JP2014071977A - Method and device for manufacturing lithium ion battery - Google Patents

Abstract

A lithium ion battery manufacturing method and a lithium ion battery manufacturing apparatus capable of maintaining electrode quality while reducing an economic burden.
After applying a paste-like electrode material 18 to the surface of an electrode foil 1, a solidified liquid containing a liquid component different from the liquid component contained in the electrode material 18 is used as a high-pressure heating vapor from above the electrode foil 1. While being supplied to the surface of the electrode material 18, a solidification process is performed in which high-pressure and low-temperature air is supplied from below the electrode foil 1 to cool the electrode material 18. Thus, after the electrode material 18 is solidified, the liquid component is removed from the electrode material 18 and dried.
[Selection] Figure 6

Description

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

  Lithium ion batteries use a positive electrode sheet, a negative electrode sheet, and a separator provided between the sheets as a cylindrical or square can structure, or as a film-like battery assembly based on Al (aluminum) or the like. It is a secondary battery manufactured by incorporating and injecting an electrolytic solution and then sealing. Although the manufacturing method and appearance vary greatly depending on the can structure or the film-like structure, the basic components for operating the battery are the same regardless of which structure is used.

  That is, the positive electrode sheet has a structure in which a positive electrode active material is applied on both sides of the electrode foil, and the negative electrode sheet has a structure in which a negative electrode active material is applied on both sides of the electrode foil. In order to prevent a short circuit between the positive electrode active material and the negative electrode active material, a separator is inserted. The active material is also called a mixture. A laminated structure of such a positive electrode sheet, a separator, and a negative electrode sheet is formed, the structure is wetted with an electrolytic solution containing lithium ions, and the laminated body is sealed in various casings. Form.

  An example of a method for manufacturing such a lithium ion battery is described in Patent Document 1 (Japanese Patent Laid-Open No. 11-288741). Patent Document 1 discloses a process for producing a lithium ion battery, in order to deposit a polymer material from an electrode material applied to the surface of an electrode body, the electrode material is a liquid that is hardly soluble in the polymer material. The process of immersing in is described. Below, an example is shown about the outline | summary of the electrode manufacturing process of a positive electrode.

  In the manufacturing process of the positive electrode, first, a slurry material (electrode material) is manufactured by kneading the powder raw material of the positive electrode active material, the conductive material powder, the binder solution and the organic solvent, and this paste is applied to a die coater or the like. Apply thinly and uniformly onto the current collecting aluminum electrode foil. Thereafter, the applied paste is dried to form an electrode film. Next, through a calendar process (a process of crushing and stretching with a roll) for adjusting the electrode film thickness to a predetermined thickness, or a slit process for processing the electrode film into a predetermined shape, etc., for a lithium ion battery The electrode is formed. Thus, the electrode film formed on the surface of the electrode foil for current collection is formed with the same thickness on both surfaces of the electrode foil, for example, and then, in order to increase the energy density of the battery, the positive electrode, the separator and A structure in which negative electrodes are laminated without gaps is formed.

JP-A-11-288874

  As described above, in the lithium ion battery manufacturing process, an electrode film is formed on both sides of the electrode foil through a series of processes of manufacturing an electrode paste, applying paste to the electrode foil, and drying, or combining these processes. It is necessary to create a sheet. However, the production of such an electrode sheet requires a large cost, and improvement in electrode quality maintenance is also desired.

  The objective of this invention is providing the manufacturing method of a lithium ion battery which can maintain electrode quality, reducing a manufacturing cost, and the manufacturing apparatus of a lithium ion battery.

  The above object and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  Of the embodiments disclosed in the present application, the outline of typical ones will be briefly described as follows.

  In one embodiment, a method for manufacturing a lithium ion battery includes applying a paste-like electrode material to the surface of an electrode foil, and then applying a solidified liquid containing a liquid component different from the liquid component contained in the electrode material to high-pressure heating steam. After performing a solidification process by supplying to the surface of an electrode material from above the electrode foil, the liquid component is removed from the electrode material and dried.

  Moreover, the manufacturing apparatus of the lithium ion battery which is one embodiment has a vapor generation mechanism, and the paste formed on the surface of the electrode foil by supplying the vapor from the vapor generation mechanism to the surface of the electrode foil Is to solidify.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the lithium ion battery which can maintain the quality of an electrode or a separator can be provided, reducing manufacturing cost.

  Moreover, according to this invention, the manufacturing apparatus of the lithium ion battery which can maintain the quality of an electrode or a separator can be provided, reducing manufacturing cost.

It is the schematic of the electrode manufacturing apparatus which comprises the manufacturing apparatus of the lithium ion battery which is Embodiment 1 of this invention. It is sectional drawing of the lithium ion battery which is Embodiment 1 of this invention. It is an overhead view of the air levitation conveyance apparatus of Embodiment 1 of this invention. It is sectional drawing of the air levitation conveyance apparatus of Embodiment 1 of this invention. It is a graph which shows the saturation point of water which changes with pressure conditions. It is the schematic of the solidification apparatus which comprises the manufacturing apparatus of the lithium ion battery which is Embodiment 1 of this invention. It is the table | surface which compared the characteristic of the electrode film of Embodiment 1 of this invention, and the electrode film of a comparative example. It is the schematic of the electrode manufacturing apparatus which comprises the manufacturing apparatus of the lithium ion battery which is Embodiment 2 of this invention. It is the schematic of the electrode manufacturing apparatus which comprises the manufacturing apparatus of the lithium ion battery which is Embodiment 3 of this invention. It is the schematic of the manufacturing apparatus of the lithium ion battery shown as a comparative example. It is the schematic of the manufacturing apparatus of the lithium ion battery shown as a comparative example. It is the schematic of the manufacturing apparatus of the lithium ion battery shown as a comparative example. It is the schematic which shows the solidification apparatus shown as a comparative example.

  Hereinafter, an embodiment of the present invention will be described in detail based on the drawings in comparison with a comparative example. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. Also, in the following embodiments, the description of the same or similar parts will not be repeated in principle unless particularly necessary.

  Lithium-ion batteries include a positive electrode sheet and a negative electrode sheet, which are electrodes, and a separator provided between the sheets, which are assembled into a cylindrical container, and an electrolyte is injected into the container, followed by sealing. It is a secondary battery manufactured by doing.

  In this application, the positive electrode sheet or the negative electrode sheet is constituted, and the film formed on the surface of the current collecting electrode foil is referred to as an electrode film. When the electrode film is formed, it is applied to the electrode foil and not dried. The film is called an electrode material or an electrode material paste. That is, the electrode film is formed by drying the electrode material. However, in the actual parent forms 1 to 3 to be described later, even a film that is solidified and loses fluidity may be called a paste. Moreover, the electrode foil in which the electrode film was formed on the surface is called a positive electrode sheet, a negative electrode sheet, or them collectively as an electrode sheet. Moreover, the paste as used in this application is a liquid substance which contains liquids, such as a binder solution or an organic solvent, and has fluidity | liquidity. In addition, in the present application, the term “surface of the electrode foil” refers not only to the entire surface including the upper surface and the bottom surface of the electrode foil, but only to the upper surface not including the back surface of the electrode foil transported by the roller transport system. .

  Below, the manufacturing method of the electrode of a lithium ion battery is demonstrated using FIGS. 10-12 as a 1st-3rd comparative example. 10 to 12 are schematic views of a lithium ion battery manufacturing apparatus shown as a comparative example.

  FIG. 10 shows a configuration of a single-side coating type electrode manufacturing apparatus as a first comparative example. The paste (electrode material) used to form a positive electrode or negative electrode film for a lithium ion battery includes, for example, an active material powder, a conductive material powder, a binder material for binding these powders, and the like. -A highly viscous slurry liquid dispersed in an organic solvent such as methylpyrrolidone (NMP). In forming the electrode film on the surface of the electrode foil 1 in the first comparative example, first, using the coating means 3 such as a die coater in which the paste is installed in the coating portion 2, the current collecting electrode foil It is applied thinly and uniformly on the electrode foil 1 supplied from the roll 4.

  Subsequently, the electrode foil 1 coated with the paste is conveyed into a hot air drying furnace shown as a drying chamber 6 by using a roller conveyance system 5 for conveying the electrode foil 1 at a constant speed while being in contact with the back surface of the electrode foil 1. . Thereafter, the solvent component in the paste is heated and evaporated in the drying chamber 6 to dry the paste, thereby forming an electrode film. The electrode foil roll 7 that has wound up the electrode foil 1 that has undergone the drying step is supplied to the next step. In the manufacturing process of the electrode film of the first comparative example, such a process is performed on the front and back surfaces of the electrode foil to manufacture an electrode sheet made of electrode foil coated on both sides. The electrode film dried here loses moisture in the film, loses fluidity, and becomes a complete solid.

  In the above manufacturing method, in order to manufacture an electrode sheet with good quality and high reliability, or in order to ensure safety during manufacturing, it is considered that drying takes a long time and a large cost. That is, in the paste drying process, the drying proceeds by evaporation of the solvent from the paste surface accompanying the supply of heat to the paste. If the evaporation rate is too high, the drying process cannot be performed uniformly on the entire surface of the electrode foil, or the composition in the thickness direction of the formed electrode film is uneven or unstable. Due to restrictions, a large burden is required on the manufacturing equipment. For such a problem, it is possible to take measures such as applying and drying the electrode material in a plurality of times or adjusting the composition of the paste applied in a plurality of times to be different.

  Moreover, the conveyance speed of the electrode foil 1 in the drying process of an electrode material uses about 1-100 m / min. At this time, as the drying time, the electrode material is dried using a time of about 1 to 100 minutes. In a region close to the lower limit of the transport speed, that is, when the transport speed is 1 m / min, for example, since the transport speed in the drying chamber 6 is slow, the drying can be performed slowly at a relatively low temperature. 6 can be small, and the quality of the electrode film to be manufactured (for example, the uniformity of the composition distribution in the electrode film) tends to be stable. However, in the region close to the lower limit of the conveyance speed, the productivity of electrode sheet manufacturing is small, so there is a problem that the manufacturing cost is relatively increased and it is difficult to supply an inexpensive lithium ion battery.

  On the other hand, in the region close to the upper limit of the conveyance speed, that is, for example, when the conveyance speed is set to 100 m / min or the like, it is possible to increase the productivity of electrode sheet manufacturing, but drying necessary to ensure electrode quality is possible. In order to secure time, the drying chamber becomes very long. In this case, there arises a problem that the equipment cost of the drying chamber 6 itself and the running cost such as a large amount of heat energy for operating the large drying chamber 6 increase. The drying chamber 6 at this time needs to have a long conveyance path of about 100 m inside, for example, in order to perform drying at a relatively low temperature for a long time.

  In order to deal with such conflicting issues, it is conceivable to construct the electrode manufacturing process and equipment by adjusting both in the extreme intermediate region and empirically obtaining the optimum value, but in this case, the advantages of both Can't make the most of it. From such a problem, it is required to realize an electrode manufacturing method that enables high-speed drying and maintains high electrode quality.

  Moreover, in order to improve the productivity of an electrode sheet, it is also conceivable to dry the electrode material rapidly at a high temperature. However, in such a method, only the surface of the electrode material is dried first, and there is a problem that a difference in concentration occurs between the inside and the surface of the electrode material. Therefore, in the method of the comparative example described above, the electrode material takes time. It needs to be dried.

  FIG. 11 shows a configuration of a sequential double-sided coating type electrode manufacturing apparatus as a second comparative example. In the manufacturing process of the electrode film in the second comparative example, first, from the collecting electrode foil roll 4 using the coating means 3 such as a die coater in which the electrode material paste (electrode material) is installed in the coating portion 2. It is applied thinly and uniformly on the surface of the electrode foil 1 to be supplied. Thereafter, the electrode foil 1 coated with the paste is conveyed to a hot air drying furnace shown as a drying chamber 6 using a roller conveyance system 5 for conveying the electrode foil 1 at a constant speed while being in contact with the back surface of the electrode foil 1. Subsequently, in the drying chamber 6, the solvent component in the paste is heated and evaporated to dry the paste, thereby forming an electrode film. This series of steps is the same as that of the first comparative example shown using FIG.

  In the first comparative example, after winding the electrode foil 1 having the electrode film formed on one side through the above steps, the step of forming the electrode film on the back surface of the electrode foil 1 was performed again. On the other hand, in the second comparative example, in the case of double-sided coating, the electrode foil 1 that has undergone the drying process is not taken up, and the paste is applied to the back surface of the electrode foil 1 using the coating means 3a in the next coating part 2a. The electrode foil 1 is conveyed using the roller conveyance system 5a, and the paste on the back surface is dried in the drying chamber 6a. Thus, an electrode sheet including the electrode film and the electrode foil 1 is formed by forming an electrode film obtained by drying the paste on both surfaces of the electrode foil 1. Then, after winding up an electrode sheet on the electrode foil roll 7, the electrode foil roll 7 is supplied to the following process.

  In the case of such continuous coating, an electrode foil having electrode films formed on both the front surface and the back surface can be manufactured, but a drying chamber is separately required for each coating. Also in this case, as described with reference to FIG. 10, there is a problem that the manufacturing cost increases in order to maintain the quality of the electrode film.

  FIG. 12 shows the configuration of a double-sided coating batch drying type manufacturing apparatus that can be considered as a third comparative example in order to solve the above problems. In the manufacturing process of the electrode film in the third comparative example, first, an electrode material paste (electrode material) is applied to a coating means 3b such as a surface die coater installed in the coating portion 2b and a back surface die coater or the like. Using the construction means 3c, the electrode foil 1 supplied from the current collecting electrode foil roll 4 is thinly and uniformly applied on the front and back surfaces. The coating means 3b is an apparatus for applying paste on the surface of the electrode foil 1, and the coating means 3c is an apparatus for applying paste on the back surface of the electrode foil 1 opposite to the surface. is there.

  Thereafter, in a hot-air drying furnace shown as a drying chamber 6b, the solvent component in the paste is heated and evaporated to dry the paste, whereby electrode films are formed on both surfaces of the electrode foil 1, and this is wound up to form an electrode foil roll. 7 is formed. In this case, since the paste applied to the front and back surfaces can be simultaneously dried in the drying chamber 6b, the drying equipment can in principle be halved compared to the second comparative example, and the equipment cost and Reduction of running costs can be expected.

  However, in this method, how to convey the electrode foil 1 in a state where the paste is applied to the front and back surfaces of the electrode foil 1 becomes a big problem. For electrode foils coated with paste on the back side, the use of a contact-type and inexpensive roller transport system shown in FIGS. 10 and 11 becomes difficult in principle, and a non-contact transport system 8 such as an air floating transport system. Is inevitable. Such a non-contact type conveyance system 8 is relatively expensive as compared with the roller conveyance system 5 and the like, and has a problem that it is difficult to control conveyance. Therefore, the method of FIG. 11 is not sufficient to solve the problem described using 11. Further, even when both surfaces of the electrode foil 1 are collectively dried as in the third comparative example, as described in the first comparative example, rapid drying cannot be performed and the paste is taken over a long time. Therefore, there is a problem that the manufacturing cost increases in order to maintain the quality of the electrode film.

  Also, when the electrode material is dried using only hot air drying, the binder in the electrode material segregates on the surface of the electrode material during the drying process due to the fluidity of the electrode material, and the bonding between the electrode material and the electrode foil There is a problem that the performance decreases.

  In addition to the problems described in the first to third comparative examples, there are the following problems. That is, when a paste using an organic solvent is used, flammable organic solvent vapor is generated in the drying chamber, so that it is necessary to prevent leakage of the vapor itself and deal with the danger of ignition and explosion. For this reason, it is necessary to collect the steam sucked from the drying chamber with a scrubber or the like, and various costs related to drying such as installation of explosion-proof equipment increase the manufacturing cost of the lithium ion battery. It is required to simultaneously solve various problems associated with drying, including such problems.

  In view of the above problems, a method for manufacturing a lithium ion battery and a device for manufacturing a lithium ion battery according to embodiments of the present application will be described below.

(Embodiment 1)
In the manufacturing methods and manufacturing apparatuses of the first to third comparative examples, the liquid electrode material paste coated on the surface of the current collecting electrode foil is directly introduced into a drying chamber and dried. On the other hand, the manufacturing method of this Embodiment adds the process of solidifying a liquid electrode material paste before a drying process, and dries the solidified electrode material. By using such a method, it is possible to simultaneously avoid various problems caused by drying the liquid electrode material paste as it is.

  A configuration of a lithium ion battery manufacturing apparatus and a lithium ion battery manufacturing process in the present embodiment will be described with reference to FIG. FIG. 1 is a schematic diagram showing a configuration of a single-sided application type electrode manufacturing apparatus according to the present embodiment.

  In the manufacturing process of the lithium ion battery in the present embodiment, first, a paste applied to a positive electrode or a negative electrode for a lithium ion battery is prepared as a high-viscosity slurry liquid, and this paste is installed in the coating unit 2. It is applied thinly and uniformly on the surface of the electrode foil 1 supplied from the current collecting electrode foil roll 4 by using a coating means 3 such as a coater.

  The liquid electrode material paste of the present embodiment includes at least a positive or negative electrode active material powder, and in some cases includes a solid component of a conductive material powder. Further, the electrode material paste includes a binder component for binding between powder components or between the powder component and the electrode foil after drying, and further includes a solidifying material according to the present embodiment, and these components are slurried. 1st solvent in connection with this Embodiment for adjusting as a high-viscosity liquid paste of a shape.

  That is, the electrode material paste includes positive or negative electrode active material powder, a binder, a solidifying material, and a first solvent, and in some cases includes a solid component of a conductive material powder. However, as a more preferable means of the present embodiment, a binder component can also be used as the solidifying material of the present embodiment. Therefore, the electrode material paste includes at least a positive or negative electrode active material powder, a binder that can be used as a solidifying material, and a first solvent. In this case, specific means of the present embodiment will be described below.

  Next, the electrode foil 1 is carried into the solidification chamber 9 using the roller conveyance system 5 for conveying the electrode foil 1 at a constant speed while contacting the back surface of the electrode foil 1 coated with the paste as described above. . Subsequently, the paste is solidified by bringing the paste into contact with a solidifying liquid (not shown) which is the second solvent according to the present embodiment.

  Note that solidification as used herein refers to changing a substance from a liquid state to a solid state and reducing the fluidity of the substance. The state of the solidified substance includes a case where it is completely solid, but includes a case where it has a very low fluidity or a case where it contains moisture or the like and has some flexibility. Even if it passes through the solidification step, if it has such low fluidity, a drying step is required thereafter. For this reason, in this Embodiment, the water | moisture content in the solidified electrode material is evaporated by providing a drying process after a solidification process.

  Unlike the first solvent, the solidified liquid that is the second solvent needs to have a property of not dissolving the solidified material and a property of being mutually soluble with the first solvent. When the second solvent is brought into contact with the coating film (paste) on the electrode foil 1, the second solvent penetrates into the coating film while replacing the first solvent in the coating film. When the concentration of the second solvent increases in the coating film, the solidification material is precipitated because the solubility of the solidification material becomes insufficient. At this time, the entire coating film is activated by activating between the active material particles contained in the paste. Solidifies. Since the solidification process occurs in a time much shorter than the time required for drying or the like, the fluidity in the coating film becomes low, and the distribution of various components in the coating film is fixed almost instantaneously.

  When the electrode foil holding the solidified coating film is transported, it is possible to use a contact-type roller transport system that comes into contact with the solidified coating film. That is, in this embodiment, since it is possible to use a contact type roller conveyance system that comes into contact with the solidified coating film, it is not necessary to use a complicated and expensive air floating conveyance system. The cheap drying room used can be used. As will be described later in Embodiment 3, this advantage is particularly effective when the electrode films are applied to both surfaces and then the electrode films on both surfaces are collectively dried.

  Next, the electrode foil 1 holding the paste solidified in the solidification chamber 9 as described above is carried into the drying chamber 6c, and the solvent component in the paste is heated and evaporated by a known method such as hot air drying to dry the paste. By doing so, an electrode film is formed. The electrode foil roll 7 that has wound up the electrode foil 1 that has undergone the drying step is supplied to the next step. However, in the case where an electrode film is also formed on the back surface of the electrode foil 1, the above process is also performed on the back surface on the opposite side of the surface of the electrode foil, and the electrode foil is formed with electrode films formed on both surfaces. After manufacturing the electrode sheet, the process proceeds to the next step.

  The drying chamber 6c is a device having the same structure as the drying chambers shown in the first to second comparative examples, but the drying chamber 6c has a shorter transport path than the drying chambers of those comparative examples, and the device The size of itself is small. For example, if the manufacturing method of this embodiment described with reference to FIG. 1 is used, the length of the drying chamber is about one-tenth as compared with the manufacturing method of the comparative example described with reference to FIG. (For example, 10 m) is sufficient.

  The positive electrode sheet is formed by forming the positive electrode film on the surface of the positive electrode foil (for example, Al (aluminum)) by the above-described steps. Moreover, a negative electrode sheet is formed by forming the electrode film for negative electrodes on the surface of the electrode foil for negative electrodes (for example, Cu (copper)) by the process mentioned above. Further, a laminated structure in which a separator is interposed between the positive electrode sheet and the negative electrode sheet is formed. Details of the separator manufacturing method will be described later.

  In the drying process in the drying chamber 6c described above, the solidified paste may be dried instead of drying the fluid liquid paste. For this reason, the introduction of the solidification process using the solidification chamber 9 causes problems in the composition variation in the paste and the film thickness fluctuation, which becomes a problem when the paste is dried in the manufacturing process of the first to third comparative examples. While preventing the occurrence, the paste can be dried, and rapid drying in a short time becomes possible.

  For this reason, in the manufacturing process of the lithium ion battery according to the present embodiment, the reliability of the electrode film is high even when the drying chamber 6c having a short transport path is used as described above, or even when a manufacturing apparatus having a high transport speed is used. It can be prevented from lowering. Even if the drying process is rapidly performed at a higher temperature, since the electrode material loses fluidity, the concentration distribution in the electrode material can be prevented from being biased. Therefore, it is possible to reduce the size of the drying equipment, further improve the throughput in the manufacturing process of the lithium ion battery, and reduce the manufacturing cost. As described above, the main feature of this embodiment is that a step of solidifying the liquid electrode material paste by replacing the solvent is added before the drying step.

  Next, as shown in FIG. 2, the positive electrode sheet 10 and the negative electrode sheet 11 formed by the process described using FIG. 1, and the separator 12 provided between the electrode sheets are stacked and cut. For example, the lithium ion battery is completed by being incorporated in a cylindrical container 13, injecting an electrolytic solution into the container, and then sealing. FIG. 2 is a cross-sectional view of a lithium ion battery. As shown in FIG. 2, the positive electrode sheet 10, the negative electrode sheet 11, and the separator 12 are sealed by the container 13, the positive electrode terminal 15, the negative electrode terminal 16, and the like. The positive electrode sheet 10 is electrically connected to a positive electrode terminal 15 having a gas discharge structure via a positive electrode lead 14 made of a metal film, and the negative electrode sheet 11 is connected to a negative electrode lead (not shown) made of a metal film. Are electrically connected to the negative terminal 16.

  In the container 13, the laminated film in which the positive electrode sheet 10, the separator 12, the negative electrode sheet 11, and the separator 12 are laminated in this order is repeatedly laminated with the positive electrode sheet 10 and the negative electrode sheet 11, and the adjacent positive electrode sheet 10 and negative electrode sheet 11. The separator 12 is interposed therebetween, and the laminated film is sealed in a state of being wound in a cylindrical container 13.

  One of the features of the present embodiment is that, as described with reference to FIG. 1, solvent replacement occurs by performing a solidification step before the drying step, and the solvent component in the paste to be removed in the drying chamber is Most of them are not the first solvent used for paste adjustment, but the second solvent of the present embodiment. Thereby, the solvent removed at the time of this drying is made into the solvent different from the solvent in the paste at the time of paste application | coating, and the problem on the manufacture accompanying drying can be avoided.

  Specifically, even if the first solvent as the solvent component contained in the paste at the time of applying the paste is a flammable solvent, the first solvent in the paste is replaced with the second solvent in the solidification step. Therefore, if a nonflammable solvent is used as the second solvent, it is possible to prevent the generation of flammable solvent vapor in the drying chamber. For this reason, it is not necessary to take various safety measures associated with the handling of combustible steam, and it is not necessary to provide a steam recovery facility, so it is possible to prevent an increase in cost on the facility.

  Below, each material which comprises the lithium ion battery in this Embodiment, and each material used when manufacturing a lithium ion battery is demonstrated in detail.

  It is conceivable to use a lithium-containing composite oxide having a spinel structure containing lithium cobaltate or manganese (Mn) as the positive electrode active material of the lithium ion battery used in this embodiment. In addition, it is considered that the positive electrode active material may be a composite oxide containing nickel (Ni), cobalt (Co), manganese (Mn), or an olivine type compound represented by olivine type iron phosphate. It is done. However, the material used for the positive electrode active material is not limited to these.

Since a lithium-containing composite oxide having a spinel structure containing manganese (Mn) is excellent in maturity stability, a battery with high safety can be formed by forming an electrode sheet containing the lithium-containing composite oxide. Further, as the positive electrode active material, only a lithium-containing composite oxide having a spinel structure containing manganese (Mn) may be used, but another positive electrode active material may be used in combination. Examples of such other positive electrode active materials include olivine represented by Li _{1 + x} MO ₂ (−0.1 <x <0.1, M: Co, Ni, Mn, Al, Mg, Zr, Ti, etc.). Type compounds. As a specific example of the lithium-containing transition metal oxide having a layered structure, LiCoO ₂ or LiNi _1-x Co _xy Al _y O 2 (0.1 ≦ x ≦ 0.3, 0.01 ≦ y ≦ 0. 2) etc. can be used. The lithium-containing transition metal oxide having a layered structure includes an oxide containing at least Co, Ni, and Mn (LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , LiMn _5/12 Ni _5/12 Co _{1 / 6} O ₂ , LiNi _3/5 Mn _1/5 Co _1/5 O _2, etc.) can be used.

  As the negative electrode active material used in the present embodiment, for example, a graphite material such as natural graphite (flaky graphite), artificial graphite, or expanded graphite can be used. Further, as the negative electrode active material, an easily graphitizable carbonaceous material such as coke obtained by firing pitch can be used. Further, a non-graphitizable carbonaceous material such as amorphous carbon obtained by low-temperature firing of furfuryl alcohol resin (PFA), polyparaphenylene (PPP), phenol resin, or the like may be used as the negative electrode active material. Good. In addition to the carbon material, lithium (Li) or a lithium-containing compound can also be used as the negative electrode active material.

  Examples of the lithium-containing compound include lithium alloys such as Li—Al, Si (silicon), and alloys containing elements that can be alloyed with Sn (tin) and lithium (Li). Furthermore, it is also possible to use an nitride-based material such as Sn oxide or Si oxide.

  The conductive material used in the present embodiment is used as an electron conduction assistant to be contained in the positive electrode mixture layer, and for example, a carbon material such as carbon black, acetylene black, graphite, carbon fiber, or carbon nanotube is preferable. Among the above carbon materials, it is particularly preferable to use acetylene black or the like from the viewpoints of the amount of addition and conductivity, and the productivity of the positive electrode mixture layer-containing composition (described later). Such a conductive material can be used as a material for the negative electrode mixture layer and may be preferable. Here, the positive electrode or negative electrode material mixture layer is the electrode material paste described above or a conductive film obtained by solidifying and drying the electrode material paste.

  In the present embodiment, since the binder component can be used as the solidifying material of the present embodiment, the following binders can be used.

  The binder of the present embodiment preferably also contains a binder for binding the active material and the electron conduction aid. As the binder, for example, a polyvinylidene fluoride polymer (a polymer of a fluorine-containing monomer group containing 80% by mass or more of vinylidene fluoride as a main component monomer) or a rubber polymer is preferably used. Two or more of the above polymers may be used in combination. Moreover, what is provided with the form of the solution melt | dissolved in the solvent for the binder of this Embodiment is preferable.

  The fluorine-containing monomer group for synthesizing the polyvinylidene fluoride-based polymer includes vinylidene fluoride or a mixture of vinylidene fluoride and another monomer, and a monomer mixture containing 80% by mass or more of vinylidene fluoride. Is mentioned. Examples of the other monomer include vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluoropropylene, and fluoroalkyl vinyl ether.

  Examples of the rubber-based polymer include styrene butadiene rubber (SBR), ethylene propylene diene rubber, and fluorine rubber.

  The content of the binder in each mixture layer of the positive electrode and the negative electrode is 0.1% by mass or more, more preferably 0.3% by mass or more, and 10% by mass or less, based on the electrode agent after drying. More preferably, it is 5 mass% or less. If the binder content is too small, not only is the solidification in the solidification step of the present embodiment insufficient, but the mechanical strength of the mixture layer after drying is insufficient, and the mixture layer peels off from the electrode foil. There's a problem. Moreover, when there is too much content of a binder, there exists a possibility that the quantity of the electrically conductive material in a mixture layer may reduce and battery capacity may become low.

  As the solidifying material of the present embodiment, the same one as the above binder or a mixture of a plurality of materials that can be used as the above binder is used. It is also possible to use a component having no performance as a binder and having a performance as a solidifying material in addition to the binder.

  Next, each material of the lithium ion battery in the present embodiment will be described.

  In the present embodiment, as a method for applying the electrode material to the electrode foil, for example, an application method using an extrusion coater, a reverse roller, a doctor blade, an applicator, or the like can be used.

  The electrode foil used in the present embodiment is representatively shown, and is not limited to a sheet-like foil. Examples of the substrate include aluminum (Al), copper (Cu), stainless steel, Alternatively, a pure metal such as titanium (Ti) or an alloy conductive material is used, and a net, a punched metal, a foam metal, a foil processed into a plate shape, or the like is used. As the thickness of the conductive substrate, for example, 5 to 30 μm, more preferably 8 to 16 μm is selected. Moreover, the thickness of the electrode film formed on one surface of the electrode foil is a thickness after drying, and can be selected, for example, from 10 to 300 μm, more preferably from 30 to 150 μm.

  As the solvent of the present embodiment, it is important to appropriately select and use the first solvent contained in the electrode material paste and the second solvent contained in the solidifying material. These solvents are selected in consideration of the solubility of the solidified material of the present embodiment or the binder component that also serves as the solidified material, and the mutual solubility of the solvent. As the first solvent, an aprotic polar solvent represented by N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide, propylene carbonate, dimethylformamide, γ-butyrolactone, or a mixture thereof can be selected. .

  Further, as the second solvent, a protic solvent represented by water, ethanol, isopropyl alcohol, acetic acid, or the like, or a mixed solution thereof can be selected, but is not limited to the examples given here. In some cases, aliphatic saturated hydrocarbons, aliphatic amines, esters, ethers, various halogen-based solvents, and the like can be selected as the second solvent. Further, in some cases, it is possible to select to exchange the first solvent and the second solvent.

  The selection of the solvent in the present embodiment depends on the selection of the solidifying component used for the electrode material and the combination of two types of solvents that match the selection. By using the first solvent contained in the electrode material paste as an aprotic polar solvent or a mixture thereof and the second solvent contained in the solidified material as an aprotic polar solvent or a mixture thereof, the electrode material The binder component is not assimilated in the paste, and the binder component can be easily solidified in the solidifying material. Thus, the electrode material paste and the binder can be widely applied to the surface of the electrode foil until the solidifying material is brought into contact with the electrode material paste. On the other hand, if the solidifying material is brought into contact with the electrode material paste, the electrode material The paste and binder can be easily solidified.

  Below, the solidification means in this Embodiment, ie, the solidification method using a solidification material, and the manufacturing apparatus used for this solidification process are demonstrated.

  The solidifying means of the present embodiment brings the second solvent into contact with the coating film (electrode material) containing the first solvent held (coated) on the electrode foil, and the first solvent in the coating film is second What is necessary is just to have a function to substitute with the solvent. As a means for performing solidification by this substitution, a system in which the coating film held on the electrode foil is passed through the liquid tank in which the second solvent is stored, and the second solvent is applied to the coating film held on the electrode foil. A method of spraying with a spray and a method of supplying the second solvent while flowing down can be considered. However, in these systems, for example, as shown in FIG. 13, it is necessary to transport the electrode foil 1 by bringing a means such as a roller transport system into contact with the opposite surface of the electrode foil 1 to which the solvent is brought into contact. FIG. 13 is a schematic view showing a solidification device for spraying a second solvent by spraying on the surface of the electrode foil, shown as a comparative example. In FIG. 13, the electrode foil 1 is conveyed from the left side to the right side of the drawing.

  As shown in FIG. 13, an apparatus for supplying a solvent using a spray has a solidification chamber 9a, and a second solvent 17 is stored in a liquid tank at the bottom of the solidification chamber 9a. Inside the solidification chamber 9a, there is a path through which the electrode foil 1 conveyed by the roller conveyance system 5 passes, and the electrode foil 1 enters the inside from the outside of the solidification chamber 9a by the roller conveyance system 5, and then the solidification chamber It is conveyed to the outside of 9a. An electrode material 18 containing a first solvent is applied on the surface of the electrode foil 1, and the second solvent 17 in the liquid tank is sent to the upper part of the solidification chamber 9 a by the pump 20, and the electrode material It sprays toward the electrode material 18 from the injector 19 above 18. Thereby, an electrode material solidifies by substitution of two kinds of solvents mentioned above. However, in the method of the comparative example in which the second solvent is sprayed by spraying, there is a problem that the thickness of the electrode material 18 varies due to the liquid of the second solvent (for example, water) colliding with the electrode material 18.

  Moreover, as a method of supplying the second solvent to the electrode material, the electrode solvent with the electrode material applied on the surface is immersed in a liquid tank in which the second solvent is stored, so that the second solvent is supplied to the electrode material. It is conceivable to carry out the solidification step by contacting the substrate. However, in this method, the binder in the electrode material is excessively exposed to the second solvent and flows down, resulting in a problem that the bonding force in the electrode material and the bonding force between the electrode material and the underlying electrode foil are lowered.

  Further, as described above, as compared with the method of transporting the electrode foil 1 using the roller transport system 5 as shown in FIG. 11, a method of stably transporting a thin and easily deformable material like the electrode foil without contact. One of these is air levitation transport technology. This is because air is spouted from the lower side of the electrode foil at a pressure higher than atmospheric pressure to form a thin air film between the electrode foil and the transfer device, and the electrode foil is slightly lifted from the transfer surface for transfer. Technology. In this case, since the electrode foil and the conveying device are not in direct contact with each other, unlike the contact-type roller conveyor, the electrode foil can be conveyed at a high speed with low vibrations, and it is possible to prevent the electrode foil sheet surface from being scratched.

  FIG. 3 shows an overhead view of the air levitation transport apparatus of the present embodiment. A plurality of pinholes 24 are uniformly distributed on the surface for transporting the electrode foil, that is, the upper surface of the air levitation transport device 21, and air is ejected from the pinhole 24 to be thin in the gap with the electrode foil. An air film is formed. A groove may be used instead of the pinhole 24 for air ejection, or a porous material may be used. By this air film, a uniform pressure can be applied to the thin metal foil having the property of being easily deformed, and the metal foil can be conveyed while preventing deformation.

  FIG. 4 shows an electrode foil transfer device using this air levitation transfer device. FIG. 4 is a cross-sectional view of the electrode foil transport device 22 used in the solidification step of the present embodiment. The electrode foil transport device 22 is disposed in the solidification chamber 9 shown in FIG. And the role of supplying the second solvent to the electrode material 18 on the electrode foil. The electrode foil transport device 22 has two air levitation transport devices 21a and 21b provided to face each other, and the electrode foil 1 is transported by floating between the air levitation transport devices 21a and 21b. An air flow forming an air film is always supplied to the surface of the electrode foil 1 from an air levitation transport device (first air levitation transport device) 21b. Similarly, an air flow that forms an air film is always supplied to the back surface of the electrode foil 1 from an air levitation transport device (second air levitation transport device) 21a. In FIG. 4, a plurality of electrode materials 18 are intermittently formed on the electrode foil 1, but the electrode materials 18 on the electrode foil 1 are applied so as to extend long collectively without being separated. It does not matter.

  As shown in FIG. 3, the air levitation transfer devices 21 a and 21 b have a plurality of pinholes 24 that exhaust air with a force higher than atmospheric pressure on the surface facing the electrode foil. Of the air levitation transfer devices 21a and 21b, for example, pinholes 24 (see FIG. 3) are regularly arranged on the upper surface of the air levitation transfer device 21a, and are uniformly formed on the back surface of the electrode foil 1 to be levitated. It is possible to supply air. In FIG. 4, high-pressure air is supplied from one place below the air levitation transfer device 21a. However, in order to supply air more uniformly to the back surface of the electrode foil 1, high-pressure air is sent to the air levitation transfer device 21a. You may divide a location into a plurality. The same applies to the air levitation transfer device 21b. The high pressure as used in the present application means a pressure higher than the atmospheric pressure unless otherwise specified.

  Next, as a means for bringing the second solvent into contact with the electrode material 18 applied to the upper surface of the electrode foil 1 that is floated and conveyed, the second solvent is passed through the air forming the air film. A method for supplying steam will be described. Here, the case where the second solvent is water will be described. However, the second solvent is not limited to water but may be one using the other liquid described above.

  In addition, the distribution of various vapors of water is shown in FIG. FIG. 5 is a graph in which the horizontal axis represents pressure and the vertical axis represents temperature, and the arc indicates a saturation point. The upper side of the saturation point is a region where water as the second solvent is gaseous water vapor, and the lower side of the arc is a region where water as the second solvent exists as a liquid. When the water vapor on the upper side of the arc, that is, in the heating vapor region is cooled, condensation occurs from the time when the temperature of the water vapor falls below the saturation point, and liquid water is produced. That is, FIG. 5 is a graph showing the saturation point of water that varies depending on the pressure condition.

  FIG. 6 shows a solidifying device 25 constituting the lithium ion battery manufacturing apparatus of the present embodiment applying the above-described principle of water vapor condensation. The solidification device 25 has an electrode foil transport device 22 including two air levitation transport devices 21a and 21b provided to face each other. Further, the solidification device 25 includes a high-pressure and low-temperature air supply unit (low-temperature air generation mechanism) 26 that supplies high-pressure and low-temperature air to the lower surface of the electrode foil 1 via an air levitation conveyance device 21 a below the electrode foil conveyance device 22, A high-pressure heating steam supply unit (steam generation mechanism) 27 that supplies high-pressure heating steam to the upper surface of the electrode foil 1 via the air levitation conveyance device 21b above the foil conveyance device 22 is provided. That is, low temperature air is blown to the electrode foil 1 through the air levitation transfer device (second air levitation transfer device) 21a, and steam is blown through the air levitation transfer device (first air levitation transfer device) 21b. It is turned on.

  The electrode foil 1 is floated and transported between the two air levitation transport devices 21a and 21b with the electrode material 18 held on the upper surface thereof. That is, the air levitation transfer devices 21a and 21b face each other with the electrode foil 1 interposed therebetween. The high-pressure and low-temperature air supply unit 26 includes heat exchangers 30 and 31 using a Peltier element 28, a temperature sensor 29, a temperature controller 32, and a current control DC power source 33. The temperature controller 32 controls the temperature of the high-pressure and low-temperature air. Made. The temperature sensor 29 is connected to the temperature controller 32, and the current control DC power source 33 is connected to the temperature controller 32 and the Peltier element 28.

  The Peltier element 28 is disposed between the two heat exchangers 30 and 31 disposed above and below, and has a function of cooling the heat exchanger 30 below the Peltier element 28. The heat exchanger 31 on the Peltier element 28 includes a container, a plurality of heat dissipating fins at the bottom of the container, and a fan that is disposed on the heat dissipating fins and sends air to the heat dissipating fins, and has a heat dissipating function. The heat exchanger 30 has a function of cooling the air in the pipe passing through the heat exchanger 30. The temperature of the low-temperature air supplied from the high-pressure low-temperature air supply unit 26 is set to a temperature lower than the saturation point shown in FIG. This is because the electrode foil 1 and the electrode material 18 are cooled by the high-pressure low-temperature air, and the second solvent is condensed on the surface of the electrode material 18.

  The high-pressure heating steam supply unit 27 injects the water 35 into the stainless steel can 34 by the pump 20a and further heats the saturated steam generated by heating the water 35 with the heater 36 with the heating coil 37. It is a device that generates heated steam. Note that the high-pressure and low-temperature air supply unit 26 and the high-pressure heating steam supply unit 27 are not limited to the above-described configuration, and may be devices that supply high-pressure and low-temperature air and high-pressure heating steam using other methods. The temperature of the vapor | steam supplied shall be temperature more than the saturation point shown in FIG. That is, when the second solvent is water, the temperature of the vapor is always 100 ° C. or higher under a pressure of atmospheric pressure or higher.

  On the lower surface of the electrode foil 1, air cooled to a temperature lower than that of the high-pressure heating steam by the high-pressure and low-temperature air supply unit 26 is supplied through the air levitation transport device 21a. It is kept at a low temperature. On the other hand, the heating steam containing the second solvent (for example, water) generated by the high-pressure heating steam supply unit 27 is supplied to the upper surface of the electrode foil 1 through the air levitation transport device 21b. When the heated steam comes into contact with the electrode foil 1 held at a low temperature, the heat is deprived and falls below the saturation point, and the condensed fine water particles are uniformly formed on the surface of the electrode material 18 that is a coating film held on the electrode foil 1. Is generated. The water particles quickly permeate the electrode material 18, and the electrode material 18 is solidified by replacing the first solvent in the electrode material 18 with water as the second solvent.

  The amount of water that is the second solvent to be replaced is mainly determined by the amount of water vapor of the high-pressure heating steam, the temperature of the high-pressure and low-temperature air, or the conveyance speed of the electrode foil, and can be easily optimized by appropriately selecting these values. The amount of water can be obtained. Further, in the method of spraying the solvent by the spray as described with reference to FIG. 13 or the method of supplying the second solvent while flowing down, the liquid of the second solvent (for example, water) collides with the coating film and is applied. Although the film thickness varies, in the present embodiment, liquid water is generated by condensation on the coating film, so that the coating film thickness is not affected and a uniform thickness is maintained.

  As described with reference to FIG. 4, pinholes 24 (see FIG. 3) are regularly arranged on the lower surface of the air levitation transfer device 21 b, and are uniformly formed on the upper surface of the electrode material 18 on the electrode foil 1. It is possible to supply steam. For this reason, since the second solvent is condensed in a uniform amount on the surface of the electrode material 18, the electrode material 18 is uniformly solidified with the same quality. Accordingly, it is possible to prevent variation in the solidified state due to the portion of the electrode material 18, and thus the quality of the lithium ion battery can be improved. In addition, the binder can be prevented from excessively flowing out as compared with the case where the electrode foil is immersed in the second solvent and solidified. Therefore, it is possible to prevent the bonding force in the electrode material and the bonding force between the electrode material and the electrode foil from being lowered, and the reliability of the lithium ion battery can be improved.

  6 may have a structure in which the high-pressure heating steam is supplied from below and the high-pressure and low-temperature steam is supplied from above.

  3, 4, and 6, the case where the pinholes 24 (see FIG. 3) are regularly arranged on one surface of the air levitation transport apparatus has been described. For example, the pinholes 24 may be arranged in a matrix by arranging a plurality of pinholes 24 in two directions perpendicular to each other along the plane. Further, for example, a plurality of circles drawn concentrically from the center of the surface may be assumed, and a plurality of pinholes 24 may be arranged along these circles.

  Further, the arrangement of the pinholes 24 may not be a regular arrangement, and can be appropriately changed as long as the arrangement can supply air or steam uniformly to the electrode foil. In addition to the pinhole, for example, a plurality of grooves are formed on the lower surface of the air levitation transfer device 21b shown in FIG. Vapor may be supplied uniformly to the upper surface of the upper electrode material 18. As a shape of the groove in this case, for example, a case where a plurality of grooves are formed radially from the center of the lower surface is conceivable. Further, a plurality of grooves and a plurality of pinholes may be combined to form, for example, a lattice-shaped groove on the lower surface, and a pinhole may be formed at the intersection of the lattice-shaped grooves.

  In addition, the air levitation transfer device shown in FIGS. 3, 4 and 6 does not use pinholes or grooves, and may supply air to the surface of the electrode foil through a porous plate. . By using a porous plate, it is possible to blow air uniformly over the entire surface of the electrode foil and to float the electrode foil. Further, by using a porous plate, it is possible to spray the vapor made of the second solvent uniformly over the entire surface of the electrode foil.

  The electrode material drying means performed in the drying chamber 6c of FIG. 1 may be hot air drying, but is not limited thereto. The drying means may be a heating method that irradiates electromagnetic waves such as infrared rays, far infrared rays or visible light. It is also possible to use a dielectric heating method using a high-frequency electric field or an induction heating method using a change in magnetic flux. Furthermore, a contact heating method using a heating roll or a hot plate incorporating a heater may be used, and a heating method combining some of the drying means described above can also be used.

  Below, each process performed in the manufacturing process of the lithium ion battery of this Embodiment is demonstrated, and the effect by performing a solidification process before a drying process in this Embodiment is demonstrated using a comparative example.

  As the positive electrode active material, lithium nickel cobalt manganate as a lithium transition metal composite oxide can be selected. 85: 8 by weight ratio of the lithium transition metal composite oxide, graphite powder of the conductive material, acetylene black of the conductive material, and polyvinylidene fluoride (PVDF) serving as a binder as the solidifying material of the present embodiment. : 2: 5, and N-methyl-2-pyrrolidone (NMP), which is the first solvent of the present embodiment, is sequentially added. These mixed components are kneaded with a planetary mixer to prepare a positive electrode paste. The paste is a slurry-like liquid, and the binder component as the solidifying material of the present embodiment is dissolved in NMP in the paste. The viscosity of the paste measured with a rotational viscometer is about 10 Pa · S.

  The paste (electrode material) thus kneaded is applied onto an aluminum foil (positive electrode current collector) having a thickness of 20 μm with an applicator so as to have a thickness of 100 μm. The above process is the first process of the present embodiment in which the liquid electrode material paste is applied to the surface of the electrode foil using a coating means.

  Next, the positive electrode paste is solidified by supplying pure water as the second solvent to the aluminum foil coated with the positive electrode paste using the solidification device 25 described with reference to FIG. The solidification phenomenon is a phenomenon in which NMP, which is the first solvent in the paste, is replaced with pure water, which is the second solvent, so that the binder in the paste is insolubilized and precipitates and binds between the positive electrode particles. It is. Since the paste solidified in this way loses fluidity and tackiness and is held on the aluminum foil, it can sufficiently withstand roller conveyance in which a roller is brought into contact with the surface of the paste.

  Said solidification process makes the electrode material paste solidify by making the electrode material paste contact the solidification liquid containing the liquid component which is the 2nd solvent different from the liquid component which is the 1st solvent contained in an electrode material paste. It is the 2nd process of this Embodiment.

  Next, the paste (electrode material) solidified in the second step is dried at a temperature of 120 ° C. for 10 minutes in a warm air drying furnace, and pure water substituted in the paste and NMP remaining in a trace amount are removed by evaporation. Thus, a positive electrode sheet for a lithium ion battery in which an electrode film is formed on an aluminum foil is formed. The drying step is the third step of the present embodiment in which the liquid component is removed from the electrode material paste and dried.

  On the other hand, as a comparative example, a manufacturing process of a lithium ion battery when the solidification process before the drying process is not performed as in the present embodiment will be described below. In the manufacturing process of the lithium ion battery of the comparative example, the paste having the same components as in the present embodiment is applied on the aluminum foil, and the paste on the aluminum foil is dried at a temperature of 120 ° C. for 10 minutes in a warm air drying furnace. Then, the NMP in the paste is removed by evaporation to form a lithium ion battery electrode in which an electrode film is formed on the aluminum foil. Thus, in the comparative example, a lithium ion battery electrode having the same composition as that of the present embodiment is manufactured by a manufacturing method in which the solidification step of the present embodiment is omitted.

  Here, FIG. 7 shows a table comparing various characteristics of the electrode films obtained by the manufacturing method of the present embodiment and the manufacturing method of the comparative example. As described above, in the present embodiment having a solidification step, the electrode material is solidified in a state before the drying step, whereas in the drying step of the manufacturing method of the comparative example, a liquid electrode material is used, for example. Dry in a warm air drying oven. Therefore, in the present embodiment, it is possible to convey a roller or the like in contact with the electrode material application surface in the drying step, whereas in the method of the comparative example, it is in principle to use such a conveyance method. Impossible.

  Further, the effect of the present embodiment appears remarkably in the composition distribution of the electrode film. For the dried electrode film, a scanning electron microscope (SEM) and an energy dispersive X-ray spectroscopy (EDX) are used as analysis techniques, so that the cross section of the electrode film It is possible to measure the composition distribution in the thickness direction. When the concentration of the binder component measured by such a method in the film thickness direction is more than twice the ratio between the electrode surface and the bottom surface in contact with the aluminum foil, the distribution is defined as large, and the case where the ratio is smaller than twice is defined as small distribution. In comparison of distribution, the electrode film of the present embodiment has a small distribution, and the electrode film of the comparative example has a large distribution, and a remarkable difference is recognized.

  In the method of the comparative example, the distribution of the binder component is estimated to occur because the paste is in a liquid state when the electrode material is dried, and thus mass transfer, that is, convection or diffusion of components such as the binder occurs in the film. On the other hand, in the present embodiment, the electrode material is solidified in the solidification step, and at the same time, the components of the electrode material are fixed, and the distribution becomes small because they do not move during drying.

  Also, the distribution of the positive electrode active material and the conductive material, which are solid particles in the film obtained from the observation of the electrode film, is large in the method of the comparative example, whereas the electrode film of the present embodiment is distributed. Is small and is recognized as a uniform film.

  As described above, the use of the solidification step of the present embodiment can improve the manufacturing apparatus and process conditions, and can improve quality such as improvement in the uniformity of the composition of the electrode film. . The effect of the present embodiment is obtained not only with the positive electrode film containing the positive electrode material described above but also with the negative electrode film.

  Further, the manufacturing method of the comparative example has a problem that the composition and film thickness of the electrode material fluctuate at the time of drying, but according to the present embodiment, by introducing a solidification step before the drying step, The composition and film thickness of the material can be stably maintained. Further, in the present embodiment, by performing the solidification step, it is possible to perform drying after eliminating the possibility that the above-described various fluctuations occur, so that rapid drying in a short time is possible. Therefore, by using the manufacturing method of the lithium ion battery using the manufacturing apparatus of the present embodiment, the quality of the electrode film can be stabilized and the drying equipment can be downsized, so the manufacturing cost of the lithium ion battery is reduced. be able to.

  In addition, before or during the drying process, it becomes possible to use a contact-type roller conveyance system in contact with the solidified coating film for conveying the electrode foil holding the solidified coating film (electrode material), The effect of improving the degree of freedom in selecting the manufacturing method, that is, the degree of freedom in selecting the configuration of the manufacturing apparatus can be obtained.

  Further, the present embodiment is characterized in that most of the solvent component in the paste to be removed in the drying chamber is not the first solvent used for paste adjustment, but the second solvent. By making the solvent at the time of drying different from the solvent at the time of applying the paste, various manufacturing problems associated with drying can be avoided.

  Specifically, even when the first solvent used as the solvent component in the paste is a combustible solvent at the time of producing the paste and applying the paste, the solvent in the paste is used in the solidification step of the present embodiment. Is replaced with the second solvent, and by selecting an incombustible solvent as the second solvent, it is possible to prevent the generation of combustible solvent vapor in the drying chamber. For this reason, it becomes possible to eliminate the problem on safety and facilities. In this way, it is possible to design a process that avoids manufacturing process problems and limitations.

  Moreover, in this Embodiment, since a drying process is performed after performing the solidification process of an electrode material, since an electrode material loses fluidity | liquidity, a binder does not segregate on the surface of an electrode material in a drying process. Thereby, it can prevent that the adhesiveness of an electrode film and electrode foil falls.

  In addition, the solidification process by the substitution of the solvent in the solidification chamber in the production process of the present embodiment described above is not limited to the production of the positive electrode sheet and the negative electrode sheet, but the separator 12 interposed between the positive and negative electrode sheets (see FIG. 2). ).

  As a manufacturing method of a separator, like the process of forming a positive electrode sheet and a negative electrode sheet, a paste-like separator material (hereinafter simply referred to as a separator material) is applied on a substrate (foil) and then dried, so that a solid A method of forming a separator is conceivable. In a specific separator manufacturing process, for example, the electrode sheet on which the electrode film is formed on the electrode foil 1 is first wound around the electrode foil roll 7 through the electrode film forming process described with reference to FIG. Thereafter, the electrode foil roll 7 is installed in a separator forming apparatus similar to the apparatus shown in FIG. 4, and in the same manner as the electrode film forming step, a positive electrode or negative electrode electrode film is placed on the electrode foil in the coating portion. After applying the paste-like separator material, the separator is laminated on the electrode film by drying in a drying chamber.

  In the completed lithium ion battery, the separator is made of, for example, a porous polypropylene film or polyethylene, and is interposed between the positive electrode sheet and the negative electrode sheet to prevent contact between the bipolar active materials of the adjacent electrodes. The electrolytic solution is held in the inner holes to form a path for ion conduction between the electrodes. The material of the separator material applied on the electrode sheet to form the separator includes silica (silicon oxide) or alumina (aluminum oxide), the binder described above, and the first solvent (for example, N-methyl-2- It is conceivable to use a mixed paste mixed with pyrrolidone (NMP).

  After applying such a paste on the electrode film, the paste is solidified by supplying a second solvent (for example, water) to the paste by the solidification step described with reference to FIGS. By performing the drying process by hot air drying or the like, the paste can be laminated on the electrode foil via the electrode film.

  As described above, in the case of forming a separator by solidifying a paste only by a drying process without introducing a solidification process using a solvent replacement action as in the comparative example manufacturing method described with reference to FIG. There arises a problem that the quality of the formed film is lowered and a problem that the manufacturing cost is increased. On the other hand, the composition of the separator material is stabilized by supplying the second solvent using the solidifying device 25 shown in FIG. 6 and solidifying the paste of the separator material before the drying step as in the present embodiment. By realizing the process, the simplification of the drying apparatus, the improvement of the throughput, etc., it is possible to maintain the quality of the separator while reducing the manufacturing cost.

  In addition, as a method for forming the separator, after forming the electrode film as the base of the separator, that is, forming the electrode film through a solidification process and a drying process, using a paste-like electrode material used when forming the positive electrode or the negative electrode Then, there is a method in which a separator material is applied in the form of an electrode film to perform a solidification step and a drying step. In addition, the separator material is applied after the electrode material solidification step and before the drying step, and after the separator material solidification step, the electrode material and the separator material drying step are collectively performed. Also good.

  In addition, after applying the paste-like electrode material on the electrode foil, the paste-like separator material is subsequently applied on the electrode material, and then the separator material and the electrode material are solidified and dried. Is possible. Accordingly, the number of times of performing the solidification step and the drying step can be omitted, the throughput can be improved, and the manufacturing apparatus can be reduced. Therefore, the manufacturing process of the lithium ion battery is simplified and the manufacturing cost is reduced. be able to.

(Embodiment 2)
A method for manufacturing a lithium ion battery in the present embodiment will be described with reference to FIG. FIG. 8 is a schematic diagram showing the configuration of a sequential double-sided coating type electrode manufacturing apparatus in the present embodiment. The description of the same configuration as that of the first embodiment is omitted.

  In this Embodiment, after performing the process of apply | coating electrode material paste to the surface of electrode foil 1, the process of solidifying electrode material paste, and the process of drying electrode foil, with respect to the back surface of electrode foil 1 The step of applying the electrode material paste, the step of solidifying the electrode material paste, and the step of drying the electrode foil 1 are characterized.

  In the manufacturing process for a lithium ion battery according to the present embodiment, first, a positive and negative electrode material paste is prepared as a high-viscosity slurry-like liquid, and this paste is installed in the surface coating portion 2 such as a die coater. Using the coating means 3, the electrode foil 1 supplied from the current collecting electrode foil roll 4 is thinly and uniformly applied.

  Using the roller transport system 5 for transporting the electrode foil 1 at a constant speed while being in contact with the back surface of the electrode foil 1 coated with the paste in this way, the electrode foil 1 is carried into the solidification chamber 9 to form an electrode material paste. The paste is solidified by contacting a solidified liquid (not shown) which is the second solvent of the present embodiment.

  Next, the electrode foil 1 holding the solidified paste is carried into the drying chamber 6c, and the solvent component in the paste is heated and evaporated by a technique such as hot air drying to dry the paste.

  Next, the dried electrode foil 1 is thinly and uniformly applied on the back surface of the electrode foil 1 by using a coating means 3a such as a die coater installed on the coating portion 2a for the back surface.

  The electrode foil 1 coated with the paste is carried into the solidification chamber 9b for the back surface, and solidified by bringing the paste into contact with a solidification liquid (not shown) as the second solvent of the present embodiment.

  Next, the electrode foil 1 holding the paste solidified by the means of this embodiment is carried into the drying chamber 6c, and the paste is dried by heating and evaporating the solvent component in the paste by a technique such as hot air drying. The electrode foil roll 7 wound up with the dried electrode foil 1 is supplied to the next step.

  In the present embodiment, the electrode formation on the front and back surfaces of the electrode foil is performed by dividing the front surface and back surface coating, solidification, and drying steps. Compared to the method of the comparative example shown in FIG. It is possible to easily realize both the improvement of the quality of the membrane and the downsizing of the drying equipment. In addition, by applying the same process to the manufacturing process of the separator, it is possible to improve the quality of the separator film and to reduce the size of the drying equipment.

  In the present embodiment, the electrode material on the back side is subjected to the application process and the solidification process without drying the electrode material on the front side, and then the electrode materials on both sides of the electrode foil are collectively dried. You may use the method to do. Accordingly, one drying chamber can be omitted, the manufacturing apparatus can be reduced, the throughput can be improved, and the manufacturing cost of the lithium ion battery can be reduced.

(Embodiment 3)
The manufacturing method of the lithium ion battery in this Embodiment is demonstrated using FIG. FIG. 9 is a schematic diagram showing the configuration of a double-sided coating batch drying type electrode manufacturing apparatus in the present embodiment. The description of the same configuration as that of the first embodiment is omitted.

  A positive and negative electrode material paste for a lithium ion battery according to the present embodiment is prepared as a high-viscosity slurry liquid, and the surface coating means 3b such as a die coater in which the paste is installed in the coating part 2b; Using the coating means 3c for the back surface, it is applied thinly and uniformly on both surfaces of the electrode foil 1 supplied from the collecting electrode foil roll 4.

  Next, the electrode foil 1 coated with the paste on both sides is carried into the solidification chamber 9, and the electrode material paste is brought into contact with the solidification liquid (not shown) as the second solvent all over the electrode foil 1, Solidify the paste. If it is the solidified paste, it can be conveyed using the roller conveyance system 5 for conveying the electrode foil 1 at a constant speed while being in contact with the back surface of the electrode foil 1.

  At this time, unlike the solidification chambers of FIGS. 1 and 8, the solidification chamber 9 includes a device for solidifying the electrode material on the surface of the electrode foil 1 and a device for solidifying the electrode material on the back surface opposite to the surface. Includes two. For example, the electrode foil 1 conveyed to the solidification chamber 9 is supplied with the second solvent from above, so that the electrode material on the surface side is solidified, and then the electrode foil 1 is supplied with the second solvent from below. As a result, the electrode material on the back side is solidified.

  That is, for example, in the solidification chamber 9, two electrode foil transfer devices 22 shown in FIG. 6 are arranged side by side, one of which is supplied with high-pressure heating steam from above and high-pressure and low-temperature steam from below. The other has a structure in which high pressure heating steam is supplied from below and high pressure and low temperature steam is supplied from above. This is because if one electrode foil transporting device 22 tries to supply the second solvent to both surfaces simultaneously, the electrode foil cannot be cooled and the second solvent can be condensed on the surface of the electrode material with high accuracy. This is because it cannot be done.

  Next, the electrode foil 1 holding the paste solidified by the means of the present embodiment on both sides is carried into the drying chamber 6c, and the solvent component in the paste is heated and evaporated at once on the both sides by a technique such as hot air drying, Dry the paste. The electrode foil roll 7 wound up with the dried electrode foil 1 is supplied to the next step. Also here, since the electrode material carried into the drying chamber 6c is already solidified, it is necessary to use a drying chamber equipped with an air-floating transport system inside as in the comparative example described with reference to FIG. Rather, in the conveyance in the drying chamber 6c, the roller conveyance system 5 that directly contacts the solidified paste on the back surface can be used.

  In the present embodiment, when the electrodes are formed on the front and back surfaces of the electrode foil at the same time, it is possible to realize a manufacturing method that takes full advantage of the present embodiment in which solidification is performed before the drying step. That is, in addition to the improvement of the electrode quality and the reduction in the size of the drying equipment as compared with the method of the comparative example shown in FIG. 13, the solidified coating film is used for transporting the electrode foil holding the solidified coating film. It is also possible to use an inexpensive contact-type roller conveyance system that comes into contact with the roller.

  That is, in this embodiment, since it is possible to use a contact type roller conveyance system that comes into contact with the solidified electrode material paste, it is necessary to use a complicated and expensive air floating conveyance system even when performing double-sided batch drying Therefore, an inexpensive drying chamber using a roller conveyance system can be used.

  In addition, by applying the same process to the separator manufacturing process, it is possible to improve the quality of the separator film and reduce the size of the drying equipment, and a roller transport system can be used for transporting the electrode foil that holds the solidified separator material. Since it can be used, the manufacturing cost of a lithium ion battery can be reduced.

  Although the invention made by the present inventors has been specifically described based on the embodiment, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention is effective when applied to a manufacturing technique of a lithium ion battery having a drying step of an electrode material or a separator material.

DESCRIPTION OF SYMBOLS 1 Electrode foil 2, 2a, 2b Coating part 3, 3a-3c Coating means 4 Collecting electrode foil roll 5, 5a Roller conveyance system 6, 6a-6c Drying chamber 7 Electrode foil roll 8 Non-contact conveyance system 9 , 9a, 9b Solidification chamber 10 Positive electrode sheet 11 Negative electrode sheet 12 Separator 13 Container 14 Positive electrode lead 15 Positive electrode terminal 16 Negative electrode terminal 17 Second solvent 18 Electrode material 19 Injector 20, 20 a Pump 21, 21 a, 21 b Air floating conveying device 22 Electrode foil conveying device 24 Pinhole 25 Solidifying device 26 High pressure low temperature air supply unit 27 High pressure heating steam supply unit 28 Peltier element 29 Temperature sensor 30, 31 Heat exchanger 32 Temperature controller 33 Current control DC power source 34 Stainless steel can body 35 Water 36 Heater 37 Heating coil

Claims (15)

(A) applying a paste to one surface of the electrode foil;
(B) supplying a solidified liquid containing a liquid component different from the liquid component contained in the paste to the paste formed on the one surface of the electrode foil as a vapor;
(C) removing and drying the liquid component from the paste;
(D) forming a lithium ion battery including the electrode foil;
A method for producing a lithium ion battery, comprising:   In the step (b), when supplying the steam, low temperature air lower than the steam is supplied to the other surface opposite to the one surface of the electrode foil at a pressure higher than atmospheric pressure. The method of manufacturing a lithium ion battery according to claim 1, further comprising:   The method of manufacturing a lithium ion battery according to claim 1, wherein the paste is an electrode material.   The method of manufacturing a lithium ion battery according to claim 1, wherein the paste is a separator material. In the step (b), a first air levitation transport device is used for transporting the electrode foil,
The method of manufacturing a lithium ion battery according to claim 1, wherein the steam is supplied by the first air levitation transfer device. In the step (b), a second air levitation transport device is used to transport the electrode foil,
3. The method of manufacturing a lithium ion battery according to claim 2, wherein the low-temperature air is supplied by the second air levitation transfer device. In the step (b), a solidifying device having a first air levitation transport device and the second air levitation transport device facing each other is used.
When the electrode foil is transported between the first air levitation transport device and the second air levitation transport device, the first air levitation transport is performed on the paste cooled through the electrode foil by the low-temperature air. The method of manufacturing a lithium ion battery according to claim 6, wherein the vapor is supplied by an apparatus. The first air levitation transport device has a plurality of pinholes or a plurality of grooves on a surface facing the electrode foil,
6. The method of manufacturing a lithium ion battery according to claim 5, wherein the vapor is supplied through the plurality of pinholes or the plurality of grooves.   6. The method of manufacturing a lithium ion battery according to claim 5, wherein after the step (b) and before the step (c), the electrode foil is conveyed using a roller in contact with the paste.   Lithium ions having a vapor generation mechanism and solidifying a paste formed on the one surface of the electrode foil by supplying the vapor from the vapor generation mechanism to one surface of the electrode foil Battery manufacturing equipment.   11. The apparatus for manufacturing a lithium ion battery according to claim 10, wherein the solidified liquid contained in the vapor contains a liquid component different from the liquid component contained in the paste.   11. The paste is cooled by supplying a low-temperature air having a low-temperature air generation mechanism, and supplying low-temperature air having a temperature lower than that of the vapor to a surface opposite to the one surface of the electrode foil. The manufacturing apparatus of the lithium ion battery as described. A solidifying device having a first air levitation transport device and a second air levitation transport device facing each other;
From the steam generation mechanism, the paste formed on the one surface of the electrode foil between the first air levitation transport device and the second air levitation transport device via the first air levitation transport device. Supplying the steam,
The lithium ion battery manufacturing apparatus according to claim 12, wherein the low temperature air is supplied from the low temperature air generation mechanism via the second air levitation transfer device. The first air levitation transport device has a plurality of pinholes or a plurality of grooves on a surface facing the electrode foil,
The lithium ion battery manufacturing apparatus according to claim 13, wherein the vapor is supplied through the plurality of pinholes or the plurality of grooves. The first air levitation transport device has a porous plate on a surface facing the electrode foil,
The apparatus for manufacturing a lithium ion battery according to claim 13, wherein the vapor is supplied through the porous plate.

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