Electrode mixture for use in all-solid-state sodium storage batteries, and storage batteries using the same

Abstract

(Problem) To provide an electrode mixture to be used in an all-solid-state sodium storage battery which makes it possible to maintain a high discharge capacity in a room temperature environment and to exhibit excellent charging and discharging cycle characteristics. Additionally, to provide a storage battery using the electrode mixture. (Solution) An electrode mixture to be used in an all-solid-state sodium storage battery, the electrode mixture containing an active material, and the active material being a cluster which is formed from a polyphosphoric acid transition metal oxide and in which a plurality of individual particles each having a particle diameter in the range of 0.1 μm to 100 μm are linked.

Description

[Technical Field]

[0001] The present invention relates to an electrode mixture for use in an all-solid-state sodium storage battery, and a storage battery using the same. [Background technology]

[0002] The use of high-energy density storage batteries (secondary batteries) has expanded in recent years from power sources for mobile devices such as smartphones and tablet terminals to electric vehicles, power storage, etc. In particular, automobile manufacturers are actively developing and commercializing clean automobiles (electric vehicles, plug-in hybrid vehicles, etc.) in order to comply with environmental regulations aimed at reducing automobile exhaust gases and carbon dioxide (CO2) worldwide.

[0003] Furthermore, renewable energy sources such as wind and solar power require large-scale battery storage systems because the amount of power generated fluctuates significantly due to environmental influences. Recently, the cost of generating electricity from renewable energy sources has fallen to less than half that of coal-fired power generation, and their share of power generation is expanding. In view of their future widespread use, there is a need to improve battery production.

[0004] Storage batteries are essential for energy conservation, the introduction of new energy sources, and clean automobiles, and are positioned as important key devices from the perspective of economic growth in each country.

[0005] Current storage batteries, including lithium-ion batteries, have driven the electronics and automotive industries, but insufficient temperature characteristics and safety measures have delayed their widespread adoption depending on the battery's application. Therefore, there is a need to develop new batteries tailored to specific applications while achieving both high performance and safety. Furthermore, for rare metals and resources with uneven geographical distribution, risk management is important, taking into account fluctuations in market prices and the risk of them becoming difficult to obtain. While progress has been made in the development of rare metal recycling technologies from various perspectives, there is a need for the development of batteries made from inexpensive, readily available materials that are not unevenly distributed (Non-Patent Documents 1 and 2).

[0006] Currently, development of sodium-ion batteries and all-solid-state batteries is progressing as battery systems that can solve these issues.

[0007] Sodium is abundant in seawater and is the sixth most abundant element in the Earth's crust. It is cheap, easy to obtain, and not unevenly distributed like lithium. This reduces the risk of procuring resources, and is expected to lead to lower battery costs.

[0008] It is an extremely attractive element given the recent trend toward rare metal-free batteries, but compared to lithium, its redox potential is about 0.3 V higher, its ion volume is more than twice as large, and its atomic weight is about 3.3 times larger. Simply replacing the ion species in conventional lithium-ion batteries with sodium ions makes it difficult to obtain sufficient electrical capacity and cycle characteristics.

[0009] Other battery systems that use sodium include sodium-sulfur batteries and sodium-metal chloride batteries. Sodium-sulfur batteries use sodium-containing aluminum oxide, such as β-alumina or β''-alumina, as the solid electrolyte, sodium as the negative electrode active material, and sulfur as the positive electrode active material.

[0010] In sodium-metal chloride batteries, the solid electrolyte and negative electrode active material are the same, but metal chlorides such as NaAlCl4, NiCl2, FeCl2, CoCl2, and CrCl2 are used as the positive electrode active material.

[0011] Although sodium-sulfur batteries and sodium-metal chloride batteries do not require an electrolyte solvent, unlike lithium-ion batteries and sodium-ion batteries, they do not operate at room temperature. For this reason, the battery temperature is maintained at 250-350°C using an external heat source, which melts the negative and positive electrode active materials and improves the ionic conductivity of the solid electrolyte.

[0012] On the other hand, all-solid-state batteries are battery systems that use a solid electrolyte. Because this solid electrolyte is responsible for ionic conduction between the positive and negative electrodes, they can be produced without using the organic solvents that were required for sodium-ion batteries (sodium storage batteries that use electrolytes). For example, sodium-ion batteries have exclusively used sodium hexafluorophosphate (NaPF6) salt as the electrolyte, but sodium ions (Na + ), as well as hexafluorophosphate ion (PF6 - ) also moves, making it difficult to make the transference number of the sodium ion 1.

[0013] However, concentration polarization does not occur in inorganic solid electrolytes, and the transference number of sodium ions is nearly 1. By selecting an electrolyte with an appropriate potential window, it is possible to suppress side reactions such as the dissolution reaction of the active material, gas generation due to electrolysis, and precipitation of electrolyte decomposition products. In addition, gas and liquid ignition and liquid leakage are less likely to occur, and this is expected to result in a storage battery with excellent safety and reliability.

[0014] Like conventional batteries, all-solid-state sodium batteries are composed of a positive electrode, a negative electrode, and an electrolyte, but the electrolyte must be solid and have sodium ion conductivity.

[0015] The positive and negative electrodes are composed of an active material capable of absorbing or alloying sodium ions during charge and discharge, and a solid electrolyte. For example, known active materials for use in the positive electrode include TiS2 (e.g., Non-Patent Document 3), NaMO2 (M = Co, Ni, Mn, Fe) (e.g., Non-Patent Documents 4-6), Na2MnO3-NaMO2 (e.g., Patent Document 1), and NaMP2O7 (e.g., Patent Document 2). Known active materials for use in the negative electrode include hard carbon (e.g., Patent Document 3), soft carbon (e.g., Patent Document 4), simple substances or compounds of tin and antimony (e.g., Patent Documents 5 and 6), and sodium metal.

[0016] Through vigorous research and development to date, various solid electrolytes exhibiting high ionic conductivity have been discovered (e.g., Patent Documents 7 to 10). Most of these are amorphous or crystalline electrolytes composed of sodium salts and inorganic derivatives.

[0017] However, these materials are in powder or sheet form, and many of them are highly reactive with water, so conventional battery production methods cannot be applied as is. Specifically, unlike liquid-type sodium-ion batteries, it is difficult to penetrate the electrolyte into the active material layer of the electrode to create an ion conduction path in all-solid-state sodium batteries. For this reason, it is necessary to incorporate a solid electrolyte into the active material layer to increase the ion conductivity between the solid electrolyte and the solid particles of the active material.

[0018] For example, Patent Document 11, Patent Document 12, and Non-Patent Document 7 propose preparing an electrode composite precursor (active material layer precursor) containing an active material precursor powder and a solid electrolyte powder, and then firing the precursor to produce an electrode composite (active material layer) consisting of an active material and a solid electrolyte, or an all-solid-state sodium storage battery using the same. For example, Na2FeP2O7 crystallized glass is used as the active material precursor. Glass and crystallized glass crystallize upon firing (heat treatment), and soften and flow during this process. Therefore, they can be integrated with the solid electrolyte powder by firing alone, without the need for pressure.

[0019] Furthermore, according to Patent Document 11, Patent Document 12, and Non-Patent Document 7, the electrode mixture precursor is applied to one surface of a solid electrolyte layer, and then fired at 400°C or higher, thereby forming an electrode mixture on one surface of the solid electrolyte layer.

[0020] However, because solid electrolytes lack electronic conductivity, it is difficult to ensure both electronic and ionic conductivity in the electrode. The obvious solution is to add a conductive additive. However, if the conductive additive content is too high, the amount of active material per unit mass of the electrode mixture decreases, which tends to reduce the charge / discharge capacity. Furthermore, inhibiting sintering can cut off the ionic conduction path, suggesting a decrease in charge / discharge capacity and discharge voltage. [Prior art documents] [Patent documents]

[0021] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-229452 [Patent Document 2] Japanese Patent Application Publication No. 2018-32536 [Patent Document 3] International Publication No. 2010 / 109889 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-171798 [Patent Document 5] International Publication No. 2013 / 065787 [Patent Document 6] Japanese Patent Application Laid-Open No. 2015-28922 [Patent Document 7] Japanese Patent Application Laid-Open No. 2010-15782 [Patent Document 8] Japanese Patent Application Laid-Open No. 2017-37769 [Patent Document 9] Japanese Patent Application Publication No. 2019-57495 [Patent Document 10] Japanese Patent Application Publication No. 2019-57496 [Patent Document 11] Japanese Patent Application Publication No. 2018-18578 [Patent Document 12] Japanese Patent Application Laid-Open No. 2016-42453 [Non-patent literature]

[0022] [Non-Patent Document 1] Takashi Mukai: Automotive Technology, 5(4), 19-24(2018) [Non-patent document 2] Takashi Mukai: "Lithium-ion Batteries - Developments for Performance Improvement and Trends in the Automotive LIB Industry", Part 1, Chapter 6, Science & Technology, pp. 91-94 (2019) [Non-patent document 3] GH Newman,LPKlemann:J.Electrochem.Soc.127,2097-2099(1980) [Non-patent document 4] J.-J. Braconnier, C. Delmas, C. Fouassier, P. Hagenmuller: Mat. Res. Bull., 15, 1797-1804 (1980) [Non-Patent Document 5] S. Okada, Y. Takahashi, T. Kiyabu, T. Doi, J. Yamaki, T. Nishida: ECS Meeting Abstr., 602, 201 (2006) [Non-patent document 6] N. Yabuuchi, M. Kajiyama, J. Iwatate, H. Nishikawa, S. Hitomi, R. Okuyama, R. Usui, Y. Yamada, S. Komaba: Nat. Mater., 11, 512-517 (2012) [Non-Patent Document 7] H. Yamauchi, J. Ikejiri, F. Sato, H. Oshita, T. Honma, T. Komatsu: J. Am. Ceram. Soc., 102(11), 6658-6667(2019) Summary of the Invention [Problem to be solved by the invention]

[0023] As mentioned above, to improve the performance of all-solid-state sodium batteries, it is important to have a technology that increases the ionic conductivity between the solid electrolyte and the solid particles of the active material while ensuring the electronic conductivity of the electrodes.

[0024] The present inventors have focused on a technology for integrating an active material and a solid electrolyte by press-molding an electrode composite precursor (electrode active material layer precursor) consisting of an active material precursor powder and a solid electrolyte powder, or by adding a solvent to form a slurry (paste), and then firing the slurry, as described in Patent Document 11, Patent Document 12, and Non-Patent Document 7.

[0025] To improve the performance of batteries, that is, to increase the capacity of the positive electrode formed per unit area of ​​the solid electrolyte layer surface, it is necessary to increase the amount of electrode mixture applied per unit area of ​​the solid electrolyte layer surface and thereby increase the amount of electrode active material supported. However, as described in Patent Documents 11 and 12, when a mixture of an active material precursor and a solid electrolyte is applied thickly to the electrolyte surface and then fired to increase the amount supported, there is a problem that only the electrode mixture layer sinters and shrinks, causing it to peel off from the electrolyte and preventing it from functioning as a battery.

[0026] Furthermore, when a mixture of an active material precursor and a solid electrolyte is fired, the active material precursor powder and the solid electrolyte powder may react with each other at the interface between the active material and the solid electrolyte, resulting in the formation of a heterogeneous crystalline phase. This heterogeneous crystalline phase does not function as a practical active material and has inferior ionic conductivity compared to the solid electrolyte layer, which has been found to be a factor in degrading battery performance.

[0027] As described above, the inventors initially conducted extensive research into improving the performance of all-solid-state sodium storage batteries by directly forming an electrode composite on the surface of an inorganic solid electrolyte. However, when electrodes are formed directly on the surface of an inorganic solid electrolyte and integrated, the battery resistance is currently high and there is a limit to how high the capacity can be achieved per unit area. Therefore, the inventors conducted extensive research into forming a battery using the electrode composite and the inorganic solid electrolyte as separate components, rather than directly forming an electrode composite on the surface of the inorganic solid electrolyte, and this led to the present invention. The present invention can solve the above-mentioned conventional problems as well as problems newly discovered by the inventors.

[0028] In order to achieve the above object, the present inventors have conducted extensive research into the composition of an electrode composite to be used in an all-solid-state sodium storage battery using sodium ions as a carrier, and have conducted repeated trial and error studies into the combinations and the effects obtained therefrom, thereby succeeding in developing an electrode composite that can be used to obtain an all-solid-state sodium storage battery using sodium ions as a carrier at a level that is practical. [Means for solving the problem]

[0029] The invention according to claim 1 is an electrode mixture for use in an all-solid-state sodium storage battery, the electrode mixture including an active material, the active material being a cluster formed of a polyphosphate transition metal oxide in which a plurality of particles having a particle size in the range of 0.1 μm to 100 μm are connected together. The polyphosphate transition metal oxide is Na 2 FeP 2 O 7 , Na 3 Fe 2 (PO 4 ) 3 , NaFe 3 P 3 O 12 , Na 2 Fe 3 (PO 4 ) 3 , Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ), Na 2 MnP 2 O 7 , Na 2 CoP 2 O 7 , Na 2 NiP 2 O 7 , Na 2 Fe 0.5 Mn 0.5 P 2 O 7 , Na 3 V 2 (PO 4 ) 3 , NaVOPO 4 , and Na 9 V 3 (P 2O 7 ) 3 (PO 4 ) 2 At least one selected from the group consisting of , an electrode composite.

[0031] Claim 2 The invention according to claim 1 further comprises an ion conduction aid, and the ion conduction aid is at least one selected from the group consisting of ethylene carbonate (EC), polyethylene carbonate (PEC), polyethylene glycol (PEG), and polyethylene oxide (PEO). 1 1. An electrode mixture according to claim 1.

[0032] Claim 3 The invention according to claim 1 further comprises a conductive additive, and the conductive additive is at least one selected from the group consisting of metals, carbon materials, conductive polymers, and conductive glasses. or 2 1. An electrode mixture according to claim 1.

[0033] Claim 4 The invention according to claim 1 is characterized in that the conductive additive is supported on a part or the entire surface of the electrode mixture. 3 1. An electrode mixture according to claim 1.

[0034] Claim 5 The invention according to claim 1 is characterized in that the conductive additive is supported on the surface of a portion of the ion conductive additive that connects individual particles of the active material. 3 or 4 1. An electrode mixture according to claim 1.

[0035] Claim 6 The invention according to claim 1 is characterized in that the conductive additive is contained inside a portion of the ion conductive additive that connects individual particles of the active material. 3 ~ 5 10. The electrode mixture according to claim 1, wherein the electrode mixture is a mixture of a fluorine-containing compound and a fluorine-containing compound.

[0036] Claim 7 The invention according to claim 1, wherein the conductive additive is carbon selected from at least one of powdered carbon, fibrous carbon, and flake carbon.3 ~ 6 10. The electrode mixture according to claim 1, wherein the electrode mixture is a mixture of a fluorine-containing compound and a fluorine-containing compound.

[0037] Claim 8 The invention according to claim 1, wherein the carbon is powdered carbon having a primary particle size in the range of 1 nm to 100 nm. 7 1. An electrode mixture according to claim 1.

[0038] Claim 9 The invention relates to a method for producing a carbon fiber having a nitrogen adsorption specific surface area of ​​20 m 2 / g~500m 2 / g of powdered carbon. 7 or 8 1. An electrode mixture according to claim 1.

[0039] Claim 10 The invention according to claim 1, wherein the carbon is fibrous carbon having a fiber diameter in the range of 1 nm to 300 nm. 7 1. An electrode mixture according to claim 1.

[0040] Claim 11 The invention according to claim 1 further provides a method for manufacturing a carbon fiber substrate, wherein the carbon is flake-shaped carbon having a thickness in the range of 1 nm to 300 nm. 7 1. An electrode mixture according to claim 1.

[0041] Claim 12 The invention according to claim 1, wherein the carbon is a combination of powdered carbon and fibrous carbon, a combination of powdered carbon and flake carbon, or a combination of powdered carbon, fibrous carbon and flake carbon. 7 ~ 11 10. The electrode mixture according to claim 1, wherein the electrode mixture is a mixture of a fluorine-containing compound and a fluorine-containing compound.

[0042] Claim 13 The invention according to claims 1 to 5 does not include a resin binder. 12 10. The electrode mixture according to claim 1, wherein the electrode mixture is a mixture of a fluorine-containing compound and a fluorine-containing compound.

[0043] Claim 14The invention according to any one of claims 1 to 5 is characterized in that the electrode mixture is porous and further contains pores, and the porosity of the electrode mixture is within the range of 5% to 50%. 13 10. The electrode mixture according to claim 1, wherein the electrode mixture is a mixture of a fluorine-containing compound and a fluorine-containing compound.

[0044] Claim 15 The invention according to claim 1 further comprises the step of: 14 1. An electrode mixture according to claim 1.

[0045] Claim 16 The present invention relates to a solid electrolyte powder having a particle size of 0.1 μm to 100 μm as an ion conduction aid. 15 10. The electrode mixture according to claim 1, wherein the electrode mixture is a mixture of a fluorine-containing compound and a fluorine-containing compound.

[0046] Claim 17 The invention relates to the surface of the pores. Gai The present invention relates to a method for manufacturing a semiconductor device, and a method for manufacturing the semiconductor device, the method comprising: 14 or 15 1. An electrode mixture according to claim 1.

[0047] Claim 18 The invention relates to a film having a thickness of 10 μm to 5000 μm and a total weight per unit area of ​​1 mg / cm 2 ~5000mg / cm 2 Claims 1 to 5 17 10. The electrode mixture according to claim 1, wherein the electrode mixture is a mixture of a fluorine-containing compound and a fluorine-containing compound.

[0048] Claim 19 The present invention relates to a non-aqueous electrolyte battery used as a positive electrode and / or a negative electrode in a non-aqueous electrolyte electricity storage device. 18 10. The electrode mixture according to claim 9, wherein the nonaqueous electrolyte electricity storage device is an all-solid-state sodium storage battery including the electrode mixture, an organic solid electrolyte, an inorganic solid electrolyte, and a current collector.

[0049] Claim 20 The invention according to claim 1 is used in a battery pack including an all-solid-state sodium storage battery as a non-aqueous electrolyte electricity storage device. 19 1. An electrode mixture according to claim 1.

[0050] Claim 21 The invention according to claim 1 is used in an electrical device including an all-solid-state sodium storage battery or a battery pack thereof as a non-aqueous electrolyte electricity storage device. 19 or 20 1. An electrode mixture according to claim 1. [Effects of the Invention]

[0051] The invention according to claim 1 is an electrode mixture for use in an all-solid-state sodium storage battery, the electrode mixture including an active material, the active material being a cluster formed of a polyphosphate transition metal oxide in which a plurality of particles having a particle size in the range of 0.1 μm to 100 μm are connected together. The polyphosphate transition metal oxide is Na 2 FeP 2 O 7 , Na 3 Fe 2 (PO 4 ) 3 , NaFe 3 P 3 O 12 , Na 2 Fe 3 (PO 4 ) 3 , Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ), Na 2 MnP 2 O 7 , Na 2 CoP 2 O 7 , Na 2 NiP 2 O 7 , Na 2 Fe 0.5 Mn 0.5 P 2 O 7 , Na 3 V 2 (PO 4 ) 3 , NaVOPO 4 , and Na 9 V 3 (P 2 O 7 ) 3 (PO 4) 2 At least one selected from the group consisting of Because it is an electrode compound, it has high ionic conductivity and can improve output characteristics, allowing it to maintain a high discharge capacity at room temperature. It also exhibits excellent charge-discharge cycle characteristics and can be shut down by overcharging. If the particle size is less than 0.1 μm, it is difficult to handle. If it is 100 μm or more, the porosity becomes large and the output characteristics deteriorate.

[0053] Claim 2 The invention further includes an ion conduction aid, which is at least one selected from the group consisting of ethylene carbonate (EC), polyethylene carbonate (PEC), polyethylene glycol (PEG), and polyethylene oxide (PEO), so that the ionic resistance of the electrode composite can be reduced, and when the battery is overcharged, the material selected from EC, PEC, PEG, and PEO contained in the electrode composite is oxidatively decomposed, thereby suppressing an increase in the battery voltage.

[0054] Claim 3 The invention according to claim 1 further comprises a conductive additive, which is at least one selected from the group consisting of metals, carbon materials, conductive polymers, and conductive glasses, thereby enabling the improvement of electronic conductivity.

[0055] Claim 4 In the invention according to the third aspect, the conductive additive is supported on a part or the entire surface of the electrode mixture, so that the electronic conductivity can be increased.

[0056] Claim 5 In the invention relating to the present invention, the conductive additive is supported on the surface of the portion connecting the individual particles of the active material, thereby improving the electronic conductivity between the particles of the active material.

[0057] Claim 6 In the invention relating to the present invention, the conductive additive is contained inside the part that connects individual particles of the active material, thereby improving the electronic conductivity between particles of the active material.

[0058] Claim 7 In the invention according to the third aspect, the conductive additive is carbon selected from at least one of powdered carbon, fibrous carbon, and flake carbon, so that high electronic conductivity and a small specific gravity can be achieved.

[0059] Claim 8 In the invention according to the present invention, the carbon is powdered carbon with a primary particle size in the range of 1 nm to 100 nm, and therefore the carbon, which is a conductive additive, improves the electronic conductivity between particles of the active material, thereby significantly improving the output characteristics of the battery.

[0060] Claim 9 The invention relates to a method for producing a carbon fiber having a nitrogen adsorption specific surface area of ​​20 m 2 / g~500m 2 / g, the carbon, which acts as a conductive additive, is present at the junctions between particles of the active material, improving the electronic conductivity of the electrode mixture, thereby significantly improving the output characteristics of the battery.

[0061] Claim 10 In the invention according to the present invention, the carbon is fibrous carbon with a fiber diameter in the range of 1 nm to 300 nm, so that when the electrode mixture undergoes a volume change due to charging and discharging, the conductive network is less likely to be broken, improving the cycle life characteristics of the battery.

[0062] Claim 11 In the invention according to the present invention, the carbon is further in the form of flakes having a thickness in the range of 1 nm to 300 nm, so that when the volume of the electrode mixture changes during charging and discharging, the conductive network is less likely to be broken, improving the cycle life characteristics of the battery.

[0063] Claim 12In the invention according to the present invention, the carbon is a combination of powdered carbon and fibrous carbon, or a combination of powdered carbon and flaked carbon, or a combination of powdered carbon, fibrous carbon and flaked carbon, so that when the volume of the electrode mixture changes during charging and discharging, the conductive network is less likely to be broken, improving the cycle life characteristics of the battery.

[0064] Claim 13 The invention according to claim 1 does not contain a resin-based binder, and therefore does not increase electronic resistance and ionic resistance. Furthermore, when an active material precursor is produced by firing, the active material precursor is thermally decomposed, so the binding function as a binder is not lost, and the performance of the active material or solid electrolyte is not reduced by water vapor or the like generated during thermal decomposition.

[0065] Claim 14 In the invention, the electrode mixture is porous and further includes pores, and the porosity of the electrode mixture is within the range of 5% to 50%, so that EC, PEC, PEG, and PEO can be sufficiently contained in the electrode mixture, increasing the proportion of active material in the electrode mixture and increasing the energy density.

[0066] Claim 15 In the invention according to the above, the pores have a pore size of 0.1 μm to 100 μm, so that EC, PEC, PEG, PEO, etc. can easily penetrate into the electrode mixture, and the electrode mixture has high strength and is less likely to break.

[0067] Claim 16 The invention according to claim 1 contains a solid electrolyte powder having a particle size of 0.1 μm to 100 μm as an ion-conducting assistant, and therefore can obtain sufficient ion conductivity.

[0068] Claim 17 The invention relates to the surface of the pores. Gai Since the electrode is coated with a solid electrolyte powder as an ion conduction aid, sufficient electron conductivity can be obtained.

[0069] Claim 18The invention relates to a film having a thickness of 10 μm to 5000 μm and a total weight per unit area of ​​1 mg / cm 2 ~5000mg / cm 2 Therefore, a sufficient charge / discharge capacity can be obtained.

[0070] Claim 19 The invention according to claim 1 is used as a positive electrode and / or a negative electrode in a nonaqueous electrolyte electricity storage device, and the nonaqueous electrolyte electricity storage device is an all-solid-state sodium storage battery including the electrode mixture, an organic solid electrolyte, an inorganic solid electrolyte, and a current collector, so that a high voltage can be obtained, and a high-performance all-solid-state sodium storage battery can be obtained.

[0071] Claim 20 The invention according to claim 1 is used in a battery pack including an all-solid-state sodium storage battery as a non-aqueous electrolyte electricity storage device, so that a high voltage can be obtained, and a high-performance battery pack can be obtained.

[0072] Claim 21 The invention according to claim 1 is used in an electrical device including an all-solid-state sodium storage battery or a battery pack thereof as a non-aqueous electrolyte electricity storage device, and therefore, an electrical device that is easy to handle and operates efficiently can be obtained. [Brief explanation of the drawings]

[0073] [Figure 1] FIG. 1 is a conceptual diagram showing a cross section of an active material cluster contained in an electrode mixture according to the present invention. [Figure 2] FIG. 1 is a conceptual diagram showing a cross section of an active material cluster contained in an electrode mixture according to the present invention. [Figure 3] FIG. 1 is a conceptual cross-sectional view of an all-solid-state sodium storage battery produced using an electrode mixture according to the present invention. [Figure 4] FIG. 1 is a conceptual cross-sectional view of an all-solid-state sodium storage battery with a bipolar structure produced using an electrode mixture according to the present invention. [Figure 5]It is a diagram showing a part of the manufacturing process of an all-solid-state sodium battery using the electrode composite material according to the present invention. [Figure 6] It is a diagram comparing the charge curves of Example 5 and Comparative Example 2.

Embodiments for Carrying Out the Invention

[0074] Hereinafter, an electrode composite material used for an all-solid-state sodium battery using sodium ions as carriers according to the present invention, and a preferred embodiment of a battery using the same will be described.

[0075] The electrode composite material according to the present invention includes a positive electrode composite material (positive electrode active material layer) and a negative electrode composite material (negative electrode active material layer). However, the electrode composite material used for the all-solid-state sodium battery of the present invention preferably contains a polyphosphate transition metal oxide, regardless of which electrode composite material it is. In particular, when the electrode composite material is used as a positive electrode composite material, the polyphosphate transition metal oxide functions as an active material.

[0076] In the electrode composite material according to the present invention, the polyphosphate transition metal oxide preferably has a crystal represented by the general formula Na a M b P c O d .

[0077] From the viewpoint of high ionic conductivity, charge-discharge capacity or output characteristics of the polyphosphate transition metal oxide, 0.0 < a ≤ 3.5, b = 1, 1.0 ≤ c ≤ 3.0, 3.0 ≤ d ≤ 30, and M is preferably at least one element selected from Fe, Mn, Co, Ni, and V.

[0078] Specifically, Na2FeP2O7, Na3Fe2(PO4)3, NaFe3P3O 12 , Na2Fe3(PO4)3, Na4Fe3(PO4)2(P2O7), Na2MnP2O7, Na2CoP2O7, Na2NiP2O7, Na2Fe 0.5 Mn 0.5Examples include P2O7, Na3V2(PO4)3, NaVOPO4, Na9V3(P2O7)3(PO4)2, etc., and one or more of these may be used.

[0079] Among the above polyphosphate transition metal oxides, glass or crystallized glass is easy to synthesize as a polyphosphate transition metal oxide precursor, and has the characteristics of softening and flowing and being easy to crystallize during the firing (heat treatment) process at 700 °C or lower. Therefore, 0.0 < a ≤ 3.0, b = 1, 1.1 ≤ c ≤ 2.9, 3.5 ≤ d ≤ 12 is more preferable, 0.7 ≤ a ≤ 2.4, b = 1, 1.2 ≤ c ≤ 2.8, 4.0 ≤ d ≤ 11 is even more preferable, and 1.7 ≤ a ≤ 2.3, b = 1, 1.4 ≤ c ≤ 2.7, 5.0 ≤ d ≤ 10 is desirable.

[0080] In addition, in the polyphosphate transition metal oxide, part of the Na site of the above material may be substituted with Li or K, or it may be a material in which part of the O site or P site is substituted with F, Cl, S, or B.

[0081] The crystal of the polyphosphate transition metal oxide can be produced from the precursor of the polyphosphate transition metal oxide. For example, a mixture of sodium metaphosphate (NaPO3), ferric oxide (Fe2O3), and orthophosphoric acid (H3PO4) adjusted to a predetermined composition is fired in an air atmosphere at 1000 °C to 2000 °C for 0.1 to 10 hours. After melting the mixture, the molten glass is poured onto a pair of rolls and rapidly cooled (50 °C / min or more) to obtain glass or polycrystalline glass of iron polyphosphate oxide. The obtained glass or polycrystalline glass of iron polyphosphate oxide is adjusted to an active material precursor within a particle size range of 0.1 μm to 100 μm by mechanical grinding treatment, and fired at 400 to 800 °C to obtain crystals of iron polyphosphate oxide.

[0082] Although it can be synthesized in the air, it is preferable to synthesize it in a reducing gas environment containing 1 vol.% or more of hydrogen, as this will result in a more crystalline transition metal oxide polyphosphate. However, since firing in a gas environment containing hydrogen involves the risk of explosion, it is desirable to mix an inert gas with the firing, taking into account the explosion limit of hydrogen. The inert gas may be nitrogen or a rare gas.

[0083] Furthermore, although the calcination temperature for obtaining crystals is set within the range of 400 to 800°C for iron oxide polyphosphate, this differs depending on the transition metal oxide polyphosphate material, so it is preferable to check the crystallization temperature of the precursor using a thermogravimetric differential thermal analyzer (TG-DTA) or similar before calcination and set the temperature at the same temperature as the crystallization temperature or slightly higher. However, temperatures 150°C higher than the crystallization temperature can cause structural and compositional changes in the material, potentially resulting in thermal decomposition.

[0084] In addition to the transition metal oxide polyphosphate, the electrode mixture may further contain an active material used in sodium ion batteries, sodium metal batteries, sodium-air batteries, sodium-sulfur batteries, sodium-metal chloride batteries, all-solid-state sodium storage batteries, etc. That is, in addition to the transition metal oxide polyphosphate, the electrode mixture may contain a known sodium metal, a known sodium alloy, or a known sodium ion storage material.

[0085] When the electrode mixture is used as a positive electrode mixture, it may contain other positive electrode active materials in addition to the transition metal oxide polyphosphate. Known materials, including transition metal oxides, sulfur-based materials, and solid solution-based materials, are used as the positive electrode active materials. When the electrode mixture is used as a negative electrode mixture, it is preferable to contain other negative electrode active materials in addition to the transition metal oxide polyphosphate, since a practical energy density cannot be obtained with the transition metal oxide polyphosphate alone. The negative electrode active material preferably contains known materials, including transition metal oxides, sulfur-based materials, sodium metal, materials that alloy with sodium, or materials that can reversibly absorb and release sodium ions.

[0086] The electrode active material (positive electrode active material or negative electrode active material) preferably has a structure in which individual particles of the active material having a particle size in the range of 0.1 μm to 100 μm are connected together by crystalline transition metal oxide polyphosphate. That is, the electrode mixture preferably forms active material clusters in which individual particles having a particle size in the range of 0.1 μm to 100 μm are connected together.

[0087] Here, the particle size means the volume-based median diameter (D50) measured by a laser diffraction / scattering particle size distribution measurement method.

[0088] In the all-solid-state sodium storage battery according to the present invention, the electrode mixture preferably contains an ion conduction aid in addition to the active material, and the ion conduction aid is preferably at least one selected from ethylene carbonate (EC), polyethylene carbonate (PEC), polyethylene glycol (PEG), and polyethylene oxide (PEO).

[0089] By including at least one ion-conducting assistant selected from EC, PEC, PEG, and PEO in the electrode mixture, the ionic resistance of the electrode mixture can be reduced.

[0090] The EC, PEC, PEG, and PEO contained in the electrode mixture may be modified to the extent that their structure and properties are not significantly changed (that is, they may be derivatives).

[0091] Although it depends on the mass of the electrode mixture, the amount of EC, PEC, PEG, and PEO contained in the electrode mixture is 0.1 mg / cm 2 ~500mg / cm 2 It is preferable that the range is 0.2 mg / cm 2 ~250mg / cm 2 More preferably, it is in the range of 0.5 mg / cm 2 ~100mg / cm 2 is more preferable.

[0092] According to this configuration, a material selected from EC, PEC, PEG, and PEO contained in the electrode composite functions as an ion-conducting additive that improves the ion conductivity of the electrode composite. Furthermore, the organic solid electrolyte interposed between the electrode composite and the inorganic solid electrolyte is fused and integrated with the electrode composite, resulting in a battery with low impedance. This allows for the production of an all-solid-state sodium storage battery that can maintain a high discharge capacity and exhibit excellent charge-discharge cycle characteristics at room temperature, even when a thick electrode composite is formed.

[0093] In addition, when the battery is overcharged, the material selected from EC, PEC, PEG, and PEO contained in the electrode mixture is oxidized and decomposed, thereby suppressing the increase in battery voltage. Fig. 3 is a conceptual cross-sectional view of an all-solid-state sodium storage battery produced using an electrode mixture according to the present invention. The all-solid-state sodium storage battery 1 shown in Fig. 3 is characterized in that an organic solid electrolyte 3 is interposed between an electrode mixture 2 (active material layer) and an inorganic solid electrolyte 4. According to this configuration, when a voltage is applied, the organic solid electrolyte 3 can move sodium ions via the electrode mixture 2 and the inorganic solid electrolyte 4. 4 is a conceptual cross-sectional view of a bipolar all-solid-state sodium storage battery fabricated using the electrode composite according to the present invention. A bipolar all-solid-state battery can obtain a high voltage from a single cell. Fig. 5 is a diagram showing part of the manufacturing process for an all-solid-state sodium storage battery using an electrode mixture according to the present invention. As shown in Fig. 5, an electrode mixture 2 and an inorganic solid electrolyte 4 are bonded together with an organic solid electrolyte 3. Specifically, the organic solid electrolyte 3 is applied to one surface of the electrode mixture 2, and the organic solid electrolyte 3 is also applied to one surface of the inorganic solid electrolyte 4, and the electrode mixture 2 and the inorganic solid electrolyte 4 are bonded together in this state. In order to improve the adhesion between the electrode mixture 2 and the inorganic solid electrolyte 4, it is preferable to provide a roughened surface 13 on the surface of the electrode mixture 2.

[0094] Among the materials selected from EC, PEC, PEG, and PEO contained in the electrode mixture, polymer materials with a molecular weight of 500 or more selected from PEC, PEG, and PEO are preferred, with PEG or PEO being more preferred, from the viewpoint of providing excellent heat resistance, high ionic conductivity, and ease of fusion with the organic solid electrolyte interposed between the electrode mixture and the inorganic solid electrolyte. However, polymer materials with a molecular weight of more than 200,000 have excessively high viscosity, making them difficult to incorporate into the electrode mixture during production, and reducing the ionic conductivity of the electrode mixture. These materials may be crosslinked or non-crosslinked.

[0095] The electrode mixture preferably contains a conductive additive. The conductive additive is not particularly limited as long as it has electronic conductivity, and examples thereof include metals, carbon materials, conductive polymers, and conductive glass. Carbon materials are preferred because of their high electronic conductivity and low specific gravity. Specific examples include acetylene black (AB), ketjen black (KB), furnace black (FB), thermal black, lamp black, channel black, roller black, disc black, carbon black (CB), and glassy carbon. One or more of these may be used.

[0096] Among these, conductive additives with a primary particle size of carbon in the range of 1 nm to 100 nm are preferred. When the electrode composite forms active material clusters in which multiple individual particles are connected, this carbon can be formed by incorporating carbon 10 into the portions (crystals 9 of polyphosphate transition metal oxide) connecting the individual particles (electrode active material particles 8), as shown in FIG. 1. This configuration allows the carbon, which serves as a conductive additive, to improve the electronic conductivity between the active material particles. This significantly improves the output characteristics of the battery.

[0097] In addition, the nitrogen adsorption specific surface area of ​​carbon is 20m 2 / g~500m 2 / g. In the case of this carbon, when the electrode mixture forms active material clusters in which multiple individual particles are connected, as shown in FIG. 2, carbon 10 can be supported on the surface of the portion (crystal 9 of polyphosphate transition metal oxide) connecting the individual particles (electrode active material particles 8). With this configuration, the carbon, which is the conductive additive, is present at the connection portion between the active material particles, thereby improving the electronic conductivity of the electrode mixture. This significantly improves the output characteristics of the battery.

[0098] The conductive additive preferably further contains fibrous carbon having a fiber diameter of 1 nm to 300 nm or flake carbon having a thickness of 1 nm to 300 nm, which makes the conductive network less likely to be broken when the electrode mixture undergoes volume changes during charge and discharge, improving the cycle life characteristics of the battery.

[0099] Here, the fiber diameter is the diameter confirmed when the cross section of the fibrous carbon is observed with a transmission electron microscope (TEM), and the thickness is the thickness confirmed when the cross section of the flake carbon is observed with a transmission electron microscope (TEM).

[0100] Fibrous carbon includes carbon fiber (for example, vapor grown carbon fiber known as VGCF, a registered trademark) and carbon nanotubes (CNT). Flake carbon includes thin graphite and graphene.

[0101] The conductive additive contained in the electrode mixture is preferably contained in an amount of 0.5 to 30 mass % relative to the electrode mixture.

[0102] For reference, the method for producing the electrode mixture is described below. The electrode mixture can be produced by filling a powder containing at least a transition metal oxide polyphosphate into a powder molding die, applying pressure to form pellets (tablets), and firing the pellets at a temperature of 400°C to 2000°C in an inert gas or reducing gas atmosphere.

[0103] However, pelletizing transition metal oxide polyphosphate powder requires high pressures exceeding 100 MPa, necessitating the use of a large-scale pressure device. Therefore, the transition metal oxide polyphosphate is preferably coated with or supported by a resin-based binder. By coating or supporting the surface of the transition metal oxide polyphosphate with a resin-based binder, it becomes possible to pelletize the powder at a pressure of 100 MPa or less.

[0104] By using this powder and molding it under pressure, the resin binders bond together at a pressure of 1 MPa to 100 MPa, resulting in dense pellets. If the pressure during molding is less than 1 MPa, the resin binders do not bond together easily. On the other hand, if the pressure exceeds 100 MPa, the equipment becomes too large.

[0105] The resulting pellets are then fired in an inert gas or reducing gas atmosphere, softening and flowing the transition metal polyphosphate oxide to obtain an integrated electrode composite. At the same time, the resin binder is thermally decomposed. Therefore, the electrode composite (the fired pellets) does not contain resin and is porous with a porosity in the range of 5% to 50%.

[0106] That is, the all-solid-state sodium storage battery according to the present invention preferably does not contain a resin-based binder in the electrode mixture. The inclusion of a resin-based binder in the electrode mixture increases the electronic resistance and ionic resistance. Furthermore, when an active material precursor is produced by firing, the binder loses its binding function due to thermal decomposition, and the water vapor generated during thermal decomposition reduces the performance of the active material and solid electrolyte.

[0107] Resin binders are compounds whose main molecular structure is carbon, and examples of such binders include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide, polyamide-imide, polyacrylic, styrene butadiene rubber (SBR), ethylene-vinyl acetate copolymer (EVA), polypropylene carbonate (PPC), styrene-ethylene-butylene-styrene copolymer (SEBS), carboxymethyl cellulose (CMC), xanthan gum, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), ethylene vinyl alcohol, polyethylene (PE), polypropylene (PP), polyacrylic acid, lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate, methyl polyacrylate, and polyacrylic acid. Examples of materials that can be used include ethyl acrylate, polyamine acrylate, polyacrylic ester, epoxy resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), nylon, vinyl chloride, silicone rubber, nitrile rubber, cyanoacrylate, urea resin, melamine resin, phenolic resin, latex, polyurethane, silylated urethane, nitrocellulose, dextrin, polyvinylpyrrolidone, vinyl acetate, polystyrene, chloropropylene, resorcinol resin, polyaromatic, modified silicone, methacrylic resin, polybutene, butyl rubber, 2-propenoic acid, cyanoacrylic acid, methyl methacrylate, glycidyl methacrylate, acrylic oligomer, 2-hydroxyethyl acrylate, polyacetal, alginic acid, starch, sucrose, lacquer, glue, and casein.

[0108] Many of these resin binders are thermally decomposed and carbonized at temperatures above 150°C, but polypropylene carbonate (PPC) is a binder that turns into carbon dioxide gas when heat treated at 200°C or above, even in an inert or reducing environment, and disappears without leaving any carbon behind, making it preferable as it has very little effect on electrodes.The carbon produced by the thermal decomposition of resin binders has low conductivity unless fired at high temperatures, and can have a negative effect on electrodes.

[0109] In an electrode composite containing not only a transition metal polyphosphate but also an active material used in a sodium ion battery, a sodium metal battery, a sodium-air battery, a sodium-sulfur battery, a sodium-metal chloride battery, an all-solid-state sodium storage battery, etc., it is preferable to coat or support not only the transition metal polyphosphate but also these active materials with or without a resin-based binder, even when a conductive additive is added.

[0110] The firing conditions are not particularly limited as long as the firing can be performed in an inert gas or reducing gas atmosphere at a temperature of 400°C to 2000°C for 5 minutes or more. However, from the viewpoint of softening and flowing the transition metal oxide polyphosphate and thermally decomposing the resin binder, it is preferable to raise the temperature at a rate of 0.1°C / min to 50°C / min, maintain the temperature at 400°C to 2000°C, and maintain the temperature for 5 minutes to 10 hours.

[0111] From the viewpoint of the input / output characteristics and energy density of the battery, the thickness of the electrode mixture after firing is set to a range of 10 μm to 5000 μm, and the total weight per unit area is set to 1 mg to 5000 mg / cm. 2 It is preferable that the range is within the range of

[0112] Polyphosphate transition metal oxide coated with a resin-based binder can be obtained by adding a solvent to a powder mixture consisting of polyphosphate transition metal oxide and a resin-based binder, mixing, volatilizing the solvent, and then pulverizing or classifying the mixture. Unless the solvent is water, it is best to work in a dry environment (dew point below -40°C).

[0113] As a method for preparing the mixed powder or for mixing by adding a solvent, a known mixing method can be used, and examples thereof include a tumbling mill, a vibration mill, a planetary mill, a rocking mill, a horizontal mill, an attritor mill, a jet mill, a crusher, a homogenizer, a fluidizer, a paint shaker, and a mixer.

[0114] As a method for removing the solvent by evaporation and pulverizing or classifying the mixture, known granulation methods can be applied, such as fluidized bed granulation, stirring and pulverizing granulation, rolling granulation, spray drying, extrusion granulation, and coating granulation, etc. Of these, spray drying and fluidized bed granulation are particularly preferred.

[0115] In the spray-drying method, for example, a suspension in which polyphosphate transition metal oxide and a resin-based binder are dispersed is sprayed from above into a greenhouse heated to 50 to 300°C at a rate of 1 to 30 mL / min and an air pressure of 0.01 to 5 MPa to form agglomerated particles, which are then dried to obtain a granulated product.

[0116] In the fluidized bed granulation method, for example, the powder raw materials are placed in a fluidized bed granulation device, and hot air heated to 50 to 300°C is blown in from below to fluidize and mix the powder raw materials (granule precursor). A liquid in which a resin binder has been dissolved or dispersed is then sprayed from above into this mixed powder raw material using a nozzle. The resin binder is sprayed uniformly onto the powder surface at 1 to 30 mL / min and an air pressure of 0.01 to 5 MPa to create agglomerated particles, which are then dried to obtain the granules.

[0117] To incorporate a material selected from EC, PEC, PEG, and PEO into an electrode composite, the active material and these materials can be mixed and pelletized, but in the case of manufacturing the electrode composite by firing polycrystalline glass or glass of transition metal oxide polyphosphate to generate transition metal oxide polyphosphate crystals, if EC, PEC, PEG, or PEO is incorporated into the composite before firing, it will be thermally decomposed, making it impossible to incorporate EC, PEC, PEG, or PEO into the composite. Therefore, it is necessary to incorporate materials such as EC, PEC, PEG, and PEO into the polycrystalline glass or glass of transition metal oxide polyphosphate after firing.

[0118] Therefore, EC, PEC, PEG, PEO, etc. can be liquefied and applied to the sintered polyphosphate transition metal oxide, or the sintered polyphosphate transition metal oxide can be immersed in liquefied EC, PEC, PEG, PEO, etc., to allow the electrode composite to contain a material selected from EC, PEC, PEG, and PEO.

[0119] To liquefy EC, PEC, PEG, PEO, etc., the temperature of the target material can be increased, but it is preferable to add an organic solvent to liquefy the material. The organic solvent is not particularly limited as long as it can dissolve and liquefy the target material. Examples include chain hydrocarbon solvents (DMC, DEC, EMC, dichloromethane, alcohols, etc.) and cyclic hydrocarbon solvents (NMP, benzene, lactones, etc.). The organic solvent is preferably removed by reducing pressure or by heat treatment. For example, a drying method for electrode slurries used in lithium-ion batteries can be used.

[0120] When the electrode composite is thick, simply applying liquefied EC, PEC, PEG, PEO, etc. is not sufficient for penetration, so it is preferable to immerse the fired transition metal oxide polyphosphate in liquefied EC, PEC, PEG, or PEO. In this state, creating a reduced pressure environment allows penetration deep into the pores of the fired transition metal oxide polyphosphate. The reduced pressure environment can be achieved by creating a pressure (negative pressure) lower than atmospheric pressure; for example, a vacuum pump can be used to create a negative pressure environment with a gauge pressure of 0 MPa to -0.1 MPa.

[0121] The electrode mixture is preferably porous, with a porosity of 5% to 50%, excluding the material selected from EC, PEC, PEG, and PEO contained in the electrode mixture. If the porosity is less than 5%, it is not possible to sufficiently incorporate EC, PEC, PEG, and PEO into the electrode mixture. If the porosity is greater than 50%, it is possible to incorporate a large amount of EC, PEC, PEG, PEO, etc. into the electrode mixture, but the proportion of active material in the electrode mixture will be reduced, resulting in a lower energy density.

[0122] Here, the porosity is a value calculated from the apparent density of the object and the true density of the constituent material using the formula: porosity (%)=100-(apparent density of object / true density of constituent material)×100.

[0123] Furthermore, the electrode composite is preferably porous, having a plurality of pores with a pore size of 0.1 μm to 100 μm, excluding the material selected from EC, PEC, PEG, and PEO contained in the electrode composite. If the pore size is outside this range, it becomes difficult to sufficiently incorporate EC, PEC, PEG, PEO, etc. into the electrode composite during production of the electrode composite. That is, if the pore size is less than 0.1 μm, EC, PEC, PEG, PEO, etc. will not easily penetrate into the electrode composite, and conversely, if it exceeds 100 μm, the strength of the electrode composite will be low and it will be easily broken.

[0124] The electrode mixture according to the present invention preferably does not contain a resin-based binder.

[0125] When pores are present in the electrode mixture according to the present invention, the surfaces of the pores are preferably coated with an electrolyte as an ion conduction assistant.

[0126] The electrolyte contains at least one selected from EC, PEC, PEG, and PEO in addition to an alkali metal salt.

[0127] The present invention also relates to an all-solid-state sodium storage battery using the electrode mixture as a positive electrode and / or a negative electrode, with sodium ions as a carrier.

[0128] In the all-solid-state sodium storage battery according to the present invention, the organic solid electrolyte is preferably a polyether polymerized with ethylene glycol or a derivative thereof, specifically, polyethylene glycol (PEG) or polyethylene oxide (PEO). The PEG or PEO functions as an adhesive that bonds the electrode mixture and the inorganic solid electrolyte, in addition to functioning as a solid electrolyte.

[0129] The PEG or PEO may contain a sulfur compound functional group, a nitrogen compound functional group, a phosphorus compound functional group, an acrylate functional group, or the like.

[0130] Furthermore, from the viewpoint of high functionality as an adhesive for bonding the electrode composite and the inorganic solid electrolyte, the PEG or PEO is preferably a polyether polymerized with ethylene glycol having a weight-average molecular weight (Mw) of 1,000 or more and 1,000,000 or less, or a derivative thereof.

[0131] In particular, when the electrode mixture or inorganic solid electrolyte, which is the adherend, has an uneven surface or has voids, the organic solid electrolyte penetrates into the unevenness or voids of the adherend, increasing the contact area between the electrode mixture and the inorganic solid electrolyte, thereby reducing the ionic resistance of the battery.

[0132] The organic solid electrolyte is preferably liquefied and applied to the electrode mixture and / or inorganic solid electrolyte. The organic electrolyte may be a non-flammable ionic liquid. The organic solid electrolyte can be liquefied by dissolving the target material in an organic solvent. The organic solvent is not particularly limited as long as it can dissolve the target material, and examples thereof include chain hydrocarbon solvents and cyclic hydrocarbon solvents. Examples of chain hydrocarbon solvents include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), tert-butyl isopropyl percarbonate, dichloromethane, nitriles, and alcohols. Examples of cyclic hydrocarbon solvents include N-methyl-2-pyrrolidone (NMP), ethylene sulfite, vinyl ethylene carbonate (VEC), propylene carbonate (PC), 1,3-dioxane-2-one, benzene, and lactones.

[0133] The non-flammable ionic liquid is not particularly limited as long as it has ionic conductivity. Examples of the non-flammable ionic liquid include pyridine-based, alicyclic amine-based, and aliphatic amine-based cations. By selecting the type of anion to be combined with the cation, a variety of non-flammable ionic liquids can be synthesized. Examples of cations include imidazolium salts, pyridinium salts, phosphonium ions, and inorganic ions. Examples of anions include bromide ions, triflates, tetraphenylborate, and hexafluorophosphate.

[0134] Non-flammable ionic liquids are, for example, cations such as imidazolinium and Br - , Cl - , BF4 - , PF6 - , (CF3SO2)2N - , CF3SO3 - , FeCl4 - Such non-flammable ionic liquids can function as electrolytes.

[0135] When assembling a battery, the battery can function even if some of the organic solvent is present, but it is preferable to thoroughly remove the organic solvent by reducing pressure or by heat treatment, since this can prevent the battery from expanding due to the evaporation of the organic solvent. The removal method is not particularly limited, but for example, a drying method for electrode slurry used in lithium ion batteries can be adopted.

[0136] When the electrode mixture or inorganic solid electrolyte that is the adherend is porous, the organic solid electrolyte flows into the adherend through the pores on the surface of the adherend, thereby significantly reducing the resistance (ionic resistance) resulting from ionic conduction in the battery.

[0137] Furthermore, when the battery is overcharged, the PEG or PEO in the organic solid electrolyte is oxidatively decomposed, suppressing an increase in the battery voltage and eliminating its function as an adhesive, thereby providing a shutdown function that separates the electrode mixture from the inorganic solid electrolyte and increases the impedance of the battery.

[0138] From the viewpoint of strongly bonding the electrode mixture and the solid electrolyte, the higher the molecular weight of the PEG or PEO, the better. However, if the weight-average molecular weight exceeds 1 million, the viscosity becomes too high, making handling difficult. Furthermore, when a sodium salt, as described below, is added, the ionic conductivity decreases. Conversely, if the weight-average molecular weight is less than 1000, the adhesiveness is poor, and when the battery is subjected to vibration or impact, the interface between the electrode mixture and the inorganic solid electrolyte is likely to be destroyed, which can lead to an increase in the battery's impedance. Furthermore, low molecular weights are hygroscopic, resulting in a time-consuming drying process. Therefore, the weight-average molecular weight is preferably 1000 or more, with 2500 or more being more preferable, with the upper limit being 1 million. These may be crosslinked or non-crosslinked.

[0139] The weight average molecular weight can be determined, for example, by measuring by gel permeation chromatography (GPC) using liquid chromatography.

[0140] The organic solid electrolyte preferably further contains a sodium salt, from the viewpoint of increasing ion conductivity.

[0141] The sodium salt content is preferably 0.1 or more, more preferably 0.3 or more, and even more preferably 0.4 or more, relative to the weight of the organic solid electrolyte taken as 1. However, if the sodium salt content is too high, the viscosity of the organic solid electrolyte increases and the adhesive properties between the electrode and the solid electrolyte decrease, so the sodium salt content is preferably 1.5 or less, more preferably 1.2 or less, and even more preferably 0.7 or less. An organic solid electrolyte with poor adhesive properties will deteriorate the charge / discharge cycle characteristics of the battery.

[0142] The sodium salt may be at least one selected from the group consisting of sodium hexafluorophosphate (NaPF), sodium perchlorate (NaClO), sodium tetrafluoroborate (NaBF), sodium trifluoromethanesulfonate (NaCFSO), sodium bis(oxalato)borate (NaBCO), sodium difluorophosphate (FNaOP), sodium bis-fluorosulfonylimide (FNaNOS), and sodium difluoroborate (NaBF0). Among the above sodium salts, NaPF is preferred because of its particularly high electronegativity and ease of ionization. Organic solid electrolytes containing NaPF offer excellent input / output characteristics and charge / discharge cycle performance.

[0143] From the viewpoint of excellent ion conductivity and high energy density of the battery, the organic solid electrolyte has a thickness of preferably 0.1 μm to 500 μm, more preferably 0.2 μm to 100 μm, further preferably 0.5 μm to 50 μm, and desirably 1 μm to 20 μm. Alternatively, the organic solid electrolyte has a mass per unit area of ​​0.1 mg / cm. 2 ~800mg / cm 2 It is preferable that the range is 0.2 mg / cm 2 ~500mg / cm 2 More preferably, it is in the range of 0.5 mg / cm 2 ~100mg / cm 2 is more preferably 1 mg / cm 2 ~20mg / cm 2 is desirable.

[0144] Inorganic solid electrolytes include sulfide-based, oxide-based, and hydride-based electrolytes, and one type may be used alone or two or more types may be used in combination. From the viewpoint of increasing the energy density of the battery and increasing the ionic conductivity, such inorganic solid electrolytes preferably have a thickness of 1 mm or less and a porosity of 20% or less. Sulfide systems include, for example, A4SiS4, A4GeS4, A3PS4, A 9.54 Si 1.74 P1.44 S 11.7 C l0.3 、A 10 GeP2S 12 、A 3.25 Ge 0.25 P 0.75 S4, A6PS5Cl, A2S - B2S3·AI, A2S - P2S5 - ABH4, A2S - SiS2·A4SiO4, A2S - P2S5, A7P3S 11 、A 3.25 P 0.95 S4 and the like can be mentioned (A represents Na or other alkali metal elements containing Na).

[0145] In the oxide system, for example, A 1.3 Al 0.3 Ti 1.7 (PO4)3, A 0.34 La 0.51 TiO 2.94 、A7LaZr2O 12 、A4SiO4·A2BO3, A3PO4 - A4SiO4, A3BO3 - A2SiO4, A3BO3 - A2SO4, A 2.9 PO 3.3 N 0.46 、A 1.07 Al 0.69 Ti 1.46 (PO4)3, A 3.3 PO 3.8 N 0.22 、A 2.9 PO 3.3 N 0.46 (A represents Na or other alkali metal elements containing Na), NASICON crystal (Na 1+x Zr2Si x P 3-x O 12 、0 < x < 3), aluminum oxide containing sodium, etc. can be mentioned.

[0146] In the hydride system, for example, ABH4, ABH4 - AI, ABH4 - ABr, ABH4 - AF, ABH4 - ACl, etc. can be mentioned (A represents an alkali metal element).

[0147] Furthermore, the inorganic solid electrolyte preferably has a porosity in the range of 0% to 20%. In other words, the inorganic solid electrolyte should be as dense as possible. By setting the porosity to 20% or less, it is possible to increase ionic conductivity. Conversely, if the porosity exceeds 20%, ionic conductivity is poor and micro-short circuits are likely to occur during charging.

[0148] In other words, the density of the inorganic solid electrolyte is preferably in the range of 2.7 g / cc to 3.5 g / cc. If the density is less than 2.7 g / cc, there will be too many voids, resulting in poor ionic conductivity and a tendency for micro-short circuits to occur during charging.

[0149] However, the production of an inorganic solid electrolyte with a porosity of 0% is not practical unless a single crystal is used. Therefore, it is preferable to infiltrate the pores of the inorganic solid electrolyte with an organic solid electrolyte to further improve ionic conductivity. Here, if the density of the inorganic solid electrolyte exceeds 3.5 g / cc, the organic solid electrolyte will not easily infiltrate, so it is preferable that the density be 3.5 g / cc or less.

[0150] The density mentioned above is the density when a container of a certain volume is filled with the inorganic solid electrolyte and the internal volume of the container is taken as the volume, and more accurately means the bulk density.

[0151] There are no particular limitations on the shape, but it may be formed into any of a film, sheet, pellet, or ribbon shape.

[0152] The inorganic solid electrolyte is preferably an oxide-based material because it is less likely to generate toxic gases when it comes into contact with water. Among these, aluminum oxide containing sodium is preferred because it has excellent electrical insulation properties and heat resistance.

[0153] Sodium-containing aluminum oxide is a crystal or ceramic expressed by the general formula Na2O-xAl2O3 (x = 2 to 20), with a structure in which sodium ions are distributed between the two-dimensional layers formed by the alumina blocks. Depending on how the alumina blocks are stacked, it is known as β-alumina (Na2O-11Al2O3) or β"-alumina (β-double prime alumina (Na2O-5Al2O3)), but in either case, sodium ions move between the two-dimensional layers formed by the alumina blocks, so it functions as a solid electrolyte.

[0154] Sodium-containing aluminum oxide can be synthesized, for example, by firing a mixture of α-alumina (Al2O3) and sodium carbonate at 1100°C to 1500°C.

[0155] The sodium-containing aluminum oxide preferably further contains at least one metal or oxide selected from Mg, Li, K, Rb, Zr, Pb, Y, Ag, Tl, Sr, Ca, and Fe. The content of these metals or oxides is preferably 5 vol.% or less relative to the sodium-containing aluminum oxide. This makes it easier to obtain dense sodium-containing aluminum oxide, further improving ionic conductivity.

[0156] The inorganic solid electrolyte may be contained in the electrode mixture as a powder having a particle size of 0.1 μm to 100 μm.

[0157] The all-solid-state sodium storage battery according to the present invention can be produced, for example, by closely adhering the electrode mixture obtained as described above to one surface of an inorganic solid electrolyte via an organic solid electrolyte in a dry environment with a dew point of −40° C. or less, and sealing the battery in a state in which a counter electrode is provided on the other surface of the inorganic solid electrolyte.

[0158] The electrode mixture of the present invention can be used as a high-loading electrode. The thickness of the electrode mixture of the present invention is preferably 10 μm to 5000 μm, more preferably 200 μm to 4000 μm, and even more preferably 500 μm to 3000 μm. The total weight per unit area of ​​the electrode mixture of the present invention is 1 mg / cm. 2 ~5000mg / cm 2 Preferably, it is 160 mg / cm 2 ~4800mg / cm 2 More preferably, it is 400 mg / cm 2 ~3600mg / cm 2 It is more preferable that:

[0159] The counter electrode is not particularly limited, and when the electrode mixture is used as a positive electrode mixture, the counter electrode may be an electrode mixture containing a negative electrode active material, a known sodium metal negative electrode, a known sodium alloy negative electrode, or a known sodium ion occluding negative electrode. When the electrode mixture is used as a negative electrode mixture, the counter electrode may be a positive electrode mixture, a known sodium alloy positive electrode, or a known sodium ion occluding positive electrode.

[0160] In addition, the all-solid-state sodium storage battery is preferably configured such that the above-mentioned organic solid electrolyte is also interposed between the counter electrode and the inorganic solid electrolyte.

[0161] As described above, the electrode composite and the all-solid-state sodium storage battery using the same have been described, but various additions, modifications, or deletions are possible within the scope of the present invention. For example, the electrolyte of the all-solid-state sodium storage battery of the present invention may further contain an electrolytic solution, an ionic liquid, or a gel electrolyte. For example, the carrier ions of the battery may be changed from sodium ions to other alkali metal ions (lithium ions, potassium ions, etc.), resulting in a nonaqueous electrolyte electricity storage device using alkali metal ions as carriers.

[0162] A battery pack according to one aspect of the present invention is characterized by including the all-solid-state sodium storage battery of the present invention. That is, the battery pack may be a battery group consisting of two or more unit cells in which the all-solid-state sodium storage batteries of the present invention are electrically connected to each other directly or via a bus bar.

[0163] An electrical device according to one aspect of the present invention is characterized by including the all-solid-state sodium storage battery or battery pack according to the present invention.

[0164] Examples of electrical equipment include irons, whisks, all-in-one computers, clothes dryers, medical equipment, intercoms, wearable devices, video equipment, air conditioners, air circulators, gardening machinery, motorcycles, ovens, music players, music recorders, hot air heaters, toys, car stereos, flashlights, loudspeakers, car navigation systems, cassette stoves, home storage batteries, nursing care machinery, humidifiers, dryers, fuel dispensers, water dispensers, suction machines, safes, glue guns, mobile phones, portable information devices, air purifiers, air-conditioned clothing, game consoles, fluorescent lights, lint removers, cordless phones, coffee makers, and - Warmers, ice shaver, kotatsu, copy machines, haircutting tools, shavers, lawn mowers, automobiles, lighting equipment, dehumidifiers, sealers, shredders, automated external defibrillators, rice cookers, stereos, stoves, speakers, trouser presses, smartphones, rice polishers, washing machines, toilet seats with cleaning functions, sensors, electric fans, submarines, blowers, vacuum cleaners, flying cars, tablets, body fat scales, fishing tackle, digital cameras, televisions, television receivers, video games, displays, disc changers, desktop computers, trains, televisions, electric carpets, desk lamps, electric heaters , electric kettles, electric blankets, calculators, electric carts, electric wheelchairs, power tools, electric vehicles, electric floats, electric toothbrushes, telephones, electric bicycles, electric insect killers, induction cookers, electronic organizers, electronic musical instruments, electronic locks, electronic cards, microwave ovens, electronic mosquito repellents, electronic cigarettes, telephones, power load levelers, toasters, hair dryers, walkie-talkies, clocks, drones, food waste disposal machines, laptops, incandescent light bulbs, soldering irons, panel heaters, halogen heaters, proofing machines, bread makers, hybrid vehicles, personal computers, computer peripherals, hair clippers, panel heaters, video cameras, video decks kitchen appliances, airplanes, emergency lights, emergency batteries, ships, beauty equipment, printers, copiers, grinders, sprayers, fax machines, forklifts, plug-in hybrid vehicles, projectors, hair dryers, hair irons, headphones, disaster prevention equipment, security equipment, home theaters, hot sandwich makers, hot plates, pumps, aroma diffusers, massagers, mixers, mills, movie players, monitors, rice cake makers, water heaters, floor heating panels, radios, radio cassette players, lanterns, radio-controlled cars, laminators, remote controls, microwave ovens, water coolers, refrigerators, air coolers, cooling fans,Examples include air conditioning equipment, robots, word processors, and GPS. [Example]

[0165] Examples of the present invention will be described in more detail below, but the present invention is not limited to these examples. In particular, the examples will be described using an all-solid-state sodium storage battery that uses β''-alumina as a solid electrolyte, but the present invention is not limited thereto. Furthermore, the examples will be described using Na2FeP2O7 as an example of an active material contained in an electrode mixture, but the present invention is not limited thereto.

[0166] (Example 1: Preparation of electrode mixture 1) <Preparation of Positive Electrode Active Material Precursor Powder> The cathode active material precursor was prepared by melt quenching. Sodium metaphosphate (NaPO3), iron oxide (Fe2O3), and orthophosphoric acid (H3PO4) were mixed to a molar ratio of 40Na2O-20Fe2O3-40P2O5 and melted at 1350°C for 1 hour in an air atmosphere. The resulting molten glass was poured between a pair of cooling rollers and rapidly cooled to form a glass film with a thickness of 0.1–1 mm. This glass was then ball milled using 20 mm diameter ZrO2 balls for 10 hours and passed through a 120 μm mesh resin sieve to obtain a coarse glass powder with an average particle size of 7 μm. This coarse glass powder was then ball milled using 3 mm diameter ZrO2 balls with ethanol as a milling aid for 80 hours to obtain a glass powder (cathode active material precursor powder) with an average particle size of 0.6 μm. Powder X-ray diffraction measurements confirmed that the glass powder was amorphous.

[0167] <Preparation of Positive Electrode Active Material Powder> The glass body obtained above was crystallized by firing at 650°C for 1 hour in a nitrogen atmosphere to obtain a crystalline material. This crystalline material was then ball milled using 20mm diameter ZrO2 balls for 10 hours and passed through a 120μm mesh resin sieve to obtain a coarse powder with an average particle size of 7μm. This coarse powder was then ball milled using 3mm diameter ZrO2 balls with ethanol as a grinding aid for 12 hours to obtain a crystalline powder with an average particle size of 0.2μm. 70wt% of this crystalline powder was mixed with 30wt% of polyethylene oxide nonylphenyl ether (mass average molecular weight: 660), a nonionic surfactant, as a carbon source, and then dried at 100°C for 1 hour. This mixture was then fired at 620°C for 30 minutes in a nitrogen atmosphere to obtain a positive electrode active material powder with an average particle size of 0.2μm. As a result of powder X-ray diffraction measurement of this positive electrode active material powder, it was confirmed that the diffraction lines were derived from Na2FeP2O7 crystals.

[0168] <Preparation of electrode mixture (active material layer)> The electrode composite (active material layer) was fabricated by filling a powder molding die (NPA Systems, Φ10mm) with polypropylene carbonate (PPC)-coated composite powder in an argon atmosphere, applying 30 MPa of pressure to form a pellet, which was then fired at 550°C for 1 hour at 3°C / min in a nitrogen (N2) / hydrogen (H2) mixed gas (=96 / 4 vol.%) atmosphere. A 300 nm thick gold film was then deposited on one side of the pellet by physical vapor deposition (PVD) to serve as a current collector. During the firing process, all of the PPC contained in the electrode composite was thermally decomposed and converted to carbon dioxide, so the weight of the resulting electrode composite was minus the PPC.

[0169] The electrode composite after firing had a thickness of 298 μm, a total weight of 0.0307 g, and a diameter of 9.242 mm, and the weight of the active material contained in the electrode composite was 0.02794 g. Examination of a cross-sectional SEM (scanning electron microscope) image of the electrode composite confirmed that it consisted of clusters of multiple connected positive electrode active material particles, and had a porous structure containing pores. These clusters were formed when the positive electrode active material precursor powder softened and flowed during firing of the composite powder, bonding the positive electrode active material powder together. It was also confirmed that the positive electrode active material precursor powder crystallized as it softened and flowed, precipitating Na2FeP2O7 crystals.

[0170] The PPC-coated composite powder was prepared by mixing the cathode active material precursor powder, cathode active material, conductive additive, and PPC (32.3:48.5:2.5:16.7 wt.%) with N-methyl-2-pyrrolidone (NMP) in a rotary mixer (Thinky, Rentaro, 2000 rpm, 1 h) in a dry environment (dew point below -40°C). The NMP was then evaporated and removed by heating and drying on a glass plate (80°C, 1 h). The mixture was then pulverized in a grinder (Nitto Scientific, AMM-140D) for 1 h. The conductive additive was a mixture of carbon black and vapor-grown carbon fiber (Showa Denko, VGCF-H) in a ratio of 5:1 wt.%.

[0171] (Example 2: Preparation of electrode mixture 2) The electrode mixture was prepared by mixing the PPC-coated composite powder with the cathode active material precursor powder, cathode active material, conductive additive, and PPC (28:42:7:23 wt.%) in a dry environment (dew point below -40°C) with N-methyl-2-pyrrolidone (NMP) in a rotary mixer (Thinky, Rentaro, 2000 rpm, 1 h). The NMP was then volatilized and removed by heat drying on a glass plate (80°C, 1 h). The mixture was then pulverized in a grinder (Nitto Scientific, AMM-140D) for 1 h. The conductive additive was a mixture of carbon black and vapor-grown carbon fiber (Showa Denko, VGCF-H) in a ratio of 8:1 wt.%. Other conditions were the same as in Example 1. The electrode mixture after firing had a thickness of 278 μm, a total weight of 0.0304 g, a diameter of 9.325 mm, and the weight of the active material contained in the electrode mixture was 0.02767 g. When an SEM image of the cross section of the electrode mixture was observed, it was confirmed that it consisted of clusters in which multiple positive electrode active material particles were connected, and had a porous structure including pores.

[0172] (Example 3: Preparation of all-solid-state sodium storage battery 1) <Inorganic solid electrolytes and organic solid electrolytes> In producing the nonaqueous electrolyte storage battery of the present invention, the inorganic solid electrolyte and the organic solid electrolyte, which are necessary components, were prepared.

[0173] As an inorganic solid electrolyte, the composition formula is Na 1.6 Li 0.34 Al 10.66 O 17 Li2O-stabilized β''-alumina (manufactured by Ionotec) was used as is. The thickness of the inorganic solid electrolyte was 1 mm.

[0174] The organic solid electrolyte was prepared by adding acetonitrile to polyethylene glycol (PEG) with a weight-average molecular weight (Mw) of 7000 and NaPF6 (1:0.3 wt.) and mixing them in a planetary mixer (Thinky Mixer, 2000 rpm, 1 h).

[0175] <Fabrication of all-solid-state sodium batteries> The battery of Example 3 was prepared in an argon environment by distributing an organic solid electrolyte at 0.005 g / cm between the electrode mixture of Example 1 and the inorganic solid electrolyte. 2 The organic solid electrolyte was prepared by applying a solution of the organic solid electrolyte dissolved in acetonitrile to the electrode mixture with a brush, followed by vacuum drying (60°C, 1 hour).

[0176] (Example 4: Preparation of all-solid-state sodium storage battery 2) The battery of Example 4 contains a mixture of PEG and NaPF6 (1:0.3 wt.) at 0.006 g / cm 2The battery had the same configuration as in Example 3, except that the electrode mixture of Example 1 was used, which was filled so that the total volume of the electrode mixture was 1000 parts by volume. The mixture filled into the electrode mixture was prepared by immersing the electrode mixture in PEG and NaPF6 dissolved in acetonitrile, and then vacuum drying (60°C, 1 hour) to remove the acetonitrile.

[0177] (Example 5: Preparation of all-solid-state sodium storage battery 3) The battery of Example 5 had the same battery configuration as Example 3, except that a mixture of ethylene carbonate (EC) and NaPF6 (1:0.3 wt%) was filled into the electrode composite of Example 1. The mixture filled into the electrode composite was prepared by immersing the electrode composite in EC and NaPF6 dissolved in diethyl carbonate (DEC), followed by vacuum drying (60°C, 1 hour) to remove the DEC.

[0178] (Example 6: Preparation of all-solid-state sodium storage battery 4) The battery of Example 6 had the same battery configuration as Example 3, except that a mixture of ethylene carbonate (EC) and NaPF6 (1:0.3 wt%) was filled into the electrode composite of Example 2. The mixture filled into the electrode composite was prepared by immersing the electrode composite in EC and NaPF6 dissolved in diethyl carbonate (DEC), followed by vacuum drying (60°C, 1 hour) to remove the DEC.

[0179] (Reference Example 1: All-solid-state sodium storage battery) The battery of Reference Example 1 has the same battery configuration as that of Example 3, except that it does not include an organic solid electrolyte.

[0180] (Reference example 2: Flooded sodium ion battery) The battery of Reference Example 2 does not include an organic solid electrolyte or an inorganic solid electrolyte, but instead uses a separator made of a laminate of a glass nonwoven fabric (GA-100 manufactured by Advantech Co., Ltd.) and a polyolefin microporous membrane (#2320 manufactured by Celgard Co., Ltd.) impregnated with 1M NaPF6 / (EC:DEC=1:1 vol.), and has the same battery configuration as Reference Example 1.

[0181] <Battery testing> The battery test was carried out by repeating constant current charge and discharge under conditions of 60° C., 0.01 C rate, and cut-off voltage of 3.8 to 2.0 V. The results of the charge and discharge tests for Examples 3 to 6 and Reference Examples 1 and 2 are shown below.

[0182] Example 3 In the all-solid-state sodium storage battery of Example 3, a mixture of PEG and NaPF6 was interposed between the electrode composite and the inorganic solid electrolyte as an organic solid electrolyte, thereby integrating the electrode composite and the inorganic solid electrolyte. However, the resistance of the battery was high, and the discharge capacity of the active material was 10.1 mAh / g (0.42 mAh / cm 2 ) was.

[0183] Example 4 In the all-solid-state sodium storage battery of Example 4, a mixture of PEG and NaPF6 was interposed between the electrode mixture and the inorganic solid electrolyte as an organic solid electrolyte, thereby integrating the electrode mixture and the inorganic solid electrolyte. In addition, the organic solid electrolyte was impregnated into the electrode mixture. As a result, the discharge capacity of the active material was 89.2 mAh / g (3.72 mAh / cm 2 ) was.

[0184] Example 5 In the all-solid-state sodium storage battery of Example 5, a mixture of PEG and NaPF6 was interposed between the electrode mixture and the inorganic solid electrolyte as an organic solid electrolyte, thereby integrating the electrode mixture and the inorganic solid electrolyte. In addition, the organic solid electrolyte was impregnated into the electrode mixture. As a result, the discharge capacity of the active material was 92.6 mAh / g (3.86 mAh / cm 2 ) was.

[0185] Example 6 In the all-solid-state sodium storage battery of Example 6, a mixture of PEG and NaPF6 was interposed between the electrode mixture and the inorganic solid electrolyte as an organic solid electrolyte, thereby integrating the electrode mixture and the inorganic solid electrolyte. The discharge capacity of the active material was 92.6 mAh / g (3.24 mAh / cm 2 ) was.

[0186] (Reference example 1) The all-solid-state sodium storage battery of Reference Example 1 did not include an organic solid electrolyte, and therefore the electrode mixture and the inorganic solid electrolyte were not integrated. In addition, the discharge capacity of the active material was 0.0 mAh / g (0 mAh / cm 2 ), and did not function as a battery at all. This means that there was a large resistance to the flow of ions at the interface between the electrodes and the solid electrolyte, even when a minute current of 0.01 C was passed through it. (Reference example 2) The discharge capacity of the active material of the flooded sodium ion battery of Reference Example 2 was 94.2 mAh / g (3.92 mAh / cm 2 ) was.

[0187] <Battery overcharge test> The battery overcharge test was performed by constant-current charging at 60°C, a 0.01C rate, and a charge cutoff voltage of 4.5V. Figure 6 compares the charge curves of Example 5 and Reference Example 2. The vertical axis represents battery voltage, and the horizontal axis represents charge time. Charging for more than 100 hours constitutes the overcharge region. As is clear from Figure 6, the battery of Example 5 exhibited a charge plateau near 4.2V and did not reach the charge cutoff voltage of 4.5V. On the other hand, the battery of Reference Example 2 did not exhibit a charge plateau near 4.2V and was charged to the charge cutoff voltage. It is believed that the organic solid electrolyte interposed between the electrode composite and the inorganic solid electrolyte in the battery of Example 5 was oxidized and decomposed near 4.2V. These results demonstrate that the inclusion of an organic solid electrolyte in the battery can prevent overcharging.

[0188] Furthermore, the battery of Example 5 was charged at a constant current and constant voltage at 60°C, a 0.01C rate, and a charge cutoff voltage of 4.5V until the SOC (State of Charge) reached 200%, and then discharged at a constant current of 0.1C until the SOC reached 2.0V. However, no discharge capacity was observed. It is believed that the oxidative decomposition of the organic solid electrolyte caused an increase in battery resistance, resulting in shutdown. [Industrial Applicability]

[0189] The electrode composite according to the present invention can be used as a component of an all-solid-state sodium storage battery. This all-solid-state sodium storage battery exhibits excellent charge-discharge cycle characteristics while maintaining a high discharge capacity at room temperature, and can also shut down due to overcharge. For this reason, it is expected to be applied to electric vehicles (EVs) and stationary power sources. [Explanation of symbols]

[0190] 1. Cross-sectional concept of electrode composite and all-solid-state sodium battery using it 2 electrode mixture 3 Organic solid electrolyte 4 Inorganic solid electrolyte 5. Opposite 6 Current collector 7. Cross-sectional concept of active material clusters 8 Electrode active material particles 9. Polyphosphate transition metal oxide crystals 10 Conductive additive (carbon) 11 Cross-sectional concept of a bipolar battery 12 Concept of the manufacturing process of an all-solid-state sodium storage battery using the electrode mixture according to the present invention 13 Roughened surface

Claims

1. An electrode mixture for use in an all-solid-state sodium storage battery, The electrode mixture contains an active material, the active material is a cluster formed of a transition metal polyphosphate oxide in which a plurality of particles having a particle size in the range of 0.1 μm to 100 μm are connected together, The polyphosphate transition metal oxides include Na2FeP2O7, Na3Fe2(PO4)3, NaFe3P3O12, Na2Fe3(PO4)3, Na4Fe3(PO4)2(P2O7), Na2MnP2O7, Na2CoP2O7, Na2NiP2O7, Na2Fe0.5Mn0.5P2O7, Na3V2(PO4)3, NaVOPO4, and Na9V3(P2O7)3(PO4)2. The electrode mixture is at least one selected from the group consisting of:

2. 2. The electrode composite according to claim 1, further comprising an ion conduction aid, wherein the ion conduction aid is at least one selected from the group consisting of ethylene carbonate (EC), polyethylene carbonate (PEC), polyethylene glycol (PEG), and polyethylene oxide (PEO).

3. 3. The electrode mixture according to claim 1, further comprising a conductive additive, wherein the conductive additive is at least one selected from the group consisting of a metal, a carbon material, a conductive polymer, and a conductive glass.

4. The electrode mixture according to claim 3 , wherein the conductive additive is supported on a part or the entire surface of the electrode mixture.

5. 5. The electrode mixture according to claim 3, wherein the conductive additive is supported on the surface of a portion that connects individual particles of the active material.

6. The electrode mixture according to claim 3 , wherein the conductive additive is contained inside portions that connect individual particles of the active material.

7. 7. The electrode mixture according to claim 3, wherein the conductive additive is carbon selected from at least one of powdered carbon, fibrous carbon, and flake carbon.

8. The electrode mixture according to claim 7, wherein the carbon is powdered carbon having a primary particle size in the range of 1 nm to 100 nm.

9. The carbon has a nitrogen adsorption specific surface area of ​​20 m ２ / g to 500m ２ The electrode mixture according to claim 7 or 8, which is powdered carbon having a carbon content in the range of 1 / g.

10. The electrode mixture according to claim 7, wherein the carbon is fibrous carbon having a fiber diameter in the range of 1 nm to 300 nm.

11. The electrode mixture according to claim 7, wherein the carbon is flaky carbon having a thickness in the range of 1 nm to 300 nm.

12. The carbon is a combination of powdered carbon and fibrous carbon, or a combination of powdered carbon and flaked carbon, or a combination of powdered carbon, fibrous carbon and flaked carbon. Electrode mixture according to any one of claims 7 to 11.

13. The electrode mixture according to any one of claims 1 to 12, which does not contain a resin-based binder.

14. The electrode mixture according to any one of claims 1 to 13, wherein the electrode mixture is porous and has a porosity in the range of 5% to 50%.

15. The electrode mixture according to claim 14, wherein the pores have a pore diameter of 0.1 μm to 100 μm.

16. The electrode mixture according to any one of claims 1 to 15, comprising a solid electrolyte powder having a particle size of 0.1 µm to 100 µm as an ion conduction assistant.

17. 16. The electrode mixture according to claim 14 or 15, wherein the surfaces of the pores are coated with a solid electrolyte powder as an ion conduction assistant.

18. Thickness: 10 μm to 5000 μm, Total weight per unit area is 1 mg / cm ２ ~5000mg / cm ２ That is, The electrode mixture according to any one of claims 1 to 17.

19. 19. The electrode composite according to claim 1, which is used as a positive electrode and / or a negative electrode in a nonaqueous electrolyte electricity storage device, wherein the nonaqueous electrolyte electricity storage device is an all-solid-state sodium storage battery including the electrode composite, an organic solid electrolyte, an inorganic solid electrolyte, and a current collector.

20. The electrode mixture according to claim 19, which is used in a battery pack including an all-solid-state sodium storage battery as a nonaqueous electrolyte electricity storage device.

21. The electrode mixture according to claim 19 or 20, which is used in an electrical device including an all-solid-state sodium storage battery or an assembled battery thereof as a nonaqueous electrolyte electricity storage device.

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