JP2014037812A - Rotary pump for manufacturing battery electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary pump which is used for transporting slurry to produce a collector electrode plate for a battery while reducing the coating defects in a coating step and also suppressing a variation in the coating thickness.SOLUTION: When using the rotary pump for transporting the slurry for a battery, clearances between each rotor and a body are kept in a range of two to five times the average particle size of main material particles of an active material to suppress the occurrence of slurry aggregations or foreign matters inside the pump. Thus, the collector electrode plate is provided which has a uniform coating amount.

Description

  The present invention relates to a rotary pump for manufacturing a battery electrode, and relates to a rotary pump used for slurry transportation in a battery electrode manufacturing process.

In recent years, interest in electric vehicles and hybrid vehicles has increased due to environmental problems, and technical demands for higher energy density and higher capacity of the secondary battery that is the driving source have further increased.
In a conventional battery electrode manufacturing method, a slurry obtained by mixing or kneading a main material, an active material, a conductivity-imparting agent, a binder, and a solvent is transported to a coating apparatus by a pump and placed on a current collector made of metal foil. The battery electrode raw material is produced by coating.

Next, a laminated battery in which a positive electrode and a negative electrode cut out from a battery electrode raw material into a predetermined shape are stacked via a separator, a wound battery in which a belt-like positive electrode and a negative electrode are wound via a separator, etc. Is making.
When transporting the positive electrode active material and the slurry for manufacturing the negative electrode active material between each process, use a rotary pump whose gear and side wall are non-contact type, or a contact type mono pump (uniaxial eccentric screw pump). Then, the slurry is transported (see, for example, Patent Document 1).

JP 2007-220380 A

In the case of a lithium ion battery, the slurry for manufacturing a positive electrode includes a positive electrode for a positive electrode such as a metal oxide particle that is a main material of a positive electrode active material such as a lithium manganese composite oxide or a lithium cobalt composite oxide. The positive electrode main material particles, a conductivity imparting agent such as carbon black, a binder such as polyvinylidene fluoride, and a solvent for dispersing them are included.
On the other hand, in the slurry for producing the negative electrode, the negative electrode main material particles for the negative electrode that occlude lithium during charging, such as graphite and amorphous carbon, a conductivity imparting agent such as carbon black, and a binder such as polyvinylidene fluoride. An adhesive and a solvent for dispersing them are included.
Both the positive electrode slurry and the negative electrode slurry contain positive electrode main material particles or negative electrode main material particles that are the main material of the battery reaction, and a conductivity imparting agent, a binder, a solvent, and the like. When the slurry is transported using the above, the following problems occur.

When the pump used for slurry transport is a contact type, there is no gap between the pump casing and the movable member, so the coating amount is easy to stabilize, but the binder in the slurry is subjected to strong shearing stress, so it is bound. The agent segregates and precipitates, and further, the main material of the active material is abnormally combined with the conductivity-imparting agent to generate aggregates. For this reason, when a battery electrode is manufactured using such a slurry, there arises a problem that an abnormality occurs in the electrode produced by the aggregate.
In addition, when using a non-contact type rotary pump, segregation and precipitation of the binder is suppressed compared to the contact type, but the clearance between the rotor and casing of the rotary pump is increased, so The force for pushing out the slurry becomes smaller than the resistance in the pipe, so that a so-called slip phenomenon is likely to occur.
As the slip phenomenon increases, the variation in the slurry flow rate increases, and as a result, the variation in the coating amount increases, resulting in an increase in abnormalities such as a variation in the coating amount of the current collector or coating thickness. It was.
In addition, in this invention, a main material particle means the particle | grains with most compounding ratios per mass in a component.

  The present invention is a rotary pump for transporting a high-viscosity slurry for battery production in the battery electrode production process, and there is no generation of slurry agglomerates inside the pump, and as a result, there is no defect in the applied coating film. It is an object of the present invention to provide a rotary pump for manufacturing a battery electrode capable of providing a battery electrode with excellent reliability.

The present invention includes a casing and two rotors having different rotational directions, the rotor including a plurality of feed blades, and a slurry for producing a battery electrode between each feed blade and the casing. It is a rotary pump for manufacturing a battery electrode provided with a clearance of 2 to 5 times the average particle diameter of each positive electrode active material acting as a main material in the battery reaction or main material particles of the negative electrode active material.
It is a rotary pump for manufacturing a battery electrode in which diamond-like carbon is coated on the surface of the casing, rotor, and feed blade.

In the rotary pump of the present invention, since the shear stress received by the binder in the slurry is reduced, segregation / precipitation of the binder is suppressed, and further, the binder and the positive electrode active material particles, the negative electrode active material particles, or Abnormal bonding with the conductivity-imparting agent and generation of aggregates are suppressed, application abnormality in the application process is greatly reduced, and yield is greatly improved.
In addition, since strong shear stress does not act on the slurry, particle breakage and damage to the wall surface of the pump housing are suppressed. As a result, it is possible to form a coating layer that maintains the characteristics of the prepared slurry, and to prevent foreign matter from being mixed due to peeling of the inner surface of the slurry pump, so that a battery having good characteristics and high reliability can be obtained.

FIG. 1 is a diagram for explaining the internal structure of a rotary pump for manufacturing a battery according to the present invention. FIG. 2 is a diagram illustrating a gap between the casing and the rotor. 3A and 3B are diagrams illustrating the casing, FIG. 3A is a plan view, and FIG. 3B is a right side view. FIG. 4 is a diagram for explaining the rotor, FIG. 4A is a plan view, and FIG. 4A is a right side view. FIG. 5 is a diagram for explaining the experimental results regarding the clearance amount and coating variation between the rotor tip of the rotary pump for slurry transportation and the casing. FIG. 6 is a diagram for explaining the experimental results regarding the clearance amount and coating variation between the rotor tip of the rotary pump for slurry transportation and the casing. FIG. 7 is a diagram for explaining a measurement method for measuring the amount of aggregates in the slurry. FIG. 8 is a graph for explaining the rate of increase in the differential pressure between the MONO pump and the rotary pump when compared with the method shown in FIG.

FIG. 1 is a diagram illustrating a rotary pump for manufacturing battery electrodes according to the present invention.
The battery electrode manufacturing rotary pump 1 of the present invention includes a casing 3 and two rotors 5a and 5b. Each rotor rotates in mutually different rotation directions 4a and 4b.
In the figure, the rotor 5a is a drive-side rotor, and the driven-side rotor 5b is rotated in the same rotational direction 4b as the rotational direction 4b different from the rotational direction 4a of the drive-side rotor 5a by a gear or the like attached to the rotational shaft of the drive-side rotor 5a. Rotate with.
The rotor 5a includes feed blades 5a1 and 5a2. Similarly, the rotor 5b includes feed blades 5b1 and 5b2.

As shown in FIG. 1 (A), the two rotors 5a and 5b are rotated at the same speed in different rotational directions 4a and 4b, so that the casing 3, the rotary shaft of the rotor 5a, and the two feed blades 5a1 and 5a2 As a result of the increase in the volume of the formed space A, the pressure in the space A decreases, and as a result, the slurry is sucked into the space A from the suction port 8.
Next, according to the rotation of the rotor, the space A filled with the slurry moves as shown in FIG. On the other hand, when the pressure of the space B decreases due to the increase in the volume of the space B formed by the casing 3, the rotating shaft of the rotor 5b, and the two feed blades 5b1 and 5b2 due to the rotation of the rotor, the slurry flows from the suction port 6 into the space B. Inhaled.

When the rotors 5a and 5b further rotate, as shown in FIG. 1 (C), the volume of the casing 3 and the internal space C decreases and pressure is generated, so that the slurry is discharged from the discharge port 16.
At the same time, the slurry is sucked into the space C as the pressure decreases due to the increase in the volume of the space C formed by the casing 3, the rotating shaft of the rotor 5a, and the feed blades 5a1 and 5a2.

  Further, when the rotors 5a and 5b rotate, the pressure decreases as the volume of the space D formed by the casing 3, the rotating shaft of the rotor 5b, and the feed blades 5b1 and 5b2 increases as shown in FIG. Thus, the slurry is sucked into the space D from the suction port 6. At the same time, the slurry introduced into the space B is discharged from the discharge port 6 as a result of the pressure rising as the volume of the space B decreases.

  As described above, the process of transferring the slurry from the suction port 6 to the discharge port 7 only by the movement of the space formed by the casing, the rotating shafts of the rotors and the feed blades, and the increase and decrease of the pressure in each space. The slurry can be sucked and discharged continuously and smoothly only by continuously. As described above, since there is no step of applying a large shearing force to the slurry in the pump, the sucked slurry for battery electrode production can be transported without being altered by the large shearing force.

In the rotary pump for slurry for battery electrode production according to the present invention, the gap between the casing and the outer peripheral surface of the rotor, that is, the gap between the casing and the tip of the feed blade has a specific size. .
FIG. 2 is a view for explaining the relationship of the gap between the casing and the outer peripheral surface of the rotor, and is a view with a part cut away.
A gap 11 exists between the inner peripheral surface 9 of the casing 3 and the outer peripheral surface 10 of the feed blade 5a1 of the rotor 3a. The clearance 11 is provided with a clearance of 2 to 5 times the average particle diameter of the main material particles of the positive electrode active material and the main material particles of the negative electrode active material that act as the main material in the battery reaction. is there.
In the present invention, a large shear force is applied to the slurry by providing a clearance 2 to 5 times larger than the particle diameters of the main material particles of the positive electrode active material and the main material particles of the negative electrode active material in the slurry. Thus, it has been found that smooth slurry transportation can be realized.

Thus, if the clearance is more than twice the average particle size of the main material particles of the active material, a large shear stress does not act on the main material particles of the active material and the conductivity-imparting agent. Damage such as peeling of the body surface is suppressed. As a result, it is possible to apply an electrode having a uniform particle diameter of the main material particles of the active material, and to prevent foreign matter from being mixed from the pump, thereby obtaining a battery having good characteristics and high reliability.
On the other hand, if the clearance is 5 times or less of the average particle size of the main material particles of the active material, since the slip phenomenon in the slurry transport process is small, it is possible to perform stable slurry transport with small variations in slurry flow rate, Uniform electrode coating is possible and the yield is greatly improved.

3A and 3B are diagrams illustrating the casing, in which FIG. 3a is a plan view and FIG. 3b is a right side view.
The casing 3 is made of a metal material such as stainless steel, and has rotor shaft mounting holes 5a5 and 5b5 for attaching a rotor shaft, and a slurry flow path 8.
A rotary pump can be produced by sealing the rotor shaft mounting hole with a gasket after mounting the rotor.

4A and 4B are diagrams for explaining an example of the rotor. FIG. 4A is a plan view and FIG. 4B is a right side view.
The rotor 5a has a rotor shaft mounting hole 5a5 at the center, and the rotor shaft mounting hole 5a5 is provided with a spline 5a8 to prevent the rotor from being displaced from the rotor shaft, thereby enabling reliable operation. Yes.

Example 1
A positive electrode slurry and a negative electrode slurry were prepared as follows.
Preparation of positive electrode slurry 56.5% by mass of lithium manganese composite oxide as a main component of the positive electrode, 2.5% by mass of carbon black particles as a conductivity imparting agent, and 2.5% by mass of a binder are sequentially charged into a mixer. .
At this time, the inside of the mixer is performed in a vacuum state of about 100 kpa. After the materials were added, the mixture was stirred and mixed at 8 rpm for 40 minutes, 38.5% by mass of N-methylpyrrolidone was added as a solvent, and the mixture was stirred and mixed at 18 rpm for 8 hours.
The positive electrode main agent had an average particle diameter of 10 μm and 20 μm, and each slurry was prepared.
In addition, the measurement of the particle size including the present example is based on a volume standard measured using a particle size distribution measuring apparatus by a laser diffraction / scattering method.

Preparation of Negative Electrode Slurry 49.5% by mass of amorphous carbon as the main component of the negative electrode, 0.5% by mass of carbon black particles as a conductivity-imparting agent, and 3% by mass of a binder were sequentially added to a mixer and stirred and mixed. Thereafter, 47% by mass of N-methylpyrrolidone was added and further stirred and mixed.
A negative electrode main agent having an average particle diameter of 25 μm was prepared to prepare a slurry.
FIG. 5 is a diagram in which the average particle size of the main agent, the results obtained when the positive electrode 10, 20 μm, and the negative electrode 25 μm were used are written together, and shows the relationship between the slurry particle size and the clearance without dependence on polarity.

The positive electrode slurry and negative electrode slurry prepared as described above were coated with a diamond-like carbon film by observing the inside of the pump with a rotary pump in which a diamond-like carbon film was coated on the rotor and casing surfaces with a thickness of 2 μm, and after 1000 hours of pump operation. The presence or absence of peeling is confirmed by the change in the color of the surface, the relationship between the clearance between the rotor and the casing and the peeling of the coating is examined, and the results are shown in FIG.
As a result, damage to the rotor and casing depends on the average particle size and clearance of the main material of the active material. If the clearance is more than twice the average particle size of the main material of the active material, the rotor and body will be damaged. Since it was not damaged, it was found that the slurry could be transported without foreign matter from the rotor or casing entering the slurry.

Example 2
In the same manner as in Example 1, the relationship between the dispersion amount of the slurry applied to the volume average particle diameter of the positive electrode main agent of 10 μm and 20 μm and the clearance between the casing of the rotary pump and the tip of the rotor was measured. The results are shown in FIG.
When the clearance is large, the ratio of the slurry leaking between the rotor tip and the casing increases, and the scraping ability decreases. Moreover, it becomes easy to be influenced by the load after the slurry discharge side, and the slurry can be sent or not sent. For this reason, the dispersion | variation in the coating amount depending on the supply amount of slurry also becomes large.
It is desirable that the coating variation be small, and the coating thickness uniformity required for the battery electrode needs to be within ± 0.3%.

FIG. 6 shows the experimental results regarding the clearance amount and coating variation between the rotor tip of the rotary pump for slurry transportation and the casing.
According to this, the coating variation increases as the clearance amount increases, but the variation also depends on the average particle size of the main material particles of the active material. When the clearance amount is larger than 5 times the average particle diameter of the main material particles of the active material, the variation rapidly increases and a thickness variation of ± 0.3% or more occurs.
From the above results, the clearance from the tip of the rotor to the casing is in the range of 2 to 5 times the average particle size of the substance that is the main material of the active material. In addition, since it is possible to make the slurry transport uniform, it is possible to obtain an electrode plate in which a uniform coating film is formed on the current collector without causing defective coating or defects.

FIG. 7 is a diagram for explaining a measurement method for measuring the amount of aggregates in the slurry.
A filter 9 for collecting foreign matter is installed on the output side of the pump 12 to be measured, and an inlet side pressure gauge 10 is provided on the inlet side of the filter and an outlet side pressure gauge 11 is provided on the outlet side. Next, from the difference between the measurement results of the inlet side pressure gauge 10 and the outlet side pressure gauge 11, the amount of foreign matter clogged in the filter 9 can be monitored. When the amount of foreign matter clogged inside the filter increases, the pressure gauge 10 on the inlet side rises and the differential pressure tends to increase. At this time, the slurry in the pipe 13 flows in the direction of the slurry direction 14.

FIG. 8 shows a comparison result of the increase in the differential pressure before and after the filter.
FIG. 8 is a graph showing the rate of increase in differential pressure between the MONO pump and the rotary pump when the method shown in FIG. 7 is compared.
In this comparative experiment, as a filter 9 shown in FIG. 7, a filter that collects foreign matters having a size of 75 μm or more is used and compared at the same flow rate. The flow of the slurry is a result of flowing for 90 hours continuously, and the differential pressure gradually increases.
As shown in FIG. 8, the differential pressure of the rotary pump is less likely to increase compared to the MONO pump. This is because the segregation / precipitation is reduced, and the segregation / precipitation in the slurry is suppressed by about 1/8 compared to the MONO pump.

  When the rotary pump for manufacturing a battery electrode of the present invention is applied to transport of a slurry of a battery active material, it can efficiently transport the slurry, and the battery electrode manufactured by the transported slurry has a quality as a battery. You can get an excellent one.

DESCRIPTION OF SYMBOLS 1 ... Battery electrode manufacturing rotary pump, 3 ... Casing, 4a, 4b ... Direction of rotation, 5a ... Driving side rotor, 5b ... Driven side rotor, 5a5, 5b5 ... Rotor shaft Mounting hole, 5a1, 5a2, 5b1, 5b2 ... feed vane, 5a8 ... spline, 6 ... suction port, 7 ... discharge port, 8 ... slurry channel, 9 ... filter, DESCRIPTION OF SYMBOLS 10 ... Inlet side pressure gauge, 11 ... Outlet side pressure gauge, 12 ... Pump, 13 ... Piping, 14 ... Slurry flow direction, A, B, C, D ... Space

Claims (2)

  A casing and two rotors having different rotational directions are provided, and the rotor is provided with a plurality of feed blades. Between each feed blade and the casing, slurry for battery electrode production is used in the battery reaction. A rotary pump for producing a battery electrode, wherein a clearance of 2 to 5 times the average particle diameter of each positive electrode active material or negative electrode active material main material particle acting as a material on a volume basis is provided.   The rotary pump for battery electrode production according to claim 1, wherein diamond-like carbon is coated on surfaces of the casing, the rotor, and the feed blade.