Fluoride ion secondary battery

Abstract

The problem to be solved by the present invention is to provide a fluoride ion secondary battery that can achieve high charge-discharge efficiency at room temperature. To solve the above problems, a fluoride ion secondary battery is provided, comprising: a positive electrode material layer containing Ag; a negative electrode material layer containing at least one of CeF3 and PbF2; and a solid electrolyte layer disposed between the positive electrode material layer and the negative electrode material layer and containing LaF3. A negative electrode current collector layer may also be provided, the negative electrode current collector layer being disposed outside the negative electrode material layer. When the negative electrode material layer contains CeF3, the negative electrode current collector layer may include carbon; and when the negative electrode material layer contains PbF2, the negative electrode current collector layer may include a Pb foil.

Description

Technical Field

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

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

[0003] For example, a fluoride ion secondary battery (see, for example, Patent Document 1) is proposed, which includes: a positive electrode; a negative electrode containing at least one of a metal containing at least La and a fluoride containing at least La; an ion conduction medium that conducts fluoride ions; and a housing portion that encloses and houses the positive electrode, the negative electrode, and the ion conduction medium, and has an oxygen concentration inside of 2 ppm or less.

[0004] [Prior Art Documents]

[0005] (Patent Document)

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-84506 Summary of the Invention

[0007] [Problems to be Solved by the Invention]

[0008] However, the existing fluoride ion secondary battery as described in Patent Document 1 can only operate at a high temperature of 150°C, and the charge-discharge efficiency is halved in 3 charge-discharge cycles, and the cycle deterioration is significant. Therefore, it is desired to develop a fluoride ion secondary battery that can obtain high charge-discharge efficiency at room temperature.

[0009] The present invention has been made in view of the above, and an object thereof is to provide a fluoride ion secondary battery that can obtain high charge-discharge efficiency at room temperature.

[0010] [Means for Solving the Problems]

[0011] (1) The present invention provides a fluoride ion secondary battery, comprising: a positive electrode material layer containing Ag; a negative electrode material layer containing at least one of CeF3 and PbF2; and a solid electrolyte layer disposed between the positive electrode material layer and the negative electrode material layer and containing LaF3.

[0012] (2) Optionally, in the fluoride ion secondary battery of (1), the negative electrode material layer contains CeF3, and the fluoride ion secondary battery further includes a negative electrode current collector layer disposed outside the negative electrode material layer and including carbon.

[0013] (3) Optionally, in the fluoride ion secondary battery of (1), the aforementioned negative electrode material layer contains PbF₂, and the fluoride ion secondary battery further includes a negative electrode current collector layer, which is disposed outside the aforementioned negative electrode material layer and includes a Pb foil.

[0014] (4) Optionally, in the fluoride ion secondary battery of any one of (1) to (3), a positive electrode current collector layer is further included, which is disposed outside the aforementioned positive electrode material layer and includes carbon.

[0015] (5) Optionally, in the fluoride ion secondary battery of any one of (1) to (4), the film thickness of the aforementioned positive electrode material layer is 10 nm or more and less than 120 nm.

[0016] (6) Optionally, in the fluoride ion secondary battery of any one of (1) to (5), the film thickness of the aforementioned positive electrode material layer is 10 nm or more and 60 nm or less.

[0017] (7) Optionally, in the fluoride ion secondary battery of any one of (1) to (6), the film thickness of the aforementioned positive electrode material layer is 10 nm or more and 30 nm or less.

[0018] (8) Optionally, in the fluoride ion secondary battery of any one of (1) to (7), the film thickness of the aforementioned negative electrode material layer is 10 nm or more and less than 200 nm.

[0019] (8) Optionally, in the fluoride ion secondary battery of any one of (1) to (8), the film thickness of the aforementioned negative electrode material layer is 10 nm or more and 50 nm or less.

[0020] (Effects of the Invention)

[0021] According to the present invention, a fluoride ion secondary battery can be provided, which can obtain high charge-discharge efficiency at room temperature. Description of the Drawings

[0022] Figure 1 is a diagram showing the structure of the fluoride ion secondary battery of the first embodiment.

[0023] Figure 2 is a diagram showing an example of the manufacturing method of the fluoride ion secondary battery of the first embodiment.

[0024] Figure 3 is a diagram showing the charge-discharge curve of the fluoride ion secondary battery of Example 1.

[0025] Figure 4 is a diagram showing the relationship between the square root of the number of cycles and the capacity of the fluoride ion secondary battery of Example 1.

[0026] Figure 5 It is a graph showing the relationship between the square root of the number of cycles and the charge-discharge efficiency of the fluoride ion secondary battery of Example 1.

[0027] Figure 6 It is a graph showing the structure of the fluoride ion secondary battery of Example 2.

[0028] Figure 7 It is a graph showing the structures of the fluoride ion secondary batteries of Comparative Examples 1 and 2.

[0029] Figure 8 It is a graph showing the intermittent charge-discharge curves of the fluoride ion secondary batteries of Example 2 and Comparative Examples 1 and 2.

[0030] Figure 9 It is a graph showing the charge-discharge curves of the fluoride ion secondary batteries of Comparative Examples 1 to 6.

[0031] Figure 10 It is a graph showing the structure of the fluoride ion secondary battery of Example 3.

[0032] Figure 11 It is a graph showing the charge-discharge curve of the fluoride ion secondary battery of Example 3.

[0033] Figure 12 It is a graph showing the relationship between the square root of the number of cycles and the capacity of the fluoride ion secondary battery of Example 3.

[0034] Figure 13 It is a graph showing the relationship between the square root of the number of cycles and the charge-discharge efficiency of the fluoride ion secondary battery of Example 3.

[0035] Figure 14 It is a graph showing the relationship between the square root of the number of cycles and the discharge capacity retention rate of the fluoride ion secondary batteries of Examples 1 and 3. Detailed Description of the Invention

[0036] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0037] Figure 1 It is a graph showing the structure of the fluoride ion secondary battery 1 of the first embodiment. As Figure 1 shown, the fluoride ion secondary battery 1 of the present embodiment includes: a positive electrode material layer 11; a negative electrode material layer 13; and a solid electrolyte layer 15 disposed between the positive electrode material layer 11 and the negative electrode material layer 13.

[0038] The positive electrode material layer 11 is configured to contain Ag. It is preferable to use the positive electrode material layer 11 including only Ag. The positive electrode material layer 11 releases fluoride ions F during discharge- which absorbs fluoride ions F during charging - The positive electrode material layer 11 containing Ag has the characteristic of less overvoltage at room temperature. The positive electrode material layer 11 containing Ag is formed by, for example, sputtering as described below.

[0039] The film thickness of the positive electrode material layer 11 is preferably 10 nm or more and less than 120 nm. If the film thickness of the positive electrode material layer 11 is less than 10 nm, film formation cannot be achieved in a particulate or island state, or even if film formation is achieved, reaction unevenness will occur, so it is not preferred. In addition, if the film thickness of the positive electrode material layer 11 exceeds 120 nm, the overvoltage increases and the charge-discharge efficiency decreases, so it is not preferred. A more preferred film thickness of the positive electrode material layer 11 is 10 nm or more and 60 nm or less, and further preferably 10 nm or more and 30 nm or less. An example in which the film thickness of the positive electrode material layer 11 is 30 nm is shown in Figure 1 .

[0040] The negative electrode material layer 13 is configured to contain at least one of CeF3 and PbF2. Preferably, the negative electrode material layer 13 configured to contain CeF3 is used. The negative electrode material layer 13 absorbs fluoride ions F during discharging - and releases fluoride ions F during charging - . The negative electrode material layer 13 composed of at least one of CeF3 and PbF2 has the characteristic of less overvoltage at room temperature. The negative electrode material layer 13 containing at least one of CeF3 and PbF2 is formed by, for example, sputtering as described below.

[0041] The film thickness of the negative electrode material layer 13 is preferably 10 nm or more and less than 200 nm. If the film thickness of the negative electrode material layer 13 is less than 10 nm, film formation cannot be achieved in a particulate or island state, or even if film formation is achieved, reaction unevenness will occur, so it is not preferred. In addition, if the film thickness of the negative electrode material layer 13 exceeds 200 nm, the overvoltage increases and the charge-discharge efficiency decreases, so it is not preferred. A more preferred film thickness of the negative electrode material layer 13 is 10 nm or more and 100 nm or less, and further preferably 10 nm or more and 50 nm or less. An example in which the film thickness of the negative electrode material layer 13 is 50 nm is shown in Figure 1 .

[0042] In addition, the negative electrode material layer 13 may further contain, for example, a solid electrolyte including a fluoride ion-conductive fluoride or a conductive aid. In addition, within the range that does not impair the effects of the present embodiment, the negative electrode material layer 13 may further contain other components such as a binder.

[0043] As the fluoride ion-conductive fluoride, any fluoride having fluoride ion conductivity may be used, and for example, CeBaF is shown x or BaLaF yFluorides such as fluoride ion conductors. By including these fluoride ion conductors, the fluoride ion conductivity is improved.

[0044] As the conductive additive, as long as it has electronic conductivity, for example, carbon black etc. can be used. As the carbon black, furnace black, Ketjen black, acetylene black etc. are listed. By including these conductive additives, the electronic conductivity is improved.

[0045] The solid electrolyte layer 15 is configured to include LaF3. The solid electrolyte layer 15 including LaF3 has excellent fluoride ion F - conductivity. As the solid electrolyte layer 15 including 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 preferably, for example, 0.1 mm to 0.5 mm. An example where the film thickness of the solid electrolyte layer 15 is 0.5 mm is shown in Figure 1

[0046] In addition, the fluoride ion secondary battery 1 of the present embodiment preferably includes a positive electrode current collector layer 12 disposed outside the positive electrode material layer 11. The positive electrode current collector layer 12 only needs to have electronic conductivity and is not limited. For example, it is preferable to use a positive electrode current collector layer 12 including carbon. The film thickness of the positive electrode current collector layer 12 is not particularly limited, and an example where the film thickness of the positive electrode current collector layer 12 is 30 nm is shown in Figure 1

[0047] In addition, the fluoride ion secondary battery 1 of the present embodiment preferably includes a negative electrode current collector layer 14 disposed outside the negative electrode material layer 13. The negative electrode current collector layer 14 only needs to have electronic conductivity and is not limited. For example, when the negative electrode material layer 13 includes CeF3, it is preferable to use a negative electrode current collector layer 14 including carbon. In contrast, when the negative electrode material layer includes PbF2, it is preferable to use a negative electrode current collector layer including a Pb foil. The film thickness of the negative electrode current collector layer 14 is not particularly limited, and an example where the film thickness of the negative electrode current collector layer 14 is 30 nm is shown in Figure 1

[0048] The fluoride ion secondary battery 1 of the present embodiment having the above structure preferably further includes an outer package such as a button battery or a laminated battery.

[0049] The fluoride ion secondary battery 1 of the present embodiment is not particularly limited in shape and size. An example of a cylindrical shape is shown in Figure 1 In addition, an example where the diameters of the positive electrode material layer 11, the positive electrode current collector layer 12, the negative electrode material layer 13, and the negative electrode current collector layer 14 are ф8 mm and the diameter of the solid electrolyte layer 15 is ф10 mm is shown. By increasing the diameter of the solid electrolyte layer 15 in this way, the short circuit between the positive electrode and the negative electrode is suppressed.

[0050] Next, the manufacturing method of the fluoride ion secondary battery according to the present embodiment will be described in detail with reference to Figure 2 .

[0051] Figure 2 FIG. is a diagram showing an example of the manufacturing method of the fluoride ion secondary battery according to the present embodiment. As Figure 2 shown, first, in an environment not exposed to the atmosphere (for example, an environment with a dew point of 80 °C or lower and an oxygen concentration of 1 ppm or lower), the LaF3 substrate serving as the solid electrolyte layer 15 is set on a predetermined jig (not shown). This operation can be performed, for example, inside a glove box manufactured by UNICO Co., Ltd. and set to the above environment.

[0052] 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 a LaF3 substrate such as ф10 mm × thickness 0.5 mm can be used. Additionally, the LaF3 substrate preferably uses a substrate with a surface mirror-polished.

[0053] Immediately afterwards, while maintaining the above environment, the LaF3 substrate set in the above jig is transported into the chamber of a sputtering device. As the sputtering device, a commercially available sputtering device such as the "EB1000" sputtering device manufactured by Canon Anelva Co., Ltd. can be used. The degree of vacuum inside the chamber before film formation is set to, for example, 5×10 -4 Pa or less.

[0054] Next, DC sputtering using the above sputtering device is performed to form a positive electrode material layer 11 including Ag on one surface of the LaF3 substrate serving as the solid electrolyte layer 15. After film formation, a predetermined time is paused.

[0055] Next, DC sputtering using the above sputtering device is performed on the formed positive electrode material layer 11 to form a positive electrode current collector layer 12 including carbon.

[0056] Next, while maintaining the above environment, the LaF3 substrate serving as the solid electrolyte layer 15 on which the positive electrode material layer 11 and the positive electrode current collector layer 12 are successively formed on one surface is transported from the chamber of the sputtering device into the above glove box. After transportation, the LaF3 substrate is removed from the above jig, turned over, and set again on the above jig in a state where the other surface faces the surface side.

[0057] Next, while maintaining the above environment, the LaF3 substrate, which has been turned over and set on the above jig again, is transported into the chamber of the sputtering device. After the transportation, RF sputtering using the above sputtering device is performed, so that the negative electrode material layer 13 made of CeF3 is formed on the other surface of the LaF3 substrate serving as the solid electrolyte layer 15. The same operation can be performed in the case of forming the negative electrode material layer made of PbF2.

[0058] Next, DC sputtering using the above sputtering device is performed on the formed negative electrode material layer 13, so that the negative electrode current collector layer 14 including carbon is formed. The same operation can be performed in the case of forming the negative electrode current collector layer including a Pb foil.

[0059] Next, while maintaining the above environment, the LaF3 substrate serving as the solid electrolyte layer 15, on which the negative electrode material layer 13 and the negative electrode current collector layer 14 are sequentially formed on the other surface, is transported from the chamber of the sputtering device into the above glove box. After the transportation, the fluoride ion secondary battery 1 of the present embodiment is obtained through the installation and assembly processes of an exterior body such as a button battery or a laminated battery.

[0060] In addition, for the film formation of each layer, the film formation rate of each layer can be verified in advance and the sputtering time can be adjusted according to the 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 a quartz plate, after performing each sputtering film formation under a certain condition, the masking tape is peeled off, and the height difference (film thickness) between the part shielded by the masking tape and the unshielded part is measured using a height difference meter. Then, a calibration curve is made based on the measurement results obtained by changing the conditions of each sputtering film formation to obtain the film formation rate. Thus, the thickness of each film formation is controlled to the desired film thickness.

[0061] Next, the battery capacity of the fluoride ion secondary battery 1 of the present embodiment will be described.

[0062] In Figure 1 In an example of the fluoride ion secondary battery 1 of the present embodiment shown below, the capacities of the positive electrode half-cell and the negative electrode half-cell are as follows.

[0063] [Positive electrode half-cell]

[0064] Theoretical capacity: 248 mAh / g

[0065] Density: 10.49 g / cm 3

[0066] Film thickness: 30 nm

[0067] Electrode area: 0.5 cm 2

[0068] Battery capacity: 3.92 μAh

[0069] [Negative electrode half-cell]

[0070] Theoretical capacity: 408 mAh / g

[0071] Density: 6.77 g / cm 3

[0072] Film thickness: 50 nm

[0073] Electrode area: 0.5 cm 2

[0074] Battery capacity: 6.9 μAh

[0075] In an example of the fluoride ion secondary battery 1 of the present embodiment, as described above, since the theoretical capacity of the positive electrode is small, the battery capacity is determined by the theoretical capacity of the positive electrode. That is, Figure 1 In an example of the battery capacity of the fluoride ion secondary battery 1 of the present embodiment shown, the capacity of the positive electrode is 3.92 μAh, and the N / P ratio is 3.92 / 6.9 = 1.76.

[0076] According to the fluoride ion secondary battery 1 of the present embodiment having the above configuration, the following effects are achieved.

[0077] The configuration of the fluoride ion secondary battery 1 of the present embodiment includes: a positive electrode material layer 11 containing Ag; a negative electrode material layer 13 containing 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 containing LaF3. That is, the fluoride ion secondary battery 1 of the present embodiment is composed of materials selected by charge-discharge tests and intermittent charge-discharge tests in a half-cell that have a small overvoltage even when operating at room temperature. Therefore, even when operating at room temperature, a large overvoltage can be avoided, and thus, charge-discharge cycle degradation can be suppressed, and high charge-discharge efficiency can be obtained.

[0078] The present invention is not limited to the above embodiment, and modifications and improvements made within the scope that can achieve the object of the present invention are included in the present invention.

[0079] [Examples]

[0080] Next, examples of the present invention will be described, but the present invention is not limited to these examples.

[0081] [Example 1]

[0082] As Example 1, it was fabricated according to the above manufacturing method Figure 1The fluoride ion secondary battery of the first embodiment shown. The constant current (CC) charge-discharge test was carried out on the fabricated Example 1 fluoride ion secondary battery under the following conditions.

[0083] The CC charge-discharge test was carried out under vacuum at room temperature of 25 °C (1×10 -4 Pa or less). In the fluoride ion secondary battery of Example 1, the battery capacity was determined by the theoretical capacity of 248 mAh / g of the positive electrode composed of Ag, and its theoretical capacity was smaller than that of the negative electrode composed of CeF3. Therefore, the current load was set to 200 nA, which is equivalent to 1 / 20C of the theoretical capacity of 248 mAh / g of the positive electrode composed of Ag. The battery area of Example 1 was approximately 0.5 cm 2 ², so this current load is equivalent to approximately 0.4 μA / cm² per unit area. 2 In addition, the cut-off conditions were a cut-off voltage of 1.0 to 4.2 V, or a cut-off time of 20 hours. In addition, each time the charge and discharge were switched, a pause of 10 minutes was made.

[0084] As the charge-discharge test procedure, a rate test was carried out on the first 10 cycles. Specifically, it was 1 / 20C in cycles 1 to 3, 1 / 10C in cycles 4 to 6, 1C in cycles 7 to 8, and 5C in cycles 9 to 10, slowly increasing to a faster rate. After the rate test, a charge-discharge test of 100 cycles was continued at a rate of 1C. In addition, midway, the rate was set to 1 / 20C to confirm the charge-discharge capacity. The charge-discharge test results are shown in Figures 3 - 5 .

[0085] Figure 3 is a graph showing the charge-discharge curve of the fluoride ion secondary battery of Example 1. Figure 4 is a graph showing 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-discharge efficiency of the fluoride ion secondary battery of Example 1. Here, Figure 3 represents the charge-discharge curve obtained by the rate test of the first 10 cycles. In addition, Figure 4 and Figure 5 represent the charge-discharge capacity and charge-discharge efficiency obtained by the charge-discharge test of 100 cycles after the rate test in addition to the rate test.

[0086] As shown in Figures 3 - 5As shown, the fluoride ion secondary battery according to Embodiment 1 can be confirmed to operate as a battery at room temperature. Additionally, at room temperature, the initial charge-discharge efficiency is 90%, and the discharge capacity at 5C remains 80% relative to the discharge capacity at 0.05C, indicating excellent rate characteristics. Furthermore, it can be known that at room temperature, the charge-discharge efficiency during 1C charge-discharge cycling is 99%, and the capacity retention rate after 100 charge-discharge cycles is 50%. Based on the above results, it can be confirmed that the fluoride ion secondary battery according to Embodiment 1 can achieve high charge-discharge efficiency at room temperature.

[0087] [Embodiment 2]

[0088] Figure 6 is a diagram showing the structure of the fluoride ion secondary battery 1a of Embodiment 2. As Embodiment 2, it is fabricated according to the above manufacturing method Figure 6 the fluoride ion secondary battery 1a shown. The fluoride ion secondary battery 1a of Embodiment 2 changes the negative electrode material layer 13 made of CeF3 with a film thickness of 50 nm in the fluoride ion secondary battery of Embodiment 1 to a negative electrode material layer 13a made of PbF2 with a film thickness of 200 nm. At the same time, the negative electrode current collector layer 14 made of carbon with a film thickness of 30 nm is changed to a negative electrode current collector layer 14a made of Pb foil with a film thickness of 0.2 mm, and it can be regarded as an Ag positive electrode half-cell. The fabricated fluoride ion secondary battery of Embodiment 2 is subjected to an intermittent charge-discharge test under the following conditions.

[0089] Under vacuum at room temperature of 25 °C (1×10 -5 Pa), an intermittent charge-discharge test is carried out. Specifically, 1 hour of CC charging and 5 hours of pause are repeated, and 1 hour of CC discharging and 5 hours of pause are repeated, thereby carrying out the intermittent charge-discharge test. In addition, the current load is set to 400 nA, which is equivalent to 1 / 10C of the positive electrode design capacity, and the voltage is set in the range of 0 to 1.7 V. The results of the intermittent charge-discharge test are shown in Figure 8 .

[0090] [Comparative Examples 1 - 6]

[0091] Figure 7 is a diagram showing the structure of the fluoride ion secondary batteries 2 of Comparative Examples 1 - 6. As Comparative Examples 1 - 6, they are fabricated using the same procedure as the above manufacturing method Figure 7The fluoride ion secondary battery 2 shown. In Comparative Examples 1 to 6, the fluoride ion secondary battery 2 changed the positive electrode material layer 11 made of Ag with a film thickness of 30 nm in the fluoride ion secondary battery 1a of Example 2 to a positive electrode material layer 21 made of Cu with a film thickness of 3 nm. At the same time, the film thickness of the positive electrode current collector layer 12 and the film thickness of the negative electrode material layer 13a made of PbF2 were changed to the film thickness of the positive electrode current collector layer 22 and the film thickness of the negative electrode material layer 23 made of PbF2, which can be said to be a Cu positive electrode half-cell. Under the conditions described later, for Figure 7 the fluoride ion secondary battery shown was subjected to an intermittent charge and discharge test. In addition, under the same conditions as in Example 1 above, for Figure 7 the fluoride ion secondary battery shown was subjected to a CC charge and discharge test. More specifically, in Comparative Example 1, it was carried out at room temperature of 25 °C, in Comparative Example 2 at 140 °C, in Comparative Example 3 at 60 °C, in Comparative Example 4 at 80 °C, in Comparative Example 5 at 100 °C, and in Comparative Example 6 at 120 °C for the CC charge and discharge test.

[0092] In Comparative Example 1, under vacuum at room temperature of 25 °C (1×10 -5 Pa), and in Comparative Example 2 under vacuum at 140 °C (1×10 -5 Pa), the intermittent charge and discharge tests were respectively carried out. Specifically, both Comparative Examples 1 and 2 repeated the CC charge for 1 hour and the pause for 3 hours, and repeated the CC discharge for 0.5 hour and the pause for 3 hours, thereby carrying out the intermittent charge and discharge test. In addition, the current load was set to 123 nA, which is equivalent to 1 / 10 C of the positive electrode design capacity, and the voltage was set in the range of 0.1 to 1.3 V. The results of the intermittent charge and discharge test are shown in Figure 8 .

[0093] Figure 8 is a graph showing the intermittent charge and discharge curves of the fluoride ion secondary batteries 1a and 2 of Example 2 and Comparative Examples 1 and 2. Figure 8 In it, the height of each peak intermittently seen at the start of charging, that is, the difference between OCV and CCV, represents the magnitude of the overvoltage. In Example 2 and Comparative Examples 1 and 2, the switching of the peak from the middle to the negative side means reaching the set charging voltage and switching to discharge. From the Figure 8 results, it can be seen that Comparative Examples 1 and 2 reached the set charging voltage earlier than Example 2.

[0094] In addition, as Figure 8 shown, it can be seen that compared with the Ag positive electrode half-cell of Example 2, in the Cu positive electrode half-cell of Comparative Example 1 where the intermittent charge and discharge test was carried out at room temperature, the overvoltage is very large. In addition, if the charging continues, the overvoltage further increases. It is speculated that this is due to the ionic conductivity of CuF2 generated in the positive electrode material layer made of Cu.

[0095] On the other hand, it can be seen that the overvoltage of the Cu positive electrode half-cell of Comparative Example 2 in which the intermittent charge and discharge test was carried out at 140 °C is the same as the overvoltage of the Ag positive electrode half-cell of Example 2 in which the intermittent charge and discharge test was carried out at room temperature, and charge and discharge can be carried out close to the theoretical capacity of the positive electrode material layer made of Cu. From this result, it can be confirmed that for operation at room temperature, it is important to reduce the resistance of the DC component that causes overvoltage (electron, ion conduction, charge transfer, etc.).

[0096] Figure 9 It is a graph showing the charge and discharge curves of the fluoride ion secondary battery 2 of Comparative Examples 1 to 6. Figure 9 In Comparative Example 1, it was 25 °C at room temperature, in Comparative Example 2, it was 140 °C, in Comparative Example 3, it was 60 °C, in Comparative Example 4, it was 80 °C, in Comparative Example 5, it was 100 °C, and in Comparative Example 6, it was 120 °C. The charge and discharge curves were obtained by carrying out the CC charge and discharge test, but it can be seen that the charge and discharge capacity gradually decreases as the temperature decreases. From this result, it is also confirmed that it is difficult to carry out charge and discharge at room temperature in the positive electrode material layer made of Cu.

[0097] [Example 3]

[0098] Figure 10 It is a graph showing the structure of the fluoride ion secondary battery 1b of Example 3. As Example 3, it was manufactured according to the above manufacturing method Figure 10 the fluoride ion secondary battery 1b shown. In the fluoride ion secondary battery 1b of Example 3, the film thickness of the positive electrode material layer 11 made of Ag in the fluoride ion secondary battery 1 of Example 1 was changed from 30 nm to 120 nm, and at the same time, the film thickness of the negative electrode material layer 13 made of CeF3 was changed from 50 nm to 200 nm.

[0099] The CC charge and discharge test was carried out on the manufactured fluoride ion secondary battery 1b of Example 3 under the same conditions as in Example 1 above. That is, first, a rate test to a faster rate was carried out, and a charge and discharge test was continued for 100 cycles at a rate of 1C. Among them, in the rate test of Example 3, it was set to 1 / 20C in cycles 1 to 3, 1 / 10C in cycles 4 to 5, 1C in cycles 6 to 7, and 2C in cycles 8 to 9. The results of the charge and discharge test are shown in Figures 11 - 14 .

[0100] Figure 11 It is a graph showing the charge and discharge curves of the fluoride ion secondary battery 1b of Example 3. Figure 12 It is a graph showing the relationship between the square root of the number of cycles and the capacity of the fluoride ion secondary battery 1b of Example 3. Figure 13It is a graph showing the relationship between the square root of the number of cycles and the charge-discharge efficiency of the fluoride ion secondary battery 1b of Example 3. Figure 14 It is a graph showing the relationship between the square root of the number of cycles and the discharge capacity retention rate of the fluoride ion secondary batteries 1b of Examples 1 and 3.

[0101] Comparison Figure 11 Comparing the charge-discharge curves of the fluoride ion secondary battery 1b of Example 3 shown in Figure 3 and the charge-discharge curves of the fluoride ion secondary battery 1 of Example 1 shown in

[0102] Comparison Figures 12 - 13 Comparing the relationship between the square root of the number of cycles and the capacity and charge-discharge efficiency of the fluoride ion secondary battery 1b of Example 3 shown in Figure 4 and Figure 5 and the relationship between the square root of the number of cycles and the capacity and charge-discharge efficiency of the fluoride ion secondary battery 1 of Example 1 shown in

[0103] According to Figure 14 Comparing the relationship between the square root of the number of cycles and the discharge capacity retention rate of the fluoride ion secondary batteries 1 and 1b of Examples 1 and 3 shown in

[0104] Reference numerals

[0105] 1, 1a, 1b Fluoride ion secondary battery

[0106] 11 Positive electrode material layer

[0107] 12 Positive current collector layer

[0108] 13, 13a Negative electrode material layer

[0109] 14, 14a Negative current collector layer

[0110] 15 Solid electrolyte layer

Claims

1. A fluoride ion secondary battery, comprising: a positive electrode material layer containing Ag; a negative electrode material layer containing at least one of CeF3 and PbF2; and, a solid electrolyte layer disposed between the positive electrode material layer and the negative electrode material layer and containing LaF3, wherein the film thickness of the positive electrode material layer is 10 nm or more and 30 nm or less, the film thickness of the negative electrode material layer is 10 nm or more and 50 nm or less, the film thickness of the solid electrolyte layer is 0.1 mm to 0.5 mm, the theoretical capacity of the positive electrode material layer is smaller than the theoretical capacity of the negative electrode material layer.

2. The fluoride ion secondary battery according to claim 1, wherein the negative electrode material layer contains CeF3, the fluoride ion secondary battery further includes a negative electrode current collector layer disposed outside the negative electrode material layer and including carbon.

3. The fluoride ion secondary battery according to claim 1, wherein the negative electrode material layer contains PbF2, the fluoride ion secondary battery further includes a negative electrode current collector layer disposed outside the negative electrode material layer and including a Pb foil.

4. The fluoride ion secondary battery according to claim 1, wherein it further includes a positive electrode current collector layer disposed outside the positive electrode material layer and including carbon.

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