Fluoride-ion secondary battery

Abstract

To provide a fluoride ion secondary battery capable of improving initial discharge capacity and capacity retention.SOLUTION: A fluoride ion secondary battery 10 includes: a positive electrode mixture layer 11a; and a positive electrode current collector layer 11b. The positive electrode current collector layer 11b has a modulus of elasticity of 1400 kgf / mm2 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, research and development into secondary batteries that contribute to energy efficiency has been conducted to ensure that many people have access to affordable, reliable, sustainable and advanced energy.

[0003] Patent Document 1 describes a fluoride ion battery having at least a positive electrode active material layer and a solid electrolyte layer, in which the positive electrode active material layer contains positive electrode active material particles mainly composed of Cu and Sn, and the solid electrolyte layer contains a solid electrolyte containing Pb, Sn, and F. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-73753 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the fluoride ion battery described in Patent Document 1, when the positive electrode active material layer expands and contracts during charging and discharging, causing a change in volume, the volume change is difficult to absorb, resulting in a decrease in the initial discharge capacity and capacity retention rate.

[0006] An object of the present invention is to provide a fluoride ion secondary battery that can improve the initial discharge capacity and capacity retention rate. [Means for solving the problem]

[0007] (1) An electrode material layer and a current collecting layer, the current collecting layer having an elastic modulus of 1400 kgf / mm 2 The following is a fluoride ion secondary battery.

[0008] (2) The fluoride ion secondary battery according to (1), wherein the current collecting layer contains carbon particles.

[0009] (3) The fluoride ion secondary battery according to (2), wherein the carbon particles are acetylene black.

[0010] (4) The fluoride ion secondary battery according to any one of (1) to (3), which does not include a current collecting foil in contact with the current collecting layer.

[0011] (5) The fluoride ion secondary battery according to any one of (1) to (4), wherein the current collecting layer is in contact with the electrode mixture layer.

[0012] (6) The fluoride ion secondary battery according to (5), wherein the electrode mixture layer is a positive electrode mixture layer.

[0013] (7) The fluoride ion secondary battery according to any one of (1) to (6), which is a bipolar battery. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a fluoride ion secondary battery capable of improving the initial discharge capacity and the capacity retention rate. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view showing a fluoride ion secondary battery according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a fluoride ion secondary battery according to another embodiment of the present invention. [Figure 3] FIG. 2 is a cross-sectional view showing a fluoride ion secondary battery according to another embodiment of the present invention. [Figure 4] 1 is a graph showing charge / discharge curves (2 cycles) of the cells of Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] [Fluoride-ion secondary battery] The fluoride ion secondary battery of this embodiment includes an electrode mixture layer and a current collecting layer. The current collecting layer has an elastic modulus of 1400 kgf / mm 2 less than 1100kgf / mm 2 The current collecting layer preferably has an elastic modulus of 1400 kgf / mm or less. 2 If the elastic modulus of the current collecting layer is equal to or less than 1024 kgf / mm, for example, even if the positive electrode mixture layer expands and contracts during charging and discharging, and the volume changes, the volume change is easily absorbed, and the capacity retention rate of the fluoride ion secondary battery of this embodiment is improved. 2 That's all.

[0018] The material that makes up the current collecting layer must have an elastic modulus of 1400 kgf / mm 2 There are no particular limitations on the electron-conductive material as long as it can achieve the following. Among these, carbon particles are preferred in terms of the energy density of the fluoride ion secondary battery of this embodiment. Examples of carbon particles include carbon black such as acetylene black and ketjen black, and graphite particles.

[0019] The thickness of the current collecting layer is preferably 40 μm or more and 100 μm or less, and more preferably 40 μm or more and 80 μm or less. When the thickness of the current collecting layer is 40 μm or more, the capacity retention rate of the fluoride ion secondary battery of this embodiment is improved, and when it is 100 μm or less, the energy density of the fluoride ion secondary battery of this embodiment is improved.

[0020] The current collecting layer is preferably in contact with the positive electrode mixture layer, so that when the voltage is high, for example, the material constituting the current collecting layer is fluorinated and becomes an insulator, thereby preventing overcharging.

[0021] FIG. 1 shows a fluoride ion secondary battery according to one embodiment of the present invention.

[0022] The fluoride ion secondary battery 10 includes a positive electrode 11, a negative electrode 12, and a solid electrolyte layer 13 disposed between the positive electrode 11 and the negative electrode 12. The positive electrode 11 includes a positive electrode mixture layer 11a and a positive electrode current collecting layer 11b. The negative electrode 12 includes a negative electrode mixture layer 12a and a negative electrode current collecting foil 12b. The positive electrode 11 may further include a positive electrode current collecting foil in contact with the positive electrode current collecting layer 11b, but in consideration of costs, it is preferable that the positive electrode 11 does not include a positive electrode current collecting foil.

[0023] FIG. 2 shows a fluoride ion secondary battery according to another embodiment of the present invention.

[0024] The fluoride ion secondary battery 20 includes a positive electrode 21, a negative electrode 22, and a solid electrolyte layer 23 disposed between the positive electrode 21 and the negative electrode 22. The positive electrode 21 includes a positive electrode mixture layer 21a and a positive electrode current collector foil 21b. The negative electrode 22 includes a negative electrode mixture layer 22a and a negative electrode current collector layer 22b. The negative electrode 22 may further include a negative electrode current collector foil in contact with the negative electrode current collector layer 22b, but in consideration of costs, it is preferable that the negative electrode 22 does not include a negative electrode current collector foil.

[0025] FIG. 3 shows a fluoride ion secondary battery according to another embodiment of the present invention.

[0026] The fluoride ion secondary battery 30 is a bipolar battery including a plurality of cells 31, current collecting layers 32 disposed between the plurality of cells 31, and current collecting foils 33. This allows the amount of exterior body to be reduced, resulting in an improved energy density of the fluoride ion secondary battery 30. Each cell 31 includes a solid electrolyte layer 31b and a positive electrode mixture layer 31c sequentially stacked on a negative electrode mixture layer 31a. The current collecting layer 32 is disposed between the negative electrode mixture layer 31a and the positive electrode mixture layer 31c of an adjacent cell 31. The current collecting foils 33 are disposed on the side of the top cell 31 where the current collecting layer 32 is not disposed and below the bottom cell 31. The current collecting foil 33 in contact with the negative electrode mixture layer 31a is a negative electrode current collecting foil, and the current collecting foil 33 in contact with the positive electrode mixture layer 31c is a positive electrode current collecting foil.

[0027] (Positive electrode mixture layer) The positive electrode mixture layer contains a positive electrode active material, and may further contain a solid electrolyte, a conductive additive, and the like, as necessary.

[0028] The positive electrode active material is not particularly limited, but examples thereof include Cu particles and Bi particles. When Cu particles are used as the positive electrode active material, the volume change of the positive electrode mixture layer during charge and discharge increases, making the current collecting layer described above particularly effective.

[0029] Examples of the positive electrode active material other than Cu particles and Bi particles include a compound represented by the general formula K x Bi 1-x F 3-2x (wherein x is 0.02 or more and 0.12 or less). Examples of the compound include particles of the compound represented by the formula:

[0030] The positive electrode active material is preferably nanoparticles, and the particle size of the positive electrode active material is, for example, 10 nm or more and 100 nm or less.

[0031] The solid electrolyte is not particularly limited as long as it has fluoride ion conductivity and is not defluorinated during discharge of the fluoride ion secondary battery. For example, metal fluoride particles can be used. Examples of the metal fluoride particles include Ce. 0.92 Sr 0.08 F 2.92 Particles can be mentioned.

[0032] The solid electrolyte is preferably in the form of nanoparticles, and the particle size of the solid electrolyte is, for example, 10 nm or more and 100 nm or less.

[0033] The conductive additive is not particularly limited as long as it has electronic conductivity, and examples thereof include acetylene black.

[0034] (Negative electrode mixture layer) The negative electrode mixture layer contains a negative electrode active material and may further contain a conductive additive, etc., as necessary. The negative electrode active material is not particularly limited, but examples thereof include PbSnF4 particles. The conductive additive is not particularly limited as long as it has electronic conductivity, but examples thereof include acetylene black.

[0035] (Solid electrolyte layer) The solid electrolyte constituting the solid electrolyte layer is not particularly limited as long as it has fluoride ion conductivity and is not defluorinated during discharge of the fluoride ion secondary battery. For example, metal fluorides can be used. Examples of metal fluorides include Ce. 0.95 Sr 0.05 F 2.85 Examples include:

[0036] (Positive current collector foil) The positive electrode current collector foil is not particularly limited as long as it has electronic conductivity, and examples thereof include metal foils such as gold foil and platinum foil.

[0037] (negative electrode current collecting foil) The negative electrode current collector foil is not particularly limited as long as it has electronic conductivity, and examples thereof include metal foils such as aluminum foil.

[0038] The fluoride ion secondary battery of this embodiment is obtained, for example, by sequentially laminating a positive electrode current collecting layer, a powder composition for a positive electrode mixture layer, a solid electrolyte layer, a powder composition for a negative electrode mixture layer, and a negative electrode current collecting foil, followed by press molding. Here, the powder composition for the positive electrode mixture layer contains, for example, a positive electrode active material, a solid electrolyte, and a conductive additive. Also, the powder composition for the negative electrode mixture layer contains, for example, a negative electrode active material and a conductive additive.

[0039] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the above-described embodiments may be modified as appropriate within the scope of the spirit of the present invention. [Example]

[0040] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0041] (K 0.06 Bi 0.94 F 2.88 powder) Potassium fluoride (manufactured by Kojundo Chemical Laboratory) and bismuth fluoride (manufactured by Kojundo Chemical Laboratory) were weighed and then premixed for about 1 hour using an agate mortar and pestle to obtain a raw material mixed powder.

[0042] The resulting raw material mixed powder was classified using a stainless steel mesh with 500 μm openings. Next, the raw material mixed powder that did not pass through the mesh was mixed using an agate mortar and pestle, and then classified, until all the raw material mixed powder passed through the mesh.

[0043] The weighing, pre-mixing and classification of the raw materials were carried out in a purged (DBO type) glove box (manufactured by Miwa Seisakusho) to prevent moisture absorption by the fluoride.

[0044] The sealed powder hopper containing the classified raw material mixed powder was removed from the glove box and connected to a high-frequency induction thermal plasma nanoparticle synthesis device TP-40020NPS (manufactured by JEOL Ltd.). Next, argon gas was supplied to the plasma torch, and the raw material mixed powder was melted by thermal plasma to form a raw material melt, which was then sprayed into a chamber in a reduced pressure environment. The raw material melt sprayed into the chamber was cooled and turned into nanoparticles, and then K 0.06 Bi 0.94 F 2.88 It became powder. Next, K was filtered through the exhaust filter. 0.06 Bi 0.94 F 2.88 After collecting the powder, the upstream and downstream of the exhaust filter are blocked with valves, and the powder is transported into a glove box. 0.06 Bi 0.94 F 2.88 The powder was collected. 0.06 Bi 0.94 F 2.88 The composition of the powder was analyzed by ICP atomic emission spectroscopy.

[0045] (Cu powder) Instead of the raw material powder mixture, copper (manufactured by Kojundo Chemical Laboratory) was used. 0.06 Bi 0.94 F 2.88 In the same manner as the powder, Cu powder having a particle size of 10 nm or more and 100 nm or less was obtained.

[0046] (Ce 0.92 Sr 0.08 F 2.92 powder) Cerium fluoride (manufactured by Kojundo Chemical Laboratory) and strontium fluoride (manufactured by Kojundo Chemical Laboratory) were weighed and then premixed for about 1 hour using an agate mortar and pestle to obtain a raw material mixed powder.

[0047] The raw material powder mixture obtained was used. 0.06 Bi 0.94 F 2.88 Ce with a particle size of 10 nm to 100 nm is prepared in the same manner as the powder. 0.92 Sr0.08 F 2.92 The powder was obtained. 0.92 Sr 0.08 F 2.92 The composition of the powder was analyzed by ICP atomic emission spectroscopy.

[0048] (Powder composition for positive electrode mixture layer) A powder composition for a positive electrode mixture layer was prepared in a purged (DBO type) glove box (manufactured by Miwa Seisakusho) filled with Ar gas. Specifically, 0.524 g of Cu powder, 0.175 g of Bi powder (manufactured by Kojundo Chemical Laboratory Co., Ltd.), and K 0.06 Bi 0.94 F 2.88 Powder 0.154g and Ce as a solid electrolyte 0.92 Sr 0.08 F 2.92 0.129 g of powder and 0.018 g of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive additive were weighed. Next, using a 45 mL silicon nitride pot mill and 40 g of silicon nitride balls with a diameter of 2 mm, the weighed material was ball milled in 8 g of cyclohexane, and then dried on a hot plate at 65 ° C. to obtain a powder composition for a positive electrode mixture layer. When mixing the weighed material in the ball mill, a cycle of mixing at 200 rpm for 15 minutes followed by a 5-minute break was performed 40 times.

[0049] (Powder composition for negative electrode mixture layer) Using a 45 mL silicon nitride pot mill and ten 10 mm diameter silicon nitride balls, 6 g of lead fluoride (manufactured by Kojundo Chemical Laboratory Co., Ltd.) and 2.8 g of stannous fluoride (manufactured by Kojundo Chemical Laboratory Co., Ltd.) were mixed in a ball mill. This was done by mixing the ball mill at 600 rpm for 3 hours followed by a 5-minute break, 8 times. Next, 0.619 g of acetylene black was added to 8.669 g of the mixture, and the mixture was mixed in a ball mill in the same manner as above. Then, the mixture was heat-treated at 400 ° C for 1 hour under an argon atmosphere to obtain a powder composition for a negative electrode mixture layer.

[0050] (Ce 0.95 Sr 0.05 F 2.85 powder) 19.3510 g of cerium fluoride (manufactured by Kojundo Chemical Laboratory) and 0.6490 g of strontium fluoride (manufactured by Kojundo Chemical Laboratory) were mixed in a ball mill and then fired at 1100°C for 6 hours in an argon atmosphere to obtain Ce. 0.95 Sr 0.05 F 2.85 The powder was obtained by ball mill mixing at 600 rpm for 1 hour followed by a 5-minute break, which was repeated 40 times.

[0051] [Example 1] A cell was fabricated using an alumina tube with an inner diameter of 10 mm in a purged glove box (DBO type) (Miwa Manufacturing Co., Ltd.) filled with Ar gas. 0.95 Sr 0.05 F 2.85 150 mg of the powder was uniaxially pressed at a surface pressure of 740 MPa to obtain a solid electrolyte layer. Next, a 20 μm thick Au foil as a positive electrode current collector foil, 10 mg of a powder composition for a positive electrode mixture layer, a solid electrolyte layer, 20 mg of a powder composition for a negative electrode mixture layer, and 15.6 mg of acetylene black were sequentially laminated, and then uniaxially pressed at 185 MPa to obtain a cell equipped with a negative electrode current collector layer. At this time, the negative electrode current collector layer had a thickness of 100 μm and an elastic modulus of 1024 kgf / mm 2 Next, the cell was sealed in a glass container under a confining pressure of approximately 340 MPa.

[0052] [Method for measuring elastic modulus] The current collecting layer was sandwiched between two plates, and the compression-strain characteristics were obtained to determine the elastic modulus.

[0053] [Example 2] A cell having a positive electrode current collecting layer was obtained in the same manner as in Example 1, except that 15.6 mg of acetylene black was used instead of the 20 μm thick Au foil, and a 20 μm thick Al foil was used as the negative electrode current collecting foil instead of the 15.6 mg of acetylene black. In this case, the positive electrode current collecting layer had a thickness of 100 μm and an elastic modulus of 1038 kgf / mm 2 It was.

[0054] [Example 3] A cell including a positive electrode current collecting layer and a negative electrode current collecting layer was obtained in the same manner as in Example 1, except that 15.6 mg of acetylene black was used instead of the 20 μm thick Au foil. In this case, the positive electrode current collecting layer and the negative electrode current collecting layer had a thickness of 100 μm and an elastic modulus of 1052 kgf / mm 2 It was.

[0055] [Comparative Example 1] A cell was obtained in the same manner as in Example 1, except that an Al foil having a thickness of 20 μm was used as the negative electrode current collector foil instead of 15.6 mg of acetylene black.

[0056] [Discharge capacity] A constant-current charge-discharge test was performed on the cell using a potentio / galvanostat SI1287 / 1255B (manufactured by Solartron). The pressure inside the glass container was reduced using a vacuum pump, and the glass container was placed in a thermostatic chamber at 140°C. Specifically, a current of 120 μA was first applied, followed by a current of 40 μA, and the cell was charged until the voltage reached 1.5 V (vs. Pb / PbF2). Next, a current of 120 μA was applied, followed by a current of 40 μA, and the cell was discharged until the voltage reached -0.5 V (vs. Pb / PbF2). This cycle was repeated twice, and the discharge capacity was determined.

[0057] 4 shows charge / discharge curves for the cells of Example 1 and Comparative Example 1. The capacity on the horizontal axis is the capacity per gram of the positive electrode mixture layer.

[0058] 4, it can be seen that the cell of Example 1 has a higher initial discharge capacity than the cell of Comparative Example 1.

[0059] [Capacity maintenance rate] The ratio of the discharge capacity at the second cycle to the initial discharge capacity was calculated and used as the capacity retention rate.

[0060] Table 1 shows the evaluation results of the initial charge capacity, initial discharge capacity, and capacity retention rate of the cells.

[0061] [Table 1]

[0062] From Table 1, it can be seen that the initial discharge capacity and capacity retention rate are high in the cells of Examples 1 to 3. In contrast, the cell of Comparative Example 1 has an elastic modulus of 1400 kgf / mm 2 Since the battery does not have a current collecting layer, the initial discharge capacity and capacity retention rate are low. [Explanation of symbols]

[0063] 10, 20 Fluoride ion secondary battery 11, 21 positive electrode 11a, 21a, 31c Positive electrode mixture layer 11b Positive electrode current collecting layer 21b Positive electrode current collector foil 12, 22 negative electrode 12a, 22a, 31a Negative electrode mixture layer 12b Negative current collector foil 22b Negative electrode current collecting layer 13, 23, 31b Solid electrolyte layer 31 cells 32 Current collecting layer 33 Current collecting foil

Claims

1. A battery comprising: a negative electrode mixture layer; a solid electrolyte layer; a positive electrode mixture layer; and a current collecting layer; the positive electrode mixture layer contains Cu particles, The current collecting layer is in contact with the positive electrode mixture layer or the negative electrode mixture layer, contains carbon particles, and has an elastic modulus of 1024 kgf / mm 2 or more and 1400 kgf / mm ２ The following is a fluoride ion secondary battery.

2. A battery comprising a plurality of cells and a current collecting layer disposed between the plurality of cells, the cell includes a negative electrode mixture layer, a solid electrolyte layer, and a positive electrode mixture layer; the positive electrode mixture layer contains Cu particles, the current collecting layer is in contact with the negative electrode mixture layer and the positive electrode mixture layer constituting the adjacent cell, contains carbon particles, and has an elastic modulus of 1024 kgf / mm 2 or more and 1400 kgf / mm 2 or less.

3. 3. The fluoride ion secondary battery according to claim 1, wherein the carbon particles are acetylene black.

4. 3. The fluoride ion secondary battery according to claim 1, wherein no current collecting foil is provided in contact with the current collecting layer.

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