binder based on the amount of components other than the solvent.
It is preferably contained in a proportion of from 10 to 10% by weight.

When a thickener is added to the negative electrode coating composition as a binder together with the rubber binder, the negative electrode coating composition is based on the amount of components other than the solvent. It is preferable that the rubber binder is contained in a proportion of 0.5 to 7% by weight, and the thickener is further contained in a proportion of 0.5 to 3% by weight.

Styrene-butadiene rubber is preferably used as the rubber-based binder.

Next, the negative electrode plate for a non-aqueous electrolyte secondary battery according to the present invention contains at least a negative electrode active material on a current collector and a rubber binder having a glass transition temperature of 0 to 120 ° C. The negative electrode active material layer is provided.

The above negative electrode plate according to the present invention is produced by using the above negative electrode coating composition, and is formed by bending the battery for assembling the battery or after loading the active material layer in the battery. A high-quality negative electrode plate that does not easily fall off or crack.

The mixing ratio of each component contained in the negative electrode active material layer of the negative electrode plate according to the present invention is the same as the mixing ratio of the coating composition for negative electrode based on the solid content.

The negative electrode plate according to the present invention can be pressed so that the negative electrode active material layer has a density of 1.5 g / cc or more.

Next, in the method for producing a negative electrode plate for a non-aqueous electrolyte secondary battery according to the present invention, at least a negative electrode active material provided on a current collector and a rubber-based material having a glass transition temperature of 0 to 120 ° C. It is characterized in that a negative electrode active material layer containing a binder is pressed.

Since the method for producing a negative electrode plate according to the present invention uses the negative electrode coating composition, it is difficult to cause the active material layer to be taken off by the pressed surface when the negative electrode active material is pressed, and the yield can be improved. it can.

It is preferable to perform roll pressing as the pressing. Further, it is preferable that the pressing temperature at the time of performing the pressing is room temperature.

Next, the non-aqueous electrolyte secondary battery according to the present invention is characterized by including the above-mentioned negative electrode plate for a non-aqueous electrolyte secondary battery according to the present invention. In this secondary battery, the active material layer of the negative electrode plate loaded inside is unlikely to drop off or crack, so it has excellent battery durability and should continue to exhibit high battery performance stably over a long period of time. You can

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Coating composition for negative electrode active material layer according to the present invention (hereinafter referred to as "negative electrode coating composition")
Is at least the negative electrode active material and has a glass transition temperature of 0.
It is characterized in that it contains a rubber binder at 120 ° C.

The negative electrode plate for a non-aqueous electrolyte secondary battery according to the present invention is produced by using the above-described coating composition for a negative electrode according to the present invention, and at least the negative electrode active material is provided on the current collector. It is characterized in that a negative electrode active material layer containing a substance and a rubber-based binder having a glass transition temperature of 0 to 120 ° C. is provided.

As the negative electrode active material blended in the negative electrode coating composition of the present invention, the materials conventionally used as the negative electrode active material of non-aqueous electrolyte secondary batteries can be used.
For example, a carbonaceous material such as natural graphite, artificial graphite, amorphous carbon, carbon black, or a material obtained by adding a different element to these components is preferably used. When the solvent is an organic solvent, a lithium-containing metal such as metallic lithium or a lithium alloy is preferably used.

The particle shape of the negative electrode active material is not particularly limited, but, for example, scaly, lumpy, fibrous, or spherical particles can be used. The negative electrode active material is preferably a powder having a particle size in the range of 1 to 100 μm and an average particle size of about 10 μm in order to uniformly disperse it in the coating layer. These negative electrode active materials may be used alone or in combination of two or more.

When it is necessary to reduce the resistance of the active material layer, a conductive agent may be mixed with the negative electrode active material. As the conductive agent, acetylene black, Ketjen black, or the like can be used.

The mixing ratio of the negative electrode active material in the coating composition is
It is usually 90 to 98.5% by weight when the compounding components excluding the solvent are used as the standard (based on the solid content). The above mixing ratio of the negative electrode active material is a ratio including the conductive agent when the conductive agent is used. The content of the conductive agent in the coating composition is 0.5 to 30% by weight based on the solid content.

The binder for forming the negative electrode active material into a film is
It is electrochemically stable to non-aqueous electrolyte solution, does not elute into the non-aqueous electrolyte solution, and is soluble or dispersible in any solvent so that it can be applied thinly on a current collector made of metal foil. is necessary. In the present invention, a glass transition temperature of 0 to 0 is particularly used as the binder of the negative electrode coating composition.
A rubber binder at 120 ° C, preferably 10 to 60 ° C is used.

Regarding the conditions under which the active material layer is removed by the pressing surface when the active material layer is pressed, the following condition 1 or condition 2 is considered to hold. -Condition 1: (cohesive force of active material layer) <(adhesive force between pressed surface and active material layer) -Condition 2: (adhesive force between active material layer and current collector) <(between pressed surface and active material layer) Adhesive force) Here, in order to simply increase the cohesive force of the active material layer and the adhesive force of the active material layer to the current collector, the amount of the binder may be increased. In reality, it is difficult to increase the amount of the binder because the performance deteriorates and there is a trade-off between performance and workability.

Under these restrictions, in order to reduce the amount of the active material layer taken up without increasing the amount of the binder, it is necessary to weaken the adhesive force between the pressing surface and the active material layer.

Here, paying attention to the glass transition temperature of the rubber resin, the rubber resin having a low glass transition temperature generally tends to have high adhesiveness and tackiness at room temperature. On the contrary, a rubber-based resin having a high glass transition temperature does not exhibit so much tackiness at room temperature.

Since the roll pressing is usually carried out at room temperature, if a material showing weak tackiness at room temperature is selected as the binder, the adhesive force between the pressing surface and the active material layer becomes weak, and the active material layer is removed. It is possible to reduce the damage. In addition, when the coating film of the active material layer is formed, the coating film is heated to room temperature or higher (50 to 140 ° C.) in a dry hood, and therefore, a material having sufficient adhesiveness and tackiness at that temperature is used as a binder. When selected as, the obtained active material layer has sufficient cohesive force and adhesiveness with the current collector.

In the step of forming the active material layer, the above-mentioned temperature conditions are passed. Therefore, the binder for the active material layer has sufficient adhesiveness and tackiness under the temperature conditions during coating and drying. It is considered that a binder having weak adhesiveness and tackiness should be used during press working. In the present invention, a rubber binder having a glass transition temperature of 0 to 120 ° C., preferably 10 to 60 ° C. is used as a material satisfying such requirements.

By using a rubber-based binder having a glass transition temperature of 0 to 120 ° C., preferably 10 to 60 ° C., the flexibility and the adhesion to the current collector are excellent, and the pressing surface is used during pressing. Since it is possible to form a negative electrode active material layer that is less likely to cause removal of the active material layer, it is possible to produce a high-quality negative electrode plate with less detachment or cracking of the active material layer during battery assembly or in the battery, with high yield. . If the glass transition temperature of the rubber-based binder is too high, the flexibility and adhesion of the active material layer tend to be poor, and if the glass transition temperature is too low, the active material layer adheres to the press surface during pressing. Becomes noticeable.

As the rubber-based binder having a glass transition temperature in the above range, a rubber composed of binary, ternary or higher components and derivatives thereof can be used. Specifically, styrene butadiene rubber (SBR), high styrene rubber (HSR), ethylene propylene rubber (EPD)
M), butyl rubber (IIR), chloroprene rubber (C
R), butadiene rubber (BR), isoprene rubber (I
R) and silicone rubber can be exemplified. Specific examples of the rubber derivative include carboxy-modified ones of the above-mentioned rubbers, hydrogenated ones and ones into which 2-vinylpyridine is introduced.

The rubber-based binder may be synthesized by any of emulsion polymerization, solution polymerization and bulk polymerization. Particularly, as an aqueous emulsifiable binder, SBR can be used.
In the case of, the copolymerization ratio of styrene is 5 to 70% by weight, H
In the case of SR, it is preferable to use one having a styrene copolymerization ratio of 70 to 95% by weight.

Among these, styrene-butadiene rubber has necessary and sufficient solvent resistance, flexibility and adhesion,
In addition, since an aqueous emulsion is available at a relatively low cost, it is advantageous in terms of cost.

The negative electrode coating composition of the present invention contains the above-mentioned rubber-based binder in order to improve the binding property of the active material layer.
It is preferable to add a thickener as a part of the binder. Specific examples of the thickener include ammonium salt and sodium salt of carboxymethyl cellulose (CMC), or
Examples thereof include polyvinylpyrrolidone.

Other binders can be added to the negative electrode coating composition of the present invention, if necessary, within the range in which the object of the present invention can be achieved. Examples of such other binders include thermoplastic resins, more specifically, polyester resins, polyamide resins, polyacrylic acid ester resins, polycarbonate resins, polyurethane resins, cellulose resins, polyolefin resins, polyvinyl resins, and fluorine. A system resin or a polyimide resin can be used. In addition, a thermosetting resin such as an acrylic resin or a urethane resin, an ionizing radiation curable resin made of an acrylate monomer, an acrylate oligomer or a mixture thereof, or a mixture of the above various resins can be used.

The compounding ratio of the rubber binder in the coating composition is usually 0.5 to 10% by weight, preferably 2 to 4% by weight, based on the solid content. When using a thickener, 0.5 to 7% by weight of a rubber-based binder and 0.5 to 3% by weight of a thickener on the basis of solid content should be added to the coating composition. Is preferred. If the amount of the thickening agent is too small, the binding property of the negative electrode active material layer will be poor, and if it is too large, the thickening agent will wrap around the surface of the active material particles and the battery performance will deteriorate. Further, since the thickener has a solubility in water of only a few percent, if the amount of the thickener is too large, a large amount of water must be added to dissolve the thickener, and the solid content of the coating composition. The concentration will decrease significantly, and the load during coating and drying will increase.

As a solvent for preparing the negative electrode coating composition, an organic solvent such as N-methyl-2-pyrrolidone, toluene, methyl ethyl ketone or a mixture thereof may be used, but water is particularly used as a solvent. At the same time, an aqueous emulsion coating liquid can be prepared by selecting a rubber-based binder capable of colloidally dispersing in water. When water is used, ion-exchanged water is usually used to prevent the influence of impurities.

When an aqueous emulsion coating solution is prepared, the negative electrode coating composition may be repelled on the surface of the current collector depending on the material of the current collector and the components blended in the negative electrode coating composition.
The coating film may have a pinhole-like or crater-like surface quality defect, which may adversely affect the battery characteristics. In order to prevent such poor surface quality, a small amount of a solvent, such as isopropyl alcohol (IPA), which is infinitely miscible with water and has a function of lowering the surface tension, may be added to the coating composition. The addition amount of the solvent for reducing the surface tension may be several percent, and if it is too much, the dispersion stability of the coating composition will be impaired.

The ratio of the solvent in the coating composition is usually 30.
-60% by weight, preferably 45-55% by weight, and the coating solution is prepared as a slurry. When the solvent other than the main solvent, for example, a solvent that lowers the surface tension is used, the above ratio of the solvent is a ratio including such other solvent.

The coating composition for the negative electrode active material layer is prepared by adding an appropriately selected negative electrode active material, a rubber binder, and other compounding ingredients to a suitable solvent, and then homogenizing, ball milling, sand milling, roll milling or planetary. A slurry can be prepared by mixing and dispersing with a disperser such as a mixer. Further, the coating composition for a negative electrode active material layer of an aqueous emulsion,
A rubber-based binder and, if necessary, other binder such as a thickener are emulsified using a solvent mainly composed of water, and the obtained binder emulsion is used as a negative electrode active material and other components. It can be prepared by putting it together with an appropriate solvent and mixing and dispersing with the above dispersing machine.

The negative electrode coating composition thus prepared is applied to one or both sides of a current collector as a substrate and dried to form a negative electrode active material layer. As the collector of the negative electrode plate,
A copper foil such as an electrolytic copper foil or a rolled copper foil is preferably used. The thickness of the current collector is usually about 5 to 50 μm.

The method of applying the coating composition for the negative electrode is not particularly limited, but a method capable of forming a thick coating layer such as slide die coating, comma direct coating, comma reverse coating, etc. is suitable. However, when the thickness required for the active material layer is relatively thin, it may be applied by gravure coating, gravure reverse coating, or the like.
The active material layer may be formed by repeating coating and drying a plurality of times.

When a part of the surface of the current collector is exposed to connect the terminal to the negative electrode plate, an intermittent die coat or an area of the surface of the current collector to be exposed (the area to be the non-coated portion) is used. The die head may be controlled by a method such as intermittent comma reverse coating to form a portion where the coating composition is not applied. Alternatively, after coating a region of the current collector surface to be exposed (a region to be a non-coated portion) with a masking tape or a coating film having poor adhesion, the negative electrode coating composition is applied to the entire surface of the current collector and dried. Then, a part of the current collector can be exposed by peeling off the masking tape or the coating film from it. Alternatively, after coating the negative electrode coating composition on the entire surface of the current collector and drying the active material layer to form an active material layer, an active material layer such as wax or thermoplastic resin is formed on the active material layer in the region to be the non-coated portion. It is also possible to expose a part of the current collector by impregnating with a component that increases the cohesive force and selectively peeling off the impregnated portion.

As the heat source in the drying step, hot air, infrared rays, microwaves, high frequencies, or a combination thereof can be used. In the drying step, a metal roller or a metal sheet that supports or presses the current collector may be heated and dried by the heat emitted. In addition, the active material layer can be obtained by subjecting the binder to a crosslinking reaction by irradiating with an electron beam or radiation after drying. The coating and drying may be repeated multiple times.

By pressing the obtained negative electrode active material layer, the density of the active material layer, the adhesion to the current collector, and the homogeneity can be improved.

The press working is performed by using, for example, a metal roll, an elastic roll, a heating roll, a sheet press machine or the like. In the present invention, the pressing temperature may be room temperature or may be warmed as long as it is lower than the temperature at which the coating film of the active material layer is dried. As a guide, the temperature is 15 to 35 ° C.).

The roll press is preferable because a long sheet negative electrode plate can be continuously pressed. When performing roll pressing, either stereotactic pressing or constant pressure pressing may be performed. Line speed of press is usually 5 to 50 m / m
in. And When the pressure of the roll press is controlled by the linear pressure, it is adjusted according to the diameter of the pressure roll, but the linear pressure is usually 0.5 kgf / cm to 1 tf / cm.

When a sheet press is performed, it is usually
4903 to 73550 N / cm ² (500 to 7500k
gf / cm ² ), preferably 29420 to 49033N
The pressure is adjusted within the range of / cm ² (3000 to 5000 kgf / cm ² ). If the pressing pressure is too low, it is difficult to obtain homogeneity of the active material layer, and if the pressing pressure is too high, the electrode plate itself including the current collector may be damaged.
The active material layer may have a predetermined thickness with one press,
It may be pressed several times for the purpose of improving homogeneity.

The coating amount of the negative electrode active material layer is usually 20 to 25.
The thickness is 0 g / m ² , and the thickness is usually 1 after drying and pressing.
The range is 0 to 200 μm, preferably 50 to 170 μm. The density of the negative electrode active material layer is 1.0 g / cc after coating.
After pressing, it increases to 1.5 g / cc or more (usually about 1.5 to 1.75 g / cc). Therefore, it is possible to increase the capacity of the battery by performing the press working without any trouble and improving the volume energy density.

The negative electrode active material layer of the negative electrode plate according to the present invention thus obtained contains at least the negative electrode active material and a rubber binder having a glass transition temperature of 0 to 120 ° C., and if necessary, further. The composition ratio of each component contained in the active material layer after drying is the same as the composition ratio based on the solid content of the negative electrode coating composition. Is.

When a secondary battery is manufactured using the negative electrode plate according to the present invention, in order to remove water in the active material layer before proceeding to the battery assembling process, heat treatment or decompression is performed in a vacuum oven or the like. Aging such as treatment is preferably performed in advance.

The volume energy density of the battery is usually calculated based on the whole including the positive electrode, the negative electrode, the separator, the outer can, etc., but the volume energy density limited to the negative electrode active material layer is calculated as follows for reference. Is.

(Condition 1) The coating film density is 1.70 g / cc,
98% by weight of active material, negative electrode discharge capacity of 340 mA
In case of h / g: 1.70 (g / cc) × 0.98 × 340 (mAh /
g) = 566.44 (mAh / cc) (Condition 2) When the coating film density is 1.40 g / cc, the ratio of the active material is 98% by weight, and the negative electrode discharge capacity is 340 mAh / g: 1.40 (g / cc) x 0.98 x 340 (mAh /
g) = 466.48 (mAh / cc) Thus, the negative electrode plate for a non-aqueous electrolyte solution secondary battery according to the present invention is obtained, and this negative electrode plate is combined with a positive electrode plate to form a non-aqueous electrolyte solution secondary battery. Can be made.

The electrode plate for a positive electrode (positive electrode plate) is prepared by applying a coating composition containing a positive electrode active material to a current collector to form a positive electrode active material layer. Examples of the positive electrode active material include LiMn ₂ O ₄ (lithium manganate) and L
iCoO ₂ (lithium cobalt oxide) or LiNiO ₂
Lithium oxide such as (lithium nickelate), or T
Examples are chalcogen compounds such as iS ₂ , MnO ₂ , MoO _{3 and} V ₂ O ₅ . In particular, LiCoO ₂
Is used as the positive electrode active material and the carbonaceous material is used as the negative electrode active material, a lithium secondary battery having a high discharge voltage of about 4 V can be obtained.

The positive electrode active material is preferably a powder having a particle size in the range of 1 to 100 μm and an average particle size of about 10 μm in order to uniformly disperse it in the coating layer. These positive electrode active materials may be used alone or in combination of two or more.

The binder for the positive electrode active material has been conventionally used, for example, thermoplastic resin, more specifically, polyester resin, polyamide resin, polyacrylic ester resin, polycarbonate resin, polyurethane resin, cellulose. Resin, polyolefin resin, polyvinyl resin, fluorine resin, polyimide resin or the like can be used. At this time, it is also possible to mix an acrylate monomer or oligomer into which a reactive functional group has been introduced into the binder. Besides, rubber-based resin,
It is also possible to use a thermosetting resin such as an acrylic resin or a urethane resin, an ionizing radiation curable resin made of an acrylate monomer, an acrylate oligomer or a mixture thereof, or a mixture of the above various resins.

As the conductive agent, for example, graphite,
A carbonaceous material such as carbon black or acetylene black is used if necessary.

Solvents for preparing the positive electrode coating composition include toluene, methyl ethyl ketone and N-methyl-2-
Organic solvents such as pyrrolidone or mixtures thereof can be used.

The positive electrode coating composition is prepared by mixing the above-mentioned positive electrode active material, a binder and, if necessary, other components into a solvent and preparing the above-mentioned negative electrode coating composition. It can be mixed and dispersed in the same manner as described above to prepare a slurry.

The mixing ratio at this time is 100 for the whole coating liquid.
The total amount of the positive electrode active material and the binder is about 40 when it is expressed as parts by weight.
It is preferable that the amount is -80 parts by weight. Further, the compounding ratio of the positive electrode active material and the binder may be the same as the conventional one, for example, positive electrode active material: binder = 5: 5 to 9: 1 (weight ratio).
It is preferably about the same.

Using the obtained positive electrode coating composition, coating on a current collector in the same manner as in the case of producing the negative electrode plate described above,
A positive electrode plate can be produced by drying. The thickness of the positive electrode active material layer is usually 10 to 20 after drying and pressing.
The range is 0 μm, preferably 50 to 170 μm. Usually, an aluminum foil having a thickness of about 5 to 30 μm is preferably used as the collector of the positive electrode plate.

The positive electrode plate and the negative electrode plate produced by the above method are spirally wound with a separator such as a polyethylene porous film interposed therebetween and inserted into an outer container. After the insertion, connect the terminal connection part of the positive electrode plate (exposed surface of the current collector) and the positive electrode terminal provided on the upper surface of the outer container with a lead, while connecting the terminal connection part of the negative electrode plate (exposed surface of the current collector). By connecting the negative electrode terminal provided on the bottom surface of the outer container with a lead, filling the outer container with a non-aqueous electrolyte, and sealing the container, a non-aqueous electrolyte secondary battery including the negative electrode plate according to the present invention is completed. .

When a lithium secondary battery is manufactured,
Non-aqueous electrolyte solution in which a solute, lithium salt, is dissolved in an organic solvent
Is used. Examples of the lithium salt include LiCl
O_Four, LiBF_Four, LiPF₆, LiAsF₆, LiC
1, an inorganic lithium salt such as LiBr, or LiB (C
₆H₅)_Four, LiN (SO_TwoCF_Three)_Two, LiC (SO
_TwoCF_Three)_Three, LiOSO_TwoCF_Three, LiOSO_TwoC_Two
F₅, LiOSO_TwoC _ThreeF₇, LiOSO_TwoC_FourF₉,
LiOSO_TwoC₅F₁₁, LiOSO_TwoC₆F _Thirteen, L
iOSO_TwoC₇F₁₅Such as organic lithium salts are used
It

Examples of the organic solvent for dissolving the lithium salt include cyclic esters, chain esters, cyclic ethers, chain ethers and the like. More specifically,
Examples of cyclic esters include propylene carbonate, butylene carbonate, γ-butyrolactone, vinylene carbonate, 2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone and γ-valerolactone.

Examples of chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl butyl carbonate, methyl propyl carbonate, ethyl butyl carbonate, ethyl propyl carbonate, butyl propyl carbonate, alkyl propionate. Examples thereof include esters, dialkyl malonates, alkyl acetates and the like.

Examples of cyclic ethers include tetrahydrofuran, alkyltetrahydrofuran, dialkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1,3-dioxolane, alkyl-1,3-dioxolane and 1,4-dioxolane.

Examples of chain ethers include 1,2-dimethoxyethane, 1,2-diethoxyethane, diethyl ether, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, tetraethylene glycol dialkyl ether, and the like. It can be illustrated.

[0081]

Example 1 As a carbonaceous material that is an active material, fibrous graphite (trade name: Melbronn Milled manufactured by Petka Materials Co., Ltd.) and scale-like artificial graphite (manufactured by Petka Materials Co., Ltd.) are used. ) Was mixed at a ratio of 10% by weight. A 1% aqueous solution of CMC (trade name Serogen EP) as a binder and SBR emulsion (# 0597c manufactured by JSR Co., Ltd., Tg = 28) on the active material
C) was mixed and kneaded to obtain a slurry negative electrode coating composition. Active material layer / CMC / SBR weight ratio is 98/1 /
It was set to 1.

This negative electrode coating composition was applied on a copper foil as a current collector by the comma direct method so that the coating amount was about 100 g / m ² , dried, and then linear pressure was applied by a roll press machine. When pressed at 0.4 to 0.6 tf / cm, a uniform negative electrode active material layer having a density of 1.68 to 1.72 g / cc could be formed without the active material layer adhering to the pressing surface of the roll.

Example 2 Flake graphite (manufactured by TIMCAL) was used as the carbonaceous material for the active material layer. A 1% aqueous solution of CMC (trade name Serogen EP) and a SBR emulsion (# 0850 manufactured by JSR Co., Ltd., Tg = 7 ° C.) are mixed and kneaded to this active material as a binder, and used as a slurry negative electrode. A coating composition was obtained. Active material layer / C
The weight ratio of MC / SBR was 98/1/1.

This negative electrode coating composition was applied on a copper foil as a current collector by the comma direct method so that the coating amount was about 100 g / m ² , dried, and then linear pressure was applied by a roll press machine. When pressed at 0.4 to 0.6 tf / cm, a uniform negative electrode active material layer having a density of 1.68 to 1.72 g / cc could be formed without the active material layer adhering to the pressing surface of the roll.

(Comparative Example 1) The same procedure as in Example 1 was carried out except that the SBR emulsion in Example 1 was replaced with a grade having a low Tg (trade name: BM-400B manufactured by Nippon Zeon Co., Ltd., Tg = -5 ° C). A slurry-like negative electrode coating composition was obtained. This negative electrode coating composition was applied onto a current collector in the same manner as in Example 1, dried and roll-pressed. When a density of 1.72 g / cc was applied, intermittent activity by the press surface was observed. Since the material layer was removed, the press work could not be performed stably. Coating density is 1.50 g / cc
It was not possible to prevent the active material layer from being removed even when the roll was pressed down and rolled.

(Evaluation of Charge / Discharge Performance) A coin type cell was assembled using the negative electrode plate obtained in each of the examples and comparative examples, and charge / discharge evaluation was performed. As the negative electrode plate of the comparative example, a portion where no active material layer was taken was used. The discharge capacity in the first cycle of each assembled coin-type cell was about 338 mAh /
g, and no difference in capacity decrease due to the difference in SBR was observed.

[0087]

As described above, the coating composition for a negative electrode according to the present invention contains a rubber binder having a glass transition temperature of 0 to 120 ° C., and therefore has flexibility and a good collecting property. It is possible to form a negative electrode active material layer that has excellent adhesion to the electric body and is less likely to cause the active material layer to be taken off by the pressing surface during press working, and the active material layer can be removed or cracked during battery assembly or in the battery. It is possible to produce a high-quality negative electrode plate having a small number of defects with a high yield.

Further, the negative electrode plate according to the present invention is produced by using the above-mentioned negative electrode coating composition, and the active material layer is formed at the time of bending for assembling the battery or after being loaded into the battery. It is a high-quality negative electrode plate that does not easily fall off or crack.

Further, since the method for producing a negative electrode plate according to the present invention uses the above-mentioned negative electrode coating composition, it is difficult to cause the active material layer to be taken off by the pressed surface when the negative electrode active material is pressed, and the yield is improved. You can

Further, in the non-aqueous electrolyte secondary battery according to the present invention, the negative electrode plate loaded inside is unlikely to cause the active material layer to fall off or crack, so that the battery has excellent durability and high battery performance. It can continue to exert its stability for a long time.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshio Tamaki             Stock exchange, 4 Towada, Kamisu-cho, Kashima-gun, Ibaraki             Company Petka Materials (72) Inventor Tadafumi Shindo             1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo             Dai Nippon Printing Co., Ltd. (72) Inventor Yuichi Miyazaki             1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo             Dai Nippon Printing Co., Ltd. F term (reference) 5H029 AJ14 AK02 AK03 AK05 AL06                       AL07 AL08 AM02 AM03 AM04                       AM05 AM07 CJ03 DJ08 EJ12                       HJ01 HJ08 HJ14                 5H050 AA19 BA17 CA07 CA08 CA09                       CA11 CB07 CB08 CB09 DA11                       EA23 GA03 HA01 HA08 HA14

Claims (13)

[Claims] 1. A coating composition for a negative electrode active material layer, comprising at least a negative electrode active material and a rubber binder having a glass transition temperature of 0 to 120 ° C. 2. The coating for a negative electrode active material layer according to claim 1, wherein the rubber binder is contained in a proportion of 0.5 to 10% by weight based on the amount of components other than the solvent. Engineering composition. 3. The rubber binder is contained in a proportion of 0.5 to 7% by weight based on the amount of components other than the solvent, and
The coating composition for a negative electrode active material layer according to claim 2, further comprising a thickener in a proportion of 0.5 to 3% by weight. 4. The negative electrode active material layer coating composition according to claim 1, wherein the rubber-based binder is styrene-butadiene rubber. 5. A non-aqueous, characterized in that a negative electrode active material layer containing at least a negative electrode active material and a rubber binder having a glass transition temperature of 0 to 120 ° C. is provided on a current collector. Negative electrode plate for electrolyte secondary battery. 6. The non-aqueous electrolyte secondary battery according to claim 5, wherein the negative electrode active material layer contains the rubber binder in a proportion of 0.5 to 10% by weight. Negative electrode plate. 7. The negative electrode active material layer contains the rubber-based binder in a proportion of 0.5 to 7% by weight and further contains a thickener in a proportion of 0.5 to 3% by weight. A negative electrode plate for a non-aqueous electrolyte secondary battery according to claim 6. 8. The negative electrode plate for a non-aqueous electrolyte secondary battery according to claim 5, wherein the rubber-based binder is styrene-butadiene rubber. 9. The density of the negative electrode active material layer is 1.5 g /
It is cc or more, The negative electrode plate for non-aqueous electrolyte secondary batteries in any one of Claims 5 thru | or 8 characterized by the above-mentioned. 10. The negative electrode active material layer, which is provided on the current collector and contains at least the negative electrode active material and a rubber-based binder having a glass transition temperature of 0 to 120 ° C., is pressed. A method for manufacturing a negative electrode plate for a non-aqueous electrolyte secondary battery. 11. The method for producing a negative electrode plate for a non-aqueous electrolyte secondary battery according to claim 10, wherein roll pressing is performed as the pressing. 12. The method for producing a negative electrode plate for a non-aqueous electrolyte secondary battery according to claim 10, wherein the pressing temperature is room temperature. 13. A non-aqueous electrolyte secondary battery comprising the negative electrode plate for a non-aqueous electrolyte secondary battery according to claim 5.