JP5723746B2 - Lithium ion battery and manufacturing method thereof - Google Patents

Description

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

  A lithium ion battery incorporates a positive electrode sheet, a negative electrode sheet, and a separator provided between both sheets into a cylindrical or square can structure, or a film-like battery case based on aluminum or the like, and an electrolyte solution. It is manufactured by sealing after pouring. Although the manufacturing method and appearance vary greatly depending on the can structure or the film-like structure, the basic part for operating the battery is common regardless of which structure is used. That is, the positive electrode active material is applied to the positive electrode sheet, the negative electrode active material is applied to both surfaces of the negative electrode sheet, and the separator is inserted to prevent short circuit between the positive electrode material and the negative electrode material. The active material is also called a mixture. A laminated structure of such a positive electrode, a separator, and a negative electrode is formed, the structure is wetted with an electrolytic solution containing lithium ions, and the laminated body is sealed in various cases to manufacture a battery.

  An example of such a method for manufacturing a lithium ion battery is described in Non-Patent Document 1 and the like. The outline of electrode manufacturing in Non-Patent Document 1 is as follows when the positive electrode is taken as an example.

  In the production of the positive electrode, a powdery raw material for the positive electrode active material, a conductive material powder, a binder solution, etc. and an organic solvent are kneaded to produce a slurry-like paste, and this paste is applied to the current collecting aluminum using a coating means such as a die coater To apply thinly and uniformly on the electrode foil, and then drying and solidifying the applied paste, and then processing the electrode film to a predetermined shape by calendering or adjusting the electrode film to a predetermined shape It is assembled as an electrode for a lithium battery through the slit processing. The electrode material formed on such a current collector foil is usually formed on both surfaces of the foil with the same thickness, and the positive and negative laminated structures are produced without gaps in order to increase the energy density of the battery.

W. van Schalkwijk et al, Advances in Lithium-Ion Batteries, Kluwer Academic / Plenum Publishers, pp267-288, 2002

  As shown above, in the manufacture of lithium ion batteries, the electrode material is formed on both sides of the electrode foil through a series of steps of manufacturing electrode paste, applying paste to the electrode foil, and drying, or combining these steps. It is necessary to create a sheet. However, the production of such an electrode sheet requires a considerable economic burden, and improvement of the maintenance of the electrode quality has been desired.

  In view of the above problems, an object of the present invention is to provide a lithium ion battery capable of maintaining electrode quality while reducing an economic burden by introducing a solidification step, and a method for manufacturing the lithium ion battery.

  In order to solve the above problems, the present invention provides a first step of applying a liquid electrode material paste to the electrode foil surface, and a solidified liquid containing a liquid component different from the liquid component contained in the electrode material paste. Lithium ion, comprising: a second step of solidifying the electrode material paste by contacting with the material paste; and a third step of removing a liquid component from the solidified electrode material paste and drying. A method for manufacturing a battery is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the lithium ion battery which can maintain electrode quality, and its manufacturing method can be provided, reducing economical burden by introduction of a solidification process.

It is a figure explaining the apparatus structure of the conventional single-sided coating type electrode manufacturing method. It is a figure explaining the apparatus structure of the conventional sequential double coated electrode production. It is a figure explaining the apparatus structure of the conventional double-side coating batch drying type electrode manufacture. It is a figure explaining the apparatus structure of the single-sided coating type electrode manufacturing method in Example 1 of this invention. It is a figure explaining the solidification apparatus structure of the immersion system in Example 1 of this invention. It is a figure explaining the solidification apparatus structure of the spray system in Example 1 of this invention. It is a figure which shows the effect of the manufacturing method in Example 1 of this invention in comparison with a conventional method. It is a figure explaining the apparatus structure of the double-sided continuous application type electrode manufacturing method in Example 2 of this invention. It is a figure explaining the apparatus structure of the double-sided batch application type electrode manufacturing method in Example 3 of this invention. It is a figure explaining the apparatus structure of the double-sided batch application type electrode manufacturing method using the direct processing solidification apparatus in Example 4 of this invention.

  A conventional electrode manufacturing method for a lithium ion battery will be described.

  FIG. 1 shows an apparatus configuration for manufacturing a conventional single-side coated electrode. Positive and negative electrode pastes for lithium ion batteries are generally high viscosity slurry liquids in which active material powder, conductive material powder, binder material for binding these powders, etc. are dispersed in an organic solvent such as NMP. is there. After applying the paste thinly and uniformly on the electrode foil supplied from the collector electrode foil roll 1-3 using a coating means 1-2 such as a die coater installed in the coating section 1-1. In the hot air drying furnace shown as the drying chamber 1-5 from the electrode foil coated with the paste, using a roller transport system 1-4 for transporting the electrode foil at a constant speed while being in contact with the back surface of the electrode foil Generally, the solvent component is heated and evaporated to dry and solidify the paste.

  The electrode foil roll 1-6 that has wound the solidified electrode foil is supplied to the next step. In normal electrode foil manufacture, this process is repeated twice for the front and back surfaces of the electrode foil to manufacture an electrode foil coated on both sides.

  In such a production method, in order to produce a high-quality electrode foil, and / or to ensure safety during production, it is common to spend considerable time and cost for drying. That is, in the drying process of the paste, the drying proceeds by the evaporation of the solvent from the paste surface accompanying the supply of heat to the paste. It is well known that when the evaporation rate is too high, uniform drying cannot be performed within the surface of the electrode foil, and the composition in the thickness direction of the applied electrode film is non-uniform and unstable. In some cases, a large burden is generated on the manufacturing equipment due to process restrictions. For such problems, there have been cases where measures are taken such as applying and drying the electrode film in a plurality of times, or adjusting the paste composition to be applied in a plurality of times with different compositions.

  In general, the conveying speed of the electrode foil in the drying process of the electrode film is about 1 to 100 m / min. The drying time is about 1 to 100 minutes. In the region close to the lower limit of the transport speed, the transport speed in the drying chamber is slow, so that slow drying is possible, the drying chamber can be small, and the quality of the electrode film to be manufactured is easily stabilized. However, in the region close to the lower limit of the conveyance speed, the productivity of electrode foil production is small, which makes it a relatively expensive process, which is an obstacle to supplying economically inexpensive lithium ion batteries to the market. There was also a case.

  On the other hand, in the region close to the upper limit of the conveyance speed, it is possible to increase the productivity of electrode foil production, but the drying chamber is very long in order to ensure the drying time necessary to ensure electrode quality. In this case, the equipment cost of the drying chamber itself and the running cost such as a large amount of heat energy for operating the large drying chamber increase.

  In general, in view of such conflicting problems, the contractor has adjusted electrode manufacturing processes and equipment by a method of adjusting both in the extreme intermediate region and empirically obtaining the optimum value. From this problem, a new, innovative, and inexpensive electrode manufacturing method that can apply at high speed, dry at high speed, and stabilize the electrode quality has been demanded.

  FIG. 2 shows an apparatus configuration for manufacturing a conventional sequential double-sided coating type electrode. Apply the electrode paste thinly and uniformly on the surface of the electrode foil supplied from the collector electrode foil roll 2-3 using a coating means 2-2 such as a die coater installed in the coating part 2-1. Then, using a roller transport system 2-4 for transporting the electrode foil at a constant speed while being in contact with the back surface of the electrode foil, the paste is applied in the hot air drying furnace shown as the drying chamber 2-5 from the electrode foil coated with the paste. In general, the solvent component is heated and evaporated to dry and solidify the paste, which is the same as the example of FIG. In the case of double-sided coating, the solidified electrode foil is not wound up, and the paste is applied to the back surface of the electrode foil using the coating means 2-7 in the next second coating section 2-6, and the roller transport system 2 After drying in the drying chamber 2-9 on the back using -8, the electrode foil roll 2-10 coated on both sides is completed and supplied to the next step.

  In the case of such continuous coating, although it is possible to produce electrode foils coated on both surfaces of the electrode foil, the drying chamber is necessary for each coating, so the drying process in electrode production However, the equipment constraints have not been drastically solved.

  FIG. 3 shows an example of a manufacturing apparatus of a double-sided coating batch drying type that has been proposed to solve the above problems. The electrode supplied from the electrode foil roll 3-4 for current collection using coating means such as the surface die coater 3-2 and the back surface die coater 3-3 in which the electrode paste is installed in the coating unit 3-1. After thinly and evenly applied on the front and back surfaces of the foil, the solvent component in the paste is heated and evaporated in a hot air drying furnace shown as a drying chamber 3-5 from the electrode foil to which the paste is applied, and the paste is dried and solidified. Generally, electrode foil roll 3-6 coated on both sides is manufactured and completed. In such a case, since the paste applied to the front and back surfaces can be simultaneously dried inside the drying chamber 3-5, the drying equipment can in principle be halved, and significant reductions in equipment costs and running costs are expected. it can.

  However, in such a system, how to convey the electrode foil with a liquid paste applied to the front and back surfaces of the electrode foil is a big problem. For electrode foils coated with a liquid paste on the back side, the use of a conventional contact type and inexpensive roller transport system becomes difficult in principle, and the non-contact transport system 3-7 such as an air levitation transport system is difficult. Adoption was inevitable. Such a non-contact type conveyance system is relatively expensive and has problems such as difficulty in controlling the conveyance. Therefore, the method of FIG. 3 is not sufficient to solve the conventional problem.

  In addition to the problems shown above, there are the following problems. In other words, in the use of a paste using an organic solvent, flammable organic solvent vapor is generated in the drying chamber, so it is necessary to prevent leakage of the vapor itself and to 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 there are various cost increasing factors related to drying such as installation of explosion-proof equipment. A new and innovative manufacturing method capable of simultaneously solving various problems associated with drying, including such problems, has been demanded.

  In view of the above problems, a method for manufacturing a lithium ion battery according to an embodiment of the present invention will be described.

  In the conventional manufacturing method, the liquid electrode material paste coated on the surface of the electrode current collector foil is directly introduced into the drying chamber and dried, whereas in the manufacturing method of this embodiment, the liquid electrode material paste is solidified. And the solidified electrode material is dried. By using this method, it is possible to simultaneously avoid various problems associated with drying the liquid electrode material paste as it is.

  The apparatus configuration in this embodiment will be described with reference to FIG.

  FIG. 4 shows an apparatus configuration for manufacturing a single-side coated electrode in this embodiment. Using a coating means 4-2 such as a die coater in which the positive and negative electrode pastes for a lithium battery according to this example are prepared as a high-viscosity slurry liquid and the paste is installed in the coating unit 4-1. Then, it is thinly and uniformly applied on the electrode foil supplied from the current collecting electrode foil roll 4-3. The liquid electrode material paste of this example includes at least a positive or negative electrode active material powder and, in some cases, a solid component of a conductive material powder, and further binds between powder components or between a powder component and an electrode foil after drying. And a solidifying material related to the present embodiment, and these components are prepared as a slurry-like high-viscosity liquid paste using the first solvent related to the present embodiment. is there. As a more preferable means of the present embodiment, a binder component can also be used as the solidifying material of the present embodiment. In this case, specific means of the present embodiment will be described below.

  Using the roller conveyance system 4-4 for conveying the electrode foil at a constant speed while being in contact with the back surface of the electrode foil coated with such paste, the electrode foil is carried into the solidification chamber 4-5, and this example is applied to the electrode paste. The solidified liquid (not shown) which is the second solvent is contacted to solidify the paste.

  Unlike the first solvent of the present embodiment, the solidified liquid that is the second solvent of the present embodiment has the property of not dissolving the solidification material and the property of being mutually soluble with the first solvent. is necessary. When the second solvent is brought into contact with the coating film on the electrode foil, the second solvent penetrates into the coating film while replacing the first solvent in the coating film. If the concentration of the second solvent increases in the coating film, the solidification material becomes insufficient because the solubility of the solidification material becomes insufficient. At this time, the active material particles contained in the paste are bound together to form the entire coating film. Is solidified. Usually, such a solidification process occurs in a time much shorter than the time required for drying or the like, so that the distribution of various components in the coating film is fixed almost instantaneously.

  Due to the characteristics of this embodiment, it is possible to use a contact-type roller conveyance system that contacts the solidified coating film for conveying the electrode foil holding the solidified coating film. The advantage of this embodiment is particularly excellent when the electrode films are applied on both sides and then the electrode films on both sides are dried together. 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, there is no need to use a complicated and expensive air floating conveyance system even when performing double-sided batch drying. An inexpensive drying room using a transport system can be used.

  Next, the electrode foil holding the paste solidified by the means of this embodiment is carried into the drying chamber 4-6, and the paste is dried by heating and evaporating the solvent component in the paste by a known method such as hot air drying. The electrode foil roll 4-7 wound up with the dried electrode foil is supplied to the next step.

  In the drying of the present embodiment, the solidified paste may be dried instead of the liquid paste. For this reason, by introducing the solidification process of the present embodiment, drying can be performed while preventing fluctuations in various compositions and film thickness that have been fluctuated in the past, so that rapid drying in a short time is possible. Such a feature of the present embodiment is directly linked to an economic advantage that the drying equipment can be downsized.

  In this embodiment, most of the solvent components in the paste removed in the drying chamber by the substitution in the solidification step are not the first solvent used for paste adjustment, but the second solvent of this embodiment. It is a feature. It is also an advantage of this embodiment that a process for avoiding manufacturing problems associated with drying can be designed by making the solvent at the time of drying different from the solvent in the paste.

  Specifically, even if the first solvent as the solvent component in the paste is a flammable solvent, the solvent in the paste is replaced with the second solvent in this example in the solidification step of this example. If a nonflammable solvent is selected as the second solvent, it is possible to eliminate the generation of flammable solvent vapor in the drying chamber. For this reason, it becomes possible to eliminate problems in facilities such as various safety measures and steam recovery equipment associated with handling of combustible steam. In this embodiment, it is possible to design a process that avoids the problems and restrictions of the manufacturing process.

  Each material of the lithium ion battery in the present embodiment will be described.

  The positive electrode active material of the lithium ion battery used in this example is lithium cobaltate, a lithium-containing composite oxide having a spinel structure containing manganese, a composite oxide containing nickel, cobalt, manganese, or olivine-type phosphorus. An olivine type compound represented by iron oxide is used, but is not limited thereto. Since the lithium-containing composite oxide having a spinel structure containing manganese is excellent in thermal stability, for example, a highly safe battery can be configured. As the positive electrode active material, only a lithium-containing composite oxide having a spinel structure containing manganese may be used, but another positive electrode active material may be used in combination. Examples of such other positive electrode active materials include olivine type compounds represented by Li1 + xMO2 (−0.1 <x <0.1, M: Co, Ni, Mn, Al, Mg, Zr, Ti, etc.) Is mentioned. Specific examples of the lithium-containing transition metal oxide having a layered structure include LiCoO2 and LiNi1-xCox-yAlyO2 (0.1 ≦ x ≦ 0.3, 0.01 ≦ y ≦ 0.2), and at least Co. An oxide containing Ni and Mn (LiMn1 / 3Ni1 / 3Co1 / 3O2, LiMn5 / 12Ni5 / 12Co1 / 6O2, LiNi3 / 5Mn1 / 5Co1 / 5O2, etc.) can be used.

  Examples of the negative electrode active material used in this example include graphite materials such as natural graphite (flaky graphite), artificial graphite, and expanded graphite; graphitizable carbonaceous materials such as coke obtained by firing pitch; and furfuryl. Examples thereof include carbon materials such as non-graphitizable carbonaceous materials such as amorphous carbon obtained by low-temperature firing of alcohol resin (PFA), polyparaphenylene (PPP), and phenol resin. In addition to the carbon material, lithium 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, and alloys containing elements that can be alloyed with lithium such as Si and Sn. Furthermore, oxide-based materials such as Sn oxide and Si oxide can also be used.

  The conductive material used in this example is usually used as an electron conduction aid to be contained in the positive electrode mixture layer. For example, carbon materials such as carbon black, acetylene black, ketjen black, graphite, carbon fiber, and carbon nanotube Is preferred. Among the above carbon materials, acetylene black or ketjen black is particularly preferable 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 may be included in the negative electrode mixture and may be preferable.

  Since the binder component can also be used as the solidifying material of this embodiment, the binder as shown below can be used.

  It is preferable that the binder of the present example 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), a rubber polymer, and the like are preferably used. Two or more of the above polymers may be used in combination. Moreover, what is provided with the form of the solution which melt | dissolved in the solvent is preferable for the binder of a present Example.

  Examples of the fluorine-containing monomer group for synthesizing the polyvinylidene fluoride-based polymer include vinylidene fluoride; a mixture of vinylidene fluoride and another monomer, and a monomer mixture containing 80% by mass or more of vinylidene fluoride; Can be mentioned.

  Examples of other monomers 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 binder content in each mixture layer of the positive and negative electrodes is 0.1% by mass or more, more preferably 0.3% by mass or more, and more preferably 10% by mass or less, based on the electrode agent after drying. Preferably it is 5 mass% or less. If the binder content is too small, not only is the solidification in the solidification step of this example insufficient, but the mechanical strength of the mixture layer after drying is insufficient, and the mixture layer peels from the current collector foil. There's a problem. Moreover, when there is too much content of a binder, there exists a possibility that the amount of active materials in a mixture layer may reduce and battery capacity may become low.

  As the solidifying material of this embodiment, the same binder as described above or a mixture thereof is used. In this embodiment, it is also possible to use a component that does not have the performance as a binder but has the performance as a solidifying material in addition to the binder.

  Each material of the lithium ion battery in the present embodiment will be described.

  In the application of the present embodiment, various application methods such as an extrusion coater, a reverse roller, a doctor blade, and an applicator can be adopted as the application method.

  The electrode foil used in this example is representatively shown, and is not limited to a sheet-like foil. Examples of the substrate include pure metals or alloys such as aluminum, copper, stainless steel, and titanium. A conductive conductive material is used, and a net, punched metal, foam metal, 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 mixture layer formed on the electrode foil surface can be selected, for example, from 10 to 300 μm, more preferably from 30 to 150 μm, as the thickness after drying.

  It is important that the solvent of this embodiment is used by appropriately selecting the first solvent contained in the electrode material paste and the second solvent contained in the solidifying material. Such a solvent should be selected from the solubility of the solidifying material of this embodiment or the binder component that also serves as the solidifying material, and the mutual solubility of the solvent. As the first solvent, N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate, dimethyl An aprotic polar solvent typified by formamide, γ-butyrolactone, or a mixture thereof can be selected. As the second solvent, a protic solvent typified 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 this embodiment depends on the selection of the solidifying component used for the electrode material and the combination of the two types of solvents. By using the first solvent contained in the electrode material paste as an aprotic polar solvent or a mixed solution thereof, and the second solvent contained in the solidified material as an aprotic polar solvent or a mixed solution thereof, The binder component does not solidify in the material paste, and the binder component can be easily solidified in the solidified 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. On the other hand, after the solidifying material is brought into contact, the electrode material paste and the binder are easily solidified. Can do.

  The solidification means in the present embodiment will be described.

  The solidifying means of the present example brings the second solvent of the present example into contact with the coating film held on the electrode foil containing the first solvent of the present example, and the first solvent in the coated film is removed. What is necessary is just to have the function substituted by the 2nd solvent, and the system which passes the coating film hold | maintained on electrode foil in the liquid tank which stored the 2nd solvent, and the coating film hold | maintained on electrode foil Examples include, but are not limited to, a method in which the second solvent is sprayed and a method in which the second solvent is supplied while flowing down. In addition, the method of spraying the second solvent onto the coating film held on the electrode foil or the method of supplying the second solvent while flowing down the liquid tank containing the second solvent on the electrode foil. Compared with the method of passing the retained coating film, the step of bringing the solidified liquid into contact with the entire electrode foil earlier and squeezing faster can be performed.

  As an example of an immersion method for allowing the coating film held on the electrode foil to pass through the liquid tank, an apparatus as shown in FIG. 5 can be used. The solidification device 5-1 of this embodiment is a solidification device provided with an overflow tank 5-5 and a circulation pump 5-6 using an electrode foil 5-3 coated with an electrode agent paste 5-2 using a roller transport system 5-4. 5-1. In the overflow tank 5-5, the electrode agent paste 5-2 is solidified by being brought into contact with the solidifying solution 5-7 of the present embodiment, and is transported to the next drying apparatus. The solidifying device 5-1 of the present embodiment can be provided with an air knife 5-8 for draining liquid.

  Further, as an example of a spray method in which the second solvent is sprayed onto the coating film held on the electrode foil, an apparatus as shown in FIG. 6 can be used. The solidifying device 6-1 of the present embodiment is a solidifying device provided with a spray nozzle 6-5 and a circulation pump 6-6 by using an electrode foil 6-3 coated with an electrode paste 6-2 using a roller transport system 6-4. 6-1. By contacting with the solidifying liquid 6-7 of this embodiment supplied from the spray nozzle 6-5, the electrode agent paste 6-2 is solidified and carried out to the next drying apparatus. The solidifying device 6-1 of the present embodiment can be provided with an air knife 6-8 for draining liquid.

  If the solidification process is continued using such a circulation type solidification apparatus, the first solvent removed by substitution from the electrode paste accumulates in the second solvent, which is the solidification liquid of this embodiment, and the concentration thereof increases. become. In this embodiment, it is possible to use a solidified liquid in which the first solvent is mixed in the second solvent, and it is necessary to appropriately control the concentration of the solidified liquid from the solidification ability of the solidified liquid.

  Further, as a lower limit of the contact time required for solidification, generally, a time for replacing the first solvent and the second solvent by interdiffusion in the coating film is required. The upper limit of the contact time depends mainly on economic constraints. From this point of view, the contact time is preferably 1 to 100 seconds, more preferably 2 to 50 seconds, and further preferably 5 to 20 seconds.

  The liquid transport means of this embodiment is preferably an inexpensive contact roller transport system, but this embodiment does not limit the use of an air floating transport system, and the use of a small amount reduces the overall productivity. Sometimes it improves.

  The liquid drying means of this embodiment is generally hot air drying, but is not limited thereto. A heating method that irradiates electromagnetic waves such as infrared rays, far-infrared rays, or visible light may be used, or a dielectric heating method that uses a high-frequency electric field, or an induction heating method that uses a change in magnetic flux may be used. . Furthermore, a contact heating method using a heating roll and a hot plate incorporating a heater, or a heating method combining these can also be used.

  Each process in the present embodiment will be described.

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

  The kneaded paste is applied to 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 a liquid electrode material paste is applied to the surface of the electrode foil using a coating means.

  The aluminum foil coated with the positive electrode paste is immersed in pure water, which is the second solvent of this embodiment, for 20 seconds to solidify the paste. The cause of the solidification phenomenon is that NMP of the first solvent in the paste is replaced with pure water as the second solvent, so that the binder in the paste is insolubilized and precipitates, and binds between the positive electrode particles. This is because the characteristic action of this embodiment occurs. Since this solidified paste loses fluidity and adhesiveness and is held on the aluminum foil, it can sufficiently withstand contact roller conveyance on the surface of the paste. In this embodiment, the process solidifies the electrode material paste by bringing the solidified liquid containing the liquid component that is the second solvent different from the liquid component that is the first solvent contained in the electrode material paste into contact with the electrode material paste. This is the second step of the example.

  The solidified paste is dried at 120 ° C. for 10 minutes in a warm air drying oven, and pure water substituted in the paste and a small amount of NMP are removed by evaporation to produce a lithium battery electrode. This drying step is the third step of this embodiment in which the liquid component is removed from the electrode material paste and dried.

  On the other hand, as a comparison, the same paste as in this example was applied onto an aluminum foil, and dried as it was in a warm air drying oven at 120 ° C. for 10 minutes to evaporate and remove NMP in the paste to produce a lithium battery electrode. . With this method, an electrode for a lithium battery having the same composition is manufactured by a manufacturing method in which the solidification step of this example is omitted. Such a manufacturing method for comparison corresponds to a conventional method.

  FIG. 7 shows a comparison of various characteristics of the electrode film obtained by the manufacturing method of this example and the conventional manufacturing method. As described above, in the present embodiment having the solidification process, the electrode film is solidified before the drying process is input, whereas in the conventional manufacturing method, the liquid electrode film is dried. Therefore, the present embodiment makes it possible to contact and convey the electrode film surface in the drying process, but is impossible in principle by the conventional method.

  Furthermore, the excellent effect of the present embodiment appears remarkably in the composition distribution of the electrode film. That is, a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer (EDX) can be used as such an analysis method that can measure the composition distribution in the thickness direction from the cross section of the dried electrode film. . A case where the ratio of the binder component measured by such a method in the film thickness direction is twice or more between the electrode surface and the bottom surface in contact with the aluminum foil is defined as a large distribution, and a case where the ratio is smaller than two times is defined as a small distribution. In comparison of such distributions, it can be seen that the electrode film of this example has a small distribution, and the conventional electrode film has a very significant difference that the distribution is large. Such a binder component distribution is presumed to occur due to mass transfer of components such as a binder, that is, convection and diffusion, in the film because the paste is in a liquid state when the electrode film is dried in the conventional method. On the other hand, in this embodiment, the electrode film is solidified in the solidification process of this embodiment, and at the same time, the components are fixed and the distribution is reduced because they do not move during drying.

  In addition, the distribution of the positive electrode active material, which is solid particles in the film obtained from the observation of the electrode film, and the conductive auxiliary agent is large in the conventional method, whereas the electrode film of this example has a small distribution. It is recognized as a uniform film.

  As is clear from the above results, the adoption of the solidification process of this example is directly related to the innovation and improvement of the manufacturing apparatus and process conditions, and at the same time, the uniformity of the composition of the electrode film to be manufactured is greatly improved. Quality innovation such as improvement is also achieved.

  It should be emphasized that the effect of this example is not obtained only with the positive electrode film made of the positive electrode material, but also with the negative electrode film.

  According to the present example, various compositions and film thicknesses that have been fluctuating during drying can be maintained extremely stably. Furthermore, in this invention, since it can dry, preventing various fluctuation | variation, rapid drying in a short time is attained. Such a feature of the present invention is directly linked to an economic advantage that the quality of the electrode film can be stabilized and the drying equipment can be downsized.

  In addition, from the feature of the present invention, it is also possible to use a contact-type roller conveyance system that contacts the solidified coating film for conveying the electrode foil holding the solidified coating film. Such an advantage of the present invention is particularly excellent when the electrode films are applied on both sides and then the electrode films on both sides are collectively dried. That is, in the present invention, since it is possible to use a contact type roller conveyance system that comes into contact with the solidified electrode material paste, it is not necessary to use a complicated and expensive air floating conveyance system even when performing double-sided batch drying. An inexpensive drying room using a transport system can be used.

  Furthermore, the present invention 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 preparing the paste, but the second solvent of the present invention. It is also an advantage of the present invention that various problems in production due to drying can be avoided by using a solvent different from the solvent in the paste as the solvent during drying.

  Specifically, even if the first solvent as the solvent component in the paste is a flammable solvent, the solvent in the paste is replaced with the second solvent in the present invention in the solidification step of the present invention. By selecting a non-flammable solvent as the solvent, it is possible to eliminate the generation of the flammable solvent vapor in the drying chamber, so that it is possible to solve the problem on equipment for safety. It is possible to design a process that avoids the problems and limitations of the manufacturing process.

  A method of manufacturing the electrode film in Example 2 will be described with reference to FIG. The description of the same configuration as that of the first embodiment is omitted.

  In this example, the electrode material paste is applied to the surface of the electrode foil, the electrode material paste is applied to the electrode foil, the electrode material paste is solidified, and the electrode foil is dried. It is characterized by performing a step of applying a paste, a step of solidifying an electrode material paste, and a step of drying an electrode foil.

  Coating means 8-such as a die coater in which the paste of positive and negative electrode materials for a lithium battery according to the present embodiment is prepared as a high-viscosity slurry-like liquid and the paste is installed in the coating unit 8-1 for the surface. 2 is applied thinly and uniformly onto the electrode foil supplied from the collector electrode foil roll 8-3.

  Using the roller conveyance system 8-4 for conveying the electrode foil at a constant speed while being in contact with the back surface of the electrode foil coated with such paste, the electrode foil is carried into the solidification chamber 8-5, and this example is applied to the electrode paste. The solidified liquid (not shown) which is the second solvent is contacted to solidify the paste.

  Next, the electrode foil holding the paste solidified by the means of the present embodiment is carried into the drying chamber 8-6, 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 is thinly and uniformly applied on the back surface of the electrode foil using a coating means 8-8 such as a die coater installed in the coating portion 8-7 for the back surface.

  The electrode foil coated with the paste is carried into the solidification chamber 8-9 for the back surface, and the solidified liquid (not shown) as the second solvent of this example is brought into contact with the electrode paste to solidify the paste.

  Next, the electrode foil holding the paste solidified by the means of this example is carried into the drying chamber 8-10, and the solvent component in the paste is heated and evaporated by a technique such as hot air drying to dry the paste. The electrode foil roll 8-11 wound with the dried electrode foil is supplied to the next step.

  In this embodiment, the electrode formation on the front and back surfaces of the electrode foil is performed in the steps of coating, solidifying and drying on the front and back surfaces, and the electrode quality is improved and dried compared to the conventional method shown in FIG. It is possible to easily realize both miniaturization of equipment.

  The manufacturing method of the electrode film in Example 3 is demonstrated using FIG. The description of the same configuration as that of the first embodiment is omitted.

  Surface coating means 9-2 such as a die coater in which positive and negative electrode pastes for lithium batteries according to the present embodiment are prepared as a high-viscosity slurry-like liquid and the paste is installed in the coating unit 9-1. And it apply | coats thinly and uniformly on both surfaces of the electrode foil supplied from the electrode foil roll 9-4 for current collection using the coating means 9-3 for back surfaces.

  The electrode foil having the paste applied on both sides thereof is carried into the solidification chamber 9-5, and the electrode paste is brought into contact with both sides of the electrode foil with a solidification liquid (not shown) as the second solvent of this embodiment. , Solidify the paste. If it is a solidified paste, it can be conveyed using a roller conveyance system 9-6 for conveying the electrode foil at a constant speed while being in contact with the back surface of the electrode foil.

  Next, the electrode foil holding the paste solidified by the means of this example is carried into the drying chamber 9-7, and the solvent component in the paste is heated and evaporated on both sides at once by a technique such as hot air drying to dry the paste. To do. The electrode foil roll 9-8 wound up with the dried electrode foil is supplied to the next step.

  In the present embodiment, when the electrodes are formed on the front and back surfaces of the electrode foil at the same time, an excellent manufacturing method that takes advantage of the present invention can be realized. Compared with the conventional method shown in FIG. 3, in addition to the improvement of the electrode quality and the downsizing of the drying equipment, the transport of the electrode foil holding the solidified coating film can be carried out by an inexpensive contact type that contacts the solidified coating film. The use of a roller conveyance system is also possible.

  That is, in this example, it is also possible to use a contact-type roller conveyance system that comes into contact with the solidified electrode material paste, so there is no need to use a complicated and expensive air-floating conveyance system even when performing double-sided batch drying, An inexpensive drying room using a roller conveyance system can be used.

  A method of manufacturing the electrode film in Example 4 will be described with reference to FIG. The description of the same configuration as that of the first embodiment is omitted.

  Surface coating means 10-2 such as a die coater in which positive and negative electrode pastes for lithium batteries according to the present embodiment are prepared as a high-viscosity slurry liquid and the paste is installed in the coating unit 10-1. And it apply | coats thinly and uniformly on both surfaces of the electrode foil supplied from the collector electrode foil roll 10-4 using the coating means 10-3 for back surfaces.

  The electrode foil coated with the paste on both sides is carried into a solidification chamber 10-5 arranged vertically, and a solidification liquid (not shown) as the second solvent of this embodiment is supplied to the electrode paste by spraying or the like. The electrode foil is conveyed from the top to the bottom (or from the bottom to the top) by vertical treatment, and the paste is solidified. If it is the solidified paste, conveyance using the roller conveyance system 10-6 for conveying the electrode foil at a constant speed while contacting the back surface of the electrode foil is possible.

  Next, the electrode foil holding the paste solidified by the means of this example is carried into the drying chamber 10-7, and the solvent component in the paste is heated and evaporated by a technique such as hot air drying to dry the paste. The electrode foil roll 10-8 wound with the dried electrode foil is supplied to the next step.

  In this example, in the step of solidifying the paste, the electrode foil was conveyed from the top to the bottom (or from the bottom to the top), but instead of or in addition to this, the electrode foil was dried in the step of drying the electrode foil. You may convey from the top to the bottom (or the bottom to the top).

  In the case where the coating unit and the solidification chamber are arranged vertically as in this actual example, it is possible to easily achieve both improvement in electrode quality and downsizing of the drying equipment, as well as arrangement of manufacturing equipment. It is possible to expect an excellent effect of reducing the capital investment in the manufacturing apparatus, such as enabling a flexible layout and reducing the area of the installation plane of the manufacturing apparatus. In this actual example, an example of the vertical arrangement of the coating unit and the solidifying chamber is shown, but this example does not limit the vertical arrangement of the drying chamber, but may be preferable.

  According to the embodiments of the present invention described above, various problems associated with the manufacture of lithium ion batteries can be avoided at the same time, so that the quality and economic effects of the present invention cannot be measured. is there.

  The embodiments described so far are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention is not limitedly interpreted by these. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof. Further, the present invention may be implemented by combining the first to fourth embodiments.

  The present invention is intended for lithium ion batteries, but the essence of the present invention is the technical idea that has revolutionized the manufacturing method in which the electrode paste is solidified in advance and then dried. Therefore, it can be used not only for the production of other primary and secondary electrode sheet laminated batteries, but also for various organic and inorganic membranes that produce products using a process of applying and drying a paste containing powder. It can be used for a wide range of manufacturing methods.

1-1: Coating section 1-2: Coating means 1-3: Electrode foil roll for current collection 1-4: Roller transport system 1-5: Drying chamber 1-6: Electrode foil roll 2-1: Coating Part 2-2: Coating means 2-3: Collecting electrode foil roll 2-4: Roller transport system 2-5: Drying chamber 2-6: Second coating part 2-7: Coating means 2- 8: Roller transport system 2-9: Back surface drying chamber 2-10: Electrode foil roll 3-1: Coating section 3-2: Front surface die coater 3-3: Back surface die coater
3-4: Electrode foil roll for current collection
3-5: Drying chamber 3-6: Electrode foil roll 3-7: Non-contact type transport system 4-1: Coating section 4-2: Coating means 4-3: Electrode foil roll for current collection
4-4: Roller transport system 4-5: Solidification chamber 4-6: Drying chamber 4-7: Electrode foil roll
5-1: Solidification device 5-2: Electrode paste 5-3: Electrode foil 5-4: Roller transport system 5-5: Overflow tank 5-6: Circulation pump 5-7: Solidification liquid 5-8: Air knife 6-1: Solidification device 6-2: Electrode paste 6-3: Electrode foil 6-4: Roller transport system 6-5: Spray nozzle 6-6: Circulation pump 6-7: Solidification liquid 6-8: Air knife 8-1: Coating section 8-2: Coating means 8-3: Electrode foil roll 8-4: Roller transport system 8-5: Solidification chamber 8-6: Drying chamber 8-7: Coating section 8-8 : Coating means 8-9: solidification chamber 8-10: drying chamber 8-11: electrode foil roll 9-1: coating section 9-2: coating means 9-3: coating means 9-4: electrode foil Roll 9-5: Solidification chamber 9-6: Roller transport system 9-7: Drying chamber 9-8: Electrode foil roll 10-1: Coating section 10-2: Coating means 10-3: Coating hand 10-4: electrode foil roll 10-5: solidification chamber 10-6: Roller conveyor system 10-7: drying chamber 10-8: electrode foil roll

Claims (9)

A first step of applying a liquid electrode material paste to the surface of the electrode foil;
A second step of solidifying the solidified material in the electrode material paste by bringing a solidified liquid containing a liquid component different from the liquid component contained in the electrode material paste into contact with the electrode material paste;
And a third step of removing the liquid component from the solidified electrode material paste and drying it.   2. The method of manufacturing a lithium ion battery according to claim 1, wherein the liquid component contained in the electrode material paste includes an aprotic polar solvent, and the solidified liquid includes a protic solvent. 2. The lithium ion battery according to claim 1, wherein the solidifying material includes a binder for bonding the electrode material to the electrode, and the binder is a polyvinylidene fluoride-based polymer, a rubber-based polymer, or a mixture thereof. Manufacturing method. In the second step, the solidified liquid and the electrode material paste applied to the electrode foil are brought into contact with each other in the liquid tank in which the solidified liquid is stored, or the electrode material paste applied on the electrode foil is solidified. The method for producing a lithium ion battery according to claim 1 , wherein the method is carried out by spraying a liquid by spraying or by causing the solidified liquid to flow down to an electrode material paste applied on the electrode foil.   The first step to the third step are performed on the back surface of the electrode foil after the first step to the third step are performed on the surface of the electrode foil. The method for producing a lithium ion battery according to claim 1. In the first step, it is a double-sided application to the electrode foil, and the conveyance after the solidification uses a roller conveyance system,
The method of manufacturing a lithium ion battery according to claim 1, wherein the third step is to dry both surfaces at once.   The method of manufacturing a lithium ion battery according to claim 6, wherein in the second step, the electrode foil is transported from top to bottom or from bottom to top.   The method of manufacturing a lithium ion battery according to claim 6, wherein in the third step, the electrode foil is transported from top to bottom or from bottom to top.   A lithium ion battery comprising an electrode film produced by the production method according to claim 1.

Images