Dispersion liquid measurement method and coating method using the same

Abstract

To provide a dispersion liquid measurement method capable of detecting a change in the concentration of dispersoid in a dispersion liquid due to precipitation or retention of the dispersoid.SOLUTION: A dispersion liquid measurement method includes processing of irradiating a dispersion liquid with X-rays through a metal substrate, and processing of detecting the intensity of fluorescent X-rays from the metal substrate and the dispersion liquid. The processing of irradiation with X-rays includes processing of irradiating a homogeneous portion of the metal substrate with X-rays while changing the irradiation timing or the irradiation place. The presence or absence of a change in concentration of the dispersion liquid is detected from the intensity ratio between the intensity of fluorescent X-rays from the metal substrate and the intensity of the corresponding fluorescent X-rays from the dispersion liquid, so that it is possible to accurately detect the presence or absence of a change in concentration of the dispersoid in the dispersion liquid.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a dispersion measurement method, and more particularly to a dispersion measurement method capable of detecting the presence or absence of settling or retention of dispersoids in a dispersion, and a coating method using said dispersion measurement method. [Background technology]

[0002] Electrodes for lithium batteries and the like are produced by applying an electrode slurry containing dispersoids such as active material particles to a metal substrate such as aluminum foil or copper foil, and then drying the slurry.

[0003] Patent Document 1 discloses that a foreign matter detector that detects an induced electromotive force due to a change in a magnetic field is provided in a path for feeding the electrode slurry, thereby detecting metallic foreign matter that has become mixed in the electrode slurry during feeding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-109029 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method described in Patent Document 1 does not detect the presence or absence of a change in the concentration of dispersoids in the electrode slurry, and therefore cannot produce a homogeneous electrode if settling or retention of dispersoids occurs during liquid transfer.

[0006] The present invention has been made in consideration of the problems associated with the conventional techniques, and an object of the present invention is to provide a dispersion measurement method capable of detecting the presence or absence of a change in the concentration of dispersoid in a dispersion due to settling or retention of the dispersoid. [Means for solving the problem]

[0007] As a result of extensive investigations to achieve the above object, the present inventors have found that the above object can be achieved by irradiating a dispersion with X-rays through a metal substrate such as a container or a pipe, using the fluorescent X-ray intensity from the metal substrate as an external standard, and calculating the intensity ratio between the external standard and the intensity of the fluorescent X-rays from the dispersion, thereby completing the present invention.

[0008] That is, the dispersion measurement method of the present invention includes a process of irradiating the dispersion with X-rays through a metal substrate, and detecting the intensity of fluorescent X-rays from the metal substrate and the dispersion liquid. The process of irradiating the X-rays includes a process of irradiating the homogeneous portion of the metal base material with X-rays while changing the irradiation timing or the irradiation portion, The present invention is characterized in that the presence or absence of a change in concentration of the dispersion liquid is detected from an intensity ratio between the fluorescent X-ray intensity from the metal base material and the corresponding fluorescent X-ray intensity from the dispersion liquid.

[0009] The coating method of the present invention is characterized in that it comprises a coating step of coating a dispersion onto a substrate surface, and the dispersion measurement method is carried out before and / or after the coating step. Effect of the Invention

[0010] According to the present invention, the fluorescent X-ray intensity from a metal substrate is used as an external standard, and the intensity ratio between the external standard and the fluorescent X-ray intensity from the dispersion is determined. This makes it possible to obtain results that are free of vibrations and deterioration over time of the measuring device, and to provide a dispersion measurement method that can accurately detect the presence or absence of a change in the concentration of dispersoid in the dispersion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <Dispersion measurement method> The dispersion liquid measuring method of the present invention will now be described in detail. The dispersion measurement method of the present invention irradiates the dispersion with X-rays multiple times through a metal substrate, determines the intensity ratio between the intensity of the fluorescent X-rays corresponding to the metal substrate and the intensity of the fluorescent X-rays corresponding to the dispersion for each X-ray irradiation, and detects whether or not there is a change in the dispersion state of the dispersion based on the presence or absence of a difference between these intensity ratios.

[0012] The X-rays are irradiated onto a homogeneous portion of the metal base material. When X-rays are irradiated to the same location on a metal substrate, the substrate will naturally be homogeneous. However, even when X-rays are irradiated to different locations, the shape and material are homogeneous, so the intensity of the fluorescent X-rays from the metal substrate can be used as the standard.

[0013] The intensity of the fluorescent X-rays emitted from this metal base material is used as an external standard, and the ratio of the intensity of the fluorescent X-rays from the metal base material to the intensity of the fluorescent X-rays emitted from the corresponding dispersion liquid is obtained. This allows obtaining results that eliminate the shaking or deterioration over time of the measuring device, making it possible to accurately detect the presence or absence of a change in the concentration of dispersoid in the dispersion liquid.

[0014] In other words, since the intensity of fluorescent X-rays from a homogeneous metal substrate should be constant, if the intensity of the detected fluorescent X-rays from a metal substrate deviates from the standard, it indicates that there is a deviation on the measurement device side, such as the intensity of the irradiated X-rays or the detection sensitivity of the generated fluorescent X-rays.

[0015] The intensity of the fluorescent X-rays from the metal substrate is used as a reference and the relative intensity ratio of the fluorescent X-rays from the detected dispersoid to the intensity of the fluorescent X-rays from the metal substrate is determined. This makes it possible to detect the presence or absence of a change in the concentration of the dispersoid in the dispersion while eliminating errors in the measurement device, thereby reducing the number of times the measurement device needs to be calibrated and enabling continuous coating of the dispersion.

[0016] The X-rays may be irradiated at different times at the same location on the metal base material, in other words, at intervals of a predetermined time or more, or different locations on the metal base material may be irradiated at different times.

[0017] Then, by comparing the intensity ratios and checking whether there is a difference, it is possible to detect the change over time in the dispersoid concentration in the dispersion liquid and the presence or absence of a concentration distribution.

[0018] Examples of the metal substrate include a container for storing the dispersion liquid, a pipe for transporting the dispersion liquid, and a metal foil coated with the dispersion liquid.

[0019] When the metal substrate is a container that contains a dispersion liquid, the presence or absence of settling of the dispersoid can be known by comparing the intensity ratio at the top of the container with the intensity ratio at the bottom of the container, or by comparing the intensity ratio before and after a predetermined time has elapsed, even at the same location of the container.

[0020] Furthermore, in the case of a pipe through which a dispersion liquid with a constant dispersoid concentration flows, the presence or absence of residual dispersoids can be determined from the difference in intensity ratio between the upstream and downstream sides of the pipe, the difference in intensity ratio before and after a bent pipe, and even from the difference in intensity ratio before and after a specified time has elapsed, even at the same part of the pipe.

[0021] Furthermore, in the case where the metal substrate is a current collecting foil coated with a dispersion liquid such as an electrode slurry, the presence or absence of unevenness in the application of the electrode slurry can be determined by irradiating different locations on the current collecting foil with X-rays and determining whether or not there is a difference in the intensity ratio from other locations.

[0022] When detecting the presence or absence of a change in concentration of the dispersion liquid flowing inside a pipe, it is preferable to provide a control pipe for measurement that branches off from a main pipe for transporting the dispersion liquid and returns to the main pipe, and to perform the measurement via this control pipe.

[0023] In order to irradiate X-rays, a controlled area must be set up to prevent X-rays from leaking outside. By installing a control pipe for measurement, the X-ray controlled area can be set regardless of the structure of the main piping, making it easy to set up the X-ray controlled area.

[0024] It is preferable that the control pipe has opposing pipe walls each having a parallel flat surface. By contacting the X-ray irradiation unit with this flat surface and irradiating X-rays from a perpendicular direction, all of the irradiated X-rays enter the control tube, preventing them from leaking elsewhere, making it possible to generate fluorescent X-rays with the correct intensity for the irradiated X-rays.

[0025] The size of the flat surface depends on the size of the X-ray irradiation part, but if it is about 5×5 mm in size, for example, X-rays can be incident without leakage.

[0026] The intensity of the X-rays irradiated to the flat portion is preferably an intensity that allows the X-rays to pass through the tube wall on the exit side, that is, an intensity that allows the X-rays to pass completely through the governing tube.

[0027] This makes it possible to reduce measurement errors because the distance traveled by X-rays through the dispersion liquid becomes constant.

[0028] The material constituting the above-mentioned metal substrate is any metal material different from the dispersoids in the dispersion liquid and has a periodic atomic arrangement, and is preferably formed of a metal selected from the group consisting of iron (Fe), aluminum (Al), chromium (Cr), nickel (Ni) and copper (Cu), or an alloy containing these metals.

[0029] The above metals and alloys are not only metallic materials generally used as materials for piping and current collecting foils, but also, when the above dispersion liquid is an electrode slurry, they are metallic materials different from those contained in general electrode slurries and are materials that easily generate fluorescent X-rays, and therefore are suitable as external standards.

[0030] The dispersion liquid may be, for example, an electrode slurry containing an active material, a conductive agent, a binder, and a solvent.

[0031] In particular, when the dispersion contains multiple types of particles made of different materials, such as an active material and a conductive agent, if the difference in specific gravity between the different materials is 4.5 or more, the ease of settling differs and concentration differences are likely to occur between the dispersoid particles, and therefore the dispersion measurement method of the present invention can be suitably used.

[0032] Examples of materials for particles such as active materials and conductive agents constituting the dispersoid include carbon (C), phosphorus (P), sulfur (S), and silicon (Si), as well as metals such as nickel (Ni), cobalt (Co), manganese (Mn), silver (Ag), tin (Sn), lithium (Li), zinc (Zn), lead (Pb), magnesium (Mg), aluminum (Al), calcium (Ca), bismuth (Bi), strontium (Sr), antimony (Sb), gallium (Ga), germanium (Ge), ruthenium (Ru), rhodium (Rh), palladium (Pd), iridium (Ir), platinum (Pt), gold (Au), thallium (Tl), and indium (In), or alloy particles containing these metals. These may be one type of particle or multiple types of particles made of different materials.

[0033] <Coating method> The coating method of the present invention has a coating step of coating a dispersion onto the surface of a substrate, and the above-mentioned dispersion measurement method is carried out before or after this coating step.

[0034] In the coating method of the present invention, by carrying out the above-mentioned dispersion measurement method before coating the dispersion, it is possible to detect the presence or absence of a change in the concentration of dispersoid in the dispersion due to settling or retention of the dispersoid, and therefore it is possible to prevent the occurrence of uneven coating of the dispersion.

[0035] Furthermore, by carrying out the above-mentioned dispersion measurement method after coating the dispersion, the presence or absence of unevenness in the coated dispersion can be detected. This makes it possible to coat a dispersion having a constant dispersoid concentration, and thus to produce an electrode that is always homogeneous.

[0036] Examples of the method for applying the dispersion include dip coating, spray coating, roll coating, doctor blade coating, gravure coating, die coating, and screen printing. EXAMPLES

[0037] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[0038] [Example] The following two types of electrode slurries with different dispersoid concentrations were prepared. Electrode slurry 1: Solids containing 70 wt% carbon particles, 23 wt% silver particles, and 7 wt% binder were dispersed in an organic solvent. Electrode slurry 2: Solids containing 47 wt% carbon, 47 wt% silver particles, and 7 wt% binder were dispersed in an organic solvent.

[0039] The electrode slurries 1 and 2 were each placed in a resin container, and a metal foil (stainless steel foil or aluminum foil) was placed on top of the electrode slurries. XRF measurement was performed through the container with the metal foil placed on top. The results are shown in Table 1.

[0040] [Table 1]

[0041] From the results in Table 1, it can be seen that the slurry concentration (% by mass of Ag) could be detected because the intensity ratio was measured to be larger for Slurry 2, which contains a larger amount of Ag.

[0042] In addition, after electrode slurry 1 and electrode slurry 2 were applied to a homogeneous iron foil, X-rays were irradiated from below the foil through the foil, and XRF measurements were performed at measurement points A and B. The results are shown in Table 2.

[0043] [Table 2] The results in Table 2 show that unevenness in the coating occurs because the intensity ratio differs between the beginning of coating (measurement location A) and the end of coating (measurement location B).

Claims

1. irradiating the dispersion with X-rays through a metal substrate; A process for detecting fluorescent X-ray intensity from the metal substrate and the dispersion liquid, The process of irradiating X-rays includes a process of irradiating X-rays to a homogeneous portion of the metal base material while changing the irradiation timing or the irradiation portion, A dispersion liquid measuring method, characterized in that the presence or absence of a change in concentration of the dispersion liquid is detected from the intensity ratio between the fluorescent X-ray intensity from the metal substrate and the corresponding fluorescent X-ray intensity from the dispersion liquid.

2. The dispersion measurement method according to claim 1, characterized in that the metal substrate is formed of a material containing at least one selected from the group consisting of iron (Fe), aluminum (Al), chromium (Cr) and nickel (Ni).

3. the metal substrate is a control pipe branched off from a main pipe for transporting the dispersion liquid, It is piping, The control pipe has opposing pipe walls each having a parallel flat surface portion, 2. The dispersion liquid measuring method according to claim 1, wherein X-rays are irradiated from a direction perpendicular to the flat surface.

4. 4. The dispersion liquid measuring method according to claim 3, wherein the intensity of the X-rays irradiated to said flat surface is an intensity that transmits through a tube wall on the exit side.

5. the dispersion is an electrode slurry containing an active material, a conductive agent, and a binder, the metal substrate is a current collector foil, 3. The dispersion liquid measuring method according to claim 1, wherein the electrode slurry coated on the current collecting foil is irradiated with the X-rays through the current collecting foil.

6. A coating process is provided for coating a dispersion onto a surface of a substrate, Before the above coating process, A coating method, comprising carrying out the dispersion measuring method according to any one of claims 1 to 4.

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