JP2006107779A - Manufacturing method of electrode plate, and electrode plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrode plate capable of forming the electrode which is a thinly coated activator layer with excellent surface quality, having high uniformity of film thickness, high conductivity, and high safety, as well as an electrode plate suited for high-output use, and a nonaqueous electrolyte solution secondary battery. <P>SOLUTION: A coating composition for an activator layer of which, a maximum particle size (D<SB>90</SB>) of activator contained therein is less than a gap (G) between a tip of a die head (1a) and a coating face of a collector (A), and less than a target thickness (T2) of the activator layer after a pressing process; and at the same time, a central particle size (D<SB>50</SB>) is not more than a half of the target thickness of the active material layer after the pressing process; is used for the electrode plate. A solid portion of a coating volume of the coating composition of the activator is made 110g/m<SP>2</SP>or less in case of a cathode, and 40g/m<SP>2</SP>or less in case of an anode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for producing an electrode plate used as a positive electrode and / or a negative electrode of a nonaqueous electrolyte liquid secondary battery or an electric double layer capacitor typified by a lithium ion secondary battery.
The present invention also relates to an electrode plate, particularly preferably an electrode plate manufactured by the above manufacturing method, and a non-aqueous electrolyte liquid secondary battery incorporating the electrode plate.

In recent years, electronic devices and communication devices are rapidly becoming smaller and lighter, and secondary batteries used as power sources for driving these devices are also required to be smaller and lighter. For this reason, a non-aqueous electrolyte secondary battery, typically a lithium ion secondary battery, having a high energy density and a high voltage has been proposed in place of the conventional alkaline storage battery.
In general, electrode plates such as non-aqueous electrolyte liquid secondary batteries and electric double layer capacitors have a configuration in which an electrode active material layer is intermittently provided in a predetermined pattern on at least one surface of a current collector. The non-coated portion where the electrode active material layer pattern does not exist is a portion where the current collector is exposed for the purpose of attaching a terminal or the like.

  The electrode plate is usually prepared by preparing a slurry of a mixture of active material particles having an average particle diameter of several μm to several tens of μm and a binder, and applying the slurry onto a current collector such as a metal foil. Forming, drying (coating process), if necessary, pressing the current collector on which the active material layer is formed (pressing process), cutting the pressed current collector to a predetermined width as necessary (Slit process), and further, it is manufactured by cutting to a predetermined length as necessary (cutting process).

  In the above coating process, an intermittent application method in which a coated part coated with the active material layer coating composition and an uncoated non-coated part are sequentially formed, or the coated part is applied to a current collector wider than the coated width. A continuous coating method is widely used in which a non-coated portion is formed outside the coated portion. In general, intermittent coating or continuous coating is performed by a method such as comma reverse, comma direct, or die coating.

  In recent years, so-called thin-coated electrodes with a reduced amount of active material per unit area have been widely studied as batteries for high-power applications such as automobiles. Thin-coated electrodes are made by spreading the active material layer widely and thinly to reduce the battery resistance and increase the effective area of the electrode plate, so that large power can be taken out. The amount of active material per unit area is Less than the active material layer having a thickness of.

However, if the coating amount of the active material layer coating composition is reduced to form a thin active material layer, the distance between the tip of the coating head (discharge hole) such as a die head and the coated surface of the current collector is limited. Even if it approaches, the coating surface becomes rough. In this case, so-called raw fabric cutting (a phenomenon in which a long current collector is cut while traveling on the conveyance path) is also likely to occur on the coating line.
In addition, when an intermediate product of an electrode plate coated with a thin coating composition for the active material layer is pressed, large particle components protrude from the coating surface, so that the film thickness after pressing becomes uniform. Difficult to damage the press roll.

If the active material layer after pressing has a non-uniform film thickness or an electrode plate with a rough film surface is laminated or rolled together with a separator and incorporated into a battery, it will not fit within a prescribed size or will tend to cause a soft short. There is also a problem.
Furthermore, when the active material layer is formed thin, the active material particles contained in the active material layer are difficult to be distributed in the thickness direction (depth direction) of the active material layer, and the surface of the current collector Since the tendency to be distributed in the form of a single-layer film along the direction is increased, the probability that the active material particles are in contact with each other is low, and the conductivity tends to be low. In addition, when the active material layer is formed thin, a portion where the current collector is exposed between particles in the coating part may occur, and in such an exposed part in the coating part, precipitation of dendrites easily occurs, May interfere with safety.

The present invention has been achieved in view of the above-mentioned actual situation, and the first object thereof is a so-called thin-coated active material layer having good surface quality, high uniformity of film thickness, conductivity, An object of the present invention is to provide a suitable manufacturing method of an electrode plate capable of forming a highly safe one.
In addition, the second object of the present invention is to have a thin-coated active material layer with good surface quality, high uniformity of film thickness, and high conductivity and safety, preferably by the production method of the present invention. The object is to provide a manufactured electrode plate.
A third object of the present invention is to provide a non-aqueous electrolyte liquid secondary battery suitable for high power applications using the electrode plate.

The method for producing an electrode plate provided by the present invention comprises a step of coating an active material layer coating composition containing at least an active material on a current collector to form an active material layer, and the active material A method for producing at least one of a positive electrode and a negative electrode plate, comprising a step of pressing an electrode plate intermediate product on which a layer is formed,
The maximum particle size (D ₉₀ ) of the active material in the coating composition for active material layer is less than the gap between the coating head tip and the current collector coating surface during coating, and the active material after press working An active material layer coating composition having a thickness less than the target thickness of the material layer and a center particle size (D ₅₀ ) of the active material being ½ or less of the target thickness of the active material layer after press working Use
On the current collector, the active material layer coating composition is applied at a solid content coating amount per unit area of 110 g / m ² or less for the positive electrode and 40 g / m ² or less for the negative electrode. It is characterized by that.

In the manufacturing method, the largest value among the maximum particle diameters (D ₉₀ ) for each type of particle component contained in the active material layer coating composition and / or the center for each type of particle component It is preferable that the particle size (D ₅₀ ) having the largest value satisfies the size requirements for the active material.

The ratio of the active material to the entire solid content contained in the active material layer coating composition is preferably 80% by mass or more.
In the production method, the target thickness of the active material layer after press working is preferably 70 μm or less for the positive electrode and 50 μm or less for the negative electrode.

Next, the electrode plate provided by the present invention is an electrode plate provided with an active material layer containing at least an active material on a current collector,
The solid content coating amount per unit area of the active material layer is 110 g / m ² or less in the case of the positive electrode and 40 g / m ² or less in the case of the negative electrode.
The maximum particle size (D ₉₀ ) of the active material in the active material layer is less than the thickness of the active material layer, and the center particle size (D ₅₀ ) of the active material in the active material layer is It is characterized by being not more than one half of the thickness.

In the electrode plate, the largest particle size (D ₉₀ ) for each type of particle component contained in the active material layer and / or the center particle size (D ₅₀₎ for each type of particle component. ) Having the largest value preferably satisfies the size requirements for the active material.
The ratio of the active material contained in the active material layer is preferably 80% by mass or more.
The thickness of the active material layer in the electrode plate is preferably 70 μm or less for the positive electrode and 50 μm or less for the negative electrode.

According to the present invention, even when the active material layer is formed thin by using the active material in the coating composition for the active material layer that has a maximum particle size and a center particle size within the above-mentioned size range. Since the large-diameter particles do not protrude from the film surface of the active material layer, an active material layer having a uniform coating film surface and high film thickness is formed.
Therefore, it is possible to prevent accidents during the manufacturing process such as raw material breakage on the coating line and damage to the press roll, and accidents during use such as soft shorts in the battery.
When the active material layer is formed thin by using the active material whose center particle diameter (D ₅₀ ) is less than half the target thickness of the active material layer after press working. However, the particles of the active material contained in the active material layer are easily distributed not only along the surface direction of the current collector but also in the thickness direction of the active material layer.

Accordingly, the probability that the active material particles come into contact with each other in the active material layer is increased, and high conductivity and safety can be ensured. Therefore, the resistance of the battery is reduced, which is advantageous for taking out large electric power.
Therefore, according to the present invention, an electrode plate suitable for high power use having a thin active material layer with good surface quality, high film thickness uniformity, high conductivity, and high safety, and a non-aqueous electrolyte solution A secondary battery is provided.

The method for producing an electrode plate provided by the present invention comprises a step of coating an active material layer coating composition containing at least an active material on a current collector to form an active material layer, and the active material A method for producing at least one of a positive electrode and a negative electrode plate, comprising a step of pressing an electrode plate intermediate product on which a layer is formed,
The maximum particle size ( _D90 ) of the active material in the active material layer coating composition is less than the gap between the coating head tip (discharge hole) and the current collector coating surface, and the active material after press working Use is made of a coating composition for an active material layer that is less than the target thickness of the layer and has a center particle size (D ₅₀ ) of the active material that is less than or equal to half the target thickness of the active material layer after press working ,
On the current collector, the active material layer coating composition is applied at a solid content coating amount per unit area of 110 g / m ² or less for the positive electrode and 40 g / m ² or less for the negative electrode. It is characterized by this.

(Coating composition for active material layer)
The active material layer coating composition used in the present invention usually contains at least a binder (binder) together with the active material and, if necessary, other components such as a conductive material.
As the active material, materials conventionally known as active materials for non-aqueous electrolyte liquid secondary batteries, electric double layer capacitors and the like can be used. Two or more active materials may be used in combination.
As the positive electrode active material of the nonaqueous electrolyte secondary battery, for example, lithium oxide such as LiCoO ₂ (lithium cobaltate), LiMn ₂ O ₄ (lithium manganate) or LiNiO ₂ (lithium nickelate), or Examples include chalcogen compounds such as TiS ₂ , MnO ₂ , MoO ₃ or V ₂ O ₅ . In particular, by using LiCoO ₂ or LiMn ₂ O ₄ as the positive electrode active material and using the carbonaceous material as the negative electrode active material, a lithium secondary battery having a high discharge voltage of about 4 volts can be obtained.

On the other hand, as the negative electrode active material of the nonaqueous electrolyte secondary battery, for example, natural graphite, artificial graphite, amorphous carbon, carbon black, acetylene black, or a carbonaceous material obtained by adding a different element to these components Is preferred. When the solvent is organic, a lithium-containing metal such as metallic lithium or a lithium alloy is preferably used.
As an active material of the electric double layer capacitor, for example, activated carbon or metal oxide can be used.

As a binder, what is conventionally known, for example, an electrode plate for a non-aqueous electrolyte secondary battery, a thermoplastic resin, more specifically, a polyester resin, a polyamide resin, a polyacrylate resin, A polycarbonate resin, a polyurethane resin, a cellulose resin, a polyolefin resin, a polyvinyl resin, a fluorine resin, a polyimide resin, or the like can be used.
At this time, an acrylate monomer or oligomer into which a reactive functional group is introduced can be mixed in the binder. In addition, thermosetting resins such as rubber resins, cellulose resins, acrylic resins, urethane resins, ionizing radiation curable resins composed of acrylate monomers, acrylate oligomers or mixtures thereof, and mixtures of the above various resins are used. You can also
Two or more binders may be used in combination.

  A conductive material may be added to the active material layer coating composition. As the conductive material, for example, in the case of an electrode plate for a non-aqueous electrolyte liquid secondary battery, a carbonaceous material such as graphite, carbon black, or acetylene black is used as necessary. Two or more kinds of conductive materials may be used in combination.

As a solvent for preparing the active material layer coating composition, for example, an organic solvent such as toluene, methyl ethyl ketone, N-methyl-2-pyrrolidone, or a mixture thereof, or water can be used.
The above active material layer, binder, and other components as required are charged into a solvent, and dissolved or dispersed by a disperser such as a homogenizer, ball mill, sand mill, or roll mill, to obtain a slurry-like active material A layer coating composition is prepared.
The content ratio of the active material contained in the active material layer coating composition is not particularly limited, but from the viewpoint of obtaining a sufficient battery capacity, the mass ratio in the solid content is 80% by mass or more, particularly 90% by mass or more. It is preferable that In addition, when the content ratio of the active material is too large, the amount of the binder is relatively small, and the adhesiveness of the active material layer is likely to be insufficient. Therefore, the active material contained in the active material layer coating composition Is preferably 99.5% by mass or less, more preferably 98.5% by mass or less in terms of mass ratio in the solid content.
Moreover, if the content rate of the electrically conductive material in the coating composition for active material layers is an electrode board for nonaqueous electrolyte liquid secondary batteries, for example, it is 1.5-10 in mass ratio in solid content normally. Weight%.
Here, the “solid content” is all components other than the solvent contained in the coating composition for active material layer, and the coating composition contains, for example, a curable liquid monomer component. In such a case, such a liquid component is also included in the solid content.
Moreover, in this invention, the mass ratio of the active material in solid content contained in the coating composition for active material layers can be considered as the content rate of the active material in the completed active material layer.

In the present invention, in order to form a thin active material layer of good quality, the particle size of the particle component in the active material layer coating composition is selected.
Specifically, as the active material in the active material layer coating composition, the maximum particle size (D ₉₀ ) is the gap between the tip of a coating head such as a die head and the current collector coating surface (in FIG. 1). And the center particle diameter (D ₅₀ ) of the active material after the press working is the target thickness of the active material layer after the press working. An active material that is less than or equal to one-half of the thickness (the thickness represented by T2 in FIG. 2), more preferably less than or equal to two-fifth, particularly preferably less than or equal to one-third. Use active material.

Here, the particle size of the active material layer and other particle components in the coating composition has the meaning described in JIS Z8901, and the measurement method includes the light mentioned in the JIS Z8901. Various methods such as a scattering method can be applied.
Further, in the present invention, the “maximum particle size (D ₉₀ )” of the particle is a particle when the proportion of particles having a particle size smaller than a certain particle size Dn in the particle size distribution reaches 90% by mass of the total powder. It means the diameter Dn.

Further, in the present invention, the “center particle size (D ₅₀ )” of the particle is a particle when the proportion of particles having a particle size smaller than a certain particle size Dn in the particle size distribution reaches 50% by mass of the total powder. It means the diameter Dn.

The active material layer is thinly formed by using the active material in the coating composition for the active material layer having the maximum particle size (D ₉₀ ) and the center particle size (D ₅₀ ) within the above-mentioned size range. Even in such a case, since the large-diameter particles do not protrude from the film surface of the active material layer, an active material layer having a uniform coating film surface and high film thickness is formed.
Therefore, it is possible to prevent accidents during the manufacturing process such as raw material breakage on the coating line and damage to the press roll, and accidents during use such as soft shorts in the battery.

Moreover, even when the active material layer is formed thin by using the active material whose center particle diameter (D ₅₀ ) is one half or less of the target thickness of the active material layer after press working, The particles of the active material contained in the active material layer are not only distributed along the surface direction of the current collector, but also easily distributed in the thickness direction of the active material layer.
Therefore, the probability that the active material particles come into contact with each other in the active material layer is increased, and high conductivity and safety can be ensured. Therefore, the resistance of the battery is reduced, which is advantageous for taking out large electric power.

From the viewpoint of achieving the object of the present invention, the smaller the maximum particle size and the center particle size of the active material, the better. However, the particle size of the active material that can be actually obtained, and the active material in the coating composition Considering the problem of aggregation, it is preferable in practice to use a particle having a particle size of a certain level or more.
From such a viewpoint, the size of the active material used in the present invention is generally in the range of about 0.1 to 25 μm, preferably 0.2 to 10 μm, more preferably when expressed in terms of average particle diameter. Is 0.5-4 μm.

Since the particle component in the coating composition for the active material layer is mainly the active material, in the present invention, the maximum particle diameter and the center particle diameter of the active material only need to satisfy the conditions within the above-described size range. However, when the active material layer coating composition contains two or more kinds of active materials, or when it contains a particle component other than the active material, the active material layer coating composition contains The largest value among the maximum particle diameters (D ₉₀ ) specified for each type of particle component included, and the center specified for each type of particle component included in the active material layer coating composition It is particularly preferable that the largest value among the particle diameters (D ₅₀ ) satisfies the size condition required for the above active material.

That is, when the active material layer coating composition contains two or more kinds of active materials, or when it contains a particle component in addition to the active material, the active material layer coating composition contains The largest value of the maximum particle size (D ₉₀ ) specified for each type of particle component contained is less than the gap between the coating head tip and the current collector coating surface, and the active material after press working It is preferably less than the target thickness of the layer.
Moreover, when the active material layer coating composition contains two or more types of active materials, or when it contains a particle component in addition to the active material, the active material layer coating composition contains those of the largest value among the median particle size specified for each type of particle component (D ₅₀₎ contained is preferably less than one-half of the target thickness of the active material layer after pressing.
In this case, it is particularly preferable that the average particle size specified for each type of particle component contained in the active material layer coating composition satisfies the size requirements for the active material described above. .

In addition, when the active material layer coating composition contains two or more kinds of active materials, or when it contains particle components in addition to the active materials, the particle size distribution of all the particle components including the active materials It is preferable that the maximum particle size (D ₉₀ ) and / or the center particle size (D ₅₀ ) specified from the above satisfy the size requirements for the active material described above.
In that case, it is particularly preferable that the average particle size of all the particle components also satisfies the size requirements for the active material described above.

(Current collector)
In this invention, the metal foil and metal sheet which are conventionally used as a collector of an electrode plate can be used. In general, an aluminum foil is preferably used as the current collector of the positive electrode plate. On the other hand, as the current collector for the negative electrode plate, a copper foil such as an electrolytic copper foil or a rolled copper foil is usually preferably used.
The thickness of the current collector is usually about 5 to 50 μm, for example, in the case of an electrode plate for a nonaqueous electrolyte secondary battery.

(Manufacture of electrode plates)
In the electrode plate manufacturing method of the present invention, the active material layer-forming coating composition is applied to the surface of the current collector from the tip of the coating head while the current collector travels and passes through the position of the coating head of the coating machine by the conveying means. The active material layer is formed by applying and intermittently applying and intermittently discharging and stopping as necessary, and then the active material layer is pressed to manufacture an electrode plate. In general, a long current collector is used as the current collector, and intermittent or non-glare coating is continuously performed on the running current collector by a die coater.

In the present invention, particularly in order to produce a thin electrode plate, the coating amount of the active material layer coating composition is limited to a small amount. The specific coating amount is appropriately determined according to the design of the battery, and is not particularly limited. However, in the case of the positive electrode, the coating composition for the active material layer and one side of the completed active material layer are usually The solid content coating amount per unit area is preferably 110 g / m ² or less, more preferably 100 g / m ² or less. On the other hand, in the case of the negative electrode, the coating amount for the active material layer and the solid material coating amount per unit area of the finished active material layer are usually 40 g / m ² or less, and further 35 g / m. It is preferable to set it to ² or less.
Moreover, the lower limit of the coating amount of the active material layer coating composition or the finished active material layer is not particularly limited, but in practice, the solid content coating amount per side / unit area is usually 3 g / m ^2. That's it.

From the viewpoint of a thin-coated electrode plate, the target thickness of the active material layer after press working and the thickness of the completed active material layer are preferably 70 μm or less in the case of the positive electrode, and 50 μm or less in the case of the negative electrode. It is preferable that
Further, the lower limit of the target thickness and the thickness after completion of the active material layer is usually 3 μm or more in practice.

  FIG. 1 shows a schematic configuration of an example of a coating apparatus (coating apparatus 101) for carrying out the electrode plate manufacturing method according to the present invention. FIG. 2 shows a schematic configuration of an example of a press apparatus (press apparatus 102) for carrying out the electrode plate manufacturing method according to the present invention.

In FIG. 1, the coating apparatus 101 includes at least a conveying unit that conveys a current collector A that is an object to be coated, a die coater 1 that is a coating unit, and a drying unit 2.
A conveyance means is a means for supplying and winding up the electrical power collector A for various processes. In the example of FIG. 1, a supply unit 4 to which an electrode plate supply roll 3 is attached, a winding unit 6 to which an electrode plate take-up roll 5 is attached, a guide roller 7 that supports a current collector A that moves on a conveyance path, The conveying means is constituted by other members as necessary.

The current collector A is fed out from the electrode plate supply roll 3, travels on the conveyance path, and reaches the die coater 1. The die coater 1 discharges the active material layer coating composition, which is a coating material, from the die head 1a, and intermittently coats the traveling current collector A so that the active material layer B is present. C and the non-coating part D are formed in a predetermined pattern.
The gap (distance) G between the tip of the die head 1a and the current collector coating surface is appropriately determined according to the coating amount of the coating film. The thickness is about 100 μm.
The intermittently coated current collector A is further transported by the transport means, reaches the drying means 2, and is also dried while traveling. As a heat source in the drying process, hot air, infrared rays, far infrared rays, microwaves, high frequencies, or a combination thereof can be used. You may dry with the heat which discharge | released the metal roller and metal sheet which support or press a collector in a drying process.
After drying, the intermediate product E of the electrode plate that has been coated is wound around the electrode plate winding roll 5 by the winding unit 6.

In FIG. 2, the press device 102 includes a transport unit that transports the intermediate product E of the electrode plate, and a pair of press rolls 8 (8 a and 8 b) that are press units.
The conveying means of the press apparatus 102 is the same as that of the coating apparatus 101, and is represented by a common symbol in the drawing. The press roll 8 has an upper roll 8a and an under roll 8b, and at least one of them is rotationally driven in accordance with the conveyance speed of the intermediate product E by a motor (not shown). As the press roll, various rolls such as a metal roll, an elastic roll or a heating roll are used in appropriate combination. Moreover, as a press means other than the press roll, for example, a sheet press machine or the like may be used.

The intermediate product E is unwound from the electrode plate supply roll 3, travels on the conveyance path, passes through a pair of press rolls 8 and is pressed to form an electrode plate F having an active material layer completed, and the winding unit 6. Is wound on the electrode plate winding roll 5. By this pressing, the thickness T2 of the active material layer after pressing becomes thinner than the thickness T1 before pressing, and the density of the active material layer, the adhesion to the current collector, and the homogeneity can be improved.
In the example of FIG. 2, pressing is performed on a line different from the coating process, but the pressing may be performed continuously from the coating process in the coating apparatus 101 of FIG. 1. In that case, a pressing means (not shown) is provided on the downstream side of the drying means 2, and after the coating, drying and pressing are all performed, the winding roll 5 is wound.

Thus, the electrode plate for positive electrodes or negative electrodes according to the present invention is obtained. The electrode plate of the present invention is either a positive electrode or a negative electrode plate in which an active material layer containing at least an active material is provided on one side or both sides of a current collector,
The solid content coating amount per unit area of the active material layer is 110 g / m ² or less in the case of the positive electrode and 40 g / m ² or less in the case of the negative electrode.
The maximum particle size (D ₉₀ ) of the active material in the active material layer is less than the thickness of the active material layer, and the center particle size (D ₅₀ ) of the active material in the active material layer is The thickness is less than or equal to one half of the thickness.

Example 1
MCMB (mesocarbon microbeads) was used as the negative electrode active material, PVDF (polyvinylidene fluoride) was used as the binder, and a slurry for negative electrode having a solid content of 50% by mass was prepared by a conventional method. A 14 μm rolled copper foil was used as a current collector.
MCMB having a particle diameter of 20 μm or more was separated and removed in advance, and the average particle diameter after separation and removal (in this case, the central particle diameter) was 6 μm.
The negative electrode slurry was applied on a current collector with a die coater so that the coating amount after drying was 30 g / m ² and dried to obtain an intermediate product of an electrode plate. At this time, the distance between the tip of the die head and the current collector surface was 70 μm. This coating process could be performed without any trouble.
Next, the intermediate product of the electrode plate was pressed so that the thickness of the active material layer was 25 μm. This pressing process could be performed without any trouble.

(Example 2)
A positive electrode slurry having a solid content of 70% by mass was prepared by a conventional method using lithium cobaltate as a positive electrode active material, acetylene black as a conductive material, and PVDF as a binder. Also, a 15 μm aluminum foil was used as a current collector.
The lithium cobalt oxide having a particle size of 25 μm or more was separated and removed in advance, and the average particle size after separation and removal (in this case, the central particle size) was 5 μm.
The positive electrode slurry was applied on a current collector with a die coater so that the coating amount after drying was 100 g / m ² and dried to obtain an intermediate product of an electrode plate. At this time, the distance between the tip of the die head and the current collector surface was 70 μm. This coating process could be performed without any trouble.
Next, the intermediate product of the electrode plate was pressed so that the thickness of the active material layer was 34 μm. This pressing process could be performed without any trouble.

(Comparative Example 1)
MCMB was used as the negative electrode active material, PVDF was used as the binder, and a negative electrode slurry having a solid content of 50% by mass was prepared by a conventional method. A 14 μm rolled copper foil was used as a current collector. MCMB having a maximum particle size of 80 μm and an average particle size of 6 μm was used.
The negative electrode slurry was applied on a current collector with a die coater so that the coating amount after drying was 30 g / m ² and dried to obtain an intermediate product of an electrode plate. At this time, the distance between the tip of the die head and the current collector surface was 80 μm.
In this comparative example, streaks frequently occurred on the film surface of the coating film in the coating step.

(Comparative Example 2)
A positive electrode slurry having a solid content of 50% by mass was prepared by a conventional method using lithium cobaltate as a positive electrode active material, acetylene black as a conductive material, and PVDF as a binder. Also, a 15 μm aluminum foil was used as a current collector. A lithium cobalt oxide having a maximum particle size of 100 μm and an average particle size of 5 μm was used.
The positive electrode slurry was applied on a current collector with a die coater so that the coating amount after drying was 100 g / m ² and dried to obtain an intermediate product of an electrode plate. At this time, the distance between the tip of the die head and the current collector surface was 70 μm. In this coating process, some streaks occurred on the film surface of the coating film.
Next, the intermediate product of the electrode plate was pressed so that the thickness of the active material layer was 34 μm. In this pressing step, a glossy granular lump appeared and an embossed mark was left on the press roll. Further, the obtained coating film was not uniform, and portions having a thickness of about 100 μm were observed in some places.

It is a figure which shows typically schematic structure of an example of the coating apparatus which can implement the manufacturing method of the electrode plate which concerns on this invention. It is a figure which shows typically schematic structure of an example of the press apparatus which can implement the manufacturing method of the electrode plate which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101: Coating apparatus 102: Press apparatus A: Current collector B: Coating layer or active material layer C: Coating part D: Non-coating part E: Intermediate product of electrode plate F: Electrode plate 1: Die coater 1a: Die head 2: Drying means 3: Electrode plate supply roll 4: Supply section 5: Electrode plate winding roll 6: Winding section 7: Guide roller 8 (8a, 8b): Press roll

Claims (11)

A step of coating an active material layer coating composition containing at least an active material on a current collector to form an active material layer; and an electrode plate intermediate product on which the active material layer is formed is pressed. A method for producing at least one of a positive electrode and a negative electrode plate, comprising:
The maximum particle size (D ₉₀ ) of the active material in the coating composition for active material layer is less than the gap between the coating head tip and the current collector coating surface during coating, and the active material after press working An active material layer coating composition having a thickness less than the target thickness of the material layer and a center particle size (D ₅₀ ) of the active material being ½ or less of the target thickness of the active material layer after press working Use
On the current collector, the active material layer coating composition is applied at a solid content coating amount per unit area of 110 g / m ² or less for the positive electrode and 40 g / m ² or less for the negative electrode. A method for manufacturing an electrode plate. Of the maximum particle size (D ₉₀ ) for each type of particle component contained in the active material layer coating composition, the largest value is less than the gap between the coating head tip and the current collector coating surface And the manufacturing method of the electrode plate of Claim 1 which is less than the target thickness of the active material layer after press work. The largest value of the center particle diameter (D ₅₀ ) for each type of particle component contained in the active material layer coating composition is one half of the target thickness of the active material layer after press working. The manufacturing method of the electrode plate of Claim 1 or 2 which is the following.   The manufacturing method of the electrode plate in any one of Claims 1 thru | or 3 whose ratio of the active material which occupies for the whole solid content contained in the said coating composition for active material layers is 80 mass% or more.   The method for producing an electrode plate according to any one of claims 1 to 4, wherein the target thickness of the active material layer after press working is 70 µm or less for a positive electrode and 50 µm or less for a negative electrode. An electrode plate provided with an active material layer containing at least an active material on a current collector,
The solid content coating amount per unit area of the active material layer is 110 g / m ² or less in the case of the positive electrode and 40 g / m ² or less in the case of the negative electrode.
The maximum particle size (D ₉₀ ) of the active material in the active material layer is less than the thickness of the active material layer, and the center particle size (D ₅₀ ) of the active material in the active material layer is An electrode plate having a thickness of half or less. The electrode plate according to claim 6, wherein the largest value among the maximum particle diameters (D ₉₀ ) for each kind of particle component contained in the active material layer is less than the thickness of the active material layer. The center particle diameter (D ₅₀ ) for each type of particle component contained in the active material layer has the largest value that is not more than one half of the thickness of the active material layer. The electrode plate as described.   The electrode plate according to claim 6, wherein a ratio of the active material contained in the active material layer is 80% by mass or more.   10. The electrode plate according to claim 6, wherein the active material layer has a thickness of 70 μm or less in the case of a positive electrode and 50 μm or less in the case of a negative electrode.   A non-aqueous electrolyte secondary battery comprising the electrode plate according to claim 6.

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