JP7525272B2 - Measuring device and measuring method - Google Patents

Description

The present invention relates to a measurement device and a measurement method for measuring the ion diffusion state of a solid-state battery.

Conventionally, the state of movement of lithium ions in secondary batteries that use electrolyte has been understood indirectly by measuring charge/discharge characteristics and impedance.
With conventional methods, it is difficult to directly observe and measure the movement of ions, and light elements in particular cannot be directly observed due to limited detection methods. In addition, since ions also move simultaneously during ion movement, it is difficult to observe and measure only a specific ion movement.
On the other hand, the behavior of lithium ions moving inside all-solid-state lithium secondary batteries has not been fully understood, and it has been difficult to accurately quantitatively evaluate the diffusion state of elements using indirect evaluation methods such as charge/discharge tests and impedance measurements.
Furthermore, in order to measure the diffusion of lithium ions inside a lithium secondary battery that uses an electrolyte, a highly sealed device is required, which makes it difficult to measure the diffusion of lithium ions inside a lithium secondary battery, for example, on a moving object.

JP 2017-62997 A

The present invention has been made in consideration of the above-mentioned background technology, and aims to provide a measurement device and a measurement method capable of acquiring a diffusion profile showing the diffusion state of a first atomic ion diffusing from a solid-state battery and a second atomic ion that is an isotope of the first atomic ion.

The inventors conducted extensive research into the evaluation of lithium diffusion in lithium metal composite oxides using labeling with the stable enriched isotope 6Li, and discovered that labeling the coating layer formed on the surface of the lithium metal composite oxide with 6Li and evaluating the changes in the behavior of the lithium ions would provide useful data for investigating improvements to output characteristics, leading to the completion of the present invention.

The present invention is a measurement device that includes a solid electrolyte between a positive electrode and a negative electrode, an application means for applying a DC voltage of a predetermined potential to the positive electrode and the negative electrode, a promotion means for irradiating the solid electrolyte and the positive electrode with primary ions or imparting energy to promote ionization, and an acquisition means for detecting the mass of the first atomic ion diffusing from the positive electrode or solid electrolyte and the mass of a second atomic ion that is an isotope of the first atomic ion based on the primary ions irradiated from the promotion means or the energy imparted while the DC voltage is applied between the positive electrode and the negative electrode, to obtain a diffusion profile.

According to the present invention, it is possible to obtain a diffusion profile that indicates the diffusion state of a first atomic ion diffusing from a solid-state battery and a second atomic ion that is an isotope of the first atomic ion.

1A to 1C are diagrams illustrating the operation of a measuring device for a solid-state battery. FIG. 2 is a diagram showing the detection intensity of diffusing ions in the secondary battery shown in FIG. 1 . 1A to 1C are diagrams illustrating the operation of a measuring device for a solid-state battery. 4 is a flowchart illustrating a method for diagnosing a solid-state battery according to the present embodiment.

In the following, in this embodiment, a lithium battery will be used as an example of a solid-state battery (secondary battery).

First Embodiment
1 is a diagram for explaining the operation of the measurement device for a solid-state battery according to the first embodiment. In this example, an example is described in which the behavior of lithium ions diffusing from a solid-state battery is analyzed and evaluated using 7Li atomic ions as first atomic ions and 6Li atomic ions as isotopic second atomic ions. Hereinafter, an example is described in which the diffusion of elements is quantitatively evaluated with high accuracy.

In FIG. 1, the power source 1 applies a DC voltage of a predetermined potential between the 7Li metal electrode mesh 4 (negative electrode) and the 6Li metal electrode 3 (positive electrode). In this example, a negative potential is applied to the 7Li metal electrode mesh 4, and a positive potential is applied to the 6Li metal electrode 3 as the positive electrode.

The primary ion irradiation unit 10 as a prompting means irradiates primary ions 11 such as bismuth, gallium, gold, carbon 60, etc., or imparts some kind of energy such as laser light, localized heating, X-rays, neutrons, etc. (not shown) as a prompting means. This allows ions to be released from the solid electrolyte 5, and the diffusing 7Li atomic ions 8 (first electron ions) and isotope 6Li atomic ions 7 (second electron ions) can be captured. When the 6Li atomic ions 7 penetrate the solid electrolyte 5 and reach the surface, the amount of 6Li atomic ions 7 released increases, and the change can be detected by the mass detector 2.

At this time, a vacuum chamber 12 is provided to maintain a vacuum so as not to impede the irradiation of the primary ions 11, the release of the Li atomic ions, and the detection. In this way, in this embodiment, the 6Li atomic ions 7 to be observed are placed in a specific location, and the 6Li atomic ions 7 can be moved by applying an appropriate potential difference such as an electric potential difference. At this time, since the 6Li atomic ions 7 have a smaller mass than the 7Li atomic ions 8, the ion movement speed is fast and the effect is theoretically proportional to the square root of the mass ratio, so it is about 1.08 times.

The mass detector 2 as an acquisition means irradiates the solid electrolyte 5 with primary ions 11, such as bismuth, gallium, gold, or carbon 60, from the primary ion irradiation unit 10, or applies energy to the solid electrolyte 5, such as laser light, localized heating, X-rays, or neutrons, as a prompting means (not shown), to acquire a diffusion profile that specifies the masses of the 7Li atomic ions 8 that have moved to an observable irradiation position, the 7Li atomic ions 8 that have released 6Li atomic ions 7 and diffused from the positive electrode or the solid electrolyte 5 or both, and the 6Li atomic ions 7 that are isotopes of the 7Li atomic ions 8.

The diagnostic unit 9 as a diagnostic means diagnoses the degradation state of the solid-state battery based on the ratio of 6Li atomic ions 7 to 7Li atomic ions 8 and the amount of movement of 6Li atomic ions 7 based on the lithium detection profile as a diffusion profile acquired by the mass detector 2, and based on the flow chart described later.

Then, the diagnostic unit 9 analyzes the movement distance, movement time, movement amount, etc. based on the measured diffusion profile of the 7Li atomic ions 8 and 6Li atomic ions 7, and diagnoses the deterioration state and charge/discharge state of the secondary battery from the ratio of the 7Li atomic ions 8 and 6Li atomic ions 7 that have diffused and moved from the positive electrode or the solid electrolyte 5, or both, and the movement amount of the 6Li atomic ions 7.

The testing device and diagnostic device shown in this embodiment can also be used when the electrolyte is liquid or semi-solid.

Therefore, it is possible to mount a diagnostic device to which this embodiment is applied on a moving body, such as a vehicle, and diagnose the deterioration state and the charge/discharge state of a secondary battery while the battery is moving.
Moreover, the analysis method using the mass detector 2 can be a secondary ion mass spectrometry method used in performing solid surface analysis of secondary battery materials.

[Experimental Example]
When comparing the ratio of 7Li atomic ions 8 and 6Li atomic ions 7 detected by the mass detector 2 within a specified time period between a state in which the secondary battery is not degraded and a state in which the secondary battery is degraded, it was observed that when the secondary battery is not degraded, the 6Li atomic ions 7 tended to increase relatively (detection intensities based on experimental values are shown in Figure 2 described later).

In addition, when comparing the detection counts of Li atomic ions 7 detected by the mass detector 2 within a specified time, it was observed that when the secondary battery was not degraded, the 6Li atomic ions 7 tended to reach the observation site earlier and had a relatively higher detection count than when the secondary battery was degraded. This indicates that the movement of the 6Li atomic ions 7 was hindered by the degradation of the secondary battery.

Here, possible inhibiting factors include deterioration of the constituent materials such as the active material and electrolyte, and separation and contamination between the constituent materials.
Based on these observations and considerations, it has been found that the deterioration diagnosis of secondary batteries based on this mass spectrometry technique is an effective technique for diagnosing deterioration in moving objects, particularly in vehicles where the batteries are actually mounted and moving.

Figure 2 corresponds to the diagram showing the change over time in the diffused ion strength of the secondary battery shown in Figure 1. The vertical axis shows the detected count number (ion strength) of 6Li atomic ions 7, and the horizontal axis shows time. The solid line shows the detected strength of diffused ions of a normal secondary battery, and the dashed line shows the detected strength of diffused ions of a deteriorated secondary battery.

As shown in Figure 2, the factors of diffusion resistance that govern the charging characteristics of a secondary battery are shown as follows: from the bottom, 21 indicates the Li-ion diffusion region within the active material, 22 indicates the Li-ion diffusion region within the solid electrolyte, and 23 indicates the diffusion region between active materials. These trends can also be clearly understood by taking the slope of the ion intensity versus time, i.e., the arrival speed.

In this way, by separating the charging characteristics into diffusion resistance factors, it is possible to determine whether the cause of a deteriorated secondary battery is deterioration of the positive electrode, electrolyte, or interface.

[Effects of the First Embodiment]
According to this embodiment, the distance, time, and amount of lithium isotope ions can be accurately measured. This makes it possible to develop battery materials suitable for lithium ion migration, design electrodes, and further design cells and optimize battery control.
It will also be possible to grasp the state of battery deterioration from changes in the speed and amount of lithium ion movement.

Furthermore, when there are multiple interfaces between materials, the effect of the interfaces on element transfer can also be measured.
Furthermore, since this embodiment, which quantitatively evaluates the diffusion of elements, can be applied to diagnosing the deterioration state of a secondary battery, it is possible to diagnose the deterioration of a secondary battery in electronic devices and mobile objects that are used in various conditions, especially in environments where a secondary battery is mounted on a vehicle.

Second Embodiment
FIG. 3 is a diagram for explaining the operation of the solid-state battery measuring device according to the second embodiment.
3 is that a positive electrode layer 14 containing a 6Li isotope-substituted positive electrode active material is sandwiched between a positive electrode collector 16 and a solid electrolyte 5, and a negative electrode layer 13 containing a negative electrode active material is sandwiched between a negative electrode collector 15 and a solid electrolyte 5. The positive electrode collector 16 is preferably made of aluminum or stainless steel, and the negative electrode collector 15 is preferably made of copper or stainless steel.

In this example, the battery has a solid secondary battery structure and is capable of being charged and discharged.
By sandwiching a positive electrode layer 14 containing a 6Li isotope-substituted positive electrode active material between the positive electrode collector 16 and the solid electrolyte 5, and a negative electrode layer 13 between the negative electrode collector 15 and the solid electrolyte 5, it becomes possible for Li ions to enter and exit the positive electrode layer and the negative electrode layer, thereby enabling the secondary battery to function.

[Effects of the second embodiment]
According to this embodiment, the migration distance, time, and amount of lithium isotope ions can be measured efficiently and accurately.

Third Embodiment
4 is a flowchart for explaining the method for diagnosing a solid-state battery according to this embodiment. ST1 to ST9 indicate each step, which is realized by a CPU or processor (not shown) reading out a control program from a ROM and executing it. In this example, a case where the diagnosing means is provided in the measuring device is shown, but the scope of this embodiment also includes the case where the diagnosing means is provided as an external device separately.

A predetermined DC voltage is applied between the negative electrode collector 15 and the positive electrode collector 16 from the power source 1 (ST1). The measurement environment in the diagnostic unit 9 is stabilized by waiting for a predetermined time to elapse using a timer (not shown) or the like (ST2).
Next, the negative electrode layer is irradiated with primary ions 11, which are bismuth, gallium, gold, or carbon 60, from a primary ion irradiating unit 10 serving as a urging means (ST3).

Then, the mass detector 2 starts the detection process of the diffusing 7Li atomic ions 8 and the isotopic 6Li atomic ions 7 (ST4). Next, it waits for the detection of the diffusing 7Li atomic ions 8 and the isotopic 6Li atomic ions 7 to finish (ST5), and calculates the travel distance, travel time, and travel amount of the detected diffusing 7Li atomic ions 8 and the isotopic 6Li atomic ions 7 (ST6).

Next, the mass detector 2 determines whether the amount of movement of the isotopic 6Li atomic ions 7 is higher than a predetermined abundance ratio compared to the amount of movement of the 7Li atomic ions 8, i.e., whether the amount of diffusing 6Li atomic ions 7 is reduced compared to the amount of 7Li atomic ions 8, based on the calculated arrival time, travel distance, travel time, and travel amount of the diffusing 7Li atomic ions 8 and the isotopic 6Li atomic ions 7 (ST7).

If it is determined that the amount of diffusing 6Li atomic ions 7 has not decreased compared to the amount of 7Li atomic ions 8, the solid-state battery is diagnosed as exhibiting normal charging characteristics (ST8), and this process ends.

On the other hand, if the diffusing mass detector 2 determines that the amount of 6Li isotope atomic ions 7 is reduced compared to the amount of 7Li atomic ions 8, the solid-state battery is diagnosed as exhibiting deteriorated charging characteristics (ST9), and the process ends.

[Effects of the third embodiment]
According to this embodiment, by comparing the amount of diffusing 6Li atomic ions 7 with the amount of 7Li atomic ions 8, the degradation state of the solid-state battery can be diagnosed.
The disclosure of the present embodiment is merely an example, and since the present invention can be applied to electronic devices that use secondary batteries, various combinations are envisioned.

1 Power supply 2 Mass detector (acquisition means)
3 6Li metal electrode (positive electrode)
4 7Li metal electrode network (negative electrode)
5 Solid electrolyte 7 6Li atomic ion (second atomic ion)
8 7Li atomic ion (first atomic ion)
9. Diagnostic section (diagnostic means)
10 Primary ion irradiation unit (prompting means)
11 Primary ions
12 Vacuum Chamber
13 Negative electrode layer
14 Positive electrode layer
15 Negative electrode current collector
16 Positive electrode current collector

Claims (6)

An apparatus for measuring an ion diffusion state in a solid-state battery, comprising:
A solid electrolyte is provided between the positive electrode and the negative electrode, and an application means applies a DC voltage of a predetermined potential to the positive electrode and the negative electrode;
A means for irradiating the solid electrolyte and the positive electrode with primary ions or imparting energy thereto to promote ionization;
and an acquisition means for detecting first atomic ions, which are 7Li ions, and second atomic ions, which are isotopes of the first atomic ions, and are 6Li ions, diffusing from the positive electrode or solid electrolyte based on the primary ions irradiated by the prompting means or the energy applied while the DC voltage is applied between the positive electrode and the negative electrode , and acquiring a diffusion profile showing a change in ion intensity over time . The measurement device according to claim 1, further comprising a diagnostic means for diagnosing the degradation state of the solid-state battery based on whether the ratio of the second atomic ions to the first atomic ions is high or not based on the diffusion profile acquired by the acquisition means. The measuring device according to claim 1 , wherein the acquisition means is provided within a predetermined moving object. 3. The measuring device according to claim 1, wherein the primary ions irradiated by said prompting means are any one of bismuth, gallium, gold, and carbon 60. 3. The measuring device according to claim 1 , wherein the energy applied by the prompting means is any one of laser light, localized heating, X-rays, and neutrons. A method for measuring an ion diffusion state in a solid-state battery, comprising:
a step of providing a solid electrolyte between a positive electrode and a negative electrode and applying a direct current voltage of a predetermined potential to the positive electrode and the negative electrode;
a step of irradiating the solid electrolyte and the positive electrode with primary ions or imparting energy to the solid electrolyte and the positive electrode to promote ionization;
and an acquisition step of detecting first atomic ions, which are 7Li ions, and second atomic ions, which are isotopes of the first atomic ions, and 6Li ions, diffusing from the positive electrode or solid electrolyte based on the primary ions irradiated in the prompting step or the energy applied in a state in which the DC voltage is applied between the positive electrode and the negative electrode , and acquiring a diffusion profile showing a change in ion intensity over time .

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