JP2000155101A - Method and apparatus for quantifying element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To selectively and inexpensively determine specific elements contained in a sheet-like matter per unit area with high accuracy. SOLUTION: This method for determining specific elements contained in a sheet-like matter includes a process for irradiating the sheet-like matter with X-rays in a region on the high-energy side of the X-ray absorbtion edge related to the specific elements, a process for measuring the incident intensity (I0) and transmitted intensity (It) of X-rays transmitted through the sheet-like matter to calculate the absorbance of the X-rays, with respect to the sheet-like matter according to the formula and a process for calculating the amt. of the specific element contained in the sheet-like matter based on the calculated absorbance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for quantifying an element, and more particularly to a method and an apparatus for quantifying a specific element contained in a sheet-like object.

[0002]

2. Description of the Related Art In the process of manufacturing sheet-like objects such as resin films and rubber sheets containing metal elements, such as magnetic tapes and electrode plates, the management of thickness and unit area weight is a matter of productivity. It is extremely important from the viewpoint of improvement of quality and quality maintenance. In particular, for the electrode plate for a battery, the content of the metal oxide contained therein has a great effect on various characteristics including the charge and discharge characteristics of the battery,
If the above management is neglected, the required battery characteristics cannot be obtained in many cases.

For example, a positive electrode for a lithium battery is manufactured by applying a paste containing lithium cobalt oxide as an active material on a metal foil. In order to realize required charge / discharge characteristics, such a positive electrode is required. It is necessary to control the thickness of the paste and its unit area weight (particularly, the weight of lithium cobalt oxide contained per unit area) with high precision in a simple manufacturing process.

In managing the thickness and unit area weight of the sheet-like object as described above, it is necessary to measure them accurately. Here, the thickness is generally measured using an eddy current thickness gauge or a thickness gauge using a laser in many cases. On the other hand, the measurement of the unit area weight, particularly the weight of the metal element contained per unit area, is often performed by a method using a β-ray sensor. However, the method of using a β-ray sensor is subject to laws and regulations in order to use β-rays, and it is necessary to obtain a public use permission or the like when implementing the method. In addition, this method requires the use of a large-scale and expensive apparatus, and it is hard to say that a specific element contained in a composite sheet having a complicated constituent material can be selectively and accurately determined.

An object of the present invention is to determine a specific element contained per unit area of a sheet-like object with high precision, selectively and at low cost.

[0006]

SUMMARY OF THE INVENTION X-rays are absorbed as they pass through a substance. For example, the X-ray of energy E has a thickness t
The following relational expression is established between the intensity (I ₀ ) of the X-ray incident on the substance and the intensity (I _t ) of the X-ray transmitted through the substance when transmitting the substance.

[0007]

(Equation 3)

Here, A is the absorbance of X-rays. Also,
μ is a linear absorption coefficient whose value is unique for each type of substance, and is a constant for X-rays having a constant energy. Therefore, when the absorbance (A) is measured, the thickness t of the substance can be obtained. Incidentally, this thickness t is proportional to the weight per unit area of the substance.

The present inventors have focused on the fact that when the energy E of X-rays changes, the linear absorption coefficient μ also changes. Here, when a change in the linear absorption coefficient μ with respect to the energy E is traced for a certain substance, the linear absorption coefficient μ gradually decreases with an increase in the energy E. However, the linear absorption coefficient μ starts at a certain critical energy Eb. μ increases rapidly. Such a critical energy Eb is defined as an X-ray absorption edge. For example, a change in the linear absorption coefficient μ of the lithium cobalt oxide (LiCoO ₂ ) used as the positive electrode active material of the lithium battery with respect to the energy E is as shown in FIG. 1, for example. From this figure, it can be seen that lithium cobalt oxide has a sharp increase in the linear absorption coefficient μ from 7.71 keV, and the energy value becomes the critical energy Eb, that is, the X-ray absorption edge. X on the higher energy side than the X-ray absorption edge
The lines are selectively absorbed by the elemental cobalt. Based on such facts, the present inventors have completed the present invention.

That is, the method for quantifying an element according to the present invention is a method for quantifying a specific element contained in a sheet-like object. Irradiating the energy side region with X-rays; and detecting the incident intensity (I
₀ ) and transmission intensity (I _t ), and determining the X-ray absorbance (A) of the sheet-like object according to the following formula (1): Determining the amount of the specific element contained in the object. The above-mentioned specific element is, for example, an element having a higher atomic number than titanium.

[0011]

(Equation 4)

The device for quantifying an element according to the present invention is a device for quantifying a specific element contained in a sheet-like object. An irradiating unit for irradiating an X-ray in a region, a first detecting unit for measuring an incident intensity (I ₀ ) of the X-ray from the irradiating unit incident on the sheet-like object, and an irradiating unit for transmitting the sheet-like object A second detection unit for measuring the transmission intensity (I _t ) of the X-ray from the sheet-like object according to the above-mentioned calculation formula (1) from the incident intensity (I ₀ ) and the transmission intensity (I _t ). A quantitative means for determining the absorbance (A) of the X-ray and determining the amount of a specific element contained in the sheet-like object based on the absorbance.

[0013]

FIG. 2 shows an electrode manufacturing apparatus for a battery employing the element quantification apparatus according to the present invention. In the figure, an electrode manufacturing apparatus 1 mainly includes an electrode manufacturing unit 2 and an element quantification device 3.

The electrode manufacturing section 2 includes an active material layer 6 on the current collector 5.
Are provided for producing the electrode 4 on which the current collector 5, for example, an aluminum foil is delivered, a take-up roll 8 for taking up the manufactured electrode 4, and a delivery roll 7. And a coating section 9 and a drying section 10 for forming the active material layer 6 on the current collector 5. The coating section 9 is made of an active material (for example, L
a supply unit 9 a for supplying the paste 11 containing iCoO ₂ ) to the current collector 5 on the delivery roll 7, and a paste 11 supplied to the current collector 5 And a scraper 9b for applying with a thickness. The drying unit 10 is disposed so as to sandwich the current collector 5 on which the paste 11 is applied, and is for heating and drying the paste 11 applied to the current collector 5.

The element quantifying device 3 is for quantifying the above-mentioned active material, that is, the cobalt element contained in LiCoO _2, and includes an X-ray generator 12 (an example of an irradiation unit) and a current collector 5. A first detector 13 (an example of a first detection unit) and a second detector 14 (an example of a second detection unit) which are arranged;
It mainly includes a counting control device 15 (an example of a quantification unit) and an electric motor 16.

The X-ray generator 12 emits X-rays (for example, X-rays in the high energy side region at the X-ray absorption edge relating to the cobalt element).
This is for irradiating the current collector 5 (an example of a sheet-like object) to which the paste 11 has been applied with 8.04 keV characteristic X-rays. The first detector 13 is for measuring the incident intensity (I ₀ ) of the characteristic X-rays from the X-ray generator 12, which is incident on the current collector 5 to which the paste 11 is applied, and The second detector 14 is for measuring the transmission intensity (I _t ) of the above-described characteristic X-ray transmitted from the X-ray generator 12 and transmitted through the current collector 5.

The counting controller 15 comprises an electronic circuit for amplifying and counting the signals from the first detector 13 and the second detector 14, and a computer system for calculating and storing the obtained data. Also, the counting control device 15
Is calculated based on the incident intensity (I ₀ ) measured by the first detector 13 and the transmission intensity (I _t ) measured by the second detector 14 using a data processing program created in advance. According to 1), the absorbance (A) of the sample with respect to the characteristic X-rays described above is set to be calculable.

[0018]

(Equation 5)

Further, from the absorbance (A) of the characteristic X-rays described above, the calculation formula of the calibration curve for calculating the amount of cobalt element per unit area of the current collector 5 coated with the paste 11 (that is, the weight of LiCoO ₂ ) ( (Hereinafter referred to as a quantitative formula) is obtained in advance by measurement using a standard sample.
Computer system. In the measurement of the unknown sample, the weight of LiCoO ₂ contained in the paste applied on the current collector 5 can be calculated from the absorbance (A) according to such a quantitative formula, and the absorbance (A) and the paste 11 Since the following relational expression (2) is established between the thickness of the current collector 5 and the thickness (t) of the current collector 5, the thickness of the paste 11 applied to the current collector 5 is determined by the absorbance (A). Can be obtained from In the relational expression (2), μ is a linear absorption coefficient specific to the sample as described above.

[0020]

(Equation 6)

The electric motor 16 is for slightly moving the scraper 9b in the vertical direction, and is set so as to be operable by the counting control device 15.

Next, the operation of the above-described electrode manufacturing apparatus 1 will be described. In the electrode manufacturing apparatus 1, the paste 11 is applied to the current collector 5 continuously transferred from the delivery roll 7 in the direction of the take-up roll 8 by the coating unit 9 on the delivery roll 7. Here, the paste 11 is supplied onto the current collector 5 from the supply unit 9a, and the paste 11 is applied onto the current collector 5 while the thickness is adjusted by the scraper 9b. The current collector 5 on which the paste 11 is applied is heated and dried in the drying unit 10 to form the electrode 4 having the active material layer 6. The electrode 4 manufactured in this manner is wound up by a winding roll 8.

In the manufacturing process of the electrode 4 as described above,
The element quantifying device 3 includes a paste 11 applied to the current collector 5.
Is continuously quantified for the cobalt element constituting LiCoO ₂ which is an active material contained in. Here, the X-ray generator 1
2 passes through the current collector 5 to which the paste 11 is applied, and the incident intensity (I ₀ ) of the current collector 5 is the first.
It is measured by the detector 13, and its transmission intensity (I _t ) is measured by the second detector 14.

The counting controller 15 measures the above-mentioned absorbance (A) in accordance with the above-mentioned equation (1) based on the measured incident intensity (I ₀ ) and transmitted intensity (I _t ), From (A), the amount of elemental cobalt contained per unit area of paste 11 (that is, LiCoO ₂
) And the thickness (t) of the current collector 5 to which the paste 11 has been applied, respectively, are determined according to the above-described quantitative expression and the relational expression (2). Here, the above-mentioned characteristic X-ray is LiCoO
₂ is selectively absorbed by the cobalt element that constitutes the element _2. Therefore, compared to the case where the elemental quantification method based on continuous X-rays or β-rays with restrictions on use is employed, the cobalt element contained per unit area of the paste 11 ( That is, LiCo
O ₂ ) can be quantified more selectively and with higher precision, and as a result, the thickness of the paste 11 applied to the current collector 5 can be determined with high precision at the same time.

On the basis of the thickness of the paste 11 thus obtained, the counting controller 15 controls the electric motor 16
Is operated to move the scraper 9b up and down. Thereby, the thickness of the paste 11 applied to the current collector 5 is adjusted to an optimum value, and the paste 11 is applied to the current collector 5 so that the weight of LiCoO ₂ contained per unit area becomes constant. Is done.

As described above, the above electrode manufacturing apparatus 1 employing the element quantification apparatus (element quantification method) according to the present invention.
In the current collector 5 to which the paste 11 has been applied, the amount of cobalt element (LiCoO ₂ ) per unit area of the applied paste 11 can be accurately and continuously measured in a non-contact state and a non-destructive state. The determination can be made immediately, and the result can be always fed back to the operation of the scraper 9b. For this reason, the electrode manufacturing apparatus 1 can perform quality control of the electrode 4 in real time, and as a result, continuously produce a stable electrode 4 in which the content of LiCoO ₂ per unit area is set uniformly. And it can be manufactured with a high yield.

The element quantifying device 3 can be constructed at a lower cost than a conventional measuring device using β-rays or the like, and does not need to be licensed for public use. It can be used only on the basis of notification.

[Other Embodiments] (1) In the above embodiment, the element quantifying device 3 is fixed and used. However, the element quantifying device 3 may be combined with, for example, a driving stage to collect the paste 11 coated. It may be set to be movable on the electric body 5. In this case, by driving the drive stage, it is possible to quantitatively determine a specific element (cobalt element in the case of the above-described embodiment) contained in the paste 11 over a wider range (having a wider unit area). .

(2) In the above embodiment, the element quantification method and apparatus according to the present invention are applied to an electrode manufacturing apparatus, and paste 11, that is, an undried sheet-like object containing a solvent or the like is used. Although the case of quantifying the contained cobalt element has been described, the method and apparatus of the present invention can also be used for quantifying a specific element contained in various sheet-like objects such as manufactured electrodes and magnetic tapes. it can.

(3) In the above embodiment, the case of quantifying elemental cobalt has been described. However, the method and the apparatus of the present invention can be applied to various types of commercially available X-ray tubes or rotary anti-cathode X-ray sources. By appropriately selecting the anode material and using X-rays having an energy suitable for the specific element to be quantified, all the elements other than the cobalt element, in particular, all of the first transition element can be quantified.

Further, if white X-rays from a tungsten or rhodium anode or the like are monochromatized by a spectral crystal, X-rays of any energy can be obtained. Even in the case of the element described above, an element having an atomic number higher than that of titanium in the atmosphere can be quantified without exception. When using an X-ray source using an X-ray tube or X-rays from a rotating anti-cathode X-ray source, if the X-rays are converted to single-energy X-rays using a spectral crystal, Higher precision quantification becomes possible.

(4) When higher precision quantification is required by the quantification method and the quantification apparatus of the present invention, the absorbance of the specific element to be quantified or an element or compound other than the compound contained in the sheet-like object is determined. It is preferable to make a correction such as subtraction. However, the quantification method and the quantification device of the present invention, even when such correction is not performed,
By using a calibration curve created using standard samples,
The specific element can be quantified with high accuracy within a general allowable error range.

(5) In the above embodiment, the case where the quantification method and the quantification apparatus of the present invention are applied to an electrode manufacturing apparatus has been described. The present invention can also be applied to various devices for manufacturing.

[0034]

EXAMPLE Lithium cobalt oxide (LiCoO ₂ ), which is a positive electrode active material of a lithium ion battery, was replaced with boron nitride (BN).
And the unit area weight as lithium cobaltate is 45.9, 47.2, 48.4 and 49.8, respectively.
Four sheet-shaped pellets of mg / cm ² were produced.

As shown in FIG. 3, the produced pellet P was fixed vertically to the holder 20, and X-ray detectors 21 and 22 were arranged before and after the pellet P, respectively. And
The pellet P is irradiated with X-rays from the X-ray generator 23,
The intensity of the X-ray incident on the pellet P (I ₀ ) and the intensity of the X-ray transmitted through the pellet P (I _t ) were measured by the line detectors 21 and 22. At this time, as the X-ray generator 23, a device provided with an X-ray tube of a copper target that generates 8.04 keV characteristic X-rays near the X-ray absorption edge of the cobalt element is used, and the X-ray tube from the X-ray tube is used. The pellet P was irradiated with X-rays.

The measured incident X-ray intensity (I ₀ ) and transmission X
The absorbance (A) was determined from the linear intensity (I _t ) by the above-mentioned equation (1). FIG. 4 shows a graph in which the determined absorbance (A) is plotted on the vertical axis and the unit area weight is plotted on the horizontal axis.
The unit area weight of lithium cobalt oxide and the absorbance (A) are in a good linear relationship (correlation coefficient = 0.995), indicating that this graph can be used as a calibration curve.

Next, lithium cobalt oxide as an active material,
Conductive agent carbon black and binder
The paste made of polyvinylidene fluoride is used as the current collector.
Aluminum cobalt foil
Weight per unit area is 47mg / cm ^TwoWas prepared. this
The electrodes are described above in the same manner as when the calibration curve was created
Measure the absorbance (A) of the characteristic X-ray and use the above calibration curve
Calculated the unit area weight of lithium cobalt oxide
The value is 47.1 mg / cm^TwoAnd the amount charged
Substantially matched.

[0038]

The method and apparatus for quantifying an element according to the present invention utilize X-rays in the high energy side region of the X-ray absorption edge relating to a specific element to be quantified, so that a sheet-like object can be measured. Specific elements contained per unit area can be quantified with high accuracy, selectively, and at low cost.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between energy X of X-rays and a linear absorption coefficient μ of lithium cobaltate.

FIG. 2 is a schematic diagram of an electrode manufacturing apparatus employing an element quantification device according to one embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an element quantification device used in Examples.

FIG. 4 is a graph showing a calibration curve used in Examples.

[Explanation of symbols]

 3 Element quantifier 12 X-ray generator 13 First detector 14 Second detector 15 Count controller

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeshi Zhao 6-6 Josaicho, Takatsuki-shi, Osaka Prefecture Inside Yu Asa Corporation (72) Inventor Tatsuharu Nakagomi 6-6 Josaicho, Takatsuki-shi, Osaka Yu Co., Ltd. Inside Asa Corporation (72) Inventor Izumi Nakai 6-7-3 Kinokudai, Taniwara-mura, Tsukuba-gun, Ibaraki F-term (reference) 2G001 AA01 AA09 BA11 BA13 CA01 FA14 GA01 HA03 KA01 LA02 LA05 MA05 NA11 NA16 NA17 PA11 RA08

Claims (3)

[Claims] 1. A method for quantifying a specific element contained in a sheet-like object, comprising irradiating the sheet-like object with X-rays in a high energy side region of an X-ray absorption edge relating to the specific element. Measuring the incident intensity (I ₀ ) and the transmitted intensity (I _t ) of the X-ray transmitted through the sheet-like object, and measuring the X-ray absorbance (A) of the sheet-like object as follows: A method for quantifying an element, comprising: a step of calculating according to a calculation formula (1); and a step of calculating an amount of the specific element contained in the sheet-like object based on the absorbance. (Equation 1) 2. The method according to claim 1, wherein said specific element is an element having an atomic number larger than that of titanium. 3. An apparatus for quantifying a specific element contained in a sheet-like object, comprising irradiating the sheet-like object with X-rays in a high energy side region of an X-ray absorption edge relating to the specific element. An irradiating unit that measures the incident intensity (I ₀ ) of the X-rays from the irradiating unit incident on the sheet-shaped object; A second detector for measuring the transmission intensity (I _t ) of the X-ray, and the sheet-like object according to the following calculation formula (1) from the incident intensity (I ₀ ) and the transmission intensity (I _t ). A quantitative means for determining the absorbance (A) of the X-ray and calculating the amount of the specific element contained in the sheet-like object based on the absorbance. (Equation 2)