Test method of all-solid battery

Abstract

To provide a test method of an all-solid battery, capable of testing a behavior of an electrode layer at a high-speed charging and discharging and an AC impedance evaluation.SOLUTION: An all-solid battery for test comprises: an evaluation cell in which a solid electrolyte layer is nipped by a positive electrode layer and a negative electrode layer; a first reference electrode cell in which the solid electrolyte layer is nipped by a first reference electrode and a first counter electrode that contain an electrode active material having a two-phase coexistence reaction; a second reference electrode cell in which the solid electrolyte layer is nipped by the second reference electrode and a second counter electrode that contain an electrode active material having the two-phase coexistence reaction. In a test method of an all-solid battery in which the first reference electrode is connected to the positive electrode layer via the solid electrolyte layer, the second reference electrode is connected to the negative electrode layer via the solid electrolyte layer, a charging rate between the first reference electrode and the first counter electrode is adjusted to a plateau region of the two-phase coexistence reaction, the charging ratio between the second reference electrode and the second counter electrode is adjusted to the plateau region of the two-phase coexistence reaction, the first and second reference electrodes are used as a reference electrode to measure a potential behavior of the positive electrode layer and the negative electrode layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for testing all-solid-state batteries.

Background Art

[0002] In recent years, lithium-ion secondary batteries have been widely used as power sources for portable electronic devices, wearable devices, IoT devices, etc. due to their high energy density. In these lithium-ion secondary batteries, an electrolytic solution using a flammable organic solvent is used as a medium for moving ions. In batteries using such a flammable electrolytic solution, problems such as leakage of the electrolytic solution, smoke generation, and ignition have been pointed out. As a means of eliminating such risks and ensuring essential safety, the development of all-solid-state batteries using a flame-retardant solid electrolyte and having all components as solids has been promoted as an alternative to the flammable organic electrolytic solution.

[0003] For secondary battery devices, the balance of the characteristics of the positive electrode, electrolyte, and negative electrode is important, and the construction of a method for independently evaluating each characteristic inside the battery is required. In liquid-based lithium-ion secondary batteries, various evaluations have been carried out by introducing a metal wire (such as Ag, Li, Li-In, etc.) between the positive and negative electrodes. Even in all-solid-state batteries, attempts have been made to introduce a reference electrode by various methods in relatively flexible sulfide-based all-solid-state batteries.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In an oxide-based all-solid-state battery, as an attempt to introduce a reference electrode, a cell using an active material having a two-phase coexistence reaction is connected in parallel via a solid electrolyte beside the evaluation cell, and a reference electrode can be introduced into the oxide-based all-solid-state battery that performs sintering in one batch (see, for example, Patent Document 1). By constructing this technology, for example, it has become possible to independently evaluate the characteristics of each of the positive and negative electrodes during low-rate charge and discharge at 0.2C or less.

[0007] However, in the technology of Patent Document 1, the distance between the evaluation electrode and the reference electrode is relatively long. Therefore, for example, it is possible to follow during low-rate charge and discharge at 0.2C or less, but it is difficult to cope with measurements that require high responsiveness such as high rates and AC impedance measurements.

[0008] In Non-Patent Document 1, a configuration in which a reference electrode is installed on the back surface of the electrode is reported. With this configuration, it may be possible to reduce the distance between the reference electrode and the evaluation electrode. However, in an oxide-based all-solid-state battery, no method for reducing the distance between the reference electrode and the evaluation electrode has been reported yet. For example, if the symmetry of the battery cell is broken by installing a reference electrode or the like, there is a risk of distortion occurring during firing of the oxide-based all-solid-state battery.

[0009] The present invention has been made in view of the above problems, and an object thereof is to provide a test method for an all-solid-state battery capable of testing the behavior of an electrode layer during high-speed charge and discharge and AC impedance evaluation.

Means for Solving the Problems

[0010] The test method of the all-solid-state battery according to the present invention includes an evaluation cell in which a solid electrolyte layer is sandwiched between a positive electrode layer containing a positive electrode active material and a negative electrode layer containing a negative electrode active material, a first reference electrode containing an electrode active material having a two-phase coexistence reaction, and a first counter electrode with respect to the first reference electrode. A first reference electrode cell in which the solid electrolyte layer is sandwiched, a second reference electrode containing an electrode active material having a two-phase coexistence reaction, and a second counter electrode with respect to the second reference electrode. A second reference electrode cell in which the solid electrolyte layer is sandwiched, wherein the first reference electrode is connected to the positive electrode layer via the solid electrolyte layer, and the second reference electrode is connected to the negative electrode layer via the solid electrolyte layer. Using the test all-solid-state battery, the charging rate between the first reference electrode and the first counter electrode is adjusted to the plateau region of the two-phase coexistence reaction of the electrode active material included in the first reference electrode, and the charging rate between the second reference electrode and the second counter electrode is adjusted to the plateau region of the two-phase coexistence reaction of the electrode active material included in the second reference electrode. And a step of measuring the potential behavior of at least one of the positive electrode layer and the negative electrode layer using the first reference electrode and the second reference electrode as reference electrodes.

[0011] In the test method of the all-solid-state battery, at least one of the electrode active material included in the first reference electrode and the electrode active material included in the second reference electrode is LiCoPO 4 , LiFePO 4 , LiCoO 2 , LiMn 2 O 4 and may include at least one of them.

[0012] In the test method of the all-solid-state battery, at least one of the electrode active material included in the first reference electrode and the electrode active material included in the second reference electrode is Li 4 Ti 5 O 12 , TiO 2 , LiTiPO 5 , LiTi 2 (PO 4 ) 3 , Li 1+x Al x Ti 2-x (PO 4 )3 It may contain at least any one of them.

[0013] In the method for testing the all-solid-state battery, the first reference electrode and the second reference electrode are short-circuited, and charge and discharge evaluation is performed using the first reference electrode and the second reference electrode as reference electrodes, and as the positive electrode potential, the potential difference between the positive electrode layer and the first reference electrode and the second reference electrode may be recorded.

[0014] In the method for testing the all-solid-state battery, the first reference electrode and the second reference electrode are short-circuited, and charge and discharge evaluation is performed using the first reference electrode and the second reference electrode as reference electrodes, and as the negative electrode potential, the potential difference between the negative electrode layer and the first reference electrode and the second reference electrode may be recorded.

[0015] In the method for testing the all-solid-state battery, an operating electrode current terminal and an operating electrode voltage terminal are connected to the positive electrode layer, a counter electrode current terminal and a counter electrode voltage terminal are connected to the negative electrode layer, a reference electrode terminal is connected to the first reference electrode and the second reference electrode, an alternating current signal is input between the positive electrode layer and the negative electrode layer, and signals between the positive electrode layer and the first reference electrode and the second reference electrode, and between the negative electrode layer and the first reference electrode and the second reference electrode may be recorded.

Advantages of the Invention

[0016] According to the present invention, it is possible to provide a method for testing an all-solid-state battery capable of testing the behavior of an electrode layer during high-speed charge and discharge or during AC impedance evaluation.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

BEST MODE FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, embodiments will be described with reference to the drawings.

[0019] (Embodiment) First, the basic structure of the evaluation cell 100 which is the test object of the test method according to this embodiment will be described.

[0020] FIG. 1 is a schematic cross-sectional view showing the basic structure of the evaluation cell 100. The evaluation cell 100 is an all-solid-state battery and has a structure in which a solid electrolyte layer 30 is sandwiched between a positive electrode layer 10 and a negative electrode layer 20. The positive electrode layer 10 is formed on the first main surface of the solid electrolyte layer 30. The negative electrode layer 20 is formed on the second main surface of the solid electrolyte layer 30. The positive electrode layer 10 and the negative electrode layer 20 face each other with the solid electrolyte layer 30 therebetween. In FIG. 1, the positive electrode layer 10 is formed under the solid electrolyte layer 30, and the negative electrode layer 20 is formed on the solid electrolyte layer 30. For example, the positive electrode layer 10, the negative electrode layer 20, and the solid electrolyte layer 30 are sintered bodies obtained by sintering a powder material.

[0021] The solid electrolyte layer 30 is mainly composed of an oxide-based solid electrolyte having ion conductivity. The solid electrolyte of the solid electrolyte layer 30 has, for example, a NASICON-type crystal structure. The solid electrolyte of the solid electrolyte layer 30 is, for example, an oxide-based solid electrolyte having lithium ion conductivity. The solid electrolyte is, for example, a phosphate-based solid electrolyte. The phosphate-based solid electrolyte having a NASICON-type crystal structure has high conductivity and the property of being stable in the atmosphere. The phosphate-based solid electrolyte is, for example, a phosphate containing lithium. The phosphate is not particularly limited, but for example, a composite lithium phosphate salt with Ti (for example, LiTi 2 (PO 4 ) 3 ) and the like. Or, Ti can be partially or entirely substituted with a tetravalent transition metal such as Ge, Sn, Hf, Zr, etc. Also, in order to increase the Li content, it may be partially substituted with a trivalent transition metal such as Al, Ga, In, Y, La, etc. More specifically, for example, Li 1+x Al x Ge 2-x (PO 4 ) 3 and, Li 1+x Al x Zr 2-x (PO 4 ) 3 , Li 1+x Al x Ti 2-x (PO 4 ) 3 and the like. For example, a Li-Al-Ge-PO 4 -based material with the same transition metal as the transition metal contained in the phosphate having an olivine-type crystal structure contained in the positive electrode layer 10 added in advance is preferable. For example, when the positive electrode layer 10 contains a phosphate containing Co and Li, it is preferable that a Li-Al-Ge-PO 4 -based material with Co added in advance is contained in the solid electrolyte layer 30. In this case, an effect of suppressing the elution of the transition metal contained in the electrode active material into the electrolyte can be obtained. When the positive electrode layer 10 contains a phosphate containing a transition element other than Co and Li, a Li-Al-Ge-PO 4The system material is preferably included in the solid electrolyte layer 30.

[0022] The positive electrode layer 10 contains, as an electrode active material, a substance having an olivine-type crystal structure. The negative electrode layer 20 may also contain the electrode active material. Examples of such an electrode active material include phosphates containing a transition metal and lithium. The olivine-type crystal structure is a crystal possessed by natural olivine and can be discriminated by X-ray diffraction.

[0023] As a typical example of an electrode active material having an olivine-type crystal structure, LiCoPO containing Co 4 and the like can be used. It is also possible to use phosphates in which Co, a transition metal, is replaced in this chemical formula. Here, the ratios of Li and PO 4 can vary depending on the valence. It is preferable to use Co, Mn, Fe, Ni, etc. as the transition metal.

[0024] The electrode active material having an olivine-type crystal structure acts as an electrode active material in the positive electrode layer 10. For example, when the positive electrode layer 10 contains only an electrode active material having an olivine-type crystal structure, the electrode active material acts as an electrode active material. When the negative electrode layer 20 also contains an electrode active material having an olivine-type crystal structure, in the negative electrode layer 20, although the action mechanism has not been fully clarified, it is presumed to be based on the formation of a partial solid solution state with the negative electrode active material, and effects such as an increase in discharge capacity and an increase in the operating potential accompanying discharge are exhibited.

[0025] When both the positive electrode layer 10 and the negative electrode layer 20 contain an electrode active material having an olivine-type crystal structure, each electrode active material preferably contains transition metals that may be the same as or different from each other. The phrase "may be the same as or different from each other" means that the electrode active materials contained in the positive electrode layer 10 and the negative electrode layer 20 may contain the same type of transition metal, or may contain different types of transition metals. The positive electrode layer 10 and the negative electrode layer 20 may contain only one type of transition metal, or may contain two or more types of transition metals. Preferably, the positive electrode layer 10 and the negative electrode layer 20 contain the same type of transition metal. More preferably, the electrode active materials contained in both electrodes have the same chemical composition. By including the same type of transition metal or the same composition of electrode active material in the positive electrode layer 10 and the negative electrode layer 20, the similarity of the compositions of both internal electrode layers is increased. Therefore, even when the attachment of the terminals of the evaluation cell 100 is reversed between positive and negative, depending on the application, there is an effect that it can withstand actual use without malfunctioning.

[0026] The negative electrode layer 20 contains a negative electrode active material. By including the negative electrode active material in only one of the electrodes, it becomes clear that the said one electrode acts as a negative electrode and the other electrode acts as a positive electrode. Note that both electrodes may contain a substance known as a negative electrode active material. For the negative electrode active material of the electrode, the prior art in secondary batteries can be appropriately referred to. Examples include compounds such as titanium oxide, lithium titanium composite oxide, lithium titanium composite phosphate, carbon, and lithium vanadium phosphate.

[0027] In the production of the positive electrode layer 10 and the negative electrode layer 20, in addition to these electrode active materials, a solid electrolyte having ionic conductivity, a conductive material (conductive aid), and the like are added. For these members, an internal electrode paste can be obtained by uniformly dispersing a binder and a plasticizer in water or an organic solvent. As the conductive aid, a carbon material or the like may be included. As the conductive aid, a metal may be included. Examples of the metal of the conductive aid include Pd, Ni, Cu, Fe, and alloys containing these. The solid electrolyte contained in the positive electrode layer 10 and the negative electrode layer 20 can be, for example, the same as the main component solid electrolyte of the solid electrolyte layer 30.

[0028] Figure 2 is a schematic cross-sectional view showing the laminated structure of the test all-solid-state battery 200. As illustrated in Figure 2, the test all-solid-state battery 200 has a structure in which the first reference electrode cell 101 is laminated under the evaluation cell 100, and the second reference electrode cell 102 is laminated on the evaluation cell 100. Specifically, the first reference electrode cell 101 is laminated under the positive electrode layer 10 via the solid electrolyte layer 30a, and the second reference electrode cell 102 is laminated on the negative electrode layer 20 via the solid electrolyte layer 30b. The thicknesses of the solid electrolyte layer 30a and the solid electrolyte layer 30b are, for example, 1 μm or more and 50 μm or less.

[0029] The first reference electrode cell 101 has a structure in which the first reference electrode 11, the solid electrolyte layer 12, and the first counter electrode 13 are laminated in this order from the solid electrolyte layer 30a side. Note that a solid electrolyte layer 30c may be laminated under the first counter electrode 13.

[0030] The second reference electrode cell 102 has a structure in which the second reference electrode 21, the solid electrolyte layer 22, and the second counter electrode 23 are laminated in this order from the solid electrolyte layer 30b side. Note that a solid electrolyte layer 30d may be laminated on the second counter electrode 23.

[0031] The first reference electrode 11 and the second reference electrode 21 include an electrode active material having a two-phase coexistence reaction. The two-phase coexistence reaction is a reaction in which two phases, namely, the crystal phase in the charged state and the crystal phase in the discharged state, coexist and proceed. Due to the two-phase coexistence reaction, a potential flat region (plateau region) occurs during charge and discharge.

[0032] When the first reference electrode 11 and the second reference electrode 21 function as the positive electrode reference electrodes, the first reference electrode 11 and the second reference electrode 21 include a positive electrode active material having a two-phase coexistence reaction. As the positive electrode active material having a two-phase coexistence reaction, for example, LiCoPO 4 LiFePO 4 LiCoO 2 LiMn 2 O 4 etc. can be used. Fig. 3(a) is a diagram illustrating the charge curves of the first reference electrode 11 and the second reference electrode 21 when the first reference electrode 11 and the second reference electrode 21 include a positive electrode active material having a two-phase coexistence reaction. Fig. 3(b) is a diagram illustrating the discharge curves of the first reference electrode 11 and the second reference electrode 21 when the first reference electrode 11 and the second reference electrode 21 include a positive electrode active material having a two-phase coexistence reaction. As illustrated in Fig. 3(a) and Fig. 3(b), a plateau region where the potential hardly changes even when the state of charge (SOC) changes is generated.

[0033] When the first reference electrode 11 and the second reference electrode 21 function as the negative electrode, the first reference electrode 11 and the second reference electrode 21 include a negative electrode active material having a two-phase coexistence reaction. As the negative electrode active material having a two-phase coexistence reaction, for example, Li 4 Ti 5 O 12 TiO 2 LiTiPO 5 LiTi 2 (PO 4 ) 3 Li 1+x Al x Ti 2-x (PO 4 ) 3etc. can be used. FIG. 4(a) is a diagram illustrating the charge curves of the first reference electrode 11 and the second reference electrode 21 when the first reference electrode 11 and the second reference electrode 21 contain a negative electrode active material having a two-phase coexistence reaction. FIG. 4(b) is a diagram illustrating the discharge curves of the first reference electrode 11 and the second reference electrode 21 when the first reference electrode 11 and the second reference electrode 21 contain a negative electrode active material having a two-phase coexistence reaction. As illustrated in FIGS. 4(a) and 4(b), a plateau region where the potential hardly changes even when the SOC changes is generated.

[0034] The first counter electrode 13 functions as a counter electrode for the first reference electrode 11. Therefore, when the first reference electrode 11 functions as a positive electrode, the first counter electrode 13 contains a negative electrode active material. When the first reference electrode 11 functions as a negative electrode, the first counter electrode 13 contains a positive electrode active material. The second counter electrode 23 functions as a counter electrode for the second reference electrode 21. Therefore, when the second reference electrode 21 functions as a positive electrode, the second counter electrode 23 contains a negative electrode active material. When the second reference electrode 21 functions as a negative electrode, the second counter electrode 23 contains a positive electrode active material.

[0035] Note that both the first reference electrode 11 and the second reference electrode 21 may be positive electrodes, or both may be negative electrodes.

[0036] Since the first reference electrode cell 101 includes the first reference electrode 11 and the first counter electrode 13 with the solid electrolyte layer 12 interposed therebetween, the first reference electrode cell 101 can be used as a secondary battery. Since the second reference electrode cell 102 includes the second reference electrode 21 and the second counter electrode 23 with the solid electrolyte layer 22 interposed therebetween, the second reference electrode cell 102 can be used as a secondary battery.

[0037] Since the evaluation cell 100 and the first reference electrode cell 101 are laminated via the solid electrolyte layer 30a, ions can move between the evaluation cell 100 and the first reference electrode cell 101. On the other hand, since the solid electrolyte layer 30a is an insulator, the electron conduction between the evaluation cell 100 and the first reference electrode cell 101 is insulated.

[0038] Since the evaluation cell 100 and the second reference electrode cell 102 are stacked via the solid electrolyte layer 30b, ions can move between the evaluation cell 100 and the second reference electrode cell 102. On the other hand, since the solid electrolyte layer 30b is an insulator, electron conduction between the evaluation cell 100 and the second reference electrode cell 102 is insulated.

[0039] By using this structure, the first reference electrode cell 101 and the second reference electrode cell 102 are charged, and by performing charge and discharge on the evaluation cell 100, the behavior of the electrode layer can be tested during high-speed charge and discharge or AC impedance evaluation. Since the first reference electrode 11 and the second reference electrode 21 use an electrode active material having a two-phase coexistence reaction, a plateau region occurs within a predetermined SOC range, and this plateau region can be used as a stable reference electrode potential.

[0040] Hereinafter, a test method for the evaluation cell 100 will be described. First, a case where both the first reference electrode 11 and the second reference electrode 21 function as positive electrodes and both the first counter electrode 13 and the second counter electrode 23 function as negative electrodes will be described. Note that the positive electrode active material will be described in the case of LiCoPO 4 is described.

[0041] First, in the first reference electrode cell 101, a charging process is performed so that the SOC of the first reference electrode 11 becomes about 20%, and adjustment is made so as to enter the plateau region of the positive electrode active material of the first reference electrode 11. Further, in the second reference electrode cell 102, a charging process is performed so that the SOC of the second reference electrode 21 becomes about 20%, and adjustment is made so as to enter the plateau region of the positive electrode active material of the second reference electrode 21.

[0042] Thereafter, the first reference electrode 11 and the second reference electrode 21 are short-circuited to function as one reference electrode. Using a 5-terminal measurable charge-discharge device, charge-discharge evaluation is performed with the first reference electrode 11 and the second reference electrode 21 as the reference electrodes, and as the positive electrode potential, the potential difference between the positive electrode layer 10 and the first reference electrode 11 and the second reference electrode 21 is recorded. Since the potentials of the first reference electrode 11 and the second reference electrode 21 are substantially constant, the charge-discharge curve of the positive electrode layer 10 can be obtained. At the same time, as the negative electrode potential, the potential difference between the negative electrode layer 20 and the first reference electrode 11 and the second reference electrode 21 is recorded. Since the potentials of the first reference electrode 11 and the second reference electrode 21 are substantially constant, the charge-discharge curve of the negative electrode layer 20 can be obtained.

[0043] Also during the AC impedance evaluation, as described above, in the first reference electrode cell 101, a charging process is performed so that the SOC of the first reference electrode 11 becomes about 20%, and it is adjusted to enter the plateau region of the positive electrode active material of the first reference electrode 11. Further, in the second reference electrode cell 102, a charging process is performed so that the SOC of the second reference electrode 21 becomes about 20%, and it is adjusted to enter the plateau region of the positive electrode active material of the second reference electrode 21.

[0044] Thereafter, the working electrode current terminal and the working electrode voltage terminal are connected to the working electrode (positive electrode layer 10), the counter electrode current terminal and the counter electrode voltage terminal are connected to the counter electrode (negative electrode layer 20), and the reference electrode terminal is connected to the reference electrode (the first reference electrode 11 and the second reference electrode 21). Thereafter, an AC signal is input between the working electrode and the counter electrode, and the signals between the working electrode and the reference electrode and between the counter electrode and the reference electrode are recorded simultaneously. From the relationship between the recorded signal and the relationship with the frequency (impedance |Z| and phase difference θ), the AC impedance evaluation of each of the positive and negative electrodes is performed simultaneously.

[0045] Next, a case will be described where the first reference electrode 11 functions as a negative electrode, the first counter electrode 13 functions as a positive electrode, the second reference electrode 21 functions as a positive electrode, and the second counter electrode 23 functions as a negative electrode. In this case, in the first reference electrode cell 101, a charging process is performed so that the SOC of the first reference electrode 11 becomes about 20%, and it is adjusted to enter the plateau region of the negative electrode active material of the first reference electrode 11. Also, in the second reference electrode cell 102, a charging process is performed so that the SOC of the second reference electrode 21 becomes about 20%, and it is adjusted to enter the plateau region of the negative electrode active material of the second reference electrode 21. After that, the evaluation cell 100 can be tested by the same method as described above.

[0046] FIG. 5 is a plan view when viewing the test all-solid-state battery 200 in a plan view. For example, when the test all-solid-state battery 200 has a substantially rectangular shape, it will be provided with four side surfaces. For example, external electrodes 40a, 40b, 40c, and 40d are provided on each of these four side surfaces. For example, the external electrode 40a and the external electrode 40c are provided on each of the two opposing side surfaces. The external electrode 40b and the external electrode 40d are provided on each of the other two opposing side surfaces. From the viewpoint of preventing a short circuit between the positive electrode layer 10 and the negative electrode layer 20, for example, the positive electrode layer 10 is led out to the external electrode 40a, and the negative electrode layer 20 is led out to the external electrode 40c.

[0047] For example, among the first reference electrode 11, the first counter electrode 13, the second reference electrode 21, and the second counter electrode 23, two electrodes having the same polarity are led out to the external electrode 40b, and the other two electrodes having the other polarity are led out to the external electrode 40d. For example, when both the first reference electrode 11 and the second reference electrode 21 function as positive electrodes, both the first reference electrode 11 and the second reference electrode 21 are led out to the external electrode 40b, and both the first counter electrode 13 and the second counter electrode 23 are led out to the external electrode 40d.

[0048] As described above, according to the present embodiment, the SOC between the first reference electrode 11 and the first counter electrode 13 is adjusted to the plateau region of the two-phase coexistence reaction, and the SOC between the second reference electrode 21 and the second counter electrode 23 is adjusted to the plateau region of the two-phase coexistence reaction. By performing the charge and discharge test between the positive electrode layer 10 and the negative electrode layer 20, the behavior of each electrode layer of the evaluation cell 100 can be individually tested. Further, since the solid electrolyte layer 30a is only interposed in the thickness direction between the positive electrode layer 10 and the first reference electrode 11, the distance between the positive electrode layer 10 and the first reference electrode 11 is shorter compared to the configuration disclosed in Patent Document 1. Further, since the solid electrolyte layer 30b is only interposed in the thickness direction between the negative electrode layer 20 and the second reference electrode 21, the distance between the negative electrode layer 20 and the second reference electrode 21 is shorter compared to the configuration disclosed in Patent Document 1. Thereby, the behavior of each electrode layer of the evaluation cell 100 can be tested even during high-speed charge and discharge or AC impedance evaluation.

[0049] In the test all-solid-state battery 200 according to the present embodiment, since the evaluation cell 100, the first reference electrode cell 101, and the second reference electrode cell 102 only need to be laminated via the solid electrolyte layer, the laminate obtained by laminating each layer can be fired collectively. Further, since the electrode active material having a two-phase coexistence reaction is included in the first reference electrode 11 and the second reference electrode 21, it is not necessary to introduce a metal foil or the like that exhibits a stable potential.

[0050] FIG. 6 is a flowchart showing an example of the procedure of the test method. First, in the first reference electrode cell 101, a charging process is performed so that the SOC of the first reference electrode 11 becomes about 20%, and it is adjusted to enter the plateau region of the electrode active material of the first reference electrode 11. In the second reference electrode cell 102, a charging process is performed so that the SOC of the second reference electrode 21 becomes about 20%, and it is adjusted to enter the plateau region of the electrode active material of the second reference electrode 21 (step S1).

[0051] Next, using a charge-discharge device capable of five-terminal measurement, the potential behavior of at least one of the positive electrode layer 10 and the negative electrode layer 20 is measured (step S2) with the first reference electrode 11 and the second reference electrode 21 used as reference electrodes. For example, a charge-discharge curve is measured or an AC impedance evaluation is performed.

[0052] Subsequently, a method for manufacturing the test all-solid-state battery 200 will be described. First, a solid electrolyte powder for the solid electrolyte layer is dispersed in a mixed solvent such as ethanol and toluene, and a slurry is prepared by thoroughly mixing it with an organic binder. This slurry is spread on a PET film subjected to a surface release treatment using a doctor blade and dried by heating to obtain a green sheet.

[0053] A thing obtained by printing the pre-firing material of the first counter electrode 13 on the green sheet, a thing obtained by printing the pre-firing material of the first reference electrode 11 on the green sheet, a thing obtained by printing the pre-firing material of the positive electrode layer 10 on the green sheet, a thing obtained by printing the pre-firing material of the negative electrode layer 20 on the green sheet, a thing obtained by printing the pre-firing material of the second reference electrode 21 on the green sheet, a thing obtained by printing the pre-firing material of the second counter electrode 23 on the green sheet, and a green sheet on which the pre-firing material of the electrode is not printed are laminated in this order to obtain a laminate.

[0054] Next, the obtained laminate is fired. The firing conditions are not particularly limited as long as they are in an oxidizing atmosphere or a non-oxidizing atmosphere, and the maximum temperature is, for example, 400°C to 1000°C, 500°C to 900°C, etc. A step of holding at a temperature lower than the maximum temperature in an oxidizing atmosphere may be provided to sufficiently remove the binder before reaching the maximum temperature. In order to reduce the process cost, it is desirable to fire at as low a temperature as possible. After firing, a re-oxidation treatment may be performed. Through the above steps, the test all-solid-state battery 200 is manufactured.

Example

[0055] Hereinafter, a test all-solid-state battery was manufactured according to the embodiment, and its characteristics were examined.

[0056] (Example) As the configuration of the evaluation cell, LiCoPO was used as the positive electrode active material. 4 For the reference electrode cell, the same configuration was used, so LiCoPO was used as the positive electrode active material. 4 The solid electrolyte was dispersed in a mixed solvent of ethanol and toluene, and a slurry was prepared by mixing well with an organic binder. This slurry was spread on a PET film with a surface release treatment using a doctor blade and heated and dried to obtain a green sheet.

[0057] The material before firing of the first counter electrode was printed on the green sheet, the material before firing of the first reference electrode containing LiCoPO as the positive electrode active material was printed on the green sheet, the material before firing of the positive electrode layer of the evaluation cell was printed on the green sheet, the material before firing of the negative electrode layer of the evaluation cell was printed on the green sheet, the material before firing of the second reference electrode containing LiCoPO as the positive electrode active material was printed on the green sheet, the material before firing of the second counter electrode was printed on the green sheet, and the green sheet without the printed material before firing of the electrode were laminated in order to obtain a laminate. 4 Thereafter, pressure bonding and degreasing were performed, and firing was performed to obtain a sintered body. External electrodes were formed at the positive and negative electrode lead-out portions of each of the evaluation cell and the reference electrode cell to fabricate a test battery cell. A predetermined charging process was applied to the positive and negative electrodes of the reference electrode cell of the fabricated test battery cell to adjust the SOC of the reference electrode to 20%. By connecting the positive electrode of the reference electrode cell after SOC adjustment as the reference electrode and performing charge and discharge on the evaluation cell, the potential behavior of the positive and negative electrodes during battery charge and discharge could be confirmed. Also, an AC impedance evaluation was performed with the same connection. 4 The material before firing of the first counter electrode was printed on the green sheet, the material before firing of the first reference electrode containing LiCoPO as the positive electrode active material was printed on the green sheet, the material before firing of the positive electrode layer of the evaluation cell was printed on the green sheet, the material before firing of the negative electrode layer of the evaluation cell was printed on the green sheet, the material before firing of the second reference electrode containing LiCoPO as the positive electrode active material was printed on the green sheet, the material before firing of the second counter electrode was printed on the green sheet, and the green sheet without the printed material before firing of the electrode were laminated in order to obtain a laminate.

[0058] Thereafter, pressure bonding and degreasing were performed, and firing was performed to obtain a sintered body. External electrodes were formed at the positive and negative electrode lead-out portions of each of the evaluation cell and the reference electrode cell to fabricate a test battery cell. A predetermined charging process was applied to the positive and negative electrodes of the reference electrode cell of the fabricated test battery cell to adjust the SOC of the reference electrode to 20%. By connecting the positive electrode of the reference electrode cell after SOC adjustment as the reference electrode and performing charge and discharge on the evaluation cell, the potential behavior of the positive and negative electrodes during battery charge and discharge could be confirmed. Also, an AC impedance evaluation was performed with the same connection.

[0059] (Comparative Example) In the comparative example, as the configuration of the evaluation cell, LiCoPO was used as the positive electrode active material. 4 For the reference electrode cell, the same configuration was used, so LiCoPO was used as the positive electrode active material.4 1. A Ti-Ta-Nb-O-based material was used as the negative electrode active material. The solid electrolyte was dispersed in a mixed solvent of ethanol and toluene, and a slurry was prepared by thoroughly mixing it with an organic binder. This slurry was spread on a PET film with a surface release treatment using a doctor blade and dried by heating to obtain a green sheet. On this green sheet, the positive electrode active material was printed by screen printing for the positive electrode layer of the evaluation cell, and the positive electrode active material was screen printed separately for the positive electrode reference electrode of the reference electrode cell to obtain a positive electrode printed green sheet. On another green sheet, the negative electrode active material was printed by screen printing for the negative electrode layer of the evaluation cell, and the negative electrode active material was screen printed separately for the negative electrode reference electrode of the reference electrode cell to obtain a negative electrode printed green sheet. The obtained positive electrode printed green sheet and negative electrode printed green sheet were laminated, pressure-bonded, degreased, and fired to obtain a test all-solid-state battery. That is, in the comparative example, on the upper surface of the common solid electrolyte layer, the positive electrode layer of the evaluation cell was formed, and a positive electrode reference electrode was formed separately from the positive electrode layer. On the lower surface of the solid electrolyte layer, a negative electrode layer was formed so as to face the positive electrode layer of the evaluation cell, and a negative electrode reference electrode was formed separately from the negative electrode layer so as to face the positive electrode reference electrode.

[0060] Figure 7(a) is a diagram showing the results of the AC impedance evaluation for the example. Figure 7(b) is a diagram showing the results of the AC impedance evaluation for the comparative example. The horizontal axis represents the real axis, and the vertical axis represents the imaginary axis.

[0061] As shown in Figure 7(a), in the example, it was confirmed that the responsiveness of the positive and negative electrodes could be obtained over the frequency range of 3 MHz to 100 mHz. On the other hand, as shown in Figure 7(b), in the comparative example, it was confirmed that the responsiveness of the positive and negative electrodes could not be obtained.

[0062] Also, as shown in Figure 8, in the example, it was confirmed that it was also possible to handle the impedance of 100 MHz and that the evaluation of the solid electrolyte layer between the electrodes was possible. On the other hand, in the comparative example, it was confirmed that it could only handle up to about 1 kHz.

[0063] As described above in detail with respect to the embodiments of the present invention, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Signs

[0064] 10 Positive electrode layer 11 First reference electrode 12 Solid electrolyte layer 13 First counter electrode 20 Negative electrode layer 21 Second reference electrode 22 Solid electrolyte layer 23 Second counter electrode 30 Solid electrolyte layer 30a to 30d Solid electrolyte layer 100 Evaluation cell 101 Cell for first reference electrode 102 Cell for second reference electrode 200 Test all-solid-state battery

Claims

1. An evaluation cell in which a solid electrolyte layer is sandwiched between a positive electrode layer containing a positive electrode active material and a negative electrode layer containing a negative electrode active material; a first reference electrode containing an electrode active material having a two-phase coexistence reaction and a first counter electrode with respect to the first reference electrode, a first reference electrode cell in which the solid electrolyte layer is sandwiched therebetween; a second reference electrode containing an electrode active material having a two-phase coexistence reaction and a second counter electrode with respect to the second reference electrode, a second reference electrode cell in which the solid electrolyte layer is sandwiched therebetween, wherein the first reference electrode is connected to the positive electrode layer via the solid electrolyte layer, and the second reference electrode is connected to the negative electrode layer via the solid electrolyte layer, using a test all-solid-state battery, A procedure for adjusting the charge rate between the first reference electrode and the first counter electrode to a plateau region of the two-phase coexistence reaction of the electrode active material included in the first reference electrode; A procedure for adjusting the charge rate between the second reference electrode and the second counter electrode to a plateau region of the two-phase coexistence reaction of the electrode active material included in the second reference electrode; A test method for an all-solid-state battery, comprising a procedure for measuring the potential behavior of at least one of the positive electrode layer and the negative electrode layer, using the first reference electrode and the second reference electrode as reference electrodes.

2. At least one of the electrode active materials included in the first reference electrode and the electrode active materials included in the second reference electrode is LiCoPO ４ , LiFePO ４ , LiCoO ２ , LiMn ２ O ４ The method for testing an all-solid-state battery according to claim 1, comprising at least one of the above.

3. At least one of the electrode active materials included in the first reference electrode and the electrode active materials included in the second reference electrode is Li ４ Ti ５ O １２ , TiO ２ , LiTiPO ５ , LiTi ２ (PO ４ ) ３ , Li １＋ｘ Al ｘ Ti ２－ｘ (PO ４ ) ３ The method for testing an all-solid-state battery according to claim 1, comprising at least any one of the above.

4. The test method for an all-solid-state battery according to claim 1, wherein the first reference electrode and the second reference electrode are short-circuited, charge-discharge evaluation is performed using the first reference electrode and the second reference electrode as reference electrodes, and as the positive electrode potential, the potential difference between the positive electrode layer and the first reference electrode and the second reference electrode is recorded.

5. The test method for an all-solid-state battery according to claim 1, wherein the first reference electrode and the second reference electrode are short-circuited, charge-discharge evaluation is performed using the first reference electrode and the second reference electrode as reference electrodes, and as the negative electrode potential, the potential difference between the negative electrode layer and the first reference electrode and the second reference electrode is recorded.

6. An operating electrode current terminal and an operating electrode voltage terminal are connected to the positive electrode layer, a counter electrode current terminal and a counter electrode voltage terminal are connected to the negative electrode layer, a reference electrode terminal is connected to the first reference electrode and the second reference electrode, an AC signal is input between the positive electrode layer and the negative electrode layer, and signals between the positive electrode layer and the first reference electrode and the second reference electrode, and between the negative electrode layer and the first reference electrode and the second reference electrode are recorded. The test method for an all-solid-state battery according to claim 1.

Images