JP2015023058A - Electrode sheet and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a novel electrode sheet in which dispersibility of an active material in the electrode sheet is improved and the control of the dispersibility of the active material is easily performed.SOLUTION: There is disclosed a method of producing an electrode sheet in which a final raw material to be used when a molded sheet is molded is prepared as follows. This final material contains a fine raw material obtained through: a first kneading step for kneading an initial raw material to obtain a first kneaded body; a first crumbing step for crumbing the first kneaded body into fine pieces; a second kneading step for kneading the fine raw material obtained by the first crumbing step to form a second kneaded body; and a second crumbing step for crumbing the second kneaded body into fine pieces.

Description

  The present invention relates to an improvement in an electrode sheet and a manufacturing method thereof. This electrode sheet is used for electric double layer capacitors, secondary batteries and the like.

In the production of electrode sheets, the use of organic solvents is being restricted in consideration of the influence on the environment. An example of a method for producing such an electrode sheet is shown in Patent Document 1.
First, a powdery active material and a conductive additive are mixed to obtain a first mixture. Water and a binder are added to the first mixture and mixed to obtain an initial raw material.
This initial raw material is roll-rolled to form a kneaded sheet. The raw material is kneaded and rolled by roll rolling and shaped into a sheet. The kneaded sheet is loosened and refined. The obtained fine raw material is used as a final stage raw material (final raw material) for forming a molded sheet, and this is roll-rolled to form a molded sheet. This molded sheet is shaped, laminated with a metal foil, and further dried to form an electrode sheet.
The degree of kneading with respect to the raw material is increased by once loosening and kneading the kneaded sheet obtained by roll rolling and then rolling the obtained fine raw material again. When the degree of kneading increases, the lump of the active material is further densified (miniaturized) and uniformly dispersed in the raw material.
Furthermore, if the degree of kneading with respect to the raw material increases, the integrated value of the shearing force applied to the binder in the raw material (the magnitude of the shearing force × time) increases, so that the fiberization is promoted to increase the viscosity. . Thereby, the mechanical strength of the molded sheet itself is increased, and the active materials are more strongly bonded to each other in the molded sheet, and the dispersion state (dense and uniform dispersion) of the active materials is stabilized.
An electrode sheet using a molded sheet in which the active material is densified and uniformly dispersed, that is, having excellent dispersibility of the active material, has improved electrical characteristics. For example, when used as an electrode of a capacitor, its electrostatic capacity (Per unit volume) is improved.

On the other hand, when the porosity is seen as a characteristic of the electrode sheet itself, according to Patent Document 2, it is preferable that the ratio of the voids on the surface of the electrode sheet is 15 to 20 area%.
In addition, please refer to Patent Documents 3 to 5 that introduce technologies related to the present invention.

JP 2011-18687 A JP 2007-53278 A JP 2006-332438 A JP 2007-258611 A JP 2002-353076 A

According to the manufacturing method described in Patent Document 1, the active material is densified to some extent and uniformly dispersed in the electrode sheet.
However, more recent capacitors are required to have a larger capacitance, and the electrode sheet obtained by the manufacturing method described in Patent Document 1 may not be able to meet the requirements sufficiently.
Accordingly, an object of the present invention is to provide a novel method for producing an electrode sheet that can easily improve the dispersibility of the active material in the electrode sheet and control it.
Another object is to provide a novel electrode sheet obtained by the novel production method.

Patent Document 1 suggests that increasing the degree of kneading of the raw material improves the dispersibility of the active material in the molded sheet, thereby improving the electrical characteristics such as the capacitance of the electrode sheet.
Therefore, the present inventors further roll-rolled the fine raw material obtained by loosening the kneaded sheet described in Patent Document 1 to form a kneaded sheet, and again loosen and refined the obtained kneaded sheet. I tried to make a molded sheet using. The electrode sheet using the molded sheet thus obtained has more excellent electrical characteristics.

The present invention has been completed based on the above-mentioned new findings by the present inventors. That is, the first aspect of the present invention is defined as follows.
A final raw material production step for producing a final raw material;
A method for producing an electrode sheet comprising a molded sheet production step of kneading and rolling a final raw material to produce a molded sheet,
In the final raw material produced in the final raw material production step,
A first kneading step of kneading the initial raw material to obtain a first kneaded body;
A first unraveling step of unraveling the first kneaded body and refining;
A second kneading step of kneading the fine raw material obtained in the first unraveling step to form a second kneaded body;
A second unraveling step of unraveling the second kneaded body and refining;
The manufacturing method of an electrode sheet in which the fine raw material obtained through this is contained.

According to the 1st aspect of this invention prescribed | regulated in this way, the degree of the kneading | mixing with respect to a raw material improves by performing a 2nd kneading | mixing step. As a result, the dispersibility of the active material in the molded sheet is improved, and the electrical characteristics of the electrode sheet using the molded sheet are improved.
The kneading method and conditions in each kneading step and the shape of the kneaded body to be obtained can be arbitrarily set.
As a kneading apparatus for executing the kneading step, a kneader type kneader can be used in addition to the roll rolling machine introduced in the embodiments.
Here, in the second kneading step, the kneader used in the first kneading step can be diverted, and also in the second unraveling step, the unraveling device used in the first unraveling step can be diverted. No burden is required. That is, an increase in manufacturing cost can be suppressed.

  In the above, the fine raw material contained in the final raw material should just pass the 2nd loosening step. In other words, the fine raw material obtained in the n-th (where n is an integer equal to or greater than 2) loosening step is contained in the final raw material. Of course, together with the fine raw material obtained in the n-th unraveling step, any one of the previous-stage unraveling steps (the n−1,..., The n−k unraveling step, where n−k ≧ 2). Or a fine raw material obtained in a plurality of steps.

Until now, there has been no electrode sheet manufacturing method and electrode sheet using final raw materials composed of a plurality of types of fine raw materials having different degrees of kneading.
As described above, the fine raw material obtained in the different stages of the unraveling step, that is, the first final raw material and the second final raw material kneaded more strongly than the first final raw material can be used as the final raw material (second aspect). ).
By preparing a plurality of raw materials (first final raw material and second final raw material) having different degrees of kneading and controlling the mixing ratio thereof, the dispersibility of the active material in the molded sheet can be controlled more finely.
The degree of kneading is considered to be controllable by adjusting (A) kneading time, (B) kneading temperature, (C) kneading speed, (D) characteristics of fine raw materials, (E) unraveling conditions, etc. It is done. When a roll mill is employed as the kneading machine, (B) roll temperature as kneading temperature, (C) roll rotation speed as kneading speed, and (F) distance between rolls as pressure applied during kneading, etc. This is a parameter for adjusting the degree of kneading.

However, it is not easy to specifically relate the change of the single parameters (A) to (F) and the degree of kneading, and further, when there are a plurality of parameters, it is not possible to relate these changes and the degree of kneading. It is even more difficult.
On the other hand, if the kneading step and the unraveling step are controlled by the execution number n, the degree of kneading can be controlled very easily.
Therefore, the third aspect of the present invention is defined as follows. That is,
The first final raw material includes the fine raw material obtained in the n th unraveling step,
The second final raw material includes the fine raw material obtained in the (n + 1) th unraveling step,
In the above, n is an integer of 2 or more.
Thus, if the degree of kneading of the raw material of the molded sheet is controlled by adjusting the execution number n of the unraveling step after the kneading step, the control of the dispersibility of the active material in the molded sheet becomes simple.

When the degree of kneading with the raw material is increased, the dispersibility (densification and homogenization) of the active material in the molded sheet is improved.
On the other hand, when the number of executions n of the kneading step and the unraveling step exceeds a predetermined threshold value, that is, when the degree of kneading with respect to the raw material becomes excessive, in other words, the integral value of the shearing force applied to the raw material is predetermined. When the threshold value is exceeded, the fiberized binder is easily broken. In that case, not only the mechanical strength of the molded sheet is lowered (that is, it becomes brittle), but also the binding force to the active material that the binder should originally have is lowered, and the dispersion of bonding between the active materials occurs, resulting in dispersibility. Decreases.

As the second final raw material, the present inventors alone have an excessive degree of kneading, and the mechanical strength of the molded sheet obtained when subjected to a roll rolling machine for forming a molded sheet is weakened. I tried to adopt. Decreasing the mechanical strength of the molded sheet caused by adopting the second final raw material of excessive kneading can be reduced by the combined use of the first final raw material. On the other hand, the high dispersibility that cannot be achieved with only the first final raw material is excessive. It was thought that it could be carried by the kneaded second final raw material. That is, the fourth aspect of the present invention is defined as follows.
In the manufacturing method defined in the second or third aspect, the second final raw material is excessively kneaded, and the mechanical strength of the molded sheet obtained when the molded sheet manufacturing step is executed alone is insufficient. Shall be
The first final raw material alone can provide a molded sheet having sufficient mechanical strength when the molded sheet production step is executed.

As a result of searching for a suitable mixing ratio of the first final raw material and the second final raw material, the blending ratio of the second final raw material in the mixture of the first final raw material and the second final raw material excessively kneaded is 35% by mass or less. Then, high dispersibility of the active material could be obtained while ensuring sufficient mechanical strength for the molded sheet. That is, the fifth aspect of the present invention is defined as follows.
In the manufacturing method according to the fourth aspect, the blending ratio of the second final raw material in the mixture of the first final raw material and the second final raw material is 35% by mass or less.
A more preferable blending ratio is 25% by mass or less.

Regarding the first final raw material to be mixed with the second final raw material, the first final raw material is less kneaded than the second final raw material. When controlling the degree of kneading of the final raw material by controlling the number of executions n of the kneading step and the unraveling step, the n number of unraveling steps applied to the first final raw material is the unraveling step applied to the second final raw material. Smaller than the n number.
When the number n of the kneading step and the loosening step is 2 or more, the fine raw material (final raw material of the prior art) obtained in the first loosening step can be used in combination.
That is, the sixth aspect of the present invention is defined as follows.
In the manufacturing method according to any one of the first to fourth aspects, the final raw material contains the fine raw material obtained in the first unraveling step.

Generally, a side edge of a sheet obtained by rolling is easily cracked, and even in a molded sheet formed in the molded sheet manufacturing step, the side edge is often cracked. Therefore, both side edges are cut off and the remaining part is adopted as a true molded sheet. In other words, the side edge portion of the sheet produced in the molded sheet production step has been discarded.
When this side edge portion is seen as a supply source of the fine raw material, it can be said that it is kneaded more strongly than the n-th kneading sheet which is the supply source of the n-th fine raw material as the final raw material.
In this specification, the n-th kneading sheet refers to a kneading sheet obtained by kneading raw materials that have been kneaded (n-1) times, where n = 2 or more. The nth fine raw material refers to a fine raw material obtained by loosening the nth kneaded sheet.

The inventors of the present invention have come up with the seventh aspect of the present invention by considering that the side edge portion that has been excised can be used as the second final raw material described above. That is,
In the manufacturing method according to any one of the first to sixth aspects, the final raw material includes a step of cutting side edges of the molded sheet obtained in the molded sheet manufacturing step, and loosening the cut side edges. The fine raw material obtained through the step of making finer is contained.
Thereby, the yield of material improves. This is because the side edge of the molded sheet that should be discarded can be used as the second final raw material.
The side edge of the molded sheet refers to a region of both side edges where cracks may occur in the molded sheet obtained by kneading and rolling the final raw material, and its width is the kneading condition, rolling condition and final raw material. It can be arbitrarily determined depending on characteristics.

If the manufacturing method of the 1st-7th aspect of this invention demonstrated above is performed, since a raw material will be knead | mixed more strongly, the solid component contained in a raw material will be densified more. As a result, the presence of voids in the molded sheet is reduced. Further, even if a void is formed, the void itself is small and the size is uniform. Further, the dispersion of the voids in the molded sheet is made uniform.
According to the study by the present inventors, in the electrode sheet obtained by executing the manufacturing method of the above first to seventh aspects, when observing the surface of the material showing suitable electrical characteristics, the proportion of voids is The standard deviation of the void area was 1.0 to 8.0 μm ² .
That is, the eighth aspect of the present invention is defined as follows.
An electrode sheet obtained by kneading a material containing an active material, a conductive additive, and a binder, the proportion of voids on the surface is 5 to 14 area%, and the standard deviation of the void area is 1 An electrode sheet having a thickness of 0.0 to 8.0 μm ² .
In addition, 7-11 area% is preferable and, as for the ratio for which the said space | gap accounts, More preferably, it is 8-10 area%. The standard deviation of the porosity is preferably 1.2 to 4.5 μm ² , and more preferably 1.5 to 3.5 μm ² .

In the ninth aspect of the present invention, attention is paid to the side edge of the molded sheet obtained in the molded sheet production step, as in the seventh aspect. In the conventional method in which the final raw material is the one obtained after the first kneading step and the first unraveling step, the side edge of the molded sheet obtained by executing the molded sheet production step using this final raw material When attention is paid to the above, the fine raw material obtained by loosening the side edges is kneaded more strongly than the first fine raw material after execution of the first loosening step.
The use of such side edges as the final raw material has never been proposed.
That is, the ninth aspect of the present invention is defined as follows.
A final raw material production step for producing a final raw material;
A molded sheet production step of kneading and rolling the final raw material to produce a molded sheet;
A method for producing an electrode sheet comprising:
In the final raw material produced in the final raw material production step,
A first kneading step of kneading the initial raw material to obtain a first kneaded body;
A first unraveling step of unraveling the first kneaded body to make it fine, and a first fine raw material obtained by the method, and a side edge of the sheet obtained by introducing the first fine raw material into the molded sheet producing step The manufacturing method of an electrode sheet containing the fine raw material obtained by the step to excise, the step which loosens and refines | miniaturizes this excised side edge.

  According to the manufacturing method of the ninth aspect defined in this way, compared to the conventional manufacturing method, the side edges that were conventionally cut and discarded in the molded sheet formed in the molded sheet manufacturing step are reused. This improves the yield. Further, since the side edge is kneaded more strongly than the first fine raw material, the dispersibility of the active material in the molded sheet is improved by including this in the final raw material, and the electrode sheet using such a molded sheet is improved. Electrical characteristics are improved.

It is a flowchart which shows the manufacturing method of 1st Example of this invention. It is a flowchart which shows the manufacturing method of 2nd Example of this invention. It is a flowchart which shows the manufacturing method of 3rd Example of this invention. It is a flowchart which shows the manufacturing method of 4th Example of this invention. It is a flowchart which shows the manufacturing method of 5th Example of this invention. It is a flowchart which shows the manufacturing method of the deformation | transformation aspect of 5th Example of this invention. It is a flowchart which shows the manufacturing method of the other deformation | transformation aspect of 5th Example of this invention. It is a flowchart which shows the manufacturing method of 6th Example of this invention.

In the above, the initial raw material includes a general-purpose powdered active material, a conductive aid and a binder, and a molding aid. It goes without saying that each material and the blending ratio thereof are appropriately selected according to the application and use conditions of the electrode sheet.
In addition to the most widely used activated carbon, particulate carbon materials such as carbon nanotubes and fibrous carbon, and particulate metal compounds such as lithium cobaltate and lithium manganate can be used as the active material. When using activated carbon, the average particle diameter can be 2-20 micrometers. A preferred particle size range is 5 to 15 μm.
The conductive auxiliary agent is intended to make the conductivity of the entire molded sheet uniform by filling the gap between the particulate active materials, and conductive particles having a smaller diameter than the active material are employed. For example, carbon black having a particle size of 0.5 μm or less can be used.
Although the compounding quantity of the conductive support agent with respect to an active material is not specifically limited, It is preferable to set it as about 1-20 mass%.
The mixing method of the active material and the conductive auxiliary agent can be arbitrarily selected according to their characteristics. For example, they can be mixed with a mixer (such as a cutter mixer or an axial mixer) equipped with stirring blades. By this mixing, a first mixture is obtained.

The binder is used to bind the active material and the conductive additive, and PTFE (polytetrafluoroethylene) which is not easily electrolyzed is used for general purposes.
As the molding aid for dispersing the binder, an aqueous system, an oil system, or a mixed system of water and oil is appropriately selected.
It is preferable to use a water-based molding aid as an environmental measure.
When water is used as a molding aid, PTFE is dispersed in this and mixed with the first mixture.
The amount of PTFE with respect to the first mixture is arbitrarily selected according to the material of the active material and the conductive additive, the use conditions of the electrode sheet, and the like. For example, 5 to 20% by mass of PTFE can be used with respect to the first mixture. A more preferable blending amount of PTFE with respect to the first mixture is 8 to 15% by mass.

The initial raw material thus obtained is kneaded to form a first kneaded body.
The kneading method and conditions, and the shape of the first kneaded body can be arbitrarily set. In the embodiment, a sheet-like kneaded body is formed using a general-purpose roll rolling mill.
This roll rolling machine heats and compresses a raw material supplied between a pair of opposed rollers and forms it into a sheet shape, and the raw material is kneaded between the rollers. The degree of kneading of the raw material is adjusted by the distance between the pair of rollers, the temperature of the rollers, the number of rotations of the rollers, and the like.
The degree of kneading received by the raw material also varies depending on the properties of the raw material itself (temperature, particle size, uniformity of particle size, viscosity, supply amount, etc.) input to the roll mill.
In addition to the roll mill, a kneader type kneader can be adopted.

In each stage of the kneading step, the kneaders are preferably the same.
As an embodiment of the present invention, it is preferable to use a kneader that kneads the initial raw material in the first kneading step as it is in the other kneading steps. This is for the common use of manufacturing equipment. Of course, the kneading conditions in each kneading step can be different.
In order to prepare the first final raw material and the second final raw material, respective dedicated kneaders may be prepared, or the kneading conditions of the same kneader may be adjusted according to the first final raw material and the second final raw material. Good.

In the molded sheet manufacturing step, the final raw material including the fine raw material is kneaded and rolled to form a sheet. The kneading device and the rolling device may be separated.
In the embodiment of the present invention, a roll mill is adopted as means for performing kneading and rolling. This roll mill is preferably prepared separately from the roll mill used as a kneader in the kneading step. This is because the latter is mainly intended for kneading the raw material, whereas the former is mainly intended for forming the formed sheet, and therefore the roll rolling conditions are often different.

In the step of unraveling each stage, the same unraveling device for unraveling and kneading the kneaded sheet can be used. This is for the common use of manufacturing equipment.
In the embodiment of the present invention, a general-purpose pulverizer is used to loosen the kneaded sheet obtained in each kneading step. The type of the pulverizer is not particularly limited as long as it can pulverize the kneaded sheet. Of course, the conditions for unraveling in each unraveling step may be made common or different.
In order to prepare the first final raw material and the second final raw material, dedicated pulverizers may be prepared.
The particle size of the fine raw material obtained by these unraveling steps is arbitrarily selected according to the roll mill into which the fine raw material is charged. Before introducing the fine raw material into the roll mill, it is preferable to adjust the particle size by sieving the fine raw material.

  The number n of kneading and unraveling in the kneading step and the unraveling step is arbitrarily selected according to the characteristics of the kneading apparatus, the characteristics of the raw materials, the use conditions of the electrode sheet, and the like.

Next, a first embodiment of the present invention will be described (see FIG. 1).
(Preparation of initial raw materials S1)
Activated charcoal (Kuraray Chemical Co., Ltd., trade name: YP50F) 90% by mass as active material and carbon black (Denki Kagaku Kogyo Co., Ltd., trade name: Denka Black) 10% by mass as a conductive additive are put into a mixer and stirred. As a result, a first mixture was obtained.
While retaining the first mixture in the mixer (this is 50% by mass), 10% by mass of PTFE dispersion (product name: PTFE 31-JR, manufactured by Mitsui DuPont Fluorochemicals) and 40% by mass of pure water The mixture was added and stirred to obtain a slurry-like initial raw material.

(First kneading step S3)
The obtained slurry-like initial raw material was put into a horizontal roll rolling mill, which was roll-rolled to obtain a first kneaded sheet (first kneaded body).
Here, the roll rolling conditions are as follows: the roll temperature is 50 ° C., and the linear pressure is 0.10 to 0.80 kN / mm, more preferably 0.15 to 0.25 kN / mm. The width was adjusted.

(First loosening step S5)
In order to loosen the first kneading sheet obtained in the first kneading step S3, the mixture was pulverized and refined with a mixer to obtain a first fine raw material. The grinding conditions at this time were 3600 rpm and 30 seconds.
The obtained first fine raw material was passed through a sieve having an aperture of 2 mm to adjust the particle size.

(Second kneading step S7)
The first fine raw material obtained in the first unraveling step S5 is charged into the horizontal roll mill used in the first kneading step S3 so as to have the same roll rolling conditions, and the second kneaded sheet (second kneaded body) )
(Second loosening step S9)
In this step, the second kneaded sheet obtained in step S7 was thrown into the cutter mixer used in the first unraveling step S5 so as to have the same pulverization conditions and further sieved to obtain a second fine raw material.
In this example, steps S1, S3, S5, S7 and S9 constitute a final raw material production step.

(Molded sheet production step S11)
In this step, the second fine raw material obtained in the second unraveling step S9 was used as a final raw material and charged into a horizontal roll mill (the same type as that used in steps S3 and S7) to obtain a molded sheet. .
At this time, the roll rolling conditions are as follows: the roll temperature is 50 ° C., and the linear pressure is 0.05 to 0.50 kN / mm, more preferably 0.08 to 0.15 kN / mm. The width was adjusted.

(Shaping sheet shaping step S13)
In this example, the obtained molded sheet was rolled to a predetermined thickness (250 μm in this example) with a general-purpose rolling mill, and further, the side edge of the sheet was excised to obtain a molded sheet. Shaped.
(Lamination / drying step S15)
In this example, a current collector made of aluminum foil was laminated on the obtained molded sheet via a conductive adhesive, and this laminate was dried to obtain an electrode sheet.
In the above, the shaping step S13 and the lamination / drying step S15 are general-purpose steps.
The molded sheet can be made into an electrode sheet by itself, that is, without stacking current collectors.

(Second embodiment)
A second embodiment of the present invention will be described with reference to FIG. The same steps as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
In this example, the kneading step and the unraveling step were repeated after the second kneading step and the second unraveling step (steps S17 and S19).
In FIG. 2, the upper limit S (see step S20) of the number n of kneading steps and loosening steps can be set arbitrarily, but in this embodiment, S = 3. The execution number n is an integer of 2 or more.
In that case, when S = 4, that is, when the number n of kneading steps and unraveling is 4 or more, the obtained fine raw material is in an excessive kneading state, and when this is used as it is as the final raw material in the forming sheet production step S11, it is obtained. The formed sheet does not have sufficient mechanical strength.

The second fine raw material (adjusted pulverized product = first final raw material) obtained in step S19 when the execution number n = 2 and the third fine raw material obtained in step S19 when the execution number n = 3 ( The second final raw material) was mixed in step S30. The mixing ratio of the two can be arbitrarily selected. Since the second final raw material is kneaded more strongly than the first final raw material, the dispersibility of the active material in the electrode sheet improves as the latter ratio increases.
In this example, steps S1, S3, S5, S17, S19, S20 and S30 constitute a final raw material preparation step.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG. The same steps as those in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.
In this example, the final raw material kneaded excessively (n = S + 1, in this example, n = 4, see step S21) was prepared as the second final raw material.
In Step 30, the second final raw material was mixed with the first final raw material (n = S, n = 3 in this example, kneading strength immediately before the excessive kneading).
According to the study by the present inventors, the blending ratio of the second final raw material excessively kneaded in the mixture obtained in step S30 is preferably 35% by mass or less. If the blending ratio of the second final raw material in this case exceeds 35% by mass, the influence of excessive kneading in the second final raw material appears on the electrode sheet, and the mechanical strength may be reduced.
In addition, the effect of the high dispersibility of the active material by the 2nd final raw material excessively kneaded by making the compounding ratio of the 2nd final raw material 10 mass% or more appears.
In this example, steps S1, S3, S5, S17, S19, S21 and S30 constitute a final raw material preparation step.

(Fourth embodiment)
A fourth embodiment of the present invention will be described with reference to FIG. The same steps as those in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.
In this example, the first fine raw material obtained in step S5 is mixed with the nth fine raw material obtained in nth step S19 to obtain the final raw material (step S31).
Also in the fourth embodiment, since the raw material constituting the molded sheet is mixed with the material that has undergone the nth unraveling step S19, the dispersibility of the active material is improved.
In this example, steps S1, S3, S5, S17, S19, S20 and S31 constitute a final raw material preparation step.

(Fifth Embodiment) A fifth embodiment of the present invention will be described with reference to FIG. The same steps as those in FIGS. 2 and 3 are denoted by the same reference numerals, and the description thereof is omitted.
In this example, a predetermined amount of the side edge portion cut from the sheet in the shaping sheet shaping step S13 in the previous lot was put into the pulverizer, and the n-th loosening step (step S19) was executed. The fine raw material obtained in the n-th loosening step S19 was used as the final raw material. When the side edge of the molded sheet is regarded as the final raw material, the degree of kneading may be excessive, but the fine raw material (second final raw material) thus excessively kneaded and the final raw material not excessively kneaded If (n = S, the first final raw material) is mixed at a predetermined blending ratio (the former is 35% by mass or less), high dispersibility of the active material can be ensured while ensuring sufficient mechanical strength.
In this example, steps S1, S3, S5, S13, S17, S19 and S20 constitute a final raw material preparation step.
As a modification of the fifth embodiment, as shown in FIG. 6, a side edge loosening step (step S39) for loosening the cut side edge is provided separately, and the fine raw material obtained there and the n th You may mix a fine raw material (step S31). The same edge crushing step S39 can be used for other side crushing steps.
In this example, steps S1, S3, S5, S13, S17, S19, S20, S31 and S39 constitute a final raw material preparation step.
Furthermore, as shown in FIG. 7, a predetermined amount of the cut-off side edge may be introduced into the first loosening step (step S3).
In this example, steps S1, S3, S5, S13, S17, S19 and S20 constitute a final raw material preparation step.

(Sixth embodiment)
A sixth embodiment of the present invention will be described with reference to FIG. 8. In FIG. 8, the same steps as those in FIG.
In this example, the excised side edge was loosened and refined in step S39, and the obtained fine raw material was mixed with the first fine raw material (step S41).
The side edge portion is kneaded more strongly than the first kneading sheet. Therefore, compared with a molded sheet obtained only from the first fine raw material obtained by loosening the first kneaded sheet, by mixing the fine raw material obtained by loosening the excised side edge portion, the resulting molded sheet is made of an active material. Excellent dispersibility.
In this example, steps S1, S3, S5, S13, S39 and S41 constitute the final raw material preparation step.

Hereinafter, physical properties of the electrode sheet of each example are shown.
Capacitance is taken as a representative index of the electrical characteristics of the electrode sheet. In this example, the capacitance of each example was measured as follows.
The obtained electrode sheet was cut into 30 mm × 30 mm, and beaker cells were assembled. The electrolyte solution in the beaker was prepared by dissolving triethylmethylammonium tetrafluoroborate at a concentration of 1.0 mol / L in propylene carbonate, charging conditions: constant current voltage method, discharging conditions: constant current method, The charging current was 30 mA / cm ² , the discharging current was 30 mA / cm ² , the charging voltage was 2.7 V, the charging time was 60 minutes, the discharging voltage was 0 V, and the discharging temperature was 25 ° C. The capacitance was calculated as the capacitance per volume of the active material layer using an energy conversion method.

Moreover, the porosity of the surface of the electrode sheet was calculated as follows.
The electrode sheet is cut into 10 mm × 10 mm, and the surface is photographed with an electron microscope (manufactured by JEOL, model: JXA-8200) at a magnification of 1000 times. The obtained image was binarized using image processing software (Image Pro Plus, manufactured by Planetron) to calculate the porosity.
The standard deviation of the air gap was also calculated using the same software function.

Table 1 shows the capacitance, porosity, and standard deviation of the voids of the electrode sheets of Examples 1 and 3 and the comparative example. In Table 1, the capacitance value is a relative value when the value of Comparative Example 1 is 100.
Example 1 is an electrode sheet obtained by executing the manufacturing method shown in FIG. 1, and Comparative Example 1 is a molded sheet using only the first fine raw material obtained in the first loosening step S5 in FIG. It is what.
In Examples 3-1, 3-2, and 3-3, the second final raw material (n = 4, one that was excessively kneaded) and the first final raw material (when the production method of the third example shown in FIG. n = 3, immediately before excessive kneading) In the mixture, the blending ratio of the second final raw material is the ratio shown in the table.
In Comparative Example 2, in the execution of the manufacturing method of the third embodiment, the particle size of the mixture is adjusted with a sieve having an opening of 3 mm, and the mixture of the second final raw material is mixed in the second final raw material and the first final raw material. The ratio is 40% by mass.

  From the results of Table 1, the electrode sheet of Example 1 that was strongly kneaded by executing the second kneading step and the second unraveling step had an increased capacitance compared to the electrode sheet of Comparative Example 1. You can see that

  The present invention is not limited to the description of the embodiment of the invention. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

Claims (9)

A final raw material production step for producing a final raw material;
A molded sheet production step of kneading and rolling the final raw material to produce a molded sheet;
A method for producing an electrode sheet comprising:
In the final raw material produced in the final raw material production step,
A first kneading step of kneading the initial raw material to obtain a first kneaded body;
A first unraveling step of unraveling the first kneaded body and refining;
A second kneading step of kneading the fine raw material obtained in the first unraveling step to form a second kneaded body;
A second unraveling step of unraveling the second kneaded body and refining;
The manufacturing method of an electrode sheet in which the fine raw material obtained through this is contained.   The manufacturing method according to claim 1, wherein the final raw material includes a first final raw material and a second final raw material, and the second final raw material is kneaded more strongly than the first final raw material. The first final raw material includes the fine raw material obtained in the n th unraveling step,
The second final raw material includes the fine raw material obtained in the (n + 1) th unraveling step,
The manufacturing method according to claim 2, wherein n is an integer of 2 or more. The second final raw material is excessively kneaded, and by itself, the mechanical strength of the molded sheet obtained when the molded sheet production step is executed becomes insufficient,
The manufacturing method according to claim 2 or 3, wherein the first final raw material is properly kneaded, and the molded sheet obtained when the molded sheet production step is executed alone has sufficient mechanical strength.   The manufacturing method of Claim 4 whose compounding ratio of the said 2nd final raw material is 35 mass% or less in the mixture of the said 1st final raw material and the said 2nd final raw material.   The manufacturing method according to any one of claims 1 to 5, wherein the final raw material contains the fine raw material obtained in the first unraveling step.   The final raw material contains a fine raw material obtained through a step of cutting a side edge of the molded sheet obtained in the step of forming the molded sheet and a step of loosening and refining the cut side edge. The manufacturing method in any one of Claims 1-6. An electrode sheet obtained by kneading a material containing an active material, a conductive additive, and a binder, the proportion of voids on the surface is 5 to 14% by area, and the standard deviation of the area of the voids is 1. The electrode sheet which is 0-8.0 micrometers ² . A final raw material production step for producing a final raw material;
A molded sheet production step of kneading and rolling the final raw material to produce a molded sheet;
A method for producing an electrode sheet comprising:
In the final raw material produced in the final raw material production step,
A first kneading step of kneading the initial raw material to obtain a first kneaded body;
A first unraveling step of unraveling the first kneaded body to make it fine, and a first fine raw material obtained by the method, and a side edge of the sheet obtained by introducing the first fine raw material into the molded sheet producing step The manufacturing method of an electrode sheet containing the fine raw material obtained by the step to excise, the step which loosens and refines | miniaturizes this excised side edge.

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