WO2016121687A1

WO2016121687A1 - Method for evaluating state of occlusion of lithium, method for manufacturing electrode, device for evaluating state of occlusion of lithium, and electrode manufacturing system

Info

Publication number: WO2016121687A1
Application number: PCT/JP2016/052006
Authority: WO
Inventors: 直井　雅也; 雅裕井上
Original assignee: Jsr株式会社
Priority date: 2015-01-30
Filing date: 2016-01-25
Publication date: 2016-08-04
Also published as: JPWO2016121687A1

Abstract

A layer containing an electrode active material that has occluded lithium is irradiated with light that includes visible light, and the state of occlusion of lithium is evaluated from the reflected light or reflectivity thereof.

Description

Method for evaluating lithium storage state, electrode manufacturing method, apparatus for evaluating lithium storage state, and electrode manufacturing system

Cross-reference of related applications

This international application claims priority based on Japanese Patent Application No. 2015-17055 filed with the Japan Patent Office on January 30, 2015. The entire contents are incorporated by reference into this international application.

The present disclosure relates to a method for evaluating an occlusion state of lithium, an electrode manufacturing method, an apparatus for evaluating an occlusion state of lithium, and an electrode manufacturing system.

In recent years, the progress of downsizing and weight reduction of electronic devices has been remarkable, and accordingly, the demand for downsizing and weight reduction of batteries used as power sources for driving the electronic devices has further increased. In order to satisfy such demands for reduction in size and weight, nonaqueous electrolyte secondary batteries represented by lithium ion secondary batteries have been developed as power storage devices. Moreover, a lithium ion capacitor is known as an electricity storage device corresponding to an application that requires high energy density characteristics and high output characteristics.

In such an electricity storage device, a process (generally called pre-doping) in which lithium is occluded in advance by an electrode is employed for various purposes. Various methods are known for inserting lithium into the electrode. For example, Patent Document 1 is characterized by measuring an open circuit potential between a metal serving as a lithium supply source and an electrode doped with lithium. A free doping method has been proposed. Patent Document 2 discloses a method in which lithium is occluded in the negative electrode active material layer by a so-called roll-to-roll method.

JP 2012-28729 A JP 2007-280926 A

In the method proposed in Patent Document 1, it is difficult to accurately measure the amount of occlusion of lithium. Further, it has been impossible to evaluate the uniformity of the amount of occlusion of lithium in the electrode surface in an electrode having a large area. Furthermore, in the method proposed in Patent Document 1, when an electrode production line by a roll-to-roll method or the like is to be constructed, the adaptability to the production line is poor.

In one aspect of the present disclosure, it is desirable to provide a method for evaluating an occlusion state of lithium that has not been sufficiently established.

A first aspect of the present disclosure provides a method of irradiating a layer containing an electrode active material that occludes lithium with light containing visible light and evaluating the occlusion state of lithium from the reflected light.

A second aspect of the present disclosure provides an electrode manufacturing method including a step based on the evaluation method according to the first aspect.
A third aspect of the present disclosure includes: (1) an irradiation unit that irradiates light containing visible light onto a layer containing an electrode active material that occludes lithium; and (2) a layer containing an electrode active material that occludes lithium. An apparatus for evaluating the occlusion state of lithium in an electrode active material is provided, which includes a measurement unit that receives the reflected light and measures information related to the reflected light.

The fourth aspect of the present disclosure provides an apparatus for causing the electrode active material of the electrode to occlude lithium and an electrode manufacturing system including the apparatus according to the third aspect.

</ RTI> By using the evaluation method according to the first aspect of the present disclosure and the apparatus according to the third aspect, the occlusion amount of lithium in the electrode active material can be measured accurately and extremely simply. In addition, if the evaluation method and apparatus of the present disclosure are used, it is possible to measure the amount of occlusion of lithium at an arbitrary position in the electrode surface in an electrode having a large area, so that the lithium occlusion amount in the electrode surface is uniform. Sex can also be evaluated. Therefore, the evaluation method and apparatus of the present disclosure are extremely useful for evaluating batteries such as lithium ion secondary batteries and lithium ion capacitors, or electrodes of capacitors.

By using the electrode manufacturing method according to the second aspect of the present disclosure and the manufacturing system according to the fourth aspect, the amount of occlusion of lithium in the manufactured electrode becomes constant, and in the electrode having a large area, The uniformity of the amount of occlusion of lithium increases. Therefore, the electrode manufacturing method and manufacturing system of the present disclosure are extremely useful for manufacturing a battery such as a lithium ion secondary battery and a lithium ion capacitor, or an electrode of a capacitor.

It is a model diagram explaining the structure of the apparatus which evaluates the occlusion state of lithium of this indication.

1 ... Device, 10 ... Irradiation part, 20 ... Measurement part

Hereinafter, the present disclosure will be described in detail.
[Method for evaluating the occlusion state of lithium]
The layer containing the electrode active material (hereinafter also referred to as “electrode active material layer”) is not particularly limited in form, but usually a slurry containing an electrode active material and a binder is prepared, and this is used. It is formed on the current collector by applying and drying on the current collector. Other forms of the electrode active material layer include an electrode active material deposited on a current collector by a physical method such as vapor deposition or sputtering, an electrode active material occluded with an alkali metal, and a cake made of an organic solvent. Examples thereof include a layer formed with a bar or the like.

The electrode active material is not particularly limited as long as it is an electrode active material used for a battery or a capacitor utilizing insertion / extraction of lithium ions, and may be a negative electrode active material or a positive electrode active material. Good.

Examples of the negative electrode active material include carbon materials such as graphite, graphitizable carbon, non-graphitizable carbon, and composite carbon materials in which graphite particles are coated with a carbide of pitch or resin; alloying with lithium such as Si and Sn is possible. Or a metal containing a semimetal or an oxide thereof. Specific examples of the carbon material include carbon materials described in JP2013-258392A. Specific examples of a material containing a metal, a semimetal, or an oxide thereof that can be alloyed with lithium include materials described in JP-A-2005-123175 and JP-A-2006-107795.

Examples of the positive electrode active material include transition metal oxides such as manganese oxide and vanadium oxide; sulfur-based active materials such as sulfur alone and metal sulfides.
The evaluation method of the present disclosure is suitable for evaluating a layer containing a negative electrode active material, and suitable for evaluating a layer containing a carbon material as an electrode active material.

Various methods are known for occluding lithium in the electrode active material. For example, a method of directly contacting the electrode active material layer and a lithium supply source in an organic solvent containing lithium ions, including lithium ions Electrochemical contact between an electrode having an electrode active material layer and a lithium source in an organic solvent, contact between an electrode active material layer and a lithium supply source without using an organic solvent containing lithium ions, lithium ions And a method in which the electrode active material particles and the lithium source are brought into direct contact in an organic solvent containing. Specific examples of the method for directly contacting the electrode active material layer and the lithium supply source in the organic solvent containing lithium ions are disclosed in JP-A-5-41249, JP-A-2007-280926, and the like. Specific examples of the method of electrochemically contacting an electrode having an electrode active material layer and a lithium supply source in an organic solvent containing lithium ions are described in JP-A-63-10462 and JP-A-64-14870. This is disclosed in Japanese Patent Laid-Open No. 9-293499. Specific examples of the method for bringing the electrode active material layer into contact with the lithium supply source without using the organic solvent containing lithium ions are disclosed in Japanese Patent Application Laid-Open Nos. 2007-214109 and 2008-29395. Yes. A specific example of the method of directly contacting the electrode active material particles and the lithium supply source in the organic solvent containing lithium ions is disclosed in JP 2012-209195 A and the like. An evaluation method according to the present disclosure is a method in which an electrode having an electrode active material layer and an lithium supply source are brought into electrochemical contact in an organic solvent containing lithium ions, or an electrode active material without using an organic solvent containing lithium ions It is suitable for evaluating the occlusion state of lithium in an electrode in which lithium is occluded by contacting the layer with a lithium supply source, and in particular, an electrode having an electrode active material layer and an lithium supply in an organic solvent containing lithium ions It is suitable for evaluating the occlusion state of lithium in an electrode in which lithium is occluded by a method in which the source is brought into electrochemical contact.

In the evaluation method of the present disclosure, the occlusion state of lithium in an electrode including an active material in which lithium is occluded is preferably 30% or more, more preferably 50% or more, particularly preferably 70% or more with respect to the theoretical capacity. Suitable for Moreover, it is suitable for evaluating the occlusion state of lithium in an electrode including an active material in which 95% or less of lithium is occluded with respect to the theoretical capacity.

In addition, in the range indicated by the description of “occlusion of lithium” and “occlusion of lithium” in the present disclosure, there is a case where intercalation is performed in a lithium ion state or a case where a lithium alloy is formed. included. Therefore, “lithium” in the description of “occlude lithium” or the like means lithium as an element. “Occlusion” is a concept that includes intercalation, alloying, and the like, and means that it contains a lithium element.

The visible light used in the evaluation method of the present disclosure is not particularly limited as long as it is an electromagnetic wave in the visible region (360 to 830 nm), and may be multiwavelength or single wavelength. It is preferably a monochromatic light having a wavelength or a wavelength whose reflected light intensity or reflectivity changes functionally with occlusion of lithium, and more preferably a multi-wavelength. When the visible light used in the evaluation method of the present disclosure has a single wavelength, it is preferable to select one monochromatic light in the range of 600-780 nm, and in particular, select one monochromatic light in the range of 650-780 nm. It is preferable. Within the above range, when the electrode active material layer before lithium occlusion is compared with the electrode active material layer having a high lithium occlusion rate, the rate of change in reflectance (or reflected light intensity) tends to increase. It is. The multi-wavelength visible light is preferably white light or contains two types of monochromatic light having different wavelengths. When such irradiation light is used, when the reflected light intensity or reflectance varies depending on the degree of flatness of the electrode active material layer surface, the reflectance (or reflected light intensity) at two wavelengths is measured, and the difference between them is measured. This is because the influence of the fluctuation on the evaluation result can be reduced by obtaining the ratio or the ratio. Further, when white light is used as the irradiation light, it is possible to measure and evaluate the color value and color difference value from the reflected light. The two types of monochromatic light having different wavelengths are preferably two types of monochromatic light having wavelengths different from each other by 50 nm or more, particularly monochromatic light in the range of 380 to 500 nm and monochromatic light in the range of 600 to 780 nm. It is preferable to include. Examples of the light source include a halogen lamp and a xenon lamp as a white light source, and an LED as a monochromatic light source. In the present disclosure, monochromatic light means light having a half width of 50 nm or less. Further, in the present disclosure, for example, monochromatic light in the range of 600-780 nm means that the wavelength showing the maximum intensity in the spectrum of monochromatic light is in the range of 600-780 nm.

In the evaluation method of the present disclosure, it is preferable to irradiate light including visible light in an environment provided with a light-shielding portion so as to reduce the influence of disturbance light, and evaluate the occlusion state of lithium from the reflected light.

In the evaluation method of the present disclosure, the intensity or reflectance of reflected light may be measured and the result may be used, or the color value or color difference value may be measured from the reflected light and the result may be used. Among these, it is preferable to use a reflectance that is not easily affected by fluctuations in irradiation light. When using reflected light intensity or reflectance, it is preferable to use reflected light intensity or reflectance at one or two or more different wavelengths. When using reflected light intensity or reflectance at a plurality of different wavelengths, for example, the reflected light intensity or reflectance at two specific wavelengths can be measured and evaluated using the difference or ratio. it can.

When the irradiation light includes white light, the reflected light is dispersed, and then the spectral reflection intensity or spectral reflectance at one specific wavelength is measured, or the spectral reflectance at two wavelengths is measured, and the difference or It is preferable to evaluate the occlusion state of lithium by determining the ratio. The specific wavelength is preferably a specific wavelength in the range of 600 to 780 nm, and particularly preferably a specific wavelength in the range of 650 to 780 nm. Within the above range, when the electrode active material layer before lithium occlusion is compared with the electrode active material layer having a high lithium occlusion rate, the rate of change in reflectance (or reflected light intensity) tends to increase. It is. The two wavelengths are preferably two wavelengths different from each other by 50 nm or more, particularly a specific wavelength in the range of 380-500 nm and a specific wavelength in the range of 600-780 nm. It is preferable. Since the spectral reflection intensity and the spectral reflectivity vary depending on the degree of flatness of the surface of the electrode active material layer, etc., in order to accurately measure the amount of occlusion of lithium, the spectral reflectivity at two wavelengths is measured and the difference between them is measured. Alternatively, it is preferable to determine the ratio, and it is particularly preferable to measure the spectral reflectance at two wavelengths and determine the difference. When comparing the electrode active material layer before lithium occlusion with the electrode active material layer with high lithium occlusion, the difference in spectral reflectance and the rate of change of the ratio are large. It is preferable to measure the spectral reflectance and obtain the difference.

On the other hand, when the visible light contained in the irradiation light is monochromatic light, the occlusion state of lithium can be evaluated by measuring the reflected light intensity or reflectance. In addition, when the irradiation light includes two types of monochromatic light having different wavelengths, the occlusion state of lithium can be evaluated by measuring the reflectance and obtaining the difference or ratio. In such a case, the irradiation light is preferably two types of monochromatic light having wavelengths different from each other by 50 nm or more, and particularly preferably includes monochromatic light in the range of 380 to 500 nm and monochromatic light in the range of 600 to 780 nm. . Reflection intensity and reflectivity vary depending on the degree of flatness of the active material layer surface. Therefore, in order to accurately measure the amount of occlusion of lithium, it is necessary to irradiate light containing two types of monochromatic light having different wavelengths. It is preferable to measure the reflectance of the light and to determine the difference or ratio. In particular, it is possible to irradiate light containing two types of monochromatic light having different wavelengths, measure the reflectance, and obtain the difference. preferable. When comparing the electrode active material layer before lithium occlusion with the electrode active material layer with high lithium occlusion, the difference in reflectance and the rate of change of the ratio are large. It is preferable to irradiate light including light, measure the reflectance, and obtain the difference.

In the present disclosure, the occlusion rate of lithium can be obtained by applying the reflectance difference between the specific wavelengths obtained as described above to a calibration curve prepared in advance. When such an evaluation method is applied, the occlusion rate of lithium can be traced while occluding lithium in the electrode active material. The calibration curve can be prepared by measuring the difference in reflectance between specific wavelengths in the same manner for an electrode active material layer with a known lithium occlusion rate and plotting the result. The electrode active material layer with a known lithium occlusion rate is prepared, for example, by passing a direct current between an electrode having an electrode active material layer and a lithium supply source in an organic solvent containing lithium ions. Can do. At that time, the occlusion rate of lithium is determined by the energization amount and the irreversible capacity of the electrode. In addition, since the aspect of the change of the hue accompanying lithium occlusion differs depending on the type of electrode active material and the composition of the electrode active material layer, the above calibration curve is prepared for each type of electrode active material and the composition of the electrode active material layer. There is a need to.

Further, in the present disclosure, the lithium occlusion in the surface of the electrode active material layer is measured by measuring a difference in reflectance between specific wavelengths as described above at a plurality of locations of the electrode active material layer having a large area. The amount uniformity can be evaluated.

The evaluation method of the present disclosure is suitable for evaluating an electrode active material layer constituting a negative electrode of a battery or a capacitor. More specifically, it is suitable for the evaluation of the electrode active material layer constituting the negative electrode of a lithium ion capacitor, lithium air battery, or lithium sulfur battery, and particularly suitable for the evaluation of the electrode active material layer constituting the negative electrode of the lithium ion capacitor. ing.
[Method for producing electrode]
The manufacturing method of the electrode of this indication includes the process of evaluating the occlusion state of lithium in an electrode active material by the evaluation method of this indication. The electrode is not particularly limited as long as it is a battery or capacitor electrode that utilizes insertion / extraction of lithium ions, but is preferably the negative electrode of the battery or capacitor, and is a lithium ion capacitor, lithium sulfur battery or A negative electrode of a lithium air battery is more preferable, and a negative electrode of a lithium ion capacitor is particularly preferable.

Although the manufacturing method of the electrode of this indication is not specifically limited, (A) The process of forming an electrode active material layer, (B) The process of occluding lithium in an electrode active material, and (C) Evaluation of this indication It is preferable that the method includes a step of evaluating the occlusion state of lithium in the electrode active material.

In the step (A), the electrode active material layer is usually produced by preparing a slurry containing an electrode active material and a binder, applying the slurry on a current collector, and drying the slurry.
As the electrode active material, those already exemplified in the above “method for evaluating the occlusion state of lithium” can be used.

Examples of the binder include rubber-based binders such as styrene-butadiene rubber (SBR) and NBR; fluorine-based resins such as polytetrafluoroethylene and polyvinylidene fluoride; polypropylene, polyethylene, and JP 2009-246137 A And fluorine-modified (meth) acrylic binders as disclosed in the above.

The electrode active material layer further includes a conductive agent such as carbon black, graphite, vapor-grown carbon fiber, metal powder; carboxyl methyl cellulose, its Na salt or ammonium salt, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol Further, a thickener such as oxidized starch, phosphorylated starch, or casein may be contained.

The thickness of the electrode active material layer is not particularly limited, but is usually 5 to 500 μm, preferably 10 to 200 μm, particularly preferably 10 to 100 μm. The density of the electrode active material layer is preferably 1.50 to 2.00 g / cc, particularly preferably 1.60 to 1.90 g / cc when the electrode is used in a lithium ion secondary battery. In the case of an electrode used for an ion capacitor, it is preferably 0.50 to 1.50 g / cc, particularly preferably 0.70 to 1.20 g / cc.

As the material of the current collector, copper, nickel, stainless steel and the like are preferable as the negative electrode current collector, while aluminum, stainless steel and the like are preferable as the positive electrode current collector. The thickness of the current collector is usually 5 to 50 μm for both positive and negative electrodes.

(B) The process is not particularly limited, and a known method can be adopted. The specific embodiment is as already described in the above “method for evaluating the occlusion state of lithium”.

(C) Process may be performed in parallel with (B) process, or may be performed after (B) process. Moreover, it is preferable to perform (C) process in the environment provided with the light-shielding part so that the influence of disturbance light may become small.

The manufacturing method of the present disclosure is suitable for manufacturing a negative electrode of a battery or a capacitor, but a battery or a capacitor including a negative electrode manufactured by the manufacturing method of the present disclosure separately manufactures a negative electrode manufactured by the manufacturing method of the present disclosure. It can manufacture by accommodating in the exterior body with the made positive electrode. In addition to the positive electrode and the negative electrode, an electrolyte capable of generating lithium ions is supplied into the exterior body. The electrolyte is usually used in the state of an electrolytic solution dissolved in a solvent. Examples of the electrolyte capable of generating lithium ions include LiClO4, LiAsF6, LiBF4, LiPF6, LiN (C2F5SO2) 2, LiN (CF3SO2) 2, LiN (FSO2) 2, LiC4BO8, and the like. These can be used alone or in admixture of two or more.

As the solvent for dissolving the electrolyte, an aprotic organic solvent is preferable. Specifically, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxy Examples include ethane, tetrahydrofuran, dioxolane, methylene chloride, sulfolane and the like. Further, ionic liquids such as quaternary imidazolium salts, quaternary pyridinium salts described in JP-A-11-307121, and quaternary pyrrolidinium salts described in JP2012-142340A can also be used. These organic solvents can be used alone or in admixture of two or more.

The concentration of the electrolyte in the electrolytic solution is preferably 0.1 mol / L or more, and more preferably in the range of 0.5 to 1.5 mol / L in order to reduce the internal resistance due to the electrolytic solution. preferable. The electrolyte also contains additives such as vinylene carbonate, vinyl ethylene carbonate, 1-fluoroethylene carbonate, 1- (trifluoromethyl) ethylene carbonate, succinic anhydride, maleic anhydride, propane sultone, diethylsulfone, and the like. It may be.

The electrolyte is usually prepared and used in a liquid state as described above, but a gel or solid electrolyte may be used. In this case, for example, leakage can be suppressed.
When the electrolyte is used in the state of an electrolyte, a separator is usually provided between the positive electrode and the negative electrode so that the positive electrode and the negative electrode are not in physical contact. As a separator, the nonwoven fabric or porous film which uses a cellulose rayon, polyethylene, a polypropylene, polyamide, polyester, a polyimide etc. as a raw material can be mentioned, for example.

As the structure of the battery or capacitor manufactured as described above, for example, a laminated cell in which a laminate in which three or more plate-like positive electrodes and negative electrodes are laminated via a separator is enclosed in an exterior film A wound cell or the like in which a laminated body in which a strip-like positive electrode and a negative electrode are wound through a separator is housed in a rectangular or cylindrical container can be given.
[Equipment for evaluating the occlusion state of lithium]
The apparatus 1 for evaluating the lithium occlusion state in the electrode 50 including the electrode active material that occludes lithium using the method for evaluating the occlusion state of lithium according to the present disclosure will be described with reference to FIG. As shown in FIG. 1, the apparatus 1 mainly includes an irradiation unit 10, a measurement unit 20, a shielding unit 30, and an evaluation unit 40. In addition, although this embodiment is applied and demonstrated to the example with which the shielding part 30 is provided in the apparatus 1, the shielding part 30 does not need to be provided.

The irradiation unit 10 irradiates the electrode 50 to be evaluated with visible light as irradiation light, and is disposed inside the shielding unit 30 together with the electrode 50 and the measurement unit 20. The wavelength of the visible light applied to the electrode 50 by the irradiating unit 10 is not particularly limited, but is preferably multi-wavelength light or monochromatic light (hereinafter referred to as multi-wavelength light) included in a wavelength region of at least 600 to 780 nm. And monochromatic light is also simply referred to as “light”.), More preferably, light included in the wavelength range of 380 to 500 nm and light included in the wavelength range of 600 to 780 nm. In particular, it preferably has at least light included in a wavelength region of 380 to 500 nm and light included in a wavelength region of 650 to 780 nm.

As a light source that generates visible light in the irradiation unit 10, a light source that emits white light using a halogen lamp, a xenon lamp, or the like may be used, or a plurality of monochromatic lights that use LEDs (light emitting diodes) or the like may be emitted. It may be an aggregate of the light sources. In the present embodiment, description will be made by applying to an example of a light source that emits white light using a pulsed xenon lamp.

In the present embodiment, the irradiation unit 10 will be described by applying to an example in which the evaluation unit 40 does not control the start or stop of irradiation of visible light, the intensity, wavelength, or irradiation direction of irradiation light. The start and stop of visible light irradiation, the intensity, wavelength, and irradiation direction of irradiation light may be controlled by the unit 40, and the form is not particularly limited.

The measuring unit 20 detects the reflected light of the electrode 50 irradiated with the irradiated light, and measures the reflectance of the reflected light (corresponding to information related to the reflected light). Note that the measurement unit 20 may measure the intensity, color value, or color difference value of the detected reflected light in addition to the above-described reflectance as the information related to the reflected light. In the present embodiment, description will be made by applying to an example in which the reflectance is less affected by the fluctuation of the irradiation light compared to the intensity, color value, and color difference value.

In the present embodiment in which the irradiation light is white light, the measurement unit 20 is provided with a spectroscopic unit (not shown) that splits the incident reflected light. Examples of the spectroscopic means in the spectroscopic unit include a prism, a diffraction grating, and an optical filter. In the present embodiment, description will be made by applying to an example in which a planar diffraction grating is used as a spectroscopic means. Moreover, in this embodiment, before evaluating the sample to be evaluated, the white standard sample is irradiated with white light, and the spectral spectrum of the reflected light is stored in the measuring unit 20. Description will be made by applying to an example in which white light is irradiated and the reflectance is measured from the spectrum of the reflected light and the spectrum of the standard sample stored in advance.

The measurement unit 20 is configured to measure the reflectance of light separated by the spectroscopic unit (hereinafter also referred to as “spectral reflectance”) and output a measurement signal related to the spectral reflectance to the evaluation unit 40. . Configurations for outputting measurement signals include configurations using wired communication that outputs measurement signals via cables, configurations using wireless communication that outputs measurement signals using radio waves, etc., and measurement signals using information recording media. An example of a configuration to output can be given. In the present embodiment, description will be made by applying the configuration in which the measurement signal is output to an example in which wired communication is performed.

Note that when the irradiation light is a single monochromatic light or two types of monochromatic lights having different wavelengths, the above-described spectroscopic unit may not be provided in the measurement unit 20.
Further, in the present embodiment, the measurement unit 20 will be described by applying to an example in which the evaluation unit 40 does not control the timing of performing reflectance measurement, measurement signal output, or the like. The timing for measuring the rate, outputting the measurement signal, and the like may be controlled.

The shielding unit 30 can accommodate the irradiation unit 10, the electrode 50, and the measurement unit 20 inside, and suppresses the incidence of light from the outside to the inside. In other words, when the reflectance of reflected light is measured by the measurement unit 20, the influence of disturbance light is suppressed. In addition, as the shielding part 30, what has a various structure using a well-known material can be used, and the form is not specifically limited.

The evaluation unit 40 evaluates the occlusion state of lithium in the electrode 50 based on the measurement signal input from the measurement unit 20. The evaluation unit 40 is a computer system having a CPU (Central Processing Unit), ROM, RAM, hard disk, input / output interface, and the like. The control program stored in the ROM or the like causes the CPU to function as the calculation unit 41, causes the input / output interface or the like to function as the transmission / reception unit 42, and causes the hard disk or the like to function as the storage unit 43. .

The calculation unit 41 performs calculation for evaluating the occlusion state of lithium in the electrode 50 based on the measurement signal. In this embodiment, a Gaussian distribution in a graph in which the difference between the spectral reflectance at a wavelength of 700 nm and the spectral reflectance at a wavelength of 440 nm is calculated, the horizontal axis is the lithium occlusion rate, and the vertical axis is the spectral reflectance difference. Calculation processing for creating a calibration curve by fitting a curve or quadratic curve, calculation processing for obtaining a correlation coefficient (R ² ) in the created calibration curve, and calculation processing for determining the lithium occlusion rate based on the created calibration curve The explanation is applied to an example. A calibration curve having a correlation coefficient (R ² ) equal to or greater than a certain value is stored in the storage unit 43.

The transmission / reception unit 42 receives the measurement signal output from the measurement unit 20. Furthermore, when outputting the evaluation result by the calculating part 41 to the outside, or displaying on the display etc., the signal regarding an evaluation result is also output. When the evaluation unit 40 controls the irradiation unit 10 and the measurement unit 20, a signal for performing the control is output to the irradiation unit 10 and the measurement unit 20.

The storage unit 43 stores information on the calibration curve input from the outside, the value of the correlation coefficient (R ² ) obtained by the calculation unit 41, the measurement signal input via the transmission / reception unit 42, and the like. It is. Further, when stored information or the like becomes necessary in the above-described calculation processing, it is also output to the calculation unit 41.
[Electrode manufacturing system]
The electrode manufacturing system of the present disclosure includes an apparatus for causing the electrode active material to store lithium and the evaluation apparatus of the present disclosure.

A device for inserting lithium into the electrode active material is not particularly limited. For example, a device for directly contacting the electrode active material layer and a lithium supply source in an organic solvent containing lithium ions, Examples include an apparatus for electrochemically contacting an electrode having an electrode active material layer in an organic solvent containing and a lithium supply source, and an apparatus for contacting an electrode active material layer and a lithium supply source without using an organic solvent containing lithium ions. It is done. Specific examples thereof include the examples of JP-A-5-41249, the examples of JP-A-10-308212, the examples of JP-A-2007-214109, the examples of JP-A-2007-280926, and the JP-A-2008. Examples disclosed in JP-A No. 1244007, JP 2012-49543 A, JP 2012-49544 A, and the like.

Prior to occluding lithium in the electrode active material, a slurry containing the electrode active material or the like is usually prepared, and this is applied onto the current collector and dried to form an electrode active material layer on the current collector. The formed electrode precursor is manufactured. As a device for forming the electrode active material layer on the current collector, a known device can be employed.

It is preferable that the evaluation apparatus of the present disclosure includes a light shielding unit or the evaluation apparatus of the present disclosure is installed in an environment including the light shielding unit so that the influence of disturbance light is reduced.
The manufacturing system of this indication is suitable for manufacture of the negative electrode of a battery or a capacitor. More specifically, it is suitable for the production of negative electrodes for lithium ion capacitors, lithium air batteries, and lithium sulfur batteries, and is particularly suitable for the production of negative electrodes for lithium ion capacitors.

Hereinafter, embodiments of the present disclosure will be described more specifically with reference to examples. However, the present disclosure is not limited to the following examples. The following examples were carried out in an air environment controlled at an air temperature of 23 ° C. and a dew point of −40 ° C.
<Manufacture of negative electrode for lithium capacitor and creation of calibration curve>
A negative electrode active material layer having a thickness of 52 mm × 52 mm and a thickness of 40 μm is provided along the longitudinal direction of the current collector on both sides of a current collector made of a copper foil having a thickness of 70 mm × 382 mm, a thickness of 15 μm, and a surface roughness Ra = 0.1 μm. A negative electrode precursor was prepared by forming six locations each. At this time, the negative electrode active material layer unformed portion having a width of 18 mm extending along the longitudinal direction at one end portion of the long side of the current collector, and both ends of the short side of the current collector and the negative electrode active material layer are short. A negative electrode active material layer-unformed portion having a width of 10 mm extending in the direction was provided. Note that the negative electrode active material layer includes graphite (active material), carboxymethylcellulose, acetylene black (conductive agent), a binder, and a dispersant (88: 3: 5: 3: 1 in mass ratio).

A lithium electrode was prepared by attaching six lithium metal plates of 50 mm × 50 mm and 1 mm thickness as a lithium supply source on a copper plate of 2 mm with an interval of 12 mm between each other. Two such lithium electrodes were produced.

The lithium electrodes were arranged on both sides of the negative electrode precursor so that the negative electrode active material layer and the lithium metal plate faced through a separator made of a polypropylene nonwoven fabric having a thickness of 1 mm. Under the present circumstances, the negative electrode precursor and the lithium electrode were arrange | positioned so that the negative electrode active material layer and center position of a lithium metal plate may correspond substantially.

The negative electrode precursor, the separator and the lithium electrode were sandwiched and fixed by a resin holding part, and inserted into a SUS chamber equipped with a liquid level sensor. At this time, a negative electrode precursor or the like was inserted so that the negative electrode active material layer unformed portion having a width of 18 mm provided at the end of the long side of the current collector was positioned on the upper side in the chamber. Thereafter, the inside of the chamber was decompressed through a resin decompression pipe connected to the lower portion of the chamber using a scroll type dry vacuum pump. After reducing the pressure in the chamber to 100 Pa, the cock provided in the decompression pipe was closed.

Next, a solution containing 1.2 M LiPF6 and 3% by mass of 1-fluoroethylene carbonate (solvent is ethylene carbonate / ethyl methyl carbonate / solvent) through a resin electrolyte supply pipe connected to the lower part of the chamber. Dimethyl carbonate = 3/4/3 (volume ratio) mixed solvent). When the liquid level of the solution containing LiPF6 and the like reached 5 mm above the upper end of the active material layer, the cock provided in the electrolyte supply pipe was closed.

Next, the leak valve provided at the top of the chamber was opened, and the chamber internal pressure was returned to atmospheric pressure. Next, the negative electrode precursor and the lithium electrode were connected to a DC power source with a current / voltage monitor via a doping electrode provided in the upper part of the chamber, and a current of 300 mA was applied. In consideration of the irreversible capacity, the energization time was set so that the lithium occlusion rate was 40% with respect to the theoretical capacity of graphite (372 mAh / g). The irreversible capacity was estimated in advance by measuring the discharge capacity of the negative electrode after occlusion of lithium. As described above, a negative electrode for a lithium ion capacitor in which lithium was occluded was manufactured.

The obtained negative electrode was taken out from the chamber, and the spectral reflectance was measured at 10 points of the negative electrode active material layer using a spectrocolorimeter (CM-700d manufactured by Konica Minolta Co., Ltd.). At this time, the light applied to the negative electrode active material layer is white light using a pulse xenon lamp as a light source. Moreover, since the measurement is performed by bringing the spectrocolorimeter into contact with the negative electrode active material layer, the influence of ambient light is extremely small.

Except that the energization time was set longer, in the same manner as described above, negative electrodes with lithium storage rates of 70%, 80%, 85%, 90%, 95%, and 100% were produced, and the spectral reflectance was measured. .

The measured data is transmitted to a personal computer, and the difference between the spectral reflectance at a wavelength of 700 nm and the spectral reflectance at a wavelength of 440 nm (spectral reflectance at a wavelength of 700 nm−spectral reflection at a wavelength of 440 nm) for seven types of negative electrodes with different lithium storage rates. Rate, hereinafter also referred to as “spectral reflectance difference”). The obtained results were plotted with the horizontal axis representing the lithium occlusion rate and the vertical axis representing the spectral reflectance difference, and a calibration curve was obtained by fitting a Gaussian distribution curve. The correlation coefficient (R ² ) when a Gaussian distribution curve was fitted was 0.989. Further, in the negative electrode having an occlusion rate of lithium of 85%, the dispersion (standard deviation) in the spectral reflectance difference when the five measurement points were measured five times (measured 25 times in total) was 0.12. .

On the other hand, when the obtained results were plotted with the horizontal axis representing the lithium occlusion rate and the vertical axis representing the spectral reflectance at a wavelength of 700 nm and a Gaussian distribution curve was fitted, the correlation coefficient (R2) was 0.615. . In addition, in a negative electrode having an occlusion rate of 85%, the dispersion (standard deviation) in spectral reflectance at a wavelength of 700 nm when five measurement points were measured five times (total 25 measurements) was 0.22. there were. When the horizontal axis is the lithium occlusion rate and the vertical axis is the spectral reflectance at a wavelength of 700 nm, the results when the lithium occlusion rate is 40%, 70%, 80%, and 85% are plotted and a quadratic curve is fitted. The correlation coefficient (R ² ) was 0.948.
<Evaluation of lithium storage rate>
In the above <Manufacture of negative electrode for lithium capacitor and creation of calibration curve>, in the same manner as described above except that the negative electrode precursor and the lithium electrode were externally short-circuited, a negative electrode for lithium ion capacitor having occluded lithium was manufactured, Spectral reflectance was measured and the spectral reflectance difference was determined. Moreover, the discharge capacity was measured about the negative electrode separately manufactured on the same conditions. The lithium storage rate obtained by applying the obtained spectral reflectance difference to the calibration curve was consistent with the lithium storage rate obtained from the discharge capacity.

Claims

A method in which a layer containing an electrode active material that occludes lithium is irradiated with light containing visible light, and the occlusion state of lithium is evaluated from the reflected light.
A method of evaluating the occlusion state of lithium from the reflectance by irradiating a layer containing an electrode active material occluded with lithium with light containing visible light.
The method according to claim 2, wherein the occlusion state of lithium is evaluated using reflectance at one or two or more different wavelengths.
The layer containing the electrode active material that occludes lithium is irradiated with white light, the reflected light is dispersed, and then the difference or ratio of spectral reflectance at two different wavelengths is measured to determine the occlusion state of lithium. How to evaluate.
The method according to claim 4, wherein the difference or ratio of spectral reflectances at two different wavelengths is a difference or ratio of spectral reflectances at two different wavelengths of 50 nm or more.
The difference or ratio of the spectral reflectances at two wavelengths different from each other by 50 nm or more is a spectral reflectance at a specific wavelength in the range of 380-500 nm and a spectral reflectance at a specific wavelength in the range of 600-780 nm. The method of claim 5, wherein the difference or ratio.
Evaluate the occlusion state of lithium by irradiating a layer containing an electrode active material that occludes lithium with light containing monochromatic light in two visible regions having different wavelengths and measuring the difference in reflectance between them. Method.
The method according to claim 7, wherein the monochromatic lights in the two visible regions having different wavelengths are two monochromatic lights having wavelengths different from each other by 50 nm or more.
The method according to claim 8, wherein the monochromatic light in the two visible regions whose wavelengths are different from each other by 50 nm or more are monochromatic light in the range of 380-500 nm and monochromatic light in the range of 600-780 nm.
The method according to any one of claims 1 to 9, wherein the electrode active material that occludes lithium is a negative electrode active material.
The method according to any one of claims 1 to 10, wherein the electrode active material contains a carbon material.
A method for producing an electrode comprising a step of evaluating the occlusion state of lithium in the electrode active material by the method according to any one of claims 1 to 11.
(1) an irradiation unit that irradiates light containing visible light to a layer containing an electrode active material that occludes lithium; and (2) receives reflected light from the layer containing an electrode active material that occludes lithium, and reflects the reflected light. The apparatus for evaluating the occlusion state of lithium in an electrode active material provided with the measurement part which measures the information regarding.
An apparatus for storing lithium in the electrode active material, and an electrode manufacturing system comprising the apparatus according to claim 13.