JP3969690B2 - Application method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating method.
[0002]
[Prior art]
The most common coating method is a die coating method using a die. As a general die of the die coating method, a die as shown in FIGS. 1 and 2 is used. FIG. 1 is an exploded perspective view of the die, and FIG. 2 is a cross-sectional view at the center of the die. The die 1 is provided with a manifold 4 and a discharge port 7 between an upper blade 2 and a lower blade 3, and a coating liquid supply port 5 is provided in the manifold 4. The coating liquid is introduced into the manifold from the coating liquid supply port 5, passes through the slit 6, and is pushed out from the discharge port 7 in a thin film shape.
[0003]
Moreover, when performing multi-strand application | coating using die | dye, die | dye like FIG.3 and FIG.4 is used. FIG. 3 is an exploded perspective view of a die that can be used for multi-strand application, and FIG. 4 is a cross-sectional view at the center of the die. The die 8 is provided with a manifold 11 and a slit 15 communicating with the discharge port 16 between the upper blade 9 and the lower blade 10, and the manifold 11 is provided with a liquid introduction port 12. A shim 13 is arranged between the upper blade and the lower blade, thereby forming a slit 14. The shim 13 is provided with a guide 14 that extends to the discharge port in the slit direction and has the same thickness as the slit. As a result, the slit 14 is divided into a plurality of parts, and a plurality of paint discharge paths are formed. The coating solution is introduced into the manifold from the coating solution supply picture port 12, passes through the slit 15, and is pushed out from the discharge port 16 in a thin film shape. At this time, since the guide 14 is provided in the slit, the electrode coating material passes through the portion of the coating material discharge path, and as a result, is applied in multiple stripes.
[0004]
However, in the application of a wide surface as described above (for example, die coating using a die as shown in FIGS. 1 and 2), the coating thickness varies between the center and the outer edge of the application surface. Had a problem. Also in multi-strand coating (for example, die coating using a die as shown in FIGS. 3 and 4), there is a variation in thickness between the coating applied near the center of the die and the coating applied near the outer edge. As a result, there was a problem that the product could not be homogenized. Although it is possible to suppress variations in coating thickness by providing a plurality of coating liquid supply ports in the lateral direction, a dedicated die must be manufactured, and the die is expensive, which is not economical.
[0005]
[Problems to be solved by the invention]
In the coating of a wide surface as described above, there is no variation in coating thickness between the central portion and the outer edge portion of the coating surface, and even in multi-strand coating, the coating applied near the center of the die coater and the vicinity of the outer edge portion. There has been a demand for an economical coating method that does not vary in thickness from the coated one.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.
That is, the gist of the present invention is a method for applying a coating liquid onto a substrate using an extrusion die, wherein the die has a manifold, and the supply amount of the coating liquid to the entire slit portion of the die The present invention resides in a coating method characterized in that a core for evenly distributing is provided in a manifold portion.
[0007]
As a preferred embodiment of the present invention, the coating method is a multi-layer coating method, the die has a guide for dividing the slit into a plurality of equal widths, and each slit portion divided by the guide in the manifold portion The above-mentioned coating method provided with a core that evenly distributes the supply amount of the coating liquid to the core; the core distributes the supply amount of the coating liquid evenly by distributing the extrusion pressure of the coating liquid evenly Application method: The above application method in which the core has a structure satisfying the following (1) to (5):
[0008]
(1) One liquid inlet, two liquid outlets, and a liquid channel that connects the liquid inlet and the liquid outlet, and the arrangement and shape of the liquid inlet, the liquid channel, and the liquid outlet Has a structure (i) that is plane-symmetrical on a vertical plane that passes through the center of the liquid inlet and is horizontal to the liquid inlet direction,
(2) The liquid outlet of the first structure (i) is connected to the liquid inlet of the next structure (i),
(3) The repetition of the connection of the liquid outlet and the liquid inlet of this structure (i) is repeated until the required number of liquid outlets is reached,
(4) The required number of liquid outlets are arranged at equal intervals,
(5) The entire internal structure after the liquid introduction port of each structure (i) is plane-symmetrical on a vertical plane that passes through the center of the liquid introduction port of each structure (i) and is horizontal in the liquid introduction direction.
The above-mentioned coating method wherein the slit is divided into 2n (n is an integer of 1 or more) by a guide; the coating liquid is an electrode paint containing an active material and / or a conductive material, a binder and a solvent; Application methods may be mentioned.
[0009]
Another embodiment of the present invention includes a step of applying an electrode paint containing an active material and / or a conductive material, a binder and a solvent on a conductive electrode substrate in multiple stripes using an extrusion die. In the electrode manufacturing method, the die has a guide that divides the slit into a plurality of equal widths, and a manifold, and the supply amount of the electrode coating material to each slit portion divided by the guide is equalized in the manifold portion. A method for producing an electrode characterized in that a core for distribution is provided.
[0010]
As a more preferred embodiment of another embodiment of the present invention, the above production method is characterized in that the core has a structure satisfying the following (1) to (5).
(1) One liquid inlet, two liquid outlets, and a liquid channel that connects the liquid inlet and the liquid outlet, and the arrangement and shape of the liquid inlet, the liquid channel, and the liquid outlet Has a structure (i) that is plane-symmetrical on a vertical plane that passes through the center of the liquid inlet and is horizontal to the liquid inlet direction,
(2) The liquid outlet of the first structure (i) is connected to the liquid inlet of the next structure (i),
(3) The repetition of the connection of the liquid outlet and the liquid inlet of this structure (i) is repeated until the required number of liquid outlets is reached,
(4) The required number of liquid outlets are arranged at equal intervals,
(5) The entire internal structure after the liquid introduction port of each structure (i) is plane-symmetrical on a vertical plane that passes through the center of the liquid introduction port of each structure (i) and is horizontal in the liquid introduction direction.
[0011]
As another embodiment of the present invention, A core used in the coating method, (1) One liquid inlet, two liquid outlets, and a liquid channel that connects the liquid inlet and the liquid outlet, and the arrangement and shape of the liquid inlet, the liquid channel, and the liquid outlet Has a structure (i) that is plane-symmetrical in a vertical plane that passes through the center of the liquid introduction port and is horizontal in the liquid introduction direction, and (2) the liquid outlet port of the first structure (i) is the next structure (i) (3) The connection of the liquid outlet and the liquid inlet of this structure (i) is repeated until the required number of liquid outlets is reached, and (4) required. The number of liquid outlets are arranged at equal intervals. (5) And the entire internal structure after the liquid inlet of each structure (i) passes through the center of the liquid inlet of each structure (i), and the direction of liquid introduction The core is characterized by being symmetrical with respect to a horizontal plane.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
There is no particular limitation on the die coating method, and various methods such as a free span coating method and a backup roll top coating method can be employed.
The die used in the present invention is a die having a manifold as shown in FIGS. 1 to 4, and a core for evenly distributing the supply amount of the coating liquid to the entire slit portion of the die is provided in the manifold portion. . When applying multiple strips, it is only necessary to provide a guide that divides the slit into a plurality of equal widths as shown in FIGS. 3 and 4. In this case, supply of the coating liquid to each slit portion divided by the guide by the above core The amount is evenly distributed. Examples of the die used in the present invention are shown in FIGS. In the die of the present invention, the coating liquid supply port 5 in FIG. 1 or the coating liquid supply port 12 in FIG. 2 is connected to a core liquid introduction port 19. Come out of exit 18.
[0013]
The core used in the present invention can distribute the supply amount of the coating liquid evenly. For example, the coating liquid is supplied from the coating liquid supply port at a constant extrusion pressure, and by distributing the extrusion pressure of the coating liquid evenly by the core, the supply amount of the coating liquid can be evenly distributed. it can.
There are various methods for evenly distributing one pressure. For example, it has one liquid inlet, two liquid outlets, and a liquid flow path connecting the liquid inlet and the liquid outlet, and the liquid introduction If the coating liquid is allowed to pass through the structure (i) in which the arrangement and shape of the mouth, the liquid flow path, and the liquid outlet port are symmetrical with respect to a vertical plane that passes through the center of the liquid introduction port and is horizontal in the liquid introduction direction, The pressure can be evenly distributed between the two. In the present invention, “vertical surface” means a surface perpendicular to the geoid surface, that is, a surface including the direction of gravity.
[0014]
By repeating the connection of the liquid outlet of the next structure (i) to the two liquid outlets of the structure (i), it is possible to evenly distribute the pressure to any required number ( If only two liquid outlets are needed, there is no need to connect them). However, the required number of liquid outlets are arranged at equal intervals, and the entire internal structure after the liquid inlet of each structure (i) passes through the center of the liquid inlet of each structure (i). It needs to be plane symmetric in a vertical plane horizontal to the direction. In the above, the whole internal structure after the liquid inlet means the internal structure from the liquid inlet to the last liquid outlet. The surface of the manifold may be used as a part of the inner structure of the core. That is, the “internal structure” of the core in the present invention includes the manifold surface in use when the surface of the manifold is used as a part thereof. Further, in the above, the “necessary number” may be arbitrarily selected so that the coating thickness does not vary between the central portion and the outer edge portion of the coated surface in the case of a wide surface coating. The number of strips (the number of divisions by slit guides) may be selected.
[0015]
Specific examples of the core as described above include those shown in FIGS. The liquid outlets 18 are arranged at equal intervals. The core is installed so that the coating liquid supply port 5 or 12 in the manifold is connected to the coating liquid inlet 19 of the core. When the core as shown in FIG. 10 is used, the surface of the manifold may be used as a part of the inner surface of the core structure. In the case of the core shown in FIG. 10, the surfaces 20 and 21 may be designed and installed so that the surfaces of the manifold and the surface 22 are in close contact with the bottom surface of the manifold. Alternatively, some of the surfaces 20, 21, and 22 may be covered with a flat plate and the remaining surfaces may be placed in close contact with the surface of the manifold.
[0016]
When there are one or more coating liquid supply ports of the die, the core may be installed at each coating liquid supply port, or a core integrated with the core may be created and installed.
The core may be divided into two or more pieces in consideration of ease of work, and may be installed in combination.
In the case of performing multi-strip application, a projection reaching the guide (14 in FIG. 7) may be provided as shown in FIG.
The material of the core is not particularly limited, and a material that has a certain degree of strength and stickiness and is easy to process is desirable, and a metal material, a plastic material, and the like are most suitable. As a machining method, milling is most suitable, and the machining accuracy is desirably ± 1% or less or ± 0.05 mm or less with respect to the target dimension, but is not limited thereto.
When applying in multiple strips, it is preferable that the number of the liquid outlets of the core and the number of divisions by the slit guide are the same. When using the core as shown in FIGS. In addition, the slit is preferably divided into 2n (n is an integer of 1 or more) by a guide.
[0017]
The coating liquid used in the present invention is not particularly limited, and is a magnetic coating for magnetic recording media, a dispersion of an abrasive, a dispersion in which various fine particles such as an electrode coating are dispersed, a paste, a hot-melt adhesive that is heated and melted, Any fluid solution such as a resin solution in which a resin is dissolved or a battery electrolyte solution can be used.
The viscosity of the coating solution is usually 0.002 Pa · s or higher, preferably 0.005 Pa · s or higher, more preferably 0.01 Pa · s or higher, as a steady-state viscosity at a shear rate of 500 (1 / s). In addition, it is usually 100 Pa · s or less, preferably 50 Pa · s or less, more preferably 20 Pa · s or less, and most preferably 10 Pa · s or less. If the viscosity is too small, it tends to spill at the die coating part, and the edge shape of the coating tends to become unstable. If it is too large, the resistance of the liquid feeding increases, and the scale is large for liquid feeding. Equipment is required, which is disadvantageous in terms of cost.
[0018]
When the coating solution is an electrode paint containing an active material and / or a conductive material, a binder and a solvent, the method of the present invention is a preferable method for producing an electrode.
The electrode paint used for coating may be an electrode paint containing an active material, a binder and a solvent, or may be an electrode paint containing a conductive material, a binder and a solvent. The layer formed using the latter paint can be a base layer (undercoat primer layer) of a layer formed using the former paint (hereinafter sometimes referred to as “active material layer”). Is also referred to as electrode paint. Hereinafter, the former paint may be referred to as “electrode material paint” and the latter paint may be referred to as “undercoat primer material paint”. The method of this invention includes the case where the coating material for electrodes is applied directly on the conductive electrode substrate and the case where it is applied through another layer.
[0019]
In the case where a tab is provided by extending on a conductive electrode base material, in particular, multi-strand coating applied in stripes is effective as a method of applying an electrode coating material on these. This is because, as shown in FIG. 12, when a thin piece to be used as a battery is cut out from the application portions 32 and 33 formed by applying multiple stripes to the elongated conductive electrode base material 31, This is because if a part of the uncoated part 34 is left as shown by the dotted line in FIG. 12, this uncoated part can be used as it is as a tab of the battery. In addition, even when the tab is not provided, since the degree of freedom of the electrode width can be increased even for the conductive electrode base material having a specific width by the multi-strip application, the multi-strip application is also performed from the aspect of productivity. Is an effective means.
The viscosity of the electrode paint is the same as the viscosity of the coating solution.
[0020]
The thickness after application of the electrode paint (wet thickness) is usually 10 μm or more, preferably 30 μm or more, more preferably 50 μm or more, and usually 1000 μm or less, preferably 500 μm or less, more preferably 400 μm or less. . If it is too thin, the charge capacity per volume will decrease, and the purpose of increasing the capacity will not be achieved. On the other hand, if it is too thick, it cannot cope with rapid charge and rapid discharge (or the rate characteristics are deteriorated), so it is not practical as a coating material for electrodes.
[0021]
Next, materials that can be used as electrode coating materials will be described. For convenience, a lithium secondary battery, particularly a lithium secondary battery using a polymer electrolyte, will be mainly described. It goes without saying that other batteries can be applied by appropriately changing materials from the following description.
As the active material used for the electrode material paint, various materials that can be used for the positive electrode or the negative electrode can be used. Examples of materials that can be used as the positive electrode active material of the lithium secondary battery include oxides of transition metals such as Fe, Co, Ni, and Mn, complex oxides with lithium, and inorganic compounds such as sulfides. Specifically, MnO, V ₂ O _Five , V ₆ O ₁₃ TiO ₂ Transition metal oxide powder such as lithium nickel oxide and lithium cobalt oxide, such as lithium oxide and transition metal composite powder, TiS ₂ And transition metal sulfide powders such as FeS. Examples of the positive electrode active material include organic compounds such as conductive polymers such as polyaniline. Preferably, it is a complex oxide of lithium and at least one metal composed of cobalt, nickel and manganese. Of course, a mixture of a plurality of the above active materials may be used. When the active material is granular, the particle size is usually about 1 to 30 μm, preferably about 1 to 10 μm, from the viewpoint of excellent battery characteristics such as rate characteristics and cycle characteristics. Examples of materials that can be used as the negative electrode active material for lithium secondary batteries include graphite and coke as compounds capable of occluding and releasing Li ions in addition to Li metal foil. Carbonaceous materials such as graphite and coke are preferred. The particle size of the granular negative electrode active material is usually about 1 to 50 μm, preferably about 5 to 30 μm, from the viewpoint of excellent battery characteristics such as initial efficiency, rate characteristics, and cycle characteristics.
[0022]
The binder used for the electrode material paint is not particularly limited as long as it is stable with respect to the electrolytic solution, etc., but various materials are used from the viewpoint of weather resistance, chemical resistance, heat resistance, flame retardancy, and the like. . Specifically, inorganic compounds such as silicate and glass, alkane polymers such as polyethylene, polypropylene and poly-1,1-dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; polystyrene, polymethylstyrene, Polymers having rings such as polyvinyl pyridine and poly-N-vinyl pyrrolidone; polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, poly Acrylic derivative polymers such as acrylamide; Fluorine resins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; Polyvinyl alcohol polymers such as polyvinyl alcohol; polyvinyl chloride, halogen-containing polymers such as polyvinylidene chloride; and conductive polymers such as polyaniline can be used. Further, a mixture such as the above-mentioned polymer, a modified product, a derivative, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer, and the like can be used. The weight average molecular weight of these resins is usually 10,000 to 3,000,000, preferably about 100,000 to 1,000,000. If it is too low, the strength of the coating film tends to decrease. On the other hand, if it is too high, the viscosity increases and it may be difficult to form an electrode. Preferred binder resins are fluororesins and CN group-containing polymers.
[0023]
The amount of the binder used relative to 100 parts by weight of the active material is usually 0.1 parts by weight or more, preferably 1 part by weight or more, and usually 30 parts by weight or less, preferably 20 parts by weight or less. If the amount of the binder is too small, the strength of the electrode tends to decrease, and if the amount of the binder is too large, the ionic conductivity tends to decrease.
In the electrode material coating material, in order to improve the conductivity and mechanical strength of the electrode, additives that exhibit various functions such as a conductive material and a reinforcing material, a powder, a filler, and the like may be contained. The conductive material is not particularly limited as long as it can provide conductivity by mixing an appropriate amount of the above active material. Usually, carbon powder such as acetylene black, carbon black, graphite, various metal fibers, Examples thereof include powder and foil. The DBP oil absorption amount of the carbon powder conductive material is preferably 120 cc / 100 g or more, and particularly preferably 150 cc / 100 g or more because the electrolyte solution is retained. Additives such as trifluoropropylene carbonate, 1,6-Dioxaspiro [4,4] nonane-2,7-dione, 12-crown-4-ether, vinylene carbonate, catechol carbonate, etc. can improve battery stability and life. Can be used to enhance. As the reinforcing material, various inorganic, organic spherical and fibrous fillers can be used.
[0024]
As the solvent used for the electrode material paint, various organic and inorganic materials can be used according to the active material and binder to be used, and examples thereof include N-methylpyrrolidone and dimethylformamide. The solvent concentration in the paint is usually 10% by weight or more, preferably 20% by weight or more, more preferably 30% by weight or more, and most preferably 35% by weight or more. Moreover, as a minimum, it is 90 weight% or less normally, Preferably it is 80 weight% or less, More preferably, it is 65 weight% or less. If the solvent concentration is too low, the viscosity of the paint may increase and the effect of the present invention may not be sufficient, and the coating itself may be difficult. On the other hand, if it is too high, the coating film thickness may be increased. It becomes difficult and the stability of the paint, particularly the edge shape of the coating film, may be deteriorated.
[0025]
The thickness of the coating film of the electrode material paint after the drying step is generally about 0.05 to 200 μm. Within this range, it is usually 10 μm or more, preferably 20 μm or more, and is usually 200 μm or less, preferably 150 μm or less. If it is too thin, the coating becomes difficult and it becomes difficult to ensure uniformity, and the battery capacity may be too small. On the other hand, if it is too thick, the rate characteristics may be deteriorated too much.
[0026]
An undercoat primer layer can be provided between the electrode material layer and the conductive electrode substrate. By providing an undercoat primer layer between the conductive electrode substrate and the electrode material layer, the adhesion of the electrode material layer to the conductive electrode substrate can be further improved, resulting in a reduction in battery internal resistance. Thus, rapid capacity reduction due to coating film detachment from the substrate during the charge / discharge cycle process can be prevented. The undercoat primer layer can be formed by applying an undercoat primer material paint containing a conductive material, a binder, and a solvent onto the conductive electrode substrate, and then drying it.
[0027]
Examples of the conductive material used for the undercoat primer layer include carbon materials such as carbon black and graphite, metal powders, and conductive organic conjugated resins. Preferably, the active material of the electrode material layer Carbon black, graphite, etc.
The binder and solvent used for the undercoat primer layer can be the same as the binder and solvent used for the electrode material paint. In addition, conductive resins such as polyaniline, polypyrrole, polyacene, disulfide compounds, polysulfide compounds and the like can have both functions of the conductive material and the binder. It can also be used for the undercoat primer layer. Of course, the binder and solvent used in the undercoat primer material paint are usually 0.05 μm or more, preferably 0.1 μm or more, and usually 10 μm or less, the same as those used for the paint among the electrode materials. Well, it can be different.
[0028]
When a conductive material and a binder are used, the ratio of the binder to the conductive material is usually 1% by weight or more, preferably 5% by weight or more, and usually 300% by weight or less, preferably 100% by weight or less. is there. If it is too low, the strength of the coating film is lowered, and peeling during the process is likely to occur when using the battery. If it is too high, the conductivity may decrease and the battery characteristics may deteriorate.
[0029]
The solvent concentration in the undercoat primer material paint is usually 10% by weight or more, preferably 20% by weight or more, more preferably 30% by weight or more, and most preferably 35% by weight or more. Moreover, as a minimum, it is 90 weight% or less normally, Preferably it is 80 weight% or less, More preferably, it is 65 weight% or less. If the solvent concentration is too low, the viscosity of the paint becomes high and the wet coating thickness becomes thin, so that the coating itself may be difficult. On the other hand, if it is too high, it is difficult to increase the coating thickness and the stability of the paint. In particular, the edge shape of the coating film may be deteriorated.
[0030]
The thickness of the coating film of the undercoat primer material paint after the drying step is not particularly limited as long as adhesion and conductivity are ensured, but is generally about 0.05 to 200 μm. This range is preferably 1 μm or less. If it is too thin, coating becomes difficult and it becomes difficult to ensure uniformity. If it is too thick, the volume capacity of the battery may decrease too much.
[0031]
Electrode material paints and undercoat primer material paints can usually be produced by dispersing each component into a dispersion paint using a ball mill, sand mill, biaxial kneader or the like.
When an undercoat primer layer is first formed on a conductive electrode substrate, an electrode material layer forming step of forming an electrode material layer thereon is provided.
[0032]
When forming the undercoat primer layer and the electrode material layer, these layers can be formed by applying the electrode material paint after applying and drying the undercoat primer material paint on the conductive electrode substrate. -on-dry application may be performed, or a so-called wet-on-wet application, in which an electrode material paint is applied on a wet undercoat primer layer, may be used. In the case of wet-on-wet coating method, wet-on-wet multi-layer simultaneous coating method that applies each layer simultaneously may be adopted, or wet-on-wet sequential coating in which each layer is sequentially applied in liquid state The coating method may be adopted, but in any case, by applying post-processing such as drying / thermosetting collectively after coating all layers, between the substrate and the undercoat primer layer, and undercoat primer layer The adhesion between the electrode material layer and the electrode material layer can be further improved. Thereby, the dispersion | variation in the battery performance regarding internal impedance and charging / discharging can be reduced significantly, and the performance degradation by repetition of charging / discharging can also be reduced.
[0033]
In the wet-on-wet multilayer simultaneous coating method or the wet-on-wet multilayer sequential coating method, the ratio of the viscosity of the undercoat primer material paint to the electrode material paint is usually 1: 100-100: 1, preferably 1:10. By setting it to about -10: 1, multilayer coating can be easily performed.
Undercoat primer material paint and electrode material paint are both wet or in the same order in this order, such as wet-on-wet multilayer simultaneous coating method or wet-on-wet multilayer sequential coating method. Even when applied on top, the coating method of the present invention can be applied using the whole as a coating material for electrodes.
[0034]
In the present invention, the conductive electrode substrate to which the electrode coating material is applied does not cause problems such as electrochemical elution, and is a current collector for batteries such as metals, alloys, metal laminated plastic films, metal-deposited plastic films, etc. Although various things which can function as a body can be used, normally a metal and an alloy are used. In the case of a lithium secondary battery, specific examples include aluminum, copper, nickel, and SUS.
[0035]
Roughening the surfaces of these base materials in advance is a preferable method because the binding effect with the electrode material layer can be improved. Current roughening methods include a method of rolling with a blasting process or a rough roll, a polishing cloth with a fixed abrasive particle, a grinding wheel, emery buff, a wire brush with a steel wire, etc. Examples thereof include a mechanical polishing method for polishing the surface, an electrolytic polishing method, and a chemical polishing method.
[0036]
Further, in order to reduce the weight of the battery, that is, to improve the weight energy density, a perforated base material such as an expanded metal or a punching metal can be used. In this case, the weight can be freely changed by changing the aperture ratio. In addition, when an electrode material layer or an undercoat primer material layer is formed on both sides of such a perforated type substrate, peeling of the coating tends to be more difficult due to the rivet effect of the coating through this hole. When the aperture ratio becomes too high, the contact area between the coating film and the substrate becomes small, so that the adhesive strength may be lowered. If the aperture ratio is too large, the edge accuracy of the coating film may be too low, and is usually 80% or less, preferably 70% or less, more preferably 50% or less, and most preferably 40% or less. From the viewpoint of edge accuracy, it is preferable not to provide openings in the conductive electrode substrate.
[0037]
In the present invention, an electrode material layer or an undercoat primer material layer can be formed on one side or both sides of a conductive electrode substrate. Single-sided coating is preferred for ease of production, and double-sided coating is preferred for battery performance. When performing double-sided coating, simultaneous double-sided coating from both sides of the substrate is preferred.
The thickness of the conductive electrode substrate is usually 1 μm or more, preferably 5 μm or more, and is usually 100 μm or less, preferably 50 or less, more preferably 35 μm or less. If it is too thick, the capacity of the entire battery will be too low. Conversely, if it is too thin, handling may be difficult.
[0038]
The electrode coating applied on the conductive electrode substrate is then dried. For drying, various methods such as a hot air drying method represented by roll support, air floating, etc., far-infrared ray treatment, and hot roll contact can be employed, and these can be used alone or in combination. The drying temperature is usually about 40 to 200 ° C., preferably about 60 to 160 ° C., but may be controlled in consideration of the evaporation rate and evaporation time of the solvent used.
[0039]
The film thickness of the coating film after drying has a certain distribution, but the maximum film thickness difference of the coating film is usually 7 μm or less, preferably 5 μm or less, more preferably 3 μm or less, and most preferably 2 μm or less. As a result, stable battery performance can be ensured. The maximum film thickness difference can be controlled by the shape of the guide tip, the viscosity of the paint, the thickness of the slit, and the like. Since there is a limit to the control of the maximum film thickness, the maximum film thickness is usually 0.05 μm or more, preferably 0.1 μm or more.
[0040]
The applied and dried coating film is preferably subjected to consolidation treatment with a calendar or the like. As a result, the strength of the coating film can be improved and the adhesion between the coating film and the conductive electrode substrate can be improved. As a result, battery performance such as cycle characteristics can be improved. In addition, in a battery using a non-fluidic electrolyte, the non-fluidic electrolyte may be contained in the gap of the electrode obtained by applying and drying the electrode paint, and in this case, by consolidation treatment, There is also an effect that the abundance of the non-fluid electrolyte inside the electrode can be adjusted. The pressure of the calendar is usually 1 kgf / cm or more, preferably 10 kgf / cm or more, and usually 2000 kgf / cm or less, preferably 1000 kgf / cm or less, more preferably 500 kgf / cm or less. If the pressure is too low, a sufficient consolidation effect may not be obtained. If the pressure is too high, the coating film will be crushed too much and the battery characteristics will be degraded, or it will tend to peel off from the substrate. In addition, the conductive electrode base material is likely to be deformed. The calendar temperature at the time of consolidation is sufficient at room temperature, but if necessary, a temperature not higher than the decomposition temperature of the binder may be added. In particular, it is preferable to keep it below the melting point of the binder.
[0041]
The electrode obtained by coating and drying is usually wound up into a roll and stored or transferred to the next process. In the case of winding in a roll shape, since the deformation of the conductive electrode substrate becomes significant due to winding, the effect of the present invention is remarkable. According to the present invention, since the high edge is effectively prevented, the winding tension can be increased. Therefore, it is difficult to cause a winding slip and is easy to handle. In this case, a long electrode is used as the conductive electrode substrate, and the obtained long electrode is wound up.
[0042]
The obtained electrode can be cut into a predetermined shape into a thin piece at an arbitrary stage. At this time, if the coated part is cut so as to leave a part of the uncoated part from the conductive support coated with multiple strips of electrode paint, the uncoated part left in the thin piece can be used as a tab of the battery. From the viewpoint of effective utilization of uncoated portions and productivity.
The obtained electrode can be used as an electrode of a battery such as a lithium secondary battery. Hereinafter, the configuration other than the electrode of the lithium secondary battery, particularly the lithium secondary battery using a non-fluidic electrolyte will be described, but it goes without saying that it can be applied to other batteries.
[0043]
Generally, a lithium secondary battery is composed of a positive electrode, a negative electrode, an electrolyte layer, and a separator. An electrolyte layer exists between the positive electrode and the negative electrode, and the separator is disposed between them so that the positive electrode and the negative electrode do not contact each other. Yes.
As the electrolyte layer formed between the positive electrode and the negative electrode, various electrolytes such as an electrolyte composed of a supporting electrolyte (solute) and a solvent, a polymer electrolyte holding this with a polymer, and a completely solid electrolyte are used. can do.
[0044]
In the case of a lithium secondary battery, it is common to use an electrolytic solution obtained by dissolving a supporting electrolyte that is a lithium salt in a non-aqueous solvent. As a lithium salt as a supporting electrolyte, LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF _Four LiClO _Four , LiI, LiBr, LiCl, LiAlCl, LiHF ₂ , LiSCN, LiSO _Three CF ₂ Etc. Of these, LiPF in particular ₆ And LiClO _Four Is preferred. The content of these supporting electrolytes in the electrolytic solution is generally 0.5 to 2.5 mol / L.
[0045]
Although the kind of solvent used for electrolyte solution is not specifically limited, The solvent of comparatively high dielectric constant is used suitably. Specifically, cyclic carbonates such as ethylene carbonate and propylene carbonate, acyclic carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, glymes such as tetrahydrofuran, 2-methyltetrahydrofuran and dimethoxyethane, γ-butyllactone, etc. Lactones, sulfur compounds such as sulfolane, nitriles such as acetonitrile, and the like, or a mixture of two or more thereof. Of these, one or more mixed solutions selected from cyclic carbonates such as ethylene carbonate and propylene carbonate, and acyclic carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly suitable.
[0046]
When a polymer electrolyte is used, the electrolyte solution is held in a gel state by being held by the polymer. The concentration of the polymer with respect to the electrolytic solution is usually 0.1 to 30% by weight, although it depends on the molecular weight of the polymer used. If the concentration is too low, it is difficult to form a gel, and the retention of the electrolytic solution is lowered, which may cause problems of flow and liquid leakage. On the other hand, when the concentration is too high, the viscosity becomes too high, resulting in difficulty in the process, and the ratio of the electrolytic solution is lowered, the ionic conductivity is lowered, and the battery characteristics such as the rate characteristics tend to be lowered.
[0047]
As a method for forming a polymer electrolyte, the electrolyte can be obtained by immersing the electrolyte in a crosslinked polymer such as polyethylene oxide, polypropylene oxide or polyethylene oxide, or a polymer such as phenylene oxide or phenylene sulfide polymer. However, a method (1) of subjecting a polymerizable monomer-containing electrolytic solution to a polymerization treatment such as ultraviolet curing or thermosetting, or a method of cooling a solution in which a polymer that forms a gel electrolyte at room temperature is dissolved at a high temperature ( 2) is preferably used.
[0048]
In the former method (1) using a polymerizable monomer-containing electrolyte, examples of the polymerizable monomer include those having an unsaturated double bond such as acryloyl group, methacryloyl group, vinyl group, and allyl group. Specifically, acrylic acid, methyl acrylate, ethyl acrylate, ethoxyethyl acrylate, methoxyethyl acrylate, ethoxyethoxyethyl acrylate, polyethylene glycol monoacrylate, ethoxyethyl methacrylate, methoxyethyl methacrylate, ethoxyethoxyethyl methacrylate, polyethylene glycol mono Methacrylate, N, N diethylaminoethyl acrylate, N, N dimethylaminoethyl acrylate, glycidyl acrylate, allyl acrylate, acrylonitrile, N-vinyl pyrrolidone, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate , Diethylene glycol Dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polyalkylene glycol diacrylate, polyalkylene glycol dimethacrylate, etc. can be used, and trimethylolpropane alkoxylate triacrylate and pentaerythritol alkoxylate tri Trifunctional monomers such as acrylate, tetrafunctional or higher functional monomers such as pentaerythritol alkoxylate tetraacrylate and ditrimethylolpropane alkoxylate tetraacrylate can also be used.
[0049]
When these monomers are polymerized by heat, ultraviolet rays, electron beams, or the like, a polymerization initiator can be added to the electrolytic solution in order to effectively advance the reaction. As the polymerization initiator, benzoin, benzyl, acetophenone, benzophenone, Michler's ketone, biacetyl, benzoylperoxide, etc. can be used, and t-butylperoxyneodecanoate, α-cumylperoxyneodecanoate, t Peroxyneodecanoates such as hexylperoxyneodecanoate, 1-cyclohexyl luo 1-methylethylperoxyneodecanoate, t-amylperoxyneodecanoate, t-butylperoxyneohepta Peroxy such as noate, α-cumylperoxyneoheptanoate, t-hexylperoxyneoheptanoate, 1-cyclohexyl lu 1-methylethylperoxyneoheptanoate, t-amylperoxyheptanoate Also use neoheptanoates Can be used.
[0050]
On the other hand, in the case of the latter method (2), in which the polymer that forms a gel electrolyte at room temperature is dissolved in the electrolyte at a high temperature, the latter method (2) forms a gel on the electrolyte. Any material can be used as long as it is stable as a battery material. For example, a polymer having a ring such as polyvinyl pyridine and poly-N-vinyl pyrrolidone; polymethyl methacrylate, polyethyl methacrylate, polymethacryl Acrylic derivative polymers such as butyl acid, poly (methyl acrylate), poly (ethyl acrylate), poly (acrylic acid), poly (methacrylic acid polyacrylamide); fluorinated resins such as polyvinyl fluoride and polyvinylidene fluoride; polyacrylonitrile, polyvinylidene cyanide, etc. CN group-containing polymers; polyvinyl acetate, polyvinyl alcohol, etc. Polyvinyl alcohol polymers; polyvinyl chloride, and halogen-containing polymers such as polyvinylidene chloride. Moreover, it can be used even if it is a mixture, a modified body, a derivative | guide_body, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer etc., such as said polymer | macromolecule. The weight average molecular weight of these polymers is usually in the range of 10,000 to 5,000,000. When the molecular weight is low, it is difficult to form a gel. If the molecular weight is high, the viscosity becomes too high and handling becomes difficult.
[0051]
Furthermore, it is possible to use a completely solid electrolyte formed of a polymer and a supporting electrolyte without using a solvent.
The electrolyte is preferably impregnated in a separator made of a porous film such as porous polyethylene and used as an electrolyte layer. It can also be present in the positive electrode and / or the negative electrode. When the polymer electrolyte is present in the positive electrode and / or the negative electrode, the binder and the polymer for holding the electrolytic solution may be the same or different.
[0052]
As a preferred method for producing a battery using a polymer electrolyte, a fluid paint as a polymer electrolyte precursor is applied on the positive electrode and / or the negative electrode and impregnated in the voids of the electrode, and then the precursor is subjected to a non-fluidization treatment. And a method of applying the polymer electrolyte. In this case, it is further preferable that the polymer electrolyte of the positive electrode and / or the negative electrode and the polymer electrolyte layer of the electrolyte layer are formed integrally at the same time from the viewpoint of improving battery safety such as rate characteristics. In the above method, as the polymer electrolyte precursor, the polymerizable monomer-containing electrolyte can be used in the method (1) in which the polymerizable monomer-containing electrolyte is subjected to a polymerization treatment such as ultraviolet curing or heat curing. In the method (2), in which the polymer that forms the gel electrolyte at room temperature is dissolved in the electrolyte at high temperature, the solution (2) is used. A solution in which the polymer is dissolved in the electrolyte at high temperature can be used.
[0053]
The production method of the present invention is preferably applied to a lithium secondary battery having a non-fluidic electrolyte such as a polymer electrolyte or a completely solid electrolyte because the effect of the invention is remarkable.
The battery element is formed by laminating a positive electrode and a negative electrode via an electrolyte layer. In this case, it is preferable that these are laminated in a flat plate shape because the effect of the present invention is great. This is because, in the case of a flat plate type battery, if the flatness of battery elements is insufficient, rate characteristics and cycle characteristics, as well as capacity and safety, may be adversely affected.
[0054]
Moreover, it is preferable that a battery element is hold | maintained by the suppression pressure below atmospheric pressure with respect to the thickness direction at the point which the effect of this invention is remarkable. This is because, in the case of being held by such a weak suppression pressure, securing the flatness of the battery element becomes a big problem as described above. Such a battery can be manufactured by vacuum-sealing the battery element in a case made of a flexible film.
A plurality of battery elements are stacked as needed, and then stored in a normal case. For example, in the case of a battery using a non-flowable electrolyte, an m thin battery can be realized by vacuum-sealing it in a case made of a flexible film such as a light and thin laminate film. As the laminate film, a film made of a laminate material of a metal foil and a polymer film can be suitably used. Of course, for the convenience of mounting the battery on the device, etc., it is possible to enclose the battery in a case and then store a plurality of cases in a rigid outer case if necessary.
[0055]
【Example】
Example 1
An electrode paint used as a negative electrode having the following composition was prepared.
94 parts by weight of mesophase carbon
6 parts by weight of polyvinylidene fluoride
90 parts by weight of N-methylpyrrolidone
The electrode coating material (viscosity 1 Pa · S in a steady state at a shear rate of 500 (1 / s)) is inserted into a die manifold as shown in FIG. After applying multiple strips (4 strips) with a wet film thickness of 200 μm on a long copper foil having a width of 300 mm and a thickness of 10 μm, it was dried. The obtained negative electrode was wound around a core having an outer diameter of about 8.6 cm at a winding tension (tension per unit width of the coated film) of 0.33 kg / cm. The die used for coating has a slit width of 26 cm, a shim (integrated with the guide) thickness of 500 μm, a guide width of 1.5 cm (only the center guide is 2.5 cm), a coating width of each stripe of 5 cm, a guide A tip having a cutting width a300 μm and a guide cutting width b300 μm was used.
[0056]
Cut out a 1 meter portion of the obtained roll before the end of coating, cut the weight of the coating into 1 cm wide and 10 cm long (running direction) strips, weigh the weight with a precision balance, and apply the width direction coating in each slit. The weight distribution was measured. The results are shown in FIG. In addition, the measurement position in FIG. 14 shows the position of a perpendicular | vertical direction with respect to the application | coating direction when the right end (the right end when the application direction is made from the top to the bottom) of the copper foil having a width of 300 mm is 0 mm.
[0057]
Example 2
The multi-strip shim of Example 1 was applied under exactly the same conditions as in the example (ie, using a die as shown in FIG. 5) except that the shim could be applied continuously over the entire width. The opening width of the shim was 26 cm. The evaluation method was also performed in the same manner as in Example 1. The results are shown in FIG. In addition, the measurement position in FIG. 15 shows the position of a perpendicular | vertical direction with respect to an application direction when the right end (right end when the application direction is made from the top to the bottom) of a copper foil having a width of 300 mm is set to 0 mm.
[0058]
Comparative Example 1
The coating was performed under exactly the same conditions as in Example 1 except that the core inserted in the manifold of Example 1 was removed. The results are shown in FIG.
Comparative Example 2
The coating was performed under exactly the same conditions as in Example 2, except that the core inserted into the manifold of Example 2 was removed. The results are shown in FIG.
[0059]
【The invention's effect】
According to the present invention, there is no variation in coating thickness between the central portion and the outer edge portion of the coated surface in the application of a wide surface, and the outer edge portion and the one coated in the vicinity of the center of the die coater also in multi-strand coating. It is possible to provide an economical coating method that does not vary in thickness with those coated in the vicinity.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a die that can be used to coat a large surface.
2 is a cross-sectional view of the die in a vertical plane passing through XY in FIG.
FIG. 3 is an exploded perspective view of a die that can be used for multi-strand application.
4 is a cross-sectional view of a die in a vertical plane passing through XY in FIG. 3;
FIG. 5 is an exploded perspective view of a die having a core that can be used for coating on a wide surface.
6 is a cross-sectional view of the die in a vertical plane passing through XY in FIG. 5;
FIG. 7 is an exploded perspective view of a die that can be used for multi-strand application with a core installed.
8 is a cross-sectional view of the die in a vertical plane passing through XY in FIG. 7;
FIG. 9 is a perspective view seen from the lower surface (a) and side surface (b) of the core.
FIG. 10 is a perspective view seen from the lower surface (a) and the side surface (b) of the core from which a part of the internal structure is exposed.
FIG. 11 is a schematic perspective view showing the structure of a typical flat-plate laminated lithium polymer secondary battery.
FIG. 12 is a top view of a conductive electrode base material showing a state of multi-strip application
FIG. 13 is a perspective view of a core with a protrusion.
[Fig.14] Coating weight of 4-strip coating
[Figure 15] Coating weight on the entire surface
[Explanation of symbols]
1,8 Extrusion die
2,9 upper blade
3, 10 Lower blade
4, 11 Manifold
5,12 Coating liquid supply port
6, 15 slit
7, 16 Discharge port
13, 35 shims
14 Guide
17 core
18 Liquid outlet
19 Liquid inlet
20, 21 Side of the core
22 Bottom of core
23 Positive electrode
24 Separator
25 Negative electrode
26 Conductive negative electrode substrate
27, 28 tabs
29 Conductive cathode substrate
30 Flat laminated lithium polymer secondary battery
31 Conductive electrode substrate
32, 33 Application part
34 Uncoated part

Claims (9)

  In a method of applying a coating liquid onto a substrate using an extrusion die, the die has a manifold, and a core that evenly distributes the supply amount of the coating liquid to the entire slit portion of the die. An application method characterized by being provided in a manifold portion.   The application method is a multi-applying method, the die has a guide that divides the slit into a plurality of equal widths, and the supply amount of the coating liquid to each slit portion divided by the guide is equalized on the manifold portion The coating method according to claim 1, further comprising a core that is distributed to the surface.   The coating method according to claim 1, wherein the core distributes the supply amount of the coating liquid evenly by distributing the extrusion pressure of the coating liquid evenly. The coating method according to claim 1, wherein the core has a structure satisfying the following (1) to (5).
(1) One liquid inlet, two liquid outlets, and a liquid channel that connects the liquid inlet and the liquid outlet, and the arrangement and shape of the liquid inlet, the liquid channel, and the liquid outlet Has a structure (i) that is plane-symmetrical on a vertical plane that passes through the center of the liquid inlet and is horizontal to the liquid inlet direction,
(2) The liquid outlet of the first structure (i) is connected to the liquid inlet of the next structure (i),
(3) The repetition of the connection of the liquid outlet and the liquid inlet of this structure (i) is repeated until the required number of liquid outlets is reached,
(4) The required number of liquid outlets are arranged at equal intervals,
(5) The entire internal structure after the liquid introduction port of each structure (i) is plane-symmetrical on a vertical plane that passes through the center of the liquid introduction port of each structure (i) and is horizontal in the liquid introduction direction.   The coating method according to claim 1, wherein the slit is divided into 2n (n is an integer of 1 or more) by a guide.   The coating method according to any one of claims 1 to 5, wherein the coating liquid is an electrode paint containing an active material and / or a conductive material, a binder and a solvent.   In the method for producing an electrode, the method includes a step of applying a coating for an electrode containing an active material and / or a conductive material, a binder and a solvent on a conductive electrode substrate using an extrusion die. Has a guide that divides the slit into a plurality of equal widths, and a manifold, and the manifold portion is provided with a core that evenly distributes the amount of electrode paint supplied to each slit portion divided by the guide. A method for producing an electrode. The manufacturing method according to claim 7, wherein the core has a structure satisfying the following (1) to (5).
(1) One liquid inlet, two liquid outlets, and a liquid channel that connects the liquid inlet and the liquid outlet, and the arrangement and shape of the liquid inlet, the liquid channel, and the liquid outlet Has a structure (i) that is plane-symmetrical on a vertical plane that passes through the center of the liquid inlet and is horizontal to the liquid inlet direction,
(2) The liquid outlet of the first structure (i) is connected to the liquid inlet of the next structure (i),
(3) The repetition of the connection of the liquid outlet and the liquid inlet of this structure (i) is repeated until the required number of liquid outlets is reached,
(4) The required number of liquid outlets are arranged at equal intervals,
(5) The entire internal structure after the liquid introduction port of each structure (i) is plane-symmetrical on a vertical plane that passes through the center of the liquid introduction port of each structure (i) and is horizontal in the liquid introduction direction. A core used in the coating method according to any one of claims 1 to 6, wherein (1) one liquid inlet, two liquid outlets, and the liquid inlet and the liquid outlet And the arrangement and shape of the liquid introduction port, the liquid flow channel, and the liquid outlet port are symmetrical with respect to a vertical plane that passes through the center of the liquid introduction port and is horizontal to the liquid introduction direction (i (2) The liquid outlet of the first structure (i) is connected to the liquid inlet of the next structure (i), and (3) the liquid outlet and the liquid inlet of this structure (i) The repetition by the connection of the mouths is repeated until the required number of liquid outlets is reached, (4) the required number of liquid outlets are arranged at equal intervals, (5) and the liquid of each structure (i) The core characterized in that the entire internal structure after the inlet is symmetrical with respect to a vertical plane that passes through the center of the liquid inlet of each structure (i) and is horizontal in the liquid inlet direction.

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