JP5708557B2 - Inspection method for electrode substrate - Google Patents

Description

  The present invention relates to a technique of an inspection method for an electrode substrate.

Some secondary batteries are equipped with a pressure-type current interruption mechanism as a safety mechanism that operates in the event of overcharge. In such secondary batteries, gas is generated in the positive electrode or electrolyte when overcharged. It is common to add an overcharge additive for the purpose.
In such a secondary battery, it is necessary to reliably generate a predetermined amount of gas capable of operating the current interruption mechanism during overcharge.
Moreover, the base material for electrodes which is a member which comprises the electrode in a secondary battery has the structure which consists of metal foil and a composite material layer (layer which consists of the coated active material).

  The inventors of the present application, in an electrode base material for constituting an electrode (particularly a positive electrode), even if the basis weight and density of the active material in the composite material layer are the same, if the production conditions (press conditions, etc.) are different. I have noticed that there may be differences in the performance of secondary batteries.

Specifically, the inventors of the present application generate air resistance (also referred to as air permeability) in the composite layer of the electrode base material used for the positive electrode of the secondary battery and the overcharge additive in the positive electrode. There is a correlation with the amount of gas, and a technique that can secure the amount of gas generation has been developed by managing the air resistance.
And about this technique, a patent application (Japanese Patent Application No. 2012-59417) has been made by the inventors of the present application, and the technique is disclosed in the specification of the patent application and the like (not disclosed at the time of filing this application).

And it has been found by the research of the inventors of the present application that such a difference in performance of the secondary battery is caused by a structural difference in the composite material layer in the electrode substrate.
Here, the “structural difference” is a concept including a difference in the physical bonding state between the binder and the active material contained in the mixture layer, a difference in the uneven distribution of the binder in the mixture layer, and the like.

More specifically, the inventors of the present application have noticed that the air permeability resistance in the state of only the composite material layer has a property as an alternative parameter representing a fine structural difference of the composite material layer, and the composite material A method of determining the quality of gas generation (and hence the quality of the electrode substrate) based on the air permeability resistance in the state of only the layer (that is, the state where the metal foil is removed) has been proposed.
In this technology, if the physical bonding state between the binder and the active material contained in the composite layer and the uneven distribution of the binder in the composite layer are different, the resistance when air is allowed to pass through the composite layer differs. Thus, the structural resistance of the composite layer is detected by measuring the air resistance.

And the structural difference (that is, the difference in air permeability resistance) of the composite material layer may affect not only the amount of gas generation but also the performance of the secondary battery manufactured using the electrode substrate. I understand.
For this reason, in the manufacturing process of the base material for electrodes, it is expected that the quality of the secondary battery can be managed more accurately by managing the air resistance in the state of only the composite layer.
As used herein, “secondary battery performance” includes the ability to generate gas that can be generated from the electrode substrate by a chemical reaction with the overcharge additive, and the charge / discharge characteristics of the secondary battery. Can be mentioned.

  Here, the experimental result which confirmed that a difference arises in the performance of a secondary battery by the structural difference of a compound material layer is illustrated.

In FIG. 10, the density of the composite material layer is the same, and each electrode base material manufactured so that a structural difference (that is, a difference in air resistance) occurs in the composite material layer is used. The result of having measured the voltage drop at the time of discharge about the secondary battery is shown.
The three types of electrode base materials prepared here have the same density of the composite layer (here, 2.9 g / cm ³ ), but the press conditions are different.
Further, the experimental conditions here will be described in detail. Each of the press conditions in the three types of electrode base materials is set to 1 times, 10 times, and 20 times, respectively. The air resistance in is different.

When the electrode substrate is molded to a desired density with a larger number of presses (ie, with a smaller gap), the desired density with a smaller number of presses (ie, with a larger gap). The inventors of the present application have found that it has the property that the air permeability resistance is increased (that is, the air permeability is good) as compared with the case of forming the glass.
That is, the electrode base material causes structural differences in the composite material layer depending on the manufacturing method (for example, due to the difference in the pressing method), and causes for structural differences in other composite material layers. For example, the difference in the manufacturing method of a paste, the difference in the drying method of a compound material layer, etc. are mentioned.

And in the electrode base material (sample X) used once in this experiment, the air resistance was 391 (sec / 100 mL), and the electrode base material (sample Y) subjected to press 10 times was The air resistance is 292 (sec / 100 mL), and the electrode base material (sample Z) with 20 presses has an air resistance of 237 (sec / 100 mL).
Further, in this experiment, two secondary batteries each including three types (each sample X to Z) of electrode base materials were prepared (total of six), and the discharge results were recorded.

  In FIG. 10, from 6 (V) to 2.0 (V) for six secondary batteries manufactured using three types of electrode base materials (positive electrodes) having different air resistances. The time required for the voltage drop when discharged is compared and displayed.

And even if the density of a compound material layer is the same according to FIG. 10, if there exists a structural difference (namely, difference in air permeability resistance), it turns out that the difference has arisen in the discharge characteristic.
Furthermore, according to FIG. 10, if the density of the composite material layer is the same, the secondary battery using the electrode base material (here, sample Z) having the composite material layer having a smaller air resistance is better. As compared with a secondary battery using a base material for an electrode (here, sample X) having a mixture layer having a higher air resistance, a voltage drop during discharge is less likely to occur (that is, output characteristics are better). )

  In addition, conventionally, there has been known an electrode substrate inspection method in which the air resistance of an electrode substrate is measured, and the quality of the electrode substrate is determined based on the measured air resistance. For example, it is disclosed in Patent Document 1 shown below and is publicly known.

  The conventional technique disclosed in Patent Document 1 is directed to an electrode substrate produced by applying an active material to a porous metal foil, and the entire electrode substrate (that is, the metal foil and the active material). The pre-doping time suitable for the electrode substrate is determined by measuring the air permeation resistance in the material layer (the whole combined with the material layer).

JP 2009-199963 A

In the conventional technique for measuring the air resistance of only the composite material layer proposed by the present inventors, it was necessary to cut out a part of the composite material layer in order to measure the air resistance.
For this reason, in the method of cutting out a part of the electrode substrate and measuring the air resistance, the quality cannot be judged unless the electrode substrate is manufactured. It was difficult to determine the quality of the electrode substrate by measuring the air resistance of the electrode substrate during the manufacturing process.
Furthermore, in the conventional method, even if the defect is found after manufacturing the electrode substrate (especially after press working), it is difficult to identify which process caused the defect. Therefore, it is difficult to feed back the cause of the defect to the manufacturing process.

  Moreover, in the prior art currently disclosed by patent document 1, electrode foil is comprised with the porous raw material, and the air permeability resistance as the whole base material for electrodes is evaluated including the air resistance of electrode foil. Thus, the quality of the electrode base material is managed by using the air resistance of only the composite layer in the conventional technology. It wasn't.

  That is, in the past, since it was difficult to measure the air resistance in-line in the manufacturing process, a method for inspecting the quality of the electrode substrate based on the air resistance in the state of only the composite layer. It was difficult to apply to an actual manufacturing process.

  The present invention has been made in view of such a current problem, and it is possible to produce a pass / fail judgment for an electrode base material based on the air permeability resistance of only the composite material layer without the need to cut out the electrode base material. It aims at providing the inspection method of the substrate for electrodes which can be performed in-line in a process.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

That is, in Claim 1, it is the method for inspecting the quality of the base material for electrodes comprised by forming the compound material layer on the surface of metal foil, Comprising: The press process in the manufacturing process of the said base material for electrodes From the colorimetry degree of the mixture layer in the electrode base material measured before and after the drying step in the electrode base material manufacturing process, and the pressing step in the electrode base material manufacturing process first obtained in advance map information, mixture layer were measured in the course of the manufacturing process of the electrode base material representing the air resistance of the mixture layer, the relation of the electrode base material was measured after From the first map information, the air resistance of the composite layer in the electrode base material is derived based on the colorimetry degree.

  In the present invention, only the L value is used as the colorimetry.

  According to a third aspect of the present invention, the colorimetry uses the L value when the light receiving angle is 75 degrees.

In Claim 4, after the press process in the manufacturing process of the said base material for electrodes, the air resistance of the compound material layer in the said base material for electrodes measured after the press process in the manufacturing process of the said base material for electrodes Second map information representing a relationship with the measured horizontal electronic resistance of the mixture layer in the electrode base material is obtained in advance, and based on the measurement result of the colorimetry, the first and second map information Therefore, the quality of the electrode base material is judged.

  As effects of the present invention, the following effects can be obtained.

  According to the first aspect of the present invention, it is possible to easily derive the air resistance in the state of only the composite layer in the middle of the manufacturing process without requiring the cutting of the electrode substrate.

In Claim 2 and Claim 3 , the fine structural difference of a compound material layer is reliably detectable by measuring the colorimetry degree of a compound material layer.

  In Claim 4, based on the detection result of the fine structural difference in a compound material layer, the quality control of the base material for electrodes can be performed exactly.

The schematic diagram which shows the flow of the inspection method of the conventional base material for electrodes. The perspective schematic diagram which shows the measuring method of the air permeability resistance with respect to a free film. The perspective schematic diagram which shows the measuring method of the horizontal electronic resistance with respect to the compound material layer of the base material for electrodes. The schematic diagram which shows the flow of the inspection method (preparation stage) of the base material for electrodes which concerns on one Embodiment of this invention. The schematic diagram which shows the flow of the inspection method (main operation | movement stage) of the base material for electrodes which concerns on one Embodiment of this invention. The schematic diagram which shows the measuring method of the colorimetry degree with respect to the compound material layer of the base material for electrodes. The figure for demonstrating the principle which detects the structural difference of a composite material layer by a colorimetry degree, (a) The schematic diagram which shows the structure of the composite material layer in case the uneven distribution of a binder has not arisen, (b) The uneven distribution of a binder The schematic diagram which shows the structure of the compound-material layer in case the case has arisen. The figure for demonstrating the principle which detects the structural difference of a compound material layer by colorimetry, (a) The schematic diagram which shows the reflective condition of the light in the surface of an active material, (b) The reflective condition of the light in the surface of a binder FIG. The figure showing the correlation of the colorimetry degree (namely, L75) and air permeation resistance degree in the compound material layer of the base material for electrodes. The figure showing the difference of the self-discharge amount in a secondary battery by the structural difference of the base material for electrodes.

Next, embodiments of the invention will be described.
First, a conventional method for inspecting an electrode substrate will be described with reference to FIG.
As shown in FIG. 1, the electrode base material is a paste manufacturing process (STEP-101), a coating process (STEP-102), a drying process (STEP-103), a pressing process (STEP-104), and the like. Are generally manufactured in the order shown in FIG. 1, and are formed by forming a composite layer on the surface of the metal foil.

The paste manufacturing process (STEP-101) is a process of manufacturing a paste containing an active material and a binder for forming a composite material layer, and the coating process (STEP-102) is a process for applying the manufactured paste to a metal foil. On the other hand, it is a step of applying a uniform thickness to form a composite layer on the surface of the metal foil.
The drying step (STEP-103) is a step of drying the applied paste (that is, the mixture layer) (volatilizing the solvent component contained in the paste), and the pressing step (STEP-104) is a drying step. This is a step of increasing the density of the composite material layer to a predetermined density by pressing the finished composite material layer and compressing it to a predetermined thickness.

  In the conventional method for inspecting an electrode substrate, after the pressing step (STEP-104) (that is, after the electrode substrate is completed), a sample is cut out from the manufactured electrode substrate (STEP- 120), the air permeability resistance measurement (STEP-130) and the horizontal electronic resistance measurement (STEP-140) are performed using the sample.

Here, a method for measuring the air resistance of the composite material layer will be described with reference to FIGS. 2 and 3.
In order to measure the air resistance of the composite layer 3 in the electrode substrate 1 as shown in FIG. 3, first, the metal foil 2 is removed from the electrode substrate 1 (that is, the composite layer 3). 2), a member 3a (hereinafter referred to as a free film 3a) as shown in FIG. 2 is generated.
The free film 3a thus obtained is a porous material having air permeability.

The measurement of the air resistance of the free film 3a is performed using a predetermined measuring device (so-called densometer) in accordance with the standard (Gurley method) of JISP8117.
More specifically, as shown in FIG. 2, the lower end of the cylindrical portion 10 having an inner diameter of 28.6 mm arranged with its axis oriented in the vertical direction is closed with a free film 3a, and in this state, the inner diameter of the cylindrical portion 10 is set. The weight 11 having a weight of 567 g that comes into contact with no gap is freely dropped from the upper end side. And in the range of the circle of diameter 28.6mm in the free film 3a, the air (compressed) with the weight 11 is passed, and the time (sec) required for 100 mL of air to pass is measured.
And the time measured in this way is prescribed | regulated as air permeability resistance (sec / 100mL).

Here, a method for measuring the horizontal electronic resistance of the composite layer will be described with reference to FIG.
The measurement of the horizontal electronic resistance with respect to the composite material layer 3 in the base material 1 for electrodes as shown in FIG. 3 applies adhesive force to the composite material layer 3 constituting the base material 1 for electrodes, and gives cohesive force. The metal foil 2 is removed with a width of 10 mm, and a test sample 4 having an embodiment as shown in FIG. 3 is first prepared.

In the test sample 4 thus obtained, the resistance value of the composite layer 3 is measured by the tester 12 using the metal foils 2A and 2B remaining on both sides of the portion where the metal foil 2 is removed as terminals.
The resistance value measured in this way is defined as the horizontal electronic resistance (Ω · cm).

As shown in FIG. 1, in the conventional inspection method for the electrode substrate (for example, the electrode substrate 1 as shown in FIG. 3), the air resistance measured as shown in FIGS. On the basis of the measurement result of the horizontal electronic resistance, the quality of the electrode base material is judged to be good (STEP-150).
Conventionally, in the step of determining the quality of the electrode substrate (STEP-150), the determination is made based on two indicators of the air resistance and the horizontal electronic resistance. It is possible to more accurately determine the quality of the product.

Next, an inspection method for an electrode substrate according to an embodiment of the present invention will be described with reference to FIGS.
In addition, the electrode base material which is the inspection object in the inspection method of the electrode base material according to one embodiment of the present invention is an electrode base material (for example, shown in FIG. 3) which is the inspection object in the conventional inspection method. It is the same as the electrode substrate 1), and is formed by forming a mixture layer on the surface of the metal foil.
Moreover, the electrode base material to which the inspection method of the electrode base material according to one embodiment of the present invention is applied is the same as the conventional one, paste manufacturing process (STEP-101), coating process (STEP-102), It manufactures through each process, such as a drying process (STEP-103) and a press process (STEP-104) in order.

  4 and 5, the electrode substrate inspection method according to one embodiment of the present invention differs from the conventional electrode substrate inspection method (see FIG. 1) in that the electrode substrate is used in earnest. The contents of the inspection to be carried out are different between the stage before the production and the stage of full-scale production of the electrode substrate.

  Specifically, in the stage before full-scale production of the electrode substrate (hereinafter referred to as the preparation stage), the air resistance is measured while measuring the colorimetry on the surface of the electrode substrate. To store the data of the colorimetry and the air resistance, and generate map information (hereinafter referred to as map information A) indicating the correlation between the colorimetry and the air resistance. .

  Further, in the preparation stage, the horizontal electronic resistance of the composite material layer constituting the electrode substrate is further measured to accumulate the air resistance and horizontal electronic resistance data, and the air resistance and horizontal Map information (hereinafter referred to as map information B) representing the correlation of electronic resistance is generated.

  In the full-scale production stage of the electrode base material (hereinafter referred to as the actual operation stage), only the colorimetry on the surface of the electrode base material is measured (that is, the air resistance and the horizontal electronic resistance are measured). In other words, the quality of the electrode base material is determined based on the measured colorimetry and the map information A and B obtained in advance.

Here, the flow of inspection at the preparation stage in the inspection method of the electrode substrate according to the embodiment of the present invention will be described in more detail.
As shown in FIG. 4, in the electrode base material inspection method according to an embodiment of the present invention, in the preparation stage, the colorimetry of the electrode base material is performed before the pressing step (STEP-104). Is measured (hereinafter referred to as a colorimetric measurement step (STEP-110)).

  Further, the colorimetry measurement step (STEP-110) is performed after the drying step (STEP-103).

  And about the colorimetry measured before the press process (STEP-104) and the base material for electrodes, the permeability in the air permeability resistance measurement process (STEP-130) performed after the press process (STEP-104). The map information A is created in association with the measurement result of the air resistance.

Further, in the preparation stage, map information B is further created based on the measurement result of the air resistance in the air resistance measurement process (STEP-130) and the measurement result of the horizontal electronic resistance in the horizontal electron resistance measurement process. Like to do.
The map information B represents the correlation between the air resistance and the horizontal electronic resistance that is a non-defective standard in the air resistance, and the electrode substrate can be determined to be non-defective at a certain air resistance. The value of the horizontal electronic resistance is accumulated in advance.

  In the preparation stage, the base material for electrodes is based on the air resistance measured in the air resistance measurement step (STEP-130) and the horizontal electronic resistance measured in the horizontal electron resistance measurement step (STEP-140). The quality of the product is determined (STEP-150).

  Note that the value of the horizontal electronic resistance is substantially constant if the manufacturing conditions (that is, the manufacturing conditions of the paste, the coating conditions, the drying conditions, the pressing conditions, etc.) are the same. The measurement result of the electronic resistance is recorded.

Here, the measurement method of the colorimetry in the colorimetry measurement step (STEP-110) will be described.
In the present embodiment, the colorimetry is measured using a spectrocolorimeter 5 as shown in FIG.

The spectrocolorimeter 5 is a device for measuring the degree of colorimetry on the surface of an object, and includes a light projecting unit 5a, a light receiving unit 5b, a calculation unit 5c, and the like.
In the spectrocolorimeter 5, the light emitted from the light projecting unit 5a toward the composite layer 3 of the electrode substrate 1 is reflected at the predetermined reflection angle θ on the composite layer 3 and reaches the light receiving unit 5b. The colorimetry degree of the composite layer 3 defined by three values of the L value, the a value, and the b value is calculated based on the light received by the light receiving unit 5b. Can be obtained.
Note that “L value, a * value, b * value”, which is actually a value in a color space defined as CIELAB, is used as “L value, a value, b value”. I have to.
However, in this description, they are simply described as “L value, a value, b value”.

The L value is a value on the lightness axis (L axis) of the received light, and takes a value between 0 and 100. The closer to 0, the closer to black, and the closer to 100, the closer to white. Represents.
The a value is a value on an axis (a axis) representing the degree of redness of received light, and takes a value of −60 to +60. The color closer to −60 is closer to green, and the color closer to +60 is closer to red. It represents that.
The b value is a value on an axis (b axis) representing the degree of yellowness of received light, and takes a value of −60 to +60. The closer to −60, the closer to blue, and the closer to +60, the closer to yellow. It represents that.
Further, the “colorimetry” here is an index defined by “L value, a value, b value”, and is different from “glossiness”.

  And in the inspection method of the base material for electrodes which concerns on one Embodiment of this invention, as a structure which evaluates the structural difference of the base material for electrodes using only L value among the measurement results by the spectrocolorimeter 5. Yes.

  Furthermore, in the inspection method for an electrode substrate according to an embodiment of the present invention, the L value (hereinafter referred to as L75) of the L values when the light receiving angle is 75 degrees is used. It is configured to evaluate structural differences in materials.

Here, the principle of detecting the structural difference of the electrode base material based on the colorimetry in the composite layer of the electrode base material will be described.
As shown in FIGS. 7A and 7B, the composite material layer 3 contains an active material 8, a binder 9, and the like.
When viewed as a single particle, the active material 8 has a number of angular portions in its outer shape.
On the other hand, the binder 9 is made of a resin or the like, and when viewed as one particle, the outer shape thereof is a shape that is relatively close to a sphere (there is almost no angular portion on the surface).

  Further, paying attention to the structure of the composition layer 3, the composition layer 3 has, for example, a structure in which a large amount of the binder 9 exists near the surface in the thickness direction of the composition layer 3 as shown in FIG. As shown in FIG. 7B, the binder 9 may be present evenly. Such a structural difference of the composite material layer 3 is caused by a difference in manufacturing method. I know that

The case where many binders 9 are distributed in the vicinity of the surface of the composite material layer 3 corresponds to the case where the binder 9 is unevenly distributed in the composite material layer 3.
The phenomenon that the binder 9 is unevenly distributed in the composite material layer 3 is likely to occur, for example, when the drying speed of the paste is increased. In this case, a barrier layer is formed at the location where the binder 9 is accumulated, and the composite material It has been found that the air permeability of the layer 3 as a whole deteriorates (that is, the air resistance increases).

On the other hand, in order to distribute the binder 9 evenly in the mixture layer 3 (the binder 9 is not unevenly distributed), for example, the drying speed of the paste may be increased (that is, dried slowly). In addition, it has been found that a space is secured between the active material 8 and the air permeability is improved (that is, the air resistance is lowered).
That is, it is considered that there is a correlation between the air resistance in the state of only the composite layer 3 and the structure of the structure of the composite layer 3.

Here, the difference in the appearance of the active material 8 and the binder 9 will be described.
As shown in FIGS. 8 (a) and 8 (b), when light is irradiated toward the active material 8 and the binder 9, the surface of the binder 9 where there are no angular portions on the surface is as shown in FIG. 8 (b). However, irregular reflection (diffuse reflection) hardly occurs, but irregular reflection is likely to occur on the surface of the active material 8 having an angular surface as shown in FIG.

When irregular reflection occurs on the surface of the object (here, the active material 8), the object looks white, and when the colorimetry of the object is measured, the L value becomes large (that is, a value close to 100). ).
On the other hand, an object that hardly causes irregular reflection (here, the binder 9) looks black, so when the colorimetry is measured, the L value becomes small (that is, takes a value close to 0).

Therefore, when the active material 8 is distributed in the vicinity of the surface of the composite material layer 3 (that is, when the binder 9 is not unevenly distributed and the air resistance is small), the surface of the composite material layer 3 looks whitish, Further, when the binder 9 is distributed in the vicinity of the surface of the composite layer 3 (that is, when the binder 9 is unevenly distributed and the air permeability resistance is large), the surface of the composite layer 3 looks dark.
That is, it is considered that there is a correlation between the L value of the colorimetry degree of the composite material layer 3 and the structure of the composition of the composite material layer 3.

From these correlations, it is assumed that there is also a correlation between the L value of the colorimetry degree of the composite material layer 3 and the air resistance in the state of the composite material layer 3 alone.
Therefore, as a result of experiments by the inventors of the present application, as shown in FIG. 9, it was confirmed that there is a correlation between the L value (here, L75) of the colorimetry degree and the air resistance.

In the electrode substrate 1 used in the present embodiment, the structural difference of the composite material layer 3 could be detected most significantly by the L value (that is, L75) when the light receiving angle was 75 degrees. However, the electrode substrate inspection method according to the present invention is not limited to the case where the light receiving angle of the spectrocolorimeter to be used is 75 degrees.
That is, in the electrode substrate inspection method according to the present invention, the measurement method of the colorimetry can be changed according to the characteristics of the electrode substrate, and the L value (for example, other than L75) with different light receiving angles L25, L45, etc.), or using a spectrocolorimeter of a type that projects light close to natural light (light reflected by an integrating sphere). A value may be adopted.

As shown in FIG. 9, in the electrode substrate 1 used in the experiment according to the present embodiment, a correlation is recognized between the colorimetry (L75) and the air resistance.
Based on the experimental results shown in FIG. 9, the air permeability resistance of 250 (sec / 100 mL) corresponds to about 29.6 of the colorimetry.
For this reason, in order to obtain the electrode base material 1 having an air permeability resistance of 250 (sec / 100 mL), the colorimetry is managed, and the colorimetry of the mixture layer 3 is about 29.6 ( Here, the electrode substrate 1 (managed within a range of 29.6 ± 10%) is selected.

And in the inspection method of the base material for electrodes which concerns on one Embodiment of this invention, instead of actually measuring the air permeability resistance in the state of only the compound material layer 3, the colorimetry degree (L75) of the compound material layer 3 By measuring the airflow resistance, the airflow resistance is derived from the measurement result of the colorimetry and the map information A representing the correlation between the colorimetry and the airflow resistance.
The quality of the electrode base material 1 is determined based on the derived air resistance, and consequently the quality of the secondary battery manufactured using the electrode base material 1 is determined.

That is, the inspection method for an electrode substrate according to an embodiment of the present invention is the quality of an electrode substrate (for example, electrode substrate 1) configured by forming a composite layer on the surface of a metal foil. It is a method for inspecting, and the colorimetry degree of the mixture layer 3 in the electrode substrate 1 and the air resistance of the mixture layer 3 (more specifically, the free film 3a) in the electrode substrate 1 The map information A, which is the first map information representing the relationship, is obtained in advance, and the colorimetry of the mixture layer 3 measured during the manufacturing process (that is, the colorimetry measurement step (STEP-110)) is obtained. Based on the map information A, the air resistance is derived.
With such a configuration, it is possible to easily derive the air resistance in the state of only the composite layer 3 in the middle of the manufacturing process without requiring the electrode substrate 1 to be cut out.

In the inspection method for an electrode substrate according to an embodiment of the present invention, only the L value is used as the colorimetry, and the inspection of the electrode substrate according to an embodiment of the present invention is used. In the method, only the L value (L75) when the light receiving angle is 75 degrees is used as the colorimetric degree.
With such a configuration, a fine structural difference of the composite material layer 3 can be detected by measuring the colorimetry (more specifically, L75) of the composite material layer 3.

Here, the timing for measuring the colorimetry of the composite layer will be described.
When the composite material layer is pressed in the pressing step (STEP-104), the thickness decreases. At this time, the active material 8 contained in the composite material layer 3 (see FIGS. 7 and 8) is crushed, and the active material 8 Since the angular part existing on the surface of the active material 8 is finely cracked, irregular reflection on the surface of the active material 8 occurs more significantly in the pressed composite material layer 3.
Such an increase in irregular reflection in the active material 8 due to the pressing process occurs even when the binder 9 is not unevenly distributed. Therefore, even if the binder 9 is not unevenly distributed, the pressing of the composite material layer 3 after the pressing process is performed. Diffuse reflection is likely to occur on the surface.
This leads to a reduction in the difference in how irregular reflection occurs on the surface of the composite layer 3 between the case where the binder 9 is unevenly distributed and the case where the binder 9 is not present after the pressing step (STEP-104). After processing, it becomes difficult to detect structural differences in the composite material layer due to differences in colorimetry.

  That is, by comparing the colorimetry of the mixture layer 3 in the state before the pressing step (STEP-104), the difference in colorimetry caused by the structural difference of the mixture layer 3 can be made more conspicuous. Therefore, it is preferable that the timing for measuring the colorimetry is before the pressing step (STEP-104).

  Further, at the timing when the composite material layer 3 is not dried (that is, before the drying step (STEP-103)), the composite material layer 3 still contains a solvent component or the like. At this time, the surface of the mixture layer 3 is glossy, and the colorimetry (more specifically, the L value) is in a state that is unlikely to occur. Therefore, the structural difference of the mixture layer 3 should be detected. The timing for measuring the colorimetry is not appropriate.

  That is, the timing for measuring the colorimetry to detect the structural difference of the composite material layer 3 is after the drying step (STEP-103) and before the pressing step (STEP-104). Is most preferable.

  Therefore, in the electrode substrate inspection method according to an embodiment of the present invention, based on such an idea, as shown in FIG. 4, the drying process (STEP-103) and the pressing process (STEP-104). It is set as the structure which implements a colorimetry degree measurement process (STEP-110) at the timing of between.

Then, by measuring the colorimetry at such timing, the structural difference of the electrode base material can be reliably detected based on the measurement result of the colorimetry.
In addition, since the colorimetry can be performed in a non-contact manner with respect to the electrode base material, the electrode base material can be transparently measured in-line without stopping the flow of the electrode base material manufacturing process. The air resistance can be derived.

  Furthermore, in the configuration for deriving the air resistance from the measured colorimetry, it is not necessary to cut out a part of the electrode base material for the measurement of the air resistance, so the time required for the inspection can be shortened, Moreover, the base material for electrodes which is expended and wasted for an inspection can be reduced.

Furthermore, in the electrode substrate inspection method according to an embodiment of the present invention, the air resistance of the composite layer can be derived before the pressing step (STEP-104).
For this reason, when the derived air permeability resistance is out of the threshold value related to the air resistance, the electrode substrate is defective without waiting for the result of the pressing step (STEP-104). It is also possible to make a determination.
For this reason, in the inspection method for an electrode substrate according to an embodiment of the present invention, the quality of the electrode substrate 1 can be judged at an early stage as compared with the conventional inspection method, and a defect occurs. In this case, feedback to the previous process (that is, the paste manufacturing process (STEP-101), the coating process (STEP-102), the drying process (STEP-103), etc.) is facilitated.

That is, in the inspection method for an electrode base material according to an embodiment of the present invention, the colorimetry is before the pressing step (STEP-104) in the manufacturing process of the electrode base material 1 and for the electrode. It is measured after the drying step (STEP-103) in the manufacturing process of the substrate 1.
With such a configuration, a fine structural difference in the composite material layer 3 can be reliably detected.

Next, the flow of inspection at the actual operation stage in the inspection method for an electrode substrate according to an embodiment of the present invention will be described.
As shown in FIG. 5, in the inspection method for an electrode substrate according to an embodiment of the present invention, in the actual operation stage, as in the preparation stage, after the drying process (STEP-103), and press Prior to the step (STEP-104), a colorimetry measurement step (STEP-110) is performed.

  Then, using the colorimetry measured before the pressing step (STEP-104), the air resistance of the electrode substrate is derived based on the map information A created in the preparation stage. ing.

  Moreover, in the inspection method of the base material for electrodes which concerns on one Embodiment of this invention, after a press process (STEP-104) in the actual operation | movement stage, the derived air permeability resistance and the horizontal electronic resistance in the present manufacturing conditions The quality of the electrode base material is determined based on the map information B (STEP-150).

  Thus, in the electrode substrate inspection method according to an embodiment of the present invention, in the actual operation stage, only the measurement result of the colorimetry is used, and the map information A obtained in advance in the preparation stage and Since the quality of the electrode base material can be determined based on the map information B (STEP-150), it is not necessary to cut out the sample (STEP-120).

  In addition, since the measurement of colorimetry (that is, the colorimetry measurement step (STEP-110)) can be performed in a non-contact manner without damaging the electrode substrate, it is easy during the manufacturing process (ie, inline). In addition, since it is not necessary to modify the production line, it is easy to additionally introduce the colorimetry measurement process (STEP-110) into the existing production process.

That is, in the inspection method for an electrode substrate according to an embodiment of the present invention, the air permeability resistance of the mixture layer 3 in the electrode substrate 1 and the horizontal electrons of the mixture layer 3 in the electrode substrate 1. The map information B, which is the second map information representing the relationship with the resistance, is obtained in advance, and the electrode information is obtained from the map information A and B as the first and second map information based on the measurement result of the colorimetry. The quality of the base material 1 for use is determined (STEP-150).
With such a configuration, the quality control of the electrode substrate 1 can be accurately performed based on the detection result of the fine structural difference in the composite material layer 3.

DESCRIPTION OF SYMBOLS 1 Electrode base material 2 Metal foil 3 Compound material layer 3a Free film

Claims (4)

A method for inspecting the quality of a base material for an electrode configured by forming a composite layer on the surface of a metal foil,
The colorimetry degree of the mixture layer in the electrode substrate measured before the pressing step in the electrode substrate manufacturing process and after the drying step in the electrode substrate manufacturing process ;
The air resistance of the mixture layer in the electrode substrate measured after the pressing step in the manufacturing process of the electrode substrate,
The first map information representing the relationship of
Based on the measured chromaticity of the mixture layer was measured in the course of the manufacturing process of the electrode base material,
From the first map information,
Deriving the air resistance of the composite layer in the electrode substrate ;
A method for inspecting a substrate for an electrode characterized by the above. The colorimetry is
Use only L value,
The method for inspecting an electrode substrate according to claim 1. The colorimetry is
Using the L value when the light receiving angle is 75 degrees,
The method for inspecting an electrode substrate according to claim 2. The air resistance of the mixture layer in the electrode substrate measured after the pressing step in the manufacturing process of the electrode substrate,
The horizontal electronic resistance of the composite layer in the electrode substrate measured after the pressing step in the manufacturing process of the electrode substrate,
The second map information representing the relationship is obtained in advance,
Based on the measurement result of the colorimetry,
From the first and second map information,
Judge the quality of the electrode substrate,
The inspection method for a substrate for an electrode according to any one of claims 1 to 3 , wherein:

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