JP6288700B2 - Method for producing electrode slurry - Google Patents

Description

  The present invention relates to a method for producing an electrode slurry used for, for example, an electrode of a lithium ion battery.

  A positive electrode and a negative electrode included in a lithium ion secondary battery are configured by applying an electrode slurry to the surface of a metal foil. This type of electrode slurry is formed by kneading a powder material and a solvent (see, for example, Patent Documents 1 to 3).

  An electrode slurry manufacturing method related to the present invention includes a mixing step of mixing an electrode active material powder, a conductive material powder, and a binder material powder including a binder powder, a solvent is added to the mixed powder material, and the powder material is mixed. A kneading step for kneading.

  In the mixing process, each powder constituting the powder material conveyed by the hopper is supplied from the input port of the mixing device, and the powder material supplied from the input port is supplied into the mixing container of the mixing device through the input path. Is done. In the mixing device, the powder material is mixed by agitating the powder material put into the mixing container with a rotating blade.

  In general, in the mixing step, the electrode active material powder, the conductive material powder, and the binder powder are put into the mixing device in this order, and then the powder material is mixed. In the kneading step, an electrode slurry is formed by charging a solvent into the powder material mixed by the mixing device and kneading using a rotating blade.

JP 09-265976 A JP 2001-351616 A JP 2013-196804 A

  Incidentally, as described above, the mixing step in the method for producing an electrode slurry related to the present invention has a problem as shown in FIG. FIG. 4 is a schematic diagram for explaining a problem caused by the binder powder in the electrode slurry manufacturing method related to the present invention.

  In the mixing step, as shown in FIG. 4A, the binder powder 9 put in last is positioned at the uppermost part in the mixing container 4. In the mixing step, when the binder powder is charged into the mixing device 1, the particulate binder powder 9 having a light specific gravity is scattered in the charging path or in the mixing container 4, and the powder material is changed by the rotating blade 5. When mixed, the binder powder 9 arranged at the top of the mixing container 4 rises. For this reason, there is a problem that the binder powder 9 adheres to the inner wall of the charging path, the inner wall of the mixing container 4, and the surface of the rotating blade 5.

  Further, in the mixing apparatus 1, the powder material is mixed after the binder powder 9 is charged, and then when the solvent is charged, as shown in FIG. Or the binder powder 9 adhering to the surface of the rotating blade 5 is wrapped in a binder film dissolved by a solvent and stuck, or as shown in FIG. There is a problem in that the arranged binder powder 9 and the like become a lump encapsulated by a binder film dissolved by a solvent, so-called lumps are generated.

  Occurrence of such lumps of the binder powder 9 may cause the lumps to remain even after the kneading step, so that the binder powder 9, the electrode active material powder 7, and the conductive material powder 8 are made uniform. There is a problem that it is difficult to disperse. For this reason, there is a problem in that the electrode active material and the conductive material are not appropriately combined by the binder, and the quality of the manufactured electrode slurry is deteriorated. As a result, in the coating process in which the manufactured electrode slurry is applied to a metal foil, manufacturing defects such as streaks occur on the surface of the electrode to which the electrode slurry is applied, leading to a decrease in yield.

  In addition, in the electrode slurry manufacturing method related to the present invention, the cleaning operation of the charging path to which the binder powder adheres, the inside of the mixing container, and the rotating blade is complicated, and the cleaning operation is performed to maintain the quality of the electrode slurry. There is a problem that the quality of the electrode slurry in each production lot varies, as well as the necessity of performing it frequently.

  Further, since there is a problem that the above-described lumps occur, there is a problem that the kneading time in the kneading process becomes long in order to obtain an appropriate dispersion state of each powder contained in the powder material.

  Then, an object of this invention is to provide the manufacturing method of the electrode slurry which can solve the subject of the said related technique. An example of the object of the present invention is to prevent the binder powder adhering to the inside of the mixing apparatus from coming into contact with the solvent, and to uniformly disperse the electrode active material powder, the conductive material powder, and the binder powder. An object of the present invention is to provide a method for producing an electrode slurry that can improve the quality of the electrode slurry.

  In order to achieve the above-described object, the method for producing an electrode slurry according to the present invention includes an electrode active material powder and a binder powder mixed in a mixing device and mixed, and a solvent is mixed after the mixing step. In a method for producing an electrode slurry having a kneading step of kneading a powder material including an electrode active material powder and a binder powder, the binder powder is charged into the mixing device in the mixing step. After that, the electrode active material powder is put into a mixing device.

  ADVANTAGE OF THE INVENTION According to this invention, it can prevent that the binder powder adhering in the mixing apparatus and a solvent contact | connect, and can disperse | distribute electrode active material powder, electrically conductive material powder, and binder powder uniformly. As a result, the present invention can improve the quality of the electrode slurry.

It is a schematic diagram which shows the mixing apparatus used with the manufacturing method of the electrode slurry of 1st Embodiment. It is a flowchart for demonstrating the mixing process in 1st Embodiment. It is a flowchart for demonstrating the mixing process which the manufacturing method of the electrode slurry of 2nd Embodiment has. It is a schematic diagram for demonstrating the problem which arises with binder powder in the manufacturing method of the electrode slurry relevant to this invention.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

  The manufacturing method of the electrode slurry of this embodiment is applied in order to manufacture the electrode slurry used for the positive electrode and negative electrode which are electrodes with which a lithium ion secondary battery is equipped.

(First embodiment)
In FIG. 1, the schematic diagram of the mixing apparatus used with the manufacturing method of the electrode slurry of 1st Embodiment is shown. In FIG. 2, the flowchart for demonstrating the mixing process which the manufacturing method of the electrode slurry of 1st Embodiment has is shown.

  The electrode slurry manufacturing method according to the first embodiment includes an electrode active material powder and a binder powder mixed in a mixing apparatus and mixed, and after the mixing process, a solvent is charged in the mixing apparatus. A kneading step of kneading a powder material including an electrode active material powder and a binder powder.

  Moreover, as shown in FIG. 1, the mixing apparatus 1 used with the manufacturing method of the electrode slurry of this embodiment includes a hopper 2 for supplying each powder, and an input path 3 for supplying each powder from the hopper 2. , And a mixing container 4 into which each powder is charged through the charging path 3. In the mixing container 4, a plurality of rotating blades 5 for stirring the powder material 6 and a rotating mechanism (not shown) for driving the rotating blades 5 are provided.

  In the first embodiment, a powder material 6 including an electrode active material powder 7, a conductive material powder 8, and a binder powder 9 is used as a powder material.

  In the mixing step, as shown in FIGS. 1 and 2, the conductive material powder 8 and the binder powder 9 are charged into the mixing device 1, and then the electrode active material powder 7 is charged into the mixing device 1. Mix.

  In the kneading step, an electrode slurry is produced by adding a solvent to the powder material 6 mixed in the mixing step and kneading. In the kneading step, for example, the solvent is added a plurality of times while repeating the addition of the solvent and the kneading of the powder material 6.

  Regarding the mixing step in the above-described electrode slurry manufacturing method, the order in which each powder is charged into the mixing apparatus 1 will be described.

  As shown in FIG. 2, the mixing process starts from step S1, and the conductive material powder 8 is charged into the mixing device 1 (step S2), and then the binder powder 9 is charged into the mixing device 1 (step S2). S3). When the binder powder 9 is charged into the mixing device 1, the binder powder 9 having a low specific gravity rises, and the binder powder 9 adheres to the inner wall of the charging path 3 and the inner wall of the mixing container 4.

  Next, as shown in step S <b> 4, after the binder powder 9 is charged, the electrode active material powder 7 is charged into the mixing device 1, whereby the binder adhered to the charging path 3 and the inner wall of the mixing container 4. The powder 9 is swept away by the electrode active material powder 7 having a high specific gravity and a large input amount. Thus, after the binder material 9 is charged, the electrode active material powder 7 is charged, so that the binder powder 9 adhering to the inner wall of the mixing device 1 can be prevented from remaining.

  Finally, as shown in step S5, each powder is mixed in a state where the binder powder 9 is sandwiched between the layer made of the conductive material powder 8 and the layer made of the electrode active material powder 7 in the mixing container 4. Thus, the mixing process ends (step S6). By mixing in this way, the binder powder 9 rises when the powder material 6 is mixed and prevents the binder powder 9 from adhering to the inner wall of the mixing container 4, and the conductive material powder 8, the binder powder. 9. A powder material in which the electrode active material powder 7 is uniformly mixed is obtained.

  As a result, when the solvent is charged into the mixing device 1 in the kneading step, it is possible to suppress the binder powder 9 from remaining on the inner wall of the charging path 3 and the mixing container 4. It is possible to prevent the material powder 9 from coming into direct contact with the solvent, and to prevent the binding material powder 9 from being damaged.

  As described above, according to the electrode slurry manufacturing method of the first embodiment, in the mixing step, the binder powder 9 is introduced after the binder powder 9 is introduced, whereby the binder powder is obtained. The binder powder 9 adhering to the inner wall of the mixing apparatus 1 is swept away by the electrode active material powder 7 having a specific gravity heavier than 9 and an input amount ten times or more that of the binder powder 9. As a result, it is possible to prevent the solvent introduced in the kneading step from coming into direct contact with the binder powder 9 introduced in the mixing step. For this reason, it is possible to prevent the binding material powder 9 from being damped and to uniformly disperse the electrode active material powder 7, the conductive material powder 8, and the binding material powder 9, and the quality of the manufactured electrode slurry. Can be increased. As a result, according to the present embodiment, in the coating process in which the manufactured electrode slurry is applied to the metal foil, production defects such as streaks are prevented from occurring on the surface of the electrode coated with the electrode slurry, and the yield is improved. be able to.

  In addition, according to the first embodiment, since the binder powder 9 can be prevented from remaining on the inner wall of the mixing device 1, a plurality of production lots can be prepared without cleaning the mixing device 1 after manufacturing the electrode slurry. Can be done continuously. Moreover, since it is suppressed that the binder powder 9 adheres in the mixing apparatus 1, the washing | cleaning operation | work of the mixing apparatus 1 becomes simple and it also becomes possible to shorten the kneading | mixing time in a kneading | mixing process.

  Further, according to the first embodiment, since the binder powder 9 can be prevented from adhering to the inner wall of the mixing device 1, the quality of the electrode slurry can be stably manufactured through a plurality of manufacturing lots.

  In the mixing step in the first embodiment, the conductive material powder 8 is first charged into the mixing apparatus 1 and then the binder powder 9 is charged into the mixing apparatus 1. However, the order is not limited to this. . As a modified example of the first embodiment, in the mixing step, after the binder powder 9 is first put into the mixing apparatus 1, the conductive material powder 8, the electrode active material powder 7, or the electrode active material powder 7, The conductive material powder 8 may be added in this order. However, when the binder powder 9 is first charged into the mixing apparatus 1, the binder powder 9 may adhere to the bottom in the mixing container 4 and cause lumps. For this reason, in the mixing step, it is preferable to put the conductive material powder 8, the binder powder 9, and the electrode active material powder 7 into the mixing device 1 in this order. As described above, by introducing the electrode active material powder 7 after the binder material 9 and the conductive material powder 8 are charged, the electrode active material powder 7 causes the binder material powder 9 and the conductive material powder 8 to flow away. The conductive material powder 8 as well as the dressing powder 9 can be prevented from remaining on the inner wall of the mixing apparatus 1.

  In addition, in the mixing step, when the binder powder 9 is first put into the mixing device 1, the mixing container 4 is washed after the production of the electrode slurry, if necessary, so that the bottom of the mixing container 4 is obtained. Since the adhering binder powder 9 can be removed, the binder powder 9 may be first introduced into the mixing apparatus 1.

  In the present embodiment, the conductive material powder 8 is charged in the mixing step. However, the conductive material powder 8 may be charged in the kneading step without being charged in the mixing step. In this case, the conductive material powder 8 and the solvent may be added in a mixed state as necessary.

  Next, another embodiment using a plurality of types of electrode active material powders and a plurality of types of conductive material powders will be described.

(Second Embodiment)
In FIG. 3, the flowchart for demonstrating the mixing process in the manufacturing method of the electrode slurry of 2nd Embodiment is shown.

  The electrode slurry production method of the second embodiment is different from the first embodiment in that a plurality of types of electrode active material powders 7 and conductive material powders 8 are used as powder materials.

  The material powder in the second embodiment includes a first electrode active material powder 7a, a second electrode active material powder 7b, a first conductive material powder 8a, a second conductive material powder 8b, and a binder powder 9. Contains.

  In the mixing step in the method for producing the electrode slurry of the second embodiment, the order in which the powders are charged into the mixing container 4 will be described.

  As shown in FIG. 3, the mixing process starts from step S11, and the first electrode active material powder 7a is charged into the mixing apparatus 1 (step S12), and then the first and second conductive material powders 8a. , 8b are charged into the mixing apparatus 1 (step S13). Next, the binder powder 9 is charged into the mixing device 1 (step S14). When the binder powder 9 is charged into the mixing device 1, the binder powder 9 having a low specific gravity rises, and the binder powder 9 adheres to the inner wall of the charging path 3 and the inner wall of the mixing container 4.

  After the binder powder 9 is charged, as shown in step S15, the second electrode active material powder 7b is charged into the mixing device 1 so as to adhere to the charging path 3 and the inner wall of the mixing container 4. The powder 9 and the first and second conductive material powders 8a and 8b are swept away by the second electrode active material powder 7b having a high specific gravity and a large input amount. Thus, after the binder powder 9 is charged, the second electrode active material powder 7b is charged, so that the binder powder 9 adhering to the inner wall of the mixing apparatus 1 can be suppressed from remaining.

  Finally, as shown in step S16, in the mixing container 4, the binder powder 9 includes a layer made of the first and second conductive material powders 8a and 8b, and a layer made of the second electrode active material powder 7b. Each powder is mixed in a state of being sandwiched between and the mixing process is completed (step S17). By mixing in this way, the binder powder 9 rises when the powder material 6 is mixed, and the binder powder 9 is prevented from adhering to the inner wall of the mixing container 4, and the first and second conductive material powders are prevented. A powder material 6 in which 8a, 8b, binder powder 9, and first and second electrode active material powders 7a, 7b are uniformly mixed is obtained.

  As a result, when the solvent is charged into the mixing device 1 in the kneading step, it is possible to suppress the binder powder 9 from remaining on the inner wall of the charging path 3 and the mixing container 4. It is possible to prevent the material powder 9 from coming into direct contact with the solvent, and to prevent the binding material powder 9 from being damaged.

  As a modification of the second embodiment, in the mixing step, any one of the first and second electrode active material powders 7a and 7b is charged into the mixing device 1 and then the binder powder 9 is charged into the mixing device 1. In addition, either the first electrode active material powder 7a or the second electrode active material powder 7b may be charged into the mixing apparatus 1 after the binder powder 9 is charged into the mixing apparatus 1.

  In the mixing step, after the first and second conductive material powders 8a and 8b and the binder powder 9 are put into the mixing apparatus 1, at least one of the first and second electrode active material powders 7a and 7b is used. May be put into the mixing apparatus 1.

  Specifically, after the first and second conductive material powders 8a and 8b and the binder powder 9 are charged, the first and second electrode active material powders 7a and 7b may be charged into the mixing apparatus 1. Good.

  In addition, one or both of the first and second conductive material powders 8a and 8b are first charged into the mixing apparatus 1 and then the binder powder 9 is charged, and the binder powder 9 is charged into the mixing apparatus 1 After that, either or both of the first and second electrode active material powders 7 a and 7 b may be put into the mixing apparatus 1. When one of the first and second electrode active material powders 7a and 7b is charged after the binder powder 9 is charged into the mixing apparatus 1, the first and second electrode active material powders 7a and 7b are charged. The other of them may be put into the mixing device 1 at any timing before the binder powder 9 is put in.

  Further, as the plurality of types of electrode active material powders, three or more types of electrode active material powders may be used. Similarly, as a plurality of types of conductive material powder, of course, three or more types of conductive material powder may be used.

  In short, the electrode active material powder 7 is charged after the binder powder 9 is charged into the mixing device 1, so that the binder powder 9 attached to the mixing device 1 is swept away by the electrode active material powder 7. Therefore, it can suppress that the binder powder 9 remains on the inner wall of the mixing apparatus 1. Therefore, also in the second embodiment, an electrode slurry with improved uniform dispersibility can be produced as in the first embodiment.

  In addition, in the second embodiment, when the first electrode active material powder 7 a is first charged into the mixing container 4, the binder powder 9 adheres to the bottom in the mixing container 4 to cause lumps. Can be prevented. This is because when the first and second conductive material powders 8a and 8b are charged in the order of the first and second binder powders 9 in this order, the charged amounts of the first and second conductive material powders 8a and 8b are mixed containers. When the size is smaller than the size (volume) of 4, the binder powder 9 with a part of the bottom in the mixing container 4 exposed from the charged first and second conductive material powders 8 a and 8 b. This is because may be inserted. In such a case, the binder powder 9 may adhere to the bottom in the mixing container 4 and cause lumps.

  However, in the second embodiment, before the binder powder 9 is charged, the first electrode active material powder 7a and the first and second conductive material powders 8a and 8b are charged, so that the mixing container 4 is Even if it is large, the exposure of the bottom in the mixing container 4 can be reduced, so that the binding material powder 9 adheres to the bottom in the mixing container 4 as described above, and the binding powder 9 is degenerated. The effect which can reduce is acquired.

(Example)
The configuration of the powder material will be described in more detail.

  The powder material 6 of the first embodiment is a powder material for forming an electrode slurry used for the positive electrode, and includes a first electrode active material powder 7a, a second electrode active material powder 7b, and a first conductive material. The material powder 8a, the second conductive material powder 8b, and the binder material powder 9 are included.

  Lithium manganate is used as the first electrode active material powder 7a, and lithium nickel layered oxide is used as the second electrode active material powder 7b. As the first conductive material powder 8a, carbon fine particles such as carbon black having a particle size of about several tens to several hundreds of nanometers are used. As the second conductive material powder 8b, fine particles having an average particle diameter of about 3 μm, such as graphite particles, and having a larger particle diameter than the first conductive material powder 8a are used. Polyvinylidene fluoride (PVdF) is used as the binder powder 9.

  As an example of the mixing ratio of the powder material, the first electrode active material powder 7a: the second electrode active material powder 7b: the sum of the first conductive material powder 8a and the second conductive material powder 8b = 7: 2 1 (weight ratio), and the binder powder is about 5% by weight with respect to the total weight of the first and second electrode active material powders 7a and 7b and the first and second conductive material powders 8a and 8b. 9 is added.

  The powder material 6 of the second embodiment is a powder material 6 for forming an electrode slurry used for the negative electrode, and is an electrode active material powder 7, a first conductive material powder 8a, and a second conductive material powder 8b. The binder powder 9 is contained.

  As the electrode active material powder 7, graphite or amorphous carbon is used. As the first conductive material powder 8a, carbon fine particles such as carbon black are used. As the second conductive material powder 8b, graphite particles having a particle size larger than that of the first conductive material powder 8a are used. PVdF is used as the binder powder 9.

  As an example of the mixing ratio of the powder material 6, the electrode active material powder 7: the sum of the first conductive material powder 8a and the second conductive material powder 8b = 99: 1 (weight ratio). 7. About 5% by weight of the binder powder 9 is added to the total weight of the first and second conductive material powders 8a and 8b.

  The method for producing an electrode slurry according to the present invention comprises kneading a powder material containing a first powder having a low specific gravity and a second powder having a high specific gravity and a large amount of input using a liquid, thereby producing a slurry. It may be applied to other slurry manufacturing methods.

DESCRIPTION OF SYMBOLS 1 Mixing device 6 Powder material 7 Electrode active material powder 7a 1st electrode active material powder 7b 2nd electrode active material powder 8 Conductive material powder 8a 1st conductive material powder 8b 2nd conductive material powder 9 Binder material powder

Claims (8)

A mixing step in which an electrode active material powder and a binder powder are put into a mixing device and mixed, and after the mixing step, a solvent is put into the mixing device, and the electrode active material powder and the binder powder are mixed. A kneading step of kneading a powder material containing, and a method for producing an electrode slurry,
In the mixing step, the electrode active material powder is charged into the mixing device after the binder powder is charged into the mixing device.   2. The method for producing an electrode slurry according to claim 1, wherein in the mixing step, a conductive material powder is charged into the mixing device before the electrode active material powder is charged into the mixing device.   The method for producing an electrode slurry according to claim 2, wherein, in the mixing step, the conductive material powder is charged into the mixing device, and then the binder powder is charged into the mixing device. The higher the mixing Engineering includes a plurality of kinds of the electrode active material powder, the method comprising mixing the binder powder, in mixing the plural kinds of the electrode active material powder of the binder material powder, wherein at least either of a plurality of types of the electrode active material powder, and mixing them put before Symbol mixing device after switching on the binder powder to the mixing device, the method of manufacturing the electrode slurry according to claim 1 .   In the mixing step, after any one of the plurality of types of electrode active material powders is charged into the mixing device, the binder powder is charged into the mixing device, and the binder powder is charged into the mixing device. The method for producing an electrode slurry according to claim 4, wherein any one of the plurality of types of electrode active material powders is introduced into the mixing device later. The higher the mixing Engineering includes a plurality of types of conductive material powder, and the plurality of types of the electrode active material powder, the method comprising mixing the binder powder, said plurality of types of conductive material powder and the plurality of types of electrodes When mixing the active material powder and the binder powder, at least one of the plurality of types of electrode active material powder is charged with the plurality of types of conductive material powder and the binder powder into the mixing device. method for producing a pre-SL mixing device for mixing was charged, the electrode slurry according to claim 4 later.   The method for producing an electrode slurry according to claim 1, wherein in the kneading step, the solvent and conductive material powder are charged into the mixing device.   The method for producing an electrode slurry according to claim 7, wherein in the kneading step, the solvent and the conductive material powder are mixed and charged into the mixing device.

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