JP2017091995A - Method of manufacturing lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a lithium ion battery, capable of improving film-forming properties by forming granulated bodies with micro diameters.SOLUTION: A method of manufacturing a lithium ion battery includes: a granulation step of stirring material powder 1 at a mixing section 13 of a stirrer 10 to form granulated bodies 2; a kneading step of kneading the granulated bodies 2 obtained in the granulation step with a solvent to form an electrode mixture paste; and a coating step of coating the electrode mixture paste formed in the kneading step. In the granulation step, the mixing section 13 is allowed to contain gas containing moisture, or the mixing section 13 is allowed to be cooled.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a lithium ion battery.

  A lithium ion battery is usually configured by storing a positive and negative electrode plate wound together with a separator in a case. The electrode plate is obtained by coating a current collector foil with an active material layer. Therefore, an electrode plate is manufactured by coating the metal foil used as current collection foil with the paste containing an active material component, and drying it. The paste is a granulation step in which two or more kinds of material powders such as an active material and a dispersing agent are put into a mixing part of a stirrer and mixed by stirring to form a granulated body, and the granulated body is kneaded with a solvent. And kneading process to be manufactured.

A method for forming a granulated body by stirring material powder is described in, for example, Patent Documents 1 to 3.
Patent Document 1 describes forming a granulated body by charging material powder into a cylindrical casing and then stirring the material powder with a plurality of rotor blades installed in the casing. .
Patent Document 2 describes that a granulated body is formed by putting a material powder and a liquid solvent into a container of a stirrer and stirring them.
Patent Document 3 describes that a material powder is put into a mixer container, and the material powder and the liquid are mixed while the liquid is gradually added to form a granulated body.

JP-A-11-169699 Japanese Patent Laying-Open No. 2015-032554 JP 2007-222861 A

However, the above-described prior art has the following problems.
In the case of producing a granulated material used for the production of a lithium ion battery by the method described in Patent Document 1, for example, in addition to an active material and a dispersant as material powders, a solvent is put into a casing, and then these are mixed with a rotor blade. Stir. Stirring is performed until the solvent is uniformly dispersed in the active material and the active material is uniformly wetted (hereinafter, the time from the start of stirring until the active material is uniformly wetted is referred to as “granulation time”. .) This is because a granulated body that is not sufficiently wet may cause cracking or chipping in the active material during the kneading process, and may activate the portion where the active material has cracked or chipping, thereby deteriorating battery characteristics. . In the method described in Patent Document 1, since the solvent is collectively supplied to a part of the material powder before stirring, the stirring is performed in a state where there is a large difference in wetness between the material powders. For this reason, it takes time to uniformly disperse the solvent in the active material and to wet the active material uniformly. That is, the granulation time was long. In the field of manufacturing lithium ion batteries, in order to obtain good film formability, it is desired to form a fine granule having an average particle size of 15 μm or less. The granulated body grows larger as the granulation time becomes longer. Therefore, in the method described in Patent Document 1, since the granulation time is long as described above, for example, a large amount of the dispersant adheres to the surface of the active material, so that the granule grows and the film formability deteriorates. There was a fear.

  Also, the method described in Patent Document 2 has the same problems as Patent Document 1 because the material powder (for example, active material and dispersant) and the solvent are put into the container of the stirrer and stirred.

  Further, according to the method described in Patent Document 3, for example, material powder (for example, an active material and a dispersant) is charged into a mixer container, and a granulated body is formed while gradually adding a solvent into the mixer container. . However, also in this method, the solvent is charged only on the upper surface of the material powder, and the solvent cannot be uniformly supplied to each material powder. Therefore, there is a gradient between the wetness of the upper surface of the material powder and the wetness of the bottom surface of the mixer container, and it takes time to uniformly disperse the added solvent in the material powder. Also in the method described in Patent Document 3, since the granulation time becomes long, the grain growth of the granulated body easily proceeds, and it is difficult to form a granulated body having an average particle diameter of 15 μm or less.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a method for manufacturing a lithium ion battery that can form a granulated body with a small diameter and improve the film formability. To do.

  One aspect of the present invention includes a granulating step of stirring a material powder in a mixing portion of a stirrer to form a granulated body, and a granulated body obtained in the granulating step kneaded with a solvent to form an electrode mixture In the manufacturing method of a lithium ion battery having a kneading step for forming a paste, and a coating step for applying the electrode mixture paste formed in the kneading step, the granulation step is performed by using a gas containing moisture. It is a manufacturing method of the lithium ion battery characterized by making it contain in the said mixing part, or cooling the said mixing part.

  In the above configuration, in the granulation step, fine moisture is dispersed in the air of the mixing unit by allowing the mixing unit to contain a gas containing moisture or by cooling the mixing unit. Since the liquid is not added to the mixing part, the material powder is stirred and relocated without containing moisture. At this time, the air in the mixing section enters the gap between the material powders to be rearranged together with fine moisture. The material powder is moistened by adsorbing moisture contained in the air that has entered the gap to the surface and absorbing the moisture. Since fine moisture is dispersed in the mixing section, when the material powder is agitated, it constantly comes into contact with air containing a lot of moisture, and adsorbs and absorbs moisture one after another, increasing the wetness. To go. Each material powder begins to stir from a state that does not contain moisture (no wet gradient), and evenly contacts the air in the mixing part during the stirring to absorb and absorb moisture, so that the wetness is uniform. To rise. Therefore, the material powder supplied to the mixing section is uniformly wetted to a sufficient wetness in a short time to become a granulated body. As described above, in the above configuration, the moisture containing gas is contained in the mixing unit, or the mixing unit is cooled, so that air containing moisture is uniformly supplied to each material powder during stirring to supply moisture to each material. Since the powder is adsorbed and absorbed, each material powder is sufficiently wetted in a short time, and a uniformly wet granulated body can be formed. Therefore, according to the said structure, a wet gradient is hard to produce at the time of stirring of material powder, and granulation time can be shortened compared with the case where a solvent is added. Since the granulation time is shortened, the granule is suppressed from growing and a granule having a small diameter is formed. Since the granule having a small diameter is uniformly dispersed in the electrode mixture paste, the film formability when the electrode mixture paste is applied can be improved.

  Therefore, according to this invention, the manufacturing method of the lithium ion battery which can form a granule of a micro diameter and can improve film forming property can be provided.

It is a schematic block diagram of the stirrer used for the manufacturing method of the lithium ion battery which concerns on embodiment of this invention. It is a figure explaining arrangement | positioning of the stirring blade of FIG. It is a graph which shows the result of having measured the granule average particle diameter of an Example and a comparative example. It is a graph which shows the result of having investigated the solid content rate of the Example and the comparative example.

  Embodiments of a method for producing a lithium ion battery according to the present invention will be described below with reference to the drawings.

  The manufacturing method of the lithium ion battery of this embodiment manufactures a lithium ion battery through the "granulation process", the "kneading process", and the "coating process". Among these, the “kneading process” and the “coating process” are not particularly different from the conventional ones. The feature of this embodiment is the “granulation step”. Therefore, the following description will focus on the “granulation step”.

<Schematic configuration of agitator>
First, the schematic structure of the stirrer 10 used for the granulation process will be described. In FIG. 1, the schematic block diagram of the stirrer 10 is shown. FIG. 2 is a diagram illustrating the arrangement of the stirring blades 16a and 16b in FIG.
As shown in FIG. 1, in the stirrer 10, the mixing unit 13 is formed by airtightly closing the opening of the mixing container 11 with the lid member 12. A motor 14 is attached to the lid member 12, and a motor shaft 15 protrudes into the mixing unit 13. A bearing 11 a that supports the tip of the motor shaft 15 is provided on the bottom surface of the mixing container 11. As shown in FIGS. 1 and 2, agitation blades 16a and 16b are fixed to the motor shaft 15 so as to rotate integrally. The lid member 12 is provided with a material powder supply unit 17 that supplies the material powder 1 and a humidified gas supply unit 18 that supplies a gas containing moisture (hereinafter referred to as “humidified gas”). A cooling unit 19 is provided in the mixing unit 13 to cool the mixing unit 13.

<Granulation process>
Next, the procedure for forming the granulated body 2 using the stirrer 10 will be described. The stirrer 10 drives the motor 14 while supplying the material powder 1 and the humidified gas from the material powder supply unit 17 and the humidified gas supply unit 18 to the mixing unit 13.

  When the humidified gas is supplied to the mixing unit 13, the volume increases and water is generated. At this time, the cooling unit 19 cools the mixing unit 13. Thereby, the air of the mixing part 13 is cooled and it becomes easy to generate | occur | produce fine moisture. Therefore, the mixing unit 13 is in a state where a lot of fine moisture is dispersed in the air.

  When the material powder 1 is supplied to the mixing unit 13, the material powder 1 is stirred by the stirring blades 16a and 16b. Since the liquid powder is not added to the mixing unit 13, the material powder 1 is agitated and rearranged without containing moisture. At this time, the air of the mixing unit 13 enters the gap between the material powders 1 to be rearranged together with fine moisture. The material powder 1 that does not contain moisture wets when moisture contained in the air that has entered the gap adheres to the surface and absorbs the moisture. Since a lot of fine moisture is dispersed in the air in the mixing section 13, the material powder is constantly agitated to come into contact with air containing a lot of moisture, and adsorbs and absorbs moisture one after another. , Increase the wetness. Each material powder 1 starts to be stirred from a state that does not contain moisture (a state in which there is no wetting gradient), and evenly contacts the air of the mixing unit 13 during the stirring to absorb and absorb moisture, so that the wetness is high. It rises uniformly. Therefore, the material powder 1 supplied to the mixing unit 13 is uniformly wetted to a sufficient wetness in a short time to become a granulated body 2.

  Thus, in this granulation process, the gas containing moisture (humidified gas) is contained in the mixing unit 13 or the mixing unit 13 is cooled, so that the air containing moisture is mixed with each material powder 1 during stirring. Since the moisture is absorbed and absorbed by each material powder 1 evenly, each material powder 1 is sufficiently wetted in a short time, and the uniformly wet granulated body 2 can be formed. Therefore, according to the said structure, a wet gradient is hard to produce at the time of stirring of the material powder 1, and granulation time can be shortened rather than the case where a solvent is added. Since the granulation time is shortened, the granulated body 2 is suppressed from growing, and the granulated body 2 having a small diameter is formed.

  Here, the stirring blades 16 a and 16 b are disposed in parallel with the bottom surface of the mixing unit 13 and are disposed above the bottom surface of the mixing unit 13. The material powder 1 that does not contain moisture (for example, an active material having an average particle diameter of less than 15 μm) is mixed so as to be scattered in the mixing unit 13 by being stirred by the stirring blades 16a and 16b. The material powder 1 becomes dull as it absorbs moisture. The sufficiently wet granulated body 2 falls below the stirring blades 16a and 16b, is collected near the bottom surface of the mixing unit 13, and is not stirred. Therefore, the granulated body 2 is uniformly wetted and formed in a substantially uniform size.

<Kneading process>
Next, a procedure for producing an electrode mixture paste using the granulated body 2 obtained in the granulation step will be described. First, after kneading the granulated body 2 and the solvent, the additive and the solvent are added and kneaded. Since the granulated body 2 is sufficiently moistened, it is difficult for the material powder to be cracked or chipped at the initial stage of kneading. Since the granulated body 2 has a small diameter, an electrode mixture paste in which a large number of granulated bodies 2 are uniformly dispersed in a solvent can be formed.

<Coating process>
Next, a procedure for applying the electrode mixture paste formed in the kneading step will be described. First, an electrode mixture layer is formed by applying and drying an electrode mixture paste on the surface of the current collector foil. The electrode mixture paste is easy to apply to the current collector foil because the granule having a small diameter is uniformly dispersed and the viscosity is low. In addition, the electrode mixture paste contains a large number of granules 2 and the amount of the solvent is small. Therefore, the drying time at the time of coating can be shortened. Therefore, the electrode mixture paste has good film formability. Moreover, since drying time becomes short, the load of drying processes, such as energy cost, can be reduced.

  The electrode plate thus provided is laminated with the separator by winding or flattening to form an electrode body, and the lithium ion battery is manufactured by housing the electrode body in a case.

  Next, examples of the present invention will be described together with comparative examples. In the embodiment, the granulated body 2 is formed by stirring the material powder until the material powder is uniformly moistened while adsorbing moisture contained in the humidified gas (for example, water vapor) to the material powder 1 (for example, natural graphite). On the other hand, in the comparative example, a granulated body (here, formed in the example) is obtained by adding a solvent (for example, water) to the material powder 1 (for example, natural graphite) and stirring until the material powder 1 is uniformly wetted. In order to distinguish from the granulated body 2 to be formed, it is referred to as “granulated body 2x”). In Examples and Comparative Examples, the same conditions [type of stirrer, type of material powder 1 (for example, natural graphite, which is an example of an active material, and dispersion) except for the moisture state (gas, liquid) that wets the material powder 1 Granules 2 and 2x are formed by sodium carboxymethylcellulose, which is an example of the agent), mixing ratio, sample weight, measurement temperature, stirring speed, wetness, and the like. Inventors measured the average particle diameter of the granulated material 2 and 2x formed by the Example and the comparative example. The result is shown in FIG.

  As shown in FIG. 3, when the average particle diameter of the granulated body 2x formed in the comparative example is 100, the average particle diameter of the granulated body 2 formed in the example was 75.6. Therefore, the Example was able to make the granulated body 2 into about 25% fine particles from the comparative example. This is considered because the granule 2 that was uniformly wetted earlier than the comparative example could be formed in the example, and the granulation time could be shortened.

  Moreover, the electrode mixture paste was formed using the granulation bodies 2 and 2x formed by the Example and the comparative example. Each electrode mixture paste has the same conditions except for the granulated bodies 2 and 2x [model of kneader, type of solvent (for example, water), type of additive (for example, styrene butadiene rubber, etc.), mixing ratio, sample weight, Measurement temperature, kneading speed, kneading time, etc.). Inventors measured the solid content rate which is the weight ratio of the granulated bodies 2 and 2x which occupy in a paste about each electrode compound material paste. The result is shown in FIG.

  As shown in FIG. 4, when the solid content rate of the comparative example was 100, the solid content rate of the example was 114.3% of the comparative example. Therefore, the Example was able to improve the solid content rate by about 15% compared with the Comparative Example. This is considered to be because the granulated body 2 was finer than the comparative example, and many granulated bodies 2 were uniformly dispersed in the electrode mixture paste. When the solid content ratio is improved, the solvent in the electrode mixture paste is reduced, so that the load of the drying process (drying time, energy cost, etc.) can be reduced.

In addition, this invention is not limited to the said embodiment, Various application is possible.
For example, in the above embodiment, the humidified gas is supplied to the mixing unit 13 and cooled by the cooling unit 19, but only the supply of the humidified gas or only the cooling of the mixing unit 13 may be performed.
For example, the mixing unit 13 may have another form.
In addition, for example, the material powder 1 and the humidified gas may be supplied by supplying the humidified gas after the material powder 1 is supplied or supplying the material powder 1 after the humidified gas is supplied.

DESCRIPTION OF SYMBOLS 1 Material powder 2 Granule 10 Stirrer 13 Mixing part

Claims (1)

A granulating step of stirring the material powder in the mixing part of the stirrer to form a granulated body;
A kneading step of kneading the granulated body obtained in the granulation step with a solvent to form an electrode mixture paste;
In a manufacturing method of a lithium ion battery having a coating step of coating the electrode mixture paste formed in the kneading step,
The method for producing a lithium ion battery, characterized in that the granulating step contains a gas containing moisture in the mixing unit or cools the mixing unit.

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