Fluoride ion secondary battery

Abstract

Provided is a fluoride ion secondary battery provided with an electrode mixture layer and a collector layer, the collector layer having an elastic modulus of 1400 kgf / mm2 or less.

Description

Technical Field

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

[0002] In recent years, research and development of secondary batteries that contribute to improving energy efficiency have been underway in order to make energy affordable, trustworthy, and accessible to a large number of people, and to ensure access to 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. 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.

[0004] [Prior Art Documents]

[0005] (Patent Document)

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-73753 Summary of the Invention

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

[0008] However, in the fluoride ion battery described in Patent Document 1, when the volume changes due to the expansion and contraction of the positive electrode active material layer during charge and discharge, the volume change is difficult to be absorbed, and as a result, the initial discharge capacity and the capacity retention rate become low.

[0009] An object of the present invention is to provide a fluoride ion secondary battery that can improve the initial discharge capacity and the capacity retention rate.

[0010] [Means for Solving the Problems]

[0011] (1) A fluoride ion secondary battery, comprising an electrode mixture layer and a current collector layer, wherein the elastic modulus of the current collector layer is 1400 kgf / mm 2 or less.

[0012] (2) The fluoride ion secondary battery according to (1), wherein the current collector layer contains carbon particles.

[0013] (3) The fluoride ion secondary battery according to (2), wherein the carbon particles are acetylene black.

[0014] (4) The fluoride ion secondary battery according to any one of (1) to (3), wherein the fluoride ion secondary battery does not include a current collector foil in contact with the current collector layer.

[0015] (5) The fluoride ion secondary battery according to any one of (1)-(4) above, wherein the current collector layer is in contact with the electrode mixture layer.

[0016] (6) The fluoride ion secondary battery according to (5) above, wherein the electrode mixture layer is a positive electrode mixture layer.

[0017] (7) The fluoride ion secondary battery according to any one of (1)-(6) above, wherein the fluoride ion secondary battery is a bipolar battery.

[0018] (Effects of the Invention)

[0019] According to the present invention, it is possible to provide a fluoride ion secondary battery that can improve the initial discharge capacity and the capacity retention rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a cross-sectional view showing a fluoride ion secondary battery according to an embodiment of the present invention.

[0021] Figure 2 It is a cross-sectional view showing a fluoride ion secondary battery according to another embodiment of the present invention.

[0022] Figure 3 It is a cross-sectional view showing a fluoride ion secondary battery according to another embodiment of the present invention.

[0023] Figure 4 It is a graph showing the charge-discharge curves (two cycles) of the monomers of Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0025] [Fluoride Ion Secondary Battery]

[0026] The fluoride ion secondary battery of the present embodiment includes an electrode mixture layer and a current collector layer. The elastic modulus of the current collector layer is 1400 kgf / mm 2 Hereinafter, preferably 1100 kgf / mm 2 Hereinafter. The elastic modulus of the current collector layer is 1400 kgf / mm 2 Hereinafter, when the elastic modulus of the current collector layer is 1400 kgf / mm 2 or more, even if the positive electrode mixture layer expands and contracts and the volume changes during charge and discharge, the volume change is easily absorbed. Therefore, the capacity retention rate of the fluoride ion secondary battery of the present embodiment is improved. In addition, the elastic modulus of the current collector layer is, for example, 1024 kgf / mm

[0027] As the material constituting the current collector layer, there is no particular limitation as long as it is an electron conductive material having an elastic modulus of 1400 kgf / mm 2 or less. Among them, in terms of the energy density of the fluoride ion secondary battery of the present embodiment, carbon particles are preferably used, for example. As the carbon particles, carbon blacks such as acetylene black and Ketjen black, and graphite particles can be mentioned, for example.

[0028] The thickness of the current collector layer is preferably 40 μm or more and 100 μm or less, more preferably 40 μm or more and 80 μm or less. When the thickness of the current collector layer is 40 μm or more, the capacity retention rate of the fluoride ion secondary battery of the present embodiment is improved. When the thickness of the current collector layer is 100 μm or less, the energy density of the fluoride ion secondary battery of the present embodiment is improved.

[0029] In addition, the current collector layer is preferably in contact with the positive electrode mixture layer. Thus, when the voltage is high, for example, since the material constituting the current collector layer is fluorinated and becomes an insulator, overcharging can be prevented.

[0030] Figure 1 A fluoride ion secondary battery according to an embodiment of the present invention is shown.

[0031] 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. Here, the positive electrode 11 includes a positive electrode mixture layer 11a and a positive electrode current collector layer 11b. In addition, the negative electrode 12 includes a negative electrode mixture layer 12a and a negative electrode current collector foil 12b. In addition, the positive electrode 11 may further include a positive electrode current collector foil in contact with the positive electrode current collector layer 11b, but in consideration of cost, it is preferably not provided with a positive electrode current collector foil.

[0032] Figure 2 A fluoride ion secondary battery according to another embodiment of the present invention is shown.

[0033] 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. Here, the positive electrode 21 includes a positive electrode mixture layer 21a and a positive electrode current collector foil 21b. In addition, the negative electrode 22 includes a negative electrode mixture layer 22a and a negative electrode current collector layer 22b. In addition, 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 cost, it is preferably not provided with a negative electrode current collector foil.

[0034] Figure 3 A fluoride ion secondary battery according to another embodiment of the present invention is shown.

[0035] The fluoride ion secondary battery 30 is a bipolar battery including a plurality of monomers 31, a current collector layer 32 disposed between the plurality of monomers 31, and current collector foils 33. Therefore, the amount of the outer package can be reduced, and as a result, the energy density of the fluoride ion secondary battery 30 is increased. Here, in the monomer 31, a solid electrolyte layer 31b and a positive electrode mixture layer 31c are sequentially laminated on the negative electrode mixture layer 31a, and the current collector layer 32 is disposed between the negative electrode mixture layer 31a and the positive electrode mixture layer 31c that constitute adjacent monomers 31. In addition, the current collector foils 33 are disposed on one side of the uppermost monomer 31 where the current collector layer 32 is not disposed and on the lower side of the lowermost monomer 31. At this time, the current collector foil 33 in contact with the negative electrode mixture layer 31a is a negative electrode current collector foil, and the current collector foil 33 in contact with the positive electrode mixture layer 31c is a positive electrode current collector foil.

[0036] (Positive electrode mixture layer)

[0037] The positive electrode mixture layer contains a positive electrode active material, and may further contain a solid electrolyte, a conductive auxiliary agent, etc. as needed.

[0038] The positive electrode active material is not particularly limited, and examples thereof include Cu particles and Bi particles. Here, if Cu particles are used as the positive electrode active material, the volume change of the positive electrode mixture layer during charge and discharge increases, and therefore, the above current collector layer is particularly effective.

[0039] As positive electrode active materials other than Cu particles and Bi particles, for example, those represented by the general formula

[0040] K x Bi 1-x F 3-2x

[0041] (In the formula, x is 0.02 or more and 0.12 or less.)

[0042] Particles of the represented compound.

[0043] The positive electrode active material is preferably nanoparticles. The particle size of the positive electrode active material is, for example, 10 nm or more and 100 nm or less.

[0044] The solid electrolyte is not particularly limited as long as it has fluoride ion conductivity and does not defluorinate during discharge of the fluoride ion secondary battery. Examples thereof include metal fluoride particles. As the metal fluoride particles, for example, Ce 0.92 Sr 0.08 F 2.92 Particles.

[0045] The solid electrolyte is preferably nanoparticles. The particle size of the solid electrolyte is, for example, 10 nm or more and 100 nm or less.

[0046] As the conductive additive, there is no particular limitation as long as it has electronic conductivity. For example, acetylene black can be cited.

[0047] (Negative electrode mixture layer)

[0048] The negative electrode mixture layer contains a negative electrode active material, and may also contain a conductive additive, etc. as needed. As the negative electrode active material, there is no particular limitation. For example, PbSnF4 particles can be cited. As the conductive additive, there is no particular limitation as long as it has electronic conductivity. For example, acetylene black can be cited.

[0049] (Solid electrolyte layer)

[0050] As the solid electrolyte constituting the solid electrolyte layer, there is no particular limitation as long as it has fluoride ion conductivity and does not release fluorine during the discharge of the fluoride ion secondary battery. For example, metal fluorides can be cited. As the metal fluoride, for example, Ce 0.95 Sr 0.05 F 2.85 .

[0051] (Positive electrode current collector foil)

[0052] As the positive electrode current collector foil, there is no particular limitation as long as it has electronic conductivity. For example, metal foils such as gold foil and platinum foil can be cited.

[0053] (Negative electrode current collector foil)

[0054] As the negative electrode current collector foil, there is no particular limitation as long as it has electronic conductivity. For example, metal foils such as aluminum foil can be cited.

[0055] The fluoride ion secondary battery of the present embodiment is obtained, for example, by sequentially laminating a positive electrode current collector layer, a positive electrode mixture layer with a powder composition, a solid electrolyte layer, a negative electrode mixture layer with a powder composition, and a negative electrode current collector foil and then performing 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. In addition, the powder composition for the negative electrode mixture layer contains, for example, a negative electrode active material and a conductive additive.

[0056] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and the above embodiments can be appropriately changed within the scope of the gist of the present invention.

[0057] [Examples]

[0058] Hereinafter, the examples of the present invention will be described, but the present invention is not limited to the examples.

[0059] (K 0.06 Bi 0.94 F 2.88 powder)

[0060] Potassium fluoride (manufactured by Kojundo Chemical Lab. Co., Ltd.) and bismuth fluoride (manufactured by Kojundo Chemical Lab. Co., Ltd.) were weighed, and then premixed for about 1 hour using an agate mortar and pestle to obtain a raw material mixed powder.

[0061] For the obtained raw material mixed powder, classification treatment was carried out using a stainless-steel sieve with a mesh size of 500 μm. Then, the raw material mixed powder that did not pass through the sieve was mixed using an agate mortar and pestle and then subjected to classification treatment. The above operations were carried out until all the raw material mixed powder passed through the sieve.

[0062] In addition, in order to prevent the fluoride from absorbing moisture, the weighing, premixing, and classification treatment of the raw materials were carried out inside a purge-type (DBO type) glove box (manufactured by Miwa Mfg Co., Ltd.).

[0063] The sealed powder hopper containing the classified raw material mixed powder was taken out of the glove box and connected to a high-frequency induction thermal plasma nanoparticle synthesis device TP-40020NPS (manufactured by JEOL Ltd.). Then, argon gas was supplied to the plasma torch, and the raw material mixed powder was melted by the thermal plasma to form a raw material melt, and the raw material melt was sprayed into the chamber under a reduced-pressure environment. The raw material melt sprayed into the chamber was subjected to a cooling process and was nanoparticleized to become K 0.06 Bi 0.94 F 2.88 powder. Then, the K 0.06 Bi 0.94 F 2.88 powder was collected with an exhaust filter, and the upstream and downstream of the exhaust filter were blocked with valves, and then it was transported into the glove box to recover the K 0.06 Bi 0.94 F 2.88 powder with a particle size of 10 nm or more and 100 nm or less. Here, the composition of the K 0.06 Bi 0.94 F 2.88 powder was analyzed by ICP emission spectrometry.

[0064] (Cu powder)

[0065] Except for using copper (manufactured by Kojundo Chemical Lab. Co., Ltd.) instead of the raw material mixed powder, the Cu powder with a particle size of 10 nm or more and 100 nm or less was obtained in the same way as the K 0.06 Bi 0.94 F 2.88 powder.

[0066] (Ce 0.92Sr 0.08 F 2.92 Powder

[0067] After weighing cerium fluoride (manufactured by High Purity Chemical Research Institute) and strontium fluoride (manufactured by High Purity Chemical Research Institute), using an agate mortar and pestle, pre-mix for about 1 hour to obtain a raw material mixed powder.

[0068] Except for using the obtained raw material mixed powder, similar to the K 0.06 Bi 0.94 F 2.88 powder, Ce 0.92 Sr 0.08 F 2.92 powder with a particle size of 10 nm or more and 100 nm or less is obtained. Here, the composition of the Ce 0.92 Sr 0.08 F 2.92 powder is analyzed by ICP emission spectrometry.

[0069] (Powder composition for positive electrode mixture layer)

[0070] The powder composition for the positive electrode mixture layer is prepared inside a purge type (DBO type) glove box (manufactured by Miwa Seisakusho) filled with Ar gas. Specifically, weigh 0.524 g of Cu powder as the positive electrode active material, 0.175 g of Bi powder (manufactured by High Purity Chemical Research Institute), and 0.154 g of K 0.06 Bi 0.94 F 2.88 powder, 0.129 g of Ce 0.92 Sr 0.08 F 2.92 powder as the solid electrolyte, and 0.018 g of acetylene black (manufactured by Denka Company Limited.) as the conductive additive. Then, using a silicon nitride pot mill with a capacity of 45 mL and 40 g of silicon nitride balls with a diameter of 2 mm, ball-mill and mix the weighed substances in 8 g of cyclohexane, and then dry them on a hot plate at 65 °C to obtain the powder composition for the positive electrode mixture layer. When ball-milling and mixing the weighed substances, perform ball-milling and mixing at 200 rpm for 15 minutes and then stop for 5 minutes, and repeat this cycle 40 times.

[0071] (Powder composition for negative electrode mixture layer)

[0072] Using a planetary ball mill made of silicon nitride with a capacity of 45 mL and 10 balls made of silicon nitride with a diameter of 10 mm, 6 g of lead fluoride (manufactured by the High Purity Chemical Research Institute) and 2.8 g of stannous fluoride (manufactured by the High Purity Chemical Research Institute) were ball-milled and mixed. At this time, after ball-milling and mixing at 600 rpm for 3 hours, it was stopped for 5 minutes, and this cycle was carried out 8 times. Then, 0.619 g of acetylene black was added to 8.669 g of the mixture, and after ball-milling and mixing in the same manner as above, it was heat-treated at 400 °C for 1 hour in an argon atmosphere to obtain a powder composition for the negative electrode mixture layer.

[0073] (Ce 0.95 Sr 0.05 F 2.85 powder)

[0074] After ball-milling and mixing 19.3510 g of cerium fluoride (manufactured by the High Purity Chemical Research Institute) and 0.6490 g of strontium fluoride (manufactured by the High Purity Chemical Research Institute), it was fired at 1100 °C for 6 hours in an argon atmosphere to obtain Ce 0.95 Sr 0.05 F 2.85 powder. When carrying out ball-milling and mixing, after ball-milling and mixing at 600 rpm for 1 hour, it was stopped for 5 minutes, and this cycle was carried out 40 times.

[0075] (Example 1)

[0076] Inside a purge-type (DBO type) glove box (manufactured by Miwa Seisakusho) filled with Ar gas, a monomer was fabricated using an alumina tube with an inner diameter of 10 mm. Specifically, first, 150 mg of Ce 0.95 Sr 0.05 F 2.85 powder was uniaxially pressed at a surface pressure of 740 MPa to obtain a solid electrolyte layer. Then, a 20-μm-thick Au foil as the positive electrode current collector foil, 10 mg of the powder composition for the positive electrode mixture layer, the solid electrolyte layer, 20 mg of the powder composition for the negative electrode mixture layer, and 15.6 mg of acetylene black were sequentially laminated and then uniaxially pressed at 185 MPa to obtain a monomer having a negative electrode current collector layer. At this time, the thickness of the negative electrode current collector layer was 100 μm, and the elastic modulus was 1024 kgf / mm 2 . Then, the monomer was sealed in a closed glass container under a constrained pressure of about 340 MPa.

[0077] [Method for measuring elastic modulus]

[0078] The current collector layer was clamped between two plates to obtain the compression-strain characteristics, and thus the elastic modulus was determined.

[0079] (Example 2)

[0080] Instead of using 15.6 mg of acetylene black, a 20-μm-thick Au foil was used, and instead of 15.6 mg of acetylene black, a 20-μm-thick Al foil was used as the negative electrode current collector foil. Otherwise, a monomer having a positive electrode current collector layer was obtained in the same manner as in Example 1. At this time, the thickness of the positive electrode current collector layer was 100 μm, and the elastic modulus was 1038 kgf / mm 2 。

[0081] (Example 3)

[0082] Instead of using 15.6 mg of acetylene black, a 20-μm-thick Au foil was used. Otherwise, a monomer having a positive electrode current collector layer and a negative electrode current collector layer was obtained in the same manner as in Example 1. At this time, the thicknesses of the positive electrode current collector layer and the negative electrode current collector layer were 100 μm, and the elastic modulus was 1052 kgf / mm 2 。

[0083] (Comparative Example 1)

[0084] Instead of using 15.6 mg of acetylene black, a 20-μm-thick Al foil was used as the negative electrode current collector foil. Otherwise, a monomer was obtained in the same manner as in Example 1.

[0085] [Discharge capacity]

[0086] Using a potentiostat / galvanostat SI1287 / 1255B (manufactured by Solartron), the inside of the glass container was evacuated using a vacuum pump, and the glass container was placed in a thermostat. A constant current charge-discharge test of the monomer was carried out at a temperature of 140°C. Specifically, first, a current of 120 μA was passed, then a current of 40 μA was passed, and charging was carried out until the voltage reached 1.5 V (vs. Pb / PbF2). Next, a current of 120 μA was passed, then a current of 40 μA was passed, and discharging was carried out until the voltage reached -0.5 V (vs. Pb / PbF2). At this time, the above cycle was carried out twice, and the discharge capacity was determined.

[0087] Figure 4 The charge-discharge curves of the monomers of Example 1 and Comparative Example 1 are shown. In addition, the capacity on the horizontal axis is the capacity per 1 g of the positive electrode mixture layer.

[0088] From Figure 4 it can be seen that the initial discharge capacity of the monomer of Example 1 is higher than that of the monomer of Comparative Example 1.

[0089] [Capacity retention rate]

[0090] The ratio of the discharge capacity of the second cycle to the initial discharge capacity was determined as the capacity retention rate.

[0091] The evaluation results of the initial charge capacity, initial discharge capacity, and capacity retention rate of the monomers are shown in Table 1.

[0092] [Table 1]

[0093] Collector layer <![CDATA[Initial discharge capacity [mAh g -1 > Capacity retention rate [%] Example 1 Negative electrode 482 92 Example 2 Positive electrode 485 92 Example 3 Positive electrode / Negative electrode 481 91 Comparative Example 1 455 90

[0094] As can be seen from Table 1, the initial discharge capacity and capacity retention rate of the monomers in Examples 1 to 3 are relatively high. In contrast, since the monomer of Comparative Example 1 does not have a current collector layer with an elastic modulus of 1400 kgf / mm 2 or less, the initial discharge capacity and capacity retention rate are low.

[0095] Reference Numerals

[0096] 10, 20: Fluoride ion secondary battery

[0097] 11, 21: Positive electrode

[0098] 11a, 21a, 31c: Positive electrode mixture layer

[0099] 11b: Positive electrode current collector layer

[0100] 21b: Positive electrode current collector foil

[0101] 12, 22: Negative electrode

[0102] 12a, 22a, 31a: Negative electrode mixture layer

[0103] 12b: Negative electrode current collector foil

[0104] 22b: Negative electrode current collector layer

[0105] 13, 23, 31b: Solid electrolyte layer

[0106] 31: Monomer

[0107] 32: Current collector layer

[0108] 33: Current collector foil

Claims

1. A fluoride ion secondary battery, the fluoride ion secondary battery comprising an electrode mixture layer and a current collector layer, The elastic modulus of the aforementioned current collector layer is 1400 kgf / mm 2 or less.

2. The fluoride ion secondary battery according to claim 1, wherein, wherein the current collector layer contains carbon particles.

3. The fluoride ion secondary battery according to claim 2, wherein, The carbon particles are acetylene black.

4. The fluoride ion secondary battery according to any one of claims 1 to 3, wherein The fluoride ion secondary battery does not have a current collector foil connected to the current collector layer.

5. The fluoride ion secondary battery according to any one of claims 1 to 3, wherein, The current collector layer is in contact with the electrode mixture layer.

6. The fluoride ion secondary battery according to claim 5, wherein, The electrode mixture layer is a positive electrode mixture layer.

7. The fluoride ion secondary battery according to any one of claims 1 to 3, wherein, The fluoride ion secondary battery is a bipolar battery.

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