JP2011113838A - Electrode paste for battery, method of producing electrode paste for battery, and method of manufacturing electrode plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode paste for battery capable of enhancing productivity of manufacturing process of a battery (electrode plate), preventing clogging of a gap portion, being applied on a collector plate to have a uniform thickness, and causing an active material layer to have a property resistant to detachment from the collector plate after it is dried, to provide a method of producing such an electrode paste for battery, and to provide a method of manufacturing an electrode plate that is highly productive, has a uniform thickness, and has an active material layer resistant to detachment from the collector plate. <P>SOLUTION: The electrode paste 21P for battery includes active material particles 22, a binding member 23, and a dispersion medium 26 in which the active material particles and the binding member are dispersed, wherein a first shear viscosity V1 at a first shear rate of 1 s<SP>-1</SP>is ≥2,000 mPa s, a second shear viscosity V2 at a second shear rate of 500 s<SP>-1</SP>is ≤350 mPa s, and a third shear viscosity V3 at a third shear rate of 10,000 s<SP>-1</SP>is ≤240 mPa s. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a battery electrode paste used for a battery electrode plate and a method for producing the battery electrode paste. Moreover, it is related with the manufacturing method of the electrode plate using such an electrode paste for batteries.

2. Description of the Related Art In recent years, secondary batteries (hereinafter simply referred to as batteries) that can be charged and discharged have been used as power sources for driving portable electronic devices such as hybrid cars, notebook computers, and video camcorders.
As literature related to such a battery, for example, a positive electrode active material paste (battery electrode paste) containing a lithium-containing metal is discharged from a nozzle, wound on a backup roll, and moved to an aluminum foil (current collector plate). Patent document 1 which disclosed the manufacturing method of the sheet-like electrode plate (electrode plate) to apply | coat is mentioned.

JP-A-7-65816

  By the way, in manufacturing a battery (electrode plate) using a battery electrode paste (hereinafter also simply referred to as paste), it is desired to apply the battery electrode paste on the current collector plate at a high speed in order to increase productivity. It is necessary to apply a uniform thickness. This is because, if the thickness of the battery electrode paste is not uniformly applied, the electric resistance becomes non-uniform in the active material layer after the battery electrode paste is dried, and the battery characteristics vary.

  Further, prior to applying the battery electrode paste to the current collector plate, it is necessary to remove aggregates in the paste using a filter. For example, if a battery electrode paste containing an agglomerate having a particle size larger than the thickness of the applied battery electrode paste is applied to the current collector plate, it is difficult to make the paste uniform, and the current collector plate and paste This is because there is a possibility that the gap portion between the blade and the tip end surface of the die that defines the thickness of the die is clogged. However, in order to industrially establish the manufacture of the paste and the electrode plate in the removal of the agglomerates using such a filter, the time taken for the paste to pass through the filter becomes a problem.

Furthermore, for the battery electrode paste after coating, the binder migration phenomenon (the phenomenon that the binder moves to the outer surface side in the paste) and the sedimentation phenomenon of the active material particles (the active material by gravity) It is necessary to prevent the phenomenon that particles move to the current collector side in the paste. If the migration phenomenon or the sedimentation phenomenon of the active material particles occurs and the ratio of the active material particles increases on the current collector plate side while the ratio of the binder decreases, The dried active material layer is easily peeled from the current collector plate. Further, among the active material layer obtained by drying the paste, the presence of a large amount of binder near the outer surface tends to prevent lithium ions from moving into the active material layer, thereby increasing resistance. This is to prevent problems.
However, Patent Document 1 does not describe a technique for solving the above-described problems.

  The present invention has been made in view of such problems, and in the battery (electrode plate) manufacturing process, productivity can be increased, gap portions are not clogged, and the current collector plate has a uniform thickness. It is an object of the present invention to provide a battery electrode paste that can be applied and has a property that the dried active material layer does not easily peel from the current collector plate. Moreover, it aims at providing the manufacturing method of such an electrode paste for batteries. It is another object of the present invention to provide a method for producing an electrode plate having an active material layer that is highly productive, has a uniform thickness, and is difficult to peel from the current collector plate.

One aspect of the present invention, the active material particles, a binder, a battery electrode paste and a liquid dispersion medium in which the active material particles and the binder is dispersed, the of 1s ^-1 the first shear viscosity at 1 shear rate, 2000 mPa · s or more, the second shear viscosity of the second shear rate of 500 s ^-1 is, 350 mPa · s or less, and third shear viscosity in the third shear rate of 10000s ^-1 Is a battery electrode paste having a pressure of 240 mPa · s or less.

According to the inventors' research, for example, in die coating, the gap (clearance) between the tip surface of the die and the current collector plate, which defines the thickness of the battery electrode paste applied to the current collector plate, is large. While the thickness (GP) is set to 100 μm, the shear rate applied to the paste at the time of coating is set to 10,000 s ⁻¹ , for example, the conveyance speed (SV) for conveying the current collector plate is set to 1 m / s to improve the productivity of the electrode plate. For the paste used to apply to the current collector plate at a high speed with a small gap such that the shear viscosity at the third shear rate (10000 s ⁻¹ ) is 240 mPa · s or less, the paste is uniform. It has been found that it can be applied.

In addition, as described above, in order to remove aggregates in the battery electrode paste before coating, it is necessary to pass the battery electrode paste through a filter. In order to prevent clogging in the gap portion by setting the gap size (GP), that is, the thickness of the application of the battery electrode paste to 100 μm, for example, an agglomerate having a particle size larger than the gap size is used. It is necessary to make the pore diameter of the filter 50 to 100 μm so as to be able to be removed.
Further, in order to pass the battery electrode paste through the filter at an industrially acceptable speed, the paste is subjected to an industrially acceptable flow rate (for example, 3 L / min · filter passing characteristics such as being able to pass through at least m ² ) are required. In order to achieve such characteristics, it has been found that the shear viscosity at the second shear rate (500 s ⁻¹ ) should be a property of 350 mPa · s or less.

Furthermore, it has been found that the migration phenomenon and the sedimentation phenomenon that occur after the battery electrode paste is applied to the current collector plate to a thickness of about 100 μm are influenced by the viscosity of the paste. In particular, it has been found that when the paste has a high shear viscosity at a sufficiently low shear rate, the migration phenomenon and the sedimentation phenomenon are unlikely to occur, and the active material layer after drying is difficult to peel off from the current collector plate. Since the shear viscosity cannot be measured when the shear rate is 0, the first shear rate (1 s ⁻¹ ) is used as a sufficiently low shear rate.
Specifically, when the paste having a thickness of about 100 μm is dried by setting the applied paste to a property having a shear viscosity of 2000 mPa · s or more at the first shear rate (1 s ⁻¹ ). However, it has been found that the migration phenomenon and the sedimentation phenomenon can be prevented.

In contrast, the battery electrode paste described above has a third shear viscosity of 240 mPa · s or less at the third shear rate, a second shear viscosity of 350 mPa · s or less at the second shear rate, and a first shear rate at the first shear rate. 1 Shear viscosity is 2000 mPa * s or more. For this reason, in the manufacturing process of the battery (electrode plate), the productivity can be increased under the application condition where the shear rate is 10,000 s ⁻¹ or less, and the gap portion is not clogged, and the current collector can be applied with a uniform thickness. . Moreover, it can be set as the battery electrode paste from which the active material layer after drying is hard to peel from a current collection board.

Examples of the active material particles include lithium transition metal composite oxide particles such as lithium cobaltate, lithium nickelate, and lithium manganate, and particles made of a material used for the positive electrode plate such as an iron olivine compound. . Moreover, for example, particles used for the negative electrode plate such as natural graphite particles such as flake graphite and massive graphite, artificial graphite graphite (graphite) particles, and amorphous carbon particles are also included.
Examples of the binder include styrene butadiene rubber (SBR), carboxymethyl cellulose, polyethylene oxide, and polytetrafluoroethylene.

  In addition, as an apparatus for measuring the shear viscosity of the battery electrode paste, for example, a rotational viscometer (for example, manufactured by Anton Paar) having a geometry (attachment for filling a sample) such as a parallel plate, a cone & plate, and a coaxial double cylinder Physica MCR) and vibration viscometer.

Furthermore, in the battery electrode paste described above, a value obtained by dividing the conveyance speed for conveying the current collector plate by the size of the gap between the current collector plate and the tip end surface of the die is 8000 to 10,000 s ⁻¹ . A battery electrode paste used for coating under certain coating conditions is preferable.
In this paste, for example, the gap size (GP) is set to about 100 μm, and the current collecting plate transfer speed (SV) is set to about 1 m / s, and the transfer speed (SV) is set to the gap size (GP). The battery electrode paste described above can be uniformly applied to the current collector plate even if it is used for application under application conditions where the value obtained by dividing the shear rate, that is, the shear rate is as high as 8000 to 10000 s ⁻¹ .

Another aspect of the present invention is a method for producing a battery electrode paste comprising active material particles, a binder, and a liquid dispersion medium in which the active material particles and the binder are dispersed. for battery electrode paste, a first confirmation step of confirming that the first shear viscosity of the first shear rate of 1s ^-1 is 2000 mPa · s or more, the second shear viscosity of the second shear rate of 500 s ^-1 A second confirmation step for confirming that the pressure is 350 mPa · s or less, and a third confirmation step for confirming that the third shear viscosity at a third shear rate of 10,000 s ⁻¹ is 240 mPa · s or less. It is a manufacturing method of an electrode paste.

In the battery electrode paste manufacturing method described above, the battery electrode paste includes the above-described confirmation steps (first confirmation step, second confirmation step, and third confirmation step). For this reason, if the battery electrode paste that has been finished is used, the battery plate has a uniform thickness on the current collector plate with high productivity and no clogging of the gap portion under application conditions of a shear rate of 10,000 s ⁻¹ or less. Electrode paste can be applied. Moreover, the active material layer after drying such a battery electrode paste can be made difficult to peel from the current collector plate.

Or the other aspect of this invention is a manufacturing method of the electrode plate formed by apply | coating the electrode paste for batteries to a current collecting plate, Comprising: The said battery electrode paste is active material particle | grains, a binder, has a liquid dispersion medium in which active material particles and the binder is dispersed, the first shear viscosity of the first shear rate of 1s ^-1 is 2000 mPa · s or more, first in the second shear rate of 500 s ^-1 2 The shear viscosity is 350 mPa · s or less, the third shear viscosity at a third shear rate of 10,000 s ⁻¹ is 240 mPa · s or less, and the battery electrode paste is collected at the shear rate of 10000 s ⁻¹ or less. It is a manufacturing method of an electrode plate provided with the application | coating process apply | coated to a board, and the drying process which dries the apply | coated said battery electrode paste.

In the electrode plate manufacturing method described above, a battery electrode paste having the above-described characteristics is used, and an application step of applying to the current collector plate at a shear rate of 10,000 s ⁻¹ or less and a drying step are performed. For this reason, in the application process, the gap electrode is not clogged, and the battery electrode paste having a uniform thickness can be applied to the current collector plate. Further, it is possible to suppress the migration phenomenon and the sedimentation phenomenon, and to form an active material layer that is difficult to peel from the current collector plate. Thus, an electrode plate having an active material layer that has a uniform thickness and is difficult to peel from the current collector plate can be manufactured with high productivity.

It is a perspective view of the battery of an embodiment. It is a perspective view of the negative electrode plate of an embodiment. It is explanatory drawing of the manufacturing method (paste formation process) of the battery of embodiment. It is a graph which shows the flow volume per minute about each negative electrode paste from which shear viscosity differs in shear rate 500s- ¹ . It is the schematic of the peeling strength measuring apparatus used for a peeling test. It is a graph which shows peeling strength about each negative electrode paste from which shear viscosity differs in shear rate 1s- ¹ . The output of each sample battery using negative electrode pastes having different shear viscosities at a shear rate of 1 s ⁻¹ (the relative value of the output when the output of the battery using the negative electrode paste having a shear viscosity of 6500 mPa · s is taken as 100) is shown. It is a graph. It is the schematic of the rotational viscometer used for the confirmation process among the manufacturing methods of the battery of embodiment. It is explanatory drawing of the application | coating process and drying process of the battery of embodiment. It is explanatory drawing (enlarged view of the B section of FIG. 9) of the application | coating process of the battery of embodiment.

(Embodiment)
Next, embodiments of the present invention will be described with reference to the drawings.
In addition, the battery 1 provided with the electrode plate (negative electrode plate 20) manufactured using the electrode paste (negative electrode paste 21P) concerning this embodiment is demonstrated, referring FIG.
The battery 1 is a lithium ion secondary battery that includes a strip-like negative electrode plate 20, a positive electrode plate 30, and a separator 40 that extend in the longitudinal direction DA, and forms a wound-type power generation element 10 wound around these. (See FIG. 1). In addition, the battery 1 accommodates the electric power generation element 10 in the battery case 80, as shown in FIG.

  The battery case 80 has a battery case body 81 and a sealing lid 82 both made of aluminum. Among these, the battery case main body 81 has a bottomed rectangular box shape, and an insulating film (not shown) made of resin and bent into a box shape is interposed between the battery case 80 and the power generation element 10. The sealing lid 82 has a rectangular plate shape, closes the opening of the battery case body 81, and is welded to the battery case body 81. Of the positive electrode current collecting member 91 and the negative electrode current collecting member 92 connected to the power generation element 10, the positive electrode terminal portion 91 </ b> A and the negative electrode terminal portion 92 </ b> A located at the tips of the sealing lid 82 pass through, respectively. 1 protrudes from the lid surface 82a facing upward. Insulating members 95 made of insulating resin are interposed between the positive electrode terminal portion 91A and the negative electrode terminal portion 92A and the sealing lid 82 to insulate each other. Further, a rectangular plate-shaped safety valve 97 is also sealed on the sealing lid 82.

The power generating element 10 is a wound type in which a strip-like positive electrode plate 30 and a negative electrode plate 20 are wound into a flat shape via a strip-like separator 40 (see FIG. 1). Only the separator 40 is wound on the outermost and innermost sides of the power generation element 10. The positive electrode plate 30 and the negative electrode plate 20 of the power generation element 10 are respectively joined to a plate-like positive current collector 91 or negative current collector 92 bent in a crank shape (see FIG. 1). Among these, the separator 40 made of polyethylene is impregnated with an electrolytic solution (not shown) obtained by adding a solute (LiPF ₆ ) to a mixed organic solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC). .

Further, the thin plate-shaped positive electrode plate 30 is made of a strip-like aluminum aluminum foil (not shown) and two positive electrode active material layers (shown in the figure) formed and arranged on both main surfaces of the aluminum foil. Not).
The positive electrode active material layer includes positive electrode active material particles made of LiCoO ₂ , a binder made of polyvinylidene fluoride (PVDF), and a conductive material made of acetylene black (none of which are shown).

On the other hand, as shown in FIG. 2, the thin negative electrode plate 20 has a strip shape extending in the longitudinal direction DA and a copper copper foil 28 and strips extending in the longitudinal direction DA on both main surfaces of the copper foil 28. And two negative electrode active material layers 21 and 21 formed and arranged on each other.
Among them, the negative electrode active material layer 21 is composed of negative electrode active material particles 22 made of graphite having an average particle diameter of 10 μm, a tap density of 0.9 g / cm ³ and a specific surface area of 4.0 m ² / g, styrene butadiene rubber (SBR). 1% viscosity (viscosity when a 1% aqueous solution is prepared and measured with a B-type viscometer) is 7000 mPa · s and the degree of etherification is 7.0. A thickening material (not shown).
The negative electrode active material layer 21 is obtained by drying a negative electrode paste 21P (described later) including negative electrode active material particles 22, a binder 23, a thickener, and ion-exchanged water 26.

Next, a method for manufacturing the battery 1 using the negative electrode plate 20 according to the first embodiment will be described with reference to the drawings.
This manufacturing method includes a paste forming step for forming the negative electrode paste 21P, a confirmation step for confirming the shear viscosity at various shear rates of the negative electrode paste 21P (first confirmation step, second confirmation step, third confirmation step), negative electrode paste An application process of applying 21P to the copper foil 28 and a drying process of drying the applied negative electrode paste 21P are included.

First, a paste forming step for forming the negative electrode paste 21P including the negative electrode active material particles 22, the binder material 23, the thickener, and the ion exchange water 26 in which these are dispersed will be described with reference to FIG.
In this paste forming step, a planetary mixer 100 including a mixing tank 110 and three blades 120, 120, 120 is used (see FIGS. 3A and 3B). The blade 120 of the planetary mixer 100 is rotated in the mixing tank 110 by a driving source, and can knead a plurality of substances in the mixing tank 110 with a strong shear stress.

  Specifically, in this paste forming step, 49 parts by weight of the negative electrode active material particles 22, 0.5 parts by weight of SBR forming the binder 23, and 0.5 parts by weight of CMC forming the thickener After being dry-mixed in the mixing tank 110, 50 parts by weight of ion-exchanged water 26 was mixed into the mixing tank 110 in a plurality of times and mixed little by little. In this way, by mixing the ion exchange water 26 in a plurality of times in small amounts, these can be mixed while applying a higher dispersion force than in the past (ie, mixing ion exchange water at a time). Thereby, the negative electrode paste 21P in which the negative electrode active material particles 22, the binder 23, and the thickener are uniformly dispersed in the ion exchange water 26 is completed.

In addition, the negative electrode paste 21P made in the above-described paste forming step is characterized by shear viscosity at each shear rate (first shear rate, second shear rate, third shear rate). That is, the first shear viscosity at the first shear rate (1 s ⁻¹ ) is 3000 mPa · s, the second shear viscosity at the second shear rate (500 s ⁻¹ ) is 280 mPa · s, and the third shear rate (10000 s ^−1). ) Has a characteristic that the third shear viscosity is 230 mPa · s. This is considered to be because a thickener having a higher viscosity (7000 mPa · s) than the conventional (the aforementioned 1% viscosity is 4000 mPa · s) was mixed, and mixed and dispersed with a higher dispersion force than before. It is done.

Meanwhile, in the coating step, the gap GP (clearance) between the copper foil 28 and the tip surface 323 of the die 320 of the coating / drying apparatus 300 (described later) is set to 100 μm, while the negative electrode plate. In order to improve productivity of 20, the conveyance speed (SV) of the copper foil 28 is set to 1 m / s. Then, the shear rate applied to the negative electrode paste 21P reaches 10,000 s ⁻¹ .
Therefore, the inventors prepared negative electrode pastes having different shear viscosities (30, 80, 185, 240, 325 mPa · s) at a shear rate of 10,000 s ⁻¹ , respectively. And using the application | coating drying apparatus 300 mentioned later, these negative electrode pastes from which shear viscosity differs were apply | coated to the copper foil 28, respectively, and it was determined whether each negative electrode paste was apply | coated to the copper foil 28 uniformly.
Specifically, first, a negative electrode paste having a shear viscosity of 30 mPa · s was charged into the paste holding unit 321 of the die 320. Then, in the coating and drying apparatus 300 in which the gap size GP is 100 μm and the transport speed SV of the copper foil 28 is 1 m / s (the shear rate at this time is 10,000 s ⁻¹ ), the discharge port 322 is directed toward the copper foil 28. A negative electrode paste was discharged and applied to the copper foil 28. Then, it was visually determined whether streaks (uneven uneven shape having a non-uniform thickness extending in the conveying direction of the copper foil 28) were generated in the applied negative electrode paste. A negative electrode paste having a shear viscosity of 80,185,240,325 mPa · s was also applied to the copper foil 28 and judged in the same manner as the negative electrode paste having a shear viscosity of 30 mPa · s.
Table 1 shows the determination results for each shear viscosity negative electrode paste.

According to Table 1, uneven lines are generated in the negative electrode paste having a shear viscosity of 325 mPa · s, and no streaks are generated in the negative electrode paste having a shear viscosity of 30, 80, 185, 240 mPa · s. Therefore, at a shear rate of 10000s ^-1, the negative electrode paste shear viscosity has the following properties 240 mPa · s, the shear rate at the following coating conditions 10000s ^-1, applied to the copper foil 28 with a uniform thickness I can see that

Further, as will be described later, in the coating process, in order to prevent clogging at the gap portion between the copper foil 28 and the tip surface 323 of the die 320 and to make the thickness of the negative electrode paste 21P to be coated uniform, Prior to introducing the negative electrode paste 21P, it is necessary to remove aggregates in the negative electrode paste 21P using the filter 310 having a plurality of 50 μm square holes. In addition, based on the experiment results of the inventors, about 500 s ⁻¹ was used as the shear rate applied to the negative electrode paste 21P in the filter 310.
On the other hand, if the negative electrode paste does not have an appropriate filter passing characteristic, it takes time to pass through the filter, and the productivity of the negative electrode paste is poor and industrially not established. Accordingly, a flow rate of 3 L / min · m ² or more is assumed as industrially acceptable paste passage characteristics.
Therefore, the inventors prepared negative electrode pastes having different shear viscosities (300, 350, 500, 600 mPa · s) at a shear rate of 500 s ⁻¹ , respectively. Then, using the filter 310 of the coating and drying apparatus 300, the flow rates per minute of these negative electrode pastes having different shear viscosities were measured.

The measurement result about each negative electrode paste is shown in the graph of FIG. According to this graph, shear viscosity is 300 mPa · s, and, although the flow rate of the negative electrode paste of 350 mPa · s are each 7.6L / min · m ² and 3.0L / min · m ^2, the shear viscosity 500mPa The flow rates of the negative electrode paste of s and 600 mPa · s are 0.4 L / min · m ² and 0.1 L / min · m ² , respectively. From this, in the negative electrode paste having a shear viscosity of 300,350 mPa · s, the flow rate can be 3.0 L / min · m ² or more, whereas in the negative electrode paste having a shear viscosity of 500,600 mPa · s, the flow rate is 3 It can be seen that it cannot reach 0.0 L / min · m ² . That is, it can be seen that if a negative electrode paste having a shear viscosity of 350 mPa · s or less is used at a shear rate of 500 s ⁻¹ , the filter 310 can be passed at an industrially acceptable flow rate.

Furthermore, in the drying process described later, depending on the viscosity of the negative electrode paste, there is a possibility that a migration phenomenon of the binder 23 or a precipitation phenomenon of the negative electrode active material particles 22 may occur. When such a migration phenomenon or sedimentation phenomenon occurs in the negative electrode paste, the negative electrode active material layer 21 formed by drying the negative electrode paste is easily peeled off from the copper foil 28, or the resistance of the negative electrode plate is increased. .
Therefore, the inventors prepared negative electrode pastes having different shear viscosities (550, 2100, 6500 mPa · s) at a shear rate of 1 s ⁻¹ , respectively. And using the application | coating drying apparatus 300 mentioned later, each negative electrode paste from which these shear viscosities differ is apply | coated to the copper foil 28, each negative electrode paste is dried with the heater 330, a negative electrode active material layer is formed, this and copper The peel strength between the foil 28 was measured.
Furthermore, the dried negative electrode paste was pressed, a battery was manufactured together with the positive electrode plate 30 and the separator 40 described above, and the output of the battery was measured.

Specifically, first, a negative electrode paste having a shear viscosity of 550 mPa · s at a shear rate of 1 s ⁻¹ is put into the paste holding unit 321 of the die 320 and applied to the copper foil 28, and then the negative electrode paste is completely removed by the heater 330. The negative electrode active material layer 21 was formed by drying.
About this negative electrode active material layer 21, the peeling strength between copper foil 28 was measured using the peeling strength measuring apparatus 500 shown in FIG. The peel strength measuring apparatus 500 includes a plate-like pedestal portion 520 and a T-shaped pulling portion 510 that moves vertically away from the pedestal portion 520 at a speed of 0.5 mm / s. A sheet-like adhesive seal 521 is interposed between the pedestal portion 520 and the copper foil, and a disk-shaped adhesive seal 511 having a diameter of 10 is interposed between the pulling portion 510 and the negative electrode active material layer. Yes.

On the other hand, the negative electrode active material layer 21 (negative electrode plate 20) was used to wind together with the positive electrode plate 30 and the separator 40 described above to manufacture a sample battery similar to the battery 1.
Next, the output of this sample battery was measured. Specifically, constant current charging and constant current discharging (both 0.05C) were repeated 3 cycles with one set of charging / discharging as one cycle in a voltage range of 3.0 to 4.1 V (conditioning). Subsequently, the battery was charged to 4.1 V at a current value of 0.3 C, and then gradually decreased while maintaining the voltage in a temperature environment of 25 ° C. and held for 90 minutes (constant current−constant). Voltage charging). Furthermore, in a temperature environment of 25 ° C., integrated power (current × voltage sum) was measured when discharged at a predetermined current value (for example, 5 C) for 5 seconds.
Similarly to the negative electrode paste having a shear viscosity of 2100,6500 mPa · s at a shear rate of 1 s ⁻¹ , it was applied to the copper foil 28 and dried in the same manner as the negative electrode paste having a shear viscosity of 550 mPa · s. A battery was manufactured, and the output of each sample battery was measured.

The measurement result of the peeling strength about each negative electrode paste is shown in the graph of FIG. According to this graph, it can be seen that the lower the shear viscosity, the lower the peel strength. This is considered to be because when the shear viscosity is low, the binder 23 in the negative electrode paste easily moves, the migration phenomenon proceeds, or the negative electrode active material particles 22 settle. That is, in the negative electrode paste after application, the ratio of the negative electrode active material particles 22 increases on the copper foil side, while the ratio of the binder 23 decreases. This indicates that a negative electrode paste having a higher shear viscosity at a shear rate of 1 s ⁻¹ is better.

Moreover, the measurement result about the output of the sample battery made using each negative electrode paste is shown in the graph of FIG. In FIG. 7, the output of a sample battery made using a negative electrode paste having a shear viscosity of 6500 mPa · s at a shear rate of 1 s ⁻¹ is 100, and the outputs of other sample batteries are shown as relative values.
According to this graph, the output of the sample battery using the negative electrode paste having a shear viscosity of 550 mPa · s is 95, whereas the output of the sample battery using the negative electrode paste having a shear viscosity of 2100 mPa · s is 101. . That is, it can be seen that there is almost no difference in output between the sample battery using the negative electrode paste having a shear viscosity of 2100 mPa · s and the sample battery using the negative electrode paste having a shear viscosity of 6500 mPa · s. From this, it can be seen that a negative electrode paste having a shear viscosity of 2100 mPa · s or more can prevent migration and sedimentation from occurring in the applied negative electrode paste, and can suppress a decrease in battery output.

Based on the above, battery electrode paste 21P according to this embodiment, the third shear viscosity in the third shear rate (10000s ^-1) is 230 mPa · s, a second shear viscosity of the second shear rate (500 s ^-1) 280 mPa · s, and the first shear viscosity (1 s ⁻¹ ) at the first shear rate is 3000 mPa · s. Thereby, when applying the negative electrode paste 21P to the copper foil 28, the application condition with a shear rate of 10000 s ⁻¹ or less, for example, the gap size GP between the copper foil 28 and the tip surface 323 of the die 320 is set to 100 μm. Even if it is applied at a high speed of 1 m / s, it can be applied to the copper foil 28 with a uniform thickness, and high productivity can be obtained. Further, clogging between the copper foil 28 and the tip end surface 323 of the die 320 does not occur. Furthermore, the negative electrode plate 20 in which the negative electrode active material layer 21 is difficult to peel from the copper foil 28 can be manufactured.

Next, confirmation steps (first confirmation step, second confirmation step, third confirmation step) for confirming the shear viscosity at various shear rates of the negative electrode paste 21P will be described with reference to the drawings.
In this confirmation step, the rotational shear meter VM of Physica MCR manufactured by Anton Paar, which is schematically shown in FIG. 8, is used to measure the first shear rate (1 s ⁻¹ ), the second shear rate (500 s ⁻¹ ), and the third shear rate. The shear viscosity of the negative electrode paste 21P at a shear rate (10000 s ⁻¹ ) was measured. The first shear viscosity (1 s ⁻¹ ) at the first shear rate was 2000 mPa · s or more, and the second shear viscosity at the second shear rate was 350 mPa. It is confirmed whether or not the third shear viscosity at the third shear rate (10000 s ⁻¹ ) is 240 mPa · s or less. The rotational viscometer VM includes a cone plate VMC having a conical shape on one side and a base VMB having a planar shape perpendicular to the axis AX that can rotate around the axis AX.

First, in the first confirmation step of the confirmation steps, the first shear viscosity V1 of the negative electrode paste 21P at the first shear rate (1 s ⁻¹ ) is measured using the above-described rotational viscometer VM. And it is confirmed whether the measured 1st shear viscosity V1 is 2000 mPa * s or more (V1> = 2000).
Next, in the second confirmation step, the above-described rotational viscometer VM is used again to measure the second shear viscosity V2 of the negative electrode paste 21P at the second shear rate (500 s ⁻¹ ). And it is confirmed whether the measured 2nd shear viscosity V2 is 350 mPa * s or less (V2 <= 350).
Next, in the third confirmation step, the above-described rotational viscometer VM is used again to measure the third shear viscosity V3 of the negative electrode paste 21P at the third shear rate (10000 s ⁻¹ ). And it is confirmed whether the measured 3rd shear viscosity V3 is 240 mPa * s or less (V3 <= 240).
In the first confirmation step, the second confirmation step, and the third confirmation step, the negative paste 21P has a first shear viscosity (1 s ⁻¹ ) at a first shear rate of 2000 mPa · s or more, and a second shear viscosity at a second shear rate. Is 350 mPa · s or less and the third shear viscosity at the third shear rate (10000 s ⁻¹ ) is 240 mPa · s or less, the negative electrode paste 21P is advanced to the next coating step.

Next, an application process for applying the negative electrode paste 21P to the copper foil 28 and a drying process for drying the applied negative electrode paste 21P using the application drying apparatus 300 will be described with reference to FIGS.
The coating and drying apparatus 300 includes an unwinding unit 301, a filter 310, a die 320, a heater 330, a winding unit 302, and a plurality of auxiliary rollers 340 (see FIG. 9).

Among these, the filter 310 has a mesh shape having a plurality of 50 μm square holes, and removes agglomerates larger than the holes present in the negative electrode paste 21P.
The die 320 continuously discharges the paste holding part 321 in which the negative electrode paste 21P having passed through the filter 310 is stored, and the negative electrode paste 21P held in the paste holding part 321 toward the copper foil 28. And a discharge port 322.
The discharge port 322 is slit-shaped in the width direction of the copper foil 28 (in the depth direction in FIG. 9) so as to discharge the negative electrode paste 21P in a strip shape on the main surface of the copper foil 28 moving in the longitudinal direction DA. Open in parallel. In addition, the magnitude | size GP of the gap between the copper foil 28 and the front end surface 323 of the die | dye 320 which opposes this copper foil 28 is 100 micrometers (refer FIG. 10).

  The heater 330 heats the copper foil 28 and the negative electrode paste 21 </ b> P applied to the copper foil 28. Thereby, while moving between the two heaters 330, 330, the drying of the negative electrode paste 21P gradually proceeds, and when it has passed through the heater 330, the negative electrode paste 21P is completely dried, that is, the negative electrode paste 21P. All the ion exchange water 26 in the inside has evaporated.

Next, the coating process and the drying process will be described.
First, the strip-shaped copper foil 28 wound around the unwinding portion 301 is moved in the longitudinal direction DA. In addition, the conveyance speed SV of the copper foil 28 is 1 m / s.
And negative electrode paste 21P is apply | coated to the copper foil 28 with the die | dye 320 (refer FIG. 9, 10). Note that the shear rate applied to the negative electrode paste 21P at the tip surface 323 of the die 320 is 10,000 s ⁻¹ .
Then, this negative electrode paste 21P was dried with the heater 330, and it was set as the uncompressed active material layer 21B. Then, the single-side supported copper foil 28 </ b> K carrying the uncompressed active material layer 21 </ b> B on the main surface on one side is temporarily wound around the winding unit 302.

As described above, since the third shear viscosity at the third shear rate is 240 mPa · s, the negative electrode paste 21P can be applied to the copper foil 28 with a uniform thickness.
In addition, since the first shear viscosity at the first shear rate is 2000 mPa · s, the negative electrode paste 21P does not cause a migration phenomenon or a sedimentation phenomenon after coating, and is difficult to peel off from the copper foil 28 after drying. It becomes the material layer 21.

  Next, by using the coating / drying apparatus 300 again, the negative electrode paste 21P is applied to the main surface of the above-described single-side supported copper foil 28K (copper foil 28) on the side not carrying the uncompressed active material layer 21B. . Then, this negative electrode paste 21 </ b> P is completely dried by the heater 330. Thus, the negative electrode active material laminate 20B before pressing in which the uncompressed active material layers 21B and 21B are laminated on both main surfaces of the copper foil 28 is manufactured.

  Thereafter, the uncompressed active material layer 21B was pressed together with the copper foil 28 with a roll press (not shown) to produce the negative electrode plate 20 (see FIG. 2).

On the other hand, a paste (not shown) formed by putting a binder made of PVDF, a positive electrode active material particle made of LiCoO ₂ and a conductive material made of acetylene black into an organic solvent and kneading them, extends in the longitudinal direction DA. It applied to the strip-shaped aluminum foil (not shown). After application, the paste on the aluminum foil was dried. The paste was similarly applied to the back side of the aluminum foil and dried. Then, the positive electrode plate 30 which compressed the paste dried on both the main surfaces of aluminum foil with the roll press which is not shown in figure was produced.

  A power generation element 10 is obtained by winding the separator 40 between the positive electrode plate 30 and the negative electrode plate 20 produced as described above. Furthermore, the positive electrode current collector member 91 and the negative electrode current collector member 92 are welded to the positive electrode plate 30 (aluminum foil 38) and the negative electrode plate 20 (copper foil 28), respectively, inserted into the battery case body 11, and an electrolyte solution (not shown). Then, the battery case body 11 is sealed by welding with the sealing lid 12. Thus, the battery 1 is completed (see FIG. 1).

As mentioned above, in the manufacturing method of the negative electrode paste 21P in the manufacturing method of the battery of this embodiment, it has the above-mentioned confirmation process (a 1st confirmation process, a 2nd confirmation process, a 3rd confirmation process) about the negative electrode paste 21P. Yes. Therefore, the use of the negative electrode paste 21P finishing this, at a shear rate of 10000s ^-1 following coating conditions (shear rate of this embodiment 10000s ^-1), with high productivity, the copper foil 28 uniform thickness The negative electrode paste 21P can be applied to the substrate. Further, clogging in the gap portion between the copper foil 28 and the tip end surface 323 of the die 320 does not occur. Furthermore, it is possible to manufacture a negative electrode paste 21 </ b> P in which the negative electrode active material layer 21 after drying is difficult to peel from the copper foil 28.

Moreover, in the manufacturing method of the negative electrode plate 21 in the manufacturing method of the battery of this embodiment, the application | coating process apply | coated to the copper foil 28 with the shear rate of 10000s < ^-1 > using the negative electrode paste 21P which has the above-mentioned characteristic, and drying Process. For this reason, in the coating process, clogging in the gap between the copper foil 28 and the tip end surface 323 of the die does not occur, and the negative electrode paste 21P having a uniform thickness can be applied to the copper foil 28. Further, it is possible to suppress the migration phenomenon and the sedimentation phenomenon, and to form the negative electrode active material layer 21 that is difficult to peel from the copper foil 28. Thus, the negative electrode plate 20 having the uniform thickness and having the negative electrode active material layer 21 that is difficult to peel off from the copper foil 28 can be manufactured with high productivity.

In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above embodiment, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.
For example, in the embodiment, among the electrodes of the battery, the negative electrode paste on the negative electrode side is shown, but it may be applied to the positive electrode paste on the positive electrode side. Further, in the confirmation process of the manufacturing method, the shear viscosity at each shear rate was measured using a rotational viscometer having a cone plate. For example, instead, the geometry of a parallel plate or a coaxial double cylinder was used. It can be measured using a rotational viscometer or a vibration viscometer.

20 Negative electrode plate (electrode plate)
21P negative electrode paste (battery electrode paste)
22 Negative electrode active material particles (active material particles)
23 Binder 26 Ion-exchanged water (dispersion medium)
28 Copper foil (current collector plate)
323 Tip surface V1 First shear viscosity V2 Second shear viscosity V3 Third shear viscosity

Claims (3)

Active material particles,
A binder,
A battery electrode paste comprising the active material particles and a liquid dispersion medium in which the binder is dispersed,
The first shear viscosity at a first shear rate of 1 s ⁻¹ is 2000 mPa · s or more,
The second shear viscosity at a second shear rate of 500 s ⁻¹ is 350 mPa · s or less, and
A battery electrode paste having a third shear viscosity at a third shear rate of 10,000 s ⁻¹ of 240 mPa · s or less. Active material particles,
A binder,
A method for producing a battery electrode paste comprising: a liquid dispersion medium in which the active material particles and the binder are dispersed;
About the battery electrode paste,
A first confirmation step for confirming that the first shear viscosity at a first shear rate of 1 s ⁻¹ is 2000 mPa · s or more;
A second confirmation step for confirming that the second shear viscosity at a second shear rate of 500 s ⁻¹ is 350 mPa · s or less;
And a third confirmation step for confirming that the third shear viscosity at a third shear rate of 10,000 s ⁻¹ is 240 mPa · s or less. A method of manufacturing an electrode plate by applying a battery electrode paste to a current collector plate,
The battery electrode paste is
Active material particles, a binder, and a liquid dispersion medium in which the active material particles and the binder are dispersed, and a first shear viscosity at a first shear rate of 1 s ⁻¹ is 2000 mPa · s or more. second shear viscosity of the second shear rate of 500 s ^-1 is 350 mPa · s or less, and third shear viscosity in the third shear rate of 10000s ^-1 is not more than 240 mPa · s,
An application step of applying the battery electrode paste to the current collector plate at a shear rate of 10,000 s ⁻¹ or less;
A drying step of drying the applied electrode paste for a battery.

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