JP2013067747A - Active material ink for nozzle dispensing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active material ink for nozzle dispensing suitable for use upon manufacturing an electrode by a nozzle dispensing method, and capable of forming a linear active material part of a high aspect ratio.SOLUTION: The active material ink for nozzle dispensing contains an active material, a binder, a conductive material, and a dispersion medium, and has a shear viscosity of 48.9 Pa s or lower at a shear rate of 100 sand 4,060 Pa s or more at a shear rate of 0.01 s.

Description

  The present invention relates to an active material ink for nozzle dispensing used when an electrode of a lithium ion secondary battery is produced by a nozzle dispensing method.

  Lithium ion secondary batteries composed of a positive electrode, negative electrode, electrolyte (electrolyte), separator, etc. are lightweight, large-capacity, and capable of high-speed charge / discharge. However, various researches have been made to further increase the capacity and charge / discharge at high speed.

  As a method for manufacturing such a lithium ion secondary battery, conventionally, for example, an active material ink is applied on a current collector such as an aluminum foil or a copper foil, dried, and then pressed to a specified density. The method is often used, and thereafter, it is inserted into a predetermined container and injected with an electrolytic solution.

  On the other hand, since the electrolytic solution contains an organic solvent and there is a concern about an ignition case due to a short circuit or the like, an all-solid battery in which a separator is omitted using a solid electrolyte has been proposed. In this all-solid-state battery, the reaction between the positive electrode active material and the negative electrode active material contained in the positive electrode and the negative electrode, respectively, and the electrolyte is rate-determined. However, the lithium ion conductivity of the solid electrolyte is low, so It needs to be narrowed.

  Focusing on this point, for example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2011-70788) intends to provide an all-solid-state battery structure that realizes low cost, high safety, high energy density, and high output. Thus, a method for manufacturing an all-solid battery having an electrode having a three-dimensional structure including an active material layer having an uneven structure has been proposed. When a thin solid electrolyte layer is formed, a battery having a higher output is obtained because the resistance is small and the ion movement distance is short, and it is better to use a positive electrode and a negative electrode having a concavo-convex structure than a flat positive electrode and a negative electrode. The reaction area is improved and effective.

  In the above Patent Document 1, for the formation of an active material layer having a concavo-convex structure, specifically, a paste or slurry-like coating liquid (ink) containing an active material is ejected from a nozzle to form a collection of substrates. There has been proposed a method (nozzle dispensing method) for forming an active material layer having a concavo-convex pattern by coating on the surface of an electric body.

  Research on coating technology using such a nozzle dispensing method is advancing, and after adjusting the composition of the coating solution as appropriate, the nozzle is moved relative to the surface of the substrate in a predetermined direction so that the coating solution is linearly formed. Apply to the material surface. According to such a configuration, it is possible to form a pattern with a stable line width and height, and it is possible to stably manufacture a battery having good performance.

JP 2011-70788 A

  However, in order to obtain an electrode having an uneven structure by applying the active material ink to the current collector by the nozzle dispensing method as described above, it is conceivable to use an active material ink having a high shear viscosity. Increasing the shear viscosity of the material ink may make it difficult to eject from the nozzle.

On the other hand, when the shear viscosity is reduced, the shape of the active material ink immediately after being applied to the current collector flows or collapses, and it is difficult to obtain an electrode having an uneven structure. In order to obtain an electrode that realizes a battery with a large capacity per unit area (Ah / cm ² ), simply thinking, a linear active material portion that forms an active material layer by increasing the amount of active material ink applied. It is preferable to increase the aspect ratio of the ink, but this cannot be realized if the shear viscosity of the active material ink is reduced.

  Therefore, an object of the present invention is to provide an active material ink for nozzle dispensing that is suitable for use in producing an electrode by a nozzle dispensing method and can form a linear active material portion having a high aspect ratio. .

In order to solve the above problems, the present inventors have
Including active material, binder, conductive material and dispersion medium,
48.9Pa · s or less at a shear rate of 100s ^-1, have a shear viscosity of more than 4060Pa · s at a shear rate of 0.01s ^-1,
An active material ink for nozzle dispensing is provided.

  The active material ink for nozzle dispensing of the present invention having such a configuration has a low shear viscosity when the shearing force is large, and thus can be reliably discharged from the nozzle, and is high when the shearing force is small. Since it has a shear viscosity, it is hard to collapse when it is discharged from a nozzle and applied onto a current collector, and an electrode having a concavo-convex structure having a linear active material portion with a high aspect ratio can be reliably obtained. it can.

Further, the active material ink for nozzle dispensing of the present invention is preferably used in a nozzle dispensing method using a nozzle having an opening area d of 7500 to 32000 μm ² .

The active material ink for nozzle dispensing of the present invention can be discharged from the nozzle more reliably when using a nozzle having an opening area d of 7500 to 32000 μm ² , and more reliably a line with a high aspect ratio. An electrode having a concavo-convex structure having a solid active material portion can be formed.

  ADVANTAGE OF THE INVENTION According to this invention, it is suitable when using at the time of producing an electrode by the nozzle dispensing method, and can obtain the active material ink for nozzle dispensing which can form the linear active material part of a high aspect ratio.

In a nozzle dispensing method, it is a figure which shows a mode that active material ink is discharged from a nozzle, and it apply | coats on a collector, and forms a linear active material part. It is a graph which shows the relationship between the shear rate of the active material inks 1-8 prepared in the experiment example of this invention, and shear viscosity.

Nozzles dispense the active material for the ink of the present invention, active material, binder, it comprises a conductive material and a dispersion medium, at a shear rate of 0.01s ^-1 at 4060Pa · s or more, 48.9Pa · at a shear rate of 100s ^-1 It has the shear viscosity below s.

  First, FIG. 1 shows a state in which an active material layer composed of a linear active material portion is formed using the nozzle dispensing method of the active material ink for nozzle dispensing of the present invention. FIG. 1A is a side view schematically showing a state in which the linear active material portion 12a constituting the active material layer is formed on the current collector 10 by the nozzle dispensing method (that is, the current collector 10 FIG. 1B shows a state in which the linear active material portion 12a constituting the active material layer is formed by the nozzle dispensing method. It is a perspective view showing typically.

  As shown in FIG. 1, the linear active material portion 12 a collects, for example, (a) a nozzle 40 that discharges an active material ink (paste-like or slurry-like coating liquid) containing an active material in a linear manner at intervals S. An application process for forming a plurality of convex linear active material portions 12a on the current collector 10 (ie, an application process using a nozzle dispensing method), and (a ) It is formed by a drying process for drying the linear active material portion 12a.

More specifically, in the coating step (A), as shown in FIG. 1 (a), by conveying the collector 10 in the direction of arrow Y _1, the nozzle 40 to the collector 10 Move relative to it. On the surface of the current collector 10 being conveyed, the active material ink is ejected from the nozzle 40 at intervals S to form the linear active material portion 12a. When the position of the nozzle 40 is fixed and the current collector 10 is transported, the nozzle 40 is moved relative to the current collector 10. Of course, the nozzle 40 may be moved relative to the current collector 10 by scanning the nozzle 40 while fixing the position of the current collector 10.

In FIG. 1, a nozzle 40 provided with a plurality of discharge ports for discharging active material ink is disposed above the current collector 10, and a current collector is discharged while discharging a certain amount of active material ink from the discharge port. the body 10 in the direction of the relative arrow Y ₁ with respect to the nozzle 40 is conveyed at a constant speed. As a result, a plurality of linear convex active material active portions 12a made of active material ink are formed at intervals S on the current collector 10 along the Y direction, and a striped line and space pattern is formed. The active material ink is applied so as to have a shape.

  If a plurality of discharge ports are provided at intervals S in the nozzle 40, a plurality of linear active material portions 12a can be formed in a single relative movement in one direction to form a stripe shape. By continuing the conveyance, it is possible to form the linear active material portion 12a having a convex shape on the entire surface of the current collector 10 in a stripe shape. The nozzle 40 may be provided with only a single discharge port. In this case, the nozzle 40 and the current collector 10 are reciprocally moved relative to each other, and the length direction of the linear active material portion 12a. In a direction substantially perpendicular to the surface, the positions of the nozzle 40 and the current collector 10 are relatively shifted to form a linear active material portion 12a that is convex in a stripe shape on the entire surface of the current collector 10. be able to.

Here, when the active material ink is ejected from the nozzle 40, a large shearing force is applied to the active material ink (for example, 100 s ^{−1 to} 10000 s ⁻¹ depending on the apparatus), but at a shear rate of 100 s ^−1. The present inventors have found that the active material ink can be reliably discharged from the nozzle if it has a shear viscosity of 48.9 Pa · s or less.

In a state where the active material ink from the nozzle 40 is applied onto the collector 10 is discharged, when not applied almost shear force to the active material ink (e.g. 0~0.01s ^-1), 0.01s ^-1 The present inventors have found that if the shear viscosity is 4060 Pa · s or more at a shear rate of not less than the shape, the shape is not easily collapsed, and a linear active material part having a high aspect ratio can be obtained reliably.

Therefore, the nozzles dispense the active material for the ink of the present invention is characterized by the following 48.9Pa · s at a shear rate of 100s ^-1, have a shear viscosity of more than 4060Pa · s at a shear rate of 0.01s ^-1, and And

Moreover, it is preferable that the active material ink for nozzle dispensing of the present invention is used for a nozzle dispensing method using a nozzle having an opening having an opening area d of 7500 to 32000 μm ² . If it is this range, it can discharge more reliably from a nozzle and can form the electrode of the uneven structure which has a linear active material part of a high aspect ratio more reliably.

The active material contained in the active material ink is a negative electrode active material or a positive electrode active material.
As the negative electrode active material, those commonly used in the technical field of the present invention can be used. For example, metals, metal fibers, carbon materials, oxides, nitrides, silicon, silicon compounds, tin, tin compounds, various alloy materials Etc. Of these, oxides, carbon materials, silicon, silicon compounds, tin, tin compounds and the like are preferable in view of the capacity density. As the oxide, for example, the _{formula: Li 4/3 Ti 5/3-} x Fe x O 4 lithium titanate represented by (0 ≦ x ≦ 0.2) and the like. Examples of the carbon material include various natural graphite (graphite), coke, graphitizing carbon, carbon fiber, spherical carbon, various artificial graphite, amorphous carbon, and the like. Examples of the silicon compound include a silicon-containing alloy, a silicon-containing inorganic compound, a silicon-containing organic compound, a solid solution, and the like. Specific examples of the silicon compound include, for example, silicon oxide represented by SiO _a (0.05 <a <1.95), silicon and Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, An alloy containing at least one element selected from In, Sn, and Ti, silicon, silicon oxide, or a part of silicon contained in the alloy is B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Examples thereof include silicon compounds or silicon-containing alloys substituted with at least one element selected from Fe, Mn, Nb, Ta, V, W, Zn, C, N, and Sn, and solid solutions thereof. Examples of the tin compound include SnO _b (0 <b <2), SnO ₂ , SnSiO ₃ , Ni ₂ Sn ₄ , Mg ₂ Sn, and the like. A negative electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type as needed.

Examples of the positive electrode active material include lithium-containing composite metal oxides, chalcogen compounds, and manganese dioxide. The lithium-containing composite metal oxide is a metal oxide containing lithium and a transition metal or a metal oxide in which a part of the transition metal in the metal oxide is substituted with a different element. Here, examples of the different elements include Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B, and Mn, Al, Co, Ni, Mg and the like are preferable. One kind or two or more kinds of different elements may be used. Among these, lithium-containing composite metal oxides can be preferably used. The lithium-containing composite metal oxide, for _{example, Li x CoO 2, Li x} NiO 2, Li x MnO 2, Li x Co y Ni 1-y O 2, Li x Co y M 1-y O z, Li x _{Ni 1-y M y O z} , Li x Mn 2 O 4, Li x Mn 2-y M y O 4, LiMPO 4, Li 2 MPO 4 F ( in the respective formulas, for example, M is Na, Mg, Sc , Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, V and B. At least one selected from the group consisting of 0 <x ≦ 1.2 and 0 <y ≦ 0. 9, 2.0 ≦ z ≦ 2.3), LiMeO ₂ (wherein Me = MxMyMz; Me and M are transition metals, x + y + z = 1), and the like. Specific examples of the lithium-containing composite metal oxide include LiNi _1/3 Mn _1/3 Co _1/3 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ . Here, x value which shows the molar ratio of lithium in each said formula increases / decreases by charging / discharging. Examples of the chalcogen compound include titanium disulfide and molybdenum disulfide. A positive electrode active material can be used individually by 1 type, and may use 2 or more types together.

  The active material ink includes a conductive material. As the conductive material, those commonly used in the technical field of the present invention can be used. For example, graphites such as natural graphite and artificial graphite, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, etc. Carbon blacks, conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide, conductive metal oxides such as titanium oxide, phenylene derivatives, etc. And organic conductive materials. A conductive agent can be used individually by 1 type, or can be used in combination of 2 or more type as needed.

  As the binder (binder) contained in the active material ink, those commonly used in the technical field of the present invention can be used. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene, polypropylene, Aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polyacrylic acid methyl ester, polyacrylic acid ethyl ester, polyacrylic acid hexyl ester, polymethacrylic acid, polymethacrylic acid methyl ester, polyethyl methacrylate Esters, poly (hexyl methacrylate), polyvinyl acetate, polyvinyl pyrrolidone, polyether, polyether sulfone, polyhexafluoropropylene, styrene-butadiene rubber, ethylene-propylene diene Coalescence, and carboxymethyl cellulose. Copolymers of monomer compounds selected from tetrafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, hexadiene, etc. May be used as a binder. A binder can be used individually by 1 type, or can be used in combination of 2 or more type as needed.

As the dispersion medium, it is preferable to use an organic solvent excluding water so as not to decompose lithium hexafluorophosphate (LiPF ₆ ) or the like that can be contained in many electrolyte solutions. As the organic solvent, those commonly used in the technical field of the present invention can be used, and examples thereof include dimethylformamide, dimethylacetamide, methylformamide, N-methyl-2-pyrrolidone (NMP), dimethylamine, acetone, and cyclohexanone. Can be mentioned. An organic solvent can be used individually by 1 type, or can mix and use 2 or more types.

  The current collector 10 is made of a material known in the technical field to which the present invention belongs, and may be a metal film such as an aluminum foil. The current collector 10 may be formed on the surface of an insulating base material. As such a base material, a flat plate member formed of an insulating material may be used. Examples of such an insulating material include resin, glass, ceramics, and the like. The base material may be a flexible flexible substrate.

  Here, the active material ink for nozzle dispensing of the present invention has various solid contents as long as the active material ink can be reliably discharged from the nozzle 40 and can maintain its shape on the current collector 10 after discharge. Can have a proportion. However, it is preferably 85% by mass.

  The shear viscosity of the active material ink for nozzle dispensing of the present invention varies depending on the type, blending amount and solid content ratio of the active material, binder, conductive material and dispersion medium (and other optional components). Thus, the strength and time during stirring and mixing (kneading) can be adjusted.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

  The active material shown in Table 1 below, acetylene black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed at a mass ratio of 8: 1: 1. Ink 1 to 8 were prepared by mixing the resulting mixture with N-methyl-2-pyrrolidone, which is a dispersion medium, so that the active material concentration becomes the concentration shown in Table 2.

  For lithium titanate, the specific surface area is the BET method, the tap density is tapping 200 times, the median diameter is the laser diffraction scattering method (LA-910, manufactured by Horiba, Ltd.), and the median diameter of lithium cobaltate is Microtrac (× 100) was used.

[Evaluation]
Using the nozzle A having a width of 70 μm and a height of 110 μm (opening area d = 7700 μm ² ) or the nozzle B having a width of 50 μm and a height of 150 μm (opening area d = 7500 μm ² ), the obtained active material inks 1 to 1 Whether or not 8 can be discharged was examined. The results are shown in Table 2. Moreover, when the shape state of the active material ink after discharge was observed visually, the shape was not collapsed in any of the inks 1 to 8.

For the active material inks 1 to 8, the shear viscosity when the shear rate was 100 s ⁻¹ or 0.01 s ⁻¹ was measured using a rheometer “Physica MCR301” manufactured by Anton Paar. The results are shown in Table 2 and shown in the graph of FIG. Note that the graph, shear rate ^{0.10 S} -1, also showed shear viscosity in the case of 1.00 s ^-1 and 10.0 s ^-1.

From the results shown in Table 2, there at a shear rate of 100s ^-1 had shear viscosity of less than 48.9Pa · s, the active material ink having a 4060Pa · s or more shear viscosity at a shear rate of 0.01s ^-1 In other words, it can be surely discharged from the nozzle, the shape is not easily broken after discharge, and a high-aspect-ratio linear active material portion can be reliably obtained.

10 ... current collector,
12a ... linear active material part,
40: Nozzle.

Claims (2)

Including active material, binder, conductive material and dispersion medium,
48.9Pa · s or less at a shear rate of 100s ^-1, have a shear viscosity of more than 4060Pa · s at a shear rate of 0.01s ^-1,
An active material ink for nozzle dispensing. An opening area d of a nozzle for discharging the nozzle dispensing active material ink is 7500 to 32000 μm ² ;
The active material ink for nozzle dispensing according to claim 1.

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