Fluoride ion secondary battery

Abstract

The problem to be solved by the present invention is to provide a fluoride ion secondary battery, which can obtain a high charge and discharge efficiency even in an environment where the oxygen concentration exceeds 2ppm. In order to solve the above problems, a fluoride ion secondary battery is provided, which comprises: a positive electrode material layer; a negative electrode material layer; a solid electrolyte layer, which is arranged between the positive electrode material layer and the negative electrode material layer; and an outer body, which accommodates and seals the positive electrode material layer, the negative electrode material layer, and the solid electrolyte layer; and the sealed space in the outer body is an Ar environment. The oxygen concentration in the sealed space in the outer body can be below 7.3ppm.

Description

Technical Field

[0001] The invention relates to a fluoride ion secondary battery. Background Art

[0002] Currently, a fluoride ion secondary battery using fluoride ions as carriers has been proposed. In recent years, fluoride ion secondary batteries are expected to have battery characteristics superior to those of lithium ion secondary batteries, and various studies have been conducted.

[0003] For example, a fluoride ion secondary battery has been proposed (for example, refer to Patent Document 1), comprising: a positive electrode; a negative electrode comprising at least one of a metal containing at least La and a fluoride containing at least La; an ion conductive medium that conducts fluoride ions; and a housing that seals and houses the positive electrode, the negative electrode, and the ion conductive medium.

[0004] [Prior Technical Literature]

[0005] (Patent Document)

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-84506 Summary of the invention

[0007] [Problems to be solved by the invention]

[0008] However, in the existing fluoride ion secondary battery described in Patent Document 1, the electrode active material is deactivated by oxygen oxidation during the fluorination and defluorination reactions of charge and discharge. Therefore, if the oxygen concentration in the interior of the housing is below 2ppm, the existing fluoride ion secondary battery cannot work, and the charge and discharge efficiency is halved in three charge and discharge cycles, and the cycle degradation is significant. Therefore, it is desirable to develop a fluoride ion secondary battery that can obtain a higher charge and discharge efficiency even in an environment where the oxygen concentration exceeds 2ppm.

[0009] The present invention has been made in view of the above, and an object of the present invention is to provide a fluoride ion secondary battery capable of achieving high charge and discharge efficiency even in an environment where the oxygen concentration exceeds 2 ppm.

[0010] [Technical means to solve the problem]

[0011] (1) The present invention provides a fluoride ion secondary battery, comprising: a positive electrode material layer; a negative electrode material layer; a solid electrolyte layer, arranged between the positive electrode material layer and the negative electrode material layer; and an outer casing, which accommodates and seals the positive electrode material layer, the negative electrode material layer and the solid electrolyte layer; and the sealed space within the outer casing is an Ar environment.

[0012] (2) Alternatively, in the fluoride ion secondary battery of (1), the oxygen concentration in the sealed space within the outer casing is 7.3 ppm or less.

[0013] (3) Optionally, in the fluoride ion secondary battery of (1), the positive electrode material layer comprises Ag, the negative electrode material layer comprises at least one of CeF 3 and PbF 2 , and the solid electrolyte layer comprises LaF 3 .

[0014] (Effects of the Invention)

[0015] According to the present invention, it is possible to provide a fluoride ion secondary battery capable of achieving high charge and discharge efficiency even in an environment where the oxygen concentration exceeds 2 ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a diagram schematically showing the structure of the fluoride ion secondary battery of the first embodiment.

[0017] Figure 2 This is a diagram showing an example of a method for manufacturing the fluoride ion secondary battery according to the first embodiment.

[0018] Figure 3 The graph shows the charge and discharge curves of the fluoride ion secondary battery of Example 1.

[0019] Figure 4 The graph shows the relationship between the square root of the number of cycles and the capacity of the fluoride ion secondary battery of Example 1.

[0020] Figure 5 This is a graph showing the relationship between the square root of the number of cycles of the fluoride ion secondary battery of Example 1 and the charge and discharge efficiency.

[0021] Figure 6 The graph shows the charge and discharge curves of the fluoride ion secondary batteries of Example 1 and Example 2.

[0022] Figure 7 This is a graph showing the change in oxygen concentration in the outer casing of the button battery of Example 2 over time.

[0023] Figure 8 This is a graph showing the relationship between time, voltage, and current in a charge and discharge test of the fluoride ion secondary battery of Example 2. DETAILED DESCRIPTION

[0024] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

[0025] Figure 1 Schematic diagram of the structure of the fluoride ion secondary battery 1 of the first embodiment. Figure 1 As shown, the fluoride ion secondary battery 1 of this embodiment includes: a positive electrode material layer 11; a negative electrode material layer 13; a solid electrolyte layer 15, which is arranged between the positive electrode material layer 11 and the negative electrode material layer 13; and an outer body 10, which accommodates and seals the positive electrode material layer 11, the negative electrode material layer 13 and the solid electrolyte layer 15.

[0026] The outer casing 10 is not particularly limited as long as it can contain and seal the positive electrode material layer 11, the negative electrode material layer 13, and the solid electrolyte layer 15. For example, in addition to the laminate film, a button battery outer casing including a container and a cover can also be used. In addition, a battery manufactured by EC Frontier Co., Ltd. can also be used as the outer casing 10. In addition, Figure 1 2 shows an example in which a button battery outer casing is used as the outer casing 10 .

[0027] The fluoride ion secondary battery 1 of this embodiment is characterized in that the sealed space in the outer casing 10 is an Ar environment. That is, the interior of the outer casing 10 is filled with Ar gas. In addition, the interior of the outer casing 10 does not need to be evacuated, and the oxygen concentration in the outer casing 10 can be higher than that of the existing fluoride ion secondary battery.

[0028] Specifically, the oxygen concentration in the sealed space in the outer body 10 is preferably below 7.3ppm. As described above, the existing fluoride ion secondary battery cannot work if the oxygen concentration inside the battery is below 2ppm, and the charge and discharge efficiency is halved in three charge and discharge cycles, and the cycle degradation is significant. In this regard, in the fluoride ion secondary battery 1 of the present embodiment, since the sealed space in the outer body 10 is an Ar environment, if the oxygen concentration in the sealed space is below 7.3ppm, the battery works and a higher charge and discharge efficiency can be obtained.

[0029] The positive electrode material layer 11 is composed of Ag. It is preferable to use a positive electrode material layer 11 composed only of Ag. The positive electrode material layer 11 releases fluoride ions F during discharge. - , absorbs fluoride ions F during charging - The positive electrode material layer 11 composed of Ag has a characteristic of having a low overvoltage at room temperature. The positive electrode material layer 11 composed of Ag is formed by, for example, sputtering as described later.

[0030] The thickness of the positive electrode material layer 11 is preferably greater than 10 nm and less than 120 nm. If the thickness of the positive electrode material layer 11 is less than 10 nm, it cannot be formed into a particle or island state, or even if it is formed, it will cause uneven reaction, so it is not preferred. In addition, if the thickness of the positive electrode material layer 11 exceeds 120 nm, the overvoltage increases and the charge and discharge efficiency decreases, so it is not preferred. The more preferred thickness of the positive electrode material layer 11 is greater than 10 nm and less than 60 nm, and more preferably greater than 10 nm and less than 30 nm. Figure 1 2 shows an example in which the thickness of the positive electrode material layer 11 is 60 nm.

[0031] The negative electrode material layer 13 is composed of at least one of CeF3 and PbF2. Preferably, the negative electrode material layer 13 is composed of CeF3. The negative electrode material layer 13 absorbs fluoride ions F during discharge. - , releases fluoride ions F during charging - The negative electrode material layer 13 composed of at least one of CeF3 and PbF2 has a characteristic of having a low overvoltage at room temperature. The negative electrode material layer 13 composed of at least one of CeF3 and PbF2 is formed by sputtering, for example, as described later.

[0032] The thickness of the negative electrode material layer 13 is preferably greater than 10 nm and less than 200 nm. If the thickness of the negative electrode material layer 13 is less than 10 nm, it cannot be formed into a particle or island state, or even if it is formed, it will cause uneven reaction, so it is not preferred. In addition, if the thickness of the negative electrode material layer 13 exceeds 200 nm, the overvoltage increases and the charge and discharge efficiency decreases, so it is not preferred. The more preferred thickness of the negative electrode material layer 13 is greater than 10 nm and less than 100 nm. Figure 1 An example is shown in which the film thickness of the negative electrode material layer 13 is 100 nm.

[0033] The negative electrode material layer 13 may further include, for example, a solid electrolyte composed of a fluoride ion conductive fluoride or a conductive auxiliary agent. In addition, the negative electrode material layer 13 may further include other components such as a binder within a range that does not impair the effects of the present embodiment.

[0034] As the fluoride ion conductive fluoride, any fluoride having fluoride ion conductivity may be used, and CeBaF is shown as an example. x or BaLaF y The fluoride ion conductivity is improved by including these fluoride ion conductive fluorides.

[0035] As the conductive auxiliary agent, any auxiliary agent having electron conductivity may be used, and for example, carbon black etc. are used. Examples of carbon black include furnace black, Ketjen black, acetylene black etc. By including these conductive auxiliary agents, electron conductivity is improved.

[0036] The solid electrolyte layer 15 is composed of LaF3. The solid electrolyte layer 15 composed of LaF3 has excellent fluoride ion F - As the solid electrolyte layer 15 composed of LaF3, a commercially available LaF3 substrate can be used. In addition, the film thickness of the solid electrolyte layer 15 is not particularly limited, and is preferably 0.1 mm to 0.5 mm, for example. Figure 1 2 shows an example in which the film thickness of the solid electrolyte layer 15 is 0.5 mm.

[0037] In addition, the fluoride ion secondary battery 1 of this embodiment preferably includes a positive electrode collector layer 12 disposed outside the positive electrode material layer 11. The positive electrode collector layer 12 is not limited as long as it has electron conductivity. For example, it is preferred to use a positive electrode collector layer 12 composed of carbon. The film thickness of the positive electrode collector layer 12 is not particularly limited. Figure 1 2 shows an example in which the thickness of the positive electrode current collector layer 12 is 30 nm.

[0038] In addition, the fluoride ion secondary battery 1 of this embodiment preferably has a negative electrode collector layer 14 disposed outside the negative electrode material layer 13. The negative electrode collector layer 14 is not limited as long as it has electron conductivity. For example, when the negative electrode material layer 13 includes CeF3, it is preferred to use a negative electrode collector layer 14 composed of carbon. On the other hand, when the negative electrode material layer includes PbF2, it is preferred to use a negative electrode collector layer composed of Pb foil. The film thickness of the negative electrode collector layer 14 is not particularly limited. Figure 1 2 shows an example in which the film thickness of the negative electrode current collector layer 14 is 30 nm.

[0039] The fluoride ion secondary battery 1 of this embodiment is not particularly limited in shape or size. Figure 1 , an example of a cylindrical button cell outer body is shown, showing an example in which the diameters of the positive electrode material layer 11, the positive electrode collector layer 12, the negative electrode material layer 13, and the negative electrode collector layer 14 are ф8 mm, and the diameter of the solid electrolyte layer 15 is ф10 mm. By increasing the diameter of the solid electrolyte layer 15 in this way, a short circuit between the positive electrode and the negative electrode is suppressed.

[0040] Next, the method for manufacturing the fluoride ion secondary battery of this embodiment is described with reference to Figure 2 Explain in detail.

[0041] Figure 2 FIG. 1 is a diagram showing an example of a method for manufacturing a fluoride ion secondary battery according to the present embodiment. Figure 2As shown, first, a LaF3 substrate as a solid electrolyte layer 15 is placed on a predetermined jig (not shown) without being exposed to the atmosphere (for example, in an environment with a dew point of 80°C or less and an oxygen concentration of 1 ppm or less). This operation can be performed in a glove box manufactured by UNICO Co., Ltd. set to the above environment, for example.

[0042] In addition, as the LaF3 substrate, a commercially available LaF3 substrate manufactured by, for example, Pier Optics Co., Ltd. can be used. The size of the LaF3 substrate is not particularly limited, and, for example, a LaF3 substrate of ф10 mm×thickness 0.5 mm can be used. In addition, the LaF3 substrate preferably uses a substrate with a mirror-polished surface.

[0043] Next, while maintaining the above environment, the LaF3 substrate set in the above fixture is transported to the chamber of the sputtering device. As the sputtering device, a commercially available sputtering device such as the sputtering device "EB1000" manufactured by Canon Anelva Co., Ltd. can be used. The vacuum degree in the chamber before film formation is set to, for example, 5×10 -4 Below Pa.

[0044] Next, DC sputtering is performed using the above-mentioned sputtering device to form a positive electrode material layer 11 composed of Ag on one surface of the LaF3 substrate as the solid electrolyte layer 15. After the film formation, a predetermined time is allowed to elapse.

[0045] Next, DC sputtering is performed on the formed positive electrode material layer 11 using the above-mentioned sputtering device to form a positive electrode current collector layer 12 made of carbon.

[0046] Next, while maintaining the above environment, a LaF3 substrate as a solid electrolyte layer 15 having a positive electrode material layer 11 and a positive electrode collector layer 12 sequentially formed on one surface is transported from the chamber of the sputtering device to the above glove box. After transport, the LaF3 substrate is removed from the above fixture, turned over, and placed again on the above fixture with the other surface facing the surface side.

[0047] Next, while maintaining the above environment, the LaF3 substrate turned over and set again on the above fixture is transported to the chamber of the sputtering device. After transporting, RF sputtering using the above sputtering device is performed to form a negative electrode material layer 13 composed of CeF3 on the other side of the LaF3 substrate as the solid electrolyte layer 15. The same operation can also be performed when forming a negative electrode material layer composed of PbF2.

[0048] Next, DC sputtering using the above-mentioned sputtering device is performed on the formed negative electrode material layer 13 to form a negative electrode current collector layer 14 made of carbon. The same operation can be performed when forming a positive electrode current collector layer made of Pb foil.

[0049] Next, while maintaining the above environment, the LaF3 substrate as the solid electrolyte layer 15 having the negative electrode material layer 13 and the negative electrode collector layer 14 sequentially formed on the other side is transported from the chamber of the sputtering device to the above glove box. After transporting, after the installation and assembly steps of the outer body 10 of the button battery or laminated battery, Ar gas is introduced into the sealed space in the outer body 10, thereby obtaining the fluoride ion secondary battery 1 of this embodiment.

[0050] In addition, for the film formation of each layer, each film formation rate can be verified in advance and the sputtering time can be adjusted according to its film formation rate, so as to control the film thickness. Specifically, for example, in a state where a masking tape such as a polyimide tape is attached to a part of the quartz plate, after each sputtering film formation is carried out under certain conditions, the masking tape is peeled off, and the height difference (film thickness) between the portion masked by the masking tape and the portion not masked is measured using a height difference meter. Then, a calibration curve is prepared based on the results of the measurements of the conditions for changing each sputtering film formation, so as to find the film formation rate. In this way, the thickness of each film formation is controlled to the desired film thickness.

[0051] Next, the battery capacity of the fluoride ion secondary battery 1 of the present embodiment will be described.

[0052] As an example of the fluoride ion secondary battery 1 of this embodiment, Figure 1 As shown, when the film thickness of the positive electrode material layer 11 composed of Ag is set to 60 nm and the film thickness of the negative electrode material layer 13 composed of CeF 3 is set to 100 nm, the capacities of the positive electrode half cell and the negative electrode half cell are as follows.

[0053] [Positive half-cell]

[0054] Theoretical capacity: 248mAh / g

[0055] Density: 10.49 g / cm 3

[0056] Film thickness: 60nm

[0057] Electrode area: 0.5 cm 2

[0058] Battery capacity: 7.84μAh

[0059] [Negative half-cell]

[0060] Theoretical capacity: 408mAh / g

[0061] Density: 6.77g / cm 3

[0062] Film thickness: 100nm

[0063] Electrode area: 0.5 cm 2

[0064] Battery capacity: 12.8μAh

[0065] In the fluoride ion secondary battery 1 of the present embodiment, as described above, the theoretical capacity of the positive electrode is small, so the battery capacity is determined by the theoretical capacity of the positive electrode. That is, the positive electrode capacity of the battery capacity of the fluoride ion secondary battery 1 of the present embodiment described above is 7.84 μAh, and the N / P ratio is 12.8 / 7.84=1.63.

[0066] According to the fluoride ion secondary battery 1 of the present embodiment having the above-described structure, the following effects are achieved.

[0067] The fluoride ion secondary battery 1 of this embodiment includes: a positive electrode material layer 11; a negative electrode material layer 13; a solid electrolyte layer 15 disposed between the positive electrode material layer 11 and the negative electrode material layer 13; and an outer casing 10 that accommodates and seals the positive electrode material layer 11, the negative electrode material layer 13, and the solid electrolyte layer 15. In addition, the sealed space in the outer casing 10 is set to an Ar environment.

[0068] Thus, since the sealed space in the outer body 10 is an Ar environment, it is possible to suppress the electrode active material from being oxidized by oxygen and deactivated during the fluorination and defluorination reactions during charge and discharge. Therefore, according to this embodiment, even if the oxygen concentration in the sealed space is high, it can work as a battery and can obtain a higher charge and discharge efficiency. Specifically, even if the oxygen concentration in the sealed space in the outer body 10 is below 7.3ppm, it can work as a battery and can obtain a higher charge and discharge efficiency.

[0069] In addition, the fluoride ion secondary battery 1 of the present embodiment comprises: a positive electrode material layer 11, comprising Ag; a negative electrode material layer 13, comprising at least one of CeF3 and PbF2; and a solid electrolyte layer 15, disposed between the positive electrode material layer 11 and the negative electrode material layer 13, and comprising LaF3. That is, the fluoride ion secondary battery 1 of the present embodiment selects a material composition having a small overvoltage even when operating at room temperature by using a charge and discharge test in a half-cell and an intermittent charge and discharge test. Therefore, even when operating at room temperature, a large overvoltage can be avoided, so that charge and discharge cycle degradation can be suppressed, and a higher charge and discharge efficiency can be obtained.

[0070] The present invention is not limited to the above-described embodiments, and modifications and improvements made within the scope that can achieve the object of the present invention are included in the present invention.

[0071] [Example]

[0072] Next, examples of the present invention will be described, but the present invention is not limited to these examples.

[0073] (Example 1)

[0074] As Example 1, according to the above-mentioned manufacturing method, Figure 1 The fluoride ion secondary battery of the first embodiment shown in the figure. In addition, in Example 1, the sealed space in the outer body of the button battery is evacuated and then filled with Ar gas. That is, the oxygen concentration in the sealed space in the outer body of the button battery of Example 1 is set to be less than 2 ppm. The fluoride ion secondary battery of Example 1 is subjected to a constant current (CC) charge and discharge test under the following conditions.

[0075] At room temperature 25°C under vacuum (1×10 -4 Pa or less) to conduct CC charge and discharge test. In the fluoride ion secondary battery of Example 1, the battery capacity is determined by the theoretical capacity of the positive electrode composed of Ag, 248 mAh / g, which is smaller than the theoretical capacity of the negative electrode composed of CeF3. Therefore, the current load is set to 400 nA, which is equivalent to 1 / 20C of the theoretical capacity of the positive electrode composed of Ag, 248 mAh / g. The battery area of ​​Example 1 is about 0.5 cm 2 , so the current load is equivalent to about 0.8μA / cm per unit area 2 In addition, the cut-off condition is a cut-off voltage of 1.0 to 4.2 V, or a cut-off time of 20 hours. In addition, a 10-minute pause is performed each time the charge and discharge are switched.

[0076] As a charge and discharge test procedure, a rate test was performed for the first 10 cycles. Specifically, the rate was 1 / 20C in the 1st to 3rd cycles, 1 / 10C in the 4th to 5th cycles, 1C in the 6th to 7th cycles, and 2C in the 8th to 9th cycles, and the rate was slowly increased to a faster rate. After the rate test, the charge and discharge test was continued for 100 cycles at a rate of 1C. In addition, halfway through, the rate was set to 1 / 20C to confirm the charge and discharge capacity. The charge and discharge test results are shown in Figure 3 to Figure 5 .

[0077] Figure 3 The graph shows the charge and discharge curves of the fluoride ion secondary battery of Example 1. Figure 4 The graph shows the relationship between the square root of the number of cycles and the capacity of the fluoride ion secondary battery of Example 1. Figure 5: is a graph showing the relationship between the square root of the number of cycles and the charge and discharge efficiency of the fluoride ion secondary battery of Example 1. Here, Figure 3 The charge and discharge curves obtained by the rate test of the first 10 cycles are shown. Figure 4 and Figure 5 In addition to the rate test, the charge and discharge capacity and charge and discharge efficiency obtained by the charge and discharge test of 100 cycles after the rate test are shown.

[0078] like Figure 3 to Figure 5 As shown, it can be confirmed that the fluoride ion secondary battery according to Example 1 works as a battery at room temperature. In addition, at room temperature, the initial charge and discharge efficiency is 90%, and the discharge capacity of 2C is maintained at 77% relative to the discharge capacity of 0.05C, which shows that it has excellent rate characteristics. It can be further known that at room temperature, the charge and discharge efficiency during 1C charge and discharge cycles is 99%, and the capacity retention rate after 100 cycles of charge and discharge is 50%. Based on the above results, it can be confirmed that the fluoride ion secondary battery according to Example 1 can obtain a higher charge and discharge efficiency at room temperature.

[0079] (Example 2)

[0080] As Example 2, the above-mentioned manufacturing method was used to prepare Figure 1 The fluoride ion secondary battery of the first embodiment shown in the figure. In Example 2, the sealed space in the button battery outer package is filled with Ar gas without evacuation. The fluoride ion secondary battery of Example 2 is subjected to a constant current (CC) charge and discharge test under the same conditions as those of Example 1.

[0081] Figure 6 Graphs showing the charge and discharge curves of the fluoride ion secondary batteries of Examples 1 and 2. Figure 6 As shown, it was confirmed that the fluoride ion secondary battery of Example 2 was not evacuated, but since the sealed space in the outer package was an Ar atmosphere as in Example 1, it also functioned as a battery.

[0082] In addition, using the fluoride ion secondary battery of Example 2, the change in oxygen concentration over time in the outer casing of the button battery of Example 2 was examined. Specifically, after the button battery type fluoride ion secondary battery of Example 2 was made, it was placed in the atmosphere, and the amount of oxygen leaking into the button battery was examined after 2 days and 3 days. The amount of oxygen leakage was measured under the following measurement conditions.

[0083] (Measurement conditions)

[0084] Measuring device: TPD-MS (Programmed Temperature Desorption-Mass Spectrometry) device

[0085] Sealed container: Sealed container for packaging analysis

[0086] GC (gas chromatography) / MS device: GC / MS device "QP2010Plus(10)" manufactured by Shimadzu Corporation

[0087] Measurement mode: 5 minutes after the start of measurement, the sample is destroyed in a sealed container and the released gas is analyzed by TPD-MS

[0088] Destruction temperature: room temperature

[0089] MS sensitivity: 0.95kV

[0090] Mass number range: m / z = 10 to 300

[0091] Environment: He flow (50ml / min)

[0092] Reference material: Air

[0093] Data processing: TRC thermal analysis processing system "THADAP-TGGC / MS"

[0094] Figure 7 Graph showing the change of oxygen concentration in the outer casing of the button battery of Example 2 over time. Figure 7 In the figure, the oxygen concentration on day 0 is set to 0.5 ppm in the glove box where the button cell is assembled. Figure 7 As shown in the figure, the oxygen concentration increased with time after 2 days and 3 days, and it can be confirmed that oxygen leaked into the button battery. In addition, according to these results, it can be obtained Figure 7 The approximate straight line shown.

[0095] Here, Figure 8 Graph showing the relationship between the elapsed time, voltage, and current in the charge and discharge test of the fluoride ion secondary battery of Example 2. Figure 8 As shown in FIG. 2 , it can be confirmed that in Example 2, the initial charge-discharge efficiency after 34 hours of the first CC charge-discharge (1 / 20C) cycle is 80%, which can support 1 cycle. Figure 7 The oxygen concentration after 34 hours (1.42 days) can be determined from the approximate straight line of , and it can be confirmed to be 7.3 ppm. Therefore, it can be confirmed that the oxygen concentration in the sealed space in the outer package is preferably 7.3 ppm or less.

[0096] Reference numerals

[0097] 1 Fluoride ion secondary battery

[0098] 10 outer body

[0099] 11. Positive electrode material layer

[0100] 12. Positive electrode collector layer

[0101] 13. Negative electrode material layer

[0102] 14 Negative electrode collector layer

[0103] 15 Solid electrolyte layer

Claims

1. A fluoride ion secondary battery, comprising: a positive electrode material layer; a negative electrode material layer; a solid electrolyte layer disposed between the positive electrode material layer and the negative electrode material layer; and an outer casing that accommodates and seals the positive electrode material layer, the negative electrode material layer, and the solid electrolyte layer; and, The sealed space in the outer package is an Ar environment, and the oxygen concentration is greater than 2 ppm and less than 7.3 ppm. The positive electrode material layer is composed of Ag, and the film thickness of the positive electrode material layer is greater than or equal to 10 nm and less than or equal to 60 nm. The negative electrode material layer is composed of at least one of CeF3 and PbF2, and the film thickness of the negative electrode material layer is greater than 10 nm and less than 100 nm. The aforementioned solid electrolyte layer is a LaF3 substrate.

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