CN111902977A - Detection method - Google Patents

Detection method Download PDF

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CN111902977A
CN111902977A CN201980022094.3A CN201980022094A CN111902977A CN 111902977 A CN111902977 A CN 111902977A CN 201980022094 A CN201980022094 A CN 201980022094A CN 111902977 A CN111902977 A CN 111902977A
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atmosphere
ionization potential
sample
secondary battery
lithium ion
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CN111902977B (en
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手嶋胜弥
是津信行
山田哲也
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Shinshu University NUC
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    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
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    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H—ELECTRICITY
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Abstract

A detection method for detecting the surface electron state of an electrode material for a lithium ion secondary battery or a solid electrolyte material under atmospheric pressure detects the surface electron state of the electrode material for a lithium ion secondary battery from the ionization potential inherent to the electrode material for a lithium ion secondary battery or the solid electrolyte material.

Description

Detection method
Technical Field
The present invention relates to a detection method for detecting a surface electron state of a material for a lithium ion secondary battery.
The present application claims priority from Japanese application No. 2018-066495 filed on 3/30.2018, the contents of which are incorporated herein by reference.
Background
Lithium ion secondary batteries have been put to practical use as small-sized power sources for mobile phone applications, notebook computer applications, and the like. Further, application to a medium-or large-sized power source for automobile use, power storage use, or the like has been attempted. In order to improve and maintain the performance of the lithium ion secondary battery, various studies have been made on a method for detecting the performance of the lithium ion secondary battery itself or the material thereof.
For example, patent document 1 describes a method for detecting a secondary battery for detecting an internal short circuit of the secondary battery.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 2012-104276
Disclosure of Invention
Problems to be solved by the invention
Lithium ion secondary batteries use lithium composite oxide and non-oxide powders as electrode active materials or solid electrolytes. The surface of the lithium composite oxide is deteriorated when exposed to the atmosphere. As an example of the deterioration phenomenon, there is a case where a resistive layer is formed on the surface by reaction with moisture in the atmosphere. The occurrence of such a deterioration phenomenon causes deterioration of the performance of the lithium ion secondary battery. In addition, when the crystal structure is disordered due to the generation of cation shuffling, lattice defects, or the like, the battery performance is greatly deteriorated.
Therefore, there is a need for a detection method that can accurately predict the performance of a material for a lithium ion secondary battery, which is used as a raw material of the lithium ion secondary battery, in a short time without performing a battery test.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for accurately detecting, in a short time, the surface electron state that generates a surface resistance layer having a thickness of 10nm from the atomic layer level or that affects the performance of a lithium ion secondary battery material, such as disturbance of the crystal structure. Therefore, the performance of the material for a lithium ion secondary battery used as a raw material for a lithium ion secondary battery can be accurately predicted in a short time without performing a battery test.
Means for solving the problems
The present invention includes the following [1] to [9 ].
The present invention in its first aspect provides the detection method as recited in [1 ].
[1] A detection method for detecting the surface electron state of an electrode material for a lithium ion secondary battery or a solid electrolyte material under atmospheric pressure, comprising a detection step in which the surface electron state of the electrode material for a lithium ion secondary battery is detected from the ionization potential inherent to the electrode material for a lithium ion secondary battery or the solid electrolyte material.
The method of the first aspect preferably comprises the following features.
[2] The detection method according to [1], wherein the ionization potential is measured by an atmospheric ultraviolet photoelectron spectroscopic analyzer.
[3] The detection method according to [1] or [2], the detection step comprising the steps of:
measuring an ionization potential of an electrode material or a solid electrolyte material for a lithium ion secondary battery immediately after exposure to the atmosphere using an atmospheric ultraviolet photoelectron spectroscopic analyzer;
thereafter further exposing the electrode material or solid electrolyte material for a lithium ion secondary battery to the atmosphere, and measuring the ionization potential of the material after further exposure to the atmosphere using the device;
determining whether the ionization potential measured for the material after further exposure to the atmosphere is lower than the ionization potential immediately after exposure to the atmosphere; and
when the determination is made to be lower, it is determined that deterioration of the surface of the electrode material for a lithium ion secondary battery has occurred.
Further, the present invention also includes the following aspects.
[4] The detection method according to [3], wherein the measurement immediately after the exposure to the atmosphere is performed within 0 to 5 minutes after the exposure of the material to the atmosphere.
[5] The detection method according to [1], comprising the steps of:
preparing an electrode material or a solid electrolyte material for a lithium ion secondary battery as a first sample;
changing the exposure time of the material after the material is exposed to the atmosphere for more than one time, measuring the exposure time for more than one time, and obtaining more than one ionization potential value;
saving the value;
preparing a second sample composed of a compound having the same chemical composition as the first sample;
measuring the ionization potential of the second sample;
comparing the stored value of the first sample with the measured value of the second sample; and
and determining the surface electron state of the second sample according to the comparison result.
[6] The detection method according to [1], comprising the steps of:
comparing a measurement result obtained by exposing the electrode material for a lithium ion secondary battery or the solid electrolyte material to the atmosphere and measuring an ionization potential thereof with at least one of a STEM-ADF measurement and an EELS measurement of the material after the exposure to the atmosphere; and
and determining the surface electronic state of the material according to the comparison result.
[7] The detection method according to [5], comprising the steps of:
comparing the value of the ionization potential of the first sample after exposure to the atmosphere with at least one of the STEM-ADF measurement and the EELS measurement of the material after exposure to the atmosphere; and
and determining the surface electronic state of the material according to the comparison result.
[8] The detection method according to [1], comprising the steps of:
comparing a measurement result obtained by exposing the electrode material for a lithium ion secondary battery or the solid electrolyte material to the atmosphere and measuring an ionization potential thereof with a measurement result obtained by using the material for a battery and measuring a discharge capacity; and
and determining the surface electronic state of the material according to the comparison result.
[9] The detection method according to [5], wherein the second sample is a separately stored material, and the step of comparing the stored value of the first sample with the measured value of the second sample is used to determine whether or not the second sample can be used for manufacturing a battery.
Effects of the invention
According to the present invention, it is possible to provide a method for accurately detecting a surface electron state closely related to the performance of a material for a lithium ion secondary battery or a solid electrolyte material used for a lithium ion secondary battery in a short time.
Drawings
FIG. 1 is a schematic view showing LiNi0.82Co0.15Al0.03O2Graph of the measurement results of powder X-ray diffraction measured immediately after exposure of the particles to the atmosphere and at regular intervals thereafter.
FIG. 2 is a schematic diagram showing LiNi0.82Co0.15Al0.03O2Graph showing the measurement results of ionization potential measured immediately after exposure of the particles to the atmosphere and at regular intervals thereafter.
FIG. 3 is a schematic view showing LiNi0.82Co0.15Al0.03O2Graph of the results of EELS measurements measured after 3 hours exposure of the particles to the atmosphere.
FIG. 4 is a graph showing LiNi0.82Co0.15Al0.03O2Graph of STEM-ADF observations measured 3 hours after exposure of the particles to the atmosphere.
Detailed Description
Preferred examples for carrying out the invention are described in detail below. The following description is of specific embodiments for better understanding of the principles of the invention and is not intended to limit the invention unless otherwise specified. Within the scope of the present invention, unless otherwise specifically limited, time, frequency, timing, number, amount, material, shape, position, kind, and the like may be changed, added, and/or omitted as necessary.
< detection method >
The present invention is a detection method for detecting the surface electron state of an electrode material or a solid electrolyte material for a lithium ion secondary battery in the atmosphere.
The present invention measures the ionization potential of an electrode material or a solid electrolyte material for a lithium ion secondary battery. The ionization potential of the electrode material or solid electrolyte material for a lithium ion secondary battery, which is inherent in the material, is measured. Furthermore, the so-called intrinsic ionization potential may be, for example, an ionization potential under a condition that the time of exposure to the atmosphere is very short.
According to the present invention, it is possible to detect a lithium ion secondary battery material such as an electrode or an electrolyte in an atmosphere in a relatively short time, for example, within 5 minutes per sample, without performing any special pretreatment or the like. In the present invention, the atmospheric pressure may be a standard atmospheric pressure, or may be a state in which pressure reduction or pressurization is not performed by a special device. The term "under the atmosphere" may mean an atmospheric environment.
Preferably, the ionization potential is measured by an atmospheric ultraviolet photoelectron spectroscopic analyzer.
In the present embodiment, examples of the "electrode material for a lithium ion secondary battery" include a positive electrode active material for a lithium ion secondary battery and a negative electrode active material for a lithium ion secondary battery. Specific examples thereof include lithium composite metal oxides containing lithium and one element selected from the group consisting of cobalt, nickel, manganese and aluminum as main components.
More specific examples of the lithium composite metal oxide include lithium nickel cobalt aluminum composite oxide, lithium nickel manganese composite oxide, and the like.
In the present embodiment, the term "solid electrolyte material" refers to a material used for an electrolyte material of an all-solid battery. Specific examples thereof include a sulfide solid electrolyte, an oxide solid electrolyte, a lithium-containing sulfide, a lithium-containing metal oxide, a lithium-containing nitride, and lithium phosphate.
The shape and size of the electrode material or solid electrolyte material are not particularly limited, and may be a particle or a bulk.
First embodiment
In the detection method of the present embodiment, the ionization potential of the electrode material or solid electrolyte material for a lithium ion secondary battery is measured using an atmospheric ultraviolet photoelectron spectroscopic analyzer. For example, the ionization potential of the material immediately after the exposure to the atmosphere is measured in advance, and whether or not the measured ionization potential is lower than the ionization potential immediately after the exposure to the atmosphere is compared. Then, when lower, it is determined that deterioration occurs on the surface of the electrode material for a lithium ion secondary battery. In the present invention, the length of the exposure time may be arbitrarily set at each time. For example, exposure may be performed continuously or intermittently using one sample, and evaluation may be performed each time a prescribed time elapses. Alternatively, one or more samples of the same kind or different kinds may be prepared, and the conditions may be changed for evaluation. Further, these data may be saved and used for comparison. For example, for a product of a particular compound, data of ionization potential when the length of exposure time is different may be determined and stored in advance for reference. Thereafter, when there is a product of the same kind of compound whose deterioration is to be judged, the ionization potential of the product can be measured and compared with the stored data.
As a specific example, an electrode material for a lithium ion secondary battery or a solid electrolyte material may be prepared as a first sample, exposure time of the material to the atmosphere is changed and measured at least once, and values of one or more ionization potentials are obtained and stored. The assay may be performed only immediately after exposure. Alternatively, a second sample composed of a compound having the same chemical composition and/or other characteristics as those of the first sample may be prepared separately, the ionization potential thereof may be measured, the stored value of the first sample may be compared with the measured value of the second sample, and the surface electron state of the second sample may be determined based on the result.
In addition, in an atmospheric ultraviolet photoelectron spectroscopic analyzer, a sample is irradiated with ultraviolet rays while changing the energy of the ultraviolet rays. The range of the ultraviolet energy used in the measurement can be arbitrarily selected. The amount of photoelectrons released from the material was measured by an open counter that can be electronically measured in the atmosphere. Therefore, the ionization potential can be measured in the atmosphere.
In the present embodiment, the time immediately after the electrode material or the solid electrolyte material for a lithium ion secondary battery is exposed to the atmosphere is defined as 0 hour. The ionization potential is then measured at arbitrarily set intervals, for example, every 1 hour. The electrode material or solid electrolyte material for a lithium ion secondary battery before measurement may be stored so as not to come into contact with the atmosphere.
When the ionization potential increases by 0.1eV or more from 0 hour, it is determined that deterioration occurs on the surface of the electrode material for a lithium ion secondary battery or the solid electrolyte material. Further, the time immediately after the exposure to the atmosphere may be arbitrarily selected. For example, it may be left in the atmosphere for a period of 0 to 15 minutes, or may be left in the atmosphere for a period of 0 to 10 minutes, 0 to 5 minutes, or 0 to 3 minutes.
By measuring the ionization potential, it is possible to determine in a short time whether or not a change from an ideal structure such as formation of a resistance layer on the surface of the lithium ion secondary battery material, in particular, a change in the surface electron state that is closely related to the battery characteristics, has occurred.
By the present invention, for example, comparing ionization potential data of a material additionally stored with a material of the same kind that has been previously measured and stored, it is possible to judge whether or not the stored material can be used for manufacturing a battery relatively easily.
The obtained ionization potential results can be determined by combining the results of the second embodiment described below, the results of STEM-ADF measurement or EELS measurement, the results of discharge capacity obtained by actually using the battery material in the battery, and the like.
Second embodiment
The inspection method of the present embodiment is to measure the ionization potential of the synthesized electrode material for a lithium ion secondary battery when the electrode material for a lithium ion secondary battery is synthesized. Then, whether the measured ionization potential is increased compared to a standard lithium ion secondary battery electrode material of the same composition measured separately is judged by comparison. When the amount of the cation is increased, it is determined that a certain change, for example, whether or not cation deintercalation has occurred, has occurred and the crystal structure is disturbed on the surface of the electrode material for a lithium ion secondary battery. For example, the ionization potential values of a plurality of battery materials obtained by changing the manufacturing conditions and the conditions of the manufacturing method can be measured and compared while using the same material and material composition. Further, as in the first embodiment, the obtained material may be evaluated for the ionization potential value based on the difference in the exposure time in the atmosphere and used for the judgment. The determination may be made in combination with the results of STEM-ADF measurement or EELS measurement, or the results of discharge capacity obtained by actually using the battery material for a battery, or the like.
STEM-ADF, EELS measurement
STEM-ADF measurement and EELS measurement may be used in combination with the measurements of the first and second embodiments. The STEM-ADF (annular Dark Field Scanning Electron microscope) measurement method can be performed as follows. The electrode material for a lithium ion secondary battery is subjected to thin film processing for cross-section measurement by a CP (cross-section polisher), FIB (focused ion beam), or the like. Then, an electron beam is irradiated to transmit a cross section of the sample, scattered electrons are measured, and the intensity of the scattered electrons is displayed as an image. The EELS measurement is a method for measuring energy lost by interaction with atoms of electrons that have passed through the same sample plane.
In the image obtained by the above method, when no lattice fringes corresponding to the crystal structure are observed on the surface of the electrode material or solid electrolyte material for a lithium ion secondary battery, it can be judged that the resistive layer is formed.
By combining the measurement values obtained in the first and second embodiments with the surface observation results based on either or both of the STEM-ADF measurement method and the EELS measurement, it is possible to better predict the change in the electronic state of the outermost surface layer that is difficult to detect in the X-ray diffraction measurement from the results of the ionization potential measurement. By collecting and accumulating such data, the surface electron state of the lithium ion secondary battery material can be detected in detail based on the detection result in a short time.
[ examples ] A method for producing a compound
The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples.
(example 1): LiNi0.82Co0.15Al0.03O2Prediction of performance degradation due to generation of particle surface resistance layer
LiNi synthesized by reacting a precursor synthesized by a coprecipitation method with lithium hydroxide0.82Co0.15Al0.03O2The particles are exposed to the atmosphere. Immediately after exposure to the atmosphere, and at regular intervals thereafter, powder X-ray diffraction measurement and ionization potential measurement were performed.
Changes in the peak position and relative intensity and changes in ionization potential in the obtained X-ray diffraction results were examined.
Ionization potential measurement
The change in ionization potential was measured using a photoelectron spectrometer (AC-3, manufactured by Racto instruments Co., Ltd.) in the atmosphere. The atmospheric photoelectron spectroscopy device is an atmospheric ultraviolet photoelectron spectroscopy device. Specifically, about 100mg of LiNi was prepared on a special sample table0.82Co0.15Al0.03O2Powder samples of the particles and measured in the energy range of 4.2-7.0 eV. Until the measurement, the specimen was stored in an argon atmosphere subjected to dew point control and sealed in a sealed bag containing dry argon gas. The sample was exposed to the atmosphere only during the exposure treatment or measurement.
The time required to measure a sample is within 5 minutes. The results obtained are plotted with energy on the horizontal axis and square root of the normalized photoelectron yield on the vertical axis. The ionization potential is estimated from the intersection of the extrapolated straight line from the least squares method with the baseline. The ionization potential results of the samples immediately after exposure and after 3 hours had elapsed are shown in fig. 2 such that the obtained ionization potential was plotted on the horizontal axis (unit: eV) and the normalized intensity was plotted on the vertical axis (in fig. 2, it is referred to as "Count (%)").
Powder X-ray diffraction measurement
Generally, in LiNi0.82Co0.15Al0.03O2In the lithium-nickel-containing composite oxide represented by the above formula, the ratio of the peak intensities of the diffraction lines belonging to the (003) plane and the (104) plane of the layered rock-salt crystal structure obtained by powder X-ray diffraction using Cu-K radiation as an X-ray source is 1.2 or more.
Based on the ratio of the peak intensities, the disorder of the crystal structure was judged. When cation exclusion occurs, that is, when the crystal structure changes from the layered rock-salt type to the rock-salt type, the X-ray diffraction intensity of the (003) plane becomes small. Therefore, a larger ratio of the peak intensities means a layered rock-salt structure with less disturbance.
FIG. 1 shows LiNi0.82Co0.15Al0.03O2Powder X-ray diffraction measurements were made immediately after exposure of the particles to the atmosphere, and after 5 hours of exposure and every 1 hour. As is apparent from fig. 1, the lines representing the results overlap, and the positions of the diffraction lines, the ratio of the diffraction line peak intensities belonging to the (003) plane and the (104) plane do not change. No change was perceptible by powder X-ray diffraction measurements.
FIG. 2 shows LiNi0.82Co0.15Al0.03O2The results of measurement of the change in ionization potential measured immediately after exposure of the particles to the atmosphere and at regular intervals thereafter.
As is also apparent from fig. 2, the ionization potential was significantly increased as seen from the intersection of the extrapolated straight line obtained by the least squares method and the base line after atmospheric exposure was performed for 3 hours.
FIG. 3 shows LiNi0.82Co0.15Al0.03O2Measured after 3 hours of exposure of the particles to the atmosphereThe EELS measurement result of (1). FIG. 4 shows LiNi0.82Co0.15Al0.03O2STEM-ADF observations measured 3 hours after exposure of the particles to the atmosphere. Among them, the measurement of one sample requires a measurement time of 2 days or more. From the STEM-ADF observation photograph, it was found that a layer having a pattern different from that of the lattice fringes was formed, indicating that a hetero-phase was formed in the surface layer. Further, from the EELS spectrum, the peak due to Ni shifts in a layer having a thickness of about 10nm from the surface. This indicates that a rock salt layer (resistive layer) of the surface layer is generated. These results correspond to the measurement results of the ionization potential.
The LiNi was prepared so as not to be exposed to the atmosphere and after exposure to the atmosphere for 3 hours0.82Co0.15Al0.03O2The particles are R2032 type half cells of electrode active material.
After the open circuit voltage was stabilized, the current density of the positive electrode was charged to 4.3V at 25 ℃ at 10mAh/g relative to the weight of the positive electrode active material, and then the discharge capacity at the time of discharging to 3.0V was measured.
As a result, it was found that LiNi was not exposed to the atmosphere0.82Co0.15Al0.03O2The initial capacity of the battery with the particles as the positive electrode active material was 200 mAh/g. In contrast, LiNi was exposed to the atmosphere for 3 hours0.82Co0.15Al0.03O2The particles were found to be reduced to less than 180mAh/g for the positive electrode active material cell. Although the lithium occupancy of the active material was about 98%, the initial discharge capacity was different. It is considered that this result is caused by the presence or absence of the resistance layer formed on the particle surface.
From the above, it was found that the performance deterioration predicted by STEM-ADF observation and EELS measurement, which require 2 days or more for measurement, can be predicted in ionization potential measurement within a measurement time of 5 minutes or less.
(example 2): LiCoO2Performance deterioration due to cation-mixing on surface of single crystal particleMeasuring
8 kinds of LiCoO synthesized by different methods were used as a pair of photoelectron spectroscopy devices (manufactured by Racto Seisakusho Co., Ltd., AC-3) in the atmosphere2The ionization potential of the single crystal particles was measured. About 100mg of isolated LiCoO was prepared on a special sample table2The powder samples of the single crystal particles were measured in an energy range of 4.2 to 7.0 eV. Until the measurement, the sample was stored in an argon atmosphere subjected to dew point control and sealed in a sealed bag containing dry argon gas. Atmospheric exposure was performed only during the measurement. The time required to measure a sample is within 5 minutes. In the determination method of the present invention, the determination may be made in accordance with the magnitude of the obtained ionization potential value.
The results obtained are plotted with energy on the horizontal axis and square root of the normalized photoelectron yield on the vertical axis. The ionization potential is estimated from the intersection of the extrapolated straight line from the least squares method with the baseline.
Table 1 shows ionization potentials and initial discharge capacities of 8 samples.
Specifically, 8 of the samples were each prepared as LiCoO2An R2032 type half cell in which single crystal grains are used as an electrode active material was subjected to a charge-discharge test in which the discharge capacity was measured after the open circuit voltage was stabilized, and after the cell was charged to 4.2 at 25 ℃ at 0.5C and then discharged to 2.8V at 10C. Table 1 shows the initial discharge capacity and the ratio of the initial discharge capacity to the LiCoO2The corresponding ionization potential of the particle.
TABLE 1
Sample(s) Initial discharge capacity (mAh/g) Ionization potential (eV)
1 130 5.58
2 125 5.88
3 130 5.72
4 120 5.92
5 140 5.68
6 125 5.83
7 140 5.63
8 135 5.66
The 8 samples were the same as in the experiment of example 1, and the morphology and composition of the particles and the X-ray diffraction pattern were the same. However, only LiCoO will have an ionization potential of 5.75eV or less2The single crystal particles used as a positive electrode active material in a secondary battery of a positive electrode showed a good initial discharge capacity of 130mAh/g or more (samples 1, 3, 5, 7, 8). LiCoO2On the surface of crystal particlesThe cation mixed row is considered to be a main cause of the difference in the physical property values. From the results, it can be seen that the advantages of the present invention are significantly exhibited.
As described above, according to the present invention, it is possible to provide a method for accurately detecting the performance of an electrode material for a lithium ion secondary battery, which is used as a raw material of the lithium ion secondary battery, in a short time.

Claims (9)

1. A detection method for detecting a surface electron state of an electrode material or a solid electrolyte material for a lithium ion secondary battery under atmospheric pressure, wherein,
the detection method has a detection step of detecting a surface electron state of the electrode material for a lithium ion secondary battery from an ionization potential inherent to the electrode material for a lithium ion secondary battery or the solid electrolyte material.
2. The detection method according to claim 1, wherein the ionization potential is measured by an atmospheric ultraviolet photoelectron spectroscopic analysis device.
3. The detection method according to claim 1 or 2, wherein the detection step comprises the steps of:
measuring an ionization potential of an electrode material or a solid electrolyte material for a lithium ion secondary battery immediately after exposure to the atmosphere using an atmospheric ultraviolet photoelectron spectroscopic analyzer;
thereafter further exposing the electrode material or solid electrolyte material for a lithium ion secondary battery to the atmosphere, and measuring the ionization potential of the material after further exposure to the atmosphere using the device;
determining whether the ionization potential measured for the material after further exposure to the atmosphere is lower than the ionization potential immediately after exposure to the atmosphere; and
when the determination is made to be lower, it is determined that deterioration of the surface of the electrode material for a lithium ion secondary battery has occurred.
4. The assay of claim 3, wherein said measurement immediately after exposure to the atmosphere is performed within 0-5 minutes of exposure of said material to the atmosphere.
5. The detection method according to claim 1, comprising the steps of:
preparing an electrode material or a solid electrolyte material for a lithium ion secondary battery as a first sample;
changing the exposure time of the material after the material is exposed to the atmosphere for more than one time, measuring the exposure time for more than one time, and obtaining more than one ionization potential value;
saving the value;
preparing a second sample composed of a compound having the same chemical composition as the first sample;
measuring the ionization potential of the second sample;
comparing the stored value of the first sample with the measured value of the second sample; and
and determining the surface electron state of the second sample according to the comparison result.
6. The detection method according to claim 1, comprising the steps of:
comparing a measurement result obtained by exposing the electrode material for a lithium ion secondary battery or the solid electrolyte material to the atmosphere and measuring an ionization potential thereof with at least one of a STEM-ADF measurement and an EELS measurement of the material after the exposure to the atmosphere; and
and determining the surface electronic state of the material according to the comparison result.
7. The detection method according to claim 5, comprising the steps of:
comparing the value of the ionization potential of the first sample after exposure to the atmosphere with at least one of the STEM-ADF measurement and the EELS measurement of the material after exposure to the atmosphere; and
and determining the surface electronic state of the material according to the comparison result.
8. The detection method according to claim 1, comprising the steps of:
comparing a measurement result obtained by exposing the electrode material for a lithium ion secondary battery or the solid electrolyte material to the atmosphere and measuring the ionization potential thereof with a measurement result obtained by using the material for a battery and measuring the discharge capacity; and
and determining the surface electronic state of the material according to the comparison result.
9. The detection method according to claim 5, wherein the second sample is a separately stored material, and the step of comparing the stored value of the first sample with the measured value of the second sample is used to determine whether or not the second sample can be used for manufacturing a battery.
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