JP7026348B2 - Chemical state analysis method for battery materials - Google Patents

Description

The present invention is a method for analyzing the chemical state of a battery material, such as the valence of the ion of an element contained in the material (battery material) constituting the battery, before, during, or after the use of the primary battery or the secondary battery. Regarding.

Secondary batteries such as lithium-ion batteries are widely used as a power source for mobile information terminals and electric vehicles, and have a charge capacity (the time during which the mobile information terminal can be used with one charge and the distance that the electric vehicle can travel). It is required to improve the life (generally shown as the number of times that charging and discharging can be repeated with a practical capacity) and the like (directly connected) and life. Therefore, materials used for electrodes for secondary batteries and the like are being actively developed.

Non-Patent Document 1 describes that XAFS (X-ray absorption fine structure) measurement is performed on an electrode of a secondary battery while charging the secondary battery and then discharging the battery. .. XAFS measurement is a method of irradiating a sample with synchrotron radiation, obtaining the spectrum of X-rays that have passed or reflected in the sample, and obtaining the electronic state of the sample from the position and shape of the peak of X-rays absorbed by the sample. .. Non-Patent Document 1 has obtained a measurement result that the position of the peak of the obtained spectrum gradually moves to the high energy side as the secondary battery is discharged. This movement of the peak position is caused by a change in the valence of elemental ions (Co ions in the example shown in Non-Patent Document 1) contained in the electrode material during discharge of the secondary battery.

Japanese Unexamined Patent Publication No. 2017-223638

Takahiro Harada, 1 others, Lithium-ion battery (7) Valuation and structural evaluation of positive electrode active material, The TRC News, published by Toray Research Center, Inc., September 2013, No. 117, pp. 31-33

Since the measuring method described in Non-Patent Document 1 uses synchrotron radiation, the measuring device for carrying out this measuring method becomes large and expensive.

In the development of secondary batteries, it is important to know the changes in the chemical state such as the valence of ions contained in the electrode material during discharge or charging. For that purpose, the chemical state is measured. Is required to be quantified. Non-Patent Document 1 describes that it is considered possible to quantitatively evaluate the valence change from the relationship between the SOC (State of Charge) of the secondary battery and the peak position. However, the evaluation method is not specifically shown in Non-Patent Document 1, and it is unclear whether the chemical state can be quantified with high accuracy. Although the description has been made for the secondary battery here, the same applies to the case of the primary battery.

The problem to be solved by the present invention can be carried out with a device smaller and cheaper than the conventional one, and the chemical state of the battery material such as the valence of ions can be quantified with high accuracy. It is to provide a method for analyzing the chemical state of a material.

The chemical state analysis method according to the present invention, which was made to solve the above problems, is
A battery dismantling step of disassembling the battery so that the analysis target portion including the battery material to be analyzed is exposed.
An excitation line for generating characteristic X-rays of the battery material is passed directly to a predetermined irradiation region in the surface of the analysis target portion or by covering the analysis target portion and passing the excitation line and the characteristic X-ray. Excitation ray irradiation step to irradiate through the protective layer,
Characteristic X-rays generated in the irradiation region by irradiation of the excitation line are transmitted to a spectroscopic crystal composed of a flat plate provided facing the irradiation region in parallel with the irradiation region and a predetermined crystal plane of the spectroscopic crystal. There is a spectroscopic step of splitting by incident through a slit provided between the irradiation region and the spectroscopic crystal.
Characteristic X-rays dispersed by the spectroscopic crystal are detected by an X-ray linear sensor provided so that linear detection elements having a length in a direction parallel to the slit are arranged in a direction perpendicular to the slit. X-ray detection process and
A wavelength spectrum is created based on the intensity of characteristic X-rays detected by the X-ray linear sensor, a peak wavelength which is a wavelength at the peak of the wavelength spectrum is obtained, and the peak wavelength and the battery material in the analysis target portion are used. A chemical state specifying step for obtaining a value for specifying the chemical state from a standard curve showing the relationship between the value representing the chemical state and the peak wavelength.
It is characterized by doing .

In the present invention, the "wavelength spectrum" also includes an energy spectrum and a wavenumber spectrum represented by energy and wavenumber, which are values corresponding to the wavelength. Similarly, the “peak wavelength” shall include peak energy and peak wave number.

In the present invention, the battery material means an electrode material whose valence can be changed electrochemically. Therefore, separators, electrolytes, supporting salts, electric tanks, etc. are not applicable.

In the chemical state analysis method according to the present invention, analysis is performed using an X-ray spectroscopic analyzer including the excitation source for generating the excitation line, the spectroscopic crystal, the slit, and the X-ray linear sensor. This X-ray spectroscopic analyzer was invented by the present inventor and is described in Patent Document 1. In this X-ray spectroscopic analyzer, by irradiating the irradiation area with excitation rays, characteristic X-rays are emitted from various positions in the irradiation area in various directions, but only those that pass through the slit are spectroscopic crystals. To reach. When the irradiation area is divided into linear portions parallel to the slit, only the characteristic X-rays having a specific wavelength (energy) that are emitted from one of the linear portions pass through the slit. Then, it is incident and diffracted at an incident angle that satisfies the diffraction condition, and is detected by a specific one of the detection elements of the X-ray linear sensor. Therefore, since characteristic X-rays having a specific wavelength different from each detection element are detected, the wavelength spectrum of the characteristic X-rays can be obtained from the intensity of each detection element. Here, as for the characteristic X-rays having different wavelengths, only those emitted from the linear portions different from each other are detected by the X-ray linear sensor, but one linear portion is within the linear portion. Therefore, even if the composition is somewhat non-uniform in the irradiation region, it can be measured without any problem.

As described above, the wavelength (peak wavelength) at the peak of the wavelength spectrum obtained by using the above-mentioned X-ray spectroscopic analyzer has a different value depending on the type of the element contained in the battery material, and even if it is the same element, the ionic value If the chemical state of the battery material such as the number is different, the value will be slightly different. Therefore, by applying the value of the peak wavelength obtained by the measurement to the standard curve showing the relationship between the peak wavelength and the value representing the chemical state of the battery material, the value representing the chemical state of the battery material in the sample to be measured is applied. Can be asked.

However, even if the battery to be analyzed irradiates the irradiation area of the analysis target part with the excitation line as it is, the path until the excitation line is irradiated to the irradiation area and the characteristic X-rays generated in the irradiation area are still present. If there are members other than the analysis target that make up the battery in the path to reach the slit, the intensity of the characteristic X-rays generated in the excitation line and irradiation region is weakened, and the detection intensity of the X-ray linear sensor is weakened. Also declines. Then, there arises a problem that the analysis accuracy is lowered, or the detection needs to be performed for a long time in order to secure the analysis accuracy, and the analysis efficiency is lowered. Therefore, in the chemical state analysis method according to the present invention, after disassembling the battery so that the analysis target portion is exposed, the analysis target portion is to be analyzed with the analysis target portion exposed or with a protective layer that allows the excitation line and the characteristic X-ray to pass through. The irradiation area is irradiated with the excitation line while the portion is covered. As a result, the intensity of the characteristic X-rays generated in the excitation line or the irradiation region is not weakened by the members constituting the battery other than the analysis target portion, and the detection intensity of the characteristic X-rays can be increased. The chemical state of the battery material can be quantified with high accuracy.

In the chemical state analysis method according to the present invention, it is desirable to perform analysis after disassembling the battery and cleaning the analysis target portion. By cleaning the analysis target portion in this way, even if the analysis target portion comes into contact with moisture in the air after the battery is disassembled, it is possible to prevent the analysis target portion from reacting with the electrolytic solution and water in the battery and deteriorating. be able to. The cleaning liquid for cleaning the analysis target portion may be any liquid that is an organic solvent that does not contain water and that can dissolve the supporting salt. For example, an aprotic chain carbonate-based organic solvent or an aprotic cyclic carbonate-based organic solvent can be used. Examples of the chain carbonate-based organic solvent include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and the like. Examples of the chain carbonate-based organic solvent include ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC) and the like. These may use one kind or two or more kinds of these. Of these cleaning liquids, side reactions are unlikely to occur when the analysis target part comes into contact with the cleaning liquid, and the cleaning liquid can be easily removed after cleaning the analysis target part, so that oxidation resistance and reduction resistance are electrochemically obtained. An aprotic chain carbonate-based organic solvent having excellent properties and a low boiling point is preferable.

The organic solvent containing no water is not limited to this as long as the water content is substantially small. Specifically, the water content with respect to the cleaning liquid may be 500 ppm or less. This water content can be measured by Karl Fischer.

Known cleaning methods such as jet cleaning, spray cleaning, shower cleaning, dip cleaning, and ultrasonic cleaning can be adopted as the cleaning method, but from the viewpoint that the analysis target portion is not easily destroyed, spray cleaning, shower cleaning, etc. Dip cleaning is preferred. The spray cleaning is a method of spraying a cleaning liquid from a spray nozzle to clean the analysis target portion. Shower cleaning is a cleaning method in which a liquid is sprayed onto an analysis target portion by a pressure difference caused by a pressure pump or a height difference. The dip cleaning is a method of immersing the analysis target portion in a cleaning liquid to clean the analysis target portion.

Alternatively, in the chemical state analysis method according to the present invention, the battery is disassembled and each step thereafter (including the case where the analysis target portion is washed) is carried out in a dry atmosphere (for example, room temperature 20 ° C., dew point-. It may be performed in an environment where the temperature is about 70 ° C.) or the air is shut off. This makes it possible to prevent the analysis target portion from reacting with the electrolytic solution and water in the battery and deteriorating. In this case, it is not necessary to wash the analysis target portion, but of course, it may be performed.

In the chemical state analysis method according to the present invention, the standard curve is chemically more stable than the battery material to be measured, is an ion composed of one of the elements possessed by the battery material, and has a mutual valence. It is desirable that the sample is prepared based on the peak wavelength and the valence of the wavelength spectrum obtained from each of the plurality of standard samples containing different ions. In this case, the value representing the chemical state of the battery material is the valence of ions possessed by the battery material. Since the valence of the battery material itself can fluctuate due to charge / discharge, chemical reaction, etc., the accuracy of the standard curve can be improved by using a standard sample that is chemically more stable than the battery material. As such a chemically stable standard sample, for example, an oxide, a hydroxide, a sulfide, a chloride, or the like of an element whose valence is to be obtained in a battery material can be used as a standard sample.

Alternatively, in the method for analyzing the chemical state of a battery material according to the present invention, the standard curve is composed of the same kind of elements as the plurality of kinds of elements possessed by the battery material to be measured, and is composed of one of the plurality of kinds of elements. It is also possible to use an ion prepared based on the peak wavelength and the valence of the wavelength spectrum obtained from each of a plurality of standard samples containing ions having different valences from each other. Also in this case, the value representing the chemical state of the battery material is the valence of ions possessed by the battery material. In this way, by using a standard sample composed of elements of the same type as the battery material to be measured, a standard curve is created with a composition close to that of the battery material actually used, so that the accuracy of the standard curve can be improved. can.

In the method for analyzing the chemical state of a battery material according to the present invention, the standard curve shows the peak wavelength of the wavelength spectrum when charged to the upper limit voltage and the wavelength spectrum when discharged to the end-of-discharge voltage in the same type of secondary battery. The peak wavelength of may be set as a reference. In this case, the valence of the battery material is not obtained. For example, in the secondary battery which is a standard sample, the peak wavelength of the wavelength spectrum when charged to the upper limit voltage is defined as 100%, and the peak wavelength when discharged to the discharge end voltage is defined as 0%, and a straight line is provided between the two. The tied product is used as a standard curve showing the relationship between the value indicating the chemical state of the battery material in the sample and the peak wavelength, and the peak wavelength obtained when the sample to be measured is measured is applied to this standard curve. A value indicating the chemical state of the sample can be obtained.

According to the method for analyzing the chemical state of a battery material according to the present invention, it can be carried out with a smaller and cheaper device than before, and the chemical state of the battery material is quantified with high accuracy by the valence of ions and the like. be able to.

The schematic side view which shows the chemical state analysis apparatus used in one Embodiment of the chemical state analysis method which concerns on this invention. The figure (a) which shows an example of the lithium ion battery to be measured, and the figure (b) which shows the state which disassembled the lithium ion battery for measurement and attached it to a sample holder. The perspective view which shows the arrangement of the slit, the spectroscopic crystal, the X-ray linear sensor and the sample holder in the chemical state analyzer used in the chemical state analysis method of this embodiment. The standard curve prepared using chemically stable Mn ₂ O ₃ and Mn O ₂ as a standard sample and the result of analyzing the valence of Mn contained in the battery material of the sample using the standard curve are shown. (A) Standard curve And a graph showing the analysis result at the time of charging, and (b) a graph showing the standard curve and the analysis result at the time of discharging. A standard curve prepared using Li Mn ₂ O ₄ and Li ₂ Mn O ₃ having multiple elements of the same type as the battery material of the sample to be analyzed as a standard sample, and the value of Mn contained in the battery material of the sample using the standard curve. A graph showing the results of numerical analysis, (a) a graph showing the standard curve and the analysis result at the time of charging, and (b) a graph showing the standard curve and the analysis result at the time of discharging. (a) Charging or discharging using a standard curve created as a standard sample of the battery material of the secondary battery charged once to the charging upper limit voltage and then discharged once to the discharge end voltage, and the standard curve. A graph showing the results of analyzing the chemical state of the secondary battery in the middle of the above, and (b) charging to the upper limit voltage and discharging to the discharge end voltage once, and then charging the second time to the upper limit voltage. A standard curve created using the battery material of the secondary battery performed and the battery material of the secondary battery subjected to the second discharge to the discharge end voltage as a standard sample, and the standard curve used during charging or discharging. The graph which shows the result of having analyzed the chemical state in a secondary battery. Changes in the valence of Mn in the positive electrode material during one charge of the lithium ion battery to the upper limit of charge and discharge to the end of discharge voltage, and up to the end of charge and discharge of the lithium ion battery to the upper limit of charge The graph which shows the result of having measured the change of the valence of Mn in a positive electrode material during one charge | charge to the charge upper limit voltage and one discharge to a discharge end voltage after one discharge of.

An embodiment of the method for analyzing the chemical state of a battery material according to the present invention will be described with reference to FIGS. 1 to 7.

(1) Configuration of the chemical state analyzer used in the chemical state analysis method of the present embodiment FIG. 1 is a schematic side view of the chemical state analysis device 10 used in the chemical state analysis method of the present embodiment. The chemical state analyzer 10 includes an excitation source 11, a slit 12, a spectroscopic crystal 13 composed of a flat plate, an X-ray linear sensor 14, a sample holder 15, a data processing unit 16, and a standard curve data storage unit 17. To prepare for.

The excitation source 11 is an X-ray source that irradiates a predetermined surface in the battery material of the battery, which is the sample S held in the sample holder 15, with X-rays as excitation light (excitation rays). An electron beam source may be used instead of the X-ray source. The region in which the predetermined surface of the battery material is irradiated with the excitation light is hereinafter referred to as “irradiation region A”. In the present embodiment, the excitation light is irradiated perpendicularly to the irradiation region A, but the excitation light may be irradiated at an angle inclined with respect to the irradiation region A.

The slit 12 is arranged between the irradiation region A and the spectroscopic crystal 13. In the present embodiment, the spectroscopic crystal 13 has a predetermined crystal plane parallel to the surface of the crystal. The slit 12 is arranged parallel to the crystal plane of the spectroscopic crystal 13 used for detecting the irradiation region A and the characteristic X-ray (referred to as the surface of the spectroscopic crystal 13 in this embodiment) (perpendicular to the paper surface in FIG. 1). To.

The X-ray linear sensor 14 is provided with a plurality of linear detection elements 141 having a length in a direction parallel to the slit 12 (perpendicular to the paper surface in FIG. 1) so as to be arranged in a direction perpendicular to the slit 12. Is. As described above, characteristic X-rays having a specific wavelength (energy) are detected by a specific one of the detection elements 141 of the X-ray linear sensor 14, and the characteristic X of a specific wavelength that differs for each detection element 141. The line is detected. Therefore, each detection element 141 only needs to detect the intensity (number of photons) of the X-rays incident on it, and does not need a function of strictly detecting the wavelength and energy of the incident X-rays.

The data processing unit 16 is embodied by hardware and software such as a personal computer, and has a wavelength spectrum creation unit 161, a peak wavelength determination unit 162, and a chemical state identification unit 163 as functional blocks.

The wavelength spectrum creation unit 161 creates a wavelength spectrum from the wavelength of the characteristic X-rays detected by each detection element 141 of the X-ray linear sensor 14 and the detection intensity of each detection element 141.

The peak wavelength determination unit 162 detects a peak from the wavelength spectrum created by the wavelength spectrum creation unit 161 and obtains the value of the peak wavelength. Well-known methods used in ordinary data processing can be applied to the detection of peaks.

The chemical state specifying unit 163 identifies the chemical state of the battery material in the sample S from the peak wavelength obtained by the peak wavelength determining unit 162 and the standard curve stored in the standard curve data storage unit 17 described below. ..

The standard curve data storage unit 17 stores data of a standard curve created in advance and showing the relationship between the peak wavelength of the wavelength spectrum of the characteristic X-ray and the chemical state. The standard curve is the peak wavelength of the characteristic X-ray wavelength spectrum emitted from the standard sample using the chemical state analyzer 10 itself or using another characteristic X-ray measuring device, and the elements contained in the standard sample. It is created by finding the relationship of values that are indicators of the chemical state of the standard sample, such as the valence of.

For example, a plurality of ions that are chemically more stable than the battery material in the battery to be actually measured and are composed of one of the elements of the battery material and contain ions having different valences from each other. Can be used as a standard sample. As a specific example, when LiMn ₂ O ₄ , which is one of the electrode materials used in lithium-ion batteries, is used as the battery material to be measured, LiMn ₂ O ₄ itself has a valence of +3.5 valence. On the other hand, MnO ₂ has an integer valence of +4 valence for Mn and Mn ₂ O ₃ has +3 valence for Mn, and MnO ₂ and Mn ₂ O ₃ are chemically more chemically than LiMn ₂ O ₄ . It is stable. Therefore, Mn O ₂ and Mn ₂ O ₃ are used as standard samples, and the peak wavelengths of Kβ1 and 3 rays, which are one of the characteristic X-rays of Mn, are obtained for each of these two standard samples. Then, two points that are the measurement results of these two standard samples are plotted on a graph in which one of the vertical axis and the horizontal axis is the valence and the other is the peak wavelength, and the straight line connecting these two points is used as the standard curve.

In addition, a plurality of ions composed of a plurality of elements of the same type as the battery material in the battery to be actually measured, and one of the plurality of elements having different valences from each other. The sample may be used as a standard sample. As a specific example, when the above-mentioned Li Mn ₂ O ₄ is used as the battery material to be measured, there are two, Li Mn ₂ O ₄ itself in which Mn is +3.5 valence and Li ₂ Mn O ₃ in which Mn is +4 valence. The peak wavelengths of Kβ1 and 3 rays, which are one of the characteristic X-rays of Mn, are measured for each standard sample, and these two are shown in the graph with one of the vertical and horizontal axes as the valence and the other as the peak wavelength. Plot the two points that are the measurement results of the standard sample, and use the straight line connecting these two points as the standard curve.

Alternatively, for a secondary battery of the same type as the battery to be actually measured, prepare a battery charged to the upper limit voltage and a battery discharged to the discharge end voltage, and use the battery material for each of the two secondary batteries. It may be used as data for creating a standard curve by measuring the peak wavelength of the characteristic X-ray emitted from the battery. In this case, one of the vertical axis and the horizontal axis is the index of the chemical state represented by a numerical value of 0 to 100%, and the other is the peak wavelength. The points to be used and the points where the peak wavelength when discharged to the discharge end voltage is 0% are plotted, and the straight line connecting these two points is used as the standard curve. When using this standard curve, the valences of the elements contained in the battery material are not taken into account.

In the above example, two standard samples are used, but three or more standard samples are used, and a straight line or curve connecting the obtained three or more data points, or an error with those three or more data points. A straight line determined so that is minimized or a curve represented by a function of quadratic or higher may be used as a standard curve.

(2) Chemical state analysis method of the present embodiment The chemical state analysis method of the present embodiment, which is executed by operating the chemical state analyzer 10, will be described below.

First, the sample S is set in the sample holder 15. Here, as an example, a case where the positive electrode material 21 of the lithium ion battery 20 shown in FIG. 2A is used as the battery material to be measured will be described. In this lithium ion battery 20, a separator 23 is provided between the positive electrode material 21 made of LiMn ₂ O ₄ and the negative electrode material 22 made of Li at the discharge end voltage, and is on the opposite side of the separator 23 when viewed from the positive electrode material 21. Is provided with a current collector 24 made of Al. The positive electrode material 21, the negative electrode material 22, the separator 23, and the current collector 24 are covered with the laminating material 26, and the inside of the laminating material 26 is filled with the electrolytic solution 25 in addition to the above-mentioned components. When measured in this form, the excitation light emitted to the positive electrode material 21 and the characteristic X-rays emitted from the positive electrode material 21 pass through either the separator 23 or the current collector 24 and are detected. The intensity of characteristic X-rays is reduced, and the accuracy of chemical state analysis is also reduced. Therefore, in the present embodiment, the lithium ion battery 20 is disassembled in a dry atmosphere (room temperature 20 ° C., dew point −70 ° C.), and the positive electrode material 21 is cleaned (aprotic carbonate-based organic solvent, for example, DMC). After washing with the above to remove the electrolytic solution 25, the positive electrode material 21 is set in the [V1] sample holder 15 so as to face the excitation source 11 (FIG. 2 (b)). However, since it is difficult to remove the current collector 24 from the positive electrode material 21, the current collector 24 is arranged on the opposite side of the excitation source 11 when viewed from the positive electrode material 21 while leaving the current collector 24. Further, in order to protect the positive electrode material 21, as shown in FIG. 2B, a new laminating material 26 provided in the lithium ion battery 20 is formed around the positive electrode material 21 (and the current collector 24). May be coated with a laminate 27. The laminated material 27 is mainly composed of a resin such as nylon or polypropylene, and has a sufficiently lower effect of weakening excitation light and characteristic X-rays than the separator 23 and the current collector 24, so that the measurement is not hindered.

Next, the irradiation region A is irradiated with X-rays, which are excitation light, from the excitation source 11. As a result, characteristic X-rays having different energies depending on the elements constituting the electrode material (positive electrode material 21 in the example of FIG. 2) are emitted from various positions in the irradiation region A in various directions from the entire irradiation region A. Will be done. For these characteristic X-rays, the irradiation region A is a linear portion parallel to the slit 12 (see A1, A2 ... In FIGS. 1 and 3. Here, FIG. 3 shows the slit 12, the spectroscopic crystal 13, and the X-ray linear sensor. When the arrangement of 14 and the sample holder 15 is divided into the perspective view), one specific incident angle (90-θ) ° (θ ° is the characteristic X-ray of the spectroscopic crystal 13) on the surface of the spectroscopic crystal 13. Only those emitted in the incident direction at the diffraction angle when reflected) pass through the slit 12. Then, the incident angles of the characteristic X-rays that pass through the slit 12 and are incident on the spectroscopic crystal 13 are different between the linear portions having different positions. For example, characteristic X-rays emitted from the linear portion A1 enter the spectroscopic crystal 13 at only one incident angle (90-θ ₁ ) ° (diffraction angle θ ₁ °) and are emitted from another linear portion A2. The characteristic X-rays to be generated are incident on the spectroscopic crystal 13 at only one incident angle (90-θ ₂ ) ° (diffraction angle θ ₂ °) different from the incident angle (90-θ ₁ ) °.

The characteristic X-rays incident on the spectroscopic crystal 13 from each linear portion of the irradiation region A are the conditions of Bragg reflection. The interval, n is diffracted (reflected) at the diffraction angle θ only when it has a wavelength satisfying the order). The characteristic X-ray diffracted (reflected) by the spectroscopic crystal 13 is detected by one of the detection elements 141 of the X-ray linear sensor 14. As described above, since the spectroscopic crystal 13 is incident on the spectroscopic crystal 13 at a specific incident angle (90-θ) ° that differs depending on the linear portion in the irradiation region A, it is different for each linear portion. Only characteristic X-rays of one wavelength are incident on the X-ray linear sensor 14 and are detected by different detection elements 141. For example, as for the characteristic X-rays emitted from the linear portion A1, only those having the wavelength λ ₁ = (2d / n) sin θ ₁ are incident on the X-ray linear sensor 14 and detected by one detection element 1411. As for the characteristic X-rays emitted from the shaped portion A2, only those having a wavelength λ ₂ = (2d / n) sin θ ₂ different from λ ₁ are incident on the X-ray linear sensor 14 and are different from the detection element 1411. Detected at 1412 (see FIGS. 1 and 3).

Therefore, the wavelength spectrum creation unit 161 acquires a signal of the X-ray intensity (number of photons) detected by each detection element 141 from the X-ray linear sensor 14 within a predetermined measurement time, and then detects the detection intensity and detection. A wavelength spectrum of characteristic X-rays emitted from the irradiation region A is created based on the wavelength to be emitted. Here, the measurement time may be appropriately determined according to the intensity of the characteristic X-rays per unit time of reaching the X-ray linear sensor 14, but as described above, the lithium ion battery 20 is disassembled to disassemble the separator 23 and the current collector. By irradiating the positive electrode material 21 with the excitation light without going through the body 24, the measurement time can be shortened.

Next, the peak wavelength determination unit 162 detects a peak from the wavelength spectrum created by the wavelength spectrum creation unit 161 and obtains the peak wavelength.

Subsequently, the chemical state specifying unit 163 selects a standard curve targeting the element based on the element possessed by the battery material to be measured, which is input in advance by the measurer from the input unit (not shown). Alternatively, the measurer may use the input unit to select the standard curve itself. Subsequently, the chemical state specifying unit 163 obtains an index representing a chemical state such as a valence corresponding to the peak wavelength obtained by the peak wavelength determining unit 162 from the selected standard curve. By the above operation, the operation of one chemical state analysis is completed.

(3) Prepared standard curve and sample analysis result The following shows the standard curve actually created in the chemical state analysis method of the present embodiment and the result of sample analysis using the standard curve.

(3-1) Standard curve prepared using a stable standard sample and analysis results In the graphs of FIGS. 4 (a) and 4 (b), chemically stable Mn ₂ O ₃ (Mn is +3 valence) and The standard curve showing the relationship between the valence of Mn and the peak energy (corresponding to the peak wavelength) created based on the results of measurement using MnO ₂ (+4 valence) as a standard sample is shown by a straight line. The horizontal axis of the graph shows the valence of Mn, and the vertical axis shows the peak energy. The standard curves shown in FIGS. 4 (a) and 4 (b) are the same. The two white circles in the figure indicate the measured value of the peak energy, and the straight line is a standard curve defined by connecting the measurement points of the two white circles with a straight line. The measurement was performed 5 times for both Mn ₂ O ₃ and Mn O ₂ , and the average value of the peak energy was taken for each. The standard deviation value was used as an error bar.

In FIG. 4A, in addition to the above standard curve, a lithium ion battery 20 using a positive electrode material 21 made of LiMn ₂ O ₄ is charged and discharged once as aging, and then charged a second time. ("SOC-0". Here, "SOC" is an abbreviation for "States of Charge"), and the same charging up to 50% capacity (SOC-50). ) And the one (SOC-100) that has been charged to 100% capacity, the peak energy values measured by the chemical state analysis method of this embodiment are indicated by black circles on the standard curve. Further, in FIG. 4 (b), in addition to the above standard curve, the same lithium ion battery 20 is charged and discharged once as aging, and then charged up to 100% for the second time (the above "SOC-". (Same as 100 "), and then discharged to 50% (referred to as" DOD-50 ". Here," DOD "is an abbreviation for" Depth of Discharge "), and discharge. The peak energy values measured by the chemical state analysis method of this embodiment are indicated by black circles on the standard curve for the 100% (up to 0% capacity) discharge (DOD-100). Similar to the standard sample, these data were also performed 5 times in each charge / discharge stage, the average value of the peak energy was taken, and the standard deviation value was used as the error bar. The values on the horizontal axis at the data points indicated by these black circles indicate the valences (chemical states) of Mn in the positive electrode material 21 in each charged or discharged state.

(3-2) Standard curve prepared using a standard sample having a plurality of elements of the same type as the battery material to be analyzed, and analysis results In the graphs of FIGS. 5 (a) and 5 (b), the material of the positive electrode material 21 is used. Li Mn 2 O 4 which is the same as Li Mn ₂ O ₄ and Li ₂ Mn O ₃ which consists of multiple elements (Li, Mn and O) of the same kind as the positive electrode material 21 were prepared based on the measurement results of the standard sample, and the valence and peak of Mn were prepared. The standard curve showing the relationship of energy (corresponding to the peak wavelength) is shown by a straight line. Similar to FIG. 4, the horizontal axis of the graph represents the valence of Mn, the vertical axis represents the peak energy, and the standard curves shown in (a) and (b) are the same. The two white circles in the figure indicate the measured value of the peak energy, and the straight line is a standard curve defined by connecting the measurement points of the two white circles with a straight line. The measurement was performed 5 times for both Li Mn ₂ O ₄ and Li ₂ MnO ₃ , the average value of the peak energy was taken for each, and the standard deviation value was used as the error bar.

FIG. 5A shows the standard curve and the lithium-ion battery 20 in the charged state of SOC-0, SOC-50 and SOC-100, respectively, in the same manner as in the example shown in FIG. 4A. The peak energy values measured by the chemical state analysis method of this embodiment are indicated by black circles on the standard curve. Further, in FIG. 5 (b), together with the above standard curve, the state of charge of SOC-100 and the state of discharge of DOD-50 and DOD-100 are lithium, as in the example shown in FIG. 4 (b). The peak energy values measured by the chemical state analysis method of the present embodiment for each of the ion batteries 20 are indicated by black circles on the standard curve. Similar to the standard sample, these data were measured 5 times at each charge / discharge stage, the average value of the peak energy was taken, and the standard deviation value was used as the error bar.

(3-3) Standard curve created using the battery materials of the secondary battery charged to the upper limit of charging voltage and the battery material of the secondary battery discharged to the end of discharge voltage as standard samples, and the analysis result In the graph of Fig. 6 (a), the upper limit of charging The positive electrode material 21 of the lithium ion battery 20 charged once to the voltage (SOC-100 (first charge)) and once charged to the upper limit voltage and then discharged once to the discharge end voltage (DOD-100 (first discharge)). ) The standard curve created by using the positive electrode material 21 of the lithium ion battery 20 as a standard sample is shown by a straight line. In this standard curve, the chemical state of SOC-100 (initial charge) is 100%, the chemical state of DOD-100 (initial discharge) is 0%, the index of these chemical states is the horizontal axis, and the peak energy value is vertical. Plots were made on the graph as axes (white circles in FIG. 6 (a)), and the two were connected by a straight line. In addition to FIG. 6A, the lithium ion battery 20 is charged to the charge upper limit voltage and discharged to the discharge end voltage once, and then charged to a capacity of 50% (SOC-50). ), And the peak energy value measured by the chemical state analysis method of this embodiment is a standard curve for the one (DOD-50) that has been charged to the upper limit voltage for the second charge and then discharged to a capacity of 50%. It is indicated by a black circle above. The value on the horizontal axis at the data points marked with black circles is an index representing the chemical state of the positive electrode material 21 in each charged or discharged state. The two standard samples, SOC-50 and DOD-50, were measured 5 times each, the average value of the peak energy was taken, and the standard deviation value was used as the error bar.

In the graph of FIG. 6B, the positive electrode material 21 of the lithium ion battery 20 is charged to the upper limit voltage and discharged to the end of discharge once, and then charged to the upper limit voltage for the second time. The standard curve created by the same method as in FIG. 6A is shown by a straight line using the positive electrode material 21 of the lithium ion battery 20 that has been discharged for the second time to the discharge end voltage as a standard sample. The data of SOC-50 and DOD-50 (black circles in the figure) are plots of peak energy values measured by the chemical state analysis method of this embodiment on a standard curve. The value on the horizontal axis at the data points marked with black circles is an index representing the chemical state of the positive electrode material 21 in each charged or discharged state. The two standard samples, SOC-50 and DOD-50, were measured 5 times each, the average value of the peak energy was taken, and the standard deviation value was used as the error bar.

(3-4) Results of measuring the chemical state of the electrode material of the secondary battery with different charge / discharge history. After performing this once, charge up to the second charge upper limit voltage and discharge up to the discharge end voltage, and use the standard curves shown in FIGS. 4 (a) and 4 (b) to perform this second charge and discharge. The result of measuring the change of the valence of Mn in the positive electrode material 21 during discharge is shown. The measurement was performed 5 times each, the peak energy value was the average value of 5 times, and the standard deviation value was used as the error bar. As shown in FIG. 7, the chemical state (valence of Mn) of the positive electrode material 21 is not different between the first charge and discharge and the second charge and discharge at the start of charging and the end of discharge, but during charging. , It became clear that there is a difference between the first and second times at the charge upper limit voltage and during discharge.

The data error bars in the standard sample and the sample to be analyzed shown so far can be reduced by lengthening the measurement time or increasing the number of measurements.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, the battery to be measured is not limited to the lithium ion battery, and various primary batteries and secondary batteries can be measured. Further, the measurement target is not limited to the positive electrode material, and any substance contained in the negative electrode material may be targeted as long as the valence changes.

Further, in the above embodiment, the lithium ion battery 20 is disassembled and the positive electrode material 21 is washed under a dry atmosphere (room temperature 20 ° C., dew point −70 ° C.), but if the positive electrode material 21 is washed, it is not under a dry atmosphere. In this state, each step after disassembling the battery may be performed. Alternatively, if each step after disassembling the battery is performed in a dry atmosphere, cleaning of the positive electrode material 21 may be omitted. Further, instead of the dry atmosphere, each step after dismantling the battery may be performed in an environment where the air is shut off.

10 ... Chemical state analyzer 11 ... Excitation source 12 ... Slit 13 ... Spectral crystal 14 ... X-ray linear sensor 141, 1411, 1412 ... Detection element 15 ... Sample holder 16 ... Data processing unit 161 ... Wavelength spectrum creation unit 162 ... Peak wavelength Determination unit 163 ... Chemical state specification unit 17 ... Standard curve data storage unit 20 ... Lithium ion battery 21 ... Positive electrode material 22 ... Negative electrode material 23 ... Separator 24 ... Current collector 25 ... Electrolyte 26, 27 ... Laminate material A ... Irradiation region S ... Sample

Claims (8)

A battery dismantling step of disassembling the battery so that the analysis target portion including the battery material to be analyzed is exposed.
An excitation line for generating characteristic X-rays of the battery material is passed directly to a predetermined irradiation region in the surface of the analysis target portion or by covering the analysis target portion and passing the excitation line and the characteristic X-ray. Excitation ray irradiation step to irradiate through the protective layer,
Characteristic X-rays generated in the irradiation region by irradiation of the excitation line are transmitted to a spectroscopic crystal composed of a flat plate provided facing the irradiation region in parallel with the irradiation region and a predetermined crystal plane of the spectroscopic crystal. There is a spectroscopic step of splitting by incident through a slit provided between the irradiation region and the spectroscopic crystal.
Characteristic X-rays dispersed by the spectroscopic crystal are detected by an X-ray linear sensor provided so that linear detection elements having a length in a direction parallel to the slit are arranged in a direction perpendicular to the slit. X-ray detection process and
A wavelength spectrum is created based on the intensity of characteristic X-rays detected by the X-ray linear sensor, a peak wavelength which is a wavelength at the peak of the wavelength spectrum is obtained, and the peak wavelength and the battery material in the analysis target portion are used. A chemical state specifying step for obtaining a value for specifying the chemical state from a standard curve showing the relationship between the value representing the chemical state and the peak wavelength.
A chemical state analysis method characterized by performing . The chemical state analysis method according to claim 1, wherein a cleaning step of cleaning the analysis target portion is performed after the battery dismantling step and before the excitation ray irradiation step . The chemical state analysis method according to claim 2, wherein the washing step is washing with an aprotic chain carbonate-based organic solvent. The chemical state analysis method according to claim 2 or 3, wherein the cleaning step is cleaning by any of a spray cleaning method, a shower cleaning method, and a dip cleaning method. The chemical state analysis method according to any one of claims 1 to 4, wherein each step from the battery dismantling step to the characteristic X-ray detection step is performed in a dry atmosphere or an environment in which air is shut off. .. A plurality of standard samples whose standard curves are chemically more stable than the battery material to be measured and contain ions consisting of one of the elements of the battery material and having different valences from each other. The chemical state analysis method according to any one of claims 1 to 5, which is prepared based on the wavelength of the peak of the wavelength spectrum obtained from each of the above and the valence thereof. The standard curve is composed of a plurality of elements of the same type as the plurality of elements of the battery material to be measured, and is composed of one of the plurality of elements and contains a plurality of ions having different valences from each other. The chemical state analysis method according to any one of claims 1 to 5, which is prepared based on the peak wavelength and the valence of the peak of the wavelength spectrum obtained from each of the standard samples. The battery is a secondary battery,
The standard curve shows the peak wavelength of the wavelength spectrum when charged to the upper limit voltage and the peak wavelength spectrum when discharged to the end-of-discharge voltage in a secondary battery containing the same type of battery material as the battery to be analyzed . The chemical state analysis method according to any one of claims 1 to 5, wherein the product is produced based on the wavelength of.

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