JP2022058019A - All-solid sodium storage battery, battery pack including storage battery, and electric apparatus including storage battery - Google Patents

Abstract

To provide an all-solid sodium storage battery that functions as a battery in the room-temperature environment and can be shut down when charging is excessive.SOLUTION: An all-solid sodium storage battery has an organic solid electrolyte held between an electrode mixture material and an inorganic solid electrolyte.SELECTED DRAWING: Figure 1

Description

The present invention relates to an all-solid-state sodium storage battery, a built-in battery including the storage battery, and an electric device provided with the storage battery.

The field of use of storage batteries (secondary batteries) having a high energy density has expanded from power sources for portable devices such as smartphones and tablet terminals to electric vehicles and power storage in recent years. In particular, automobile manufacturers are developing and commercializing clean automobiles (electric vehicles, plug-in hybrid automobiles, etc.) in order to comply with environmental regulations aimed at reducing automobile exhaust gas and carbon dioxide (CO ₂ ) worldwide. It is being actively promoted.

In addition, for renewable energy such as wind power and solar power, the amount of power generation fluctuates greatly due to the influence of the environment, so a large power storage system is required. Recently, the cost of power generation from renewable energy has been reduced to less than half that of coal-fired power generation, and the share of power generation is expanding. In view of future widespread use, it is required to improve battery production.

Storage batteries are indispensable for energy saving, introduction of new energy, clean automobiles, etc., and are positioned as important key devices from the viewpoint of economic growth of each country.

Current storage batteries such as lithium-ion batteries have been the driving force in the electronic equipment industry and the automobile industry, but depending on the application of the battery, inadequate temperature characteristics and ensuring safety are delaying the full-scale spread. Therefore, it is desired to develop a new battery according to the application while achieving both high performance and high safety of the battery. For rare metals and resources with uneven distribution of producing areas, risk management is important in consideration of fluctuations in market prices and the risk of difficulty in obtaining them. Although the development of rare metal recycling technology is progressing from various perspectives, the development of batteries made of materials that are inexpensive, easily available, and whose production areas are not unevenly distributed is required (Non-Patent Document 1 and Non-Patent Document 1). See Patent Document 2).

Currently, the development of sodium-ion batteries and all-solid-state batteries is progressing as a battery system that can solve such problems.

Sodium is abundant in seawater and is the sixth element present in the crust. It is inexpensive and easily available, and its origin is not unevenly distributed like lithium. Therefore, it is expected that the risk of resource procurement will be reduced and the cost of batteries will be reduced.

Although it is a very attractive element from the recent trend of rare metal-free, its redox potential is about 0.3V higher than that of lithium, its ion volume is more than doubled, and its atomic weight is about 3.3 times higher. It is difficult to obtain sufficient electric capacity and cycle characteristics simply by replacing the ion species of the conventional lithium-ion battery with sodium ions.

In addition, as a battery system using sodium, there are a sodium-sulfur battery and a sodium-metal chloride battery. The sodium-sulfur battery is composed of aluminum oxide containing sodium such as β-alumina and β ″ -alumina as a solid electrolyte, sodium as a negative electrode active material, and sulfur as a positive electrode active material.

In the sodium-metal chloride battery, the solid electrolyte and the negative electrode active material are the same, but metal chlorides such as NaAlCl ₄ , NiCl ₂ , FeCl ₂ , CoCl ₂ , and CrCl ₂ are used as the positive electrode active material.

Sodium-sulfur batteries and sodium-metal chloride batteries do not require an electrolyte solvent, but unlike lithium-ion batteries and sodium-ion batteries, they do not operate at room temperature. Therefore, the temperature of the battery is maintained at 250 to 350 ° C. by a heat source from the outside, and the negative electrode active material and the positive electrode active material are put into a molten state to improve the ionic conductivity of the solid electrolyte.

On the other hand, the all-solid-state battery is a battery system using a solid electrolyte. Since this solid electrolyte is responsible for ionic conduction between the positive electrode and the negative electrode, the all-solid-state battery can be produced without using the organic solvent required by the sodium ion battery (sodium storage battery using an electrolytic solution). For example, a sodium ion battery has exclusively used sodium hexafluorophosphate (NaPF ₆ ) salt as an electrolytic solution, but in addition to sodium ion (Na ⁺ ), hexafluorophosphate ion (PF ₆ ) is used for charging and discharging the battery. ^- ) Also moves, so it was difficult to set the sodium ion export rate to 1.

However, the concentration polarization of the inorganic solid electrolyte does not occur, and the sodium ion transport number becomes almost 1. The all-solid-state battery can suppress side reactions such as dissolution reaction of active material, gas generation by electrolysis, and precipitation of electrolyte decomposition product, if an appropriate electrolytic window electrolyte is selected. Further, the all-solid-state battery is expected to be a storage battery having excellent safety and reliability because it is less likely to cause ignition of gas or liquid or leakage of liquid.

The all-solid-state sodium storage battery is composed of a positive electrode, a negative electrode, and an electrolyte, like a conventional storage battery, but the electrolyte must be solid and have sodium ion conductivity.

The positive electrode and the negative electrode are composed of an active material capable of occluding or alloying sodium ions with charge and discharge, and a solid electrolyte. For example, examples of the active material used for the positive electrode include TiS ₂ (see, for example, Non-Patent Document 3) and NaMO ₂ (hereinafter, M is Co, Ni, Mn, or Fe) (for example, Non-Patent Documents 4 to 6). Materials such as Na ₂ MnO ₃ -NaMO ₂ (see, for example, Patent Document 1), Namp ₂ O ₇ (see, for example, Patent Document 2) and the like are known. Examples of the active material used for the negative electrode include hard carbon (see, for example, Patent Document 3), soft carbon (see, for example, Patent Document 4), simple substances such as tin and antimony, or compounds (for example, see Patent Documents 5 and 6). ), Sodium metal, etc. are known.

Through vigorous research and development so far, various solid electrolytes exhibiting high ionic conductivity have been found (see, for example, Patent Documents 7 to 10). Most of them are amorphous or crystalline composed of sodium salts and inorganic derivatives. However, since these are powdery or sheet-like materials and many of them have a property of being highly reactive with water, the conventional battery production method cannot be applied as they are. Specifically, in an all-solid-state sodium storage battery, unlike a liquid-type sodium ion battery, it is difficult to infiltrate an electrolyte into the active material layer of the electrode to construct an ion conduction path. Therefore, it is necessary to include the solid electrolyte in the active material layer to enhance the ionic conductivity between the solid electrolyte and the solid particles of the active material.

For example, in Patent Document 11, Patent Document 12, and Non-Patent Document 7, an electrode mixture precursor (active material layer precursor) containing an active material precursor powder and a solid electrolyte powder is prepared and fired. Therefore, an electrode mixture (active material layer) composed of an active material and a solid electrolyte or an all-solid sodium storage battery using the electrode mixture has been proposed. For example, Na ₂ FeP ₂ O ₇ crystallized glass is used as the active material precursor. Glass and crystallized glass are crystallized by firing (heat treatment), and softening flow occurs in this process. Therefore, it can be integrated with the solid electrolyte powder only by firing without pressurizing.

Further, according to Patent Document 11, Patent Document 12, and Non-Patent Document 7, the electrode mixture precursor is applied to one surface of the solid electrolyte layer and then fired at 400 ° C. or higher to form the solid electrolyte layer. An electrode mixture is formed on one surface.

However, since the solid electrolyte has no electron conductivity, it is difficult to secure both the electron conductivity and the ionic conductivity of the electrode. On the other hand, although it is possible to include a conductive auxiliary agent, if the content of the conductive auxiliary agent is too large, the amount of active material per unit mass of the electrode mixture decreases, and the charge / discharge capacity tends to decrease. It is in. In addition, the inhibition of sintering cuts off the ion conduction path, and there is a concern (suggestion) that the charge / discharge capacity and the discharge voltage will decrease.

Japanese Unexamined Patent Publication No. 2014-229452 Japanese Unexamined Patent Publication No. 2018-32536 International Publication No. 2010/109889 Japanese Unexamined Patent Publication No. 2013-171798 International Publication No. 2013/06578 Japanese Unexamined Patent Publication No. 2015-28922 Japanese Unexamined Patent Publication No. 2010-15782 Japanese Unexamined Patent Publication No. 2017-37769 JP-A-2019-57495 Japanese Unexamined Patent Publication No. 2019-57496 Japanese Unexamined Patent Publication No. 2018-18578 Japanese Unexamined Patent Publication No. 2016-42453

Takashi Mukai: In-vehicle technology, 5 (4), 19-24 (2018) Takashi Mukai: "Lithium Ion Battery-Development for Improving Performance and Trends in the Automotive LIB Industry-", Part 1, Chapter 6, Science & Technology, pp. 91-94 (2019) G. H. Newman, L. et al. P. Klemann: J.M. Electrochem. Soc. 127, 2097-2099 (1980) J. -J. Braconnier, C.I. Delmas, C.I. Foausier, P. et al. Hagenmuller: Mat. Res. Bull. , 15, 1797-1804 (1980) S. Okada, Y. Takahashi, T.M. Kiyabu, T.I. Doi, J. et al. Yamaki, T.K. Nishida: ECS Meeting Abstr. , 602,201 (2006) N. Yabuuchi, M. et al. Kaziyama, J.M. Iwate, H.I. Nishikawa, S.A. Hitomi, R.M. Okuyama, R.M. Usui, Y. Yamada, S.A. Komaba: Nat. Mater. , 11,512-517 (2012) H. Yamauchi, J.M. Ikejiri, F.I. Sato, H. et al. Oshita, T.M. Honma, T.I. Komatsu: J.M. Am. Ceram. Soc. , 102 (11), 6658-6667 (2019)

As described above, in order to improve the performance of the all-solid-state sodium storage battery, a technique for enhancing the ionic conductivity between the solid electrolyte and the solid particles of the active material while ensuring the electron conductivity of the electrode is important.

As described in Patent Document 11, Patent Document 12, and Non-Patent Document 7, the present inventors have an electrode mixture precursor (electrode active material layer precursor) composed of an active material precursor powder and a solid electrolyte powder. Attention was paid to the technique of integrating the active material and the solid electrolyte by press molding or further adding a solvent to form a slurry (paste) and firing the slurry.

In order to increase the capacity of the positive electrode formed per unit area of the solid electrolyte layer surface as a high performance battery, the amount of the electrode mixture formed per unit area of the solid electrolyte layer surface is increased to increase the coating amount of the electrode active material. It is necessary to increase the carrying amount. However, as described in Patent Documents 11 and 12, the present inventors thickly coat the surface of the electrolyte with a mixture consisting of the active material precursor and the solid electrolyte in order to increase the carrying amount, and fire the electrode mixture. We have found the problem that only the layer is sintered and shrinks, so that it peels off from the electrolyte and does not operate as a battery.

As described above, the present inventors initially made diligent studies on improving the performance of the all-solid-state sodium storage battery by directly forming an electrode mixture on the surface of the inorganic solid electrolyte. When formed and integrated, the battery resistance is currently high, and there is a limit to increasing the capacity per unit area. Therefore, instead of directly forming the electrode mixture on the surface of the inorganic solid electrolyte, the present inventors have conducted repeated studies so that the electrode mixture and the inorganic solid electrolyte can be used as separate members to form a battery. The present invention has been completed. The present invention can solve the above-mentioned problems (problems) of the prior art and the problems newly discovered by the present inventors.

The above-mentioned problem (objective) of the present invention is solved by the following claims 1 to 29.

The first aspect of the present invention relates to an all-solid sodium storage battery in which an organic solid electrolyte is interposed between an electrode mixture and an inorganic solid electrolyte.

The second aspect of the present invention relates to the all-solid-state sodium storage battery according to claim 1, wherein the organic solid electrolyte contains polyethylene glycol or polyethylene oxide.

According to claim 3, the organic solid electrolyte further contains a sodium salt, and the sodium salt is in the range of 0.1 to 1.5 when the weight of the organic solid electrolyte is 1. The all-solid-state sodium storage battery according to 1 or 2.

The fourth aspect of the present invention relates to the all-solid-state sodium storage battery according to any one of claims 1 to 3, wherein the thickness of the organic solid electrolyte is in the range of 0.1 μm to 500 μm.

Claim 5 of the present invention is any of claims 1 to 4, wherein the inorganic solid electrolyte is a sulfide-based, oxide-based, or hydride-based solid electrolyte having a thickness of 1 mm or less and a void ratio of 20% or less. Regarding the all-solid-state sodium storage battery described in the invention.

The sixth aspect of the present invention relates to the all-solid-state sodium storage battery according to any one of claims 1 to 5, wherein the inorganic solid electrolyte is aluminum oxide containing sodium.

The seventh aspect of the present invention relates to the all-solid-state sodium storage battery according to any one of claims 1 to 6, wherein the inorganic solid electrolyte has a density in the range of 2.7 g / cc to 3.5 g / cc.

According to claim 8, the electrode mixture contains a polyphosphate transition metal oxide, and the polyphosphate transition metal oxide is a crystal represented by the general formula Na _a M _b P _{c Od} . M is at least one selected from Fe, Mn, Co, Ni, and V, and a, b, and c are 0.0 <a≤3.5, b = 1,1.0≤c. The all-solid sodium storage battery according to any one of claims 1 to 7, wherein ≦ 3.0 and ≦ d ≦ 30.

Claim 9 of the present invention is one of claims 1 to 8, wherein the electrode mixture forms an active material cluster in which a plurality of particles having a particle size in the range of 0.1 μm to 100 μm are connected. With respect to the described all-solid-state sodium storage battery.

According to a tenth aspect of the present invention, the electrode mixture contains at least one ion conduction aid selected from ethylene carbonate, polyethylene carbonate, polyethylene glycol, and polyethylene oxide in addition to the active material. 9. The all-solid sodium storage battery according to any one of 9.

11. The all-solid-state according to claim 10, wherein the electrode mixture contains at least one conductive auxiliary agent selected from a metal, a carbon material, a conductive polymer, and a conductive glass. Regarding sodium storage batteries.

12. The all-solid-state sodium storage battery according to claim 11, wherein the conductive auxiliary agent is at least one selected from powdered carbon, fibrous carbon, and flake-shaped carbon.

13. All of claims 13 of the present invention, wherein the electrode mixture is porous with a void ratio in the range of 5% to 50% when the organic solid electrolyte is removed. Regarding solid-state sodium storage batteries.

The 14th aspect of the present invention relates to the all-solid-state sodium storage battery according to any one of claims 1 to 13, wherein the electrode mixture is porous with a pore size of 0.1 μm to 100 μm when the organic solid electrolyte is removed. ..

The 15th aspect of the present invention relates to the all-solid-state sodium storage battery according to any one of claims 1 to 14, wherein the electrode mixture contains an inorganic solid electrolyte powder having a particle size of 0.1 μm to 100 μm.

16. The 16th aspect of the present invention relates to the all-solid-state sodium storage battery according to any one of claims 1 to 15, wherein the electrode mixture does not contain a resin-based binder.

17 of the present invention relates to the all-solid sodium storage battery according to any one of claims 1 to 16, wherein the all-solid sodium storage battery uses a sodium metal, a sodium alloy or a sodium ion storage material as a counter electrode.

Claim 18 of the present invention is an all-solid-state sodium storage battery having a structure in which the electrode mixture is in electrical contact with a current collector having electronic conductivity, and the current collector is a metal having a through hole. The all-solid-state sodium storage battery according to any one of claims 1 to 17, which is made of a non-penetrating metal.

19 of the present invention relates to an assembled battery comprising the all-solid-state sodium storage battery according to claims 1 to 18.

20 of the present invention relates to an electric device including the all-solid-state sodium storage battery according to claims 1 to 18.

According to the all-solid-state sodium storage battery according to claim 1 of the present invention, since the organic solid electrolyte is formed by interposing between the electrode mixture and the inorganic solid electrolyte, it exhibits excellent charge / discharge cycle characteristics and is excessive. It is possible to realize a storage battery that can be shut down by charging.

According to claim 2 of the present invention, since the organic solid electrolyte contains polyethylene glycol or polyethylene oxide, the function as a solid electrolyte and the function as a pressure-sensitive adhesive for binding the electrode mixture and the inorganic solid electrolyte are realized. Can be done.

According to claim 3 of the present invention, when the organic solid electrolyte further contains a sodium salt and the weight of the organic solid electrolyte is 1, the sodium salt is in the range of 0.1 to 1.5. Ion conductivity can be maintained by the adhesive action between the electrode and the solid electrolyte, and the charge / discharge cycle characteristics of the battery can be obtained.

According to claim 4, since the thickness of the organic solid electrolyte is in the range of 0.1 μm to 500 μm, the ionic conductivity is excellent and the energy density of the battery is high.

According to claim 5 of the present invention, since the inorganic solid electrolyte is a sulfide-based, oxide-based, or hydride-based solid electrolyte having a thickness of 1 mm or less and a void ratio of 20% or less, the energy density of the battery Is high, and ionic conductivity is maintained.

According to claim 6, since the inorganic solid electrolyte is aluminum oxide containing sodium, excellent electrical insulation and excellent heat resistance can be obtained.

According to claim 7, since the inorganic solid electrolyte has a density in the range of 2.7 g / cc to 3.5 g / cc, it has good ionic conductivity and is unlikely to cause a minute short circuit during charging.

According to claim 8 of the present invention, the electrode mixture contains a polyphosphate transition metal oxide, and the polyphosphate transition metal oxide is a crystal represented by the general formula Na _a M _b P _{c Od} . Yes, M is at least one selected from Fe, Mn, Co, Ni, and V, and a, b, and c are 0.0 <a≤3.5, b = 1,1.0. Since ≦ c ≦ 3.0 and 3.0 ≦ d ≦ 30, the polyphosphate transition metal oxide functions as an active material, so that ionic conductivity, charge / discharge capacity, and output characteristics can be improved.

According to claim 9, the electrode mixture forms an active material cluster in which a plurality of particles having a particle size in the range of 0.1 μm to 100 μm are connected to each other, so that a practical energy density can be obtained. can get.

According to claim 10 of the present invention, the electrode mixture contains at least one ion conduction aid selected from ethylene carbonate, polyethylene carbonate, polyethylene glycol, and polyethylene oxide in addition to the active material, so that the electrode is an electrode. The ionic resistance of the mixture can be reduced.

According to claim 11 of the present invention, since the electrode mixture contains at least one conductive auxiliary agent selected from metal, carbon material, conductive polymer, and conductive glass, high electron conductivity is obtained. can get.

According to claim 12, since the conductive auxiliary agent is at least one selected from powdered carbon, fibrous carbon, and flake-shaped carbon, high electronic conductivity can be obtained.

According to claim 13, when the organic solid electrolyte is removed, the electrode mixture is porous with a porosity in the range of 5% to 50%, so that excellent conductivity can be obtained.

According to claim 14, when the organic solid electrolyte is removed, the electrode mixture is porous with a pore size of 0.1 μm to 100 μm, so that excellent conductivity can be obtained.

According to claim 15, since the electrode mixture contains an inorganic solid electrolyte powder having a particle size of 0.1 μm to 100 μm, excellent conductivity can be obtained.

According to claim 16, since the electrode mixture does not contain a resin-based binder, the ionic conductivity is increased and the electrode is not adversely affected.

According to claim 17 of the present invention, since the all-solid sodium storage battery uses a sodium metal, a sodium alloy, or a sodium ion storage material as a counter electrode, a high voltage and high capacity battery can be obtained.

According to claim 18 of the present invention, the all-solid-state sodium storage battery has a structure in which the electrode mixture is in electrical contact with a current collector having electronic conductivity, and the current collector has a through hole. Since it is made of a metal having or a non-penetrating metal, it is possible to collect electricity from a power source, so that the output characteristics (rapid charge / discharge characteristics) are improved.

According to the assembled battery according to claim 19 of the present invention, since it is composed of the all-solid-state sodium storage battery according to any one of claims 1 to 18, a high voltage can be obtained.

According to claim 20, since the all-solid-state sodium storage battery according to any one of claims 1 to 18 is provided, a highly versatile, compact and high-capacity electric device is realized.

It is a figure which shows the cross-sectional concept of the all-solid-state sodium storage battery which concerns on this invention. It is a figure which shows the cross-sectional concept of the all-solid-state sodium storage battery of the bipolar structure which concerns on this invention. It is a figure which compared the charge curve of Example 3 and Comparative Example 2.

The all-solid-state sodium storage battery according to the embodiment of the present invention will be described in detail below.

In order to achieve the above-mentioned object, in the all-solid-state sodium storage battery 1 according to the present invention, as shown in FIG. 1, the organic solid electrolyte 3 is placed between the electrode mixture 2 (active material layer) and the inorganic solid electrolyte 4. It is characterized by being an all-solid-state sodium storage battery configured by interposing the battery. According to this configuration, by applying a voltage, the organic solid electrolyte 3 can move sodium ions via the electrode mixture 2 and the inorganic solid electrolyte 4.

The all-solid sodium storage battery according to the present invention is configured such that the organic solid electrolyte is a polyether obtained by polymerizing ethylene glycol or a derivative thereof, and specifically contains polyethylene glycol (PEG) or polyethylene oxide (PEO). Is preferable. The PEG or the PEO has a function as a solid electrolyte as well as a function as a pressure-sensitive adhesive for binding an electrode mixture and an inorganic solid electrolyte.

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.

The above-mentioned PEG or the above-mentioned PEO is a polyether or a derivative thereof polymerized with ethylene glycol having a weight average molecular weight (Mw) of 1000 or more and 1 million or less from the viewpoint of having a high function as a pressure-sensitive adhesive for binding an electrode mixture and an inorganic solid electrolyte. It is preferable to have. Although it is possible to use other substances such as ethylene carbonate (EC) as the organic solid electrolyte, PEG or PEO is preferable because it has an excellent function as a pressure-sensitive adhesive.

In particular, when the electrode mixture or the inorganic solid electrolyte as an adherend has an uneven shape on the surface or has voids, the organic solid electrolyte bites into the irregularities or voids of the adherend, and the electrode mixture It is preferable because the ionic resistance of the battery is lowered in order to improve the contact area between the and the inorganic solid electrolyte.

It is preferable to liquefy the organic solid electrolyte and apply it to the electrode mixture or (/ and) the inorganic solid electrolyte. Further, the organic electrolyte may be a nonflammable 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 a chain hydrocarbon solvent and a cyclic hydrocarbon solvent. Examples of the chain hydrocarbon solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), tert-butyl isopropyl percarbonate, dichloromethane, nitrile-based solvent, alcohol-based solvent, and the like. , N-Methyl-2-pyrrolidone (NMP), ethylene sulfite, vinylethylene carbonate (VEC), propylene carbonate (PC), 1,3-dioxane-2-one, benzene, lactones and the like.

The nonflammable ionic liquid is not particularly limited as long as it has ionic conductivity, and examples thereof include nonflammable ionic liquids such as pyridine-based, alicyclic amine-based, and aliphatic amine-based cations. By selecting the type of anion to be combined with this, various nonflammable ionic liquids can be synthesized. Examples of cations such as imidazolium salts, pyridinium salts, phosphonium-based ions, and inorganic-based ions include bromide ions, trifurates, tetraphenylborates, and hexafluorophosphates.

Nonflammable ionic liquids include cations such as imidazolinium, Br-, ^{Cl- ,} BF _4- ^, PF _6- ^, (CF ₃ SO ₂ ⁾ ₂ N- ^, CF ₃ SO _3- ^, FeCl _4- It can be obtained by a known synthetic method such that it is composed in combination with an anion such as. Such a nonflammable ionic liquid can function as an electrolyte.

When assembling the battery, the above organic solvent can be operated as a battery even if it is mixed to some extent, but since the expansion of the battery due to the volatilization of the organic solvent can be suppressed, it is sufficiently removed by decompression or heat treatment. Is preferable. The removal method is not particularly limited, and for example, a method for drying the electrode slurry used in the lithium ion battery can be adopted.

When the electrode mixture or the inorganic solid electrolyte, which is an adherend, is porous, the organic solid electrolyte flows through the pores on the surface of the adherend, so that the resistance (ionic resistance) derived from the ionic conduction of the battery is increased. It can be greatly reduced.

When the battery is overcharged, the PEG or the PEO is oxidatively decomposed in the organic solid electrolyte, so that the voltage rise of the battery is suppressed and the function as an adhesive is lost. Therefore, the electrode mixture and the inorganic solid are used. It also has a shutdown function that separates it from the electrolyte and raises the impedance of the battery.

From the viewpoint of strongly binding the electrode mixture and the solid electrolyte, the higher the molecular weight of the PEG or the PEO, the more preferable, but when the weight average molecular weight exceeds 1 million, the viscosity becomes too high and it is difficult to handle. Not only that, but also when the sodium salt described later is contained, the ionic conductivity becomes low. On the contrary, when the weight average molecular weight is less than 1000, the adhesiveness is poor, and when the battery is vibrated or shocked, the interface between the electrode mixture and the inorganic solid electrolyte is destroyed, which tends to be a factor of increasing the battery impedance. ..

At low molecular weights, it exhibits hygroscopicity and takes a long time in the drying process. Therefore, the weight average molecular weight is preferably 1000 or more, more preferably 2500 or more, with the upper limit being 1 million. These may be crosslinked or non-crosslinked.

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

The organic solid electrolyte preferably further contains a sodium salt from the viewpoint of increasing ionic conductivity.

When the weight of the organic solid electrolyte is 1, the sodium salt is preferably 0.1 or more, more preferably 0.3 or more, still more preferably 0.4 or more. However, if the content of the sodium salt is too high, the viscosity of the organic solid electrolyte increases and the adhesive action between the electrode mixture and the solid electrolyte decreases, so the content is preferably 1.5 or less, preferably 1.2 or less. Is more preferable, and 0.7 or less is further preferable. With an organic solid electrolyte having a low adhesive action, the charge / discharge cycle characteristics of the battery deteriorate.

The sodium salts are sodium hexafluorophosphate (NaPF ₆ ), sodium perchlorate (NaClO ₄ ), sodium tetrafluoroborate (NaBF ₄ ), sodium trifluoromethanesulfonate (NaCF ₃ SO ₄ ), sodium bisoxalate. From the group consisting of borate (NaBC ₄ O ₈ ), sodium difluorophosphate (F ₂ NaO ₂ P), sodium bis-fluorosulfonylimide (F ₂ NaNO ₄ S ₂ ), sodium difluoroborate (NaBF ₂ O), etc. At least one selected can be used. Of the above sodium salts, NaPF ₆ is preferable because it has a particularly high electronegativity and is easily ionized. An organic solid electrolyte containing NaPF ₆ is excellent in input / output characteristics and charge / discharge cycle characteristics.

The thickness of the organic solid electrolyte is preferably in the range of 0.1 μm to 500 μm, preferably in the range of 0.2 μm to 100 μm, from the viewpoint of excellent ionic conductivity and high energy density of the battery. Is more preferable, 0.5 μm to 50 μm is further preferable, and 1 μm to 20 μm is desirable. Alternatively, the mass of the organic solid electrolyte is preferably in the range of 0.1 mg / cm ² to 800 mg / cm ² and in the range of 0.2 mg / cm ² to 500 mg / cm ² . More preferably, 0.5 mg / cm ² to 100 mg / cm ² is more preferable, and 1 mg / cm ² to 20 mg / cm ² is most preferable.

The inorganic solid electrolyte includes a sulfide type, an oxide type, a hydride type, and the like, 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 of such an inorganic solid electrolyte, it is preferable that the thickness is 1 mm or less and the void ratio is 20% or less.

For sulfide systems, for example, A ₄ SiS ₄ , A ₄ GeS ₄ , A ₃ PS ₄ , A _9.54 Si _1.74 P _1.44 S _11.7 C _l0.3 , A ₁₀ GeP ₂ S ₁₂ , A _3.25 Ge _0.25 P _0.75 S ₄ , A ₆ PS ₅ Cl, A ₂ SB ₂ S ₃ AI, A ₂ SP ₂ S ₅ -ABH ₄ , A ₂ S-SiS _2. A ₄ SiO ₄ , A ₂ SP ₂ S ₅ , A ₇ P ₃ S ₁₁ , A _3.25 P _0.95 S ₄ and the like (A is Na or other alkali metal elements containing Na). Shows).

For the oxide system, for example, A _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , A _0.34 La _0.51 TiO _2.94 , A ₇ LaZr ₂ O ₁₂ , A ₄ SiO ₄・ A ₂ BO ₃ , A ₃ PO ₄ -A ₄ SiO ₄ , A ₃ BO ₃ -A ₂ SiO ₄ , A ₃ BO ₃ -A ₂ SO ₄ , A _2.9 PO _3.3 N _0.46 , A _1.07 Al _0.69 Ti _1.46 (PO ₄ ) ₃ , A _3.3 PO _3.8 N _0.22 , A _2.9 PO _3.3 N _0.46 (A is Na or Na (Indicating other alkali metal elements including), aluminum oxide containing sodium, NASICON crystals (Na _{1 + x} Zr ₂ Si _x P _3-x O ₁₂ , 0 <x <3) and the like.

Examples of the hydride system include ABH ₄ , ABH ₄ -AI, ABH ₄ -ABr, ABH ₄ -AF, ABH ₄ -ACl and the like (A indicates an alkali metal element).

The inorganic solid electrolyte preferably has a porosity in the range of 0% to 20%. That is, the inorganic solid electrolyte may be as dense as possible. By setting the porosity to 20% or less, the ionic conductivity can be increased. On the contrary, when the porosity exceeds 20%, the ionic conductivity is poor and a minute short circuit is likely to occur during charging.

In other words, the inorganic solid electrolyte preferably has a density in the range of 2.7 g / cc to 3.5 g / cc. If it is less than 2.7 g / cc, the ion conductivity is poor because there are too many voids, and a minute short circuit is likely to occur during charging.

However, the production of an inorganic solid electrolyte having a porosity of 0% is not realistic except that a single crystal is used. Therefore, it is preferable to infiltrate the voids of the inorganic solid electrolyte with the organic solid electrolyte to further improve the ionic conductivity. Here, when the density of the inorganic solid electrolyte exceeds 3.5 g / cc, it becomes difficult for the organic solid electrolyte to permeate, so the density is preferably 3.5 g / cc or less.

The above-mentioned density is a density when a container having a constant volume is filled with an inorganic solid electrolyte and the internal volume thereof is taken as a volume, and more accurately, it means a bulk density (Aerated Bulk Density).

The shape is not particularly limited, but it may be molded into a film shape, a sheet shape, a pellet shape, or a ribbon shape.

The inorganic solid electrolyte is preferably an oxide-based electrolyte from the viewpoint that toxic gas is unlikely to be generated when it comes into contact with water. Of these, aluminum oxide containing sodium is preferable because it has excellent electrical insulation and heat resistance.

Aluminum oxide containing sodium is a crystal or ceramic represented by the general formula Na ₂ O-xAl ₂ O ₃ (x = 2 to 20), and has a structure in which sodium ions are distributed between the two-dimensional layers formed by the alumina block. Will be. Β-Alumina (Na ₂ O-11Al ₂ O ₃ ) and β "-Alumina (β-Double Prime Alumina (Na ₂ O-5 Al ₂ O ₃ )) are known as the way of overlapping alumina blocks. Even so, it functions as a solid electrolyte because sodium ions move between the two-dimensional layers created by the alumina block. Aluminum oxide containing sodium is composed of, for example, α-alumina (Al ₂ O ₃ ) and sodium carbonate. The mixture can be synthesized by firing at 1100 ° C to 1500 ° C.

Aluminum oxide containing sodium further contains at least one metal or oxide selected from Mg, Li, K, Rb, Zr, Pb, Y, Ag, Tl, Sr, Ca and Fe. Is preferable. These contents are 5 vol. For aluminum oxide containing sodium. % Or less is preferable. As a result, aluminum oxide containing dense sodium can be easily obtained, and the ionic conductivity can be further improved.

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.

The electrode mixture includes a positive electrode mixture (positive electrode active material layer) and a negative electrode mixture (negative electrode active material layer). In the present invention, the polyphosphate transition metal oxide is used in any of the electrode mixture. It is preferable that it is contained. In particular, when the electrode mixture is used as the positive electrode mixture, the polyphosphate transition metal oxide functions as an active material.

The polyphosphate transition metal oxide is preferably a crystal represented by the general formula Na _a M _b P _{c Od} .

0.0 <a≤3.5, b=1,1.0≤c≤3.0,3.0 from the viewpoint of high ionic conductivity, charge / discharge capacity or output characteristics of polyphosphate transition metal oxides. It is preferable that M is at least one element selected from Fe, Mn, Co, Ni, and V with ≦ d ≦ 30.

Specifically, 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 , Na ₉ V ₃ (P ₂ O ₇ ) ₃ (PO ₄ ) ₂ , etc., and these may be used alone or in combination of two or more.

Among the above polyphosphate transition metal oxides, glass or crystallized glass is easy to synthesize as a polyphosphate transition metal oxide precursor, and it is said that it softens and flows and easily crystallizes in the firing (heat treatment) process at 700 ° C. or lower. 0.0 <a ≦ 3.0, b = 1, 1.1 ≦ c ≦ 2.9, 3.5 ≦ d ≦ 12 is more preferable, and 0.7 ≦ a ≦ 2.4 because of the characteristics. , B = 1,1.2 ≦ c ≦ 2.8, 4.0 ≦ d ≦ 11 are more preferable, 1.7 ≦ a ≦ 2.3, b = 1,1.4 ≦ c ≦ 2.7, Most preferably 5.0 ≦ d ≦ 10.

In the polyphosphate transition metal oxide, Li or K may be substituted in a part of the Na site of the above material, and F, Cl, in a part of the O site (octahedron position) or P site (octahedron position). It may be a material in which S and B are substituted.

In addition to polyphosphate transition metal oxides, the electrode mixture can be used in sodium ion batteries, sodium metal batteries, sodium air batteries, sodium-sulfur batteries, sodium-metal chloride batteries, all-solid sodium storage batteries, etc. It may contain substances. That is, in addition to the polyphosphate transition metal oxide, a known sodium metal, a known sodium alloy, or a known sodium ion occlusion material may be contained.

When the electrode mixture is used as the positive electrode mixture, it may contain a polyphosphate transition metal oxide and another positive electrode active material. As the positive electrode active material, a known material including a transition metal oxide-based material, a sulfur-based material, a solid solution system, and the like is used. When the electrode mixture is used as the negative electrode mixture, the polyphosphate transition metal oxide alone cannot obtain a practical energy density. Therefore, the polyphosphate transition metal oxide and other negative electrode active materials should be contained. Is preferable. The negative electrode active material may include known materials including transition metal oxide-based materials, sulfur-based materials, sodium metals, materials that alloy with sodium, and materials that can reversibly occlude and release sodium ions. preferable.

The above-mentioned electrode active material (positive electrode active material or negative electrode active material) is not particularly limited in shape, but individual particles of the active material having a particle size in the range of 0.1 μm to 100 μm are crystalline polyphosphate transition metal oxidation. It is preferable to have a structure in which a plurality of objects are connected. That is, it is preferable that the electrode mixture forms an active material cluster in which a plurality of particles having a particle size in the range of 0.1 μm to 100 μm are connected.

Here, the particle size means the median diameter (D50), which is the median value on a volume basis in the laser diffraction / scattering type particle size distribution measurement method.

Further, in the all-solid-state sodium storage battery according to the present invention, the electrode mixture is selected from ethylene carbonate (EC), polyethylene carbonate (PEC), polyethylene glycol (PEG), and polyethylene oxide (PEO) in addition to the active material. It is preferable to contain at least one of them.

It is preferable that the electrode mixture contains at least one selected from EC, PEC, PEG, and PEO as the conductive agent because the ionic resistance of the electrode mixture can be reduced.

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

Although it depends on the mass of the electrode mixture, the amount of EC, PEC, PEG, and PEO contained in the electrode mixture is preferably in the range of 0.1 mg / cm ² to 500 mg / cm ² , and is preferably 0.2 mg. The range of / cm ² to 250 mg / cm ² is more preferable, and 0.5 mg / cm ² to 100 mg / cm ² is even more preferable.

According to this configuration, the material selected from EC, PEC, PEG, and PEO contained in the electrode mixture functions as an electrolyte that improves the ionic conductivity in the electrode mixture. Further, the organic solid electrolyte interposed between the electrode mixture and the inorganic solid electrolyte is fused and integrated with the electrode mixture to form a battery having a low impedance. As a result, an all-solid-state sodium storage battery capable of exhibiting excellent charge / discharge cycle characteristics while maintaining a high discharge capacity in a room temperature environment can be obtained even if a thick electrode mixture is formed.

Further, when the battery is overcharged, the material selected from EC, PEC, PEG, and PEO contained in the electrode mixture is oxidatively decomposed and has a function of suppressing the voltage rise of the battery.

Among the materials selected from EC, PEC, PEG, and PEO contained in the electrode mixture, the electrode mixture has excellent heat resistance, high ionic conductivity, and is interposed between the electrode mixture and the inorganic solid electrolyte. From the viewpoint of easy fusion with the organic solid electrolyte, a polymer material having a molecular weight of 500 or more selected from PEC, PEG, and PEO is preferable, and PEG or PEO is more preferable. However, in the case of a polymer material having a molecular weight of more than 200,000, the viscosity becomes too high, and it becomes difficult to include it in the electrode mixture by the manufacturing method described later, and the ionic conductivity of the electrode mixture decreases. These may be crosslinked or non-crosslinked.

Further, it is preferable that the electrode mixture contains a conductive auxiliary agent. The conductive auxiliary agent is not particularly limited as long as it has electronic conductivity, and examples thereof include metals, carbon materials, conductive polymers, conductive glass, etc., but it is said that it has high electronic conductivity and a small specific gravity. From the viewpoint, a carbon material is preferable. 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.

In the above electrode mixture, a powder containing at least a polyphosphate transition metal oxide is filled in a powder molding die, and pellets (tablets) molded by applying pressure are 400 in an inert gas or reducing gas atmosphere. It can be manufactured by firing at a temperature of ° C to 2000 ° C.

However, since a high pressure exceeding 100 MPa is required to pelletize the polyphosphate transition metal oxide powder, a large-scale pressure device is required. Therefore, it is preferable that the polyphosphate transition metal oxide is coated or supported with a resin-based binder. By coating or supporting a resin-based binder on the surface of the polyphosphate transition metal oxide, pelletization can be performed at a pressure of 100 MPa or less.

By pressure molding using such a powder, the resin binders adhere to each other at a pressure of 1 MPa to 100 MPa, and a dense pellet can be obtained. If the pressure in pressure molding is less than 1 MPa, it is difficult for the resin binders to adhere to each other. On the other hand, if the pressure exceeds 100 MPa, the device becomes large-scale.

The obtained pellets are further fired in an atmosphere of an inert gas or a reducing gas to soften and flow the polyphosphate transition metal oxide to obtain an integrated electrode mixture. At the same time, the resin binder is thermally decomposed. Therefore, the electrode mixture (pellets after firing) does not contain a resin, and a porous electrode mixture having a porosity in the range of 5% to 50% can be obtained.

In addition to polyphosphate transition metal oxides, it is further composed of active materials used in sodium ion batteries, sodium metal batteries, sodium air batteries, sodium-sulfur batteries, sodium-metal chloride batteries, all-solid sodium storage batteries, etc. It is preferable to coat or support the resin-based binder not only in the polyphosphate transition metal oxide but also in these active materials in the electrode mixture. The same applies even when a conductive auxiliary agent is added.

The firing conditions are not particularly limited as long as the temperature can be maintained in the range of 400 ° C. to 2000 ° C. for 5 minutes or more under an inert gas or reducing gas atmosphere, but the polyphosphate transition metal oxide is softened and flowed, and a resin-based binder is used. From the viewpoint of thermal decomposition, it is preferable that the temperature is raised in the range of 0.1 ° C./min to 50 ° C./min, the temperature is 400 ° C. to 2000 ° C., and the maintenance time is 5 minutes or more and 10 hours or less.

From the viewpoint of battery input / output characteristics and energy density, the electrode mixture after firing should have a thickness in the range of 10 μm to 5000 μm and a total weight per unit area in the range of 1 mg to 5000 mg / cm ² . preferable.

The polyphosphate transition metal oxide coated with the resin-based binder is prepared by adding a solvent to a mixed powder consisting of the polyphosphate transition metal oxide and the resin-based binder, mixing the mixture, volatilizing and removing the solvent, and pulverizing or classifying the mixture. Obtained by doing. Unless the solvent is water, it is preferable to work in a dry environment (dew point −40 ° C. or lower).

As a mixing method for producing the above-mentioned mixed powder or adding a solvent, a known mixing method can be used. For example, a rolling mill, a vibration mill, a planetary mill, a rocking mill, a horizontal mill, and an attritor mill can be used. , Jet mills, grinders, homogenizers, fluidizers, paint shakers, mixers, etc.

As a method for volatilizing and removing the solvent and pulverizing or classifying the mixture, known granulation methods can be applied. For example, a fluidized bed granulation method, a stirring pulverization granulation method, and a rolling granulation method can be applied. , Spray-drying method, extrusion granulation method, coating granulation method and the like. Of these, the spray-drying method and the fluidized bed granulation method are particularly preferable.

In the spray-drying method, for example, a suspension in which a polyphosphate transition metal oxide and a resin-based binder are dispersed is placed in a greenhouse heated to 50 to 300 ° C. from above at 1 to 30 mL / min and an air pressure of 0.01 to. By spraying at 5 MPa, agglomerated granules are formed, and these are dried to obtain granulated products.

In the fluidized layer granulation method, for example, a powder raw material is placed in a fluidized layer granulator and warm air heated to 50 to 300 ° C. is sent from below to flow the powder raw material (granulation precursor). Then, the mixed powder raw material is sprayed with a liquid in which a resin-based binder is dissolved or dispersed from above, and the resin-based binder is uniformly spread on the powder surface at 1 to 30 mL / min and an air pressure of 0.01 to 5 MPa. By spraying, aggregated particles are formed, and these are dried to obtain granulated materials.

In order to include a material selected from EC, PEC, PEG, and PEO in the electrode mixture, the active material and these materials may be mixed and pelletized, but the polycrystalline glass of the polyphosphate transition metal oxide is used. Alternatively, in the case of producing crystals of polyphosphate transition metal oxide by firing glass, if it is fired in a state where EC, PEC, PEG, and PEO are contained in advance, it is thermally decomposed and EC, PEC is added to the mixture. , PEG, PEO cannot be contained. Therefore, it is necessary to contain materials such as EC, PEC, PEG, and PEO after firing the polycrystalline glass of the polyphosphate transition metal oxide or the glass.

Therefore, EC, PEC, PEG, PEO, etc. are liquefied and applied to the polyphosphate transition metal oxide after calcination, or EC, PEC, PEG, PEO, etc. are liquefied and calcinated polyphosphorus. By immersing the acid transition metal oxide, the electrode mixture can contain a material selected from EC, PEC, PEG, and PEO.

For liquefaction of EC, PEC, PEG, PEO and the like, the temperature of the target material may be raised, but it is preferable to add an organic solvent to liquefy. The organic solvent is not particularly limited as long as it can dissolve and liquefy the target material. For example, a chain hydrocarbon solvent (DMC, DEC, EMC, dichloromethane, alcohol type, etc.), a cyclic hydrocarbon solvent (NMP, benzene, lactone type, etc.), and the like can be mentioned. The organic solvent is preferably removed by reducing the pressure or heat treatment. For example, a method for drying an electrode slurry used in a lithium ion battery can be adopted.

When the thickness of the electrode mixture is large, it is difficult to penetrate by simply applying liquefied EC, PEC, PEG, PEO, etc., so EC, PEC, PEG, which is a liquefied polyphosphate transition metal oxide after firing. It is preferable to immerse in PEO. In this state, by further reducing the pressure, it is possible to penetrate deep into the pores contained in the polyphosphate transition metal oxide after firing. The conditions of the reduced pressure environment may be a pressure lower than the atmospheric pressure (negative pressure). For example, a vacuum pump may be used to create a negative pressure environment having a gauge pressure of 0 MPa to −0.1 MPa.

The electrode mixture is preferably porous with a porosity in the range of 5% to 50% when the material selected from EC, PEC, PEG, and PEO contained in the electrode mixture is excluded. If the porosity is less than 5%, EC, PEC, PEG, and PEO cannot be sufficiently contained in the electrode mixture. If it exceeds 50%, it is possible to include a large amount of EC, PEC, PEG, PEO, etc. in the electrode mixture, but the energy density is low because the proportion of the active material in the electrode mixture is small. Become.

Here, the porosity is a value calculated by the following formula from the apparent density of the target and the true density of the constituent materials.

Porosity (%) = 100- (apparent density of target / true density of constituent materials) x 100

Further, the electrode mixture is preferably porous having a plurality of pores having a pore diameter of 0.1 μm to 100 μm when the material selected from EC, PEC, PEG, and PEO contained in the electrode mixture is excluded. This is because it becomes difficult to sufficiently include EC, PEC, PEG, PEO, etc. in the electrode mixture in the method for producing the electrode mixture, which will be described later, when the pore size is out of the range. That is, if the pore diameter is less than 0.1 μm, EC, PEC, PEG, PEO and the like are difficult to penetrate into the electrode mixture, and conversely, if it exceeds 100 μm, the strength of the electrode mixture is low and it is easily damaged.

In the all-solid-state sodium storage battery according to the present invention, for example, the electrode mixture obtained as described above is adhered to one surface of the inorganic solid electrolyte via the organic solid electrolyte in a dry environment with a dew point of −40 ° C. or lower. It can be manufactured by sealing the inorganic solid electrolyte with a counter electrode on the other surface.

The counter electrode is not particularly limited, and when the electrode mixture is used as the positive electrode mixture, the counter electrode is 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 storage. A negative electrode can be used. When the electrode mixture is used as the negative electrode mixture, a positive electrode mixture, a known sodium alloy positive electrode, or a known sodium ion occlusion positive electrode can be used as the counter electrode.

Further, the all-solid-state sodium storage battery is preferably configured via the above-mentioned organic solid electrolyte between the counter electrode and the inorganic solid electrolyte.

That is, it is preferable that the all-solid-state sodium battery according to the present invention does not contain a resin-based binder in the electrode mixture. If a resin-based binder is contained in the electrode mixture, it becomes a factor of increasing electronic resistance and ionic resistance.

The resin-based binder is a binder of a compound having carbon as a main molecular skeleton, and is, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide, polyamideimide, polyacrylic acid, styrene. Butadiene rubber (SBR), ethylene-vinyl acetate copolymer (EVA), polypropylene carbonate (PPC), styrene-ethylene-butylene-styrene copolymer (SEBS), carboxymethyl cellulose (CMC), xansan gum, polyvinyl alcohol ( PVA), polyvinyl butyral (PVB), ethylene vinyl alcohol, polyethylene (PE), polypropylene (PP), polyacrylic acid, lithium polyacrylic acid, sodium polyacrylic acid, potassium polyacrylic acid, ammonium polyacrylic acid, polyacrylic acid. Methyl, ethyl polyacrylic acid, amine polyacrylic acid, polyacrylic acid ester, epoxy resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), nylon, vinyl chloride, silicone rubber, nitrile rubber, cyanoacrylate, urea resin, Melamine resin, phenol resin, latex, polyurethane, silylated urethane, nitrocellulose, dextrin, polyvinylpyrrolidone, vinyl acetate, polystyrene, chloropropylene, resorcinol resin, polyaromatic, modified silicone, methacrylic resin, polybutene, butyl rubber, 2-propen Materials such as acid, cyanoacrylic acid, methyl methacrylate, glycidyl methacrylate, acrylic oligomer, 2-hydroxyethyl acrylate, polyacetal, alginic acid, starch, sucrose, urushi, sardine, and casein can be mentioned.

Many of these resin-based binders are thermally decomposed and carbonized from 150 ° C or higher, but in polypropylene carbonate (PPC), even in an inert environment or a reducing environment, heat treatment at 200 ° C or higher results in carbonization. It is a binder that changes and disappears without leaving carbon, and is more preferable because it has very little effect on the electrodes. The carbon produced by the thermal decomposition of the resin binder has low conductivity unless it is fired at a high temperature, and may adversely affect the electrodes.

Further, the all-solid-state sodium storage battery according to the present invention preferably has a structure in which the electrode mixture is in electrical contact with a current collector having electronic conductivity. The current collector may be either a metal having a through hole or a non-penetrating metal, but by using the non-penetrating metal, an all-solid-state battery having a bipolar structure as shown in FIG. 2 is manufactured. be able to. The bipolar electrode may be manufactured by contacting a current collector 6 made of a non-penetrating metal such as a metal foil or a metal plate with the electrode mixture 2, or electroplating or a vapor phase growth method on the electrode mixture. It may be obtained by forming the current collector 6 by a method such as. With an all-solid-state battery having a bipolar structure, a high voltage can be obtained with one cell.

On the other hand, when a metal having a through hole is used as the current collector, the current collector can be filled with the electrode mixture three-dimensionally to collect electricity from the electrode mixture. As a result, the electron conductivity of the electrode mixture is improved, and a battery having excellent output characteristics can be obtained. Further, when the mixture containing the active material precursor is made into an electrode mixture by firing, the active material precursor causes a large volume shrinkage, which causes a large stress, but a metal that does not penetrate the electrode mixture. By filling in, the cohesive stress is relaxed, and the occurrence of cracks in the electrode mixture can be suppressed. Further, when an active material whose volume changes greatly due to charging / discharging is used, the electrode mixture is suppressed from falling off from the current collector, and the battery has a long life.

The material of such a current collector is not particularly limited as long as it has electron conductivity and can energize the active material contained in the electrode mixture. For example, metal, carbon, conductive ceramics, conductive glass and the like can be mentioned. Specifically, conductive substances such as gold, aluminum, carbon, copper, molybdenum, titanium, chromium, nickel, tantalum, tungsten, and platinum, and metals containing two or more of these conductive substances (for example, stainless steel, Al—Fe alloy, etc.) can be used. Of these, from the viewpoint of obtaining a battery in which the material is inexpensive and the output characteristics are excellent, a current collector in which aluminum or an aluminum alloy is coated with carbon is preferable. More specifically, a current collector having a carbon layer having a thickness of 0.1 μm to 3 μm on the surface of the metal is preferable.

As described above, the shape of the current collector is roughly classified into a metal having a through hole and a non-penetrating metal. Examples of the metal having a through hole include foamed metal, an embossed body having a through hole, an expanded body, a punching body, a non-woven fabric, a woven fabric, and the like, and the porosity is preferably 10% to 98%. However, when the porosity is less than 10%, it is not much different from the non-penetrating metal, and when it exceeds 98%, the strength of the current collector is low and the electrode is easily damaged. Non-penetrating metals include, for example, foils, plates, non-penetrating embossed bodies and the like.

In this way, the electrode is composed of an electrode mixture and a current collector. However, if the outer body (electric tank) of the battery has electrical conductivity and can also serve as a current collector by itself, the current collector is not always required.

As described above, the all-solid-state sodium storage battery has been described, but various additions, changes, or deletions can be made without departing from the spirit of the present invention. For example, the electrolyte of the all-solid-state sodium storage battery of the present invention may be further added with an electrolytic solution, an ionic liquid, and a gel electrolyte. For example, the carrier ion of the battery may be replaced with another alkali metal ion (lithium ion, potassium ion, etc.) from sodium ion to be an all-solid lithium ion storage battery or an all-solid potassium ion storage battery.

The assembled battery of one aspect according to the present invention is characterized by comprising the all-solid-state sodium storage battery of the present invention. That is, it may be a battery group consisting of two or more single batteries in which the all-solid-state sodium storage batteries of the present invention are directly connected to each other or electrically connected via a bus bar.

One aspect of the electrical equipment according to the present invention is characterized by comprising the all-solid-state sodium storage battery or the assembled battery of the present invention.

Electrical equipment includes, for example, irons, whisks, integrated personal computers, clothes dryers, medical equipment, interphones, wearable terminals, video equipment, air conditioners, air circulators, gardening machines, motorcycles, ovens, music players, music recorders. , Hot air heater, toys, car components, flashlights, loudspeakers, car navigation systems, cassette stoves, household storage batteries, nursing machines, humidifiers, dryers, refueling machines, water dispensers, suction machines, safes, glue guns, mobile phones, Portable information equipment, air purifiers, air conditioners, game machines, fluorescent lights, fluff removers, cordless phones, coffee makers, coffee warmers, ice scrapers, kotatsu, copy machines, haircuts, shavers, lawn mowers, automobiles, Lighting equipment, dehumidifier, sealer, shredder, automatic extracorporeal defibrillator, rice cooker, stereo, stove, speaker, trouser press, smartphone, rice mill, washing machine, toilet seat with washing function, sensor, fan, submarine, blower , Vacuum cleaner, flying car, tablet, body fat meter, fishing tackle, digital camera, TV, TV receiver, video game, display, disk changer, desktop computer, railroad, TV, electric carpet, electric stand, electric stove , Electric pot, electric blanket, calculator, electric cart, electric wheelchair, electric tool, electric car, electric float, electric toothbrush, telephone, electric bicycle, electric shock insecticide, electromagnetic cooker, electronic notebook, electronic musical instrument, electronic Locks, electronic cards, microwave ovens, electronic mosquito repellents, electronic cigarettes, telephones, power load levelers, toasters, dryers, transceivers, watches, drones, food waste disposers, laptops, incandescent bulbs, soldering irons, panel heaters, halogens. Heater, fermenter, pan baking machine, hybrid car, personal computer, personal computer peripherals, varican, panel heater, video camera, video deck, airplane, emergency electric light, emergency storage battery, ship, beauty equipment, printer, copying machine, crusher , Atomizer, Facsimile, Forklift, Plug-in hybrid car, Projector, Hair dryer, Hair iron, Headphones, Disaster prevention equipment, Security equipment, Home theater, Hot sand maker, Hot plate, Pump, Fragrance machine, Massage machine, Mixer, Mill, Movie player , Monitor, Mochitsuki machine, Water heater, Floor heating panel, Radio, Radio cassette, Lantern, Radicon, Laminator, Remote control, Range, Water cooler, Refrigerator, Cold air blower, Examples include cold air fans, air conditioners, robots, word processors, GPS, and the like.

<Example>
Hereinafter, examples of the present invention will be specifically described, but the present invention is not limited to these examples. In particular, in the examples, an all-solid-state sodium storage battery using β''-alumina as a solid electrolyte will be described as an example, but the present invention is not limited to this. Further, Na ₂ FeP ₂ O ₇ will be described as an example as the active material contained in the electrode mixture, but the present invention is not limited to this.

<Preparation of positive electrode active material precursor powder>
The positive electrode active material precursor was prepared by the melt quenching method. Sodium metaphosphate (NaPO ₃ ), iron oxide (Fe ₂ O ₃ ), orthophosphoric acid (H ₃ PO ₄ ) are used as raw materials so that the composition is 40 Na ₂ O-20 Fe _{2 O 3-40P 2 O 5 in terms} of molar ratio. It was prepared and melted in an air atmosphere at 1350 ° C. for 1 hour. The obtained molten glass was poured between a pair of cooling rollers and molded while quenching to obtain a film-shaped glass body having a thickness of 0.1 to 1 mm. This glass body was pulverized by a ball mill using a ZrO ₂ ball stone having a diameter of 20 mm for 10 hours and passed through a resin sieve having an opening of 120 μm to obtain a coarse glass powder having an average particle diameter of 7 μm. Further, the crude glass powder was pulverized by a ball mill using ethanol as a pulverizing aid and using a φ3 mm ZrO ₂ ball stone for 80 hours to obtain a glass powder having an average particle diameter of 0.6 μm (positive electrode active material precursor powder). ) Was obtained. As a result of powder X-ray diffraction measurement, it was confirmed that the glass powder was amorphous.

<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 crystal body. This crystal was pulverized by a ball mill using a ZrO2 ball stone having a diameter of ₂₀ mm for 10 hours and passed through a resin sieve having an opening of 120 μm to obtain a coarse powder having an average particle diameter of 7 μm. Further, this crude powder was subjected to ball mill pulverization using ethanol as a pulverizing aid and using a φ3 mm ZrO ₂ ball stone for 12 hours to obtain a crystal powder having an average particle diameter of 0.2 μm. This crystal powder 70 wt. %, As a carbon source, polyethylene oxide nonylphenyl ether (mass average molecular weight: 660), which is a nonionic surfactant, was added at 30 wt. % Was mixed and then dried at 100 ° C. for 1 hour. Then, it was calcined at 620 ° C. for 30 minutes in a nitrogen atmosphere to obtain a positive electrode active material powder having an average particle diameter of 0.2 μm. As a result of powder X-ray diffraction measurement, it was confirmed that the positive electrode active material powder was a diffraction line derived from Na ₂ FeP ₂ O ₇ crystals.

<Preparation of electrode mixture (active material layer)>
The electrode mixture (active material layer) is prepared by filling a powder molding die (manufactured by NPA System Co., Ltd., Φ10 mm) with a mixture powder coated with polypropylene carbonate (PPC) in an argon environment, and then applying a pressure of 30 MPa. In addition, the molded pellets are fired in a nitrogen (N ₂ ) / hydrogen (H ₂ ) mixed gas (= 96/4 vol.%) Atmosphere under the conditions of 550 ° C, 1h, and 3 ° C / min, and then a current collector. It was produced by forming a 300 nm-thick gold film on one side of the pellet by a physical gas phase growth method (PVD). By the firing step, all the PPC contained in the electrode mixture was thermally decomposed and changed to carbon dioxide gas, so that the obtained electrode mixture had the weight obtained by subtracting the PPC.

The electrode mixture after firing had a thickness of 298 μm, a total weight of 0.0307 g, a diameter of 9.242 mm, and a weight of the active material contained in the electrode mixture was 0.02794 g. When the SEM (scanning electron microscope) image of the cross section of the electrode mixture was confirmed, it was confirmed that the positive electrode active material particles formed clusters in which a plurality of positive electrode active material particles were connected and had a porous structure including pores. This cluster is formed by softening and flowing the positive electrode active material precursor powder and binding the positive electrode active material powders to each other when the mixture powder is fired. It was confirmed that the positive electrode active material precursor powder softened and flowed and crystallized to precipitate Na ₂ FeP ₂ O ₇ crystals.

The PPC-coated mixture powder was prepared in a dry environment (dew point −40 ° C. or lower), a positive electrode active material precursor powder and a positive electrode active material, a conductive auxiliary agent, and PPC (32.3: 48.5: 2. 5: 16.7 wt%) is added with N-methyl-2-pyrrolidone (NMP), mixed with a self-revolving mixer (Sinky, Neritaro, 2000 rpm, 1 h), and then heat-dried (80 ° C.) on a glass plate. , 1h) to volatilize and remove NMP, and the mixture was crushed (1h) with a crusher (manufactured by Nikko Kagaku, AMM-140D). As the conductive auxiliary agent, carbon black and vapor phase grown carbon fiber (Showa Denko, VGCF-H) were used at 5: 1 wt. A mixture was used so as to be%.

<Inorganic solid electrolyte>
Li ₂ O stabilized β''-alumina (manufactured by Ionotec) of composition formula Na _1.6 Li _0.34 Al _10.66 O ₁₇ was used as it was. The thickness of the inorganic solid electrolyte was 1 mm.

<Preparation of organic solid electrolyte>
The organic solid electrolyte is prepared by adding acetonitrile to polyethylene glycol (PEG) having a weight average molecular weight (Mw) of 7000 and NaPF ₆ (1: 0.3 wt.) And using a self-revolving mixer (Sinky, Neritaro, 2000 rpm, 1 h). It was produced by mixing.

<Manufacturing of all-solid-state sodium storage battery>
(Example 1: All-solid-state sodium storage battery)
In the battery of Example 1, the organic solid electrolyte prepared as described above is interposed between the electrode mixture prepared as described above and the inorganic solid electrolyte in an argon environment so as to be 0.005 g / cm ² . It was prepared by using a sodium metal as a counter electrode. The organic solid electrolyte was interposed by applying the organic solid electrolyte dissolved in acetonitrile to the electrode mixture with a brush and then vacuum drying (60 ° C., 1 h).

(Example 2: All-solid-state sodium storage battery)
The battery of Example 2 was the same as that of Example 1, except that an electrode mixture filled with a mixture of PEG and NaPF ₆ (1: 0.3 wt.) So as to be 0.006 g / cm ² was used. Battery configuration. The mixture to be filled in the electrode mixture was filled by immersing the electrode mixture in PEG and NaPF ₆ dissolved in acetonitrile and then vacuum drying (60 ° C., 1 h) to remove acetonitrile.

(Example 3: All-solid-state sodium storage battery)
The battery of Example 3 has the same battery configuration as that of Example 2, except that the electrode mixture is filled with a mixture of ethylene carbonate (EC) and NaPF ₆ (1: 0.3 wt%). The mixture to be filled in the electrode mixture is subjected to a de-DEC treatment by immersing the electrode mixture in EC and NaPF ₆ dissolved in diethyl carbonate (DEC) and then vacuum drying (60 ° C., 1 h). Filled.

(Comparative Example 1: All-solid-state sodium storage battery)
The battery of Comparative Example 1 is not provided with the organic solid electrolyte and has the same battery configuration as that of Example 1.

(Comparative Example 2: Liquid Sodium Ion Battery)
The battery of Comparative Example 2 was not provided with an organic solid electrolyte or an inorganic solid electrolyte, but instead had a glass non-woven fabric (Advantech, GA-100) and a polyolefin-based microporous film (Celguard, # 2320) laminated on top of each other. The battery configuration is the same as that of the first embodiment, except that the separator is impregnated with 1M NaPF ₆ / (EC: DEC = 1: 1 vol.).

<Battery test>
The battery test was carried out by repeating constant current charging / discharging under the conditions of 60 ° C., 0.01 C rate, and cutoff voltage of 3.8 to 2.0 V. Hereinafter, the charge / discharge test results of Examples 1 to 3 and Comparative Examples 1 and 2 are shown.

(Example 1)
In the all-solid-state sodium storage battery of Example 1, a mixture consisting of PEG and NaPF ₆ as an organic solid electrolyte was interposed between the electrode mixture and the inorganic solid electrolyte, so that the electrode mixture and the inorganic solid electrolyte were formed. It was integrated. 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 ).

(Example 2)
In the all-solid sodium storage battery of Example 2, a mixture of PEG and NaPF ₆ as an organic solid electrolyte was interposed between the electrode mixture and the inorganic solid electrolyte, so that the electrode mixture and the inorganic solid electrolyte could be separated. It was integrated. In addition, the organic solid electrolyte was impregnated in the electrode mixture. As a result, the discharge capacity of the active material was 89.2 mAh / g (3.72 mAh / cm ² ).

(Example 3)
In the all-solid-state sodium storage battery of Example 3, a mixture of PEG and NaPF ₆ as an organic solid electrolyte was interposed between the electrode mixture and the inorganic solid electrolyte, so that the electrode mixture and the inorganic solid electrolyte could be separated from each other. It was integrated. In addition, the organic solid electrolyte was impregnated in the electrode mixture. As a result, the discharge capacity of the active material was 92.6 mAh / g (3.86 mAh / cm ² ).

(Comparative Example 1)
Since the all-solid-state sodium storage battery of Comparative Example 1 does not have an organic solid electrolyte, 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 it 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 electrode and the solid electrolyte even when a minute current of 0.01 C rate was applied.

(Comparative Example 2)
In the liquid sodium ion battery of Comparative Example 2, the discharge capacity of the active material was 94.2 mAh / g (3.92 mAh / cm ² ).

Table 1 shows the battery test results of Examples 1-3 and Comparative Example 1-2 described above.

<Battery overcharge test>
In the overcharge test of the battery, the battery was charged with a constant current under the conditions of 60 ° C., 0.01 C rate, and a charge cutoff voltage of 4.5 V. The charge curves of Example 3 and Comparative Example 2 are compared and shown in FIG. The vertical axis shows the battery voltage, and the horizontal axis shows the charging time. Charging for more than 100 hours is the overcharge area. As is clear from FIG. 3, in the battery of Example 3, a charging plateau was confirmed in the vicinity of 4.2V, and the charging cutoff voltage of 4.5V was not reached. On the other hand, in the battery of Comparative Example 2, no charging plateau near 4.2V was confirmed, and the battery was charged to the charging cutoff voltage. In the battery of Example 3, it is considered that the organic solid electrolyte interposed between the electrode mixture and the inorganic solid electrolyte is oxidatively decomposed at around 4.2 V. From this result, it was shown that overcharging can be suppressed by having the organic solid electrolyte in the battery (see Table 2).

Further, the battery of Example 3 is charged with a constant current and constant voltage until the SOC (State of Charge) reaches 200% under the conditions of 60 ° C., 0.01C rate, and charge cutoff voltage of 4.5V, and then 0.1C rate. When a constant current was discharged until the voltage reached 2.0 V, the discharge capacity was not shown. It is probable that the battery resistance increased due to the oxidative decomposition of the organic solid electrolyte, and the battery was shut down.

The all-solid-state sodium storage battery according to the present invention exhibits excellent charge / discharge cycle characteristics while maintaining a high discharge capacity in a room temperature environment, and can be shut down by overcharging. Therefore, it is expected to be applied to EV (electric vehicle) and stationary power sources.

1 Cross-sectional concept of all-solid-state sodium storage battery 2 Electrode mixture 3 Organic solid electrolyte 4 Inorganic solid electrolyte 5 Counterpole 6 Collector 11 Cross-sectional concept of battery with bipolar structure

Claims (20)

An all-solid-state sodium storage battery in which an organic solid electrolyte is interposed between an electrode mixture and an inorganic solid electrolyte. The all-solid-state sodium storage battery according to claim 1, wherein the organic solid electrolyte contains polyethylene glycol or polyethylene oxide. The organic solid electrolyte further contains a sodium salt and contains
The all-solid-state sodium storage battery according to claim 1 or 2, wherein the sodium salt is in the range of 0.1 to 1.5 when the weight of the organic solid electrolyte is 1. The thickness of the organic solid electrolyte is in the range of 0.1 μm to 500 μm.
The all-solid-state sodium storage battery according to any one of claims 1 to 3. The inorganic solid electrolyte is a sulfide-based, oxide-based, or hydride-based solid electrolyte having a thickness of 1 mm or less and a void ratio of 20% or less.
The all-solid-state sodium storage battery according to any one of claims 1 to 4. The inorganic solid electrolyte is aluminum oxide containing sodium.
The all-solid-state sodium storage battery according to any one of claims 1 to 5. The inorganic solid electrolyte has a density in the range of 2.7 g / cc to 3.5 g / cc.
The all-solid-state sodium storage battery according to any one of claims 1 to 6. The electrode mixture contains a polyphosphate transition metal oxide and contains.
The polyphosphate transition metal oxide is a crystal represented by the general formula Na _a M _b P _{c Od} .
M is at least one selected from Fe, Mn, Co, Ni, and V, and a, b, and c are 0.0 <a≤3.5, b = 1,1.0≤c. The all-solid-state sodium storage battery according to any one of claims 1 to 7, wherein ≦ 3.0 and ≦ d ≦ 30. The electrode mixture forms an active material cluster in which a plurality of particles having a particle size in the range of 0.1 μm to 100 μm are connected.
The all-solid-state sodium storage battery according to any one of claims 1 to 8. The whole according to any one of claims 1 to 9, wherein the electrode mixture contains at least one ionic conduction aid selected from ethylene carbonate, polyethylene carbonate, polyethylene glycol, and polyethylene oxide in addition to the active material. Solid sodium storage battery. The all-solid-state sodium storage battery according to claim 1 to 10, wherein the electrode mixture contains at least one conductive auxiliary agent selected from a metal, a carbon material, a conductive polymer, and a conductive glass. The all-solid-state sodium storage battery according to claim 11, wherein the conductive auxiliary agent is at least one selected from powdered carbon, fibrous carbon, and flake-shaped carbon. The electrode mixture is porous with a porosity in the range of 5% to 50% when the organic solid electrolyte is removed.
The all-solid-state sodium storage battery according to any one of claims 1 to 12. The electrode mixture is porous with a pore size of 0.1 μm to 100 μm when the organic solid electrolyte is removed.
The all-solid-state sodium storage battery according to any one of claims 1 to 13. The electrode mixture contains an inorganic solid electrolyte powder having a particle size of 0.1 μm to 100 μm.
The all-solid-state sodium storage battery according to any one of claims 1 to 14. The electrode mixture does not contain a resin binder.
The all-solid-state sodium storage battery according to any one of claims 1 to 15. The all-solid-state sodium battery uses a sodium metal, a sodium alloy or a sodium ion storage material as a counter electrode.
The all-solid-state sodium storage battery according to any one of claims 1 to 16. An all-solid-state sodium storage battery having a structure in which the electrode mixture and a current collector having electronic conductivity are in electrical contact with each other.
The current collector is made of a metal having a through hole or a non-penetrating metal.
The all-solid-state sodium storage battery according to any one of claims 1 to 17. An assembled battery comprising the all-solid-state sodium storage battery according to any one of claims 1 to 18. An electrical device comprising the all-solid-state sodium storage battery according to any one of claims 1 to 18.

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